Atomic-scale investigation of cation doping and defect clustering in the anti-perovskite Na3OCI sodium-ion conductor

Professor Saiful Islam and his former colleagues from the University of Bath made the front cover of Journal of Materials Chemistry A with their paper 'Atomic-scale investigation of cation doping and defect clustering in the anti-perovskite Na₃OCI sodium-ion conductor'.  

Solid state batteries present potential advantages over their liquid-based electrolyte equivalents, including enhanced safety and increased energy density.  In the search for novel solid electrolytes, the anti-perovskite family of materials are attracting growing interest, however, there is a significant work on Li-rich anti-perovskites, their Na-based counterparts and the atomistic effects of aliovalent doping on these materials are not fully characterised.

In this paper, Professor Islam and researchers from the University of Bath investigate the effects on Na-ion conductivity of doping with divalent (Mg, Ca, Sr and Ba) and trivalent cations (Al and Ga) and of possible dopant-vacancy clustering in the anti-perovskite Na₃OCI by employing atomistic simulation techniques.

The results highlight the potential of Mg²⁺, Ca²⁺, Al³⁺ and Ga³⁺ doping due to their favourable incorporation and increased Na-ion vacancy concentration.  Local defect clustering and binding energies are analysed, and such effects inhibit Na-ion conductivity in the doped N_a3OCI solid electrolyte at operating temperatures.  These results provide a framework to guie future work on anti-perovskites to enhance their solid electrolyte properties.