RESUMEN
In cases involving high levels of sulfur loading or high levels of current discharge, constructing sulfur composite cathodes via traditional coating preparation processes is an unsuitable way to overcome intractable problems relating to cathodes for use in lithium-sulfur batteries, such as poor conductivity, severe volume expansion, and the detrimental shuttle effect. Herein, a novel three-dimensional self-supported TiO2@C membrane with hierarchical interlinked porosity and oxygen vacancies was prepared via a phase-inversion method to act as a sulfur host. The procured TiO2-x@C membrane facilitates the infiltration of electrolyte, provides fast lithium-ion and electron transport channels and abundant sulfur loading sites, and shows superb structural buffering against the large volume changes during the conversion process between sulfur and lithium sulfide. More importantly, the introduction of oxygen vacancies not only enhances the conductivity of the original TiO2, but it also improves the corresponding adsorption abilities toward polysulfides and the subsequent transformation dynamics. Therefore, the TiO2-x@C membrane can significantly inhibit the polysulfide shuttle effect through polar chemisorption and conversion catalysis. Based on the above superiorities, the TiO2-x@C/S membrane electrode exhibits an impressive lifespan of more than 500 cycles at 2 C with a prominent ultimate specific discharge capacity of 715.2 mA h g-1.
RESUMEN
Lithium-sulfur (Li-S) batteries face a few vital issues, including poor conductivity, severe volume expansion/contraction, and especially the detrimental shuttle effect during the long-term electrochemical process. Herein, we designed a hierarchical MXene@TiO2 nanoarray via in situ solvothermal strategies followed by heat treatment. The MXene@TiO2 heterostructure achieves superior charge transfer and sulfur encapsulation. Based on the polar-polar and Lewis acid-base mechanism, the robust dual chemisorption capability to trap polysulfides can be synergistically realized through the intense polarity of TiO2 and the abundant acid metal sites of MXene. Hence, the MXene@TiO2 nanoarray as a sulfur host retains a substantially stable discharge capacity of 612.7 mA h g-1 after 500 cycles at a rate of 2 C, which represents a low fading rate of 0.058% per cycle.
RESUMEN
Nowadays, the development of advanced anode materials is highly desirable for the increasing demand for high-performance lithium-ion batteries (LIBs). Nanostructured MnO2 has received utmost attention due to high theoretical capacity (1230â mA h g-1 ), abundant resources, environmental benignity, and shortened electron and ion diffusion paths. Unfortunately, poor electronic conductivity and strong aggregation inclination of MnO2 nanostructures result in disappointing electrochemical performances, which restrict their practical application as sole institute. Here, we propose smartly designed MnO2 @Fe3 O4 /CNT hybrid films, in which MnO2 nanosheets, Fe3 O4 nanoparticles and CNTs are hierarchically assembled in a unique stage of nanosheets-nanoparticles-nanotubes. The resulting MnO2 @Fe3 O4 /CNT hybrid films can be directly used as anodes without any polymer binders, and exhibit significant synergistic interactions among three components, achieving excellent reversible capacity and rate performance.
