Optimization of Prussian Blue Analogues for Na-Ion Desalination Batteries

With a growing need for clean water worldwide, interest in capacitive deionization (CDI) is growing as a potentially low energy desalination methodology. Current commercial technologies are using activated charcoal at both electrodes, but these materials suffer from low capacity and poor durability.<br/>Inspired by the recent advances in sodium-ion batteries, several studies have proposed to use intercalation materials to increase the desalination potential of electrodes. Among the proposed materials for desalination batteries, hexacyanoferrate Prussian blue analogue materials (PBAs) are especially interesting because of their open framework structure that allow insertion of Na with high reversibility and fast kinetics.<br/>This study focused on the development of heterostructured NaM_xN_y(HCF) PBs with M and N being Ni, Mn or Fe, with an optimization for performance and durability in 1M NaCl electrolyte. Materials were synthesized using a simple, cost-effective and scalable coprecipitation synthesis process at room temperature. Different compositions and electrode architecture were tested and salt absorption above 75 mg/g of electrode at rates above 100 mg/g/min will be reported for PBAs containing Ni and Mn.