Efficient Sulfur Research Articles

Simple synthesis of Ni/high porosity biomass carbon composites with enhanced electrochemical performance of lithium–sulfur battery

Biomass charcoal with high porosity has been widely used in the field of energy storage materials. In this work, high-porosity biochar(HPBC) was prepared by a carbonization-activation method using a high-efficiency pore-forming agent KOH. The prepared HPBC was a porous material dominated by micropores and mesopores with a specific surface area of 2500 m2/g, and the pore volume of 1.18 cm3/g. Then, nickel nanoparticles were uniformly grown on the surface of HPBC via the electroless nickel plating to form HPBC/Ni. And finally, sublimed sulfur was introduced to prepare HPBC/Ni/S composites as cathode material for lithium sulfur battery. In this structure, HPBC can served as an efficient sulfur storage material, and nickel can be used to catalyze the reaction to enhance the reaction kinetics, while the two materials can also synergistically perform physicochemical adsorption of lithium polysulfide. The results showed that the prepared HPBC/Ni/S composite electrode has a first discharge capacity of 907.3 mAh/g at a rate of 0.5C. After 200 cycles, it still maintains 610.6 mAh/g, and the single-turn attenuation rate is only 0.16%.

Free-standing ZIF-8 derived nitrogen and sulfur co-doped porous carbon nanofibers host for high mass loading lithium-sulfur battery

Lithium–sulfur batteries are promising next-generation energy storage device, but polysulfide shuttling which results in the capacity decay, still remains a great challenge. In this work, we proposed a sulfur and nitrogen co-doped strategy to increase interaction between the lithium sulfides and host. Herein, free-standing S and N dually doped porous carbon nanofibers (donated as SN-PCNF) are prepared and serve as efficient sulfur host materials. Benefitting from the S and N co-doped strategy, the chemical adsorption of lithium polysulfides increases, thus the free-standing SN-PCNF@S cathode delivers an initial discharge capacity of 1133 mA h·g−1 with 80% sulfur loading. Furthermore, the DFT calculations reveals the stronger polysulfide binding with nitrogen and sulfur co-doped carbons than that with nodoped or nitrogen single-doped carbons.

Multifunctional NiCo2O4 nanosheet-assembled hollow nanoflowers as a highly efficient sulfur host for lithium–sulfur batteries

Herein, a simple approach was developed to fabricate novel NiCo2O4 hollow nanoflowers (NCOHFs), which were explored as a sulfur carrier material for lithium-sulfur (Li-S) batteries. Remarkably, the capacity of the NCOHF/S composite electrode was ∼666.8 mA h g-1 in the fourth cycle, which was maintained at ∼432.9 mA h g-1 in the 400th cycle under a current density of 1.0C, with a low decay rate of 0.087% per cycle. The overall outstanding properties of the NCOHF/S composite are attributed to the successful new strategy in structural design via in situ and ex situ procedures. Firstly, NCOHF with bifunctional catalytic activity and chemical adsorption can efficiently promote the redox reactions of lithium polysulfides (LiPSs) and suppress the diffusion of polysulfides. Secondly, NCOHF with inherently high electronic conductivity acts as a conduit to accelerate the transport of electrons and ions. Thirdly, the flower-like NiCo2O4 nanosheets are anchored tightly to the conductive carbon and binder during the Li+ insertion and extraction processes, which can effectively suppress the aggregation of the NCOHF/S composite during cycling. Finally, the hollow space inside the NCOHF/S composite provides sufficient free space for the expansion of encapsulated pure sulfur.

Facile synthesis of Co3-xMnxO4/C nanocages as an efficient sulfur host for lithium-sulfur batteries with enhanced rate performance.

Capacity reduction mainly caused by the shuttle effect and low conductivity restricts the commercial application of lithium-sulfur batteries (LSBs). Herein, we developed a method to overcome these two obstacles synchronously by designing nitrogenous carbon decorated hollow Co3-xMnxO4/C nanocages as hosts of sulfur. These hosts were derived from manganese doped ZIF-67 by a facile sintering method, which provided polar surface to anchor lithium polysulfides and considerable electronic conductivity. The polar material Co3-xMnxO4 and special hollow frame contribute to efficient synergistic sulfur-fixation, resulting in great cycling stabilities. The manganese elements ensure an efficient conversion among LSPs. At the same time, N-doped carbon provides excellent electrical conductivity, thereby leading to splendid rate performances. Thus, a battery with great stability and high capacity could be achieved. As a result, Co3-xMnxO4/C/S with 66 wt% sulfur content delivered a high initial capacity of 1082 mA h g-1 at 1C, together with a slow average capacity decay of 0.056% per cycle at 10C over 500 cycles. When the average sulfur loading is 1.3 mg cm-2, a capacity of 628 mA h g-1 can be maintained at 5C after 500 cycles.

Rational design of polar/nonpolar mediators toward efficient sulfur fixation and enhanced conductivity

Schematic of the classification of polar and nonpolar materials for LSBs.

Constructing a 3D compact sulfur host based on carbon-nanotube threaded defective Prussian blue nanocrystals for high performance lithium–sulfur batteries

Towards practical lithium–sulfur batteries, a highly efficient sulfur host material based on intertwined carbon-nanotubes (CNTs) and defective Prussian blue (PB) nanocrystals is developed.

A MIL-47(V) derived hierarchical lasagna-structured V2O3@C hollow microcuboid as an efficient sulfur host for high-performance lithium-sulfur batteries.

Lithium-sulfur batteries are promising candidates for the next generation of energy storage systems owing to their high energy density, low toxicity and abundant reserves of sulfur. However, sulfur has poor conductivity, large volume change during charge/discharge, and more importantly, the intermediate polysulfide (Li2Sn, 3 ≤ n≤8) produced in the cycling process is easily soluble in the electrolyte resulting in the "shuttle effect", which have greatly limited the commercialization of lithium-sulfur batteries. Therefore, it is of great value to develop optimized sulfur cathode materials to improve electrode conductivity, buffer volume change and restrain the diffusion of polysulfide. In this work, we construct a V-MOF (MIL-47) derived V2O3@C hollow microcuboid with a hierarchical lasagna-like structure through hydrothermal synthesis followed by calcination, and employ it as a sulfur host for the first time. The fast anchoring of polysulfide by V2O3 nanoparticles and the high electronic conductivity of the 3D carbon framework can simultaneously inhibit the "shuttle effect" in the charge-discharge process and accelerate the kinetics of the redox process. Moreover, the special lasagna-like structure with appropriate voids generated during calcination not only provides many sites for sulfur loading, but also effectively alleviates the volume expansion problem during the electrochemical reaction. Therefore, the final fabricated sulfur cathode via the melt impregnation method exhibits good cycling stability (62.3% after 1000 cycles at 1C) and rate performance (663 mA h g-1 at 2C) at a relatively high sulfur loading of 3.7 mg cm-2.

Rational design of well-dispersed ultrafine CoS2 nanocrystals in micro–mesoporous carbon spheres with a synergistic effect for high-performance lithium–sulfur batteries

Micro–mesoporous carbon (MMC) embedded with well-dispersed ultrafine CoS2 (uCoS2) nanocrystals as an efficient sulfur host is prepared by a new method. As a result, a S/uCoS2@MMC cathode exhibits outstanding cycling stability and rate performance.

Controllable electrolytic formation of Ti2O as an efficient sulfur host in lithium–sulfur (Li–S) batteries

Highly conductive Ti2O is controllably prepared by a molten salt electrochemical synthesis method and used as an efficient anchor and catalytic conversion center of polysulfides, the cells possess superior rate capability and ultra-long cycle life.

A “boxes in fibers” strategy to construct a necklace-like conductive network for high-rate and high-loading lithium–sulfur batteries

Following a “boxes in fibers” strategy, a 3D conductive network is constructed by necklace-like N-doped carbon nanofibers with carbon nanoboxes and TiC as an efficient sulfur host, showing excellent performance even under high-rate and high-loading.

An MXene-based aerogel with cobalt nanoparticles as an efficient sulfur host for room-temperature Na–S batteries

A network-like MG-Co composite with adsorption and catalysis for Na2Sx is synthesized as a S host for room temperature Na–S batteries, exhibiting excellent electrochemical performance.

Hollow spheres of Mo2C@C as synergistically confining sulfur host for superior Li–S battery cathode

Lithium–sulfur batteries (LSBs) have attracted much attention in the field of electrochemical energy storage due to their high energy density and low cost. However, the ‘shuttle effect’ of sulfur cathode, resulting in the poor cyclic performance of batteries, is a big barrier for the development of LSBs. To overcome this critical drawback, herein, a matrix of well-designed double carbon shells-encapsulated metallic Mo2C nanoparticles (Mo2C/C@C) is facilely achieved as an efficient sulfur host for high-performance LSBs. During the electrochemical process, the embedded polar and metallic Mo2C nanoparticles could effectively retard polysulfide migration. While for the carbon layers, they can not only act as conductive matrix but also promote the restriction for all sulfur species and maintain the structural stability simultaneously. Specially, the inner carbon layer is mainly for encapsulation and the outside one for surface-modification. As a result, such well-designed Mo2C/C@C–S cathode could effectively adsorb soluble polysulfides both from chemical and physical aspects, and well confines them inside the porous structure of Mo2C/C@C, thus achieving a high reversible capacity and superior cycling performance.

Amorphous TiO2 nanofilm interface coating on mesoporous carbon as efficient sulfur host for Lithium–Sulfur batteries

Lithium sulfur (Li–S) batteries are regarded as one of the most promising next-generation secondary batteries. However, the insulating nature of active materials, inevitable shuttle effect caused by dissolution of intermediate polysulfides, and severe volume expansion during lithiation prevent their practical application. Herein, we report a novel sulfur host composed of amorphous TiO2 nanofilm interfaces coating on mesoporous carbon by controlling the hydrolytic process of tetrabutyl titanate on the surface of 3D interconnect conductive carbon matrix. The sulfur host shows high surface area, considerable electrolyte wetting capability and strong absorption for lithium polysulfides. Owe to the rational design and outstanding properties, the sulfur cathode with the high active material content of ∼74% and mass loading of ∼3.2 mg cm−2 exhibits a high initial specific capacity of 1455 mAh·g−1 and maintained 1242 mAh·g−1 after 200 cycles at 0.1 C (1C = 1675 mAh·g−1) current density, and also delivers excellent long term cycling performance at 1 C with initial capacity of 720 mAh·g−1 and capacity remained up to 81% after 1000 cycles.

One-pot hydrothermal synthesis of nano-sheet assembled NiO/ZnO microspheres for efficient sulfur dioxide detection

The nano-sheet assembled NiO/ZnO microspheres with a diameter of ca. 2 μm have been synthesized via facile hydrothermal method followed by a thermal treatment process. The gas-sensing measurement results show that the sensor using nano-sheet assembled NiO/ZnO microspheres exhibits improved response to sulfur dioxide gas compared with the pure ZnO microspheres sensor. In particular, the sensor with a Ni/Zn molar ratio of 0.5 (0.5 mol% NiO/ZnO) shows high response value (S = 107) and superior selectivity to 10 ppm sulfur dioxide at a low operating temperature of 160 °C and the detection limit of the NiO/ZnO sensor toward sulfur dioxide is down to 1 ppm (S = 6). The enhanced sensing performance is attributed to the formation of p-n heterojunctions on the interface, the catalytic function of NiO and the three-dimensional microspheres composed of the lamellar structure with a large specific surface area. The three-dimensional microspheres provide more active sites for gas adsorption, and the interlayer gap facilitates the diffusion of gas in three-dimensional structure, resulting in high sensitivity and superior selectivity. This work provides a simple method for the synthesis of NiO/ZnO heterojunction microspheres with superior gas-sensing performance, which can be used as a potential material for sulfur dioxide detection.

Anion Extraction-Induced Polymorph Control of Transition Metal Dichalcogenides.

Controlled phase conversion in polymorphic transition metal dichalcogenides (TMDs) provides a new synthetic route for realizing tunable nanomaterials. Most conversion methods from the stable 2H to metastable 1T phase are limited to kinetically slow cation insertion into atomically thin layered TMDs for charge transfer from intercalated ions. Here, we report that anion extraction by the selective reaction between carbon monoxide (CO) and chalcogen atoms enables predictive and scalable TMD polymorph control. Sulfur vacancy, induced by anion extraction, is a key factor in molybdenum disulfide (MoS2) polymorph conversion without cation insertion. Thermodynamic MoS2-CO-CO2 ternary phase diagram offers a processing window for efficient sulfur vacancy formation with precisely controlled MoS2 structures from single layer to multilayer. To utilize our efficient phase conversion, we synthesize vertically stacked 1T-MoS2 layers in carbon nanofibers, which exhibit highly efficient hydrogen evolution reaction catalytic activity. Anion extraction induces the polymorph conversion of tungsten disulfide (WS2) from 2H to 1T. This reveals that our method can be utilized as a general polymorph control platform. The versatility of the gas-solid reaction-based polymorphic control will enable the engineering of metastable phases in 2D TMDs for further applications.

Co–TiO2 nanoparticles anchored in porous carbon matrix as an efficient sulfur host for lithium/sulfur batteries

Although Lithium/sulfur (Li/S) battery is a promising candidate for the next-generation battery technologies, some serious issues including poor electrical conductivity of sulfur, capacity decay and kinetically sluggish still impede its further development. In this work, Co–TiO2@C composite was prepared via facile impregnation and carbonization of the mixture of Ti-MOF (MIL-125) and Co(NO3)2 as an efficient sulfur host for the Li/S batteries. The composite exhibits a tablet-like structure consisting of porous carbon, on which the TiO2 and Co nanoparticles with the diameter of around 8 nm are uniformly dispersed. The porous carbon matrix and TiO2 nanoparticles can effectively trap polysulfides through physical and chemical adsorption, respectively. Furthermore, the catalytic metal Co accelerates the conversion of adsorbed long-chain lithium polysulfides into short-chain sulfides, resulting in the improvements of reaction kinetics and sulfur utilization. The Co–TiO2@C/sulfur composite shows outstanding electrochemical performance duo to the above synergistic effect. The cell with the composite cathode delivers a high initial specific capacity of 1245 mAh g−1 at a current rate of 0.2C. After 200 cycles, a reversible capacity of 698 mAh g−1 was maintained. The results indicate its great potential for high performance Li/S batteries.

Synergetic restriction to polysulfides by hollow FePO4 nanospheres wrapped by reduced graphene oxide for lithium–sulfur battery

Lithium-sulfur battery has been considered as the prospective competitive candidate for energy storage device, because of its huge advantages in specific capacity and energy density. Nevertheless, the application of lithium-sulfur battery is impeded by intrinsic polysulfide shuttle effect and poor electric conductivity of sulfur. To overcome these obstacles, hollow FePO4 spheres wrapped by reduced graphene oxide (FePO4@rGO) as efficient sulfur host material is synthesized. The hollow FePO4 spheres with large inner space are in favors of sulfur loading and buffer the volume expansion between S and discharge products (Li2S/Li2S2) during cycling process. Meanwhile, the hollow and polar FePO4 spheres afford synergy of physical confinement and chemical interaction to restrict polysulfides shuttle effect. Furthermore, the wrinkled rGO tightly-wrapped on the surface of FePO4 offers an interconnected conductive network. Profit from these merits, the FePO4@rGO as sulfur host manifests an impressive cycle stability with a low capacity decay rate of 0.037% per cycle at 0.5 C upon 1000 cycles, suggesting its enormous potential for high-performance Li–S battery.

Carbon confinement synthesis of interlayer-expanded and sulfur-enriched MoS2+x nanocoating on hollow carbon spheres for advanced Li-S batteries

High energy density and low-cost lithium-sulfur batteries have been considered as one of the most promising candidates for next-generation energy storage systems. However, the intrinsic problems of the sulfur cathode severely restrict their further practical application. Here, a unique double-shell architecture composed of hollow carbon spheres@interlayer-expanded and sulfur-enriched MoS2+x nanocoating composite has been developed as an efficient sulfur host. A uniform precursor coating derived from heteropolyanions-induced polymerization of pyrrole leads to space confinement effect during the in-situ sulfurization process, which generates the interlayer-expanded and sulfur-enriched MoS2+x nanosheets on amorphous carbon hollow spheres. This new sulfur host possesses multifarious merits including sufficient voids for loading sulfur active materials, high electronic conductivity, and fast lithium-ion diffusive pathways. In addition, additional active edge sites of MoS2+x accompanied by the nitrogen-doped carbon species endow the sulfur host with immobilizing and catalyzing effects on the soluble polysulfide species, dramatically accelerating their conversion kinetics and re-utilization. The detailed defect-induced interface catalytic reaction mechanism is firstly proposed. As expected, the delicately-designed sulfur host exhibits an outstanding initial discharge capacity of 1,249 mAh·g−1 at 0.2 C and a desirable rate performance (593 mAh·g−1 at 5.0 C), implying its great prospects in achieving superior electrochemical performances for advanced lithium sulfur batteries.

Unique Flexible NiFe2O4@S/rGO-CNT Electrode via the Synergistic Adsorption/Electrocatalysis Effect toward High-Performance Lithium-Sulfur Batteries.

A unique flexible NiFe2O4 hollow sphere@S/rGO-CNT (NiFe2O4@S/C) cathode was rationally designed and synthesized to tackle the issues of lithium-sulfur batteries. In this strategy, the introduced rGO and CNTs offer a flexible and conductive skeleton to facilitate the transport of electrons and/or ions and a physical barrier to confine polysulfides. Furthermore, as an efficient sulfur host, NiFe2O4 hollow spheres can further absorb the soluble polysulfides by strong chemical interaction due to their intrinsic polarity and also serve as a catalyst to promote the redox kinetics of polysulfide conversion. Benefiting from the synergism of the physical confinement, polar chemical adsorption, and catalytic conversion, the as-prepared flexible NiFe2O4@S/C electrode delivers a high initial capacity of 1193 mAh g-1 at 100 mA g-1 and excellent long-term cycling stability up to 500 cycles with a low decay rate of 0.059% per cycle at 500 mA g-1.

Improving confinement and redox kinetics of polysufides through hollow NC@CeO2 nanospheres for high-performance lithium-sulfur batteries

Lithium-sulfur batteries are regarded as next generation energy storage systems because of their high theoretical specific capacity and low cost. However, the polysulfide shuttle effect, low electronic conductivity of sulfur/lithium sulfides and slow redox kinetics of polysulfide conversion still limit their practical application. Herein, we design a hollow nanosphere structure with CeO2 shell/ultrathin nitrogen-doped carbon shell as highly efficient sulfur host for lithium-sulfur batteries. The unique structure not only offers physical entrapment for sulfur species by CeO2/carbon shells, but also provides strong chemical adsorption and activation sites for chemical adsorption and catalytic conversion of polysulfides through CeO2 nanoparticles. Moreover, the unique hollow structure offers enough space for volume variations of sulfur during charge/discharge process and facilitates fast electron/ion transport to continuously activate active material, therefore improving the electrochemical performances of lithium-sulfur batteries. By combining these advantages, the obtained NC@H-CeO2/S cathodes exhibit high reversible capacity (1348 mAh g−1 at 0.2 C), excellent rate capability (548 mAh g−1 at 5 C) and superior cycle stability (632 and 458 mAh g−1 at 2 and 5 C after 500 cycles, respectively). Moreover, the cathodes with high sulfur loading of 3.5 mg cm−2 remain excellent rate capability and cycling stability. This work provides a new strategy to the design of advanced cathode materials for high-performance lithium-sulfur batteries.