WO2020075749A1 - 固体電解質組成物、全固体二次電池用シート、全固体二次電池用電極シート及び全固体二次電池 - Google Patents
固体電解質組成物、全固体二次電池用シート、全固体二次電池用電極シート及び全固体二次電池 Download PDFInfo
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Definitions
- the present invention relates to a solid electrolyte composition, an all-solid secondary battery sheet, an all-solid secondary battery electrode sheet, and an all-solid secondary battery.
- a lithium ion secondary battery is a storage battery that has a negative electrode, a positive electrode, and an electrolyte sandwiched between the negative electrode and the positive electrode, and can charge and discharge by moving lithium ions back and forth between both electrodes.
- Organic electrolytes have been conventionally used as electrolytes in lithium ion secondary batteries.
- the organic electrolytic solution is liable to leak, and there is a possibility that a short circuit may occur inside the battery due to overcharge or overdischarge, and further improvement in safety and reliability is required. Under these circumstances, an all-solid secondary battery using an inorganic solid electrolyte instead of the organic electrolyte has been receiving attention.
- the all-solid secondary battery has a solid negative electrode, electrolyte, and positive electrode, and can greatly improve the safety and reliability of a battery using an organic electrolytic solution.
- a negative electrode active material layer as a material for forming a constituent layer such as a solid electrolyte layer and a positive electrode active material layer, an inorganic solid electrolyte, further containing an active material, a conductive auxiliary agent, Further, a material containing a binder (binder) for binding these solid particles has been studied. Further, the kind and structure of the polymer forming the binder used for such a material, and the shape of the binder have been studied.
- Patent Document 1 describes a slurry containing a binder made of a particulate polymer having a core-shell structure having a specific average particle diameter and an inorganic solid electrolyte.
- Patent Document 2 describes a solid electrolyte composition containing non-spherical polymer particles having a specific group, a dispersion medium, and an inorganic solid electrolyte.
- the constituent layers of the all-solid secondary battery are formed of solid particles, it is generally difficult to form a good interface state between the solid particles. For example, if the interfacial contact between the inorganic solid electrolyte and the active material is not sufficient, the interfacial resistance will be high (the ionic conductivity and the battery capacity will decrease). If the solid particles are weakly bound to each other, the constituent layer will not have sufficient strength. Furthermore, contact failure between solid particles occurs due to contraction and expansion of the constituent layers, especially the active material layer, associated with charge / discharge (release and absorption of lithium ions) of the all-solid secondary battery. In this way, the electric resistance increases, and further, the battery performance deteriorates rapidly, leading to a shortened battery life. Moreover, in recent years, the development of all-solid-state secondary batteries has been rapidly progressing, and in addition to overcoming the above problems, further improvement in battery performance such as discharge capacity and discharge capacity density is required.
- the present invention by using as a material forming a constituent layer of an all-solid secondary battery, in the resulting all-solid secondary battery, solid particles are firmly bound by suppressing an increase in interfacial resistance between solid particles,
- An object of the present invention is to provide a solid electrolyte composition that can maintain excellent discharge capacity and discharge capacity density even when charging and discharging are repeated.
- Another object of the present invention is to provide a sheet for an all-solid secondary battery and an electrode sheet for an all-solid secondary battery which have a layer composed of this solid electrolyte composition and have excellent film strength. Further, it is an object of the present invention to provide an all-solid secondary battery capable of maintaining excellent discharge capacity, discharge capacity density and resistance.
- the present inventors have formed binder particles used in combination with an inorganic solid electrolyte in the material forming the above-mentioned constituent layer with primary particles having a specific average particle diameter, It was found that by using a non-spherical secondary particle, it is possible to form a high-strength layer in which solid particles are firmly bound while suppressing the interfacial resistance between the solid particles. Moreover, it has been found that an all-solid secondary battery including this layer as a constituent layer can maintain a high discharge capacity and discharge capacity density even after repeated charging and discharging, and exhibits a good battery life. The present invention has been completed through further studies based on these findings.
- a solid electrolyte composition comprising an inorganic solid electrolyte having ion conductivity of a metal belonging to Group 1 or Group 2 of the periodic table, and a binder composed of a polymer,
- ⁇ 4> The solid electrolyte composition according to any one of ⁇ 1> to ⁇ 3>, in which the polymer exhibits a breaking elongation of 10% or more.
- ⁇ 5> The solid electrolyte composition according to any one of ⁇ 1> to ⁇ 4>, which contains a dispersion medium.
- ⁇ 6> The solid electrolyte composition according to any one of ⁇ 1> to ⁇ 5 >> containing an active material.
- ⁇ 7> The solid electrolyte composition according to ⁇ 6>, wherein the active material is an active material capable of alloying with lithium.
- ⁇ 10> The solid electrolyte composition according to any one of ⁇ 1> to ⁇ 9>, wherein the inorganic solid electrolyte is a sulfide-based solid electrolyte.
- An all-solid secondary battery comprising a positive electrode active material layer, a solid electrolyte layer, and a negative electrode active material layer in this order, At least one layer of the positive electrode active material layer, the negative electrode active material layer, and the solid electrolyte layer is a layer composed of the solid electrolyte composition according to any one of ⁇ 1> to ⁇ 10>, which is an all solid secondary. battery.
- the ⁇ 14> negative electrode active material layer is a layer comprised with the solid electrolyte composition as described in ⁇ 6> or ⁇ 7>, The all-solid secondary battery according to claim 13.
- the solid electrolyte composition of the present invention firmly binds the solid particles by suppressing an increase in the interfacial resistance between the solid particles, and a solid electrolyte layer capable of maintaining excellent discharge capacity and discharge capacity density even after repeating charge and discharge. Can be formed.
- the sheet for all-solid-state secondary batteries and the electrode sheet for all-solid-state secondary batteries of the present invention have a layer composed of the solid electrolyte composition of the present invention, and have excellent membrane strength. Further, the all-solid secondary battery of the present invention can maintain excellent discharge capacity, discharge capacity density and resistance.
- FIG. 1 is a vertical sectional view schematically showing an all solid state secondary battery according to a preferred embodiment of the present invention.
- FIG. 2 is a vertical cross-sectional view schematically showing the all-solid-state secondary battery (coin battery) produced in the example.
- the numerical range represented by “to” means the range including the numerical values before and after “to” as the lower limit value and the upper limit value.
- acrylic or “(meth) acrylic”
- it means acrylic and / or methacrylic.
- the expression of a compound means the compound itself, its salt, and its ion. Further, it is meant to include a derivative in which a part of the derivative is changed, such as by introducing a substituent, within the range where the desired effect is exhibited. With respect to a substituent, a linking group, etc.
- a substituent which is not specified as substituted or unsubstituted in the present specification, it means that the group may have an appropriate substituent. Therefore, in the present specification, even when simply described as YYY group, the YYY group includes not only a mode having no substituent but also a mode having a substituent. This is also synonymous for compounds that do not specify substituted or unsubstituted. Examples of the preferable substituent include the substituent T described later.
- the respective substituents when there are a plurality of substituents or the like represented by a specific symbol, or when a plurality of substituents or the like are simultaneously or alternatively defined, the respective substituents may be the same or different from each other. It means good. Further, even when not specifically stated, when a plurality of substituents and the like are adjacent to each other, they may be linked to each other or condensed to form a ring.
- the molecular weight of a polymer and an oligomer means a mass average molecular weight in terms of standard polystyrene by gel permeation chromatography (GPC), unless otherwise specified.
- GPC gel permeation chromatography
- condition 1 or condition 2 priority
- an appropriate eluent can be appropriately selected depending on the type of polymer or the like.
- Carrier 10 mM LiBr / N-methylpyrrolidone Measurement temperature: 40 ° C
- Carrier Tetrahydrofuran Measurement temperature: 40 ° C
- the solid electrolyte composition of the present invention (also referred to as an inorganic solid electrolyte-containing composition) contains an inorganic solid electrolyte and binder particles made of a polymer.
- the binder particles include non-spherical binder particles composed of secondary particles formed of primary particles having an average primary particle diameter of 1 to 1,000 nm.
- Non-spherical binder particles when the constituent layer, or a coating dry layer of the solid electrolyte composition described later, solid particles such as inorganic solid electrolyte, further adjacent layers (for example, current collector) and solid particles It is sufficient that the solid particles can be bound to each other, and the solid particles do not necessarily have to be bound to each other in the solid electrolyte composition.
- the constituent layer formed by this solid electrolyte composition has an interfacial resistance between the solid particles.
- the solid particles are tightly bound while suppressing the increase in the discharge capacity, and the all-solid secondary battery having this constituent layer can maintain excellent discharge capacity and discharge capacity density even after repeated charge and discharge. The details of the reason are not clear yet, but it is considered as follows.
- non-spherical binder particles contained in the solid electrolyte composition of the present invention will be described in detail later, but are non-spherical instead of spherical, and in the constituent layers, etc., without excessively coating the surface of the solid particles. It can be adsorbed (attached) to the surface of solid particles. Therefore, contact between the uncoated surfaces of the solid particles can be secured, and a sufficient ionic conduction path and / or electronic conduction path can be formed. Further, since the surface area of the binder particles becomes large, the solid particles can be firmly bound to each other, and when the constituent layer is formed on the current collector, the current collector and the solid particles can be firmly bound. .
- the volume due to contraction and expansion is particularly large when a plurality of binder particles form a network. It is considered that the material can be deformed by following the change well or absorbing the volume change. Due to such deformation of the bander particles, the solid binding state between the solid particles can be maintained. It is considered that the above-described function makes it possible to increase the discharge capacity (discharge capacity density) while suppressing the interfacial resistance between solid particles to be low, and to suppress the increase in battery resistance and further the shortening of battery life.
- the constituent layer composed of the solid electrolyte composition of the present invention has a well-balanced improvement in the contact state between solid particles (amount of ion conduction path or the like) and the binding force between solid particles, etc. It is considered that the solid particles are bound to each other with a strong binding property while the ionic conduction path and the like are constructed, and the interface resistance between the solid particles is reduced.
- Each sheet or all-solid-state secondary battery provided with a constituent layer exhibiting such excellent characteristics shows a high discharge capacity (discharge capacity density) by suppressing an increase in electrical resistance, and even if charging and discharging are repeated. , This high discharge capacity can be maintained.
- the solid electrolyte composition of the present invention also includes, as a dispersoid, an active material in addition to the inorganic solid electrolyte, and further includes a mode in which a conductive aid is appropriately added (the composition of this mode is also referred to as a composition for electrodes). Say.).
- the solid electrolyte composition of the present invention even if it contains a negative electrode active material whose volume change due to charge and discharge is large, follows the volume change of the negative electrode active material (negative electrode active material layer) or absorbs the volume change to produce solid particles. The binding state and contact state of the above can be maintained, and the above-mentioned excellent operational effects are exhibited. Therefore, the embodiment of the solid electrolyte composition of the present invention containing the negative electrode active material is one of the preferred embodiments.
- the solid electrolyte composition of the present invention is preferably used as a material for forming the constituent layers of an all-solid secondary battery, an embodiment containing a dispersion medium is preferable.
- the solid electrolyte composition of the present invention contains a dispersion medium, it is preferable that the inorganic solid electrolyte and the non-spherical binder particles are dispersed in the dispersion medium in a solid state.
- the solid electrolyte composition of the present invention is a non-aqueous composition.
- the non-aqueous composition includes not only an embodiment containing no water but also a form having a water content (also referred to as water content) of 50 ppm or less.
- the water content is preferably 20 ppm or less, more preferably 10 ppm or less, and further preferably 5 ppm or less.
- the water content indicates the amount of water contained in the solid electrolyte composition (mass ratio with respect to the solid electrolyte composition).
- the water content can be determined by Karl Fischer titration by filtering the solid electrolyte composition with a 0.45 ⁇ m membrane filter.
- the inorganic solid electrolyte is an inorganic solid electrolyte
- the solid electrolyte is a solid electrolyte in which ions can move. Since it does not contain an organic substance as a main ion conductive material, it is an organic solid electrolyte (a polymer electrolyte typified by polyethylene oxide (PEO) or the like, an organic typified by lithium bis (trifluoromethanesulfonyl) imide (LiTFSI) or the like. Electrolyte salt) is clearly distinguished.
- the inorganic solid electrolyte is solid in the steady state, it is usually not dissociated or liberated into cations and anions.
- the electrolytic solution or an inorganic electrolyte salt LiPF 6 , LiBF 4 , LiFSI, LiCl, etc.
- the inorganic solid electrolyte is not particularly limited as long as it has ion conductivity of a metal belonging to Group 1 or 2 of the periodic table, and generally has no electron conductivity.
- the inorganic solid electrolyte preferably has ion conductivity of lithium ions.
- inorganic solid electrolyte a solid electrolyte material usually used for all solid state secondary batteries can be appropriately selected and used.
- the inorganic solid electrolyte include (i) sulfide-based inorganic solid electrolyte, (ii) oxide-based inorganic solid electrolyte, (iii) halide-based inorganic solid electrolyte, and (iv) hydride-based solid electrolyte.
- the sulfide-based inorganic solid electrolyte is It is preferably used.
- the sulfide-based inorganic solid electrolyte contains a sulfur atom, has ion conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation. Compounds having properties are preferred.
- the sulfide-based inorganic solid electrolyte preferably contains at least Li, S and P as elements and has lithium ion conductivity, but other than Li, S and P depending on the purpose or case. It may contain an element.
- Examples of the sulfide-based inorganic solid electrolyte include a lithium ion conductive sulfide-based inorganic solid electrolyte satisfying the composition represented by the following formula (1).
- L represents an element selected from Li, Na and K, and Li is preferable.
- M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al and Ge.
- A represents an element selected from I, Br, Cl and F.
- a1 to e1 represent the composition ratio of each element, and a1: b1: c1: d1: e1 satisfies 1 to 12: 0 to 5: 1: 2 to 12: 0 to 10.
- a1 is preferably 1 to 9, and more preferably 1.5 to 7.5.
- b1 is preferably 0 to 3, and more preferably 0 to 1.
- d1 is preferably 2.5 to 10, and more preferably 3.0 to 8.5.
- e1 is preferably 0 to 5, and more preferably 0 to 3.
- composition ratio of each element can be controlled by adjusting the compounding ratio of the raw material compounds when producing the sulfide-based inorganic solid electrolyte as described below.
- the sulfide-based inorganic solid electrolyte may be amorphous (glass) or crystallized (glass-ceramic), or only part thereof may be crystallized.
- glass glass
- glass-ceramic glass-ceramic
- Li—P—S based glass containing Li, P and S, or Li—P—S based glass ceramics containing Li, P and S can be used.
- the sulfide-based inorganic solid electrolyte is, for example, lithium sulfide (Li 2 S), phosphorus sulfide (eg, phosphorus pentasulfide (P 2 S 5 )), elemental phosphorus, elemental sulfur, sodium sulfide, hydrogen sulfide, lithium halide (eg, LiI, LiBr, LiCl) and a sulfide of the element represented by M (for example, SiS 2 , SnS, GeS 2 ) can be produced by the reaction of at least two raw materials.
- Li 2 S lithium sulfide
- phosphorus sulfide eg, phosphorus pentasulfide (P 2 S 5 )
- elemental phosphorus elemental sulfur
- sodium sulfide sodium sulfide
- hydrogen sulfide lithium halide
- a sulfide of the element represented by M for example, SiS 2 , Sn
- the ratio of Li 2 S and P 2 S 5 is, Li 2 S: at a molar ratio of P 2 S 5, preferably 60: 40 ⁇ 90:10, more preferably 68:32 to 78:22.
- the lithium ion conductivity can be increased.
- the lithium ion conductivity can be preferably 1 ⁇ 10 ⁇ 4 S / cm or more, more preferably 1 ⁇ 10 ⁇ 3 S / cm or more. There is no particular upper limit, but it is practically 1 ⁇ 10 ⁇ 1 S / cm or less.
- Li 2 S-P 2 S 5 Li 2 S-P 2 S 5 -LiCl, Li 2 S-P 2 S 5 -H 2 S, Li 2 S-P 2 S 5 -H 2 S-LiCl, Li 2 S-LiI-P 2 S 5 , Li 2 S-LiI-Li 2 O-P 2 S 5 , Li 2 S-LiBr-P 2 S 5 , Li 2 S-Li 2 O-P 2 S 5 , Li 2 S-Li 3 PO 4 -P 2 S 5 , Li 2 S-P 2 S 5 -P 2 O 5 , Li 2 S-P 2 S 5 -SiS 2 , Li 2 S-P 2 S 5 -SiS 2- LiCl, Li 2 S-P 2 S 5 -SnS, Li 2 S-P 2 S 5 -Al 2 S 3 , Li 2 S-Ge
- the mixing ratio of each raw material does not matter.
- An example of a method for synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition is an amorphization method.
- Examples of the amorphization method include a mechanical milling method, a solution method, and a melt quenching method. This is because the treatment can be performed at room temperature and the manufacturing process can be simplified.
- the oxide-based inorganic solid electrolyte contains an oxygen atom, has ion conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation. Compounds having properties are preferred.
- the ionic conductivity of the oxide-based inorganic solid electrolyte is preferably 1 ⁇ 10 ⁇ 6 S / cm or more, more preferably 5 ⁇ 10 ⁇ 6 S / cm or more, and 1 ⁇ 10 ⁇ 5 S. / Cm or more is particularly preferable.
- the upper limit is not particularly limited, but it is practically 1 ⁇ 10 ⁇ 1 S / cm or less.
- nb ( Mbb is at least one element of Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, Sn, xb satisfies 5 ⁇ xb ⁇ 10, and yb satisfies 1 ⁇ yb ⁇ 4, zb satisfies 1 ⁇ zb ⁇ 4, mb satisfies 0 ⁇ mb ⁇ 2, and nb satisfies 5 ⁇ nb ⁇ 20.), Li xc Byc M cc zc O nc (M cc is At least one element of C, S, Al, Si, Ga, Ge, In, and Sn, xc satisfies 0 ⁇ xc ⁇ 5, yc satisfies 0 ⁇ yc ⁇ 1, and zc satisfies 0 ⁇ zc ⁇ met 1, nc satisfies 0 ⁇ nc ⁇ 6.), Li xd ( l,
- a phosphorus compound containing Li, P and O is also desirable.
- lithium phosphate Li 3 PO 4
- LiPON and LiPOD 1 LiPON and LiPOD 1 (D 1 is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr) obtained by substituting nitrogen for part of oxygen in lithium phosphate. , Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.).
- LiA 1 ON (A 1 is at least one selected from Si, B, Ge, Al, C, Ga, etc.) and the like can also be preferably used.
- the halide-based inorganic solid electrolyte is generally used, and has a ionic conductivity of a metal that contains a halogen atom and belongs to Group 1 or 2 of the periodic table. A compound having and having an electronic insulating property is preferable.
- the halide-based inorganic solid electrolyte is not particularly limited, and examples thereof include compounds such as LiCl, LiBr, LiI, and Li 3 YBr 6 and Li 3 YCl 6 described in ADVANCED MATERIALS, 2018, 30, 1803075. Of these, Li 3 YBr 6 and Li 3 YCl 6 are preferable.
- the hydride-based inorganic solid electrolyte is generally used, and it shows the ionic conductivity of a metal containing a hydrogen atom and belonging to Group 1 or 2 of the periodic table. A compound having and having an electronic insulating property is preferable.
- the hydride-based inorganic solid electrolyte is not particularly limited, but examples thereof include LiBH 4 , Li 4 (BH 4 ) 3 I, and 3LiBH 4 —LiCl.
- the inorganic solid electrolyte is preferably particles.
- the average particle size (volume average particle size) of the inorganic solid electrolyte is not particularly limited, but is preferably 0.01 ⁇ m or more, more preferably 0.1 ⁇ m or more.
- the upper limit is preferably 100 ⁇ m or less, more preferably 50 ⁇ m or less.
- the average particle size of the inorganic solid electrolyte is measured by the following procedure.
- the inorganic solid electrolyte particles are prepared by diluting a 1% by mass dispersion liquid in a 20 mL sample bottle with water (heptane in the case of a substance which is unstable to water).
- the diluted dispersion sample is irradiated with 1 kHz ultrasonic waves for 10 minutes, and immediately thereafter, used for the test.
- a laser diffraction / scattering particle size distribution analyzer LA-920 (trade name, manufactured by HORIBA) was used, and data was captured 50 times at a temperature of 25 ° C. using a quartz cell for measurement. Obtain the volume average particle size.
- JIS Z 8828 2013 “Particle size analysis-Dynamic light scattering method” for other detailed conditions as necessary. Five samples are prepared for each level, and the average value is adopted.
- the inorganic solid electrolyte may be used alone or in combination of two or more.
- the content of the inorganic solid electrolyte in the solid electrolyte composition is not particularly limited, but in terms of dispersibility, reduction of interfacial resistance and binding property, it is 50% by mass or more at a solid content of 100% by mass. It is preferably 70% by mass or more, more preferably 90% by mass or more. From the same viewpoint, the upper limit is preferably 99.9% by mass or less, more preferably 99.5% by mass or less, and particularly preferably 99% by mass or less.
- the content of the inorganic solid electrolyte in the solid electrolyte composition is the total content of the inorganic solid electrolyte and the active material.
- the solid content means a component which does not disappear by volatilization or evaporation when the solid electrolyte composition is dried for 6 hours at 150 ° C. under a nitrogen atmosphere under a pressure of 1 mmHg. .
- it refers to components other than the dispersion medium described below.
- the binder contained in the solid electrolyte composition of the present invention may contain at least one kind of non-spherical binder particles described below, and may contain a binder other than the non-spherical binder particles.
- the binder (other binder) other than the non-spherical binder particles is not particularly limited, and may be spherical binder particles or a binder that dissolves in a dispersion medium. Further, the binder particles may be primary particles.
- the material forming the binder is not particularly limited, but a polymer is preferable, and examples thereof include a usual polymer forming a binder used in an all-solid secondary battery, and a polymer forming non-spherical binder particles, which will be described later.
- a polymer is preferable, and examples thereof include a usual polymer forming a binder used in an all-solid secondary battery, and a polymer forming non-spherical binder particles, which will be described later.
- the content of the other binder in the solid electrolyte composition of the present invention is not particularly limited and is appropriately determined.
- Non-spherical binder particles consist of secondary particles formed of primary particles having an average primary particle size of 1 to 1,000 nm.
- the secondary particles are particles formed by aggregating a plurality of primary particles (unit particles), and the interparticle force acting when the primary particles are aggregated is a physical force (for example, Van der).
- the secondary particles include aggregates or aggregates of primary particles.
- the number of primary particles forming secondary particles is not particularly limited. It can be confirmed by a known method that the non-spherical binder particles are composed of secondary particles. For example, a method of observing a shape using an electron microscope or the like, and a method of measuring a light scattering or the like with a particle size measuring device can be mentioned. In the present invention, it can be confirmed at the time of measuring the aspect ratio of secondary particles described later.
- the non-spherical binder particles (secondary particles) need not be spherical (true spherical) and have an irregular shape (shape having anisotropy).
- the shape thereof is not particularly limited, but may be an amorphous shape, an elliptic spherical shape, a flat shape, a (acicular) fibrous shape, or the like, but is not particularly limited.
- the non-spherical binder particles (secondary particles) have an (average) aspect ratio [ratio of average length Ly / average width Lx] of 1.1 to 1,000, which reduces the interfacial resistance and binding property.
- the aspect ratio of the secondary particles is preferably 1.5 or more, more preferably 2 or more, still more preferably 4 or more, and particularly preferably 9 or more in terms of binding property and the like.
- the battery performance is preferably 500 or less, more preferably 100 or less, and further preferably 50 or less, particularly in terms of battery life.
- the aspect ratio can be adjusted by the composition or synthesis conditions of the polymer forming the binder, and further by the preparation conditions of the dispersion liquid described later. For example, when the stirring speed is increased among the preparation conditions of the dispersion liquid, the aspect ratio tends to decrease. Further, when the polarity of the dispersion medium is improved, the aspect ratio tends to be small. A method for measuring the aspect ratio will be described later.
- the average length (Ly) of the non-spherical binder particles is not particularly limited, but is, for example, preferably 10 to 10,000 nm, more preferably 20 to 1,000 nm.
- the average width (Lx) of the non-spherical binder particles is not particularly limited, but is, for example, preferably 5 to 1,000 nm, more preferably 10 to 500 ⁇ m.
- the average particle size (also referred to as the average secondary particle size) of the non-spherical binder particles (secondary particles) is not particularly limited, but is, for example, 2 with respect to the average particle size of the primary particles (also referred to as the average primary particle size). It is preferably from about 1,000 times in terms of reduction of interfacial resistance, binding property and improvement of battery performance.
- the average secondary particle size is preferably 2.2 times or more, more preferably 2.5 times or more, further preferably 3.0 times or more with respect to the average primary particle diameter in terms of stability of the secondary particles. It is preferably 6.2 times or more and particularly preferably.
- the average secondary particle diameter is, for example, preferably 5 nm or more, more preferably 10 nm or more, further preferably 20 nm or more, particularly preferably 30 nm or more, and 230 nm
- the above can be applied.
- the upper limit is preferably 1,000 nm or less, more preferably 500 nm or less, further preferably 400 nm or less, and particularly preferably 300 nm or less.
- the primary particles forming the secondary particles are, for example, particles made of a polymer described later, and have an average primary particle diameter of 1 to 1,000 nm.
- the average primary particle diameter is preferably 2 nm or more, more preferably 3 nm or more, still more preferably 5 nm or more, from the viewpoint of reduction of interface resistance.
- it is preferably 500 nm or less, more preferably 400 nm or less, further preferably 300 nm or less, further preferably 100 nm or less.
- the average primary particle size can be adjusted by the composition of the polymer or the synthesis conditions, and further the preparation conditions of the dispersion liquid described later. For example, when the molecular weight of the polymer is increased, the average primary particle size tends to increase. Further, when the polarity of the dispersion medium is lowered, the average primary particle size tends to be reduced.
- the shape of the primary particles is not particularly limited and may be spherical or non-spherical.
- the aspect ratio and average particle diameter (average primary particle diameter and average secondary particle diameter) of the non-spherical binder particles are measured as follows.
- Non-spherical binder particles are mixed with a dispersion medium (for example, octane) to prepare a dispersion liquid for measurement.
- the concentration of the binder particles is not particularly limited, but the binder particles are diluted to a concentration (for example, about 0.5% by mass) in which the binder particles are dispersed in an isolated state in the measurement dispersion liquid.
- the measurement dispersion thus prepared is dropped on a transmission electron microscope (TEM) observation grid mesh, and then dried at room temperature. Then, it observes with TEM and takes a TEM image.
- TEM transmission electron microscope
- the length along the shape of the binder particle in the longest direction is defined as Ly.
- Lx is the length of the shortest binder particle that is orthogonal to Ly measured along the shape of the binder (in other words, Ly when the binder particle is linearly deformed and the shortest length (width) that is orthogonal) is Lx and Ly is measured respectively.
- the ratio [Ly / Lx] of Ly to the measured Lx is obtained.
- the average value of the ratios thus obtained for 50 binder particles is defined as the (average) aspect ratio.
- the non-spherical binder particles extracted (extracted) from the composition or constituent layer as follows. Is the measurement target.
- the non-spherical binder particles may be taken out by any method (condition) that does not cause the non-spherical binder particles to change in size. For example, a method of washing the composition or the constituent layer with a solvent used as a dispersion medium is applied. it can. At this time, a solvent that does not dissolve the non-spherical binder particles is used.
- the polymer that forms the primary particles (non-spherical binder particles) (hereinafter sometimes referred to as the binder-forming polymer) is not particularly limited, and a normal polymer that forms the binder used in the all-solid secondary battery, and further described below. Polymers to be used.
- the binder-forming polymer preferably has a breaking elongation of 10% or more, more preferably 30% or more, and more preferably 50% or more, from the viewpoint of realizing a strong binding property while reducing the interfacial resistance and maintaining the battery performance. % Or more is more preferable.
- the upper limit of the elongation at break is not particularly limited, but it is practically, for example, 10,000% or less, and it is possible to realize a strong binding property while reducing the interfacial resistance and maintaining the battery performance. , 1,000% or less is preferable, and 800% or less is more preferable.
- the elongation at break of the binder-forming polymer may be measured by applying stress to the primary particles alone, or may be measured by subjecting a film prepared from the secondary particles to a tensile test. Below, the measuring method using a film is demonstrated.
- a film as a test piece is prepared. That is, a dispersion liquid of non-spherical binder particles, for example, a dispersion liquid of non-spherical binder particles obtained by the synthesis method described below is applied onto a Teflon (registered trademark) sheet using a Baker type applicator (manufactured by Paltec Co., Ltd.).
- JIS K 7161-1 2014 "Plastic-Test method for tensile properties”
- tensile fracture strain (referred to as “elongation at break” in the present invention) is calculated.
- the glass transition temperature of the binder-forming polymer is not particularly limited, but it is preferably ⁇ 120 to 80 ° C., and preferably ⁇ 100 to 60 ° C., in that it has a shape depending on the shape of solid particles or the surface irregularities. Is more preferable, and -80 to 40 ° C is even more preferable.
- the binder-forming polymer has a plurality of glass transition temperatures, at least one glass transition temperature (usually the highest glass transition temperature) is preferably within the above range, and all glass transition temperatures are within the above range. Is more preferable.
- the glass transition temperature (Tg) is measured under the following conditions using a differential scanning calorimeter “X-DSC7000” (trade name, manufactured by SII Nanotechnology Inc.) using a dry sample.
- Tg is calculated by rounding off the decimal point of the intermediate temperature between the falling start point and the falling end point of the DSC chart.
- the glass transition temperature of the binder-forming polymer is, for example, after the composition or constituent layer is placed in water to disperse its contained components, followed by filtration. Then, the remaining solid can be collected and measured by the above measuring method.
- the mass average molecular weight of the binder-forming polymer is not particularly limited, but is preferably 5,000 or more, more preferably 10,000 or more, and particularly preferably 30,000 or more.
- the upper limit is preferably 1,000,000 or less, more preferably 200,000 or less.
- the binder-forming polymer is not particularly limited, and various polymers that form the binder used in the all-solid secondary battery can be applied.
- sequential polymerization (polycondensation, polyaddition or addition condensation) type polymers such as polyurethane, polyurea, polyamide, polyimide, polyester, polyether and polycarbonate, as well as fluorine-containing polymers, hydrocarbon type polymers, vinyl polymers, ( Examples thereof include chain polymerization type polymers such as (meth) acrylic polymers.
- Examples of the hydrocarbon-based polymer include natural rubber, polybutadiene, polyisoprene, polystyrene butadiene, and hydrogenated (hydrogenated) polymers thereof.
- the binder-forming polymer is preferably a sequential polymerization type polymer or a (meth) acrylic polymer, and more preferably a polyurethane, polyurea, polyamide, polyimide or (meth) acrylic polymer.
- Each of the above polymers may be a polymer composed of one segment or a polymer composed of two or more segments.
- the main chain of a polymer means a linear molecular chain in which all the other molecular chains constituting the polymer can be regarded as branched or pendant with respect to the main chain. Although it depends on the mass average molecular weight of the molecular chain considered as a pendant, the longest chain is typically the main chain among the molecular chains constituting the polymer. However, the functional group at the polymer end is not included in the main chain.
- the side chain of the polymer means a molecular chain other than the main chain, and includes a short molecular chain and a long molecular chain.
- a sequential polymerization type polymer suitable as a binder-forming polymer is a combination of two or more (preferably two or three) constituent components represented by any of the following formulas (I-1) to (I-4). Or a main chain formed by sequentially polymerizing a carboxylic acid dianhydride represented by the following formula (I-5) and a diamine compound leading to a constituent component represented by the following formula (I-6) Polymers are preferred. The combination of each component is appropriately selected according to the polymer type.
- the main chain made of polycarbonate, a configuration component formula (I-3) as a constituent or R P1 is represented by the following formula was introduced oxygen atoms at both ends of R P1 (I-2)
- Examples thereof include a main chain having a constituent component represented by the following formula (I-2) and a constituent component represented by the following formula (I-3).
- One kind of constituent in the combination of constituents means the number of kinds of constituents represented by any one of the following formulas, and has two kinds of constituents represented by the following formula. Is not to be construed as two constituents.
- R P1 and R P2 each represent a molecular chain having a (mass average) molecular weight of 20 or more and 200,000 or less.
- the molecular weight of this molecular chain cannot be unambiguously determined because it depends on its type, but is preferably 30 or more, more preferably 50 or more, still more preferably 100 or more, and particularly preferably 150 or more.
- the upper limit is preferably 100,000 or less, more preferably 10,000 or less.
- the (mass average) molecular weight of a molecular chain is measured for a raw material compound before being incorporated into the main chain of a polymer.
- the molecular chain that can be taken as R P1 and R P2 is not particularly limited, but is preferably a hydrocarbon chain, a polyalkylene oxide chain, a polycarbonate chain or a polyester chain, more preferably a hydrocarbon chain or a polyalkylene oxide chain, and a hydrocarbon chain. , Polyethylene oxide chains or polypropylene oxide chains are more preferred.
- the hydrocarbon chain which can be taken as R P1 and R P2 means a hydrocarbon chain composed of a carbon atom and a hydrogen atom, and more specifically, at least two compounds of a compound composed of a carbon atom and a hydrogen atom. It means a structure in which an atom (for example, a hydrogen atom) or a group (for example, a methyl group) is eliminated.
- the hydrocarbon chain also includes a chain having a group containing an oxygen atom, a sulfur atom or a nitrogen atom in the chain, such as a hydrocarbon group represented by the following formula (M2).
- M2 hydrocarbon group represented by the following formula
- This hydrocarbon chain may have a carbon-carbon unsaturated bond and may have a ring structure of an aliphatic ring and / or an aromatic ring. That is, the hydrocarbon chain may be a hydrocarbon chain composed of a hydrocarbon selected from an aliphatic hydrocarbon and an aromatic hydrocarbon.
- Such a hydrocarbon chain may be one that satisfies the above-mentioned molecular weight, and both a chain composed of a low molecular weight hydrocarbon group and a hydrocarbon chain composed of a hydrocarbon polymer (also referred to as a hydrocarbon polymer chain).
- the low molecular weight hydrocarbon chain is a chain composed of a normal (non-polymerizable) hydrocarbon group, and examples of this hydrocarbon group include an aliphatic or aromatic hydrocarbon group. Is an alkylene group (having preferably 1 to 12 carbon atoms, more preferably 1 to 6 and still more preferably 1 to 3), an arylene group (having 6 to 22 carbon atoms, preferably 6 to 14 and preferably 6 to 10).
- an alkylene group is more preferable, an alkylene group having 2 to 6 carbon atoms is further preferable, and an alkylene group having 2 or 3 carbon atoms is particularly preferable.
- the aliphatic hydrocarbon group is not particularly limited and includes, for example, a hydrogen-reduced product of an aromatic hydrocarbon group represented by the following formula (M2), a partial structure of a known aliphatic diisosonate compound (for example, from isophorone And the like) and the like.
- the aromatic hydrocarbon group is preferably a phenylene group or a hydrocarbon group represented by the following formula (M2).
- X represents a single bond, —CH 2 —, —C (CH 3 ) 2 —, —SO 2 —, —S—, —CO— or —O—, which is a binding point.
- —CH 2 — or —O— is preferable, and —CH 2 — is more preferable.
- the alkylene group exemplified above may be substituted with a substituent T, preferably a halogen atom (more preferably a fluorine atom).
- R M2 to R M5 each represent a hydrogen atom or a substituent, and a hydrogen atom is preferable.
- the substituent which can be taken as R M2 to R M5 is not particularly limited, but examples thereof include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 1 to 20 carbon atoms, —OR M6 , —N (R M6 ) 2 , —SR M6 (R M6 represents a substituent, preferably an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 10 carbon atoms), halogen atom (eg, fluorine atom, chlorine atom, bromine atom) Is mentioned.
- R M6 represents a substituent, preferably an alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 10 carbon atoms
- halogen atom eg, fluorine atom, chlorine atom, bromine atom
- R M6 -N (R M6 ) 2 is an alkylamino group (having preferably 1 to 20 carbon atoms, more preferably 1 to 6) or an arylamino group (having 6 to 40 carbon atoms, preferably 6 to 20 carbon atoms). More preferable).
- the hydrocarbon polymer chain may be a polymer chain formed by polymerizing (at least two) polymerizable hydrocarbons, and a chain composed of a hydrocarbon polymer having a larger number of carbon atoms than the above-mentioned low molecular weight hydrocarbon chain.
- a chain composed of a hydrocarbon polymer composed of 30 or more, more preferably 50 or more carbon atoms is preferably a chain composed of a hydrocarbon polymer composed of 30 or more, more preferably 50 or more carbon atoms.
- the upper limit of the number of carbon atoms constituting the hydrocarbon polymer is not particularly limited and may be, for example, 3,000.
- This hydrocarbon polymer chain is preferably a chain composed of a hydrocarbon polymer having a main chain satisfying the above-mentioned number of carbon atoms and composed of an aliphatic hydrocarbon, and is composed of an aliphatic saturated hydrocarbon or an aliphatic unsaturated hydrocarbon. It is more preferable that the chain is a polymer (preferably elastomer) chain. Specific examples of the polymer include a diene polymer having a double bond in the main chain and a non-diene polymer having no double bond in the main chain.
- diene polymer examples include a styrene-butadiene copolymer, a styrene-ethylene-butadiene copolymer, a copolymer of isobutylene and isoprene (preferably butyl rubber (IIR)), a butadiene polymer, an isoprene polymer and ethylene.
- IIR butyl rubber
- non-diene polymer examples include olefin polymers such as ethylene-propylene copolymer and styrene-ethylene-butylene copolymer, and hydrogen reduction products of the above diene polymers.
- the hydrocarbon chain that can be taken as R P1 and R P2 may have a substituent as described later, and preferably has an ether group, a carbonyl group, or both.
- the hydrocarbon chain that can be adopted as R P2 of the component represented by formula (I-3) or formula (I-4) is an ether group, a carbonyl group, or both (eg, —CO—O— group). And preferably has a carboxy group). It is preferable to have an atom such as a hydrogen atom or a substituent (for example, a substituent T described later) at the ends of the ether group and the carbonyl group.
- the hydrocarbon that becomes the hydrocarbon chain preferably has a reactive group at its terminal, and more preferably has a polycondensable terminal reactive group.
- the terminal reactive group capable of polycondensation or polyaddition forms a group bonded to R P1 or R P2 in the above formulas by polycondensation or polyaddition.
- Examples of such a terminal reactive group include an isocyanate group, a hydroxy group, a carboxy group, an amino group and an acid anhydride, and the hydroxy group is preferable.
- hydrocarbon polymer having a terminal reactive group examples are, under the trade names, NISSO-PB series (manufactured by Nippon Soda Co., Ltd.), Claysol series (manufactured by Tomoe Kogyo Co., Ltd.), PolyVEST-HT series (manufactured by Evonik). , Poly-bd series (manufactured by Idemitsu Kosan Co., Ltd.), poly-ip series (manufactured by Idemitsu Kosan Co., Ltd.), EPOL (manufactured by Idemitsu Kosan Co., Ltd.) and Polytail series (manufactured by Mitsubishi Chemical Co., Ltd.) are preferably used.
- polyalkylene oxide chain examples include known polyalkylene oxide chains.
- the alkyleneoxy group preferably has 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and further preferably 2 or 3 (polyethylene oxide chain or polypropylene oxide chain).
- the polyalkylene oxide chain may be a chain composed of one kind of alkylene oxide or a chain composed of two or more kinds of alkylene oxide (for example, a chain composed of ethylene oxide and propylene oxide).
- polycarbonate chain or polyester chain examples include known chains of polycarbonate or polyester.
- Each of the polyalkylene oxide chain, the polycarbonate chain and the polyester chain preferably has an alkyl group (having 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms) at the end.
- Polyalkylene oxide chain which can be taken as R P1 and R P2 end of the polycarbonate chain and a polyester chain, appropriately changing the constituents as R P1 and R P2 are represented by the formulas above the embeddable ordinary chemical structure be able to.
- the terminal oxygen atom of the polyalkylene oxide chain is removed and incorporated as R P1 or R P2 of the above constituents.
- R N is a hydrogen atom, It may have an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 10 carbon atoms).
- R P1 and R P2 are divalent molecular chains, but at least one hydrogen atom is replaced with —NH—CO—, —CO—, —O—, —NH— or —N ⁇ . Therefore, it may have a trivalent or higher molecular chain.
- R P1 is preferably a low molecular weight hydrocarbon chain, more preferably a hydrocarbon chain consisting of an aliphatic or aromatic hydrocarbon group, and a hydrocarbon chain consisting of an aromatic hydrocarbon group. Hydrogen chains are more preferred.
- R P2 is preferably an aliphatic hydrocarbon group or a molecular chain other than a low molecular weight hydrocarbon chain, and more preferably an embodiment containing an aliphatic hydrocarbon group and a molecular chain other than a low molecular weight hydrocarbon chain, respectively.
- R P2 is a low molecular weight aliphatic hydrocarbon group. At least two kinds of constituent components and constituent components in which R P2 is a molecular chain other than a low molecular weight hydrocarbon chain are included.
- constituent components represented by the above formula (I-1) are shown below.
- the raw material compound (diisocyanate compound) for deriving the constituent component represented by the formula (I-1) include diisocyanate compounds represented by the formula (M1) described in WO2018 / 020827 and Specific examples thereof include, further, polymeric 4,4′-diphenylmethane diisocyanate and the like.
- the constituent component represented by the formula (I-1) and the raw material compound leading to the constituent component are not limited to those described in the following specific examples and the above-mentioned documents.
- the raw material compound (carboxylic acid or acid chloride thereof, etc.) leading to the constituent component represented by the above formula (I-2) is not particularly limited and is described in, for example, paragraph [0074] of International Publication No. 2018/020827. , Carboxylic acid or acid chloride compounds and specific examples thereof.
- the constituent components represented by the above formula (I-3) or formula (I-4) are shown below.
- the raw material compound (diol compound or diamine compound) for deriving the constituent component represented by the above formula (I-3) or formula (I-4) is not particularly limited, and includes, for example, International Publication No. 2018 / Each compound described in No. 020827 and specific examples thereof are mentioned, and further dihydroxyoxamide is also mentioned.
- the constituent components represented by formula (I-3) or formula (I-4) and the raw material compounds leading to them are not limited to those described in the following specific examples and the above-mentioned documents.
- the repeating number is an integer of 1 or more and is appropriately set within a range satisfying the molecular weight or the number of carbon atoms of the molecular chain.
- R P3 represents an aromatic or aliphatic linking group (tetravalent), and a linking group represented by any of the following formulas (i) to (ix) is preferable.
- X 1 represents a single bond or a divalent linking group.
- the divalent linking group is preferably an alkylene group having 1 to 6 carbon atoms (eg methylene, ethylene, propylene). As propylene, 1,3-hexafluoro-2,2-propanediyl is preferable.
- L represents —CH 2 ⁇ CH 2 — or —CH 2 —.
- R X and R Y each represent a hydrogen atom or a substituent.
- * represents a binding site to the carbonyl group in formula (1-5).
- the substituent that can be used as R X and R Y is not particularly limited, and examples thereof include the substituent T described later.
- alkyl group having 1 to 12 carbon atoms, preferably 1 to 6 carbon atoms, more preferably 1 to 3 carbon atoms
- an aryl group having 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms, and further preferably 6 to 10 carbon atoms
- 6 to 22 carbon atoms having 6 to 22 carbon atoms, more preferably 6 to 14 carbon atoms, and further preferably 6 to 10 carbon atoms
- the carboxylic acid dianhydride represented by the above formula (I-5) and the starting compound (diamine compound) leading to the constituent components represented by the above formula (I-6) are not particularly limited, and include, for example, Each compound described in WO2018 / 020827 and WO2015 / 046313 and specific examples thereof can be mentioned.
- R P1 , R P2, and R P3 may each have a substituent.
- the substituent is not particularly limited, and examples thereof include the substituent T described later, and the above-mentioned substituent that can be adopted as R M2 is preferably exemplified.
- the binder-forming polymer has a structure in which R P2 is an aliphatic hydrocarbon group (preferably an ether group or a group represented by the formula (I-3) or the formula (I-4), preferably the formula (I-3). A carbonyl group or both, more preferably a group having a carboxy group) (preferably a component represented by the following formula (I-3A)), and R P2 is a polyalkylene oxide chain as a molecular chain.
- R P2 is an aliphatic hydrocarbon group (preferably an ether group or a group represented by the formula (I-3) or the formula (I-4), preferably the formula (I-3).
- R P2 is a polyalkylene oxide chain as a molecular chain.
- the binder-forming polymer may have a constituent represented by the following formula (I-1), a constituent represented by the formula (I-3A) and a constituent represented by the formula (I-3B).
- a constituent represented by formula (I-3C) preferably a constituent represented by the following formula (I-B)
- a constituent component in which R P2 is the above-mentioned hydrocarbon polymer chain as a molecular chain preferably It is more preferable to have at least three kinds of components represented by the following formula (I-3C).
- the binder-forming polymer may have a constituent represented by the following formula (I-1), a constituent represented by the formula (I-3A) and a constituent represented by the formula (I-3B).
- R P1 is as described above.
- R P2A represents an aliphatic hydrocarbon group (preferably an aliphatic hydrocarbon group), and preferably has an ether group or a carbonyl group or both, more preferably a carboxy group. There is. Examples thereof include bis (hydroxymethyl) acetic acid compounds such as 2,2-bis (hydroxymethyl) butyric acid.
- R P2B represents a polyalkylene oxide chain.
- R P2C represents a hydrocarbon polymer chain.
- the aliphatic hydrocarbon group that can be taken as R P2A , the polyalkylene oxide chain that can be taken as R P2B , and the hydrocarbon polymer chain that can be taken as R P2C are each an aliphatic that can be taken as R P2 in the above formula (I-3).
- the contents of the constituent components represented by the above formulas in the binder-forming polymer will be described later.
- the binder-forming polymer may have constituents other than the constituents represented by the above formulas. Such constituents are not particularly limited as long as they can be successively polymerized with the constituents represented by the above formulas.
- the (total) content of the constituent components represented by the above formula in the binder-forming polymer is not particularly limited, but is preferably 5 to 100% by mass, more preferably 10 to 100% by mass, and 50 More preferably, it is from 100 to 100 mass%.
- the upper limit of this content may be, for example, 90% by mass or less, regardless of the above 100% by mass.
- the content of constituent components other than the constituent components represented by the above formulas in the binder-forming polymer is not particularly limited, but is preferably 80% by mass or less.
- the content of the component represented by formula (I-1) or formula (I-2) or the component derived from the carboxylic dianhydride represented by formula (I-5) in the binder-forming polymer is It is not particularly limited, but is preferably 10 to 50 mol%, more preferably 20 to 50 mol%, and further preferably 30 to 50 mol%.
- the content of the constituent component represented by formula (I-3), formula (I-4) or formula (I-6) in the binder-forming polymer is not particularly limited and is 10 to 50 mol%. Is preferable, 20 to 50 mol% is more preferable, and 30 to 50 mol% is further preferable.
- the binder-forming polymer has a plurality of constituent components represented by each formula, the above content of each constituent component is the total content.
- R P2 has an aliphatic hydrocarbon group (having an ether group or a carbonyl group or both, more preferably a carboxy group).
- the content of the constituent component of B in the binder-forming polymer is not particularly limited, but is, for example, preferably 0 to 50 mol% of the polymer, more preferably 1 to 30 mol%, and 2 to It is more preferably 20 mol%.
- the content of constituents in which R P2 is the above polyalkylene oxide chain in the binder-forming polymer is particularly limited.
- the amount is preferably 0 to 50 mol%, more preferably 1 to 45 mol%, and further preferably 3 to 40 mol%.
- the content of constituents in which R P2 is the above hydrocarbon polymer chain as a molecular chain in the binder-forming polymer is particularly limited.
- the amount is preferably 0 to 50 mol%, more preferably 1 to 45 mol%, and further preferably 3 to 40 mol%.
- polyurethane, polyurea, polyamide, and polyimide polymers that can be used as the binder-forming polymer include, in addition to those synthesized in Examples, for example, International Publication No. 2018/020827 and International Publication No. 2015/046313, and further Examples thereof include the polymers described in JP-A-2015-088480.
- the chain-polymerization type polymer suitable as the binder-forming polymer is a polymer obtained by chain-polymerizing one or more monomers having a non-aromatic carbon-carbon double bond.
- Each polymer may be mentioned.
- a polymer obtained by polymerizing at least one (meth) acrylic compound selected from (meth) acrylic acid, (meth) acrylic acid ester compound, (meth) acrylamide compound and (meth) acrylonitrile compound (( (Meth) acrylic polymer) is preferred.
- the copolymer of a (meth) acrylic compound and other polymerizable compounds is also mentioned.
- the other polymerizable compound is not particularly limited, and examples thereof include a styrene compound, a vinylnaphthalene compound, a vinylcarbazole compound, an allyl compound, a vinyl ether compound, a vinyl ester compound, and a dialkyl itaconate compound.
- Specific examples of the copolymer with other polymerizable compound include a copolymer of methyl (meth) acrylate and styrene, a copolymer of butyl (meth) acrylate, acrylonitrile and styrene. .
- the copolymer may be either a statistical copolymer or a periodic copolymer, and a block copolymer is preferable.
- Examples of the (meth) acrylic polymer include the polymers described in JP-A-2005-088486.
- the (meth) acrylic acid ester compound is not particularly limited, and examples thereof include compounds represented by any of the formulas (b-1) to (b-6) described in JP-A-2005-088486. Specific examples include (meth) acrylic acid alkyl ester compounds and (meth) acrylic acid (hetero) aryl ester compounds. Examples of the alkyl group, aryl group and heteroaryl group contained in these (meth) acrylic acid ester compounds include an alkyl group, an aryl group and an aromatic heterocyclic group in the substituent T described later. Further, the alkyl group, aryl group and heteroaryl group may have a substituent.
- substituents examples include a substituent selected from the substituent T described below, and preferably a functional group selected from the functional group group (a) described below. More specific examples include compounds (monomers) A-1 to A-60 described in JP-A-2005-088486.
- the (meth) acrylic polymer at least two (meth) acrylic compounds selected from (meth) acrylic acid, (meth) acrylic acid alkyl ester compounds, (meth) acrylamide compounds and (meth) acrylonitrile compounds are polymerized.
- a polymer obtained by polymerizing at least two (meth) acrylic compounds selected from (meth) acrylic acid, (meth) acrylic acid alkyl ester compounds and (meth) acrylonitrile compounds is more preferable. Is more preferable.
- Examples of the (meth) acrylic acid alkyl ester compound constituting the chain polymerization type polymer include (meth) acrylic acid having 1 to 6 carbon atoms and (meth) acrylic acid having 7 to 20 carbon atoms. It is preferable to include and.
- the content of the constituent components in the (meth) acrylic polymer is not particularly limited and is set appropriately.
- the total content of the (meth) acrylic compound can be 20 to 100% by mass.
- the content of the constituent component derived from (meth) acrylic acid is preferably 0 to 50% by mass, more preferably 3 to 20% by mass.
- the content of the constituent component derived from the (meth) acrylic acid alkyl ester compound is preferably 20 to 99% by mass, more preferably 30 to 95% by mass.
- the content of the constituent component derived from the alkyl ester compound having 1 to 6 carbon atoms is preferably 5 to 80% by mass, more preferably 20 to 60% by mass.
- the content of the constituent component derived from the alkyl compound having 7 to 20 carbon atoms is preferably 5 to 80% by mass, more preferably 10 to 60% by mass.
- the content of the constituent component derived from the (meth) acrylonitrile compound is preferably 0 to 80% by mass, more preferably 5 to 60% by mass.
- the content in the (meth) acrylic polymer is as described above, but the content of the constituent component derived from the compound having a functional group selected from the functional group group (a) is preferably 1 to 80% by mass. It is more preferably from about 60% by mass. When there are a plurality of corresponding constituents, the above contents are the total contents.
- the binder-forming polymer When the binder-forming polymer has at least one functional group selected from the following functional group group (a), the binder-forming polymer exhibits high binding property to solid particles and can firmly bind the solid particles to each other. It is preferable in that respect.
- This functional group may be contained in the main chain or the side chain.
- the functional group (adsorbable functional group on the surface of the inorganic particles) of the binder-forming polymer is chemically or physically interacted with the surface of the inorganic solid electrolyte in the solid electrolyte composition, optionally coexisting active material or conduction aid.
- This interaction is not particularly limited, but is, for example, by a hydrogen bond, an ionic bond by an acid-base, a covalent bond, a ⁇ - ⁇ interaction by an aromatic ring, or a hydrophobic-hydrophobic interaction.
- the functional groups interact, the chemical structure of the functional groups may or may not change. For example, in the above ⁇ - ⁇ interaction and the like, the functional group usually does not change and maintains the structure as it is.
- an active hydrogen such as a carboxylic acid group becomes an anion from which the active hydrogen is desorbed (the functional group is changed) to bond with the solid electrolyte or the like.
- This interaction contributes to the adsorption of the non-spherical binder particles with the solid particles during or during the preparation of the solid electrolyte composition.
- the functional groups also interact with the surface of the current collector.
- the acidic functional group is not particularly limited, but a carboxylic acid group (—COOH), a sulfonic acid group (sulfo group: —SO 3 H) and a phosphoric acid group (phospho group: —OPO (OH) 2 etc.) are preferred.
- the acidic functional group may be a salt or ester thereof.
- the salt include sodium salt, calcium salt and the like.
- the ester include alkyl ester and aryl ester. In the case of an ester, it preferably has 1 to 24 carbon atoms, more preferably 1 to 12 carbon atoms, and particularly preferably 1 to 6 carbon atoms.
- the basic functional group is not particularly limited, but an amino group is preferable.
- the amino group is not particularly limited, and examples thereof include an amino group having 0 to 20 carbon atoms.
- the amino group includes an alkylamino group and an arylamino group.
- the carbon number of the amino group is preferably 0 to 12, more preferably 0 to 6, and further preferably 0 to 2.
- Examples of the amino group include amino, N, N-dimethylamino, N, N-diethylamino, N-ethylamino, anilino and the like.
- Those capable of forming a salt such as a hydroxy group and an amino group may be a salt.
- the alkoxysilyl group is not particularly limited and includes a mono-, di- or tri-alkoxysilyl group, preferably an alkoxysilyl group having 1 to 20 carbon atoms, for example, monomethoxysilyl, dimethoxysilyl, trimethoxysilyl. , Triethoxysilyl and the like.
- the aryl group may be a single ring or a condensed ring.
- the carbon number is preferably 6 to 26, more preferably 6 to 20.
- the heteroaryl group is not particularly limited, and examples thereof include a 5- or 6-membered heteroaryl group having at least one selected from an oxygen atom, a sulfur atom and a nitrogen atom as a ring-constituting atom.
- the heteroaryl group may be a monocyclic ring or a condensed ring and preferably has 2 to 20 carbon atoms.
- the aliphatic hydrocarbon ring group in which three or more rings are condensed is not particularly limited as long as the aliphatic hydrocarbon ring is a ring group in which three or more rings are condensed.
- the condensed aliphatic hydrocarbon ring include a saturated aliphatic hydrocarbon ring and an unsaturated aliphatic hydrocarbon ring.
- the aliphatic hydrocarbon ring is preferably a 5-membered ring or a 6-membered ring.
- the number of condensed rings is not particularly limited, but is preferably 3 to 5, more preferably 3 or 4.
- the cyclic group in which three or more saturated aliphatic hydrocarbon rings or unsaturated aliphatic hydrocarbon rings are condensed is not particularly limited, and examples thereof include a cyclic group composed of a compound having a steroid skeleton.
- the compound having a steroid skeleton include cholesterol, ergosterol, testosterone, estradiol, aldosterone, hydrocortisone, stigmasterol, timosterol, lanosterol, 7-dehydrodesmosterol, 7-dehydrocholesterol, colanic acid, cholic acid, lithocole.
- Examples thereof include acids, deoxycholic acid, sodium deoxycholic acid, lithium deoxycholic acid, hyodeoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid, dehydrocholic acid, foquecholic acid, hyocholic acid, and compounds containing these skeletons.
- acids deoxycholic acid, sodium deoxycholic acid, lithium deoxycholic acid, hyodeoxycholic acid, chenodeoxycholic acid, ursodeoxycholic acid, dehydrocholic acid, foquecholic acid, hyocholic acid, and compounds containing these skeletons.
- a ring group composed of a compound having a cholesterol skeleton is more preferable.
- the functional group selected from the functional group group (a) is appropriately selected, but when the solid electrolyte composition contains an inorganic solid electrolyte or a positive electrode active material, it is acidic in terms of binding property with the active material.
- a functional group, a basic functional group, a hydroxy group, a cyano group or an alkoxysilyl group is preferable, and a carboxylic acid group is more preferable.
- the solid electrolyte composition contains a negative electrode active material or a conductive additive, an aryl group, a heteroaryl group or an aliphatic hydrocarbon ring group in which 3 or more rings are condensed is preferable, and a fat in which 3 or more rings are condensed.
- Group hydrocarbon ring groups are more preferred.
- a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, and an aryl group are preferable, and a carboxylic acid group is more preferable, from the viewpoint of exhibiting high binding property regardless of the active material.
- the number of functional groups that the binder-forming polymer has in one molecule may be one or more, and it is preferable to have a plurality of functional groups.
- the number of types of functional groups is not particularly limited as long as it has at least one functional group, and may be one type or two or more types.
- two or more functional groups selected from the above functional group group (a) can be separately and appropriately combined.
- two or more kinds of functional groups selected from the above functional group group (a) may be appropriately combined to have one composite functional group.
- the composite functional group for example, an aryl group, a heteroaryl group or an aliphatic hydrocarbon ring group in which three or more rings are condensed, and an acidic functional group, a basic functional group, a hydroxy group, a cyano group or an alkoxysilyl group are formed.
- the content of the constituent having a functional group is not particularly limited, but it can be set within the range of the content corresponding to the constituent before the functional group is introduced among the constituents of each polymer. .
- the binder-forming polymer may have a substituent.
- substituent T examples include groups selected from the following substituent T.
- the substituent T is shown below, but the substituent T is not limited thereto.
- Alkyl group preferably alkyl group having 1 to 20 carbon atoms, for example, methyl, ethyl, isopropyl, t-butyl, pentyl, heptyl, 1-ethylpentyl, benzyl, 2-ethoxyethyl, 1-carboxymethyl, etc.
- alkenyl group Preferably an alkenyl group having 2 to 20 carbon atoms such as vinyl, allyl, oleyl etc.
- an alkynyl group preferably an alkynyl group having 2 to 20 carbon atoms such as ethynyl, butadiynyl, phenylethynyl etc.
- a cycloalkyl group preferably an alkynyl group
- a cycloalkyl group having 3 to 20 carbon atoms for example, cyclopropyl, cyclopentyl, cyclohexyl, 4-methylcyclohexyl, etc.
- an aryl group preferably an aryl group having 6 to 26 carbon atoms, for example, phenyl, 1-naphthyl) , 4-methoxyphenyl, 2-chlorophenyl, -Methylphenyl, etc.
- a heterocyclic group preferably a heterocyclic group having 2 to 20 carbon atoms, and preferably a 5- or 6-membered heterocyclic group having at least one oxygen atom, sulfur atom or nitrogen atom
- the heterocyclic group includes an aromatic heterocyclic group (heteroaryl group) and an aliphatic heterocyclic group, for example, tetrahydropyran ring group, tetrahydrofuran ring group, 2-pyridyl, 4-pyridyl, 2-
- an aryloxycarbonyl group preferably an aryloxycarbonyl group having 6 to 26 carbon atoms, for example, phenoxycarbonyl, 1-naphthyloxycarbonyl, 3-methylphenoxycarbonyl, 4-methoxyphenoxycarbonyl, etc.
- an amino group Preferably, it includes an amino group having 0 to 20 carbon atoms, an alkylamino group, an arylamino group, and examples thereof include amino (—NH 2 ), N, N-dimethylamino, N, N-diethylamino, N-ethylamino, anilino and the like.
- a sulfamoyl group (preferably having 0 carbon atoms) 20 sulfamoyl groups such as N, N-dimethylsulfamoyl, N-phenylsulfamoyl, etc., acyl groups (alkylcarbonyl groups, alkenylcarbonyl groups, alkynylcarbonyl groups, arylcarbonyl groups, heterocyclic carbonyl groups) And preferably an acyl group having 1 to 20 carbon atoms, for example, acetyl, propionyl, butyryl, octanoyl, hexadecanoyl, acryloyl, methacryloyl, crotonoyl, benzoyl, naphthoyl, nicotinoyl, etc., acyloxy group (alkylcarbonyloxy group, alkenylcarbonyl).
- It includes an oxy group, an alkynylcarbonyloxy group, an arylcarbonyloxy group, and a heterocyclic carbonyloxy group, preferably an acyloxy group having 1 to 20 carbon atoms, for example, acetyloxy, propionyl.
- a loyloxy group such as benzoyloxy, a carbamoyl group (preferably a carbamoyl group having 1 to 20 carbon atoms such as N, N-dimethylcarbamoyl, N-phenylcarbamoyl etc.), an acylamino group (preferably having 1 to 10 carbon atoms).
- acylamino groups such as acetylamino, benzoylamino, etc., alkylthio groups (preferably alkylthio groups having 1 to 20 carbon atoms such as methylthio, ethylthio, isopropylthio, benzylthio, etc.), arylthio groups (preferably).
- an arylthio group having 6 to 26 carbon atoms eg, phenylthio, 1-naphthylthio, 3-methylphenylthio, 4-methoxyphenylthio, etc., a heterocyclic thio group (an —S— group bonded to the above heterocyclic group) Group), an alkylsulfonyl group (preferably an alkylsulfonyl group having 1 to 20 carbon atoms, for example, methylsulfonyl, ethylsulfonyl and the like), an arylsulfonyl group (preferably an arylsulfonyl group having 6 to 22 carbon atoms, for example, benzenesulfonyl and the like) ), An alkylsilyl group (preferably an alkylsilyl group having 1 to 20 carbon atoms, for example, monomethylsilyl, dimethylsilyl, trimethylsilyl, triethylsilyl
- the compound, the substituent, the linking group and the like include an alkyl group, an alkylene group, an alkenyl group, an alkenylene group, an alkynyl group and / or an alkynylene group, these may be cyclic or linear, or linear or branched. Good.
- the content of the non-spherical binder particles is preferably 5 to 100% by mass, more preferably 30 to 100% by mass, based on 100% by mass of all the binders contained in the solid electrolyte composition. It is more preferably 50 to 100% by mass. When the content is not 100% by mass, the balance is preferably the above-mentioned other binder.
- the solid electrolyte composition of the present invention contains primary particles that do not lead to the formation of non-spherical binder particles (secondary particles), the ratio (rate) of the secondary particles is such that the secondary particles and the primary particles are The total number is preferably 20 to 100%, more preferably 30 to 100%, further preferably 40 to 100%.
- the ratio of the secondary particles the number N of the binder particles forming the secondary particles among the 50 binder particles is counted using the TEM image obtained in the measurement of the aspect ratio. The obtained number N is divided by 50 to calculate the ratio [N / 50] of the secondary particles in 50 binder particles, and this is used as the ratio of the secondary particles.
- the content of the non-spherical binder particles in the solid electrolyte composition is capable of forming a layer having excellent film strength, a contact state between solid particles and a binding force, and maintains excellent battery performance even after repeated charge and discharge. From the viewpoint that it can be used as an all-solid secondary battery, 0.01 mass% or more is preferable, 0.05 mass% or more is more preferable, and 0.1 mass% or more is further preferable in 100 mass% of solid component. From the viewpoint of battery capacity, the upper limit is preferably 20% by mass or less, more preferably 10% by mass or less, and further preferably 5% by mass or less.
- the mass ratio [(mass of inorganic solid electrolyte + mass of active material) / (mass of binder)] of the total mass (total mass) of the inorganic solid electrolyte and the active material to the mass of the binder is , 1,000 to 1 is preferable. This ratio is more preferably 500 to 2, and even more preferably 100 to 5.
- the solid electrolyte composition of the present invention may contain one kind of non-spherical binder particles or two or more kinds thereof.
- the non-spherical binder particles are not particularly limited, for example, by dispersing the synthesized binder-forming polymer in a dispersion medium, to form primary particles, which are further aggregated to form secondary particles, prepared. can do. At this time, the synthesis conditions, the dispersion conditions, etc. are appropriately set to the conditions capable of forming secondary particles.
- the binder-forming polymer may be any combination of raw material compounds leading to predetermined constituents depending on the type of the main chain, and if necessary, sequential polymerization in the presence of a catalyst (including a polymerization initiator, a chain transfer agent, etc.), Alternatively, it can be synthesized by chain polymerization such as addition polymerization.
- a catalyst including a polymerization initiator, a chain transfer agent, etc.
- chain polymerization such as addition polymerization.
- the method and conditions for the sequential polymerization or the chain polymerization are not particularly limited, and known methods and conditions can be appropriately selected.
- the above-mentioned respective properties and physical properties of the binder-forming polymer can be adjusted by the kind of the binder-forming polymer, further the kind of the constituent component (raw material compound), the binding mode or content, the molecular weight of the polymer or the glass transition temperature.
- the raw material compound a known compound is appropriately selected according to the kind of the binder-forming polymer.
- the solvent for synthesizing the binder-forming polymer is not particularly limited, and those listed as the dispersion medium described later can be preferably used.
- the solvent used when synthesizing the binder-forming polymer when preparing the binder-forming polymer solution, is changed to the binder-forming polymer.
- a method of substituting with a dispersion medium capable of emulsifying and dispersing and removing the solvent used in synthesizing the binder-forming polymer is preferable.
- the boiling point of the solvent used in synthesizing the binder-forming polymer is preferably lower than the boiling point of the dispersion medium in which the binder-forming polymer can be emulsified and dispersed.
- the dispersion medium capable of emulsifying and dispersing the binder-forming polymer a dispersion medium capable of emulsifying and dispersing the binder-forming polymer described below can be preferably used.
- the method for preparing the dispersion liquid of the binder-forming polymer is not particularly limited, and the binder-forming polymer can also be prepared by synthesizing the binder-forming polymer (for example, emulsion polymerization method).
- the synthesized binder-forming polymer is dispersed in an appropriate dispersion medium. It can also be prepared.
- Examples of the method of dispersing the binder-forming polymer in the dispersion medium include a method of using a flow reactor (a method of colliding primary particles of the binder-forming polymer with each other), a method of stirring using a homogenizer, and a phase inversion emulsification method. .
- the method of phase inversion emulsification of the synthesized binder-forming polymer is preferable from the viewpoint of productivity, and further, the properties and physical properties of the binder-forming polymer to be obtained.
- the phase inversion emulsification method includes a step of dispersing the binder-forming polymer and a step of removing the solvent used during the synthesis of the binder-forming polymer.
- the dispersing step includes a method of adding a solution of the binder-forming polymer dropwise (for example, at -20 to 150 ° C. for 0.5 to 8 hours) in a dispersion medium in which the binder-forming polymer can be emulsified and dispersed, A method of emulsifying by slowly dropping a dispersion medium capable of emulsifying and dispersing the binder-forming polymer while vigorously stirring the solution of the binder-forming polymer can be mentioned.
- Examples of the step of removing the solvent include a method in which the dispersion liquid of the binder-forming polymer thus obtained is concentrated under reduced pressure or heated under an inert gas stream.
- the solvent used during the synthesis of the binder-forming polymer can be selectively removed, and the concentration of the dispersion medium in which the binder-forming polymer can be emulsified and dispersed can be increased.
- the “strong stirring” is not particularly limited as long as mechanical energy such as impact, shear, shear stress, friction, vibration is applied to the polymer solution.
- a homogenizer for example, a homogenizer, a homodisper, a shinto machine, a dissolver, a Titec mixer, a stirring blade in a stirring tank, a high-pressure jet disperser, an ultrasonic disperser, a ball mill, a bead mill, etc. are used, for example, at 300 to 1000 rpm.
- a mode in which stirring is performed under conditions such as the number of rotations can be mentioned.
- the term “slowly dropping” is not particularly limited unless it is added all at once. Conditions for mixing may be mentioned.
- the dispersion medium in which the binder-forming polymer can be emulsified and dispersed is appropriately determined according to the type of constituent components of the binder-forming polymer.
- a solvent which can easily dissolve this constituent component and hardly dissolve other components such as the constituent component represented by the formula (I-1) can be mentioned.
- the solvent is not particularly limited, but among the above dispersion media, non-aqueous dispersion media (aliphatic compounds and aromatic compounds) are preferable.
- Examples of the aliphatic compound include hexane, heptane, normal octane, isooctane, nonane, decane, dodecane, cyclohexane, cycloheptane, cyclooctane, methylcyclohexane, ethylcyclohexane, decalin, light oil, kerosene, gasoline and the like.
- Examples of aromatic hydrocarbons include benzene, toluene, ethylbenzene, xylene, mesitylene, and tetralin.
- the dispersion medium may be used alone or in combination of two or more.
- a polar solvent (ether solvent, ketone solvent, ester solvent, etc.) may be added as long as it does not hinder the emulsion dispersion of the polymer.
- the mass ratio [mass of non-aqueous dispersion medium / mass of polar solvent] of the non-aqueous dispersion medium and the polar solvent is preferably 100/0 to 70/30, more preferably 100/0 to 90/10, and 100 / 0- Most preferred is 99/1.
- the boiling point at normal pressure of the dispersion medium in which the binder-forming polymer can be emulsified and dispersed is preferably 80 ° C or higher, preferably 100 ° C or higher, and more preferably 120 ° C or higher.
- the preferable range of the SP value of the dispersion medium is preferably the same range as the SP value of the hydrocarbon polymer chain. In this way, it is possible to form secondary particles (non-spherical binder particles) formed of primary particles made of a binder-forming polymer.
- the non-spherical binder particles have an average primary particle diameter, an average secondary particle diameter, an aspect ratio, a ratio of secondary particles, a solid content concentration or a dropping rate of a binder forming polymer solution to be used, a binder forming polymer. It can be prepared according to the type of the component, further, the type of the component, the binding mode or the content. For example, when the content of the constituent component represented by the formula (I-3) in which R P2 is the above-mentioned hydrocarbon polymer chain as a molecular chain in the binder-forming polymer increases, the primary particles become too small and the secondary particles The particles tend to be large or it is difficult to form secondary particles. Further, when the solid content concentration of the binder-forming polymer solution used is increased, the secondary particles tend to be large. Further, when the dropping speed is increased, the secondary particles tend to be large.
- the solid electrolyte composition of the present invention can also contain an active material.
- This active material is a material capable of inserting and releasing ions of a metal element belonging to Group 1 or Group 2 of the periodic table. Examples of such an active material include a positive electrode active material and a negative electrode active material.
- a solid electrolyte composition containing a positive electrode active material (a composition for electrodes) may be referred to as a positive electrode composition
- a solid electrolyte composition containing a negative electrode active material may be referred to as a negative electrode composition.
- the positive electrode active material is preferably one that can reversibly insert and release lithium ions.
- the material is not particularly limited as long as it has the above-mentioned characteristics, and may be a transition metal oxide, an organic material, an element such as sulfur that can be composited with Li, or a composite of sulfur and a metal.
- the element M b (elements of Group 1 (Ia), elements of Group 2 (IIa), Al, Ga, In, Ge, Sn, Pb of the metal periodic table other than lithium, Elements such as Sb, Bi, Si, P or B) may be mixed.
- the mixing amount is preferably 0 ⁇ 30 mol% relative to the amount of the transition metal element M a (100mol%). That the molar ratio of li / M a was synthesized were mixed so that 0.3 to 2.2, more preferably.
- transition metal oxide examples include (MA) a transition metal oxide having a layered rock salt structure, (MB) a transition metal oxide having a spinel structure, (MC) a lithium-containing transition metal phosphate compound, (MD) ) Lithium-containing transition metal halogenated phosphoric acid compounds and (ME) lithium-containing transition metal silicic acid compounds.
- MA a transition metal oxide having a layered rock salt structure
- MB transition metal oxide having a spinel structure
- MC lithium-containing transition metal phosphate compound
- MD Lithium-containing transition metal halogenated phosphoric acid compounds
- ME lithium-containing transition metal silicic acid compounds.
- transition metal oxide having a (MA) layered rock salt structure examples include LiCoO 2 (lithium cobalt oxide [LCO]), LiNi 2 O 2 (lithium nickelate), LiNi 0.85 Co 0.10 Al 0. 05 O 2 (lithium nickel cobalt aluminum oxide [NCA]), LiNi 1/3 Co 1/3 Mn 1/3 O 2 (lithium nickel manganese cobalt oxide [NMC]) and LiNi 0.5 Mn 0.5 O 2 ( Lithium manganese nickelate).
- transition metal oxide having a (MB) spinel structure examples include LiMn 2 O 4 (LMO), LiCoMnO 4 , Li 2 FeMn 3 O 8 , Li 2 CuMn 3 O 8 , Li 2 CrMn 3 O 8 and Li.
- Examples of the (MC) lithium-containing transition metal phosphate compound include olivine-type iron phosphate salts such as LiFePO 4 and Li 3 Fe 2 (PO 4 ) 3 , iron pyrophosphates such as LiFeP 2 O 7 , LiCoPO 4 and the like. And monobasic Nasicon-type vanadium phosphate salts such as Li 3 V 2 (PO 4 ) 3 (lithium vanadium lithium phosphate).
- (MD) as the lithium-containing transition metal halogenated phosphate compound for example, Li 2 FePO 4 F such fluorinated phosphorus iron salt, Li 2 MnPO 4 hexafluorophosphate manganese salts such as F and Li 2 CoPO 4 F And the like, such as cobalt fluorophosphates.
- the (ME) lithium-containing transition metal silicic acid compound include Li 2 FeSiO 4 , Li 2 MnSiO 4, and Li 2 CoSiO 4 .
- a transition metal oxide having a (MA) layered rock salt type structure is preferable, and LCO or NMC is more preferable.
- the shape of the positive electrode active material is not particularly limited, but a particle shape is preferable.
- the average particle size (sphere-converted average particle size) of the positive electrode active material is not particularly limited. For example, it can be 0.1 to 50 ⁇ m.
- the average particle size of the positive electrode active material particles can be measured in the same manner as the average particle size of the inorganic solid electrolyte.
- An ordinary crusher or classifier is used to make the positive electrode active material have a predetermined particle size. For example, a mortar, a ball mill, a sand mill, a vibrating ball mill, a satellite ball mill, a planetary ball mill, a swirling airflow type jet mill or a sieve is preferably used.
- wet pulverization in which an organic solvent such as water or methanol is allowed to coexist during pulverization can also be performed.
- the classification method is not particularly limited, and a sieve, an air classifier, or the like can be used as necessary. Classification can be performed both dry and wet.
- the positive electrode active material obtained by the firing method may be used after washing with water, an acidic aqueous solution, an alkaline aqueous solution, or an organic solvent.
- the positive electrode active material may be used alone or in combination of two or more.
- the mass (mg) (unit weight) of the positive electrode active material per unit area (cm 2 ) of the positive electrode active material layer is not particularly limited. It can be appropriately determined according to the designed battery capacity.
- the content of the positive electrode active material in the electrode composition is not particularly limited, and is preferably 10 to 95% by mass, more preferably 30 to 90% by mass, and further preferably 50 to 85% by mass in 100% by mass of solid content. It is preferably 55 to 80% by mass, and particularly preferably.
- the negative electrode active material is preferably one that can reversibly insert and release lithium ions.
- the material is not particularly limited as long as it has the above characteristics, and it is a carbonaceous material, a metal oxide, a metal composite oxide, a simple substance of lithium, a lithium alloy, or a negative electrode active that can be alloyed with lithium (can form an alloy). Examples include substances. Above all, a carbonaceous material, a metal composite oxide, or a simple substance of lithium is preferably used from the viewpoint of reliability. An active material that can be alloyed with lithium is preferable from the viewpoint that the capacity of the all-solid secondary battery can be increased.
- the solid electrolyte layer formed of the solid electrolyte composition of the present invention maintains a solid binding state and a contact state between solid particles even when a volume change occurs. Therefore, in the present invention, the negative electrode active material As the active material, it is possible to use an active material that can be alloyed with lithium, which has a large expansion and contraction due to charge and discharge and has room for improvement in terms of battery life. As a result, it is possible to increase the capacity of the all-solid-state secondary battery and extend the life of the battery.
- the carbonaceous material used as the negative electrode active material is a material consisting essentially of carbon.
- carbon black such as acetylene black (AB)
- graphite natural graphite, artificial graphite such as vapor-grown graphite
- various synthetic materials such as PAN (polyacrylonitrile) resin or furfuryl alcohol resin.
- a carbonaceous material obtained by firing a resin can be used.
- various carbon fibers such as PAN-based carbon fibers, cellulose-based carbon fibers, pitch-based carbon fibers, vapor-grown carbon fibers, dehydrated PVA (polyvinyl alcohol) -based carbon fibers, lignin carbon fibers, glassy carbon fibers and activated carbon fibers.
- Examples thereof include mesophase microspheres, graphite whiskers, and flat graphite.
- These carbonaceous materials can be classified into non-graphitizable carbonaceous materials (also referred to as hard carbon) and graphitic carbonaceous materials depending on the degree of graphitization.
- the carbonaceous material preferably has the interplanar spacing or density and crystallite size described in JP-A-62-22066, JP-A-2-6856 and JP-A-3-45473.
- the carbonaceous material does not have to be a single material, and a mixture of natural graphite and artificial graphite described in JP-A-5-90844, graphite having a coating layer described in JP-A-6-4516, etc. may be used.
- You can also Hard carbon or graphite is preferably used as the carbonaceous material, and graphite is more preferably used.
- the metal or metalloid element oxide applied as the negative electrode active material is not particularly limited as long as it is an oxide capable of occluding and releasing lithium, and it is an oxide of a metal element (metal oxide) or a composite of metal elements. Examples thereof include oxides or composite oxides of metal elements and metalloid elements (collectively referred to as metal composite oxides), and oxides of metalloid elements (metalloid oxides). As these oxides, amorphous oxides are preferable, and chalcogenide, which is a reaction product of a metal element and an element of Group 16 of the periodic table, is also preferable.
- the term “metalloid element” refers to an element exhibiting intermediate properties between a metal element and a non-metalloid element, and usually contains 6 elements of boron, silicon, germanium, arsenic, antimony and tellurium, and further selenium. , Polonium and astatine.
- Amorphous means an X-ray diffraction method that uses CuK ⁇ rays and has a broad scattering band having an apex in the region of 20 ° to 40 ° at a 2 ⁇ value. You may have.
- the highest intensity of the crystalline diffraction lines observed at 2 ⁇ values of 40 ° to 70 ° is 100 times or less than the diffraction line intensity of the apex of the broad scattering band observed at 20 ° to 40 ° of 2 ⁇ values. Is preferred, more preferably 5 times or less, and particularly preferably free of crystalline diffraction lines.
- the amorphous oxide of a metalloid element or the above chalcogenide is more preferable, and an element of group 13 (IIIB) to 15 (VB) of the periodic table (for example, , Al, Ga, Si, Sn, Ge, Pb, Sb and Bi) are preferably used alone or as a (composite) oxide consisting of a combination of two or more thereof, or a chalcogenide.
- an element of group 13 (IIIB) to 15 (VB) of the periodic table for example, Al, Ga, Si, Sn, Ge, Pb, Sb and Bi
- preferable amorphous oxides and chalcogenides include, for example, Ga 2 O 3 , GeO, PbO, PbO 2 , Pb 2 O 3 , Pb 2 O 4 , Pb 3 O 4 , Sb 2 O 3 , and Sb 2.
- O 4, Sb 2 O 8 Bi 2 O 3, Sb 2 O 8 Si 2 O 3, Sb 2 O 5, Bi 2 O 3, Bi 2 O 4, GeS, PbS, PbS 2, Sb 2 S 3 or Sb 2 S 5 is preferably mentioned.
- Examples of the negative electrode active material that can be used together with the amorphous oxide centered on Sn, Si, and Ge include carbonaceous materials capable of occluding and / or releasing lithium ions or lithium metal, lithium simple substance, lithium alloy, lithium.
- An active material that can be alloyed with is preferably used.
- the metal or semimetal element oxide, particularly the metal (composite) oxide, and the chalcogenide contain at least one of titanium and lithium as a constituent component.
- the metal composite oxide containing lithium (lithium composite metal oxide) for example, a composite oxide of lithium oxide and the above metal (composite) oxide or the above chalcogenide, more specifically, Li 2 SnO 2 is Can be mentioned.
- the negative electrode active material for example, a metal oxide contains a titanium atom (titanium oxide).
- Li 4 Ti 5 O 12 (lithium titanate [LTO]) is excellent in rapid charging / discharging characteristics because of its small volume fluctuation during storage and release of lithium ions, and deterioration of the electrodes is suppressed, and lithium ion secondary It is preferable in that the life of the battery can be improved.
- the lithium alloy as the negative electrode active material is not particularly limited as long as it is an alloy usually used as the negative electrode active material of a secondary battery, and examples thereof include a lithium aluminum alloy.
- the active material that can be alloyed with lithium is not particularly limited as long as it is one that is usually used as the negative electrode active material of a secondary battery.
- Such an active material has a large expansion and contraction due to charge and discharge of the all-solid secondary battery, and accelerates deterioration of battery performance, but the inorganic solid electrolyte-containing composition of the present invention contains non-spherical binder particles, It is possible to suppress deterioration of battery performance.
- Examples of such active material include (negative electrode) active material (alloy or the like) containing silicon element or tin element, and each metal such as Al and In, and the negative electrode active material containing silicon element that enables higher battery capacity.
- a silicon element-containing active material is preferable, and a silicon element-containing active material in which the content of silicon element is 50 mol% or more of all the constituent elements is more preferable.
- a negative electrode containing such a negative electrode active material Si negative electrode containing a silicon element-containing active material, Sn negative electrode containing a tin element-containing active material, etc.
- a carbon negative electrode graphite, acetylene black, etc.
- silicon element-containing active material examples include silicon materials such as Si and SiOx (0 ⁇ x ⁇ 1), and silicon-containing alloys including titanium, vanadium, chromium, manganese, nickel, copper, lanthanum (for example, LaSi 2 , VSi 2 , La-Si, Gd-Si, Ni-Si), or an organized active material (eg, LaSi 2 / Si), as well as silicon and tin elements such as SnSiO 3 and SnSiS 3.
- Examples include active materials containing.
- SiOx can be used as a negative electrode active material (semi-metal oxide) itself, and since Si is generated by the operation of an all-solid secondary battery, negative electrode active material that can be alloyed with lithium. It can be used as a precursor substance).
- the negative electrode active material having a tin element include Sn, SnO, SnO 2 , SnS, SnS 2 , and an active material containing the silicon element and the tin element.
- a complex oxide with lithium oxide for example, Li 2 SnO 2 can also be mentioned.
- the above-mentioned negative electrode active material can be used without particular limitation, but in terms of battery capacity, a negative electrode active material that can be alloyed with lithium is a preferred embodiment, among which,
- the above-mentioned silicon material or silicon-containing alloy (alloy containing elemental silicon) is more preferable, and silicon (Si) or silicon-containing alloy is further preferable.
- the chemical formula of the compound obtained by the above calcination can be calculated from the mass difference of the powder before and after calcination as a simple method, and as a simple method.
- the shape of the negative electrode active material is not particularly limited, but a particulate shape is preferable.
- the volume average particle size of the negative electrode active material is not particularly limited, but is preferably 0.1 to 60 ⁇ m.
- the volume average particle diameter of the negative electrode active material particles can be measured in the same manner as the average particle diameter of the inorganic solid electrolyte. In order to obtain a predetermined particle size, an ordinary crusher or classifier is used as with the positive electrode active material.
- the negative electrode active material may be used alone or in combination of two or more.
- the mass (mg) (unit weight) of the negative electrode active material per unit area (cm 2 ) of the negative electrode active material layer is not particularly limited. It can be appropriately determined according to the designed battery capacity.
- the content of the negative electrode active material in the electrode composition is not particularly limited, and is preferably 10 to 80% by mass, and more preferably 20 to 80% by mass based on 100% by mass of the solid content.
- the negative electrode active material layer when the negative electrode active material layer is formed by charging a secondary battery, instead of the negative electrode active material, a metal belonging to Group 1 or 2 of the periodic table generated in the all-solid secondary battery is used. Ions can be used. A negative electrode active material layer can be formed by combining these ions with an electron and depositing as a metal.
- the surfaces of the positive electrode active material and the negative electrode active material may be surface-coated with another metal oxide.
- the surface coating agent include metal oxides containing Ti, Nb, Ta, W, Zr, Al, Si or Li. Specific examples include spinel titanate, tantalum-based oxides, niobium-based oxides, lithium niobate-based compounds, and the like. Specifically, Li 4 Ti 5 O 12 , Li 2 Ti 2 O 5 , and LiTaO 3 are included.
- the surface of the electrode containing the positive electrode active material or the negative electrode active material may be surface-treated with sulfur or phosphorus. Further, the surface of the particles of the positive electrode active material or the negative electrode active material may be surface-treated with active rays or active gas (plasma etc.) before and after the surface coating.
- the solid electrolyte composition of the present invention can also contain a conductive auxiliary agent.
- the conductive aid is not particularly limited, and those known as general conductive aids can be used.
- electronic conductive materials such as graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, Ketjen black, furnace black, amorphous carbon such as needle coke, vapor grown carbon fiber or carbon nanotube.
- Carbon fibers such as, carbonaceous materials such as graphene or fullerene, metal powders such as copper and nickel, metal fibers may be used, conductive polymers such as polyaniline, polypyrrole, polythiophene, polyacetylene, polyphenylene derivatives. You may use.
- an active material and a conductive auxiliary agent when a battery is charged and discharged, an ion of a metal belonging to Group 1 or Group 2 of the periodic table (preferably Li Ions are not inserted and released, and those that do not function as an active material are used as the conduction aid. Therefore, among the conduction aids, those that can function as the active material in the active material layer when the battery is charged and discharged are classified as the active material, not the conduction aid. Whether or not the battery functions as an active material when charged and discharged is not unique and is determined by a combination with the active material.
- the conductive additive one type may be used, or two or more types may be used.
- the total content of the conductive additive in the electrode composition is preferably 0.1 to 10% by mass, more preferably 0.1 to 5% by mass, and 0.5 to 10% by mass based on 100% by mass of the solid content. 3% by mass is more preferable.
- the shape of the conductive additive is not particularly limited, but a particulate form is preferable.
- the median diameter D50 of the conductive additive is not particularly limited and is, for example, preferably 0.01 to 1 ⁇ m, and more preferably 0.02 to 0.1 ⁇ m.
- the solid electrolyte composition of the present invention preferably contains a dispersion medium.
- this solid electrolyte composition contains a dispersion medium, in addition to the usual effects as a dispersion medium (improvement in composition uniformity, improvement in handleability, etc.), the effect of controlling the cohesiveness of non-spherical binder particles is obtained.
- the dispersion medium may be one which disperses each component contained in the solid electrolyte composition of the present invention, and preferably one which disperses the above-mentioned non-spherical binder particles (polymer constituting the binder) in a particulate form. Is selected.
- Examples of the dispersion medium used in the present invention include various organic solvents, and examples of the organic solvent include alcohol compounds, ether compounds, amide compounds, amine compounds, ketone compounds, aromatic compounds, aliphatic compounds, nitrile compounds, and esters. Each solvent such as a compound may be mentioned.
- Examples of the alcohol compound include methyl alcohol, ethyl alcohol, 1-propyl alcohol, 2-propyl alcohol, 2-butanol, ethylene glycol, propylene glycol, glycerin, 1,6-hexanediol, cyclohexanediol, sorbitol, xylitol, and 2 -Methyl-2,4-pentanediol, 1,3-butanediol and 1,4-butanediol may be mentioned.
- alkylene glycol diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, etc.
- alkylene glycol alkyl ether ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether
- Ether dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether, etc.
- dialkyl ether dimethyl ether, diethyl ether, diisopropyl ether, dibutyl ether, etc.
- cyclic ether Tetrahydrofuran, dioxane (1,2, including 1,3- and 1,4-isomers of), etc.
- amide compound examples include N, N-dimethylformamide, N-methyl-2-pyrrolidone, 2-pyrrolidinone, 1,3-dimethyl-2-imidazolidinone, 2-pyrrolidinone, ⁇ -caprolactam, formamide, N- Examples thereof include methylformamide, acetamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropanamide, hexamethylphosphoric triamide and the like.
- Examples of the amine compound include triethylamine, diisopropylethylamine, tributylamine and the like.
- Examples of the ketone compound include acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, cyclohexanone, diisobutyl ketone (DIBK) and the like.
- Examples of the aromatic compound include aromatic hydrocarbon compounds such as benzene, toluene and xylene.
- Examples of the aliphatic compound include aliphatic hydrocarbon compounds such as hexane, heptane, octane and decane.
- Examples of the nitrile compound include acetonitrile, propionitrile, isobutyronitrile and the like.
- Examples of the ester compound include ethyl acetate, butyl acetate, propyl acetate, propyl butyrate, isopropyl butyrate, butyl butyrate, isobutyl butyrate, butyl pentanoate, ethyl isobutyrate, propyl isobutyrate, isopropyl isobutyrate, isobutyl isobutylate, and pivalic acid.
- Examples thereof include carboxylic acid esters such as propyl, isopropyl pivalate, butyl pivalate, and isobutyl pivalate.
- Examples of the non-aqueous dispersion medium include the above aromatic compounds and aliphatic compounds.
- the dispersion medium is preferably a ketone compound, an ester compound, an aromatic compound or an aliphatic compound, and more preferably contains at least one selected from a ketone compound, an ester compound, an aromatic compound and an aliphatic compound. ..
- the dispersion medium contained in the solid electrolyte composition may be one kind or two or more kinds, and preferably two or more kinds.
- the total content of the dispersion medium in the solid electrolyte composition is not particularly limited and is preferably 20 to 80% by mass, more preferably 30 to 70% by mass, and particularly preferably 40 to 60% by mass.
- the solid electrolyte composition of the present invention may further include a lithium salt, an ionic liquid, a thickening agent, and a cross-linking agent (radical polymerization, condensation polymerization, or ring-opening polymerization as a cross-linking reaction, etc., if desired, as components other than the above components. ), A polymerization initiator (such as one that generates an acid or a radical by heat or light), a defoaming agent, a leveling agent, a dehydrating agent, and an antioxidant.
- the solid electrolyte composition of the present invention is an inorganic solid electrolyte, non-spherical binder particles, a dispersion medium, other binders, other components, etc., for example, by mixing with a commonly used various mixers, preferably slurry Can be prepared as
- the mixing method is not particularly limited and may be mixed all at once or sequentially.
- the non-spherical binder particles are usually used as a dispersion liquid of non-spherical binder particles, but not limited thereto.
- the environment for mixing is not particularly limited, but examples thereof include dry air or an inert gas.
- the sheet for all-solid-state secondary batteries of the present invention is a sheet-shaped molded product that can form the constituent layers of all-solid-state secondary batteries, and includes various modes depending on its use.
- a sheet also referred to as a solid electrolyte sheet
- a sheet preferably used for the solid electrolyte layer, an electrode, or a sheet (electrode sheet for an all-solid secondary battery) preferably used for a laminate of the electrode and the solid electrolyte layer, and the like can be mentioned. .
- the solid electrolyte sheet may be any sheet as long as it has a solid electrolyte layer, even if the solid electrolyte layer is formed on a base material, it does not have a base material and is a sheet formed from a solid electrolyte layer. Good.
- the solid electrolyte sheet may have other layers in addition to the solid electrolyte layer. Examples of the other layer include a protective layer (release sheet), a current collector, and a coat layer.
- Examples of the solid electrolyte sheet of the present invention include a sheet having, on a substrate, a layer composed of the solid electrolyte composition of the present invention, a normal solid electrolyte layer, and, if necessary, a protective layer in this order.
- the solid electrolyte layer formed by the solid electrolyte composition of the present invention contains an inorganic solid electrolyte and non-spherical binder particles as one of the binders, and as described above, a contact state between the inorganic solid electrolytes and The binding force between solid particles is improved in a well-balanced manner.
- the inorganic solid electrolyte and the non-spherical binder particles are in a state in which the inorganic solid electrolyte is bound by the non-spherical binder particles.
- the content of each component in this solid electrolyte layer is not particularly limited, but is preferably synonymous with the content of each component in the solid content of the solid electrolyte composition of the present invention.
- the solid electrolyte layer is the same as the solid electrolyte layer in the all-solid-state secondary battery described later, and usually contains no active material.
- the solid electrolyte sheet can be suitably used as a material forming the solid electrolyte layer of the all-solid secondary battery.
- the base material is not particularly limited as long as it can support the solid electrolyte layer, and examples thereof include a sheet (plate-shaped body) of a material, an organic material, an inorganic material, and the like, which will be described later with reference to a current collector.
- the organic material include various polymers, and specific examples thereof include polyethylene terephthalate, polypropylene, polyethylene, and cellulose.
- the inorganic material include glass and ceramics.
- the electrode sheet for an all-solid secondary battery of the present invention may be an electrode sheet having an active material layer, and the active material layer is on a base material (current collector).
- the sheet may be a sheet formed of an active material layer or a sheet having no base material.
- This electrode sheet is usually a sheet having a current collector and an active material layer, but an embodiment having a current collector, an active material layer and a solid electrolyte layer in this order, and a current collector, an active material layer and a solid electrolyte.
- a mode having a layer and an active material layer in this order is also included.
- the electrode sheet of the present invention may have the other layers described above.
- the layer thickness of each layer constituting the electrode sheet of the present invention is the same as the layer thickness of each layer described in the all-solid secondary battery described later.
- the electrode sheet of the present invention has a negative electrode active material in that when used as a negative electrode active material layer of an all-solid secondary battery, the discharge capacity (discharge capacity density) is further increased while maintaining low resistance and long battery life.
- a preferred embodiment is a negative electrode sheet for an all-solid secondary battery containing an active material capable of alloying with lithium.
- the active material layer of the electrode sheet is preferably formed of the solid electrolyte composition (composition for electrodes) of the present invention containing an active material, and particularly, the negative electrode sheet contains a negative electrode active material capable of alloying with lithium.
- the solid electrolyte composition of the present invention is preferably used.
- the active material layer of the electrode sheet similarly to the solid electrolyte layer formed by the solid electrolyte composition of the present invention, solid particles containing an active material and a conductive auxiliary agent are bound by non-spherical binder particles, solid.
- the contact state between particles and the binding force between solid particles are improved in a well-balanced manner.
- the content of each component in the active material layer of the electrode sheet is not particularly limited, but is preferably synonymous with the content of each component in the solid content of the solid electrolyte composition (electrode composition) of the present invention. .
- This electrode sheet can be suitably used as a material forming an (negative electrode or positive electrode) active material layer of an all solid state secondary battery.
- the method for manufacturing the sheet for an all-solid secondary battery is not particularly limited.
- the sheet for all-solid secondary batteries can be manufactured using the solid electrolyte composition of the present invention.
- the solid electrolyte composition of the present invention is prepared as described above, and the obtained solid electrolyte composition is formed into a film (coating and drying) on a substrate (may be via another layer).
- a method of forming a solid electrolyte layer (coating dried layer) on a substrate is mentioned. This makes it possible to produce an all-solid-state secondary battery sheet having an appropriate base material (current collector) and a coating and drying layer.
- the coating dry layer is a layer formed by applying the solid electrolyte composition of the present invention and drying the dispersion medium (that is, using the solid electrolyte composition of the present invention, the solid of the present invention A layer composed of a composition obtained by removing the dispersion medium from the electrolyte composition).
- the inorganic solid electrolyte is bound by non-spherical binder particles.
- the dispersion medium may remain in the active material layer and the coating / drying layer as long as the effects of the present invention are not impaired. The remaining amount can be, for example, 3% by mass or less in each layer.
- the solid electrolyte composition of the present invention is preferably used as a slurry, and if desired, the solid electrolyte composition of the present invention can be slurried by a known method.
- Each process such as application and drying of the solid electrolyte composition of the present invention will be described in the following method for manufacturing an all solid state secondary battery.
- the dried coating layer obtained as described above may be pressed.
- the pressurizing condition and the like will be described later in the method for manufacturing an all-solid-state secondary battery.
- the base material, the protective layer (particularly the release sheet) and the like can be peeled off.
- the all-solid secondary battery of the present invention includes a positive electrode active material layer, a negative electrode active material layer facing the positive electrode active material layer, and a solid electrolyte layer disposed between the positive electrode active material layer and the negative electrode active material layer.
- the positive electrode active material layer is formed on the positive electrode current collector, if necessary, and constitutes a positive electrode.
- the negative electrode active material layer is, if necessary, formed on the negative electrode current collector to form a negative electrode.
- At least one layer of the solid electrolyte layer, the positive electrode active material layer, and the negative electrode active material layer of the all-solid secondary battery is preferably formed of the solid electrolyte composition of the present invention, and all layers are the solid of the present invention.
- each component such as the non-spherical binder contained in each layer may be the same or different.
- the negative electrode active material layer is formed of the solid electrolyte composition of the present invention containing an active material capable of alloying with lithium.
- the all-solid-state secondary battery in which the negative electrode active material layer is formed of the solid electrolyte composition of the present invention containing an active material that can be alloyed with lithium has a large discharge capacity while maintaining low resistance and long battery life. Discharge capacity density).
- the positive electrode active material layer and the negative electrode active material layer Formed by the solid electrolyte composition of the present invention, the positive electrode active material layer and the negative electrode active material layer, an inorganic solid electrolyte, an active material, a non-spherical binder particles, as appropriate, other binders, conductive aids and Each of the above components is contained.
- the negative electrode active material layer when not formed by the solid electrolyte composition of the present invention, a layer containing the inorganic solid electrolyte and the active material and the above components as appropriate, a layer composed of the metal or alloy described as the negative electrode active material (lithium A metal layer or the like), and a layer (sheet) made of the carbonaceous material described as the negative electrode active material are adopted.
- the layer made of metal or alloy includes, for example, a layer formed by depositing or molding powder of metal or alloy such as lithium, metal foil or alloy foil, and vapor deposition film.
- the thickness of the layer made of a metal or alloy and the layer made of a carbonaceous material are not particularly limited, and may be, for example, 0.01 to 100 ⁇ m.
- the solid electrolyte layer formed of the solid electrolyte composition of the present invention is a solid electrolyte having conductivity of ions of a metal belonging to Group 1 or Group 2 of the periodic table, a non-spherical binder, and the above-mentioned components as appropriate. Contains.
- the solid electrolyte composition or active material layer can be formed of the solid electrolyte composition of the present invention or the above-mentioned sheet for all-solid secondary batteries.
- the solid electrolyte layer and the active material layer to be formed are preferably the same as those in the solid content of the solid electrolyte composition, unless otherwise specified, regarding the respective components and the content thereof.
- the thicknesses of the negative electrode active material layer, the solid electrolyte layer, and the positive electrode active material layer are not particularly limited.
- each layer is preferably 5 to 1,000 ⁇ m, more preferably 10 ⁇ m or more and less than 500 ⁇ m, in consideration of the dimensions of a general all-solid secondary battery.
- the thickness of at least one of the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer is more preferably 20 ⁇ m or more and less than 500 ⁇ m.
- the positive electrode active material layer and the negative electrode active material layer may each have a current collector on the side opposite to the solid electrolyte layer.
- the all-solid-state secondary battery of the present invention may be used as an all-solid-state secondary battery with the above structure depending on the application, but in order to obtain the form of a dry battery, it should be further enclosed in a suitable casing before use.
- the housing may be made of metal or resin (plastic).
- metallic casing is preferably divided into a casing on the positive electrode side and a casing on the negative electrode side and electrically connected to the positive electrode current collector and the negative electrode current collector, respectively. It is preferable that the housing on the positive electrode side and the housing on the negative electrode side are joined and integrated via a gasket for preventing a short circuit.
- FIG. 1 is a sectional view schematically showing an all-solid-state secondary battery (lithium ion secondary battery) according to a preferred embodiment of the present invention.
- the all-solid-state secondary battery 10 of the present embodiment has a negative electrode current collector 1, a negative electrode active material layer 2, a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector 5 in this order when viewed from the negative electrode side. .
- the layers are in contact with each other and have a laminated structure. By adopting such a structure, during charging, electrons (e ⁇ ) are supplied to the negative electrode side, and lithium ions (Li + ) are accumulated there.
- the solid electrolyte composition of the present invention can be preferably used as a material for forming a solid electrolyte layer, a negative electrode active material layer or a positive electrode active material layer.
- the sheet for all-solid secondary batteries of the present invention is suitable as a solid electrolyte layer, a negative electrode active material layer, or a positive electrode active material layer.
- the positive electrode active material layer hereinafter, also referred to as positive electrode layer
- the negative electrode active material layer hereinafter, also referred to as negative electrode layer
- this all-solid secondary battery When the all-solid secondary battery having the layer structure shown in FIG. 1 is put in a 2032 type coin case, this all-solid secondary battery is referred to as an all-solid secondary battery laminate, and this all-solid secondary battery laminate is referred to as A battery produced by putting it in a 2032 type coin case may be referred to as an all-solid secondary battery.
- any one of the solid electrolyte layer and the active material layer is formed by using the solid electrolyte composition of the present invention or the above-mentioned sheet for all-solid secondary battery.
- all layers are formed using the solid electrolyte composition of the present invention or the above-mentioned sheet for all-solid-state secondary battery, and in another preferred embodiment, the negative electrode active material layer contains an active material capable of alloying with lithium.
- the solid electrolyte composition of the present invention or the negative electrode sheet for all-solid secondary batteries is formed.
- the negative electrode active material layer is made of a metal or an alloy as the negative electrode active material.
- Layer a layer made of a carbonaceous material as the negative electrode active material, and further by depositing a metal belonging to Group 1 or 2 of the periodic table on the negative electrode current collector during charging.
- the components contained in the positive electrode active material layer 4, the solid electrolyte layer 3, and the negative electrode active material layer 2 may be the same or different from each other.
- the positive electrode current collector 5 and the negative electrode current collector 1 are preferably electron conductors.
- either or both of the positive electrode current collector and the negative electrode current collector may be simply referred to as a current collector.
- a current collector aluminum, aluminum alloy, stainless steel, nickel, titanium, etc., as well as aluminum or stainless steel whose surface is treated with carbon, nickel, titanium or silver (a thin film is formed) Those), and among them, aluminum and aluminum alloys are more preferable.
- As a material for forming the negative electrode current collector in addition to aluminum, copper, copper alloy, stainless steel, nickel and titanium, etc., carbon, nickel, titanium or silver is treated on the surface of aluminum, copper, copper alloy or stainless steel. Preferred are aluminum, copper, copper alloys and stainless steel.
- the shape of the current collector is usually a film sheet shape, but a net, a punched shape, a lath body, a porous body, a foamed body, a molded body of fibers, and the like can also be used.
- the thickness of the current collector is not particularly limited, but is preferably 1 to 500 ⁇ m. Further, it is also preferable that the surface of the current collector is made uneven by surface treatment.
- a functional layer, a member or the like is appropriately interposed or disposed between or outside each layer of the negative electrode current collector, the negative electrode active material layer, the solid electrolyte layer, the positive electrode active material layer and the positive electrode current collector. You may. Each layer may be composed of a single layer or multiple layers.
- the all-solid secondary battery of the present invention is not particularly limited, and can be manufactured by (including) the manufacturing method of the solid electrolyte composition. Focusing on the raw material used, the solid electrolyte composition of the present invention can also be used for production. Specifically, the all-solid secondary battery, the solid electrolyte composition of the present invention is prepared as described above, using the obtained solid electrolyte composition and the like, the solid electrolyte layer of the all-solid secondary battery and It can be manufactured by forming an active material layer. This makes it possible to manufacture an all-solid secondary battery that maintains excellent battery performance even after repeated charging and discharging. Since the method for preparing the solid electrolyte composition is as described above, it is omitted.
- the all-solid secondary battery of the present invention includes a step of applying the solid electrolyte composition of the present invention onto a substrate (for example, a metal foil serving as a current collector) to form a coating film (forming a film). It can be manufactured by the (passage) method.
- a positive electrode active material layer is formed by applying the solid electrolyte composition (electrode composition) of the present invention as a positive electrode composition onto a metal foil that is a positive electrode current collector, and forming a positive electrode for an all-solid secondary battery. Make a sheet. Then, the solid electrolyte composition of the present invention for forming a solid electrolyte layer is applied onto the positive electrode active material layer to form a solid electrolyte layer.
- the solid electrolyte composition (electrode composition) of the present invention is applied as a negative electrode composition onto the solid electrolyte layer to form a negative electrode active material layer.
- a negative electrode current collector metal foil
- each layer is reversed, and a negative electrode active material layer, a solid electrolyte layer, and a positive electrode active material layer are formed on the negative electrode current collector, and the positive electrode current collector is stacked to manufacture an all-solid secondary battery. You can also do it.
- the positive electrode sheet for all-solid-state secondary batteries is produced as described above. Further, the solid electrolyte composition of the present invention is applied as a negative electrode composition onto a metal foil that is a negative electrode current collector to form a negative electrode active material layer, and thus a negative electrode sheet for an all-solid secondary battery is produced. Then, the solid electrolyte layer-forming composition of the present invention is applied onto any one of the active material layers of these sheets as described above to form a solid electrolyte layer. Further, the other of the positive electrode sheet for all-solid secondary battery and the negative electrode sheet for all-solid secondary battery is laminated on the solid electrolyte layer so that the solid electrolyte layer and the active material layer are in contact with each other.
- the all solid state secondary battery can be manufactured.
- the following method can be given as another method. That is, the positive electrode sheet for all-solid-state secondary batteries and the negative electrode sheet for all-solid-state secondary batteries are produced as described above. Separately from this, the solid electrolyte composition is applied onto the substrate to prepare a solid electrolyte sheet comprising a solid electrolyte layer. Further, the positive electrode sheet for all-solid secondary battery and the negative electrode sheet for all-solid secondary battery are laminated so as to sandwich the solid electrolyte layer peeled from the base material. In this way, the all solid state secondary battery can be manufactured.
- Each of the above production methods is a method of forming a solid electrolyte layer, a negative electrode active material layer and a positive electrode active material layer with the solid electrolyte composition of the present invention, but in the production method of this all-solid secondary battery, At least one of the solid electrolyte layer, the negative electrode active material layer, and the positive electrode active material layer is formed from the solid electrolyte composition of the present invention.
- the solid electrolyte layer is formed with a composition other than the solid electrolyte composition of the present invention, examples of the material include a solid electrolyte composition that is usually used.
- the negative electrode active material layer When forming the negative electrode active material layer with a material other than the solid electrolyte composition of the present invention, a known negative electrode active material composition, a metal or alloy (metal layer) as the negative electrode active material, or a carbonaceous material (as the negative electrode active material ( Carbonaceous material layer) and the like. Further, the negative electrode active material layer was not formed during the production of the all-solid-state secondary battery, and the negative electrode current collector accumulated in the negative electrode current collector during initialization or charging during use described later belongs to Group 1 or 2 of the periodic table.
- the negative electrode active material layer can also be formed by combining a metal ion with an electron and depositing it as a metal on a negative electrode current collector or the like.
- the solid electrolyte layer or the like can be formed, for example, on the substrate or the active material layer by pressure-molding the solid electrolyte composition or the like under the pressure condition described below, or the solid electrolyte or the active material layer. Sheet moldings of the material can also be used.
- the method of applying the composition used for manufacturing the all-solid secondary battery is not particularly limited and can be appropriately selected. Examples thereof include coating (preferably wet coating), spray coating, spin coating, dip coating, slit coating, stripe coating and bar coating.
- the composition may be subjected to a drying treatment after each coating, or may be subjected to a multi-layer coating and then a drying treatment.
- the drying temperature is not particularly limited.
- the lower limit is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, even more preferably 80 ° C. or higher.
- the upper limit is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and further preferably 200 ° C. or lower. By heating in such a temperature range, the dispersion medium can be removed and a solid state (coating dried layer) can be obtained. It is also preferable because the temperature is not too high and each member of the all solid state secondary battery is not damaged.
- solid electrolyte composition of the present invention When the solid electrolyte composition of the present invention is applied and dried as described above, solid particles and the like are firmly bound to each other, and a dry coating layer having a small interfacial resistance between solid particles can be formed.
- the pressurize it is preferable to pressurize the applied composition, or each layer or all-solid secondary battery after the all-solid secondary battery is manufactured. It is also preferable to pressurize each layer in a laminated state.
- the pressurizing method include a hydraulic cylinder press machine and the like.
- the pressure applied is not particularly limited, and generally ranges from 10 (preferably 50) to 1500 MPa.
- the applied composition may be heated simultaneously with the pressurization.
- the heating temperature is not particularly limited and is generally in the range of 30 to 300 ° C. It is also possible to press at a temperature higher than the glass transition temperature of the inorganic solid electrolyte.
- the pressurization may be performed in a state in which the coating solvent or dispersion medium has been dried in advance, or may be performed in a state in which the coating solvent or dispersion medium remains.
- each composition may be applied at the same time or may be applied and dried simultaneously and / or sequentially. After coating on different substrates, they may be laminated by transfer.
- the atmosphere during pressurization is not particularly limited, and may be air, dry air (dew point ⁇ 20 ° C. or lower), inert gas (eg, argon gas, helium gas, nitrogen gas). Since the inorganic solid electrolyte reacts with water, the atmosphere during pressurization is preferably under dry air or in an inert gas.
- the pressing time may be short time (for example, within several hours) and high pressure may be applied, or long time (one day or more) may be applied with medium pressure.
- a retainer screw tightening pressure, etc.
- all-solid-state secondary batteries can be used in order to keep applying a moderate pressure.
- the pressing pressure may be uniform or different with respect to the pressed portion such as the sheet surface.
- the pressing pressure can be changed according to the area and film thickness of the pressed portion. It is also possible to change the same part stepwise by different pressures.
- the pressed surface may be smooth or roughened.
- the all-solid-state secondary battery manufactured as described above is preferably initialized after manufacturing or before use. Initialization is not particularly limited, and can be performed, for example, by performing initial charge / discharge in a state where the press pressure is increased, and then releasing the pressure until it becomes a general working pressure of the all solid state secondary battery.
- the all-solid secondary battery of the present invention can be applied to various uses.
- the application mode is not particularly limited, but for example, when it is mounted on an electronic device, it is a notebook computer, a pen input computer, a mobile computer, an electronic book player, a mobile phone, a cordless phone handset, a pager, a handy terminal, a mobile fax, a mobile phone. Examples include copy, portable printer, headphone stereo, video movie, LCD TV, handy cleaner, portable CD, mini disk, electric shaver, transceiver, electronic organizer, calculator, portable tape recorder, radio, backup power supply and memory card.
- consumer products include automobiles (electric vehicles, etc.), electric vehicles, motors, lighting equipment, toys, game machines, road conditioners, clocks, strobes, cameras, medical equipment (pacemakers, hearing aids, shoulder scuffers, etc.), etc. . Furthermore, it can be used for various military purposes and space applications. It can also be combined with a solar cell.
- non-spherical binder particles and the inorganic solid electrolyte used in Examples and Comparative Examples were synthesized as follows.
- Neostan U-600 (trade name, manufactured by Nitto Kasei Co., Ltd.) was added and stirred at 60 ° C. for 5 hours.
- V-601 trade name, manufactured by Wako Pure Chemical Industries, Ltd.
- the polymer P-11 is a (meth) acrylic polymer having a carboxy group and a cyano group in a side chain among the functional groups contained in the functional group group (a), and the content of the constituent component having these functional groups in the polymer. Is 40% by mass.
- ⁇ Synthesis Example 12 Binder-forming polymer P-12 (Preparation of polymer solution P-12)>
- the same procedure as in the synthesis of the polymer P-11 was performed except that 24.0 g of methyl methacrylate was changed to 18.0 g, and 18.0 g of acrylonitrile was changed to 24.0 g of hydroxyethyl acrylate.
- Polymer P-12 (polymer solution P-12) was synthesized (prepared).
- the polymer P-12 is a (meth) acrylic polymer having a carboxy group and a hydroxy group in the side chain among the functional groups contained in the functional group group (a), and the content of the constituent component having these functional groups in the polymer. Is 50% by mass.
- Tg glass transition temperature of binder-forming polymer
- the synthesized binder-forming polymers P-1 to P-7 and P-10 to 12 are shown below.
- the numbers in the lower right of the constituents in the binder-forming polymers P-1 to P-7 and P-10 indicate the content (mol%) of the constituents in the binder-forming polymer, and the binder-forming polymers P-11 and
- the number described in the lower right of the constituent component in P-12 indicates the content (% by mass) of the constituent component in the binder-forming polymer.
- the binder-forming polymers P-8 and P-9 have the same constituents as the binder-forming polymer P-1 and therefore are not described.
- constituent component 1 represents a constituent component represented by formula (I-1).
- the constituent component 2 corresponds to a constituent component represented by the formula (I-3) (a constituent component represented by the above formula (I-3A), in which R P2 is an aliphatic hydrocarbon group having a carboxy group. .) Is shown.
- the constituent component 3 is a constituent component represented by the formula (I-3) (corresponding to the constituent component represented by the formula (I-3B)) in which R P2 is a polyalkylene oxide chain as a molecular chain. Show.
- Constituent component 4 is a constituent component represented by formula (I-3) in which R P2 is the above hydrocarbon polymer chain as a molecular chain (corresponding to a constituent component represented by the above formula (I-3C)). Indicates.
- the constituent component 5 represents another constituent component. Specifically, R P2 is a polycarbonate chain as a molecular chain, and a component represented by the formula (I-3) (binder-forming polymer P-7) and R P2 is an aliphatic group having no carboxy group. And a constituent component represented by the formula (I-3) which is a hydrocarbon group (corresponding to the binder-forming polymer P-10 and the constituent component represented by the above formula (I-3A)).
- MDI 4,4'-Methylenediphenyl diisocyanate (manufactured by Fujifilm Wako Pure Chemical Industries)
- HMDI 4,4'-dicyclohexylmethane diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.)
- TDI 2,4-tolylene diisocyanate (manufactured by Tokyo Chemical Industry Co., Ltd.)
- DMBA 2,2-bis (hydroxymethyl) butyric acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
- PEG200 polyethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight 200)
- PEG400 Polyethylene glycol (Fujifilm Wako Pure Chemical Industries, Ltd., number average molecular weight 400)
- PPG400 Polypropylene glycol (Aldrich, number average molecular weight 400)
- GI-1000 Hydrogenated polybutadiene modified with hydroxyl groups at both ends
- LMA Lauryl methacrylate (Fujifilm Wako Pure Chemical Industries)
- AA Acrylic acid (Fujifilm Wako Pure Chemical Industries)
- MMA Methyl methacrylate (Fujifilm Wako Pure Chemical Industries)
- AN Acrylonitrile (manufactured by FUJIFILM Wako Pure Chemical Industries)
- HEA Droxyethyl acrylate (Fujifilm Wako Pure Chemical Industries) wt%: means% by mass.
- ⁇ Preparation Example 1 Preparation of dispersion liquid PA-1 of non-spherical binder particles> To a 500 mL three-necked flask, 135 g of octane (boiling point 135 ° C.) was added, and the polymer solution P-1 (30 g) prepared above was added dropwise at room temperature over 1 hour while stirring at 500 rpm to obtain an emulsion of polymer P-1. Got This emulsion was heated at 85 ° C. for 120 minutes while flowing a nitrogen gas. Further, the operation of adding 50 g of octane to the residue and heating at 85 ° C. for 60 minutes was repeated 4 times to remove THF (boiling point 66 ° C.) to obtain a 5 mass% octane dispersion of polymer P-1.
- Dispersion PA was prepared in the same manner as in Preparation of Dispersion PA-1, except that the polymer solution and dispersion medium were changed to the polymer solution and dispersion medium shown in Table 2 below. -2 to PA-12 were prepared respectively.
- the boiling point of toluene used as the dispersion medium is 110 ° C.
- ⁇ Preparation Example 15 Preparation of dispersion liquid CP-1 of non-spherical binder particles> A dispersion CP-1 of non-spherical binder particles was prepared with reference to Example A-5 of Patent Document 2 (JP-A-2015-167126). That is, 5 g of propylene glycol monomethyl ether acetate (PGMEA) was added to a 200 mL three-necked flask and heated to 80 ° C. under a nitrogen gas stream.
- PGMEA propylene glycol monomethyl ether acetate
- ⁇ Preparation Example 16 Preparation of dispersion liquid CP-2 of spherical binder particles> 400 parts by mass of water, 200 parts by mass of methyl methacrylate (manufactured by Wako Pure Chemical Industries, Ltd.), and 50 parts by mass of styrene (manufactured by Wako Pure Chemical Industries, Ltd.) in a 5 L three-necked flask equipped with a reflux condenser and a gas introduction cock.
- ⁇ Preparation Example 17 Preparation of binder solution CP-3> Hydrogenated styrene butadiene rubber (HSBC, DYNARON 1321P (trade name), manufactured by JSR, styrene content 10% by mass, mass average molecular weight 229000) was dissolved in toluene as a polymer to prepare a polymer solution CP-3.
- HSBC Hydrogenated styrene butadiene rubber
- JSR styrene content 10% by mass, mass average molecular weight 229000
- the binder in dispersions PA-1 to PA-12 was a non-spherical particle composed of primary particles of urethane polymer.
- the binder in dispersions PA-13 and PA-14 contains non-spherical secondary particles composed of primary particles of (meth) acrylic polymer, and the binder in CP-1 is These were non-spherical primary particles, and the binder in dispersion CP-2 was spherical.
- the aspect ratio of the secondary particles, the average secondary particle diameter, and the ratio of the secondary particles were measured by the above method using the TEM image. Further, the average primary particle diameter of the primary particles forming the binder particles was measured by the above method. A particle size ratio [average secondary particle size / average primary particle size] was calculated from the obtained average secondary particle size and average primary particle size. Table 2 shows the results. In the dispersion liquid CP-2 of spherical binder particles, the binder particles do not contain secondary particles, but the aspect ratio of the binder particles is shown in the “Aspect of secondary particles” column of Table 2.
- Solid electrolyte composition described below measured or calculated for non-spherical binder particles taken out from the sheet for all-solid secondary battery by the method described above, the aspect ratio, the average particle size, the ratio of the secondary particles and elongation at break, the table It was almost the same as the value shown in 2.
- the dispersion medium of PA-3 is a 1: 1 (mass ratio) mixed dispersion medium of octane and toluene.
- Li 2 S lithium sulfide
- P 2 S diphosphorus pentasulfide
- Example 1 Using the obtained non-spherical binder particles, a solid electrolyte composition, an all-solid secondary battery sheet and an all-solid secondary battery are manufactured, respectively, and an all-solid secondary battery electrode sheet and an all-solid secondary battery are produced. The following characteristics were evaluated. The results are shown in Table 5.
- ⁇ Preparation of solid electrolyte composition 180 pieces of zirconia beads having a diameter of 5 mm were placed in a zirconia 45 mL container (manufactured by Fritsch), 4.85 g of LPS synthesized in Synthesis Example 13 above, and 0.15 g of the dispersion liquid shown in Table 3 in terms of solid content, And 8.0 g of heptane was added as a dispersion medium. Then, this container was set in a planetary ball mill P-7 (trade name) manufactured by Fritsch Ltd., and mixing was continued for 60 minutes at a temperature of 25 ° C. and a rotation speed of 250 rpm to obtain solid electrolyte compositions S-1 to S-3, respectively. Prepared.
- Negative electrode compositions a-2 to a-23 were prepared in the same manner as in the preparation of a-1. In the preparation of the negative electrode compositions a-17 and a-18, 2.3 g each of graphite and Si were used as negative electrode active materials.
- the negative electrode compositions a-19 to a-21 are negative electrode compositions for comparison.
- compositions c-2 to c-6 are positive electrode compositions for comparison.
- the composition for positive electrode prepared above was applied to a 20 ⁇ m thick aluminum foil (positive electrode current collector) as a current collector with a Baker type applicator (trade name: SA-201, manufactured by Tester Sangyo Co., Ltd.) to give a basis weight shown in Table 4.
- the amount of the composition was applied, heated at 80 ° C. for 1 hour, and further heated at 110 ° C. for 1 hour to dry the positive electrode composition.
- the dried positive electrode composition (coating dried layer) is pressed (120 MPa, 1 minute) while being heated at 120 ° C. to form a laminated structure of the positive electrode active material layer and the aluminum foil.
- Positive electrode sheets C-1 to C-6 for all solid state secondary batteries having the above were produced respectively.
- the positive electrode sheets C-4 to C-6 for all solid state secondary batteries are positive electrode sheets for comparison.
- ⁇ Manufacture of all solid state secondary battery> (Preparation of electrode sheet) An all-solid secondary battery was manufactured using the electrode sheet that was subjected to the following bending test. The bending test was carried out for each of the prepared negative electrode sheet for all-solid-state secondary battery and positive electrode sheet for all-solid-state secondary battery in ⁇ Evaluation 1: Membrane strength test of negative-electrode sheet for all-solid-state secondary battery> described later, with a diameter of 10 mm The procedure was performed in the same manner as in ⁇ Evaluation 1: Membrane strength test of negative electrode sheet for all-solid-state secondary battery>, except that the bending was repeated three times using a mandrel.
- a sheet having a structure in which the foil and the foil were laminated in this order was produced and cut into a disk shape having a diameter of 15 mm (referred to as a disk-shaped negative electrode sheet).
- the positive electrode sheet for all-solid-state secondary batteries shown in Table 5 which was subjected to the bending test was cut into a disk shape having a diameter of 13 mm.
- the positive electrode active material layer of the disk-shaped positive electrode sheet thus obtained and the solid electrolyte layer of the disk-shaped negative electrode sheet are arranged to face each other (laminate), and then a heat press machine is used. Then, pressure (40 MPa, 1 minute) was applied while heating (120 ° C.).
- the resulting sheet laminate was pressed (30 MPa, 1 minute) in the thickness direction using a pressing machine, and the aluminum foil, which is the support of the solid electrolyte sheet, was peeled off.
- a sheet having a structure in which the solid electrolyte layer, the negative electrode active material layer, and the stainless steel foil were laminated in this order was produced.
- This sheet was cut into a disk shape having a diameter of 15 mm to prepare a disk-shaped negative electrode sheet.
- ⁇ Evaluation 1 Film strength test of negative electrode sheet for all solid state secondary battery>
- the film strength of the negative electrode active material layers in the negative electrode sheets A-1 to A-23 for all solid state secondary batteries was evaluated by a bending resistance test using a mandrel tester (in accordance with JIS K5600-5-1). Specifically, using a test piece cut out from an all-solid secondary battery negative electrode sheet into a strip shape with a width of 50 mm and a length of 100 mm, the negative electrode active material layer is on the opposite side to the mandrel (SUS foil is on the mandrel side).
- ⁇ Evaluation 2 Battery performance test of all solid state secondary battery (discharge capacity)> The discharge capacity of the all-solid-state secondary battery manufactured above was measured by a charge / discharge evaluation device “TOSCAT-3000” (trade name, manufactured by Toyo System Co., Ltd.). Specifically, the all-solid secondary battery was charged at a current value of 0.2 mA until the battery voltage reached 4.2 V, and then discharged at a current value of 0.2 mA until the battery voltage reached 3.0 V. This charging once and discharging once were set as one cycle of charging / discharging, and three cycles were repeated to perform charging / discharging. The discharge capacity at the 3rd cycle was determined.
- This discharge capacity was converted into the discharge capacity of the all-solid-state secondary battery (expressed simply as “capacity” in Table 5) by converting it per 100 cm 2 of surface area of the positive electrode active material layer.
- the discharge capacity was evaluated according to which of the following evaluation criteria was included. In this test, the evaluation standard C or higher is the pass level.
- ⁇ Evaluation 4 Resistance measurement of all solid state secondary battery> The resistance of each of the all-solid-state secondary batteries manufactured above was measured by a charge / discharge evaluation device “TOSCAT-3000” (trade name, manufactured by Toyo System Co., Ltd.). Specifically, the all-solid secondary battery was charged at a current value of 0.2 mA until the battery voltage reached 4.2 V, and then discharged at a current value of 2.0 mA until the battery voltage reached 3.0 V. The battery voltage 10 seconds after the start of discharge was read and evaluated according to which of the following evaluation criteria was included. In this test, the higher the battery voltage, the smaller the resistance of the all-solid-state secondary battery, and the evaluation level C or higher is the pass level. -Evaluation criteria- A: 4.1V or more B: 4.0V or more, less than 4.1V C: 3.8V or more, less than 4.0V D: 3.6V or more, less than 3.8V E: less than 3.6V
- the discharge capacity at the 5th charge / discharge cycle and the discharge capacity at the 100th charge / discharge cycle were determined as follows. Out of the 10 specimen batteries, the average values of the discharge capacities at the 5th cycle and the 100th cycle in the 6 specimens of all-solid-state secondary batteries excluding the 2 specimens above and below the performance were obtained, and the average discharge capacity at the 5th cycle was obtained. The ratio of the average discharge capacity at the 100th cycle to the above ([average discharge capacity at the 100th cycle / average discharge capacity at the 5th cycle] ⁇ 100 (%)) was calculated. It was evaluated according to which of the following evaluation criteria this ratio was included.
- the evaluation standard C or higher is the pass level. -Evaluation criteria- A: 85% or more B: 75% or more, less than 85% C: 65% or more, less than 75% D: 55% or more, less than 65% E: less than 55%
- the unit of the weight per unit area and the film thickness are mg / cm 2 and ⁇ m, respectively.
- the results shown in Table 5 show the following.
- the negative electrode sheets A-19 to A-21 for all-solid-state secondary batteries formed of the solid electrolyte composition (electrode composition) containing no non-spherical binder particles specified in the present invention all have sufficient film strength. Does not exert.
- the all-solid-state secondary battery c01 using binder particles composed of primary particles as the binder and the all-solid-state secondary battery c02 using spherical binder particles do not have sufficient resistance and are inferior in battery life.
- the all-solid-state secondary battery c03 using the dissolution type binder does not have sufficient discharge capacity, discharge capacity density and resistance, and also has a short battery life.
- the solid electrolyte composition containing the non-spherical binder particles defined in the present invention in the all-solid secondary battery, to suppress the increase in interfacial resistance between the solid particles to firmly bind the solid particles, It contributes to exhibiting a small resistance and maintaining an excellent discharge capacity and discharge capacity density even when charging and discharging are repeated.
- the all-solid secondary battery in which the positive electrode active material layer, the solid electrolyte layer, and the negative electrode active material layer are formed of the solid electrolyte composition or the electrode composition defined in the present invention has a reduced interfacial resistance, a binding property, and a battery. You can establish a high level of performance.
- all of the solid-state secondary batteries 101 to 107 and 109 to 121 using Si, Sn or SiO as the negative electrode active material are compared with the all solid state secondary battery 108 using graphite as the negative electrode active material layer.
- the discharge capacity density is increasing.
- these all-solid-state secondary batteries maintain a strong film strength and a long battery life despite the large volume change of the negative electrode active material layer.
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Abstract
Description
このような状況下、有機電解液に代えて、無機固体電解質を用いた全固体二次電池が注目されている。全固体二次電池は負極、電解質及び正極の全てが固体からなり、有機電解液を用いた電池の安全性及び信頼性を大きく改善することができる。
ポリマーの構造等に着目した材料としては、例えば、特許文献1に、特定の平均粒径を有するコアシェル構造の粒子状ポリマーからなる結着剤と無機固体電解質とを含有するスラリーが記載されている。また、バインダーの形状等に着目した材料については、例えば、特許文献2に、特定の基を有する非球状ポリマー粒子と分散媒体と無機固体電解質とを含有する固体電解質組成物が記載されている。
しかも、近年、全固体二次電池の開発が急速に進展しており、上記問題の克服に加えて、放電容量及び放電容量密度等の電池性能の更なる改善も求められている。
<1>周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有する無機固体電解質と、ポリマーからなるバインダーとを含有する固体電解質組成物であって、
バインダーが、1~1,000nmの平均一次粒径を持つ一次粒子で形成された二次粒子からなる、非球状のバインダー粒子を含む、固体電解質組成物。
<2>二次粒子が、平均一次粒径の2~1,000倍の平均粒径を有する、<1>に記載の固体電解質組成物。
<3>二次粒子が、1.1~1,000のアスペクト比を有する、<1>又は<2>に記載の固体電解質組成物。
<4>ポリマーが、10%以上の破断伸びを示す、<1>~<3>のいずれか1つに記載の固体電解質組成物。
<5>分散媒を含有する<1>~<4>のいずれか1つに記載の固体電解質組成物。
<6>活物質を含有する<1>~<5>>のいずれか1つに記載の固体電解質組成物。
<7>活物質が、リチウムと合金化可能な活物質である<6>に記載の固体電解質組成物。
<8>ポリマーが、下記官能基群(a)から選ばれる少なくとも1つの官能基を有する<1>1~<7>のいずれか1つに記載の固体電解質組成物。
官能基群(a)
酸性官能基、塩基性官能基、ヒドロキシ基、シアノ基、アルコキシシリル基、アリール基、ヘテロアリール基、3環以上が縮環した脂肪族炭化水素環基
<9>ポリマーが、ポリアミド、ポリイミド、ポリウレア、ポリウレタン又は(メタ)アクリルポリマーある、<1>~<8>のいずれか1つに記載の固体電解質組成物。
<10>無機固体電解質が、硫化物系固体電解質である<1>~<9>のいずれか1つに記載の固体電解質組成物。
<11>上記<1>~<10>のいずれか1つに記載の固体電解質組成物で構成した層を有する全固体二次電池用シート。
<12>上記<6>又は<7>に記載の固体電解質組成物で構成した活物質層を有する全固体二次電池用電極シート。
<13>正極活物質層と固体電解質層と負極活物質層とをこの順で具備する全固体二次電池であって、
正極活物質層、負極活物質層及び固体電解質層の少なくとも1つの層が、<1>~<10>のいずれか1つに記載の固体電解質組成物で構成した層である、全固体二次電池。
<14>負極活物質層が、<6>又は<7>に記載の固体電解質組成物で構成した層である請求項13に記載の全固体二次電池。
本発明の上記及び他の特徴及び利点は、適宜添付の図面を参照して、下記の記載からより明らかになるであろう。
本明細書において、単に「アクリル」又は「(メタ)アクリル」と記載するときは、アクリル及び/又はメタクリルを意味する。
本明細書において化合物の表示(例えば、化合物と末尾に付して呼ぶとき)については、この化合物そのもののほか、その塩、そのイオンを含む意味に用いる。また、所望の効果を奏する範囲で、置換基を導入するなど一部を変化させた誘導体を含む意味である。
本明細書において置換又は無置換を明記していない置換基、連結基等(以下、置換基等という。)については、その基に適宜の置換基を有していてもよい意味である。よって、本明細書において、単に、YYY基と記載されている場合であっても、このYYY基は、置換基を有しない態様に加えて、更に置換基を有する態様も包含する。これは置換又は無置換を明記していない化合物についても同義である。好ましい置換基としては、後述する置換基Tが挙げられる。
本明細書において、特定の符号で示された置換基等が複数あるとき、又は複数の置換基等を同時若しくは択一的に規定するときには、それぞれの置換基等は互いに同一でも異なっていてもよいことを意味する。また、特に断らない場合であっても、複数の置換基等が隣接するときにはそれらが互いに連結したり縮環したりして環を形成していてもよい意味である。
(条件1)
カラム:TOSOH TSKgel Super AWM-H(商品名、東ソー社製)を2本つなげる。
キャリア:10mMLiBr/N-メチルピロリドン
測定温度:40℃
キャリア流量:1.0ml/min
試料濃度:0.1質量%
検出器:RI(屈折率)検出器
(条件2)
カラム:TOSOH TSKgel Super HZM-H、TOSOH TSKgel Super HZ4000、TOSOH TSKgel Super HZ2000(いずれも商品名、東ソー社製)をつないだカラムを用いる。
キャリア:テトラヒドロフラン
測定温度:40℃
キャリア流量:1.0ml/min
試料濃度:0.1質量%
検出器:RI(屈折率)検出器
本発明の固体電解質組成物(無機固体電解質含有組成物ともいう)は、無機固体電解質と、ポリマーからなるバインダー粒子とを含有する。このバインダー粒子は、1~1,000nmの平均一次粒径を持つ一次粒子で形成された二次粒子からなる、非球状のバインダー粒子を含んでいる。
上述のように、本発明の固体電解質組成物で構成した構成層は、固体粒子同士の接触状態(イオン伝導パス等の構築量)及び固体粒子同士等の結着力がバランスよく改善され、十分なイオン伝導パス等を構築しつつも、固体粒子同士等が強固な結着性で結着され、固体粒子間の界面抵抗が小さくなると考えられる。このような優れた特性を示す構成層を備えた各シート又は全固体二次電池は、電気抵抗の上昇を抑えて高い放電容量(放電容量密度)を示し、更には充放電を繰り返したとしても、この高い放電容量を維持できる。
本発明において、無機固体電解質とは、無機の固体電解質のことであり、固体電解質とは、その内部においてイオンを移動させることができる固体状の電解質のことである。主たるイオン伝導性材料として有機物を含むものではないことから、有機固体電解質(ポリエチレンオキシド(PEO)などに代表される高分子電解質、リチウムビス(トリフルオロメタンスルホニル)イミド(LiTFSI)などに代表される有機電解質塩)とは明確に区別される。また、無機固体電解質は定常状態では固体であるため、通常カチオン及びアニオンに解離又は遊離していない。この点で、電解液、又は、ポリマー中でカチオン及びアニオンが解離若しくは遊離している無機電解質塩(LiPF6、LiBF4、LiFSI、LiClなど)とも明確に区別される。無機固体電解質は周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有するものであれば特に制限されず電子伝導性を有さないものが一般的である。本発明における全固体二次電池がリチウムイオン電池の場合、無機固体電解質は、リチウムイオンのイオン伝導性を有することが好ましい。
硫化物系無機固体電解質は、硫黄原子を含有し、かつ、周期律表第一族若しくは第二族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。硫化物系無機固体電解質は、元素として少なくともLi、S及びPを含有し、リチウムイオン伝導性を有しているものが好ましいが、目的又は場合に応じて、Li、S及びP以外の他の元素を含んでもよい。
La1Mb1Pc1Sd1Ae1 式(I)
式中、LはLi、Na及びKから選択される元素を示し、Liが好ましい。Mは、B、Zn、Sn、Si、Cu、Ga、Sb、Al及びGeから選択される元素を示す。Aは、I、Br、Cl及びFから選択される元素を示す。a1~e1は各元素の組成比を示し、a1:b1:c1:d1:e1は1~12:0~5:1:2~12:0~10を満たす。a1は1~9が好ましく、1.5~7.5がより好ましい。b1は0~3が好ましく、0~1がより好ましい。d1は2.5~10が好ましく、3.0~8.5がより好ましい。e1は0~5が好ましく、0~3がより好ましい。
硫化物系無機固体電解質は、例えば硫化リチウム(Li2S)、硫化リン(例えば五硫化二燐(P2S5))、単体燐、単体硫黄、硫化ナトリウム、硫化水素、ハロゲン化リチウム(例えばLiI、LiBr、LiCl)及び上記Mで表される元素の硫化物(例えばSiS2、SnS、GeS2)の中の少なくとも2つ以上の原料の反応により製造することができる。
酸化物系無機固体電解質は、酸素原子を含有し、かつ、周期律表第1族若しくは第2族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。
酸化物系無機固体電解質は、イオン伝導度として、1×10-6S/cm以上であることが好ましく、5×10-6S/cm以上であることがより好ましく、1×10-5S/cm以上であることが特に好ましい。上限は特に限定されないが、1×10-1S/cm以下であることが実際的である。
ハロゲン化物系無機固体電解質は、一般に用いられるものであり、ハロゲン原子を含有し、かつ、周期律表第一族若しくは第二族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。
ハロゲン化物系無機固体電解質としては、特に制限されないが、例えば、LiCl、LiBr、LiI、ADVANCED MATERIALS,2018,30,1803075に記載のLi3YBr6、Li3YCl6等の化合物が挙げられる。中でも、Li3YBr6、Li3YCl6を好ましい。
水素化物系無機固体電解質は、一般に用いられるものであり、水素原子を含有し、かつ、周期律表第一族若しくは第二族に属する金属のイオン伝導性を有し、かつ、電子絶縁性を有する化合物が好ましい。
水素化物系無機固体電解質としては、特に制限されないが、例えば、LiBH4、Li4(BH4)3I、3LiBH4-LiCl等が挙げられる。
無機固体電解質の、固体電解質組成物中の含有量は、特に制限されないが、分散性、界面抵抗の低減及び結着性の点で、固形分100質量%において、50質量%以上であることが好ましく、70質量%以上であることがより好ましく、90質量%以上であることが更に好ましい。上限としては、同様の観点から、99.9質量%以下であることが好ましく、99.5質量%以下であることがより好ましく、99質量%以下であることが特に好ましい。ただし、固体電解質組成物が後述する活物質を含有する場合、固体電解質組成物中の無機固体電解質の上記含有量は、無機固体電解質と活物質との合計含有量とする。
本発明において、固形分(固形成分)とは、固体電解質組成物を、1mmHgの気圧下、窒素雰囲気下150℃で6時間乾燥処理を行ったときに、揮発若しくは蒸発して消失しない成分をいう。典型的には、後述の分散媒以外の成分を指す。
本発明の固体電解質組成物が含有するバインダーは、後述する非球状のバインダー粒子を少なくとも1種含んでいればよく、非球状のバインダー粒子以外のバインダーを含んでいてもよい。非球状のバインダー粒子以外のバインダー(他のバインダー)は、特に制限されず、球状のバインダー粒子でもよく、分散媒に溶解するバインダーでもよい。また、一次粒子からなるバインダー粒子であってもよい。
バインダーを形成する材料は、特に制限されないが、ポリマーが好ましく、例えば、全固体二次電池に用いるバインダーを形成する通常のポリマー、更には後述する、非球状のバインダー粒子を形成するポリマー等が挙げられる。本発明の固体電解質組成物中における、他のバインダーの含有量は、特に制限されず、適宜に決定される。
非球状のバインダー粒子は、1~1,000nmの平均一次粒径を持つ一次粒子で形成された二次粒子からなる。固体電解質組成物に含有させるバインダーとしてこのような非球状のバインダー粒子を含んでいると、固体粒子同士の接触状態と結着力とに優れた層を形成でき、充放電を繰り返しても優れた電池性能を維持する全固体二次電池とすることができる。また、充放電による電池抵抗の上昇も抑えることも可能になる。
本発明において、二次粒子とは、一次粒子(単位粒子)が複数個集合して形成される粒子をいい、一次粒子が集合する際に作用する粒子間力は物理的な力(例えばVan der Waals力)であっても化学力(例えば化学結合)であってもよい。例えば、二次粒子としては、一次粒子の集合体若しくは凝集体等が挙げられる。本発明において、二次粒子を形成する一次粒子の数は特に制限されない。
非球状のバインダー粒子が二次粒子からなることは、公知の方法により確認できる。例えば、電子顕微鏡等を用いて形状観察する方法、光散乱等の粒径測定器による測定法が挙げられる。本発明においては、後述する二次粒子のアスペクト比の測定時に確認することもできる。
非球状のバインダー粒子(二次粒子)は、球状(真球状)でなければよく、いびつな形状(異方性を有する形状)をしている。その形状としては、特に制限されないが、不定形、楕円球状、扁平状、(針状)繊維状等が挙げられるが、特に制限されない。
非球状のバインダー粒子(二次粒子)は、1.1~1,000の(平均)アスペクト比[平均長さLy/平均幅Lxの比]を有することが、界面抵抗の低減、結着性、電池性能(放電容量、放電容量密度及び電池寿命)の点で、好ましい。二次粒子のアスペクト比は、結着性等の点で、1.5以上が好ましく、2以上がより好ましく、4以上が更に好ましく、9以上が特に好ましい。一方、電池性能のうち特に電池寿命等の点で、500以下が好ましく、100以下がより好ましく、50以下が更に好ましい。アスペクト比は、バインダーを形成するポリマーの組成若しくは合成条件、更には後述する分散液の調製条件、等により、調整できる。例えば、分散液の調製条件のうち撹拌速度を高めるとアスペクト比は小さくなる傾向がある。また、分散媒の極性を向上させるとアスペクト比は小さくなる傾向がある。
アスペクト比の測定方法は後述する。
平均二次粒径は、具体的には、例えば、5nm以上であることが好ましく、10nm以上であることがより好ましく、20nm以上であることが更に好ましく、30nm以上であることが特に好ましく、230nm以上とすることもできる。上限としては、1,000nm以下であることが好ましく、500nm以下であることがより好ましく、400nm以下であることが更に好ましく、300nm以下であることが特に好ましい。
二次粒子を形成する一次粒子は、例えば後述するポリマーからなる粒子であって、1~1,000nmの平均一次粒径を有している。平均一次粒径が上記範囲にあると、二次粒子を形成しやすく、界面抵抗の低減、結着性及び電池性能を鼎立できる。平均一次粒径は、界面抵抗の低減等の点で、2nm以上が好ましく、3nm以上がより好ましく、5nm以上が更に好ましい。一方、結着性等の点で、500nm以下が好ましく、400nm以下がより好ましく、300nm以下が更に好ましく、100nm以下が更に好ましい。平均一次粒径はポリマーの組成若しくは合成条件、更には後述する分散液の調製条件等により、調整できる。例えば、ポリマーの分子量を大きくすると、平均一次粒子径は大きくなる傾向がある。また、分散媒の極性を低下させると平均一次粒子径は小さくなる傾向がある。
一次粒子の形状は、特に制限されず、球状でも非球状でもよい。
非球状のバインダー粒子について、アスペクト比、平均粒径(平均一次粒径及び平均二次粒径)は、以下のようにして測定する。
非球状のバインダー粒子を分散媒(例えばオクタン)と混合して測定用分散液を調製する。バインダー粒子の濃度は、特に制限されないが、測定用分散液中において、各バインダー粒子が互いに孤立した状態で分散する濃度(例えば0.5質量%程度)まで希釈化する。こうして調製した測定用分散液を、透過型電子顕微鏡(TEM)観察用グリッドメッシュに滴下した後、室温にて乾燥させる。その後、TEMで観察してTEM画像を撮影する。得られたTEM画像をBMP(ビットマップ)ファイルに変換し、IP-1000PC(商品名、旭エンジニアリング社製)の統合アプリケーションである「A像くん」で、孤立しているバインダー粒子50個を取り込み、各バインダー粒子について、このバインダー粒子を形成している50個の一次粒子の直径を測定する。こうして測定した直径の平均値を求めて、この平均値を平均一次粒径とする。
一次粒子(非球状のバインダー粒子)を形成するポリマー(以下、バインダー形成ポリマーということがある。)は、特に制限されず、全固体二次電池に用いるバインダーを形成する通常のポリマー、更には後述するポリマーが挙げられる。
バインダー形成ポリマーは、界面抵抗の低減及び電池性能を維持しつつ強固な結着性を実現できる点で、破断伸びが10%以上であることが好ましく、30%以上であることがより好ましく、50%以上であることが更に好ましい。一方、破断伸びの上限は、特に制限されないが、例えば、10,000%以下であることが実際的であり、界面抵抗の低減及び電池性能を維持しつつ強固な結着性を実現できる点で、1,000%以下であることが好ましく、800%以下であることがより好ましい。
以下に、フィルムを用いた測定方法を説明する。
- 試験用試験片の作製 -
まず、試験片としてのフィルムを作製する。すなわち、非球状のバインダー粒子の分散液、例えば後述する合成方法によって得られた非球状のバインダー粒子の分散液を、テフロン(登録商標)シート上にベーカー式アプリケーター(パルテック社製)を用いて塗布し、送風乾燥機(ヤマト科学製)内に静置して、200℃で40時間乾燥させる。次に、乾燥後の膜を、ショッパー形試料打抜器(安田精機製作所製)を用いて、JIS K 7127「プラスチック-引張特性の試験方法 第3部:フィルム及びシートの試験条件」により規定される標準試験片タイプ5を作製する。
- 引っ張り試験の実施概要 -
こうして得られた標準試験片タイプ5を試験片として、デジタルフォースゲージZTS-5N及び縦型電動計測スタンドMX2シリーズ(いずれも商品名、イマダ社製)を用いて、引っ張り試験を行う。試験片の中央部には50mm離れて平行な2本の標線をつけ、1分間に10mmの速度で試験片を引き延ばし、JIS K 7161-1:2014「プラスチック-引張特性の試験方法」JIS K 7161-1:2014「プラスチック-引張特性の求め方-第1部:通則」に基づいて、引張破壊ひずみ(本発明において「破断伸び」という。)を算出する。
バインダー形成ポリマーが複数のガラス転移温度を有する場合、少なくとも1つのガラス転移温度(通常、最も高いガラス転移温度)が上記範囲内にあることが好ましく、すべてのガラス転移温度が上記範囲内にあることがより好ましい。
ガラス転移温度(Tg)は、乾燥試料を用いて、示差走査熱量計「X-DSC7000」(商品名、SII・ナノテクノロジー社製)を用いて下記の条件で測定する。測定は同一の試料で二回実施し、二回目の測定結果を採用する。
測定室内の雰囲気:窒素(50mL/min)
昇温速度:5℃/min
測定開始温度:-100℃
測定終了温度:200℃
試料パン:アルミニウム製パン
測定試料の質量:5mg
Tgの算定:DSCチャートの下降開始点と下降終了点の中間温度の小数点以下を四捨五入することでTgを算定する。
なお、固体電解質組成物又は構成層中の非球状のバインダー粒子について、バインダー形成ポリマーのガラス転移温度は、例えば、上記組成物又は構成層を水に入れてその含有成分を分散させた後、ろ過して残った固体を収集し、上記測定法で測定できる。
上記各ポリマーは、1つのセグメントからなるポリマーでもよく、2つ以上のセグメントからなるポリマーでもよい。
バインダー形成ポリマーとして好適な逐次重合系のポリマーは、下記式(I-1)~(I-4)のいずれかで表される構成成分を2種以上(好ましくは2種又は3種)組み合わせてなる主鎖、又は下記式(I-5)で表されるカルボン酸二無水物と下記式(I-6)で表される構成成分を導くジアミン化合物とを逐次重合してなる主鎖を有するポリマーが好ましい。各構成成分の組み合わせは、ポリマー種に応じて適宜に選択される。ポリカーボネートからなる主鎖としては、RP1の両端部に酸素原子を導入した下記式(I-2)で表される構成成分若しくはRP1として式(I-3)で表される構成成分を採る下記式(I-2)で表される構成成分と、下記式(I-3)で表される構成成分とを有する主鎖が挙げられる。構成成分の組み合わせにおける1種の構成成分とは、下記のいずれか1つの式で表される構成成分の種類数を意味し、1つの下記式で表される構成成分を2種有していても、2種の構成成分とは解釈しない。
RP1及びRP2としてとりうる上記分子鎖は、特に制限されないが、炭化水素鎖、ポリアルキレンオキシド鎖、ポリカーボネート鎖又はポリエステル鎖が好ましく、炭化水素鎖又はポリアルキレンオキシド鎖がより好ましく、炭化水素鎖、ポリエチレンオキシド鎖又はポリプロピレンオキシド鎖が更に好ましい。
低分子量の炭化水素鎖は、通常の(非重合性の)炭化水素基からなる鎖であり、この炭化水素基としては、例えば、脂肪族若しくは芳香族の炭化水素基が挙げられ、具体的には、アルキレン基(炭素数は1~12が好ましく、1~6がより好ましく、1~3が更に好ましい)、アリーレン基(炭素数は6~22が好ましく、6~14が好ましく、6~10がより好ましい)、又はこれらの組み合わせからなる基が好ましい。RP2としてとりうる低分子量の炭化水素鎖を形成する炭化水素基としては、アルキレン基がより好ましく、炭素数2~6のアルキレン基が更に好ましく、炭素数2又は3のアルキレン基が特に好ましい。
芳香族の炭化水素基は、フェニレン基又は下記式(M2)で表される炭化水素基が好ましい。
RM2~RM5は、それぞれ、水素原子又は置換基を示し、水素原子が好ましい。RM2~RM5としてとりうる置換基としては、特に制限されないが、例えば、炭素数1~20のアルキル基、炭素数1~20のアルケニル基、-ORM6、―N(RM6)2、-SRM6(RM6は置換基を示し、好ましくは炭素数1~20のアルキル基又は炭素数6~10のアリール基を示す。)、ハロゲン原子(例えば、フッ素原子、塩素原子、臭素原子)が挙げられる。―N(RM6)2としては、アルキルアミノ基(炭素数は、1~20が好ましく、1~6がより好ましい)又はアリールアミノ基(炭素数は、6~40が好ましく、6~20がより好ましい)が挙げられる。
末端反応性基を有する炭化水素ポリマーとしては、例えば、いずれも商品名で、NISSO-PBシリーズ(日本曹達社製)、クレイソールシリーズ(巴工業社製)、PolyVEST-HTシリーズ(エボニック社製)、poly-bdシリーズ(出光興産社製)、poly-ipシリーズ(出光興産社製)、EPOL(出光興産社製)及びポリテールシリーズ(三菱化学社製)等が好適に用いられる。
ポリカーボネート鎖又はポリエステル鎖としては、公知のポリカーボネート又はポリエステルからなる鎖が挙げられる。
ポリアルキレンオキシド鎖、ポリカーボネート鎖又はポリエステル鎖は、それぞれ、末端にアルキル基(炭素数は1~12が好ましく、1~6がより好ましい)を有することが好ましい。
RP1及びRP2としてとりうるポリアルキレンオキシド鎖、ポリカーボネート鎖及びポリエステル鎖の末端は、RP1及びRP2として上記各式で表される構成成分に組み込み可能な通常の化学構造に適宜に変更することができる。例えば、実施例で合成したポリウレタンのように、ポリアルキレンオキシド鎖の末端酸素原子は取り除かれて上記構成成分のRP1又はRP2として組み込まれる。
上記各式において、RP1及びRP2は2価の分子鎖であるが、少なくとも1つの水素原子が-NH-CO-、-CO-、-O-、-NH-又は-N<で置換されて、3価以上の分子鎖となっていてもよい。
RP2は、脂肪族の炭化水素基、又は低分子量の炭化水素鎖以外の分子鎖が好ましく、脂肪族の炭化水素基及び低分子量の炭化水素鎖以外の分子鎖をそれぞれ含む態様がより好ましい。この態様においては、式(I-3)、式(I-4)及び式(I-6)のいずれかで表される構成成分は、RP2が低分子量の脂肪族の炭化水素基である構成成分と、RP2が低分子量の炭化水素鎖以外の分子鎖である構成成分の少なくとも2種を含む。
なお、下記具体例において、構成成分中に繰り返し構造を有する場合、その繰り返し数は1以上の整数であり、上記分子鎖の分子量又は炭素原子数を満たす範囲で適宜に設定される。
なお、バインダー形成ポリマー中における上記各式で表される構成成分の含有量は後述する。
バインダー形成ポリマー中の、上記各式で表される構成成分以外の構成成分の含有量は、特に限定されないが、80質量%以下であることが好ましい。
バインダー形成ポリマー中の、式(I-3)、式(I-4)又は式(I-6)で表される構成成分の含有量は、特に制限されず、10~50モル%であることが好ましく、20~50モル%であることがより好ましく、30~50モル%であることが更に好ましい。
なお、バインダー形成ポリマーが各式で表される構成成分を複数有する場合、各構成成分の上記含有量は合計含有量とする。
式(I-3)又は式(I-4)で表される構成成分のうち、RP2が分子鎖として上記ポリアルキレンオキシド鎖である構成成分の、バインダー形成ポリマー中の含有量は、特に制限されないが、例えば、0~50モル%であることが好ましく、1~45モル%であることがより好ましく、3~40モル%であることが更に好ましい。
式(I-3)又は式(I-4)で表される構成成分のうち、RP2が分子鎖として上記炭化水素ポリマー鎖である構成成分の、バインダー形成ポリマー中の含有量は、特に制限されないが、例えば、0~50モル%であることが好ましく、1~45モル%であることがより好ましく、3~40モル%であることが更に好ましい。
バインダー形成ポリマーとして好適な連鎖重合系のポリマーは、非芳香族性の炭素-炭素二重結合を有する1種又は2種以上のモノマーが連鎖重合してなるポリマーであり、具体的には上記の各ポリマーが挙げられる。中でも、(メタ)アクリル酸、(メタ)アクリル酸エステル化合物、(メタ)アクリルアミド化合物及び(メタ)アクリルニトリル化合物から選択される少なくとも1種の(メタ)アクリル化合物を重合して得られるポリマー((メタ)アクリルポリマー)が好ましく挙げられる。また、(メタ)アクリル化合物とその他の重合性化合物との共重合体も挙げられる。その他の重合性化合物としては、特に制限されず、スチレン化合物、ビニルナフタレン化合物、ビニルカルバゾール化合物、アリル化合物、ビニルエーテル化合物、ビニルエステル化合物、イタコン酸ジアルキル化合物等が挙げられる。その他の重合性化合物との共重合体としては、具体的には、(メタ)アクリル酸メチルとスチレンとの共重合体、(メタ)アクリル酸ブチルとアクリロニトリルとスチレンとの共重合体が挙げられる。本願明細書において、共重合体は、統計共重合体及び周期共重合体のいずれでもよく、ブロック共重合体が好ましい。(メタ)アクリルポリマーとしては、例えば、特開2015-088486号公報に記載のポリマー等が挙げられる。
(メタ)アクリルポリマーとしては、(メタ)アクリル酸、(メタ)アクリル酸アルキルエステル化合物、(メタ)アクリルアミド化合物及び(メタ)アクリルニトリル化合物から選択される少なくとも2種の(メタ)アクリル化合物を重合して得られるポリマーがより好ましく、(メタ)アクリル酸、(メタ)アクリル酸アルキルエステル化合物及び(メタ)アクリルニトリル化合物から選択される少なくとも2種の(メタ)アクリル化合物を重合して得られるポリマーが更に好ましい。連鎖重合系のポリマーを構成する(メタ)アクリル酸アルキルエステル化合物としては、(メタ)アクリル酸の炭素数1~6のアルキルエステル化合物と、(メタ)アクリル酸の炭素数7~20のアルキル化合物とを含むことが好ましい。
(メタ)アクリルポリマーにおける構成成分の含有量は、特に限定されず、適宜に設定される。例えば、(メタ)アクリル化合物の合計含有量は20~100質量%とすることができる。
また、(メタ)アクリル酸に由来する構成成分の含有量は、0~50質量%が好ましく、3~20質量%がより好ましい。
(メタ)アクリル酸アルキルエステル化合物に由来する構成成分の含有量は、20~99質量%が好ましく、30~95質量%がより好ましい。(メタ)アクリル酸アルキルエステル化合物の中でも炭素数1~6のアルキルエステル化合物に由来する構成成分の含有量は、5~80質量%が好ましく、20~60質量%がより好ましい。炭素数7~20のアルキル化合物に由来する構成成分の含有量は、5~80質量%が好ましく、10~60質量%がより好ましい。
(メタ)アクリルニトリル化合物に由来する構成成分の含有量は、0~80質量%が好ましく、5~60質量%がより好ましい。
(メタ)アクリルポリマーにおける含有量は上述の通りであるが、官能基群(a)から選択される官能基を有する化合物に由来する構成成分の含有量は、1~80質量%が好ましく、5~60質量%がより好ましい。
上記各含有量は、対応する構成成分が複数存在する場合、合計含有量とする。
官能基群(a)
酸性官能基、塩基性官能基、ヒドロキシ基、シアノ基、アルコキシシリル基、アリール基、ヘテロアリール基、3環以上が縮環した脂肪族炭化水素環基
塩基性官能基としては、特に制限されないが、アミノ基が好ましく挙げられる。アミノ基としては、特に限定されず、例えば、炭素数0~20のアミノ基が挙げられる。アミノ基は、アルキルアミノ基及びアリールアミノ基を含む。アミノ基の炭素数は、0~12が好ましく、0~6がより好ましく、0~2が更に好ましい。アミノ基としては、例えば、アミノ、N,N-ジメチルアミノ、N,N-ジエチルアミノ、N-エチルアミノ、アニリノ等が挙げられる。
ヒドロキシ基及びアミノ基等のように塩を形成可能なものは塩であってもよい。
アルコキシシリル基としては、特に限定されず、モノ-、ジ-若しくはトリ-アルコキシシリル基が挙げられ、好ましくは炭素数1~20のアルコキシシリル基、例えば、モノメトキシシリル、ジメトキシシリル、トリメトキシシリル、トリエトキシシリル等が挙げられる。
ヘテロアリール基としては、特に限定されず、環構成原子として酸素原子、硫黄原子及び窒素原子から選択される少なくとも1つを有する5又は6員環のヘテロアリール基が挙げられる。ヘテロアリール基は単環でも縮合環でもよく、炭素数2~20が好ましい。
飽和脂肪族炭化水素環若しくは不飽和脂肪族炭化水素環が3環以上縮環した環基としては、特に限定されないが、例えば、ステロイド骨格を有する化合物からなる環基が挙げられる。ステロイド骨格を有する化合物としては、例えば、コレステロール、エルゴステロール、テストステロン、エストラジオール、アルドステロン、ヒドロコルチゾン、スチグマステロール、チモステロール、ラノステロール、7-デヒドロデスモステロール、7-デヒドロコレステロール、コラン酸、コール酸、リトコール酸、デオキシコール酸、デオキシコール酸ナトリウム、デオキシコール酸リチウム、ヒオデオキシコール酸、ケノデオキシコール酸、ウルソデオキシコール酸、デヒドロコール酸、ホケコール酸、ヒオコール酸又はこれらの骨格を含む化合物等が挙げられる。中でも、コレステロール骨格を有する化合物からなる環基がより好ましい。
上記官能基としては、活物質にかかわらず高い結着性を示す点で、カルボン酸基、スルホン酸基、リン酸基、アリール基が好ましく、カルボン酸基がより好ましい。
官能基を有する構成成分の含有量は、特に制限されないが、上記各ポリマーを構成する構成成分のうち、上記官能基が導入される前の上記構成成分に対応する含有量の範囲内に設定できる。
アルキル基(好ましくは炭素数1~20のアルキル基、例えばメチル、エチル、イソプロピル、t-ブチル、ペンチル、ヘプチル、1-エチルペンチル、ベンジル、2-エトキシエチル、1-カルボキシメチル等)、アルケニル基(好ましくは炭素数2~20のアルケニル基、例えば、ビニル、アリル、オレイル等)、アルキニル基(好ましくは炭素数2~20のアルキニル基、例えば、エチニル、ブタジイニル、フェニルエチニル等)、シクロアルキル基(好ましくは炭素数3~20のシクロアルキル基、例えば、シクロプロピル、シクロペンチル、シクロヘキシル、4-メチルシクロヘキシル等)、アリール基(好ましくは炭素数6~26のアリール基、例えば、フェニル、1-ナフチル、4-メトキシフェニル、2-クロロフェニル、3-メチルフェニル等)、ヘテロ環基(好ましくは炭素数2~20のヘテロ環基で、好ましくは、少なくとも1つの酸素原子、硫黄原子、窒素原子を有する5又は6員環のヘテロ環基である。ヘテロ環基には芳香族ヘテロ環基(ヘテロアリール基)及び脂肪族ヘテロ環基を含む。例えば、テトラヒドロピラン環基、テトラヒドロフラン環基、2-ピリジル、4-ピリジル、2-イミダゾリル、2-ベンゾイミダゾリル、2-チアゾリル、2-オキサゾリル等)、アルコキシ基(好ましくは炭素数1~20のアルコキシ基、例えば、メトキシ、エトキシ、イソプロピルオキシ、ベンジルオキシ等)、アリールオキシ基(好ましくは炭素数6~26のアリールオキシ基、例えば、フェノキシ、1-ナフチルオキシ、3-メチルフェノキシ、4-メトキシフェノキシ等)、ヘテロ環オキシ基(上記ヘテロ環基に-O-基が結合した基)、アルコキシカルボニル基(好ましくは炭素数2~20のアルコキシカルボニル基、例えば、エトキシカルボニル、2-エチルヘキシルオキシカルボニル等)、アリールオキシカルボニル基(好ましくは炭素数6~26のアリールオキシカルボニル基、例えば、フェノキシカルボニル、1-ナフチルオキシカルボニル、3-メチルフェノキシカルボニル、4-メトキシフェノキシカルボニル等)、アミノ基(好ましくは炭素数0~20のアミノ基、アルキルアミノ基、アリールアミノ基を含み、例えば、アミノ(-NH2)、N,N-ジメチルアミノ、N,N-ジエチルアミノ、N-エチルアミノ、アニリノ等)、スルファモイル基(好ましくは炭素数0~20のスルファモイル基、例えば、N,N-ジメチルスルファモイル、N-フェニルスルファモイル等)、アシル基(アルキルカルボニル基、アルケニルカルボニル基、アルキニルカルボニル基、アリールカルボニル基、ヘテロ環カルボニル基を含み、好ましくは炭素数1~20のアシル基、例えば、アセチル、プロピオニル、ブチリル、オクタノイル、ヘキサデカノイル、アクリロイル、メタクリロイル、クロトノイル、ベンゾイル、ナフトイル、ニコチノイル等)、アシルオキシ基(アルキルカルボニルオキシ基、アルケニルカルボニルオキシ基、アルキニルカルボニルオキシ基、アリールカルボニルオキシ基、ヘテロ環カルボニルオキシ基を含み、好ましくは炭素数1~20のアシルオキシ基、例えば、アセチルオキシ、プロピオニルオキシ、ブチリルオキシ、オクタノイルオキシ、ヘキサデカノイルオキシ、アクリロイルオキシ、メタクリロイルオキシ、クロトノイルオキシ、ベンゾイルオキシ、ナフトイルオキシ、ニコチノイルオキシ等)、アリーロイルオキシ基(好ましくは炭素数7~23のアリーロイルオキシ基、例えば、ベンゾイルオキシ等)、カルバモイル基(好ましくは炭素数1~20のカルバモイル基、例えば、N,N-ジメチルカルバモイル、N-フェニルカルバモイル等)、アシルアミノ基(好ましくは炭素数1~20のアシルアミノ基、例えば、アセチルアミノ、ベンゾイルアミノ等)、アルキルチオ基(好ましくは炭素数1~20のアルキルチオ基、例えば、メチルチオ、エチルチオ、イソプロピルチオ、ベンジルチオ等)、アリールチオ基(好ましくは炭素数6~26のアリールチオ基、例えば、フェニルチオ、1-ナフチルチオ、3-メチルフェニルチオ、4-メトキシフェニルチオ等)、ヘテロ環チオ基(上記ヘテロ環基に-S-基が結合した基)、アルキルスルホニル基(好ましくは炭素数1~20のアルキルスルホニル基、例えば、メチルスルホニル、エチルスルホニル等)、アリールスルホニル基(好ましくは炭素数6~22のアリールスルホニル基、例えば、ベンゼンスルホニル等)、アルキルシリル基(好ましくは炭素数1~20のアルキルシリル基、例えば、モノメチルシリル、ジメチルシリル、トリメチルシリル、トリエチルシリル等)、アリールシリル基(好ましくは炭素数6~42のアリールシリル基、例えば、トリフェニルシリル等)、ホスホリル基(好ましくは炭素数0~20のリン酸基、例えば、-OP(=O)(RP)2)、ホスホニル基(好ましくは炭素数0~20のホスホニル基、例えば、-P(=O)(RP)2)、ホスフィニル基(好ましくは炭素数0~20のホスフィニル基、例えば、-P(RP)2)、スルホ基(スルホン酸基)、カルボキシ基、ヒドロキシ基、スルファニル基、シアノ基、ハロゲン原子(例えばフッ素原子、塩素原子、臭素原子、ヨウ素原子等)が挙げられる。RPは、水素原子又は置換基(好ましくは置換基Tから選択される基)である。
また、これらの置換基Tで挙げた各基は、上記置換基Tが更に置換していてもよい。
二次粒子の比率は、上記アスペクト比の測定において得られたTEM画像を用いて、50個のバインダー粒子のうち二次粒子を形成しているバインダー粒子の数Nを計数する。得られた数Nを50で除して、バインダー粒子50個中の二次粒子の比率[N/50]を算出し、これを二次粒子の比率とする。
本発明の固体電解質組成物において、バインダーの質量に対する、無機固体電解質と活物質の合計質量(総量)の質量比[(無機固体電解質の質量+活物質の質量)/(バインダーの質量)]は、1,000~1の範囲が好ましい。この比率は500~2がより好ましく、100~5が更に好ましい。
非球状のバインダー粒子は、特に制限されないが、例えば、合成したバインダー形成ポリマーを分散媒に分散させることにより、一次粒子を形成し、これを更に凝集等させた二次粒子を形成して、調製することができる。このときの、合成条件、分散条件等は、二次粒子を形成可能な条件に適宜に設定される。
- バインダー形成ポリマーの合成 -
バインダー形成ポリマーは、主鎖の種類に応じて、所定の構成成分を導く原料化合物を任意に組み合わせて、必要により触媒(重合開始剤、連鎖移動剤等を含む。)の存在下、逐次重合、又は付加重合等の連鎖重合させることで、合成することができる。逐次重合又は連鎖重合させる方法及び条件は、特に限定されず、公知の方法及び条件を適宜に選択できる。バインダー形成ポリマーの上記各特性、物性は、バインダー形成ポリマーの種類、更には、構成成分(原料化合物)の種類、結合様式若しくは含有量、ポリマーの分子量若しくはガラス転移温度等により、調整できる。
原料化合物は、バインダー形成ポリマーの種類に応じて適宜に公知の化合物が選択される。例えば、上述した原料化合物の他にも、特開2015-088480号公報に記載の、ウレタン結合を有するポリマー、ウレア結合を有するポリマー、アミド結合を有するポリマー(ポリアミド樹脂)、イミド結合を有するポリマー等を形成する各原料化合物が挙げられる。
バインダー形成ポリマーの分散液を調製する方法は、特に制限されず、上記バインダー形成ポリマーの合成(例えば乳化重合法)により調製することもでき、合成したバインダー形成ポリマーを適宜の分散媒に分散して調製することもできる。分散媒にバインダー形成ポリマーを分散させる方法としては、例えば、フローリアクターを用いる方法(バインダー形成ポリマーの一次粒子同士を衝突させる方法)、ホモジナイザーを用いて撹拌する方法、転相乳化法等が挙げられる。中でも、生産性の点、更には得られるバインダー形成ポリマーの特性、物性等の点で、合成したバインダー形成ポリマーを転相乳化する方法が好ましい。
本発明において、上記「強く撹拌」とは、ポリマー溶液に衝撃、せん断、ずり応力、摩擦、振動等の機械的エネルギーを加える限り特に制限されない。例えば、ホモジナイザー、ホモディスパー、しんとう機、ディゾルバー、タイテックミキサー、攪絆槽での攪絆羽、高圧噴射式分散機、超音波分散機、ボールミル、ビーズミル等の装置を用い、例えば、300~1000rpmの回転数等の条件で撹拌する態様が挙げられる。また、「ゆっくりと滴下」とは、一括で添加しない限り特に制限されないが、例えば、滴下する分散媒を2時間以上かけて(滴下速度:1時間当たり5~20mL)、バインダー形成ポリマー溶液に滴下混合する条件が挙げられる。
バインダー形成ポリマーを乳化分散し得る分散媒の常圧における沸点は、80℃以上が好ましく、100℃以上が好ましく、120℃以上が好ましい。分散媒の好ましいSP値の範囲は粒子分散性向上の観点から、炭化水素ポリマー鎖のSP値と同じ範囲であることが好ましい。
こうして、バインダー形成ポリマーからなる一次粒子で形成された二次粒子(非球状のバインダー粒子)を形成することができる。
本発明の固体電解質組成物は、活物質を含有することもできる。この活物質は、周期律表第一族若しくは第二族に属する金属元素のイオンの挿入放出が可能な物質である。このような活物質としては、正極活物質及び負極活物質が挙げられる。
本発明において、正極活物質を含有する固体電解質組成物(電極用組成物)を正極用組成物と、また、負極活物質を含有する固体電解質組成物を負極用組成物ということがある。
正極活物質は、可逆的にリチウムイオンを挿入及び放出できるものが好ましい。その材料は、上記特性を有するものであれば、特に制限はなく、遷移金属酸化物、又は、有機物、硫黄などのLiと複合化できる元素若しくは硫黄と金属の複合物などでもよい。
中でも、正極活物質としては、遷移金属酸化物を用いることが好ましく、遷移金属元素Ma(Co、Ni、Fe、Mn、Cu及びVから選択される1種以上の元素)を有する遷移金属酸化物がより好ましい。また、この遷移金属酸化物に元素Mb(リチウム以外の金属周期律表の第1(Ia)族の元素、第2(IIa)族の元素、Al、Ga、In、Ge、Sn、Pb、Sb、Bi、Si、P又はBなどの元素)を混合してもよい。混合量としては、遷移金属元素Maの量(100mol%)に対して0~30mol%が好ましい。Li/Maのモル比が0.3~2.2になるように混合して合成されたものが、より好ましい。
遷移金属酸化物の具体例としては、(MA)層状岩塩型構造を有する遷移金属酸化物、(MB)スピネル型構造を有する遷移金属酸化物、(MC)リチウム含有遷移金属リン酸化合物、(MD)リチウム含有遷移金属ハロゲン化リン酸化合物及び(ME)リチウム含有遷移金属ケイ酸化合物等が挙げられる。
(MB)スピネル型構造を有する遷移金属酸化物の具体例として、LiMn2O4(LMO)、LiCoMnO4、Li2FeMn3O8、Li2CuMn3O8、Li2CrMn3O8及びLi2NiMn3O8が挙げられる。
(MC)リチウム含有遷移金属リン酸化合物としては、例えば、LiFePO4及びLi3Fe2(PO4)3等のオリビン型リン酸鉄塩、LiFeP2O7等のピロリン酸鉄類、LiCoPO4等のリン酸コバルト類並びにLi3V2(PO4)3(リン酸バナジウムリチウム)等の単斜晶ナシコン型リン酸バナジウム塩が挙げられる。
(MD)リチウム含有遷移金属ハロゲン化リン酸化合物としては、例えば、Li2FePO4F等のフッ化リン酸鉄塩、Li2MnPO4F等のフッ化リン酸マンガン塩及びLi2CoPO4F等のフッ化リン酸コバルト類が挙げられる。
(ME)リチウム含有遷移金属ケイ酸化合物としては、例えば、Li2FeSiO4、Li2MnSiO4及びLi2CoSiO4等が挙げられる。
本発明では、(MA)層状岩塩型構造を有する遷移金属酸化物が好ましく、LCO又はNMCがより好ましい。
焼成法によって得られた正極活物質は、水、酸性水溶液、アルカリ性水溶液、有機溶剤にて洗浄した後使用してもよい。
正極活物質層を形成する場合、正極活物質層の単位面積(cm2)当たりの正極活物質の質量(mg)(目付量)は特に限定されるものではない。設計された電池容量に応じて、適宜に決めることができる。
負極活物質は、可逆的にリチウムイオンを挿入及び放出できるものが好ましい。その材料は、上記特性を有するものであれば、特に制限はなく、炭素質材料、金属酸化物、金属複合酸化物、リチウム単体、リチウム合金、リチウムと合金化可能(合金形成可能)な負極活物質等が挙げられる。中でも、炭素質材料、金属複合酸化物又はリチウム単体が信頼性の点から好ましく用いられる。全固体二次電池の大容量化が可能となる点では、リチウムと合金化可能な活物質が好ましい。上述のように、本発明の固体電解質組成物で形成した固体電解質層は体積変化が生じても固体粒子同士の強固な結着状態及び接触状態が維持されるため、本発明では、負極活物質として、充放電による膨張収縮が大きく、電池寿命の点で改善の余地がある上記リチウムと合金化可能な活物質を用いることができる。これにより、全固体二次電池の大容量化と電池の長寿命化とが可能となる。
これらの炭素質材料は、黒鉛化の程度により難黒鉛化炭素質材料(ハードカーボンともいう。)と黒鉛系炭素質材料に分けることもできる。また炭素質材料は、特開昭62-22066号公報、特開平2-6856号公報、同3-45473号公報に記載される面間隔又は密度、結晶子の大きさを有することが好ましい。炭素質材料は、単一の材料である必要はなく、特開平5-90844号公報記載の天然黒鉛と人造黒鉛の混合物、特開平6-4516号公報記載の被覆層を有する黒鉛等を用いることもできる。
炭素質材料としては、ハードカーボン又は黒鉛が好ましく用いられ、黒鉛がより好ましく用いられる。
Sn、Si、Geを中心とする非晶質酸化物に併せて用いることができる負極活物質としては、リチウムイオン又はリチウム金属を吸蔵及び/又は放出できる炭素質材料、リチウム単体、リチウム合金、リチウムと合金化可能な活物質が好適に挙げられる。
負極活物質、例えば金属酸化物は、チタン原子を含有すること(チタン酸化物)も好ましく挙げられる。具体的には、Li4Ti5O12(チタン酸リチウム[LTO])がリチウムイオンの吸蔵放出時の体積変動が小さいことから急速充放電特性に優れ、電極の劣化が抑制されリチウムイオン二次電池の寿命向上が可能となる点で好ましい。
一般的に、これらの負極活物質を含有する負極(ケイ素元素含有活物質を含有するSi負極、スズ元素を有する活物質を含有するSn負極等)は、炭素負極(黒鉛及びアセチレンブラックなど)に比べて、より多くのLiイオンを吸蔵できる。すなわち、単位質量あたりのLiイオンの吸蔵量が増加する。そのため、電池容量を大きくすることができる。その結果、バッテリー駆動時間を長くすることができるという利点がある。
ケイ素元素含有活物質としては、例えば、Si、SiOx(0<x≦1)等のケイ素材料、更には、チタン、バナジウム、クロム、マンガン、ニッケル、銅、ランタン等を含むケイ素含有合金(例えば、LaSi2、VSi2、La-Si、Gd-Si、Ni-Si)、又は組織化した活物質(例えば、LaSi2/Si)、他にも、SnSiO3、SnSiS3等のケイ素元素及びスズ元素を含有する活物質等が挙げられる。なお、SiOxは、それ自体を負極活物質(半金属酸化物)として用いることができ、また、全固体二次電池の稼働によりSiを生成するため、リチウムと合金化可能な負極活物質(その前駆体物質)として用いることができる。
スズ元素を有する負極活物質としては、例えば、Sn、SnO、SnO2、SnS、SnS2、更には上記ケイ素元素及びスズ元素を含有する活物質等が挙げられる。また、酸化リチウムとの複合酸化物、例えば、Li2SnO2を挙げることもできる。
負極活物質層を形成する場合、負極活物質層の単位面積(cm2)当たりの負極活物質の質量(mg)(目付量)は特に限定されるものではない。設計された電池容量に応じて、適宜に決めることができる。
正極活物質及び負極活物質の表面は別の金属酸化物で表面被覆されていてもよい。表面被覆剤としてはTi、Nb、Ta、W、Zr、Al、Si又はLiを含有する金属酸化物等が挙げられる。具体的には、チタン酸スピネル、タンタル系酸化物、ニオブ系酸化物、ニオブ酸リチウム系化合物等が挙げられ、具体的には、Li4Ti5O12、Li2Ti2O5、LiTaO3、LiNbO3、LiAlO2、Li2ZrO3、Li2WO4、Li2TiO3、Li2B4O7、Li3PO4、Li2MoO4、Li3BO3、LiBO2、Li2CO3、Li2SiO3、SiO2、TiO2、ZrO2、Al2O3、B2O3等が挙げられる。
また、正極活物質又は負極活物質を含む電極表面は硫黄又はリンで表面処理されていてもよい。
更に、正極活物質又は負極活物質の粒子表面は、上記表面被覆の前後において活性光線又は活性気体(プラズマ等)により表面処理を施されていてもよい。
本発明の固体電解質組成物は、導電助剤を含有することもできる。導電助剤としては、特に制限はなく、一般的な導電助剤として知られているものを用いることができる。例えば、電子伝導性材料である、天然黒鉛、人造黒鉛などの黒鉛類、アセチレンブラック、ケッチェンブラック、ファーネスブラックなどのカーボンブラック類、ニードルコークスなどの無定形炭素、気相成長炭素繊維若しくはカーボンナノチューブなどの炭素繊維類、グラフェン若しくはフラーレンなどの炭素質材料であってもよいし、銅、ニッケルなどの金属粉、金属繊維でもよく、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセチレン、ポリフェニレン誘導体など導電性高分子を用いてもよい。
本発明において、活物質と導電助剤とを併用する場合、上記の導電助剤のうち、電池を充放電した際に周期律表第一族若しくは第二族に属する金属のイオン(好ましくはLiイオン)の挿入と放出が起きず、活物質として機能しないものを導電助剤とする。したがって、導電助剤の中でも、電池を充放電した際に活物質層中において活物質として機能しうるものは、導電助剤ではなく活物質に分類する。電池を充放電した際に活物質として機能するか否かは、一義的ではなく、活物質との組み合わせにより決定される。
導電助剤の、電極用組成物中の総含有量は、固形分100質量%に対して、0.1~10質量%が好ましく、0.1~5質量%がより好ましく、0.5~3質量%が更に好ましい。
本発明の固体電解質組成物は、分散媒を含有することが好ましい。この固体電解質組成物が分散媒を含有すると、分散媒としての通常の効果(組成均一性の向上、取扱性の向上等)に加え、非球状のバインダー粒子の凝集性を制御する効果が得られる。
分散媒は、本発明の固体電解質組成物に含まれる各成分を分散させるものであればよく、好ましくは、上述の非球状のバインダー粒子(このバインダーを構成するポリマー)を粒子状で分散させるものが選択される。
ケトン化合物としては、例えば、アセトン、メチルエチルケトン(MEK)、メチルイソブチルケトン、シクロヘキサノン、ジイソブチルケトン(DIBK)などが挙げられる。
芳香族化合物としては、例えば、ベンゼン、トルエン、キシレンなどの芳香族炭化水素化合物等が挙げられる。
脂肪族化合物としては、例えば、ヘキサン、ヘプタン、オクタン、デカンなどの脂肪族炭化水素化合物等が挙げられる。
ニトリル化合物としては、例えば、アセトニトリル、プロピオニトリル、イソブチロニトリルなどが挙げられる。
エステル化合物としては、例えば、酢酸エチル、酢酸ブチル、酢酸プロピル、酪酸プロピル、酪酸イソプロピル、酪酸ブチル、酪酸イソブチル、ペンタン酸ブチル、イソ酪酸エチル、イソ酪酸プロピル、イソ酪酸イソプロピル、イソ酪酸イソブチル、ピバル酸プロピル、ピバル酸イソプロピル、ピバル酸ブチル、ピバル酸イソブチルなどのカルボン酸エステル等が挙げられる。
非水系分散媒としては、上記芳香族化合物、脂肪族化合物等が挙げられる。
固体電解質組成物に含有される分散媒は、1種であっても、2種以上であってもよく、2種以上であることが好ましい。
本発明の固体電解質組成物は、上記各成分以外の他の成分として、所望により、リチウム塩、イオン液体、増粘剤、架橋剤(ラジカル重合、縮合重合又は開環重合により架橋反応するもの等)、重合開始剤(酸又はラジカルを熱又は光によって発生させるものなど)、消泡剤、レベリング剤、脱水剤、酸化防止剤等を含有することができる。
本発明の固体電解質組成物は、無機固体電解質、非球状のバインダー粒子、分散媒、更には他のバインダー、他の成分等を、例えば通常用いる各種の混合機で混合することにより、好ましくはスラリーとして、調製することができる。
混合方法は特に制限されず、一括して混合してもよく、順次混合してもよい。非球状のバインダー粒子は、通常、非球状のバインダー粒子の分散液として用いるが、これに限定されない。混合する環境は特に制限されないが、乾燥空気下又は不活性ガス下等が挙げられる。
本発明の全固体二次電池用シートは、全固体二次電池の構成層を形成しうるシート状成形体であって、その用途に応じて種々の態様を含む。例えば、固体電解質層に好ましく用いられるシート(固体電解質シートともいう。)、電極、又は電極と固体電解質層との積層体に好ましく用いられるシート(全固体二次電池用電極シート)等が挙げられる。
本発明の固体電解質シートとして、例えば、基材上に、本発明の固体電解質組成物で構成した層、通常固体電解質層と、必要により保護層とをこの順で有するシートが挙げられる。本発明の固体電解質組成物で形成される固体電解質層は、無機固体電解質とバインダーの1つとして非球状のバインダー粒子とを含有しており、上述のように、無機固体電解質同士の接触状態と固体粒子同士等の結着力とがバランスよく改善されている。固体電解質層において、無機固体電解質と非球状のバインダー粒子とは、非球状のバインダー粒子で無機固体電解質が結着した状態にある。この固体電解質層中の各成分の含有量は、特に限定されないが、好ましくは、本発明の固体電解質組成物の固形分中における各成分の含有量と同義である。固体電解質層は、後述する全固体二次電池における固体電解質層と同じであり、通常、活物質を含まない。固体電解質シートは、全固体二次電池の固体電解質層を構成する材料として好適に用いることができる。
本発明の電極シートは、全固体二次電池の負極活物質層として用いた場合に低抵抗及び長電池寿命を維持しつつも放電容量(放電容量密度)が更に増大する点で、負極活物質としてリチウムと合金可能な活物質を含む全固体二次電池用負極シートが好ましい態様である。
電極シートの活物質層は、活物質を含有する本発明の固体電解質組成物(電極用組成物)で形成されることが好ましく、特に、負極シートはリチウムと合金化可能な負極活物質を含有する本発明の固体電解質組成物で形成されることが好ましい。電極シートの活物質層は、本発明の固体電解質組成物で形成した固体電解質層と同様に、活物質及び導電助剤を含む固体粒子同士が非球状のバインダー粒子で結着されており、固体粒子同士の接触状態と固体粒子同士等の結着力とがバランスよく改善されている。電極シートの活物質層中の各成分の含有量は、特に限定されないが、好ましくは、本発明の固体電解質組成物(電極用組成物)の固形分中における各成分の含有量と同義である。この電極シートは、全固体二次電池の(負極又は正極)活物質層を構成する材料として好適に用いることができる。
全固体二次電池用シートの製造方法は、特に限定されない。全固体二次電池用シートは、本発明の固体電解質組成物を用いて製造することができる。例えば、上述のようにして本発明の固体電解質組成物を調製し、得られた固体電解質組成物を基材上(他の層を介していてもよい。)に製膜(塗布乾燥)して、基材上に固体電解質層(塗布乾燥層)を形成する方法が挙げられる。これにより、適宜の基材(集電体)と塗布乾燥層とを有する全固体二次電池用シートを作製することができる。ここで、塗布乾燥層とは、本発明の固体電解質組成物を塗布し、分散媒を乾燥させることにより形成される層(すなわち、本発明の固体電解質組成物を用いてなり、本発明の固体電解質組成物から分散媒を除去した組成からなる層)をいう。この塗布乾燥層は、無機固体電解質が非球状のバインダー粒子で結着されている。活物質層及び塗布乾燥層は、本発明の効果を損なわない範囲であれば分散媒が残存していてもよく、残存量としては、例えば、各層中、3質量%以下とすることができる。
上記製造方法において、本発明の固体電解質組成物はスラリーとして用いることが好ましく、所望により、公知の方法で本発明の固体電解質組成物をスラリー化することができる。本発明の固体電解質組成物の塗布、乾燥等の各工程については、下記全固体二次電池の製造方法において説明する。
また、全固体二次電池用シートの製造方法においては、基材、保護層(特に剥離シート)等を剥離することもできる。
本発明の全固体二次電池は、正極活物質層と、この正極活物質層に対向する負極活物質層と、正極活物質層及び負極活物質層の間に配置された固体電解質層とを有する。正極活物質層は、必要により正極集電体上に形成され、正極を構成する。負極活物質層は、必要により負極集電体上に形成され、負極を構成する。
全固体二次電池の、固体電解質層、正極活物質層及び負極活物質層の少なくとも1つの層は、本発明の固体電解質組成物で形成されることが好ましく、全ての層が本発明の固体電解質組成物で形成されることがより好ましい。この態様において、各層に含有される非球状バインダー等の各成分は同一であっても異なっていてもよい。本発明においては、負極活物質層がリチウムと合金化可能な活物質を含む本発明の固体電解質組成物で形成される態様も好ましい。負極活物質層がリチウムと合金化可能な活物質を含む本発明の固体電解質組成物で形成された全固体二次電池は、低抵抗及び長電池寿命を維持しつつも、更に大きな放電容量(放電容量密度)を示す。
本発明の固体電解質組成物で形成された、正極活物質層及び負極活物質層は、無機固体電解質と、活物質と、非球状のバインダー粒子と、適宜に、その他のバインダー、導電助剤及び上記各成分とを含有する。負極活物質層は、本発明の固体電解質組成物で形成されない場合、無機固体電解質と活物質と適宜に上記各成分を含有する層、上記負極活物質として説明した金属若しくは合金からなる層(リチウム金属層等)、更には上記負極活物質として説明した炭素質材料からなる層(シート)等が採用される。金属若しくは合金からなる層とは、例えば、リチウム等の金属若しくは合金の粉末を堆積又は成形してなる層、金属箔若しくは合金箔、及び蒸着膜等を包含する。金属若しくは合金からなる層及び炭素質材料からなる層の厚さは、それぞれ、特に限定されず、例えば、0.01~100μmとすることができる。本発明の固体電解質組成物で形成された固体電解質層は、周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有する固体電解質と非球状のバインダーと適宜に上記各成分とを含有する。
本発明の全固体二次電池においては、上述のように、固体電解質組成物又は活物質層は、本発明の固体電解質組成物又は上記全固体二次電池用シートで形成することができる。形成される固体電解質層及び活物質層は、好ましくは、含有する各成分及びその含有量について、特段の断りがない限り、固体電解質組成物の固形分におけるものと同じである。
負極活物質層、固体電解質層及び正極活物質層の厚さは、それぞれ、特に限定されない。各層の厚さは、一般的な全固体二次電池の寸法を考慮すると、それぞれ、5~1,000μmが好ましく、10μm以上500μm未満がより好ましい。本発明の全固体二次電池においては、正極活物質層、固体電解質層及び負極活物質層の少なくとも1層の厚さが、20μm以上500μm未満であることが更に好ましい。
本発明の全固体二次電池は、用途によっては、上記構造のまま全固体二次電池として使用してもよいが、乾電池の形態とするためには更に適当な筐体に封入して用いることが好ましい。筐体は、金属性のものであっても、樹脂(プラスチック)製のものであってもよい。金属性のものを用いる場合には、例えば、アルミニウム合金及びステンレス鋼製のものを挙げることができる。金属性の筐体は、正極側の筐体と負極側の筐体に分けて、それぞれ正極集電体及び負極集電体と電気的に接続させることが好ましい。正極側の筐体と負極側の筐体とは、短絡防止用のガスケットを介して接合され、一体化されることが好ましい。
本発明の固体電解質組成物は、固体電解質層、負極活物質層又は正極活物質層の形成材料として好ましく用いることができる。また、本発明の全固体二次電池用シートは、固体電解質層、負極活物質層又は正極活物質層として好適である。
本明細書において、正極活物質層(以下、正極層とも称す。)と負極活物質層(以下、負極層とも称す。)をあわせて電極層又は活物質層と称することがある。
全固体二次電池10においては、固体電解質層及び活物質層のいずれか1つが本発明の固体電解質組成物又は上記全固体二次電池用シートを用いて形成される。好ましい態様では全ての層が本発明の固体電解質組成物又は上記全固体二次電池用シートを用いて形成され、好ましい別の態様では、負極活物質層がリチウムと合金化可能な活物質を含む、本発明の固体電解質組成物若しくは全固体二次電池用負極シートで形成される。
固体電解質層及び正極活物質層少なくとも一方を本発明の固体電解質組成物又は上記全固体二次電池用シートを用いて形成する場合、負極活物質層は、負極活物質としての金属若しくは合金からなる層、負極活物質としての炭素質材料からなる層等を用いて、更には充電時に負極集電体等に周期律表第一族若しくは第二族に属する金属を析出させることにより、形成することもできる。
正極活物質層4、固体電解質層3及び負極活物質層2が含有する各成分は、それぞれ、互いに同種であっても異種であってもよい。
本発明において、正極集電体及び負極集電体のいずれか、又は、両方を合わせて、単に、集電体と称することがある。
正極集電体を形成する材料としては、アルミニウム、アルミニウム合金、ステンレス鋼、ニッケル及びチタンなどの他に、アルミニウム又はステンレス鋼の表面にカーボン、ニッケル、チタンあるいは銀を処理させたもの(薄膜を形成したもの)が好ましく、その中でも、アルミニウム及びアルミニウム合金がより好ましい。
負極集電体を形成する材料としては、アルミニウム、銅、銅合金、ステンレス鋼、ニッケル及びチタンなどの他に、アルミニウム、銅、銅合金又はステンレス鋼の表面にカーボン、ニッケル、チタンあるいは銀を処理させたものが好ましく、アルミニウム、銅、銅合金及びステンレス鋼がより好ましい。
集電体の厚みは、特に限定されないが、1~500μmが好ましい。また、集電体表面は、表面処理により凹凸を付けることも好ましい。
本発明の全固体二次電池は、特に限定されず、固体電解質組成物の製造方法を経て(含んで)製造することができる。用いる原料に着目すると、本発明の固体電解質組成物を用いて製造することもできる。具体的には、全固体二次電池は、上述のようにして本発明の固体電解質組成物を調製し、得られた固体電解質組成物等を用いて、全固体二次電池の固体電解質層及び/又は活物質層を形成することにより、製造できる。これにより、充放電を繰り返しても優れた電池性能を維持する全固体二次電池を製造できる。固体電解質組成物の調製方法は上述の通りであるので省略する。
例えば、正極集電体である金属箔上に、正極用組成物として本発明の固体電解質組成物(電極用組成物)を塗布して正極活物質層を形成し、全固体二次電池用正極シートを作製する。次いで、この正極活物質層の上に、固体電解質層を形成するための本発明の固体電解質組成物を塗布して、固体電解質層を形成する。更に、固体電解質層の上に、負極用組成物として本発明の固体電解質組成物(電極用組成物)を塗布して、負極活物質層を形成する。負極活物質層の上に、負極集電体(金属箔)を重ねることにより、正極活物質層と負極活物質層の間に固体電解質層が挟まれた構造の全固体二次電池を得ることができる。必要によりこれを筐体に封入して所望の全固体二次電池とすることができる。
また、各層の形成方法を逆にして、負極集電体上に、負極活物質層、固体電解質層及び正極活物質層を形成し、正極集電体を重ねて、全固体二次電池を製造することもできる。
また別の方法として、次の方法が挙げられる。すなわち、上記のようにして、全固体二次電池用正極シート及び全固体二次電池用負極シートを作製する。また、これとは別に、固体電解質組成物を基材上に塗布して、固体電解質層からなる固体電解質シートを作製する。更に、全固体二次電池用正極シート及び全固体二次電池用負極シートで、基材から剥がした固体電解質層を挟むように積層する。このようにして、全固体二次電池を製造することができる。
上記各製造方法において、固体電解質層等は、例えば基板若しくは活物質層上で、固体電解質組成物等を後述する加圧条件下で加圧成形して形成することもできるし、固体電解質又は活物質のシート成形体を用いることもできる。
全固体二次電池の製造に用いる組成物の塗布方法は、特に限定されず、適宜に選択できる。例えば、塗布(好ましくは湿式塗布)、スプレー塗布、スピンコート塗布、ディップコート、スリット塗布、ストライプ塗布及びバーコート塗布が挙げられる。
このとき、組成物は、それぞれ塗布した後に乾燥処理を施してもよいし、重層塗布した後に乾燥処理をしてもよい。乾燥温度は特に限定されない。下限は30℃以上が好ましく、60℃以上がより好ましく、80℃以上が更に好ましい。上限は、300℃以下が好ましく、250℃以下がより好ましく、200℃以下が更に好ましい。このような温度範囲で加熱することで、分散媒を除去し、固体状態(塗布乾燥層)にすることができる。また、温度を高くしすぎず、全固体二次電池の各部材を損傷せずに済むため好ましい。
また、塗布した組成物は、加圧と同時に加熱してもよい。加熱温度としては、特に限定されず、一般的には30~300℃の範囲である。無機固体電解質のガラス転移温度よりも高い温度でプレスすることもできる。
加圧は塗布溶媒又は分散媒を予め乾燥させた状態で行ってもよいし、塗布溶媒又は分散媒が残存している状態で行ってもよい。
なお、各組成物は同時に塗布しても良いし、塗布乾燥プレスを同時及び/又は逐次行っても良い。別々の基材に塗布した後に、転写により積層してもよい。
プレス時間は短時間(例えば数時間以内)で高い圧力をかけてもよいし、長時間(1日以上)かけて中程度の圧力をかけてもよい。全固体二次電池用シート以外、例えば全固体二次電池の場合には、中程度の圧力をかけ続けるために、全固体二次電池の拘束具(ネジ締め圧等)を用いることもできる。
プレス圧はシート面等の被圧部に対して均一であっても異なる圧であってもよい。
プレス圧は被圧部の面積や膜厚に応じて変化させることができる。また同一部位を段階的に異なる圧力で変えることもできる。
プレス面は平滑であっても粗面化されていてもよい。
上記のようにして製造した全固体二次電池は、製造後又は使用前に初期化を行うことが好ましい。初期化は、特に限定されず、例えば、プレス圧を高めた状態で初充放電を行い、その後、全固体二次電池の一般使用圧力になるまで圧力を解放することにより、行うことができる。
本発明の全固体二次電池は種々の用途に適用することができる。適用態様には特に制限はないが、例えば、電子機器に搭載する場合、ノートパソコン、ペン入力パソコン、モバイルパソコン、電子ブックプレーヤー、携帯電話、コードレスフォン子機、ページャー、ハンディーターミナル、携帯ファックス、携帯コピー、携帯プリンター、ヘッドフォンステレオ、ビデオムービー、液晶テレビ、ハンディークリーナー、ポータブルCD、ミニディスク、電気シェーバー、トランシーバー、電子手帳、電卓、携帯テープレコーダー、ラジオ、バックアップ電源、メモリーカードなどが挙げられる。その他民生用として、自動車(電気自動車等)、電動車両、モーター、照明器具、玩具、ゲーム機器、ロードコンディショナー、時計、ストロボ、カメラ、医療機器(ペースメーカー、補聴器、肩もみ機など)などが挙げられる。更に、各種軍需用、宇宙用として用いることができる。また、太陽電池と組み合わせることもできる。
500mL3つ口フラスコに、2,2-ビス(ヒドロキシメチル)酪酸2.5gと、PEG200(ポリエチレングリコール)10.6gと、両末端水酸基水素化ポリブタジエンGI-1000(商品名、NISSO PB GI-1000)19.9g、4,4’-ジイソシアン酸メチレンジフェニル20.8gとを加え、テトラヒドロフラン(THF)215gに溶解した。この溶液に、ネオスタンU-600(商品名、日東化成社製)80mgを添加して、60℃で5時間攪伴した。この溶液にメタノール1.8gを加えて、60℃で30分撹拌を続け、バインダー形成ポリマーP-1を合成し、ポリマー溶液P-1を得た。
上記ポリマーP-1の合成において、各構成成分を導く化合物として下記表1-1に記載の構成成分を導く化合物を同表に記載の含有量となる使用量で用いたこと以外は、上記ポリマーP-1の合成と同様にして、ポリマーP-2~P-10(ポリマー溶液P-2~P-10)をそれぞれ合成(調製)した。
ポリマーP-1~P-10は、いずれも、官能基群(a)に含まれる官能基のうちカルボキシ基を側鎖に有するポリウレタンポリマーである。
還流冷却管、ガス導入コックを付した500mL3つ口フラスコに、ラウリルメタクリレート12.0gと、アクリル酸6.0gと、メチルメタクリレート24.0gと、アクリロニトリル18.0gとを加え、酢酸ブチル130gに溶解した。その後、流速200mL/minにて窒素ガスを30分間導入した後に80℃に昇温した。これに、別容器にて調製した液(ラジカル重合開始剤V-601(商品名、和光純薬工業社製)0.6gと酢酸ブチル10gを混合した液)を2時間かけて滴下し、引き続き80℃で2時間攪拌を継続した。その後、ラジカル重合開始剤V-601を更に1.2g添加し、95℃で2時間攪拌した。得られた溶液を室温まで冷却して、バインダー形成ポリマーP-11を合成し、ポリマー溶液P-11を得た。
ポリマーP-11は、官能基群(a)に含まれる官能基のうちカルボキシ基及びシアノ基を側鎖に有する(メタ)アクリルポリマーであり、これら官能基を有する構成成分のポリマー中の含有量は40質量%である。
上記ポリマーP-11の合成において、メチルメタクリレート24.0gを18.0gに変え、アクリロニトリル18.0gをヒドロキシエチルアクリレート24.0gに変えたこと以外は、上記ポリマーP-11の合成と同様にして、ポリマーP-12(ポリマー溶液P-12)を合成(調製)した。
ポリマーP-12は、官能基群(a)に含まれる官能基のうちカルボキシ基及びヒドロキシ基を側鎖に有する(メタ)アクリルポリマーであり、これら官能基を有する構成成分のポリマー中の含有量は50質量%である。
得られた各ポリマーの質量平均分子量(Mw)を、上述の方法により、測定した。その結果を表1-1及び表1-2(まとめて表1という。)に示す。
得られた各ポリマーのガラス転移温(Tg)を、上述の方法により、測定した。その結果を表1に示す。なお、複数のガラス転移温度を観測した場合、表1-1において「/」を介して低温のTgから順に表記した。
なお、バインダー形成ポリマーP-8及びP-9はバインダー形成ポリマーP-1と構成成分が同じであるので、記載していない。
表1-1において、構成成分1は式(I-1)で表される構成成分を示す。構成成分2は、RP2がカルボキシ基を有する脂肪族の炭化水素基である、式(I-3)で表される構成成分(上記式(I-3A)で表される構成成分に相当する。)を示す。構成成分3は、RP2が分子鎖としてポリアルキレンオキシド鎖である、式(I-3)で表される構成成分(上記式(I-3B)で表される構成成分に相当する。)を示す。構成成分4は、RP2が分子鎖として上記炭化水素ポリマー鎖である、式(I-3)で表される構成成分(上記式(I-3C)で表される構成成分に相当する。)を示す。構成成分5は、その他の構成成分を示す。具体的には、RP2が分子鎖としてポリカーボネート鎖である、式(I-3)で表される構成成分(バインダー形成ポリマーP-7)と、RP2がカルボキシ基を有さない脂肪族の炭化水素基である、式(I-3)で表される構成成分(バインダー形成ポリマーP-10、上記式(I-3A)で表される構成成分に相当する。)とである。
MDI:4,4’-ジイソシアン酸メチレンジフェニル(富士フイルム和光純薬製)
HMDI:4,4’-ジシクロヘキシルメタンジイソシアネート(東京化成工業社製)
TDI:2,4-トリレンジイソシアネート(東京化成工業社製)
DMBA:2,2-ビス(ヒドロキシメチル)酪酸(東京化成工業社製)
PEG200:ポリエチレングリコール(富士フイルム和光純薬社製、数平均分子量200)
PEG400:ポリエチレングリコール(富士フイルム和光純薬社製、数平均分子量400)
PPG400:ポリプロピレングリコール(アルドリッチ社製、数平均分子量400)
GI-1000:両末端水酸基変性水素化ポリブタジエン(NISSO PB GI-1000(商品名)、日本曹達社製、数平均分子量1,500)
EPOL:両末端水酸基変性水素化ポリイソプレン(エポール(商品名)、出光興産社製、数平均分子量2,500)
G3450J:ポリカーボネートジオール(デュラノールG3450J(商品名)、旭化成社製、数平均分子量800)
BD:1,4-ブタンジオール
LMA:ラウリルメタクリレート(富士フイルム和光純薬製)
AA:アクリル酸(富士フイルム和光純薬製)
MMA:メチルメタクリレート(富士フイルム和光純薬製)
AN:アクリロニトリル(富士フイルム和光純薬製)
HEA:ドロキシエチルアクリレート(富士フイルム和光純薬製)
wt%:質量%を意味する。
500mL3つ口フラスコにオクタン(沸点135℃)135gを加え、500rpmで撹拌しながら、上記で調製したポリマー溶液P-1(30g)を室温で1時間かけて滴下し、ポリマーP-1の乳化液を得た。窒素ガスフローしながらこの乳化液を85℃で120分加熱した。更に、残留物にオクタン50gを加えて85℃で60分加熱する操作を4回繰り返して、THF(沸点66℃)を除去してポリマーP-1の5質量%オクタン分散液を得た。
上記分散液PA-1の調製において、ポリマー溶液及び分散媒を下記表2に記載のポリマー溶液及び分散媒に変更したこと以外は、上記分散液PA-1の調製と同様にして、分散液PA-2~PA-12をそれぞれ調製した。
なお、分散媒として用いたトルエンの沸点は110℃である。
上記分散液PA-1の調製において、ポリマー溶液を下記表2に記載のポリマー溶液に変更し、その後超音波ホモジナイザーにて1分間の分散処理を行ったこと以外は、上記分散液PA-1の調製と同様にして、分散液PA-13及びPA-14をそれぞれ調製した。
非球状のバインダー粒子の分散液CP-1を、特許文献2(特開2015-167126号公報)の実施例A-5を参考にして、調製した。すなわち、200mLの3口フラスコに、プロピレングリコールモノメチルエーテルアセテート(PGMEA)5gを加えて窒素ガス気流下で80℃に加熱した。これに、メタクリル酸ベンジル15.5g、メタクリル酸1.0g、メタクリル酸2-ヒドロキシエチル3.2g及びV-601(0.23g、和光純薬社製)のPGMEA45g溶液を、4時間かけて滴下した。滴下終了後80℃で更に2時間加熱攪拌した。得られたポリマー溶液をヘキサン/酢酸エチル(80/20)1Lで晶析させ、得られたポリマーを80℃で6時間真空乾燥した。得られたメタクリル系ポリマーの質量平均分子量は52300、ガラス転移温度は23℃であった。
続いて、ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを180個投入し、得られたポリマー1.0g、分散媒として、トルエン15.0gを投入した後に、遊星ボールミルP-7(フリッチュ社製)に容器をセットし、25℃で、回転数300rpmで2時間機械分散を続け、メタクリル系ポリマーからなる粒子が粉砕された非球状ポリマー粒子の分散液を得た。この非球状ポリマー粒子は二次粒子を含んでいない。
還流冷却管、ガス導入コックを付した5L三口フラスコに水を400質量部と、メチルメタクリレート(和光純薬工業社製)200質量部と、スチレン(和光純薬工業社製)50質量部と、ジビニルベンゼン(和光純薬工業社製)5質量部と、ドデシルベンゼンスルホン酸ナトリウム(和光純薬工業社製)10質量部と、アゾビスブチロニトリル(和光純薬工業社製)10質量部を加え、流速200mL/minにて窒素ガスを10分間導入した後に80℃に昇温した。これに、別容器にて調製した液(ノニルフェノキシポリエチレングリコールアクリレート(日立化成工業社製)400質量部と、スチレン(和光純薬工業社製)100質量部と、水800質量部と、アゾビスブチロニトリル(和光純薬工業社製)10質量部を混合した液)を滴下し、引き続き80℃で5時間攪拌を継続した。その後、デカリン(和光純薬工業社製)15,000質量部を加え、十分に撹拌した後、水を減圧乾燥により除去して、球状のバインダー粒子の分散液CP-2を得た。
ポリマーとして水素添加スチレンブタジエンゴム(HSBC、DYNARON1321P(商品名)、JSR社製、スチレン含有量10質量%、質量平均分子量229,000)をトルエンに溶解して、ポリマー溶液CP-3を調製した。
得られた各バインダー粒子について、上述の方法によりTEM画像を撮影して、バインダー粒子の形状を確認したところ、分散液PA-1~PA-12中のバインダーはウレタンポリマーの一次粒子からなる非球状の二次粒子を含んでおり、分散液PA-13及びPA-14中のバインダーは(メタ)アクリルポリマーの一次粒子からなる非球状の二次粒子を含んでおり、CP-1中のバインダーは非球状の一次粒子であり、分散液CP-2中のバインダーは球状であった。また、上記TEM画像を用いた上述の方法により、二次粒子のアスペクト比、平均二次粒径及び二次粒子の比率を測定した。更に、バインダー粒子を形成する一次粒子の平均一次粒径を上述の方法により測定した。また得られた平均二次粒径及び平均一次粒径から粒径比[平均二次粒径÷平均一次粒径]を算出した。それらの結果を表2に示す。
なお、球状のバインダー粒子の分散液CP-2において、バインダー粒子は二次粒子を含んでいないが、バインダー粒子のアスペクト比を表2の「二次粒子のアスペクト」欄に記載した。
上述のフィルムを用いた測定方法により、合成した各バインダー形成ポリマー及び上記HSBRの破断伸びを測定した。その結果を表2に示す。
粒径比:一次粒子の平均一次粒径に対する二次粒子の平均二次粒径の比
アスペクト比:二次粒子の平均径に対する平均長さの比
二次粒子の比率:二次粒子と一次粒子との合計100%に対する二次粒子の比率
分散液No.PA-3の分散媒は、オクタンとトルエンの1:1(質量比)混合分散媒である。
硫化物系無機固体電解質として、T.Ohtomo,A.Hayashi,M.Tatsumisago,Y.Tsuchida,S.Hama,K.Kawamoto,Journal of Power Sources,233,(2013),pp231-235及びA.Hayashi,S.Hama,H.Morimoto,M.Tatsumisago,T.Minami,Chem.Lett.,(2001),pp872-873の非特許文献を参考にして、Li-P-S系ガラスを合成した。
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを66個投入し、上記硫化リチウムと五硫化二リンの混合物全量を投入し、アルゴン雰囲気下で容器を密閉した。フリッチュ社製の遊星ボールミルP-7(商品名)にこの容器をセットし、温度25℃、回転数510rpmで20時間メカニカルミリングを行い、黄色粉体の硫化物系無機固体電解質(Li-P-S系ガラス、LPS)6.20gを得た。イオン伝導度は0.28mS/cmであった。上記測定方法によるLi-P-S系ガラスの平均粒径は15μmであった。
得られた非球状のバインダー粒子を用いて、固体電解質組成物、全固体二次電池用シート及び全固体二次電池をそれぞれ製造して、全固体二次電池用電極シート及び全固体二次電池について下記特性を評価した。その結果を表5に示す。
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを180個投入し、上記合成例13で合成したLPSを4.85g、表3に示す分散液を固形分相当で0.15g、及び分散媒としてヘプタンを8.0g投入した。その後に、この容器をフリッチュ社製遊星ボールミルP-7(商品名)にセットし、温度25℃、回転数250rpmで60分間混合を続けて、固体電解質組成物S-1~S-3をそれぞれ調製した。
上記で調製した各固体電解質組成物を、支持体として、厚み20μmのアルミニウム箔に、ベーカー式アプリケーター(商品名:SA-201、テスター産業社製)により塗布し(目付量:7mg/cm2)、80℃で1時間加熱した。こうして、アルミニウム箔と固体電解質層との積層構造を有する固体電解質シートSS-1~SS-3をそれぞれ作製した。
(負極用組成物a-1の調製)
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを180個投入し、合成例13で合成したLPSを4.6g、及び、分散媒としてヘプタン12.3g(総量)を投入した。その後、この容器に、負極活物質としてSi(アルドリッチ社製)を4.6g、導電助剤としてアセチレンブラック(AB)を0.7g、非球状のバインダー粒子の分散液PA-1を固形分相当で0.1g投入し、遊星ボールミルP-7に容器をセットして、温度25℃、回転数200rpmで30分間混合を続け、負極用組成物a-1を調製した。
負極用組成物a-1の調製において、無機固体電解質、負極活物質、バインダー粒子の分散液及び導電助剤の種類及び使用量を表4に示すように変更したこと以外は、負極用組成物a-1の調製と同様にして、負極用組成物a-2~a-23をそれぞれ調製した。
負極用組成物a-17及びa-18の調製においては、負極活物質として、黒鉛及びSiの2種を、それぞれ、2.3gずつ用いた。
なお、負極用組成物a-19~a-21は比較のための負極用組成物である。
上記で調製した負極用組成物を、負極集電体として厚み15μmのステンレス鋼(SUS)箔に、ベーカー式アプリケーター(商品名:SA-201、テスター産業社製)により、表4に示す目付量となるように、塗布し、80℃で1時間加熱し、更に110℃で1時間加熱して、負極用組成物を乾燥した。その後、ヒートプレス機を用いて、乾燥させた負極用組成物(塗布乾燥層)を120℃で加熱しながら加圧(20MPa、1分間)して、負極活物質層とSUS箔との積層構造を有する全固体二次電池用負極シートA-1~A-23をそれぞれ作製した。
なお、全固体二次電池用負極シートA-19~A-21は比較のため負極シートである。
(正極用組成物c-1の調製)
ジルコニア製45mL容器(フリッチュ社製)に、直径5mmのジルコニアビーズを180個投入し、合成例13で合成したLPS系ガラスを1.7g、及び、分散媒としてヘプタン12.3g(総量)を投入した。フリッチュ社製遊星ボールミルP-7(商品名)にこの容器をセットし、25℃で、回転数200pmで30分間攪拌した。その後、この容器に、正極活物質としてLiNi1/3Co1/3Mn1/3O2(NMC、アルドリッチ社製)を8.0g、導電助剤としてアセチレンブラック(AB)を0.2g、非球状のバインダー粒子の分散液PA-1を固形分相当で0.1g投入し、遊星ボールミルP-7に容器をセットし、温度25℃、回転数200rpmで30分間混合を続け、正極用組成物c-1を調製した。
(正極用組成物c-2~c-6の調製)
正極用組成物c-1の調製において、正極活物質及びバインダー粒子の分散液の種類を表4に示すように変更したこと以外は、正極用組成物c-1の調製と同様にして、正極用組成物c-2~c-6をそれぞれ調製した。
なお、正極用組成物c-4~c-6は比較のための正極用組成物である。
上記で調製した正極用組成物を、集電体として厚み20μmのアルミニウム箔(正極集電体)に、ベーカー式アプリケーター(商品名:SA-201、テスター産業社製)により、表4に示す目付量となるように、塗布し、80℃で1時間加熱し、更に110℃で1時間加熱して、正極用組成物を乾燥した。その後、ヒートプレス機を用いて、乾燥させた正極用組成物(塗布乾燥層)を120℃で加熱しながら加圧(20MPa、1分間)して、正極活物質層とアルミニウム箔との積層構造を有する全固体二次電池用正極シートC-1~C-6をそれぞれ作製した。
なお、全固体二次電池用正極シートC-4~C-6は比較のため正極シートである。
Si:シリコン
Sn:スズ
SiO:一酸化ケイ素
C:黒鉛
NMC:LiNi1/3Co1/3Mn1/3O2
LCO:LiCoO2
LPS:合成例13で合成した硫化物系無機固体電解質(Li-P-S系ガラス)
LLZ:Li7La3Zr2O12
AB:アセチレンブラック
(電極シートの準備)
下記の屈曲試験を行った電極シートを用いて全固体二次電池を製造した。
屈曲試験は、作製した全固体二次電池用負極シート及び全固体二次電池用正極シートそれぞれについて、後述する<評価1:全固体二次電池用負極シートの膜強度試験>において、直径10mmのマンドレルを用いて3回繰り返して屈曲させたこと以外は、<評価1:全固体二次電池用負極シートの膜強度試験>と同様にして、行った。
上記屈曲試験を行った各全固体二次電池用負極シートの負極活物質層上に、上記で調製した表5に示す固体電解質組成物を、表5に示す目付量となるように、アプリケーターにより塗布し、80℃で1時間加熱後、更に110℃で6時間乾燥させた。負極活物質層上に塗布乾燥層を形成したシートを、ヒートプレス機を用いて、加熱(120℃)しながら加圧(30MPa、1分間)して、固体電解質層と負極活物質層とステンレス箔とをこの順で積層した構造を有するシートを作製して、直径15mmの円板状に切り出した(円盤状負極シートという。)。
上記屈曲試験を行った表5に示す全固体二次電池用正極シートを直径13mmの円板状に切り出した。こうして得た円盤状正極シートの正極活物質層と、円盤状負極シートの固体電解質層が向かい合うように、円盤状負極シートと円盤状正極シートとを配置(積層)した後に、ヒートプレス機を用いて、加熱(120℃)しながら加圧(40MPa、1分間)した。こうして、図1に示す積層構成、すなわちアルミニウム箔と正極活物質層と固体電解質層と負極活物質層(各層の膜厚を表5に示す。)とSUS箔とをこの順で積層した構造を有する全固体二次電池用積層体を作製した。
このようにして作製した全固体二次電池用積層体12を、図2に示すように、スペーサーとワッシャー(図2において図示せず)を組み込んだステンレス製の2032型コインケース11に入れ、2032型コインケース11をかしめることで、No.101~103、106~130、c01及びc03の全固体二次電池13を作製した。
上記全固体二次電池No.101の製造において、下記のようにして固体電解質層を負極活物質層に転写して作製した円盤状負極シートを用いたこと以外は上記全固体二次電池No.101の製造と同様にして、全固体二次電池No.104、105及びc02をそれぞれ製造した。
- 転写法による円盤状負極シートの作製 -
上記屈曲試験を行った各全固体二次電池用負極シートの負極活物質層上に、上記で調製した表5に示す固体電解質シート(作製時の目付量を表5に示す)を、向かい合わせて配置し、得られたシート積層体をその厚さ方向にプレス機を用いて加圧(30MPa、1分間)し、固体電解質シートの支持体であるアルミニウム箔を剥離した。こうして、固体電解質層と負極活物質層とステンレス箔とをこの順で積層した構造を有するシートを作製した。このシートを直径15mmの円板状に切り出して、円盤状負極シートを作製した。
全固体二次電池用負極シートA-1~A-23における負極活物質層の膜強度を、マンドレル試験機を用いた耐屈曲性試験(JIS K5600-5-1に準拠)により、評価した。
具体的には、全固体二次電池用負極シートから、幅50mm、長さ100mmの短冊状に切り出した試験片を用いて、負極活物質層をマンドレルとは逆側(SUS箔をマンドレル側)、かつ試験片の幅方向がマンドレルの軸に平行となるようにセットし、マンドレルの外周面に沿って180°屈曲(1回)させた後、負極活物質層の表面にヒビ又は割れの有無を目視で観察した。この屈曲試験は、まず、直径32mmのマンドレルを用いて行い、ヒビ又は割れが発生していない場合、マンドレルの直径(mm)を、25、20、16、12、10、8、6、5、4、3、2と徐々に小さくしていき、最初にヒビ又は割れが発生したマンドレルの直径を記録した。
このヒビ又は割れ剥離が最初に発生したマンドレルの直径(欠陥発生径)が下記評価基準のいずれに含まれるかにより、評価した。本試験において、欠陥発生径が小さいほど固体粒子が強固に結着し、かつ負極活物質の屈曲に対してよく追従して膜強度が高いことを示し、評価基準C以上が合格レベルである。
-評価基準-
A:5mm以下
B:6mm又は8mm
C:10mm
D:12mm又は16mm
E:20mm又は25mm
F:32mm
上記で製造した全固体二次電池の放電容量を、充放電評価装置「TOSCAT-3000」(商品名、東洋システム社製)により、測定した。具体的には、全固体二次電池を電池電圧が4.2Vになるまで電流値0.2mAで充電した後、電池電圧が3.0Vになるまで電流値0.2mAで放電した。この充電1回と放電1回とを充放電を1サイクルとして、3サイクル繰り返して充放電した。3サイクル目の放電容量を求めた。この放電容量を、正極活物質層の表面積100cm2当たりに換算して、全固体二次電池の放電容量(表5において単に「容量」と表記する。)とした。この放電容量が以下の評価基準のいずれに含まれるかにより、評価した。本試験において、評価基準C以上が合格レベルである。
-評価基準-
A:200mAh以上
B:160mAh以上、200mAh未満
C:100mAh以上、160mAh未満
D: 60mAh以上、100mAh未満
E: 60mAh未満
各全固体二次電池について、上記評価2で測定した放電容量(表面積100cm2当たりの換算値)を、正極活物質層、固体電解質層及び負極活物質層の合計体積(両集電体の体積を除く)で除して、放電容量密度(表5において単に「容量密度」と表記する。)を算出した。本試験において、評価基準C以上が合格レベルである。
-評価基準-
A:180Ah/L以上
B:130Ah/L以上、180Ah/L未満
C: 90Ah/L以上、130Ah/L未満
D: 60Ah/L以上、 90Ah/L未満
E: 60Ah/L未満
上記で製造した各全固体二次電池の抵抗を、充放電評価装置「TOSCAT-3000」(商品名、東洋システム社製)により、測定した。具体的には、全固体二次電池を電池電圧が4.2Vになるまで電流値0.2mAで充電した後、電池電圧が3.0Vになるまで電流値2.0mAで放電した。放電開始10秒後の電池電圧を読み取り、以下の評価基準のいずれに含まれるかにより、評価した。本試験において、電池電圧が高いほど、全固体二次電池の抵抗が小さいことを示し、評価基準C以上が合格レベルである。
-評価基準-
A:4.1V以上
B:4.0V以上、4.1V未満
C:3.8V以上、4.0V未満
D:3.6V以上、3.8V未満
E:3.6V未満
各試料No.の全固体二次電池を10検体製造し、10検体の全固体二次電池について、充放電評価装置「TOSCAT-3000」(商品名、東洋システム社製)により、放電容量を測定して、電池寿命(表5において単に「寿命」と表記する。)を評価した。具体的には、各全固体二次電池を、それぞれ、電池電圧が4.2Vになるまで電流値0.2mAで充電した後、電池電圧が3.0Vになるまで電流値2.0mAで放電した。この充電1回と放電1回とを充放電1サイクルとして、同じ条件で充放電を100サイクル繰返して行った。充放電5サイクル目の放電容量と充放電100サイクル目の放電容量とを次のようにして求めた。10検体の電池の内、性能の上下2検体を除く6検体の全固体二次電池における、5サイクル目と100サイクル目との放電容量の平均値をそれぞれ求めて、5サイクル目の平均放電容量に対する100サイクル目の平均放電容量の割合([100サイクル目の平均放電容量/5サイクル目の平均放電容量]×100(%))を算出した。この割合が以下の評価基準のいずれに含まれるかにより、評価した。本試験において、上記割合が高いほど、電池寿命が長く、充放電を複数回繰り返しても(長期の使用においても)初期の電池性能(放電容量及び放電容量密度)を維持できる。本試験において、評価基準C以上が合格レベルである。
-評価基準-
A:85%以上
B:75%以上、85%未満
C:65%以上、75%未満
D:55%以上、65%未満
E:55%未満
本発明で規定する非球状のバインダー粒子を含有しない固体電解質組成物(電極用組成物)で形成した全固体二次電池用負極シートA-19~A-21は、いずれも、十分な膜強度を発揮しない。しかも、バインダーとして、一次粒子からなるバインダー粒子を用いた全固体二次電池c01及び球状のバインダー粒子を用いた全固体二次電池c02は、抵抗が十分ではなく、電池寿命にも劣る。また、溶解型バインダーを用いた全固体二次電池c03は、放電容量、放電容量密度及び抵抗が十分ではなく、電池寿命にも劣る。
これに対して、本発明で規定する非球状のバインダー粒子を含有する固体電解質組成物(電極用組成物)で形成した全固体二次電池用負極シートA-1~A-18、A-22及びA-23は、いずれも、十分な膜強度を示している。また、正極活物質層、固体電解質層及び負極活物質層の少なくとも1層を本発明で規定する非球状のバインダー粒子を含有する固体電解質組成物又は電極用組成物で形成した全固体二次電池101~130は、いずれも、放電容量、放電容量密度及び抵抗に優れ、長い電池寿命を示すものである。このように、本発明で規定する非球状のバインダー粒子を含有する固体電解質組成物は、全固体二次電池において、固体粒子間の界面抵抗の上昇を抑えて固体粒子を強固に結着させ、小さな抵抗を示し、かつ、充放電を繰り返しても優れた放電容量及び放電容量密度を維持できることに寄与する。特に、正極活物質層、固体電解質層及び負極活物質層を本発明で規定する固体電解質組成物又は電極用組成物で形成した全固体二次電池は、界面抵抗の低減、結着性及び電池性能を高い水準で鼎立できる。
2 負極活物質層
3 固体電解質層
4 正極活物質層
5 正極集電体
6 作動部位
10 全固体二次電池
11 2032型コインケース
12 全固体二次電池用積層体
13 全固体二次電池
Claims (14)
- 周期律表第一族若しくは第二族に属する金属のイオンの伝導性を有する無機固体電解質と、ポリマーからなるバインダーとを含有する固体電解質組成物であって、
前記バインダーが、1~1,000nmの平均一次粒径を持つ一次粒子で形成された二次粒子からなる、非球状のバインダー粒子を含む、固体電解質組成物。 - 前記二次粒子が、前記平均一次粒径の2~1,000倍の平均粒径を有する、請求項1に記載の固体電解質組成物。
- 前記二次粒子が、1.1~1,000のアスペクト比を有する、請求項1又は2に記載の固体電解質組成物。
- 前記ポリマーが、10%以上の破断伸びを示す、請求項1~3のいずれか1項に記載の固体電解質組成物。
- 分散媒を含有する請求項1~4のいずれか1項に記載の固体電解質組成物。
- 活物質を含有する請求項1~5のいずれか1項に記載の固体電解質組成物。
- 前記活物質が、リチウムと合金化可能な活物質である請求項6に記載の固体電解質組成物。
- 前記ポリマーが、下記官能基群(a)から選ばれる少なくとも1つの官能基を有する請求項1~7のいずれか1項に記載の固体電解質組成物。
官能基群(a)
酸性官能基、塩基性官能基、ヒドロキシ基、シアノ基、アルコキシシリル基、アリール基、ヘテロアリール基、3環以上が縮環した脂肪族炭化水素環基 - 前記ポリマーが、ポリアミド、ポリイミド、ポリウレア、ポリウレタン又は(メタ)アクリルポリマーある、請求項1~8のいずれか1項に記載の固体電解質組成物。
- 前記無機固体電解質が、硫化物系固体電解質である請求項1~9のいずれか1項に記載の固体電解質組成物。
- 請求項1~10のいずれか1項に記載の固体電解質組成物で構成した層を有する全固体二次電池用シート。
- 請求項6又は7に記載の固体電解質組成物で構成した活物質層を有する全固体二次電池用電極シート。
- 正極活物質層と固体電解質層と負極活物質層とをこの順で具備する全固体二次電池であって、
前記正極活物質層、前記負極活物質層及び前記固体電解質層の少なくとも1つの層が、請求項1~10のいずれか1項に記載の固体電解質組成物で構成した層である、全固体二次電池。 - 前記負極活物質層が、請求項6又は7に記載の固体電解質組成物で構成した層である請求項13に記載の全固体二次電池。
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EP19870107.0A EP3866245A4 (en) | 2018-10-11 | 2019-10-09 | COMPOSITION OF SOLID ELECTROLYTE, SHEET FOR ALL SOLID SECONDARY BATTERY, SHEET OF ELECTRODE FOR ALL SOLID SECONDARY BATTERY AND ALL SOLID SECONDARY BATTERY |
JP2020551192A JP7143433B2 (ja) | 2018-10-11 | 2019-10-09 | 固体電解質組成物、全固体二次電池用シート、全固体二次電池用電極シート及び全固体二次電池 |
CN201980066099.6A CN112805862B (zh) | 2018-10-11 | 2019-10-09 | 固体电解质组合物、全固态二次电池用片材、全固态二次电池用电极片及全固态二次电池 |
KR1020217011587A KR20210058946A (ko) | 2018-10-11 | 2019-10-09 | 고체 전해질 조성물, 전고체 이차 전지용 시트, 전고체 이차 전지용 전극 시트 및 전고체 이차 전지 |
US17/225,126 US12034115B2 (en) | 2018-10-11 | 2021-04-08 | Solid electrolyte composition, sheet for all-solid state secondary battery, electrode sheet for all-solid state secondary battery, and all-solid state secondary battery |
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EP3869588A4 (en) * | 2018-10-15 | 2022-01-26 | FUJIFILM Corporation | ELECTRODE COMPOSITION, ELECTRODE LAYER FOR SOLID STATE SECONDARY BATTERY AND SECONDARY BATTERY, AND METHOD OF MAKING ELECTRODE LAYER FOR SOLID STATE SECONDARY BATTERY AND SECONDARY BATTERY |
EP4402740A1 (en) * | 2021-09-17 | 2024-07-24 | Battelle Memorial Institute | Lithium-metal compatible solid electrolytes for all-solid-state battery |
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- 2019-10-09 EP EP19870107.0A patent/EP3866245A4/en not_active Withdrawn
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- 2019-10-09 WO PCT/JP2019/039800 patent/WO2020075749A1/ja unknown
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US12034115B2 (en) | 2024-07-09 |
JPWO2020075749A1 (ja) | 2021-09-02 |
KR20210058946A (ko) | 2021-05-24 |
US20210234194A1 (en) | 2021-07-29 |
CN112805862A (zh) | 2021-05-14 |
JP7143433B2 (ja) | 2022-09-28 |
CN112805862B (zh) | 2023-05-05 |
EP3866245A4 (en) | 2021-12-08 |
EP3866245A1 (en) | 2021-08-18 |
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