In recent years, power storage systems to be applied for small apparatuses that need high energy density, such as information technology-related apparatuses or communication apparatuses, specifically, personal computers, video cameras, digital still cameras, and cell phones, and power storage systems to be applied for large apparatuses that need power, such as electric vehicles, hybrid vehicles, auxiliary power for fuel cell vehicles, and energy storage have received attention. As a candidate therefor, non-aqueous electrolyte batteries such as a lithium ion battery, a lithium battery, a lithium ion capacitor, or a sodium ion battery, have been actively developed.
Many of these non-aqueous electrolyte batteries have already been put into practical use, however, none of these batteries are sufficient for various applications in terms of respective characteristics. In particular, a battery to be applied for a vehicle such as an electric vehicle is required to have a high input output characteristic even in a cold season. Hence, improvement in a low-temperature characteristic is important. Moreover, such a battery is required to have a high-temperature cycle characteristic such that it is capable of maintaining its characteristics (less increase in internal resistance) even when charging and discharging are performed repeatedly under a high-temperature environment.
As a means for improving the high-temperature characteristic, and the battery characteristics (a cycle characteristic) wherein charging and discharging are repeated, optimization of various battery components including active materials of positive electrodes and negative electrodes has been studied. A non-aqueous electrolytic solution-related technology is not an exception, and it has been proposed that deterioration due to decomposition of an electrolytic solution on the surface of an active positive electrode or an active negative electrode is suppressed by various additives. For example, Patent Document 1 proposes that battery characteristics are improved by the addition of a vinylene carbonate to an electrolytic solution. However, this is problematic in that battery characteristics at high temperatures are improved, but the internal resistance is significantly increased to lower the low-temperature characteristic. Furthermore, a number of examinations on the addition of an imide salt to an electrolytic solution have been conducted. For example, there have been proposed a method (Patent Document 2) for suppressing deterioration in a high-temperature cycle characteristic or a high-temperature storage characteristic by combining a specific sulfonimide salt or a phosphoryl imide salt with an oxalato complex, and a method (Patent Document 3) for suppressing deterioration in a cycle characteristic or an output characteristic by combining a specific sulfonimide salt with a fluorophosphate.
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