Negative Electrode Sheet Particle Clusters for Energy Density and Cycle Life
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Solution Overview
Problem
Existing secondary battery cells face a trade-off between energy density and cycling performance, with increases in energy density leading to reduced dynamics performance and cycle life due to polarization and increased path lengths for ion movement.
Innovation Solution
A negative electrode sheet with a first particle cluster and a second particle cluster, where the compaction density ratio (P1/P2) is maintained between 1.0 and 1.5, ensuring balanced graphitization and minimizing lattice defects and grain boundaries, thereby optimizing ion movement and reducing side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the compaction density of the negative electrode sheet is increased to improve energy density, then the energy density is improved, but the dynamics performance deteriorates due to polarization
Solution Approach 1:
The patent applies local quality by creating two distinct particle clusters with different compaction densities (P1 and P2) within the same negative electrode sheet. The first particle cluster has a higher compaction density to increase energy density, while the second particle cluster has a lower compaction density to maintain dynamics performance and reduce polarization. This spatial differentiation of compaction density allows the electrode to simultaneously achieve high energy storage capacity and good rate capability.
Solution Approach 2:
The patent uses composite materials by combining two types of graphite particles with different properties into a single negative electrode material system. The first particle cluster contains graphite particles with specific size distribution (Dv50: 13-20 μm) and higher compaction density, while the second particle cluster contains graphite particles with different size distribution (Dv50: 5-12 μm) and lower compaction density. This composite structure enables the electrode to exhibit both high energy density and good dynamics performance.
2Quantity of substance
If the active material content is increased to improve energy density, then the energy density is improved, but the cycle life deteriorates due to side reactions
Solution Approach 1:
The patent applies local quality by creating zones with different active material densities. The first particle cluster has higher compaction density (P1) providing more active material per unit volume for energy density, while the second particle cluster has lower compaction density (P2) reducing side reactions and improving cycle stability. The ratio P1/P2 is controlled within 1.05-1.30 to balance these competing requirements.
Solution Approach 2:
The patent uses parameter changes by precisely controlling the compaction density ratio (P1/P2) between 1.05 and 1.30, and particle size distributions (Dv50 values) of both clusters. These parameter optimizations ensure that the first particle cluster contributes maximally to energy density while the second particle cluster maintains structural stability and minimizes side reactions during cycling, thereby extending cycle life.
3Quantity of substance
If the compaction density is increased to improve energy density, then the energy density is improved, but the polarization increases reducing performance
Solution Approach 1:
The patent converts the harmful effect of compaction density increase (which causes polarization) into a benefit by strategically distributing different compaction densities in different regions. The higher compaction density in the first particle cluster increases energy density, while the lower compaction density in the second particle cluster acts as a buffer that reduces overall polarization. This transforms what would be a uniformly harmful effect into a beneficial spatial distribution.
Data Source
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AI summary
A negative electrode sheet, a battery cell, a battery pack, and an electricity-consumption device are involved in the disclosure. The negative electrode sheet includes a negative-electrode current collector and a negative-electrode material layer. The negative-electrode material layer is disposed on a surface of the negative-electrode current collector and includes a first active material. The first active material includes a first particle cluster and a second particle cluster. A compaction density of the first particle cluster after being compressed at a pressure of 5 tons is P1, and a compaction density of the second particle cluster after being compressed at a pressure of 5 tons is P2, where P1 and P2 satisfy: 1.0 ≤ P1/P2 ≤ 1.5. When a volume percentage in the first particle cluster reaches 50%, a corresponding particle size value Dv50 satisfies: 13 µm ≤ Dv50 ≤ 20 µm, and when a volume percentage in the second particle cluster reaches 50%, a corresponding particle size value Dv50' satisfies: 5 µm ≤ Dv50' ≤ 12 µm. In the case where the negative electrode is applied in the battery cell, the battery cell may have a relatively high energy density and a relatively good cycling performance.