Hydrophobic Organic‐Electrolyte‐Protected Zinc Anodes for Aqueous Zinc Batteries

Abstract

Aqueous Zn batteries are promising energy-storage devices.H owever,t heir lifespan is limited by irreversible Zn anodes owingtowater decomposition and Zn dendrite growth. Here,w es eparate aqueous electrolyte from Zn anode by coating at hin MOF layer on anode and filling the pores of MOF with hydrophobic Zn(TFSI) 2-tris(2,2,2-trifluoroethyl)phosphate (TFEP) organic electrolyte that is immiscible with aqueous Zn(TFSI) 2-H 2 Obulk electrolyte.The MOF encapsulated Zn(TFSI) 2-TFEP forms aZnF 2-Zn 3 (PO 4) 2 solid electrolyte interphase (SEI) preventing Zn dendrite and water decomposition. The Zn(TFSI) 2-TFEP@MOF electrolyte protected Zn anode enables aZ n jjTi cell to achieveahigh average Coulombic efficiency of 99.1 %f or 350 cycles.T he highly reversible Zn anode brings ah igh energy density of 210 Wh kg À1 (of cathode and anode mass) and al ow capacity decayr ate of 0.0047 %p er cycle over 600 cycles in aZ njj MnO 2 full cell with al ow capacity ratio of Zn:MnO 2 at 2:1.

Electrochemical Zinc Ion Capacitors: Fundamentals, Materials, and Systems

“…Wang et al proposed a hydrophobic coating layer to suppress parasitic reactions by reducing the water activity on the zinc anode. [205] The hydrophobic coating layer is composed of a MOF confined hydrophobic electrolyte layer. Moreover, a Zn(TFSI) 2 -tris(2,2,2-trifluoroethyl)phosphate (TFEP) organic electrolyte was filled into the pores of MOF to separate zinc anode from the electrolyte.…”

“…On the other hand, HER can be suppressed by reducing the water activity on the surface of the zinc anode. [205] By optimizing electrolyte components or designing an artificial interlayer, aqueous zinc electrolytes show quite different HER behaviors. In particular, the WIS electrolytes and the artificial interlayer on the zinc anode can slow down the HER rate by reducing water activity.…”

“…In particular, the WIS electrolytes and the artificial interlayer on the zinc anode can slow down the HER rate by reducing water activity. [205] Also, HER may be suppressed by adding metals with high HER overpotentials, such as In, [221] Bi, [222] and Pb. [198] Passivation layers on zinc anodes, like polyaniline, [223] TiO 2 , [196] HfO 2 , [224] and ZnO, [225] could also suppress HER.…”

“…However, chlorine evolution reaction may occur in the ZnCl 2 WIS electrolyte and be responsible for the unstable cycling performance. [162] Hydrophobic artificial layers coating on the zinc anodes [205] can suppress water decomposition by reducing the water activity around zinc anodes.…”

Unveiling the Synergistic Effect of Ferroelectric Polarization and Domain Configuration for Reversible Zinc Metal Anodes

“…[15,16] Consequently, Zn dendrites continuously grow and eventually penetrate the separators, causing internal short circuits and the battery failure. [17] Extensive efforts have been dedicated to tackling the issue of Zn dendrites, including interfacial engineering by building artificial protective layers, [18][19][20][21][22] optimizing electrolyte components, [23][24][25][26][27] designing 3D host structures, [28][29][30] modifying the separators, [31][32][33] and controlling the preferential orientation of Zn deposition. [5,14,[34][35][36][37] Among all these strategies, the construction of an advanced protective layer on Zn anode surface is a highly scalable and low-cost approach to stabilize Zn metal anode and improve the reversibility of Zn plating/stripping.…”