High Lithium Ion Transference Number Research Articles

Retarding anion migration for alleviating concentration polarization towards stable polymer lithium-metal batteries

Traditional dual-ion lithium salts have been widely used in solid polymer lithium-metal batteries (LMBs). Nevertheless, concentration polarization caused by uncontrolled migration of free anions has severely caused the growth of lithium dendrites. Although single-ion conductor polymers (SICP) have been developed to reduce concentration polarization, the poor ionic conductivity caused by low carrier concentration limits their application. Herein, a dual-salt quasi-solid polymer electrolyte (QSPE), containing the SICP network as a salt and traditional dual-ion lithium salt, is designed for retarding the movement of free anions and simultaneously providing sufficient effective carriers to alleviate concentration polarization. The dual salt network of this designed QSPE is prepared through in-situ crosslinking copolymerization of SICP monomer, regular ionic conductor, crosslinker with the presence of the dual-ion lithium salt, delivering a high lithium-ion transference number (0.75) and satisfactory ionic conductivity (1.16 × 10−3 S cm−1 at 30 °C). Comprehensive characterizations combined with theoretical calculation demonstrate that polyanions from SICP exerts a potential repulsive effect on the transport of free anions to reduce concentration polarization inhibiting lithium dendrites. As a consequence, the Li||LiFePO4 cell achieves a long-cycle stability for 2000 cycles and a 90% capacity retention at 30 °C. This work provides a new perspective for reducing concentration polarization and simultaneously enabling enough lithium-ions migration for high-performance polymer LMBs.

A Thiol Branched 3D Network Quasi Solid-State Polymer Electrolyte Reinforced by Covalent Organic Frameworks for Lithium Metal Batteries.

Quasi solid-state polymer electrolytes (QSPEs) are particularly attractive due to their high ionic conductivity and excellent safety for lithium metal batteries (LMBs). However, it is still a great challenge for QSPEs to achieve strong mechanical strength and high electrochemical performance simultaneously. Herein, a QSPE (SCOF-PEP-PEA) using a covalent organic framework (COF) containing abundant allyl groups (SCOF) as a rigid porous filler as well as a cross-linker to reinforce the polymer network is reported. Benefitting from the unique 3D nanonetwork structure and abundant lithiophilic functional groups, SCOF-PEP-PEA QSPE exhibits high ionic conductivity (4.0 × 10-4 S cm-1) and high lithium-ion transference number (0.82) at room temperature. Moreover, SCOF-PEP-PEA QSPE displays much improved mechanical strength compared to PEP-PEA QSPE (AFM Young's modulus: 453 vs 36MPa). As a result, the Li/LFP full cell with SCOF-PEP-PEA QSPE shows great rate performance of 141 mAh g-1 at 1C and delivers a high specific capacity retention of 92% after 220 cycles at 0.5 C (60 °C). This work provides a new strategy to design and prepare high-performance QSPEs with COFs as porous organic filler, and further expand the application of COFs for energy storage applications.

In-situ curing poly(N,N'-Methylenebisacrylamide)-based composite electrolyte reinforced with high-strength glass fiber skeleton for solid state lithium ion batteries

Polymer solid-state electrolytes have been extensively studied for their favorable flexibility, ease of processing, and good interfacial contact. However, the low ionic conductivity, narrow electrochemical window and poor mechanical properties restrict their practical application. Here, a novel poly(N,N'-Methylenebisacrylamide) (PMBA)-based composite electrolyte reinforced with high-strength glass fiber (GF) skeleton is fabricated via in-situ polymerization. Due to the high electrolyte uptake of PMBA network and the strong interaction between the amide units and other components in the electrolyte, it displays high ionic conductivity (1.53 mS cm−1) and lithium-ion transference number (0.74) at ambient temperature, respectively. The synergistic effect of the polymer network and GF skeleton endows the electrolyte with excellent mechanical properties (2.05 GPa), thermal stability, and flame-retardant characteristics. Furthermore, the electrolyte exhibits favorable interface compatibility with the anode and cathode. The Li||Li symmetrical cell exhibits excellent Li plating/stripping reversibility for over 1200 h at 0.1 mA cm−2. The LFP||Li exhibit high discharge capacity of 138.5 mAh/g at 1C. Noteworthy, the LFP|DEE@PMBA-GF|Li cell demonstrates outstanding cycling stability with 83.7 % capacity retention after 600 cycles at 1C and 99.89 % average Coulombic efficiency. Additionally, the LFP|DEE@PMBA-GF|graphite pouch cell with high cathode mass loading (∼12 mg cm−2) demonstrates satisfactory safety and electrochemical performance.

Low-cost and high-safety montmorillonite-based solid electrolyte for lithium metal batteries

Composite solid-state electrolyte have good interfacial compatibility and mechanical properties, but their safety (such as easy to catch fire) and economic cost are still problems. In present work, an composite solid-state electrolyte was prepared by inserting poly(vinylidene fluoride)-based polymer electrolyte matrix into the interlayer of a low cost clay mineral-montmorillonite. The composite electrolyte exhibited remarkable characteristics, including excellent flame retardancy, high room temperature ionic conductivity of 2.28 × 10−4 S cm−1, wide electrochemical stability window of 4.8 V, high lithium-ion transference number of 0.57 and good mechanical strength of 12.58 MPa. Furthermore, LiFePO4-based solid-state battery, utilizing this composite solid-state electrolyte, exhibited stable cycling with discharge specific capacity of 130 mAh g−1 for over 100 cycles at a rate of 0.5C at room temperature. This successful performance demonstrated the potential of utilizing low-cost and environmentally friendly raw clay mineral materials in high energy density solid-state battery applications.

In Situ Construction of a Polymer Coating Layer on the LiNi0.8Co0.1Mn0.1O2 Cathode for High-Performance Lithium-Ion Batteries.

Lithium-ion batteries (LIBs) are known for their high energy density but exhibit poor cyclic stability and safety risks due to side reactions between the electrode and electrolyte. To address these issues, a novel approach involving construction of a polymer coating layer (PCL) via in situ self-polymerization using 2,2,3,4,4,4-hexafluorobutyl methacrylate (HFBM) as an electrolyte additive on the cathode is proposed. The PCL endows the electrolyte with a high onset oxidation potential (4.78 V) and lithium-ion transference number (0.52). The uniform and robust in situ constructed PCL can effectively inhibit the severe irreversible side reactions and suppress harmful reactions, thus providing a protective barrier against degradation. The resulting Li||LiNi0.8Co0.1Mn0.1O2 batteries exhibit an improved discharge capacity retention of 80% at 1C over 100 cycles. These results demonstrate that the in situ self-polymerization strategy holds promising potential for enhancing LIB performance and long-term stability, especially when high-voltage cathode materials are used.

Ion-dipole interactions assist small molecular additives to regulate Li+ coordination of poly(ethylene) oxide-based polymer electrolyte

Polymer electrolyte is an attractive material for constructing high-performance solid-state batteries. However, the overall low room-temperature ionic conductivity and low transference number impede the practical application of polymer electrolyte. Ion-dipole interaction, as non-covalent interactions, has the potential to regulate Li+ coordination. It will contribute to the selectivity filter of ion conduction and improve overall ion conduction performance. Herein, we introduced benzene sulfonamide (BS) and N-methylbenzenesulfonamide (NBS) into PEO-LiTFSI complexes, respectively. The ion-dipole interactions of Li···-N-H might be provided by the organic molecules. Due to the difference in the molecular structure between BS and NBS, the stronger ion-dipole interactions between NBS and Li+ could significantly improve the coordination of Li+. As a result, PEO-LiTFSI-NBS delivers an extraordinary ionic conductivity of 1.08 × 10−4 S cm−1 at 30 °Ϲ and a high lithium ion transference number of 0.77. When employed in assembling LiFePO4|Li solid-state battery, the specific discharge capacity could reach 151.90 mAh g−1 with a high coulombic efficiency of around 99.92 % at 50 μA cm−2 (35 °Ϲ).

Borate-containing triblock copolymer electrolytes for improved lithium-ion transference number and interface stability

The electrolytes with high lithium-ion transference number (tLi+) can reduce the formation of concentration polarization during charge/discharge process and improve the electrochemical performance of lithium-ion batteries (LIBs). Herein, we report triblock copolymer electrolytes (PBOEE) containing borate. The sp2 hybridized boron atoms acting as Lewis acids can anchor the anions of lithium salts, enabling PBOEE to achieve high tLi+ of up to 0.53. Also, the borate groups can promote the formation of stable organic-rich solid electrolyte interphase (SEI) film, which enables the Li symmetric cell to cycle stably at 0.1 mA cm−2/0.1 mAh cm−2 for more than 3100 h with a low overpotential of 0.08 V under 50 °C. The optimized PBOEE_24 has an ionic conductivity of 1.41 × 10−4 S cm−1 and electrochemical stability window of 4.8 V vs. Li+/Li at 50 °C. Combining these advantages, the LiFePO4/PBOEE_24/Li cell exhibits an initial discharge specific capacity of 157.3 mA h g−1 at 0.5C with a capacity retention of 85 % after 600 cycles under 50 °C. At a higher current density of 1C, the discharge capacity maintains at 128.0 mA h g−1 after 400 cycles with a capacity retention of 84.88 %. These results suggest that block copolymer containing sp2 hybridized boron atoms is a promising all-solid-state polymer electrolyte.

Interfacial polymerization achieved integration of pore size adjustment, electrostatic repulsion and physical adsorption into one to inhibit polysulfide shuttle for enhanced lithium–sulfur battery

The application of lithium-sulfur battery is seriously hindered by the shuttle of dissolved polysulfide between sulfur cathode and lithium anode, by which is not selectively inhibited by the conventional separator. Developing functional separator is considered as a preferred solution for this issue, but it is always challenged by the tedious preparation process. Herein, interfacial polymerization (IP) is employed to modify the surface property of ZrO2 nanoparticles embedded polyetherimide (PZ) based separator, and the integration of pore size adjustment, electrostatic repulsion and physical adsorption into one is facilely achieved to effectively inhibit the polysulfide shuttle. Consequently, the optimized PZ separator presents a high lithium-ion transference number (0.55) and diffusion coefficient (2.16 × 10−8 cm s−1). Compared with the pristine one, the electrochemical performance of the assembled lithium-sulfur battery is obviously enhanced, and an initial discharge specific capacity of 1242 mAh g−1 and a capacity retention of 68 % after 200 cycles are obtained.

A tetraphenylborate-based anionic metal-organic framework as a versatile solid electrolyte for fast Li+, Na+, K+, Mg2+, Ca2+, and Zn2+ transportation.

Tetraphenylborate (BPh4 -) has been widely employed in the field of electrolytes and displayed better ionic conductivities in polymer solid-state Li+ conductors. However, the fabrication of tetraphenylborate monomers into metal-organic frameworks (MOFs) and the exploration of their potential in solid-state electrolytes have never been reported. In this work, carboxylic acid functionalized lithium tetraphenylborate was purposefully synthesized and employed to construct an anionic MOF as a solid electrolyte. The counter cation Li+ was encapsulated into the anionic channel to become the free mobile charge carrier that produced a lithium-ion solid electrolyte with outstanding ion conductivity (2.75 × 10-3 S cm-1 at 25 °C), an impressively high lithium-ion transference number (t Li+ = 0.89), and low activation energy (0.15 eV). Acting as a solid electrolyte, the anionic MOF-based lithium iron phosphate battery delivered an initial specific capacity of 135 mA h g-1 and retained 95% capacity after 220 charge-discharge cycles with a coulombic efficiency close to 100%. Moreover, by exchanging the free Li+ with Na+, K+, Mg2+, Ca2+, and Zn2+, our anionic MOF is also available for other types of solid electrolytes with the corresponding conductivities all above that of the functional battery electrolyte. Our work provided a convenient and tunable route to prepare conducting MOFs for alkali metal ions, alkaline earth metal ions, and other possible metal cations of interest, which could be used in solid-state electrolytic devices in the future.

Dual Interface Compatibility Enabled via Composite Solid Electrolyte with High Transference Number for Long-Life All-Solid-State Lithium Metal Batteries.

The development of solid-state electrolytes (SSEs) effectively solves the safety problem derived from dendrite growth and volume change of lithium during cycling. In the meantime, the SSEs possess non-flammability compared to conventional organic liquid electrolytes. Replacing liquid electrolytes with SSEs to assemble all-solid-state lithium metal batteries (ASSLMBs) has garnered significant attention as a promising energy storage/conversion technology for the future. Herein, a composite solid electrolyte containing two inorganic components (Li6.25Al0.25La3Zr2O12, Al2O3) and an organic polyvinylidene difluoride matrix is designed rationally. X-ray photoelectron spectroscopy and density functional theory calculation results demonstrate the synergistic effect among the components, which results in enhanced ionic conductivity, high lithium-ion transference number, extended electrochemical window, and outstanding dual interface compatibility. As a result, Li||Li symmetric battery maintains a stable cycle for over 2500h. Moreover, all-solid-state lithium metal battery assembled with LiNi0.6Co0.2Mn0.2O2 cathode delivers a high discharge capacity of 168mAhg-1 after 360 cycles at 0.1C at 25°C, and all-solid-state lithium-sulfur battery also exhibits a high initial discharge capacity of 912mAhg-1 at 0.1C. This work demonstrates a long-life flexible composite solid electrolyte with excellent interface compatibility, providing an innovative way for the rational construction of next-generation high-energy-density ASSLMBs.

A 3D Cross-Linked Metal-Organic Framework (MOF)-Derived Polymer Electrolyte for Dendrite-Free Solid-State Lithium-Ion Batteries.

Lithium metal batteries (LMBs) with high energy density have received widespread attention; however, there are usually issues with lithium dendrite growth and safety. Therefore, there is a demand for solid electrolytes with high mechanical strength, room-temperature ionic conductivity, and good interface performance. Herein, a 3D cross-linked metal-organic framework (MOF)-derived polymer solid electrolyte exhibits good mechanical and ionic conductive properties simultaneously, in which the MOF with optimized pore size and strong imidazole cation sites can restrict the migration of anions, resulting in a uniform Li+ flux and a high lithium-ion transference number (0.54). Moreover, the MOF-derived polymer solid electrolytes with the 3D cross-linked network can promote the rapid movement of Li+ and inhibit the growth of lithium dendrites. Lithium symmetric batteries assembled with the 3D MOF-derived polymer solid electrolytes are subjected to lithium plating/stripping and cycled over 2000h at a current density of 0.1mA cm-2 and over 800h at a current density of 0.2mA cm-2. The Li/P-PETEA-MOF/LiFePO4 batteries exhibit excellent long-cycle stability and cycle reversibility.

Self-healing polymer electrolytes with nitrogen‑boron coordinated boroxine for all-solid-state lithium metal batteries

Polymer networks with dynamic covalent cross-linked boroxine have received a great deal of attention as recyclable and self-healing materials, but their application was rarely mentioned in all-solid-state polymer electrolytes. In this work, the boroxine-based self-healing solid polymer electrolytes (ONBSPE-x) with nitrogen‑boron (NB) coordination were prepared by the amidation reaction between different molecular weight NH2-PEG-NH2 and ortho-triphenylboroxine with the plasticization of lithium salt. To highlight the effect of NB coordination on the self-healing ability of the polymer electrolytes, PNBSPE-2000 with para-triphenylboroxine structure was prepared for comparison. It was proved that the ortho-triphenylboroxine is conducive to the formation of NB coordination and the NB coordination can accelerate the equilibrium of boroxine, further speeding the self-healing ability of ONBSPE-x without external stimulation at room temperature. More importantly, given the strong electron-withdrawing effect of boroxines groups, the ONBSPE-2000 membranes show an ionic conductivity value up to 0.168 mS cm−1 and comparatively high lithium-ion transference number (0.60) at 25 °C, which will minimize concentration polarization between electrolytes and lithium metal anode, then inhibiting lithium dendrite generation. The NB coordination and the interaction between boroxine groups and anions in ONBSPE-2000 were further studied with density functional theory (DFT). The Li|ONBSPE-2000|LiFePO4 coin cell performs excellent cycling stability with an initial discharge capacity of 130.9 mAh g−1 at 0.1C and coulombic efficiency of 94.8 %. Thus, the self-healing solid polymer electrolytes with nitrogen‑boron coordinated boroxine provide a prospective application for high-performance lithium metal batteries.

Bifunctional TiO2−x nanofibers enhanced gel polymer electrolyte for high performance lithium metal batteries

Exploration of advanced gel polymer electrolytes (GPEs) represents a viable strategy for mitigating dendritic lithium (Li) growth, which is crucial in ensuring the safe operation of high energy density Li metal batteries (LMBs). Despite this, the application of GPEs is still hindered by inadequate ionic conductivity, low Li+ transference number, and subpar physicochemical properties. Herein, TiO2−x nanofibers (NF) with oxygen vacancy defects were synthesized by a one-step process as inorganic fillers to enhance the thermal/mechanical/ionic-transportation performances of composite GPEs. Various characterizations and theoretical calculations reveal that the oxygen vacancies on the surface of TiO2−x NF accelerate the dissociation of LiPF6, promote the rapid transfer of free Li+, and influence the formation of LiF-enriched solid electrolyte interphase. Consequently, the composite GPEs demonstrate enhanced ionic conductivity (1.90 mS cm−1 at room temperature), higher lithium-ion transference number (0.70), wider electrochemical stability window (5.50 V), superior mechanical strength, excellent thermal stability (210 °C), and improved compatibility with lithium, resulting in superior cycling stability and rate performance in both Li||Li, Li||LiFePO4, and Li||LiNi0.8Co0.1Mn0.1O2 cells. Overall, the synergistic influence of nanofiber morphology and enriched oxygen vacancy structure of fillers on electrochemical properties of composite GPEs is comprehensively investigated, thus, it is anticipated to shed new light on designing high-performance GPEs LMBs.

Uniform lithium deposition regulated by lithiophilic Mo3N2/MoN heterojunction nanobelts interlayer for stable lithium metal batteries

Lithium metal batteries (LMBs) are of significant importance for high-energy rechargeable batteries owing to its ultra-high theoretical specific capacity and lowest reduction potential. However, the lithium dendrite growth during the continuous plating/stripping process results in poor cycle property, serious security issues and low Coulombic efficiency to working LMBs. To effectively inhibit lithium dendrite issues, a multifunctional lithiophilic interlayer constructed by heterostructural Mo3N2/MoN nanobelt (MoNx) is exploited as regulator to adjust lithium deposition. The results reveal that MoNx/PP exhibits high lithium-ion transference number, ion conductivity and excellent electrolyte wettability, which action synergistically to regulate lithium-ion diffusion and flux. DFT calculation further demonstrates that the co-existence of heterostructure and polar bonds can effectively enhance the interaction between MoNx and lithium, which can supply more deposition sites for promoting homogenous and smooth lithium plating. The advantages mentioned above endow symmetric Li//Li cell used MoNx/PP with a super-long-life of 1500 h at 5 mA cm−2. Furthermore, Li//LiFePO4 full cell presents excellent cycling stability and ultra-low-capacity decay rate of 0.033 %/cycle after 500 cycles even at 3C. This work offers a creative strategy and insight to reasonably design lithiophilic interlayer to regulate Li uniform depositions in working LMBs.

In-situ polymerized gel polymer electrolytes for stable solid-state lithium batteries with long-cycle life

The practical application of high energy density lithium batteries is significantly limited by serious safety concerns and chemical instability of traditional organic liquid electrolytes. In this work, polyethylene glycol (PEG) based gel polymer electrolyte (GPE) supported by polyethylene (PE) separator is proposed by in-situ polymerization. The obtained GPE with 50% liquid electrolyte (LE) exhibits an ionic conductivity of 2.22 × 10−4 S cm−1 at 30 °C, a wide electrochemical stability window up to 4.7 V and high lithium ion transference number of 0.502. Furthermore, the GPE displays good interfacial compatibility with lithium anode and the Li//Li symmetric battery with PE supported GPE can cycle stably for 2800 h. In addition, the LiFePO4//Li solid state batteries show outstanding charging/discharging performances at both 30 °C and 60 °C. Particularly, the battery can stable cycle over 1000 cycles at 1 C under 30 °C with capacity retention of 83.36%; meanwhile, it shows a high initial reversible capacity of 149.8 mAh g−1 with excellent cycling stability over 200 cycles at 1 C under 60 °C. This work provides an in-situ polymerized GPE and its promising potential application in lithium metal batteries with a long-cycle life.

In Situ Forming Gel Polymer Electrolyte for High Energy-Density Lithium Metal Batteries.

In situ forming gel polymer electrolyte (GPE) is one of the most feasible ways to improve the safety and cycle performances of lithium metal batteries with high energy density. However, most of the in situ formed GPEs are not compatible with high-voltage cathode materials. Here, this work provides a novel strategy to in situ form GPE based on the mechanism of Ritter reaction. The Ritter reaction in liquid electrolyte has the advantage of appropriate reaction temperature and no additional additives. The polymer chains are cross-linked by amide groups with the formation of GPE with superior electrochemical properties. The GPE has high ionic conductivity (1.84 mS cm-1 ), wide electrochemical stability window (>5.25V) and high lithium ion transference number (≈0.78), compatible with high-voltage cathode materials. The Li|LiNi0.6 Co0.2 Mn0.2 O2 batteries with in situ formed GPE show excellent long-term cycle stability (93.4%, 300 cycles). The density functional theory calculation and X-ray photoelectron spectroscopyresults verify that the amide and nitrile groups are beneficial for stabilizing cathode structure and promoting uniform Li deposition on Li anode. Furthermore, the in situ formed GPE exhibits excellent electrochemical performance in Graphite|LiMn2 O4 and Graphite|LiNi0.5 Co0.2 Mn0.3 O2 pouch batteries. This approach is adaptable to current battery technologies, which will be sure to promote the development of high energy-density lithium-ion batteries.

Fluorine grafted gel polymer electrolyte by in situ construction for high-voltage lithium metal batteries

Gel polymer electrolytes (GPEs) are promising candidates for next generation lithium metal batteries (LMBs) due to their reassuring safety and high ionic conductivity at room temperature. However, they are still plagued by incompatible interfaces and poor compatibility with Ni-rich cathodes, imposing great restrictions on the scalability of high-voltage cathodes. To overcome these problems, a GPE with a polyacrylonitrile porous membrane, together with 2,2,3,4,4,4-hexafluorobutyl acrylate grafted pentaerythritol tetraacrylate, is fabricated via in-situ thermal polymerization. By virtue of the effective transport channels provided by PAN and PETEA molecules, our GPE exhibits both a high lithium-ion transference number and a high ionic conductivity of 0.87 and 4.06 × 10−3 S cm−1, respectively at 30 °C. Moreover, the GPE ensures a high electrochemical window, stable at potentials up to 5.35 V, enabling the application of LiNi0.8Co0.1Mn0.1O2 (NCM811) cathodes. Due to the uniform cathode electrolyte interface (CEI) formed by our GPE on the surface of NCM811, the assembled NCM811|GPE|Li batteries present an excellent cycling life of 300 cycles in the voltage range of 3 ∼ 4.5 V with a capacity retention of 84% at 2C. Our study provides a novel strategy for constructing fast Li+ transport channels and stable CEI membranes in LMBs operating at high voltages.

Construction and performance of PVDF-HFP-matrix comb-like gel copolymer electrolyte for high-performance quasi-solid-state lithium-metal batteries

Rechargeable lithium metal batteries (LMBs) have encountered bottlenecks in energy density, durability, and safety issues. Designing functional polymer electrolytes has been considered as an effective way to develop high-performance of LMBs. In this study, PVDF-HFP-matrix polymeric electrolytes blended with copolymer P(MMA-co-PEGMEMA) (PPxPy) via a simple one-pot free-radical polymerization are successfully designed and prepared. It has been found that the PPxPy electrolytes can construct different comb-like networks via systematically tuning monomer ratios. The tailored PP5P5 gel electrolyte exhibited high ionic conductivity of 0.74 × 10−3 S cm−1 at room temperature (RT), an enlarged electrochemical window up to 4.77 V, high lithium-ion transference number tLi+ of 0.65, and good mechanical property with Yang's modulus up to 131 MPa. Benefited from these good properties, the Li||LiFePO4 batteries assembled with PP5P5 gel electrolyte achieved an exceptional discharge capacity of 152 mAh g−1 with nearly 100 % Coulombic efficiency after 150 cycles at 1C. Furthermore, the Li|PP5P5|NCM811 cell exhibits excellent reversible specific capacity of 188 mAh g−1 at 0.1C. Consequently, it can be anticipated the as-prepared functional polymer structure to provide a reliable method for the preparation of polymer electrolytes in quasi-solid-state batteries with high-energy-density.

Quasi‐Solid‐State Composite Electrolytes with Multifunctional 2D Molecular Brush Fillers for Long‐Cycling Lithium Metal Batteries†

Comprehensive SummaryThe ever‐growing demand for next‐generation high‐energy‐density devices drives the development of lithium metal batteries with enough safety and high performance, in which quasi‐solid‐state composite electrolytes (QSCEs) with high ionic conductivity and lithium ion transference number () are highly desirable. Herein, we successfully synthesize a kind of two‐dimensional (2D) molecular brush (GO‐g‐PFIL) via grafting poly(ionic liquid) side‐chain (poly(3‐(3,3,4,4,4‐pentafluorobutyl)‐1‐vinyl‐1H‐imidazol‐3‐ium bis(trifluoromethanesulfonyl)imide), denoted as PFIL) on the surface of 2D graphene oxide (GO) sheet. GO‐g‐PFIL is used as multifunctional filler to prepare novel composite membranes and corresponding QSCEs (e.g., QSCE‐PH/GPFIL3/P). The as‐obtained QSCE‐PH/GPFIL3/P integrates features of PFIL side‐chain‐enhanced lithium ion conduction, poly(vinylidene fluoride‐co‐hexafluoropropene) backbone‐induced flexibility, and GO‐strengthened mechanical property. As a result, our ultrathin (21 μm) self‐supporting QSCE‐PH/GPFIL3/P exhibits high ionic conductivity (3.24 × 10−4 S·cm−1) and excellent (0.82) at room temperature, and Li/LFP full cell with QSCE‐PH/GPFIL3/P shows superior rate performance (high specific capacities of 79 mAh·g−1 at 30 °C and 5 C) and excellent cycling performance (high capacity retention of 91% after 500 cycles at 80 °C and 1 C).

High performance of solid electrolyte endowed by SiO2 cross-linking agent towards lithium metal battery

A dual network solid polymer electrolyte is prepared, the cross-linked part is constructed using ring-opening polymerization reaction, in which SiO2 particles connect with polyethylene glycol diglycidyl ether (PEGDE) and polyetheramine (PEA) as cross-linking point. The introduction of SiO2 is conducive to reduce the crystallization of polymer matrix, improve the strength and promote the fast migration of Li ions. The abundant C-O segments in PEGDE and PEA are advantageous to the hopping behavior of Li ions and improve the ionic conductivity of electrolyte. Poly (vinylidenefluoride-hexaflouropropylene) (PVDF-HFP) is selected as linear part due to its robust mechanical behavior and outstanding electrochemical property. The obtained SiO2 functionalized PEGDE and PEA-PVDF-HFP solid polymer electrolyte (referred to as SGPP-ASPE) demonstrates excellent ionic conductivity of 2.4 × 10−4 S cm−1, high lithium-ion transference number of 0.54 and minor interfacial polarization of 0.09 V after 1000 h using Li//Li symmetrical cell. After assembling Li/LiFePO4 cell, a favorable cycling stability with the capacity retention of 93.8% after 100 cycles at 0.2 C is delivered. The reasonable design of advanced polymer electrolytes with dual network opens up a new path for the development of solid high-performance LMBs.