Anode Active Material Coating for Battery Stability
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Solution Overview
Problem
Lithium secondary batteries face challenges in maintaining stability and power capacity due to side reactions and mechanical damage from repeated charging and discharging, which degrades the conductivity of anode active materials.
Innovation Solution
An anode for secondary batteries is developed using a combination of first and second anode active material particles, where the first particles have a core with a coating layer and the second particles have a larger diameter, improving hardness and sphericity, and a content ratio of 60-90 wt% of the first particles enhances pressing and high-rate properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the anode active material composition is changed to improve stability, then the stability is improved, but the conductivity is degraded and power is deteriorated
Solution Approach 1:
The patent uses a composite material system consisting of soft carbon particles (graphite-based) and hard carbon particles (amorphous carbon-based). The soft carbon provides stability and structural integrity, while the hard carbon maintains conductivity and power properties. This composite approach allows simultaneous improvement of stability and preservation of conductivity by combining materials with complementary properties.
2Stability of the object's composition
If the anode active material composition is changed to improve stability, then the stability is improved, but the power is deteriorated
Solution Approach 1:
The composite of soft carbon and hard carbon particles enables simultaneous achievement of stability and power. The hard carbon component with its amorphous structure provides better ionic conductivity and power properties, while the graphite-based soft carbon provides structural stability. The synergistic effect of this composite system resolves the trade-off between stability and power.
Solution Approach 2:
The patent applies local quality by having different particle types distributed throughout the anode active material layer. Each particle type contributes its specific properties locally - soft carbon particles provide stability in their regions while hard carbon particles maintain conductivity and power in their regions. This spatial distribution of different material qualities allows the overall system to achieve both stability and power.
3Strength
If a coating layer is formed on the core particle, then the hardness is improved, but the manufacturing complexity increases
Solution Approach 1:
The coating layer is formed on the core particle in advance during the manufacturing process, before the particles are mixed and assembled into the electrode. This preliminary coating action ensures that the core particle is pre-protected with a harder outer layer, improving overall particle hardness and resistance to mechanical damage. By performing this action beforehand, the process integrates smoothly into the existing manufacturing workflow without requiring additional complex steps later.
Data Source
AI summary
Secondary batteries including an anode and having improved capacity properties and stability are disclosed. In an aspect, an anode for a secondary battery includes first anode active material particles, each of the first anode active material particles having a single particle structure that includes a core particle and a coating layer formed on a surface of the core particle, and second anode active material particles having an average particle diameter greater than that of the first anode active material particles. A ratio of a weight of the first anode active material particles to a total weight of the first anode active material particles and the second anode active material particles is in a range from 50 wt % to 100 wt %.