Endowing Cobalt-Free Li-Rich Li1.2Ni0.2Mn0.6O2 with Superior Electrochemical Performance via Simultaneous Surface Coating and Ion Co-Doping

The commercialization of the layered Li-rich materials as one of the promising cathode materials to provide high energy density still suffers from low initial Coulombic efficiency, rapid capacity loss, and voltage degradation of the materials. To overcome the intrinsic drawbacks of the materials, herein, a multifunctional modification strategy involving surface coating along with ion codoping is proposed. It is revealed that the codoping of the Ti4+ and PO43+ ions achieved during high-temperature calcination can synergistically stabilize the crystal structure and enlarge the crystal lattice of cobalt-free Li1.2Ni0.2Mn0.6O2, consequently enhancing the electrochemical stability and rate capability of the materials. As a result, with optimized modification, the material exhibits excellent initial charge/discharge capacity of 346.1/298.7 mAh·g–1 and cycling stability with capacity retention of 90.0% after 300 cycles at 1 C. The surface LiTi2(PO4)3 coating can reduce the decomposition of the electrolyte and stabilize the electrode/electrolyte interface during cycling, which contributes to the improvement of the cycling performance of the materials. Furthermore, the multifunctional modification to the materials can efficiently prevent the materials from the irreversible crystal phase conversion and crack formation upon cycling, to maintain the integrity of the materials. The strategy might be beneficial to the design of the layered Li-rich material.