Silicon Anode Composite Particles for Expansion-Stable Conductivity
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Solution Overview
Problem
Si-containing materials for negative electrodes in secondary batteries face challenges due to their low conductivity and significant expansion and contraction with lithium ion absorption and release, leading to electrode expansion and deteriorated current collecting ability.
Innovation Solution
A negative electrode active material comprising composite particles with a conductive polymer linking Si-containing particles, where the particles have a sulfur content less than 0.05 mass % and a particle diameter D50 of 100 μm or less, is developed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-containing materials are used as negative electrode active material, then capacity is improved, but conductivity deteriorates and electrode expansion occurs
Solution Approach 1:
The patent employs composite materials by combining Si-containing particles with conductive polymer particles. The Si-containing particles provide high lithium ion storage capacity, while the conductive polymer matrix provides electrical conductivity and structural stability. This composite structure resolves the contradiction by allowing both high capacity and reliable electrode performance to coexist.
Solution Approach 2:
The conductive polymer acts as an intermediary material between the Si-containing particles and the electrolyte. It mediates the electrical conductivity issue while allowing lithium ion transport, and simultaneously buffers the expansion and contraction of Si particles during charging and discharging cycles, preventing electrode deterioration.
2Quantity of substance
If Si-containing material expands during lithium ion absorption, then capacity is improved, but current collecting ability deteriorates
Solution Approach 1:
The conductive polymer forms a flexible matrix that surrounds and supports the Si-containing particles. This flexible structure can accommodate the expansion and contraction of Si particles during lithium ion absorption and release, maintaining structural integrity and current collecting ability while allowing high capacity operation.
Solution Approach 2:
The composite structure of conductive polymer and Si-containing particles creates a material that combines the high capacity of Si with the mechanical stability and conductivity of the polymer matrix, resolving the contradiction between capacity and current collecting ability.
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 solution effectively suppresses the expansion of the negative electrode, maintains high capacity, and ensures good conductivity, thereby enhancing the performance and longevity of the battery.
Implementation Method 1
a first step of mixing a monomer which is a raw material of conductive polymer, a polymerization initiator containing sulfur element, and Si-containing particles, and allowing polymerization of the monomer to proceed, to synthesize a composite containing a conductive polymer and Si-containing particles
Implementation Method 2
When the Si-containing material expands, the negative electrode expands, and when the Si-containing material contracts, the current collecting ability of the negative electrode deteriorates. In view of the above, one aspect of the present invention relates to a negative electrode active material for secondary batteries, including: composite particles each containing a conductive polymer and Si-containing particles
Data Source
AI summary
A negative electrode active material for secondary batteries including composite particles each containing a conductive polymer and Si-containing particles. In each of the composite particles, a plurality of the Si-containing particles are linked together by the conductive polymer, a particle diameter D50 at 50% cumulative volume in a volume-based particle size distribution of the composite particles is 100 μm or less, the composite particles contain sulfur element, and a content of the sulfur element in the composite particles is less than 0.05 mass %.