Electrolyte Concentration Regulation Boosting Zinc Storage Stability of High-Capacity K0.486V2O5 Cathode for Bendable Quasi-Solid-State Zinc Ion Batteries

Abstract

Vanadium-based cathodes have attracted great interest in aqueous zinc ion batteries (AZIBs) due to their large capacities, good rate performance and facile synthesis in large scale. However, their practical application is greatly hampered by vanadium dissolution issue in conventional dilute electrolytes. Herein, taking a new potassium vanadate K0.486V2O5 (KVO) cathode with large interlayer spacing (~ 0.95 nm) and high capacity as an example, we propose that the cycle life of vanadates can be greatly upgraded in AZIBs by regulating the concentration of ZnCl2 electrolyte, but with no need to approach “water-in-salt” threshold. With the optimized moderate concentration of 15 m ZnCl2 electrolyte, the KVO exhibits the best cycling stability with ~ 95.02% capacity retention after 1400 cycles. We further design a novel sodium carboxymethyl cellulose (CMC)-moderate concentration ZnCl2 gel electrolyte with high ionic conductivity of 10.08 mS cm−1 for the first time and assemble a quasi-solid-state AZIB. This device is bendable with remarkable energy density (268.2 Wh kg−1), excellent stability (97.35% after 2800 cycles), low self-discharge rate, and good environmental (temperature, pressure) suitability, and is capable of powering small electronics. The device also exhibits good electrochemical performance with high KVO mass loading (5 and 10 mg cm−2). Our work sheds light on the feasibility of using moderately concentrated electrolyte to address the stability issue of aqueous soluble electrode materials.

Insight into Potassium Vanadates as Visible-Light-Driven Photocatalysts: Synthesis of V(IV)-Rich Nano/Microstructures for the Photodegradation of Methylene Blue

“…According to the literature, a decrease in wavenumber is evidence of the binding of water with other atoms. 55 In case of anhydrous KV 3 O 8 (KVO-80), physisorbed water molecules are only weakly bonded to the samples’ surface, while for hydrated K 2 V 6 O 16 · n H 2 O (KVO-20), water molecules are trapped in the crystalline lattice by either interactions with potassium ion or vanadium-oxide layers. Moreover, in the KVO-20, KVO-40, and KVO-60 spectra, an additional band at 950 cm –1 can be observed.…”

Surface-Alloyed Nanoporous Zinc as Reversible and Stable Anodes for High-Performance Aqueous Zinc-Ion Battery

“…This is primarily caused by poor reversibility of metallic Zn anode because of its unique metallurgic characteristics and undesirable side reactions (e.g., hydrogen evolution, corrosion and by-product formation), which usually lead to large voltage polarization, dendrite formation and low coulombic efficiency (CE), during the Zn stripping/plating in ambient aqueous electrolytes [ 16 – 18 , 31 – 33 ]. With an aim at improving the reversibility of Zn stripping/plating, many strategies have been proposed to tackle these irreversibility issues [ 34 ], and initial strides have been made in electrolyte modulation with additives to regulate solvation/desolvation process of Zn 2+ [ 35 – 40 ] and/or electrical field distribution of Zn protuberances [ 41 – 43 ], crystallographic plane manipulation to guide epitaxial electrodeposition of Zn [ 44 – 46 ], and interface engineering of artificial solid electrolyte interphase (SEI) to inhibit side reactions [ 47 – 55 ]. Nevertheless, these bulk Zn metal-based anodes still undergo large voltage polarizations particularly at high current densities and thus inevitably trigger side reactions and dendrite formation during the long-term Zn stripping/plating, which result in significant compromise in rate capabilities and cycling stability of AR-ZMBs.…”

Proton-Dominated Reversible Aqueous Zinc Batteries with an Ultraflat Long Discharge Plateau

“…Recently, the hybrid ions storage has been investigated in zinc-based energy storage devices. , For instance, the reversible zinc-ion/proton co-insertion into layered host cathodes, such as manganese dioxide, sodium vanadate, and potassium vanadate, was demonstrated in mild AZB systems. The auxiliary insertion of protons diminishes the strong Coulombic ion–lattice interactions and further enhances the ion insertion kinetics.…”

“…11,12 Recently, the hybrid ions storage has been investigated in zinc-based energy storage devices. 13,14 For instance, the reversible zinc-ion/proton co-insertion into layered host cathodes, such as manganese dioxide, 15 sodium vanadate, 16 and potassium vanadate, 17 insertion of a high proportion of zinc ions, the host lattices gradually collapse during the charge/discharge processes, which leads to significant capacity fading. A feasible strategy is to increase the proportion of protons in charge carriers.…”