High Areal Sulfur Loading Research Articles

Enhanced Li bonds enable bidirectional sulfur catalysis by a molecular Co-N4 catalyst for lithium-sulfur batteries

Sulfur conversion catalysis is an effective strategy to tackle the inherent polysulfide shutting and fast capacity decay in lithium-sulfur batteries. Previous studies identified cobalt phthalocyanine as a unique molecular catalyst with Co-N4 active sites to promote sulfur reduction reactions. Herein, enhancing the Li bonds with the pyridinic N atoms on the phthalocyanine ligand is demonstrated to endow further catalytic activity in sulfur oxidation reactions. This is enabled by peripheral substitution with electron-donating methoxy groups that strengthens the electronegativity of the pyridinic N atoms. DFT calculations and metadynamics simulations identify the key role of Li bonds in reducing the energy barrier of Li2S dissociation. The highly lithiophilic methoxy groups also stabilize the dissociated Li cations in their solvation structure. The dissociated S anion can then be oxidized to higher-order polysulfides or radicals by electron donation to the Co-N4 center, which activates Li2S for subsequent oxidation. Meanwhile, the catalytic activity in sulfur reduction reactions is also improved by a more efficient electron transfer to adsorbed Li2S4, during which the strengthened Li bonds are beneficial in mediating the breakage of the bridging S-S bond. Significant performance improvements are achieved with the bidirectional catalyst under high areal sulfur loading and in Li-S pouch cells.

Ultrathin Two-Dimensional Ordered Porous Carbon Host with Atomically Dispersed Electrocatalytic Sites toward High Volumetric Energy Lithium-Sulfur Battery

Despite multimodal approaches to increase the gravimetric capacity of lithium-sulfur (Li-S) batteries over the years, strategies on achieving high volumetric capacity (Qv) at close to practical cell operating conditions with high areal sulfur loading and low electrolyte-to-sulfur (E/S) ratio are still lacking. Here, we report that a synergistic effect of a carbonaceous framework with precisely-controlled porous structure/dimension and highly-active, surface-mediated electrocatalysis by a ruthenium (Ru) single-atom electrocatalyst (SAC) composed of N2RuCl2 achieves high Qv in Li-S batteries. Two-dimensional (2D) and hierarchically ordered porous structures of polymer interfacial self-assembly derived N-doped carbon nanosheets (NCNS) realize a highly-packed sulfur cathode with outstanding Li+ ion diffusivity and electrode stability, which have been considered as main impediments to achieving high Qv in a dense sulfur cathode. Moreover, homogeneous incorporation of N2RuCl2 SAC which has novel Ru coordination environment with two N and Cl atoms on the surface of NCNS remarkably accelerated the reaction kinetics of Li-S electrochemistry and achieved high Qv even at high sulfur loading (5.0 mg cm−2), extremely low E/S ratio (4.5 μL mg−1), and low electrode porosity (50 %).

Iron, cobalt co-embedded in situ graphitized xerogel-derived carbon as sulfur host for ultrahigh rate and high-performance lithium-sulfur batteries

Lithium‑sulfur battery (LSB) is an enticing technology because of its high specific capacity, potential energy density, and natural abundance of sulfur in the earth's crust. However, some notorious issues need to mitigate before commercialization. Here we report a novel and scalable iron, cobalt co-embedded resorcinol formaldehyde derived carbon framework as sulfur host for high-performance LSB. To further increase the specific surface area and porosity of carbon, polyvinyl alcohol (PVA) is used as a sacrificial polymer. One pot synthesis method is used for preparing the Fe, Co co-embedded PVA incorporated RF xerogel-derived carbon (FC-PRFC) framework. The first-principles calculations suggest the advantage of bimetallic doping in enhancing the binding energy and reducing the energy gap of the carbon host for polysulfide anchoring. The porous structure and higher specific area of FC-PRFC enable high sulfur loading in the composite and show excellent rate performance and cyclability, as suggested by detailed electrochemical analysis. Moreover, the FC-PRFC cathode host with a high areal sulfur loading of 4.2 mg cm−2 delivers a high initial discharge capacity of 1283 mAh g−1 at 0.1C. During long-cycling at a high current rate of 4C, it retains a capacity of 372 mAh g−1 after 400 charge-discharge cycles with a capacity retention of 73 %. This scalable, innovative, low-cost fabrication technique has the potential to pave the way for developing an outstanding xerogel-derived carbon framework for high-performance LSBs for commercial applications.

Selective Reduction of Multivariate Metal-Organic Frameworks for Advanced Electrocatalytic Cathodes in High Areal Capacity and Long-Life Lithium-Sulfur Batteries.

Lithium-sulfur batteries hold great promise as next-generation high-energy-density batteries. However, their performance has been limited by the low cycling stability and sulfur utilization. Herein, we demonstrate that a selective reduction of the multivariate metal-organic framework, MTV-MOF-74 (Co, Ni, Fe), transforms the framework into a porous carbon decorated with bimetallic CoNi alloy and Fe3O4 nanoparticles capable of entrapping soluble lithium polysulfides while synergistically facilitating their rapid conversion into Li2S. Electrochemical studies on coin cells containing 89 wt % sulfur loading revealed a reversible capacity of 1439.8 mA h g-1 at 0.05 C and prolonged cycling stability for 1000 cycles at 1 C/1060.2 mA h g-1 with a decay rate of 0.018% per cycle. At a high areal sulfur loading of 6.9 mg cm-2 and lean electrolyte/sulfur ratio (4.5 μL:1.0 mg), the battery based on the 89S@CoNiFe3O4/PC cathode provides a high areal capacity of 6.7 mA h cm-2. The battery exhibits an outstanding power density of 849 W kg-1 at 5 C and delivers a specific energy of 216 W h kg-1 at 2 C, corresponding to a specific power of 433 W kg-1. Density functional theory shows that the observed results are due to the strong interaction between the CoNi alloy and Fe3O4, facilitated by charge transfer between the polysulfides and the substrate.

Uniform loading of ultrathin MoS2 nanosheets on hollow carbon spheres with mesoporous walls as efficient sulfur hosts for promising lithium-sulfur batteries

The electrochemical performance of lithium-sulfur batteries (LSBs) can be improved by combining rational structural design with the high-efficient catalyst to construct sulfur host materials. The PVP-assisted hydrothermal method was used to synthesize a composite (HCSM@uMoS2) with ultrathin MoS2 nanosheets uniformly loaded on hollow carbon spheres with mesoporous walls (HCSM). The ultrathin MoS2 nanosheets containing 1T metal phase (uMoS2) improved the electrical conductivity of the material while exposing more active sites, enhanced the adsorption to polysulfide and improved the redox reaction kinetics for polysulfide, thus fully suppressing the shuttle effect. Together with the advantages of HCSM, the mesoporous walls and internal cavity can offer enough sulfur storage room and significantly buffer the volume expansion of sulfur species; the high specific surface area and abundant porosity favor electron/ion transfers. As a result, the HCSM@uMoS2-S electrode exhibited outstanding electrochemical performance (675.4 mAh g−1 retention capacity at 0.5 C for 500 cycles) even under the conditions of high areal sulfur loading (5.6 mg cm−2) and less electrolyte (E/S = 10 μL mg−1). This study provides a reference for building sulfur hosts for high-capacity, long-life, and practical LSBs.

Bidirectional Catalyst with Robust Lithiophilicity and Sulfiphilicity for Advanced Lithium–Sulfur Battery

AbstractThe application of lithium–sulfur batteries (LSBs) is immensely impeded by notorious shuttle effect, sluggish redox kinetics, and irregular Li2S deposition, which result in large polarization and rapid capacity decay. To obtain the LSBs with high energy density and fast reaction kinetics, herein, a heterostructure composed by nitrogen‐deficient graphitic carbon nitride (ND‐g‐C3N4) and MgNCN is fabricated via a magnesiothermic denitriding technology. Lithophilic C3N4 with abundant nitrogen‐deficient acts as a conductive framework, together with the sulfiphilic MgNCN, lithium‐polysulfides (LiPSs) can be effectively captured followed by a regulated Li2S nucleation. Furthermore, the oxidation conversion kinetics can be accelerated as well. As expected, the LSBs with catalytic MgNCN/ND‐g‐C3N4 as the interlayer exhibit remarkable electrochemical performance with a discharge capacity of 650 mAh g−1 at 4 C. Meanwhile, a low capacity decay of 0.008% per cycle can be reached at 1 C after 400 cycles. Even with a high areal sulfur loading of 5.1 mg cm−2, outstanding capacity retention can be achieved at 0.5 C (64.18%) and 1 C (90.46%). The presented strategy unlocks a new way for the LSBs design with highly efficient catalyst.

Bioinspired urchin-like murray carbon nanostructure with protection shell for advanced lithium-sulfur batteries

Commercial application of lithium-sulfur (Li-S) batteries is hindered by the insulating nature of sulfur and the dissolution of polysulfides. Here, a bioinspired 3D urchin-like N-doped Murray’s carbon nanostructure (N-MCN) with interconnected micro-meso-macroporous structure and a polydopamine protection shell has been designed as an effective sulfur host for high-performance Li-S batteries. The advanced 3D hierarchically porous framework with the characteristics of the generalized Murray’s law largely improves electrolyte diffusion, facilitates electrons/ions transfer and provides strong chemisorption for active species, leading to the synergistic structural and chemical confinement of polysulfides. As a result, the obtained P@S/N-MCN electrode with high areal sulfur loading demonstrates high capacity at high current densities after long cycles. This work reveals that following the generalized Murray’s law is feasible to design high-performance sulfur cathode materials for potentially practical Li-S battery applications.

Selenium defects of 2D VSe2/CNTs composite as an efficient sulfur host for high-performance Li-S batteries

Introducing defects into two-dimensional materials can increase the ligand-unsaturated sites, thereby enhancing the redox catalysis of polysulphides. In this study, the selenium defects in the two-dimensional material VSe2 can effectively improve the electrochemical performance of lithium-sulfur batteries. Compared with VSe2, VSe2−x could strongly adsorb polysulfides, catalyze the conversion and accelerate the redox reactions of polysulfides. S/VSe2−x/CNTs cathode with an initial discharge specific capacity of 1457 mAh g−1 at 0.1 C current density and capacity decay rate per cycle of only 0.039% after 800 cycles at 0.5 C, showing excellent cycling stability. In addition, a high areal capacity of 4.35 mAh cm−2 and a reversible capacity of 4.106 mAh cm−2 after 100 cycles at 0.1 C can be achieved with the S/VSe2−x/CNTs cathode with a high areal sulfur loading of 4.5 mg cm−2. The results show that the shuttle effect is effectively suppressed by introducing defects in the two-dimensional transition metal dihalide compounds. Thus, the electrochemical performance of the sulfur electrode for lithium-sulfur batteries is improved. This work is expected to provide a new perspective for the rational design of sulfur host materials for high-performance lithium-sulfur batteries.

High‐entropy stabilized oxides derived via a low‐temperature template route for high‐performance lithium‐sulfur batteries

AbstractIt is a long‐standing issue that the sluggish polysulfide conversion and adverse shuttling effects impede the development of lithium‐sulfur (Li‐S) batteries with high energy density and cycling stability, which necessitate the exploration of new electrocatalysts to facilitate the practical applications of Li‐S batteries. Herein, a single‐phase high‐entropy stabilized oxide (Ni0.2Co0.2Cu0.2Mg0.2Zn0.2)O (HEO850) is successfully prepared through a novel low‐temperature annealing strategy from a self‐sacrificing metal–organic frameworks (MOFs) template and then integrated into the sulfur host, where it functions as both the catalytic converter and chemical inhibitor towards the shuttle species. Furthermore, the synergistic contribution of randomly dispersed metal elements and the exposure of affluent active sites enable the chemical encapsulation of soluble polysulfides and accelerate conversion kinetics. The HEO850/S/KB cathode (KB: ketjen black; sulfur content: 70 wt.%) delivers a substantially higher initial specific discharge capacity of ~1244 mAh g−1 in comparison to MEO/S/KB (MEO: medium entropy oxide; ~980 mAh g−1), LEO/S/KB (LEO: low entropy oxide; ~908 mAh g−1), and routine S/KB cathodes (~966 mAh g−1), which is well retained at ~784 mAh g−1 after 800 cycles at 0.5 C with a low capacity decay rate of ~0.043% per cycle. Moreover, when the HEO850/S/KB cathode is processed with a high areal sulfur loading (~4.4 mg cm−2), the resulting Li‐S battery also performs well, with a high initial specific capacity of ~1044 mAh g−1 at 0.1 C and 85% capacity retention after 100 cycles. This study highlights the potential application of HEOs in enhancing the performance of Li‐S batteries and provides a novel strategy in synthesizing the HEOs at a relatively low annealing temperature for various energy conversion and storage applications.image

Ultra-thin MoO2 nanosheets loaded on hollow mesoporous carbon spheres promoting polysulfide adsorption and redox kinetics for lithium-sulfur batteries

Inhibiting polysulfide shuttle and improving cycling stability are crucial for the commercialization of lithium-sulfur batteries (LSBs). Developing multifunctional sulfur host materials that combine rational carbon structure with highly catalytic metal compounds is pivotal for LSBs. Herein, Ultra-thin MoO2 nanosheets loaded on hollow mesoporous carbon (HMC@MoO2) were rationally designed and synthesized. In this structure, the hollow mesoporous carbon provides sufficient space to store sulfur and buffer volume fluctuations, the mesoporous carbon shell and the MoO2 nanosheets on its surface can act as a double defensive system to effectively prevent polysulfide dissolution through physical and chemical trapping. Moreover, the ultra-thin MnO2 nanosheets with more exposed active sites facilitate the capture and catalytic conversion of LiPSs, thereby effectively suppressing the shuttle effect of polysulfide. Consequently, the HMC@MoO2-S cathode exhibits impressive cycling stability, maintaining 771 mAh g−1 after 500 cycles at 0.5 C with a very low capacity decay of 0.045% per cycle. In particular, the HMC@MoO2-S cathode with high areal sulfur loading of 5.0 mg cm−2 achieved initial areal capacities of 4.48 mAh cm−2 and retention capacities of 3.32 mAh cm−2 after 500 cycles at 0.1 C.

Rational design of ultrathin Mo2C/C nanosheets decorated on mesoporous hollow carbon spheres as a multifunctional sulfur host for advanced Li-S batteries

Developing sulfur hosts with reasonable structure and effective catalyst is essential for lithium-sulfur (Li-S) batteries. Herein, a novel multifunctional sulfur host composed of hollow carbon spheres with mesoporous channels (MHCS) coupled with few ultrathin Mo2C/C nanosheets embedded with Mo2C nanocrystals ([email protected]2C/C) has been prepared via one-pot self-assembly and in-situ grown strategies. The Mo2C/C nanosheets with heterostructure can shorten the electron/ion transport path, and ultra-small Mo2C nanocrystals with abundant active sites contribute to enhancing chemical adsorption towards polysulfides and propel their conversion. Meanwhile, the MHCS facilitates physical adsorption towards polysulfides, effective sulfur/electrolyte permeation, fast electron/ion transportation, and sufficient buffering for volume change. Given these, the multifunctional [email protected]2C/C-S cathode demonstrates an initial specific capacity of 1316.8 mAh g−1 at 0.1 C and outstanding cycling stability with an average capacity decay rate of 0.045 % for 500 cycles at 0.5 C. Moreover, [email protected]2C/C-S cathode with high areal sulfur loading of 4.5 mg cm−2 can deliver a high initial discharge specific capacity of 797.4 mAh g−1, and a reversible capacity of 542.7 mAh g−1 after 500 cycles at 0.5 C. It is expected this work could provide a new perspective to the rational design of sulfur hosts for Li-S batteries with enhanced performance.

A multifunctional separator based on dilithium tetraaminophthalocyanine self-assembled on rGO with improved cathode and anode performance in Li–S batteries

Li–S batteries are strong candidates for next-generation energy-storage applications. However, practical cells face critical challenges including the dissolution and shuttling of polysulfides on the cathode as well as the uncontrolled dendrite growth and degradation of the anode. Herein, we demonstrate a multifunctional separator based on dilithium tetraaminophthalocyanine (Li2TaPc) self-assembled on rGO that exhibits a comprehensive regulation effect on important ion transport properties to address the above issues in one configuration. Li2TaPc presents strong sulfiphilic/lithiophilic binding sites for the confinement of polysulfides within the cathode region to improve sulfur utilization. Charge transfers from the central cavity of the TaPc ligand to the rGO promotes the dissociation of Li+ cations to produce additional charge carriers. The negatively-charged TaPc ligand exhibits strong electrostatic repulsions to the salt anions and hinders their migration across the separator. The apparently increased Li+ transference number (0.41–0.89) suppresses dendrite formation and improves the reversibility of the Li anode. Meanwhile, the strong coordination effects of Li+ with Li2TaPc enable a high retention of Li + conductivity. The comprehensive functionalities of the separator result in significantly improved electrochemical performance of Li–S full cells. Pouch cells with a high areal sulfur loading and limited electrolyte addition are also demonstrated.

Built-In Electric Field on the Mott-Schottky Heterointerface-Enabled Fast Kinetics Lithium-Sulfur Batteries.

Lithium-sulfur (Li-S) batteries (LSBs) have been considered one of the most potential candidates to substitute traditional Li-ion batteries (LIBs), owing to their high theoretical energy density and low cost. Nevertheless, the shuttle effect and the sluggish redox kinetics of lithium polysulfides (LiPSs) have long been obstacles to realizing stable LSBs with high reversible capacity. In this study, we proposed a metal-semiconductor (Mo and MoO2) heterostructure with the hollow microsphere morphology as an effective Mott-Schottky electrocatalyst to boost sulfur electrochemistry. The hollow structure can physically inhibit the shuttling of LiPSs and accommodate the volume fluctuation during cycling. More importantly, the built-in electric field at the heterointerfacial sites can effectively accelerate the reduction of LiPSs and oxidation of Li2S, thereby reaching a high sulfur utilization. With the assistance of the Mo/MoO2 catalyst, the cell exhibited prominent rate capability and stable long-term cycling performance, showing a high capacity of 630 mA h·g-1 at 4 C and a low decay of 0.073% at 1 C after 500 cycles. Even with high areal sulfur loading of 10.0 mg·cm-2, high capacity and good cycle stability were achieved at 0.2 C under lean electrolyte conditions (E/S ratio of 6 μL·mg-1).

Bifunctional hydrogen-bonding cross-linked polymeric binder for high sulfur loading cathodes in lithium/sulfur batteries

Construction of high sulfur loading electrode is one of the effective ways to achieve high specific energy density lithium/sulfur batteries. Therefore, the optimization of polymeric binders has been considered as effective strategy to improve the volume changes of sulfur electrodes during charge/discharge processes. In this work, an effective route for the preparation of three dimensional polymeric binder (PAA-PANI) via multiple hydrogen bonds was developed and fabricated through in situ polymerization between polyacrylic acid (PAA) and polyaniline (PANI), which possess bifunctional effects on high sulfur loading cathodes in lithium/sulfur batteries. The carboxyl polar groups of PAA could effectively adsorb polysulfides and the conductive PANI enhance the electronic conductivity of the sulfur electrode. The three dimensional polymeric binder of PAA-PANI has enhanced the active material adhesion, mechanical properties and electronic conductivity, which decreased overpotential polarization, improved the lithium ions diffusion coefficient, and reduced the self-discharge. More importantly, the PAA-PANI functional binder could alleviate the expansion of high sulfur loading electrode. Taking advantages of PAA-PANI binder, the carbon nanotubes modified sulfur electrode (CNTs@S; sulfur content: 84.3 wt%) with PAA-PANI binder exhibits an initial discharge capacity of 906 mAh g–1 at 2.56 mA cm–2 (0.3 C) under a sulfur loading of 5.1 mg cm–2. Even at higher current density of 8.54 mA cm–2 (1 C), the PAA-PANI binder electrode delivers a high capacity of 846 mAh g–1. Moreover, with an extremely high areal sulfur loading of 17 mg cm–2, the cathode shows an areal specific capacity of 16.7 mAh cm–2.

Ultra-high-rate lithium-sulfur batteries with high sulfur loading enabled by Mn2O3-carbonized bacterial cellulose composite as a cathode host

Lithium-sulfur batteries have received significant attention due to their high specific capacity and natural abundance of the sulfur cathode. However, the notorious issue of higher-order lithium-polysulfides dissolution causes inferior cycling and poor electrochemical performance. To overcome the challenge, here, biodegradable and environmentally friendly carbonized bacterial cellulose (CBC) is used as the sulfur host. Further, Mn2O3 is incorporated in bacterial cellulose using hydrothermal synthesis and investigated as a sulfur host. The composite is prepared by a facile encapsulation “melt-diffusion” strategy. The high electronic conductivity of the CBC provides an efficient pathway to carry out redox reactions, and Mn2O3 helps to restrain and convert higher-order lithium-polysulfides to lower-order lithium-polysulfides. Further, the first-principle density functional theory calculation is performed to investigate and understand the role of carbon (CBC) and Mn2O3 in the host material. The lithium-sulfur cell with Mn2O3@CBC cathode host delivers a significantly high initial reversible capacity of 1150 mAh g−1(cathode) (i.e., 1450 mAh g−1(sulfur)) at 0.1 C. It retains a reversible capacity of 254 mAh g−1(cathode) (i.e., 554 mAh g−1(sulfur)) even at the ultra-high rate of 15.0 C. Furthermore, to achieve a practical high energy density and its commercial adoption, we tested lithium-sulfur cells with high areal sulfur loading of 4.2 mg cm−2. The cell shows promising electrochemical performance for long 500 cycles with a capacity retention of 70%. The cell performance is competitive and superior to the current state-of-the-art lithium-sulfur cells reported in the literature.

Catalytic Mo2C decorated hollow mesoporous carbon spheres as sulfur host for lithium-sulfur batteries with high sulfur loading

Hybrid structures as sulfur host materials have been proven to be an effective way to improve the electrochemical property of lithium-sulfur (Li–S) batteries. However, how to construct hybrid nanomaterials with reasonable structure and composition remains a challenge. Herein, the Mo2C nanoparticles grown on the surface of hollow mesoporous carbon spheres (HMCS@Mo2C) are synthesized as an effective sulfur host for Li–S batteries with high sulfur loading. In this hybrid structure, the HMCS can guarantee high sulfur loading, high-speed electron/ion transport, and sufficient buffer for volume change, and the Mo2C nanoparticles as effective catalysts significantly accelerate the conversion of polysulfides. Consequently, the as-prepared HMCS@Mo2C–S cathode demonstrates superb cyclic stability with a capacity decay rate of 0.065% for 500 cycles at 1 ​C. Impressively, HMCS@Mo2C–S cathode with high areal sulfur loading of 5.4 ​mg ​cm−2 can deliver a high specific capacity of 451.2 mAh g−1 after 500 cycles at 0.5 ​C. In addition, the preparation of HMCS@Mo2C is simple, feasible, and low cost. It is hoped that this work will provide new insight into the rational design of sulfur host materials integrating reasonable structure with an effective catalyst for Li–S batteries with high sulfur loading.

Interface engineering of metal phosphide on hollow carbons by Dual-template method for High-performance Lithium-sulfur batteries

• Hollow polyhedral sulfur hosts were constructed using a core–shell dual template. • Multi-phase interfaces boost the LiPSs kinetics. • The In-situ regulation of the surface physiochemistry on hollow substrates. • Excellent electrochemical performance of long lifespan with high sulfur loading. Tailoring well-dispersed nanoparticles on the sulfur host with high catalytic activity is of great importance yet remains challenging in lithium-sulfur batteries (LSBs). Herein, a novel multi-phase interface structure of embedded CoP and Co 2 P nanoparticles (Co x P NPs) on hollow N-doped carbon substance (Co x P/NC) was successfully fabricated by the in-situ conversion of ZIF-67@ZIF-8 dual templates. The abundant multi-phase interfaces on Co x P/NC enabled efficient lithium polysulfides (LiPSs) capture, accelerated Li-ion diffusion, and boosted LiPSs conversion, thus forming a rapid and robust “adsorption-diffusion-conversion” network. Moreover, the well-defined hollow carbon polyhedrons physically inhibit the LiPSs diffusion and provide superior conductivity. As a result, the assembled S@Co x P/NC cathode with a high sulfur loading of 82% delivers an excellent rate capability (617.7 mAh g −1 at 3C), impressive stability (a small capacity decay of 0.053% per cycle over 1250 cycles at 1C), and favorable durability of thick sulfur cathodes (with a high areal sulfur loading of 4.68 mg cm 2 over 300 cycles).

A Highly Efficient Sulfur Host Enabled by Nitrogen/Oxygen Dual‐Doped Honeycomb‐Like Carbon for Advanced Lithium–Sulfur Batteries

High energy density and long cycle life of lithium-sulfur (Li-S) batteries suffer from the shuttle/expansion effect. Sufficient sulfur storage space, local fixation of polysulfides, and outstanding electrical conductivity are crucial for a robust cathode host. Herein, a modified template method is proposed to synthesize a highly regular and uniform nitrogen/oxygen dual-doped honeycomb-like carbon as sulfur host (N/O-HC-S). The unique structure not only offers physical entrapment for polysulfides (LiPSs) but also provides chemical adsorption and catalytic conversion sites of polysulfides. In addition, this structure offers enough space for loading sulfur, and a regular space of nanometer size can effectively prevent sulfur particles from accumulating. As expected, the as-prepared N/O-HC900-S with high areal sulfur loading (7.4mg cm-2 ) shows a high areal specific capacity of 7.35 mAh cm-2 at 0.2 C. Theoretical calculations also reveal that the strong chemical immobilization and catalytic conversion of LiPSs attributed to the spin density and charge distribution of carbon atoms will be influenced by the neighbor nitrogen/oxygen dopants. This structure that provides cooperative chemical adsorption, high lithium ions flux, and catalytic conversion for LiPSs can offer a new strategy for constructing a polysulfide confinement structure to achieve robust Li-S batteries.

Defect Engineering in a Multiple Confined Geometry for Robust Lithium–Sulfur Batteries

AbstractThe decay of lithium–sulfur (Li–S) batteries is mainly due to the shuttle effect caused by intermediate polysulfides (LiPSs). Herein, a multiple confined cathode architecture is prepared by filling graphitized Pinus sylvestris with carbon nanotubes and defective LaNiO3−x (LNO‐V) nanoparticles. The composite electrode with high areal sulfur loading of 11.6 mg cm−2 shows a high areal specific capacity of 8.5 mAh cm−2 at 1 mA cm−2 (0.05 C). Both experimental results and theoretical calculations reveal that this unique structure not only provides physical restriction on LiPSs within microchannels but also offers strong chemical immobilization and catalytic conversion of LiPSs attributed to the spin density around oxygen vacancies of LaNiO3−x. These oxygen vacancies elongate the SS and LiS bonds and make them easy to break. Furthermore, the lengthwise channels derived from cytoderm restrict the transverse diffusion of polysulfides, leading to a uniform areal current and thus homogeneous lithium infiltration. This suppresses the corrosion of the lithium anode due to polysulfides confinement. The discovery of the multiple confined structure that provides chemical adsorption, fast diffusion, and catalytic conversion for polysulfides can broaden the application of biomass materials and offer a new strategy to achieve robust Li–S batteries.

Highly catalytic porous MoN nanosheets anchored carbon microtubes interlayer for lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have been widely considered as one of the most promising next-generation energy storage devices owing to the ultrahigh theoretical capacity (1,672 mAh/g) and energy density (2,600 Wh/kg). However, the shuttle effect of lithium-polysulfides (LiPSs) and the sluggish conversion kinetics impede the wide commercialization of LSBs. In this work, porous and catalytic MoN nanosheets were fabricated on the conductive carbonized cotton cloth (denoted as CCC@MoN) to serve as an interlayer for LSBs. The porous structure of MoN nanosheets provides abundant catalytic sites to capture LiPSs and accelerates conversion kinetics. Notably, hollow and conductive fibers in CCC substrate can physically restrain LiPSs and serve as a secondary current collector to recycle the dissolved sulfur species. Thus, the highly catalytic porous MoN and conductive CCC can synergistically generate an efficient trapping-conversion ability toward polysulfides. With the assistance of the CCC@MoN interlayer, the LSBs exhibit remarkable cycling stability and rate performance. Even with a high areal sulfur loading (5 mg/cm−1) cathode, an impressive areal specific capacity of 4 mAh/cm−1 can still be achieved at 0.1 C. This work paves a new way for the design of multifunctional interlayers in the commercial application of LSBs.