Solid-electrolyte material, nonaqueous-electrolyte secondary battery, and method for producing solid-electrolyte material

Abstract

The solid-electrolyte material of the present disclosure includes a polymer having a main chain having, bonded thereto, an acidic functional group having an alkali metal ion, the polymer having a crosslinked structure containing an electron-donating polar group. The nonaqueous-electrolyte secondary battery of the present disclosure comprises a positive electrode including a positive-electrode active material, a negative electrode including a negative-electrode active material, a separator, and a nonaqueous electrolyte and satisfies at least one requirement selected from the group consisting of (A) to (D). (A) The nonaqueous-electrolyte secondary battery further includes a membrane including this solid-electrolyte material, the membrane having been disposed on the separator-side surface of at least one electrode selected from the group consisting of the positive electrode and the negative electrode. (B) The nonaqueous-electrolyte secondary battery further includes a membrane including this solid-electrolyte material, the membrane having been disposed on the surfaces of particles of at least one active material selected from the group consisting of the positive-electrode active material and the negative-electrode active material. (C) The nonaqueous-electrolyte secondary battery further includes a membrane including this solid-electrolyte material, the membrane having been disposed on at least some of the surfaces of the separator. (D) The separator includes this solid-electrolyte material.

Description

Solid electrolyte material, non-aqueous electrolyte secondary battery, and method for manufacturing solid electrolyte material

[0001] The present disclosure relates to a solid electrolyte material, a nonaqueous electrolyte secondary battery, and a method for producing the solid electrolyte material.

[0002] Nonaqueous electrolyte secondary batteries such as lithium ion secondary batteries are widely used in applications requiring high capacity, such as vehicle applications, power storage applications, etc. Nonaqueous electrolyte secondary batteries generally include an electrode assembly in which a positive electrode and a negative electrode are stacked or wound with a separator interposed therebetween, and a nonaqueous electrolyte.

[0003] One way to improve battery performance is, for example, to improve the separation technology between the various components of the battery. In recent years, solid electrolyte materials for use in batteries have been actively studied. Such solid electrolyte materials are not only used in place of electrolyte solutions, but also as materials for coating electrode active materials. For example, Patent Document 1 discloses an all-solid-state lithium battery including a lithium ion conductive solid electrolyte mainly composed of sulfide and an active material whose surface is coated with a lithium ion conductive oxide.

[0004] WO 2007 / 004590

[0005] The solid electrolyte material used to separate the components of a non-aqueous electrolyte secondary battery is required to have the ability to separate the non-aqueous solvent used in the battery and the ionic conductivity of the ions involved in the battery reaction.

[0006] The present disclosure provides a solid electrolyte material for a non-aqueous electrolyte secondary battery that can achieve both ionic conductivity and non-aqueous solvent separability.

[0007] The present disclosure provides a solid electrolyte material for a non-aqueous electrolyte secondary battery, the solid electrolyte material including a polymer having an acidic functional group having an alkali metal ion bonded to a main chain, the polymer having a cross-linked structure including an electron-donating polar group.

[0008] According to the present disclosure, it is possible to provide a solid electrolyte material for a non-aqueous electrolyte secondary battery that can achieve both ionic conductivity and non-aqueous solvent separability.

[0009] Fig. 1 is a cross-sectional view schematically showing a part of the configuration of a nonaqueous electrolyte secondary battery according to a second embodiment. Fig. 2 shows a cross-sectional view of an electrode when the nonaqueous electrolyte secondary battery shown in Fig. 1 satisfies the configuration (A). Fig. 3 shows a cross-sectional view of an active material when the nonaqueous electrolyte secondary battery shown in Fig. 1 satisfies the configuration (B). Fig. 4 shows a cross-sectional view of a separator when the nonaqueous electrolyte secondary battery shown in Fig. 1 satisfies the configuration (C). Fig. 5 is a cross-sectional view schematically showing an axial cross-section of a nonaqueous electrolyte secondary battery including a wound electrode assembly, which is an example of the nonaqueous electrolyte secondary battery according to the second embodiment.

[0010] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. The present disclosure is not limited to the following embodiments.

[0011] First Embodiment A solid electrolyte material according to a first embodiment of the present disclosure is a solid electrolyte material used in a nonaqueous electrolyte secondary battery.

[0012] The solid electrolyte material according to the first embodiment includes a polymer having an acidic functional group having an alkali metal ion bonded to its main chain, and the polymer has a cross-linked structure including an electron-donating polar group.

[0013] By having the above-described configuration, the solid electrolyte material according to the first embodiment can have both ion conductivity (e.g., lithium ion conductivity) and separability from non-aqueous solvents used in non-aqueous electrolyte secondary batteries.

[0014] In the polymer contained in the solid electrolyte material according to the first embodiment, an acidic functional group having an alkali metal ion is bonded to the main chain. That is, in the polymer contained in the solid electrolyte material according to the first embodiment, an anion that serves as a scaffold for the alkali metal ion (e.g., lithium ion) is fixed to the main chain. This acidic functional group functions as an anion that serves as a scaffold for the alkali metal ion and captures the alkali metal ion. Furthermore, the polymer contained in the solid electrolyte material according to the first embodiment has a crosslinked structure. This crosslinked structure contains an electron-donating polar group, so it serves as a conduction path for the alkali metal ion captured by the acidic functional group and can conduct the alkali metal ion. Due to this mechanism, the solid electrolyte material according to the first embodiment can have ionic conductivity. Furthermore, because the polymer contained in the solid electrolyte material according to the first embodiment has a crosslinked structure, the solid electrolyte material according to the first embodiment can suppress the migration of a nonaqueous solvent. Therefore, the solid electrolyte material according to the first embodiment can achieve both ionic conductivity and nonaqueous solvent separability.

[0015] Hereinafter, the polymer contained in the solid electrolyte material according to the first embodiment will be referred to as the polymer according to the first embodiment. In this specification, unless otherwise specified, the polymer refers to a molecule having a weight average molecular weight (Mw) of 500 or more.

[0016] The main chain of the polymer according to the first embodiment may have any molecular structure that is electrochemically stable and can be easily applied to each component of a battery. Examples of the main chain include polysaccharides such as polyethylene glycol, polyethylene oxide, polyvinyl alcohol, and cellulose, and derivatives thereof. For example, the main chain of the polymer according to the first embodiment may include at least one selected from the group consisting of cellulose, cellulose derivatives, polyvinyl alcohol, polyvinyl alcohol derivatives, polyethylene oxide, polyethylene oxide derivatives, polyethylene glycol, and polyethylene glycol derivatives. It is particularly desirable that the main chain of the polymer according to the first embodiment include at least one selected from the group consisting of cellulose and its derivatives (e.g., carboxymethyl cellulose (CMC)). The main chain of the polymer according to the first embodiment may be at least partially composed of cellulose or a derivative thereof, or may be substantially entirely composed of cellulose or a derivative thereof.

[0017] In the polymer according to the first embodiment, the acidic functional group is Li + The acidic functional group is an anionic group that pairs with alkali metal ions such as carboxylate, carboxyl, methyl ...

[0018] A suitable example of the polymer according to the first embodiment is Li + The polymer has a constitutional unit represented by the following formula (3), in which a phosphorous acid group capable of capturing alkali metal ions such as those mentioned above is bonded to the main chain of cellulose. In formula (3), Y + represents an alkali metal ion, and m represents a positive integer. The OH group shown in formula (3) may be replaced with a bond to a structural unit constituting a structure formed by reaction with a second compound described below, which is a crosslinking agent, i.e., a crosslinked structure.

[0019] In the constitutional unit represented by formula (3), it is desirable that 20% to 80%, or 30% to 50% of the OH groups of the cellulose are substituted with phosphorous groups. This configuration can improve the ionic conductivity of the solid electrolyte material according to the first embodiment.

[0020] The polymer according to the first embodiment may include a structural unit in which a phosphite group having an alkali metal ion is introduced into the main chain of cellulose, as represented by formula (3). The polymer according to the first embodiment may consist essentially of structural units represented by formula (3), excluding structural units constituting crosslinked structures. Here, "the polymer according to the first embodiment consists essentially of structural units represented by formula (3), excluding structural units constituting crosslinked structures" means that in the polymer according to the first embodiment, the structural units represented by formula (3) account for 90 mol % or more, preferably 95 mol % or more, of the total of all structural units excluding structural units constituting crosslinked structures. The polymer according to the first embodiment may consist solely of structural units in which a phosphite group having an alkali metal ion is introduced into the main chain of cellulose, excluding structural units constituting crosslinked structures.

[0021] In the polymer according to the first embodiment, examples of the electron-donating polar group contained in the crosslinked structure include an ether group and a nitrile group. That is, the crosslinked structure may contain at least one polar group selected from the group consisting of an ether group and a nitrile group. Among these, an ether group is preferable because it can further improve ionic conductivity. The ether group may be a polyether group. For example, the crosslinked structure in the polymer according to the first embodiment may contain an ether group or a polyether group as the polar group. Note that such a crosslinked structure can be formed, for example, by using a polyether-based crosslinking agent containing a polyether group. The ether group is, for example, a polyethylene oxide group.

[0022] The crosslinked structure in the polymer according to the first embodiment may include a structure represented by the following formula (1):

[0023] The structure of the above formula (1) can be formed by the reaction of a hydroxy group (OH group) with an epoxy group in a crosslinking reaction.

[0024] The crosslinked structure in the polymer according to the first embodiment may include a structure represented by the following formula (2): In the formula (2), n represents a positive integer.

[0025] The structure of the above formula (2) can be formed in a crosslinking reaction by reacting a hydroxy group (OH group) with, for example, polyethylene glycol diglycidyl ether used as a crosslinking agent.

[0026] The polymer according to the first embodiment may contain a constitutional unit represented by the above formula (3) and may also contain a structure represented by the above formula (2) as a crosslinked structure. In this case, the polymer according to the first embodiment may also contain a structure represented by the following formula (4): In the formula (4), m and n represent positive integers.

[0027] In the polymer according to the first embodiment, the ratio (molar ratio) of the constituent units constituting the crosslinked structure to the total of other constituent units other than the constituent units constituting the crosslinked structure can be adjusted as appropriate, taking into consideration, for example, the balance between the desired ionic conductivity and separability from a non-aqueous solvent, the type of functional group used in the crosslinking reaction, the polar group contained in the crosslinked structure, etc.

[0028] The solid electrolyte material according to the first embodiment may contain other components in addition to the polymer according to the first embodiment. For example, it may contain some of the materials used in synthesizing the polymer according to the first embodiment, such as the crosslinking agent used.

[0029] Next, a method for producing the solid electrolyte material according to the first embodiment will be described.

[0030] A method for producing a solid electrolyte material according to a first embodiment includes crosslinking a first compound, which is a polymer having an acidic functional group containing an alkali metal ion attached to its main chain, with a second compound having an electron-donating polar group. The first compound includes a first functional group. The second compound includes at least one second functional group in a molecular building block, the second functional group having the function of reacting with the first functional group to form a chemical bond.

[0031] The main chain of the first compound may have any molecular structure that is electrochemically stable and can be easily applied to each component of a battery. Examples of the main chain include polysaccharides such as polyethylene glycol, polyethylene oxide, polyvinyl alcohol, and cellulose, and derivatives thereof. For example, the main chain of the first compound may include at least one selected from the group consisting of cellulose, cellulose derivatives, polyvinyl alcohol, polyvinyl alcohol derivatives, polyethylene oxide, polyethylene oxide derivatives, polyethylene glycol, and polyethylene glycol derivatives. It is particularly desirable that the main chain of the first compound include at least one selected from the group consisting of cellulose and its derivatives (e.g., CMC, etc.). The main chain of the first compound may be at least partially composed of cellulose or a derivative thereof, or may be substantially entirely composed of cellulose or a derivative thereof.

[0032] The acidic functional group of the first compound is Li + The acidic functional group is an anionic group that pairs with alkali metal ions such as carboxylate, carboxyl, methyl ...

[0033] The first compound may be a polymer containing an acidic functional group that captures alkali metal ions, and has a weight average molecular weight (Mw) of 500 or more. The molecular weight of the first compound is not particularly limited, but may be, for example, Mw of 100,000 or more, or Mw of 300,000 or more. The alkali metal ions captured by the acidic functional group include sodium ions (Na + ) or potassium ion (K + ), etc., but preferably lithium ions (Li + )

[0034] The first compound can be synthesized, for example, by introducing an acidic functional group into the main chain and exchanging the counter cation of the acidic functional group with an alkali metal ion. The following formula (5) represents a polymer containing a constitutional unit represented by formula (3) in which an alkali metal ion (Y + ) is lithium ion (Li + An example of a method for synthesizing a first compound used in producing a polymer having the formula (I) is shown below. As shown in formula (5) below, an acidic imidazolium salt (e.g., imidazolium phosphate) can be used to introduce an acidic functional group. Then, the imidazolium cation is removed using an ion exchange resin, and the acidic polymer is neutralized with lithium hydroxide or the like, thereby exchanging the counter cation of the acidic functional group for a lithium ion.

[0035]

[0036] The first compound used in the method for producing a solid electrolyte material according to the first embodiment may be composed of one type of polymer, or may be composed of multiple types of polymers.

[0037] The second compound is used as a cross-linking agent to cross-link the first compound. The second compound may be a polymer containing an electron-donating polar group and at least one second functional group in its molecular constituent unit that has the function of reacting with the first functional group of the first compound to form a chemical bond. The constituent units that constitute the cross-linked structure contained in the polymer according to the first embodiment are formed by the second compound. That is, the constituent units derived from the second compound serve as a conduction path for alkali metal ions captured in the acidic functional groups, conducting the alkali metal ions. As a result, the solid electrolyte material of the first embodiment is considered to have high ionic conductivity.

[0038] In the second compound, the second functional group for the crosslinking reaction with the first compound may include, for example, an epoxy group. The second compound may include two or more second functional groups. When the second compound includes two or more second functional groups, the second functional groups may be the same or different from each other.

[0039] Examples of the polar group in the second compound include an ether group and a nitrile group. That is, the second compound may contain at least one selected from the group consisting of an ether group and a nitrile group as the polar group. Among these, an ether group is preferable because it can further improve ionic conductivity. The ether group may be a polyether group. For example, the second compound may contain an ether group or a polyether group as the polar group. The second compound may be a polyether-based crosslinking agent containing a polyether group. The ether group is, for example, a polyethylene oxide group.

[0040] The second compound may include an ether group as the polar group and an epoxy group as the second functional group. The second compound may include, for example, polyethylene glycol diglycidyl ether. The second compound may consist essentially of polyethylene glycol diglycidyl ether. Here, "the second compound consists essentially of polyethylene glycol diglycidyl ether" means that the molar ratio (i.e., molar fraction) of the total amount of polyethylene glycol diglycidyl ether to the total amount of all polymers constituting the second compound is 90% or more. As an example, the molar ratio may be 95% or more. The second compound may consist solely of polyethylene glycol diglycidyl ether.

[0041] The Mw of the second compound is not particularly limited, but is, for example, not more than 6000. The Mw of the second compound may be, for example, not less than 100, or not less than 150. The second compound may be a polymer.

[0042] The second compound used in the method for producing a solid electrolyte material according to the first embodiment may be composed of one type of compound, or may be composed of multiple types of compounds.

[0043] In the method for producing a solid electrolyte material according to the first embodiment, the specific method and procedure for crosslinking the first compound with the second compound, as well as the temperature and other conditions, can be appropriately selected depending on the first and second compounds used. For example, if the first compound is a polymer in which a phosphorous acid group that captures alkali metal ions is bonded to the cellulose main chain, and the second compound is polyethylene glycol diglycidyl ether, for example, a crosslinking liquid containing the second compound and a solvent is prepared, and the first compound (e.g., a membrane formed with the first compound) is added to the crosslinking liquid. The first compound and the second compound are reacted by maintaining the crosslinking liquid at a temperature that does not cause dehydration condensation of the first compound for 5 hours or more to obtain a solid electrolyte material according to the first embodiment. The temperature at which dehydration condensation of the first compound does not occur is preferably 150 ° C. or less, and may be, for example, room temperature (25 ° C.).

[0044] Second Embodiment A second embodiment will be described below, and the matters described in the first embodiment will be omitted as appropriate.

[0045] The nonaqueous electrolyte secondary battery according to the second embodiment includes a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, a separator disposed between the positive electrode and the negative electrode, and a nonaqueous electrolyte. The nonaqueous electrolyte secondary battery according to the second embodiment satisfies at least one of the following conditions (A) to (D): (A) the battery further includes a membrane including the solid electrolyte material according to the first embodiment provided on a surface of at least one electrode selected from the group consisting of a positive electrode and a negative electrode that faces the separator. (B) the battery further includes a membrane including the solid electrolyte material according to the first embodiment provided on surfaces of particles of at least one active material selected from the group consisting of a positive electrode active material and a negative electrode active material. (C) the battery further includes a membrane including the solid electrolyte material according to the first embodiment provided on at least a portion of the surface of the separator. (D) the separator includes the solid electrolyte material according to the first embodiment.

[0046] The nonaqueous electrolyte secondary battery according to the second embodiment includes the solid electrolyte material according to the first embodiment in at least one of the forms (A) to (D) described above. As described in the first embodiment, the solid electrolyte material according to the first embodiment has both ionic conductivity and nonaqueous solvent separability. Therefore, when the nonaqueous electrolyte secondary battery according to the second embodiment satisfies the above (A) or (B), the nonaqueous electrolyte secondary battery according to the second embodiment can suppress various problems, such as side reactions and elution of active material components into the nonaqueous solvent, that occur when the electrodes or electrode active material come into contact with the nonaqueous solvent while maintaining ionic conduction. Furthermore, when the nonaqueous electrolyte secondary battery according to the second embodiment satisfies the above (C) or (D), the separator of the nonaqueous electrolyte secondary battery according to the second embodiment can suppress migration of the nonaqueous solvent while maintaining ionic conduction. Therefore, migration of by-products generated by side reactions or active material components eluted from the active material on one electrode side to the other electrode side can be suppressed. Furthermore, when the nonaqueous electrolyte secondary battery according to the second embodiment satisfies the above (C) or (D), it becomes possible to selectively use, for example, a nonaqueous solvent that is suitable as a nonaqueous solvent for the positive electrode side (or negative electrode side) but not as a nonaqueous solvent for the negative electrode side (or positive electrode side), on the positive electrode side (or negative electrode side), thereby increasing the degree of freedom in design for improving battery performance.

[0047] 1 is a cross-sectional view schematically showing a part of the configuration of a nonaqueous electrolyte secondary battery according to Embodiment 2. Here, a lithium ion secondary battery will be described as an example of the nonaqueous electrolyte secondary battery according to Embodiment 2.

[0048] The nonaqueous electrolyte secondary battery 100 shown in FIG. 1 includes a positive electrode 1, a negative electrode 2, a separator 3 disposed between the positive electrode 1 and the negative electrode 2, and a nonaqueous electrolyte. In FIG. 1 , reference numeral 4 denotes the nonaqueous electrolyte on the positive electrode side, and reference numeral 5 denotes the nonaqueous electrolyte on the negative electrode side. The positive electrode 1 includes, for example, a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11. The positive electrode active material layer 12 contains a positive electrode active material 13. The negative electrode 2 includes, for example, a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on the negative electrode current collector 21. The negative electrode active material layer 22 contains a negative electrode active material 23.

[0049] FIG. 2 shows a cross-sectional view of an electrode in the nonaqueous electrolyte secondary battery shown in FIG. 1 when the configuration (A) is satisfied. Here, an example is shown in which the positive electrode 1 satisfies the above-mentioned (A). The positive electrode 1 shown in FIG. 2 further includes a coating 6 provided on the surface facing the separator 3. The coating 6 is a film containing the solid electrolyte material according to the first embodiment. The coating 6 may be composed of the solid electrolyte material according to the first embodiment. The coating 6 may be provided on a portion of the surface of the positive electrode active material layer 12 facing the separator 3, or may cover the entire surface facing the separator 3. The thickness of the coating 6 is, for example, 1 nm to 1000 nm, preferably 1 nm to 100 nm. This coating 6 separates the positive electrode active material layer 12 from the nonaqueous solvent of the nonaqueous electrolyte 4 while maintaining ionic conduction. Therefore, a side reaction between the positive electrode active material 13 and the non-aqueous solvent is suppressed, and elution of active material components from the positive electrode active material 13 into the non-aqueous solvent is also suppressed. The thickness of the coating 6 is determined, for example, by forming a cross section of the positive electrode 1 using a cross section polisher (CP) and observing the cross section of the positive electrode 1 with a scanning electron microscope (SEM). The coating 6 may be provided on the negative electrode active material layer 22 of the negative electrode 2.

[0050] The coating 6 can be formed, for example, by applying a dispersion of the solid electrolyte material according to the first embodiment onto the positive electrode active material layer 12 and drying the coating. The application method is not particularly limited, and a known application method such as die coating or spray coating can be appropriately selected. As another method, the coating 6 can be formed, for example, by applying a solution containing a first compound onto the positive electrode active material layer 12 and then contacting the solution with a solution containing a second compound to cause a crosslinking reaction of the first compound. The coating 6 can also be formed by a method in which a thin film is formed using the solid electrolyte material according to the first embodiment and the thin film is then laminated on the surface of the positive electrode active material layer 12 by transfer or the like.

[0051] FIG. 3 shows a cross-sectional view of an active material when the nonaqueous electrolyte secondary battery shown in FIG. 1 satisfies the configuration (B). Here, an example is shown in which the cathode active material 13 satisfies the above-mentioned (B). A coating 7 containing the solid electrolyte material according to the first embodiment is provided on the surface of the particles of the cathode active material 13 shown in FIG. 3 . The coating 7 may be composed of the solid electrolyte material according to the first embodiment. The coating 7 may be provided on a portion of the surface of the particles of the cathode active material 13, or may cover the entire particle surface. It is desirable that the coating 7 be formed with a uniform thickness over the entire particle surface. The thickness of the coating 7 is, for example, 1 nm to 1000 nm, preferably 1 nm to 100 nm. When the thickness of the coating 7 is within this range, the coating 7 can more effectively separate the active material from the nonaqueous solvent while ensuring smooth movement of alkali metal ions such as lithium ions. Therefore, side reactions between the positive electrode active material 13 and the non-aqueous solvent are suppressed, and elution of active material components from the positive electrode active material 13 into the non-aqueous solvent is also suppressed. The thickness of the coating 7 can be determined, for example, by forming a cross section of a particle of the positive electrode active material 13 by CP and observing the cross section with an SEM. The coating 7 may be provided on the surface of a particle of the negative electrode active material 23 of the negative electrode 2.

[0052] The coating 7 can be formed on the particle surfaces of the positive electrode active material 13, for example, by spray-drying a raw material liquid in which the particles of the positive electrode active material 13 are dispersed and the solid electrolyte material according to the first embodiment is dissolved. Note that examples of methods other than spray-drying include a method of spraying a solution of the solid electrolyte material onto the particles of the positive electrode active material 13, and a method of immersing the particles of the positive electrode active material 13 in a solution of the solid electrolyte material.

[0053] FIG. 4 shows a cross-sectional view of the separator 3 when the nonaqueous electrolyte secondary battery shown in FIG. 1 satisfies the configuration (C). A separation membrane 8 containing the solid electrolyte material according to the first embodiment is provided on at least a portion of the surface of the separator 3 shown in FIG. 4 . The separation membrane 8 may be provided on one of the main surfaces of the separator 3 as shown in FIG. 4 , or on both main surfaces of the separator 3. The thickness of the separation membrane 8 is, for example, 1 nm to 1000 nm, preferably 1 nm to 100 nm. This separation membrane 8 suppresses the migration of the nonaqueous solvent while maintaining ion conduction through the separator 3. That is, since migration between the nonaqueous solvent of the nonaqueous electrolyte 4 on the positive electrode side and the nonaqueous solvent of the nonaqueous electrolyte 5 on the negative electrode side is suppressed, migration of by-products generated by side reactions or active material components eluted from the active material on one electrode side to the other electrode side can be suppressed. Furthermore, it is possible to select a solvent suitable as a nonaqueous solvent for the positive electrode side and a solvent suitable as a nonaqueous solvent for the negative electrode side, and use them on each electrode side. The thickness of separation membrane 8 can be determined, for example, by forming a cross section of a laminate of separator 3 and separation membrane 8 by CP and observing the cross section of this laminate by SEM.

[0054] The separation membrane 8 can be formed, for example, by applying a dispersion of the solid electrolyte material according to the first embodiment onto the surface of the separator 3 and drying it. The application method is not particularly limited, and known application methods such as die coating and spray coating can be appropriately selected. As another method, for example, the separation membrane 8 can be formed by applying a solution containing a first compound onto the separator 3 and then contacting the solution with a solution containing a second compound to cause a crosslinking reaction of the first compound. The separation membrane 8 can also be formed by a method in which a thin film is formed using the solid electrolyte material according to the first embodiment and the thin film is laminated on the surface of the separator 3 by transfer or the like.

[0055] When the nonaqueous electrolyte secondary battery 100 satisfies the configuration (D), the separator 3 shown in Fig. 1 contains the solid electrolyte material according to the first embodiment. The separator 3 may be made of the solid electrolyte material according to the first embodiment. When the nonaqueous electrolyte secondary battery 100 satisfies the above-mentioned (D), the same effects as when the nonaqueous electrolyte secondary battery 100 satisfies the above-mentioned (C) can be obtained.

[0056] As described above, the positive electrode 1 includes, for example, a positive electrode current collector 11 and a positive electrode active material layer 12 disposed on the positive electrode current collector 11 .

[0057] The positive electrode current collector 11 can be a sheet or film made of a metal material that is stable within the potential range of the positive electrode 1, such as aluminum, stainless steel, titanium, or an alloy thereof. Aluminum and its alloys are suitable materials for the positive electrode current collector 11 because they are inexpensive and can be easily formed into thin films. The sheet or film may be porous or non-porous. Metal foil, metal mesh, or the like may be used as the sheet or film. A carbon material such as carbon may be applied to the surface of the positive electrode current collector 11 as a conductive auxiliary material.

[0058] The positive electrode active material 13 contained in the positive electrode active material layer 12 is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. Examples of the positive electrode active material 13 that can be used include lithium-containing transition metal oxides, lithium-containing transition metal phosphates, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal oxysulfides, and transition metal oxynitrides. Typically, a lithium-containing transition metal oxide is used as the positive electrode active material 13. The lithium-containing transition metal oxide is a composite oxide containing, in addition to Li, transition metal elements such as Co, Mn, Ni, and Al. The metal element contained in the lithium-containing transition metal oxide is, for example, at least one selected from Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, and Bi. Among these, it is preferable that the positive electrode active material 13 contains at least one selected from Co, Mn, Ni, and Al. Examples of lithium-containing transition metal oxides include lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium iron phosphate. The positive electrode active material 13 contains, for example, at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium iron phosphate.

[0059] The lithium-containing transition metal oxide has, for example, a layered crystal structure, specifically a layered structure belonging to the space group R-3m or a layered structure belonging to the space group C2 / m.

[0060] The lithium-containing transition metal oxide particles may be secondary particles formed by agglomeration of a large number of primary particles. The volume-based median diameter (D50) of the lithium-containing transition metal oxide particles is, for example, 3 μm to 30 μm, preferably 5 μm to 25 μm. When the lithium-containing transition metal oxide is a secondary particle of primary particles, the D50 of the composite oxide refers to the D50 of the secondary particles. D50 refers to the particle size at which the cumulative frequency in the volume-based particle size distribution is 50% from the smallest particle size, and is also called the median diameter. The particle size distribution of the composite oxide can be measured using a laser diffraction particle size distribution analyzer (e.g., MT3000II, manufactured by Microtrac-Bell Corporation) using water as a dispersion medium.

[0061] The positive electrode active material layer 12 may contain other materials such as a conductive additive and a binder. Examples of the conductive additive include carbon black such as acetylene black and ketjen black, graphite, carbon nanotubes (CNT), carbon nanofibers, and graphene. Examples of the binder include fluorine-containing resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), polyacrylonitrile (PAN), polyimide, acrylic resin, and polyolefin. These resins may also be used in combination with carboxymethyl cellulose (CMC) or a salt thereof, polyethylene oxide (PEO), or the like.

[0062] As described above, the negative electrode 2 includes, for example, a negative electrode current collector 21 and a negative electrode active material layer 22 disposed on the negative electrode current collector 21 .

[0063] The negative electrode current collector 21 may be a sheet or film made of a metal material that is stable within the potential range of the negative electrode 2, such as stainless steel, nickel, copper, or an alloy thereof. The sheet or film may be porous or non-porous. Examples of the sheet or film include metal foil and metal mesh. A carbon material such as carbon may be applied to the surface of the negative electrode current collector 21 as a conductive auxiliary material.

[0064] The negative electrode active material 23 contained in the negative electrode active material layer 22 is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. Examples of the negative electrode active material 23 include carbon materials, silicon, silicon compounds, tin, tin compounds, lithium titanate, and NiBi alloys. The negative electrode active material 23 includes, for example, at least one selected from the group consisting of carbon materials, silicon, silicon compounds, tin, tin compounds, lithium titanate, and NiBi alloys. Suitable examples of carbon materials include natural graphite such as flake graphite, lump graphite, and amorphous graphite, and artificial graphite such as lump artificial graphite (MAG) and graphitized mesophase carbon microbeads (MCMB). Graphite may be used in combination with silicon and silicon-containing materials such as silicon compounds as the negative electrode active material.

[0065] The negative electrode active material layer 22 may contain other materials such as a conductive additive, a binder, etc. The same conductive additive as that usable for the positive electrode active material layer 13 can be used for the negative electrode active material layer 22. As with the positive electrode active material layer 13, fluororesin, PAN, polyimide, acrylic resin, polyolefin, etc. can also be used for the binder, but styrene-butadiene rubber (SBR) is preferably used. The negative electrode active material layer 22 may also contain CMC or a salt thereof, polyacrylic acid (PAA) or a salt thereof, polyvinyl alcohol (PVA), etc. Among these, it is preferable to use SBR in combination with CMC or a salt thereof, or PAA or a salt thereof.

[0066] The separator 3 is made of a porous sheet having ion permeability and insulating properties. Specific examples of the porous sheet include a microporous thin film, a woven fabric, and a nonwoven fabric. Suitable materials for the separator 3 include polyolefins such as polyethylene and polypropylene, and cellulose. The separator 3 may have a single-layer structure or a multi-layer structure. A highly heat-resistant resin layer such as an aramid resin may be formed on the surface of the separator 3. A filler layer containing an inorganic filler may be formed at the interface between the separator 3 and at least one of the positive electrode 1 and the negative electrode 2. When the nonaqueous electrolyte secondary battery 100 according to the second embodiment satisfies the above (D), the separator 3 contains the solid electrolyte material according to the first embodiment.

[0067] The nonaqueous electrolyte 4 on the positive electrode side and the nonaqueous electrolyte 5 on the negative electrode side each contain a nonaqueous solvent and an electrolyte salt dissolved in the nonaqueous solvent. Examples of nonaqueous solvents that can be used include esters, ethers, nitriles, amides, and mixed solvents of two or more of these. The nonaqueous solvent may contain a halogen-substituted solvent in which at least a portion of the hydrogen atoms in these solvents are substituted with halogen atoms such as fluorine. Examples of nonaqueous solvents include ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), diethyl carbonate (DEC), fluoroethylene carbonate (FEC), methyl 3,3,3-trifluoropropionate (FMP), and mixed solvents thereof. Examples of the electrolyte salt that can be used include lithium hexafluorophosphate (LiPF), lithium tetrafluoroborate (LiBF), lithium perchlorate (LiClO), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bisperfluoroethylsulfonylimide (LiN(SO2C2F5)2), LiAsF6, LiCF3SO3, and lithium difluoro(oxalato)borate (LiFOB). One selected from these electrolyte salts may be used, or two or more may be used in combination.

[0068] Next, a nonaqueous electrolyte secondary battery having a configuration including a wound electrode assembly will be described as a more specific configuration example of the nonaqueous electrolyte secondary battery according to the second embodiment. Fig. 5 is a cross-sectional view schematically showing an axial cross section of a nonaqueous electrolyte secondary battery 200 including a wound electrode assembly, which is an example of the nonaqueous electrolyte secondary battery according to the second embodiment.

[0069] 5 , the nonaqueous electrolyte secondary battery 200 includes a wound electrode assembly 34, a nonaqueous electrolyte, and an outer can 36 that accommodates the electrode assembly 34 and the nonaqueous electrolyte. The electrode assembly 34 has a positive electrode 31, a negative electrode 32, and a separator 33, and has a wound structure in which the positive electrode 31 and the negative electrode 32 are spirally wound with the separator 33 interposed therebetween. The outer can 36 is a cylindrical metal container with a bottom and an open axial end, and the opening of the outer can 36 is closed by a sealing member 37. For ease of explanation, the sealing member 37 side of the battery 200 will be referred to as the top, and the bottom side of the outer can 36 will be referred to as the bottom.

[0070] The nonaqueous electrolyte secondary battery 200, like the nonaqueous electrolyte secondary battery 100 described above, includes the solid electrolyte material according to the first embodiment in at least one of the forms (A) to (D) described above.

[0071] The positive electrode 31, negative electrode 32, and separator 33 that constitute the electrode assembly 34 are all long, strip-like bodies that are spirally wound and alternately stacked in the radial direction of the electrode assembly 34. The negative electrode 32 is formed to be slightly larger than the positive electrode 31 in order to prevent lithium deposition. That is, the negative electrode 32 is formed to be longer in the longitudinal direction and width direction (i.e., the short direction) than the positive electrode 31. The separator 33 is formed to be at least slightly larger than the positive electrode 31, and, for example, two separators 33 are arranged to sandwich the positive electrode 31. The electrode assembly 34 has a positive electrode lead 40 connected to the positive electrode 31 by welding or the like, and a negative electrode lead 41 connected to the negative electrode 32 by welding or the like.

[0072] Although a cylindrical battery in which an electrode assembly 34 having a wound structure is housed in a cylindrical outer can 36 with a bottom is exemplified as a more specific configuration example of the nonaqueous electrolyte secondary battery according to the second embodiment, the electrode assembly may be a laminated electrode assembly in which a plurality of positive electrodes and negative electrodes are alternately stacked with separators interposed therebetween. Furthermore, the shape of the nonaqueous electrolyte secondary battery according to the second embodiment is not limited to a cylindrical shape, and may be a prismatic battery, a laminated battery, a coin battery, or the like.

[0073] The positive electrode 31 has a positive electrode current collector 31a and a positive electrode active material layer 31b formed on the positive electrode current collector 31a. The positive electrode active material layer 31b is preferably formed on both sides of the positive electrode current collector 31a, excluding an exposed portion to which the positive electrode lead 40 is welded. The positive electrode 31 can be produced, for example, by applying a positive electrode slurry containing a positive electrode active material, a conductive additive, a binder, and the like onto the positive electrode current collector 31a, drying the coating, and then compressing it to form the positive electrode active material layer 31b on both sides of the positive electrode current collector 31a. The detailed descriptions of the positive electrode current collector 31 a, the positive electrode active material layer 31 b, and the positive electrode active material, conductive additive, and binder contained in the positive electrode active material layer 31 b in the positive electrode 31 are the same as those of the positive electrode current collector 11, the positive electrode active material layer 12, and the positive electrode active material 13, conductive additive, and binder contained in the positive electrode active material layer 12 in the positive electrode 1 of the nonaqueous electrolyte secondary battery 100, respectively.

[0074] The negative electrode 32 has a negative electrode current collector 32a and a negative electrode active material layer 32b formed on the negative electrode current collector 32a. The negative electrode active material layer 32b is preferably formed on both sides of the negative electrode current collector 32a except for an exposed portion to which the negative electrode lead 31 is welded. The negative electrode 32 can be produced by applying a negative electrode slurry containing a negative electrode active material, a conductive additive, a binder, etc. to the surface of the negative electrode current collector 32a, drying the coating, and then compressing it to form the negative electrode active material layer 32b on both sides of the negative electrode current collector. The detailed descriptions of the negative electrode current collector 32 a, the negative electrode active material layer 32 b, and the negative electrode active material, conductive additive, and binder contained in the negative electrode active material layer 32 b in the negative electrode 32 are the same as those of the negative electrode current collector 21, the negative electrode active material layer 22, and the negative electrode active material 23, conductive additive, and binder contained in the negative electrode active material layer 22 in the negative electrode 2 of the nonaqueous electrolyte secondary battery 100, respectively.

[0075] The detailed description of the separator 33 is the same as that of the separator 3 in the nonaqueous electrolyte secondary battery 100 .

[0076] Insulating plates 38, 39 are disposed above and below the electrode body 34. In the example shown in Fig. 5, the positive electrode lead 40 passes through a through-hole in the insulating plate 38 and extends toward the sealing body 37, and the negative electrode lead 41 passes outside the insulating plate 39 and extends toward the bottom side of the outer can 36. The positive electrode lead 40 is connected to the underside of an internal terminal plate 43 of the sealing body 37 by welding or the like, and a cap 47, which is the top plate of the sealing body 37 and is electrically connected to the internal terminal plate 43, serves as the positive electrode terminal. The negative electrode lead 41 is connected to the inner bottom surface of the outer can 36 by welding or the like, and the outer can 36 serves as the negative electrode terminal.

[0077] A gasket 48 is provided between the exterior can 36 and the sealing body 37 to ensure airtightness inside the battery. The exterior can 36 has a groove 32 formed on its side surface that protrudes inward and supports the sealing body 37. The groove 42 is preferably formed in an annular shape along the circumferential direction of the exterior can 36, and supports the sealing body 37 on its top surface. The sealing body 37 is fixed to the top of the exterior can 36 by the groove 32 and the open end of the exterior can 36 that is crimped to the sealing body 37.

[0078] The sealing body 37 has a structure in which, in order from the electrode body 34 side, an internal terminal plate 43, a lower valve body 44, an insulating member 45, an upper valve body 46, and a cap 47 are stacked. Each component constituting the sealing body 47 has, for example, a disk or ring shape, and all components except for the insulating member 45 are electrically connected to each other. The lower valve body 44 and the upper valve body 46 are connected at their respective centers, and the insulating member 45 is interposed between their respective peripheral edges. When abnormal heat generation causes an increase in the internal pressure of the battery, the lower valve body 44 deforms and breaks, pushing the upper valve body 46 toward the cap 47, thereby interrupting the current path between the lower valve body 44 and the upper valve body 46. When the internal pressure further increases, the upper valve body 46 breaks, and gas is released from the opening of the cap 47.

[0079] (Other Embodiments) (Additional Notes) The above description of the embodiments discloses the following techniques.

[0080] (Technology 1) A solid electrolyte material for a non-aqueous electrolyte secondary battery, the solid electrolyte material including a polymer having an acidic functional group having an alkali metal ion bonded to a main chain, the polymer having a cross-linked structure including an electron-donating polar group.

[0081] This configuration makes it possible to provide a solid electrolyte material for a non-aqueous electrolyte secondary battery that can achieve both ion conductivity and non-aqueous solvent separability (solvent separability).

[0082] (Technology 2) The solid electrolyte material according to Technology 1, wherein the acidic functional group is a phosphorous group.

[0083] This configuration can improve the ionic conductivity of the solid electrolyte material.

[0084] (Technology 3) The solid electrolyte material according to Technology 1 or 2, wherein the main chain of the polymer includes at least one selected from the group consisting of cellulose, a cellulose derivative, polyvinyl alcohol, a polyvinyl alcohol derivative, polyethylene oxide, a polyethylene oxide derivative, polyethylene glycol, and a polyethylene glycol derivative.

[0085] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0086] (Technology 4) The solid electrolyte material according to any one of Technologies 1 to 3, wherein the crosslinked structure includes at least one polar group selected from the group consisting of an ether group and a nitrile group.

[0087] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0088] (Technology 5) The solid electrolyte material according to Technology 4, wherein the ether group is a polyethylene oxide group.

[0089] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0090] (Technology 6) The solid electrolyte material according to any one of Technologies 1 to 5, wherein the crosslinked structure includes a structure represented by the following formula (1):

[0091] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0092] (Technology 7) The solid electrolyte material according to Technology 6, wherein the crosslinked structure includes a structure represented by the following formula (2): In the formula (2), n represents a positive integer.

[0093] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0094] (Technology 8) A non-aqueous electrolyte secondary battery comprising: a positive electrode containing a positive electrode active material; a negative electrode containing a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; and a non-aqueous electrolyte, wherein the non-aqueous electrolyte secondary battery satisfies at least one selected from the group consisting of the following (A) to (D): (A) further comprising a film comprising the solid electrolyte material according to any one of Technologies 1 to 7, provided on a surface of at least one electrode selected from the group consisting of the positive electrode and the negative electrode, facing the separator. (B) further comprising a film comprising the solid electrolyte material according to any one of Technologies 1 to 7, provided on surfaces of particles of at least one active material selected from the group consisting of the positive electrode active material and the negative electrode active material. (C) further comprising a film comprising the solid electrolyte material according to any one of Technologies 1 to 7, provided on at least a portion of a surface of the separator. (D) The separator comprises the solid electrolyte material according to any one of Technologies 1 to 7.

[0095] This configuration allows the use of a solid electrolyte material that has both ion conductivity and solvent separability to separate the components of a nonaqueous electrolyte secondary battery, thereby improving the performance and reliability of the nonaqueous electrolyte secondary battery.

[0096] (Technology 9) The nonaqueous electrolyte secondary battery according to Technology 8, wherein the positive electrode active material includes at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium iron phosphate, and the negative electrode active material includes at least one selected from the group consisting of carbon materials, silicon, silicon compounds, tin, tin compounds, lithium titanate, and NiBi alloys.

[0097] According to this configuration, a high-performance and highly reliable lithium ion secondary battery can be obtained.

[0098] (Technology 10) A method for producing a solid electrolyte material for a non-aqueous electrolyte secondary battery, the method comprising: reacting a first compound, which is a polymer having an acidic functional group having an alkali metal ion bound to a main chain, with a second compound having an electron-donating polar group to form a crosslink; the first compound comprises a first functional group; and the second compound comprises at least one second functional group in a molecular building block, the second functional group having a function of reacting with the first functional group to form a chemical bond.

[0099] This configuration makes it possible to provide a solid electrolyte material for a non-aqueous electrolyte secondary battery that can achieve both ion conductivity and solvent separability.

[0100] (Technology 11) The production method according to Technology 10, wherein the main chain of the first compound includes at least one selected from the group consisting of cellulose, cellulose derivatives, polyvinyl alcohol, polyvinyl alcohol derivatives, polyethylene oxide, polyethylene oxide derivatives, polyethylene glycol, and polyethylene glycol derivatives.

[0101] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0102] (Technology 12) The solid electrolyte material according to Technology 10 or 11, wherein the second functional group of the second compound includes an epoxy group.

[0103] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0104] (Technology 13) The production method according to any one of Techniques 10 to 12, wherein the second compound contains at least one selected from the group consisting of an ether group and a nitrile group as the polar group.

[0105] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0106] (Technology 14) The method according to Technology 13, wherein the ether group is a polyethylene oxide group.

[0107] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0108] (Technology 15) The method according to any one of techniques 10 to 14, wherein the second compound comprises polyethylene glycol diglycidyl ether.

[0109] This configuration can improve the ionic conductivity and solvent separability of the solid electrolyte material.

[0110] The present disclosure will be further described below with reference to examples, but the present disclosure is not limited to these examples.

[0111] Example 1 Synthesis of Solid Electrolyte Material Synthesis of First Compound First, the first compound was synthesized. The synthesis procedure for the first compound was as follows: (1) 0.5 g of cellulose (Mw: approximately 300,000) was dispersed in 2 mL of dimethyl sulfoxide (DMSO). (2) 24.5 g of 1-ethyl-3-methylimidazolium methylphosphonate was placed in a recovery flask, and a stirrer was placed inside and heated to 80°C. (3) The cellulose dispersion obtained in (1) was added to the recovery flask, and the contents were stirred at 80°C to dissolve the cellulose. (4) The contents were heated to 100°C and stirred for 48 hours. (5) The reaction solution was diluted with water and purified with ultrapure water using a dialysis membrane. (6) The resulting aqueous solution was mixed with a strongly acidic ion exchange resin to remove the imidazolium cations from the phosphorous acid terminal groups. (7) A lithium hydroxide aqueous solution was added to the acidic aqueous solution to neutralize it, and the phosphorous acid group terminals were lithiated. (8) The resulting aqueous solution was concentrated using an evaporator, and the concentrated solution was placed in a flat PFA dish and allowed to dry naturally. (9) The membrane obtained on the dish was vacuum dried at 100°C to obtain lithium ion-containing phosphite cellulose.

[0112] As described above, the method for synthesizing the lithium ion-containing phosphite cellulose, which is the first compound, is as shown in the following formula (5).

[0113] (Method for Crosslinking First Compound) Next, the obtained first compound was reacted with a second compound, which served as a crosslinker, to crosslink the first compound using the second compound. The crosslinking method was carried out as follows: (1) A 1% by mass aqueous solution of the lithium ion-containing phosphite cellulose obtained by the above synthesis method was prepared. This aqueous solution of lithium ion-containing phosphite cellulose was cast into a petri dish and dried to prepare a lithium ion-containing phosphite cellulose film. (2) The obtained lithium ion-containing phosphite cellulose film was placed in a crosslinking solution containing the second compound, polyethylene glycol diglycidyl ether (degree of polymerization n = 9), and maintained at 60°C for 3 hours to react the lithium ion-containing phosphite cellulose film with the polyethylene glycol diglycidyl ether. The crosslinking solution used was a 2-propanol solution containing polyethylene glycol diglycidyl ether at a concentration of 0.5 mol / L and LiOH at a concentration of 0.0017 mol / L. (3) The membrane obtained in (2) was washed with 70% by mass of methanol and dried to obtain a membrane of a solid electrolyte material having a cross-linked structure.

[0114] The thickness of the film of the solid electrolyte material having a cross-linked structure obtained in Example 1 was 18 μm.

[0115] [Evaluation of Solvent Separation Properties] A test to evaluate the solvent separation performance of the membrane of the solid electrolyte material having a crosslinked structure obtained by the above method (hereinafter referred to as a solvent separation test) was carried out using an H-shaped cell. A nonaqueous electrolyte for the positive electrode (positive electrode liquid) was placed in one cell of the H-shaped cell, and a nonaqueous electrolyte for the negative electrode (negative electrode liquid) was placed in the other cell, and the two cells were separated by the membrane of the solid electrolyte material having a crosslinked structure of Example 1. The positive electrode liquid and negative electrode liquid were as follows.

[0116] Positive electrode solution: 0.7M LiPF6 / FEC+FMP (FEC / FMP=2 / 8 (volume ratio)) Negative electrode solution: 3M LiTFSI+0.1M LiFOB / DME

[0117] This test cell was kept at 25°C for 50 hours, and then the amount of the solvent (DME) of the negative electrode liquid mixed into the cell containing the positive electrode liquid was quantitatively analyzed by H-NMR. The transfer coefficient of the solvent (DME) to the positive electrode side was calculated from the amount of DME mixed, the thickness and area of ​​the film of the solid electrolyte material, and the concentration difference. The results are as shown in Table 1 below. Note that the "concentration difference" refers to the difference in the initial bulk concentration of the target non-aqueous solvent between the positive electrode liquid and the negative electrode liquid, and in this example, it is the molar concentration of DME in the negative electrode liquid before the solvent separation test. Here, the unit of the transfer coefficient is "mol cm / (h cm 2 The units constituting this transfer coefficient are as follows: mol: DME concentration detected on the positive electrode side cm: film thickness of the solid electrolyte material film h: solvent separation test time (50 hours in this example) cm 2 : area of ​​membrane of solid electrolyte material mol / L: concentration difference (in this example, DME concentration in the negative electrode solution before the solvent separation test)

[0118] Furthermore, the liquid separation rate after 10 years was determined. Specifically, the solvent separation test was evaluated at two different time points, and the results were plotted using Root's law (horizontal axis = √(time), vertical axis = liquid separation rate). The liquid separation rate was determined by extrapolating the value after 10 years. The liquid separation rate was calculated by subtracting the molar ratio of DME in the positive electrode solution from 100 when the molar ratio of FEC + FMP + DME = 100.

[0119] [Evaluation of Ion Conductivity] Using a membrane of the solid electrolyte material having the crosslinked structure of Example 1, the ionic conductivity and Li of the solid electrolyte material of Example 1 were measured. + The transference numbers were measured.

[0120] A non-blocking electrode in which a film of the solid electrolyte material having a crosslinked structure of Example 1 was sandwiched between metal lithium electrodes was placed in a measurement cell, and the impedance of the solid electrolyte material was measured by AC impedance measurement at 60°C.

[0121] In the Nyquist plot obtained by the impedance measurement, the real value of the impedance at the measurement point where the absolute value of the phase of the complex impedance was smallest was regarded as the resistance value to the ionic conduction of the film of the solid electrolyte material. Using this resistance value, the ionic conductivity was calculated based on the following formula (6).

[0122] σ +、- = (R SE × S / t) -1 ...(6)

[0123] In equation (6), σ +、- represents the ionic conductivity in AC impedance measurement. S represents the area of ​​the membrane of the solid electrolyte material. R SE represents the resistance value of the film of the solid electrolyte material in AC impedance measurement, and t represents the thickness of the film of the solid electrolyte material.

[0124] In addition, the non-blocking electrode was placed in the measurement cell, and the DC resistance σ + was also measured.

[0125] Li + The transport number is the ionic conductivity σ in AC impedance measurement. +、- DC resistance σ in constant voltage measurement + The ratio of (σ + / σ +、- ) was calculated.

[0126] Ionic conductivity σ in AC impedance measurements +、- , ionic conductivity σ in constant voltage measurement + , and Li + The results of the transport numbers are shown in Table 2.

[0127] Example 2 Synthesis of Solid Electrolyte Material A solid electrolyte material was synthesized in the same manner as in Example 1, except that the crosslinking reaction time in the crosslinking method for the first compound was changed from 3 hours to 20 hours. The thickness of the film of the solid electrolyte material having a crosslinked structure obtained in Example 2 was 11 μm.

[0128] [Evaluation of Solvent Separation Property] The solvent separation property of the membrane of the solid electrolyte material of Example 2 was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0129] [Evaluation of Ion Conductivity] The ion conductivity of the membrane of the solid electrolyte material of Example 2 was evaluated in the same manner as in Example 1. The results are shown in Table 2.

[0130] Reference Example 1 Using the membrane of the first compound prepared in Example 1, solvent separability and ionic conductivity were evaluated in the same manner as in Example 1. The thickness of the membrane of the first compound obtained in Reference Example 1 was 35 μm. The results of solvent separability are shown in Table 1. Regarding ionic conductivity, no arc was observed in the Nyquist plot obtained by AC impedance measurement, and ionic conductivity was not confirmed.

[0131]

[0132]

[0133] As can be seen from Tables 1 and 2, the membranes of the solid electrolyte materials of Examples 1 and 2, which were composed of polymers having a crosslinked structure, had ionic conductivity and also high solvent separability. In contrast, the membrane of Reference Example 1, which was composed of a polymer not having a crosslinked structure, had lower solvent separability than the membranes of Examples 1 and 2, and furthermore, no ionic conductivity was confirmed. These results confirmed that the solid electrolyte material of the present disclosure has both ionic conductivity and non-aqueous solvent separability.

[0134] The technology of the present disclosure is useful for lithium secondary batteries.

Claims

1. A solid electrolyte material for a non-aqueous electrolyte secondary battery, comprising: the solid electrolyte material includes a polymer having an acidic functional group having an alkali metal ion bonded to a main chain, the acidic functional group is a phosphorous group; The polymer has a crosslinked structure containing an electron-donating polar group. Solid electrolyte material.

2. the main chain of the polymer contains at least one selected from the group consisting of cellulose, cellulose derivatives, polyvinyl alcohol, polyvinyl alcohol derivatives, polyethylene oxide, polyethylene oxide derivatives, polyethylene glycol, and polyethylene glycol derivatives; The solid electrolyte material according to claim 1 .

3. The crosslinked structure includes, as the polar group, at least one selected from the group consisting of an ether group and a nitrile group. The solid electrolyte material according to claim 1 .

4. The ether group is a polyethylene oxide group. The solid electrolyte material according to claim 3 .

5. The crosslinked structure includes a structure represented by the following formula (1): The solid electrolyte material according to claim 1 . 【Chemistry 1】

6. The crosslinked structure includes a structure represented by the following formula (2): The solid electrolyte material according to claim 5 . 【Chemistry 2】 In the formula (2), n represents a positive integer.

7. a positive electrode including a positive electrode active material; a negative electrode including a negative electrode active material; a separator disposed between the positive electrode and the negative electrode; A non-aqueous electrolyte; A non-aqueous electrolyte secondary battery comprising: The nonaqueous electrolyte secondary battery satisfies at least one selected from the group consisting of the following (A) to (D): (A) Further comprising a membrane comprising the solid electrolyte material according to any one of claims 1 to 6, the membrane being provided on a surface of at least one electrode selected from the group consisting of the positive electrode and the negative electrode, the surface facing the separator. (B) The battery further includes a film comprising the solid electrolyte material according to any one of claims 1 to 6, the film being provided on a surface of particles of at least one active material selected from the group consisting of the positive electrode active material and the negative electrode active material. (C) The battery further comprises a membrane including the solid electrolyte material according to any one of claims 1 to 6, the membrane being provided on at least a portion of a surface of the separator. (D) The separator comprises the solid electrolyte material according to any one of claims 1 to 6.

8. the positive electrode active material includes at least one selected from the group consisting of lithium cobalt oxide, lithium nickel cobalt aluminum oxide, lithium nickel cobalt manganese oxide, lithium nickel manganese oxide, and lithium iron phosphate; The negative electrode active material includes at least one selected from the group consisting of a carbon material, silicon, a silicon compound, tin, a tin compound, lithium titanate, and a NiBi alloy. The nonaqueous electrolyte secondary battery according to claim 7 .

9. A method for producing a solid electrolyte material for a non-aqueous electrolyte secondary battery, comprising: The production method includes reacting a first compound, which is a polymer having an acidic functional group having an alkali metal ion bonded to a main chain, with a second compound having an electron-donating polar group to crosslink the first compound, the first compound comprises a first functional group; the second compound contains at least one second functional group in a molecular building block, the second functional group having a function of reacting with the first functional group to form a chemical bond; A method for producing a solid electrolyte material.

10. the main chain of the first compound includes at least one selected from the group consisting of cellulose, a cellulose derivative, a polyvinyl alcohol, a polyvinyl alcohol derivative, a polyethylene oxide, a polyethylene oxide derivative, a polyethylene glycol, and a polyethylene glycol derivative; The method of claim 9.

11. the second functional group of the second compound comprises an epoxy group; The method of claim 9.

12. The second compound includes at least one selected from the group consisting of an ether group and a nitrile group as the polar group. The method of claim 9.

13. The ether group is a polyethylene oxide group. The method of claim 12.

14. the second compound comprises a polyethylene glycol diglycidyl ether; The method of claim 9.

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