Electrochemically activated Mn3O4 nanoparticles as higher performing electrode than MnO2 for Al-ion batteries – An insight into the crystallographic changes caused by Al3+ intercalation

Abstract

Aluminium is the third most abundant element in the earth's crust, with a high theoretical capacity and volumetric energy density, making aluminium ion batteries (AIBs) a preferred technology for future large-scale energy storage applications amongst all of the proposed nonlithium-based battery systems. However, the practical realization of AIBs has so far been impeded by the frequent collapse of the host framework of the cathode materials. Here, nanostructure of Mn3O4 is being reported as a cathode material for aqueous AIBs to enhance the specific capacity, rate capability, and cycling stability. The various salts of aluminium were used as an electrolyte to verify how the composition of the electrolyte affected the intercalation and deintercalation of Al3+ in Mn3O4 electrode. In AlCl3 aqueous electrolyte, the Mn3O4 cathode exhibits the highest initial discharge capacity of ∼ 271 mAh g−1, at a high current density of 0.5 A g−1, with an excellent capacity retention of 98 % after 1,000 cycles. The outstanding cycling stability of the synthesized Mn3O4 nanoparticles is established by considering the phase transition from Mn3O4 spinel to MnO2 layered structure. The intercalation/deintercalation of Al3+ into/from the Mn3O4 crystal structure is also being confirmed by analysing the electrochemical performance in NaCl, KCl, and H2SO4 electrolyte.