An advance in the technology for flow batteries may lead to systems for electric vehicles (EVs) that allow them to be refueled with liquid, much like conventional combustion vehicles do now. MIT researchers have developed a semi-solid flow cell which offers 10 times the performance of liquid chemical flow batteries.
Flow batteries are similar to fuel cells but they differ in that the reaction in flow batteries is much more readily reversible. Flow batteries have been used for large-scale energy storage and grid load balancing applications, but until now, they have not had the energy density to make them competitive for use with EVs.
Since the electrolytes for flow batteries are kept on-board the vehicle, rather than being consumed and exhausted like more conventional liquid fuels, the process of refueling the vehicle would also include emptying and collecting the old electrolyte for reprocessing. It would likely take longer than refueling with a combustion fuel, but could be faster than even quick-charge electrical chargers.
Because much of the electrolyte material is kept in separate storage, flow batteries are not susceptible to self-discharge that conventional batteries are. Flow batteries may also offer a better way of extending the current range limits of electric vehicles. The size and cost of a battery system could be half that of current EV battery systems.