As renewable energy storage demand grows, the limitations of aqueous zinc metal batteries (AZMBs) in subzero environments become more pronounced. Now, researchers from Harbin University of Science and Technology and Fudan University, led by Professor Xin Liu and Professor Dongliang Chao, have presented a breakthrough solution using trace Na₂SO₄ as an electrolyte additive. This work offers valuable insights into developing next-generation energy storage technologies that can overcome low-temperature challenges.

Why Na₂SO₄ Matters

• Cost-Effective: Na₂SO₄ is an abundant, low-cost inorganic salt that avoids the flammability and conductivity issues of organic antifreeze agents
• Electrostatic Regulation: Na⁺ preferentially adsorbs at the zinc anode surface, repelling Zn²⁺ and promoting uniform deposition
• Suppressed Side Reactions: Fewer water molecules coordinate with Na⁺, reducing hydrogen evolution and harmful byproducts
• Ultra-Stable Cycling: Zn||Zn cells achieve over 2500 hours at −40°C, and Zn||PANI full cells retain >90% capacity after 8000 cycles

Innovative Design and Features

• Electrolyte Formulation: The optimized 5ZClO/0.2Na electrolyte (5m Zn(ClO₄)₂+ 0.2m Na₂SO₄) maintains high ionic conductivity down to −60°C
• Hydrogen Bond Disruption: Spectroscopic analyses reveal Na₂SO₄ further breaks water-water hydrogen bonds, enhancing antifreeze capability
• Interfacial Engineering: DFT calculations show Na⁺ adsorption energy (−7.32 eV) exceeds Zn²⁺(−2.49 eV), enabling preferential interface regulation
• Nucleation Control: Na⁺ increases nucleation overpotential, promoting denser, more uniform zinc deposition

Applications and Future Outlook

• Low-Temperature Energy Storage: Enables reliable battery operation in extreme cold environments for EVs and grid systems
• Long-Life Power Supplies: Zn||Cu cells maintain 99.5% Coulombic efficiency for >1000 cycles at −40°C
• Safe and Scalable: Organic-free design maintains aqueous battery safety while improving performance
• Challenges and Opportunities: Future work will focus on optimizing additive concentrations and exploring other cost-effective inorganic salts

This breakthrough provides a roadmap for developing high-performance, low-temperature AZMBs using simple electrolyte modifications. It highlights the importance of interfacial engineering and cost-effective materials design in advancing energy storage technologies. Stay tuned for more groundbreaking work from Professor Xin Liu and Professor Dongliang Chao's teams!