Abstract
Lithium-sulfur (Li-S) batteries have received enormous interest as a promising energy storage system to compete against limited, non-renewable, energy sources due to their high energy density, sustainability, and low cost. Among the main challenges of this technology, researchers are concentrating on reducing the well-known “shuttle effect” that generates the loss and corrosion of the active material during cycling. To tackle this issue, metal-organic frameworks (MOF) are considered excellent sulfur host materials to be part of the cathode in Li-S batteries, showing efficient confinement of undesirable polysulfides. In this study, MIL-88A, based on iron fumarate, was synthesised by a simple and fast ultrasonic-assisted probe method. Techniques such as X-ray diffraction (XRD), Raman spectroscopy, Thermogravimetric Analysis (TGA), Scanning Electron Microscopy (SEM), and N2 adsorption/desorption isotherms were used to characterise structural, morphological, and textural properties. The synthesis process led to MIL-88A particles with a central prismatic portion and pyramidal terminal portions, which exhibited a dual micro-mesoporous MOF system. The composite MIL-88A@S was prepared, by a typical melt-diffusion method at 155 °C, as a cathodic material for Li-S cells. MIL-88A@S electrodes were tested under several rates, exhibiting stable specific capacity values above 400 mAh g−1 at 0.1 C (1C = 1675 mA g−1). This polyhedral and porous MIL-88A was found to be an effective cathode material for long cycling in Li-S cells, retaining a reversible capacity above 300 mAh g−1 at 0.5 C for more than 1000 cycles, and exhibiting excellent coulombic efficiency.
Highlights
The current energy economy based on the demand for non-renewable sources, such as fossil fuels and oil, continues to be a high-risk social problem
Despite the various problems that still present, these two attractive systems exceed the initial expectations of them evolving rapidly, improving the efficiency and achieving high performances, which could lead to these devices to their possible implantation in the development of renewable energy sources, electric vehicles and modern electronics [9,10,11]
Li-S batteries are at the forefront in the development of efficient and sustainable high energy systems receiving great interest in recent years [12]
Summary
The current energy economy based on the demand for non-renewable sources, such as fossil fuels and oil, continues to be a high-risk social problem. Li-S batteries are at the forefront in the development of efficient and sustainable high energy systems receiving great interest in recent years [12] These types of batteries consist of a sulfur cathode, a lithium metal anode, and a polymeric or liquid electrolyte, and are based on the following electrochemical reaction: 16 Li + S8 8 Li2S [13,14]. MIL88-A has been considered as an electronic semiconductor material showing this ability for electronic conduction in photocatalytic [49] or in microbial reduction processes [50] Some investigations of this material have already been reported in the field of Li-ion batteries, showing highly promising performances and improvements in electrochemical activity due to its high porosity which allows greater contact surface between electrode-electrolyte and an increase in the number of active reaction sites [51,52,53,54]. The resulting composite is considered a promising candidate as a cathode in Li-S batteries, showing remarkable electrochemical performances, especially during long-cycle testing
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