SiMxCy Negative Electrode Material for Silicon Expansion Stability
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Solution Overview
Problem
Lithium-ion batteries using silicon materials face issues with volume expansion, structural instability, and cycle stability due to lithium intercalation, leading to micro-short circuits and lithium source consumption, especially at high temperatures.
Innovation Solution
A negative electrode material composed of SiMxCy, where M includes boron, nitrogen, oxygen, or aluminum, with controlled particle size distribution and specific surface area, enhanced by the presence of carbon and high molecular polymers, to improve cycle stability and reduce volume expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon materials are used as negative electrode material, then theoretical gram capacity is improved (4200 mAh/g), but volume expansion reaches 300% causing structural instability and cycle stability deterioration
Solution Approach 1:
The patent applies nesting by placing silicon particles inside a porous carbon matrix structure, where the carbon matrix acts as a container that accommodates silicon's volume expansion during lithium intercalation. This nested configuration allows silicon to maintain its high capacity function while the outer carbon structure provides structural stability and prevents particle disintegration during cycling.
Solution Approach 2:
The patent creates a composite material system combining silicon with carbon matrix and conductive polymers. The composite structure integrates silicon's high theoretical capacity with carbon's structural stability and conductivity, producing a negative electrode material that achieves both high capacity retention and structural stability during repeated charge-discharge cycles.
2Quantity of substance
If silicon materials are used as negative electrode material, then theoretical gram capacity is improved (4200 mAh/g), but volume expansion easily causes destruction of separator to form micro-short circuit
Solution Approach 1:
The patent applies beforehand cushioning by designing a porous carbon matrix structure that anticipates and accommodates silicon's 300% volume expansion during lithium intercalation. The porous structure provides pre-configured space for expansion, acting as a cushion that prevents the silicon particles from expanding uncontrollably and destroying the separator, thereby avoiding micro-short circuits before they can occur.
Solution Approach 2:
The patent uses a flexible porous carbon matrix that can deform and expand alongside the silicon particles during lithiation. This flexible carbon shell structure accommodates volume changes without breaking, maintaining structural integrity and preventing separator destruction that would lead to micro-short circuits.
3Quantity of substance
If silicon materials are used as negative electrode material, then high theoretical gram capacity is achieved, but by-products continue to be generated on surface consuming lithium source in electrolyte especially at high temperature
Solution Approach 1:
The patent introduces a carbon matrix and conductive polymer as intermediary layers between the silicon particles and the electrolyte. These intermediary structures serve as protective interfaces that reduce direct contact between silicon surface by-products and the electrolyte, thereby minimizing continuous lithium consumption from the electrolyte while allowing silicon to maintain its high capacity function.
4Volume of stationary object
If particle size distribution is optimized, then compaction density is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by defining specific particle size distribution ranges (D10-D90) and porosity parameters for the carbon matrix structure. By establishing quantitative parameter ranges rather than requiring precise single-value control, the patent achieves improved compaction density while maintaining feasible manufacturing precision requirements through parameter optimization within acceptable ranges.
Data Source
AI summary
A negative electrode material, and a negative electrode plate, an electrochemical device, and an electronic device including the same. The negative electrode material includes SiMxCy, where 0.5≤x≤2, 0.5≤y≤4, and M includes at least one of boron, nitrogen, oxygen, or aluminum; for SiMxCy, a particle size at a quantity accumulation degree of A % is DNA, a particle size at a volume accumulation degree of B % is DVB, and a half-peak width of a quantity distribution curve is ΔDN; and 2 μm≤(DV50−DN50)≤6 μm, and 1≤(DN99−DN1)/ΔDN≤1.3. The use of the negative electrode material, and the negative electrode plate, the electrochemical device and the electronic device including the same according to the present application achieve good cycle performance and energy density.