The design of high voltage and high capacity cathode materials for lithium ion batteries is important for the pressing demands of both electric vehicles and portable devices. Lithium excess layered oxides, where the lithium-to-transition metal ratio is greater than 1, have been widely explored due to the possibility of utilizing more than 1 lithium in the chemical formula unit to significantly increase the capacity. Despite much research, commercial application of the lithium excess material has been impeded due to low initial coulombic efficiency, poor cycle life, voltage fade, and poor rate performance. These deficiencies have mainly been attributed to the complicated structural evolution and the formation of a cathode solid electrolyte interface (SEI) layer at higher voltages (>4.5V). Therefore, the role of surface modification on improving the electrochemical properties has been investigated by Wildcat.

The use of chemical treatments and post-annealing steps to induce the formation of a surface spinel structure prior to electrochemical cycling can improve the first cycle coulombic efficiency and rate performance. However, further improvements in the first cycle coulombic efficiency and cycle life of these materials are still required. This work investigates several families of surface coatings and compositional dopants in lithium rich layered oxides.  Modification of the surface coating and addition of dopants can greatly enhance the first cycle coulombic efficiency while also maintaining or improving cycle stability, voltage fade, and rate performance of the lithium excess material. Wildcat evaluation of the performance of hundreds of surface coatings and dopants shows that certain families tend to improve all metrics. In addition we have demonstrated that certain families, such as metal phosphate and metal fluoride coatings, reduce gas generation during the first cycle as well as subsequent cycles relative to the pristine lithium excess material.