Silicon Negative Electrode Surface Layer for Battery Dispersibility
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Solution Overview
Problem
Silicon-based active materials for negative electrodes in nonaqueous electrolyte secondary batteries face challenges in electron conductivity and dispersibility, leading to decreased capacity retention when particle size is reduced, resulting in uneven distribution and poor cycle characteristics.
Innovation Solution
A silicon-containing negative electrode active material with a surface layer containing oxygen, silicon, and carbon, and a particle size distribution of 0.1 μm to 5.0 μm, enhanced by surface treatment with silane coupling agents and specific additives like boron, to improve reactivity and dispersibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the particle size of silicon-based active material is reduced to increase capacity, then the capacity per mass increases, but the dispersibility decreases and particles aggregate unevenly
Solution Approach 1:
The patent introduces a silane coupling agent as an intermediary substance that coats the surface of silicon particles. This surface treatment layer acts as a mediator that prevents direct contact and aggregation between silicon particles while maintaining their high capacity characteristics, thereby resolving the contradiction between high capacity and poor dispersibility
Solution Approach 2:
The patent creates a composite structure by combining silicon particles with silane coupling agent coating. This composite material approach allows the silicon core to provide high capacity while the silane coating layer provides improved dispersibility and surface properties, simultaneously addressing both contradictory requirements
2Reliability
If the particle size is reduced to improve reactivity, then the cycle characteristics improve, but the uniform distribution in the electrode deteriorates
Solution Approach 1:
The silane coupling agent serves as a mediator that modifies the surface properties of fine silicon particles, enabling them to distribute uniformly in the electrode slurry while maintaining their high reactivity. The surface coating prevents particle aggregation and ensures homogeneous distribution during electrode manufacturing
3Quantity of substance
If conventional silicon-based active materials are used, then the capacity is high, but the electron conductivity is insufficient
Solution Approach 1:
The patent creates a composite material system where silicon particles are coated with silane coupling agent and potentially combined with conductive materials. This composite structure maintains the high capacity of silicon while the additional components provide the necessary electron conductivity pathway
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 enhances the reactivity and cycle characteristics of the battery, ensuring uniform distribution of active material particles and increased capacity retention, while reducing side reactions and electrical resistance.
Implementation Method 1
enhanced by surface treatment with silane coupling agents
Implementation Method 2
a D50 based on a volume-based particle size distribution obtainable through an analysis by a laser diffraction scattering type particle size distribution analysis method
Data Source
AI summary
In order to propose a new negative electrode for nonaqueous electrolyte secondary batteries having excellent dispersibility even with a negative electrode active material having a relatively small particle size, there is proposed a negative electrode active material for nonaqueous electrolyte secondary batteries, the negative electrode active material containing silicon and having negative electrode active material particles that have a D50 based on a volume-based particle size distribution obtainable by measurement by a laser diffraction scattering type particle size distribution analysis method, of 0.1 μm to 5.0 μm, and include a surface layer containing oxygen, silicon and carbon on the entire surface or a portion of the active material surface.