Ionic Liquid-Impregnated ZIF-8/Polypropylene Solid-like Electrolyte for Dendrite-free Lithium-Metal Batteries

MOF-based nanomaterials for advanced aqueous-ion batteries

Metal-organic frameworks (MOFs)-based nanomaterials have great potential in the field of electrochemical energy storage due to their abundant pore size, high specific surface area, controllable structure and porosity, and homogeneous metal center. MOFs complexes and derivatives not only inherit the original morphology characteristics of MOFs but also provide excellent electrochemical performance. Batteries operating in aqueous electrolytes are cheaper, safer, and have higher ionic conductivity than those operating in conventional organic electrolytes. Therefore, it is useful to summarize the MOFs that should be used for aqueous electrochemical energy storage devices. This manuscript firstly introduces the composition and energy storage mechanism of aqueous Li/Na/Zn ion batteries. In addition, a detailed review of the development of MOFs-based nanomaterials and their commonly used characterization under aqueous conditions is presented. The relationship between the structure and composites of MOFs-based nanomaterials and electrochemical performance is highlighted. The applications of MOFs composites in aqueous batteries in terms of electrode materials and electrolytes are presented and summarized. Finally, research directions and perspectives for MOFs-based nanomaterials in advanced aqueous batteries are presented.

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.

Robust MOF-Based Composite Solid-State Electrolyte Membrane for High-Performance Lithium-Metal Batteries

In this work, we construct a robust MOF-based flexible composite membrane based on PVDF-HFP, UIO-66, and ionic liquid (IL). Through their synergistic reinforcement effect, the obtained solid-state electrolytes can simultaneously achieve high ionic conductivity, good mechanical properties, and flame retardance. The abundant pores of the MOF are capable of loading IL, which not only builds continuous ion channels and facilitates the dissociation of Li+ but also balances the mechanical properties and electrochemical performance. Consequently, the as-prepared electrolyte membranes exhibit excellent ionic conductivity (5.55 × 10-4 S cm-1), high Li+ transference number (0.52), moderate electrochemical window (4.3 V), outstanding mechanical properties (tensile strength of 6.63 MPa and elongation of 232%), and good interfacial stability (stable Li plating/stripping behavior). Meanwhile, the assembled LiFePO4//Li battery exhibits an excellent rate capability and long cycle stability. This work demonstrates a realistic strategy for the fabrication of MOF-based composite SSEs toward next generation high-performance lithium metal batteries.

Confining Liquid Electrolytes in a Nitrogen-Rich Nanoporous Carbon Sponge for Superior Lithium-Ion Conduction

Solid-state Li-ion batteries are recognized as highly promising energy storage devices due to their ability to overcome issues related to the inferior cycle life and potential risks of traditional liquid Li-ion batteries. However, developing solid-state electrolytes with fast Li-ion conductivity continues to be a major challenge. In this study, we present a family of quasi-solid-state electrolytes (QSSEs) synthesized by confining liquid electrolytes within a N-rich porous carbon sponge, exhibiting superior Li-ion conduction for solid-state battery applications. The N-rich porous carbon sponge was prepared by carbonizing ZIF-8 under an argon atmosphere, followed by the incorporation of organic liquid salt electrolytes into the pores and channels of the sponge to create composite QSSEs. Notably, the resulting composite QSSEs demonstrate exceptional Li-ion conduction at room temperature, with a record-high conductivity exceeding 10-2 S cm-1 and a remarkable Li+ transference number of 0.75, along with a wide electrochemical stability window of 4.8 V. Furthermore, these composite QSSEs show significant potential for use in solid-state Li-ion batteries, delivering a specific capacity of 133 mAh g-1 at 0.1 C and possessing a high Coulombic efficiency of 98.6%.

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.

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.

MOF-modified dendrite-free gel polymer electrolyte for zinc-ion batteries

Zinc-ion batteries are promising candidates for large-scale energy storage, and gel polymer electrolytes (GPEs) play an important role in zinc-ion battery applications. Metal-organic frameworks (MOFs) are characterized by large specific surface areas and ordered pores. This highly ordered microporous structure provides a continuous transport channel for ions, thus realizing the high-speed transmission of ions. In this paper, an MOF-modified dendrite-free GPE was designed. The incorporation of MOF particles not only reduces the crystallinity of the polymer, increases the motility of the molecular chains, and facilitates the transfer of Zn2+, but also attracts anions to reduce polarization during electrochemical reactions. It was shown that this MOF-modified gel polymer electrolyte has a higher ionic conductivity compared to other PVDF-based polymer electrolytes (approximate range of 2 × 10-4 to 3 × 10-3 S cm-1), with a very high conductivity (1.63 mS cm-1) even at -20 °C. The Zn/Zn symmetric cell could maintain operation for more than 3600 h at a current density of 1 mA cm-2, and SEM showed that the MOF-modified gel electrolyte had uniform Zn2+ deposition.

An Ultrahigh Modulus Gel Electrolytes Reforming the Growing Pattern of Li Dendrites for Interfacially Stable Lithium-Metal Batteries

Gel polymer electrolytes (GPEs) have aroused intensive attention for their moderate comprehensive performances in lithium-metal batteries (LMBs). However, GPEs with low elastic moduli of MPa magnitude cannot mechanically regulate the Li deposition, leading to recalcitrant lithium dendrites. Herein, a porous Li7 La3 Zr2 O12 (LLZO) framework (PLF) is employed as an integrated solid filler to address the intrinsic drawback of GPEs. With the incorporation of PLF, the composite GPE exhibits an ultrahigh elastic modulus of GPa magnitude, confronting Li dendrites at a mechanical level and realizing steady polarization at high current densities in Li||Li cells. Benefiting from the compatible interface with anodes, the LFP|PLF@GPE|Li cells deliver excellent rate capability and cycling performance at room temperature. Theoretical models extracted from the topology of solid fillers reveal that the PLF with unique 3D structures can effectively reinforce the gel phase of GPEs at the nanoscale via providing sufficient mechanical support from the load-sensitive direction. Numerical models are further developed to reproduce the multiphysical procedure of dendrite propagation and give insights into predicting the failure modes of LMBs. This work quantitatively clarifies the relationship between the topology of solid fillers and the interface stability of GPEs, providing guidelines for designing mechanically reliable GPEs for LMBs.

Confining Ionic Liquids in Developing Quasi-Solid-State Electrolytes for Lithium Metal Batteries

The concept of confining ionic liquids (ILs) in developing quasi-solid-state electrolytes (QSSEs) has been proposed, where ILs are dispersed in polymer networks/backbones and/or filler/host pores, forming the so-called confinement, and great research progress and promising research results have been achieved. In this review, the progress and achievement in developing QSSEs using IL-confinement for lithium metal batteries (LMBs), together with advanced characterizations and simulations, were surveyed, summarized, and analyzed, where the influence of specific parameters, such as IL (type, content, etc.), substrate (type, structure, surface properties, etc.), confinement methods, and so on, was discussed. The confinement concept was further compared with the conventional one in other research areas. It indicates that the IL-confinement in QSSEs improves the performance of electrolytes, for example, increasing the ionic conductivity, widening the electrochemical window, and enhancing the cycle performance of the assembled cells, and being different from those in other areas, that is, the IL-confinement concept in the battery area is in a broad extent. Finally, insights into developing QSSEs in LMBs with the confinement strategy were provided to promote the development and application of QSSE LMBs.

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

Metal-organic frameworks (MOFs) have been reported as promising materials for electrochemical applications owing to their tunable porous structures and ion-sieving capability. However, it remains challenging to rationally design MOF-based electrolytes for high-energy lithium batteries. In this work, by combining advanced characterization and modeling tools, a series of nanocrystalline MOFs is designed, and the effects of pore apertures and open metal sites on ion-transport properties and electrochemical stability of MOF quasi-solid-state electrolytes are systematically studied. It isdemonstrated that MOFs with non-redox-active metal centers can lead to a much wider electrochemical stability window than those with redox-active centers. Furthermore, the pore aperture of MOFs is found to be a dominating factor that determines the uptake of lithium salt and thus ionic conductivity. The ab initio molecular dynamics simulations further demonstrate that open metal sites of MOFs can facilitate the dissociation of lithium salt and immobilize anions via Lewis acid-base interaction, leading to good lithium-ion mobility and high transference number. The MOF quasi-solid-state electrolyte demonstrates great battery performance with commercial LiFePO4 and LiCoO2 cathodes at 30 °C. This work provides new insights into structure-property relationships between tunable structure and electrochemical properties of MOFs that can lead to the development of advanced quasi-solid-state electrolytes for high-energy lithium batteries.

MOFs Containing Solid-State Electrolytes for Batteries

The use of metal-organic frameworks (MOFs) in solid-state electrolytes (SSEs) has been a very attractive research area that has received widespread attention in the modern world. SSEs can be divided into different types, some of which can be combined with MOFs to improve the electrochemical performance of the batteries by taking advantage of the high surface area and high porosity of MOFs. However, it also faces many serious problems and challenges. In this review, different types of SSEs are classified and the changes in these electrolytes after the addition of MOFs are described. Afterward, these SSEs with MOFs attached are introduced for different types of battery applications and the effects of these SSEs combined with MOFs on the electrochemical performance of the cells are described. Finally, some challenges faced by MOFs materials in batteries applications are presented, then some solutions to the problems and development expectations of MOFs are given.

Advances of Electroactive Metal-Organic Frameworks

The preparation of electroactive metal-organic frameworks (MOFs) for applications of supercapacitors and batteries has received much attention and remarkable progress during the past few years. MOF-based materials including pristine MOFs, hybrid MOFs or MOF composites, and MOF derivatives are well designed by a combination of organic linkers (e.g., carboxylic acids, conjugated aromatic phenols/thiols, conjugated aromatic amines, and N-heterocyclic donors) and metal salts to construct predictable structures with appropriate properties. This review will focus on construction strategies of pristine MOFs and hybrid MOFs as anodes, cathodes, separators, and electrolytes in supercapacitors and batteries. Descriptions and discussions follow categories of electrochemical double-layer capacitors (EDLCs), pseudocapacitors (PSCs), and hybrid supercapacitors (HSCs) for supercapacitors. In contrast, Li-ion batteries (LIBs), Lithium-sulfur batteries (LSBs), Lithium-oxygen batteries (LOBs), Sodium-ion batteries (SIBs), Sodium-sulfur batteries (SSBs), Zinc-ion batteries (ZIBs), Zinc-air batteries (ZABs), Aluminum-sulfur batteries (ASBs), and others (e.g., LiSe, NiZn, H⁺ , alkaline, organic, and redox flow batteries) are categorized for batteries.

A New In Situ Prepared MOF-Natural Polymer Composite Electrolyte for Solid Lithium Metal Batteries with Superior High- Rate Capability and Long-Term Cycling Stability at Ultrahigh Current Density

Lithium metal batteries hold promise for energy storage applications but suffer from uncontrolled lithium dendrites. In this study, a new composite membrane based on modified natural polymer and ZIF-67 is designed and prepared by the in situ composite method for the first time. Among them, a modified natural polymer composed of lithium alginate (LA) and polyacrylamide (PAM) can be obtained by electrospinning. Importantly, the polar functional groups of natural polymers can interact by hydrogen bonding and MOFs can construct lithium-ion transport channels. Consequently, compared with LA-PAM electrolyte without MOF, the electrochemical stability window of ZIF-67-LA-PAM electrolyte becomes wider from 4.5 to 5.2 V, and the lithium-ion transference number (tLi+ ) enhances from 0.326 to 0.627 at 30°C. It is worth noting that the symmetric cells with ZIF-67-LA-PAM have superior stable cycling performance at 40 and 100 mA cm-2 , and a high rate at 10C and 20C for LFP cells. Besides, the cell with NCM811 high-voltage cathode can run stably for 400 cycles with an initial discharge capacity of 136.1 mAh g-1 at 0.5C. This work provides an effective method for designing and preparing MOF-natural polymer composite electrolytes and exhibits an excellent application prospect in high-energy-density lithium metal batteries.

Novel In Situ Growth of ZIF-8 in Porous Epoxy Matrix for Mechanically Robust Composite Electrolyte of High-Performance, Long-Life Lithium Metal Batteries

Polymer electrolytes (PEs) with high flexibility, low cost, and excellent interface compatibility have been considered as an ideal substitute for traditional liquid electrolytes for high safety lithium metal batteries (LMBs). Nevertheless, the mechanical strength of PEs is generally poor to prevent the growth of lithium dendrites during the charge/discharge process, which seriously restricts their wide practical applications. Herein, a mechanical robust ZIF-8/epoxy composite electrolyte with unique pore structure was prepared, which effectively inhibited the growth of lithium dendrites. Meanwhile, the in situ growth of ZIF-8 in porous epoxy matrix can promote the uniform flux and fast transport of lithium ions. Ultimately, the optimal electrolyte shows high ionic conductivity (2.2 × 10−3 S cm−1), wide electrochemical window (5 V), and a large Li+ transference number (0.70) at room temperature. The Li||NCM811 cell using the optimal electrolyte exhibits high capacity and excellent cycling performance (83.2% capacity retention with 172.1 mA h g−1 capacity retained after 200 cycles at 0.2 C). These results indicate that the ZIF-8/epoxy composite electrolyte is of great promise for the application in LMBs.

Exploring ionic liquid-laden metal-organic framework composite materials as hybrid electrolytes in metal (ion) batteries

This review focuses on the combination of metal-organic frameworks (MOFs) and ionic liquids (ILs) to obtain composite materials to be used as solid electrolytes in metal-ion battery applications. Benefiting from the controllable chemical composition, tunable pore structure and surface functionality, MOFs offer great opportunities for synthesizing high-performance electrolytes. Moreover, the encapsulation of ILs into porous materials can provide environmentally benign solid-state electrolytes for electrochemical devices. Due to the versatility of MOF-based materials, in this review we also explore their use as anodes and cathodes in Li- and Na-ion batteries. Finally, solid IL@MOF electrolytes and their implementation into Li and Na batteries have been analyzed, as well as the design and advanced manufacturing of solid IL@MOF electrolytes embedded on polymeric matrices.

Uniform In Situ Grown ZIF-L Layer for Suppressing Hydrogen Evolution and Homogenizing Zn Deposition in Aqueous Zn-Ion Batteries

The hydrogen evolution and dendrite of Zn anode are the major troubles hindering the commercialization of aqueous Zn-ion batteries (AZIBs). ZIF-Ls, a typical metal-organic framework (MOF) with a highly ordered structure and abundant functional groups, seem to be the answer for the above bottlenecks. In this paper, a uniform ZIF-L layer was obtained on the Zn surface (Zn@ZIF-L) via an in situ synthesis method to moderate the solvation structure of solid-liquid interface electrolyte reducing the contact between water and Zn, thereby relieving the hydrogen evolution and corrosion. Furthermore, density functional theory (DFT) analysis reveals the binding energy of H (-4.01 eV) and Zn (-0.82 eV) for ZIF-L is superior to that of pure Zn (H (-1.49 eV) and Zn (-0.68 eV)). Due to the multifunctional ZIF-L layer, the Zn@ZIF-L can regulate Zn deposition to overcome the dendrite for obtaining a long-life Zn anode. Consequently, the modified Zn@ZIF-L anode can cycle for 800 h at 0.25 mA cm^-2 for 0.25 mAh cm^-2, while the bare Zn anode is only maintained for 422 h. Finally, a designed V₂O₅ grown on carbon cloth (V₂O₅@CC) was used as the cathode and coupled with the Zn@ZIF-L anode to assemble the full-cell. The Zn@ZIF-L//V₂O₅@CC full-cell possesses a capacity retention rate of 84.9% after 250 cycles at 0.5 C, prominently higher than Zn//V₂O₅@CC (40.7%).