Silicon-Graphite Negative Electrode for Lithium Battery Volume Expansion
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Solution Overview
Problem
Si-based negative active materials in rechargeable lithium batteries suffer from volume swelling and reduced cycle-life and safety due to lithium ion intercalation and deintercalation, which affects the battery's performance and reliability.
Innovation Solution
A negative electrode composition comprising non-sheet-shaped graphite particles, silicon-based particles, and sheet-shaped graphite powder, where the silicon particles are smaller than the longest axis of the graphite powder, forming a structure that controls volume expansion and positions silicon particles in voids or gaps, thereby reducing deformation and enhancing cycle-life and safety.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Si-based negative active material is used, then battery capacity is improved, but volume swelling occurs during charge and discharge
Solution Approach 1:
The patent embeds Si-based particles inside hollow graphite particles, creating a nested structure where the Si particle is contained within the graphite cavity. This nesting approach allows the Si particle to expand within the confined space of the hollow graphite particle during lithiation, preventing external volume swelling while maintaining high capacity.
Solution Approach 2:
The patent creates a localized structure where Si-based particles are specifically positioned within hollow regions of graphite particles. This local arrangement allows the Si particles to be contained in specific zones (the hollow spaces) while the outer graphite shell maintains structural integrity and prevents overall volume expansion of the electrode material.
2Quantity of substance
If Si-based negative active material is used, then battery capacity is improved, but cycle-life is reduced
Solution Approach 1:
The hollow graphite particles serve as protective containers for Si-based particles, nesting the Si inside the graphite shell. This nested structure protects the Si particles from mechanical degradation during repeated charge-discharge cycles, maintaining structural integrity and extending cycle-life while preserving the high capacity benefits of Si.
Solution Approach 2:
The hollow graphite structure provides pre-established cushioning space around the Si particles. During lithiation, the Si particles expand into this pre-designed hollow space, preventing direct contact and mechanical stress between Si particles and the electrode matrix, thereby reducing degradation and extending cycle-life.
3Quantity of substance
If Si-based negative active material is used, then battery capacity is improved, but safety is reduced
Solution Approach 1:
The hollow graphite particles act as containment vessels for Si-based particles, nesting them in a stable and structurally sound environment. This nested configuration prevents Si particle detachment, aggregation, and direct exposure to electrolyte, thereby improving battery safety and reliability while maintaining high capacity.
Solution Approach 2:
The patent creates a localized protective environment where Si particles are confined within hollow graphite structures. This local containment isolates the reactive Si particles from direct interaction with the electrolyte and other electrode components, reducing safety risks such as dendrite formation and thermal runaway while preserving Si's high capacity characteristics.
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 proposed structure effectively suppresses volume expansion of silicon-based particles during charge and discharge, improving the cycle-life and safety of rechargeable lithium batteries by maintaining structural integrity and performance.
Implementation Method 1
A lithium-transition metal oxide having a structure being capable of intercalating lithium ions... Si-based negative active material has higher capacity than the carbon-based negative active material, but swelling and extraction during charge and discharge...
Implementation Method 2
Various carbon-based negative active materials such as artificial graphite, natural graphite, and hard carbon, which may all intercalate and deintercalate lithium...
Data Source
AI summary
Disclosed are a negative electrode for a rechargeable lithium battery that includes a plurality of non-sheet-shaped graphite particles, at least one silicon-based particle in a void formed by assembling the non-sheet-shaped graphite particles, and a sheet-shaped graphite powder between the non-sheet-shaped graphite particles, the void, or both thereof, wherein a size of the silicon particle is smaller than a length of the longest axis of the sheet-shaped graphite powder.