Structure and primary particle double-tuning by trace nano-TiO2 for a high-performance LiNiO2 cathode material†
The elevation of energy density is the constant pursuit of the lithium-ion battery industry. LiNiO2 has reacquired recognition because it exhibits high capacity without an increase in the cut-off voltages. To address the flaws of this kind of cathodes, herein, trace nano-TiO2-modified LiNiO2 was synthesized via a simple solid-state method. Via combined characterization, the Ti element was verified to be doped into the bulk lattice and located at the transition-metal sites; after Ti doping, the Ni2+ content was clearly increased due to charge balance, followed by an increase in the Li/Ni disorder. The doped Ti and the as-generated Ni pillar mutually facilitated the stabilization of the material structure and benefitted the Li+ de/insertion. Nanosized TiO2 participating in the calcination process could effectively homogenize the size of the primary particles, adjust the surface morphology and reduce the specific surface area of the material. This morphological regulation may be favorable for reducing the contact area of the cathode with the electrolyte and establishing a stable electrode/electrolyte interface, where some detrimental side-reactions take place. With respect to electrochemical properties, Ti doping could decrease the electrode polarization, lower the impedance and promote the Li+ transfer. As a result, the Ti-modified LiNiO2 cathodes, especially the 0.2% Ti-doped (Ti-2) material, presented enhanced electrochemical performances.