Composite Cathode Material for Stable Power in Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face limitations in maintaining stable power across a wide state of charge (SOC) range, particularly in electric vehicles, due to rapid resistance increases and capacity degradation in low SOC conditions, which poses safety concerns and limits their application in medium and large-sized devices.
Innovation Solution
A composite cathode active material is developed by mixing layered lithium manganese oxide with a lithium-containing metal oxide, such as Li(Ni x Co y Al z )O 2, to enhance discharge potential and stability across a wide SOC range, incorporating additional elements like Al, Mg, Ni, Co, and others for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If LiCoO2 is used as cathode material to achieve high energy density, then capacity is improved, but structural stability deteriorates causing safety issues at high temperature
Solution Approach 1:
The patent uses a composite cathode material consisting of LiCoO2 particles coated with a lithium manganese oxide layer. This composite structure combines the high capacity of LiCoO2 with the thermal stability of lithium manganese oxide, preventing structural degradation and oxygen release at high temperatures while maintaining high energy density
2Quantity of substance
If lithium manganese oxide is used to improve safety and capacity, then capacity is improved, but resistance increases rapidly at low SOC range
Solution Approach 1:
The patent applies a gradient composition structure where the cathode material has different compositions at different locations: the core contains lithium manganese oxide for safety and capacity, while the outer shell contains LiCoO2 with higher conductivity. This local differentiation ensures good power characteristics at low SOC while maintaining overall safety and capacity
3Quantity of substance
If high capacity cathode materials are used to increase energy density, then energy density is improved, but power characteristics deteriorate due to rapid resistance increase
Solution Approach 1:
The patent creates a composite cathode structure combining lithium manganese oxide and LiCoO2 in specific ratios, where the lithium manganese oxide provides high capacity and safety while the LiCoO2 component maintains good electrical conductivity and power characteristics, achieving both high energy density and sustained power delivery
Data Source
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AI summary
Provided is a composite cathode active material including layered lithium manganese oxide and lithium-containing metal oxide. Also, the present invention provides a secondary battery, a battery module, and a battery pack which have improved power characteristics by including the composite cathode active material.