Realizing high-capacity all-solid-state lithium-sulfur batteries using a low-density inorganic solid-state electrolyte

Conducting Composite Polymer-Based Solid-State Electrolyte with High Ion Conductivity via Amorphous Condensed Structure and Multiple Li+ Transport Channels

Traditional PEO electrolyte has high crystallinity which hinders the transmission of Li+, resulting in poor ion conductivity and complicated processing technology. Herein, a polymer electrolyte (p-electrolyte) with a wide electrochemical window and high ionic conductivity is designed, which possesses an amorphous condensed structure. The amorphous structure provides fast transport channels for Li+, so the p-electrolyte possesses an electrochemical window of 4.2 V, and high ionic conductivity of 1.58 × 10-5 S cm-1 at room temperature, which is 1-2 orders of magnitude higher than that of traditional PEO electrolyte. By using the designed polymer electrolyte as the foundation, an in situ curable composite polymer electrolyte (CPE-L) with multiple Li+ transport channels is elaborately constructed. The Cu-BTC MOF stores abundant Li+, which is introduced into the p-electrolyte. The rich unsaturated Cu2+ coordination sites of Cu-BTC can anchor TFSI- to release Li+, and the pore structure of Cu-BTC MOF cooperates with LLZTO nanoparticles to provide multiple fast transport channel for Li+, resulting in remarkable ionic conductivity (1.02 × 10-3 S cm-1) and Li+ transference number (0.58). The Li||CPE-L||Li symmetric battery cycles stably for more than 700 h at 0.1 mA cm-2, while the specific capacity of full battery is ≈153 mAh g-1 (RT, 0.2 C).

Progresses and Perspectives of Carbon-Free Metal Compounds-Modified Separators for High-Performance Lithium-Sulfur Batteries

Lithium-sulfur batteries (LSBs) have the advantages of high theoretical specific capacity, excellent energy density, abundant elemental sulfur reserves. However, the LSBs is mainly limited by shuttling of lithium polysulfides (LiPSs), slow reaction kinetics of sulfur cathode. For solving the above problems, by developing high-performance battery separators, the reversible capacity, Coulombic efficiency (CE) and cycle life of LSBs can be effectively enhanced. Carbon-free based metal compounds are expected to be highly efficient separator modifiers for a new generation of high-performance LSBs by virtue of superior chemical adsorption capacity, strong catalytic properties and excellent lithophilicity to a certain extent. They can give play to the synergistic effect of their "adsorption-catalysis" sites to accelerate the redox kinetics of LiPSs, and their good lithophilicity can accelerate the Li+ transport kinetics, thus showing more remarkable electrochemical performances. However, a comprehensive summary of carbon-free metal compounds-modified separators for LSBs is still lacking. Here, this review systematically summarizes the researching progresses and performance characteristics of carbon-free-based metal compounds modified materials for separators of LSBs, and summarizes the corresponding mechanisms of using carbon-based separators to enhance the performance of LSBs. Finally, the review also looks forward to the prospects of LSBs using carbon-free metal compounds separators.

High Areal Capacity Cation and Anionic Redox Solid-State Batteries Enabled by Transition Metal Sulfide Conversion

Pure sulfur (S8 and Li2S) all solid-state batteries inherently suffer from low electronic conductivities, requiring the use of carbon additives, resulting in decreased active material loading at the expense of increased loading of the passive components. In this work, a transition metal sulfide in combination with lithium disulfide is employed as a dual cation-anion redox conversion composite cathode system. The transition metal sulfide undergoes cation redox, enhancing the electronic conductivity, whereas the lithium disulfide undergoes anion redox, enabling high-voltage redox conducive to achieving high energy densities. Carbon-free cathode composites with active material loadings above 6.0 mg cm-2 attaining areal capacities of ∼4 mAh cm-2 are demonstrated with the possibility to further increase the active mass loading above 10 mg cm-2 achieving cathode areal capacities above 6 mAh cm-2, albeit with less cycle stability. In addition, the effective partial transport and thermal properties of the composites are investigated to better understand FeS:Li2S cathode properties at the composite level. The work introduced here provides an alternative route and blueprint toward designing new dual conversion cathode systems, which can operate without carbon additives enabling higher active material loadings and areal capacities.

Immobilization and Catalytic Conversion of Polysulfide by In-Situ Generated Nickel in Hollow Carbon Fibers for High-Rate Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries are considered promising energy-storage systems because of their high theoretical energy density, low cost, and eco-friendliness. However, problems such as the shuttle effect can result in the loss of active materials, poor cyclability, and rapid capacity degradation. The utilization of a structural configuration that enhances electrochemical performance via dual adsorption-catalysis strategies can overcome the limitations of Li-S batteries. In this study, an integrated interlayer structure, in which hollow carbon fibers (HCFs) were modified with in-situ-generated Ni nanoparticles, was prepared by scalable one-step carbonization. Highly hierarchically porous HCFs act as the carbon skeleton and provide a continuous three-dimensional conductive network that enhances ion/electron diffusion. Ni nanoparticles with superior anchoring and catalytic abilities can prevent the shuttle effect and increase the conversion rate, thereby promoting the electrochemical performance. This synergistic effect resulted in a high capacity retention of 582 mAh g-1 at 1 C after 100 cycles, providing an excellent rate capability of up to 3 C. The novel structure, wherein Ni nanoparticles are embedded in cotton-tissue-derived HCFs, provides a new avenue for enhancing electrochemical performance at high C rates. This results in a low-cost, sustainable, and high-performance hybrid material for the development of practical Li-S batteries.

All-Solid-State Lithium-Sulfur Batteries of High Cycling Stability and Rate Capability Enabled by a Self-Lithiated Sn-C Interlayer

All-solid-state lithium-sulfur batteries (ASSLSBs) have attracted intense interest due to their high theoretical energy density and intrinsic safety. However, constructing durable lithium (Li) metal anodes with high cycling efficiency in ASSLSBs remains challenging due to poor interface stability. Here, a compositionally stable, self-lithiated tin (Sn)-carbon (C) composite interlayer (LSCI) between Li anode and solid-state electrolyte (SSE), capable of homogenizing Li-ion transport across the interlayer, mitigating decomposition of SSE, and enhancing electrochemical/structural stability of interface, is developed for ASSLSBs. The LSCI-mediated Li metal anode enables stable Li plating/stripping over 7000 h without Li dendrite penetration. The ASSLSBs equipped with LSCI thus exhibit excellent cycling stability of over 300 cycles (capacity retention of ≈80%) under low applied pressure (<8 MPa) and demonstrate improved rate capability even at 3C. The enhanced electrochemical performance and corresponding insights of the designed LSCI broaden the spectrum of advanced interlayers for interface manipulation, advancing the practical application of ASSLSBs.

Achieving a smooth "adsorption-diffusion-conversion" of polysulfides enabled by MnO2-ZnS p-n heterojunction for Li-S battery

The commercial application of lithium-sulfur batteries is primarily impeded by the constant shuttling of soluble polysulfides and sluggish redox kinetics. Nowadays, the discovery of the heterojunction, which combines materials with diverse properties, offers a new perspective for overcoming these obstacles. Herein, a functional coating separator for the lithium-sulfur battery is designed using a MnO2-ZnS p-n heterojunction with a spontaneous built-in electric field (BIEF). The MnO2 nanowire provides suitable adsorption capacity for polysulfides, while the abundant reactive sites brought by ZnS ensure efficient conversion. Moreover, the BIEF significantly facilitates the migration of electrons and polysulfides at the MnO2-ZnS interface, enabling a smooth "adsorption-diffusion-conversion" reaction mechanism. By serving as both the adsorption module and catalytic sites, this BIEF allows batteries utilizing separators modified with MnO2-ZnS heterojunction to achieve an impressive initial capacity of 1511.1 mAh g-1 at 0.1C and maintain a capacity decay rate of merely 0.048% per cycle at 2.0C after 1000 cycles. Even when increasing sulfur loading to 9.4 mg cm-2 in lean electrolyte (5.4 μL mg-1), the battery still exhibits an ultrahigh areal capacity of 6.0 mAh cm-2 after 100 cycles.

The Progress of Polymer Composites Protecting Safe Li Metal Batteries: Solid-/Quasi-Solid Electrolytes and Electrolyte Additives

The impressive theoretical capacity and low electrode potential render Li metal anodes the most promising candidate for next-generation Li-based batteries. However, uncontrolled growth of Li dendrites and associated parasitic reactions have impeded their cycling stability and raised safety concerns regarding future commercialization. The uncontrolled growth of Li dendrites and associated parasitic reactions, however, pose challenges to the cycling stability and safety concerns for future commercialization. To tackle these challenges and enhance safety, a range of polymers have demonstrated promising potential owing to their distinctive electrochemical, physical, and mechanical properties. This review provides a comprehensive discussion on the utilization of polymers in rechargeable Li-metal batteries, encompassing solid polymer electrolytes, quasi-solid electrolytes, and electrolyte polymer additives. Furthermore, it conducts an analysis of the benefits and challenges associated with employing polymers in various applications. Lastly, this review puts forward future development directions and proposes potential strategies for integrating polymers into Li metal anodes.

Enhanced Cycling Stability of All-Solid-State Lithium-Sulfur Battery through Nonconductive Polar Hosts

All-solid-state lithium-sulfur batteries (ASSLSBs) are promising next-generation battery technologies with a high energy density and excellent safety. Because of the insulating nature of sulfur/Li2S, conventional cathode designs focus on developing porous hosts with high electronic conductivities such as porous carbon. However, carbon hosts boost the decomposition of sulfide electrolytes and suffer from sulfur detachment due to their weak bonding with sulfur/Li2S, resulting in capacity decays. Herein, we propose a counterintuitive design concept of host materials in which nonconductive polar mesoporous hosts can enhance the cycling life of ASSLSBs through mitigating the decomposition of adjacent electrolytes and bonding sulfur/Li2S steadily to avoid detachment. By using a mesoporous SiO2 host filled with 70 wt % sulfur as the cathode, we demonstrate steady cycling in ASSLSBs with a capacity reversibility of 95.1% in the initial cycle and a discharge capacity of 1446 mAh/g after 500 cycles at C/5 based on the mass of sulfur.

Bridging the gap between academic research and industrial development in advanced all-solid-state lithium-sulfur batteries

The energy storage and vehicle industries are heavily investing in advancing all-solid-state batteries to overcome critical limitations in existing liquid electrolyte-based lithium-ion batteries, specifically focusing on mitigating fire hazards and improving energy density. All-solid-state lithium-sulfur batteries (ASSLSBs), featuring earth-abundant sulfur cathodes, high-capacity metallic lithium anodes, and non-flammable solid electrolytes, hold significant promise. Despite these appealing advantages, persistent challenges like sluggish sulfur redox kinetics, lithium metal failure, solid electrolyte degradation, and manufacturing complexities hinder their practical use. To facilitate the transition of these technologies to an industrial scale, bridging the gap between fundamental scientific research and applied R&D activities is crucial. Our review will address the inherent challenges in cell chemistries within ASSLSBs, explore advanced characterization techniques, and delve into innovative cell structure designs. Furthermore, we will provide an overview of the recent trends in R&D and investment activities from both academia and industry. Building on the fundamental understandings and significant progress that has been made thus far, our objective is to motivate the battery community to advance ASSLSBs in a practical direction and propel the industrialized process.

Lithium Superionic Conductive Nanofiber-Reinforcing High-Performance Polymer Electrolytes for Solid-State Batteries

Although composite solid-state electrolytes (CSEs) are considered promising ionic conductors for high-energy lithium metal batteries, their unsatisfactory ionic conductivity, low mechanical strength, poor thermal stability, and narrow voltage window limit their practical applications. We have prepared a new lithium superionic conductor (Li-HA-F) with an ultralong nanofiber structure and ultrahigh room-temperature ionic conductivity (12.6 mS cm-1). When it is directly coupled with a typical poly(ethylene oxide)-based solid electrolyte, the Li-HA-F nanofibers endow the resulting CSE with high ionic conductivity (4.0 × 10-4 S cm-1 at 30 °C), large Li+ transference number (0.66), and wide voltage window (5.2 V). Detailed experiments and theoretical calculations reveal that Li-HA-F supplies continuous dual-conductive pathways and results in stable LiF-rich interfaces, leading to its excellent performance. Moreover, the Li-HA-F nanofiber-reinforced CSE exhibits good heat/flame resistance and flexibility, with a high breaking strength (9.66 MPa). As a result, the Li/Li half cells fabricated with the Li-HA-F CSE exhibit good stability over 2000 h with a high critical current density of 1.4 mA cm-2. Furthermore, the LiFePO4/Li-HA-F CSE/Li and LiNi0.8Co0.1Mn0.1O2/Li-HA-F CSE/Li solid-state batteries deliver high reversible capacities over a wide temperature range with a good cycling performance.

Advances in All-Solid-State Lithium-Sulfur Batteries for Commercialization

Solid-state batteries are commonly acknowledged as the forthcoming evolution in energy storage technologies. Recent development progress for these rechargeable batteries has notably accelerated their trajectory toward achieving commercial feasibility. In particular, all-solid-state lithium-sulfur batteries (ASSLSBs) that rely on lithium-sulfur reversible redox processes exhibit immense potential as an energy storage system, surpassing conventional lithium-ion batteries. This can be attributed predominantly to their exceptional energy density, extended operational lifespan, and heightened safety attributes. Despite these advantages, the adoption of ASSLSBs in the commercial sector has been sluggish. To expedite research and development in this particular area, this article provides a thorough review of the current state of ASSLSBs. We delve into an in-depth analysis of the rationale behind transitioning to ASSLSBs, explore the fundamental scientific principles involved, and provide a comprehensive evaluation of the main challenges faced by ASSLSBs. We suggest that future research in this field should prioritize plummeting the presence of inactive substances, adopting electrodes with optimum performance, minimizing interfacial resistance, and designing a scalable fabrication approach to facilitate the commercialization of ASSLSBs.

Healable and conductive sulfur iodide for solid-state Li-S batteries

Solid-state Li-S batteries (SSLSBs) are made of low-cost and abundant materials free of supply chain concerns. Owing to their high theoretical energy densities, they are highly desirable for electric vehicles1-3. However, the development of SSLSBs has been historically plagued by the insulating nature of sulfur4,5 and the poor interfacial contacts induced by its large volume change during cycling6,7, impeding charge transfer among different solid components. Here we report an S9.3I molecular crystal with I2 inserted in the crystalline sulfur structure, which shows a semiconductor-level electrical conductivity (approximately 5.9 × 10-7 S cm-1) at 25 °C; an 11-order-of-magnitude increase over sulfur itself. Iodine introduces new states into the band gap of sulfur and promotes the formation of reactive polysulfides during electrochemical cycling. Further, the material features a low melting point of around 65 °C, which enables repairing of damaged interfaces due to cycling by periodical remelting of the cathode material. As a result, an Li-S9.3I battery demonstrates 400 stable cycles with a specific capacity retention of 87%. The design of this conductive, low-melting-point sulfur iodide material represents a substantial advancement in the chemistry of sulfur materials, and opens the door to the practical realization of SSLSBs.

Self-Assembly of Ultrathin, Ultrastrong Layered Membranes by Protic Solvent Penetration

Flexible membranes with ultrathin thickness and excellent mechanical properties have shown great potential for broad uses in solid polymer electrolytes (SPEs), on-skin electronics, etc. However, an ultrathin membrane (<5 μm) is rarely reported in the above applications due to the inherent trade-off between thickness and antifailure ability. We discover a protic solvent penetration strategy to prepare ultrathin, ultrastrong layered films through a continuous interweaving of aramid nanofibers (ANFs) with the assistance of simultaneous protonation and penetration of a protic solvent. The thickness of a pure ANF film can be controlled below 5 μm, with a tensile strength of 556.6 MPa, allowing us to produce the thinnest SPE (3.4 μm). The resultant SPEs enable Li-S batteries to cycle over a thousand times at a high rate of 1C due to the small ionic impedance conferred by the ultrathin characteristic and regulated ionic transportation. Besides, a high loading of the sulfur cathode (4 mg cm-2) with good sulfur utilization was achieved at a mild temperature (35 °C), which is difficult to realize in previously reported solid-state Li-S batteries. Through a simple laminating process at the wet state, the thicker film (tens of micrometers) obtained exhibits mechanical properties comparable to those of thin films and possesses the capability to withstand high-velocity projectile impacts, indicating that our technique features a high degree of thickness controllability. We believe that it can serve as a valuable tool to assemble nanomaterials into ultrathin, ultrastrong membranes for various applications.

A Review on Engineering Design for Enhancing Interfacial Contact in Solid-State Lithium-Sulfur Batteries

The utilization of solid-state electrolytes (SSEs) presents a promising solution to the issues of safety concern and shuttle effect in Li-S batteries, which has garnered significant interest recently. However, the high interfacial impedances existing between the SSEs and the electrodes (both lithium anodes and sulfur cathodes) hinder the charge transfer and intensify the uneven deposition of lithium, which ultimately result in insufficient capacity utilization and poor cycling stability. Hence, the reduction of interfacial resistance between SSEs and electrodes is of paramount importance in the pursuit of efficacious solid-state batteries. In this review, we focus on the experimental strategies employed to enhance the interfacial contact between SSEs and electrodes, and summarize recent progresses of their applications in solid-state Li-S batteries. Moreover, the challenges and perspectives of rational interfacial design in practical solid-state Li-S batteries are outlined as well. We expect that this review will provide new insights into the further technique development and practical applications of solid-state lithium batteries.

Universal F4-Modified Strategy on Metal-Organic Framework to Chemical Stabilize PVDF-HFP as Quasi-Solid-State Electrolyte

Solid-state electrolytes (SSEs) based on metal organic framework (MOF) and polymer mixed matrix membranes (MMMs) have shown great promotions in both lithium-ion conduction and interfacial resistance in lithium metal batteries (LMBs). However, the unwanted structural evolution and the and the obscure electrochemical reaction mechanism among two phases limit their further optimization and commercial application. Herein, fluorine-modified zirconium MOF with diverse F-quantities is synthesized, denoted as Zr-BDC-Fx (x = 0, 2, 4), to assemble high performance quais-solid-state electrolytes (QSSEs) with PVDF-HFP. The chemical complexation of F-sites in Zr-BDC-F4 stabilized PVDF-HFP chains in β-phase and disordered oscillation with enhanced charge transfer and Li transmit property. Besides, the porous confinement and electronegativity of F-groups enhanced the capture and dissociation of TFSI- anions and the homogeneous deposition of LiF solid electrolyte interphase (SEI), promoting the high-efficient transport of Li+ ions and inhibiting the growth of Li dendrites. The superb specific capacities in high-loaded Li.

Multifunctional Asymmetric Separator Constructed by Polyacrylonitrile-Derived Nanofibers for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries hold great promise as next-generation high-energy storage devices owing to the high theoretical specific capacity of sulfur, but polysulfide shuttling and lithium dendrite growth remain key challenges limiting cycling life. In this work, we propose a polyacrylonitrile-derived asymmetric (PDA) separator to enhance Li-S battery performance by accelerating sulfur redox kinetics and guiding lithium plating and stripping. A PDA separator was constructed from two layers: the cathode-facing side consists of polyacrylonitrile nanofibers carbonized at 800 °C and doped with titanium nitride, which can achieve rapid polysulfide conversion via electrocatalysis to suppress their shuttling; the anode-facing side consists of polyacrylonitrile oxidized at 280 °C, on which the abundant electronegative groups guide uniform lithium ion plating and stripping. Li-S batteries assembled with the PDA separator exhibited enhanced rate performance, cycling stability, and sulfur utilization, retaining 426 mA h g-1 capacity at 1 C over 1000 cycles and 632 mA h g-1 at 4 C over 200 cycles. Attractively, the PDA separator showed high thermal stability, which could mitigate the risk of internal short circuits and thermal runaway. This work demonstrates an original path to addressing the most critical issues with Li-S batteries.