Silicon-Carbon Composite Particles With Low Resistivity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing lithium-ion rechargeable batteries using silicon as a negative electrode active material face high electrical resistivity due to excessive silicon precipitation on the surface, leading to reduced coulombic efficiency and poor cycle characteristics.
Innovation Solution
Composite particles comprising porous carbon and silicon, with controlled silicon content, oxygen content, and specific density and structural properties, are produced by a method that fills carbon pores with silicon and forms a thin coat layer, ensuring uniform silicon distribution and reduced surface coverage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon is filled in the pores of porous carbon material to increase capacity, then the theoretical specific capacity is improved, but excessive silicon precipitates on the surface causing high electrical resistivity
Solution Approach 1:
The patent applies local quality by creating a non-uniform silicon distribution within the porous carbon structure. Silicon is preferentially deposited in the internal pores rather than on the external surface, achieving high silicon content (40-70 wt%) while maintaining low surface coverage. This localized placement ensures high capacity without excessive surface silicon that would cause high electrical resistivity.
Solution Approach 2:
The patent utilizes porous carbon material as the base structure to host silicon. The porous structure provides internal volume for silicon deposition, allowing high silicon content to be achieved while the carbon matrix maintains electrical conductivity. The pores act as reservoirs for silicon, preventing surface precipitation and the associated electrical resistivity problems.
2Quantity of substance
If silicon is used as negative electrode active material to achieve high capacity, then the theoretical specific capacity is improved, but the volume expansion and contraction causes structural self-destruction and poor cycle characteristics
Solution Approach 1:
The patent uses porous carbon as a flexible matrix that can accommodate silicon's volume changes during lithium insertion and desorption. The carbon structure acts as a buffer that absorbs expansion stress and prevents structural self-destruction. This flexible containment maintains electrode integrity over many cycles, solving the reliability problem while preserving high capacity.
Solution Approach 2:
The patent creates a composite material system combining silicon and porous carbon. The composite structure leverages silicon's high capacity while using carbon's structural stability and flexibility to mitigate volume expansion issues. The synergistic combination achieves both high specific capacity and good cycle characteristics.
3Manufacturing precision
If porous carbon material with small pore diameter is used for silicon filling, then the silicon distribution is improved, but excessive silicon still precipitates on the surface resulting in high electrical resistivity
Solution Approach 1:
The patent applies local quality by creating a non-uniform silicon distribution within the porous carbon structure. Silicon is preferentially deposited in the internal pores rather than on the external surface, achieving high silicon content (40-70 wt%) while maintaining low surface coverage. This localized placement ensures high capacity without excessive surface silicon that would cause high electrical resistivity.
Solution Approach 2:
The patent optimizes the pore diameter parameter of the porous carbon material to balance silicon distribution and electrical resistivity. By selecting appropriate pore size ranges, the patent achieves uniform silicon filling in the pores while controlling surface precipitation, thereby maintaining low electrical resistivity despite high silicon content.
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 composite particles achieve lower electrical resistivity, improved cycle durability, and increased discharge capacity by isotropic expansion and contraction during charging and discharging.
Implementation Method 1
a method for producing silicon in the pores of a porous carbon material by bringing a porous carbon material and silane gas into contact at a high temperature
Implementation Method 2
silicon (Si) expands and contracts in response to electrochemical lithium insertion and desorption, and the volume at the time of expansion is up to approximately 3 to 4 times the volume at the time of contraction
Data Source
AI summary
The present invention provides a composite particle, which includes a carbon material and silicon, wherein electrical resistivity is reduced. The present invention includes a composite particle including a carbon material and silicon, wherein a He true density by dry density measurement using helium gas is 1.85 g/cm3 or more and 2.10 g/cm3 or less, a silicon content is 30 mass% or more and 80 mass% or less, an oxygen content is 4.0 mass% or less, and a BET specific surface area is 0.5 m2/g or more and 30.0 m2/g or less.