Surface modulation induced oxygen vacancies/stacking faults and spinel-carbon composite coatings toward high-performance Li-rich Mn-based cathode

Lithium-rich manganese-based cathode (LRM) is considered to be the most promising cathode materials for next-generation lithium-ion batteries due to its high energy density. However, the low initial coulombic efficiency and poor rate performance are severe problems in the commercialization of LRM. Herein, we use an ascorbic acid (VC) modulation strategy to create spinel-carbon composite coatings and dual defects (oxygen vacancies, stack faults) on the surface of LRM. The composite surface coating and defects play a synergistic role in inhibiting interfacial side reactions, enhancing structural stability, and improving electrical conductivity as well as lithium-ion diffusion kinetics. As a result, the modified LRMs exhibit a specific capacity of 251.7mAh/g with an improved initial coulombic efficiency (ICE) of 82.3 % (pristine 72.9 %), enhanced rate capability (135 mAh/g at 5C), and long-term cyclability of 90 % retention after 200 cycles compared with the pristine (78 % retention after 200 cycles). The performance improvement of the modified LRMs is attributable to the composite coating and the dual defects, which ensure the LRM with a more stable structure (smaller volume change of 2.4 % compared with the original sample of 3.65 %). This strategy provides an efficient and environmentally friendly idea of surface modification for boosting the electrochemical performance.