2, University College London, London, , United Kingdom
3, University of Birmingham, Birmingham, , United Kingdom
Room temperature Sodium ion batteries (NIB) may offer key benefits over other commercial battery technologies such as lithium-ion batteries and lead acid batteries particularly in cost and safety. Sodium is the fourth most abundant element on the planet and is found in sea water. Therefore not only is it a low cost material but it is not geographically limited in terms of supply, unlike for lithium. Safety benefits include the low toxicity of sodium compared to lead acid batteries and the potential for safe transport of cells at zero state of charge and volts. NIB technology however is still in its infancy and despite recent advances, significant knowledge gaps in terms of cell design, life-time and performance still exist. Here we discuss a novel sodium ion cell chemistry based upon Sn-containing nickelate sodium layered oxide materials and a hard carbon. The energy density and the life-time is significantly affected by the balance of the anode to the cathode, and the voltage ranges of the cell. The influence on cell design is discussed, and the performance characteristics and failure mechanisms presented. In particular the failure mechanisms relating to the structural changes of the cathode during cycling and the relationship to the charging profiles and cycle life.