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

Area of Science:

• Materials Science
• Electrochemistry
• Energy Storage

Background:

• Magnesium hydride (MgH2) shows potential as a conversion-type anode for lithium-ion batteries.
• A key challenge for MgH2 anodes is achieving high reversible capacity during electrochemical cycling.
• Existing MgH2 anodes suffer from poor cycling stability and performance limitations.

Purpose of the Study:

• To develop and investigate a novel mixed metal hydride-oxide conversion-type anode for lithium-ion batteries.
• To evaluate the electrochemical performance, cycling capability, and reversibility of the new composite anode.
• To assess the compatibility of the designed composite electrode with a solid-state electrolyte.

Main Methods:

• Fabrication of 75MgH2·25CoO composite anodes using optimized mixing conditions, avoiding high-energy ball-milling reactions.
• Electrochemical testing to analyze cycling performance, reversibility, and discharge-charge hysteresis.
• Electron microscopy and X-ray photoelectron spectroscopy (XPS) for material characterization and compatibility assessment.

Main Results:

• The 75MgH2·25CoO composite electrode formed a stable single-plateau nanocomposite structure after cycling.
• The composite anode exhibited higher reversibility yield, reduced discharge-charge hysteresis, and mitigated kinetic effects at high C-rates compared to pure MgH2 anodes.
• Electron microscopy and XPS confirmed the good preservation and compatibility of the composite electrode with LiBH4 solid electrolyte.

Conclusions:

• The electrochemical co-existence of MgH2 and CoO in a composite anode significantly improves lithium-ion battery performance.
• Reduced diffusion pathways and less polarized electrodes are attributed to the enhanced properties of the composite.
• The developed MgH2-CoO composite anode demonstrates suitability for solid-state lithium-ion batteries.