Silicon Oxide-Carbon Composite for Battery Capacity Retention
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Solution Overview
Problem
Lithium secondary batteries using silicon-based negative electrode active materials face significant capacity retention issues due to volume changes when lithium is absorbed and stored, leading to insufficient performance for high-capacity applications.
Innovation Solution
A silicon oxide-carbon composite material is developed, comprising an amorphous matrix with crystalline silicon and carbon grains, including multilayer crystalline carbon phases and mesopores, which is synthesized through a process involving plasma generation, thermal treatment, and specific reactants to enhance conductivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active material is used to improve theoretical capacity, then capacity increases, but volume change of 300% or more occurs leading to decreased capacity retention ratio
Solution Approach 1:
The patent embeds crystalline silicon oxide particles within an amorphous carbon matrix, creating a nested structure where the silicon oxide is contained within the carbon framework. This nesting approach allows the silicon oxide to expand and contract during lithium insertion/extraction while the carbon matrix maintains structural integrity, resolving the contradiction between high capacity and capacity retention.
Solution Approach 2:
The patent creates a composite material consisting of crystalline silicon oxide particles dispersed in an amorphous carbon matrix. This composite structure combines the high capacity benefits of silicon oxide with the structural stability and conductivity of carbon, directly addressing the capacity retention issue while maintaining high theoretical capacity.
2Quantity of substance
If silicon-based negative electrode active material is used to increase capacity, then energy storage capacity improves, but integrity of components is destroyed due to volume change
Solution Approach 1:
The amorphous carbon matrix acts as a flexible shell surrounding the crystalline silicon oxide particles. This carbon shell can accommodate the volume changes of the silicon oxide during lithiation and delithiation cycles without compromising structural integrity, thus maintaining component stability while enabling high energy storage capacity.
Solution Approach 2:
The composite structure of crystalline silicon oxide within amorphous carbon provides both high capacity and structural stability. The carbon phase compensates for the volume expansion of silicon oxide, preventing component destruction while maintaining energy storage capacity over multiple cycles.
3Reliability
If amorphous carbon matrix is used to maintain structural integrity, then capacity retention improves, but conductivity may be reduced
Solution Approach 1:
The patent employs local quality by creating distinct regions with different properties: the amorphous carbon matrix provides structural stability and flexibility, while the crystalline silicon oxide particles provide high capacity. The interface between these phases is optimized to ensure good electrical contact, thus maintaining conductivity while preserving the structural benefits of the amorphous matrix.
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 silicon oxide-carbon composite significantly improves capacity retention and conductivity, enabling better performance in lithium secondary batteries by inhibiting volume expansion and maintaining high discharge capacities over multiple cycles.
Implementation Method 1
Crystalline carbon structures are formed by generating plasma in the reaction solution
Implementation Method 2
The slurry is separated from the organic solvent and then subjected to thermal treatment
Data Source
AI summary
Provided are a silicon oxide-carbon composite, a method of preparing the same, and an energy storage device containing the same. In the method of preparing a silicon oxide-carbon composite, a reaction solution containing an organic solvent including an aromatic compound is provided. Crystalline carbon structures are formed by generating plasma in the reaction solution. A slurry is formed by adding silicon halide and a polyol in the reaction solution in which the crystalline carbon structures are dispersed. The slurry is separated from the organic solvent and subjected to thermal treatment.