Electrolyte Modification: The choice of electrolyte significantly impacts AZCB performance.
Solute, Concentration, and Solvent: Factors like the dehydration energy of Zn-based clusters, the electrochemical window of the electrolyte, and the ability to suppress side reactions are crucial. For instance, a deep eutectic solvent composed of urea and choline chloride expanded the voltage window to 4.65 V and effectively suppressed side reactions. ("Aqueous Zinc-Chalcogen Batteries...", p. 5)
Additives: Introducing additives like iodine (I2) can improve reaction kinetics and reduce the reaction barrier by acting as a Zn2+ carrier. ("Aqueous Zinc-Chalcogen Batteries...", p. 10)
Cathode Optimization: Conductivity and Volume Change: Addressing the poor electronic conductivity and large volume change of sulfur and its discharge products is critical for stable cycling.
Conversion Mechanisms: The solid-solid conversion mechanisms in aqueous electrolytes, while avoiding the shuttle effect, can slow down reaction kinetics.
Strategies: Various approaches are employed to enhance cathode performance, including nano-structuring, conductive carbon coating, and the use of redox mediators.
2. Rechargeable Zinc–Air Batteries (ZABs)
The focuses is
on rechargeable ZABs, highlighting the advantages of non-alkaline electrolytes.
Non-Alkaline Electrolytes: These electrolytes offer enhanced reversibility and stability compared to traditional alkaline electrolytes.
Enhanced ZUR: A 1 mol kg−1 Zn(OTf)2 electrolyte demonstrated a Zn utilization ratio (ZUR) of 83.1%, significantly higher than the 8.1% achieved with a 6 mol kg−1 KOH electrolyte. ("Aqueous, Rechargeable Zinc//Air Battery...", p. 3)
Improved Stability: ZnO2 was identified as the primary discharge product in the Zn(OTf)2 electrolyte, exhibiting higher chemical stability compared to discharge products in ZnSO4 electrolytes. ("Aqueous, Rechargeable Zinc//Air Battery...", p. 4)
Oxygen Consumption Analysis: Precise measurement of oxygen consumption during cycling using pressure monitoring techniques confirms the two-electron reaction pathway in ZABs employing non-alkaline electrolytes. ("Rechargeable Zn–O2 Batteries...", p. 7)
Molecular Dynamics Simulations: These simulations provide insights into the solvation structure of Zn2+ ions in different electrolytes, explaining the improved performance observed with Zn(OTf)2. ("Rechargeable Zn–O2 Batteries...", p. 8)
3. Overall Advancements & Future Perspectives:
High-Performance Anodes: Research on advanced Zn anodes focuses on mitigating dendrite formation and enhancing cycling stability. Strategies include alloying Zn with other metals, surface modifications, and 3D structuring.
Electrocatalyst Development: Exploring highly active and durable bifunctional electrocatalysts for both oxygen reduction and evolution reactions is crucial to improve round-trip efficiency and reduce overpotentials.
Solid-State Electrolytes: Transitioning towards solid-state or quasi-solid-state electrolytes can address issues related to electrolyte leakage, corrosion, and dendrite formation, paving the way for flexible and safe ZABs.
Quotes:
"Although AZSBs are relatively mature AZCB systems, the following issues need to be solved: (1) The poor electronic conductivity of S (5 × 10−28 S m−1) and ZnS (10−9 S m−1), and the large volume change (50.3%) during cycling seriously affect the rate performance and cycling stability of AZSBs [...]" ("Aqueous Zinc-Chalcogen Batteries...", p. 4)
"Nonalkaline electrolyte of 1 mol kg−1 Zn(OTf)2 presents a well-defined discharge plateau at ~1.0 V with an areal capacity of 52 mA·hour cm−2, corresponding to a specific capacity of 684 mA·hour g−1 (based on Zn anode) and a Zn utilization ratio (ZUR) of 83.1%." ("Aqueous, Rechargeable Zinc//Air Battery...", p. 3)
"Zinc–air batteries (ZABs) have garnered attention as a promising alternative due to their compelling attributes, including impressive theoretical energy densities of 1218 Wh kg−1 (gravimetric) and 6136 Wh L−1 (volumetric) [...], eco-friendliness of harnessing power from Zn and atmospheric oxygen, and their compact form factor attributed to the air cathode, and significantly low operating cost of < $10 kW−1 h−1 [...]" ("Rechargeable Zn–O2 Batteries...", p. 2)
Conclusion:
The development of high-performance, rechargeable zinc-based batteries represents a significant step towards sustainable energy storage solutions. Continued research efforts focusing on material optimization, electrolyte engineering, and interface design are crucial to fully realize the potential of these promising battery technologies.
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