Metal-Supported Carbon Nanostructure for Lithium-Ion Battery
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Solution Overview
Problem
Lithium-ion secondary batteries face challenges with negative electrodes made from metals like silicon and tin, which experience volume expansion during lithium absorption, leading to reduced electric capacity and stability due to insufficient specific surface area and high production costs.
Innovation Solution
A carbon nanostructure with air-sac-like pores formed by graphene multilayer membrane walls, where metals like silicon or tin are supported, enhancing porosity and electric conductivity, and allowing for reversible lithium absorption, thus stabilizing the electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If metal nanoparticles (silicon, tin) are used as negative electrode material to achieve large capacity, then the electric capacity increases, but the volume expansion during lithium absorption causes the metal to break apart and lose contact, reducing capacity retention and charge/discharge efficiency
Solution Approach 1:
Metal nanoparticles are encapsulated within hollow carbon spheres, creating a nested structure where the metal is protected inside the carbon shell. This prevents the metal from breaking apart during volume expansion while maintaining electrical contact, resolving the contradiction between high capacity and capacity retention.
Solution Approach 2:
The invention creates a composite material consisting of metal nanoparticles embedded in hollow carbon spheres. This composite structure combines the high capacity of metal with the structural stability and conductivity of carbon, preventing electrode breakage while maintaining performance.
2Reliability
If silicon-carbon complex materials are deposited on carbon particles to achieve high capacity retention, then capacity retention improves, but the specific surface area is insufficient and the structure becomes too dependent on internal void spaces, reducing performance at high current densities
Solution Approach 1:
The invention uses hollow carbon spheres with controlled porosity and surface area. The hollow structure provides internal void space for volume expansion while the outer surface maintains sufficient specific surface area for high current density performance, resolving the contradiction between capacity retention and surface area availability.
3Stability of the object's composition
If active material is supported in micropores of activated carbon to form negative electrode, then the structure provides stability, but the upper limited value of additive amount is only 30% relative to carbon weight, preventing sufficient charge/discharge efficiency
Solution Approach 1:
The invention changes the structural parameters of the carbon support from traditional activated carbon micropores to hollow carbon spheres with controlled shell thickness and internal volume. This allows higher metal loading (exceeding 30% by weight) while maintaining structural stability and enabling sufficient charge/discharge efficiency through the hollow space accommodation of volume expansion.
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 carbon nanostructure with metal support improves charge/discharge efficiency and capacity retention, preventing electrode breakage and maintaining performance even at high current densities, while reducing production costs.
Implementation Method 1
air-sac-like pores, which are defined by graphene multilayer membrane walls, are formed in the rod-shaped materials and/or the sheet-shaped materials
Implementation Method 2
when the metal absorbs lithium so that the metal is normally broken apart
Data Source
AI summary
This invention provides a carbon nanostructure including: carbon containing rod-shaped materials and/or carbon containing sheet-shaped materials which are bound three-dimensionally; and graphene multilayer membrane walls which are formed in the rod-shaped materials and/or the sheet-shaped materials; wherein air-sac-like pores, which are defined by the graphene multilayer membrane walls, are formed in the rod-shaped materials and/or the sheet-shaped materials.