Sodium ion batteries are being developed as a  lower cost alternative to lithium ion batteries which find application in consumer electronics, power tools , stationary energy storage and electric vehicles. The lower cost of  sodium makes it an attractive technology r for application in stationary energy storage and other applications which require lower cost energy storage technologies. One of the limitations with sodium ion batteries for use in other applications is their low energy density.  Sharp laboratories of Europe Ltd (SLE) have been developing and optimising higher energy density cathodes for sodium ion batteries.

Several layered oxide systems have been reported as potential cathodes [i]^,[ii]  SLE has performed an optimisation of tin containing nickel based layered oxide materials which exhibit high specific capacities[iii]. In particular we have looked at the O3 type mixed nickel and manganese containing layered oxides of the formula  Na_υNi¹_v M²_w M³_xO_2±6wherein Μ² comprises tin, optionally in combination with one or more transition metals,  Μ³ comprises one or more transition metals. The incorporation of Sn is interesting because it leads to higher observed average voltages upon discharge, and exhibits higher specific capacities compared to other O3 type layered oxides with similar compositions. The main contribution to the higher average voltage upon discharge is the observation of a high voltage reversible plateaux.  An optimisation of the material composition has been performed which looks at the effect of the different dopants and dopant levels upon the observed voltage and specific capacity. Here we discuss the optimisation of the high energy sodium ion cathode material, and the origin of the voltage plateaus and the mechanism for charge and discharge mechanism for the Sn containing layered oxide materials.