Electrocatalytic Selenium Redox Reaction for High-Mass-Loading Zinc-Selenium Batteries with Improved Kinetics and Selenium Utilization

摘要

Batteries usually deliver mass loading-dependent electrochemicalperformance. Taking the selenium cathode as an example, the Sereaction kinetics, utilization, and cycling lifespan seriously deterioratewith increased Se mass loading. Here, an electrocatalytic Se reduction/oxidation reaction strategy to realize high-Se-loading Zn‖Se batterieswith fast kinetics and high Se utilization is proposed. Specifically, thesynergetic effects of Cu and Co transition-metal species inside the channelstructure of the host can effectively immobilize and catalytically convertSe_n during cycling, which thus facilitates Se utilization and 6-electron(Se~(4+) ? Se~(2-)) conversion kinetics. In particular, the Cu[Co(CN)_6] hostexhibits a remarkably low energy barrier (1.63 kJ mol~(-1)) and low Tafelslope (95.23 mV dec~(-1)) for the Se reduction, and the highest currentresponse for Se oxidation. Accordingly, the Zn battery employing a Se-in-Cu[Co(CN)_6] cathode delivers a capacity of 664.7 mAh g~(-1) at 0.2 A g~(-1), anexcellent rate capability with 430.6 mAh g-1 achieved even at 10 A g~(-1),and long-cyclic life over 6000 cycles with 90.6% capacity retention.Furthermore, an A-h-level (≈1350 mAh) Zn‖Se pouch-type battery withhigh Se loading (≈12.3 mg_((Se)) cm~(-2)) shows a high Se utilization of 83.3%and outstanding cyclic stability with 89.4% initial capacity retained after400 cycles at exceeding 98% Coulombic efficiency.