Carbonaceous catholyte for high energy density semi-solid Li/O2flow battery

Li/O2batteries are considered the future response to the requirement of specific energy >500 Wh kg−1. The use of a carbonaceous semi-solid catholyte in flow Li/O2batteries is a valuable strategy to improve cycling performance. Indeed, it permits to: i) decouple energy and power; ii) increase cell areal capacity and energy by alleviating current collector passivation; iii) improve current rate response and decrease recharge overvoltage by the carbon percolating network. The development of slurries that match high electrochemical performance and rheological features suitable for an efficient flow in a battery is challenging. Here we report a study on the electrochemical response of different formulations of carbonaceous catholyte of flow Li/O2battery. Slurries based on different wt.% of Super-P®and Pureblack®carbons in 0.5 m of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) in tetraethylene glycol dimethyl-ether (TEGDME) have been investigated. The results are discussed in relation to the conductivity, morphology and rheological properties of the catholyte. The work demonstrates that up to hundreds of cycles with areal capacity of 4 mAh cm−2and currents higher than 0.5 mA cm−2are achievable using 10 wt.% Pureblack®catholyte. These outstanding results open new paths towards the development of post-Li-ion and new redox flow batteries.