A versatile strategy to activate self-sacrificial templated Li2MnO3 by defect engineering toward advanced lithium storage

Abstract

Despite the dazzling theoretical capacity, the devasting electrochemical activity of Li2MnO3 (LMO) caused by the difficult oxidation of Mn4+ impedes its practical application as the lithium-ion battery (LIB) cathode. The efficacious activation of the Li2MnO3 by importing electrochemically active Mn3+ ions or morphological engineering is instrumental to its lithium storage activity and structural integrity upon cycling. Herein, we propose a conceptual strategy with metal-organic frameworks (MOFs) as self-sacrificial templates to prepare oxygen-deficient Li2MnO3 (Ov-LMO) for exalted lithium storage performance. Attributed to optimized morphological features, LMO materials derived from Mn-BDC (H2BDC = 1,4-dicarboxybenzene) delivered superior cycling/rate performances compared with their counterparts derived from Mn-BTC (H3BTC = 1,3,5-benzenetricarboxylicacid) and Mn-PTC (H4PTC = pyromellitic acid). Both experimental and theoretical studies elucidate the efficacious activation of primitive LMO materials toward advanced lithium storage by importing oxygen deficiencies. Impressively, Ov-LMO derived from Mn-BDC (Ov-BDC-LMO) delivered intriguing reversible capacities (179.2 mA h g−1 at 20 mA g−1 after 200 cycles and 100.1 mA h g−1 at 80 mA g−1 after 300 cycles), which can be attributed to the small particle size that shortens pathways for Li+/electron transport, the enhanced redox activity induced by abundant oxygen vacancies, and the optimized electronic configuration that contributes to the faster lithium diffusivity. This work provides insights into the rational design of LMO by morphological and atomic modulation to direct its activation and practical application as an advanced LIB cathode.