Issues Of Lithium-sulfur Batteries Research Articles

Effective polysulfide control in lithium–sulfur batteries utilizing BiFeO3 nanoparticles

Lithium–sulfur batteries (LiSBs) offer high energy density, cost-effectiveness, and eco-friendliness, making them promising for future energy storage. This study explores using BiFeO3 (BFO) nanoparticles (NPs) to tackle challenges such as lithium polysulfides (LiPs) and shuttle issues in LiSBs. It employs a solid-state melt diffusion technique, encapsulates sulfur in single-walled carbon nanotubes (SCNTs), and utilizes BFO for effective polysulfide control. Herein, composite cathodes of sulfur (S)/SCNTs (abbr. SCNT) were fabricated, and cells were designed using a BFO-coated separator (SCNT-BFS). In addition, a cathode modification was performed with composite S/SCNTs/BFO (SCNT-BF), and a comparative analysis was conducted to assess the effectiveness of the BFO in the separator and the cathode. Cyclic voltammetry measurements revealed that the increased current peak intensity at lower reduction potential in SCNT-BF and SCNT-BFS indicated control of higher-order LiPs (Li2Sx, where 4 ≤ x ≤ 8), resulting in the generation of more stable lower-order products (Li2S2/Li2S). The charge/discharge analysis revealed controlled LiPs, resulting in high-capacity retention in SCNT-BF (∼75%) and SCNT-BFS (∼88%) over 200 cycles, which yielded capacities of 526 and 700 mAh/g at C/8 (1C = 1675 mA/g). These promising results suggest that incorporating BFO into the cathode and separator can advance the commercialization of durable LiSBs.

Controllable sulfur redox multi-pathway reactions regulated by metal-free electrocatalysts anchored with LiS3* radicals

Regulating sulfur redox kinetics is an effective strategy for addressing the critical issues in lithium-sulfur batteries and improving their comprehensive performance. However, the sluggish and complex sulfur reduction reaction (SRR) kinetics can seriously deteriorate the electrochemical performance of lithium-sulfur batteries, hindering a clear comprehension of the electrocatalytic mechanism and presenting challenges for targeted design. Hence, it is crucial to elucidate the SRR mechanism and further refine the catalytic principle. In this study, the SRR mechanism and the pivotal role of radicals are comprehensively explored using ultrathin nitrogen-oxygen co-doped carbon nanosheets (UN/O-CNS) as an electrocatalytic model, combining density functional theory calculations with experimental techniques, such as X-ray absorption near-edge structure spectroscopy. The abundant N-O active sites of UN/O-CNS can synergistically anchor LiS3* radicals, facilitating efficient multi-pathway sulfur conversion. Additionally, UN/O-CNS can capture and catalyze polysulfides while also bi-directionally catalyzing Li2S. The S@UN/O-CNS cells ultimately demonstrate ultra-long cycling performance and high load capacity. The successful operation in pouch cells validates the practical effectiveness of UN/O-CNS. Overall, this study offers novel insights into the complexity and potential pathways of sulfur redox reaction, providing new perspectives for exploring the catalytic mechanism of cost-effective metal-free electrocatalysts.

Theoretical Calculations Facilitating Catalysis for Advanced Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have emerged as one of the most hopeful alternatives for energy storage systems. However, the commercialization of Li-S batteries is still confronted with enormous hurdles. The poor conductivity of sulfur cathodes induces sluggish redox kinetics. The shuttling of polysulfides incurs the heavy failure of electroactive substances. Tremendous efforts in experiments to seek efficient catalysts have achieved significant success. Unfortunately, the understanding of the underlying catalytic mechanisms is not very detailed due to the complicated multistep conversion reactions in Li-S batteries. In this review, we aim to give valuable insights into the connection between the catalyst activities and the structures based on theoretical calculations, which will lead the catalyst design towards high-performance Li-S batteries. This review first introduces the current advances and issues of Li-S batteries. Then we discuss the electronic structure calculations of catalysts. Besides, the relevant calculations of binding energies and Gibbs free energies are presented. Moreover, we discuss lithium-ion diffusion energy barriers and Li2S decomposition energy barriers. Finally, a Conclusions and Outlook section is provided in this review. It is found that calculations facilitate the understanding of the catalytic conversion mechanisms of sulfur species, accelerating the development of advanced catalysts for Li-S batteries.

Enhanced catalytic activity of Co-CoO via VC0.75 heterostructure enables fast redox kinetics of polysulfides in Lithium-Sulfur batteries

The shuttle effect and sluggish redox kinetics of lithium polysulfides lead to a short lifespan and poor rate capability of lithium-sulfur (Li-S) batteries. Introducing electrocatalysts into sulfur host materials has been deemed a promising strategy to overcome these issues in Li-S batteries. Herein, an efficient catalytic sulfur host material (i.e., VC0.75/Co-CoO) has been fabricated by simply pyrolyzing the electrospun vanadium and cobalt salt-based polymer fibers. Electrochemical measurements demonstrated that the as-formed heterostructure of Co-CoO with VC0.75 evidently strengthens the redox kinetics of polysulfides due to the enhanced adsorption ability to polysulfides and adjusts the electronic structure of heterostructure via the introduction of VC0.75. Further theoretical computation discloses that Co-CoO mainly plays the role in stretching the SS bond in polysulfides to facilitate the reduction of polysulfide, extending the Li-S bond in Li2S and reducing energy barriers of Li2S decomposition to promote the oxidation process of Li2S. Accordingly, the collaboration of Co-CoO and VC0.75 synergetically facilitates the redox kinetics of polysulfides, prolonging the lifespan of Li-S batteries. Impressively, VC0.75/Co-CoO composites endow Li-S batteries with a discharge capacity decay rate as low as 0.02 % per cycle at the current density of 0.2 C. The specific capacity reaches 626 mAh/g at the high current density of 1.0 C even after 450 cycles. This work sheds light on a facile methodology for improving the catalytic activity of sulfur host materials in Li-S batteries.

Three-dimensional carbon foam decorated with SnO2 as multifunctional host for lithium sulfur batteries.

Lithium-sulfur (Li-S) batteries with high theoretical capacity and abundant sulfur resources are potential energy storage systems. Nevertheless, there are several roadblocks that strongly limit the commercial application of Li-S batteries, including the insulating nature of sulfur and Li2S, large volume change and the shuttle effect of lithium polysulfides. Herein, a three-dimensional carbon foam (CF) decorated with SnO2 (SnO2/CF) is fabricated by the simple electrodeposition and used as a sulfur host to resolve the bottleneck issues in Li-S batteries. Thanks to the synergetic effect of the polar SnO2 and conductive carbon framework, the SnO2/CF framework is endowed with multifunctionalities such as providing three-dimensional conductive framework, inhibiting the migration of polysulfides and improved reaction kinetics. Consequently, durable cycle performance with a capacity of 458.2 mAh g-1 after 1000 cycles at 1 C is achieved. Furthermore, a high capacity of 749.5 mAh g-1 at a high rate of 5 C is attained. Remarkably, under high sulfur loading of 8.84mgcm-2, the S@SnO2/CF cathode can still deliver a high specific capacity of 389.8 mAh g-1 after 300 cycles at 0.5 C. This work demonstrates a novel strategy to improve the performance of Li-S batteries for energy storage applications.

Development prospects of metal-based two-dimensional nanomaterials in lithium-sulfur batteries

A lithium-sulfur (Li-S) system is an important candidate for future lithium-ion system due to its low cost and high specific theoretical capacity (1675 mAh/g, 2600 Wh/kg), which is greatly hindered by the poor conductivity of sulfur, large volume change and dissolution of lithium polysulfides. Two-dimensional (2D) materials with monolayers or few-layers usually have peculiar structures and physical/chemical properties, which can resolve the critical issues in Li-S batteries. Especially, the metal-based 2D nanomaterials, including ferrum, cobalt or other metal-based composites with various anions, can provide high conductivity, large surface area and abundant reaction sites for restraining the diffusion for lithium polysulfides. In this mini-review, we will present an overview of recent developments on metal-based 2D nanomaterials with various anions as the electrode materials for Li-S batteries. Since the main bottleneck for the Li-S system is the shuttle of polysulfides, emphasis is placed on the structure and components, physical/chemical interaction and interaction mechanisms of the 2D materials. Finally, the challenges and prospects of metal-based 2D nanomaterials for Li-S batteries are discussed and proposed.

A spatially efficient “tube-in-tube” hybrid for durable sulfur electrochemistry

A spatially efficient “tube-in-tube” carbonaceous host decorated with defective metallic nitride nanoparticles (Fe2N1−x-NCT) is constructed to alleviate the insufficient sulfur utilization and inferior cycling issues of lithium sulfur batteries.

Elastic three-dimensional Fe-doped polypyrrole aerogel current collector for high-loading and high-energy-density lithium-sulfur batteries

Development of high-loading and high-energy-density lithium-sulfur (Li-S) batteries has aroused increasing research interests recently. However, the performance of a conventional two-dimensional Al foil current collector is limited by its smooth/nonporous surface and poor flexibility, which is unfavorable for the achievement of high sulfur loading and sufficient polysulfide adsorption. Hence, a three-dimensional porous Fe-doped polypyrrole aerogel (FPA) is developed by a simple and scalable strategy combing the solution reaction with the freeze-drying technique, aiming at acting as the current collector of cathode to address these issues in Li-S batteries. This FPA possesses a conductive porous network structure with high elasticity and abundant Fe dopants, which can not only buffer the large volume change of sulfur and ensure fast ion/electron transfer, but also effectively anchor the polysulfides and lower the negative polarization effect during cycling. As a result, the FPA@S cathode delivers a high initial capacity of 1196.7 mAh g−1 at 0.2 C and a retained capacity of 829.5 mAh g−1 after 200 cycles, with stabilized Coulombic efficiency and excellent rate performance. This FPA@S cathode also achieves a high cell-level gravimetric energy density of 199.7 Wh kgcell−1 even under a high sulfur-loading (8.57 mg cm−2) and low electrolyte/sulfur ratio (6 mL g−1), demonstrating its practical potential in future advanced high-energy battery systems.

Cation-Selective Separators for Addressing the Lithium-Sulfur Battery Challenges.

Lithium-sulfur batteries (LSBs) have become one of the most promising candidates for next-generation energy storage systems owing to their high theoretical energy density, environmental friendliness, and cost effectiveness. However, real-word applications are seriously restricted by an undesirable shuttle effect and Li dendrite formation. In essence, uncontrollable anion transport is a key factor that causes both polysulfide shuttling and dendrite formation, which creates the possibility of simultaneously addressing the two critical issues in LSBs. An effective strategy to control anion transport is the construction of cation-selective separators. Significant progress has been achieved in the inhibition of the shuttle effect, whereas addressing the problem of Li dendrite formation by utilizing a cation-selective separator is still under way. From this viewpoint, this Review analyzes critical issues with regard to the shuttle effect and Li dendrite formation caused by uncontrollable anion transport, based on which roles and advantages of cation-selective separators toward high-performance LSBs are presented. According to the separator-construction principle, the latest advances and progress in cation-selective separators in inhibiting the shuttle effect and Li dendrite formation are reviewed in detail. Finally, some challenges and prospects are proposed for the future development of cation-selective separators. This Review is anticipated to provide a new perspective for simultaneously addressing the two critical issues in LSBs.

Recent Advances in Hollow Porous Carbon Materials for Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries are considered as one of the most potential next-generation rechargeable batteries due to their high theoretical energy density. However, some critical issues, such as low capacity, poor cycling stability, and safety concerns, must be solved before Li-S batteries can be used practically. During the past decade, tremendous efforts have been devoted to the design and synthesis of electrode materials. Benefiting from their tunable structural parameters, hollow porous carbon materials (HPCM) remarkably enhance the performances of both sulfur cathodes and lithium anodes, promoting the development of high-performance Li-S batteries. Here, together with the templated synthesis of HPCM, recent progresses of Li-S batteries based on HPCM are reviewed. Several important issues in Li-S batteries, including sulfur loading, polysulfide entrapping, and Li metal protection, are discussed, followed by a summary on recent research on HPCM-based sulfur cathodes, modified separators, and lithium anodes. After the discussion on emerging technical obstacles toward high-energy Li-S batteries, prospects for the future directions of HPCM research in the field of Li-S batteries are also proposed.

Urchin-like NiCo2S4 infused sulfur as cathode for lithium–sulfur battery

A shuttle effect caused by soluble intermediates is one of the most crucial issues in lithium sulfur batteries, which results in a short cycle life and low coulombic efficiency. Recently, binary metal sulfides as electrode materials have been used for miscellaneous application accounting for their larger redox reaction sites and higher electrical conductivity. Herein, a novel urchin-like NiCo2S4 was synthesized via two steps of hydrothermal process and then firstly used as a conductive and polar host for sulfur in lithium sulfur batteries. The obtained NiCo2S4/S composite demonstrates a capacity of 1028 mAh g−1 for the first discharge and maintains 421 mAh g−1 after 100 cycles at 0.1 C. Furthermore, the composite still shows a remarkable cycling stability at a higher rate, a low capacity fade rate of 0.18% per cycle can be achieved and a reversible capacity of 329 mAh g−1 can be obtained after 300 cycles at 1 C. This excellent performance results from a weakened polysulfide shuttle caused by a strong affinity between NiCo2S4 and polysulfides.

A polymeric nanocomposite interlayer as ion-transport-regulator for trapping polysulfides and stabilizing lithium metal

Inserting an interlayer between cathode and separator represents a feasible approach for potentially addressing two severe issues in lithium-sulfur batteries: diffusion of polysulfides and growth of lithium dendrites. Thus far, there is a lack of cost-effective strategies to fabricate and characterize the interlayers, as well as a comprehensive understanding of their roles. Herein, we design, fabricate, characterize and gain understanding of an advanced battery interlayer capable of addressing the above two critical issues simultaneously. This porous-structured interlayer with a design of integrating polysulfide-blocking function, good mechanical properties and good adhesion to separator is fabricated by coating a functional porous polymeric nanocomposite on the separator. These functions/properties are realized via a rational combination of two polymers (a “functional” polymer of ultra-high molecular weight poly(ethylene oxide) and a “structural” polymer of poly(vinylidene fluoride)) with conductive fillers. The synergistic effect from the two polymers and the resulting porous structure make the interlayer an excellent ion-transport-regulator, which can benefit trapping the dissolved polysulfides, and more importantly, improve the stability of the lithium metal anode. Further, through comprehensive characterizations on the interlayer, the structure-property-performance relationships for the multifunctional interlayer are established, which favors the development of advanced energy storage devices pursuing controllable and express ion-transport between two electrodes.