Polymer Electrolytes For Lithium Ion Batteries Research Articles

A Parallel Bicomponent TPU/PI Membrane with Mechanical Strength Enhanced Isotropic Interfaces Used as Polymer Electrolyte for Lithium-Ion Battery.

In this work, a side-by-side bicomponent thermoplastic polyurethane/polyimide (TPU/PI) polymer electrolyte prepared with side-by-side electrospinning method is reported for the first time. Symmetrical TPU and PI co-occur on one fiber, and are connected by an interface transition layer formed by the interdiffusion of two solutions. This structure of the as-prepared TPU/PI polymer electrolyte can integrate the advantages of high thermal stable PI and good mechanical strength TPU, and mechanical strength is further increased by those isotropic interface transition layers. Moreover, benefiting from micro-nano pores and the high porosity of the structure, TPU/PI polymer electrolyte presents high electrolyte uptake (665%) and excellent ionic conductivity (5.06 mS·cm−1) at room temperature. Compared with PE separator, TPU/PI polymer electrolyte exhibited better electrochemical stability, and using it as the electrolyte and separator, the assembled Li/LiMn2O4 cell exhibits low inner resistance, stable cyclic and notably high rate performance. Our study indicates that the TPU/PI membrane is a promising polymer electrolyte for high safety lithium-ion batteries.

Influence of Hydrothermally Synthesized Cubic-Structured BaTiO3 Ceramic Fillers on Ionic Conductivity, Mechanical Integrity, and Thermal Behavior of P(VDF–HFP)/PVAc-Based Composite Solid Polymer Electrolytes for Lithium-Ion Batteries

Solid polymer electrolytes (SPEs) with high ionic conductivity and wide electrochemical window are highly desirable for all-solid-state rechargeable lithium batteries. Herein, we report the use of ...

Fabrication of PEO-PMMA-LiClO4-Based Solid Polymer Electrolytes Containing Silica Aerogel Particles for All-Solid-State Lithium Batteries

To improve the ionic conductivity and thermal stability of a polyethylene oxide (PEO)-ethylene carbonate (EC)-LiClO4-based solid polymer electrolyte for lithium-ion batteries, polymethyl methacrylate (PMMA) and silica aerogel were incorporated into the PEO matrix. The effects of the PEO:PMMA molar ratio and the amount of silica aerogel on the structure of the PEO-PMMA-LiClO4 solid polymer electrolyte were studied by X-ray diffraction, Fourier-transform infrared spectroscopy and alternating current (AC) impedance measurements. The solid polymer electrolyte with PEO:PMMA = 8:1 and 8 wt% silica aerogel exhibited the highest lithium-ion conductivity (1.35 × 10−4 S∙cm−1 at 30 °C) and good mechanical stability. The enhanced amorphous character and high degree of dissociation of the LiClO4 salt were responsible for the high lithium-ion conductivity observed. Silica aerogels with a high specific surface area and mesoporosity could thus play an important role in the development of solid polymer electrolytes with improved structure and stability.

Robust Succinonitrile-Based Gel Polymer Electrolyte for Lithium-Ion Batteries Withstanding Mechanical Folding and High Temperature.

Fabrication of a gel polymer electrolyte containing succinonitrile (GPE-SN) with high mechanical strength is quite challenging because the SN electrolyte always suppresses the formation of polymer networks during in situ polymerization. In this work, a mechanically robust GPE-SN was successfully prepared by using a solution immersion method. During fabrication, the paste-like SN electrolyte was transformed into a liquid SN electrolyte with low viscosity by heating at 50 °C and then infiltrated into the UV-cured highly cross-linked polyurethane acrylate (PUA) skeleton. The resulted GPE-SN film exhibits superior tensile strength (6.5 MPa) compared to the one (0.5 MPa) prepared by in situ polymerization (GPE-SN-IN). The high mechanical strength of the GPE-SN-IM film enables the LiCoO2/Li4Ti5O12 film battery to withstand 100-cycle folding without electrolyte damage and capacity loss. Besides, the GPE-SN presents a high ionic conductivity (1.63 × 10-3 S·cm-1 at 25 °C), which is comparable to GPE with a commercial liquid electrolyte (GPE-LE). Because of good thermal stability of the GPE-SN, the LiCoO2/Li cell with this electrolyte shows better charge-discharge cycling stability than that with GPE-LE at high temperature (55 °C). Thus, the GPE-SN prepared by our method could be a promising polymer electrolyte offering better safety and reliability for lithium-ion batteries.

In Operando Small-Angle X-ray Scattering Investigation of Nanostructured Polymer Electrolyte for Lithium-Ion Batteries

Electrochemical energy storage still presents one of the biggest challenges that society has to face by developing alternative lithium-ion batteries (LIBs) as they already satisfy important preconditions by providing the highest energy and power densities of all battery systems. Nowadays, the employed liquid electrolytes in LIBs do not merge the world’s increasing demand of safely working batteries. Here, we use a lithium salt-doped diblock copolymer electrolyte:poly(styrene)-block-poly(ethylene oxide)/bis(trifluoromethane) lithium salt, denoted PS-b-PEO/LiTFSI, as a solid-state electrolyte. The evolving nanoscale morphology of the electrolyte material in a capillary-based LIB cell is investigated using in operando small-angle X-ray scattering (SAXS). The electrolyte is sandwiched between two opposing electrodes inside of a glass capillary and investigated during cycling at 90 °C while the X-ray beam is oriented orthogonally to the ionic current. Lithium iron phosphate (LFP) is used as a cathode, while bo...

Six-arm star polymer based on discotic liquid crystal as high performance all-solid-state polymer electrolyte for lithium-ion batteries

All-solid-state polymer electrolyte (SPE) matrices prepared by molecular design are still needed to be further perfected with excellent performance. In this paper, a controlled-structure discotic liquid crystal (DLC)-based six-arm star copolymer was designed and synthesized from a DLC initiator (2,3,6,7,10,11-hexakis(2-bromoisobutyryloxy)triphenylene) via the sequential atom transfer radical polymerization (ATRP) of styrene and poly(ethylene glycol) methyl ether methacrylate (PEGMA). Here, this class of discotic liquid crystal star polymer is applied as an SPE in LIBs for the first time. By solution casting, a suitable self-standing SPE film composed of the six-arm copolymer and lithium bis(trifluoromethanesulfonimide (LiTFSI)) can be easily formed, and the film shows long-range molecular orientation after annealing. It is confirmed that the electrolyte shows wide electrochemical window (5.1 V) and high lithium-ion transference number (0.37). Especially, the ionic conductivity (1.46 × 10−4, S cm−1, 30 °C) of the obtained SPE is more than 8 times higher than that of the corresponding linear copolymer electrolytes. Furthermore, the results of battery performance demonstrate that the polymer electrolyte displays eminently reversible electrochemical reaction and outstanding cycling performance. The present work not only shows the advantages of DLC-based star SPE for LIBs but also paves the way for the design of SPE with excellent performances.

Ionic raises funds for polymer electrolyte

Boston-area start-up Ionic Materials has raised $65 million in its third round of venture funding. Backers include unnamed electronics firms and auto manufacturers. Last month, an alliance of Renault, Nissan, and Mitsubishi Motors identified Ionic Materials as the first investment of their new venture fund. Founded by Tufts University materials scientist Michael Zimmerman, Ionic Materials is developing a solid polymer electrolyte for lithium-ion batteries. It will use the funds for hiring and to meet what it calls “significant market demand” for its material.

ε-Caprolactone-based solid polymer electrolytes for lithium-ion batteries: synthesis, electrochemical characterization and mechanical stabilization by block copolymerization.

In this work, three types of polymers based on ε-caprolactone have been synthesized: poly(ε-caprolactone), polystyrene-poly(ε-caprolactone), and polystyrene-poly(ε-caprolactone-r-trimethylene carbonate) (SCT), where the polystyrene block was introduced to improve the electrochemical and mechanical performance of the material. Solid polymer electrolytes (SPEs) were produced by blending the polymers with 10–40 wt% lithium bis(trifluoromethane)sulfonimide (LiTFSI). Battery devices were thereafter constructed to evaluate the cycling performance. The best performing battery half-cell utilized an SPE consisting of SCT and 17 wt% LiTFSI as both binder and electrolyte; a Li|SPE|LiFePO4 cell that cycled at 40 °C gave a discharge capacity of about 140 mA h g−1 at C/5 for 100 cycles, which was superior to the other investigated electrolytes. Dynamic mechanical analysis (DMA) showed that the storage modulus E’ was about 5 MPa for this electrolyte.

Preparation, characterization and properties of poly(propylene carbonate)/poly(methyl methacrylate)-coated polyethylene gel polymer electrolyte for lithium-ion batteries

A poly(propylene carbonate) (PPC)/poly(methyl methacrylate) (PMMA) polymer precursor was developed via solution polymerization with different mass ratios of methyl methacrylate (MMA) and PPC. Then, PPC/PMMA-coated Celgard PE membranes were prepared by the dip-coating method with this polymer precursor and activated to fabricate gel polymer electrolytes (GPEs). The structure and performance of the samples were characterized with FTIR, DSC, SEM, water contact angle analysis and electrochemical performance tests, such as electrochemical impedance spectroscopy (EIS), linear sweep voltammetry (LSV) and galvanostatic charge-discharge measurements. The effect of the ratio of MMA to PPC on the performance of the as-prepared PPC/PMMA-coated Celgard PE GPEs was considered. Benefiting from the composite structure, the GPE produced from the Celgard PE coating polymer with a PPC to MMA ratio of 8:2 (by weight) had the highest ionic conductivity and showed superior electrolyte wettability with 347% electrolyte uptake. Additionally, the as-prepared GPEs displayed good compatibility with the anodes and cathodes of lithium-ion batteries (LIBs), and their oxidation potentials were stable to 5.0V (vs Li/Li+). The LiFePO4 battery using this PPC/PMMA-coated Celgard PE GPE exhibited an excellent initial discharge capacity of 154mAhg−1, cyclic stability and rate capability.

Lithium-Containing Zwitterionic Poly(Ionic Liquid)s as Polymer Electrolytes for Lithium-Ion Batteries

Polymer electrolytes are considered as the good candidates for the new-generation-safe lithium-ion battery. Herein, a free-standing and flexible polymer electrolyte film based on a lithium-containing zwitterionic poly(ionic liquid) (PIL) was constructed with and without propylene carbonate (PC) by in-situ photopolymerization. In this system, the lithium-containing IL synthesized by equimolecular neutralization of imidazolium-type zwitterion 3-(1-vinyl-3-imidazolio)propanesulfonate (VIPS) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) can both serve as the polymeric matrix of the polymer electrolytes to maintain sufficient mechanical strength and form Li+-rich channels for lithium-ion transportation. The ion–dipole interaction between the lithium ion and the polar solvent PC can further improve the lithium-ion conduction, resulting in a comparable ionic conductivity of ∼10–3 S/cm at 30 °C. Charge–discharge cycling performance of Li/LiFePO4 half-cell equipped with the PIL-based polymer electrolyte i...

Preparation and Characterization of Super Cross-Linked Poly(ethylene oxide) Gel Polymer Electrolyte for Lithium-Ion Battery

Preparation and Characterization of Super Cross-Linked Poly(ethylene oxide) Gel Polymer Electrolyte for Lithium-Ion Battery

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).

Self-supported PVdF/P(VC-VAc) blended polymer electrolytes for LiNi0.5Mn1.5O4/Li batteries

New self-supported poly(vinylidene fluoride)/poly (vinyl chloride-co-vinyl acetate) (PVdF/P(VC-VAc)) blended polymer membranes are prepared via a phase inversion method, and then their electrochemical performances, immersed in the liquid electrolyte as the polymer electrolyte for lithium-ion batteries (LIBs), are evaluated. The Fourier transform infrared spectroscopy analysis, the differential scanning calorimeter test and the X-ray diffraction measurement demonstrate that homogeneous PVdF/P(VC-VAc) polymer composites can form at all blend compositions and the crystallinity degree of the blended polymers decreases as the P(VC-VAc) content increases. Specifically, when the proportion of PVdF/P(VC-VAc) is 70:30 (wt%), membranes with a rich surface and internal porous structure can be acquired. The ionic conductivity of the polymer electrolyte achieves a maximum value of 3.57mScm−1 at room temperature, and favourable electrochemical performances of LIBs can be obtained. LiNi0.5Mn1.5O4/Li cells with the as-prepared polymer electrolyte exhibit a higher initial discharge capacity of 131.0mAhg−1 and superior cycle stability with a capacity retention of 96.1% at 0.2C after 200 cycles compared to cells based on pure PVdF and P(VC-VAc) membranes. This can be attributed to the superior compatibility of the electrolyte with the electrodes. The results also indicate this electrolyte has promising applications in high-voltage LIBs.

Liquid perfluoropolyether electrolytes with enhanced ionic conductivity for lithium battery applications

We prepared nonflammable liquid polymer electrolytes for lithium-ion batteries by mixing ethoxylated perfluoropolyethers (PFPEs) with LiN(SO2CF3)2 salt. Interestingly, we identified the presence of chain coupling in the PFPE polymers and their functionalized derivatives, resulting in a mixture of PFPEs with varying molecular weights. The distribution of molecular weights, along with PFPE's multiple functionalities, allows systematic manipulation of structure to enhance electrochemical and physical properties. Furthermore, the electrolytes exhibited a wide thermal stability window (5% degradation temperature >180 °C). Despite substantial increases in viscosity upon loading the PFPEs with lithium salt, the conductivity (σ ≈ 5 × 10−5 S cm−1 at 28 °C) of the novel electrolytes was about an order of magnitude higher than that of our previously reported PFPE electrolytes. Ethoxylated derivatives of PFPE electrolytes exhibit elevated conductivity compared to non-ethoxylated derivatives, demonstrating our capability to enhance the conductive properties of the PFPE platform by attaching various functional groups to the polymer backbone.

A New All-Solid-State Hyperbranched Star Polymer Electrolyte for Lithium Ion Batteries: Synthesis and Electrochemical Properties

A new hyperbranched multi-arm star polymer with hyperbranched polystyrene (HBPS) as core and polymethyl methacrylate-block-poly(ethylene glycol) methyl ether methacrylate(PMMA-b-PPEGMA) as arms was firstly synthesized by atom transfer radical polymerization. The obtained hyperbranched multi-arm star polymer (HBPS-(PMMA-b-PPEGMA)x) exhibited good thermal stability with a thermal decomposition temperature of 372°C. The transparent, free-standing, flexible polymer electrolyte film of the blending of HBPS-(PMMA-b-PPEGMA)x and lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) was successfully fabricated by a solution casting method. The ionic conductivity of the hyperbranched star polymer electrolyte with a molar ratio of [EO]/[Li] of 30 could reach 8.3×10−5Scm−1 at 30°C (with the content of PPEGMA of 83.7%), and 2.0×10−4Scm−1 at 80°C (with the content of PPEGMA of 51.6%). The effect of the concentration of lithium salts on ionic conductivity was also investigated. The obtained all-solid-state polymer electrolyte possessed a wide electrochemical stability window of 4.7V (vs. Li+/Li), and a lithium-ion transference number (tLi+) up to 0.31. The interfacial impedance of the fabricated Li│polymer electrolyte│Li symmetric cell based on hyperbranched star multi-arm polymer electrolyte exhibited good interfacial compatibility between all-solid-state polymer electrolyte and electrodes. The excellent properties of the hyperbranched star polymer electrolyte made it attractive as solid-state polymer electrolyte for lithium-ion batteries.

Employing Gradient Copolymer To Achieve Gel Polymer Electrolytes with High Ionic Conductivity

A new type of polymer electrolyte based on gradient copolymers is proposed to resolve the problem of low ionic conductivity faced by polymer electrolytes. A series of random, block, and gradient copolymers of styrene (St) and methyl acrylate (MA) are synthesized by a living radical polymerization method and employed as polymer electrolytes for lithium-ion batteries. The gradient copolymer has gradual change in the monomeric composition along polymer chains. There is no abrupt composition change between the adjacent blocks. This design minimizes possible sharp domain boundaries and generates highly conductive smooth ion pathways. The gradient copolymer gel electrolyte filled with a regular ester electrolyte gives the highest ionic conductivity of 1.20 × 10–3 S cm–1 at room temperature, which meets the requirement of practical applications.

A novel electrospun poly(vinylidene fluoride)/thermoplastic polyurethane/poly(vinylidene fluoride)-g-(maleic anhydride) porous fibrous polymer electrolyte for lithium-ion batteries

A novel gel polymer electrolyte films based on poly(vinylidene fluoride) (PVDF)/thermoplastic polyurethane (TPU) with and without poly(vinylidene fluoride)-g-(maleic anhydride) (PVDF-g-MA) are prepared by electrospinning. Its morphological characteristics are observed by scanning electron microscope (SEM). The crystallinity of the electrospun PVDF/TPU blending membrane is found to decrease with PVDF-g-MA, which is confirmed by differential scanning calorimeter (DSC). The PVDF/TPU/PVDF-g-MA blending membrane has high tensile strength (10.3MPa) and elongation at break (96.5%). The gel polymer electrolytes with PVDF-g-MA exhibits high ionic conductivity of 4.7×10−3Scm−1 with electrochemical stability up to 5.0V (vs. Li+/Li) at room temperature. A Li/LiFePO4 cell with a gel polymer electrolytes based on PVDF/TPU/PVDF-g-MA delivers high first charge–discharge capacity of 166.9mAhg−1 when evaluated at 0.1C-rate and a stable cycle performance. The results reveal that PVDF/TPU/PVDF-g-MA is an excellent polymer matrice as gel polymer electrolyte for lithium-ion battery.

Elastomers uploaded electrospun nanofibrous membrane as solid state polymer electrolytes for lithium-ion batteries

Good electrochemical properties and reversible charge/discharge solid state composite electrolytes were achieved at high temperature by uploading 3PEG onto electrospun membranes.

Transference Number Measurements on Gel Polymer Electrolytes for Lithium-Ion Batteries

Gel polymer electrolytes for Lithium-Ion batteries based on MMA and LiPF6 in EC:DMC (1:1 wt.) with different salt concentration were prepared by radical photo polymerization. These samples were measured on transference number using Bruce-Vincent method based on combination of DC polarization and AC Electrochemical Impedance Spectroscopy (EIS) techniques. This method gave values ranging from 0.24 at 0.05 mol l-1 LiPF6 to 0.69 at 1 mol l-1 LiPF6 salt concentration.

Gel polymer electrolyte for lithium-ion batteries comprising cyclic carbonate moieties

A polymer system based on oligo (ethylene glycol) methyl ether methacrylate (OEGMA) and cyclic carbonate methacrylate (CCMA) was chosen as matrix to realize high-performance gel polymer electrolytes due to the fact that both monomers are able to interact with the liquid electrolyte, thus, retaining it inside the matrix. Additionally, OEGMA enables high flexibility, while CCMA provides mechanical stability. The polymer displays a high thermal stability up to 200 °C and a glass transition temperature below room temperature (5 °C) allowing an easy handling of the obtained films. By immobilizing the liquid electrolyte 1 M LiPF6 in EC:DMC 1:1 w:w in the polymer host a gel polymer electrolyte with a high conductivity of 2.3 mS cm−1 at 25 °C and a stable cycling behavior with high capacities and efficiencies in Li(Ni1/3Co1/3Mn1/3)O2 (NCM)/graphite full cells is obtained. The investigated gel polymer electrolyte is identified as promising electrolyte for lithium-ion batteries, because it combines good electrochemical properties comparable to that of liquid electrolytes with the safety advantage that no leakage of the flammable electrolyte solvents can occur.