Opportunity
The increasing demand for large-scale energy storage applications has driven significant interest in rechargeable aqueous zinc-ion batteries due to the cost-effectiveness, intrinsic safety, low redox potential, and competitive energy density of metallic zinc. However, the practical deployment of these batteries is severely hindered by critical challenges associated with the zinc anode in mildly acidic aqueous electrolytes. Uncontrolled zinc deposition typically accompanies the nucleation of zinc hydroxyl complexes and the hydrogen evolution reaction (HER), leading to excessive electrolyte consumption and the pervasive growth of zinc dendrites. These dendrites can penetrate the separator, causing internal short circuits and ultimately battery failure. Existing strategies to mitigate these issues, such as complex anode and separator geometric designs or the use of high donor number organic solvent molecules to reconfigure the Zn²⁺ solvation sheath, often introduce new complications. These include the inevitable dissolution of conversion-type cathode materials, economic impracticality, and limited universal applicability across various zinc battery systems. Consequently, there is a pressing need for a simple, cost-effective, and universally compatible solution that can effectively suppress dendrite formation and parasitic side reactions without compromising battery performance or economic viability, thereby unlocking the full potential of aqueous zinc batteries for reliable grid-scale energy storage.
Technology
This patent addresses the core challenges by introducing a threshold-level electrolyte additive engineering approach. The innovation centers on incorporating specific organic phosphorus compounds, such as hydroxyphosphonoacetic acid (HPAA), mono-hydrated ethylphosphonic acid (HEDP), alendronic acid, or aminotris (methylenephosphonic acid), into the aqueous electrolyte at remarkably low concentrations (e.g., 5 to 10 parts per million). These additives function through a dual mechanism. Primarily, their molecular structure, featuring electronegative oxygen atoms and labile hydrogen protons, enables them to adsorb onto the zinc metal surface, particularly along favorable crystal planes like (002). This adsorption passivates the anode surface. Secondly, the additives interact with the surrounding water molecules by forming strong hydrogen bonds (e.g., -OH…OH₂), which disrupts the inherent hydrogen-bond network of water. This interaction suppresses water activity, thereby inhibiting the HER and the nucleation/growth of insulating zinc hydroxyl complexes like basic zinc sulfate. The combined effect regulates Zn²⁺ flux, promotes uniform zinc deposition, and prevents dendritic growth. The technology is applied to both static aqueous zinc batteries (comprising an anode, cathode, additive-containing electrolyte, and separator) and zinc-bromine flow batteries, where the additive is included in both the anolyte and catholyte. This minimal additive approach requires no complex electrode redesign and maintains compatibility with various cathode materials and zinc salts, offering a universal and economical enhancement.
Advantages
- The ppm-level additive concentration ensures a straightforward, simple, and cost-effective electrolyte preparation process.
- The additive engineering strategy is environmentally benign due to minimal chemical usage and is highly compatible with a wide range of energy storage systems and cathode chemistries.
- Batteries equipped with the modified electrolyte demonstrate exceptional long-term cycling stability. For instance, Zn||Zn symmetric cells can operate for nearly a year (up to 365 days), and Zn||Br₂ flow batteries can sustain over 800 cycles without capacity loss.
- The technology enables stable operation under high current densities and areal capacities, such as 2000 hours at 5 mA cm⁻², 2 mAh cm⁻² and 500 hours at 10 mA cm⁻², 10 mAh cm⁻².
- It effectively suppresses zinc dendrite growth and hydrogen evolution, leading to highly reversible zinc plating/stripping with high Coulombic efficiency (e.g., ~99.2% in Zn||Cu cells).
- The strategy is highly compatible and focuses on anode stabilization without interfering with or being hindered by the cathode's electrochemical reactions.
Applications
- Large-scale stationary energy storage systems for grid stabilization and renewable energy integration.
- Rechargeable aqueous zinc-ion batteries for consumer electronics and backup power supplies.
- Zinc-bromine redox flow batteries for long-duration, high-capacity energy storage.
- Development of next-generation, safe, and low-cost battery systems for electric vehicles and portable devices.
- Industrial applications requiring robust, durable, and non-flammable battery solutions.
