Silicon Anode Composition Balancing Porosity and Conductivity
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries experience rapid volume expansion during charging, leading to disconnection of conductive paths and degradation of battery performance, while carbon-based materials lack sufficient electric conductivity for high-capacity applications.
Innovation Solution
A negative electrode composition for lithium secondary batteries is developed, featuring a porosity range of 10% to 50% and electric conductivity between 1 S/cm² and 3,000 S/cm², utilizing a specific combination of silicon-based active materials, conductive materials, and binders to maintain conductivity and prevent volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based active material is used to increase capacity, then discharge capacity is improved, but volume expansion occurs during charging causing conductive path disconnection
Solution Approach 1:
A thin film coating layer is applied on the silicon-based active material surface to suppress volume expansion and prevent conductive path disconnection during charging/discharging cycles
Solution Approach 2:
The negative electrode uses a composite structure combining silicon-based active material with conductive material and binder, creating a robust network that maintains conductivity despite silicon's volume changes
2Quantity of substance
If silicon-based active material is used to enhance capacity, then discharge capacity is improved, but electric conductivity deteriorates due to non-conductive nature of silicon
Solution Approach 1:
The negative electrode comprises a composite of silicon-based active material (60-95 wt%), conductive material (2-30 wt%), and binder (1-10 wt%), where the conductive material compensates for silicon's poor conductivity while maintaining high capacity
Solution Approach 2:
Different components are strategically distributed: silicon-based material provides high capacity in specific regions, while conductive material and binder form a continuous network throughout to ensure overall electrode conductivity
3Quantity of substance
If high content of silicon-based compound is used to achieve high energy density, then capacity is improved, but volume expansion deteriorates battery performance
Solution Approach 1:
A thin film coating is applied on silicon-based active material to suppress volume expansion, enabling high silicon content (60-95 wt%) while maintaining battery performance and cycle life
Solution Approach 2:
The patent optimizes the composition parameters (silicon-based material 60-95 wt%, conductive material 2-30 wt%, binder 1-10 wt%) and controls negative electrode porosity (10-50%) to balance capacity and performance
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 solution ensures the maintenance of electric conductivity and prevents conductive path disconnection, enabling the production of high-capacity lithium secondary batteries with improved performance and cycle characteristics.
Implementation Method 1
The negative electrode includes a negative electrode active material for intercalating and deintercalating lithium ions coming out from the positive electrode
Implementation Method 2
the silicon-based active material is a non-conductive material, so conductivity should be imparted by adding a negative electrode conductive material
Data Source
AI summary
A negative electrode for a lithium secondary battery according to the present invention comprises a negative electrode current collector layer, and a negative electrode active material layer disposed on one or both surfaces of the negative electrode current collector layer and including a negative electrode active material layer composition, wherein the negative electrode active material layer composition includes a silicon-based active material, the negative electrode active material layer has a porosity of 10-50%, and an electrical conductivity of the negative electrode for a lithium secondary battery satisfies a range of 1 S/cm2 or greater and 3,000 S/cm2 or less.