Water in Rechargeable Multivalent‐Ion Batteries: An Electrochemical Pandora's Box

Abstract

Multivalent‐ion batteries built on water‐based electrolytes represent energy storage at suitable price points, competitive performance, and enhanced safety. However, to comply with modern energy‐density requirements, the battery must be reversible within an operating voltage window greater than 1.23 V or the electrochemical stability limits of free water. Taking advantage of its powerful solvation and catalytic activities, adding water to electrolyte preparations can unlock a wider gamut of liquid mixtures compared with strictly nonaqueous systems. However, a point‐by‐point sweep of all potential formulations is arduous and ineffective without some form of systematic rationalization. The present Review consolidates recent progress, pitfalls, limits, and insights critical to expediting aqueous electrolyte designs to boost multivalent‐ion battery outputs.

Rechargeable aqueous electrolyte batteries: from univalent to multivalent cation chemistry

“…More insights into the mechanisms involved were recently obtained combining especially FTIR, 1 H, 7 Li and 19 F NMR and electrochemical experiments [76]. Indeed, these results clearly evidence that water reduction to form H2 does indeed take place in these systems ( Fig.…”

“…Metal/air and redox flow concepts will not be discussed either. Different from the already existing reviews on aqueous electrolyte batteries [3][4][5][6][7][8][9][10][11], hereby, we keep the scope to univalent and multivalent cation chemistries namely Li/Na-ion and Zn-ion technologies providing in-depth description of their reaction mechanisms by probing different characterization tools as well as covering common technological challenging issues and perspectives to solve them.…”

Recent Progress in “Water-in-Salt” Electrolytes Toward Non-lithium Based Rechargeable Batteries

“…It is well-known that it is an effective strategy to increase the energy density of batteries by raising the operating voltage (Xia et al, 2017 ; Manalastas et al, 2018 ). The voltage, according to the following Nernst equation, is highly dependent upon the half-cell potentials of both positive and negative electrodes.…”

Electrolytes for Dual‐Carbon Batteries

“…The use of an aqueous solution instead of organic liquids as an electrolyte solvent for DCBs would be safer and more environmentally benign. However, the narrow electrochemical stability window of aqueous electrolytes (<1.5 V) restricts their application in DCBs ,. Fortunately, the aqueous electrolytes with expanded electrochemical windows have been well established through increasing the salt concentration; and a state‐of‐the‐art aqueous electrolyte can withstand a voltage of 5.1 V vs. Li/Li + .…”

“…However, the narrow electrochemical stability window of aqueous electrolytes (< 1.5 V) restricts their application in DCBs. [124,[148][149][150] Fortunately, the aqueous electrolytes with expanded electrochemical windows have been well established through increasing the salt concentration; and a state-of-the-art aqueous electrolyte can withstand a voltage of 5.1 V vs. Li/ Li + . [151][152][153] Recently, Kondo et al reported a highly concentrated aqueous solution, 21 M NaFSI/H 2 O (salt-to-solvent MR = 1 : 3), in which the graphite cathode can be charged to 1.7 V vs. Ag/ AgCl (corresponding to 4.6 V vs. Na/Na + ) and showed a discharge capacity of 20 mAh g À 1 at 10 mA g À 1 .…”