Non-aqueous electrolytic solution and lithium secondary battery

a lithium secondary battery, non-aqueous electrolytic technology, applied in the direction of non-aqueous electrolyte cells, cell components, electrochemical generators, etc., can solve the problems of unsatisfactory battery performance of conventional lithium secondary batteries, and achieve high battery performance, high electric capacity, and high cycling performance.

Inactive Publication Date: 2006-02-02
HAMAMOTO TOSHIKAZU +2
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0008] It is another object of the invention to provide a lithium secondary battery which shows high battery performances such as high electric capacity and high cycling performance, particularly, under the conditions that the maximum operating voltage exceeds 4.1 V and / or the battery is used at high temperatures such as 40° C. or higher.

Problems solved by technology

It is supposed that this trouble is caused by oxidative decomposition of a portion of the non-aqueous solvent of the electrolytic solution on the surface of the positive electrode when the maximum operating voltage exceeds 4.1 V, and the decomposition product disturbs the desired electrochemical reaction in the battery.
Therefore, the conventional lithium secondary batteries are not satisfactory in their battery performances such as the cycling performance and an electric capacity when the batteries are operated in the charge-discharge cycles of which maximum operating voltage exceeds 4.1 V.

Method used

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  • Non-aqueous electrolytic solution and lithium secondary battery
  • Non-aqueous electrolytic solution and lithium secondary battery
  • Non-aqueous electrolytic solution and lithium secondary battery

Examples

Experimental program
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example 1

[0027] 1) Preparation of Electrolytic Solution

[0028] A non-aqueous solvent, i.e., a mixture (1:2, volume ratio) of propylene carbonate (PC) and diethyl carbonate (DEC), was prepared. Subsequently, LiPF6 was dissolved in the non-aqueous solvent to give a 1M concentration solution. Further, biphenyl was added to give a 0.1 wt. % solution. Thus, an electrolytic solution was prepared.

[0029] 2) Preparation of Lithium Secondary Battery and Measurement of Battery Performances

[0030] LiCoO2 (positive electrode active material, 80 wt. %), acetylene black (electro-conductive material, 10 wt. %), and poly(vinylidene fluoride) (binder, 10 wt. %) were mixed. The resulting mixture was diluted with 1-methyl-2-pyrrolidone. Thus produced positive electrode composition was coated on aluminum foil, dried, molded under pressure, and heated to give a positive electrode.

[0031] Natural graphite (d002=0.3354, 90 wt. %) and poly-(vinylidene fluoride) (binder, 10 wt. %) were mixed. The mixture was then di...

example 2

[0062] A secondary battery was prepared in the same manner as in Example 1, except that 0.1 wt. % of biphenyl was replaced with 0.05 wt. % of 4-methoxybiphenyl.

[0063] The prepared secondary battery was subjected to the 100 cycle charge-discharge procedure.

[0064] The initial discharge capacity was 1.03 (relative value based on 1 for that measured in a battery of Comparison Example 1 which contained no biphenyl in the electrolytic solution).

[0065] After the 100 cycle charge-discharge procedure, the discharge capacity was 90.8% of the initial discharge capacity.

example 3

[0066] A secondary battery was prepared in the same manner as in Example 1, except that 0.1 wt. % of biphenyl was replaced with 0.1 wt. % of 4-methoxybiphenyl.

[0067] The prepared secondary battery was subjected to the 100 cycle charge-discharge procedure.

[0068] The initial discharge capacity was 1.03 (relative value based on 1 for that measured in a battery of Comparison Example 1 which contained no biphenyl in the electrolytic solution).

[0069] After the 100 cycle charge-discharge procedure, the discharge capacity was 92.4% of the initial discharge capacity.

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Abstract

A non-aqueous electrolytic solution favorably employable for a lithium secondary battery employs a non-aqueous electrolytic solution which comprises a non-aqueous solvent and an electrolyte which further contains 0.001 to 0.8 weight % of a biphenyl derivative having the formula:
in which each of Y1 and Y2 represents hydroxyl, alkoxy, hydrocarbyl, hydrogen, acyloxy, alkoxycarbonyloxy, alkylsulfonyloxy, or halogen, and each of p and q is an integer of 1 to 3.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a non-aqueous electrolytic solution and a lithium secondary battery employing the non-aqueous electrolytic solution. In particular, the invention relates to a lithium secondary battery having improved electric capacity and cycling performance, and a non-aqueous electrolytic solution which is advantageously employable for preparing the lithium secondary battery. BACKGROUND OF THE INVENTION [0002] At present, potable small electronic devices such as personal computers, cellular phones, and video recorders equipped with camera are widely used, and a small sized secondary battery having light weight and high electric capacity is desired to provide an electric source for driving such small electronic devices. From the view-points of small size, light weight, and high electric capacity, a lithium secondary battery is paid attention. [0003] The lithium secondary battery employs a positive active electrode material comprising a ...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): H01M10/40H01M6/16H01M10/05H01M10/052H01M10/0567
CPCH01M10/0525Y02E60/122H01M2300/0037H01M10/0567Y02E60/10
Inventor HAMAMOTO, TOSHIKAZUABE, KOJIUEKI, AKIRA
Owner HAMAMOTO TOSHIKAZU
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