Strategies to suppress the shuttle effect of redox mediators in lithium-oxygen batteries

Rechargeable lithium-oxygen(Li-O_(2))batteries are the next generation energy storage devices due to their ultrahigh theoretical capacity.Redox mediators(RMs)are widely used as a homogenous electrocatalyst in non-aqueous Li-O_(2)batteries to enhance their discharge capacity and reduce charge overpotential.However,the shuttle effect of RMs in the electrolyte solution usually leads to corrosion of the Li metal anode and uneven Li deposition on the anode surface,resulting in unwanted consumption of electrocatalysts and deterioration of the cells.It is therefore necessary to take some measures to prevent the shuttle effect of RMs and fully utilize the soluble electrocatalysts.Herein,we summarize the strategies to suppress the RM shuttle effect reported in recent years,including electrolyte additives,protective separators and electrode modification.The mechanisms of these strategies are analyzed and their corresponding requirements are discussed.The electrochemical properties of Li-O_(2)batteries with different strategies are summarized and compared.The challenges and perspectives on preventing the shuttle effect of RMs are described for future study.This review provides guidance for achieving shuttle-free redox mediation and for designing Li-O_(2)cells with a long cycle life,high energy efficiency and highly reversible electrochemical reactions.

High-temperature diffusion behavior of ZrC in C matrix and its promotion on graphitization

C/C composite material is widely used in aerospace field and others, however, it is easy to be oxidized at high temperature.In order to improve the oxidation resistance, ZrC is introduced as an oxidation inhibitor used in matrix modification of C/C composite material. Flat plate samples of ZrC/C composite materials were prepared by hot-pressing sintering. The degree of graphitization increases with rising sintering temperature, and layer structure of carbon matrix is observed clearly in the sample treated at 2273 K. Diffusion behavior of Zr in C matrix at high temperature is studied, which can be generally expressed as D=3.382×10?11 exp[2.029×105/(RT)]. The diffusion of Zr in C matrix leads to the over-saturation of C in the micro area and the oversaturated C precipitates as graphite. This continuous process promotes the transformation of carbon to graphite.

Nanonet-/fiber-structured flexible ceramic membrane enabling dielectric energy storage

Ceramics are considered intrinsically brittle at macro scale due to the lack of slip mechanism and pre-existing defects,which greatly limits their potential applications in emerging fields including wearable electronic devices and flexible display.In this contribution,we developed BiFeO_(3)/SiO_(2) dual-networks with exceptional flexibility through a coupled electronetting/electrospun method.The hybrid nanostructured networks endow the material with high tensile strength(2.7 MPa),excellent flexibility(80%recoverable deformation),and robust fatigue resistance performance(maintain flexibility after a 1000-cyclic compress test).After in-situ compounded with dielectric polymer via a layer-by-layer solution casting method,the resultant three-dimensional(3D)composite film exhibits a twice higher dielectric constant(εr)than polyether imide(PEI)film.More importantly,the breakdown strength of the 3D composite film is almost the same as that of the PEI film,resulting in an enhanced energy density of~6.0 J/cm^(3) and a high efficiency of 80%at 4.58 MV/cm.The unique structure,combined with the excellent balance between mechanical and dielectric properties in flexible structures,is of critical significance to the design of flexible functional ceramics and broadening their applications in wearable electric devices.

Structure designing,interface engineering,and application prospects for sodium-ion inorganic solid electrolytes

All-solid Na-ion batteries(ASNIBs)present significant potential for integration into large-scale energy storage systems,capitalizing on their abundant raw materials,exemplary safety,and high energy density.Among the pivotal components propelling the advancement of ASNIBs,inorganic solid electrolytes(ISEs)have garnered substantial attention in recent years due to their high ionic conductivity(σ),wide electrochemical stability window(ESW),and high shear modulus.Herein,this review systematically encapsulates the latest strides in Na-ion ISEs,furnishing a comprehensive panorama of various ISE systems along with their interface engineering strategies against the electrodes.The prime focus resides in accentuating key strategies for refining ion conduction properties and interfacial compatibility of ISEs through structure design and interface modification.Furthermore,the review explores the foremost challenges and prospects inherent to sodium-ion ISEs,striving to deepen our understanding of how to engineer more robust and efficient ISEs and interface stability,poised for the forthcoming era of advanced ASNIBs.

In-plane isotropic separator-induced highly efficient sodium plating for unlocking the fast-charging capability of anode-free sodium battery at practical conditions

Ether-based electrolytes with excellent reductive stability are compatible with sodium(Na)metal an-odes,which enables stable cycling for Na metal batteries even in an anode-free configuration.However,the practical applications of anode-free sodium batteries(AFSBs)with a high theoretical energy density are restricted by the low-rate capability and limited cycle life.Here we demonstrate that the mechanical properties of the separators,which have been overlooked in previous studies,can significantly affect the cycling stability of AFSBs due to the intrinsic softness of Na and the large volume variation of AFSBs during Na plating/stripping.By using various separators including polypropylene(PP),polyethylene(PE),PP/PE/PP tri-layer,and aluminum oxide-coated separators,we find that the balanced elastic moduli of the separator along the machine direction and transverse direction are crucial for enabling highly effi-cient Na plating and unlocking the 4 C fast-charging capability of the AFSBs at practical conditions including a high cathode active mass loading(13.5 mg/cm^(2)),lean electrolyte addition(8.8 mL/cm^(2)),and no pre-sodiation process.This study provides an important separator design principle for the develop-ment of high-rate and long-cycle-life AFSBs.

Modification of solid electrolyte interface layer between PVDF-based electrolyte and lithium anode

Poly(vinylidene fluoride)(PVDF)-based polymer electrolytes(PEs)with good electrochemical performance and processability as well as low-cost advantage,have great potential applications in solid-state lithium(Li)metal batteries(SSLMBs).PVDF-based PEs are generally produced by employing a solution-casting approach with N,N-dimethylformamide(DMF)as the solvent,accompanied by the formation of[DMF-Li^(+)]complex,which facilitates the Li-ion transport.However,the residual DMF can react continuously with lithium(Li)metal,thereby deteriorating the interface layer in the middle of the PVDF-based PEs and Li anodes.Herein,we introduce propylene carbonate(PC)into the PVDF-based PEs to regulate the solvation structure and stabilize the interface layer between the PEs and Li anodes.PC accelerates the dissociation of lithium oxalyldifluoroborate(LiODFB).Consequently,“lithium propylene dicarbonate(LPDC)‒B-O”oligomer forms as the interfacial layer with high tenacity,homogeneity,and densification,which improves the interfacial contact and suppresses the continuous reaction between the residual DMF and Li anode.We further demonstrate that the PVDF-based PE prepared with DMF-PC mix-solvents shows improved room-temperature ionic conductivity(1.18×10^(-3) S/cm),enhanced stability against electrodes,and superior cycling performance in LiCoO_(2)-based SSLMBs(maintaining 84% of the initial discharge capacity after 300 cycles).

Self-powered sensor based on compressible ionic gel electrolyte for simultaneous determination of temperature and pressure

The simultaneous detection of multiple stimuli,such as pressure and temperature,has long been a persistent challenge for developing electronic skin(eskin)to emulate the functionality of human skin.Meanwhile,the demand for integrated power supply units is an additional pressing concern to achieve its lightweightness and flexibility.Herein,we propose a self-powered dual temperature–pressure(SPDM)sensor,which utilizes a compressible ionic gel electrolyte driven by the potential difference between MXene and Al electrodes.The SPDM sensor exhibits a rapid and timely response to changes in pressure-induced deformation,while exhibiting a slow and hysteretic response to temperature variations.These distinct response characteristics enable the differentiation of current signals generated by different stimuli through machine learning,resulting in an impressive accuracy rate of 99.1%.Furthermore,the developed SPDM sensor exhibits a wide pressure detection range of 0–800 kPa and a broad temperature detection range of 5–75C,encompassing the environmental conditions encountered in daily human life.The dual-mode coupled strategy by machine learning provides an effective approach for temperature and pressure detection and discrimination,showcasing its potential applications in wearable electronics,intelligent robots,human–machine interactions,and so on.

Interfacial Oxygen Octahedral Coupling-Driven Robust Ferroelectricity in Epitaxial Na_(0.5)Bi_(0.5)TiO_(3)Thin Films

The oxygen octahedral rotation(OOR)forms fundamental atomic distortions and symmetries in perovskite oxides and definitely determines their properties and functionalities.Therefore,epitaxial strain and interfacial structural coupling engineering have been developed to modulate the OOR patterns and explore novel properties,but it is difficult to distinguish the 2 mechanisms.Here,different symmetries are induced in Na_(0.5)Bi_(0.5)TiO_(3)(NBT)epitaxial films by interfacial oxygen octahedral coupling rather than epitaxial strain.The NBT film grown on the Nb:SrTiO_(3)substrate exhibits a paraelectric tetragonal phase,while with La_(0.5)Sr_(0.5)MnO_(3)as a buffer layer,a monoclinic phase and robust ferroelectricity are obtained,with a remanent polarization of 42μC cm^(-2)and a breakdown strength of 7.89 MV cm^(-1),which are the highest record among NBT-based films.Moreover,the interfacial oxygen octahedral coupling effect is demonstrated to propagate to the entire thickness of the film,suggesting an intriguing long-range effect.This work provides a deep insight into understanding the structure modulation in perovskite heterostructures and an important avenue for achieving unique functionalities.

Self-etching Ni-Co hydroxides@Ni-Cu nanowire arrays with enhancing ultrahigh areal capacitance for flexible thin-film supercapacitors

Flexible thin-film supercapacitors with high specific capacitance are highly desirable for modern wearable or micro-sized electrical and electronic applications. In this contribution, Ni-Co hydroxides（NCH）nanosheets were deposited on top of Ni-Cu alloy（NCA）nanowire arrays forming a freestanding thin-film composite electrode with hierarchical structure for supercapacitors.During electrochemical cycling, the dissolution of Cu into Cu ions will create more active sites on NCA, and the redeposited copper oxide can be coated onto NCH, giving rise to substantial increase in specific capacitance with cycling. Meanwhile, NCA and NCH have excellent conductivity, thus leading to excellent rate performance. This flexible thin-film electrode delivers an ultrahigh initial specific capacitance of 0.63 F·cm^（-2）（or 781.3 F·cm^（-3））.During charge-discharge cycles, the specific capacitance can increase up to 1.18 F·cm^（-2）（or 1475 F·cm^（-3）） along with the“self-etching”process. The electrode presents a better specific capacitance and rate capability compared with previously reported flexible thin-film electrode, and this novel design of etching technique may expand to other binary or ternary materials.

High-throughput data-driven interface design of high-energy-density polymer nanocomposites

Understanding the interface effect in dielectric nanocomposites is crucial to the enhancement of their performance.In this work,a data-driven interface design strategy based on high-throughput phase-field simulations is developed to study the interface effect and then optimize the permittivity and breakdown strength of nanocomposites.Here,we use two microscopic features that are closely related to the macroscopic dielectric properties,the thickness and permittivity of the interface phases,to evaluate the role of interfaces in experimental configuration,and thus provide quantitative design schemes for the interfacial phases.Taking the polyvinyl difluoride(PVDF)-BaTiO_(3) nanocomposite as an example,the calculation results demonstrate that the interfacial polarization could account for up to 83.6% of the increase in the experimentally measured effective permittivity of the nanocomposite.Based on the interface optimized strategy,a maximum enhancement of ~156% in the energy density could be achieved by introducing an interface phase with d/r=0.55 and ε_(interface)/ε_(filler)=0:036,compared to the pristine nanocomposite.Overall,the present work not only provides fundamental understanding of the interface effect in dielectric nanocomposites,but also establishes a powerful data-driven interface design framework for such materials that could also be easily generalized and applied to study interface issues in other functional nanocomposites,such as solid electrolytes and thermoelectrics.

Designing polymer nanocomposites with high energy density using machine learning

Addressing microstructure-property relations of polymer nanocomposites is vital for designing advanced dielectrics for electrostatic energy storage.Here,we develop an integrated phase-field model to simulate the dielectric response,charge transport,and breakdown process of polymer nanocomposites.Subsequently,based on 6615 high-throughput calculation results,a machine learning strategy is schemed to evaluate the capability of energy storage.We find that parallel perovskite nanosheets prefer to block and then drive charges to migrate along with the interfaces in x-y plane,which could significantly improve the breakdown strength of polymer nanocomposites.To verify our predictions,we fabricate a polymer nanocomposite P(VDF-HFP)/Ca_(2)Nb_(3)O_(10),whose highest discharged energy density almost doubles to 35.9 J cm^(−3) compared with the pristine polymer,mainly benefit from the improved breakdown strength of 853 MVm^(−1).This work opens a horizon to exploit the great potential of 2D perovskite nanosheets for a wide range of applications of flexible dielectrics with the requirement of high voltage endurance.

Ordered coalescence of nano-crystals in alkaline niobate ceramics with high remanent polarization

Lead-free alkali niobates Na_(0.5)K_(0.5)NbO_(3)(NKN)ceramics,with significantly enhanced ferroelectric remanent polarization(Pr),were prepared using Spark Plasma Sintering(SPS).Three types of boundaries were observed in the ceramics,being grain boundaries between faceted grains,domain boundaries that separate ferroelectric domains inside individual grains,and nanoscale sub-grain boundaries that reveal the nano-scale mosaicity of individual grains.Part of the sub-grain boundaries were from initial powder particles.The other sub-grain boundaries were built by ordered coalescence of nano-crystals during rapid SPS process.It was worthwhile to emphasize that the ordered coalescence of nano-crystals in bulk ceramics during sintering takes place and completes within minutes.These sub-grain features would disappear at higher temperature by long time sintering.Rapid Spark Plasma Sintering allowed us to capture this transient microstructure.The significantly enhanced ferroelectric Pr of NKN was attributed to nanoscale sub-boundaries,which stimulated the dynamics of ferroelectric domain formation and switching.

Low-dimensional nanostructured photocatalysts

Low-dimensional nanostructures are a promising class of ideal high-performance candidates for energy storage and conversion owing to their unique structural,optical,and chemical properties.Low-dimensional nanostructured photocatalysts have attracted ever-growing research attention.In this review,we mainly emphasize on summarizing the 0-,1-,and 2-dimensional nanostructured photocatalysts systematically,including their photocatalytic performance,synthesis methods,and theoretical analysis.From the viewpoint of dimension,we try to figure out the way to design more high-efficiency photocatalysts towards numerous applications in the field of solar energy conversion,hoping to promote efficient control and rational development of photocatalysts.

Contribution of point defects and nano-grains to thermal transport behaviours of oxide-based thermoelectrics

Point defects and nano-grains are very effective ways to control the thermal conductivity in oxide-based thermoelectrics.Here we use the optimised Debye–Callaway model to understand how the effect of point defects and nano-grains to reduce the thermal conductivity by inducing normal process and oxygen vacancy in oxide-based thermoelectrics.Our results reveal that this model can be effective to fit the experimental data of thermal conductivity in ZnO-,CaMnO_(3)-,BiCuSeO-,SrTiO_(3)^(-)and In_(2)O_(3)-based systems,which indicate that the normal scattering process and the oxygen vacancy will make obvious contribution to the thermal conductivity as compared with alloy compounds system.These calculations also propose that it could be desirable to obtain higher ZT by controlling the concentration of oxygen vacancy in the nano-grained thermoelectric oxides.

Flexible high-performance microcapacitors enabled by all-printed two-dimensional nanosheets

Chemically exfoliated nanosheets have exhibited great potential for applications in various electronic devices.Solution-based processing strategies such as inkjet printing provide a low-cost,environmentally friendly,and scalable route for the fabrication of flexible devices based on functional inks of twodimensional nanosheets.In this study,chemically exfoliated high-k perovskite nanosheets(i.e.,Ca_(2)Nb_(3)O_(10)and Ca_(2)NaNb_(4)O_(13))are well dispersed in appropriate solvents to prepare printable inks,and then,a series of microcapacitors with Ag and graphene electrodes are printed.The resulting microcapacitors,Ag/Ca_(2)Nb_(3)O_(10)/Ag,graphene/Ca_(2)Nb_(3)O_(10)/graphene,and graphene/Ca_(2)NaNb_(4)O_(13)/graphene,demonstrate high capacitance densities of 20,80,and 150 nF/cm^(2) and high dielectric constants of 26,110.and 200,respectively.Such dielectric enhancement in the microcapacitors with graphene electrodes is possibly attributed to the dielectric/graphene interface.In addition,these microcapacitors also exhibit good insulating performance with a moderate electrical breakdown strength of approximately 1 MV/cm,excellent flexibility,and thermal stability up to 200℃.This work demonstrates the potential of high-k perovskite nanosheets for additive manufacturing of flexible high-performance dielectric capacitors.

Versatile memristor implemented in van der Waals CuInP_(2)S_(6)

Memristors are playing an increasingly important role in developing in-memory computing.Versatile memristors which offer both volatile and non-volatile performances can be employed as both memories and selectors,displaying unique advantages for developing novel electronic circuits.Herein,the remarkable multifunctional memristor with switchable operating modes between volatile and non-volatile by regulating compliance currents is implemented in Ag/CIPS/Au(CIPS:CuInP_(2)S_(6))device.Diode-like volatile memristor performances with the rectification ratio of 10^(3) and an endurance of 500 switching cycles were obtained.Meanwhile,significant non-volatile memory performances with on/off ratio of 10^(3)and retention up to 10^(4)s were also developed,which enables it to be utilized as selectors and memories simultaneously.Moreover,such versatile memristor can emulate the short-term plasticity(STP)and long-term plasticity(LTP)of artificial synapse,demonstrating its advantages in neuromorphic computing applications.

Electric-field control of topological spin textures in BiFe_(O3)/La_(0.67)Sr_(0.33)MnO_(3)heterostructure at room temperature

Electric-field control of topological magnetic states in thinfilm heterostructures is promising for applications in nextgeneration memory or logic devices with ultrahigh density and low-power consumption.Multiferroic materials,where spin and polar degrees of freedom coexist,provide a versatile playground to manipulate magnetism(converse magnetoelectric effect).Here,we report that the topological spin textures can be controlled by electric field in rhombohedral BiFeO_(3)/monoclinic La_(0.67)Sr_(0.33)MnO_(3)thin-film heterostructure at room temperature.

Local symmetry distortion induced anomalous thermal conduction in thermoelectric layered oxyselenides

Polyhedral distortion,associated closely with the atomic arrangement and interatomic interactions,drives many unique behaviors in solids,such as phase transition and negative thermal expansion.In thermoelectric heteroanionic oxides,the anionic polyhedra are widely present,but their effect on thermal transport is rarely investigated.Here,we report an anomalous thermal conduction induced by local symmetry distortion in layered oxyselenides via solving the Boltzmann transport equation based on first-principles calculations.We found interestingly that lighter BiCuSeO exhibits lower thermal conductivity than heavier BiAgSeO.Due to the different distorted degrees of CuSe4 and AgSe4 tetrahedrons,Cu prefers the in-plane vibration,while Ag has more tendency of out-of-plane vibration.Thus,the heat-carrying phonons dominated by the rattling-like vibration of Cu are significantly suppressed,resulting in lower thermal conductivity of BiCuSeO.This study highlights the importance of polyhedral distortion in regulating thermal conduction in layered heteroanionic materials.

A molecular sieve-containing protective separator to suppress the shuttle effect of redox mediators in lithium-oxygen batteries

Lithium-oxygen(Li-O_(2))batteries have a great potential in energy storage and conversion due to their ultra-high theoretical specific energy,but their applications are hindered by sluggish redox reaction kinetics in the charge/discharge processes.Redox mediators(RMs),as soluble catalysts,are widely used to facilitate the electrochemical processes in the Li-O_(2)batteries.A drawback of RMs is the shuttle effect due to their solubility and mobility,which leads to the corrosion of a Li metal anode and the degradation of the electrochemical performance of the batteries.Herein,we synthesize a polymer-based composite protective separator containing molecular sieves.The nanopores with a diameter of 4Åin the zeolite powder(4A zeolite)are able to physically block the migration of 2,2,6,6-tetramethylpiperidinyloxy(TEMPO)molecules with a larger size;therefore,the shuttle effect of TEMPO is restrained.With the assistance of the zeolite molecular sieves,the cycle life of the Li-O_(2)batteries is significantly extended from~20 to 170 cycles at a current density of 250 mA·g^(-1)and a limited capacity of 500 mAh·g^(-1).Our work provides a highly effective approach to suppress the shuttle effects of RMs and boost the electrochemical performance of Li-O_(2)batteries.

电容储能的构型熵调节

Dielectric materials play a crucial and unique role in modern advanced electrical and electronics engineering applications,lending their applicability to their desirable characteristics such as ultrafast charge/discharge rate(~μs),long cycling life(>10^(6)without observable capacity deterioration).