Modulating Mn⁴⁺ Ions and Oxygen Vacancies in Nonstoichiometric LaMnO3 Perovskite by a Facile Sol-Gel Method as High-Performance Supercapacitor Electrodes

A series of LaMn1±xO3 perovskite (x = 0, 0.05, 0.1) has been synthesized via a facile sol–gel method and applied as supercapacitor electrodes. The morphology, phase structure, composition, chemical states of constituents and electrochemical properties are investigated. As a result, all the LaMn1±xO3 samples revealed a single mesoporous phase of perovskite with typical pore sizes from 2 to 5 nm. The nonstoichiometric LaMn1.1O3 sample showed much higher specific capacity (202.1 mAhg−1/727.6 Cg−1 at 1 Ag−1) than stoichiometric LaMnO3 perovskite (114.4 mAhg−1/411.8 Cg−1 at 1 Ag−1). Detailed chemical analysis demonstrated that the presence of point defects such as oxygen and cation vacancies, and a high Mn4+/Mn3+ ratio contributed to the excellent electrochemical performance. Furthermore, the cycle stability analyses of the LaMn1±xO3 perovskite revealed that LaMn1.1O3 manifested an exceptionally high rate capability. These results prove that nonstoichiometric LaMn1.1O3 can be a promising material for supercapacitor electrodes.