Lithium Cobalt Composite Oxide with Inorganic Fluoride for Battery Cycle Stability
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Solution Overview
Problem
Lithium secondary batteries face issues with deterioration of cycle characteristics, high voltage tolerance, and energy density retention, requiring improvements in average operation voltage maintenance and energy density.
Innovation Solution
A positive electrode active substance comprising a mixture of titanium-containing lithium cobalt composite oxide particles and inorganic fluoride particles, with specific molar ratios and elemental compositions, is used to enhance cycle characteristics and maintain high average operation voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium cobaltate is used as a positive electrode active substance, then high capacity and energy enhancement are achieved, but cycle characteristics deteriorate due to dissolving-out of cobalt atoms
Solution Approach 1:
The patent uses a composite material consisting of lithium cobalt-based composite oxide particles combined with fluorinated hydrocarbon compounds. This composite structure allows the lithium cobaltate to provide high capacity while the fluorinated hydrocarbon forms a protective layer that prevents cobalt dissolution, thereby maintaining both high capacity and improved cycle characteristics.
Solution Approach 2:
The fluorinated hydrocarbon acts as an intermediary substance that forms a protective interface between the lithium cobaltate active material and the electrolyte. This intermediary layer prevents direct contact and chemical reactions that would cause cobalt dissolution, while still allowing lithium ion transport, thus preserving cycle stability without sacrificing capacity.
2Quantity of substance
If high voltage tolerance is pursued for capacity enhancement, then energy enhancement is achieved, but average operation voltage drops and energy density retention decreases
Solution Approach 1:
The patent modifies the chemical composition parameters of the positive electrode by incorporating fluorinated hydrocarbons with specific fluorine content (0.1-5.0 at%). This parameter change in composition allows the material to maintain high operating voltage by stabilizing the crystal structure and preventing voltage fade, while still achieving high capacity through the lithium cobaltate base material.
Data Source
AI summary
The positive electrode active substance for a lithium secondary battery includes a mixture of a titanium-containing lithium cobalt composite oxide particle and an inorganic fluoride particle. The method for producing a positive electrode active substance for a lithium secondary battery includes a first step of subjecting a titanium-containing lithium cobalt composite oxide particle and an inorganic fluoride particle to a mixing treatment to thereby obtain a mixture of the titanium-containing lithium cobalt composite oxide particle and the inorganic fluoride particle. The lithium secondary battery uses, as a positive electrode active substance, the positive electrode active substance for a lithium secondary battery of the present invention.