Negative Electrode Particle Clusters for High-Density Battery Cycling
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Solution Overview
Problem
Existing secondary battery cells face a trade-off between increased energy density, which can lead to reduced dynamic performance and shorter cycle life due to increased compaction density and active material thickness, causing polarization and inefficient ion movement.
Innovation Solution
A negative electrode sheet with a specific composition of first and second particle clusters, where the compaction densities of these clusters are optimized to maintain a balanced degree of graphitization, particle size distribution, and surface area, reducing polarization and enhancing cycling performance.
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 and cycle life are reduced due to polarization and inefficient ion movement
Solution Approach 1:
The negative electrode material is divided into two distinct particle clusters: a first particle cluster with larger particle sizes (Dv50: 13-20 μm) and higher compaction density (P1), and a second particle cluster with smaller particle sizes (Dv50': 5-12 μm) and lower compaction density (P2), where P1/P2 is controlled within 1.0-1.5. This segmentation allows the larger particles to provide high energy density while the smaller particles ensure efficient ion movement and reduce polarization, thereby maintaining good cycle life.
Solution Approach 2:
Different regions of the negative electrode material exhibit different properties through the two particle clusters. The first particle cluster contributes to high compaction density and energy storage capacity in specific regions, while the second particle cluster ensures good ion transport and electrochemical activity in other regions. This local quality differentiation resolves the contradiction between energy density and cycle life.
2Quantity of substance
If the thickness of the active material layer is increased to improve energy density, then the energy density is improved, but the ion movement efficiency is reduced leading to shorter cycle life
Solution Approach 1:
The active material layer contains two particle clusters with different size distributions. The smaller second particle cluster (Dv50': 5-12 μm) with lower compaction density creates more void spaces and shorter ion transport paths, ensuring efficient ion movement even when the overall layer thickness is increased for higher energy density. The larger first particle cluster (Dv50: 13-20 μm) provides the necessary energy storage capacity.
3Quantity of substance
If the compaction density is increased to improve energy density, then the energy density is improved, but polarization increases reducing dynamics performance
Solution Approach 1:
The negative electrode material is segmented into two particle clusters with different compaction densities. The first particle cluster has higher compaction density (P1) contributing to energy density, while the second particle cluster has lower compaction density (P2) where P1/P2 is controlled at 1.0-1.5. The smaller particles in the second cluster create more interstitial spaces that facilitate electrolyte penetration and ion transport, thereby reducing polarization effects while maintaining high energy density through the combined structure.
Solution Approach 2:
The patent controls the ratio of compaction densities (P1/P2) within a specific range of 1.0-1.5, and controls the particle size distribution (Dv50: 13-20 μm for first cluster, Dv50': 5-12 μm for second cluster). By optimizing these parameters, the structure achieves high energy density while minimizing polarization through balanced packing density and adequate ion transport pathways.
Data Source
AI summary
A negative electrode sheet includes a negative-electrode current collector and a negative-electrode material layer disposed on the negative-electrode current collector. The negative-electrode material layer includes a first active material that 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.