(645h) Solid Dispersion Flow Battery Material Synthesis and Battery Characterization

Flow batteries are energy storage systems that store reversible electrochemical energy within active material species contained within the liquid electrolyte. Conventional flow battery systems are limited in their energy density by the solubility of the active materials within the electrolyte because above the solubility limit electrochemically inactive solid particles will precipitate. In addition, most conventional flow battery systems involve aqueous electrolytes, which limit the operating voltage due to the electrochemical stability window of water. Recently, researchers have explored using solid particles as the active material in flow batteries because starting with solid electroactive materials bypasses solubility limitations and results in substantial increases in the energy density of the flow battery system. In addition, often these semisolid flow batteries are comprised of lithium-ion battery materials dispersed in organic electrolytes. Using organic electrolytes and lithium-ion battery electrode materials increases the operating voltage of the battery system and further improves the energy density of the flow battery. One of the major challenges within this system, however, is that carbon additives are used to form interconnected particle structures within the fluid. This structured solvent results in high electrical connectivity and thus high power density in the semisolid flow batteries, however, the tradeoff is extremely high viscosities in the system making the electroactive fluids difficult and energy-intensive to pump.

Within our research group, we have developed a flow battery that consists of a solid dispersion of particles in the electrolyte. This solid dispersion flow battery consists of solid particles, and thus has the improved energy density that comes with bypassing the solubility limitations of conventional flow batteries. However, in contrast to many other semisolid flow batteries reported in the literature, by avoiding the use of carbon additives the viscosity is kept much lower in these fluids. The tradeoff of having a lower viscosity is that the power density is lower because electrochemical reactions proceed via collisions with the current collector, rather than throughout and interconnected carbon structure.

In this talk, recent efforts in our group to synthesize and characterize materials for the solid dispersion flow battery will be described. In particular, we have developed a scalable templated synthesis of active material nanoparticles of lithium-ion battery cathode materials that are electrochemically active and small enough to remain stably dispersed within the flow battery electrolytes. Recent efforts to characterize and understand the electrorheological coupling within this system, and the limits of the power capability within the flow battery architecture, will also be discussed.