According to a study published in Advanced Energy Materials, a research team led by Prof. Linhua Hu from the Chinese Academy of Sciences’ Hefei Institutes of Physical Science created a hydrogel electrolyte formula that uses ClO4- anions and polyacrylamide chains to anchor water molecules, while glucose molecules preferentially govern Zn2+ solvation.
a. Schematic illustration of the design and construction of electrolyte structure; b. Schematic illustration of Zn plating behavior in Glu/ZC/PAM (left) and pure ZC (right). Image Credit: LI Zhaoqian
Effectively interrupted water clusters and increased water covalency resulted in a wider voltage stability window and stable functioning across a wide temperature range.
This means that the aqueous zinc batteries could operate stably considering the seasonal and altitude factors. Importantly, the temperature resistance mechanism in the water environment, Zn2+ solvation, and Zn/electrolyte interface are systematically analyzed.
Zhao Li, Hefei Institutes of Physical Science, Chinese Academy of Sciences
Irreversible electrolyte phase changes and an increased parasitic reaction severely limit the climate adaptability of aqueous Zn-ion batteries. Water activity influences the electrolyte’s freezing point, voltage stability window, and interfacial Zn deposition behavior.
The hydrogel electrolyte’s rational design increases the battery’s climate adaptability by preventing leakage, stabilizing the polymer structure, and providing various anchoring sites for free water.
The researchers in this study created a “covalency reinforced” hydrogel electrolyte with excellent interfacial adhesion and potent moisture-retaining capabilities.
Using theoretical calculations and spectral analysis, they discovered reduced bulk water activity and controlled Zn2+ solvation, which helped the electrolyte retain moisture longer, delay its freezing point, and prevent side reactions caused by water.
The improved mechanical characteristics of the electrolyte and the thermodynamically stable Zn interface are demonstrated by morphological evolution and COMSOL simulation. These benefits provide a broad operating temperature range of -40~130 °C for the batteries by preventing dendrite development and resolving electrode–electrolyte contact issues.
Dr Li added, “When the electrolyte is used in pouch batteries, it shows an impressive capacity of 254 mAh/g at -30 °C and 438.1 mAh/g at room temperature. This is a big deal because most previous batteries didn’t go beyond 200 mAh/g at -30 °C or 400 mAh/g at room temperature. This work shows how effective these batteries are, both in terms of capacity and their ability to operate over a wide range of temperatures.”
They also constructed the Zn//Zn and Zn//Cu batteries to test their long-term stability and Zn plating/stripping reversibility. At low current density, the Zn anode’s lifespan reaches 2,000 hours, which is longer than the liquid electrolyte's. Even at high current density, the Glu/ZC/PAM battery can operate continuously for more than 500 hours.
The Zn//Cu batteries could operate continuously for more than 800 hours, with an average Coulomb efficiency of 99.2%, which was highly competitive with earlier hydrogel electrolytes.
The study uses a multifunctional hydrogel electrolyte to control the coordination structure and tailors thermodynamic activity at the electrolyte/Zn interface, degenerating detrimental parasitic processes and expanding the operational temperature range. It offers a safe and extremely efficient approach to developing all-climate aqueous zinc-ion devices.
Journal Reference:
Wang, Y., et. al. (2024) Regulating Water Activity for All-Climate Aqueous Zinc-Ion Batteries. Advanced Energy Materials. doi:10.1002/aenm.202402041