Lithium Bond Chemistry in Lithium-Sulfur Batteries

Beyond graphene: exploring the potential of MXene anodes for enhanced lithium-sulfur battery performance

The high theoretical energy density of Li-S batteries makes them a viable option for energy storage systems in the near future. Considering the challenges associated with sulfur's dielectric properties and the synthesis of soluble polysulfides during Li-S battery cycling, the exceptional ability of MXene materials to overcome these challenges has led to a recent surge in the usage of these materials as anodes in Li-S batteries. The methods for enhancing anode performance in Li-S batteries via the use of MXene interfaces are thoroughly investigated in this study. This study covers a wide range of techniques such as surface functionalization, heteroatom doping, and composite structure design for enhancing MXene interfaces. Examining challenges and potential downsides of MXene-based anodes offers a thorough overview of the current state of the field. This review encompasses recent findings and provides a thorough analysis of advantages and disadvantages of adding MXene interfaces to improve anode performance to assist researchers and practitioners working in this field. This review contributes significantly to ongoing efforts for the development of reliable and effective energy storage solutions for the future.

A Sustainable and Cost-Effective Nitrogen-Doped Three-Dimensional Porous Carbon for High-Performance Lithium-Sulfur Batteries

Affordable clean energy is one of the major sustainable development goals that can transform our world. At present, researchers are working to develop cheap electrode materials to develop energy storage devices, the Lithium-sulfur (Li-S) battery is considered a promising energy storage device owing to its excellent theoretical specific capacity and energy density. Herein, utilizing the ramie degumming waste liquid as raw materials, after freeze-drying and high-temperature calcination, a sustainable and cost-effective three-dimensional (3D) porous nitrogen-doped ramie carbon (N-RC) was synthesized. The N-RC calcined at 800 °C (N-RC-800) shows a superior high specific surface area of 1491.85 m2 ⋅ g-1 and a notable high pore volume of 0.90 cm3 ⋅ g-1. When employed as a sulfur host, the S@N-RC-800 cathode illustrates excellent initial discharge capacity (1120.6 mAh ⋅ g-1) and maintains a reversible capacity of 625.4 mAh ⋅ g-1 after 500 cycles at 1 C. Simultaneously, the S@N-RC-800 cathode also shows excellent coulombic efficiency and ideal rate performance. Such exceptional electrochemical performance of S@N-RC-800 can be primarily attributable to N-RC's high specific surface area, high porosity, and abundant polar functional groups. This green and low-cost synthesis strategy offers a new avenue for harnessing the potential of waste biomass in the context of clean energy storage.

A fresh perspective on dissociation mechanism of cellulose in DMAc/LiCl system based on Li bond theory

In this case, various characterization technologies have been employed to probe dissociation mechanism of cellulose in N,N-dimethylacetamide/lithium chloride (DMAc/LiCl) system. These results indicate that coordination of DMAc ligands to the Li+-Cl- ion pair results in the formation of a series of Lix(DMAc)yClz (x = 1, 2; y = 1, 2, 3, 4; z = 1, 2) complexes. Analysis of interaction between DMAc ligand and Li center indicate that Li bond plays a major role for the formation of these Lix(DMAc)yClz complexes. And the saturation and directionality of Li bond in these Lix(DMAc)yClz complexes are found to be a tetrahedral structure. The hydrogen bonds between two cellulose chains could be broken at the nonreduced end of cellulose molecule via combined effects of basicity of Cl- ion and steric hindrance of [Li (DMAc)4]+ unit. The unique feature of Li bond in Lix(DMAc)yClz complexes is a key factor in determination of the dissociation mechanism.

Materials descriptors of machine learning to boost development of lithium-ion batteries

Traditional methods for developing new materials are no longer sufficient to meet the needs of the human energy transition. Machine learning (ML) artificial intelligence (AI) and advancements have caused materials scientists to realize that using AI/ML to accelerate the development of new materials for batteries is a powerful potential tool. Although the use of certain fixed properties of materials as descriptors to act as a bridge between the two separate disciplines of AI and materials chemistry has been widely investigated, many of the descriptors lack universality and accuracy due to a lack of understanding of the mechanisms by which AI/ML operates. Therefore, understanding the underlying operational mechanisms and learning logic of AI/ML has become mandatory for materials scientists to develop more accurate descriptors. To address those challenges, this paper reviews previous work on AI, machine learning and materials descriptors and introduces the basic logic of AI and machine learning to help materials developers understand their operational mechanisms. Meanwhile, the paper also compares the accuracy of different descriptors and their advantages and disadvantages and highlights the great potential value of accurate descriptors in AI/machine learning applications for battery research, as well as the challenges of developing accurate material descriptors.

Establishing reaction networks in the 16-electron sulfur reduction reaction

The sulfur reduction reaction (SRR) plays a central role in high-capacity lithium sulfur (Li-S) batteries. The SRR involves an intricate, 16-electron conversion process featuring multiple lithium polysulfide intermediates and reaction branches1-3. Establishing the complex reaction network is essential for rational tailoring of the SRR for improved Li-S batteries, but represents a daunting challenge4-6. Herein we systematically investigate the electrocatalytic SRR to decipher its network using the nitrogen, sulfur, dual-doped holey graphene framework as a model electrode to understand the role of electrocatalysts in acceleration of conversion kinetics. Combining cyclic voltammetry, in situ Raman spectroscopy and density functional theory calculations, we identify and directly profile the key intermediates (S8, Li2S8, Li2S6, Li2S4 and Li2S) at varying potentials and elucidate their conversion pathways. Li2S4 and Li2S6 were predominantly observed, in which Li2S4 represents the key electrochemical intermediate dictating the overall SRR kinetics. Li2S6, generated (consumed) through a comproportionation (disproportionation) reaction, does not directly participate in electrochemical reactions but significantly contributes to the polysulfide shuttling process. We found that the nitrogen, sulfur dual-doped holey graphene framework catalyst could help accelerate polysulfide conversion kinetics, leading to faster depletion of soluble lithium polysulfides at higher potential and hence mitigating the polysulfide shuttling effect and boosting output potential. These results highlight the electrocatalytic approach as a promising strategy for tackling the fundamental challenges regarding Li-S batteries.

High Entropy Oxide (CrMnFeNiMg)3 O4 with Large Compositional Space Shows Long-Term Stability as Cathode in Lithium-Sulfur Batteries

The repeated formation and irreversible diffusion of liquid-state lithium polysulfides (LiPSs) are the primary challenges in the development of high-energy-density lithium-sulfur battery (LSB). An effective strategy to alleviate the resulting polysulfide loss is critical for the stability of LSBs. In this regard, high entropy oxides (HEOs) appear as a promising additive for the adsorption and conversion of LiPSs owing to the diverse active sites, offering unparalleled synergistic effects. Herein, we have developed a (CrMnFeNiMg)₃ O₄ HEO as a functional polysulfide trapper in LSB cathode. The adsorption of LiPSs by the metal species (i. e., Cr, Mn, Fe, Ni, and Mg) in the HEO takes place through two different paths and leads to enhanced electrochemical stability. We demonstrate that the optimal sulfur cathode with the (CrMnFeNiMg)₃ O₄ HEO attains a high peak and reversible discharge capacities of 857 mAh g^-1 and 552 mAh g^-1 , respectively, at a cycling rate of C/10, a long cycle life of 300 cycles, and a high rate performance at the cycling rates from C/10 to C/2.

A room temperature rechargeable Li2O-based lithium-air battery enabled by a solid electrolyte

A lithium-air battery based on lithium oxide (Li₂O) formation can theoretically deliver an energy density that is comparable to that of gasoline. Lithium oxide formation involves a four-electron reaction that is more difficult to achieve than the one- and two-electron reaction processes that result in lithium superoxide (LiO₂) and lithium peroxide (Li₂O₂), respectively. By using a composite polymer electrolyte based on Li₁₀GeP₂S₁₂ nanoparticles embedded in a modified polyethylene oxide polymer matrix, we found that Li₂O is the main product in a room temperature solid-state lithium-air battery. The battery is rechargeable for 1000 cycles with a low polarization gap and can operate at high rates. The four-electron reaction is enabled by a mixed ion-electron-conducting discharge product and its interface with air.

Non-trivial Contribution of Carbon Hybridization in Carbon-based Substrates to Electrocatalytic Activities in Li-S Batteries

Appling an electrochemical catalyst is an efficient strategy for inhibiting the shuttle effect and enhancing the S utilization of Li-S batteries. Carbon-based materials are the most common conductive agents and catalyst supports used in Li-S batteries, but the correlation between the diversity of hybridizations and sulfur reduction reaction (SRR) catalytic activity remains unclear. Here, by establishing two forms of carbon models, i.e., graphitic carbon (GC) and amorphous carbon (AC), we observe that the nitrogen atom doped in the GC possesses a higher local charge density and a lower Gibbs free energy towards the formation of polysulfides than in the AC. And the GC-based electrode consistently inherits considerably enhanced SRR kinetics and superior cycling stability and rate capability in Li-S batteries. Therefore, the function of carbon in Li-S batteries is not only limited as conductive support but also plays an unignorable contribution to the electrocatalytic activities of SRR.

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.

Versatile Asymmetric Separator with Dendrite-Free Alloy Anode Enables High-Performance Li-S Batteries

Lithium-sulfur batteries (LSBs) with extremely-high theoretical energy density (2600 Wh kg^-1 ) are deemed to be the most likely energy storage system to be commercialized. However, the polysulfides shuttling and lithium (Li) metal anode failure in LSBs limit its further commercialization. Herein, a versatile asymmetric separator and a Li-rich lithium-magnesium (Li-Mg) alloy anode are applied in LSBs. The asymmetric separator is consisted of lithiated-sulfonated porous organic polymer (SPOP-Li) and Li_6.75 La₃ Zr_1.75 Nb_0.25 O₁₂ (LLZNO) layers toward the cathode and anode, respectively. SPOP-Li serves as a polysulfides barrier and Li-ion conductor, while the LLZNO functions as an "ion redistributor". Combining with a stable Li-Mg alloy anode, the symmetric cell achieves 5300 h of Li stripping/plating and the modified LSBs exhibit a long lifespan with an ultralow fading rate of 0.03% per cycle for over 1000 cycles at 5 C. Impressively, even under a high-sulfur-loading (6.1 mg cm^-2 ), an area capacity of 4.34 mAh cm^-2 after 100 cycles can still be maintained, demonstrating high potential for practical application.

Ni3Sn2/nitrogen-doped graphene composite with chemisorption and electrocatalysis as advanced separator modifying material for lithium sulfur batteries

Lithium-sulfur batteries have been widely studied because of their advantages of abundant reserves, environmental friendliness, low cost andhighspecific capacity. However, the volume expansionand the low electrical conductivity of sulfur, and the shuttle effect of polysulfides limit their application. Herein,wesynthesizea two-dimensional layered Ni₃Sn₂/nitrogen-doped graphene (NG) composite asseparator modifying material for lithium-sulfur batteries. The Ni₃Sn₂formed by dual metal salts Ni(NO₃)₂·6H₂O and SnCl₂·2H₂O can adsorb polysulfide and catalyze its transformation to improve the electrochemical reaction kinetics. Moreover, the layered NG can not only disperse the Ni₃Sn₂particles, but alsoensure rapid electron transfer. Therefore, the lithium-sulfur battery with the Ni₃Sn₂/NG modified separator shows excellent electrochemical performance. At a current rate of 1 C, the lithium-sulfur battery with the Ni₃Sn₂/NG modified separator can provide a high initial discharge capacity of 1022.1 mAh g^-1and maintain a reversible specific capacity of 758.3 mAh g^-1after 400 cycles.

VN and SeS2 embedded porous carbon-nanofiber film as a free-standing electrode for improved Li-SeS2 batteries

We design a vanadium nitride (VN) modified porous carbon nanofiber film as the host to load SeS₂ as the cathode (SeS₂@VN/CNFs) for improving Li storage capacity. The conductive porous carbon nanofibers can accommodate active SeS₂ and release the volume change. The introduced VN nanoparticles can chemically anchor the intermediate species and improve the utilization of SeS₂. As a result, the SeS₂@VN/CNFs cathode displays a superior electrochemical performance including a high reversible capacity of 806 mAh g^-1 at 0.2 C and good long-term cycling stability in Li-SeS₂ batteries.

N, P, O-codoped biochar from phytoremediation residues: a promising cathode material for Li-S batteries

Environment and energy are two key issues in today's society. In terms of environmental protection, the treatment of phytoremediation residues has become a key problem to be solved urgently, while for energy storage, it tends to utilize low-cost and high specific energy storage materials (i.e. porous carbon). In this study, the phytoremediation residues is applied to the storage materials with low-cost and high specific capacity. Firstly, the phosphorous acid assisted pyrolysis of oilseed rape stems from phytoremediation is effective in the removal of Zn, Cu, Cd and Cr from the derived biochar. Moreover, the derived biochar from phytoremediation residues shows abundant porous structure and polar groups (-O/-P/-N), and it can deliver 650 mAh g^-1with 3.0 mg cm^-2_sulfur, and keeps 80% capacity after 200 cycles when employing it as a sulfur host for lithium-sulfur (Li-S) batteries. Hence, phosphorous acid assisted pyrolysis and application in Li-S battery is a promising approach for the disposal of phytoremediation residues, which is contributed to the environmental protection as well as energy storage.

CoS2@montmorillonite as an efficient separator coating for high-performance lithium-sulfur batteries

The shuttle effect and sluggish redox kinetic of polysulfides still hinder the large-scale application of lithium-sulfur (Li-S) batteries. Herein, we adopt a CoS2-intercalated/coated-montmorillonite (CoS2@montmorillonite) composite to work as an efficient...

Direct Atomic-Scale Structure and Electric Field Imaging of Triazine-Based Crystalline Carbon Nitride

Crystalline carbon nitrides (CNs) have recently attracted considerable attention owing to their superior photocatalytic activity. However, the electron-beam-sensitive nature of crystalline CNs hinders atomic-resolution imaging of their local structures by conventional (scanning) transmission electron microscopy ((S)TEM) techniques. Here, the atomic structure of a triazine-based crystalline CN, poly(triazine imide) (PTI) incorporated with lithium and chloride ions, is unambiguously revealed using the emerging imaging technique of differential phase contrast STEM under a low dose. The lightest-element Li/H configuration is resolved within framework cavities of PTI and significantly affects the electronic structure for photoabsorption. The atomic electric field of PTI crystal directly determined in real space provides a fundamental evidence for the chemical bonding of Li ions and adjacent atoms for the migration of photogenerated carriers. These results facilitate the comprehension on local atomic configuration and chemical bonding state of crystalline CNs and can lead to a deeper understanding of the photocatalytic mechanism.

Engineering Oversaturated Fe-N5 Multifunctional Catalytic Sites for Durable Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as a promising next-generation system for advanced energy storage owing to a high theoretical energy density of 2600 Wh kg^-1 . However, the practical implementation of Li-S batteries has been thwarted by the detrimental shuttling behavior of polysulfides, and the sluggish kinetics in electrochemical processes. Herein, a novel single atom (SA) catalyst with oversaturated Fe-N₅ coordination structure (Fe-N₅ -C) is precisely synthesized by an absorption-pyrolysis strategy and introduced as an effective sulfur host material. The experimental characterizations and theoretical calculations reveal synergism between atomically dispersed Fe-N₅ active sites and the unique carbon support. The results exhibit that the sulfur composite cathode built on the Fe-N₅ -C can not only adsorb polysulfides via chemical interaction, but also boost the redox reaction kinetics, thus mitigating the shuttle effect. Meanwhile, the robust three-dimensional nitrogen doped carbon nanofiber with large surface area, and high porosity enables strong physical confinement and fast electron/ion transfer process. Attributed to such unique features, Li-S batteries with S/Fe-N₅ -C composite cathode realize outstanding cyclability and rate capability, as well as high areal capacities under raised sulfur loading, which demonstrates great potential in developing advanced Li-S batteries.

Applying Machine Learning to Rechargeable Batteries: From the Microscale to the Macroscale

Emerging machine learning (ML) methods are widely applied in chemistry and materials science studies and have led to a focus on data-driven research. This Minireview summarizes the application of ML to rechargeable batteries, from the microscale to the macroscale. Specifically, ML offers a strategy to explore new functionals for density functional theory calculations and new potentials for molecular dynamics simulations, which are expected to significantly enhance the challenging descriptions of interfaces and amorphous structures. ML also possesses a great potential to mine and unveil valuable information from both experimental and theoretical datasets. A quantitative "structure-function" correlation can thus be established, which can be used to predict the ionic conductivity of solids as well as the battery lifespan. ML also exhibits great advantages in strategy optimization, such as fast-charge procedures. The future combination of multiscale simulations, experiments, and ML is also discussed and the role of humans in data-driven research is highlighted.

Large Scale Synthesis of Three-dimensional Hierarchical Porous Framework with High Conductivity and its Application in Lithium Sulfur Battery

Quick capacity loss due to the polysulfide shuttle effects and poor rate performance caused by low conductivity of sulfur have always been obstacles to the commercial application of lithium sulfur batteries. Herein, an in-situ doped hierarchical porous biochar materials with high electron-ion conductivity and adjustable three-dimensional (3D) macro-meso-micropore is prepared successfully. Due to its unique physical structure, the resulting material has a specific surface area of 2124.9 m²  g^-1 and a cumulative pore volume of 1.19 cm³  g^-1 . The presence of micropores can effectively physically adsorb polysulfides and mesopores ensure the accessibility of lithium ions and active sites and give the porous carbon material a high specific surface area. The large pores provide channels for the storage of electrolyte and the transmission of ions on the surface of the substrate. The combined effect of these three kinds of pores and the N doping formed in-situ can effectively promote the cycle and rate performance of the battery. Therefore, prepared cathode can still reach a reversible discharge capacity of 616 mAh g^-1 at a rate of 5 C. After 400 charge-discharge cycles at 1 C, the reversible capacity is maintained at 510.0 mAh g^-1 . This new strategy has provided a new approach to the research and industrial-scale production of adjustable hierarchical porous biochar materials.

A Supramolecular Complex of C60 -S with High-Density Active Sites as a Cathode for Lithium-Sulfur Batteries

The well-known "shuttle effect" of the intermediate lithium polysulfides (LiPSs) and low sulfur utilization hinder the practical application of lithium-sulfur (Li-S) batteries. Herein, we describe a novel C₆₀ -S supramolecular complex with high-density active sites for LiPS adsorption that was formed by a simple one-step process as a cathode material for Li-S batteries. Benefiting from the cocrystal structure, 100 % of the C₆₀ molecules in the complex can offer active sites to adsorb LiPSs and catalyze their conversion. Furthermore, the lithiated C₆₀ cores promote internal ion transport inside the composite cathode. At a low electrolyte/sulfur ratio of 5 μL mg^-1 , the C₆₀ -S cathode with a sulfur loading of 4 mg cm^-2 exhibited a high capacity of 809 mAh g^-1 (3.2 mAh cm^-2 ). The development of the C₆₀ -S supramolecular complex will inspire the invention of a new family of S/fullerenes as cathodes for high-performance Li-S batteries and extend the application of fullerenes.

Liquid-Like Phase of N,N-Dimethylpyrrolidinium Iodide Impregnated into COFs Endows Fast Lithium Ion Conduction in the Solid State

A novel kind of solid-state lithium electrolyte was fabricated by impregnating organic ionic plastic crystals (OIPCs) into the pores of covalent organic frameworks (COFs). The liquid-like phase of confined N,N-dimethylpyrrolidinium iodide (P_1,1 I) and the ordered nanochannels of COFs simultaneously stimulated the lithium ion conduction.

In Situ Self-Polymerization to Form Hollow Graphitized Carbon Nanocages with Embedded Cobalt Nanoparticles for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries, owing to the multi-electron participation in the redox reaction, possess enormous energy density, which has aroused much attention. Nevertheless, the detrimental shuttle effect, volume expansion, and electrical insulation of sulfur, have hindered their application. To improve the cyclability, a functional host, consisting of Co nanoparticles and N-doped hollow graphitized carbon (Co-NHGC) material, is elaborated, which has the advantages of: 1) the graphitized carbon material working as an electronic matrix to improve the utilization rate of sulfur; 2) the hollow structure relieving the stress change caused by volume expansion; 3) the rich active sites catalyze the electrochemical reaction of sulfur and entrap polysulfides. These advantages significantly improve the performance of the lithium-sulfur batteries. Accordingly, the S@Co-NHGC cathode exhibits excellent initial specific capacity, high coulombic efficiency, and excellent rate performance. This work utilizes a novel method of dopamine in situ etching of a metal-organic framework to synthetize the Co-NHGC host of sulfur, which will hopefully provide inspiration for other energy materials.

A Flexible Ceramic/Polymer Hybrid Solid Electrolyte for Solid-State Lithium Metal Batteries

Ceramic/polymer hybrid solid electrolytes (HSEs) have attracted worldwide attentions because they can overcome defects by combining the advantages of ceramic electrolytes (CEs) and solid polymer electrolytes (SPEs). However, the interface compatibility of CEs and SPEs in HSE limits their full function to a great extent. Herein, a flexible ceramic/polymer HSE is prepared via in situ coupling reaction. Ceramic and polymer are closely combined by strong chemical bonds, thus the problem of interface compatibility is resolved and the ions can transport rapidly by an expressway. The as-prepared membrane demonstrates an ionic conductivity of 9.83 × 10^-4 S cm^-1 at room temperature and a high Li⁺ transference numbers of 0.68. This in situ coupling reaction method provides an effective way to resolve the problem of interface compatibility.

A Four-Electron Sulfur Electrode Hosting a Cu2+ /Cu+ Redox Charge Carrier

The elemental sulfur electrode with Cu²⁺ as the charge carrier gives a four-electron sulfur electrode reaction through the sequential conversion of S↔CuS↔Cu₂ S. The Cu-S redox-ion electrode delivers a high specific capacity of 3044 mAh g^-1 based on the sulfur mass or 609 mAh g^-1 based on the mass of Cu₂ S, the completely discharged product, and displays an unprecedently high potential of sulfur/metal sulfide reduction at 0.5 V vs. SHE. The Cu-S electrode also exhibits an extremely low extent of polarization of 0.05 V and an outstanding cycle number of 1200 cycles retaining 72 % of the initial capacity at 12.5 A g^-1 . The remarkable utility of this Cu-S cathode is further demonstrated in a hybrid cell that employs an Zn metal anode and an anion-exchange membrane as the separator, which yields an average cell discharge voltage of 1.15 V, the half-cell specific energy of 547 Wh kg^-1 based on the mass of the Cu₂ S/carbon composite cathode, and stable cycling over 110 cycles.

Biotemplating Growth of Nepenthes-like N-Doped Graphene as a Bifunctional Polysulfide Scavenger for Li-S Batteries

The practical application of lithium-sulfur (Li-S) batteries is hindered by their poor cycling stabilities that primarily stem from the "shuttle" of dissolved lithium polysulfides. Here, we develop a nepenthes-like N-doped hierarchical graphene (NHG)-based separator to realize an efficient polysulfide scavenger for Li-S batteries. The 3D textural porous NHG architectures are realized by our designed biotemplating chemical vapor deposition (CVD) approach via the employment of naturally abundant diatomite as the growth substrate. Benefiting from the high surface area, devious inner-channel structure, and abundant nitrogen doping of CVD-grown NHG frameworks, the derived separator favorably synergizes bifunctionality of physical confinement and chemical immobilization toward polysulfides, accompanied by smooth lithium ion diffusions. Accordingly, the batteries with the NHG-based separator delivers an initial capacity of 868 mAh g^-1 with an average capacity decay of only 0.067% per cycle at 2 C for 800 cycles. A capacity of 805 mAh g^-1 can further be achieved at a high sulfur loading of ∼7.2 mg cm^-2. The present study demonstrates the potential in constructing high-energy and long-life Li-S batteries upon separator modification.

Hierarchically Porous Multilayered Carbon Barriers for High-Performance Li-S Batteries

As one of the most promising energy storage devices, the practical application of lithium-sulfur batteries is limited by the low electrical conductivity of sulfur and the notable "shuttle effects" of sulfur-based electrodes. In this work, we describe a hierarchically porous N-doped zeolitic imidazolate framework-8 (ZIF-8)-derived carbon nanosphere (N-ZDC) with an outer shell and an inner honeycomb-like interconnected nanosheet network as sulfur host material for high-performance and long-term lithium-sulfur batteries. The N-ZDC serves as multilayered barrier against the dissolution of lithium polysulfides. The porously inner interconnected carbon network of the N-ZDC facilitates the electron and ion transportation, ensures a high sulfur loading, and accommodates a volume expansion of the sulfur species. As a result, the optimized N-ZDC⁴ /S electrodes displayed high initial specific capacities of 1343, 1182, and 698 mAh g^-1 at 0.5, 1, and 2 C, respectively, and an ultraslow capacity decay of only 0.048 % per cycle at 2 C over 800 cycles. Even with a high sulfur loading of 3.1 mg cm^-2 , N-ZDC⁴ /S still delivered a reversible capacity of 956 mAh g^-1 and stabilizes at 544 mAh g^-1 after 500 cycles at 0.5 C, revealing the great potential of the novel carbon nanospheres for energy storage application.