Rapid One-Step Synthesis of Sodium-Ion Battery Cathodes from Desalination Waste: A Sustainable Approach to High-Performance Energy Storage

Desalination brine, a hypersaline byproduct of water treatment processes, represents an underutilized sodium feedstock with significant potential for battery material production. In this work, we report a streamlined rapid one-step synthesis (ROSS) method for Na 3 V 2 (PO 4 ) 3 (NVP), a highperformance sodium-ion battery cathode material with demonstrated electrochemical comparability with lithium-based alternatives, directly from desalination brine. Sequential filtration and chemical precipitation were used to selectively isolate sodium ions from brine, effectively removing divalent cations (Ca 2+ , Mg 2+ ), heavy metal impurities and organic contaminants. The purified sodiumion solution was subsequently used to prepare a sodium-vanadium-oxalate precursor, from which phase-pure NVP crystals with carbon coating were obtained via a single-step combustion reaction. Notably, the entire crystallization process was completed within 45 minutes using an open crucible setup under ambient atmosphere, representing a significant reduction in both processing time and operational complexity compared to conventional NVP synthesis routes, which typically require 2–4 hours under inert gas conditions. Our method offers a dual environmental benefit: mitigating the ecological impact of brine discharge while supplying a low-cost, sustainable sodium source for the growing sodium-ion battery industry.