2023 Wilson P Type Sodium Ion Cathodes

The shift to renewable, low-carbon energy generation creates intermittency in supply. To reduce reliance on fossil fuels, large-scale energy storage is required to store energy when it is in abundance and supply it when scarce. Sodium-ion batteries (NIBs) can enable this transition by using low-cost, sustainable materials. The P3 and P2 phases of Na0.67Mn0.9Mg0.1O2 (NMMO) are presented here as candidates for large-scale storage. In Chapter 3, a biotemplating synthesis using naturally occurring polysaccharide dextran successfully synthesised these materials without impurities. Conventional solid state methods could not produce single phase P3-NMMO, and its initial capacity was 95 mAh g-1, compared to 142 mAh g-1 for the biotemplated P3 phase. Biotemplating produced sharply faceted plates of P2-NMMO, with a higher initial capacity than those synthesised via solid state methods. In Chapter 4, P-type NMMO was produced using only a biotemplating synthesis, with calcination improving capacity retention for P3 phase. Doping P-type NMMO with Ca improved capacity retention in P2-NCMM. Finally, Chapter 5 examined biphasic samples, enhancing retention and rate capability by altering P3/P2 ratios. These insights offer potential pathways for optimising NIB performance.