Polyether polymer, polyether electrolyte for lithium ion secondary battery, composite solid electrolyte for lithium ion secondary battery, and lithium ion secondary battery

Abstract

The present invention provides: a polyether polymer capable of suppressing a side reaction with a sulfide-based solid electrolyte, and having high lithium ion conductivity; a polyether electrolyte for a lithium ion secondary battery using the polyether polymer; a composite solid electrolyte for a lithium ion secondary battery; and a lithium ion secondary battery. The present invention relates to a polyether polymer including 20 mol% or more of an X unit, which is a constituent unit derived from a specific alkylene oxide, in 100 mol% of constituent units.

Description

Polyether polymer, polyether electrolyte for lithium ion secondary battery, composite solid electrolyte for lithium ion secondary battery, and lithium ion secondary battery

[0001] The present invention relates to a polyether polymer, a polyether electrolyte for a lithium ion secondary battery, a composite solid electrolyte for a lithium ion secondary battery, and a lithium ion secondary battery.

[0002] All-solid-state batteries are batteries that have a solid electrolyte layer between a positive electrode layer and a negative electrode layer, and have the advantage that safety devices can be more easily simplified compared to liquid-based batteries that have an electrolyte solution containing a flammable organic solvent.

[0003] Among all-solid-state batteries, all-solid-state lithium-ion batteries have attracted attention because they have a high energy density due to the use of a battery reaction involving the movement of lithium ions, and because they use a solid electrolyte instead of an electrolytic solution containing an organic solvent as the electrolyte interposed between the positive electrode and the negative electrode (for example, Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2020-107414

[0005] Sulfide-based solid electrolytes are sometimes used as inorganic solid electrolytes in all-solid-state batteries. However, sulfide-based solid electrolytes generally undergo side reactions when in contact with other materials constituting the battery, which can lead to decomposition of the sulfide-based solid electrolyte itself. Therefore, there is a demand for materials that can suppress side reactions with sulfide-based solid electrolytes and suppress decomposition reactions of the sulfide-based solid electrolyte.

[0006] Furthermore, because there are few contact points between inorganic solid electrolytes, polymer electrolytes have been added to inorganic solid electrolytes to improve ionic conductivity. In conventional technology, polyether-based polymers primarily composed of polyethylene oxide (PEO) structures have been used as polymer electrolytes added to inorganic solid electrolytes. However, the inventors' research has revealed that conventional polyether-based polymers have room for improvement in terms of suppressing side reactions with sulfide-based solid electrolytes and providing high lithium ion conductivity. Lithium ion conductivity is a property that can be calculated by the product of ionic conductivity and lithium ion transport number. Many inventions in this technical field generally aim to improve ionic conductivity. This invention is novel in that it focuses on the ionic transport number, which is a trade-off between ionic conductivity and the properties calculated from the ionic transport number.

[0007] An object of the present invention is to provide a polyether polymer that can suppress side reactions with a sulfide-based solid electrolyte and has high lithium ion conductivity, a polyether electrolyte for a lithium ion secondary battery that uses the polyether polymer, a composite solid electrolyte for a lithium ion secondary battery, and a lithium ion secondary battery.

[0008] As a result of extensive investigations to achieve the above object, the present inventors have found that a specific polyether-based polymer can suppress side reactions with a sulfide-based solid electrolyte and has high lithium ion conductivity, and have thus completed the present invention.

[0009] The aspects of the present invention are as follows: Item 1. A polyether polymer containing, relative to 100 mol % of structural units, 20 mol % or more of X units, which are structural units derived from alkylene oxide and are represented by the following general formula (1): [In the formula, R １ and are the same or different and each represents an alkyl group having 2 to 6 carbon atoms.] Item 2. The polyether polymer according to Item 1, further comprising Y units which are structural units derived from an alkylene oxide represented by the following general formula (2), wherein, based on 100 mol % of the structural units, the content of X units is 20 to 99.5 mol % and the content of Y units is 0.5 to 80 mol %: [In the formula, R２ are the same or different and are —CH ２ O (CH ２ ) ａ O (CH ２ ) ｂ an alkylene glycol alkyl ether group represented by H, —CH ２ OR ８ or a bridging group containing an ethylenically unsaturated double bond represented by —CH ２ O (CH ２ ) ｃ (CHR ６ ) ｄ (CH ２ ) ｅ R ７ The number of repeating units, a, may be the same or different and is an integer from 1 to 10, and the number of repeating units, b, may be the same or different and is an integer from 0 to 6. R ８ are the same or different and are an acrylic group, a methacrylic group, an allyl group, or a methallyl group. ６ are the same or different and are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R ７ are the same or different and are a hydrogen atom, a hydroxyl group, a nitrile group, a trifluoromethyl group, an alkoxy group, or a cyclic ether group which may have a substituent. The repeating unit numbers c are the same or different and are an integer from 0 to 4, the repeating unit number d are the same or different and are an integer from 0 to 4, and the repeating unit numbers e are the same or different and are an integer from 0 to 10.] Item 3. A polyether electrolyte for a lithium ion secondary battery, comprising the polyether polymer according to Item 1 or 2, and a lithium salt compound. Item 4. A composite solid electrolyte for a lithium ion secondary battery, comprising an inorganic solid electrolyte and the polyether electrolyte for a lithium ion secondary battery according to Item 3. Item 5. The composite solid electrolyte for a lithium ion secondary battery according to Item 4, wherein the inorganic solid electrolyte is a sulfide-based solid electrolyte. Item 6. A lithium ion secondary battery using the polyether electrolyte for a lithium ion secondary battery according to Item 3. Item 7. A lithium ion secondary battery using the composite solid electrolyte for a lithium ion secondary battery according to Item 4 or 5.

[0010] The polyether polymer of the present invention is a polymer having specific structural units, and therefore can suppress side reactions with sulfide-based solid electrolytes and has high lithium ion conductivity.

[0011] The polyether polymer of the present invention contains, relative to 100 mol % of structural units, 20 mol % or more of X units, which are structural units derived from alkylene oxide represented by the general formula (1), thereby suppressing side reactions with sulfide-based solid electrolytes and imparting high lithium ion conductivity.

[0012] The reason why the above-mentioned effect is obtained in the present invention is not clear, but is presumed as follows: １ is an alkyl group having 2 to 6 carbon atoms, and the steric hindrance effect of introducing the alkyl group into the polyether structure effectively suppresses the coordination of lithium ions to the ether oxygen of the main chain, resulting in a higher ion transport number (lithium ion conductivity) and suppressing side reactions with sulfide-based solid electrolytes. Although nonpolar groups such as alkyl groups do not directly coordinate with lithium ions, they are thought to be involved in optimizing the coordination state of polar groups such as ether oxygen with lithium ions.

[0013] <Polyether Polymer> The polyether polymer of the present invention contains 20 mol % or more X units, which are structural units derived from alkylene oxide represented by the following general formula (1), out of 100 mol % of structural units. In the polyether polymer of the present invention, the X units may be the same or different. Thus, the polyether polymer of the present invention may be a polymer in which one or more types of units corresponding to X units are combined. In the polyether polymer of the present invention, it is preferable that the units in the X units are the same. [In the formula, R １ are the same or different and are alkyl groups having 2 to 6 carbon atoms.

[0014] R in formula (1) １The alkyl group having 2 to 6 carbon atoms (preferably 2 to 4 carbon atoms, more preferably 2 to 3 carbon atoms) may be linear or branched, and examples thereof include an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, and a hexyl group. Of these, an ethyl group is preferred.

[0015] R in formula (1) １ When R is an alkyl group having one carbon atom, sufficient lithium ion conductivity cannot be obtained. １ When R has one carbon atom (methyl group), the alkyl chain length is short and the molecular mobility is relatively low, so the effect as a steric hindrance group is strong, which is thought to be detrimental to the transport of Li ions. On the other hand, when R has two or more carbon atoms, the alkyl chain length is long and the molecular mobility is relatively excellent, so the steric hindrance effect is kept to a certain level, and the coordination state between the ether oxygen and the Li ion is optimized, which is thought to result in a high ion transport number (lithium ion conductivity). Similarly, in terms of sulfide resistance, R １ When is an alkyl group having 2 to 6 carbon atoms, the effect tends to be more favorably obtained due to the steric hindrance effect caused by the introduction of the alkyl group.

[0016] Preferred embodiments of the X unit, which is a structural unit derived from the alkylene oxide represented by formula (1), are shown below. Among these, the structural unit represented by formula (1-1) is preferred.

[0017] The polyether polymer of the present invention preferably contains, in addition to the X units, Y units, which are structural units derived from alkylene oxide and are represented by the following general formula (2). In the polyether polymer of the present invention, the Y units may be the same or different. Thus, the polyether polymer of the present invention may be a polymer in which one or more units corresponding to X units are combined with one or more units corresponding to Y units. In the polyether polymer of the present invention, it is preferred that the units in the X units and the units in the Y units are the same. [In the formula, R ２ are the same or different and are —CH ２ O (CH ２ )ａ O (CH ２ ) ｂ an alkylene glycol alkyl ether group represented by H, —CH ２ OR ８ or a bridging group containing an ethylenically unsaturated double bond represented by —CH ２ O (CH ２ ) ｃ (CHR ６ ) ｄ (CH ２ ) ｅ R ７ The number of repeating units, a, may be the same or different and is an integer from 1 to 10, and the number of repeating units, b, may be the same or different and is an integer from 0 to 6. R ８ are the same or different and are an acrylic group, a methacrylic group, an allyl group, or a methallyl group. ６ are the same or different and are a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; R ７ are the same or different and are a hydrogen atom, a hydroxyl group, a nitrile group, a trifluoromethyl group, an alkoxy group, or a cyclic ether group which may have a substituent. c, which is the number of repeating units, is the same or different and is an integer from 0 to 4. d, which is the number of repeating units, is the same or different and is an integer from 0 to 4. e, which is the number of repeating units, is the same or different and is an integer from 0 to 10.]

[0018] R in formula (2) ２ No-CH ２ O (CH ２ ) ａ O (CH ２ ) ｂ The alkylene glycol alkyl ether group represented by H has superior molecular mobility compared to the polymer main chain and has a structure in which the distance between oxygen atoms is kept appropriate, thereby achieving high ionic conductivity (lithium ion conductivity).

[0019] R in formula (2) ２ In the formula (2), a is an integer of 1 to 10, preferably an integer of 1 to 9, more preferably an integer of 2 to 9, even more preferably an integer of 2 to 8, particularly preferably an integer of 2 to 7, most preferably an integer of 2 to 6, and most preferably an integer of 2 to 4. ２In the formula, b is an integer of 0 to 6, preferably an integer of 0 to 4, more preferably an integer of 1 to 3, and even more preferably an integer of 1 to 2.

[0020] R in formula (2) ２ No-CH ２ OR ８ The crosslinking group containing an ethylenically unsaturated double bond represented by the formula (I) is capable of crosslinking, and therefore, by crosslinking, it is possible to improve the mechanical properties of the polymer, and further, it is possible to introduce another functional group into the polymer to impart functionality to the polymer.

[0021] R in formula (2) ２ In this case, R ８ is an acrylic group, a methacrylic group, an allyl group, or a methallyl group, preferably an acrylic group, a methacrylic group, or an allyl group, more preferably a methacrylic group or an allyl group, and even more preferably an allyl group.

[0022] R in formula (2) ２ No-CH ２ O (CH ２ ) ｃ (CHR ６ ) ｄ (CH ２ ) ｅ R ７ The group represented by the formula (I) can adjust the coordination of lithium ions, and therefore a high ion transport number (lithium ion conductivity) can be obtained.

[0023] R in formula (2) ２ In this case, R ６ The alkyl group having 1 to 4 carbon atoms (preferably 1 to 3 carbon atoms, more preferably 1 to 2 carbon atoms) may be linear or branched, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group. Of these, a methyl group and an ethyl group are preferred.

[0024] R in formula (2) ２ In this case, R ６ As the alkyl group, an alkyl group having 1 to 4 carbon atoms is preferred.

[0025] R in formula (2) ２ In this case, R ７Examples of the alkoxy group include alkoxy groups having 1 to 6 carbon atoms (preferably 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms). The alkoxy group may be linear or branched, and examples include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, isobutoxy, sec-butoxy, tert-butoxy, n-pentoxy, isopentoxy, and n-hexyloxy. Of these, methoxy and ethoxy groups are preferred.

[0026] R in formula (2) ２ In this case, R ７ The number of ring members of the cyclic ether group, which may have a substituent, is preferably 3 to 10, more preferably 3 to 8, and even more preferably 3 to 6. The number of oxygen atoms in the cyclic ether group is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3. In this specification, the number of ring members refers to the number of atoms constituting the skeleton of the ring, and is, for example, 5 in the case of a 5-membered ring.

[0027] Examples of the substituent that the cyclic ether group has include a carbonyl group, an alkyl group having 1 to 4 carbon atoms, and an alkoxy group having an alkyl group having 1 to 4 carbon atoms. Of these, a carbonyl group and an alkyl group having 1 to 4 carbon atoms are preferred, and a carbonyl group is more preferred. Examples of the alkyl group having 1 to 4 carbon atoms include R ６ The same applies to the alkyl group having 1 to 4 carbon atoms as in R , including preferred embodiments. Similarly, the alkyl group having 1 to 4 carbon atoms contained in the alkoxy group can also be ６ The same applies to the alkyl group having 1 to 4 carbon atoms as above, including preferred embodiments.

[0028] R ７ The cyclic ether group, which may have a substituent, preferably has a substituent. The cyclic ether group preferably has a carbonate group (—O—(C═O)—O—) in the group. ７ Preferred embodiments of the cyclic ether group which may have a substituent are shown below: wherein * represents a bond.

[0029] R in formula (2) ２ In this case, R ７R is preferably a hydrogen atom, a nitrile group, a trifluoromethyl group, an alkoxy group, or a cyclic ether group which may have a substituent, more preferably a hydrogen atom, a hydroxyl group, an alkoxy group, a nitrile group, or a cyclic ether group which may have a substituent, still more preferably a hydrogen atom, a hydroxyl group, or an alkoxy group, particularly preferably a hydrogen atom or an alkoxy group, and most preferably a hydrogen atom. ７ As the alkyl group, a hydrogen atom, a nitrile group, a trifluoromethyl group, and a cyclic ether group which may have a substituent are also preferred.

[0030] R in formula (2) ２ In the formula (2), c is an integer of 0 to 4, preferably an integer of 0 to 3, more preferably an integer of 0 to 2, even more preferably an integer of 0 to 1, and particularly preferably an integer of 0. d is an integer of 0 to 4, preferably an integer of 1 to 3, more preferably an integer of 1 to 2, and even more preferably an integer of 1. ２ In the formula, e is an integer of 0 to 10, preferably an integer of 1 to 8, more preferably an integer of 1 to 6, even more preferably an integer of 1 to 3, and particularly preferably an integer of 1.

[0031] R in formula (2) ２ As the group, -CH ２ O (CH ２ ) ｃ (CHR ６ ) ｄ (CH ２ ) ｅ R ７ a group represented by —CH ２ O (CH ２ ) ａ O (CH ２ ) ｂ an alkylene glycol alkyl ether group represented by H, —CH ２ OR ８ Preferred is a crosslinking group containing an ethylenically unsaturated double bond represented by the formula: ２ OR ８ A crosslinking group containing an ethylenically unsaturated double bond represented by the following formula is preferred.

[0032] Preferred embodiments of the Y unit, which is a structural unit derived from the alkylene oxide represented by formula (2), are shown below. Among these, the structural units represented by formulas (2-1) to (2-5) and (2-11) are preferred, the structural units represented by formulas (2-1) to (2-4) and (2-11) are more preferred, and the structural unit represented by formula (2-4) is even more preferred.

[0033] Although preferred embodiments of the X unit and the Y unit have been exemplified, combinations of each preferred structure of the X unit and each preferred structure of the Y unit are also preferred embodiments.

[0034] * in formulas (1) and (2) represents a bond, and when it is located at the end of the polymer, it represents a hydrogen atom, a hydroxyl group, or an alkoxy group.

[0035] In the polyether polymer of the present invention, the content of X units, which are structural units derived from the alkylene oxide represented by the general formula (1), in 100 mol% of structural units is 20 mol% or more, and may be 100 mol%, but is preferably 20 to 99.9 mol%, more preferably 20 to 99.5 mol%, and even more preferably 20 to 90 mol%. The lower limit is more preferably 30 mol% or more, particularly preferably 40 mol% or more, most preferably 50 mol% or more, even most preferably 60 mol% or more, even most preferably 70 mol% or more, particularly most preferably 80 mol% or more, and even more preferably 85 mol% or more. Within this range, sufficient sulfide resistance is obtained and lithium ion conductivity tends to be further enhanced. In this specification, the notation "to" means at least the value before "to" and at most the value after "to". In addition, in this specification, the content of X units means the total content when multiple types of structural units are contained as X units. The same applies to other contents.

[0036] In the polyether polymer of the present invention, the content of Y units, which are structural units derived from the alkylene oxide represented by the general formula (2), in 100 mol% of structural units is preferably 0.5 to 80 mol%, more preferably 0.5 to 70 mol%, even more preferably 1.0 to 60 mol%, particularly preferably 1.0 to 50 mol%, most preferably 1.5 to 40 mol%, even more preferably 1.5 to 30 mol%, even more preferably 1.5 to 20 mol%, and particularly most preferably 1.5 to 15 mol%. Within this range, sufficient sulfide resistance can be obtained, and the crystallinity of the polyether polymer can be adjusted, so that lithium ion conductivity tends to be increased.

[0037] In the polyether polymer of the present invention, the total content of X units and Y units in 100 mol% of structural units is preferably 80 mol% or more, more preferably 90 mol% or more, even more preferably 95 mol% or more, particularly preferably 98 mol% or more, and may be 100 mol%.

[0038] In this specification, the content of each structural unit in the polyether polymer can be determined by nuclear magnetic resonance spectroscopy of the polymer.

[0039] The polyether polymer of the present invention may contain units other than X units and Y units, such as units having a thioether group and units having a sulfonyl group, as long as the units do not deviate from the spirit of the present invention. These may be used alone or in combination of two or more.

[0040] The weight average molecular weight (Mw) of the polyether polymer of the present invention is preferably 5,000 to 3,000,000, more preferably 10,000 to 3,000,000, and even more preferably 50,000 to 2,500,000. This tends to more suitably achieve the effects of the present invention.

[0041] The polydispersity (Mw / Mn) of the polyether polymer of the present invention is preferably 1 to 40, more preferably 1 to 30, and even more preferably 2 to 20. This tends to more suitably achieve the effects of the present invention. In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) of the polymer are measured by the method described in the Examples.

[0042] The polyether polymer of the present invention may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer, but is preferably a random copolymer because it disrupts the crystallinity of the polymer and provides a better ion transport number (lithium ion conductivity).

[0043] Preferred embodiments of the polyether polymer of the present invention are as follows: <<Embodiment 1-1>> Polymer having an X unit content of 80 mol % or more

[0044] <<Aspect 1-2>> Polymer containing X units and Y units, with the content of X units being 30 mol % or more

[0045] <<Aspect 1-3>> Polymer containing X units and the following Y units Y units: R of formula (2) ２ But -CH ２ O (CH ２ ) ａ O (CH ２ ) ｂ an alkylene glycol alkyl ether group represented by H or —CH ２ OR ８ is a bridging group containing an ethylenically unsaturated double bond represented by

[0046] <Method for producing polyether polymer> Next, the monomers used in the polymerization of the polyether polymer of the present invention will be described. The X unit and the Y unit are formed by synthesis using, for example, a compound represented by formula (1-a) and a compound represented by formula (2-a), respectively, as monomers.

[0047] (In formula (1-a), R １ is R in formula (1). １ (Similar to the above.) (In formula (2-a), R ２ is R in formula (2) ２ (Similar to the above.)

[0048] The polymerization method for the polyether polymer of the present invention is not particularly limited, and a conventional polymerization reaction can be used. Those skilled in the art can appropriately produce the polyether polymer of the present invention using the above-mentioned monomers by known polymerization methods, etc. For example, a ring-opening polymerization catalyst can be used in the form of a coordinated anion initiator such as an organoaluminum-based catalyst system, an organozinc-based catalyst system, or an organotin-phosphate ester condensate catalyst system, or a catalyst containing K as a counter ion. ＋ A polyether polymer can be obtained by reacting each monomer with an anionic initiator such as potassium alkoxide containing the above compound, diphenylmethyl potassium, or potassium hydroxide in the presence or absence of a solvent at a reaction temperature of 10 to 120°C with stirring.

[0049] Furthermore, the compound represented by formula (1-a) and the compound represented by formula (2-a) may be commercially available products, but when they are synthesized, they can be obtained, for example, by reacting epichlorohydrin with alkylene glycol alkyl ethers.

[0050] <Polyether electrolyte for lithium ion secondary battery> The polyether electrolyte for lithium ion secondary battery of the present invention is not particularly limited as long as it contains the polyether polymer of the present invention, but it preferably contains the polyether polymer of the present invention and a lithium salt compound. Here, the polyether polymer of the present invention may be used alone or in combination of two or more types.

[0051] The polyether electrolyte for a lithium ion secondary battery of the present invention is preferably a polymer solid electrolyte that is solid at room temperature. In this specification, a solid electrolyte refers to an electrolyte that is solid (not fluid) at room temperature. Here, room temperature refers to the temperature range in which a power supply is expected to operate normally. The temperature range in which a power supply is expected to operate normally has an upper limit of about 120°C, or in some cases about 60°C, and a lower limit of about -40°C, or in some cases about -20°C.

[0052] In the polyether electrolyte for lithium ion secondary batteries of the present invention, the content of the polyether polymer of the present invention in 100% by mass of polyether polymer is preferably 60% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass. This tends to more suitably achieve the effects of the present invention. In this specification, the content of each polymer can be determined by nuclear magnetic resonance spectroscopy.

[0053] The lithium salt compound is preferably a lithium salt compound having a wide potential window, such as those commonly used in lithium ion batteries. Examples of the lithium salt compound include LiBF ４ , LiPF ６ , LiClO ４ , LiCF ３ SO ３ , Li(CF ３ SO ２ ) ２ N, LiN(CF ３ SO ２ ) ２ (LiTFSI), LiN(SFO ２ ) ２ (LiFSI), LiN(C ２ F ５ SO ２ ) ２ , LiN[CF ３ SC (C ２ F ５ SO ２ ) ３ ] ２ These may be used alone or in combination of two or more.

[0054] When the polyether electrolyte for a lithium ion secondary battery of the present invention contains a lithium salt compound, the content of the lithium salt compound is preferably 5 to 300 parts by mass, more preferably 5 to 200 parts by mass, still more preferably 5 to 100 parts by mass, and particularly preferably 5 to 70 parts by mass, per 100 parts by mass of the polyether polymer (preferably the polyether polymer of the present invention). This tends to more suitably achieve the effects of the present invention.

[0055] In the polyether electrolyte for lithium ion secondary batteries of the present invention, the total content of the polyether polymer and the lithium salt compound is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, based on 100% by mass of the polyether electrolyte for lithium ion secondary batteries of the present invention, and may even be 100% by mass. This tends to more suitably achieve the effects of the present invention.

[0056] The polyether electrolyte for a lithium ion secondary battery of the present invention may contain a room-temperature molten salt. The room-temperature molten salt refers to a salt that is at least partially liquid at room temperature.

[0057] Room-temperature molten salts are also called ionic liquids, and known examples include pyridine-based, aliphatic amine-based, and alicyclic amine-based quaternary ammonium organic cations. These may be used alone or in combination of two or more. Examples of quaternary ammonium organic cations include imidazolium ions such as dialkylimidazolium and trialkylimidazolium ions, tetraalkylammonium ions, alkylpyridinium ions, pyrazolium ions, pyrrolidinium ions, and piperidinium ions.

[0058] The polyether electrolyte for a lithium ion secondary battery of the present invention may contain a plasticizer. The plasticizer is not particularly limited, but dicyano compounds and branched ether compounds are preferred. These may be used alone or in combination of two or more. When the polyether electrolyte for a lithium ion secondary battery of the present invention contains a plasticizer, it is preferable to crosslink the polyether polymer of the present invention after blending the plasticizer. This can prevent the plasticizer from leaking out.

[0059] The polyether electrolyte for a lithium ion secondary battery of the present invention may contain, in addition to the above components, for example, a reaction initiator, a cross-linking aid, a binder, etc. These may be used alone or in combination of two or more. The reaction initiator and the cross-linking aid will be described in detail when explaining the cross-linked film. The polyether electrolyte for a lithium ion secondary battery of the present invention may be cross-linked or uncross-linked.

[0060] The polyether electrolyte for a lithium ion secondary battery of the present invention can be prepared by a conventionally known method, for example, by adding a lithium salt compound or the like to the polyether polymer of the present invention as needed, and mixing the mixture. The mixture may also be dried as needed.

[0061] The lithium ion conductivity (25°C) of the polyether electrolyte for lithium ion secondary batteries of the present invention is preferably 2 x 10 －７ (S / cm) or more, more preferably 3×10 －７ (S / cm) or more, more preferably 4×10 －７ (S / cm) or more, particularly preferably 5×10 －７ (S / cm) or more, and the upper limit is not particularly limited, but for example, 1×10 －４ In this specification, the lithium ion conductivity of the electrolyte for a lithium ion secondary battery is calculated as the product of the ionic conductivity and the lithium ion transport number, and specifically, is measured by the method described in the examples.

[0062] <Composite Solid Electrolyte for Lithium-Ion Secondary Battery> The composite solid electrolyte for lithium-ion secondary batteries of the present invention (sometimes simply referred to as the composite solid electrolyte) includes an inorganic solid electrolyte and a polyether electrolyte for lithium-ion secondary batteries of the present invention (the polyether polymer of the present invention). Since the composite solid electrolyte of the present invention contains the polyether electrolyte for lithium-ion secondary batteries of the present invention (the polyether polymer of the present invention) in addition to the inorganic solid electrolyte, it is believed that the contact area at the interface between the electrode material layer and the solid electrolyte layer is larger than when the solid electrolyte is formed solely from an inorganic solid electrolyte. As a result, it is believed that the interfacial resistance between the electrode and the electrolyte is reduced, and excellent charge / discharge characteristics are exhibited. Furthermore, within the composite solid electrolyte, the polyether electrolyte for lithium-ion secondary batteries of the present invention (the polyether polymer of the present invention) is believed to reduce the internal resistance of the composite solid electrolyte by forming adhesion between particles of the inorganic solid electrolyte. Here, the polyether electrolyte for lithium-ion secondary batteries of the present invention (the polyether polymer of the present invention) may be used alone or in combination of two or more types.

[0063] Examples of inorganic solid electrolytes include oxide-based solid electrolytes and sulfide-based solid electrolytes. These may be used alone or in combination of two or more. In the composite solid electrolyte of the present invention, the inorganic solid electrolyte is contained, for example, in the form of particles, and has a structure in which the particles of the inorganic solid electrolyte are tightly adhered to each other by the polyether electrolyte for lithium ion secondary batteries of the present invention (the polyether polymer of the present invention).

[0064] The oxide-based solid electrolyte is not particularly limited as long as it contains oxygen, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties.

[0065] Specific compounds constituting the oxide-based solid electrolyte include Li ｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍ O ｎ (M is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, x satisfies 5≦x≦10, y satisfies 1≦y≦4, z satisfies 1≦z≦4, m satisfies 0≦m≦2, and n satisfies 5≦n≦20.) Li ｘ B ｙ M ｚ O ｎ (wherein M is at least one element selected from C, S, Al, Si, Ga, Ge, In, and Sn, x satisfies 0≦x≦5, y satisfies 0≦y≦1, z satisfies 0≦z≦1, and n satisfies 0≦n≦6), Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (wherein 1≦x≦3, 0≦y≦1, 0≦z≦2, 0≦a≦1, 1≦m≦7, 3≦n≦13), Li （３－２ｘ） M ｘ DO (x represents a number of 0 or more and 0.1 or less, M represents a divalent metal atom, and D represents a halogen atom or a combination of two or more halogen atoms), Liｘ Si ｙ O ｚ (1≦x≦5, 0<y≦3, 1≦z≦10), Li ｘ S ｙ O ｚ (1≦x≦3, 0<y≦2, 1≦z≦10), Li ３ BO ３ -Li ２ SO ４ , Li ２ Alumni ２ O ３ -P ２ O ５ , Li ２ O—SiO ２ , Li ６ BaLa ２ Ta ２ O １２ , Li ３ P.O. （４－３／２ｗ） N ｗ (w is w<1), Li having a LISICON (Lithium super ionic conductor) type crystal structure ３．５ Zn ０．２５ GeO ４ , La having a perovskite crystal structure ０．５５ Li ０．３５ TiO ３ , LiTi having a NASICON (sodium super ionic conductor) type crystal structure ２ P ３ O １２ , Li （１＋ｘ＋ｙ） (Al, Ga) ｘ (Ti, Ge) （２－ｘ） Si ｙ P （３－ｙ） O １２ (where 0≦x≦1, 0≦y≦1), Li having a garnet-type crystal structure ７ La ３ Zr ２ O1 ２ Also preferred are phosphorus compounds containing Li, P, and O. For example, lithium phosphate (Li ３ P.O. ４and LiPON and LiPOD (where D is at least one selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Ag, Ta, W, Pt, Au, etc.), in which part of the oxygen in lithium phosphate has been substituted with nitrogen. Also preferably used are LiAON (where A is at least one selected from Si, B, Ge, Al, C, Ga, etc.).

[0066] Among them, Li ｘ La ｙ TiO ３ [x=0.3~0.7, y=0.3~0.7] (LLT), Li ｘ La ｙ Zr ｚ M ｍ O ｎ (M is at least one element selected from Al, Mg, Ca, Sr, V, Nb, Ta, Ti, Ge, In, and Sn, x satisfies 5≦x≦10, y satisfies 1≦y≦4, z satisfies 1≦z≦4, m satisfies 0≦m≦2, and n satisfies 5≦n≦20.), Li ７ La ３ Zr ２ O １２ (LLZ), Li ３ BO ３ , Li ３ BO ３ -Li ２ SO ４ , Li ３ BO ３ -Li ２ CO ３ , Li ｘ (Al, Ga) ｙ (Ti, Ge) ｚ Si ａ P ｍ O ｎ (wherein 1≦x≦3, 0≦y≦1, 0≦z≦2, 0≦a≦1, 1≦m≦7, 3≦n≦13) is preferred.

[0067] The sulfide-based solid electrolyte is not particularly limited as long as it contains sulfur, has the ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and has electronic insulation properties.

[0068] The sulfide-based solid electrolyte may be a glass-based sulfide solid electrolyte or a glass-ceramic-based sulfide solid electrolyte. These may be used alone or in combination of two or more. The glass-based sulfide solid electrolyte can be obtained by vitrifying raw materials. The glass-ceramic-based sulfide solid electrolyte can be obtained, for example, by heat-treating a glass-based sulfide solid electrolyte. Furthermore, the sulfide-based solid electrolyte preferably has a crystalline structure. Examples of the crystalline structure include a Thio-LISICON-type crystalline structure, a LGPS-type crystalline structure, and an Argyrodite-type crystalline structure.

[0069] Examples of glass-based sulfide solid electrolytes include Li ２ S-P ２ S ５ , Li ２ S-LiI-P ２ S ５ , Li ２ S-LiI-Li ２ O-P ２ S ５ , Li ２ S-LiBr-P ２ S ５ , Li ２ S-Li ２ O-P ２ S ５ , Li ２ S-Li ３ P.O. ４ -P ２ S ５ , Li ２ S-P ２ S ５ -P ２ O ５ , Li ２ S-P ２ S ５ -SiS ２ , Li ２ S-P ２ S ５ - SnS, Li ２ S-P ２ S ５ -Al ２ S ３ , Li ２ S-GeS ２ , Li ２ S-GeS２ These may be used alone or in combination of two or more.

[0070] Examples of sulfide-based solid electrolytes having a crystalline structure include Li １０ GeP ２ S １２ , Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ , Li ９．４２ Si １．０２ P ２．１ S ９．９６ O ２．２４ LGPS-type sulfide solid electrolytes such as Li ６ P.S. ５ Cl, Li ６．６ Ge ０．６ P ０．４ S ５ I, Li ７ Ge ３ P.S. １２ Argyrodite-type sulfide solid electrolytes such as Li ４．２７５ Ge ０．６１ Ga ０．２５ S ４ , Li ４ SnS ４ , β-Li ３ P.S. ４ Thio-LISICON type sulfide solid electrolytes such as these can be used. Among these, argyrodite type sulfide solid electrolytes and thio-LISICON type sulfide solid electrolytes are preferred, and argyrodite type sulfide solid electrolytes are more preferred. These can be used alone or in combination of two or more.

[0071] The sulfide-based solid electrolyte is preferably a sulfide-based solid electrolyte having high ionic conductivity from the viewpoint of improving the electrical characteristics of the all-solid-state lithium ion secondary battery. Specific examples of the ionic conductivity include sulfide-based solid electrolytes having a conductivity of 1×10 －４ S / cm or more, and preferably 1×10 －３ It is more preferable that the viscosity is 200 S / cm or more.

[0072] The inorganic solid electrolyte is preferably a sulfide-based solid electrolyte. The polyether polymer of the present invention can suppress side reactions with the sulfide-based solid electrolyte and has high lithium ion conductivity, so that the effects of the present invention can be more suitably exhibited.

[0073] When the inorganic solid electrolyte is in the form of particles, the particle size is, for example, 0.01 to 100 μm, preferably 0.1 to 20 μm.

[0074] In the composite solid electrolyte for a lithium ion secondary battery of the present invention, the mass ratio of the inorganic solid electrolyte to the polyether electrolyte for a lithium ion secondary battery of the present invention (preferably the polyether polymer of the present invention) is not particularly limited, but from the viewpoint of more suitably exhibiting excellent charge / discharge characteristics in the secondary battery, the content of the polyether electrolyte for a lithium ion secondary battery of the present invention (preferably the polyether polymer of the present invention) per 100 parts by mass of the inorganic solid electrolyte is preferably 0.1 to 1000 parts by mass, more preferably 0.5 to 800 parts by mass, even more preferably 5 to 600 parts by mass, and particularly preferably 10 to 400 parts by mass.

[0075] In the composite solid electrolyte for a lithium ion secondary battery of the present invention, the total content of the inorganic solid electrolyte and the polyether electrolyte for a lithium ion secondary battery of the present invention is preferably 60% by mass or more, more preferably 80% by mass or more, still more preferably 90% by mass or more, particularly preferably 95% by mass or more, and may even be 100% by mass, based on 100% by mass of the composite solid electrolyte for a lithium ion secondary battery of the present invention. This tends to more suitably achieve the effects of the present invention.

[0076] The composite solid electrolyte for a lithium ion secondary battery of the present invention contains the polyether electrolyte for a lithium ion secondary battery of the present invention in addition to an inorganic solid electrolyte, and therefore, unlike a case in which only an inorganic solid electrolyte is used, it can be suitably formed into a sheet. When the composite solid electrolyte of the present invention is used in a secondary battery, the thickness is not particularly limited, but may be, for example, about 0.01 to 1 mm, preferably about 0.05 to 0.3 mm.

[0077] The composite solid electrolyte for a lithium ion secondary battery of the present invention may contain, in addition to the polyether electrolyte for a lithium ion secondary battery of the present invention, for example, a reaction initiator, a crosslinking aid, a binder, etc. These may be used alone or in combination of two or more kinds.

[0078] The composite solid electrolyte for a lithium ion secondary battery of the present invention can be prepared by using a conventionally known method, for example, by mixing an inorganic solid electrolyte with the polyether electrolyte for a lithium ion secondary battery of the present invention (the polyether polymer of the present invention). Specifically, the composite solid electrolyte can be produced by a method in which the inorganic solid electrolyte is dispersed in a solvent containing the polyether electrolyte for a lithium ion secondary battery of the present invention (the polyether polymer of the present invention) to prepare a composite solid electrolyte slurry, and the slurry is then sprayed into hot air and dried to obtain a composite solid electrolyte; a method in which the solvent of the dispersed slurry is evaporated by heating under atmospheric pressure or reduced pressure to dryness; or a method in which the dispersed slurry is applied to a current collecting sheet or the like and then dried.

[0079] The dispersion solvent can be water, an organic solvent, or a mixture of these in any ratio. Whether the resulting dispersion slurry is a homogeneous solution or the solute that is insoluble in the dispersion solvent is an inorganic solid electrolyte and / or the polyether electrolyte for lithium-ion secondary batteries of the present invention, it can be prepared by the general preparation method described above. It is desirable to remove as much remaining solvent and water as possible from the composite solid electrolyte obtained by removing the dispersion solvent. For example, this can be achieved by heating at 30°C to 200°C and evacuating the mixture for 1 hour to 48 hours. The dried composite solid electrolyte of the present invention has high lithium ion conductivity and binding properties, so the electrolyte powder itself can be pressure-molded and used as a solid electrolyte material. Furthermore, pressure heat treatment can reduce the porosity and increase the particle interface adhesion. Polar solvents are preferred as the organic solvent. Specifically, acetonitrile, ethyl alcohol, methyl alcohol, tetrahydrofuran, dimethylformamide, dimethyl sulfoxide, dioxane, methyl ethyl ketone, methyl isobutyl ketone, etc. can be used alone or in combination. When an inorganic solid electrolyte is molded alone under pressure, it has almost no binding property, resulting in a thick electrolyte film. However, in the case of a composite solid electrolyte, the binding property of the polyether electrolyte for a lithium ion secondary battery of the present invention (the polyether polymer of the present invention) makes it possible to produce a thinner solid electrolyte.

[0080] The composite solid electrolyte of the present invention may be crosslinked or uncrosslinked, but is preferably crosslinked. By crosslinking the composite solid electrolyte of the present invention, the bonding strength between the inorganic solid electrolyte in the composite solid electrolyte and the polyether electrolyte for lithium ion secondary batteries of the present invention (the polyether polymer of the present invention) can be further improved, and short-circuiting of the battery due to confining pressure or dendrite precipitation can be more effectively prevented. As a crosslinking method, crosslinking can be achieved by applying heat or by irradiating with active energy rays such as ultraviolet rays.

[0081] In the case of thermal crosslinking, a radical initiator selected from organic peroxides, azo compounds, etc. is used. These may be used alone or in combination of two or more. As organic peroxides, those typically used for crosslinking applications, such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters, are used. As azo compounds, those typically used for crosslinking applications, such as azonitrile compounds, azoamide compounds, and azoamidine compounds, are used. The amount of radical initiator added varies depending on the type, but is typically within the range of 0.1 to 10 parts by mass per 100 parts by mass of polyether polymer (ion-conductive polymer).

[0082] In the case of crosslinking by irradiation with active energy rays, alkylphenones, benzophenones, acylphosphine oxides, titanocenes, triazines, bisimidazoles, oxime esters, and the like are used as radical initiators. These may be used alone or in combination of two or more. The amount of these radical polymerization initiators added varies depending on the type, but is typically within the range of 0.01 to 5.0 parts by mass per 100 parts by mass of the polyether polymer (ion-conductive polymer).

[0083] When crosslinking the composite solid electrolyte, a crosslinking aid may be used as needed. Examples of crosslinking aids that can be used include ethylene glycol diacrylate, ethylene glycol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane triacrylate, allyl methacrylate, allyl acrylate, diallyl maleate, triallyl isocyanurate, maleimide, phenylmaleimide, maleic anhydride, pentaerythritol tetrakis(3-mercaptobutyrate), and 1,4-bis(3-mercaptobutyryloxy)butane. These may be used alone or in combination of two or more.

[0084] <Lithium-ion secondary battery> The lithium-ion secondary battery of the present invention is a lithium-ion secondary battery that uses the polyether electrolyte for lithium-ion secondary batteries of the present invention. The lithium-ion secondary battery of the present invention is not particularly limited as long as it uses the polyether electrolyte for lithium-ion secondary batteries of the present invention. A preferred embodiment is a lithium-ion secondary battery that uses the composite solid electrolyte for lithium-ion secondary batteries of the present invention. The laminate structure of the secondary battery may be, for example, a laminate structure in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order, but it is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention as one of the layers, and it is preferable to use the composite solid electrolyte for lithium-ion secondary batteries of the present invention as the solid electrolyte layer.

[0085] <<Crosslinked Film>> In the secondary battery of the present invention, a crosslinked film of the polyether electrolyte for a lithium ion secondary battery of the present invention may be disposed between at least one of the positive electrode and the solid electrolyte layer and the negative electrode and the solid electrolyte layer. By disposing the crosslinked film, the interfacial resistance of the electrode and the solid electrolyte layer can be further reduced.

[0086] The crosslinked film is preferably formed by crosslinking the polyether electrolyte for lithium ion secondary batteries of the present invention, which is a composition containing at least a lithium salt compound and the polyether polymer of the present invention. That is, the crosslinked film is a crosslinked film of a composition containing a lithium salt compound and the polyether polymer of the present invention. The polyether polymer of the present invention and the polyether electrolyte for lithium ion secondary batteries of the present invention are as described above.

[0087] A crosslinked film may be formed by blending a reaction initiator or a crosslinking aid with the polyether electrolyte for a lithium ion secondary battery of the present invention. Examples of the reaction initiator include a thermal reaction initiator and a photoreaction initiator. These may be used alone or in combination of two or more.

[0088] The thermal reaction initiator is a radical initiator selected from organic peroxides, azo compounds, etc. As the organic peroxides, those typically used for crosslinking purposes, such as ketone peroxides, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, and peroxyesters, are used, while as the azo compounds, those typically used for crosslinking purposes, such as azonitrile compounds, azoamide compounds, and azoamidine compounds, are used. The amount of radical initiator added varies depending on the type, but is typically within the range of 0.1 to 10 parts by mass, based on 100 parts by mass of the ion-conductive polymer.

[0089] As the photoreaction initiator, radical initiators such as alkylphenones, benzophenones, acylphosphine oxides, titanocenes, triazines, bisimidazoles, oxime esters, etc. The amount of these radical polymerization initiators added varies depending on the type, but is usually within the range of 0.01 to 5.0 parts by mass per 100 parts by mass of the ion conductive polymer.

[0090] Examples of crosslinking aids that can be used include ethylene glycol diacrylate, ethylene glycol dimethacrylate, oligoethylene glycol diacrylate, oligoethylene glycol dimethacrylate, trimethylolpropane triacrylate, allyl methacrylate, allyl acrylate, diallyl maleate, triallyl isocyanurate, maleimide, phenylmaleimide, maleic anhydride, pentaerythritol tetrakis(3-mercaptobutyrate), 1,4-bis(3-mercaptobutyryloxy)butane, etc. These may be used alone or in combination of two or more.

[0091] The polyether electrolyte for a lithium ion secondary battery of the present invention may contain an organic solvent, and examples of the organic solvent include toluene, xylene, benzene, acetonitrile, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, THF (tetrahydrofuran), etc. These may be used alone or in combination of two or more.

[0092] The crosslinked film can be produced, for example, by mixing and dissolving the polyether electrolyte for a lithium ion secondary battery of the present invention in an organic solvent to form a composition, casting the composition on a substrate (e.g., a PET film or a Teflon (registered trademark) plate), removing the solvent, and then heating or irradiating with active energy rays such as ultraviolet rays to produce a crosslinked film. Alternatively, the composition can be directly cast on the surface of a solid electrolyte layer to produce a crosslinked film.

[0093] The thickness of the crosslinked film is preferably in the range of 0.1 μm to 200 μm, more preferably 0.5 μm to 100 μm.

[0094] In the secondary battery of the present invention, the crosslinked film is preferably a crosslinked film using the polyether electrolyte for lithium ion secondary batteries of the present invention, but the crosslinked film may also be a crosslinked film using a "composition containing an ion-conductive polymer that contains a lithium salt compound" other than the polyether electrolyte for lithium ion secondary batteries of the present invention.

[0095] <<Specific Structures of Lithium-Ion Secondary Battery>> Examples of the laminate structure of the secondary battery of the present invention include the following structures. The composite solid electrolyte for lithium-ion secondary batteries of the present invention is preferably used as the solid electrolyte layer. The crosslinked film is also preferably a crosslinked film using the polyether electrolyte for lithium-ion secondary batteries of the present invention. A laminate structure in which a positive electrode, a solid electrolyte layer, and a negative electrode are laminated in this order; A laminate structure in which a positive electrode, a crosslinked film, a solid electrolyte layer, a crosslinked film, and a negative electrode are laminated in this order; A laminate structure in which a positive electrode, a solid electrolyte layer, a crosslinked film, a solid electrolyte layer, and a negative electrode are laminated in this order; A laminate structure in which a positive electrode ....

[0096] In the secondary battery of the present invention, it is preferable that the solid electrolyte layer is in contact with a crosslinked film using the polyether electrolyte for lithium ion secondary batteries of the present invention. Since the crosslinked film is a crosslinked product of the polyether electrolyte for lithium ion secondary batteries of the present invention, it has high lithium ion conductivity and is more flexible than inorganic materials. Therefore, the crosslinked film has a large contact area with the solid electrolyte layer, which effectively reduces the interfacial resistance of the solid electrolyte layer, and it is believed that the secondary battery of the present invention exhibits excellent charge / discharge characteristics. It is also preferable that the crosslinked film be in contact with the electrode material layer of the electrode, or that the crosslinked film be in contact with both the electrode material layer and the solid electrolyte layer.

[0097] The secondary battery of the present invention includes at least a positive electrode, a negative electrode, and a solid electrolyte layer. As described above, the composite solid electrolyte for lithium ion secondary batteries of the present invention is preferably used as the solid electrolyte layer. Furthermore, as described above, when the secondary battery of the present invention includes a crosslinked film, the crosslinked film is preferably a crosslinked film using the polyether electrolyte for lithium ion secondary batteries of the present invention.

[0098] Known materials can be used for both the positive electrode and the negative electrode, and an example of the electrode is an electrode having an electrode material layer, that is, a positive electrode material layer or a negative electrode material layer, on a current collector.

[0099] Known current collectors can be used for the positive electrode and the negative electrode. Specifically, metals such as aluminum, nickel, stainless steel, gold, platinum, and titanium are used as the current collector for the positive electrode. Metals such as copper, nickel, stainless steel, gold, platinum, and titanium are used as the current collector for the negative electrode.

[0100] The positive electrode material layer and the negative electrode material layer contain at least a positive electrode active material and a negative electrode active material, respectively, and may further contain a conductive additive, a binder, and a thickener, and may also contain the inorganic solid electrolyte or the composite solid electrolyte for a lithium ion secondary battery of the present invention, as necessary.

[0101] The positive electrode active material used in the present invention is a lithium metal-containing composite oxide powder having any one of the following compositions: LiMO2, LiMO4, LiMO3, and LiMEO4. In this formula, M is primarily composed of a transition metal and contains at least one of Co, Mn, Ni, Cr, Fe, and Ti. While M is composed of a transition metal, other elements such as Al, Ga, Ge, Sn, Pb, Sb, Bi, Si, P, and B may also be added. E contains at least one of P and Si. The particle diameter of the positive electrode active material is preferably 50 μm or less, and more preferably 20 μm or less. These active materials have an electromotive force of 3 V (vs. Li / Li+) or more.

[0102] Specific examples of the positive electrode active material include lithium cobalt oxide, lithium nickel oxide, nickel / cobalt / lithium manganese oxide (ternary system), spinel-type lithium manganese oxide, and lithium iron phosphate.

[0103] The negative electrode active material used in the present invention is a carbon material (natural graphite, artificial graphite, amorphous carbon, etc.) having a structure (intercalation compound) capable of absorbing and releasing alkali metal ions such as lithium ions, or a metal such as lithium, an aluminum-based compound, a tin-based compound, a silicon-based compound, or a titanium-based compound capable of absorbing and releasing alkali metal ions such as lithium ions. In the case of a powder, the particle size is preferably 10 nm or more and 100 μm or less, more preferably 20 nm or more and 20 μm or less. A mixed active material of a metal and a carbon material may also be used.

[0104] When a conductive aid is used, a known conductive aid can be used, and examples thereof include conductive carbon black such as graphite, furnace black, acetylene black, and ketjen black, carbon fibers such as carbon nanotubes, and metal powders. These conductive aids may be used alone or in combination of two or more.

[0105] The binder may be one or more compounds selected from fluororesins such as PVdF, fluororubbers, acrylic rubbers, modified acrylic rubbers, styrene-butadiene rubbers, acrylic polymers, and vinyl polymers. These binders are added in an amount of preferably 5 parts by mass or less, more preferably 3 parts by mass or less, for example, 0.01 to 2 parts by mass, per 100 parts by mass of the active material.

[0106] Specific examples of thickeners include carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose, ethyl cellulose, and salts thereof (alkali metal salts such as sodium salts, and ammonium salts), polyvinyl alcohol, polyacrylates, polyethylene oxide, etc. These thickeners may be used alone or in combination. These thickeners are added in an amount of preferably 5 parts by mass or less, more preferably 3 parts by mass or less, for example, 0.01 to 2 parts by mass, per 100 parts by mass of the active material. Furthermore, when the viscosity of the coating liquid is low, a thickener can be used in combination.

[0107] The method for producing the positive electrode and negative electrode comprising the current collector and the positive electrode material layer and the negative electrode material layer is not particularly limited, and a common method can be used, for example, by uniformly applying a paste (coating liquid) of the positive electrode material or negative electrode material comprising the positive electrode active material or negative electrode active material, a conductive additive, a binder, a solvent such as water or N-methyl-2-pyrrolidone (NMP), and optionally a thickener, onto the surface of the current collector to an appropriate thickness by a doctor blade method, silk screen method, or the like.

[0108] For example, in the doctor blade method, negative electrode active material powder, positive electrode active material powder, conductive additive, binder, etc. are dispersed in water to form a slurry, which is then applied to a metal electrode substrate and uniformly spread to an appropriate thickness using a blade with a specified slit width. After applying the active material, the electrode is dried, for example, with hot air at 100°C or under reduced pressure at 80°C to remove excess organic solvent. After drying, the electrode is press-molded using a press device to produce an electrode.

[0109] The method for manufacturing the secondary battery of the present invention is not particularly limited, and the battery is manufactured by a known method, comprising at least a positive electrode, a negative electrode, and a solid electrolyte. For example, in the case of a coin-type lithium-ion battery, the positive electrode, the solid electrolyte, and the negative electrode are inserted into an outer can. Then, the battery is joined to a sealing body by tab welding or the like, and the sealing body is sealed and crimped to obtain a storage battery. The shape of the battery is not limited, and examples include coin type, cylindrical type, and sheet type, and a structure in which two or more batteries are stacked may also be used.

[0110] The secondary battery of the present invention is preferably an all-solid-state battery, which allows for a higher level of safety.

[0111] The polyether polymer of the present invention, the polyether electrolyte for lithium ion secondary batteries using the polyether polymer, the composite solid electrolyte for lithium ion secondary batteries, and the lithium ion secondary battery can suppress side reactions with sulfide-based solid electrolytes and have high lithium ion conductivity, and are therefore useful in automotive storage batteries for electric vehicles, hybrid vehicles, and the like, storage batteries for home power storage, and storage batteries for electronic devices such as mobile phones and personal computers.

[0112] The present invention will be specifically explained by way of examples and comparative examples, but the present invention is not limited to these.

[0113] [Production Example 1-1] (Synthesis of cyclic ether compound 1 (2-((3-methoxybutoxy)methyl)oxirane)) 533 parts by mass (5.76 mol) of epichlorohydrin and 93 parts by mass (2.33 mol) of sodium hydroxide were added, and the reaction liquid was heated to 40°C. Thereafter, while maintaining the temperature, 201 parts by mass (1.93 mol) of 1,4-butanediol monomethyl ether was added dropwise. After completion of the dropwise addition, the reaction was carried out for 46 hours. Thereafter, an oil-water separation operation was performed, and the obtained organic layer was concentrated to obtain 144 parts by mass of 2-((3-methoxybutoxy)methyl)oxirane.

[0114] [Production Example 1-2] (Synthesis of cyclic ether compound 2 (2-((3-methoxypropoxy)methyl)oxirane)) 2-((3-methoxypropoxy)methyl)oxirane was obtained in the same manner as in Production Example 1-1, except that 1,4-butanediol monomethyl ether was changed to 1,3-propanediol monomethyl ether.

[0115] [Production Example 1-3] (Synthesis of cyclic ether compound 3 (2-((2-methoxyethoxy)methyl)oxirane)) 2-((2-methoxyethoxy)methyl)oxirane was obtained in the same manner as in Production Example 1-1, except that 1,4-butanediol monomethyl ether was changed to ethylene glycol monomethyl ether.

[0116] The structures of the resulting cyclic ether compounds are shown below.

[0117] In the following experiments, 1,2-butylene oxide, 1,2-hexylene oxide, allyl glycidyl ether, 1,2-epoxy-3-isopropoxypropane, and propylene oxide manufactured by Tokyo Chemical Industry Co., Ltd. were used.

[0118] [Example 1] (Polyether Polymer 1) Using toluene as a solvent, 100 parts by mass of 1,2-butylene oxide, 1% by mass (1 part by mass) of the polymerization catalyst used in the Examples section of JP 2019-70087 A relative to the charged monomers, and 0.3% by mass (0.3 parts by mass) of triethylaluminum diluted with hexane to 1 mol / L relative to the charged monomers were added, and the polymerization reaction was carried out for 24 hours while maintaining the reaction solution at 50°C. Thereafter, the reaction solution was vacuum dried at 50°C to obtain Polyether Polymer 1. The obtained Polyether Polymer 1 was tested and evaluated as follows, and the results are shown in Table 1. The content of each unit shown in Table 1 was calculated from the NMR spectrum.

[0119] <Weight-average molecular weight (Mw) and number-average molecular weight (Mn)> The polymer was dissolved in tetrahydrofuran (THF) as a solvent, and the molecular weight was measured in terms of polystyrene using gel permeation chromatography (GPC). The weight-average molecular weight (Mw) and number-average molecular weight (Mn) were calculated based on the measurement results. The measurement was performed using an LC-2030 (RID-20A) manufactured by Shimadzu Corporation and three connected GPC columns, KF-801, KF-803L, and KF-806L manufactured by Resonac Inc., at a flow rate of 1.0 mL / min, a concentration of 10 mg polymer / 8 mL THF, an injection volume of 100 μL, and a column temperature of 40°C.

[0120] <Evaluation of Deterioration of Sulfide Solid Electrolyte> The above-mentioned polyether polymer 1 was dissolved in toluene to a solid content concentration of 10 mass % to prepare polyether solution 1. An argyrodite-type sulfide solid electrolyte (manufactured by NEI, Li ６ P.S. ５ 0.4 parts by mass of sulfide solid electrolyte (Cl) and 1.0 part by mass of polyether solution 1 (polyether: 0.1 part by mass) were added and mixed. The solvent was removed by vacuum heating and drying to prepare composite 1 of sulfide solid electrolyte and polymer. Composite 1 was filled into a solid NMR sample tube and subjected to heat treatment at 60°C for one week. ３１ P-NMR test was carried out. ３１ P-NMR test) Measurement was carried out using an NMR device (device name: ECA400WB, manufactured by JEOL Ltd.). ４ ３－ The spectrum of the unit and the P generated by the decomposition reaction of the sulfide solid electrolyte ２ S ７ ４－Resistance was evaluated based on the presence or absence of a spectrum derived from the unit. A score of ◯ was given when no spectrum generated by the decomposition reaction of the sulfide solid electrolyte was detected, and a score of × was given when a spectrum generated by the decomposition reaction of the sulfide solid electrolyte was detected. A score of ◯ indicates that side reactions with the sulfide-based solid electrolyte can be suppressed. Measurement temperature: room temperature Rotation speed: 10 kHz Number of integrations: 8 Waiting time for repetition: 2,000 seconds Chemical shift standard: ammonium dihydrogen phosphate (1 ppm)

[0121] [Evaluation of ionic conductivity of polyether electrolyte] 100 parts by mass of polyether polymer 1 obtained in Example 1 and Li(CF) as a lithium salt compound were used so that the ratio of oxygen to lithium ([Li] / [O]) contained in polyether polymer 1 was 0.06. ３ SO ２ ) ２ Polyether electrolyte 1, which was a mixture of 23.9 parts by mass of N, was dissolved in tetrahydrofuran to a solids concentration of 10% by mass to prepare polyether electrolyte solution 1. Polyether electrolyte solution 1 was applied to a SUS spacer to a predetermined thickness and dried to prepare a polyether electrolyte membrane (electrolyte membrane thickness: 100 μm). Subsequently, a SUS spacer was attached to the counter electrode to prepare a SUS blocking cell, and an AC impedance test was performed using a potentio / galvanostat device.

[0122] [AC Impedance Test] An SUS blocking cell of polyether electrolyte 1 was prepared, and an AC impedance test was performed using a potentio / galvanostat device (device name: SP-300 manufactured by BioLogic). The resistance (Ω) of the composite material was calculated from the diameter of the semicircular arc in the real axis direction obtained from the Cole-Cole plot. The ionic conductivity of the cell was calculated using the following formula from the thickness and surface area of ​​the cell. The test temperature was set to 25°C. Measurements were performed at a voltage amplitude of 20 mV and a measurement frequency range of 7 MHz to 1 Hz. σ = 1 / R × (d / A), where σ is the ionic conductivity of the composite material (S / cm), R is the resistance of the composite material (Ω), d is the thickness of the composite material (cm), and A is the surface area of ​​the composite material (cm2).

[0123] [Evaluation of Li-ion transport number of polyether electrolyte] (Preparation of evaluation cell) 100 parts by mass of the polyether polymer 1 obtained above and Li(CF) as a lithium salt compound were added so that the ratio of oxygen to lithium contained in the polyether polymer ([Li] / [O]) was 0.06. ３ SO ２ ) ２ Polyether electrolyte 1, which was a mixture of 23.9 parts by mass of N, was dissolved in tetrahydrofuran to a solids concentration of 10% by mass to prepare polyether electrolyte solution 1. This polyether electrolyte solution 1 was applied to a nonwoven fabric separator and dried to prepare separator-containing polyether electrolyte membrane 1 (electrolyte membrane thickness: 100 μm). Subsequently, separator-containing polyether electrolyte membrane 1 was sandwiched between Li foils to prepare a Li symmetric cell. (Calculation of Li ion transport number) The Li ion transport number can be calculated using the interfacial resistance values ​​before and after polarization, the initial current value obtained in the chronoamperometry test, and the steady-state current value according to the following formula: t Ｌｉ＋ = (I ｓ × (VI ０ ×R ０ )) / ((I ０ × (VI ｓ ×R ｓ ))) t Ｌｉ＋ : Li ion transport number of polyether electrolyte I ０ : Initial current value (A) of chronoamperometry test ｓ R: Steady-state current value (A) in chronoamperometry test ０ R: Interface resistance before polarization (Ω) ｓ: Interfacial resistance value after polarization (Ω) V: DC voltage (V) (Measurement of interfacial resistance value before and after polarization (AC impedance test)) A Li symmetric cell of polyether electrolyte was prepared, and an AC impedance test was performed using a potentio / galvanostat device. The interfacial resistance value was calculated from the size of the semicircular arc derived from the interfacial resistance obtained from the Cole-Cole plot. The test temperature was set to 25°C, and the measurement was performed at a voltage amplitude of 20 mV and a measurement frequency range of 7 MHz to 100 mHz. (Chronoamperometry test) After performing the AC impedance test, the open circuit voltage (OCV) was measured for 1 minute, and then chronoamperometry measurement was performed. The test temperature was set to 25°C. The measurement was performed at a DC voltage of 20 mV for a measurement time of 3 hours, and the initial current value and the steady-state current value after 3 hours were measured.

[0124] [Evaluation of Lithium Ion Conductivity] The lithium ion conductivity can be calculated by the product of the ionic conductivity and the lithium ion transport number. －７ (S / cm) or more was judged to be good. Lithium ion conductivity = ionic conductivity × lithium ion transport number

[0125] [Example 2] (Polyether Polymer 2) Using hexane as a solvent, 96 parts by mass of 1,2-butylene oxide, 4 parts by mass of allyl glycidyl ether, and 1% by mass (1 part by mass) of the polymerization catalyst used in the Examples section of JP 2008-106104 A were added relative to the charged monomers, and a polymerization reaction was carried out for 24 hours while the reaction solution was maintained at 30°C. Thereafter, the solution was vacuum dried at 50°C to obtain Polyether Polymer 2. Polyether Polymer 2 and Polyether Electrolyte 2 were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[0126] Example 3 (Polyether Polymer 3) Using toluene as a solvent, 31.1 parts by mass of 1,2-butylene oxide, 68.9 parts by mass of 2-((3-methoxybutoxy)methyl)oxirane, ultrapure water (5 mol % (0.08 parts by mass) based on the charged monomers), and diethyl zinc (hexane solution, approximately 1.0 mol / L) (5 mol % (3.2 parts by mass) based on the charged monomers) were added, and the reaction solution was maintained at 50°C to carry out a polymerization reaction for 2 hours. Thereafter, the reaction solution was vacuum dried at 50°C to obtain Polyether Polymer 3. Polyether Polymer 3 and Polyether Electrolyte 3 were evaluated as described above, and the results are shown in Table 1.

[0127] [Example 4] (Polyether polymer 4) The same procedure as in Example 3 was carried out, except that the composition was changed to that shown in Table 1, to obtain polyether polymer 4, which was then subjected to the same tests as above. The results are shown in Table 1.

[0128] [Example 5] (Polyether polymer 5) Polyether polymer 5 was obtained in the same manner as in Example 3, except that the composition was changed to that shown in Table 1, and tested in the same manner as above. The results are shown in Table 1.

[0129] [Example 6] (Polyether polymer 6) The same procedure as in Example 3 was carried out, except that the composition was changed to that shown in Table 1, to obtain polyether polymer 6, which was then subjected to the same tests as above. The results are shown in Table 1.

[0130] [Example 7] (Polyether polymer 7) Polyether polymer 7 was obtained in the same manner as in Example 2, except that the composition was changed to that shown in Table 1, and tested in the same manner as above. The results are shown in Table 1.

[0131] Comparative Example 1 (Polyether Polymer 8) Using toluene as a solvent, 100.0 parts by mass of 2-((3-methoxypropoxy)methyl)oxirane, 1 mol % (0.02 parts by mass) of 1-butanol relative to the monomer, and a phosphazene base P4-t-Bu solution (0.8 mol / L hexane solution, manufactured by Sigma-Aldrich) were charged in an amount of 1 mol % (0.22 parts by mass) relative to the monomer, and a polymerization reaction was carried out at room temperature for 24 hours. Thereafter, benzoic acid was added to terminate the reaction, and the mixture was vacuum dried at 50°C to obtain Polyether Polymer 8. Polyether Polymer 8 and Polyether Electrolyte 8 were evaluated as described above, and the results are shown in Table 1.

[0132] Comparative Example 2 (Polyether Polymer 9) Polyether polymer 9 was obtained in the same manner as in Comparative Example 1, except that the composition was changed to that shown in Table 1. Tests were carried out in the same manner as above, and the results are shown in Table 1.

[0133] Comparative Example 3 (Polyether Polymer 10) Polyether polymer 10 was obtained in the same manner as in Example 2, except that the composition was changed to that shown in Table 1, and tested in the same manner as above. The results are shown in Table 1.

[0134] Comparative Example 4 The above test was carried out in the same manner as in Example 1, except that the polyether polymer 1 obtained in Example 1 was changed to polyethylene oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), and the evaluation results are shown in Table 1.

[0135]

[0136] From Table 1, it was found that the polyether polymers of the examples, which contain 20 mol % or more of X units, which are structural units derived from alkylene oxide represented by the general formula (1), can suppress side reactions with sulfide-based solid electrolytes and have high lithium ion conductivity.

[0137] The polyether polymer of the present invention, the polyether electrolyte for lithium ion secondary batteries using the polyether polymer, the composite solid electrolyte for lithium ion secondary batteries, and the lithium ion secondary battery can suppress side reactions with sulfide-based solid electrolytes and have high lithium ion conductivity, and are therefore useful in automotive storage batteries for electric vehicles, hybrid vehicles, and the like, storage batteries for home power storage, and storage batteries for electronic devices such as mobile phones and personal computers.

Claims

1. A polyether polymer containing, out of 100 mol % of structural units, 20 mol % or more of X units, which are structural units derived from alkylene oxide and are represented by the following general formula (1): [In the formula, R １ are the same or different and are alkyl groups having 2 to 6 carbon atoms.

2. A polyether electrolyte for a lithium ion secondary battery, comprising the polyether polymer of claim 1 and a lithium salt compound.

3. A composite solid electrolyte for a lithium ion secondary battery, comprising an inorganic solid electrolyte and the polyether electrolyte for a lithium ion secondary battery according to claim 2.

4. The composite solid electrolyte for a lithium ion secondary battery according to claim 3, wherein the inorganic solid electrolyte is a sulfide-based solid electrolyte.

5. A lithium ion secondary battery using the polyether electrolyte for lithium ion secondary batteries according to claim 2.

6. A lithium ion secondary battery using the composite solid electrolyte for lithium ion secondary batteries according to claim 3.

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