Commercial LiNi 0.5 Co 0.2 Mn 0.3 O 2 as an Efficient Bifunctional Separator Modifier for Lithium–Sulfur Batteries

Lithium sulfur (Li-S) battery is considered the next generation lithium ion batteries for energy storage. However, several issues have to be addressed before the full potential of Li-S battery can be realized. The intrinsically low electronic conductivity of sulfur renders incomplete material utilization; the dissolution of charge/discharge intermediates, lithium polysulfides, results in the shuttle phenomenon that leads to low a coulombic efficiency and fast capacity fading upon cycling; the 80% volume expansion of sulfur upon full lithiation changes the electrode structure and shortens battery cycle life. Magnéli phase Ti4O7 is known for its high electronic conductivity, which is as high as that of metal, and the polar nature of the compound allows strong chemisorption of lithium polysulfides onto Ti4O7 surface. In this study, Magnéli phase Ti4O7 nanotube array (Ti4O7 NTA) grown on a titanium nitride mesh is synthesized via anodization of titanium mesh followed by high-temperature reduction under a hydrogen atmosphere. The effect of the duration of the reduction reaction is investigated, and from X-ray diffraction patterns, a 45-minute reaction time generates a product that most closely resembles pure Magnéli phase Ti4O7. Sulfur is introduced inside the Ti4O7 NTA via electrodeposition followed by melt-infusion under vacuum. The electrodeposition of sulfur onto the free-standing Ti4O7 NTA electrode allows a precise control of the areal loading of sulfur, simply via adjusting the duration of electrodeposition under a constant current density of 20mA/cm2. A conductive carbon coating is applied onto the sulfur-incorporated Ti4O7 NTA mesh to further confine sulfur inside the Ti4O7 nanotubes. This produces a composite material of C-S-Ti4O7 The Ti4O7 NTA provides sulfur with a large electronically conductive and strong polysulfide-absorbing surface that facilitates the redox chemistry of sulfur. The NTA structure promises ample access of electrolyte to sulfur, and allows a high areal sulfur loading in the cathode. Excellent battery performance is obtained using this composite as the cathode material. Under a moderate sulfur loading in the range of 1.3~2.8mg/cm2, a high initial specific capacity (1604mAh/g at 0.05C), ultra-low capacity decay rates (0.0322% per cycle, Figure (a)) for 1800 cycles, and good rate capability (660mAh/g at 2C and 500mAh/g and 4C, Figure (b)) are achieved. Under a higher sulfur loading in the range of 3.5~4.8mg/cm2, stable cycling (capacity decay rates below 0.10% per cycle, Figure (c)) with very high values areal capacity (4.97mAh/cm2 at 0.05C, 3.82mAh/cm2 0.1C, and 2.74 mAh/cm2 at 0.2C) are obtained, making a high-volumetric-energy-density Li-S battery more practical. The low capacity decay rate and the high areal capacity in this study are among the best reported polar sulfur hosts such as graphitic carbon nitride C3N4, α-MnO2, MXene phase Ti2C, Co9S8, and Magnéli phase Ti4O7 nanoparticles. The interaction between Magnéli phase Ti4O7 and lithium polysulfides is investigated via X-ray photoelectron spectroscopy. It is discovered that the interaction is of a redox nature, where titanium atoms on Ti4O7 NTA are partially reduced while sulfur atoms in lithium polysulfides are partially oxidized with peaks corresponding to sulfate and sulfite becoming more dominant when lithium polysulfides are in contact with Ti4O7 NTA. The positive effects of Ti4O7 NTA and those of carbon coating are studied via cyclic voltammetry and electrochemical impedance spectroscopy. It is found that the Ti4O7 NTA decreases the charge transfer resistance of the Li-S cell, and that the carbon coating produces a stable cycling performance through gradually decreasing polarization as reflected by a lowering of overpotential during charge and discharge. Figure 1

Lithium-sulfur (Li-S) batteries are well knowned as one of the promising energy applications with high specific capacity, such as electric vehicles and energy storage system, owing to their high theoretical capacity of 1672 mA h g−1, eco friendliness, and the abundance all over the world. However, Li-S batteries have some challenge, such as the poor Coulombic efficiency, fast capacity fading, and unstable cycle performance by the dissolution of lithium polysulfides (LiPSs) in the electrolyte by shuttle mechanism during long cycling. To challenge these problems, we suggest that P, O, and N co-doped hollow carbons with graphene from LiFePO4 nanoparticles are very efficient as sulfur hosts for Li-S batteries. This sample from LiFePO4 nanoparticles provides sufficient spaces with the variety of pore sizes for storage of sulfur and various heteroatoms doping to minimize the dissolution of the LiPSs. This sample can block the dissolution of LiPSs due to the efficient hosts and the excellent chemical affinity with LiPSs. Its electrode indicates the very stable cycle performance and high rate capability, as proved by LiPSs adsorption test. We suggest that this sample has high potential as a sulfur host for real application in Li-S batteries with more optimization.

Lithium-Sulfur batteries have been intensively studied as a power source of the electric transportation and energy storage system for renewable energy due to their high theoretical capacity of 1675 mAh g-1 and relatively inexpensive raw materials than commercial lithium ion batteries.1 To introduce lithium sulfur batteries to commercial market, there are some drawbacks to be solved. The major problems of lithium sulfur batteries are low active material utilization, severe capacity decay and low coulombic efficiency. Several successive approaches have been adopted to develop practical lithium sulfur batteries either by selecting electrolyte more adequate than conventional carbonate solutions, such as 1,3 dioxolane (DOL), dimethyl ether (DME), and tetraethylene glycol dimethyl ether (TEGDME), or by the addition of soluble polysulfides.2–7 On sulfur cathode side, modification of morphology of active materials have been studied by mixing conductive carbons with sulfur particles, encapsulating sulfur into porous carbon matrix and conductive polymer coating on the surface of active materials. These approaches have led to the development of lithium–sulfur battery with improved cycle life and rate capability. However these progresses of lithium sulfur batteries have not satisfied requirements of commercialization. These lithium sulfur batteries are still suffered from the problem of the solubility of the polysulfides. Recentely, Tarascon and co-workers8 and Zhang and Read reported noticeable achievement by addition soluble lithium polysulfide into the electrolyte.7 In this work, we studied the electrochemical and physical effect of the Li2S8 polysulfide additive diminishing the dissolution of the sulfur cathode and small participation in redox reaction as a dissolved cathode.7, 8 We demonstrated intentionally dissolved Li2S8 polysulfides in the electrolyte suppress polysulfide dissolution from the sulfur cathode by controlling its concentration according to Le Chatelier’s principle. Li2S8 polysulfide additives was deposited on the cathode as sulfur on charging to compensate eventual capacity losses that result from partial cathode dissolution during discharge.2– 8 Fig. 1 shows the cycling performance and efficiency of a mesoporous carbon-sulfur electrode in a lithium cell using the TEGDME–LiCF3SO3 electrolyte with addition of 5 wt% Li2S8. The cell cycled at 20 ℃ shows a small initial capacity decay, that is, from 1650 to 1500 mAh g-1s, followed by a stable trend with an acceptable, minor capacity decay, that is, from 1500 to about 1200 mAh g-1 Sover 50 cycles, with a coulombic efficiency approaching 95%.

Lithium-Sulfur (Li-S) batteries are among the popular candidates for next-generation rechargeable energy storage devices due to their high specific capacity and superior energy storage capabilities. However, commercialization of Li-S batteries has been hindered by several challenges such as the insulating nature of sulfur, and the shuttling of soluble lithium polysulfides and accumulation of insulating deposits on the electrodes – leading to capacity degradation over extended cycling1.Several research efforts have been devoted to mitigating these challenges. Among the different approaches, many studies focus on addressing the poor conductivity of sulfur and lithium polysulfide shuttling simultaneously by developing conductive carbon hosts2,3. While improvements have been achieved in the development of host structures with better electronic conductivity and improved polysulfide trapping capability, many of those structures have advanced architectures that demand complex processing, expensive precursors, and often lower gravimetric sulfur loading (<70 wt%).This leads to expensive-to-produce electrodes that have lower true energy density than desired. What is needed are simple preparation methods that address the issues discussed above without overly complicated processing, and preferably already commercialized materials.In this work, we systematically investigate the effect of different electrode components, including various common carbons and polymeric binders. The effect of carbon type and loading is discussed. The effect of solvent to binder ratio in the electrode slurry preparation is also studied. By tuning the binder composition, types of conductive carbon black, and the amount of solvent, we observed a difference in the structure of the host medium and consequently the sulfur electrode. Specifically, a shell covering surrounding the sulfur particles was observed at low solvent/binder ratio. Increasing the solvent/binder ratio led to the disappearance of the shell coverings and particle agglomeration, which resulted in lower achieved capacity and reduced cycle life. Ketjen black offered the highest specific capacity, while the presence of shell covering achieved at a low solvent/binder ratio was found necessary for cycling stability.This work demonstrates the importance of electrode processing parameters on the structure and electrochemical performance of sulfur cathode in Li-S batteries. The new understandings from this work can provide guidance on electrode designs to achieve Li-S batteries with enhanced capacity and longevity.References G. Li et al., Adv. Mater., 30, 1705590 (2018).D.-W. Wang et al., J. Mater. Chem. A, 1, 9382 (2013).Y. Li and S. Guo, Matter, 4, 1142–1188 (2021).

Lithium-sulfur (Li-S) batteries are considered a prospective energy storage system because of their high theoretical specific capacity and high energy density, whereas Li-S batteries still face many serious challenges on the road to commercialization, including the shuttle effect of lithium polysulfides (LiPSs), their insulating nature, the volume change of the active materials during the charge-discharge process, and the tardy sulfur redox kinetics. In this work, double transition metal oxide TiNb2O7 (TNO) nanometer particles are tactfully deposited on the surface of an activated carbon cloth (ACC), activating the surface through a hydrothermal reaction and high-temperature calcination and finally forming the flexible self-supporting architecture as an effective catalyst for sulfur conversion reaction. It has been found that ACC@TNO possesses many catalytic activity sites, which can inhibit the shuttle effect of LiPSs and increase the Coulombic efficiency by boosting the redox reaction kinetics of LiPS transformation reaction. As a consequence, the ACC@TNO/S cathode exhibits an impressive electrochemical performance, including a high initial discharge capacity of 885 mAh g-1 at a high rate of 1 C, a high discharge specific capacity of 825 mAh g-1 after 200 cycles with a prominent capacity retention rate of 93%, and a small decay rate of 0.034% per cycle. Although TNO is extensively used in the fields of lithium ion batteries and other rechargeable batteries, it is first introduced as sulfur host materials to boost the redox reaction kinetics of the LiPS transformation reaction and increase the electrochemical performance of Li-S batteries. Therefore, studies of the synergistic effect on the chemical absorption and catalytic conversion effect of TNO for LiPSs of Li-S batteries provide a good strategy for boosting further the comprehensive electrochemical performances of Li-S batteries.

Rechargeable lithium-sulfur (Li-S) batteries have gathered widespread attention due to their high theoretical energy density and the abundance of sulfur. However, the practical application of Li-S batteries has been hindered by issues including low electronic conductivity of sulfur, sluggish redox kinetics, and the notorious “shuttle effect,” which entails soluble lithium polysulfides (LiPSs) diffusing to the anode and causing corrosion. To address these problems, this work introduces an in-situ fabricated Mn2O3/β-MnO2 heterostructure electrocatalyst anchored on freestanding multi-walled carbon nanotube (MWCNT) films, further enhanced by the partial substitution of Mn sites with atomically dispersed Zr4+ cations. These Zr4+ species coordinate with oxygen to form Zr-Ox bonds toward newly generated electronic and structural environments that effectively optimize LiPSs adsorption energies and catalytic properties. Synchrotron-based X-ray absorption spectroscopy, transmission electron microscopy, and density functional theory calculations validate the formation of exclusive Zr-Ox coordination units (ZrO4/ZrO6) within the Mn2O3 and β-MnO2 domains. By introducing an appropriate concentration of Zr4+ species, this modified Mn2O3/β-MnO2 heterostructure achieves a balanced d-band center, facilitating strong yet not excessive LiPSs binding. This subtle tuning markedly reduces the overpotentials during sulfur redox reactions, enhances Li+ diffusivity, and boosts the sluggish transformation between Li2Sx intermediates and Li2S. Such synergistic effects further promote a three-dimensional Li2S nucleation mechanism for generating a more uniform Li2S deposition and preventing the formation of passivation surface that degrade cycling stability. Electrochemical tests emphasize the effectiveness of this approach. The Zr0.1-Mn2O3/β-MnO2@MWCNT cathode shows a high initial discharge capacity of 808.0 mAh g-1 at 1 C, retaining 67.5% of that capacity after 1000 cycles with a minimal decay rate of 0.068% per cycle. Even under a 5 C rate, it delivers 559.3 mAh g-1 and shows a low 0.170% decay rate through 200 cycles. Operando X-ray diffraction analysis also demonstrates that the Zr0.1-Mn2O3/β-MnO2@MWCNT cell could show rapid Li2S nucleation and efficient transformation kinetics, and the shuttle current measurements confirm the Zr0.1-Mn2O3/β-MnO2@MWCNT electrocatalyst could efficiently reduce LiPSs crossover and diminish anode corrosion. Consequently, the electrocatalyst-integrated cell demonstrates a high areal capacity in both half- and full-cell configurations (N/P ratio: 2.86), reaching 4.45/3.88 mAh cm-2 with a retention of 61.7%/70.1% over 110/50 cycles under a sulfur loading of 4.6/5.4 mg cm-2 and an electrolyte-to-sulfur (E/S) ratio of 8 μL mgsulfur -1. In summary, this work presents an atomically engineered heterostructure strategy to optimize polysulfide adsorption and conversion in Li-S systems. The incorporation of carefully tuned Zr4+ centers in the Mn2O3/β-MnO2 scaffold effectively addresses shuttle-related losses, boosts Li2S kinetics, and safeguards the Li metal anode. These results provide a promising avenue toward advanced Li-S batteries with high energy density, long lifespan, and favorable rate performance, bridging the gap between laboratory prototypes and real-world commercial applications. Figure 1

Engineering stable electrode-separator interfaces with ultrathin conductive polymer layer for high-energy-density Li-S batteries

Lithium-sulfur (Li‒S) batteries are regarded as highly promising next-generation energy storage technologies due to their high theoretical specific energy (2600 Wh kg^–1), low cost, and the abundance of sulfur. However, their practical application is severely hindered by the shuttle effect of soluble lithium polysulfides (LiPSs) and sluggish sulfur redox kinetics, leading to rapid capacity degradation. The inherent electronic structure of CoSe₂, employed as a catalyst, restricts its catalytic efficiency. This work proposed a synergistic strategy combining nickel doping and heterointerface engineering to modulate the electronic structure of CoSe₂ and enhance bidirectional sulfur electrochemistry. Combined structural characterization and density functional theory (DFT) calculations demonstrated that Ni doping induced lattice distortion in CoSe₂, forming shortened Ni‒Se bonds. This prompted a shift of the Co 3d band towards the Fermi level, thereby significantly enhancing the intrinsic conductivity of the material. Concurrently, lattice defects enhanced the availability of active sites for Li₂S nucleation. Augmented by the dual physical/chemical confinement of LiPSs provided by the N-doped carbon skeleton, this design established an “adsorption-catalysis” synergistic mechanism, effectively suppressing the shuttle effect and accelerating conversion kinetics. The fabricated Ni‒CoSe₂/NC-based Li‒S battery delivered a high initial specific capacity of 1219 mAh g^‒1 at 0.1C and maintained an ultralow capacity decay rate of 0.064% per cycle over 1000 cycles at 1C. Notably, the battery also exhibited exceptional cycling stability under lean electrolyte and high sulfur loading conditions. This study elucidated the enhancement mechanism through electronic structure modulation via integrated experimental and theoretical approaches, providing a novel design concept for advanced energy storage materials.

Engineering rare earth metal Ce-N coordination as catalyst for high redox kinetics in lithium-sulfur batteries

Exploring Advanced Polymeric Binders and Solid Electrolytes for Energy Storage Devices

Lithium ion batteries (LIBs) have been used in portable electronic devices due to high energy density, rechargeable characteristics, and tiny memory effect. However, advanced portable electronic device, electric vehicles (EVs), and large scale energy storage system (EES) require high specific capacity (energy density), light weight, and low cost LIBs. One of the important factors in determining the specific capacity of LIBs is the cathode active material. During the decades, general cathode active materials (lithium, cobalt, nickel, etc.) have some issue of rapid price rise as the demand increment for cathodic materials of EVs and EES. Especially, cobalt, which is the most essential cathode active material, the Democratic Republic of the Congo (DRC) accounts for more than 50% of the world's production. Cobalt supply is very unstable due to civil war in the DRC and exploitation of labor in the process of cobalt production. Therefore, a new cathode active material is necessary. Lithium sulfur (Li-S) batteries use an elemental sulfur as cathode and lithium metal as anode. The elemental sulfur is one of the most abundant materials on earth and has a high theoretical capacity. The theoretical capacity of 1675 mAh/g is up to seven times higher than that of LIBs. And elemental sulfur also has high theoretical gravimetric energy density of 2500 Wh/kg which is over four times higher than the ideal state of common LIBs. Additionally, sulfur is a stable and cost affordable material. Hence, the Li-S battery has attracted attention as a next-generation battery, and much researches have been reported. However, there are some problems that commercialization. The first problem is the dissolution of the polysulfide. The intermediate lithium polysulfides which was formed during the charge and discharge process are soluble in the typical organic electrolytes for LIBs. This phenomenon is called “polysulfide shuttle effect”. This leads to continuous cathode active material consumption, eventually the capacity is faded during cycle. The second problem is the safety and stability of the lithium metal used as the anode. Lithium metal surface control is a necessary step not only for the stability of Li metal anode, but also for a high capacity with a high coulombic efficiency. In this study, we developed poreless poly (vinylidene fluoride-co-hexafluoropropene) (PVdF-HFP) coated anodic aluminum oxide (PAAO) separator to blocking polysulfide shuttle effect and to control lithium metal interface. PAAO was prepared by coating PVdF-HFP solution on anodic aluminum oxide (AAO). AAO provides a highly ordered vertical pore structure and AAO has less tortuosity than conventional separator. The vertical pore structure of AAO evenly distributes the Li ion flux in battery system, so proposed separator effectively prevents the ununiformed growth of lithium. It is also mechanically, chemically, and thermally stable. The vertical aligned pores of AAO are filled with PVdF-HFP which has been used as gel polymer electrolyte, offer high lithium ion conductivity with conventional electrolyte. PVdF-HFP selectively passes lithium ions and effectively blocks dissolution of the polysulfide into the anode region. Consequently, the proposed system conserved high specific capacity with high coulombic efficiency during the cycle. Prepared PAAO showed high specific capacity (∼850 mAh/g, 0.2C), high coulombic efficiency (>98%), and long cycle life (>100 cycles, 0.5C). Reference polyethylene separator shoed low specific capacity (∼550 mAh/g, 0.2C), low coulombic efficiency (~95%) and fast capacity fade during cycle. Compared with a commercial polyethylene separator and bare AAO separator, PAAO separator showed better initial capacity, coulombic efficiency, and electrochemical stability. The suggested PAAO separator effectively block the polysulfide shuttle effect and improve the poor cyclability of the LI-S system. It suggests that this novel poreless separator can be a possible candidate of the powerful separator for LI-S batteries.

MOFs derived ZnSe/N-doped carbon nanosheets as multifunctional interlayers for ultralong-Life lithium-sulfur batteries

With the rapid development of portable devices and Energy Storage Systems (ESS), secondary batteries with high energy density and high capacity are in great demand. Among various candidates, Lithium-sulfur (Li-S) batteries have been considered for next-generation energy devices given their high theoretical capacity (1675 mAh g&lt;sup&gt;-1&lt;/sup&gt;) and energy density (2500 Wh kg&lt;sup&gt;-1&lt;/sup&gt;). However, the commercialization of Li-S batteries faces challenges due to sulfur’s low electrical conductivity and the shuttle effect, caused by the dissolution of lithium polysulfide intermediates in the electrolyte during the charge-discharge process. Herein, to resolve these problems, we report the fabrication of a vanadium dioxide (VO&lt;sub&gt;2&lt;/sub&gt;) composite via a simple hydrothermal method and optimize the structure of VO&lt;sub&gt;2&lt;/sub&gt; for constructing an effective Multi-Walled Carbon Nano Tube (MWCNT) and 3D flower-shaped VO&lt;sub&gt;2&lt;/sub&gt; (MWCNT@VO&lt;sub&gt;2&lt;/sub&gt;) binary sulfur host by a simple melt diffusion method. In particular, the polar VO&lt;sub&gt;2&lt;/sub&gt; composite not only physically absorbs the soluble lithium polysulfides but also has strong chemical bonds with a higher affinity for lithium polysulfides, which act as a catalyst, enhancing electrochemical reversibility. Additionally, MWCNT improves sulfur’s poor electrical conductivity and buffers volume expansion during cycling. The designed S-MWCNT@VO&lt;sub&gt;2&lt;/sub&gt; electrode also exhibits better capacity retention and cycling performance than a bare S-MWCNT electrode as a lithium polysulfide reservoir.

B/N co-doping rGO/BNNSs heterostructure with synergistic adsorption-electrocatalysis function enabling enhanced electrochemical performance of lithium-sulfur batteries

Asymmetric N-coordinated iron single-atom catalysts supported on graphitic carbon for polysulfide conversion in lithium-sulfur batteries