Cross-Linked Multilayer Anode for Silicon Expansion Buffering
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Solution Overview
Problem
Lithium secondary batteries face issues with mechanical stability and cycle life due to volume expansion of silicon-based anode active materials, despite improvements in binder types and contents.
Innovation Solution
An anode with a multi-layer structure is developed, comprising a first layer without or with minimal cross-linker and a second layer with a cross-linker, using specific binders and cross-linkers to enhance adhesion and flexibility, and a combination of carbon-based and silicon-based active materials to buffer volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode active material is used to increase capacity, then the energy density and charging speed are improved, but volume expansion occurs during charging and discharging leading to deterioration in capacity and cycle life
Solution Approach 1:
The anode active material layer is divided into multiple sub-layers with different compositions and functions. The first sub-layer contains silicon-based material for high capacity, while the second sub-layer contains carbon-based material for structural stability, creating a segmented structure that addresses both energy density and cycle life requirements
Solution Approach 2:
A composite anode structure is formed by combining silicon-based active material with carbon-based active material in a multi-layer configuration. This composite approach allows the silicon layer to provide high energy density while the carbon layer provides structural integrity and buffers volume expansion, resolving the contradiction between capacity and reliability
2Strength
If binder type and content are adjusted to improve adhesive strength and flexibility, then the mechanical stability is enhanced, but the mechanical stability is still not sufficiently secured
Solution Approach 1:
The anode is segmented into multiple functional layers including active material layers and buffer layers. This segmentation allows different layers to perform specialized functions - the buffer layers specifically address mechanical stability by accommodating volume changes, while binder adjustments in active material layers optimize adhesive strength without compromising overall mechanical stability
Solution Approach 2:
The binder content in each sub-layer is optimized at different parameters rather than using a uniform binder concentration throughout. This parameter change approach allows the first sub-layer to have binder content optimized for adhesion to the current collector, while the second sub-layer has binder content optimized for inter-layer bonding and flexibility, collectively achieving sufficient mechanical stability
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 anode achieves improved mechanical stability, surface strength, and durability, leading to enhanced cycle life and efficiency of the lithium secondary battery.
Implementation Method 1
a second anode active material layer formed on at least one surface of the first anode active material layer and including a second anode active material, a second binder and a cross-linker
Data Source
AI summary
An anode for a lithium secondary battery according to exemplary embodiments includes: an anode current collector; a first anode active material layer formed on at least one surface of the anode current collector and including a first anode active material and a first binder; and a second anode active material layer formed on at least one surface of the first anode active material layer and including a second anode active material, a second binder and a cross-linker, wherein the first anode active material layer does not include a cross-linker or includes the cross-linker in a content smaller than that in the second anode active material layer based on weight. Accordingly, the adhesive strength, flexibility, brittleness, and rigidity of the anode are enhanced, and the cycle life characteristics of the lithium secondary battery are improved.