In-situ synthesis of graphdiyne on Mn3O4 nanoparticles for efficient Zn ions diffusion and storage

Recently, aqueous zinc-ion batteries (ZIBs) have attracted widespread attention owing to their high energy density, low cost, and high security. However, the traditional manganese oxide electrode materials are facing the issues of rapid capacity decay and poor cyclic stability caused by structure collapse. Herein, we report an in-situ chemical synthesis method that enables uniform Mn3O4 nanoparticles to be covered by graphdiyne (GDY) (Mn3O4-GDY). Synergistic advantages have been found in this as-prepared Mn3O4-GDY composite material as a result of the unique conjugated porous chemical structure of GDY and strong interaction with Mn3O4 by acetylenic bond. In the meantime, the buffer space provided by structural pores of GDY effectively sustains the volume change of Mn3O4 in the storage of Zn ions. In particular, due to the interaction with GDY, a direct interconversion of the manganese ions from Mn2+ to Mn4+ is achieved instead of the normal conversion from Mn3+ to Mn4+. By electrochemical characterization, it can be found Mn3O4-GDY can obtain a reversible capacity up to 490.3 mAh g−1 at the current density of 50 mA g−1, double times of the theoretical capacity of MnO2. Even at a current density of 600 mA g−1, the reversible capacity is maintained around 200.4 mAh g−1 after 240 cycles. The improved electrochemical performance of the cell with Mn3O4-GDY suggests that this simple synthesis method offers a new avenue for the development of efficient manganese oxide electrode materials.