Lithium secondary cell

Abstract

The cathode collector retains mixed cathode active material in such a manner that the mixing ratio of lithium cobaltate X thereof should fall in a range of 0.1 <= X <= 0.9, that the bulk density Y (g / cm<3>) of the cathode mixed agent should be confined in a range satisfying the relation of 0.5X + 2.7 <= Y <= 0.6X + 3.3, and that the mean particle diameter of spinel type lithium manganate should be greater than the mean particle diameter of lithium cobaltate. Even in case a mixed cathode active material comprising mixed therein spinel type lithium manganate and lithium cobaltate is used, the invention still is capable of yielding improved load characteristics such as high rate discharge properties by optimizing, not only the bulk density of the cathode mixed agent, but also the mean particle diameter of both active materials, thereby suppressing the lithium cobaltate particles from being oriented.

Description

technical field [0001] The present invention relates to a lithium secondary battery with a positive electrode containing a positive electrode active material capable of storing and releasing lithium ions, a negative electrode containing a negative electrode active material capable of storing and releasing lithium ions, and a non-aqueous electrolyte, and particularly relates to the improvement of the positive electrode active material. Background technique [0002] In recent years, as batteries used in portable electronic and communication devices such as small video recorders, portable phones, and notebook computers, carbon materials that can absorb and release lithium ions are used as negative electrode active materials, and lithium-containing cobalt oxides (LiCoO 2 ), lithium-containing nickel oxide (LiNiO 2 ) and other lithium-containing transition metal oxides that can occlude and release lithium ions as positive electrode active material materials have been put into pra...

AI Technical Summary

Problems solved by technology

[0008] However, since lithium cobaltate has flat particles, the orientation is high. If the packing density is increased, lithium cobaltate will be oriented parallel to the current collector, so the permeability based on the electrolyte will be reduced, and lithium ion absorption will occur. The problem of lower load characteristics such as so-called deep discharge characteristics occurs due to the fact that crystal planes released from storage do not easily exist on the electrode surface.

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