Facile synthesis of Cu-intercalated MnO2 nanoflakes cathode for enhanced energy storage in zinc-ion batteries

Background: Rechargeable aqueous zinc-ion batteries are considered sustainable energy storage systems due to low cost and inherent safety. Rational design of cathode materials for reliable energy storage receives great interest to the research field. Methods: This work reveals advanced Cu-intercalated MnO2 (CMO) cathode can be obtained through an ion exchange treatment. Ex situ XPS, TEM, and XRD analyses are used to reveal the charge storage mechanism of CMO. Significant findings: CMO with highly porous morphology boosts ion transport kinetics and shows better utilization of electrolyte Mn2+. The ion diffusion coefficient in CMO is much higher than pristine MnO2 (MO) by a factor of similar to 10 times. Moreover, CMO undergoes displacement mechanism forming metallic Cu during battery operation, leading to improved electronic conductivity. As a result, CMO exhibits promising electrochemical performance with higher capacity (236 vs. 156 mAh g(-1) at 0.5 A g(-1)), better rate performance (95 vs. 61 mAh g(-1) at 8 A g(-1)), improved electrochemical reversibility (0.26 vs 0.48 Vat 1.5 mV s(-1)), higher energy efficiency (83.7 vs. 79.0 % at 8 A g(-1)), reduced charge-transfer resistance (45 vs. 212 Omega), and enhanced energy storage (322.7 vs. 214.4 Wh kg(-1) at 0.5 A g(-1)) in comparison with the MO counterpart. (C) 2021 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.