Kabushiki Kaisha Toshiba

Masashi Fujiwara

Hiroyuki Hasebe

Masahiro Sekino

Asako Satoh

Masayuki Oguchi

Makoto Kato

Koichi Kubo

Shuji Yamada

Motoya Kanda

Kaoru Koiwa

Shinji Arai

Jun Momma

Nao Shimura

Masayuki Onuma

Disclosed is a nonaqueous electrolyte secondary battery, comprising a nonaqueous electrolyte containing ethylene carbonate and &#x3b3;-butyrolactone, wherein, when a charge-discharge cycle test satisfying conditions (A) to (D) given below is performed under an environment of 45&#xb0; C., the capacity retention rate at 100-th charge-discharge cycle is at least 85% based on the discharge capacity in the first charge-discharge cycle, (A) for the charging, the constant current-constant voltage charging to 4.2V is performed for 3 hours under a current of 1C, (B) the discharging is performed to 3V under a current of 1C, (C) after the charging, the secondary battery is left to stand for 10 minutes, followed by performing the discharging, and (D) after the discharging, the secondary battery is left to stand for 10 minutes, followed by performing the charging.

Nonaqueous electrolyte and nonaqueous electrolyte secondary battery

Disclosed is a nonaqueous electrolyte secondary battery, comprising a case having a wall thickness not larger than 0.3 mm, a positive electrode provided in the case, a negative electrode provided in the case and the negative electrode containing a carbonaceous material capable of absorbing-desorbing lithium ions, and a nonaqueous electrolyte provided in the case and the nonaqueous electrolyte containing a nonaqueous solvent including &#x3b3;-butyrolactone and a solute dissolved in the nonaqueous solvent, wherein after being discharged to 3V with a current of 0.2 C at room temperature, the voltage reduction caused by the self-discharge at 60&#xb0; C. is not larger than 1.5V in 3 weeks.

Nonaqueous electrolyte secondary battery having a carbonaceous material containing negative electrode and a nonaqueous electrolyte containing a nonaqueous solvent

Disclosed is a nonaqueous electrolyte comprising a nonaqueous solvent which contains ethylene carbonate (EC), propylene carbonate (PC), &ggr;-butyrolactone (BL), and a fourth component, which is a solvent other than the EC, PC and BL, and the mixing ratio x (% by volume) of EC based on the total amount of the nonaqueous solvent falls within a range of between 15 and 50, the mixing ratio y (% by volume) of PC based on the total amount of the nonaqueous solvent falls within a range of between 2 and 35, the mixing ratio z (% by volume) of BL based on the total amount of the nonaqueous solvent falls within a range of between 30 and 85, and the mixing ratio p (% by volume) of the fourth component based on the total amount of the nonaqueous solvent is larger than 0 and is not larger than 5.

Disclosed is a nonaqueous electrolyte secondary battery, comprising a nonaqueous electrolyte containing ethylene carbonate and &ggr;-butyrolactone, wherein, when a charge-discharge cycle test satisfying conditions (A) to (D) given below is performed under an environment of 45&deg; C., the capacity retention rate at 100-th charge-discharge cycle is at least 85% based on the discharge capacity in the first charge-discharge cycle, (A) for the charging, the constant current-constant voltage charging to 4.2V is performed for 3 hours under a current of 1C, (B) the discharging is performed to 3V under a current of 1C, (C) after the charging, the secondary battery is left to stand for 10 minutes, followed by performing the discharging, and (D) after the discharging, the secondary battery is left to stand for 10 minutes, followed by performing the charging.

This invention provides a nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode and a nonaqueous electrolyte, wherein the positive electrode comprises a lithium-containing nickel oxide having a composition represented by Li.sub.1+x Ni.sub.1-x O.sub.u-y F.sub.y where the ranges of x, y and u meet the following equations (1) to (3):

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Chigasaki, Japan

Masashi Fujiwara