Roles of Fast‐Ion Conductor LiTaO3 Modifying Ni‐rich Cathode Material for Li‐Ion Batteries

Abstract 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. Ni‐rich LiNi 0.9 Co 0.06 Mn 0.04 O 2 layered cathode was modified with different amounts of LiTaO 3 , and the influences of fast‐ion conductor material on cathode materials were explored. 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 increased 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+ increased 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 ions, have adverse effects on electrochemical performances. This finding may help to understand the roles of the coating layer better.