Architecting\nRobust Full Concentration Gradient NCM712\nCathodes for High-Energy Li-Ion Batteries

Abstract

Full concentration gradient ternary oxide cathodes, with\na Ni-rich\ncore and a Mn-rich surface, have been identified to effectively enhance\ntheir interfacial and structural stability for long-life Li-ion batteries.\nNevertheless, a big challenge is to address the degradient effect\nduring high-temperature lithiation. Herein, we demonstrate the synthesis\nof gradient LiNi_0.70Co_0.10Mn_0.20O₂ cathodes by F-doping and intergranular Li_<i>x</i>W_<i>y</i>O_<i>z</i> coating. The coating layer served as a physical barrier to mitigate\nthe interdiffusion of transition metal ions during grain boundary\nmerging. Meanwhile, the doped F ions, occupying the O sites, can further\nrestrict ion transfer to inner primary particles by the formation\nof extremely strong M–F bonds. Accordingly, the resultant gradient\ncathodes deliver a high reversible capacity of 211.2 mAh g^–1 at 0.1C in coin-type half-cells. A superior cycling stability is\nachieved with a high capacity retention of 93.0% at 1C after 500 cycles\nwithin 2.7–4.5 V in pouch-type full cells. This work provides\na reliable technical route to obtain high-energy Li-ion batteries\nby the design of high-voltage concentration gradient Ni-rich cathodes.