Silicon-Carbon Anode Composite with SWCNT Network for Cycle Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Silicon-based negative electrode active materials in lithium secondary batteries suffer from volume expansion and contraction during charging and discharging, leading to electrical short circuits and rapid lifespan deterioration.
Innovation Solution
A composite negative electrode active material comprising silicon-based core particles with an outer carbon coating layer and single-walled carbon nanotubes (SWCNTs) partially spaced apart, forming a conductive network to prevent short circuits and improve lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If silicon-based negative electrode active materials are used to achieve high capacity and high energy density, then the capacity increases about 10 times compared to carbon-based materials, but volume expansion occurs during charging and discharging causing active material particles to crack and electrical short circuits between particles
Solution Approach 1:
The patent applies nesting by placing silicon-based core particles inside a carbon coating layer, forming a core-shell structure. This nested configuration allows the high-capacity silicon core to be protected by the stable carbon shell, preventing volume expansion cracks while maintaining the high capacity advantage of silicon-based materials.
Solution Approach 2:
The patent uses composite materials by combining silicon-based particles with carbon coating and conducting polymer coating. This composite structure integrates the high capacity of silicon with the structural stability and electrical conductivity of carbon and conducting polymers, resolving the contradiction between high capacity and lifespan durability.
2Quantity of substance
If silicon-based negative electrode active materials undergo volume expansion during charging, then high capacity is achieved, but the distance between active materials increases causing electrical short circuits and loss of electric charge moving paths
Solution Approach 1:
The patent introduces conducting polymer and carbon coating as intermediary materials between silicon-based particles. These intermediaries maintain stable electrical contact and conductive paths during volume expansion, preventing electrical short circuits while allowing the silicon particles to achieve high capacity through volume changes.
Solution Approach 2:
The patent applies flexible shells by using carbon coating and conducting polymer coating that can accommodate volume expansion of silicon particles. These flexible coatings maintain structural integrity and electrical connectivity during charging-discharging cycles, preventing particle cracking and electrical short circuits.
3Stability of the object's composition
If conventional carbon coating is applied to silicon-based particles to prevent volume expansion, then structural stability improves, but electrical conductivity decreases and short circuit prevention is insufficient
Solution Approach 1:
The patent merges carbon coating with conducting polymer coating to create a dual-coating structure. This combination integrates the structural stability benefits of carbon coating with the electrical conductivity advantages of conducting polymers, simultaneously achieving both structural stability and reliable electrical conductivity for short circuit prevention.
Solution Approach 2:
The patent uses composite materials by combining carbon coating with conducting polymer materials. This composite coating structure provides both the structural stability of carbon and the electrical conductivity of conducting polymers, resolving the contradiction between structural stability and electrical conductivity.
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 effectively prevents electrical short circuits and enhances lifespan characteristics by maintaining stable electrical contact despite volume changes, improving the performance of lithium secondary batteries.
Implementation Method 1
silicon-based negative electrode active materials have a problem in that a distance between the active materials may increase and an electrical short circuit may occur between the active materials due to the volume expansion/contraction caused by charging and discharging
Implementation Method 2
single-walled carbon nanotubes are in contact with the outer carbon coating layer and comprise a body partially spaced apart from the outer carbon coating layer
Data Source
AI summary
Disclosed is a composite negative electrode active material comprising silicon-based core particles, an outer carbon coating layer present on the silicon-based core particles, and single-walled carbon nanotubes, wherein the single-walled carbon nanotubes are in contact with the outer carbon coating layer and comprise a body partially spaced apart from the outer carbon coating layer, and the outer carbon coating layer comprises oxygen in an amount of 35 wt % to 55 wt % therein.