Lithium Ion Transference Number Research Articles

Electrochemical characterization of in situ polymerized composite solid electrolyte incorporating three dimensional Li1·5Al0.5Ge1.5(PO4)3 framework

In pursuit of safer lithium-ion batteries, research is veering towards all-solid-state lithium batteries (ASSLBs) featuring solid electrolytes due to the safety concerns and low metal interfacial compatibility of liquid electrolytes. ASSLBs combined with composite solid electrolytes (CSEs) incorporating NASICON-type active fillers are especially appealing because of their inherent safety, ease of production, and high energy density. This study introduces a Li1·5Al0.5Ge1.5(PO4)3 (LAGP) framework created via tape casting and in situ thermal polymerization, achieving a CSE with notable ionic conductivity (0.791 mS cm−1), electrochemical stability up to 5.09 V, and a lithium-ion transference number of 0.72 at 30 °C. The Li|CSE|Li cell demonstrates low overpotential over 1000 h, and the Li|CSE|NCM811 coin cell delivers a discharge capacity of 180.9 mAh g−1, maintaining 84.6 % capacity after 200 cycles. Moreover, the Li|CSE|NCM811 pouch cell upholds a capacity of 116.41 mAh g−1 after 100 cycles, underscoring the 3D LAGP framework and in situ polymerization's role in enhancing ASSLB safety and functionality.

Fluorine-Doped Li7La3Zr2O12 Fiber-Based Composite Electrolyte for Solid-State Lithium Batteries with Enhanced Electrochemical Performance.

Garnet-based electrolytes with high ionic conductivity and excellent stability against lithium metal anodes are promising for commercial applications in solid-state lithium batteries (SSLBs). However, the further development of SSLBs is inhibited by issues such as low ionic conductivity and uncontrolled lithium dendrite growth. Herein, we report the synthesis of fluorine-doped Li7La3Zr2O12 (LLZO-F0.2) fibers by electrospinning and the subsequent calcination at high temperatures. The solid composite electrolyte with LLZO-F0.2 exhibits an ionic conductivity of 5.37 × 10-4 S cm-1 and a high lithium-ion transference number of 0.61 at room temperature. Meanwhile, it exhibits lower resistance and more uniform lithium metal stripping and deposition in symmetric cells. The full cell with LiFePO4 cathode exhibits excellent rate capability and cycling stability for 800 cycles at 0.5 C with a discharge specific capacity retention of 97.7%. This fluorine-doped fibrous garnet-type electrolyte provides a viable option for preparing high-performance SSLBs.

Robust asymmetric gel polymer electrolytes with 2D h-BN as protective layer for highly stable solid-state lithium metal batteries

Gel polymer electrolytes (GPEs) have emerged as a highly promising alternative to conventional liquid electrolytes for stable lithium-metal batteries (LIBs). However, their inherent poor mechanical properties and limited interfacial compatibility with lithium metal usually lead to unexpected growth of lithium dendrites, hindering commercial viability. Herein, an asymmetric polymer electrolyte with h-BN (HGPE) as protective layer was fabricated via a facile one-step coating strategy. Compared to pure GPE, the asymmetric polymer electrolytes exhibit significantly enhanced mechanical strength from 4.4 MPa to 7.4 MPa, effectively suppressing lithium dendrite growth. Furthermore, the HGPE improves interfacial compatibility with the anodes by preventing direct contact between GPE and lithium metals. The addition of h-BN also enhances the lithium-ion transfer number (tLi+), reaching 0.87 compared to 0.53 for pure GPE, attributed to the hindrance of anion movement by the protective layer. Consequently, the Li symmetric battery assembled with HGPE demonstrate exceptional long-term stability, maintaining performance over 1600 h at 0.1 mA cm−2. Furthermore, the assembled Li|LiFePO4 battery can deliver a high-capacity retention rate of 93.8 % after 500 cycles at room temperature, showcasing the promising potential of asymmetric polymer electrolytes for high-performance LMBs.

Halloysite nanotubes enhanced polyimide/oxidized-lignin nanofiber separators for long-cycling lithium metal batteries

The high energy density and robust cycle properties of lithium-ion batteries contribute to their extensive range of applications. Polyolefin separators are often used for the purpose of storing electrolytes, hence ensuring the efficient internal ion transport. Nevertheless, the electrochemical performance of lithium-ion batteries is constrained by its limited interaction with electrolytes and poor capacity for cation transport. This work presents the preparation of a new bio-based nanofiber separator by combining oxidized lignin (OL) and halloysite nanotubes (HNTs) with polyimide (PI) using an electrospinning technique. Analysis was conducted to examine and compare the structure, morphology, thermal characteristics, and EIS of the separator with those of commercially available polypropylene separator (PP). The results indicate that the PI@OL and PI-OL@ 10 % HNTs separators exhibit higher lithium ion transference number and ionic conductivity. Moreover, the use of HNTs successfully impeded the proliferation of lithium dendrites, hence exerting a beneficial impact on both the cycle performance and multiplier performance of the battery. Consequently, after undergoing 300 iterations, the battery capacity of LiFePO4|PI-OL@ 10 % HNTs|Li stays at 92.1 %, surpassing that of PP (86.8 %) and PI@OL (89.6 %). These findings indicate that this new bio-based battery separator (PI-OL@HNTs) has the great potential to serve as a substitute for the commonly used PP separator in lithium metal batteries.

Three-Component Construction of Mesoporous Metal-Organic Frameworks and Their Incorporation into Solid Polymer Electrolytes for Li-Ion Conduction.

Solid electrolytes with high ionic conductivity and satisfactory electrochemical stability are essential for the development of solid-state batteries. However, current strategies, including polymer (and polymer-based composite) electrolytes, still face challenges in meeting the bar set by real operations. We seek to improve the Li-ion conduction of the electrolytes by incorporating mesoporous metal-organic frameworks (MOFs) into the polymer matrix. Specifically, MOFs with pores larger than 3.0 nm are constructed by three-component reactions that involve the construction of both coordinative and dynamic imine linkages. The MOFs allow polymer penetration and amorphization and efficient lithium salt dissociation in the confined channels. Numerous metal sites and organic functionalities in the MOF backbone further assist the ion migration by providing strong interactions with the fluorinated polymer and the Li+. Remarkable ionic conductivity (0.95 mS cm-1) and a large lithium transference number (0.64) are achieved. Overall, the study fully utilizes both the MOF structural units with atomic precision and the encompassed space at the mesoscale for solid-state electrolyte development.

Coconstruction of Supramolecular Lithium-Conducting Cross-Linked Networks Based on PVDF and Triblock Polymer Nanomicrosphere Solid-State Polymer Electrolytes for Lithium-Metal Batteries.

Uneven lithium plating and low ionic conductivity currently impede the realization of high-capacity rechargeable lithium metal batteries. And the conventional poly(ethylene oxide) (PEO) solid-state electrolytes are unsuitable for high-energy-density Li anode applications due to their low lithium-ion transference number and high reactivity with Li metal, leading to detrimental dendrite formation and potentially hazardous exothermic reactions with the electrolyte. In this study, we employ a supramolecular approach to develop a novel polymer solid-state electrolyte based on poly(vinylidene fluoride) (PVDF) and a novel triblock polymer nanomicrosphere, (poly(ε-caprolactone)-poly(ethylene glycol)-poly(ε-caprolactone), (PCL-PEG-PCL). The abundance of carbonyl and ether-oxygen functional groups in PCL-PEG-PCL enhances the lithium coordination environment within the polymer solid-state electrolyte. Additionally, the original C-F moieties of PVDF form hydrogen bonds with C-H and terminal hydroxyl groups in PCL-PEG-PCL, collectively creating a multichannel fast Li+-conducting supramolecular cross-linked network. The resulting electrolyte demonstrates a high ionic conductivity of 1.4 × 10-3 S cm-1 and an extended electrochemical window of 5.2 V. Moreover, the electrolyte exhibits a high lithium-ion transference number (tLi+ = 0.63) at room temperature and exhibits excellent interfacial compatibility with the lithium metal anode. For the resulting electrolyte utilized in LiFePO4 batteries, the capacity retention of the cells assembled with this electrolyte exceeds 91.3% after 1000 cycles at 25 °C and 2 C (0.281 mA cm-2).

Functionalized polypropylene separator coated with polyether/polyester blend for high-performance lithium metal batteries

Commercial polyolefin separators used in lithium metal batteries (LMBs) have the disadvantages of insufficient thermal stability and poor wettability with electrolytes, which causes bad safety and battery performance. Poly(ε-caprolactone) (PCL)-based electrolytes have drawn widespread attention in the field of polymer electrolytes owing to their electrochemical stability and high lithium-ion transference number. This work proposes a strategy of functionalizing commercial polypropylene (PP) separator coated by blending PCL (M w ~ 50,000) and poly(ethylene oxide) (PEO, M V ~ 600,000). Compared to commercial PP separators, PP-blended PEO60w/PCL5w separators possess better wettability with electrolytes and electrochemical performances. The initial discharge specific capacity of LiFePO4-based LMBs assembled with PP-blended PEO60w/PCL5w separators reaches 144 mAh g-1 (1C) and 103 mAh g-1 (5C) at room temperature, respectively. Notably, Li/PP-blended PEO60w/PCL5w/LiFePO4 shows an improved capacity retention rate of 77% after 800 cycles, confirming that the functionalized separator with coated PEO/PCL blend has great potential for application in the field of LMBs.

A Large-Scale Fabrication of Flexible, Ultrathin, and Robust Solid Electrolyte for Solid-State Lithium-Sulfur Batteries.

All-solid-state lithium metal batteries (ASSLMBs) are considered as the most promising candidates for the next-generation high-safety batteries. To achieve high energy density in ASSLMBs, it is essential that the solid-state electrolytes (SSEs) are lightweight, thin, and possess superior electrochemical stability. In this study, a feasible and scalable fabrication approach to construct 3D supporting skeleton using an electro-blown spinning technique is proposed. This skeleton not only enhances the mechanical strength but also hinders the migration of Li-salt anions, improving the lithium-ion transference number of the SSE. This provides a homogeneous distribution of Li-ion flux and local current density, promoting uniform Li deposition. As a result, based on the mechanically robust and thin SSEs, the Li symmetric cells show outstanding Li plating/stripping reversibility. Besides, a stableinterfacecontact between SSE and Li anode has been established with the formation of an F-enriched solid electrolyte interface layer. The solid-state Li|sulfurized polyacrylonitrile (Li|SPAN) cell achieves a capacity retention ratio of 94.0% after 350 cycles at 0.5 C. Also, the high-voltage Li|LCO cell shows a capacity retention of 92.4% at 0.5 C after 500 cycles. This fabrication approach for SSEs is applicable for commercially large-scale production and application in high-energy-density and high-safety ASSLMBs.

A general strategy for all-solid-state batteries with agglomeration-free and high conductivity achieved by improving the interface compatibility of fillers and polymer matrix

Composite solid electrolytes (CSEs) composed of polymer matrix and inorganic fillers show considerable potential for applications in all-solid-state lithium (Li) metal batteries. However, challenges such as fillers agglomeration and low lithium ion transference number (tLi+) remain significant obstacles to the practical application of CSEs. Herein, a general strategy of graft polymerization on the fillers surface to modulate the interface compatibility with the polymer matrix is proposed, and CSEs are prepared to verify the feasibility. The microstructure and composition of the surface coating of the fillers are analyzed, with subsequent studies of the fillers distribution within the CSEs confirming the improved interface compatibility. The enhancement of interface compatibility facilitates uniform dispersion of fillers, thereby greatly improving the utilization of fillers. CSEs exhibits high ionic conductivity (0.163 mS·cm−1 at 30 °C) and tLi+ (0.77), which gives the battery excellent rate performance and cycle stability. Therefore, chemical grafting of polymer onto the fillers surface to enhance the interface compatibility with the polymer matrix represents a promising strategy for the practical application of solid-state batteries.

Architecting precise and ultrathin nanolayer interface on 4.5V LiCoO2 cathode to realize poly (ethylene oxide) cycling stability

The poly (ethylene oxide) (PEO) solid polymer electrolytes suffer from narrow electrochemical stability window and cannot match high voltage lithium cobalt oxide (LCO) cathode. Herein, an ultrathin Al2O3 nanolayer was uniformly deposited on the surface of LCO via powder atomic layer deposition (PALD) to realize poly (ethylene oxide) polymer electrolyte cycling stability. The PEO solid polymer electrolyte contains 20 % (w/w) lithium difluoro(oxalate)borate (LiDFOB) and 7.5 % (w/w) lithium titanium aluminum phosphate (LATP) with cellulose nonwoven as a support substrate. The electrolyte exhibitsionic conductivity of 1.2×10−4 S cm−1, an electrochemical stability window of 4.5 V (vs. Li+/Li) and lithium-ion transference number of 0.38. Al2O3@LCO/PEO-LiDFOB20%-LATP7.5%/Li cell at high cut-off 4.5 V delivered better initial discharge specific capacity of 178.5 mAh g−1 and achieved a capacity retention ratio of 81.6 % after 200 cycles under 0.1 C at 50 °C. Further analysis showed that Al2O3 layer served as stable a protective layer to suppress the generation of strong oxidative Co4+ and O– species and separate from the PEO solid polymer electrolyte, inhibiting the side reactions at the cathode-side interface. Therefore, architecting precise and ultrathin protective nanolayer interface on high voltage LCO cathode via PALD is conducive to cycling performance of solid polymer electrolyte.

Polymer solid electrolytes with ultra-stable cycles and high-capacity retention for all-solid-state Li-metal battery

Polymer electrolytes have become widely popular on account of their low expenses, reduced weight, simple processing, and excellent safety features. However, polymer electrolytes have yet to find use in commercial batteries because of their limited mechanical durability and poor ionic conductivity. In this paper, an ultra-stable cycles and interfaces blending polymer electrolyte (BPE) suitable for all solid-state Li metal batteries was prepared by blending three polymers: polymethyl methacrylate (PMMA), polyvinylidene fluoride hexafluoropropylene (PVDF-HFP), and polyethylene oxide (PEO). Microstructure characterization showed numerous amorphous areas with strong interfacial strength of the BPE. The BPE3 exhibited a maximum of 15.65 MPa in tensile strength. BPE2 have excellent electrochemical performance, such as wide electrochemical windows (up to 4.7 V vs Li/Li+), high lithium ion transference numbers (up to 0.75), high ion conductivity (up to 1.87 × 10-4 S cm−1 at 60 °C), and excellent interface stability. By assembling all state-solid LiFePO4/BPE2/Li batteries for electrochemical testing, BPE2 exhibit high electrochemical characteristics. BPE2 discharge specific capacity is as high as 154.7 mAh g−1 at 1C. The BPE2 underwent 200 cycles at 0.5C and 400 cycles at 1C, with capacity retention rates of 95.7 % and 96.6 %, respectively. BPE is a promising electrolyte candidate for flexible lithium metal batteries.

Utilizing methacrylated lignin as a sustainable macro-crosslinker for synthesizing innovative PVA/AMPS composites crosslinked hydrogel nanofibers: A potential application for lithium-ion battery separators

There are significant issues with commercial separators that must be resolved before they can be used in high-energy-density batteries. These problems include low porosity, poor electrolyte wetting, and low mechanical properties. This study presents a facile method for preparing composite crosslinked hydrogel nanofibers of polyvinyl alcohol (PVA) with 2-acrylamide-2-methylpropanesulfonic acid (AMPS) for lithium-ion battery separators by utilizing methacrylated lignin (LMA) as a bio-based crosslinker. Initially, LMA was synthesized by grafting glycidyl methacrylate (GMA) onto lignin via esterification. Subsequently, a crosslinked hydrogel nanofiber membrane (PVA/AMPS-LMA) was electrospun with varying LMA fractions, which were polymerized by combining free radical copolymerization and esterification reactions. The effectiveness of LMA as a crosslinker was assessed against the N, N′-methylene bisacrylamide (MBA). The study showed that using LMA as a crosslinker significantly improved the membrane's properties. The PVA/AMPS-LMA separator displayed superior features such as mechanical strength, thermal stability, porosity, electrolyte uptake, ionic conductivity, and lithium-ion transference number, when compared with PVA/AMPS, PVA, and Celgard separators. Specifically, the PVA/AMPS-LMA separator demonstrated a high mechanical strength of 24.9 MPa, strong thermal stability at 170 °C with no shrinkage, high porosity (84.3 %), and electrolyte uptake (661.4 %). It also exhibited exceptional ionic conductivity (2.75 mS/cm) and a notable lithium-ion transference number (tLi+ = 0.717). In coin batteries, the PVA/AMPS-LMA separator retained over 96 % capacity (142.4 mAh/g) after 200 cycles at 1C. This performance exceeded that of PVA/AMPS, PVA, and Celgard separators, suggesting that PVA/AMPS-LMA separators have the potential to replace their commercial counterparts.

Enhanced performance of solid polymer electrolytes combining poly(vinylidene fluoride-co-hexafluoropropylene), metal-organic framework and ionic liquid for advanced solid state lithium-ion batteries

The search for sustainable and high-performance materials for lithium-ion batteries is leading to significant advances in solid polymer electrolyte (SPE) technology. However, the current drawbacks of this approach prove the need for further research and development in the field. Herein, novel ternary solid polymer electrolytes have been developed using varying loads of MOF-808 metal-organic framework and [BMIM][SCN] ionic liquid (IL) incorporated in a poly(vinylidene fluoride-co-hexafluoropropylene) matrix. The solid polymer electrolytes were evaluated at morphological, structural, thermal, mechanical and electrochemical levels, and their performance in cycling battery testing was assessed. The results showed a homogeneous structure throughout all the samples and a good dispersion of the distinct components. The polymer polar phase and degree of crystallinity of the samples are increased with increasing IL content, and the thermal and mechanical properties are appropriate for battery application. The ionic conductivity of the samples reaches maximum values of 4.68 × 10−5 S‧cm−1 at room temperature, lithium transference numbers up to 0.65, and high electrochemical stability, making them well-suited for battery applications. The assembled stability after 50 cycles at C/10 with a discharge capacity value of 150 mAh‧g−1 at room temperature was tested/derived. The obtained results show the potential of this system for high performance room temperature solid polymer electrolytes.

Composite solid electrolyte with improved ionic conductivity and high lithium transference number through reduced PVDF-HFP crystallinity

Solid-state electrolytes (SSEs) with excellent stability and flexibility have been used to overcome the safety and stability issues associated with the liquid electrolyte used in lithium-ion batteries (LIBs). In this study, thin composite solid electrolytes (CSEs) based on poly(vinylidenefluoride-cohexafluoropropylene) (PVDF-HFP) with high mechanical strength were fabricated. Garnet-type Li6.5Ga0.2La2.95Rb0.05Zr2O12 (Ga-Rb LLZO) with high ionic conductivity was added to investigate the improvements in mechanical strength and ionic conductivity. The CSEs with Ga-Rb LLZO added to PVDF-HFP were referred to as PVDF-HFP + LLZO (PHL). Next, the interfacial resistance of the CSEs was reduced by adding a low-molecular-weight poly(ethylene glycol) (PEG) polymer, and the improvement in ionic conductivity and Li transfer was investigated. The CSEs with Ga-Rb LLZO and PEG added to the PVDF-HFP were referred to as PVDF-HFP + LLZO + PEG (PHLP). The ionic conductivity of the fabricated CSEs was 6.58 × 10−10 S cm−1 for the PVDF-HFP sheet, which increased to 1.10 × 10−5 S cm−1 and 2.33 × 10−4 S cm−1 for PHL and PHLP, respectively, at 70 °C. PHLP also had a very high lithium transference number of 0.789, and exhibited a discharge capacity of 123.16 mAh g−1 and a capacity retention rate of 88.29% after 200 cycles at 0.33C and 70 °C.

A novel composite solid electrolyte based on chemical bonding and physical reinforcing for all-solid-state lithium metal batteries

Sulfide electrolytes are a highly promising type of electrolyte due to their intrinsically soft properties and ultrahigh ionic conductivity. However, compatibility issues at the lithium interface have hindered their development in all-solid-state lithium metal batteries. Composite polymer electrolytes can indeed address interface issues, enhancing battery safety. Nonetheless, the incompatibility at the inorganic-organic interface within composite electrolytes can lead to reduced conductivity and diminished mechanical performance. Herein, we demonstrate a composite polymer electrolyte (CPE) composed of the Li6PS5Cl and polyethylene oxide (PEO) by the chemical bridging effect of (3-chloropropyl) trimethoxysilane (CTMS) on the 3D PET nonwoven framework to resolving the incompatibility between the inorganic and organic components, thereby reinforcing the chemical and mechanical performance of the electrolyte. The CPE shows superior characteristics, including elevated ionic conductivity (7.5 × 10−4 S cm−1), an extended electrochemical stability window (5.3 V versus Li/Li+), an expanded lithium transference number (t(Li+) = 0.52), and higher mechanical strength (9.35 MPa). The assembly of a Li/Li symmetric cell, operating steadily for 400 h at a current density of 0.3 mA cm−2 while maintaining a stable and relatively low polarization voltage (70 mV), demonstrates exceptional stability with respect to the lithium electrode. Moreover, the LiFePO4/Li cell initially exhibits a discharge-specific capacity of 163.6 mAh g−1 with a coulombic efficiency approaching 100 % after 100 cycles at 0.1C. This endeavor offers a robust, attainable, and scalable methodology for crafting composite electrolytes, thereby paving the path for the practical implementation of all-solid-state lithium metal batteries.

Multifunctional Additive Enables a "5H" PEO Solid Electrolyte for High-Performance Lithium Metal Batteries.

The solid-state battery with a lithium metal anode is a promising candidate for next-generation batteries with improved energy density and safety. However, the current polymer electrolytes still cannot fulfill the demands of solid-state batteries. In this work, we propose a "5H" poly(ethylene oxide) (PEO) electrolyte via introducing a multifunctional additive of tris(pentafluorophenyl)borane (TPFPB) for high-performance lithium metal batteries. The addition of TPFPB improves the ionic conductivity from 6.08 × 10-5 to 1.54 × 10-4 S cm-1 via reducing the crystallinity of the PEO electrolyte and enhances the lithium-ion transference number from 0.19 to 0.53 via anion trapping due to its Lewis acid nature. Furthermore, the fluorine and boron segments from TPFPB can optimize the composition of the solid-electrolyte interphase and cathode-electrolyte interphase, providing a high electrochemical stability window over 4.6 V of the PEO electrolyte along with significantly improved interface stability. At last, TPFPB can ensure improved safety through a self-extinguishing effect. As a result, the "5H" electrolyte enables the Li/Li symmetric cells to achieve a stable cycle over 2200 h at the current density of 0.2 mA cm-2 with a capacity of 0.2 mA h cm-2; the LiFePO4/Li full cells with a high LFP loading of 8 mg cm-2 exhibits decay-free capacity of 140 mA h g-1 (99% capacity retention) after 100 cycles; and the NCM811/Li cells exhibit a high capacity of 160 mA h g-1 after 50 cycles at 0.5 C. This work presents an innovative approach to utilizing a "5H" electrolyte for high-performance solid-state lithium batteries.

Excellent Stable Cycle Performance of Polyethylene Oxide‐Based 3D Solid Dual‐Salt Composite Electrolyte with Porous Polyimide Thin Films Host

AbstractPolyethylene oxide composite electrolytes are widely used in lithium‐ion batteries because of their excellent moldability, good flexibility, and favorable chemical compatibility. However, they still suffer from low ionic conductivity and weak mechanical strength. Herein, a 3D nanofiber‐reinforced dual‐salt composite solid electrolyte (PI@PCB) is synthesized. Benefiting from the support of the porous polyimide films and the addition of lithium bis(oxalate)borate, the obtained PI@PCB electrolyte exhibits high mechanical strength, good thermal stability, excellent electrochemical stability, and a high lithium ion transference number (0.70). In addition, the assembled Li/PI@PCB/Li cell shows the lowest overpotential of 200 mV at the initial cycling stage and increases to 246 mV slightly after 1500 h. The capacity retention rate of Li/PI@PCB/LFP battery is about 88.3% after 500 cycles at 60 °C.

Covalent Organic Framework Enhanced Solid Polymer Electrolyte for Lithium Metal Batteries.

High ionic conductivity, outstanding mechanical stability, and a wide electrochemical window are the keys to the application of solid-state lithium metal batteries (LMBs). Due to their regular channels for ion transport and tailored functional groups, covalent organic frameworks (COFs) have been applied to solid electrolytes to improve their performance. Herein, we report a flexible polyethylene oxide-COF-LZU1 (abbreviated as PEO-COF) electrolyte membrane with a high lithium ion transference number and satisfactory mechanical strength, allowing for dendrite-free and long-time cycling for LMBs. Benefiting from the interaction between bis(triflfluoromethanesulonyl)imide anions (TFSI-) and aldehyde groups in COF-LZU1, the Li+ transference number of the PEO-5% COF-LZU1 electrolyte reached up to 0.43, much higher than that of neat PEO electrolyte (0.18). Orderly channels are conducive to the homogenous Li-+ deposition, thereby inhibiting the lithium dendrites. The assembled LiFePO4|PEO-5% COF-LZU1/Li cells delivered a discharge specific capacity of 146 mAh g-1 and displayed a capacity retention of 80% after 200 cycles at 0.1 C (60 °C). The Li/Li symmetrical cells of the PEO-5% COF-LZU1 electrolyte presented a longer working stability at different current densities compared to that of the PEO electrolyte. Therefore, the enhanced comprehensive performance of the solid electrolyte shows potential application prospects for use in LMBs.

The interface modification with polyethyleneimine enhances both ionic conductivity and interfacial compatibility of composite solid electrolyte

The composite solid electrolyte (CSE), polyethylene oxide (PEO)-Li6.4La3Zr1.4Ta0.6O12 (LLZTO), is deemed a promising candidate for all-solid-state batteries. Nevertheless, due to the poor interfacial compatibility between LLZTO nanoparticles and PEO, achieving a homogeneous dispersion of LLZTO nanoparticles within PEO is not readily attainable. The aggregation of LLZTO within PEO leads to a decline in the ionic conductivity of the CSE and poor interface stability with the electrode, ultimately resulting in deteriorated battery cyclic performance. In this work, the interface between LLZTO and PEO is designed and comprehensively investigated. Initially, dopamine self-polymerization is employed to form a uniform coating layer on the surface of LLZTO nanoparticles. Subsequently, by utilizing the amino groups present in polyethyleneimine (PEI), which can react with the phenolic hydroxyl groups of dopamine and the ether linkages in PEO, PEI serves as a bridging agent, enhancing the interfacial compatibility between LLZTO and PEO. Here it is shown that, the ionic conductivity of the LLZTO-PEO CSE containing 40 wt% modified LLZTO increases from 6.14✕10−5 S cm−1 to 1.89✕10−4 S cm−1. Furthermore, this CSE exhibits improved thermal stability, an enlarged electrochemical window of 4.8 V, a lithium-ion transference number of 0.45, and excellent interface stability with the lithium anode. The assembled LiFePO4 | 40 wt% LLZTO@PDA@PEI-PEO CSE | Li all-solid-state battery demonstrates an initial discharge specific capacity of 151.8 mA h g−1 at 0.2 C, with a capacity retention of 85.8% after 200 cycles. This work provides a novel strategy for interface-modified polymer- inorganic composite solid electrolytes, which will advance the development of high-energy-density all-solid-state lithium batteries.

SiO2-Decorated-Montmorillonite reinforced Poly(1,3-dioxolane) as a multifunctional solid electrolyte for High-Performance lithium batteries

Solid polymer electrolytes (SPEs) have garnered considerable attention owing to their remarkable flexibility, manufacturability, and cost-effectiveness. However, SPEs are hampered by critical limitations such as inadequate ionic conductivity at room temperature and issues related to lithium-ion migration, which curtail their practical applications. To tackle these challenges, the incorporation of inorganic additives into SPEs is considered as an effective strategy. Montmorillonite (MMT), a typical two-dimensional material, has emerged as an advanced filler for SPEs, displaying increased ionic conductivity, lithium-ion transference, and electrochemical stability. Herein, siliconized-modified montmorillonite (SiO2-MMT) nanosheets are synthesized and incorporated into poly(1,3-dioxolane) (PDOL)-based SPEs, resulting in a multifunctional composite solid electrolyte (CSE). The CSE shows an ionic conductivity as high as 5.58 × 10−4 S cm−1 at 30 °C, with a lithium-ion transference number close to 0.58. Symmetrical Li||Li cells utilizing the CSE exhibits stable performance for over 1200 h at a current density of 0.2 mA cm−2. Additionally, the CSE contributes to the stability of electrolytes, facilitates superior Li+ mobility and uniform deposition, thereby forming a stable solid electrolyte interface (SEI). Density functional theory (DFT) simulation confirms that SiO2-MMT, containing a large number of adsorption sites, facilitated fast reaction kinetics and effective anchoring of lithium polysulfides (LiPSs). As a result, the composite electrolyte is cycled in Lithium-sulfur (Li-S) batteries at 200 mA g−1 and 30 °C for 250 cycles, achieving a high coulombic efficiency (CE > 99.4 %) and a capacity decay rate of 0.15 %. Additionally, when paired with high-voltage Li(Ni0.8Co0.1Mn0.1)O2 (NCM811) cathodes and LiFePO4 (LFP) cathodes, both display excellent electrochemical performance. This research presents a highly promising approach for constructing multifunctional solid electrolytes for high-performance lithium batteries.