Realizing the Embedded Growth of Large LiO Aggregations by Matching Different Metal Oxides for High-Capacity and High-Rate Lithium Oxygen Batteries.

Large LiO aggregations can produce high-capacity of lithium oxygen (Li-O) batteries, but the larger ones usually lead to less-efficient contact between LiO and electrode materials. Herein, a hierarchical cathode architecture based on different discharge characteristics of α-MnO and CoO is constructed, which can enable the embedded growth of large LiO aggregations to solve this problem. Through experimental observations and first-principle calculations, it is found that α-MnO nanorod tends to form uniform LiO particles due to its preferential Li adsorption and similar LiO adsorption energies of different crystal faces, whereas CoO nanosheet tends to simultaneously generate LiO film and LiO nanosheets due to its preferential O adsorption and different LiO adsorption energies of varied crystal faces. Thus, the composite cathode architecture in which CoO nanosheets are grown on α-MnO nanorods can exhibit extraordinary synergetic effects, i.e., α-MnO nanorods provide the initial nucleation sites for LiO deposition while CoO nanosheets provide dissolved LiO to promote the subsequent growth of LiO. Consequently, the composite cathode achieves the embedded growth of large LiO aggregations and thus exhibits significantly improved specific capacity, rate capability, and cyclic stability compared with the single metal oxide electrode.