Layered Silicon Anode Structure for Fast-Charging Cycle Life
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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 a first anode mixture layer containing a silicon-based active material doped with a first metal and a first conductive material, and a second anode mixture layer containing a silicon-based active material doped with a second metal and a second conductive material, where the first conductive material has a higher Raman R value than the second, and the metal doping concentrations are adjusted 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 occurs during charging/discharging
Solution Approach 1:
The anode is divided into multiple layers (first anode mixture layer, second anode mixture layer, third anode mixture layer) with different compositions and functions. The first layer contains silicon-based active material with first conductive material, the second layer contains different silicon-based active material with second conductive material, and the third layer contains carbon-based active material, creating a gradient structure that manages volume changes across layers
Solution Approach 2:
Each anode mixture layer comprises a composite of silicon-based active material (or carbon-based active material), conductive material, and binder. The silicon-based active material is combined with conductive materials in specific ratios to create a composite structure that maintains electrical conductivity while accommodating volume changes during lithiation/delithiation
2Quantity of substance
If silicon-based active materials are applied to reduce loading weight, then energy density is improved, but resistance increases due to side reactions with electrolyte
Solution Approach 1:
Different layers have different local compositions optimized for their specific functions. The first anode mixture layer has higher silicon content for capacity, the second layer has different silicon-based active material for stability, and the third carbon-based layer provides a stable protective interface with the electrolyte, creating local quality variations that address resistance issues
Solution Approach 2:
The carbon-based active material in the third anode mixture layer serves as an intermediary between the silicon-based active materials and the electrolyte. This carbon layer reduces direct contact between silicon and electrolyte, minimizing side reactions and resistance increase while still allowing lithium ion transport
3Quantity of substance
If silicon-based active materials are applied to increase discharge capacity, then capacity characteristics are improved, but lifespan characteristics deteriorate due to volume contraction/expansion
Solution Approach 1:
The multi-layer structure is designed beforehand to cushion and accommodate the volume expansion/contraction of silicon-based active materials during cycling. The carbon-based third layer and the gradient composition across layers provide a buffer that prevents crack formation and maintains structural integrity over extended cycling, thereby improving lifespan characteristics
4Quantity of substance
If silicon-based active materials are applied to reduce loading weight, then energy density is improved, but rapid charging performance deteriorates
Solution Approach 1:
The conductive material content is dynamically adjusted across different layers to optimize electron transport. The first layer has first conductive material at a first content, the second layer has second conductive material at a second content, creating a dynamic conductivity gradient that facilitates rapid electron transport during charging while maintaining the low loading weight benefit of silicon-based materials
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 structure effectively alleviates volume expansion/contraction, reduces resistance, and enhances lifespan and rapid charging characteristics in both room temperature and high-temperature environments, while maintaining 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. 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
Implementation Method 2
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
Data Source
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.Raman R=ID/IG [Formula 1](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.)