Layered Negative Electrode Structure to Prevent 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 design featuring a first active material layer with a mix of high-capacity and low-volume variation materials, topped with a second active material layer exhibiting a uni-modal particle diameter distribution, allowing uniform lithium ion reception and diffusion to prevent structural deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a mixed negative electrode active material comprising carbon-based active material and active material having high volume expansion rate is used, then capacity is improved, but surface deformation occurs during pre-lithiation
Solution Approach 1:
The negative electrode active material layer is segmented into multiple layers with different compositions and functions. The first layer contains high-capacity active material (silicon, silicon oxide, or silicon alloy) for high capacity, while the second layer contains carbon-based active material with low volume expansion for structural stability. This segmentation allows each layer to perform its specific function without interfering with the other, resolving the contradiction between high capacity and surface deformation.
Solution Approach 2:
Different regions of the negative electrode are assigned different material compositions tailored to local requirements. The first layer (closer to the electrolyte) uses high-capacity material that benefits from pre-lithiation, while the second layer (outer layer) uses low-expansion material that resists deformation. This local differentiation of material properties allows the electrode to simultaneously achieve high capacity and maintain structural integrity during pre-lithiation.
2Loss of energy
If pre-lithiation is performed to reduce initial irreversibility, then initial irreversibility is improved, but surface deformation occurs due to different volume expansion rates
Solution Approach 1:
The negative electrode is segmented into functional layers where the first layer undergoes pre-lithiation to reduce initial irreversibility, while the second layer provides structural support to prevent deformation. This segmentation allows the benefits of pre-lithiation to be realized without suffering from the harmful effects of surface deformation.
Solution Approach 2:
The second layer of carbon-based active material acts as a cushioning layer that compensates for the volume expansion of the first layer during pre-lithiation. This beforehand cushioning prevents surface deformation before it can occur, allowing pre-lithiation to proceed effectively while maintaining electrode integrity.
3Quantity of substance
If active material having high volume expansion rate and high capacity is used, then capacity is improved, but manufacturing complexity increases due to deformation issues
Solution Approach 1:
By segmenting the electrode into functional layers, the patent simplifies the manufacturing process compared to attempting to use pure high-expansion materials. The layered structure can be manufactured using conventional coating techniques, and each layer serves a specific function, making the overall manufacturing process more manageable and less complex than dealing with deformation issues in single-layer high-capacity electrodes.
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 design ensures no surface deformation during pre-lithiation, enhancing battery performance and maintaining electrode structure integrity, leading to improved capacity and lifetime characteristics.
Implementation Method 1
a second negative electrode active material layer which is present on the first negative electrode active material layer and comprises a second negative electrode active material having an average particle diameter D50 of 0.1 μm to 10 μm
Data Source
AI summary
A negative electrode for a lithium secondary battery and a lithium secondary battery including the negative electrode are disclosed. The negative electrode includes a negative electrode current collector, a first negative electrode active material layer present on the negative electrode current collector, and a second negative electrode active material layer present on the first negative electrode active material layer. The first negative electrode active material layer includes two or more kinds of first negative electrode active materials, and the second negative electrode active material layer includes a second negative electrode active material having swelling that is smaller than that of the first negative electrode active material layer. Therefore, the surface of the negative electrode does not exhibit deformation during pre-lithiation.