Stable Lithium Sulfur Batteries Research Articles

Interfacial synergy of nanoengineered PANI/MnO2 for strong anchoring and fast conversion of polysulfides in Li-S batteries

The shuttle of polysulfides and slow sulfur redox kinetics are the two main issues in the practical application of lithium sulfur (Li-S) batteries. The interface-induced electric fields produced in MnO2-based conductive composites are proposed to solve the above obstacles. Herein, a novel hybrid structure of birnessite-MnO2 nanosheets in situ formed inside polyaniline nanotubes (NSs-MnO2@PANI) is prepared and applied as a catalytic host in Li-S batteries. The DFT calculation combined with experiments reveal the interface-induced electric field with a direction pointing from PANI to birnessite-MnO2 is created, which would induce interface charge redistribution and result in electron-rich MnO2 region and electron-deficient PANI region, optimizing the strong anchoring of polysulfides and their fast catalytic conversions. Owing to the interfacial synergy, the NSs-MnO2@PANI/S cathode delivers higher capacity than PANI/S at rates from 0.1 C (1473.7 vs. 467.5 mAh g−1) to 5 C (513.2 vs. 38.1 mAh g−1), with a low decay rate of 0.054% during 500 cycles at 0.2 C. Further, at an extremely high sulfur loading of 15.9 mg cm−2, the areal capacity achieves a high level of 10.2 mAh cm−2 at 0.05 C, with stable cycling at 1 C. Our work provides new insights for attaining high-energy and stable Li-S batteries.

Decoration on the inner surface of low-tortuosity microchannels derived from wood plate for highly stable lithium sulfur batteries

The low-tortuosity microchannels of wood-based carbon matrix in free-standing cathodes for lithium sulfur batteries (LSBs) were a double-edged sword, which brought in both a high energy density due to a high sulfur loading and severe shuttle effect for poor cycling stability. Herein, a layer of cellulose aerogel extracted from the wood wall was coated on the inner surface of the low-tortuosity microchannels of the wood plate, which was further transformed into a hierarchical carbon matrix using in free-standing cathode for LSBs. The decorated cathode exhibited a maximal specific capacity of 1377.2 mAh g−1 due to the enhanced utilizing ratio of active materials and exceptional cycling stability even under a high current density (1 C) for more than 500 cycles. Furthermore, the decorated cathode maintained good cycling stability with a higher sulfur areal loading (6.3 mg cm−2). The cellulose-based carbon aerogel coated on the inner surface of low-tortuosity microchannels provided a large specific surface area. This decoration strategy not only provided physical restriction on polysulfides but also increased conversion sites for polysulfides, improving the cycling performance of the wood-based free-standing cathode of LSBs. This work provided a potential structural design strategy for the advanced free-standing cathode of LSBs.

In Situ Growth Strategy to Construct "Four-In-One" Separators with Functionalized Polyphosphazene Coatings for Safe and Stable Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) are facing many challenges, such as the inadequate conductivity of sulfur, the shuttle effect caused by lithium polysulfide (LiPSs), lithium dendrites, and the flammability, which have hindered their commercial applications. Herein, a "four-in-one" functionalized coating is fabricated on the surface of polypropylene (PP) separator by using a novel flame-retardant namely InC-HCTB to meet these challenges. InC-HCTB is obtained by cultivating polyphosphazene on the surface of carbon nanotubes with an in situ growth strategy. First, this unique architecture fosters an enhanced conductive network, bolstering the bidirectional enhancement of both ionic and electronic conductivities. Furthermore, InC-HCTB effectively inhibits the shuttle effect of LiPSs. LSBs exhibit a remarkable capacity of 1170.7mAhg-1 at 0.2C, and the capacity degradation is a mere 0.0436% over 800 cycles at 1C. Third, InC-HCTB coating serves as an ion migration network, hindering the growth of lithium dendrites. More importantly, InC-HCTB exhibits notable flame retardancy. The radical trapping action in the gas phase and the protective effect of the shielded char layer in the condensed phase are simulated and verified. This facile in situ growth strategy constructs a "four-in-one" functional separator coating, rendering InC-HCTB a promising additive for the large-scale production of safe and stable LSBs.

Metal Nanoclusters as a Superior Polysulfides Immobilizer toward Highly Stable Lithium–Sulfur Batteries (Small 2/2024)

Metal Nanoclusters as a Superior Polysulfides Immobilizer toward Highly Stable Lithium–Sulfur Batteries (Small 2/2024)

Cationic charge effect of glutamine repulsion adsorbate on Li metal surfaces for highly stable lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs) are superior next-generation batteries compared to commercial lithium-ion batteries (LiBs) because of their gravimetric energy densities, which provide longer battery life in a lighter package. However, the biggest hurdle for commercializing LSBs is their poor long-term cycling performance, which stems from polysulfide shuttling. To address this issue, we propose a novel approach: the use of glutamine, an amino acid, as an electrolyte additive to increase the cycling stability. Due to its molecular structure containing amines, the formation of Li dendrites was obstructed by homogenizing the Li-ion flux to shield the exceedingly active Li surfaces with glutamine, thereby reducing the overvoltage during Li plating and stripping. Additionally, the redox reactions of lithium polysulfides were enhanced, which helped to alleviate the shuttling of lithium polysulfides. Therefore, the addition of glutamine improved the stability and reduced the cell degradation rate by approximately 0.066% during high C-rate long-term cycling tests.

A Facile Molten Salt Method for Diverse TiC/C Hybrid as Effective Polysulfide Confinement toward Stable Lithium–Sulfur Batteries

Traditional carbon materials suffer from weak adsorption of lithium polysulfides and excessive consumption of electrolyte. A simple and feasible molten salt method is applied for constructing an active nanocrystalline TiC shell on the surface of porous carbon. The highly active TiC nanoshells endow the core–shell composite with efficient chemical–physical synergistic adsorption, which can effectively confine and convert polysulfides, thereby improving the electrochemical performance of lithium–sulfur batteries. The lithium–sulfur batteries assembled with modified separator deliver a high initial discharge specific capacity of 1396 mAh g−1 at a discharge rate of 0.5 C and a high capacity retention of 747.1 mAh g−1 after 500 cycles, with a high coulombic efficiency of 98% during cycling. Besides, this molten salt method can be applied to modify the porous carbon materials of various composite sulfur cathodes such as graphene, carbon nanotubes, and 3D nonwoven carbon fabrics.

N/P Codoped Carbon Nanofibers Coupled with Chrysanthemum-Like Cobalt Phosphide Hybrid for Stable Lithium–Sulfur Batteries

N/P Codoped Carbon Nanofibers Coupled with Chrysanthemum-Like Cobalt Phosphide Hybrid for Stable Lithium–Sulfur Batteries

Flame-retardant ammonium polyphosphate/MXene decorated carbon foam materials as polysulfide traps for fire-safe and stable lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries are one of the most promising modern-day energy supply systems because of their high theoretical energy density and low cost. However, the development of high-energy density Li-S batteries with high loading of flammable sulfur faces the challenges of electrochemical performance degradation owing to the shuttle effect and safety issues related to fire or explosion accidents. In this work, we report a three-dimensional (3D) conductive nitrogen-doped carbon foam supported electrostatic self-assembled MXene-ammonium polyphosphate (NCF-MXene-APP) layer as a heat-resistant, thermally-insulated, flame-retardant, and freestanding host for Li-S batteries with a facile and cost-effective synthesis method. Consequently, through the use of NCF-MXene-APP hosts that strongly anchor polysulfides, the Li-S batteries demonstrate outstanding electrochemical properties, including a high initial discharge capacity of 1191.6 mA h g−1, excellent rate capacity of 755.0 mA h g−1 at 1 C, and long-term cycling stability with an extremely low-capacity decay rate of 0.12% per cycle at 2 C. More importantly, these batteries can continue to operate reliably under high temperature or flame attack conditions. Thus, this study provides valuable insights into the design of safe high-performance Li-S batteries.

Titanium nitride nanorod array/carbon cloth as flexible integrated host for highly stable lithium–sulfur batteries

Titanium nitride nanorod array/carbon cloth as flexible integrated host for highly stable lithium–sulfur batteries

N-Doped Graphene Nanofibers with Porous Channel Comprising Fe x S y Nanocrystals and Intertwined N-Doped CNTs as Efficient Interlayers for Li-S Batteries

Hierarchically porous and conductive nanofibers (NFs) comprising nitrogen-doped reduced graphene oxide (N-rGO) and iron sulfide (Fe x S y ) nanocrystals along with highly intertwined nitrogen-doped carbon nanotubes (N-CNTs) abbreviated as “P-rGO@Fe x S y /N-CNT NFs” were synthesized via electrospinning technique as multifunctional interlayers via coating on the commercial separator for stable lithium-sulfur (Li-S) batteries. The porous N-rGO framework acts as a backbone to enhance the structural integrity of the nanostructure. The N-CNTs and N-rGO guarantee various conductive channels for quick electron transfer thus allowing fast redox reactions. The thermal breakdown of polystyrene (PS) resulted in the formation of continuous longitudinal channels. Correspondingly, the Li-S cell incorporating the P-rGO@Fe x S y /N-CNT NF-modified separator and S electrode (2.41 mg cm-2) exhibited boosted electrochemical properties such as justifiable rate capability and steady cycling performance (after 800 charge-discharge, cell exhibits a capacity of 464 mA h g-1 with 44% retention at 0.1 C). The novel synthesis strategy discussed herein will provide significant intuitions to the advancement of innovative nanostructures for different rechargeable purposes.

A flame-retardant binder with high polysulfide affinity for safe and stable lithium-sulfur batteries

A flame-retardant binder with high polysulfide affinity for safe and stable lithium-sulfur batteries

Metal Nanoclusters as a Superior Polysulfides Immobilizer toward Highly Stable Lithium-Sulfur Batteries.

Due to their high designability, unique geometric and electronic structures, and surface coordination chemistry, atomically precise metal nanoclusters are an emerging class of functional nanomaterials at the forefront of materials research. However, the current research on metal nanoclusters is mainly fundamental, and their practical applications are still uncharted. The surface binding properties and redox activity of Au24 Pt(PET)18 (PET: phenylethanethiolate, SCH2 CH2 Ph) nanoclusters are herein harnessed as an high-efficiency electrocatalyst for the anchoring and rapid conversion of lithium polysulfides in lithium-sulfur batteries (LSBs). Au24 Pt(PET)18 @G composites are prepared by using the large specific surface area, high porosity, and conductive network of graphene (G) for the construction of battery separator that can inhibit polysulfide shuttle and accelerate electrochemical kinetics. Resultantly, the LSB using a Au24 Pt(PET)18 @G-based separator presents a high reversible specific capacity of 1535.4mA h g-1 for the first cycle at 0.2 A g-1 and a rate capability of 887mA h g-1 at 5 A g-1 . After 1000 cycles at 5 A g-1 , the capacity is 558.5mA h g-1 . This study is a significant step toward the application of metal nanoclusters as optimal electrocatalysts for LSBs and other sustainable energy storage systems.

Anchoring and catalyzing polysulfides by rGO/MoS2/C modified separator in lithium–sulfur batteries

Effective adsorption and catalysis are vital in developing high-efficient and stable lithium-sulfur (Li–S) batteries. Here, a coral-like porous composite containing molybdenum sulfide (rGO/MoS2/C) as interlayer on the separator to mitigate polysulfide shuttling. Since the rGO/MoS2/C composite exhibits promising electrolyte wetting properties with a large specific surface area, which can be fully utilized for the adsorption of lithium polysulfides (LiPSs). In addition, the molybdenum sulfide active site can effectively bind to and catalyze the conversion of LiPSs, further preventing the penetration of LiPSs. As a result, the assembled device shows excellent cycle stability with a low capacity decay of 0.022% per cycle over 1000 cycles (2.0C). In addition, the device still preserves a decent cycle ability even at low electrolyte and high sulfur loading conditions. This work presents a feasible strategy to anchor and accelerate the conversion of LiPSs by designing multifunctional transition metal sulfide composites with high adsorption properties and catalytic activity to achieve stable cycle of Li–S batteries.

Mott-Schottky MXene@WS2 Heterostructure: Structural and Thermodynamic Insights and Application in Ultra Stable Lithium-Sulfur Batteries.

Due to the "shuttle effect" and low conversion kinetics of polysulfides, the cycle stability of lithium sulfur (Li-S) battery is unsatisfactory, which hinders its practical application. The Mott-Schottky heterostructures for Li-S batteries not only provide more catalytic/adsorption active sites, but also facilitate electrons transport by a built-in electric field, which are both beneficial for polysulfides conversion and long-term cycle stability. Here, MXene@WS2 heterostructure was constructed by in-situ hydrothermal growth for separator modification. In-depth ultraviolet photoelectron spectroscopy and ultraviolet visible diffuse reflectance spectroscopy analysis reveals that there is an energy band difference between MXene and WS2 , confirming the heterostructure nature of MXene@WS2 . DFT calculations indicate that the Mott-Schottky MXene@WS2 heterostructure can effectively promote electron transfer, improve the multi-step cathodic reaction kinetics, and further enhance polysulfides conversion. The built-in electric field of the heterostructure plays an important role in reducing the energy barrier of polysulfides conversion. Thermodynamic studies reveal the best stability of MXene@WS2 during polysulfides adsorption. As a result, the Li-S battery with MXene@WS2 modified separator exhibits high specific capacity (1613.7 mAh g-1 at 0.1 C) and excellent cycling stability (2000 cycles with 0.0286 % decay per cycle at 2 C). Even at a high sulfur loading of 6.3 mg cm-2 , the specific capacity could be retained by 60.0 % after 240 cycles at 0.3 C. This work provides deep structural and thermodynamic insights into MXene@WS2 heterostructure and its promising prospect of application in high performance Li-S batteries.

Stable Lithium-Sulfur Batteries Ensured by GeS2 and α-S8 Lattice Matching During the Charge Process.

The charge process of lithium-sulfur batteries (LSBs) is a process in which molecular polarity decreases and the volume shrinks gradually, which is the process most likely to cause lithium polysulfides (LiPSs) loss and interfacial collapse. In this work, GeS2 is utilized, whose (111) lattice plane exactly matches with the (113) lattice of α-S8 , to solve these problems. GeS2 can regulate the interconversion-deposition behavior of S-species during the charge process. Soluble LiPSs can be spontaneously adsorbed on the GeS2 surface, then obtain electrons and eventually convert to α-S8 molecules. More importantly, the α-S8 molecules will crystallize uniformly along the (111) lattice plane of GeS2 to maintain a stable cathode-electrolyte interface. Therefore, outstanding charge/discharge LSBs are successfully accomplished.

Gel electrolyte with flame retardant polymer stabilizing lithium metal towards lithium-sulfur battery

Gel polymer electrolytes have the advantages of both solid and liquid electrolytes. Generally speaking, the liquid electrolyte is physically stored in the porous structure of polymer matrix which cannot block the reactions between the liquid electrolyte and the thermodynamically unstable lithium metal. At the same time, the stored liquid electrolyte still presents a safety hazard. This work designed and prepared a flame-retardant polymer Polyimide (PI) that can gelatinize the classic carbonate liquid electrolyte to form a flame-retardant gel polymer electrolyte, which greatly improved the safety of the battery. More importantly, there was CH/π interaction between the PI and the carbonate solvents which obviously reduced electrolyte consumption and side reactions with lithium metal. The proposed gel polymer electrolyte achieved a high lithium ion transference number of 0.727 and ensured remarkably stable lithium-sulfur batteries with SPAN cathodes.

Ordered porous metal oxide embedded dense carbon network design as high-performance interlayer for stable lithium-sulfur batteries

The design of multifunctional interlayer is important for the suppression of lithium polysulfides (LiPSs) shuttle effect in lithium-sulfur (Li-S) batteries. Herein, a multifunctional interlayer fabrication strategy is developed by depositing ordered porous metal oxide embedded with nitrogen-doped carbon nanotubes (NCNT) on the carbon nanofibers (CNFs) skeleton. In this design strategy, three-dimensional ordered macroporous N, Co-doped titanium oxides (N,Co-TiOx) is uniformly deposited on CNFs network, then in-situ growth of NCNT is implemented within the ordered porous oxides framework and CNFs, forming dense-structured adsorption/catalytic multifunctional interlayer (N,Co-TiOx/NCNT@CNFs). The ordered porous N,Co-TiOx together with the implemented NCNT not only provides an effective physical barrier for polysulfides diffusion, but also offers strong chemical interaction with LiPSs adsorption and promoted catalytic conversion kinetics. With these merits, the Li-S battery with N,Co-TiOx/NCNT@CNFs interlayer delivers an impressive rate capability of 638 mAh g-1 at a current density of 5 C. The cell also shows excellent cycling performance with a capacity decay of 0.033 % per cycle after 500 cycles at 1 C. More importantly, the Li-S pouch cells with N,Co-TiOx/NCNT@CNFs interlayer achieve a capacity of 806 mA h g−1 at sulfur loading of 4.0 mg cm−2 after 50 cycles at 0.1 C. This ordered porous metal oxide embedded dense carbon network design provides alternative strategy for the development of high-performance Li-S batteries interlayer.

Highly stable lithium sulfur batteries enhanced by flocculation and solidification of soluble polysulfides in routine ether electrolyte

Lithium-sulfur batteries (LSBs) are among the most promising next-generation high energy density energy-storage systems. However, practical application has been hindered by fundamental problems, especially shuttling by the higher-order polysulfides (PSs) and slow redox kinetics. Herein, a novel electrolyte-based strategy is proposed by adding an ultrasmall amount of the low-cost and commercially available cationic antistatic agent octadecyl dimethyl hydroxyethyl quaternary ammonium nitrate (SN) into a routine ether electrolyte. Due to the strong cation–anion interaction and bridge-bonding with SN, rapid flocculation of the soluble polysulfide intermediates into solid-state polysulfide-SN sediments is found, which significantly inhibited the adverse shuttling effect. Moreover, a catalytic effect was also demonstrated for conversion of the polysulfide-SN intermediates, which enhanced the redox kinetics of Li–S batteries. Encouragingly, for cells with only 0.1 % added SN, an initial specific capacity of 783.6 mAh/g and a retained specific capacity of 565.7 mAh/g were found at 2C after 200 cycles, which corresponded to an ultralow capacity decay rate of only 0.014 % per cycle. This work may provide a simple and promising regulation strategy for preparing highly stable Li–S batteries.

Tubular C3N4 Nanotubes as Metal-Free Sulfur Hosts toward Stable Lithium–Sulfur Batteries

Lithium–sulfur batteries (LSBs) with high energy density have the potential to replace current commercial lithium-ion batteries. However, the shuttle effect and the low conversion kinetics of lithium polysulfide (LiPS) remain the main challenges in the development of LSBs. In this study, a metal-free and simple-to-prepare carbon nitride with a high surface area and tubular morphology (CN-nt) is used as the sulfur host for LSBs. Due to its unique nanostructure and rich active sites, it not only effectively disperses the active sulfur material and anchors soluble polysulfide species, but it also promotes the nucleation process of Li2S, thus achieving fast and sustainable Li-S redox reactions. Experimental results show that the obtained S@CN-nt electrodes exhibit a high sulfur utilization of 1296.2 mAh g−1 at 0.1 C and a significant rate capability of 689.4 mAh g−1 at the high current rate of 3C. More importantly, the capacity retention reaches 87.7% after 500 cycles. This simple strategy of engineering unique carbon-based nanostructured hosts can inspire new ideas for developing cost-effective and metal-free host materials for sulfur-based batteries.

A sandwich-structured bifunctional separator for durable and stable lithium-sulfur batteries

The shuttle effect of polysulfide (PS) and dendrite growth are two main obstacles in the development of lithium-sulfur (Li-S) batteries. Herein, we propose a sandwich-structured metal–organic framework (MOF)-based separator with UiO-66-(OH)2 membranes symmetrically prepared on polypropylene separator for these challenges. On one aspect, the UiO-66-(OH)2 membrane can selectively block PS through the size sieving and electrostatic repulsion effect towards the neutral PS molecules and negatively charged PS ions, respectively. In addition, the reaction kinetics are also promoted by the introduced MOF membrane. On the other aspect, with lipophilic groups and ordered channels, this MOF membrane facilitates a rapid and uniform Li+ diffusion, thereby suppressing the Li dendrites. Consequently, Li-S batteries with this double-side modified separator exhibit a surprising capacity of 903 mAh g−1 and a long cycling stability with a low decay of 0.046% per cycle for 600 cycles under 2C. Even at raised sulfur loading and lean electrolyte conditions, exceptional cycling and rate performance can be still achieved. This work will advance the construction of multifunctional nanomaterials for Li-S batteries.