Layered Lithium Battery Anode to Limit Pre-Lithiation Deformation
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Solution Overview
Problem
Lithium secondary batteries face surface deformation issues during pre-lithiation due to varying volume expansion rates of mixed negative electrode active materials, affecting battery assembly and performance.
Innovation Solution
A negative electrode with a uni-modal particle diameter distribution in the second active material layer, ranging from 0.1 to 10 um, is formed on a first layer containing a carbon-based material and high-capacity materials like silicon or silicon oxide, ensuring uniform lithium ion diffusion and minimizing structural deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If mixed negative electrode active materials (carbon-based and high-capacity materials) are used to increase energy density, then capacity is improved, but surface deformation occurs during pre-lithiation due to different volume expansion rates
Solution Approach 1:
The negative electrode active material layer is segmented into multiple layers with different particle size distributions. The first layer contains particles with a broader size distribution, while the second layer contains particles with a uni-modal distribution (D10/D90 ≤ 0.5). This segmentation allows each layer to contribute differently to capacity while the second layer's uniform particle sizes ensure uniform lithium ion diffusion and minimize surface deformation during pre-lithiation.
Solution Approach 2:
Different regions of the negative electrode active material layer are given different local qualities through the multi-layer structure. The second layer, positioned at specific locations, has a specialized uni-modal particle diameter distribution specifically designed to control lithium ion diffusion rates and prevent surface deformation, while the first layer provides overall capacity. This local quality differentiation resolves the contradiction between high capacity and surface stability.
2Loss of energy
If pre-lithiation is performed to reduce initial irreversibility, then initial capacity loss is reduced, but surface bending and deformation occur due to uniform volume expansion of mixed materials
Solution Approach 1:
The negative electrode is designed with a multi-layer particle size distribution structure before pre-lithiation occurs. The second layer's uni-modal particle diameter distribution (D10/D90 ≤ 0.5) is prepared in advance to ensure uniform lithium ion diffusion during the pre-lithiation process. This preliminary structural preparation allows pre-lithiation to proceed uniformly across the electrode surface, reducing initial irreversibility while preventing surface bending and deformation that would occur with mixed particle sizes.
3Quantity of substance
If high-capacity active materials with high volume expansion rates are used, then energy density is increased, but electrode structure integrity deteriorates due to swelling
Solution Approach 1:
The negative electrode active material is segmented into a first layer with broader particle size distribution and a second layer with uni-modal distribution (D10/D90 ≤ 0.5). The second layer's uniform particle sizes ensure consistent lithium ion diffusion and uniform swelling behavior, which maintains electrode structure integrity even when high-capacity materials with high volume expansion rates are included in the first layer, thereby preserving energy density while preventing structural deterioration.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution prevents surface deformation during pre-lithiation, enhancing the battery's performance and maintaining electrode structure integrity, leading to improved capacity and lifetime characteristics.
Implementation Method 1
ensuring uniform lithium ion diffusion and minimizing structural deformation
Data Source
Figure 1~2
AI summary
Provided herein are a negative electrode for a lithium secondary battery and a lithium secondary battery comprising the same. The negative electrode comprises a negative electrode current collector, a first negative electrode active material layer formed on the negative electrode current collector, and a second negative electrode active material layer formed on the first negative electrode active material layer. The first negative electrode active material layer comprises two or more kinds of negative electrode active materials, and the second negative electrode active material layer comprises a negative electrode active material having swelling that is smaller than that of the first negative electrode active material layer.