Regulating the Unhybridized O 2p Orbitals of High-Performance Li-Rich Mn-Based Layered Oxide Cathode by Gd-Doping Induced Bulk Oxygen Vacancies

Li-rich Mn-based layered oxides (LRLOs) with ultrahigh specific capacities are promising cathode materials for high energy density lithium-ion batteries. Nevertheless, severe irreversible oxygen release, structure degradation, capacity and voltage attenuation hinder their commercialization due to the uncontrollable oxygen redox chemistry originated from unhybridized O 2p orbitals. Herein, a strategy to generate bulk oxygen vacancies is proposed. And bulk oxygen vacancies are constructed by lowering the formation energy of oxygen vacancies in LRLOs via Gd-doping. The energy level and the amount of unhybridized O 2p states are reduced to partly inhibit the oxygen redox activity. Surprisingly, the oxygen redox is not fully activated in the first cycle and is further activated in the second cycle. Moreover, the reduced oxygen redox activity significantly suppresses the oxygen release, lattice volume change, layered-to-spinel phase transition. As a result, the amount of oxygen gas release is reduced from 98.80 to approximate to 0 nmol mg(-1) in the first cycle. Superior cycle stability of 90.4% capacity retention after 300 cycles and small voltage decay of only 1.013 mV per cycle are achieved. This study provides a valuable bulk oxygen vacancies strategy to regulate the unhybridized O 2p orbitals for designing high-performance Li-rich Mn-based layered oxide cathode materials.