Kinetic and galvanostatic studies of a polymer electrolyte for lithium-ion batteries

Quaternary polymer electrolyte (PE) based on poly(acrylonitrile) (PAN), 1-ethyl-3-methylimidazolium tetrafluoroborate ionic liquid (EMImBF₄), sulfolane (TMS) and lithium hexafluorophosphate salt (LiPF₆) (PAN-EMImBF₄-sulfolane-LIPF₆) was prepared by the casting technique. Obtained PE films of ca. 0.2–0.3 mm in thickness showed good mechanical properties. They were examined using scanning electron microscopy (SEM), thermogravimetry (TGA, DSC), the flammability test, electrochemical impedance spectroscopy (EIS) and galvanostatic charging/discharging. SEM images revealed a structure consisting of a polymer network (PAN) and space probably occupied by the liquid phase (LiPF₆ + EMImBF₄ + sulfolane). The polymer electrolyte in contact with an outer flame source did not ignite; it rather underwent decomposition without the formation of flammable products. Room temperature specific conductivity was ca. 2.5 mS cm^?1. The activation energy of the conding process was ca. 9.0 kJ mol^?1. Compatibility of the polymer electrolyte with metallic lithium and graphite anodes was tested applying the galvanostatic method. Charge transfer resistance for the C₆Li → Li⁺ + e^? anode processes, estimated from EIS curve, was ca. 48 Ω. The graphite anode capacity stabilizes at ca. 350 mAh g^?1 after the 30th cycle (20 mA g^?1).     

二维二氧化硅改性聚环氧乙烷基固态聚合物电解质用于增强锂离子电池性能

通过改性由酸蚀二维蛭石制备的二维二氧化硅,得到带正电荷的二维介孔二氧化硅(PSN⁺)纳米片,并将PSN⁺用作聚环氧乙烷(PEO)基固体聚合物电解质(SPEs)的填料。由于PSN⁺具有丰富的正电荷,PSN⁺与锂盐解离的阴离子能够有效结合,从而促进锂离子的运输,获得较好的锂离子转移数。在50 ℃时,基于PSN⁺的SPEs表现出较高的离子电导率(7.5×10^-5 S·cm^-1),锂离子迁移数为0.30,稳定电压窗为4.41 V。因此,组装后的LiFePO₄锂电池在50 ℃、0.2C下具有优异的初始放电比容量(155.7 mAh·g^-1),在循环100次后容量保持率为97.1%。     

二维二氧化硅改性聚环氧乙烷基固态聚合物电解质用于增强锂离子电池性能

通过改性由酸蚀二维蛭石制备的二维二氧化硅,得到带正电荷的二维介孔二氧化硅(PSN⁺)纳米片,并将PSN⁺用作聚环氧乙烷(PEO)基固体聚合物电解质(SPEs)的填料。由于PSN⁺具有丰富的正电荷,PSN⁺与锂盐解离的阴离子能够有效结合,从而促进锂离子的运输,获得较好的锂离子转移数。在50℃时,基于PSN⁺的SPEs表现出较高的离子电导率(7.5×10^-5 S·cm^-1),锂离子迁移数为0.30,稳定电压窗为4.41 V。因此,组装后的LiFePO₄锂电池在50℃、0.2C下具有优异的初始放电比容量(155.7 mAh·g^-1),在循环100次后容量保持率为97.1%。     

Determination of anions in lithium-ion batteries electrolyte by ion chromatography

A sensitive and accurate method based on ion chromatography was established for determination of five lithium salts in lithium-ion batteries electrolytes. Chromatographic analyses were carried out on an anion exchange column at flow rate of 1 m L/min. Under the optimal conditions, five target anions(BF_4~-,PF_6~-, TFSI~-, BOB~-and FSI~-) exhibited satisfactory linearity with a correlation coefficient of 0.9996. The relative standard derivations of the target anions were less than less than 0.94%(n = 7). The limits of detections were in the range of 0.068–0.29 mg/L with average spiked recoveries ranging from 96.8% to 105.1%.     

Plasticized polymer electrolyte membranes based on PEO/PVdF-HFP for use as an effective electrolyte in lithium-ion batteries

Plasticized polymer electrolytes were prepared using poly(ethylene oxide)(PEO)/poly(vinylidene fluoridehexafluoro propylene)(PVd F-HFP) with lithium perchlorate(Li Cl O4) and different plasticizers. XRD and FTIR spectroscopic techniques were used to characterize the structure and the complexation of plasticizer with the host polymer matrix. The role of interaction between polymer hosts and plasticizer on conductivity is discussed using the results of alternating current(a.c.) impedance studies. TG-DTA and SEM were used for thermal and physical characterizations. Maximum ionic conductivity(3.26 × 10~(-4) S·cm~(-1)) has been observed for ethylene carbonate(EC)-based polymer electrolytes. Electrochemical performance of the plasticized polymer electrolyte is evaluated in LiFePO_4/plasticized polymer electrolytes(PPEs)/Li coin cell. Good performance with low capacity fading on charge discharge cycling is demonstrated.     

Protective electrode/electrolyte interphases for high energy lithium-ion batteries with p-toluenesulfonyl fluoride electrolyte additive

High energy density lithium-ion batteries using Ni-rich cathode(such as LiNi0.6Co0.2Mn0.2O2) suffer from severe capacity decay.P-toluenesulfonyl fluoride(pTSF) has been investigated as a novel film-forming electrolyte additive to enhance the cycling performances of graphite/LiNi0.6Co0.2Mn0.2O2 pouch cell.In comparison with the baseline electrolyte,a small dose of pTSF can significantly improve the cyclic stability of the cell.Theoretical calculations together with experimental results indicate that pTSF would be oxidized and reduced to construct protective interphase film on the surfaces of LiNi0.6Co0.2Mn0.2O2 cathode and graphite anode,respectively.These S-containing surface films derived from pTSF effectively mitigate the decomposition of electrolyte,reduce the interphasial impedance,as well as prevent the dissolution of transition metal ions from Ni-rich cathode upon cycling at high voltage.This finding is beneficial for the practical application of high energy density graphite/LiNi0.6Co0.2Mn0.2O2 cells.     

Electrochemical performances of a new solid composite polymer electrolyte based on hyperbranched star polymer and ionic liquid for lithium-ion batteries

Journal of Solid State Electrochemistry - A new composite polymer electrolyte membrane composed of hyperbranched star polymers (HBPS-(PMMA-b-PPEGMA)30 (the hyperbranched star polymer with...     

Polyacrylonitrile-based gel polymer electrolyte filled with Prussian blue forhigh-performance lithium polymer batteries

Lithium polymer batteries(LPBs) rely on a high ion transport to gain improved cell performance.Thermostable and porous gel polymer electrolytes(GPEs) have attracted much attention due to their excellent properties in electrolyte wettability and ionic conductivity.In this work,iron-nickel-cobalt trimetal Prussian blue analogue(PBA) nanocubes are filled into the electro spun polyacrylonitrile(PAN)-based membranes to generate GPE composites with morphological superiority consisting of fine fibers and interconnected pores.The thus obtained PBA@PAN fibrous membrane showcases good thermal stability,high porosity and electrolyte uptake,as well as a peak io nic conductivity of 2.7 mS/cm with the addition of 10% PBA,Consequently,the assembled lithium iron phosphate(LiFePO_4) battery using PBA@PAN-10 as the GPE delivers a high capacity of 152.2 mAh/g at 0.2 C and an ultralow capacity decay of0.09% per cycle in a long-te rm cycle life of 350 cycles at 1 C,endorsing its promising applications in LPBs.     

Tritium separation from heavy water by electrolysis with solid polymer electrolyte

A tritium separation from heavy water by electrolysis using a solid polymer electrode layer was specified. The cathode was made of stainless steel or nickel. The electrolysis was performed for 1 hour at 5, 10, 20, and 30 °C. Using a palladium catalyst, generated hydrogen and oxygen gases were recombined, which was collected with a cold trap. The activities of the samples were measured by a liquid scintillation counter. The apparent tritium separation factors of the heavy and light water at 20 °C were 2 and 12, respectively.     

Electrode-compatible fluorine-free multifunctional additive regulating solid electrolyte interphase and solvation structure for high-performance lithium-ion batteries

The rapid development and widespread application of lithium-ion batteries(LIBs) have increased demand for high-safety and high-performance LIBs. Accordingly, various additives have been used in commercial liquid electrolytes to severally adjust the solvation structure of lithium ions, control the components of solid electrolyte interphase, or reduce flammability. While it is highly desirable to develop low-cost multifunctional electrolyte additives integrally that address both safety and perform...     

PVDF-HFP composite polymer electrolyte with excellent electrochemical properties for Li-ion batteries

Poly (vinylidene fluoride-co-hexafluoropropylene)-based composite polymer electrolyte (CPE) was prepared by phase inversion technique. In this work, we first applied a novel surface-modified sub-micro-sized alumina, PC-401, as ceramic filler. Various electrochemical methods were applied to investigate the electrochemical properties of the polymer electrolytes. We found that the CPE with 10 wt.% PC-401 has excellent electrochemical properties, including the ionic conductivity as high as 0.89 mS cm⁻¹ and the Li-ion transference number of 0.46. Polymer Li-ion batteries using LiFePO₄ as cathode active material exhibited excellent cycling and high-temperature performances. PC-401 shows a promising applicability in the preparation of polymer electrolyte with high electrochemical properties.     

High-safety and high-efficiency electrolyte design for 4.6 V-class lithium-ion batteries with a non-solvating flame-retardant

Nonflammable electrolytes are critical for the safe operation of high-voltage lithium-ion batteries (LIBs). Although organic phosphates are effective flame retardants, their poor electrochemical stability with a graphite (Gr) anode and Ni-rich cathodes would lead to the deterioration of electrode materials and fast capacity decay. Herein, we develop a safe and high-performance electrolyte formulation for high-voltage (4.6 V-class) LIBs using flame-retarding ethoxy(pentafluoro) cyclotriphosphazene (PFPN) as a non-solvating diluent for the high-concentration carbonate–ether hybrid electrolyte. In contrast to conventional nonflammable additives with restricted dosage, the high level of PFPN (69% mass ratio in our electrolyte design) could significantly increase the electrolyte flash point and protect the favored anion-rich inner solvation sheath because of its non-solvating feature, thus preventing solvent co-intercalation and structural damage to the Gr anode. The nonflammable electrolyte could also form a stable LiF-rich cathode electrolyte interphase (CEI), which enables superior electrochemical performances of Gr‖LiNi_0.8Mn_0.1Co_0.1O₂ (NMC811) full cells at high voltages (∼82.0% capacity retention after 1000 cycles at 4.5 V; 89.8% after 300 cycles at 4.6 V) and high temperatures (50 °C). This work sheds light on the electrolyte design and interphase engineering for developing practical safe high-energy-density LIBs.

This paper develops a high-safety and high-performance electrolyte with a carbonate–ether hybrid solvent and a highly fluorinated phosphazene-based flame-retarding diluent.     

Study of poly (organic palygorskite-methyl methacrylate)/poly(vinylidene fluoride-co-hexafluoropropylene) blended gel polymer electrolyte for lithium-ion batteries

Journal of Solid State Electrochemistry - The composite membrane (PDFP-POPM) based on the blending of poly(vinylidene fluoride-co-hexafluoropropylene) (PDFP) and POPM (the copolymer of organic...     

Effects of the porous structure on conductivity of nanocomposite polymer electrolyte for lithium ion batteries

A kind of porous nanocomposite polymer membranes (NCPMs) based on poly(vinylidene difluoride-co-hexafluoropropylene) (P(VdF-HFP)) incorporated with different amounts of TiO₂ nanoparticles from in situ hydrolysis of Ti(OC₄H₉)₄ was prepared by a non-solvent induced phase separation (NIPS) technology. The SEM micrographs reveal that a porous structure exists in the NCPMs, which changes with the incorporated amount of TiO₂. The NCPMs incorporated with 9.0 wt.% of mass fraction of TiO₂ possess the highest porosity, 67.3%, and appear as flexile fracture with an elongation ratio, 74.4%. At this content, the ionic conductivity of the NCPE is up to 0.94 × 10⁻³ S cm⁻¹ at room temperature and the activation energy for ions transport reaches the lowest, 18.71 kJ mol⁻¹. It is of great potential application in lithium ion batteries.     

Properties of composite solid polymer electrolyte using hyperbranched polymer with ether-linkage

The cross-linked composite solid polymer electrolytes composed of poly(ethylene oxide), lithium salt (LiN(SO₂CF₃)₂), and a hyperbranched polymer whose repeating units were connected by ether-linkage (hyperbranched polymer (HBP)-2) were prepared, and their ionic conductivity, thermal properties, electrochemical stability, mechanical property, and chemical stability were investigated in comparison with the non-cross-linked or cross-linked composite solid polymer electrolytes using hyperbranched polymers whose repeating units were connected by ester-linkage (HBP-1a, 1b). The cross-linked composite solid polymer electrolyte using HBP-2 exhibited higher ionic conductivity than the non-cross-linked and cross-linked composite solid polymer electrolytes using HBP-1a and HBP-1b, respectively. The structure of the hyperbranched polymer did not have a significant effect on the thermal properties and electrochemical stability of the composite solid polymer electrolytes. The tensile strength of the cross-linked composite solid polymer electrolyte using HBP-2 was lower than that of the cross-linked composite solid polymer electrolyte using HBP-1b, but higher than that of the non-cross-linked composite solid polymer electrolyte using HBP-1a. The HBP-2 with ether-linkage showed higher chemical stability against alkaline hydrolysis compared with HBP-1a with ester-linkage.     

A new flame-retardant polymer electrolyte with enhanced Li-ion conductivity for safe lithium-sulfur batteries

Flame-retardant polymer electrolytes(FRSPEs)are attractive due to their potential for fundamentally settling the safety issues of liquid electrolytes.However,the current FRSPEs have introduced large quantity of flame-retardant composition which cannot conduct lithium ions,thus decreasing the Li-ion conductivity.Here,we synthesize a novel liquid monomer 2-((bis((2-oxo-1,3-dioxolan-4-yl)methoxy)phosphoryl)oxy)ethyl acrylate(BDPA)for preparing FRSPE by in-situ polymerization,in which PBDPA polymer can not only conduct lithium ions,but also prevent burning.The prepared FRSPE demonstrated outstanding flame-retardant property,favorable lithium-ion conductivity of 5.65×10^-4 S cm^-1 at ambient temperature,and a wide electrochemical window up to 4.5 V.Moreover,the Li/in-situ FRSPE/S@pPAN cell exhibited favorable electrochemical performances.We believe that this work provides an effective strategy for establishing high-performance fireproof quasi-solid-state battery system.     

Lead–carbon hybrid ultracapacitors fabricated by using sulfur,nitrogen-doped reduced graphene oxide as anode material derived from spent lithium-ion batteries

Journal of Solid State Electrochemistry - The electrochemical-grade natural graphite flake prices are increasing day by day. Reusing and recycling graphite materials from the spent lithium-ion...     

Synthesis of aminoalkylsilanes with oligo(ethylene oxide) unit as multifunctional electrolyte additives for lithium-ion batteries

Aminoalkylsilanes with oligo(ethylene oxide) units were designed and synthesized as multifunctional electrolyte additives for lithium-ion batteries. The chemical structures were fully characterized by nuclear magnetic resonance (NMR) spectroscopy and their thermal properties, viscosities, electrochemical windows, and ionic conductivities were systematically measured. With adding one of these compounds (1 vol. %, DSC3N1) in the baseline electrolyte 1.0 M LiPF₆ in EC: DEC (1:1, in volume), Li/LiCoO₂ half cell tests showed an improved cyclability after 100 cycles and improved rate capability at 5C rate condition. Electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and energy dispersive spectroscopic (EDS) analysis confirmed the acid scavenging function and film forming capability of DSC3N1. These results demonstrated that the multifunctional organosilicon compounds have considerable potential as additives for use in lithium-ion batteries.     

Macroporous polymer monoliths fabricated by using a metal-organic coordination gel template

We have found a new way, a metal-organic coordination gel template method, to generate polymer monoliths with an essentially macropore size, in which the pores are organized spontaneously into continuous networks; furthermore, the resulting macroporous monoliths have potential applications in high-throughput and high-efficiency separation of proteins.