Regulate transportation of ions and polysulfides in all-solid-state Li-S batteries using ordered-MOF composite solid electrolyte

New materials for lithium-sulfur batteries: challenges and future directions

This review explores recent advances in lithium-sulfur (Li-S) batteries, promising next-generation energy storage devices known for their exceptionally high theoretical energy density (∼2500 W h kg-1), cost-effectiveness, and environmental advantages. Despite their potential, commercialization remains limited by key challenges such as the polysulfide shuttle effect, sulfur's insulating nature, lithium metal anode instability, and thermal safety concerns. This review provides a comprehensive and forward-looking perspective on emerging material strategies-focusing on cathode, electrolyte, and anode engineering-to overcome these barriers. Special emphasis is placed on advanced sulfur-carbon composites, including three-dimensional graphene frameworks, metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and MXene-based materials, which have demonstrated significant improvements in sulfur utilization, redox kinetics, and cycling stability. Innovations in electrolytes-particularly solid-state and gel polymer systems-are discussed for their roles in suppressing polysulfide dissolution and enhancing safety. This review also examines lithium metal anode protection strategies, such as use of artificial SEI layers and 3D lithium scaffolds and lithium alloying. Finally, it discusses critical issues related to large-scale manufacturing, safety, and commercial scalability. With ongoing innovation in multifunctional materials and electrode design, Li-S batteries are well positioned to transform energy storage for electric vehicles, portable electronics, and grid-scale systems.

Constructing Ionic Transport Network via Supramolecular Composite Binder in Cathode for All-Solid-State Lithium Batteries

Binders play a pivotal role in maintaining the structural integrity and stability of electrodes. However, conventional polyvinylidene fluoride binder with low ionic conductivity could not meet the ionic transport requirements of the cathode in all-solid-state lithium batteries (ASSLBs). Herein, a composite binder (PPCL) derived from the cross-linking of linear molecules and mechanically interlocked molecules with typical supramolecular channel structure is designed. The supramolecular channel structure is afforded through β-cyclodextrin rings crosslinked polyethylene oxide chains by hydrogen bond interaction. Through the coordination of supramolecular with linear polymer, the PPCL binder provides multiple and synergistic Li+ transport channels to achieve stable Li+ transport inside the cathode. As a result, the obtained PPCL binder not only maintains exceptional adhesive strength which could achieve robust electrode structural stability but also helps to construct multiple and highly efficient Li+ transport channels. Therefore, with PPCL binder, the LiFePO4-based ASSLBs show an excellent rate capability and long cyclic stability over 1000 cycles at 1 C. Notably, a pouch ASSLB shows excellent cycling stability over 250 cycles at 0.2 C. This work provides guidance on designing high-loading cathodes for advanced ASSLBs.

Recent Advances in 3D Printing Technologies for Lithium-Sulfur Batteries

Lithium-sulfur (Li-S) batteries have heretofore raised burgeoning interest due to their cost effectiveness and high theoretical energy densities. However, the inherent porous and fluffy structure of sulfur impedes the path to constructing high-loading electrodes (over 5 mg cm-2) for their practicability. Furthermore, especially in thick electrodes, challenges like the retarded redox kinetics, notorious polysulfide shuttling, and wanton electrode expansion seriously give rise to low sulfur utilization, poor rate performance, and unsatisfactory cycling stability. Constructing free-standing architectures has been demonstrated as an effective strategy to tackle the aforementioned issues for high-loading Li-S batteries. As an emerging technique, 3D printing (3DP) shows merits in rapidly fabricating precise microstructures with controllable loadings and rationally organized porosity. For the Li-S realm, 3DP offers optimized Li+/e- transmission path with well-dispersed electrocatalysts, which achieves efficient polysulfide regulation and guarantees favorable performance. This review covers the design principle and preparation of printable inks, and their practical applications to manufacture self-supported frameworks (such as cathodes, anodes, and separators) for Li-S batteries. Challenges and perspectives on the potential future development of 3DP Li-S batteries are also outlined.

Salt-Segregated Solid Polymer Electrolytes for High-Rate Solid-State Lithium Batteries

Solid-polymer electrolytes (SPEs) demonstrate great potential for solid-state lithium batteries (SSLBs), however, interfacial instability and sluggish ion transport at the interface critically hinder their high-rate capability and long-term stability. Here, a novel salt-segregation methodology with spatial salt grade for SPEs is introduced. This approach leverages the differential solubility of lithium salts and PVDF matrix in a commercially available fluoroethylene carbonate during fabrication, which drives the formation of an ion-enriched surface layer. The strategy simultaneously enhances interfacial and bulk ionic conductivity while effectively mitigating parasitic reactions. These advancements optimize Li+ flux at the lithium metal interphase, promoting a spherical Li growth with minimized surface area and leading to dense lithium deposition. Consequently, the engineered SPE achieves a remarkable cycling of 500 h in Li||Li cells at 2 mA cm-2. Solid-state Li||LiFePO4 cells exhibit a record stability for 20 000 cycles at 1.12 A g-1 (2 mg cm-2 LiFePO4 cathode), and a high capacity of 147 mAh g-1 over 300 cycles at 0.84 mA cm-2 under a high-loading 2 mAh cm-2 cathode. The strategy addresses interfacial limitations in SPEs and further introduces a paradigm shift by emphasizing the critical role of spatial salt-graded engineering at the surface over uniform ion distribution for stabilizing high-rate SSLBs.

In Situ Welding Ionic Conductive Breakpoints for Highly Reversible All-Solid-State Lithium-Sulfur Batteries

Poly(ethylene oxide) (PEO)-based solid-state lithium-sulfur batteries (SSLSBs) have garnered considerable interest owing to their impressive energy density and high safety. However, the dissolved lithium polysulfide (LiPS) together with sluggish reaction kinetics disrupts the electrolyte network, bringing about ionic conductive breakpoints and severely limiting battery performance. To cure this, we propose an in situ welding strategy by introducing phosphorus pentasulfide (P2S5) as the welding filler into PEO-based solid cathodes. P2S5 can react with LiPS to form ion-conducting lithium polysulfidophosphate (LSPS), which suppresses the interaction with PEO and in situ weld breakpoints within the ionic conductive network. Of interest, LSPS also shows another function, that is, to catalyze sulfur redox reactions by decreasing the activation energy of sulfur reduction reaction from 0.87 to 0.75 eV, mitigating the shuttle effect. The in situ welding strategy helps the assembled SSLSB to feature exceptional cycling stability and a high energy density of up to 358 Wh·kg-1 due to the high sulfur utilization. Our findings pave an avenue for practical high-performance SSLSBs with a novel welding filler for in situ welding of ionic conductive network.

High-Strength MOF-Based Polymer Electrolytes with Uniform Ionic Flow for Lithium Dendrite Suppression

The uneven formation of lithium dendrites during electroplating/stripping leads to a decrease in the utilization of active lithium, resulting in poor cycling stability and posing safety hazards to the battery. Herein, introducing a 3D continuously interconnected zirconium-based metal-organic framework (MOF808) network into a polyethylene oxide polymer matrix establishes a synergistic mechanism for lithium dendrite inhibition. The 3D MOF808 network maintains its large pore structure, facilitating increased lithium salt accommodation, and expands anion adsorption at unsaturated metal sites through its diverse large-space cage structure, thereby promoting the flow of Li+. Infrared-Raman and synchrotron small-angle X-ray scattering results demonstrate that the transport behavior of lithium salt ion clusters at the MOF/polymer interface verifies the increased local Li+ flux concentration, thereby raising the mobility number of Li+ to 0.42 and ensuring uniform Li+ flux distribution, leading to dendrite-free and homogeneous Li+ deposition. Furthermore, nanoindentation tests reveal that the high modulus and elastic recovery of MOF-based polymer electrolytes contribute to forming a robust, dendrite-resistant interface. Consequently, in symmetric battery systems, the system exhibits minimal overpotential, merely 35 mV, while maintaining stable cycling for over 1800 h, achieving low-overpotential lithium deposition. Moreover, it retains redox stability under high voltages up to 5.3 V.

Dual Ionic Pathways in Semi-Solid Electrolyte based on Binary Metal-Organic Frameworks Enable Stable Operation of Li-Metal Batteries at Extremely High Temperatures

The rapid development of the electronics market necessitates energy storage devices characterized by high energy density and capacity, alongside the ability to maintain stable and safe operation under harsh conditions, particularly elevated temperatures. In this study, a semi-solid-state electrolyte (SSSE) for Li-metal batteries (LMB) is synthesized by integrating metal-organic frameworks (MOFs) as host materials featuring a hierarchical pore structure. A trace amount of liquid electrolyte (LE) is entrapped within these pores through electrochemical activation. These findings demonstrate that this structure exhibits outstanding properties, including remarkably high thermal stability, an extended electrochemical window (5.25 V vs Li/Li+), and robust lithium-ion conductivity (2.04 × 10-4 S cm-1), owing to the synergistic effect of the hierarchical MOF pores facilitating the storage and transport of Li ions. The Li//LiFePO4 cell incorporating prepared SSSE shows excellent capacity retention, retaining 97% (162.8 mAh g-1) of their initial capacity after 100 cycles at 1 C rate at an extremely high temperature of 95 °C. It is believed that this study not only advances the understanding of ion transport in MOF-based SSSE but also significantly contributes to the development of LMB capable of stable and safe operation even under extremely high temperatures.

A Review on Architecting Rationally Designed Metal-Organic Frameworks for the Next-Generation Li-S Batteries

The modern era demands the development of energy storage devices with high energy density and power density. There is no doubt that lithium‒sulfur batteries (Li‒S) claim high theoretical energy density and have attracted great attention from researchers, but fundamental exploration and practical applications cannot converge to utilize their maximum potential. The design parameters of Li-S batteries involve various complex mechanisms, and their obliviousness has resulted in failure at the commercial level. This article presents a review on rationally designed metal-organic frameworks (MOFs) for improving next-generation Li-S batteries. The use of MOFs in Li-S batteries is of great interest because of their large surface area, porous structure, and selective permeability for ions. The working principles of Li-S batteries, the commercialization of Li-S batteries, and the use of MOFs as electrodes, electrolytes, and separators are critically examined. Finally, designed strategies (host structure, binder improvement, separator modification, lithium metal protection, and electrolyte optimization) are developed to increase the performance of Li-S batteries.

Developing Cathode Films for Practical All-Solid-State Lithium-Sulfur Batteries

The development of all-solid-state lithium-sulfur batteries (ASSLSBs) toward large-scale electrochemical energy storage is driven by the higher specific energies and lower cost in comparison with the state-of-the-art Li-ion batteries. Yet, insufficient mechanistic understanding and quantitative parameters of the key components in sulfur-based cathode hinders the advancement of the ASSLSB technologies. This review offers a comprehensive analysis of electrode parameters, including specific capacity, voltage, S mass loading and S content toward establishing the specific energy (Wh kg-1) and energy density (Wh L-1) of the ASSLSBs. Additionally, this work critically evaluates the progress in enhancing lithium ion and electron percolation and mitigating electrochemical-mechanical degradation in sulfur-based cathodes. Last, a critical outlook on potential future research directions is provided to guide the rational design of high-performance sulfur-based cathodes toward practical ASSLSBs.

Design of Ultrathin Asymmetric Composite Electrolytes for Interfacial Stable Solid-State Lithium-Metal Batteries

Ultrathin composite electrolytes hold great promise for high energy density solid-state lithium metal batteries (SSLMBs). However, finding an electrolyte that can simultaneously balance the interfacial stability of the lithium anode and high-voltage cathode is challenging. The present study utilized the both-side tape casting technique to fabricate ultrathin asymmetric composite electrolytes reinforced with polyimide (PI) fiber membrane, with a thickness of 26.8 μm. The implementation of this asymmetric structural design enables SSLMBs to attain favorable interfacial characteristics, such as exceptional resistance to lithium dendrite puncture and compatibility with high voltages. The suppression of lithium dendrite growth and the extension of the cycle life of lithium symmetric batteries by 4000 h are both experimental and theoretically demonstrated under the dual confinement of PI fiber membrane and Li7La3Zr2O12 ceramic fibers. Furthermore, the integration of multicomponent solid electrolyte interphase and cathode electrolyte interface interfacial layers into the lithium anode and high-voltage cathode enhance theirs cycling stability. With a gravimetric/volumetric energy density of 333.1 Wh kg-1/713.2 Wh L-1, the assembled LiNi0.8Co0.1Mn0.1O2 pouch cell demonstrates exceptional safety. The extensive application of this design concept to SSLMBs enables the resolution of electrode/electrolyte interface issues.

Advances in Nano-Electrochemical Materials and Devices

Nano-electrochemical materials and devices are at the frontier of research and development, advancing electrochemistry and its applications in energy storage, sensing, electrochemical processing, etc [...].