JP7278090B2 - All-solid lithium secondary battery and manufacturing method thereof - Google Patents

Description

TECHNICAL FIELD The present invention relates to an all-solid lithium secondary battery having good discharge characteristics and a method for producing the same.

In recent years, with the development of portable electronic devices such as mobile phones and notebook personal computers, and the commercialization of electric vehicles, there is a growing need for secondary batteries that are compact, lightweight, and have high capacity and high energy density. It has become to.

At present, lithium-containing composite oxides such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ) are used as positive electrode active materials in non-aqueous secondary batteries, particularly lithium ion secondary batteries, which can meet this demand. , graphite or the like is used as a negative electrode active material, and an organic electrolyte containing an organic solvent and a lithium salt is used as a non-aqueous electrolyte.

With the further development of equipment to which non-aqueous secondary batteries are applied, there is a demand for longer life, higher capacity, and higher energy density of non-aqueous secondary batteries. There is also a strong demand for reliability of non-aqueous secondary batteries with increased capacity and increased energy density.

However, since the organic electrolyte used in lithium-ion secondary batteries contains an organic solvent, which is a combustible substance, the organic electrolyte generates abnormal heat when an abnormal situation such as a short circuit occurs in the battery. there is a possibility. In addition, with the trend toward higher energy densities in non-aqueous secondary batteries and an increase in the amount of organic solvents in organic electrolytes in recent years, there is a demand for greater reliability of non-aqueous secondary batteries.

Under the circumstances described above, an all-solid-state secondary battery that does not use an organic solvent is also being studied (Patent Documents 1 and 2, etc.). The all-solid secondary battery uses a solid electrolyte molded body that does not use an organic solvent in place of the conventional organic solvent-based electrolyte. ing.

Various studies have been made in order to improve the characteristics of all-solid secondary batteries. For example, Patent Document 3 discloses that a From the viewpoint of preventing contamination of the active material and improving the adhesion between the active material layer and the solid electrolyte layer, either one of the slurry for forming the active material layer and the slurry for forming the solid electrolyte layer is applied. A manufacturing method has been proposed in which the active material layer and the solid electrolyte layer are formed by drying the slurry with a spray and then applying the other slurry by spray coating.

In addition, in Patent Document 4, although it is not a method for manufacturing an all-solid secondary battery, in an electrode layer containing an active material, the amount of voids for holding an electrolytic solution is controlled to ensure Li ion conductivity. In order to do so, a suspension containing an active material is sprayed on a substrate having a predetermined surface temperature or an electrode layer provided on the substrate side to form a first electrode layer, and a surface different from the predetermined surface temperature is formed. spraying the suspension onto the first electrode layer or another electrode layer at a temperature to form a second electrode layer that is more distal to the substrate than the first electrode layer, thereby forming a secondary battery; A method has been proposed for manufacturing a multi-layer electrode for use in

JP 2017-40531 A JP 2017-168387 A JP 2012-252833 A JP 2015-50055 A

All-solid secondary batteries are expected to be used more and more in the future, and in order to cope with this, it is required to further improve discharge characteristics, for example.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an all-solid lithium secondary battery having good discharge characteristics, and a method for producing the same.

An all-solid lithium secondary battery of the present invention has a positive electrode, a negative electrode, and a solid electrolyte layer, and at least one of the positive electrode and the negative electrode is an active material layer containing active material particles and a solid electrolyte. and wherein the active material layer is formed by laminating regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte is unevenly distributed in a stripe pattern.

The all-solid-state lithium secondary battery of the present invention includes an electrode manufacturing process for manufacturing an electrode having an active material layer formed by laminating regions in which active material particles are unevenly distributed and regions in which solid electrolytes are unevenly distributed in a stripe pattern. , and at least a battery assembling step of assembling an all-solid lithium secondary battery using the electrode, wherein the electrode manufacturing step includes at least active material particles and / or a solid electrolyte and a solvent, and the active material particles or the The method of the present invention has a step of using a plurality of active material layer-forming compositions having different contents of solid electrolyte particles, and forming an active material layer through an operation of sequentially applying the plurality of active material layer-forming compositions. It can be manufactured by a manufacturing method.

ADVANTAGE OF THE INVENTION According to this invention, the all-solid-state lithium secondary battery which has a favorable discharge characteristic, and its manufacturing method can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which shows typically a part of cross section of an example of the electrode which concerns on the all-solid-state lithium secondary battery of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing which represents typically the cross section of an example of the all-solid-state lithium secondary battery of this invention. 4 is a graph showing evaluation results of discharge characteristics of all-solid-state lithium secondary batteries of Examples and Comparative Examples.

The all-solid lithium secondary battery of the present invention has a positive electrode, a negative electrode, and a solid electrolyte layer, and at least one of the positive electrode and the negative electrode is an active material containing active material particles and solid electrolyte particles. The active material layer is formed by laminating regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte is unevenly distributed in a stripe pattern.

FIG. 1 shows a drawing schematically showing a part of the cross section of an example of the electrode according to the all-solid lithium secondary battery of the present invention. Electrode 100 shown in FIG. 1 has active material layer 200 containing active material particles 211 and solid electrolyte particles 212 on one side of current collector 300 . The active material layer 200 is formed by laminating regions 201 in which the active material particles 211 are unevenly distributed and regions 202 in which the solid electrolyte particles 212 are unevenly distributed in a stripe pattern.

The active material layer may contain a binder for binding the active material particles and the solid electrolyte particles, but this is not shown in FIG.

The active material layer in the electrode of an all-solid-state lithium secondary battery is generally prepared by uniformly mixing active material particles, solid electrolyte particles, a solvent, etc., and applying an active material layer-forming composition to a base such as a current collector. It is applied to the material and formed through the process of drying. In the active material layer thus formed, the active material particles and the solid electrolyte particles are evenly mixed. need to do more. In this case, since the solid electrolyte particles have Li ion conductivity but do not have electronic conductivity, the electron conductivity of the entire active material layer is lowered by arranging them evenly between the active material particles. . As a result, the utilization rate of the active material becomes low when the battery is discharged, and the original capacity of the electrode cannot be sufficiently drawn out.

Therefore, in the all-solid lithium secondary battery of the present invention, at least one of the positive electrode and the negative electrode has a structure in which regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte particles are unevenly distributed are laminated in a stripe pattern. It was decided to have an active material layer. As a result, in the active material layer of the electrode, the electron conductivity between the active material particles and the electron conductivity of the entire active material layer are improved without impairing the Li ion conductivity. Since the utilization rate is improved, it becomes possible to ensure better discharge characteristics.

In the present invention, the electrode having an active material layer having a structure in which regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte particles are unevenly distributed are laminated in a stripe pattern is either a positive electrode or a negative electrode. Good, but more preferably both positive and negative electrodes, which can further enhance the discharge characteristics of the battery.

In addition, an electrode having an active material layer having a structure in which regions where active material particles are unevenly distributed and regions where solid electrolyte particles are unevenly distributed are laminated in a stripe pattern is used for batteries other than all-solid lithium secondary batteries, such as non-aqueous electrolytic It can also be applied to a lithium secondary battery having a liquid.

In the all-solid lithium secondary battery, only one of the positive electrode and the negative electrode has an active material layer having a structure in which a region in which active material particles are unevenly distributed and a region in which solid electrolyte particles are unevenly distributed are laminated in a stripe pattern. When electrodes are used, the other electrode can be, for example, an electrode having an active material layer in which active material particles and solid electrolyte particles are evenly mixed.

In an electrode having an active material layer having a structure in which regions where the active material particles are unevenly distributed and regions where the solid electrolyte particles are unevenly distributed are laminated in a striped pattern, the regions where the active material particles are unevenly distributed and the solid electrolyte particles are unevenly distributed. The region does not necessarily have to reach both ends of the active material layer. A part of the region where the solid electrolyte particles are unevenly distributed may exist on the side of the region where the solid electrolyte particles are distributed. In the electrode 100 shown in FIG. 1 , the side portion (see A region 201 in which the active material particles are unevenly distributed exists in the middle left side).

In particular, when the region where the active material particles are unevenly distributed is located on the side of the region where the solid electrolyte particles are unevenly distributed, it can be expected that the electron conductivity of the entire active material layer will be further improved.

In an electrode having an active material layer having a structure in which regions where active material particles are unevenly distributed and regions where solid electrolyte particles are unevenly distributed are laminated in a stripe pattern, from the viewpoint of improving the discharge characteristics of the battery, the entire active material layer When the total of the active material particles and the solid electrolyte particles is 100% by mass, the ratio of the active material particles is preferably 50% by mass or more, more preferably 60% by mass or more, and 70% by mass or more. is more preferably 95% by mass or less, more preferably 90% by mass or less (that is, the proportion of solid electrolyte particles is preferably 5% or more, 10% by mass % or more, preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less).

When manufacturing an electrode having an active material layer with a structure in which regions where active material particles are unevenly distributed and regions where solid electrolyte particles are unevenly distributed are laminated in a striped pattern, the contents of the active material particles and the solid electrolyte particles are different. Two or more active material layer-forming compositions (compositions containing active material particles and/or solid electrolyte particles and a solvent, etc.) are prepared, and these are successively applied to the surface of a substrate such as a current collector. An electrode can be obtained by forming an active material layer by stacking the above regions in a striped manner.

For example, a composition (A) for forming an active material layer [hereinafter referred to as "composition (A)"] and a composition (A) having a lower content of active material particles or a content of solid electrolyte particles than that of the composition (A) When forming an active material layer using a large active material layer-forming composition (B) [hereinafter referred to as "composition (B)"], the composition (A) is applied to a substrate such as a current collector. Coating, drying if necessary to form a coating film of the composition (A), coating the composition (B) thereon, drying if necessary to form a coating of the composition (B) form a film. Subsequently, the formation of the coating film of the composition (A) and the formation of the coating film of the composition (B) are successively carried out a necessary number of times, so that the regions where the active material particles are unevenly distributed and the regions where the solid electrolyte particles are unevenly distributed are formed. It is possible to form an active material layer having a striped laminated structure.

From the viewpoint of increasing the electron conductivity between the active material particles, the active material layer-forming composition (A) may not contain solid electrolyte particles, and from the viewpoint of increasing the Li ion conductivity, The active material layer-forming composition (B) may not contain active material particles.

Although there is no particular limitation on the number of layers of regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte particles are unevenly distributed in the active material layer, there are usually two or more layers of regions in which the active material particles are unevenly distributed. In order to improve the conductivity between the electric body or the terminal and the active material layer, at least the side of the active material layer not facing the solid electrolyte layer is provided with a region in which the active material particles are unevenly distributed. is desirable. Further, the number of layers in the region where the solid electrolyte particles are unevenly distributed changes according to the number of layers in the region where the active material particles are unevenly distributed. Moreover, there is no particular upper limit for the total number of the regions because it usually depends on the thickness of the electrode.

The method of applying each active material layer-forming composition is not particularly limited, and various known coating methods can be used, but spray coating is preferably employed. In the case of spray coating, it is preferable to spray each active material layer-forming composition from a different nozzle because the active material layer can be formed more efficiently. Furthermore, during spray coating, it is preferable to heat the substrate from the lower surface (the surface opposite to the coating surface) by plate heating or the like. Since a dry coating film is formed by drying, the subsequent spray coating of the composition for forming an active material layer can be carried out at an early stage, so that the active material layer can be formed more efficiently. The heating temperature may be appropriately selected depending on the boiling point of the solvent used in the active material layer-forming composition, within a range that does not impair the properties of the constituent components of the active material layer.

Further, when the composition for forming an active material layer is spray-coated, a so-called impact pulse (registered trademark) method is more preferable. In general, an active material layer formed by spray coating tends to have a lower density than an active material layer formed by other coating methods, which is disadvantageous in terms of battery capacity, for example. When the active material layer is formed, the density of the active material layer formed by a coating method other than spray coating can be increased to the same degree. It is possible to manufacture an electrode that is advantageous in terms of

When the impact pulse (registered trademark) method is used for spray coating, the air pressure should be 0.3 to 0.5 Pa, and the distance between the nozzle and the object to be coated should be 30 to 110 mm.

When manufacturing an electrode having a current collector, the first application of the composition for forming an active material layer may be performed on the current collector. On the other hand, when producing an electrode without a current collector, the first composition for forming an active material layer is applied on a substrate such as a release film to form a coating film, and then each active material layer is formed. After forming an active material layer by applying a composition for the electrode and forming a coating film, the active material layer can be peeled off from the substrate to form an electrode. That is, the electrodes (positive electrode and negative electrode) in the all-solid lithium secondary battery do not necessarily have current collectors. On the other hand, in electrodes using current collectors, electrodes having active material layers on only one side of the current collector can be used, and electrodes having active material layers on both sides of the current collector can also be used.

After forming the active material layer, the electrode can be optionally subjected to pressure molding such as calendering to increase the density of the active material layer.

The positive electrode of the all-solid lithium secondary battery contains a positive electrode active material used in conventionally known lithium ion secondary batteries, that is, particles of an active material capable of absorbing and releasing Li ions, and further A positive electrode having an active material layer containing solid electrolyte particles is used.

As the positive electrode active material, LiM _x Mn _2-x O ₄ (where M is Li, B, Mg, Ca, Sr, Ba, Ti, V, Cr, Fe, Co, Ni, Cu, Al, Sn, At least one element selected from the group consisting of Sb, In, Nb, Mo, W, Y, Ru and Rh, and a spinel-type lithium-manganese composite oxide represented by 0.01≦x≦0.5) Li _x Mn _(1-y-x) Ni _y M _z O _(2-k) F _l (where M is Co, Mg, Al, B, Ti, V, Cr, Fe, Cu, Zn, at least one element selected from the group consisting of Zr, Mo, Sn, Ca, Sr and W, and 0.8≦x≦1.2, 0<y<0.5, 0≦z≦0. 5, k+l<1, −0.1≦k≦0.2, 0≦l≦0.1), LiCo _1-x M _x O ₂ (where M is Al, Mg, At least one element selected from the group consisting of Ti, Zr, Fe, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba, represented by 0 ≤ x ≤ 0.5) lithium cobalt composite oxide, LiNi _1-x M _x O ₂ (where M is Al, Mg, Ti, Zr, Fe, Co, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and LiM _1-x N _x PO ₄ (wherein M is Fe, at least one element selected from the group consisting of Mn and Co, where N is the group consisting of Al, Mg, Ti, Zr, Ni, Cu, Zn, Ga, Ge, Nb, Mo, Sn, Sb and Ba and an olivine-type composite oxide represented by 0≦x≦0.5), a lithium-titanium composite oxide represented by Li ₄ Ti ₅ O ₁₂ , and the like. Only one of these may be used, or two or more thereof may be used in combination.

As the solid electrolyte particles of the positive electrode, for example, particles of various solid electrolytes exemplified later as those constituting the solid electrolyte layer can be used. At least one kind of resin selected from the group consisting of butyl rubber, chloropyrene rubber, acrylic resin and fluororesin can be used as the positive electrode binder.

Furthermore, the active material layer of the positive electrode may contain a conductive aid such as a carbon material such as carbon black.

When a current collector is used for the positive electrode, the current collector may be foil of a metal such as aluminum, punching metal, mesh, expanded metal, foamed metal, or the like.

The positive electrode active material layer-forming composition (paste, slurry, etc.) used in manufacturing the positive electrode is prepared by dispersing, for example, positive electrode active material particles and solid electrolyte particles, as well as a binder, a conductive aid, etc. in a solvent. do. In this case, the binder may be dissolved in the solvent.

It is preferable to select a solvent that does not easily deteriorate the solid electrolyte as the solvent used in the composition for forming the positive electrode active material layer. In particular, sulfide-based solid electrolytes and hydride-based solid electrolytes are represented by hydrocarbon solvents such as hexane, heptane, octane, nonane, decane, decalin, toluene, and xylene because they cause chemical reactions with minute amounts of moisture. Preference is given to using non-polar aprotic solvents. In particular, it is more preferable to use a super-dehydrated solvent with a water content of 0.001% by mass (10 ppm) or less. In addition, fluorine-based solvents such as "Vertrel (registered trademark)" manufactured by Mitsui-DuPont Fluorochemicals, "Zeorolla (registered trademark)" manufactured by Nippon Zeon, "Novec (registered trademark)" manufactured by Sumitomo 3M, and , dichloromethane, and diethyl ether can also be used.

As for the composition of the positive electrode active material layer, for example, the content of the positive electrode active material particles is preferably 50 to 90% by mass, and the content of the solid electrolyte particles is preferably 10 to 50% by mass. The content is preferably 0.1 to 10% by mass. Further, when the positive electrode active material layer contains a conductive aid, the content is preferably 0.1 to 10% by mass. Furthermore, the thickness of the positive electrode active material layer is preferably 50 to 1000 μm.

The negative electrode of the all-solid lithium secondary battery contains a negative electrode active material used in conventionally known lithium ion secondary batteries, that is, particles of an active material capable of absorbing and releasing Li ions, and further A negative electrode containing solid electrolyte particles is used.

Examples of negative electrode active materials include graphite, pyrolytic carbons, cokes, vitreous carbons, sintered organic polymer compounds, mesocarbon microbeads (MCMB), carbon fibers, and the like, which can occlude and release lithium. One or a mixture of two or more carbonaceous materials is used. Elements, compounds, and alloys thereof containing elements such as Si, Sn, Ge, Bi, Sb, and In; compounds that can be charged and discharged at low voltages close to lithium metal, such as lithium-containing nitrides or lithium-containing oxides; lithium metal a lithium/aluminum alloy; can also be used as the negative electrode active material.

In the negative electrode, the negative electrode active material particles, solid electrolyte particles (such as particles of various solid electrolytes exemplified later as those constituting the solid electrolyte layer), binders such as butyl rubber, chloropyrene rubber, acrylic resin and fluororesin, and further If necessary, a conductive additive (carbon material such as carbon black) is added to the negative electrode mixture, and the current collector is used as a core material to form a molded body (active material layer), or the various alloys or A lithium metal foil can be used alone, or a current collector laminated as an active material layer can be used.

When a current collector is used for the negative electrode, the current collector may be copper or nickel foil, punching metal, mesh, expanded metal, foam metal, or the like.

A composition for forming a negative electrode active material layer (paste, slurry, etc.) used in manufacturing a negative electrode having an active material layer containing negative electrode active material particles, solid electrolyte particles, and the like is, for example, negative electrode active material particles and solid electrolyte particles. Furthermore, it is prepared by dispersing a binder, a conductive aid used as necessary, and the like in a solvent. In this case, the binder may be dissolved in the solvent.

As for the solvent used in the composition for forming the negative electrode active material layer, it is desirable to select a solvent that does not easily deteriorate the solid electrolyte, similarly to the solvent used in the composition for forming the positive electrode active material layer. It is preferable to use the various solvents exemplified above as the solvent for the composition, and it is particularly preferable to use an ultra-dehydrated solvent having a water content of 0.001% by mass (10 ppm) or less.

In the case of a negative electrode having a negative electrode active material layer containing negative electrode active material particles and solid electrolyte particles, the composition of the negative electrode active material layer is preferably such that the content of the negative electrode active material particles is, for example, 50 to 80% by mass. , the content of the solid electrolyte particles is preferably 20 to 50% by mass, and the content of the binder is preferably 0.1 to 10% by mass. Moreover, when the negative electrode active material layer contains a conductive aid, the content is preferably 0.1 to 10% by mass. Furthermore, the thickness of the negative electrode active material layer containing the negative electrode active material particles and the solid electrolyte particles is preferably 50 to 1000 μm.

A hydride-based solid electrolyte, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or the like can be used as the solid electrolyte that constitutes the solid electrolyte layer of the all-solid-state lithium secondary battery. may be used, or two or more may be used in combination.

Specific examples of hydride-based solid electrolytes include LiBH ₄ , solid solutions of LIBH ₄ and the following alkali metal compounds (for example, those having a molar ratio of LiBH ₄ to the alkali metal compound of 1:1 to 20:1), and the like. is mentioned. Examples of alkali metal compounds in the solid solution include lithium halides (LiI, LiBr, LiF, LiCl, etc.), rubidium halides (RbI, RbBr, RbiF, RbCl, etc.), and cesium halides (CsI, CsBr, CsF, CsCl, etc.). , lithium amide, rubidium amide and cesium amide.

Specific examples of sulfide-based solid electrolytes include Li ₂ SP ₂ S ₃ , Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₃ —P ₂ S ₅ , Li ₂ S—SiS ₂ , LiI—Li ₂ SP ₂ S ₅ , LiI—Li ₂ S—SiS ₂ —P ₂ S ₅ , Li ₂ S—SiS ₂ —Li ₄ SiO ₄ , Li ₂ S—SiS ₂ —Li ₃ PO ₄ , Li _{3PS 4} —Li ₄ GeS ₄ , Li _3.4 P _0.6 Si _0.4 S ₄ , Li _3.25 P _0.25 Ge _0.76 S ₄ , Li _4-x Ge _1-x P _x S ₄ , _{Li7P3S11 ,} and the _like .

Specific examples of oxide- _based solid electrolytes include _Li7La3Zr2O12 , _LiTi ( _PO4 ) ₃ , LiGe _{( PO4} ) ₃ , _LiLaTiO3, and the like.

The solid electrolyte layer is formed by applying a composition for forming a solid electrolyte layer prepared by dispersing solid electrolyte particles in a solvent onto a base material, a positive electrode, and a negative electrode, drying it, and applying pressure such as press treatment as necessary. It can be formed by molding.

As with the solvent used for the positive electrode active material layer-forming composition, it is desirable to select a solvent that is less likely to degrade the solid electrolyte. It is preferable to use the various solvents exemplified above as solvents for substances, and it is particularly preferable to use a super-dehydrated solvent having a water content of 0.001% by mass (10 ppm) or less.

The thickness of the solid electrolyte layer is preferably 100-200 μm.

When assembling an all-solid lithium secondary battery, for example, a positive electrode and a negative electrode are laminated with a solid electrolyte layer interposed to form an electrode body (laminated electrode body, etc.), and this electrode body is enclosed in an outer package. .

FIG. 2 shows a drawing schematically showing a cross section of an example of the all-solid lithium secondary battery of the present invention. In the all-solid lithium secondary battery 1 shown in FIG. 2, a laminated electrode body configured by laminating a positive electrode 10 and a negative electrode 20 with a solid electrolyte layer 30 interposed therebetween is composed of an outer can 40, a sealing can 50, and these. It is enclosed in an exterior body (a flat exterior body called a coin shape or a button shape) formed with a resin gasket 60 interposed therebetween. In the all-solid-state lithium secondary battery 1 shown in FIG. 2, the sealing can 50 is fitted to the opening of the outer can 40 via the gasket 60, and the open end of the outer can 40 is tightened inward. As a result, the gasket 60 comes into contact with the sealing can 50, thereby sealing the opening of the outer can 40 and forming a sealed structure inside the battery. Then, the upper surface of the negative electrode 20 in the figure contacts the inner surface of the sealed can 50 that also serves as the negative electrode terminal, thereby making an electrical connection. electrically connected. In addition, in FIG. 2, each layer of the positive electrode 10 and the negative electrode 20 is not shown separately.

In the case of an outer package composed of an outer can and a sealed can, the shape thereof may be polygonal (triangle, quadrangle, pentagon, hexagon, heptagon, octagon) in plan view, circular or circular in plan view. It may be oval.

A stainless steel can or the like can be used for the outer can and the sealing can. In addition, polypropylene, nylon, etc. can be used for gasket materials, and tetrafluoroethylene-perfluoroalkoxyethylene copolymer (PFA), etc., can be used when heat resistance is required in relation to battery applications. Heat resistance with a melting point exceeding 240°C such as fluorine resin, polyphenylene ether (PEE), polysulfone (PSF), polyarylate (PAR), polyethersulfone (PES), polyphenylene sulfide (PPS), polyetheretherketone (PEEK), etc. Resin can also be used. Moreover, when the battery is applied to applications requiring heat resistance, a glass hermetic seal can be used for the sealing.

In addition, a sheet-like exterior body composed of a resin film, a metal laminate film in which a resin film and a metal film (such as aluminum foil) are laminated, or the like can be used as the exterior body of the all-solid-state lithium secondary battery. .

The all-solid lithium secondary battery of the present invention can be applied to the same applications as conventionally known secondary batteries, but has excellent heat resistance because it has a solid electrolyte instead of an organic electrolyte. It can be preferably used in applications exposed to high temperatures.

The present invention will be described in detail below based on examples. However, the following examples do not limit the present invention.

Example 1
<Positive electrode>
(Composition A)
LiNi _0.6 Co _0.2 Mn _0.2 O ₂ having an average particle size of 3 μm and having an amorphous composite oxide of Li and Nb formed on the surface, using xylene (“ultra-dehydrated” grade) as a solvent; A sulfide solid electrolyte (Li ₆ PS ₅ Cl) with an average particle size of 0.7 μm, a carbon nanotube ("VGCF" (trade name) manufactured by Showa Denko Co., Ltd.), which is a conductive agent, and an acrylic resin binder, in a mass ratio They were mixed in a ratio of 85:10:3:2 so that the solid content ratio was 30%, and stirred for 10 minutes with a Thinky mixer to prepare a uniform slurry (composition A).

(Composition B)
Using xylene (“super-dehydrated” grade) as a solvent, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) with an average particle size of 0.7 μm, an acrylic resin binder, and a dispersant were mixed in a mass ratio of 96:3. : 1 and a solid content ratio of 20%, and stirred for 10 minutes with a Thinky mixer to prepare a uniform slurry (composition B).

Composition A was applied to an Al foil with a thickness of 15 μm by an impact pulse method (air pressure: 0.4 MPa, distance between the nozzle and the object to be coated: 60 mm) and dried to form a layer with a thickness of 8 μm. Then, the composition B was applied thereon and dried to form a layer having a thickness of 2 μm. After alternately repeating application/drying of composition A and application/drying of composition B 10 times, composition A was finally applied and vacuum drying was performed at 120 ° C. to obtain a total thickness of about 100 μm. A positive electrode having a positive electrode active material layer was obtained.

The ratio of the active material particles and the solid electrolyte particles in the active material layer was 73.4% by mass of the positive electrode active material and 26.6% by mass of the solid electrolyte particles when the total was 100% by mass.

<Solid electrolyte layer>
Using xylene (“super-dehydrated” grade) as a solvent, a sulfide-based solid electrolyte (Li ₆ PS ₅ Cl) having an average particle size of 0.7 μm, an acrylic resin binder, and a dispersant were mixed in a mass ratio of 100:3. : 1 and a solid content ratio of 40%, and stirred for 10 minutes with a thinky mixer to prepare a uniform slurry. A PET nonwoven fabric (“05TH-8” manufactured by Hirose Paper Co., Ltd.) with a thickness of 40 μm and a basis weight of 8 g/m ² was passed through this slurry, and then pulled up to apply the slurry to the PET nonwoven fabric. By performing vacuum drying for 1 hour, a solid electrolyte sheet having a thickness of 50 µm was obtained.

<Negative Electrode>
Using xylene (“super dehydrated” grade) as a solvent, graphite with an average particle size of 20 μm, a sulfide solid electrolyte (Li ₆ PS ₅ Cl), and an acrylic resin binder were mixed in a mass ratio of 50:47:3. and mixed so that the solid content ratio was 50%, and stirred for 10 minutes with a Thinky mixer to prepare a uniform slurry.

Next, the slurry was applied onto a SUS foil having a thickness of 20 μm using an applicator with a gap of 200 μm, followed by vacuum drying at 120° C. to obtain a negative electrode.

<Battery assembly>
The prepared positive electrode, negative electrode and solid electrolyte sheet were all punched to a size of 10 mmφ, and the positive electrode-solid electrolyte sheet-negative electrode were stacked in this order between the upper and lower pins of SUS of a pressing machine, placed in a PET cylinder and weighed 10 tons. /cm ² and kept in a sealed state so as not to come into contact with the atmosphere, thereby producing an all-solid lithium secondary battery.

(Comparative example 1)
LiNi _0.6 Co _0.2 Mn _0.2 O ₂ having an average particle size of 3 μm and having an amorphous composite oxide of Li and Nb formed on the surface, using xylene (“ultra-dehydrated” grade) as a solvent; A sulfide solid electrolyte (Li ₆ PS ₅ Cl) with an average particle size of 0.7 μm, a carbon nanotube ("VGCF" (trade name) manufactured by Showa Denko Co., Ltd.), which is a conductive agent, and an acrylic resin binder, in a mass ratio They were mixed in a ratio of 70:25:3:2 so that the solid content ratio was 50%, and stirred for 10 minutes with a thinky mixer to prepare a uniform slurry.

Next, the slurry was applied to an Al foil having a thickness of 20 μm using an applicator with a gap of 200 μm, and vacuum-dried at 120° C. to obtain a positive electrode having a positive electrode active material layer of about 100 μm. .

The ratio of the active material particles and the solid electrolyte particles in the active material layer was 73.7% by mass of the positive electrode active material and 26.3% by mass of the solid electrolyte particles when the total was 100% by mass.

An all-solid lithium secondary battery was produced in the same manner as in Example 1, except that the positive electrode was used.

[Evaluation of discharge characteristics]
The discharge characteristics of the batteries of Examples and Comparative Examples were evaluated under the following conditions while being pressurized by a pressing machine.

Each battery was subjected to constant current charging at a current value of 0.05C until the voltage reached 4.2V. ) until the voltage reached 2.7 V, and the discharge capacity at each discharge rate was measured.

Table 1 and FIG. 3 show the results of converting the measured discharge capacity per 1 g of the positive electrode active material.

As shown in Table 1 and FIG. 3, the all-solid-state lithium secondary battery of Example 1 had good discharge characteristics with little decrease in discharge capacity even when the discharge rate was increased.

1 All Solid Lithium Secondary Battery 10 Positive Electrode 20 Negative Electrode 30 Solid Electrolyte Layer 40 Outer Can 50 Sealing Can 60 Gasket 100 Electrode 200 Active Material Layer 201 Area Where Active Material Particles Are Unevenly Distributed 202 Area Where Solid Electrolyte Particles Are Unevenly Distributed 211 Active material particles 212 Solid electrolyte particles 300 Current collector

Claims (7)

An all-solid lithium secondary battery having a positive electrode, a negative electrode, and a solid electrolyte layer,
at least one of the positive electrode and the negative electrode has an active material layer containing active material particles and solid electrolyte particles;
The active material layer is formed by laminating regions in which the active material particles are unevenly distributed and regions in which the solid electrolyte particles are unevenly distributed in a striped shape, each having an irregular width in the plane direction. An all-solid lithium secondary battery characterized by: The all-solid lithium ion battery according to claim 1, wherein the proportion of the active material particles is 60 to 90% by mass when the total of the active material particles and the solid electrolyte particles in the active material layer is 100% by mass. next battery. 3. The all-solid lithium secondary battery according to claim 1, wherein the solid electrolyte particles forming the solid electrolyte layer and the solid electrolyte particles forming the active material layer are particles of the same solid electrolyte. 4. The all-solid lithium secondary battery in accordance with claim 3, wherein said solid electrolyte particles are particles of a sulfide-based solid electrolyte. 5. The all-solid lithium secondary battery in accordance with claim 1, wherein said active material layer contains a binder. A method for manufacturing an all-solid lithium secondary battery according to any one of claims 1 to 5,
an electrode manufacturing process for manufacturing an electrode having an active material layer formed by laminating regions in which active material particles are unevenly distributed and regions in which solid electrolyte particles are unevenly distributed in a stripe pattern;
At least a battery assembling step of assembling an all-solid lithium secondary battery using the electrode,
The electrode manufacturing step includes using a plurality of active material layer-forming compositions containing at least active material particles and/or solid electrolyte particles and a solvent and having different ratios of the active material particles or the solid electrolyte particles, A method for producing an all-solid lithium secondary battery, characterized by comprising a step of forming an active material layer through an operation of sequentially applying the composition for forming an active material layer of (1). 7. The method for manufacturing an all-solid lithium secondary battery according to claim 6, wherein the plurality of active material layer-forming compositions are applied by spray coating.

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