Cathode For Lithium-sulfur Batteries Research Articles

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

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

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

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

Cellulose Fiber based self-supporting paper cathode with multi-scale network structure for high performance lithium-sulfur battery

Lithium-sulfur batteries (LSBs) are gaining attention as a potential energy storage option due to their impressive theoretical specific capacity. However, the main challenges hindering its implementation include the expansion in volume of sulfur and lithium sulfide during the conversion process of charge-discharge, the limited conductivity of the active material, and specifically, the phenomenon known as shuttle effect caused by lithium polysulfides (LiPSs). The development of high-performance LSBs have led to the need for self-supporting cathode materials that can efficiently accommodate volume expansion, build up efficient conductive pathways, and suppress shuttle effects. The poly(3,4-ethylenedioxythiophene) (PEDOT) was synthesized in situ on cellulose nanofibers (CNFs), resulting in the formation of CNF@PEDOT. Subsequently, CNF@PEDOT was combined with plant fibers (PFs) and multi-wall carbon nanotubes (MWCNTs) to fabricate a self-supporting cathode featuring a multi-scale network structure denoted as CNF@PEDOT/MWCNT/PF/S. The PFs serve as the primary backbone network, CNF@PEDOT to form the secondary conductive network, and MWCNTs act as tertiary conducting networks. In fact, the design of multi-level conductive network effectively improves the conductivity of the material, and PEDOT can further adsorb and catalyze LiPSs. The incorporation of PFs significantly enhanced the mechanical robustness of the cathode and augmented its electrolyte permeability. The self-supporting CNF@PEDOT/MWCNT/PF/S cathode exhibits an initial capacity of 1204.6 mA h g−1 when loaded with 2.4 mg cm−2 of sulfur at a rate of 0.2 C. Notably, it maintains an initial discharge specific capacity of 712.9 mA h g−1 even when the sulfur load is increased to 4.3 mg cm−2. This study presents a comprehensive framework for the development of self-supporting cathodes in LSBs.

Versatile separators toward advanced lithium-sulfur batteries: status, recent progress, challenges and perspective.

Lithium-sulfur batteries (LSBs) have recently gained extensive attention due to their high energy density, low cost, and environmental friendliness. However, serious shuttle effect and uncontrolled growth of lithium dendrites restrict them from further commercial applications. As "the third electrode", functional separators are of equal significance as both anodes and cathodes in LSBs. The challenges mentioned above are effectively addressed with rational design and optimization in separators, thereby enhancing their reversible capacities and cycle stability. The review discusses the status/operation mechanism of functional separators, then primarily focuses on recent research progress in versatile separators with purposeful modifications for LSBs, and summarizes the methods and characteristics of separator modification, including heterojunction engineering, single atoms, quantum dots, and defect engineering. From the perspective of the anodes, distinct methods to inhibit the growth of lithium dendrites by modifying the separator are discussed. Modifying the separators with flame retardant materials or choosing a solid electrolyte is expected to improve the safety of LSBs. Besides, in-situ techniques and theoretical simulation calculations are proposed to advance LSBs. Finally, future challenges and prospects of separator modifications for next-generation LSBs are highlighted. We believe that the review will be enormously essential to the practical development of advanced LSBs.

Flower-like covalent organic frameworks as host materials for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) batteries have emerged as a promising alternative energy storage system due to their high energy density and cost-effectiveness. However, practical applications of Li-S batteries are hindered by challenges such as the shuttle effect and sluggish redox kinetics. In this study, a three-dimensional (3D) flower-like diaminoanthraquinone (DAAQ)-covalent organic framework (COF) was developed, featuring nanorod-like petals and enriched with abundant N and O adsorption sites, serving as a host material for the sulfur cathode of Li-S batteries. Through a process of sulfur melting-diffusion, the resulting DAAQ-COF@S cathode material demonstrated a stable 3D cross-linked morphology with a hierarchical pore structure, maximizing the exposure of N/O adsorptive sites and facilitating rapid ion diffusion. This effectively inhibited the shuttling effect of lithium polysulfides (LiPSs) and enhanced rate performance. Consequently, DAAQ-COF@S cathodes exhibited a high initial discharge capacity of 1182.0 mAh g−1 at 0.1 C, with a capacity retention rate of 79.6% after 500 cycles at 2 C. Even at a high current density of 4 C, they maintained a high capacity of 616.8 mAh g−1, surpassing the majority of previously reported COF-based host materials for Li-S batteries. This work underscores the significance of COF micromorphology and advances the development of high-performance cathodes for Li-S batteries.

Consistent behaviors of KI in heat, light and electric fields towards the inversely vulcanized dicyclopentadiene cathode for lithium-sulfur batteries

The sulfured dicyclopentadiene (S-DCPD) is a promising cathode candidate for Li-S batteries. Enlightened by the function of KI in dye-sensitized solar cells, we employ KI as a catalyst in the preparation of S-DCPD without eliminating it in the assembly of Li-S batteries. As a result, the sulfurizing reaction proceeds more completely at a lower temperature. The as-prepared material exhibits a different light response to the blank sample, changing from a higher energy level to a lower one. And the electrochemistry is greatly elevated as well. Theoretical calculations validate that KI plays the key role by altering the electron transmitting path. We can thus unify the behaviors of KI in the field of heat, light, and electricity, phenomenally. Furthermore, we investigate the morphology changes of the electrode by dipping it in an ordinary solution and subjecting it to a cycle calendar life in the electrolyte, respectively. As a result, we make clear that the difference of the behaviors between ordinary solutions and electrolytes is also in associated with the electronic path of KI.

Iodine-doped carbon nanotubes boosting the adsorption effect and conversion kinetics of lithium-sulfur batteries

Compared with lithium-ion batteries (LIBs), lithium-sulfur batteries (LSBs), based on electrochemical reactions involving multi-step 16-electron transformations provide higher specific capacity (1672 mAh g−1) and specific energy (2600 Wh kg−1), exhibiting great potential in the field of energy storage. However, the inherent insulation of sulfur, slow electrochemical reaction kinetics and detrimental shuttle-effect of lithium polysulfides (LiPSs) restrict the development of LSBs in practical applications. Herein, the iodine-doped carbon nanotubes (I-CNTs) is firstly reported as sulfur host material to the enhance the adsorption-conversion kinetics of LSBs. Iodine doping can significantly improve the polarity of I-CNTs. Iodine atoms with lone pair electrons (Lewis base) in iodine-doped CNTs can interact with lithium cations (Lewis acidic) in LiPSs, thereby anchoring polysulfides and suppressing subsequent shuttling behavior. Moreover, the charge transfer between iodine species (electron acceptor) and CNTs (electron donor) decreases the gap band and subsequently improves the conductivity of I-CNTs. The enhanced adsorption effect and conductivity are beneficial for accelerating reaction kinetics and enhancing electrocatalytic activity. The in-situ Raman spectroscopy, quasi in-situ electrochemical impedance spectroscopy (EIS) and Li2S potentiostatic deposition current–time (i-t) curves were conducted to verify mechanism of complex sulfur reduction reaction (SRR). Owing to above advantages, the I-CNTs@S composite cathode exhibits an ultrahigh initial capacity of 1326 mAh g−1 as well as outstanding cyclicability and rate performance. Our research results provide inspirations for the design of multifunctional host material for sulfur/carbon composite cathodes in LSBs.

FeSx/MoS2 heterostructure decorated S-coated hydroxylated carbon nanotubes for boosting catalytic activity and mitigating polysulfide shuttling in lithium-sulfur batteries

Heterostructure was widely study to figure out the inferior shuttle effect of intermediate lithium polysulfides and the sluggish kinetics of sulfur redox reaction in lithium-sulfur batteries (LSBs). However, they have low electrical conductivity and no clear discharge/charge catalytic mechanism as LSBs cathode. Combination of heterostructure and functional carbonaceous is a promising choice. Herein, FeSx/MoS2 heterostructure decorated S-coated hydroxylated carbon nanotubes (FSM/SHC) were successfully designed and the catalytic mechanism of FSM was elucidated by in-/ex- situ electrochemical characterizations. Compared to FeSx/MoS2 heterostructure decorated carbon nanotubes (FSM/C)-based sulfur cathode, the chemical adsorption capacity to anchor intermediate polysulfides and the Li-S conversion reaction kinetics of FSM/SHC has been enhanced ascribed to the introduction of polar bonds and functional groups. As a consequence, FSM/SHC-based sulfur modified cathode delivers a marked sulfur reversion (1280 mAh g−1 after 800 cycles at 0.2C and 1048 mAh g−1 after 300 cycles at 4C) and a high capacity retention of 6 mAh cm−2 over 70 cycles at 0.5C (8 mg cm−2). Moreover,the FSM heterostructuredemonstrates an accelerated electron transfer caused by the valence change of Fe0/Fe3+transition, Mo4+/Mo6+ transition and heterointerface, and thus facilitates the redox reaction kinetics of polysulfide. This work reveals the advantages of multi metal-based heterostructures and functional group modification in LSBs.

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

Sulfur Encapsulation into Carbon Nanospheres as an Effective Technique to Limit Sulfide Dissolution and Extend the Cycle Life of Lithium–Sulfur Batteries

CeO2/Co heterostructure encapsulated in hollow necklace-like carbon fiber as an advanced host material for high-performance lithium-sulfur batteries

The shuttle effect of lithium polysulfides (LiPSs) and the sluggish reaction kinetics of LiPSs conversion pose serious challenges to the commercial feasibility of lithium-sulfur (Li-S) batteries. To address these obstacles, herein, we construct CeO2/Co heterostructures in hollow necklace-like carbon fibers (CeO2/Co-CNFs) as the cathode host material for Li-S batteries. The specific surface area of fibers is significantly enhanced by using a template, thereby promoting the utilization efficiency of sulfur. Meanwhile, CeO2/Co-CNFs show strong conductivity, effective adsorption to LiPSs, and robust catalytic activity for LiPSs conversion. As a result, the Li-S battery with CeO2/Co-CNFs displays 961 mAh g−1 at 0.2 C, with an 86 % capacity retention rate after 100 cycles. At 2.0 C current density, the composite cathode maintains an initial discharge capacity of 782 mAh g−1, with a mere 0.044 % capacity loss per cycle. Furthermore, in situations with limited electrolytes, high sulfur loading, and high areal mass loading, the composite cathode can provide a high areal capacity of 6.2 mg cm−2 over 100 cycles. This work provides a useful approach for investigating high-performance Li-S battery cathodes.

Sulfur confinement into highly porous banana peduncle-derived carbon for high-rate performance lithium‑sulfur battery

In this work, we introduce a facile route to synthesize an eco-friendly and inexpensive cathode host material to address the critical challenges of insulating sulfur, polysulfide shutting, and volume changes for lithium‑sulfur batteries (LSBs). The cathode uses banana peduncle, a biomass as a carbon precursor, to enhance the specific surface area and porosity after chemical activation. The two approaches (with/without the outer layer and with/without activation) have been compared to substantiate the role of banana skin and activation in boosting the performance of LSB. The carbon‑sulfur composite prepared with a sulfur loading of 75 % yields a significantly high initial discharge capacity of 1498 mA h g−1 at 0.1C, which remains stable with a very minimal capacity decay for the subsequent 100 charge-discharge cycles. Even at a high current rate (2C), the electrode shows a remarkable discharge capacity of 1076 mA h g−1, reflecting the efficacy of the as-fabricated cathode for LSB for high current applications. Further, the cycling performance is corroborated with high aerial sulfur loading (4 mg cm−2) to investigate the commercial feasibility. This confirms the advantage of the highly porous cathode matrix (surface area: 3148.42 m2 g−1 and pore volume: 2.51 cm3 g−1) in confining the lithium polysulfides and the volume expansion during charge-discharge cycles. To the best of our knowledge, this is the first-time banana peduncle has been used as a source of electrode material, and the present approach may pave the path for developing a green and sustainable, low-cost, highly porous carbon made from waste material as a sulfur host for high-performance LSB.

Rational Design of Non-Noble Metal Single-Atom Catalysts in Lithium-Sulfur Batteries through First Principles Calculations.

Lithium-sulfur (Li-S) batteries with a high theoretical energy density of 2600 Wh·kg-1 are hindered by challenges such as low S conductivity, the polysulfide shuttle effect, low S reduction conversion rate, and sluggish Li2S oxidation kinetics. Herein, single-atom non-noble metal catalysts (SACs) loaded on two-dimensional (2D) vanadium disulfide (VS2) as the potential host materials for the cathode in Li-S batteries were investigated systematically by using first-principles calculations. Based on the comparisons of structural stability, the ability to immobilize sulfur, electrochemical reactivity, and the kinetics of Li2S oxidation decomposition between these non-noble metal catalysts and noble metal candidates, Nb@VS2 and Ta@VS2 were identified as the potential candidates of SACs with the decomposition energy barriers for Li2S of 0.395 eV (Nb@VS2) and of 0.162 eV (Ta@VS2), respectively. This study also identified an exothermic reaction for Nb@VS2 and the Gibbs free energy of 0.218 eV for Ta@VS2. Furthermore, the adsorption and catalytic mechanisms of the VS2-based SACs in the reactions were elucidated, presenting a universal case demonstrating the use of unconventional graphene-based SACs in Li-S batteries. This study presents a universal surface regulation strategy for transition metal dichalcogenides to enhance their performance as host materials in Li-S batteries.

Synergistic Pyridinic N/Pyrrolic N configurations in rGO/CNT composite sulfur hosts for high-performance lithium-sulfur batteries

Significant progress has been made in the field of nitrogen-doped carbon sulfur host materials to address the shuttle effect, expansion effect, and conductivity issues of lithium-sulfur (Li-S) battery cathode materials. However, there has been limited study on the synergistic effects of different nitrogen configurations. In this work, ammonia and hydrazine hydrate were used as nitrogen source precursors to prepare three kinds of rGO and CNT composite sulfur hosts with different nitrogen configurations. Ammonia is conducive to the formation of Pyrrolic N, while hydrazine hydrate is conducive to the formation of Pyridinic N. Lithium-sulfur batteries assembled with 3NG/CNT/S which has similar Pyridinic N and Pyrrolic N contents, have a specific initial discharge capacity of 1345 mAh/g at 0.2 C. The initial discharge specific capacity at 2 C was 819 mAh/g, and after 400 cycles, the remaining capacity is 667 mAh/g. The synergistic impact mechanism of Pyridinic N/Pyrrolic N configurations was further revealed by first principles calculations. The results indicate that Pyridinic N/Pyrrolic N configurations enhance electronic non-locality, significantly improve the reactivity of carbon materials, reduce the Gibbs free energy during polysulfide reactions, and accelerate the reaction rate.

Metal-Coordinated Covalent Organic Frameworks as Advanced Bifunctional Hosts for Both Sulfur Cathodes and Lithium Anodes in Lithium-Sulfur Batteries.

The shuttling of polysulfides on the cathode and the uncontrollable growth of lithium dendrites on the anode have restricted the practical application of lithium-sulfur (Li-S) batteries. In this study, a metal-coordinated 3D covalent organic framework (COF) with a homogeneous distribution of nickel-bis(dithiolene) and N-rich triazine centers (namely, NiS4-TAPT) was designed and synthesized, which can serve as bifunctional hosts for both sulfur cathodes and lithium anodes in Li-S batteries. The abundant Ni centers and N-sites in NiS4-TAPT can greatly enhance the adsorption and conversion of the polysulfides. Meanwhile, the presence of Ni-bis(dithiolene) centers enables uniform Li nucleation at the Li anode, thereby suppressing the growth of Li dendrites. This work demonstrated the effectiveness of integrating catalytic and adsorption sites to optimize the chemical interactions between host materials and redox-active intermediates, potentially facilitating the rational design of metal-coordinated COF materials for high-performance secondary batteries.

Insights into the aspect ratio effects of ordered mesoporous carbon on the electrochemical performance of sulfur cathode in lithium-sulfur batteries

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 OMCs 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.

Heteroatom doping carbon film derived from hyphae as a self-supporting cathode for advanced lithium sulfur batteries

Much attention has been paid to lithium sulfur battery due to its high energy density. However, low S loading and poor cycling stability have hindered their commercialization. In this work, a porous carbon film with rich heteroatom doping was prepared from the Penicillium chrysogenum hyphae film by freezing drying and high-temperature carbonization. Then the carbon film loaded polysulfide solution was utilized as a self-supporting cathode for Li-S batteries. The self-supporting cathode exhibited good rate performance (513.1 mAh/g at 1C) and improved cycling stability (more than 400 cycles) under a high current density (0.5C). This is mainly attributed to the abundant heteroatoms that provided active sites with superior adsorption ability for lithium polysulfide, which not only enhanced the cycling stability but also facilitated the conversion kinetics. Besides, the fibrous network morphology with affluent porous structures inherited from hyphae provided a large specific surface area and sufficient space for accommodating active substances. This work shows the great potential of hyphae derived porous carbon electrodes for high-performance energy storage applications.

Co-Fe dual-atom isolated in N-doped graphydine as an efficient sulfur conversion catalyst in Li-S batteries

Lithium-sulfur (Li-S) batteries have garnered considerable attention as a prospective energy storage device for the future due to their exceptionally high theoretical energy density. Unfortunately, sluggish sulfur reactions create a bottleneck in Li–S batteries, hindering their ability to deliver all their promised energy. In this work, we reported the N-doped graphydine as a sulfur host in a Li-S battery cathode. The graphydine host is decorated with isolated cobalt/iron dual-atom catalyst. Co/Fe sites in Li–S batteries play a double role as an electrocatalyst, speeding up the two-way conversion between sulfur and lithium sulfide during the battery's cycle. These composite electrocatalysts, built with a remarkable 70 wt% sulfur content, achieve a high specific capacity of 1520 mA h g⁻¹ at a low charging current density (0.1 C). At a low current density of 0.1 C, they present remarkable cycling consistency, losing only 0.07% of capacity for each cycle for 1000 cycles.

Solid-State Transformations of Active Materials in the Pores of Sulfurized-Polyacrylonitrile Fiber Membranes via Nucleophilic Reactions for High-Loading and Free-Standing Lithium–Sulfur Battery Cathodes

Solid-State Transformations of Active Materials in the Pores of Sulfurized-Polyacrylonitrile Fiber Membranes via Nucleophilic Reactions for High-Loading and Free-Standing Lithium–Sulfur Battery Cathodes

Juice Vesicles Bioreactors Technology for Constructing Advanced Carbon-Based Energy Storage.

The construction of high-quality carbon-based energy materials through biotechnology has always been an eager goal of the scientific community. Herein, juice vesicles bioreactors (JVBs) bio-technology based on hesperidium (e.g., pomelo, waxberry, oranges) is first reported for preparation of carbon-based composites with controllable components, adjustable morphologies, and sizes. JVBs serve as miniature reaction vessels that enable sophisticated confined chemical reactions to take place, ultimately resulting in the formations of complex carbon composites. The newly developed approach is highly versatile and can be compatible with a wide range of materials including metals, alloys, and metal compounds. The growth and self-assembly mechanisms of carbon composites via JVBs are explained. For illustration, NiCo alloy nanoparticles are successfully in situ implanted into pomelo vesicles crosslinked carbon (PCC) by JVBs, and their applications as sulfur/carbon cathodes for lithium-sulfur batteries are explored. The well-designed PCC/NiCo-S electrode exhibits superior high-rate properties and enhanced long-term stability. Synergistic reinforcement mechanisms on transportation of ions/electrons of interface reactions and catalytic conversion of lithium polysulfides arising from metal alloy and carbon architecture are proposed with the aid of DFT calculations. The research provides a novel biosynthetic route to rational design and fabrication of carbon composites for advanced energy storage.

Decoration on the inner surface of low-tortuosity microchannels derived from wood plate for highly stable lithium sulfur batteries

The low-tortuosity microchannels of wood-based carbon matrix in free-standing cathodes for lithium sulfur batteries (LSBs) were a double-edged sword, which brought in both a high energy density due to a high sulfur loading and severe shuttle effect for poor cycling stability. Herein, a layer of cellulose aerogel extracted from the wood wall was coated on the inner surface of the low-tortuosity microchannels of the wood plate, which was further transformed into a hierarchical carbon matrix using in free-standing cathode for LSBs. The decorated cathode exhibited a maximal specific capacity of 1377.2 mAh g−1 due to the enhanced utilizing ratio of active materials and exceptional cycling stability even under a high current density (1 C) for more than 500 cycles. Furthermore, the decorated cathode maintained good cycling stability with a higher sulfur areal loading (6.3 mg cm−2). The cellulose-based carbon aerogel coated on the inner surface of low-tortuosity microchannels provided a large specific surface area. This decoration strategy not only provided physical restriction on polysulfides but also increased conversion sites for polysulfides, improving the cycling performance of the wood-based free-standing cathode of LSBs. This work provided a potential structural design strategy for the advanced free-standing cathode of LSBs.