Core-double shell sulfur@carbon black nanosphere@oxidized carbon nanosheet composites as the cathode materials for Li-S batteries

Attenuating the Polysulfide Shuttle Mechanism by Separator Coating

Lithium-sulfur batteries have a high energy density but lack cycle stability to reach market maturity. This is mainly due to the polysulfide shuttle mechanism, i. e., the leaching of active material from the cathode into the electrolyte and subsequent side reactions. We demonstrate how to attenuate the polysulfide shuttle by magnetron sputtering molybdenum oxysulfide, manganese oxide, and chromium oxide onto microporous polypropylene separators. The morphology of the amorphous coatings was analyzed by SEM and XRD. Electrochemical cyclization quantified how these coatings improved Coulombic efficiency and cycle stability. These tests were conducted in half cells. We compare the different performances of the different coatings with the known chemical and adsorption properties of the respective coating materials.

Customized Structure Design and Functional Mechanism Analysis of Carbon Spheres for Advanced Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) are attracting much attention due to their high theoretical energy density and are considered to be the predominant competitors for next-generation energy storage systems. The practical commercial application of LSBs is mainly hindered by the severe "shuttle effect" of the lithium polysulfides (LiPSs) and the serious damage of lithium dendrites. Various carbon materials with different characteristics have played an important role in overcoming the above-mentioned problems. Carbon spheres (CSs) are extensively explored to enhance the performance of LSBs owing to their superior structures. The review presents the state-of-the-art advances of CSs for advanced high-energy LSBs, including their preparation strategies and applications in inhibiting the "shuttle effect" of the LiPSs and protecting lithium anodes. The unique restriction effect of CSs on LiPSs is explained from three working mechanisms: physical confinement, chemical interaction, and catalytic conversion. From the perspective of interfacial engineering and 3D structure designing, the protective effect of CSs on the lithium anode is also analyzed. Not only does this review article contain a summary of CSs in LSBs, but also future directions and prospects are discussed. The systematic discussions and suggested directions can enlighten thoughts in the reasonable design of CSs for LSBs in near future.

Polyaniline-grafted hydrolysed polyethylene as a dual functional interlayer/separator for high-performance Li-S@C core-shell batteries

A modified hydrolysed polyethylene with polyaniline was used as a dual functional interlayer/separator for high-performance lithium-sulphur batteries (LSBs) to reduce the migration of soluble polysulphide intermediates. Also, the sulphur cathode was encapsulated with carbon nanoparticles with a S@C core-shell structure using a solvent-free coating process. The chemical interaction between the imine group of the quinoid ring in the PANI structure and the polysulphides reducing the shuttle effect as well as the high electrical conductivity and less volume change of the carbon encapsulated sulphur can provide high-performance Li-S@C core-shell batteries.

A 3D MoS₂/Graphene Microsphere Coated Separator for Excellent Performance Li-S Batteries

Lithium-sulfur (Li-S) batteries are the most prospective energy storage devices. Nevertheless, the poor conductivity of sulfur and the shuttling phenomenon of polysulfides hinder its application. In this paper, flower-like MoS₂/graphene nanocomposite is prepared and deposited on a multi-functional separator to enhance the electrochemical behavior of Li-S batteries. The results demonstrated that the MoS₂/graphene-coated separator is contributing to inhibit the shuttling phenomenon of polysulfides and improve the integrity of sulfur electrode. The initial discharge capacity of the battery using MoS₂/graphene-coated separator at 0.2 C was up to 1516 mAh g⁻¹. After 100 cycles, a reversible capacity of 880 mAh g⁻¹ and a coulombic efficiency of 98.7% were obtained. The improved electrochemical behavior can be due to the nanostructure and Mo-S bond of the MoS₂/graphene composite, which can combine physical shielding and chemisorption to prohibit the shuttle effect of polysulfides. The results prove that the MoS₂/graphene-coated separator has the potential for feasible application in Li-S batteries to enhance their electrochemical performance.

Three-Dimensional Hierarchical Porous Structure of PPy/Porous-Graphene to Encapsulate Polysulfides for Lithium/Sulfur Batteries

Herein, we demonstrate the fabrication of a three-dimensional (3D) polypyrrole-coated-porous graphene (PPy/PG) composite through in-situ polymerization of pyrrole monomer on PG surface. The PPy/PG displays a 3D hierarchical porous structure and the resulting PPy/PG hybrid serves as a conductive trap to lithium polysulfides enhancing the electrochemical performances. Owing to the superior conductivity and peculiar structure, a high initial discharge capacity of 1020 mAh g⁻¹ and the reversible capacity of 802 mAh g⁻¹ over 200 cycles are obtained for the S/PPy/PG cathode at 0.1 C, remaining the remarkable cyclic stability. In addition, the S/PPy/PG cathodes demonstrate an excellent rate performance exhibiting 477 mAh g⁻¹ at 2 C.

Structural Design of Lithium–Sulfur Batteries: From Fundamental Research to Practical Application

Abstract

Lithium–sulfur (Li–S) batteries have been considered as one of the most promising energy storage devices that have the potential to deliver energy densities that supersede that of state-of-the-art lithium ion batteries. Due to their high theoretical energy density and cost-effectiveness, Li–S batteries have received great attention and have made great progress in the last few years. However, the insurmountable gap between fundamental research and practical application is still a major stumbling block that has hindered the commercialization of Li–S batteries. This review provides insight from an engineering point of view to discuss the reasonable structural design and parameters for the application of Li–S batteries. Firstly, a systematic analysis of various parameters (sulfur loading, electrolyte/sulfur (E/S) ratio, discharge capacity, discharge voltage, Li excess percentage, sulfur content, etc.) that influence the gravimetric energy density, volumetric energy density and cost is investigated. Through comparing and analyzing the statistical information collected from recent Li–S publications to find the shortcomings of Li–S technology, we supply potential strategies aimed at addressing the major issues that are still needed to be overcome. Finally, potential future directions and prospects in the engineering of Li–S batteries are discussed.

Graphical Abstract

Chemical Adsorption and Physical Confinement of Polysulfides with the Janus-faced Interlayer for High-performance Lithium-Sulfur Batteries

We design the Janus-like interlayer with two different functional faces for suppressing the shuttle of soluble lithium polysulfides (LPSs) in lithium-sulfur batteries (LSBs). At the front face, the conductive functionalized carbon fiber paper (f-CFP) having oxygen-containing groups i.e., -OH and -COOH on its surface was placed face to face with the sulfur cathode serving as the first barrier accommodating the volume expansion during cycling process and the oxygen-containing groups can also adsorb the soluble LPSs via lithium bonds. At the back face, a crystalline coordination network of [Zn(H₂PO₄)₂(TzH)₂]_n (ZnPTz) was coated on the back side of f-CFP serving as the second barrier retarding the left LPSs passing through the front face via both physical confinement and chemical adsorption (i.e. Li bonding). The LSB using the Janus-like interlayer exhibits a high reversible discharge capacity of 1,416 mAh g⁻¹ at 0.1C with a low capacity fading of 0.05% per cycle, 92% capacity retention after 200 cycles and ca. 100% coulombic efficiency. The fully charged LSB cell can practically supply electricity to a spinning motor with a nominal voltage of 3.0 V for 28 min demonstrating many potential applications.