Bilayer Silicon Anode Composition for Crack-Resistant Li-Ion Cells
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Solution Overview
Problem
Lithium-ion batteries with carbon-based anodes face limitations due to volume changes in alloy-type anodes, such as silicon, which lead to cracking and reduced capacity over cycles, and existing solutions like reducing active material content compromise performance.
Innovation Solution
A bilayer anode composition with a first layer having a high anode active material content and a second layer with a lower content, both including conductive additives and optionally solid electrolyte materials, is used to maintain interfacial contact and stability, reducing volume expansion issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon alloy-type anode material is used to increase lithium-ion storage capacity, then the specific capacity is improved, but volume expansion and cracking occur during cycling
Solution Approach 1:
The anode is divided into multiple layers with different compositions and functions. The first layer contains silicon-based alloy material for high capacity, while the second layer has reduced active material content and includes solid electrolyte material to accommodate volume changes and maintain stability during cycling.
Solution Approach 2:
The patent creates a composite anode structure combining silicon-based alloy material with solid electrolyte material in a bilayer configuration. This composite approach allows the high-capacity silicon to expand and contract while the solid electrolyte layer provides structural stability and prevents cracking.
2Stability of the object's composition
If the amount of active material in the anode is reduced to decrease volume expansion, then structural stability is improved, but the specific capacity deteriorates
Solution Approach 1:
The anode is segmented into two functional layers: the first layer is optimized for high lithium-ion storage capacity with silicon-based alloy material, while the second layer is optimized for structural stability with reduced active material content and inclusion of solid electrolyte material. This segmentation allows each layer to perform its specialized function without compromising the other.
Solution Approach 2:
Different regions of the anode are assigned different compositions and properties. The first layer has high active material content for capacity, while the second layer has lower active material content and includes solid electrolyte for stability. Each local region is optimized for its specific function.
3Duration of action of moving object
If continuous expansion and contraction of the active area occur during cycling, then lithium-ion storage function is maintained, but cracking and loss of electrical connection occur
Solution Approach 1:
The bilayer composite anode structure allows the silicon-based first layer to expand and contract during lithium-ion insertion and extraction, while the second layer with solid electrolyte material provides a stable framework that prevents cracking and maintains electrical connection reliability throughout the cycling 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 bilayer anode design enhances the specific discharge capacity and stability of lithium-ion batteries by minimizing cracking and maintaining contact with the electrolyte layer, leading to improved cycle life and reduced internal resistance.
Implementation Method 1
In the alloy-type anode, rather than intercalating between sheets of carbon in graphite particles, the lithium ions alloy with the active anode material.
Implementation Method 2
The weight percent amount of the anode active material, binder, conductive additive, and/or solid-state electrolyte material in the first anode layer is different from the amount in the second anode layer
Data Source
AI summary
Provided herein is a negative electrode or anode for an electrochemical cell having two or more layers. Each layer may include different concentrations of an anode active material to provide improved electrical and physical qualities as compared to a mono-layer anode.