A Safe Polyzwitterionic Hydrogel Electrolyte for Long‐Life Quasi‐Solid State Zinc Metal Batteries

Abstract

Aqueous zinc metal batteries are safe, economic, and environmentally friendly. However, the dendrite growth and inevitable corrosion issues under aqueous condition greatly restrict the development of long cycling life zinc metal batteries. To achieve the long‐term reversible zinc deposition/dissolution, a polyzwitterionic hydrogel electrolyte (PZHE) is constructed with record high room temperature ionic conductivity of 32.0 mS cm−1 and Zn2+ transference number of 0.656. The abundant hydrophilic and charged groups in the zwitterionic polymer can well immobilize water molecules in the polymer skeleton and reduce side reactions. The charged groups of the zwitterionic polymer can also homogenize the ion distribution and achieve uniform zinc deposition. Long cycling life of over 3500 h is achieved for the symmetric batteries with PZHE. Full cells with VS2 and MnO2 cathodes are also demonstrated to exhibit excellent cycling stability. With combined advantages of physical and chemical crosslinking gels, the PZHE enabled flexible quasi‐solid state zinc metal batteries with excellent processability, self‐healing property and safety, can operate even under various extreme conditions such as cutting, soaking, hammering, washing, burning, and freezing. It is believed that the PZHE can provide a promising opportunity and pave the way for other long‐life aqueous batteries.

Fundamental Concepts of Hydrogels: Synthesis, Properties, and Their Applications

“…A long cycling life of 3500 h was attained. In addition, the batteries showed consistent performance under extreme conditions, such as cutting, self-healing, soaking, hammering, washing, burning, and freezing [ 211 ]. Multivalent ion batteries have been introduced recently to improve the performance of batteries and to overcome the limited potential window due to the presence of hydrogel electrolytes and can work below the freezing temperature of water.…”

Electrochemical Zinc Ion Capacitors: Fundamentals, Materials, and Systems

“…[176] The cationic exchange PAN coating layer can regulate cation flux and promote homogeneous zinc nucleation (Figure 14b). Besides the artificial coating layer, hydrogel [208,209] and polymer electrolytes [148,210] are also physical barriers to suppress the growth of zinc dendrite. Additionally, special configurations, such as backside metal plating, [211] are also considered as good choices to avoid the dendrite problem in ZICs.…”

An Interface‐Bridged Organic–Inorganic Layer that Suppresses Dendrite Formation and Side Reactions for Ultra‐Long‐Life Aqueous Zinc Metal Anodes

“…[21] To address the above issues,t he currently reported solutions can be divided into two aspects:s uppressing dendrite formation and minimizing side reactions.D endrite suppression can be achieved by introducing coating layers on Zn anode surface,which effectively modified the current and electrolyte flux on anode surface,s uch as CaCO 3 and SiO 2 layer, [22] porous active carbon layer and reduced graphene oxide (rGO) layer, [23,24] and so on. Furthermore,m any strategies have also been reported for relieving the side reactions beside suppressing dendrites,i ncluding coating az incophilic protective layer, [25] replacing ZnSO 4 with Zn-(CF 3 SO 3 ) 2 , [26] using electrolyte additives, [27][28][29] adoption of ah ighly concentrated zincic salt as electrolyte, [30] using modified conductive host, [31][32][33][34] employing single ion conduc-tive electrolyte, [35,36] alloying with Al, [37] adopting gel electrolyte or all solid electrolyte, [38][39][40] coating inorganic layer, [41][42][43][44] or organic (polyamide) layer. [45] Indeed, the side reactions and dendrite are very important issues for long life AZBs.…”