On the incorporation of fluorine into the manganese spinel cathode lattice

A series of spinel oxy-fluorides with the formula LiMn1.8Li0.1Ni0.1O4 − ηFη have been synthesized by both the conventional high-temperature (800 °C) firing method with LiF and a low temperature (450 °C) firing process with NH4HF2. Interestingly, the samples obtained by the high temperature (800 °C) procedure show no fluorine in the sample as revealed by the chemical analysis data, but an increase in lattice parameter and capacity values was observed due to a decrease in lithium content caused by the volatilization of LiF during the high temperature (800 °C) firing process. In contrast, the low-temperature fluorine doping approach was successful in incorporating fluorine into the spinel lattice, and the sample LiMn1.8Li0.1Ni0.1O3.85F0.15 exhibits a significant increase in discharge capacity compared to the oxide analog.