Sodium vanadate hydrate has emerged as a compelling electrode material for both sodium-ion batteries and electrochemical desalination batteries, leveraging its layered hydrated structure for high capacity and dual-function performance.
1. Sodium-Ion Battery Cathodes
The hydrated form, typically NaV₃O₈·xH₂O, offers wider interlayer spacing compared to its anhydrous counterparts, facilitating facile Na⁺ intercalation and exceptional electrochemical properties.
Key performance metrics:
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High specific capacity: Up to 280 mAh g⁻¹ at 50 mA g⁻¹ current density, far exceeding many conventional cathode materials.pubs.rsc
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Stable cycling: Retains >90% capacity after 150 charge–discharge cycles, reflecting robust structural integrity.pubs.rsc
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Rate capability: Maintains ~175 mAh g⁻¹ at 1 A g⁻¹, demonstrating rapid sodium diffusion within hydrated layers.pubs.rsc
Mechanism:
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During discharge, Na⁺ reversibly intercalates into the V–O layers, accompanied by V⁵⁺/V⁴⁺ redox transitions.
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Hydration water molecules act as “pillars,” preserving the layered framework and buffering volume changes.pubs.rsc
2. Electrochemical Desalination Batteries
In a novel “desalination battery” configuration, sodium vanadate hydrate operates alongside a carbon-based counter electrode to achieve simultaneous energy storage and salt removal from brackish water.
Operational principle:
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Cation capture: Na⁺ ions migrate into the vanadate hydrate cathode during charging, reducing the salt concentration in the treated water.
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Anion capture: Concurrently, Cl⁻ ions are electrostatically adsorbed by a porous graphite anode.
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Upon discharge, ions are released, regenerating both electrodes and allowing continuous cyclic desalination.pubs.rsc+1
Performance highlights:
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Desalination capacity: 173 mg NaCl per gram of vanadate hydrate, competitive with state-of-the-art membrane-based methods.pubs.rsc
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Energy efficiency: Consumes ~0.5 Wh g⁻¹ NaCl removed, making it energy-efficient relative to reverse osmosis at similar salinities.eurekalert
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Cycling durability: Over 100 consecutive cycles with >95% retention of desalination capacity, underscoring electrode resilience in saline media.pubs.rsc
3. Advantages Over Conventional Materials
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Dual functionality: Combines electrochemical energy storage and desalination in a single device, reducing system complexity and footprint.
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Aqueous operation: Avoids flammable organic electrolytes, enhancing safety and environmental compatibility.
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Scalability: Sodium and vanadium are more abundant than lithium and cobalt, offering cost and supply advantages for large-scale applications.
These developments position sodium vanadate hydrate as a versatile material for next-generation aqueous batteries, addressing both renewable energy storage and sustainable water treatment needs.
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