Secondary battery and method for manufacturing same

Abstract

Disclosed is a novel technique for reducing the resistance of a secondary battery having a sulfide solid electrolyte and improving cycle characteristics. This secondary battery has a first electrode, an electrolyte layer, and a second electrode, and is characterized in that the first electrode and / or the electrolyte layer contains a sulfide solid electrolyte, and the first electrode contains an active material having voids and a perfluoropolyether represented by formula (1). E1-Rf1-RF-O-Rf2-E2 (1)

Description

Technical Field

[0001] The present application discloses a secondary battery and a method for manufacturing the same. Background Art

[0002] Patent document 1 discloses that in order to suppress the increase in the restraining pressure of the battery during charging, a predetermined porous silicon particle is used as a negative electrode active material. Patent document 2 discloses silicon inclusion compound particles having voids as an active material with a small volume change caused by charge and discharge. Patent document 3 discloses a 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: Japanese Patent Application Publication No. 2020-170605

[0006] Patent Document 2: Japanese Patent Application Publication No. 2020-087886

[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. However, when the electrode or the like is pressed under high pressure, the active material contained in the electrode is easily deformed. For example, when high pressure pressing is applied to an active material with a void as disclosed in patent documents 1 and 2, the active material is crushed and the void is easily eliminated. When the voids of the active material are eliminated, the volume change of the active material accompanying the charge and discharge becomes larger, and the cycle characteristics of the secondary battery are easily reduced. On the other hand, when manufacturing a secondary battery with a sulfide solid electrolyte, in order to avoid the crushing of the active material, etc., it is difficult to obtain the above-mentioned resistance reduction effect when the electrode or the like is pressed under low pressure. As such, in a secondary battery with a sulfide solid electrolyte, there is room for improvement in terms of both the improvement of the cycle characteristics and the reduction of the resistance.

[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 an active material having voids and 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 is arbitrary in the formula.]

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

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

[0042] R 7is 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

[0072] The first electrode is a negative electrode.

[0073] The active material having the voids contains Si or a Si alloy.

[0074] <Method 10>

[0075] The secondary battery according to any one of aspects 1 to 9, wherein the first electrode includes the sulfide solid electrolyte, the active material having the voids, and the perfluoropolyether.

[0076] <Method 11>

[0077] A method for manufacturing a secondary battery, comprising:

[0078] forming the first electrode composite material to obtain a first electrode;

[0079] forming the electrolyte composite material to obtain an electrolyte layer; and

[0080] forming the second electrode composite material to obtain a second electrode,

[0081] At least one of the first electrode composite material and the electrolyte composite material includes a sulfide solid electrolyte,

[0082] The first electrode composite material comprises an active material having voids and a perfluoropolyether represented by the following formula (1):

[0083] When the first electrode composite material is formed, a pressure greater than 0 kN / cm and less than or equal to 15 kN / cm is applied to the first electrode composite material.

[0084] E1-Rf1-R F -O-Rf2-E2 (1)

[0085] [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,

[0086] 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,

[0087] R F is a divalent fluoropolyether group.]

[0088] Effects of the Invention

[0089] In the secondary battery of the present invention, it is easy to achieve both excellent cycle characteristics and low resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Figure 1 An example of the configuration of a secondary battery is schematically shown. DETAILED DESCRIPTION

[0091] 1. Secondary battery

[0092] 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 includes a sulfide solid electrolyte. In addition, the first electrode 10 includes an active material having voids and a perfluoropolyether represented by the following formula (1).

[0093] 1.1 First Electrode

[0094] The first electrode 10 may be a negative electrode or a positive electrode. When the first electrode 10 is a negative electrode, the second electrode 30 is a positive electrode. The first electrode 10 may have various structures as long as it contains an active material having voids and a predetermined perfluoropolyether and can appropriately function as a negative electrode or a positive electrode of a secondary battery.

[0095] 1.1.1 Active substances with voids

[0096] During the charge and discharge of a secondary battery, carrier ions are absorbed or released into the active material, so the volume of the active material changes. Excessive expansion of the active material during charge or discharge may have an adverse effect on the cycle characteristics of the battery. It is believed that in order to alleviate the expansion of the active material, it is effective to form a gap in the active material. That is, in an active material with a gap, the expansion during charge or discharge is absorbed by the gap, and the volume change tends to become smaller.

[0097] As active materials with voids, various active materials can be cited. For example, the active material can have voids by being porous, or by being hollow. That is, the voids in the active material can exist only inside the active material, or can reach the surface from the inside of the active material, or can be mixed with voids that exist only inside the active material and voids that reach the surface from the inside. The active material can be an active material having voids in the primary particle itself (for example, an active material having voids inside the primary particle), or an active material having voids between the agglomerated primary particles when multiple primary particles agglomerate to form secondary particles. It should be noted that the void has a size that can absorb the expansion of the volume of the active material. At least a portion of the void may be filled with a perfluoropolyether described later, or may not be filled. The void may not be a tiny gap such as that used to insert carrier ions. Whether the active material has voids can be judged, for example, by observing the cross section of the active material using a scanning electron microscope (SEM).

[0098] The porosity of the active material is not particularly limited. For example, the porosity of the active material may be more than 1%, more than 2%, more than 3% or more than 4%, or less than 60%, less than 50%, less than 40%, less than 30% or less than 20%. The porosity of the active material can be determined, for example, as follows. First, the first electrode 10 containing the active material is exposed in section by ion milling. Then, the cross section is observed with SEM to obtain a photograph of the particles. The active material portion and the void portion in the active material are strictly distinguished from the obtained photograph using image analysis software and binarized. The area of ​​the active material portion and the void portion is obtained, and the porosity (%) is calculated by the following formula. It should be noted that the specific conditions for calculating the porosity may be, for example, conditions as specifically described in Patent Document 2 (Japanese Patent Publication No. 2020-087886).

[0099] Porosity (%) = 100 × (void area) / ((active material area) + (void area))

[0100] The active material with voids may be a negative electrode active material or a positive electrode active material. In particular, when the first electrode 10 is a negative electrode and the active material with voids is a negative electrode active material, and in particular, when the active material with voids is an active material containing Si or a Si alloy, the effect produced by the technology of the present invention is more easily improved. The volume of Si-based active materials containing Si or Si alloys is easily expanded during charging, and the volume expansion can be alleviated by the presence of voids in the active material. As a specific example of Si-based active materials containing Si or Si alloys, for example, active materials having inclusion structures can be cited. Whether the Si-based active material has an inclusion structure can be easily judged based on Raman spectroscopy, XRD, and the like. For example, at 325±10cm measured by Raman spectroscopy, -1 The maximum peak intensity I 325 and 205±10cm -1 The maximum peak intensity I 205 Ratio I 325 / I 205 In the case of being above 1.03 and within the range of 1.21, it can be judged that the Si-based active material has an inclusion compound structure. Alternatively, the first electrode 10 can be a positive electrode, and the active material having a void can be a positive electrode active material such as a sulfur-based active material (elemental sulfur, Li2S, etc.). Such a positive electrode active material is easy to expand in volume during discharge, and the active material has voids, so that the volume expansion can be alleviated. It should be noted that an oxide film or the like can be formed in the active material, and impurities such as carbon can also be contained.

[0101] The active material with voids may be, for example, in the form of particles. The size of the active material with voids is not particularly limited. The average particle size of the active material with voids may be, for example, 1 nm or more, 5 nm or more, 10 nm or more, 50 nm or more, 100 nm or more, 300 nm or more, or 500 nm or more, and may be 50 μm or less, 30 μm or less, 10 μm or less, or 5 μm or less. It should be noted that the average particle size of the active material 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%.

[0102] 1.1.2 Perfluoropolyether (PFPE)

[0103] In order to reduce the resistance of the secondary battery, etc., when manufacturing the secondary battery, high-pressure pressing is sometimes applied to the electrodes, etc. In this case, the above-mentioned active material with voids is crushed, the voids are easily eliminated, and it is difficult to obtain the effect of alleviating the expansion of the active material. In order to avoid the crushing of such active materials, it is effective to press at low pressure when manufacturing the secondary battery, but in this case, the resistance of the secondary battery tends to become higher. In contrast, in the secondary battery 100 of the present invention, by containing a prescribed perfluoropolyether (PFPE) in the first electrode 10, even when low-pressure pressing is adopted when manufacturing the secondary battery, the resistance of the first electrode 10 and the secondary battery 100 is easily reduced by utilizing the lubricating effect generated by the PFPE.

[0104] 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.

[0105] The perfluoropolyether is represented by the following formula (1).

[0106] E1-Rf1-R F -O-Rf2-E2 (1)

[0107] [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,

[0108] 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,

[0109] R F is a divalent fluoropolyether group.]

[0110] 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.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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, the reaction of PFPE with the sulfide solid electrolyte is further suppressed, and 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.

[0115] In the above formula (1), each occurrence of R F Each is independently a divalent fluoropolyether group.

[0116] R F Preferred is a group represented by formula (2).

[0117] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3R Fa 6) d -(OC2F4) e -(OCF2) f - (2)

[0118] [In formula (2): Each occurrence of R Fa are each independently a hydrogen atom, a fluorine atom or a chlorine atom,

[0119] a, b, c, d, e and f are each independently an integer of 0 to 200,

[0120] The sum of a, b, c, d, e and f is greater than 1,

[0121] The order of the repeating units indicated by a, b, c, d, e or f and enclosed in parentheses is arbitrary in the formula.

[0122] 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.]

[0123] R Fa It is preferably a hydrogen atom or a fluorine atom, and more preferably a fluorine atom.

[0124] Preferably, a, b, c, d, e and f are each independently an integer of 0 to 100.

[0125] 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.

[0126] These repeating units can be straight chain or branched chain. For example,

[0127] -(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))-.

[0128] -(OC5F 10 )- can be any of -(OCF2CF2CF2CF2CF2)-, -(OCF(CF3)CF2CF2CF2)-, -(OCF2CF(CF3)CF2CF2)-, -(OCF2CF2CF(CF3)CF2)-, -(OCF2CF2CF(CF3)CF2)- and -(OCF2CF2CF2CF(CF3))-.

[0129] -(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))-.

[0130] -(OC3F6)- (i.e., R Fa In the case of a fluorine atom), it may be any of -(OCF2CF2CF2)-, -(OCF(CF3)CF2)- and -(OCF2CF(CF3))-.

[0131] -(OC2F4)- can be any of -(OCF2CF2)- and -(OCF(CF3))-.

[0132] 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).

[0133] -(OC3F6) d -(OC2F4) e - (2-1)

[0134] [In formula (2-1), d is an integer of 1 to 200, and e is 0 or 1.]

[0135] -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-2)

[0136] [In formula (2-2), c and d are each independently an integer of 0 to 30,

[0137] e and f are each independently an integer of 1 to 200,

[0138] The sum of c, d, e and f is greater than 2,

[0139] The order of presence of the repeating units marked with the subscript c, d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0140] -(R 6 -R 7 ) g - (2-3)

[0141] [In formula (2-3), R 6 For OCF2 or OC2F4,

[0142] 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,

[0143] g is an integer from 2 to 100.]

[0144] -(OC6F 12 ) a -(OC5F 10 ) b -(OC4F8) c -(OC3F6) d -(OC2F4) e -(OCF2) f - (2-4)

[0145] [In formula (2-4), e is an integer of 1 to 200,

[0146] a, b, c, d and f are each independently an integer of 0 to 200,

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

[0149] [In formula (2-5), f is an integer of 1 to 200,

[0150] a, b, c, d and e are each independently an integer of 0 to 200,

[0151] 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.]

[0152] 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.

[0153] 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.

[0154] 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 -.

[0155] 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.

[0156] 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.

[0157] In one embodiment, the above R F It is a group represented by the above formula (2-1).

[0158] In one embodiment, the above R F It is a group represented by the above formula (2-2).

[0159] In one embodiment, the above R FIt is a group represented by the above formula (2-3).

[0160] In one embodiment, the above R F It is a group represented by the above formula (2-4).

[0161] In one embodiment, the above R F It is a group represented by the above formula (2-5).

[0162] 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.

[0163] In one embodiment, the above R F It may be a group represented by the following formula (2-6).

[0164] -(OCF2CF2CF2) a -(OCF(CF3)CF2) b -(OCF2CF(CF3)) c -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-6)

[0165] [In formula (2-6), a, b, c, d, e and f are each independently an integer of 0 to 200,

[0166] The sum of a, b, c, d, e and f is greater than 1,

[0167] 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.]

[0168] In one embodiment, the above R F It may be a group represented by the following formula (2-7).

[0169] -(OCF2CF2) d -(OCF(CF3)) e -(OCF2) f - (2-7)

[0170] [In formula (2-7), d, e and f are each independently an integer of 0 to 200,

[0171] The sum of d, e and f is greater than 1,

[0172] The order of presence of the repeating units marked with d, e or f and enclosed in parentheses is arbitrary in the formula.]

[0173] 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.

[0174] 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.

[0175] 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.

[0176] 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 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 first active material layer 11 measured in advance is calculated.

[0177] 1.1.3 First active material layer

[0178] like Figure 1 As shown, the first electrode 10 may be an electrode having a first active material layer 11 and a first current collector 12. In this case, the first active material layer 11 may contain the above-mentioned active material having voids and a specified 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 negative electrode active material layer, the second active material layer 31 is a positive electrode active material layer.

[0179] 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 also 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 a negative electrode active material, and optional electrolytes, conductive aids, binders and PFPE, and the remaining part may be a void 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.

[0180] 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 the potential of the positive electrode active material described later. For example, the negative electrode active material can be at least one selected from Si, Si alloys, silicon oxide and other Si-based active materials; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. In particular, as described above, in the case where the negative electrode active material is a Si-based active material containing Si or Si alloy, it is easy to obtain a higher effect produced by the technology of the present invention. The negative electrode active material can be used alone or in combination of two or more.

[0181] 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. As described above, the negative electrode active material can be, for example, in a particle shape. As described above, the negative electrode active material can have voids, for example, can be porous or hollow. In the case of including an active material having voids as the positive electrode active material described later, the negative electrode active material can be an active material having voids, can be an active material without voids, or can be a combination of an active material having voids and an active material without voids. 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.

[0182] The electrolyte that can be included in the negative electrode active material layer can 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, especially when the negative 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 first electrode 10 contains a sulfide solid electrolyte, the above-mentioned active material having voids, and the above-mentioned PFPE (for example, when the first active material layer 11 contains a sulfide solid electrolyte, the above-mentioned active material having voids, and the above-mentioned PFPE), it is easy to obtain a higher effect.

[0183] 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.

[0184] 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.

[0185] As the conductive aid that can be included in the negative 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.

[0186] As the binder that can be included in the negative electrode active material layer, for example, 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, polyimide (PI) binders, etc. The binder can be used alone or in combination of two or more.

[0187] 1.1.4 First current collector

[0188] like Figure 1As 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 negative electrode current collector or a positive electrode current collector. When the first current collector 12 is a negative electrode current collector, the second current collector 32 is a positive electrode current collector.

[0189] 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.

[0190] 1.2 Electrolyte layer

[0191] 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. There is no particular restriction on the content of each component in the electrolyte layer 20, and it can be appropriately determined according to the target battery performance. There is no particular restriction on the shape of the electrolyte layer 20, for example, it can be a sheet with a roughly flat surface. There is no particular restriction on the thickness of the electrolyte layer 20, for example, it can be more than 0.1μm or more than 1μm, or it can be less than 2mm or less than 1mm.

[0192] 1.2.1 Electrolyte

[0193] The electrolyte contained in the electrolyte layer 20 can be appropriately selected from the electrolytes exemplified as the electrolytes that can be contained in the above-mentioned negative electrode active material layer. In particular, 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 has high performance. 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.

[0194] In the secondary battery 100, the 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, since PFPE has low reactivity with the sulfide solid electrolyte, even if 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.

[0195] 1.2.2 Binder

[0196] The binder that can be contained in the electrolyte layer 20 can be appropriately selected from, for example, the binders exemplified as the binders that can be contained in the above-mentioned negative electrode active material layer.

[0197] 1.3 Second Electrode

[0198] The second electrode 30 may be a positive electrode or a negative electrode. When the first electrode 10 is a negative electrode, the second electrode 30 is a positive 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.

[0199] 1.3.1 Second active material layer

[0200] 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 negative electrode active material layer, the second active material layer 31 is a positive electrode active material layer.

[0201] The positive electrode active material layer contains at least a positive electrode active material. 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 such as the above-mentioned PFPE. 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 a total of 85% by volume, 90% by volume or more, or 95% by volume or more of the positive electrode active material, and optional electrolytes, conductive aids, binders and PFPE can be included, and the remaining part can be a gap 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.

[0202] 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 above-mentioned negative electrode active material. 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.

[0203] The shape of the positive electrode active material is any shape that is generally used as a positive electrode active material for a battery. As described above, the positive electrode active material may be, for example, in a particle shape. As described above, the positive electrode active material may have voids, and may be, for example, porous or hollow. In the case where an active material having voids is included as the above-mentioned negative electrode active material, the positive electrode active material may be an active material having voids, an active material without voids, or a combination of an active material having voids and an active material without voids.

[0204] A protective layer containing an ion-conductive oxide can 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 above-mentioned sulfide solid electrolyte). 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.

[0205] The electrolyte that may be included in the positive electrode active material layer may 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, a higher effect is easily obtained. The positive 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 positive 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 positive 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 negative electrode active material layer.

[0206] 1.3.2 Second current collector

[0207] 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 negative electrode current collector, the second current collector 32 is a positive electrode current collector.

[0208] 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.

[0209] 1.4 Other components

[0210] 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.

[0211] 2. Method for manufacturing secondary battery

[0212] 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.

[0213] (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.

[0214] (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.

[0215] (3) The layers are stacked in such a manner 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 obtained by molding an electrolyte mixture containing an electrolyte and a binder, or an electrolyte layer obtained by compression molding. Here, the laminate may be further compression molded. Other components such as terminals may be installed on the laminate as needed.

[0216] (4) The stacked body is housed in a battery case and sealed to obtain a secondary battery.

[0217] Here, in at least one of the steps (1) and (2) above, by making the active material layer contain the above-mentioned PFPE, the filling rate of the active material layer can be increased even when the active material layer is pressed and formed at a low pressure, and as a result, a secondary battery with low resistance can be easily obtained. In addition, by pressing and forming the active material layer at a low pressure, it is easy to suppress the crushing of the active material having voids, and as a result, a secondary battery with excellent cycle characteristics can be easily obtained. In addition, in the steps (1) to (3) above, by making at least one of the active material layer and the electrolyte layer contain a sulfide solid electrolyte, even if PFPE contacts the sulfide solid electrolyte, the reaction between PFPE and the sulfide solid electrolyte is not easy to occur, and it is easy to maintain the high ion conductivity as a sulfide solid electrolyte.

[0218] 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 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,

[0219] At least one of the first electrode composite material and the electrolyte composite material includes a sulfide solid electrolyte,

[0220] The first electrode composite material comprises an active material having voids and a perfluoropolyether represented by the above formula (1).

[0221] When the first electrode composite material is formed, a pressure greater than 0 kN / cm and less than or equal to 15 kN / cm is applied to the first electrode composite material.

[0222] The first electrode composite material and the second electrode composite material may contain the above-mentioned materials constituting the negative electrode active material layer or the positive electrode active material layer, and the electrolyte composite material may contain the above-mentioned materials constituting the electrolyte layer. In the manufacturing method of the present invention, the crushing of the active material with voids contained in the first electrode composite material is suppressed by making the pressure when the first electrode composite material is formed to be a low pressure of 15kN / cm or less. In addition, the first electrode composite material contains a specified PFPE, so even if the first electrode composite material is pressed under low pressure, the filling rate of the composite material in the first electrode 10 is easy to become high. The lower limit of the pressure during pressing is not particularly limited, and can be greater than 0kN / cm, 1kN / cm or more, 2kN / cm or more, 3kN / cm or more, 4kN / cm or more, 5kN / cm or more, 6kN / cm or more, 7kN / cm or more, 8kN / cm or more, 9kN / cm or more or 10kN / cm or more. There is no particular limitation 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.

[0223] 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.

[0224] 3. Supplement

[0225] 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.

[0226] Example

[0227] 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.

[0228] 1. Production of positive electrode for pressing

[0229] Add binder (PVdF), conductive additive (VGCF), sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5) and positive electrode active material (LiNi 0.80 Co 0.15 Mn 0.05 O2), and kneaded using an ultrasonic homogenizer to obtain a positive electrode composite material slurry. The obtained positive electrode composite material slurry is coated on an Al foil and dried to obtain a positive electrode for pressing.

[0230] 2. Preparation of negative electrode for pressing

[0231] A binder (PVdF), a conductive aid (VGCF), a sulfide solid electrolyte (LiI-LiBr-Li2S-P2S5), a negative electrode active material (porous Si) and an optional perfluoropolyether (PFPE) 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. Here, by changing the amount of PFPE added, a plurality of pressed negative electrodes having different volume ratios of PFPE in the composite material are obtained. The volume ratio of PFPE in each pressed negative 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, CF3 and CF2CF3).

[0232]

[0233] 3. Preparation of Electrolyte Layer for Pressing

[0234] 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.

[0235] 4. Battery production

[0236] 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 rolled at 165°C at a pressure of 50 kN / cm to peel off the Al foil of the electrolyte layer for pressing, thereby obtaining a stack (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 is overlapped with the composite material surface of the electrolyte layer for pressing, and then rolled at 25°C at the pressure shown in the following Table 1 to peel off the Al foil of the electrolyte layer for pressing, thereby obtaining a stack (B) of Cu foil, negative electrode active material layer and electrolyte layer. The stack (A) is punched into φ11.28 mm, and the stack (B) is punched into φ13.00 mm. The electrolyte layer is further transferred to the stack (B) using a uniaxial press, and then the stack (A) and the stack (B) are overlapped to obtain 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.

[0237] 5. Evaluation of battery resistance

[0238] 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.

[0239] 6. Evaluation of battery cycle characteristics

[0240] The evaluation battery prepared as described above was repeatedly subjected to a charge and discharge test 100 times in which the battery was charged at a constant current of 1 mA to 4.05 V and then discharged at a constant current of 1 mA to 1.5 V. The battery resistance (initial resistance) before the charge and discharge test and the battery resistance after the charge and discharge test were measured by the same method as above, and the rate of increase of the battery resistance after the charge and discharge test was calculated from the ratio of the battery resistance after the charge and discharge test to the battery resistance before the charge and discharge test.

[0241] 7. Evaluation results

[0242] The results are shown in the following Table 1. It should be noted that the configuration and production conditions of the positive electrode and electrolyte layer are common to the Examples and Comparative Examples and are therefore omitted from Table 1. In addition, the evaluation results of the battery resistance (initial resistance) before the charge and discharge test are shown relative to the resistance value in Comparative Example 1 (100.0).

[0243] [Table 1]

[0244]

[0245] From the results shown in Table 1, the following can be concluded.

[0246] (1) As shown in Comparative Examples 1 to 5, the lower the pressure during forming the negative electrode, the greater the resistance of the battery. It is believed that when the pressure during forming becomes lower, the filling rate of the composite material decreases, and the active material layer becomes more spaced, resulting in a larger resistance of the battery. On the other hand, the lower the pressure during forming the negative electrode, the better the cycle characteristics of the battery. It is believed that this is because by lowering the pressure during forming, the active material with voids (porous Si) is less likely to be crushed, and voids can be maintained in the active material, resulting in the volume expansion of the active material during charging being suppressed.

[0247] (2) As shown in Comparative Examples 3 to 5 and Examples 1 to 3, when the pressure during the negative electrode molding is the same, the resistance of the battery is lower in the case where PFPE is included (Examples 1 to 3) than in the case where PFPE is not included in the composite material (Comparative Examples 3 to 5). It is believed that in Examples 1 to 3, the fluidity of the composite material during the negative electrode molding is increased by the lubricating effect of PFPE, and an active material layer with a high filling rate is obtained, resulting in a lower resistance of the battery.

[0248] (3) As shown in Examples 4 to 7, regardless of the amount (volume ratio) of PFPE added to the composite material, the resistance of the battery is reduced and the cycle characteristics of the battery are improved.

[0249] 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 the active material having voids is a negative electrode active material and PFPE is included on the negative electrode side is exemplified, but the same effect can be expected when the active material having voids is a positive electrode active material and PFPE is included on the positive 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 composition.

[0250] As described above, in a secondary battery having the following structure, it is easy to achieve both excellent cycle characteristics and low resistance.

[0251] (1) It has a first electrode, an electrolyte layer and a second electrode.

[0252] (2) At least one of the first electrode and the electrolyte layer contains a sulfide solid electrolyte.

[0253] (3) The first electrode includes an active material having voids and a predetermined perfluoropolyether.

[0254] Explanation of symbols

[0255] 10First electrode

[0256] 11First active material layer

[0257] 12 First current collector

[0258] 20 electrolyte layer

[0259] 30 Second electrode

[0260] 31 Second active material layer

[0261] 32 Second current collector

[0262] 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 an active material having voids and 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 negative electrode, The active material having the voids includes Si or a Si alloy.

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

11. A method for manufacturing a secondary battery, comprising: forming the first electrode composite material to obtain a first electrode; forming the electrolyte composite material to obtain an electrolyte layer; as well as forming the second electrode composite material to obtain a second electrode, At least one of the first electrode composite material and the electrolyte composite material comprises a sulfide solid electrolyte, The first electrode composite material comprises an active material having voids and a perfluoropolyether represented by the following formula (1): When the first electrode composite material is formed, a pressure greater than 0 kN / cm and less than 15 kN / cm is applied to the first electrode composite material. 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.

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