Degradation and Structural Evolution ofxLi₂MnO₃·(1–x)LiMn_1/3Ni_1/3Co_1/3O₂during Cycling

In the present work, the electrochemical degradation and structural evolution of x Li 2 MnO 3 ·(1– x )LiMn 1/3 Ni 1/3 Co 1/3 O 2 ( x = 0.3, 0.5, and 0.7) materials and the role of Li 2 MnO 3 component during electrochemical cycling are systematically studied through careful analysis of electrochemical data, ex-situ XRD, and HR-TEM observations. The materials consisting of higher Li 2 MnO 3 content show better cyclic performance with more significant voltage decay compared to that of x Li 2 MnO 3 ·(1– x )LiMn 1/3 Ni 1/3 Co 1/3 O 2 electrodes with low Li 2 MnO 3 content. The electrochemical degradation of x Li 2 MnO 3 ·(1– x )LiMn 1/3 Ni 1/3 Co 1/3 O 2 electrodes upon cycling not only results from the remarkably increase in impedance caused by the damage of the electrode surface, in particular for low Li 2 MnO 3 content; but also arises from structural rearrangement, especially for high Li 2 MnO 3 content. Upon cycling, high Li 2 MnO 3 content in the crystal structure of lithium-rich transition metal oxides can stabilize the electrode\electrolyte interface at high potentials, facilitates the rapid formation of cracks and porosity in the cycled electrodes, and promotes the distortions and breakdown of the original well-layered lattice.