Lithium Battery Separator Research Articles

Influence of the porosity degree of poly(vinylidene fluoride-co-hexafluoropropylene) separators in the performance of Li-ion batteries

Polyvinylidenedifluoride–hexafluoropropylene, (P(VdF–HFP))-based polymer electrolytes, as separators for lithium batteries, were prepared through different polymer/solvent (N,N-dimethylformamide, DMF) ratios and physicochemically investigated. Scanning electron microscopy measurements have shown a homogeneously distributed porosity within the membranes, with moderately tortuous pathways, resulting in a liquid uptake up to 77 wt.% with respect to the overall weight and conduction values above 10−3 S cm−1 at room temperature.Prolonged cycling tests, performed on Li/Sn–C and Li/LiFePO4 half-cells based on P(VdF–HFP) polymer electrolyte separator membranes, have evidenced nominal capacities ranging from 70% to 90% of the theoretical value with very good capacity retention and charge/discharge efficiency close at 100% even at high current rates. A capacity decay is observed at high current regime, associated to the diffusion phenomena occurring within the electrode and the polymer electrolyte separator membrane.

Measurement and Analysis of Metal Element Contents in Lithium Battery Separator by ICP-OES

Measurement and Analysis of Metal Element Contents in Lithium Battery Separator by ICP-OES

Improving the properties of HDPE based separators for lithium ion batteries by blending block with copolymer PE-b-PEG

To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 × 10−3 S·cm−1 at 25°C, and the electrochemical stability window was up to 4.5 V (versus Li+/Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.

Progress in research on the performance and service life of batteries membrane of new energy automotive

Batteries membrane materials are widely used in new energy automotives such as hybrid vehicles, fuel cell vehicles, and pure electric vehicles. Membrane consists of two categories: fuel cell membrane (power unit) and power battery membrane (charge and discharge device). With rapid development of the processes and technology of cell membrane materials, there is urgent need to study their properties and service life. The article summarizes the recent research progress in proton exchange membrane materials, lithium battery separator materials, and nickel-hydrogen battery separator materials. Based on our laboratory research, the paper features the affecting factors and mitigation strategy of performance and service life for automotive battery membrane materials. Future direction for the batteries membrane material of new energy automotive is discussed.

Sulfonation Surface Treatment of Plasma Alkali Secondary Lithium Battery Separator

Modified membrane separators with lower cost using non-woven Polypropylene (PP) were widely used in the field of the secondary lithium batteries. Sulfonation is one of the most commonly modified methods for the surface modification of polymers. In order to make it effective in industry production, plasma surface treatment is applied to one, and it is an effective surface activation technology without changing its original properties. The characteristic properties of modified PP membrane separators have been studied by Alkali Absorption property Test, Tensile Strength Test, Fourier-Transform Infrared Measurements (FTIR), Scanning Electron Microscopy (SEM) and X-Ray Photoelectron Spectroscopy (XPS). Sulfonic acid groups in the polymer membranes were evidenced by the FTIR and the XPS spectroscopy. The results showed that the plasma sulfonation treatment reaction was very effective to improve the surface hydrophilicity of the non-woven membranes. The suitable sulfonation process could keep the lower cost in industry production.

A powder particle size effect on ceramic powder based separator for lithium rechargeable battery

To improve the thermal stability of separators for lithium batteries, we have developed heat-resistant separator films based on ceramic powder. These ceramic powder based separators (CPS) consist of ceramic powder with binder resin. We used two different particle size powders of aluminum oxide (0.01 or 0.3 μm). By mixing ceramic powder and resin at an appropriate content ratio, both types of CPS films satisfied needs for the heat-resistance. Furthermore, CPS film using 0.01 μm powder showed excellent charge–discharge cycling properties when applied to lithium rechargeable batteries as a separator.

Characterization of PEO-lithium triflate polymer electrolytes: Conductivity, DSC and Raman Investigations

Polymeric membranes to be used as electrolytic separators in lithium batteries were prepared from Poly Ethylene Oxide (PEO) and Lithium Triflate salt (LiTf) via a solventfree procedure. Several membranes, having different PEO/LiTf molar ratios, were characterized by Electrochemical Impedance Spectroscopy (EIS) to obtain their ionic conductivity. Most of the compositions exhibit an Arrhenius-like behaviour with two different activation energies above and below 60 °C. Only the sample having the highest LiTf concentration showed a non-Arrhenius trend. Differential Scanning Calorimetry (DSC) study was performed to determine the various phases present in the system. The degree of association of the mobile ions changes vs. composition and temperature was investigated by Raman spectroscopy, a powerful technique which allows to follow these changes in details by studying the spectral parameters of the SO3 stretching vibration of triflate ions. These data were correlated with the conductivity and thermodynamic data.

Polymer Electrolytes for Lithium-Ion Batteries

The motivation for lithium battery development and a discussion of ion conducting polymers as separators begin this review, which includes a short history of polymer electrolyte research, a summary of the major parameters that determine lithium ion transport in polymer matrices, and consequences for solid polymer electrolyte development. Two major strategies for the application of ion conducting polymers as separators in lithium batteries are identified: One is the development of highly conductive materials via the crosslinking of mobile chains to form networks, which are then swollen by lithium salt solutions ("gel electrolytes"). The other is the construction of solid polymer electrolytes (SPEs) with supramolecular architectures, which intrinsically give rise to much enhanced mechanical strength. These materials as yet exhibit relatively common conductivity levels but may be applied as very thin films. Molecular composites based on poly(p-phenylene)- (PPP)-reinforced SPEs are a striking example of this direction. Neither strategy has as yet led to a "breakthrough" with respect to technical application, at least not for electrically powered vehicles. Before being used as separators, the gel electrolytes must be strengthened, while the molecularly reinforced solid polymer electrolytes must demonstrate improved conductivity.

Bibliographical notice

Polyvinylidenedifluoride–hexafluoropropylene, (P(VdF–HFP))-based polymer electrolytes, as separators for lithium batteries, were prepared through different polymer/solvent (N,N-dimethylformamide, DMF) ratios and physicochemically investigated. Scanning electron microscopy measurements have shown a homogeneously distributed porosity within the membranes, with moderately tortuous pathways, resulting in a liquid uptake up to 77 wt.% with respect to the overall weight and conduction values above 10−3 S cm−1 at room temperature.Prolonged cycling tests, performed on Li/Sn–C and Li/LiFePO4 half-cells based on P(VdF–HFP) polymer electrolyte separator membranes, have evidenced nominal capacities ranging from 70% to 90% of the theoretical value with very good capacity retention and charge/discharge efficiency close at 100% even at high current rates. A capacity decay is observed at high current regime, associated to the diffusion phenomena occurring within the electrode and the polymer electrolyte separator membrane.