Silicon Core Negative Electrode with Graphene Carbon Coating
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Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries face degradation due to volume expansion/contraction and side reactions with electrolyte solutions, leading to reduced lifespan and high-temperature storage performance.
Innovation Solution
A negative electrode active material is developed with a silicon-based core particle coated with an outer carbon layer containing graphene, which has a low D/G ratio, improving electrical conductivity and preventing side reactions, and a method involving mixing silicon-based core particles with graphene flakes and heat-treating the mixture to form the coating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a silicon-based active material is used in the negative electrode, then the capacity and energy density are improved, but the lifespan properties are degraded due to volume expansion/contraction blocking conductive paths
Solution Approach 1:
The patent applies a carbon coating layer (thin film) on the silicon-based active material particles. This carbon shell accommodates the volume expansion and contraction of silicon during charge/discharge cycles while maintaining structural integrity and electrical conductivity, thus improving lifespan properties without sacrificing capacity
Solution Approach 2:
The patent creates a composite structure by coating silicon-based particles with carbon material. This composite approach combines the high capacity of silicon with the structural stability and conductivity of carbon, resolving the contradiction between capacity and lifespan
2Quantity of substance
If a silicon-based active material is used in the negative electrode, then the capacity and energy density are improved, but the high-temperature storage properties are deteriorated due to side reactions with electrolyte solution
Solution Approach 1:
The carbon coating layer acts as an intermediary barrier between the silicon-based active material and the electrolyte solution. This intermediate layer prevents direct contact and side reactions while allowing lithium ion transport, thus improving high-temperature storage properties without compromising capacity
3Stability of the object's composition
If a porous silicon-carbon composite is used (as in prior art), then some structural stability is achieved, but the electrical conductivity and prevention of side reactions are insufficient
Solution Approach 1:
The patent optimizes the carbon coating parameters including thickness, composition, and structure to achieve the right balance between structural stability and electrical conductivity. By controlling the carbon layer properties, both structural integrity and electrical performance are improved
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 effectively maintains electrical contact and prevents side reactions, enhancing the lifespan and high-temperature storage properties of the battery by utilizing graphene with a low D/G ratio in the carbon coating layer.
Implementation Method 1
graphene having a D/G ratio of 0.35 or less in the Raman spectrum... excellent in electrical conductivity... smoothly maintain the electrical contact between an active material
Implementation Method 2
outer carbon coating layer contains graphene... prevent side reactions with an electrolyte solution... low in defects
Implementation Method 3
mixing silicon-based core particles and graphene flakes, and heat-treating the mixture
Data Source
AI summary
The present invention relates to a negative electrode active material including a silicon-based core particle and an outer carbon coating layer formed on the silicon-based core particle, wherein the outer carbon coating layer contains graphene having a D/G ratio of 0.35 or less in the Raman spectrum.