Microwave-Assisted Accelerated Synthesis of High-Capacity Lithium- Manganese- Rich Cathode Materials for Solid-State Batteries

Layered Lithium Nickel-Manganese-Cobalt oxides are a type of cathode materials used in high-performance lithium batteries. They have the potential of delivering high energy densities of up to 900 - 1,000 Wh/kg, benefiting portable consumer electronics as well as electric vehicles. The ratio between the three transition elements varies, and the Manganese-rich type is chosen here as this type of material can achieve the aforementioned level of energy density, also because of that Cobalt is a known carcinogen while high Nickel concentrations result in thermal instability. Traditional synthesis routes of such materials generally include a hydrothermal co-precipitation step, precipitating the Mn, Ni, and Co precursors into insoluble hydroxide or carbonate intermediates, generally taking > 12 hours. A unique microwave-assisted solvo-thermal process is proposed and tested, which significantly reduced the intermediate processing time to 1 hour or less. The intermediate products and final products are characterized to verify their compositions and micro-structures. The pristine products are tested in lithium-metal batteries to evaluate their actual electrochemical performance. Such pristine cathodes had been tested with Garnet-type solid-state electrolyte and lithium-metal anode preliminarily. Additionally, since the performance of pristine layered materials may suffer from capacity fading due to reasons such as the attacking of fluorinated species in liquid electrolyte or the stress-induced cracking, oxide modification layers have been applied to the cathode materials utilizing the microwave process to speed up the coating process. Preliminary results show improvement in capacity fading performance over pristine ones.