Gradient-Hardness Electrode Structure for High-Density Lithium Batteries
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Solution Overview
Problem
Lithium batteries face challenges in achieving high energy density due to uneven force distribution during electrode rolling, leading to cracking of active material particles, increased internal resistance, and reduced battery life.
Innovation Solution
The electrode is designed with multiple active material sub-layers having gradual hardness increments, ensuring that the hardness difference between sub-layers is within a specific range to prevent cracking and maximize compaction density, thereby improving energy density and extending battery life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the electrode is subjected to rolling to increase compaction density, then the energy density of the lithium battery is improved, but the electrode active material particles crack due to uneven force distribution
Solution Approach 1:
The patent applies local quality by creating a gradient hardness structure within the electrode active material layer. The hardness of the active material varies continuously from the surface toward the interior, with the surface having higher hardness to resist cracking during rolling, while the interior maintains lower hardness for good electrochemical performance. This localized variation in material property resolves the contradiction between achieving high compaction density through rolling and maintaining particle integrity.
2Quantity of substance
If the compaction density of the electrode is increased, then the energy density is improved, but the internal resistance of the battery increases due to particle cracking
Solution Approach 1:
The gradient hardness structure ensures that only the surface region has increased hardness to withstand rolling pressure, while the bulk material maintains its original properties for optimal electrochemical performance. This localized modification prevents the widespread particle cracking that would otherwise increase internal resistance, thus resolving the contradiction between energy density improvement and reliability maintenance.
3Strength
If the electrode active material is hardened to prevent cracking, then particle integrity is improved, but the compaction density decreases
Solution Approach 1:
Instead of uniformly hardening the entire active material layer which would reduce compaction density, the patent implements a gradient where only the surface portion has increased hardness. The interior material remains softer and more compressible, allowing high compaction density to be achieved while the hardened surface protects against cracking during the rolling process.
4Strength
If multiple sub-layers with different hardness are created, then particle integrity is improved, but the device complexity increases
Solution Approach 1:
The patent implements a continuous gradient in the hardness parameter throughout the active material layer, transitioning from high hardness at the surface to low hardness in the interior. This continuous parameter variation achieves the protective effect of multiple discrete hard layers while avoiding the structural complexity of actually creating multiple separate layers, thus resolving the contradiction between particle integrity and structural simplicity.
Data Source
AI summary
An electrode, a lithium battery, and a motor vehicle are provided. The electrode includes a current collector and an electrode active material layer arranged on at least one side surface of the current collector. The electrode active material layer includes at least two electrode active material sub-layers. The electrode active material sub-layers meet: n×δi≤10000, n≥2, and δi≤5000; and Hi-1<Hi. The first electrode active material sub-layer is in contact with the current collector.