Characterization and electrochemical performance of lithium-active titanium dioxide inlaid LiNi_0.5Co_0.2Mn_0.3O₂ material prepared by lithium residue-assisted method

Highlights: • LiTiO₂-inlaid LiNi_0.5Co_0.2Mn_0.3O₂ is prepared by lithium residue-assisted method. • The unique inlaid architecture inherits the advantages of coating and doping. • LiTiO₂ inlaying enhances the pristine at high cyclability and rate properties. • Excess LiTiO₂ modification results in low Li⁺ diffusion coefficient. • The 3 mol% LiTiO₂ inlaid sample exhibits the best electrochemical performance. - Abstract: The lithium residues are consumed as raw materials to in-situ synthesize the LiTiO₂-inlaid LiNi_0.5Co_0.2Mn_0.3O₂ composites. The effects of various LiTiO₂ contents on the morphology, structure, and electrochemical properties of LiNi_0.5Co_0.2Mn_0.3O₂ 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 LiNi_0.5Co_0.2Mn_0.3O₂ 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 LiNi_0.5Co_0.2Mn_0.3O₂ 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