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

Abstract

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 ≈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.

Oxygen Vacancy Modulation towards High‐Performance Layered Oxide Cathodes for Lithium/Sodium‐Ion Batteries

“…[20] Han's group proposed that Vo reduced the energy level and the number of unhybridized O 2p states, which effectively delayed the oxygen-redox behaviors and inhibited the oxygen loss. [21] The inhibitory effect of Vo on oxygen release was also reported by Liu and co-workers, who found that Vo could tune the d-d Coulombic interactions (terms U) in Li 1.2 Mn 0.6 Ni 0.2 O 2-δ through a small amount of Mn 3 + (Figure 3a). [22] The decreased U prevented more oxygen escape and ensured the reversible anionic redox reaction.…”

“…demonstrated that Vo shortened the TM‐O bond lengths in P2‐Na 0.7 Mn 0.75 Ni 0.25 O 2 , resulting in strong ionic character of TM‐O bonds and thus improving the structural stability [20] . Han's group proposed that Vo reduced the energy level and the number of unhybridized O 2 p states, which effectively delayed the oxygen‐redox behaviors and inhibited the oxygen loss [21] . The inhibitory effect of Vo on oxygen release was also reported by Liu and co‐workers, who found that Vo could tune the d ‐ d Coulombic interactions (terms U ) in Li 1.2 Mn 0.6 Ni 0.2 O 2‐δ through a small amount of Mn 3+ (Figure 3a).…”

Engineering built-in electric fields in oxygen-deficient MnO-CeO2@Cs catalysts: enhanced performance and kinetics for the oxygen reduction reaction in aqueous/flexible zinc–air batteries

“…1c displays the electron paramagnetic resonance (EPR) spectra of the samples, with peak intensity positively correlated with the oxygen vacancy content ( g = 2.002). 31 Remarkably, MnO@Cs exhibits the highest concentration of oxygen vacancies, attributable to the formation of vacancies during the oxidation with potassium permanganate and calcination processes. Conversely, CeO 2 @Cs displays the lowest concentration of oxygen vacancies, possibly due to the loading of Ce species stabilizing the lattice structure of CeO 2 .…”

High Entropy-Induced Kinetics Improvement and Phase Transition Suppression in K-Ion Battery Layered Cathodes

“…It is obvious that the bandgap of HE-KMO is reduced, which is expected to enhance the electronic conduction and electrochemical performance of HE-KMO. 27,28 Based on the partial DOS of HE-KMO, shown in Figure 1b, Mn 3d, Ni 3d, Fe 3d, Co 3d, and Cu 3d electron densities imply that these TMs can participate in the charge compensation due to the electron occupation near Fermi energy, while Ti and Mg are inactive. Additionally, the electronic structures of Mn 3d in HE-KMO (Figure 1b) is obviously different from that of Mn 3d in KMO (Figure 1c), suggesting that multielement doping in high-entropy oxides can modulate the electronic structure of both overall material and specific atoms in layered oxide cathodes.…”