Composite Conductive Material for Dispersible Battery Electrodes
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Solution Overview
Problem
Existing conductive materials for secondary batteries face challenges in achieving excellent electrical conductivity and dispersibility, particularly with carbon nanofibers and graphene, which tend to aggregate and limit electrolyte mobility, and current methods for dispersing carbon nanotubes are inefficient.
Innovation Solution
A composite conductive material is developed, comprising spherical carbon particles with a catalyst impregnated beneath their surfaces and carbon nanofibers extending from these contact points, grown through a process involving heat treatment in a helium or hydrogen atmosphere, enhancing dispersibility and binding force between particles and nanofibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If carbon nanofibers are used as conductive material, then electrical conductivity is improved, but dispersibility deteriorates due to bundle-type growth and entanglement
Solution Approach 1:
The carbon nanofibers are segmented into individual fibers rather than remaining as bundles. The patent achieves this by using a surfactant during the growth process to separate the nanofibers from each other, preventing bundle formation and enabling individual fiber dispersion in the electrode matrix.
Solution Approach 2:
A surfactant is introduced as an intermediary substance during the carbon nanofiber growth process. The surfactant molecules interact with the nanofiber surfaces and prevent direct contact between nanofibers, thereby preventing aggregation and enabling stable dispersion without requiring post-synthesis mechanical treatment.
2Ease of operation
If mechanical dispersion treatment such as ultrasonic treatment is used to disperse carbon nanotubes, then dispersibility is improved during treatment, but aggregation occurs after treatment when concentration increases
Solution Approach 1:
The surfactant is introduced during the nanofiber growth process itself, before the nanofibers are collected and processed. This preliminary action of surface modification during synthesis prevents aggregation from occurring in the first place, eliminating the need for subsequent mechanical dispersion treatments that provide only temporary dispersion.
3Ease of operation
If dispersants are used to disperse and stabilize carbon nanotubes, then dispersibility is improved, but handling becomes difficult due to increased viscosity at high concentrations
Solution Approach 1:
The patent uses a surfactant that can be easily removed or decomposed after serving its dispersion function during electrode formation. This allows the surfactant to provide temporary dispersion assistance during manufacturing, then be eliminated from the final product, avoiding long-term viscosity issues and handling problems.
4Quantity of substance
If high-pressure press is used to form high-density electrode, then electrode density is improved, but electrolyte permeability is lowered due to reduced space between particles
Solution Approach 1:
The conductive material is applied locally at the contact points between active material particles rather than uniformly throughout the electrode. The carbon nanofiber slurry is selectively deposited in the inter-particle spaces, providing conductivity enhancement without requiring high-pressure compression that would reduce overall electrolyte permeability.
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 improves electrical conductivity and dispersibility, minimizing contact resistance and preventing dendrite formation, while allowing for higher energy density and reduced viscosity, thus enhancing the performance of secondary batteries.
Implementation Method 1
a catalyst (i.e., a carbon nanofiber (CNF) synthesis catalyst) impregnated beneath surfaces of the carbon particles
Implementation Method 2
heat treatment in a helium or hydrogen atmosphere, enhancing dispersibility and binding force between particles and nanofibers
Data Source
AI summary
A method for producing a composite conductive material having excellent dispersibility is provided. The method includes supporting a catalyst on surfaces of carbon particles; heat treating the catalyst in a helium or hydrogen atmosphere such that the catalyst penetrate the surfaces of the carbon particles and are impregnated beneath the surfaces of the carbon particles at a contact point between the carbon particles and the impregnated catalyst; and heating the carbon particles having the impregnated catalyst disposed therein in the presence of a source gas to grow carbon nanofibers from the impregnated catalyst to form a composite conductive material, wherein the source gas contains a carbon source, and wherein the carbon nanofibers extend from the contact point to above the surfaces of the carbon particles.