Aging-Responsive Phase Transition of VOOH to V₁₀O₂₄·nH₂O vs Zn²⁺ Storage Performance as a Rechargeable Aqueous Zn-Ion Battery Cathode

Abstract

Vanadium oxyhydroxide has been recently investigated as a starting material to synthesize different phases of vanadium oxides by electrochemical or thermal conversion and has been used as an aqueous zinc-ion battery (AZIB) cathode. However, the low-valent vanadium oxides have poor phase stability under ambient conditions. So far, there is no study on understanding the phase evolution of such low-valent vanadium oxides and their effect on the electrochemical performance toward hosting the Zn2+ ions. The primary goal of the work is to develop a high-performance AZIB cathode, and the highlight of the current work is the insight into the auto-oxidation-induced phase transition of VOOH to V10O24·nH2O under ambient conditions and Zn2+ intercalation behavior thereon as an aqueous zinc-ion battery cathode. Herein, we demonstrate that hydrothermally synthesized VOOH undergoes a phase transition to V10O24·nH2O during both the electrochemical cycling and aerial aging over 38–45 days. However, continued aging till 150 days at room temperature in an open atmosphere exhibited an increased interlayer water content in the V10O24·nH2O, which was associated with a morphological change with different surface area/porosity characteristics and notably reduced charge transfer/diffusion resistance as an aqueous zinc-ion battery cathode. Although the fresh VOOH cathode had impressive specific capacity at rate performance, (326 mAh/g capacity at 0.1 A/g current and 104 mAh/g capacity at 4 A/g current) the cathode suffered from a continuous capacity decay. Interestingly, the aged VOOH electrodes showed gradually decreasing specific capacity with aging at low current and however followed the reverse order at high current. At a comparable specific power of ∼64–66 W/kg, the fresh VOOH and aged VOOH after 60, 120, and 150 days of aging showed the respective energy densities of 208.3, 281.2, 269.2, and 240.6 Wh/kg. Among all the VOOH materials, the 150 day-aged VOOH cathode exhibited the highest energy density at a power density beyond 1000 W/kg. Thanks to the improved kinetics, the 150 day-aged VOOH cathode delivered a considerable energy density of 39.7 Wh/kg with a high specific power of 4466 W/kg. Also, it showed excellent cycling performance with only 0.002% capacity loss per cycle over 20 300 cycles at 10 A/g.

Operando chemical strain analysis of CNT/VOOH during zinc insertion in Zn-ion batteries

“…3(e) illustrates that the rate performance of CNT/VOOH is superior to that of most vanadium-based materials reported in the literature. 16,[30][31][32][33][34][35][36][37][38] The excellent rate performance of CNT/VOOH composite cathode may stem from the enhanced Zn 2+ diffusion kinetics by the introduction of CNTs, as evidenced by the CV (Fig. S10, ESI †) and EIS (Fig.…”

Anchoring Polar Organic Molecules in Defective Ammonium Vanadate for High‐Performance Flexible Aqueous Zinc‐Ion Battery

“…The assembled device is capable of delivering an ultrahigh energy density of 436 Wh kg −1 at a power density of 400 W kg −1 , exceeding most previously reported aqueous ZIBs. [44,67,[70][71][72][73][74][75][76] The gravimetric energy density remains 180 Wh kg −1 at an ultrahigh power density of 4000 W kg −1 , signifying that our FARZIBs can simultaneously demonstrate high energy and power densities. To test the application of FARZIB in flexibility, we repeatedly bend FARZIBs, and measure its capacity retention at different bending angles.…”

High-performance solid-state zinc-ion batteries enabled by flexible and highly Zn2+ conductive solid-polymer electrolyte

“…The V 2p 3/2 peak of the pristine electrode can be deconvoluted into two binding energy peaks located at 516.23 and 517.78 eV, corresponding to the characteristic binding energy of V 4+ and V 5+ , respectively. 67 Aer full discharge, the peak intensity of V 4+ increased due to the intercalation of Zn 2+ (while V 5+ is reduced to V 4+ during the intercalation process). Aer complete charge, however, V 5+ again becomes the leading species, analogous to the pristine electrode peak intensity.…”