Characterization and electrochemical performance of lithium-active titanium dioxide inlaid LiNi0.5Co0.2Mn0.3O2 material prepared by lithium residue-assisted method

The lithium residues are consumed as raw materials to in-situ synthesize the LiTiO2-inlaid LiNi0.5Co0.2Mn0.3O2 composites. The effects of various LiTiO2 contents on the morphology, structure, and electrochemical properties of LiNi0.5Co0.2Mn0.3O2 materials are investigated in detail. Energy dispersive spectrometer mapping, high-resolution transmission electron microscopy and fast Fourier transform analysis confirm that the spherical particles of LiNi0.5Co0.2Mn0.3O2 are completely coated by crystalline LiTiO2 phase; X-ray diffraction, cross-section SEM and corresponding EDS results indicate that Ti ions are also doped into the bulk LiNi0.5Co0.2Mn0.3O2 with gradient distribution. Electrochemical tests show that the LiTiO2-inlaid samples exhibit excellent reversible capacity, enhanced cyclability, superior lithium diffusion coefficient and rate properties. Specially, the 3 mol% LiTiO2 inlaid sample maintains 153.7 mA h g−1 with 94.4% capacity retention after 100 cycles between 2.7-4.4 V at 1 C, take 30% advantage than that of the pristine one (118.2 mA h g−1). This improvement can be attributed to the removal of lithium residues and suitable LiTiO2 inlaying. The absence of lithium residue is helpful to retard the decomposition of LiPF6. While, suitable LiTiO2 inlaying can protect the bulk from directly contacting the electrolyte, buffer the volume change of core and shell during cycles, increase the surface electronic conductivity and offer a 3D path for Li+ diffusion from the bulk to interface.