Secondary battery electrolyte solution and secondary battery

Abstract

Provided is a secondary battery with which it is possible to obtain excellent battery characteristics. This secondary battery comprises a positive electrode, a negative electrode, and an electrolyte solution. The electrolyte solution contains an anisole compound represented by formula (1) and a nonaqueous solvent, and the molar ratio of the anisole compound to the nonaqueous solvent is 1.6 or more.

Description

Electrolyte for secondary battery and secondary battery

[0001] The present technology relates to an electrolyte for a secondary battery and a secondary battery.

[0002] Due to the widespread use of various electronic devices such as mobile phones, secondary batteries have been developed as small, lightweight power sources that can provide high energy density. These secondary batteries contain a positive electrode, a negative electrode, and an electrolyte solution, and various studies have been conducted on the configuration of these secondary batteries.

[0003] Specifically, the non-aqueous electrolyte solution contains a fluorine-containing organic compound, and the content of the fluorine-containing organic compound in the non-aqueous electrolyte solution is 0.01% by weight to 20% by weight (see, for example, Patent Document 1). Also, the electrolyte solution contains dimethoxyethane and anisole, and the mixture ratio (molar ratio) of the dimethoxyethane to the anisole is 1:2 (see, for example, Non-Patent Document 1).

[0004] Patent No. 4127355

[0005] Nature Communications, volume 13, Article number: 4538, 2022

[0006] Although various studies have been conducted on the configuration of secondary batteries, the battery characteristics of the secondary batteries are still insufficient and there is room for improvement.

[0007] There is a demand for an electrolyte solution for a secondary battery and a secondary battery that can provide excellent battery characteristics.

[0008] According to one embodiment of the present technology, there is provided an electrolyte solution for a secondary battery, which contains an anisole compound represented by formula (1) and a non-aqueous solvent, and the molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or more.

[0009] (R1, R2, R3, R4, and R5 each represent a hydrogen group, a halogen group, or a halogenated alkyl group, provided that at least one of R1, R2, R3, R4, and R5 represents a halogen group or a halogenated alkyl group.)

[0010] A secondary battery according to an embodiment of the present technology includes a positive electrode, a negative electrode, and an electrolyte solution, and the electrolyte solution has a configuration similar to that of the electrolyte for a secondary battery according to the embodiment of the present technology described above.

[0011] According to the secondary battery electrolyte or secondary battery of an embodiment of the present technology, the secondary battery electrolyte contains an anisole compound and a non-aqueous solvent, and the molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or more, so that excellent battery characteristics can be obtained.

[0012] Note that the effects of the present technology are not necessarily limited to the effects described here, but may be any of a series of effects related to the present technology described below.

[0013] Fig. 1 is a perspective view illustrating a configuration of a secondary battery according to an embodiment of the present technology. Fig. 2 is an enlarged cross-sectional view illustrating the configuration of a battery element illustrated in Fig. 1. Fig. 3 is a block diagram illustrating the configuration of an application example of the secondary battery.

[0014] Hereinafter, an embodiment of the present technology will be described in detail with reference to the drawings. The description will be made in the following order: 1. Electrolyte for secondary battery 1-1. Configuration 1-2. Manufacturing method 1-3. Action and effect 2. Secondary battery 2-1. Configuration 2-2. Operation 2-3. Manufacturing method 2-4. Action and effect 3. Modification 4. Use of secondary battery

[0015] 1. Electrolyte for Secondary Battery First, an electrolyte for a secondary battery (hereinafter simply referred to as "electrolyte") according to an embodiment of the present technology will be described.

[0016] This electrolytic solution is a liquid electrolyte used in a secondary battery, which is an electrochemical device. However, the electrolytic solution may also be used in other electrochemical devices. The type of other electrochemical device is not particularly limited, but specifically, it may be a capacitor or the like.

[0017] <1-1. Composition> The electrolyte solution contains a solvent and an electrolyte salt.

[0018] [Solvent] The solvent contains an anisole compound represented by formula (1) and a non-aqueous solvent. Here, the non-aqueous solvent is defined separately from the anisole compound, and therefore the anisole compound is excluded from the non-aqueous solvent.

[0019] (R1, R2, R3, R4, and R5 each represent a hydrogen group, a halogen group, or a halogenated alkyl group, provided that at least one of R1, R2, R3, R4, and R5 represents a halogen group or a halogenated alkyl group.)

[0020] (Anisole Compound) The anisole compound is a compound having an anisole-type skeleton as shown in formula (1). The type of the anisole compound may be one type or two or more types.

[0021] As described above, each of R1 to R5 is not particularly limited as long as it is any one of a hydrogen group, a halogen group, and a halogenated alkyl group. The types of R1 to R5 may be the same or different from one another. Of course, any two or more types of R1 to R5 may be the same as one another.

[0022] However, as described above, since one or more of R1 to R5 are either a halogen group or a halogenated alkyl group, the anisole compound contains one or more halogens as constituent elements. Therefore, a compound in which all of R1 to R5 are hydrogen groups, i.e., an anisole compound that does not contain one or more halogens as constituent elements, is excluded from the anisole compounds described here.

[0023] As is clear from formula (1), this anisole compound has a methoxy group (—OCH 3　 ) does not contain one or more halogens as constituent elements, but contains one or more halogens as constituent elements at a site other than the methoxy group.

[0024] The type of halogen group is not particularly limited, but specific examples include a fluorine group, a chlorine group, a bromine group, and an iodine group.

[0025] Among these, it is preferable that the halogen group contains one or both of a fluorine group and a chlorine group, because, as will be described later, a good coating containing halogen derived from the anisole compound as a constituent element is easily formed on the surface of the negative electrode, and the decomposition reaction of the electrolyte on the surface of the negative electrode is sufficiently suppressed.

[0026] A halogenated alkyl group is an alkyl group in which one or more hydrogen groups have been replaced with a halogen group, and the details of the halogen group are as described above. The alkyl group may be linear or branched with one or more side chains.

[0027] Specific examples of alkyl groups include methyl, ethyl, propyl, butyl, pentyl, and hexyl groups. However, as described above, the alkyl group may be linear or branched. Thus, for example, the propyl group may be an n-butyl group, a sec-butyl group, an isobutyl group, or a tert-butyl group.

[0028] The number of carbon atoms in the alkyl group is not particularly limited, but is preferably 5 or less, because this improves the solubility and compatibility of the anisole compound.

[0029] Specific examples of the anisole compound include compounds represented by the formulas (1-1) to (1-10).

[0030]

[0031] However, since the content of the anisole compound in the electrolyte solution is determined in relation to the content of the non-aqueous solvent in the electrolyte solution, the mixing ratio of the anisole compound to the non-aqueous solvent is determined to be within a predetermined range. The details of the mixing ratio of the anisole compound to the non-aqueous solvent described here will be described later.

[0032] In order to confirm that the electrolyte solution contains an anisole compound, the electrolyte solution is analyzed by any method, including, but not limited to, one or more of inductively coupled plasma (ICP) emission spectroscopy, nuclear magnetic resonance spectroscopy (NMR), and gas chromatography-mass spectroscopy (GC-MS).

[0033] When a secondary battery containing the electrolyte is used to analyze the electrolyte, the secondary battery is disassembled to recover the electrolyte, and the electrolyte is then analyzed, thereby identifying the type of component (anisole compound) contained in the electrolyte.

[0034] (Non-aqueous solvent) The type of non-aqueous solvent is not particularly limited as long as it is a so-called organic solvent. The type of non-aqueous solvent may be one type or two or more types. As described above, anisole compounds are excluded from the non-aqueous solvents described here.

[0035] Specifically, the non-aqueous solvent is an ester or an ether, more specifically, a carbonate ester compound, a carboxylic acid ester compound, a lactone compound, etc. This is because the dissociation property of the electrolyte salt is improved and the mobility of ions is also improved.

[0036] The carbonate ester compounds include cyclic carbonate esters and chain carbonate esters, etc. Specific examples of cyclic carbonate esters include ethylene carbonate and propylene carbonate, and specific examples of chain carbonate esters include dimethyl carbonate, diethyl carbonate and ethyl methyl carbonate.

[0037] The carboxylic acid ester compound is a chain carboxylic acid ester, etc. Specific examples of the chain carboxylic acid ester include ethyl acetate, ethyl propionate, propyl propionate, and ethyl trimethylacetate.

[0038] The lactone compound is lactone, etc. Specific examples of lactone include γ-butyrolactone and γ-valerolactone.

[0039] The ethers may be 1,2-dimethoxyethane, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, anisole, or the like.

[0040] The non-aqueous solvent may be an unsaturated cyclic carbonate, a fluorinated cyclic carbonate, a sulfonate, a phosphate, an acid anhydride, a nitrile compound, an isocyanate compound, or the like, because the electrochemical stability of the electrolyte solution is improved.

[0041] Specific examples of unsaturated cyclic carbonates include vinylene carbonate, vinylethylene carbonate, and methyleneethylene carbonate. Specific examples of fluorinated cyclic carbonates include monofluoroethylene carbonate and difluoroethylene carbonate. Specific examples of sulfonic acid esters include propane sultone and propene sultone. Specific examples of phosphate esters include trimethyl phosphate and triethyl phosphate. Specific examples of acid anhydrides include succinic anhydride, 1,2-ethanedisulfonic anhydride, and 2-sulfobenzoic anhydride. Specific examples of nitrile compounds include succinonitrile. Specific examples of isocyanate compounds include hexamethylene diisocyanate.

[0042] In particular, the non-aqueous solvent preferably contains one or both of a carbonate ester compound and an ether, because this allows a high battery capacity to be obtained in a secondary battery using the electrolyte solution.

[0043] In particular, it is preferable that the carbonate ester compound and the ethers are chain compounds rather than cyclic compounds. This is because the viscosity of the electrolyte solution is reduced and the solubility of the electrolyte salt is improved. Specific examples of carbonate ester compounds that are chain compounds include the chain carbonate esters described above, and specific examples of ethers that are chain compounds include 1,2-dimethoxyethane described above.

[0044] The method for confirming that the electrolyte contains a non-aqueous solvent is the same as the method for confirming that the electrolyte contains an anisole compound.

[0045] (Mixing Ratio) As described above, the mixing ratio of the anisole compound to the non-aqueous solvent is specified to be within a predetermined range.

[0046] Specifically, the molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or more. That is, when the content of the non-aqueous solvent in the electrolytic solution is 1 mol, the content of the anisole compound in the electrolytic solution is 1.6 mol or more.

[0047] This molar ratio is calculated based on the formula: Molar ratio = [substance amount (mol) of anisole compound / substance amount (mol) of non-aqueous solvent] x 100. However, the molar ratio value is rounded to one decimal place.

[0048] The electrolytic solution contains an anisole compound and a non-aqueous solvent, and the molar ratio is 1.6 or more because the mixing ratio of the anisole compound and the non-aqueous solvent is optimized, thereby suppressing the decomposition reaction of the electrolytic solution during charging and discharging of a secondary battery using the electrolytic solution.

[0049] Specifically, anisole compounds have the property of being less likely to coordinate with alkali metal ions than non-aqueous solvents. These alkali metal ions are alkali metal ions derived from cations contained in the electrolyte salt, more specifically, lithium ions, etc., as described below. As a result, in the electrolyte solution, non-aqueous solvents are more likely to coordinate with alkali metal ions, whereas anisole compounds are less likely to coordinate with alkali metal ions.

[0050] It is known that non-aqueous solvents coordinated with alkali metal ions are more susceptible to reductive decomposition than non-aqueous solvents not coordinated with alkali metal ions. The tendency regarding the reductive decomposition of non-aqueous solvents described here is also observed in anions contained in electrolyte salts. In contrast, anisole compounds, as described above, are less likely to coordinate with alkali metal ions and are therefore less susceptible to reductive decomposition.

[0051] Therefore, while the non-aqueous solvent and the anion are each easily reductively decomposed, the anisole compound is less susceptible to reductive decomposition. Therefore, by changing the types of the non-aqueous solvent and the anion, it is possible to adjust the electrochemical state of the coating film formed on the surface of the negative electrode, which will be described later.

[0052] Furthermore, as described above, the anisole compound contains a halogen as a constituent element. Therefore, when the anisole compound is decomposed during charging and discharging of the secondary battery, a good coating containing a halogen as a constituent element is formed on the surface of the negative electrode, and the surface of the negative electrode is electrochemically protected by the coating. As a result, even if the negative electrode has high reactivity, the decomposition reaction of the electrolyte on the surface of the negative electrode is suppressed.

[0053] For these reasons, as described above, the mixing ratio of the anisole compound and the non-aqueous solvent is optimized, and therefore the decomposition reaction of the electrolyte solution is suppressed during charging and discharging of the secondary battery using the electrolyte solution.

[0054] In particular, the molar ratio is preferably 2.0 or more, because the decomposition reaction of the electrolyte solution is further suppressed during charging and discharging of the secondary battery.

[0055] [Electrolyte Salt] The electrolyte salt contains one or more types of light metal salts such as lithium salts.

[0056] A specific example of the lithium salt is lithium hexafluorophosphate (LiPF 6　 ), lithium tetrafluoroborate (LiBF 4　 ), lithium trifluoromethanesulfonate (LiCF 3　 SO 3　 ), lithium bis(fluorosulfonyl)imide (LiN(FSO 2　 ) 2　 ), lithium bis(trifluoromethanesulfonyl)imide (LiN(CF 3　 SO 2　 ) 2　 ), lithium tris(trifluoromethanesulfonyl)methide (LiC(CF 3　 SO 2　 ) 3　), lithium bis(oxalato)borate (LiB(C 2　 O 4　 ) 2　 ), lithium monofluorophosphate (Li 2　 PFO 3　 ) and lithium difluorophosphate (LiPF 2　 O 2　 ) etc. This is because a high battery capacity can be obtained.

[0057] The content of the electrolyte salt is not particularly limited, but specifically, it is 0.3 mol / kg to 3.0 mol / kg relative to the solvent, because high ionic conductivity can be obtained.

[0058] <1-2. Manufacturing Method> When manufacturing an electrolytic solution, an electrolyte salt is added to a solvent containing an anisole compound and a non-aqueous solvent. In this case, the mixing ratio of the anisole compound and the non-aqueous solvent is adjusted so that the molar ratio falls within the above-mentioned range. As a result, the electrolyte salt is dispersed or dissolved in the solvent, and the electrolytic solution is prepared.

[0059] <1-3. Actions and Effects> According to this electrolytic solution, the electrolytic solution contains an anisole compound and a non-aqueous solvent, and the molar ratio is 1.6 or more.

[0060] In this case, as described above, the mixing ratio of the anisole compound and the non-aqueous solvent is optimized, and by utilizing the difference in properties between the anisole compound and the non-aqueous solvent, a good coating is formed on the surface of the negative electrode during charging and discharging of a secondary battery using the electrolyte. As a result, the surface of the negative electrode is electrochemically protected by the coating, and the decomposition reaction of the electrolyte on the surface of the negative electrode is suppressed. Therefore, the decomposition reaction of the electrolyte is suppressed during charging and discharging of the secondary battery, and a secondary battery with excellent battery characteristics can be realized using the electrolyte.

[0061] In particular, if the molar ratio is 2.0 or more, the decomposition reaction of the electrolyte solution during charging and discharging of the secondary battery is further suppressed, and therefore a greater effect can be obtained.

[0062] Furthermore, if the halogen group contains one or both of a fluorine group and a chlorine group, the decomposition reaction of the electrolyte solution is sufficiently suppressed, and therefore a higher effect can be obtained.

[0063] Furthermore, if the number of carbon atoms in the halogenated alkyl group is 5 or less, the solubility and compatibility of the anisole compound are improved, and therefore, a greater effect can be obtained.

[0064] Furthermore, if the non-aqueous solvent contains one or both of a carbonate ester compound and an ether, a high battery capacity can be obtained in the secondary battery, thereby achieving a greater effect. In this case, if the carbonate ester compound and the ether are each chain compounds, the viscosity of the electrolyte solution can be reduced and the solubility of the electrolyte salt can be improved, thereby achieving an even greater effect.

[0065] 2. Secondary Battery Next, a secondary battery using the above-described electrolytic solution will be described.

[0066] The secondary battery described here is a secondary battery that obtains battery capacity by utilizing the absorption and desorption of electrode reactants, and is equipped with a positive electrode, a negative electrode, and an electrolyte.

[0067] The type of electrode reactant is not particularly limited, but specifically includes light metals such as alkali metals and alkaline earth metals. Specific examples of alkali metals include lithium, sodium, and potassium, and specific examples of alkaline earth metals include beryllium, magnesium, and calcium.

[0068] In the following, we will take the case where the electrode reactant is lithium as an example. A secondary battery that obtains battery capacity by utilizing the absorption and desorption of lithium is called a lithium secondary battery (or lithium ion secondary battery). In this lithium secondary battery, lithium is absorbed and desorbed in the ionic state.

[0069] The charge capacity of the negative electrode is preferably larger than the discharge capacity of the positive electrode. That is, the electrochemical capacity per unit area of ​​the negative electrode is preferably larger than the electrochemical capacity per unit area of ​​the positive electrode. This is to prevent deposition of electrode reactants on the surface of the negative electrode during charging.

[0070] 2-1. Structure FIG. 1 shows a perspective view of the secondary battery, and FIG. 2 shows an enlarged cross-sectional view of the battery element 20 shown in FIG.

[0071] 1 shows a state in which the exterior film 10 and the battery element 20 are separated from each other, and a cross section of the battery element 20 taken along the XZ plane is shown by a broken line. In FIG. 2, only a part of the battery element 20 is shown.

[0072] As shown in FIGS. 1 and 2, this secondary battery includes an exterior film 10, a battery element 20, a positive electrode lead 31, a negative electrode lead 32, and sealing films 41 and .

[0073] As described above, the secondary battery described here uses the exterior film 10 as an exterior member for housing the battery element 20. Therefore, the secondary battery shown in Fig. 1 is a so-called laminate film type secondary battery.

[0074] 1, the exterior film 10 is a flexible or pliable exterior member, and has a sealed bag-like structure when the battery element 20 is housed therein. As a result, the exterior film 10 houses the positive electrode 21, the negative electrode 22, the separator 23, and an electrolyte solution (not shown), which will be described later.

[0075] Here, the exterior film 10 is a single film-like member that is folded in a folding direction F. The exterior film 10 is provided with a recessed portion 10U for accommodating the battery element 20, and the recessed portion 10U is a so-called deep-drawn portion.

[0076] Specifically, the exterior film 10 is a three-layer laminate film in which a fusion layer, a metal layer, and a surface protection layer are laminated in this order from the inside out, and when the exterior film 10 is folded, the outer peripheral edges of the opposing fusion layers are fused to each other. The fusion layer contains a polymer compound such as polypropylene. The metal layer contains a metal material such as aluminum. The surface protection layer contains a polymer compound such as nylon.

[0077] However, the configuration (number of layers) of the exterior film 10 is not particularly limited, and may be one layer, two layers, or four or more layers.

[0078] [Battery Element] The battery element 20 is housed in an exterior film 10. This battery element 20 is a so-called power generation element, and as shown in Figures 1 and 2, includes a positive electrode 21, a negative electrode 22, a separator 23, and an electrolyte (not shown).

[0079] Here, battery element 20 is a so-called wound electrode body, and therefore positive electrode 21 and negative electrode 22 are wound around winding axis P while facing each other with separator 23 interposed therebetween. This winding axis P is a virtual axis extending in the Y-axis direction, as shown in FIG.

[0080] There are no particular limitations on the three-dimensional shape of battery element 20. Here, battery element 20 has a flat three-dimensional shape, and therefore the shape of a cross section (cross section along the XZ plane) of battery element 20 intersecting winding axis P is a flat shape defined by major axis J1 and minor axis J2.

[0081] The major axis J1 is an imaginary axis extending in the X-axis direction and has a length greater than that of the minor axis J2. The minor axis J2 is an imaginary axis extending in the Z-axis direction intersecting the X-axis direction and has a length less than that of the major axis J1. Here, the three-dimensional shape of the battery element 20 is a flattened cylinder, and therefore the cross-sectional shape of the battery element 20 is a flattened, approximately elliptical shape.

[0082] (Positive Electrode) As shown in Fig. 2, the positive electrode 21 includes a positive electrode current collector 21A and a positive electrode active material layer 21B. However, the positive electrode current collector 21A may be omitted.

[0083] The positive electrode current collector 21A has a pair of surfaces on which the positive electrode active material layer 21B is provided. The positive electrode current collector 21A contains a conductive material such as a metal material, and a specific example of the conductive material is aluminum.

[0084] The positive electrode active material layer 21B contains one or more types of positive electrode active materials that absorb and release lithium. However, the positive electrode active material layer 21B may further contain one or more types of other materials such as a positive electrode binder and a positive electrode conductive agent. The method for forming the positive electrode active material layer 21B is not particularly limited, but specifically includes a coating method.

[0085] Here, the positive electrode active material layer 21B is provided on both sides of the positive electrode current collector 21A. However, the positive electrode active material layer 21B may be provided on only one side of the positive electrode current collector 21A, on the side where the positive electrode 21 faces the negative electrode 22.

[0086] The type of positive electrode active material is not particularly limited, but specifically includes a lithium-containing compound. This lithium-containing compound is a compound containing lithium and one or more transition metal elements as constituent elements, and may further include one or more other elements as constituent elements. The type of other element is not particularly limited as long as it is an element other than lithium and transition metal elements, but specifically includes elements belonging to Groups 2 to 15 of the long period periodic table. The type of lithium-containing compound is not particularly limited, but specifically includes oxides, phosphate compounds, silicate compounds, borate compounds, and the like.

[0087] A specific example of the oxide is LiNiO 2　 , LiCoO 2　 , LiCo 0.98 Al 0.01 Mg 0.01 O 2　 , LiNi 0.5　 Co 0.2　 Mn 0.3　 O 2　 , LiNi 0.8　 Co 0.15 Al 0.05 O 2　 , LiNi 0.33 Co 0.33 Mn 0.33 O 2　 , Li 1.2　 Mn 0.52 Co 0.175　 Ni 0.1　 O 2　 , Li 1.15(Mn 0.65 Ni 0.22 Co 0.13 ) O 2　 and LiMn 2　 O 4　 Specific examples of phosphate compounds include LiFePO 4　 , LiMnPO 4　 , LiFe 0.5　 Mn 0.5　 P.O. 4　 and LiFe 0.3　 Mn 0.7　 P.O. 4　 And so on.

[0088] The positive electrode binder contains one or more of materials such as synthetic rubber and polymer compounds. Specific examples of synthetic rubber include styrene-butadiene rubber, fluorine-containing rubber, and ethylene-propylene-diene. Specific examples of polymer compounds include polyvinylidene fluoride, polyimide, and carboxymethyl cellulose.

[0089] The positive electrode conductive agent contains one or more conductive materials such as a carbon material, a metal material, and a conductive polymer compound, and specific examples of the carbon material include graphite, carbon black, acetylene black, and ketjen black.

[0090] (Negative Electrode) The negative electrode 22 includes a negative electrode current collector 22A and a negative electrode active material layer 22B, as shown in Fig. 2. However, the negative electrode current collector 22A may be omitted.

[0091] The negative electrode current collector 22A has a pair of surfaces on which the negative electrode active material layer 22B is provided. The negative electrode current collector 22A contains a conductive material such as a metal material, and a specific example of the conductive material is copper.

[0092] The negative electrode active material layer 22B includes one or more types of negative electrode active materials that absorb and release lithium. However, the negative electrode active material layer 22B may further include one or more types of other materials, such as a negative electrode binder and a negative electrode conductive agent. The method for forming the negative electrode active material layer 22B is not particularly limited, and specifically includes one or more types of a coating method, a vapor phase method, a liquid phase method, a thermal spraying method, and a firing method (sintering method).

[0093] Here, the anode active material layer 22B is provided on both sides of the anode current collector 22A. However, the anode active material layer 22B may be provided on only one side of the anode current collector 22A on the side where the anode 22 faces the cathode 21.

[0094] The type of negative electrode active material is not particularly limited, but specific examples include carbon materials and metal-based materials, because high energy density can be obtained.

[0095] Specific examples of carbon materials include graphitizable carbon, non-graphitizable carbon, and graphite, etc. The graphite may be natural graphite, artificial graphite, or both.

[0096] Metallic materials are a general term for materials containing one or more of metal elements and semi-metal elements that can form an alloy with lithium as constituent elements, and specific examples of the metal elements and semi-metal elements include silicon and tin. This metallic material may be a simple substance, an alloy, a compound, a mixture of two or more of these, or a material containing two or more of these phases. However, the simple substance may contain any amount of impurities. A specific example of a metallic material is TiSi 2　 and SiO x　 (0<x≦2 or 0.2<x<1.4), etc.

[0097] The details regarding the negative electrode binder are the same as those regarding the positive electrode binder, and the details regarding the negative electrode conductive agent are the same as those regarding the positive electrode conductive agent.

[0098] 2, the separator 23 is an insulating porous film interposed between the positive electrode 21 and the negative electrode 22, and allows lithium to pass through in an ionic state while preventing the occurrence of a short circuit due to contact between the positive electrode 21 and the negative electrode 22. The separator 23 contains one or more insulating polymer compounds, and a specific example of the insulating polymer compound is polyethylene.

[0099] (Electrolyte) The electrolyte is impregnated into each of the positive electrode 21, the negative electrode 22, and the separator 23, and has the above-described configuration. That is, the electrolyte contains an anisole compound and a non-aqueous solvent, and the molar ratio is 1.6 or more.

[0100] 1 and 2, the positive electrode lead 31 is a positive electrode wiring connected to the positive electrode current collector 21A of the positive electrode 21, and is led out of the exterior film 10. The positive electrode lead 31 contains one or more types of conductive materials such as metal materials, and a specific example of the conductive material is aluminum. The positive electrode lead 31 has a shape such as a thin plate or a mesh.

[0101] [Negative Electrode Lead] As shown in FIGS. 1 and 2 , the negative electrode lead 32 is a negative electrode wiring connected to the negative electrode current collector 22A of the negative electrode 22, and is led out of the exterior film 10. Here, the lead-out direction of the negative electrode lead 32 is the same as the lead-out direction of the positive electrode lead 31. This negative electrode lead 32 contains one or more types of conductive materials such as metal materials, and a specific example of the conductive material is copper. Details regarding the shape of the negative electrode lead 32 are the same as the details regarding the shape of the positive electrode lead 31.

[0102] [Sealing Film] As shown in Fig. 1, the sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31. As shown in Fig. 1, the sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32. However, one or both of the sealing films 41, 42 may be omitted.

[0103] The sealing film 41 is a sealing member that prevents outside air and the like from entering the inside of the exterior film 10. This sealing film 41 contains a polymer compound such as polyolefin that has adhesiveness to the positive electrode lead 31, and a specific example of the polymer compound is polypropylene.

[0104] The configuration of the sealing film 42 is the same as the configuration of the sealing film 41, except that the sealing film 42 is a sealing member that has adhesiveness to the negative electrode lead 32. That is, the sealing film 42 contains a polymer compound such as polyolefin that has adhesiveness to the negative electrode lead 32.

[0105] <2-2. Operation> The secondary battery operates in the battery element 20 as follows.

[0106] During charging, lithium is released from the positive electrode 21 and is absorbed into the negative electrode 22 via the electrolyte. During discharging, lithium is released from the negative electrode 22 and is absorbed into the positive electrode 21 via the electrolyte. During both discharging and charging, lithium is absorbed and released in an ionic state.

[0107] <2-3. Manufacturing Method> When manufacturing a secondary battery, the positive electrode 21 and the negative electrode 22 are each produced using the procedure described below as an example, and then the secondary battery is assembled and subjected to a stabilization process after assembly.

[0108] Since the method for producing the electrolyte solution has already been described, the description of the method for producing the electrolyte solution will be omitted below.

[0109] [Preparation of Positive Electrode] First, a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent are mixed together to form a positive electrode mixture. Then, the positive electrode mixture is poured into a solvent to prepare a paste-like positive electrode mixture slurry. This solvent may be an aqueous solvent or an organic solvent.

[0110] Finally, the cathode mixture slurry is applied to both surfaces of the cathode current collector 21A to form the cathode active material layer 21B. The cathode active material layer 21B may then be compression-molded using a compression device such as a roll press. In this case, the cathode active material layer 21B may be heated, or the compression molding may be repeated multiple times. As a result, the cathode active material layer 21B is formed on both surfaces of the cathode current collector 21A, and the cathode 21 is thus fabricated.

[0111] [Fabrication of Negative Electrode] The negative electrode 22 is formed by the same procedure as the fabrication procedure for the positive electrode 21 described above. Specifically, a mixture (negative electrode mixture) of a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent is mixed together and poured into a solvent to prepare a paste-like negative electrode mixture slurry. Details regarding the solvent are as described above. Next, the negative electrode mixture slurry is applied to both surfaces of the negative electrode current collector 22A to form the negative electrode active material layer 22B. Thereafter, the negative electrode active material layer 22B may be compression-molded. Details regarding compression molding are as described above. As a result, the negative electrode active material layer 22B is formed on both surfaces of the negative electrode current collector 22A, and the negative electrode 22 is fabricated.

[0112] [Assembly of Secondary Battery] First, the positive electrode lead 31 is connected to the positive electrode current collector 21A of the positive electrode 21 using a joining method such as welding, and the negative electrode lead 32 is connected to the negative electrode current collector 22A of the negative electrode 22 using a joining method such as welding.

[0113] Next, the positive electrode 21 and the negative electrode 22 are stacked together with the separator 23 interposed therebetween to form a laminate (not shown). Next, the laminate is wound to form a wound body (not shown), and then the wound body is pressed using a compression device such as a press to form a flat shape. The wound body after this formation has a configuration similar to that of the battery element 20, except that the positive electrode 21, the negative electrode 22, and the separator 23 are not impregnated with an electrolyte solution.

[0114] Next, after the roll is accommodated in the recess 10U, the exterior film 10 (adhesive layer / metal layer / surface protection layer) is folded to face each other. Next, the outer peripheral edges of two sides of the opposing adhesive layers are joined together using an adhesive method such as heat fusion, thereby accommodating the roll in the bag-shaped exterior film 10.

[0115] Finally, after injecting the electrolyte solution into the bag-shaped exterior film 10, the outer peripheral edges of the remaining sides of the opposing fusion layers are joined together using an adhesive method such as heat fusion. In this case, a sealing film 41 is inserted between the exterior film 10 and the positive electrode lead 31, and a sealing film 42 is inserted between the exterior film 10 and the negative electrode lead 32.

[0116] This allows the wound body to be impregnated with the electrolyte, thereby producing the battery element 20. The battery element 20 is then sealed in the bag-shaped exterior film 10, thereby assembling the secondary battery.

[0117] [Stabilization Treatment of Assembled Secondary Battery] The assembled secondary battery is charged and discharged. Stabilization conditions such as the ambient temperature, the number of charge / discharge cycles (number of cycles), and charge / discharge conditions can be set arbitrarily.

[0118] As a result, a coating is formed on each surface of the positive electrode 21 and the negative electrode 22. In this case, as described above, a coating derived from the anisole compound is formed on the surface of the negative electrode 22.

[0119] As a result, the state of the battery element 20 becomes electrochemically stable, and the secondary battery is completed.

[0120] <2-4. Actions and Effects> In this secondary battery, the electrolyte has the above-described structure. Therefore, for the reasons described above, the decomposition reaction of the electrolyte is suppressed during charging and discharging of the secondary battery, thereby achieving excellent battery characteristics.

[0121] In particular, if the secondary battery is a lithium secondary battery, a sufficient battery capacity can be stably obtained by utilizing the absorption and desorption of lithium, and therefore a greater effect can be obtained.

[0122] Other functions and effects of this secondary battery are similar to those of the above-mentioned electrolyte solution.

[0123] 3. Modifications Next, modifications will be described. The configuration of the secondary battery can be modified as appropriate, as described below. However, the series of modifications described below may be combined with each other.

[0124] [Variation 1] The negative electrode 22 contains a negative electrode active material that absorbs and releases lithium, and thus the secondary battery is a lithium secondary battery that utilizes the absorption and release of lithium (a so-called lithium ion secondary battery). However, although not specifically illustrated here, the secondary battery may also be a secondary battery that utilizes the deposition and dissolution of lithium (a so-called lithium metal secondary battery).

[0125] The secondary battery described here has a configuration similar to that of the secondary battery described above, except that the negative electrode 22 contains elemental lithium (so-called lithium metal). Specifically, the negative electrode 22 is a lithium metal foil or the like. However, the lithium metal may contain any amount of impurities.

[0126] In this secondary battery, when lithium is released in an ionic state from the positive electrode 21 during charging, metallic lithium is deposited on the surface of the negative electrode 22. In addition, when lithium metal is eluted from the negative electrode 22 during discharging, lithium is absorbed in an ionic state in the positive electrode 21.

[0127] The method for manufacturing this secondary battery is the same as the method for manufacturing the secondary battery described above, except that lithium metal is used as the negative electrode 22 .

[0128] In this secondary battery, the battery capacity is obtained by utilizing the deposition and dissolution of lithium, and therefore the same effect can be obtained.

[0129] [Modification 2] A porous film separator 23 is used. However, although not specifically shown here, a laminated separator including a polymer compound layer may also be used.

[0130] Specifically, the laminated separator includes a porous membrane and a polymer compound layer. The porous membrane has a pair of surfaces, and the polymer compound layer is provided on one or both surfaces of the porous membrane. This is because the separator improves adhesion to the positive electrode 21 and the negative electrode 22, respectively, thereby suppressing misalignment of the battery element 20. This suppresses miswinding of the positive electrode 21, the negative electrode 22, and the separator 23, thereby suppressing swelling of the secondary battery even if a decomposition reaction of the electrolyte occurs. The polymer compound layer includes polyvinylidene fluoride or the like. This is because polyvinylidene fluoride has excellent physical strength and is electrochemically stable.

[0131] One or both of the porous film and the polymer compound layer may contain one or more types of insulating particles. This is because the insulating particles dissipate heat when the secondary battery generates heat, improving the safety (heat resistance) of the secondary battery. The insulating particles contain one or more types of insulating materials, such as inorganic materials and resin materials. Specific examples of inorganic materials include aluminum oxide, aluminum nitride, boehmite, silicon oxide, titanium oxide, magnesium oxide, and zirconium oxide. Specific examples of resin materials include acrylic resin and styrene resin.

[0132] When a laminated separator is produced, a precursor solution containing a polymer compound and an organic solvent is prepared, and then the precursor solution is applied to one or both sides of a porous film. In this case, the precursor solution may contain a plurality of insulating particles.

[0133] Even when this laminated separator is used, the same effect can be obtained because lithium can move in an ionic state between the positive electrode 21 and the negative electrode 22. In this case, as described above, swelling of the secondary battery is further suppressed, and therefore a greater effect can be obtained.

[0134] [Modification 3] An electrolytic solution that is a liquid electrolyte is used. However, although not specifically shown here, an electrolyte layer that is a gel electrolyte may also be used.

[0135] In the battery element 20 using the electrolyte layer, the positive electrode 21 and the negative electrode 22 are wound facing each other with the separator 23 and the electrolyte layer interposed therebetween. The electrolyte layer is interposed between the positive electrode 21 and the separator 23, and also between the negative electrode 22 and the separator 23.

[0136] Specifically, the electrolyte layer contains a polymer compound together with an electrolytic solution, and the electrolytic solution is held by the polymer compound. This is because leakage of the electrolytic solution is prevented. The composition of the electrolytic solution is as described above. The polymer compound contains polyvinylidene fluoride, etc. When forming the electrolyte layer, a precursor solution containing the electrolytic solution, the polymer compound, and a solvent is prepared, and then the precursor solution is applied to one or both surfaces of each of the positive electrode 21 and the negative electrode 22.

[0137] Even when this electrolyte layer is used, the same effect can be obtained because lithium can move in an ionic state through the electrolyte layer between the positive electrode 21 and the negative electrode 22. In this case, leakage of the electrolyte solution is particularly prevented as described above, and therefore a greater effect can be obtained.

[0138] 4. Uses of Secondary Batteries Finally, uses (application examples) of secondary batteries will be described.

[0139] The use of the secondary battery is not particularly limited. The secondary battery used as a power source may be a main power source or an auxiliary power source in electronic devices, electric vehicles, etc. The main power source is a power source that is used preferentially regardless of the presence or absence of other power sources. The auxiliary power source may be a power source used in place of the main power source or a power source that can be switched from the main power source.

[0140] Specific examples of uses for secondary batteries are as follows: Electronic devices such as video cameras, digital still cameras, mobile phones, laptop computers, headphone stereos, portable radios, and portable information terminals; Storage devices such as backup power supplies and memory cards; Power tools such as power drills and power saws; Battery packs installed in electronic devices; Medical electronic devices such as pacemakers and hearing aids; Electric vehicles such as electric cars (including hybrid cars); Power storage systems such as home or industrial battery systems that store power in preparation for emergencies, etc. In these uses, one secondary battery may be used, or multiple secondary batteries may be used.

[0141] The battery pack may include a single cell or a battery pack. The electric vehicle is a vehicle that runs on a secondary battery as a driving power source, and may be a hybrid vehicle that also includes a driving source other than the secondary battery. In a home power storage system, power stored in a secondary battery, which is a power storage source, can be used to power home electrical appliances, etc.

[0142] Here, an example of the use of the secondary battery will be specifically described. The configuration described below is merely an example and can be modified as appropriate.

[0143] Figure 3 shows the block diagram of a battery pack, which is an example of an application of a secondary battery. The battery pack described here is a battery pack (a so-called soft pack) that uses a single secondary battery, and is installed in electronic devices such as smartphones.

[0144] 3, the battery pack includes a power supply 51 and a circuit board 52. The circuit board 52 is connected to the power supply 51 and includes a positive terminal 53, a negative terminal 54, and a temperature detection terminal 55.

[0145] The power source 51 includes one secondary battery. The positive electrode lead of this secondary battery is connected to a positive electrode terminal 53, and the negative electrode lead is connected to a negative electrode terminal 54. The power source 51 is connected to the outside via the positive electrode terminal 53 and the negative electrode terminal 54, and is therefore capable of charging and discharging. The circuit board 52 includes a control unit 56, a switch 57, a PTC element 58 which is a thermosensitive resistor, and a temperature detection unit 59. However, the PTC element 58 may be omitted.

[0146] The control unit 56 includes a central processing unit (CPU) and memory, and controls the operation of the entire battery pack. The control unit 56 detects and controls the usage state of the power source 51.

[0147] When the voltage of power supply 51 (secondary battery) reaches the overcharge detection voltage or the overdischarge detection voltage, control unit 56 turns off switch 57 to prevent charging current from flowing through the current path of power supply 51. The overcharge detection voltage is not particularly limited, but specifically, it is 4.20 V±0.05 V, and the overdischarge detection voltage is not particularly limited, but specifically, it is 2.40 V±0.10 V.

[0148] Switch 57 includes a charge control switch, a discharge control switch, a charging diode, a discharging diode, etc., and switches between the connection and disconnection of power supply 51 and an external device in response to instructions from control unit 56. Switch 57 includes a metal oxide semiconductor field effect transistor (MOSFET), etc., and the charge current and the discharge current are detected based on the ON resistance of switch 57.

[0149] Temperature detection unit 59 includes a temperature detection element such as a thermistor. Temperature detection unit 59 measures the temperature of power supply 51 using temperature detection terminal 55 and outputs the temperature measurement result to control unit 56. The temperature measurement result measured by temperature detection unit 59 is used when control unit 56 controls charging and discharging in the event of abnormal heat generation, and when control unit 56 performs correction processing when calculating the remaining capacity.

[0150] An embodiment of the present technology will be described.

[0151] Examples 1 to 7 and Comparative Examples 1 to 10 As will be explained below, secondary batteries were manufactured, and then the battery characteristics of the secondary batteries were evaluated.

[0152] [Fabrication of Secondary Battery] In order to simply evaluate the battery characteristics, a test secondary battery was fabricated using the following procedure: This test secondary battery was a simple lithium metal secondary battery.

[0153] First, an anisole compound and a non-aqueous solvent were mixed together to obtain a solvent.

[0154] The anisole compounds used were the compound shown in formula (1-1), the compound shown in formula (1-2), the compound shown in formula (1-4), the compound shown in formula (1-5), and the compound shown in formula (1-7). 1,2-Dimethoxyethane (DME) was used as the non-aqueous solvent. When obtaining the solvent, the molar ratio was changed by changing the mixing ratio of the anisole compound and the non-aqueous solvent, as shown in Table 1.

[0155] Subsequently, an electrolyte salt (lithium bis(fluorosulfonyl)imide) was added to the solvent, and the solvent was stirred to prepare an electrolyte solution (Examples 1 to 7 and Comparative Examples 1 to 8). In this case, the content of the electrolyte salt relative to the solvent was 2 mol / L (=1 mol / dm 3　 )

[0156] For comparison, electrolyte solutions were prepared in the same manner as in Comparative Examples 9 and 10, except that no anisole compound was used as the solvent, and only a non-aqueous solvent was used (1,2-dimethoxyethane and anisole (ANS)), as shown in Table 1.

[0157] Subsequently, a lithium metal foil (thickness=0.1 mm) was pressed onto a copper foil (thickness=0.01 mm) using a press to prepare a test electrode.

[0158] Next, the electrolyte solution was dropped onto a separator (microporous polyethylene film, thickness = 10 μm) to impregnate the separator with the electrolyte solution. The amount of the electrolyte solution dropped was 0.01 ml (= 0.01 cm 3　 )

[0159] Next, a copper foil (thickness = 0.012 mm) was prepared as a counter electrode, and the test electrode and the counter electrode were laminated together with a separator impregnated with an electrolytic solution interposed therebetween, thereby completing a test secondary battery.

[0160] [Evaluation of Battery Characteristics] When the battery characteristics were evaluated, the results shown in Table 1 were obtained.

[0161] Here, in order to examine the reversibility of the deposition and dissolution of lithium on the surface of the counter electrode, the charge-discharge characteristics were evaluated as the battery characteristics.

[0162] When evaluating the charge / discharge characteristics, first, the secondary battery was charged in a room temperature environment (temperature = 23°C) to measure the charge capacity, and then the secondary battery was discharged to measure the discharge capacity.

[0163] During charging, 0.22mA / cm 2　 The battery was charged at a current density of 0.1 V for a total charging time of 3 hours.

[0164] Subsequently, the coulombic efficiency was calculated based on the formula: coulombic efficiency (%)=(discharge capacity / charge capacity)×100.

[0165] Subsequently, in the same environment, the secondary battery was repeatedly charged and discharged until the total number of cycles reached 25, while calculating the coulombic efficiency for each cycle. The charge and discharge conditions were as described above.

[0166] Finally, the average Coulombic efficiency (%), which is an index for evaluating charge-discharge characteristics, was calculated by averaging the 16 Coulombic efficiencies calculated for each of the 10th to 25th cycles. This average Coulombic efficiency value was rounded to one decimal place.

[0167] The nine Coulombic efficiencies calculated during the initial charge / discharge (1st to 9th cycles) are not used to calculate the average Coulombic efficiency because the Coulombic efficiency tends to vary during the initial charge / discharge. By using only the Coulombic efficiencies calculated during the later charge / discharge (10th to 25th cycles) instead of the Coulombic efficiencies calculated during the initial charge / discharge, the Coulombic efficiency is less likely to vary. This ensures the accuracy and reproducibility of the calculation of the average Coulombic efficiency.

[0168]

[0169] [Discussion] As shown in Table 1, the average coulombic efficiency varied depending on the composition of the electrolyte solution.

[0170] Specifically, when the solvent contained only the non-aqueous solvent (DME) (Comparative Example 9), the average Coulombic efficiency increased, whereas when the solvent contained only the non-aqueous solvent (ANS) (Comparative Example 10), the average Coulombic efficiency significantly decreased.

[0171] In contrast to this, when the solvent contained an anisole compound and a non-aqueous solvent (DME) (Examples 1 to 7 and Comparative Examples 1 to 8), the average coulombic efficiency changed depending on the molar ratio.

[0172] That is, when the molar ratio was less than 1.6 (Comparative Examples 1 to 8), the average Coulombic efficiency was significantly reduced. However, when the molar ratio was 1.6 or more (Examples 1 to 7), the average Coulombic efficiency was significantly increased, and more specifically, the average Coulombic efficiency was further increased compared to when the solvent contained only a nonaqueous solvent (DME) (Comparative Example 9).

[0173] In particular, when the molar ratio was 1.6 or more, the following trends were observed. First, a high average Coulombic efficiency was obtained regardless of the type of anisole compound. Second, when the anisole compound contained a fluorine group or a chlorine group as a halogen group, a high average Coulombic efficiency was obtained. Third, when the molar ratio was 2.0 or more, the average Coulombic efficiency increased further.

[0174] [Summary] From the results shown in Table 1, when the electrolyte solution contained an anisole compound and a non-aqueous solvent and the molar ratio was 1.6 or more, a high average coulombic efficiency was obtained. Therefore, the charge-discharge characteristics were improved, and excellent battery characteristics were obtained.

[0175] The present technology has been described above with reference to an embodiment and examples. However, the configuration of the present technology is not limited to the configuration described in the embodiment and examples, and can be modified in various ways.

[0176] Specifically, the secondary battery has been described as having a laminate film structure, but the structure of the secondary battery is not particularly limited, and may be cylindrical, prismatic, coin-shaped, button-shaped, or the like.

[0177] The battery element has been described as having a wound structure. However, the structure of the battery element is not particularly limited, and may be a stacked structure or a zigzag structure. In the stacked structure, positive and negative electrodes are alternately stacked with a separator interposed therebetween, while in the zigzag structure, the positive and negative electrodes are folded in a zigzag pattern while facing each other with the separator interposed therebetween.

[0178] Although the electrode reactant is lithium in the above description, the electrode reactant is not particularly limited. Specifically, as described above, the electrode reactant may be other alkali metals such as sodium and potassium, or alkaline earth metals such as beryllium, magnesium, and calcium. Alternatively, the electrode reactant may be other light metals such as aluminum.

[0179] The effects described in this specification are merely examples, and the effects of the present technology are not limited to the effects described in this specification. Therefore, other effects may be obtained with respect to the present technology.

[0180] The present technology may also be configured as follows: <1> A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte solution, wherein the electrolyte solution contains an anisole compound represented by formula (1) and a non-aqueous solvent, and the molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or more. (Each of R1, R2, R3, R4, and R5 is either a hydrogen group, a halogen group, or a halogenated alkyl group. However, at least one of R1, R2, R3, R4, and R5 is either a halogen group or a halogenated alkyl group.) <2> The secondary battery according to <1>, wherein the molar ratio is 2.0 or more. <3> The secondary battery according to <1> or <2>, wherein the halogen group includes at least one of a fluorine group and a chlorine group. <4> The secondary battery according to any one of <1> to <3>, wherein the halogenated alkyl group has 5 or less carbon atoms. <5> The secondary battery according to any one of <1> to <4>, wherein the non-aqueous solvent includes at least one of a carbonate ester compound and an ether. <6> The secondary battery according to <5>, wherein each of the carbonate ester compound and the ether is a chain compound. <7> The secondary battery according to any one of <1> to <6>, wherein the secondary battery is a lithium secondary battery. <8> An electrolyte solution for a secondary battery, comprising: an anisole compound represented by formula (1); and a non-aqueous solvent, wherein the molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or more. (R1, R2, R3, R4, and R5 each represent a hydrogen group, a halogen group, or a halogenated alkyl group, provided that at least one of R1, R2, R3, R4, and R5 represents a halogen group or a halogenated alkyl group.)

[0181] 21...positive electrode, 22...negative electrode

Claims

1. Equipped with a positive electrode, a negative electrode, and an electrolyte, The aforementioned electrolyte is The anisole compound represented by formula (1), Non-aqueous solvents and Includes, The molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or greater. Secondary battery. 【Chemistry 1】 (Each of R1, R2, R3, R4, and R5 is either a hydrogen group, a halogen group, or an alkyl halide. However, at least one of R1, R2, R3, R4, and R5 is either a halogen group or an alkyl halide.)

2. The aforementioned molar ratio is 2.0 or greater. The secondary battery according to claim 1.

3. The halogen group comprises at least one of a fluorine group and a chlorine group. The secondary battery according to claim 1 or 2.

4. The number of carbon atoms in the alkyl halogen is 5 or less. The secondary battery according to claim 1 or 2.

5. The non-aqueous solvent comprises at least one of a carbonate ester compound and an ether. The secondary battery according to claim 1 or 2.

6. Each of the aforementioned carbonate ester compounds and ethers is a chain-like compound. The secondary battery according to claim 5.

7. Lithium-ion secondary batteries, The secondary battery according to claim 1 or 2.

8. The anisole compound represented by formula (1), Non-aqueous solvents and Includes, The molar ratio of the anisole compound to the non-aqueous solvent is 1.6 or greater. Electrolyte for secondary batteries. 【Chemistry 2】 (Each of R1, R2, R3, R4, and R5 is either a hydrogen group, a halogen group, or an alkyl halide. However, at least one of R1, R2, R3, R4, and R5 is either a halogen group or an alkyl halide.)

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