Secondary battery and manufacturing method therefor

Abstract

Disclosed is a new technology for improving cycle characteristics, while reducing resistance, of a secondary battery having 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 contains a sulfide solid electrolyte. The first electrode contains: an active material including voids; and perfluoropolyether represented by formula (1). (1): E1-Rf1-RF-O-Rf2-E2

Description

Secondary battery and manufacturing method thereof

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

[0002] Patent Document 1 discloses the use of specific porous silicon particles as a negative electrode active material to suppress an increase in the battery's confining pressure during charging. Patent Document 2 discloses voided silicon clathrate particles as an active material that exhibits little volume change during charging and discharging. Patent Document 3 discloses perfluoropolyether as an additive component of a non-aqueous electrolyte. Patent Document 4 discloses the presence of a perfluoropolyether group-containing compound on the surface of an electrode to improve the storage stability of the electrode.

[0003] JP 2020-170605 A JP 2020-087886 A JP 2018-200866 A JP 2018-147887 A

[0004] When manufacturing a secondary battery, pressing electrodes and other components at high pressure is thought to reduce the resistance of the electrodes and other components. The resistance-reducing effect of high-pressure pressing is thought to be particularly pronounced when manufacturing a secondary battery having a sulfide solid electrolyte. However, when electrodes and other components are pressed at high pressure, the active material contained in the electrode is likely to deform. For example, when high-pressure pressing is applied to active materials having voids, such as those disclosed in Patent Documents 1 and 2, the active material is likely to be crushed and the voids are likely to be eliminated. When the voids in the active material are eliminated, the volume change of the active material during charge and discharge increases, and the cycle characteristics of the secondary battery are likely to deteriorate. On the other hand, when manufacturing a secondary battery having a sulfide solid electrolyte, if electrodes and other components are pressed at low pressure to avoid crushing the active material, the above-mentioned resistance-reducing effect is difficult to achieve. As such, there is room for improvement in secondary batteries having a sulfide solid electrolyte in terms of achieving both improved cycle characteristics and reduced resistance.

[0005] The present application discloses the following multiple aspects as means for solving the above problems. <Aspect 1> A secondary battery having a first electrode, an electrolyte layer, and a second electrode, wherein at least one of the first electrode and the electrolyte layer contains a sulfide solid electrolyte, and the first electrode contains an active material having voids and a perfluoropolyether represented by the following formula (1): E １ -Rf １ -R Ｆ -O-Rf ２ -E ２ (1) [In formula (1), Rf １ and Rf ２ each independently represents a C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms, 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 is a divalent fluoropolyether group.] <Aspect 2> The R Ｆ is expressed by the formula (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 Ｆａare each independently a hydrogen atom, a fluorine atom, or a chlorine atom in each occurrence; 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 1 or more; the order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula; provided that all R Ｆａ is a hydrogen atom or a chlorine atom, at least one of a, b, c, e, and f is 1 or more. Ｆａ The secondary battery of Aspect 2, wherein R is a fluorine atom. Ｆ each occurrence independently represents the following formula (2-1), (2-2), (2-3), (2-4) or (2-5): -(OC ３ F ６ ) ｄ - (OC ２ F ４ ) ｅ - (2-1) [In formula (2-1), d is an integer of 1 to 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 formula (2-2), c and d each independently represent an integer of 0 to 30, e and f each independently represent an integer of 1 to 200, the sum of c, d, e and f is an integer of 10 to 200, and the order of occurrence of each repeating unit enclosed in parentheses with the subscript c, d, e or f is arbitrary in the formula.], - (R ６ -R ７ ) ｇ - (2-3) [In formula (2-3), R ６ is OCF ２ or O.C. ２ F ４ and R ７ is O.C. ２ F４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０ and O.C. ６ F １２ or a combination of two or three groups selected from these groups, and g is an integer of 2 to 100. 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 formula (2-4), e represents an integer of 1 or more and 200 or less, a, b, c, d, and f each independently represent an integer of 0 or more and 200 or less, and the order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula.] - (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 formula (2-5), f is an integer of 1 or more and 200 or less, a, b, c, d, and e are each independently an integer of 0 or more and 200 or less, and the order of the repeating units enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula]. Ｆ is represented by the following formula (2-6): -(OCF ２ CF ２ CF ２ ) ａ -(OCF(CF ３ )CF ２ ) ｂ -(OCF ２ CF (CF ３ )) ｃ -(OCF ２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-6) [in formula (2-6), a, b, c, d, e, and f each independently represent an integer of 0 to 200, the sum of a, b, c, d, e, and f is 1 or more, and the order of the repeating units enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula]. Ｆ is represented by the following formula (2-7): -(OCF ２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-7) [in formula (2-7), d, e, and f each independently represent an integer of 0 to 200, the sum of d, e, and f is 1 or more, and the order of the repeating units enclosed in parentheses with d, e, or f is arbitrary in the formula]. １ -Rf １ and the above E ２ -Rf ２ are each independently -CF３ , -CF ２ CF ３ , and -CF ２ CF ２ CF ３ and wherein the first electrode comprises a first active material layer, and the first active material layer contains 1 volume % or more and 25 volume % or less of the perfluoropolyether. <Aspect 9> The secondary battery of any of Aspects 1 to 8, wherein the first electrode is a negative electrode, and the active material having voids contains Si or a Si alloy. <Aspect 10> The secondary battery of any of Aspects 1 to 9, wherein the first electrode comprises the sulfide solid electrolyte, the active material having voids, and the perfluoropolyether. <Aspect 11> A method for manufacturing a secondary battery, comprising: forming a first electrode mixture to obtain a first electrode; forming an electrolyte mixture to obtain an electrolyte layer; and forming a second electrode mixture to obtain a second electrode, wherein at least one of the first electrode mixture and the electrolyte mixture contains a sulfide solid electrolyte, and the first electrode mixture contains an active material having voids and a perfluoropolyether represented by the following formula (1), and wherein a pressure of more than 0 kN / cm and not more than 15 kN / cm is applied to the first electrode mixture when forming the first electrode mixture. １ -Rf １ -R Ｆ -O-Rf ２ -E ２ (1) [In formula (1), Rf １ and Rf ２ each independently represents a C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms, 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 is a divalent fluoropolyether group.

[0006] In the secondary battery of the present disclosure, excellent cycle characteristics and low resistance are likely to be compatible.

[0007] 1 shows a schematic diagram of an example of the configuration of a secondary battery.

[0008] 1. Secondary Battery Hereinafter, embodiments of the technology of the present disclosure will be described, but the technology of the present disclosure is not limited to the following embodiments. As shown in FIG. 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. Furthermore, the first electrode 10 contains an active material having voids and a perfluoropolyether represented by the following formula (1):

[0009] 1.1 First Electrode The first electrode 10 may be either 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 configurations as long as it contains an active material having voids and a predetermined perfluoropolyether and can function appropriately as a negative electrode or a positive electrode of a secondary battery.

[0010] 1.1.1 Active Material Having Porosity During the charge and discharge of a secondary battery, carrier ions are absorbed into or released from the active material, causing a change in the volume of the active material. Excessive expansion of the active material during charge or discharge may adversely affect the cycle characteristics of the battery. Forming voids in the active material is considered effective in mitigating the expansion of the active material. That is, in an active material having voids, the expansion during charge or discharge is absorbed by the voids, and the volume change is likely to be small.

[0011] Various active materials may have voids. For example, the active material may have voids due to its porous nature or due to its hollow nature. That is, the voids in the active material may exist only within the active material, may extend from the interior of the active material to the surface, or may be a mixture of voids existing only within the active material and those extending from the interior to the surface. The active material may have voids within the primary particles themselves (e.g., voids within primary particles), or may be formed by aggregating multiple primary particles to form secondary particles, with voids between the aggregated primary particles. The voids are large enough to accommodate the volume expansion of the active material. At least a portion of the voids may or may not be filled with a perfluoropolyether, as described below. The voids do not have to be minute gaps such as those used for carrier ion intercalation. Whether an active material has voids can be determined, for example, by observing the cross section of the active material using a scanning electron microscope (SEM) or the like.

[0012] The porosity of the active material is not particularly limited. For example, the porosity of the active material may be 1% or more, 2% or more, 3% or more, or 4% or more, or 60% or less, 50% or less, 40% or less, 30% or less, or 20% or less. The porosity of the active material can be determined, for example, as follows. First, a cross section of the first electrode 10 containing the active material is taken by ion milling. The cross section is then observed with an SEM to obtain a photograph of the particles. From the obtained photograph, image analysis software is used to clearly distinguish between the active material portion and the void portion in the active material, and the image is binarized. The areas of the active material portion and the void portion are determined, and the porosity (%) is calculated using the following formula. Note that the specific conditions for calculating the porosity may be, for example, the conditions specifically described in Patent Document 2 (JP 2020-087886 A). Porosity (%) = 100 × (void portion area) / ((active material portion area) + (void portion area))

[0013] The active material having voids may be either 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 having voids is a negative electrode active material, and especially when the active material having voids contains Si or a Si alloy, the effect of the technology of the present disclosure is more likely to be enhanced. Si-based active materials containing Si or a Si alloy tend to expand in volume during charging, and the presence of voids in the active material can alleviate this volume expansion. Specific examples of Si-based active materials containing Si or a Si alloy include those having a clathrate structure. Whether or not a Si-based active material has a clathrate structure can be easily determined from Raman spectroscopy, XRD, or the like. For example, a 325±10 cm －１ Maximum peak intensity I ３２５ and 205±10cm －１ Maximum peak intensity I ２０５ Relative to I ３２５ / I ２０５ If the value of the pore structure is in the range of 1.03 to 1.21, the Si-based active material may be determined to have a clathrate structure. Alternatively, the first electrode 10 may be a positive electrode, and the active material having pores may be a sulfur-based active material (such as elemental sulfur or Li ２ The positive electrode active material may be a positive electrode active material such as SiO 2 (SiO 3 , SiO 4 , SiO 5 , SiO 6 , SiO 7 , SiO 8 , SiO 9 , SiO 10 , SiO 2 , SiO 3 , SiO 4 ...

[0014] The active material having voids may be, for example, particulate. The size of the active material having voids is not particularly limited. The average particle diameter of the active material having 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, or may be 50 μm or less, 30 μm or less, 10 μm or less, or 5 μm or less. The average particle diameter of the active material is the particle diameter (median diameter) at 50% of the integrated value in the volume-based particle size distribution determined by a laser diffraction / scattering method.

[0015] 1.1.2 Perfluoropolyether (PFPE) During secondary battery manufacturing, electrodes and other components may be subjected to high-pressure pressing for purposes such as reducing the resistance of the secondary battery. In this case, the active material having the voids described above is crushed, easily eliminating the voids, and the effect of mitigating the expansion of the active material is difficult to achieve. To avoid this crushing of the active material, low-pressure pressing during secondary battery manufacturing is effective, but this tends to increase the resistance of the secondary battery. In contrast, in the secondary battery 100 disclosed herein, the first electrode 10 contains a specific perfluoropolyether (PFPE). Therefore, even when low-pressure pressing is used during secondary battery manufacturing, the lubricating effect of the PFPE tends to reduce the resistance of the first electrode 10 and the secondary battery 100.

[0016] Furthermore, according to the inventors' new findings, PFPE, due to its ether bond, is believed to have a high affinity for the surfaces of various battery materials, and is believed to be able to appropriately reside in, for example, voids between active materials or between sulfide solid electrolyte materials. This further enhances the lubricating effect of the first electrode 10, making it easier to further increase the density of the material in the first electrode 10 even when the first electrode 10 is pressed at a low pressure, and making it easier to further reduce the resistance of the first electrode 10.

[0017] The perfluoropolyether is represented by the following formula (1).

[0018] E １ -Rf １ -R Ｆ -O-Rf ２ -E ２ (1) [In formula (1), Rf １ and Rf ２ each independently represents a C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms, 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 Ｆis a divalent fluoropolyether group.

[0019] In the above formula (1), Rf １ and Rf ２ are each independently a C1-16 divalent alkylene group optionally substituted with one or more fluorine atoms.

[0020] In one aspect, the "C1-16 divalent alkylene group" in the above-mentioned C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms may be straight-chain or branched-chain, and may preferably be a straight-chain or branched-chain C1-6 alkylalkylene group, particularly a C1-3 alkylene group, and more preferably a straight-chain C1-6 alkylene group, particularly a C1-3 alkylene group.

[0021] In one embodiment, the "C1-16 divalent alkylene" in the C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms may be a straight chain or a branched chain, and is preferably a straight chain or branched chain C1-6 fluoroalkylene group, particularly a C1-3 fluoroalkylene group, and specifically, -CF ２ CH ２ - and -CF ２ CF ２ CH ２ -, and more preferably a linear C1-6 perfluoroalkylene group, particularly a C1-3 perfluoroalkylene group, specifically -CF ２ -, -CF ２ CF ２ - and -CF ２ CF ２ CF ２ - may be a group selected from the group consisting of

[0022] In the above formula (1), 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.

[0023] The above-mentioned PFPE has low reactivity with the sulfide solid electrolyte. Therefore, even when the PFPE comes into contact with the sulfide solid electrolyte, the ionic conductivity is unlikely to decrease due to the alteration or deterioration of the sulfide solid electrolyte. In particular, when the first electrode contains a PFPE having a non-polar group as a terminal group, the reaction between the PFPE and the sulfide solid electrolyte is further suppressed, and even greater effects can be expected. In this regard, the above-mentioned E １ and E ２ are each independently preferably a fluorine group. １ -Rf １ and E ２ -Rf ２ are each independently -CF ３ , -CF ２ CF ３ , and -CF ２ CF ２ CF ３ It may be a group selected from the group consisting of:

[0024] In the above formula (1), R Ｆ is independently at each occurrence a divalent fluoropolyether group.

[0025] R Ｆ is preferably represented by the formula (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 Ｆａare each independently a hydrogen atom, a fluorine atom, or a chlorine atom in each occurrence; 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 1 or more; the order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula; provided that all R Ｆａ is a hydrogen atom or a chlorine atom, then at least one of a, b, c, e and f is 1 or greater.]

[0026] R Ｆａ is preferably a hydrogen atom or a fluorine atom, and more preferably a fluorine atom.

[0027] a, b, c, d, e and f may preferably each independently be an integer of 0 to 100.

[0028] 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.

[0029] These repeating units may be linear or branched. For example, -(OC ６ F １２ )- is -(OCF ２ CF ２ CF ２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ CF ２ CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )CF ２ CF２ ) -, -(OCF ２ CF ２ CF ２ CF (CF ３ )CF ２ )-, and -(OCF ２ CF ２ CF ２ CF ２ CF (CF ３ ))-. ５ F １０ )- is -(OCF ２ CF ２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )CF ２ )-, and -(OCF ２ CF ２ CF ２ CF (CF ３ ))-. ４ F ８ )- is -(OCF ２ CF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ CF ２ ) -, -(OCF ２ CF (CF ３ )CF ２ ) -, -(OCF ２ CF ２ CF (CF ３ )) -, -(OC(CF ３ ) ２ CF ２ ) -, -(OCF ２ C (CF ３ ) ２ )-,-(OCF(CF３ )CF(CF ３ ))-,-(OCF(C ２ F ５ )CF ２ )-, and -(OCF ２ CF (C ２ F ５ ))-. ３ F ６ ) - (i.e., in the above formula (2), R Ｆａ is a fluorine atom), -(OCF ２ CF ２ CF ２ )-,-(OCF(CF ３ )CF ２ )-, and -(OCF ２ CF (CF ３ ))-. ２ F ４ )- is -(OCF ２ CF ２ )-, and -(OCF(CF ３ ))-.

[0030] In one embodiment, R Ｆ may be, independently in each occurrence, a group represented by any one of the following formulas (2-1) to (2-5):

[0031] - (OC ３ F ６ ) ｄ - (OC ２ F ４ ) ｅ - (2-1) [In formula (2-1), d is an integer of 1 to 200, and e is 0 or 1.]

[0032] - (OC ４ F ８ ) ｃ - (OC ３ F ６ ) ｄ - (OC ２ F ４ ) ｅ -(OCF ２ ) ｆ- (2-2) [In formula (2-2), c and d each independently represent an integer of 0 or more and 30 or less, e and f each independently represent 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 occurrence of each repeating unit enclosed in parentheses with the subscript c, d, e, or f is arbitrary in the formula.],

[0033] - (R ６ -R ７ ) ｇ - (2-3) [In formula (2-3), R ６ is OCF ２ or O.C. ２ F ４ and R ７ is O.C. ２ F ４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０ and O.C. ６ F １２ or a combination of two or three groups selected from these groups, and g is an integer from 2 to 100;

[0034] - (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 formula (2-4), e represents an integer of 1 or more and 200 or less, a, b, c, d, and f each independently represent an integer of 0 or more and 200 or less, and the order of the repeating units enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula.]

[0035] - (OC６ 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 formula (2-5), f represents an integer of 1 or more and 200 or less, a, b, c, d, and e each independently represent an integer of 0 or more and 200 or less, and the order of the repeating units enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula.]

[0036] In the above formula (2-1), d is preferably an integer of 5 to 200, more preferably 10 to 100, and even more preferably 15 to 50, for example, an integer of 25 to 35. The above formula (2-1) is preferably -(OCF ２ CF ２ CF ２ ) ｄ -, or -(OCF(CF ３ )CF ２ ) ｄ -, and more preferably -(OCF ２ CF ２ CF ２ ) ｄ In one embodiment, e is 0. In another embodiment, e is 1.

[0037] In the formula (2-2), e and f are each independently an integer of preferably 5 to 200, more preferably 10 to 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 aspect, the formula (2-2) is preferably -(OCF ２ CF ２ CF ２ CF ２ ) ｃ -(OCF２ CF ２ CF ２ ) ｄ -(OCF ２ CF ２ ) ｅ -(OCF ２ ) ｆ In another embodiment, formula (2-2) is a group represented by -(OC ２ F ４ ) ｅ -(OCF ２ ) ｆ It may be a group represented by -.

[0038] In the above formula (2-3), R ６ is preferably OC ２ F ４ In the above (2-3), R ７ is preferably OC ２ F ４ , O.C. ３ F ６ and O.C. ４ F ８ or a combination of two or three groups independently selected from these groups, more preferably OC ３ F ６ and O.C. ４ F ８ is a group selected from ２ F ４ , O.C. ３ F ６ and O.C. ４ F ８ The combination of two or three groups independently selected from the group consisting of, but not limited to, —OC ２ F ４ O.C. ３ F ６ -, -OC ２ F ４ O.C. ４ F ８ -, -OC ３ F ６ O.C. ２ F ４ -, -OC ３ F ６ O.C. ３ F ６ -, -OC ３ F６ OC ４ F ８ -, -OC ４ F ８ OC ４ F ８ -, -OC ４ F ８ OC ３ F ６ -, -OC ４ F ８ OC ２ F ４ -, -OC ２ F ４ OC ２ F ４ OC ３ F ６ -, -OC ２ F ４ OC ２ F ４ OC ４ F ８ -, -OC ２ F ４ OC<00​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​４ O.C. ２ F ４ In the above formula (2-3), g is preferably an integer of 3 or more, more preferably an integer of 5 or more. The above g is preferably an integer of 50 or less. In the above formula (2-3), OC ２ F ４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０、 and O.C. ６ F １２ may be either a straight chain or a branched chain, and is preferably a straight chain. In this embodiment, the above formula (2-3) is preferably -(OC ２ F ４ -OC ３ F ６ ) ｇ -, or - (OC ２ F ４ -OC ４ F ８ ) ｇ - is.

[0039] In the above formula (2-4), e is preferably an integer of 1 or more and 100 or less, more preferably an integer of 5 or more and 100 or less. 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.

[0040] In the above formula (2-5), f is preferably an integer of 1 or more and 100 or less, more preferably an integer of 5 or more and 100 or less. 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.

[0041] In one embodiment, the R Ｆ is a group represented by the above formula (2-1).

[0042] In one embodiment, the R Ｆ is a group represented by the above formula (2-2).

[0043] In one embodiment, the R Ｆ is a group represented by the above formula (2-3).

[0044] In one embodiment, the R Ｆ is a group represented by the above formula (2-4).

[0045] In one embodiment, the R Ｆ is a group represented by the above formula (2-5).

[0046] R Ｆ In the formula, 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, the lubricity and chemical stability are further improved. The smaller the e / f ratio, the more 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 increased. The larger the e / f ratio, the more the stability of the fluoropolyether structure is improved. In this case, the value of f is preferably 0.8 or more.

[0047] In one embodiment, the R Ｆ is represented by the following formula (2-6): -(OCF ２ CF ２ CF ２ ) ａ -(OCF(CF ３ )CF ２ ) ｂ -(OCF ２ CF (CF ３ )) ｃ -(OCF ２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-6) [In formula (2-6), a, b, c, d, e, and f each independently represent an integer of 0 to 200, the sum of a, b, c, d, e, and f is 1 or more, and the order of the repeating units enclosed in parentheses after a, b, c, d, e, or f is arbitrary in the formula.]

[0048] In one embodiment, the R Ｆ is represented by the following formula (2-7): -(OCF２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-7) [In formula (2-7), d, e, and f each independently represent an integer of 0 to 200, the sum of d, e, and f is 1 or more, and the order of the repeating units enclosed in parentheses with d, e, or f is arbitrary in the formula.]

[0049] R Ｆ In the formula, the ratio of d to f (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, the lubricity and chemical stability are further improved. The smaller the d / f ratio, the more 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 increased. The larger the d / f ratio, the more the stability of the fluoropolyether structure is improved. In this case, the value of f is preferably 0.8 or more.

[0050] In the above fluoropolyether group-containing compound, R Ｆ The number average molecular weight of the portion 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. Ｆ The number average molecular weight of １９ The value is measured by F-NMR.

[0051] The content of PFPE in the first electrode 10 is not particularly limited and can be appropriately selected depending on the desired performance. In particular, when the first electrode 10 has a first active material layer 11 described below, a higher effect is likely to be obtained when the first active material layer 11 contains the PFPE in an amount of 1 vol% or more and 25 vol% or less. The first active material layer 11 may contain the PFPE in an amount of, for example, 1 vol% or more, 3 vol% or more, 5 vol% or more, 7 vol% or more, 8 vol% or more, 9 vol% or more, 10 vol% or more, 11 vol% or more, or 12 vol% or more, and 25 vol% or less, 24 vol% or less, 22 vol% or less, 20 vol% or less, 18 vol% or less, 16 vol% or less, 14 vol% or less, or 12 vol% or less.

[0052] The volume fraction of PFPE in the first active material layer 11 is measured as follows. That is, the volume of the first active material layer 11 is measured in advance using an optical microscope or SEM. The PFPE content volume may be determined by washing the first active material layer 11 with a solvent (one that can dissolve PFPE but does not dissolve other electrode materials), recovering the filtrate in which PFPE has been dissolved by suction filtration or the like, and analyzing the recovered solvent by GC-MS. Alternatively, if the solvent has a boiling point significantly different from that of PFPE, the PFPE may be extracted by distillation, and the volume of the PFPE may be measured directly. This allows the volume fraction of PFPE relative to the previously measured volume of the first active material layer 11 to be calculated.

[0053] 1.1.3 First Active Material Layer As shown in FIG. 1 , the first electrode 10 may include a first active material layer 11 and a first current collector 12. In this case, the first active material layer 11 may contain the above-described active material having voids and a predetermined 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.

[0054] The negative electrode active material layer contains at least a negative electrode active material and may further contain, optionally, an electrolyte, a conductive additive, a binder, and the like. 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 may be appropriately determined depending on the desired battery performance. For example, the total solid content of the negative electrode active material layer is taken as 100% by mass, and the content of the 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 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, the total content of the negative electrode active material layer may be taken as 100% by volume, and the negative electrode active material, optionally the electrolyte, the conductive additive, the binder, and the PFPE may be 85% by volume or more, 90% by volume or more, or 95% by volume or more, with the remainder being voids or other components. The shape of the negative electrode active material layer is not particularly limited, and may be, for example, a substantially flat sheet-like negative electrode active material layer. 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, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0055] As the negative electrode active material, various substances can be used that have a potential (charge / discharge potential) at which a predetermined carrier ion (e.g., lithium ion) is absorbed and released that is lower in potential than the positive electrode active material described below. For example, the negative electrode active material may be at least one selected from Si-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, and the like. In particular, as described above, when the negative electrode active material is a Si-based active material containing Si or a Si alloy, the technology of the present disclosure is more likely to achieve a higher effect. The negative electrode active material may be used alone or in combination of two or more.

[0056] The shape of the negative electrode active material may be any shape commonly used for negative electrode active materials in batteries. As described above, the negative electrode active material may be, for example, particulate. As described above, the negative electrode active material may have voids, for example, may be porous or hollow. When an active material having voids is included as the positive electrode active material described below, the negative electrode active material may have voids, may not have voids, or may be a combination of voids and non-voids. 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 be made of a sheet of negative electrode active material.

[0057] The electrolyte that can be contained in the negative electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolytic solution), or a combination thereof. In particular, when the negative electrode active material layer contains at least a solid electrolyte as the electrolyte, particularly when the negative electrode active material layer does not contain any liquid other than the PFPE, a higher effect is likely to be obtained. Furthermore, when the first electrode 10 contains a sulfide solid electrolyte, the active material having the voids, and the PFPE (for example, when the first active material layer 11 contains a sulfide solid electrolyte, the active material having the voids, and the PFPE), a higher effect is likely to be obtained.

[0058] The solid electrolyte may be any known solid electrolyte for 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－Ｘ (P.O. ４ ) ３ oxide solid electrolytes such as Li—SiO-based glass and Li—Al—S—O-based glass; Li ２ S-P ２ S ５ , Li ２ S-SiS ２ , LiI-Li ２ S-SiS ２ , LiI-Si ２ S-P２ S ５ , Li ２ S-P ２ S ５ -LiI-LiBr, LiI-Li ２ S-P ２ S ５ , LiI-Li ２ S-P ２ O ５ , LiI-Li ３ P.O. ４ -P ２ S ５ , Li ２ S-P ２ S ５ -GeS ２ Examples of sulfide solid electrolytes include sulfide solid electrolytes such as those described above. 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, particulate. Only one type of solid electrolyte may be used alone, or two or more types may be used in combination.

[0059] 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 of a known electrolyte for a secondary battery. For example, the electrolyte may be a solution in which a lithium salt is dissolved in a carbonate-based solvent at a predetermined concentration. Examples of carbonate-based solvents include fluoroethylene carbonate (FEC), ethylene carbonate (EC), and dimethyl carbonate (DMC). Examples of lithium salts include LiPF ６ etc.

[0060] Examples of conductive additives that can be contained in the negative electrode active material layer include carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, aluminum, and stainless steel. The conductive additive may be, for example, particulate or fibrous, and its size is not particularly limited. Only one type of conductive additive may be used alone, or two or more types may be used in combination.

[0061] Examples of binders that can be contained in the negative electrode active material layer include butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. Only one type of binder may be used alone, or two or more types may be used in combination.

[0062] 1, the first electrode 10 may include 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.

[0063] Any of the common negative electrode current collectors for batteries can be used as the negative electrode current collector. The negative electrode current collector may be in the form of a foil, plate, mesh, punched metal, foam, or the like. The negative electrode current collector may be a metal foil or metal mesh, or a carbon sheet. Metal foil is particularly advantageous in terms of ease of handling. The negative electrode current collector may be composed 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, stainless steel, and the like. In particular, from the viewpoint of ensuring reduction resistance and being less likely to alloy 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 a coating layer on its surface for purposes such as adjusting resistance. The negative electrode current collector may also be a metal foil or a substrate plated or vapor-deposited with the above metal. In addition, when the negative electrode current collector is made of multiple metal foils, some layer may be present 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 or 1 μm or more, or may be 1 mm or less or 100 μm or less.

[0064] 1.2 Electrolyte Layer The electrolyte layer 20 is disposed 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 further contain, optionally, a binder or the like. The electrolyte layer 20 may further contain other components such as a dispersant or the above-mentioned PFPE. The content of each component in the electrolyte layer 20 is not particularly limited and may be determined appropriately depending on the desired battery performance. The shape of the electrolyte layer 20 is not particularly limited and may be, for example, a sheet-like shape having 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, and may be 2 mm or less or 1 mm or less.

[0065] 1.2.1 Electrolyte The electrolyte contained in the electrolyte layer 20 may be appropriately selected from the electrolytes exemplified above as electrolytes that can be contained in the negative electrode active material layer. In particular, the electrolyte layer 20 containing a solid electrolyte, particularly a sulfide solid electrolyte, and even more particularly a sulfide solid electrolyte containing at least Li, S, and P as constituent elements, exhibits high performance. When the electrolyte is a solid electrolyte, the solid electrolyte may be amorphous or crystalline. When the electrolyte is a solid electrolyte, the solid electrolyte may be, for example, particulate. Only one type of electrolyte may be used alone, or two or more types may be used in combination.

[0066] 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 can come into 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 the PFPE comes into contact with the sulfide solid electrolyte, alteration or deterioration of the sulfide solid electrolyte is unlikely to occur, and the high ionic conductivity of the sulfide solid electrolyte is likely to be maintained.

[0067] 1.2.2 Binder The binder that can be contained in the electrolyte layer 20 may be appropriately selected from, for example, the binders that can be contained in the negative electrode active material layer described above.

[0068] 1.3 Second Electrode 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 any electrode that can appropriately function as a positive electrode or a negative electrode of a secondary battery, and its configuration is not particularly limited.

[0069] 1.3.1 Second Active Material Layer As shown in FIG. 1 , 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 or may not contain the above-mentioned predetermined PFPE. When 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. 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.

[0070] The positive electrode active material layer contains at least a positive electrode active material. The positive electrode active material layer may optionally contain an electrolyte, a conductive additive, a binder, and the like. Furthermore, 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 may be appropriately determined depending on the desired battery performance. For example, the total solid content of the positive electrode active material layer may be 100% by mass, and the content of the 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 100% by mass or less, 95% by mass or less, or 90% by mass or less. Alternatively, the total content of the positive electrode active material layer may be 100% by volume, and the positive electrode active material, optionally the electrolyte, the conductive additive, the binder, and the PFPE may be 85% by volume or more, 90% by volume or more, or 95% by volume or more, and the remainder may be voids or other components. The shape of the positive electrode active material layer is not particularly limited, and may be, for example, 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, and may be 2 mm or less, 1 mm or less, or 500 μm or less.

[0071] As the positive electrode active material, any known positive electrode active material for secondary batteries may be used. Among known active materials, a material having a relatively noble potential (charge / discharge potential) for absorbing and releasing a predetermined carrier ion (e.g., lithium ion) can be used as the positive electrode active material, and a relatively base material can be used as the above-mentioned negative electrode active material. The positive electrode active material may be at least one selected from, for example, various lithium-containing compounds, elemental sulfur, sulfur compounds, etc. Examples of lithium-containing compounds as the positive electrode active material include lithium cobalt oxide, lithium nickel oxide, Li １±α Ni １／３ Co １／３ Mn １／３ O ２±δ , lithium manganate, spinel-based lithium compounds (Li １＋ｘ Mn ２－ｘ－ｙ M ｙ O ４ (wherein M is one or more selected from Al, Mg, Co, Fe, Ni, and Zn)), lithium titanate, lithium metal phosphate (LiMPO ４ and the like, where M is one or more selected from Fe, Mn, Co, and Ni). In particular, when the positive electrode active material contains a lithium-containing oxide containing at least Li, at least one of Ni, Co, and Mn, and O as constituent elements, a higher effect can be expected. Only one type of positive electrode active material may be used alone, or two or more types may be used in combination.

[0072] The shape of the positive electrode active material may be any shape commonly used for a positive electrode active material of a battery. As described above, the positive electrode active material may be, for example, particulate. As described above, the positive electrode active material may have voids, for example, may be porous or hollow. When an active material having voids is included as the above-mentioned negative electrode active material, the positive electrode active material may have voids, may not have voids, or may be a combination of a material having voids and a material not having voids.

[0073] A protective layer containing an ion-conductive oxide may be formed on the surface of the positive electrode active material. This makes it easier to suppress the reaction between the positive electrode active material and a sulfide (for example, the above-mentioned sulfide solid electrolyte). Examples of the ion-conductive oxide include Li ３ BO ３ , LiBO ２ , Li ２ CO ３ , LiAlO ２ , Li ４ SiO ４ , Li ２ SiO ３ , Li ３ P.O. ４ , Li ２ SO ４ , Li ２ TiO ３ , Li ４ Ti ５ O １２ , Li ２ Ti ２ O ５ , Li ２ ZrO ３ , LiNbO ３ , Li ２ MoO ４ , Li ２ WO ４ and the like. The ion conductive oxide may be one in which some elements are substituted with a doping element such as P or B. The coverage (area ratio) of the protective layer with respect to 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, and may be 100 nm or less, or 20 nm or less.

[0074] The electrolyte that can be contained in the positive electrode active material layer may be a solid electrolyte, a liquid electrolyte (electrolytic solution), or a combination thereof. In particular, when the positive electrode active material layer contains at least a solid electrolyte as the electrolyte, a higher effect is likely to be obtained. The positive electrode active material layer may contain a solid electrolyte, particularly a sulfide solid electrolyte, and further, a sulfide solid electrolyte containing Li, S, and P as constituent elements. Examples of conductive additives that can be contained in the positive electrode active material layer include the above-mentioned carbon materials and the above-mentioned metal materials. The binder that can be contained in the positive electrode active material layer may be appropriately selected from, for example, the binders that can be contained in the above-mentioned negative electrode active material layer.

[0075] 1, the second electrode 30 may include 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.

[0076] Any common positive electrode current collector for a battery can be used as the positive electrode current collector. The positive electrode current collector may be in the form of a foil, plate, mesh, punched metal, foam, or the like. The positive electrode current collector may be composed of a metal foil or metal mesh. Metal foil is particularly easy to handle. The positive electrode current collector may be composed of multiple foils. Examples of metals that may be used to compose the positive electrode current collector include Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, stainless steel, and the like. In particular, the positive electrode current collector may contain Al from the viewpoint of ensuring oxidation resistance. The positive electrode current collector may have a coating layer on its surface for the purpose of adjusting resistance, etc. The positive electrode current collector may also be a metal foil or a substrate plated or vapor-deposited with the above metal. When the positive electrode current collector is composed of multiple metal foils, some layer may be present between the multiple metal foils. The thickness of the positive electrode current collector is not particularly limited. For example, it may be 0.1 μm or more or 1 μm or more, and may be 1 mm or less or 100 μm or less.

[0077] 1.4 Other Configurations The secondary battery 100 may have the above-described configurations housed inside an exterior body. Any known exterior body for a battery can be used as the exterior body. Furthermore, a plurality of secondary batteries 100 may be electrically connected and stacked in any manner to form an assembled battery. In this case, the assembled battery may be housed inside a known battery case. The secondary battery 100 may also have other obvious configurations such as necessary terminals. Examples of shapes of the secondary battery 100 include coin type, laminate type, cylindrical type, and square type.

[0078] 2. Method for Manufacturing Secondary Battery 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 method described below, and each layer may be formed by, for example, dry molding. (1) A negative electrode active material and the like that constitute 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 water or various organic solvents can be used, and N-methylpyrrolidone (NMP) can also be used. Thereafter, the negative electrode slurry is applied to the surface of the negative electrode current collector or the electrolyte layer described below using a doctor blade or the like, 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 a negative electrode. Here, the negative electrode active material layer may be press-molded. (2) A positive electrode slurry is obtained by dispersing a positive electrode active material and the like that constitute the positive electrode active material layer in a solvent. The solvent used in this case is not particularly limited, and water or various organic solvents can be used, and N-methylpyrrolidone (NMP) can also be used. Thereafter, the positive electrode slurry is applied to the surface of a positive electrode current collector or an electrolyte layer (described later) using a doctor blade or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode current collector or the electrolyte layer, thereby forming a positive electrode. Here, the positive electrode active material layer may be press-molded. (3) The layers are stacked so that the electrolyte layer is sandwiched between the negative electrode and the positive electrode, thereby obtaining a laminate having the negative electrode current collector, the negative electrode active material layer, the electrolyte layer, the positive electrode active material layer, and the 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 may be obtained by press-molding. Here, the laminate may be further press-molded. Other components such as terminals may be attached to the laminate as necessary. (4) The laminate is housed in a battery case and sealed to obtain a secondary battery.

[0079] Here, by including the PFPE in the active material layer in at least one of steps (1) and (2), the packing ratio of the active material layer can be increased even when the active material layer is press-molded at low pressure, resulting in a secondary battery with low resistance. Furthermore, by press-molding the active material layer at low pressure, crushing of the active material having voids can be easily suppressed, resulting in a secondary battery with excellent cycle characteristics. Furthermore, by including a sulfide solid electrolyte in at least one of the active material layer and the electrolyte layer in steps (1) to (3), even if the PFPE comes into contact with the sulfide solid electrolyte, a reaction between the PFPE and the sulfide solid electrolyte is unlikely to occur, and the high ionic conductivity of the sulfide solid electrolyte can be easily maintained.

[0080] The technology of the present disclosure also has an aspect as a method for manufacturing a secondary battery as follows. That is, in one embodiment, a method for manufacturing a secondary battery 100 includes: forming a first electrode composite to obtain a first electrode 10; forming an electrolyte composite to obtain an electrolyte layer 20; and forming a second electrode composite to obtain a second electrode 30; wherein at least one of the first electrode composite and the electrolyte composite contains a sulfide solid electrolyte, the first electrode composite contains an active material having voids and a perfluoropolyether represented by the above formula (1), and when forming the first electrode composite, a pressure of more than 0 kN / cm and not more than 15 kN / cm is applied to the first electrode composite.

[0081] The first electrode composite and the second electrode composite may contain the material constituting the negative electrode active material layer or the positive electrode active material layer described above, and the electrolyte composite may contain the material constituting the electrolyte layer described above. In the manufacturing method disclosed herein, the pressure applied when molding the first electrode composite is a low pressure of 15 kN / cm or less, thereby suppressing crushing of the active material having voids contained in the first electrode composite. Furthermore, since the first electrode composite contains a predetermined PFPE, the filling rate of the composite in the first electrode 10 is likely to be high even when the first electrode composite is pressed at a low pressure. The lower limit of the pressing pressure is not particularly limited, and may be greater than 0 kN / cm, 1 kN / cm or more, 2 kN / cm or more, 3 kN / cm or more, 4 kN / cm or more, 5 kN / cm or more, 6 kN / cm or more, 7 kN / cm or more, 8 kN / cm or more, 9 kN / cm or more, or 10 kN / cm or more. The means and method for applying pressure to the first electrode mixture are not particularly limited, and various pressure means and pressure methods such as roll press and CIP can be used.

[0082] In the above description, the unit of pressure applied to the first electrode composite is described as "kN / cm," but this is merely an example. That is, the pressure applied to the first electrode composite is not limited to linear pressure, but may be surface pressure. Even when the pressure applied to the first electrode composite is surface pressure, the surface pressure can be converted to linear pressure. The specific conversion method is not particularly limited, and the surface pressure may be converted to linear pressure by experimentally and statistically identifying the relationship between surface pressure and linear pressure through various experiments, or the surface pressure may be theoretically converted to linear pressure through 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.

[0083] 3. Supplementary Note: The technology of the present disclosure can be applied not only to lithium-ion secondary batteries, but also to secondary batteries other than lithium-ion secondary batteries (e.g., sodium-ion secondary batteries), etc. However, when the technology of the present disclosure is applied to lithium-ion secondary batteries, it is likely to exhibit even greater effects.

[0084] The technology of the present disclosure will be described in more detail below with reference to examples, but the technology of the present disclosure is not limited to the following examples.

[0085] 1. Preparation of pressed positive electrode A binder (PVdF), a conductive additive (VGCF), and a sulfide solid electrolyte (LiI-LiBr-Li ２ S-P ２ S ５ ) and a positive electrode active material (LiNi ０．８０ Co ０．１５ Mn ０．０５ O ２ The mixture was mixed using an ultrasonic homogenizer to obtain a positive electrode composite slurry. The obtained positive electrode composite slurry was applied to an Al foil and dried to obtain a positive electrode for pressing.

[0086] 2. Preparation of a pressed negative electrode A binder (PVdF), a conductive additive (VGCF), and a sulfide solid electrolyte (LiI-LiBr-Li ２ S-P ２ S ５ ), a negative electrode active material (porous Si), and optionally perfluoropolyether (PFPE) were added, and the mixture was kneaded using an ultrasonic homogenizer to obtain a negative electrode composite slurry. The obtained negative electrode composite slurry was applied to a Cu foil and dried to obtain a negative electrode for pressing. Here, by changing the amount of PFPE added, a plurality of negative electrodes for pressing with different volume fractions of PFPE in the composite were obtained. The volume fraction of PFPE in each negative electrode for pressing is as shown in Table 1 below. PFPE is a compound represented by the following formula (I) (m / n is 1.2, number average molecular weight is 5120, and terminal R is CF ３ and CF ２ CF ３ It is a liquid having a chemical structure represented by the formula (wherein hydroxypropyl methylcellulose and hydroxypropyl methylcellulose exist in an average ratio of 1:0.17).

[0087]

[0088] 3. Preparation of electrolyte layer for pressing A binder (PVdF) and a sulfide solid electrolyte (LiI-LiBr-Li ２ S-P ２ S ５The mixture was mixed using an ultrasonic homogenizer to obtain an electrolyte mixture slurry. The obtained electrolyte mixture slurry was applied onto an Al foil and dried to obtain an electrolyte layer for pressing.

[0089] 4. Battery Preparation The positive electrode, negative electrode, and electrolyte layer for pressing were each formed into a rectangular shape, and the composite surface of the positive electrode for pressing and the composite surface of the electrolyte layer for pressing were superimposed on each other. Then, the composite surface of the negative electrode for pressing and the composite surface of the electrolyte layer for pressing were roll-pressed at 165 ° C. and a pressure of 50 kN / cm, and the Al foil of the electrolyte layer for pressing was peeled off to obtain a laminate (A) of Al foil, a positive electrode active material layer, and an electrolyte layer. On the other hand, the composite surface of the negative electrode for pressing and the composite surface of the electrolyte layer for pressing were superimposed on each other. Then, the composite surface of the negative electrode for pressing and the composite surface of the electrolyte layer for pressing were roll-pressed at 25 ° C. and a pressure shown in Table 1 below to obtain a laminate (B) of Cu foil, a negative electrode active material layer, and an electrolyte layer by peeling off the Al foil of the electrolyte layer for pressing. The laminate (A) was punched to φ11.28 mm, and the laminate (B) was punched to φ13.00 mm. An electrolyte layer was further transferred to the laminate (B) using a uniaxial press, and the laminate (A) and the laminate (B) were then superimposed to obtain an electrode body having a 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, and the electrode body was sealed in a laminate pack using a vacuum lami-sealer to produce a battery for evaluation.

[0090] 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 resistance.

[0091] 6. Evaluation of Battery Cycle Characteristics A charge / discharge test was performed 100 times on the evaluation batteries prepared as described above, in which the batteries were charged at a constant current of 1 mA up to 4.05 V and then discharged at a constant current of 1 mA down to 1.5 V. The battery resistance before the charge / discharge test (initial resistance) and the battery resistance after the charge / discharge test were measured in the same manner as described above, and the increase rate of the battery resistance after the charge / discharge test was calculated from the ratio of the battery resistance after the charge / discharge test to the battery resistance before the charge / discharge test.

[0092] 7. Evaluation Results The results are shown in Table 1 below. Note that the configurations and preparation conditions of the positive electrode and electrolyte layer are common to the Examples and Comparative Examples, and are therefore omitted from Table 1. Furthermore, the evaluation results of the battery resistance (initial resistance) before the charge-discharge test are shown relative to the resistance value in Comparative Example 1 as the reference (100.0).

[0093]

[0094] The results shown in Table 1 reveal the following. (1) As shown in Comparative Examples 1 to 5, the lower the pressure used to mold the negative electrode, the higher the battery resistance. It is believed that lower molding pressure reduces the packing rate of the composite, resulting in an active material layer with many voids, resulting in higher battery resistance. On the other hand, the lower the pressure used to mold the negative electrode, the better the battery cycle characteristics. This is believed to be because the low molding pressure makes it difficult for the active material (porous Si) to collapse, allowing the voids to be maintained in the active material, thereby suppressing volumetric expansion of the active material during charging. (2) As shown in Comparative Examples 3 to 5 and Examples 1 to 3, when the pressure used to mold the negative electrode was the same, the battery resistance was lower when PFPE was included in the composite (Examples 1 to 3) than when PFPE was not included (Comparative Examples 3 to 5). In Examples 1 to 3, the lubricating effect of PFPE increased the fluidity of the composite when molding the negative electrode, resulting in a highly packed active material layer, which is thought to have reduced the battery resistance. (3) As shown in Examples 4 to 7, the battery resistance was reduced and the battery cycle characteristics were improved regardless of the amount (volume ratio) of PFPE added to the composite.

[0095] In the above examples, PFPE having a specific chemical structure is exemplified, but the chemical structure of PFPE is not limited to this. Furthermore, in the above examples, the active material having voids is the negative electrode active material, and PFPE is included in the negative electrode side, but the same effect can be expected even when the active material having voids is the positive electrode active material, and PFPE is included in the positive electrode side. In addition, the composite composition of the positive electrode, electrolyte layer, and negative electrode is not limited to the above.

[0096] As described above, a secondary battery having the following configurations is likely to achieve both excellent cycle characteristics and 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; and (3) The first electrode contains an active material having voids and a specified perfluoropolyether.

[0097] REFERENCE SIGNS LIST 10 First electrode 11 First active material layer 12 First current collector 20 Electrolyte layer 30 Second 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 includes a sulfide solid electrolyte; The first electrode contains an active material having voids and a perfluoropolyether represented by 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 independently represents a C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms, E １ and E ２ each independently represents 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 is a divalent fluoropolyether group.

2. The R Ｆ is expressed by the formula (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 is independently at each occurrence a hydrogen atom, a fluorine atom, or a chlorine atom; a, b, c, d, e, and f each independently represent an integer from 0 to 200; the sum of a, b, c, d, e, and f is greater than or equal to 1; The order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f in the formula is arbitrary. However, all R Ｆａ is a hydrogen atom or a chlorine atom, at least one of a, b, c, e and f is 1 or more. is a group represented by The secondary battery according to claim 1 .

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

4. The R Ｆ each occurrence independently represents the following formula (2-1), (2-2), (2-3), (2-4) or (2-5): -(OC ３ F ６ ) ｄ -(OC ２ F ４ ) ｅ - (2-1) [In formula (2-1), d is an integer of 1 to 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 formula (2-2), c and d each independently represent an integer of 0 to 30, e and f each independently represent an integer from 1 to 200; The sum of c, d, e, and f is an integer from 10 to 200, The order of occurrence of each repeat unit enclosed in parentheses with the subscript c, d, e, or f is arbitrary in the formula. -(R ６ -R ７ ) ｇ - (2-3) [In formula (2-3), R ６ is O.C.F. ２ Or O.C. ２ F ４ and R ７ , O.C. ２ F ４ , O.C. ３ F ６ , O.C. ４ F ８ , O.C. ５ F １０ and O.C. ６ F １２ or a combination of two or three groups selected from these groups, g is an integer from 2 to 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 formula (2-4), e represents an integer of 1 or more and 200 or less, a, b, c, d, and f each independently represent an integer of 0 to 200; The order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula. -(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 formula (2-5), f represents an integer of 1 or more and 200 or less, a, b, c, d, and e each independently represent an integer of 0 to 200; The order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula. is a group represented by The secondary battery according to claim 3 .

5. The R Ｆ is expressed by the following formula (2-6): -(OCF ２ CF ２ CF ２ ) ａ -(OCF(CF ３ )CF ２ ) ｂ -(OCF ２ CF(CF ３ )) ｃ -(OCF ２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-6) [In formula (2-6), a, b, c, d, e and f each independently represent an integer of 0 to 200, the sum of a, b, c, d, e, and f is greater than or equal to 1; The order of occurrence of each repeating unit enclosed in parentheses with a, b, c, d, e, or f is arbitrary in the formula. is a group represented by The secondary battery according to claim 4 .

6. The R Ｆ is expressed by the following formula (2-7): -(OCF ２ CF ２ ) ｄ -(OCF(CF ３ )) ｅ -(OCF ２ ) ｆ - (2-7) [In formula (2-7), d, e and f each independently represent an integer of 0 to 200, the sum of d, e, and f is 1 or more; The order of occurrence of each repeating unit enclosed in parentheses with d, e, or f is arbitrary in the formula. is a group represented by The secondary battery according to claim 4 .

7. The above E １ -Rf １ and the above E ２ -Rf ２ are each independently -CF ３ , -CF ２ CF ３ , and -CF ２ CF ２ CF ３ is a group selected from the group consisting of The secondary battery according to any one of claims 1 to 6.

8. the first electrode having a first active material layer; The first active material layer contains the perfluoropolyether in an amount of 1 vol % or more and 25 vol % or less. The secondary battery according to any one of claims 1 to 6.

9. The first electrode is a negative electrode, The active material having the voids contains Si or a Si alloy. The secondary battery according to any one of claims 1 to 6.

10. The first electrode includes the sulfide solid electrolyte, the active material having the voids, and the perfluoropolyether. The secondary battery according to any one of claims 1 to 6.

11. A method for manufacturing a secondary battery, comprising: shaping the first electrode mixture to obtain a first electrode; shaping the electrolyte mixture to obtain an electrolyte layer; and shaping the second electrode mixture to obtain a second electrode; Including, At least one of the first electrode mixture and the electrolyte mixture contains a sulfide solid electrolyte; The first electrode mixture contains an active material having voids and a perfluoropolyether represented by the following formula (1), When forming the first electrode mixture, a pressure of more than 0 kN / cm and not more than 15 kN / cm is applied to the first electrode mixture. Manufacturing method. E １ -Rf １ -R Ｆ -O-Rf ２ -E ２ (1) [In formula (1), Rf １ and Rf ２ each independently represents a C1-16 divalent alkylene group optionally substituted by one or more fluorine atoms, E １ and E ２ each independently represents 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 is a divalent fluoropolyether group.