Battery

Abstract

A nonaqueous electrolyte secondary battery includes: a positive electrode; a negative electrode; a nonaqueous electrolyte containing an electrolyte salt; and a separator, wherein in the electrolyte salt, a molar fraction x of at least one member selected among electrolyte salts represented by the following formulae (1) and (2) occupying in the whole electrolyte salt satisfies a relationship of (0.5<x!<=1) LiPFaAc (1) LiBFbB'd (2) wherein a represents an integer of from 0 to 5; b represents an integer of from 0 to 3; each of A and B' independently represents CnF2n+1; n represents an integer of from 1 to 6; c represents an integer of 1 or more and satisfies a relationship of (a+c=6); and d represents a an integer of 1 or more and satisfies a relationship of (b+d=4).

Description

[0001] References to related applications [0002] The present application contains subject matter related to Japanese Priority Patent Application JP 2009-140378 filed in the Japan Patent Office on Jun. 11, 2009, the entire content of which is hereby incorporated by reference. technical field [0003] The present invention relates to a battery using a positive electrode active material containing lithium (Li), and a nonaqueous electrolyte used in the battery. Background technique [0004] Due to the rapid development of portable electronic technologies in recent years, electronic devices such as mobile phones and laptop personal computers have come to be considered as basic technologies supporting a highly informational society. Also, research and development for higher functionality of such electronic devices is actively advancing, and the electric power consumed by such electronic devices is steadily increasing in proportion thereto. On the contrary, such electronic devic...

AI Technical Summary

Problems solved by technology

[0013] However, in the case of stabilizing only the transition metal oxide contained in the positive electrode active material as in Japanese Patent No. 3172388 and JP-A-2000-195517, the transition metal is integrally accumulated on the separator once eluted from the positive electrode or Deposited on the negative electrode, although it may be beneficial to improve the deterioration of capacity, but the effect is still insufficient

In addition, since the surface of the positive electrode in a highly oxidized state in the charged state is sufficiently active, there arises a problem of gas generation due to the decomposition of the non-aqueous electrolyte, or a problem that the separator that makes physical contact with the surface of the positive electrode is large

[0014] Furthermore, in the case where a specific compound is added to the nonaqueous electrolyte as in JP-A-2002-270181 and JP-A-2005-72003, especially at a voltage higher than 4.2 V in open circuit voltage, generally It happens that the effect cannot be achieved due to the fact that it acts unfavorably as a trigger to actively dissolve transition metals from the positive electrode

Also, many nitrogen-containing compounds are reductively decomposed on the negative electrode side, deteriorating the cycle, therefore, it is not preferable

[0015] Furthermore, for the non-aqueous electrolytes proposed in JP-A-2002-138095 and JP-A-2002-356491, the possibility of their use is mentioned, but there arises a defect that their conductivity is lower than that of the actually used electrolyte is poor; and there are no examples of practical application of such non-aqueous electrolytes to electrochemical devices, and their effects are not described

JP-A-2002-280066 reported that LiPF 3 (C 2 f 5 ) 3 As a specific use example of the electrolyte salt in the secondary battery, and the possibility of its application is explained; however, a remarkably good effect has not yet been found, and it is also difficult to expect the effect according to the embodiment of the present invention

[0016] In view of the above introduction, in many cases, the method of improving the stability of the modified positive electrode active material in the non-aqueous electrolyte, or the method of preventing the deterioration of the battery by utilizing the function of the compound added in the non-aqueous electrolyte, is still not enough to achieve Secondary battery with high capacity and good high temperature characteristics

Moreover, almost all effects for the application of batteries have not been accounted for for alternative technologies of non-aqueous electrolytes

[0017] In addition, in the case of combining the above-mentioned technologies, although a higher effect can be expected from the viewpoint of improving battery characteristics, in the results of actual research, there are often cases where the positive electrode is unfavorably corroded, or the inside of the battery Impedance increases, which impairs battery characteristics

In particular, adverse effects are noticeable in batteries that are used under high temperature conditions or whose voltage is set to 4.25V or higher after charging

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