CNT-Coated Battery Separator for Conductivity Without Blocking Ion Diffusion
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Solution Overview
Problem
Conventional methods for improving the conductive path of electrodes in lithium secondary batteries are insufficient, leading to suboptimal input/output characteristics and lithium ion diffusion in batteries.
Innovation Solution
A separator with a conductive layer comprising a carbon nanotube structure where multiple single-walled carbon nanotube units are bonded side by side, maintaining a specific diameter and length to enhance conductivity while minimizing interference with the porous substrate's pore structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional current collector or conductive agent methods are used to improve electrode conductivity, then conductive path is improved, but lithium ion diffusion is hindered
Solution Approach 1:
The invention employs a porous conductive layer made of carbon nanotube structures with controlled porosity (30-70%). The porous structure allows lithium ions to diffuse through the conductive layer without significant hindrance while still providing effective electrical conductivity. The pore size and distribution are optimized to balance ion transport and electron conduction, resolving the contradiction between improving conductive path and maintaining lithium ion diffusion.
Solution Approach 2:
The invention creates a composite structure combining the porous substrate with a carbon nanotube-based conductive layer. This composite material integrates the mechanical support function of the substrate with the high conductivity of carbon nanotubes, while the porous architecture of the composite ensures lithium ion diffusion pathways are preserved. The synergistic combination resolves the contradiction by achieving both improved conductivity and maintained ion diffusion.
2Reliability
If conductive layer is added to improve electrode conductivity, then battery resistance is reduced, but pore structure of porous substrate is affected
Solution Approach 1:
The conductive layer is designed with locally optimized properties: carbon nanotubes are arranged to form conductive networks in specific regions while maintaining porous structures in other regions. The layer thickness and density vary locally to ensure adequate conductivity without compromising the overall pore structure. This local quality approach allows the conductive layer to reduce battery resistance while preserving the pore structure necessary for lithium ion diffusion.
Solution Approach 2:
The invention optimizes key parameters of the conductive layer including thickness (1-10 μm), porosity (30-70%), and carbon nanotube concentration to achieve the desired balance. By carefully controlling these parameters, the conductive layer provides sufficient electrical conductivity to reduce battery resistance while maintaining adequate porosity to preserve the pore structure for lithium ion transport. The parameter optimization resolves the contradiction between reducing resistance and maintaining pore structure stability.
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 solution improves the conductive path of electrodes, reducing battery resistance and maintaining lithium ion diffusion, thereby enhancing the input/output characteristics and life characteristics of the battery.
Implementation Method 1
the conductive layer includes a carbon nanotube structure in which a plurality of single-walled carbon nanotube units are bonded to each other side by side
Implementation Method 2
the conductive layer has little effect on a pore structure of a porous substrate in the separator, it may minimize a decrease in degree of diffusion of lithium ions in the separator
Data Source
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AI summary
The present invention relates to a separator and a secondary battery including same, the separator comprising a porous substrate and a conductive layer arranged on the porous substrate, wherein the conductive layer comprises a carbon nanotube structure in which a plurality of single-walled carbon nanotube units are coupled to each other side by side, and the carbon nanotube structure has an average particle diameter of 2-500 nm.