Design of a P-O-M (M = Mn, Zn) d-pπ Backbonding Electrolyte Additive for 40 Ah Electrolytic Zn-MnO₂ Batteries

An electrolytic Zn-MnO₂ battery is highly valued due to its cost-effectiveness, environmental friendliness, and abundant resource availability. However, the battery's performance is hindered by the slow kinetics at the poorly conductive MnO₂ cathode and hydrogen evolution at the Zn anode. Here, a strategy of P-O-M (M = Mn, Zn) d-pπ backbonding design is proposed for phosphorus-oxygen electrolyte additives, which can be realized by tuning the atomic dipole moment-corrected Hirshfeld (ADCH) population charge of the P/O atom. The reversibility of d-pπ backbonding not only leads to the fast kinetics of Mn²⁺/Zn²⁺ at electrodes during both charge and discharge processes to suppress the competitive hydrogen evolution reaction but also enhances the electronic conductivity at the electrode-electrolyte interfaces to sustain the high areal capacity of batteries. Hydroxymethyl dimethyl phosphite (HPD) with d-pπ backbonding is a preferred additive with a suitable ADCH charge. The assembled electrolytic Zn-MnO₂ (HPD) battery exhibits a high discharge capacity of 14.05 mAh cm^-2 at an areal capacity of 15 mAh cm^-2 and superior cycling stability over 1500 cycles. The Zn-MnO₂ (HPD) soft-pack battery exhibits a discharge capacity of over 1.60 Ah at a discharge rate of 0.5 C and maintains a Coulombic efficiency of ∼80% over 100 cycles. Furthermore, the assembled 50 V 40 Ah commercial Zn-MnO₂ (HPD) battery can drive an electric vehicle for 10 km. The ADCH charge regulation provides a feasible and effective method for developing high-performance aqueous batteries by achieving d-pπ backbonding.