A team of chemical engineers has developed a novel electrolyte formula that significantly enhances the performance of aqueous zinc-ion batteries, a safer and more sustainable alternative to the ubiquitous lithium-ion technology. The innovation addresses long-standing issues of short lifecycles and temperature instability that have hindered the widespread adoption of these next-generation batteries. By using a unique dual-salt combination, the researchers have created a battery that maintains its capacity over thousands of cycles and operates efficiently in extreme temperatures, from freezing cold to moderate heat.
This breakthrough, detailed in the journal Nature Sustainability, centers on a “Decoupled Dual-Salt Electrolyte” (DDSE) that leverages two distinct zinc salts to perform separate, crucial functions simultaneously. One salt optimizes the electrolyte’s properties for rapid charging and low-temperature operation, while the other forms a protective layer on the zinc anode to prevent degradation. This elegant solution creates a stable, non-flammable, and high-performance energy storage system built from abundant materials, paving the way for its use in applications where safety and cost are paramount.
Overcoming Zinc-Ion Battery Hurdles
Aqueous zinc-ion batteries (AZBs) have long been a promising alternative to lithium-ion technology. Their primary appeal lies in safety and sustainability. Using a water-based electrolyte instead of a flammable organic solvent eliminates the fire risk associated with lithium-ion cells. Furthermore, zinc is an abundant and environmentally benign material, offering a more secure supply chain and lower manufacturing impact. However, the commercialization of AZBs has been plagued by significant technical challenges.
The primary obstacles have been poor durability and a narrow operating temperature range. Inside the battery, unwanted chemical reactions occur between the zinc metal anode and the water-based electrolyte. These reactions lead to the formation of dendrites—tiny, needle-like structures that degrade the anode—and the release of flammable hydrogen gas. This process severely shortens the battery’s usable life. The performance of conventional AZBs also suffers in cold conditions, limiting their practical applications.
A Decoupled Dual-Salt Solution
The research team, led by Professor Zaiping Guo from the University of Adelaide’s School of Chemical Engineering, engineered the DDSE to solve these problems through a novel division of labor. The formula contains two carefully selected zinc salts, zinc perchlorate (Zn(ClO4)2) and zinc sulfate (ZnSO4), each assigned a specific role. This “decoupling” strategy is the key to the system’s enhanced performance.
Protecting the Anode
In the DDSE system, the zinc sulfate salt primarily functions to protect the anode. It selectively precipitates onto the surface of the zinc metal, forming a stable barrier. This protective layer shields the anode from the electrolyte, effectively suppressing the unwanted side reactions that cause corrosion and dendrite growth. First author Guanjie Li explains that this salt “helps protect the zinc metal inside the battery, so it lasts much longer.” By stabilizing the anode, the formula dramatically extends the battery’s cycle life.
Enhancing Ion Mobility
Simultaneously, the zinc perchlorate salt remains largely dissolved in the liquid electrolyte. Its main purpose is to improve the battery’s electrochemical performance. This salt helps the battery function well across a wide range of temperatures and increases the speed at which zinc ions can move, which is critical for fast charging capabilities. According to Li, this salt “helps the battery work well in different temperatures and improves how fast the battery can charge.” Because each salt focuses on its specific task without interfering with the other, the overall system achieves a superior balance of stability and power.
Demonstrated Performance and Stability
The new electrolyte formula delivered exceptional results in laboratory testing. Pouch cell batteries built with the DDSE demonstrated remarkable durability and resilience under various conditions. At a standard room temperature of 25°C, the batteries retained 93% of their initial capacity after 900 charge-discharge cycles, a significant improvement over previous aqueous zinc designs.
The performance in extreme temperatures was particularly noteworthy. The batteries maintained 100% of their capacity over 3,000 cycles when operating at a frigid -40°C. At the upper end of their tested range, 40°C, they retained 91% capacity after 300 cycles. Co-author Dr. Shilin Zhang stated, “This is the first time such a well-balanced performance has been achieved in our field.” This wide operational window makes the technology viable for use in demanding environments where other batteries might fail.
Implications for Future Energy Storage
The development of this DDSE formula represents a significant step toward making aqueous zinc-ion batteries a commercially viable technology. The design’s use of affordable, non-flammable, and sustainable materials addresses the core safety and supply chain issues associated with lithium-ion batteries. The decoupling strategy provides a new and effective method for designing electrolytes, moving beyond conventional approaches that often involve trade-offs between safety, cost, and performance.
This improved stability and performance could open the door for AZBs in a variety of sectors. Their inherent safety makes them ideal for residential energy storage and other applications where fire risk is a major concern. The low cost and abundance of zinc could also make them a compelling choice for grid-scale storage, helping to integrate renewable energy sources like wind and solar more effectively. As researchers continue to refine the technology, this dual-salt formula provides a clear and promising path toward a new class of safer, longer-lasting, and more sustainable batteries.