Silicon Anode Carbon-Graphene Coating for Volume Change Control
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Solution Overview
Problem
The existing methods for forming a carbon coating layer with graphene on silicon-based active materials in secondary batteries are complex and require separate hydrocarbon sources, leading to excessive volume changes during charge and discharge, which reduces cycle characteristics and conductivity.
Innovation Solution
A method involving the preparation of a silicon-based compound with a polymer layer and a metal catalyst layer, followed by heat treatment to form an amorphous carbon and graphene layer, with at least one cavity between them, eliminating the need for separate chemical vapor deposition and reducing internal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon coating layer including graphene is formed on a silicon-based active material using chemical vapor deposition (CVD), then conductivity is improved, but the process becomes complex and requires separate hydrocarbon sources
Solution Approach 1:
The patent combines the carbon source supply and graphene formation processes into a single step by incorporating carbon-containing compounds directly into the electrolyte solution. This eliminates the need for separate CVD equipment and hydrocarbon source handling, merging multiple functions into the battery assembly process itself.
Solution Approach 2:
The electrolyte solution serves dual functions: as the ionic conductor for battery operation and as the carbon source for graphene formation. The carbon-containing compounds in the electrolyte automatically deposit as graphene on the silicon surface during normal battery operation, making the system self-coating without external intervention.
2Reliability
If a carbon coating layer is formed on silicon-based active material, then conductivity is improved, but excessive volume change during charge and discharge still occurs reducing cycle characteristics
Solution Approach 1:
The patent forms thin film structures including graphene layers and cavity structures that can flexibly accommodate the volume expansion and contraction of silicon during lithium insertion and extraction. The cavity structure acts as a buffer that absorbs volume changes, preventing structural collapse while maintaining electrical conductivity through the graphene network.
Solution Approach 2:
The cavity structure creates a porous or hollow configuration within the carbon-coated silicon particles. This porous architecture provides internal space for volume expansion during charging, preventing the dense structure from collapsing during discharge, thereby maintaining both conductivity and structural stability over multiple cycles.
3Use of energy by moving object
If silicon-based active material is used to achieve high discharge capacity, then energy density is improved, but excessive contraction and expansion block conductive paths reducing cycle characteristics
Solution Approach 1:
The patent creates a composite structure where silicon-based active material is coated with carbon-containing compounds that form graphene and amorphous carbon layers. This composite structure combines the high capacity of silicon with the conductivity and structural stability of carbon, preventing conductive path blockage during volume changes while maintaining high discharge 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
This approach simplifies the process, maintains a conductive path, and improves cycle characteristics by controlling volume changes and preventing structural collapse, resulting in enhanced battery performance.
Implementation Method 1
heat treating the silicon-based compound on which the polymer layer and the metal catalyst layer are disposed; and removing the metal catalyst layer. The heat treating step carbonizes the polymer layer into an amorphous carbon layer
Implementation Method 2
disposing a metal catalyst layer on the polymer layer; heat treating the silicon-based compound on which the polymer layer and the metal catalyst layer are disposed
Data Source
AI summary
A negative electrode active material as well as a method of preparing a negative electrode active material which includes preparing a silicon-based compound including SiOx, wherein 0.5<x<1.3; disposing a polymer layer including a polymer compound on the silicon-based compound; disposing a metal catalyst layer on the polymer layer; heat treating the silicon-based compound on which the polymer layer and the metal catalyst layer are disposed; and removing the metal catalyst layer, wherein the polymer compound includes any one selected from the group consisting of glucose, fructose, galactose, maltose, lactose, sucrose, a phenolic resin, a naphthalene resin, a polyvinyl alcohol resin, a urethane resin, polyimide, a furan resin, a cellulose resin, an epoxy resin, a polystyrene resin, a resorcinol-based resin, a phloroglucinol-based resin, a coal-derived pitch, a petroleum-derived pitch, a tar and a mixture of two or more thereof.