Rational construction of 3D hierarchical yolk–shell MnMoO4 micro/nanospheres for electrochemical energy storage

Abstract

Transition metal oxides are promising materials for electrochemical energy storage, but they still have the problem of volume change during electrochemical processes. Through the reasonable design of the microstructure of materials, the stress caused by electrode materials during the electron transmission process can be alleviated. This study successfully synthesized MnMoO₄ with a yolk–shell structure using a novel self-templating method. A systematic investigation of the precursor metal ratio (Mn : Mo) and annealing temperature revealed their critical influence on the formation of the yolk–shell structure and the resulting electrochemical performance. When used as a supercapacitor electrode material, MMA-500 delivers a high specific capacitance of 361 F g⁻¹ at a current density of 0.5 A g⁻¹. Additionally, the assembled MMA-500//AC asymmetric supercapacitor showed outstanding cycling stability, maintaining 81.14% capacitance retention after 9000 cycles. This performance surpasses that of most reported MnMoO₄-based cathode materials. Our findings provide robust experimental evidence and valuable insights into optimizing the electrochemical performance of yolk–shell structured binary transition metal oxides for energy storage applications.