Silicon-Graphite Negative Electrode Layout for Low-Swelling Li-Ion Cells
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Solution Overview
Problem
Existing lithium-ion batteries face challenges in achieving high cycle performance and reducing deformation rates due to the inconsistent volume swelling of silicon oxide particles and graphite particles during lithiation.
Innovation Solution
A negative electrode is developed comprising silicon-based particles and graphite particles, where the graphite particles are configured within a specific range (0 to 6 μm) around the silicon-based particles, ensuring that more than 50% of the silicon-based particles have 6 to 17 graphite particles within this range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If silicon-based particles are used to increase capacity, then energy density is improved, but volume swelling during lithiation causes deformation and poor cycle performance
Solution Approach 1:
The patent applies the nesting principle by placing graphite particles inside or around silicon-based particles, creating a core-shell or surrounding structure. The graphite particles (with smaller volume expansion) nest around the silicon-based particles (with larger volume expansion), constraining the silicon expansion and preventing deformation, thus improving cycle performance while maintaining high energy density.
Solution Approach 2:
The patent uses composite materials by combining silicon-based particles with graphite particles in a specific configuration. This composite structure leverages the high capacity of silicon and the structural stability of graphite, creating a hybrid negative electrode that achieves both high energy density and good cycle performance.
2Use of energy by moving object
If silicon-based particles are used to increase capacity, then energy density is improved, but inconsistent volume swelling causes deformation rate to increase
Solution Approach 1:
The patent applies the counterweight principle by using graphite particles as a counterbalancing structure around silicon-based particles. The graphite particles, which have smaller volume swelling, act as a counterweight to the large volume expansion of silicon, constraining and balancing the overall volume change, thus reducing deformation rate while maintaining high energy density.
Solution Approach 2:
The nesting structure of graphite particles around silicon-based particles creates a physical constraint that prevents inconsistent swelling. The graphite shell or surrounding particles nest around the silicon core, limiting its expansion in all directions, thereby maintaining shape stability during charge-discharge cycles.
3Reliability
If graphite particles are added around silicon-based particles to constrain swelling, then cycle performance is improved, but device complexity increases due to specific particle configuration requirements
Solution Approach 1:
The patent applies parameter changes by specifying quantitative parameters for the graphite-silicon configuration: graphite particles within 0-6 μm of silicon-based particles, with 6-17 graphite particles per silicon-based particle. These parameter specifications provide clear manufacturing guidelines that simplify the complexity by transforming a complex structural problem into controllable numerical parameters.
Data Source
AI summary
A negative electrode includes silicon-based particles and graphite particles, where a quantity of graphite particles present within a vertical distance of about 0 to 6 μm to respective edges of the silicon-based particles is N, and based on a total quantity of the silicon-based particles, more than about 50% of the silicon-based particles satisfy: 6≤N≤17. The negative electrode has good cycle performance, and a battery prepared by using the negative electrode has good rate performance and a low deformation rate.