Secondary Battery Cathode Mix for End-of-Discharge Resistance Balance
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Solution Overview
Problem
Secondary batteries with silicon-based compounds in the negative electrode active material layer face issues of increased resistance at the end of discharge, leading to a significant difference in resistance between the negative and positive electrodes, which shortens battery life and deteriorates room temperature cycle characteristics.
Innovation Solution
Incorporating a lithium nickel-based active material in the form of a single particle with 55 mol.% or more nickel content, along with one or more of LCO (LiCoO2), LMO (LiMn2O4), and LFP (LiFePO4) in the form of secondary particles, in the positive electrode active material layer to reduce resistance differences and improve battery performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a silicon-based compound is included in the negative electrode active material layer to enable rapid charging, then charging speed is improved, but the resistance of the negative electrode increases rapidly at the end of discharge, resulting in a large difference between the resistance of the negative electrode and the resistance of the positive electrode, which shortens battery life and deteriorates room temperature cycle characteristics
Solution Approach 1:
The patent changes the particle morphology parameter of the positive electrode active material from aggregated secondary particles to single particles. This parameter change modifies the electrode's resistance characteristics, specifically reducing the rapid decrease in positive electrode resistance at the end of discharge, thereby balancing the resistance difference between electrodes and improving battery life and cycle characteristics while maintaining rapid charging capability
Solution Approach 2:
The patent uses a composite positive electrode active material consisting of multiple components including LCO, LMO, LFP, and silicon oxide. This composite material approach allows optimization of both charging speed and battery reliability by combining materials with complementary properties, where each component contributes to different aspects of performance
2Ease of manufacture
If the positive electrode uses conventional secondary particle structure, then manufacturing is easier, but the resistance decreases rapidly at the end of discharge, increasing the resistance difference between electrodes
Solution Approach 1:
The patent inverts the conventional particle structure approach by using single particles instead of aggregated secondary particles for the positive electrode active material. This inversion of the structural paradigm achieves improved resistance stability at the end of discharge while still being manufacturable through established single-particle synthesis methods
Data Source
AI summary
A secondary battery including a positive electrode and a negative electrode. The negative electrode includes a silicon-based active material and a carbon-based active material. The positive electrode includes a lithium nickel-based active material in the form of a single particle, and one or more of LCO (LiCoO2), LMO (LiMn2O4) and LFP (LiFePO4) in the form of secondary particles. The lithium nickel-based active material in the form of a single particle contains 55 mol. % or more of nickel with respect to 100 mol. % of metals excluding lithium.