TWI787485B - Electrolyte composition, electrolyte sheet, and secondary battery - Google Patents

Abstract

One aspect of the present invention provides an electrolyte composition comprising: a matrix polymer; at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; oxide particles; fibers; and, the ionic liquid; and, the average length of the fibers is equal to or greater than the average particle diameter of the oxide particles.

Description

Electrolyte composition, electrolyte sheet, and secondary battery

The invention relates to an electrolyte composition, an electrolyte sheet and a secondary battery.

In recent years, due to the popularization of portable electronic devices, electric vehicles, and the like, high-performance secondary batteries are required. Among them, lithium secondary batteries have attracted attention as power sources such as batteries for electric vehicles and batteries for power storage because of their high energy density. Specifically, lithium secondary batteries as batteries for electric vehicles have been adopted in the following electric vehicles: zero-emission electric vehicles without an engine; hybrid electric vehicles equipped with both an engine and a secondary battery; Charging plug-in hybrid electric vehicles, etc. In addition, lithium secondary batteries as batteries for power storage have been used in stationary power storage systems and the like for supplying pre-stored power in an emergency when the power system is interrupted.

In order to be used in such a wide range of applications, a lithium secondary battery having a higher energy density has been sought and developed. In particular, since lithium secondary batteries for electric vehicles are required to have high safety in addition to high input/output characteristics and high energy density, higher technologies for ensuring safety are required.

In the past, as a method of improving the safety of lithium secondary batteries, the following methods are known: the method of making the electrolyte solution flame retardant by adding a flame retardant, and the method of changing the electrolyte solution to a polymer electrolyte or a gel electrolyte. method etc. In particular, since the gel electrolyte has the same ionic conductivity as the electrolyte solution used in conventional lithium secondary batteries, by changing the electrolyte solution to a gel electrolyte, it is possible to maintain the battery without deteriorating the battery characteristics. Under certain circumstances, reduce the amount of free electrolyte and inhibit the combustion of electrolyte.

Patent Document 1 discloses a solid electrolyte sheet comprising a sheet-like porous substrate and an inorganic solid electrolyte material, and the inorganic solid electrolyte material is filled in the pores of the porous substrate. Patent Document 2 discloses an invention related to a lithium secondary battery, which is composed of a positive electrode, a negative electrode, a separator, and a gel electrolyte; the gel electrolyte includes: filler particles, a matrix polymer compound for holding the electrolyte Composition of resin, and electrolyte. Patent Document 2 discloses a technique for improving the transparency of a gel electrolyte and ensuring safety without sacrificing capacity by setting the shape of particles and the refractive index of particles to predetermined conditions. Patent Document 3 also discloses an invention related to a gel electrolyte, and discloses an electrolyte formed by setting the following as prescribed conditions: the particle diameter of the particles, the refractive index of the particles, and the mass ratio of the particles to the matrix polymer compound ( particles/matrix polymer compound), and the mass ratio of particles to electrolyte salt (particles/electrolyte salt). [Prior Art Literature] (patent documents)

Patent Document 1: Japanese Patent Laid-Open No. 2015-153460 Patent Document 2: International Publication No. 2015/068324 Patent Document 3: International Publication No. 2015/097952

[Problem to be solved by the invention] However, conventional gel electrolytes such as those described above have room for improvement in terms of safety. According to the research of the present inventors, the gel electrolytes of Patent Documents 1 to 3 may cause a problem in terms of safety due to thermal shrinkage of the gel electrolyte at high temperature, causing a short circuit in the secondary battery. Furthermore, tests under severe conditions such as a nail penetration test and a crush test are known as tests for evaluating the safety of lithium secondary batteries. Excellent evaluation results are expected in such tests.

Therefore, an object of the present invention is to provide an electrolyte composition and an electrolyte sheet in several aspects, which can suppress short circuits even at high temperatures. Moreover, the object of this invention is to provide the secondary battery which suppresses the short circuit at high temperature and improves safety among other aspects. [Technical means to solve the problem]

A first aspect of the present invention provides an electrolyte composition comprising: a matrix polymer; at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; oxide particles ; fibers; and, an ionic liquid; and, the average length of the fibers is equal to or greater than the average particle diameter of the oxide particles.

The fibers are preferably at least one selected from the group consisting of cellulose fibers, resin fibers, and glass fibers.

The matrix polymer preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

Among the structural units constituting the matrix polymer, it is preferable to contain: a first structural unit; selected from the group consisting of methyl methacrylate.

The electrolyte salt preferably includes an imide-based lithium salt.

m及n各自獨立地表示0～5的整數。The ionic liquid preferably contains at least one anionic component represented by the following formula (1) as an anionic component:

m and n each independently represent the integer of 0-5.

The ionic liquid preferably contains at least one selected from the group consisting of chain quaternary onium salt cations, piperidinium salt cations, pyrrolidinium salt cations, pyridinium salt cations and imidazolium salt cations. as a cationic component.

A second aspect of the present invention provides an electrolyte sheet comprising: a substrate; and an electrolyte layer provided on the substrate and formed of the above-mentioned electrolyte composition.

A third aspect of the present invention provides a secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode and formed of the above electrolyte composition.

In the second aspect and the third aspect, the average fiber diameter of the fibers is preferably not more than the thickness of the electrolyte layer. [effect]

According to several aspects of the present invention, it is possible to provide an electrolyte composition and an electrolyte sheet capable of suppressing short circuits at high temperatures. According to another aspect of the present invention, it is possible to provide a secondary battery capable of suppressing short circuits at high temperatures and improving safety.

Hereinafter, embodiments of the present invention will be described while appropriately referring to the drawings. However, the present invention is not limited to the following embodiments. In the following embodiments, the constituent elements (including steps, etc.) are not essential unless otherwise specified. The size of the constituent elements in each figure is only a concept, and the relative size relationship between the constituent elements is not limited to the relationship shown in each figure.

The numerical values and their ranges in this specification are not intended to limit the present invention. In this specification, the numerical range represented by "-" means the range which includes the numerical value described before and after "-" as a minimum value and a maximum value, respectively. In the numerical ranges described step by step in this specification, the upper limit or lower limit described in one numerical range may be replaced with the upper limit or lower limit of the numerical range described in other steps. In addition, in the numerical range described in the specification, the upper limit or the lower limit of the numerical range may be replaced by the value disclosed in the Examples.

[First Embodiment] Fig. 1 is a perspective view showing a secondary battery according to a first embodiment. As shown in FIG. 1 , a secondary battery 1 includes: an electrode group 2 composed of a positive electrode, a negative electrode, and an electrolyte layer; and a pouch-shaped battery case 3 for housing the electrode group 2 . A positive electrode current collecting terminal (tab) 4 and a negative electrode current collecting terminal 5 are provided on the positive electrode and the negative electrode, respectively. The positive electrode current collecting terminal 4 and the negative electrode current collecting terminal 5 protrude from the inside of the battery case 3 toward the outside so that the positive electrode and the negative electrode can be electrically connected to the outside of the secondary battery 1 .

The battery case 3 can be formed of, for example, laminated films. The laminated film may be, for example, a laminated film which is formed by sequentially laminating resin films such as polyethylene terephthalate (PET) films; metal foils such as aluminum, copper, and stainless steel; and, polypropylene, etc. sealant layer.

Fig. 2 is an exploded perspective view showing an embodiment of the electrode group 2 in the secondary battery 1 shown in Fig. 1 . Fig. 3 is a schematic perspective view showing an embodiment of the electrode group 2 in the secondary battery 1 shown in Fig. 1 . As shown in FIGS. 2 and 3 , an electrode group 2A of this embodiment includes a positive electrode 6 , an electrolyte layer 7 , and a negative electrode 8 in this order. The positive electrode 6 includes a positive electrode current collector 9 and a positive electrode mixture layer 10 provided on the positive electrode current collector 9 . The positive electrode current collector terminal 4 is provided on the positive electrode current collector 9 . The negative electrode 8 includes a negative electrode current collector 11 and a negative electrode mixture layer 12 provided on the negative electrode current collector 11 . A negative electrode current collector terminal 5 is provided on the negative electrode current collector 11 .

The positive electrode current collector 9 can be formed of aluminum, stainless steel, titanium, or the like. Specifically, the positive electrode current collector 9 may be, for example, an aluminum perforated foil having holes with a diameter of 0.1 to 10 mm, an expand metal, a foamed metal plate, or the like. Positive electrode current collector 9 may be formed of any material other than the above, as long as it does not undergo changes such as dissolution and oxidation during use of the battery, and its shape, manufacturing method, etc. are also not limited.

The thickness of the positive electrode current collector 9 can be more than 10 μm and can be less than 100 μm. From the viewpoint of reducing the overall volume of the positive electrode, it is preferably 10 to 50 μm. When forming a battery, it can be formed with a smaller curvature. From the viewpoint of positive electrode winding, 10 to 20 μm is preferable.

In one embodiment, the positive electrode mixture layer 10 contains a positive electrode active material, a conductive agent, and a binder.

The positive electrode active material can be: LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ , Li ₄ Mn ₅ O ₁₂ , LiMn _{2 -a} M ¹ _a O ₂ (wherein, M ¹ ₌ One selected from the group consisting of Co, Ni, Fe, Cr, Zn and Ta, a=0.01～0.2), Li ₂ Mn ₃ M ² O ₈ (wherein, M ² = from Fe, Co , one selected from the group consisting of Ni, Cu and Zn), Li _1-b M ³ _b Mn ₂ O ₄ (wherein, M ³ = selected from Mg, B, Al, Fe, Co, Ni, Cr , one selected from the group consisting of Zn and Ca, b=0.01～0.1), LiFeO ₂ , Fe ₂ (SO ₄ ) ₃ , LiCo _{1 - d} M ⁵ _d O ₂ (wherein, M ⁵ = from One selected from the group consisting of Ni, Fe and Mn, d=0.01～0.2), LiNi _{1 - e} M ⁶ _e O ₂ (wherein, M ⁶ = selected from Mn, Fe, Co, Al, Ga, One selected from the group consisting of Ca and Mg (e=0.01 to 0.2), Fe(MoO ₄ ) ₃ , FeF ₃ , LiFePO ₄ , LiMnPO ₄ , and the like.

The positive electrode active material may be ungranulated primary particles or granulated secondary particles.

The particle diameter of the positive electrode active material is adjusted so as to be equal to or less than the thickness of the positive electrode mixture layer 10 . When there are coarse particles having a particle diameter above the thickness of the positive electrode mixture layer 10 in the positive electrode active material, the coarse particles are removed in advance by screening classification, airflow classification, etc., and the particle diameters below the thickness of the positive electrode mixture layer 10 are selected. positive active material.

From the perspective of suppressing the deterioration of the filling property of the positive electrode active material as the particle size decreases and improving the retention capacity of the electrolyte, the average particle size of the positive electrode active material is preferably 0.1 μm or more, more preferably 1 μm or more, and at least 1 μm. More preferably 2 μm or more, more preferably 20 μm or less, more preferably 10 μm or less, more preferably 8 μm or less. The average particle diameter of the positive electrode active material is the particle diameter (D ₅₀ ) when the ratio (volume fraction) to the volume of the entire positive electrode active material is 50%. The average particle size (D ₅₀ ) of the positive electrode active material is obtained by using a laser scattering particle size measuring device (such as Microtrac) to measure the suspension by the laser scattering method. The suspension is obtained by suspending the positive electrode active material in water made.

Based on the total amount of the positive electrode mixture layer, the content of the positive electrode active material may be 70% by mass or more, 80% by mass or more, or 85% by mass or more. Based on the total amount of the positive electrode mixture layer, the content of the positive electrode active material may be 95% by mass or less, 92% by mass or less, or 90% by mass or less.

The conductive agent can be carbon black, acetylene black, graphite, carbon fiber, carbon nanotube, etc.

Based on the total amount of the positive electrode mixture layer, the content of the conductive agent may be 0.1% by mass or more, 1% by mass or more, or 3% by mass or more. From the viewpoint of suppressing the volume increase of the positive electrode 6 and reducing the energy density of the secondary battery 1 along with the volume increase, the content of the conductive agent is preferably 15% by mass or less based on the total amount of the positive electrode mixture layer. It is preferably at most 10% by mass, more preferably at most 8% by mass.

The binder is not particularly limited as long as it does not decompose on the surface of the positive electrode 6 , and is, for example, a polymer. The binder can be: carboxymethyl cellulose, acetyl cellulose, ethyl cellulose and other celluloses; polyvinylidene fluoride, copolymer of vinylidene fluoride and hexafluoropropylene; styrene-butadiene rubber , Fluorine rubber, ethylene-propylene rubber, polyacrylic acid, polyimide, polyamide, etc.

Based on the total amount of the positive electrode mixture layer, the content of the binder may be 0.5% by mass or more, 1% by mass or more, or 3% by mass or more. Based on the total amount of the positive electrode mixture layer, the content of the binder may be 15% by mass or less, 10% by mass or less, or 7% by mass or less.

The positive electrode mixture layer 10 may further contain an ionic liquid described later. When the positive electrode mixture layer 10 contains an ionic liquid, based on the total amount of the positive electrode mixture layer, the content of the ionic liquid is preferably 3% by mass or more, preferably 5% by mass or more, more preferably 10% by mass or more, and It is preferably at most 30% by mass, more preferably at most 25% by mass, more preferably at most 20% by mass.

From the viewpoint of improving electrical conductivity, the thickness of the positive electrode mixture layer 10 may be equal to or greater than the average particle size of the positive electrode active material, preferably greater than 5 μm, more preferably greater than 10 μm, and more preferably greater than 20 μm. The thickness of the positive electrode mixture layer 10 is preferably not more than 100 μm, more preferably not more than 80 μm, more preferably not more than 50 μm. By setting the thickness of the positive electrode mixture layer 10 to be 100 μm or less, it is possible to suppress the charge and discharge bias caused by the vicinity of the surface of the positive electrode mixture layer 10 and the surface of the positive electrode current collector 9 The charge level of the positive electrode active material is uneven.

From the viewpoint of reducing the resistance of the positive electrode mixture layer 10 by making the conductive agent and the positive electrode active material adhere to each other, the mixture density of the positive electrode mixture layer 10 is preferably 2 g/cm ³ or more.

The negative electrode current collector 11 can be formed of copper, stainless steel, titanium, nickel, or the like. The negative electrode current collector 11 can specifically be: a rolled copper foil, for example, a perforated copper foil having holes with a diameter of 0.1 to 10 mm, a developed metal, a foamed metal plate, or the like. The negative electrode current collector 11 may be formed of any material other than the above, and its shape, manufacturing method, etc. are also not limited.

The thickness of the negative electrode current collector 11 can be 10 μm or more and can be 100 μm or less. From the viewpoint of reducing the overall volume of the negative electrode, it is preferably 10 to 50 μm. When forming a battery, the negative electrode is wound with a small curvature. From the point of view, 10~20μm is better.

In one embodiment, the negative electrode mixture layer 12 contains a negative electrode active material and a binder.

As the negative electrode active material, one commonly used in the field of energy devices can be used. Specific examples of the negative electrode active material include metallic lithium, lithium alloys, metal compounds, carbon materials, metal complexes, and organic polymer compounds. As the negative electrode active material, one of the above-mentioned ones may be used alone, or two or more of the above-mentioned ones may be used in combination.

The negative electrode active material is preferably carbon material. Examples of carbon materials include: natural graphite (flaky graphite, etc.), graphite such as artificial graphite; amorphous carbon; carbon fiber; and carbon such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Black and so on. The negative electrode active material can be natural graphite (theoretical capacity: 372 Ah/kg) covered by amorphous carbon. From the viewpoint of obtaining a larger theoretical capacity (such as 500-1500 Ah/kg), it can contain silicon , tin or compounds of these elements (oxides, nitrides, alloys with other metals). If a material with a large capacity is used, the thickness of the negative electrode mixture layer 12 can be reduced, and the electrode area that can be accommodated in the secondary battery 1 can be increased. As a result, the resistance of the secondary battery 1 can be reduced to achieve high output, and at the same time, the capacity of the secondary battery 1 can be increased more than when a graphite negative electrode is used.

From the viewpoint of obtaining a well-balanced negative electrode 8 that can suppress an increase in irreversible capacity as the particle size decreases while increasing electrolyte holding capacity, the average particle size (D ₅₀ ) of the negative electrode active material is preferably 1 μm or more, and preferably in the range of It is preferably at least 5 μm, more preferably at least 10 μm, more preferably at most 50 μm, more preferably at most 30 μm, and more preferably at most 20 μm. The average particle diameter (D ₅₀ ) of the negative electrode active material is measured by the same method as the average particle diameter (D ₅₀ ) of the positive electrode active material.

Based on the total amount of the negative electrode mixture layer, the content of the negative electrode active material may be 60% by mass or more, 65% by mass or more, or 70% by mass or more. Based on the total amount of the negative electrode mixture layer, the content of the negative electrode active material may be 99% by mass or less, 95% by mass or less, or 90% by mass or less.

The binder and its content may be the same as the binder and its content in the above-mentioned positive electrode mixture layer 10 .

From the viewpoint of further reducing the resistance of the negative electrode 8, the negative electrode mixture layer 12 may further contain a conductive agent and an ionic liquid. The types and contents of the conductive agent and the ionic liquid are the same as those of the conductive agent and the ionic liquid in the positive electrode mixture layer 10 described above.

From the viewpoint of improving the electrical conductivity, the thickness of the negative electrode mixture layer 12 is equal to or greater than the average particle size of the negative active material, specifically, preferably 10 μm or greater, more preferably 15 μm or greater, and more preferably 20 μm or greater. The thickness of the negative electrode mixture layer 12 is preferably not more than 50 μm, more preferably not more than 40 μm, more preferably not more than 30 μm. By setting the thickness of the negative electrode mixture layer 12 to 50 μm or less, it is possible to suppress the charge-discharge bias caused by the negative electrode near the surface of the negative electrode mixture layer 12 and the surface of the negative electrode collector 11. The charging level of the active material is not uniform.

From the viewpoint of reducing the resistance of the negative electrode mixture layer 12 by making the conductive agent and the negative electrode active material adhere to each other, the mixture density of the negative electrode mixture layer 12 is preferably 1 g/cm ³ or more.

Electrolyte layer 7 is formed of an electrolyte composition. The electrolyte layer 7 (electrolyte composition) contains: a matrix polymer; at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; oxide particles; fibers; and, ions liquid.

The matrix polymer is a polymer (binder polymer) that serves as a matrix (forms a continuous phase) for holding other materials contained in the electrolyte composition. The matrix polymer preferably has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride.

The matrix polymer is preferably one or more polymers, and among the structural units (monomer units) constituting one or more polymers, it is preferable to include: a first structural unit (monomer unit) , the first structural unit is selected from the group consisting of tetrafluoroethylene and vinylidene fluoride; and, the second structural unit (monomer unit), the second structural unit is selected from the group consisting of hexafluoropropylene, acrylic acid , maleic acid, ethyl methacrylate and methyl methacrylate selected from the group.

The first structural unit and the second structural unit may be contained in one polymer to constitute a copolymer. In other words, in one embodiment, the electrolyte composition contains at least one kind of copolymer including both the first structural unit and the second structural unit. The copolymer can be: a copolymer of vinylidene fluoride and hexafluoropropylene, a copolymer of vinylidene fluoride and maleic acid, a copolymer of vinylidene fluoride and methyl methacrylate, etc. When the electrolyte composition contains a copolymer, it may further contain other polymers.

The first structural unit and the second structural unit may be contained in different polymers to form at least two polymers: a first polymer having the first structural unit, and a second polymer having the second structural unit polymer. In other words, in one embodiment, the electrolyte composition contains, as a matrix polymer, at least two or more of the following polymers: a first polymer including a first structural unit, and a second polymer including a second structural unit. When the electrolyte composition contains the first polymer and the second polymer, it may further contain other polymers.

The first polymer may be a polymer composed of only the first structural unit, or may further have other structural units in addition to the first structural unit. Other structural units may be oxygen-containing hydrocarbon structures such as ethylene oxide (-CH ₂ CH ₂ O-), carboxylate (-CH ₂ COO-). The first polymer may be polytetrafluoroethylene, polyvinylidene fluoride, or a polymer obtained by introducing the aforementioned oxygen-containing hydrocarbon structure into these molecular structures.

The second polymer may be a polymer composed of only the second structural unit, or may further have another structural unit in addition to the second structural unit. Other structural units may be oxygen-containing hydrocarbon structures such as ethylene oxide (-CH ₂ CH ₂ O-), carboxylate (-CH ₂ COO-).

Examples of combinations of the first polymer and the second polymer include: polyvinylidene fluoride and polyacrylic acid, polytetrafluoroethylene and polymethyl methacrylate, polyvinylidene fluoride and polymethyl methacrylate Wait.

From the viewpoint of further improving the strength of the electrolyte composition (electrolyte layer 7) when the electrolyte composition is formed into a sheet, based on the total amount of structural units constituting the matrix polymer, the content of the first structural unit is 5% by mass or more More preferably, it is more preferably at least 10% by mass, more preferably at least 20% by mass. From the viewpoint of further improving the affinity with the ionic liquid contained in the electrolyte composition, the content of the first structural unit is preferably 60% by mass or less based on the total amount of structural units constituting the matrix polymer. , preferably at most 40% by mass, more preferably at most 30% by mass.

From the viewpoint of further improving the strength of the electrolyte composition when it is formed into a sheet (electrolyte layer 7), the content of the first structural unit is preferably based on the total content of the first structural unit and the second structural unit. It is 50 mass % or more, 70 mass % or more, 80 mass % or more, 90 mass % or more, or 95 mass % or more. From the viewpoint of further improving the affinity with the ionic liquid (details will be described later) contained in the electrolyte composition, based on the total content of the first structural unit and the second structural unit, the second The content of the structural unit is preferably at most 99% by mass, at most 98% by mass, at most 97% by mass, or at most 96% by mass.

From the viewpoint of further improving the affinity with the ionic liquid contained in the electrolyte composition, the content of the second structural unit is preferably 1% by mass or more based on the total amount of structural units constituting the matrix polymer. , preferably at least 3% by mass, more preferably at least 5% by mass. From the viewpoint of further improving the strength of the electrolyte composition when it is made into a sheet (electrolyte layer 7), the content of the second structural unit is 50% by mass or less based on the total amount of structural units constituting the matrix polymer. More preferably, it is at most 20% by mass, more preferably at most 10% by mass.

From the viewpoint of further improving the affinity with the ionic liquid contained in the electrolyte composition, based on the total content of the first structural unit and the second structural unit, the content of the second structural unit is preferably 1 Mass % or more, 3 mass % or more, or 4 mass % or more. From the viewpoint of further improving the strength of the electrolyte composition when it is formed into a sheet (electrolyte layer 7), the content of the second structural unit is preferably based on the total content of the first structural unit and the second structural unit. It is 50 mass % or less, 40 mass % or less, 30 mass % or less, 20 mass % or less, 10 mass % or less, or 5 mass % or less.

From the viewpoint of further improving the strength of the electrolyte composition (electrolyte layer 7) when the electrolyte composition is formed into a sheet, the total amount of the electrolyte composition (excluding the dispersion medium described later, in other words, the total amount of the electrolyte layer, the same applies hereinafter) as The content of the matrix polymer is preferably at least 10% by mass, more preferably at least 15% by mass, more preferably at least 20% by mass, and particularly preferably at least 25% by mass. From the standpoint of improving the electrical conductivity, the content of the matrix polymer is preferably not more than 40% by mass, more preferably not more than 35% by mass, more preferably not more than 30% by mass, based on the total amount of the electrolyte composition. It is especially preferable that it is 28 mass % or less.

Since the matrix polymer has excellent affinity with the ionic liquid contained in the electrolyte composition, it can hold the electrolyte salt in the ionic liquid, and can suppress the occurrence of ionic liquid when a load is applied to the electrolyte composition (electrolyte layer 7). of leakage.

The electrolyte salt is at least one selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts. The electrolyte salt is a compound for receiving cations between the positive electrode 6 and the negative electrode 8 . The above-mentioned electrolyte salt has a low dissociation degree at low temperature and is easy to diffuse in the ionic liquid, and since it does not thermally decompose at high temperature, it is preferable from the viewpoint that the ambient temperature in which the secondary battery can be used is wide. The electrolyte salt may be an electrolyte salt used in a fluoride ion battery.

The anions of the electrolyte salt can be: halide ions (I ^－ , Cl ^－ , Br ^－ etc.), SCN ^－ , BF ₄ ^－ , BF ₃ (CF ₃ ) ^－ , BF ₃ (C ₂ F ₅ ) ^－ , PF ₆ ^－ , ClO ₄ ^－ , SbF ₆ ^－ , N(SO ₂ F) ₂ ^－ , N(SO ₂ CF ₃ ) ₂ ^－ , N(SO ₂ C ₂ F ₅ ) ₂ ^－ , B(C ₆ H ₅ ) ₄ ^－ , B(O ₂ C ₂ H ₄ ) ₂ ^－ , C(SO ₂ F) ₃ ^－ , C(SO ₂ CF ₃ ) ₃ ^－ , CF ₃ COO ^－ , CF ₃ SO ₂ O ^－ , C ₆ F ₅ SO ₂ O ^- , B(O ₂ C ₂ O ₂ ) ₂ ^- and so on. The anion is preferably PF ₆ ^- , BF ₄ ^- , N(SO ₂ F) ₂ ^- , N(SO ₂ CF ₃ ) ₂ ^- , B(O ₂ C ₂ O ₂ ) ₂ ^- , or ClO ₄ ^- .

In addition, the following abbreviation may be used below. [FSI] ^－ : N(SO ₂ F) ₂ ^－ , bis(fluorosulfonyl)imide anion [TFSI] ^－ : N(SO ₂ CF ₃ ) ₂ ^－ , bis(trifluoromethanesulfonyl)imide anion [ BOB] ^- : B(O ₂ C ₂ O ₂ ) ₂ ^- , bisoxalatoborate anion [f3C] ^- : C(SO ₂ F) ₃ ^- , ginseng (fluorosulfonyl) carbanion

Lithium salts can be made from LiPF ₆ , LiBF ₄ , Li[FSI], Li[TFSI], Li[f3C], Li[BOB], LiClO ₄ , LiBF ₃ (CF ₃ ), LiBF ₃ (C ₂ F ₅ ) , LiBF ₃ (C ₃ F ₇ ), LiBF ₃ (C ₄ F ₉ ), LiC(SO ₂ CF ₃ ) ₃ , LiCF ₃ SO ₂ O, LiCF ₃ COO and LiRCOO (R is an alkyl group with 1 to 4 carbons , phenyl, or naphthyl) at least one selected from the group consisting of.

The sodium salt can be obtained from NaPF ₆ , NaBF ₄ , Na[FSI], Na[TFSI], Na[f3C], Na[BOB], NaClO ₄ , NaBF ₃ (CF ₃ ), NaBF ₃ (C ₂ F ₅ ) , NaBF ₃ (C ₃ F ₇ ), NaBF ₃ (C ₄ F ₉ ), NaC(SO ₂ CF ₃ ) ₃ , NaCF ₃ SO ₂ O, NaCF ₃ COO and NaRCOO (R is an alkyl group with 1 to 4 carbons , phenyl, or naphthyl) at least one selected from the group consisting of.

Calcium salts can be selected from Ca(PF ₆ ) ₂ , Ca(BF ₄ ) ₂ , Ca[FSI] ₂ , Ca[TFSI] ₂ , Ca[f3C] ₂ , Ca[BOB] ₂ , Ca(ClO ₄ ) ₂ , Ca[BF ₃ (CF ₃ )] ₂ , Ca[BF ₃ (C ₂ F ₅ )] ₂ , Ca[BF ₃ (C ₃ F ₇ )] ₂ , Ca[BF ₃ (C ₄ F ₉ )] ₂ , Ca[C(SO ₂ CF ₃ ) ₃ ] ₂ , Ca(CF ₃ SO ₂ O) ₂ , Ca(CF ₃ COO) ₂ and Ca(RCOO) ₂ (R is an alkyl group with 1 to 4 carbons, benzene group, or naphthyl) at least one selected from the group consisting of.

Magnesium salts can be selected from Mg(PF ₆ ) ₂ , Mg(BF ₄ ) ₂ , Mg[FSI] ₂ , Mg[TFSI] ₂ , Mg[f3C] ₂ , Mg[BOB] ₂ , Mg(ClO ₄ ) ₂ , Mg[BF ₃ (CF ₃ )] ₂ , Mg[BF ₃ (C ₂ F ₅ )] ₂ , Mg[BF ₃ (C ₃ F ₇ )] ₂ , Mg[BF ₃ (C ₄ F ₉ )] ₂ , Mg[C(SO ₂ CF ₃ ) ₃ ] ₂ , Mg(CF ₃ SO ₃ ) ₂ , Mg(CF ₃ COO) ₂ and Mg(RCOO) ₂ (R is an alkyl group with 1 to 4 carbons, phenyl , or naphthyl) at least one selected from the group consisting of.

The electrolyte salt is preferably one selected from the group consisting of amide-based lithium salt, amide-based sodium salt, amide-based calcium salt, and amide-based magnesium salt, more preferably amide-based magnesium salt. Amine lithium salt.

The imide-based lithium salt can be Li[TFSI], Li[FSI] and the like. The imide-based sodium salt can be Na[TFSI], Na[FSI] and the like. The imide calcium salt can be Ca[TFSI] ₂ , Ca[FSI] ₂ or the like. The imide-based magnesium salt may be Mg[TFSI] ₂ , Mg[FSI] ₂ or the like.

In order to suitably produce the electrolyte layer 7, the content of the electrolyte salt may be not less than 10% by mass and not more than 60% by mass based on the total amount of the electrolyte composition. From the viewpoint of improving the conductivity of the electrolyte layer, the content of the electrolyte salt is preferably 20% by mass or more, and from the viewpoint of being able to charge and discharge the lithium secondary battery at a high load rate, it is preferably 30% by mass or more. good.

The oxide particles are, for example, particles of inorganic oxides. The inorganic oxide may be, for example, an inorganic oxide containing the following as constituent elements: Li, Mg, Al, Si, Ca, Ti, Zr, La, Na, K, Ba, Sr, V, Nb, B, Ge, etc. . The oxide particles are preferably at least one selected from the group consisting of SiO ₂ , Al ₂ O ₃ , AlOOH, MgO, CaO, ZrO ₂ , TiO ₂ , Li ₇ La ₃ Zr ₂ O ₁₂ and BaTiO ₃ particle. Since the oxide particles have polarity, they promote the dissociation of the electrolyte in the electrolyte layer 7 , and accelerate the amorphization of the matrix polymer to increase the diffusion rate of the cationic component of the electrolyte.

From the viewpoint of improving electrical conductivity, the average primary particle diameter of the oxide particles (average primary particle diameter) is preferably 0.005 μm (5 nm) or more, preferably 0.01 μm (10 nm) or more, and 0.015 μm or more. More than μm (15 nm) is more preferable. From the viewpoint of thinning the electrolyte layer 7, the average primary particle diameter of the oxide particles is preferably not more than 1 μm (1000 nm), more preferably not more than 0.1 μm (100 nm), and not more than 0.05 μm (50 nm). better. From the viewpoint of increasing the conductivity while making the electrolyte layer 7 thinner and suppressing the protrusion of oxide particles from the surface of the electrolyte composition (electrolyte layer 7), the average primary particle diameter of the oxide particles is 0.005 to 1 μm, It is preferably 0.01-0.1 μm, or 0.015-0.05 μm. The average primary particle diameter of the oxide particles can be measured by observing the oxide particles using a transmission electron microscope or the like.

The average particle diameter of the oxide particles is preferably at least 0.005 μm, more preferably at least 0.01 μm, more preferably at least 0.03 μm. The average particle size of the oxide particles is preferably not more than 5 μm, more preferably not more than 3 μm, more preferably not more than 1 μm. The average particle diameter of the oxide particles is measured by the laser diffraction method, and when the volume accumulation particle size distribution curve is drawn on the small particle diameter side, it corresponds to the particle diameter at which the volume accumulation becomes 50%.

The shape of the oxide particles may be, for example, massive or approximately spherical. The aspect ratio of the oxide particles is preferably 10 or less, more preferably 5 or less, and more preferably 2 or less from the viewpoint of making electrolyte layer 7 thinner. The aspect ratio is defined as the ratio of the length in the long axis direction of the particle (the maximum length of the particle) to the length in the short axis direction of the particle (the minimum length of the particle) in the scanning electron microscope photograph of the oxide particle. The length of the particles can be obtained by statistically calculating the aforementioned photographs using commercially available image processing software (for example, image analysis software manufactured by Asahi Kasei Engineering Co., Ltd.: A Xiangjun (registered trademark)).

From the viewpoint of promoting dissociation of the electrolyte, the content of the oxide particles is preferably at least 5% by mass, more preferably at least 7% by mass, and more preferably at least 10% by mass, based on the total amount of the electrolyte composition. From the viewpoint of further improving the electrical conductivity, the content of the oxide particles is preferably at most 50% by mass, more preferably at most 40% by mass, and more preferably at most 20% by mass.

The fibers may be organic fibers or inorganic fibers, or organic-inorganic hybrid fibers obtained by mixing organic fibers and inorganic fibers. Examples of organic fibers include cellulose fibers, resin fibers, and carbon fibers, and examples of inorganic fibers include glass fibers and ceramic fibers. The fibers are preferably at least one selected from the group consisting of cellulose fibers, resin fibers, and glass fibers. From the viewpoint of improving the smoothness of the electrolyte layer, the fibers are preferably cellulose fibers.

Cellulosic fibers, which can be, for example, natural cellulose fibers such as conifer wood pulp, hardwood wood pulp, reed (esparto) pulp, abaca pulp, sisal pulp, cotton pulp, or organic solvent spinning of these natural cellulose fibers Regenerated cellulose fibers such as lyocell fibers obtained from yarn.

Resin fiber can be natural resin fiber or synthetic resin fiber. The natural resin constituting the natural resin fiber may be, for example, latex, natural rubber or the like. The synthetic resin constituting the synthetic resin fiber may be, for example, polyetheretherketone, polyimide, polyester, polyacrylonitrile, or the like. In one embodiment, the resin fibers are fibers of a resin (polymer) different from the matrix polymer.

From the viewpoint of further suppressing short circuiting, the fiber is preferably a fiber having heat resistance. The term "heat resistance" refers to the characteristic that the fiber maintains its original state (solid state) without melting or decomposing at high temperature. The fiber may be a fiber that does not melt or decompose in an environment of preferably 150°C or higher, more preferably 200°C or higher, further preferably 300°C or higher. The so-called melted or decomposed state of the fiber is equivalent to using the thermogravimetric differential thermal analysis method (TG; Thermalgravimetry, DTA; Differential Thermal Analysis), under the condition of atmospheric circulation, the fiber is heated at a certain heating rate and the weight decreases. Or in the case of exothermic/endothermic reactions. As an example of a method for judging melting or decomposition of fibers (when there is weight loss), when the weight loss of the sample continues after the weight loss of the sample reaches 1%, it can be determined that the fiber has been thermally decomposed. In addition, the starting temperature of melting or decomposition is the temperature at which the tangent of the above-mentioned weight loss curve is extended to the baseline before the weight loss starts, and comes into contact with the intersection of the tangent and the baseline. In addition, in the air, after the fiber is left in the above-mentioned temperature environment, the disappearance of the fiber can be confirmed with the naked eye, and the case where the fiber is deformed or discolored due to melting also corresponds to this state.

The shape of the fiber should just be an elongated shape with a certain length. From the viewpoint of easily suppressing thermal shrinkage of the electrolyte composition, the aspect ratio of the fibers may be 10 or more, preferably more than 10, more preferably 20 or more, more preferably 50 or more, and most preferably 100 or more. The aspect ratio of the fiber can be obtained by the same method as the method for calculating the aspect ratio of the above-mentioned oxide particles. In other words, the fiber length and fiber diameter can be obtained from the scanning electron microscope photograph of the fiber and statistically calculated.

In the present embodiment, from the viewpoint of easily suppressing thermal shrinkage of the electrolyte composition, the average length of the fibers is not less than the average particle diameter of the oxide particles, preferably at least two times, or at least five times the average particle diameter of the oxide particles. , 10 times or more, 20 times or more, 50 times or more, or 100 times or more. The average length of the fibers is preferably at least 1 μm, at least 5 μm, at least 10 μm, at least 30 μm, and at least 40 μm. From the viewpoint of suppressing the fibers protruding from the electrolyte layer and making the electrolyte layer 7 smooth when forming a secondary battery, the average length of the fibers is preferably 10000 μm or less, 5000 μm or less, 3000 μm or less, 2000 μm or less, 1500 μm or less. Below μm, below 1000 μm, below 500 μm, below 100 μm, or below 50 μm. In this specification, the average length of fibers is a scanning electron microscope photograph, select 3 photographs in which the fibers are taken as a whole in order to avoid repeated measurements, and divide the cumulative value of the fiber length by the fiber for each photograph. The average of the values obtained from the total number of .

In general, an electrolyte composition can be produced as long as the above-mentioned matrix polymer, oxide particles, and electrolyte salt are used, but in an environment of, for example, 150°C or higher or 200°C or higher, the matrix polymer softens or melts, and the electrolyte composition Things shrink slowly. At this time, since the oxide particles contained in the electrolyte composition move along with the shrinkage, the electrical insulation of the electrolyte composition may deteriorate. For example: if a metal such as a nail is pierced into the secondary battery for some reason and a short circuit caused by the metal occurs locally between the positive electrode and the negative electrode, a rapid heat release will occur here, and the battery composed of electrolyte The electrolyte layer formed by the material will shrink due to heat. In this case, there is a possibility that the short-circuit area between the positive electrode and the negative electrode will further expand, the short-circuit current will also increase, and heat generation may continue or expand. As a result, the secondary battery may catch fire, emit smoke, or rupture, which poses a problem in terms of safety.

The inventors of the present invention considered that movement of oxide particles due to heat shrinkage of the electrolyte composition has become one of the main causes of short circuit (expansion of the short circuit area), and after searching for the composition of the electrolyte composition in which the oxide particles do not move at high temperature, As a result, the electrolyte composition of this embodiment was found. It is estimated that the electrolyte composition of this embodiment contains fibers having an average length equal to or greater than the average particle diameter of the oxide particles, so that the fibers function as obstacles to suppress the movement of the oxide particles, thereby suppressing the heat dissipation of the electrolyte composition. Shrinkage, as a result, short circuit at high temperature can be suppressed.

The average fiber diameter of the fibers is preferably not more than the thickness of the electrolyte layer 7 , more preferably not more than 1/3 of the thickness of the electrolyte layer 7 . The average fiber diameter of the fibers is preferably at most 10 μm, more preferably at most 5 μm, more preferably at most 1 μm. By setting the average fiber diameter to be equal to or smaller than the thickness of the electrolyte layer 7 , a thin electrolyte layer 7 can be produced, and the migration of oxide particles can be suppressed even by adding a small amount of fibers. The average fiber diameter of the fibers may be, for example, 0.01 μm or more. In this specification, the average fiber diameter of the fiber is selected from the scanning electron microscope photographs, and the whole fiber is captured in the photographs in order to avoid repeated measurements, and the accumulated value of the diameter of the fibers is divided by Average value of values obtained with total number of fibers.

Based on the total amount of the electrolyte composition, the fiber content is preferably at least 0.05% by mass, more preferably at least 0.1% by mass, and more preferably at least 0.3% by mass. Thereby, the fibers are uniformly prepared in the electrolyte composition, and the migration of oxide particles can be effectively suppressed. Based on the total amount of the electrolyte composition, the fiber content is preferably not more than 10 mass%, more preferably not more than 8 mass%, more preferably not more than 5 mass%. Thereby, more oxide particles with high heat resistance can be blended in the electrolyte composition, and when a slurry containing the electrolyte composition is blended to form the electrolyte layer 7 in the secondary battery 1, the fluidity of the slurry is good , and a thinner electrolyte layer 7 can be formed.

The ionic liquid contains the following anionic components and cationic components. In addition, in this embodiment, an ionic liquid is a substance which becomes liquid at -20 degreeC or more.

式(1)中，m及n各自獨立地表示0～5的整數。m及n可相互為相同或不同，較佳是相互為相同。The anion components of the ionic liquid are not particularly limited, and can be anions of halogens such as Cl ^－ , Br ^－ , I ^－ ; inorganic anions such as BF ₄ ^－ , N(SO ₂ F) ₂ ^－ ; B(C ₆ H ₅ ) ₄ ^－ , CH ₃ SO ₂ O ^－ , CF ₃ SO ₂ O ^－ , N(SO ₂ C ₄ F ₉ ) ₂ ^－ , N(SO ₂ CF ₃ ) ₂ ^－ , N(SO ₂ C ₂ F ₅ ) ₂ ^－ and other organic anions Wait. The anionic component of the ionic liquid preferably contains at least one anionic component represented by the following formula (1).

In formula (1), m and n each independently represent the integer of 0-5. m and n may be the same as or different from each other, and are preferably the same as each other.

The cationic component of the ionic liquid is preferably at least 1 selected from the group consisting of chain quaternary onium salt cations, piperidinium salt cations, pyrrolidinium salt cations, pyridinium salt cations and imidazolium salt cations. kind.

式(2)中，R¹ ～R⁴ 各自獨立地表示碳數1～20的鏈狀烷基、或由R－O－(CH₂ )_n －表示的鏈狀烷氧基烷基，且R表示甲基或乙基，n表示1～4的整數，X表示氮原子或磷原子；由R¹ ～R⁴ 表示的烷基的碳數以1～20為佳，以1～10較佳，以1～5更佳。The chain quaternary onium salt cation is, for example, a compound represented by the following formula (2).

In formula (2), R ¹ to R ⁴ each independently represent a chained alkyl group having 1 to 20 carbons, or a chained alkoxyalkyl group represented by R—O—(CH ₂ ) _n -, and R Represents a methyl or ethyl group, n represents an integer of 1 to 4, X represents a nitrogen atom or a phosphorus atom; the carbon number of the alkyl group represented by R ¹ to R ⁴ is preferably 1 to 20, more preferably 1 to 10, 1-5 is better.

式(3)中，R⁵ 及R⁶ 各自獨立地表示碳數1～20的烷基、或由R－O－(CH₂ )_n －表示的烷氧基烷基，且R表示甲基或乙基，n表示1～4的整數；由R⁵ 及R⁶ 表示的烷基的碳數以1～20為佳，以1～10較佳，以1～5更佳。The piperidinium salt cation is, for example, a nitrogen-containing six-membered ring compound represented by the following formula (3).

In formula (3), R ⁵ and R ⁶ each independently represent an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R-O-(CH ₂ ) _n -, and R represents methyl or Ethyl, n represents an integer of 1-4; the carbon number of the alkyl group represented by R ⁵ and R ⁶ is preferably 1-20, more preferably 1-10, more preferably 1-5.

式(4)中，R⁷ 及R⁸ 各自獨立地表示碳數1～20的烷基、或由R－O－(CH₂ )_n －表示的烷氧基烷基，且R表示甲基或乙基，n表示1～4的整數；R⁷ 及R⁸ 表示的烷基的碳數以1～20為佳，以1～10較佳，以1～5更佳。The pyrrolidinium salt cation is, for example, a five-membered ring compound represented by the following formula (4).

In formula (4), R ⁷ and R ⁸ each independently represent an alkyl group having 1 to 20 carbon atoms, or an alkoxyalkyl group represented by R-O-(CH ₂ ) _n -, and R represents methyl or Ethyl, n represents an integer of 1-4; the carbon number of the alkyl group represented by R ⁷ and R ⁸ is preferably 1-20, more preferably 1-10, more preferably 1-5.

式(5)中，R⁹ ～R¹³ 各自獨立地表示碳數1～20的烷基、由R－O－(CH₂ )_n －表示的烷氧基烷基、或氫原子，且R表示甲基或乙基，n表示1～4的整數；由R⁹ ～R¹³ 表示的烷基的碳數以1～20為佳，以1～10較佳，以1～5更佳。The pyridinium salt cation is, for example, a compound represented by the following formula (5).

In formula (5), R ⁹ to R ¹³ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group represented by R-O-(CH ₂ ) _n -, or a hydrogen atom, and R represents Methyl or ethyl, n represents an integer of 1-4; the number of carbons in the alkyl group represented by R ⁹ -R ¹³ is preferably 1-20, more preferably 1-10, more preferably 1-5.

式(6)中，R¹⁴ ～R¹⁸ 各自獨立地表示碳數1～20的烷基、由R－O－(CH₂ )_n －表示的烷氧基烷基、或氫原子，且R表示甲基或乙基，n表示1～4的整數；由R¹⁴ ～R¹⁸ 表示的烷基的碳數以1～20為佳，以1～10較佳，以1～5更佳。The imidazolium salt cation is, for example, a compound represented by the following formula (6).

In formula (6), R ¹⁴ to R ¹⁸ each independently represent an alkyl group having 1 to 20 carbon atoms, an alkoxyalkyl group represented by R—O—(CH ₂ ) _n— , or a hydrogen atom, and R represents Methyl or ethyl, n represents an integer of 1-4; the number of carbons in the alkyl group represented by R ¹⁴ -R ¹⁸ is preferably 1-20, more preferably 1-10, more preferably 1-5.

From the standpoint of suitable fabrication of the electrolyte layer 7, the content of the ionic liquid may be not less than 10% by mass and not more than 60% by mass based on the total amount of the electrolyte composition. From the viewpoint of increasing the conductivity of the electrolyte layer 7 by increasing the content of the electrolyte salt, the lithium secondary battery can be charged and discharged at a high load rate, based on the total amount of the electrolyte composition, the content of the ionic liquid is It is preferably at most 55% by mass, more preferably at most 50% by mass.

From the viewpoint of further improving the conductivity and suppressing the reduction in the capacity of the secondary battery, the total content of the electrolyte salt and the ionic liquid is preferably at least 10% by mass, and at least 25% by mass based on the total amount of the electrolyte composition. Preferably, it is more preferably at least 40% by mass. From the viewpoint of suppressing the decrease in the strength of the electrolyte composition, the total content of the electrolyte salt and the ionic liquid is preferably 80% by mass or less, more preferably 70% by mass or less, based on the total amount of the electrolyte composition.

From the viewpoint of further improving the charge and discharge characteristics, the concentration of the electrolyte salt per unit volume of the ionic liquid is preferably 0.5 mol/L or more, preferably 0.7 mol/L or more, more preferably 1.0 mol/L or more, and It is preferably below 2.0 mol/L, more preferably below 1.8 mol/L, more preferably below 1.6 mol/L.

The electrolyte composition may further contain, for example, the following non-aqueous solvents for the purpose of further improving the conductivity: propylene carbonate, butyl carbonate, vinylene carbonate, γ-butyrolactone, diethyl carbonate, methyl carbonate Ethyl ester, 1,2-dimethoxyethane, 2-methyltetrahydrofuran, dimethylsulfene, 1,3-dioxolane (1,3-dioxolane), formamide, dimethyl Methyl formamide, methyl propionate, ethyl propionate, phosphate triester, trimethoxymethane, dioxolane, diethyl ether, cyclobutane, 3-methyl-2-oxazolidinone ( 3-methyl-2-oxazolidinone), tetrahydrofuran, 1,2-diethoxyethane, ethyl chloride carbonate, propyl chloride carbonate, etc.

From the viewpoint of improving the electrical conductivity and improving the strength, the thickness of the electrolyte layer 7 is preferably 5 μm or more, more preferably 10 μm or more. From the viewpoint of suppressing the resistance of the electrolyte layer 7, the thickness of the electrolyte layer 7 is preferably not more than 100 μm, more preferably not more than 50 μm, more preferably not more than 30 μm.

In the electrolyte composition of the present embodiment, as described above, there is an effect that thermal shrinkage is less likely to occur and short-circuiting (enlargement of the short-circuit area) is suppressed. This effect can be confirmed, for example, by subjecting the electrolyte composition to a nail penetration simulation test. The nail penetration simulation test is a test assuming a state where a metal such as a nail penetrates into the secondary battery, and is a test for evaluating the safety of the secondary battery. In the nail penetration simulation test, a soldering iron or the like heated to a constant temperature of 100° C. or higher may be used. The temperature can be set arbitrarily, and may be, for example, 150° C. or higher. A sample is produced by sandwiching the electrolyte composition between metal foils such as copper foils which are assumed to be electrodes, and a voltage is applied to the sample. It is also possible to use positive and negative electrodes actually used in batteries instead of the metal foil, and to interpose the electrolyte composition therebetween. If a constant voltage is maintained between the positive electrode and the negative electrode, the current will gradually decay. However, since the electrolyte composition has ion conductivity, after a certain voltage is applied, a current will flow due to the movement of ions for a short period of time. After the current reaches the bottom value, insert the tip of the heated soldering iron toward the layered direction of the sample. Then, the tip of the soldering iron was pulled out from the sample, and the insulation resistance between the copper foils after the tip of the soldering iron was inserted was confirmed. Then, for example, if a resistance value of 1 kΩ or more is obtained, it can be judged that short circuit due to thermal contraction of the electrolyte composition has been sufficiently suppressed. Furthermore, the voltage that can be applied in the nailing simulation test only needs to be 10 mV or more and 1 V or less. In order to shorten the test time, the voltage is preferably small, and in order to improve the measurement accuracy of resistance, the voltage is preferably high. high. As a condition for satisfying both, the applied voltage is preferably not less than 0.1 V and not more than 0.5 V.

Next, a method of manufacturing the above-mentioned secondary battery 1 will be described. The manufacturing method of the secondary battery 1 of the present embodiment includes: a first step of forming the positive electrode mixture layer 10 on the positive electrode collector 9 to obtain the positive electrode 6; a second step of forming the positive electrode mixture layer 10 on the negative electrode collector 11. Negative electrode mixture layer 12 to obtain negative electrode 8;

In the first step, the positive electrode 6 is obtained by, for example, using a kneader, a disperser, etc. to disperse the materials used in the positive electrode mixture layer in a dispersion medium to obtain a slurry-like positive electrode mixture, and then This positive electrode mixture is applied to the positive electrode current collector 9 by doctor blade coating method, dip coating method, spraying method, etc., and then the dispersion medium is volatilized. After volatilizing the dispersion medium, a compression molding step can be performed by rolling if necessary. The positive electrode mixture layer 10 can be formed into a multilayered positive electrode mixture layer by performing the steps from the above-mentioned application of the positive electrode mixture to the volatilization of the dispersion medium a plurality of times.

The dispersion medium used in the first step may be water, 1-methyl-2-pyrrolidone (hereinafter also referred to as NMP), or the like.

In the second step, the method of forming the negative electrode mixture layer 12 on the negative electrode current collector 11 may be the same method as that in the above-mentioned first step.

In the third step, in one embodiment, the electrolyte layer 7 is formed on at least any one of the positive electrode mixture layer 10 side of the positive electrode 6 and the negative electrode mixture layer 12 side of the negative electrode 8 by coating, preferably by It is applied and formed on both the positive electrode mixture layer 10 side of the positive electrode 6 and the negative electrode mixture layer 12 side of the negative electrode 8 . At this time, for example, the positive electrode 6 provided with the electrolyte layer 7 and the negative electrode 8 provided with the electrolyte layer 7 are stacked such that the electrolyte layers 7 are in contact with each other, for example, by lamination to obtain the secondary battery 1 .

The method of forming the electrolyte layer 7 on the positive electrode mixture layer 10 by coating is, for example, the following method: After dispersing the material used in the electrolyte layer 7 in a dispersion medium to obtain a slurry, use an applicator (applicator) to This electrolyte composition is coated on the positive electrode mixture layer 10 . The dispersion medium is preferably water, NMP, etc. The electrolyte salt can be dissolved in the ionic liquid and then dispersed in the dispersion medium together with other materials.

The method of forming the electrolyte layer 7 on the negative electrode mixture layer 12 by coating may be the same method as the method of forming the electrolyte layer 7 on the positive electrode mixture layer 10 by coating.

In the third step, in other embodiments, the electrolyte layer 7 is formed by, for example, manufacturing an electrolyte sheet having an electrolyte composition on a substrate. Fig. 4(a) is a schematic cross-sectional view showing an electrolyte sheet according to an embodiment. As shown in FIG. 4( a ), electrolyte sheet 13A has base material 14 and electrolyte layer 7 provided on base material 14 .

Electrolyte sheet 13A is produced, for example, by dispersing the material used in electrolyte layer 7 in a dispersion medium to obtain a slurry, applying the slurry on substrate 14, and volatilizing the dispersion medium. The dispersion medium is preferably water, NMP, toluene, etc.

The substrate 14 is not limited as long as it has heat resistance to withstand the heat to volatilize the dispersion medium, does not react with the electrolyte composition, and is not swelled by the electrolyte composition. For example, it is a film-like resin. The substrate 14, specifically, can be a film composed of polyethylene terephthalate, polytetrafluoroethylene, polyimide, polyether ketone, polyether ketone and other resins (generally used) engineering plastics).

The condition of the substrate 14 is such that it can withstand the processing temperature at which the dispersion medium is vaporized during the production of the electrolyte layer. When the softening point of the base material 14 (the temperature at which the plastic begins to deform) or the melting point is set as the heat-resistant temperature, the temperature is the lowest from the viewpoint of compatibility with the ionic liquid used in the electrolyte layer 7 The temperature is preferably 50°C or higher, more preferably 100°C or higher, more preferably 150°C or higher, and may be, for example, 400°C or lower. If a base material having the above-mentioned heat-resistant temperature is used, the above-mentioned dispersion medium (NMP, toluene, etc.) can be preferably used.

The thickness of the base material 14 is preferably as thin as possible while maintaining the strength capable of withstanding the tensile force generated by the coating device. From the viewpoint of reducing the overall volume of the electrolyte sheet 13A while ensuring strength when the electrolyte composition is applied to the substrate 14, the thickness of the substrate 14 is preferably 5 μm or more, preferably 10 μm or more, and at least 10 μm. More preferably 25 μm or more, more preferably 100 μm or less, more preferably 50 μm or less, more preferably 40 μm or less.

The electrolyte sheet can also be continuously produced while being wound into a roll. At this time, a part of the electrolyte layer 7 may stick to the base material 14 due to the contact between the surface of the electrolyte layer 7 and the back surface of the base material 14, and the electrolyte layer 7 may be damaged. In order to prevent such a situation, the electrolyte sheet may be provided with a protective material on the side opposite to the base material 14 of the electrolyte layer 7 as another embodiment. Fig. 4(b) is a schematic cross-sectional view showing an electrolyte sheet according to another embodiment. As shown in FIG. 4( b ), the electrolyte sheet 13B further includes a protective material 15 on the side opposite to the base material 14 of the electrolyte layer 7 .

The protective material 15 is only required to be easily peelable from the electrolyte layer 7, and is preferably a nonpolar resin film such as polyethylene, polypropylene, or polytetrafluoroethylene. If a nonpolar resin film is used, the protective material 15 can be easily peeled off without the electrolyte layer 7 and the protective material 15 sticking to each other.

From the viewpoint of ensuring strength while reducing the volume of the entire electrolyte sheet 13B, the thickness of the protective material 15 is preferably at least 5 μm, more preferably at least 10 μm, and preferably at most 100 μm, preferably at most 50 μm. Good, more preferably below 30 μm.

From the viewpoint of suppressing deterioration in a low-temperature environment and suppressing softening in a high-temperature environment, the heat-resistant temperature of the protective material 15 is preferably -30°C or higher, preferably 0°C or higher, and preferably 100°C or lower. It is better below 50°C. When the protective material 15 is provided, since the volatilization step of the above-mentioned dispersion medium is not required, it is not necessary to increase the heat-resistant temperature.

As a method of using the electrolyte sheet 13A to provide the electrolyte layer 7 between the positive electrode 6 and the negative electrode 8, for example, the substrate 14 is peeled off from the electrolyte sheet 13A, and the positive electrode 6, the electrolyte layer 7, and the negative electrode 8 are separated, for example, by layering These are laminated together to obtain a secondary battery 1 . At this time, the electrolyte layer 7 is positioned on the positive electrode mixture layer 10 side of the positive electrode 6 and the negative electrode mixture layer 12 side of the negative electrode 8, that is, the positive electrode current collector 9, the positive electrode mixture layer 10, the electrolyte layer 7, The negative electrode mixture layer 12 and the negative electrode current collector 11 are laminated. When the electrolyte sheet has been continuously produced while being wound into a roll shape, the roll-shaped electrolyte sheet can be unwound (unrolled), and the electrolyte layer 7 is placed between the positive electrode 6 and the negative electrode 8 before cutting. cutting, and the electrolyte layer 7 can also be arranged between the positive electrode 6 and the negative electrode 8 after cutting the roll-shaped electrolyte sheet.

In the third step, an adhesive layer (not shown) is further provided on the electrolyte layer 7 for the purpose of suitably laminating the electrolyte layer 7 and the positive electrode 6 or the negative electrode 8 . The adhesive layer can be provided by pressing a film-like adhesive or laminating an adhesive layer made on a release film to the electrolyte layer 7, peeling off the release film and removing the adhesive layer. Transfer or apply a liquid adhesive to the electrolyte layer 7 . When the electrolyte sheet 13A is used, the electrolyte sheet on which the adhesive layer is formed can be prepared in advance when the electrolyte sheet 13A is manufactured.

The adhesive layer may contain at least 1 selected from the group consisting of acrylic resin, methacrylic resin, silicone resin, urethane resin, polyvinyl ether, and styrene-butadiene rubber. kind.

When the adhesive layer is provided on the electrolyte layer 7 , the adhesive layer only needs to be provided on at least a part of the electrolyte layer 7 , and may be provided on one end of the electrolyte layer 7 . Thereby, when the electrolyte layer 7 is laminated with the positive electrode 6 or the negative electrode 8, or when the electrolyte layer 7 formed on the positive electrode mixture layer 10 and the negative electrode mixture layer 12 is laminated to each other, the layers are laminated through the adhesive layer, Therefore, wrinkles or ripples are not easily generated during lamination, and a secondary battery in which electrodes (positive electrode 6 and negative electrode 8 ) and electrolyte layer 7 are properly laminated can be produced.

[Second Embodiment] Next, the secondary battery of the second embodiment will be described. Fig. 5 is a schematic cross-sectional view showing one embodiment of the electrode group of the secondary battery according to the second embodiment. As shown in FIG. 5 , the difference between the secondary battery in the second embodiment and the secondary battery in the first embodiment is that the electrode group 2B includes bipolar electrodes 16 . In other words, electrode group 2B includes, in order, positive electrode 6 , first electrolyte layer 7 , bipolar electrode 16 , second electrolyte layer 7 , and negative electrode 8 .

The bipolar electrode 16 is equipped with: a bipolar electrode current collector 17; a positive electrode mixture layer 10, which is arranged on the surface (positive electrode surface) of the negative electrode 8 side of the bipolar electrode current collector 17; and, a negative electrode mixture layer 12, which is arranged on The surface (negative electrode surface) of the positive electrode 6 side of the bipolar electrode current collector 17 .

In the bipolar electrode current collector 17, the positive electrode surface is preferably formed of a material having excellent oxidation resistance, such as aluminum, stainless steel, titanium, or the like. In the bipolar electrode current collector 17 using graphite or an alloy as the negative electrode active material, the negative electrode surface can be formed of a material that does not form an alloy with lithium, specifically stainless steel, nickel, iron, titanium, or the like. When different metals are used for the positive electrode surface and the negative electrode surface, the bipolar electrode current collector 17 may be a coating material in which different kinds of metal foils are laminated. However, when using the negative electrode 8 that operates at a potential that does not form an alloy with lithium, such as lithium titanate, there is no such limitation, and the negative electrode surface may be made of the same material as the positive electrode current collector 9 . At this time, the bipolar electrode current collector 17 may be a single metal foil. The bipolar electrode current collector 17 as a single metal foil may be an aluminum perforated foil having holes with a diameter of 0.1 to 10 mm, a developed metal, a foamed metal plate, or the like. The bipolar electrode current collector 17 can be formed of any material other than the above, as long as it does not undergo changes such as dissolution and oxidation during use of the battery, and its shape, manufacturing method, etc. are also not limited.

The thickness of the bipolar electrode current collector 17 can be more than 10 μm and can be less than 100 μm. From the viewpoint of reducing the overall volume of the positive electrode, it is preferably 10 to 50 μm. From the viewpoint of winding the bipolar electrode, 10 to 20 μm is preferable.

Next, a method of manufacturing the secondary battery according to the second embodiment will be described. The manufacturing method of the secondary battery of this embodiment has: the first step, this step forms the positive electrode mixture layer 10 on the positive electrode current collector 9 to obtain the positive electrode 6; the second step, this step forms the negative electrode on the negative electrode current collector 11 mixture layer 12 to obtain the negative electrode 8; the 3rd step, this step forms the positive electrode mixture layer 10 on one side of the bipolar electrode collector 17 and forms the negative electrode mixture layer 12 on the other side to obtain the bipolar electrode 16; and, the 4th Step, this step provides the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16 and between the negative electrode 8 and the bipolar electrode 16 .

The first step and the second step may be the same method as the first step and the second step of the first embodiment.

In the third step, the method for forming the positive electrode mixture layer 10 on one side of the bipolar electrode current collector 17 may be the same method as that in the first step in the first embodiment. The method of forming the negative electrode mixture layer 12 on the other surface of the bipolar electrode current collector 17 may be the same method as the second step in the first embodiment.

In the fourth step, as a method of providing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16, in one embodiment, the electrolyte layer 7 is formed on the positive electrode mixture layer 10 side of the positive electrode 6 and the bipolar electrode by coating. At least one of the negative electrode mixture layer 12 side of the electrode 16 is preferably formed by coating on both the positive electrode mixture layer 10 side of the positive electrode 6 and the negative electrode mixture layer 12 side of the bipolar electrode 16 . At this time, for example, the positive electrode 6 provided with the electrolyte layer 7 and the bipolar electrode 16 provided with the electrolyte layer 7 are laminated such that the electrolyte layers 7 are in contact with each other, for example, by lamination.

The method of forming the electrolyte layer 7 on the positive electrode mixture layer 10 of the positive electrode 6 and the negative electrode mixture layer 12 of the bipolar electrode 16 by coating may be the same as the following method: Regarding the first embodiment in the first embodiment One embodiment of the three steps is a method of forming the electrolyte layer 7 on the positive electrode mixture layer 10 by coating, and a method of forming the electrolyte layer 7 on the negative electrode mixture layer 12 by coating.

In the fourth step, as a method of providing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16, in other embodiments, the electrolyte layer 7 is formed by, for example, the following method: manufacturing a substrate with an electrolyte composition The electrolyte sheet. The method of manufacturing the electrolyte sheet may be the same method as the method of manufacturing the electrolyte sheets 13A, 13B in the first embodiment.

In the fourth step, the method of disposing the electrolyte layer 7 between the negative electrode 8 and the bipolar electrode 16 may be the same as the method of disposing the electrolyte layer 7 between the positive electrode 6 and the bipolar electrode 16 described above. [Example]

The following examples illustrate the present invention in more detail, but the present invention is not limited by these examples.

[Production of Electrolyte Sheet]

<Example 1>

30 parts by mass of the matrix polymer, that is, a copolymer of vinylidene fluoride and hexafluoropropylene (PVDF-HFP), and ₂₀ parts by mass of oxide particles, that is, SiO particles (product name: AEROSIL OX50, manufactured by Japan AEROSIL Co., Ltd.) Parts, bis(fluorosulfonyl)imide N-methyl-N-propane obtained by dissolving the electrolyte salt, lithium bis(fluorosulfonyl)imide (Li[FSI]) at a concentration of 1.5mol/L Pyrrolidinium (Py13-FSI) (Hereinafter, when expressing the composition of an ionic liquid obtained by dissolving an electrolyte salt, it may be expressed in the form of "concentration of lithium salt/type of lithium salt/type of ionic liquid")50 Parts by mass and 0.4 parts by mass of cellulose fibers (average length 50 μm, average fiber diameter 0.1 μm) were dispersed in 1-methyl-2-pyrrolidone (NMP) as a dispersion medium to prepare a slurry containing an electrolyte composition . This slurry was applied to a substrate made of polyethylene terephthalate (product name: Teonex R-Q51, manufactured by Dupont Teijin Films Co., Ltd., thickness 38 μm) using an applicator. The dispersion medium was volatilized by heating and drying the applied slurry at 80° C. for 1 hour to obtain an electrolyte sheet. In the obtained electrolyte sheet, the thickness of the electrolyte layer was 25±5 μm.

<Example 2>

An electrolyte sheet was produced in the same manner as in Example 1, except that the content of the cellulose fibers in the electrolyte sheet in Example 1 was changed to 1.0 parts by mass.

[Production of 3-layer sample]

Prepare two copper foils which are supposed to be the positive electrode and the negative electrode. The substrates were peeled off from the electrolyte sheets of Examples 1 and 2, and the electrolyte layer was sandwiched between two copper foils to prepare three-layer samples. In the three-layer sample, each layer was arranged so that the electrolyte layer insulated two copper foils (so that the copper foils would not contact each other).

[Evaluation 1 of safety (nail-piercing simulation test)] For the prepared 3-layer samples, a nail penetration simulation test device was used to implement a nail penetration simulation test. The nail puncture simulation test device uses the following: With a support with a movable part that can be lifted up and down, the front end of the soldering iron (FX-600, manufactured by Baiguang Co., Ltd.) is approximately vertically facing downward relative to the ground. fixed. Before the test, a voltage of 0.1 V was applied to the three-layer sample, and after about 10 seconds, it was confirmed that the current almost reached the bottom value. Then, as shown in FIG. 6, a three-layer sample 19 in which the electrolyte layer 7 is sandwiched between two copper foils 18 and 18 is placed under the tip of the soldering iron 20, and the three-layer sample 19 is heated. After reaching 200° C., the tip of the soldering iron 20 was inserted toward the lamination direction of the three-layer sample 19 and held there for about 3 seconds. At this time, the insertion depth D of the tip of the soldering iron 20 was set to 0.5 mm so that the through hole of the copper foil would be 3 mm. Then, with the tip of the soldering iron 20 inserted, the current between the two copper foils 18 and 18 was recorded. Then, the tip of the soldering iron 20 was pulled out above the three-layer sample 19 . The insulation resistance of the three-layer sample 19 was calculated by the following formula (7) from the maximum value of the electric current during 3 seconds when the tip of the soldering iron 20 was inserted. In addition, when the insulation resistance is 1 kΩ or more, it can be said that the short circuit is sufficiently suppressed. Insulation resistance (Ω) = voltage (V) ÷ maximum current (A) during 3 seconds (7)

As a result, the insulation resistance of Example 1 was 1.7 kΩ, and that of Example 2 was 1.1 kΩ. It can be seen that in all examples, there is still sufficient insulation after the nail penetration simulation test.

>Example 3> (Making of positive electrode) 78.5 parts by mass of layered lithium-nickel-manganese-cobalt composite oxide (positive electrode active material), acetylene black (conductive agent, product name: HS-100, DENKA Co., Ltd. 5 parts by mass, 2.5 parts by mass of a copolymer solution of vinylidene fluoride and hexafluoropropylene (solid content 12 mass%), and 14 parts by mass of ionic liquid (1.5 mol/L/Li[FSI]/Py13-FSI) Mix to prepare positive electrode mixture slurry. The positive electrode mixture slurry was coated on both sides of the positive electrode current collector (aluminum foil with a thickness of 15 μm) at a coating amount of 125 g/m ² , and dried by heating. By applying pressure to this electrode, the mixture density was adjusted to 2.7 g/cm ³ . This was punched out so that the size of the mixture layer might become 82 mm x 112 mm, and the positive electrode was produced.

(Preparation of Negative Electrode) 80.4 parts by mass of graphite (negative electrode active material, manufactured by Hitachi Chemical Co., Ltd.), 0.6 parts by mass of carbon fiber (conductive agent, product name: VGCF-H, manufactured by Showa Denko Co., Ltd.), vinylidene fluoride It was mixed with 5 parts by mass of a copolymer solution of hexafluoropropylene (12% by mass of solid content) and 14 parts by mass of an ionic liquid (1.5 mol/L/Li[FSI]/Py13-FSI) to prepare a negative electrode mixture slurry. This negative electrode mixture slurry was coated on both sides of the current collector (copper foil with a thickness of 10 μm) with a coating amount of 60 g/m ² , and heated and dried. By applying pressure to this electrode, the mixture density was adjusted to 1.8 g/cm ³ . This was punched out so that the size of the mixture layer might become 86 mm x 116 mm, and the negative electrode was produced.

(Production of batteries for evaluation) Using the positive electrode, the negative electrode, and the electrolyte layer obtained from the electrolyte sheet produced in Example 1, an evaluation battery was fabricated. Negative electrodes, electrolyte layers, and positive electrodes were stacked in sequence to stack 9 negative electrodes, 16 electrolyte layers, and 8 positive electrodes to form an electrode group. The Al terminal was welded to the positive electrode of the electrode group by ultrasonic waves, the Ni terminal was connected to the negative electrode, and the electrode group was sealed with aluminum lamination to produce a battery for evaluation.

>Example 4> An evaluation battery was produced in the same manner as in Example 3 except that the electrolyte layer obtained from the electrolyte sheet of Example 2 was used.

[Evaluation 2 of safety (nail prick test)] A nail penetration test was performed on the produced battery for evaluation. The battery for evaluation was charged under the following charge and discharge conditions using a charge and discharge device (manufactured by Toyo System Co., Ltd.) before performing the nail penetration test. (1) Perform 3 cycles for initialization: charge with a constant current of 0.1 C until the cut-off voltage is 4.2 V, then charge with a constant voltage with a cut-off voltage of 4.2 V until the total charging time becomes 15 hours or the charging current becomes 0.02 C , and after constant current and constant voltage (CCCV) charging, discharge at 0.1 C constant current (CC) until the cut-off voltage is 2.7 V. Furthermore, the so-called C means "current value (A)/battery capacity (Ah)". (2) Then, after charging at a constant current of 0.1 C to a cut-off voltage of 4.2 V, charge at a constant voltage of a cut-off voltage of 4.2 V until the total charging time becomes 15 hours or the charging current becomes 0.02 C, and CCCV charging is performed.

The aforementioned unit for evaluating the state of charge was fixed to the fixture for the nail penetration test, and then the nail penetration test was performed. In the nail penetration test, a SUS nail (φ3 mm) with a thermocouple was used, the nail penetration speed was set to 40 mm/s, and the penetration depth of the nail was set to penetrate the cell. The evaluation results of the nail penetration test are shown in Table 1. In addition, the drop rate of the voltage by the nail penetration test was calculated|required by the following formula. Voltage reduction rate (%) = (voltage after test (after 5 seconds) - voltage after test (after 600 seconds)) / voltage after test (after 5 seconds) × 100

[Table 1]

After the nailing test, the evaluation batteries of Examples 3 and 4 had a small voltage drop immediately after the nailing (1 second) and after a predetermined time, and all of them could suppress the short circuit. In addition, if the decrease rate of voltage is less than 10%, it can be said that short-circuiting was fully suppressed. In this case, smoke, fire, battery rupture, etc. were not confirmed in the evaluation of the battery, indicating high safety. In addition, the highest battery surface temperature was as low as 39°C in Example 3 and 50°C in Example 4. Furthermore, if the maximum battery surface temperature is 150° C. or lower, it can be said that the safety is sufficient. From the above results, it can be seen that the evaluation batteries of Examples 3 and 4 have sufficient insulation and safety.

1‧‧‧Secondary battery 2, 2A, 2B‧‧‧electrode group 3‧‧‧Battery case 4‧‧‧Positive collector terminal 5‧‧‧Negative collector terminal 6‧‧‧Positive electrode 7‧‧‧electrolyte layer 8‧‧‧Negative electrode 9‧‧‧Cathode collector 10‧‧‧Positive electrode mixture layer 11‧‧‧Negative electrode collector 12‧‧‧Negative electrode mixture layer 13A, 13B‧‧‧electrolyte sheet 14‧‧‧Substrate 15‧‧‧protection material 16‧‧‧bipolar electrode 17‧‧‧Bipolar Electrode Current Collector 18‧‧‧copper foil 19‧‧‧3 layer sample 20‧‧‧Soldering iron D‧‧‧Insertion Depth

Fig. 1 is a perspective view showing a secondary battery according to a first embodiment. Fig. 2 is an exploded perspective view showing an embodiment of the electrode group in the secondary battery shown in Fig. 1 . Fig. 3 is a schematic perspective view showing an embodiment of the electrode group in the secondary battery shown in Fig. 1 . Fig. 4(a) is a schematic cross-sectional view showing an electrolyte sheet according to one embodiment, and Fig. 4(b) is a schematic cross-sectional view showing an electrolyte sheet according to another embodiment. Fig. 5 is a schematic cross-sectional view showing an embodiment of the electrode group in the secondary battery of the second embodiment. Fig. 6 is a schematic cross-sectional view showing the state of a nail penetration simulation test.

Domestic deposit information (please note in order of depositor, date, and number) none

Overseas storage information (please note in order of storage country, organization, date, and number) none

Claims (11)

An electrolyte composition comprising: a matrix polymer; at least one electrolyte salt selected from the group consisting of lithium salts, sodium salts, calcium salts, and magnesium salts; oxide particles; fibers; and, ionic liquids; In addition, the average length of the fibers is equal to or greater than the average particle diameter of the oxide particles, and the content of the fibers is 10% by mass or less based on the total amount of the electrolyte composition. The electrolyte composition according to claim 1, wherein the fibers are at least one selected from the group consisting of cellulose fibers, resin fibers, and glass fibers. The electrolyte composition according to claim 1 or 2, wherein the matrix polymer has a first structural unit selected from the group consisting of tetrafluoroethylene and vinylidene fluoride. The electrolyte composition according to claim 3, wherein, among the structural units constituting the aforementioned matrix polymer, there are: the aforementioned first structural unit; and, a second structural unit, the second structural unit is composed of hexafluoropropylene , acrylic acid, maleic acid, ethyl methacrylate and methyl methacrylate selected from the group. The electrolyte composition according to claim 1 or 2, wherein the electrolyte salt includes an imide-based lithium salt. The electrolyte composition according to claim 1 or 2, wherein the ionic liquid contains at least one anion component represented by the following formula (1): N(SO ₂ C _m F _2m+1 ) (SO ₂ C _n F _2n+1 ) ^- (1) m and n each independently represent an integer of 0 to 5. The electrolyte composition as described in Claim 1 or 2, wherein the aforementioned ionic liquid contains chain quaternary onium salt cations, piperidinium salt cations, pyrrolidinium salt cations, pyridinium salt cations and imidazolium salt cations At least one selected from the formed group is used as a cationic component. An electrolyte sheet comprising: a substrate; and an electrolyte layer provided on the substrate and formed of the electrolyte composition described in any one of claims 1 to 7. The electrolyte sheet according to claim 8, wherein the average fiber diameter of the fibers is not more than the thickness of the electrolyte layer. A secondary battery comprising: a positive electrode; a negative electrode; and an electrolyte layer provided between the positive electrode and the negative electrode, and It is formed by the electrolyte composition described in any one of claims 1 to 7. The secondary battery according to claim 10, wherein the average fiber diameter of the fibers is not more than the thickness of the electrolyte layer.

Images