Zhang Peng, Zhang Shoufeng, He Mu, Lang Junwei, Ren Aimin, Xu Shan, Yan Xingbin
Laboratory of Clean Energy Chemistry and Materials State Key Laboratory of Solid Lubrication Lanzhou Institute of Chemical Physics Chinese Academy of Sciences Lanzhou 730000 P. R. China.
University of Chinese Academy of Sciences Beijing 100039 P. R. China.
Adv Sci (Weinh). 2017 Jul 20;4(11):1700172. doi: 10.1002/advs.201700172. eCollection 2017 Nov.
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.
大尺寸的LiO聚集体能够产生高容量的锂氧（Li - O）电池，但尺寸较大的聚集体通常会导致LiO与电极材料之间的接触效率降低。在此，基于α - MnO和CoO的不同放电特性构建了一种分级阴极结构，该结构能够使大尺寸LiO聚集体进行嵌入式生长以解决这一问题。通过实验观察和第一性原理计算发现，α - MnO纳米棒由于其优先吸附Li以及不同晶面具有相似的LiO吸附能，倾向于形成均匀的LiO颗粒，而CoO纳米片由于其优先吸附O以及不同晶面具有不同的LiO吸附能，倾向于同时生成LiO薄膜和LiO纳米片。因此，CoO纳米片生长在α - MnO纳米棒上的复合阴极结构能够展现出非凡的协同效应，即α - MnO纳米棒为LiO沉积提供初始成核位点，而CoO纳米片提供溶解的LiO以促进LiO的后续生长。结果，该复合阴极实现了大尺寸LiO聚集体的嵌入式生长，因此与单一金属氧化物电极相比，展现出显著提高的比容量、倍率性能和循环稳定性。
