High Sulfur Loading Research Articles

Ultrathin Mixed Ionic-Electronic Conducting Interlayer via the Solution Shearing Technique for High-Performance Lithium-Sulfur Batteries.

The commercialization of lithium-sulfur (Li-S) batteries has been hampered by diverse challenges, including the shuttle phenomenon and low electrical/ionic conductivity of lithium sulfide and sulfur. To address these issues, extensive research has been devoted to developing multifunctional interlayers. However, interlayers capable of simultaneously suppressing the polysulfide (PS) shuttle and ensuring stable electrical and ionic conductivity are relatively uncommon. Moreover, the use of thick and heavy interlayers results in an unavoidable decline in the energy density of Li-S batteries. We developed an ultrathin (750 nm), lightweight (0.182 mg cm-2) interlayer that facilitates mixed ionic-electronic conduction using the solution shearing technique. The interlayer, composed of carbon nanotube (CNT)/Nafion/poly-3,4-ethylenedioxythiophene:tetracyanoborate (PEDOT:TCB), effectively suppresses the shuttle phenomenon through the synergistic segregation and adsorption effects on PSs by Nafion and CNT/PEDOT, respectively. Furthermore, the electrical/ionic conductivity of the interlayer can be improved via counterion exchange and homogeneous Li+ ion flux/good wettability from SO3- functional group of Nafion, respectively. Enhanced sulfur utilization and reaction kinetics through polysulfide shuttle inhibition and facilitated electron/ion transfer by interlayer enable a high discharge capacity of 1029 mA h g-1 in the Li-S pouch cell under a high sulfur loading of 5.3 mg cm-2 and low electrolyte/sulfur ratio of 5 μL mg-1.

Synergistic enhancement of chemisorption and catalytic conversion in lithium-sulfur batteries via Co3Fe7/Co5.47N separator mediator

Lithium-sulfur batteries (LSBs) show considerable potential in next-generation high performance batteries, but the heavy shuttle effect and sluggish redox kinetics of polysulfide hinder their further applications. In this paper, to address these shortcomings of LSBs, Co3Fe7/Co5.47N heterostructure were prepared and constructed from their Fe-Co Prussian blue analogue precursors under the condition of high temperature pyrolysis. The obtained Co3Fe7/Co5.47N display excellent immobilization-diffusion-conversion performance for polysulfides by synergistic effect in successfully hindering the shuttle effect of polysulfides. When the Co3Fe7/Co5.47N heterostructure were applied to modify the commercial polypropylene (PP) separator, the batteries displayed fantastic rate capacity and cycling stability. Specifically, the Co3Fe7/Co5.47N-PP batteries exhibit an extremely satisfactory initial specific capacity of 1430 m Ah/g at 0.5C, wonderful rate capacity of around 780 m Ah/g at 3C and superior per cycle decaying rate of 0.08 % for 500 cycles at 0.5C. When the current density reaches to 2C, the batteries still exhibit 501 m Ah/g after 900 cycles with 0.015 % per cycle decay rate. Besides, even in the high loading of sulfur (3.0 mg cm−2) at 0.5C, the superior cycling stability (0.075 % per cycle decay rate after 200 cycles) and high specific capacity (741 mAh/g after 200 cycles) can still be performed. Thus, this work provides a facile method for high-powered and long-life Li-S batteries with eminent entrapping-conversion processes of polysulfides.

GO-CoNiP New Composite Material Modified Separator for Long Cycle Lithium-Sulfur Batteries.

Lithium-sulfur batteries with high capacity are considered the most promising candidates for next-generation energy storage systems. Mitigating the shuttle reaction and promoting catalytic conversion within the battery are major challenges in the development of high-performance lithium-sulfur batteries. To solve these problems, a novel composite material GO-CoNiP is synthesized in this study. The material has excellent conductivity and abundant active sites to adsorb polysulfides and improve reaction kinetics within the battery. The initial capacity of the GO-CoNiP separator battery at 1 C is 889.4 mAh g-1, and the single-cycle decay is 0.063% after 1000 cycles. In the 4 C high-rate test, the single-cycle decay is only 0.068% after 400 cycles. The initial capacity is as high as 828.2 mAh g-1 under high sulfur loading (7.3mg cm-2). In addition, high and low-temperature performance tests are performed on the GO-CoNiP separator battery. The first cycle discharge reaches 810.9 mAh g-1 at a low temperature of 0 °C, and the first cycle discharge reaches 1064.8 mAh g-1 at a high temperature of 60 °C, and both can run stably for 120 cycles. In addition, in situ Raman tests are conducted to explain the adsorption of polysulfides by GO-CoNiP from a deeper level.

An oxygen-vacancy-boosted heterostructured catalyst with synergistically integrated dual transition-metal oxides for high-performance lithium-sulfur batteries

The practical use of high-energy–density Li–S batteries (LSBs) is significantly hampered by the severe dissolution of soluble Li polysulfides (LiPSs) and their sluggish redox kinetics. To address these issues, a novel heterostructured electrocatalyst comprising nano-RuO2-decorated hexagonal CeO2 (NRHC) was developed in this study. The hetero-growth of RuO2 on the plate-shaped HC induced beneficial oxygen vacancies (OVs), which provided positively charged sites and free electrons owing to the lattice disorder between RuO2 and CeO2, thereby boosting the ability of the NRHC to adsorb LiPSs, exhibit enhanced conversion kinetics, and facilitate Li+ transport. Moreover, the NRHC heterostructure comprising RuO2 (a polar but highly conductive material) and CeO2 (a polar and surface-OV-rich material) effectively improved the “trapping–diffusion–conversion” process to transform LiPSs into Li2S on its surface. Benefiting from the synergistic catalytic attributes of the NRHC, an LSB with the NRHC-modified separator exhibited superior cyclability (844.7 mAh/g after 1000 cycles with a low-capacity decay rate of 0.029% per cycle) at a high current density of 1 C. Even at a high sulfur loading (6.4 mg cm−2), the LSB achieved a high areal capacity of over 4.5 mAh cm−2 at 0.1 C, highlighting its practical applicability.

Defects-rich TiO2(B) in-situ grown on carbon fiber cloth as self-standing electrode for high-loading lithium–sulfur batteries

Poor conductivity, severe shuttling of soluble lithium polysulfides (LiPSs), and sluggish sulfur redox kinetics are inherent issues existing in lithium-sulfur batteries (LSBs). Herein, a self-standing electrode was designed and constructed via the in-situ growth of defects-rich TiO2(B) on a carbon cloth (CC) (denoted as TiO2-x(B)@CC). The strong polarity and high electrochemical activity of TiO2-x(B) enables strong chemical adsorption for LiPSs and catalyzes sulfur conversion reactions. CC as growth substrate inhibits the agglomeration of TiO2-x(B) nanosheets and improves electrical conductivity, as well as holds high sulfur loadings. Benefiting from these synergistic effects, TiO2-x(B)@CC-based cathode with a sulfur loading of ∼ 2.5 mgS cm−2 maintained a high specific capacity of 500 mAh/g over 200cycles at 2.0C. Even under high sulfur loading of ∼ 8.1 mgS cm−2 and a low electrolyte/sulfur (E/S) ratio of ∼ 6.5 μL mgS-1, it still achieved good rate capacities.

High-areal-capacity all-solid-state Li-S battery enabled by dry process technology

All-solid-state lithium-sulfur batteries (ASSLSBs) based on sulfide solid electrolyte (SSE) hold great promise as the next-generation energy storage technology with great potential for high energy density and improved safety. However, the development of practical ASSLSBs is restricted by the scalable fabrication of sulfur cathode sheets with outstanding electrochemical performance, which remains a complex and challenging endeavor. Herein, we employ dry electrode technology to fabricate free-standing sulfur cathode sheets with both high sulfur content and loading. By utilizing polytetrafluoroethylene (PTFE) binders with unique fibrous morphologies in the dry electrodes, we achieved sulfur cathode sheets with high flexibility without compromising ionic and electronic conductivity. Remarkably, even with thickened dry cathode sheets featuring high sulfur loading of 4.5 mg cm-2, the sulfur cathodes exhibit high initial discharge capacity of 1114.8 mAh g-1 with good cycle stability and rate capability. Additionally, we successfully demonstrate the construction of sheet-type all-solid-state Li3.75Si/SSE/S cells, showcasing favorable electrochemical performance with a high reversible capacity of 1067.4 mAh g-1 after 30 cycles even at a high sulfur loading of 4.5 mg cm-2 and high current density of 1 mA cm-2 (0.2C). Our findings represent a demonstration of batteries coupled with high-capacity sulfur cathode and lithiated silicon anode exhibiting exceptional electrochemical performance. It also underscores the significant potential of dry-process technology in addressing the critical challenges associated with the practical production of ASSLSBs. This contribution propels ongoing endeavors in the development of next-generation energy storage systems.

Rational design of bidirectional electrocatalysts and accelerated sulfur redox reactions in lithium-sulfur batteries

Lithium–sulfur (Li–S) batteries have emerged as one of the most promising energy storage solutions. However, its commercial application still faces a significant challenge: the sluggish redox reaction kinetics of the reversible lithium polysulfide (LiPS) conversion process. The strategic design of cathode structures and electrocatalysts can help accelerate polysulfide conversion. In this study, systematic density functional theory (DFT) calculations predict that the incorporation of platinum (Pt) nanoparticles, as a model electrocatalyst, into biomass carbon materials can effectively promote the bidirectional conversion of polysulfides. Detailed kinetic analyses reveal that Pt-doped biomass carbon materials possess exceptional electrocatalytic abilities for Li2S nucleation and dissociation. These findings are further elucidated by ex situ X–ray photoelectron spectroscopy measurements, elucidating the bidirectional mechanism of Pt. The sulfur cathode delivers a remarkable specific discharge capacity of 1386.9 mAh g–1 at 0.1 C. Even more impressive is its potential for practical applications, exemplified by a high initial capacity of 1218.7/1015.3 mAh g−1 and excellent cycling stability under a high sulfur loading of 4.5/7.5 mg cm−2, which achieved substantial capacity retention (83.9/81.1%) after 100 cycles. This bidirectional electrocatalysis, achieved through the synergy of metal with biomass carbon materials, presents an attractive approach for advancing Li–S systems.

Phosphorous-Based Heterostructure for the Effective Catalysis of Polysulfide Reactions with Phase Changes in High-Sulfur-Loading Lithium-Sulfur Batteries.

High sulfur loading and long cycle life are the design targets of commercializable lithium-sulfur (Li-S) batteries. The sulfur electrochemical reactions from Li2 S4 to Li2 S, which account for 75% of the battery's theoretical capacity, involve liquid-to-solid and solid-to-solid phase changes in all Li-S battery electrolytes in use today. These are kinetically hindered processes that are exacerbated by a high sulfur loading. In this study, it is observed that an in situ grown bimetallic phosphide/black phosphorus (NiCoP/BP) heterostructure can effectively catalyze the Li2 S4 to Li2 S reactions to increase the sulfur utilization at high sulfur loadings. The NiCoP/BP heterostructure is a good polysulfide adsorber, and the electric field prevailing at the Mott-Schottky junction of the heterostructure can facilitate charge transfer in the Li2 S4 to Li2 S2 liquid-to-solid reaction and Li+ diffusion in the Li2 S2 to Li2 S solid-state reaction. Consequently, a sulfur cathode with the NiCoP/BP catalyst can deliver a specific capacity of 830 mAh g-1 at the sulfur loading of 6mg cm-2 for 500 cycles at the 0.5 C rate. High sulfur utilization is also possible at a higher sulfur loading of 8mg cm-2 for 440 cycles at the 1 C rate.

Metal‐Halide Gelated MXene and Its Use as a Bifunctional Sulfur Host Stabilizing Both Cathode and Anode for Practical Lithium–Sulfur Batteries

AbstractThe gelation of MXene promises to assemble a 3D conductive and catalytic monolith for various applications. However, controllable assembly and function customization are still challenging. Here, with a “killing two birds with one stone” initiator (metal halide, typically ZnI2), the controllable gelation of MXene is enabled, which produces a sulfur host that stabilizes not only the cathode but also the lithium metal anode for lithium‐sulfur batteries. Zn2+ cations trigger the gelation and act as linkers between MXene nanosheets (NSs), while the iodine anions as spacers avoid the NSs restacking, forming a monolith with a well‐tunable 3D structure. As a sulfur host, the formed 3D monolith with adsorptive Zn─O sites and highly accessible surface greatly enhances the sulfur redox kinetics, effectively suppressing the shuttling and sulfur loss. At the same time, iodine anions are released into the electrolyte as additives eliminating dead Li for the anode in cycling. Thus, the assembled battery shows high Coulombic efficiency (∼above 99%, even under high sulfur loading: 6.6 mg cm−2) and long cycling stability. Under the practical condition (E/S ratio: 5 µL mgs−1, sulfur loading: 5 mg cm−2), high capacity retention of >70% for 200 cycles is achieved.

Synergistic polarization engineering on BaTiO3 bulk and surface for boosting redox kinetics of polysulfides in lithium–sulfur batteries

The notorious shuttle effect of intermediate lithium polysulfides and the sluggish kinetics of sulfur redox reactions restrict the further development of high-energy-density lithium-sulfur (Li–S) batteries. Herein, a strategy of synergistic polarization engineering on ferroelectric barium titanate (BaTiO3) bulk and surface is reported, aiming to collectively improve the adsorption-catalytic ability of ferroelectric BaTiO3 to polysulfides. Differential phase contrast-scanning transmission electron microscopy (DPC-STEM) demonstrates that the introduction of ultrathin heteroepitaxial TiOx surface can give rise to the surface local electric field differing from bulk internal polarization field. Experimental and theoretical results further reveal that synergistic polarization engineering by integrating the enhanced bulk internal polarization field with the surface local electric field can collaboratively realize excellent adsorption-catalytic activity resulting from rapid electrons transfer and optimized active sites. As a result, employing BaTiO3@TiOx modified separator can endow the batteries with favorable rate performance (the discharge specific capacity achieves 710 mAh g−1 at 4 C) and substantial enhancement on cyclic performance (64.5 % capacity retention at 2 C over 500 cycles). Impressively, even at high sulfur loading of 2.5 mg cm−2, the BaTiO3@TiOx-based cell still stabilizes 78 % capacity retention with at 1 C over 150 cycles, showing the practical potential of BaTiO3@TiOx in optimizing catalytic efficiency.

Synergistic Effect of Bimetallic MOF Modified Separator for Long Cycle Life Lithium‐Sulfur Batteries

AbstractSevere polysulfide dissolution and shuttling are the main challenges that plague the long cycle life and capacity retention of lithium‐sulfur (Li‐S) batteries. To address these challenges, efficient separators are designed and modified with a dual functional bimetallic metal‐organic framework (MOF). Flower‐shaped bimetallic MOFs (i.e., Fe‐ZIF‐8) with nanostructured pores are synthesized at 35 °C in water by introducing dopant metal sites (Fe), which are then coated on a polypropylene (PP) separator to provide selective channels, thereby effectively inhibiting the migration of lithium polysulfides while allowing homogeneous transport of Li‐ions. The active sites of the Fe‐ZIF‐8 enable electrocatalytic conversion, facilitating the conversion of lithium polysulfides. Moreover, the developed separator can prevent dendrite formation due to the uniform pore size and hence the even Li‐ion transport and deposition. A coin cell using a Fe‐ZIF‐8/PP separator with S‐loaded carbon cathode displayed a high cycle life of 1000 cycles with a high initial discharge capacity of 863 mAh g−1 at 0.5 C and a discharge capacity of 746 mAh g−1 at a high rate of 3 C. Promising specific capacity has been documented even under high sulfur loading of 5.0 mg cm−2 and electrolyte to the sulfur ratio (E/S) of 5 µL mg−1.

PTFE nanofiber cross-linked acetylene black: A flexible self-supporting semi-confined architecture for ultra-high sulfur loading and areal capacity

Lithium-sulfur batteries attract great interest due to their high energy density, sulfur abundance and environment friendly. However, the shuttle effect of lithium polysulfide and serious capacity fading especially at high sulfur loading remains a challenge for their commercial applications. In this work, we propose a scalable and feasible strategy to construct a flexible host for sulfur and catalyst carrier, in which polytetrafluoroethylene is employed as a precursor and in-situ polymerized into nanofibers to link acetylene black (PTFE NF/AB) through a blend and low temperature (∼ 180 °C) treatment process. The PTFE NF/AB exhibits semi-confined architecture for sulfur accommodation, electrolyte infiltration and electron transformation. Impressively, the electrode achieves a high areal capacity of 14.6 mAh cm−2 at the current density of 4.82 mA cm−2 with a sulfur loading of 20.6 mg cm−2. Moreover, the PTFE NF/AB architecture can be employed as the catalyst supports. The capacity can be further enhanced to 17.4 mAh cm−2 when MoS2 fabricated into the PTFE NF/AB using a ball mill approach. Assembled into a pouch cell, the PTFE NF/AB architecture delivers a high capacity of 825.4 mAh g−1 in the folded state, showing its excellent potential in the high-energy flexible territory.

Temperature-dependent Viscoelastic Liquid MOFs Based Cellulose Gel Electrolyte for Advanced Lithium-Sulfur Batteries Over an Extensive Temperature Range

The uncontrolled growth of lithium dendrites severely limits the practical use of Li-S batteries. Additionally, cell temperature increases during operation, accelerating dendrite growth and side reactions. To stabilize the anode over a wide temperature range, we proposed a promising solution of a novel temperature-dependent viscoelastic liquid UiO66 MOFs-based cellulose gel electrolyte. This specially engineered electrolyte demonstrated superior stabilization of the anode. It adopted the “blocking anions and promoting Li+ transfer” strategy, resulting in a uniform Li+ flux deposition and the formation of a stable and dense solid electrolyte interphase layer, effectively suppressing dendrite growth. To further improve the cycling performance of the cell, a hollow transition bi-metal selenide (FeCo-Se2/NC) was developed as the sulfur host material. This complex exhibited a strong chemisorption capacity for polysulfides and a high catalytic ability to expedite the conversion process of lithium polysulfides. The final cell achieved a high capacity of 687.2 mAh g−1 after 500 cycles at 3 C with a minimal fading rate of 0.04% per cycle. It also demonstrated a high area capacity of 5.78 mAh cm−2 at a high sulfur loading of 6.2 mg cm−2, along with excellent cycling stability under temperature-varying conditions. The findings not only highlighted the commercialization potential of Li-S batteries but also underscored the effectiveness of porous liquid MOFs as a modified layer, effectively stabilizing the Li anode and reducing interfacial impedance between the electrolyte and electrode. Our research paved the way for advanced energy storage solutions that could significantly contribute to a sustainable and eco-friendly future.

A permselective protection layer assembled by two-dimensional organic vermiculite produces a highly stable lithium metal anode for lithium-sulfur batteries

Designing a protective coating for the lithium metal anode is the crucial yet challenging solution to its practical applications. How to well isolate the reactants in electrolytes but allow fast and uniform ion diffusion is the greatest challenge for various high energy density batteries, e.g., lithium–sulfur batteries. Herein, we propose a permselective protect coating, which has the ability to accelerate the homogeneous fast Li-ion diffusion but block the polysulfide anion penetration, and obtain a dendrite-free and corrosion-resistive lithium metal anode. The above ion-sieving function is realized by a membrane assembled with cetyltrimethylammonium (CTA+)-modified two-dimensional organic vermiculite nanosheets. The enlarged interlayer spacing of the membrane with CTA+ and the negative charges on the vermiculite nanosheets enhance the fast Li-ion transmission across the membrane for uniform Li deposition. At the same time, the non-polar alkyl of CTA+ and the negatively charged surface effectively block the polysulfide adsorption and penetration. Therefore, the side reactions and dendrite growth are effectively suppressed, and with the high sulfur loading (5 mg/cm2) and limited E/S ratio, the assembled lithium–sulfur cell shows good cycling stability at 0.1C, revealing a high capacity retention of 65.9 % over 300 cycles.

Interfacial Engineering and Coupling of MXene/Reduced Graphene Oxide/C3 N4 Aerogel with Optimized d-Band Center as a Free-Standing Sulfur Carrier for High-Performance Li-S Batteries.

To overcome the shuttle effect and improve the energy density of Li-S batteries, developing free-standing sulfur carriers with high capture and catalytic effect towards polysulfides is an effective strategy. Herein, a MXene/reduced graphene oxide/C3 N4 aerogel (MG/C3 N4 ) with three-dimensional architecture prepared through low-temperature hydrothermal approach followed by thermal treatment is used as sulfur carrier for free-standing cathode of Li-S batteries. In the MG/C3 N4 , MXene and rGO construct a highly conductive framework, and the MXene nanosheets offer chemical capture and catalytic activity towards lithium polysulfides, in favor of good cycling stability. The introduction of g-C3 N4 further enhances the reactivity of C-Ti-N at the hetero-interface by engineering the electronic state of Ti atoms, leading to the optimized metal d-band for expediting the multistep conversion of sulfur electrochemistry. Therefore, the free-standing sulfur cathode with MG/C3 N4 carrier achieves excellent performance with a capacity of 1315.6 mAh g-1 at 0.2 C and a capacity retention of 97.5% after 100 cycles as well as superior rate capability with 1167.4 mAh g-1 at 2 C. Even at a high sulfur loading of 4.92mg cm-2 , the cathode remains 940.3 mAh g-1 (4.62 mAh cm-2 ) after 200 cycles, indicating its promising potential for achieving high-performance Li-S batteries.

Vacancy-rich, multi-heterostructured MXene/Fe3S4@FeSe2 catalyst for high performance lithium-sulfur batteries

Due to fast electron/ion transfer at interfaces, heterostructure catalysts can be used in lithium-sulfur (Li-S) batteries to boost sulfur-polysulfides-lihtium sulfide conversion and inhibit the polysulfides shuttle effect, thus giving rise to improved battery performance. However, traditional heterostructure catalysts still lack in the number of active centers that can guarantee high performance of Li-S batteries. Here, we designed and synthesized multi-heterostructured MXene/Fe3S4@FeSe2 catalyst through in-situ hydrothermal growth, sulfurization, and selenization steps. The resulting multi-heterostructure material is rich in vacancies and thus can provide more active centers than other heterostructured catalysts. Experiments and theoretical calculations show that MXene/Fe3S4@FeSe2 catalyst has a good synergistic conduction-adsorption-catalysis effect. Its high specific surface area and plural catalytic active centers can improve the conversion kinetics of LiPSs; the built-in electric field may reduce the energy barrier, and accelerate the electron/ion transfer. As a result, the Li-S battery assembled with MXene/Fe3S4@FeSe2 exhibits a high initial discharge capacity of 1185.6 mAh/g at 0.2 C (557.1 mAh/g at 5 C). Even at a high sulfur loading of 8.16 mg cm-2, the capacity retention rate is 82.4 % after 135 cycles. This work provides a new idea for the development of defect engineering in catalysts of Li-S battery.

Dual Functionalities of Rb Cation in Lean Electrolyte Lithium Sulfur Batteries

Achieving large discharge capacity and high cycling stability under high sulfur loading and lean electrolyte condition is critical for practical lithium sulfur batteries. However, it is impeded by the large overpotential for lithium sulfide (Li2S) nucleation at the cathode, caused by the sluggish reduction kinetics of lithium polysulfide and the short-circuit triggered by inhomogeneous Li electroplating at the anode. In this study, we report that adding rubidium cation to lean electrolyte in an additive level (0.05 M) can address the two challenges owing to the modifications of the cathode and anode surfaces by the formation of rubidium sulfide. At the sulfur cathode, the rubidium sulfide acts as a catalyst, accelerating the reduction of lithium polysulfides. At the Li metal anode, a rubidium sulfide-enriched inner SEI quickly passivates the surface, suppressing electrolyte decomposition and promoting uniform lithium deposition due to its lithiophilicity. The drop-in-solution leads to impressive results, delivering more than 3 mAh cm−2 over approximately 80 cycles at a sulfur loading of 3.8 mgsulfur cm−2 and an electrolyte to sulfur ratio of 3 μl mg−1.

Polysulfide regulation by defect-modulated Ta3N5−x electrocatalyst toward superior room-temperature sodium-sulfur batteries

Resolving low sulfur reaction activity and severe polysulfide dissolution remains challenging in metal-sulfur batteries. Motivated by a theoretical prediction, herein, we strategically propose nitrogen-vacancy tantalum nitride (Ta3N5−x) impregnated inside the interconnected nanopores of nitrogen-decorated carbon matrix as a new electrocatalyst for regulating sulfur redox reactions in room-temperature sodium-sulfur batteries. Through a pore-constriction mechanism, the nitrogen vacancies are controllably constructed during the nucleation of Ta3N5−x. The defect manipulation on the local environment enables well-regulated Ta 5d-orbital energy level, not only modulating band structure toward enhanced intrinsic conductivity of Ta-based materials, but also promoting polysulfide stabilization and achieving bifunctional catalytic capability toward completely reversible polysulfide conversion. Moreover, the interconnected continuous Ta3N5−x-in-pore structure facilitates electron and sodium-ion transport and accommodates volume expansion of sulfur species while suppressing their shuttle behavior. Due to these attributes, the as-developed Ta3N5−x-based electrode achieves superior rate capability of 730 mAh g−1 at 3.35 A g−1, long-term cycling stability over 2000 cycles, and high areal capacity over 6 mAh cm−2 under high sulfur loading of 6.2 mg cm−2. This work not only presents a new sulfur electrocatalyst candidate for metal-sulfur batteries, but also sheds light on the controllable material design of defect structure in hopes of inspiring new ideas and directions for future research.

A macrocyclic amine-based electrolyte for lithium–sulfur batteries: Li ion encapsulation regulates electrode performance

The widespread use of lithium–sulfur (Li–S) batteries is hindered by slow cathode kinetics, the shuttle effect, and dendrite growth on the anode. We show that these challenges can be overcome by replacing a linear ether (i.e., 1,2-dimethoxyethane) in commonly used electrolytes with a macrocyclic amine, 1,4,7,10-tetramethyl-1,4,7,10-tetraazacyclododecane (TMTAC). Theoretical studies and experimental data indicate that the cavity of TMTAC matches a Li ion to form a robust solvation structure. Such a solvation structure not only leads to 3D deposition of Li2S on the cathode, which is responsible to the reduced overpotentials of Li2S nucleation and decomposition, but also suppresses Li dendrite growth on the anode. Moreover, the shuttle effect of polysulfides is effectively suppressed as the quantity of free TMTAC in the TMTAC-based electrolyte is substantially reduced. As a result, coin-type cells prepared with TMTAC-based electrolytes exhibit outstanding performance metrics for all key device parameters. Furthermore, pouch-type cells can be prepared with high sulfur loadings (e.g., 3.43 mg cm−2) and a low electrolyte to sulfur ratio (e.g., 6.16 μl mg−1) while maintaining a high areal specific capacity (3.38 mA h cm−2). This work demonstrates that the effective solvation of critical ions in energy storage devices is paramount to achieving peak performance.

Highly dispersed conductive and electrocatalytic mediators enabling rapid polysulfides conversion for lithium sulfur batteries

The practical application of Li-S batteries encounters hurdles in maintaining cycling durability and rate capability under realistic conditions. Electrostatic self-assembly stands as a captivating avenue for exploring new frontiers in nanoscale catalysis. Leveraging renewable bio-oil both as a carbon source and self-polymerization precursor, ultrafine Mo2C nanocrystals anchored on bio-oil-derived 3D hierarchical carbon matrix (Mo2C@BOC) are fabricated by a facile NaCl template-assisted electrostatic self-assembly and followed annealing procedure. Densely anchored ultrafine Mo2C nanocrystals, intertwined with highly conductive carbon nanosheets, unveil an enhanced exposure of catalytically active sites for lithium polysulfide immobilization, conversion, and supply amply nucleation sites to mediate the fast precipitation of Li2S2/Li2S. Attributed to these favorable features, Li-S cells based on the as-designed catalytic host attain satisfactory cyclability with a minimum capacity fading rate of 0.0144 % over 1000 cycles and excellent rate capability. Decent performance can be achieved even at a high sulfur loading of 8.0 mg cm−2 and a low electrolyte-to-sulfur ratio of 3.5 µL mg−1. This strategy for solving the shuttle effect under high sulfur loading provides a promising solution for the further development of high-performance Li-S batteries. This work provides a rational strategy for solving the shuttle effect under high sulfur loading and sheds light on the great potential of Mo2C@BOC for developing more practical Li-S batteries.