Effect of sol composition on solid electrode/solid electrolyte interface for all-solid-state lithium ion battery

A property of interface between solid electrode and solid electrolyte is one of the most important keys to fabricate all-solid-state lithium ion battery. In this study, an influence of sol composition used for preparation of the electrode on the property of interface between electrode and electrolyte was examined. LiMn₂O₄/honeycomb Li_0.55La_0.35TiO₃ (LLT) and Li₄Mn₅O₁₂/honeycomb LLT half cells were fabricated by impregnation of mixture of active materials with various precursor sols into honeycomb holes. In the case of LiMn₂O₄ cathode, the sol composed of nitrate salt provides large contact area of LiMn₂O₄ and LLT, resulting in higher performance of the cell. Li₂MnO₃ impurity was produced at Li₄Mn₅O₁₂/LLT interface prepared by the precursor sol composed of only nitrate or acetate salts although no impurity phase was observed at the interface prepared by acetate–nitrate sol containing lithium acetate and manganese nitrate. Li₄Mn₅O₁₂/honeycomb LLT half cell prepared by the acetate–nitrate sol showed the best performance among them. It is concluded that composition of the precursor sol strongly influenced on the interface of electrode and electrolyte. The all-solid-state Li ion battery composed of LiMn₂O₄/honeycomb LLT/Li₄Mn₅O₁₂ was successfully operated and the discharge capacity was 32 μAh cm⁻².     

Fabrication and characterization of PEO/PPC polymer electrolyte for lithium‐ion battery

A new poly(propylene carbonate)/poly(ethylene oxide) (PEO/PPC) polymer electrolytes (PEs) have been developed by solution‐casting technique using biodegradable PPC and PEO. The morphology, structure, and thermal properties of the PEO/PPC polymer electrolytes were investigated by scanning electron microscopy, X‐ray diffraction, and differential scanning calorimetry methods. The ionic conductivity and the electrochemical stability window of the PEO/PPC polymer electrolytes were also measured. The results showed that the T_g and the crystallinity of PEO decrease, and consequently, the ionic conductivity increases because of the addition of amorphous PPC. The PEO/50%PPC/10%LiClO₄ polymer electrolyte possesses good properties such as 6.83 × 10^?5 S cm^?1 of ionic conductivity at room temperature and 4.5 V of the electrochemical stability window. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

锂离子电池用聚氧化乙烯电解质膜的阻抗性能研究

为研究聚氧化乙烯(PEO)电解质膜的最佳配方,探究双三氟甲磺酰亚胺锂(LiTFSI)在不同含量下对PEO阻抗性能的影响。结果表明:n(EO)∶n(Li⁺)为12∶1,PEO电解质膜在阻塞电池、锂对称电池以及全电池中均具有最低的阻抗值,说明其具有较高的离子电导率和较好的界面接触。经过全电池循环测试,证实最佳样品具有良好的循环性能和实际应用潜力。     

A novel polymer electrolyte based on PMAML/PVDF-HFP blend

A gel polymer electrolyte based on the blend of poly(methyl methacrylate-co-acrylonitrile-co-lithium methacrylate) (PMAML) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) was prepared and characterized. The synthesized PMAML were characterized by FTIR and NMR, respectively, and the surface morphology of the PMAML and PVDF-HFP blend membrane was also observed by scanning electron microscope (SEM). The electrochemical properties of composite electrolyte membranes were studied. The ionic conductivity of the polymer electrolyte composed of 75 wt.% 1 M LiBF₄ in ethylene carbonate (EC) and dimethyl carbonate (DMC) (EC:DMC=1:1 by weight) was about 2.6×10⁻³ S cm⁻¹ at ambient temperature. The electrochemical window of the polymer electrolyte was about 4.6 V determined from the linear sweep voltammetry plot. The lithium ion polymer batteries were assembled by sandwiching gel polymer electrolyte between LiCoO₂ cathode and mesophase carbon fibre (MPCF) anode. Charge-discharge test results display that lithium ion batteries with these gel polymer electrolytes have good electrochemical performance.     

Improving ionic conductivity of polymer-based solid electrolytes for lithium metal batteries

Because of its superior safety and excellent processability, solid polymer electrolytes (SPEs) have attracted widespread attention. In lithium based batteries, SPEs have great prospects in replacing leaky and flammable liquid electrolytes. However, the low ionic conductivity of SPEs cannot meet the requirements of high energy density systems, which is also an important obstacle to its practical application. In this respect, escalating charge carriers (i.e. Li⁺) and Li⁺ transport paths are two major aspects of improving the ionic conductivity of SPEs. This article reviews recent advances from the two perspectives, and the underlying mechanism of these proposed strategies is discussed, including increasing the Li⁺ number and optimizing the Li⁺ transport paths through increasing the types and shortening the distance of Li⁺ transport path. It is hoped that this article can enlighten profound thinking and open up new ways to improve the ionic conductivity of SPEs.     

Effect of the addition of hydrophobic clay on the electrochemical property of polyacrylonitrile/LiClO4 polymer electrolytes for lithium battery

In this study, an organoclay, ALA-MMT, was prepared by the ionic exchange reaction of montmorillonite (MMT) with 12-aminododecanoic acid (ALA). ALA-MMT was then used as a filler to prepare a series of composite polymer electrolytes based on polyacrylonitrile (PAN) and LiClO₄. The effect of the addition of ALA-MMT on the properties of the composite polymer electrolytes (CPEs) was investigated by XRD, FT-IR, DSC, tensile strength, AC impedance, and cyclic voltammetry measurements. It was found that the ALA-MMT particles were well dispersed in the CPEs. Owing to the incorporation of ALA-MMT, a higher fraction of the free anions was obtained, indicating that the lithium salt dissolved in the PAN matrix more effectively for the CPE than in the PAN/LiClO₄ polymer electrolyte. Moreover, the glass-transition temperature was reduced, benefiting the ion transport. The best ionic conductivity at room temperature was obtained from the CPE with 7 wt% of the modified clay and 0.6 M LiClO₄ per PAN repeat unit (CPE-7) and was more than seven times higher than that from the corresponding PAN/LiClO₄ polymer electrolyte (CPE-0). The mechanical property and the cation transference number, t₊, of CPE-7 are largely increased compared to that of CPE-0. Besides, the CPEs were electrochemically stabilized up to 4.75 V and the corresponding cell exhibited excellent electrochemical stability and cyclability over the potential range between 0 V and 4.0 V vs. Li/Li⁺.     

Preparation and electrochemical properties of composite polymer electrolytes containing 1-ethyl-3-methylimidazolium tetrafluoroborate salts

The effects of room-temperature molten salt addition on the micro-structure and electrochemical properties of composite electrolytes (CEs) based on poly(ethylene oxide) (PEO)/ethylene carbonate (EC)/LiBF₄ were studied. Additional salt, 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF₄), was found to influence the crystalline structure and heterogeneous morphology, resulting in changes to the ionic conductivity of the CE. The CE containing 0.2 mol of EMIBF₄ showed a small crystallinity, 27.9%. These CEs showed the highest ion conductivity, 3.1 × 10⁻⁴ S/cm, five times higher than that of the pristine PEO/EC/LiBF₄. This enhanced conductivity originated from the decreased crystallinity and improved ion transference due to a Lewis acid-base interaction. The CE containing 0.3 mol of EMIBF₄ showed decreased conductivity due to the lower mobility, reflecting the high viscosity of the molten salt.     

Electrochemical properties of Li ion polymer battery with gel polymer electrolyte based on polyurethane

Gel polymer electrolyte (GPE) was prepared using polyurethane acrylate as polymer host and its performance was evaluated. LiCoO₂/GPE/graphite cells were prepared and their electrochemical performance as a function of discharge currents and temperatures was evaluated. The precursor containing a 5 vol % curable mixture had a viscosity of 4.5 mPa s. The ionic conductivity of the GPE at 20 °C was about 4.5 × 10^–3 S cm^–1. The GPE was stable electrochemically up to a potential of 4.8 V vs Li/Li⁺. LiCoO₂/GPE/graphite cells showed a good high rate and low-temperature performance. The discharge capacity of the cell was stable with charge–discharge cycling.     

Effect of cation structure on the electrochemical and thermal properties of ion conductive polymers obtained from polymerizable ionic liquids

Several onium cations having vinyl group formed ionic liquids after coupling with bis(trifluoromethanesulfonyl)imide. These monomers were polymerized, and the relation between onium cation structure and properties of thus polymerized ionic liquids was investigated. The polymerized ionic liquid having ethylimiadzolium cation unit showed the highest ionic conductivity of around 10⁻⁴ S cm⁻¹ at 30 °C among the obtained polymers reflecting the lowest glass transition temperature of −59 °C. These polymers were thermally stable and their decomposition temperatures were about 350 °C. The ionic conductivity of the polymerized ionic liquids decreased by both the addition of lithium bis(trifluoromethanesulfonyl)imide and the polymerization in the presence of cross-linker. However, the polymerized ionic liquid having 1-methylpiperidinium cation structure showed good lithium ion transference number of 0.43 at room temperature.     

Effect of zwitterionic salt on the electrochemical properties of a solid polymer electrolyte with high temperature stability for lithium ion batteries

In this study, we prepare a kind of solid polymer electrolyte (SPE) based on N-ethyl-N′-methyl imidazolium tetrafluoroborate (EMIBF₄), LiBF₄ and poly(vinylidene difluoride-co-hexafluoropropylene) [P(VdF-HFP)] copolymer. The resultant SPE displays high thermal stability above 300 °C and high room temperature ionic conductivity near to 10⁻³ S cm⁻¹. Its electrochemical properties are improved with incorporation of a zwitterionic salt 1-(1-methyl-3-imidazolium)propane-3-sulfonate (MIm3S). When the SPE contains 1.0 wt% of the MIm3S, it has a high ionic conductivity of 1.57 × 10⁻³ S cm⁻¹ at room temperature, the maximum lithium ions transference number of 0.36 and the minimum apparent activation energy for ions transportation of 30.9 kJ mol⁻¹. The charge-discharge performance of a Li₄Ti₅O₁₂/SPE/LiCoO₂ cell indicates the potential application of the as-prepared SPE in lithium ion batteries.     

High performance binder-free quaternary composite CuO/Cu/TiO2NT/Ti anode for lithium ion battery

High performance binder-free quaternary composite CuO/Cu/TiO₂ nanotube/Ti (CuO/Cu/TiO₂NT/Ti) electrode for lithium ion battery was designed and synthesized via anodization, electrodeposition and thermal oxidation at 450 °C in the air. The as-prepared binder-free quaternary composite CuO/Cu/TiO₂NT/Ti electrode was studied in terms of XRD, XPS, SEM, EDX, galvanostatic charge/discharge, cycle stability, cyclic voltammetry (CV) and AC impedance. As expected, the binder-free quaternary composite CuO/Cu/TiO₂NT/Ti electrode displayed much higher discharge capacity, cycle stability, Li⁺ diffusion coefficient than bare TiO₂NT/Ti electrode. High Li-storage activity of CuO, high conductivity of Cu and the synergy effect among various components should be responsible for improved electrochemical performances. Additionally, binder-free combination of the various components may also contribute into the modifications due to the exclusion of negative effect of polymer binder.     

Effect of modified montmorillonites on the ionic conductivity of (PEO)16LiClO4 electrolytes

Three kinds of modified montmorillonites were prepared by ion exchange method, and added into (PEO)₁₆LiClO₄ matrix to study the effect on the ionic conductivity of (PEO)₁₆LiClO₄ electrolytes. The structure of the modified montmorillonites and polymer composites were characterized by wide-angle X-ray diffraction. HP 4192A was used to measure the ionic conductivity of the polymer electrolytes. The results show that the addition of optimum content of 250-Li-mont enhances the ionic conductivity of the PEO based electrolyte by nearly 30 times more than the plain system and that is much higher than the other two modified montmorillonites. The difference of enhancement in conductivity caused by adding these three montmorillonites can be attributed to the difference in structure of the samples as characterized by wide-angle X-ray diffraction.     

Vanadium doped ceramic matrix Li6.7La3Zr1.7V0.3O12 enabled PEO-based solid composite electrolyte with high lithium ion transference number and cycling stability

Solid polymer electrolytes (SPEs) have attracted much attention because of their potential in improving energy density and safety. Vanadium doped ceramic matrix Li_6.7La₃Zr_1.7V_0.3O₁₂ (LLZVO) was synthesized by high-temperature annealing, and formed a composite electrolyte with polyethylene oxide (PEO). Compared with pure PEO electrolyte membrane, the composite electrolyte membrane exhibited better ionic conductivity (30 °C: 3.2 × 10^?5 S cm^?1; 80 °C: 3.6 × 10^?3 S cm^?1). The combination of LLZVO was beneficial to improve the lithium ion transference number (t_Li⁺) of SPE, which was as high as 0.81. The Li/SPE/LiFePO₄ battery shows good cycling ability, with a specific capacity of 142 mAh g^?1 after a stable cycle of 150 cycles. Meanwhile, the symmetrical lithium battery with composite electrolyte can work continuously for 1200 h without short circuit at the current density of 0.1 mA cm^?2 at 50 °C, and the capacity is 0.176 mAh. Vanadium doped ceramic matrix LLZVO as an active ionic conductor, improved the overall performance of solid electrolyte.     

Ionic conductivity in polyethylene-b-poly(ethylene oxide)/lithium perchlorate solid polymer electrolytes

The ionic conductivity and phase arrangement of solid polymeric electrolytes based on the block copolymer polyethylene-b-poly(ethylene oxide) (PE-b-PEO) and LiClO₄ have been investigated. One set of electrolytes was prepared from copolymers with 75% of PEO units and another set was based on a blend of copolymer with 50% PEO units and homopolymers. The differential scanning calorimetry (DSC) results, for electrolytes based on the copolymer with 75% of PEO units, were dominated by the PEO phase. The PEO block crystallinity dropped and the glass transition increased with salt addition due to the coordination of the cation by PEO oxygen. The conductivity for copolymers 75% PEO-based electrolyte with 15 wt% of salt was higher than 10⁻⁵ S/cm at room temperature and reached to 10⁻³ S/cm at 100 °C on a heating measurement. The blend of PE-b-PEO (50% PEO)/PEO/PE showed a complex thermal behavior with decoupled melting of the blocks and the homopolymers. Upon salt addition the endotherms associated with PEO domains disappeared and the PE crystals remained untouched. The conductivity results were limited at 100 °C to values close to 10⁻⁴ S/cm and at room temperature values close to 3 × 10⁻⁶ S/cm were obtained for the 15 wt% salt electrolyte. Raman study showed that the ionic association of the highly concentrated blend electrolytes at room temperature is not significant. Therefore, the lower values of conductivity in the case of the blend with 50% PEO can be assigned to the higher content of PE domains leading to a morphology with lower connectivity for ionic conduction both in the crystalline and melted state of the PE domains.     

Solid polymer electrolytes V: microstructure and ionic conductivity of epoxide-crosslinked polyether networks doped with LiClO4

A crosslinked polyether network was prepared from poly(ethylene glycol) diglycidyl ether (PEGDE) cured with poly(propylene oxide) polyamine. Significant interactions between ions and polymer host have been observed for the crosslinked polyether network in the presence of LiClO₄ by means of FT-IR, DSC, TGA, and ⁷Li MAS solid-state NMR. Thermal stability and ionic conductivity of these complexes were also investigated by TGA and AC impedance measurements. The results of FT-IR, DSC, TGA and ⁷Li MAS solid-state NMR measurements indicate the formation of different types of complexes through the interaction of ions with different coordination sites of polymer electrolyte networks. The dependence of ionic conductivity was investigated as a function of temperature, LiClO₄ concentration and the molecular weight of polyether curing agents. It is observed that the behavior of ion transport follows the empirical Vogel-Tamman-Fulcher (VTF) type relationship for all the samples, implying the diffusion of charge carrier is assisted by the segmental motions of polymer chains. Moreover, the conductivity is also correlated with the interactions between ions and polymer host, and the maximum ionic conductivity occurs at the LiClO₄ concentration of [O]/[Li⁺]=15.     

Complicated phase behavior and ionic conductivities of PVP-co-PMMA-based polymer electrolytes

We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate the interactions that occur within complexes of poly(vinylpyrrolidone-co-methyl methacrylate) (PVP-co-PMMA) and lithium perchlorate (LiClO₄) as well as these systems' phase behavior and ionic conductivities. The presence of MMA moieties in the PVP-co-PMMA random copolymer has an inert diluent effect that reduces the degree of self-association of the PVP molecules and causes a negative deviation in the glass transition temperature (T_g). In the binary LiClO₄/PVP blends, the presence of a small amount of LiClO₄ reduces the strong dipole-dipole interactions within PVP and leads to a lower T_g. Further addition of LiClO₄ increases T_g as a result of ion-dipole interactions between LiClO₄ and PVP. In LiClO₄/PVP-co-PMMA blend systems, for which the three individual systems—the PVP-co-PMMA copolymer and the LiClO₄/PVP and LiClO₄/PMMA blends—are miscible at all compositional ratios, a phase-separated loop exists at certain compositions due to a complicated series of interactions among the LiClO₄, PVP and PMMA units. The PMMA-rich component in the PVP-co-PMMA copolymer tends to be excluded, and this phenomenon results in phase separation. At a LiClO₄ content of 20 wt% salt, the maximum ionic conductivity occurred for a LiClO₄/VP57 blend (i.e., 57 mol% VP units in the PVP-co-PMMA copolymer).     

Improved performance of solid polymer electrolytes for structural batteries utilizing plasticizing co‐solvents

This study describes the formulation, curing, and characterization of solid polymer electrolytes (SPE) based on plasticized poly(ethylene glycol)‐methacrylate, intended for use in structural batteries that utilizes carbon fibers as electrodes. The effect of crosslink density, salt concentration, and amount of plasticizer has been investigated. Adding a plasticizing solvent increases the overall performance of the SPE. Increased ionic conductivity and mechanical performance can be attained compared to similar systems without plasticizer. At ambient temperature, ionic conductivity (σ) of 3.3 × 10^?5 S cm^?1, with a corresponding storage modulus (E ′) of 20 MPa are reached. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44917.     

Effect of calix[6]pyrrole anion receptor addition on properties of PEO-based solid polymer electrolytes doped with LiTf and LiTfSI salts

In this article the impact of anion receptor (1,1,3,3,5,5-meso-hexaphenyl-2,2,4,4,6,6-meso-hexamethyl-calix[6]pyrrole) on physicochemical and ion transport properties of poly(ethylene oxide)-salt composites is discussed. Two salts, lithium triflate and lithium bis(trifluoromethane) sulfonamide, were tested. It is shown that addition of the anion receptor significantly increases glass transition temperature of the composite suggesting changes in the velocity of segmental motions of the polymeric matrix. Also some discrepancies between crystallinity of the electrolyte measured by means of DSC and the one measured by means of XRD for lithium triflate containing electrolytes are discussed. It is proved that the influence of the anion receptor on electrolyte properties depends on the coordinating properties of the anion. In consequence this two structurally similar anions are found to reveal opposite behavior. In systems containing LiTf significant changes in properties are observed upon receptor addition. Contrastively, LiTfSI does not interact with receptor and obtained samples exhibit non-homogenous structure with consequent receptor participation.     

Sulfur–carbon composite electrode for all-solid-state Li/S battery with Li2S–P2S5 solid electrolyte

All-solid-state Li/S batteries with Li₂S–P₂S₅ glass–ceramic electrolytes were fabricated and their electrochemical performance was examined. Sulfur–carbon composite electrodes were prepared by grinding with a mortar and milling with a planetary ball-mill apparatus. Milling of a mixture of sulfur, acetylene black and the Li₂S–P₂S₅ glass–ceramic electrolyte resulted in the amorphization of sulfur and a reduction in the particle size of the mixture. The charge–discharge properties of all-solid-state cells with the composite electrode were investigated at temperatures from −20 °C to 80 °C. The cells retained a reversible capacity higher than 850 mAh g⁻¹ for 200 cycles under 1.3 mA cm⁻² (333 mA g⁻¹) at 25 °C. The cell performance was influenced by the crystallinity of sulfur and the particle size of the electrode material, whereby improved contact among the electrode components achieved by milling contributed to enhancement of the capacity of an all-solid-state Li/S cell.     

Characterization of (PEO)LiClO4‐Li1.3Al0.3Ti1.7(PO4)3 composite polymer electrolytes with different molecular weights of PEO

A group of polyethylene oxide (PEO)LiClO₄‐Li_1.3Al_0.3Ti_1.7(PO₄)₃ composite polymer electrolyte (CPE) films was prepared by the solution‐cast method. In each film, EO/Li = 8 and the Li_1.3Al_0.3Ti_1.7(PO₄)₃ content of 15 wt % were fixed, but the number averaged molecular weight of PEO (M_n) was altered from 5 to 7 × 10⁴ to 10⁶, 2.2–2.7 × 10⁶, 3–4 × 10⁶, 4–5 × 10⁶, and 5.5–6 × 10⁶, respectively. Several techniques including X‐ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), and electrical impedance spectroscopy (EIS) were used to characterize the CPE films. LiClO₄ was found to have a strong tendency to complex with PEO, but Li_1.3Al_0.3Ti_1.7(PO₄)₃ was rather dispersed in PEO matrix. DSC analysis revealed that the amorphous phase was dominant in the CPE films although the PEOs before‐use was considerably crystalline. SEM study showed smooth and homogeneous morphologies of the films with low molecular weight PEO and a dual phase characteristic for those with high molecular weight PEO. EIS results indicated that the CPE films are all ionic conductor and the conducting behavior obeys Vogel‐Tamman‐Fulcher (VTF) equation. The parameters in VTF equation were obtained and discussed by taking into considerations PEO molecular weights and crystallinities of the CPE films. Of all the films, the one with PEO with the smallest M_n = 5–7 × 10⁴ had the maximum conductivity, i.e., 1.590 × 10^?5 S cm^?1 at room temperature and 1.886 × 10^?3 S cm^?1 at 373 K. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4269–4275, 2006