Solid polymer electrolytes(SPEs)are considered promising candidates for all-solid-state lithium metal batteries because of their easy preparation and good compatibility with lithium metal.However,their applications ar...Solid polymer electrolytes(SPEs)are considered promising candidates for all-solid-state lithium metal batteries because of their easy preparation and good compatibility with lithium metal.However,their applications are restricted by their low ionic conductivity and poor mechanical properties.In this study,a composite solid polymer electrolyte composed of poly(ethylene oxide)(PEO),poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP),plasticizer succinonitrile(SN),and polytetrafluoroethylene(PTFE)fibrous porous membranes was prepared.The PTFE fibrous membrane significantly enhanced the mechanical strength of the electrolyte as a supporting framework.SN reduced the crystalline regions of PEO and facilitated rapid lithium-ion transport.PVDF-HFP promoted lithium salt dissolution and improved the electrochemical stability of the electrolyte.Accordingly,the optimized PTFE/PEO/PVDF-HFP/SN polymer electrolyte exhibited a tensile strength of 3.31 MPa at 352%elongation and demonstrated an ionic conductivity of 7.6×10^(-4)S·cm^(-1)at 60℃.Lithium symmetric cells maintained stable cycling for over 2500 h at 0.15 m A·cm^(-2),and Li//Li Fe PO_(4) full cells showed a high capacity retention of 91.6%after 300 cycles at 0.5 C,with coulombic efficiency consistently exceeding 99.9%throughout cycling.展开更多
Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane cont...Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.展开更多
In this study, we modified a polytetrafluoroethylene （PTFE） hollow-fiber membrane element used for submerged membrane bioreactors （MBRs） to reduce the energy consumption during MBR processes. The high mechanical s...In this study, we modified a polytetrafluoroethylene （PTFE） hollow-fiber membrane element used for submerged membrane bioreactors （MBRs） to reduce the energy consumption during MBR processes. The high mechanical strength of the PTFE membrane made it possible to increase the effective length of the membrane fiber from 2 to 3 m. In addition, the packing density was increased by 20% by optimizing the membrane element configuration. These modifications improve the efficiency of membrane cleaning associated with aeration. The target of specific energy consumption was less than 0.4 kWh·m^-3 in this study. The continuous operation of a pilot MBR treating real municipal wastewater revealed that the MBR utilizing the modified membrane element can be stably operated under a specific air demand per membrane surface area （SADm） of 0.13 m^3·m^-2. hr I when the daily- averaged membrane fluxes for the constant flow rate and flow rate fluctuating modes of operation were set to 0,6 and 0.5m^3·m^-2·d^-1 respectively. The specific energy consumption under these operating conditions was estimated to be less than 0.37 kWh.m^-3. These results strongly suggest that operating an MBR equipped with the modified membrane element with a specific energy consumption of less than 0.4 kWh·m^-3 is highly possible.展开更多
基金financially supported by the National Key Research and Development Program of China(No.2021YFB3801500)Fundamental Research Funds of Zhejiang Sci-Tech University(No.24202105-Y)。
文摘Solid polymer electrolytes(SPEs)are considered promising candidates for all-solid-state lithium metal batteries because of their easy preparation and good compatibility with lithium metal.However,their applications are restricted by their low ionic conductivity and poor mechanical properties.In this study,a composite solid polymer electrolyte composed of poly(ethylene oxide)(PEO),poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP),plasticizer succinonitrile(SN),and polytetrafluoroethylene(PTFE)fibrous porous membranes was prepared.The PTFE fibrous membrane significantly enhanced the mechanical strength of the electrolyte as a supporting framework.SN reduced the crystalline regions of PEO and facilitated rapid lithium-ion transport.PVDF-HFP promoted lithium salt dissolution and improved the electrochemical stability of the electrolyte.Accordingly,the optimized PTFE/PEO/PVDF-HFP/SN polymer electrolyte exhibited a tensile strength of 3.31 MPa at 352%elongation and demonstrated an ionic conductivity of 7.6×10^(-4)S·cm^(-1)at 60℃.Lithium symmetric cells maintained stable cycling for over 2500 h at 0.15 m A·cm^(-2),and Li//Li Fe PO_(4) full cells showed a high capacity retention of 91.6%after 300 cycles at 0.5 C,with coulombic efficiency consistently exceeding 99.9%throughout cycling.
基金the financial support from Dalian Institute of Chemical Physics (DMTO201604)Focus Area Innovation Team Support Plan of Dalian (2021RT03)+1 种基金National Natural Science Foundation of China (21878284)Regional Development Young Scholars of the Chinese Academy of Sciences。
文摘Membrane contactor is regarded as a promising method for reaction and process intensification. The feasibility of formaldehyde carbonylation to synthesize glycolic acid using polytetrafluoroethylene(PTFE)membrane contactor has been proved in our previous study. In this paper, the effect of membrane microstructure on process performance was further investigated. Three porous PTFE hollow fibers with different pore sizes and one polydimethylsiloxane(PDMS)/PTFE composite membrane with dense layer were fabricated for comparison. The physical and chemical properties of four membranes, including chemical composition, morphology, contact angle, liquid entry pressure, thermodynamic analysis and gas permeability, were systemically characterized. Experiments of formaldehyde carbonylation under different reaction conditions were conducted. The results indicated that the yield of glycolic acid increased with decreasing pore size for porous membranes, which was due to the improvement of wetting behavior. The dense layer of PDMS in composite hollow fiber could effectively prevent the solvent from entering membrane pores, thus the membrane exhibited the best performance. At reaction temperature of 120℃ and operation pressure of 3.0 MPa, the yield of glycolic acid was always higher than 90% as the mass ratio of trioxane and phosphotungstic acid increased from 0.2:1 to 0.8:1. The highest turnover frequency was up to 26.37 mol·g^(-1)·h^(-1). This study provided a reference for the understanding and optimization of membrane contactors for the synthesis of glycolic acid using solvent with low surface tension.
文摘In this study, we modified a polytetrafluoroethylene （PTFE） hollow-fiber membrane element used for submerged membrane bioreactors （MBRs） to reduce the energy consumption during MBR processes. The high mechanical strength of the PTFE membrane made it possible to increase the effective length of the membrane fiber from 2 to 3 m. In addition, the packing density was increased by 20% by optimizing the membrane element configuration. These modifications improve the efficiency of membrane cleaning associated with aeration. The target of specific energy consumption was less than 0.4 kWh·m^-3 in this study. The continuous operation of a pilot MBR treating real municipal wastewater revealed that the MBR utilizing the modified membrane element can be stably operated under a specific air demand per membrane surface area （SADm） of 0.13 m^3·m^-2. hr I when the daily- averaged membrane fluxes for the constant flow rate and flow rate fluctuating modes of operation were set to 0,6 and 0.5m^3·m^-2·d^-1 respectively. The specific energy consumption under these operating conditions was estimated to be less than 0.37 kWh.m^-3. These results strongly suggest that operating an MBR equipped with the modified membrane element with a specific energy consumption of less than 0.4 kWh·m^-3 is highly possible.
