Secondary batteries

Abstract

The present invention discloses a new technology for reducing the resistance of a secondary battery that has a sulfide solid electrolyte. A secondary battery according to the present disclosure has a first electrode, an electrolyte layer, and a second electrode, at least one of the first electrode and the electrolyte layer including a sulfide solid electrolyte, and the first electrode including a perfluoropolyether indicated by formula (1). Formula (1): E1-Rf1-RF-O-Rf2-E2 (In formula (1), Rf1 and Rf2 each independently represent a C1-16 divalent alkylene group that may be substituted with one or more fluorine atoms; E1 and E2 each independently represent a monovalent group selected from the group consisting of fluorine groups, hydrogen groups, hydroxyl groups, aldehyde groups, carboxylic acid groups, C1-10 alkyl ester groups, amide groups that may have one or more substituents, and amino groups that may have one or more substituents; and RF is a divalent fluoropolyether group.)

Description

[Technical Field]

[0001] This application discloses a secondary battery. [Background technology]

[0002] Patent Document 1 discloses that when manufacturing a secondary battery, electrodes and electrolyte layers are pressed at a pressure of 200 MPa to 1000 MPa. Patent Document 2 discloses that an insulating layer is placed on the peripheral portion of the electrode to suppress cracking of the electrolyte layer during high-pressure pressing. Patent Document 3 discloses perfluoropolyether as an additive component of a non-aqueous electrolyte. Patent Document 4 discloses that a perfluoropolyether group-containing compound is present on the surface of the electrode to improve the shelf life of the electrode. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] International Publication No. 2014 / 010042 [Patent Document 2] International Publication No. 2019 / 103008 [Patent Document 3] Japanese Patent Publication No. 2018-200866 [Patent Document 4] Japanese Patent Publication No. 2018-147887 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] When manufacturing secondary batteries, it is believed that pressing electrodes and other components under high pressure reduces their resistance. This resistance reduction effect is particularly pronounced when manufacturing secondary batteries containing sulfide solid electrolytes. On the other hand, to simplify the manufacturing process and reduce manufacturing costs, it is necessary to press electrodes and other components under low pressure. However, when using low-pressure pressing in the manufacture of secondary batteries containing sulfide solid electrolytes, the aforementioned resistance reduction effect is difficult to achieve. Therefore, new technologies are needed to reduce the resistance of secondary batteries containing sulfide solid electrolytes. [Means for solving the problem]

[0005] This application discloses several embodiments as means for solving the above-mentioned problems. <Aspect 1> A secondary battery having 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, The first electrode contains a perfluoropolyether shown in the following formula (1): Secondary battery. 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 monovalent groups 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. R F It is a divalent fluoropolyether group. <Aspect 2> The aforementioned R F Equation (2): -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8)c -(OC3R Fa 6) d -(OC2F4) e -(OCF2) f - (2) [In formula (2), R Fa is, in each occurrence, independently a hydrogen atom, a fluorine atom or a chlorine atom, a, b, c, d, e and f are each independently an integer from 0 to 200, the sum of a, b, c, d, e and f is 1 or more, the order of existence of each repeating unit enclosed in parentheses with a, b, c, d, e or f is arbitrary in the formula, however, when all of the R Fa are hydrogen atoms or chlorine atoms, at least one of a, b, c, e and f is 1 or more.] is a group represented by The secondary battery of Embodiment 1. <Embodiment 3> Said R Fa is a fluorine atom, The secondary battery of Embodiment 2. <Embodiment 4> Said R F is, in each occurrence, independently 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 from 1 to 200 and 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 from 0 to 30, e and f are each independently an integer from 1 to 200, the sum of c, d, e and f is an integer from 10 to 200, The order of existence of each repeating unit, denoted by the subscripts c, d, e, or f and enclosed in parentheses, is arbitrary within the expression. -(R 6 -R 7 ) g - (2-3) [In formula (2-3), R 6 This is either OCF2 or OC2F4; R 7 OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 It is a group selected from these groups, or a combination of two or three groups selected from these groups. g is an integer between 2 and 100. -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-4) [In equation (2-4), e is an integer between 1 and 200, a, b, c, d, and f are each independent integers between 0 and 200. The order in which each repeating unit, denoted by a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the expression. -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-5) [In equation (2-5), f is an integer between 1 and 200, a, b, c, d, and e are each independent integers between 0 and 200, The order in which each repeating unit, denoted by a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the expression. The base represented by A secondary battery according to embodiment 3. <Aspect 5> The aforementioned R F The following equation (2-6): -(OCF2CF2CF2) d1 -(OCF(CF3)CF2) d2 -(OCF2CF(CF3)) d3 -(OCF2CF2) e1 -(OCF(CF3)) e2 -(OCF2) f - (2-6) [In formula (2-6), d1, d2, d3, e1, e2 and f are independent integers between 0 and 200. d1, d2, d3, e1, e2 The sum of and f is 1 or greater, The sum of d1, d2, and d3 is less than or equal to 200. The sum of e1 and e2 is less than or equal to 200. d1, d2, d3, e1, e2 The order in which each repeating unit enclosed in parentheses with the letter f is arbitrary within the expression. The base represented by A secondary battery according to embodiment 4. <Aspect 6> The aforementioned R F This is expressed by the following equation (2-7): -(OCF2CF2) e1 -(OCF(CF3)) e2 -(OCF2) f - (2-7) [In formula (2-7), e1, e2 and f are independent integers between 0 and 200. e1, e2 The sum of and f is 1 or greater, The sum of e1 and e2 is less than or equal to 200. e1, e2 The order in which each repeating unit enclosed in parentheses with the letter f is arbitrary within the expression. The base represented by A secondary battery according to embodiment 4. <Aspect 7> The aforementioned E1-Rf1 and E2-Rf2 are each independently selected from the group consisting of -CF3, -CF2CF3, and -CF2CF2CF3. A secondary battery according to any of the embodiments 1 to 6. <Aspect 8> The first electrode has a first active material layer, The first active material layer contains 1% to 25% by volume of the perfluoropolyether. A secondary battery according to any of the embodiments 1 to 7. <Pattern 9> The aforementioned electrode 1 is the positive electrode. A secondary battery according to any of the embodiments 1 to 8. <Aspect 10> The first electrode comprises the sulfide solid electrolyte and the perfluoropolyether, A secondary battery according to any of the embodiments 1 to 9. [Effects of the Invention]

[0006] The secondary battery described herein tends to have low resistance. [Brief explanation of the drawing]

[0007] [Figure 1] This shows a schematic example of a secondary battery configuration. [Modes for carrying out the invention]

[0008] 1. Secondary battery The following describes embodiments of the technology of this disclosure, but the technology of this disclosure is not limited to the embodiments described below. As shown in Figure 1, a secondary battery 100 according to one embodiment has 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. The first electrode 10 also contains a perfluoropolyether shown in the following formula (1).

[0009] 1.1 First electrode The first electrode 10 may be either a positive or negative electrode. If the first electrode 10 is a positive electrode, the second electrode 30 is a negative electrode. The first electrode 10 only needs to contain a predetermined perfluoropolyether and be capable of functioning appropriately as the positive or negative electrode of a secondary battery, and can take various configurations. For example, a higher effect is more likely to be obtained when the first electrode 10 contains a sulfide solid electrolyte and a predetermined perfluoropolyether (for example, when the first active material layer 11 contains a sulfide solid electrolyte and a predetermined perfluoropolyether).

[0010] 1.1.1 Perfluoropolyether (PFPE) The first electrode 10 contains a perfluoropolyether (PFPE) as shown in formula (1) below.

[0011] According to the inventor's new findings, sulfide solid electrolytes that may be included in electrodes and electrolyte layers have high chemical reactivity and may react with other materials, causing alteration and degradation. In this case, the ionic conductivity of the electrodes and electrolyte layers tends to decrease. In contrast, a certain PFPE included in the first electrode 10 can impart lubricity to various battery materials and has low reactivity with sulfide solid electrolytes. That is, when the first electrode 10 contains the certain PFPE, even when the first electrode 10 is pressed at low pressure, the lubricating effect of the PFPE can increase the density of the material in the first electrode 10. In other words, the filling rate of the material in the first electrode 10 increases, making it easier to reduce the resistance of the first electrode 10.

[0012] Furthermore, according to the inventors' new findings, PFPE is thought to have high affinity for the surfaces of various battery materials because it has ether bonds, and can appropriately exist in voids between active material materials and voids between sulfide solid electrolyte materials, for example. As a result, the lubrication effect at the first electrode 10 is further enhanced, making it easier to further increase the density of the material at the first electrode 10 even when the first electrode 10 is pressed at low pressure, and thus making it easier to further reduce the resistance of the first electrode 10.

[0013] Perfluoropolyethers are represented by the following formula (1).

[0014] 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 monovalent groups 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. R F It is a divalent fluoropolyether group.

[0015] In formula (1) above, Rf1 and Rf2 are each independently divalent C1-16 alkylene groups which may be substituted with one or more fluorine atoms.

[0016] In one embodiment, the "C1-16 divalent alkylene group" in the C1-16 divalent alkylene group which may be substituted with one or more fluorine atoms may be linear or branched, preferably a linear or branched C1-6 alkylalkylene group, particularly a C1-3 alkylene group, and more preferably a linear C1-6 alkylene group, particularly a C1-3 alkylene group.

[0017] 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 linear or branched, preferably a linear or branched C1-6 fluoroalkylene group, particularly a C1-3 fluoroalkylene group, specifically -CF2CH2- and -CF2CF2CH2-, and more preferably a linear C1-6 perfluoroalkylene group, particularly a C1-3 perfluoroalkylene group, specifically a group selected from the group consisting of -CF2-, -CF2CF2-, and -CF2CF2CF2-.

[0018] In formula (1) above, E1 and E2 are each independently monovalent groups 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.

[0019] The PFPE described above has low reactivity with sulfide solid electrolytes. Therefore, even when PFPE and sulfide solid electrolytes come into contact, a decrease in ionic conductivity due to alteration or degradation of the sulfide solid electrolyte is unlikely to occur. In particular, an even higher effect can be expected when the first electrode contains PFPE having a nonpolar group as a terminal group. In this regard, E1 and E2 are each independently preferably fluorine groups. In one embodiment, E1-Rf1 and E2-Rf2 may each be independently groups selected from the group consisting of -CF3, -CF2CF3, and -CF2CF2CF3.

[0020] In the above equation (1), R F Each instance is independently a divalent fluoropolyether group.

[0021] R F Preferably, formula (2): -(OC6F 12 ) a -(OC5F 10 ) b-(OC4F8) c -(OC3R Fa 6) d -(OC2F4) e -(OCF2) f - (2) [In formula (2): R Fa In each instance, it is independently a hydrogen atom, a fluorine atom, or a chlorine atom. a, b, c, d, e, and f are each independent integers between 0 and 200. The sum of a, b, c, d, e, and f is 1 or greater. The order in which each repeating unit, denoted by a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the formula. However, all R Fa If is a hydrogen atom or a chlorine atom, then at least one of a, b, c, e, and f is 1 or more. It is a base represented by .

[0022] R Fa Preferably, it is a hydrogen atom or a fluorine atom, and more preferably a fluorine atom.

[0023] a, b, c, d, e, and f may preferably be independent integers between 0 and 100.

[0024] The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, and may be, 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, and even more preferably 60 or less, and may be, for example, 50 or less or 30 or less.

[0025] These repeating units may be linear or branched. For example, -(OC6F 12)- may be any of the following: -(OCF2CF2CF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2CF2CF2)-, -(OCF2CF(CF3)CF2CF2CF2)-, -(OCF2CF2CF(CF3)CF2CF2)-, -(OCF2CF2CF2CF(CF3)CF2)-, and -(OCF2CF2CF2CF2CF(CF3))-. -(OC5F 10 )- may be any of the following: -(OCF2CF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2CF2)-, -(OCF2CF(CF3)CF2CF2)-, -(OCF2CF2CF(CF3)CF2)-, and -(OCF2CF2CF2CF(CF3))-. -(OC4F8)- may be any 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))-. -(OC3F6)-(that is, in equation (2) above, R Fa If (is a fluorine atom), it may be any of -(OCF2CF2CF2)-, -(OCF(CF3)CF2)-, or -(OCF2CF(CF3))-. -(OC2F4)- may be either -(OCF2CF2)- or -(OCF(CF3))-.

[0026] In one embodiment, R F Each occurrence may independently represent a base that can be expressed by any of the following formulas (2-1) to (2-5).

[0027] -(OC3F6) d -(OC2F4) e - (2-1) [In equation (2-1), d is an integer between 1 and 200, and e is either 0 or 1.]

[0028] -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-2) [In formula (2-2), c and d are each independently an integer of 0 or more and 30 or less, e and f are each independently an integer of 1 or more and 200 or less, the sum of c, d, e and f is 2 or more, and the order of existence of each repeating unit enclosed in parentheses with subscript c, d, e or f is arbitrary in the formula.],

[0029] -(R 6 -R 7 ) g - (2-3) [In formula (2-3), R 6 is OCF2 or OC2F4, R 7 is a group selected from OC2F4, OC3F6, OC4F8, OC5F 10 and OC6F 12 or a combination of two or three groups selected from these groups, and g is an integer of 2 to 100.];

[0030] -(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 or more and 200 or less, a, b, c, d and f are each independently an integer of 0 or more and 200 or less, and the order of existence of each repeating unit enclosed in parentheses with subscript a, b, c, d, e or f is arbitrary in the formula.]

[0031] -(OC6F 12 ) a-(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-5) [In equation (2-5), f is an integer between 1 and 200, a, b, c, d, and e are each independent integers between 0 and 200, The order in which each repeating unit, denoted by a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the expression.

[0032] In the above formula (2-1), d is preferably an integer between 5 and 200, more preferably between 10 and 100, and even more preferably between 15 and 50, for example between 25 and 35. The above formula (2-1) is preferably -(OCF2CF2CF2) d -, or -(OCF(CF3)CF2) d - is a group represented by -, more preferably -(OCF2CF2CF2). d It is a base represented by -. In one embodiment, e is 0. In another embodiment, e is 1.

[0033] In the above formula (2-2), e and f are each an integer, preferably between 5 and 200, more preferably between 10 and 200. The sum of c, d, e, and f is preferably 5 or more, more preferably 10 or more, and may be, 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 - is the base represented by -. In another embodiment, formula (2-2) is -(OC2F4) e -(OCF2) f It may also be represented as a base by -.

[0034] In the above equation (2-3), R 6Preferably, R is OC2F4. In (2-3) above, 7 Preferably, the group is 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. The combination of two or three groups independently selected from OC2F4, OC3F6, and OC4F8 is not particularly limited, but examples include -OC2F4OC3F6-, -OC2F4OC4F8-, -OC3F6OC2F4-, -OC3F6OC3F6-, -OC3F6OC4F8-, -OC4F8OC4F8-, -OC4F8OC3F6-, -OC4F8OC2F4-, and -OC2 Examples include F4OC2F4OC3F6-, -OC2F4OC2F4OC4F8-, -OC2F4OC3F6OC2F4-, -OC2F4OC3F6OC3F6-, -OC2F4OC4F8OC2F4-, -OC3F6OC2F4OC2F4-, -OC3F6OC2F4OC3F6-, -OC3F6OC3F6OC2F4-, and -OC4F8OC2F4OC2F4-. In the above formula (2-3), g is preferably an integer of 3 or more, more preferably 5 or more. The above g is preferably an integer of 50 or less. In the above formula (2-3), OC2F4, OC3F6, OC4F8, OC5F 10、 And OC6F 12 The chain may be either linear or branched, and is preferably linear. In this embodiment, the above formula (2-3) is preferably -(OC2F4-OC3F6) g -, or -(OC2F4-OC4F8) g - is

[0035] In the above formula (2-4), e is preferably an integer between 1 and 100, more preferably between 5 and 100. The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, for example between 10 and 100.

[0036] In the above formula (2-5), f is preferably an integer between 1 and 100, more preferably between 5 and 100. The sum of a, b, c, d, e, and f is preferably 5 or more, more preferably 10 or more, for example between 10 and 100.

[0037] In one embodiment, the above R F This is the group represented by the above formula (2-1).

[0038] In one embodiment, the above R F This is the group represented by the above formula (2-2).

[0039] In one embodiment, the above R F This is the group represented by the above formula (2-3).

[0040] In one embodiment, the above R F This is the group represented by the above formula (2-4).

[0041] In one embodiment, the above R F This is the group represented by the above formula (2-5).

[0042] R F In this case, the ratio of e to f (hereinafter referred to as the "e / f ratio") may 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 better the lubricity. On the other hand, by setting the e / f ratio to 0.5 or more, the stability of the compound can be further enhanced. The larger the e / f ratio, the better the stability of the fluoropolyether structure. In this case, it is preferable that the value of f is 0.8 or more.

[0043] In one embodiment, the above R F The following equation (2-6): -(OCF2CF2CF2) d1 -(OCF(CF3)CF2) d2 -(OCF2CF(CF3))d3 -(OCF2CF2) e1 -(OCF(CF3)) e2 -(OCF2) f - (2-6) [In formula (2-6), d1, d2, d3, e1, e2 and f are independent integers between 0 and 200. d1, d2, d3, e1, e2 The sum of and f is 1 or greater, The sum of d1, d2, and d3 is less than or equal to 200. The sum of e1 and e2 is less than or equal to 200. d1, d2, d3, e1, e2 The order in which each repeating unit enclosed in parentheses with the letter f is arbitrary within the expression. It may also be a base represented by .

[0044] In one embodiment, the above R F This is expressed by the following equation (2-7): -(OCF2CF2) e1 -(OCF(CF3)) e2 -(OCF2) f - (2-7) [In formula (2-7), e1, e2 and f are independent integers between 0 and 200. e1, e2 The sum of and f is 1 or greater, The sum of e1 and e2 is less than or equal to 200. e1, e2 The order in which each repeating unit enclosed in parentheses with the letter f is arbitrary within the expression. It may also be a base represented by .

[0045] R F In this case, the ratio of d to f , or the ratio of d1+d2+d3 to fThe d / f ratio (hereinafter referred to as the "d / f ratio") may 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 better the lubricity. On the other hand, by setting the d / f ratio to 0.5 or more, the stability of the compound can be further enhanced. The larger the d / f ratio, the better the stability of the fluoropolyether structure. In this case, the value of f is preferably 0.8 or more.

[0046] In the above fluoropolyether group-containing compound, R F The number-average molecular weight of the part is not particularly limited, but is, for example, 500 to 30,000, preferably 1,500 to 30,000, and more preferably 2,000 to 10,000. In this specification, R F The number-average molecular weight is, 19 The value shall be measured by 1F-NMR.

[0047] The PFPE content in the first electrode 10 is not particularly limited and can be appropriately selected according to the desired performance. In particular, if the first electrode 10 has a first active material layer 11 described later, a higher effect is more likely to be obtained when the first active material layer 11 contains 1% to 25% by volume of the above-mentioned PFPE. The first active material layer 11 may contain, for example, 1% or more by volume, 3% or more by volume, 5% or more by volume, 7% or more by volume, 8% or more by volume, 9% or more by volume, 10% or more by volume, 11% or more by volume, or 12% or more by volume, and 25% or less by volume, 24% or less by volume, 22% or less by volume, 20% or less by volume, 18% or less by volume, 16% or less by volume, 14% or less by volume, or 12% or less by volume.

[0048] Furthermore, the volume fraction of PFPE in the first active material layer 11 is measured as follows. Specifically, the volume of the first active material layer 11 is measured in advance using an optical microscope or SEM. The volume t of PFPE can be determined by washing the first active material layer 11 with a solvent (capable of dissolving PFPE but not other electrode materials), recovering the filtrate containing dissolved PFPE by suction filtration, etc., and analyzing the recovered solvent by GC-MS. Alternatively, if the solvent has a boiling point significantly different from that of PFPE, the volume of PFPE can be directly measured by extraction by distillation. This allows the volume ratio of PFPE to the total volume of the first active material layer 11 measured in advance to be calculated.

[0049] 1.1.2 First active material layer As shown in Figure 1, the first electrode 10 may comprise a first active material layer 11 and a first current collector 12. In this case, the first active material layer 11 may include the PFPE described above. The first active material layer 11 may be a positive electrode active material layer or a negative electrode active material layer. If the first active material layer 11 is a positive electrode active material layer, then the second active material layer 31 is a negative electrode active material layer.

[0050] The positive electrode active material layer contains at least positive electrode active material in addition to the PFPE mentioned above. The positive electrode active material layer may also optionally contain an electrolyte, a conductive additive, and a binder. Furthermore, the positive electrode active material layer may contain various other additives. The content of each component in the positive electrode active material layer can be appropriately determined according to the desired battery performance. For example, taking the total solid content of the positive electrode active material layer as 100% by mass, the content of positive electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or it may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, taking the total volume of the positive electrode active material layer as 100% by volume, the PFPE, positive electrode active material, and optionally the electrolyte, conductive additive, and binder may together be 85% by volume or more, 90% by volume or more, or 95% by volume or more, with the remainder being void or other components. The shape of the positive electrode active material layer is not particularly limited, and may, for example, be a sheet-like positive electrode active material layer having a substantially 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 more, or 2 mm or less, 1 mm or less, or 500 μm or less.

[0051] As the positive electrode active material, any known positive electrode active material for secondary batteries may be used. Among the known active materials, a material with a relatively noble potential (charge / discharge potential) for intercalating and releasing a predetermined carrier ion (e.g., lithium ion) can be used as the positive electrode active material, and a material with a relatively noble potential can be used as the negative electrode active material described later. The positive electrode active material may be at least one selected from, for example, various lithium-containing compounds, elemental sulfur, and sulfur compounds. Lithium-containing compounds used as positive electrode active materials include lithium cobaltate, lithium nickelate, and Li 1±α Ni 1 / 3 Co 1 / 3 Mn 1 / 3 O 2±δ Lithium manganate, spinel-type lithium compounds (Li 1+x Mn 2-x-y M yVarious lithium-containing oxides may be used, such as O4 (where M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn), heteroatom-substituted Li-Mn spinel, lithium titanate, and metallic lithium phosphate (such as LiMPO4, where M is one or more selected from Fe, Mn, Co, and Ni). In particular, a higher effect can be expected when the positive electrode active material contains a lithium-containing oxide that includes at least Li, at least one of Ni, Co, and Mn, and O as constituent elements. The positive electrode active material may be used alone or in combination of two or more types.

[0052] The shape of the positive electrode active material may be any shape that is common for positive electrode active materials in batteries. The positive electrode active material may be, for example, particulate. The positive electrode active material may be hollow, have voids, or be porous. The positive electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter D50 of the positive electrode active material may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may also be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. In this application, the average particle diameter D50 refers to the particle diameter (median diameter) at 50% of the cumulative value in the volume-based particle size distribution determined by laser diffraction-scattering.

[0053] A protective layer containing an ion-conducting oxide may be formed on the surface of the positive electrode active material. This makes it easier to suppress reactions between the positive electrode active material and sulfides (for example, sulfide solid electrolytes described later). Examples of ion-conducting oxides include Li3BO3, LiBO2, Li2CO3, LiAlO2, Li4SiO4, Li2SiO3, Li3PO4, Li2SO4, Li2TiO3, and Li4Ti5O 12Examples include Li2Ti2O5, Li2ZrO3, LiNbO3, Li2MoO4, and Li2WO4. Ion-conducting oxides may have some elements substituted by doping elements such as P and B. The coverage rate (area ratio) 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 more, 100 nm or less, or 20 nm or less.

[0054] The electrolyte contained in the positive electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolyte solution), or a combination thereof. In particular, a higher effect is more likely to be obtained when the positive electrode active material layer contains at least a solid electrolyte, and especially when the positive electrode active material layer does not contain any liquid other than the PFPE mentioned above. Furthermore, an even higher effect is more likely to be obtained when the positive electrode contains a sulfide solid electrolyte and the PFPE mentioned above (for example, when the positive electrode active material layer contains a sulfide solid electrolyte and the PFPE mentioned above).

[0055] The solid electrolyte can be any known solid electrolyte used in secondary batteries. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, inorganic solid electrolytes have excellent ionic conductivity and heat resistance. Examples of inorganic solid electrolytes include lithium lanthanum zirconate, LiPON, and Li 1+X Al X Ge 2-XExamples of oxide solid electrolytes include (PO4)3, Li-SiO glass, and Li-Al-SO glass; and sulfide solid electrolytes such as Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Si2S-P2S5, Li2S-P2S5-LiI-LiBr, LiI-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, and Li2S-P2S5-GeS2. In particular, sulfide solid electrolytes, especially those containing at least Li, S, and P as constituent elements, exhibit high performance. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may also be particulate, for example. One type of solid electrolyte may be used alone, or two or more types may be used in combination.

[0056] The electrolyte may contain a predetermined carrier ion (e.g., lithium ion). The electrolyte may be, for example, a non-aqueous electrolyte. The composition of the electrolyte may be the same as that known for the electrolytes of secondary batteries. For example, a solution of lithium salt dissolved at a predetermined concentration in a carbonate-based solvent can be used as the electrolyte. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), and dimethyl carbonate (DMC). Examples of lithium salts include LiPF6.

[0057] Examples of conductive additives that may be included in the positive electrode active material layer include carbon materials such as vapor-processed carbon fiber (VGCF), acetylene black (AB), Ketjenblack (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metallic materials such as nickel, aluminum, and stainless steel. The conductive additive may be in the form of parts or fibers, and its size is not particularly limited. One type of conductive additive may be used alone, or two or more types may be used in combination.

[0058] Examples of binders that may be included in the positive electrode active material layer include butadiene rubber (BR) binders, butylene rubber (IIR) binders, acrylate butadiene rubber (ABR) binders, styrene butadiene rubber (SBR) binders, polyvinylidene fluoride (PVdF) binders, polytetrafluoroethylene (PTFE) binders, and polyimide (PI) binders. A single binder may be used alone, or two or more binders may be used in combination.

[0059] 1.1.3 First Current Collector As shown in Figure 1, the first electrode 10 may include a first current collector 12 that contacts the first active material layer 11. The first current collector 12 may be a positive electrode current collector or a negative electrode current collector. If the first current collector 12 is a positive electrode current collector, the second current collector 32 is a negative electrode current collector.

[0060] The positive electrode current collector can be any of the commonly used positive electrode current collectors for batteries. The positive electrode current collector may be in the form of foil, plate, mesh, perforated metal, or foam. The positive electrode current collector may be composed of metal foil or metal mesh. Metal foil, in particular, offers superior handling. The positive electrode current collector may consist of multiple foils. Examples of metals that can constitute the positive electrode current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, the positive electrode current collector may contain Al to ensure oxidation resistance. The positive electrode current collector may have some kind of coating layer on its surface for purposes such as adjusting resistance. Furthermore, the positive electrode current collector may be a metal foil or substrate on which the above metals are plated or vapor-deposited. Also, if the positive electrode current collector consists of multiple metal foils, there may be some kind of layer between the multiple metal foils. The thickness of the positive electrode current collector is not particularly limited. For example, the thickness may be 0.1 μm or more, or 1 μm or more, or 1 mm or less, or 100 μm or less.

[0061] 1.2 Electrolyte layer The electrolyte layer 20 is positioned 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 or the like. The electrolyte layer 20 may further contain a dispersant and other components such as the PFPE mentioned above. The content of each component in the electrolyte layer 20 is not particularly limited and may be appropriately determined according to the desired battery performance. The shape of the electrolyte layer 20 is not particularly limited and may, for example, be a sheet with a substantially flat surface. The thickness of the electrolyte layer 20 is not particularly limited and may be, for example, 0.1 μm or more or 1 μm or more, or 2 mm or less or 1 mm or less.

[0062] 1.2.1 Electrolytes The electrolyte included in the electrolyte layer 20 may be appropriately selected from among the examples of electrolytes that can be included in the positive electrode active material layer described above. In particular, electrolyte layers 20 containing solid electrolytes, especially sulfide solid electrolytes, and among those, sulfide solid electrolytes containing at least Li, S, and P as constituent elements, exhibit high performance. When the electrolyte is a solid electrolyte, it may be amorphous or crystalline. When the electrolyte is a solid electrolyte, it may be, for example, particulate. Only one type of electrolyte may be used alone, or two or more types may be used in combination.

[0063] In the secondary battery 100, the above-mentioned sulfide solid electrolyte is included in at least one of the first electrode 10 and the electrolyte layer 20. That is, the PFPE included in the first electrode 10 can come into contact with at least one of the sulfide solid electrolyte included in the first electrode 10 and the sulfide solid electrolyte included in the electrolyte layer 20. In the secondary battery 100, even if the above-mentioned PFPE and the sulfide solid electrolyte come into contact, alteration or degradation of the sulfide solid electrolyte is unlikely to occur, and the high ionic conductivity of the sulfide solid electrolyte is easily maintained.

[0064] 1.2.2 Binder The binder that may be included in the electrolyte layer 20 can be appropriately selected from, for example, the binders exemplified above as binders that may be included in the positive electrode active material layer.

[0065] 1.3 Second electrode The second electrode 30 may be either a positive or negative electrode. If the first electrode 10 is a positive electrode, then the second electrode 30 is a negative electrode. The second electrode 30 only needs to be capable of functioning appropriately as the positive or negative electrode of a secondary battery, and its configuration is not particularly limited.

[0066] 1.3.1 Second active material layer As shown in Figure 1, the second electrode 30 may comprise a second active material layer 31 and a second current collector 32. The second active material layer 31 may or may not contain the predetermined PFPE described above. If the second active material layer 31 contains the predetermined PFPE, its specific configuration may be similar to that of 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. If the first active material layer 11 is a positive electrode active material layer, then the second active material layer 31 is a negative electrode active material layer.

[0067] The negative electrode active material layer contains at least negative electrode active material, and optionally also contains electrolyte, conductive additive, binder, etc. The negative electrode active material layer may also contain various other additives. 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 desired battery performance. For example, taking the total solid content of the negative electrode active material layer as 100% by mass, the content of negative electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, or it may be 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, taking the total volume of the negative electrode active material layer as 100% by volume, the negative electrode active material and optionally electrolyte, conductive additive, binder, and PFPE may together be 85% by volume or more, 90% by volume or more, or 95% by volume or more, and the remainder may be void or other components. The shape of the negative electrode active material layer is not particularly limited, and may, for example, be a sheet-like negative electrode active material layer having a substantially 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 more, or 2 mm or less, 1 mm or less, or 500 μm or less.

[0068] As the negative electrode active material, various materials can be used whose charge-discharge potential (potential for intercalating and releasing a predetermined carrier ion (e.g., lithium ions) is lower than that of the positive electrode active material. For example, the negative electrode active material may 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; or metallic lithium and lithium alloys. The negative electrode active material may be used alone or in combination of two or more types.

[0069] The shape of the negative electrode active material may be any shape that is common for negative electrode active materials in batteries. The negative electrode active material may be, for example, particulate. The negative electrode active material may be hollow, have voids, or be porous. The negative electrode active material may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter D50 of the negative electrode active material may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, or 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil or film) such as lithium foil. That is, the negative electrode active material layer may consist of a sheet of negative electrode active material.

[0070] The electrolyte that may be included in the negative electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolyte solution), or a combination thereof. In particular, a higher effect is more likely to be obtained when the negative electrode active material layer contains at least a solid electrolyte. The negative electrode active material layer may contain a solid electrolyte, especially a sulfide solid electrolyte, and moreover, a sulfide solid electrolyte containing Li, S, and P as constituent elements. Examples of conductive additives that may be included in the negative electrode active material layer include the carbon materials and metal materials mentioned above. The binder that may be included in the negative electrode active material layer may be appropriately selected from, for example, the binders exemplified above that may be included in the positive electrode active material layer.

[0071] 1.3.2 Second Current Collector As shown in Figure 1, the second electrode 30 may include a second current collector 32 that contacts the second active material layer 31. The second current collector 32 may be a positive electrode current collector or a negative electrode current collector. If the first current collector 12 is a positive electrode current collector, the second current collector 32 is a negative electrode current collector.

[0072] The negative electrode current collector can be any of the commonly used negative electrode current collectors for batteries. The negative electrode current collector may be in the form of foil, plate, mesh, perforated metal, or foam. The negative electrode current collector may be metal foil or metal mesh, or a carbon sheet. Metal foil is particularly advantageous in terms of handling. The negative electrode current collector may consist of multiple foils or sheets. Examples of metals constituting the negative electrode current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, and stainless steel. In particular, from the viewpoint of ensuring reduction resistance and avoiding alloying with lithium, the negative electrode current collector may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector may have some kind of coating layer on its surface for purposes such as adjusting resistance. Furthermore, the negative electrode current collector may be a metal foil or substrate on which the above metals are plated or vapor-deposited. Furthermore, if the negative electrode current collector consists of multiple metal foils, there may be some layer between the multiple metal foils. The thickness of the negative electrode current collector is not particularly limited. For example, it may be 0.1 μm or more, 1 μm or more, 1 mm or less, or 100 μm or less.

[0073] 1.4 Other Configurations The secondary battery 100 may have all of the above components housed inside an outer casing. Any known battery casing can be used. Furthermore, multiple secondary batteries 100 may be electrically connected and stacked as desired to form a battery pack. In this case, the battery pack may be housed inside a known battery case. The secondary battery 100 may also have other obvious components such as necessary terminals. Examples of shapes for the secondary battery 100 include coin-type, laminate-type, cylindrical, and prismatic types.

[0074] 2. Manufacturing method of secondary batteries The secondary battery 100 can be manufactured by applying known methods. 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 may be formed by, for example, dry molding. (1) The negative electrode active material and other materials constituting the negative electrode active material layer are dispersed in a solvent to obtain a negative electrode slurry. The solvent used in this case is not particularly limited and can be water or various organic solvents, and may also be N-methylpyrrolidone (NMP). Then, using a doctor blade or the like, the negative electrode slurry is coated onto the surface of the negative electrode current collector or the electrolyte layer described later, and then dried to form a negative electrode active material layer on the surface of the negative electrode current collector or the electrolyte layer, thereby forming the negative electrode. The negative electrode active material layer may be press-formed. (2) A positive electrode slurry is obtained by dispersing the positive electrode active material and other materials constituting the positive electrode active material layer in a solvent. The solvent used in this case is not particularly limited and can be water or various organic solvents, and may also be N-methylpyrrolidone (NMP). Then, using a doctor blade or the like, the positive electrode slurry is coated onto the surface of the positive electrode current collector or the electrolyte layer described later, and then dried to form a positive electrode active material layer on the surface of the positive electrode current collector or the electrolyte layer, which is the positive electrode. Here, the positive electrode active material layer may be press-formed. (3) The layers are stacked so that the electrolyte layer is sandwiched between the negative electrode and the positive electrode, to obtain a laminate having a negative electrode current collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer, and a positive electrode current collector in this order. The electrolyte layer may be obtained, for example, by molding an electrolyte mixture containing an electrolyte and a binder, or by press molding. The laminate may also be press molded. Other members such as terminals are attached to the laminate as needed. (4) A secondary battery is obtained by housing the laminate in a battery case and sealing it.

[0075] Here, by incorporating the above-mentioned PFPE into the active material layer in at least one of the steps (1) and (2) above, the filling density of the active material layer can be increased even when the active material layer is press-molded at low pressure, and as a result, a secondary battery with low resistance can be easily obtained.

[0076] Furthermore, the technology disclosed herein also has aspects as a method for manufacturing a secondary battery, as follows: In one embodiment, the method for manufacturing the secondary battery 100 of this disclosure is: The first electrode composite material is molded to obtain the first electrode 10. The electrolyte mixture is molded to obtain an electrolyte layer 20, and The second electrode composite material is molded to obtain the second electrode 30. Includes, At least one of the first electrode mixture and the electrolyte mixture contains a sulfide solid electrolyte, The first electrode composite material contains the perfluoropolyether shown in formula (1) above, The first electrode composite material is characterized in that pressure is applied to it when it is molded.

[0077] The first electrode mixture and the second electrode mixture may contain the materials that constitute the positive electrode active material layer or the negative electrode active material layer described above, and the electrolyte mixture may contain the materials that constitute the electrolyte layer described above. In the manufacturing method of this disclosure, the pressure applied when forming the first electrode mixture is not particularly limited. For example, when forming the first electrode mixture, a pressure greater than 0 kN / cm and 75 kN / cm or less, 50 kN / cm or less, 25 kN / cm or less, or 15 kN / cm or less may be applied to the first electrode mixture. The means and methods for applying pressure to the first electrode mixture are also not particularly limited, and various pressurizing means and methods such as roll pressing and CIP can be used.

[0078] In the above explanation, the unit of pressure applied to the first electrode mixture was described as "kN / cm," but this is merely an example. That is, the pressure applied to the first electrode mixture is not limited to linear pressure, but may also be surface pressure. Even when the pressure applied to the first electrode mixture is surface pressure, it can be converted to linear pressure. The specific conversion method is not particularly limited; the relationship between surface pressure and linear pressure may be experimentally and statistically determined through various experiments, and the surface pressure may be converted to linear pressure, or it may be theoretically converted to linear pressure by calculation. As far as the inventors have confirmed, for example, when the surface pressure is about 37.5 kN / cm, the linear pressure is about 75 kN / cm, and when the surface pressure is about 7.5 kN / cm, the linear pressure is about 15 kN / cm.

[0079] 3. Supplement The technology disclosed herein can be applied not only to lithium-ion secondary batteries but also to other secondary batteries (e.g., sodium-ion secondary batteries). However, the technology disclosed herein is more likely to be effective when applied to lithium-ion secondary batteries. [Examples]

[0080] The technology of this disclosure will be described in more detail below with reference to examples, but the technology of this disclosure is not limited to the following examples.

[0081] 1. Fabrication of the positive electrode for pressing. The organic solvent contains a binder (PVdF), a conductive additive (VGCF), a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5), and a positive electrode active material (LiNi 0.80 Co 0.15 Mn 0.05A cathode composite slurry was obtained by adding O2 and optionally perfluoropolyether (PFPE) and kneading them using an ultrasonic homogenizer. The obtained cathode composite slurry was coated onto an Al foil and dried to obtain a cathode for pressing. Here, by changing the amount of PFPE added, several cathodes for pressing with different volume percentages of PFPE in the composite were obtained. The volume percentages of PFPE in each cathode for pressing are shown in Table 1 below. Furthermore, PFPE is a liquid substance having the chemical structure shown by the following formula (I) (m / n is 1.2, number average molecular weight is 5120, and terminal Rs are CF3 and CF2CF3 in an average ratio of 1:0.17).

[0082] [ka]

[0083] 2. Fabrication of the negative electrode for pressing A binder (PVdF), a conductive additive (VGCF), a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5), and a negative electrode active material (Si) were added to an organic solvent and kneaded using an ultrasonic homogenizer to obtain a negative electrode mixture slurry. The obtained negative electrode mixture slurry was coated onto a Cu foil and dried to obtain a negative electrode for pressing.

[0084] 3. Preparation of the electrolyte layer for pressing. An electrolyte slurry was obtained by adding a binder (PVdF) and a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5) to an organic solvent and kneading the mixture using an ultrasonic homogenizer. The obtained electrolyte slurry was coated onto an aluminum foil and dried to obtain an electrolyte layer for pressing.

[0085] 4. Making a battery The positive electrode, negative electrode, and electrolyte layer for pressing were each formed into strips. The composite material surface of the positive electrode for pressing and the composite material surface of the electrolyte layer for pressing were overlapped, and roll-pressed at 165°C at the pressure shown in Table 1 below to remove the Al foil from the electrolyte layer for pressing, thereby obtaining a laminate (A) of Al foil, positive electrode active material layer, and electrolyte layer. On the other hand, the composite material surface of the negative electrode for pressing and the composite material surface of the electrolyte layer for pressing were overlapped, and roll-pressed at 25°C at a pressure of 30 kN / cm to remove the Al foil from the electrolyte layer for pressing, thereby obtaining a laminate (B) of Cu foil, negative electrode active material layer, and electrolyte layer. Laminate (A) was punched out to a diameter of φ11.28 mm, and laminate (B) was punched out to a diameter of φ13.00 mm. An electrolyte layer was further transferred to laminate (B) using a uniaxial press, and then laminate (A) and laminate (B) were stacked to obtain an electrode body having the configuration 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 Cu foil of the electrode body, respectively, and the bodies were sealed in a laminate pack using a vacuum laminating sealer to produce a battery for evaluation.

[0086] 5. Evaluation of battery resistance 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 from the Nyquist plot obtained by the AC impedance method, and this was identified as the battery's resistance.

[0087] 6. Evaluation Results The results are shown in Table 1 below. Note that the configuration and manufacturing conditions of the electrolyte layer and negative electrode are the same for both the examples and the comparative examples, and are therefore omitted from Table 1. Furthermore, the battery resistance evaluation results are shown relative to the resistance value in Comparative Example 1 (100.0).

[0088] [Table 1]

[0089] The following can be concluded from the results shown in Table 1. (1) As shown in Comparative Examples 1 to 5, the lower the pressure applied when forming the positive electrode, the greater the battery's resistance. It is thought that when the pressure during forming decreases, the filling rate of the composite material decreases, resulting in an active material layer with many gaps, which in turn increases the battery's resistance. (2) As shown in Comparative Examples 1-5 and Examples 1-5, when the pressure during molding the positive electrode was the same, the battery resistance was lower when PFPE was included in the composite material (Examples 1-5) than when PFPE was not included in the composite material (Comparative Examples 1-5). In Examples 1-5, it is considered that the lubricating effect of PFPE increased the fluidity of the composite material during molding the positive electrode, resulting in a highly packed active material layer and thus lower battery resistance. (3) As shown in Examples 6 to 9, the battery resistance was reduced regardless of the amount (volume ratio) of PFPE added to the composite material.

[0090] In the above examples, PFPE having a specific chemical structure was illustrated, but the chemical structure of PFPE is not limited thereto. Furthermore, in the above examples, the case in which PFPE is included on the positive electrode side was illustrated, but similar effects can be expected when PFPE is included on the negative electrode side. In addition, the composite material composition of the positive electrode, electrolyte layer, and negative electrode is not limited to those described above.

[0091] As described above, secondary batteries with the following configuration tend to have low resistance. (1) Having a first electrode, an electrolyte layer, and a second electrode. (2) At least one of the first electrode and the electrolyte layer contains a sulfide solid electrolyte. (3) The first electrode contains a predetermined perfluoropolyether. [Explanation of Symbols]

[0092] 10 1st electrode 11 First active material layer 12. First current collector 20 Electrolyte layer 30 2nd electrode 31 Second active material layer 32. Second current collector 100 Secondary battery

Claims

1. A secondary battery having 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, The first electrode contains a perfluoropolyether shown in the following formula (1): Secondary battery. E １ -Rf １ -R Ｆ -O-Rf ２ -E ２ (1) [In formula (1), Rf １ and Rf ２ Each of these is a C1-16 divalent alkylene group which may be independently substituted with one or more fluorine atoms. E １ and E ２ 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. R Ｆ It is a divalent fluoropolyether group.

2. The aforementioned R Ｆ Equation (2): -(OC ６ F １２ ) ａ -(OC ５ F １０ ) ｂ -(OC ４ F ８ ) ｃ -(OC ３ R Ｆａ ６ ) ｄ -(OC ２ F ４ ) ｅ -(OCF ２ ) ｆ - (2) [In formula (2), R Ｆａ In each instance, it is independently a hydrogen atom, a fluorine atom, or a chlorine atom. a, b, c, d, e, and f are each independent integers between 0 and 200. The sum of a, b, c, d, e, and f is 1 or greater. The order in which each repeating unit, denoted by a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the formula. However, all R Ｆａ If is a hydrogen atom or a chlorine atom, then at least one of a, b, c, e, and f is 1 or more. The base represented by The secondary battery according to claim 1.

3. The aforementioned R Ｆａ This is a fluorine atom, The secondary battery according to claim 2.

4. The aforementioned R Ｆ Each occurrence independently satisfies the following equations (2-1), (2-2), (2-3), (2-4), or (2-5): -(OC ３ F ６ ) ｄ -(OC ２ F ４ ) ｅ - (2-1) [In equation (2-1), d is an integer between 1 and 200, and e is 0 or 1.] -(OC ４ F ８ ) ｃ -(OC ３ F ６ ) ｄ -(OC ２ F ４ ) ｅ -(OCF ２ ) ｆ - (2-2) [In equation (2-2), c and d are each independent integers between 0 and 30.] e and f are each independent integers between 1 and 200. The sum of c, d, e, and f is an integer between 10 and 200. The order of existence of each repeating unit, which is subscripted c, d, e, or f and enclosed in parentheses, is arbitrary within the formula. -(R ６ -R ７ ) ｇ - (2-3) [In formula (2-3), R ６ OCF ２ or OC ２ F ４ And; R ７ OC ２ F ４ , OC ３ F ６ , OC ４ F ８ , OC ５ F １０ and OC ６ F １２ It is a group selected from these groups, or a combination of two or three groups selected from these groups. g is an integer between 2 and 100. -(OC ６ F １２ ) ａ -(OC ５ F １０ ) ｂ -(OC ４ F ８ ) ｃ -(OC ３ F ６ ) ｄ -(OC ２ F ４ ) ｅ -(OCF ２ ) ｆ - (2-4) [In equation (2-4), e is an integer between 1 and 200, a, b, c, d, and f are each independent integers between 0 and 200. The order in which each repeating unit, denoted a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the expression. -(OC ６ F １２ ) ａ -(OC ５ F １０ ) ｂ -(OC ４ F ８ ) ｃ -(OC ３ F ６ ) ｄ -(OC ２ F ４ ) ｅ -(OCF ２ ) ｆ - (2-5) [In equation (2-5), f is an integer between 1 and 200, a, b, c, d, and e are each independent integers between 0 and 200. The order in which each repeating unit, denoted a, b, c, d, e, or f and enclosed in parentheses, exists is arbitrary within the expression. The base represented by The secondary battery according to claim 3.

5. The aforementioned R Ｆ The following equation (2-6): -(OCF ２ CF ２ CF ２ )d1-(OCF(CF ３ )CF ２ )d2-(OCF ２ CF(CF ３ ))d3-(OCF ２ CF ２ )e1-(OCF(CF ３ ))e2-(OCF ２ ) ｆ - (2-6) [In equation (2-6), d1, d2, d3, e1, e2, and f are each independent integers between 0 and 200.] The sum of d1, d2, d3, e1, e2, and f is 1 or greater. The sum of d1, d2, and d3 is 200 or less. The sum of e1 and e2 is 200 or less. The order in which each repeating unit, denoted by d1, d2, d3, e1, e2, or f and enclosed in parentheses, exists is arbitrary within the expression. The base represented by The secondary battery according to claim 4.

6. The aforementioned R Ｆ The following equation (2-7): -(OCF ２ CF ２ )e1-(OCF(CF ３ ))e2-(OCF ２ ) ｆ - (2-7) [In equation (2-7), e1, e2, and f are each independent integers between 0 and 200.] The sum of e1, e2, and f is 1 or greater. The sum of e1 and e2 is 200 or less. The order in which each repeating unit, denoted as e1, e2, or f and enclosed in parentheses, exists is arbitrary within the expression. The base represented by The secondary battery according to claim 4.

7. The aforementioned E １ -Rf １ and E ２ -Rf ２ Each of these is independently -CF ３ , -CF ２ CF ３ , and -CF ２ CF ２ CF ３ A group selected from the group consisting of, A secondary battery according to any one of claims 1 to 6.

8. The first electrode has a first active material layer, The first active material layer contains 1% to 25% by volume of the perfluoropolyether. A secondary battery according to any one of claims 1 to 6.

9. The first electrode is the positive electrode. A secondary battery according to any one of claims 1 to 6.

10. The first electrode comprises the sulfide solid electrolyte and the perfluoropolyether, A secondary battery according to any one of claims 1 to 6.

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