Tensile-strained Mxene/carbon nanotube (CNT) porous microspheres were developed as an electrocatalyst for the lithium polysulfide (LiPS) redoxr eaction. The internal stress on the surface results in lattice distortion with expanding TiÀTi bonds,e ndowing the Mxene nanosheet with abundant active sites and regulating the d-band center of Ti atoms upshifted closer to the Fermi level, leading to strengthened LiPS adsorbability and accelerated catalytic conversion. The macroporous framework offers uniformed sulfur distribution, potent sulfur immobilization, and large surface area. The composite interwoven by CNT tentacle enhances conductivity and prevents the restacking of Mxene sheets.This combination of tensile strain effect and hierarchical architecture design results in smooth and favorable trapping-diffusion-conversion of LiPS on the interface.T he Li-S battery exhibits an initial capacity of 1451 mAh g À1 at 0.2 C, rate capability up to 8C,and prolonged cycle life.
Lithium-sulfur (Li-S) batteries present one of the most promising energy storage systems owing to their high energy density and low cost. However, the commercialization of Li-S batteries is still hindered by several technical issues; the notorious polysulfide shuttling and sluggish sulfur conversion kinetics. In this work, unique hierarchical Fe 3-x C@C hollow microspheres as an advanced sulfur immobilizer and promoter for enabling high-efficiency Li-S batteries is developed. The porous hollow architecture not only accommodates the volume variation upon the lithiation-delithiation processes, but also exposes vast active interfaces for facilitated sulfur redox reactions. Meanwhile, the mesoporous carbon coating establishes a highly conductive network for fast electron transportation. More importantly, the defective Fe 3-x C nanosized subunits impose strong LiPS adsorption and catalyzation, enabling fast and durable sulfur electrochemistry. Attributed to these structural superiorities, the obtained sulfur electrodes exhibit excellent electrochemical performance, i.e., high areal capacity of 5.6 mAh cm -2 , rate capability up to 5 C, and stable cycling over 1000 cycles with a low capacity fading rate of 0.04% per cycle at 1 C, demonstrating great promise in the development of practical Li-S batteries.
Over the past decade, lithium−sulfur (Li−S) batteries have been thought of as promising alternatives for the new generation of battery systems. Although the Li−S batteries possess high-theoretical energy density (2600 Wh kg −1 ) and capacity (1675 mAh g −1 ), the problems of poor electron and ion conduction, volumetric expansion, and sulfur immobilization greatly impede the wide applicability of Li−S batteries. Herein, a defect-rich multishelled Co 3 O 4 microsphere structure doped with Fe was synthesized via a one-step hydrothermal method and subsequent thermal treatment. The unique multishelled structure provides multiple spatial confinements for lithium polysulfides trapping and buffering the volume variation during cycling. Moreover, the rich oxygen defect designed by controlled Fe doping can provide numerous catalytic sites for polysulfide redox reactions. Attributed to the synergistic effect of structural design and oxygen-defect fabrication, the sulfur composite electrode delivers a notable cycle performance, presenting a much lower capacity fading of 0.017% per cycle over 1000 cycles at 1 C and an excellent rate capability of 571.3 mAh g −1 at 5 C. This work proposes a potential approach for designing a transition metal oxide-based multishelled hollow structure combined with oxygen defect, which also offers a new perspective on high-performance Li−S batteries.
Lithium–sulfur
(Li–S) batteries hold great promise
for next-generation electronics owing to their high theoretical energy
density, low cost, and eco-friendliness. Nevertheless, the practical
implementation of Li–S batteries is hindered by the shuttle
effect and sluggish reaction kinetics of polysulfides. Herein, the
spray drying and chemical etching strategies are implemented to fabricate
hierarchically porous MXene microspheres as a multifunctional sulfur
electrocatalyst. The interconnected skeleton offers uniform sulfur
distribution and prevents the restacking of MXene sheets, while the
abundant edges endow the nanosheet-like Ti3C2 with rich active sites and regulated a d-band center of Ti atoms,
leading to strong lithium polysulfide (LiPS) adsorption. The unsaturated
Ti on edge sites can further act as multifunctional sites for chemically
anchoring LiPS and lowering Li-ion migration barriers, accelerating
LiPS conversion. Owing to these structural advantages, excellent cycling
and rate performances of the sulfur cathode can be obtained, even
under a raised sulfur loading and lean electrolyte content.
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