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.