查看更多>>摘要：Polar promotors have been proven effective in catalyzing the polysulfide(PS)reduction reaction(PSRR)process in lithium-sulfur(Li-S)batteries.However,the promotor surface tends to be poisoned due to the accumulation of insoluble discharging products of lithium disulfide(Li2S2)and lithium sulfide(Li2S)during Li-S battery operation.Herein,we investigate the detailed PSRR mechanism on the surface of manganese sulfides(MnS)as a representative promoter by performing in-situ Raman mapping measurements.The catalytic ability of MnS enables thorough electrochemical reduction of PSs to Li2S2 and Li2S on the MnS surface.The generated Li2S2 and Li2S then adsorb the dissolved PSs via chemical reactions among sulfur species during the subsequent PSRR process.This phenomenon mitigates promotor poisoning and continuously improves the reversible capacity.Consequently,the assembled Li-S cell demonstrates excellent electrochemical performance after introducing a conductive interlayer containing a thin piece of carbon nanotube film and MnS promotors.
查看更多>>摘要：Polyethylene oxide(PEO)-based solid-state electrolytes are considered ideal for electrolyte materials in solid-state lithium metal batteries(SSLMBs).However,practical applications are hindered by the lower conductivity and poor interfacial stability.Here,we propose a strategy to construct a three-dimensional(3D)fiber network of metal-organic frameworks(MOFs).Composite solid electrolytes(CSEs)with continuous ion transport pathways were fabricated by filling a PEO polymer matrix in fibers containing interconnected MOFs.This 3D fiber network provides a fast Li+transport path and effectively improves the ionic conductivity(1.36 × 10-4 S·cm-1,30 ℃).In addition,the network of interconnected MOFs not only effectively traps the anions,but also provides sufficient mechanical strength to prevent the growth of Li dendrites.Benefiting from the advantages of structural design,the CSEs stabilize the Li/electrolyte interface and extend the cycle life of the Li-symmetric cells to 3000 h.The assembled SSLMBs exhibit excellent cycling performance at both room and high temperatures.In addition,the constructed pouch cells can provide an areal capacity of 0.62 mA·h·cm-2,which can still operate under extreme conditions.This work provides a new strategy for the design of CSEs with continuous structure and stable operation of SSLMBs.
查看更多>>摘要：Sodium-ion batteries(SIBs)are required to possess long cycle life when used for large-scale energy storage.The polyanionic Na4MnV(PO4)3(NMVP)reveals good cyclic stability due to its unique three-dimensional(3D)frame structure,but it still faces the challenge of interfacial degradation in practical applications.In this work,NASICON-type Na1.3Al0.7Ti1.3(PO4)3(NATP)was deposited on the surface of NMVP to promote interface stability by surface modification and gradient doping.As a result,the optimized NMVP@2％NATP released a capacity retention of 44.8％after 1000 cycles at 5 C,much higher than that of the initial NMVP(28.9％).The enhanced electrochemical performance was mainly attributed to NATP coating acting as a fast ion transport carrier and physical barrier,significantly facilitating the Na+diffusion and isolating side reaction at the electrode/electrolyte interface.On the other hand,Ti4+and Al3+cations from the NATP were partially doped inside the NMVP surface to boost the transport of Na+,and the perfect lattice matching of NVMP and NATP improved the interface and structural stability accompanying long cycling.This work demonstrated the effectiveness of surface modification with high lattice match material and provided new perspectives for high energy density solid-state SIBs.
查看更多>>摘要：The low electrical conductivity of sulfur,strong volume expansion,shuttle effect,and sluggish redox reactions in Li-S batteries limit their practical application.MoP nanoparticles encapsulated in nitrogen-doped carbon nanotubes(MoP/NC NTs)were synthesized using MoO3 nanorods as templates via a polypyrrole coating,heat-carbonization,MoO3 partial reduction,ammonia washing,and phosphorization.The MoP/NC NTs had a hollow nanostructure with a high specific surface area,which can alleviate the volume expansion of the cathode and the shuttle effect of polysulfides.The encapsulated MoP nanoparticles can anchor the polysulfides and enhance the redox reaction kinetics.Thus,the MoP/NC NTs combined with sulfur(MoP/S/NC NTs)exhibited 440.8 mAh·g-1 over 500 cycles at 1.0 A·g-1 with a decay rate of 0.06％per cycle.The density functional theory calculations and X-ray photoelectron spectroscopy results confirmed that MoP/NC NTs could anchor polysulfides and alleviate the shuttle effect by chemical interactions.This study supplies a novel route to prepare nanoparticle-embedded in N-doped carbon nanotubes for advanced Li-S battery.
查看更多>>摘要：Lithium metal batteries(LMBs)have been extensively investigated during the past decades because of their ultrahigh energy densities.With the increasing demand for energy density,however,the safety issue of LMBs has become a significant challenge.In particular,localized areas of increased temperature(namely,hotspots)may be induced and even exacerbated within LMBs by uneven current distribution,internal short circuits,or inadequate heat dissipation,which significantly sacrifices battery safety and cycle life.Here,we report the rational design and fabrication of a fast thermal responsive separator capable of inhibiting the growth of lithium dendrites and mitigating thermal propagation,thereby reducing the risk of thermal runaway.The as-achieved separator comprises both an electrospun membrane using a phase change material with superior thermal-storage ability and a thermally conductive modification layer of hexagonal boron nitride nanosheets with a fast heat-transfer feature.It is demonstrated that such a unique integration of heat conduction and heat storage enables the functional separator with attractive abilities to mitigate hotspots and inhibit the growth of lithium dendrites upon the cycling of LMBs.Moreover,pouch cells with the thermal-responsive separator,as well as numerical simulations,verify much enhanced safety and cycle life of LMBs.This work may offer a new conceptual design of intelligent separators that acts as a functional unit encapsulated within a single cell to boost in-situ thermal management,which will help to develop high-safety and energy-dense LMBs.
查看更多>>摘要：Layered P2-type cathodes with high voltage,large capacity,and easy synthesis show great potential for developing sodium(Na)-ion batteries(NIBs).However,the P2-O2 phase transition makes their structural degradation and the Na+/vacancy ordering lowers their redox kinetics.Here,we rationally propose a compositionally graded P2-type cathode,where nickel(Ni)and manganese(Mn)fractions decrease gradually,and cobalt(Co)content increases contiguously from the inside to the outside of a secondary particle.Inside these particles,the Ni/Mn-based compound delivers high capacity and high voltage.On the surface of particles,the Co/Mn-based solid solution offers a stable buffer matrix.Benefiting from these synergistic effects,this graded P2-type cathode shows the elimination of P2-O2 transformation even when charged to 4.4 V,which enables good structural stability,maintaining capacity retention reaching～80％within 300 cycles.Moreover,the Na+/vacancy ordering superstructure is further suppressed,and the Na+diffusion kinetics is significantly improved.The proposed graded structure with optimized chemical composition offers a new perspective for eliminating the unwanted phase transition and thus enhancing the electrochemistry of high-voltage layered cathodes for advanced NIBs.
查看更多>>摘要：Recently,three-dimensional(3D)conductive frameworks have been chosen as the host for composite lithium(Li)metal anode because of their exceptional electrical conductivity and remarkable thermal and electrochemical stability.However,Li tends to accumulate on the top of the 3D frameworks with homogenous lithiophilicity and Li dendrite still growth.This work firstly designed a bimetallic metal-organic framework(MOF)(CuMn-MOF)derived Cu2O and Mn3O4 nanoparticles decorated carbon cloth(CC)substrates(CC@Cu2O/Mn3O4)to fabricate a composite Li anode.Thanks to the synergistic effects of lithiophilic Cu2O and Mn3O4,the CC@Cu2O/Mn3O4@Li symmetrical cell can afford a prolonged cycling lifespan(1400 h)under an ultrahigh current density and areal capacity(6 mA·cm-2/6 mAh·cm-2).When coupled with the LiFePO4(LFP)cathode,the LFP‖CC@Cu2O/Mn3O4@Li full cell demonstrated a superior performance of 89.7 mAh·g-1 even at an extremely high current density(10 C).Furthermore,it can also be matched well with LiNi0.5Co0.2Mn0.3O2(NCM523)cathode.Importantly,to explain the excellent performances of the CC@Cu2O/Mn3O4@Li composite anode,an intermittent model was also proposed.This study offers a novel model that can enhance our comprehension of the Li deposition behavior and pave the way to attain stable and safe Li metal anodes by employing bimetallic MOF-derived materials to construct 3D frameworks.
查看更多>>摘要：Understanding the influence of electrode material's morphology on electrochemical behavior is of great significance for the development of rechargeable batteries,however,such studies are often limited by the inability to precisely control the morphology of electrode materials.Herein,nanostructured titanium niobium oxides(TiNb2O7)with three different morphologies(one-dimensional(1D),two-dimensional(2D),and three-dimensional(3D))were synthesized via a facile microwave-assisted solvothermal method.The influence of the morphological dimension of TiNb2O7 as electrode material on the electrochemical performance in Li-ion batteries(LIBs)and the underlying correlation with the electrochemical kinetics were studied in detail.2D TiNb2O7(TNO-2D)shows a superior rate capability and cycling stability,associated with improved kinetics for charge transfer and Li-ion diffusion,compared to the 1D and 3D materials.Operando X-ray diffraction measurements reveal the structural stability and crystallographic evolution of TNO-2D upon lithiation and delithiation and correlate the Li-ion diffusion kinetics with the lattice evolution during battery charge and discharge.Moreover,carbon-coated TNO-2D achieves enhanced rate capability(205 mAh·g-1 at 50 C)and long-term cycling stability(87％after 1000 cycles at 5 C).This work provides insights into the rational morphology design of electrode materials for accelerated charge transfer and enhanced fast-charging capability,pushing forward the development of electrode materials for high-power rechargeable batteries in future energy storage.
查看更多>>摘要：Mn-based zinc ion battery has the advantages of low cost and high performance,which makes it the promising energy storage system.However,the poor conductivity and the agglomeration in the synthesis process of manganese-based materials restrict the performance of batteries.Herein,the Se-doped MnS/Ti3C2Tx(Se-MnS/Ti3C2Tx)composite material derived from Mn-based metal-organic framework is reported.Electrochemical tests show that Se-doped could generate S defects and enhance the electrochemical activity of MnS.At the same time,the introduction of Ti3C2Tx substrate is conducive to exposing more sulfur defects and improving the utilization rate of defects.In the mechanism study,it is found that Se-MnS/Ti3C2Tx is transformed into S/Se co-doped Mn3O4 at the first charge,which innovatively elucidated the behavior of S/Se during activation.In the electrochemical performance test,the specific capacity can reach 74.7 mAh·g-1 at 5.0 A·g-1.In addition,the Zn-Ti3C2Tx membrane electrode is prepared by vacuum filtration as the zinc-poor anode,which is assembled into the rocking chair full battery to avoid dendrite growth and exhibit excellent rate performance.The addition of Zn2+weakens the electrostatic repulsion between the interlayers of MXene,and the formation of the folded morphology aids the penetration of the electrolyte.At 1.0 A·g-1,the capacity can reach 50.6 mAh·g-1.This work is helpful to promote the research and development of the reaction mechanism of manganese based rocking chair batteries.
查看更多>>摘要：The leakage of liquid electrolyte and the formation of lithium dendrites pose challenges to safety and stability of lithium metal batteries(LMBs).The appearance of gel polymer electrolyte(GPE)has obviously improved the safety of traditional LMBs.However,the limited inhibition of GPE on lithium dendrites is detrimental to the safety of LMBs.Herein,a kind of poly(vinylidene fluoride-co-hexafluoropropylene)(PVDF-HFP)/gelatin(GN)GPE with high ionic conductivity,high-temperature resistance,and flame-retardancy,was prepared by electrospinning and soaking method.Utilizing the electrospinning network of PVDF-HFP,its affinity to liquid electrolytes,makes this GPE more beneficial to ions transport and the formation of gel.And,the GN with sol-gel properties,enhances the mechanical property(13.5 MPa)of HFP-GN GPE.Meanwhile,X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT)suggest that the attraction of polar groups of GN to Li+can regulate the distribution of Li+and protect Li anodes.Consequently,the application of HFP-GN GPEs to LMBs with cathodes of LiFePO4 and LiCoO2 deliver excellent electrochemical performances:after 300 cycles,the LiFePO4/HFP-GN GPE/Li battery keeps a low capacity decay rate of 0.09％at 5 C;after 400 cycles at 2 C,the LiCoO2/HFP-GN GPE/Li cell retains a high capacity retention of 74％.This GPE is demonstrated for the application prospect of safe LMBs.
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