In situ generated spinel-phase skin on layered Li-rich short nanorods as cathode materials for lithium-ion batteries

As main electrochemical power sources for portable electronic devices, lithium-ion batteries (LIBs) restricted by cathode materials should be further developed for the application in electric vehicles. Despite the restrictions of low Coulombic efficiency and serious voltage fading, high-capacity Li-rich layered oxides with high voltage are still attractive cathode materials for high-energy-density LIBs. Here, spinel-phase skin is in situ generated on Fe-containing Li-rich short nanorods by employing a direct hydrothermal method. The rational design of morphology and structure features is beneficial for the removal and embedding of lithium ions. Two-dimensional nanorod structure can greatly shorten the pathway length of Li-ion diffusion and electron transport, increase the interface area between the electrode and electrolyte, and provide more free space for Li-ion storage and transmission. Large porosity between short nanorods is conducive to the penetration and infiltration of the electrolyte. Moreover, the ultrathin spinel marginal nanolayer (~ 3 nm) can provide 3D diffusion channels for Li+ ions transportation due to its fast kinetics. Good electrochemical performances are exhibited by controlling the concentration of lithium source (LiOH·H2O). Owning to this unique structure and morphology design, the prepared compound delivers a high discharge specific capacity of 247.5 mAh g−1 at 20 mA g−1 and a good rate capability. The first Coulombic efficiency and voltage fading issue are also significantly improved. These Li-rich short nanorods with spinel-phase skin are considered promising as cathode materials for LIBs.