First-principles theory of cation and intercalation ordering in LixCoO2

Several types of cation- and vacancy-ordering are of interest in the LixCoO2 battery cathode material since they can have a profound effect on the battery voltage. We present a first-principles theoretical approach which can be used to calculate both cation- and vacancy-ordering patterns at both zero and finite temperatures. This theory also provides quantum-mechanical predictions (i.e., without the use of any experimental input) of battery voltages of both ordered and disordered LixCoO2/Li cells from the energetics of the Li intercalation reactions. Our calculations allow us to search the entire configurational space to predict the lowest-energy ground-state structures, search for large voltage cathodes, explore metastable low-energy states, and extend our calculations to finite temperatures, thereby searching for order–disorder transitions and states of partial disorder. We present the first prediction of the stable spinel structure LiCo2O4 for the 50% delithiated Li0.5CoO2.