Faculty Sponsor's Department(s):
Lithium (Li) ion batteries that function by intercalation exhibit excellent performance as electrochemical energy storage for portable electronics and electric vehicles. Some disadvantages include high cost, toxicity, and limited storage capacity of less than one mole of Li per formula unit mass. We investigate conversion systems based on elemental sulfur as alternatives for next-generation secondary batteries in view of its lower cost and higher abundance. Li–S batteries promise a considerably higher storage capacity than intercalation Li-ion systems. To design an improved material for conversion batteries, various transition metal sulfide cathode materials are prepared. The cathode materials consist of a transition metal to be readily reduced and oxidized in the cell; binary and ternary compounds are synthesized, including CoS2, FeS2, and CuTi2S4. To synthesize our sulfur-based cathode materials, the elements are mixed, pressed into bar pellets and sealed in silica tubes. We carry out conventional solid-state preparation, which consists of multiple heating steps, each lasting five to seven days. We introduce an efficient and quick microwave-assisted heating as an alternative that significantly decreases preparation time for these compounds. Phase purity as well as particle size and morphology of the transition metal sulfides are confirmed through Powder X-Ray Diffraction (PXRD) and Scanning Electron Microscopy (SEM), respectively. Subsequently, batteries are assembled with prepared materials as the cathode with a liquid electrolyte. Electrochemical cycling is investigated by constant current cycling. We present a novel, rapid microwave-assisted preparation for transition metal sulfides of interest as alternative battery materials.