WO2017061102A1 - Nonaqueous electrolyte secondary battery and method for manufacturing nonaqueous electrolyte secondary battery - Google Patents

Abstract

The purpose of the present invention is to provide a nonaqueous electrolyte secondary battery which includes a positive electrode containing a spinel-type lithium manganese oxide and which is improved in capacity retention rate after being kept at a high temperature. In this nonaqueous electrolyte secondary battery including a positive electrode containing a spinel-type lithium manganese oxide, a nonaqueous electrolyte contains a particular cyclic sulfate ester compound. Accordingly, the nonaqueous electrolyte secondary battery including a positive electrode containing a spinel-type lithium manganese oxide can be improved in capacity retention rate after being kept at a high temperature.

Description

Non-aqueous electrolyte secondary battery and method for producing non-aqueous electrolyte secondary battery

The present invention relates to a non-aqueous electrolyte secondary battery.

As a positive electrode active material of a non-aqueous electrolyte secondary battery, lithium cobalt oxide, lithium nickel oxide having a layered rock salt structure with an operating voltage of about 4 V, and lithium manganese oxide having a spinel structure (hereinafter, spinel type lithium manganese) Oxides) and the like are known.

Since spinel type lithium manganese oxide has high thermal stability of crystal structure, it is known that a battery using spinel type lithium manganese oxide as a positive electrode has high safety. On the other hand, it is known that a battery using spinel type lithium manganese oxide as a positive electrode has problems such as capacity reduction and battery swelling associated with a charge / discharge cycle in a high temperature environment.

Patent Document 1 states that “the non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte, and the potential of the positive electrode after charging is 4.35 V or more based on Li, The positive electrode contains, as an active material, a lithium-containing composite oxide having a layered structure containing manganese as a constituent element or a lithium-containing composite oxide having a spinel structure containing manganese as a constituent element. Characterized by containing a cyclic sulfate derivative represented by the general formula (1) or a cyclic sulfonate derivative represented by the following general formula (2) "(paragraph [0010]), According to the invention, a high voltage non-aqueous electrolyte secondary battery having excellent safety, charge / discharge cycle characteristics and high temperature storage characteristics can be provided "(paragraph [0018]).

Patent Document 2 states, “According to the present invention, a positive electrode active material having an α-NaFeO ₂ type crystal structure and containing a lithium transition metal composite oxide containing Co, Ni, and Mn, among which“ lithium-excess type ” By using a non-aqueous electrolyte containing the above cyclic sulfonic acid compound in a non-aqueous electrolyte secondary battery using a positive electrode active material, there is an effect that the charge / discharge cycle performance is significantly improved ”(paragraph [0018]. And “a non-aqueous electrolyte battery using a lithium transition metal oxide having no α-NaFeO ₂ structure, such as LiMn ₂ O ₄ having a spinel structure, as a positive electrode active material, has the effect of the present invention. It is not preferable because it is not played "(paragraph [0020]). Further, Table 2 of Patent Document 2 (paragraph [0101]), "LiMeO ₂ type" positive active material and a non-aqueous electrolyte secondary battery using a diglycol sulfate (DGLST) (Example 10), and, " The rate of increase in internal resistance of each non-aqueous electrolyte secondary battery (Comparative Example 5) using a “LiMeO ₂ type” positive electrode active material and not using DGLST is disclosed. According to the above disclosure, it is shown that the battery of Example 10 using DGLST has a higher rate of increase in internal resistance when left standing than the battery of Comparative Example 5 (Example 10 and Comparative Example 5). The rate of increase in internal resistance when the battery is left is 178% and 142%, respectively).

JP 2014-089800 A JP 2006-344390 A

An object of the present invention is to improve the capacity retention rate of a nonaqueous electrolyte secondary battery having a positive electrode containing spinel type lithium manganese oxide after high temperature storage.

［一般式（１）中、Ｒ^１及びＲ^２は、式（２）で表される互いに結合した基を示すか、又は、いずれか一方が水素原子若しくは炭素数が３以下の炭化水素基を示し、かつ他方が一般式（３）、一般式（４）若しくは一般式（５）で表される基を示す。一般式（１）中、Ｘ^１は、ハロゲン原子又は水素原子を示す。式（２）中、＊の部分は、結合位置を示す。一般式（３）中、Ｒ^３は、ハロゲン原子又は炭素数５以下の炭化水素基を示し、該炭素数５以下の炭化水素基は、ハロゲン原子で置換されていてもよい。一般式（３）中、＊の部分は、結合位置を示す。一般式（４）中、Ｘ^２は、ハロゲン原子又は水素原子を示す。一般式（４）中、＊の部分は、結合位置を示す。一般式（５）中、Ｘ^３は、ハロゲン原子又は水素原子を示す。一般式（５）中、＊の部分は、結合位置を示す。］ Patent Document 1 discloses a non-aqueous electrolyte secondary battery using a spinel-structured lithium-containing composite oxide containing manganese as a constituent element and a specific cyclic sulfate derivative or a specific cyclic sulfonate derivative. However, the use of a cyclic sulfate compound represented by the following general formula (1) is not described.

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In General Formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, and the hydrocarbon group having 5 or less carbon atoms may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ]

Patent Document 2 states that “a non-aqueous electrolyte battery using a lithium transition metal oxide having no α-NaFeO ₂ structure, such as LiMn ₂ O ₄ having a spinel structure, as a positive electrode active material has the effect of the present invention. It is not preferable because it does not play "(paragraph [0020]).

［一般式（１）中、Ｒ^１及びＲ^２は、式（２）で表される互いに結合した基を示すか、又は、いずれか一方が水素原子若しくは炭素数が３以下の炭化水素基を示し、かつ他方が一般式（３）、一般式（４）若しくは一般式（５）で表される基を示す。一般式（１）中、Ｘ^１は、ハロゲン原子又は水素原子を示す。式（２）中、＊の部分は、結合位置を示す。一般式（３）中、Ｒ^３は、ハロゲン原子又は炭素数５以下の炭化水素基を示し、該炭素数５以下の炭化水素基は、ハロゲン原子で置換されていてもよい。一般式（３）中、＊の部分は、結合位置を示す。一般式（４）中、Ｘ^２は、ハロゲン原子又は水素原子を示す。一般式（４）中、＊の部分は、結合位置を示す。一般式（５）中、Ｘ^３は、ハロゲン原子又は水素原子を示す。一般式（５）中、＊の部分は、結合位置を示す。］ A first aspect of the present invention is a nonaqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode active material comprises spinel-type lithium manganese oxide. The nonaqueous electrolyte is a nonaqueous electrolyte secondary battery including a cyclic sulfate ester compound represented by the following general formula (1).

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In General Formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, and the hydrocarbon group having 5 or less carbon atoms may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ]

Thus, the capacity | capacitance after high temperature preservation | save of a non-aqueous electrolyte secondary battery provided with the positive electrode containing a spinel type lithium manganese oxide by making the cyclic | annular sulfate ester compound represented by General formula (1) contain in a non-aqueous electrolyte. The retention rate can be improved.

According to the present invention, it is possible to improve the capacity retention rate of a nonaqueous electrolyte secondary battery having a positive electrode containing spinel type lithium manganese oxide after high temperature storage.

FIG. 1 is a schematic cross-sectional view of one embodiment of the nonaqueous electrolyte secondary battery of the present invention. FIG. 2 is a schematic diagram showing a power storage device provided with the nonaqueous electrolyte secondary battery of the present invention. FIG. 3 is a schematic diagram showing an automobile provided with a power storage device including the nonaqueous electrolyte secondary battery of the present invention.

According to a second aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the first aspect, a separator is disposed between the positive electrode and the negative electrode. The separator includes a base material layer and a surface of the base material layer. And an insulating layer.

According to such a configuration, the insulating layer is formed on the surface of the base material layer of the separator, so that the high-temperature storage of the nonaqueous electrolyte secondary battery including the spinel type lithium manganese oxide in the positive electrode is more effectively performed. Later capacity retention can be improved.

According to a third aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the second aspect, the insulating layer is formed on the surface of the base material layer facing the positive electrode.

According to such a configuration, the insulating layer is formed on the surface of the base material layer of the separator, and the insulating layer is formed on the surface of the base material layer that faces the positive electrode, thereby further effectively. In addition, the capacity retention after high temperature storage of a non-aqueous electrolyte secondary battery containing spinel type lithium manganese oxide in the positive electrode can be improved, and further, the oxidation reaction of the base material layer of the separator, so-called polyeneization can be suppressed.

According to a fourth aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the second or third aspect, the average thickness of the insulating layer is not less than 0.5 μm and not more than 20 μm. The “average thickness” means an average value of 10 arbitrarily selected thicknesses.

According to such a configuration, even if a negative electrode surface coating decomposition product derived from the cyclic sulfate compound represented by the general formula (1) is generated, the negative electrode surface coating decomposition product remains in the insulating layer, and the positive electrode It becomes difficult to reach.

According to a fifth aspect of the present invention, in the nonaqueous electrolyte secondary battery according to the second to fourth aspects, the insulating layer includes an inorganic oxide.

According to a sixth aspect of the present invention, in the nonaqueous electrolyte secondary battery according to any one of the first to third aspects, the cyclic sulfate compound represented by the general formula (1) is represented by the following formula (6): Or a cyclic sulfate compound represented by formula (7).

According to such a configuration, the cyclic sulfate compound represented by the general formula (1) is changed into the cyclic sulfate compound represented by the formula (6) or the formula (7), thereby further effectively. In addition, the capacity retention rate of a nonaqueous electrolyte secondary battery containing spinel type lithium manganese oxide in the positive electrode after high temperature storage can be improved.

［一般式（１）中、Ｒ^１及びＲ^２は、式（２）で表される互いに結合した基を示すか、又は、いずれか一方が水素原子若しくは炭素数が３以下の炭化水素基を示し、かつ他方が一般式（３）、一般式（４）若しくは一般式（５）で表される基を示す。一般式（１）中、Ｘ^１は、ハロゲン原子又は水素原子を示す。式（２）中、＊の部分は、結合位置を示す。一般式（３）中、Ｒ^３は、ハロゲン原子又は炭素数５以下の炭化水素基を示し、該炭素数５以下の炭化水素基は、ハロゲン原子で置換されていてもよい。一般式（３）中、＊の部分は、結合位置を示す。一般式（４）中、Ｘ^２は、ハロゲン原子又は水素原子を示す。一般式（４）中、＊の部分は、結合位置を示す。一般式（５）中、Ｘ^３は、ハロゲン原子又は水素原子を示す。一般式（５）中、＊の部分は、結合位置を示す。］ A seventh aspect of the present invention is a method for manufacturing a nonaqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode, and a nonaqueous electrolyte, wherein the positive electrode active material is spinel type lithium manganese The nonaqueous electrolyte is a method for producing a nonaqueous electrolyte secondary battery including an oxide, and the nonaqueous electrolyte includes a cyclic sulfate ester compound represented by the following general formula (1).

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In the general formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, carbon number of 5 or less hydrocarbon groups may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ]

Using such a method for manufacturing a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery in which the positive electrode containing spinel lithium manganese oxide is improved in capacity retention after high-temperature storage of the non-aqueous electrolyte secondary battery is manufactured. can do.

The eighth aspect of the present invention is a power storage device in which a plurality of nonaqueous electrolyte secondary batteries according to any one of the first to sixth aspects are combined.

The non-aqueous electrolyte secondary battery of the present invention includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, and the non-aqueous electrolyte includes a cyclic sulfate ester compound represented by the general formula (1). In the nonaqueous electrolyte secondary battery of the present invention, a separator may be disposed between the positive electrode and the negative electrode, and an insulating layer may be formed on the surface of the base material layer of the separator, as will be described later. Hereinafter, the member which can be used for the nonaqueous electrolyte secondary battery of this invention is demonstrated.

[Positive electrode]
The nonaqueous electrolyte secondary battery of the present invention includes a positive electrode, and a positive electrode in which a positive electrode mixture layer is formed on the surface of the positive electrode current collector foil can be used as the positive electrode.

The positive electrode mixture layer contains a positive electrode active material, and the positive electrode active material contains spinel type lithium manganese oxide. The spinel type lithium manganese oxide in the present invention is not particularly limited as long as it is capable of inserting and releasing lithium ions and has a spinel crystal structure containing manganese. Preferably, the general formula Li _{1 + α} Mn _2-α-β A _β O ₄ (A is a group consisting of Ti, V, Cr, Fe, Cu, Zn, B, P, Mg, Al, Ca, Zr, Mo and W) It is possible to use a lithium manganese oxide represented by at least one kind of atom selected from 0 ≦ α ≦ 0.2 and 0 ≦ β ≦ 0.2.

The content of the spinel type lithium manganese oxide is not particularly limited, but is preferably 50% by mass or more, more preferably 60% by mass or more, and still more preferably 70% by mass or more with respect to the mass of the positive electrode active material. It is desirable. The content of the spinel type lithium manganese oxide is preferably 90% by mass or less, more preferably 85% by mass or less, and still more preferably 80% by mass or less with respect to the mass of the positive electrode active material.

The method for synthesizing the spinel type lithium manganese oxide is not particularly limited, and a solid phase method, a liquid phase method, a sol-gel method, a hydrothermal method, or the like can be employed. For example, a solution in which lithium hydroxide and MnO ₂ are mixed at a predetermined molar ratio is dried by a spray drying method, a precursor containing Li and Mn is synthesized, and the precursor is fired to spinel lithium manganese oxide Can be obtained.

Further, as the positive electrode active material in the present invention, another kind of positive electrode active material can be mixed with the above spinel type lithium manganese oxide. The positive electrode active material that can be mixed is not particularly limited as long as lithium ions can be reversibly occluded and released. As a positive electrode active material that can be mixed, for example, a lithium transition metal oxide having a spinel type crystal structure represented by a spinel type lithium nickel manganese oxide represented by LiNi _1.5 Mn _0.5 O ₄ or the like; LiCoO ₂ , LiNiO ₂ , LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiCo _2/3 Ni _1/6 Mn _1/6 O ₂ , LiCo _1/5 Ni _1/2 Mn _3/10 O ₂ LiMeO ₂ type (Me is a transition metal) lithium transition metal composite oxide having an α-NaFeO ₂ structure typified by, etc .; LiFePO ₄ , LiFe _1-x Mn _x PO ₄ (0 <x <1), Li ₃ V _{2 (PO 4) 3, Fe} 2 (SO 4) polyanionic compound typified by _3; polyaniline, conductive polymer material such as polypyrrole; disulfide Polymeric materials; sulfur (S); include sulfides such as iron sulfide (FeS _2). These mixable positive electrode active materials can be used alone or in combination of two or more. From the viewpoint of improving the capacity of the non-aqueous electrolyte secondary battery, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ , LiCo _2/3 Ni _1/6 Mn _1/6 O ₂ , LiCo _1/5 It is preferable to use a mixture of LiMeO ₂ type lithium transition metal composite oxide having α-NaFeO ₂ structure containing Ni, Co and Mn as transition metal species such as Ni _1/2 Mn _3/10 O _2. .

The positive electrode in the present invention can be produced by applying a positive electrode mixture to the surface of the positive electrode current collector foil and drying it. In addition to the positive electrode active material, the positive electrode mixture may contain a conductive additive, a binder, a thickener, and the like as necessary.

Although the positive electrode current collector foil is not particularly limited, for example, metal materials such as aluminum, tantalum, niobium, titanium, hafnium, zirconium, zinc, tungsten, bismuth, and alloys containing these metals; carbon cloth, carbon paper, etc. Examples thereof include carbonaceous materials. Among these, aluminum and aluminum alloys are preferable.

The conductive auxiliary agent is not particularly limited, but for example, natural graphite (scale-like graphite, scale-like graphite, earth-like graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (aluminum) Etc.) Conductive materials such as powder, metal fibers, and conductive ceramic materials. These electrically conductive agents can be used individually or in combination of 2 or more types.

The binder is not particularly limited, and examples thereof include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer, styrene-butadiene rubber (SBR), polyacrylonitrile, fluorine. Examples thereof include rubber, polybutadiene, butyl rubber, polyvinyl pyridine, chlorosulfonated polyethylene, polyester resin, phenol resin, and epoxy resin. These binders can be used alone or in combination of two or more.

The thickener is not particularly limited, and examples thereof include carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxypropyl methyl cellulose (HPMC), sodium cellulose sulfate, methyl ethyl cellulose, and ethyl cellulose. These thickeners can be used alone or in combination of two or more.

The method for producing the positive electrode in the present invention is not particularly limited, and a known method can be adopted. For example, a positive electrode mixture layer is formed on the surface of the positive electrode current collector foil by applying a positive electrode material mixture on the surface of the positive electrode current collector foil so as to have a predetermined shape and drying, and then rolling it with a roll press or the like By doing so, the porosity and thickness of a positive mix layer can be adjusted and a positive electrode can be manufactured. Known methods and conditions such as coating and drying can be employed.

［一般式（１）中、Ｒ^１及びＲ^２は、式（２）で表される互いに結合した基を示すか、又は、いずれか一方が水素原子若しくは炭素数が３以下の炭化水素基を示し、かつ他方が一般式（３）、一般式（４）若しくは一般式（５）で表される基を示す。一般式（１）中、Ｘ^１は、ハロゲン原子又は水素原子を示す。式（２）中、＊の部分は、結合位置を示す。一般式（３）中、Ｒ^３は、ハロゲン原子又は炭素数５以下の炭化水素基を示し、該炭素数５以下の炭化水素基は、ハロゲン原子で置換されていてもよい。一般式（３）中、＊の部分は、結合位置を示す。一般式（４）中、Ｘ^２は、ハロゲン原子又は水素原子を示す。一般式（４）中、＊の部分は、結合位置を示す。一般式（５）中、Ｘ^３は、ハロゲン原子又は水素原子を示す。一般式（５）中、＊の部分は、結合位置を示す。］ [Nonaqueous electrolyte]
The nonaqueous electrolyte of the nonaqueous electrolyte secondary battery of the present invention contains a supporting salt and a nonaqueous solvent in addition to the cyclic sulfate compound represented by the general formula (1).

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In General Formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, and the hydrocarbon group having 5 or less carbon atoms may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ]

It is considered that the cyclic sulfate compound is reduced and decomposed on the negative electrode during the battery charging process to form a negative electrode surface film. Among the cyclic sulfate compounds, the compound represented by the general formula (1) has a structure in which a functional group having a sulfate group or a sulfone group is bonded to the cyclic sulfate compound. Compared with a compound having a structure in which a functional group having a sulfate group or a sulfone group is not bonded (such as pentene glycol sulfate (PEGLST)), the reduced decomposition product is considered to have a stronger polymerized structure. That is, when the cyclic sulfate ester compound represented by the general formula (1) is used, the negative electrode surface coating formed has a strong polymerization structure, so that the negative electrode surface even after a certain period of time has elapsed under a high temperature environment. It can be considered that the coating can exist stably.

On the other hand, when a compound having a structure in which a functional group having a sulfate group or a sulfone group is not bonded to the cyclic sulfate compound (such as pentene glycol sulfate (PEGLST)), the formed negative electrode surface film is relatively strong. It is considered that the negative electrode surface coating can be decomposed after a certain period of time in a high temperature environment because it has no polymerized structure. It is considered that elution of Mn ions occurs when a negative electrode surface coating decomposition product is generated with the decomposition of the negative electrode surface coating and the negative electrode surface coating decomposition product acts on the spinel type lithium manganese oxide. It is considered that the eluted Mn ions are reduced on the negative electrode to cause metal precipitation and the like, and the capacity retention rate of the battery is lowered. Further, it is considered that the negative electrode surface coating decomposition product contains sulfate ions and SO ³⁻ ions.

It is considered that elution of Mn ions occurs when the negative electrode surface coating decomposition product acts on the spinel type lithium manganese oxide. On the other hand, the negative electrode surface coating decomposition product acts on the positive electrode active material containing manganese elements other than spinel type lithium manganese oxide (for example, LiCo _1/3 Ni _1/3 Mn _1/3 O ₂ etc.), and elution of Mn ions It is considered that there is relatively little to generate.

Compared with the manganese element which comprises positive electrode active materials other than spinel type lithium manganese oxide, the valence changes with the charge / discharge reaction of the manganese element which comprises spinel type lithium manganese oxide. It is considered that manganese elements constituting the spinel type lithium manganese oxide are likely to be acted on by decomposition of the negative electrode surface coating due to the valence change, and Mn ions are likely to be eluted. That is, the cyclic sulfate compound represented by the general formula (1) can specifically improve the capacity retention after high-temperature storage in a non-aqueous electrolyte secondary battery using spinel type lithium manganese oxide. Conceivable.

The cyclic sulfate compound represented by the general formula (1) is preferably a cyclic sulfate compound represented by the following formula (6) or formula (7).

The cyclic sulfate compound represented by the formula (6) or the formula (7) has, for example, a functional group having a cyclic sulfate group in the cyclic sulfate compound as compared with the cyclic sulfate ester compound represented by the formula (8). It is thought that the negative electrode surface film formed has a much stronger polymerized structure due to the directly bonded structure. That is, it is considered that the capacity retention after high-temperature storage can be more effectively improved by using the cyclic sulfate ester compound represented by formula (6) or formula (7).

The content of the cyclic sulfate compound represented by the general formula (1) is not particularly limited. The content of the cyclic sulfate compound represented by the general formula (1) is preferably 8 masses with respect to the mass of the nonaqueous electrolyte from the viewpoint of favorably maintaining battery characteristics other than capacity retention after high-temperature storage. % Or less, more preferably 5% by mass or less, still more preferably 3% by mass or less, and even more preferably 2% by mass or less. The content of the cyclic sulfate compound represented by the general formula (1) is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and still more preferably with respect to the mass of the nonaqueous electrolyte. Desirably, it is 0.1% by weight or more, even more preferably 0.5% by weight or more, and even more preferably 1% by weight or more.

The nonaqueous electrolyte in the present invention may contain a supporting salt. The supporting salt is not particularly limited, and a lithium salt that is stable in a voltage region generally used for a nonaqueous electrolyte battery can be used. Examples of the supporting salt include LiBF ₄ , LiPF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C _{4 F 9 SO 2), LiC (} CF 3 SO 2) 3, LiB (C 2 O 4) 2, LiC (C 2 F 5 SO 2) 3 and the like. These supporting salts can be used alone or in combination of two or more. The content of the supporting salt is not particularly limited, but is preferably 5 mol / L or less, more preferably 3 mol / L or less, and even more preferably 2 mol / L or less. The content of the supporting salt is not particularly limited, but is preferably 0.1 mol / L or more, more preferably 0.5 mol / L or more, and even more preferably 0.8 mol / L or more.

The non-aqueous solvent in the present invention is not particularly limited, and an organic solvent generally used as a non-aqueous solvent can be used. Examples of the non-aqueous solvent include propylene carbonate (PC), ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate (EMC). These nonaqueous solvents can be used alone or in combination of two or more.

In addition to the cyclic sulfate compound represented by the general formula (1), the nonaqueous electrolyte in the present invention may contain additives as necessary. Examples of the additive include vinylene carbonate (VC), vinyl ethylene carbonate (VEC), propane sultone (PS), propene sultone (PRS), monofluorophosphate, difluorophosphate, and the like. The monofluorophosphate is preferably lithium monofluorophosphate, and the difluorophosphate is preferably lithium difluorophosphate. These additives can be used individually or in combination of 2 or more types.

[Separator]
The nonaqueous electrolyte secondary battery of the present invention may be provided with a separator between the positive electrode and the negative electrode, and the separator includes a base material layer and an insulating layer formed on the surface of the base material layer. It may be.

The base material layer of the separator in the present invention is not particularly limited, and a microporous film, a nonwoven fabric or the like can be adopted. The base material layer may contain a thermoplastic resin, and examples of the thermoplastic resin include polyolefin resins such as polyethylene (PE) and polypropylene (PP). These materials can be used alone or in combination of two or more.

[Insulation layer]
As will be described later, an insulating layer may be formed on the surface of the base material layer of the separator. An electricity storage element including a separator in which an insulating layer is formed on the surface of a base material layer is compared with an electricity storage element including a separator made only of a base material layer, and the usage form of the electricity storage element is normally predicted. Even if, for example, the power storage element generates abnormal heat, the separator is difficult to thermally contract, and the positive electrode and the negative electrode can be prevented from being in electrical contact.

Moreover, in this invention, even if the insulating layer was formed on the surface of the base material layer of the separator, the negative electrode surface coating decomposition product derived from the cyclic sulfate compound represented by the general formula (1) was generated. However, it is considered that the decomposed product of the negative electrode surface film remains in the insulating layer and does not easily reach the positive electrode. In other words, by forming an insulating layer on the surface of the base material layer of the separator, the capacity retention rate after high-temperature storage of a nonaqueous electrolyte secondary battery containing spinel-type lithium manganese oxide in the positive electrode can be more effectively improved. It is thought that it can be improved.

In addition, the insulating layer is formed on the surface of the base material layer facing the positive electrode, thereby improving the capacity retention after high temperature storage more effectively. The so-called polyene conversion can be suppressed.

The insulating layer can be an insulating porous layer, for example, a porous layer containing an inorganic oxide, a porous layer containing resin beads, and a porous material containing a heat resistant resin such as an aramid resin. It can be selected from the quality layer. The insulating layer in the present invention is preferably a porous layer containing an inorganic oxide. The porous layer containing an inorganic oxide may contain a binder or a thickener as necessary. About each kind of a binder and a thickener, the thing similar to what is mix | blended with a positive mix layer or a negative mix layer is employable.

As the inorganic oxide, a known one can be used, but an inorganic oxide excellent in chemical stability is preferable. Examples of such inorganic oxides include alumina, titania, zirconia, magnesia, silica, boehmite, and alumina silicate. These inorganic oxides can be used alone or in combination of two or more.

It is preferable to use a powdered inorganic oxide, and the average particle diameter is not particularly limited. The average particle size of the inorganic oxide is preferably 10 μm or less, more preferably 8 μm or less, even more preferably 5 μm or less, and even more preferably 3 μm or less. The average particle size of the inorganic oxide is not particularly limited, but is preferably 0.01 μm or more, more preferably 0.05 μm or more, and even more preferably 0.1 μm or more. Even if the negative electrode surface coating decomposition product derived from the cyclic sulfate ester compound represented by the general formula (1) is generated when the average particle diameter of the inorganic oxide satisfies the above range, the negative electrode surface coating decomposition occurs. It is considered that the material stays inside the insulating layer (porous layer containing an inorganic oxide) and does not easily reach the positive electrode.

The average particle diameter of the inorganic oxide indicates a particle diameter having a cumulative degree of 50% (D50) in a volume standard particle size distribution. Specifically, using a laser diffraction particle size distribution measuring device, the scattering distribution is obtained by irradiating a wet cell in which a dispersion liquid in which a measurement target sample (inorganic oxide) is dispersed in a dispersion solvent circulates, By approximating the scattering distribution with a lognormal distribution, a cumulative degree of 50% (D50) is measured. In addition, the average particle diameter based on the above measurement almost coincides with the average particle diameter measured by extracting 100 inorganic oxides from the SEM image while avoiding extremely large inorganic oxides and extremely small inorganic oxides. It has been confirmed.

As the method for forming the insulating layer, a known method can be employed. For example, it can be formed by applying an insulating layer forming mixture containing an inorganic oxide and a binder to the surface of the base material layer of the separator and drying it.

When the inorganic oxide and the binder are contained, the content of the binder is not particularly limited, but is preferably 20% by mass or less, more preferably based on the total amount of the inorganic oxide and the binder. It is desirable that the content be 10% by mass or less, and more preferably 5% by mass or less. The content of the binder is preferably 1% by mass or more, more preferably 2% by mass or more with respect to the total amount of the inorganic oxide and the binder. By satisfying such a range, the mechanical strength and lithium ion conductivity of the insulating layer can be achieved in a balanced manner.

The average thickness of the insulating layer is not particularly limited, but is preferably 20 μm or less, more preferably 10 μm or less, still more preferably 8 μm or less, and even more preferably 5 μm or less. The average thickness of the insulating layer is preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more. Even if a negative electrode surface coating decomposition product derived from the cyclic sulfate ester compound represented by the general formula (1) is generated by satisfying the above range of the average thickness of the insulating layer, the negative electrode surface coating decomposition product is generated. Is considered to remain inside the insulating layer, making it difficult to reach the positive electrode.

The porosity of the insulating layer is not particularly limited, but is preferably 70% or less, more preferably 65% or less, even more preferably 60% or less, even more preferably 55% or less, and even more preferably 50% or less. It is desirable that The porosity of the insulating layer is preferably 30% or more, more preferably 35% or more, even more preferably 40% or more, and even more preferably 45% or more. When the porosity of the insulating layer satisfies the above range, even if a negative electrode surface coating decomposition product derived from the cyclic sulfate compound represented by the general formula (1) is generated, the negative electrode surface coating decomposition product is generated. It is considered that it stays inside the insulating layer and it is difficult to reach the positive electrode.

[Negative electrode]
The nonaqueous electrolyte secondary battery of the present invention includes a negative electrode, and a negative electrode in which a negative electrode mixture layer is formed on the surface of the negative electrode current collector foil can be used as the negative electrode.

The negative electrode mixture layer may contain a negative electrode active material. The negative electrode active material is not particularly limited as long as it can reversibly store and release lithium ions. Examples of the negative electrode active material include amorphous carbon such as non-graphitizable carbon (hard carbon) and graphitizable carbon (soft carbon); natural graphite such as scaly graphite, scaly graphite, and earth graphite; artificial graphite Alloy of metal such as Al, Si, Pb, Sn, Zn, Cd and lithium; tungsten oxide; molybdenum oxide; iron sulfide; titanium sulfide; lithium titanate; These negative electrode active materials can be used individually or in combination of 2 or more types.

The negative electrode of the nonaqueous electrolyte secondary battery of the present invention can be manufactured by applying a negative electrode mixture to the surface of the negative electrode current collector foil and drying it. In addition to the negative electrode active material, the negative electrode mixture layer may contain a conductive additive, a binder, a thickener, etc. as necessary. The conductive additive, the binder, the thickener, etc. About each of these, the thing similar to what is mix | blended with a positive mix layer is employable.

The negative electrode current collector foil is not particularly limited, and examples thereof include metal materials such as copper, copper alloy, nickel, stainless steel, nickel-plated steel, and chrome-plated steel. Among these, copper and copper alloys are preferable.

The method for producing the negative electrode in the present invention is not particularly limited, and a known method can be adopted. For example, a negative electrode mixture is applied to the surface of the negative electrode current collector foil so as to have a predetermined shape and dried to form a negative electrode material mixture layer on the surface of the negative electrode current collector foil, which is then rolled with a roll press or the like By doing so, the porosity and thickness of a negative mix layer can be adjusted, and a negative electrode can be manufactured. Known methods and conditions such as coating and drying can be employed.

[Production method]
The non-aqueous electrolyte secondary battery of the present invention is manufactured by using a positive electrode, a negative electrode, and a non-aqueous electrolyte. As one aspect of the method for producing a non-aqueous electrolyte secondary battery of the present invention, the first step using spinel type lithium manganese oxide for the positive electrode and the non-containing electrolyte containing the cyclic sulfate compound represented by the general formula (1) The manufacturing method including the 2nd process of assembling a nonaqueous electrolyte secondary battery using a water electrolyte is mentioned.

[Other components]
Other constituent members of the nonaqueous electrolyte secondary battery include a terminal, an insulating plate, a battery case, and the like. In the nonaqueous electrolyte secondary battery of the present invention, those used in the past can be appropriately adopted as these constituent members.

[Power storage device]
The non-aqueous electrolyte secondary battery of the present invention can be configured by combining a plurality of the non-aqueous electrolyte secondary batteries, and the power storage device can be configured using the assembled battery. One embodiment of a power storage device is shown in FIG. The power storage device 30 includes a plurality of power storage units 20. Each power storage unit 20 can be configured using an assembled battery including a plurality of nonaqueous electrolyte secondary batteries 1. As shown in FIG. 3, the power storage device 30 can be mounted as a power source for vehicles such as an electric vehicle (EV), a hybrid vehicle (HEV), and a plug-in hybrid vehicle (PHEV).

Hereinafter, the present invention will be specifically described using examples, but the present invention is not construed as being limited to these examples.

A schematic cross-sectional view of the nonaqueous electrolyte secondary battery of this example is shown in FIG.
This non-aqueous electrolyte secondary battery 1 has a negative electrode mixture prepared by applying a negative electrode mixture to the positive electrode 3 on which a positive electrode mixture layer is formed by applying a positive electrode mixture to an aluminum current collector foil and a copper current collector foil. It is manufactured by housing the power generation element 2 in which the negative electrode 4 on which the layer is formed is wound via the separator 5 and the nonaqueous electrolyte in the battery case 6.

The nonaqueous electrolyte secondary battery shown in FIG. 1 was manufactured as follows.
1. Production of Nonaqueous Electrolyte Secondary Battery of Example 1 (1) Production of Positive Electrode Plate LiMn _1.9 Al _0.1 O ₄ and LiNi _1/3 Co _1/3 Mn at a mass ratio of 70:30 as a positive electrode active material _A mixture obtained by mixing _1/3 O ₂ , acetylene black as a conductive assistant, and polyvinylidene fluoride (PVdF) as a binder were used. An appropriate amount of N-methyl-2-pyrrolidone (NMP) is added to a mixture in which the ratio of the positive electrode active material, the conductive auxiliary agent, and the binder is 90% by mass, 5% by mass, and 5% by mass, respectively. It adjusted and produced the paste-form positive mix. This positive electrode mixture was applied to both surfaces of an aluminum foil (positive electrode current collector foil) having a thickness of 20 μm and dried to prepare a positive electrode plate in which a positive electrode mixture layer was formed on the positive electrode current collector foil. The positive electrode mixture layer was not formed on the positive electrode plate, but a portion where the positive electrode current collector foil was exposed was provided, and the portion where the positive electrode current collector foil was exposed and the positive electrode lead were joined.

(2) Production of Negative Electrode Plate Graphite (graphite) was used as the negative electrode active material, styrene-butadiene rubber (SBR) was used as the binder, and carboxymethyl cellulose (CMC) was used as the thickener. An appropriate amount of water was added to a mixture containing 95% by mass, 3% by mass, and 2% by mass of a negative electrode active material, a binder, and a thickener, respectively, to adjust the viscosity, thereby preparing a paste-like negative electrode mixture. This negative electrode mixture was applied to both sides of a 10 μm thick copper foil (negative electrode current collector foil) and dried to prepare a negative electrode plate. A portion where the negative electrode current collector foil was exposed was provided on the negative electrode plate without forming a negative electrode mixture, and the portion where the negative electrode current collector foil was exposed was bonded to the negative electrode plate lead.

(3) Production of non-injected battery Power is generated by winding the positive electrode plate and the negative electrode plate with a separator made of only the base material layer interposed between the positive electrode plate and the negative electrode plate produced as described above. The element was made. As the separator made of only the base material layer, a microporous film made of polyethylene (PE) which is a thermoplastic resin was adopted. The power generation element is housed inside the battery case from the opening of the battery case, the positive electrode plate lead is joined to the battery lid, the negative electrode plate lead is joined to the negative electrode terminal, and then the battery lid is fitted into the opening of the battery case. By joining the battery case and the battery lid by laser welding, a non-injected battery in which the nonaqueous electrolyte was not injected was produced.

(4) Preparation and injection of non-aqueous electrolyte Ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 30:70 to prepare a non-aqueous solvent. LiPF ₆ is dissolved in a non-aqueous solvent at a concentration of 1 mol / L, vinylene carbonate (VC) is added in an amount of 1.0% by mass with respect to the mass of the non-aqueous electrolyte, and the cyclic sulfate represented by the formula (6) The nonaqueous electrolyte was adjusted by adding 0.5% by mass of the compound with respect to the mass of the nonaqueous electrolyte. That is, the cyclic sulfate compound represented by the formula (6) was used as the cyclic sulfate compound represented by the general formula (1). The nonaqueous electrolyte of Example 1 having a nominal capacity of 550 mAh is obtained by injecting the nonaqueous electrolyte into the battery case from the injection port provided on the side surface of the battery case and sealing the injection port with a stopper. A battery (hereinafter sometimes simply referred to as “battery”) was produced.

2. Production of Nonaqueous Electrolyte Secondary Battery of Example 2 In Example 1, the content of the cyclic sulfate compound represented by the formula (6) was 1.0% by mass with respect to the mass of the nonaqueous electrolyte. Except for this, the battery of Example 2 was produced in the same manner as the battery of Example 1.

3. Production of Nonaqueous Electrolyte Secondary Batteries of Example 3 and Example 4 In Example 1, the cyclic sulfate compound represented by the formula (6) was changed to the cyclic sulfate compound represented by the formula (7). A battery of Example 3 was produced in the same manner as the battery of Example 1 except for the above. In Example 1, Example 4 was performed in the same manner as the battery of Example 1, except that the cyclic sulfate compound represented by Formula (6) was changed to the cyclic sulfate compound represented by Formula (8). A battery was prepared.

4). Production of Nonaqueous Electrolyte Secondary Battery of Example 5 In Example 1, except that the separator made of only the base material layer was changed to a separator in which an insulating layer was formed on the surface of the base material layer facing the positive electrode. Produced the battery of Example 5 by the same method as Example 1. An insulating layer-forming mixture containing an inorganic oxide and a binder is applied to the surface of the base material layer of the separator and dried, so that an insulating layer (a porous material containing an inorganic oxide) is formed on the surface of the base material layer. Layer). The insulating layer was opposed to the positive electrode, and the positive electrode and the negative electrode were wound through a separator. Further, alumina (Al ₂ O ₃ ) having an average particle diameter of 1 μm as an inorganic oxide and PVdF as a binder, the inorganic oxide and the binder are 94% by mass and 6% by mass, respectively. An insulating layer-forming mixture was prepared by adjusting the viscosity by adding an appropriate amount of NMP to the mixture.

5). Production of Nonaqueous Electrolyte Secondary Battery of Comparative Example 1 The battery of Example 1 is the same as Example 1 except that the cyclic sulfate ester compound represented by the formula (6) is pentene glycol sulfate (PEGLST). A battery of Comparative Example 1 was produced by the method.

6). Production of Nonaqueous Electrolyte Secondary Battery of Comparative Example 2 In Example 1, the same method as the battery of Example 1 except that the cyclic sulfate ester compound represented by formula (6) was not added to the nonaqueous electrolyte. A battery of Comparative Example 2 was produced.

7). Evaluation test of Examples 1 to 5 and Comparative Examples 1 and 2 (capacity retention after high temperature storage)
The initial discharge capacity confirmation test of each battery of Examples 1 to 5 and Comparative Examples 1 and 2 was performed by the following method.
Each battery was charged to 4.1 V at a constant current of 550 mA at 25 ° C., further charged for a total of 3 hours at a constant voltage of 4.1 V, and then discharged at a final voltage of 2.75 V at a constant current of 550 mA. The discharge capacity was measured.

For each battery after the initial discharge capacity measurement, a capacity retention measurement test after high temperature storage was performed by the following method. Each battery after the initial discharge capacity measurement is charged to 4.1 V at a constant current of 550 mA at 25 ° C., and further charged for a total of 3 hours at a constant voltage of 4.1 V, so that the SOC (State Of Charge) of each battery is obtained. It was set to 100% and left for 180 days in a 45 ° C. environment with no voltage applied. Each battery after being left for 180 days is kept at 25 ° C. for 5 hours or more and then discharged with a constant current of 550 mA and a final voltage of 2.75 V. The obtained discharge capacity is the discharge capacity after storage at high temperature. did.

As shown in the following formula (9), the discharge capacity retention after high temperature storage was calculated by dividing the discharge capacity after high temperature storage by the initial discharge capacity.
Capacity retention [%] after storage at high temperature = (discharge capacity [mAh] after storage at high temperature / initial discharge capacity [mAh]) × 100 (9)

Table 1 shows the test results of the batteries (Examples 1 to 5 and Comparative Examples 1 and 2) measured as described above. In Table 1, LMO represents LiMn _1.9 Al _0.1 O ₄ , and NCM represents LiNi _1/3 Co _1/3 Mn _1/3 O ₂ .

8). Discussion on Table 1 The batteries (Examples 1 to 5) in which the cyclic sulfate ester compound represented by the general formula (1) is contained in the nonaqueous electrolyte had a capacity retention of 94.1% or more after high-temperature storage. It was. On the other hand, the battery (Comparative Example 1) containing a cyclic sulfate ester compound (PEGLST) not represented by the general formula (1) in the nonaqueous electrolyte had a capacity retention of 90.5% after high-temperature storage. By comparing these with the battery of Comparative Example 2 (the capacity retention after high-temperature storage is 89.8%), the battery using the spinel type lithium manganese oxide for the positive electrode has the general formula (1) It was found that the battery using the cyclic sulfate compound represented by the formula has improved capacity retention after high-temperature storage as compared with the battery using PEGLST.

In the battery of Comparative Example 1, the negative electrode surface coating derived from the cyclic sulfate ester compound (PEGLST) not represented by the general formula (1) is the negative electrode surface coating derived from the cyclic sulfate ester compound represented by the general formula (1). Therefore, it is considered that the negative electrode surface coating derived from PEGLST was decomposed and a negative electrode surface coating decomposition product was generated after a certain period of time in a high temperature environment. It is considered that the capacity retention rate after high-temperature storage was lowered by the dissolution of the negative electrode surface coating on the spinel type lithium manganese oxide, whereby Mn ions were eluted and Mn ions were reduced and deposited on the negative electrode.

In the batteries of Examples 1 to 5, the cyclic sulfate compound represented by the general formula (1) has a structure in which a functional group having a sulfate group or a sulfone group is bonded to the cyclic sulfate compound. It is considered that a strong negative electrode surface film was formed. Due to the strong formation of the negative electrode surface coating, it is difficult to produce a degradation product of the negative electrode surface coating even when a certain period of time has elapsed under a high temperature environment, and the elution of Mn ions in the spinel type lithium manganese oxide is reduced. It is considered that the capacity retention after storage at high temperature was improved.

The capacity retention after storage at high temperature of the batteries (Examples 1 and 3) containing the cyclic sulfate compound represented by the formula (6) or the formula (7) was 96.3% and 96.5%, respectively. Met. On the other hand, the capacity retention after high temperature storage of the battery (Example 4) containing the cyclic sulfate compound represented by the formula (8) was 94.1%. That is, among the cyclic sulfate compounds represented by the general formula (1), the batteries (Examples 1 and 3) containing the cyclic sulfate compound represented by the formula (6) or the formula (7) are represented by the formula As compared with the battery (Example 4) containing the cyclic sulfate compound represented by (8), it was found that the capacity retention after high-temperature storage was further improved. This is because the cyclic sulfate compound represented by the formula (6) or the formula (7) has a structure in which a functional group having a cyclic sulfate group is directly bonded to the cyclic sulfate compound, so that the negative electrode surface coating is further improved. It is considered that the capacity retention rate after high-temperature storage was further improved because it became stronger.

The capacity retention after storage at high temperature of the battery (Example 5) comprising the separator containing the cyclic sulfate compound represented by the formula (6) and having an insulating layer formed on the surface of the base material layer is 97. 0%. On the other hand, the capacity retention after storage at high temperature of the battery (Example 1) containing the cyclic sulfate compound represented by the formula (6) and having the separator composed only of the base material layer was 96.3%. It was. That is, a battery (Example 5) including a separator having an insulating layer formed on the surface of a base material layer has a capacity after high-temperature storage as compared with a battery (Example 1) including a separator consisting only of a base material layer. It was found that the retention rate was further improved. Even if a negative electrode surface coating decomposition product derived from the cyclic sulfate ester compound represented by the general formula (1) is generated by forming an insulating layer on the surface of the base material layer, the negative electrode surface coating decomposition is generated. It is thought that the capacity retention rate after high-temperature storage was improved because the material stayed inside the insulating layer and did not easily reach the positive electrode.

9. Production of Nonaqueous Electrolyte Secondary Battery of Example 6 In Example 5, the mixing ratio of LiMn _1.9 Al _0.1 O ₄ and LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (LiMn _1.9 Al _0.1 O ₄ : LiNi _1/3 Co _1/3 Mn _1/3 O ₂ = 70: 30), LiMn _1.9 Al _0.1 O ₄ : LiNi _1/3 Co _1/3 Mn _{1 /} A battery of Example 6 was produced in the same manner as Example 5 except that ₃ O ₂ = 30: 70 and the nominal capacity was changed to 650 mAh.

11. Production of Nonaqueous Electrolyte Secondary Battery of Comparative Example 3 In Example 6, the same as the battery of Example 6, except that the cyclic sulfate ester compound represented by the formula (6) was pentene glycol sulfate (PEGLST). A battery of Comparative Example 3 was produced by the method.

12 Evaluation test of Example 6 and Comparative Example 3 (capacity retention after high temperature storage)
The initial discharge capacity confirmation test of each battery of Example 6 and Comparative Example 3 was performed by the following method.
Each battery was charged at a constant current of 650 mA at 25 ° C. to 4.2 V, charged at a constant voltage of 4.2 V for a total of 3 hours, and then discharged at a final voltage of 2.75 V at a constant current of 650 mA. The discharge capacity was measured.

For each battery after the initial discharge capacity measurement, a capacity retention measurement test after high temperature storage was performed by the following method. Each battery after the initial discharge capacity measurement is charged to 4.2 V at a constant current of 650 mA at 25 ° C., and further charged for a total of 3 hours at a constant voltage of 4.2 V, thereby setting the SOC of each battery to 100%. The sample was left in a 45 ° C. environment for 120 days with no voltage applied. Each battery after being left for 120 days is kept at 25 ° C. for 5 hours or more and then discharged with a constant current of 650 mA and a final voltage of 2.75 V. The obtained discharge capacity is the discharge capacity after storage at high temperature. did.

As shown in the above equation (9), the discharge capacity retention rate after high temperature storage was calculated by dividing the discharge capacity after high temperature storage by the initial discharge capacity.

Table 2 shows the test results of each battery (Example 6 and Comparative Example 2) measured as described above. In Table 2, LMO represents LiMn _1.9 Al _0.1 O ₄ and NCM represents LiNi _1/3 Co _1/3 Mn _1/3 O ₂ .

13. Consideration on Table 2 Battery in which the content of LiMn _1.9 Al _0.1 O ₄ is 30% by mass with respect to the mass of the positive electrode active material and the cyclic sulfate compound represented by formula (6) is contained ( The capacity retention after storage at high temperature in Example 6) was 89.0%. On the other hand, the content of LiMn _1.9 Al _0.1 O ₄ was 30% by mass with respect to the content of the positive electrode active material, and the battery containing the pentene glycol sulfate (PEGLST) (Comparative Example 3) was stored at high temperature. The subsequent capacity retention was 88.9%.

Comparing Example 6 and Comparative Example 3, the battery containing the cyclic sulfate compound represented by the formula (6) has improved capacity retention compared to the battery containing PEGLST. For example, LiMn Compared with the case of Example 1 and Comparative Example 1 in which the content of _1.9 Al _0.1 O ₄ is 70% by mass with respect to the mass of the positive electrode active material, the degree of improvement in capacity retention decreases. I understood it. In Example 6, this is achieved by suppressing the elution of Mn ions because the content of LiMn _1.9 Al _0.1 O ₄ is as small as 30% by mass with respect to the mass of the positive electrode active material. This is probably because the magnitude of the effect is relatively small. From the above, from the viewpoint of relatively increasing the effect exerted by suppressing elution of Mn ions, the content of the spinel type lithium manganese oxide is 50% by mass or more with respect to the mass of the positive electrode active material. It is considered preferable. Further, when the content of the spinel type lithium manganese oxide is a value larger than 50% by mass (for example, 70% by mass) with respect to the mass of the positive electrode active material, the effect exerted by suppressing elution of Mn ions. Is considered to be more preferred because it is relatively larger.

In this specification, the Example using the cyclic sulfate compound represented by Formula (6), Formula (7), or Formula (8) as a cyclic sulfate compound represented by General formula (1) is disclosed. is doing. Even if it is a compound other than the cyclic sulfate compound represented by the formulas (6) to (8), when the compound is represented by the general formula (1), it is represented by the formulas (6) to (8). Similar to the cyclic sulfate ester compound, it is considered that the non-aqueous electrolyte secondary battery having a positive electrode containing spinel type lithium manganese oxide has an effect of improving the capacity retention after high temperature storage.

It should be understood that the embodiments disclosed herein and examples embodying the embodiments are illustrative in all respects, and the scope of the present invention is not limited thereby. Those skilled in the art will readily understand that appropriate modifications can be made without departing from the spirit of the present invention based on the above-described embodiments and examples. Accordingly, other embodiments modified without departing from the spirit of the present invention are naturally included in the scope of the present invention.

For example, the shape of the non-aqueous electrolyte secondary battery is not limited to a rectangular shape, and can be a cylindrical or laminated non-aqueous electrolyte secondary battery.

The present invention relates to a non-aqueous electrolyte secondary battery or a method for producing a non-aqueous electrolyte secondary battery, and can improve the capacity retention rate of the non-aqueous electrolyte secondary battery after high-temperature storage. It can be effectively used as a power source for electronic equipment, a power storage power source, and the like.

1 Nonaqueous electrolyte secondary battery 2 Power generation element 3 Positive electrode plate (positive electrode)
4 Negative electrode plate (negative electrode)
DESCRIPTION OF SYMBOLS 5 Separator 6 Battery case 7 Battery cover 8 Safety valve 9 Negative electrode terminal 10 Positive electrode lead 11 Negative electrode lead 20 Power storage unit 30 Power storage device 40 Car body 100 Car

Claims (8)

A non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode, and a non-aqueous electrolyte,
The positive electrode active material includes a spinel type lithium manganese oxide,
The nonaqueous electrolyte is a nonaqueous electrolyte secondary battery containing a cyclic sulfate compound represented by the following general formula (1).

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In General Formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, and the hydrocarbon group having 5 or less carbon atoms may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ] A separator is disposed between the positive electrode and the negative electrode,
The non-aqueous electrolyte secondary battery according to claim 1, wherein the separator includes a base material layer and an insulating layer formed on a surface of the base material layer. The non-aqueous electrolyte secondary battery according to claim 2, wherein the insulating layer is formed on a surface of the base material layer facing the positive electrode. The non-aqueous electrolyte secondary battery according to claim 2 or 3, wherein an average thickness of the insulating layer is 0.5 µm or more and 20 µm or less. The non-aqueous electrolyte secondary battery according to any one of claims 2 to 4, wherein the insulating layer includes an inorganic oxide. The cyclic sulfate compound represented by the general formula (1) is a cyclic sulfate compound represented by the following formula (6) or (7), according to any one of claims 1 to 5. The nonaqueous electrolyte secondary battery as described.

A method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode having a positive electrode active material, a negative electrode, and a non-aqueous electrolyte,
The positive electrode active material includes a spinel type lithium manganese oxide,
The nonaqueous electrolyte is a method for producing a nonaqueous electrolyte secondary battery, which includes a cyclic sulfate compound represented by the following general formula (1).

[In General Formula (1), R ¹ and R ² represent a group bonded to each other represented by Formula (2), or either one represents a hydrogen atom or a hydrocarbon group having 3 or less carbon atoms. And the other represents a group represented by general formula (3), general formula (4) or general formula (5). In the general formula (1), X ¹ represents a halogen atom or a hydrogen atom. In formula (2), the part * indicates a bonding position. In General Formula (3), R ³ represents a halogen atom or a hydrocarbon group having 5 or less carbon atoms, and the hydrocarbon group having 5 or less carbon atoms may be substituted with a halogen atom. In the general formula (3), the part * indicates a bonding position. In general formula (4), X ² represents a halogen atom or a hydrogen atom. In the general formula (4), the part * indicates a bonding position. In General Formula (5), X ³ represents a halogen atom or a hydrogen atom. In the general formula (5), the part * indicates a bonding position. ] A power storage device comprising the nonaqueous electrolyte secondary battery according to any one of claims 1 to 6.

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