Conductive Material Dispersed Liquid for Secondary Battery Electrodes
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Solution Overview
Problem
The challenge is to improve the dispersibility of carbon nanotubes in electrode production for secondary batteries while maintaining conductivity, as existing methods face issues with aggregation and high viscosity, limiting their use in high-output electrodes.
Innovation Solution
A conductive material dispersed liquid is developed, comprising bundle-type carbon nanotubes, a hydrogenated nitrile-based rubber as a dispersant, and a suitable dispersion medium, with controlled complex modulus and shear viscosity to enhance dispersibility and reduce powder resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If carbon nanotubes are dispersed in a dispersion medium using mechanical dispersion treatment such as ultrasonic treatment, then dispersibility is excellent while the ultrasonic wave is irradiated, but the carbon nanotubes start to aggregate when the ultrasonic irradiation is finished
Solution Approach 1:
A surfactant is introduced as an intermediary substance between carbon nanotubes and the dispersion medium. The surfactant adsorbs onto the carbon nanotube surface, providing steric or electrostatic repulsion that prevents aggregation after ultrasonic treatment stops, thereby maintaining long-term dispersibility and stability
Solution Approach 2:
The carbon nanotubes are subjected to ultrasonic treatment in advance to achieve initial dispersion before being stabilized with surfactant. This preliminary mechanical energy input breaks up aggregates, and the subsequent surfactant addition locks in this dispersed state for long-term stability
2Stability of the object's composition
If carbon nanotubes are dispersed at a high concentration in a dispersion medium using dispersants, then dispersibility improves, but handling becomes difficult due to an increase in viscosity
Solution Approach 1:
The molecular structure and concentration of the surfactant are optimized to provide effective steric or electrostatic repulsion at minimal concentrations. This allows high carbon nanotube concentration to be achieved while maintaining low viscosity and good handling properties through precise parameter control of the dispersing system
3Volume of stationary object
If a high-density electrode is formed by molding electrode active material particles using a high-pressure press, then electrode density is improved, but particles are deformed and the space between the particles is reduced, lowering electrolyte permeability
Solution Approach 1:
Carbon nanotubes act as an intermediary structural element between active material particles. They form a conductive network that maintains porosity and facilitates electrolyte penetration even at high electrode densities, mediating between the conflicting requirements of density and permeability
Solution Approach 2:
Carbon nanotubes are selectively distributed in the spaces between active material particles, creating localized conductive pathways and maintaining local porosity. This allows the bulk electrode to achieve high density while local regions retain the necessary structure for electrolyte flow and ion transport
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 achieves optimal dispersion of carbon nanotubes, reducing powder resistance and improving output characteristics of electrodes, making it suitable for high-output applications such as batteries for automobiles.
Implementation Method 1
carbon nanotubes do not stably disperse in the dispersion medium, and an aggregation phenomenon occurs due to the strong van der Waals attraction between the carbon nanotubes
Implementation Method 2
the resistance in the electrode can be lowered due to excellent conductivity
Data Source
AI summary
The present invention provides a conductive material dispersed liquid including a conductive material which includes bundle-type carbon nanotubes; a dispersant which includes a hydrogenated nitrile-based rubber; and a dispersion medium, where a complex modulus (|G*| @ 1 Hz) is in a range of 20 to 500 Pa when measured by a rheometer at a frequency of 1 Hz, and a secondary battery manufactured using the same. The conductive material dispersed liquid has a controlled complex modulus to exhibit excellent dispersibility and powder resistance characteristics, and as a result, can greatly improve the output characteristics of batteries.