Controlled Lithium Foil Patterns for Negative Electrodes
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Solution Overview
Problem
Existing methods for lithium attachment to negative electrodes in energy storage devices, such as lithium-ion batteries, face challenges with non-uniform lithium distribution and metal residue, leading to sub-optimal performance and safety issues due to the Li attachment and pre-dope methods, and premature cell failure due to the direct contact method.
Innovation Solution
A method involving determining the thickness and pattern of a lithium foil layer on an active layer of the electrode to achieve controlled lithium distribution, using commercially available Li foil thicknesses and patterns like discrete dots or stripes to minimize diffusion distance and ensure uniform lithium attachment, thereby stabilizing electrode potentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li film is laminated on current collector and used for pre-doping, then lithium ions can be supplied to negative electrode, but non-uniform Li distribution and metal Li residue occur on electrode package
Solution Approach 1:
The Li foil is divided into multiple discrete Li layers, each with thickness of 1-50 μm, instead of using a single thick Li film. This segmentation allows uniform Li distribution across the electrode surface while preventing metal Li residue, as the thinner segmented layers dissolve more uniformly during pre-doping.
Solution Approach 2:
The Li layers are pre-formed on the current collector before electrode assembly, with controlled thickness and uniform distribution. This preliminary preparation ensures that Li ions are uniformly supplied during subsequent pre-doping, eliminating the non-uniform distribution problem associated with post-assembly Li attachment.
2Duration of action of stationary object
If thin Li metal films are provided on electrode package, then Li pre-doping can be performed, but Li metal films remain on electrode package after pre-doping and 20 days are required for uniform doping
Solution Approach 1:
The Li foil thickness parameter is changed from conventional thick films (typically >50 μm) to thin layers (1-50 μm). This parameter change enables complete Li dissolution during pre-doping, eliminating metal Li residue, and reduces the pre-doping time from 20 days to a much shorter duration while maintaining uniform Li distribution.
3Manufacturing precision
If Li powder is mechanically deposited onto negative electrode surface, then uniform Li attachment can be achieved, but Li particles detach and migrate to positive electrode through separator voids
Solution Approach 1:
Instead of using loose Li powder that can detach, the invention uses Li foil that is pressed into the negative electrode surface, creating a stable replicated structure. The Li foil conforms to the electrode surface topology while maintaining mechanical stability, preventing particle detachment and migration through separator voids.
Solution Approach 2:
The mechanical deposition of loose Li powder is replaced by pressing Li foil directly onto the electrode surface. This substitution creates a mechanically stable Li layer that maintains uniform attachment without the particle detachment problems inherent in powder-based methods.
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
This approach allows for the fabrication of electrodes with controlled electrode potentials and uniform lithium distribution, enhancing energy storage device performance and safety by optimizing lithium attachment and reducing metal residue and premature failure.
Implementation Method 1
The Li layer is converted into Li ions through the electrode and the Li ions migrate and pre-dope the negative electrode
Implementation Method 2
pressing the Li layer pattern into the surface of the active layer
Data Source
AI summary
A method for fabricating an electrode, includes: determining a thickness of an active layer; selecting a lithium (Li) foil having a specified thickness; determining a Li layer pattern for the Li foil based on a portion of a surface of the active layer to be covered by the Li foil; and pressing the Li layer pattern into the surface of the active layer.