Silicon Oxide Graphite Negative Electrode Mitigating Volume Expansion
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Solution Overview
Problem
Silicon-based negative electrode materials for non-aqueous electrolyte secondary batteries face challenges such as high volume expansion, low initial efficiency, and poor cycle performance due to volumetric changes during charge/discharge cycles, which limit their capacity and durability.
Innovation Solution
A negative electrode material comprising silicon oxide particles coated with graphite and 1 to 50 wt% silicon particles, with a polyimide resin binder, is developed to mitigate volume expansion and enhance conductivity, resulting in improved cycle performance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon particles are used as negative electrode active material to increase battery capacity, then theoretical capacity increases to 4200 mAh/g, but volume expansion exceeds 300% during charge/discharge cycles
Solution Approach 1:
Silicon particles are encapsulated within silicon oxide particles, forming a core-shell structure where the silicon oxide shell accommodates the volume expansion of the silicon core during lithiation, preventing particle fracture and maintaining electrode integrity
Solution Approach 2:
The negative electrode uses a composite material system combining silicon particles (for high capacity) with silicon oxide matrix (for structural stability and low volume expansion), achieving both high capacity and minimal volume change during cycling
2Volume of moving object
If silicon oxide particles are used as negative electrode active material to reduce volume expansion, then volume expansion is suppressed to 10%, but initial charge/discharge efficiency is low at 70%
Solution Approach 1:
The electrode combines silicon oxide particles (providing structural stability and low volume expansion) with conductive carbon materials (providing electrical conductivity and high initial efficiency), achieving both low volume expansion and high initial charge/discharge efficiency
3Reliability
If carbon coating is applied to silicon particles to improve conductivity, then electrical conductivity increases, but cycle performance degrades due to inability to mitigate volumetric changes
Solution Approach 1:
The electrode uses a composite system where silicon oxide provides structural stability to withstand volumetric changes, while carbon materials provide electrical conductivity, achieving both good cycle performance and high conductivity without relying on carbon-coated silicon particles
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 achieves high initial charge/discharge efficiency and increased battery capacity while maintaining low volume expansion, leading to improved cycle performance and durability of non-aqueous electrolyte secondary batteries.
Implementation Method 1
silicon oxide particles which have been coated with carbon by chemical vapour deposition
Data Source
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AI summary
A negative electrode material comprising an active material and 1-20 wt% of a polyimide resin binder is suitable for use in non-aqueous electrolyte secondary batteries. The active material comprises silicon oxide particles and 1-50 wt% of silicon particles. The negative electrode exhibits improved cycle performance while maintaining the high battery capacity and low volume expansion of silicon oxide. The non-aqueous electrolyte secondary battery has a high initial efficiency and maintains improved performance and efficiency over repeated charge/discharge cycles by virtue of mitigated volumetric changes during charge/discharge cycles.