Investigation of the Inorganic Compounds NaMV₂ (PO₄)₃ (M = Fe, Co,Ni) as Anode Materials for Sodium-Ion Batteries

<p dir="ltr">The new compounds NaMV₂(PO₄)₃ (M = Fe, Co, Ni) were synthesized via a sol–gel synthesis route, and their crystal structures were refined using the Rietveld method from X-ray powder diffraction data. NaCoV₂(PO₄)₃ was also characterized by TGA, cyclic voltammetry, and galvanostatic cycling. The three phases crystallize with the orthorhombic symmetry and the space group <i>Imma</i>. The structures are isotypic to the stuffed α-CrPO₄-type structure and contain two vacant sites in which two sodium atoms can be intercalated. When NaCoV₂(PO₄)₃ is cycled at a 1C rate in the voltage ranges of 0.1–3 and 0.7–3 V vs Na⁺/Na, it delivers specific capacities of 190 and 75 mA h/g, respectively, with an average operation potential of ∼1.4 V. This attests to the electrochemical activity of this compound and indicates that the α-CrPO₄-type compounds could be suitable for hosting other guest ions.</p><h2>Other Information</h2><p dir="ltr">Published in: ACS Omega<br>License: <a href="https://pubs.acs.org/page/policy/authorchoice_termsofuse.html" rel="noreferrer" target="_blank">https://pubs.acs.org/page/policy/authorchoice_termsofuse.html</a><br>See article on publisher's website: <a href="https://dx.doi.org/10.1021/acsomega.0c01922" target="_blank">https://dx.doi.org/10.1021/acsomega.0c01922</a></p>