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 the School of Material Science and Engineering at the 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 Ultralong Lifetime and High Capacity: the Role of a Sodium Polyacrylate Hydrogel Electrolyte” and “An Intrinsically Self-healing NiCo//Zn Rechargeable Battery with a Self-healable Ferric-Ion-Crosslinking Sodium Polyacrylate Hydrogel Electrolyte” respectively.
With water as an electrolyte solvent, aqueous batteries, which solve 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, which 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, Prof. Huang Yan synthesized a new type of sodium polyacrylate-based hydrogel electrolyte.
The strong interaction between sodium polyacrylate and water molecules causes the electrolyte to have high water-retaining capability. Moreover, the forming of an SEI-like film on the surface of the anode by negative charges (acrylate groups) will effectively inhibit 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 current documents. In addition, the sodium polyacrylate hydrogel molecular chains are crosslinked by ferric ions to promote the dynamic reconstruction of the overall electrolyte network. These non-covalent crosslinkers can form ionic bonds to reconnect damaged surfaces when the hydrogel is cut off, enabling the batteries to be inherently self-healable. Therefore, the nickel-zinc batteries with hydrogel as the electrolyte can be autonomically self-healed, retaining more than 87% of their original capacity after 4 cycles of breaking/healing.
In brief, the innovative invention made by Prof. Huang Yan has solved problems related to the cycle stability and intrinsic self-healing property of aqueous alkaline batteries with unprecedented success.