Zeitschriftenartikel zum Thema „Nano-Li2S“

Lithium sulfide (Li2S) is considered to be the best potential substitution for sulfur-based cathodes due to its high theoretical specific capacity (1166 mAh g−1) and good compatibility with lithium metal-free anodes. However, the electrical insulation nature of Li2S and severe shuttling of lithium polysulfides lead to poor rate capability and cycling stability. Confining Li2S into polar conductive porous carbon is regarded as a promising strategy to solve these problems. In this work, N-doped porous carbon microspheres (NPCMs) derived from yeasts are designed and synthesized as a host to confine Li2S. Nano Li2S is successfully entered into the NPCMs’ pores to form N-doped porous carbon microspheres–Li2S composite (NPCMs–Li2S) by a typical liquid infiltration–evaporation method. NPCMs–Li2S not only delivers a high initial discharge capacity of 1077 mAh g−1 at 0.2 A g−1, but also displays good rate capability of 198 mAh g−1 at 5.0 A g−1 and long-term lifespan over 500 cycles. The improved cycling and high-rate performance of NPCMs–Li2S can be attributed to the NPCMs’ host, realizing the strong fixation of LiPSs and enhancing the electron and charge conduction of Li2S in NPCMs–Li2S cathodes.

NASICON-type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) is a remarkable solid-state electrolyte due to its high ionic conductivity and excellent air stability. However, the weak LAGP|Li interfacial compatibility (e.g., chemical instability of LAGP with Li metal and lithium dendrite growth) limits its practical application. Herein, an ultrathin CuS layer was fabricated on the surface of the LAGP electrolyte by magnetron sputtering (MS). Then, an in situ Li2S/Cu nano-layer formed via the conversion reaction between CuS and molten Li was constructed at the LAGP|Li interface. The Li2S/Cu nano-layer enables effective hindering of the reduction reactions of LAGP with Li metals and the suppression of lithium dendrite growth. The assembled Li symmetric battery with the Li2S/Cu@LAGP electrolyte shows a promising critical current density (CCD) of 0.6 mA cm−2 and a steady battery operation for over 700 h. Furthermore, the full LiFePO4 battery comprising the Li2S/Cu@LAGP electrolyte shows excellent capacity retention of 94.5% after 100 cycles, providing an appropriate interface modification strategy for all-solid-state Li metal batteries.

Abstract Lithium–sulfur (Li–S) batteries, regarded as one of the most promising alternatives to current state-of-the-art rechargeable Li-ion battery technologies, have received tremendous attention as potential candidates for next-generation portable electronics and the rapidly advancing electric vehicle market. However, substantial capacity decay, miserable cycle life, and meagre stability remain critical challenges. More specifically, shuttling of polysulfide (Li2S x (3 < x ⩽ 8)) species severely hinders the cycle performance resulting in capacity fade and cycling instability. In the present work, a highly conducting three-dimensional (3D) carbon nanofiber (CNF) foam has been synthesized using the lyophilization method followed by thermal pyrolysis. The highly porous foam materials have a bimodal porosity distribution in the nano and micro regime and were successfully investigated to serve as a potential host for sulfur species intended for Li–S battery application. 3D x-ray microtomography was employed to estimate the nature of sulfur impregnation and distribution in the 3D porous networks. On utilizing the final product as cathode material, sulfur impregnated carbonized CNF foam and modified the separator with functionalized multiwalled carbon nanotubes delivered a specific capacity of ∼845 mAh g−1 at 100 mA g−1.

Flow battery innovations should offer significant improvements in performance, without compromising the durability / lifetime, and be cost-effective and scalable. The presentation will review some of the progress that has been made to enhance flow battery performance, and will discuss a number of recent innovations that aim to deliver these characteristics. These will include: Magnetic flowable electrodes applied in a polysulfide-iodide flow battery. Using flow through the current feeder to enhance mass transport and enable dendrite free zinc deposition in the zinc-iodide flow battery. Graphene modified membrane for enhanced power density. Flowable electrodes have emerged as a novel concept for high energy density batteries. To date, in most cases the flowable solid phase includes a redox active energy storage material, for example in zinc-nickel, sodium-sulfur, and lithium-sulfur systems [1-3]. In contrast, we have demonstrated the use of a carbon – magnetite nanocomposite which acts as an electrocatalyst but is not redox active [4,5]. This nanomaterial can be dispersed in the electrolyte and circulated through the battery to enhance the performance of a conventional static electrode. The magnetic characteristics of the nanocomposite can also be exploited, by using a magnetic field to assemble a high surface area electrode comprising a percolating network of the nanomaterial on the current feeder. The electrode also can be removed by releasing the magnetic field at the current feeder, and after being washed out of the cell the nanocomposite can be separated in a magnetic field. This enables replacement of the active electrode without the need to dismantle the cell. Zinc-iodide flow batteries offer high energy density due to the high aqueous solubility of the ZnI2. However, the power density that can be achieved is limited by potential for the dendritic growth of zinc deposits, and as zinc metal builds up in the cell the areal capacity is limited. We have found that by drawing some of the electrolyte through the current feeder, improved performance can be obtained [6]. This enables operation at higher power density and the denser uniform deposit should enable increased areal capacity. We attempted to reduce crossover in the all-vanadium redox flow battery by using a graphene modified nafion membrane. However, we found that the addition of the graphene reduced the losses in the battery and enabling a significant increase in the power density and discharge capacity. Currently we are working to optimize and scale up the membrane modification process, and to explore the mechanism of performance enhancement. References G. Zhu et al. (2020) High-energy and high-power Zn–Ni flow batteries with semi-solid electrodes. Sustainable Energy Fuels, 4, 4076-4085. Yang et al. (2018) Sodium–Sulfur Flow Battery for Low-Cost Electrical Storage. Advanced Energy Materials, 11, 1711991. Suo et al. (2015) Carbon cage encapsulating nano-cluster Li2S by ionic liquid polymerization and pyrolysis for high performance Li–S batteries. Nano Energy, 13, 467-473. Rahimi, A.M. Dehkordi, E.P.L. Roberts (2021) Magnetic nanofluidic electrolyte for enhancing the performance of polysulfide/iodide redox flow batteries. Electrochimica Acta, 309, 137687. Rahimi, A.M. Dehkordi, H. Gharibi, E.P.L. Roberts (2021) Novel Magnetic Flowable Electrode for Redox Flow Batteries: A Polysulfide/Iodide Case Study. Ind. Eng. Chem. Res., 60, 824-841. F. ShakeriHosseinabad et al. (2021) Influence of Flow Field Design on Zinc Deposition and Performance in a Zinc-Iodide Flow Battery. ACS Applied Mat. & Interfa

Lithium-sulfur (Li-S) batteries are one of the promising alternatives to modern Lithium-ion Battery (LIB) technology due to their superior specific energy density, which can satisfy the emerging needs of advanced energy storage applications such as electric vehicles and grid-scale energy storage and delivery. However, achieving this high specific energy density is hampered by several challenges inherent to the properties of sulfur and its discharge products. One major issue is related to the insulating nature of S and its fully discharged product (Li2S), which often leads to low utilization of the active material and poor rate capability. The poor electronic conductivity of these species can be overcome by utilizing conductive hosts, though they are dilutive and decrease the energy density, meaning that their mass ratio to the active material should be as low as possible [1]. Another crucial issue relates to the undesired solubility of certain sulfur discharge products, so-called long-chain Li polysulfides (LiPSs), in the conventional ether-based liquid electrolyte. The solubility of long-chain LiPSs promotes their free back-and-forth transport between the positive and negative electrodes, which results in poor cyclability and capacity decay [2, 3]. Despite the efforts to engineer and control the undesired LiPSs shuttling effect, advances have been mostly limited to a small number of cycles (100-200), or the need for complex and often expensive synthesis that has limited the rational development of new sulfur cathodes. At present, a large majority of the sulfur cathode research has focused on nano-architectured electrodes using 2D and 3D host materials for sulfur, such as carbon nanotubes, graphene, conductive scaffolds, yolk-shell structures, and the like, to increase the conductivity and alleviate the LiPSs shuttling [4]. Although these approaches have helped to increase the achievable capacity, and sometimes the cyclability, their synthesis methods have been highly complex, meaning that their manufacturing cost will be high. Also, in operating cells, it is highly unlikely that these complex structures can be effectively reproduced upon many charge-discharge cycles – meaning that capacity loss is essentially inevitable. Thus, developing novel, yet affordable and scalable, cathode architectures that can enhance the rapid transport of Li-ions to active sites for electrode reactions, accommodate discharge-induced volume expansion, and minimize the shuttling mechanism by sulfur encapsulation are still in great need. In this work, we present a low-cost and scalable processing method for highly durable sulfur cathodes containing commercial sulfur, carbon black, and polyvinylidene fluoride (PVDF). The sulfur cathode slurry was prepared through a simple and scalable recipe where the degree of binder dissolution into the solvent was controlled before electrode deposition. Variables such as the solvent:binder ratio, dissolution time, and agitation will be discussed. The microstructure of the sulfur cathodes was characterized using scanning electron microscopy. Through controlled dissolution of binder, a porous, swollen network of binder was achieved that adhered the sulfur and carbon particles while providing a highly porous structure that can accommodate the sulfur volume expansion during discharge and impede dissolution of the discharge products into the electrolyte by physically trapping them. The cycling performance of the sulfur cathodes prepared through the present novel processing was tested at C/10 and compared with those prepared through the conventional production techniques. The sulfur cathodes prepared with this novel electrode processing offered impressive capacity retention of 80% after 1000 cycles suggesting a considerable improvement in the shuttling effect and active material preservation. These results are expected to help move the production and manufacturing of Li-S batteries forward. References -J. Lee, T.-H. Kang, H.-Y. Lee, J. S. Samdani, Y. Jung, C. Zhang, Z. Yu, G.-L. Xu, L. Cheng, S. Byun et al., Advanced Energy Materials, vol. 10, no. 22, p. 1903934, 2020. Yang, G. Zheng, and Y. Cui, Chemical Society Reviews, vol. 42, no. 7, pp. 3018–3032, 2013. She, Y. Sun, Q. Zhang, and Y. Cui., Chemical society reviews, vol. 45, no. 20, pp. 5605-5634, 2016. Zhou, D. L. Danilov, R.-A. Eichel, and P. H. L. Notten, Advanced Energy Materials, vol. 1, p. 2001304, 2020.

We face an immediate need for more energy-dense batteries that are stable over long-term cycling, to address the increased electrification of the transportation sector. All-solid state batteries (ASSBs) that combine a solid-state electrolyte with a Li metal anode offer the potential to achieve this objective by replacing intercalation anodes such as graphite with Li metal. However, interfacial degradation at the Li | solid electrolyte interface currently compromises the safety and cycling stability of ASSBs [1]. This interfacial degradation is usually a combination of instabilities of mechanical, chemical or electrochemical origin. This in turn compromises the structural and morphological stability of ASSBs over cycling, causing them to fail in fewer cycles than required for implementation as next-generation batteries in automobiles [2]. Thus, in order to improve their cycling stability, the understanding of the origin and nature of these interfacial instabilities needs to be multimodal, to understand the interplay between the different degradation mechanisms. Argyrodite (Li6PS5Cl) is a particularly attractive solid-state electrolyte (SSE) due to a high ionic conductivity (comparable to liquid electrolytes), as well as potential for batch processing [3]. However, its brittle nature and chemical composition makes it susceptible to cracking and deleterious side reactions, which hamper its stability. This work will focus on elucidating the effect of (1) current density and (2) processing conditions on the cycling stability of Li | LPSCl | Li ASSBs. We use 4-D XRD-CT (X-ray diffraction computed tomography) combined with phase contrast micro-computed tomography (μCT) to conduct the multimodal investigation of interfacial degradation, under pseudo operando conditions. The methodology is to obtain a 3-D XRDCT scan around the interface in a particular cycled condition, followed by a higher-resolution 3D μCT scan on the same region. This sequence is repeated after every stripping/plating cycle, starting from the pristine cell up to cell failure. These experiments are conducted at a synchrotron source, to enable the acquisition at high spatial resolution (~5 μm) over large volumes (~mm3), in a reasonable amount of time. A standard swagelok-style cell is used for repeatability of results and optimal geometry for conducting tomography. XRD-CT can furnish quantitative phase maps of all phases (argyrodite and reaction by-products), as well as the elastic strain in the sample. The μCT on the other hand gives information on the evolution of morphology around the interface with cycling (cracks/voids). Thus, by correlating the two datasets together over cycling, we are able to connect mechanical instabilities to the chemical/electrochemical instabilities. Here, we focus on varying two specific processing parameters for argyrodite: the sintering temperature and pressure, and studying their effect on nucleation and propagation of interfacial instabilities over repeated cycling. Through cycling, we track the evolution of cracks/voids, chemical by-products such as LiCl, Li3P and Li2S using XRD-CT and μCT. Finally, we track the filling of metallic Li into certain cracks in dendritic form, which leads to shorting and failure of the cell. We find that both of these parameters heavily influence the behavior of the interface, with cells failing between 4-20 cycles, and a marked difference in how the degradation initiates and propagates. Finally, for the processing condition that shows the best cycling behavior, we do a C-rate study, by increasing the current density for plating/stripping with each cycle up to failure. This discusses the utility of a parameter such as critical current density for a cell, where the local current densities are very heterogeneous and different from the global current reading while cycling. We envisage these results being used as inputs into modeling studies to optimize strategies for interfacial stabilization in ASSBs going forward. [1] Paul, P. P. et al. Interfaces in all solid state Li-metal batteries: a review on instabilities, stabilization strategies, and scalability. Energy Storage Materials 2022, 45, 969-1001. [2] Hao, S. et al. Tracking lithium penetration in solid electrolytes in 3D by in-situ synchrotron X-ray computed tomography. Nano Energy 2021, 82, 105744. [3] Chen, Y-T. et al., Investigating dry room compatibility of sulfide solid-state electrolytes for scalable manufacturing, Journal of Materials Chemistry A 2022, 10, 7155-7164.

The chemical composition and structure of the solid electrolyte interphase (SEI) are two of the key factors that determine the reversibility of lithium-metal (Li) anodes for next-generation batteries. As a result, much of the research aimed at enabling practical Li-metal batteries emphasizes tuning SEI composition, either via electrolyte formulation1–5 or synthesis of artificial SEIs.6–8 Ideally, the lithium SEI should minimize parasitic side reactions by effectively passivating Li while also promoting facile conduction of lithium ions (Li+). To do this, SEI materials must have high (electro)chemical stability, be ionically conductive, and be sufficiently mechanically robust to accommodate substantial volume changes. However, studying these properties in bulk-scale materials often yields values that diverge by orders of magnitude from those observed in SEIs. For example, typical SEI ionic conductivities lie in the range of 10-7-10-9 S cm-1, yet bulk ionic conductivity measurements of relevant materials such as lithium carbonate, lithium fluoride, and lithium oxide ranges from 10-18 and 10-10 S cm-1.9 Our group has developed a technique to directly study these materials at realistic length scales by synthesizing model interphases through the reaction of gases with Li.10,11 Our previous work on Li2O and LiF revealed that Li2O is a better Li+ conductor than LiF (~1 x 10-9 S cm-1 vs ~5.2 x 10-10 S cm-1),11 and that these species’ chemical stability varies substantially in different electrolytes.12 One of the remaining key SEI materials is lithium carbonate, which has been proposed to act as a metastable phase in the outer portion of the SEI.13 In this work, we have developed a technique to synthesize Li2CO3 films via sequential reaction of oxygen and carbon dioxide with clean lithium surfaces. Using scanning electron microscopy and air-exposure tests, we can confirm that these films are conformal and generally pinhole-free. Titration gas chromatography (TGC)14 was used to quantify relative proportions of lithium carbonate, metallic lithium, and lithium carbide, and X-ray photoelectron spectroscopy (XPS) offers insights into how composition changes across the depth of the film. These films were then used as a platform to further investigate the reactivity of Li2CO3 with different electrolytes, comparing carbonates versus ethers and varying the lithium salt used. Electrochemical impedance spectroscopy (EIS) offers insights into the evolution of transport properties at these interphases, while electrolyte soak tests coupled with gas chromatography of gas-phase products and TGC of solid-phase products can track their chemical evolution. Taken together, this work illuminates how lithium carbonate may evolve during battery cycling, offering perspective that can help guide future design of Li-metal SEIs. References Liu, Y. et al. Solubility-mediated sustained release enabling nitrate additive in carbonate electrolytes for stable lithium metal anode. Nat. Commun. 1–10 (2018). Suo, L. et al. Fluorine-donating electrolytes enable highly reversible 5-V-class Li metal batteries. Proc. Natl. Acad. Sci. 115, 1156–1161 (2018). Chae, O. B., Adiraju, V. A. K. & Lucht, B. L. Lithium Cyano Tris(2,2,2-trifluoroethyl) Borate as a Multifunctional Electrolyte Additive for High-Performance Lithium Metal Batteries. ACS Energy Lett. 6, 3851–3857 (2021). Li, Y. et al. Correlating Structure and Function of Battery Interphases at Atomic Resolution Using Cryoelectron Microscopy. Joule 2, 2167–2177 (2018). Zhao, Q. et al. Upgrading Carbonate Electrolytes for Ultra‐stable Practical Lithium Metal Batteries. Angew. Chemie Int. Ed. 61, e2021162 (2021). Zhao, J. et al. Surface Fluorination of Reactive Battery Anode Materials for Enhanced Stability. J. Am. Chem. Soc. 139, 11550–11558 (2017). Li, Y. et al. Robust Pinhole-free Li3N solid electrolyte grown from molten lithium. ACS Cent. Sci. 4, 97–104 (2018). Kozen, A. C. et al. Next-Generation Lithium Metal Anode Engineering via Atomic Layer Deposition. ACS Nano 9, 5884–5892 (2015). Lorger, S., Narita, K., Usiskin, R. & Maier Films of Li, J. Enhanced ion transport in Li2O and Li2S films. Chem. Commun 57, 6503–6506 (2021). He, M., Guo, R., Hobold, G. M., Gao, H. & Gallant, B. M. The intrinsic behavior of lithium fluoride in solid electrolyte interphases on lithium. PNAS 117, 73–79 (2020). Guo, R. & Gallant, B. M. Li 2 O Solid Electrolyte Interphase: Probing Transport Properties at the Chemical Potential of Lithium. Chem. Mater 32, 5525–5533 (2020). Guo, R., Wang, D., Zuin, L. & Gallant, B. M. Reactivity and Evolution of Ionic Phases in the Lithium Solid−Electrolyte Interphase. ACS Energy Lett. 877–885 (2021) doi:10.1021/acsenergylett.1c00117. Han, B. et al. Poor Stability of Li2CO3 in the Solid Electrolyte Interphase of a Lithium-Metal Anode Revealed by Cryo-Electron Microscopy. Adv. Mater. 33, 2100404 (2021). Hobold, G. M. & Gallant, B. M. Quantifying Capacity Loss Mechanisms of Li Metal Anodes beyond Inactive Li0. ACS Energy Lett. 4, 3458–3466 (2022).

AbstractThe 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.

AbstractTransition metal oxides, fluorides, and sulfides are extensively studied as candidate electrode materials for lithium‐ion batteries driven by the urgency of developing next‐generation higher energy density lithium batteries. These conversion‐type electrode materials often require nanosized active materials to enable a “smooth” lithiation and de‐lithiation process during charge/discharge cycles, determined by their size, structure, and phase. Herein, the structural and chemical changes of Copper Disulfide (CuS2) hollow nanoparticles during the lithiation process through an in situ transmission electron microscopy (TEM) method are investigated. The study finds the hollow structure of CuS2 facilitates the quick formation of fluidic Li2S “drops,” accompanied by a de‐sulfurization to the Cu7S4 phase. Meanwhile, the metallic Cu phase emerges as fine nanoparticles and grows into nano‐strips, which are embedded in the Li2S/Cu7S4 matrix. These complex nanostructured phases and their spatial distribution can lead to a low de‐lithiation barrier, enabling fast reaction kinetics.

AbstractElectrocatalysis is considered to be an effective method to solve the sluggish kinetics of lithium–sulfur batteries. However, a single catalyst cannot simultaneously catalyze multi‐step sulfur reductions. And once the catalyst surface is covered by the initially deposited solid products, the subsequent catalytic activity will significantly deteriorate. Here, microporous ZIF‐67 and its derivative nano‐metallic Co0 are used as dual‐catalyst aiming to address these drawbacks. The dual catalytic center effectively cooperates the adsorption and electron transfer for multi‐steps of sulfur reductions, transforming the potential‐limited step (Li2S4→Li2S2/Li2S) into a thermodynamic spontaneous reaction. ZIF‐67 first adsorbs soluble Li2S4 to form a coordination structure of ZIF‐Li2S4. Then nano‐metallic Co0 attracts uncoordinated S atoms in ZIF‐Li2S4 and facilitates the breaking of S–S bonds to form transient reductive ZIF‐Li2S2 and Co‐S2 via. spontaneous electron transfer. These intermediates facilitate continuous conversion to Li2S with reduced formation energy, which is beneficial to the regeneration of the catalyst. As a result, the cathode with ZIF@CNTs/Co@CNFs synergetic catalyst achieves initial areal capacity of 4.7 mAh cm−2 and maintains 3.5 mAh cm−2 at low electrolyte/sulfur ratio (E/S) of 5 µL mg−1. This study provides valuable guidance for improving the electrochemical performance of lithium–sulfur batteries through catalyst synergistic strategies for multi‐step reactions.

AbstractCommercialization of high energy density Lithium‐Sulfur (Li‐S) batteries is impeded by challenges such as polysulfide shuttling, sluggish reaction kinetics, and limited Li+ transport. Herein, a jigsaw‐inspired catalyst design strategy that involves in situ assembly of coherent nano‐heterocrystal ensembles (CNEs) to stabilize high‐activity crystal facets, enhance electron delocalization, and reduce associated energy barriers is proposed. On the catalyst surface, the stabilized high‐activity facets induce polysulfide aggregation. Simultaneously, the surrounded surface facets with enhanced activity promote Li2S deposition and Li+ diffusion, synergistically facilitating continuous and efficient sulfur redox. Experimental and DFT computations results reveal that the dual‐component hetero‐facet design alters the coordination of Nb atoms, enabling the redistribution of 3D orbital electrons at the Nb center and promoting d‐p hybridization with sulfur. The CNE, based on energy level gradient and lattice matching, endows maximum electron transfer to catalysts and establishes smooth pathways for ion diffusion. Encouragingly, the NbN‐NbC‐based pouch battery delivers a Weight energy density of 357 Wh kg−1, thereby demonstrating the practical application value of CNEs. This work unveils a novel paradigm for designing high‐performance catalysts, which has the potential to shape future research on electrocatalysts for energy storage applications.

Abstract The battery performance of sulfur cathode has obviously depended on the redox reaction kinetics of polysulfides upon cycling. Herein, an effective strategy was proposed to achieve the conversion from 2H (semiconductor phase) to 1T (metal phase) in hollow nano-flowered molybdenum selenide sphere (HFSMS) through crystal phase engineering. The HFSMS with different phase ratio was realized by regulating the proportion of reducing agents. Specifically, the 1T phase content can reach up to 60.8%, and then subsequently decreased to 59.1% with the further increase of the reducing agent. The as-prepared HFSMS with the 1T phase content of 60.8% showed a smallest Tafel slopes (49.99 and 79.65 mV/dec in reduction and oxidation process, respectively), fastest response time and highest response current (520 s, 0.459 mA in Li2S deposition test), which further exhibited excellent catalytic activity and faster reaction kinetics. This result was verified by electrochemical performance, which manifested as stable cycle life with only 0.112% capacity decay per cycle. It was found that the hollow structure can ensures a rich sulfur storage space, and effectually buffer the volume changes of the active substance. More importantly, the improved performance is attributed to the introduction of the 1T phase, which significantly improves the catalytic activity of MoSe2 with promoting the polysulfide conversion.