A novel concept of Semi-solid, Li Redox Flow Air (O2) Battery: A breakthrough towards high energy and power batteries

Worldwide efforts are being devoted to promote an efficient use of renewable energy sources and sustainable electric transportation. High efficiency energy conversion systems like batteries, which store/deliver high energy and power densities, are under development. While Li-ion batteries (LIBs) are the best performing batteries on the market and redox flow batteries are already used for stationary plants, a drastic step forward is needed to increase energy and power performance and decrease costs. Li/O2 batteries are considered the next generation due to significantly higher energy delivery than LIBs. We demonstrate a radically new battery concept: a non-aqueous Li/O2 battery that operates with a semi-solid, flowable catholyte. The proof-of-concept is proven by a catholyte based on 2% wt. SuperP carbon dispersed in tetraethylene glycol dimethyl ether - lithium bis(trifluoromethane)sulfonimide. Oxygen redox reaction at the semi-solid catholyte is investigated by electrochemical, morphological and spectroscopic analyses. The perfomance of a semi-solid, flow Li/O2 battery prototype operating at high discharge rates (up to 4 mA cm-2) with high discharge capacity (>175 mAh cm-2), energy (>500 mWh cm-2) and power (>7 mW cm-2) is reported. The strategies to approach the challenging target of 1 kWh kg-1 and 2 kWh L-1 are also discussed.