Using Synchrotron Based X-ray Absorption and Diffraction to Study Electrolyte and Cathode Materials for Lithium Batteries

摘要

1. Using a commercial available LiCoO_2 as starting material, surface modified cathode material was obtained by coating amorphous Al_2O_3. Specific capacity of 190mAh/g can been achieved with excellent capacity retention when a cell Li/Al_2O_3-coated LiCoO_2 was cycled between 3.2V and 4.5V. 2. The in situ XRD studies presented here provide important information about the difference between the structural changes of the Al_2O_3-coated and the pristine LiCoO_2 during high voltage cycling. It is the surface of the LiCoO_2, not the bulk structural changes, holding the key to solve the problem of capacity fading of LiCoO_2 during high voltage cycling. 3. In order to improve the capacity retention, one should try to preserve the variation range of the lattice parameters when cycling between the two voltage limits, not to suppress it. The Al_2O_3 surface coating used in this study is quite effective in this aspect.