High-performance Solid-state Electrolyte Research Articles

Constructing Donor–Acceptor-Linked COFs Electrolytes to Regulate Electron Density and Accelerate the Li+ Migration in Quasi-Solid-State Battery

HighlightsDonor–acceptor-linked covalent organic framework (COF)-based electrolyte can not only fulfill highly-selective Li+ conduction, but also offer a crucial opportunity to understand the role of electronic density in quasi-solid-state Li metal batteries.Donor–acceptor-linked COF electrolyte results in Li+ transference number 0.83, high ionic conductivity 6.7 × 10–4 S cm−1 and excellent cyclic ability in Li metal batteries.In situ characterizations, density functional theory calculation and time-of-flight secondary ion mass spectrometry are adopted to expound the mechanism of the rapid migration of Li+ in the “donor–acceptor” electrolyte system.

Enhancing the electrochemical properties of polyethylene oxide solid-state electrolytes based on a small nano-sized UiO-66 metal-organic framework

Metal-organic frameworks (MOFs) have garnered significant attention in the field of Lithium-ion batteries due to their porous periodic network properties. However, this is a challenge to design high-performance solid-state electrolytes reasonably. Herein, a small nano-sized MOF Small-UiO-66 is reported, which has high surface area and mesoporous properties that can effectively inhibit PEO matrix crystallization. The presence of Small-UiO-66 accelerates the dissociation of lithium salts, which disrupts the ordered arrangement of the PEO chain segments. The abundant Lewis acidic sites on the surface of Small-UiO-66 facilitate the construction of abundant Li+ transport channels and promote Li+ conduction. Furthermore, the smaller nano-sized increase the interfacial wettability with lithium metal, which promotes the uniform diffusion of Li+ and inhibits the growth of lithium dendrites. The results indicate that 0.1 Zr-CSE exhibits high ionic conductivities of 6.94 × 10−4 S/cm at 60 °C. Based on 0.1 Zr-CSE, the Li||Li symmetric cell can operate stably for 1200 h at a current density of 0.1 mA/cm2, and the LFP||Li cell also achieves a high initial capacity of 147.65 mAh·g−1 at current densities of 0.5C. This work presents a novel approach for preparing high-performance solid-state Lithium-ion batteries using MOFs as fillers for polymer solid-state electrolytes.

Microporous Materials in Polymer Electrolytes: The Merit of Order.

Solid-state batteries (SSBs) have garnered significant attention in the critical field of sustainable energy storage due to their potential benefits in safety, energy density, and cycle life. The large-scale, cost-effective production of SSBs necessitates the development of high-performance solid-state electrolytes. However, the manufacturing of SSBs relies heavily on the advancement of suitable solid-state electrolytes. Composite polymer electrolytes (CPEs), which combine the advantages of ordered microporous materials (OMMs) and polymer electrolytes, meet the requirements for high ionic conductivity/transference number, stability with respect to electrodes, compatibility with established manufacturing processes, and cost-effectiveness, making them particularly well-suited for mass production of SSBs. This review delineates how structural ordering dictates the fundamental physicochemical properties of OMMs, including ion transport, thermal transfer, and mechanical stability. The applications of prominent OMMs are critically examined, such as metal-organic frameworks, covalent organic frameworks, and zeolites, in CPEs, highlighting how structural ordering facilitates the fulfillment of property requirements. Finally, an outlook on the field is provided, exploring how the properties of CPEs can be enhanced through the dimensional design of OMMs, and the importance of uncovering the underlying "feature-function" mechanisms of various CPE types is underscored.

Ternary stabilization strategies for succinonitrile-based in situ polymerized electrolyte enabling high-performance solid lithium metal batteries

Solid-state lithium metal batteries with high energy density and safety have gained increasing attention due to their potential applications. However, the practical use of solid electrolytes is hindered by several challenges. These include poor compatibility at the electrode–electrolyte interface, low ionic conductivity at room temperature, and fast capacity degradation. To address these issues, here we propose ternary strategies by in-situ cross-linked plastic crystal electrolyte (in-situ PCE) based on succinonitrile (SN). Through the in-situ polymerization of SN with polyacrylonitrile/poly(vinylidene difluoride) (PAN/PVDF) nanofibers separator, excellent mechanical strength and compatibility at the electrode–electrolyte interface are achieved. The cross-linked structure of thermally polymerized ethoxylated trimethylolpropane triacrylate (ETPTA) immobilizes the SN molecule, preventing its contact with the lithium metal and inhibiting irreversible side reactions. Additionally, a LiF-rich passivation layer is employed to further protect the SN at the electrolyte-lithium metal interface. The dual protection from ETPTA and LiF offers excellent stability to lithium. Hence, the in-situ PCE exhibits high ionic conductivity (0.79 mS cm−1 at 30 °C) and wide electrochemical window (4.56 V, vs Li+/Li). The cells exhibit excellent cycling stability and high-rate performance. LiFePO4//Li cells retain 96.6 % capacity after 1000 cycles at 10C rate. This study provides valuable insights into the development of high-performance solid-state electrolytes.

Biomass Solid-State Electrolyte with Abundant Ion and Water Channels for Flexible Zinc-Air Batteries.

Flexible zinc-air batteries are the leading candidates as the next-generation power source for flexible/wearable electronics. However, constructing safe and high-performance solid-state electrolytes (SSEs) with intrinsic hydroxide ion (OH-) conduction remains a fundamental challenge. Herein, by adopting the natural and robust cellulose nanofibers (CNFs) as building blocks, the biomass SSEs with penetrating ion and water channels are constructed by knitting the OH--conductive CNFs and water-retentive CNFs together via an energy-efficient tape casting. Benefiting from the abundant ion and water channels with interconnected hydrated OH- wires for fast OH- conduction under a nanoconfined environment, the biomass SSEs reveal the high water-uptake, impressive OH- conductivity of 175mScm-1 and mechanical robustness simultaneously, which overcomes the commonly existed dilemma between ion conductivity and mechanical property. Remarkably, the flexible zinc-air batteries assemble with biomass SSEs deliver an exceptional cycle lifespan of 310h and power density of 126mWcm-2. The design methodology for water and ion channels opens a new avenue to design high-performance SSEs for batteries.

Synergistic effect of Ti3C2Tx MXene/PAN nanofiber and LLZTO particles on high-performance PEO-based solid electrolyte for lithium metal battery

Solid polymer electrolytes (SPEs) have been considered the most promising separators for all-solid-state lithium metal batteries (ASSLMBs) due to their ease of processing and low cost. However, the practical applications of SPEs in ASSLMBs are limited by their low ionic conductivities and mechanical strength. Herein, we developed a three-dimensional (3D) interconnected MXene (Ti3C2Tx) network and Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles synergistically reinforced polyethylene oxide (PEO)-based SPE, where the association of Li+ with ether-oxygen in PEO could be significantly weakened through the Lewis acid-base interactions between the electron-absorbing group (Ti–F, −O–) of Ti3C2Tx and Li+. Besides, the TFSI− in lithium salts could be immobilized by hydrogen bonds from the Ti–OH of Ti3C2Tx. The 3D interconnected Ti3C2Tx network not only alleviated the agglomeration of inorganic fillers (LLZTO), but also improved the mechanical strength of composite solid electrolyte (CSE). Consequently, the assembled Li||CSE||Li symmetric battery showed excellent cycling stability at 35 ℃ (stable cycling over 3000 h at 0.1 mA cm−2, 0.1 mAh cm−2) and −2 ℃ (stable cycling over 2500 h at 0.05 mA cm−2, 0.05 mAh cm−2). Impressively, the LiFePO4||CSE||Li battery showed a high discharge capacity of 145.3 mAh/g at 0.3 C after 300 cycles at 35 ℃. This rational structural design provided a new strategy for the preparation of high-performance solid-state electrolytes for lithium metal batteries.

Utilizing machine learning and phonon density of states for innovative approaches to design and optimize high-performance solid-state Mg-ion electrolytes

This study presents the development of machine learning (ML) model for the enhancement of ionic conductivity in solid-state electrolytes for Mg-ion batteries (MIBs), utilizing phonon density of states (PhDOS) as tool for predicting ionic conductivity. Data comprising compounds with PhDOS calculations are sourced from the Materials Project (MP) and processed to extract frequencies and PhDOS values, enabling the calculation of the total phonon band center, a practical proxy for ionic conductivity. Learning process involving three ML algorithms (Extra Random Trees (XT), Gradient Boosting (GB), Extreme Gradient Boosting (XGB)) is conducted using these band centers. Cross-validation results indicated the superior accuracy of XT-model where its performance, is validated through density functional theory (DFT)-based phonon calculations on Mg2Ge, Mg2Gd, MgSe2 and Mg3P2. The XT-model was further employed to predict total phonon band centers of ∼9 K Mg compounds obtained from MP with no previous PhDOS calculations containing Mg–O, Mg–S and Mg–Se compounds which show that the band center median of Mg–Se materials is the lowest of the systems. Additionally, Nudged Elastic Band (NEB) and Ab initio Molecular Dynamics (AIMD) calculations is used to calculate the migration energy of MgSe2 which shows potential as an Mg-ion solid electrolyte when compared to other Mg electrolytes.

Construction of high-performance solid-state electrolytes for lithium metal batteries by UV-curing technology

With high energy density and high safety, all-solid-state lithium metal batteries (ASSLMBs) are considered the most competitive next-generation energy storage batteries. In this work, different formulations of PEGDA-based solid-state electrolytes were prepared by solution flow casting and UV-irradiated in situ polymerization. Polyethylene oxide (PEO) was introduced to solve the problem of improving the flexibility of the substrate, and a 1:5 mass ratio between them was determined. Inorganic ceramic filler Li1.25Al0.25Zr1.75(PO4)3 (LAZP) and plasticizer butanedinitrile (SCN) were introduced to improve the ionic conductivity (σ) of the electrolyte. The best performing PP15-30-SCN sample showed a 40-fold improvement in room temperature ionic conductivity over PEGDA and lithium ion mobility number of 0.43. The ASSLMBs were assembled with composite electrolytes and tested at 60 °C. The polarization of PP15-30-SCN was significantly reduced, and the battery cycled stably at current densities from 0.1 to 2 C, with an average discharge specific capacity of 111.78 mAh g−1 at 1C. The average specific capacity at 1C was 111.78 mAh g−1. Meanwhile, the capacity retention rate was more than 99% after more than 70 long cycles at 0.5C.

Flexible self-supporting inorganic nanofiber membrane-reinforced solid-state electrolyte for dendrite-free lithium metal batteries.

Compounding of suitable fillers with PEO-based polymers is the key to forming high-performance electrolytes with robust network structures and homogeneous Li+-transport channels. In this work, we innovatively and efficiently prepared Al2O3 nanofibers and deposited an aqueous dispersion of Al2O3 into a membrane via vacuum filtration to construct a nanofiber membrane with a three-dimensional (3D) network structure as the backbone of a PEO-based solid-state electrolyte. The supporting effect of the nanofiber network structure improved the mechanical properties of the reinforced composite solid-state electrolyte and its ability to inhibit the growth of Li dendrites. Meanwhile, interconnected nanofibers in the PEO-based electrolyte and the strong Lewis acid-base interactions between the chemical groups on the surface of the inorganic filler and the ionic species in the PEO matrix provided facilitated pathways for Li+ transport and regulated the uniform deposition of Li+. Moreover, the interaction between Al2O3 and lithium salts as well as the PEO polymer increased free Li+ concentration and maintained its stable electrochemical properties. Hence, assembled Li/Li symmetric cells achieved a cycle life of more than 2000 h. LFP/Li and NMC811/Li cells provided high discharge specific capacities of up to 146.9 mA h g-1 (0.5C and 50 °C) and 166.9 mA h g-1 (0.25C and 50 °C), respectively. The prepared flexible self-supporting 3D nanofiber network structure construction can provide a simple and efficient new strategy for the exploitation of high-performance solid-state electrolytes.

In-Situ Polymerized Solid-State Polymer Electrolytes for High-Safety Sodium Metal Batteries: Progress and Perspectives

The practical usage of sodium metal batteries is mainly hampered by their potential safety risks caused by conventional liquid-state electrolytes. Hence, solid-state sodium metal batteries, which employ inorganic solid electrolytes and/or solid-state polymer electrolytes, are considered an emerging technology for addressing the safety hazards. Unfortunately, these traditional inorganic/polymer solid electrolytes, most of which are prepared via ex-situ methods, frequently suffer from inadequate ionic conductivity and sluggish interfacial transportation. In light of this, in-situ polymerized solid-state polymer electrolytes are proposed to simplify their preparation process and simultaneously address these aforementioned challenges. In this review, the up-to-date research progress of the design, synthesis, and applications of this kind of polymer electrolytes for sodium batteries of high safety via several in-situ polymerization methods (including photoinduced in-situ polymerization, thermally induced in-situ free radical polymerization, in-situ cationic polymerization, and cross-linking reaction) are summarized. In addition, some perspectives, opportunities, challenges, and potential research directions regarding the further development of in-situ fabricated solid-state polymer electrolytes are also provided. We expect that this review will shed some light on designing high-performance solid-state polymer electrolytes for building next-generation sodium batteries with high safety and high energy.

3D core-shell nanofibers framework and functional ceramic nanoparticles synergistically reinforced composite polymer electrolytes for high-performance all-solid-state lithium metal battery

Satisfactory ionic conductivity, excellent mechanical stability, and high-temperature resistance are the prerequisites for the safe application of solid polymer electrolytes (SPEs) in all-solid-state lithium metal batteries (ASSLMBs). In this study, a novel poly(m-phenylene isophthalamide) (PMIA)-core/poly(ethylene oxide) (PEO)-shell nanofiber membrane and the functional Li6.4La3Zr1.4Ta0.6O12 (LLZTO) ceramic nanoparticle are simultaneously introduced into the PEO-based SPEs to prepare composite polymer electrolytes (CPEs). The core PMIA layer of composite nanofibers can greatly improve the mechanical strength and thermal stability of the CPEs, while the shell PEO layer can provide the 3D continuous transport channels for lithium ions. In addition, the introduction of functional LLZTO nanoparticle not only reduces the crystallinity of PEO, but also promotes the dissociation of lithium salts and releases more Li+ ions through its interaction with the Lewis acid-base of anions, thereby overall improving the transport of lithium ions. Consequently, the optimized CPEs present high ionic conductivity of 1.38×10−4 S/cm at 30 °C, significantly improved mechanical strength (8.5 MPa), remarkable thermal stability (without obvious shrinkage at 150 °C), and conspicuous Li dendrites blocking ability (>1800 h). The CPEs also both have good compatibility and cyclic stability with LiFePO4 (>2000 cycles) and high-voltage LiNi0.8Mn0.1Co0.1O2 (NMC811) (>500 cycles) cathodes. In addition, even at low temperature (40 °C), the assembled LiFePO4/CPEs/Li battery still can cycle stably. The novel design can provide an effective way to exploit high-performance solid-state electrolytes.

Improving the Ionic Conductivity and Electrochemical Performance of NASICON Based Ca2+ Doped NZSP Solid-State Electrolyte for Solid State Sodium Batteries

Major efforts have been made in the search of high-energy and power density batteries to keep up with the demands of the rapidly growing portable electronics market and EV industry. Though lithium-ion batteries have dominated this field, sodium ion batteries are increasing in popularity due it’s wide availability and low cost. Conventional Sodium ion batteries with liquid electrolyte usually have several problems, including limited electrochemical window, flammability, and leakages which are a potential safety hazard. One of the most promising approaches to improve the safety of a battery is to replace the liquid ion conducting electrolyte to a solid ion conducting electrolyte. Even so, how to develop such a high-performance solid-state electrolyte (SSE) that is compatible with both the anode and cathode interface is still challenging. Furthermore, low ionic conductivity electrolytes, dendrite formation and poor cycling capabilities are adding on to the challenges. As one means to tackle these challenges and improve the electrochemical performances of the battery, cation substitution can be considered. Here, NASICON (Sodium Super Ionic Conductor) based Na1+xZr2SixP3-xO12 (NZSP) solid state electrolyte, its phase behavior and its performances in solid state batteries are introduced. Current trends & perspectives on interface engineering and cation substitution of the NZSP electrolyte is also discussed. Although NASICON material lacks mechanical flexibility, it has high ionic conductivity. Substitutions with La3+ and Sc3+ have shown to improve the ionic conductivity of the battery but have also proven to be expensive. In order to make it more feasible, cations such as Ca2+ should be considered. Pure phase NZSP materials with Ca2+ substitution for Zr4+ will be synthesized using solid-state sintering. Along with the Ca-ion substitution, addition of excess sodium into the Ca-ion substituted NZSP system will be performed and a comparative analysis will be conducted. Here, we will analyze the electrochemical performance through XRD Analysis, SEM Analysis, Impedance Spectroscopy and Galvanostatic Charge/Discharge testing. The development of solid-state sodium electrolytes lead to a brighter future where all solid state sodium batteries could be used to power electric vehicles, electronic devices and contribute towards large scale storage and grid applications.

Bilayer Zwitterionic Metal-Organic Framework for Selective All-Solid-State Superionic Conduction in Lithium Metal Batteries.

Solid-state batteries (SSBs) hold immense potential for improved energy density and safety compared to traditional batteries. However, existing solid-state electrolytes (SSEs) face challenges in meeting the complex operational requirements of SSBs. In this study, weintroduce a novel approach to address this issue by developing a metal-organic framework (MOF) with customized bilayer zwitterionic nano-channels (MOF-BZN) as high-performance SSEs. The bilayer zwitterionic nano-channels consist of a rigid anionic MOF channel with chemically grafted soft multi-cationic oligomers (MCOs) on the pore wall. This design enables selective superionic conduction, with MCOs restricting the movement of anions while coulombic interaction between MCOs and anionic framework promoting the dissociation of Li+ . MOF-BZN exhibits remarkable Li+ conductivity (8.76 × 10-4 S cm-1 ), high Li+ transference number (0.75), and a wide electrochemical window of up to 4.9V at 30°C. Ultimately, the SSB utilizing flame retarded MOF-BZN achieves an impressive specific energy of 419.6Wh kganode+cathode+electrolyte -1 under constrained conditions of high cathode loading (20.1mg cm-2 ) and limited lithium metal source. The constructed bilayer zwitterionic MOFs presents a pioneering strategy for developing advanced SSEs for highly efficient SSBs. This article is protected by copyright. All rights reserved.

PEO-based solid-state electrolyte modified by cationic covalent organic frameworks enabling high-performance all-solid-state Li metal and graphite anode batteries

Covalent organic frameworks (COFs) with regular and ordered channels have been proved that they could offer extra space to accommodate ions and fast conduction pathways for ion motion. However, the ion conductivities of their own are not high because of most of them have no enough active segmental motion of polymer chains for ion transport. Polyethylene oxide (PEO) is the most typical and efficient solid-state polymer material for Li+ migration by the segmental motion of molecular chains. Herein, we propose a simple and effective strategy of introducing a small quantity of cationic COF additive EB-COF-TFSI into the PEO of low glass transition temperature to obtain high-performance solid-state electrolyte (SSEs) and Li batteries. The cationic COF structure not only provides fast pathway for Li+ but also these cations on it accelerate Li salt dissociation and Li+ conduction. As a result, the cycling time of Li symmetrical cells increases to triplication at a same test condition; the corresponding all-solid-state LFP and NMC//Li metal cells are stimulated to release higher specific capacities, exhibit an enhanced cycling stability and better rate capability. It is surprising that all-solid-state LFP//graphite cells show excellent charging and discharging performance no matter on longtime cycling or rate performance test which are both much better than that of Li metal cells and provide a great strategy for building commercial all-solid-state Li battery based the current structure of it.

Anion Trapping and Ionic Conductivity Enhancement in PEO-Based Composite Polymer–Li7La3Zr2O12 Electrolytes: The Role of the Garnet Li Molar Content

The successful development of all-solid-state batteries will provide solutions for many problems facing current Li-ion batteries, such as high flammability, limited energy density, poor cyclability and low cation transference number. In this quest, the development of high-performance solid-state electrolytes is critical. Composite polymer electrolytes (CPE), comprising ion-conducting (active) inorganic fillers and polymer matrices, have emerged as a promising strategy to yield better conductivity, interfacial stability, and mechanical strength than their single-phase counterparts. Recent experiments indicate that active garnet fillers may enhance the ionic conductivity of CPEs by inducing anion trapping onto their surface. Moreover, substitutions that modify the lithium molar content within the filler were shown to impact this enhancement. However, the molecular underpinning behind this phenomenon is poorly understood, hindering the development of strategies to exploit it optimally. In this study, we use an enhanced hybrid Monte Carlo technique in combination with extensive molecular dynamics simulations to bridge this gap. By focusing on the archetypal CPE formed by Ga-doped Li7–3xGaxLa3Zr2O12 (Gax-LLZO) embedded within a poly(ethylene oxide) (PEO) and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) polymer matrix, we describe how the dynamic electrostatic trapping of anions leads to overall conductivity enhancement by increasing the lithium transference number and tracer diffusivity in the polymer phase. The extent of this enhancement can be fine-tuned by modulating the Li molar content of LLZO through the doping of Ga. We predict an optimal Li molar content of 5.95, which is lower than the optimal 6.50 reported in the literature for single LLZO.

High-Efficiency Lithium-Ion Transport in a Porous Coordination Chain-Based Hydrogen-Bonded Framework

Fast and selective Li+ transport in solid plays a key role for the development of high-performance solid-state electrolytes (SSEs) of lithium metal batteries. Porous compounds with tunable Li+ transport pathways are promising SSEs, but the comprehensive performances in terms of Li+ transport kinetics, electrochemical stability window, and interfacial compatibility are difficult to be achieved simultaneously. Herein, we report a porous coordination chain-based hydrogen-bonded framework (NKU-1000) containing arrayed electronegative sites for Li+ transport, exhibiting a superior Li+ conductivity of 1.13 × 10-3 S cm-1, a high Li+ transfer number of 0.87, and a wide electrochemical window of 5.0 V. The assembled solid-state battery with NKU-1000-based SSE shows a high discharge capacity with 94.4% retention after 500 cycles and can work over a wide temperature range without formation of lithium dendrites, which derives from the linear hopping sites that promote a uniformly high-rate Li+ flux and the flexible structure that can buffer the structural variation during Li+ transport.

Composite Solid Electrolyte with Continuous and Fast Organic-Inorganic Ion Transport Highways Created by 3D Crimped Nanofibers@functional Ceramic Nanowires.

A 3D crimped sulfonated polyethersulfone-polyethylene oxide(C-SPES/PEO) nanofiber membrane and long-range lanthanum cobaltate(LaCoO3 ) nanowires are collectively doped into a PEO matrix to acquire a composite solid electrolyte (C-SPES-PEO-LaCoO3 ) for all-solid-state lithium metal batteries(ASSLMBs). The 3D crimped structure enables the fiber membrane to have a large porosity of 90%. Therefore, under the premise of strongly guaranteeing the mechanical properties of C-SPES-PEO-LaCoO3 , the ceramic nanowires conveniently penetrated into the 3D crimped SPES nanofiber without being blocked, which can facilitate fast ionic conductivity by forming 3D continuous organic-inorganic ion transport pathways. The as-prepared electrolyte delivers an excellent ionic conductivity of 2.5 × 10-4 Scm-1 at 30°C. Density functional theory calculations indicate that the LaCoO3 nanowires and 3D crimped C-SPES/PEO fibers contribute to Li+ movement. Particularly, the LiFePO4 /C-SPES-PEO-LaCoO3 /Li and NMC811/C-SPES-PEO-LaCoO3 /Li pouch cell have a high initial discharge specific capacity of 156.8mAhg-1 and a maximum value of 176.7mAhg-1 , respectively. In addition, the universality of the penetration of C-SPES/PEO nanofibers to functional ceramic nanowires is also reflected by the stable cycling performance of ASSLMBs based on the electrolytes, in which the LaCoO3 nanowires are replaced with Gd-doped CeO2 nanowires. The work will provide a novel approach to high performance solid-state electrolytes.

A high-performance solid-state polymer electrolyte for lithium-metal battery

Solid-state polymer electrolyte is a promising alternative to the flammable liquid electrolyte due to its improved safety. In this work, we develop a novel polymer electrolyte with fire-retardant property and excellent electrochemical performance. This fire-proof polymer electrolyte (FPE) demonstrates an outstanding ionic conductivity of 6.7 × [Formula: see text]S [Formula: see text] at [Formula: see text]C. The Li//FPE//Li symmetric cell using such FPE could stably charge/discharge for 500 h at a current density of 0.5 mA [Formula: see text] and an areal capacity of 0.5 mAh [Formula: see text]. The Li//FPE//LiFePO4 lithium-metal cell also presents a good cycling performance with a discharge capacity of 127.8 mAh [Formula: see text] after 450 cycles at 0.5 C.

Application and Research Progress of Covalent Organic Frameworks for Solid-State Electrolytes in Lithium Metal Batteries.

Covalent organic frameworks (COFs) are a class of crystalline porous organic polymers with periodic networks that are constructed from small molecular units via covalent bonds, which have low densities, high porosity, large specific surface area, and ease of functionalization. The one-dimension nanochannels in COFs offer an effective means of transporting lithium ions while maintaining a stable structure over a wide range of temperatures. As a new category of ionic conductors, COFs exhibit unparalleled application potential in solid-state electrolytes. Here, we provide a comprehensive summary of recent applications and research progress for COFs in solid-state electrolytes of lithium metal batteries and discuss the possible development directions in the future. This review is expected to provide theoretical guidance for the design of high-performance solid-state electrolytes.

Flexible Solid-State Metal-Air Batteries: The Booming of Portable Energy Supplies.

The rapid development of portable and wearable electronics has given rise to new challenges and provoked research in flexible, lightweight, and affordable energy storage devices. Flexible solid-state metal-air batteries (FSSMABs) are considered promising candidates, owing to their large energy density, mechanical flexibility, and durability. However, the practical applications of FSSMABs require further improvement to meet the demands of long-term stability, high power density, and large operating voltage. This Review presents a detailed discussion of innovative electrocatalysts for the air cathode, followed by a sequential overview of high-performance solid-state electrolytes and metal anodes, and a summary of the current challenges and future perspectives of FSSMABs to promote practical application and large-scale commercialization in the near future.