Sulfur Loading Research Articles

Synergistic implementation of efficient adsorption-diffusion-conversion in lithium-sulfur batteries via built-in electric field constructed by transition metal selenides

The adsorption of lithium polysulfides (LiPSs), the transport of lithium ions, and the redox kinetics collectively play pivotal roles in determining the application of lithium-sulfur (Li-S) batteries. Herein, a defect-rich p-Co3Se4/n-ZnSe p-n junction (ZCSNC) is engineered by chemical vapor deposition (CVD)-selenation. The n-type semiconductor ZnSe and the p-type semiconductor Co3Se4 contained in ZCSNC effectively anchor LiPSs and promote the catalytic reaction kinetics through synergistic effects, respectively. Meanwhile, the presence of heterogeneous interfaces in the p-n junction and the difference in work functions spontaneously form a built-in electric field, which promotes the transport and transfer of lithium ions and LiPSs. Therefore, the ZCSNC functional material contributes to improving the electrochemical performance of Li-S batteries through the process of adsorption-diffusion-conversion. The Li-S cells with ZCSNC-modified separators show excellent rate performance (741.1 mAh/g at 5C) and long-lasting cycling performance (only 0.04 % capacity decay per cycle over 1000 cycles). Notably, the ZCSNC still has excellent rate discharge capacities (683.9 and 649.7 mAh/g at 2C, respectively) at high sulfur loading and low temperature of 0 °C. This study illustrates that a p-n junction containing a built-in electric field can effectively modulate the kinetics of redox reactions of LiPSs through synergistic interactions.

One-step pyrolysis route to N, O, S co-doped hierarchical carbon as multi-functional separator for lithium-sulfur batteries

Lithium-sulfur batteries have high theoretical energy density while their practical application is trapped because of severe shuttle effect and sluggish conversion kinetics of polysulfides. Here, a nitrogen, oxygen, and sulfur co-doped porous carbon (NOSAKC) is prepared by one-step pyrolysis of acesulfame potassium, which is employed as an efficient component on polypropylene separators to restrict the shuttle of polysulfides based on Lewis acid-base theory. The NOSAKC exhibits a hierarchical porous structure with high specific surface area and abundant adsorption/catalytic sites. The substantial mesoporous channels are conducive to rapid ion transfer, and the micropores minimize the polysulfide shuttle. The abundant heteroatoms doped in NOSAKC can achieve synergistic constraint and conversion of lithium polysulfides. So the Li-S battery with the NOSAKC separator displays distinguished electrochemical performance with a high discharge capacity of 1598 mAh g-1 at 0.2C and 1012 mAh g-1 at 1C. It maintains 84% of the initial capacity after 500 cycles with a stable coulombic efficiency of 99.8%. Moreover, the Li-S battery achieves a capacity retention of 67% after 200 cycles for a high sulfur loading of 4.33mgcm-2. This work reports a one-step preparation of hierarchical porous carbon with tri-doped heteroatoms for synergistic polysulfide adsorption and conversion.

Spatial structure design of interlayer for advanced lithium–sulfur batteries

The practical application of lithium-sulfur (Li–S) batteries has been hindered by the lithium polysulfide shuttle effect. An effective way to solve this problem is to utilize interlayer engineering to confine polysulfides and promote their catalytic conversion. From a spatial perspective, we designed a carbon nanofiber conductive layer (CNF, without Sn content, labeled as 0) and two Sn-doped carbon nanofiber catalytic layers (SCNF, with 10 wt% and 20 wt% Sn content, labeled as 1 and 2, respectively) with different contents of catalyst content, and verified an efficient interlayer structure by adjusting the order of preferential contact between the conductive layer and the catalytic layer with the sulfur cathode to form a hierarchical system for the inhibition and conversion of lithium polysulfide. Electrochemical measurements show that different spatial configurations have significant discrepancies on the electrochemical performance of Li–S batteries. Thus, the space configuration of 210 enables the Li–S battery to provide a specific capacity of up to 1088 mAh g−1 after 100 cycles at 0.2C. Even under the harsh conditions of high sulfur loading (5.6 mg cm−2) and lean electrolyte (E/S = 10 μL mg−1), the Li–S battery was able to cycle stably for 94 cycles at 0.2C with 87 % capacity retention. This study provides a novel spatial strategy for advancing the spatial design of high-performance Li–S batteries.

Accelerated Reversible Conversion of Li2S2 to Li2S by Spidroin Regulated Li+ Flux for High-performance Li-Sulfur Batteries.

Regulating the transformation of sulfur species is the key to improving the electrochemical performance of lithium-sulfur (Li-S) batteries, in particular, to accelerate the reversible conversion between solid phase Li2S2 and Li2S. Herein, we introduced Spidroin, which is a main protein in spider silk, as a dual functional separator coating in Li-S batteries to effectively adsorb polysulfides via the sequence of amino acids in its primary structure and regulate Li+ flux through the β-sheet of its secondary structure, thus accelerating the reversible transformation between Li2S2 and Li2S. Spidroin-based Li-S cells exhibited an exceptional electrochemical performance with a high specific capacity of 744.1 mAh g-1 at 5 C and a high areal capacity of 7.5 mAh cm-2 at a low electrolyte-to-sulfur (E/S) ratio of 6 μL mgs -1 and a sulfur loading of 8.6 mgs cm-2.

Accelerated Reversible Conversion of Li2S2 to Li2S by Spidroin Regulated Li+ Flux for High‐performance Li‐Sulfur Batteries

Regulating the transformation of sulfur species is the key to improving the electrochemical performance of lithium‐sulfur (Li‐S) batteries, in particular, to accelerate the reversible conversion between solid phase Li2S2 and Li2S. Herein, we introduced Spidroin, which is a main protein in spider silk, as a dual functional separator coating in Li‐S batteries to effectively adsorb polysulfides via the sequence of amino acids in its primary structure and regulate Li+ flux through the β‐sheet of its secondary structure, thus accelerating the reversible transformation between Li2S2 and Li2S. Spidroin‐based Li‐S cells exhibited an exceptional electrochemical performance with a high specific capacity of 744.1 mAh g‐1 at 5C and a high areal capacity of 7.5 mAh cm‐2 at a low electrolyte‐to‐sulfur (E/S) ratio of 6 μL mgs‐1 and a sulfur loading of 8.6 mgs cm‐2.

Machine learning-based design of electrocatalytic materials towards high-energy lithium||sulfur batteries development

The practical development of Li | |S batteries is hindered by the slow kinetics of polysulfides conversion reactions during cycling. To circumvent this limitation, researchers suggested the use of transition metal-based electrocatalytic materials in the sulfur-based positive electrode. However, the atomic-level interactions among multiple electrocatalytic sites are not fully understood. Here, to improve the understanding of electrocatalytic sites, we propose a multi-view machine-learned framework to evaluate electrocatalyst features using limited datasets and intrinsic factors, such as corrected d orbital properties. Via physicochemical characterizations and theoretical calculations, we demonstrate that orbital coupling among sites induces shifts in band centers and alterations in the spin state, thus influencing interactions with polysulfides and resulting in diverse Li-S bond breaking and lithium migration barriers. Using a carbon-coated Fe/Co electrocatalyst (synthesized using recycled Li-ion battery electrodes as raw materials) at the positive electrode of a Li | |S pouch cell with high sulfur loading and lean electrolyte conditions, we report an initial specific energy of 436 Wh kg−1 (whole mass of the cell) at 67 mA and 25 °C.

Zinc Tellurium with Anionic Vacancies Anchored on Ordered Macroporous Carbon Skeleton Enabling Accelerated Polysulfide Conversion for Lithium-Sulfur Batteries.

Lithium-sulfur batteries (LSBs) showcase great promise for large-scale energy storage systems, however, their practical commercialization is seriously hindered by the sluggish redox reaction kinetics and detrimental shuttle effect of soluble polysulfides. Herein, small ZnTe1- x nanoparticles with anionic vacancies firmly anchored on 3D ordered macroporous N-doped carbon skeleton (3DOM-ZnTe1- x@NC) are elaborately constructed as a high-efficiency electrocatalyst for LSBs. The ordered macroporous carbon skeleton not only greatly increases the external surface area to expose sufficient active sites but also facilitates the electrolyte penetration. Additionally, the experimental studies combined with theoretical calculations confirm the presence of Te vacancies optimizes the electronic structure to enhance the intrinsic catalytic activity and chemical absorption. Consequently, LSBs assembled with the 3DOM-ZnTe1- x@NC modified separators exhibit high specific discharge capacity, as well as superior rate performance and good long-term cycling stability. Even under a high sulfur loading of 6.5 mg cm-2 and lean electrolyte, an impressive areal capacity of 5.28 mAh cm-2 is achieved at 0.1C after 100 cycles. More significantly, the 3DOM-ZnTe1- x@NC based pouch cells are also fabricated to demonstrate its potential for practical applications. This work highlights that the rational combination of 3DOM architecture and vacancy engineering is important for designing advanced Li-S electrocatalysts.

A fresh perspective to synthesizing and designing carbon/sulfur composite cathodes using supercritical CO2 technology for advanced Li-S battery cathodes

The morphology and surface chemistry of the sulfur host within lithium-sulfur (Li-S) batteries significantly influence the overall battery performance. To investigate this relationship, we employed a non-toxic heat treatment to produce reduced graphene oxide (rGO) with varying degrees of reduction, resulting in distinct surface chemistries. The physicochemical characteristics and electrochemical properties of four differently reduced GO samples and rGO/sulfur composite cathodes developed with supercritical CO2 technology were examined. Our study established a clear correlation between the specific surface area and porosity of rGO and the electrochemical performance of the corresponding rGO/sulfur composite cathodes. Notably, rGO samples reduced at 350°C (rGO350) exhibited superior discharge capacity and long-term cycling stability compared to those reduced at higher temperatures. This performance enhancement can be attributed to the combination of high surface area, porosity, and an open morphology in rGO350. These findings underscore the importance of optimizing carbon chemistry, microstructure, and cathode synthesis strategies in Li-S batteries. By effectively controlling sulfur loading and distribution within the rGO network, we can enhance active material utilization, boost electronic conductivity, and ensure the long-term stability of rGO/sulfur composite cathodes. Our research suggests that SC-CO2-assisted synthesis offers a promising approach for designing high-performance carbon/sulfur composite cathodes for Li-S batteries. This method provides a versatile platform for tailoring the rGO morphology and surface chemistry, optimizing battery performance. By carefully considering the interplay between these factors, we can unlock the full potential of Li-S batteries for various applications.

Hollow bimetallic layered hydroxides nanocages/mxenes electrocatalysts as superior accelerators for boosting sulfur redox kinetics under high sulfur loadings

Addressing the challenge of designing a high sulfur loading cathode while ensuring rapid sulfur redox kinetics and minimizing lithium polysulfides (LiPSs) shuttling is crucial for achieving high-energy density lithium-sulfur batteries (LSBs). Herein, we design hollow bimetallic layered hydroxide nanocages/MXenes electrocatalysts (denoted as NiCo-LDHs@MXenes) as superior accelerators. The synergistic integration of NiCo-LDHs and MXenes substantially enhances the electronic conductivity and catalytic activity, thereby promoting fast LiPSs conversions and facilitating Li2S nucleation/decomposition within high sulfur loading cathodes. Consequently, the NiCo-LDHs@MXenes/S cathode with a sulfur loading of 2.4 mg cm−2 achieves a high specific capacity of 1174.6 mAh g−1 at 0.1 C after 100 cycles. Remarkably, it exhibits an ultrastable lifespan over 600 cycles with a minimal capacity decay of ∼ 0.062 % per cycle at 1.0 C. Even under a high sulfur loading of 7.5 mg cm−2 and lean electrolyte of 4.5 μL mg−1, it still maintains a high areal capacity of 6.02 mAh cm−2 after 100 cycles. These exceptional outcomes underscore the potential of bimetallic LDHs/MXenes as high-performance cathodes for LSBs, offering valuable insights into the design and application of multifunctional electrocatalysts for LSBs with remarkably long lifespans.

The complex of ethyl viologen halides and UIO-67 as separator materials for upgrading performance of lithium-sulfur batteries

Lithium-sulfur (LiS) batteries are considered to be the most promising energy storage system to replace lithium-ion batteries due to their ultra-high energy density. However, the shuttling of polysulfides and the growth of lithium dendrites lead to several challenges for practical use. This study, UIO-67 separator modified material coating with zwitterionic of ethyl viologen halides (EV2+2X−, X = Cl, Br, I) is prepared by a simple one-step method. The cation (EV2+) can adsorb polysulfides through electrostatic interaction, and then promote the conversion of polysulfides. The free halogen anions contribute to the desolvation of Li+ by coordination, thereby accelerating the transport of Li+. Among them, the UIO-67@EV2+2I− modified separator exhibits the best electrochemical performance for LiS batteries. The capacity decay rate is 0.022 % after 800 cycles at 2C, and it still has excellent cycle stability under high sulfur loading of 5 mg cm−2 and lean electrolyte of E/S = 3 μL mg−1. This work sheds new light on the selection of modified materials for LiS battery separators.

Heteroelectrocatalyst MoS2@CoS2 modified separator for Li-S battery: Unveiling superior polysulfides conversion and reaction kinetics

Mitigating the shuttle effect of polysulfides and enhancing their conversion efficiency are critical challenges for the practical application of Li-S batteries. Herein, we present a novel MoS2@CoS2 heteroelectrocatalyst synthesized via a hydrothermal method, used to modify the separator for Li-S batteries. This innovative heterostructure combines the exceptional properties of metallic CoS2 and semiconductor MoS2, creating a synergistic effect that significantly improves electrochemical performance. The built-in electric field at the heterointerface promotes rapid charge transport and enhances surface reaction kinetics, effectively addressing polysulfide shuttle and sluggish redox kinetics. The Li-S battery with MoS2@CoS2 separator exhibits an impressive initial capacity of 1480 mAh g−1 at 0.1 C and maintains 811 mAh g−1 at 3 C, with long-term cycling stability showing a minimal decay rate of 0.05 % per cycle at 1 C. Even with high sulfur loading (6 mg cm−2) and a low electrolyte/sulfur ratio, the cell achieves a high reversible capacity of 4.5 mAh cm−2 at 0.2 C. The innovative approach of integrating semimetal-semiconductor heterointerfaces opens new avenues for the development of high-performance Li-S batteries, addressing critical challenges and paving the way for future technological advancements in the field.

Synergistic improvement of the sulfur redox reaction by MOF-driven dual-defect polyhedral Mn-doped Co1-xS embedded in an N-doped carbon composite host for practical lithium-sulfur batteries

In the quest for practical sulfur hosts for lithium-sulfur batteries, a novel approach has been delineated. By meticulously adjusting the Mn:Co (1:5/1:9/1:1) ratio and the sulfidation temperature, a series of nitrogen-doped carbon nanopolyhedron composites have been synthesized, denoted as 1:9 Mn-Co1-xS-NC@NC, 1:5 Mn-Co1-xS-NC@NC, 1:1 Mn-Co1-xS-NC@NC, and Co1-xS-NC@NC. These materials, inheriting the polyhedral shape and a novel cavity structure from their precursors, exhibit enhanced lithium polysulfide adsorption and catalytic activity due to the introduction of Mn heteroatoms and cobalt vacancies. The resultant S@1:9 Mn-Co1-xS-NC@NC cathode excels in electrochemical performance, delivering an initial discharge capacity of 999.37 mA h g−1 at 1 C, and sustaining 715.65 mA h g−1 over 100 cycles. Notably, at an elevated sulfur loading of 3.05 mg cm−2 (E/S, 14.5 uL g−1), the cathode retains an areal capacity of 3.24 cmmA h cm−2 (corresponding specific capacity of 1067.59 mA h g−1) after 61 cycles at 0.2 C. The synergistic effect of manganese dopants and cobalt vacancies confers superior adsorptive and catalytic properties, presenting a promising avenue for the development of sulfur host materials with tailored morphologies and defect-rich structures.

Challenges and Approaches to Designing High‐Energy Density Lithium‐Sulfur Pouch Cells

Lithium‐sulfur (Li‐S) batteries are of great interest as next‐generation energy storage devices in a wide variety of applications, due to their high specific capacity and the environmental abundance of sulfur. However, liquid electrolyte Li‐S technology faces several challenges such as polysulfide shuttling, anode corrosion and sluggish cathode kinetics. Practical deployment of Li‐S batteries requires evaluation in large‐format, high energy density pouch cells. Stringent operating conditions such as high sulfur loading and operating current, low electrolyte amount, and limited anode quantity are required for high energy density pouch cells, which further curtails the electrochemical performance and cycle life. This review aims to provide an understanding of the different failure mechanisms of large‐format Li‐S pouch cells and formulate key design parameters of Li‐S pouch cells that have high capacity, coulombic efficiency and long cycle life. Recent developments in Li‐S pouch cells are then discussed, focusing on cathode and electrolyte design for polysulfide immobilization, accelerated sulfur conversion kinetics, and Li anode protection. A review of advanced characterization techniques suitable for Li‐S pouch cell studies is also provided. Finally, viewpoints are offered on the remaining challenges and prospects to guide future research in scaling up Li‐S technology for real‐world applications.

Built-in Electric Field Within CoSe2-FeSe2 Heterostructure for Enhanced Sulfur Reduction Reaction in Li-S Batteries.

The conversion of Li2S4 to Li2S is the most important and slowest rate-limiting step in the complex sulfur reduction reaction (SRR) for Li-S batteries, the adjustment of which can effectively inhibit the notorious "shuttle effect". Herein, a CoSe2-FeSe2 heterostructure embedded in 3D N-doped nanocage as a modified layer on commercial separator is designed (CoSe2-FeSe2@NC//PP). The CoSe2-FeSe2 heterostructure forms a built-in electric field at the two-phase interface, which leads to the optimized adsorption force on polysulfides and the accelerated reaction kinetics for Li2S4-Li2S evolution. Density functional theory (DFT) calculations and experimental results combine to show that the liquid-solid reaction (Li2S4-Li2S2/Li2S) is significantly enhanced in terms of thermodynamics and electrodynamics. Consequently, the batteries assembled with CoSe2-FeSe2@NC//PP delivered an excellent rate capability (606 mAh g-1 under 8.0 C) and a long cycling lifespan (only 0.056% at 1.0 C after 1000 cycles). In addition, the cells can provide high initial capacity of 887 mAh g-1 at sulfur loading of 5.8mg cm-2 and 0.1 C. This work would provide valuable insights into binary metal selenide heterostructures for liquid-solid conversion in Li-S batteries.

A bifunctional thiobenzamide additive for improvement of cathode kinetics and anode stability in lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are considered as the key candidates for the next generation of energy storage devices. However, the practical applications of LSBs are hindered by the slow conversion of sulfur species and the inhomogeneous Li+ precipitation /stripping of lithium anode. Here, we report a bifunctional thiobenzamide electrolyte additive, 4-(trifluoromethyl) thiobenzamide (TFBCA), which synergistically improves cathode redox kinetics and anode stability. Polysulfides (LiPSn) are in-situ transferred to more reactive polysulfide intermediates (T-Sn-T), which significantly improve the liquid–solid reduction process by promoting the deposition dimension of Li2S. A LiF/Li3N-rich solid electrolyte interphase is formed with TFBCA, the uniform lithium deposition is achieved and the growth of lithium dendrites is suppressed. Correspondingly, LSBs with TFBCA show a high capacity (888 mAh·g−1 at 5C) and cycling stability (0.055 % per cycle after 600 cycles at 2C). Even under high sulfur loading (7.1 mg·cm−2) and low E/S ratio of 7, the LSBs also exhibit an areal capacity of 7 mAh·cm−2 after 50 cycles, and an energy density of 314 Wh·kg−1 is achieved for the pouch cell. This work demonstrates an efficient additive strategy through molecular structure design to construct high-performance LSBs.

Bimetallic Coupling Strategy Modulating Electronic Construction to Accelerate Sulfur Redox Reaction Kinetics for High-Energy Flexible Li-S Batteries.

Lithium-sulfur (Li-S) batteries are considered the most promising energy storage battery due to their low cost and high theoretical energy density. However, the low utilization rate of sulfur and slow redox kinetics have seriously limited the development of Li-S batteries. Herein, the electronic state modulation of metal selenides induced by the bi-metallic coupling strategy is reported to enhance the redox reaction kinetics and sulfur utilization, thereby improving the electrochemical performance of Li-S batteries. Theoretical calculations reveal that the electronic structure can be modulated by Ni-Co coupling, thus lowering the conversion barrier of lithium polysulfides (LiPSs)and Li+, and the synergistic interaction between NiCoSe nanoparticles and nitrogen-doped porous carbon (NPC) is facilitating to enhance electron transport and ion transfer kinetics of the NiCoSe@NPC-S electrodes. As a result, the assembled Li-S batteries based on NiCoSe@NPC-S exhibit high capacities (1020mAhg-1 at 1C) and stable cycle performance (80.37% capacity retention after 500 cycles). The special structural design and bimetallic coupling strategy promote the batteries working even under lean electrolyte (7.2µLmg-1) with a high sulfur loading (6.5mgcm-2). The proposed bimetallic coupling strategy modulating electronic construction with N-doping porous carbon has jointly contributed the good redox reaction kinetics and high sulfur utilization.

Sulfidation of Nanoscale Zero-Valent Iron by Sulfide: The Dynamic Process, Mechanism, and Role of Ferrous Iron.

Sulfidation of nanoscale zerovalent iron (nZVI) can enhance particle performance. However, the underlying mechanisms of nZVI sulfidation are poorly known. We studied the effects of Fe2+ on 24-h dynamics of nZVI sulfidation by HS- using a dosed S to Fe molar ratio of 0.2. This shows that in the absence of Fe2+, HS- rapidly adsorbed onto nZVI particles and reacted with surface iron oxide to form mackinawite and greigite (<0.5 h). As nZVI corrosion progressed, amorphous FeSx in solution deposited on nZVI, forming S-nZVI (0.5-24 h). However, in the initial presence of Fe2+, the rapid reaction between HS- and Fe2+ produced amorphous FeSx, which deposited on the nZVI and corroded the surface iron oxide layer (<0.25 h). This was followed by redeposition of colloidal iron (hydr)oxide on the particle surface (0.25-8 h) and deposition of residual FeSx (8-24 h) on S-nZVI. S loading on S-nZVI was 1 order of magnitude higher when Fe2+ was present. Surface characterization of the sulfidated particles by TEM-SAED, XPS, and XAFS verified the solution dynamics and demonstrated that S2- and S22-/Sn2- were the principal reduced S species on S-nZVI. This study provides a methodology to tune sulfur loading and S speciation on S-nZVI to suit remediation needs.

Core-shell Ru@Co2P synergistic catalyst as polysulfides adsorption-catalytic conversion mediator with enhanced redox kinetics in lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) have emerged as the research hotspot due to their compelling merits, including high specific capacity (1675 mAh g−1), theoretical energy density (2600 Wh kg−1), environmental friendliness, and economic advantages. However, challenges still exist for further application due to their inherent issues such as the natural insulation, shuttle effect, and volume expansion of sulfur cathode during the continuous cycle processes. These factors obstruct the lithium ions (Li+) transfer process and sulfur utilization, resulting in significant impedance and inducing inferior battery performance. Herein, the core–shell nanocube anchoring ruthenium atoms and dicobalt phosphate (Ru@Co2P@NC) were fabricated as the effective catalyst and inhibited barrier for LSBs. On the one hand, the core–shell structure offers numerous channels to expedite Li+ diffusion. On the other hand, ruthenium (Ru) and dicobalt phosphate (Co2P) active sites facilitate the chemical capture of lithium polysulfides (LiPSs), accelerating sluggish kinetics. Ru@Co2P@NC modified cells not only exhibited a high initial specific capacity (1609.35 mAh g−1) at 0.5C and enduring stability with high specific capacity retention of 906.60 mAh g−1 at 0.5C after 400 cycles but also possessed low capacity attenuation rate of 0.07 % per cycle after 600 cycles (1C, Sulfur loading: 1.2 mg). Interestingly, the modified cells demonstrated a high specific capacity and long-cycle stability with high sulfur loading (from 1.984 to 3.137 mg), which provides a promising research approach for high-performance LSBs.

Quantum-Sized Co Nanoparticles with Rich Vacancies Enabled the Uniform Deposition of Lithium Metal and Fast Polysulfide Conversion.

The notorious polysulfide shuttling and uncontrollable Li-dendrite growth are the main obstacles to the marketization of Li-S batteries. Herein, a dual-functional material consisting of vacancy-rich quantum-sized Co nanodots anchored on a mesoporous carbon layer (v-Co/meso-C) is proposed. This material exposes more active sites to improve its reaction performance and simultaneously realizes excellent lithiophilicity and sulfiphilicity characteristics in Li-S electrochemistry. As Li metal deposition hosts, v-Co/meso-C shows small nucleation overpotential, low polarization, and ultra-long cycling stability in both half and symmetric cells, as confirmed by experimental studies. On the S cathode side, experimental and theoretical calculations demonstrate that v-Co/meso-C enhances the adsorption of polysulfides and boosts their catalytic conversion rate. This, in turn, suppresses the shuttle effect of polysulfides and improves sulfur utilization efficiency. Finally, a shuttle-free and dendrite-free v-Co/meso-C@Li//v-Co/meso-C@S full cell is fabricated, exhibiting excellent rate performance (739 mAhg-1 at 5.0 C) and good cyclability (capacity decay rate is 0.033% and 0.035% per cycle at 2.0 and 5.0 C, respectively). Even a pouch cell with high sulfur loading (5.5mgcm-2) and lean electrolyte/sulfur (4.8µLmg-1) can still work 50 cycles with 80% capacity retention rate. This study shows far-reaching implications in the design of dendrite-free, shuttle-free Li-S batteries.

Seeding Co Atoms on Size Effect‐Enabled V2C MXene for Kinetically Boosted Lithium–Sulfur Batteries

AbstractLithium‐sulfur (Li–S) batteries are facing a multitude of challenges, mainly pertaining to the sluggish sulfur redox kinetics and rampant lithium dendrite growth on the cathode and anode side, respectively. In this sense, MXene has shown conspicuous advantages in serving as a dual‐functional promotor for Li–S batteries throughout the morphologic engineering, but still suffers from poor electrocatalytic activity and insufficient lithophilic sites. Herein, atomically dispersed Co sites are seeded onto the size effect‐enabled V2C MXene spheres (Co‐VC), leading to the generation of unique coordination configurations and rich active sites. Electrochemical tests combined with synchrotron radiation X‐ray 3D nano‐computed tomography and theoretical calculations unravel that Co‐VC with optimal coordination environments simultaneously boost sulfur reaction kinetics and lithium nucleation. As a consequence, Li–S batteries with Co‐VC modified separator can sustain a stable operation over 700 cycles with negligible capacity decay at 1.0 C, and delivers an areal capacity of 9.0 mAh cm−2 and desired cyclic performance at a high sulfur loading of 7.6 mg cm−2 with a lean electrolyte dosage of 4.0 µL mgS−1 at 0.1 C. The work opens a new avenue for boosting atomic‐scale site design with the aid of 2D substrates toward pragmatic Li–S batteries.