Exploring damping effect of oxygen vacancies for lithium-rich layered cathode cycling at high rate

Abstract

Lithium-rich manganese-based oxide (LRMO) cathode has emerged as a particularly promising candidate for achieving high energy densities in lithium-ion batteries due to its capability to access anion redox reactions at high voltage. The successful implementation of LRMO in energy storage systems is contingent upon the enhancement of their rate capabilities. However, the underlying relationship between high-rate cycling and electrode degradation for LRMO, particularly concerning structural evolution, still remains unclear. Benefiting from the high time resolution abilities of liquid-metal-jet operando two-dimensional X-ray diffraction, it is observed that the Li₂MnO₃ phase in LRMO is gradually activated accompanied by the emergence of oxygen vacancies during cycling at 1 C (1 C = 250 mA/g). Consequently, the crystal lattice flexibility of LRMO is systematically enhanced, thereby preventing the collapse of the bulk structure. While, continuous release of oxygen during extended cycling results in deteriorations of the self-adjusting damping effect of the structure, ultimately leading to a decline in capacity. The findings of this study not only contribute to a more profound understanding of the structural changes of LRMOs at high rates, but also provide novel perspectives for the rational design of LRMOs with superior rate performances.