Novel Protection Strategies for Sulfur and Silicon in Advanced Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are regarded as one of the most promising next-generation energy storage technologies due to their high theoretical specific capacity, material abundance, and low production costs. Despite these advantages, the commercialization of Li-S batteries remains limited, primarily due to significant technical challenges,1-3 including the dissolution and shuttling of lithium polysulfides (PS), a major cause of fast capacity degradation over cycling in Li-S batteries. In our recent work,4 we introduced a novel sulfur cathode design comprising a thin film of nanolayer-polymer-coated carbons (NPC) deposited on sulfur electrodes (NPC-S). This advanced architecture enabled Li-S battery cells to achieve a high specific capacity of ~1,600 mAh/g, approaching sulfur's theoretical specific capacity, without introducing appreciable dead weight or volume to the battery.In this talk, we will present our continued efforts to further develop the advanced Li-S battery technology with the novel strategy of combining the NPC-S approach with a cycle-stabilizing and safety-enhancing approach in the advanced Li-S batteries. This synergistic strategy resulted in not only the near-theoretical specific capacity of sulfur (Figure 1a), but also a significantly improved long-term cycle stability, ~90% capacity retention after cycling at 1C rate for 500 charge-discharge cycles (Figure 1b). We will present various analytical characterizations and theoretical calculations to elucidate the reaction mechanisms of the outstanding performance of the advanced Li-S battery technology. Acknowledgment This work was supported by the Linda and Larry Pearson Endowed Chair at the Leslie A. Rose Department of Mechanical Engineering, South Dakota School of Mines & Technology, and the South Dakota Governor Research Center for Electrochemical Energy Storage. References Wang, S.; Wang, Z.; Chen, F.; Peng, B.; Xu, J.; Li, J.; Lv, Y.; Kang, Q.; Xia, A.; Ma, L. "Electrocatalysts in lithium-sulfur batteries". Nano Research 2023, 1-30.Zhao, F. L.; Xue, J. H.; Shao, W.; Yu, H.; Huang, W.; Xiao, J. "Toward high-sulfur-content, high-performance lithium-sulfur batteries: Review of materials and technologies". J Energy Chem 2023, 80, 625-657. DOI: 10.1016/j.jechem.2023.02.009.Hu, X.; Huang, T.; Zhang, G.; Lin, S.; Chen, R.; Chung, L.-H.; He, J. "Metal-organic framework-based catalysts for lithium-sulfur batteries.". Coordination Chemistry Reviews 2023, 475, 214879.Hasan, M. W.; Huynh, K.; Lama, B.; Razzaq, A. A.; Smdani, M. G.; Akter, F. N.; Maddipudi, B.; Shende, R.; Paudel, T. R.; Xing, W. "A Highly Effective Polysulfide-Trapping Approach for the Development of High Energy Density, Scalable Lithium-Sulfur Batteries". J Electrochem Soc 2024. DOI: 10.1149/1945-7111/ad3ebf. Figure 1

Lithium – sulfur (Li-S) battery, with highest predicted theoretical capacity of ~1675 mAh/g, is a promising technology meeting the demands of next-generation electric vehicles. Abundance of sulfur and environmental friendliness are major factors that make Li-S batteries interesting and important. However, Li-S battery is plagued by its own limitations, which include low electrical conductivity of pure sulfur cathode and loss of active material due to dissolution of intermediate polysulfides from the cathode during reduction reactions. These factors limit the performance of Li-S batteries. Developing superior cathode structures to mitigate these problems has been the major focus of research in recent times. Carbon-based materials such as fibers, nanospheres and nanotubes embedded with sulfur are being explored as cathodes for Li-S batteries. In particular, graphene, which has superior electrical conductivity and mechanical flexibility, has been studied as potential candidate for cathodes and cathode supports in Li-S batteries. However, economical synthesis of pure graphene is a major hurdle for their use in commercially-viable Li-S batteries. Graphene oxide – sulfur composite based structures are viable alternatives that could provide required electrical conductivity, based on the concentration of functional groups (epoxy and hydroxyl). Additionally, graphene oxides are believed to act like anchors to sulfur/polysulfides particles and help reduce their dissolution, leading to significantly improved performance of Li-S batteries. However, leveraging the advantages of enhanced electrical conductivity and reduced polysulfide shuttle requires tuning of the functional groups present in the graphene oxide. In an effort to determine the most favorable graphene oxide structure, we performed molecular dynamics (MD) simulations to calculate the mobility of polysulfide species in the vicinity of different graphene oxide structures with varying concentration of functional groups. Diffusion coefficients of polysulfides were calculated along the surface of these graphene oxide sheets using MD simulations. Initially graphene oxide sheets with pure epoxy and hydroxyl functional groups were simulated. Partial charge on carbon atoms in graphene oxide with epoxy and hydroxyl groups were evaluated from the optimized structures obtained using Density Functional Theory (DFT) calculations. Bond, angle and dihedral parameters along with partial charges on sulfur particles in polysulfides S8 2- were evaluated from the optimized structure using DFT. A standard electrolyte DME – DOL in 1:1 v/v ratio, modeled using OPLS force filed parameters, was used in all the MD simulations. The density of equilibrated solvent was within 5% of the experimental value. A system comprising graphene oxide solvated with electrolyte containing polysulfides was simulated at 300K. Overall charge neutrality of the system was maintained by incorporating counter ions, while using specific strategy to screen out long range electrostatic interactions between the polysulfides and counter ions. The surface diffusion coefficients of polysulfide was evaluated in the vicinity of graphene oxide and compared to that near pure graphene. Our simulations evaluated the effectiveness of various groups in reducing dissolution of polysulfides. The concentration of polysulfides in the vicinity of the graphene/graphene oxide structures tend to increase from graphene to graphene oxide with pure epoxy groups and maximizes for graphene oxide with pure hydroxyl functional groups. The relatively greater binding of polysulfides to graphene oxide structures leads to reduced surface diffusion coefficients for polysulfides on graphene oxide compared to that near graphene interfaces.

An effective strategy to tackle the twin crises of global deforestation and fossil fuel depletion is to recycle bio-mass materials for energy storage devices. Batteries have been proven to be the most effective electrochemical energy conversion and storage devices. As the most widely used battery system, lithium-ion (Li-ion) batteries have served our daily life and changed the world extensively in the past two decades. However, the potential of Li-ion battery system is approaching its limit and unable to fulfill diverse requirements. Among all possible candidates, lithium sulfur (Li-S) battery chemistry is considered to be one of the most promising next-generation, high energy density battery chemistries. The theoretical gravimetric capacity of this reaction is 1675 mAh g-1, and with the expected average voltage during discharge, the maximum energy density can be 2600 mWh g-1. However, how to build high-capacity and long-life span Li-S batteries via accessible and scalable methods is still questionable. Here we report a unique and innovative solution to capitalize on a currently overlooked resource to produce high-performance lithium-sulfur (Li-S) batteries from recycled paper. Common paper hardboard was peeled into long stripes and integrated with graphene oxide (GO) sheets by a capillary absorption method. The paper/GO hybrid was then activated at high temperature, forming activated paper carbon (APC)/graphene scaffold. The capillary absorbed GO sheets were homogeneously coated on the APC fibers and shrined geometrically during heating, forming nano sized bulges and pores, which remarkably improved sulfur loading and cathode conductivity. The recycled paper derived graphene Li-S battery exhibited superior life span of 620 cycles with an excellent capacity retention rate of 60.5%. More importantly, the APC/graphene/S stayed integral without pulverization even after such long cycling, indicating excellent mechanical robustness of cathode material. Since the malfunction of the battery can be ascribed to the anode, an activated paper carbon (APC) interlayer was sandwiched between the Li anode and the separator to suppress the degradation of Li anode by protecting the Li from unfavorable reactions, stretching the battery lifespan up to 980 cycles with a capacitance retention rate of 52.3% and improved rate ability. The capillary adsorption method and the porous anode interlayer configuration should find more applications in other porous bio-mass materials for energy storage devices. Figure 1

<p indent="0mm">The pursuit of next-generation energy storage systems has intensified research on lithium-sulfur (Li-S) batteries, which offer high energy density and low cost. However, the practical application of Li-S batteries is hindered by issues such as the shuttle effect, low electrical conductivity of sulfur, and large volume changes during cycling. Organic electrode materials possess advantages such as safety, environmental friendliness, sustainability, design flexibility, and low cost, making them promising cathode materials for high-capacity lithium batteries. Among them, organosulfur has received increasing attention with the development of lithium-sulfur batteries. Similar to sulfur cathodes, organosulfur electrodes can provide a relatively high theoretical capacity based on the reversible breaking and formation of S–S bonds. However, inherent problems such as poor conductivity, sluggish redox kinetics, unsatisfactory cycling stability, and the solubility of cycling products seriously hinder the development of organosulfur cathode materials. Doping heteroatoms into organosulfur molecules to design and synthesize new organosulfur molecules is an effective strategy to improve the performance of organic sulfur cathodes. Heteroatom doping offers a versatile method to modify the electronic structure and chemical reactivity of organosulfur cathodes. By introducing elements such as oxygen (O), nitrogen (N), selenium (Se), tellurium (Te) and phosphorus (P), researchers aim to tailor the material’s properties to improve conductivity, accelerate redox reactions, stabilize electrode interfaces, and mitigate dissolution issues of reaction intermediates. Hybridized organosulfur cathode materials have received more and more attention due to their unique design strategy and flexible electrochemical modulation. Therefore, the research progress in heteroatom-containing organosulfur cathode materials is reviewed comprehensively in this paper, summarizing their applications in lithium battery systems. It primarily discusses heteroatom-containing small molecule organic sulfur and polymer organic sulfur materials, and concludes with the challenges and prospects for organic sulfur cathode materials. It covers synthetic strategies to incorporate heteroatoms, characterization techniques to elucidate their structural and electrochemical properties, and their performance as cathode materials in various battery configurations. The discussion encompasses mechanistic insights into how heteroatoms influence charge storage mechanisms, ion diffusion kinetics, and overall battery performance metrics. Despite the promising advances, challenges remain, including the precise control of heteroatom doping levels, maintaining structural integrity during cycling, and optimizing synthesis methods for scalability and cost-effectiveness. Furthermore, the environmental impact and recyclability of these materials are critical considerations for their sustainable application in energy storage technologies. Looking forward, the development of heteroatom-containing organic sulfur cathode materials holds significant potential to address current limitations and unlock new opportunities for next-generation rechargeable batteries. Future research directions focus on refining synthetic techniques, enhancing material stability and cycling performance, exploring novel heteroatom combinations, and integrating these materials into practical battery systems that meet the increasing demands for high-energy-density and sustainable energy storage solutions. In conclusion, heteroatom-doped organic sulfur cathode materials represent a significant advancement in the field of Li-S batteries. The synergistic effect of organic-inorganic hybridization, combined with the tunability of heteroatom doping, offers a promising avenue for the development of high-performance energy storage systems. Further research is needed to fully exploit the potential of these materials and to address the remaining challenges for their practical application.

In the last two decades, rechargeable Li-ion batteries have dominated the market. However, the increasing demand for energy storage creates new challenges for further use of lithium-ion batteries mainly due to the problems associated with limited energy density and high cost. To improve the specific energy of rechargeable batteries, a lithium-sulphur (Li-S) battery attracts particular interest in recent years as next-generation energy storage device due to its highest energy density (2600 Wh/kg) and theoretical capacity (1672 mAh/g) among all known systems. Furthermore, sulphur is cheap, abundant and environmentally benign. Despite this, due to its insulating nature, large volume changes during cycling of cell, and solubility of the polysulfides formed during these processes, the practical application of lithium-sulphur rechargeable batteries has not been successful yet [1]. To overcome these problems, we developed and investigated a free-standing and flexible carbon membrane as an interlayer between the sulfur/PANI composite cathode and the separator to prevent the shuttling of the intermediate polysulfides in Li-S batteries. Sulphur/PANI composites were prepared based on the as-prepared sulphur powder via a self-assembly process. 15 ml of aqueous suspension, containing 1 g sulphur was sonicated for 10min. 15 ml of aniline (An) monomer solution in water was dissolved into the suspension and stirred magnetically for 0.5 h at room temperature. pH of the suspension was adjusted to pH 2.0 with 1 M HCl solution then replaced into ice bath. A precooled FeCl3 aqueous solution was added into the resulting mixture together with diluted HCl. The mixture was reacted for 5 h at 0−5 °C. A black precipitate was separated by filtration and then thouroghly washed several times with deionized water, ethanol, acetone and 0.01 M HCl, and dried overnight under reduced pressure at room temperature to get the final composite product. Different molar ratio of aniline to sulphur were used to optimize the formation condition for preparation of the sulphur/PANI composites. Cathode electrodes were prepared by mixing 80 wt% sulphur/PANI, 10 wt% polyvinylidene fluoride (PVdF, Kynar, HSV900) as a binder and 10 wt% acetylene black as a conducting agent in 1-methyl-2-pyrrolidinone (NMP, Sigma-Aldrich). The resultant slurry was coated on aluminium foil as a current collector, and vacuum dried at 60 °C for 3 h. Free-standing and flexible carbon membranes have been prepared by mixing carbon source and a binder at different molar ratio, coated on aluminium foil and vacuum dried at 60 °C for 4 h. After drying the composite has been detached from aluminium foil, cuted and set between the sulphur/PANI cathode and separator (Celgard). Lihium metal used as anode. The coin cell type cells were assembled in an argon filled glove box (MBRAUN LABMASTER). 1 M LiPF6solution in EC:DMC:DEC (1:1:1) was used as electrolyte. In summary, we have successfully prepared flexible and free-standing carbon membrane for Li–S batteries. Carbon membrane adsorbed the intermediate polysulfides and prevented their shuttling, and a battery with the sulphur/PANI composite exhibited excellent lithium storage performance, enhanced cycle stability and high rate capacity. This publication has been made within the Sub-project #157-2013 which is funded under the Technology Commercialization Project, supported by the World Bank and the Government of the Republic of Kazakhstan Keywords: lithium-sulphur batteries, free-standing membrane, energy storage.

Graphene oxide; Sulfur/carbon composite; Graphene nanoscroll; Metal oxides nanowires; Interlayer; Li−S batteries Nowadays, the growing grievous environmental problems together with the exhaustion of energy resources put urgent demands for developing high energy density devices, whereas traditional lithium-ion batteries (LIBs) are getting close to their energy density. Consideration of the factors including capacity, resource and environment, lithium sulfur (Li-S) batteries are the most potential lithium secondary batteries.[1] However, many drawbacks need to be overcome before its industrial application, such as low electronic conductivity of sulfur, serious shuttling effects of dissolution polysulfides, volume change of electrode during charging-discharging process and problems such as lithium dendrites, passivation and corrosion of lithium anode. This work aims to improve the properties of Li-S batteries by preparation of sulfur/carbon composite cathode materials and building high-efficiency interlayer .[2-4] Firstly, a modified lyophilization approach is developed and used for highly efficient transformation of 2D graphene oxide sheet into 1D graphene nanoscroll (GNS) with high topological transforming efficiency (94%). Because of the unique open tubular structure and large specific surface area (545 m2 g−1), GNS is utilized for the first time as a porous cathode scaffold for encapsulating sulfur with a high loading (81 wt%). The interlayer space and pores of obtained GNS provide large sites for sulfur loading, and this unique structure can accommodate volume expansion and prevent the dissolution of polysulfides. As a result, the composite deliver good rate performance and cycling stability (the capacity decay is only 0.04% per cycle after 400 cylces at 2C).[5] Furthermore, a flexible self-standing hybrid interlayer is engineered by intertwining one-dimensional (1D) metal oxides nanowires (NWs) with GNS into a robust interconnected 3D network to be used as both an upper current collector and physical/chemical polysulfide-trapper. Combining GNS with MnO2, V2O5 and MoO3 respectively, free-standing membranes are obtained to serve as interlayers for Li-S battery (namely, GNSMn, GNSV and GNSMo). The highly conductive and open GNS framework provides bicontinuous transfer channels for rapid electron and ion transport across the cathode/separator interface. Meanwhile, the metal oxides nanowires act as ideal redox mediators to dynamically block polysulfide dissolution and facilitate their conversion into sulfides via formation of active intermediate polythionate complexes. Even though GNSV is used as an interlayer for lithium sulfur battery with bare sulfur as cathodethese cells with 70 wt% sulfur content in the whole cathode have significantly improved performance with a long cycling life (1000 cycles), low capacity decay (0.041% per cycle), and considerable areal capacity (>4 mA h cm- 2), even at a high sulfur loading of 5.5 mg cm- 2. This novel interlayer design strategy has great potential for promoting the practical use of Li–S batteries.[6] In summary, the work described here shows a potential of GNS as a promising functional carbon material to realize high sulfur loading and electrochemically stable electrode configuration aimed toward developing high-performance Li−S batteries. Figure 1 (a) SEM images and (b) TEM images of GNS, (c) schematic illustration on the advantages in entrapping polysulfides of the S@GNS (insert: typical colors of the cycled S@GNS and Gs-S cathodes after soaking in a mixture of DOL/DME for 24 h), (d) schematic model of the cell (insert: photos of the free-standing and flexible GNSM interlayer).

Facile fabrication of permselective g-C3N4 separator for improved lithium-sulfur batteries

Li-S batteries are among the most promising candidates for the next generation rechargeable batteries due to their high energy density, low raw material cost and environmental friendliness [1]. Despite this great potential, the complicated electrochemical process introduces many challenges for Li-S batteries, including low conductivity of both elemental sulfur and end discharge product Li2S, large volume expansion of 80% upon discharge, and unfavorable redox shuttle effect due to soluble nature of intermediate lithium polysulfide LiPS [2,3]. Although Li-S batteries possess a high theoretical cathode specific capacity of 1,672 mAh g-1, the energy density of practical Li-S batteries is much smaller and depends on electrolyte/sulfur (E/S in mL g-1) ratio. From previous works, successful operation of Li-S batteries under lean electrolyte conditions can be challenging, especially in the case when the solubility of LiPS sets an upper bound for polysulfide dissolution. Very recently, we have demonstrated that the E/S ratio of Li-S cells has a significant effect on both performance and theoretical energy density of Li-S batteries. Since the lower-bound for E/S ratio is restricted by the solubility of LiPS in the organic electrolyte, the theoretical energy density of Li-S batteries is significantly reduced. Experimentally, it was approved that when the LiPS concentration reached to the solubility limitation in the electrolyte, the reaction rate of reducing sulfur to LiPS in the cathode will reduce significantly [4]. In this talk, we will discuss the relationship between theoretical specific energy and the solubility of LiPS in the electrolyte. The theoretical specific energy of a Li-S battery can be expressed as: e=CLVcell/(MC+MA+Mele) (1) where, CL is the lower capacity in amount of cathode and anode, Vcell is the cell voltage (e.g. 2.1 V), MC, MA, Mele are weights of sulfur (cathode), lithium (anode), and electrolyte, respectively. In an ideal case, capacities of cathode and anode are equal and to be MA=2×6.94MC/32.065, the atomic weights of lithium and sulfur are 6.94 and 32.065 g/mol, respectively, the capacity is CL=cSMC where cS=1,672 mAh/g is the theoretical specific capacity of sulfur. The minimum weight ratio of electrolyte to sulfur is: Mele/MC=rele/32.065S (2) where, rele is the mass density of electrolyte (e.g. 1.2 g/cm3) and S is the solubility of LiPS in unit of M[S]/L; therefore, the theoretical specific energy for a Li-S battery is: e=3511/(1.4327+37.42/S[M/L])[Wh/kg] (3) Fig. 1 shows the theoretical specific energy of Li-S batteries when the LiPS solubility is considered as an intrinsic limitation for Li-S battery capacity. Here only the weight of active electrode material, such as sulfur and lithium, as well as electrolyte weight is included in calculation. From Fig. 1, it can be seen that for commonly used electrolytes with LiPS solubility less than 8 M[S]/L, the theoretical energy is less than 575 Wh/g. Fig. 2 further presents a series of specific energy calculation for Li-S battery with different E/S ratios. From Fig. 2(a), it can be seen that the electrolyte weight would dominate in a Li-S battery even in relatively low E/S conditions. Fig. 2(b) plots the effective theoretical specific capacity of a Li-S battery. Fig. 2(c) that the reduced effective specific capacity introduced by LiPS solubility limit would offset electrolyte weight loss under low E/S conditions, making the theoretical specific energy curve relatively flat under low E/S region, while without considering LiPS solubility the specific energy will increase sharply when E/S ratio is decreased. The above results imply that reducing E/S ratio would become pointless when LiPS solubility is reached. For further boosting capacity of Li-S batteries, electrolyte with even higher LiPS solubility is favorable. Fig. 2(d) plots the specific energy of an ideal Li-S cell under different LiPS solubility. Reference: [1] A. Manthiram, Y. Fu, S. Chung, C. Zu, Y. Su, Rechargeable Lithium–Sulfur Batteries, Chem. Rev. 114 (2014) 11751–11787. [2] Z.W. Seh, Y. Sun, Q. Zhang, Y. Cui, Designing high-energy lithium–sulfur batteries, Chem. Soc. Rev. (2016). [3] W. Kang, N. Deng, J. Ju, Q. Li, D. Wu, X. Ma, et al., A review of recent developments in rechargeable lithium-sulfur batteries, Nanoscale. 1 (2016) 16541–16588. [4] C. Shen, J. Xie, M. Zhang, J.P. Zheng, M. Hendrickson, and E.J. Plichta, J. Electrochem. Soc., 164 (2017) A1220-A1222. Figure 1

The lithium-sulfur (Li-S) battery has emerged as a next-generation rechargeable battery, owing to the involvement of multiple electrons during the redox reactions between Li and S, which provides high theoretical energy density (2,600 Wh kg-1) and specific capacity (1,675 mAh g-1). In addition, due to abundance of elemental sulfur and its environmental compatibility, Li-S battery has been considered the much more attractive power sources.1,2 The present study demonstrates how to improve the electrochemical performance and energy density of lithium-sulfur batteries based on controlling the wettability between the freestanding electrode and the electrolyte. First, to improve the volumetric energy density, we reduced the thickness of freestanding electrode by the applying pressure. Second, in order to improve electrolyte conductivity and wettability for pressed freestanding electrode, we reduced the viscosity of electrolyte solution by reducing the LiTFSI salt concentration.3,4 Through these controls, the Li-S cell is constructed from a pressed freestanding carbon nanotube-sulfur cathode, 0.5 M LiTFSI in DME/DOL with 0.4 M LiNO3 as a low-viscosity electrolyte (0.72 cP), and Li-metal foil as an anode. As a result, we can obtain a high discharge capacity of 1,400 mAh g-1 at 0.1 C and excellent cycle retention of 95% after 80 cycles at 0.5 C in coin-type cell. In addition, scale-up (3 by 5 cm) pouch-type Li-S cell delivers a high discharge capacity of 500 mAh at 0.1 C with high gravimetric and volumetric energy densities.5 References B. Scrosati, J. Hassoun, Y.-K. Sun, Energy Environ. Sci. 2011, 4, 3287 J.-Y. Hwang, H. M. Kim, S. K. Lee, J. H. Lee, A. Abouimrane, M. A. Khaleel, I. Belharouak, A. Manthiram, Y.-K. Sun, Adv. Energy Mater. 2016, 6, 1501480 J.J. Hu, G. K. Long, S. Liu, G. R. Li, X. P. Gao, Chem. Commun., 2014, 50, 14647 H.-S. Kang, Y.-K. Sun, Adv. Funct. Mater., 2016, 26, 1225 H.-S. Kang, E. Park, J.-Y. Hwang, H. Kim, D. Aurbach, A. Rosenman, Y.-K. Sun, Adv. Mater. Technol. 2016, 1600052

Lithium-sulfur (Li-S) batteries afford great promise on achieving practical high energy density beyond lithium-ion batteries. Lean-electrolyte conditions constitute the prerequisite for achieving high-energy-density Li-S batteries but inevitably deteriorates battery performances, especially the sulfur cathode kinetics. Herein, the polarizations of the sulfur cathode are systematically decoupled to identify the key kinetic limiting factor in lean-electrolyte Li-S batteries. Concretely, an electrochemical impedance spectroscopy combined galvanostatic intermittent titration technique method is developed to decouple the cathodic polarizations into activation, concentration, and ohmic parts. Therein, activation polarization during lithium sulfide nucleation emerges as the dominant polarization as the electrolyte-to-sulfur ratio (E/S ratio) decreases, and the sluggish interfacial charge transfer kinetics is identified as the main reason for degraded cell performances under lean-electrolyte conditions. Accordingly, a lithium bis(fluorosulfonyl)imide electrolyte is proposed to decrease activation polarization, and Li-S batteries adopting this electrolyte provide a discharge capacity of 985 mAh g-1 under a low E/S ratio of 4 μL mg-1 at 0.2 C. This work identifies the key kinetic limiting factor of lean-electrolyte Li-S batteries and provides guidance on designing rational promotion strategies to achieve advanced Li-S batteries.

Silicon monoxide (SiO) is a very promising anode material for the next generation high energy lithium ion batteries due to its high theoretical specific capacity of 1710 mAh/g and volumetric capacity of 1547 Ah/L.[1] Compared to commercially used graphite, SiO can offer 18% cell stack level improvement in volumetric energy density and 11% in gravimetric energy density (calculated based on the same cell stack model), enabling utilization of smaller and lighter batteries. It also offers more stable cycle performance compared to Si due to less volume change (134% initial volume expansion and 117% reversible volume expansion), making it a more practical choice for lithium ion batteries in the near future.SiO is composed of Si nanodomains in a SiO2 matrix. An interphase region of transitional stoichiometry (SiOx, 0 < x < 2) is also present between Si and SiO2 and takes up 20-25 at.% of the entire composition.[2] During the lithiation and delithiation, the Si nanodomains react reversibly with lithium, similar to amorphous silicon, to give the reversible capacity. The SiO2 matrix reacts irreversibly with lithium to form lithium silicates and lithium oxide. Therefore, the Si domain size and interphase suboxide between Si and SiO2 have effect on the electrochemical performance of SiO. In this study, we gradually changed the microstructure of SiO via annealing treatment and thoroughly studied the change of the SiO microstructure and its impact on the electrochemical performance of the SiO. Together with electrode formulation optimization, up to 99% capacity retention during 50 cycles was obtained in full cells when using pure SiO as anode and LiNi0.5Mn0.3Co0.2O2 as cathode. Acknowledgement We gratefully acknowledge the support from Peter Faguy at the U.S. Department of Energy’s (DOE) office of Energy Efficiency & Renewable Energy (EERE) - Vehicle Technologies Office. This work is conducted under the Cell Analysis, Modeling, and Prototyping (CAMP) Facility at Argonne National Laboratory. Argonne National Laboratory is a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357.Reference: Obrovac, M. N.; Chevrier, V. L., Alloy Negative Electrodes for Li-Ion Batteries. Chemical Reviews 2014, 114 (23), 11444-11502.Hirata, A.; Kohara, S.; Asada, T.; Arao, M.; Yogi, C.; Imai, H.; Tan, Y.; Fujita, T.; Chen, M., Atomic-scale disproportionation in amorphous silicon monoxide. Nature Communications 2016, 7, 11591.

A major breakthrough in battery materials is required to meet the ever-increasing proliferation of portable electronic devices, electric vehicles and their variants, as well as the need for incorporating renewable energy resources into the main energy supply [1]. In this context, lithium-sulfur (Li-S) batteries attract attention owing to their very high energy density (2,600 Wh kg-1) and specific capacity (1,675 mAh g-1) and significantly lower weight and cost, compared to lithium-ion batteries (LIBs) [2]. Fully packaged, it is expected that future Li-S batteries can operate at close to 500 Wh kg-1, which is more than twice the energy density of LIBs (200 Wh kg-1) [3]. The problem of realizing the expected high energy density is defined by several issues including the dissolution of Li-Polysulfide (PS) species into the electrolyte, insulating properties of sulfur and Li-PS species, and volume change at the cathode [4]. Overcoming these challenges requires a fundamental understanding of the interplay between events occurring over wide spatial and temporal scales, and accurate prediction of electrode and electrolyte properties to obtain design metrics for new improved materials.In this talk, I will first discuss the details of a high-throughput multi-scale computational infrastructure developed by our group called MISPR (Materials Informatics for Structure-Property-Relationship) to design optimal materials for different applications such as Li-S batteries. MISPR is a high-fidelity and robust computational tool that seamlessly integrates classical molecular dynamics (MD) simulations with density functional theory (DFT) calculations through force field generation and information flow between the two-length scales. It allows automatic handling of thousands of computational materials science simulations and multiple systems with a strong focus on data provenance.I will then discuss the usage of MISPR to mitigate dissolution of LiPS species by altering the atomistic interactions between the electrolyte components through high-throughput screening of potential co-solvent molecules. This approach guides and accelerates our rational selection of co-solvents that enable optimal compromise between the solubility of PS species and the transport properties of the electrolyte through automated DFT calculations. We use the selected candidates in detailed MD studies to comprehend the relationship between the structure of the co-solvent and the electrolyte properties. The approach allows for creating a database of well-characterized materials to be used in machine learning-based methods as well as for testing computationally identified structures in experiments. This work provides crucial information to alleviate the dissolution of PS species during cycling, which is the main reason for rapid capacity decay in Li-S batteries.References Larcher, D. and J.-M. Tarascon, Towards greener and more sustainable batteries for electrical energy storage. Nature chemistry, 2015. 7(1): p. 19. Manthiram, A., X. Yu, and S. Wang, Lithium battery chemistries enabled by solid-state electrolytes. Nature Reviews Materials, 2017. 2(4): p. 1-16. Fang, R., et al., More reliable lithium‐sulfur batteries: status, solutions and prospects. Advanced materials, 2017. 29(48): p. 1606823. Manthiram, A., Y. Fu, and Y.-S. Su, Challenges and prospects of lithium–sulfur batteries. Accounts of chemical research, 2013. 46(5): p. 1125-1134. Figure 1

Lithium-sulfur (Li-S) batteries face significant challenges including polysulfide shuttling, sluggish redox kinetics, and Li dendrite growth. This work introduces molybdenum (Mo)-doped Co9S8 superstructures as a dual-function separator modifier to synergistically address these challenges. Atomic Mo doping, achieved through solvothermal synthesis, induces charge redistribution via Mo/Co9S8 electronic coupling, optimizing the d-band center to both enhance polysulfide adsorption and catalyze their conversion. The Li-S battery equipped with a Mo/Co9S8-modified polypropylene (PP) separator delivers a high reversible capacity of 1663.5 mA h g-1 at 0.1 C, an exceptional rate capability of 593.4 mA h g-1 at 5 C, and demonstrates long-term stability with 56.1% capacity retention after 1000 cycles at 1 C. Additionally, the Mo/Co9S8 modification layer helps reduce the inhomogeneity of Li+ flux distribution and enhance the stability of the metallic Li anode. Under strict operating conditions (0.5 mA cm-2/1.0 mA h cm-2), the Li-S battery equipped with a Mo/Co9S8-modified PP separator can stably operate for 400 h during the Li plating and stripping processes. This work is expected to provide new insights and approaches for designing separators that synergistically optimize the anodes and cathodes in Li-S batteries.

Synthesis and Characterization of LiFeBO3/C Composite By Spray Pyrolysis with Heat Treatment

A synergistic modification of polypropylene separator toward stable lithium–sulfur battery