Dense-Stacking Porous Conjugated Polymer as Reactive-Type Host for High-Performance Lithium Sulfur Batteries

Origin of the High Catalytic Activity of MoS2 in Na-S Batteries: Electrochemically Reconstructed Mo Single Atoms

Room-temperature sodium-sulfur (RT Na-S) batteries with high energy density and low cost are considered promising next-generation electrochemical energy storage systems. However, their practical feasibility is seriously impeded by the shuttle effect of sodium polysulfide (NaPSs) resulting from the sluggish reaction kinetics. Introducing a suitable catalyst to accelerate conversion of NaPSs is the most used strategy to inhibit the shuttle effect. Traditional catalytic approaches often want to avoid the irreversible phase transition of the catalyst at a deep discharge. On the contrary, here, we leverage the intrinsic structural tunability of the MoS2 catalyst in the opposite direction and innovatively propose a voltage modulation strategy for in situ generation of trace Mo single atoms (MoSAC) during the first charge-discharge process, leading to the formation of highly active catalytic phases (MoS2/MoSAC) through the self-reconstruction. Theoretical calculations reveal that the incorporation of MoSAC modulates the electronic structure of the Mo d-band center, which not only effectively promotes the d-p orbital hybridization but also accelerates the catalytic intermediate desorption by the bonding transition, the dynamic single-atom synergistic catalytic mechanism enhances the adsorption response between the metal active site and NaPSs, which significantly improves the sulfur redox reaction (SRR), and the initial capacity of the MoS2/MoSAC/CF@S cell at 0.2 A g-1 is increased by 46.58% compared to that of the MoS2/CF@S cell. The discovery of the MoS2/MoSAC/CF catalyst provides new insights into adjusting the structure and function of transition metal disulfide catalysts at the atomic scale, offering hope for the development of high-specific-energy RT Na-S batteries.

Locally boosted Li2S nucleation on VO2 by loading carbon quantum dots for soft-packaged lithium-sulfur pouch cells

VO2 affords ultrafast polysulfide adsorption on account of its oxidation potential, which matches the sulfur working window (1.7-2.8 V). Nevertheless, its nonconductive surface limits direct sulfur conversion. Herein, we gently load carbon quantum dots on VO2 to increase direct Li2S nucleation by enhanced electron conductivity. As a result, the soft-packaged lithium-sulfur pouch cell yields a capacity retention of 88.8% at 0.5C after 100 cycles and a decay rate of 0.17% per cycle over 200 cycles at 2C. The cell energy density of the multilayer cell is up to 386.1 W h kg-1.

Synergistic Effect of Lactam and Pyridine Nitrogen on Polysulfide Chemisorption and Electrocatalysis in Lithium Sulfur Batteries

Sulfur undergoes various changes, including the formation of negative charge-bearing lithium polysulfides during the operation of Li-S batteries. Dissolution of some of the polysulfides in battery electrolytes is one of the reasons for the poor performance of Li-S batteries. The charge injection into the sulfur and polysulfides from the electrode is also a problem. To address these issues, a small-molecule additive, 3,6-di(pyridin-4-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, was designed and synthesized with carbonyl oxygen atoms and two types of nitrogen. The pyridinic nitrogen increases the electronegativity of the carbonyl oxygen atoms. The pyridinic nitrogen, carbonyl oxygen, and lactam nitrogen provide multiple binding sites concurrently to the polysulfides, which increases the binding efficiency between the additive and polysulfides. A control molecule without the pyridine moiety displayed decreased binding to lithium polysulfides. Furthermore, the band edges of lithium polysulfide and 3,6-di(pyridin-4-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione are commensurate for efficient charge transfer between them, leading to the efficient electrocatalysis of lithium polysulfides. The cyclic voltammogram of the Li-S battery fabricated with 3,6-di(pyridin-4-yl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione exhibited sharp and well-defined peaks, confirming the formation of Li2Sy (where y varies between one and eight) from S8. These Li-S batteries showed a specific capacity of 950 mA h/g at 0.5 C, with a capacity retention of 70% at the 300th cycle. The pyridine-free control molecule, 3,6-diphenyl-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione, showed relatively poor performance in a Li-S battery.

Integrated Design for Discrete Sulfur@Polymer Nanoreactor with Tandem Connection as Lithium-Sulfur Battery Cathodes

Apart from electrode material modification, architecture design and optimization are important approaches for improving lithium-sulfur battery performance. Herein, an integrated structure with tandem connection is constructed by confining nanosulfur (NS) in conductive poly(3,4-ethylenedioxythiophene) (PEDOT) reaction chambers, forming an interface of discrete independent nanoreactor units bonded onto carbon nanotubes (noted as CNT/NS@PEDOT). The unique spatial confinement and concentration gradients of sulfur@PEDOT nanoreactors (SP-NRs) can promote reaction kinetics while facilitating rapid polysulfide transformation and minimizing dissolution and diffusion losses. Meanwhile, overall ultrahigh energy input and output are achieved through tandem connection with carbon nanotubes, isolation with PEDOT coating, and synergistic multiplicative effects among SP-NRs. As a result, it delivers a high initial discharge capacity of 1246 mAh g-1 at 0.1 C and 918 mAh g-1 at 1 C, the low capacity decay rate per lap of 0.011 % is achieved at a current density of 1 C after 1000 cycles. This research emphasizes the innovative structural design to provide a fresh trajectory for the further advancement of high-performance energy storage devices.

The spin polarization strategy regulates heterogeneous catalytic activity performance: from fundamentals to applications

In recent years, there has been significant attention towards the development of catalysts that exhibit superior performance and environmentally friendly attributes. This surge in interest is driven by the growing demands for energy utilization and storage as well as environmental preservation. Spin polarization plays a crucial role in catalyst design, comprehension of catalytic mechanisms, and reaction control, offering novel insights for the design of highly efficient catalysts. However, there are still some significant research gaps in the current study of spin catalysis. Therefore, it is urgent to understand how spin polarization impacts catalytic reactions to develop superior performance catalysts. Herein, we present a comprehensive summary of the application of spin polarization in catalysis. Firstly, we summarize the fundamental mechanism of spin polarization in catalytic reactions from two aspects of kinetics and thermodynamics. Additionally, we review the regulation mechanism of spin polarization in various catalytic applications and several approaches to modulate spin polarization. Moreover, we discuss the future development of spin polarization in catalysis and propose several potential avenues for further progress. We aim to improve current catalytic systems through implementing a novel and distinctive spin engineering strategy.

Rational Design of High-Loading Electrodes with Superior Performances Toward Practical Application for Energy Storage Devices

High-loading electrodes play a crucial role in designing practical high-energy batteries as they reduce the proportion of non-active materials, such as current separators, collectors, and battery packaging components. This design approach not only enhances battery performance but also facilitates faster processing and assembly, ultimately leading to reduced production costs. Despite the existing strategies to improve rechargeable battery performance, which mainly focus on novel electrode materials and high-performance electrolyte, most reported high electrochemical performances are achieved with low loading of active materials (<2 mg cm-2). Such low loading, however, fails to meet application requirements. Moreover, when attempting to scale up the loading of active materials, significant challenges are identified, including sluggish ion diffusion and electron conduction kinetics, volume expansion, high reaction barriers, and limitations associated with conventional electrode preparation processes. Unfortunately, these issues are often overlooked. In this review, the mechanisms responsible for the decay in the electrochemical performance of high-loading electrodes are thoroughly discussed. Additionally, efficient solutions, such as doping and structural design, are summarized to address these challenges. Drawing from the current achievements, this review proposes future directions for development and identifies technological challenges that must be tackled to facilitate the commercialization of high-energy-density rechargeable batteries.

Conformal 3D Li/Li13Sn5 Scaffolds Anodes for High-Areal Energy Density Flexible Lithium Metal Batteries

Achieving a high depth of discharge (DOD) in lithium metal anodes (LMAs) is crucial for developing high areal energy density batteries suitable for wearable electronics. Yet, the persistent growth of dendrites compromises battery performance, and the significant lithium consumption during pre-lithiation obstructs their broad application. Herein, A flexible 3D Li13Sn5 scaffold is designed by allowing molten lithium to infiltrate carbon cloth adorned with SnO2 nanocrystals. This design markedly curbs the troublesome dendrite growth, thanks to the uniform electric field distribution and swift Li+ diffusion dynamics. Additionally, with a minimal SnO2 nanocrystals loading (2 wt.%), only 0.6 wt.% of lithium is consumed during pre-lithiation. Insights from in situ optical microscope observations and COMSOL simulations reveal that lithium remains securely anchored within the scaffold, a result of the rapid mass/charge transfer and uniform electric field distribution. Consequently, this electrode achieves a remarkable DOD of 87.1% at 10 mA cm-2 for 40 mAh cm-2. Notably, when coupled with a polysulfide cathode, the constructed flexible Li/Li13Sn5@CC||Li2S6/SnO2@CC pouch cell delivers a high-areal capacity of 5.04 mAh cm-2 and an impressive areal-energy density of 10.6 mWh cm-2. The findings pave the way toward the development of high-performance LMAs, ideal for long-lasting wearable electronics.

Progress and Perspectives on the Development of Pouch-Type Lithium Metal Batteries

Lithium (Li) metal batteries (LMBs) are the "holy grail" in the energy storage field due to their high energy density (theoretically >500 Wh kg-1 ). Recently, tremendous efforts have been made to promote the research & development (R&D) of pouch-type LMBs toward practical application. This article aims to provide a comprehensive and in-depth review of recent progress on pouch-type LMBs from full cell aspect, and to offer insights to guide its future development. It will review pouch-type LMBs using both liquid and solid-state electrolytes, and cover topics related to both Li and cathode (including LiNix Coy Mn1-x-y O2 , S and O2 ) as both electrodes impact the battery performance. The key performance criteria of pouch-type LMBs and their relationship in between are introduced first, then the major challenges facing the development of pouch-type LMBs are discussed in detail, especially those severely aggravated in pouch cells compared with coin cells. Subsequently, the recent progress on mechanistic understandings of the degradation of pouch-type LMBs is summarized, followed with the practical strategies that have been utilized to address these issues and to improve the key performance criteria of pouch-type LMBs. In the end, it provides perspectives on advancing the R&Ds of pouch-type LMBs towards their application in practice.

Constructing Wide-Temperature Lithium-Sulfur Batteries by Using a Covalent Organic Nanosheet Wrapped Carbon Nanotube

Lithium-sulfur (Li-S) batteries hold the superiority of eminent theoretical energy density (2600 Wh kg-1 ). However, the ponderous sulfur reduction reaction and the issue of polysulfide shuttling pose significant obstacles to achieving the practical wide-temperature operation of Li-S batteries. Herein, a covalent organic nanosheet-wrapped carbon nanotubes (denoted CON/CNT) composite is synthesized as an electrocatalyst for wide-temperature Li-S batteries. The design incorporates the CON skeleton, which contains imide and triazine functional units capable of chemically adsorbing polysulfides, and the underlaid CNTs facilitate the conversion of captured polysulfides enabled by enhanced conductivity. The electrocatalytic behavior and chemical interplay between polysulfides and the CON/CNT interlayer are elucidated by in situ X-ray diffraction detections and theoretical calculations. Resultantly, the CON/CNT-modified cells demonstrate upgraded performances, including wide-temperature operation ranging from 0 to 65 °C, high-rate performance (625 mAh g-1 at 5.0 C), exceptional high-rate cyclability (1000 cycles at 5.0 C), and stable operation under high sulfur loading (4.0 mg cm-2 ) and limited electrolyte (5 µL mgs -1 ). These findings might guide the development of advanced Li-S batteries.

Quantum Spin Exchange Interactions to Accelerate the Redox Kinetics in Li-S Batteries

Spin-engineering with electrocatalysts have been exploited to suppress the "shuttle effect" in Li-S batteries. Spin selection, spin-dependent electron mobility and spin potentials in activation barriers can be optimized as quantum spin exchange interactions leading to a significant reduction of the electronic repulsions in the orbitals of catalysts. Herein, we anchor the MgPc molecules on fluorinated carbon nanotubes (MgPc@FCNT), which exhibits the single active Mg sites with axial displacement. According to the density functional theory calculations, the electronic spin polarization in MgPc@FCNT not only increases the adsorption energy toward LiPSs intermediates but also facilitates the tunneling process of electron in Li-S batteries. As a result, the MgPc@FCNT provides an initial capacity of 6.1 mAh cm-2 even when the high sulfur loading is 4.5 mg cm-2, and still maintains 5.1 mAh cm-2 after 100 cycles. This work provides a new perspective to extend the main group single-atom catalysts enabling high-performance Li-S batteries.

High-Mass-Loading Li-S Batteries Catalytically Activated by Cerium Oxide: Performance and Failure Analysis under Lean Electrolyte Conditions

Increasing sulfur mass loading and minimizing electrolyte amount remains a major challenge for the development of high-energy-density Li-S batteries, which needs to be tackled with combined efforts of materials development and mechanistic analysis. This work, following the same team's most recent identification of the potential-limiting step of Li-S batteries under lean electrolyte conditions, seeks to advance the understanding by extending it to a new catalyst and into the high-sulfur-mass-loading region. CeOx nanostructures are integrated into cotton-derived carbon to develop a multifunctional 3D network that can host a large amount of active material, facilitate electron transport, and catalyze the sulfur lithiation reaction. The resulting S/CeOx /C electrode can deliver a stable areal capacity of 9 mAh cm-2 with a high sulfur loading of 14 mg cm-2 at a low electrolyte/sulfur ratio of 5 µL mg-1 . This study discovers that Li||S/CeOx /C cells usually fail during charging at high current density, as a consequence of local short circuiting caused by electrochemically deposited Li dendrites penetrating through the separator, a previously overlooked failure pattern distinctive to cells operating under lean electrolyte conditions. This work highlights the importance of developing new material structures and analyzing failure mechanisms in the advancement of Li-S batteries.

Design of Size-Controlled Sulfur Nanoparticle Cathodes for Lithium-Sulfur Aviation Batteries

Lithium-sulfur (Li-S) battery has been considered as a strong contender for commercial aerospace battery, but the commercialization requires Ah-level pouch cells with both efficient discharge at high rates and ultra-high energy density. In this paper, the application of lithium-sulfur batteries for powering drones by using the cathode of highly dispersed sulfur nanoparticles with well-controlled particle sizes have been realized. The sulfur nanoparticles are prepared by a precipitation method in an eco-friendly and efficient way, and loaded on graphene oxide-cetyltrimethylammonium bromide by molecular grafting to realize a large-scale fabrication of sulfur-based cathodes with superior electrochemical performance. A button cell based on the cathode exhibits an excellent discharge capacity of 62.8 mAh cm-2 at a high sulfur loading of 60 mg cm-2 (i.e., 1046.7 mAh g-1 ). The assembled miniature pouch cell (PCmini) shows a discharge capacity of 130 mAh g-1 , while the formed Ah-level pouch cell (PCAh) achieves energy density of 307 Wh kg-1 at 0.3C and 92 Wh kg-1 at 4C. Especially, a four-axis propeller drone powered by the PC has successfully completed a long flight (>3 min) at high altitudes, demonstrating the practical applicability as aviation batteries.

Structural Transformation in a Sulfurized Polymer Cathode to Enable Long-Life Rechargeable Lithium-Sulfur Batteries

Sulfurized polyacrylonitrile (SPAN) represents a class of sulfur-bonded polymers, which have shown thousands of stable cycles as a cathode in lithium-sulfur batteries. However, the exact molecular structure and its electrochemical reaction mechanism remain unclear. Most significantly, SPAN shows an over 25% 1st cycle irreversible capacity loss before exhibiting perfect reversibility for subsequent cycles. Here, with a SPAN thin-film platform and an array of analytical tools, we show that the SPAN capacity loss is associated with intramolecular dehydrogenation along with the loss of sulfur. This results in an increase in the aromaticity of the structure, which is corroborated by a >100× increase in electronic conductivity. We also discovered that the conductive carbon additive in the cathode is instrumental in driving the reaction to completion. Based on the proposed mechanism, we have developed a synthesis procedure to eliminate more than 50% of the irreversible capacity loss. Our insights into the reaction mechanism provide a blueprint for the design of high-performance sulfurized polymer cathode materials.

Interface Engineering Toward Expedited Li2 S Deposition in Lithium-Sulfur Batteries: A Critical Review

Lithium-sulfur batteries (LSBs) with superior energy density are among the most promising candidates of next-generation energy storage techniques. As the key step contributing to 75% of the overall capacity, Li₂ S deposition remains a formidable challenge for LSBs applications because of its sluggish kinetics. The severe kinetic issue originates from the huge interfacial impedances, indicative of the interface-dominated nature of Li₂ S deposition. Accordingly, increasing efforts have been devoted to interface engineering for efficient Li₂ S deposition, which has attained inspiring success to date. However, a systematic overview and in-depth understanding of this critical field are still absent. In this review, the principles of interface-controlled Li₂ S precipitation are presented, clarifying the pivotal roles of electrolyte-substrate and electrolyte-Li₂ S interfaces in regulating Li₂ S depositing behavior. For the optimization of the electrolyte-substrate interface, efforts on the design of substrates including metal compounds, functionalized carbons, and organic compounds are systematically summarized. Regarding the regulation of electrolyte-Li₂ S interface, the progress of applying polysulfides catholytes, redox mediators, and high-donicity/polarity electrolytes is overviewed in detail. Finally, the challenges and possible solutions aiming at optimizing Li₂ S deposition are given for further development of practical LSBs. This review would inspire more insightful works and, more importantly, may enlighten other electrochemical areas concerning heterogeneous deposition processes.

An Electrocatalytic Model of the Sulfur Reduction Reaction in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) battery is strongly considered as one of the most promising energy storage systems due to its high theoretical energy density and low cost. However, the sluggish reduction kinetics from Li₂ S₄ to Li₂ S during discharge hinders the practical application of Li-S batteries. Although various electrocatalysts have been proposed to improve the reaction kinetics, the electrocatalytic mechanism is unclear due to the complexity of sulfur reduction reactions (SRR). It is crucial to understand the electrocatalytic mechanism thoroughly for designing advanced electrocatalysts. Herein an electrocatalytic model is constructed to reveal the chemical mechanism of the SRR in Li-S batteries based on systematical density functional theory calculations, taking heteroatoms-doped carbon materials as an example. The adsorption energy of LiS_y ⋅ (y=1, 2, or 3) radicals is used as a key descriptor to predict the reaction pathway, rate-determining step, and overpotential. A diagram for designing advanced electrocatalysts is accordingly constructed. This work establishes a theoretical model, which is an intelligent integration for probing the complicated SRR mechanisms and designing advanced electrocatalysts for high-performance Li-S batteries.

Oxygen Vacancies in Bismuth Tantalum Oxide to Anchor Polysulfide and Accelerate the Sulfur Evolution Reaction in Lithium-Sulfur Batteries

The shuttling effect of soluble lithium polysulfides (LiPSs) and the sluggish conversion kinetics of polysulfides into insoluble Li₂S₂/Li₂S severely hinders the practical application of Li-S batteries. Advanced catalysts can capture and accelerate the liquid-solid conversion of polysulfides. Herein, we try to make use of bismuth tantalum oxide with oxygen vacancies as an electrocatalyst to catalyze the conversion of LiPSs by reducing the sulfur reduction reaction (SRR) nucleation energy barrier. Oxygen vacancies in Bi₄TaO₇ nanoparticles alter the electron band structure to improve instinct electronic conductivity and catalytic activity. In addition, the defective surface could provide unsaturated bonds around the vacancies to enhance the chemisorption capability with LiPSs. Hence, a multidimensional carbon (super P/CNT/Graphene) standing sulfur cathode is prepared by coating oxygen vacancies Bi₄TaO_7-x nanoparticles, in which the multidimensional carbon (MC) with micropores structure can host sulfur and provide a fast electron/ion pathway, while the outer-coated oxygen vacancies with Bi₄TaO_7-x with improved electronic conductivity and strong affinities for polysulfides can work as an adsorptive and conductive protective layer to achieve the physical restriction and chemical immobilization of lithium polysulfides as well as speed up their catalytic conversion. Benefiting from the synergistic effects of different components, the S/C@Bi₃TaO_7-x coin cell cathode shows superior cycling and rate performance. Even under a high level of sulfur loading of 9.6 mg cm^-2, a relatively high initial areal capacity of 10.20 mAh cm^-2 and a specific energy density of 300 Wh kg^-1 are achieved with a low electrolyte/sulfur ratio of 3.3 µL mg^-1. Combined with experimental results and theoretical calculations, the mechanism by which the Bi₄TaO₇ with oxygen vacancies promotes the kinetics of polysulfide conversion reactions has been revealed. The design of the multiple confined cathode structure provides physical and chemical adsorption, fast charge transfer, and catalytic conversion for polysulfides.

Toward Practical High-Energy-Density Lithium-Sulfur Pouch Cells: A Review

Lithium-sulfur (Li-S) batteries promise great potential as high-energy-density energy-storage devices due to their ultrahigh theoretical energy density of 2600 Wh kg^-1 . Evaluation and analysis on practical Li-S pouch cells are essential for achieving actual high energy density under working conditions and affording developing directions for practical applications. This review aims to afford a comprehensive overview of high-energy-density Li-S pouch cells regarding 7 years of development and to point out further research directions. Key design parameters to achieve actual high energy density are addressed first, to define the research boundaries distinguished from coin-cell-level evaluation. Systematic analysis of the published literature and cutting-edge performances is then conducted to demonstrate the achieved progress and the gap toward practical applications. Following that, failure analysis as well as promotion strategies at the pouch cell level are, respectively, discussed to reveal the unique working and failure mechanism that shall be accordingly addressed. Finally, perspectives toward high-performance Li-S pouch cells are presented regarding the challenges and opportunities of this field.

Challenges and advances of organic electrode materials for sustainable secondary batteries

Organic electrode materials (OEMs) emerge as one of the most promising candidates for the next-generation rechargeable batteries, mainly owing to their advantages of bountiful resources, high theoretical capacity, structural designability, and sustainability. However, OEMs usually suffer from poor electronic conductivity and unsatisfied stability in common organic electrolytes, ultimately leading to their deteriorating output capacity and inferior rate capability. Making clear of the issues from microscale to macroscale level is of great importance for the exploration of novel OEMs. Herein, the challenges and advanced strategies to boost the electrochemical performance of redox-active OEMs for sustainable secondary batteries are systematically summarized. Particularly, the characterization technologies and computational methods to elucidate the complex redox reaction mechanisms and confirm the organic radical intermediates of OEMs have been introduced. Moreover, the structural design of OEMs-based full cells and the outlook for OEMs are further presented. This review will shed light on the in-depth understanding and development of OEMs for sustainable secondary batteries.

Development of quasi-solid-state anode-free high-energy lithium sulfide-based batteries

Anode-free lithium batteries without lithium metal excess are a practical option to maximize the energy content beyond the conventional design of Li-ion and Li metal batteries. However, their performance and reliability are still limited by using low-capacity oxygen-releasing intercalation cathodes and flammable liquid electrolytes. Herein, we propose quasi-solid-state anode-free batteries containing lithium sulfide-based cathodes and non-flammable polymeric gel electrolytes. Such batteries exhibit an energy density of 1323 Wh L^-1 at the pouch cell level. Moreover, the lithium sulfide-based anode-free cell chemistry endows intrinsic safety thanks to a lack of uncontrolled exothermic reactions of reactive oxygen and excess Li inventory. Furthermore, the non-flammable gel electrolyte, developed from MXene-doped fluorinated polymer, inhibits polysulfide shuttling, hinders Li dendrite formation and further secures cell safety. Finally, we demonstrate the improved cell safety against mechanical, electrical and thermal abuses.

Thiol-Containing Metal-Organic Framework-Decorated Carbon Cloth as an Integrated Interlayer-Current Collector for Enhanced Li-S Batteries

Lithium-sulfur (Li-S) batteries hold great promise for new-generation energy storage technologies owing to their overwhelming energy density. However, the poor conductivity of active sulfur and the shuttle effect limit their widespread use. Herein, a carbon cloth decorated with thiol-containing UiO-66 nanoparticles (CC@UiO-66(SH)₂) was developed to substitute the traditional interlayer and current collector for Li-S batteries. One side of CC@UiO-66(SH)₂ acts as a current collector to load active materials, while the other side serves as an interlayer to further restrain polysulfide shuttling. This two-in-one integrated architecture endows the sulfur cathode with fast electron/ion transport and efficient chemical confinement of polysulfides. More importantly, rich thiol groups in the pores of UiO-66(SH)₂ serve to tether polysulfides by both covalent interactions and lithium bonding. Therefore, the Li-S battery equipped with this integrated interlayer-current collector not only delivers an enhanced specific capability (1209 mAh g^-1 at 0.1 C) but also exhibits prominent cycling stability (an attenuation rate of 0.037% per cycle for 1000 cycles at 1 C). Meanwhile, the battery achieves a high discharge capacity of 795 mAh g^-1 at a sulfur loading of 3.83 mg cm^-2. The new metal-organic framework (MOF)-based electrode material reported in this study undoubtedly provides insights into the exploration of functional MOFs for robust Li-S batteries.

Self-Supporting Carbon Nanofibers with Ni-Single-Atoms and Uniformly Dispersed Ni-Nanoparticles as Scalable Multifunctional Hosts for High Energy Density Lithium-Sulfur Batteries

The energy density of lithium-sulfur batteries (LSBs) is currently hampered by modest sulfur loadings and high electrolyte/sulfur ratios (E/S). These limitations can potentially be overcome using easy-to-infiltrate sulfur hosts with high catalytic materials. However, catalytic materials in such hosts are very susceptible to agglomeration due to the lack of efficient confinement in easy-to-infiltrate structures. Herein, using carbon dots as an aggregation limiting agent, the successful fabrication of self-supporting carbon nanofibers (CNF) containing Ni-single-atoms (Ni_SA ) and uniformly dispersed Ni-nanoparticles (Ni_NP ) of small sizes as multifunctional sulfur hosts is reported. The Ni_SA sites coordinated by such Ni_NP offer outstanding catalytic activity for sulfur reactions and CNF is an easy-to-infiltrate sulfur host with a large-scale preparation method. Accordingly, such hosts that can be prepared on a large scale enable sulfur cathodes to exhibit high sulfur utilization (66.5 mAh cm^-2 at ≈0.02 C) and cyclic stability (≈86.1% capacity retention after 100 cycles at ≈0.12 C) whilst operating at a high sulfur loading (50 mg cm^-2 ) and low E/S (5 µL mg^-1 ). This work provides a blueprint toward practical LSBs with high energy densities.

Regulating the Molecular Interactions in Polymer Binder for High-Performance Lithium-Sulfur Batteries

Polymer binders have been shown to efficiently conquer the notorious lithium polysulfide (LiPS) shuttle effects in lithium-sulfur (Li-S) batteries for years, but more study is needed. Herein, a water dispersible and molecular interaction regulated polymer binder (PNAVS) for Li-S batteries was elaborately designed by co-polymerizing N-acryloyl glycinamide and 3-(1-vinyl-3-imidazolio)propanesulfonate. We demonstrate that by modulating the multiple interactions between the functional groups through copolymerization the binder was able to coordinate the LiPSs with higher binding energy for shuttle effect alleviation and cycling performance improvement. In addition, the Li⁺ diffusion coefficient is also optimized in the PNAVS binder, which facilitates acceleration of the redox kinetics during cycling. Consequently, the PNAVS binder renders the Li-S battery with an ultrastable open circuit voltage for more than 3000 h. Even with a high sulfur loading of 11.7 mg cm^-2, the battery can still exhibit excellent areal capacity of 12.21 mA h cm^-2. As proof of concept, a pouch cell was also demonstrated with the stable cycling performance for 110 cycles. The binder engineering strategy in this work will propel the practical applications of high-performance batteries.

Construction of Macroporous Co2SnO4 with Hollow Skeletons as Anodes for Lithium-Ion Batteries

Increasing the energy density of lithium-ion batteries (LIBs) can broaden their applications in energy storage but remains a formidable challenge. Herein, with polyacrylic acid (PAA) as phase separation agent, macroporous Co₂SnO₄ with hollow skeletons was prepared by sol-gel method combined with phase separation. As the anode of LIBs, the macroporous Co₂SnO₄ demonstrates high capacity retention (115.5% at 200 mA·g⁻¹ after 300 cycles), affording an ultrahigh specific capacity (921.8 mA h·g⁻¹ at 1 A·g⁻¹). The present contribution provides insight into engineering porous tin-based materials for energy storage.

Polysulfide Regulation by Hypervalent Iodine Compounds for Durable and Sustainable Lithium-Sulfur Battery

Herein, a type of hypervalent iodine compound-iodosobenzene (PhIO)-is proposed to regulate the LiPSs electrochemistry and enhance the performance of Li-S battery. PhIO owns the practical advantages of low-cost, commercial availability, environmental friendliness and chemical stability. The lone pair electrons of oxygen atoms in PhIO play a critical role in forming a strong Lewis acid-base interaction with terminal Li in LiPSs. Moreover, the commercial PhIO can be easily converted to nanoparticles (≈20 nm) and uniformly loaded on a carbon nanotube (CNT) scaffold, ensuring sufficient chemisorption for LiPSs. The integrated functional PhIO@CNT interlayer affords a LiPSs-concentrated shield that not only strongly obstructs the LiPSs penetration but also significantly enhances the electrolyte wettability and Li⁺ conduction. The PhIO@CNT interlayer also serves as a "vice current collector" to accommodate various LiPSs and render smooth LiPSs transformation, which suppresses insulating Li₂ S₂ /Li₂ S layer formation and facilitates Li⁺ diffusion. The Li-S battery based on PhIO@CNT interlayer (6 wt% PhIO) exhibits stable cycling over 1000 cycles (0.033% capacity decay per cycle) and excellent rate performance (686.6 mAh g^-1 at 3 C). This work demonstrates the great potential of PhIO in regulating LiPSs and provides a new avenue towards the low-cost and sustainable application of Li-S batteries.

High-Performance Microsized Si Anodes for Lithium-Ion Batteries: Insights into the Polymer Configuration Conversion Mechanism

Microsized silicon particles are desirable Si anodes because of their low price and abundant sources. However, it is challenging to achieve stable electrochemical performances using a traditional microsized silicon anode due to the poor electrical conductivity, serious volume expansion, and unstable solid electrolyte interface. Herein, a composite microsized Si anode is designed and synthesized by constructing a unique polymer, poly(hexaazatrinaphthalene) (PHATN), at a Si/C surface (PCSi). The Li⁺ transport mechanism of the PCSi is elucidated by using in situ characterization and theoretical simulation. During the lithiation of the PCSi anode, CN groups with high electron density in the PHATN first coordinate Li⁺ to form CNLi bonds on both sides of the PHATN molecule plane. Consequently, the original benzene rings in the PHATN become active centers to accept lithium and form stable Li-rich PHATN coatings. PHATN molecules expand due to the change of molecular configuration during the consecutive lithiation process, which provides controllable space for the volume expansion of the Si particles. The PCSi composite anode exhibits a specific capacity of 1129.6 mAh g^-1 after 500 cycles at 1 A g^-1 , and exhibits compelling rate performance, maintaining 417.9 mAh g^-1 at 16.5 A g^-1 .

Quantification of the Dynamic Interface Evolution in High-Efficiency Working Li Metal Batteries

Lithium (Li) metal has been considered a promising anode for next-generation high-energy-density batteries. However, the low reversibility and intricate Li loss hinder the widespread implement of Li metal batteries. Herein, we quantitatively differentiate the dynamic evolution of inactive Li, and decipher the fundamental interplay among dynamic Li loss, electrolyte chemistry, and the structure of solid electrolyte interphase (SEI). The actual domination form in inactive Li loss is practically determined by the relative growth rates of dead Li0 and SEI Li+ because of the persistent evolving of Li metal interface during cycling. Distinct inactive Li evolution scenarios are disclosed when ingeniously tuning the inorganic anion-derived SEI chemistry with low amount of film-forming additive. An optimal polymeric film enabler of 1,3-dioxolane is demonstrated to derive a highly uniform multilayer SEI and declined SEI Li+/dead Li0 growth rates, thus achieving enhanced Li cycling reversibility.

Enormous-sulfur-content cathode and excellent electrochemical performance of Li-S battery accouched by surface engineering of Ni-doped WS2@rGO nanohybrid as a modified separator

The poor conductivity of sulfur, the lithium polysulfide's shuttle effect, and the lithium dendrite problem still impede the practical application of lithium-sulfur (Li-S) batteries. In this work, the ultrathin nickel-doped tungsten sulfide anchored on reduced graphene oxide (Ni-WS₂@rGO) is developed as a new modified separator in the Li-S battery. The surface engineering of Ni-WS₂@rGO could enhance the cell conductivity and afford abundant chemical anchoring sites for lithium polysulfides (LiPSs) adsorption, which is convinced by the high adsorption energy and the elongate SS bond given using density-functional theory (DFT) calculation. Concurrently, the Ni-WS₂@rGO as a modified separator could effectively catalyze the conversion of LiPSs during the charging/discharging process. The Li-S cell with Ni-WS₂@rGO modified separator achieves a high initial capacity of 1160.8 mA h g^-1 at the current density of 0.2C with a high-sulfur-content cathode up to 80 wt%, and a retained capacity of 450.7 mA h g^-1 over 500 cycles at 1C, showing an efficient preventing polysulfides shuttle to the anode while having no influence on Li⁺ ion transference across the decorating separator. The strategy adopted in this work would afford an effective pathway to construct an advanced functional separator for practical high-energy-density Li-S batteries.

Surface Gelation on Disulfide Electrocatalysts in Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are deemed as future energy storage devices due to ultrahigh theoretical energy density. Cathodic polysulfide electrocatalysts have been widely investigated to promote sluggish sulfur redox kinetics. Probing the surface structure of electrocatalysts is vital to understanding the mechanism of polysulfide electrocatalysis. In this work, we for the first time identify surface gelation on disulfide electrocatalysts. Concretely, the Lewis acid sites on disulfides trigger the ring-opening polymerization of the dioxolane solvent to generate a surface gel layer, covering disulfides and reducing the electrocatalytic activity. Accordingly, a Lewis base triethylamine (TEA) is introduced as a competitive inhibitor. Consequently, Li-S batteries with disulfide electrocatalysts and TEA afford high specific capacity and improved rate responses. This work affords new insights on the actual surface structure of electrocatalysts in Li-S batteries.