To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was propos...To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was proposed.Thermodynamic calculations showed that the magnesiothermic reduction of TiO_(2) was feasible.However,hindrance of the reduction reaction by the reduction by-product of MgO resulted in a considerably high O concentration in the titanium powder.The addition of HoCl_(3) to the system significantly reduces the activity of MgO to produce low-oxygen titanium powder.Thermochemical deoxidation and reduction experiments were conducted with MgCl_(2)−HoCl_(3) molten salt in the temperature range of 1023−1273 K.The results showed that titanium powder with oxygen concentration(mass fraction)below 5.00×10^(-4) can be prepared at the Mg−MgCl_(2)−HoOCl−HoCl_(3) equilibrium.展开更多
High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reac...High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reaction to get the mixture of V and MgO,and then the products were further nitrided at 1473 K in N2 atmosphere.Finally,the as-prepared samples were acid-leached to obtain pure VN powders.X-ray diffractometry and field-emission scanning electron microscopy were used to analyze the phase transition and morphological evolution of the samples.The results reveal that the overall morphology of the obtained VN powder retains the morphology of the initial V2 O3 powders.After removing MgO by acidic leaching,the porous VN particles can be obtained,with the oxygen content of 0.178 wt.%.Compared with the traditional methods,high purity VN powders with a small amount of oxygen and no carbon can be obtained.展开更多
RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE_(2)O_(3)(RE=Y,Nd and Gd)and Mg metal as raw materials.The thermomechanical analysis of the magnesiothermic re...RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE_(2)O_(3)(RE=Y,Nd and Gd)and Mg metal as raw materials.The thermomechanical analysis of the magnesiothermic reduction reactions in molten salt was investigated.Then the molten-salt-mediated magnesiothermic reduction process was studied from three different perspectives.After that,the RE-containing magnesium alloy was characterized by using chemical analysis,XRD analysis and SEM analysis.The magnesiothermic reduction was a liquid-liquid reaction with relatively weak driving force.During the melting process and the magnesiothermic reduction process,magnesium metal and the obtained alloy went up and down as a whole in molten salt,which improved the process safety without introducing chloride inclusions.Meanwhile,the hydrolysis of the RECl_(3^(-))containing molten salt occurred at elevated temperature,which severely impeded the magnesiothermic reduction process.After the magnesiothermic reduction at 750°C for 2.0 h,the content of RE and the common impurity elements in the obtained RE-containing alloy met the both requirements of the commercial WE43A and WE43B.展开更多
Two kinds of porous silicon（PS） were synthesized by magnesiothermic reduction of rice husk silica（RHS） derived from the oxidization of rice husks（RHs）. One was obtained from oxidization/reduction at 500 ℃ of th...Two kinds of porous silicon（PS） were synthesized by magnesiothermic reduction of rice husk silica（RHS） derived from the oxidization of rice husks（RHs）. One was obtained from oxidization/reduction at 500 ℃ of the unleached RHs, the other was synthesized from oxidization/reduction at 650 ℃ of the acidleached RHs. The structural difference of the above PS was compared： the former had a high pore volume（PV, 0.31 cm3/g） and a large specific surface area（SSA, 45.2 m^2/g）, 138 % and 17 % higher than the latter, respectively. As anode materials for lithium ion batteries, the former had reversible capacity of 1 400.7 m Ah/g, 987 m Ah/g lower than the latter; however, after 50 cycles, the former had 64.5 % capacity retention（907 m Ah/g）, which was 41.2 % higher than the latter（555.7 m Ah/g）. These results showed that the electrochemical performance of PS was significantly affected by its pore structures, and low reduction temperature played the key role in increasing its porosity, and therefore improving its cycling performance.展开更多
Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.Ho...Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.However,fabrication of porous structures tends to be difficult to control and complex,so,the final electrochemical performance can be compromised.Herein,a modest magnesiothermic reduction(MMR)reaction is demonstrated to produce blackberry-like porous Si nanospheres(PSSs)controllably using magnesium silicide(Mg_(2)Si)as Mg source and SiO_(2)nanospheres as the reactant.This improved MR method provides good control of the kinetics and heat release compared to the traditional MR(TMR)method using Mg powder as the reactant.The PSSs obtained by MMR reaction has higher structural integrity than that fabricated by TMR.After encapsulation with reduced graphene oxide,the Si/C composite exhibits superior cycling stability and rates such as a high reversible capacity of 1034 mAh·g^(-1)at0.5 C(4200 mAh·g^(-1)at 1.0 C)after 1000 cycles,capacity retention of 79.5%,and high rate capacity of 497 mAh·g^(-1)at 2.0 C.This strategy offers a new route to fabricate highperformance porous Si anodes and can be extended to other materials such as germanium.展开更多
As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is pres...As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is presented herein.Using an auxiliary molten salt,V_(2)O_(3)was successfully transformed into V by Mg reduction.The by-product,MgO,was transformed into MgCl_(2)by adding ZrCl_(4),which prevented the generation of MgV_(2)O_(4)and allowed the reaction to proceed smoothly.The rod-like alloy phases,Zr_(0.03)V_(1.97),which formed in the presence of excess Mg,may hinder the diffusion of oxygen from the product.The recovery rate of vanadium after separation and purification was approximately 45%–50%,where the main loss occurred during ball milling.Under the optimal conditions(Mg content of 48.3%,reduction time of 1.5 h,and temperature of 850℃),the purity of vanadium exceeded 99 wt.%,and the O content decreased to 0.34 wt.%.展开更多
As the cleanest energy source,hydrogen energy is regarded as the most promising fuel.Water electrolysis,as the primary means of hydrogen production,has constantly been the focus of attention in the energy conversion f...As the cleanest energy source,hydrogen energy is regarded as the most promising fuel.Water electrolysis,as the primary means of hydrogen production,has constantly been the focus of attention in the energy conversion field.Developing eco-friendly,cheap,safe and efficient catalysts for electrochemical water splitting(EWS)is the key challenge.Herein,the intermetallic silicide alloy is first synthesized via a facile magnesiothermic reduction and employed as bifunctional electrocatalysts for EWS.Ferric-nickel silicide(denoted as FeNiSi)alloy is designed and shows a good electrocatalytic performance for EWS.The lattice distortions of FeNiSi enhance the electrocatalytic activity.Besides,the porous structure affords more active sites and improves the reaction kinetics.As a consequence,FeNiSi delivers an excellent performance with overpotential of 308 mV for oxygen evolution reaction(OER)and 386 mV for hydrogen evolution reaction(HER)at 10 mA·cm−2 in 1 M KOH.The stability structure of intermetallic silicide achieves an outstanding durability with an unchanged potential of 1.66 V for overall water splitting at 10 mA·cm−2 for 15 h.This work not only provides a facile method for the synthesis of intermetallic silicide with considerable porous structures,but also develops the potential of intermetallic silicide alloy as bifunctional electrocatalysts for EWS,which opens up a new avenue for the design and application of intermetallic silicide alloy.展开更多
Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550-600 ℃ （below the melting point of Mg） b...Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550-600 ℃ （below the melting point of Mg） by means of a magnesiothermic reduction process. The MCM-48/polyacrylamide precursor nanocomposite was prepared by in-situ polymerization of acrylamide monomer in the presence of mesoporous MCM-48 synthesized by sol-gel method. The physicochemical properties and microstructures of the nanocomposite precursor and the low-temperature SiC product were characterized by X-ray diffraction （XRD）, differential scanning calorimetry-thermo gravimetric analysis （DSC-TGA）, transmission electron microscopy （TEM） and N2 adsorption-desorption. TEM micrographs and Brunauer-Emmett-Teller （BET） gas adsorption studies showed that the SiC powder was nanocrystalline and had a specific surface area of 330 m2/g and a mesoporosity in the range of 2-10 nm. The presence of an exothermic peak in the DSC trace corresponds to the self-combustion process of the SiC magnesiothermic synthesis. The results also show that the carbon in excess to that required to produce SiC plays a role in the reduction of the SiO2. The mechanism of magnesiothermic synthesis of mesoporous SiC is discussed.展开更多
Graphene aerogels are desirable for energy storage and conversion, as catalysis supports, and as adsorbents for environmental remediation. To produce graphene aerogels with low density, while maintaining high electric...Graphene aerogels are desirable for energy storage and conversion, as catalysis supports, and as adsorbents for environmental remediation. To produce graphene aerogels with low density, while maintaining high electrical conductivity and strong mechanic performance, we synthesized graphene aerogels by the magnesiothermic reduction of a freeze-dried graphene oxide （GO） self-assembly and subsequent etching of the formed MgO in acid solution. The reduced graphene oxide （rGO） aerogel samples exhibited densities as low as 1.1 mg·cm^-3. The rGO aerogel was very resilient, exhibiting full recoveryeven after being compressed by strains of up to 80%; its elastic modulus （E） scaled with density （p） as E-p^2. The rGO aerogels also exhibited high conductivities （e.g., 27.7 S·m^-1 at 3.6 mg·cm^-3） and outperformed many rGO aerogels fabricated by other reduction processes. Such outstanding properties were ascribed to the microstructures inherited from the freeze-dried GO self-assembly and the magnesiothermic reduction process.展开更多
Meso-porous Si-coated carbon nanotube （CNT） composite powders were prepared by combining a sol-gel method and the magnesiothermic reduction process. Meso-porous Si-coated CNT electrodes exhibit excellent cycle and r...Meso-porous Si-coated carbon nanotube （CNT） composite powders were prepared by combining a sol-gel method and the magnesiothermic reduction process. Meso-porous Si-coated CNT electrodes exhibit excellent cycle and rate performances as anodes in Li-ion batteries （LIBs）, which can be attributed to the efficient accommodation of volume change from meso-porous Si structure and the enhanced electrical conductivity from CNT core. This simple synthesis and subsequent reduction process provide a scalable route for the large-scale production of Si-C composite nanostructures, which can be utilized in a variety of applications, such as in photocatalysis, photoelectrochemical cells （PECs）, and LIBs.展开更多
Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny sili...Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC.Skillfully exploiting the high heat from magnesiothermic reduction,SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability.The silicon anchored to the carbon shell provides multipoint contact mode,that together with the carbon shell frame,significantly promoting the transfer of dual charge.Besides,the pomegranate-type microcluster structure also improves the tap density of the electrode,reduces the direct contact area between active material and electrolyte,and enhances the electrochemical performance.展开更多
Porous Si can be synthesized from diverse silica(SiO_(2))via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries.However,concerns regarding the influence of re...Porous Si can be synthesized from diverse silica(SiO_(2))via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries.However,concerns regarding the influence of residual silicon oxide(SiO_(x))component on resulted Si anode after reduction are still lacked.In this work,we intentionally fabricate a cauliflower-like silicon/silicon oxide(CF-Si/SiO_(x))particles from highly porous SiO_(2)spheres through insufficient magnesiothermic reduction,where residual SiO_(x)component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase.Moreover,the hierarchically structured CF-Si/SiO_(x)exhibits uniformly-dispersed channels,which can improve ion transport and accommodate large volume expansion,simultaneously.As a result,the CF-Si/SiO_(x)-700 anode shows excellent electrochemical performance with a specific capacity of^1,400 mA·h·g^(−1)and a capacity retention of 98%after 100 cycles at the current of 0.2 A·g^(−1).展开更多
基金financially supported by the National Natural Science Foundation of China (No.21968013)。
文摘To reduce the production cost of titanium,a new method for direct preparation of low-oxygen titanium powder by the magnesiothermic reduction of TiO_(2) with the assistance of a MgCl_(2)−HoCl_(3) molten salt was proposed.Thermodynamic calculations showed that the magnesiothermic reduction of TiO_(2) was feasible.However,hindrance of the reduction reaction by the reduction by-product of MgO resulted in a considerably high O concentration in the titanium powder.The addition of HoCl_(3) to the system significantly reduces the activity of MgO to produce low-oxygen titanium powder.Thermochemical deoxidation and reduction experiments were conducted with MgCl_(2)−HoCl_(3) molten salt in the temperature range of 1023−1273 K.The results showed that titanium powder with oxygen concentration(mass fraction)below 5.00×10^(-4) can be prepared at the Mg−MgCl_(2)−HoOCl−HoCl_(3) equilibrium.
基金Project(51725401) supported by the National Natural Science Foundation of China
文摘High purity vanadium nitride(VN)powders were prepared via a two-step process using vanadium trioxide(V2 O3)as the raw material.The V2 O3 was firstly reduced at 873 K in Ar atmosphere via magnesiothermic reduction reaction to get the mixture of V and MgO,and then the products were further nitrided at 1473 K in N2 atmosphere.Finally,the as-prepared samples were acid-leached to obtain pure VN powders.X-ray diffractometry and field-emission scanning electron microscopy were used to analyze the phase transition and morphological evolution of the samples.The results reveal that the overall morphology of the obtained VN powder retains the morphology of the initial V2 O3 powders.After removing MgO by acidic leaching,the porous VN particles can be obtained,with the oxygen content of 0.178 wt.%.Compared with the traditional methods,high purity VN powders with a small amount of oxygen and no carbon can be obtained.
基金supported by the National Natural Science Foundation of China(51501178)Autonomous Research Fund of State Key Laboratory of Multiphase Complex Systems(MPCS-2019-A-10)
文摘RE-containing magnesium alloys were prepared via molten-salt-mediated magnesiothermic reduction by using RE_(2)O_(3)(RE=Y,Nd and Gd)and Mg metal as raw materials.The thermomechanical analysis of the magnesiothermic reduction reactions in molten salt was investigated.Then the molten-salt-mediated magnesiothermic reduction process was studied from three different perspectives.After that,the RE-containing magnesium alloy was characterized by using chemical analysis,XRD analysis and SEM analysis.The magnesiothermic reduction was a liquid-liquid reaction with relatively weak driving force.During the melting process and the magnesiothermic reduction process,magnesium metal and the obtained alloy went up and down as a whole in molten salt,which improved the process safety without introducing chloride inclusions.Meanwhile,the hydrolysis of the RECl_(3^(-))containing molten salt occurred at elevated temperature,which severely impeded the magnesiothermic reduction process.After the magnesiothermic reduction at 750°C for 2.0 h,the content of RE and the common impurity elements in the obtained RE-containing alloy met the both requirements of the commercial WE43A and WE43B.
基金Funded by the National Natural Science Foundation of China(No.51264016)the Analysis and Testing Foundation of Kunming University o fScience and Technology,China(No.20140967)
文摘Two kinds of porous silicon（PS） were synthesized by magnesiothermic reduction of rice husk silica（RHS） derived from the oxidization of rice husks（RHs）. One was obtained from oxidization/reduction at 500 ℃ of the unleached RHs, the other was synthesized from oxidization/reduction at 650 ℃ of the acidleached RHs. The structural difference of the above PS was compared： the former had a high pore volume（PV, 0.31 cm3/g） and a large specific surface area（SSA, 45.2 m^2/g）, 138 % and 17 % higher than the latter, respectively. As anode materials for lithium ion batteries, the former had reversible capacity of 1 400.7 m Ah/g, 987 m Ah/g lower than the latter; however, after 50 cycles, the former had 64.5 % capacity retention（907 m Ah/g）, which was 41.2 % higher than the latter（555.7 m Ah/g）. These results showed that the electrochemical performance of PS was significantly affected by its pore structures, and low reduction temperature played the key role in increasing its porosity, and therefore improving its cycling performance.
基金the National Natural Science Foundation of China(Nos.51974208 and51504171)the Major Project of Technology Innovation of Hubei Province(No.2018AAA011)+4 种基金the Special Project of Central Government for Local Science and Technology Development of Hubei Province(No.2019ZYYD024)the Innovation Group of Natural Science Foundation of Hubei Province(No.2019CFA020)Wuhan Yellow Crane Talents ProgramCity University of Hong Kong Applied Research Grant(ARG)(No.9667122)Hong Kong Research Grants Council(RGC)General Research Funds(GRF)(No.City U 11205617)。
文摘Porous silicon(Si)nanostructures have aroused much interest as lithium-ion battery anodes because of the large space to accommodate the volume change in lithiation and delithiation and shorter ion transfer distance.However,fabrication of porous structures tends to be difficult to control and complex,so,the final electrochemical performance can be compromised.Herein,a modest magnesiothermic reduction(MMR)reaction is demonstrated to produce blackberry-like porous Si nanospheres(PSSs)controllably using magnesium silicide(Mg_(2)Si)as Mg source and SiO_(2)nanospheres as the reactant.This improved MR method provides good control of the kinetics and heat release compared to the traditional MR(TMR)method using Mg powder as the reactant.The PSSs obtained by MMR reaction has higher structural integrity than that fabricated by TMR.After encapsulation with reduced graphene oxide,the Si/C composite exhibits superior cycling stability and rates such as a high reversible capacity of 1034 mAh·g^(-1)at0.5 C(4200 mAh·g^(-1)at 1.0 C)after 1000 cycles,capacity retention of 79.5%,and high rate capacity of 497 mAh·g^(-1)at 2.0 C.This strategy offers a new route to fabricate highperformance porous Si anodes and can be extended to other materials such as germanium.
基金the National Key Research and Development Program of China(2018YFC1900500)Technology of Preparing High Purity Metal Vanadium Powder by Magnesium Reduction(2018CDPZH-16)the open project founded by State Key Laboratory of Vanadium and Titanium Resources Comprehensive Utilization for financial support of this research.
文摘As an important strategic metal,vanadium is generally used to prepare special steels,titanium alloys,and hydrogen storage materials.A new method of producing vanadium(metal)powder from V_(2)O_(3)using block Mg is presented herein.Using an auxiliary molten salt,V_(2)O_(3)was successfully transformed into V by Mg reduction.The by-product,MgO,was transformed into MgCl_(2)by adding ZrCl_(4),which prevented the generation of MgV_(2)O_(4)and allowed the reaction to proceed smoothly.The rod-like alloy phases,Zr_(0.03)V_(1.97),which formed in the presence of excess Mg,may hinder the diffusion of oxygen from the product.The recovery rate of vanadium after separation and purification was approximately 45%–50%,where the main loss occurred during ball milling.Under the optimal conditions(Mg content of 48.3%,reduction time of 1.5 h,and temperature of 850℃),the purity of vanadium exceeded 99 wt.%,and the O content decreased to 0.34 wt.%.
基金the Natural Science Foundation of Liaoning Province(No.2023-MS-115)and Large Instrument and Equipment Open Foundation of Dalian University of Technology.
文摘As the cleanest energy source,hydrogen energy is regarded as the most promising fuel.Water electrolysis,as the primary means of hydrogen production,has constantly been the focus of attention in the energy conversion field.Developing eco-friendly,cheap,safe and efficient catalysts for electrochemical water splitting(EWS)is the key challenge.Herein,the intermetallic silicide alloy is first synthesized via a facile magnesiothermic reduction and employed as bifunctional electrocatalysts for EWS.Ferric-nickel silicide(denoted as FeNiSi)alloy is designed and shows a good electrocatalytic performance for EWS.The lattice distortions of FeNiSi enhance the electrocatalytic activity.Besides,the porous structure affords more active sites and improves the reaction kinetics.As a consequence,FeNiSi delivers an excellent performance with overpotential of 308 mV for oxygen evolution reaction(OER)and 386 mV for hydrogen evolution reaction(HER)at 10 mA·cm−2 in 1 M KOH.The stability structure of intermetallic silicide achieves an outstanding durability with an unchanged potential of 1.66 V for overall water splitting at 10 mA·cm−2 for 15 h.This work not only provides a facile method for the synthesis of intermetallic silicide with considerable porous structures,but also develops the potential of intermetallic silicide alloy as bifunctional electrocatalysts for EWS,which opens up a new avenue for the design and application of intermetallic silicide alloy.
文摘Mesoporous silicon carbide with high specific surface area was successfully synthesized from an MCM-48/ polyacrylamide nanocomposite precursor in the temperature range of 550-600 ℃ （below the melting point of Mg） by means of a magnesiothermic reduction process. The MCM-48/polyacrylamide precursor nanocomposite was prepared by in-situ polymerization of acrylamide monomer in the presence of mesoporous MCM-48 synthesized by sol-gel method. The physicochemical properties and microstructures of the nanocomposite precursor and the low-temperature SiC product were characterized by X-ray diffraction （XRD）, differential scanning calorimetry-thermo gravimetric analysis （DSC-TGA）, transmission electron microscopy （TEM） and N2 adsorption-desorption. TEM micrographs and Brunauer-Emmett-Teller （BET） gas adsorption studies showed that the SiC powder was nanocrystalline and had a specific surface area of 330 m2/g and a mesoporosity in the range of 2-10 nm. The presence of an exothermic peak in the DSC trace corresponds to the self-combustion process of the SiC magnesiothermic synthesis. The results also show that the carbon in excess to that required to produce SiC plays a role in the reduction of the SiO2. The mechanism of magnesiothermic synthesis of mesoporous SiC is discussed.
基金This work was supported Foundation for Returned Education of China, Key by the Scientific Research Scholars, the Ministry of Basic Research Projects of Science and Technology Commission of Shanghai （No.11JC1412900）, and the National Science Foundation of China program （Nos. 21271140, 51472182）.
文摘Graphene aerogels are desirable for energy storage and conversion, as catalysis supports, and as adsorbents for environmental remediation. To produce graphene aerogels with low density, while maintaining high electrical conductivity and strong mechanic performance, we synthesized graphene aerogels by the magnesiothermic reduction of a freeze-dried graphene oxide （GO） self-assembly and subsequent etching of the formed MgO in acid solution. The reduced graphene oxide （rGO） aerogel samples exhibited densities as low as 1.1 mg·cm^-3. The rGO aerogel was very resilient, exhibiting full recoveryeven after being compressed by strains of up to 80%; its elastic modulus （E） scaled with density （p） as E-p^2. The rGO aerogels also exhibited high conductivities （e.g., 27.7 S·m^-1 at 3.6 mg·cm^-3） and outperformed many rGO aerogels fabricated by other reduction processes. Such outstanding properties were ascribed to the microstructures inherited from the freeze-dried GO self-assembly and the magnesiothermic reduction process.
文摘Meso-porous Si-coated carbon nanotube （CNT） composite powders were prepared by combining a sol-gel method and the magnesiothermic reduction process. Meso-porous Si-coated CNT electrodes exhibit excellent cycle and rate performances as anodes in Li-ion batteries （LIBs）, which can be attributed to the efficient accommodation of volume change from meso-porous Si structure and the enhanced electrical conductivity from CNT core. This simple synthesis and subsequent reduction process provide a scalable route for the large-scale production of Si-C composite nanostructures, which can be utilized in a variety of applications, such as in photocatalysis, photoelectrochemical cells （PECs）, and LIBs.
基金the Shenzhen Science and Technology Projects(No.JCYJ20180306172957494)National Natural Science Foundation of China(No.5187224)for financial support.
文摘Severe volume expansion and inherently poor lithium ion transmission are two major problems of silicon anodes.To address these issues,we proposed a pomegranate-type Si/C composite anode with highly dispersed tiny silicon particles as the core assisted by small amount of SiC.Skillfully exploiting the high heat from magnesiothermic reduction,SiC can assist the good dispersion of silicon and provide good interface compatibility and chemical stability.The silicon anchored to the carbon shell provides multipoint contact mode,that together with the carbon shell frame,significantly promoting the transfer of dual charge.Besides,the pomegranate-type microcluster structure also improves the tap density of the electrode,reduces the direct contact area between active material and electrolyte,and enhances the electrochemical performance.
基金supported by the National Natural Science Foundation of China(No.51872157)Shenzhen Technical Plan Project(Nos.JCYJ20170817161753629 and JCYJ20180508152135822)+4 种基金the Shenzhen Graphene Manufacturing Innovation Center(No.201901161513)Shenzhen Key Lab of Security Research of Power Batteries(No.ZDSYS201707271615073)Guangdong Technical Plan Project(Nos.2015TX01N011 and 2017B090907005)Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(No.2017BT01N111)the Special Fund Project for Strategic Emerging Industry Development of Shenzhen(No.20170428145209110).
文摘Porous Si can be synthesized from diverse silica(SiO_(2))via magnesiothermic reduction technology and widely employed as potential anode material in lithium ion batteries.However,concerns regarding the influence of residual silicon oxide(SiO_(x))component on resulted Si anode after reduction are still lacked.In this work,we intentionally fabricate a cauliflower-like silicon/silicon oxide(CF-Si/SiO_(x))particles from highly porous SiO_(2)spheres through insufficient magnesiothermic reduction,where residual SiO_(x)component and internal space play an important role in preventing the structural deformation of secondary bulk and restraining the expansion of Si phase.Moreover,the hierarchically structured CF-Si/SiO_(x)exhibits uniformly-dispersed channels,which can improve ion transport and accommodate large volume expansion,simultaneously.As a result,the CF-Si/SiO_(x)-700 anode shows excellent electrochemical performance with a specific capacity of^1,400 mA·h·g^(−1)and a capacity retention of 98%after 100 cycles at the current of 0.2 A·g^(−1).
