Shmatok Y. Effect of microwave exposure on morphology and electrochemical characteristics of Co- and Mn-containing electrode materials for lithium-ion batteries

The dissertation is devoted to the obtaining of electrode materials (Co3O4, LiCoO2 and LiMn2O) for lithium-ion batteries by means of microwave (MW) heating and investigation of their morphology, composition, structural and electrochemical characteristics. By varying the power of the MW radiation and the duration of its action individually for each of the materials, optimal conditions for the pyrolysis of solid state mixtures and for obtaining of citrate precursors and their subsequent pyrolysis have been determined. It is shown that the duration of corresponding stages of the synthesis with the use of MW heating is much shorter than in the case of the use of conventional thermal heating. It is shown that depending on the synthesis method (MW solid state or MW citric acid aided) and raw materials (carbonates, acetates, oxides, citrates) electrode materials have different morphology and particle size. Electrode materials obtained by means of MW solid state synthesis consist of either highly aggregated submicron particles (Co3O4 and LiMn2O4) or particles of 1-10 μm in size with a low level of aggregation (LiCoO2). When using the MW citric acid aided method, the particles are practically not aggregated, and their size are smaller and vary from ~30 nm for Co3O4 and 50-120 nm for LiMn2O4 to 200-500 nm for LiCoO2. Electrochemical tests show that the better electrochemical performance, including specific capacity, cycling stability and high-rate capability, are characteristic of electrode materials synthesized by the MW citric acid aided route due to their relatively smaller particle size and low aggregation.