Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/052—Li-accumulators
  • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M10/00—Secondary cells; Manufacture thereof
  • H01M10/05—Accumulators with non-aqueous electrolyte
  • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
  • H01M10/0561—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of inorganic materials only
  • H01M10/0562—Solid materials
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/411—Organic material
  • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/409—Separators, membranes or diaphragms characterised by the material
  • H01M50/44—Fibrous material
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/491—Porosity
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/497—Ionic conductivity
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
  • H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
  • H01M50/489—Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
  • H01M50/494—Tensile strength
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/30—Hydrogen technology
  • Y02E60/50—Fuel cells
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
  • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
  • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

• the present invention relates to a support contained in a solid electrolyte layer interposed between a positive electrode and a negative electrode of a lithium ion secondary battery, and a lithium ion secondary battery including a solid electrolyte layer having this support.
• a lithium-ion secondary battery using a liquid electrolyte (hereinafter referred to as "electrolytic solution”) is used.
• electrolytic solution a lithium-ion secondary battery using a liquid electrolyte
• a lithium-ion secondary battery using an electrolytic solution has a structure in which a separator is interposed between a positive electrode and a negative electrode and filled with an electrolytic solution.
• Organic electrolyte solutions are mainly used as electrolyte solutions used in lithium-ion secondary batteries using electrolyte solutions. Since the organic electrolytic solution is a liquid, there is a possibility of liquid leakage, and since it is flammable, there is a possibility of ignition. Under such circumstances, in order to further improve the safety of lithium-ion secondary batteries, lithium-ion secondary batteries using a solid electrolyte (hereinafter referred to as all-solid-state battery) instead of electrolytic solution have been developed. All-solid-state batteries are of course attracting attention as lithium-ion secondary batteries with excellent safety because the electrolyte is solid, so there is no liquid leakage, and they are flame-retardant and heat-resistant compared to electrolyte solutions. ing.
• all-solid-state batteries are of course attracting attention as lithium-ion secondary batteries with excellent safety because the electrolyte is solid, so there is no liquid leakage, and they are flame-retardant and heat-resistant compared to electrolyte solutions. ing
• all-solid-state batteries do not require a cooling device because their characteristics deteriorate less at high temperatures. is also an advantageous secondary battery.
• all-solid-state batteries are expected to be used as large-sized secondary batteries such as batteries for electric vehicles, because they are advantageous as secondary batteries with high energy density. In other words, there is a strong demand for larger size all-solid-state batteries.
• the solid electrolyte layer interposed between the positive electrode and the negative electrode of an all-solid-state battery is required to have the function of conducting lithium ions between the positive electrode and the negative electrode, and the function of preventing short circuits between the positive electrode active material and the negative electrode active material.
• the thickness of the solid electrolyte layer is required to be thin in order to obtain a battery with excellent energy density and low internal resistance.
• a method of forming a solid electrolyte layer a method of mixing a solid electrolyte and a binder and rolling under heating to form a sheet, a method of coating a solid electrolyte slurry on an electrode, and drying, etc. are adopted. .
• the solid electrolyte layer may be distorted and cracked during drying when the size of the all-solid-state battery is increased. . Therefore, it is difficult to stably form a thin and uniform solid electrolyte layer. If a thin and uniform solid electrolyte layer cannot be stably formed, ionic conduction deteriorates and a short circuit occurs.
• Patent Literature 1 proposes a solid electrolyte sheet including a nonwoven fabric support made of electronically insulating inorganic fibers and having a porosity of 80 to 99%. Since this solid electrolyte sheet has a support, it is excellent in self-sustainability and can be expanded in area.
• This support is said to contain 40% by weight or less of a binder for binding fibers together in the nonwoven fabric in order to form a self-supporting sheet. Since the binder is contained in an amount of 40% by weight or less, a strong support can be obtained, which is excellent in battery manufacturing process suitability. However, since the support contains 40% by weight or less of the binder, the binder tends to form a web-like layered substance inside the support.
• the all-solid-state battery using the support of Patent Document 1 may become a battery with high resistance, and further reduction in resistance is desired.
• the thickness of the support may be large, and after forming the solid electrolyte layer, the solid electrolyte layer may become thick. As a result, the battery may have a high internal resistance.
• Patent Document 2 proposes a solid electrolyte sheet containing a solid electrolyte on the surface and inside of the nonwoven fabric, the nonwoven fabric having a weight per square meter of 8 g or less and a thickness of 10 to 25 ⁇ m.
• the solid electrolyte layer formed by using the nonwoven fabric described in Patent Document 2 as a support can hold the solid electrolyte necessary for ionic conduction between the positive electrode and the negative electrode while maintaining self-supporting properties, thereby producing a battery that suppresses an increase in impedance. can do.
• Patent Document 3 proposes a solid electrolyte sheet having a porosity of 60% or more and 95% or less and a thickness of 5 ⁇ m or more and less than 20 ⁇ m, in which a heat-resistant support is filled with a solid electrolyte. It is described that this solid electrolyte sheet is thin but has self-supporting properties and is excellent in heat resistance, so that it can prevent a short circuit even if it is pressed at a high temperature. In addition, since this solid electrolyte sheet can be pressed at a high temperature, it contributes to the reduction of the interfacial resistance between the solid electrolytes, and the output of the battery can be increased.
• the filling of the solid electrolyte was sometimes insufficient.
• the battery has a high internal resistance, and further reduction in resistance has been desired.
• the strength of the support may be weak. If the strength is weak, the support may break during the solid electrolyte sheet formation process. was sought.
• Patent Document 4 proposes a nonwoven fabric base material for a lithium secondary battery separator, characterized by containing unstretched polyester fibers and wet heat adhesive fibers as binder fibers. Undrawn polyester fibers are softened or melted by heat and pressure treatment such as calendering, and are strongly bonded to other fibers. Also, it is described that the wet heat adhesive fiber flows or easily deforms in a wet state to exhibit an adhesive function. It is described that by including these binders in the nonwoven fabric substrate, it is possible to provide a nonwoven fabric substrate for a lithium secondary battery separator having high tensile strength and high separator productivity.
• the wet heat adhesive fibers contained in the nonwoven fabric substrate undergo flow or deformation when the adhesive function is exhibited, so the wet heat adhesive fibers in the nonwoven fabric substrate cannot maintain their fibrous state.
• the interstices between the fibers are blocked.
• the nonwoven substrate of US Pat As a result, the penetration of the solid electrolyte into the inside of the support becomes insufficient, and it is difficult to uniformly fill the inside of the support with the solid electrolyte, which may result in a battery with high internal resistance. There has been a demand for lower resistance of
• Patent Document 5 proposes a solid electrolyte sheet having a plurality of through holes formed by etching a film that serves as a support. It is described that filling the through-holes formed by etching with a solid electrolyte can provide an all-solid-state battery with excellent energy density and output characteristics.
• the solid electrolyte sheet of Patent Document 5 is produced, the through-holes are filled with the solid electrolyte, so the solid electrolyte is filled only inside the formed through-holes. Therefore, at the interface between the solid electrolyte sheet and the positive or negative electrode, an interface between the support, which is an insulating material, and the positive or negative electrode occurs. In other words, the resistance at the interface between the solid electrolyte sheet and the positive electrode or negative electrode tends to increase, and even an all-solid-state battery using this support has been required to further reduce the resistance of the all-solid-state battery.
• the present invention has been made in view of the above problems, and the support has sufficient physical strength and the permeability of the solid electrolyte to the inside of the support is improved, so that the solid electrolyte layer contains lithium.
• An object of the present invention is to sufficiently form ion path lines and obtain a solid electrolyte layer with low internal resistance.
• Another object of the present invention is to provide a lithium ion secondary battery with low internal resistance by using this support.
• a support according to the present invention has been made for the purpose of solving the above problems, and has, for example, the following configuration. That is, the support included in the solid electrolyte layer of the lithium ion secondary battery, and the air permeability of the support is 1 to 50 L/cm 2 /min. , a thickness of 5 to 30 ⁇ m, and a density of 0.15 to 0.45 g/cm 3 . Moreover, the lithium ion secondary battery of the present invention is characterized by comprising a solid electrolyte layer having the support of the above invention.
• the internal resistance of the solid electrolyte layer is reduced by having the physical strength to withstand the force during formation of the solid electrolyte layer and by improving the permeability of the solid electrolyte into the inside of the support. It is possible to obtain a support that can contribute to Moreover, the use of the support of the present invention in a lithium ion secondary battery can contribute to the reduction of the internal resistance of the battery.
• a support in a lithium-ion secondary battery configured as an all-solid-state battery, a support is configured which is used to form a solid electrolyte layer existing between a positive electrode and a negative electrode.
• the support of the present invention is a support contained in a solid electrolyte layer of a lithium ion secondary battery, and has an air permeability of 1 to 50 L/cm 2 /min. , a thickness of 5 to 30 ⁇ m and a density of 0.15 to 0.45 g/cm 3 .
• the solid electrolyte layer that exists between the positive and negative electrodes is required to conduct lithium ions between the positive and negative electrodes during charging and discharging. In other words, it is necessary to form a pass line by the solid electrolyte so that lithium ions can be conducted not only between the solid electrolyte layer and the positive electrode or negative electrode but also inside the support. In other words, a solid electrolyte layer with low internal resistance can be formed if the solid electrolyte is sufficiently adhered to the surface of the support, and if many path lines of lithium ions can be formed by the solid electrolyte inside the support.
• the inventors of the present invention have found that it is important to form a solid electrolyte layer having a continuous connection inside the support in order to form a lithium ion pass-line between the positive electrode and the negative electrode. We have found that it is important to sufficiently fill the interior of the support with the electrolyte, as well as to adhere the electrolyte sufficiently to the surface of the support. Further, by increasing the permeability of the solid electrolyte of the support, the fillability of the solid electrolyte can be improved, and a solid electrolyte layer with low internal resistance can be formed.
• air permeability is used as an index for measuring the permeability of the solid electrolyte into the inside of the support.
• the air permeability indicates the amount of air flowing per unit area and unit time under a constant differential pressure, and the higher the air permeability, the more air is flowing. That is, the higher the permeability of the support, the higher the gas permeability of the support. It is considered that if the air permeability of the support is high, the permeability of the solid electrolyte into the inside of the support is also high. In other words, it is considered that a support with high air permeability can be filled with a sufficient amount of solid electrolyte inside the support.
• the support of the present invention has an air permeability of 1 to 50 L/cm 2 /min. is in the range of A support having air permeability in the above range is excellent in fillability with a solid electrolyte.
• a support having air permeability within the above range has an appropriate overlap of fibers laminated in the thickness direction, and when the support is filled with a solid electrolyte, the impediment to penetration into the interior is small. Therefore, not only can the solid electrolyte adhere sufficiently to the surface of the support, but the inside of the support can be filled with the solid electrolyte. As a result, an all-solid-state battery using this support can have a low internal resistance.
• Air permeability is 1 L/cm 2 /min. If it is less than that, it may not be possible to uniformly fill the solid electrolyte. It is considered that it is based on the following reasons.
• the air permeability is 1 L/cm 2 /min. If it is less than that, the number of fibers constituting the support will be large and the support will be dense, impeding permeation of the solid electrolyte into the support. As a result, the solid electrolyte remains on the surface of the support, making it difficult to uniformly fill the inside of the support with the solid electrolyte.
• air permeability is 50 L/cm 2 /min.
• the effect of using the support cannot be obtained.
• Air permeability is 50 L/cm 2 /min.
• the solid electrolyte does not stay on the support when filled with the solid electrolyte, making it difficult to hold and reinforce the solid electrolyte. For this reason, it is conceivable that the solid electrolyte layer cannot be formed, or the distortion of the solid electrolyte layer that occurs during drying cannot be suppressed, leading to the generation of cracks. That is, it is not preferable because a thin and uniform solid electrolyte layer cannot be obtained.
• the air permeability of the support is 2 to 40 L/cm 2 /min. is more preferable.
• the thickness of the support is preferably in the range of 5-30 ⁇ m. If the thickness is less than 5 ⁇ m, the thickness of the solid electrolyte layer becomes thin, making it difficult to prevent a short circuit between the positive electrode and the negative electrode. Further, in order to increase the distance between the electrodes for the purpose of preventing short circuits, a thick solid electrolyte layer can be formed on the support surface, but a solid electrolyte layer portion where the support does not exist is generated. In other words, it is conceivable that the solid electrolyte layer portion having no support may not be able to suppress the distortion of the solid electrolyte layer that occurs during drying, leading to the generation of cracks. On the other hand, if the thickness exceeds 30 ⁇ m, the thickness of the solid electrolyte layer becomes too thick, making it difficult to suppress the internal resistance of the all-solid-state battery.
• the density of the support is preferably in the range of 0.15-0.45 g/cm 3 . If the density is less than 0.15 g/cm 3 , the number of fibers constituting the support is reduced and the voids in the support are increased. Therefore, the solid electrolyte does not stay on the support, and it becomes difficult to uniformly hold and reinforce the solid electrolyte. On the other hand, if the density is more than 0.45 g/cm 3 , the permeability of the solid electrolyte into the inside of the support deteriorates, and the inside of the support may not be sufficiently filled with the solid electrolyte. Therefore, it becomes difficult to suppress the internal resistance of the all-solid-state battery.
• the density of the support is more preferably in the range of 0.18 to 0.42 g/cm 3 .
• the support of the present invention is composed of a nonwoven fabric.
• the reason is as follows. Since the nonwoven fabric has a structure in which fibers are randomly arranged, a support made of the nonwoven fabric has voids of various sizes and through-holes of various sizes inside. Therefore, the solid electrolyte may remain on the surface of the support, may permeate into the support and fill the internal voids and remain, or may permeate from the surface side to be filled to the back side through the through holes. There are things, and they are in close contact with each other. In other words, a support made of nonwoven fabric allows a solid electrolyte to adhere to the surface of the support and fills the inside of the support with the solid electrolyte.
• the solid electrolyte in the solid electrolyte layer prepared using a nonwoven fabric as a support, the solid electrolyte can be sufficiently present inside and on the surface of the solid electrolyte layer, and the internal resistance of the solid electrolyte layer can be reduced. interface resistance can be reduced. As a result, it is thought that the internal resistance of the all-solid-state battery can be reduced.
• the support of the present invention preferably contains binder fibers.
• the binder fibers used in the support of the present invention refer to fibers that constitute the support in a fibrous state and point-bond the fibers together. From the viewpoint of heat resistance and tensile strength, the support of the present invention preferably contains 20 to 80% by mass of binder fibers.
• the binder fiber has a role as a constituent fiber of the support and a role as a binder.
• the binder component forms a large number of film layers inside the support and closes inter-fiber gaps when the binder function is exhibited. As a result, the permeation of the solid electrolyte into the inside of the support may be inhibited.
• the binder fiber content is less than 20% by mass, the desired tensile strength cannot be obtained because the number of bonding points between fibers is too small. As a result, tearing may occur during the manufacturing process, leading to a decrease in manufacturing yield. If the binder fiber content exceeds 80% by mass, the heat resistance may deteriorate, and a uniform solid electrolyte layer may not be formed in the manufacturing process, which is not preferable. In addition, the support may become too dense, and it may be difficult to uniformly fill the inside of the support with the solid electrolyte.
• the amount of binder fibers contained in the support is 25 to 75% by mass. preferable.
• the material that can be used as the binder fiber is not particularly limited as long as it does not repel the solid electrolyte slurry, does not adversely affect the solid electrolyte, and has insulating properties.
• polyester binder fiber examples include polyamide binder fibers.
• the support according to the present invention preferably has a tensile strength of 1.0 N/15 mm or more. If the tensile strength is less than 1.0 N/15 mm, breakage is likely to occur during filling of the solid electrolyte.
• Materials that can be used as other constituent fibers are not particularly limited as long as they do not repel the solid electrolyte slurry, do not adversely affect the solid electrolyte, and have insulating properties.
• polyester fiber polyamide fibers and cellulose fibers, and inorganic fibers such as glass fibers and alumina fibers.
• one or more types of fibers selected from these fibers can be used. By using these fibers, it is possible to obtain a support excellent in solid electrolyte filling properties and heat resistance. Beatable fibers, such as polyamide fibers and cellulose fibers, may be beaten to improve the fracture resistance of the support.
• binder fibers and other constituent fibers with an average fiber diameter of 1 to 15 ⁇ m. If fibers having a fiber diameter of less than 1 ⁇ m are contained, the formed support becomes dense, making it difficult to fill the inside of the support with the solid electrolyte. On the other hand, if the fiber diameter is more than 15 ⁇ m, it becomes difficult to form a support with a uniform thickness, the formed solid electrolyte layer becomes uneven, and the resistance between the positive electrode and the negative electrode may increase. .
• the method for manufacturing the support is not particularly limited, and it can be manufactured by a dry method or a wet method.
• a wet method is used in which fibers dispersed in water are deposited on a wire, dehydrated, and dried to form a paper. , from the viewpoint of homogeneity of the formation of the support.
• a wet-laid nonwoven fabric formed using a papermaking method was used as the support.
• the paper-making form of the support is not particularly limited as long as it satisfies the air permeability, thickness and density. A combination of a plurality of formed layers may also be used. Additives such as dispersants, antifoaming agents, and paper strength enhancers may be added during papermaking. may be subjected to post-processing.
• Method for producing support and all-solid-state battery and method for measuring characteristics The method for producing the support and the all-solid-state battery of the present embodiment and the method for measuring characteristics were performed under the following conditions and methods.
• ⁇ thickness ⁇ The thickness of one support is measured at even intervals using a dial thickness gauge G type (measurement reaction force 2 N, probe: ⁇ 10 mm), and the average value of the measured points is the thickness of the support ( ⁇ m ).
• Basis weight The basis weight of the absolute dry support was measured by the method specified in "JIS C 2300-2 'Cellulose paper for electrical use-Part 2: Test method' 6 Basis weight".
• Density (g/cm 3 ) W/T W: basis weight (g/m 2 ), T: thickness ( ⁇ m)
• LiNiCoAlO 2 ternary powder as a positive electrode active material, Li 2 SP 2 S 5 amorphous powder as a sulfide solid electrolyte, and carbon fiber as a conductive aid were mixed.
• This mixed powder was mixed with a dehydrated xylene solution in which SBR (styrene-butadiene rubber) was dissolved as a binder to prepare a positive electrode coating liquid.
• a positive electrode structure was obtained by applying a positive electrode coating liquid to an aluminum foil current collector, which is a positive electrode current collector, drying, and further rolling.
• a negative electrode structure Graphite as a negative electrode active material, Li 2 SP 2 S 5 amorphous powder as a sulfide-based solid electrolyte, PVdF as a binder, and NMP as a solvent were mixed together to form a negative electrode coating solution. made.
• a negative electrode structure was obtained by applying a negative electrode coating liquid to a copper foil current collector, which is a negative electrode current collector, drying, and further rolling.
• Solid electrolyte layer Li 2 SP 2 S 5 amorphous powder as a sulfide-based solid electrolyte, SBR as a binder, and xylene as a solvent were mixed together to prepare a solid electrolyte layer coating solution.
• a solid electrolyte layer coating liquid was applied to the supports of Examples, Comparative Examples, and Conventional Examples shown below and dried to obtain solid electrolyte layers.
• a negative electrode structure with a size of 88 mm ⁇ 58 mm, a solid electrolyte layer with a size of 92 mm ⁇ 62 mm, and a positive electrode structure with a size of 87 mm ⁇ 57 mm are laminated, dry laminated, and laminated to form a single cell of an all-solid-state battery. got The obtained single cell was placed in an aluminum laminate film to which a terminal was attached, degassed, heat-sealed, and packed.
• the all-solid-state battery was charged to 4.0 V at a current density of 0.1 C in an environment of 25 ° C., then discharged to 2.5 V at a current density of 0.1 C, and the discharge capacity at that time was measured. .
• Example 1 A raw material obtained by mixing 50% by mass of polyester binder fiber and 50% by mass of polyester fiber was used to make cylinder paper, and a support of Example 1 was obtained.
• the support of Example 1 had a thickness of 15 ⁇ m, a basis weight of 2.6 g/m 2 , a density of 0.17 g/cm 3 , a porosity of 87.4%, and an air permeability of 48.7 L/cm 2 /min. , and a tensile strength of 1.1 N/15 mm.
• Example 2 A raw material obtained by mixing 50% by mass of polyester binder fiber and 50% by mass of polyester fiber was used to make short mesh paper. The resulting nonwoven fabric was subjected to hot calendering to obtain the support of Example 2.
• the support of Example 2 had a thickness of 20 ⁇ m, a basis weight of 8.0 g/m 2 , a density of 0.40 g/cm 3 , a porosity of 71.0%, and an air permeability of 1.2 L/cm 2 /min. , and a tensile strength of 8.9 N/15 mm.
• Example 3 A raw material obtained by mixing 20% by mass of polyamide binder fiber and 80% by mass of cellulose fiber was used to make short mesh paper to obtain a support of Example 3.
• the support of Example 3 had a thickness of 29 ⁇ m, a basis weight of 11.9 g/m 2 , a density of 0.41 g/cm 3 , a porosity of 71.3%, and an air permeability of 2.9 L/cm 2 /min. , the tensile strength was 7.3 N/15 mm.
• Example 4 A raw material obtained by mixing 80% by mass of polyester binder fiber and 20% by mass of cellulose fiber was used to make cylinder paper, and a support of Example 4 was obtained.
• the support of Example 4 had a thickness of 5 ⁇ m, a basis weight of 2.2 g/m 2 , a density of 0.43 g/cm 3 , a porosity of 68.7%, and an air permeability of 25.1 L/cm 2 /min. , and a tensile strength of 4.3 N/15 mm.
• Example 5 A raw material obtained by mixing 25% by mass of polyester binder fiber and 75% by mass of polyester fiber was used to make cylinder paper, and a support of Example 5 was obtained.
• the support of Example 5 had a thickness of 15 ⁇ m, a basis weight of 5.3 g/m 2 , a density of 0.35 g/cm 3 , a porosity of 74.6%, and an air permeability of 32.2 L/cm 2 /min. , and a tensile strength of 2.5 N/15 mm.
• Example 6 A raw material obtained by mixing 75% by mass of polyamide binder fiber and 25% by mass of polyamide fiber was used to make a short mesh paper, and a support of Example 6 was obtained.
• the support of Example 6 had a thickness of 25 ⁇ m, a basis weight of 4.8 g/m 2 , a density of 0.19 g/cm 3 , a porosity of 83.2%, and an air permeability of 38.9 L/cm 2 /min. , and a tensile strength of 6.1 N/15 mm.
• Comparative Example 1 A raw material obtained by mixing 50% by mass of polyester binder fiber and 50% by mass of polyester fiber was used to make cylinder paper, and a support of Comparative Example 1 was obtained.
• the support of Comparative Example 1 had a thickness of 30 ⁇ m, a basis weight of 3.5 g/m 2 , a density of 0.12 g/cm 3 , a porosity of 91.5%, and an air permeability of 52.1 L/cm 2 /min. , and a tensile strength of 1.0 N/15 mm.
• Comparative Example 2 A raw material obtained by mixing 85% by mass of polyamide binder fiber and 15% by mass of polyamide fiber was used to make cylinder paper, and a support of Comparative Example 2 was obtained.
• the support of Comparative Example 2 had a thickness of 5 ⁇ m, a basis weight of 2.3 g/m 2 , a density of 0.45 g/cm 3 , a porosity of 62.5%, and an air permeability of 20.6 L/cm 2 /min. , and a tensile strength of 5.6 N/15 mm.
• Comparative Example 3 A raw material obtained by mixing 70% by mass of polyamide binder fiber and 30% by mass of polyamide fiber was used to make cylinder paper, and a support of Comparative Example 3 was obtained.
• the support of Comparative Example 3 had a thickness of 4 ⁇ m, a basis weight of 1.8 g/m 2 , a density of 0.45 g/cm 3 , a porosity of 63.4%, and an air permeability of 27.1 L/cm 2 /min. , and a tensile strength of 4.1 N/15 mm.
• Comparative Example 4 A raw material in which 50% by mass of polyamide binder fiber and 50% by mass of cellulose fiber were mixed was used to make short mesh paper, and a support of Comparative Example 4 was obtained.
• the support of Comparative Example 4 had a thickness of 43 ⁇ m, a basis weight of 8.6 g/m 2 , a density of 0.20 g/cm 3 , a porosity of 84.8%, and an air permeability of 10.6 L/cm 2 /min. , and a tensile strength of 7.8 N/15 mm.
• a support was produced by the same method as described in Example 1 of Patent Document 4, and a support of Conventional Example 2 was obtained.
• Conventional Example 2 10% by mass of polyester binder fiber, 10% by mass of ethylene vinyl alcohol fiber, and 80% by mass of polyester fiber are mixed.
• the support of Conventional Example 2 has a thickness of 12 ⁇ m, a basis weight of 7.0 g/m 2 , a density of 0.58 g/cm 3 , a porosity of 57.7%, and an air permeability of 0.7 L/cm 2 /min. , the tensile strength was 11.2 N/15 mm.
• a support was produced by the same method as described in Example 1 of Patent Document 5, and a support of Conventional Example 3 was obtained.
• a polyimide film is etched to form a hole of 800 ⁇ m square to produce a support.
• the support of Conventional Example 3 has a thickness of 30 ⁇ m, a basis weight of 5.2 g/m 2 , a density of 0.17 g/cm 3 , a porosity of 88.0%, and an air permeability of 28.8 L/cm 2 /min. , and a tensile strength of 4.0 N/15 mm.
• Reference example A raw material in which 30% by mass of polyester binder fiber, 50% by mass of polyester fiber and 20% by mass of polyvinyl alcohol fiber were mixed was used to make short mesh paper to obtain a support of Reference Example.
• the support of Reference Example had a thickness of 20 ⁇ m, a basis weight of 8.0 g/m 2 , a density of 0.40 g/cm 3 , a porosity of 70.8%, and an air permeability of 0.8 L/cm 2 /min. , and a tensile strength of 9.7 N/15 mm.
• Table 2 shows the characteristics of each support, the independence of the solid electrolyte layer, and the battery characteristics of Examples 1 to 6, Comparative Examples 1 to 4, Conventional Examples 1 to 3, and Reference Example described above. Evaluation results are shown.
• the support of Example 1 has lower air permeability and higher density than the support of Comparative Example 1.
• the support of Comparative Example 1 could not form a uniform solid electrolyte layer. This is because the air permeability of the support of Comparative Example 1 is 52.1 L/cm 2 /min. , and the density is as low as 0.12 g/cm 3 .
• the air permeability of the support of Comparative Example 1 was 50 L/cm 2 /min. Below, it is understood that a density of 0.15 g/cm 3 or more is preferable.
• the all-solid-state battery using the support of each example has lower impedance and higher discharge capacity than the all-solid-state battery using the support of Comparative Example 2. Moreover, unlike the support of Comparative Example 2, the support of each example had self-supporting properties.
• the support of Comparative Example 2 has a high binder fiber content of 85% by mass. Therefore, when the solid electrolyte layer coating solution was applied to the support of Comparative Example 2 and the solvent was dried, a solid electrolyte layer with cracks was obtained. This is probably because the binder fiber content was as high as 85% by mass, so that the heat resistance of the support was poor and the shape of the support was changed by heat. Therefore, when the solid electrolyte layer was lifted, it cracked and was not self-sustaining. Although cracks were generated in the solid electrolyte layer using the support of Comparative Example 2, an all-solid battery could be produced by laminating the positive electrode and the negative electrode.
• the all-solid-state battery using the support of Comparative Example 2 had high impedance and could not be discharged. This is considered to be due to the fact that the solid electrolyte layer is non-uniform due to the occurrence of cracks, and there are few lithium ion pass lines that can conduct electricity between the positive electrode and the negative electrode. From a comparison between each example and Comparative Example 2, it can be seen that the amount of binder fibers contained in the support is preferably 80% by mass or less so that the support has heat resistance that can withstand the formation of the solid electrolyte layer.
• the support of Comparative Example 3 is thinner than the support of each example. Therefore, a short circuit occurred in the all-solid-state battery using the support of Comparative Example 3. This is probably because the support of Comparative Example 3 had a thin thickness of 4 ⁇ m and could not prevent a short circuit between the positive electrode and the negative electrode. Since a short circuit occurred, various battery evaluations of the all-solid-state battery using the support of Comparative Example 3 could not be performed. From the comparison between each example and comparative example 3, it can be seen that the thickness of the support is preferably 5 ⁇ m or more.
• the support of Comparative Example 4 is thicker than the support of each example.
• the all-solid-state battery using the support of Comparative Example 4 has lower impedance, higher discharge capacity, and improved battery characteristics than the all-solid-state battery using the support of each conventional example.
• the thickness of the support is as thick as 43 ⁇ m, the resulting battery is large. From the viewpoint of miniaturization of the obtained all-solid-state battery, the thickness of the support is considered to be preferably 30 ⁇ m or less.
• the support of each example has a higher tensile strength than the support of Conventional Example 1.
• the support of Conventional Example 1 was torn when the solid electrolyte layer coating solution was applied and excess coating solution was removed. This is probably because the support of Conventional Example 1 has a weak tensile strength of 0.7 N/15 mm. In Conventional Example 1, since the solid electrolyte layer could not be formed, the fabrication and evaluation of the all-solid-state battery were not performed. The reason why the tensile strength of the support of Conventional Example 1 was weak was that the binder fiber content was as low as 15% by mass, so that the number of bonding points between fibers was too small, and the desired tensile strength could not be obtained. Conceivable. From a comparison between each example and Conventional Example 1, it can be seen that a support containing 20% by mass or more of binder fibers is preferable in order to suppress breakage of the support during production of the solid electrolyte layer.
• the all-solid-state battery using the support of each example has lower impedance and higher discharge capacity than the all-solid-state battery using the support of Conventional Example 2 and Conventional Example 3. Moreover, unlike the support of Conventional Example 2, the support of each example had self-supporting properties.
• the support of Conventional Example 2 has an air permeability of 0.7 L/cm 2 /min. and low. Therefore, when the solid electrolyte layer coating solution was applied to the support of Conventional Example 2, the solid electrolyte layer coating solution did not permeate into the support and remained on the surface of the support. As a result, the solid electrolyte layer coating solution remained on the surface of the support and was dried, forming a solid electrolyte layer on the surface of the support. Since the solid electrolyte layer formed on the surface of the support was dried in the absence of the support, the solid electrolyte was not reinforced, resulting in cracks. Therefore, when the solid electrolyte layer was lifted, it cracked and was not self-sustaining.
• the support of Conventional Example 2 has a tensile strength of 11.2 N/15 mm, which is equal to or higher than each example, despite the low binder fiber content of 10% by mass. is. This is probably because the density is as high as 0.58 g/cm 3 and there are many contact points between the fibers.
• the battery using the support of Conventional Example 2 had a very high impedance and could not be discharged. It has a high density of 0.58 g/cm 3 and an air permeability of 0.7 L/cm 2 /min.
• Example 2 In order to further strengthen the strength, it has 10% by mass of ethylene-vinyl alcohol fiber that cannot maintain the fiber state in the non-woven fabric state, so it is thought that the filling of the solid electrolyte was insufficient. be done. From the comparison between Example 2 and Conventional Example 2, it was found that the air permeability of the support was 1 L/cm in order to achieve both the physical strength to withstand the force during the production of the solid electrolyte layer and the fillability of the solid electrolyte. 2 /min. From the above, it can be seen that the density is preferably 0.45 g/cm 3 or less, and the binder fiber content is preferably 20% by mass or more.
• the support of Conventional Example 3 is a support in which through holes are formed in a film, unlike the nonwoven fabric support of each example.
• the through-holes of the support of Conventional Example 3 can be filled with a solid electrolyte, the solid electrolyte can be filled only inside the formed through-holes.
• the solid electrolyte layer made of the support of Conventional Example 3 has an interface between the film, which is an insulator, and the positive electrode or negative electrode at the interface between the solid electrolyte layer and the positive electrode or negative electrode. .
• the impedance of the all-solid-state battery of the support of Conventional Example 3 is considered to be higher than that of the support of each example. From the comparison between each example and conventional example 3, it can be seen that a nonwoven fabric is suitable as a support for reducing the impedance of an all-solid-state battery.
• the support of Reference Example had lower air permeability than each Example.
• the all-solid-state battery using the support of the reference example has a higher impedance and a lower discharge capacity than the all-solid-state battery using the support of each example.
• the support of Reference Example is a support containing 20% by mass of polyvinyl alcohol fiber in addition to polyester binder fiber and polyester fiber.
• Polyvinyl alcohol fibers are effective fibers for improving tensile strength. Polyvinyl alcohol fibers can reinforce the fiber contact points and improve the tensile strength of the support by changing shape due to wet heat.
• the polyvinyl alcohol fibers are not in a fibrous state when forming the support, but instead form a large number of film layers inside the support, closing the interstices between the fibers.
• the air permeability is lowered and the permeation of the coating liquid for the solid electrolyte layer into the inside of the support is inhibited.
• the air permeability of the support is set to 1 to 50 L/cm 2 /min. , a thickness of 5 to 30 ⁇ m, and a density of 0.15 to 0.45 g/cm 3 .
• a support can be obtained which has good permeability to the By using this support, an all-solid-state battery with low resistance can be obtained.

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• 2022
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