Development of Novel High Energy Density Sodium Layered Oxide Cathode Materials

The large-scale utilisation of renewable energy technologies depends on solving the intermittency of energy production with large scale energy-storage solutions. The Lithium-ion battery has been widely considered as the technology of choice to meet the future energy challenge. However, increasing demand for Li based energy storage technologies is likely to tax current Li production. There is growing research and commercial interest in other metal ion battery technologies that could be developed to meet the needs of large scale energy storage applications. As such, the room temperature Na-ion secondary battery has been the subject of increasing research and development due to its feasibility to compete with the already well-established Li-ion secondary battery.¹ Although, there are many technical barriers to overcome before Na-ion technology becomes competitive with current metal ion batteries. However, recent research into Na-ion systems has shown that some of the known Na-ion battery materials have advantages over the current Li-ion counterparts.²

 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 Ni_x T_MyO₂, T_M = Ti, V, Cr, Mn, Fe, Co, Ni, and a mixture of 2 or 3 elements). Single T_M layered oxide systems are well characterised not only for their electrochemical performance but also for their structural transitions during electrochemical cycling.¹ Binary T_M 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 T_M 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 T_M systems have shown exceptional stability and rate capability.⁴

Herein, we present development work of Na Ni_x Mn_y T_M1T_M2 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.

 

1. N. Yabuuchi, et al. Chem. Rev., 2014, 114 (23), pp 11636–11682
2. L. Yuechuan, et al. Chem. Mater. 2014, 26, 5288−5296
3. X. Li et al.  Electrochemistry Communications 49 (2014) 51–54

4. H. Yoshida, N. Yabuuchi and  S. Komaba Electrochem. Commun., 34 (2013), pp. 60–6
5. J. Barker, et al. Doped Nickelate Compounds WO 2014/009710A1