Non-aqueous electrolyte, and energy storage device comprising the non-aqueous electrolyte

Abstract

To suppress a fluoride ion from being residual in a power storage device, the power storage device comprising a non-aqueous electrolyte containing lithium salt containing fluorine as electrolyte salt.SOLUTION: A non-aqueous electrolyte is used for a power storage device. The non-aqueous electrolyte contains electrolyte salt which is lithium salt containing fluorine, a non-aqueous solvent which is carbonates, and a scavenger which scavenges a fluoride ion. The scavenger is a compound indicated by the following general formula (1). In the general formula (1), R1 is any one of an alkyl group, an alkenyl group and a phenyl group of which the carbon number is 6 or less and in which at least one hydrogen atom is halogen-substituted or is not halogen-substituted; and R2, R3 and R4 are any one of a methyl group, an ethyl group, an n-propyl group, an iso-propyl group and an n-butyl group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This disclosure relates to a non-aqueous electrolyte and an energy storage device comprising the non-aqueous electrolyte. [Background technology]

[0002] Patent Document 1 discloses a non-aqueous electrolyte containing an electrolyte salt and an additive which is an SO4 group-containing compound having a specific structure. In such an SO4 group-containing compound, one hydrogen atom of sulfuric acid (H2SO4) is substituted with an alkyl group, alkoxyalkyl group, aryl group, alkenyl group, alkynyl group, linear or cyclic ester group, alkylcarbonyl group, arylcarbonyl group, organic group containing a sulfur atom, organic group containing a silicon atom, organic group containing a cyano group, organic group containing a phosphorus atom, or a -P(=O)F2 group having a specific number of carbon atoms. The other hydrogen atom of sulfuric acid is a compound substituted with an alkali metal such as lithium, an alkaline earth metal such as magnesium, a quaternary onium, or a silyl group. This publication describes that, due to these chemical structural characteristics, a portion of the SO4 group-containing compound decomposes at the negative electrode to form a film, and also decomposes at the positive electrode to form a film with low electrical resistance. It is stated that this significantly improves the electrochemical properties of energy storage devices over a wide temperature range.

[0003] Non-patent document 1 describes the mechanism by which Li2CO3 formed on the surface of layered lithium transition metal oxides decomposes. This document states that hydrogen fluoride generated by the reaction of a supporting salt (e.g., LiPF6) contained in the electrolyte with water or hydrogen ions decomposes Li2CO3, causing the transition metal to dissolve and potentially increasing the resistance between the positive and negative electrodes. The document also states that hydrogen fluoride can increase resistance by dissolving an aluminum current collector.

[0004] Non-patent document 2 describes that when high voltage is applied to the positive electrode of a lithium-ion battery, a reaction can occur in the cathode-electrolyte interphase in which the solvent decomposes, producing water and hydrogen fluoride. This document further states that hydrogen fluoride can attack both the positive and negative electrodes, potentially causing the dissolution of transition metals from the positive electrode and deterioration of the SEI film on the negative electrode. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2015-159120 [Non-patent literature]

[0006] [Non-Patent Document 1] Freiberg,et.al.,Electrochimica.Acta.,2020,346,136271 [Non-Patent Document 2] Yu,et.al.,Electrochem.Commun.,2022,138,107286 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Incidentally, the inventors of this invention want to suppress the residual presence of fluoride ions in an energy storage device that includes a non-aqueous electrolyte containing a lithium salt containing fluorine as the electrolyte salt. [Means for solving the problem]

[0008] The non-aqueous electrolyte disclosed herein is used in energy storage devices. The non-aqueous electrolyte comprises an electrolyte salt which is a lithium salt containing fluorine, a non-aqueous solvent which is a carbonate, and a scavenger which captures fluoride ions. The scavenger is a compound shown in the following general formula (1).

[0009] [ka]

[0010] In the above general formula (1), R1 is one of an alkyl group, alkenyl group, or phenyl group having 6 or fewer carbon atoms and at least one hydrogen atom substituted with a halogen or unsubstituted with a halogen; R2, R3, and R4 are one of a methyl group, ethyl group, n-propyl group, iso-propyl group, and n-butyl group. With this configuration, it is possible to suppress the residual fluoride ions in an energy storage device equipped with a non-aqueous electrolyte containing a lithium salt containing fluorine.

[0011] In one preferred embodiment of the non-aqueous electrolyte disclosed herein, R2, R3, and R4 in general formula (1) are all methyl groups. With this configuration, the steric hindrance of the scavenger can be reduced. Therefore, the effect of suppressing the residual fluoride ions in the non-aqueous electrolyte can be enhanced.

[0012] In one preferred embodiment of the non-aqueous electrolyte disclosed herein, R1 in general formula (1) comprises at least one halogen atom. With this configuration, the ester group is more easily detached from the silicon atom due to the electron-withdrawing effect of the halogen atom. This enhances the effect of suppressing the residual fluoride ions in the non-aqueous electrolyte.

[0013] In one preferred embodiment of the non-aqueous electrolyte disclosed herein, the scavenger is trimethylsilyl acetate, trimethylsilyl propionate, triisopropylsilyl acrylate, or trimethylsilyl trifluoroacetate. Such compounds are suitable for achieving an effect of suppressing the residual fluoride ions in the non-aqueous electrolyte.

[0014] In a preferred embodiment, the non-aqueous electrolyte disclosed herein contains a scavenger at 0.1 M or more. According to such a configuration, the remaining amount of fluoride ions in the non-aqueous electrolyte can be appropriately reduced.

[0015] Also, according to the technology disclosed herein, an electric storage device is disclosed that includes an electrode body, the non-aqueous electrolyte described above, and a battery case that houses the electrode body and the non-aqueous electrolyte. In the electric storage device having such a configuration, since the above-described non-aqueous electrolyte is provided, a decrease in battery performance is suppressed.

Brief Description of the Drawings

[0016] [Figure 1] FIG. 1 is a longitudinal sectional view of the electric storage device 100. [Figure 2] FIG. 2 is a schematic diagram of the electrode body 20.

Modes for Carrying Out the Invention

[0017] Hereinafter, an embodiment of the non-aqueous electrolyte disclosed herein and an electric storage device including the non-aqueous electrolyte will be described. The embodiments described herein are not intended to particularly limit the technology disclosed herein. The technology disclosed herein is not limited to the embodiments described herein unless otherwise specifically mentioned. The drawings are schematically drawn and do not necessarily reflect the actual objects. Also, members and parts having the same function are appropriately assigned the same reference numerals, and duplicate descriptions are omitted. Also, the notation "A~B" indicating a numerical range means "A or more and B or less" and also includes the meaning of "exceeding A and less than B" unless otherwise specifically mentioned.

[0018] In this specification, the "power storage device" refers to a device in which a charge carrier moves between a pair of electrodes (a positive electrode and a negative electrode) through an electrolyte, thereby causing a charge-discharge reaction. Such power storage devices include secondary batteries such as lithium-ion secondary batteries, nickel-metal hydride batteries, and nickel-cadmium batteries; capacitors such as lithium-ion capacitors and electric double-layer capacitors. Hereinafter, as an example of the above-described power storage device, embodiments in the case of a lithium-ion secondary battery will be described.

[0019] FIG. 1 is a longitudinal sectional view of the power storage device 100. FIG. 2 is a schematic view of the electrode body 20. As shown in FIG. 1, the power storage device 100 includes an electrode body 20, a battery case 30, and a non-aqueous electrolyte 80.

[0020] As shown in FIGS. 1 and 2, the electrode body 20 is a wound electrode body in which a long sheet-like positive electrode sheet 50 and a long sheet-like negative electrode sheet 60 are overlapped with a long sheet-like separator 70 interposed therebetween and wound in the sheet longitudinal direction (hereinafter, also simply referred to as the "longitudinal direction"). In the electrode body 20, an exposed region 52a on the positive electrode sheet 50 and an exposed region 62a on the negative electrode sheet 60 protrude outward from both ends in the short direction orthogonal to the longitudinal direction.

[0021] As shown in FIGS. 1 and 2, the positive electrode sheet 50 includes a long sheet-like positive electrode current collector foil 52 and a positive electrode active material layer 54. The positive electrode current collector foil 52 is, for example, an aluminum foil. In this embodiment, the positive electrode current collector foil 52 has a region where the positive electrode active material layer 54 is provided and an exposed region 52a where the surface of the positive electrode current collector foil 52 is exposed without the positive electrode active material layer 54. The positive electrode active material layer 54 is provided in a strip shape along the longitudinal direction on one side or both sides (here, both sides) of the positive electrode current collector foil 52. The positive electrode active material layer 54 is not provided at the end in the short direction (the left end in the figure). The exposed region 52a is a strip-shaped region at the end in the short direction (the left end in the figure). As shown in FIG. 1, a current collector plate 42a is attached to the exposed region 52a.

[0022] The positive electrode active material layer 54 contains, for example, a positive electrode active material. The positive electrode active material may be, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNiO2, LiCoO2, LiFeO2, LiMn2O4, LiNi 0.5 Mn 1.5 Examples include lithium transition metal oxides such as O4; lithium transition metal phosphate compounds such as LiFePO4; and so on. The positive electrode active material layer 54 may contain conductive materials, binders, etc., in addition to the positive electrode active material. Examples of conductive materials include carbon black such as acetylene black (AB); and other carbon materials such as graphite. Examples of binders include polyvinylidene fluoride (PVDF).

[0023] As shown in Figures 1 and 2, the negative electrode sheet 60 comprises a long, sheet-like negative electrode current collector foil 62 and a negative electrode active material layer 64. The negative electrode current collector foil 62 is, for example, copper foil. In this embodiment, the negative electrode current collector foil 62 has a region on which the negative electrode active material layer 64 is provided and an exposed region 62a where the negative electrode active material layer 64 is not provided and its surface is exposed. The negative electrode active material layer 64 is provided, for example, in a strip shape along the longitudinal direction on one or both sides (here, both sides) of the negative electrode current collector foil 62. The negative electrode active material layer 64 is not provided at the ends in the short direction perpendicular to the longitudinal direction (the right end in the figures). The exposed region 62a is, here, a strip-shaped region at the end in the short direction (the right end in the figures). As shown in Figure 1, a current collector plate 44a is attached to the exposed region 62a.

[0024] The negative electrode active material layer 64 contains, for example, a negative electrode active material. Examples of negative electrode active materials include carbon materials such as graphite, hard carbon, and soft carbon. In addition to the negative electrode active material, the negative electrode active material layer 64 may also contain a binder, a thickener, etc. Examples of binders include styrene-butadiene rubber (SBR). Examples of thickeners include carboxymethylcellulose (CMC).

[0025] Examples of separators 70 include porous sheets (films) made of resin materials such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide. Such porous sheets may have a single-layer structure or a laminated structure of two or more layers (for example, a three-layer structure in which PP layers are laminated on both sides of a PE layer). A heat-resistant layer (HRL) may be provided on the surface of the separator 70.

[0026] The battery case 30 is, for example, an outer container that houses the electrode body 20 and the non-aqueous electrolyte 80. In this case, the battery case 30 is a flat, rectangular case. As shown in Figure 1, the battery case 30 has a positive electrode terminal 42, a negative electrode terminal 44, a safety valve 36, and an electrolyte injection hole (not shown). The positive electrode terminal 42 is, for example, an external connection terminal on the positive electrode side. In this case, the positive electrode terminal 42 is electrically connected to the positive electrode sheet 50 of the electrode body 20 via a current collector plate 42a. The negative electrode terminal 44 is, for example, an external connection terminal on the negative electrode side. In this case, the negative electrode terminal 44 is electrically connected to the negative electrode sheet 60 of the electrode body 20 via a current collector plate 44a. The safety valve 36 is, for example, a thin-walled portion that is set to release internal pressure when the internal pressure of the battery case 30 rises above a predetermined level. The injection port is, for example, a point from which a non-aqueous electrolyte 80 is injected into the battery case 30.

[0027] The non-aqueous electrolyte 80 includes, for example, an electrolyte salt, a non-aqueous solvent, and a scavenger. The electrolyte salt in this case is a lithium salt containing fluorine. Examples of such electrolyte salts include LiPF6, LiBF4, lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethane)sulfonimide (LiTFSI). These can be used individually or in combination of two or more. LiPF6 can be preferably used as the electrolyte salt. The concentration of the electrolyte salt in the non-aqueous electrolyte 80 is not particularly limited, but is preferably 0.7 mol / L or more and 1.3 mol / L or less.

[0028] The non-aqueous solvent may be, for example, a carbonate. Examples of carbonates include ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), monofluoroethylene carbonate (MFEC), difluoroethylene carbonate (DFEC), monofluoromethyldifluoromethyl carbonate (F-DMC), trifluorodimethyl carbonate (TFDMC), and the like. These can be used individually or in combination of two or more. The carbonates preferably contain at least one of EC, DMC, and EMC. More preferably, the carbonates are a mixed solvent containing at least two of EC, DMC, and EMC.

[0029] The scavenger is, for example, a compound that can capture fluoride ions. Preferably, the scavenger is a compound represented by the following general formula (1).

[0030] [ka]

[0031] In general formula (1), R1 may be, for example, an alkyl group, an alkenyl group, or a phenyl group having 6 or fewer carbon atoms. Examples of alkyl groups include linear alkyl groups such as methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, and n-hexyl group; and branched alkyl groups such as iso-propyl group, iso-butyl group, sec-butyl group, tert-butyl group, iso-pentyl group, 1-ethylpropyl group, 3-methylbutyl group, 2,2-dimethylpropyl group, iso-hexyl group, 3-ethylbutyl group, and 3,3-dimethylbutyl group. Examples of alkenyl groups include linear alkenyl groups such as ethenyl, n-propenyl, n-butenyl, n-pentenyl, and n-hexenyl groups; and branched alkenyl groups such as iso-propenyl, iso-butenyl, sec-butenyl, iso-pentenyl, 1-ethylpropenyl, 3-methylbutenyl, 2,2-dimethylpropenyl, iso-hexenyl, 3-ethylbutenyl, and 3,3-dimethylbutenyl groups. From the viewpoint of enhancing the electron-withdrawing effect at R1 and facilitating the ester group containing R1 from the silicon atom, it is preferable that one or more hydrogen atoms in R1 are substituted with halogens (e.g., fluorine, chlorine, bromine, or iodine). Furthermore, when R1 is an alkyl group or an alkenyl group, it is preferable that the number of carbon atoms be 3 or less from the viewpoint of enhancing the electron-withdrawing effect.

[0032] In general formula (1), R2, R3, and R4 may be any one of the following, for example, CH3 (methyl group), CH2CH3 (ethyl group), CH2CH2CH3 (n-propyl group), CH(CH3)2 (iso-propyl group), and CH2CH2CH2CH3 (n-butyl group). When R2, R3, and R4 are alkyl groups as described above, the steric hindrance around the silicon atom in general formula (1) can be reduced, making it easier for fluoride ions to access the silicon atom. From this viewpoint, it is preferable that R2, R3, and R4 are alkyl groups with a small number of carbon atoms, and it is preferable that they are all methyl groups.

[0033] As scavenging agents, trimethylsilyl acetate, trimethylsilyl propionate, triisopropylsilyl acrylate, or trimethylsilyl trifluoroacetate are preferably used. Note that the scavenging agent may be used alone or in combination of two or more.

[0034] The concentration of the scavenger in the non-aqueous electrolyte 80 is not particularly limited as long as the effects of the technology disclosed herein are realized, but can generally be set to 0.01 M to 10 M. From the viewpoint of sufficiently capturing fluoride ions in the non-aqueous electrolyte 80, the concentration of the scavenger is preferably 0.05 M or higher, and more preferably 0.1 M or higher. On the other hand, from the viewpoint of suppressing the deterioration of battery performance due to the scavenger, the concentration of the scavenger is preferably 7.5 M or lower, more preferably 5 M or lower, or may be 2.5 M or lower, or 2 M or lower.

[0035] As described above, the non-aqueous electrolyte 80 comprises an electrolyte salt, a non-aqueous solvent, and a scavenger. The electrolyte salt is a lithium salt containing fluorine. The non-aqueous solvent is a carbonate. The scavenger is the compound shown in the general formula (1) above. The non-aqueous electrolyte 80 having this configuration can capture fluoride ions by containing the scavenger shown in the general formula (1) above. Therefore, it is possible to suppress the residual fluoride ions in the solution. The inventors hypothesize that the mechanism by which the scavenger captures fluoride ions is shown in the following formula (X). However, it is not intended to limit the mechanism by which the effects of the technology disclosed herein are obtained to this mechanism.

[0036] [ka]

[0037] When fluoride ions are present in the non-aqueous electrolyte 80, as shown in formula (X) above, the fluoride ions approach the silicon atoms of the scavenger and bond with the silicon atoms, and the ester portion R1COO -It dissociates from the silicon atom. Since the bond between the fluoride ion and the silicon atom is a covalent bond, the fluoride ion captured by the scavenger does not dissociate into the non-aqueous electrolyte 80. In this way, the remaining of fluoride ions is suppressed in the non-aqueous electrolyte 80.

[0038] And the power storage device 100 includes an electrode body 20, a non-aqueous electrolyte 80, and a battery case 30. As described above, in the non-aqueous electrolyte 80, the remaining of fluoride ions in the liquid is suppressed. Thereby, in the power storage device 100, the occurrence of problems (for example, dissolution of the positive electrode active material, deterioration of the SEI film, etc.) that may be caused by fluoride ions is suppressed. For this reason, in the power storage device 100, the decrease in battery performance is suppressed.

[0039] The power storage device 100 can be used for various applications. Suitable applications include power sources for driving mounted on vehicles such as battery electric vehicles (BEVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs). Further, the power storage device 100 can be used as a storage battery such as a small power storage device. Further, the power storage device 100 can also be used in the form of a battery pack formed by connecting a plurality of them in series and / or in parallel.

[0040] Hereinafter, examples of the present invention will be described, but the present invention is not intended to be limited to those shown in the following examples.

[0041] <Fabrication of Lithium-Ion Secondary Battery for Evaluation> As follows, lithium-ion secondary batteries for evaluation according to Examples 1 to 9 were fabricated. - Example 1 - LiNi as the positive electrode active material 1 / 3 Co 1 / 3 Mn 1 / 3O2 (LNCM), acetylene black (AB) as a conductive material, and polyvinylidene fluoride (PVDF) as a binder were mixed with N-methylpyrrolidone (NMP) in a mass ratio of LNCM:AB:PVDF = 87:10:3 to prepare a slurry for forming the positive electrode active material layer. This slurry was applied to aluminum foil and dried. In this way, a positive electrode sheet with a positive electrode active material layer was fabricated. The dimensions of the positive electrode active material layer were 47 mm × 45 mm.

[0042] A slurry for forming the negative electrode active material layer was prepared by mixing graphite (C) as the negative electrode active material, styrene-butadiene rubber (SBR) as a binder, and carboxymethylcellulose (CMC) as a thickener with deionized water in a mass ratio of C:SBR:CMC = 98:1:1. A negative electrode sheet with a negative electrode active material layer was fabricated by applying this slurry to copper foil and drying it. The dimensions of the negative electrode active material layer were 49 mm × 47 mm.

[0043] A microporous polypropylene sheet with a thickness of 12 μm was prepared as the separator substrate. This separator substrate was processed into a bag shape. In this way, a bag-shaped separator was fabricated. The dimensions of the separator were 51 mm x 49 mm.

[0044] A positive electrode sheet was placed in a bag-shaped separator. A negative electrode sheet was placed in another bag-shaped separator. The electrode sheets placed in each bag-shaped separator were stacked so that the positive electrode active material layer and the negative electrode active material layer faced each other to create an electrode body. Current collection terminals were attached to this electrode body, and it was placed in a laminate case. Then, a non-aqueous electrolyte was poured into the laminate case, and the laminate case was heat-sealed. In this way, an evaluation lithium-ion secondary battery for Example 1 was obtained. The non-aqueous electrolyte consisted of an electrolyte salt of 1.16 M LiPF6, a mixed non-aqueous solvent containing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of EC:EMC:DMC = 3:3:4, and 1.0 M of the following formula (A): [ka] It contained a scavenger which was trimethylsilyl acetate as shown in [reference].

[0045] -Example 2- As a scavenging agent, use the following formula (B): [ka] The trimethylsilylpropionate shown was used. Aside from that, the same materials and procedures as in Example 1 were used to obtain the lithium-ion secondary battery for evaluation in Example 2.

[0046] -Example 3- As a scavenging agent, use the following formula (C): [ka] The triisopropylsilyl acrylate shown in [reference] was used. Aside from this, the same materials and procedures as in Example 1 were used to obtain the lithium-ion secondary battery for evaluation in Example 3.

[0047] -Example 4- As a scavenging agent, use the following formula (D): [ka] The trimethylsilyl trifluoroacetate shown was used. Aside from that, the same materials and procedures as in Example 1 were used to obtain the evaluation lithium-ion secondary battery for Example 4.

[0048] -Example 5- The concentration of the scavenging agent was set to 0.1 M. Aside from this, the same materials and procedures as in Example 4 were used to obtain the lithium-ion secondary battery for evaluation in Example 5.

[0049] -Example 6- The concentration of the scavenging agent was set to 2M. Aside from this, the same materials and procedures as in Example 4 were used to obtain the lithium-ion secondary battery for evaluation in Example 6.

[0050] -Example 7- The concentration of the scavenging agent was set to 5M. Aside from this, the same materials and procedures as in Example 4 were used to obtain the lithium-ion secondary battery for evaluation in Example 7.

[0051] -Example 8- As a scavenging agent, use the following formula (E): [ka] The trimethylphenyl acetate shown in [formula] was used. Except for this, the same materials and procedures as in Example 1 were used to obtain the lithium-ion secondary battery for evaluation in Example 8. Note that "Ph" in the above formula (E) represents a phenyl group.

[0052] -Example 9- No scavenging agent was used. Aside from this, the same materials and procedures as in Example 1 were used to obtain the evaluation lithium-ion secondary battery for Example 9.

[0053] <Evaluation of the effect of suppressing residual fluoride ions> For each example of lithium-ion secondary battery used for evaluation, five charge-discharge cycles were performed, each consisting of constant-current charging from 3.0V to 4.3V at a current of 1C and constant-current discharging from 4.3V to 3.0V at a current of 0.5C. Afterward, the evaluation lithium-ion secondary batteries were disassembled, and the fluoride ion concentration was measured using ion chromatography (IC). For the IC analysis, an analytical instrument (ICS-600) manufactured by Nippon Dionex Corporation was used. An acetonitrile solution containing sodium carbonate (0.1M) and sodium bicarbonate (0.1M) was used as the developing solvent. The specific procedure is as follows.

[0054] First, the negative electrode sheet was removed from the disassembled evaluation secondary battery, and a test specimen measuring 30 mm x 30 mm was obtained. Next, the test specimen was placed in a developing solution in a platinum (Pt) beaker. Then, sonication was performed for 10 minutes to detach the negative electrode active material from the negative electrode sheet and to dissolve the components into the developing solution, thereby obtaining an eluate. Next, the negative electrode active material was removed from the eluate by suction filtration. Finally, the eluate was diluted to a volume of 50 ml with the developing solution, and IC analysis was performed. The concentration (mass%) of fluoride ions in the eluate was calculated by IC analysis.

[0055] Based on the measurements obtained as described above, the effect of suppressing residual fluoride ions in the evaluation lithium-ion secondary battery was evaluated. First, the percentage of fluoride ion concentration in each example was calculated, with the fluoride ion concentration in Example 9 set to 100%. This value (%) is defined as the residual rate of fluoride ions (%) and is shown in the "Residual Rate (%)" column of Table 1. Furthermore, based on the residual rate (%) of each example, the effect of suppressing residual fluoride ions was evaluated as follows. The evaluation results are shown in the "Evaluation" column of Table 1. E (Excellent inhibitory effect): Fluoride ion residue rate is 75% or less. G (Good inhibitory effect): The residual rate of fluoride ions is greater than 75% but less than 95%. P (No inhibitory effect): Fluoride ion retention rate is 95% or higher.

[0056] [Table 1]

[0057] <Battery Performance Evaluation> For each example of evaluation lithium-ion secondary battery, five charge-discharge cycles were performed, each consisting of constant-current charging from 3.0V to 4.3V at a current of 1C and constant-current discharging from 4.3V to 3.0V at a current of 0.5C. Afterward, the capacity of the evaluation lithium-ion secondary battery was measured, and the value calculated using the following formula (P) was defined as the capacity retention rate (%) for each example. The results are shown in the "Capacity Retention Rate (%)" column of Table 1. Examples where the capacity retention rate exceeded 95% were evaluated as having "no degradation in battery performance." Formula (P): Capacity retention rate (%) = (Capacity after 5 cycles / Initial capacity) × 100

[0058] Comparing the results shown in Table 1 for Examples 1-7 with those for Examples 8 and 9, it was found that a non-aqueous electrolyte containing a lithium salt electrolyte containing fluorine, a non-aqueous solvent of the carbonate type, and a scavenger compound represented by the general formula (1) above can suppress the residue of fluoride ions in energy storage devices. Furthermore, it was found that using such a non-aqueous electrolyte can suppress the degradation of the performance of energy storage devices (for example, the effect of suppressing the decrease in capacity retention rate due to charging and discharging).

[0059] As described above, specific embodiments of the technology disclosed herein include those described in the following sections. Section 1: A non-aqueous electrolyte used in energy storage devices, An electrolyte salt which is a lithium salt containing fluorine, Carbonates are non-aqueous solvents, A scavenger that captures fluoride ions, Includes, Here, the scavenging agent is defined by general formula (1): [ka] (Here, R1 is one of an alkyl group, alkenyl group, or phenyl group having 6 or fewer carbon atoms and at least one hydrogen atom substituted with a halogen or unsubstituted with a halogen; R2, R3, and R4 are one of a methyl group, ethyl group, n-propyl group, iso-propyl group, and n-butyl group.) A non-aqueous electrolyte, which is the compound shown. Section 2: The non-aqueous electrolyte according to item 1, wherein R2, R3, and R4 in the general formula (1) are all methyl groups. Section 3: The non-aqueous electrolyte according to item 1 or 2, wherein R1 in the general formula (1) contains at least one halogen atom. Section 4: The non-aqueous electrolyte according to any one of claims 1 to 3, wherein the scavenging agent is trimethylsilyl acetate, trimethylsilyl propionate, triisopropylsilyl acrylate, or trimethylsilyl trifluoroacetate. Section 5: A non-aqueous electrolyte according to any one of items 1 to 4, comprising 0.1 M or more of the aforementioned scavenging agent. Item 6: Electrode body and A non-aqueous electrolyte as described in any one of items 1 to 5, A battery case containing the electrode body and the non-aqueous electrolyte, A power storage device equipped with the following features.

[0060] While embodiments of the technology disclosed herein have been described above, the technology disclosed herein is not intended to be limited to the embodiments described herein. The technology disclosed herein can also be implemented in other embodiments. The technology described in the claims includes various modifications and changes to the embodiments exemplified above. For example, it is possible to replace parts of the above embodiments with other modifications, and it is also possible to add other modifications to the above embodiments. Furthermore, if a technical feature is not described as essential, it may be deleted as appropriate. [Explanation of Symbols]

[0061] 20 Electrode body 30 Battery Cases 50 Positive Electrode Sheets 60 Negative Electrode Sheets 70 Separators 80 Nonaqueous electrolyte 100 Energy Storage Devices

Claims

1. A non-aqueous electrolyte used in energy storage devices, Electrolyte salts, Carbonates are non-aqueous solvents, A scavenger of 1 M or more that captures fluoride ions, Includes, The aforementioned electrolyte salt is LiPF ６ Solo, LiBF ４ Standalone, or LiPF ６ and LiBF ４ It is both, Here, the scavenging agent is defined by general formula (1): 【Chemistry 1】 (Here, R １ R is one of the following: an alkyl group having 6 or fewer carbon atoms, with at least one hydrogen atom substituted with a halogen or unsubstituted with a halogen, and a phenyl group; R ２ , R ３ , and R ４ (This is one of the following: a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, and an n-butyl group.) A non-aqueous electrolyte, which is the compound shown.

2. R in the general formula (1) ２ , R ３ , and R ４ are all methyl groups The non-aqueous electrolyte according to claim 1.

3. R in the general formula (1) １ contains at least one halogen atom, The non-aqueous electrolyte according to claim 1.

4. The aforementioned scavenger is trimethylsilyl acetate, trimethylsilyl propionate, or trimethylsilyl trifluoroacetate. The non-aqueous electrolyte according to claim 1.

5. Electrode body and The non-aqueous electrolyte according to claim 1, A battery case containing the electrode body and the non-aqueous electrolyte, A power storage device equipped with the following features.

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