Developing high-efficiency dual-functional catalysts to promote oxygen electrode reactions is critical for achieving high-performance aprotic lithium–oxygen (Li–O2) batteries. Herein, Sr and Fe cation-codoped LaCoO3 perovskite (La0.8Sr0.2Co0.8Fe0.2O3−σ, LSCFO) porous nanoparticles are fabricated as promising electrocatalysts for Li–O2 cells. The results demonstrate that the LSCFO-based Li–O2 batteries exhibit an extremely low overpotential of 0.32 V, ultrahigh specific capacity of 26 833 mA h g–1, and superior long-term cycling stability (200 cycles at 300 mA g–1). These prominent performances can be partially attributed to the existence of abundant coordination unsaturated sites caused by oxygen vacancies in LSCFO. Most importantly, density functional theory (DFT) calculations reveal that codoping of Sr and Fe cations in LaCoO3 results in the increased covalency of Co 3d–O 2p bonds and the transition of Co3+ from an ordinary low-spin state to an intermediate-spin state, eventually resulting in the transformation from nonconductor LCO to metallic LSCFO. In addition, based on the theoretical calculations, it is found that the inherent adsorption capability of LSCFO toward the LiO2 intermediate is reduced due to the increased covalency of Co 3d–O 2p bonds, leading to the formation of large granule-like Li2O2, which can be effectively decomposed on the LSCFO surface during the charging process. Notably, this work demonstrates a unique insight into the design of advanced perovskite oxide catalysts via adjusting the covalency of transition-metal–oxygen bonds for high-performance metal–air batteries.

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In order to not change the space vector pulse width modulation (SVPWM) control strategy during one phase fault, the five-phase six-bridge arm SVPWM fault tolerant control method for fifteen-phase permanent magnet synchronous motor (PMSM) is proposed in this paper, and the thermal stress of fifteen-phase PMSM under different fault-tolerant operations is analyzed. Firstly, the control model of the fifteen-phase PMSM based on three dq axes is established, the generation mode of the SVPWM is analyzed, and the speed and current loop PI regulators of the control system are designed. Secondly, the fault-tolerant control principle of the five-phase six-bridge arm is analyzed and compared with the hysteresis control strategy of equal amplitude and minimum stator loss. Thirdly, the 3D model of the fifteen-phase PMSM is established, the steady-state temperature and the transient temperature rise considering operating conditions under different fault tolerant operations are analyzed, and corresponding temperature rise results of the stator armature windings are compared separately. Finally, the experimental platform is established, the phase current waveforms tested under load conditions confirm the theoretical analysis of five-phase six-bridge arms and hysteresis control, and the test results of steady-state and transient temperature rise confirm the correctness of the simulation prediction.

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ultimately increasing the charge transfer resistance. [8] During the OER process, the insulated Li 2 O 2 can only be decomposed at high overpotential, which can trigger severe parasitic reactions. [9][10][11] Therefore, exploring efficient bifunctional electrocatalysts and understanding the formation and decomposition mechanism of Li 2 O 2 is of great significance for effectively reducing ORR and OER overpotential and improving the electrochemical performance of LOBs.Currently, two types of mechanisms (solution-mediated pathway and surface adsorption pathway) were commonly recommended to explain the deposition process of Li 2 O 2 on the electrode surface during ORR. Different mechanisms lead to various structure (crystallinity or defect) and morphology (toroid or thin film) of Li 2 O 2 , eventually determining the battery performance. [12] For the solution-mediated pathway, disproportionation reaction of dissolved intermediate LiO 2 usually forms a large-size toroid-like Li 2 O 2 , resulting in a large discharge capacity but a high charge overpotential which is due to the limited contact between large-size discharge products and electrode surface. [3,12] For the surface adsorption pathway, electrode surface shows strong adsorption toward intermediate LiO 2 , finally leading to the deposition of thin film-like amorphous Li 2 O 2 on the oxygen electrode. The thin film-like Li 2 O 2 is in close contact with electrode, which is beneficial to reduce the charging overpotential. However, film-like discharge product will deliver a small discharge capacity because of the quickly passivated electrode surface. [13] As a result, designing porous oxygen electrodes with tuned adsorption capacity towards O-containing intermediates is essential for LOBs with both large discharge capacity and small charge overpotential. Generally, regulating the heterogeneous interfaces in the catalytic materials to realize the electronic modulation through interfacial coupling has proved to be an effective strategy for optimizing the chemical adsorption of the O-containing intermediates and accelerating the kinetics of oxygen electrode reactions. [14][15][16] Specifically, to achieve the thermodynamic equilibrium state, two regions of opposing charge distribution and a built-in electric field will be created at the interface of the heterostructure, where the strong charge region can modulate the adsorption of reactant, while the built-in Lithium-oxygen batteries (LOBs) with ultra-high theoretical energy density (≈3500 Wh kg −1 ) are considered as the most promising energy storage systems. However, the sluggish kinetics during the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) can induce large voltage hysteresis, inferior roundtrip efficiency and unsatisfactory cyclic stability. Herein, hydrangea-like NiO@Ni 2 P heterogeneous microspheres are elaborately designed as high-efficiency oxygen electrodes for LOBs. Benefitting from the interfacial electron redistribution on NiO@Ni 2 P heterostructure, the electronic structure can b...

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Summary The present study aims to examine fruit cell wall‐associated fruit softening in Lycium barbarum L. by the microstructure of the fruit cells and the changes in the contents of cell wall components, molecular weights of cell wall polysaccharides and the activities of related cell wall degrading enzymes at different development stages of L. barbarum L. fruit. Fruit firmness significantly declined during ripening, with the greatest reduction between the 28 and 35 days stages. The decrease in firmness correlated with an extensively deformed microstructure in the parenchyma tissues and positively correlated with reductions in the contents of fruit cell wall materials and molecular weight in cell wall polysaccharide. Cellulase, α‐galactosidase, polygalactosidase and pectin methylesterase showed higher activities during 28 days; whereas, the activities of β‐galactosidase were higher during 35 days. These results indicate that cell wall‐related processes are a key feature of early softening in L. barbarum L.