The electrochemical performance of hard carbon in sodium storage is still limited by its poor cycling stability and rate capability because of the sluggish kinetics process.In this study,we use a simple and effective ...The electrochemical performance of hard carbon in sodium storage is still limited by its poor cycling stability and rate capability because of the sluggish kinetics process.In this study,we use a simple and effective method to accelerate the kinetics process by engineering the structure of the electrode to promote its surface and near-surface reactions.This goal is realized by the use of slightly aggregated ultra-small carbon spheres.The large specific surface area formed by the small spheres can provide abundant active sites for electrochemical reactions.The abundant mesopores and macropores derived from the secondary particle piled structure of the carbon spheres could facilitate the transport of electrolytes,shorten the diffusion distance of Na^(+)and accommodate the volume expansion during cycling.Benefiting from these unique structure features,PG700-3(carbon spheres with the diameters of 40-60 nm carbonized at 700℃)exhibits high performance for sodium storage.A high reversible capacity of 163 mAh g^(-1) could be delivered at a current density of 1.0 A g^(-1) after 100 cycles.Interestingly,at a current density of 10.0 A g^(-1),the specific capacity of PG700-3 gradually increases to 140 mAh g^(-1) after 10000 cycles,corresponding to a capacity retention of 112%.Given the enhanced kinetics of SIBs reactions,PG700-3 exhibits an excellent rate capability,i.e.,230 and 138 mAh g^(-1) at 0.1 and 5.0 A g^(-1),respectively.This study provides a facile method to attain high performance anode materials for SIBs.The design strategy and improvement mechanism could be extended to other materials for high rate applications.展开更多
Environmental economics is accelerating the urgency to develop recycling technologies for the ever-growing quantity of discarded thermoset polymers.Herein,we developed a mild and energy-saving pro-cess for high-eficie...Environmental economics is accelerating the urgency to develop recycling technologies for the ever-growing quantity of discarded thermoset polymers.Herein,we developed a mild and energy-saving pro-cess for high-eficiency degradation and reuse of anhydride-cured epoxy thermoset with the aid of hy-drazine hydrate.The degradation degree of the epoxy resin reached 99.6%at 120℃ within a short time of 60min.During the reaction,the ester bonds in the cross-linked network were selectively cleaved by the amination of hydrazine hydrate,and the epoxy resin was fully converted to new monomers that con-tained hydrazide and hydroxyl groups,respectively.Moreover,the degradation mechanism of the epoxy resin in hydrazine hydrate was studied and a nucleation model was utilized to predict the actual degra-dation behavior of the system.Finally,the degradation products can be directly mixed with epoxy precur-sor to prepare a new waterborne epoxy coating with good comprehensive properties.This work not only demonstrates a new way to realize the efficient degradation of epoxy resins,but also provides a facile and efficient recycling protocol for thermosets.展开更多
Bio-based epoxy thermoset prepared from renewable biomass raw materials can alleviate fossil energy crisis and reduce environmental pollution,which satisfies the needs of sustainable social development.In this study,a...Bio-based epoxy thermoset prepared from renewable biomass raw materials can alleviate fossil energy crisis and reduce environmental pollution,which satisfies the needs of sustainable social development.In this study,a bio-based epoxy thermoset precursor(MGOL-EP) was synthesized from a naturally occurring magnolol through a facile and efficient one-step process.And the fully bio-based epoxy thermoset(MGOL-EP-SC) was obtained by self-curing without adding any other hardener.MGOL-EP-SC revealed an extremely high glass-transition temperature(T_(g)) of 265℃ and char yield of 53.2%(in N;),which were at the highest level among the fully bio-based epoxy thermosets reported so far.In addition,when the MGOL-EP was cured with 4,4’-methylenedianiline(DDM),T_(g)of the MGOL-EP/DDM was decreased by 61℃ and the other comprehensive performance had also been decreased,which was due to a reduction in biphenyl structure content and cross-linking density by adding the external curing agents.Moreover,the MGOL-EP-SC presented certain killing rate(48.4%) to Staphylococcus aureus.These findings provide a new design strategy for engineering high-performance and functional epoxy thermoset with high biomass content.展开更多
Hard carbons are promising anodes for sodium-ion batteries.However,there is still considerable controversy regarding the sodium storage behaviors in hard carbons,which are mainly attributed to the varied precursors,co...Hard carbons are promising anodes for sodium-ion batteries.However,there is still considerable controversy regarding the sodium storage behaviors in hard carbons,which are mainly attributed to the varied precursors,confused pyrolysis mechanism,and different characterization methods.Herein,benefiting from the flexible molecular structure of polymers,a series of hard carbons with carefully tunedmicrostructures are fabricated by adjusting the ratio of aryl and alkyl groups in the epoxy resins.The results of dynamic mechanical analysis,insitu Fourier transform infrared spectra,and synchronous thermal gravimetricinfrared spectrum-gas chromatography/mass spectrometry reveal that replacing the alkyl with aryl groups in the resin can enhance the crosslink density,inhibit the degradation and rearrangement process,and further lead to a more disordered microstructure.In addition,it is suggested that accessible channels provided by sufficiently wide interlayer spacing are necessary for closed pore filling.The optimized anode delivers a high capacity of 375 mAh/g in half cell with an initial Coulombic efficiency of 80.61%,and an energy density of 252 Wh/kg is attained in full cell.Finally,a reliable relationship among precursor-pyrolysis mechanism-structure-performance is established,and the sodium storagemechanism of“adsorption-insertion-pore filling”iswell proved.展开更多
基金the support from the National Key Research and Development Program(No.2018YFB1107500)Liao Ning Revitalization Talents Program(XLYC1907144)+1 种基金the National Natural Science Foundation of China(No.51503024)Dalian Youth Science and Technology Star Project Support Program(No.2017RQ104)。
文摘The electrochemical performance of hard carbon in sodium storage is still limited by its poor cycling stability and rate capability because of the sluggish kinetics process.In this study,we use a simple and effective method to accelerate the kinetics process by engineering the structure of the electrode to promote its surface and near-surface reactions.This goal is realized by the use of slightly aggregated ultra-small carbon spheres.The large specific surface area formed by the small spheres can provide abundant active sites for electrochemical reactions.The abundant mesopores and macropores derived from the secondary particle piled structure of the carbon spheres could facilitate the transport of electrolytes,shorten the diffusion distance of Na^(+)and accommodate the volume expansion during cycling.Benefiting from these unique structure features,PG700-3(carbon spheres with the diameters of 40-60 nm carbonized at 700℃)exhibits high performance for sodium storage.A high reversible capacity of 163 mAh g^(-1) could be delivered at a current density of 1.0 A g^(-1) after 100 cycles.Interestingly,at a current density of 10.0 A g^(-1),the specific capacity of PG700-3 gradually increases to 140 mAh g^(-1) after 10000 cycles,corresponding to a capacity retention of 112%.Given the enhanced kinetics of SIBs reactions,PG700-3 exhibits an excellent rate capability,i.e.,230 and 138 mAh g^(-1) at 0.1 and 5.0 A g^(-1),respectively.This study provides a facile method to attain high performance anode materials for SIBs.The design strategy and improvement mechanism could be extended to other materials for high rate applications.
基金supported by the National Natural Science Foundation of China(Nos.52073038 and 51873027)the Fundamental Research Funds for the Central Universities(Nos.DUT20TD114 and DUT22LAB605).
文摘Environmental economics is accelerating the urgency to develop recycling technologies for the ever-growing quantity of discarded thermoset polymers.Herein,we developed a mild and energy-saving pro-cess for high-eficiency degradation and reuse of anhydride-cured epoxy thermoset with the aid of hy-drazine hydrate.The degradation degree of the epoxy resin reached 99.6%at 120℃ within a short time of 60min.During the reaction,the ester bonds in the cross-linked network were selectively cleaved by the amination of hydrazine hydrate,and the epoxy resin was fully converted to new monomers that con-tained hydrazide and hydroxyl groups,respectively.Moreover,the degradation mechanism of the epoxy resin in hydrazine hydrate was studied and a nucleation model was utilized to predict the actual degra-dation behavior of the system.Finally,the degradation products can be directly mixed with epoxy precur-sor to prepare a new waterborne epoxy coating with good comprehensive properties.This work not only demonstrates a new way to realize the efficient degradation of epoxy resins,but also provides a facile and efficient recycling protocol for thermosets.
基金supported by the National Natural Science Foundation of China (Nos. 51873027, 52073038 and 51673033)the Natural Science Foundation of Liaoning Province (No. 2019-ZD-0139)+1 种基金the Fundamental Research Funds for the Central Universities (No. DUT20TD114)the National Key Research and Development Program of China (No. 2017YFB0307600)。
文摘Bio-based epoxy thermoset prepared from renewable biomass raw materials can alleviate fossil energy crisis and reduce environmental pollution,which satisfies the needs of sustainable social development.In this study,a bio-based epoxy thermoset precursor(MGOL-EP) was synthesized from a naturally occurring magnolol through a facile and efficient one-step process.And the fully bio-based epoxy thermoset(MGOL-EP-SC) was obtained by self-curing without adding any other hardener.MGOL-EP-SC revealed an extremely high glass-transition temperature(T_(g)) of 265℃ and char yield of 53.2%(in N;),which were at the highest level among the fully bio-based epoxy thermosets reported so far.In addition,when the MGOL-EP was cured with 4,4’-methylenedianiline(DDM),T_(g)of the MGOL-EP/DDM was decreased by 61℃ and the other comprehensive performance had also been decreased,which was due to a reduction in biphenyl structure content and cross-linking density by adding the external curing agents.Moreover,the MGOL-EP-SC presented certain killing rate(48.4%) to Staphylococcus aureus.These findings provide a new design strategy for engineering high-performance and functional epoxy thermoset with high biomass content.
基金Dalian Youth Science and Technology Star Project Support Program,Grant/Award Number:2017RQ104Dalian University of Technology Xinghai Youqing Program,Grant/Award Number:X20200303+1 种基金National Key Research and Development Program of China,Grant/Award Number:2020YFB0311600Liaoning Revitalization Talents Program,Grant/Award Number:XLYC1907144。
文摘Hard carbons are promising anodes for sodium-ion batteries.However,there is still considerable controversy regarding the sodium storage behaviors in hard carbons,which are mainly attributed to the varied precursors,confused pyrolysis mechanism,and different characterization methods.Herein,benefiting from the flexible molecular structure of polymers,a series of hard carbons with carefully tunedmicrostructures are fabricated by adjusting the ratio of aryl and alkyl groups in the epoxy resins.The results of dynamic mechanical analysis,insitu Fourier transform infrared spectra,and synchronous thermal gravimetricinfrared spectrum-gas chromatography/mass spectrometry reveal that replacing the alkyl with aryl groups in the resin can enhance the crosslink density,inhibit the degradation and rearrangement process,and further lead to a more disordered microstructure.In addition,it is suggested that accessible channels provided by sufficiently wide interlayer spacing are necessary for closed pore filling.The optimized anode delivers a high capacity of 375 mAh/g in half cell with an initial Coulombic efficiency of 80.61%,and an energy density of 252 Wh/kg is attained in full cell.Finally,a reliable relationship among precursor-pyrolysis mechanism-structure-performance is established,and the sodium storagemechanism of“adsorption-insertion-pore filling”iswell proved.
