Secondary battery

Abstract

Disclosed is a novel technique for reducing the resistance of a secondary battery having a sulfide solid electrolyte. This secondary battery has a first electrode, an electrolyte layer, and a second electrode, at least one of the first electrode and the electrolyte layer contains a sulfide solid electrolyte, and the first electrode contains a perfluoropolyether represented by formula (1). E1-Rf1-RF-O-Rf2-E2 (1) [In formula (1), Rf1 and Rf2 each independently represent a C1-16 divalent alkylene group which may be substituted by one or more fluorine atoms; e1 and E2 are each independently a monovalent group selected from the group consisting of a fluorine group, a hydrogen group, a hydroxyl group, an aldehyde group, a carboxylic acid group, a C1-10 alkyl ester group, an amide group which may have one or more substituents, and an amino group which may have one or more substituents, and RF is a divalent fluoropolyether group].

Description

Technical Field

[0001] The present application relates to a secondary battery. Background Art

[0002] Patent document 1 discloses that when manufacturing a secondary battery, the electrode and the electrolyte layer are pressed at a pressure of 200 MPa or more and 1000 MPa or less. Patent document 2 discloses that in order to suppress the rupture of the electrolyte layer during high-pressure pressing, an insulating layer is arranged on the peripheral portion of the electrode. Patent document 3 discloses perfluoropolyether as an additive component of a non-aqueous electrolyte. Patent document 4 discloses that in order to improve the storage property of the electrode, a compound containing a perfluoropolyether group is present on the surface of the electrode.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2014 / 010042

[0006] Patent Document 2: International Publication No. 2019 / 103008

[0007] Patent Document 3: Japanese Patent Application Publication No. 2018-200866

[0008] Patent Document 4: Japanese Patent Application Publication No. 2018-147887 Summary of the invention

[0009] Problems to be solved by the invention

[0010] It is believed that when manufacturing a secondary battery, the resistance of the electrode or the like can be reduced by pressing the electrode or the like under high pressure. It is believed that the resistance reduction effect caused by high-pressure pressing becomes significant, especially in the case of manufacturing a secondary battery with a sulfide solid electrolyte. On the other hand, in order to simplify the manufacturing process of the secondary battery and reduce the manufacturing cost, it is required to press the electrode or the like under low pressure. However, when low-pressure pressing is used in the case of manufacturing a secondary battery with a sulfide solid electrolyte, it is difficult to obtain the above-mentioned resistance reduction effect. In this regard, a new technology for reducing the resistance of a secondary battery with a sulfide solid electrolyte is needed.

[0011] Methods used to solve problems

[0012] The present application discloses the following multiple aspects as means for solving the above-mentioned problems.

[0013] <Method 1>

[0014] A secondary battery comprising a first electrode, an electrolyte layer, and a second electrode,

[0015] At least one of the first electrode and the electrolyte layer includes a sulfide solid electrolyte,

[0016] The first electrode includes a perfluoropolyether represented by the following formula (1).

[0017] E1-Rf1-R F -O-Rf2-E2 (1)

[0018] [In formula (1), Rf1 and Rf2 are each independently a C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms,

[0019] E1 and E2 are each independently a monovalent group selected from the group consisting of a fluoro group, a hydrogen group, a hydroxyl group, an aldehyde group, a carboxylic acid group, a C1-10 alkyl ester group, an amide group which may have one or more substituents, and an amino group which may have one or more substituents,

[0020] R F is a divalent fluoropolyether group.]

[0021] <Method 2>

[0022] The secondary battery according to embodiment 1, wherein the R F It is a group represented by formula (2).

[0023] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3R Fa 6) d -(OC2F4) e -(OCF2) f - (2)

[0024] [In formula (2), each occurrence of R Fa are each independently a hydrogen atom, a fluorine atom or a chlorine atom,

[0025] a, b, c, d, e and f are each independently an integer of 0 to 200,

[0026] The sum of a, b, c, d, e and f is greater than 1,

[0027] The order of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.

[0028] Among them, in all R Fa When it is a hydrogen atom or a chlorine atom, at least one of a, b, c, e and f is 1 or more.]

[0029] <Method 3>

[0030] The secondary battery according to embodiment 2, wherein the R Fa A fluorine atom.

[0031] <Method 4>

[0032] The secondary battery according to Embodiment 3, wherein each of the above-mentioned R F Each independently represents a group represented by the following formula (2-1), (2-2), (2-3), (2-4) or (2-5).

[0033] -(OC3F6) d -(OC2F4) e - (2-1)

[0034] [In formula (2-1), d is an integer of 1 to 200, and e is 0 or 1.]

[0035] -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-2)

[0036] [In formula (2-2), c and d are each independently an integer of 0 to 30,

[0037] e and f are each independently an integer of 1 to 200,

[0038] The sum of c, d, e and f is an integer from 10 to 200,

[0039] The order of presence of the repeating units marked with the subscript c, d, e or f and enclosed in parentheses in the formula is arbitrary.]

[0040] -(R 6 -R 7 ) g - (2-3)

[0041] [In formula (2-3), R 6 For OCF2 or OC2F4,

[0042] R 7 is selected from OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 or a combination of two or three groups selected from these groups,

[0043] g is an integer from 2 to 100]

[0044] -(OC6F 12 )a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-4)

[0045] [In formula (2-4), e is an integer of 1 to 200,

[0046] a, b, c, d and f are each independently an integer of 0 to 200,

[0047] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0048] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-5)

[0049] [In formula (2-5), f is an integer of 1 to 200,

[0050] a, b, c, d and e are each independently an integer of 0 to 200,

[0051] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0052] <Method 5>

[0053] The secondary battery according to embodiment 4, wherein the R F It is a group represented by the following formula (2-6).

[0054] -(OCF2CF2CF2) a -(OCF(CF3)CF2) b -(OCF2CF(CF3)) c -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-6)

[0055] [In formula (2-6), a, b, c, d, e and f are each independently an integer of 0 to 200,

[0056] The sum of a, b, c, d, e and f is greater than 1,

[0057] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0058] <Method 6>

[0059] The secondary battery according to embodiment 4, wherein the R F It is a group represented by the following formula (2-7).

[0060] -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-7)

[0061] [In formula (2-7), d, e and f are each independently an integer of 0 to 200,

[0062] The sum of d, e and f is greater than 1,

[0063] The order of presence of the repeating units marked with d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0064] <Method 7>

[0065] The secondary battery according to any one of aspects 1 to 6, wherein the E1-Rf1 and the E2-Rf2 are each independently a group selected from the group consisting of -CF3, -CF2CF3, and -CF2CF2CF3.

[0066] <Method 8>

[0067] The secondary battery according to any one of aspects 1 to 7, wherein

[0068] The first electrode has a first active material layer.

[0069] The first active material layer contains 1 volume % or more and 25 volume % or less of the perfluoropolyether.

[0070] <Method 9>

[0071] The secondary battery according to any one of aspects 1 to 8, wherein the first electrode is a positive electrode.

[0072] <Method 10>

[0073] The secondary battery according to any one of aspects 1 to 9, wherein the first electrode includes the sulfide solid electrolyte and the perfluoropolyether.

[0074] Effects of the Invention

[0075] The secondary battery of the present invention can easily become a secondary battery having low resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] Figure 1 An example of the configuration of a secondary battery is schematically shown. DETAILED DESCRIPTION

[0077] 1. Secondary battery

[0078] Hereinafter, the embodiments of the technology of the present invention will be described, but the technology of the present invention is not limited to the following embodiments. Figure 1 As shown, a secondary battery 100 according to one embodiment includes a first electrode 10, an electrolyte layer 20, and a second electrode 30. Here, at least one of the first electrode 10 and the electrolyte layer 20 contains a sulfide solid electrolyte. In addition, the first electrode 10 contains a perfluoropolyether represented by the following formula (1).

[0079] 1.1 First Electrode

[0080] The first electrode 10 may be a positive electrode or a negative electrode. When the first electrode 10 is a positive electrode, the second electrode 30 is a negative electrode. As long as the first electrode 10 contains a specified perfluoropolyether and can function appropriately as a positive electrode or a negative electrode of a secondary battery, various structures may be used. For example, when the first electrode 10 contains a sulfide solid electrolyte and a specified perfluoropolyether (for example, when the first active material layer 11 contains a sulfide solid electrolyte and a specified perfluoropolyether), a higher effect is easily obtained.

[0081] 1.1.1 Perfluoropolyether (PFPE)

[0082] The first electrode 10 contains perfluoropolyether (PFPE) represented by the following formula (1).

[0083] According to the new findings of the present inventors, the sulfide solid electrolyte that can be included in the electrode and the electrolyte layer has high chemical reactivity, so there is a possibility that it reacts with other materials and deteriorates. In this case, the ion conductivity of the electrode and the electrolyte layer is easily reduced. In contrast, the specified PFPE contained in the first electrode 10 can impart lubricity to various battery materials and has low reactivity with the sulfide solid electrolyte. That is, when the specified PFPE is included in the first electrode 10, even when the first electrode 10 is pressed at a low pressure, the density of the material in the first electrode 10 can be increased by the lubrication effect generated by the PFPE. That is, the filling rate of the material in the first electrode 10 becomes high, and the resistance of the first electrode 10 is easily reduced.

[0084] In addition, according to the new findings of the present inventors, it is believed that PFPE has a high affinity for the surfaces of various battery materials due to its ether bond, and it is believed that, for example, it can be appropriately present in the gaps between active material materials and the gaps between sulfide solid electrolyte materials. As a result, the lubrication effect in the first electrode 10 is further improved, and even when the first electrode 10 is pressed at a low pressure, it is easy to further increase the density of the material in the first electrode 10, and the resistance of the first electrode 10 is also easy to further reduce.

[0085] The perfluoropolyether is represented by the following formula (1).

[0086] E1-Rf1-R F -O-Rf2-E2 (1)

[0087] [In formula (1), Rf1 and Rf2 are each independently a C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms,

[0088] E1 and E2 are each independently a monovalent group selected from the group consisting of a fluoro group, a hydrogen group, a hydroxyl group, an aldehyde group, a carboxylic acid group, a C1-10 alkyl ester group, an amide group which may have one or more substituents, and an amino group which may have one or more substituents,

[0089] R F is a divalent fluoropolyether group.]

[0090] In the above formula (1), Rf1 and Rf2 are each independently a C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms.

[0091] In one embodiment, the "C1-16 divalent alkylene" in the above-mentioned C1-16 divalent alkylene which may be substituted with one or more fluorine atoms may be a linear or branched chain, preferably a linear or branched C1-6 alkyl alkylene, particularly a C1-3 alkylene, more preferably a linear C1-6 alkylene, particularly a C1-3 alkylene.

[0092] In one embodiment, the "C1-16 divalent alkylene group" in the above-mentioned C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms may be a linear or branched group, and is preferably a linear or branched C1-6 fluoroalkylene group, in particular a C1-3 fluoroalkylene group, and specifically -CF2CH2- and -CF2CF2CH2-. In addition, a linear C1-6 perfluoroalkylene group, in particular a C1-3 perfluoroalkylene group, and specifically a group selected from the group consisting of -CF2-, -CF2CF2- and -CF2CF2CF2- is more preferred.

[0093] In the above formula (1), E1 and E2 are each independently a monovalent group selected from the group consisting of a fluoro group, a hydrogen group, a hydroxyl group, an aldehyde group, a carboxylic acid group, a C1-10 alkyl ester group, an amide group which may have one or more substituents, and an amino group which may have one or more substituents.

[0094] The above-mentioned PFPE has low reactivity to sulfide solid electrolytes. Therefore, even when PFPE is in contact with a sulfide solid electrolyte, it is not easy to cause a decrease in ionic conductivity caused by the deterioration and degradation of the sulfide solid electrolyte. In particular, when the first electrode contains a PFPE having a non-polar group as an end group, a higher effect can be expected. In this regard, the above-mentioned E1 and E2 are each independently preferably a fluorine group. In one embodiment, E1-Rf1 and E2-Rf2 can each independently be a group selected from the group consisting of -CF3, -CF2CF3 and -CF2CF2CF3.

[0095] In the above formula (1), each occurrence of R F Each is independently a divalent fluoropolyether group.

[0096] R F Preferred is a group represented by formula (2).

[0097] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3R Fa 6) d -(OC2F4) e-(OCF2) f - (2)

[0098] [In formula (2): Each occurrence of R Fa are each independently a hydrogen atom, a fluorine atom or a chlorine atom,

[0099] a, b, c, d, e and f are each independently an integer of 0 to 200,

[0100] The sum of a, b, c, d, e and f is greater than 1,

[0101] The order of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.

[0102] Among them, in all R Fa When it is a hydrogen atom or a chlorine atom, at least one of a, b, c, e and f is 1 or more.]

[0103] R Fa It is preferably a hydrogen atom or a fluorine atom, and more preferably a fluorine atom.

[0104] Preferably, a, b, c, d, e and f are each independently an integer of 0 to 100.

[0105] The sum of a, b, c, d, e and f is preferably 5 or more, more preferably 10 or more, for example, 15 or more or 20 or more. The sum of a, b, c, d, e and f is preferably 200 or less, more preferably 100 or less, further preferably 60 or less, for example, 50 or less or 30 or less.

[0106] These repeating units can be straight chain or branched chain. For example,

[0107] -(OC6F 12 )- can be any of -(OCF2CF2CF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2CF2CF2)-, -(OCF2CF(CF3)CF2CF2CF2)-, -(OCF2CF2CF(CF3)CF2CF2CF2)-, -(OCF2CF2CF(CF3)CF2CF2)-, -(OCF2CF2CF2CF(CF3)CF2)-, -(OCF2CF2CF2CF(CF3)CF2)- and -(OCF2CF2CF2CF2CF(CF3))-.

[0108] -(OC5F 10 )- can be any of -(OCF2CF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2CF2)-, -(OCF2CF(CF3)CF2CF2)-, -(OCF2CF2CF(CF3)CF2)-, -(OCF2CF2CF(CF3)CF2)- and -(OCF2CF2CF2CF(CF3))-.

[0109] -(OC4F8)- can be any one of -(OCF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2)-, -(OCF2CF(CF3)CF2)-, -(OCF2CF2CF(CF3))-, -(OC(CF3)2CF2)-, -(OCF2C(CF3)2)-, -(OCF(CF3)CF(CF3))-, -(OCF(C2F5)CF2)- and -(OCF2CF(C2F5))-.

[0110] -(OC3F6)- (i.e., R Fa In the case of a fluorine atom), it may be any of -(OCF2CF2CF2)-, -(OCF(CF3)CF2)- and -(OCF2CF(CF3))-.

[0111] -(OC2F4)- can be any of -(OCF2CF2)- and -(OCF(CF3))-.

[0112] In one approach, each occurrence of R F Each independently may be a group represented by any one of the following formulae (2-1) to (2-5).

[0113] -(OC3F6) d -(OC2F4) e - (2-1)

[0114] [In formula (2-1), d is an integer of 1 to 200, and e is 0 or 1.]

[0115] -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-2)

[0116] [In formula (2-2), c and d are each independently an integer of 0 to 30,

[0117] e and f are each independently an integer of 1 to 200,

[0118] The sum of c, d, e and f is greater than 2,

[0119] The order of presence of the repeating units marked with the subscript c, d, e or f and enclosed in parentheses in the formula is arbitrary.]

[0120] -(R 6 -R 7 ) g- (2-3)

[0121] [In formula (2-3), R 6 For OCF2 or OC2F4,

[0122] R 7 is selected from OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 or a combination of two or three groups selected from these groups,

[0123] g is an integer from 2 to 100.]

[0124] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-4)

[0125] [In formula (2-4), e is an integer of 1 to 200,

[0126] a, b, c, d and f are each independently an integer of 0 to 200,

[0127] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0128] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-5)

[0129] [In formula (2-5), f is an integer of 1 to 200,

[0130] a, b, c, d and e are each independently an integer of 0 to 200,

[0131] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0132] In the above formula (2-1), d is preferably 5 to 200, more preferably 10 to 100, further preferably 15 to 50, for example, an integer of 25 to 35. The above formula (2-1) is preferably -(OCF2CF2CF2) d -or-(OCF(CF3)CF2) d -, more preferably -(OCF2CF2CF2) d In one embodiment, e is 0. In another embodiment, e is 1.

[0133] In the above formula (2-2), e and f are each independently preferably an integer of 5 to 200, more preferably an integer of 10 to 200. In addition, the sum of c, d, e and f is preferably 5 or more, more preferably 10 or more, for example, 15 or more or 20 or more. In one embodiment, the above formula (2-2) is preferably -(OCF2CF2CF2CF2) c -(OCF2CF2CF2) d -(OCF2CF2) e -(OCF2) f In another embodiment, formula (2-2) may be -(OC2F4) e -(OCF2) f -represented group.

[0134] In the above formula (2-3), R 6 Preferably, it is OC2F4. In the above (2-3), R 7It is preferably a group selected from OC2F4, OC3F6 and OC4F8 or a combination of two or three groups independently selected from these groups, and more preferably a group selected from OC3F6 and OC4F8. There is no particular limitation on the combination of two or three groups independently selected from OC2F4, OC3F6 and OC4F8, and examples thereof include: -OC2F4OC3F6-, -OC2F4OC4F8-, -OC3F6OC2F4-, -OC3F6OC3F6-, -OC3F6OC4F8-, -OC4F8OC4F8-, -OC4F8OC3F6-, -OC4F8OC2F4-, -OC2 F4OC2F4OC3F6-, -OC2F4OC2F4OC4F8-, -OC2F4OC3F6OC2F4-, -OC2F4OC3F6OC3F6-, -OC2F4OC4F8OC2F4-, -OC3F6OC2F4OC2F4-, -OC3F6OC2F4OC3F6-, -OC3F6OC3F6OC2F4- and -OC4F8OC2F4OC2F4-. In the above formula (2-3), g is preferably an integer greater than or equal to 3, and more preferably an integer greater than or equal to 5. The above g is preferably an integer less than or equal to 50. In the above formula (2-3), OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 It may be either a straight chain or a branched chain, preferably a straight chain. In this embodiment, the above formula (2-3) is preferably -(OC2F4-OC3F6) g -or-(OC2F4-OC4F8) g -.

[0135] In the above formula (2-4), e is preferably an integer of 1 to 100, more preferably an integer of 5 to 100. The sum of a, b, c, d, e and f is preferably 5 or more, more preferably 10 or more, for example 10 or more and 100 or less.

[0136] In the above formula (2-5), f is preferably an integer of 1 to 100, more preferably an integer of 5 to 100. The sum of a, b, c, d, e and f is preferably 5 or more, more preferably 10 or more, for example 10 or more and 100 or less.

[0137] In one embodiment, the above R F It is a group represented by the above formula (2-1).

[0138] In one embodiment, the above R F It is a group represented by the above formula (2-2).

[0139] In one embodiment, the above R FIt is a group represented by the above formula (2-3).

[0140] In one embodiment, the above R F It is a group represented by the above formula (2-4).

[0141] In one embodiment, the above R F It is a group represented by the above formula (2-5).

[0142] In R F In the embodiment of the present invention, the ratio of e to f (hereinafter referred to as "e / f ratio") can be 0.5 to 4, preferably 0.6 to 3, more preferably 0.7 to 2, and even more preferably 0.8 to 1.4. By setting the e / f ratio to 4 or less, lubricity and chemical stability are further improved. The smaller the e / f ratio, the further the lubricity is improved. On the other hand, by setting the e / f ratio to 0.5 or more, the stability of the compound can be further improved. The larger the e / f ratio, the further the stability of the fluoropolyether structure is improved. In this case, the value of f is preferably 0.8 or more.

[0143] In one embodiment, the above R F It may be a group represented by the following formula (2-6).

[0144] -(OCF2CF2CF2) a -(OCF(CF3)CF2) b -(OCF2CF(CF3)) c -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-6)

[0145] [In formula (2-6), a, b, c, d, e and f are each independently an integer of 0 to 200,

[0146] The sum of a, b, c, d, e and f is greater than 1,

[0147] The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0148] In one embodiment, the above R F It may be a group represented by the following formula (2-7).

[0149] -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-7)

[0150] [In formula (2-7), d, e and f are each independently an integer of 0 to 200,

[0151] The sum of d, e and f is greater than 1,

[0152] The order of presence of the repeating units marked with d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0153] In R F In the formula (hereinafter referred to as "d / f ratio"), the ratio of d to f can be 0.5 to 4, preferably 0.6 to 3, more preferably 0.7 to 2, and even more preferably 0.8 to 1.4. By setting the d / f ratio to 4 or less, lubricity and chemical stability are further improved. The smaller the d / f ratio, the further the lubricity is improved. On the other hand, by setting the d / f ratio to 0.5 or more, the stability of the compound can be further improved. The larger the d / f ratio, the further the stability of the fluoropolyether structure is improved. In this case, the value of f is preferably 0.8 or more.

[0154] In the above-mentioned fluoropolyether group-containing compounds, R F The number average molecular weight of the part is not particularly limited, and is, for example, 500 to 30,000, preferably 1,500 to 30,000, and more preferably 2,000 to 10,000. F The number average molecular weight is 19 The value measured by F-NMR.

[0155] The content of PFPE in the first electrode 10 is not particularly limited and can be appropriately selected according to the target performance. In particular, when the first electrode 10 has a first active material layer 11 described later, a higher effect is easily obtained when the first active material layer 11 contains the above-mentioned PFPE at 1 volume % or more and 25 volume % or less. The first active material layer 11 may contain, for example, 1 volume % or more, 3 volume % or more, 5 volume % or more, 7 volume % or more, 8 volume % or more, 9 volume % or more, 10 volume % or more, 11 volume % or more, or 12 volume % or more and 25 volume % or less, 24 volume % or less, 22 volume % or less, 20 volume % or less, 18 volume % or less, 16 volume % or less, 14 volume % or less, or 12 volume % or less of the above-mentioned PFPE.

[0156] It should be noted that the volume ratio of PFPE in the first active material layer 11 is determined as follows. That is, the volume of the first active material layer 11 is measured in advance using an optical microscope or SEM. Regarding the volume t of PFPE contained, the first active material layer 11 can be washed with a solvent (a solvent that can dissolve PFPE and does not dissolve other electrode materials), and the filtrate in which PFPE is dissolved can be recovered by suction filtration, and the recovered solvent can be analyzed by GC-MS to determine that in the case of a solvent with a boiling point significantly different from that of PFPE, the volume of PFPE can be directly measured by extraction by distillation. Thus, the volume ratio of PFPE in the volume of the entire first active material layer 11 measured in advance is calculated.

[0157] 1.1.2 First active material layer

[0158] like Figure 1 As shown, the first electrode 10 may include a first active material layer 11 and a first current collector 12. In this case, the first active material layer 11 may include the above-mentioned PFPE. The first active material layer 11 may be a positive electrode active material layer or a negative electrode active material layer. When the first active material layer 11 is a positive electrode active material layer, the second active material layer 31 is a negative electrode active material layer.

[0159] The positive electrode active material layer contains at least a positive electrode active material in addition to the above-mentioned PFPE. In addition, the positive electrode active material layer may optionally contain an electrolyte, a conductive aid, a binder, etc. In addition, the positive electrode active material layer may also contain various additives in addition to this. The content of each component in the positive electrode active material layer can be appropriately determined according to the target battery performance. For example, the solid content of the positive electrode active material layer is set to 100% by mass as a whole, and the content of the positive electrode active material can be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or it can be 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, the positive electrode active material layer is set to 100% by volume as a whole, and can include a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of PFPE, a positive electrode active material, and optional electrolytes, conductive aids and binders, and the remainder can be voids or other components. The shape of the positive electrode active material layer is not particularly limited, for example, it can be a sheet-like positive electrode active material layer with a roughly flat surface. The thickness of the positive electrode active material layer is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or less, or 2 mm or less, 1 mm or less, or 500 μm or less.

[0160] As the positive electrode active material, an active material known as a positive electrode active material for a secondary battery can be used. Among the known active materials, a material with a relatively high potential (charge and discharge potential) for absorbing and releasing specified carrier ions (for example, lithium ions) can be used as the positive electrode active material, and a material with a relatively low potential can be used as the negative electrode active material described later. The positive electrode active material can be, for example, at least one selected from various lithium-containing compounds, elemental sulfur, and sulfur compounds. The lithium-containing compound used as the positive electrode active material can be lithium cobalt oxide, lithium nickel oxide, Li 1±α Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2±δ , lithium manganate, spinel lithium compounds (composed of Li 1+x Mn 2-x-y M y O4 (M is one or more selected from Al, Mg, Co, Fe, Ni and Zn) represented by heterogeneous element substitution Li-Mn spinel, etc.), lithium titanate, lithium metal phosphate (LiMPO4, etc., M is one or more selected from Fe, Mn, Co and Ni). In particular, in the case where the positive electrode active material includes a lithium-containing oxide containing at least one of Ni, Co and Mn, Li and O as constituent elements, a higher effect can be expected. The positive electrode active material can be used alone or in combination of two or more.

[0161] The shape of the positive electrode active material can be any shape generally used as a positive electrode active material for a battery. The positive electrode active material can be, for example, in a particle shape. The positive electrode active material can be hollow, can have voids, or can be porous. The positive electrode active material can be a primary particle, or a secondary particle obtained by agglomerating multiple primary particles. The average particle size D50 of the positive electrode active material can be, for example, greater than 1 nm, greater than 5 nm, or greater than 10 nm, and can be less than 500 μm, less than 100 μm, less than 50 μm, or less than 30 μm. It should be noted that the average particle size D50 described in this application refers to the particle size (median particle size) when the cumulative value in the volume-based particle size distribution obtained by the laser diffraction / scattering method is 50%.

[0162] A protective layer containing an ion-conductive oxide may be formed on the surface of the positive electrode active material. This makes it easy to suppress the reaction between the positive electrode active material and the sulfide (for example, the sulfide solid electrolyte described later). Examples of ion-conductive oxides include: Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, Li4Ti5O 12, Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, Li2WO4, etc. The ion conductive oxide may also be a substance in which a part of the elements are replaced by doping elements such as P and B. The coverage rate (area rate) of the protective layer on the surface of the positive electrode active material may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer may be, for example, 0.1 nm or more or 1 nm or less, or 100 nm or less or 20 nm or less.

[0163] The electrolyte that can be included in the positive electrode active material layer can be a solid electrolyte, a liquid electrolyte (electrolyte), or a combination thereof. In particular, when the positive electrode active material layer contains at least a solid electrolyte as an electrolyte, especially when the positive electrode active material layer does not contain a liquid except for the above-mentioned PFPE, it is easy to obtain a higher effect. In addition, when the positive electrode contains a sulfide solid electrolyte and the above-mentioned PFPE (for example, when the positive electrode active material layer contains a sulfide solid electrolyte and the above-mentioned PFPE), it is easy to obtain a higher effect.

[0164] The solid electrolyte can be a solid electrolyte known as a solid electrolyte for a secondary battery. The solid electrolyte can be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ion conductivity and heat resistance. Examples of inorganic solid electrolytes include lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X (PO4)3, Li-SiO glass, Li-Al-SO glass and other oxide solid electrolytes; Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5-GeS2 and other sulfide solid electrolytes. In particular, sulfide solid electrolytes, especially sulfide solid electrolytes containing at least Li, S and P as constituent elements, have high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be, for example, in a particle form. The solid electrolyte may be used alone or in combination of two or more.

[0165] The electrolyte may contain specified carrier ions (e.g., lithium ions). The electrolyte may be, for example, a non-aqueous electrolyte. The composition of the electrolyte may be the same as the composition known as the composition of the electrolyte of a secondary battery. For example, as the electrolyte, an electrolyte in which a lithium salt is dissolved in a carbonate solvent at a specified concentration may be used. Examples of carbonate solvents include: fluoroethylene carbonate (FEC), ethylene carbonate (EC), dimethyl carbonate (DMC), and the like. Examples of lithium salts include LiPF6, and the like.

[0166] As the conductive aid that can be included in the positive electrode active material layer, for example, carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); metal materials such as nickel, aluminum, and stainless steel. The conductive aid can be, for example, in the form of particles or fibers, and its size is not particularly limited. The conductive aid can be used alone or in combination of two or more.

[0167] As the binder that can be included in the positive electrode active material layer, for example, can be listed: butadiene rubber (BR) type binder, butylene rubber (IIR) type binder, acrylate butadiene rubber (ABR) type binder, styrene butadiene rubber (SBR) type binder, polyvinylidene fluoride (PVdF) type binder, polytetrafluoroethylene (PTFE) type binder, polyimide (PI) type binder, etc. The binder can be used alone or in combination of two or more.

[0168] 1.1.3 First current collector

[0169] like Figure 1 As shown, the first electrode 10 may have a first current collector 12 in contact with the first active material layer 11. The first current collector 12 may be a positive electrode current collector or a negative electrode current collector. When the first current collector 12 is a positive electrode current collector, the second current collector 32 is a negative electrode current collector.

[0170] The positive electrode collector can adopt any of the collectors generally used as the positive electrode collector of the battery. In addition, the positive electrode collector can be in the form of foil, plate, mesh, punched metal, foam, etc. The positive electrode collector can be composed of metal foil or metal mesh. In particular, the metal foil has excellent operability. The positive electrode collector can be composed of multiple foils. As metals constituting the positive electrode collector, Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. can be listed. In particular, from the perspective of ensuring oxidation resistance, the positive electrode collector can contain Al. The positive electrode collector may have a coating on its surface for the purpose of adjusting resistance, etc. In addition, the positive electrode collector may be plated or vapor-deposited with the above-mentioned metal on the metal foil or substrate. In addition, when the positive electrode collector is composed of multiple metal foils, there may be a certain layer between the multiple metal foils. The thickness of the positive electrode collector is not particularly limited. For example, the thickness may be 0.1 μm or more or 1 μm or less, or 1 mm or less or 100 μm or less.

[0171] 1.2 Electrolyte layer

[0172] The electrolyte layer 20 is arranged between the first electrode 10 and the second electrode 30, and can function as a separator. The electrolyte layer 20 contains at least an electrolyte, and may optionally contain a binder, etc. The electrolyte layer 20 may also contain other components such as a dispersant and the above-mentioned PFPE. The content of each component in the electrolyte layer 20 is not particularly limited, and can be appropriately determined according to the target battery performance. The shape of the electrolyte layer 20 is not particularly limited, for example, it can be a sheet with a roughly flat surface. The thickness of the electrolyte layer 20 is not particularly limited, for example, it can be more than 0.1μm or more than 1μm, or it can be less than 2mm or less than 1mm.

[0173] 1.2.1 Electrolyte

[0174] As the electrolyte contained in the electrolyte layer 20, it can be appropriately selected from the electrolytes exemplified as the electrolytes that can be contained in the above-mentioned positive electrode active material layer. In particular, the performance of the electrolyte layer 20 containing a solid electrolyte, especially a sulfide solid electrolyte, and more particularly a sulfide solid electrolyte containing at least Li, S and P as constituent elements is high. In the case where the electrolyte is a solid electrolyte, the solid electrolyte may be amorphous or crystalline. In the case where the electrolyte is a solid electrolyte, the solid electrolyte may be, for example, in a particle form. The electrolyte may be used alone or in combination of two or more.

[0175] In the secondary battery 100, the above-mentioned sulfide solid electrolyte is contained in at least one of the first electrode 10 and the electrolyte layer 20. That is, the PFPE contained in the first electrode 10 may be in contact with at least one of the sulfide solid electrolyte contained in the first electrode 10 and the sulfide solid electrolyte contained in the electrolyte layer 20. Here, in the secondary battery 100, even if the above-mentioned predetermined PFPE is in contact with the sulfide solid electrolyte, the sulfide solid electrolyte is unlikely to be altered or deteriorated, and the high ion conductivity of the sulfide solid electrolyte is easily maintained.

[0176] 1.2.2 Binder

[0177] The binder that can be contained in the electrolyte layer 20 can be appropriately selected from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer.

[0178] 1.3 Second Electrode

[0179] The second electrode 30 may be a positive electrode or a negative electrode. When the first electrode 10 is a positive electrode, the second electrode 30 is a negative electrode. The second electrode 30 may be configured without particular limitation as long as it can appropriately function as a positive electrode or a negative electrode of a secondary battery.

[0180] 1.3.1 Second active material layer

[0181] like Figure 1 As shown, the second electrode 30 may include a second active material layer 31 and a second current collector 32. The second active material layer 31 may contain the above-mentioned PFPE or may not contain it. In the case where the second active material layer 31 contains the specified PFPE, its specific composition may be based on the composition in the first active material layer 11. The second active material layer 31 may be a positive electrode active material layer or a negative electrode active material layer. In the case where the first active material layer 11 is a positive electrode active material layer, the second active material layer 31 is a negative electrode active material layer.

[0182] The negative electrode active material layer contains at least a negative electrode active material, and may optionally contain an electrolyte, a conductive aid, a binder, etc. The negative electrode active material layer may contain various additives in addition to this. For example, it may contain the above-mentioned PFPE, etc. The content of each component in the negative electrode active material layer can be appropriately determined according to the target battery performance. For example, the solid content of the negative electrode active material layer is set to 100% by mass as a whole, and the content of the negative electrode active material can be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or it can be 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, the negative electrode active material layer is set to 100% by volume as a whole, and may contain a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of the negative electrode active material, and optional electrolytes, conductive aids, binders and PFPE, and the remaining part may be voids or other components. The shape of the negative electrode active material layer is not particularly limited, for example, it may be a sheet-like negative electrode active material layer having a roughly flat surface. The thickness of the negative electrode active material layer is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, or 10 μm or less, or 2 mm or less, 1 mm or less, or 500 μm or less.

[0183] As the negative electrode active material, various materials can be used whose potential (charge and discharge potential) of absorbing and releasing specified carrier ions (for example, lithium ions) is lower than that of the above-mentioned positive electrode active material. For example, the negative electrode active material can be at least one selected from silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. The negative electrode active material can be used alone or in combination of two or more.

[0184] The shape of the negative electrode active material can be any shape that is generally used as a negative electrode active material for a battery. The negative electrode active material can be, for example, in a particle shape. The negative electrode active material can be hollow, have voids, or be porous. The negative electrode active material can be a primary particle, or a secondary particle obtained by agglomerating multiple primary particles. The average particle size D50 of the negative electrode active material can be, for example, greater than 1 nm, greater than 5 nm, or greater than 10 nm, and can also be less than 500 μm, less than 100 μm, less than 50 μm, or less than 30 μm. Alternatively, the negative electrode active material can be in the form of a sheet (foil, film) such as lithium foil. That is, the negative electrode active material layer can be composed of sheets of negative electrode active material.

[0185] The electrolyte that may be included in the negative electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolyte), or a combination thereof. In particular, when the negative electrode active material layer contains at least a solid electrolyte as an electrolyte, a higher effect is easily obtained. The negative electrode active material layer may contain a solid electrolyte, especially a sulfide solid electrolyte, and further especially a sulfide solid electrolyte containing Li, S and P as constituent elements. As conductive aids that may be included in the negative electrode active material layer, the above-mentioned carbon materials, the above-mentioned metal materials, etc. may be listed. The binder that may be included in the negative electrode active material layer may be appropriately selected, for example, from the binders exemplified as the binders that may be included in the above-mentioned positive electrode active material layer.

[0186] 1.3.2 Second current collector

[0187] like Figure 1 As shown, the second electrode 30 may have a second current collector 32 in contact with the second active material layer 31. The second current collector 32 may be a positive electrode current collector or a negative electrode current collector. When the first current collector 12 is a positive electrode current collector, the second current collector 32 is a negative electrode current collector.

[0188] The negative electrode collector can adopt any of the collectors generally used as negative electrode collectors of batteries. In addition, the negative electrode collector can be in the form of foil, plate, mesh, punched metal, foam, etc. The negative electrode collector can be a metal foil or a metal mesh, or can be a carbon sheet. In particular, the metal foil has excellent operability. The negative electrode collector can be composed of multiple foils and sheets. As metals constituting the negative electrode collector, there can be listed: Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, etc. In particular, from the viewpoint of ensuring reduction resistance and the viewpoint of not being easy to alloy with lithium, the negative electrode collector can contain at least one metal selected from Cu, Ni and stainless steel. The negative electrode collector may have a coating on its surface for the purpose of adjusting resistance, etc. In addition, the negative electrode collector may be plated or vapor-deposited with the above-mentioned metal on the metal foil or substrate. In addition, when the negative electrode collector is composed of multiple metal foils, there may be a certain layer between the multiple metal foils. The thickness of the negative electrode current collector is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or more, or 1 mm or less or 100 μm or less.

[0189] 1.4 Other components

[0190] In the secondary battery 100, each of the above-mentioned structures can be housed inside the outer casing. The outer casing can be any of the outer casings known as the outer casing of the battery. In addition, a plurality of secondary batteries 100 can be electrically connected arbitrarily, and can be arbitrarily overlapped to form a battery pack. In this case, the battery pack can be housed inside a known battery casing. The secondary battery 100 can have obvious structures such as necessary terminals in addition. As the shape of the secondary battery 100, for example, coin-shaped, laminated, cylindrical, and square shapes can be listed.

[0191] 2. Method for manufacturing secondary battery

[0192] The secondary battery 100 can be manufactured by applying a known method. For example, it can be manufactured as follows. However, the manufacturing method of the secondary battery 100 is not limited to the following method, and each layer can be formed by dry molding or the like, for example.

[0193] (1) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode slurry. The solvent used in this case is not particularly limited, and water, various organic solvents, or N-methylpyrrolidone (NMP) can be used. Then, the negative electrode slurry is coated on the surface of the negative electrode collector or the electrolyte layer described later using a doctor blade, and then dried to form a negative electrode active material layer on the surface of the negative electrode collector or the electrolyte layer to prepare a negative electrode. Here, the negative electrode active material layer can be pressed into shape.

[0194] (2) The positive electrode active material constituting the positive electrode active material layer is dispersed in a solvent to obtain a positive electrode slurry. The solvent used in this case is not particularly limited, and water, various organic solvents, or N-methylpyrrolidone (NMP) can be used. Then, the positive electrode slurry is coated on the surface of the positive electrode collector or the electrolyte layer described later using a doctor blade, and then dried to form a positive electrode active material layer on the surface of the positive electrode collector or the electrolyte layer to prepare a positive electrode. Here, the positive electrode active material layer can be pressed into shape.

[0195] (3) The layers are stacked in a manner such that the electrolyte layer is sandwiched between the negative electrode and the positive electrode to obtain a laminate having a negative electrode collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector in sequence. The electrolyte layer may be, for example, an electrolyte layer formed by molding an electrolyte mixture containing an electrolyte and a binder, or an electrolyte layer obtained by press molding. Here, the laminate may be further press molded. Other components such as terminals may be installed on the laminate as needed.

[0196] (4) The stacked body is housed in a battery case and sealed to obtain a secondary battery.

[0197] Here, in at least one of the steps (1) and (2), by making the active material layer contain the PFPE, the filling rate of the active material layer can be increased even when the active material layer is press-formed at a low pressure, and as a result, a secondary battery with low resistance can be easily obtained.

[0198] It should be noted that the technology of the present invention also has an aspect as a method for manufacturing a secondary battery as described below. That is, in one embodiment, the method for manufacturing a secondary battery 100 of the present invention is characterized in that it includes: forming a first electrode composite material to obtain a first electrode 10; forming an electrolyte composite material to obtain an electrolyte layer 20; and forming a second electrode composite material to obtain a second electrode 30,

[0199] At least one of the first electrode composite material and the electrolyte composite material includes a sulfide solid electrolyte,

[0200] The first electrode composite material comprises a perfluoropolyether represented by the above formula (1),

[0201] When the first electrode composite material is formed, pressure is applied to the first electrode composite material.

[0202] The first electrode composite material and the second electrode composite material may contain the above-mentioned materials constituting the positive electrode active material layer or the negative electrode active material layer. In addition, the electrolyte composite material may contain the above-mentioned materials constituting the electrolyte layer. In the manufacturing method of the present invention, there is no particular restriction on the pressure when the first electrode composite material is formed. For example, when the first electrode composite material is formed, a pressure greater than 0 kN / cm and less than 75 kN / cm, less than 50 kN / cm, less than 25 kN / cm or less than 15 kN / cm may be applied to the first electrode composite material. There is no particular restriction on the means and method of applying pressure to the first electrode composite material. For example, various pressurization means and pressurization methods such as roller pressing and CIP can be used.

[0203] It should be noted that, in the above, the unit of the pressure applied to the first electrode composite material is set to "kN / cm" for explanation, but this is only an example. That is, the pressure applied to the first electrode composite material is not limited to the line pressure, but may also be the surface pressure. In the case where the pressure applied to the first electrode composite material is the surface pressure, the surface pressure may also be converted into the line pressure. There is no particular limitation on the specific conversion method, and the relationship between the surface pressure and the line pressure may be experimentally / statistically determined through various experiments, thereby converting the surface pressure into the line pressure, or the surface pressure may be theoretically converted into the line pressure by calculation. According to the confirmation of the inventors, for example, when the surface pressure is about 37.5 kN / cm, the line pressure is about 75 kN / cm, and when the surface pressure is about 7.5 kN / cm, the line pressure is about 15 kN / cm.

[0204] 3. Supplement

[0205] The technology of the present invention can be applied not only to lithium ion secondary batteries but also to secondary batteries other than lithium ion secondary batteries (for example, sodium ion secondary batteries), etc. However, when the technology of the present invention is applied to lithium ion secondary batteries, a higher effect is likely to be exerted.

[0206] Example

[0207] Hereinafter, the technology of the present invention will be described in further detail while showing examples, but the technology of the present invention is not limited to the following examples.

[0208] 1. Production of positive electrode for pressing

[0209] Add a binder (PVdF), a conductive additive (VGCF), a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5), a positive electrode active material (LiNi 0.80 Co 0.15 Mn 0.05 O2) and optional perfluoropolyether (PFPE), using an ultrasonic homogenizer for mixing, thereby obtaining a positive electrode composite material slurry. The obtained positive electrode composite material slurry is coated on Al foil and dried to obtain a pressed positive electrode. Here, by changing the amount of PFPE added, a plurality of pressed positive electrodes with different volume ratios of PFPE in the composite material are obtained. The volume ratio of PFPE in each pressed positive electrode is shown in Table 1 below. In addition, PFPE is a liquid compound having a chemical structure represented by the following formula (I) (m / n is 1.2, the number average molecular weight is 5120, and the terminal R exists in an average ratio of 1:0.17 of CF3 and CF2CF3).

[0210]

[0211] 2. Preparation of negative electrode for pressing

[0212] A binder (PVdF), a conductive additive (VGCF), a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5) and a negative electrode active material (Si) are added to an organic solvent and kneaded using an ultrasonic homogenizer to obtain a negative electrode composite material slurry. The obtained negative electrode composite material slurry is coated on a Cu foil and dried to obtain a pressed negative electrode.

[0213] 3. Preparation of Electrolyte Layer for Pressing

[0214] A binder (PVdF) and a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5) are added to an organic solvent and kneaded using an ultrasonic homogenizer to obtain an electrolyte composite material slurry. The obtained electrolyte composite material slurry is coated on an Al foil and dried to obtain a pressing electrolyte layer.

[0215] 4. Battery production

[0216] The positive electrode, negative electrode and electrolyte layer for pressing are respectively formed into long strips, and the composite material surface of the positive electrode for pressing is overlapped with the composite material surface of the electrolyte layer for pressing, and then the Al foil of the electrolyte layer for pressing is peeled off at 165°C with the pressure shown in the following Table 1, thereby obtaining a laminate (A) of the Al foil, the positive electrode active material layer and the electrolyte layer. On the other hand, the composite material surface of the negative electrode for pressing is overlapped with the composite material surface of the electrolyte layer for pressing, and then the Al foil of the electrolyte layer for pressing is peeled off at 25°C with a pressure of 30kN / cm, thereby obtaining a laminate (B) of the Cu foil, the negative electrode active material layer and the electrolyte layer. The laminate (A) is punched into φ11.28mm, and the laminate (B) is punched into φ13.00mm. The electrolyte layer is further transferred to the laminate (B) using a uniaxial press, and then the laminate (A) and the laminate (B) are overlapped, thereby obtaining an electrode body having a structure of Al foil / positive electrode active material layer / electrolyte layer / negative electrode active material layer / Cu foil. Current extraction tabs were attached to the Al foil and the Cu foil of the electrode body, respectively, and the electrode body was sealed in a laminate package using a vacuum laminator sealer to prepare an evaluation battery.

[0217] 5. Evaluation of battery resistance

[0218] The resistance of the evaluation battery prepared as described above was measured. Specifically, the resistance value of the real axis intercept on the low-frequency side of the arc component was read using the Nyquist plot obtained by the AC impedance method and determined as the battery resistance.

[0219] 6. Evaluation results

[0220] The results are shown in the following Table 1. It should be noted that the configurations and production conditions of the electrolyte layer and the negative electrode are common to the Examples and Comparative Examples and are therefore omitted from Table 1. In addition, the evaluation results of the battery resistance are shown relative to the resistance value in Comparative Example 1 (100.0).

[0221] [Table 1]

[0222]

[0223] From the results shown in Table 1, the following can be concluded.

[0224] (1) As shown in Comparative Examples 1 to 5, the lower the pressure during positive electrode molding, the greater the battery resistance. It is believed that when the molding pressure becomes lower, the filling rate of the composite material decreases, resulting in an active material layer with many gaps, resulting in a greater battery resistance.

[0225] (2) As shown in Comparative Examples 1 to 5 and Examples 1 to 5, when the pressure during positive electrode molding is the same, the resistance of the battery is lower in the case where PFPE is included (Examples 1 to 5) than in the case where PFPE is not included in the composite material (Comparative Examples 1 to 5). It is believed that in Examples 1 to 5, due to the lubricating effect of PFPE, the fluidity of the composite material during positive electrode molding increases, and an active material layer with a high filling rate is obtained, resulting in a lower resistance of the battery.

[0226] (3) As shown in Examples 6 to 9, the resistance of the battery decreases regardless of the amount (volume ratio) of PFPE added to the composite material.

[0227] It should be noted that, in the above-mentioned embodiments, PFPE having a specific chemical structure is exemplified, but the chemical structure of PFPE is not limited thereto. In addition, in the above-mentioned embodiments, the case where PFPE is included on the positive electrode side is exemplified, but the same effect can be expected when PFPE is included on the negative electrode side. In addition, the composite material composition of the positive electrode, the electrolyte layer and the negative electrode is not limited to the above-mentioned composition.

[0228] As described above, a secondary battery having the following structure is likely to be a secondary battery having low resistance.

[0229] (1) It has a first electrode, an electrolyte layer and a second electrode.

[0230] (2) At least one of the first electrode and the electrolyte layer contains a sulfide solid electrolyte.

[0231] (3) The first electrode contains a predetermined perfluoropolyether.

[0232] Explanation of symbols

[0233] 10First electrode

[0234] 11First active material layer

[0235] 12 First current collector

[0236] 20 electrolyte layer

[0237] 30 Second electrode

[0238] 31 Second active material layer

[0239] 32 Second current collector

[0240] 100 Secondary Batteries

Claims

1. A secondary battery comprising a first electrode, an electrolyte layer and a second electrode, At least one of the first electrode and the electrolyte layer includes a sulfide solid electrolyte, The first electrode comprises a perfluoropolyether represented by the following formula (1): E1-Rf1-R F -O-Rf2-E2 (1) In formula (1), Rf1 and Rf2 are each independently a C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms, E1 and E2 are each independently a monovalent group selected from the group consisting of a fluoro group, a hydrogen group, a hydroxyl group, an aldehyde group, a carboxylic acid group, a C1-10 alkyl ester group, an amide group which may have one or more substituents, and an amino group which may have one or more substituents, R F It is a divalent fluoropolyether group.

2. The secondary battery according to claim 1, wherein The R F is a group represented by formula (2), -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3R Fa 6) d -(OC2F4) e -(OCF2) f - (2) In formula (2), each occurrence of R Fa are each independently a hydrogen atom, a fluorine atom or a chlorine atom, a, b, c, d, e and f are each independently an integer of 0 to 200, The sum of a, b, c, d, e and f is greater than 1, The order of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula. Among them, in all R Fa When it is a hydrogen atom or a chlorine atom, at least one of a, b, c, e and f is 1 or more.

3. The secondary battery according to claim 2, wherein: The R Fa A fluorine atom.

4. The secondary battery according to claim 3, wherein Each occurrence of R F are each independently a group represented by the following formula (2-1), (2-2), (2-3), (2-4) or (2-5), -(OC3F6) d -(OC2F4) e - (2-1) In formula (2-1), d is an integer of 1 to 200, e is 0 or 1, -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-2) In formula (2-2), c and d are each independently an integer of 0 to 30, e and f are each independently an integer of 1 to 200, The sum of c, d, e and f is an integer from 10 to 200, The order of the repeating units marked with the subscript c, d, e or f and enclosed in parentheses is arbitrary in the formula. -(R 6 -R 7 ) g - (2-3) In formula (2-3), R 6 For OCF2 or OC2F4, R 7 is selected from OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 or a combination of two or three groups selected from these groups, g is an integer from 2 to 100, -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-4) In formula (2-4), e is an integer of 1 to 200, a, b, c, d and f are each independently an integer of 0 to 200, The order of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula. -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-5) In formula (2-5), f is an integer greater than or equal to 1 and less than or equal to 200, a, b, c, d and e are each independently an integer of 0 to 200, The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses in the formula is arbitrary.

5. The secondary battery according to claim 4, wherein The R F is a group represented by the following formula (2-6), -(OCF2CF2CF2) a -(OCF(CF3)CF2) b -(OCF2CF(CF3)) c -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-6) In formula (2-6), a, b, c, d, e and f are each independently an integer of 0 to 200, The sum of a, b, c, d, e and f is greater than 1, The order of presence of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses in the formula is arbitrary.

6. The secondary battery according to claim 4, wherein The R F is a group represented by the following formula (2-7), -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-7) In formula (2-7), d, e and f are each independently an integer of 0 to 200, The sum of d, e and f is greater than 1, The order of presence of the repeating units indicated by d, e or f and enclosed in parentheses is arbitrary in the formula.

7. The secondary battery according to any one of claims 1 to 6, wherein The E1-Rf1 and the E2-Rf2 are each independently a group selected from the group consisting of -CF3, -CF2CF3 and -CF2CF2CF3.

8. The secondary battery according to any one of claims 1 to 7, wherein The first electrode has a first active material layer. The first active material layer contains 1 volume % or more and 25 volume % or less of the perfluoropolyether.

9. The secondary battery according to any one of claims 1 to 8, wherein The first electrode is a positive electrode.

10. The secondary battery according to any one of claims 1 to 9, wherein The first electrode includes the sulfide solid electrolyte and the perfluoropolyether.

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