Hydrogen-bond chemistry inhibits Jahn–Teller distortion caused by Mn 3d orbitals for long-lifespan aqueous Zn//MnO2 batteries

Abstract

Manganese dioxide (MnO₂) is a promising cathode for aqueous Zn batteries owing to its high theoretical capacity and operating voltage. However, it is still confronted with poor conductivity, structural collapse, sluggish ion kinetics, and Jahn–Teller (J–T) distortion. Herein, we propose hydrogen bond-modulated MnO₂ by introducing NH₄⁺ (NHMO) for prominent zinc-ion storage. The formation of a hydrogen bond in MnO₂ reduces its layer spacing, presenting a more stable structure. The theoretical calculation results demonstrate that the pre-intercalation of NH₄⁺ can effectively reduce the bandgap of the MnO₂, enhancing its conductivity. More importantly, the formation of the hydrogen bond can significantly decrease the variation of Mn–O bond length and the proportion of Mn 3d_z² orbitals, meaning that the hydrogen-bond chemistry can effectively suppress J–T distortion. As expected, a high capacity of 287.9 mA h g⁻¹ at 0.1 A g⁻¹ and an ultrahigh rate performance (99.4 mA h g⁻¹ at 6.0 A g⁻¹) can be achieved for the NHMO, as well as a fantastically outstanding cycling stability of 90.0% after 13 000 cycles, far exceeding previously reported Mn-based materials. The rational introduction of a hydrogen bond provides a novel strategy for the development of ultralong lifespan aqueous Zn batteries.