Layered Silicon Anode Structure for Volume Change and Resistance
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Solution Overview
Problem
Silicon-based active materials for anodes in lithium secondary batteries face issues such as increased resistance due to side reactions with the electrolyte and significant volume contraction/expansion during charging/discharging, leading to poor lifespan and rapid charging performance.
Innovation Solution
A multilayer anode structure with different doping levels of metals and conductive materials in each layer, where the first layer has a lower metal content and higher Raman R value conductive material, and the second layer has a higher metal content and lower Raman R value conductive material, to manage volume changes and resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active materials are applied to increase discharge capacity, then energy density is improved, but volume expansion/contraction during charging/discharging increases causing active material cracking
Solution Approach 1:
The anode is divided into multiple layers with different compositions. The first anode mixture layer contains silicon-based active material with first metal dopant and first conductive material, while the second anode mixture layer contains silicon-based active material with second metal dopant and second conductive material. This segmentation allows different regions to handle different aspects of volume change and conductivity requirements, resolving the contradiction between high capacity and structural integrity.
Solution Approach 2:
Different metal dopants and conductive materials are used in different layers to create local quality variations. The first conductive material has higher Raman R value than the second conductive material, indicating different structural properties optimized for their respective positions. This local optimization allows each layer to specifically address either capacity or structural stability needs.
2Quantity of substance
If silicon-based active materials are applied to increase discharge capacity, then energy density is improved, but resistance increases due to side reactions with electrolyte
Solution Approach 1:
The invention changes the parameters of conductive materials by selecting different types with different Raman R values for different layers. The first conductive material with higher Raman R value provides different electrical conductivity characteristics compared to the second conductive material with lower Raman R value. This parameter variation optimizes the balance between capacity and resistance across the anode structure.
3Stability of the object's composition
If uniform metal doping is applied to silicon-based active material, then structural stability is improved, but conductivity decreases
Solution Approach 1:
Different metal dopants are used in different layers with different doping contents. The first metal dopant is used in the first layer with specific doping content, while the second metal dopant is used in the second layer with different doping content. This local quality approach allows each layer to optimize the balance between structural stability and conductivity according to its specific function.
Solution Approach 2:
The anode uses composite materials with different metal dopants and conductive materials in different layers. The first anode mixture layer combines silicon-based active material with first metal dopant and first conductive material, while the second layer combines silicon-based active material with second metal dopant and second conductive material. This composite structure achieves both structural stability and conductivity through material combination.
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 design effectively alleviates volume expansion and contraction, reduces resistance, and enhances lifespan and rapid charging capabilities, while maintaining high capacity characteristics.
Implementation Method 1
the first conductive material may have a Raman R value according to the following formula 1 that is greater than that of the second conductive material
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Provided is an anode for a lithium secondary battery of the present disclosure, comprising: an anode current collector; a first anode mixture layer formed on at least one surface of the anode current collector and including a first silicon-based active material doped with a first metal and a first conductive material; and a second anode mixture layer formed on the first anode mixture layer and including a second silicon-based active material doped with a second metal and a second conductive material, and the first conductive material has a Raman R value according to the following formula 1 that is greater than that of the second conductive material. RamanR=ID/IG (In formula 1, ID is a Raman peak intensity value in an absorption region of 1330 to 1380 cm-1, and IG is a Raman peak intensity value in an absorption region of 1550 to 1625 cm-1.)