Lithium secondary cell and positive electrode active material, positive plate, and method for manufacturing them

Abstract

Provided is lithium secondary cell and positive electrode active material, positive plate, and method for manufacturing them. A lithium secondary cell comprises a positive electrode active material containing a crystal in which the size of crystallite in the direction parallel to the (003) plane of the crystal of lithium cobaltate is 800 ANGSTROM or more and the coordinate number of a cobalt atom with respect to another cobalt atom is 5.7 or more. The characteristics such as the rate characteristics, low-temperature characteristics, and cycle characteristics of the lithium secondary cell are improved. By adding preferable modes of the positive plate, for example, (a mode in which 50% or less of the surface of the positive electrode active material is covered with an electrically conductive material), (a mode in which the porosity of the positive electrode coating layer lies in the range from 0.08 cc/g to 0.14 cc/g by using two kinds of electrically conductive material having a particle size of 3 mu m or more and 2 mu m or less or by using one kind of electrically conductive material having a particle size of 10 mu m or less), and (a mode in which the specific area of the positive plate coating layer lies in the range from 0.5 m<2>/g to 1.0 m<2>/g by using an electrically conductive material containing at least carbon black), and further adding a mode of a combination of a preferable negative electrode active material and a preferable electrolyte, a more preferable lithium secondary cell has a sufficient cell capacity, and excellent characteristics such as the cycle characteristics, preservation characteristics, safety, and low-temperature characteristics.

Description

technical field [0001] The present invention relates to a positive electrode active material for a lithium storage battery, a positive electrode plate using the same and a manufacturing method thereof, and more specifically relates to the positive electrode active material and a lithium storage battery using the positive electrode plate. Background technique [0002] A lithium secondary battery generally has a structure in which a separator impregnated in an electrolyte is sandwiched between positive and negative plates. The positive electrode plate and the negative electrode plate are formed by placing a positive electrode coating material layer or a negative electrode coating material layer composed of a positive electrode active material or a negative electrode active material mixed with a conductive material or a binder, etc., on a current collector such as metal foil. of. Usually, using LiCoO 2 As the positive electrode active material, a carbon material is used as th...

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Problems solved by technology

[0006] However, the inventors of the present invention have newly discovered that even if the crystallite size of lithium cobalt oxide is controlled within a specific range, the cycle characteristics are not sufficient when it comes to charging and discharging for 500 cycles.

In addition, it was found that even if the crystallite size, lattice constant, chemical composition, etc. are the same, the cycle characteristics, retardation characteristics, and low-temperature characteristics are different depending on the active material.

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