Semi-solid lithium-ion secondary battery

Abstract

To provide a lithium ion secondary battery having an excellent charging and discharging cycle characteristic and an excellent ion conductivity, a manufacturing method therefor, a solid electrolyte membrane which is used as a cathode and anode separation membrane to thereby materialize a battery excellent in charging and discharging cycle characteristic and excellent in ion conductivity, and a manufacturing method for the solid electrolyte membrane.SOLUTION: A lithium ion secondary battery is provided, comprising a solid electrolyte membrane 22, a cathode layer, and an anode layer, wherein the solid electrolyte membrane 22 includes: an electron-insulating inorganic particle 26 having a particle diameter of 10 to 500 nm; an inorganic solid electrolyte particle 25 larger than the electron-insulating inorganic particle 26 and having electrolyte resistance and an ion conductivity; and a hot melt solidified product 27 filling a void between solid particles and composed of electron-insulating material heat-melted in a specific temperature range, and wherein in the lithium ion secondary battery, the hot melt solidified product composed of the electron-insulating material is in an amorphous state, and the solid electrolyte membrane is formed by arranging the inorganic solid electrolyte particle in a substantially single layer. There are also provided the manufacturing method for the lithium ion secondary battery, and a solid electrolyte suitable for the lithium ion secondary battery, and manufacturing method for the solid electrolyte.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a lithium ion secondary battery and a method for manufacturing the same, and also to a solid electrolyte membrane for a lithium ion secondary battery and a method for manufacturing the same. [Background technology]

[0002] A lithium-ion secondary battery is a storage battery that has a negative electrode, a positive electrode, and an electrolyte sandwiched between the negative and positive electrodes, and is capable of charging and discharging by moving lithium ions back and forth between the two electrodes. Lithium-ion secondary batteries have traditionally used organic electrolyte solutions as the electrolyte. To further improve reliability and safety, development of all-solid-state secondary batteries using non-flammable inorganic solid electrolytes instead of organic electrolyte solutions is underway. All-solid-state secondary batteries, in which the negative electrode, electrolyte, and positive electrode are all solid, are expected to significantly improve the safety and reliability issues associated with batteries using organic electrolyte solutions, and also enable longer battery life.

[0003] During charging, electrons move from the positive electrode to the negative electrode. At the same time, lithium ions are released from the lithium oxides that make up the positive electrode. These lithium ions then travel through the electrolyte to the negative electrode, where they are stored. Some of the lithium ions stored in the negative electrode then absorb electrons and precipitate as metallic lithium. If these metallic lithium deposits grow into dendrites through repeated charge / discharge cycles, they eventually reach the positive electrode, causing internal short circuits and preventing the battery from functioning properly. These dendrites (Li dendrites) are extremely thin, posing a problem not only in lithium ion batteries using organic electrolytes, but also in all-solid-state secondary batteries that use solid electrolytes. Specifically, Li dendrites can grow through even the smallest voids between solid particles in the solid electrolyte layer, such as cracks or pinholes. In order to address the problem of internal short circuits caused by dendrites, Patent Document 1 describes that when the solid electrolyte layer of an all-solid-state secondary battery is formed from an inorganic solid electrolyte material, a thermally molten material of an electronic insulating material such as sulfur or modified sulfur is spread by capillary action into voids between the inorganic solid electrolyte material, and then the molten material is solidified by cooling, thereby filling the voids between the inorganic solid electrolyte material with the thermally molten solidified material of the electronic insulating material and strengthening the dendrite blocking function of the solid electrolyte layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2018 / 164051 Summary of the Invention [Problem to be solved by the invention]

[0005] According to the technology described in Patent Document 1, the gaps between the solid particles in the solid electrolyte layer can be completely filled with an electronic insulating material, blocking the growth of Li dendrites and resulting in an all-solid-state secondary battery with excellent charge-discharge cycle characteristics. As a result of further investigation into the technology described in Patent Document 1, the inventors have found that while this technology can effectively suppress internal short circuits caused by the growth of Li dendrites, it also tends to result in batteries with high resistance. The reason for this is unclear, but it is thought that the electronic insulating material filled in the voids between the inorganic solid electrolyte particles acts as an impediment to lithium ion conduction between the inorganic solid electrolyte particles connected in the thickness direction.

[0006] An object of the present invention is to provide a lithium ion secondary battery that has excellent charge / discharge cycle characteristics and ionic conductivity, and a method for producing the same. Another object of the present invention is to provide a solid electrolyte membrane that can be used as a positive / negative electrode separator for insulating between the positive and negative electrodes of a lithium ion secondary battery, thereby enabling the resulting lithium ion secondary battery to have excellent charge / discharge cycle characteristics and excellent ionic conductivity, and a method for producing the same. [Means for solving the problem]

[0007] The above-mentioned problems of the present invention have been solved by the following means. [1] Electronically insulating inorganic particles having a particle diameter of 10 to 500 nm; inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and ionic conductivity; a solid electrolyte membrane having a thermally melted and solidified material of an electronic insulating material that is solid at 100°C and thermally melts in a temperature range of 200°C or lower, filling the gaps between the particles; a positive electrode layer disposed on one side of the solid electrolyte membrane; a negative electrode layer disposed on the side of the solid electrolyte membrane opposite to the side on which the positive electrode layer is disposed; and The thermally fused and solidified electronic insulating material is in an amorphous state, The lithium ion secondary battery has a thickness of the solid electrolyte film of not less than [particle diameter of the inorganic solid electrolyte particles × 0.7] and not more than [particle diameter of the inorganic solid electrolyte particles × 1.3]. [2] The lithium ion secondary battery according to [1], wherein the positive electrode active material layer constituting the positive electrode layer contains an electrolyte solution, and the positive electrode active material layer has a thickness of 200 to 2000 μm. [3] The lithium ion secondary battery according to [1] or [2], wherein the negative electrode active material constituting the negative electrode layer contains metallic lithium. [4] The lithium ion secondary battery according to any one of [1] to [3], wherein the negative electrode layer is entirely made of a metallic lithium layer, and a sulfide-based inorganic solid electrolyte layer is disposed between the metallic lithium layer and the solid electrolyte membrane. [5] The lithium ion secondary battery according to [1] or [2], wherein the negative electrode active material layer constituting the negative electrode layer contains an electrolyte solution. [6] The lithium ion secondary battery according to [1], wherein the lithium ion secondary battery is an all-solid-state lithium ion secondary battery. [7] The lithium ion secondary battery according to any one of [1] to [7], wherein the electronic insulating material contains sulfur. [8] The lithium ion secondary battery according to [7], wherein the electronic insulating material is at least one of sulfur and modified sulfur. [9] The lithium ion secondary battery according to any one of [1] to [8], wherein the particle diameter of the electronically insulating inorganic particles and the particle diameter of the inorganic solid electrolyte particles satisfy the following formula: 5≦[particle diameter of inorganic solid electrolyte particles] / [particle diameter of electronically insulating inorganic particles]

[10] Electronically insulating inorganic particles having a particle diameter of 10 to 500 nm; inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and ionic conductivity; a thermally fused solid of an electronic insulating material that is solid at 100°C and thermally melts in a temperature range of 200°C or less, the solid filling the gaps between the particles; The thermally fused and solidified electronic insulating material is in an amorphous state, A solid electrolyte membrane for a lithium ion secondary battery having a thickness of not less than [particle diameter of the inorganic solid electrolyte particles × 0.7] and not more than [particle diameter of the inorganic solid electrolyte particles × 1.3].

[11]

[11] The solid electrolyte membrane for a lithium ion secondary battery according to

[10] , wherein the electronic insulating material contains sulfur.

[12] 12. The solid electrolyte membrane for a lithium ion secondary battery according to claim 11, wherein the electronic insulating material is at least one of sulfur and modified sulfur.

[13] Electronically insulating inorganic particles with a particle size of 10 to 500 nm inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and Li ion conductivity; An electronic insulating material that is solid at 100°C and melts in a temperature range of 200°C or less. and solidifying the thermally molten electronic insulating material under a pressure of 100 MPa or more.

[14] A method for producing a lithium ion secondary battery, comprising disposing the solid electrolyte membrane for a lithium ion secondary battery according to any one of

[10] to

[12] between a positive electrode and a negative electrode.

[0008] In this specification, a numerical range expressed using "to" means a range that includes the numerical values before and after "to" as the lower and upper limits. [Effects of the Invention]

[0009] The lithium ion secondary battery of the present invention has excellent charge-discharge cycle characteristics and excellent ionic conductivity. Furthermore, by using the solid electrolyte membrane for a lithium ion secondary battery of the present invention as a positive / negative electrode separator that insulates the positive and negative electrodes of a lithium ion secondary battery, the resulting lithium ion secondary battery can have excellent charge-discharge cycle characteristics and excellent ionic conductivity. Furthermore, the method for producing a lithium ion secondary battery of the present invention can provide a lithium ion secondary battery having excellent charge / discharge cycle characteristics and excellent ionic conductivity. Furthermore, the method for producing a solid electrolyte membrane for a lithium ion secondary battery of the present invention can provide a solid electrolyte membrane that can be used as a positive / negative electrode separator for insulating between the positive and negative electrodes of a lithium ion secondary battery, thereby providing the resulting lithium ion secondary battery with excellent charge / discharge cycle characteristics and excellent ionic conductivity. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a longitudinal sectional view schematically illustrating the basic structure of an all-solid-state lithium-ion secondary battery that is one embodiment of the lithium-ion secondary battery. FIG. [Figure 2] FIG. 1 is a longitudinal cross-sectional view schematically showing a preferred stacking configuration of a lithium ion secondary battery of the present invention. [Figure 3] FIG. 2 is a longitudinal sectional view schematically showing another preferred stacking configuration of the lithium ion secondary battery of the present invention. [Figure 4] FIG. 2 is a longitudinal sectional view schematically showing another preferred stacking configuration of the lithium ion secondary battery of the present invention. [Figure 5] FIG. 2 is a longitudinal sectional view schematically showing another preferred stacking configuration of the lithium ion secondary battery of the present invention. [Figure 6] FIG. 2 is a longitudinal sectional view schematically showing another preferred stacking configuration of the lithium ion secondary battery of the present invention. [Figure 7] FIG. 2 is a longitudinal sectional view schematically showing another preferred stacking configuration of the lithium ion secondary battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Lithium-ion secondary battery] First, the operating mechanism of a general lithium-ion (Li-ion) secondary battery will be described using the configuration of an all-solid-state Li-ion secondary battery shown in FIG. 1 as an example. FIG. 1 is a cross-sectional view showing a typical layer structure of an all-solid-state Li-ion secondary battery, which is one type of Li-ion secondary battery. The all-solid-state Li-ion secondary battery 10 shown in FIG. 1 has a structure in which, viewed from the negative electrode side, a negative electrode current collector 1, a negative electrode active material layer 2 (the negative electrode current collector 1 and the negative electrode active material layer 2 are collectively referred to as the negative electrode layer), a solid electrolyte layer 3, a positive electrode active material layer 4, and a positive electrode current collector 5 (the positive electrode active material layer 4 and the positive electrode current collector 5 are collectively referred to as the positive electrode layer) are laminated in this order, with adjacent layers in direct contact with each other. By employing such a structure, electrons (e -) is supplied, Li ions are released from the positive electrode active material layer 4, and these Li ions pass through the solid electrolyte layer 3 (Li ion conduction) to move to the negative electrode side and are accumulated in the negative electrode active material layer 2. On the other hand, during discharge, the Li ions stored in the negative electrode active material layer 2 are released, and these Li ions pass through the solid electrolyte layer 3 and are returned to the positive electrode side, where they are stored in the positive electrode active material layer 4. At this time, electrons move from the negative electrode side to the positive electrode side via the circuit wiring 7, and are thereby supplied to the operating part 6. In the all-solid-state Li-ion secondary battery 10 shown in the figure, a light bulb is used as the operating part 6, and this is designed to light up when the battery is discharged.

[0012] Furthermore, the all-solid-state Li-ion secondary battery can also be configured such that the solid electrolyte layer 3 and the negative electrode current collector 1 are in direct contact with each other, without the negative electrode active material layer 2. This type of all-solid-state Li-ion secondary battery utilizes the phenomenon in which some of the Li ions accumulated in the negative electrode bond with electrons during charging and deposit as metallic lithium (metallic Li) on the surface of the negative electrode current collector. That is, this type of all-solid-state secondary battery uses the metallic Li deposited on the negative electrode surface as the negative electrode active material layer. For example, metallic Li is said to have a theoretical capacity 10 times or more greater than that of graphite, which is commonly used as a negative electrode active material. Therefore, by depositing metallic Li on the negative electrode and pressing a solid electrolyte layer against the deposited metallic Li, a metallic lithium layer can be formed on the surface of the current collector, making it possible to realize a secondary battery with high energy density. Furthermore, since the thickness of an all-solid-state secondary battery from which the negative electrode active material layer has been removed is thinner, when the battery is wound into a roll, it has the advantage of being able to further suppress the occurrence of cracks and the like in the solid electrolyte layer. In this specification, an all-solid-state Li-ion secondary battery having no anode active material layer simply means that no anode active material layer is formed in the layer formation step in battery production, and as described above, a cathode active material layer is formed between the solid electrolyte layer and the anode current collector by charging (repeated charging and discharging). Furthermore, the all-solid-state Li-ion secondary battery can also be configured such that a layer of metallic lithium, such as a lithium foil, functions as both the negative electrode current collector and the negative electrode active material layer. That is, the negative electrode layer can be a single metallic lithium layer.

[0013] The layer structure and operating mechanism of a general Li-ion secondary battery have been described above using an all-solid-state Li-ion secondary battery as an example. In the above configuration, the solid electrolyte layer 3 has Li-ion conductivity and also functions as a positive / negative electrode separator that insulates the positive and negative electrodes of the Li-ion secondary battery.

[0014] Next, a preferred embodiment of the Li-ion secondary battery of the present invention will be described.

[0015] The Li-ion secondary battery of the present invention is characterized by the configuration of the separator, that is, the Li-ion secondary battery of the present invention employs a solid electrolyte membrane with a specific configuration as the separator. The Li-ion secondary battery of the present invention is not limited to an all-solid-state Li-ion secondary battery, but may also be a Li-ion secondary battery using a liquid electrolyte (liquid electrolyte Li-ion secondary battery), as long as it employs a solid electrolyte membrane formed by combining specific materials and having a specific thickness as defined in the present invention as a separator. In the present invention, the term "liquid electrolyte Li-ion secondary battery" broadly encompasses secondary batteries using a liquid electrolyte. For example, the "liquid electrolyte secondary battery" of the present invention also encompasses so-called semi-solid batteries in which a viscous slurry is prepared by mixing an electrolyte with an electrode active material (a positive electrode active material or a negative electrode active material), and then the slurry is applied thickly to form a semi-solid electrode active material layer (a positive electrode active material layer or a negative electrode active material layer). The formation of such semi-solid electrodes is well known; see, for example, JP 2016-511521 A. A semi-solid electrode active material layer can be made thick, which is advantageous for increasing the energy density of the battery. The thickness of the semi-solid electrode active material layer can be, for example, about 200 to 2000 μm. In addition, in the Li-ion secondary battery of the present invention, it is also preferable that one of the positive electrode active material layer and the negative electrode active material layer contains an electrolytic solution (preferably a semi-solid electrode), and the other does not contain an electrolytic solution (an all-solid electrode). Alternatively, the positive electrode active material layer may contain an electrolyte solution, and no negative electrode active material layer may be provided. In this case, as described above, a negative electrode active material layer made of metallic Li may be formed between the solid electrolyte layer and the negative electrode current collector upon charging. It is also preferable that the negative electrode layer be made of metallic Li.

[0016] The materials, electrolyte, component composition or stacking configuration of layers, and members used in the lithium-ion secondary battery of the present invention, as well as the manufacturing method of the lithium-ion secondary battery, are not particularly limited except for the configuration of the solid electrolyte membrane used as a separator. These materials, electrolytes, members, etc. used in ordinary lithium-ion secondary batteries can be appropriately applied. Furthermore, with regard to the manufacturing method of the lithium-ion secondary battery of the present invention, ordinary methods can be appropriately adopted, except for the configuration of the solid electrolyte membrane used as a separator. For example, International Publication No. 2018 / 164051, Japanese Patent Application Laid-Open No. 2016-201308, Japanese Patent Application Laid-Open No. 2019-12688, etc. can be appropriately referenced. The solid electrolyte membrane, which is a characteristic feature of the Li-ion secondary battery of the present invention, will be described below. Hereinafter, this solid electrolyte membrane will also be referred to as the "solid electrolyte membrane of the present invention."

[0017] <Solid electrolyte membrane (separator)> One embodiment of the solid electrolyte membrane of the present invention contains electronically insulating inorganic particles, inorganic solid electrolyte particles having both electrolyte resistance and Li-ion conductivity, and a thermally melted and solidified product of an electronically insulating material having a thermal melting temperature within a specific temperature range, which fills the voids between these particles. The "electronically insulating inorganic particles," "inorganic solid electrolyte particles," and "electronically insulating material" contained in the solid electrolyte membrane of the present invention are preferably made of different materials. The particle size of the "electronically insulating inorganic particles" contained in the solid electrolyte membrane of the present invention is 10 to 500 nm, and the particle size of the "inorganic solid electrolyte particles" is larger than the particle size of the "electronically insulating inorganic particles". The thickness of the solid electrolyte membrane of the present invention is between [particle diameter of the inorganic solid electrolyte particles × 0.7] and [particle diameter of the inorganic solid electrolyte particles × 1.3]. That is, in the solid electrolyte membrane of the present invention, the inorganic solid electrolyte particles are arranged in a substantially single layer (one layer) in the plane direction. Therefore, in a Li-ion secondary battery using this solid electrolyte layer as a separator, Li ion conduction in the thickness direction of the solid electrolyte layer can be completed by ion conduction within a single particle. Therefore, the resistance of the battery can be kept low. Furthermore, the solid electrolyte membrane of the present invention has voids between the inorganic solid electrolyte particles filled with electronically insulating inorganic particles having a particle size smaller than the inorganic solid electrolyte particles and a thermally melted solidified product of the electronic insulating material. Therefore, even though the inorganic solid electrolyte particles are a thin layer in which they are arranged in a substantially single layer in the planar direction, by using the solid electrolyte membrane as a separator for a Li-ion secondary battery, the growth of Li dendrites can be sufficiently blocked, and a Li-ion secondary battery having excellent charge-discharge cycle characteristics can be provided.

[0018] The materials for forming the solid electrolyte membrane of the present invention will be described in order.

[0019] - Electronically insulating inorganic particles - The electronically insulating inorganic particles contained in the solid electrolyte membrane of the present invention have a particle diameter of 10 to 500 nm, which is smaller than that of inorganic solid electrolyte particles. Therefore, the electronically insulating inorganic particles can penetrate into the voids between the inorganic solid electrolytes. Furthermore, when the electronically insulating material described above is thermally melted with the electronically insulating particles in the voids between the inorganic solid electrolytes, the thermally melted material easily moves into the voids between the solid particles due to capillary action, allowing the voids between the solid particles to be sufficiently filled without gaps with the thermally melted material of the electronically insulating material. Furthermore, when the thermally melted material is cooled (released from the heated state), the electronically insulating inorganic particles restrict the movement of the thermally melted material by their cohesive force, etc., thereby suppressing crystallization of the thermally melted material (maintaining a predetermined amorphous state). In other words, the formation of even small voids through which Li dendrites can penetrate can be suppressed in the solidified material (thermally melted solidified material) obtained by cooling after thermal melting. By melting and solidifying the electronically insulating material under high pressure (for example, 100 MPa or more, preferably 140 MPa or more, more preferably 160 MPa or more, even more preferably 200 MPa or more, and usually 1000 MPa or less), the thermally molten material can be solidified while maintaining an amorphous state more satisfactorily. Note that the electronically insulating inorganic particles themselves have the effect of blocking dendrite growth. Electronically insulating inorganic particles usually do not have lithium ion conductivity. In the solid electrolyte membrane of the present invention, it is essentially the inorganic solid electrolyte particles that are responsible for the Li ion conductivity. However, the electronically insulating inorganic particles may have lithium ion conductivity as long as the effects of the present invention are not impaired. That is, as long as the electronically insulating inorganic particles have a particle diameter of 10 to 500 nm, they may have Li ion conductivity, and their cohesive force suppresses crystallization during solidification of the thermally molten material. If the electronically insulating inorganic particles and the inorganic solid electrolyte particles have the same composition, the selection of a slurry solvent becomes easier, leading to cost reduction. In this specification, the term "solid particles" in the solid electrolyte membrane is used to refer to both inorganic solid electrolyte particles and electronically insulating inorganic particles. In the present invention, whether or not "the thermally melted and solidified material of the electronic insulating material is in an amorphous state" can be determined by micro-Raman spectroscopy. Specifically, whether or not the material is in an amorphous state can be determined by observing the surface of the sample using a micro-Raman spectroscopy device with a resolution of 3 μm. For example, when the electronic insulating material is sulfur, the bandwidth of the Raman shift detected in crystalline sulfur is 3.8 to 4.0 cm. -1 In amorphous sulfur, the band width is 4.5-5.2 cm. -1 Therefore, the Raman shift bandwidth is 4.5-5.2 cm -1 Similarly, when the electronic insulating material is other than sulfur, it is possible to determine whether the material is in an amorphous state by examining in advance the bandwidth in which the peak exists in the crystalline state and the bandwidth in which the peak exists in the amorphous state.

[0020] The particle size of the electronically insulating inorganic particles is preferably 15 to 400 nm, more preferably 20 to 300 nm, even more preferably 20 to 200 nm, still more preferably 25 to 150 nm, and particularly preferably 25 to 100 nm.

[0021] The relationship between the particle sizes of the electronically insulating inorganic particles and the inorganic solid electrolyte particles described in detail later is preferably [particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≧5, and more preferably [particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≧10. The relationship between the particle sizes of the electronic insulating inorganic particles and the inorganic solid electrolyte particles is as follows: 5≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦10000 is preferred, 5≦[Particle size of inorganic solid electrolyte particles] / [Particle size of electronically insulating inorganic particles]≦8000 is more preferred, 5≦[Particle diameter of inorganic solid electrolyte particles] / [Particle diameter of electronically insulating inorganic particles]≦6000 is more preferred, 5≦[Particle diameter of inorganic solid electrolyte particles] / [Particle diameter of electronically insulating inorganic particles]≦4000 is more preferred, 5≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦2000 is more preferred, 5≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦1000 is more preferred, 10≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦600 is more preferred, 10≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦400 is more preferred, 20≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦300 It is also preferable that 20≦[particle size of inorganic solid electrolyte particles] / [particle size of electronically insulating inorganic particles]≦200 It is also preferable to set the following. In the present invention, the term "particle size" refers to the primary particle size, which is the volume-based median diameter (d50).

[0022] The constituent material of the electronically insulating inorganic particles is not particularly limited as long as the inorganic particles have electronic insulation properties. In the present invention, "electronically insulating" means an inorganic particle having an electronic conductivity of 10 at a measurement temperature of 25°C. -9 This means that the electrical conductivity is less than or equal to S / cm. Examples of electronically insulating inorganic particles include aluminum oxide, silicon oxide, boron nitride, cerium oxide, diamond, and zeolite, but the present invention is not limited to these. Metal oxides are preferred as electronically insulating inorganic particles, and aluminum oxide is particularly suitable from the viewpoint that fine particles of about 50 nm can be produced inexpensively with high purity.

[0023] The content of the electronically insulating inorganic particles in the solid electrolyte membrane of the present invention is preferably 5 to 45% by volume, more preferably 10 to 40% by volume, and even more preferably 20 to 30% by volume.

[0024] - Inorganic solid electrolyte particles - The inorganic solid electrolyte particles contained in the solid electrolyte membrane of the present invention are Li-ion conductive inorganic particles composed of a material different from the electronically insulating inorganic particles. As described above, the particle diameter is larger than that of the electronically insulating inorganic particles. The particle diameter of the inorganic solid electrolyte particles is preferably 0.1 μm or more, and also preferably 0.5 μm or more. Furthermore, the particle diameter is usually 200 μm or less, and also preferably 100 μm or less. Specifically, the preferred range of the particle size of the inorganic solid electrolyte particles is preferably 0.1 to 200 μm, more preferably 0.2 to 100 μm, even more preferably 0.4 to 80 μm, still more preferably 0.8 to 50 μm, still more preferably 1 to 40 μm, also preferably 1 to 30 μm, and also preferably 1 to 20 μm. Furthermore, the inorganic solid electrolyte particles preferably have resistance to an electrolyte solution. Since the inorganic solid electrolyte particles have resistance to an electrolyte solution, the inorganic solid electrolyte particles are less likely to cause side reactions, decomposition, etc., even when used as a separator for a Li-ion secondary battery in which the positive electrode layer or negative electrode layer contains an electrolyte solution. Particles of an oxide-based inorganic solid electrolyte, which will be described below, can be preferably used as such inorganic solid electrolyte particles. Oxide-based inorganic solid electrolytes themselves are well known and are widely used as solid electrolytes in all-solid-state secondary batteries.

[0025] (Oxide-based inorganic solid electrolyte) The oxide-based inorganic solid electrolyte contains oxygen atoms (O) and has Li-ion conductivity, and is preferably an electronically insulating compound.

[0026] Specific examples of compounds include Li xa La ya TiO3 [xa=0.3~0.7, ya=0.3~0.7] (LLT), Li xb La yb Zr zb M bb mb O nb (M bbis at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, where xb satisfies 5≦xb≦10, yb satisfies 1≦yb≦4, zb satisfies 1≦zb≦4, mb satisfies 0≦mb≦2, and nb satisfies 5≦nb≦20.), Li xc B yc M cc zc O nc (M cc is at least one element selected from C, S, Al, Si, Ga, Ge, In, and Sn, where xc satisfies 0≦xc≦5, yc satisfies 0≦yc≦1, zc satisfies 0≦zc≦1, and nc satisfies 0≦nc≦6.), Li xd (Al,Ga) yd (Ti,Ge) zd Si ad P md O nd (where 1≦xd≦3, 0≦yd≦1, 0≦zd≦2, 0≦ad≦1, 1≦md≦7, 3≦nd≦13), Li (3-2xe) M ee xe D ee O(xe represents a number between 0 and 0.1, and M ee represents a divalent metal atom. ee represents a halogen atom or a combination of two or more halogen atoms.) Li xf Si yf O zf (1≦xf≦5, 0 <yf≦3、1≦zf≦10)、Li xg S yg O zg (1≦xg≦3, 0 <yg≦2、1≦zg≦10)、Li3BO3-Li2SO4、Li2O-B2O3-P2O5、Li2O-SiO2、Li6BaLa2Ta2O 12 , LiPO (4-3 / 2w) N w (w<1), Li with LISICON (Lithium super ionic conductor) type crystal structure 3.5 Zn 0.25 GeO4, La with perovskite crystal structure 0.55 Li 0.35TiO3, LiTi2P3O with NASICON (sodium super ionic conductor) type crystal structure 12 , Li 1+xh+yh (Al,Ga) xh (Ti,Ge) 2-xh Si yh P 3-yh O 12 (where 0≦xh≦1, 0≦yh≦1), Li7La3Zr2O with a garnet-type crystal structure 12 (LLZ), etc. Phosphorus compounds containing Li, P, and O are also desirable. For example, lithium phosphate (Li3PO4), LiPON, LiPOD, etc., in which some of the oxygen in lithium phosphate is replaced with nitrogen, are also desirable. 1 (D 1 is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc. 1 ON(A 1 is at least one selected from Si, B, Ge, Al, C, Ga, etc.) can also be preferably used.

[0027] The content of inorganic solid electrolyte particles in the solid electrolyte membrane of the present invention is preferably 10 to 90% by volume, more preferably 20 to 80% by volume, even more preferably 30 to 70% by volume, and still more preferably 40 to 60% by volume.

[0028] - Thermally fused and solidified electronic insulating material - The solid electrolyte membrane of the present invention contains a thermally melted solidified product of an electronically insulating material. The voids between solid particles contained in the solid electrolyte membrane of the present invention are filled with a thermally melted solidified product of the electronically insulating material. "Filled with a thermally melted solidified product of the electronically insulating material" means that the electronically insulating material is present in the voids between the solid particles, following the shape of the solid particles and virtually leaving no gaps, and that the electronically insulating material present in the voids between the solid particles has a thermal melting history (has been thermally melted and then cooled and solidified). The electronically insulating material in a thermally melted state permeates the voids between the solid particles due to capillary action and / or pressure, and by solidifying in that state, the voids between the solid particles can be filled with a thermally melted solidified product of the electronically insulating material.

[0029] The electronically insulating material used has physical properties that make it solid at 100°C (i.e., have a melting point above 100°C) but melt at temperatures below 200°C (i.e., have a melting point below 200°C). "Solid at 100°C" means that it is solid at 100°C under 1 atmosphere. Furthermore, "melts at temperatures below 200°C" means that it melts at temperatures below 200°C under 1 atmosphere. By using such an electronically insulating material, a layer can be easily formed using a mixture containing electronically insulating inorganic particles, inorganic solid electrolyte particles, and an electronically insulating material, and heated to a temperature at which the electronically insulating material melts. This heating allows the molten filler to migrate into the gaps between the solid particles by capillary action and / or pressure. The electronically insulating material is then solidified by cooling, creating a state in which the molten and solidified electronically insulating material is embedded in the gaps between the solid particles, conforming to the shape of the solid particles and leaving virtually no gaps.

[0030] The electronic insulating material is preferably a material that is harder than dendrites in the solid state in order to block dendrite growth. Examples include sulfur, modified sulfur, iodine, and a mixture of sulfur and iodine, with sulfur and / or modified sulfur being particularly preferred. Sulfur that can be used as an electronic insulating material refers to elemental sulfur (including sulfur itself and sulfur present in the form of a polymer). Modified sulfur is obtained by kneading sulfur with a modifier. For example, pure sulfur can be kneaded with an olefin-based compound, which is a modifying additive, to obtain modified sulfur in which part of the sulfur is modified into a sulfur polymer. The presence of sulfur or modified sulfur as a thermally molten solid between solid particles without gaps can physically block Li dendrites that have grown between the solid particles. Furthermore, contact between dendrites and sulfur can also cause a reaction between the Li dendrites and sulfur. When Li dendrites come into contact with sulfur, the reaction 2Li+S→Li2S occurs, which is thought to stop the growth of the Li dendrites. When this reaction occurs, reaction products also coexist between the solid particles. These reaction products are electronically insulating compounds that are harder than Li dendrites, and are therefore thought to be able to block the growth of Li dendrites. The reaction between Li dendrites and sulfur expands the volume of the electronically insulating material between the solid particles, which is expected to have the effect of more reliably sealing any small voids remaining between the solid particles.

[0031] In the solid electrolyte membrane of the present invention, the content of the thermally melted and solidified electronic insulating material is preferably 5 to 45% by volume, more preferably 10 to 40% by volume, and even more preferably 20 to 30% by volume.

[0032] In the solid electrolyte membrane of the present invention, an organic binder may be contained between the solid particles. As such an organic binder, any organic binder commonly used in the solid electrolyte layer of a secondary battery can be appropriately used.

[0033] <Manufacturing solid electrolyte membranes (separators)> The method for producing the solid electrolyte membrane of the present invention is not particularly limited as long as it can produce a solid electrolyte membrane that satisfies the requirements of the present invention. An example of the method for producing the solid electrolyte membrane of the present invention will be described below. A composition is prepared by kneading at least the electronically insulating inorganic particles, the inorganic solid electrolyte particles, and the electronically insulating material. This kneading is preferably carried out at a temperature equal to or higher than the thermal melting temperature of the electronically insulating material. The kneaded mixture is then stretched using a roller or the like at a temperature equal to or higher than the thermal melting temperature of the electronically insulating material to form a thin sheet having a thickness specified in the present invention. The resulting mixture is then cooled, whereby the electronically insulating material solidifies from its thermally molten state, yielding a solid electrolyte membrane in which the solid particles are filled with the thermally molten solid of the electronically insulating material. The solidification of the thermally molten electronic insulating material is preferably carried out under pressure. For example, by cooling and solidifying the thermally molten electronic insulating material under a pressure of 100 MPa or more (preferably 140 MPa or more, more preferably 160 MPa or more, even more preferably 200 MPa or more, and usually 1000 MPa or less), the amorphous state of the thermally molten electronic insulating material can be sufficiently maintained during solidification. In other words, crystallization of the thermally molten solidified electronic insulating material, which fills the voids between solid particles, can be suppressed, and the generation of even small voids that could serve as passageways for Li dendrites, electrolyte, etc. can be effectively suppressed.

[0034] The thickness of the solid electrolyte membrane thus obtained is between [particle diameter of inorganic solid electrolyte particles × 0.7] and [particle diameter of inorganic solid electrolyte particles × 1.3]. Even if the thickness of the solid electrolyte membrane is larger than the particle diameter of the inorganic solid electrolyte particles, this "particle diameter" is the primary particle diameter (volume-based median diameter (d50)) as described above. Therefore, as long as the thickness is less than 1.3 times the particle diameter of the inorganic solid electrolyte particles, a sufficient number of inorganic solid electrolyte particles can contact both the positive and negative electrodes. This allows for smooth Li-ion conduction. From the viewpoint of further enhancing Li-ion conductivity, the thickness of the solid electrolyte film is preferably [particle diameter of inorganic solid electrolyte particles × 1.2] or less, also preferably [particle diameter of inorganic solid electrolyte particles × 1.15] or less, also preferably [particle diameter of inorganic solid electrolyte particles × 1.1] or less, and also preferably [particle diameter of inorganic solid electrolyte particles × 1.0] or less. In the present invention, the thickness of the solid electrolyte membrane is defined as the arithmetic mean value of thickness measurements taken at 50 locations at 10 μm intervals on the cross section of the solid electrolyte membrane. The thickness can be measured by observing the cross section of the solid electrolyte membrane with a scanning electron microscope (SEM).

[0035] <Layer structure of lithium-ion secondary batteries> The Li-ion secondary battery of the present invention includes various battery configurations as described above, so long as it has the solid electrolyte membrane of the present invention as a separator. A preferred embodiment of the Li-ion secondary battery of the present invention will be described with reference to the drawings. In the drawings referred to below, the positive electrode current collector and the negative electrode current collector are omitted unless otherwise specified. Furthermore, each drawing is a schematic diagram for facilitating understanding of the present invention, and the size or relative size relationship of each component may be changed for convenience of explanation and does not directly represent the actual relationship. Furthermore, the present invention is not limited to the external shapes and configurations shown in these drawings, except for matters specified in the present invention.

[0036] --Embodiment 1-- The Li-ion secondary battery of Embodiment 1 shown in FIG. 2 employs a semi-solid cathode active material layer 21 containing an electrolytic solution as the cathode active material layer. A solid electrolyte membrane 22 of the present invention, containing inorganic solid electrolyte particles 25, electronically insulating inorganic particles 26, and a thermally fused solid 27 of an electronically insulating material, is provided in contact with the semi-solid cathode active material layer 21, and a solid electrolyte layer 23 containing sulfide-based inorganic solid electrolyte particles is laminated in contact with the solid electrolyte membrane 22. The sulfide-based inorganic solid electrolyte has a lower lithium ion trapping ability and higher Li-ion conductivity than oxide-based inorganic solid electrolytes. However, sulfide-based inorganic solid electrolytes are prone to side reactions and decomposition when in contact with an electrolytic solution. In the first embodiment, a metallic Li anode 24 is provided on the solid electrolyte layer 23. By providing the solid electrolyte layer 23 between the metallic lithium anode 24 and the solid electrolyte membrane 22, the contact resistance with the metallic Li anode is low, and a battery having excellent resistance to Li dendrites can be obtained. The solid electrolyte layer 23 may contain, in addition to sulfide-based inorganic solid electrolyte particles, various components that may be contained in the solid electrolyte layer of a typical all-solid-state secondary battery. Examples of such components include an organic binder such as an organic polymer, an ion-conducting additive, and the like. Furthermore, similar to the solid electrolyte membrane 22, the solid particles of the solid electrolyte layer 23 may be filled with a thermally fused and solidified electronic insulating material.

[0037] As described above, this first embodiment employs a semi-solid cathode active material layer 21 containing an electrolyte solution. Meanwhile, the inorganic solid electrolyte particles 25 constituting the solid electrolyte film 22 in contact with the semi-solid cathode active material layer 21 are composed of an oxide-based inorganic solid electrolyte or the like that is resistant to the electrolyte solution. Therefore, the solid electrolyte film 22 can be directly laminated on the semi-solid cathode active material layer 21. Furthermore, the voids between the solid particles of the solid electrolyte film 22 are tightly filled with a thermally molten solidified product 27 of an electronically insulating material, and this solidified product 27 is also suppressed from crystallizing. This more reliably blocks permeation of the electrolyte solution from the semi-solid cathode active material layer 21 to the negative electrode side, thereby preventing a side reaction between the electrolyte solution and the sulfide-based inorganic solid electrolyte constituting the solid electrolyte layer 23 thereon. Furthermore, the solid electrolyte membrane 22 is a thin separator in which inorganic solid electrolyte particles are arranged in a substantially single layer, yet it can effectively block Li dendrites growing from the negative electrode. In the first embodiment, the semi-solid positive electrode active material layer 21 is used, which allows the positive electrode active material layer to be thick. This allows a high energy density to be achieved. In addition, the negative electrode is formed from metallic Li, which has a large theoretical capacity, which also contributes to a high energy density.

[0038] The sulfide-based inorganic solid electrolyte constituting the solid electrolyte layer 23 will now be described. Sulfide-based inorganic solid electrolytes themselves are well known, and those widely used as solid electrolytes for all-solid-state secondary batteries can be used without any particular restrictions. The sulfide-based inorganic solid electrolyte preferably contains a sulfur atom (S), has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties. The sulfide-based inorganic solid electrolyte preferably contains at least Li, S, and P as elements and has lithium ion conductivity, but may contain elements other than Li, S, and P depending on the purpose. An example of the sulfide-based inorganic solid electrolyte is a lithium ion conductive inorganic solid electrolyte that satisfies the composition represented by the following formula (I). L a1 M b1 P c1 S d1 A e1 Formula (I) In the formula, L represents an element selected from Li, Na, and K, and Li is preferred. M represents an element selected from B, Zn, Sn, Si, Cu, Ga, Sb, Al, and Ge. A represents an element selected from I, Br, Cl, and F. a1 to e1 represent the composition ratio of each element, and a1:b1:c1:d1:e1 satisfies the ratio of 1-12:0-5:1:2-12:0-10. a1 is more preferably 1-9, and more preferably 1.5-7.5. b1 is preferably 0-3. d1 is more preferably 2.5-10, and more preferably 3.0-8.5. e1 is more preferably 0-5, and more preferably 0-3.

[0039] The composition ratio of each element can be controlled by adjusting the blending amounts of raw material compounds when producing the sulfide-based inorganic solid electrolyte, as described below.

[0040] The sulfide-based inorganic solid electrolyte may be amorphous (glass) or crystallized (glass-ceramic), or may be only partially crystallized. For example, Li-PS-based glass containing Li, P, and S, or Li-PS-based glass-ceramic containing Li, P, and S, may be used. The sulfide-based inorganic solid electrolyte can be produced by reacting at least two or more raw materials selected from the group consisting of lithium sulfide (LiS), phosphorus sulfide (e.g., diphosphorus pentasulfide (PS)), elemental phosphorus, elemental sulfur, sodium sulfide, hydrogen sulfide, lithium halides (e.g., LiI, LiBr, LiCl), and sulfides of the elements represented by M above (e.g., SiS, SnS, GeS).

[0041] In the Li-PS glass and Li-PS glass ceramics, the ratio of Li2S to P2S5 is preferably 60:40 to 90:10, more preferably 68:32 to 78:22, in terms of the molar ratio of Li2S:P2S5. By setting the ratio of Li2S to P2S5 within this range, the lithium ion conductivity can be increased. Specifically, the lithium ion conductivity is preferably 1×10 -4 S / cm or more, preferably 1×10 -3 S / cm or more. There is no upper limit, but it is 1×10 -1 It is practical to have a value of S / cm or less.

[0042] Specific examples of sulfide-based inorganic solid electrolytes, including combinations of raw materials, are shown below: Li2S-P2S5, Li2S-P2S5-LiCl, Li2S-P2S5-H2S, Li2S-P2S5-H2S-LiCl, Li2S-LiI-P2S5, Li2S-LiI-Li2O-P2S5, Li2S-LiBr-P2S5, Li2S-Li2O-P2S5, Li2S-Li3PO4-P2S5, Li2S-P2S5-P2O5, Li2S-P2S5-SiS2, Li2S-P2S5-SiS2-LiCl, Li2S-P2S5-SnS, and Li2S-P2S5-Al2S3 , Li2S-GeS2, Li2S-GeS2-ZnS, Li2S-Ga2S3, Li2S-GeS2-Ga2S3, Li2S-GeS2-P2S5, Li2S-GeS2-Sb2S5, Li2S-GeS2-Al2S3, Li2S-SiS2, L i2S-Al2S3, Li2S-SiS2-Al2S3, Li2S-SiS2-P2S5, Li2S-SiS2-P2S5-LiI, Li2S-SiS2-LiI, Li2S-SiS2-Li4SiO4, Li2S-SiS2-Li3PO4, Li 10 GeP2S 12 However, the mixing ratio of each raw material is not important. As a method for synthesizing a sulfide-based inorganic solid electrolyte material using such a raw material composition, for example, an amorphization method can be mentioned. Examples of the amorphization method include a mechanical milling method, a solution method, and a melt quenching method. This is because processing at room temperature becomes possible, and the manufacturing process can be simplified.

[0043] --Embodiment 2-- 3, the semi-solid positive electrode active material layer 31 and the solid electrolyte membrane 32 are the same as the semi-solid positive electrode active material layer 21 and the solid electrolyte membrane 22 of Embodiment 1. In this Embodiment 2, a semi-solid negative electrode active material layer 33 containing an electrolyte is disposed in contact with the solid electrolyte membrane 32 on the negative electrode side thereof. In embodiment 2, the solid electrolyte membrane of the present invention is disposed as a separator between the positive and negative electrodes. Although the separator is thin and has inorganic solid electrolyte particles arranged in a substantially single layer, it can effectively block Li dendrites growing from the negative electrode. In the second embodiment, a semi-solid positive electrode active material layer 31 and a semi-solid negative electrode active material layer 33 are employed, allowing both electrode active material layers to be thick. This allows for a high energy density. Furthermore, the electrolyte solution in the semi-solid positive electrode active material layer 31 and the electrolyte solution in the semi-solid negative electrode active material layer 33 are separated by the solid electrolyte membrane 32 and do not intermingle. Therefore, the electrolyte solution in the semi-solid positive electrode active material layer 31 and the electrolyte solution in the semi-solid negative electrode active material layer 33 can be different electrolyte solutions. This allows for a wider range of choices for the active materials used in the positive and negative electrodes.

[0044] --Embodiment 3-- 4 is a so-called all-solid-state Li-ion secondary battery. A solid electrolyte membrane 42 of the present invention is disposed as an inorganic solid electrolyte layer between a positive electrode active material layer 41 and a negative electrode active material layer 43. The solid electrolyte membrane 42 is the same as the solid electrolyte membrane 22 of the first embodiment.

[0045] --Embodiment 4-- The Li-ion secondary battery of Embodiment 4 shown in FIG. 5 has a configuration similar to that of Embodiment 1, except that a separator sheet 28 is further disposed between the semi-solid positive electrode active material layer 21 and the solid electrolyte membrane 22. A wide variety of separators commonly used in liquid electrolyte Li-ion secondary batteries can be used as this separator sheet 28. Examples of materials for the separator sheet 28 include porous polymer materials, inorganic materials, organic-inorganic hybrid materials, and glass fibers. The volume ratio of the gaps in the separator sheet 28, i.e., the porosity, is preferably 20% to 90%, and more preferably 35% to 80%. Examples of the polymer material include cellulose nonwoven fabric, polyethylene, and polypropylene, and a separator sheet made of a combination of these materials can also be used. A laminate of two or more microporous films with different pore sizes, porosities, pore-closing temperatures, etc. is also preferred. Examples of the inorganic material include oxides such as alumina and silicon dioxide; nitrides such as aluminum nitride and silicon nitride; and sulfates such as barium sulfate and calcium sulfate. By further disposing a separator sheet 28 between the semi-solid positive electrode active material layer 21 and the solid electrolyte membrane 22, it is possible to prevent the positive electrode active material, the conductive additive, the thermally molten solid (sulfur) of the electronic insulating material, etc. from coexisting in the presence of the electrolyte, and it is possible to prevent a side reaction between the positive electrode active material or the conductive additive and the thermally molten solid (sulfur) of the electronic insulating material.

[0046] --Embodiment 5-- The Li-ion secondary battery of Embodiment 5 shown in Fig. 6 has a configuration in which a separator sheet 37 is further disposed between the semi-solid positive electrode active material layer 31 and the solid electrolyte membrane 32 in Embodiment 2. This separator sheet 37 is the same as the separator sheet 28 described in Embodiment 4. By further disposing a separator sheet 37 between the semi-solid positive electrode active material layer 31 and the solid electrolyte membrane 32, it is possible to prevent the positive electrode active material, the conductive additive, the thermally molten solid (sulfur) of the electronic insulating material, etc. from coexisting in the presence of the electrolyte, and it is possible to prevent a side reaction between the positive electrode active material or the conductive additive and the thermally molten solid (sulfur) of the electronic insulating material.

[0047] --Embodiment 6-- 7 has a configuration similar to that of Embodiment 2, except that a separator sheet 37 is further disposed between the semi-solid positive electrode active material layer 31 and the solid electrolyte membrane 32, and a separator sheet 38 is also disposed between the solid electrolyte membrane 32 and the semi-solid negative electrode active material layer 33. These separator sheets 37 and 38 are the same as the separator sheet 28 described in Embodiment 4. By further disposing a separator sheet 37 between the semi-solid positive electrode active material layer 31 and the solid electrolyte membrane 32, it is possible to prevent the positive electrode active material, the conductive additive, the thermally molten solid (sulfur) of the electronic insulating material, etc. from coexisting in the presence of the electrolyte, and it is possible to prevent a side reaction between the positive electrode active material or the conductive additive and the thermally molten solid (sulfur) of the electronic insulating material. Similarly, by further disposing a separator sheet 38 between the semi-solid negative electrode active material layer 33 and the solid electrolyte membrane 32, it is possible to prevent the negative electrode active material, the conductive additive, the thermally molten solid (sulfur) of the electronic insulating material, etc. from coexisting in the presence of the electrolyte, and it is possible to prevent a side reaction between the negative electrode active material or the conductive additive and the thermally molten solid (sulfur) of the electronic insulating material.

[0048] Although preferred embodiments of the Li-ion secondary battery of the present invention have been described with reference to the drawings, the present invention is not limited to these embodiments except as defined in the present invention. For example, the Li-ion secondary battery of the present invention may have a plurality of solid electrolyte membranes of the present invention. For example, two solid electrolyte membranes of the present invention may be stacked and used as a separator.

[0049] <Applications of lithium-ion secondary batteries> The lithium ion secondary battery of the present invention can be used in a variety of applications. While there are no particular limitations on the application, examples of applications include notebook computers, pen-input PCs, mobile PCs, electronic book players, mobile phones, cordless phone handsets, pagers, handheld terminals, portable fax machines, portable copiers, portable printers, headphone stereos, video camcorders, LCD televisions, handheld vacuum cleaners, portable CD players, mini-discs, electric shavers, transceivers, electronic organizers, calculators, memory cards, portable tape recorders, radios, backup power supplies, and memory cards. Other consumer applications include automobiles, electric vehicles, motors, lighting fixtures, toys, game consoles, road conditioners, clocks, flash devices, cameras, and medical devices (pacemakers, hearing aids, shoulder massagers, etc.). Furthermore, the battery can be used for various military and space applications. It can also be combined with solar cells.

[0050] In particular, it is preferable to apply the battery to applications that require both high capacity and high-rate discharge characteristics. For example, in energy storage facilities and the like, which are expected to see an increase in capacity in the future, high safety is essential, while also requiring battery performance. In addition, electric vehicles and the like are expected to be equipped with high-capacity secondary batteries that are charged daily at home. The present invention can be suitably adapted to such usage patterns and exhibits its excellent effects. [Example]

[0051] The present invention will be described in more detail based on examples, but the present invention is not limited to these embodiments.

[0052] [Example 1] Example 1-1 Preparation of solid electrolyte membrane (separator) LLZ (Li7La3Zr2O 12 50% by volume of ammonium hydroxide (particle diameter 3.0 μm, manufactured by Toshima Manufacturing Co., Ltd.), 25% by volume of Al2O3 (particle diameter 50 nm, manufactured by SkySpring Nanomaterials), and 25% by volume of sulfur (S, manufactured by Aldrich, purity >99.98%) were mixed and kneaded at 140°C. The kneaded mixture was sandwiched between two sheets of aluminum foil in a roller machine heated to 150°C and stretched by roll pressing at 160 MPa to produce a sheet with a thickness of 3.5 μm excluding the aluminum foil. This sheet was hot-pressed in warm water at 160°C and 550 MPa, and then cooled to obtain the solid electrolyte membrane of Example 1-1. The resulting solid electrolyte membrane had a thickness of 3.0 μm.

[0053] <Example 1-2> Preparation of Li-ion secondary battery <Preparation of positive electrode sheet> 180 zirconia beads with a diameter of 5 mm were placed in a 45 mL zirconia container (manufactured by Fritsch), and 2.0 g of LPS (sulfide-based inorganic solid electrolyte) synthesized by the method described in [Reference Example 1] of International Publication No. 2018 / 164051, 0.1 g of styrene butadiene rubber (product code 182907, manufactured by Aldrich), and 22 g of octane as a dispersion medium were added. The container was then placed in a Fritsch planetary ball mill P-7 and stirred at a temperature of 25°C and a rotation speed of 300 rpm for 2 hours. Then, the positive electrode active material LiNi 0.85 Co 0.10 Al 0.05 7.9 g of O2 (lithium nickel-cobalt aluminum oxide) was added to the container, and the container was again set in the planetary ball mill P-7, where mixing was continued for 15 minutes at a temperature of 25°C and a rotation speed of 100 rpm, thereby obtaining a positive electrode composition. Next, the positive electrode composition obtained above was applied to a 20 μm thick aluminum foil as a current collector using a Baker applicator and heated at 80 ° C for 2 hours to dry the positive electrode composition. Thereafter, using a heat press, the dried positive electrode layer composition was heated (120 ° C) and pressed (600 MPa, 1 minute) to a predetermined density. In this way, a positive electrode sheet having a positive electrode active material layer with a thickness of 110 μm was produced.

[0054] The positive electrode sheet was placed on the surface of the solid electrolyte membrane of Example 1-1 so that the positive electrode active material layer was in contact with the surface. Furthermore, lithium foil was placed on the side of the solid electrolyte membrane opposite the positive electrode sheet. The laminate thus obtained was fitted with a constraining plate and screws as constraining members, and the tightening force of the screws was adjusted with a torque wrench to a constraining pressure of 8 MPa, to obtain an all-solid-state Li-ion secondary battery of Example 1-2.

[0055] [Example 2] Example 2-1 Preparation of solid electrolyte membrane (separator) A solid electrolyte membrane (thickness: 8.5 μm) of Example 2-1 was obtained in the same manner as in Example 1-1, except that the particle size of the LLZ used in Example 1-1 was changed to 8.0 μm.

[0056] <Example 2-2> Preparation of Li-ion secondary battery The solid electrolyte membrane of Example 2-1 was used to obtain an all-solid-state Li-ion secondary battery of Example 2-2 in the same manner as in Example 1-2.

[0057] [Comparative Example 1] <Comparative Example 1-1> Preparation of solid electrolyte membrane (separator) LLZ (Li7La3Zr2O 12 A mixture of 50% by volume of ammonium nitrate (particle diameter 3.0 μm, manufactured by Toshima Manufacturing Co., Ltd.), 25% by volume of Al2O3 (particle diameter 500 nm, manufactured by SkySpring Materials), and 25% by volume of sulfur (S, manufactured by Aldrich, purity >99.98%) was kneaded at 140°C. The mixture was sandwiched between two sheets of aluminum foil in a roller machine heated to 150°C and stretched by roll pressing at 24 MPa to produce a sheet with a thickness of 100 μm excluding the aluminum foil. The resulting sheet was cooled, and the aluminum foil was peeled off to obtain the solid electrolyte membrane of Comparative Example 1-1.

[0058] <Comparative Example 1-2> Preparation of Li-ion secondary battery Using the solid electrolyte membrane of Comparative Example 1-1, an all-solid-state Li-ion secondary battery of Comparative Example 1-2 was obtained in the same manner as in Example 1-2.

[0059] Comparative Example 2 Comparative Example 2-1 Preparation of solid electrolyte membrane (separator) A solid electrolyte membrane (thickness 100 μm) of Comparative Example 2-1 was obtained in the same manner as in Comparative Example 1-1, except that Al2O3 with a particle diameter of 50 nm (the same as in Example 1-1) was used.

[0060] <Comparative Example 2-2> Preparation of Li-ion secondary battery Using the solid electrolyte membrane of Comparative Example 2-1, an all-solid-state Li-ion secondary battery of Comparative Example 1-2 was obtained in the same manner as in Example 1-2.

[0061] Comparative Example 3 Comparative Example 3-1 Preparation of solid electrolyte membrane (separator) A solid electrolyte membrane (thickness: 3.5 μm) of Comparative Example 3-1 was obtained in the same manner as in Example 1-1, except that the stretching by roll press was performed under conditions of 150°C and 24 MPa, and the hot water hot pressing was not performed.

[0062] <Comparative Example 3-2> Preparation of Li-ion secondary battery Using the solid electrolyte membrane of Comparative Example 3-1, an all-solid-state Li-ion secondary battery of Comparative Example 3-2 was obtained in the same manner as in Example 1-2.

[0063] [Test example] <Evaluation of the state of thermally molten sulfur solids> Using the above-mentioned micro-Raman spectroscopy, it was investigated whether the thermally melted and solidified sulfur filling the spaces between the solid particles was in an amorphous state or a crystalline state.

[0064] <Evaluation of charge / discharge cycle characteristics> Using each of the all-solid-state Li-ion secondary batteries prepared above, a charge-discharge cycle characteristic test was carried out by charging and discharging under the following conditions. One cycle consists of one charge and one subsequent discharge. (conditions) 30℃, current density 0.09mA / cm 2 (equivalent to 0.05C), 4.2V, constant current condition (0.36mA / cm 2 ) charging and discharging

[0065] If an internal short circuit occurs, charging will not be completed, so charging was terminated after 50 hours and the battery was discharged. The presence or absence of an internal short circuit was determined by the presence or absence of a sudden voltage drop during charging. The charge / discharge cycle characteristics were evaluated based on the following evaluation criteria. -Charge / Discharge Cycle Characteristics Evaluation Standards- A: No short circuit even after 3 or more cycles B: Short circuit for 2 or more cycles but less than 3 cycles C: Short circuit for 1 or more cycles but less than 2 cycles D: Short circuit in less than one cycle The results are shown in the table below.

[0066] [Table 1]

[0067] As shown in the above table, the solid electrolyte membrane of the present invention has an ultrathin film shape in which inorganic solid electrolyte particles are arranged in a virtually single layer, thereby reducing battery resistance. However, the Li-ion secondary battery using this as a separator had excellent charge-discharge cycle characteristics. The solid electrolyte membrane of the present invention uses an inorganic solid electrolyte having electrolyte resistance, and therefore can be used as a separator for any Li-ion secondary battery, whether it is a liquid electrolyte secondary battery or an all-solid-state secondary battery, and can further improve the cycle characteristics of the resulting Li-ion secondary battery while suppressing its battery resistance.

[0068] While the present invention has been described in connection with embodiments thereof, we do not intend to limit our invention to any of the details of the description unless otherwise specified, and believe that the claims should be construed broadly without departing from the spirit and scope of the invention as set forth in the appended claims.

[0069] This application claims priority based on Japanese Patent Application No. 2019-197748, filed on October 30, 2019, the contents of which are incorporated herein by reference as part of the present specification. [Explanation of symbols]

[0070] 10 All-solid-state secondary battery 1 Negative electrode current collector 2 Negative electrode active material layer 3 Solid electrolyte layer 4 Cathode active material layer 5 Positive electrode current collector 6. Operating parts 21, 31 Semisolid positive electrode active material layer 22, 32, 42 Solid electrolyte membrane (separator) 23 Solid electrolyte layer (layer containing sulfide-based inorganic solid electrolyte) 24 Metallic lithium layer (Li foil) 25, 34, 44 Inorganic solid electrolyte particles 26, 35, 45 Electronically insulating inorganic particles 27, 36, 46 Thermally fused and solidified electronic insulating materials 28, 37, 38 Separator sheets 33 Semi-solid negative electrode active material layer 41 All solid cathode active material layer 43 All solid negative electrode active material layer

Claims

1. electronically insulating inorganic particles having a particle diameter of 10 to 500 nm; inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and ionic conductivity; a solid electrolyte membrane having a thermally melted and solidified substance of an electronic insulating material that is solid at 100°C and thermally melts in a temperature range of 200°C or less, the solid electrolyte membrane filling the gaps between the particles; a positive electrode layer disposed on one side of the solid electrolyte membrane; a negative electrode layer disposed on the side of the solid electrolyte membrane opposite to the side on which the positive electrode layer is disposed; and the negative electrode layer includes a semi-solid active material layer containing an electrolyte solution, the thermally fused solid of the electronic insulating material is in an amorphous state; A semi-solid lithium ion secondary battery, wherein the thickness of the solid electrolyte film is equal to or greater than [particle diameter of the inorganic solid electrolyte particles × 0.7] and equal to or less than [particle diameter of the inorganic solid electrolyte particles × 1.2]. However, the particle diameters of the electronically insulating inorganic particles and the inorganic solid electrolyte particles are volume-based median diameters (d50).

2. the positive electrode active material layer constituting the positive electrode layer is a semi-solid positive electrode active material layer containing an electrolyte solution, 2. The semi-solid lithium ion secondary battery according to claim 1, wherein the thickness of the semi-solid positive electrode active material layer is 200 to 2000 μm.

3. 3. The semi-solid lithium ion secondary battery according to claim 1, wherein the negative electrode active material constituting the negative electrode layer contains metallic lithium.

4. Electronically insulating inorganic particles having a particle diameter of 10 to 500 nm; inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and ionic conductivity; a solid electrolyte membrane having a thermally melted and solidified substance of an electronic insulating material that is solid at 100°C and thermally melts in a temperature range of 200°C or less, the solid electrolyte membrane filling the gaps between the particles; a positive electrode layer disposed on one side of the solid electrolyte membrane; a negative electrode layer disposed on the side of the solid electrolyte membrane opposite to the side on which the positive electrode layer is disposed; and a positive electrode active material layer constituting the positive electrode layer is a semi-solid positive electrode active material layer containing an electrolyte solution, and a negative electrode active material layer constituting the negative electrode layer is a semi-solid negative electrode active material layer containing an electrolyte solution, the electrolyte solution in the semi-solid negative electrode active material layer and the electrolyte solution in the semi-solid positive electrode active material layer are different electrolyte solutions, the thermally fused solid of the electronic insulating material is in an amorphous state; A semi-solid lithium ion secondary battery, wherein the thickness of the solid electrolyte film is equal to or greater than [particle diameter of the inorganic solid electrolyte particles × 0.7] and equal to or less than [particle diameter of the inorganic solid electrolyte particles × 1.2]. However, the particle diameters of the electronically insulating inorganic particles and the inorganic solid electrolyte particles are volume-based median diameters (d50).

5. Electronically insulating inorganic particles having a particle diameter of 10 to 500 nm; inorganic solid electrolyte particles having a particle size larger than that of the electronically insulating inorganic particles and having electrolyte resistance and ionic conductivity; a solid electrolyte membrane having a thermally melted and solidified substance of an electronic insulating material that is solid at 100°C and thermally melts in a temperature range of 200°C or less, the solid electrolyte membrane filling the gaps between the particles; a positive electrode layer disposed on one side of the solid electrolyte membrane; a negative electrode layer disposed on the side of the solid electrolyte membrane opposite to the side on which the positive electrode layer is disposed; and At least one of the positive electrode layer and the negative electrode layer includes a semi-solid active material layer containing an electrolyte solution, the thermally fused solid of the electronic insulating material is in an amorphous state; the thickness of the solid electrolyte membrane is equal to or greater than [particle diameter of the inorganic solid electrolyte particles × 0.7] and equal to or less than [particle diameter of the inorganic solid electrolyte particles × 1.2]; The electronically insulating inorganic particles and the inorganic solid electrolyte particles have the same composition. However, the particle diameters of the electronically insulating inorganic particles and the inorganic solid electrolyte particles are volume-based median diameters (d50).

6. The semi-solid lithium ion secondary battery according to any one of claims 1 to 5, wherein the particle diameter of the electronically insulating inorganic particles and the particle diameter of the inorganic solid electrolyte particles satisfy the following formula: 5≦[particle diameter of inorganic solid electrolyte particles] / [particle diameter of electronically insulating inorganic particles]

7. the content of the inorganic solid electrolyte particles in the solid electrolyte membrane is 10 to 90% by volume, and the content of the electronically insulating inorganic particles is 5 to 45% by volume; The semi-solid lithium ion secondary battery according to any one of claims 1 to 6, wherein the inorganic solid electrolyte particles have a particle diameter of 1 to 20 µm.

8. 7. The semi-solid lithium ion secondary battery according to claim 1, wherein the content of the inorganic solid electrolyte particles in the solid electrolyte membrane is 40 to 60% by volume, and the content of the thermally melted solidified product of the electronic insulating material in the solid electrolyte membrane is 10 to 40% by volume.

9. the positive electrode active material layer constituting the positive electrode layer is a semi-solid positive electrode active material layer containing an electrolyte solution, The semi-solid lithium ion secondary battery according to any one of claims 1 to 8, further comprising a separator sheet disposed between the semi-solid positive electrode active material layer and the solid electrolyte membrane.

10. the negative electrode active material layer constituting the negative electrode layer is a semi-solid negative electrode active material layer containing an electrolyte solution, 10. The semi-solid lithium ion secondary battery according to claim 9, further comprising a separator sheet disposed between the semi-solid negative electrode active material layer and the solid electrolyte membrane.

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