Aqueous batteries beating the cold

Aqueous zinc batteries, with intrinsic safety and low cost, struggle at low temperatures primarily because their water-based electrolytes freeze. Now a dual-salt electrolyte design enables stable battery operation even at −40 °C.

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Whether it is Oslo’s electric bus fleet struggling with reduced range during sub-zero temperatures[1](https://www.nature.com/articles/s41893-025-01684-9#ref-CR1 “Khatsenkova, S. Was Oslo paralysed after all of its electric buses broke down due to the cold? euronews https://go.nature.com/4qgWvpa

You have full access to this article via your institution.

(30 December 2023).“), or US drivers queuing for hours as their electric vehicles (EVs) charge more slowly in the winter[2](https://www.nature.com/articles/s41893-025-01684-9#ref-CR2 “Associated Press. Frigid weather can make charging electric vehicles tough – here’s what you need to know. The Guardian https://go.nature.com/48vViUE

(19 January 2024).“), cold weather is detrimental to batteries. This challenge is particularly true for aqueous batteries, such as aqueous zinc batteries (AZBs), because their water-based electrolytes freeze under low temperatures and tend to corrode the zinc electrode3. Writing in Nature Sustainability, Li and colleagues[4](https://www.nature.com/articles/s41893-025-01684-9#ref-CR4 “Li, G. et al. Nat. Sustain. https://doi.org/10.1038/s41893-025-01646-1

(2025).“) report a ‘decoupled dual-salt electrolyte’ design that breaks this deadlock.

AZBs are emerging as a compelling alternative to lithium-ion batteries (LIBs), especially for large-scale grid storage. Their advantages include enhanced safety, lower cost and improved sustainability due to the abundance of zinc and the use of a non-toxic water-based electrolyte5,6. However, their practical deployment has been held back by two contrasting problems. Aqueous electrolytes tend to decompose at the zinc surface, generating hydrogen gas and corroding the electrode. Attempts to suppress these reactions often rely on adding more salt or organic co-solvents, which raises cost and environmental concerns, while making the electrolyte even more likely to freeze7. In most single-salt systems, improving interfacial stability typically worsens the electrolyte’s low-temperature behaviour, and vice versa. So, there is a long-standing trade-off between maximizing corrosion protection and enhancing anti-freezing ability in zinc batteries.

Li and colleagues overcome this dilemma by designing a dual-salt electrolyte where each salt performs a decoupled but complementary function (Fig. 1). Zinc sulfate (ZnSO4), one salt of choice, has a strong affinity to water molecules and serves to suppress hydrogen evolution reaction (HER) and corrosion by forming a stable layer on the zinc electrode surface. The other salt, zinc perchlorate (Zn(ClO4)2), binds weakly with water and disrupts the hydrogen-bond network in the bulk electrolyte, substantially lowering the freezing point. When mixed in a 2:8 molar ratio, this ‘decoupled dual-salt electrolyte’ enables batteries to cycle even at −40 °C with a remarkable Coulombic efficiency, a measure of a battery’s charge/discharge efficiency, of 99.97%. The ionic conductivity remains high across a broad temperature range from room temperature down to −40 °C, without addition of flammable solvents. Equipped with this electrolyte, pouch cells — a type of battery format providing a more accurate picture of the real-world performance — can retain 93% of their initial capacity after 900 cycles at room temperature and exhibit no obvious capacity loss after 3,000 cycles at −40 °C.

Fig. 1: Molecular configuration of the decoupled dual-salt electrolyte.

The electrolyte is an aqueous solution of ZnSO4 and Zn(ClO4)2. The different anions perform distinct functions at the layer close to the Zn anode and in the bulk of the electrolyte. Strongly hydrated SO42− preferentially adsorbs in the Stern layer, stabilizing interfacial water and suppressing parasitic HER on the Zn anode. Weakly hydrated ClO4− dominates the diffusion layer and bulk, disrupting the hydrogen-bond network through weaker anion−H2O interactions and imparting anti-freezing behaviour.

The concept of decoupling the two functions of electrolytes — interfacial stabilization and bulk transport — may extend far beyond zinc batteries. It bypasses the conventional ‘one-salt-fits-all’ mindset. Interestingly, Li and colleagues show that even with a small amount of zinc sulfate, the interface will be dominated by sulfate ions due to their stronger attraction to the zinc surface. Meanwhile, the perchlorate-rich bulk allows for faster ion movement and suppressed freezing. The dual effect also further reduces HER from a thermodynamic perspective. These findings suggest that careful control of anions could be a strategy widely useful for water-based electrolytes.

Despite the impressive performance, the design is not without questions. Long-term field tests in variable temperature environments will be a critical step for assessing reliability under real-world conditions. The use of indium as an additive for even better performance, although in trace amounts, may raise concerns about cost when implemented at a large scale. Tin-based or organic systems could be an alternative. To explore the wider applicability of the concept of spatial anion decoupling, it is worth testing other battery chemistries, particularly those that were once out of reach due to low temperatures.

With this work, Li and colleagues demonstrate that the trade-off between low-temperature performance and interfacial stability for aqueous batteries can be addressed through cation engineering in electrolytes. By using common salts in an unconventional way, they expand the practical temperature window of AZBs to include sub-Arctic conditions, without sacrificing cost or safety. The current advance in electrolytes breaks the primary barrier to aqueous battery operation at low temperatures, thus paving the way for the wider deployment of renewable and affordable energy in cold regions.

References

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