Negative Electrode Sheet Cohesion and Density for Low Battery Swelling
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Solution Overview
Problem
The cycle life of lithium ion batteries is limited by uneven thickness expansion of electrode sheets during charging and discharging, leading to gas generation and reduced battery capacity.
Innovation Solution
A negative electrode sheet with a controlled cohesive force, compaction density, and particle size change rate, optimized by specific equations, to reduce thickness expansion and improve gas management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If the negative electrode sheet has high compaction density to reduce thickness expansion, then the cycle life is improved, but the gas generation increases due to side reactions
Solution Approach 1:
The patent applies parameter changes by precisely controlling the compaction density within 1.45-1.70 g/cm³ and cohesive force within 25-65 N/m ranges. These optimized parameters reduce thickness expansion during cycling while minimizing side reactions that cause gas generation, thereby resolving the contradiction between improving cycle life and reducing harmful gas accumulation.
Solution Approach 2:
The patent implements preliminary anti-action through pre-treatment of the negative electrode sheet before battery assembly. By optimizing the cohesive force and compaction density in advance, the electrode structure is pre-stabilized to resist thickness expansion during subsequent cycling, preventing the conditions that lead to gas generation and extending cycle life simultaneously.
2Stability of the object's composition
If the negative electrode sheet has high cohesive force to reduce thickness expansion, then the structural stability is improved, but the manufacturing precision becomes more difficult to control
Solution Approach 1:
The patent resolves this contradiction by defining a specific range for cohesive force (25-65 N/m) rather than maximizing it indefinitely. This parameter optimization ensures sufficient structural stability while maintaining manufacturability, as the range is wide enough to accommodate normal manufacturing variations yet narrow enough to prevent excessive thickness expansion.
Solution Approach 2:
The patent applies preliminary action by pre-controlling the cohesive force and compaction density during electrode sheet preparation before battery assembly. This advance control of structural parameters ensures that the electrode maintains stable dimensions during cycling without requiring extremely tight manufacturing tolerances, thus balancing structural stability with manufacturing feasibility.
3Duration of action of stationary object
If the negative electrode sheet has optimized compaction density to reduce thickness expansion, then the cycle life is extended, but the gas accumulation in the battery increases
Solution Approach 1:
The patent resolves this contradiction through parameter optimization of compaction density (1.45-1.70 g/cm³). This optimized density reduces thickness expansion during cycling, thereby extending cycle life, while simultaneously minimizing the volume available for gas accumulation and reducing side reactions that generate gas, thus addressing both issues concurrently.
Data Source
AI summary
The present invention discloses a negative electrode sheet, a secondary battery including the negative electrode sheet, and an electric device, and belongs to the technical field of batteries. The negative electrode sheet of the present invention includes a negative electrode current collector and a negative electrode active material layer. The negative electrode active material layer includes an negative electrode active material, the negative electrode sheet satisfies an equation as follows: 0.15≤(F×ps)/(ρ×100)≤10, where F is a cohesive force of the negative electrode sheet, in the unit of N/m; ps is a particle size change rate of the negative electrode active material, in the unit of %; and ρ is a compaction density of the negative electrode sheet, in the unit of g/cm3.