Toward High-Performance Metal-Organic-Framework-Based Quasi-Solid-State Electrolytes: Tunable Structures and Electrochemical Properties

Engineering 3D Lattice Oxygen Metal-Organic Frameworks for Fast-Charging Quasi-Solid-State Lithium Metal Batteries

Metal-organic frameworks (MOFs) show great promise in composite solid polymer electrolytes by simultaneously immobilizing anions and facilitating cation transport, yet the synergy between these mechanisms remains unclear. To elucidate this interplay, a series of isoreticular indium-based MOFs (InOF-1, MIL-60, and MIL-68(In)) are designed, all featuring identical In-O6 coordination centers while exhibiting systematically varies pore architectures. Among them, MIL-60 stands out by achieving an optimal balance between physical size exclusion and chemical mediation of ion transport. It's precisely engineered 6.5 Å pores effectively block bulky TFSI- anions while allowing the diffusion of lithium ion (Li+)-solvent complexes. Concurrently, its exceptionally high lattice oxygen density (19.97 nm-3, confirmed by density functional theory calculations) forms a 3D fast Li+ conduction network, enabling barrier-free ion hopping. This dual mechanism results in superior electrochemical performance, including an ultrahigh room-temperature Li+ conductivity of 1.11 × 10-3 S cm-1 at 30 °C, an unprecedented Li+ transference number of 0.54, and outstanding cycling stability with 95.2% capacity retention after 1800 cycles at 10 C in LiFePO4||Li cells. This study proposes a new design strategy aligning pore size with Li+ transport sites to optimize ion conduction. MIL-60 exemplifies a promising model for single-ion conductors and guides next-generation solid-state batteries.

Molecular Design of Polymeric Metal-Organic Nanocapsule Networks for Solid-State Lithium Batteries

Solid-state electrolytes (SSEs) have emerged as high-priority materials for ensuring the safe operation of solid-state lithium (Li) batteries. However, current SSEs still face challenges of balancing stability and ionic conductivity, which limits their practical applications in solid-state Li batteries. Here, we report a general strategy for achieving high-performance SSEs by constructing a Li+-conducted polymeric metal-organic nanocapsule (PolyMONC(Li)) network through molecular design. With the unique cage structure and pore size, metal-organic nanocapsule (MONC) can achieve excellent anion confinement effects. The PolyMONC(Li) network with continuous Li+ conduction pathways serves as a solid electrolyte exhibiting a high ionic conductivity (0.18 mS cm-1 at 25 °C) and a high Li+ transference number (0.83). Combining the two superiorities of optimal balance between mechanical strength and excellent Li+ conductivity, the PolyMONC(Li) can still restrain the dendrite growth and prevent Li symmetric batteries from short-circuiting even over 900 h cycling. The PolyMONC(Li)-based SSEs Li-metal batteries achieved a higher specific capacity than common polymer electrolytes such as polyethylene oxide-based SSE. Additionally, taking advantage of the PolyMONC(Li) electrode binder, the solid-state Li-O2 battery achieves a stable cycling over 400 cycles. This work provides a comprehensive guideline for developing porous solids from molecule design to practical application.

Inhibition of manganese ion migration and dissolution by selective ions sieving effect of MOF-based solid electrolytes

Lithium manganese oxide (LiMn2O4) is a promising cathode material for Li-ion batteries due to its abundant reserves and high discharge voltage. However, the dissolution and migration of transition metal Mn ions during the cycling process will cause a significant deterioration of capacity. In this study, a MOF-based quasi-solid electrolyte (UiO-QSE) is proposed to tackle this issue. The large specific surface area and open metal sites of UiO-QSE facilitate the adsorption of Mn ions, thereby inhibiting their migration. Furthermore, the disproportionation of Mn3+ on LiMn2O4 is suppressed by maintaining a highly concentrated Mn2+ layer around the cathode surface, thereby providing cathode protection in accordance with Le Chatelier's principle. The excellent inhibitory effect of UiO-QSE on the dissolution and migration of Mn ions is reflected in the fact that the prepared LiMn2O4|UiO-QSE|Li battery exhibits high discharge capacity (100.2 mAh·g-1 after 100 cycles), which is much higher than LiMn2O4|LE|Li (78.1 mAh·g-1), and a high capacity retention of 97.91 % after 50 cycles at a high-temperature of 45 °C. The Li|Li symmetrical cell exhibits an ultralong cycle life of more than 1300 h even at a high current density of 1 mA cm-2 due to the uniform Li-ion transport channel and high Young's modulus in the UiO-QSE. This study is the first to employ the MOF-QSE strategy to inhibit the dissolution and migration of manganese during cycling, providing a new perspective on the development and enhancement of lithium-manganese-based batteries.

Constructing Matching Interfaces by Amorphous Engineering for Enhanced Lithium Ion Transport in Quasi-Solid-State Lithium-Iodine Batteries

Quasi-solid-state lithium-iodine (Li-I2) batteries have shown prospects as their high theoretical capacity, high safety, and abundant iodine resources. However, the interface between the crystalline filler and the flexible polymer skeleton of composite solid electrolytes exhibits inadequate bonding, leading to higher interface energy and sluggish migration dynamics of Li+. In this work, a continuous interface solid electrolyte is designed by combining the atomic structure rearrangement of metal-organic framework (MOF) to achieve interface coupling between MOF and aramid fiber. Based on the experimental results and theoretical calculations, the amorphous engineering promotes Li+ migration and polyiodide confinement effects for Li-I2 batteries. The batteries show a high capacity of 170.7 mAh g-1 at 5 C and achieve a capacity retention rate of 97.8% after 450 cycles. More impressively, the batteries achieve a long life of 3000 cycles at the high current density of 20 C with a good capacity retention of 94.1%. This work reveals the mechanism of coupled interface with structure matching in Li+ migration and polyiodide integration process, providing guidance for the design of novel composite solid electrolytes to achieve high-performance Li-I2 batteries.

Enhanced Lithium-Ion Battery Electrodes with Metal-Organic Framework Additives Featuring Undercoordinated Zr4+ Sites

Performances of lithium-ion batteries (LIBs) are dictated by processes of electron-ion separation, transfers, and combination. While carbon additives are routinely used to ensure electronic conductivity, additives capable of simultaneously boosting ion conduction and delivering step-change performance remain elusive. Herein, metal-organic frameworks (MOFs) possessing coordinately unsaturated Zr4+ sites are exploited as a new material library of electrode additives. The MOFs imbue infused electrolytes with an expanded electrochemical stability window (0 to 5 V vs Li/Li⁺) and enhanced Li⁺ transport efficiency. Mechanistically, strong interactions between Zr4+ sites and Li+ solvation sheaths result in trimmed, anion-fixed, and solvent-separated ion pairs, mitigating electrostatic coupling and enabling efficient Li⁺ translocation in the porous nanospace. Concomitantly, these solvation structural modulations foster interfacial and electrochemical stabilities. When implemented at 1.7 wt.% in graphite and sub-Ah full cell, the MOF additives significantly improved Li+ diffusional kinetic, rate capability beyond 2C, and cycling longevity doubling lifespan. This work offers a straightforward yet effective route to remedy the bottlenecks of industrial LIBs.

Defect-Tailoring Metal-Organic Frameworks for Highly Fast-Charging Quasi-Solid-State Electrolytes Lithium Metal Batteries

Metal-organic frameworks (MOFs) show revolutionary potential in quasi-solid-state electrolytes (QSSEs) designed for high-energy-density batteries, owing to their tunable nanoporous structures and open metal sites (OMSs). However, their application is hindered by insufficient Li+ dissociation and low ionic conductivity, attributed to limited metal active sites. This study employed defect engineering to modulate hafnium-based MOFs, increasing OMS density while optimizing the pore microenvironment. The engineered defects improve the Lewis acid strength of OMSs, driving lithium salt dissociation and establishing strong chemisorption of TFSI- anions. By synergistically optimizing defect density, Lewis acidity, and structural stability, the defect-engineered Hf-MOF-QSSE achieved an ionic conductivity of 1.0 mS cm-1 at 30 °C and delivered a critical current density of 2 mA cm-2, surpassing previously reported MOF-QSSEs, underscoring the pivotal role of defect engineering in electrolyte optimization. Furthermore, Li||LiFePO4 cells exhibited excellent cycling stability and ultrahigh rate capability, retaining 93% of their capacity after 1500 cycles at 10C, while Li||NCM811 cells maintained a specific capacity of 85 mAh g-1 after 600 cycles at 5C.

Anthraquinone substituents modulate ionic hydrogen-bonded organic frameworks to achieve high ionic conductivity for alkali metal ions

Herein, we report two charge-assisted hydrogen-bonded organic frameworks (iHOF-24 and iHOF-25) with 3D/2D hydrogen-bonding networks, which exhibit high ionic conductivity for alkali metal ions. Among them, the conductivity of Li+ is higher than that of Na+ and K+, and the ionic conductivities of Li@iHOF-24 and Li@iHOF-25 at 30 °C were 9.44 × 10-5 and 9.85 × 10-5 S cm-1. This change is attributed to the distance between neighboring carbonyl groups in iHOF-24 and iHOF-25, as well as the radius of the loaded alkali metal ions.

Engineering 4-Connecting 3D Covalent Organic Frameworks with Oriented Li+ Channels for High-Performance Solid-State Electrolyte in Lithium Metal Battery

The development of rapid and stable ion-conductive channels is pivotal for solid-state electrolytes (SSEs) in achieving high-performance lithium metal batteries (LMBs). Covalent organic frameworks (COFs) have emerged as promising Li-ion conductors due to their well-defined channel architecture, facile chemical tunability, and mechanical robustness. However, the limited active sites and restricted segmental motion for Li+ migration significantly impede their ionic conductivity. Herein, a rational design strategy is presented to construct 3D porous COF frameworks (TP-COF and TB-COF) using linear ditopic monomers connected via C─C and C─N linkages. These COFs, integrated with polymer electrolytes, provide enhanced Li+ transport pathways and stabilize lithium anodes in LMBs. The TB-COF, featuring larger pore apertures and abundant ─C═N─ active sites, facilitates superior Li+ conduction (8.89 × 10-4 S cm-1) and a high transference number (0.80) by enhancing lithium salt dissolution. LiF/Li3N-rich SEI enables uniform Li deposition, enabling PEO-TB-COF SSEs to achieve >1000 h stability at 1 mA cm⁻2 while retaining 90% capacity through 800 cycles (0.5 C) in LFP||Li cells. Molecular dynamics simulations and COMSOL Multiphysics modeling reveal that extended Li+ transport channels and reduced interfacial diffusion barriers are key to enhanced performance.

Carving Metal-Organic-Framework Glass Based Solid-State Electrolyte Via a Top-Down Strategy for Lithium-Metal Battery

Traditional polymer solid electrolytes (PSEs) suffer from low ions conductivity, poor kinetics and safety concerns. Here, we present a novel porous MOF glass gelled polymer electrolyte (PMG-GPE) prepared via a top-down strategy, which features a unique three-dimensional interconnected graded-aperture structure for efficient ions transport. Comprehensive analyses, including time-of-flight secondary ion mass spectrometry (TOF-SIMS), Solid-state 7Li magic-angle-spinning nuclear magnetic resonance (MAS NMR), Molecular Dynamics (MD) simulations, and electrochemical tests, quantify the pore structures, revealing their relationship with ions conductivity that increases and then decreases as macropore proportion rises. The introduced dispersed macropores (17 % fraction) can serve as bridges, connecting adjacent transport units to accelerate ions transport. Taking advantage of the cross-linked ion-conductive paths constructed by hierarchical pore structures, the PMG-GPE achieves a high ions conductivity of 1.9 mS cm-1. Additionally, the robust mechanical properties of PMG-GPE effectively suppress dendrite growth and penetration, outperforming crystal MOF-based electrolytes. The prepared Li symmetric batteries with PMG-GPE demonstrate a high critical current density of 5.1 mA cm-2 (two times higher than crystal MOF-electrolytes) and stable cycling for over 6000 hours without short circuits. Furthermore, a Li/PMG-GPE/LFP half-cell exhibits exceptional capacity retention of 83.12 % after 1400 cycles. These findings highlight the potential of structural design in advancing PSE performance, offering a promising pathway for the commercialization of high-performance solid-state batteries.

Quasi-Solid Gel Electrolytes for Alkali Metal Battery Applications

Alkali metal batteries (AMBs) have undergone substantial development in portable devices due to their high energy density and durable cycle performance. However, with the rising demand for smart wearable electronic devices, a growing focus on safety and durability becomes increasingly apparent. An effective strategy to address these increased requirements involves employing the quasi-solid gel electrolytes (QSGEs). This review focuses on the application of QSGEs in AMBs, emphasizing four types of gel electrolytes and their influence on battery performance and stability. First, self-healing gels are discussed to prolong battery life and enhance safety through self-repair mechanisms. Then, flexible gels are explored for their mechanical flexibility, making them suitable for wearable devices and flexible electronics. In addition, biomimetic gels inspired by natural designs are introduced for high-performance AMBs. Furthermore, biomass materials gels are presented, derived from natural biomaterials, offering environmental friendliness and biocompatibility. Finally, the perspectives and challenges for future developments are discussed in terms of enhancing the ionic conductivity, mechanical strength, and environmental stability of novel gel materials. The review underscores the significant contributions of these QSGEs in enhancing AMBs performance, including increased lifespan, safety, and adaptability, providing new insights and directions for future research and applications in the field.

Fluoride Graphdiyne Enhances Polymer Electrolytes Through Regional Electric Potential Synergies for High-Performance Solid-State Lithium-Metal Batteries

Solid-state polymer electrolytes (SSPEs) have attracted considerable attention for use in all-solid-state lithium-metal batteries (ASSLMBs). However, their low Li-ion conductivity, small Li-ion transference number, and poor interfacial compatibility hinder their practical application, which may be associated with the uncoordinated interactions between the key components in SSPEs including polymers, lithium salts, and nanofillers. In this study, fluoride graphdiyne (FGDY) is used as a nanofiller to enhance the overall performance of PVDF-HFP/LiTFSI in ASSLMBs through regional electric potential synergies (REPS), which refers to the proper interaction between particular ordered electric potential difference regions in the 2D plane and key components of SSPEs. Consequently, the dissociation of LiTFSI is promoted, and the migration of Li-ions is accelerated. Moreover, a uniform LiF-rich solid electrolyte interphase efficiently inhibits the growth of lithium dendrites, guaranteeing excellent interfacial stability. The assembled Li//LiFePO4 and Li//LiNi0.6Co0.2Mn0.2O2 full cells exhibit excellent reversible capacity and stable cycling performance at 30 °C. This study presents a strategy for improving the overall performance of SSPEs by fabricating nanofillers with highly ordered electric potential difference regions. Graphdiyne-based materials, which serve as nanofillers to optimize the performance of SSPEs through REPS, provide a wide scope for the practical application of ASSLMBs.

2D Vertically Conductive Metal─Organic Framework Electrolytes: Will They Outperform 3D MOFs for Solid State Batteries?

Lithium-ion batteries are currently the mainstream for almost all portables, and quickly expand in electrical vehicles and grid storage applications. However, they are challenged by the poor safety regarding organic liquid electrolytes and relatively low energy density. Solid-state batteries, characterized by using solid-state electrolytes (SSEs), are recognized as the next-generation energy technology, owing to their intrinsically high safety and potentially superior energy density. However, developing SSEs is impeded by several key factors, including low ionic conductivity, interfacial issues, and high-cost in industrial scales. Recently, a novel category of SSEs, known as frameworked electrolytes (FEs), has emerged as a formidable contender for the transition to all-solid-state batteries. FEs exhibit a unique macroscopically solid-state nature and microscopically sub-nanochannels offering high ionic conductivity. In this perspective, the unique lithium-ion transport mechanisms within FEs are explored and 2D vertically conductive metal-organic framework (MOF) is proposed as an even more promising FE candidate. The abundant active sites in the 1D sub-nanochannels of 2D vertically conductive MOFs facilitate efficient ion transport, favorable interfacial compatibility, and scalable industrial applications. This perspective aims to boost the emergence of novel SSEs, promoting the realization of long-expected all-solid-state batteries and inspiring future energy storage solutions.

PEO-Based Solid-State Polymer Electrolytes for Wide-Temperature Solid-State Lithium Metal Batteries

Developing solid-state lithium metal batteries with wide operating temperature range is important in future. Polyethylene oxide (PEO)-based solid-state electrolytes are extensively studied for merits including superior flexibility and low glass transition temperature. However, ideal usage temperatures for conventional PEO-based solid-state electrolytes are between 60 and 65 °C, and unequable temperature degrades their electrochemical performances at low and high temperatures (≤25 °C and ≥80 °C). Herein, modification methods of PEO electrolytes for low, high especially wide-temperature applications are reviewed based on detailed analyses of mechanisms involved in its modification at different temperatures. First, shortcomings of PEO solid electrolytes due to influence of temperature are pointed out. Second, existing modification strategies are summarized in detail from three aspects of high, low especially wide temperatures, including application of PEO derivatives or chain segment modification treatment of PEO, addition of fillers, and other modification methods such as reasonable regulation of lithium salts, introduction of functional layers and addition of metal-organic frameworks (MOFs) or covalent organic frameworks (COFs). Finally, a summary and description of PEO-based solid electrolyte research and development trends for wide-temperature applications are provided. The review aims to offer some guidance for the creation of PEO solid batteries with wider working temperature ranges.

Two-Dimensional (2D) Conductive Metal-Organic Framework Thin Films: The Preparation and Applications in Electrochemistry

Two-dimensional conductive MOF thin films have attracted attention due to their rich pore structure and unique electrical properties, and their applications in many fields, including batteries, sensing, supercapacitors, electrocatalysis, etc. This paper discusses several preparation methods for 2D conductive MOF thin films. And the applications of 2D conductive MOF thin films are summarized. In addition, the current challenges in the preparation of 2D conductive MOF thin films and the great potential in practical applications are discussed.

Electric Field and Nanocontact Effects in Metal-Organic Framework/Li6.4La3Zr1.4Ta0.6O12 Ionic Conductors for Fast Interfacial Lithium-Ion Transport Kinetics

The slow ion transport kinetics inside or between the nanofillers in composite polymer electrolytes (CPEs) lead to the formation of lithium dendrites for solid-state lithium batteries. To address the critical issues, CPEs (U@UNL) composed of a UIO-66@UIO-66-NH2 (U@UN) core-shell heterostructure and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) filler is designed. Due to the different band structures of the U@UN heterostructure, a built-in electric field is constructed to promote the transfer kinetics of carriers. Besides, the introduction of LLZTO facilitates the formation of a close nanometer contact interface between U@UN and LLZTO, reducing interface impedance and accelerating the lithium-ion transfer rate. As a benefit from the built-in electric field and the nanometer contact interface, U@UNL exhibits a wide electrochemical window of 5.17 V, a large lithium-ion transference number of 0.76, and a high ionic conductivity of 3.50 × 10-3 S cm-1. Consequently, the U@UNL electrolyte possesses excellent interfacial stability against Li metal after 1200 h at 0.1 mA cm-2 and shows a high specific capacity of 160.2 and 152.6 mAh g-1 at 0.5 and 1 C, respectively. This work proposes a complete strategy for building high-performance solid-state lithium batteries by a built-in electric field and nanometer contact interface between U@UN and LLZTO.

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.

Hydrogen-Bonded Organic Frameworks-based Electrolytes with Controllable Hydrogen Bonding Networks for Solid-State Lithium Batteries

The lack of stable solid-state electrolytes (SSEs) with high-ionic conductivity and the rational design of electrode/electrolyte interfaces remains challenging for solid-state lithium batteries. Here, for the first time, a high-performance solid-state lithium-oxygen (Li-O2) battery is developed based on the Li-ion-conducted hydrogen-bonded organic framework (LHOF) electrolyte and the HOF-DAT@CNT composite cathode. Benefiting from the abundant dynamic hydrogen bonding network in the backbone of LHOF-DAT SSEs, fast Li+ ion transport (2.2×10-4 S cm-1), a high Li+ transference number (0.88), and a wide electrochemical window of 5.05 V are achieved. Symmetric batteries constructed with LHOF-DAT SSEs exhibit a stably cycled duration of over 1400 h with uniform deposition, which mainly stems from the jumping sites that promote a uniformly high rate of Li+ flux and the hydrogen-bonding network structure that can relieve the structural changes during Li+ transport. LHOF-DAT SSEs-based Li-O2 batteries exhibit high specific capacity (10335 mAh g-1), and stable cycling life up to 150 cycles. Moreover, the solid-state lithium metal battery with LHOF-DAT SSEs endow good rate capability (129.6 mAh g-1 at 0.5 C), long-term discharge/charge stability (210 cycles). The design of LHOF-DAT SSEs opens an avenue for the development of novel SSEs-based solid-state lithium batteries.

Missing-Linker Defect Functionalized Metal-Organic Frameworks Accelerating Zinc Ion Conduction for Ultrastable All-Solid-State Zinc Metal Batteries

Solid-state polymer electrolytes (SPEs) are promising for high-performance zinc metal batteries (ZMBs), but they encounter critical challenges of low ionic conductivity, limited Zn2+ transference number (tZn2+), and an unstable electrolyte-electrode interface. Here, we present an effective approach involving a missing-linker metallic organic framework (MOF)-catalyzed poly(ethylene glycol) diacrylate (PEGDA)/polyacrylamide (PAM) copolymer SPE for single Zn2+ conduction and seamless electrolyte-electrode contact. The single-Zn2+ conduction is facilitated by the anchoring of the OTF- anions onto the unsaturated metal sites of missing-linker MOF, while the PEGDA and PAM chains in competitive coordination with Zn2+ ions promote rapid Zn ion transport. Our all-solid-state electrolyte simultaneously achieves a superior ionic conductivity of 1.52 mS cm-1 and a high tZn2+ of 0.83 at room temperature, alongside uniform Zn metal deposition (1000 cycles in symmetric cells) and high Zn plating/striping efficiencies (>99% after 600 cycles in asymmetric cells). Applications of our SPE in Zn//VO2 full cells are further demonstrated with a long lifespan of 2000 cycles and an extremely low-capacity degradation rate of 0.012% per cycle. This work provides an effective strategy for using a missing-linker MOF to catalyze competitively coordinating copolymers for accelerating Zn2+ ion conduction, assisting the future design of all-solid-state ZMBs.

Porous Organic Framework Materials (MOF, COF, and HOF) as the Multifunctional Separator for Rechargeable Lithium Metal Batteries

The separator is an important component in batteries, with the primary function of separating the positive and negative electrodes and allowing the free passage of ions. Porous organic framework materials have a stable connection structure, large specific surface area, and ordered pores, which are natural places to store electrolytes. And these materials with specific functions can be designed according to the needs of researchers. The performance of porous organic framework-based separators used in rechargeable lithium metal batteries is much better than that of polyethylene/propylene separators. In this paper, the three most classic organic framework materials (MOF, COF, and HOF) are analyzed and summarized. The applications of MOF, COF, and HOF separators in lithium-sulfur batteries, lithium metal anode, and solid electrolytes are reviewed. Meanwhile, the research progress of these three materials in different fields is discussed based on time. Finally, in the conclusion, the problems encountered by MOF, COF, and HOF in different fields as well as their future research priorities are presented. This review will provide theoretical guidance for the design of porous framework materials with specific functions and further stimulate researchers to conduct research on porous framework materials.

Solid-State Electrolytes: Probing Interface Regulation from Multiple Perspectives

Solid-state electrolytes (SSEs), as the heart of all-solid-state batteries (ASSBs), are recognized as the next-generation energy storage solution, offering high safety, extended cycle life, and superior energy density. SSEs play a pivotal role in ion transport and electron separation. Nonetheless, interface compatibility and stability issues pose significant obstacles to further enhancing ASSB performance. Extensive research has demonstrated that interface control methods can effectively elevate ASSB performance. This review delves into the advancements and recent progress of SSEs in interfacial engineering over the past years. We discuss the detailed effects of various regulation strategies and directions on performance, encompassing enhancing Li+ mobility, reducing energy barriers, immobilizing anions, introducing interlayers, and constructing unique structures. This review offers fresh perspectives on the development of high-performance lithium-metal ASSBs.

Molten Guest-Mediated Metal-Organic Frameworks Featuring Multi-Modal Supramolecular Interaction Sites for Flame-Retardant Superionic Conductor in All-Solid-State Batteries

The development of solid-state electrolytes (SSEs) with outstanding comprehensive performance is currently a critical challenge for achieving high energy density and safer solid-state batteries (SSBs). In this study, a strategy of nano-confined in situ solidification is proposed to create a novel category of molten guest-mediated metal-organic frameworks, named MGM-MOFs. By embedding the newly developed molten crystalline organic electrolyte (ML20) into the nanocages of anionic MOF-OH, MGM-MOF-OH, characterized by multi-modal supramolecular interaction sites and continuous negative electrostatic environments within nano-channels, is achieved. These nanochannels promote ion transport through the successive hopping of Li+ between neighbored negative electrostatic environments and suppress anion movement through the chemical constraint of the hydroxyl-functionalized pore wall. This results in remarkable Li+ conductivity of 7.1 × 10-4 S cm-1 and high Li+ transference number of 0.81. Leveraging these advantages, the SSBs assembled with MGM-MOF-OH exhibit impressive cycle stability and a high specific energy density of 410.5 Wh kganode + cathode + electrolyte -1 under constrained conditions and various working temperatures. Unlike flammable traditional MOFs, MGM-MOF-OH demonstrates high robustness under various harsh conditions, including ignition, high voltage, and extended to humidity.

Strategies to improve the ionic conductivity of quasi-solid-state electrolytes based on metal-organic frameworks

The low ionic conductivity of quasi-solid-state electrolytes (QSSEs) at ambient temperature is a barrier to the development of solid-state batteries (SSBs). Conversely, metal-organic frameworks (MOFs) with porous structure and metal sites show great potential for the fabrication of QSSEs. Numerous studies have proven that the structure and functional groups of MOFs could significantly impact the ionic conductivity of QSSEs based on MOFs (MOFs-QSSEs). This review introduces the transport mechanism of lithium ions in various MOFs-QSSEs, and then analyses how to construct an effective and consistent lithium ions pathway from the perspective of MOFs modification. It is shown that the ion conductivity could be enhanced by modifying the morphology and functional groups, as well as applying amorphous MOFs. Lastly, some issues and future perspectives for MOFs-QSSEs are examined. The primary objective of this review is to enhance the comprehension of the mechanisms and performance optimization methods of MOFs-QSSEs. Consequently, this would guide the design and synthesis of QSSEs with high ionic conductivity, and ultimately enhance the performance of commercial SSBs.

Recent progress and perspectives on metal-organic frameworks as solid-state electrolytes for lithium batteries

Solid-state electrolytes (SSEs) are the key materials in the new generation of all-solid-state lithium ion/metal batteries. Metal-organic frameworks (MOFs) are ideal materials for developing solid electrolytes because of their structural diversity and porous properties. However, there are several significant issues and obstacles involved, such as lower ion conductivity, a smaller ion transport number, a narrower electrochemical stability window and poor interface contact. In this review, a comprehensive analysis and summary of the unique ion-conducting behavior of MOF-based electrolytes in rechargeable batteries are presented, and the different design principles of MOF-based SSEs are classified and emphasized. Accordingly, four design principles for achieving these MOF-based SSEs are presented and the influence of SSEs combined with MOFs on the electrochemical performance of the batteries is described. Finally, the challenges in the application of MOF materials in lithium ion/metal batteries are explored, and directions for future research on MOF-based electrolytes are proposed. This review will deepen the understanding of MOF-based electrolytes and promote the development of high-performance solid-state lithium ion/metal batteries. This review not only provides theoretical guidance for research on new MOF-based SSE systems, but also contributes to further development of MOFs applied to rechargeable batteries.

Janus Quasi-Solid Electrolyte Membranes with Asymmetric Porous Structure for High-Performance Lithium-Metal Batteries

Quasi-solid electrolytes (QSEs) based on nanoporous materials are promising candidates to construct high-performance Li-metal batteries (LMBs). However, simultaneously boosting the ionic conductivity (σ) and lithium-ion transference number (t+) of liquid electrolyte confined in porous matrix remains challenging. Herein, we report a novel Janus MOFLi/MSLi QSEs with asymmetric porous structure to inherit the benefits of both mesoporous and microporous hosts. This Janus QSE composed of mesoporous silica and microporous MOF exhibits a neat Li+ conductivity of 1.5 × 10-4 S cm-1 with t+ of 0.71. A partially de-solvated structure and preference distribution of Li+ near the Lewis base O atoms were depicted by MD simulations. Meanwhile, the nanoporous structure enabled efficient ion flux regulation, promoting the homogenous deposition of Li+. When incorporated in Li||Cu cells, the MOFLi/MSLi QSEs demonstrated a high Coulombic efficiency of 98.1%, surpassing that of liquid electrolytes (96.3%). Additionally, NCM 622||Li batteries equipped with MOFLi/MSLi QSEs exhibited promising rate performance and could operate stably for over 200 cycles at 1 C. These results highlight the potential of Janus MOFLi/MSLi QSEs as promising candidates for next-generation LMBs.

Highly Stable Organic Molecular Porous Solid Electrolyte with One-Dimensional Ion Migration Channel for Solid-State Lithium-Oxygen Battery

Solid-state lithium-oxygen (Li-O2 ) batteries have been widely recognized as one of the candidates for the next-generation of energy storage batteries. However, the development of solid-state Li-O2 batteries has been hindered by the lack of solid-state electrolyte (SSE) with high ionic conductivity at room temperature, high Li+ transference number, and the high stability to air. Herein, the organic molecular porous solid cucurbit[7]uril (CB[7]) with one-dimensional (1D) ion migration channels is developed as the SSE for solid-state Li-O2 batteries. Taking advantage of the 1D ion migration channel for Li+ conduction, CB[7] SSE achieves high ionic conductivity (2.45 × 10-4 S cm-1 at 25 °C). Moreover, the noncovalent interactions facilitated the immobilization of anions, realizing a high Li+ transference number (tLi + = 0.81) and Li+ uniform distribution. The CB[7] SSE also shows a wide electrochemical stability window of 0-4.65 V and high thermal stability and chemical stability, as well as realizes stable Li+ plating/stripping (more than 1000 h at 0.3 mA cm-2 ). As a result, the CB[7] SSE endows solid-state Li-O2 batteries with superior rate capability and long-term discharge/charge stability (up to 500 h). This design strategy of CB[7] SSE paves the way for stable and efficient solid-state Li-O2 batteries toward practical applications.

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.

Continuous Amorphous Metal-Organic Frameworks Layer Boosts the Performance of Metal Anodes

Employing metal anodes can greatly increase the volumetric/gravimetric energy density versus a conventional ion-insertion anode. However, metal anodes are plagued by dendrites, corrosion, and interfacial side reaction issues. Herein, a continuous and flexible amorphous MOF layer was successfully synthesized and used as a protective layer on metal anodes. Compared with the crystalline MOF layer, the continuous amorphous MOF layer can inhibit dendrite growth at the grain boundary and eliminate ion migration near the grain boundary, showing high interfacial adhesion and a large ion migration number (tZn2+ = 0.75). In addition, the continuous amorphous MOF layer can effectively solve several key challenges, e.g., corrosion of the zinc anode, hydrogen evolution reaction, and dendrite growth on the zinc surface. The prepared Zn anode with the continuous amorphous MOF (A-MOF) layer exhibited an ultralong cycling life (around one year, more than 7900 h) and a low overpotential (<40 mV), which is 12 times higher than that of the crystalline MOF protective layer. Even at 10 mA cm-2, it still showed high stability for more than 5500 cycles (1200 h). The enhanced performance is realized for full cells paired with a MnO2 cathode. In addition, a flexible symmetrical battery with the Zn@A-ZIF-8 anode exhibited good cyclability under different bending angles (0°, 90°, and 180°). More importantly, various metal substrates were successfully coated with compact A-ZIF-8. The A-ZIF-8 layer can obviously improve the stability of other metal anodes, including those of Mg and Al. These results not only demonstrate the high potential of amorphous MOF-decorated Zn anodes for AZIBs but also propose a type of protective layer for metal anodes.