Carbon skeleton materials derived from rare earth phthalocyanines (MPcs) (M = Yb, La) used as high performance anode materials for lithium-ion batteries

Abstract

In this work, novel carbon skeleton materials were prepared by high-temperature carbonization of rare earth phthalocyanines (MPcs) (M = Yb, La) under a nitrogen atmosphere. The resulting carbon materials of YbPc-900 (carbonisation temperature of 900 °C for 2 h) and LaPc-1000 (carbonization temperature of 1000 °C for 2 h) have a graphite-layered structure in predominantly ordered states, with a smaller particle size, a larger specific surface area and a higher degree of hard carbonization compared to those of the uncarbonized sample. As a result, the batteries using the YbPc-900 and LaPc-1000 carbon skeleton materials as electrodes display excellent energy storage behaviors. The initial capacities of the YbPc-900 and LaPc-1000 electrodes at 0.05 A g⁻¹ were 1100 and 850 mA h g⁻¹, respectively. After 245 cycles and 223 cycles, the capacities remain at 780 and 716 mA h g⁻¹ with retention ratios of 71% and 84%. At a high rate of 1.0 A g⁻¹, the initial capacities of the YbPc-900 and LaPc-1000 electrodes were 400 and 520 mA h g⁻¹, respectively, and after 300 cycles, the capacities can still remain at 526 and 587 mA h g⁻¹ with retention ratios of 131.5% and 112.8%, respectively, which were much higher than those of the pristine rare earth phthalocyanine (MPc) (M = Yb, La) electrodes. Moreover, better rate capabilities were also observed during the YbPc-900 and LaPc-1000 electrode tests. The capacities of the YbPc-900 electrode at 0.05, 0.1, 0.2, 0.5, 1 and 2C were 520, 450, 407, 350, 300 and 260 mA h g⁻¹ respectively, which were higher than those of the YbPc electrode (550, 450, 330, 150, 90 and 40 mA h g⁻¹). Similarly, the rate performance of the LaPc-1000 electrode at different rates was also significantly improved compared to that of the pristine LaPc electrode. In addition, the initial Coulomb efficiencies of the YbPc-900 and LaPc-1000 electrodes were also greatly improved compared to those of pristine YbPc and LaPc electrodes. After carbonization, the YbPc-900 and LaPc-1000 carbon skeleton materials derived from rare earth phthalocyanines (MPcs) (M = Yb, La) exhibit improved energy storage behaviors, which would provide new ideas for developing novel organic carbon skeleton negative materials for lithium ion batteries.