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

Batteries usually deliver mass loading-dependent electrochemical performance. Taking the selenium cathode as an example, the Se reaction kinetics, utilization, and cycling lifespan seriously deteriorate with increased Se mass loading. Here, an electrocatalytic Se reduction/oxidation reaction strategy to realize high-Se-loading Zn||Se batteries with fast kinetics and high Se utilization is proposed. Specifically, the synergetic effects of Cu and Co transition-metal species inside the channel structure of the host can effectively immobilize and catalytically convert Se-n during cycling, which thus facilitates Se utilization and 6-electron (Se4+ <-> Se2-) conversion kinetics. In particular, the Cu[Co(CN)(6)] host exhibits a remarkably low energy barrier (1.63 kJ mol(-1)) and low Tafel slope (95.23 mV dec(-1)) for the Se reduction, and the highest current response 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), an excellent 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 (approximate to 1350 mAh) Zn||Se pouch-type battery with high Se loading (approximate to 12.3 mg((Se)) cm(-2)) shows a high Se utilization of 83.3% and outstanding cyclic stability with 89.4% initial capacity retained after 400 cycles at exceeding 98% Coulombic efficiency.