Defect Engineered Ternary Spinel: An Efficient Cathode for an Aqueous Rechargeable Zinc-Ion Battery of Long-Term Cyclability

Abstract

The rational defect engineering of Mn-based spinel cathode materials by metal-ion doping and vacancy creation fosters reversible intercalation/deintercalation of charge carriers and boosts the charge storage performance of an aqueous rechargeable zinc-ion battery (ZIB). Herein, we demonstrate the Zn²⁺ ion storage performance of a defect-engineered ternary spinel cathode based on Zn, Ni, and Mn. The defect engineering of ZnMn₂O₄ is achieved by Ni²⁺ doping and creating a cation (Mn³⁺ and Zn²⁺) deficiency. The engineered cathode material has cubic spinel structure in contrast to the defect-free ZnMn₂O₄. The DFT studies show that the defect engineering modifies the electronic structure and improves the electronic conductivity. An aqueous rechargeable ZIB is fabricated by using the spinel cathode, and its performance is evaluated in terms of charge–discharge cycling stability, specific capacity, and so on. The ternary spinel-based ZIB has a very long charge–discharge cycling stability with a specific capacity as high as 265 mAh g^–1 (at 100 mA g^–1). A 2-fold enhancement in the specific capacity is observed after 5000 cycles. Ni doping affords ultralong cycling stability. The self-discharge studies for a year show that the device retains 63% of the initial performance.