Carbon nanofibers enabling manganese oxide cathode superior low temperature performance for aqueous zinc-ion batteries

Mn-based aqueous zinc-ion batteries are potential candidates for energy storage owing to the low cost, high efficiency, and safety. Nevertheless, the Jahn–Teller effect induces Mn2+ dissolution and irreversible phase changes, seriously deteriorating the cycling life. Herein, the facile construction and low temperature performance of the core–shell composites of polyimide derived nitrogen-doped carbon nanofibers and δ-MnO2 (δ-MnO2-CNFs) are reported, where ultrafine MnO2 arrays are tightly anchored on carbon nanofibers. The hybrid effect of nitrogen doping, porous structure, and abundant active sites effectively inhibits the structural damage of MnO2. The as-prepared δ-MnO2-CNFs cathode achieves a high specific capacity of 232.9 mAh g−1 and energy density of 450.7 Wh kg−1 at a current density of 100 mA g−1, and could be stably cycled for 500 cycles at a high current rate of 1 A g−1. The density functional theory calculation results show that the synergistic effect in δ-MnO2-CNFs is more conducive to the transfer of zinc ions. Furthermore, a salty ice electrolyte Zn(ClO4)2 has been used for the Zn//δ-MnO2-CNFs cell, which can work at a low temperature of −20 °C, and a stable low temperature (0 °C) cycle of 500 cycles is achieved at 1 A g−1.