Negative Electrode Interface Structure for Overcharge Protection
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Solution Overview
Problem
Lithium-ion batteries face safety hazards due to internal overheating, which can lead to thermal runaway and explosions, necessitating improved high-temperature cycle expansion and overcharge protection performance.
Innovation Solution
The electrochemical device incorporates a negative electrode with a negative active material layer of specific weight and a conductive material with an average particle diameter smaller than the negative active material, positioned between the negative active material layer and the negative current collector, along with an electrolytic solution containing specific compounds to enhance safety performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the negative active material layer weight is increased to improve capacity, then the energy storage increases, but the high-temperature cycle expansion performance deteriorates
Solution Approach 1:
The patent optimizes the weight per unit area of the negative active material layer to a specific range (3-12 mg/cm²) to balance capacity and high-temperature stability. This parameter optimization prevents excessive material deposition that would cause thermal runaway while maintaining sufficient energy storage capacity.
Solution Approach 2:
The patent uses composite materials including conductive materials (carbon black, carbon fiber, graphene, or carbon nanotubes) with specific particle size ratios relative to the negative active material. This composite structure improves both capacity and thermal stability by creating a hierarchical architecture that facilitates heat dissipation and maintains structural integrity at high temperatures.
2Reliability
If the conductive material particle diameter is decreased to improve conductivity, then the electrical performance increases, but the manufacturing complexity increases
Solution Approach 1:
The patent specifies that the average particle diameter of the conductive material should be smaller than that of the negative active material, with a preferred range of less than or equal to 1 μm. This parameter control achieves optimal conductivity without requiring excessively fine particles that would be difficult to manufacture.
Solution Approach 2:
The conductive material is strategically positioned between the negative active material layer and the negative current collector, creating localized high-conductivity pathways at the interface where electron transfer is most critical, rather than uniformly distributing conductive material throughout the entire electrode structure.
3Strength
If the tensile strength of the negative current collector is increased to improve mechanical strength, then the structural integrity increases, but the device complexity increases
Solution Approach 1:
The patent specifies that the tensile strength of the negative current collector should be F N/mm² where F is greater than or equal to 400, and satisfies the relationship 100/3 ≤ F/W ≤ 150. This parameter optimization ensures sufficient mechanical strength for structural integrity while preventing excessive strength requirements that would increase device complexity and cost.
Solution Approach 2:
The negative current collector is pre-designed and pre-manufactured with the required tensile strength properties before assembly into the electrochemical device. This preliminary preparation of the current collector with optimized mechanical properties simplifies the overall device assembly process and reduces the need for complex reinforcement structures during device fabrication.
Data Source
AI summary
An electrochemical device including a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a negative current collector and a negative active material layer formed on the negative current collector. The negative active material layer contains a negative active material. A conductive material is disposed between the negative active material layer and the negative current collector. An average particle diameter of the conductive material is smaller than that of the negative active material. The negative active material layer possesses a specific weight. The electrochemical device improves high-temperature cycle expansion performance and overcharge protection performance.