Understanding the Design Principles of Advanced Aqueous Zinc‐Ion Battery Cathodes: From Transport Kinetics to Structural Engineering, and Future Perspectives

Abstract

have also greatly aroused the positive exploration of alternative LIB technologies in recent years. [44] In contrast to the flammable organic electrolyte in LIBs, the aqueous one exhibits lower cost, higher safety, and especially the superior ionic conductivity, which is generally two orders of magnitude higher than that of the organic system. [9,10] All those unparalleled advantages would make the aqueous battery technologies to be the promising candidates in the future. [11] Rechargeable aqueous zinc-ion batteries (AZIBs), which is mainly composed of zinc metal anode, zinc salt-based aqueous electrolyte, and Zn 2+ host cathode, hold the great promise for energy storage applications in very recent years. [12,13] Compared with nonaqueous alkali-ion batteries, the use of cheap and high ambient stable zinc metal anode and inexpensive aqueous electrolyte with superior ionic conductivity (Figure 1a) would make such type of battery to be one of the most promising commercial candidates in the future market. [14-17] To date, extensive studies have been reported for AZIBs, and relating publications have dramatically increased especially in these two years, as shown in Figure 1b. However, the insufficient energy density seems to become the bottleneck that hinder their practical applications at current status. [4,5,18] Such issue could be ascribed to the narrow operating voltage of aqueous electrolyte, insufficient electrochemical performance of cathode materials, and Zn anode. [13,19,20] Besides, the influence of other components such as separator and collector also should be considered to some extent. [20,21] Among them, the studies of widening operating voltage of electrolyte and the optimization of other components only received less attention, which still remain at the early stage. [22,23] On the contrary, more attentions were paid to the electrochemical performance tuning of electrode materials. [24-26] Besides, considering the fixed operating voltage of Zn metal anode, the modification of cathode materials seems to provide more possibilities to effectively improve the energy density of AZIBs, owing to their rich material systems. [20,26,27] Under these considerations, the rational design of advanced cathodes is expected to be a preferential task to develop. Up to now, many types of materials have been exploited as cathode candidates and applied for AZIBs, however, those Rechargeable aqueous zinc-ion batteries (AZIBs) have attracted extensive attention and are considered to be promising energy storage devices, owing to their low cost, eco-friendliness, and high security. However, insufficient energy density has become the bottleneck for practical applications, which is greatly influenced by their cathodes and makes the exploration of high-performance cathodes still a great challenge. This review underscores the recent advances in the rational design of advanced cathodes for AZIBs. The review starts with a brief summary and evaluation of cathode material systems, as well as the introduction of proposed storage mechani...

Interfacial adsorption–insertion mechanism induced by phase boundary toward better aqueous Zn‐ion battery

“…Despite the various cathode may apply, such as manganese‐based, 11–18 vanadium‐based, 19–25 cobalt‐based, 26 and organized materials, 27–32 most of the reported aqueous ZIBs system are based on the conventional Zn 2+ intercalation and the performance of the systems is therefore largely limited by the inferior reaction kinetics. The electrochemical reaction kinetics in ZIBs on the cathode side can be generally described as follows 33 : cation first releases from liquid electrolyte to the electrolyte/cathode interface, then passes through the electrolyte/cathode interface and inserts into host structure, and eventually the ions complete solid‐state diffusion process within the host framework. The first step is dominated by the electrolyte properties, 34 while the last two steps significantly rely on the material properties.…”

Eliminating Dendrites and Side Reactions via a Multifunctional ZnSe Protective Layer toward Advanced Aqueous Zn Metal Batteries

“…Figure a shows the cyclic voltammetry (CV) curves of the bare Zn||MnO 2 and Zn@ZnSe||MnO 2 full cells at 0.5 mV s −1 with a voltage range of 1.0–1.8 V. The distinct cathodic and anodic peaks stem from the reversible redox reactions between MnO 2 and MnOOH. [ 35 ] Moreover, the voltage polarization of Zn@ZnSe||MnO 2 is smaller than that of bare Zn||MnO 2 , implying improved reversibility due to the presence of the ZnSe protective layer. [ 24,36 ] This low polarization may be caused by the reduced R ct of Zn@ZnSe||MnO 2 (Figure S12, Supporting Information).…”

Supplementary Networking of Interpenetrating Polymer System (SNIPSy) Strategy to Develop Strong & High Water Content Ionic Hydrogels for Solid Electrolyte Applications

“…The Zn/SNIPSy1/LCO‐SS battery, based on Zn anode and LCO cathode material displayed an impressive open‐circuit voltage (OCV) of 1.72 V. The value is comparable to that of the conventional liquid electrolyte‐based Zn 2+ /Zn batteries further suggesting that the SNIPSy1‐based solid electrolyte systems owing to their high water content are able to emulate their liquid counterparts in terms of the cell potential (Figure S12, Supporting Information). [ 59 ] The stability of the cell was assessed by observing the extent of self‐discharge at 1.6 V over a 50 h period (Figure 4C). Negligible drop in voltage was noticed over the time period suggesting the cell configuration is stable and suitable for further performance analysis.…”