Doping LiNiCoMnO (NCM523) cathode material by small amount of Mo ions, around 1 mol %, affects pronouncedly its structure, surface properties, and electronic and electrochemical behavior. Cathodes comprising Mo-doped NCM523 exhibited in Li cells higher specific capacities, higher rate capabilities, lower capacity fading, and lower charge-transfer resistance that relates to a more stable electrode/solution interface due to doping. This, in turn, is ascribed to the fact that the Mo ions tend to concentrate more at the surface, as a result of a synthesis that always includes a necessary calcination, high-temperature stage. This phenomenon of the Mo dopant segregation at the surface in NCM523 material was discovered in the present work for the first time. It appears that Mo doping reduces the reactivity of the Ni-rich NCM cathode materials toward the standard electrolyte solutions of Li-ion batteries. Using density functional theory (DFT) calculations, we showed that Mo ions are preferably incorporated at Ni sites and that the doping increases the amount of Ni ions at the expense of Ni ions, due to charge compensation, in accord with X-ray absorption fine structure (XAFS) spectroscopy measurements. Furthermore, DFT calculations predicted Ni-O bond length distributions in good agreement with the XAFS results, supporting a model of partial substitution of Ni sites by molybdenum.

Li-rich electrode materials of the family xLi 2 MnO 3 •(1-x)LiNi a Co b Mn c O 2 (a + b + c = 1) suffer a voltage fade upon cycling that limits their utilization in commercial batteries despite their extremely high discharge capacity, ca. 250 mAhg -1 . We exposed Li-rich, 0.35Li 2 MnO 3 •0.65LiNi 0.35 Mn 0.45 Co 0.20 O 2 , to NH 3 at 400 °C , producing materials with improved characteristics: enhanced electrode capacity and a limited average voltage fade during 100 cycles in half cells vs. Li. We established three main changes caused by NH 3 treatment. First, a general bulk reduction of Co and Mn was observed via XPS and XANES. Next, a structural rearrangement lowered the coordination number of Co-O and Mn-O bonds, as well as formation of a surface spinel-like structure. Additionally, Li + removal from the bulk causes the formation of surface LiOH, Li 2 CO 3 , and Li 2 O. These structural and surface changes can enhance the voltage and capacity stability of the Li-rich material electrodes after moderate NH 3treatment times of 1 -2 hours.

In this work, carbon-supported cobalt monoxides with an average size of 3.5, 4.9, and 6.5 nm are synthesized via a facile colloidal method avoiding any surfactants of long chains. Along with controlling the CoO particle size, we investigate the dependence of ORR activity on particle size of the CoO/C composite. It is discovered that the turnover frequency of the ORR per CoO site is largely independent of the particle size in the range of 3–7 nm, and the enhanced ORR activity for the smaller CoO particles is attributed to the enlarged interface between CoO and carbon