High-performance Li-S Batteries Research Articles

Holey graphene anchoring of the monodispersed nano-sulfur with covalently-grafted polyaniline for lithium sulfur batteries

The homogeneous distribution of nano-sulfur onto 3D structures for the development of high-performance Li-S batteries (LSBs) is a top concern to solve the low utilization of sulfur, sluggish redox kinetics, and lithium polysulfide (LiPS) shuttle effect. Herein, a novel “egg tray” hierarchical architecture of confining and uniformly distributing nano-sulfur into a 3D holey graphene (HG) framework with polyaniline crosslinking (3DHG/NS/CPANI) via photo-assisted method was designed for high-mass-loading LSB cathode. Notably, HG contains both conductive skeletons as electron transfer paths and abundant void spaces in favor of homogenous sulfur anchoring. This configuration improves the contact between nano-sulfur and graphene for effective charge transportation and provides buffering space for volume variations during electrochemical processes. Moreover, a facile photo-assisted method was developed to cross link HG with polyaniline to act as an efficient polysulfide adsorbent, allowing nano-sulfur (NS) to be firmly embedded into the holes of graphene through physical and chemical effects, thus prohibiting the dissolution and shuttle effect of polysulfide. Considering these advantages, the prepared 3DHG/NS/CPANI electrode exhibited excellent performance with high sulfur utilization and specific capacity, resulting in specific discharge capacities at 0.5 and 1C of 1082 and 921 mA h −1, respectively, and small capacity decay of 0.04% per cycle over 500 cycles at 1C. The strategy in this work, which synergistically combines morphology control, nano-sulfur positioning, and structural engineering to enhance the electrochemical performance for Li−S batteries, will offer a valuable reference to energy storage and conversion advances.

Atomically Dispersed and O, N-Coordinated Mn-Based Catalyst for Promoting the Conversion of Polysulfides in Li2S-Based Li-S Battery.

Nowadays, Li-S batteries are facing many thorny challenges like volume expansion and lithium dendrites on the road to commercialization. Due to the peculiarity of complete lithiation and the capability to match non-lithium anodes, Li2S-based Li-S batteries have attracted more and more attention. Nevertheless, the same notorious shuttle effect of polysulfides as in traditional Li-S batteries and the poor conductivity of Li2S lead to sluggish conversion reaction kinetics, poor Coulombic efficiency, and cycling performance. Herein, we propose the interconnected porous carbon skeleton as the host, which is modified by an atomically dispersed Mn catalyst as well as O, N atoms (named as ON-MnPC) via the melt salt method, and introduce the Li2S nanosheet into the carbon host with poly(vinyl pyrrolidone) ethanol solution. It has been found that the introduction of O, N to bind with Mn atoms can endow the nonpolar carbon surface with ample unsaturated coordination active sites, restrain the shuttle effect, and enhance the diffusion of Li+ and accelerate the conversion reaction kinetics. Besides, due to the ultra-high catalyst activity of atomically dispersed Mn catalysts, the Li2S/ON-MnPC cathode shows good electrochemical performance, e.g., an initial capacity of 534 mAh g-1, a capacity of 514.18 mAh g-1 after 100 cycles, a high retention rate of 96.23%, and a decay rate of 0.04% per cycle. Hence, use of atomically dispersed Mn catalysts to catalyze the chemical conversion reactions of polysulfides from multiple dimensions is a significant exploration, and it can provide a brand-new train of thought for the development and commercialization of the economical, high-performance Li2S-based Li-S batteries.

Multifunctional cation-vacancy-rich ZnCo2O4 polysulfide-blocking layer for ultrahigh-loading Li-S battery

The major hurdle in Li-S battery commercialization is the severe shuttle effect and sluggish reaction kinetics of polysulfide conversion during charge-discharge cycling. Herein, to overcome these barriers, we designed and synthesized Zn defective Zn/Co oxide (ZDZCO) nanosheets, a cation-vacancy-rich bimetallic oxide for the construction of a multifunctional polysulfide-blocking layer. Both theoretical and experimental studies have comprehensively demonstrated that the ZDZCO shows robust binding capability towards polysulfides and a high catalytic ability for fast polysulfide conversion. Through a facile coating process, the multifunctional ZDZCO polysulfide-blocking layer is incorporated on a commercial polypropylene separator, forming a composite separator. The resultant separator facilitates an ultrahigh sulfur loading of 21.06 mg cm -2 and an areal capacity as high as 24.25 mAh cm -2 . This study illuminates a promising and practical strategy to construct high-performance Li-S batteries with high sulfur loading. A multifunctional cation-vacancy-rich ZnCo 2 O 4 modified separator has been developed to create a strong affinity to polysulfides and rapid catalytic conversion between the polysulfides for the achievement of ultrahigh areal loading and high-performance Li-S batteries. • Cation-vacancy-rich bimetallic oxide constructs a novel multifunctional polysulfide-blocking layer. • Cation vacancies boost catalytic performance of the multifunctional polysulfide-blocking layer. • The Li-S battery achieves an ultrahigh loading of 21.06 mg cm -2 and prolonged lifespan of 60 cycles.

Boosting the polysulfides adsorption-catalysis process on carbon nanotube interlayer via a simple polyelectrolyte-assisted strategy for high-performance lithium sulfur batteries

The introduction of conductive interlayer is an effective strategy to improve the sulfur utilization and restrict the migration of polysulfides for high-performance Li-S battery. Herein, a multifunctional CNT based interlayer was obtained by a simple polyelectrolyte (PDDA-TFSI) modified method. Due to the electro-positivity of PDDA-TFSI and the electronic coupling between CNT and PDDA-TFSI, the CNT/PDDA-TFSI interlayer exhibits a strong adsorption and effective catalysis towards polysulfides. Furthermore, the continuous CNT network ensures the successful electron transport during the charge-discharge process. As expected, the electrochemical properties of Li-S battery can be promoted significantly with the assistance of CNT/PDDA-TFSI interlayer. Even after 300 cycles, the CNT/PDDA-TFSI interlayer-based Li-S battery also delivers a higher capacity retention of 79.2%, proceeding Li-S batteries with and without CNT interlayer. This work proves that CNT/PDDA-TFSI film as a multifunctional interlayer has a promising application in advanced Li-S battery.

TiO2 nanotube/RGO modified separator as an effective polysulfide-barrier for high electrochemical performance Li-S batteries

The “shuttle effect” in lithium-sulfur cell causes the terrible cycles stability, that hinders the Li-S batteries served as the next generation high energy density batteries. To address the issue, we investigated that anatase/bate crystal phase titanium dioxide nanotubes (TiO2 NTs) combined with reduced graphene oxide (RGO) to modify the initial polypropylene separator. The TiO2 NTs/RGO film not only localizes the migrating polysulfides by the common effects of chemical binding and physical adsorption but also enhances the lithium-ion migration by reducing the electrochemical resistance. The excellent chemical and physical adsorption ability were proved by the measurement of the X-ray photoelectron spectroscopy and adsorption experiments. The fast lithium-ion migration was analyzed by the diffusion experiment and electrochemical impedance systems. The outstanding initial discharge capacity of 1303.3 mAhg−1 at 0.2 C, which was 78% of the theoretical capacity. Over 100 cycles, the cell with TiO2 NTs/RGO coating separator still retained 620.6 mAhg−1 discharge capacity. The TiO2 NTs/RGO modifying separator exhibits great promise to develop the high energy Li-S batteries.

Bidirectionally catalytic polysulfide conversion by high-conductive metal carbides for lithium-sulfur batteries

Utilizing catalysts to accelerate the redox kinetics of lithium polysulfides (LiPSs) is a promising strategy to alleviate the shuttle effect of lithium–sulfur (Li–S) batteries. Nevertheless, most of the reported catalysts are only effective for LiPSs reduction, resulting in the devitalization of catalysts over extended cycles as a consequence of the continuous accumulation of Li2S passivation layer. The situation gets even worse when employing mono-directional catalyst with poor electron conductivity because the charge transfer for the decomposition of solid Li2S is severely hampered. Herein, a high-conductive and dual-directional catalyst Co3C decorated on porous nitrogen-doped graphene-like structure and carbon nanotube (Co3C@PNGr-CNT) is fabricated as sulfur host, which not only promotes the precipitation of Li2S from LiPSs during discharge but also facilitates the decomposition of Li2S during subsequent charge, as evidenced by the reduced activation energies for both reduction and oxidation processes. Furthermore, the long-term catalytic stability of Co3C is corroborated by the reversible evolution of Co–C bond length over extended cycles as observed from X-ray absorption fine structure results. As a consequence, the fabricated Co3C@PNGr-CNT/S cathode delivers a low capacity decay of 0.043% per cycle over 1000 cycles at 2C. Even at high sulfur loading (15.6 mg cm−2) and low electrolyte/sulfur (E/S) ratio (∼8 μL mg−1) conditions, the battery still delivers an outstanding areal capacity of 11.05 mAh cm−2 after 40 cycles. This work provides a rational strategy for designing high-efficient bidirectional catalyst with single component for high-performance Li-S batteries.

Facile and low-cost preparation of Co and N co-doped hierarchical porous carbon as a functional separator for Li-S batteries

Despite their ultrahigh theoretical capacity, the practical application of lithium-sulfur batteries (LiSBs) is still severely hindered by the shuttle effect of lithium polysulfides. Herein, we develop a Co and N co-doped carbon (CoN-CNT/HPC) as a modifying separator material to suppress this shuttle effect. The production of the material is low-cost and can be easily scaled up. The as-prepared CoN-CNT/HPC has a hybrid structure consisting of carbon nanotube (CNT) and hierarchical porous carbon sheet (HPC). This structure not only provides efficient pathways for charge transport but also encourages physical adsorption of polysulfides during the lithiation process. Additionally, the Co and N co-doping promotes the chemical adsorption of polysulfides and catalyzes polysulfide conversion. When used as a separator layer in Li-S batteries, CoN-CNT/HPC delivers excellent cycling stability with a low decay rate of 0.04% per cycle over 500 cycles at 2C. Even at high area sulfur loading of 5.5 mg/cm2, the cell using CoN-CNT/HPC separator still exhibits a high initial capacity of 646 mAh/g at 0.5 C and an outstanding cycling stability (561 mAh/g after 100 cycles). The present work provides a simple and effective design strategy of separator materials for high performance Li-S batteries.

Attapulgite and multiwalled carbon nanotubes co-integrated hierarchical porous polyacrylonitrile membrane as a multifunctional interlayer for lithium-sulfur batteries with enhanced performance

• ATTP and MWCNTs co-integrated porous PAN membrane was first fabricated. • The membrane was investigated as a multifunctional interlayer for Li-S batteries. • A synergistic effect of ATTP and MWCNTs effectively suppress the shuttle effect. • The cell with such interlayer demonstrates superior cycling stability . As a kind of natural porous nanorods, attapulgites (ATTP) are widely used in many fields because of their high specific surface area, high porosity and strong adsorption ability. In this work, ATTP and multiwalled carbon nanotubes (MWCNTs) co-integrated polyacrylonitrile (PAN) hierarchical porous membrane (ATTP/CNTs@PAN) has been fabricated and investigated as a multifunctional interlayer for lithium-sulfur batteries. Due to a synergistic effect of ATTP and the carboxylated MWCNTs, the porous interlayer is able to effectively suppress the shuttle effect by trapping and confining the dissolved polysulfides. Meanwhile, the addition of MWCNTs improves the conductivity of the composite membrane, which is beneficial for the reutilization of the active species. Therefore, the cells with the interlayer demonstrates superior electrochemical performance, delivering a high initial discharge capacity of 1283 mAh g −1 at 0.2 C, and retaining 785 mAh g −1 after 300 cycles with a Coulombic efficiency exceeding 99%. Meaningfully, this porous composite membrane is low-cost and very effective for high performance Li-S batteries.

Realizing High‐Performance Li‐S Batteries through Additive Manufactured and Chemically Enhanced Cathodes

Numerous efforts are made to improve the reversible capacity and long-term cycling stability of Li-S cathodes. However, they are susceptible to irreversible capacity loss during cycling owing to shuttling effects and poor Li+ transport under high sulfur loading. Herein, a physically and chemically enhanced lithium sulfur cathode is proposed to address these challenges. Additive manufacturing is used to construct numerous microchannels within high sulfur loading cathodes, which enables desirable deposition mechanisms of lithium polysulfides and improves Li+ and e- transport. Concurrently, cobalt sulfide is incorporated into the cathode composition and demonstrates strong adsorption behavior toward lithium polysulfides during cycling. As a result, excellent electrochemical performance is obtained by the design of a physically and chemically enhanced lithium sulfur cathode. The reported electrode, with a sulfur loading of 8 mg cm-2 , delivers an initial capacity of 1118.8 mA h g-1 and a reversible capacity of 771.7 mA h g-1 after 150 cycles at a current density of 3 mA cm-2 . This work demonstrates that a chemically enhanced sulfur cathode, manufactured through additive manufacturing, is a viable pathway to achieve high-performance Li-S batteries.

All-in-One Sulfur Host: Smart Controls of Architecture and Composition for Accelerated Liquid-Solid Redox Conversion in Lithium-Sulfur Batteries.

The development of Li-S batteries (LSBs) is largely impeded by sluggish redox kinetics and notorious polysulfide shuttling. Herein, hierarchical MoC@Ni-NCNT arrays are reported as a multifunctional sulfur host in Li-S batteries, which comprised a flexible carbon fiber cloth substrate decorated with vertical MoC porous nanorods rooted by interconnected nitrogen-doped carbon nanotubes (NCNTs). In the designed host, the inner MoC porous backbone (composed of nanoparticles) along with the in situ-grafted interwoven NCNT shell can greatly maximize the host-guest interactive surface for homogeneous sulfur dispersion, thus realizing decent high-sulfur-loading performance. Ni nanoparticles, encapsulated within NCNTs in the outer shell, act as strong chemical-anchoring centers effectively trap-escaped polysulfides and propel the bidirectional sulfur transformation kinetics. In merit of sufficient adsorption and catalytic sites, the cell configured with the MoC@Ni-NCNT cathode delivers not only high capacity (1421 mA h g-1 at 0.1 C) but also superior rate performance and ultralong lifespan. The cell can still achieve a superb areal capacity of 6.1 mA h cm2 under an increased sulfur loading up to 6 mg cm-2. This work could open a new avenue for the construction of a multifunctional cathode for high-performance LSBs.

Thickness-independent scalable high-performance Li-S batteries with high areal sulfur loading via electron-enriched carbon framework

Increasing the energy density of lithium-sulfur batteries necessitates the maximization of their areal capacity, calling for thick electrodes with high sulfur loading and content. However, traditional thick electrodes often lead to sluggish ion transfer kinetics as well as decreased electronic conductivity and mechanical stability, leading to their thickness-dependent electrochemical performance. Here, free-standing and low-tortuosity N, O co-doped wood-like carbon frameworks decorated with carbon nanotubes forest (WLC-CNTs) are synthesized and used as host for enabling scalable high-performance Li-sulfur batteries. EIS-symmetric cell examinations demonstrate that the ionic resistance and charge-transfer resistance per unit electro-active surface area of S@WLC-CNTs do not change with the variation of thickness, allowing the thickness-independent electrochemical performance of Li-S batteries. With a thickness of up to 1200 µm and sulfur loading of 52.4 mg cm−2, the electrode displays a capacity of 692 mAh g−1 after 100 cycles at 0.1 C with a low E/S ratio of 6. Moreover, the WLC-CNTs framework can also be used as a host for lithium to suppress dendrite growth. With these specific lithiophilic and sulfiphilic features, Li-S full cells were assembled and exhibited long cycling stability.

A porous rGO with high specific surface area and high content of doped-N modifying the separator for high performance Li-S battery

HSN-rGO with high specific surface area and high content of N is prepared via GO reduction and N-doping of DMF, corrosion oxidation pore-forming of H2O2 as well as further reduction and N-doping of N2H4•H2O under the solvothermal condition. The porous HSN-rGO has a high BET specific surface area of 464.3 m2 g−1. The N content in HSN-rGO is 5.27 at.%. The HSN-rGO shows a strong adsorption capability for the soluble lithium polysulfides (LiPSs) and more importantly it presents an excellent catalytic capability for the redox conversion of LiPSs. The HSN-rGO modified separator can inhibit the shuttle effect of LiPSs in Li-S battery. Besides, the HSN-rGO based separator has a good electrolyte wettability. The catalytic activity of HSN-rGO and Li+ diffusion property in Li-S battery are well studied quantitatively. The Li-S battery with HSN-rGO-PP separator exhibits a high initial discharge capacity of 1372.8 mAh g−1 at 0.1 C and 681.5 mAh g−1 at 2 C, and a low-capacity decay rate of 0.055% per cycle for 1000 cycles at 1 C. This study proves the strategy that the HSN-rGO modified separator can effectively inhibit the shuttle effect of LiPSs and accelerate the redox reaction kinetics for high-performance Li-S battery.

Nano storage-boxes constructed by the vertical growth of MoS2 on graphene for high-performance Li-S batteries

In order to accelerate the reaction kinetics of lithium-sulfur batteries, the introduction of electro catalysis and proper structural control of the sulfur cathode is urgently needed. MoS2 nano sheets was selectively grown vertically (V-MoS2) on the microwave-reduced graphene (rGO) sheets through chemical coupling to construct a self-supporting sulfur cathode with a nano storage-box structure (V-MoS2 as the wall and rGO as the bottom). RGO, which has a high conductivity of 37 S cm−1, greatly accelerates the transfer of electrons from the active sites on the edge of the layer to the solution. The introduction of carbon tubes can connect the abundant pores in the foam and act as a long-range conductive path. The 2D-orthogonal-2D structure maximally exposes the edge active sites of MoS2, and together with graphene form a nano reactor of sulfur, intermediate lithium polysulfides and discharge product Li2S(2). The effective combination of the microstructure confinement of the nano storage-boxes and the efficient synchronous catalytic mechanism of V-MoS2 greatly improves the electrochemical performance of the lithium-sulfur batteries. As a result, the assembled lithium-sulfur battery displays a high initial discharge capacity of 1379 mAh g−1, good cycle stability (86% capacity retention after 500 cycles at 0.1C) and superior rate performance.

Functionalized Mo2B2 MBenes: Promising anchoring and electrocatalysis materials for Lithium-Sulfur battery

Applications of Li-S batteries are primarily hindered by shuttling effect, poor electronic conductivity of sulfur and inactive decomposition of low-order lithium polysulfide (LiPS). To solve these problems, the anchoring and electrocatalysis properties of two-dimensional transition metal boride (MBene) have been extensively studied to provide general design principles for enhanced electrochemical performance in Li-S batteries. Our results show that direct application of bare Mo2B2 MBene in Li-S battery gives rise to the decomposition of high-order LiPSs, which originates from the excessively strong binding strength between S atoms and surface Mo atoms. Then, we highlight that surface functionalization on Mo2B2 MBene possesses suitable anchoring performance to suppress the shuttling effect. Meanwhile, owing to the excellent electronic conductivity even after the adsorption of LiPS, the functionalized MBenes effectively stimulate the redox electrochemistry in Li-S battery. Finally, accompanied with omnidirectional fast diffusion of Li atom, the functionalized MBene exhibits superior electrocatalysis activity for Li2S decomposition with ultra-low diffusion (0.191 eV) and decomposition (0.441 eV) barriers, improving the capability and coulombic efficiency of Li-S batteries. Our findings pioneer the application of MBenes as anchoring and electrocatalysis materials for Li-S batteries and provide a developed insight on the design of high-performance Li-S battery cathodes.

Binder Free Three-Dimensional Hybrid Cathode for Stable and High-Performance Li-S Batteries

Lithium-sulfur batteries (LSBs) represent a promising energy storage technology with a potential for next-generation high-energy storage systems due to their high specific capacity, abundant resources, low cost, non-toxicity, and environmentally friendly characteristics. However, due to many critical limitations such as insulating nature of elemental sulfur, poor lithium polysulfide (LiPS) conversion kinetics, polysulfide shuttle effect resulting in capacity fading, and low cyclic stability, commercialization of LSBs are far from realization. One of the most essential strategy to mitigate the issues with LSBs is to prevent polysulfide shuttling thereby maximizing the sulfur utilization and enhance the overall Li-S battery performance. In this work, we develop a binder free three-dimensional hybrid cathode for Li-S battery using multiwall carbon nanotubes (CNTs) and molybdenum sulfide (MoS2) as a catalyst, collectively enhancing LiPS conversion and ion transport ability and hence increased energy density, both gravimetric and volumetric. Different uniform mixtures of CNTs, MoS2, and conductive carbon black are prepared and loaded with high sulfur loading of ~6 mg cm-2. Various electrochemical performance parameters influencing cathode performance with respect to both gravimetric and volumetric energy densities are studied. Parameters that help improve the overall battery performance are identified and discussed.

Multifunctional Trilayer Separator for High-Performance Lithium-Sulfur Batteries Under Extreme Conditions

Lithium-ion Batteries (LIBs) have transformed mankind's lives beyond imagination in the past few decades. They have found their use in a variety of applications such as defense, transportation, portable electronics, and space explorations. To keep up with the demand, stress is applied for discovering materials with higher capacity and energy densities. High capacity anodes like silicon, tin, antimony, carbon composites have been identified. However, limited cathode materials are available at disposal viz., LiCoO2, LiMnNiCoO2, LiFePO4, LiMn2O4. Most of these cathodes have capacities <250 mAh g-1, and thus LIBs cannot keep up with the ever-growing demand from the applications. The high-theoretical capacity chemistry of lithium-sulfur comes to the rescue. It is the lightest element to be used as a cathode, which has attractive properties such as capacity of 1672 mAh g-1, economical (~$50 per metric tonne), and abundance in nature. However, chemistry suffers from three critical issues viz., poor sulfur conductivity, polysulfide shuttling, and lithium dendrite growth. To tackle the insulative sulfur and polysulfide shuttling effect approaches such as coating sulfur with metal sulfide or oxides, mesoporous carbon, conductive polymers, inverse vulcanization have been applied. Unfortunately, these techniques lead to a reduction in the energy density of the system, involve complex fabrication steps or raw materials are expensive. On the issue of lithium metal dendrites growth, electrolytic additives, exotic electrode coatings, and special shutdown separators are used. The downside to all of these is that they impede cell performance or are uneconomical.Here we report, the use of a multifunctional trilayer separator in Li-S battery to tackle all three issues simultaneously. Modified separator acted as a barricade for polysulfide from shuttling by trapping them preferably due to the favorable interactions. The performance of Li-S cells with and without modified separator was compared for long term cycling and rate studies. It was found that cells with modified separator outperformed those with pristine separator. Modified separator cell exhibited capacities of 925, 833, 644, 480, 326, 260, and 220 mAh g-1 at 0.1C, 0.2C, 0.5C, 1C, 2C, 3C and 4C rates, respectively with 95% capacity retention. The choice of electrolyte affects battery performance drastically. However, using 1M LiTFSI in 1:1 (v/v) 1, 3-Dioxolane (DOL): 1, 2-Dimethoxyethane (DME) with additives, provided remarkable results at low and high-temperature ranges. At 0 ℃, the cell with the modified separator yielded about 350 mAh g-1 capacity at 0.5C over 200 cycles. The performance of the cells was stellar even at 50 ℃ with 500 mAh g-1 capacity at 0.5C rate after 100 cycles. Multiple module calorimetry provided the thermal heat signature to elucidate the safety features of the Li-S system with the modified separator and compared with the existing LIBs. High-performance Li-S batteries proposed here can be valuable to a variety of applications like defense, transportation, and space explorations, where drastic conditions affect the battery functionalities, in the times ahead.

Defective graphene coating-induced exposed interfaces on CoS nanosheets for high redox electrocatalysis in lithium-sulfur batteries

Herein, we propose the construction of sandwich-structured hosts filled with continuous 3D catalysis-conduction interfaces. The RG@CoS@C-C-RG@CoS@C architecture enables fast electron and Li+ diffusion, strong adsorption of S/Li2Sx and high-efficiency conversion on two-sided RG@CoS surfaces. With detailed experimental and theoretical characterization, we reveal that although the conformal graphene coating largely shields the catalytic activity and adsorbing ability of CoS nanosheets, the exposed interfaces of CoS at the defective sites of the graphene coating exhibit especially strong lithium polysulfide (LiPSs) anchoring and high conversion efficiency, with high-flux Li+ and electron transfer from the circumjacent graphene coating and the buried carbon nanofibers. Furthermore, the exposed interfaces exhibit an effective decrease in Li2S decomposition by releasing Li+ onto the circumjacent graphene surface with a low Li+ diffusion barrier and anchoring the remaining Li-S bond on the exposed CoS interface with a high adsorption energy. The unique structure consisting of catalytic CoS nanosheets, defective RG coating, and interwoven C fiber interlayers enables not only the coupling of Li+ diffusion and electron transfer but also efficient regulation of the polysulfide reaction, thereby producing a synergistic catalyzing effect on both LiPS conversion and Li2S decomposition. As a result, the batteries with RG@CoS@C membranes as interlayers exhibit stable cycle performance and reversible capacities of 629.2 mA h g−1 after 420 cycles at 2.0 C. The proposed strategy will contribute to guiding the design of novel composite materials for high-performance Li-S batteries.

High-performance Li-S batteries enabled by polysulfide-infiltrated free-standing 3D carbon cloth with CeO2 nanorods decoration

To achieve scale-up commercialization of Li-S batteries, parasitic shuttle effect, leading to low utilization of active material and fast capacity decay, has to be resolved effectively. Herein, we prepared CeO2 nanorods decorated interwoven 3-D carbon cloth via facile one-step hydrothermal reaction and Li2S6-containing polysulfide as starting material to successfully improve the electrochemical performance of Li-S battery. First, strong chemical interaction toward polysulfides was successfully constructed by polar CeO2 nanorods and numerous oxygen vacancies on their surface acting as efficient polysulfides anchoring sites significantly enhanced the utilization of active material sulfur. Second, interwoven freestanding carbon cloth can considerably enhance redox kinetics through a 3-D interconnected network with abundant long-range electron transfer channels and can significantly improve redox kinetics by easy accessibility to electrolyte and abundant ion transport pathways. Third, the utilization of Li2S6-containing catholyte leads to uniform distribution of active material and improves sulfur utilization. Benefiting from the aforementioned advantages, free-standing 3-D carbon cloth with CeO2 nanorods decoration combined with Li2S6-containing catholyte (CC@CeO2@Li2S6) electrode delivered an initial discharge capacity of 1311 mA h g−1 at 0.2C and approximately 95% of the initial discharge capacity was remained after 100 galvanostatic cycles, manifesting superior capacity retention with minimal capacity fading of 0.050% per cycle.

Facilitating redox kinetics of sulfur species by cobalt-nitrogen co-doped porous hollow carbon for high-performance Li-S battery

The shuttle effect of polysulfides is the main obstacle restricting the development of lithium-sulfur batteries. However, most efforts focused on physical adsorption and polar adsorption cannot fundamentally solve the problem of sluggish conversion of polysulfides, especially for high sulfur loading. Herein, a cobalt-nitrogen co-doped porous hollow carbon sphere (Co-CN) is synthesized in one step. The porous conductive carbon spheres can realize a rapid charge transfer, mitigate volume expansion during cycling and enhanced physical adsorption for polysulfides. Nitrogen and cobalt doping provide chemisorption and catalysis for the restriction and conversion of polysulfides. Furthermore, liquid Li2S8 polysulfide was used as sulfur source to guarantee high sulfur loading and fast redox kinetic. Benefiting from the triple effect of physical adsorption, chemical adsorption and catalysis, the Co-CN@Li2S8 cell with sulfur loading of 5.15 mg cm−2 delivers a high reversible initial capacity of 1499 mAhg−1 at 0.1C and 880.9 mAhg−1 after 100 cycles. More excitingly, the capacity decay rate was only 0.012% per cycle at 1C over 1000 cycles, indicating excellent long cycle stability. This work provides a facile and effective route for Co-CN as a sulfur host in lithium-sulfur battery.

A novel hierarchical porous carbon derived from durian shell as enhanced sulfur carrier for high performance Li-S batteries

Herein, this study reports a durian shell derived hierarchical porous carbon (DPC) material as the cathode precursor for lithium-sulfur batteries. The DPC with special pore feature is synthesized through carbonizing durian shell and activating by KOH, and then the sulfur is encapsulated into hierarchical porous carbon (DPC/S) successfully for the cathode material. The synthesis conditions of alkali/carbon ratio and activation temperature have important influence on the pore features of DPC and the electrochemical performance of DPC/S composites. When the activation temperature is 900 °C, the pore volume of 4DPC with the alkali/carbon ratio of 4 is 1.6 cm3 g−1 while the range of pore size distribution is 0.5–20 nm. At a current density of 0.5C, the discharge capacity of 4DPC-900/S reaches 604 mAh g−1 after 100 cycles. Not only the pore volume can influence on the electrochemical performance of DPC/S composites, but the pore size distribution plays an important role as well.