NCA Cathode Powder Surface Treatment for Gas-Suppressed Li-Ion Cells
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Solution Overview
Problem
Lithium ion batteries face challenges with NCA-based positive electrode active materials, which exhibit high gas generation during repeated charging and discharging, leading to safety issues and reduced cycle characteristics, especially in laminate cells.
Innovation Solution
A lithium metal composite oxide powder with a composition of LiaNibCocAldO2, treated with an aqueous solution of an organic metal salt and a soluble aluminum salt or thiosulfate, is used as a positive electrode active material, reducing gas generation and enhancing cycle retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If NCA based positive electrode active material is used to achieve high discharge capacity, then the discharge capacity exceeds 190 mAh/g, but gas generation increases significantly during repeated charging and discharging
Solution Approach 1:
An aqueous solution containing an organic metal salt and a soluble aluminum salt is introduced as an intermediary treatment medium. This solution is applied to the surface of the NCA positive electrode active material, where the aluminum salt forms a protective layer that suppresses gas generation during battery operation, while the organic metal salt facilitates proper drying and coating of the material
Solution Approach 2:
The chemical composition and surface properties of the NCA material are modified by changing parameters such as aluminum content concentration in the aqueous solution, drying temperature, and treatment time. These parameter changes create an optimized surface state that reduces gas generation while preserving the high discharge capacity of the material
2Use of energy by moving object
If NCA based positive electrode active material is used to achieve high discharge capacity, then the discharge capacity exceeds 190 mAh/g, but cycle characteristics deteriorate due to gas generation and structural changes
Solution Approach 1:
The aqueous solution of organic metal salt and soluble aluminum salt serves as a protective intermediary layer on the NCA material surface. This layer stabilizes the material structure during repeated charging and discharging cycles, preventing structural changes and gas generation that would otherwise deteriorate cycle characteristics
Solution Approach 2:
The surface treatment with aqueous solution is performed in advance before the battery is assembled and put into service. This preliminary action prepares the NCA material with optimized surface properties that will maintain stability throughout the battery's operational life, ensuring good cycle characteristics from the start
3Object-generated harmful factors
If conventional washing treatment is applied to suppress gas generation, then gas generation is reduced, but the capacity of the positive electrode active material is reduced
Solution Approach 1:
Instead of conventional washing that removes surface materials, the invention uses a carefully controlled aqueous solution treatment with specific concentrations of organic metal salt and soluble aluminum salt. The parameters are optimized so that the treatment suppresses gas generation through chemical modification rather than physical removal, thereby preserving the material's discharge capacity
Data Source
AI summary
To provide a positive electrode active material of a lithium ion battery which has a large discharge capacity, excellent cycle characteristics, and suppressed gas generation. Resolution Means: A lithium metal composite oxide powder for use in a positive electrode active material for a lithium ion battery, the powder thereof having a composition of LiaNibCocAldO2 (wherein, a=0.8 to 1.2, b=0.7 to 0.95, c=0.02 to 0.2, d=0.005 to 0.1, and b+c+d=1) treated with an aqueous solution of an organic metal salt and soluble aluminum salt, and not causing volume expansion due to gas generation.