Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transit...Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transition elements,following the cuprate and iron-pnictide superconductors.However,there are several critical questions that have been perplexing the scientificommunity:(1)What factors contribute to the inconsistent reproducibility of the experimental results?(2)What is the fundamental nature of pressure-induced superconductivity:bulk or nonbulk(filamentary-like)(3)Where is the superconducting phase located within the sample if it is filamentary-like(4)Is the oxygen content important for the development and stabilization of superconductivity?In this study,we employ comprehensive high-pressure techniques to address these questions.Through our modulated ac susceptibility measurements,we are the firs to fin that the superconductivity in this nickelate is filamentary-like Our scanning transmission electron microscopy investigations suggest that the filamentary-lik superconductivity most likely emerges at the interface between La_(3)Ni_(2)O_(7)and La_(4)Ni_(3)O_(10)phases.By tuning the oxygen content of polycrystalline La_(3)Ni_(2)O_(7),we also fin that it plays vital role in the development and stabilization of superconductivity in this material.The upper and lower bounds on the oxygen content are 7.35 and 6.89,respectively.Our results provide not only new insights into the puzzling issues regarding this material,but also significan information that will enable a better understanding of its superconductivity.展开更多
Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfo...Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfortunately, the rapid and uncontrollable degradation rate of Mg alloys in chloride-rich body microenvironments limits their clinical orthopedic applications. Recently, Calcium Phosphate(Ca-P)biomaterials, especially Hydroxyapatite(HA), have been broadly applied in the surface functional modification of metal-based biomaterials attributed to their excellent bioactivity and biocompatibility. Hydrothermal modification of Ca-P coatings on Mg alloys has been extensively exploited by researchers for its significant superiorities in controlling coating structure and improving interfacial bonding strength for better osseointegration and corrosion resistance. This work focuses on the up-to-the-minute advances in Ca-P coatings on the surface of Mg and its alloys via hydrothermal methods, including the strategies and mechanisms of hydrothermal modification. Herein, we are inclined to share some feasible and attractive hydrothermal surface modification strategies. From the perspectives of hydrothermal manufacturing technique innovation and coating structure optimization, we evaluate how to foster the corrosion resistance, coating bonding strength, osseointegration and antibacterial properties of Mg alloys with Ca-P coatings synthesized by hydrothermal method. The challenges and future perspectives on the follow-up exploration of Mg alloys for orthopedic applications are also elaborately proposed.展开更多
At present,replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards.Composite solid electrolytes(CP...At present,replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards.Composite solid electrolytes(CPEs)have excellent ionic conductivity and flexibility owing to the combination of functional inorganic materials and polymer solid electrolytes(SPEs).Nevertheless,the ionic conductivity of CPEs is still lower than those of commercial liquid electrolytes,so the development of high-performance CPEs has important practical significance.Herein,a novel fast lithium-ion conductor material LiTa_(2)PO_(8) was first filled into poly(ethylene oxide)(PEO)-based SPE,and the optimal ionic conductivity was achieved by filling different concentrations(the ionic conductivity is 4.61×10^(-4)S/cm with a filling content of 15 wt%at 60℃).The enhancement in ionic conductivity is due to the improvement of PEO chain movement and the promotion of LiTFSI dissociation by LiTa_(2)PO_(8).In addition,LiTa_(2)PO_(8) also takes the key in enhancing the mechanical strength and thermal stability of CPEs.The assembled LiFePO_(4) solid-state lithium metal battery displays better rate performance(the specific capacities are as high as 157.3,152,142.6,105 and 53.1 mAh/g under0.1,0.2,0.5,1 and 2 C at 60℃,respectively)and higher cycle performance(the capacity retention rate is86.5%after 200 cycles at 0.5 C and 60℃).This research demonstrates the feasibility of LiTa_(2)PO_(8) as a filler to improve the performance of CPEs,which may provide a fresh platform for developing more advanced solid-state electrolytes.展开更多
Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the e...Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the expansion of their applications in deep-sea exploration,aerospace and military equipment,special working conditions have placed higher demands on the low-temperature performance of LIBs.However,at low temperatures,the severe polarization and inferior electrochemical activity of electrode materials cause the acute capacity fading upon cycling,which greatly hindered the further development of LIBs.In this review,we summarize the recent important progress of LIBs in low-temperature operations and introduce the key methods and the related action mechanisms for enhancing the capacity of the various cathode and anode materials.It aims to promote the development of high-performance electrode materials and broaden the application range of LIBs.展开更多
MnS as anode material for sodium-ion batteries(SIBs)has recently attracted great attention because of the high theoretical capacity,great natural abundance,and low cost.However,it suffers from inferior electrical cond...MnS as anode material for sodium-ion batteries(SIBs)has recently attracted great attention because of the high theoretical capacity,great natural abundance,and low cost.However,it suffers from inferior electrical conductivity and large volume expansion during the charge/discharge process,leading to tremendous damage of electrodes and subsequently fast capacity fading.To mitigate these issues,herein,a three-dimensional(3D)interlaced carbon nanotubes(CNTs)threaded into or between MnS hollow microspheres(hollow MnS/CNTs composite)has been designed and synthesized as an enhanced anode material.It can effectively improve the electrical conductivity,buffer the volume change,and maintain the integrity of the electrode during the charging and discharging process based on the synergistic interaction and the integrative structure.Therefore,when evaluated as anode for SIBs,the hollow MnS/CNTs electrode displays enhanced reve rsible capacity(275 mAh/g at 100 mA/g after 100 cycles),which is much better than that of pure MnS electrode(25 mAh/g at 100 mA/g after 100 cycles)prepared without the addition of CNTs.Even increasing the current density to 500 mA/g,the hollow MnS/CNTs electrode still delivers a five times higher reversible capacity than that of the pure MnS electrode.The rate performance of the hollow MnS/CNTs electrode is also superior to that of pure MnS electrode at various current densities from 50 mA/g to 1000 mA/g.展开更多
The emergency of high-power electrical appliances has put forward higher requirements for the power density of lithium-ion batteries.Vanadium oxides with large theoretical capacities and high operating voltages are co...The emergency of high-power electrical appliances has put forward higher requirements for the power density of lithium-ion batteries.Vanadium oxides with large theoretical capacities and high operating voltages are considered as prospective alternatives for the cathode of a new generation of lithium-ion batteries.However,the poor rate and cycling performance caused by the sluggish electrons/lithium transportation,irreversible phase changes,vanadium dissolution and large volume changes during the repeated lithium intercalation/deintercalation hinder their commercial development.Several optimizing routes have been carried out and extensively explored to address these problems.Taking V_(2)O_(5),VO_(2)(B),V_(6)O_(13),and V_(2)O_(3)as examples,this article reviewed their crystal structures and lithium storage reactions.Besides,recent progress in modification methods for the electrochemical insufficiencies of vanadium oxides,including nanostructure,heterogeneous atom doping,composite and self-supported electrodes has been systematically summarized and finally,the challenges for the industrialization of vanadium oxide cathodes and their development opportunities are proposed.展开更多
A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduce...A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduced by other teams,it would be a major scientific breakthrough.Here,we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al.Our x-ray diffraction measurements indicate that the obtained sample contains three substances:the facecentered-cubic(FCC)-1 phase(Fm-3m)with lattice parameter a=5.03Å,the FCC-2 phase(Fm-3m)with a lattice parameter a=4.755Å,and Lu metal.The two FCC phases are identical to the those reported in the so-called near-ambient superconductor.However,we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity.We also use a laser heating technique to heat a sample to 1800 XC and find no superconductivity in the produced dark blue material below 6.5 GPa.In addition,both samples remain dark blue in color in the pressure range investigated.展开更多
In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state informa...In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state information(CSI)can be obtained at the transmitter(Alice),while eavesdropper's(Eve's)CSI is unknown.Firstly,the analytical expression of the achievable ergodic rate at Bob is obtained.Then,by exploiting Bob's statistical CSI,we jointly design the transmit covariance matrix at Alice and the phase shift matrix at the RIS to minimize the transmit power of the information signal under the quality-of-service(QoS)constraint of Bob.Finally,we propose an artificial noise(AN)-aided method without Eve's CSI to enhance the security of this system and use the residual power to design the transmit covariance for AN.Simulation results verify the convergence of the proposed method,and also show that there exists a trade-off between the secrecy rate and QoS of Bob.展开更多
SnS nanoparticles/CNTs composite(SnS]CNTs composite)is synthesized by a facile one-pot solvothermal reaction.The structural characterizations reveal pure SnS nanoparticles with the size of less than 10 nm distribute o...SnS nanoparticles/CNTs composite(SnS]CNTs composite)is synthesized by a facile one-pot solvothermal reaction.The structural characterizations reveal pure SnS nanoparticles with the size of less than 10 nm distribute on the surface of CNTs with the diameter of less than 20 nm.The SnS]CNTs composite electrode performs high reversible capacity and good cyclability(365 mAh/g at 50 mA/g after 50 cycles),which is superior to that of pure SnS electrode synthesized without the adding of CNTs(115.9 mAh/g at 50 mA/g after 50mA/cycles).Even increasing the current density to 500mA/g,the SnS]CNTs composite electrode still delivers a reversible capacity up to 210 mAh/g after 100 cycles,nearly two times higher than that of the pure SnS electrode(108 mAh/g after 100 cycles).The rate performance of the SnS/CNTs composite electrode is also better than that of pure SnS electrode at different current densities from 50mA/g to 800mA/g.The enhanced electrochemical performance of SnS/CNTs composite can be attributed to the adding of CNTs as a flexible and conductive structure supporter and the formation of SnS nanoparticles with small size.The SnS nanoparticles CNTs composite structure not only benefits for buffering the volume change during charge and discharge process,but also increases the surface area for sufficient electrode-electrolyte contacting,and shortens Na+diffusion length,which improves the conductivity and stability of active material and finally provides desirable electrochemical performance.展开更多
What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law kn...What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law known as Homes'law,there is a growing consensus in the community that the Tc value of the cuprate superconductors is closely linked to the superfluid density(ρ_(s))of its ground state and the conductivity(σ)of its normal state.However,all the data supporting this empirical law(ρ_(s)=AσT_(c))have been obtained from the ambientpressure superconductors.In this study,we present the first high-pressure results about the connection of the quantities ofρ_(s)andσwith T_(c),through the studies on the Bi_(1.74)Pb_(0.38)Sr_(1.88)CuO_(6+δ)and Bi_(2)Sr_(2)CaCu_(2)O_(8+δ),in which the value of their high-pressure resistivity(ρ=1/σ)is achieved by adopting our newly established method,while the quantity ofρs is extracted using Homes'law.We highlight that the Tc values are strongly linked to the joint response factors of magnetic field and electric field,i.e.,ρ_(s)andσ,respectively,implying that the physics determining T_(c)is governed by the intrinsic electromagnetic fields of the system.展开更多
Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume...Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume expansion. In order to solve these problems, we used a graphene network loaded with cobalt metal nanoparticles(rGO-Co) to coat SiO_(2) porous hollow spheres(SiO_(2)@rGO-Co). The construction of porous hollow structure and graphene network can shorten the lithium-ion(Li^(+)) diffusion distance and enhance the conductivity of the composite, which improves the electrochemical activity of SiO_(2) effectively. They also alleviate the volume expansion of the anode in the cycling process. Moreover,nano-scale cobalt metal particles dispersed on graphene catalyze the conversion reaction of SiO_(2) and activate the locked Li+in Li_(2)O through a reversible reaction, which improves the charge and discharge capacity of the anode. The capacity of SiO_(2)@rGO-Co reaches 370.4 m Ah/g after 100 cycles at 0.1 A/g,which is 6.19 times the capacity of pure SiO_(2)(59.8 mAh/g) under the same circumstance. What is more,its structure also exhibits excellent cycle stability, with a volume expansion rate of only 13.0% after 100 cycles at a current density of 0.1 A/g.展开更多
Bi draws increasing attention as anode materials for lithium-ion batteries and sodium-ion batteries due to its unique layered crystal structure,which is in favor of achieving fast ionic diffusion kinetics during cycli...Bi draws increasing attention as anode materials for lithium-ion batteries and sodium-ion batteries due to its unique layered crystal structure,which is in favor of achieving fast ionic diffusion kinetics during cycling.However,the dramatic volume expansion upon lithiation/sodiation and an insufficient theoretical capacity of Bi greatly hinder its practical application.Herein,we report the Fe_(2 )O_(3) nanoparticle-pinning Bi-encapsulated carbon fiber composites through the electrospinning technique.The introduction of Fe_(2 )O_(3) nanoparticles can prevent the growth and aggregation of Bi nanoparticles during synthetic and cycling processes,re s pectively.Fe_(2)O_(3) with high specific capacity also contributes to the specific capacity of the composites.Consequently,the as-prepared Bi-Fe_(2)O_(3)/carbon fiber composite exhibits outstanding long-term stability,which delivers reversible capacities 504 and 175 mAh/g after1000 cycles at 1 A/g for lithium-ion and sodium-ion batteries,respectively.展开更多
The stability of superconductivity in superconductors is widely recognized to be determined by various factors,including charge,spin,orbit,lattice,and other related degrees of freedom.Here,we report our findings on th...The stability of superconductivity in superconductors is widely recognized to be determined by various factors,including charge,spin,orbit,lattice,and other related degrees of freedom.Here,we report our findings on the pressure-induced coevolution of superconductivity and Hall coefficient in KCa_(2)Fe_(4)As_(24F_(2),an iron-based superconductor possessing a hybrid crystal structure combining KFe_(2)As_(2) and CaFeAsF.Our investigation,involving high-pressure resistance,Hall effect and x-ray diffraction(XRD) measurements,allows us to observe the connection of the superconductivity and Hall coefficient with the anisotropic lattice shrinkage.We find that its ambient-pressure tetragonal(T) phase presents a collapse starting at around 18 GPa,where the sign of the Hall coefficient(R_(H)) changes from positive to negative.Upon further compression,both superconducting transition temperature(T_(c)) and R_(H) exhibit a monotonous decrease.At around 41 GPa,the superconductivity is completely suppressed(T_(c)=0),where the parameter a begins to decline again and the Hall coefficient remains nearly unchanged.Our experiment results clearly demonstrate that the pressure-induced anisotropic lattice collapse plays a crucial role in tuning the interplay among multiple degrees of freedom in the superconducting system and,correspondingly,the stability of the superconductivity.展开更多
We report the observation of a magnetic transition at the temperature about 56 K,through the high-pressure heat capacity and magnetic susceptibility measurements on the samples that have been claimed to be a nearroom-...We report the observation of a magnetic transition at the temperature about 56 K,through the high-pressure heat capacity and magnetic susceptibility measurements on the samples that have been claimed to be a nearroom-temperature superconductor[Dasenbrock-Gammon et al.Nature 615,244(2023)].Our results show that this magnetic phase is robust against pressure up to 4.3 GPa,which covers the critical pressure of boosting the claimed superconductivity.展开更多
The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced...The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced by pressure in the three crystallographic directions of the sample.In this study,we introduce a novel and effective method that addresses these technical challenges.This method is anticipated to offer a valuable foundation for high-pressure investigations on quantum materials,particularly those with anisotropic layered structures.展开更多
The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconducto...The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconductor known for its high critical current and magnetic field tolerance.Here,we systematically investigated the physical properties of Nb_(3)Sn under high pressures.Our findings reveal that superconductivity in Nb_(3)Sn remains robust up to∼142 GPa,demonstrating remarkable stability despite a gradual suppression of��c with increasing pressure.First-principles calculations indicate that the pressure-dependent superconducting behavior is primarily driven by variations in the density of states of Nb’s d-electrons,particularly contributions from the d_(x^(2)-y^(2)) and d_(z^(2)) orbitals.Furthermore,we predict the potential for synthesizing Nb_(3)Sn films and demonstrate that biaxial strain induced by suitable substrates can preserve their superconducting properties.This comprehensive study not only enhances our understanding of Nb_(3)Sn’s superconducting mechanism under high pressure but also opens new avenues for its application in advanced superconducting technologies.展开更多
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214,12122414,12104487,and 12004419)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)support from the Youth Innovation Promotion Association of the CAS(2019008)supported by the Synergetic Extreme Condition User Facility(SECUF)。
文摘Signatures of superconductivity near 80 K have recently been discovered in single crystals of La_(3)Ni_(2)O_(7)under pressure,which makes it a new candidate for high-temperature superconductors dominated by 3d transition elements,following the cuprate and iron-pnictide superconductors.However,there are several critical questions that have been perplexing the scientificommunity:(1)What factors contribute to the inconsistent reproducibility of the experimental results?(2)What is the fundamental nature of pressure-induced superconductivity:bulk or nonbulk(filamentary-like)(3)Where is the superconducting phase located within the sample if it is filamentary-like(4)Is the oxygen content important for the development and stabilization of superconductivity?In this study,we employ comprehensive high-pressure techniques to address these questions.Through our modulated ac susceptibility measurements,we are the firs to fin that the superconductivity in this nickelate is filamentary-like Our scanning transmission electron microscopy investigations suggest that the filamentary-lik superconductivity most likely emerges at the interface between La_(3)Ni_(2)O_(7)and La_(4)Ni_(3)O_(10)phases.By tuning the oxygen content of polycrystalline La_(3)Ni_(2)O_(7),we also fin that it plays vital role in the development and stabilization of superconductivity in this material.The upper and lower bounds on the oxygen content are 7.35 and 6.89,respectively.Our results provide not only new insights into the puzzling issues regarding this material,but also significan information that will enable a better understanding of its superconductivity.
基金supported by National Natural Science Foundation of China(Grant No.51872197,81772363 and 81972076)Shanghai Committee of Science and Technology,China(Grant No.15411951000)。
文摘Magnesium(Mg) and its alloys have emerged as a favored candidate for bio-regenerative medical implants due to their superior biocompatibility, biodegradability and the elastic modulus close to that of human bone. Unfortunately, the rapid and uncontrollable degradation rate of Mg alloys in chloride-rich body microenvironments limits their clinical orthopedic applications. Recently, Calcium Phosphate(Ca-P)biomaterials, especially Hydroxyapatite(HA), have been broadly applied in the surface functional modification of metal-based biomaterials attributed to their excellent bioactivity and biocompatibility. Hydrothermal modification of Ca-P coatings on Mg alloys has been extensively exploited by researchers for its significant superiorities in controlling coating structure and improving interfacial bonding strength for better osseointegration and corrosion resistance. This work focuses on the up-to-the-minute advances in Ca-P coatings on the surface of Mg and its alloys via hydrothermal methods, including the strategies and mechanisms of hydrothermal modification. Herein, we are inclined to share some feasible and attractive hydrothermal surface modification strategies. From the perspectives of hydrothermal manufacturing technique innovation and coating structure optimization, we evaluate how to foster the corrosion resistance, coating bonding strength, osseointegration and antibacterial properties of Mg alloys with Ca-P coatings synthesized by hydrothermal method. The challenges and future perspectives on the follow-up exploration of Mg alloys for orthopedic applications are also elaborately proposed.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.52073212,51772205,51772208)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘At present,replacing the liquid electrolyte in a lithium metal battery with a solid electrolyte is considered to be one of the most powerful strategies to avoid potential safety hazards.Composite solid electrolytes(CPEs)have excellent ionic conductivity and flexibility owing to the combination of functional inorganic materials and polymer solid electrolytes(SPEs).Nevertheless,the ionic conductivity of CPEs is still lower than those of commercial liquid electrolytes,so the development of high-performance CPEs has important practical significance.Herein,a novel fast lithium-ion conductor material LiTa_(2)PO_(8) was first filled into poly(ethylene oxide)(PEO)-based SPE,and the optimal ionic conductivity was achieved by filling different concentrations(the ionic conductivity is 4.61×10^(-4)S/cm with a filling content of 15 wt%at 60℃).The enhancement in ionic conductivity is due to the improvement of PEO chain movement and the promotion of LiTFSI dissociation by LiTa_(2)PO_(8).In addition,LiTa_(2)PO_(8) also takes the key in enhancing the mechanical strength and thermal stability of CPEs.The assembled LiFePO_(4) solid-state lithium metal battery displays better rate performance(the specific capacities are as high as 157.3,152,142.6,105 and 53.1 mAh/g under0.1,0.2,0.5,1 and 2 C at 60℃,respectively)and higher cycle performance(the capacity retention rate is86.5%after 200 cycles at 0.5 C and 60℃).This research demonstrates the feasibility of LiTa_(2)PO_(8) as a filler to improve the performance of CPEs,which may provide a fresh platform for developing more advanced solid-state electrolytes.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.51772205,51572192,51772208,51472179)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘Lithium-ion batteries(LIBs)have evolved into the mainstream power source of ene rgy sto rage equipment by reason of their advantages such as high energy density,high power,long cycle life and less pollution.With the expansion of their applications in deep-sea exploration,aerospace and military equipment,special working conditions have placed higher demands on the low-temperature performance of LIBs.However,at low temperatures,the severe polarization and inferior electrochemical activity of electrode materials cause the acute capacity fading upon cycling,which greatly hindered the further development of LIBs.In this review,we summarize the recent important progress of LIBs in low-temperature operations and introduce the key methods and the related action mechanisms for enhancing the capacity of the various cathode and anode materials.It aims to promote the development of high-performance electrode materials and broaden the application range of LIBs.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.51772205,51572192,51772208,51472179)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘MnS as anode material for sodium-ion batteries(SIBs)has recently attracted great attention because of the high theoretical capacity,great natural abundance,and low cost.However,it suffers from inferior electrical conductivity and large volume expansion during the charge/discharge process,leading to tremendous damage of electrodes and subsequently fast capacity fading.To mitigate these issues,herein,a three-dimensional(3D)interlaced carbon nanotubes(CNTs)threaded into or between MnS hollow microspheres(hollow MnS/CNTs composite)has been designed and synthesized as an enhanced anode material.It can effectively improve the electrical conductivity,buffer the volume change,and maintain the integrity of the electrode during the charging and discharging process based on the synergistic interaction and the integrative structure.Therefore,when evaluated as anode for SIBs,the hollow MnS/CNTs electrode displays enhanced reve rsible capacity(275 mAh/g at 100 mA/g after 100 cycles),which is much better than that of pure MnS electrode(25 mAh/g at 100 mA/g after 100 cycles)prepared without the addition of CNTs.Even increasing the current density to 500 mA/g,the hollow MnS/CNTs electrode still delivers a five times higher reversible capacity than that of the pure MnS electrode.The rate performance of the hollow MnS/CNTs electrode is also superior to that of pure MnS electrode at various current densities from 50 mA/g to 1000 mA/g.
基金supported by the National Natural Science Foundation of China,NSFC(51772205,51772208)the General Program of Municipal Natural Science Foundation of Tianjin(17JCYBJC17000,17JCYBJC22700)。
文摘The emergency of high-power electrical appliances has put forward higher requirements for the power density of lithium-ion batteries.Vanadium oxides with large theoretical capacities and high operating voltages are considered as prospective alternatives for the cathode of a new generation of lithium-ion batteries.However,the poor rate and cycling performance caused by the sluggish electrons/lithium transportation,irreversible phase changes,vanadium dissolution and large volume changes during the repeated lithium intercalation/deintercalation hinder their commercial development.Several optimizing routes have been carried out and extensively explored to address these problems.Taking V_(2)O_(5),VO_(2)(B),V_(6)O_(13),and V_(2)O_(3)as examples,this article reviewed their crystal structures and lithium storage reactions.Besides,recent progress in modification methods for the electrochemical insufficiencies of vanadium oxides,including nanostructure,heterogeneous atom doping,composite and self-supported electrodes has been systematically summarized and finally,the challenges for the industrialization of vanadium oxide cathodes and their development opportunities are proposed.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214,12104487,12122414,and 12004419)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)J.G.and S.C.are grateful for support from the Youth Innovation Promotion Association of the CAS(Grant No.2019008)the China Postdoctoral Science Foundation(Grant No.E0BK111).
文摘A material described as lutetium–hydrogen–nitrogen(Lu-H-N in short)was recently claimed to have“near-ambient superconductivity”[Dasenbrock-Gammon et al.,Nature 615,244–250(2023)].If this result could be reproduced by other teams,it would be a major scientific breakthrough.Here,we report our results of transport and structure measurements on a material prepared using the same method as reported by Dasenbrock-Gammon et al.Our x-ray diffraction measurements indicate that the obtained sample contains three substances:the facecentered-cubic(FCC)-1 phase(Fm-3m)with lattice parameter a=5.03Å,the FCC-2 phase(Fm-3m)with a lattice parameter a=4.755Å,and Lu metal.The two FCC phases are identical to the those reported in the so-called near-ambient superconductor.However,we find from our resistance measurements in the temperature range from 300 K down to 4 K and the pressure range 0.9–3.4 GPa and our magnetic susceptibility measurements in the pressure range 0.8–3.3 GPa and the temperature range down to 100 K that the samples show no evidence of superconductivity.We also use a laser heating technique to heat a sample to 1800 XC and find no superconductivity in the produced dark blue material below 6.5 GPa.In addition,both samples remain dark blue in color in the pressure range investigated.
基金supported in part by the National Key Research and Development Program of China under Grant 2020YFB1804900in part by the National Natural Science Foundation of China under Grant 92067201,U1805262,62071247,62071249,62171240+2 种基金in part by the Jiangsu Provincial Key Research and Development Program of China under Grant BE2020084-5in part by Special Funds of the Central Government Guiding Local Science and Technology Development under Grant 2021L3010in part by Key provincial scientific and technological innovation projects under Grant 2021G02006.
文摘In this paper,we consider a reconfigurable intelligent surface(RIS)-assisted multiple-input multiple-output(MIMO)secure communication system,where only legitimate user's(Bob's)statistical channel state information(CSI)can be obtained at the transmitter(Alice),while eavesdropper's(Eve's)CSI is unknown.Firstly,the analytical expression of the achievable ergodic rate at Bob is obtained.Then,by exploiting Bob's statistical CSI,we jointly design the transmit covariance matrix at Alice and the phase shift matrix at the RIS to minimize the transmit power of the information signal under the quality-of-service(QoS)constraint of Bob.Finally,we propose an artificial noise(AN)-aided method without Eve's CSI to enhance the security of this system and use the residual power to design the transmit covariance for AN.Simulation results verify the convergence of the proposed method,and also show that there exists a trade-off between the secrecy rate and QoS of Bob.
基金supported by funding from the National Natural Science Foundation of China(NSFC)(Nos.51572192,51472179)General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)
文摘SnS nanoparticles/CNTs composite(SnS]CNTs composite)is synthesized by a facile one-pot solvothermal reaction.The structural characterizations reveal pure SnS nanoparticles with the size of less than 10 nm distribute on the surface of CNTs with the diameter of less than 20 nm.The SnS]CNTs composite electrode performs high reversible capacity and good cyclability(365 mAh/g at 50 mA/g after 50 cycles),which is superior to that of pure SnS electrode synthesized without the adding of CNTs(115.9 mAh/g at 50 mA/g after 50mA/cycles).Even increasing the current density to 500mA/g,the SnS]CNTs composite electrode still delivers a reversible capacity up to 210 mAh/g after 100 cycles,nearly two times higher than that of the pure SnS electrode(108 mAh/g after 100 cycles).The rate performance of the SnS/CNTs composite electrode is also better than that of pure SnS electrode at different current densities from 50mA/g to 800mA/g.The enhanced electrochemical performance of SnS/CNTs composite can be attributed to the adding of CNTs as a flexible and conductive structure supporter and the formation of SnS nanoparticles with small size.The SnS nanoparticles CNTs composite structure not only benefits for buffering the volume change during charge and discharge process,but also increases the surface area for sufficient electrode-electrolyte contacting,and shortens Na+diffusion length,which improves the conductivity and stability of active material and finally provides desirable electrochemical performance.
基金supported by the National Key Research and Development Program of China(Grant Nos.2021YFA1401800 and 2022YFA1403900)the National Natural Science Foundation of China(Grant Nos.U2032214,12122414,12104487,and 12004419)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)supported by the US Department of Energy,Office of Basic Energy Sciences(Grant No.DOE-sc0012704)。
文摘What factors fundamentally determine the value of superconducting transition temperature Tc in high temperature superconductors has been the subject of intense debate.Following the establishment of an empirical law known as Homes'law,there is a growing consensus in the community that the Tc value of the cuprate superconductors is closely linked to the superfluid density(ρ_(s))of its ground state and the conductivity(σ)of its normal state.However,all the data supporting this empirical law(ρ_(s)=AσT_(c))have been obtained from the ambientpressure superconductors.In this study,we present the first high-pressure results about the connection of the quantities ofρ_(s)andσwith T_(c),through the studies on the Bi_(1.74)Pb_(0.38)Sr_(1.88)CuO_(6+δ)and Bi_(2)Sr_(2)CaCu_(2)O_(8+δ),in which the value of their high-pressure resistivity(ρ=1/σ)is achieved by adopting our newly established method,while the quantity ofρs is extracted using Homes'law.We highlight that the Tc values are strongly linked to the joint response factors of magnetic field and electric field,i.e.,ρ_(s)andσ,respectively,implying that the physics determining T_(c)is governed by the intrinsic electromagnetic fields of the system.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.52073212,51772205,51772208)the General Program of Municipal Natural Science Foundation of Tianjin(Nos.17JCYBJC17000,17JCYBJC22700)。
文摘Although SiO_(2)-based anode is a strong competitor to supersede graphite anode for lithium-ion batteries,it still has problems such as low electrochemical activity, enormous loss of active lithium, and serious volume expansion. In order to solve these problems, we used a graphene network loaded with cobalt metal nanoparticles(rGO-Co) to coat SiO_(2) porous hollow spheres(SiO_(2)@rGO-Co). The construction of porous hollow structure and graphene network can shorten the lithium-ion(Li^(+)) diffusion distance and enhance the conductivity of the composite, which improves the electrochemical activity of SiO_(2) effectively. They also alleviate the volume expansion of the anode in the cycling process. Moreover,nano-scale cobalt metal particles dispersed on graphene catalyze the conversion reaction of SiO_(2) and activate the locked Li+in Li_(2)O through a reversible reaction, which improves the charge and discharge capacity of the anode. The capacity of SiO_(2)@rGO-Co reaches 370.4 m Ah/g after 100 cycles at 0.1 A/g,which is 6.19 times the capacity of pure SiO_(2)(59.8 mAh/g) under the same circumstance. What is more,its structure also exhibits excellent cycle stability, with a volume expansion rate of only 13.0% after 100 cycles at a current density of 0.1 A/g.
基金financial support by the National Natural Science Foundation of China (NSFC,Nos.52073212,51772205,51772208)General Program of Municipal Natural Science Foundation of Tianjin (Nos.17JCYBJC17000,17JCYBJC22700)。
文摘Bi draws increasing attention as anode materials for lithium-ion batteries and sodium-ion batteries due to its unique layered crystal structure,which is in favor of achieving fast ionic diffusion kinetics during cycling.However,the dramatic volume expansion upon lithiation/sodiation and an insufficient theoretical capacity of Bi greatly hinder its practical application.Herein,we report the Fe_(2 )O_(3) nanoparticle-pinning Bi-encapsulated carbon fiber composites through the electrospinning technique.The introduction of Fe_(2 )O_(3) nanoparticles can prevent the growth and aggregation of Bi nanoparticles during synthetic and cycling processes,re s pectively.Fe_(2)O_(3) with high specific capacity also contributes to the specific capacity of the composites.Consequently,the as-prepared Bi-Fe_(2)O_(3)/carbon fiber composite exhibits outstanding long-term stability,which delivers reversible capacities 504 and 175 mAh/g after1000 cycles at 1 A/g for lithium-ion and sodium-ion batteries,respectively.
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900,2021YFA1401800,2018YFA0704201,and 2023YFA1406103)the National Natural Science Foundation of China(Grant Nos.U2032214,12122414,12104487,and 12004419)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)。
文摘The stability of superconductivity in superconductors is widely recognized to be determined by various factors,including charge,spin,orbit,lattice,and other related degrees of freedom.Here,we report our findings on the pressure-induced coevolution of superconductivity and Hall coefficient in KCa_(2)Fe_(4)As_(24F_(2),an iron-based superconductor possessing a hybrid crystal structure combining KFe_(2)As_(2) and CaFeAsF.Our investigation,involving high-pressure resistance,Hall effect and x-ray diffraction(XRD) measurements,allows us to observe the connection of the superconductivity and Hall coefficient with the anisotropic lattice shrinkage.We find that its ambient-pressure tetragonal(T) phase presents a collapse starting at around 18 GPa,where the sign of the Hall coefficient(R_(H)) changes from positive to negative.Upon further compression,both superconducting transition temperature(T_(c)) and R_(H) exhibit a monotonous decrease.At around 41 GPa,the superconductivity is completely suppressed(T_(c)=0),where the parameter a begins to decline again and the Hall coefficient remains nearly unchanged.Our experiment results clearly demonstrate that the pressure-induced anisotropic lattice collapse plays a crucial role in tuning the interplay among multiple degrees of freedom in the superconducting system and,correspondingly,the stability of the superconductivity.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the National Natural Science Foundation of China(Grant Nos.U2032214,12122414,12104487,and 12004419)+2 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)supports from the Youth Innovation Promotion Association of the CAS(Grant No.2019008)the China Postdoctoral Science Foundation(Grant No.E0BK111)。
文摘We report the observation of a magnetic transition at the temperature about 56 K,through the high-pressure heat capacity and magnetic susceptibility measurements on the samples that have been claimed to be a nearroom-temperature superconductor[Dasenbrock-Gammon et al.Nature 615,244(2023)].Our results show that this magnetic phase is robust against pressure up to 4.3 GPa,which covers the critical pressure of boosting the claimed superconductivity.
基金supported by the National Key Research and Development Program of China(Grant Nos.2022YFA1403900 and 2021YFA1401800)the NSF of China(Grant Nos.U2032214 and 12104487).
文摘The measurement of resistivity in a compressed material within a diamond anvil cell presents significant challenges.The high-pressure exper-imental setup makes it difficult to directly measure the size changes induced by pressure in the three crystallographic directions of the sample.In this study,we introduce a novel and effective method that addresses these technical challenges.This method is anticipated to offer a valuable foundation for high-pressure investigations on quantum materials,particularly those with anisotropic layered structures.
基金supported by the National Key Research and Development Program of China(Grant No.2021YFA1401800 and 2022YFA1403900)the NSF of China(Grant Numbers Grants No.12122414,12474054,U2032214 and 12122405)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB25000000)the Fundamental Research Funds for the Central Universities,China.
文摘The studies on superconductors under extreme conditions offer valuable insights for assessing their potential in new applications.Nb_(3)Sn,an intermetallic alloy with an A15 structure,is a key commercial superconductor known for its high critical current and magnetic field tolerance.Here,we systematically investigated the physical properties of Nb_(3)Sn under high pressures.Our findings reveal that superconductivity in Nb_(3)Sn remains robust up to∼142 GPa,demonstrating remarkable stability despite a gradual suppression of��c with increasing pressure.First-principles calculations indicate that the pressure-dependent superconducting behavior is primarily driven by variations in the density of states of Nb’s d-electrons,particularly contributions from the d_(x^(2)-y^(2)) and d_(z^(2)) orbitals.Furthermore,we predict the potential for synthesizing Nb_(3)Sn films and demonstrate that biaxial strain induced by suitable substrates can preserve their superconducting properties.This comprehensive study not only enhances our understanding of Nb_(3)Sn’s superconducting mechanism under high pressure but also opens new avenues for its application in advanced superconducting technologies.
