Li‐rich oxides can be regarded as the next‐generation cathode materials for high‐energy‐density Li‐ion batteries since additional oxygen redox activities greatly increase output energy density. However, the oxygen loss and structural distortion induce low initial coulombic efficiency and severe decay of cycle performance, further hindering their industrial applications. Herein, the representative layered Li‐rich cathode material, Li1.2Ni0.2Mn0.6O2, is endowed with novel single‐crystal morphology. In comparison to its polycrystal counterpart, not only can serious oxygen release be effectively restrained during the first oxygen activation process, but also the layered/spinel phase transition can be well suppressed upon cycling. Moreover, the single‐crystal cathode exhibits the limited volume change and persistent presence of superlattice peaks upon Li+ (de)intercalation processes, resulting in enhanced structural stability with absence of crack generation and successive utilization of oxygen redox reaction during long‐term cycling. Benefiting from these unique features, the single‐crystal Li‐rich electrode not only yields a high reversible capacity of 257 mAh g−1, but also achieves excellent cycling performance with 92% capacity retention after 200 cycles. These findings demonstrate that the morphology design of single crystals can be regarded as an effective strategy to realize high‐energy density and long‐life Li‐ion batteries.

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Cu-doped ZnO nanorods have been grown at 90°C for 90 min onto a quartz substrate pre-coated with a ZnO seed layer using a hydrothermal method. The influence of copper (Cu) precursor and concentration on the structural, morphological, and optical properties of ZnO nanorods was investigated. X-ray diffraction analysis revealed that the nanorods grown are highly crystalline with a hexagonal wurtzite crystal structure grown along the c-axis. The lattice strain is found to be compressive for all samples, where a minimum compressive strain of −0.114% was obtained when 1 at.% Cu was added from Cu(NO3)2. Scanning electron microscopy was used to investigate morphologies and the diameters of the grown nanorods. The morphological properties of the Cu-doped ZnO nanorods were influenced significantly by the presence of Cu impurities. Near-band edge (NBE) and a broad blue-green emission bands at around 378 and 545 nm, respectively, were observed in the photoluminescence spectra for all samples. The transmittance characteristics showed a slight increase in the visible range, where the total transmittance increased from approximately 80% for the nanorods doped with Cu(CH3COO)2 to approximately 90% for the nanorods that were doped with Cu(NO3)2.

Compared with the polycrystal (PC) Ni-rich cathode materials, the single-crystal (SC) counterpart displayed excellent structural stability, high reversible capacity and limited voltage decay during cycling, which received great attention from academics and industry. However, the origin of fascinating high-voltage stability within SC is poorly understood yet. Herein, we tracked the evolution of phase transitions, in which the destructive volume change and H3 phase formation presented in PC, are effectively suppressed in SC when cycling at a high cut-off voltage of 4.6 V, further clarifying the origin of high-voltage stability in SC cathode. Moreover, SC electrode displayed crack-free morphology, and excellent electrochemical stability during long-term cycling, whereas PC suffered severe capacity and voltage fade because of the spinel-like phase, decoding the failure mechanisms of PC and SC during cycling at high cut-off voltages. This finding provides universal insights into high-voltage stability and failure mechanisms of layered Ni-rich cathode materials.