Structure and Primary Particle Double-tuning by Trace Nano-TiO2 for High-performance LiNiO2 Cathode Material
The elevation of energy density is the constant pursuit for Lithium-ion battery industry. LiNiO2 reacquires recognition because of its high capacity without raising the cut-off voltages. To address the flaws of this kind of cathodes, trace nano-TiO2 modified LiNiO2 is synthesized via a simple solid-state method. Combined with the characterizations, the Ti element is verified to dope into the bulk lattice and locate in the transition-metal sites. After Ti doping, the Ni2+ content is visibly increased due to charge balance, followed by the elevated degree of Li/Ni disorder. The doped Ti and as-generated Ni pillar jointly help to stabilize the material structure and benefit the Li+ de/insertion. The nanosized TiO2 participating in the calcination process can effectively homogenize the size of primary particle, adjust the surface morphology and reduce the specific surface area of material. This morphological regulation may be in favor of reducing the contact area with electrolyte and establishing a stable electrode/electrolyte interface, where some detrimental side-reactions take place. As to electrochemical properties, Ti doping can decrease the electrode polarization, lower the impedance and promote the Li+ transfer. As a result, the Ti-modified LiNiO2 cathodes present enhanced electrochemical performances, especially for the 0.2% Ti-doped (Ti-2) material.