Silicon Negative Electrode Active Material with Coupling Agent Modification Layer
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Solution Overview
Problem
Conventional graphite materials fail to meet the design requirements for high specific energy lithium-ion batteries due to the expansion and pulverization of silicon-based negative electrodes during lithium alloying, which reduces cycle life and coulombic efficiency.
Innovation Solution
A negative electrode active material comprising a silicon or carbon-based active particle with a modification layer containing reactive functional groups of a coupling agent and a metal compound, forming chemical bonds to enhance stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode active material, then capacity increases up to 4200mAh/g, but volume expands by 300% or more during lithium alloying causing pulverization and destruction of SEI
Solution Approach 1:
The patent employs a multi-layer nested structure where a carbon coating layer is applied on the surface of silicon oxide particles, and further a silane coupling agent layer is formed on the carbon coating. This nested multi-layer protection structure accommodates the volume expansion of silicon during lithium alloying while maintaining structural integrity and preventing pulverization.
Solution Approach 2:
The patent creates a composite material system combining silicon oxide core particles with carbon coating and silane coupling agent shell layers. This composite structure leverages the high capacity of silicon oxide while the carbon and silane layers provide mechanical stability and chemical resistance, resolving the contradiction between capacity and cycle life.
2Quantity of substance
If silicon oxide material is used for high-capacity negative electrode, then capacity increases, but first cycle coulombic efficiency becomes much less than graphite and silicon carbide materials
Solution Approach 1:
The patent introduces a carbon coating layer and silane coupling agent layer as intermediary layers between the silicon oxide core and the electrolyte. These intermediary layers mediate the electrochemical reactions, reducing direct contact between silicon oxide and electrolyte that causes excessive SEI formation, thereby improving first cycle coulombic efficiency while maintaining high capacity.
3Quantity of substance
If silicon material is alloyed with lithium, then high capacity is achieved, but particle pulverizes and crushing occurs
Solution Approach 1:
The patent applies a carbon coating layer and silane coupling agent layer beforehand on the silicon oxide particles to create a protective cushioning shell. This pre-applied protective structure accommodates the volume expansion stress during lithium alloying, preventing particle pulverization and maintaining structural integrity 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 modified negative electrode active material results in a battery with improved cycle life and higher coulombic efficiency, maintaining capacity retention over multiple cycles.
Implementation Method 1
The modification layer contains a reactive functional group of a coupling agent and a residual functional group of a metal compound. The reactive functional group of the coupling agent is bounded between the active particle and the residual functional group of the metal compound.
Data Source
AI summary
A negative electrode active material, a negative electrode and a battery are provided. The negative electrode active material includes an active particle and a modification layer. The active particle contains a silicon element, a carbon element, or a combination thereof. The modification layer covers on the surface of the active particle. The modification layer contains a reactive functional group of a coupling agent and a residual functional group of a metal compound. The reactive functional group of the coupling agent is bounded between the active particle and the residual functional group of the metal compound. The residual functional group of the metal compound contains a metal atom.