High-loading Lithium-sulfur Batteries Research Articles

Improving redox kinetics of sulfur cathode via bidirectional catalysis enhanced by nitrogen vacancy

The high-energy-density lithium-sulfur (Li-S) batteries (2600 Wh kg−1) are seriously hampered by the slow redox reaction kinetics and obnoxious shuttle effects of sulfur cathode. Introducing a catalytic host to promote sulfur redox kinetics is a promising way to inhibit polysulfide shuttling. Previous studies mainly focus on the unidirectional catalysis conversion from S8 to Li2S, and usually ignore the inverse reaction. Herein, defective vanadium nitride (VN1−x) is designed to promote the conversion of sulfur. The catalytic analysis suggests that introducing nitrogen vacancies effectively improves the nucleation and decomposition kinetics of Li2S, and prefers to promote the nucleation process, leading to superior capacity. Benefit from the bidirectional enhanced sulfur redox kinetics, the VN1−x/S composite electrode presents an impressively high capacity of 1417 mAh g−1 at 0.1 C at the first charge/discharge process, which is very close to the theoretical capacity of sulfur cathode (1675 mAh g−1). The Coulombic efficiency of the composite electrode reaches 99.89% even after 1000 cycles, showing reversible redox reactions. The pouch cell using VN1−x/S cathode shows a high initial discharge capacity (1180.3 mAh g−1) and can stably cycle over 100 cycles. This work can support the development of bidirectional catalytic host design for high-loading Li-S batteries.

Diminishing Self-Discharge of High-Loading Li-S Batteries with Oxygen-Rich Biomass Carbon Interlayers.

Lithium-sulfur batteries (Li-S) have possessed gratifying development in the past decade due to their high theoretical energy density. However, the severe polysulfide shuttling provokes undesirable self-discharge effect, leading to low energy efficiency in Li-S batteries. Herein, an interlayer composed of oxygen-rich carbon nanosheets (OCN) derived from bagasse is elaborated to suppress the shuttle effect and reduce the resultant self-discharge effect. The OCN interlayer is able to physically block the shuttling behavior of polysulfides and its oxygen-rich functional groups can strongly interact with polysulfides via O-S bonds to chemically immobilize mobile polysulfides. The self-discharge test for seven days further shows that the self-discahrge rate is diminished by impressive 93 %. As a result, Li-S batteries with the OCN interlayer achieve an ultrahigh discharge specific capacity of 710 mAh g-1 at a high mass loading of 7.18 mg. The work provides a facile method for designing functional interlayers and opens a new avenue for realizing Li-S batteries with high energy efficiency.

Dual-stage polyporate framework with redox mediator for high loading lithium sulfur batteries

Realizing a high sulfur loading cathode is a necessary measure for assembling a high actual energy density lithium sulfur battery, which requires consideration of conductivity, reaction interface, confinement of lithium polysulfide, and redox kinetics. Herein, a pomegranate-inspired dual-stage porous graphene foam with large cavity skeletons and submicron small cavity carriers is obtained by combining the bubble-template and the flash-freezing ice-template. Furthermore, the redox mediator of poly (1-aminoanthraquinone) is electropolymerized onto it to obtain a sulfur host with high specific surface area and strong confinement capability. The nanosized sulfur deposition behavior and the rich electronic relay capability of the sulfur host are analyzed by the independent gradient model combined with in-situ Raman spectroscopy. Besides, a few of electro-depolymerization products of poly (1-aminoanthraquinone) are confirmed to be able to migrate to the anode surface to stabilize lithium deposition. With these merits, the assembled lithium sulfur batteries exhibit a discharge capacity of 1214 mAh g−1 and a high capacity retention rate of 75.1 % after 800 cycles at a sulfur loading of 10.0 mg cm−2, and provide an excellent areal capacity of 17.5 mAh cm−2 (867 mAh g−1) even at an ultra-high sulfur loading of 20.1 mg cm−2.

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

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

InPc-modified gel electrolyte based on in situ polymerization in practical high-loading lithium-sulfur batteries

Lithium-sulfur batteries (LSBs) are currently being investigated as a potential candidate for high-energy–density rechargeable batteries. However, the notorious shuttle effect and uncontrolled dendrite growth posed problems for the practical applications of LSBs. Here, a new solid polymer electrolyte (SPE) was developed by in-situ polymerization of 1,3-dioxolane (DOL) in the presence of a multifunctional indium phthalocyanine (PDOL@InPc). The InPc endows the SPE with improved ionic conductivity and merit inhibition of the shuttle effect, in addition to being an effective additive for inducing uniform Li deposition by reconstructing the electric field at the interface. The characteristics of ionic migration in PDOL@InPc were quantified, and agreement between experiment and simulation established a relationship between macroscopic characteristics and molecular-level processes. The interfacial side reaction was controlled by the PDOL@InPc electrolyte, which also improved the distribution of the Li+ flux for dense Li deposition. Li symmetrical batteries designed with PDOL@lnPc can withstand a current density of up to 0.5 mA cm−2 and cycle reliably for 1500 h. The PDOL@InPc electrolyte displayed a high ionic conductivity at room temperature of 3.7 mS cm−1 and a significant Li+ transference number of 0.63. The resulting Li-S battery (Li|PDOL@lnPc|Sulfur) delivered a significant 325.5 Wh kg−1 of energy density at 0.2 C (1 C = 1000 mA g−1) at the level of the multilayer-pouch cell under an extremely low electrolyte of 3.5 g g−1Sulfur and high loading of 8.0 mg cm−2. This work provides a feasible strategy for the widespread implementation of LSBs with increased safety and a longer lifetime.

Furnishing Continuous Efficient Bidirectional Polysulfide Conversion for Long-Life and High-Loading Lithium-Sulfur Batteries via the Built-In Electric Field.

Most catalysts cannot accelerate uninterrupted conversion of polysulfides, resulting in poor long-cycle and high-loading performance of lithium-sulfur (Li-S) batteries. Herein, rich p-n junction CoS2 /ZnS heterostructures embedded on N-doped carbon nanosheets are fabricated by ion-etching and vulcanization as a continuous and efficient bidirectional catalyst. The p-n junction built-in electric field in the CoS2 /ZnS heterostructure not only accelerates the transformation of lithium polysulfides (LiPSs), but also promotes the diffusion and decomposition for Li2 S the from CoS2 to ZnS avoiding the aggregation of lithium sulfide (Li2 S). Meanwhile, the heterostructure possesses a strong chemisorption ability to anchor LiPSs and superior affinity to induce homogeneous Li deposition. The assembled cell with a CoS2 /ZnS@PP separator delivers a cycling stability with a capacity decay of 0.058% per cycle at 1.0 C after 1000 cycles, and a decent areal capacity of 8.97 mA h cm-2 at an ultrahigh sulfur mass loading of 6 mg cm-2 . This work reveals that the catalyst continuously and efficiently converts polysulfides via abundant built-in electric fields to promote Li-S chemistry.

Self-Assembled Macrocyclic Copper Complex Enables Homogeneous Catalysis for High-Loading Lithium-Sulfur Batteries.

The practical viability of high energy density lithium-sulfur (Li-S) batteries stipulates the use of a high-loading cathode and lean electrolyte. However, under such harsh conditions, the liquid-solid sulfur redox reaction is much-retarded due to the poor sulfur and polysulfides utilization, leading to low capacity and fast fading. Herein, a self-assembled macrocyclic Cu(II) complex (CuL) is designed as an effective catalyst to homogenize and maximize the liquid-involved reaction. The four-N atoms coordinated Cu(II) ion features a planar dsp 2 hybridization, showing a strong bonding affinity towards lithium polysulfides (LiPSs) along the dz 2 orbital via steric effect. Such a structure not only lowers the energy barrier of the liquid-solid conversion (Li2 S4 to Li2 S2 ) but also guides a 3D deposition of Li2 S2 /Li2 S. As such, with a 1 wt% electrolyte additive of CuL, a high initial capacity of 925 mAh g-1 and areal capacity of 9.62 mAh cm-2 with a low decay of 0.3%/cycle can be achieved under a high sulfur loading of 10.4mg cm-2 and low electrolyte/sulfur ratio of 6μL mgs -1 . This work is expected to inspire the design of homogenous catalysts and accelerate the uptake of high-energy-density Li-S batteries. This article is protected by copyright. All rights reserved.

Construction of strong built-in electric field in binary metal sulfide heterojunction to propel high-loading lithium-sulfur batteries

The practical application of lithium-sulfur (Li-S) batteries is greatly hindered by soluble polysulfides shuttling and sluggish sulfur redox kinetics. Rational design of multifunctional hybrid materials with superior electronic conductivity and high electrocatalytic activity, e.g., heterostructures, is a promising strategy to solve the above obstacles. Herein, a binary metal sulfide MnS-MoS2 heterojunction electrocatalyst is first designed for the construction of high-sulfur-loaded and durable Li-S batteries. The MnS-MoS2 p-n heterojunction shows a unique structure of MoS2 nanosheets decorated with ample MnS nanodots, which contributes to the formation of a strong built-in electric field at the two-phase interface. The MnS-MoS2 hybrid host shows strong soluble polysulfide affinity, enhanced electronic conductivity, and exceptional catalytic effect on sulfur reduction. Benefiting from the synergistic effect, the as-derived S/MnS-MoS2 cathode delivers a superb rate capability (643 mA h g−1 at 6 C) and a durable cyclability (0.048% decay per cycle over 1000 cycles). More impressively, an areal capacity of 9.9 mA h cm−2 can be achieved even under an extremely high sulfur loading of 14.7 mg cm−2 and a low electrolyte to sulfur ratio of 2.9 μL mg−1. This work provides an in-depth understanding of the interfacial catalytic effect of binary metal compound heterojunctions on sulfur reaction kinetics.

MoP nanoparticles dispersed on P, N co-doped graphite nanosheets as separator-modified material in high-loading lithium-sulfur batteries

The cruising range of lithium batteries in new energy vehicles became main issue, so lithium-sulfur batteries (LSBs) with high theoretical energy density are becoming great expectations. However, the polysulfide-shuttle behavior and slow redox kinetics of the electrochemical processes result in a fast capacity and cycle life fade in LSBs, especially at high sulfur loads. In this paper, MoP nanoparticles were dispersed on P, N co-doped graphitic nanosheets (MoP/PNC) by one-step high-temperature phosphating method, which as a separator-modified material achieved an excellent electrochemical performance. The initial discharge specific capacity can reach 1470 mAh g−1 at a current density of 0.2C and the capacity attenuation per cycle in 600 cycles is only 0.074% (1C). Surprisingly, LSBs with MoP/PNC -modified separator can deliver a high area capacity of 9.30 mAh cm−2 with a sulfur loading up to 7.43 mg cm−2 on the positive electrode. The above-mentioned excellent electrochemical performances benefited from the synergistic effects of strong catalytic conversion ability of MoP and the physical/chemical adsorption and catalytic capability of PNC, which resulted in low polysulfide permeability and high sulfur utilization.

Dual-Mediation pathways promote redox kinetics for High-Loading Lithium–Sulfur batteries under lean electrolyte

The high energy density (2500 Wh kg−1) makes that lithium–sulfur batteries (LSBs) have a great potential in energy storages. However, the practical application of LSBs is severely hampered by several inherent problems, including the sluggish sulfur redox kinetics, the shuttling of lithium polysulfides (LiPSs) and poor electronic conductivity. Although heterogeneous or homogeneous mediators could improve the cycling performance of LSBs to a certain extent, single mediators could not completely promote sulfur conversions, especially under high sulfur loading and lean electrolyte. Herein, dual-mediator systems consist of heterogeneous and homogeneous mediators that are introduced to address the above issues. Density functional theory (DFT) calculations and electrochemical analysis indicate that CoSe nanoparticles embedded in urchin-like nitrogen-doped porous carbon with in-situ growth of CNTs (CoSe@CNTs) as heterogeneous mediators and soluble CoCp2 as homogeneous mediators could effectively accelerate the bidirectional conversion kinetics of liquid LiPSs ↔ solid Li2S through the synergistic effect. As a consequence, the cell with dual-mediators delivers a high initial specific capacity of 1005 mAh/g with a low attenuation rate of 0.045 % per cycle at a current density of 1.0C under sulfur loading of 2.8 mg cm−2 after 800cycles. Importantly, it still maintains a high areal capacity of 6.53 mAh cm−2 under lower electrolyte/sulfur ratio (E/S, 4.2 µL mg−1) and higher sulfur loading of 7.3 mg cm−2 over 100cycles at 0.1C.

Long-cycling and high-loading lithium-sulfur battery enabled by free-standing three-dimensional porous NiCo2O4 nanosheets

The lithium-sulfur (Li-S) battery is a promising electrochemical energy storage system with ultrahigh theoretical energy density and abundant raw material, however, issues of “shuttle effect”, low sulfur utilization and dendrite of lithium anode restrict its wide applications. Herein, hierarchical porous NiCo2O4 nanosheets anchored on carbon cloth framework (NCO-CC) have been prepared and applied as highly efficient sulfur host for Li-S battery. NiCo2O4 nanosheets are composed of interconnected nanoparticles and mesopores of about 300–600 nm. The porous NCO-CC can offer adequate space to increase sulfur loading and relieve the volumetric change during charge/discharge processes, and provide strong chemisorption for trapping lithium polysulfides, to effectively increase utilization and redox kinetics. The three-dimensional conductive carbon cloth substrate can be directly used as current collector, and the free-standing cathode without any carbon black and binder displays high specific capacities of 1275.1 and 732.1 mAh/g at respectively 0.1 and 5 C, and a low capacity decay rate (∼0.022 %/cycle) over 1500 cycles at 2 C. The novel porous NiCo2O4 nanosheet based sulfur cathode is promising to construct highly efficient and long cycling Li-S battery, and the rational design of flexible CC based hierarchical porous composites might be extended for various applications of energy and catalysis.

A ductile and strong-affinity network binder coupling inorganic oligomers and biopolymers for high-loading lithium-sulfur batteries.

Lithium sulfur (Li-S) batteries have become the predominant energy storage devices of the future. However, the reasons why Li-S batteries have not been widely commercialized include the shuttle effect of polysulfides and the volume expansion of sulfur active substances. In this study, a binder with a stretchable 3D reticular structure was induced using inorganic oligomers. Potassium tripolyphosphate (PTP) has been used to powerfully connect the tamarind seed gum (TSG) chain through robust intermolecular forces due to the strong electronegativity of P-O- groups. With this binder, the volume expansion of sulfur active substances can be well restrained. In addition, a large amount of -OH groups in TSG and P-O- bonds in PTP can also effectively adsorb polysulfides and inhibit the shuttle effect. Therefore, the S@TSG-PTP electrode shows an improved cycle performance. When the sulfur loading is as high as 4.29 mg cm-2, the areal specific capacity can reach 3.37 mA h cm-2 after 70 cycles. This study highlights a new way for the binder design of high-loading sulfur electrodes.

High Capacity Lithium-Sulfur Batteries (> 12 mAh cm–2) Enabled By 3D-Compact Sulfur Cathode and Polysulfide Adjoining Interface Engineering

Beyond the theoretical limitation of current Li-ion batteries technology, there have been large efforts to develop practical next-generation batteries. Among them, lithium-sulfur (Li-S) batteries have been eagerly studied due to their attractive features; the low cost and expected high energy density. To maximize the energy density of Li−S batteries, it is crucial to increase the loading level of sulfur cathode and minimize the electrolyte content. However, excessive amounts of lithium polysulfides (LiPSs) generated in the high loading Li-S batteries limit the stable cycling. In this study, a high-loading S cathode (15 mg cm−2) with a three-dimensional (3D) network structure is fabricated using a simple pelletizing method, and the exhausting overcharging phenomenon, which occurs in the high loading Li−S cell, is successively prevented by pre-treating the lithium metal anode. Moreover, adding a diluent to the electrolyte containing viscous LiPSs enables the facile conversion between S species during the cycling of high loading Li−S cells under lean electrolyte conditions. Finally, a prototype Li−S pouch cell with high energy density (427 Wh kg−1) was realized by combining a compacted 3D cathode with a high-loading, pretreated thin lithium metal and diluent-modified electrolyte. We believe that the results reported herein will be a good guideline to establish proper strategies to achieve high energy density Li−S batteries. Reference s : [1] J.-Y. Hwang, S. Shin, C. S. Yoon, Y.-K. Sun, ACS Energy Lett. 4 (2019) 2787–2795. [2] J.-Y. Hwang, S.-J. Park, C. S. Yoon, Y.-K. Sun, Energy Environ. Sci. 12 (2019) 2174–2784. [3] H. Kim, S. Bang, K.-J. Min, Y.-G. Ham, S.-J. Park and Y.-K. Sun, ACS Appl. Mater. Interfaces 13 (2021) 39435–39445.

Application of transition metal boride nanosheet as sulfur host in high loading Li-S batteries

Two-dimensional (2D) metal boride material (MBene) has aroused concern recently. However, the research and application exploration for MBene materials with more exposure sites are seriously restricted due to lack of suitable preparation methods. Herein, a kind of composites of monolayer MBene nanosheets and carbon nanotube (mono-MBene/CNT) is prepared through ice template method for the first time and applicated as a novel cathode host in high-loading lithium-sulfur (Li-S) batteries. Benefiting from multifunctional advantages of mono-MBene/CNT cathode including anchoring lithium polysulfides (LiPS), multiple functional sites and fast lithium-ion transport, the cells with S@mono-MBene/CNT cathode exhibit superior long-term cycling performance over 1000 cycles. Most notably, even if the sulfur loading is up to 15.28 mg cm−2, the cells with S@mono-MBene/CNT cathode deliver an initial area capacity of 12.73 mAh cm−2 and the capacity can also maintain at 11.07 mAh cm−2 after 120 cycles (86.96 % capacity retention) with current density of 21.80 mA cm−2, which is approximately 3 times higher than the capacity of commercial lithium-ion batteries. This work not only provides a guiding role in preparing monolayer MBene material, but also exhibits the application prospect for MBene material in the fields of energy storage.

Bifunctional binder enables controllable deposition of polysulfides for high-loading Li-S battery

Lithium-sulfur (Li-S) battery are regarded as a strong candidate for the next generation of high-performance battery due to its ultra-high capacity and low cost. However, severe shuttle effect of polysulfides (LiPSs) and the random deposition of lithium sulfide (Li2S) are vital challenges that impede the popularization of Li-S chemistry. Herein, inspired by charge-coordination interaction, a novel lithiophilic and sulfiphilic bifunctional polymer (LSBP) synthesized by in situ dynamic cross-linked is proposed to anchor LiPSs and enable controllable deposition of Li2S. The LSBP binder significantly improves the conversion reaction activity of LiPSs while the co-existence of lithiophilic (–COO-, -SO3-) and sulfiphilic (–NH2) sites effectively suppresses the shuttle of LiPSs, which is confirmed by in-situ time-resolved ultraviolet–visible (UV–vis) measurement. As a result, a high-loading (3.5 mgcm−2) and crack-free sulfur-based cathode with LSBP binder is achieved. Besides its stable cycling performance, the cathode exhibits an outstanding rate capacity under a high rate of 2.5C. This work proposes a scalable strategy to obtain practicable Li-S battery through the improvement in binder, which is inherently low-cost and environmentally friendly.

Nitrogen-doped hollow carbon boosting the anchoring of sulfur capacity for high-loading lithium–sulfur batteries

As one of the best candidates, lithium sulfur battery (Li–S) is extensively explored due to the high theoretical capacity and abundant sources of sulfur. Carbon-based materials take an important role as a host for sulfur in the cathode. In this paper, a nitrogen-doped hollow carbon for sulfur cathode (NHC–S) with high sulfur loading of 92% is studied for Li–S batteries. The structural characterization demonstrates that the N-doping can improve the graphitization of the hollow carbon material, which increases the electrical conductivity. The catalytic and deposition nucleation tests indicate that the N doping can increase the nucleation rate of Li 2 S, which is also illustrated by the larger binding energies of Li 2 S on N-doping substrates than on carbon via density functional theory (DFT) analysis. The initial specific capacity of NHC–S is 864.8 mAh g −1 at the current density of 0.2 C, and 460.8 mAh g −1 after 500 cycles. When the sulfur content loading was up to 2.8 mg cm −2 , the electrode material could achieve 85% capacity retention after 100 reversible cycles. • The sulfur loading of the Li–S batteries achieves 92% in the N-doped sample. • The improved graphitization by N doping accelerates the transportation of electrons. • The N-doped system promotes the redox reaction kinetics in Li–S batteries. • The initial specific capacity of NHC–S achieves 864.8 mAh g −1 at the current density of 0.2 C.

A flexible self-supporting ultralong MnO2 nanowires-expanded graphite nanosheets current collector with enhanced catalytic reaction kinetics for high-loading lithium-sulfur batteries

Owing to the shuttle effect of lithium polysulfides (LiPSs), poor conductivity and low loading mass of active sulfur, and its large volume expansion during cycling, these shortcomings still restrict practical application of high performance lithium-sulfur (Li-S) batteries. Herein, a stable flexible current collector, composed of ultralong MnO 2 nanowires and expanded graphite nanosheets (MnO 2 NW/EG) with high electronic conductivity, is combined with Li 2 S 6 to serve as a self-supporting cathode in Li-S batteries, in which the maximum loading mass of sulfur can be regulated to 7 mg cm −2 , the ultralong MnO 2 nanowires has the ability to accelerate the adsorption and catalytic conversion of LiPSs through the chemical action of the polar active surface and the good mechanical flexibility caused by the introduction of ultralong nanowires and nanosheets can buffer the large volume expansion of sulfur during charging/discharging. Moreover, Li-S batteries with MnO 2 NW/EG current collector still maintain a high capacity of 538 mAh g −1 after 500 cycles at 1 C and the capacity decay is only 1.2 mAh g −1 per cycle, even when the sulfur loading is 7 mg cm −2 , the capacity can be as high as 2.5 mAh cm −2 , indicating a practical application ability. • A stable flexible current collector is applied in Li-S batteries. • The loading mass of sulfur can be regulated to 7 mg cm −2 • The MnO 2 nanowires can accelerate the adsorption and catalytic conversion of LiPSs. • The cathode with high sulfur loading mass exhibits excellent cyclic stability.

Core–shell zeolite imidazole framework-derived ZnSe@CoSe2/C heterostructure enabling robust polysulfide adsorption and rapid Li+ diffusion in high-rate and high-loading lithium–sulfur batteries

Due to their remarkable energy density of 2600 Wh kg−1, light weight, and low cost, lithium–sulfur (Li–S) batteries find promising uses in such emerging transportation areas as large commercial vehicles, high-altitude pseudosatellites, electric passenger aircraft, and etc. However, several challenges including the shuttle effect and sluggish sulfur redox reaction hinder their availability. Herein, a catalytic interlayer (ZnSe@CoSe2/C@CC) integrated with the ZnSe@CoSe2/C heterostructure, derived from well-designed core–shell zeolite imidazole frameworks, is proposed for Li–S batteries. On one hand, the ZnSe surface regulates dissolved polysulfides around the interlayer owing to its strong adsorption on polysulfides. On the other hand, the conductive CoSe2 surface offers fast lithium-ion diffusion paths to accelerate the polysulfide conversion. Through their respective advantages, both ZnSe and CoSe2 could makeaconcertedefforttofacilitate a smooth adsorption-diffusion-catalytic conversion process of polysulfides and guide the 3D growth of lithium sulfides around their heterointerfaces. Therefore, a high initial capacity of 1041.9 mAh g−1 at 0.5C and stable cycling performance with a high capacity retention of 70% over 550 cycles at 5C are achieved by the Li–S cells containing ZnSe@CoSe2/C@CC. Under a high sulfur loading of 8.2 mg cm−2 with a sulfur content of 85%, the high areal capacity and impressive capacity retention could also be obtained in the ZnSe@CoSe2/C@CC-based cell. We believe that the heterostructure arming itself with robust polysulfide adsorption and rapid surface ion diffusion might also find potential uses for other rechargeable metal (Na, Mg, Al, Ca, etc.)–sulfur batteries.

Defects Engineering of Lightweight Metal-Organic Frameworks-Based Electrocatalytic Membrane for High-Loading Lithium-Sulfur Batteries.

The sluggish kinetics and shuttle effect of lithium polysulfide intermediates are the major issues that retard the practical applications of lithium-sulfur (Li-S) batteries. Herein, we introduce a defect engineering strategy to construct a defected-UiO-66-NH2-4/graphene electrocatalytic membrane (D-UiO-66-NH2-4/G EM) which could accelerate the conversion of lithium polysulfides in high sulfur loadings and low electrolyte/sulfur (E/S) ratio Li-S batteries. Metal-organic frameworks (UiO-66-NH2) can be directionally chemical engraved to form concave octahedra with abundant defects. According to electrocatalytic kinetics and DFT calculations studies, the D-UiO-66-NH2-4 architecture effectively provides ample sites to capture polysulfides via strong chemical affinity and effectively delivers electrocatalytic activity of polysulfide conversion. As a result, a Li-S battery with such an electrocatalytic membrane delivers a high capacity of 12.3 mAh cm-2 (1013 mAh g-1) at a sulfur loading up to 12.2 mg·S cm-2 under a lean electrolyte condition (E/S = 5 μL mg-1-sulfur) at 2.1 mA cm-2 (0.1 C). Moreover, a prototype soft package battery also exhibits excellent cycling stability with a maintained capacity of 996 mAh g-1 upon 100 cycles.

Vanadium Monoxide-Based Free-Standing Nanofiber Hosts for High-Loading Lithium-Sulfur Batteries

We report the fabrication of free-standing vanadium monoxide-based carbon nanofiber/sulfur (VO-CNFs/S) cathodes via electrospinning and in situ carbothermal reduction reaction followed by sulfur impregnation using an ultrarapid (<90 s) hybrid solution/melt deposition technique. The assembled Li-S batteries using VO-CNFs/S cathodes delivered a stable capacity of 950 mAh·g–1 with 97% retention after 200 cycles at a 0.5 C rate with a moderate electrolyte/sulfur ratio of 20 mL·g–1 of sulfur. Additionally, we develop cathodes with a high sulfur loading of 8.32 mg·cm–2 that exhibits a stable capacity of 900 mAh·g–1 after a few cycles with near 100% retention over 100 cycles. These cells correspond to a stable aerial capacity of 7.5 mAh·cm–2. We integrate our fabrication and electrochemical performance study with fundamental investigations of Li+ diffusion kinetics, in situ visual monitoring of polysulfides, and ex situ post-mortem X-ray photoelectron spectroscopy study to elucidate polysulfide shuttling and polysulfide–host interactions. The unique integration of oxide and nitride groups in this work results in a synergistic effect of strong Lewis acid–base interactions originating from the vacant d-orbitals of the vanadium monoxide phase and improved conductivity originating from the nitrogen doping in CNFs from a polymeric precursor, thus offering active sites for strong polysulfide binding as well as faster reaction kinetics.