Silicon Negative Electrode Porous Micropowder Expansion Control
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Solution Overview
Problem
Conventional graphite-based negative electrode materials in lithium-ion batteries struggle to meet the demand for higher energy density due to silicon-based materials' large volume expansion and shrinkage during charging and discharging, leading to material separation and rapid capacity fading.
Innovation Solution
A negative electrode material comprising a combination of porous silicon-based material and micropowder silicon-based material, where the micropowder fills the voids between porous silicon-based material particles, relieving stress through pore channels and interstices, thereby limiting expansion and enhancing energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based material is used as negative electrode material to increase theoretical specific capacity, then energy density is improved, but volume expansion and shrinkage during charging and discharging causes material separation and rapid capacity fading
Solution Approach 1:
The silicon-based material is divided into porous particles with internal pore channels, segmenting the material structure to accommodate volume changes internally rather than causing external expansion and separation
Solution Approach 2:
Porous silicon-based material with internal pore channels (1 nm to 100 nm) is used to provide internal volume for expansion, preventing material separation while maintaining structural integrity during charging and discharging cycles
2Reliability
If porous silicon-based material is used to accommodate volume expansion, then capacity retention is improved, but voids between particles reduce energy density
Solution Approach 1:
Micropowder silicon-based material is nested within the voids between porous silicon-based material particles, filling the empty space with additional active material to increase energy density while the porous structure continues to accommodate expansion
Solution Approach 2:
A composite structure combining porous silicon-based material and micropowder silicon-based material is created, where the porous material provides expansion accommodation and the micropowder fills voids to maximize space utilization and energy density
3Quantity of substance
If micropowder silicon-based material fills voids between porous particles, then energy density is improved, but stress concentration may occur during expansion
Solution Approach 1:
The micropowder silicon-based material is specifically placed in the voids between porous particles, creating local regions of filled and unfilled areas that distribute stress evenly during expansion and contraction cycles
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 effectively suppresses outward expansion of the negative electrode material, increases theoretical gravimetric capacity, and improves lithium-ion diffusion and kinetic performance.
Implementation Method 1
relieving stress through pore channels and interstices, thereby limiting expansion
Implementation Method 2
silicon-based material is prone to large volume expansion and shrinkage during charging and discharging
Implementation Method 3
improves lithium-ion diffusion and kinetic performance
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
A negative electrode material, a negative electrode plate (101), an electrode assembly (20), a battery (40), and an electrical device (50) 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, thereby limiting the expansion of the two types of silicon-based materials to the interior of the two types of silicon-based materials, and reducing the expansion rate of the negative electrode material.