title: Na2CoSiO4as a cathode material for sodium-ion batteries: structure, electrochemistry and diffusion pathways.
abstract: 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, Na2CoSiO4, 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 Na2CoSiO4have been investigated with the compound found to yield a reversible capacity greater than 100 mA h g-1at a rate of 5 mA g-1. Insights into the crystal structures of Na2CoSiO4were 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 Na2CoSiO4as a cathode for Na-ion batteries can be based.
authors.affiliation: Sharp Laboratories of Europe Ltd., Oxford Science Park, Oxford, OX4 4GB, UK. emma.kendrick@sharp.co.uk.
authors.forename: Joshua C
authors.initials: JC
authors.lastname: Treacher
authors.affiliation: Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. m.s.islam@bath.ac.uk.
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Wood
authors.affiliation: Department of Chemistry, University of Bath, Bath, BA2 7AY, UK. m.s.islam@bath.ac.uk.
authors.forename: M Saiful
authors.initials: MS
authors.lastname: Islam
authors.affiliation: Sharp Laboratories of Europe Ltd., Oxford Science Park, Oxford, OX4 4GB, UK. emma.kendrick@sharp.co.uk and School of Chemistry, University of Birmingham, Birmingham, B15 2TT, UK.
authors.forename: Emma
authors.initials: E
authors.lastname: Kendrick