Liquid-type cathode enabled by 3D sponge-like carbon nanotubes for high energy density and long cycling life of Li-S batteries

Revamping Lithium-Sulfur Batteries for High Cell-Level Energy Density by Synergistic Utilization of Polysulfide Additives and Artificial Solid-Electrolyte Interphase Layers

Despite the high theoretical capacity of lithium-sulfur (Li-S) batteries, a high cell-level energy density and a long cycling life are barely achieved, mainly due to the large electrolyte-to-sulfur ratio, polysulfide (PS) shuttle causing the loss of active sulfur, and the formation of passivation layers on the Li anode. To raise the energy density, holding PS in the cathode has been the most popular approach. Still, it has failed, particularly, when the sulfur loading is high enough to have energy densities similar to those of commercial Li-ion batteries. Here, a practical approach of achieving high "cell-level" energy densities is attempted using lithium PS (LPS)-containing electrolytes instead of a pure electrolyte, reducing the electrolyte-to-sulfur ratio and PS diffusion out of the cathode due to concentration differences. Meanwhile, the persistent problems including PS passivation and Li dendrites are suppressed using Li₂ S-phobic artificial solid-electrolyte interphase (A-SEI) layers on Li metal. The synergistic effects from the LPS additives and A-SEI result in a superior cell-level volumetric energy density of 650 Wh L^-1 as well as large cumulative energy densities considering cycling life. This approach provides an important stepping stone to realize commercial Li-S batteries rivaling the current Li-ion batteries.

Sustainable Materials from Fish Industry Waste for Electrochemical Energy Systems

Fish industry waste is attracting growing interest for the production of environmentally friendly materials for several different applications, due to the potential for reduced environmental impact and increased socioeconomic benefits. Recently, the application of fish industry waste for the synthesis of value-added materials and energy storage systems represents a feasible route to strengthen the overall sustainability of energy storage product lines. This review focused on an in-depth outlook on the advances in fish byproduct-derived materials for energy storage devices, including lithium-ion batteries (LIBs), sodium-ion (NIBs) batteries, lithium-sulfur batteries (LSBs), supercapacitors and protein batteries. For each of these, the latest applications were presented together with approaches to improve the electrochemical performance of the obtained materials. By analyzing the recent literature on this topic, this review aimed to contribute to further advances in the sustainability of energy storage devices.

Construction of all-carbon micro/nanoscale interconnected sulfur host for high-rate and ultra-stable lithium-sulfur batteries: Role of oxygen-containing functional groups

Carbon nanotubes (CNTs) are often used to settle down the sluggish reaction kinetics in lithium-sulfur batteries (LSBs). However, the self-aggregation of CNTs often makes them fail to effectively inhibit the shuttling effect of soluble lithium polysulfide (LiPS) intermediates. Herein, a type of ultra-stable carbon micro/nano-scale interconnected "carbon cages" has been designed by incorporating polar acid-treated carbon fibers (ACF) into three-dimensional (3D) CNT frameworks during vacuum filtration processes. Results show that the ACF-CNT composite frameworks possess a reinforced-concrete-like structure, in which the ACFs can well work as the main mechanical supporting frames for the composite electrodes, and the oxygen-containing functional groups (OFGs) formed on them as cross linker between ACFs and CNTs. Benefitted from this design, the ACF-CNT/S cathodes deliver an excellent rate capability (retain 72.6% at 4C). More impressively, the ACF-CNT/S cathodes also show an ultrahigh cycling stability (capacity decay rate of 0.001% per cycle over 350 cycles at 2C). And further optimization suggests that the suitable treatment on CFs could balance the chemical adsorption (OFGs) and physical confinement (carbon cages), leading to fast and durable electrochemical reaction dynamics. In addition, the assembled soft-pack LSBs further show a high dynamic bending stability.

Long-life lithium-sulfur batteries with high areal capacity based on coaxial CNTs@TiN-TiO2 sponge

Rational design of heterostructures opens up new opportunities as an ideal catalyst system for lithium polysulfides conversion in lithium-sulfur battery. However, its traditional fabrication process is complex, which makes it difficult to reasonably control the content and distribution of each component. In this work, to rationally design the heterostructure, the atomic layer deposition is utilized to hybridize the TiO₂-TiN heterostructure with the three-dimensional carbon nanotube sponge. Through optimizing the deposited thickness of TiO₂ and TiN layers and adopting the annealing post-treatment, the derived coaxial sponge with uniform TiN-TiO₂ heterostructure exhibits the best catalytic ability. The corresponding lithium-sulfur battery shows enhanced electrochemical performance with high specific capacity of 1289 mAh g⁻¹ at 1 C and capacity retention of 85% after 500 cycles at 2 C. Furthermore, benefiting from the highly porous structure and interconnected conductive pathways from the sponge, its areal capacity reaches up to 21.5 mAh cm⁻².

It is challenging to optimize catalytic heterostructures for lithium sulfur (Li-S) batteries. Here, authors prepare nanometer-scale TiN-TiO₂ heterostructures via atomic layer deposition on carbon nanotube sponge to realize stable Li-S batteries with high areal capacity and improved rate capability.

Restraining polysulfide shuttling by designing a dual adsorption structure of bismuth encapsulated into carbon nanotube cavity

The shuttle effect derived from the dissolution of lithium polysulfides (LIPs) seriously hinders commercialization of lithium-sulfur (Li-S) batteries. Hence, we skillfully designed 1D cowpea-like CNTs@Bi composites with a double adsorption structure, where the bismuth nanoparticles/nanorods are encapsulated in the cavities of CNTs, avoiding the aggregation of bismuth nanoparticles during cycling and improving the conductivity of the electrode. Meanwhile, the sulfur was evenly distributed on the surface of bismuth nanoparticles/nanorods, ensuring effective catalytic activity and displaying high sulfur loading. Under the synergetic effects of the physical detention of abundant pores and chemical adsorption of bismuth, LIPs can be minimised, effectively curbing the shuttle effect. Benefiting from the above advantages, the CNTs@Bi/S cathodes exhibit a high capacity of 1352 mA h g-1, long cycling lifespan (708 mA h g-1 after 200 cycles at 1 C) and excellent coulombic efficiency. As the anodes of lithium-ion batteries (LIBs), the CNTs@Bi composites also show excellent performance due to the encapsulated structure to accommodate the serious volume change. This work offers an innovative strategy for improving the performances of the Li-S batteries and LIBs.

Application-Driven Carbon Nanotube Functional Materials

Carbon nanotube functional materials (CNTFMs) represent an important research field in transforming nanoscience and nanotechnology into practical applications, with potential impact in a wide realm of science, technology, and engineering. In this review, we combine the state-of-the-art research activities of CNTFMs with the application prospect, to highlight critical issues and identify future challenges. We focus on macroscopic long fibers, thin films, and bulk sponges which are typical CNTFMs in different dimensions with distinct characteristics, and also cover a variety of derived composite/hierarchical materials. Critical issues related to their structures, properties, and applications as robust conductive skeletons or high-performance flexible electrodes in mechanical and electronic devices, advanced energy conversion and storage systems, and environmental areas have been discussed specifically. Finally, possible solutions and directions are proposed for overcoming current obstacles and promoting future efforts in the field.

A Dendrite-Free Lithium/Carbon Nanotube Hybrid for Lithium-Metal Batteries

Lithium (Li) metal is promising in the next-generation energy storage systems. However, its practical application is still hindered by the poor cycling performance and serious safety issues for the consequence of dendritic Li. Herein, a dendrite-free Li/carbon nanotube (CNT) hybrid is proposed, which is fabricated by direct coating molten Li on CNTs, for Li-metal batteries. The favorable thermodynamic and kinetic conditions are the powerful force to drive the rapid lift upwards and infusion of molten Li into CNTs network, which is the key to form a uniform metallic layer in Li/CNTs hybrid. The obtained hybrid indicates super-stable functions even at an ultrahigh current density of 40 mA cm^-2 for 2000 cycles with a stripping/plating capacity of 2 mAh cm^-2 in symmetric cells. Subsequently, this hybrid also demonstrates a significantly decreased resistance, excellent cycling stability at high current density and flexibility in the full Li-S battery. This work provides valuable concepts in fabricating Li anodes toward Li-metal batteries and beyond for their high-level services.

Design considerations for lithium-sulfur batteries: mass transport of lithium polysulfides

Irreversible loss of soluble lithium polysulfides (LiPSs) is a major obstacle deteriorating the performance of lithium-sulfur batteries. Multiple innovative approaches have recently been developed to resolve these LiPS issues. Melt-diffusion of sulfur into porous carbon is a representative solution for preventing the diffusion out of LiPSs, which aims to coordinate the sulfur on the electrochemically active site, accordingly. However, it has been overlooked that the mass transport motion of LiPSs has a crucial role in achieving high-performance. In this paper, we highlight the importance of the mass transport of soluble sulfur in the cathode structure by introducing various starting materials, i.e., solid sulfur using melt-diffusion and a catholyte, using 3-dimensional ordered macroporous carbon. The capacity of the sulfur cathode using melt-diffusion is well conserved in carbon with small pores because LiPSs are slowly diffused away, however, the catholyte derived sulfur cathode shows superior performance in carbon with large pores due to their rapid mass transport. The comparison with the four different combinations that control the pore size and mass transport reveals that proper selection of the initial state of starting materials using porous carbons demonstrates the optimal cell performance.

Understanding of Lithium Insertion into 3D Porous Carbon Scaffolds with Hybridized Lithiophobic and Lithiophilic Surfaces by In-Operando Study

In-operando study coupled with voltage/current profiles are presented in order to unveil lithium insertion processes into 3D porous carbon nanotube (CNT) structures whose surfaces were altered to have lithiophobic, lithiophilic, and hybridized lithiophobic/philic characteristics using graphitic surfaces with/without carboxyl/hydroxyl groups. We found the lithiophobic graphitic surfaces hindered lithium insertion into the scaffold despite the high conductivity of CNT. The lithiophilic surface caused another problem of lithium deposition on the outer surface of the electrode, clogging pores and engendering dendrites. Conversely, in the hybridized CNT, lithiophilic trenches partially created on the pristine CNT allowed for uniform lithium deposition into the pores by simultaneously improved lithium attraction and charge transfer, reaching a high areal capacity of 16 mAh cm^-2 even with a current density of 8 mA cm^-2 without noticeable dendrite formation and volume expansion. Our hybridization approach provides valuable insight to realize a high-energy-density anode by uniformly impregnating lithium into porous media.

Interfacially Polymerized Polyamide Interlayer onto Ozonated Carbon Nanotube Networks for Improved Stability of Sulfur Cathodes

Lithium-sulfur (Li-S) batteries are considered promising energy-storage devices owing to the high specific capacity and low cost of the S cathode. However, they suffer from capacity decay and poor coulombic efficiency arising from the dissolution of long-chain polysulfides and their shuttling. A facile and scalable method was developed to directly coat a thin (≈57.3 nm) and porous polyamide (PA) interlayer onto a S cathode by interfacial polymerization. This PA interlayer prevented the shuttling of polysulfides by creating a physical barrier and, through chemical interactions between the amide functionalities of PA and the polysulfides, allowing access to the S electrode by the Li ions. The resulting PA-coated cathode exhibited approximately 64.2 % capacity retention over 1000 cycles at 1 C with only 0.0358 % decay per cycle and a moderate capacity of 1008 mAh g^-1 at 0.1 C.

2 D Materials for Inhibiting the Shuttle Effect in Advanced Lithium-Sulfur Batteries

A lithium-sulfur battery is a new energy storage device with low cost, high energy storage density, and environmental protection. It is an important tool for future battery systems. However, owing to the shuttle of polysulfides, insulation performance of sulfur, and volume change, capacity decay and cycle instability result, which limits the future application of lithium-sulfur batteries. 2 D materials, such as graphene, carbide, nitride, sulfide, oxide, and their aggregates, provide high surface area to improve sulfur utilization and cycle performance. In this Minireview, various 2 D materials are summarized that use physical confinement and chemical interactions to inhibit the shuttle of polysulfides. We outline the controlled spacing of 2 D materials, abundant active sites, and large transverse size separators and interlayers. The effects on the interlayer and separator based on 2 D materials at the lithium anode prevent polysulfide dissolution are also reviewed. Finally, the challenges and prospects of 2 D materials for lithium-sulfur batteries are discussed.

Enhanced Chemical Immobilization and Catalytic Conversion of Polysulfide Intermediates Using Metallic Mo Nanoclusters for High-Performance Li-S Batteries

Rechargeable lithium-sulfur batteries have attracted tremendous scientific attention owing to their high energy density. However, their practical application is greatly hindered by the notorious shuttling of soluble lithium polysulfide (LPS) intermediates with sluggish redox reactions and uncontrolled precipitation behavior. Herein, we report a semiliquid cathode composed of an active LPS solution/carbon nanofiber (CNF) composite layer, capped with a carbon nanotube (CNT) thin film decorated with metallic Mo nanoclusters that regulate the electrochemical redox reactions of LPS. The trace amount (0.05 mg cm^-2) of metallic Mo on the CNT film provides sufficient capturing centers for the chemical immobilization of LPS. Together with physical blocking of LPS by the compact CNT film, free diffusion of LPS is significantly restrained and the self-discharge behavior of the Li-S cell is thus effectively suppressed. Importantly, the metallic Mo nanoclusters enable fast catalytic conversion of LPS and regular deposition of lithium sulfide. As a result, the engineered cathode exhibits a high active sulfur utilization (1401 mAh g^-1 at 0.1 C), stable cycling (500 cycles at 1 C with 0.06% decay per cycle), high rate performance (694 mAh g^-1 at 5 C), and low self-discharge rate (3% after 72 h of rest). Moreover, a high reversible areal capacity of 4.75 mAh cm^-2 is maintained after 100 cycles at 0.2 C for a cathode with a high sulfur loading of 7.64 mg cm^-2. This work provides significant insight into the structural and materials design of an advanced sulfur-based cathode that effectively regulates the electrochemical reactions of sulfur species in high-energy Li-S batteries.

Revisiting the positive roles of liquid polysulfides in alkali metal-sulfur electrochemistry: from electrolyte additives to active catholyte

Polysulfide dissolution and shuttling in liquid organic electrolytes are considered as the most challenging detrimental effects of an Li-S cell, which is one of the most promising next-generation high-energy-density batteries. Therefore, considerable efforts have been devoted to confining solid sulfur or sulfide so as to avoid the formation and diffusion of dissolved polysulfides. However, the positive roles played by the liquid polysulfides in Li-S electrochemistry should not be overlooked. Polysulfide dissolution can promote the cell kinetics and sulfur utilization; as electrolyte additives, polysulfides can help stabilize the Li metal anode, redistribute the active mass in the cathode and act as extra back-up active sulfur sources. After being applied directly as active catholytes, a novel Li-polysulfide redox flow battery (Li-PS RFB) and an Li-polysulfide battery (Li-PS battery) have been developed. This review revisited these beneficial effects of polysulfides and provided a summary of the recent progress on Li-PS RFB and Li-PS batteries, especially with a more comprehensive emphasis on the latter. Furthermore, dissolved polysulfides applied as active catholytes in Na-S and K-S systems and as catholytes or anolytes in aqueous batteries were also briefly discussed. Hopefully, the Li-S electrochemistry can be better understood so as to overcome challenging issues in the way of the practical commercialization of the Li-S batteries.

Core-Shell Fiber-Based 2D Woven Triboelectric Nanogenerator for Effective Motion Energy Harvesting

Personal electronic devices have a general development trend of miniaturization, functionality, and wearability. Their wireless, sustainable, and independent operation is critically important, which requests new power technologies that can harvest the ambient environmental energy. Here, we report a new kind of 2D woven wearable triboelectric nanogenerator (2DW-WTNG) composed of core-shell fibers via the twisting process and weaving process in the textile manufacture. The 2DW-WTNG can convert the body motion energy into electricity with an output current of 575 nA and an output voltage of 6.35 V. At an external load of 50 MΩ, it generated a maximum power density of 2.33 mW/m². Electricity can be produced from the 2DW-WTNG driven in arbitrary in-plane directions. A tiny displacement of 0.4 mm can drive the 2DW-WTNG, which verified its capability to harvest energy from small human movement. The robust 2DW-WTNG can work continuously for 12 h without obvious performance degradation.

Current Status and Future Prospects of Metal-Sulfur Batteries

Lithium-sulfur batteries are a major focus of academic and industrial energy-storage research due to their high theoretical energy density and the use of low-cost materials. The high energy density results from the conversion mechanism that lithium-sulfur cells utilize. The sulfur cathode, being naturally abundant and environmentally friendly, makes lithium-sulfur batteries a potential next-generation energy-storage technology. The current state of the research indicates that lithium-sulfur cells are now at the point of transitioning from laboratory-scale devices to a more practical energy-storage application. Based on similar electrochemical conversion reactions, the low-cost sulfur cathode can be coupled with a wide range of metallic anodes, such as sodium, potassium, magnesium, calcium, and aluminum. These new "metal-sulfur" systems exhibit great potential in either lowering the production cost or producing high energy density. Inspired by the rapid development of lithium-sulfur batteries and the prospect of metal-sulfur cells, here, over 450 research articles are summarized to analyze the research progress and explore the electrochemical characteristics, cell-assembly parameters, cell-testing conditions, and materials design. In addition to highlighting the current research progress, the possible future areas of research which are needed to bring conversion-type lithium-sulfur and other metal-sulfur batteries into the market are also discussed.

Hypervelocity cluster ion impacts on free standing graphene: Experiment, theory, and applications

We present results from experiments and molecular dynamics (MD) simulations obtained with C₆₀ and Au₄₀₀ impacting on free-standing graphene, graphene oxide (GO), and graphene-supported molecular layers. The experiments were run on custom-built ToF reflectron mass spectrometers with C₆₀ and Au-LMIS sources with acceleration potentials generating 50 keV C₆₀ ²⁺ and 440-540 keV Au₄₀₀ ⁴⁺. Bombardment-detection was in the same mode as MD simulation, i.e., a sequence of individual projectile impacts with separate collection/identification of the ejecta from each impact in either the forward (transmission) or backward (reflection) direction. For C₆₀ impacts on single layer graphene, the secondary ion (SI) yields for C₂ and C₄ emitted in transmission are ∼0.1 (10%). Similar yields were observed for analyte-specific ions from submonolayer deposits of phenylalanine. MD simulations show that graphene acts as a trampoline, i.e., they can be ejected without destruction. Another topic investigated dealt with the chemical composition of free-standing GO. The elemental composition was found to be approximately COH₂. We have also studied the impact of Au₄₀₀ clusters on graphene. Again SI yields were high (e.g., 1.25 C^-/impact). 90-100 Au atoms evaporate off the exiting projectile which experiences an energy loss of ∼72 keV. The latter is a summation of energy spent on rupturing the graphene, ejecting carbon atoms and clusters and a dipole projectile/hole interaction. The charge distribution of the exiting projectiles is ∼50% neutrals and ∼25% either negatively or positively charged. We infer that free-standing graphene enables detection of attomole to zeptomole deposits of analyte via cluster-SI mass spectrometry.

Mechanism Investigation of High-Performance Li-Polysulfide Batteries Enabled by Tungsten Disulfide Nanopetals

Understanding the reaction kinetics and mechanism of Li-polysulfide batteries is critical in designing advanced host materials for improved performance. However, up to now, the reaction mechanism within the Li-polysulfide batteries is still unclear. Herein, we study the reaction mechanism of a high-performance Li-polysulfide battery by in situ X-ray diffraction (XRD) and density functional theory (DFT) calculations based on a multifunctional host material composed of WS₂ nanopetals embedded in rGO-CNT (WS₂-rGO-CNT) aerogel. The WS₂ nanopetal serves as a "catalytic center" to chemically bond the polysulfides and accelerate the polysulfide redox reactions, and the 3D porous rGO-CNT scaffold provides fast and efficient e^-/Li⁺ transportation. Thus, the resulting WS₂-rGO-CNT aerogel accommodating the polysulfide catholyte enables a stable cycling performance, excellent rate capability (614 mAh g^-1 at 2 C), and a high areal capacity (6.6 mAh cm^-2 at 0.5 C). In situ XRD results reveal that the Li₂S starts to form at an early stage of discharge (at a depth of 25% of the lower voltage plateau) during the discharge process, and β-S₈ nucleation begins before the upper voltage plateau during the recharge process, which are different from the conventional Li-S battery. Moreover, the WS₂ itself could be lithiated/delithiated during the cycling, making the lithiated WS₂ (Li _xWS₂, 0 ≤ x ≤ 0.3) a real host material for Li-polysulfide batteries. DFT calculations suggest that Li _xWS₂ (0 ≤ x ≤ 0.3) exhibits moderate binding/anchoring interactions toward polysulfides with adsorption energies of 0.51-1.4 eV. Our work reveals the reaction mechanism of the Li-polysulfide batteries and indicates that the lithiated host plays an important role in trapping the polysulfides.

A highly efficient double-hierarchical sulfur host for advanced lithium-sulfur batteries

Li-S batteries have attracted enormous interest due to their potentially high energy density, non-toxicity and the low cost of sulfur. The main challenges of sulfur cathodes are the short cycling life and limited power density caused by the low conductivity of sulfur and dissolution of Li polysulfides. Here we design a new double-hierarchical sulfur host to address these problems. Hierarchical carbon spheres (HCSs), constructed from building blocks of hollow carbon nanobubbles for loading sulfur, are sealed within a thin, polar MoS2 coating composed of ultrathin nanosheets. Experimental and theoretical studies show a strong absorption of the MoS2 nanoshell to polysulfides, and the excellent stability of the MoS2 nanosheets after the adsorption of polysulfides. Moreover, MoS2 promotes the electrochemical redox kinetics in Li-S batteries. Benefiting from the unique hierarchical, hollow and compositional characteristics of the host, the S/MoS2@HCS composite electrode shows a high capacity of 1048 mA h g-1 at 0.2C, good rate capacity and long cycling life with a slow capacity decay of 0.06% per cycle.

Exploration of the Electrical Conductivity of Double-Network Silver Nanowires/Polyimide Porous Low-Density Compressible Sponges

Stress-responsive, highly flexible, and breathable nanocomposite sponges show an electrical conductivity from 1.7 to 166.6 S/cm depending on the applied stress. Key for the responsive electrical conductivity of the sponges is the change of percolation of the silver nanowires. These sponges made of short electrospun fibers and silver nanowires could be applied without any amplifier for the operation of automobile bulbs and as an efficient Joule heater. The time required for electric heating (current on) and cooling is very short. Interestingly, the maximum temperature reached by electric heating depends on the compression status. The higher the compression status, the lower is the maximum temperature, which is in accordance with the understanding of Joule heaters. It is noteworthy that these sponges are thermally, chemically, and mechanically very stable. These conductive sponges will open a new area for novel conductive devices with relevance for real-world applications.

Unusual Mesoporous Carbonaceous Matrix Loading with Sulfur as the Cathode of Lithium Sulfur Battery with Exceptionally Stable High Rate Performance

Unusual three-dimensional mesoporous carbon/reduced graphene oxide (MP-C/rGO) matrix possessing graphene nanolayer pore walls built up by three to five graphene monosheets and some carbon particles with the sizes of about 5 nm located between the graphene nanolayers was prepared by facile freeze-drying and then carbonization of the poly(vinyl alcohol) and graphene oxide mixture. The mesoporous carbonaceous MP-C/rGO sample has a high specific surface area of 661.6 m² g^-1, large specific pore volume of 1.54 m³ g^-1, and focused pore size distribution of 2-10 nm. About 64 wt % sulfur could be held in the pores of the MP-C/rGO matrix. As the cathode of a Li-S battery, the MP-C/rGO/S composite showed excellent electrochemical property including a high initial specific capacity of 919 mA h g^-1 at 1 C with the capacity retention ratio of 63.3% and the Coulombic efficiency above 90% after 500 cycles. Meanwhile, the initial specific capacity of 602 mA h g^-1 at 5 C and remaining capacity of 391 mA h g^-1 after 500 cycles with an outstanding Coulombic efficiency of 97% indicate its exceptionally stable rate performance.

Three-Dimensional Carbon Nanotubes Forest/Carbon Cloth as an Efficient Electrode for Lithium-Polysulfide Batteries

The development of a three-dimensionally flexible, large-surface area, high-conductivity electrode is important to improve the low conductivity and utilization of active materials and restrict the shuttle of long-chain polysulfides in Li-polysulfide batteries. Herein, we constructed an integrated three-dimensional carbon nanotube forest/carbon cloth electrode with heteroatom doping and high electrical conductivity. The as-constructed electrode provides strong trapping on the polysulfide species and fast charge transfer. Therefore, the Li-polysulfide batteries with as-constructed electrodes achieved high specific capacities of ∼1200 and ∼800 mA h g^-1 at 0.1 and 1 C, respectively. After 300 cycles at 0.5 C, a specific capacity of 623 mA h g^-1 was retained.

Phosphorene as a Polysulfide Immobilizer and Catalyst in High-Performance Lithium-Sulfur Batteries

Theoretical and experimental studies together show phosphorene as a highly potent polysulfide immobilizer for lithium-sulfur batteries, enabling a high capacity, good rate capability, and excellent cycling stability.

Safe and Durable High-Temperature Lithium-Sulfur Batteries via Molecular Layer Deposited Coating

Lithium-sulfur (Li-S) battery is a promising high energy storage candidate in electric vehicles. However, the commonly employed ether based electrolyte does not enable to realize safe high-temperature Li-S batteries due to the low boiling and flash temperatures. Traditional carbonate based electrolyte obtains safe physical properties at high temperature but does not complete reversible electrochemical reaction for most Li-S batteries. Here we realize safe high temperature Li-S batteries on universal carbon-sulfur electrodes by molecular layer deposited (MLD) alucone coating. Sulfur cathodes with MLD coating complete the reversible electrochemical process in carbonate electrolyte and exhibit a safe and ultrastable cycle life at high temperature, which promise practicable Li-S batteries for electric vehicles and other large-scale energy storage systems.

3D dual-confined sulfur encapsulated in porous carbon nanosheets and wrapped with graphene aerogels as a cathode for advanced lithium sulfur batteries

Although lithium-sulfur (Li-S) batteries have attracted much attention due to their high theoretical specific energy and low cost, their practical applications have been severely hindered by poor cycle life, inadequate sulfur utilization, and the insulating nature of sulfur. Here, we report a rationally designed Li-S cathode with a dual-confined configuration formed by confining sulfur in 2D carbon nanosheets with an abundant porous structure followed by 3D graphene aerogel wrapping. The porous carbon nanosheets act as the sulfur host and suppress the diffusion of polysulfide, while the graphene conductive networks anchor the sulfur-adsorbed carbon nanosheets, providing pathways for rapid electron/ion transport and preventing polysulfide dissolution. As a result, the hybrid electrode exhibits superior electrochemical performance, including a large reversible capacity of 1328 mA h g(-1) in the first cycle, excellent cycling stability (maintaining a reversible capacity of 647 mA h g(-1) at 0.2 C after 300 cycles) with nearly 100% Coulombic efficiency, and a high rate capability of 512 mA h g(-1) at 8 C for 30 cycles, which is among the best reported rate capabilities.

Rational Design of Si/SiO2 @Hierarchical Porous Carbon Spheres as Efficient Polysulfide Reservoirs for High-Performance Li-S Battery

Integrated design of Si/SiO2 @hierar-chical porous carbon spheres is made and used as efficient polysulfide reservoir for enhancing lithium-sulfur battery (LSB) in terms of capacity, rate ability, and cycling stability via combined chemical and physical effects.

Sulfur Embedded in a Mesoporous Carbon Nanotube Network as a Binder-Free Electrode for High-Performance Lithium-Sulfur Batteries

Sulfur-porous carbon nanotube (S-PCNT) composites are proposed as cathode materials for advanced lithium-sulfur (Li-S) batteries. Abundant mesopores are introduced to superaligned carbon nanotubes (SACNTs) through controlled oxidation in air to obtain porous carbon nanotubes (PCNTs). Compared to original SACNTs, improved dispersive behavior, enhanced conductivity, and higher mechanical strength are demonstrated in PCNTs. Meanwhile, high flexibility and sufficient intertube interaction are preserved in PCNTs to support binder-free and flexible electrodes. Additionally, several attractive features, including high surface area and abundant adsorption points on tubes, are introduced, which allow high sulfur loading, provide dual protection to sulfur cathode materials, and consequently alleviate the capacity fade especially during slow charge/discharge processes. When used as cathodes for Li-S batteries, a high sulfur loading of 60 wt % is achieved, with excellent reversible capacities of 866 and 526 mAh g(-1) based on the weights of sulfur and electrode, respectively, after 100 cycles at a slow charge/discharge rate of 0.1C, revealing efficient suppression of polysulfide dissolution. Even with a high sulfur loading of 70 wt %, the S-PCNT composite maintains capacities of 760 and 528 mAh g(-1) based on the weights of sulfur and electrode, respectively, after 100 cycles at 0.1C, outperforming the current state-of-the-art sulfur cathodes. Improved high-rate capability is also delivered by the S-PCNT composites, revealing their potentials as high-performance carbon-sulfur composite cathodes for Li-S batteries.

Nanoscale Polysulfides Reactors Achieved by Chemical Au-S Interaction: Improving the Performance of Li-S Batteries on the Electrode Level

In this work, the chemical interaction of cathode and lithium polysulfides (LiPSs), which is a more targeted approach for completely preventing the shuttle of LiPSs in lithium-sulfur (Li-S) batteries, has been established on the electrode level. Through simply posttreating the ordinary sulfur cathode in atmospheric environment just for several minutes, the Au nanoparticles (Au NPs) were well-decorated on/in the surface and pores of the electrode composed of commercial acetylene black (CB) and sulfur powder. The Au NPs can covalently stabilize the sulfur/LiPSs, which is advantageous for restricting the shuttle effect. Moreover, the LiPSs reservoirs of Au NPs with high conductivity can significantly control the deposition of the trapped LiPSs, contributing to the uniform distribution of sulfur species upon charging/discharging. The slight modification of the cathode with <3 wt % Au NPs has favorably prospered the cycle capacity and stability of Li-S batteries. Moreover, this cathode exhibited an excellent anti-self-discharge ability. The slight decoration for the ordinary electrode, which can be easily accessed in the industrial process, provides a facile strategy for improving the performance of commercial carbon-based Li-S batteries toward practical application.

Long-life Li/polysulphide batteries with high sulphur loading enabled by lightweight three-dimensional nitrogen/sulphur-codoped graphene sponge

Lithium–sulphur batteries with a high theoretical energy density are regarded as promising energy storage devices for electric vehicles and large-scale electricity storage. However, the low active material utilization, low sulphur loading and poor cycling stability restrict their practical applications. Herein, we present an effective strategy to obtain Li/polysulphide batteries with high-energy density and long-cyclic life using three-dimensional nitrogen/sulphur codoped graphene sponge electrodes. The nitrogen/sulphur codoped graphene sponge electrode provides enough space for a high sulphur loading, facilitates fast charge transfer and better immobilization of polysulphide ions. The hetero-doped nitrogen/sulphur sites are demonstrated to show strong binding energy and be capable of anchoring polysulphides based on first-principles calculations. As a result, a high specific capacity of 1,200 mAh g⁻¹ at 0.2C rate, a high-rate capacity of 430 mAh g⁻¹ at 2C rate and excellent cycling stability for 500 cycles with ∼0.078% capacity decay per cycle are achieved.

There is intensive research underway into the cathode development of lithium–sulphur batteries. Here, the authors report a lithium–sulphur battery using nitrogen/sulphur codoped graphene structure which displays excellent electrochemical performance with high sulphur loading.

A self-charging power unit by integration of a textile triboelectric nanogenerator and a flexible lithium-ion battery for wearable electronics

A novel integrated power unit realizes both energy harvesting and energy storage by a textile triboelectric nanogenerator (TENG)-cloth and a flexible lithium-ion battery (LIB) belt, respectively. The mechanical energy of daily human motion is converted into electricity by the TENG-cloth, sustaining the energy of the LIB belt to power wearable smart electronics.