IN-SITU X-RAY DIFFRACTION OF LAYERED LiCoO_2-TYPE CATHODE MATERIALS

摘要

We have investigated LiNi_(0.8)Co_(0.2)O_2 (Sumitomo) and LiNi_(5/8)Co_(1/4)Mn_(1/16)Al_(1/16)O_2 (Sandia chemical preparation method) cathode powders via in-situ X-ray Diffraction and Cyclic Voltammetry using a "coffee-bag" type electrochemical cell. Both cathode materials did not show a monoclinic distortion during de-intercalation but sustained the hexagonal structure up to 4.3 V. The doping of Co into the LiNiO_2 structure appears to stabilize this lattice as the hexagonal structure over the full range of charging (up to 4.3 V). The LiNi_(5/8)Co_(1/4)Mn_(1/16)Al_(1/16)O_2 cathode material exhibited a 160 mAh/g capacity (to 4.1 V) on its 1~(st) cycle, while displayed a much smaller volume change (as compared to LiNi_(0.8)Co_(0.2)O_2) during de-intercalation. This reduced overall volume change (2.5 vol%) may have important implications for cycle life of this material.