Coupling abundant active sites and Ultra-short ion diffusion path: R-VO 2 /carbon nanotubes composite microspheres boosted high performance aqueous ammonium-ion batteries

Abstract

Ammonium (NH4+) ions as charge carriers have exposed tremendous potentials in aqueous batteries because of the rich resources, ultrafast reaction kinetics, and negligible dendrite risks. However, the choices for cathode materials have encountered relatively low capacities in aqueous ammonium ions batteries (AAIBs). Herein, the double tunnel NH4+ ions insertion behaviors with hydrogen bond building-breaking in rutile-phase VO2 (R-VO2) microspheres were revealed for the first time and the capacity contribution forms were confirmed to be dominated by surface-control according to kinetic analysis and density functional theory (DFT) calculations. Those commensal composite microspheres with R-VO2 and carbon nanotubes (R-VO2/CNTs) were acquired to comprehensively promote the capacity, rate performance, and cycling stability for R-VO2 microspheres. In addition, R-VO2/CNTs composite microspheres exhibited the distinguished capacity (950 mAh g-1) within -1.3-0.8 V under 0.05 A g-1, which was maintained at 170 mAh g-1 under 5 A g-1, and achieved an eminent capacity retention of 113% at 5000th cycle and 0-0.4 V. To explore the practical application, a full cell was constructed by coupling R-VO2/CNTs composite microspheres cathode with a urea-perylene diimide polymer (UP) anode. An excellent capacity (130 mAh g-1) with imperceptible capacity decay following 2500 cycles at 1 A g-1 was achieved within the 0-0.9 V pragmatic voltage range. In brief, R-VO2/CNTs composite microspheres have been demonstrated the potential application for sustainable energy storage in AAIBs.