Silicon-Carbon Composite Anode for Battery Cycle Life
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Solution Overview
Problem
Nonaqueous electrolyte secondary batteries using silicon as a negative electrode material face challenges in maintaining high capacity and cycle characteristics due to volume changes during charge-discharge cycles, which affect the stability and performance of the active material.
Innovation Solution
A composite active material is developed, comprising silicon-containing particles dispersed in a carbonaceous substance, where the carbonaceous substance is amorphous carbon, and specific conditions in the argon ion laser Raman spectrum are met to optimize the half-width and intensity ratio of peaks, enhancing conductivity and cycle characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is used as negative electrode material to achieve high capacity, then the negative electrode capacity per mass increases about 10 times compared to graphitic carbon, but the cycle characteristics deteriorate due to significant volume changes during charge-discharge cycles
Solution Approach 1:
Silicon-containing particles are embedded within carbonaceous substance particles, creating a core-shell structure where the silicon core provides high capacity while the carbon shell maintains structural integrity during volume changes, enabling both high capacity and good cycle characteristics
Solution Approach 2:
The invention uses a composite material consisting of silicon-containing particles dispersed in a carbonaceous substance matrix. This composite structure combines the high lithium absorption capacity of silicon with the structural stability and conductivity of carbon, resolving the contradiction between high capacity and cycle stability
2Reliability
If silicon-containing particles are combined with carbonaceous substance to improve cycle characteristics, then cycle stability improves, but both high capacity and cycle characteristics are not sufficiently maintained
Solution Approach 1:
The invention optimizes the local distribution and concentration of silicon-containing particles within the carbonaceous substance, ensuring that silicon particles are dispersed at appropriate densities to maintain high capacity while the carbon matrix provides sufficient structural support for cycle stability
Solution Approach 2:
The invention controls specific parameters including the size of silicon-containing particles (0.1-10 μm), the ratio of silicon to carbonaceous substance, and the structural properties of carbon (amorphous or graphitic with specific crystallite sizes) to simultaneously achieve high capacity and excellent cycle characteristics
3Quantity of substance
If silicon is used as negative electrode material, then high capacity is achieved, but particle deformation and aggregation occur during charge-discharge cycles
Solution Approach 1:
The carbonaceous substance forms an outer shell or matrix that encapsulates silicon-containing particles, constraining them during volume expansion and contraction. This nested structure prevents particle aggregation and maintains individual particle integrity throughout charge-discharge cycles while preserving high capacity
Solution Approach 2:
The carbonaceous substance acts as a cushioning matrix that anticipates and absorbs the volume changes of silicon particles during lithiation and delithiation. This pre-established protective structure prevents deformation and aggregation before they can occur, maintaining particle stability throughout cycling
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 composite active material achieves improved cycle characteristics and conductivity, maintaining high capacity and stability during charge-discharge cycles, while preventing deformation and aggregation of silicon-containing particles.
Implementation Method 1
attempts have been made to use elements that form an alloy with lithium, such as silicon and tin
Implementation Method 2
substances having a large lithium absorption capacity
Implementation Method 3
the carbonaceous substance is amorphous carbon
Data Source
AI summary
An active material for a nonaqueous electrolyte battery according to the embodiment is a composite including at least: a carbonaceous substance; and silicon-containing particles dispersed in the carbonaceous substance, the silicon-containing particles including at least one of silicon, a silicon alloy and a silicon oxide, wherein in an argon ion laser Raman spectrum, the half-width (ΔG) of a peak having a maximum intensity I1 in the range of 1575 cm−1 or more and 1625 cm−1 or less is 100 cm−1 or more and 150 cm−1 or less, and the intensity ratio of a peak having a maximum intensity I2 in the range of 500 cm−1 or more and 550 cm−1 or less to the peak having the maximum intensity I1 in the range of 1575 cm−1 or more and 1625 cm−1 or less (I2/I1) is 0.25 or more and 0.50 or less.