ZnCl₂ “Water‐in‐Salt” Electrolyte Transforms the Performance of Vanadium Oxide as a Zn Battery Cathode

Abstract

Zn batteries potentially offer the highest energy density among aqueous batteries that are inherently safe, inexpensive, and sustainable. However, most cathode materials in Zn batteries suffer from capacity fading, particularly at a low current rate. Herein, it is shown that the ZnCl 2 "water-in-salt" electrolyte (WiSE) addresses this capacity fading problem to a large extent by facilitating unprecedented performance of a Zn battery cathode of Ca 0.20 V 2 O 5 •0.80H 2 O. Upon increasing the concentration of aqueous ZnCl 2 electrolytes from 1 m to 30 m, the capacity of Ca 0.20 V 2 O 5 •0.80H 2 O rises from 296 mAh g −1 to 496 mAh g −1 ; its absolute working potential increases by 0.4 V, and most importantly, at a low current rate of 50 mA g −1 , that is, C/10; its capacity retention increases from 8.4% to 51.1% over 100 cycles. Ex situ characterization results point to the formation of a new ready-to-dissolve phase on the electrode in the dilute electrolyte. The results demonstrate that the Zn-based WiSE may provide the underpinning platform for the applications of Zn batteries for stationary grid-level storage.

New Insight on Open‐Structured Sodium Vanadium Oxide as High‐Capacity and Long Life Cathode for Zn–Ion Storage: Structure, Electrochemistry, and First‐Principles Calculation

“…[52][53][54][55] Another strategy is to use water-in-salt electrolyte, which was shown to improve capacity retention in ZIBs. [56] Therefore, it is anticipated to improve Zn 2+ ion transfer and long-term cyclability in Zn cells.…”

A Na3V2(PO4)2O1.6F1.4 Cathode of Zn‐Ion Battery Enabled by a Water‐in‐Bisalt Electrolyte

“…For the capacity fading during the initial several cycles in Figure 3c, it should be ascribed to the formation of some side products such as Zn 5 (OH) 8 Cl 2 ·H 2 O, which diminishes in the subsequent cycles, as shown in Figure 3c,e. [ 28,31 ]…”

“…Interestingly, as the discharge cutoff potential is lower than the OCV, we postulate that from sample 6 to sample 7, where the SOC is identical to sample 2, a minor event of proton insertion has taken place. [ 28 ]…”

Interlayer Doping in Layered Vanadium Oxides for Low‐cost Energy Storage: Sodium‐ion Batteries and Aqueous Zinc‐ion Batteries

“…The small amount of dissolved strong oxidizing ions would pass through the separator and oxidize the metal anode, which will lead to serious internal friction (self‐discharging) and battery failure. Thus, until now such issue has been preliminary addressed by surface coating, [29] electrolyte modification [30] and the most important interlayer doping defect, in which the pre‐intercalated species could buffer the oxidation of transition metal cations and firmly bond with the adjacent [VO x ] plates to prevent further reduction and dissolution.…”