New Materials for Mg-ion batteries - Mn3O4 as cathode

Abstract

Due to drawbacks with the lithium ion battery technology, magnesium ion batteries are being researched as an alternative replacement system. An optimal combination of component materials has however not been discovered yet. This thesis investigates the unexplored Mn3O4 as a cathode material. A commercial powder was studied, and performance was determined for both pure Mn3O4 and powder subjected to simple treatments first. The treatments were milling and mixing with reduced graphene oxide. Mixing with reduced graphene oxide resulted in the highest performance, i.e. 78 mAh/g. Through charge-discharge cycling of cathodes with active mass between 1 and 2.7 mg, an active mass dependency on the capacity output was found. Long term cycling proved that the batteries can withstand 500 cycles, with no sign of failure. A rate dependency was also discovered, where it was found to occur more oxidation than reduction at low rates, owed to oxidation of the electrolyte solvent, THF. Ex situ study of cathodes, using SEM, XRD and TEM, revealed that Mg-ions attach on the cathode through a surface reaction during discharge.