Lithium-Ion Cell Pressure Regulation for Silicon Anode Expansion
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Solution Overview
Problem
Silicon-dominant anodes in lithium ion batteries experience mechanical failure due to expansion and contraction during cycling, leading to reduced capacity and cycle life, as the expansion can deform current collectors and compress the separator, causing short circuits and impaired ion mobility.
Innovation Solution
A pressure regulation system using a spring layer between lithium ion cells, in combination with a housing, maintains an initial pressure of 25-170 kPa on the cell stack to control expansion, using materials like silicone foam or EPDM rubber foam, to mitigate mechanical failure and capacity loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-dominant anodes are used to increase energy density, then volumetric and gravimetric energy densities are improved, but mechanical failure occurs due to expansion and contraction during cycling
Solution Approach 1:
A compressible layer is positioned between the silicon-dominant anode and the separator to provide beforehand cushioning. This layer compresses during charging when the anode expands, preventing direct contact between the anode and separator, and maintains contact during discharge when the anode contracts, thereby preventing mechanical failure and improving cycle life while maintaining high energy density
2Stability of the object's composition
If the cell is confined in a specific volume with little or no expansion capability, then structural stability is improved, but electrode deformation occurs reducing contact area between layers
Solution Approach 1:
A compressible layer with flexible, compressible structure is inserted between the anode and separator. This layer can deform and compress to accommodate anode expansion while maintaining the overall cell structure, preventing electrode deformation and preserving contact area between layers during cycling
3Stability of the object's composition
If the separator is compressed during expansion, then cell confinement is maintained, but ion mobility is impaired and short circuits occur
Solution Approach 1:
The compressible layer provides beforehand cushioning by compressing during anode expansion, preventing direct compression of the separator. This maintains cell confinement while protecting the separator from deformation, ensuring ion mobility is preserved and short circuit risk is eliminated
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 pressure regulation system effectively maintains cell stack pressure within an acceptable range, reducing irreversible capacity loss and improving cycle life by preventing deformation of electrodes and separators.
Implementation Method 1
a pressure regulation system comprising a spring layer between two of the plurality of lithium-ion cells
Data Source
AI summary
The disclosure herein pertains to a pressure regulation system for use in a silicon dominate anode lithium-ion cell. The pressure regulation system regulates a lifetime pressure on the lithium-ion cell in order to correct for capacity loss and mechanical failure due the expansion of silicon during operation. The pressure regulation system along with a housing maintains a certain pressure range on the lithium-ion cells during the cycling and the operational life of the energy storage device.