PE Separator Research Articles

Synthesis of a photocrosslinkable polyimide with a chalcone side chain and its properties as a coating material for a secondary battery separator

A carboxyl-containing polyimide (PI) was synthesized with a flexible main chain. Then, a polymer reaction was conducted to introduce a chalcone side chain. The polymer reaction occurred stoichiometrically, and a high yield of the resulting photocrosslinkable polyimide (PI-Ch) polymer was obtained (91 %) along with a high molecular weight of 9.4 × 104 g/mol. The PI-Ch had a density of 1.15 g/cm3, a fractional free volume of 0.20, and a solubility parameter of 18.8 MPa1/2. Due to its low polarity, the PI-Ch was very soluble in a moderately polar, low-boiling-point solvent of THF. Moreover, the temperature required to promote 5 % weight loss was quite high at 383 °C, while the glass transition temperature was relatively low at 146 °C. The THF solution was considered to be optimal for the dip-coating method and was applied to PE separator coating. The ATR-mode FTIR analysis of the separator coated with a 1 wt% PI-Ch solution showed that the PI-Ch was coated extensively on the surface of the PE separator. Further, the photodimerization reaction of the chalcone side chain via UV irradiation was successful. The PE separator had a thermal shrinkage of 46 % before coating, which decreased to 29 % after coating and UV treatment. When coated with a 3 wt% PI-Ch solution, some of the pores in the separator were blocked, while the air permeability and average pore size also decreased. All the pores appeared blocked after coating with the 5 wt% PI-Ch solution.

Design of a LiF-rich solid electrolyte interphase layer through a fluorinated carbon (CFX) complex separator for stable lithium metal batteries

The formation of a stable solid electrolyte interphase (SEI) layer is very important for improving the cycling stability and safety of lithium metal batteries (LMBs). However, since the reactivity of lithium metal anodes (LMAs) is very high, controlling the movement of Li+ at the anode/electrolyte interface remains challenging. In this study, an approach involving coating a fluorine functional-controlled fluorinated carbon (CFX) layer onto a commercial PE separator to form a stable SEI layer was proposed. The strong reaction between the fluorine functional groups constituting CFX and Li+ facilitated the rapid formation of a LiF-rich SEI layer in the resting and initial cycling stages. This initial stable SEI layer promoted a subsequent homogeneous Li+ flux, thus improving the LMA stability. In addition, the mechanism by which the total amount of fluorine and the fluorine functional groups control the Li+ dynamics through the CFX-coated PE separator with controlled fluorine functional groups was used to identify the mechanism by which the total amount of fluorine and the fluorine functional groups provide the advantage of the creation of a stable SEI layer. Therefore, this study contributes to the energy storage field by solving the cycling stability problem related to LMAs and emphasizes that a stable SEI layer can be formed based on the important interface control according to the type of fluorine functional group.

Mechanical Characterization and Modeling of Large-Format Lithium-Ion Battery Cell Electrodes and Separators for Real Operating Scenarios

This study presents a novel application-oriented approach to the mechanical characterization and subsequent modeling of porous electrodes and separators in lithium-ion cells to gain a better understanding of their real mechanical operating behavior. An experimental study was conducted on the non-linear stiffness of LiNi0.8Co0.15Al0.05O2 and graphite electrodes as well as PE separators, harvested from large-format lithium-ion cells, using compression tests. The mechanical response of the components was determined for different operating conditions, including nominal stress levels, mechanical loading rates, and mechanical cycles. The presented work describes the test procedure, the experimental setup, and an objective evaluation method, allowing for a detailed summary of the observed mechanical behavior. A distinct nominal stress level and mechanical cycle dependency of the non-linear stiffnesses of the porous materials were found. However, no clear dependency on compression rate was observed. Based on the experimental data, a poroelastic mechanical model was utilized to predict the non-linear behavior of these porous materials under real mechanical operating scenarios with a normalized root-mean-squared error less than 5.5%. The results provide essential new insights into the mechanical behavior of porous electrodes and separators in lithium-ion cells under real operating conditions, enabling the accelerated development of high-performing and safe batteries for various applications.

Effect of Li-Mg Alloy Anode on Li Dendrite Suppressionfor Li-Air Secondary Batteries

Non aqueous Li-air battery (LAB) has been attracting much attention as one of the next-generation batteries because it has a theoretical capacity about ten times that of the conventional Li-ion battery (3505 Wh kg-1). However, there is a risk of short-circuit due to Li dendrite formation on the surface of Li metal anode by charge/discharge cycling. Recently, a small amount of Mg addition into the Li metal anode was reported to work as a good scaffolding and suppress the Li dendrites in Li-sulfur batteries (LSBs) [1]. In addition, the SEI film derived from the Li-Mg alloy anode reduced an electrolyte decomposition and improved the cycle performance of LSBs. Moreover, the Li-Mg alloy anode has a higher Li diffusion coefficient than pure Li one, and the interfacial stability between the electrolyte and electrode was also improved [2]. However, there are almost no report on its application to LABs. In this study, Li dissolution/deposition behavior under O2 gas atmosphere was investigated using a Li-Mg | Li-Mg symmetric cell to reveal the effect of Mg addition into the Li metal anode.The Li | Li and Li-Mg | Li-Mg symmetric cells was assembled using 1.0 M LiTFSI/G4 electrolyte solution, a pair of 0.5 mm thick pure Li foil, Li-10 wt%Mg (Li-0.1Mg) and Li-20 wt%Mg (Li-0.2Mg) alloy foil, and PE separator in a dry box filled with Ar gas. The Li dissolution/deposition test was repeated upto 200 cycles at a constant current density of 0.50 mA cm-2 in the voltage range of -2.0 V to 2.0 V under the O2 atmosphere, and the magnitude of overvoltage and flatness of the polarization curves were evaluated. Each resistance value was also analyzed by AC impedance measurement for each charge /discharge cycle. Furthermore, the electrode surfaces before and after the cycle tests were evaluated by a scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS) and X-ray photoelectron spectroscopy (XPS) analysis to investigate the differences in the Li and Mg deposition morphology and the chemical composition of SEI films. Fig. 1 shows the polarization curves for the Li | Li and Li-Mg | Li-Mg symmetric cells. In the case of pure Li metal, the overpotential increased from 120th cycle. This suggests that Li dendrite gradually formed and caused to increase in the surface area of Li metal and electrolyte decomposition, following to generate a relatively thick SEI film. On the other hand, Li-0.1Mg alloy electrode shows smaller overpotential through the 200 cycles. This indicates that the Li-0.1Mg alloy electrode suppressed the Li dendrite by stabilizing the interphase between the electrode and electrolyte solution. In contrast, the Li-20 wt%Mg alloy electrode rather increased the overpotential during initial cycle, but gradually reduced it and was stabilized as same as Li-10 wt%Mg alloy one. These results were in good agreement with the morphologies of electrode surface after the cycling tests by SEM observation.The results of SEM-EDS and XPS analyses in more detail, their correlation, and the mechanism of the effect of Mg addition into the Li metal electrode will be presented in the meeting.

Synergistic Dual Electrolyte System of LATP and In‐ Situ Solod‐State PDOL System and its Improvement on the Performance of NCM811 Batteries

Abstract1,3‐Dioxolane (DOL) can undergo in‐situ polymerization in batteries to form solid‐state organic electrolyte PDOL. When applied to NCM811||Li battery system, PDOL electrolyte helps optimize the contact and interface stability between electrolyte and electrodes. This study explores the effects of PDOL with PE separators coated with Li1.3Al0.3Ti1.7(PO4)3(LATP) on the performance of NCM811||Li batteries. 2,2,2‐trifluoroethyl phosphite (DETFPi), was mixed with DOL at a 1 : 35 mass ratio. Then, LiBF4 was used to initiate in‐situ polymerization and thereby obtained DETFPi‐PDOL electrolyte after 24 h at room temperature. The composite electrolyte exhibits enhanced ion conductivity (1.59×10−4 S cm−1), high lithium ion transference number (0.78), wide electrochemical stability window (4.53 V), and high critical current density (2.2 mA cm−2). Li||PDOL@LATP||Li battery shows extremely low overpotential (35 mV) after a constant current stable cycle of 500 h at 1.0 mA cm−2. After 500 cycles at 1 C, the remaining capacity is 153.9 mAh g−1 with a capacity retention of 82.1 % in NCM811||PDOL@LATP||Li batteries. This indicates that the LATP coating on the surface of the PE separator plays an important role in optimizing the performance of DETFPI‐PDOL electrolyte batteries. LATP and DETFPI‐PDOL are effective in improving the cycling stability, rate performance, and interface state of NCM811 batteries.

Low-cost and durable polyvinyl alcohol modified polyethylene separator for vanadium redox flow battery

Porous separators are considered a viable alternative to the high cost Nafion membrane for vanadium redox flow battery (VRFB) commercialization. However, the porous separators suffer from high vanadium ion crossover due to the presence of large micron size pores, which leads to decay in capacity of the VRFB system. To tackle the same, a composite separator is synthesized wherein a cross-linked polyvinyl alcohol (PVA) layer is coated on to the porous polyethylene silica separator (PE separator) to mitigate the vanadium ion crossover rate and employed in the VRFB application. Scanning electron microscopy (SEM) analysis confirmed the successful coating of the PVA film on to the PE separator. Synthesized PE-PVA separator showed a significant decrease in the vanadium ion crossover by 31.44 times compared to the pristine PE separator. Consequently, the self-discharge time increases by 8 and 1.66 times compared to the pristine PE separator and the Nafion117 membrane, respectively. VRFB cell equipped with the synthesized separator showed better capacity retention with a capacity fade rate of 0.2 % Ah·cycle−1 than the Nafion117 membrane (0.5 % Ah·cycle−1). In-situ and ex-situ oxidative stability of the separator is explored in detail and a degradation mechanism of the cross-linked PVA membrane is proposed accordingly. The synthesized single side coated PE-PVA´ separator exhibits higher coulombic efficiency of 99 % and comparable energy efficiency of 71 % at a current density of 120 mA·cm−2 and demonstrated excellent lifetime durability tested up to 1600 charge-discharge cycles at 80 mA·cm−2.

Effects of particle size and flow properties on the performance of ceramic-coated separators in Lithium-ion batteries

This study investigates the relationship between particle size and flow properties of boehmite powders and their impact on ceramic-coated separators for lithium-ion batteries, specifically exploring how these properties influence the performance of the separators. The separators coated with BH-3 powder, with larger sizes and better flow properties than BH-1 and BH-2, showed superior characteristics with the minimum deviation when measuring physical properties such as thickness and roughness. The BH-3 coated separators, with <10% shrinkage at 150 °C for 1 h, showed the highest ion conductivity (0.69 mS cm−1) and superior electrochemical properties compared to bare PE separators. These results highlight the importance of the excellent flow properties of the boehmite powders, which reduces the slurry viscosity, facilitates the formation of a uniform coating layer, and consequently enhances the performance of the separator.

Revealing the materials, design, and performance of Ni-rich LiNi1-x-yCoxMnyO2/graphite pouch cells

Among lithium-ion batteries (LIBs), Ni-rich LiNi1-x-yCoxMnyO2/Graphite batteries hold a dominant position in electric vehicles due to high energy density, good cycling stability, and low content of Co element. In this work, Ni-rich LiNi1-x-yCoxMnyO2 (LiNi0.83Co0.07Mn0.10O2, NCM83)/Graphite pouch cells with a capacity of around 2.1 Ah are designed and manufactured. The structure and micromorphology of NCM83 as well as graphite are revealed. The XRD Rietveld refinement method clarifies the lattice parameters of NCM83. The PE separator modified by Al2O3 and PVDF (PE/Al2O3/PVDF) is used in the cells. The design parameters, formation, and aging processes are disclosed as well. Charge-discharge tests demonstrate that the NCM83/Graphite pouch cells have good electrochemical performance. Notably, the cell delivers an initial discharge capacity of 2.158 Ah at 1 A and 25 °C, and retains a high reversible discharge capacity of 1.715 Ah after 500 cycles with a capacity retention of close to 80 %. Additionally, the polarization characteristics during charging and discharging are discussed in detail, demonstrating that a good linear relationship exists between polarization voltage and cycle number. This work systematically reveals the materials, and design technology of NCM83/Graphite battery cells and helps deepen the understanding of commercial LIBs based on Ni-rich LiNi1-x-yCoxMnyO2 cathode materials.

Fabrication electro-spun Poly(vinyl alcohol)-Melamine nonwoven membrane composite separator for high-power lithium-ion batteries

Current commercial separators used in lithium-ion batteries have inherent flaws, especially poor thermal stability, which pose substantial safety risks. This study introduces a high-safety composite membrane made from electrospun poly(vinyl alcohol)-melamine (PVAM) and polyvinylidene fluoride (PVDF) polymer solutions via a dip coating method, designed for high-voltage battery systems. The poly(vinyl alcohol) and melamine components enhance battery safety, while the PVDF coating improves lithium-ion conductivity. The dip-coated PVDF/Esp-PVAM composite separators were evaluated for electrolyte uptake, contact angle, thermal stability, porosity, electrochemical stability and ionic conductivity. Notably, our Dip 1 % PVDF@Esp-PVAM composite separator exhibited excellent wettability and a lithium-ion conductivity of approximately 7.75 × 10⁻⁴ S cm⁻1 at room temperature. These separators outperformed conventional PE separators in half-cells with Ni-rich NCM811 cathodes, showing exceptional cycling stability with 93.4 % capacity retention after 100 cycles at 1C/1C, as compared to 84.8 % for PE separators. Our Dip 1 % PVDF@Esp-PVAM composite separator demonstrates significant potential for enhancing the long-term durability and high-rate performance of lithium-ion batteries, making it a promising option for long-term energy storage applications.

A novel Al2O3/polyvinyl pyrrolidone-coated polyethylene separator for high-safety lithium-ion batteries

In this study, a novel ceramic-polyethylene (PE) composite separator is designed and achieved by a very facile preparation strategy for high-safety lithium-ion batteries (LIBs). The optimized ceramic slurry composed of Al2O3 and polyvinyl pyrrolidone (PVP) is coated on one side of PE separator in an economically efficient way to form the novel Al2O3/PVP-PE separator. It is found that the superior PVP binder can improve the adherence of heat-resistant Al2O3 ceramic powders on the PE substrate, which significantly enhances the thermal stability of the optimized separator. The Al2O3/PVP-PE separator shows negligible shrinkage at a high temperature of 180 °C after 30 min thermal treatment. In addition, the prepared Al2O3/PVP-PE separator shows excellent wettability with electrolyte, large porosity and high liquid storage capacity, which are quite beneficial to the ionic conductivity and charge storage kinetics. Furthermore, LIBs (LiFePO4/graphite) assembled with the optimized Al2O3/PVP-PE separator shows superior electrochemical performance than LIBs assembled with bare PE separator. This study provides insight into the practical application and commercialization of novel Al2O3/PVP-PE separator for high-safety LIBs with improved electrochemical performance.

Tri-monomer polyamide acid nanofiber separator for safe and high performance lithium-ion batteries

The separators play a crucial role in ensuring the safety of lithium batteries and greatly affect the electrochemical performance of the battery. However, the weak thermal stability and non-polar surface of commercial polyolefin separators severely restrict the development of the high-performance lithium batteries. In this work, we initially proposed polyamide acid (PAA) nanofiber separator with three monomers through a two-step synthesis method, which was prepared by electrospinning. By controlling different processing temperatures, PAA separators containing different amount of carboxyl groups were obtained. PAA separator had better wettability and thermal stability than PE separator. Meanwhile, the electrospinning method brings ultra-high porosity (95.3 %) to the membrane, resulting a much higher electrolyte absorption and retention rate of PAA (initially 3214 %, 240 % at 50 min) compared to PE separator. In particular, carboxyl groups serve as functional groups to provide an electronegative atmosphere, promoting the transport of lithium ion between the anode and cathode, and playing an important role in improving ionic conductivity. Consequently, batteries with PAA-SOH-50 separator showed the best rate charging/discharging performance, maintaining 87.7 % and 73.6 % of its initial capacity at 2.0 C. Moreover, cells with PAA separator exhibited much higher initial discharge capacity (164.3 mAh g−1) than that with PE separator (126.8 mAh g−1). After 100 cycles at 0.5 C, the PAA nanofiber separator achieved an ultralow attenuation rate of only 0.04 % per cycle, which was less than half of the commercial PE separator (0.10 % per cycle). This work provides a new vision for the development of separator materials, revealing the great influence of functional groups, such as carboxyl groups, on the performance of separators, which provides a strong basis for the further research of high-performance separators.

Conformation inversion of succinonitrile towards long-life solid-state lithium metal batteries

Solid-state lithium metal batteries are considered as the next-generation energy storage devices, but their application is significantly hindered by poor interfacial compatibility between Li anodes and solid-state electrolytes, especially for succinonitrile (SN) based electrolyte. Herein, this issue is addressed by a conformation inversion strategy via introducing a PE separator grafted with poly-(lithium 2-acrylamido-2-methylpropanesulfonic acid) (PAMPSLi) brushes into a SN-based electrolyte. The PAMPSLi brushes inverse the conformation of SN molecules through the multiple interactions between −SO3Li and cyanide groups, alleviating the corrosion reactions of SN on Li anodes. Significantly, the PAMPSLi brushes regulate Li+ transport pathway with the inversed SN molecules at the anode/electrolyte interface to achieve uniform Li deposition. Notably, the PAMPSLi brushes contribute to a solid electrolyte interphase (SEI) film rich in LiF and Li3N. Consequently, the solid-state Li||LiFePO4 batteries with the resulting electrolyte exhibit a specific discharge capacity of 115.0 mAh/g and a considerably long cycle life of 1500 cycles at 3 C. A pouch cell with a high-loading LiFePO4 cathode (18 mg cm−2) also exhibits a high areal capacity and superior safety. This study provides a novel strategy for achieving a stable electrolyte/anode interface in SN-based electrolytes, which facilitates the practical application of solid-state batteries with long life and high energy density.

Dual-functional Separators Regulating Ion Transport Enabled by 3D-Reinforced Polyimide Microspheres Protective Layer for Dendrite-Free and High-Temperature Lithium Metal Batteries.

High-energy-density lithium metal batteries (LMBs) are confronted with crucial concerns of security and a short cycle lifespan caused by the uncontrollable formation of lithium (Li) dendrites. The poor thermal stability and heterogeneous Li deposition of conventional polyolefin separators often cause battery short circuiting and thermal runaway in LMBs. Herein, a novel dual-functional PE composite separator (PI-COOH/PE) coated by carboxyl polyimide (PI) microspheres is fabricated by an etching-acidification method. The three-dimensional (3D) high-temp PI microsphere with rich carboxyl groups on the surface improve the security of LMBs at extremely high temperatures and facilitate the formation of a stable and uniform SEI layer, which contributes to accelerating the Li+ transport and stabilizing the formation of the SEI layer. Consequently, the Li symmetric cell assembled with the (PI-COOH)/PE separator exhibits stable overpotential over 3000 h, and the corresponding Li//NCM811 full cells also show a high-level discharge capacity of 146.6 mAh g-1 at 5 C. Meanwhile, it also demonstrates outstanding cycling stability and thermal safety, which can survive continuously over 160 min at 140 °C (vs 21 min for PE). The above results indicate the (PI-COOH)/PE separator constructed by a low-cost and industrial-friendly strategy simultaneously addresses high-temperature stability and dendrite resistance.

Anchoring Carbon Spheres on Titanium Dioxide Modified Commercial Polyethylene (PE) Separator to Suppress Lithium Dendrites for Lithium Metal Batteries.

Lithium dendrites are easily generated for excessively-solved lithium ions (Li+) inside the lithium metal batteries, which will lead serious safety issues.In this experiment, carbon spheres (CS) are successfully anchored on TiO2(CS@TiO2) in the hydrothermal polymerization, which is filtrated on the commercial PE separator (CS@TiO2@PE). Thenegative charge in CS can suppress random diffusion of anions through electrostatic interactions. Density functional theory (DFT) calculations show that CS contributes to the desolvation of Li+, thereby increasing the migration rate of Li+. Furthermore, TiO2exhibits high affinity to liquid electrolytes and acts as a physical barrier to lithium dendrite formation. CS@TiO2 is a combination of the advantages of CS and TiO2. As results, the Li+transference number of the CS@TiO2@PE separator can be promoted to 0.63. The Li||Li cell with the CS@TiO2@PE separator exhibits a stable cycle performance for more than 600h and lower polarization voltage (17mV) at 1mA cm-2. The coulombic efficiency (CE) of the Li||Cu cells employe the CS@TiO2@PE separator is 81.63% over 130 cycles. The discharge capacity of LiFePO4||Li cells based on the CS@TiO2@PE separator is 1.73 mAh (capacity retention = 91.53% after 260 cycles). Thus, the CS@TiO2 layer inhibits lithium dendrite formation.

Preparation and characterization of hybrid solid-state electrolytes for high performance lithium-ion batteries

Hybrid solid-state electrolytes are emerging as a promising solution to achieve high ionic conductivity, excellent mechanical properties and good safety for developing high-performance rechargeable batteries. In this work, a polymer (PAN)-based hybrid solid-state electrolyte is designed and synthesized. The composite membrane (PLL) is composed of polyacrylonitrile (PAN) matrix, bistrifluoromethanesulfonimide lithium salt (LiTFSI) and Li1.3Al0.3Ti1.7(PO4)3 (LATP) particles. The solid-state lithium battery including the as-synthesized composite membrane, Li metal and LiNi0.8Co0.1Mn0.1O2 exhibits an initial discharge capacity of 197 mAh g−1 at a charge/discharge current density of 0.5 C at room temperature. The battery using the PLL-20 electrolyte exhibits the highest stable cycling performance and highest reversible capability than those of the batteries with PLL-10, PLL-30 membrane electrolytes and commercial PE separator, respectively.

Electrospun nanofiber-based tri-layer separators with CuO/TiO2 nanowires for high-performance and long-cycle stability of lithium-ion batteries

The tri-layer nanofiber membranes of (PAN containing CuO/TiO2 nanowires) / (PVDF-HFP + PMMA) / (PAN containing CuO/TiO2 nanowires) as separator in lithium-ion battery were manufactured by electrospinning technique. PVDF-HFP with excellent mechanical properties hinders the mobility of lithium ions because of its high crystallinity. By blending the amorphous PMMA polymer with PVDF-HFP, the crystallinity of PVDF-HFP + PMMA composite nanofiber was lowered, while high mechanical strength was maintained due to the dipole–dipole interaction between two polymers. The (PVDF-HFP + PMMA) nanofiber membrane was employed as the middle layer. The PAN nanofiber membranes containing CuO/TiO2 nanowires were prepared as top and bottom layers. The electrochemical properties and performance of the manufactured tri-layer membrane were evaluated, and it showed superior performance than polyolefin-based membranes. The tri-layer membrane maintained stable voltage changes for 700 h during galvanostatic cycling. Furthermore, it exhibited excellent performance in terms of rate capability and life cycle performance. The PE separator maintained a capacity retention of 67 % after 400 cycles, while the tri-layer membrane separator showed a capacity retention of 87 %. These results suggest the potential utility of tri-layer membrane separators as high-performance separators required in the lithium-ion battery.

A sacrificial separator facilitating in situ creation of a durable CEI layer and tailoring lithium dendrites for practical lithium metal batteries

The TBB–PE separator can form a robust and uniform boron-rich CEI (cathode electrolyte interphase) layer on the cathode surface via electrochemical oxidation as well as inhibit the growth of lithium dendrites by anion anchoring.

Chemical and physical synergism between PAF-54 and SFPEEKK for effective shuttle effect inhibition of lithium–sulfur battery

Lithium-sulfur batteries (LSBs) have garnered considerable interest due to their high theoretical discharge specific capacity and energy density. However, the formation of lithium polysulfides during the electrochemical redox process leads to the loss of active material and undesirable electrochemical properties. In this study, we developed a novel Janus separator (FSP-PAF) prepared by coating PAF-54 compounded sulfonated poly (ether ether ketone ketone) and Super P onto the PE separator to effectively mitigate the shuttle effects. The FSP-PAF exhibited a high ionic conductivity of 6.4 × 10−4 S/cm and a Li+ transfer number (tLi+) of 0.72. Lithium-sulfur batteries assembled with FSP-PAF demonstrated a capacity of 1112 mA h/g at 0.2 °C, and a remarkable capacity retention rate of 65 % after 500 cycles, and maintained a capacity of 720 mA h/g even at a high rate of 3 °C. This synergistic effect involving PAF-54, sulfonated poly (ether ether ketone ketone), and Super P held great promise for the application of LSBs.

Anion receptor and heavy metal-free redox mediator decorated separator for lithium-sulfur batteries

The adsorption-catalysis synergy for accelerated conversion of polysulfides is critical toward the electrochemical stability of lithium-sulfur battery (LSB). Herein, a non-metallic polymer network with anion receptor units, trifluoromethanesulfonyl (CF3SO2-) substituted aza-ether, was in-situ integrated on PE separator, working as an efficient host for anchoring lithium thiophosphates (LPS) as redox mediators and polysulfides through Lewis acid-base interaction. The anchored LPS on the modified PE separator displayed a robust chemical adsorption ability towards polysulfides through the formation of SS bond. Meanwhile, LPS decreased the energy barrier of Li2S nucleation and promoted redox reaction kinetics. The battery with LPS decorated separator revealed a long cycling lifespan with a per cycle decay of 0.056 % after 600 cycles, and a competitive initial capacity of 889.1 mAh/g when the of sulfur cathode increased to 3 mg cm−2. This work developed a new design strategy to promote the utilization of lithium phosphorus sulfide compounds in LSB.

The fabrication of high-performance α-Al2O3 coated PE separator for lithium-ion batteries based on multiple hydrogen bonds

The separator acts as a crucial role in lithium-ion batteries (LIBs). However, commercial separators possess serious shortcomings such as poor thermal stability and compatibility with liquid electrolyte. Although the coating of ceramic powder on the separator can alleviate these disadvantages, it is still challenging to solve the problem of ceramic coating falling off the separators surface. Herein, by improving the surface structure of PE separator and α-Al2O3 particles, KH550 modified α-Al2O3 (mAl2O3) is anchored on the surface of dopamine modified PE separator (PDA-PE) with multiple hydrogen bonds to prepare high-performance battery separator (PDA@mAl2O3-PE). The results demonstrate that the PDA@mAl2O3-PE separator has excellent thermal stability, mechanical performance and electrolyte wettability. Moreover, the ionic conductivity of the PDA@mAl2O3-PE separator increases from 0.531 mS cm−1 for the pristine PE separator to 0.693 mS cm−1. When the PDA@mAl2O3-PE separator is used in LIBs, the LiCoO2/Li batteries present superior cycling capability with a discharge capacity of 132 mAh g − 1 at 1 C after 100 cycles and the capacity retention rate is 95.8%, much higher than that of the batteries with PE separator (86.4%), suggesting that the PDA@mAl2O3-PE separator has a stable ceramic surface anchored by multiple hydrogen bonds and has greater compatibility with electrolyte, leading to a quicker lithium-ion diffusion and outstanding cycling stability.