Na2CoSiO4 as a cathode material for sodium-ion batteries: structure, electrochemistry and diffusion pathwaysElectronic supplementary information (ESI) available. See DOI: 10.1039/c6cp06777h

• Main Authors: Treacher, Joshua C, Wood, Stephen M, Islam, M. Saiful, Kendrick, Emma
• Format: Article
• Language: English
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c6cp06777h

The importance of developing new low-cost and safe cathodes for large-scale sodium batteries has led to recent interest in silicate compounds. A novel cobalt orthosilicate, Na 2 CoSiO 4 , shows promise as a high voltage (3.3 V vs. Na/Na + ) cathode material for sodium-ion batteries. Here, the synthesis and room temperature electrochemical performance of Na 2 CoSiO 4 have been investigated with the compound found to yield a reversible capacity greater than 100 mA h g −1 at a rate of 5 mA g −1 . Insights into the crystal structures of Na 2 CoSiO 4 were obtained through refinement of structural models for its two polymorphs, Pn and Pbca . Atomistic modelling results indicate that intrinsic defect levels are not significant and that Na + diffusion follows 3D pathways with low activation barriers, which suggest favourable electrode kinetics. The new findings presented here provide a platform on which future optimisation of Na 2 CoSiO 4 as a cathode for Na-ion batteries can be based. A novel cobalt orthosilicate, Na 2 CoSiO 4 , shows promise as a high voltage (3.3 V vs. Na/Na + ) cathode material for sodium-ion batteries.