New strategy brings advances to the development of powerful, safe and environmentally friendly zinc batteries

In order to meet the world’s growing need for affordable and efficient energy storage, particularly for renewable sources like solar and wind, there is a pressing demand for advanced batteries. While lithium-ion batteries, commonly used in smartphones and electric cars, have been effective, their high cost and flammability pose significant challenges.

Fortunately, a team of researchers led by ETH Zurich has made significant strides in developing an alternative: water-based zinc batteries. This innovative approach offers a promising solution that enhances power output, safety, and environmental sustainability.

By leveraging their expertise, the international research team has devised a strategy that brings forth crucial advancements in the field of zinc batteries. These improvements address the limitations of lithium-ion batteries, making zinc batteries more powerful, safer to use, and environmentally friendly.

With these advancements, we move closer to realizing the goal of affordable and efficient energy storage, enabling the utilization of sustainably generated electricity even during periods of darkness or low wind activity. The water-based zinc batteries offer a viable alternative that holds great potential for the future of energy storage, paving the way for a more sustainable and resilient energy landscape.

Durability is a challenge

The utilization of zinc batteries brings forth a multitude of advantages. Firstly, zinc, the primary material used in these batteries, is abundant, cost-effective, and boasts a well-established recycling infrastructure. Additionally, zinc batteries possess a high energy storage capacity, making them capable of storing significant amounts of electricity.

One of the most notable advantages of zinc batteries is their versatility in terms of electrolyte selection. Unlike lithium-ion batteries that often rely on highly flammable organic solvents, zinc batteries can utilize water-based electrolytes, eliminating the need for hazardous materials.

However, engineers encounter certain challenges when developing zinc batteries. One such challenge arises when the batteries are charged at high voltages. In this scenario, the water present in the electrolyte reacts with one of the electrodes, leading to the formation of hydrogen gas. This reaction depletes the electrolyte fluid and subsequently decreases battery performance. Additionally, the accumulation of excess pressure within the battery due to this reaction can pose safety risks.

Another issue that engineers must address is the formation of dendrites during the charging process. These spikey zinc deposits can grow within the battery and potentially penetrate its structure, resulting in a short circuit and rendering the battery inoperable.

Despite these challenges, researchers and engineers are actively working towards mitigating these issues and optimizing the performance of zinc batteries. By devising innovative strategies and implementing advanced technologies, they aim to overcome these obstacles and unlock the full potential of zinc batteries as a safe, efficient, and environmentally friendly energy storage solution.

Salts make batteries toxic

In recent years, engineers have been exploring the approach of enriching the aqueous electrolyte with salts to minimize water content in zinc batteries. However, this approach comes with its own drawbacks. One major drawback is the increased viscosity of the electrolyte fluid, which significantly slows down the charging and discharging processes. Additionally, many of the salts utilized in this method contain fluorine, rendering them toxic and environmentally harmful.

To address these challenges, Maria Lukatskaya, an esteemed Professor of Electrochemical Energy Systems at ETH Zurich, collaborated with researchers from various institutions in the United States and Switzerland. Together, they embarked on a systematic search for the optimal salt concentration for water-based zinc-ion batteries. By conducting experiments and leveraging computer simulations, the team made a significant discovery contrary to previous assumptions: the ideal salt concentration is not the highest achievable, but rather a relatively low one, specifically five to ten water molecules per positive ion of the salt. These insightful findings have been published in the journal Energy & Environmental Science.

This research breakthrough provides crucial guidance for enhancing the performance of water-based zinc batteries. By identifying the optimal salt concentration, the scientists have paved the way for improving the efficiency and overall effectiveness of these batteries. This advancement represents a significant step forward in the quest to develop safe, sustainable, and high-performing energy storage solutions based on zinc batteries.

Long-lasting performance and fast charging

Moreover, the researchers achieved their improvements without resorting to environmentally harmful salts, instead opting for acetates—a type of environmentally friendly salt derived from acetic acid. Dario Gomez Vazquez, the lead author of the study and a doctoral student in Lukatskaya’s group, explains that the ideal concentration of acetates minimized electrolyte depletion and prevented the formation of zinc dendrites, matching the results previously obtained using high concentrations of toxic salts. Additionally, the new approach enabled faster charging and discharging of the batteries.

Although the ETH researchers have conducted tests on a smaller laboratory scale thus far, the next phase involves upscaling the approach to evaluate its viability for larger batteries. The ultimate goal is to integrate these batteries into the power grid as storage units to compensate for fluctuations or install them in individual homes’ basements, allowing the utilization of solar power generated during the day in the evening.

Before zinc batteries can be successfully introduced to the market, there are still challenges to overcome, as highlighted by ETH Professor Lukatskaya. Batteries comprise two crucial components—the anode and the cathode—separated by the electrolyte fluid. While the researchers demonstrated the ability to optimize the charging of zinc anodes through electrolyte composition, further work is needed to optimize cathode materials. This optimization process is vital to achieve durable and efficient zinc batteries, ensuring their long-term performance and suitability for commercial applications.

Source:  ETH Zurich

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