Silicon-Core Negative Electrode With Carbon Layer Against Expansion Cracking
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Solution Overview
Problem
Rechargeable lithium batteries using silicon negative active materials face issues with cracking due to volumetric expansion during charging and discharging, leading to reduced cycle-life characteristics and energy density.
Innovation Solution
A negative electrode with a silicon core coated with an amorphous carbon layer and a high amount of carbon-based conductive material, optimized through magnetic field orientation, is used to enhance electrical contact and mitigate expansion, resulting in improved cycle-life and energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon negative active material is used to achieve high discharge specific capacity, then energy density is improved, but cracking occurs due to volumetric expansion during charging and discharging, leading to deteriorated cycle-life characteristics
Solution Approach 1:
The patent applies the nesting principle by placing the silicon core inside a carbon-based conductive material matrix. The silicon particles are embedded within the conductive material, forming a nested structure where the inner silicon core provides high capacity while the outer carbon material provides structural support and conductivity, preventing cracking during volume changes
Solution Approach 2:
The patent uses composite materials by combining silicon core with carbon-based conductive material in a specific weight ratio (10-30 wt% conductive material). This composite structure integrates the high capacity advantage of silicon with the structural stability and conductivity of carbon materials, resolving the contradiction between capacity and cycle life
2Quantity of substance
If silicon negative active material is used to achieve high discharge specific capacity, then energy density is improved, but volumetric expansion during charging and discharging causes structural deterioration
Solution Approach 1:
The patent applies the flexible shell principle by using a carbon-based conductive material as a flexible matrix that can accommodate the volumetric expansion and contraction of the silicon core during lithium insertion and extraction. The carbon material acts as a flexible container that maintains structural integrity while allowing the silicon to expand and contract
Solution Approach 2:
The composite structure of silicon core embedded in carbon-based conductive material provides both high capacity and structural stability. The carbon material forms a stable matrix that constrains the silicon, preventing uncontrolled expansion while maintaining the electrochemical activity needed for high capacity
3Reliability
If carbon-based conductive material is increased to about 10 wt % or more, then electrical contact is enhanced, but the composition ratio of silicon is reduced
Solution Approach 1:
The patent applies parameter changes by optimizing the weight ratio of carbon-based conductive material to silicon core within the range of 10-30 wt%. This specific parameter range ensures sufficient electrical conductivity and structural stability while maximizing the silicon content for high capacity, representing an optimized balance point that resolves the trade-off between conductivity and capacity
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 achieves high energy density and extended cycle-life by maintaining electrical contact and minimizing volumetric expansion, outperforming conventional batteries in capacity retention and resistance increase rates.
Implementation Method 1
a silicon core and an amorphous carbon layer on a surface of the silicon core... silicon suffers from cracking due to contraction and expansion during charging and discharging
Implementation Method 2
a carbon-based conductive material... An amount of the carbon-based conductive material is about 10 wt % or more based on the total, 100 wt % of the negative active material layer
Implementation Method 3
optimized through magnetic field orientation... The negative electrode includes a negative active material layer and a carbon-based conductive material
Data Source
AI summary
A negative electrode for a rechargeable lithium battery and a rechargeable lithium battery including the negative electrode. The negative electrode for the rechargeable lithium battery includes a negative a negative active material layer including a negative active material including a silicon core and an amorphous carbon layer on a surface of the core. An amount of the carbon-based conductive material is about 10 wt % or more based on the total, 100 wt % of the negative active material layer, and the negative electrode has a peak intensity ratio (I(010)/I(002)) at a (110) plane relative to a (002) plane of about 1.0 or more measured by x-ray diffraction (XRD).