Cathode For Lithium-sulfur Batteries Research Articles

WO2 nanoparticle anchored hollow carbon spheres enhanced performance of lithium-sulfur battery

Lithium–sulfur battery has drawn considerable attention because of its high theoretical capacity and density, but poor electrical conductivity, volume expansion, and slow redox reactions in lithium–sulfur batteries limit their commercial applications. Hollow carbon nanospheres (HCN) loaded with tungsten dioxide (WO2) nanoparticles were prepared using polystyrene spheres as templates via in situ polymerization, heat treatment, soaking, and high-temperature decomposition reduction. The composites possessed a hollow spherical structure, which can alleviate the volume change of sulfur and anchored the polysulfides. The anchored WO2 nanoparticles with abundant oxygen vacancies can generate many active sites and accelerate the electrochemical reaction kinetics. Therefore, the WO2/HCN/S cathode exhibited 593.5 mAh g−1 over 300 cycles at 1.0 A g−1 with a capacity decay rate of 0.15 % per cycle. This study provides a feasible solution for fabricating high performance cathode for lithium-sulfur battery.

High Areal Capacity and Sustainable High Energy in Ferroelectric Doped Holey Graphene/Sulfur Composite Cathode for Lithium-Sulfur Batteries

In this study, we are reporting the impact of the incorporation of ferroelectric nanoparticles (FNPs), such as BaTiO3 (BTO), BiFeO3 (BFO), Bi4NdTi3Fe0.7Ni0.3O15 (BNTFN), and Bi4NdTi3Fe0.5Co0.5O15 (BNTFC), as well as the mass loading of sulfur to fabricated solvent-free sulfur/holey graphene-carbon black/polyvinylidene fluoride (S/FNPs/CBhG/PVDF) composite electrodes to achieve high areal capacity for lithium-sulfur (Li-S) batteries. The dry-press method was adopted to fabricate composite cathodes. The hG, a conductive and lightweight scaffold derived from graphene, served as a matrix to host sulfur and FNPs for the fabrication of solvent-free composites. Raman spectra confirmed the dominant hG framework for all the composites, with strong D, G, and 2D bands. The surface morphology of the fabricated cathode system showed a homogeneous distribution of FNPs throughout the composites, confirmed by the EDAX spectra. The observed Li+ ion diffusion coefficient for the composite cathode started at 2.17 × 10−16 cm2/s (S25(CBhG)65PVDF10) and reached up to the highest value (4.15 × 10−15 cm2/s) for S25BNTFC5(CBhG)60PVDF10. The best discharge capacity values for the S25(CBhG)65PVDF10 and S25BNTFC5(CBhG)60PVDF10 composites started at 1123 mAh/gs and 1509 mAh/gs and dropped to 612 mAh/gs and 572 mAh/gs, respectively, after 100 cycles; similar behavior was exhibited by the other composites that were among the best. These are better values than those previously reported in the literature. The incorporation of ferroelectric nanoparticles in the cathodes of Li-S batteries reduced the rapid formation of polysulfides due to their internal electric fields. The areal capacity for the S25(CBhG)65PVDF10 composites was 4.84 mAh/cm2 with a mass loading of 4.31 mgs/cm2, while that for the S25BNTFC5(CBhG)60PVDF10 composites was 6.74 mAh/cm2 with a mass loading of 4.46 mgs/cm2. It was confirmed that effective FNP incorporation within the S cathode improves the cycling response and stability of cathodes, enabling the high performance of Li-S batteries.

Freestanding cathode design for lithium-sulfur batteries: CoP/Co-PCNF sandwich structure to enhance adsorption and catalysis for polysulfides

Lithium-sulfur (Li-S) batteries are exceedingly restrained in practical application originating from the shuttling of soluble lithium polysulfides (LiPSs), despite their superelevated theoretical specific capacity as well as energy density. Herein, a flexible carbon nanofiber membrane in situ embedded with Co, CoP nanoparticles (Co-PCNF, CoP/Co-PCNF) was designed to fabricate a unique sandwich structure, as a free-standing cathode for Li-S batteries. These innovative Li-S batteries deliver an initial capacity of 993.5 mAh g−1 at 1 C, along with a substantial capacity of 814.18 mAh g−1 even over 300 cycles, which corresponds to a low capacity decay of only 0.06% per cycle. Besides, with a sulfur content of 4.5 mg cm−2, an initial discharge capacity of 700.1 mAh g−1 was realized at 0.2 C with an excellent capacity retention rate of 91% over 200 cycles, prominent in long-cycle Li-S batteries. In this aspect, rosy cycling stability was achieved because of the impeded shuttle effect by the synergistic effect of Co and CoP compared with Co-PCNF sandwich structure as well as traditional aluminum foil. Moreover, underlying the DFT calculation, the enhanced overlap of electronic state ascribed to the conversion of fraction Co nanoparticles to CoP, triggering the adsorption capacity of CoP/Co-PCNF crucially higher than that of Co-PCNF. This observation paves ways into implementing the CoP/Co-PCNF sandwich structure as a free-standing cathode for the high-performance Li-S batteries.

Turning yerba mate waste into high-performance lithium–sulfur battery cathodes

In this study, a non-activated carbon (YMCC) derived from waste yerba mate was examined as a matrix for the development of a carbon‑sulfur composite cathode (YMC-C@S). The carbonaceous material is produced through a simple process of pyrolyzing extracted cellulose from residual yerba mate, avoiding costly and complex stages of chemical activation or additional purification. Due to its high carbon content and mesoporous structure, YMC-C can serve as an effective host for sulfur. After adding 70 % sulfur via the melt diffusion method, the YMC-C@S composite shown a remarkable initial capacity of 1678 mAh gS−1 as a cathode material, along with high reversible capacity at a low charge/discharge rate. Additionally, even when subjected to an increased C-rate during long cycling, discharge capacities at 1C of 777 mAh gS−1 and 674 mAh gS−1 after 165 cycles demonstrate good rate capability. When the cycling protocol is optimized, the YMC-C@S composite exhibits very low loss of capacity per cycle, even when using fast charge stages. The efficacy of YMC-C as an efficient cathode material in LSB is confirmed by the positive results of a self-discharge test conducted over a period of 7.5 months.

Design of Size-Controlled Sulfur Nanoparticle Cathodes for Lithium-Sulfur Aviation Batteries.

Lithium-sulfur (Li-S) battery has been considered as a strong contender for commercial aerospace battery, but the commercialization requires Ah-level pouch cells with both efficient discharge at high rates and ultra-high energy density. In this paper, the application of lithium-sulfur batteries for powering drones by using the cathode of highly dispersed sulfur nanoparticles with well-controlled particle sizes have been realized. The sulfur nanoparticles are prepared by a precipitation method in an eco-friendly and efficient way, and loaded on graphene oxide-cetyltrimethylammonium bromide by molecular grafting to realize a large-scale fabrication of sulfur-based cathodes with superior electrochemical performance. A button cell based on the cathode exhibits an excellent discharge capacity of 62.8 mAh cm-2 at a high sulfur loading of 60mg cm-2 (i.e., 1046.7 mAh g-1 ). The assembled miniature pouch cell (PCmini) shows a discharge capacity of 130 mAh g-1 , while the formed Ah-level pouch cell (PCAh) achieves energy density of 307Wh kg-1 at 0.3C and 92Wh kg-1 at 4C. Especially, a four-axis propeller drone powered by the PC has successfully completed a long flight (>3 min) at high altitudes, demonstrating the practical applicability as aviation batteries.

Application of Strontium-Doped Bismuth Ferrate in Lithium-Sulfur Battery Cathode

The modification of high-performance lithium-sulfur battery cathode have been extensively studied. Suppressing the shuttle effect of polysulfide, solving the volume expansion of sulfur and the poor electrical conductivity of sulfur are the main directions for scientists to modify the cathode. Here we prepared bismuth ferrate powder doped with different molecular percentages of strontium by sol-gel method. Compared with the unmodified cell, the capacity and cycle stability were improved by adding as-prepared material to the cathode, which indicates that bismuth ferrate doped with certain amount of strontium plays a positive role in the cathode material modification.

Highly monodispersed Li2SO4 crystals towards Li2S-based lithium-sulfur battery cathodes

Li2S as a cathode of lithium sulfur batteries (LSB) and a precursor of advanced solid electrolytes have been widely investigated. However, suffered from the high cost and the low ionic/electronic conductivity, the controllable fabrication of Li2S crystals from the carbothermal conversion of Li2SO4 need to be improved urgently. Herein, polyacrylic acid (PAA) as a blocking agent is introduced to fabricate the monodispersed Li2SO4 (m-Li2SO4) crystals and the m-Li2S/carbon nanotube (CNT) cathode via subsequent carbothermal reaction. Our constructed Li2S/CNT||Li cells deliver a high initial discharge capacity of ∼900 mAh/g and a reversible specific capacity of 500 mAh/g at 2C. These results suggest the importance of regulating size and morphology of Li2SO4 crystals towards high-performance Li2S crystals.

A review of cathode for lithium-sulfur batteries: progress and prospects

A review of cathode for lithium-sulfur batteries: progress and prospects

Structural Transformation in a Sulfurized Polymer Cathode to Enable Long-Life Rechargeable Lithium–Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) represents a class of sulfur-bonded polymers, which have shown thousands of stable cycles as a cathode in lithium-sulfur batteries. However, the exact molecular structure and its electrochemical reaction mechanism remain unclear. Most significantly, SPAN shows an over 25% 1st cycle irreversible capacity loss before exhibiting perfect reversibility for subsequent cycles. Here, with a SPAN thin-film platform and an array of analytical tools, we show that the SPAN capacity loss is associated with intramolecular dehydrogenation along with the loss of sulfur. This results in an increase in the aromaticity of the structure, which is corroborated by a >100× increase in electronic conductivity. We also discovered that the conductive carbon additive in the cathode is instrumental in driving the reaction to completion. Based on the proposed mechanism, we have developed a synthesis procedure to eliminate more than 50% of the irreversible capacity loss. Our insights into the reaction mechanism provide a blueprint for the design of high-performance sulfurized polymer cathode materials.

Enhancement of Organic Oxygen Atoms on Metal Cobalt for Sulfur Adsorption and Catalytic Polysulfide Conversion

Metals and their compounds effectively suppress the polysulfide shuttle effect on the cathodes of a lithium-sulfur (Li-S) battery by chemisorbing polysulfides and catalyzing their conversion. However, S fixation on currently available cathode materials is below the requirements of large-scale practical application of this battery type. In this study, perylenequinone was utilized to improve polysulfide chemisorption and conversion on cobalt (Co)-containing Li-S battery cathodes. According to IGMH analysis, the binding energies of DPD and carbon materials as well as polysulfide adsorption were significantly enhanced in the presence of Co. According to in situ Fourier transform infrared spectroscopy, the hydroxyl and carbonyl groups in perylenequinone are able to form O-Li bonds with Li2Sn, facilitating chemisorption and catalytic conversion of polysulfides on metallic Co. The newly prepared cathode material demonstrated superior rate and cycling performances in the Li-S battery. It exhibited an initial discharge capacity of 780 mAh g-1 at 1 C and a minimum capacity decay rate of only 0.041% over 800 cycles. Even with a high S loading, the cathode material maintained an impressive capacity retention rate of 73% after 120 cycles at 0.2 C.

Multiscale Structural Engineering of Sulfur/Carbon Cathodes Enables High Performance All-Solid-State LiS Batteries.

Constructing all-solid-state lithium-sulfur batteries (ASSLSBs) cathodes with efficient charge transport and mechanical flexibility is challenging but critical for the practical applications of ASSLSBs. Herein, a multiscale structural engineering of sulfur/carbon composites is reported, where ultrasmall sulfur nanocrystals are homogeneously anchored on the two sides of graphene layers with strong SC bonds (denoted as S@EG) in chunky expanded graphite particles via vapor deposition method. After mixing with Li9.54 Si1.74 P1.44 S11.7 Cl0.3 (LSPSCL) solid electrolytes (SEs), the fabricated S@EG-LSPSCL cathode with interconnected "Bacon and cheese sandwich" feature can simultaneously enhance electrochemical reactivity, charge transport, and chemomechanical stability due to the synergistic atomic, nanoscopic and microscopic structural engineering. The assembled InLi/LSPSCL/S@EG-LSPSCL ASSLSBs demonstrate ultralong cycling stability over 2400 cycles with 100% capacity retention at 1 C, and a record-high areal capacity of 14.0mAhcm-2 at a record-breaking sulfur loading of 8.9mgcm-2 at room temperature as well as high capacities with capacity retentions of ≈100% after 600 cycles at 0 and 60°C. Multiscale structural engineered sulfur/carbon cathode has great potential to enable high-performance ASSLSBs for energy storage applications.

Lithium Iron Phosphate Enhances the Performance of High-Areal-Capacity Sulfur Composite Cathodes.

Lithium iron phosphate (LiFePO4, "LFP") was investigated as an additive in the cathode of lithium-sulfur (Li-S) batteries. LFP addition boosted the sulfur utilization during Li-S cycling, achieving an initial capacity of 1465 mAh/gS and a long cycle life (>300 cycles). Polysulfide adsorption experiments showed that LFP attracted polysulfides, and thus, the presence of LFP should alleviate the shuttle effect, a common failure mode. Postmortem characterization found iron phosphides, iron phosphates, and LiF in the electrode, indicating that LFP underwent dynamic reconstruction during Li-S cycling. We suspect that the formation of these species played a role in the observed performance. From the processing standpoint, adding LFP improved slurry rheology, making the preparation of a high-loading electrode more consistent. Benefiting from the high sulfur utilization and the ability to prepare electrodes with high mass loading, the S-LFP hybrid cell showed an excellent areal capacity of 2.65 mAh/cm2 and could be stably cycled at 2 mAh/cm2 for 250 cycles. Our results demonstrated the LFP addition as a promising strategy for realizing Li-S batteries with high sulfur loading and areal capacity.

Recent Advances of Metal Groups and Their Heterostructures as Catalytic Materials for Lithium-Sulfur Battery Cathodes

Recent Advances of Metal Groups and Their Heterostructures as Catalytic Materials for Lithium-Sulfur Battery Cathodes

High Entropy Oxide (CrMnFeNiMg)3 O4 with Large Compositional Space Shows Long-Term Stability as Cathode in Lithium-Sulfur Batteries.

The repeated formation and irreversible diffusion of liquid-state lithium polysulfides (LiPSs) are the primary challenges in the development of high-energy-density lithium-sulfur battery (LSB). An effective strategy to alleviate the resulting polysulfide loss is critical for the stability of LSBs. In this regard, high entropy oxides (HEOs) appear as a promising additive for the adsorption and conversion of LiPSs owing to the diverse active sites, offering unparalleled synergistic effects. Herein, we have developed a (CrMnFeNiMg)3 O4 HEO as a functional polysulfide trapper in LSB cathode. The adsorption of LiPSs by the metal species (i. e., Cr, Mn, Fe, Ni, and Mg) in the HEO takes place through two different paths and leads to enhanced electrochemical stability. We demonstrate that the optimal sulfur cathode with the (CrMnFeNiMg)3 O4 HEO attains a high peak and reversible discharge capacities of 857 mAh g-1 and 552 mAh g-1 , respectively, at a cycling rate of C/10, a long cycle life of 300 cycles, and a high rate performance at the cycling rates from C/10 to C/2.

Holey Graphene/Ferroelectric/Sulfur Composite Cathodes for High-Capacity Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have attracted considerable interest as next-generation high-density energy storage devices. However, their practical applications are limited by rapid capacity fading when cycling cells with high mass loading levels. This could be largely attributed to the inferior electron/ion conduction and the severe shuttling effect of soluble polysulfide species. To address these issues, composites of sulfur/ferroelectric nanoparticles/ho ley graphene (S/FNPs/hG) cathodes were fabricated for high-mass-loading S cathodes. The solvent-free and binder-free procedure is enabled using holey graphene as a unique dry-pressable electrode for Li-S batteries. The unique structure of the holey graphene framework ensures fast electron and ion transport within the electrode and affords enough space to mitigate the electrode's volume expansion. Moreover, ferroelectric polarization due to FNPs within S/hG composites induces an internal electric field, which effectively reduces the undesired shuttling effect. With these advantages, the S/FNPs/hG composite cathodes exhibit sustainable and ultrahigh specific capacity up to 1409 mAh/gs for the S/BTO/hG cathode. A capacity retention value of 90% was obtained for the S/BNTFN/hG battery up to cycle 18. The high mass loading of sulfur ranging from 5.72 to 7.01 mgs/cm2 allows maximum high areal capacity up to ∼10 mAh/cm2 for the S/BTO/hG battery and superior rate capability at 0.2 and 0.5 mA/cm2. These results suggest sustainable and high-yielding Li-S batteries can be obtained for potential commercial applications.

Metal Coordinated Polymer as Three-Dimensional Network Binder for High Sulfur Loading Cathode of Lithium-Sulfur Battery.

The construction of high sulfur (S) loading cathode is one of the critical parameters to obtain lithium-sulfur (Li-S) batteries with high energy density, but the slow redox reaction rate of high S loading cathode limits the development process. In this paper, a metal coordinated polymer-based three-dimensional network binder, which can improve the reaction rate and stability of S electrode. Compared with traditional linear polymer binders, the metal coordinated polymer binder can not only increase the load amount of S through the three-dimensional cross-linking, but also promote the interconversion reactions between S and lithium sulfide (Li2 S), avoiding the passivation of electrode and improving the stability of the positive electrode. At an S load of 4-5mg cm-2 and an E/S ratio of 5.5µL mg-1 , the discharged voltage in the second platform is 2.04V and the initial capacity is 938 mA h g-1 with metal coordinated polymer binder. Moreover, the capacity retention rate approaches 87% after 100 cycles. In comparison, the discharged voltage in the second platform is lost and the initial capacity is 347 mA h g-1 with PVDF binder. It demonstrates the advanced properties of metal-coordinated polymer binders for improving the performance of Li-S batteries.

Lithium–sulfur battery cathode design:Sulfur-infiltrated PVDF nanofiber-based Fe3O4 network for polysulfide adsorption and volume expansion suppression

A sustainable polymer/nanomagnetic (PVDF/Fe3O4) composite nanofiber membrane is prepared on the Al current collector using electrospinning to serve as matrix for sulfur. The paramagnetic adsorption of polysulfides by Fe3O4 can suppress the shuttling effect, and the PVDF reserves as an elastic skeleton for alleviating volume changes of sulfur cathode. The results show that the cathode with PVDF/Fe3O4 composite nanofiber membrane has an initial discharge capacity of 1555.5 mA h g−1 at a rate of 0.1 C, and remains at 994.7 mA h g−1 after 300 cycles, showing a better cycle life than others without Fe3O4 or PVDF. This work provides a strategy for further promoting the commercialization of lithium-sulfur batteries.

Activating redox kinetics of polysulfides within edge-rich nitrogen doped porous interconnected carbon nanosphere

Theoretically, lithium-sulfur batteries (LSBs) are highly competitive in achieving high energy density storage systems. However, the shuttle effect of polysulfides (LiPSs) and sluggish redox kinetics have severely hampered the commercialization of LSBs. Although a number of catalysts have been applied to solve these problems, their preparation processes and costs are hardly compatible with universalization. Herein, we presented an edge-rich nitrogen-doped porous carbon nanospheres with an interconnection structure (N-PCS) as sulfur redox host, of which mesoporous voids accommodated sulfur to achieve homogenization of sulfur, microporous spaces acted as physical confinement to bind the LiPSs. The interconnected carbon nanosphere could be regarded as penetrated conductive network, which greatly shorten the diffusion distance of Li+ and accelerated carrier diffusion. Moreover, abundant edge doped-nitrogen substances introduced a large number of chemisorption centers and catalytic active sites, realizing the strong adsorption and rapid conversion of LiPSs within the N-PCS skeleton. As a result, the S/N-PCS cathode had a first discharge specific capacity of 755 mAh g−1 at 1.0 C and operated enduringly with an ultra-low capacity decay rate (0.04% per cycle) up to 1000 cycles. Not to be outdone, the S/N-PCS cathode provided area specific capacities of up to 4.76 and 5.27 mAh cm−2 at elevated sulfur loadings of 4.31 and 5.49 mg cm−2. This work not only provides a low-cost improvement strategy, but also expands new research ideas for the development of high-performance LSBs cathodes.

Cobalt-Carbon nanotubes supported on V2O3 nanorods as sulfur hosts for High-performance Lithium-Sulfur batteries

Exploring advanced sulfur cathode materials with high catalytic activity to accelerate the slow redox reactions of lithium polysulfides (LiPSs) is of great significance for lithium-sulfur batteries (LSBs). In this study, a coral-like hybrid composed of cobalt nanoparticle-embedded N-doped carbon nanotubes supported by Vanadium (III) oxide (V2O3) nanorods (Co-CNTs/C @V2O3) was designed as an efficient sulfur host using a simple annealing process. Characterization combined with electrochemical analysis confirmed that the V2O3 nanorods exhibited enhanced LiPSs adsorption capacity, and the in situ grown short-length Co-CNTs improved electron/mass transport and enhanced the catalytic activity for conversion to LiPSs. Owing to these merits, the S@Co-CNTs/C@V2O3 cathode exhibits effective capacity and cycle lifetime. Its initial capacity was 864 mAh g−1 at 1.0C and remained at 594 mAh g−1 after 800cycles with a decay rate of 0.039%. Furthermore, even at a high sulfur loading (4.5 mg cm−2), S@Co-CNTs/C@V2O3 also shows acceptable initial capacity of 880 mAh g−1 at 0.5C. This study provides new ideas for preparing long-cycle S-hosting cathodes for LSBs.

Single‐atomic tungsten‐doped Co3O4 nanosheets for enhanced electrochemical kinetics in lithium–sulfur batteries

AbstractThe practical application of lithium–sulfur batteries (LSBs) is severely hindered by the undesirable shuttling of lithium polysulfides (LiPSs) and sluggish redox kinetics of sulfur species. Herein, a series of ultrathin single‐atomic tungsten‐doped Co3O4 (Wx‐Co3O4) nanosheets as catalytic additives in the sulfur cathode for LSBs are rationally designed and synthesized. Benefiting from the enhanced catalytic activity and optimized electronic structure by W doping, the Wx‐Co3O4 not only reduces the shuttling of LiPSs but also decreases the energy barrier of sulfur redox reactions of sulfur species, leading to accelerated electrode kinetic. As a result, LSB cathodes with the use of 5.0 wt% W0.02‐Co3O4 as the electrocatalyst show the high reversible capacities of 1217.0 and 558.6 mAh g−1 at 0.2 and 5.0 C, respectively, and maintain a high reversible capacity of 644.6 mAh g−1 at 1.0 C (1.0 C = 1675 mA g−1) after 500 cycles. With a high sulfur loading of 5.5 mg cm−2 and electrolyte–electrode ratio of 8 μLelectrolyte mgsulfur−1, the 5.0 wt% W0.02‐Co3O4‐based sulfur cathode also retains a high reversible areal capacity of 3.86 mAh cm−2 at 0.1 C after 50 cycles with an initial capacity retention of 84.7%.