Written by: Huang Yan
Translated by: Wang Min
Edited by: William Mosteller
Recently, Huang Yan, professor of the Research Center for Flexible and Printed Electronics as well as School of Material Science and Engineering in Shenzhen Campus of Harbin Institute of Technology (HIT), has made great progress in the cycling stability and self-healing property of aqueous alkaline batteries. Her research papers were published in the internationally renowned journal Advanced Energy Materials (IF: 21.875) and Angewante Chemie International Edition (IF: 12.102). The papers are titled “Solid-State Rechargeable Zn//NiCo and Zn-air Batteries with Ultra-Long Lifetime and High Capacity: the Role of a Sodium Polyacrylate Hydrogel Electrolyte” and “An intrinsically self‐healing NiCo//Zn rechargeable battery by self-healable ferric-ion-crosslinking sodium polyacrylate hydrogel electrolyte” respectively.
With water as an electrolyte solvent, aqueous batteries which solved the safety risks caused by flammable organic electrolytes, have attracted the attention of researchers in the field of flexible wearable electronics. However, there still exist certain problems in aqueous batteries. For one thing, water loss occurs during the charging-discharging process of the gel electrolyte, resulting in a decrease in ionic conductivity, segregation of electrolyte composition and a drastic drop in battery capacity. It ultimately leads to poor cycle stability of the battery. For another, aqueous batteries tend to be inevitably affected by various deformations and local stresses in daily use, severely limiting the service life and reliability of the battery, which ultimately leads to failure of the electronic system.
To solve the above-mentioned problems, a new type of sodium polyacrylate-based hydrogel electrolyte was synthesized by Prof. Huang Yan.
The strong interaction between sodium polyacrylate and water molecules brings the electrolyte high water retentivity. Moreover, the forming of an SEI-like film on the surface of the anode by negative charges (acrylate groups) will effectively inhibit the dendrite formation. Thus, the flexible nickel-zinc and zinc-air batteries prepared from this electrolyte have shown the longest cycle stability performance, and the cycles/time ratio is 8~40 times higher than those of other batteries reported in all the current documents. In addition, the sodium polyacrylate hydrogel molecular chain is cross-linked by iron ions to promote the dynamic reconstruction of the overall electrolyte network. These non-covalent cross-links will reattach to the damaged surface as the hydrogel is severed, enabling the batteries to be inherently self-healable. Therefore, the nickel-zinc batteries with hydrogel as the electrolyte can be recovered by themselves, retaining more than 87% of their original capacity after 4 break/self-healing cycles.
In brief, the innovative invention made by Prof. Huang Yan has solved the problems related to the cycle stability and intrinsic self-healing property of aqueous alkaline batteries with an unprecedented success.