Li/Cr0.5Nb1.5(PO4)3 secondary batteries: further characterization and influence of macro-structural modifications on the cathode performance

This paper reports on the investigation of cathode material, which is of interest for the development of secondary (rechargeable) lithium batteries with improved characteristics and performances. Li/Cr0.5Nb1.5(PO4)3 cells have been compared with analogous cells such as Cr0.5Nb1.5(SO4)3 and Cr2(SO4)3 cathodes in our recent study. The results have demonstrated that this Cr0.5Nb1.5(PO4)3 cathode can be ranked among the cathode materials studied as it was more tolerant to repeated lithium insertion and extraction and exhibited capacity retention. This has encouraged attempts aimed at improving the electrochemical properties of Cr0.5Nb1.5(PO4)3 with particular attention being paid to the influence of discharge current, effect of charge current rate on cycle life of a rechargeable lithium battery and investigating a lower cut-off voltage till 0.5 V versus Li. None of these attempts led to realizing improved performance and our studies on these factors were not highly successful. On the other hand, the mixing technique for cathode preparation led to the realization of a good host but only for the first cycle, and was not suitable for repeated cycling. A significant improvement in cell performance was obtained with the stability of PTFE as a cathode binder in lithium batteries.