Reversible sodiation in maricite NaMn1/3Co1/3Ni1/3PO4 for renewable energy storage

Battery technology is now at a point where water based sodium batteries may take a place in large-scale applications such as electrical grid stabilization. The starting point for new aqueous based sodium battery technology is to understand the fundamental differences between lithium versus sodium in similar host materials synthesized via non-ceramic synthetic approaches. The new sodium phosphate host compound, NaMn1/3Co1/3Ni1/3PO4, has been synthesized using sol–gel and combustion routes. The framework of sodium phosphate with a maricite structure is analogous to olivine based lithium phosphate compound, except the M(1) and M(2) sites have reverse occupancies. Physical and electrochemical characterization indicate that the combustion synthesized sodium analogue is fully reversible (electrochemically intercalating and de-intercalating sodium ions) in water based NaOH electrolyte for multiple cycles.

► A new mixed transition metal sodium phosphate NaMn1/3Co1/3Ni1/3PO4 was synthesized by sol–gel and combustion approaches.
► Maricite host material electrochemically intercalates and de-intercalates sodium ions in a water based NaOH electrolyte.
► Intercalation was greater for the combustion product, attributed to the smaller particle size and lower diffusion barrier.
► Water-based sodium battery may have potential application as stationary storage devices for electrical grid stabilization.