MICROWAVE-ASSISTED SOL-GEL SYNTHESIS OF SODIUM-BASED LAYERED OXIDE CATHODE MATERIALS FOR HIGH-PERFORMANCE SODIUM-ION BATTERIES

Abstract

Layered oxide cathode materials are of great interest in sodium-ion batteries due to their high theoretical capacity, availability, low cost, and environmentally benign raw materials. This work compares the structural, thermal, and electrochemical properties of Na1Ni0.33Mn0.33Fe0.33O2 (NNMF), an O3-type layered oxide material developed using a conventional solid-state synthesis route and a facile microwave-assisted sol-gel synthesis technique. Structural characterization techniques confirm phase purity, high crystallinity, and formation of the desired crystal structure. Thermal analysis (TGA) demonstrates superior thermal stability. At the same time, galvanostatic charge/discharge, CV, GITT, PITT etc. tests confirm that the electrochemical performance of the cathode material is comparable to the same cathode material produced through the conventional sintering process. PITT analysis demonstrates that the intercalation/deintercalation of Na+ into/from the host structure occurs through a single-phase rather than a biphasic reaction. High phase purity, good crystallinity, improved thermal stability, comparable electrochemical performance, and cost-effectiveness of the Na1Ni0.33Mn0.33Fe0.33O2 developed by microwave-assisted sol-gel method make it attractive for commercial applications. By adapting the optimized microwave sintering route, successful synthesis needed to be investigated for the binary system O3-type Na1Mn0.5 Fe0.5O2- NMFO and the single component system of NaFeO2 materials phase purity, high crystallinity, and formation of the desired crystal structure by various structural characterization technique. Furthermore, the electrochemical performance of NNMF and NFO materials is yet to be investigated as a future aspect of this work. Moreover, the proposed synthesis route can also be applied to other families of cathode materials to develop at a competitive cost.