Silicon Anode Composite Structure for Expansion-Stable Li-Ion Batteries
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Solution Overview
Problem
Silicon-based negative electrode materials in lithium-ion batteries experience large volume expansion and shrinkage during charging and discharging, leading to capacity fading and instability of the solid electrolyte interface (SEI) film.
Innovation Solution
A negative electrode material comprising a combination of porous silicon-based material and micropowder silicon-based material, where the micropowder fills voids between particles of the porous silicon-based material, reducing stress and expansion rates, and potentially including a carbon material like graphite for improved conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode material to achieve high theoretical specific capacity, then energy density is improved, but volume expansion and shrinkage during charging and discharging causes separation and shedding from current collector, resulting in rapid capacity fading
Solution Approach 1:
The patent uses porous silicon-based material with controlled pore structures to accommodate volume expansion during lithiation. The porous structure provides internal space for expansion without causing external stress that would lead to particle cracking or detachment from the current collector, thereby maintaining capacity stability while preserving high specific capacity.
Solution Approach 2:
The patent creates composite structures by filling voids between porous silicon-based material particles with micropowder silicon-based material. This composite approach optimizes both volumetric energy density and mechanical stability, preventing particle separation while maintaining high capacity performance.
2Quantity of substance
If silicon-based material undergoes large volume expansion during charging, then theoretical specific capacity is achieved, but this causes separation and shedding of negative electrode material layer from current collector
Solution Approach 1:
The porous silicon-based material provides internal void space that absorbs volume expansion during lithiation, preventing the material from exerting excessive stress on the electrode structure. This maintains the stability of the electrode material layer on the current collector while achieving high specific capacity.
Solution Approach 2:
The patent performs preliminary filling of voids with micropowder silicon-based material before electrode assembly. This pre-positioning of fine particles in the interstices creates a more stable packed structure that resists expansion-induced separation during subsequent charging cycles.
3Quantity of substance
If micropowder silicon-based material is used to fill voids to increase energy density, then volumetric energy density is improved, but particle size distribution affects lithium-ion diffusion kinetics
Solution Approach 1:
The patent applies different particle sizes in specific locations: porous silicon-based material with larger particles provides the main structural framework and high capacity, while micropowder silicon-based material fills the interstitial voids to maximize volumetric density. This spatial differentiation optimizes both energy density and maintains adequate lithium-ion diffusion pathways.
Solution Approach 2:
The composite structure of porous and micropowder silicon-based materials creates a hierarchical architecture that balances volumetric energy density with ion transport. The porous structure provides diffusion channels while the micropowder filling optimizes space utilization without completely blocking ion pathways.
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 solution effectively limits the expansion of the negative electrode material, preventing peeling from the current collector and enhancing the kinetic performance and energy density of the battery by ensuring rapid lithium-ion diffusion and charge exchange.
Implementation Method 1
a micropowder silicon-based material configured to fill voids between particles of the porous silicon-based material
Implementation Method 2
The stress generated by the two types of silicon-based materials during intercalation and deintercalation of lithium is relieved by a pore channel structure in the porous silicon-based material
Implementation Method 3
ensuring rapid lithium-ion diffusion and charge exchange
Data Source
AI summary
A negative electrode material, a negative electrode plate, an electrode assembly, a battery, and an electrical device are disclosed. The negative electrode material includes a silicon-based material. The silicon-based material includes a porous silicon-based material and a micropowder silicon-based material configured to fill voids between particles of the porous silicon-based material. A volume median diameter of the porous silicon-based material is greater than a volume median diameter of the micropowder silicon-based material. The small-grained micropowder silicon-based material fills the voids between particles of the large-grained porous silicon-based material. The stress generated by the two types of silicon-based materials during intercalation and deintercalation of lithium is relieved by a pore channel structure in the porous silicon-based material and by an interstice between the porous silicon-based material and the micropowder silicon-based material.