NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is...NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is significant for industrial applications.In this work,a porous Na_(3)V_(2)(PO_(4))_(3)/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method.The Na_(3)V_(2)(PO_(4))_(3)/C cathode displayed specific capacities of 113.4 mAh·g^(-1),107.0 mAh·g^(-1) and 87.1 mAh·g^(-1) at 0.1 C,1 C and 10 C,respectively.For the first time,the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C electrodes are successfully fabricated.The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83%at 0℃ owing to the rapid sodium ion migration ability and structural stability of Na_(3)V_(2)(PO_(4))_(3)/C.Moreover,the thermal runaway features are revealed by accelerating rate calorimetry(ARC)test for the first time.Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries.Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C have a prospect of practical application in high safety requirement fields.展开更多
Electrolyte design strategies are closely related to the capacities, cycle life and safety of sodium–ion batteries. In this study, we aimed to optimize electrolyte with the focus on engineering aspects. The basic phy...Electrolyte design strategies are closely related to the capacities, cycle life and safety of sodium–ion batteries. In this study, we aimed to optimize electrolyte with the focus on engineering aspects. The basic physicochemical properties including ionic conductivity, viscosity,wettability and thermochemical stability of the electrolytes using Na PF6 as the solute and the mixed solvent with different components of EMC,DMC or DEC in PC or EC were systematically measured. Ah pouch cell with NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)/hard carbon electrodes was used to evaluate the performance of the prepared electrolytes. By using the Inductive Coupled Plasma Emission Spectrometer(ICP), X-ray photoelectron spectroscopy(XPS), Thermogravimetric-differential scanning calorimetry(TG-DSC) and Accelerating Rate Calorimeter(ARC), we show that an optimized electrolyte can effectively promote the formation of a protective interfacial layer on two electrodes, which not only retards parasitic reactions between the electrodes and electrolyte but also suppresses dissolution of metal ions from the cathode. With an optimized electrolyte, a NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)/hard carbon cell can attain 56.16% capacity retention under the low temperature of -40℃, and can be able to retain 80%capacity retention after more than 2500 cycles while presenting excellent thermal safety.展开更多
Location based social networks（ LBSNs） provide location specific data generated from smart phone into online social networks thus people can share their points of interest（ POIs）. POI collections are complex and c...Location based social networks（ LBSNs） provide location specific data generated from smart phone into online social networks thus people can share their points of interest（ POIs）. POI collections are complex and can be influenced by various factors,such as user preferences,social relationships and geographical influence. Therefore,recommending new locations in LBSNs requires to take all these factors into consideration. However,one problem is how to determine optimal weights of influencing factors in an algorithm in which these factors are combined. The user similarity can be obtained from the user check-in data,or from the user friend information,or based on the different geographical influences on each user＇s check-in activities. In this paper,we propose an algorithm that calculates the user similarity based on check-in records and social relationships,using a proposed weighting function to adjust the weights of these two kinds of similarities based on the geographical distance between users. In addition,a non-parametric density estimation method is applied to predict the unique geographical influence on each user by getting the density probability plot of the distance between every pair of user＇s check-in locations. Experimental results,using foursquare datasets,have shown that comparisons between the proposed algorithm and the other five baseline recommendation algorithms in LBSNs demonstrate that our proposed algorithm is superior in accuracy and recall,furthermore solving the sparsity problem.展开更多
As one of the most promising cathodes for sodium-ion batteries(SIBs),the layered transition metal oxides have attracted great attentions due to their high specific capacities and facile synthesis.However,their applica...As one of the most promising cathodes for sodium-ion batteries(SIBs),the layered transition metal oxides have attracted great attentions due to their high specific capacities and facile synthesis.However,their applications are still hindered by the problems of poor moisture stability and sluggish Na^(+)diffusion caused by intrinsic structural Jahn–Teller distortion.Herein,we demonstrate a new approach to settle the above issues through introducing K^(+)into the structures of Ni/Mn-based materials.The physicochemical characterizations reveal that K^(+)induces atomic surface reorganization to form the birnessite-type K_(2)Mn_(4)O_(8).Combining with the phosphate,the mixed coating layer protects the cathodes from moisture and hinders metal dissolution into the electrolyte effectively.Simultaneously,K^(+)substitution at Na site in the bulk structure can not only widen the lattice-spacing for favoring Na^(+)diffusion,but also work as the rivet to restrain the grain crack upon cycling.The as achieved K^(+)-decorated P2-Na_(0.67)Mn_(0.75)Ni_(0.2)5O_(2)(NKMNO@KM/KP)cathodes are tested in both coin cell and pouch cell configurations using Na metal or hard carbon(HC)as anodes.Impressively,the NKMNO@KM/KP||Na half-cell demonstrates a high rate performance of 50 C and outstanding cycling performance of 90.1%capacity retention after 100 cycles at 5 C.Furthermore,the NKMNO@KM/KP||HC fullcell performed a promising energy density of 213.9 Wh·kg^(−1).This performance significantly outperforms most reported state-ofthe-art values.Additionally,by adopting this strategy on O3-NaMn_(0.5)Ni_(0.5)O_(2),we further proved the universality of this method on layered cathodes for SIBs.展开更多
甲醇具有结构简单、含氢量高、产能大等优点,利用甲醇与水蒸气进行重整是一种节能高效的现场制氢方式。甲醇水蒸气重整(MSR)与燃料电池联用能够实现多场景应用,但由于反应温度较高(250~300℃),存在启动速度较慢、副产CO含量较高和热效...甲醇具有结构简单、含氢量高、产能大等优点,利用甲醇与水蒸气进行重整是一种节能高效的现场制氢方式。甲醇水蒸气重整(MSR)与燃料电池联用能够实现多场景应用,但由于反应温度较高(250~300℃),存在启动速度较慢、副产CO含量较高和热效率较低等问题。低温甲醇水重整(LT-Methanol Water Reforming,LT-MWR)包括低温甲醇水蒸气重整(LT-MSR)与液相甲醇水重整(Aqueous-phase Reforming of Methanol,APRM),反应通常在200℃以下进行,同时保持较高的反应活性,进而能够减少预热时间、减弱副反应发生,且能与燃料电池实现更强的热耦合。本工作首先介绍了商用催化剂优异的性能与存在的缺陷,然后对低温甲醇水重整制氢催化剂,诸如Cu基催化剂、贵金属催化剂与光协同催化剂的研究进展进行了回顾。归纳了低温铜基催化剂的改性策略,包括合成方法、结构设计与元素掺杂。对国内外商用CuZnAlO_(x)催化剂结构与性能的测试表明,其转化率高和稳定性好,存在的缺陷是价格较贵且在低温区催化活性急剧下降。Cu基催化剂活性受温度影响较大,在低温区活性很低,但通过适当的改性能够实现其应用价值,其改性策略包括合成方法、结构设计与元素掺杂。贵金属催化剂低温下活性较高,但存在价格昂贵、合成复杂等缺点。光协同催化剂则是在光照条件下进行催化重整,尚处于研究阶段。对于Cu基催化剂,合成方法的改进能够大大改善催化剂的微观混合程度与可重现性。适当的结构设计可提升催化剂的比表面积与热稳定性。元素掺杂则能够提升活性组分的分散度,修饰催化剂表面结构。三种改性策略能够有效提升Cu基催化剂低温下甲醇重整制氢的性能,在保持较高活性的同时,降低CO副产物的含量。展望了低温甲醇水重整制氢催化剂的发展前景和挑战,对催化剂的开发与应用有指导意义。要点:(1)低温甲醇重整制氢可大幅降低CO含量。(2)低温技术有助于提升甲醇重整—燃料电池系统热效率。(3)合成方法、晶型结构和元素掺杂的改进可有效提升Cu基催化剂低温性能。展开更多
Hydrogen safety in storage and transport is one of the major obstacles for the widespread adoption of hydrogen fuel cells,making it critical to assuage public concerns on the safety of compressed hydrogen storage.Meth...Hydrogen safety in storage and transport is one of the major obstacles for the widespread adoption of hydrogen fuel cells,making it critical to assuage public concerns on the safety of compressed hydrogen storage.Methanol in bountiful supply is a promising hydrogen energy carrier.Accordingly,a novel MSR-HT-PEMFC system coupling the hydrogen production via methanol steam reforming(MSR)and energy generation via high temperature proton exchange membrane fuel cell(HT-PEMFC)was firstly introduced by Prof.Zi-Feng Ma from Shanghai Jiaotong University and Prof.Shan-Tung Tu from East China University of Science and Technology,in collaboration with Shanghai Palcan Energy Co.Ltd.The MSRHT-PEMFC system eliminates the potential risks of compressed hydrogen storage.展开更多
基金This work was supported by the National Key Research and Development Program(2016YFB0901505)the Natural Science Foundation of China(22005190,21938005)+1 种基金the Science&Technology Commission of Shanghai Municipality(19DZ1205500)Zhejiang Key Research and Development Program(2020C01128).
文摘NASICON-type Na_(3)V_(2)(PO_(4))_(3) is a promising electrode material for developing advanced sodium-ion batteries.Preparing Na_(3)V_(2)(PO_(4))_(3) with good performance by a cost-effective and large-scale method is significant for industrial applications.In this work,a porous Na_(3)V_(2)(PO_(4))_(3)/C cathode material with excellent electrochemical performance is successfully prepared by an agar-gel combined with freeze-drying method.The Na_(3)V_(2)(PO_(4))_(3)/C cathode displayed specific capacities of 113.4 mAh·g^(-1),107.0 mAh·g^(-1) and 87.1 mAh·g^(-1) at 0.1 C,1 C and 10 C,respectively.For the first time,the 500-mAh soft-packed symmetrical sodium-ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C electrodes are successfully fabricated.The 500-mAh symmetrical batteries exhibit outstanding low temperature performance with a capacity retention of 83%at 0℃ owing to the rapid sodium ion migration ability and structural stability of Na_(3)V_(2)(PO_(4))_(3)/C.Moreover,the thermal runaway features are revealed by accelerating rate calorimetry(ARC)test for the first time.Thermal stability and safety of the symmetrical batteries are demonstrated to be better than lithium-ion batteries and some reported sodium-ion batteries.Our work makes it clear that the soft-packed symmetrical sodium ion batteries based on Na_(3)V_(2)(PO_(4))_(3)/C have a prospect of practical application in high safety requirement fields.
基金supported by Natural Science Foundation of China,China(21938005,21676165)Science&Technology Commission of Shanghai Municipality,China(19DZ1205500)+1 种基金Zhejiang Key Research and Development Program,China(2020C01128)National Key Research and Development Program,China(2016YFB0901500)。
文摘Electrolyte design strategies are closely related to the capacities, cycle life and safety of sodium–ion batteries. In this study, we aimed to optimize electrolyte with the focus on engineering aspects. The basic physicochemical properties including ionic conductivity, viscosity,wettability and thermochemical stability of the electrolytes using Na PF6 as the solute and the mixed solvent with different components of EMC,DMC or DEC in PC or EC were systematically measured. Ah pouch cell with NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)/hard carbon electrodes was used to evaluate the performance of the prepared electrolytes. By using the Inductive Coupled Plasma Emission Spectrometer(ICP), X-ray photoelectron spectroscopy(XPS), Thermogravimetric-differential scanning calorimetry(TG-DSC) and Accelerating Rate Calorimeter(ARC), we show that an optimized electrolyte can effectively promote the formation of a protective interfacial layer on two electrodes, which not only retards parasitic reactions between the electrodes and electrolyte but also suppresses dissolution of metal ions from the cathode. With an optimized electrolyte, a NaNi_(1/3)Fe_(1/3)Mn_(1/3)O_(2)/hard carbon cell can attain 56.16% capacity retention under the low temperature of -40℃, and can be able to retain 80%capacity retention after more than 2500 cycles while presenting excellent thermal safety.
文摘Location based social networks（ LBSNs） provide location specific data generated from smart phone into online social networks thus people can share their points of interest（ POIs）. POI collections are complex and can be influenced by various factors,such as user preferences,social relationships and geographical influence. Therefore,recommending new locations in LBSNs requires to take all these factors into consideration. However,one problem is how to determine optimal weights of influencing factors in an algorithm in which these factors are combined. The user similarity can be obtained from the user check-in data,or from the user friend information,or based on the different geographical influences on each user＇s check-in activities. In this paper,we propose an algorithm that calculates the user similarity based on check-in records and social relationships,using a proposed weighting function to adjust the weights of these two kinds of similarities based on the geographical distance between users. In addition,a non-parametric density estimation method is applied to predict the unique geographical influence on each user by getting the density probability plot of the distance between every pair of user＇s check-in locations. Experimental results,using foursquare datasets,have shown that comparisons between the proposed algorithm and the other five baseline recommendation algorithms in LBSNs demonstrate that our proposed algorithm is superior in accuracy and recall,furthermore solving the sparsity problem.
基金the National Natural Science Foundation of China(Nos.52271222,51971146,51971147,52171218,22005190,and 21938005)We also acknowledge the supports of Shanghai Outstanding Academic Leaders Plan,the Innovation Program of Shanghai Municipal Education Commission(No.2019-01-07-00-07-E00015)+4 种基金Shanghai Pujiang Program(No.21PJ1411100)Shanghai Rising-Star Program(Nos.20QA1407100 and 21QA1406500)the Shanghai Science and Technology Commission(Nos.21010503100,20ZR1438400 and 22ZR1443900)Zhejiang Provincial Natural Science Foundation of China(No.LGG22F010017)the Key R&D Program of Zhejiang Province(Nos.2019C01155 and 2020C01128).
文摘As one of the most promising cathodes for sodium-ion batteries(SIBs),the layered transition metal oxides have attracted great attentions due to their high specific capacities and facile synthesis.However,their applications are still hindered by the problems of poor moisture stability and sluggish Na^(+)diffusion caused by intrinsic structural Jahn–Teller distortion.Herein,we demonstrate a new approach to settle the above issues through introducing K^(+)into the structures of Ni/Mn-based materials.The physicochemical characterizations reveal that K^(+)induces atomic surface reorganization to form the birnessite-type K_(2)Mn_(4)O_(8).Combining with the phosphate,the mixed coating layer protects the cathodes from moisture and hinders metal dissolution into the electrolyte effectively.Simultaneously,K^(+)substitution at Na site in the bulk structure can not only widen the lattice-spacing for favoring Na^(+)diffusion,but also work as the rivet to restrain the grain crack upon cycling.The as achieved K^(+)-decorated P2-Na_(0.67)Mn_(0.75)Ni_(0.2)5O_(2)(NKMNO@KM/KP)cathodes are tested in both coin cell and pouch cell configurations using Na metal or hard carbon(HC)as anodes.Impressively,the NKMNO@KM/KP||Na half-cell demonstrates a high rate performance of 50 C and outstanding cycling performance of 90.1%capacity retention after 100 cycles at 5 C.Furthermore,the NKMNO@KM/KP||HC fullcell performed a promising energy density of 213.9 Wh·kg^(−1).This performance significantly outperforms most reported state-ofthe-art values.Additionally,by adopting this strategy on O3-NaMn_(0.5)Ni_(0.5)O_(2),we further proved the universality of this method on layered cathodes for SIBs.
文摘甲醇具有结构简单、含氢量高、产能大等优点,利用甲醇与水蒸气进行重整是一种节能高效的现场制氢方式。甲醇水蒸气重整(MSR)与燃料电池联用能够实现多场景应用,但由于反应温度较高(250~300℃),存在启动速度较慢、副产CO含量较高和热效率较低等问题。低温甲醇水重整(LT-Methanol Water Reforming,LT-MWR)包括低温甲醇水蒸气重整(LT-MSR)与液相甲醇水重整(Aqueous-phase Reforming of Methanol,APRM),反应通常在200℃以下进行,同时保持较高的反应活性,进而能够减少预热时间、减弱副反应发生,且能与燃料电池实现更强的热耦合。本工作首先介绍了商用催化剂优异的性能与存在的缺陷,然后对低温甲醇水重整制氢催化剂,诸如Cu基催化剂、贵金属催化剂与光协同催化剂的研究进展进行了回顾。归纳了低温铜基催化剂的改性策略,包括合成方法、结构设计与元素掺杂。对国内外商用CuZnAlO_(x)催化剂结构与性能的测试表明,其转化率高和稳定性好,存在的缺陷是价格较贵且在低温区催化活性急剧下降。Cu基催化剂活性受温度影响较大,在低温区活性很低,但通过适当的改性能够实现其应用价值,其改性策略包括合成方法、结构设计与元素掺杂。贵金属催化剂低温下活性较高,但存在价格昂贵、合成复杂等缺点。光协同催化剂则是在光照条件下进行催化重整,尚处于研究阶段。对于Cu基催化剂,合成方法的改进能够大大改善催化剂的微观混合程度与可重现性。适当的结构设计可提升催化剂的比表面积与热稳定性。元素掺杂则能够提升活性组分的分散度,修饰催化剂表面结构。三种改性策略能够有效提升Cu基催化剂低温下甲醇重整制氢的性能,在保持较高活性的同时,降低CO副产物的含量。展望了低温甲醇水重整制氢催化剂的发展前景和挑战,对催化剂的开发与应用有指导意义。要点:(1)低温甲醇重整制氢可大幅降低CO含量。(2)低温技术有助于提升甲醇重整—燃料电池系统热效率。(3)合成方法、晶型结构和元素掺杂的改进可有效提升Cu基催化剂低温性能。
文摘Hydrogen safety in storage and transport is one of the major obstacles for the widespread adoption of hydrogen fuel cells,making it critical to assuage public concerns on the safety of compressed hydrogen storage.Methanol in bountiful supply is a promising hydrogen energy carrier.Accordingly,a novel MSR-HT-PEMFC system coupling the hydrogen production via methanol steam reforming(MSR)and energy generation via high temperature proton exchange membrane fuel cell(HT-PEMFC)was firstly introduced by Prof.Zi-Feng Ma from Shanghai Jiaotong University and Prof.Shan-Tung Tu from East China University of Science and Technology,in collaboration with Shanghai Palcan Energy Co.Ltd.The MSRHT-PEMFC system eliminates the potential risks of compressed hydrogen storage.
