Lithium Ion Transference Number Research Articles

Single ion conducting gel polymer electrolytes containing polybenzimidazole-based ionomers with abundant Li+ transport channels for dendrite-free lithium metal batteries

Single ion conducting polymer electrolytes (SIPEs) have attracted much attention due to their ability to effectively inhibit the growth of lithium dendrites, but still confront the problems of low ionic conductivity and poor mechanical properties. In this study, a new polybenzimidazole-based ionomer (M-OPBI) is synthesized by chemically modifying aromatic poly(2,2′-(p-oxydiphenylene)-5,5′-bibenzimidazole) (OPBI), and two series of novel SIPEs (i.e. M-OPBI/PEO and M-OPBI/PVDF) are achieved after blending with different polymer matrices (i.e. poly(ethylene oxide) (PEO) and poly(vinylidene fluoride) (PVDF)). Afterwards, some single ion conducting gel polymer electrolytes (SIGPEs) with abundant Li+ transport channels are fabricated by absorbing appropriate amount of plasticizers. The imidazole anions and sulfonylimide anions in the ionomer present low binding energies with Li+, which is beneficial for the dissociation and transport of Li+. Moreover, in view of the presence of rigid aromatic structure in the main chain of the ionomer and the interactions between the polymers, polybenzimidazole-based SIPEs all exhibit excellent thermal and mechanical properties. Most importantly, in comparison with PVDF matrix, PEO is approved to be more compatible with the ionomer and provide additional Li+ conduction sites, and this will enhance the interfacial compatibility and facilitate the construction of abundant Li+ transport channels in M-OPBI/PEO membranes. As a result, M-OPBI/PEO-0.4 membrane shows the lowest activation energy of 0.098 eV, the highest room-temperature ionic conductivity of 9.9 × 10-5 S cM-1, and a satisfactory lithium ion transference number of 0.88. Thanks to these merits, the symmetric Li||Li cell assembled with M-OPBI/PEO-0.4 membrane exhibits an excellent reversible lithium plating/stripping performance without short circuit over 2160 h. This study provides a new design strategy for the development of SIGPEs for application in dendrite-free lithium metal batteries.

Electrospun PAN membrane encapsulated in PEO as a polymer electrolyte for lithium metal batteries

The novel two-step fabrication method of polymer electrolyte membrane was proposed. In the first step, the polyacrylonitrile nano fibrous membrane was prepared with the help of electrospinning. In the second step, the polyethylene oxide solution was prepared along with lithium salt and plasticizers. The solution was poured on the electrospun polyacrylonitrile to get polymer electrolyte membrane in the form of PAN membrane encapsulated in PEO. The polymer electrolyte membrane was boosted by the liquid LiPF6 before assembled in the lithium metal batteries. The polymer electrolyte membrane was compared with the commercial Celgard separator when assembled in coin cell for the application of lithium metal batteries. The polymer electrolyte membrane outperformed and exhibited a good ultimate tensile strength of 20 MPa and the better thermal stability of 97 % at 305 °C. Moreover, the polymer electrolyte membrane also exhibited excellent ionic conductivity of 1.2 mS cm−1, good lithium-ion transference number of 0.57 and uniform lithium plating/stripping cycles for up to 500 cycles without internal short circuiting. The polymer electrolyte membrane represented outstanding rate capability and exhibited the good discharge capacity of 141 mA h g−1 after 100 cycles at 0.5 C rate.

Li-ion batteries with poly[poly(ethylene glycol) methyl ether methacrylate]-grafted oxidized starch solid and gel polymer electrolytes

Polymer electrolytes are considered in lithium-ion batteries because of their high safety and properties such as flexibility, easy moldability, etc. Starch is one of these polymers from renewable resources. Considering the semi-crystal structure of starch and ion conduction in amorphous phase, herein starch is oxidized and then modified with poly[poly(ethylene glycol) methyl ether methacrylate]. Solid polymer electrolytes (SPEs) are prepared by dissolution of lithium salt within polymer while gel polymer electrolytes (GPEs) as crosslinked structures are swollen in lithium salt solution. After validation of successful syntheses, all SPEs and GPEs with different oxidation state and various PEGMA/oxidized starch are evaluated in Li-ion battery performance. The synthesized GPEs and SPEs show the highest ionic conductivity of 5.5 × 10−3 and 2.19 × 10⁻⁴ S cm⁻1, respectively at room temperature. Lithium ion transfer number (t+) of 0.6–0.9 and electrochemical stability window of 4.4–4.9 V are obtained for SPEs and GPEs. The discharge capacity is ∼180 mAh g−1 at 0.2 C with capacity retention of 75 % after 100 cycles.

A PET-enhanced PEO-ionic liquid-based gel polymer electrolyte for solid state lithium metal batteries

Gel polymer electrolytes (GPEs) are attractive for their promising prospect in lithium metal batteries (LMBs) owing to their outstanding thermal stability and remarkable electrochemical performance. Nevertheless, the practical application of traditional GPEs is significantly impeded by their limited mechanical strength. In order to address this issue, this study introduces an ultrathin and mechanically-strong poly(ethylene terephthalate) (PET) nonwoven fabric (PET-NW) as a rigid support layer for the GPEs composed of poly (ethylene oxide) (PEO) and ionic liquid (IL) EMIM-TFSI. The resulting PEO-IL/PET-NW-based GPE (NW GPE) demonstrates an excellent lithium ionic conductivity of 4.21 × 10−4 S cm−1, a lithium ion transference number of 0.20, and an ultrahigh mechanical strength of 53.2 MPa. These characteristics collectively contribute to the suppression of lithium dendrites growth and improved electrochemical performance of Li|NW GPE|LiFePO4 full cells which exhibit enhanced rate capability and cycling stability in comparison with Li|GPE-I30|LiFePO4 full cells. The employment of PET-NW in the fabrication of GPEs can pave a viable way for significant advancements in high-performance solid state LMBs for various practical applications.

Solvate Complex LiAlCl4·SO2: Synthesis and Physical-Chemical Properties.

This work describes the synthesis of the LiAlCl4·SO2 solvate complex and its properties. Its composition was determined using thermogravimetric analysis, Raman spectroscopy, and UV-vis spectroscopy. The specific ionic conductivity of LiAlCl4·SO2 is 4.7 × 10-2 S·cm-1. The dynamic viscosity is 19 cP at 25 °C, and the lithium transference number is 0.78. The melting point (+2.5 °C) and decomposition temperature (+60 °C) of LiAlCl4·SO2 were determined by simultaneous thermogravimetric analysis and differential scanning calorimetry. The structure of the solvate complex LiAlCl4·SO2 has been studied using a molecular dynamics method. A lithium cation is coordinated by one atom of Cl of the anion AlCl4- and one oxygen atom of SO2. The coordination number of lithium ions of LiAlCl4·SO2 is 4. The lithium cation is coordinated by three anions of AlCl4- and one molecule of SO2. Anion AlCl4- acts as a bridging ligand and binds different lithium cations.

Surface-functionalized metal–organic framework with high specific surface area optimizing composite solid electrolyte for high-performance solid-state lithium metal batteries

Solid-state lithium metal batteries (SSLMBs) are the potential candidates of next-generation batteries for safety and remarkable energy density against lithium ion batteries with liquid electrolyte widely applied these days. Even if composite solid electrolytes (CSEs), as the core of SSLMBs, have drawn much attention and devotion for the promising application potential, they are subject to low ionic conductivity, insufficient mechanical strength, and severe interfacial stability deficiency. Herein, we prepare a composite solid electrolyte containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) as a polymer matrix and polydopamine-modified ZIF-8 (ZIF-8@PDA) as a filler to tackle the challenges, and named as PHZP. The existing PDA on ZIF-8 particle’s surface is helpful to the uniform dispersal of filler in the whole composite solid electrolyte. Consequently, the PHZP membrane exhibits the good properties in ionic conductivity of 0.31 mS cm−1 at 25 ℃, enhanced lithium-ion transference number of 0.41, and extended electrochemical window of 4.8 V. More importantly, the PHZP membrane demonstrates the plating/stripping performance of Li in Li||PHZP||Li symmetric cell for over 2700 h with a small overpotential. LiNi0.5Co0.2Mn0.3O2||PHZP||Li (NCM523||PHZP||Li) cell possesses the first discharge capacity of 150 mAh/g and a capacity retention rate up to 95.8 % after 400 cycles at 0.5 C, and a capacity retention rate of 89 % after 800 cycles at 1 C. In the meantime, LiFePO4||PHZP||Li (LFP||PHZP||Li) cell also provides a capacity retention rate of 94.2 % after 100 cycles at 0.1 C. This work provides a simple and promising strategy to enhance the electrochemical performance of CSEs in SSLMBs, which would also be applied to the other energy storage/conversion fields.

Preparation and Study of Poly(Vinylidene Fluoride-Co-Hexafluoropropylene)-Based Composite Solid Electrolytes

Solid-state electrolytes are widely anticipated to revitalize lithium-ion batteries with high energy density and safety. However, low ionic conductivity and high interfacial resistance at room temperature pose challenges for practical applications. This study combines the rigid oxide electrolyte LLZTO with the flexible polymer electrolyte poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) to achieve effective coupling of rigidity and flexibility. The semi-interpenetrating network structure endows the PEL composite solid electrolyte with excellent lithium-ion transport capabilities, resulting in an ionic conductivity of up to 5.1 × 10−4 S cm−1 and lithium-ion transference number of 0.41. The assembled LiFePO4/PEL/Li solid-state battery demonstrates an initial discharge capacity of 132 mAh g−1 at a rate of 0.1 C. After 100 charge–discharge cycles, the capacity retention is 81%. This research provides a promising strategy for preparing composite solid electrolytes in solid-state lithium-ion batteries.

Nanofillers modified with aluminum carboxylate for application in Polymer composite electrolytes for lithium-ion batteries

One of the additives that positively influence the parameters of the electrolyte for lithium-ion cells are ceramic nanoparticles, such as SiO2 and α-Al2O3. However, they tend to agglomerate and sediment, which is an unfavorable phenomenon. An effective strategy to prevent this is to modify the surface of the particles with polymeric compounds, which can increase compatibility and stability in the electrolyte system. To reduce agglomeration and sedimentation, a method was developed to modify aluminum oxide and silica particles using aluminum carboxylate, which chemically combines with inorganic particles that have hydroxyl groups on their surface through an alkoxide bond. This method allows the introduction of oligooxyethylene groups to the ceramic surface, thus obtaining more stable systems. The effectiveness of this modification was confirmed through dynamic light scattering (DLS) measurements of particle size in liquid organic solvents, which are potential solvents for liquid electrolytes in lithium-ion cells. The modified nanosilica and aluminum oxide particles were then used as additives to solid polymer electrolytes made of poly(ethylene oxide) (PEO). This led to higher conductivity values compared to the use of unmodified fillers. The obtained values of lithium transference number for solid polymer electrolyte with PEO/CF3SO3Li and nanosilica or aluminum oxide modified with aluminum carboxylate are equal to 0.32–0.40.

Perfluoropolyether-terminated Single-ion Polymer for Enhancing Performance of PEO-based Solid Polymer Electrolyte.

Solid-state electrolytes are receiving increasing attention in lithium metal batteries due to the advantage of high energy density. Poly(ethylene oxide) (PEO) electrolyte possesses good compatibility with lithium salts. However, PEO suffers from a low lithium-ion transference number and poor high-voltage resistance, which significantly hinder its application in lithium metal batteries. Herein, a perfluoropolyether-terminated single-ion polymer (PFPE-polymer) is designed and synthesized in this contribution. By incorporating the PFPE-polymer and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) into PEO via casting, the polymer electrolyte (PFPE-SE) is successfully prepared. Compared to PEO-based electrolytes, PFPE-SE forms a solid electrolyte interface (SEI) layer and inhibits the growth of lithium dendrites on the anode. At 70°C, the lithium-ion transference number and the electrochemical window reach 0.72 and 4.7V, respectively. When tested at a discharge rate of 0.5 C, the Li|PFPE-SE|LFP cell exhibits a specific capacity of 156.0 mAh g-1, with a capacity retention of 74.3% after 230 cycles, superiority the performance of the electrolyte prepared by mixing PEO with LiTFSI. This work presents a promising polymer electrolyte strategy for achieving high-performance lithium metal batteries, leveraging the in situ construction of the SEI layer and the utilization of a single-ion polymer.

Chitosan-based gel polymer electrolytes for high performance Li-ion battery

This study explores the use of glutaraldehyde-crosslinked chitosan-based gel polymer electrolytes (GPEs) in lithium-ion batteries (LIBs). GPEs are prepared by solution casting using two different molecular weights of chitosan including 150 kDa as medium and 400 kDa as high molecular weight (MMWCS and HMWCS, respectively) with varying amounts of crosslinker. Degree of crystallinity was 25.9 and 24.1 % for HMWCS and MMWCS, respectively that was decreased to 18.3 and 22.7 % by using 5 % crosslinker and 17.8 and 21.1 % by using 10 % crosslinker, and 17.2 and 17.6 % by using 20 % crosslinker. The obtained ionic conductivity for HMWCS and MMWCS was 3.1 × 10−3 and 2.9 × 10−3 S.cm−1. After crosslinking by 5, 10, and 20 % crosslinker, the ionic conductivity was obtained to 0.9 × 10−3 and 0.3 × 10−3 S.cm−1, 6.3 × 10−3 and 5 × 10−3 S.cm−1, and 1.1 × 10−3 and 0.5 × 10−3 S.cm−1 for high and medium molecular weight, respectively. Lithium-ion transfer number was obtained between 0.34 and 0.83 and the highest t+ value was obtained for the MMWCS-GA10. Electrochemical stability window of the prepared polymer electrolytes was >5 V and samples showed no remarkable dendrite growth after cycling analyses. The symmetric cells demonstrated reliable performance, operating for over 300 h without any short-circuiting, which indicates excellent reversible cycling stability for chitosan-based lithium-ion batteries. Furthermore, the Gr/GPE cell exhibited very low voltage polarization, with the over-potential decreasing from 10 mV initially to 6 mV after 300 h at the same current density. Discharge capacity was obtained higher than 170 mAh/g at 0.2C with CE = 97 % for both HMWCS-GA20 and HMWCS-GA20.

Polymeric Lithium Battery using Membrane Electrode Assembly

Alternative configuration lithium cell exploits electrode and polymer electrolyte cast all‐in‐one to form a membrane electrode assembly (MEA), in analogy to fuel cell technology. The electrolyte is based on polyethylene oxide (PEO), lithium bis‐trifluoro sulfonyl imide (LiTFSI) conducting salt, LiNO3 sacrificial film‐forming agent to stabilize the lithium metal, and fumed silica (SiO2) to increase the polymer amorphous degree. The membrane has conductivity ranging from ~5×10−4 S cm‐1 at 90 °C to 1×10−4 S cm‐1 at 50 °C, lithium transference number of ~0.4, and relevant interphase stability. The MEA including LiFePO4 (LFP) cathode is cycled in polymer lithium cells operating at 3.4 V and 70 °C, with specific capacity of ~155 mAh g‐1 (1C = 170 mA gLFP‐1) for over 100 cycles, without signs of decay or dendrite formation. The cell exploiting the MEA shows enhanced electrochemical performance as compared with the one using simple polymeric membrane stacked between cathode and anode. Furthermore, the MEA reveals the key advantage of possible scalability and applicability in roll‐to‐roll systems for achieving high‐energy lithium metal battery, as demonstrated by pouch‐cell application. These data may trigger new interest on this challenging battery exploiting the polymer configuration for achieving environmentally/economically sustainable, and safe energy storage.

Functional Separator with Poly(Acrylic Acid)-Enabled Li2CO3-Free Garnet Coating for Long-Cycling Lithium Metal Batteries.

Lithium metal batteries (LMBs) possess a theoretical energy density far surpassing that of commercial lithium-ion batteries (LIBs), positioning them as one of the most promising next-generation energy storage systems. Modifying separators with composite coatings comprising oxide solid-state electrolyte (SSE) particles and polymers can improve the cycling stability and safety of LMBs. However, exposure to air forms Li2CO3 on oxide SSE particles, diminishing their ion flux regulation at the electrode/electrolyte interface. Utilizing the reaction of Li2CO3 with polyacrylic acid (PAA) to form lithium polyacrylate (LiPAA), an ultra-thin composite coating on polyethylene (PE) separator with Li2CO3-free Li6.4La3Zr1.4Ta0.6O12 (LLZTO) particles and LiPAA binder is fabricated in one step. The exposed Li2CO3-free LLZTO surface increases the ionic conductivity and lithium ion (Li+) transference number of the functional separator, resulting in small resistance and uniform Li deposition of the Li metal anode. Consequently, the Li//LiCoO2 cell with the functional separator exhibits a significantly improved life of 980 cycles with 80.9% capacity retention under lean-electrolyte conditions. Both the Li//LiCoO2 coin cell and pouch cell using thin Li foil anode demonstrate good cycling stability and high mechanical robustness. This study provides a green and scalable approach for fabricating advanced separators for LMBs.

Polymer electrolytes based on PEO and lithium tetraalkoxyborate salts with ionic liquid properties for lithium-based batteries

The development of lithium-ion batteries (LIBs) with improved safety features is crucial due to the inherent risks associated with liquid electrolytes, such as fires, explosions, and leakage. This study explores the potential of solid polymer electrolytes (SPEs) based on poly(ethylene oxide) (PEO) and lithium tetraalkoxyborate salts (LiTAB) with ionic liquid properties as a safer alternative. Ionic liquids (ILs) are examined for their high ionic conductivity, wide electrochemical window, and excellent thermal stability, despite their high synthesis costs and viscosity challenges. The study proposes the use of a novel LiTAB salt with an oligomeric star-shaped anion structure that reduces mobility, enhancing lithium ion transference numbers. This IL serves as both a lithium salt and an active plasticizer in PEO-based SPEs, offering potential for 3D printing applications. Experimental results demonstrate that these electrolytes exhibit favorable rheological properties, high ionic conductivities, and significant lithium ion transference numbers, addressing the key limitations of conventional PEO-based electrolytes. The findings suggest that incorporating these LiTAB salts in SPEs could significantly enhance the safety and performance of LIBs, particularly for applications in miniaturized consumer electronics and electronic implants.

Robust polymer electrolytes with fast ion-transport nanochannels constructed by carbon dots for long lifespan Li metal batteries

As an anode material in energy storage systems, Li metal has exceptional merits, including high specific capacity, low density, and low redox potential. However, challenges such as lithium dendrites and unstable solid electrolyte interphase (SEI) hinder the practical application of lithium metal batteries (LMBs). Solid polymer electrolytes (SPEs), notably PVDF-HFP, are expected to overcome the above problems because of their mechanical merits and safe features, but their limited ion transportation behaviors result in insufficient ionic conductivity at room temperature. Herein, we invent an approach to prepare high performance electrolytes composed by porous PVDF-HFP and functionalized carbon dots (CDs). Such porous PVDF-HFP polymer membranes are created by a subtle phase inversion process, possessing a sponge-like structure, vertical lithium-ion transport channels and CDs decorated surfaces, thus able to uptake the liquid electrolyte (LE) to form gel polymer electrolytes (GPEs). The CDs fillers are produced in large scale with adjustable surface states, which can enhance Li salts disassociation to release free Li ions. As a result, the optimal conductivity of the as-prepared GPEs at room temperature is up to 8.7 mS cm−1 and the lithium transference number reaches 0.64. Our GPEs endow Li symmetric batteries with very stable SEI and long cycling life over 2200 h, and help realize high capacities and retention rates of the LMBs using LiFePO4(LFP) or LiCoO2(LCO) cathodes.

ETPTA polymer network confined amide-based eutectic electrolyte for safe and long- life lithium metal battery

Serious safety issues and uncontrollable lithium dendrites hinder the commercial application of high-voltage lithium metal batteries (LMBs) that employ carbonate-based electrolytes. Herein, we propose a eutectogel electrolyte, an amide-based eutectic electrolyte consisting of lithium bis (trifluoromethyl sulfonyl) imide (LiTFSI) and N-methyl-2,2,2-trifluoroacetamide (3F-NMA) confined by trimethylolpropane ethoxylate triacrylate (ETPTA) polymer network. Compared with the carbonate-based electrolyte, the non-flammable eutectogel electrolyte facilitates the formation of LiF/LixN-rich solid electrolyte interfaces, therefore expands the electrochemical window, enhances the interfacial compatibility, and improves the cycling stability of LMB. Besides, it shows a high lithium-ion transference number of 0.63 and a stable long-term lithium stripping/plating (>2300 h) in a Li||Li symmetric cell, at a current density of 0.2 mA cm−2. Additionally, the Li||LiFePO4 full cell with eutectogel electrolyte exhibits a commendable cycling stability, achieving a capacity retention of 77.4 % after 1000 cycles at 5 C (30 °C) and maintaining 82 % capacity following 400 cycles at 1 C (60 °C). When used as the electrolyte in Li||LiCoO2 full cell, it renders the battery appealing performance including a notable initial discharge capacity of 170.3 mAh g−1 and a retained capacity of 86.3 % after 300 cycles, at a high charge voltage of 4.45 V. This research may provide insight into the design of eutectogel electrolytes for high-performance lithium metal batteries.

An oxygen-defective framework with intensified Lewis acidity reinforcing composite electrolyte for all-solid-state lithium metal batteries

Composite solid electrolytes (CSEs) are considered a key component of all-solid-state lithium metal batteries, regarded as the next generation of energy storage devices with high energy density and long operating life. Numerous studies have shown that the performance of CSEs is closely related to the structure of the fillers and the interactions between fillers and other components, including polymer matrices and lithium salts. To create more abundant interaction sites in CSEs, we designed a nanostructured framework with intensified Lewis acidity (PVDF-HFP/Ov-CeO2) for poly(ethylene) oxide (PEO) electrolyte (denoted as Ov-CeO2-CSE). The mystery concerning the nanostructured framework adsorbs with PEO polymer and dissociates TFSI− and its influence on the electrochemical lithium ions storage performance is meticulously revealed by coupling experimental with theoretical results. Impressively, the prepared Ov-CeO2-CSE shows improved ionic conductivity (1.76 × 10−4 S cm−1 at 30 °C) and a good lithium-ion transference number (0.49). The Li||Ov-CeO2-CSE||Li cell exhibits great cyclability over 3,500 h at a current density of 0.1 mA cm−2 (areal capacity: 0.1 mAh cm−2, 60 °C). Furthermore, the Li||Ov-CeO2-CSE||LFP cell delivers a high specific capacity of 154.6 mAh g−1 at a current density of 0.5 C, stably maintained over 500 cycles. This work provides a potential strategy for designing multifunctional frameworks by efficient interfaces to build advanced all-solid-state lithium metal batteries.

Preparation, Characterization and Conductivity of SiO2 doped rGO-WO3 Composite for Battery Application

High-performance solid polymer electrolytes are regarded as one of the most promising materials to be used in the development of lithium ion batteries with improved extended life, increased recyclability and increased safety for electric vehicles and energy storage. In this work, a microwave-assisted hydrothermal technique was used to produce SiO2-doped rGO-WO3 composite, which possesses outstanding supercapacitor capabilities. This method is simple, low-cost method without using any other capping and reducing agents. The obtained SiO2 doped rGO-WO3 composite structural, morphology and components have been examined by XRD, FT-IR, FE-SEM, TEM, EDX, UV-visible techniques. It was found that the SiO2 doped rGO-WO3 composite well crystalline and the size range is about 20-30 nm. The SEM morphology results showed that the nanoparticles were stabilized by rGO, having cavity like structure and randomly distributed on the rGO-WO3 matrix. The solid state electrolyte revealed superior lithium ion transference number and cyclic stability. The SiO2 doped rGO-WO3 composite shows improved ionic conductivity of 2.74 × 10-5 S cm-1 at room temperature.

On the Electrochemical Properties of Poly(Vinylidene Fluoride)/Polythiophene Blends Doped with Lithium‐Based Salt

AbstractIn this study, polymer blends of polythiophene (PTH) and poly(vinylidene fluoride) (PVDF) are investigated by focusing on their structural and electrochemical characteristics. These blends displayed immiscibility confirmed through field emission scanning electron microscopy (FE‐SEM) and interaction assessments. PTH's role as a plasticizer is evident, diminishing crystallinity. A rise in PTH level led to a lower glass transition temperature and a higher melting point, suggesting reduced intermolecular forces and increased polymer chain flexibility. Conversely, a dispersed phase presence elevated the melting point, restricting chain movement and crystallization. The thermal properties of blends are enhanced by increased PTH content. Applying the Vogel–Tammann–Fulcher model to ionic conductivity measurements, it observed a direct relationship between temperature and free volume, impacting conductivity and ion transport numbers. Certain materials exhibit increased activation energies, indicating substantial thermodynamic barriers to local motion. Higher PTH content within the PVDF matrix notably increased the lithium ion transfer number from 0.22 to 0.71, a change tied to the C–S–C structure of polythiophene. However, elevated PTH levels also led to diminished negative charge transfer and ionic conductivity in the PTH‐PVDF blend compared to pure PVDF, likely due to an ionic conduction hindrance.

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.

Waterborne Polyurethane Micelles Reinforce PEO-Based Electrolytes for Lithium Metal Batteries.

Although solid polymer electrolytes have been developed for several decades, poly(ethylene oxide) (PEO) or polymers with ethoxy (EO) segments are still one of the most promising candidates for advanced batteries. The low ionic conductivity and lithium-iontransference number as well as the deterioration of mechanical properties after coupling with lithium salts restrict its further adoption. Herein, a serial of PEO-based composite electrolytes optimized by waterborne polyurethane are prepared via blend method. With the assistance of H2O, ionic type waterborne polyurethane assembles into flexible micelles, in which hydrophobic segments as the core and hydrophilic groups as the shell. Utilizing this feature of waterborne polyurethane, PEO and Li salt (LiTFSI) aqueous solution is slowly added to the organic solution of waterborne polyurethane to compoundin situ, and polymer composite electrolytes are fabricated. The multilevel (hydrogen bonds with different binding energy) and multiscale (deformation of flexible micelles) dynamic interaction endows the composite electrolyte with attractive mechanical properties. The assembled Li|Li symmetric battery with the molar ratio of EO to Li salts of 8:1 exhibits excellent cycling stability up to 800 h at 0.1 mA cm-2, and the assembled Li|LiFePO4battery can be stably cycled at 1C for >400 cycles.