MgH₂-CoO: a conversion-type composite electrode for LiBH₄-based all-solid-state lithium ion batteries

Several studies have demonstrated that MgH₂ is a promising conversion-type anode toward Li. A major obstacle is the reversible capacity during cycling. Electrochemical co-existence of a mixed metal hydride-oxide conversion type anode is demonstrated for lithium ion batteries using a solid-state electrolyte. 75MgH₂·25CoO anodes are obtained from optimized mixing conditions avoiding reactions occurring during high-energy ball-milling. Electrochemical tests are carried out to investigate the cycling capability and reversibility of the on-going conversion reactions. The cycling led to formation of a single-plateau nanocomposite electrode with higher reversibility yield, lowered discharge-charge hysteresis and mitigated kinetic effect at high C-rate compared to MgH₂ anodes. It is believed that reduced diffusion pathways and less polarized electrodes are the origin of the improved properties. The designed composite-electrode shows good preservation and suitability with LiBH₄ solid electrolyte as revealed from electron microscopy analyses and X-ray photoelectron spectroscopy.