Conductive Elastic Shell for Li-Ion Active Material Particles
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Solution Overview
Problem
Li-ion cells face significant capacity loss due to electronic isolation of active material particles from the conductive electrode laminate, exacerbated by expansion and contraction during cycling and aging, leading to increased impedance and premature cell failure.
Innovation Solution
A composite for Li-ion cells is developed, where an electronically conductive elastic material is bound or attached to the active material particles, maintaining electronic contact and improving cycling efficiency and reversible capacity, using electronically conductive elastic carbon materials like expanded graphite, and an attaching phase that can perform its role at temperatures below 650°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If active material particles are used in Li-ion electrodes, then reversible capacity is provided through Li-ion diffusion, but electronic isolation occurs during cycling leading to capacity loss
Solution Approach 1:
An electronically conductive elastic material is bound to the active material particle, forming a flexible conductive shell that maintains electronic contact during volume changes. This elastic shell accommodates the expansion and contraction of the active material during Li-ion insertion and extraction, preventing electronic isolation while maintaining conductivity throughout cycling.
Solution Approach 2:
The invention creates a composite structure combining active material particles with electronically conductive elastic materials. This composite approach integrates the electrochemical activity of the active material with the mechanical flexibility and electrical conductivity of the elastic material, achieving both capacity retention and cycling stability.
2Productivity
If deep discharge cycling is performed to meet high capacity demands, then reversible capacity utilization increases, but particle expansion and contraction accelerate leading to faster electronic isolation
Solution Approach 1:
The electronically conductive elastic material serves as a pre-established protective layer that cushions the active material particle against the mechanical stresses of deep discharge cycling. This protective shell is in place before cycling begins, accommodating volume changes from the outset and preventing the development of electronic isolation pathways even under aggressive cycling conditions.
3Speed
If elevated temperature operation is used to increase reaction kinetics, then power delivery improves, but binder absorption of electrolyte increases leading to particle separation
Solution Approach 1:
The electronically conductive elastic material forms a temperature-resilient shell that maintains its structural integrity and conductive properties at elevated temperatures. This shell continues to provide mechanical coupling between the active material particle and the conductive matrix even when the binder becomes softened and less effective due to thermal effects.
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 composite significantly enhances the cycling efficiency and maintains specific capacity of Li-ion cells by ensuring continuous electronic contact during expansion and contraction, thereby extending the life and performance of the cells.
Implementation Method 1
an electronically conductive elastic material bound or attached to the active material particle... the electronically conductive elastic material is capable of reversibly expanding and contracting
Implementation Method 2
The electronically conductive elastic material may be bound or attached to the active material particle by an attaching phase
Data Source
AI summary
Disclosed herein is a composite for Li-ion cells, comprising an active material particle for Li-ion cells and an electronically conductive elastic material bound or attached to the active material particle. According to the present invention, the electronically conductive elastic material bound or attached to the active material particle allows the particle to maintain electronic contact with the electrode laminate matrix despite ongoing movement or expansion and contraction of the active material particles, such that the cycling efficiency and reversible capacity of the Li-ion cells prepared from the composite of the present invention is improved.