Highly Efficient Materials Assembly Via Electrophoretic Deposition for Electrochemical Energy Conversion and Storage Devices

Abstract

and fi lms can be assembled on substrates with this versatile method. Film thickness, particle size and inter structure of EPD fi lms are controllable by adjusting the suspension/process parameters. [ 2,3 ] Energy conversion and storage devices have been developed rapidly in the past few decades, and proposed as the foundation of modern society. Novel carbon materials such as graphene and carbon nanotubes (CNTs) are investigated widely for high-effi ciency rechargeable battery and supercapacitor (SC) applications. [ 4,5 ] Traditional methods such as blade coating and slot die are employed to prepare electrodes to realize such applications. [ 6,7 ] In these methods, active materials are dissolved into a solvent to form a viscous solution, and a fi lm is obtained after coating and solvent evaporation. Nevertheless, neither thickness control nor a high fi lm assembly effi ciency can be realized via these methods. In addition, traditional methods exhibit limitation on the fabrication of nanostructured energy materials due to the aggregation of nanoparticles. On the other hand, methods for micro-batteries such as vapor deposition methods, [ 8 ] radio-frequency sputtering, [ 9 ] and pulsed laser deposition [ 10,11 ] are expensive and diffi cult to scale up. Indeed, a versatile EPD technique with cost-effectiveness, short formation time, and high scalability is promising for efficient fabrication of energy conversion and storage materials and devices. A typical EPD process is performed in two steps, including the dispersion of powder particles in a solvent to form a stable suspension and the deposition of particles on a substrate in the presence of an electric fi eld. [ 12,13 ] Preparation of a stable suspension is essential to the deposition process. The stability of suspension, adjustable with surfactants, is correlated with electrostatic repulsive and van der Waals attractive interactions. The stability of suspension/colloid is characterized by zeta potential, the value of which represents the magnitude of repulsive interaction while the sign represents the migration direction of particles. Zeta potential is mainly determined by temperature, pH, and type of surfactant. On the other hand, the migration velocity of particles in deposition depends on the applied voltage/current, particle size, zeta potential, suspension concentration, and solvent viscosity. [ 14 ] The utilization of EPD in the energy storage/conversion devices fi eld enables the direct deposition of active particles on the current collector.Featuring pronounced controllability, versatility, and scalability, electrophoretic deposition (EPD) has been proposed as an effi cient method for fi lm assembly and electrode/solid electrolyte fabrication in various energy storage/conversion devices including rechargeable batteries, supercapacitors, and fuel cells. High-quality electrodes and solid electrolytes have been prepared through EPD and exhibit advantageous performances in comparison with those realized with traditional methods. Recent advances in the appli...

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