Lithium Battery Anode with Dissolvable Layer for Uniform Lithiation
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Solution Overview
Problem
Existing lithium secondary batteries face issues with uneven lithiation of silicon-based negative electrodes, leading to increased initial irreversible capacity and reduced cycle life due to rapid lithiation of active material particles near the current collector and slow lithiation at a distance, along with potential resistance and safety risks from uneven lithium distribution.
Innovation Solution
A negative electrode structure with a lithiation retardation layer made of polymers containing acrylate or carbonate repeating units, which is soluble in electrolyte solutions, is introduced between the negative electrode active material layer and the lithium layer, controlling lithium diffusion and ensuring even lithiation through thermal evaporation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a lithium layer is directly laminated on the negative electrode active material layer, then lithiation speed is improved, but lithium diffusion becomes uneven causing large initial irreversible capacity
Solution Approach 1:
A lithiation retardation layer made of polymer (acrylate or carbonate repeating units) is introduced as an intermediary between the lithium layer and negative electrode active material layer. This layer controls and retards lithium diffusion, preventing direct rapid contact while ensuring uniform lithiation across the electrode thickness.
Solution Approach 2:
The surface roughness of the lithium layer is precisely controlled to be 0.4 μm or less, and the lithiation retardation layer is designed with specific polymer composition and thickness parameters to optimize lithium diffusion control, achieving uniform lithiation while maintaining high lithiation speed.
2Manufacturing precision
If the lithiation retardation layer remains in the negative electrode after lithiation, then lithium diffusion control is improved, but resistance increases
Solution Approach 1:
The lithiation retardation layer is designed to be soluble in carbonate-containing electrolyte solutions. After completing its function of controlling lithium diffusion during lithiation, the layer dissolves in the electrolyte and is removed from the electrode structure, eliminating resistance while maintaining lithium diffusion control benefits.
3Manufacturing precision
If lithium layer is formed by thermal evaporation method, then lithiation uniformity is improved, but heat resistance requirement increases
Solution Approach 1:
The lithiation retardation layer is formed using thermal evaporation method with controlled parameters (surface roughness ≤0.4 μm, specific polymer composition), achieving uniform lithiation while the polymer material selection provides sufficient heat resistance for the thermal evaporation process.
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 lithiation retardation layer delays lithium diffusion, allowing uniform lithiation across the electrode thickness, reducing irreversible capacity loss, preventing desorption of active materials, and maintaining low resistance by dissolving post-lithiation, thus enhancing battery performance and safety.
Implementation Method 1
lithium of the lithium layer attached to the negative electrode may be unevenly moved into the negative electrode (solid-diffusion)
Implementation Method 2
the lithiation retardation layer is soluble in a carbonate-containing electrolyte solution
Implementation Method 3
forming a lithium layer by depositing lithium on the lithiation retardation layer
Data Source
Figure 1
Figure 2
AI summary
The negative electrode for a lithium secondary battery of the present invention comprises: a negative electrode active material layer; a lithiation retardation layer formed on the negative electrode active material layer; and a lithium layer formed on the lithiation retardation layer, wherein the lithiation retardation layer can be dissolved in an electrolyte.