Nonaqueous electrolyte solution and nonaqueous electrolyte battery using same

Abstract

A nonaqueous electrolyte solution for a secondary battery that inhibits increases in resistance during high-temperature storage in a charged state and decreases in capacity, as well as a secondary battery that uses this lithium nonaqueous electrolyte solution. A lithium nonaqueous electrolyte secondary battery that incorporates this non-aqeuous electrolyte solution and that demonstrates a favorable overall balance of battery performance with respect to performance such as durability, capacity, resistance and output characteristics.

Description

TECHNICAL FIELD[0001]The present invention relates to a nonaqueous electrolyte solution and a nonaqueous electrolyte battery using the same.BACKGROUND ART[0002]Accompanying the rapid progress made in the area of cell phones, laptop personal computers and other portable electronic devices, there is a growing demand for batteries used as the main and backup power supplies thereof to demonstrate higher capacities, and nonaqueous electrolyte batteries such as lithium ion secondary batteries are attracting attention for such applications since they demonstrate higher energy density in comparison with nickel-cadmium batteries or nickel-hydrogen batteries.[0003]Typical examples of the electrolyte solution of lithium ion secondary batteries include nonaqueous electrolyte solutions obtained by dissolving an electrolyte, such as LiPF6, LiBF4, LiN(CF3SO2)2 or LiCF3(CF2)3SO3, in a mixed solvent consisting of a solvent having a high dielectric constant, such as ethylene carbonate or propylene ca...

AI Technical Summary

Benefits of technology

[0046]According to the present invention, a lithium nonaqueous electrolyte secondary battery can be provided that demonstrates favorable overall balance of battery performance with respect to performance such as durability, capacity, resistance and output characteristics.

[0047]Although the action and principle behind a nonaqueous electrolyte secondary battery fabricated using the nonaqueous electrolyte solution of the present invention and the nonaqueous electrolyte secondary battery of the present invention demonstrating favorable overall balance of battery performance is not clear, they are thought to be as indicated below. However, the present invention is not limited to the action and principle described below.

[0048]Although the compounds described in Patent Documents 1 to 5 are reported to improve high-temperature storage characteristics and cycle characteristics of a battery by acting on the positive electrode or negative electrode of the battery to inhibit a decomposition reaction of the electrolyte solution, the majority of the effects thereof were limited to improvement of high-temperature storage characteristics and those effects were unable to be said to be adequate. In addition, the effect of improving cycle characteristics described in Patent Document 2 was also inadequate and was not satisfactory.

[0049]Although it is described in Patent Document 6 that a fluorinated cyclic carbonate such as fluoroethylene carbonate is used as a cyclic carbonate in an electrolyte solution, the optimum amount thereof and the like are not clear.

[0050]In order to solve the aforementioned problems, the present invention contains a compound containing a structure represented by formula (A) and (1) at least one compound selected from the group consisting of a nitrile compound, an isocyanate compound, a difluorophosphate, a fluorosulfonate, a lithium bis(fluorosulfonyl)imide and a compound represented by general formula (B). As a result, it was found that not only high-temperature storage characteristics, but also cycle characteristics and rate characteristics are also improved, thereby leading to completion of the present invention.

[0051]In order to solve the aforementioned problems, the present invention contains a compound containing a structure represented by formula (A) and (2) a cyclic carbonate compound having a fluorine atom in an amount of 0.01% by mass to 50.0% by mass based on the total amount of the nonaqueous electrolyte solution. As a result, the suitable amount of cyclic carbonate having a fluorine atom contained in the nonaqueous electrolyte solution was found, thereby leading to completion of the present invention.

Problems solved by technology

In addition, lithium ion secondary batteries have conventionally been known to undergo a decrease in capacity when repeatedly charged and discharged, an increase in battery internal resistance when stored under high-temperature conditions while in the charged state, deterioration such as a decrease in battery capacity, or in the worst possible scenario, have the potential for being extremely dangerous due to rupturing or ignition of the battery due to a runaway reaction within the battery per se, and various studies have also been conducted on nonaqueous solvents and electrolytes in order to rectify this situation.

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