Optimizing the electrochemical performance of LiCoO2 at 4.5 V via synergistic modification of Mg2+ ion doping and Li1.3La0.3Ti1.7(PO4)3 coating

Abstract Increasing the operating voltage can significantly increase the energy density of LiCoO 2 , but it is accompanied by severe structural damage and interface degradation. Especially at a high voltage above 4.5 V, LiCoO 2 faces severe challenges, such as irreversible phase transition, lattice oxygen loss, and electrode–electrolyte interface evolution. Herein, a high-voltage LiCoO 2 cathode material with bulk doping and surface coating synergistic modification was designed and prepared. The doped Mg 2+ ions entered the lithium layers as pillars, stabilizing the layered framework. Meanwhile, Li 1.3 La 0.3 Ti 1.7 (PO 4 ) 3 was uniformly coated on the surface of LiCoO 2 , which is beneficial for suppressing Co 3+/2+ ion leaching and interface side reactions during cycling. Furthermore, Li 1.3 La 0.3 Ti 1.7 (PO 4 ) 3 is a fast ion conductor, which facilitates the rapid transport of lithium ions on the surface of the cathode material. Owing to the synergistic effect of Mg 2+ ion doping and Li 1.3 La 0.3 Ti 1.7 (PO 4 ) 3 coating, the orbitals of Co 3d and O 2p in LiCoO 2 crystal are changed, and the irreversible phase transition and oxygen loss are inhibited. The modified material exhibited an excellent electrochemical performance. A discharge capacity of 175.5 mAh·g −1 at 10 C rate, as well as a capacity retention of 90.14% after 200 cycles at 1 C rate, was achieved in the modified material. This work supplies a new method for developing high-voltage oxide cathodes through bulk and interfacial modification.