Eutectic Electrolyte with Unique Solvation Structure for High‐Performance Zinc‐Ion Batteries

Abstract

Zinc-ion batteries (ZIB) present great potential in energy storage due to low cost and high safety. However, the poor stability, dendrite growth, and narrow electrochemical window limit their practical application. Herein, we develop a new eutectic electrolyte consisting of ethylene glycol (EG) and ZnCl 2 for dendrite-free and long-lifespan ZIBs. The EG molecules participate in the Zn 2 + solvation via coordination and hydrogen-bond interactions. Optimizing the ZnCl 2 /EG molar ratio (1 : 4) can strengthen intermolecular interactions to form [ZnCl(EG)] + and [ZnCl(EG) 2 ] + cations. The dissociation-reduction of these complex cations enables the formation of a Cl-rich organic-inorganic hybrid solid electrolyte interphase film on a Zn anode, realizing highly reversible Zn plating/stripping with long-term stability of � 3200 h. Furthermore, the polyaniline j j Zn cell manifests decent cycling performance with � 78 % capacity retention after 10 000 cycles, and the assembled pouch cell demonstrates high safety and stable capacity. This work opens an avenue for developing eutectic electrolytes for high-safety and practical ZIBs.

A hydrated deep eutectic electrolyte with finely-tuned solvation chemistry for high-performance zinc-ion batteries

“…4e). 25,28,30,31,34,35,[39][40][41][42][43][44][45] To explore the feasibility of HDES electrolyte for practical use, Zn-NVO full cells were assembled. As shown in Fig.…”

“…It is should be noted that, in addition to good cycling stability, the capacities (À436 mA h g À1 at 0.5 A g À1 ) of full cells in the HDES electrolyte also exceed those of most reported eutectic solvents due to the excellent Zn 2+ transfer kinetics from the relatively high ionic conductivity. 25,28,31,34,35,39,40,42,43,45 Multiple ex situ and in situ characterizations were carried out to study the Zn 2+ storage mechanism behind the electrochemical performance. The X-ray photoelectron spectroscopy (XPS) spectra present changes in the valence state of V and intercalation/deintercalation of Zn 2+ during charge/discharge processes in HDES electrolyte.…”

“…24 Different from AEs ([Zn(H 2 O) 6 ] 2+ ), Zn 2+ ions are solvated by hydrogen bond donors, thereby effectively eliminating active water-induced side reactions. 25,26 However, DESs generally exhibit high viscosity and low ionic conductivity, stemming from the insufficient solvation and ion clustering, which result in inferior Zn 2+ kinetics. 27 The inferior Zn 2+ kinetics not only leads to sluggish Zn plating/stripping on the anode, but also severely limits the performance of cathode materials.…”

Electrolytes in Organic Batteries

“…This effectively suppressed the continuous decomposition of electrolytes on the surface of the graphite anode and resulted in a high Coulombic efficiency of 99.6% (Figure 5e). Very recently, Geng et al 125 developed a new electrolyte composed of EG and zinc chloride (ZnCl 2 ), which realized dendrite-free Zn anode and long cycle life of Zn-PANI battery. Via the hydrogen-bond interactions between EG molecules and ZnCl 2 , EG molecules participate in the Zn 2+ solvation and form [ZnCl(EG)] + and [ZnCl(EG) 2 ] + complex cations, leading to the formation of a Clrich organic−inorganic SEI film on the surface of Zn anode, thus realizing reversible and uniform Zn plating/stripping (Figure 5f).…”

“…(f) Schematic illustration of Zn plating/stripping in ZnCl 2 -EG electrolyte. Reproduced with permission from ref . Copyright 2022 Wiley-VCH.…”