Hard Carbon Negative Electrode Composition for First-Cycle Efficiency
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Solution Overview
Problem
Hard carbon materials used in batteries face challenges with low first-cycle discharge efficiency, poor cycle stability, and poor rate characteristics, making them unsuitable as negative materials despite their potential due to large interlayer spacing and disordered structure.
Innovation Solution
A negative electrode plate is designed with a hard carbon material layer comprising primary and secondary particles, where the primary particles have a defect value different from the secondary particles, optimizing the structure to enhance energy density and first-cycle discharge efficiency while minimizing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If hard carbon materials are used as negative electrode materials, then large interlayer spacing and disordered structure are achieved, but low first-cycle discharge efficiency and poor cycle stability occur
Solution Approach 1:
The patent applies local quality by creating a heterogeneous particle system where primary particles and secondary particles have different defect values. Primary particles with higher defect values provide more active sites for ion insertion, while secondary particles with lower defect values provide structural stability. This local differentiation resolves the contradiction by allowing different regions of the electrode to fulfill different functions: high defect areas enhance discharge efficiency while low defect areas maintain cycle stability.
Solution Approach 2:
The patent uses composite materials by combining primary particles and secondary particles with different defect characteristics into a unified negative electrode structure. This composite approach allows the electrode to simultaneously exhibit high discharge efficiency (from high-defect primary particles) and good cycle stability (from low-defect secondary particles), resolving the technical contradiction through material composition rather than uniform structure.
2Quantity of substance
If hard carbon materials with many defects are designed, then energy density is improved, but first-cycle discharge efficiency decreases
Solution Approach 1:
The patent implements local quality by spatially distributing particles with different defect values throughout the electrode structure. High-defect primary particles are dispersed among low-defect secondary particles, creating localized regions of high energy density without sacrificing overall discharge efficiency. This allows the electrode to achieve high energy density through defect-rich particles while maintaining good first-cycle efficiency through defect-poor particles.
Solution Approach 2:
The patent applies parameter changes by varying the defect value parameter across different particle types rather than using a uniform defect value. By controlling the defect values of primary and secondary particles to be different, the patent optimizes both energy density (through high-defect particles) and first-cycle discharge efficiency (through low-defect particles), resolving the contradiction through parameter differentiation.
3Ease of manufacture
If uniform defect value particles are used, then manufacturing simplicity is maintained, but both energy density and first-cycle efficiency cannot be optimized simultaneously
Solution Approach 1:
The patent applies segmentation by dividing the negative electrode material into two distinct particle types: primary particles and secondary particles, each with different defect values. This segmentation allows independent optimization of each particle type's properties while maintaining a relatively simple manufacturing process. The segmented structure enables simultaneous achievement of high energy density and first-cycle efficiency without significantly complicating manufacturing.
Data Source
AI summary
A negative electrode plate, a battery, and a battery pack are provided. The negative electrode plate includes a negative current collector and a negative material layer disposed on a surface of the negative current collector. The negative material layer includes a hard carbon material containing primary particles and secondary particles, and the primary particles have a defect value different from that of the secondary particles. In comparison with the solution of only using one kind of hard carbon particles having the same defect value as the negative material layer, the negative electrode plate of the present disclosure includes two kinds of hard carbon particles with different defect values, which combines the excellent properties of the two kinds of hard carbon particles. Therefore the negative electrode plate has excellent properties while satisfying the requirements of a battery, such as high energy density, high first-cycle discharge efficiency, and excellent rate performance.