Red Phosphorus-Carbon Anode Structure for Conductivity and Volume Stability
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Solution Overview
Problem
Existing phosphorus-based negative electrodes in lithium-ion batteries suffer from poor conductivity, high volume expansion, and poor wettability to lithium metal, while carbon-based electrodes have low specific capacity and limited lithium ion diffusion, leading to poor rate performance and cycle stability.
Innovation Solution
A phosphorus-carbon composite negative electrode is prepared using carbon nanotubes doped with red phosphorus and low-melting transition metal compounds through a low-temperature liquid phase immersion process, enhancing conductivity and stability by forming a 3D porous structure and improving wettability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If phosphorus-based negative electrode material is used, then theoretical specific capacity is improved, but conductivity deteriorates and volume expansion increases
Solution Approach 1:
The patent uses composite materials by combining red phosphorus with carbon nanotubes and transition metal compounds. The carbon nanotubes provide conductivity and structural stability, while the transition metal compounds (embedded in the carbon nanosphere) improve wettability to lithium metal. This composite structure allows the material to achieve high theoretical specific capacity from phosphorus while maintaining good conductivity and volume stability through the carbon and metal compound matrix.
2Reliability
If carbon-based negative electrode is used, then conductivity and structural stability are improved, but specific capacity deteriorates
Solution Approach 1:
The patent merges carbon-based materials (carbon nanotubes forming a 3D skeleton structure) with phosphorus-based materials (red phosphorus). The carbon nanotubes provide the conductivity and structural stability, while the red phosphorus provides the high specific capacity. The transition metal compounds are embedded in the carbon nanosphere to enhance the interface between the two materials, ensuring good electrical contact and lithium ion diffusion pathways, thus achieving synergistic effects that combine the advantages of both material systems.
3Quantity of substance
If red phosphorus is adsorbed on carbon nanotubes, then specific capacity is improved, but wettability to lithium metal deteriorates
Solution Approach 1:
The patent introduces transition metal compounds as intermediaries between the red phosphorus and lithium metal. These transition metal compounds are embedded in the carbon nanosphere and serve as a mediating layer that improves the wettability to lithium metal. The transition metals facilitate better contact and interaction with lithium metal, enabling more effective lithium ion diffusion and deposition, thus improving the electrochemical performance without compromising the high specific capacity provided by red phosphorus.
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 electrode achieves a 30% increase in specific capacity, improved cycling performance, and reduced side reactions, with a capacity retention rate of 85% after 150 cycles, and a stable structure even at high current densities.
Implementation Method 1
the difference in surface electronegativity of red phosphorus and carbon nanotubes in a solvent enables the red phosphorus to be uniformly adsorbed on the wall of the carbon nanotubes by means of a low-temperature liquid phase method
Implementation Method 2
the red phosphorus and the composite carbon nanospheres are mixed in a solvent and experience a thermal reaction to give a product
Data Source
AI summary
A new phosphorus-carbon negative electrode material based on red phosphorus and a preparation method thereof are disclosed. The material comprises red phosphorus and composite carbon nanospheres. The red phosphorus and the composite carbon nanospheres are mixed in a solvent and experience a thermal reaction to give a product, wherein a mass concentration of the composite carbon nanospheres in the solution is 10%-20%. The half-cell assembled by using the phosphorus-carbon composite material still maintains a low overpotential at a high current density of 2.5 mA·cm−2, and the capacity retention rate after 150 cycles still reaches 85%.