Roles of fast-ion conductor LiTaO3 modifying Ni-rich cathode material for Li-ion batteries.

Limited cycling stability hampers the commercial application of Ni-rich materials, which are regarded as one of the most promising cathode materials for Li-ion batteries. We modified Ni-rich LiNi 0.9 Co 0.06 Mn 0.04 O 2 layered cathode with different amounts of LiTaO 3 and explored the influences of fast-ion conductor material on cathode materials. Detailed analysis of the materials revealed the formation of a uniformly epitaxial LiTaO 3 coating layer and a little Ta 5+ doping into the lattice structure of Ni-rich materials. The coating-layer thickness increases with the amount of LiTaO 3 added, protecting the electrode from erosion by electrolyte and suppressing undesired parasitic reactions on the cathode-electrolyte interface. Meanwhile, the doped Ta 5+ increases the interplanar spacing of materials, accelerating Li + transfer. Using the positive synergistic effects of LiTaO 3 -coating and Ta 5+ -doping, improved capacity retentions of the modified materials, especially for 0.25 and 0.5 wt% coated Ni-rich materials, were obtained after long-term cycling, showing the potential applications of LiTaO 3 modification. Further, the relations between one excessively thick coating layer and transfer of Li + /electron between the cathode and electrolyte was established, proving that very thick coating layers, even layers containing Li-ion, have adverse effects on electrochemical performances. This finding may help us to understand the roles of the coating layer better.