Mechanistic Investigation of a Hybrid Zn/V₂O₅ Rechargeable Battery with a Binary Li⁺/Zn²⁺ Aqueous Electrolyte

Abstract

Abstract Low‐cost, easily processable, and environmentally friendly rechargeable aqueous zinc batteries have great potential for large‐scale energy storage, which justifies their receiving extensive attention in recent years. An original concept based on the use of a binary Li + /Zn 2+ aqueous electrolyte is described herein for the case of the Zn/V 2 O 5 system. In this hybrid, the positive side involves mainly the Li + insertion/deinsertion reaction of V 2 O 5 , whereas the negative electrode operates according to zinc dissolution–deposition cycles. The Zn//3 mol L −1 Li 2 SO 4 –4 mol L −1 ZnSO 4/ //V 2 O 5 cell worked in the narrow voltage range of 1.6–0.8 V with capacities of approximately 136–125 mA h g −1 at rates of C/20–C/5, respectively. At 1 C, the capacity of 80 mA h g −1 was outstandingly stable for more than 300 cycles with a capacity retention of 100 %. A detailed structural study by XRD and Raman spectroscopy allowed the peculiar response of the V 2 O 5 layered host lattice on discharge–charge and cycling to be unraveled. Strong similarities with the well‐known structural changes reported in nonaqueous lithiated electrolytes were highlighted, although the emergence of the usual distorted δ‐LiV 2 O 5 phase was not detected on discharge to 0.8 V. The pristine host structure was restored and maintained during cycling with mitigated structural changes leading to high capacity retention. The present electrochemical and structural findings reveal a reaction mechanism mainly based on Li + intercalation, but co‐intercalation of a few Zn 2+ ions between the oxide layers cannot be completely dismissed. The presence of zinc cations between the oxide layers is thought to relieve the structural stress induced in V 2 O 5 under operation, and this resulted in a limited volume expansion of 4 %. This fundamental investigation of a reaction mechanism operating in an environmentally friendly aqueous medium has not been reported before.