Reduced graphene oxide thin layer induced lattice distortion in high crystalline MnO2 nanowires for high-performance sodium- and potassium-ion batteries and capacitors

The large-radius of both K- and Na-ions gives rise to a serious concern towards exploring high-performance electrode materials for potassium ion batteries (KIBs) and sodium ion batteries (SIBs), respectively. Herein, MnO2 nanowires coated with reduced graphene oxide (denoted MnO2@rGO) are demonstrated as excellent anode materials in KIBs and SIBs. The coating of rGO not only facilitates a lattice distortion in the spacing of high crystallinity MnO2 nanowires allowing the faster transfer of K- and Na-ions, but also creates an interfacial structure between rGO and MnO2. Both enhance the electronic conductivity and further protect the nanowires from degradation. As an anode for KIBs and SIBs, the MnO2@rGO nanowires deliver a stable cycling performance with capacity retention of 81.7% over 400 cycles and 75% after 500 cycles, respectively. The potassiation and depotassiation reaction mechanisms are also revealed. Furthermore, the uniqueness of our hybrid designs allows high crystallinity MnO2@rGO nanowires to be used as anodes for both K-ion capacitors (KICs) and Na-ion capacitors (SICs). Considering their easy synthesis, environmental benignity and low cost, MnO2@rGO nanowires are potential anode materials for Na- and K-ion based energy storage devices. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

MnO2 nanowires coated with reduced graphene oxide (MnO2@rGO) show excellent performance as anode materials for potassium ion batteries (KIBs) and sodium ion batteries (SIBs). The coating of rGO facilitates ion transfer and enhances electronic conductivity.