Development of Novel High Energy Density Sodium Layered Oxide Cathode Materials
In this publication, we present detailed characterisation of novel sodium ion cathode materials based on a layered oxide framework as strong candidates for Na-ion battery cathode materials. We will present a review of layered oxides (Na Nix TMyO2, TM = Ti, V, Cr, Mn, Fe, Co, Ni, and a mixture of 2 or 3 elements). Single TM layered oxide systems are well characterised not only for their electrochemical performance but also for their structural transitions during electrochemical cycling.1 Binary TM systems are often favoured as modifications through doping seem to address issues of low reversible capacity, capacity retention, operating voltage, and structural stability when compared to the single TM analogues.2 As a consequence, some materials already have reached a specific energy density of 578 mW h g−1 comparable to that of LiFePO4.3 Furthermore, some binary and ternary TM systems have shown exceptional stability and rate capability.4
Herein, we present development work of Na Nix Mny TM1TM2 O2 quaternary and higher substituted sodium layered oxides.5 We demonstrate that further substitution within the layered oxide structure is beneficial to improving reversible capacity, capacity retention and operating voltage of these materials. These higher order substitutions leading to materials which show comparable electrochemical properties to simple Li ion technologies. We have begun development of Full cell technology based on some of the best performing layered oxides.
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