Role of Ordered Ni Atoms in Li Layers for Li‐Rich Layered Cathode Materials

Abstract

Li‐rich layered oxide materials are promising candidates for high‐energy Li‐ion batteries. They show high capacities of over 200 mAh g−1 with the additional occupation of Li in their transition metal layers; however, the poor cycle performance induced by an irreversible phase transition limits their use in practical applications. In recent work, an atomic‐scale modified surface, in which Ni is ordered at 2c sites in the Li layers, significantly improves the performance in terms of reversible capacity and cycling stability. The role of the incorporated Ni on this performance, however, is not yet clearly understood. Here, the effects of the ordered Ni on Li battery performance are presented, based on first‐principles calculations and experimental observations. The Ni substitution suppresses the oxygen loss by moderating the oxidation of oxygen ions during the delithiation process and forms bonds with adjacent oxygen after the first deintercalation of Li ions. These NiO bonds contribute to the formation of a solid surface, resulting in the improved cycling stability. Moreover, the multivalent Ni suppresses Mn migration to the Li‐sites that causes the undesired phase transition. These findings from theoretical calculations and experimental observations provide insights to enhance the electrochemical performance of Li‐rich layered oxides.

First-principles study of Mn antisite defect in Li 2 MnO 3

“…Figure 3(a) is the total DOS of Li 2 MnO 3 with and without a Mn Li in Li/TM layer. Similar to the previous theoretical results of defect-free Li 2 MnO 3 [16,18], the states near the top of the valence band are almost contributed by O 2p orbitals and the e g orbitals of Mn are unoccupied, which is the typical electronic structure of the Mn 4+ ion at octahedral sites (see top panel of figure 3(a)). For the Mn Li -Li 2 MnO 3 , the e g orbitals of Mn are partly occupied, indicating the presence of Mn ions with a valence below +4.…”

Sodium Doping to Enhance Electrochemical Performance of Overlithiated Oxide Cathode Materials for Li-Ion Batteries via Li/Na Ion-Exchange Method

“…The SOLO sample has a stronger ability to transfer ions, so it has better electrochemical performance than the POLO sample. 3,47,48 In our previous study, 16 due to the high content of sodium, it exists in the material in the form of secondary phase of Na 0.7 MO 2.05 . And, partial sodium de-intercalates preferentially during first charge, and the rest of the sodium ions remain stable in the structure in subsequent cycles.…”

Large-Scale Fabrication of Egg-Carton-Inspired Bi/C Composite toward High Volumetric Capacity and Long-Life Lithium Ion Batteries

“…The specific surface area and the total pore volume decreased upon increasing the carbonization temperature, indicating that Bi nanoparticles become more tightly packed under higher temperature. The tap density of Bi/C-500, Bi/C-700, and Bi/C-1000 is 0.87, 0.99, and 1.07 g/cm 3 , respectively. As shown in Figure S5 (SI), Bi/C-1000 shows the lowest volume at the same mass among three samples, which is in good agreement with the SEM images and BET results.…”