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Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries
Abstract
Tailoring porous host materials, as an effective strategy for storing sulfur and restraining the shuttling of soluble polysulfides in electrolyte, is crucial in the design of high-performance lithium-sulfur (Li-S) batteries. However, for the widely studied conductive hosts such as mesoporous carbon, how the aspect ratio affects the confining ability to polysulfides, ion diffusion as well as the performances of Li-S batteries has been rarely studied. Herein, ordered mesoporous carbon (OMC) is chosen as a proof-of-concept prototype of sulfur host, and its aspect ratio is tuned from over ∼ 2 down to below ∼ 1.2 by using ordered mesoporous silica hard templates with variable length/width scales. The correlation between the aspect ratio of OMC and the electrochemical performances of the corresponding sulfur-carbon cathodes are systematically studied with combined electrochemical measurements and microscopic characterizations. Moreover, the evolution of sulfur species in OMCs at different discharge states is scrutinized by small-angle X-ray scattering. This study gives insight into the aspect ratio effects of mesoporous host on battery performances of sulfur cathodes, providing guidelines for designing porous host materials for high-energy sulfur cathodes.
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The development of lithium–sulfur (Li–S) batteries is hindered by the disadvantages of shuttling of polysulfides and the sluggish redox kinetics of the conversion of sulfur species during discharge and charge. Herein, the crystallinities of a titanium nitride (TiN) film on copper‐embedded carbon nanofibers (Cu‐CNFs) are regulated and the nanofibers are used as interlayers to resolve the aforementioned crucial issues. A low‐crystalline TiN‐coated Cu‐CNF (L‐TiN‐Cu‐CNF) interlayer is compared with its highly crystalline counterpart (H‐TiN‐Cu‐CNFs). It is demonstrated that the L‐TiN coating not only strengthens the chemical adsorption toward polysulfides but also greatly accelerates the electrochemical conversion of polysulfides. Due to robust carbon frameworks and enhanced kinetics, impressive high‐rate performance at 2 C (913 mAh g⁻¹ based on sulfur) as well as remarkable cyclic stability up to 300 cycles (626 mAh g⁻¹) with capacity retention of 46.5% is realized for L‐TiN‐Cu‐CNF interlayer‐configured Li–S batteries. Even under high loading (3.8 mg cm⁻²) of sulfur and relatively lean electrolyte (10 μL electrolyte per milligram sulfur) conditions, the Li–S battery equipped with L‐TiN‐Cu‐CNF interlayers delivers a high capacity of 1144 mAh g⁻¹ with cathodic capacity of 4.25 mAh cm⁻² at 0.1 C, providing a potential pathway toward the design of multifunctional interlayers for highly efficient Li–S batteries.
Polyethylene oxide (PEO)‐based polymer solid electrolytes (PSE) have been pursued for the next‐generation extremely safe and high‐energy‐density lithium metal batteries due to their exceptional flexibility, manufacturability, and lightweight nature. However, the practical application of PEO‐PSE has been hindered by low ionic conductivity, limited lithium‐ion transfer number ( t Li+ ), and inferior stability with lithium metal. Herein, an ultrathin composite solid‐state electrolyte (CSSE) film with a thickness of 20 μm, incorporating uniformly dispersed two‐dimensional fluorinated boron nitride (F‐BN) nanosheet fillers (F‐BN CSSE) is fabricated via a solution‐casting process. The integration of F‐BN effectively reduces the crystallinity of the PEO polymer matrix, creating additional channels that facilitate lithium‐ion transport. Moreover, the presence of F‐BN promotes an inorganic phase‐dominated electrolyte interface film dominated by LiF, Li 2 O, and Li 3 N on the lithium anode surface, greatly enhancing the stability of the electrode‐electrolyte interface. Consequently, the F‐BN CSSE exhibits a high ionic conductivity of 0.11 mS cm ⁻¹ at 30°C, high t Li+ of 0.56, and large electrochemical window of 4.78 V, and demonstrates stable lithium plating/striping behavior with a voltage of 20 mV for 640 h, effectively mitigating the formation of lithium dendrites. When coupled with LiFePO 4 , the as‐assembled LiFePO 4 |F‐BN CSSE|Li solid‐state battery achieves a high capacity of 142 mAh g ⁻¹ with an impressive retention rate of 82.4% after 500 cycles at 5 C. Furthermore, even at an ultrahigh rate of 50 C, a capacity of 37 mAh g ⁻¹ is achieved. This study provides a novel and reliable strategy for the design of advanced solid‐state electrolytes for high‐rate and long‐life lithium metal batteries.
Lithium–sulfur (Li–S) batteries has emerged as a promising post‐lithium‐ion battery technology due to their high potential energy density and low raw material cost. Recent years have witnessed substantial progress in research on Li–S batteries, yet no high‐energy Li–S battery products have reached the market at scale. Achieving high‐energy Li–S batteries necessitates a multidisciplinary approach involving advanced electrode material design, electrochemistry, and electrode and cell engineering. In this perspective, we offer a holistic view of pathways for realizing high‐energy Li–S batteries under practical conditions. Starting with a market outlook for high‐energy batteries, we present a comprehensive quantitative analysis of the critical parameters that dictate the cell‐level energy density for a Li–S battery. Thereby we establish a protocol to expedite the integration of lab‐scale Li–S research results into practical cell. Furthermore, we underscore several key considerations for promotion of commercial viability of high‐energy Li–S batteries from the perspective of battery industrialization.
Due to their high designability, unique geometric and electronic structures, and surface coordination chemistry, atomically precise metal nanoclusters are an emerging class of functional nanomaterials at the forefront of materials research. However, the current research on metal nanoclusters is mainly fundamental, and their practical applications are still uncharted. The surface binding properties and redox activity of Au24Pt(PET)18 (PET: phenylethanethiolate, SCH2CH2Ph) nanoclusters are herein harnessed as an high‐efficiency electrocatalyst for the anchoring and rapid conversion of lithium polysulfides in lithium–sulfur batteries (LSBs). Au24Pt(PET)18@G composites are prepared by using the large specific surface area, high porosity, and conductive network of graphene (G) for the construction of battery separator that can inhibit polysulfide shuttle and accelerate electrochemical kinetics. Resultantly, the LSB using a Au24Pt(PET)18@G‐based separator presents a high reversible specific capacity of 1535.4 mA h g⁻¹ for the first cycle at 0.2 A g⁻¹ and a rate capability of 887 mA h g⁻¹ at 5 A g⁻¹. After 1000 cycles at 5 A g⁻¹, the capacity is 558.5 mA h g⁻¹. This study is a significant step toward the application of metal nanoclusters as optimal electrocatalysts for LSBs and other sustainable energy storage systems.
Nowadays solid‐state batteries have become a hot spot in the research of batteries and a significant candidate for commercial batteries for the increasing demands for good safety and excellent energy density. Metal‐organic frameworks (MOFs) have been considered as suitable materials for solid‐state electrolytes (SSEs) for the merits of regular channels and large specific surface areas, which can provide a promising structural platform for fast‐ion conduction. Therefore, numerous kinds of MOF‐based SSEs with enhanced electrochemical performance have been successfully synthesized and studied in recent years. In this review, the recent progress (synthesis methods, physical and chemical characteristics) of MOF‐based SSEs for secondary batteries have been summarized. Finally, the challenges and opportunities faced by the future development in this field are put forward, hoping to provide some enlightenment for the synthesis of MOF‐based SSEs, so as to create more efficient, long‐lasting, and safe SSE‐based secondary batteries.
Abstract The application of lithium‐based batteries is challenged by the safety issues of leakage and flammability of liquid electrolytes. Polymer electrolytes (PEs) can address issues to promote the practical use of lithium metal batteries. However, the traditional preparation of PEs such as the solution‐casting method requires a complicated preparation process, especially resulting in side solvents evaporation issues. The large thickness of traditional PEs reduces the energy density of the battery and increases the transport bottlenecks of lithium‐ion. Meanwhile, it is difficult to fill the voids of electrodes to achieve good contact between electrolyte and electrode. In situ polymerization appears as a facile method to prepare PEs possessing excellent interfacial compatibility with electrodes. Thus, thin and uniform electrolytes can be obtained. The interfacial impedance can be reduced, and the lithium‐ion transport throughput at the interface can be increased. The typical in situ polymerization process is to implant a precursor solution containing monomers into the cell and then in situ solidify the precursor under specific initiating conditions, and has been widely applied for the preparation of PEs and battery assembly. In this review, we focus on the preparation and application of in situ polymerization method in gel polymer electrolytes, solid polymer electrolytes, and composite polymer electrolytes, in which different kinds of monomers and reactions for in situ polymerization are discussed. In addition, the various compositions and structures of inorganic fillers, and their effects on the electrochemical properties are summarized. Finally, challenges and perspectives for the practical application of in situ polymerization methods in solid‐state lithium‐based batteries are reviewed.
Abstract Thanks to the significantly higher energy density compared with universal commercialized Li‐ion batteries, lithium–sulfur (Li–S) batteries are being investigated for use in prospective energy storage devices. However, the inadequate electrochemical kinetics of reactants and intermediates hinder commercial utilization. This limitation results in substantial capacity degradation and short battery lifespans, thereby impeding the battery's power export. Meanwhile, the capacity attenuation induced by the undesirable shuttle effect further hinders their industrialization. Considerable effort has been invested in developing electrocatalysts to fix lithium polysulfides and boost their conversion effectively. In the conventional process, the planar electrodes are prepared by slurry‐casting, which limits the electron and ion transfer paths, especially when the thickness of the electrodes is relatively large. Compared with traditional manufacturing methods, direct ink writing (DIW) technology offers unique advantages in both geometry shaping and rapid prototyping, and even complex three‐dimensional structures with high sulfur loading. Hence, this review presents a detailed description of the current developments in terms of Li–S batteries in DIW of metal‐based electrocatalysts. A thorough exploration of the behavior chemistry of electrocatalysis is provided, and the adhibition of metal‐based catalysts used for Li–S batteries is summarized from the aspect of material usage and performance enhancement. Then, the working principle of DIW technology and the requirements of used inks are presented, with a detailed focus on the latest advancements in DIW of metal‐based catalysts in Li–S battery systems. Their challenges and prospects are discussed to guide their future development.
Abstract Silicon (Si)‐based solid‐state batteries (Si‐SSBs) are attracting tremendous attention because of their high energy density and unprecedented safety, making them become promising candidates for next‐generation energy storage systems. Nevertheless, the commercialization of Si‐SSBs is significantly impeded by enormous challenges including large volume variation, severe interfacial problems, elusive fundamental mechanisms, and unsatisfied electrochemical performance. Besides, some unknown electrochemical processes in Si‐based anode, solid‐state electrolytes (SSEs), and Si‐based anode/SSE interfaces are still needed to be explored, while an in‐depth understanding of solid–solid interfacial chemistry is insufficient in Si‐SSBs. This review aims to summarize the current scientific and technological advances and insights into tackling challenges to promote the deployment of Si‐SSBs. First, the differences between various conventional liquid electrolyte‐dominated Si‐based lithium‐ion batteries (LIBs) with Si‐SSBs are discussed. Subsequently, the interfacial mechanical contact model, chemical reaction properties, and charge transfer kinetics (mechanical–chemical kinetics) between Si‐based anode and three different SSEs (inorganic (oxides) SSEs, organic–inorganic composite SSEs, and inorganic (sulfides) SSEs) are systemically reviewed, respectively. Moreover, the progress for promising inorganic (sulfides) SSE‐based Si‐SSBs on the aspects of electrode constitution, three‐dimensional structured electrodes, and external stack pressure is highlighted, respectively. Finally, future research directions and prospects in the development of Si‐SSBs are proposed.
Abstract Graphite offers several advantages as an anode material, including its low cost, high theoretical capacity, extended lifespan, and low Li+‐intercalation potential. However, the performance of graphite‐based lithium‐ion batteries (LIBs) is limited at low temperatures due to several critical challenges, such as the decreased ionic conductivity of liquid electrolyte, sluggish Li+ desolvation process, poor Li+ diffusivity across the interphase layer and bulk graphite materials. Various approaches have therefore been explored to address these challenges. On the basis of graphite anode and corresponding LIBs, this review herein offers a comprehensive analysis of the latest advances in electrolyte engineering and electrode modification. First, electrolyte engineering is discussed in detail, highlighting the design of new electrolyte formula with broad liquid temperature range, optimized solvation structure, and well‐performed inorganic‐rich solid electrolyte interface. The advances in material modification have been then depicted with the view of improving the solid bulk diffusion rate to show general strategies with excellent performance at low temperatures. Finally, the corresponding challenges and opportunities have also been outlined to shed light on viable strategies for developing efficient and reliable graphite anode and graphite‐based LIBs under low‐temperature scenarios.
Abstract Sodium (Na) ion batteries (SIBs) promise low‐cost energy storage systems but are still restricted by insufficient energy density. Introducing oxygen (O) redox into the design of the Na‐storage cathode is presently considered an effective avenue to generate extra capacity in solving the energy density bottleneck. The succeeding issues are how to overcome the irreversible electrochemical behavior accompanied by O release. Meanwhile, the O redox chemistry and subsequent structural evolution remain ambiguous so far. Here, we deliberate on the O redox mechanism in Na‐storage transition metal oxides. Challenges associated with the reaction irreversibility and structural collapse are summarized by virtue of the advanced characterization techniques. Beyond that, strategies that potentially enhance the electrochemical properties of O redox and future research perspectives on exploring useable O redox cathode materials are outlined.
The chief culprit impeding the commercialization of lithium-sulfur (Li-S) batteries is the parasitic shuttle effect and restricted redox kinetics of lithium polysulfides (LiPSs). To circumvent these key stumbling blocks, incorporating electrocatalysts with rational electronic structure modulation into sulfur cathode plays a decisive role in vitalizing the higher electrocatalytic activity to promote sulfur utilization efficiency. Breaking the stereotype of contemporary electrocatalyst design kept on pretreatment, field-assisted electrocatalysts offer strategic advantages in dynamically controllable electrochemical reactions that might be thorny to regulate in conventional electrochemical processes. However, the highly interdisciplinary field-assisted electrochemistry puzzles researchers for a fundamental understanding of the ambiguous correlations among electronic structure, surface adsorption properties, and catalytic performance. In this review, the mechanisms, functionality explorations, and advantages of field-assisted electrocatalysts including electric, magnetic, light, thermal, and strain fields in Li-S batteries have been summarized. By demonstrating pioneering work for customized geometric configuration, energy band engineering, and optimal microenvironment arrangement in response to decreased activation energy and enriched reactant concentration for accelerated sulfur redox kinetics, cutting-edge insights into the holistic periscope of charge-spin-orbital-lattice interplay between LiPSs and electrocatalysts are scrutinized, which aspires to advance the comprehensive understanding of the complex electrochemistry of Li-S batteries. Finally, future perspectives are provided to inspire innovations capable of defeating existing restrictions.
Lithium‐ion batteries (LIBs) have monopolized energy storage markets in modern society. The reliable operation of LIBs at cold condition (<0°C), nevertheless, is inevitably hampered by the sluggish kinetics and parasite reactions, which falls behind the increasing demands for portable electronics and electric vehicles. The electrolyte controls both Li⁺ transport and interfacial reaction, dictating the low‐temperature performance substantially. Therefore, the rational formulation of electrolytes is significant for realizing superior low‐temperature performance and broadening application niches of LIBs. Herein, we first discuss the kinetic limitations of low‐temperature LIBs, highlighting the importance of electrolyte structure and interfacial chemistry. Then, the advancements for formulating subzero‐temperature electrolyte are summarized with in‐depth discussions about electrolyte formulation, solvation structure, interfacial chemistry, and low‐temperature behaviors. Moreover, some opportunities for lithium metal batteries and the corresponding low‐temperature electrolyte are covered. Finally, the major challenges and future perspectives are outlined for low‐temperature LIBs.
Room temperature sodium‐sulfur (RT Na‐S) batteries are highly competitive as potential energy storage devices. Nevertheless, their actually achieved reversible capacities are far below the theoretical value due to incomplete transformation of polysulfides. Herein, atomically dispersed Fe‐N/S active center by regulating the second‐shell coordinating environment of Fe single atom is proposed. The Fe−N4S2 coordination structure with enhanced local electronic concentration around the Fermi level is revealed via synchrotron radiation X‐ray absorption spectroscopy (XAS) and theoretical calculations, which can not only significantly promote the transformation kinetics of polysulfides, but induce uniform Na deposition for dendrite‐free Na anode. As a result, the obtained S cathode delivers a high initial reversible capacity of 1590 mAh g⁻¹, nearly the theoretical value. This work opens up a new avenue to facilitate the complete transformation of polysulfides for RT Na‐S batteries.
Covalent organic frameworks (COFs), as a class of crystalline porous polymers, featuring designable structures, tunable frameworks, well‐defined channels, and tailorable functionalities, have emerged as promising organic electrode materials for rechargeable metal‐ion batteries in recent years. Tremendous efforts have been devoted to improving the electrochemical performance of COFs. However, although significant achievements have been made, the electrochemical behaviors of developed COFs are far away from the desirable performance for practical batteries owing to intrinsic problems, such as poor electronic conductivity, the trade‐off relationship between capacity and redox potential, and unfavorable micromorphology. In this review, the recent progress in the development of COFs for rechargeable metal‐ion batteries is presented, including Li, Na, K, and Zn ion batteries. Various research strategies for improving the electrochemical performance of COFs are summarized in terms of the molecular‐level design and the material‐level modification. Finally, the major challenges and perspectives of COFs are also discussed in the aspect of large‐scale production and electrochemical performance improvements. Covalent organic frameworks (COFs), as a class of crystalline porous polymers, have emerged as promising organic electrode materials for rechargeable metal‐ion batteries in recent years. Here we summarize the latest progress of COFs in Li, Na, K, and Zn ion batteries, and discuss various research strategies, major challenges, and perspectives.
The inadequate understanding of the mechanisms that reversibly convert molecular sulfur (S) into lithium sulfide (Li2S) via soluble polysulfides (PSs) formation impedes the development of high-performance lithium-sulfur (Li-S) batteries with non-aqueous electrolyte solutions. Here, we use operando small and wide angle X-ray scattering and operando small angle neutron scattering (SANS) measurements to track the nucleation, growth and dissolution of solid deposits from atomic to sub-micron scales during real-time Li-S cell operation. In particular, stochastic modelling based on the SANS data allows quantifying the nanoscale phase evolution during battery cycling. We show that next to nano-crystalline Li2S the deposit comprises solid short-chain PSs particles. The analysis of the experimental data suggests that initially, Li2S2 precipitates from the solution and then is partially converted via solid-state electroreduction to Li2S. We further demonstrate that mass transport, rather than electron transport through a thin passivating film, limits the discharge capacity and rate performance in Li-S cells.
In honor of Professor John B. Goodenough for his 100th birthday, this article tries to find the relationship between the discovery of cathode materials for lithium‐ion batteries and the interdisciplinary research in his career. The original ideas of lithium cobalt oxide, lithium manganese oxide, and LiFePO4 came from his early research in solid state physics and from his strong knowledge of chemical structure and bonding. Some examples are given to demonstrate the importance of interdisciplinary interactions among materials, chemistry, and physics. With the rapid development of rechargeable batteries, such interdisciplinarity is further extended to engineering, information, and even artificial intelligence. Although there are still many challenges like energy density and safety in the batteries, we are confident that a better solution will be soon found. Yunhui Huang worked with Prof. Goodenough from 2004 to 2007 and received a great benefit in academic research from Goodenough's interdisciplinary thought and scientific spirit.
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 highly 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 seven years of development and to point out further research directions. Key design parameters to achieve actual high energy density are firstly addressed to define the research boundaries distinguished from coin‐cell‐level evaluation. Systematical analysis on the published literatures and cutting‐edge performances are then conducted to demonstrate the achieved progresses and the gap towards practical applications. Following that, failure analysis as well as promotion strategies at the pouch cell level is respectively discussed to reveal the unique working and failure mechanism that shall be accordingly addressed. Finally, perspectives towards high‐performance Li–S pouch cells are presented regarding the challenges and opportunities of this field. This article is protected by copyright. All rights reserved
Abstract Lithium–sulfur (Li–S) batteries, although a promising candidate of next‐generation energy storage devices, are hindered by some bottlenecks in their roadmap toward commercialization. The key challenges include solving the issues such as low utilization of active materials, poor cyclic stability, poor rate performance, and unsatisfactory Coulombic efficiency due to the inherent poor electrical and ionic conductivity of sulfur and its discharged products (e.g., Li2S2 and Li2S), dissolution and migration of polysulfide ions in the electrolyte, unstable solid electrolyte interphase and dendritic growth on anodes, and volume change in both cathodes and anodes. Owing to the high specific surface area, pore volume, low density, good chemical stability, and particularly multimodal pore sizes, hierarchical porous carbon (HPC) materials have received considerable attention for circumventing the above problems in Li–S batteries. Herein, recent progress made in the synthetic methods and deployment of HPC materials for various components including sulfur cathodes, separators and interlayers, and lithium anodes in Li–S batteries is presented and summarized. More importantly, the correlation between the structures (pore volume, specific surface area, degree of pores, and heteroatom‐doping) of HPC and the electrochemical performances of Li–S batteries is elaborated. Finally, a discussion on the challenges and future perspectives associated with HPCs for Li–S batteries is provided.
The commercialization of lithium–sulfur (Li−S) batteries is still hindered by the unsatisfactory cell performance under practical working conditions, which is mainly caused by the sluggish cathode redox kinetics, severe polysulfide shuttling, and poor Li stripping/plating reversibility. Herein, we report an effective strategy by combining Se‐doped S hosted in an ordered macroporous framework with a highly fluorinated ether (HFE)‐based electrolyte to simultaneously address the aforementioned issues in both cathode and anode. A reversible and stable high areal capacity of >5.4 mAh cm⁻² with high Coulombic efficiency >99.2 % can be achieved under high areal Se/S loading (5.8 mg cm⁻²), while the underlying mechanism was further revealed through synchrotron X‐ray probes and Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS). The practical application potential was further evaluated at low (0 °C) and high (55 °C) temperatures under high areal Se/S loading (>5.0 mg cm⁻²) and thin Li metal (40 μm).
In this study, cycle life performance of a prototype lithium‐sulfur (Li−S) pouch cell is investigated using system identification and X‐ray tomography methods. Li−S cells are subjected to characterization and ageing tests while kept inside a controlled‐temperature chamber. After completing the experimental tests, two analytical approaches are used: i) The parameter variations of an equivalent‐circuit model due to ageing are determined using a system identification technique. ii) Physical changes of the aged Li−S cells are analyzed using X‐ray tomography. The results demonstrate that Li−S cell's degradation is significantly affected by temperature. Comparing to 10 °C, Li−S cell capacity fade happens 1.4 times faster at 20 °C whereas this number increases to 3.3 at 30 °C. In addition, X‐ray results show a significant swelling when temperature rises from 10 to 20 °C, correspondingly the gas volume increases from 13 to 62 mm³.
A comprehensive description of electrochemical processes in the positive electrode of lithium-sulfur batteries is crucial for the utilization of active material. However, the discharge mechanisms are complicated due to various reactions in multiple phases and the tortuosity of the highly porous carbon matrix. In this work, simultaneous measurements of small-angle and wide-angle scattering and cell resistance are performed on operating lithium-sulfur cells. Results indicate that precipitates grow mostly in number, not in size, and that the structure of the carbon matrix is not affected. The comparison of the small-angle and wide-angle scattering reveals the amorphous discharge products found at a low discharge rate. Further analysis demonstrates the correlation between the diffusion resistance and the compositional change of electrolyte in the mesopores at the end of discharge, which suggests that Li-ion deficiency is the limiting factor for sulfur utilization at a medium discharge rate.
Although lithium–sulfur batteries have high theoretical energy density of 2600 Wh kg⁻¹, the sluggish redox kinetics of soluble liquid polysulfide intermediates during discharge and charge is one of the main reasons for their limited battery performance. Designing highly efficient electrocatalysts with a core–shell like structure for accelerating polysulfide conversion is vital for the development of Li–S batteries. Herein, core–shell MoSe2@C nanorods are proposed to manipulate electrocatalytic polysulfide redox kinetics, thereby improving the Li–S battery performance. The 1D MoSe2@C is synthesized via a facile hydrothermal and subsequent selenization reaction. The electrocatalysis of MoSe2 is confirmed by the analysis of symmetric batteries, Tafel curves, changes of activation energy, and lithium‐ion diffusion. Density functional theory calculations also prove the low Gibbs free energy of the reaction pathway and the lithium‐ion diffusion barrier. Therefore, the Li–S batteries using MoSe2 electrocatalyst exhibit an excellent rate performance of 560 mAh g⁻¹ at 1 C with a high sulfur loading of 3.4 mg cm⁻² and an areal capacity of 4.7 mAh cm⁻² at a high sulfur loading of 4.7 mg cm⁻² under lean electrolyte conditions. This work provides a deeper insight into regulation of polysulfide redox kinetics in electrocatalysts for Li–S batteries.
Lithium–sulfur batteries (LSBs) are severely impeded by their poor cycling stability and low sulfur utilization due to the inevitable polysulfide shuttle effect and sluggish reaction kinetics. This work reports a Mott–Schottky RGO‐PANI/MoS2 (RPM) heterogeneous layer modified separator for commercial‐sulfur‐based LSBs through the vertical growth of molybdenum sulfide (MoS2) arrays on the polyaniline (PANI) in situ reduced graphene oxide (RGO). Due to the synergistic effects of the “reservoir” constructed by MoS2 and RGO‐PANI, strong absorbability, high conductivity, and electrocatalytic activity, RPM exhibits a successive “trapping–interception–conversion” behavior toward lithium polysulfides. As a result, the LSBs assembled using a commercial‐sulfur as the cathode and RPM as modified layer exhibit high sulfur utilization (3.8 times higher than that of the unmodified separator at 5 C), excellent rate performance (553 mAh g⁻¹ at 10 C), and outstanding high‐rate cycle stability (524 mAh g⁻¹ after 700 cycles at 5 C). Moreover, even at a high sulfur loading of 5.4 mg cm⁻², a favorable areal capacity of 3.8 mAh cm⁻² is still maintained after 80 cycles. Theoretical calculations elucidate that such a systematic strategy can effectively suppress the shuttling effect and boost the catalytic conversion of intercepted polysulfides. This work may provide a feasible strategy to promote the practical application of commercial‐sulfur‐based LSBs.
Rechargeable magnesium batteries are identified as a promising next‐generation energy storage system, but their development is hindered by the anode−electrolyte−cathode incompatibilities and passivation of magnesium metal anode. To avoid or alleviate these problems, the exploitation of alternative anode materials is a promising choice. Herein, we present titanium pyrophosphate (TiP2O7) as anode materials for magnesium‐ion batteries (MIBs) and investigate the effect of the crystal phase on its magnesium storage performance. Compared with the metastable layered TiP2O7, the thermodynamically stable cubic TiP2O7 displays a better rate capability of 72 mAh g−1 at 5000 mA g−1. Moreover, cubic TiP2O7 exhibits excellent cycling stability with the capacity of 60 mAh g−1 after 5000 cycles at 1000 mA g−1, which are better than previously reported Ti‐based anode materials for MIBs. In situ X‐ray diffraction technology confirms the single‐phase magnesium‐ion intercalation/deintercalation reaction mechanism of cubic TiP2O7 with a low volume change of 3.2%. In addition, the density functional theory calculation results demonstrate that three‐dimensional magnesium‐ion diffusion can be allowed in cubic TiP2O7 with a low migration energy barrier of 0.62 eV. Our work demonstrates the promise of TiP2O7 as high‐rate and long‐life anode materials for MIBs and may pave the way for further development of MIBs. Titanium pyrophosphate with three‐dimensional ion channel is presented as low‐strain anode materials for magnesium‐ion batteries and exhibits high rate capability and long cycling life. In situ X‐ray diffraction technology is employed to confirm the magnesium storage mechanism of titanium pyrophosphate. The magnesium‐ion diffusion behavior in titanium pyrophosphate is investigated by density function theory calculation.
Solid phase conversion sulfur cathode is an effective strategy for eliminating soluble polysulfide intermediates (LiPSs) and improving cyclability of Li‐S batteries. However, realizing such a sulfur cathode with high sulfur loading and high capacity utilization is very challenging due to the insulating nature of sulfur. In this work, a strategy is proposed for fabricating solid phase conversion sulfur cathode by encapsulating sulfur in the mesoporous channels of CMK‐3 carbon to form a coaxially assembled sulfur/carbon (CA‐S/C) composite. Vinyl carbonate (VC) is simultaneously utilized as the electrolyte cosolvent to in‐situ form a dense solid electrolyte interface (SEI) on the CA‐S/C composite surface through its nucleophilic reaction with the freshly generated polysulfides at the beginning of initial discharge, thus separating the direct contact of interior sulfur with the outer electrolyte. As expected, such a CA‐S/C cathode can operate in a solid phase conversion manner in the VC‐ether cosolvent electrolyte to exhibit a full capacity utilization (1667 mA h g–1, ≈100%), a high rate capability of 2.0 A g–1 and excellent long‐term cyclability over 500 cycles even at a high sulfur loading (75%, based on the weight of CA‐S/C composite), demonstrating great promise for constructing high‐energy‐density and cycle‐stable Li‐S batteries.
Given the inherent performance limitations of intercalation‐based lithium‐ion batteries, solid‐state conversion batteries are promising systems for future energy storage. A high specific capacity and natural abundancy make iron disulfide (FeS2) a promising cathode‐active material. In this work, FeS2 nanoparticles were prepared solvothermally. By adjusting the synthesis conditions, samples with average particle diameters between 10 nm and 35 nm were synthesized. The electrochemical performance was evaluated in solid‐state cells with a Li‐argyrodite solid electrolyte. While the reduction of FeS2 was found to be irreversible in the initial discharge, a stable cycling of the reduced species was observed subsequently. A positive effect of smaller particle dimensions on FeS2 utilization was identified, which can be attributed to a higher interfacial contact area and shortened diffusion pathways inside the FeS2 particles. These results highlight the general importance of morphological design to exploit the promising theoretical capacity of conversion electrodes in solid‐state batteries.
Lithium‐ion batteries, which have revolutionized portable electronics over the past three decades, were eventually recognized with the 2019 Nobel Prize in chemistry. As the energy density of current lithium‐ion batteries is approaching its limit, developing new battery technologies beyond lithium‐ion chemistry is significant for next‐generation high energy storage. Lithium–sulfur (Li–S) batteries, which rely on the reversible redox reactions between lithium and sulfur, appears to be a promising energy storage system to take over from the conventional lithium‐ion batteries for next‐generation energy storage owing to their overwhelming energy density compared to the existing lithium‐ion batteries today. Over the past 60 years, especially the past decade, significant academic and commercial progress has been made on Li–S batteries. From the concept of the sulfur cathode first proposed in the 1960s to the current commercial Li–S batteries used in unmanned aircraft, the story of Li–S batteries is full of breakthroughs and back tracing steps. Herein, the development and advancement of Li–S batteries in terms of sulfur‐based composite cathode design, separator modification, binder improvement, electrolyte optimization, and lithium metal protection is summarized. An outlook on the future directions and prospects for Li–S batteries is also offered. The major developments and advancements of lithium–sulfur batteries over the past 60 years are presented. The prospects and an outlook on the future development of lithium–sulfur batteries for large‐scale practical applications are also discussed.
Lithium–sulfur (Li–S) batteries hold the promise of the next generation energy storage system beyond state‐of‐the‐art lithium‐ion batteries. Despite the attractive gravimetric energy density (WG), the volumetric energy density (WV) still remains a great challenge for the practical application, based on the primary requirement of Small and Light for Li–S batteries. This review highlights the importance of cathode density, sulfur content, electroactivity in achieving high energy densities. In the first part, key factors are analyzed in a model on negative/positive ratio, cathode design, and electrolyte/sulfur ratio, orientated toward energy densities of 700 Wh L⁻¹/500 Wh kg⁻¹. Subsequently, recent progresses on enhancing WV for coin/pouch cells are reviewed primarily on cathode. Especially, the “Three High One Low” (THOL) (high sulfur fraction, high sulfur loading, high density host, and low electrolyte quantity) is proposed as a feasible strategy for achieving high WV, taking high WG into consideration simultaneously. Meanwhile, host materials with desired catalytic activity should be paid more attention for fabricating high performance cathode. In the last part, key engineering technologies on manipulating the cathode porosity/density are discussed, including calendering and dry electrode coating. Finally, a future outlook is provided for enhancing both WV and WG of the Li–S batteries.
The tremendous improvement in performance and cost of lithium-ion batteries (LIBs) have made them the technology of choice for electrical energy storage. While established battery chemistries and cell architectures for Li-ion batteries achieve good power and energy density, LIBs are unlikely to meet all the performance, cost, and scaling targets required for energy storage, in particular, in large-scale applications such as electrified transportation and grids. The demand to further reduce cost and/or increase energy density, as well as the growing concern related to natural resource needs for Li-ion have accelerated the investigation of so-called "beyond Li-ion" technologies. In this review, we will discuss the recent achievements, challenges, and opportunities of four important "beyond Li-ion" technologies: Na-ion batteries, K-ion batteries, all-solid-state batteries, and multivalent batteries. The fundamental science behind the challenges, and potential solutions toward the goals of a low-cost and/or high-energy-density future, are discussed in detail for each technology. While it is unlikely that any given new technology will fully replace Li-ion in the near future, "beyond Li-ion" technologies should be thought of as opportunities for energy storage to grow into mid/large-scale applications.
Material and energy efficiencies are two key parameters that benchmark the electrochemical energy conversion and storage devices (EECSDs). Maximizing both requires researchers to grasp the limits of the physiochemical properties of core electrode materials. Ordered mesoporous materials (OMMs) have been regarded as promising electrode materials; however, their intrinsic deficiencies (e.g., plugs, inaccessible pores, and surfaces) impose limits for wide applications. 2D ordered mesoporous materials (2DOMMs) featured with an extended lateral dimension and a nanometer thickness not only inherit the structure advantages of mesoporous materials, but also have a unique 2D ultrathin feature that can fully address the imperfections of conventional OMMs. Herein, recent achievements on the preparation of 2DOMMs by combining single micelle assembly strategy with 2D bottom‐up patterning techniques including the molecular/space confined, interfacial orientated, and surface limited assembly are focused. Special focus is devoted to the newly developed synthetic strategies and their fundamental mechanisms for accurate control of some key structural parameters. Recent advances of 2DOMMs in EECSDs are also highlighted, which suggest that 2DOMMs are excellent material platforms for developing new battery chemistry as well as targeting performance optimization and cost reduction. Finally, the challenges and prospects are proposed based on current development.
Lithium‒sulfur (Li–S) battery is considered as a promising energy storage system to realize high energy density. Nevertheless, unstable lithium metal anode emerges as the bottleneck towards practical applications, especially with limited anode excess required in a working full cell. In this contribution, a mixed diisopropyl ether‐based (mixed‐DIPE) electrolyte was proposed to effectively protect lithium metal anode in Li–S batteries with sulfurized polyacrylonitrile (SPAN) cathodes. The mixed‐DIPE electrolyte improves the compatibility to lithium metal and suppresses the dissolution of lithium polysulfides, rendering significantly improved cycling stability. Concretely, Li | Cu half cells with the mixed‐DIPE electrolyte cycled stably for 120 cycles, which is nearly five times longer than that with routine carbonate‐based electrolyte. Moreover, the mixed‐DIPE electrolyte contributed to a doubled lifespan of 156 cycles at 0.5 C in Li | SPAN full cells with ultrathin 50 μm Li metal anodes compared with the routine electrolyte. This contribution affords an effective electrolyte formula for Li metal anode protection and is expected to propel the practical applications of high‐energy‐density Li‒S batteries.
Three-dimensional interconnected nanoporous graphene (NPG) microfoams and nanofoams are developed via a new approach of solid-state catalytic growth. Both NPG microfoam and nanofoam exhibit similar nanoporous structures that contain close tubular pores and open non-tubular pores but with different particle sizes. As electrochemical reactors for sulfur cathodes, sulfur is encapsulated inside the tubular pores. It is found that NPG nanoreactors can enhance the electrochemical performances in comparison with NPG microreactors, including improved reversible capacities, cyclic performances and rate performances in particular. The electrochemical impedance spectroscopy analysis reveals that NPG nanoreactors facilitate Li+ transportation and decrease the charge-transfer resistance in comparison with the microreactors, promoting the redox kinetics of multi-step conversions between sulfur and lithium sulfides. This work demonstrates a significant particle size effect of nanoporous graphene on the Li–S electrochemistry and can be useful for designing Li–S batteries as well as other electrochemical energy storage systems.
The development of rechargeable Na-S batteries is very promising, thanks to their considerably high energy density, abundance of elements, and low costs and yet faces the issues of sluggish redox kinetics of S species and the polysulfide shuttle effect as well as Na dendrite growth. Following the theory-guided prediction, the rare-earth metal yttrium (Y)-N4 unit has been screened as a favorable Janus site for the chemical affinity of polysulfides and their electrocatalytic conversion, as well as reversible uniform Na deposition. To this end, we adopt a metal-organic framework (MOF) to prepare a single-atom hybrid with Y single atoms being incorporated into the nitrogen-doped rhombododecahedron carbon host (Y SAs/NC), which features favorable Janus properties of sodiophilicity and sulfiphilicity and thus presents highly desired electrochemical performance when used as a host of the sodium anode and the sulfur cathode of a Na-S full cell. Impressively, the Na-S full cell is capable of delivering a high capacity of 822 mAh g-1 and shows superdurable cyclability (97.5% capacity retention over 1000 cycles at a high current density of 5 A g-1). The proof-of-concept three-dimensional (3D) printed batteries and the Na-S pouch cell validate the potential practical applications of such Na-S batteries, shedding light on the development of promising Na-S full cells for future application in energy storage or power batteries.
Lithium-sulfur batteries suffer from poor cycling stability because of the intrinsic shuttling effect of intermediate polysulfides and sluggish reaction kinetics, especially at high rates and high sulfur loading. Herein, we report the construction of a CoP-Co2[email protected] carbon polyhedron uniformly anchored on three-dimensional carbon nanotubes/graphene (CoP-Co2[email protected]/CG) scaffold as a sulfur reservoir to achieve the trapping-diffusion-conversion of polysulfides. Highly active CoP-Co2N shows marvelous catalytic effects by effectively accelerating the reduction of sulfur and the oxidation of Li2S during the discharging and charging process, respectively, while the conductive NC/CG network with massive mesoporous channels ensures fast and continuous long-distance electron/ion transportation. DFT calculations demonstrate that the CoP-Co2N with excellent intrinsic conductivity serves as job-synergistic immobilizing-conversion sites for polysulfides through the formation of P···Li/N···Li and Co···S bonds. As a result, the [email protected]2[email protected]/CG cathode (sulfur content 1.7 mg cm⁻²) exhibits a high capacity of 988 mAh g⁻¹ at 2 C after 500 cycles, which is superior to most of the electrochemical performance reported. Even under high sulfur content (4.3 mg cm⁻²), it also shows excellent cyclability with high capacity at 1 C.
High-energy lithium-sulfur batteries (LSBs) have experienced relentless development over the past decade with discernible improvements in electrochemical performance. However, a scrutinization of the cell operation conditions reveals a huge gap between the demands for practical batteries and those in the literature. Low sulfur loading, a high electrolyte/sulfur (E/S) ratio and excess anodes for lab-scale LSBs significantly offset their high-energy merit. To approach practical LSBs, high loading and lean electrolyte parameters are needed, which involve budding challenges of slow charge transfer, polysulfide precipitation and severe shuttle effects. To track these obstacles, the exploration of electrocatalysts to immobilize polysulfides and accelerate Li-S redox kinetics has been widely reported. Herein, this review aims to survey state-of-the-art catalytic materials for practical LSBs with emphasis on elucidating the correlation among catalyst design strategies, material structures and electrochemical performance. We also statistically evaluate the state-of-the-art catalyst-modified LSBs to identify the remaining discrepancy between the current advancements and the real-world requirements. In closing, we put forward our proposal for a catalytic material study to help realize practical LSBs.
The Cover Feature illustrates a discharge profile of a 19 Ah lithium‐sulfur (Li‐S) pouch cell subject to the required power on the Millbrook London Transport Bus (MLTB) driving cycle. In this study, cycle life performance of the Li‐S cell is investigated at various temperatures using system identification and X‐ray tomography methods. More information can be found in the Research Article by A. Fotouhi and co‐workers.
Owing to the ultrahigh theoretical energy density and low-cost, lithium-sulfur (Li-S) batteries hold broad prospects as one of the promising substitutes for commercial lithium-ion batteries. The polysulfides shuttling originated from sulfur cathode and the lithium dendrite growth from lithium anode are the main challenges that hinder the commercial survival of Li-S batteries. Herein, thermal stable bacterial cellulose (BC) separator is successfully fixed with polyethyleneimine (PEI) by a scalable chemical grafting. The hydroxyl groups and amino groups in PEI grafted BC ([email protected]) separator can participate in the formation of Li2O and Li3N, respectively, contributing to robust solid electrolyte interface with high ionic conductivity. Therefore, the lithium deposition is well regulated, resulting in a spherical and dendrite-free Li deposit pattern. The Li/Li symmetrical cell assembled with [email protected] separator exhibits excellent cyclic stability, which can continuously plate/stripe for more than 820 hours with an overpotential of ∼40 mV at 2 mA cm⁻². Meanwhile, the polar amino group can restrain the polysulfide migration via chemosorption. As a consequence of these merits, ultrahigh initial capacity (1402 mAh g⁻¹ at 0.1C) and excellent rate performance (440.5 mAh g⁻¹ at 2C) for Li-S full cell are achieved, presenting new insights into the fabrication of multifunctional separators for Li-S batteries.
The commercialization of lithium–sulfur (Li−S) batteries is still hindered by the unsatisfactory cell performance under practical working conditions, which is mainly caused by the sluggish cathode redox kinetics, severe polysulfide shuttling, and poor Li stripping/plating reversibility. Herein, we report an effective strategy by combining Se‐doped S hosted in an ordered macroporous framework with a highly fluorinated ether (HFE)‐based electrolyte to simultaneously address the aforementioned issues in both cathode and anode. A reversible and stable high areal capacity of >5.4 mAh cm−2 with high Coulombic efficiency >99.2 % can be achieved under high areal Se/S loading (5.8 mg cm−2), while the underlying mechanism was further revealed through synchrotron X‐ray probes and Time‐of‐Flight Secondary Ion Mass Spectrometry (ToF‐SIMS). The practical application potential was further evaluated at low (0 °C) and high (55 °C) temperatures under high areal Se/S loading (>5.0 mg cm−2) and thin Li metal (40 μm). The synergy of cathode engineering and electrolyte manipulation effectively enhance redox kinetics and cycling stability of Li−S batteries. This strategy is demonstrated to be effective in achieving high performance under wide temperature situations and enabling a stable Li−S pouch cell under a thin Li‐metal anode, thick S cathode, and lean electrolyte conditions.
Li-S batteries have attracted great attention from academia and industry because of their very high theoretical capacity and energy density, arising from the multi electron electrochemical reactions. Although significant progress has been made to improve the capacity and cycle life of these batteries, a major challenge has been overlooked. Ether-based electrolytes, commonly used in Li-S batteries are highly volatile and impractical for many applications. On the other hand, carbonate-based electrolytes have been used in commercial Li-ion batteries for three decades and are a natural and practical choice to replace ether-based electrolytes in Li-S batteries. The lack of attention towards the use of carbonate-based electrolytes in Li-S battery, is in part from the irreversible reaction between carbonate solvents and polysulfides anion that results in battery shut down, when conventional material designs and strategies are employed. Here, a comprehensive and critical review of recent progress on the use of carbonate-based electrolyte is presented. Throughout this work, we provide our insight to different approaches that can mitigate the irreversible reaction between carbonate solvents and sulfur cathode. First, we introduce the solid-solid direct conversion reaction of sulfur, which enables the successful use of carbonate electrolytes in Li-S batteries. Then, we discuss the progress made on design of cathodes, engineering of electrolyte, and strategies for Li metal protection, when carbonate electrolytes are used in Li-S batteries. Furthermore, the future directions to achieve a long-term cycling Li-S battery with carbonate electrolytes is provided. We believe that this work can be a useful source to draw the attention of Li-S battery field to develop better performance and more practical Li-S batteries.
Porous organic polymers (POPs), a versatile class of materials that possess many tunable properties such as high chemical absorptivity and ionic conductivity, are emerging candidate electrode materials, permselective membranes, ionic conductors, interfacial stabilizers and functional precursors to synthesize advanced porous carbon. Based on their crystal structure features, the emerging POPs can be classified into two subclasses: amorphous POPs (hyper cross-linked polymers, polymers with intrinsic microporosity, conjugated microporous polymers, porous aromatic frameworks, etc.) and crystalline POPs (covalent organic frameworks, etc.). This tutorial review provides a brief introduction of different types of POPs in terms of their classification and functions for tackling the remaining challenges in various types of Li-chemistry-based batteries. In situ and ex situ characterization studies are also discussed to highlight their importance and applicability for the structural investigation of POPs to reveal the underlying mechanism of POPs over the course of the electrochemical process. Although some revolutionary advances have been achieved, the development of POPs in Li-chemistry-based batteries is still in its infancy. Perspectives regarding future application and mechanistic insights of POPs in battery studies are outlined at the end.
The movement of the sulfur species of a lithium-sulfur battery cathode was directly observed through pioneering operando SAXS analysis. Micropores are a prior repository for sulfur before and after the...
Multivalent metal–sulfur (M–S, where M=Mg, Al, Ca, Zn, Fe, etc.) batteries offer unique opportunities to achieve high specific capacity, elemental abundancy and cost-effectiveness beyond lithium-ion batteries (LIBs). However, the slow diffusion of multivalent-metal ions and the shuttle of soluble polysulfide result in impoverished reversible capacity and limited cycle performance of M–S (Mg–S, Al–S, Ca–S, Zn–S, Fe–S, etc.) batteries. It is a necessity to optimize the electrochemical performance, while deepening the understanding of the unique electrochemical reaction mechanism, such as the intrinsic multi-electron reaction process, polysulfides dissolution and the instability of metal anodes. To solve these problems, we have summarized the state-of-the-art progress of current M–S batteries, and sorted out the existing challenges for different multivalent M–S batteries according to sulfur cathode, electrolytes, metallic anode and current collectors/separators, respectively. In this literature, we have surveyed and exemplified the strategies developed for better M–S batteries to strengthen the application of green, cost-effective and high energy density M–S batteries.
Considering the unprecedented advantages such as superb theoretical capacity, high energy density and low cost, lithium-sulfur batteries (LSBs) have been under spotlight in past several years. Nevertheless, limited by its intrinsic drawbacks of highly insulating character, serious shuttle effect and lithium dendrites growth, there is still a long way from large-scale application of LSBs. Here, a [email protected] organic frameworks ([email protected]) composite-derived heteroatoms doped [email protected] CoS2 nanoparticles ([email protected]2) modified separator is designed to surmount these issues. Notably, the modified separator shows improved flame retardancy. By using this separator, the effective suppression on shuttle behavior as well as boost in polysulfides conversion kinetics are realized, which can be assigned to the integrative superiorities of conductive carbon fiber network, electrocatalytic activity, polar-polar interaction and Lewis acid-base interaction. The cell with modified separator shows an initial discharge capacity of 1140.7 mAh g⁻¹. After running for 100 cycles, a high capacity of 631.6 mAh g⁻¹ is retained. Notably, the inhibited growth of lithium dendrites is also obtained, indicating the promoted battery safety. Overall, this work may provide useful inspirations for the utilization of MOFs-derived hierarchical composite in implementing safer high-performance LSBs.
Despite the intriguing merits of lithium-sulfur (Li-S) systems, they still suffer from the notorious “shuttling-effect” of polysulfides. Herein, carbon materials with rational tailoring of morphology and pores were designed for strong loading/adsorption with the controlling of energy-storage ability. Through rational tailoring, it is strongly verified that such engineering of evolutions result in variational of sulfur immobilization in the obtained carbon. As expected, the targeted sample delivers a stable capacity of 925 mAh g⁻¹ after 100 loops. Supporting by the “cutting-off” manners, it is disclosed that mesopores in carbon possess more fascinated traits than micro/macropores in improving the utilization of sulfur and restraining Li2Sx (4 ≤ x ≤ 8). Moreover, the long-chain polysulfide could be further consolidated by auto-doping oxygen groups. Supported by in-depth kinetic analysis, it is confirmed that the kinetics of ion/e⁻ transfer during charging and discharging could be accelerated by mesopores, especially in stages of the formation of solid S8 and Li2S, further improving the capacity of ion-storage in Li-S battery. Given this, the elaborate study provide significant insights into the effect of pore structure on kinetic performance about Li-storage behaviors in Li-S battery, and give guidance for improving sulfur immobilization.
Lithium-sulfur (Li-S) battery is considered to be a promising energy storage system due to its high energy density and low cost. However, the commercialization of Li-S battery is hindered by several problems such as the insulating nature of active materials, notorious “shuttle effect" and damage of lithium dendrites. Cellulose-based materials have attracted widespread attention in the development of Li-S battery on account of their environmentally friendly nature, unique network structure, and possibility for chemical functionalization. This review summarizes the application of cellulose-based materials in Li-S batteries mainly as either the separator, the carbon material for binder assisted modification of separator or as carbon hosts for sulfur cathode and discusses the challenges that utilization of the cellulose-based materials could potentially encountered in Li-S battery. Perspectives regarding the future development of cellulose-based materials for Li-S battery are also discussed.
The high theoretical energy density, high environmental adaptability and safety of lithium sulfide (Li2S)-oriented cathodes attract enough attention among lithium-sulfur batteries (LSBs). In this work, the lithium sulfide (Li2S)-oriented composite is fabricated via an in-situ carbothermic reduction method, in which lithium sulfate is reduced by CMK3 at an optimized temperature and subsequently the as-prepared Li2S is protected via the conformal carbon layer by carbonization of phenol-formaldehyde resin (PF). With the aid of the porous carbon structure of CMK3 and protection of PF-derived conformal carbon layer, the dispersity of Li2S and conductivity of cathode are availably enhanced. It has been found that the Li2[email protected] prepared at optimum carbothermic reduction temperature of 835 °C has excellent electrochemical performance. The lithium-sulfur battery using Li2[email protected] as cathode and metal Li as anode can deliver a high initial discharge capacity of 979 mAh g⁻¹ at 0.1 C, the capacity retention after running at various current density is 94%, and the discharge specific capacity is still 530 mAh g⁻¹ at 2 C after 450 cycles. Therefore, the preparation of CMK3-supported Li2S-based cathode material provides a new approach for the development and industrialization of new high-performance Li–S battery.
Zirconium metal-organic frameworks (Zr-MOFs) are renowned for their extraordinary stability and versatile chemical tunability. Several Zr-MOFs demonstrate a tolerance for missing linker defects, which create “open sites” that can be used to bind guest molecules on the node cluster. Herein, we strategically utilize these sites to stabilize reactive lithium thiophosphate (Li3PS4) within the porous framework for targeted application in lithium-sulfur (Li-S) batteries. Successful functionalization of the Zr-MOF with PS43- is confirmed by an array of techniques including NMR, XPS, and Raman spectroscopies, X-ray pair distribution function analysis, and various elemental analyses. During electrochemical cycling, we find even a low incorporation extent of lithium thiophosphate in Zr-MOFs improves sulfur utilization and polysulfide encapsulation to deliver a sustainably high capacity over prolonged cycling. The functionalized MOF additives also prevent cell damage under abusive cycling conditions and recover high capacities when returned to lower charge/discharge rates, imperative for future energy storage devices. Our unique approach marries the promising chemical attributes of the purely inorganic Li3PS4 with the stability and high surface area of MOFs, creating a Li-S cathode architecture with a performance beyond the sum of its component parts. More broadly, this novel functionalization strategy opens new avenues for facile syntheses of “designer materials” where chemical components from discrete disciplines can be united and tailored for specific applications.
Lithium-sulfur batteries hold broad prospects as the low-cost and high-energy storage system. However, the practical application is limited by the intrinsic insulating nature of sulfur and severe shuttle effect of soluble polysulfide intermediates. Herein, we demonstrate a convenient self-assembly strategy for encapsulating carbon nanotubes in nitrogen-doped hollow carbon shells, to construct a nitrogen-doped tube-in-tube carbon nanostructure (NTTC) as a host material of sulfur. In this peculiar structure, the highly conductive carbon nanotube cores facilitate the electron transfer while the hollow porous structure is capable of accommodating high sulfur content of 70 wt% in the composites. Moreover, the nitrogen doping helps to alleviate the shuttle effect owing to enhanced chemisorption towards polysulfides. Benefiting from these merits, the NTTC/S composite with the high areal mass loading of ~2.5 mg cm-2 presents a high reversible capacity (1346.9 mAh g-1 at 0.05 C) and excellent rate capability (533.5 mAh g-1 at 3C). More impressively, NTTC/S electrode exhibits good cycling stability at a high rate of 2 C corresponding to slight capacity decay of 0.055% per cycle over 500 discharge/charge cycles.