LiCoO2 Cathode Coating for High Energy Density and Capacity
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Solution Overview
Problem
Lithium secondary batteries using LiCoO2 as cathode material face issues with high cost, low charge/discharge capacity, unstable crystal structure at high voltages, and poor high-temperature storage properties, limiting their application and mass production potential, especially in electric vehicles.
Innovation Solution
A cathode material comprising a mixture of oxide powder (a) and oxide powder (b) with specific compositions, where oxide powder (a) is represented by Li x (Co y A m D z )O t and oxide powder (b) by Li x (Ni 1-a-b Mn a CO b ) y O 2, with a mix ratio of 50:50 to 90:10, which stabilizes crystal structures and enhances energy density and capacity properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LiCoO2 is used as cathode material, then high energy density is achieved, but charge/discharge capacity is limited to about 150 mAh/g
Solution Approach 1:
The patent uses a composite cathode material consisting of LiCoO2 particles coated with a layered structured lithium transition metal oxide. This composite structure allows the inner LiCoO2 core to provide high energy density while the outer coating layer provides additional charge/discharge capacity, achieving both high energy density and high capacity simultaneously. The coating layer composition is controlled to have 0.05≤a≤0.4, 0.1≤b≤0.4, and 0.4≤1-a-b≤0.7, optimizing the synergistic effect between the two materials.
2Use of energy by moving object
If LiCoO2 operates at high electric potential (4.3 V or higher), then energy density is improved, but crystal structure becomes unstable and reacts with electrolyte causing combustion
Solution Approach 1:
The patent applies a protective coating of layered structured lithium transition metal oxide on the surface of LiCoO2 particles before battery operation. This pre-applied protective layer acts as a buffer that prevents direct contact between the unstable LiCoO2 surface and the electrolyte, thereby preventing combustion reactions while allowing the battery to operate at high electric potentials (4.3 V or higher) for improved energy density.
Solution Approach 2:
The layered structured lithium transition metal oxide coating serves as an intermediary layer between the LiCoO2 core and the electrolyte. This intermediate layer stabilizes the crystal structure at high potentials by preventing direct interaction with the electrolyte, while still allowing lithium ion transport. The coating composition parameters (0.05≤a≤0.4, 0.1≤b≤0.4, 0.4≤1-a-b≤0.7) are optimized to ensure this mediating function.
3Reliability
If LiCoO2 is coated with metal or thermally treated to improve stability, then crystal structure stability is improved, but manufacturing complexity increases
Solution Approach 1:
The patent combines the coating material synthesis and coating application into a single integrated process. The layered structured lithium transition metal oxide is prepared with specific composition parameters (0.05≤a≤0.4, 0.1≤b≤0.4, 0.4≤1-a-b≤0.7) and directly coated on LiCoO2 particles, merging the material preparation and coating steps to simplify manufacturing while achieving stable crystal structure at high potentials.
4Reliability
If mixture of two or more different lithium transition metal oxides is used, then drawbacks of single oxide are solved, but superior synergetic effects are difficult to obtain
Solution Approach 1:
The patent optimizes the composition parameters of the layered structured lithium transition metal oxide coating to achieve superior synergetic effects. By controlling the parameters 0.05≤a≤0.4, 0.1≤b≤0.4, and 0.4≤1-a-b≤0.7, the patent transforms the simple mixture into a highly effective composite material that achieves both high capacity and high rate properties, overcoming the limitation of conventional mixture-type cathode materials.
Data Source
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AI summary
Disclosed is a cathode material comprising a mixture of an oxide powder (a) defined herein and an oxide powder (b) selected from the group consisting of an oxide powder (b1) defined herein and an oxide powder (b2) defined herein and a combination thereof wherein a mix ratio of the two oxide powders (oxide powder (a): oxide powder (b)) is 50:50 to 90:10. The cathode material uses a combination of an oxide powder (a) and 50% or less of an oxide powder (b) which can exert high capacity, high cycle stability, superior storage stability and high-temperature stability, thus advantageously exhibiting high energy density and realizing high capacity batteries.