Synthesis and reversible lithium storage of Cr_2O_5 as a new high energy density cathode material for rechargeable lithium batteries

摘要

Chromium trioxide is calcined from 350 to 400 ℃ yielding pure Cr_2O_5. The electrochemical properties of the resulting chromium oxides have been measured in the potential range 2.0-4.5 V (vs. Li~+/Li) when used in lithium batteries. The first discharge process, the intercalation of lithium into Cr_2O_5, proceeds via two steps. In the following cycles, lithium is found to be reversibly de-lithiated/lithiated via a solid solution process with an un-known single phase Li_xCr_2O_5 (u-phase) characterized by an X-ray diffractive lattice spacing of about 0.20 nm. The sample that results from chromium trioxide being calcined at 350 ℃ shows the highest capacity of 273 mAh g~(-1) (the first discharge at 0.5 C rate) and the sample calcined at 400 ℃ shows the best cyclability with the capacity retention of 96% after 100 cycles. The energy density of Cr_2O_5 can reach 819 Wh kg~(-1) with the energy conversion efficiency of 83%.