Multi‐Healable, Mechanically Durable Double Cross‐Linked Polyacrylamide Electrolyte Incorporating Hydrophobic Interactions for Dendrite‐Free Flexible Zinc‐Ion Batteries

Abstract

Flexible aqueous zinc‐ion batteries (ZIBs) are considered as one of the most promising energy storage candidates for wearable electronics, owing to their environmental friendliness, low cost, high safety, and high theoretical capacity. However, the practical application of flexible ZIBs is significantly impeded by the Zn dendrite growth and the poor mechanical endurability at the electrolyte–electrode interface. Mechanically durable hydrogel electrolyte with dendrite growth restriction and self‐healing ability is highly desirable to improve the durability and extend the lifetime of the flexible ZIBs. However, it is still a big challenge to simultaneously endow hydrogel electrolytes with all necessary properties. Herein, multi‐healable and mechanically durable hydrogels are fabricated by the synergy effect of strong chemical cross‐linking and dynamic physical hydrophobic associations. The obtained double cross‐linked polyacrylamide electrolyte (PAAm‐O‐B) has good tensile strain, strength, and stable electrochemical performance, with tensile strength up to 75 kPa, high self‐healing efficiency up to 50 broken‐healed cycles and lifespan up to 900 h dendrite inhibition behavior. The flexible Zn//MnO2 batteries using PAAm‐O‐B hydrogel electrolytes exhibit good mechanical durability with high specific capacity and long cycle lifespan even under 1000 bending deformations and superior self‐healing ability.

3D-Polyacrylamide/Ti-MXene: A Newer Hybrid Hydrogel Electrolyte Featuring High Mechanical Strength and Durability for Flexible Aqueous Zinc-Ion Batteries

“…It is the foremost cause for the higher ionic conductivity along with a reduction of the polarization losses. Compared with PAM ( t zn 2+ :0.55), PAM/Ti-MXene (0.1 wt %) HHGE clearly states that the incorporation of 2D-Ti-MXene enhances the transference number. The higher t zn 2+ of PAM/Ti-MXene (0.1 wt %) HHGE is attributed to the more Zn 2+ favorable ions, which could result in a uniform Zn 2+ -ion distribution at the anode interface and a stable network.…”

“…The higher stability implies that no oxidative currents are observed during the electrochemical performance, enabling a smooth line up to 2.7 V without any decomposition. In the aqueous-based system, the PAM/Ti-MXene (0.1 wt % Ti-MXene) HHGE system has a higher ESW compared with the other systems and double the times higher than liquid electrolytes (2 M ZnSO 4 ; 1.6 V), and this higher stability window enhances the cycling performances of aqueous ZIB.…”

Environmentally Friendly and Self-Healable Supercapacitors Realized by a NaCl-Penetrable Polyampholyte Conductive Hydrogel

“…Figure a schematically illustrates the preparation of supercapacitor electrodes through a simple spray-coating method. The 2D PANI nanomaterials prepared by supramolecular cross-linking method (Supporting Information, Figure S2) were chosen due to its high specific capacitance, good dispersity, and high rate-capability. − We constructed a two-electrode symmetric supercapacitor without any encapsulation by sandwiching the PA hydrogel electrolyte between two gold electrodes sprayed with PANI nanosheets (Figure b). Based on the excellent self-healing property, high stretchability, and adhesion characteristics, a PA hydrogel is expected to compatible with supercapacitor electrodes.…”

A Review of the Synthesis of Biopolymer Hydrogel Electrolytes for Improved Electrode–Electrolyte Interfaces in Zinc-Ion Batteries

“…Hydrogel electrolytes with reduced free water content and quasi-solid-state properties can suppress water splitting side reactions, zinc dendrite growth, electrode dissolution, and water leakage [50,51]. Moreover, hydrogel electrolytes enhance the stability of electrodeelectrolyte interfaces through (i) the adhesion effect of hydrogel polar groups [50,52], (ii) close contact achievable with electrode active materials due to the mechanical elasticity of hydrogel electrolytes [53,54], and (iii) controlled Zn 2+ deposition through the interaction between Zn 2+ and hydrogel functional groups fixed in the hydrogel 3D network with evenly distributed ion transfer channels [55]. Hydrogels, with their hydrophilic polymer 3D network matrix, can hold aqueous electrolytes [56].…”