Separators have been gaining increasing attention to improve the performance of lithium ion batteries(LIBs),especially for high safe and long cycle life.However,commercial polyolefin separators still face the problems...Separators have been gaining increasing attention to improve the performance of lithium ion batteries(LIBs),especially for high safe and long cycle life.However,commercial polyolefin separators still face the problems of rapid capacity decay and safety issues due to the poor wettability with electrolytes and low thermal stability.Herein,a novel composite separator is proposed by introducing a surfactant of sodium dodecyl thiosulfate(SDS)into the polytetrafluoroethylene(PTFE)substrate with the binder of polyacrylic acid(PAA)through the suction filtration method.The introduction of PAA/SDS enhances the adsorption energy between PTFE substrate and electrolyte through density functional theory calculations,which improves wettability and electrolyte uptake of the separator significantly.The asachieved composite separator enables the LIBs to own high Li^(+)conductivity(0.64×10^(-3)S cm^(-1))and Li^(+)transference number(0.63),further leading to a high capacity retention of 93.50%after 500 cycles at 1 C.In addition,the uniform and smooth surface morphology of Li metal employed the composite separator after cycling indicates that the lithium dendrites can be successfully inhibited.This work indicates a promising route for the preparation of a novel composite separator for high safe LIBs.展开更多
As the energy density of lithium-ion batteries (LIBs) continues to increase,their safety has become a great concern for further practical large-scale applications.One of the ultimate solution of the safety issue is to...As the energy density of lithium-ion batteries (LIBs) continues to increase,their safety has become a great concern for further practical large-scale applications.One of the ultimate solution of the safety issue is to develop intrinsically safe battery components,where the battery separators and liquid electrolytes are critical for the battery thermal runaway process.In this review,we summarize recent progress in the rational materials design on battery separators and liquid electrolyte towards the goal of improving the safety of LIBs.Also,some strategies for further improving safety of LIBs are also briefly outlooked.展开更多
Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is im- portant for the battery energy density. In this study, we grafted organic/ino...Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is im- portant for the battery energy density. In this study, we grafted organic/inorganic hybrid crosslinked networks on the separators, simply by grafting polymerization and condensation reaction. The considerable silicon-oxygen crosslinked heat-resistance networks are responsible for the reduced thermal shrinkage. The strong chemical bonds between networks and separators promise enough mechanical support even at high temperature. The shrinkage at 150 ℃ for 30 min in the mechanical direction was 38.6% and 4.6% for the pristine and present graft-modified separators, respectively. Meanwhile, the grafting organic-inorganic hybrid crosslink networks mainly occupied part of void in the internal pores of the separators, so the thicknesses of the graft-modified separators were similar with the pristine one. The half cells prepared with the modified separators exhibited almost identical electrochemical properties to those with the commercial separators, thus proving that, in order to enhance the thermal stability of lithium ion battery, this kind of grafting-modified separators may be a better alternative to conventional silica nanoparticle layers-coated polyolefin separators.展开更多
Thermal runaway is the main factor contributing to the unsafe behaviors of lithium-ion batteries(LIBs)in practical applications.The application of separators for the thermal shutdown has been proven as an effective ap...Thermal runaway is the main factor contributing to the unsafe behaviors of lithium-ion batteries(LIBs)in practical applications.The application of separators for the thermal shutdown has been proven as an effective approach to protecting LIBs from thermal runaway.In this work,we developed a thermal shutdown separator by coating a thin layer of low-density polyethylene microspheres(PM)onto a commercial porous polypropylene(PP)membrane and investigated the thermal response behaviors of the as-prepared PM/PP separator in LIBs.The structural and thermal analysis results revealed that the coated PM layer had a porous structure,which facilitated the occurrence of normal charge-discharge reactions at ambient temperature,although it could melt completely and fuse together within very short time periods:3 s at 110℃and 1 s at 120℃,to block off the pores of the PP substrate,thereby cutting off the ion transportation between the electrodes and interrupting the battery reaction.Consequently,the PM/PP separator exhibits very similar electrochemical performance to that of a conventional separator at ambient temperature.However,it performs a rapid thermal shutdown at an elevated temperature of^110℃,thus controlling the temperature rise and maintaining the cell in a safe status.Due to its synthetic simplicity and low cost,this separator shows promise for possible application in building safe LIBs.展开更多
Membranes of polypropylene (PP), PP coated with nano-A1203, PP electrospun with polyvinylidene fluoride- hexafluoropropylene (PVdF-HFP), and trilayer laminates of polypropylene-polyethylene-polypropylene (PP/PE/P...Membranes of polypropylene (PP), PP coated with nano-A1203, PP electrospun with polyvinylidene fluoride- hexafluoropropylene (PVdF-HFP), and trilayer laminates of polypropylene-polyethylene-polypropylene (PP/PE/PP) were comparatively studied. Their physical properties were characterized by means of thermal shrinkage test, liquid electrolyte uptake, and field emission scanning electron microscopy (FESEM). Results show that, for the different membranes as PP, PP coated with nanowA1203, PP electrospun with PVdF-HFP, and PP/PE/PP, the thermal shrinkages are 14%, 6%, 12.6%, and 13.3%, while the liquid electrolyte uptakes are 110%, 150%, 217%, and 129%, respectively. In addition, the effects on the performance of lithium-ion batteries (LiFePO4 and LiNil/3Col/3Mn1/302 as the cathode material) were investigated by AC impedance and galvanostatic charge/discharge test. It is found that PP coated with A1203 and PP electrospun with PVdF-HFP can effectively increase the wettability between the cathode material and liquid electrolyte, and therefore reduce the charge transfer resistance, which improves the capacity retention and battery performance.展开更多
To improve the affinity between separators and electrolyte in lithium-ion battery,microporous polyethylene(PE) separator was grafted of polyacrylamide(PAAm) by radiation.Chemical structure of the PAAmgrafted PE separa...To improve the affinity between separators and electrolyte in lithium-ion battery,microporous polyethylene(PE) separator was grafted of polyacrylamide(PAAm) by radiation.Chemical structure of the PAAmgrafted PE separators(denoted as PE-g-PAAm) was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.Properties of the pristine PE and PE-g-PAAm were tested by scanning electron microscope,liquid electrolyte uptake and lithium-ion conductivity.Electrochemical performances of the grafted PE separators(up to 0.76 × 10^(-3) S/cm of ionic conductivity at room temperature) were much better than pristine PE,and performance of the battery with the grafted separator behaved better than with the virgin PE separator,under the same condition(assembled in Ar-filled glove box).展开更多
The separator with excellent mechanical and thermal properties are highly required for lithium ion batteries(LIBs).Therefore,it is crucial to develop novel nanofbrous membranes with enhanced mechanical strength and th...The separator with excellent mechanical and thermal properties are highly required for lithium ion batteries(LIBs).Therefore,it is crucial to develop novel nanofbrous membranes with enhanced mechanical strength and thermal stability.In this work,the fuorinated polyimide(FPI)was synthesized and blended with polyvinylidene fuoride(PVDF)to fabricate composite nanofbrous membranes(CNMs)via electrospinning method.Benefting from the introduction of aromatic FPI,the prepared PVDF/FPI nanofbrous membranes were endowed with enhanced mechanical strength and thermal stability.When the FPI content increased from 0 to 30 wt%,the tensile strength of composite nanofbrous membranes enhanced from 1.57 to 2.30 MPa.Moreover,there are almost no dimensional shrinkage for the CNM-30 containing 30 wt%FPI after heat treatment at 160℃ for 1 h.Furthermore,the prepared CNMs show improved electrochemical performances in comparison with neat PVDF and commercial Celgard membranes.The electrolyte uptake and ionic conductivity of the CNMs could reach to 522.4% and 1.14 ms·cm^(−1),respectively.The prepared CNMs could provide an innovative and promising approach for the development and design of high-performance separators.展开更多
The performances of lithium-ion batteries(LIBs)are dependent on the wettability and stability of porous separators.Musselinspired coatings seem to be useful to improve the surface wettability of commercialized polyole...The performances of lithium-ion batteries(LIBs)are dependent on the wettability and stability of porous separators.Musselinspired coatings seem to be useful to improve the surface wettability of commercialized polyolefin separators.However,it is still a challenge to guarantee their stability under polar electrolytes.Herein,we report a facile and versatile way to enhance the wettability and stability of polypropylene separators by constructing robust polydopamine(PDA)coatings triggered with CuSO4/H2O2.These coatings were conveniently deposited on the polypropylene separator surfaces and the PDA-coated separators exhibited the improved surface wettability and thermal stability.The electrolyte uptake increased nearly two folds from the pristine separator to the modified ones.Correspondingly,the ionic conductivity also rose from 0.82 mS·cm^-1 to 1.30 mS·cm^-1.Most importantly,the CuSO4/H2O2-triggered PDA coatings were very stable under strong polar electrolytes,endowing the cells with excellent cycle performance and enhanced C-rate capacity.Overall,the results unequivocally demonstrate that application of PDA coatings on polyolefin separator triggered by CuSO4/H2O2 is a facile and efficient method for improving the wettability and stability of separators for high LIBs performance.展开更多
To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation ...To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 ×10^-3 S.cm^-1 at 25℃, and the electrochemical stability window was up to 4.5 V (versus Li^+/Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.展开更多
Lithium-sulfur(Li-S)batteries are highly regarded as the next-generation high-energy-density secondary batteries due to their high capacity and large theoretical energy density.However,the practical application of the...Lithium-sulfur(Li-S)batteries are highly regarded as the next-generation high-energy-density secondary batteries due to their high capacity and large theoretical energy density.However,the practical application of these batteries is hindered mainly by the polysulfide shuttle issue.Herein,we designed and synthesized a new lithium sulfonylimide covalent organic framework(COF)material(COF-LiSTFSI,LiSTFSI=lithium(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide),and further used it to modify the common polypropylene(PP)separator of Li-S batteries.The COF-LiSTFSI with sulfonylimide anion groups features stronger electronegativity,thus can effectively facilitate the lithium ion conduction while significantly suppress the diffusion of polysulfides via the electrostatic interaction.Compared with the unmodified PP separator,the COF-LiSTFSI modified separator results in a high ionic conductivity(1.50 mS·cm^(−1))and Li+transference number(0.68).Consequently,the Li-S battery using the COF-LiSTFSI modified separator achieves a high capacity of 1229.7 mAh·g^(−1)at 0.2 C and a low decay rate of only 0.042%per cycle after 1000 cycles at 1 C,compared with those of 941.5 mAh·g^(−1)and 0.061%using the unmodified PP separator,respectively.These results indicate that by choosing suitable functional groups,an effective strategy for COF-modified separators could be developed for high-performance Li-S batteries.展开更多
Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous b...Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores (-1.0 μm) and two surfaces with small pores (-30 nm). This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity (1.72 mS.cm-1) at room temperature. Lithium iron phosphate (LiFePO4)/lithium (Li) cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.展开更多
Coating commercial porous polyolefin separators with inorganic materials can improve the thermal stability of the polyolefin separators and hence improve the safety of lithium-ion batteries. Several different inorgani...Coating commercial porous polyolefin separators with inorganic materials can improve the thermal stability of the polyolefin separators and hence improve the safety of lithium-ion batteries. Several different inorganic materials have been studied for the coating. However, there lacks a study on how different the properties of separators, in inorganic materials affect terms of thermal stability and cell performance. Herein, we present such a study on coating a commercial polypropylene separator with four inorganic materials, i.e., Al2O3, SiO2, ZrO2 and zeolite. All inorganic coatings have improved thermal stability of the separators although with differences. The coating layers add 28%-45% of electrical resistance compared with the pure polypropylene separator, but all the cells prepared with the coated polypropylene separators have the same electrical chemical performance as the uncoated separator in terms of rate capability and capacities at different temperatures.展开更多
In lithium-ion batteries(LIBs),separators play a vital role in lithium-ion(Li+)transport,and thus affect rate performance,battery life,and safety.Here,a new kind of multifunctional copolymer poly(acrylonitrile-co-lith...In lithium-ion batteries(LIBs),separators play a vital role in lithium-ion(Li+)transport,and thus affect rate performance,battery life,and safety.Here,a new kind of multifunctional copolymer poly(acrylonitrile-co-lithium acrylate-co-butyl acrylate)(PAAB-Li)is synthesized through soap-free emulsion polymerization,and is used to form homogeneous-covered separator based on PP matrix by a simple dip-annealing process.Compared to the bare PP separator,the modified separators with PAAB-Li enable higher ionic conductivity,higher lithium ion transference number(increased from 0.360 to 0.525),and lower interface impedance(reduced from 155Ω to 34Ω).It has been indicated that PAAB-Li functional layer significantly promotes the fast transport of Li+and improves the compatibility of the separator/electrolyte-electrode interface.The LiCo02/graphite cells with the PAAB-Li-assisted separator demonstrate excellent cycle stability and rate performance.In addition,the Li symmetric cells with the modified separator stably cycle over 800 h,indicating the functional layer effectively suppresses the lithium dendrite growth.This facile strategy can be easily applied to LIBs requiring high safety and even be scalable to Li metal batteries.Moreover,the possible mechanism of the PAAB-Li functional layer promoting fast and uniform Li+transport is discussed in this paper.展开更多
Lithium-ion batteries(LIB)are the dominant power sources for many consumer electronics,and they can also be large-scale power sources/energy storage devices,which can be credited to their advantages:high efficiency,hi...Lithium-ion batteries(LIB)are the dominant power sources for many consumer electronics,and they can also be large-scale power sources/energy storage devices,which can be credited to their advantages:high efficiency,high energy density,long cycling life.The separator membrane is a critical component of LIB.It is an electron insulator between the cathode and anode electrodes in order to prevent electrical short circuits,and it also functions as an ionic conductor to let ions pass freely in the charging and discharging cycles.The critical parameters to meet high quality separator membranes include:high dimensional/thermal/chemical stability,good wettability towards electrolyte,high mechanical strength,appropriate porosity and pore size distribution.Conventionally,plastic materials,such as polyolefin,are the main materials for manufacturing LIB separator membrane.However,polyolefin separator s have a number of drawbacks such as poor thermal stability and wettability.Cellulosic materials have unique properties,and can meet the quality specifications of LIB separator membranes;in addition,they are abundant,low cost,biodegradable,renewable and sustainable.Therefore,cellulose and its related materials can be promising alternatives to replace polyolefin for LIB separator membranes.In this short review,relevant literature on the topic was reviewed and further development/improvement of cellulose-based LIB separator membrane will be discussed.展开更多
To improve the electrolyte wettability and thermal stability of polypropylene (PP) separators, nano- SiO2/poly(vinyl alcohol)-coated PP composite separators were prepared using a simple but efficient sol-gel and d...To improve the electrolyte wettability and thermal stability of polypropylene (PP) separators, nano- SiO2/poly(vinyl alcohol)-coated PP composite separators were prepared using a simple but efficient sol-gel and dip-coating method. The effects of the tetraethoxysilane (TEOS) dosage on the morphology, wettability, and thermal stability of the composite separators were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, and contact-angle measurements. All the composite separators gave a smaller contact angle, higher electrolyte uptake, and lower thermal shrinkage compared with the PP separator, indicating enhanced wettability and thermal stability. Unlike the case for a traditional physical mixture, Si-O-C covalent bonds were formed in the coating layer. The composite separator with a TEOS dosage of 7.5 wt% had a unique porous structure combining hierarchical pores with interstitial voids, and gave the best wettability and thermal stability. The ionic conductivity of the composite separator containing 7.5 wt% TEOS was 1.26 mS/cm, which is much higher than that of the PP separator (0.74 mS/cm). The C-rate and cycling performances of batteries assembled with the composite separator containing 7.5 wt% TEOS were better than those of batteries containing PP separators.展开更多
1 Results A separator for rechargeable batteries is a microporous membrane placed between electrodes of opposite polarity, keeping them apart to prevent electrical short circuits and at the same time allowing rapid tr...1 Results A separator for rechargeable batteries is a microporous membrane placed between electrodes of opposite polarity, keeping them apart to prevent electrical short circuits and at the same time allowing rapid transport of lithium ions that are needed to complete the circuit during the passage of current in an electrochemical cell, and thus plays a key role in determining the performance of the lithium ion battery. Here provides a comprehensive overview of various types of separators for lithium io...展开更多
The absence of control over carriers transport during electrochemical cycling,accompanied by the deterioration of the solid electrolyte interphase(SEI)and the growth of lithium dendrites,has hindered the development o...The absence of control over carriers transport during electrochemical cycling,accompanied by the deterioration of the solid electrolyte interphase(SEI)and the growth of lithium dendrites,has hindered the development of lithium metal batteries.Herein,a separator complexion consisting of polyacrylonitrile(PAN)nanofiber and MIL-101(Cr)particles prepared by electrospinning is proposed to bind the anions from the electrolyte utilizing abundant effective open metal sites in the MIL-101(Cr)particles to modulate the transport of non-effective carriers.The binding effect of the PANM separator promotes uniform lithium metal deposition and enhances the stability of the SEI layer and long cycling stability of ultra-high nickel layered oxide cathodes.Taking PANM as the Li||NCM96 separator enables high-voltage cycling stability,maintaining 72%capacity retention after 800 cycles at a charging and discharging rate of 0.2 C at a cut-off voltage of 4.5 V and 0°C.Meanwhile,the excellent high-rate performance delivers a specific capacity of 156.3 mA h g^(-1) at 10 C.In addition,outstanding cycling performance is realized from−20 to 60°C.The separator engineering facilitates the electrochemical performance of lithium metal batteries and enlightens a facile and promising strategy to develop fast charge/discharge over a wide range of temperatures.展开更多
The global carbon neutrality strategy brings a wave of rechargeable lithium‐ion batteries technique development and induces an ever-growing consumption and demand for lithium(Li).Among all the Li exploitation,extract...The global carbon neutrality strategy brings a wave of rechargeable lithium‐ion batteries technique development and induces an ever-growing consumption and demand for lithium(Li).Among all the Li exploitation,extracting Li from spent LIBs would be a strategic and perspective approach,especially with the low energy consumption and eco-friendly membrane separation method.However,current membrane separation systems mainly focus on monotonous membrane design and structure optimization,and rarely further consider the coordination of inherent structure and applied external field,resulting in limited ion transport.Here,we propose a heterogeneous nanofluidic membrane as a platform for coupling multi-external fields(i.e.,lightinduced heat,electrical,and concentration gradient fields)to construct the multi-field-coupled synergistic ion transport system(MSITS)for Li-ion extraction from spent LIBs.The Li flux of the MSITS reaches 367.4 mmol m^(−2)h^(−1),even higher than the sum flux of those applied individual fields,reflecting synergistic enhancement for ion transport of the multi-field-coupled effect.Benefiting from the adaptation of membrane structure and multi-external fields,the proposed system exhibits ultrahigh selectivity with a Li^(+)/Co^(2+)factor of 216,412,outperforming previous reports.MSITS based on nanofluidic membrane proves to be a promising ion transport strategy,as it could accelerate ion transmembrane transport and alleviate the ion concentration polarization effect.This work demonstrated a collaborative system equipped with an optimized membrane for high-efficient Li extraction,providing an expanded strategy to investigate the other membrane-based applications of their common similarities in core concepts.展开更多
Metal-organic nanosheets(MONs)as a novel material with tunable pore structures and low mass transfer resistance,have emerged as molecular sieves for the separation of gases and liquids.In theory,they can also serve as...Metal-organic nanosheets(MONs)as a novel material with tunable pore structures and low mass transfer resistance,have emerged as molecular sieves for the separation of gases and liquids.In theory,they can also serve as ion sieves for lithium metal batteries(LMBs),realizing the high-energy and dendritic free LMBs.However,there are rarely relevant reports,because it is difficult to simultaneously balance efficient ion sieving ability,high ion passing rate and high electrochemical stability.Here,we synthesized a stable ultrathin MON[Zn_(2)(Bim)_(4)]([Zn_(2)(Bim)_(4)]Nanosheet,HBim=benzimidazolate),which can achieve both efficient lithium ion sieving ability,high lithium ion passing rate and high electrochemical stability at the same time.The separator assembled by this MON exhibits high Li^(+)transfer number of 0.81 due to the accurate lithium ion and anion/solvent separation.The battery containing such separator shows high lithium ionic conductivity of 0.74 m S cm^(-1)and low activation energy of 0.099 eV,which can be attributed to the nanometer level thickness and the ion sieving effect.What is more,we realized the application of MONs-based ion sieves in LMBs with intercalation cathodes for the first time.And the LiFePO_(4)|Li battery with as-assembled separator demonstrates improved Coulombic efficiency(>99%)and significantly extended cycling life(>1600 cycles)with 80%capacity retention.展开更多
基金supported by the Science Foundation of the National Key Laboratory of Science and Technology on Advanced Composites in Special Environmentsthe National Natural Science Foundation of China(12002109)+1 种基金the China Postdoctoral Science Foundation(2020M670898)the Heilongjiang Postdoctoral Fund(LBH-Z20060)。
文摘Separators have been gaining increasing attention to improve the performance of lithium ion batteries(LIBs),especially for high safe and long cycle life.However,commercial polyolefin separators still face the problems of rapid capacity decay and safety issues due to the poor wettability with electrolytes and low thermal stability.Herein,a novel composite separator is proposed by introducing a surfactant of sodium dodecyl thiosulfate(SDS)into the polytetrafluoroethylene(PTFE)substrate with the binder of polyacrylic acid(PAA)through the suction filtration method.The introduction of PAA/SDS enhances the adsorption energy between PTFE substrate and electrolyte through density functional theory calculations,which improves wettability and electrolyte uptake of the separator significantly.The asachieved composite separator enables the LIBs to own high Li^(+)conductivity(0.64×10^(-3)S cm^(-1))and Li^(+)transference number(0.63),further leading to a high capacity retention of 93.50%after 500 cycles at 1 C.In addition,the uniform and smooth surface morphology of Li metal employed the composite separator after cycling indicates that the lithium dendrites can be successfully inhibited.This work indicates a promising route for the preparation of a novel composite separator for high safe LIBs.
基金the support from the National Natural Science Foundation of China(General Program no.51874041)。
文摘As the energy density of lithium-ion batteries (LIBs) continues to increase,their safety has become a great concern for further practical large-scale applications.One of the ultimate solution of the safety issue is to develop intrinsically safe battery components,where the battery separators and liquid electrolytes are critical for the battery thermal runaway process.In this review,we summarize recent progress in the rational materials design on battery separators and liquid electrolyte towards the goal of improving the safety of LIBs.Also,some strategies for further improving safety of LIBs are also briefly outlooked.
基金supported by the MOST(Grant No.2013CB934000,2014DFG71590,2011CB935902,2010DFA72760,2011CB711202,2013AA050903,2011AA11A257 and 2011AA11A254)China Postdoctoral Science Foundation(Grant No.2013M530599 and 2013M540929)+2 种基金Tsinghua University Initiative Scientific Research Program(Grant No.2010THZ08116,2011THZ08139,2011THZ01004 and 2012THZ08129)the State Key Laboratory of Automotive Safety and Energy(No.ZZ2012-011)Suzhou(Wujiang)Automotive Research Institute,Tsinghua University,Project No.2012WJ-A-01
文摘Surface chemical modification of polyolefin separators for lithium ion batteries is attempted to reduce the thermal shrinkage, which is im- portant for the battery energy density. In this study, we grafted organic/inorganic hybrid crosslinked networks on the separators, simply by grafting polymerization and condensation reaction. The considerable silicon-oxygen crosslinked heat-resistance networks are responsible for the reduced thermal shrinkage. The strong chemical bonds between networks and separators promise enough mechanical support even at high temperature. The shrinkage at 150 ℃ for 30 min in the mechanical direction was 38.6% and 4.6% for the pristine and present graft-modified separators, respectively. Meanwhile, the grafting organic-inorganic hybrid crosslink networks mainly occupied part of void in the internal pores of the separators, so the thicknesses of the graft-modified separators were similar with the pristine one. The half cells prepared with the modified separators exhibited almost identical electrochemical properties to those with the commercial separators, thus proving that, in order to enhance the thermal stability of lithium ion battery, this kind of grafting-modified separators may be a better alternative to conventional silica nanoparticle layers-coated polyolefin separators.
基金The authors acknowledge the financial support from the National Key Research and Development Program for New Energy Vehicles(No.2016YFB0100200).
文摘Thermal runaway is the main factor contributing to the unsafe behaviors of lithium-ion batteries(LIBs)in practical applications.The application of separators for the thermal shutdown has been proven as an effective approach to protecting LIBs from thermal runaway.In this work,we developed a thermal shutdown separator by coating a thin layer of low-density polyethylene microspheres(PM)onto a commercial porous polypropylene(PP)membrane and investigated the thermal response behaviors of the as-prepared PM/PP separator in LIBs.The structural and thermal analysis results revealed that the coated PM layer had a porous structure,which facilitated the occurrence of normal charge-discharge reactions at ambient temperature,although it could melt completely and fuse together within very short time periods:3 s at 110℃and 1 s at 120℃,to block off the pores of the PP substrate,thereby cutting off the ion transportation between the electrodes and interrupting the battery reaction.Consequently,the PM/PP separator exhibits very similar electrochemical performance to that of a conventional separator at ambient temperature.However,it performs a rapid thermal shutdown at an elevated temperature of^110℃,thus controlling the temperature rise and maintaining the cell in a safe status.Due to its synthetic simplicity and low cost,this separator shows promise for possible application in building safe LIBs.
基金supported by the Fundamental Research Funds for the Central Universities of China(No.FRF-MP-12-005B)the Project on International Cooperation Research with Johnson Controls Battery Group,Inc.
文摘Membranes of polypropylene (PP), PP coated with nano-A1203, PP electrospun with polyvinylidene fluoride- hexafluoropropylene (PVdF-HFP), and trilayer laminates of polypropylene-polyethylene-polypropylene (PP/PE/PP) were comparatively studied. Their physical properties were characterized by means of thermal shrinkage test, liquid electrolyte uptake, and field emission scanning electron microscopy (FESEM). Results show that, for the different membranes as PP, PP coated with nanowA1203, PP electrospun with PVdF-HFP, and PP/PE/PP, the thermal shrinkages are 14%, 6%, 12.6%, and 13.3%, while the liquid electrolyte uptakes are 110%, 150%, 217%, and 129%, respectively. In addition, the effects on the performance of lithium-ion batteries (LiFePO4 and LiNil/3Col/3Mn1/302 as the cathode material) were investigated by AC impedance and galvanostatic charge/discharge test. It is found that PP coated with A1203 and PP electrospun with PVdF-HFP can effectively increase the wettability between the cathode material and liquid electrolyte, and therefore reduce the charge transfer resistance, which improves the capacity retention and battery performance.
基金supported by National Science Foundation of China(Grants 11575277,11175234,11505270,51473183 and 11475246)
文摘To improve the affinity between separators and electrolyte in lithium-ion battery,microporous polyethylene(PE) separator was grafted of polyacrylamide(PAAm) by radiation.Chemical structure of the PAAmgrafted PE separators(denoted as PE-g-PAAm) was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.Properties of the pristine PE and PE-g-PAAm were tested by scanning electron microscope,liquid electrolyte uptake and lithium-ion conductivity.Electrochemical performances of the grafted PE separators(up to 0.76 × 10^(-3) S/cm of ionic conductivity at room temperature) were much better than pristine PE,and performance of the battery with the grafted separator behaved better than with the virgin PE separator,under the same condition(assembled in Ar-filled glove box).
基金The authors gratefully acknowledge the supports from the Emergency Support and Public Safety Scientifc Research Projects of National Advanced Functional Fiber Innovation Center(2020-fx020009)The Postgraduate Innovation Foundation of Xi’an Polytechnic University(CHX2020037)Natural Science Foundation of Education Department of Shaanxi Province(21JK0657).
文摘The separator with excellent mechanical and thermal properties are highly required for lithium ion batteries(LIBs).Therefore,it is crucial to develop novel nanofbrous membranes with enhanced mechanical strength and thermal stability.In this work,the fuorinated polyimide(FPI)was synthesized and blended with polyvinylidene fuoride(PVDF)to fabricate composite nanofbrous membranes(CNMs)via electrospinning method.Benefting from the introduction of aromatic FPI,the prepared PVDF/FPI nanofbrous membranes were endowed with enhanced mechanical strength and thermal stability.When the FPI content increased from 0 to 30 wt%,the tensile strength of composite nanofbrous membranes enhanced from 1.57 to 2.30 MPa.Moreover,there are almost no dimensional shrinkage for the CNM-30 containing 30 wt%FPI after heat treatment at 160℃ for 1 h.Furthermore,the prepared CNMs show improved electrochemical performances in comparison with neat PVDF and commercial Celgard membranes.The electrolyte uptake and ionic conductivity of the CNMs could reach to 522.4% and 1.14 ms·cm^(−1),respectively.The prepared CNMs could provide an innovative and promising approach for the development and design of high-performance separators.
基金financially supported by the Zhejiang Provincial Natural Science Foundation of China (No. LZ15E030001)the National Natural Science Foundation of China (No. 21534009)
文摘The performances of lithium-ion batteries(LIBs)are dependent on the wettability and stability of porous separators.Musselinspired coatings seem to be useful to improve the surface wettability of commercialized polyolefin separators.However,it is still a challenge to guarantee their stability under polar electrolytes.Herein,we report a facile and versatile way to enhance the wettability and stability of polypropylene separators by constructing robust polydopamine(PDA)coatings triggered with CuSO4/H2O2.These coatings were conveniently deposited on the polypropylene separator surfaces and the PDA-coated separators exhibited the improved surface wettability and thermal stability.The electrolyte uptake increased nearly two folds from the pristine separator to the modified ones.Correspondingly,the ionic conductivity also rose from 0.82 mS·cm^-1 to 1.30 mS·cm^-1.Most importantly,the CuSO4/H2O2-triggered PDA coatings were very stable under strong polar electrolytes,endowing the cells with excellent cycle performance and enhanced C-rate capacity.Overall,the results unequivocally demonstrate that application of PDA coatings on polyolefin separator triggered by CuSO4/H2O2 is a facile and efficient method for improving the wettability and stability of separators for high LIBs performance.
基金financially supported by the National Natural Science Foundation of China (Nos. 20974094, U1134002)
文摘To improve the performances of HDPE-based separators, polyether chains were incorporated into HDPE membranes by blending with poly(ethylene-block-ethylene glycol) (PE-b-PEG) via thermally induced phase separation (TIPS) process. By measuring the composition, morphology, crystallinity, ion conductivity, etc, the influence of PE-b-PEG on structures and properties of the blend separator were investigated. It was found that the incorporated PEG chains yielded higher surface energy for HDPE separator and improved affinity to liquid electrolyte. Thus, the stability of liquid electrolyte trapped in separator was increased while the interfacial resistance between separator and electrode was reduced effectively. The ionic conductivity of liquid electrolyte soaked separator could reach 1.28 ×10^-3 S.cm^-1 at 25℃, and the electrochemical stability window was up to 4.5 V (versus Li^+/Li). These results revealed that blending PE-b-PEG into porous HDPE membranes could efficiently improve the performances of PE separators for lithium batteries.
基金support from the National Natural Science Foundation of China(No.52090034)the Higher Education Discipline Innovation Project(No.B12015).
文摘Lithium-sulfur(Li-S)batteries are highly regarded as the next-generation high-energy-density secondary batteries due to their high capacity and large theoretical energy density.However,the practical application of these batteries is hindered mainly by the polysulfide shuttle issue.Herein,we designed and synthesized a new lithium sulfonylimide covalent organic framework(COF)material(COF-LiSTFSI,LiSTFSI=lithium(4-styrenesulfonyl)(trifluoromethanesulfonyl)imide),and further used it to modify the common polypropylene(PP)separator of Li-S batteries.The COF-LiSTFSI with sulfonylimide anion groups features stronger electronegativity,thus can effectively facilitate the lithium ion conduction while significantly suppress the diffusion of polysulfides via the electrostatic interaction.Compared with the unmodified PP separator,the COF-LiSTFSI modified separator results in a high ionic conductivity(1.50 mS·cm^(−1))and Li+transference number(0.68).Consequently,the Li-S battery using the COF-LiSTFSI modified separator achieves a high capacity of 1229.7 mAh·g^(−1)at 0.2 C and a low decay rate of only 0.042%per cycle after 1000 cycles at 1 C,compared with those of 941.5 mAh·g^(−1)and 0.061%using the unmodified PP separator,respectively.These results indicate that by choosing suitable functional groups,an effective strategy for COF-modified separators could be developed for high-performance Li-S batteries.
基金financially supported by the National Natural Science Foundation of China(Nos.21174124 and 21534009)
文摘Dual-asymmetric poly(vinylidene fluoride) (PVDF) separators have been fabricated by thermally induced phase separation with dimethyl sulfone (DMSO2) and glycerol as mixed diluents. The separators have a porous bulk with large interconnected pores (-1.0 μm) and two surfaces with small pores (-30 nm). This dual-asymmetric porous structure endows the separators with higher electrolyte uptake amount and rapider uptake rate, as well as better electrolyte retention ability than the commercialized Celgard 2400. The separators even maintain their dimensional stability up to 160 ℃, at which temperature the surface pores close up, leading to a dramatic decrease of air permeability. The electrolyte filled separators also show high ion conductivity (1.72 mS.cm-1) at room temperature. Lithium iron phosphate (LiFePO4)/lithium (Li) cells using these separators display superior discharge capacity and better rate performance as compared with those from the commercialized ones. The results provide new insight into the design and development of separators for high-performance lithium ion batteries with enhanced safety.
文摘Coating commercial porous polyolefin separators with inorganic materials can improve the thermal stability of the polyolefin separators and hence improve the safety of lithium-ion batteries. Several different inorganic materials have been studied for the coating. However, there lacks a study on how different the properties of separators, in inorganic materials affect terms of thermal stability and cell performance. Herein, we present such a study on coating a commercial polypropylene separator with four inorganic materials, i.e., Al2O3, SiO2, ZrO2 and zeolite. All inorganic coatings have improved thermal stability of the separators although with differences. The coating layers add 28%-45% of electrical resistance compared with the pure polypropylene separator, but all the cells prepared with the coated polypropylene separators have the same electrical chemical performance as the uncoated separator in terms of rate capability and capacities at different temperatures.
基金supported by the National 863 Program of China(No.2012AA03A602)National Key R&D Program of China(No.2017YFE0114100)+1 种基金Science and Technology Project of Guangdong Province of China(No.2019 ST115)the National Natural Science Foundation of China(No.21805240).
文摘In lithium-ion batteries(LIBs),separators play a vital role in lithium-ion(Li+)transport,and thus affect rate performance,battery life,and safety.Here,a new kind of multifunctional copolymer poly(acrylonitrile-co-lithium acrylate-co-butyl acrylate)(PAAB-Li)is synthesized through soap-free emulsion polymerization,and is used to form homogeneous-covered separator based on PP matrix by a simple dip-annealing process.Compared to the bare PP separator,the modified separators with PAAB-Li enable higher ionic conductivity,higher lithium ion transference number(increased from 0.360 to 0.525),and lower interface impedance(reduced from 155Ω to 34Ω).It has been indicated that PAAB-Li functional layer significantly promotes the fast transport of Li+and improves the compatibility of the separator/electrolyte-electrode interface.The LiCo02/graphite cells with the PAAB-Li-assisted separator demonstrate excellent cycle stability and rate performance.In addition,the Li symmetric cells with the modified separator stably cycle over 800 h,indicating the functional layer effectively suppresses the lithium dendrite growth.This facile strategy can be easily applied to LIBs requiring high safety and even be scalable to Li metal batteries.Moreover,the possible mechanism of the PAAB-Li functional layer promoting fast and uniform Li+transport is discussed in this paper.
文摘Lithium-ion batteries(LIB)are the dominant power sources for many consumer electronics,and they can also be large-scale power sources/energy storage devices,which can be credited to their advantages:high efficiency,high energy density,long cycling life.The separator membrane is a critical component of LIB.It is an electron insulator between the cathode and anode electrodes in order to prevent electrical short circuits,and it also functions as an ionic conductor to let ions pass freely in the charging and discharging cycles.The critical parameters to meet high quality separator membranes include:high dimensional/thermal/chemical stability,good wettability towards electrolyte,high mechanical strength,appropriate porosity and pore size distribution.Conventionally,plastic materials,such as polyolefin,are the main materials for manufacturing LIB separator membrane.However,polyolefin separator s have a number of drawbacks such as poor thermal stability and wettability.Cellulosic materials have unique properties,and can meet the quality specifications of LIB separator membranes;in addition,they are abundant,low cost,biodegradable,renewable and sustainable.Therefore,cellulose and its related materials can be promising alternatives to replace polyolefin for LIB separator membranes.In this short review,relevant literature on the topic was reviewed and further development/improvement of cellulose-based LIB separator membrane will be discussed.
基金This work was supported by the Natural Science Foundation of Guangdong Province, China (No. 2016A030313475) Dongguan Science and Technology Project, China (No. 201521510201 ), and the Project for Science and Technology of Guandong Province, China (No. 2015B010135009). The authors claim that there are no conflicts of interest.
文摘To improve the electrolyte wettability and thermal stability of polypropylene (PP) separators, nano- SiO2/poly(vinyl alcohol)-coated PP composite separators were prepared using a simple but efficient sol-gel and dip-coating method. The effects of the tetraethoxysilane (TEOS) dosage on the morphology, wettability, and thermal stability of the composite separators were investigated using Fourier-transform infrared spectroscopy, scanning electron microscopy, and contact-angle measurements. All the composite separators gave a smaller contact angle, higher electrolyte uptake, and lower thermal shrinkage compared with the PP separator, indicating enhanced wettability and thermal stability. Unlike the case for a traditional physical mixture, Si-O-C covalent bonds were formed in the coating layer. The composite separator with a TEOS dosage of 7.5 wt% had a unique porous structure combining hierarchical pores with interstitial voids, and gave the best wettability and thermal stability. The ionic conductivity of the composite separator containing 7.5 wt% TEOS was 1.26 mS/cm, which is much higher than that of the PP separator (0.74 mS/cm). The C-rate and cycling performances of batteries assembled with the composite separator containing 7.5 wt% TEOS were better than those of batteries containing PP separators.
文摘1 Results A separator for rechargeable batteries is a microporous membrane placed between electrodes of opposite polarity, keeping them apart to prevent electrical short circuits and at the same time allowing rapid transport of lithium ions that are needed to complete the circuit during the passage of current in an electrochemical cell, and thus plays a key role in determining the performance of the lithium ion battery. Here provides a comprehensive overview of various types of separators for lithium io...
基金financially supported by the National Key Research and Development Program of China(No.2021YFB2400300)the IPE Talent Start-up Program of Institute of Process Engineering of Chinese Academy of Sciences(Grant No.E0293507)。
文摘The absence of control over carriers transport during electrochemical cycling,accompanied by the deterioration of the solid electrolyte interphase(SEI)and the growth of lithium dendrites,has hindered the development of lithium metal batteries.Herein,a separator complexion consisting of polyacrylonitrile(PAN)nanofiber and MIL-101(Cr)particles prepared by electrospinning is proposed to bind the anions from the electrolyte utilizing abundant effective open metal sites in the MIL-101(Cr)particles to modulate the transport of non-effective carriers.The binding effect of the PANM separator promotes uniform lithium metal deposition and enhances the stability of the SEI layer and long cycling stability of ultra-high nickel layered oxide cathodes.Taking PANM as the Li||NCM96 separator enables high-voltage cycling stability,maintaining 72%capacity retention after 800 cycles at a charging and discharging rate of 0.2 C at a cut-off voltage of 4.5 V and 0°C.Meanwhile,the excellent high-rate performance delivers a specific capacity of 156.3 mA h g^(-1) at 10 C.In addition,outstanding cycling performance is realized from−20 to 60°C.The separator engineering facilitates the electrochemical performance of lithium metal batteries and enlightens a facile and promising strategy to develop fast charge/discharge over a wide range of temperatures.
基金supported by the National Key R&D Program of China(2022YFB3805904,2022YFB3805900)the National Natural Science Foundation of China(22122207,21988102,21905287)CAS Project for Young Scientists in Basic Research(YSBR-039).
文摘The global carbon neutrality strategy brings a wave of rechargeable lithium‐ion batteries technique development and induces an ever-growing consumption and demand for lithium(Li).Among all the Li exploitation,extracting Li from spent LIBs would be a strategic and perspective approach,especially with the low energy consumption and eco-friendly membrane separation method.However,current membrane separation systems mainly focus on monotonous membrane design and structure optimization,and rarely further consider the coordination of inherent structure and applied external field,resulting in limited ion transport.Here,we propose a heterogeneous nanofluidic membrane as a platform for coupling multi-external fields(i.e.,lightinduced heat,electrical,and concentration gradient fields)to construct the multi-field-coupled synergistic ion transport system(MSITS)for Li-ion extraction from spent LIBs.The Li flux of the MSITS reaches 367.4 mmol m^(−2)h^(−1),even higher than the sum flux of those applied individual fields,reflecting synergistic enhancement for ion transport of the multi-field-coupled effect.Benefiting from the adaptation of membrane structure and multi-external fields,the proposed system exhibits ultrahigh selectivity with a Li^(+)/Co^(2+)factor of 216,412,outperforming previous reports.MSITS based on nanofluidic membrane proves to be a promising ion transport strategy,as it could accelerate ion transmembrane transport and alleviate the ion concentration polarization effect.This work demonstrated a collaborative system equipped with an optimized membrane for high-efficient Li extraction,providing an expanded strategy to investigate the other membrane-based applications of their common similarities in core concepts.
基金the financial support of the Natural Science Foundation of Shanxi Province(20210302124055)the National Natural Science Foundation of China(22301170,22271211 and 91961201)1331 Project of Shanxi Province。
文摘Metal-organic nanosheets(MONs)as a novel material with tunable pore structures and low mass transfer resistance,have emerged as molecular sieves for the separation of gases and liquids.In theory,they can also serve as ion sieves for lithium metal batteries(LMBs),realizing the high-energy and dendritic free LMBs.However,there are rarely relevant reports,because it is difficult to simultaneously balance efficient ion sieving ability,high ion passing rate and high electrochemical stability.Here,we synthesized a stable ultrathin MON[Zn_(2)(Bim)_(4)]([Zn_(2)(Bim)_(4)]Nanosheet,HBim=benzimidazolate),which can achieve both efficient lithium ion sieving ability,high lithium ion passing rate and high electrochemical stability at the same time.The separator assembled by this MON exhibits high Li^(+)transfer number of 0.81 due to the accurate lithium ion and anion/solvent separation.The battery containing such separator shows high lithium ionic conductivity of 0.74 m S cm^(-1)and low activation energy of 0.099 eV,which can be attributed to the nanometer level thickness and the ion sieving effect.What is more,we realized the application of MONs-based ion sieves in LMBs with intercalation cathodes for the first time.And the LiFePO_(4)|Li battery with as-assembled separator demonstrates improved Coulombic efficiency(>99%)and significantly extended cycling life(>1600 cycles)with 80%capacity retention.