Antimony(Sb) is an attractive cathode for liquid metal batteries(LMBs) because of its high theoretical voltage and low cost.The main obstacles associated with the Sb-based cathodes are unsatisfactory energy density an...Antimony(Sb) is an attractive cathode for liquid metal batteries(LMBs) because of its high theoretical voltage and low cost.The main obstacles associated with the Sb-based cathodes are unsatisfactory energy density and poor rate-capability.Herein,we propose a novel Sb_(64)Cu_(36)cathode that effectively tackles these issues.The Sb_(64)Cu_(36)(melting point:525℃) cathode presents a novel lithiation mechanism involving sequentially the generation of Li_(2)CuSb,the formation of Li_(3)Sb,and the conversion reaction of Li_(2)CuSb to Li_(3)Sb and Cu.The generated intermetallic compounds show a unique microstructure of the upper floated Li_(2)CuSb layer and the below cross-linked structure with interpenetrated Li_(2)CuSb and Li_(3)Sb phases.Compared with Li_(3)Sb,the lower Li migration energy barrier(0.188 eV) of Li_(2)CuSb significantly facilitates the lithium diffusion across the intermediate compounds and accelerates the reaction kinetics.Consequently,the Li‖Sb_(64)Cu_(36)cell delivers a more excellent electrochemical performance(energy density:353 W h kg^(-1)at 0.4 A cm^(-2);rate capability:0.59 V at 2.0 A cm^(-2)),and a much lower energy storage cost of only 38.45 $ kW h^(-1)than other previously reported Sb-based LMBs.This work provides a novel cathode design concept for the development of high-performance LMBs in applications for large-scale energy storage.展开更多
In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics,herein,2 D meshlike vert...In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics,herein,2 D meshlike vertical structures(NiCo_2 S_4@Ni(OH)_2) with a high mass loading of 2.17 mg cm^(-2) and combined merits of both 1 D nanowires and 2 D nanosheets are designed for fabricating flexible hybrid supercapacitors.Particularly,the seamlessly interconnected NiCo_2 S_4 core not only provides high capacity of 287.5 μAh cm^(-2) but also functions as conductive skeleton for fast electron transport;Ni(OH)_2 sheath occupying the voids in NiCo_2 S_4 meshes contributes extra capacity of 248.4 μAh cm^(-2);the holey features guarantee rapid ion diffusion along and across NiCO_2 S_4@Ni(OH)_2 meshes.The resultant flexible electrode exhibits a high areal capacity of 535.9 μAh cm^(-2)(246.9 mAh g^(-1)) at 3 mA cm^(-2) and outstanding rate performance with 84.7% retention at 30 mA cm^(-2),suggesting efficient utilization of both NiCo_2 S_4 and Ni(OH)_2 with specific capacities approaching to their theoretical values.The flexible solid-state hybrid device based on NiCo_2 S_4@Ni(OH)_2 cathode and Fe_2 O_3 anode delivers a high energy density of 315 μWh cm^(-2) at the power density of 2.14 mW cm^(-2) with excellent electrochemical cycling stability.展开更多
Due to the abundant sodium reserves and high safety,sodium ion batteries(SIBs)are foreseen a promising future.While,hard carbon materials are very suitable for the anode of SIBs owing to their structure and cost advan...Due to the abundant sodium reserves and high safety,sodium ion batteries(SIBs)are foreseen a promising future.While,hard carbon materials are very suitable for the anode of SIBs owing to their structure and cost advantages.However,the unsatisfactory initial coulombic efficiency(ICE)is one of the crucial blemishes of hard carbon materials and the slow sodium storage kinetics also hinders their wide application.Herein,with spherical nano SiO_(2)as pore-forming agent,gelatin and polytetrafluoroethylene as carbon sources,a multi-porous carbon(MPC)material can be easily obtained via a co-pyrolysis method,by which carbonization and template removal can be achieved synchronously without the assistance of strong acids or strong bases.As a result,the MPC anode exhibited remarkable ICE of 83%and a high rate capability(208 m Ah/g at 5 A/g)when used in sodium-ion half cells.Additionally,coupling with Na3V2(PO4)3as the cathode to assemble full cells,the as-fabricated MPC//NVP full cell delivered a good rate capability(146 m Ah/g at 5 A/g)as well,implying a good application prospect the MPC anode has.展开更多
An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-...An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-drying and annealing.The intimately coupled Nb_(2)C/rGO hybrid aerogel combines the advantages of large specific surface area and rich 3D interconnected porous structure of aerogel as well as high conductivity and low potassium diffusion energy barrier of Nb_(2)C,which not only effectively prevents the self-restacking of Nb2C nanosheets to allow more active sites exposed and accommodate the volume change during the charge/discharge process,but also increases the accessibility of electrolyte and promotes the rapid transfer of ions/electrons.As a result,Nb_(2)C/rGO-2 as the anode of potassium ion batteries(KIBs)delivers a large reversible specific capacity(301.7 mAh·g^(−1)after 500 cycles at 2.0 A·g^(−1)),an ultrahigh rate capability(155.5 mAh·g^(−1)at 20 A·g^(−1)),and an excellent long-term large-current cycle stability(198.8 mAh·g^(−1)after 1,000 cycles at 10 A·g^(−1),with a retention of 83.3%).Such a high-level electrochemical performance,especially the ultrahigh rate capability,is the best among transition metal carbides and nitride(MXene)-based materials reported so far for KIBs.The diffusion kinetics of K+is investigated thoroughly,and the synergetic charge–discharge mechanism and the structure–performance relationship of Nb_(2)C/rGO are revealed explicitly.The present work provides a good strategy to solve the self-restacking problem of two-dimensional materials and also enlarges the potential applications of MXenes.展开更多
The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structura...The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structural instability.Herein,Pr^(3+),a large radius ion is introduced to single-crystal LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2)to enhance Li^(+)conductivity and structural stability.With 0.4%Pr doping,the Li(Ni_(0.5)Mn_(0.3)Co_(0.2))_(0.996)Pr_(0.004)O_(2)cathode displays a capacity retention of 79.72%at 10 C,and a 98.17%capacity retention after 50 cycles at 25°C and 96.3%capacity retention after 50 cycles at 55°C within a 3.0–4.5 V voltage window.Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li^(+)on the surface of LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2).The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling.In addition,differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.展开更多
MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors(MSCs).Despite its superior electrochemical performance,only a few studies have reported MXene-based ultrahigh-rate(...MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors(MSCs).Despite its superior electrochemical performance,only a few studies have reported MXene-based ultrahigh-rate(>1000 mV s^(−1))on-paper MSCs,mainly due to the reduced electrical conductance of MXene films deposited on paper.Herein,ultrahigh-rate metal-free on-paper MSCs based on heterogeneous MXene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)-stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing.With a footprint area of only 20 mm^(2),the on-paper MSCs exhibit excellent high-rate capacitive behavior with an areal capacitance of 5.7 mF cm^(−2)and long cycle life(>95%capacitance retention after 10,000 cycles)at a high scan rate of 1000 mV s^(−1),outperforming most of the present on-paper MSCs.Furthermore,the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal-free on-paper MSC arrays,which can also be simultaneously charged/discharged at 1000 mV s^(−1),showing scalable capacitive performance.The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on-paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics.展开更多
The capability of fast charge and fast discharge is highly desirable for the electrode materials used in supercapacitors and lithium ion batteries.In this article,we report a simple strategy to considerably improve th...The capability of fast charge and fast discharge is highly desirable for the electrode materials used in supercapacitors and lithium ion batteries.In this article,we report a simple strategy to considerably improve the high rate capability of Co_(3)O_(4)nanowire array electrodes by uniformly loading Ag nanoparticles onto the surfaces of the Co_(3)O_(4)nanowires via the silver-mirror reaction.The highly electrically conductive silver nanoparticles function as a network for the facile transport of electrons between the current collectors(Ti substrates)and the Co_(3)O_(4)active materials.High capacity as well as remarkable rate capability has been achieved through this simple approach.Such novel Co_(3)O_(4)-Ag composite nanowire array electrodes have great potential for practical applications in pseudo-type supercapacitors as well as in lithium ion batteries.展开更多
High energy density and enhanced rate capability are highly sought-after for supercapacitors in today's mobile world.In this work,polyaniline/titanium carbide(MXene)(PANI/Ti3C2Tx)nanohybrid is synthesized through ...High energy density and enhanced rate capability are highly sought-after for supercapacitors in today's mobile world.In this work,polyaniline/titanium carbide(MXene)(PANI/Ti3C2Tx)nanohybrid is synthesized through a facile and cost-effective self-assembly of.one-dimensional(10)PANI nanofibers and two-dimensional(20)Ti3C2Tx nanosheets.PANl!Ti3C2Tx delivers greatly improved specific capacitance,ultrahigh rate capability(67%capacitance retention from 1 to 100 A·g^(-1))as well as good cycle stability.Electrochemical kinetic analysis reveals that PANI/Ti3C2Tx is featured with surface capacitance-dominated process and has a quasi-reversible kinetics at high scan rates,giving rise to an ultrahigh rate capability.By using PANl!Ti3C2Tx as positive electrode,an 1.8 V aqueous asymmetric supercapacitor(ASC)is successfully assembled,showing a maximum energy density of 50.8 Wh·kg^(-1)·(at 0.9 kW-kg-1)and a power density of 18 kW·kg^(-1)(at 26 Wh·kg^(-1)).Moreover,an 3.0 V organic ASC is also elaborately fabricated,·by using PANI/Ti3C2Tx,achieving an ultrahigh energy density of 67.2 Wh·kg^(-1)(at 1.5 kW·kg^(-1))and a power density of 30 kW·kg^(-1)·(at 26.8 Wh·kg^(-1)).The present work not only improves fundamental understanding of the structure-property relationship towards ultrahigh rate capability electrode materials,but also provides valuable guideline for the rational design of high-performance:energy storage devices with both high energy and power densities.展开更多
Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries(SIBs).However,realizing the orientated growth and u...Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries(SIBs).However,realizing the orientated growth and uniform distribution of the heterostructure is still a great challenge.Herein,the regulated novel CoSe_(2)/NiSe_(2)heterostructure confined in N-doped carbon nanofibers(CoSe_(2)/NiSe_(2)@N-C)are prepared by using Co/Ni-ZIF template,in which,the CoSe_(2)/NiSe_(2)heterostructures realize uniform distribution on a micro level.Benefiting from the unique heterostructure and N-doped carbon nanofibers,the CoSe_(2)/NiSe_(2)@N-C deliveries superior rate capability and durable cycle lifespan with a reversible capacity of 400.5 mA h g^(-1)after 5000 cycles at 2 A g^(-1).The Na-ion full battery with CoSe_(2)/NiSe_(2)@N-C anode and layered oxide cathode displays a remarkable energy density of 563 W h kg^(-1)with 241.1 W kg^(-1)at 0.1 A g^(-1).The theoretical calculations disclose that the periodic and directional built-in electric-field along with the heterointerfaces of CoSe_(2)/NiSe_(2)@N-C can accelerate electrochemical reaction kinetics.The in(ex)situ experimental measurements reveal the reversible conversion reaction and stable structure of CoSe_(2)/NiSe_(2)@N-C during Na+insertion/extraction.The study highlights the potential ability of precisely controlled heterostructure to stimulate the electrochemical performances of advanced anode for SIBs.展开更多
In this work,we have prepared the hierarchically nanostructured core–shell NiCo layered double hydroxide(NiCo-LDH)nanosheets-and ZnFe_(2)O_(4) nanocubes-decorated polyacrylonitrile(PAN)/pitch-based carbon nanofibers(...In this work,we have prepared the hierarchically nanostructured core–shell NiCo layered double hydroxide(NiCo-LDH)nanosheets-and ZnFe_(2)O_(4) nanocubes-decorated polyacrylonitrile(PAN)/pitch-based carbon nanofibers(PPCNs)webs(NiCo-LDH@PPCNs as cathode and ZnFe_(2)O_(4)@PPCNs as anode materials)with the bonded network structure by a facile and scalable hydrothemal method.Herein,the low-cost pitch with lower softening point(~90℃)as co-precursor was utilized to produce the PAN/pitch-based carbon nanofibers(PPCNs)with enhanced electrical conductivity.The obtained PPCNs with pitch content of 30%(PP30CNs)electrode material delivered higher specific capacitance(~67 F g^(-1))than that(~48 F g^(-1))of the PAN-based carbon nanofibers(PCNs)at 1 A g^(-1),due to the increased electrical conductivity and lower interfacial charge transfer resistance(RCT)of~0.16 U.Further,the NiCo-LDH-decorated PP30CNs(NiCoLDH@PP30CNs)as cathode material showed superior specific capacitance of 1162 F g^(-1) at 1.0 A g^(-1) and ultra-high retention rate of 91.56%at 10 A g^(-1).The ZnFe_(2)O_(4)@PP30CNs as anode material also showed higher specific capacitance of 282 F g^(-1) at 1 A g^(-1) and good rate capability with capacitance retention of 56.73%at 10 A g^(-1).The as-fabricated asymmetric NiCo-LDH@PP30CNs//ZnFe_(2)O_(4)@PP30CNs hybrid supercapacitor device delivered a specific capacitance of~98 F g^(-1) at 1 A g^(-1) and excellent capacitance retention of~88%after 5000 charge–discharge cycles.展开更多
Lithium ion batteries(LIBs)have been widely used in portable and smart devices because of their high energy densities,long cycle life and environmental friendliness.In order to meet the evergrowing demand for human-be...Lithium ion batteries(LIBs)have been widely used in portable and smart devices because of their high energy densities,long cycle life and environmental friendliness.In order to meet the evergrowing demand for human-beings utilizing electronic devices,electric vehicles and energy storage grids.展开更多
Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Sca...Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy (SEM) investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared LiMn2O4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that LiMn2O4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than LiMn2O4 solid microspheres and LiMn2O4 hollow microspheres with thick wall. The LiMn2O4 hollow microspheres with thin wall have discharge capacity of 132.7 mA.h-g^-1 at C/10 (14.8 mA.g^-1) in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 mAh-gq at a high rate of 5C. The apparent lithium-ion diffusion coefficient (Dapp) of as-prepared LiMn2O4 determined by capacity intermittent titration technique (CITT) varies from 10-11 to 10-8.5 cm2.s^-1 showing a regular "W" shape curve plotted with test voltages. The D app of LiMn2O4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of LiMn2O4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.展开更多
NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion(MOF-C) technique, for use as an anode material in rechargeable lithium ion batteries(LIBs)...NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion(MOF-C) technique, for use as an anode material in rechargeable lithium ion batteries(LIBs). The structural and electronic properties of these nanoparticles are studied using various techniques, including powder X-ray diffraction(PXRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), and N_2 adsorption/desorption studies. The as-synthesized NiO nanoparticles sustained reversible stable capacities of 748 and 410 mAh/g at applied current densities of 500 and 1000 m A/g, respectively, after 100 cycles. Furthermore, the anode displays a notable rate capability, achieving a stable capacity of ~200 mAh/g at a high current density of10 A/g. These results indicate that the size of the NiO nanoparticles and their high surface area influence their electrochemical properties. Specifically, this combustion strategy is clearly favorable for improving the cyclability and rate capability of various metal oxides in rechargeable battery electrodes.展开更多
Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 m Ah g^(-1));however,its lower rate capability and cyclability limit its applicati...Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 m Ah g^(-1));however,its lower rate capability and cyclability limit its applications.Structural distortion at a weak N-coordinated crystal field during cycling disintegrates Co,yielding an irreversible reaction.Different Zn amounts ranging 0–1 were added to the Co site to suppress the structural irreversibility of CoHCF,yielding Co_(1-x)Zn_(x)HCF powder;this Zn (x≤0.09) addition reduced the powder’s dimension because the lower four coordination of Zn–N,not the six coordination of Co–N,limits the powder growth.Simultaneously,a small lattice parameter and interaxial angle (~90°) are obtained,implying that a narrower Co_(1-x)Zn_(x)HCF inner structure is formed to accommodate Na ions.Moreover,the electronic conductivity of Co_(1-x)Zn_(x)HCF gradually increased within 0–0.09 range.A smaller particle size with a high surface area leads to a near-surface-limited redox process,similar to a capacitive reaction.Both the surface-limited reaction and electronic conductivity enhances the reversibility due to the smaller charge transfer resistance at the electrode/electrolyte interface caused by Zn addition.Replacing redox-active Co with non-active Zn amount of 0.07 (Co_(1-x)Zn_(x)HCF) slightly reduces the specific capacity from 127 to 119 mAh g^(-1)at 0.1 A g^(-1)due to the shrunken Co charging sites.Rate performance is enhanced by compromising the capacity and reduced distortion,resulting in 81%retention at a 20-times-faster charging rate.Notably,the Co_(1-x)Zn_(x)HCF sample exhibited the good stability while preserving 74%of the initial capacity at 0.5 A g^(-1)after 200 cycles.展开更多
As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-string...As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.展开更多
Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has received considerable interest as a promising cathode material for sodium-ion batteries because of its high working voltage and good structural/thermal stability.However,the slu...Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has received considerable interest as a promising cathode material for sodium-ion batteries because of its high working voltage and good structural/thermal stability.However,the sluggish electrode reaction resulting from its low intrinsic electronic conductivity significantly restricts its electrochemical performance and thus its practical application.Herein,Nb-doped Na_(3)V_(2-x)Nb_(x)(PO_(4))_(2)O_(2)F/graphene(rGO)composites(x=0,0.05,0.1)were prepared using a solvothermal method followed by calcination.Compared to the un-doped NVPOF/r GO,doping V-site with high-valence Nb element(Nb^(5+))(Na_(3)V_(1.95)Nb_(0.05)(PO_(4))_(2)O_(2)F/r GO(NVN05POF/rGO))can result in the generated V4^(+)/V3^(+)mixed-valence,ensuring the lower bandgap and thus the increased intrinsic electronic conductivity.Besides,the expanded lattice space favors the Na^(+)migration.With the structure feature where NVN05POF particles are attached to the rGO sheets,the electrode reaction kinetics is further accelerated owing to the well-constructed electron conductive network.As a consequence,the as-prepared NVN05POF/r GO sample exhibits a high specific capacity of~72 m Ah·g^(-1)at 10C(capacity retention of 65.2%(vs.0.5C))and excellent long-term cycling stability with the capacity fading rate of~0.099%per cycle in 500 cycles at 5C.展开更多
Micro-sized silicon anodes have shown much promise in large-scale industrial production of high-energy lithium batteries.However,large volume change(>300%)of silicon anodes causes severe particle pulverization and ...Micro-sized silicon anodes have shown much promise in large-scale industrial production of high-energy lithium batteries.However,large volume change(>300%)of silicon anodes causes severe particle pulverization and the formation of unstable solid electrolyte interphases during cycling,leading to rapid capacity decay and short cycle life of lithium-ion batteries.When addressing such issues,binder plays key roles in obtaining good structural integrity of silicon anodes.Herein,we report a biopolymer composite binder composed of rigid poly(acrylic acid)(PAA)and flexible silk fibroin(SF)tailored for micro-sized silicon anodes.The PAA/SF binder shows robust gradient binding energy via chemical interactions between carboxyl and amide groups,which can effectively accommodate large volume change of silicon.This PAA/SF binder also shows much stronger adhesion force and improved binding towards high-surface/defective carbon additives,resulting in better electrochemical stability and higher coulombic efficiency,than conventional PAA binder.As such,micro-sized silicon/carbon anodes fabricated with novel PAA/SF binder exhibit much better cyclability(up to 500 cycles at 0.5 C)and enhanced rate capability compared with conventional PAA-based anodes.This work provides new insights into the design of functional binders for high-capacity electrodes suffering from large volume change for the development of nextgeneration lithium batteries.展开更多
The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional...The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional to the molar ratio of F to C atoms(F/C).In this study,B-doped graphene(BG)is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_(x).The B-doping enhances the F/C ratio of CF_(x)without hindering the electrochemical activity of the C–F bond.During the fluorination process,B-containing functional groups are removed from the graphene lattice.This facilitates the formation of a defect-rich graphene matrix,which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li+storage.The prepared CF_(x)exhibits the maximum specific capacity of 1204 mAh g^(−1),which is 39.2%higher than that of CF_(x)obtained directly from graphene oxide(without B-doping).An unprecedented energy density of 2974 Wh kg^(−1)is achieved for the asprepared CF_(x)samples,which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite(2180 Wh kg^(−1)).Therefore,this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_(x)cathodes for practical applications.展开更多
Surface modification of graphite anode with electroactive matters has been proven of a more practical strategy in enhancing the performance of Li-ion batteries than exploring alternative novel anode materials.Herein,r...Surface modification of graphite anode with electroactive matters has been proven of a more practical strategy in enhancing the performance of Li-ion batteries than exploring alternative novel anode materials.Herein,rutile TiNbO_(4-x) nanoparticles with a tunnel structure are employed as multifunctional decoration substances in combination with a carbon coating layer to improve the rate and cycle properties of mesocarbon microbeads(MCMBs).As compared to pristine MCMB,the Li^(+)diffusion coefficients of the composite anodes are enhanced due to the synergistic effect of TiNbO_(4-x)@C.Meanwhile,the overcharge and voltage polarization of the composite anodes at high rate are obviously minimized due to the current sharing effect of the high-potential TiNbO_(4-x).Moreover,the amorphous Li_(y)TiNbO_(4-x) converted from TiNbO_(4-x) in the initial lithiation process can deliver pseudocapacitive capacity to the composite anodes from the second cycle.All of these functions of TiNbO_(4-x)@Ccoating layer have directly contributed to the improved rate and cycle performance of the MCMB/TiNbO_(4-x)@C composite anodes.The one containing 12.0 wt%TiNbO_(4-x) exhibits a high reversible specific capacity of 118 m Ah·g^(-1)at 10C(1C=372 m A·g^(-1)),together with a high capacity retention of 90.9%after 300 cycles at 3C,which are all much superior to those of pristine MCMB.展开更多
A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for...A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for lithium-ion batteries, Li0.95Fe0.95Ti0.05PO4 exhibited improved rate capability.展开更多
基金financially supported by the National Natural Science Foundation of China(52074023)the Beijing Natural Science Foundation(2222062)+1 种基金the National Key R&D Program of China(2018YFB0905600)the Interdisciplinary Research Project for Young Teachers of USTB(Fundamental Research Funds for the Central Universities)(FRF-IDRY-21-023)。
文摘Antimony(Sb) is an attractive cathode for liquid metal batteries(LMBs) because of its high theoretical voltage and low cost.The main obstacles associated with the Sb-based cathodes are unsatisfactory energy density and poor rate-capability.Herein,we propose a novel Sb_(64)Cu_(36)cathode that effectively tackles these issues.The Sb_(64)Cu_(36)(melting point:525℃) cathode presents a novel lithiation mechanism involving sequentially the generation of Li_(2)CuSb,the formation of Li_(3)Sb,and the conversion reaction of Li_(2)CuSb to Li_(3)Sb and Cu.The generated intermetallic compounds show a unique microstructure of the upper floated Li_(2)CuSb layer and the below cross-linked structure with interpenetrated Li_(2)CuSb and Li_(3)Sb phases.Compared with Li_(3)Sb,the lower Li migration energy barrier(0.188 eV) of Li_(2)CuSb significantly facilitates the lithium diffusion across the intermediate compounds and accelerates the reaction kinetics.Consequently,the Li‖Sb_(64)Cu_(36)cell delivers a more excellent electrochemical performance(energy density:353 W h kg^(-1)at 0.4 A cm^(-2);rate capability:0.59 V at 2.0 A cm^(-2)),and a much lower energy storage cost of only 38.45 $ kW h^(-1)than other previously reported Sb-based LMBs.This work provides a novel cathode design concept for the development of high-performance LMBs in applications for large-scale energy storage.
基金supported by the National Natural Science Foundation of China (Nos. 21975123, 61704076)the Natural Science Basic Research Program of Shaanxi (No. 2020JM-092)+2 种基金the Natural Science Foundation of Jiangsu Province (No. BK20171018)the Six Talent Peaks Project in Jiangsu Province (No. XCL-024)the Fundamental Research Funds for the Central Universities。
文摘In order to balance electrochemical kinetics with loading level for achieving efficient energy storage with high areal capacity and good rate capability simultaneously for wearable electronics,herein,2 D meshlike vertical structures(NiCo_2 S_4@Ni(OH)_2) with a high mass loading of 2.17 mg cm^(-2) and combined merits of both 1 D nanowires and 2 D nanosheets are designed for fabricating flexible hybrid supercapacitors.Particularly,the seamlessly interconnected NiCo_2 S_4 core not only provides high capacity of 287.5 μAh cm^(-2) but also functions as conductive skeleton for fast electron transport;Ni(OH)_2 sheath occupying the voids in NiCo_2 S_4 meshes contributes extra capacity of 248.4 μAh cm^(-2);the holey features guarantee rapid ion diffusion along and across NiCO_2 S_4@Ni(OH)_2 meshes.The resultant flexible electrode exhibits a high areal capacity of 535.9 μAh cm^(-2)(246.9 mAh g^(-1)) at 3 mA cm^(-2) and outstanding rate performance with 84.7% retention at 30 mA cm^(-2),suggesting efficient utilization of both NiCo_2 S_4 and Ni(OH)_2 with specific capacities approaching to their theoretical values.The flexible solid-state hybrid device based on NiCo_2 S_4@Ni(OH)_2 cathode and Fe_2 O_3 anode delivers a high energy density of 315 μWh cm^(-2) at the power density of 2.14 mW cm^(-2) with excellent electrochemical cycling stability.
基金financially supported by the Start-up Funding of Jinan University(No.88016105)the Discipline Construction Outstanding Young Backbone Project(No.12819023)+3 种基金the Fundamental Research Funds for the Central Universities(No.21620317)the Guangdong Basic and Applied Basic Research Foundation(Nos.2020A1515110611 and 2021A1515010362)the Guangzhou Basic and Applied Basic Research Foundation(No.202102020995)supported by the Open Fund of Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications(No.2020B121201005)。
文摘Due to the abundant sodium reserves and high safety,sodium ion batteries(SIBs)are foreseen a promising future.While,hard carbon materials are very suitable for the anode of SIBs owing to their structure and cost advantages.However,the unsatisfactory initial coulombic efficiency(ICE)is one of the crucial blemishes of hard carbon materials and the slow sodium storage kinetics also hinders their wide application.Herein,with spherical nano SiO_(2)as pore-forming agent,gelatin and polytetrafluoroethylene as carbon sources,a multi-porous carbon(MPC)material can be easily obtained via a co-pyrolysis method,by which carbonization and template removal can be achieved synchronously without the assistance of strong acids or strong bases.As a result,the MPC anode exhibited remarkable ICE of 83%and a high rate capability(208 m Ah/g at 5 A/g)when used in sodium-ion half cells.Additionally,coupling with Na3V2(PO4)3as the cathode to assemble full cells,the as-fabricated MPC//NVP full cell delivered a good rate capability(146 m Ah/g at 5 A/g)as well,implying a good application prospect the MPC anode has.
基金the National Natural Science Foundation of China(No.21773116)and Modern Analysis Center of Nanjing University.
文摘An effective method is designed to construct three-dimensional(3D)Nb_(2)C/reduced graphene oxide(rGO)hybrid aerogels through a low-temperature graphene oxide(GO)-assisted hydrothermal self-assembly followed by freeze-drying and annealing.The intimately coupled Nb_(2)C/rGO hybrid aerogel combines the advantages of large specific surface area and rich 3D interconnected porous structure of aerogel as well as high conductivity and low potassium diffusion energy barrier of Nb_(2)C,which not only effectively prevents the self-restacking of Nb2C nanosheets to allow more active sites exposed and accommodate the volume change during the charge/discharge process,but also increases the accessibility of electrolyte and promotes the rapid transfer of ions/electrons.As a result,Nb_(2)C/rGO-2 as the anode of potassium ion batteries(KIBs)delivers a large reversible specific capacity(301.7 mAh·g^(−1)after 500 cycles at 2.0 A·g^(−1)),an ultrahigh rate capability(155.5 mAh·g^(−1)at 20 A·g^(−1)),and an excellent long-term large-current cycle stability(198.8 mAh·g^(−1)after 1,000 cycles at 10 A·g^(−1),with a retention of 83.3%).Such a high-level electrochemical performance,especially the ultrahigh rate capability,is the best among transition metal carbides and nitride(MXene)-based materials reported so far for KIBs.The diffusion kinetics of K+is investigated thoroughly,and the synergetic charge–discharge mechanism and the structure–performance relationship of Nb_(2)C/rGO are revealed explicitly.The present work provides a good strategy to solve the self-restacking problem of two-dimensional materials and also enlarges the potential applications of MXenes.
基金Financial supports from National Natural Science Foundation of China(51872027)Beijing Natural Science Foundation(Z200011)are gratefully acknowledged。
文摘The massive application of single crystal(SC)ternary cathode material LiNi_(1-x-y)Mn_(x)Co_(y)O_(2)is largely restricted by the unsatisfactory rate capability which is caused by the sluggish Li+diffusion and structural instability.Herein,Pr^(3+),a large radius ion is introduced to single-crystal LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2)to enhance Li^(+)conductivity and structural stability.With 0.4%Pr doping,the Li(Ni_(0.5)Mn_(0.3)Co_(0.2))_(0.996)Pr_(0.004)O_(2)cathode displays a capacity retention of 79.72%at 10 C,and a 98.17%capacity retention after 50 cycles at 25°C and 96.3%capacity retention after 50 cycles at 55°C within a 3.0–4.5 V voltage window.Electrochemical impedance spectroscopy confirms that the Pr doping can effectively lower the charge-transfer resistance and facilitate the transportation of Li^(+)on the surface of LiNi_(0.5)Mn_(0.3)Co_(0.2)O_(2).The Direct current internal resistance result implies that the structure of the Pr-doped cathode particles is more stable during cycling.In addition,differential scanning calorimetry measurements measurement combined with in situ X-ray diffraction confirms the thermo-stabilization effect of the Pr dopant.
基金China Scholarship Council,Grant/Award Number:201906230359Vetenskapsrådet,Grant/Award Number:2019-04731+4 种基金HORIZON EUROPE Digital,Industry and Space,Grant/Award Number:101070255Stiftelsen Olle Engkvist Byggmästare,Grant/Award Number:2014/799Swedish National Infrastructure in Advanced Electron Microscopy,Grant/Award Numbers:2021-00171,RIF21-0026KTH Energy Platform,Grant/Award Number:HT2021Swedish Foundation for Strategic Research,Grant/Award Number:STP19-0014。
文摘MXene is a promising energy storage material for miniaturized microbatteries and microsupercapacitors(MSCs).Despite its superior electrochemical performance,only a few studies have reported MXene-based ultrahigh-rate(>1000 mV s^(−1))on-paper MSCs,mainly due to the reduced electrical conductance of MXene films deposited on paper.Herein,ultrahigh-rate metal-free on-paper MSCs based on heterogeneous MXene/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)-stack electrodes are fabricated through the combination of direct ink writing and femtosecond laser scribing.With a footprint area of only 20 mm^(2),the on-paper MSCs exhibit excellent high-rate capacitive behavior with an areal capacitance of 5.7 mF cm^(−2)and long cycle life(>95%capacitance retention after 10,000 cycles)at a high scan rate of 1000 mV s^(−1),outperforming most of the present on-paper MSCs.Furthermore,the heterogeneous MXene/PEDOT:PSS electrodes can interconnect individual MSCs into metal-free on-paper MSC arrays,which can also be simultaneously charged/discharged at 1000 mV s^(−1),showing scalable capacitive performance.The heterogeneous MXene/PEDOT:PSS stacks are a promising electrode structure for on-paper MSCs to serve as ultrafast miniaturized energy storage components for emerging paper electronics.
基金This work was jointly supported by the City University of Hong Kong(Project 7002465)the National Natural Science Foundation of China(No.21001117/B0107).
文摘The capability of fast charge and fast discharge is highly desirable for the electrode materials used in supercapacitors and lithium ion batteries.In this article,we report a simple strategy to considerably improve the high rate capability of Co_(3)O_(4)nanowire array electrodes by uniformly loading Ag nanoparticles onto the surfaces of the Co_(3)O_(4)nanowires via the silver-mirror reaction.The highly electrically conductive silver nanoparticles function as a network for the facile transport of electrons between the current collectors(Ti substrates)and the Co_(3)O_(4)active materials.High capacity as well as remarkable rate capability has been achieved through this simple approach.Such novel Co_(3)O_(4)-Ag composite nanowire array electrodes have great potential for practical applications in pseudo-type supercapacitors as well as in lithium ion batteries.
基金support of the National Natural Science Foundation of China(No.21773116)the Specialized Research Fund for the Doctoral Program of Higher Education(SRFDP,20130091110010)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK2011438)the National Science Fund for Talent Training in Basic Science(No.J1103310)the Modern Analysis Center of Nanjing University and the Program B for Outstanding PhD Candidate of Nanjing University.
文摘High energy density and enhanced rate capability are highly sought-after for supercapacitors in today's mobile world.In this work,polyaniline/titanium carbide(MXene)(PANI/Ti3C2Tx)nanohybrid is synthesized through a facile and cost-effective self-assembly of.one-dimensional(10)PANI nanofibers and two-dimensional(20)Ti3C2Tx nanosheets.PANl!Ti3C2Tx delivers greatly improved specific capacitance,ultrahigh rate capability(67%capacitance retention from 1 to 100 A·g^(-1))as well as good cycle stability.Electrochemical kinetic analysis reveals that PANI/Ti3C2Tx is featured with surface capacitance-dominated process and has a quasi-reversible kinetics at high scan rates,giving rise to an ultrahigh rate capability.By using PANl!Ti3C2Tx as positive electrode,an 1.8 V aqueous asymmetric supercapacitor(ASC)is successfully assembled,showing a maximum energy density of 50.8 Wh·kg^(-1)·(at 0.9 kW-kg-1)and a power density of 18 kW·kg^(-1)(at 26 Wh·kg^(-1)).Moreover,an 3.0 V organic ASC is also elaborately fabricated,·by using PANI/Ti3C2Tx,achieving an ultrahigh energy density of 67.2 Wh·kg^(-1)(at 1.5 kW·kg^(-1))and a power density of 30 kW·kg^(-1)·(at 26.8 Wh·kg^(-1)).The present work not only improves fundamental understanding of the structure-property relationship towards ultrahigh rate capability electrode materials,but also provides valuable guideline for the rational design of high-performance:energy storage devices with both high energy and power densities.
基金financially supported by the Natural Science Foundation of Shandong Province(ZR2021QB055,ZR2023MB017,ZR2022JQ10)the National Natural Science Foundation of China(21901146,220781792,22274083)。
文摘Constructing heterostructure is considered as an effective strategy to address the sluggish electronic and ionic kinetics of anode materials for sodium ion batteries(SIBs).However,realizing the orientated growth and uniform distribution of the heterostructure is still a great challenge.Herein,the regulated novel CoSe_(2)/NiSe_(2)heterostructure confined in N-doped carbon nanofibers(CoSe_(2)/NiSe_(2)@N-C)are prepared by using Co/Ni-ZIF template,in which,the CoSe_(2)/NiSe_(2)heterostructures realize uniform distribution on a micro level.Benefiting from the unique heterostructure and N-doped carbon nanofibers,the CoSe_(2)/NiSe_(2)@N-C deliveries superior rate capability and durable cycle lifespan with a reversible capacity of 400.5 mA h g^(-1)after 5000 cycles at 2 A g^(-1).The Na-ion full battery with CoSe_(2)/NiSe_(2)@N-C anode and layered oxide cathode displays a remarkable energy density of 563 W h kg^(-1)with 241.1 W kg^(-1)at 0.1 A g^(-1).The theoretical calculations disclose that the periodic and directional built-in electric-field along with the heterointerfaces of CoSe_(2)/NiSe_(2)@N-C can accelerate electrochemical reaction kinetics.The in(ex)situ experimental measurements reveal the reversible conversion reaction and stable structure of CoSe_(2)/NiSe_(2)@N-C during Na+insertion/extraction.The study highlights the potential ability of precisely controlled heterostructure to stimulate the electrochemical performances of advanced anode for SIBs.
基金supported by the National Research Foundation of Korea grant funded by the Korea government(MSIT)(No.2020R1A2C2012356)the National Research Foundation of Korea grant funded by the Korea government(MSIT)(2020R1I1A1A01073937).
文摘In this work,we have prepared the hierarchically nanostructured core–shell NiCo layered double hydroxide(NiCo-LDH)nanosheets-and ZnFe_(2)O_(4) nanocubes-decorated polyacrylonitrile(PAN)/pitch-based carbon nanofibers(PPCNs)webs(NiCo-LDH@PPCNs as cathode and ZnFe_(2)O_(4)@PPCNs as anode materials)with the bonded network structure by a facile and scalable hydrothemal method.Herein,the low-cost pitch with lower softening point(~90℃)as co-precursor was utilized to produce the PAN/pitch-based carbon nanofibers(PPCNs)with enhanced electrical conductivity.The obtained PPCNs with pitch content of 30%(PP30CNs)electrode material delivered higher specific capacitance(~67 F g^(-1))than that(~48 F g^(-1))of the PAN-based carbon nanofibers(PCNs)at 1 A g^(-1),due to the increased electrical conductivity and lower interfacial charge transfer resistance(RCT)of~0.16 U.Further,the NiCo-LDH-decorated PP30CNs(NiCoLDH@PP30CNs)as cathode material showed superior specific capacitance of 1162 F g^(-1) at 1.0 A g^(-1) and ultra-high retention rate of 91.56%at 10 A g^(-1).The ZnFe_(2)O_(4)@PP30CNs as anode material also showed higher specific capacitance of 282 F g^(-1) at 1 A g^(-1) and good rate capability with capacitance retention of 56.73%at 10 A g^(-1).The as-fabricated asymmetric NiCo-LDH@PP30CNs//ZnFe_(2)O_(4)@PP30CNs hybrid supercapacitor device delivered a specific capacitance of~98 F g^(-1) at 1 A g^(-1) and excellent capacitance retention of~88%after 5000 charge–discharge cycles.
基金financial support from the“Young Talent Fellowship”program through South China University of Technologythe Fundamental Research Funds for the Central Universities(2018JQ06)。
文摘Lithium ion batteries(LIBs)have been widely used in portable and smart devices because of their high energy densities,long cycle life and environmental friendliness.In order to meet the evergrowing demand for human-beings utilizing electronic devices,electric vehicles and energy storage grids.
基金Funded by the National Natural Science Foundation of China(Nos.20803056,11474226)the Fundamental Research Funds for the Central Universities(WUT:2015-IB-001,WUT:2016-IB-005)
文摘Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy (SEM) investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared LiMn2O4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that LiMn2O4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than LiMn2O4 solid microspheres and LiMn2O4 hollow microspheres with thick wall. The LiMn2O4 hollow microspheres with thin wall have discharge capacity of 132.7 mA.h-g^-1 at C/10 (14.8 mA.g^-1) in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 mAh-gq at a high rate of 5C. The apparent lithium-ion diffusion coefficient (Dapp) of as-prepared LiMn2O4 determined by capacity intermittent titration technique (CITT) varies from 10-11 to 10-8.5 cm2.s^-1 showing a regular "W" shape curve plotted with test voltages. The D app of LiMn2O4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of LiMn2O4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.
基金supported by National Research Foundation of Korea(NRF)grant funded by the Korean government(MSIP)(2014R1A2A1A10050821)
文摘NiO nanoparticles with average particles size of 30 nm are synthesized using a one-pot metal–organic framework-combustion(MOF-C) technique, for use as an anode material in rechargeable lithium ion batteries(LIBs). The structural and electronic properties of these nanoparticles are studied using various techniques, including powder X-ray diffraction(PXRD), transmission electron microscopy(TEM), scanning electron microscopy(SEM), X-ray photoelectron spectroscopy(XPS), and N_2 adsorption/desorption studies. The as-synthesized NiO nanoparticles sustained reversible stable capacities of 748 and 410 mAh/g at applied current densities of 500 and 1000 m A/g, respectively, after 100 cycles. Furthermore, the anode displays a notable rate capability, achieving a stable capacity of ~200 mAh/g at a high current density of10 A/g. These results indicate that the size of the NiO nanoparticles and their high surface area influence their electrochemical properties. Specifically, this combustion strategy is clearly favorable for improving the cyclability and rate capability of various metal oxides in rechargeable battery electrodes.
基金supported by the National Research Foundation of Korea (NRF) grant funded by the Korean government (Ministry of Science, ICT & Future Planning) (NRF-2020R1F1A1075601, NRF-2021R1A4A2001658)supported by the National Natural Science Foundation of China (51904059)+1 种基金the Fundamental Research Funds for the Central Universities (N182505036, N2002005)the Liao Ning Revitalization Talents Program (XLYC1807123)。
文摘Cobalt hexacyanoferrate (CoHCF) is a potential cathode for aqueous Na-ion batteries due to its high theoretical specific capacity (170 m Ah g^(-1));however,its lower rate capability and cyclability limit its applications.Structural distortion at a weak N-coordinated crystal field during cycling disintegrates Co,yielding an irreversible reaction.Different Zn amounts ranging 0–1 were added to the Co site to suppress the structural irreversibility of CoHCF,yielding Co_(1-x)Zn_(x)HCF powder;this Zn (x≤0.09) addition reduced the powder’s dimension because the lower four coordination of Zn–N,not the six coordination of Co–N,limits the powder growth.Simultaneously,a small lattice parameter and interaxial angle (~90°) are obtained,implying that a narrower Co_(1-x)Zn_(x)HCF inner structure is formed to accommodate Na ions.Moreover,the electronic conductivity of Co_(1-x)Zn_(x)HCF gradually increased within 0–0.09 range.A smaller particle size with a high surface area leads to a near-surface-limited redox process,similar to a capacitive reaction.Both the surface-limited reaction and electronic conductivity enhances the reversibility due to the smaller charge transfer resistance at the electrode/electrolyte interface caused by Zn addition.Replacing redox-active Co with non-active Zn amount of 0.07 (Co_(1-x)Zn_(x)HCF) slightly reduces the specific capacity from 127 to 119 mAh g^(-1)at 0.1 A g^(-1)due to the shrunken Co charging sites.Rate performance is enhanced by compromising the capacity and reduced distortion,resulting in 81%retention at a 20-times-faster charging rate.Notably,the Co_(1-x)Zn_(x)HCF sample exhibited the good stability while preserving 74%of the initial capacity at 0.5 A g^(-1)after 200 cycles.
基金This work was supported by Guangdong Basic and Applied Basic Research Foundation,China(No.2019A1515110980)research project from the National Natural Science Foundation of China(No.21361162004)China Scholarship Council,and CSIRO.We acknowledge Dr Yesim Gozukara,Dr Malisja de Vries,and Dr Yunxia Yang from CSIRO(Clayton)for their help with material characterization training.
文摘As promising anodes for sodium-ion batteries,metal sulfides ubiquitously suffer from low-rate and high-plateau issues,greatly hindering their application in full-cells.Herein,exemplifying carbon nanotubes(CNTs)-stringed metal sulfides superstructure(CSC)assembled by nano-dispersed SnS_(2) and CoS_(2) phases,cocktail mediation effect similar to that of high-entropy materials is initially studied in ether-based electrolyte to solve the challenges.The high nano-dispersity of metal sulfides in CSC anode underlies the cocktail-like mediation effect,enabling the circumvention of intrinsic drawbacks of different metal sulfides.By utilizing ether-based electrolyte,the reversibility of metal sulfides is greatly improved,sustaining a long-life effectivity of cocktail-like mediation.As such,CSC effectively overcomes low-rate flaw of SnS_(2) and highplateau demerit of CoS_(2),simultaneously realizes a high rate and a low plateau.In half-cells,CSC delivers an ultrahigh-rate capability of 327.6 mAh g^(−1) anode at 20 A g^(−1),far outperforming those of monometallic sulfides(SnS_(2),CoS_(2))and their mixtures.Compared with CoS_(2) phase and SnS_(2)/CoS_(2) mixture,CSC shows remarkably lowered average charge voltage up to ca.0.62 V.As-assembled CSC//Na1.5VPO4.8F0.7 full-cell shows a good rate capability(0.05~1.0 A g^(−1),120.3 mAh g^(−1) electrode at 0.05 A g^(−1))and a high average discharge voltage up to 2.57 V,comparable to full-cells with alloy-type anodes.Kinetics analysis verifies that the cocktail-like mediation effect largely boosts the charge transfer and ionic diffusion in CSC,compared with single phase and mixed phases.Further mechanism study reveals that alternative and complementary electrochemical processes between nano-dispersed SnS_(2) and CoS_(2) phases are responsible for the lowered charge voltage of CSC.This electrolyte/structure-dependent cocktail-like mediation effect effectively enhances the practicability of metal sulfide anodes,which will boost the development of high-rate/-voltage sodium-ion full batteries.
基金supported by the Interdisciplinary Research Project for Young Teachers of USTB (Fundamental Research Funds for the Central Universities) (No.FRFIDRY-21-023)the Beijing Natural Science Foundation (Nos.2194079 and 2222062)the National Natural Science Foundation of China (Nos.52074023 and 52102205)。
文摘Na_(3)V_(2)(PO_(4))_(2)O_(2)F(NVPOF)has received considerable interest as a promising cathode material for sodium-ion batteries because of its high working voltage and good structural/thermal stability.However,the sluggish electrode reaction resulting from its low intrinsic electronic conductivity significantly restricts its electrochemical performance and thus its practical application.Herein,Nb-doped Na_(3)V_(2-x)Nb_(x)(PO_(4))_(2)O_(2)F/graphene(rGO)composites(x=0,0.05,0.1)were prepared using a solvothermal method followed by calcination.Compared to the un-doped NVPOF/r GO,doping V-site with high-valence Nb element(Nb^(5+))(Na_(3)V_(1.95)Nb_(0.05)(PO_(4))_(2)O_(2)F/r GO(NVN05POF/rGO))can result in the generated V4^(+)/V3^(+)mixed-valence,ensuring the lower bandgap and thus the increased intrinsic electronic conductivity.Besides,the expanded lattice space favors the Na^(+)migration.With the structure feature where NVN05POF particles are attached to the rGO sheets,the electrode reaction kinetics is further accelerated owing to the well-constructed electron conductive network.As a consequence,the as-prepared NVN05POF/r GO sample exhibits a high specific capacity of~72 m Ah·g^(-1)at 10C(capacity retention of 65.2%(vs.0.5C))and excellent long-term cycling stability with the capacity fading rate of~0.099%per cycle in 500 cycles at 5C.
文摘Micro-sized silicon anodes have shown much promise in large-scale industrial production of high-energy lithium batteries.However,large volume change(>300%)of silicon anodes causes severe particle pulverization and the formation of unstable solid electrolyte interphases during cycling,leading to rapid capacity decay and short cycle life of lithium-ion batteries.When addressing such issues,binder plays key roles in obtaining good structural integrity of silicon anodes.Herein,we report a biopolymer composite binder composed of rigid poly(acrylic acid)(PAA)and flexible silk fibroin(SF)tailored for micro-sized silicon anodes.The PAA/SF binder shows robust gradient binding energy via chemical interactions between carboxyl and amide groups,which can effectively accommodate large volume change of silicon.This PAA/SF binder also shows much stronger adhesion force and improved binding towards high-surface/defective carbon additives,resulting in better electrochemical stability and higher coulombic efficiency,than conventional PAA binder.As such,micro-sized silicon/carbon anodes fabricated with novel PAA/SF binder exhibit much better cyclability(up to 500 cycles at 0.5 C)and enhanced rate capability compared with conventional PAA-based anodes.This work provides new insights into the design of functional binders for high-capacity electrodes suffering from large volume change for the development of nextgeneration lithium batteries.
基金financialy supported by the State Key Program of National Natural Science Foundation of China(no.52130303)the National Natural Science Foundation of China(no.51773147 and 51973151)
文摘The enhancement of the fluorination degree of carbon fluorides(CF_(x))compounds is the most effective method to improve the energy densities of Li/CF_(x)batteries because the specific capacity of CF_(x)is proportional to the molar ratio of F to C atoms(F/C).In this study,B-doped graphene(BG)is prepared by using boric acid as the doping source and then the prepared BG is utilized as the starting material for the preparation of CF_(x).The B-doping enhances the F/C ratio of CF_(x)without hindering the electrochemical activity of the C–F bond.During the fluorination process,B-containing functional groups are removed from the graphene lattice.This facilitates the formation of a defect-rich graphene matrix,which not only enhances the F/C ratio due to abundant perfluorinated groups at the defective edges but also serves as the active site for extra Li+storage.The prepared CF_(x)exhibits the maximum specific capacity of 1204 mAh g^(−1),which is 39.2%higher than that of CF_(x)obtained directly from graphene oxide(without B-doping).An unprecedented energy density of 2974 Wh kg^(−1)is achieved for the asprepared CF_(x)samples,which is significantly higher than the theoretically calculated energy density of commercially available fluorinated graphite(2180 Wh kg^(−1)).Therefore,this study demonstrates a great potential of B-doping to realize the ultrahigh energy density of CF_(x)cathodes for practical applications.
基金supported by the Natural Science Foundation Project of Fujian Province(Nos.2020J01287 and 2020H0024)。
文摘Surface modification of graphite anode with electroactive matters has been proven of a more practical strategy in enhancing the performance of Li-ion batteries than exploring alternative novel anode materials.Herein,rutile TiNbO_(4-x) nanoparticles with a tunnel structure are employed as multifunctional decoration substances in combination with a carbon coating layer to improve the rate and cycle properties of mesocarbon microbeads(MCMBs).As compared to pristine MCMB,the Li^(+)diffusion coefficients of the composite anodes are enhanced due to the synergistic effect of TiNbO_(4-x)@C.Meanwhile,the overcharge and voltage polarization of the composite anodes at high rate are obviously minimized due to the current sharing effect of the high-potential TiNbO_(4-x).Moreover,the amorphous Li_(y)TiNbO_(4-x) converted from TiNbO_(4-x) in the initial lithiation process can deliver pseudocapacitive capacity to the composite anodes from the second cycle.All of these functions of TiNbO_(4-x)@Ccoating layer have directly contributed to the improved rate and cycle performance of the MCMB/TiNbO_(4-x)@C composite anodes.The one containing 12.0 wt%TiNbO_(4-x) exhibits a high reversible specific capacity of 118 m Ah·g^(-1)at 10C(1C=372 m A·g^(-1)),together with a high capacity retention of 90.9%after 300 cycles at 3C,which are all much superior to those of pristine MCMB.
文摘A novel Ti-doped M-site deficient olivine LiFePO4, i.e. Li0.95Fe0.95Ti0.05PO4, was synthesized by a solid-state reaction method. XRD and VTR were used to characterize the as-prepared samples. As a cathode material for lithium-ion batteries, Li0.95Fe0.95Ti0.05PO4 exhibited improved rate capability.