NaCrO2 has been studied lately as a promising cathode material for Na-ion batteries. Consequently, this study was conducted to investigate how... Show moreNaCrO2 has been studied lately as a promising cathode material for Na-ion batteries. Consequently, this study was conducted to investigate how high-energy ball milling before the high temperature reaction influences the synthesis reaction and electrochemical performance of NaCrO2 cathodes for Na-ion batteries. In-situ synchrotron X-ray diffractometry is employed for the first time to provide a comprehensive understanding of the critical reaction temperatures and reaction pathway. It is found that high-energy ball milling at room temperature can result in significant changes in the synthesis reaction of NaCrO2 when compared to reactants without high-energy ball milling. These changes include a decreased onset temperature for the formation of O3-NaCrO2, an increased reaction kinetics, an alternation of the reaction pathway, and a complete reaction at 900℃ to form thermally-stable O3-NaCrO2 phase. In contrast, without high-energy ball milling the reaction product at 900℃ is a highly impure NaCrO2 with a poor thermal stability. Equally important, it is found that mechanical activation enhances the bulk ionic conductivity as well as the conductivity at the interface of NaCrO2 particles; moreover, high-energy ball milling before reaction can lead to higher specific discharge capacities of NaCrO2 half cells and contribute to the best capacity retention over 50 cycles among all the reported NaCrO2 without coatings. All these improvements of NaCrO2 cathodes for Na-ion batteries are ascribed to the mechanical activation induced by high-energy ball milling before high temperature reaction. Show less
