Silicon-Carbon Anode Composition for Lithium Transfer and Cycle Life
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Solution Overview
Problem
Conventional non-aqueous secondary batteries face issues with insufficient cycle characteristics, rapid charging and discharging performance, and irreversible capacity due to the separation of Si composite carbon particles during expansion and contraction, hindered lithium transfer, and low mobility of lithium within the active material.
Innovation Solution
A carbon material for negative electrodes comprising Si composite carbon particles and amorphous composite graphite particles, with optional addition of natural graphite particles, to enhance electrical conductivity, lithium mobility, and suppress particle deformation during charging and discharging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si composite carbon particles are used to increase capacity, then theoretical capacity exceeds 372 mAh, but cycle characteristics deteriorate due to particle separation during expansion and contraction
Solution Approach 1:
The patent uses composite carbon particles formed by carbonizing a mixture of Si compound fine powder, graphite powder, and carbonaceous material. This creates a composite structure where Si particles are embedded in a carbon matrix, allowing the Si to provide high capacity while the carbon matrix maintains structural integrity during expansion and contraction, preventing particle separation and ensuring good cycle characteristics.
2Quantity of substance
If Si composite carbon particles are used to increase capacity, then theoretical capacity exceeds 372 mAh, but output characteristics deteriorate due to hindered lithium transfer
Solution Approach 1:
The composite structure with Si particles embedded in carbonized graphite and carbonaceous material provides both high capacity from Si and good lithium transfer from the conductive carbon matrix, resolving the contradiction between capacity and output characteristics.
Solution Approach 2:
The patent creates different regions within the composite particles: Si compound regions for high capacity and carbonized graphite/carbonaceous material regions for electrical conductivity and lithium ion transport. This local differentiation allows simultaneous achievement of high capacity and good output characteristics.
3Quantity of substance
If carbon materials are mixed to increase filling rate, then discharge capacity is enhanced, but cycle characteristics deteriorate due to particle separation
Solution Approach 1:
The patent merges Si compound fine powder, graphite powder, and carbonaceous material into a single composite particle structure through carbonization. This unified structure prevents particle separation during cycling while maintaining high discharge capacity, overcoming the limitation of simple mixing.
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 carbon material achieves high capacity, high output, excellent cycle characteristics, and low irreversible capacity in non-aqueous secondary batteries by facilitating lithium transfer and maintaining electrode integrity.
Implementation Method 1
a positive electrode and a negative electrode that can occlude and release lithium ions
Implementation Method 2
amorphous composite graphite particles (B) in which graphite particles (C) and amorphous carbon are composited
Data Source
AI summary
An object of the present invention is to provide a carbon material for negative electrodes of non-aqueous secondary batteries having a high capacity, a high output, excellent cycle characteristics and a low irreversible capacity.The present invention relates to a carbon material for negative electrodes of non-aqueous secondary batteries, the carbon material comprising: (1) a composite carbon particles (A) containing elemental silicon, and (2) amorphous composite graphite particles (B) in which graphite particles (C) and amorphous carbon are composited.