Chemical delithiation, thermal transformations and electrochemical behaviour of iron-substituted lithium nickelate

摘要

Chemical deintercalation in Fe-substituted lithium nickelate and its effects on the thermal stability and electrochemical behaviour are studied. A sample with Fe:Ni ratio of 1:9 was used as the starting material. Chemical deintercalation of the ceramic product was achieved by acid treatment with 0.6 M aqueous hydrochloric acid solutions at room temperature. The atomic Fe:Ni ratio remained unaffected while the Li: (Fe+Ni) ratio decreased significantly down to ca. 0.5 after acid treatment. Infrared spectroscopy was used to discard a proton exchange side reaction. The initial open circuit voltage (OCV) of non-aqueous electrolyte lithium cells using the chemically deintercalated solids was ca. 3.7 V, while 3.0 V went obtained with the pristine oxide. Heat treating the deintercalated solids lead to oxygen evolution at 230°C with the formation of spinel rock-salt structure solids at 600°C. The improved thermal stability as compared with iron-free lithium nickelate is an interesting factor for battery safety.