Abstract

I will present results on our work on developing high voltage, high capacity cathodes for Mg-ion batteries and the emergent charges which arise in Ising Kagome lattices. Divalent Mg-ion batteries offer an attractive alternative to Li-ion batteries due to the increased capacity offered by cycling a divalent cation and possibility of using a Mg metal anode. Despite demonstration of reversible cycling in the molybdenum sulphide chevrel phase over 15 years ago¹, improvements have been slow and limiting factors include the lack of a suitable electrolyte and challenges associated with intercalation of Mg2+ at high voltages and multiple electron redox on an individual ions. I will present out results on pyro-, MgxM2-xB2O5 and orthoborates, MgxM3-x(BO3)2 M = Mn,Fe,Co,Ni and discuss the role of disorder between Mg and M sites, and the crystal structure on the observed electrochemical properties[2,3]. I will then discuss the novel emergent charge order in Ising Kagome magnets. These are predicted to show formation of a number of exotic states on cooling, which differ significantly from their three-dimensional analogue, spin-ice. I will show how 3:1 ordering in pyrochlores, A3A .B3B.O14, can be used to generate undistorted Kagome lattices and present results on the Ising system Dy3Mg2Sb3O14. Bulk thermodynamic properties measurements, diffuse scattering and monte-carlo simulations will be used to demonstrate the existence of emergent charges below T* ~ 100 mK⁴.

1 Aurbach et al Nature, 407, 724 (2000) 2 Glass et al. Chemistry of Materials, 29(7), 3118 (2017) 3 Glass et al. in preparation 4 Paddison et al. Nature Communications, 7, 13842 (2016)