Recent Advances in Electrolytes for “Beyond Aqueous” Zinc‐Ion Batteries

Abstract

Designing high performance electrolyte is an efficient strategy to circumvent these problems. As one of the most important components, electrolytes provide the basic operating environment to guarantee the transmission of the Zn 2+ between the two electrodes during the charge-discharge processes, affect the Zn 2+ /Zn plating/ stripping on the anode and deciding the electrochemically stable potential windows. [12] Since the utilization of alkaline electrolytes in batteries in earlier studies, Zn|KOH|MnO 2 batteries became a hot topic. [13] However, the using of an alkaline electrolyte always leads to the growth of Zn dendrites and the corrosion of the anode, resulting in rapid capacity fading. [14][15][16] Until 1986, the replacement of corrosive alkaline electrolyte systems by neutral aqueous electrolytes greatly improved the performance and safety of ZIBs. [17] Although the aqueous electrolytes alleviated the corrosion of the Zn electrode in some extent, the problems related to the growth of dendrites and the dissolution of the cathode, especially the limited electrochemical stability window (≈1.23 V) still are the challenge in the application of ZIBs. [18][19][20] The aqueous electrolytes of ZIBs often suffer from the water splitting process, including hydrogen evolution reaction and oxygen evolution reaction. [21][22][23] Therefore, in order to overcome the problems mentioned above, "beyond aqueous" electrolytes for ZIBs have attracted extensive attention in recent years. [24][25][26] At present, the "beyond aqueous" electrolytes for ZIBs have been reported mainly include liquid organic electrolytes and solid electrolytes. Zn anode in the organic electrolytes have high thermodynamic stability, avoiding the appearance of passivation products inevitably generated in traditional aqueous solution, i.e., ZnO and Zn(OH) 4 −2. [27] Solid-state electrolytes have sufficient mechanical strength to inhibit the growth of dendrites. [28] Moreover, the "beyond aqueous" electrolytes without water fundamentally avoid the decomposition of water and the formation of side products related to water. Compared with aqueous electrolytes, the "beyond aqueous" electrolytes exhibit a wide electrochemical stability window (Figure 1) and excellent thermodynamic stability of Zn anode leading to Zn plating/ stripping high reversibility with higher Coulombic efficiencies (CEs). [29] Although significant advances have been made in improving the electrochemical performance of the "beyond aqueous" electrolytes for ZIBs, several severe issues still exist, which largely prevent the development of "beyond aqueous" ZIBs. [30][31][32][33][34][35] The main issues of "beyond aqueous" electrolytes With the growing demands for large-scale energy storage, Zn-ion batteries (ZIBs) with distinct advantages, including resource abundance, low-cost, high-safety, and acceptable energy density, are considered as potential substitutes for Li-ion batteries. Although numerous efforts are devoted to design and develop high performance cathodes and aqueous electrolyt...

Surface Transformation Enables a Dendrite‐Free Zinc‐Metal Anode in Nonaqueous Electrolyte

“…Among these strategies, electrolyte formulation plays an essential role in regulating the Zn growth behavior and reducing the parasitic reaction on Zn-metal anodes, because of its effectiveness, simple procedure and easy realization. [12] However, although some electrolytes have partly realized dendrite-free Zn-metal anodes by manipulating the solvation structure, [13] the hydrogen evolution problem seems inevitable in dilute aqueous electrolytes because of the low electrochemical potential of Zn-metal (−0.762 V versus the standard hydrogen electrode), which is far below the reduction potential of H + . Recently, concentrated electrolytes provide Significant challenges remain in developing rechargeable zinc batteries mainly because of reversibility problems on zinc-metal anodes.…”

Advanced Buffering Acidic Aqueous Electrolytes for Ultra‐Long Life Aqueous Zinc‐Ion Batteries

“…[7][8][9] Due to the lack of pH buffering effect in the mild acidic electrolytes, the local OH − concentration could vary significantly along with the release of H 2 from H 2 O, which correspondingly leads to the formation of Zn salt hydroxide compounds and passivates the Zn electrodes. [9][10][11][12] The parasitic reactions on Zn electrodes contribute to low coulombic efficiency (CE) and short cycle life of aqueous Zn batteries.…”

Covalent Organic Framework for Rechargeable Batteries: Mechanisms and Properties of Ionic Conduction

“…In a typical battery system, as shown in Figure 1b, the liquid electrolyte includes protic solvent electrolyte and aprotic solvent electrolyte, while the solid conductors can be divided into electrode material and solid-state electrolyte. [53][54][55][56][57][58][59] Besides, the ionic conduction at the interface is also an important factor affecting the battery performance, mainly including solid electrolyte interphase (SEI), cathode electrolyte interphase (CEI), and electrode/solid-state electrolyte interface. [60][61][62][63][64] In condensed materials, the ionic diffusion can be achieved by the jumps of ions with their neighbors leading to the position exchange.…”