The decay mechanism related to structural and morphological evolution in Li-rich cathode materials for Li-ion batteries.

Li-rich oxides have garnered intense interest recently for their excellent capacity in rechargeable lithium-ion batteries (LIBs). However, poor cycling stability and capacity degradation during the cycling process impede their practical application. Herein, two ball-shaped cobalt-free oxide materials, Li1.1Mg0.05Ni0.3Mn0.55O2 and Li1.1Zn0.05Ni0.3Mn0.55O2, which exhibit excellent cycling performance at a high current between 2 V and 4.8 V, are demonstrated. The two Li-rich materials are prepared from hydrothermally synthesized carbonated precursors. Both oxides exhibit high reversible capacities of 237 and 231 mAh g(-1) at 20 mA g(-1), respectively, originating from the redox of Ni2+/Ni4+ and O2-/(O-2)(n-). Li1.1Mg0.05Ni0.3Mn0.55O2 presents excellent cycling stability after 200 cycles with 90 % capacity retention. Studies of the structural evolution upon electrochemical cycling implies the cathodes undergo a volume expansion, which results in continuous expanding, cracking, and crushing of the spherical particles, which further induces capacity fading in the cathodes.