Multilayer Silicon-Carbon Anode Structure for Stable Lithium Batteries
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Solution Overview
Problem
Lithium secondary batteries face challenges in achieving high energy density, lifespan performance, and rapid charging capabilities due to the volumetric expansion of silicon-based active materials during charge/discharge cycles, leading to electrode detachment and increased internal resistance.
Innovation Solution
A lithium secondary battery design featuring a multilayer anode structure with alternating electrode groups, where the first anode layer includes only carbon-based active materials and the subsequent layers include silicon-based active materials, with varying content and composition to mitigate expansion issues and enhance performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are used to increase energy density, then capacity is improved, but volumetric expansion occurs during charge/discharge cycles leading to electrode detachment and increased internal resistance
Solution Approach 1:
The anode is divided into multiple anode mixture layers (first anode mixture layer, second anode mixture layer, third anode mixture layer) with different silicon-based active material contents. This segmentation allows each layer to handle different aspects of the charge/discharge process, distributing the expansion stress and preventing catastrophic electrode detachment while maintaining high capacity.
Solution Approach 2:
Different regions of the anode have different compositions optimized for their specific functions. The first anode mixture layer (closest to current collector) has lower silicon content for structural stability, the second layer has intermediate content for balanced performance, and the third layer has highest silicon content for maximum capacity. This local quality variation resolves the contradiction between high capacity and electrode integrity.
2Quantity of substance
If silicon-based active materials are used to enhance energy density, then capacity is improved, but internal resistance increases due to electrode detachment
Solution Approach 1:
By segmenting the anode into multiple layers with gradient silicon content, the patent prevents uniform expansion-induced detachment that causes high internal resistance. The gradual transition in silicon content across layers distributes mechanical stress, maintaining continuous electrical contact and low internal resistance while achieving high capacity.
Solution Approach 2:
The anode uses composite material structure combining carbon-based active materials and silicon-based active materials in specific ratios across different layers. This composite approach leverages the dimensional stability of carbon materials to constrain silicon expansion, preventing detachment and maintaining low internal resistance while utilizing silicon's high capacity.
3Reliability
If multilayer anode structure with varying silicon content is implemented, then electrode integrity is maintained, but device complexity increases
Solution Approach 1:
While segmentation into multiple layers does increase structural complexity, it is justified by the significant improvement in electrode integrity. The segmented structure with gradient silicon content prevents expansion-induced detachment, ensuring reliable long-term operation. The complexity is managed through systematic variation of a single parameter (silicon content) across layers rather than introducing multiple different material systems.
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 design improves energy density, lifespan, and rapid charging capabilities by stabilizing the anode structure, reducing resistance, and maintaining electrode integrity through balanced active material distribution.
Implementation Method 1
Lithium secondary batteries with high discharge voltage and output stability are mainly used as power sources for such electric vehicles (EV) and hybrid electric vehicles (HEV)
Implementation Method 2
the volumetric expansion of silicon-based active materials during charge/discharge cycles, leading to electrode detachment and increased internal resistance
Data Source
AI summary
A lithium secondary battery according to an embodiment includes an electrode assembly 1 in which a first electrode group 2 including at least one first unit cell 10; and a second electrode group 4 including at least one second unit cell 30 are alternately assembled. The first unit cell 10 includes a first-first anode mixture layer 111a on the first anode current collector 110; and a first-second anode mixture layer 111b on the first-first anode mixture layer. The second unit cell 30 includes a second-first anode mixture layer 311a on the second anode current collector 310; and a second-second anode mixture layer 311b on the second-first anode mixture layer. The first-first anode mixture layer 111a includes a carbon-based active material, and each of the first-second anode mixture layer 111b, the second-first anode mixture layer 311a and the second-second anode mixture layer 311b includes a silicon-based active material.