An integrated strategy of surface coating and dual-element doping to enhance electrochemical performances of Li-rich layered oxide for lithium-ion batteries

Li-rich oxides are one kind of promising cathodes for the advanced lithium-ion batteries owing to ultrahigh specific discharge capacity and low cost. Whereas, their high energy density stemmed from oxygen anion redox easily triggers irreversible phase transition and oxygen release, simultaneously companied with low initial Coulombic efficiency, rapid capacity degradation and poor cycling stability. Herein, an integrated strategy of Li 0.35 La 0.55 TiO 3 (LLTO) coating and Ti 4+ /La 3+ dual-element doping is introduced to improve the electrochemical performances of Li 1.2 Mn 0.56 Ni 0.17 Co 0.07 O 2 (LMNCO) via facile sol-gel method and annealing treatment. Various characterizations including in-situ XRD and DEMS demonstrate that LLTO coating can accelerate Li + diffusion and alleviate side reactions at cathode-electrolyte interface, meanwhile Ti 4+ /La 3+ -doping can stabilize lattice oxygen and restrain oxygen release in the charge-discharge process. Electrochemical test results manifest that the LLTO-modified LMNCO cathode exhibits excellent rate property and long-term cycling stability, e.g. , a discharge capacity of 153.6 mAh g −1  at 5C, and a superior capacity retention of 83 % after 400 cycles at 1C. This work presents one simple strategy for the modification of Li-rich material to rationally utilize TM cationic and oxygen anionic redox reactions, and to promote the electrochemical performance and structure stability of layered-structure cathode in long-term cycling even under elevated temperature.