Abstract
A library of 28 doped sodium manganese oxide compositions was synthesised via the sol–gel method to isolate improved cathode materials for sodium-ion batteries (SIBs). These compositions were fully characterised for elemental ratios, phases, and electrochemical performance in sodium-ion half-cells. All compositions in the primary library consisted of the stoichiometry Na 0.5 Mn 0.66 V x Fe y Ti z O 2 ( x + y + z = 0.33), mostly yielding phase-pure layered P3 ( R 3̄ m ) space group or ‘Tunnel Type’ ( Pbam ) structures. Although several iron- and titanium-containing sodium manganese oxides are well known, and vanadium-doped manganese oxides previously measured, a systematic investigation of their ratios and their effects on sodium-ion cathode performance remains largely unexplored. In this large study, the Ti : Fe ratio is explored within the new Ti : Fe : V ternary substituted system, taking steps to establish both optimised heat treatment and sodium content for future development. Interestingly, compositional/performance relationships were discovered; Fe imparted the highest specific capacity, V provided high stability, and a small addition of Ti greatly improved rate capability. The resulting dataset was used to train a machine-learning model to predict test materials. This work establishes a scalable framework for the targeted design and prediction of sodium-ion cathodes tailored to application-specific requirements, including high energy density, fast charging, and extended cycle life.