| Lithium-ion batteries(LIBs) have been considered as a main energy storage device for new energy vehicles owing to their high energy density, long cycle life, and minimal memory effects. One of the critical components that affect the safety of LIBs is the liquid electrolyte. Hence, the improvement in electrolyte composition is critical for the increasing demand for the safety of LIBs.Poly(propylene carbonate) PPC has received considerable attention due to its similar structure to carbonate-based solvents applied in conventional polymer electrolytes(PEs), which suggests that it may have good compatibility with the lithium salts as well as offer good interfacial contact with commonly used electrodes. PPC is also a type of completely biodegradable polymer which can contribute to prepare environmentally friendly PEs. In this work,in order to improve the ionic conductivity of PPC based PEs and the compatibility of PPC based PEs with electrode, several kinds of PPC based PEs were synthesized. The structure and performances of the synthesized PEs were studied with fourier transform infrared analysis(FTIR), X-ray diffraction(XRD), X-ray photoelectron spectroscopy(XPS), scanning electron microscope(SEM), transmission electron microscopy(TEM), thermogravimetric analysis(TG), differential scanning calorimetry(DSC), linear sweep voltammetry(LSV), electrochemical impedance spectroscopy(EIS) and charge-discharge test. Following results were obtained:The PEO/ PPC/nano Ti O2-PMMA composite polymer electrolytes for lithium ion batteries have been prepared by solution casting technique using PPC, polyethylene oxide(PEO) as polymer matrix and the poly(methyl methacrylate)(PMMA) graft-modified nano-Ti O2 as filler. The effect of nano Ti O2-PMMA on the structure and the electrochemical performance of CPE membrane were characterized by thermo gravimetric analysis(TGA), infrared spectroscopy(IR), SEM and electrochemical impedance spectroscopic(EIS) measurements. The results showed that the ionic conductivity of CPE membrane was up to 1.3×10-5 S?cm-1 at room temperature, its electrochemical stability window was wider than 4.5 V, and the lithium ion transference number was 0.49 when the grafting rate of nano-Ti O2 was 8.0%.Polybutadiene rubber-interpenetrating cross-linking poly(propylene carbonate)(named as XBRPC) membrane can be readily synthesized from polybutadiene rubber(BR), PPC, polyethylene glycol(PEG), and using benzoyl peroxide(BPO) as cross-linking agent, then activated by absorbing liquid electrolyte to fabricate a novel XBRPC gel polymer electrolyte(GPE) for lithium-ion battery. The results show that the XBRPC GPEs possess good mechanical strength and high electrolyte uptake. The ionic conductivity was up to 1.25×10-3 S?cm-1 at room temperature and 3.51×10-3 S?cm-1 at 80? for XBRPC70(70/30 of PPC/BR, w/w) sample. Furthermore, the electrochemical stability window had been established to with stand voltages greater than 4.5 V. The results of charge/discharge tests showed that the initial discharge capacity of Li/XBRPC70 GPE/Li Fe PO4 cell was 119 m Ah g-1 at a current rate of 0.1C and in voltage range of 2.5–4.0 V at room temperature. It also exhibited excellent cycling retention performance for high performance lithium rechargeable battery. The cell delivered discharge capacity of 100 m Ah g-1 after 70 cycles.A poly(methyl methacrylate)(PMMA)-interpenetrating cross-linking poly(propylene carbonate)(PPC) polymer precursor was synthesized by solution polymerization with different mass ratios of methyl methacrylate(MMA) and PPC. Polyethylene(PE) supported copolymer and GPEs were prepared with this polymer precursor. The effect of the ratio of MMA to PPC on the performance of the prepared membranes was considered. It was found that the GPE using the PE-supported copolymer with PPC to MMA= 8:2(in weight) had the largest ionic conductivity(1.71×10-3 S?cm-1 at room temperature) and shows superior electrolyte wettability with 347%±5% of electrolyte uptake. The GPE displayed good compatibility with anode and cathode of LIB and its electrochemical window was 5.0V. The Li Fe PO4 battery using this PE-supported GPE exhibited superior initial discharge capacity with 154 m Ah g-1. After 100 cycles, the capacity retention of the battery was found to be 94.2%.A novel high-performance GPE based on an electrospun polymer membrane of poly(vinylidene fluoride)/poly(propylene carbonate)(PVd F/PPC) was prepared and investigated for high-performance lithium-ion battery applications. This study presents a methodology for introducing PPC into PVd F-based GPEs designed for high performance lithium-ion batteries. SEM images and porosity measurements showed that the electrospun membrane had a uniform and highly interconnected porous structure with an average fiber diameter of 300-850 nm. Such a morphology resulted in excellent electrolyte uptake amount(500wt %) and retention in PVd F/PPC membrane. The DSC result indicated that the PVd F crystallinity was deteriorated by the incorporation of PPC. The PVd F/PPC electrospun membrane(CGE-20) showed significantly higher ionic conductivity(4.05×10-3 S?cm-1) than that of the PVd F electrospun membrane(2.11×10-3 S?cm-1) at 30 °C. The PVd F/PPC GPE was stable at a potential higher than 5.0 V. The capacity of Li/CGE-20/Li Fe PO4 was 155.4, 153.3, 137.0, 118.4, 103.2 and 148.2 m Ah g-1 at a charge/discharge rate of 0.1, 0.2, 0.5, 1, and 2 C, respectively. Moreover, in order to study the electrochemical performance of PVd F/PPC GPE which is applied to the self-made Fe2O3@C@ Mo S2 anode material with high capacity, the Fe2O3@C nanofiber was synthesized by electrospinning technique using Fe2O3 and polyacrylonitrile(PAN)as raw material. Then the Fe2O3@C@ Mo S2 anode material was synthesized by a hydrothermal method using the Fe2O3@C nanofiber as template. The PVd F/PPC GPE displayed good compatibility and excellent electrochemical performance with Fe2O3@C@ Mo S2 anode of LIB. It exhibited 839 m Ah g-1 after 100 cycles at 200 m A/g with good cycling performance. |
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