Rational electrode structure design is of great significance for realizing superior Na^(+)storage performance.Herein,a metal salt-induced polymer blowing-bubble approach followed by selenization procedure is developed...Rational electrode structure design is of great significance for realizing superior Na^(+)storage performance.Herein,a metal salt-induced polymer blowing-bubble approach followed by selenization procedure is developed to in-situ generate abundant sub-10 nm CoSe_(2) nanocrystals on 3D Se/N co-doped carbon networks(CoSe_(2)@3DSNC).The phase transition from Co to CoSe_(2) and the incorporation of Se into the carbon layer are realized simultaneously to establish above configuration,in which the CoSe_(2) nanocrystals are anchored on interlayer expanded carbon networks.Such unique configuration endows electrode with lower Na+diffusion energy barrier,higher Na+storage capability and better structural durability.Reflected in SIBs,the optimized CoSe_(2)@3 DSNC delivers superior rate capability(310 m Ah g^(-1) at 10 A g^(-1))and excellent longterm cycling stability(409 m Ah g^(-1) after 1200 cycles at 5 A g^(-1)).Moreover,this configuration can also be obtained in other metal selenides-carbon composite through a similar approach.展开更多
Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT...Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT of 0.82 at 300 K and a peak ZT of 1.24 at 498 K,which is comparable to the n-type Bi_(2)Te_(3) and Te doped Mg_(3)Bi_(1.4)Sb_(0.6).The improved thermoelectric performance is benefited from the high carrier concentration and mobility as well as the thermal conductivity reduction.The reduced resistivity increased the power factor at all measured temperatures,leading to a higher engineering ZT(ZTeng)and engineering power factor(PFeng)for n-type Mg_(3)Bi_(2).The n-type Mg_(3)Bi_(1.4)Sb_(0.6) materials are promising for thermoelectric power generation and cooling applications near room temperature.展开更多
Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the doub...Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.展开更多
For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chie...For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chief approach to improve their thermoelectric performance. Herein, we report the multiple effects of Se doping on thermoelectric performance of p-type Bi0.5Sb1,5Te3-xSex ＋ 3 wt% Te ZM ingots, which increases carrier concentration, reduces lattice thermal conductivity and deteriorates the carrier mobility. As a result, the peak figure of merit （ZT） is shifted to a higher temperature and a high ZT 1.2 at 350 K is obtained, due to the reduced thermal conductivity and suppressed intrinsic conduction. Further, decreasing Sb content is followed to optimize the room temperature performance and a ZT - 1.1 at 300 K is obtained. These results are significant for designing and optimizing the thermoelectric performance of commercial Bi0.5Sb1.5Te3＋ 3 wt% Te ZM alloys.展开更多
We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune...We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune the carrier concentration of the nanocomposites. Due to the Se doping, the thermoelectric figure of merit （ZT） of the nanocomposites is significantly enhanced due to the increased power factor and reduced thermal conductivity. We also find that thermal transport in our hot-pressed pellets is anisotropic, which results in different thermal conductivities along the in-plane and cross-plane directions. Theoretical calculations for both electronic and thermal transport are carried out to establish fundamental understanding of the material system and provide directions for further ZT optimization with adjustments to carrier concentration and mobility.展开更多
In_4Se_3-based materials are noticeable n-type thermoelectric materials because of lead-free and intrinsically low lattice thermal conductivity,but the In4Se_3-δ crystals（with Se-deficiency,δ） suffer strong anisot...In_4Se_3-based materials are noticeable n-type thermoelectric materials because of lead-free and intrinsically low lattice thermal conductivity,but the In4Se_3-δ crystals（with Se-deficiency,δ） suffer strong anisotropy and cleavage habit. Thus the researches on polycrystalline In_4Se_3-based materials are of great importance. Herein,we experimentally and theoretically investigated the thermoelectric properties of In_（4-x）Se_（2.95）Ag_x polycrystalline compounds. Ag occupying the intercalation or In4 site is energetically most favorable in light of the density functional theory calculation. The maximum solubility of Ag（x_m） is very low（xm 〈 0.03） and the experimental result indicates that the electrical transport behavior of In_（4-x）Se_（2.95）Ag_x compounds is not significantly optimized by Ag-dopant. Consequently,a maximum ZT of 0.92 at 723 K is obtained by In_（3.98）Se_（2.95）Ag_（0.02） compound that represents 15% enhancement over that of the un-doped one which benefits from the slightly enhanced power factor and the reduced total thermal conductivity.展开更多
基金financially supported by the National Natural Science Foundation of China(21471040)。
文摘Rational electrode structure design is of great significance for realizing superior Na^(+)storage performance.Herein,a metal salt-induced polymer blowing-bubble approach followed by selenization procedure is developed to in-situ generate abundant sub-10 nm CoSe_(2) nanocrystals on 3D Se/N co-doped carbon networks(CoSe_(2)@3DSNC).The phase transition from Co to CoSe_(2) and the incorporation of Se into the carbon layer are realized simultaneously to establish above configuration,in which the CoSe_(2) nanocrystals are anchored on interlayer expanded carbon networks.Such unique configuration endows electrode with lower Na+diffusion energy barrier,higher Na+storage capability and better structural durability.Reflected in SIBs,the optimized CoSe_(2)@3 DSNC delivers superior rate capability(310 m Ah g^(-1) at 10 A g^(-1))and excellent longterm cycling stability(409 m Ah g^(-1) after 1200 cycles at 5 A g^(-1)).Moreover,this configuration can also be obtained in other metal selenides-carbon composite through a similar approach.
基金supported by Young Scientist Fund of National Natural Science Foundation of China(No.51601152)Chunhui Program from Education Ministry of China,Open Research Subject of Key Laboratory of Fluid and Power Machinery of Ministry of Education(No.SZJJ2017-082)the Sichuan Science and Technology Program(No.2019JDTD0024).
文摘Bi_(2)Te_(3) based alloys have been the most widely used thermoelectric material at low temperature for many decades.Here we report Se doped n-type Mg_(3)Bi_(2) based materials with a thermoelectric figure-of-merit ZT of 0.82 at 300 K and a peak ZT of 1.24 at 498 K,which is comparable to the n-type Bi_(2)Te_(3) and Te doped Mg_(3)Bi_(1.4)Sb_(0.6).The improved thermoelectric performance is benefited from the high carrier concentration and mobility as well as the thermal conductivity reduction.The reduced resistivity increased the power factor at all measured temperatures,leading to a higher engineering ZT(ZTeng)and engineering power factor(PFeng)for n-type Mg_(3)Bi_(2).The n-type Mg_(3)Bi_(1.4)Sb_(0.6) materials are promising for thermoelectric power generation and cooling applications near room temperature.
基金The funding support from the Natural Science Research Project of Jiangsu Higher Education Institutions(Grant No.21KJA530004)the 2021 Young Scientist Exchange Program between the Republic of Korea and the People’s Republic of Chinaa Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Rationally designed hierarchical structures and heteroatomic doping of carbon are effective strategies to enhance the stability and electrical conductivity of materials.Herein,SnSe_(2)flakes were generated in the double-walled hollow carbon spheres(DWHCSs),in which N and Se atoms were doped in the carbon walls,to construct SnSe_(2)@N,Se-DWHCSs by confined growth and in-situ derivatization.The N and Sedoped DWHCSs can effectively limit the size increase of SnSe_(2),promote ion diffusion kinetics,and buffer volume expansion,which can be proved by electron microscope observation and density functional theory calculation.Consequently,the SnSe_(2)@N,Se-DWHCSs as an anode material for sodium ion batteries(SIBs)demonstrated a distinguished reversible capacity of 322.8 mAh g^(-1)at 5 A g^(-1)after 1000 cycles and a superior rate ability of 235.3 m Ah g^(-1)at an ultrahigh rate of 15 A g^(-1).Furthermore,the structure evolution and electrochemical reaction processes of SnSe2@N,Se-DWHCSs in SIBs were analyzed by exsitu methods,which confirmed the consecutive hybrid mechanism and the phase transition process.
基金supported by the National Natural Science Foundation of China (Nos. 61534001 and 11574267)the National Science Fund for Distinguished Young Scholars (No.51725102)
文摘For zone-melted （ZM） bismuth telluride-based alloys, which are widely commercially available for solidstate cooling and low-temperature power generation around room temperature, introducing point defects is the chief approach to improve their thermoelectric performance. Herein, we report the multiple effects of Se doping on thermoelectric performance of p-type Bi0.5Sb1,5Te3-xSex ＋ 3 wt% Te ZM ingots, which increases carrier concentration, reduces lattice thermal conductivity and deteriorates the carrier mobility. As a result, the peak figure of merit （ZT） is shifted to a higher temperature and a high ZT 1.2 at 350 K is obtained, due to the reduced thermal conductivity and suppressed intrinsic conduction. Further, decreasing Sb content is followed to optimize the room temperature performance and a ZT - 1.1 at 300 K is obtained. These results are significant for designing and optimizing the thermoelectric performance of commercial Bi0.5Sb1.5Te3＋ 3 wt% Te ZM alloys.
基金H. Y. F. thanks Scott Finefrock and Tianyue Gao for the help in Hall measurement. H. Y. F. and Y. W. acknowledge the use of the hot press setup in Prof. Chin-The Sun＇s lab at Purdue University. H. Y. F. and Y. W. acknowledge Air Force Office of Scientific Research （No. FA9550-12-1-0061）. T. L. F. and X. L. R. acknowledge the partial support from National Science Foundation （No. 1150948）.
文摘We report the investigation of the thermoelectric properties of large-scale solution-synthesized Bi2Te3 nanocomposites prepared from nanowires hot- pressed into bulk pellets. A third element, Se, is introduced to tune the carrier concentration of the nanocomposites. Due to the Se doping, the thermoelectric figure of merit （ZT） of the nanocomposites is significantly enhanced due to the increased power factor and reduced thermal conductivity. We also find that thermal transport in our hot-pressed pellets is anisotropic, which results in different thermal conductivities along the in-plane and cross-plane directions. Theoretical calculations for both electronic and thermal transport are carried out to establish fundamental understanding of the material system and provide directions for further ZT optimization with adjustments to carrier concentration and mobility.
基金supported by the National Natural Science Foundation of China(91422303,21225104,21571020,21233009,and 21301175)
文摘In_4Se_3-based materials are noticeable n-type thermoelectric materials because of lead-free and intrinsically low lattice thermal conductivity,but the In4Se_3-δ crystals（with Se-deficiency,δ） suffer strong anisotropy and cleavage habit. Thus the researches on polycrystalline In_4Se_3-based materials are of great importance. Herein,we experimentally and theoretically investigated the thermoelectric properties of In_（4-x）Se_（2.95）Ag_x polycrystalline compounds. Ag occupying the intercalation or In4 site is energetically most favorable in light of the density functional theory calculation. The maximum solubility of Ag（x_m） is very low（xm 〈 0.03） and the experimental result indicates that the electrical transport behavior of In_（4-x）Se_（2.95）Ag_x compounds is not significantly optimized by Ag-dopant. Consequently,a maximum ZT of 0.92 at 723 K is obtained by In_（3.98）Se_（2.95）Ag_（0.02） compound that represents 15% enhancement over that of the un-doped one which benefits from the slightly enhanced power factor and the reduced total thermal conductivity.
