Solid polymer electrolytes (SPEs) are urgently required for achieving practical all-solid-state lithium metal batteries (ASSLMBs) but remain plagued by low ionic conductivity.Herein,we propose a strategy of salt polar...Solid polymer electrolytes (SPEs) are urgently required for achieving practical all-solid-state lithium metal batteries (ASSLMBs) but remain plagued by low ionic conductivity.Herein,we propose a strategy of salt polarization to fabricate a highly ion-conductive SPE by employing a high-dielectric polymer that can interact strongly with lithium salts.Such a polymer with large dipole moments can guide lithium cations (Li^(+)) to be arranged along the chain,forming a continuous pathway for Li^(+) hopping within the SPE.The as-fabricated SPE,poly(vinylidene difluoride)(PVDF)-LiN(SO_(2)F)_(2)(LiFSI),has an extraordinarily high dielectric constant (up to 10^(8)) and ultrahigh ionic conductivity (0.77×10^(-3)S cm^(-1)).Based on the PVDF–LiFSI SPE,the assembled Li metal symmetrical cell shows excellent Li plating/stripping reversibility at 0.1 m A cm^(-2),0.1 m Ah cm^(-2)over 1500 h^(-1) the ASS LiFePO_(4) batteries deliver long-term cycling stability at 1 C over 350 cycles (2.74 mg cm^(-2)) and an ultralong cycling lifespan of over 2600 h(100 cycles) with high loading (11.5 mg cm^(-2)) at 28°C.First-principles calculations further reveal the ion-dipole interactions-controlled conduction of Li^(+) in PVDF–LiFSI SPE along the PVDF chain.This work highlights the critical role of dielectric permittivity in SPE,and provides a promising path towards high-energy,long-cycling lifespan ASSLMBs.展开更多
Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of poly...Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of polymeric PCMs is a bottleneck for fast and efficient heat harvesting.Simultaneously,it is also a challenge to achieve a high thermal conductivity for phase change nanocomposites at low filler loading.Although constructing a three-dimensional(3D)thermally conductive network within PCMs can address these problems,the anisotropy of the 3D framework usually leads to poor thermal conductivity in the direction perpendicular to the alignment of fillers.Inspired by the interlaced structure of spider webs in nature,this study reports a new strategy for fabricating highly thermally conductive phase change composites(sw-GS/PW)with a 3D spider web(sw)-like structured graphene skeleton(GS)by hydrothermal reaction,radial freeze-casting and vacuum impregnation in paraffin wax(PW).The results show that the sw-GS hardly affected the phase transformation behavior of PW at low loading.Especially,sw-GS/PW exhibits both high cross-plane and in-plane thermal conductivity enhancements of~1260%and~840%,respectively,at an ultra-low filler loading of 2.25 vol.%.The thermal infrared results also demonstrate that sw-GS/PW possessed promising applications in battery thermal management.展开更多
Thermal management has become a crucial problem for high-power-density equipment and devices.Phase change materials(PCMs)have great prospects in thermal management applications because of their large capacity of heat ...Thermal management has become a crucial problem for high-power-density equipment and devices.Phase change materials(PCMs)have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition.However,low intrinsic thermal conductivity,ease of leakage,and lack of flexibility severely limit their applications.Solving one of these problems often comes at the expense of other performance of the PCMs.In this work,we report core–sheath structured phase change nanocomposites(PCNs)with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning,electrostatic spraying,and hot-pressing.The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m^(-1)K^(-1)at a low BNNS loading(i.e.,32 wt%),which thereby endows the PCNs with high enthalpy(>101 J g^(-1)),outstanding ductility(>40%)and improved fire retardancy.Therefore,our core–sheath strategies successfully balance the trade-off between thermal conductivity,flexibility,and phase change enthalpy of PCMs.Further,the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators,displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.展开更多
Dielectric polymer nanocomposites are considered as one of the most promising candidates for high-power-density electrical energy storage applications.Inorganic nanofillers with high insulation property are frequently...Dielectric polymer nanocomposites are considered as one of the most promising candidates for high-power-density electrical energy storage applications.Inorganic nanofillers with high insulation property are frequently introduced into fluoropolymer to improve its breakdown strength and energy storage capability.Normally,inorganic nanofillers are thought to introducing traps into polymer matrix to suppress leakage current.However,how these nanofillers effect the leakage current is still unclear.Meanwhile,high dopant(>5 vol%)is prerequisite for distinctly improved energy storage performance,which severely deteriorates the processing and mechanical property of polymer nanocomposites,hence brings high technical complication and cost.Herein,boron nitride nanosheet(BNNS)layers are utilized for substantially improving the electrical energy storage capability of polyvinylidene fluoride(PVDF)nanocomposite.Results reveal that the high conduction band minimum of BNNS produces energy barrier at the interface of adjacent layers,preventing the electron in PVDF from passing through inorganic layers,leading to suppressed leakage current and superior breakdown strength.Accompanied by improved Young’s modulus(from 1.2 GPa of PVDF to 1.6 GPa of nanocomposite),significantly boosted discharged energy density(14.3 J cm^(-3)) and charge-discharge efficiency(75%)are realized in multilayered nanocomposites,which are 340 and 300% of PVDF(4.2 J cm^(-3),25%).More importantly,thus remarkably boosted energy storage performance is accomplished by marginal BNNS.This work offers a new paradigm for developing dielectric nanocomposites with advanced energy storage performance.展开更多
Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ...Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ultra-low resilience after compression.Some methods can realize a well-aligned structure,however,they involve high costs and complex technology.Herein,a 3 D graphene hybrid aerogel with an anisotropic open-cell and well-oriented structure is realized by unidirectional freeze casting,which combines the‘soft’(e.g.graphene oxide,Tween-80)and‘hard’(e.g.graphene assembly)components to realize full recovery after flattening.A graphene aerogel annealed at a moderate temperature(200℃)can possess superhydrophilicity and outstanding wet-resilience properties,including after being pressed under40 MPa.Furthermore,the graphene aerogel annealed at a high temperature of 1500℃exhibits excellent thermal conductivity enhancement efficiency in polydimethylsiloxane(PDMS).The resultant nanocomposites clearly demonstrate anisotropic thermal conductivity and promising applications as thermal interface materials.This strategy offers new insights into the design and fabrication of 3 D multifunctional graphene aerogels.展开更多
Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of inter...Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of interfacial property on electrical ene rgy storage of dielectric polymer nanocomposites is still not clear.Herein,the role of the polarity of the interfacial region is investigated.For this purpose,three polymers with different polarity,polymethyl methacrylate(PMMA),polyglycidyl methacrylate,and polymethylsulfonyl ethyl methacrylate(PMSEMA)are attached onto BaTi0_(3)(BT)na noparticle surface via surface-initiated reversible addition-fragmentation chain transfer polymerization.It is found that the polarity of shell polymers shows an apparent effect on the dielectric and energy storage of dielectric polymer nanocomposites.For example,PMSEMA@BT(shell polymer possesses the highest polarity)increases dielectric loss and decreases the breakdown strength of the nanocomposites,leading to lower ene rgy storage capability.However,PMMA@BT(shell polymer possesses the lowest polarity)can induce higher breakdown strength of the nanocomposites.As a result,the PMMA@BT nanocomposite exhibits the highest electrical energy sto rage capability among the three nanocomposites.This re search provides new insight into the design of core-shell nanofillers for dielectric energy storage applications.展开更多
The development of wearable and portable electronics calls for flexible piezoelectric materials to fabricate selfpowered devices.However,a big challenge in piezoelectric material design is to boost the output performa...The development of wearable and portable electronics calls for flexible piezoelectric materials to fabricate selfpowered devices.However,a big challenge in piezoelectric material design is to boost the output performance while ensuring its flexibility and biocompatibility.Here,all-organic and core-shell structured silk fibroin(SF)/poly(vinylidene difluoride)(PVDF)piezoelectric nanofibers(NFs)with excellent flexibility are fabricated using a simple electrospinning strategy.The strong intermolecular interaction between SF and PVDF promotes theβ-phase nucleation in the core-shell structure,which significantly enhances the output performance.An output of 16.5 V was achieved in SF/PVDF NFs,which is more than 6-fold enhancement compared with that of pure PVDF NFs.In addition,the piezoelectric device can sensitively detect the mechanical stimulation from joint bending,demonstrating its great potential in self-powered sensor.Otherwise,the piezoelectric device can be also applied to control the movement of a smart car,successfully,achieving its application in the human-machine interaction.展开更多
Polymeric dielectrics have wide range of applications in the field of electrical energy storage because of their light weight and easy processing. However, the state-of-the-art polymer dielectrics, such as biaxially o...Polymeric dielectrics have wide range of applications in the field of electrical energy storage because of their light weight and easy processing. However, the state-of-the-art polymer dielectrics, such as biaxially orientated polypropylene, could not meet the demand of minimization of electronic devices because of its low energy density. Recently, poly（vinylidene fluoride） （PVDF） based ferroelectric polymers have attracted considerable interests for energy storage applications because of their high permittivity and high breakdown strength. Unfortunately, the high dielectric loss and/or high remnant polarization of PVDF-based polymers seriously limits their practical applications for electrical energy storage. Since the discovery of relaxor ferroelectric behavior was firstly reported in irradiated poly（vinylidene fluoride- trifluoroethylene） （P（VDF-TrFE）） copolyrner, many strategies have been developed to enhanced the electrical energy storage capability, including copolymerization, grafting, blending and fabricating of multilayer How these methods affect the polymorphs, crystallinity, crystal size of PVDF-based polymers and the connection between these microstructures and their corresponding energy storage properties are discussed in detail.展开更多
Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to...Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to provide additional functionalities for various artificial-intelligence-driven systems,such as tactile sensing ability.Herein,a layering design strategy is proposed to fabricate ultrathin Ti_(3)C_(2)T_(x)MXene-aramid nanofiber(MA)films by a layer-by-layer assembling process.Compared to that of randomly mixed films,the designed MA films exhibited a higher EMI shielding efficiency at an ultrathin thickness of 9 pm,which increased from 26.4 to 40.7 dB,owing to the additional multiple-interface scattering mechanism.Importantly,the novel MA films displayed strong EMI shielding ability even after heating/cooling treatments within a wide temperature range of-196 to 300℃.Moreover,the same material displayed a tensile strength of 124.1±2.7 MPa and a toughness of 6.3±1.1 MJ·m^(-3),which are approximately 9.1 times and 45 times higher than those of pure MXene films,respectively.The MA film is also capable of detecting tactile signals via the triboelectric effect.A 2×4 tactile sensor array was developed to achieve an accurate signal catching capability.Therefore,in addition to the shielding performance,the manifestation of tactile perception by the MA films offers exciting opportunities in the fields of soft robotics and human-machine interactions.展开更多
Lithium(Li)metal batteries(LMBs)can potentially deliver much higher energy density but remain plagued by uncontrollable Li plating with dendrite growth,unstable interfaces,and highly abundant excess Li(>50 mAh·...Lithium(Li)metal batteries(LMBs)can potentially deliver much higher energy density but remain plagued by uncontrollable Li plating with dendrite growth,unstable interfaces,and highly abundant excess Li(>50 mAh·cm^(-2)).Herein,different from the artificial layer or three-dimensional(3D)matrix host constructions,various dielectric polymers are initially well-comprehensively investigated from experimental characterizations to theoretical simulation to evaluate their functions in modulating Li ion distribution.As a proof of concept,a 3D interwoven high dielectric functional polymer(HDFP)nanofiber network with polar C-F dipole moments electrospun on copper(Cu)foil is designed,realizing uniform and controllable Li deposition capacity up to 5.0 mAh·cm^(-2),thereby enabling stable Li plating/stripping cycling over 1400 h at 1.0 mA·cm^(-2).More importantly,under the highcathode loading(~3.1 mAh·cm^(-2))and only 0.6×excess Li(N/P ratio of 1.6),the full cells retain capacity retention of 97.4%after 200 cycles at 3.36 mA·cm^(-2)and achieve high energy density(297.7 Wh·kg^(-1)at cell-level)under lean electrolyte conditions(15μL),much better than ever-reported literatures.Our work provides a new direction for designing high dielectric polymer coating toward high-retention-rate practical Li full batteries.展开更多
Boron nitride nanosheets(BNNSs)have gained significant attraction in energy and environment fields because of their two-dimensional(2D)nature,large band gap and high thermal/mechanical performance.However,the current ...Boron nitride nanosheets(BNNSs)have gained significant attraction in energy and environment fields because of their two-dimensional(2D)nature,large band gap and high thermal/mechanical performance.However,the current low production efficiency of high-quality BNNSs is still a bottleneck limiting their applications.Herein,based on sonication-assisted liquid-phase exfoliation,we demonstrated a rapid,high-efficient and scalable production strategy of BNNSs and documented the effects of a spectrum of exfoliation factors(e.g.,ultrasonic condition,solvent and bulk material feeding)on the yield of BNNSs.A record of yield of 72.5%was achieved while the exfoliated BNNSs have few-layer and defect-free feature.Thanks to the Lewis acid sites of the boron atoms,the BNNSs can interact with the polysulfide anions in liquid electrolyte and also can facilitate the uniform lithium deposition,which finally endow a lithium-sulfur(Li-S)battery with long life.This work provides a facile and rapid strategy for large scale preparation of high-quality BNNSs,also contributes a long-life strategy for dendrite-free Li-S battery,opens new avenues of BNNSs in energy application.展开更多
Relaxor ferroelectric polymers display great potential in capacitor dielectric applications because of their excellent flexibility,light weight,and high dielectric constant.However,their electrical energy storage capa...Relaxor ferroelectric polymers display great potential in capacitor dielectric applications because of their excellent flexibility,light weight,and high dielectric constant.However,their electrical energy storage capacity is limited by their high conduction losses and low dielectric strength,which primarily originates from the impact-ionization-induced electron multiplication,low mechanical modulus,and low thermal conductivity of the dielectric polymers.Here a matrix free strategy is developed to effectively suppress electron multiplication effects and to enhance mechanical modulus and thermal conductivity of a dielectric polymer,which involves the chemical adsorption of an electron barrier layer on boron nitride nanosheet surfaces by chemically adsorbing an amino-containing polymer.A dramatic decrease of leakage current(from 2.4×10^(-6)to 1.1×10^(-7)A cm^(-2)at 100 MV m^(-1))and a substantial increase of breakdown strength(from 340 to 742 MV m^(-1))were achieved in the nanocompostes,which result in a remarkable increase of discharge energy density(from 5.2 to 31.8 J cm^(-3)).Moreover,the dielectric strength of the nanocomposites suffering an electrical breakdown could be restored to 88%of the original value.This study demonstrates a rational design for fabricating dielectric polymer nanocomposites with greatly enhanced electric energy storage capacity.展开更多
Heat dissipation becomes a critical problem because of the miniaturisation and the increase of power density in electronic devices and electric equipment,which calls for electrical insulating materials with high therm...Heat dissipation becomes a critical problem because of the miniaturisation and the increase of power density in electronic devices and electric equipment,which calls for electrical insulating materials with high thermal management capability.Epoxy thermosets have been widely used as electrical insulating materials,but suffer from their low thermal conductivity.This study reviewed the research progress on the development of epoxy thermosets with high pristine thermal conductivity.First,the thermal conduction mechanism of polymers was briefly introduced.Second,the approaches used to enhance the thermal conductivity of epoxy thermosets were summarised,which mainly dealt with the formation of microscopically anisotropic but macroscopically isotropic structure in the epoxy thermosets.Third,the applications of high thermal conductivity epoxy thermoset resins were reviewed.Finally,the review provided the existing challenges and the future directions for the development of epoxy thermosets with high pristine thermal conductivity.展开更多
The long-term safe operation of high-power equipment and integrated electronic devices requires efficient thermal management,which in turn increases the energy consumption further.Hence,the sustainable development of ...The long-term safe operation of high-power equipment and integrated electronic devices requires efficient thermal management,which in turn increases the energy consumption further.Hence,the sustainable development of our society needs advanced thermal management with low,even zero,energy consumption.Harvesting water from the atmosphere,followed by moisture desorption to dissipate heat,is an efficient and feasible approach for zero-energy-consumption thermal management.However,current methods are limited by the low absorbance of water,low water vapor transmission rate(WVTR)and low stability,thus resulting in low thermal management capability.In this study,we report an innovative electrospinning method to process hierarchically porous metal–organic framework(MOF)composite fabrics with high-efficiency and zero-energy-consumption thermal management.The composite fabrics are highly loaded with MOF(75 wt%)and their WVTR value can be up to 3138 g m^(-2) d^(-1).The composite fabrics also exhibit stable microstructure and performance.Under a conventional environment(30℃,60%relative humidity),the composite fabrics adsorb water vapor for regeneration within 1.5 h to a saturated value Wsat of 0.614 g g^(-1),and a corresponding equivalent enthalpy of 1705.6 J g^(-1).In the thermal management tests,the composite fabrics show a strong cooling capability and significantly improve the performance of thermoelectric devices,portable storage devices and wireless chargers.These results suggest that hierarchically porous MOF composite fabrics are highly promising for thermal management of intermittent-operation electronic devices.展开更多
High voltage power cables play a critical role in global electricity transmission and distribution.The currently used power cables cannot fulfil the green and sustainable requirement of modern society because of the t...High voltage power cables play a critical role in global electricity transmission and distribution.The currently used power cables cannot fulfil the green and sustainable requirement of modern society because of the thermoset nature of cable insulation and shields.This study is aimed at developing thermoplastic shields for high voltage power cable,which is one bottleneck restricting the development of environmental-friendly cables.Using carbon black(CB)as the main conductive component and a small amount of carbon nanotubes(CNTs)or graphene as the second filler,highly conductive polypropylene based composite materials were prepared for potential shield applications.It was found that,at a fixed conductive filler loading,the replacement of a small amount CB by CNTs can significantly enhance the electrical conductivity and suppress its temperature dependence.However,when CB was replaced by graphene,only limited enhancement of electrical conductivity could be achieved and the electrical conductivity is still highly dependent on temperature.Dissipative particle dynamics simulations demonstrated that the enhanced conduction property in the CNTs-containing composites could be understood by the shorter average distance between CB and CNTs.Finally,the coordination between the newly developed conductive composites and the environmental-friendly thermoplastic polypropylene insulation was evaluated via high voltage direct current measurements,and the results revealed that the CNTs-containing composites showed excellent suppression effect on the space charge injection and accumulation in the insulation.This research paved a new way for developing environmental-friendly high voltage power cable shields.展开更多
Surface charge density has been demostrated to be sigiantly impacted by the detric properties of tibomaterals.However,the ambiguous physical mechanism of dielectric manipulated charge behavior still restricts the cons...Surface charge density has been demostrated to be sigiantly impacted by the detric properties of tibomaterals.However,the ambiguous physical mechanism of dielectric manipulated charge behavior still restricts the construction of high performance tribomaterials.Here,using the atomic force microscopy and Kelvin probe force microscopy,an in situ method was conducted to investigate the contact letrification and charge dynamics on a typical tribomaterial(ie,BaTiOj/PVDF-TrFE nanocomposite)at nanoscale.Combined with the characterization of triboelectric device at macroscale,it is found that the number of transferred electrons increases with contact force/area and tends to reach saturation under increased friction cycles.The incorporated high permittivity BaTiO,nanoparticles enhance the capacitance and electron trapping capability of the nanocomposites,eficiently inhibiting the lateral difusion of electrons and improving the output performance of the triboelectric devices.Exponential decay of the surface potential is observed over monitoring time for all dielectric samples.At high BaTiO,loadings,more electrons can drift into the bulk and combine with the induced charges on the back electrode,forming a large leakage current and accordingly accelerating the electron dissipation.Hence,the charge trapping/storing and dissipating,as well as the charge attracting properties,should be comprehensively considered in the design of high-performance tribomateras.展开更多
基金supported by the National Natural Science Foundation of China (No. 51877132)the Program of Shanghai Academic Research Leader (No. 21XD1401600)the Beijing Natural Science Foundation (No. 2214061)。
文摘Solid polymer electrolytes (SPEs) are urgently required for achieving practical all-solid-state lithium metal batteries (ASSLMBs) but remain plagued by low ionic conductivity.Herein,we propose a strategy of salt polarization to fabricate a highly ion-conductive SPE by employing a high-dielectric polymer that can interact strongly with lithium salts.Such a polymer with large dipole moments can guide lithium cations (Li^(+)) to be arranged along the chain,forming a continuous pathway for Li^(+) hopping within the SPE.The as-fabricated SPE,poly(vinylidene difluoride)(PVDF)-LiN(SO_(2)F)_(2)(LiFSI),has an extraordinarily high dielectric constant (up to 10^(8)) and ultrahigh ionic conductivity (0.77×10^(-3)S cm^(-1)).Based on the PVDF–LiFSI SPE,the assembled Li metal symmetrical cell shows excellent Li plating/stripping reversibility at 0.1 m A cm^(-2),0.1 m Ah cm^(-2)over 1500 h^(-1) the ASS LiFePO_(4) batteries deliver long-term cycling stability at 1 C over 350 cycles (2.74 mg cm^(-2)) and an ultralong cycling lifespan of over 2600 h(100 cycles) with high loading (11.5 mg cm^(-2)) at 28°C.First-principles calculations further reveal the ion-dipole interactions-controlled conduction of Li^(+) in PVDF–LiFSI SPE along the PVDF chain.This work highlights the critical role of dielectric permittivity in SPE,and provides a promising path towards high-energy,long-cycling lifespan ASSLMBs.
基金This work was supported by the National Natural Science Foundation of China(Numbers:U19A20105,51877132).
文摘Phase change materials(PCMs)can be used for efficient thermal energy harvesting,which has great potential for cost-effective thermal management and energy storage.However,the low intrinsic thermal conductivity of polymeric PCMs is a bottleneck for fast and efficient heat harvesting.Simultaneously,it is also a challenge to achieve a high thermal conductivity for phase change nanocomposites at low filler loading.Although constructing a three-dimensional(3D)thermally conductive network within PCMs can address these problems,the anisotropy of the 3D framework usually leads to poor thermal conductivity in the direction perpendicular to the alignment of fillers.Inspired by the interlaced structure of spider webs in nature,this study reports a new strategy for fabricating highly thermally conductive phase change composites(sw-GS/PW)with a 3D spider web(sw)-like structured graphene skeleton(GS)by hydrothermal reaction,radial freeze-casting and vacuum impregnation in paraffin wax(PW).The results show that the sw-GS hardly affected the phase transformation behavior of PW at low loading.Especially,sw-GS/PW exhibits both high cross-plane and in-plane thermal conductivity enhancements of~1260%and~840%,respectively,at an ultra-low filler loading of 2.25 vol.%.The thermal infrared results also demonstrate that sw-GS/PW possessed promising applications in battery thermal management.
基金financially National Natural Science Foundation of China(51877132)Joint Funds of National Natural Science Foundation of China(U19A20105)the Program of Shanghai Academic Research Leader(No.21XD1401600)。
文摘Thermal management has become a crucial problem for high-power-density equipment and devices.Phase change materials(PCMs)have great prospects in thermal management applications because of their large capacity of heat storage and isothermal behavior during phase transition.However,low intrinsic thermal conductivity,ease of leakage,and lack of flexibility severely limit their applications.Solving one of these problems often comes at the expense of other performance of the PCMs.In this work,we report core–sheath structured phase change nanocomposites(PCNs)with an aligned and interconnected boron nitride nanosheet network by combining coaxial electrospinning,electrostatic spraying,and hot-pressing.The advanced PCN films exhibit an ultrahigh thermal conductivity of 28.3 W m^(-1)K^(-1)at a low BNNS loading(i.e.,32 wt%),which thereby endows the PCNs with high enthalpy(>101 J g^(-1)),outstanding ductility(>40%)and improved fire retardancy.Therefore,our core–sheath strategies successfully balance the trade-off between thermal conductivity,flexibility,and phase change enthalpy of PCMs.Further,the PCNs provide powerful cooling solutions on 5G base station chips and thermoelectric generators,displaying promising thermal management applications on high-power-density equipment and thermoelectric conversion devices.
基金supported by China Postdoctoral Science Foundation(2021M690103)National Natural Science Foundation of China(52003153,51877132,and 52002300)+2 种基金Program of Shanghai Academic Research Leader(21XD1401600)State Key Laboratory of Electrical Insulation and Power Equipment(EIPE20203,EIPE21206)the Major Research Plan of National Natural Science Foundation of China(92066103)。
文摘Dielectric polymer nanocomposites are considered as one of the most promising candidates for high-power-density electrical energy storage applications.Inorganic nanofillers with high insulation property are frequently introduced into fluoropolymer to improve its breakdown strength and energy storage capability.Normally,inorganic nanofillers are thought to introducing traps into polymer matrix to suppress leakage current.However,how these nanofillers effect the leakage current is still unclear.Meanwhile,high dopant(>5 vol%)is prerequisite for distinctly improved energy storage performance,which severely deteriorates the processing and mechanical property of polymer nanocomposites,hence brings high technical complication and cost.Herein,boron nitride nanosheet(BNNS)layers are utilized for substantially improving the electrical energy storage capability of polyvinylidene fluoride(PVDF)nanocomposite.Results reveal that the high conduction band minimum of BNNS produces energy barrier at the interface of adjacent layers,preventing the electron in PVDF from passing through inorganic layers,leading to suppressed leakage current and superior breakdown strength.Accompanied by improved Young’s modulus(from 1.2 GPa of PVDF to 1.6 GPa of nanocomposite),significantly boosted discharged energy density(14.3 J cm^(-3)) and charge-discharge efficiency(75%)are realized in multilayered nanocomposites,which are 340 and 300% of PVDF(4.2 J cm^(-3),25%).More importantly,thus remarkably boosted energy storage performance is accomplished by marginal BNNS.This work offers a new paradigm for developing dielectric nanocomposites with advanced energy storage performance.
基金financially supported by the National Natural Science Foundation of China(No.U19A20105)。
文摘Three-dimensional(3 D)graphene-based aerogels have significant potential for adsorption,sensors,and thermal management applications.However,their practical applications are limited by their disorganized structure and ultra-low resilience after compression.Some methods can realize a well-aligned structure,however,they involve high costs and complex technology.Herein,a 3 D graphene hybrid aerogel with an anisotropic open-cell and well-oriented structure is realized by unidirectional freeze casting,which combines the‘soft’(e.g.graphene oxide,Tween-80)and‘hard’(e.g.graphene assembly)components to realize full recovery after flattening.A graphene aerogel annealed at a moderate temperature(200℃)can possess superhydrophilicity and outstanding wet-resilience properties,including after being pressed under40 MPa.Furthermore,the graphene aerogel annealed at a high temperature of 1500℃exhibits excellent thermal conductivity enhancement efficiency in polydimethylsiloxane(PDMS).The resultant nanocomposites clearly demonstrate anisotropic thermal conductivity and promising applications as thermal interface materials.This strategy offers new insights into the design and fabrication of 3 D multifunctional graphene aerogels.
基金The financial support from National Natural Science Foundation of China(No.51877132)。
文摘Nanocomposites comprising flexible polymers and high dielectric constant inorganic nanoparticles are considered to be one of the promising candidates for electrostatic capacitor dielectrics.However,the effect of interfacial property on electrical ene rgy storage of dielectric polymer nanocomposites is still not clear.Herein,the role of the polarity of the interfacial region is investigated.For this purpose,three polymers with different polarity,polymethyl methacrylate(PMMA),polyglycidyl methacrylate,and polymethylsulfonyl ethyl methacrylate(PMSEMA)are attached onto BaTi0_(3)(BT)na noparticle surface via surface-initiated reversible addition-fragmentation chain transfer polymerization.It is found that the polarity of shell polymers shows an apparent effect on the dielectric and energy storage of dielectric polymer nanocomposites.For example,PMSEMA@BT(shell polymer possesses the highest polarity)increases dielectric loss and decreases the breakdown strength of the nanocomposites,leading to lower ene rgy storage capability.However,PMMA@BT(shell polymer possesses the lowest polarity)can induce higher breakdown strength of the nanocomposites.As a result,the PMMA@BT nanocomposite exhibits the highest electrical energy sto rage capability among the three nanocomposites.This re search provides new insight into the design of core-shell nanofillers for dielectric energy storage applications.
基金Medical Engineering Cross Research Foundation of Shanghai Jiao Tong University(YG2021QN63).
文摘The development of wearable and portable electronics calls for flexible piezoelectric materials to fabricate selfpowered devices.However,a big challenge in piezoelectric material design is to boost the output performance while ensuring its flexibility and biocompatibility.Here,all-organic and core-shell structured silk fibroin(SF)/poly(vinylidene difluoride)(PVDF)piezoelectric nanofibers(NFs)with excellent flexibility are fabricated using a simple electrospinning strategy.The strong intermolecular interaction between SF and PVDF promotes theβ-phase nucleation in the core-shell structure,which significantly enhances the output performance.An output of 16.5 V was achieved in SF/PVDF NFs,which is more than 6-fold enhancement compared with that of pure PVDF NFs.In addition,the piezoelectric device can sensitively detect the mechanical stimulation from joint bending,demonstrating its great potential in self-powered sensor.Otherwise,the piezoelectric device can be also applied to control the movement of a smart car,successfully,achieving its application in the human-machine interaction.
基金support from Special Fund of the National Priority Basic Research of China (No. 2014CB239503)the National Natural Science Foundation of China (Nos. 51522703, 51477096) was acknowledged
文摘Polymeric dielectrics have wide range of applications in the field of electrical energy storage because of their light weight and easy processing. However, the state-of-the-art polymer dielectrics, such as biaxially orientated polypropylene, could not meet the demand of minimization of electronic devices because of its low energy density. Recently, poly（vinylidene fluoride） （PVDF） based ferroelectric polymers have attracted considerable interests for energy storage applications because of their high permittivity and high breakdown strength. Unfortunately, the high dielectric loss and/or high remnant polarization of PVDF-based polymers seriously limits their practical applications for electrical energy storage. Since the discovery of relaxor ferroelectric behavior was firstly reported in irradiated poly（vinylidene fluoride- trifluoroethylene） （P（VDF-TrFE）） copolyrner, many strategies have been developed to enhanced the electrical energy storage capability, including copolymerization, grafting, blending and fabricating of multilayer How these methods affect the polymorphs, crystallinity, crystal size of PVDF-based polymers and the connection between these microstructures and their corresponding energy storage properties are discussed in detail.
基金supported by the National Natural Science Foundation of China(No.51877132).
文摘Ultrathin and flexible electromagnetic shielding materials hold great potential in civil and military applications.Despite tremendous research efforts,the development of advanced shielding materials is still needed to provide additional functionalities for various artificial-intelligence-driven systems,such as tactile sensing ability.Herein,a layering design strategy is proposed to fabricate ultrathin Ti_(3)C_(2)T_(x)MXene-aramid nanofiber(MA)films by a layer-by-layer assembling process.Compared to that of randomly mixed films,the designed MA films exhibited a higher EMI shielding efficiency at an ultrathin thickness of 9 pm,which increased from 26.4 to 40.7 dB,owing to the additional multiple-interface scattering mechanism.Importantly,the novel MA films displayed strong EMI shielding ability even after heating/cooling treatments within a wide temperature range of-196 to 300℃.Moreover,the same material displayed a tensile strength of 124.1±2.7 MPa and a toughness of 6.3±1.1 MJ·m^(-3),which are approximately 9.1 times and 45 times higher than those of pure MXene films,respectively.The MA film is also capable of detecting tactile signals via the triboelectric effect.A 2×4 tactile sensor array was developed to achieve an accurate signal catching capability.Therefore,in addition to the shielding performance,the manifestation of tactile perception by the MA films offers exciting opportunities in the fields of soft robotics and human-machine interactions.
基金This work was financial supported by the National Natural Science Foundation of China(Nos.51877132,52003153,and 22005186)the Program of Shanghai Academic Research Leader(No.21XD1401600).
文摘Lithium(Li)metal batteries(LMBs)can potentially deliver much higher energy density but remain plagued by uncontrollable Li plating with dendrite growth,unstable interfaces,and highly abundant excess Li(>50 mAh·cm^(-2)).Herein,different from the artificial layer or three-dimensional(3D)matrix host constructions,various dielectric polymers are initially well-comprehensively investigated from experimental characterizations to theoretical simulation to evaluate their functions in modulating Li ion distribution.As a proof of concept,a 3D interwoven high dielectric functional polymer(HDFP)nanofiber network with polar C-F dipole moments electrospun on copper(Cu)foil is designed,realizing uniform and controllable Li deposition capacity up to 5.0 mAh·cm^(-2),thereby enabling stable Li plating/stripping cycling over 1400 h at 1.0 mA·cm^(-2).More importantly,under the highcathode loading(~3.1 mAh·cm^(-2))and only 0.6×excess Li(N/P ratio of 1.6),the full cells retain capacity retention of 97.4%after 200 cycles at 3.36 mA·cm^(-2)and achieve high energy density(297.7 Wh·kg^(-1)at cell-level)under lean electrolyte conditions(15μL),much better than ever-reported literatures.Our work provides a new direction for designing high dielectric polymer coating toward high-retention-rate practical Li full batteries.
基金This work was supported by the National Natural Science Foundation of China(No.51877132).
文摘Boron nitride nanosheets(BNNSs)have gained significant attraction in energy and environment fields because of their two-dimensional(2D)nature,large band gap and high thermal/mechanical performance.However,the current low production efficiency of high-quality BNNSs is still a bottleneck limiting their applications.Herein,based on sonication-assisted liquid-phase exfoliation,we demonstrated a rapid,high-efficient and scalable production strategy of BNNSs and documented the effects of a spectrum of exfoliation factors(e.g.,ultrasonic condition,solvent and bulk material feeding)on the yield of BNNSs.A record of yield of 72.5%was achieved while the exfoliated BNNSs have few-layer and defect-free feature.Thanks to the Lewis acid sites of the boron atoms,the BNNSs can interact with the polysulfide anions in liquid electrolyte and also can facilitate the uniform lithium deposition,which finally endow a lithium-sulfur(Li-S)battery with long life.This work provides a facile and rapid strategy for large scale preparation of high-quality BNNSs,also contributes a long-life strategy for dendrite-free Li-S battery,opens new avenues of BNNSs in energy application.
基金supported by the National Natural Science Foundation of China(52003153,51877132 and 52002300)Program of Shanghai Academic Research Leader(21XD1401600)+1 种基金State Key Laboratory of Electrical Insulation and Power Equipment(EIPE20203,EIPE21206)the Major Research Plan of National Natural Science Foundation of China(92066103)。
文摘Relaxor ferroelectric polymers display great potential in capacitor dielectric applications because of their excellent flexibility,light weight,and high dielectric constant.However,their electrical energy storage capacity is limited by their high conduction losses and low dielectric strength,which primarily originates from the impact-ionization-induced electron multiplication,low mechanical modulus,and low thermal conductivity of the dielectric polymers.Here a matrix free strategy is developed to effectively suppress electron multiplication effects and to enhance mechanical modulus and thermal conductivity of a dielectric polymer,which involves the chemical adsorption of an electron barrier layer on boron nitride nanosheet surfaces by chemically adsorbing an amino-containing polymer.A dramatic decrease of leakage current(from 2.4×10^(-6)to 1.1×10^(-7)A cm^(-2)at 100 MV m^(-1))and a substantial increase of breakdown strength(from 340 to 742 MV m^(-1))were achieved in the nanocompostes,which result in a remarkable increase of discharge energy density(from 5.2 to 31.8 J cm^(-3)).Moreover,the dielectric strength of the nanocomposites suffering an electrical breakdown could be restored to 88%of the original value.This study demonstrates a rational design for fabricating dielectric polymer nanocomposites with greatly enhanced electric energy storage capacity.
基金the finical support from National Natural Science Foundation of China(nos.51522703,51477096)the Special Fund of the National Priority Basic Research of China(2014CB239503).
文摘Heat dissipation becomes a critical problem because of the miniaturisation and the increase of power density in electronic devices and electric equipment,which calls for electrical insulating materials with high thermal management capability.Epoxy thermosets have been widely used as electrical insulating materials,but suffer from their low thermal conductivity.This study reviewed the research progress on the development of epoxy thermosets with high pristine thermal conductivity.First,the thermal conduction mechanism of polymers was briefly introduced.Second,the approaches used to enhance the thermal conductivity of epoxy thermosets were summarised,which mainly dealt with the formation of microscopically anisotropic but macroscopically isotropic structure in the epoxy thermosets.Third,the applications of high thermal conductivity epoxy thermoset resins were reviewed.Finally,the review provided the existing challenges and the future directions for the development of epoxy thermosets with high pristine thermal conductivity.
基金supported by the National Natural Science Foundation of China(51877132,U19A20105,and 52003153)the Program of Shanghai Academic Research Leader(21XD1401600)。
文摘The long-term safe operation of high-power equipment and integrated electronic devices requires efficient thermal management,which in turn increases the energy consumption further.Hence,the sustainable development of our society needs advanced thermal management with low,even zero,energy consumption.Harvesting water from the atmosphere,followed by moisture desorption to dissipate heat,is an efficient and feasible approach for zero-energy-consumption thermal management.However,current methods are limited by the low absorbance of water,low water vapor transmission rate(WVTR)and low stability,thus resulting in low thermal management capability.In this study,we report an innovative electrospinning method to process hierarchically porous metal–organic framework(MOF)composite fabrics with high-efficiency and zero-energy-consumption thermal management.The composite fabrics are highly loaded with MOF(75 wt%)and their WVTR value can be up to 3138 g m^(-2) d^(-1).The composite fabrics also exhibit stable microstructure and performance.Under a conventional environment(30℃,60%relative humidity),the composite fabrics adsorb water vapor for regeneration within 1.5 h to a saturated value Wsat of 0.614 g g^(-1),and a corresponding equivalent enthalpy of 1705.6 J g^(-1).In the thermal management tests,the composite fabrics show a strong cooling capability and significantly improve the performance of thermoelectric devices,portable storage devices and wireless chargers.These results suggest that hierarchically porous MOF composite fabrics are highly promising for thermal management of intermittent-operation electronic devices.
基金This work was financially supported by National Basic Research Program of China(2014CB239503)National Natural Science Foundation of China(51877132).
文摘High voltage power cables play a critical role in global electricity transmission and distribution.The currently used power cables cannot fulfil the green and sustainable requirement of modern society because of the thermoset nature of cable insulation and shields.This study is aimed at developing thermoplastic shields for high voltage power cable,which is one bottleneck restricting the development of environmental-friendly cables.Using carbon black(CB)as the main conductive component and a small amount of carbon nanotubes(CNTs)or graphene as the second filler,highly conductive polypropylene based composite materials were prepared for potential shield applications.It was found that,at a fixed conductive filler loading,the replacement of a small amount CB by CNTs can significantly enhance the electrical conductivity and suppress its temperature dependence.However,when CB was replaced by graphene,only limited enhancement of electrical conductivity could be achieved and the electrical conductivity is still highly dependent on temperature.Dissipative particle dynamics simulations demonstrated that the enhanced conduction property in the CNTs-containing composites could be understood by the shorter average distance between CB and CNTs.Finally,the coordination between the newly developed conductive composites and the environmental-friendly thermoplastic polypropylene insulation was evaluated via high voltage direct current measurements,and the results revealed that the CNTs-containing composites showed excellent suppression effect on the space charge injection and accumulation in the insulation.This research paved a new way for developing environmental-friendly high voltage power cable shields.
基金supported by the National Natural Science Foundation of China(52103303,51877132,and 52003153)China Postdoctoral,Science Foundation(2021M702089)+2 种基金Program of Shanghai Academic Research Leader(21XD1401600)State Key Laboratory of Electrical InsulationandPower Equipment(EIPE20203and EIPE21206)and Science and Technology Project of State Grid(SGSHDK00SPJS2100196).
文摘Surface charge density has been demostrated to be sigiantly impacted by the detric properties of tibomaterals.However,the ambiguous physical mechanism of dielectric manipulated charge behavior still restricts the construction of high performance tribomaterials.Here,using the atomic force microscopy and Kelvin probe force microscopy,an in situ method was conducted to investigate the contact letrification and charge dynamics on a typical tribomaterial(ie,BaTiOj/PVDF-TrFE nanocomposite)at nanoscale.Combined with the characterization of triboelectric device at macroscale,it is found that the number of transferred electrons increases with contact force/area and tends to reach saturation under increased friction cycles.The incorporated high permittivity BaTiO,nanoparticles enhance the capacitance and electron trapping capability of the nanocomposites,eficiently inhibiting the lateral difusion of electrons and improving the output performance of the triboelectric devices.Exponential decay of the surface potential is observed over monitoring time for all dielectric samples.At high BaTiO,loadings,more electrons can drift into the bulk and combine with the induced charges on the back electrode,forming a large leakage current and accordingly accelerating the electron dissipation.Hence,the charge trapping/storing and dissipating,as well as the charge attracting properties,should be comprehensively considered in the design of high-performance tribomateras.
