Revealing Interstitial Diffusion and Vacancy Diffusion Kinetics of Battery-like Electrodes for High-Performance Pseudocapacitors

Battery-type materials have been identified as highlypromisingelectrode materials for supercapacitors due to their high theoreticalcapacitance. However, their substantially lower practical capacitanceis due to their poor electrode kinetics, which severely restrict theusage of redox-active regions on the electrode surface. To addressthis issue, the oxygen-vacancy-abundant Co-MoO3-x microsphere structure is used as a representativeexample to explore the interstitial diffusion and vacancy diffusionkinetics by adjusting the internal crystal structure, ultimately achievingan accelerated H+ ion transport rate. First-principlessimulations show that the defect structure in Co-MoO3-x , which originates from Co 3d orbitals and is generatedclose to the Fermi level, can modulate the electronic states. Theprepared asymmetric supercapacitor device using Co-MoO3-x exhibits a very high specific capacitance of 167.7C/g at 1 A/g, a high energy density of 30.2 Wh/kg at a power densityof 865 W/kg, and an excellent capacitance retention of 82.1% after5000 cycles in H2SO4 electrolyte. This researchdemonstrates the potential for internal crystal structure adjustmentto enhance the performance of electrode materials, especially battery-likeelectrode materials, for high-performance supercapacitors.