Suppressing proton-induced HER and cathode fading by an aprotic hybrid electrolyte for long-cycle stability of aqueous Na||Zn hybrid batteries

Aqueous zinc metal batteries with unique advantages of intrinsic safety and low cost are considered as one of the most promising next-generation energy-storage technologies. However, their lifespan is significantly constrained by the electrolyte, specifically due to limitations caused by proton-induced HER and dendritic growth at the anode side and dissolution phenomena at the cathode. Unlike most studies on the protic electrolyte systems, herein, a new aprotic hybrid electrolyte of Na/Zn tetrafluoroborate-trimethyl phosphate with ultralow proton activity tuned by reconstruction of hydrogen bonding network and ultrahigh interfacial stability endowed by simultaneous formation of SEI and CEI were designed for the first time. Attributed to the synergistic effect of proton activity attenuation and ZnF 2 -Zn 3 (PO 4 ) 2 SEI formation, HER-trigged corrosion current was decreased by 96.52%, which leads to an exceptionally high coulombic efficiency up to 99.63%, and operational lifespan exceeding 2000 hours at 1 mA cm − 2 / 1 mAh cm − 2 for Zn||Cu asymmetric cell and Zn||Zn symmetric cell, respectively. Furthermore, the suppression of excess hydrated proton co-insertion reaction and construction of inorganic-organic CEI enabled the PBAs||Zn full cell a prolonged cycling life of 6000 cycles with an ultralow decay rate of 0.004% per cycle. The special electrolyte utilizing cheap tetrafluoroborate salts in conjunction with cost-effective PBA cathode and Zn anode provides a new choice for low-cost, high-safety, non-toxic batteries for practical applications.