3D Netted Silicon-Carbon Anode Structure for Low-Expansion Cycling
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Solution Overview
Problem
Silicon-based anode materials for lithium-ion batteries experience significant volume changes during electrochemical processes, leading to the formation of an unstable SEI membrane and structural damage due to micro-cracks, which affects charging and discharging performance and cycling stability.
Innovation Solution
A three-dimensional netted structure composite material is developed by in-situ growing silicon nanowires within the through holes of porous carbon microspheres using chemical deposition or molten salt electrolysis, followed by carbon coating, forming a high-strength skeleton structure that inhibits volume expansion and enhances electrical conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based anode materials are used to achieve high specific capacity, then the battery capacity is improved, but significant volume changes occur during electrochemical processes leading to unstable SEI membrane and structural damage
Solution Approach 1:
The patent employs porous carbon microspheres with a three-dimensional netted structure as the host material for silicon nanowires. The porous structure provides缓冲 space for silicon volume expansion during lithium insertion, preventing structural collapse and maintaining cycling stability while enabling high capacity
Solution Approach 2:
The patent creates a composite material system consisting of silicon nanowires embedded in porous carbon microspheres with a carbon shell coating. This composite structure combines the high capacity of silicon with the structural stability and conductivity of carbon, resolving the contradiction between capacity and stability
Solution Approach 3:
The patent implements a nested structure where silicon nanowires are grown inside the through-holes of porous carbon microspheres, and the entire structure is coated with a carbon shell. This nested design allows silicon to expand within the confined porous space while being protected by the outer carbon shell
2Quantity of substance
If silicon particles are used to increase capacity, then the mass specific capacity is improved, but micro-cracks form on the material surface during cycling affecting performance
Solution Approach 1:
The patent applies a carbon shell coating around the porous carbon microspheres containing silicon nanowires. This flexible carbon shell accommodates volume changes of silicon during cycling while maintaining surface integrity, preventing micro-crack formation and ensuring stable electrochemical performance
Solution Approach 2:
The patent creates different structural zones: the inner porous carbon microsphere structure provides expansion space for silicon, while the outer carbon shell provides a stable protective surface. Each zone has optimized properties for its specific function, resolving the surface stability issue
3Reliability
If carbon coating is applied to stabilize SEI membrane and prevent pulverization, then structural stability is improved, but the charging and discharging performance may be affected due to additional resistance
Solution Approach 1:
The patent uses a porous carbon structure rather than dense carbon coating. The porous structure provides sufficient mechanical stability while maintaining high ion transport efficiency, avoiding the resistance issue associated with dense coatings while still protecting the silicon structure
Solution Approach 2:
The patent applies carbon stabilization locally where needed (as a thin shell coating and as the porous host structure) rather than using thick dense coatings. This localized application provides stability while minimizing resistance to ion transport, maintaining high charging and discharging performance
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 material achieves a lower volume expansion rate, higher mass specific capacity, and improved cycling stability by preventing cracking and forming an interconnected conductive network, resulting in better electrical conductivity and longer cycle life.
Implementation Method 1
the silicon nanowires are formed by catalyzing silicon-containing gas by Au or Ag and depositing same in the through holes
Implementation Method 2
the silicon nanowires are formed by catalyzing silicon-containing gas by Au or Ag and depositing same in the through holes by Au or Ag
Implementation Method 3
Au or Ag is first evaporated and deposited onto walls of the through holes of the porous carbon microspheres
Implementation Method 4
Au or Ag is first evaporated and deposited onto walls of the through holes
Implementation Method 5
electrolyzeing the silicon dioxide nanoparticles in the through holes under a molten salt system
Data Source
Figure 1
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Figure 3~4
AI summary
Disclosed in the present invention are a three-dimensional netted structure composite material for lithium batteries, and a preparation method and the use thereof.The three-dimensional netted structure composite material comprises:a porous carbon microsphere containing netted structure through holes, silicon nanowires distributed in the through holes of the porous carbon microsphere, and a carbon shell. The silicon nanowires are formed by catalyzing, by means of Au or Ag,a silicon-containing gas and depositing same in the through holes; or the silicon nanowires are formed by depositing a silane gas in the through holes to form silicon oxide nanoparticles, then electrolyzing the silicon oxide nanoparticles in the through holes undder a molten salt system. The silicon nanowires form three- dimensional netted structures in through holes of the porous carbon microsphere. Applying the three- dimensional netted structure composite material as a negative electrode active material in a lithium battery can endow the lithium battery with a relatively low volume expansion rate, a relatively high mass specific capacity, and good conductive performance and cycling stability.