Nonaqueous-electrolyte secondary battery and nonaqueous electrolyte for use therein

Abstract

Provided is a nonaqueous electrolyte for secondary batteries which comprises at least one trithiane compound selected from the group consisting of compounds (A) represented by general formula (A) and compounds (B) represented by general formula (B). In general formula (A), R1 to R6 are each independently a hydrogen atom, an organic group, or an inorganic group, and l, m, and n are each independently an integer of 0 or larger and at least one of l, m, and n is 1 or larger. In general formula (B), R1 to R6 are each independently a hydrogen atom, an organic group, or an inorganic group, and l, m, and n are each independently an integer of 0 or larger and at least one of l, m, and n is 1 or larger. The compounds (A) and the compounds (B) are independent of each other.

Description

Nonaqueous electrolyte secondary battery and nonaqueous electrolyte used therein CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This disclosure claims the benefit of priority to Japanese Patent Application No. 2024-24638, filed on February 21, 2024 in the Japan Patent Office, the entire contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a non-aqueous electrolyte secondary battery and a non-aqueous electrolyte used therein.

[0003] Patent Document 1 proposes "an ion-conducting solid electrolyte containing at least one of (A) an electron-donating organic compound containing 1 to 3 atoms selected from the group consisting of nitrogen, oxygen, phosphorus, and sulfur atoms, or (B) an anion having a cyclic structure containing at least one atom selected from the group consisting of nitrogen, phosphorus, and sulfur atoms."

[0004] Patent Document 2 proposes a nonaqueous electrolyte solution containing unsaturated sultone. Patent Document 1 states that "by using an electrolyte solution to which unsaturated sultone has been added, it is possible to obtain a nonaqueous electrolyte secondary battery with low self-discharge, significantly suppressed deterioration in load characteristics and resistance, and significantly reduced gas generation within the battery."

[0005] JP 2013-214510 A JP 2002-329528 A

[0006] Although sulfur-containing heterocyclic compounds are effective in improving the durability of non-aqueous electrolyte secondary batteries, they tend to increase the initial resistance.

[0007] One aspect of the present disclosure is a compound (A) represented by general formula (A): and a compound (B) represented by general formula (B):

[0008]

[0009] and R in general formula (A) contains at least one trithiane compound selected from the group consisting of １ ~R ６are each independently a hydrogen atom, an organic group, or an inorganic group; l, m, and n in general formula (A) are each independently an integer of 0 or more, and at least one of l, m, and n is 1 or more; R in general formula (B) １ ~R ６ are each independently a hydrogen atom, an organic group, or an inorganic group; l, m, and n in general formula (B) are each independently an integer of 0 or more, and at least one of l, m, and n is 1 or more; and the compound (A) and the compound (B) are independent of each other.

[0010] Another aspect of the present disclosure relates to a non-aqueous electrolyte secondary battery including a positive electrode, a negative electrode, and the non-aqueous electrolyte for the secondary battery.

[0011] According to the present disclosure, it is possible to reduce the initial resistance in a non-aqueous electrolyte secondary battery. The novel features of the present invention are set forth in the appended claims, but the present invention, both in terms of structure and content, together with other objects and features of the present invention, will be better understood from the following detailed description taken in conjunction with the drawings.

[0012] 1 is a longitudinal sectional view of an example of a nonaqueous electrolyte secondary battery according to an embodiment of the present disclosure.

[0013] The following describes embodiments of the present disclosure using examples, but the present disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be exemplified, but other numerical values ​​and materials may be applied as long as the effects of the present disclosure are obtained. In this specification, the term "numerical value A to numerical value B" includes numerical value A and numerical value B and can be read as "numerical value A or more and numerical value B or less." In the following description, when lower and upper limits for specific physical properties or conditions are exemplified, any of the exemplified lower limits and any of the exemplified upper limits can be arbitrarily combined, as long as the lower limit is not equal to or greater than the upper limit. When multiple materials are exemplified, one of the materials may be selected and used alone, or two or more materials may be used in combination.

[0014] The present disclosure encompasses any combination of two or more claims arbitrarily selected from the appended claims, i.e., any combination of two or more claims arbitrarily selected from the appended claims may be combined unless a technical contradiction arises.

[0015] [Non-aqueous electrolyte for secondary battery] The present disclosure relates to a non-aqueous electrolyte for secondary batteries. The non-aqueous electrolyte includes a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. The solute includes, for example, a lithium salt. Components of the non-aqueous electrolyte other than the non-aqueous solvent and the solute are additives. The non-aqueous electrolyte according to the present disclosure includes, as an additive, at least one trithiane compound (hereinafter, sometimes collectively referred to as "trithiane compound (C)") selected from the group consisting of compound (A) represented by the following general formula (A) and compound (B) represented by the following general formula (B):

[0016]

[0017] The trithiane compound (C) has the effect of reducing the initial reaction resistance of the electrodes (particularly the positive electrode) during the charge-discharge cycle of a non-aqueous electrolyte secondary battery. The trithiane compound (C) is recognized to have the function of increasing the ionic conductivity at the interface between the electrode (particularly the positive electrode) and the non-aqueous electrolyte. It is believed that such a function is exhibited by the formation of a protective coating on the surface of the electrode (particularly the positive electrode) that prevents decomposition of the non-aqueous solvent.

[0018] In addition, when the non-aqueous electrolyte contains both the compound (A) and the compound (B), the compound (A) and the compound (B) are independent of each other. In other words, R ｎ (n is an integer of 1 to 6) is R of compound (B). ｎ (n is an integer of 1 to 6). That is, R ｋ (k is an integer selected from 1 to 6) may be the same or different.

[0019] R in general formula (A) or (B) １ ~R ６ are independent of each other. １ ~R ６Two or more of these may be the same, or all may be different. １ ~R ６ Compounds in which all of the above are the same are preferred in that they tend to form a good quality protective coating and are relatively easy to produce and obtain.

[0020] R １ ~R ６ are each a hydrogen atom, an organic group, or an inorganic group.

[0021] The organic group is an aliphatic group or an aromatic group, and may contain a heteroatom, a halogen atom, a silicon atom, etc. The organic group may be linear or branched.

[0022] The inorganic group may be a halogen atom, an amino group, a silyl group, etc. Examples of the halogen atom include a fluorine atom, a chlorine atom, and a bromine atom. Of these, a fluorine atom is preferred.

[0023] R １ ~R ６ are each preferably a hydrogen atom or an organic group. Among organic groups, alkyl groups are preferred, and alkyl groups having 1 to 5 carbon atoms are particularly preferred. Examples of alkyl groups having 1 to 5 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, an i-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a neopentyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 1,1-dimethylpropyl group, and a 1,2-dimethylpropyl group.

[0024] Preferable examples of the compound (A) include compounds represented by the general formula (A): １ , R and R are all hydrogen atoms, and R ２ , R ４ and R ６ are each independently an alkyl group having 1 to 5 carbon atoms. In such compounds, the alkyl group may have 1 to 4 carbon atoms or 1 to 3 carbon atoms, and R ２ , R ４ and R ６ may all be methyl groups.

[0025] Preferable examples of the compound (B) include compounds represented by the general formula (B):１ , R and R are all hydrogen atoms, and R ２ , R ４ and R ６ are each independently an alkyl group having 1 to 5 carbon atoms. In such compounds, the alkyl group may have 1 to 4 carbon atoms or 1 to 3 carbon atoms, and R ２ , R ４ and R ６ may all be methyl groups.

[0026] In general formula (A) or (B), l, m, and n are each independently an integer of 0 or greater, and at least one of l, m, and n is greater than or equal to 1. In terms of high structural stability, the sum of l, m, and n (l+m+n) is preferably 2, 3, or 4, and all of l, m, and n are preferably 1 or greater, or all of l, m, and n may be 1.

[0027] A specific example of the compound (B) is trithiane hexaoxide represented by the following formula (B1).

[0028] (B1)

[0029] Trithiane hexaoxide may account for 50% by mass or more, preferably 70% by mass or more, or 80% by mass or more of the trithiane compound (C) contained in the non-aqueous electrolyte.

[0030] The content of the trithiane compound (C) in the non-aqueous electrolyte is, for example, 0.1% by mass or more and 10% by mass or less, and may be 0.25% by mass to 5% by mass, or may be 0.25% by mass to 1% by mass. When the content of the trithiane compound (C) in the non-aqueous electrolyte is within the above range, the effect of reducing the initial resistance is significant. From the viewpoints of suppressing side reactions and ensuring higher ionic conductivity, the content of the trithiane compound (C) in the non-aqueous electrolyte is particularly preferably 0.25% by mass to 1% by mass.

[0031] The content of the trithiane compound (C) is a value determined for a nonaqueous electrolyte used as a raw material for manufacturing a nonaqueous electrolyte secondary battery. In a nonaqueous electrolyte secondary battery, the trithiane compound (C) is used to form a coating, and therefore the content of the trithiane compound (C) in the nonaqueous electrolyte may change during storage or during charge-discharge cycles. Therefore, the content of the trithiane compound (C) in the nonaqueous electrolyte sampled from the nonaqueous electrolyte secondary battery may be equal to or greater than the detection limit, and may be, for example, 0.01% by mass or greater.

[0032] The non-aqueous electrolyte may contain additives other than the trithiane compound (C). Examples of such additives include fluorine-containing cyclic carbonates, phosphates (lithium difluorophosphate (LiPO ２ F ２ ), cyclic carbonates having a carbon-carbon unsaturated bond (VC, vinyl ethylene carbonate (VEC)), aromatic compounds (cyclohexylbenzene, etc.), sulfates, sulfites, and sulfonates (propane sultone, propene sultone, etc.). The non-aqueous electrolyte may contain one or more of these additives.

[0033] The nonaqueous solvent contained in the nonaqueous electrolyte may be a typical nonaqueous solvent used in nonaqueous electrolyte secondary batteries. Examples of nonaqueous solvents include cyclic carbonates, chain carbonates, cyclic carboxylic acid esters, chain carboxylic acid esters, chain ethers, and cyclic ethers. Examples of cyclic carbonates include propylene carbonate (PC), ethylene carbonate (EC), and vinylene carbonate (VC). Examples of chain carbonates include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of chain carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP). One type of nonaqueous solvent may be used alone, or two or more types may be used in combination. The nonaqueous solvent is not limited to these.

[0034] Examples of lithium salts include lithium salts of chlorine-containing acids (LiClO4, LiAlCl4, LiB 10 Cl 10 etc.), lithium salts of fluorine-containing acids (LiPF6, LiPF ２ O ２ , LiBF4, LiSbF6, LiAsF6, LiCF3SO3, LiCF3CO2, etc.), lithium salts of fluorine-containing acid imides (LiN(FSO2)2, LiN(CF3SO2)2, LiN(CF3SO2)(CF4F9SO2), LiN(CF5SO2)2, etc.), lithium halides (LiCl, LiBr, LiI, etc.), etc., can be used. One type of lithium salt may be used alone, or two or more types may be used in combination.

[0035] The concentration of the lithium salt in the non-aqueous electrolyte may be 1 mol / L or more and 2 mol / L or less, or 1 mol / L or more and 1.5 mol / L or less. By controlling the lithium salt concentration within the above range, a non-aqueous electrolyte having excellent ionic conductivity and appropriate viscosity can be obtained. However, the lithium salt concentration is not limited to the above.

[0036] Next, a non-aqueous electrolyte secondary battery according to an embodiment of the present disclosure will be described in detail. The non-aqueous electrolyte secondary battery includes, for example, a negative electrode, a positive electrode, and a non-aqueous electrolyte as described below.

[0037] Non-aqueous electrolyte secondary batteries include at least lithium ion batteries, lithium metal secondary batteries, and the like.

[0038] [Negative Electrode] The negative electrode includes at least a negative electrode current collector, and may include a negative electrode mixture layer formed on the surface of the negative electrode current collector and containing a negative electrode active material. The negative electrode mixture layer can be formed by applying a negative electrode slurry, in which the negative electrode mixture is dispersed in a dispersion medium, to the surface of the negative electrode current collector and drying it. The dried coating may be rolled as necessary. The negative electrode mixture layer may be formed on one surface or both surfaces of the negative electrode current collector.

[0039] The negative electrode mixture contains a negative electrode active material as an essential component, and may contain optional components such as a binder, a conductive agent, and a thickener. The negative electrode active material contains a material that electrochemically absorbs and releases lithium ions. Examples of the material that electrochemically absorbs and releases lithium ions include carbon materials and Si-containing materials. Examples of the Si-containing material include silicon oxide (SiO ｘ : 0.5≦x≦1.5), and composite materials containing a silicate phase and silicon particles dispersed within the silicate phase.

[0040] Examples of carbon materials include graphite, easily graphitizable carbon (soft carbon), and non-graphitizable carbon (hard carbon). Among these, graphite is preferred because of its excellent charge / discharge stability and low irreversible capacity. Graphite refers to a material having a graphite-type crystal structure, and includes natural graphite, artificial graphite, graphitized mesophase carbon particles, and the like. One type of carbon material may be used alone, or two or more types may be used in combination.

[0041] The negative electrode current collector may be a metal foil, a mesh, a net, a punched sheet, etc. Examples of the material for the negative electrode current collector include stainless steel, nickel, a nickel alloy, copper, and a copper alloy.

[0042] [Positive Electrode] The positive electrode comprises, for example, a positive electrode current collector and a positive electrode mixture layer formed on the surface of the positive electrode current collector and containing a positive electrode active material. The positive electrode mixture layer can be formed by applying a positive electrode slurry, in which the positive electrode mixture is dispersed in a dispersion medium, to the surface of the positive electrode current collector and drying it. The dried coating may be rolled as necessary. The positive electrode mixture layer may be formed on one surface or both surfaces of the positive electrode current collector.

[0043] The positive electrode mixture contains a positive electrode active material as an essential component, and may contain optional components such as a binder and a conductive agent. The positive electrode active material includes a material that electrochemically absorbs and releases lithium ions. A lithium transition metal composite oxide is preferred as the material that electrochemically absorbs and releases lithium ions. Examples of the lithium transition metal composite oxide that can be used include layered compounds with a rock salt crystal structure, spinel compounds, and polyanion compounds. Among these, lithium transition metal composite oxides (especially layered compounds) that contain Ni and Mn and in which the total proportion of Ni and Mn to all metal elements other than Li is greater than 90 atomic % are preferred in terms of achieving high capacity.

[0044] However, the greater the amount of nickel or the total amount of nickel and manganese in the lithium transition metal composite oxide (especially the layered compound), the higher the reaction resistance of the positive electrode. In contrast, when the non-aqueous electrolyte contains a trithiane compound (C), the ionic conductivity at the interface between the positive electrode and the non-aqueous electrolyte is increased, and the initial reaction resistance is significantly reduced.

[0045] Examples of the layered compound that is preferably used in combination with the trithiane compound (C) in terms of high reaction resistance include a layered compound (first layered compound) that contains at least Ni, and in which the proportion of Ni in all metal elements other than Li is 90 atomic % or more, and a layered compound (second layered compound) that contains at least Ni and Mn, and in which the total proportion of Ni and Mn in all metal elements other than Li is greater than 90 atomic %, and in which the proportion of Ni is 50 atomic % to 70 atomic %.

[0046] More specifically, the composition is represented by the formula (C): Li α Ni(1-x1-x2-x3-y)Co ｘ１ Mnｘ２ Al ｘ３ M ｙ O ２＋β Examples of the first layered compound include those represented by the formula (C). However, the formula (C) satisfies 0.95≦α≦1.05, 0.8≦1-x1-x2-x3-y≦0.99, 0≦x1≦0.1, 0≦x2≦0.1, 0≦x3≦0.1, 0≦y≦0.1, and -0.05≦β≦0.05. M is at least one element selected from the group consisting of Ti, Zr, Nb, Mo, W, Fe, Zn, B, Si, Mg, Ca, Sr, and Y. It is preferable that the formula (C) satisfies 0.9≦1-x1-x2-x3-y≦0.99, and more preferably 0.95≦1-x1-x2-x3-y≦0.99.

[0047] Also, the composition is represented by the formula (D): Li α Ni （１－ｘ１－ｙ） Mn ｘ１ M ｙ O ２＋β where formula (D) satisfies 0.95≦α≦1.05, 0.5≦1−x1−y≦0.7, 0.3≦x1≦0.5, 0≦y≦0.1, and −0.05≦β≦0.05. M is at least one element selected from the group consisting of Co, Al, Ti, Zr, Nb, Mo, W, Fe, Zn, B, Si, Mg, Ca, Sr, and Y.

[0048] The positive electrode current collector is, for example, a metal foil, and examples of the material include stainless steel, aluminum, aluminum alloy, and titanium.

[0049] Examples of binders for each electrode include resin materials, such as fluororesins such as polytetrafluoroethylene and polyvinylidene fluoride (PVDF); polyolefin resins such as polyethylene and polypropylene; polyamide resins such as aramid resin; polyimide and polyamideimide; acrylic resins such as polyacrylic acid, polyacrylates (e.g., lithium polyacrylate), polymethyl acrylate, and ethylene-acrylic acid copolymers; vinyl resins such as polyacrylonitrile and polyvinyl acetate; polyvinylpyrrolidone; polyethersulfone; and rubber-like materials such as styrene-butadiene copolymer rubber (SBR). These may be used alone or in combination of two or more.

[0050] Examples of conductive agents include carbon blacks such as acetylene black, conductive fibers such as carbon fibers and metal fibers, carbon fluoride, metal powders such as aluminum, conductive whiskers such as zinc oxide and potassium titanate, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene derivatives. These may be used alone or in combination of two or more.

[0051] The dispersion medium is not particularly limited, but examples thereof include water, alcohol, and N-methyl-2-pyrrolidone (NMP).

[0052] [Separator] A separator is usually interposed between the positive electrode and the negative electrode. The separator has high ion permeability and adequate mechanical strength and insulating properties. The separator can be made of a microporous thin film, woven fabric, nonwoven fabric, or the like. The separator is preferably made of polyolefin such as polypropylene or polyethylene.

[0053] An example of the structure of a secondary battery is a structure in which an electrode group formed by winding a positive electrode and a negative electrode with a separator interposed therebetween and an electrolyte are housed in an outer casing. Alternatively, instead of a wound electrode group, other types of electrode groups may be used, such as a stacked electrode group formed by stacking a positive electrode and a negative electrode with a separator interposed therebetween. The secondary battery may be in any shape, such as a cylindrical shape, a prismatic shape, a coin shape, a button shape, or a laminate shape.

[0054] The structure of the secondary battery will be described below with reference to Fig. 1. Fig. 1 is a longitudinal cross-sectional view of a cylindrical nonaqueous electrolyte secondary battery 10 that is an example of this embodiment. However, the present disclosure is not limited to the following configuration.

[0055] The secondary battery 10 includes an electrode group 18, an electrolyte (not shown), and a cylindrical battery can 22 with a bottom that accommodates these. A sealing body 11 is crimped to the opening of the battery can 22 via a gasket 21, thereby sealing the battery. The sealing body 11 includes a valve body 12, a metal plate 13, and an annular insulating member 14 interposed between the valve body 12 and the metal plate 13. The valve body 12 and the metal plate 13 are connected to each other at their respective centers. A positive electrode lead 15a extending from a positive electrode plate 15 is connected to the metal plate 13. Thus, the valve body 12 functions as an external terminal for the positive electrode. A negative electrode lead 16a extending from a negative electrode plate 16 is connected to the inner bottom surface of the battery can 22. An annular groove 22a is formed near the open end of the battery can 22. A first insulating plate 23 is disposed between one end face of the electrode group 18 and the annular groove portion 22a. A second insulating plate 24 is disposed between the other end face of the electrode group 18 and the bottom of the battery can 22. The electrode group 18 is formed by winding a positive electrode plate 15 and a negative electrode plate 16 with a separator 17 interposed therebetween.

[0056] (Additional Note) The above description discloses the following technology: (Technology 1) Compound (A) represented by general formula (A) and compound (B) represented by general formula (B):

[0057]

[0058] and R in general formula (A) contains at least one trithiane compound selected from the group consisting of１ ~R ６ are each independently a hydrogen atom, an organic group, or an inorganic group; l, m, and n in general formula (A) are each independently an integer of 0 or more, and at least one of l, m, and n is 1 or more; R in general formula (B) １ ~R ６ are each independently a hydrogen atom, an organic group, or an inorganic group, and in general formula (B), l, m, and n are each independently an integer of 0 or greater, and at least one of l, m, and n is 1 or greater, and the compound (A) and the compound (B) are independent of each other. (Technology 2) A non-aqueous electrolyte for a secondary battery according to Technology 1, wherein in general formulas (A) and (B), l, m, and n are all 1. (Technology 3) A non-aqueous electrolyte for a secondary battery according to Technology 1, wherein in general formula (A), R １ , R and R are hydrogen atoms; R ２ , R ４ and R ６ and R are each independently an alkyl group having 1 to 5 carbon atoms. １ , R and R are hydrogen atoms; R ２ , R ４ and R ６ and each independently represent an alkyl group having 1 to 5 carbon atoms.

[0059]

[0060] The non-aqueous electrolyte for secondary batteries according to any one of Techniques 1 to 4, comprising a trithiane hexaoxide represented by the formula: (Technology 6) The non-aqueous electrolyte for secondary batteries according to any one of Techniques 1 to 5, wherein the content of the trithiane compound is 0.1 mass % or more and 10 mass % or less. (Technology 7) A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte for secondary batteries according to any one of Techniques 1 to 6. (Technology 8) The non-aqueous electrolyte secondary battery according to Technique 7, wherein the positive electrode comprises a lithium transition metal composite oxide, and the lithium transition metal composite oxide contains at least Ni and Mn, and the total proportion of Ni and Mn to all metal elements other than Li is greater than 90 atomic %.

[0061] EXAMPLES The present invention will be specifically described below based on examples and comparative examples, but the present invention is not limited to the following examples.

[0062] Example 1 A nonaqueous electrolyte secondary battery (battery A1) was fabricated and evaluated according to the following procedure. (1) Fabrication of Negative Electrode 96 parts by mass of graphite powder, 4 parts by mass of SiO powder, 0.8 parts by mass of carboxymethyl cellulose (CMC), 1.2 parts by mass of styrene butadiene rubber (SBR), and an appropriate amount of water were mixed to obtain a negative electrode mixture slurry. Next, the negative electrode slurry was applied to the surface of a copper foil, the coating was dried, and then rolled to form a negative electrode mixture layer (thickness 80 μm, density 1.6 g / cm ) on both sides of the copper foil. ３ ) was formed to obtain a negative electrode.

[0063] (2) Preparation of the positive electrode: Lithium-containing composite oxide (LiNi ０．８ Co ０．１８ Al ０．０２ O ２ 95 parts by mass of acetylene black, 2.5 parts by mass of polyvinylidene fluoride, and an appropriate amount of N-methyl-2-pyrrolidone (NMP) were mixed with 95 parts by mass of acetylene black to obtain a positive electrode slurry. Next, the positive electrode slurry was applied to the surface of an aluminum foil, the coating was dried, and then rolled to form a positive electrode mixture layer (thickness 95 μm, density 3.6 g / cm ) on both sides of the aluminum foil. ３ ) was formed to obtain a positive electrode.

[0064] (3) Preparation of non-aqueous electrolyte: LiPF was dissolved in a mixed solvent of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (EC:EMC = 30:70 (volume ratio)). ６ to a concentration of 1 mol / L to prepare a non-aqueous electrolyte. Trithiane hexaoxide (trithiane compound (C) represented by formula (B1)) was added and dissolved in the obtained non-aqueous electrolyte to give the content shown in Table 1.

[0065] (4) Fabrication of a Non-Aqueous Electrolyte Secondary Battery An Al positive electrode lead was attached to the positive electrode obtained above, and a Ni negative electrode lead was attached to the negative electrode obtained above. The positive electrode and negative electrode were spirally wound with a polyethylene thin film (separator) interposed therebetween in an inert gas atmosphere to prepare a wound electrode assembly. The electrode assembly was housed in a bag-shaped exterior body formed of a laminate sheet with an Al layer, and the non-aqueous electrolyte was injected. The exterior body was then sealed to complete Battery A1.

[0066] Comparative Example 1 Battery B1 was fabricated in the same manner as Battery A1 in Example 1, except that the trithiane compound (C) was not added to the non-aqueous electrolyte.

[0067] Comparative Example 2 Battery B2 was fabricated in the same manner as battery A1 in Example 1, except that ethylene sulfite was added to the non-aqueous electrolyte instead of the trithiane compound (C).

[0068] Comparative Example 3 Battery B3 was fabricated in the same manner as battery A1 in Example 1, except that 1,3-propene sultone was added to the non-aqueous electrolyte instead of the trithiane compound (C).

[0069] Evaluation: The initial internal resistance (DCR) of the obtained nonaqueous electrolyte secondary battery was measured. The battery was charged at a constant current of 0.3 It at a temperature of 40°C until the voltage reached 4.2 V, and then charged at a constant voltage of 4.2 V until the current reached 0.05 It. The battery was then discharged at a constant current of 0.3 It until the state of charge (SOC) reached 5%.

[0070] The voltage values ​​were measured when a battery with an SOC of 5% was discharged for 10 seconds at current values ​​of 0 A, 0.1 A, 0.5 A, and 1.0 A. The relationship between the discharge current value and the voltage value after 10 seconds was approximated to a straight line using the least squares method, and the DCR (initial DCR) was calculated from the absolute value of the slope. The initial DCR (ΔDCR) of each battery example, with the initial DCR of battery B1 set to a reference value of 0, is shown in Table 1.

[0071]

[0072] As shown in Table 1, Battery A1, which used a non-aqueous electrolyte containing the trithiane compound (C), had a lower initial DCR than Battery B1 of Comparative Example 1, which did not contain the trithiane compound (C). On the other hand, Battery B2 of Comparative Example 2, in which ethylene sulfite was contained in the non-aqueous electrolyte instead of the trithiane compound (C), and Battery B3 of Comparative Example 3, in which 1,3-propene sultone was contained in the non-aqueous electrolyte instead of the trithiane compound (C), showed an increase in initial DCR compared to Battery B1.

[0073] Non-aqueous electrolyte secondary batteries comprising the non-aqueous electrolyte for secondary batteries according to the present disclosure are useful as main power sources for mobile communication devices, portable electronic devices, electric vehicles, hybrid vehicles, and the like. Note that these applications are merely examples, and the applications of non-aqueous electrolyte secondary batteries are not limited thereto. While the present invention has been described with reference to presently preferred embodiments, such disclosure should not be construed as limiting. Various modifications and alterations will no doubt become apparent to those skilled in the art to which the present invention pertains upon reading the above disclosure. Accordingly, the appended claims should be construed to embrace all modifications and alterations within the true spirit and scope of the present invention.

[0074] 10: Secondary battery, 11: Sealing body, 12: Valve body, 13: Metal plate, 14: Insulating member, 15: Positive electrode plate, 15a: Positive electrode lead, 16: Negative electrode plate, 16a: Negative electrode lead, 17: Separator, 18: Electrode group, 21: Gasket, 22: Battery can, 22a: Groove portion, 23: First insulating plate, 24: Second insulating plate

Claims

1. A compound (A) represented by general formula (A), and a compound (B) represented by general formula (B): and R in general formula (A) contains at least one trithiane compound selected from the group consisting of １ ~R ６ are each independently a hydrogen atom, an organic group, or an inorganic group; l, m, and n in general formula (A) are each independently an integer of 0 or more, and at least one of l, m, and n is 1 or more; R in general formula (B) １ ~R ６ each independently represent a hydrogen atom, an organic group, or an inorganic group; in general formula (B), l, m, and n each independently represent an integer of 0 or more, and at least one of l, m, and n is 1 or more; and the compound (A) and the compound (B) are independent of each other.

2. The non-aqueous electrolyte for a secondary battery according to claim 1, wherein l, m and n are all 1 in general formulae (A) and (B).

3. In general formula (A), R １ , R and R are hydrogen atoms; R ２ , R ４ and R ６ 2. The nonaqueous electrolyte for a secondary battery according to claim 1, wherein each of the groups independently represents an alkyl group having 1 to 5 carbon atoms.

4. In general formula (B), R １ , R and R are hydrogen atoms; R ２ , R ４ and R ６ 2. The nonaqueous electrolyte for a secondary battery according to claim 1, wherein each of the groups independently represents an alkyl group having 1 to 5 carbon atoms.

5. The compound (B) has at least one of the formula (B1): The non-aqueous electrolyte for a secondary battery according to claim 1 , comprising a trithiane hexaoxide represented by the formula:

6. The non-aqueous electrolyte for a secondary battery according to claim 1, wherein the content of the trithiane compound is 0.1% by mass or more and 10% by mass or less.

7. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and the non-aqueous electrolyte for secondary batteries according to claim 1.

8. The nonaqueous electrolyte secondary battery according to claim 7, wherein the positive electrode contains a lithium transition metal composite oxide, the lithium transition metal composite oxide contains at least Ni and Mn, and the total proportion of Ni and Mn to all metal elements other than Li is greater than 90 atomic %.

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