Polydopamine hydrophilic modification of polypropylene separator for lithium ion battery

The modified polypropylene (PP) separators with self‐polymerization of dopamine on the surfaces are prepared by a simple solution‐immersion method to improve the interfacial hydrophilic and discharge performance. The contact angle test and the liquid electrolyte uptake capacity test results show that the wettability and the electrolyte‐retention ability of polydopamine‐modified separator are improved significantly. The robust and thin polydopamine layer on the surface also enhances thermal performance and tensile strength of the modified PP separator certified by DSC and tensile strength tests. The ionic conductivity of the modified PP separator is up to 3.08 mS·cm^?1, ～2.5 times of the bare separator. Good discharge capacity retention and C‐rate discharge performance are demonstrated by a 2025 coin half‐cell with the liquid electrolyte‐soaked polydopamine modified PP separator sandwiched between lithium metal anode and LiFePO₄ cathode. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40543.     

A poly(ethylene terephthalate) nonwoven sandwiched electrospun polysulfonamide fibrous separator for rechargeable lithium ion batteries

A poly(ethylene terephthalate) nonwoven sandwiched electrospun polysulfonamide (PSA) fibrous separator was developed for application in lithium‐ion batteries (LIBs). The poly(ethylene terephthalate) nonwoven served as a mechanical support and the PSA layers provided the separators with nanoporous structures. This novel composite separator possessed better thermal stability and electrolyte wettability than commercial polypropylene separator and the sandwiched nonwoven endowed the separator with an improved mechanical strength (17.7 MPa) compared to the pure electrospun PSA separator. The cells assembled with this composite separator displayed excellent discharge capacity (122.0 mAh g^?1 after 100 cycles) and discharge C‐rate capacity. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44907.     

Model based analysis of lithium batteries considering particle‐size distribution

Performance of lithium ion batteries whose electrodes are composed of particles of different sizes is studied. Simplified model developed in (Henquín and Aguirre, AIChE J. 2015; 61:90–102) is extended and the simulations are compared with experiments from the literature so as to validate this new model. The differences in current density observed in particles of different sizes, which are in contact, depend on particle size and state of charge. Internal particle to particle discharge currents are observed during relaxation times. A parametric study of the applied current and particle sizes of electrodes is performed to evaluate cell performance, with emphasis on cell voltage and final capacity measurement. The evolution of reaction rates on the surface of electrode particles and their corresponding states of charge are depicted. An analysis of relaxation times in terms of cell voltage, current density, equilibrium potentials, and overpotentials is included. © 2017 American Institute of Chemical Engineers AIChE J, 64: 904–915, 2018     

Use of multiple regression analysis to develop equations for predicting Li-Al/iron sulphide cell performance

A multiple regression analysis was conducted to develop predictive equations for the specific energy and specific power of Li-Al/iron sulphide cells over a wide range of cell designs and operating variables. The intent was to make these equations as general as possible such that one set of equations would predict the performance of Li-Al/FeS or Li-Al/FeS₂ cells with bicell (one positive electrode and two facing negative electrodes) or multiplate cell configurations. Data from 33 cells were used in the analysis of specific energy, and 26 cells were used to develop the specific power equation. The calculated specific energy and specific power showed good agreement with the measured values for these cells. In general, the deviation between the calculated and measured values was within ±10%. A check of the predictive capability of these equations also showed good agreement. The specific energy and specific power calculated for 14 cells not used in the regression analysis deviated by ±10% from the measured values. These equations were used to identify the most likely cell designs to meet selected electric-vehicle battery performance goals. These designs were included in an experimental programme for further performance evaluation.Nomenclature A _e limiting electrode area (cm²) - AHREFF coulombic efficiency (%) - b _i constants in multiple regression equation - CCO cell charge cut-off voltage (V) - CF charge factor (1.0 for fully charged cell, 0.5 for cell 50% discharged, 0.05 for cell discharged to a cut-off of 0.9–l.0 V) - DCO cell discharge cut-off voltage (V) - FCCF fully charged correction factor (1.0 for fully charged cell, 0.05 for any state of discharge) - FSLMUL product of FSUBL and MUL (defined below) - FSUBL calculated utilization factor of the limiting electrode (%) - i _c charge current density (A cm^–2) - i _D discharge current density (A cm^–2) - MUL theoretical specific energy factor (W h kg^–1) - NSPTHC negative-to-positive capacity ratio - OCV cell open-circuit voltage (V) - OFFEUT factor related to LiCl composition in electrolyte (%) - PF power factor (W kg^–1) - POSPIN reciprocal of the number of positive electrode plates - PPXCYC product of the number of positive electrode plates in the cell and the number of deep discharge cycles - R ² correlation coefficient - ¯R _c average cell resistance () - SP calculated cell specific power (W kg^–1) - SPECYC calculated cell specific energy (W h kg^–1) - SPEBAS calculated cell specific energy early in life (W h kg^–1) - TEMPR temperature ratio - TSUBCR thickness ratio of counter electrode and electrode separator - VFSNEG volume fraction salt in the negative electrode - VFSPOS volume fraction salt in the positive electrode - VOLT1R discharge voltage factor - VOLT2R charge voltage factor - W cell weight (kg) - X _i independent variables in regression equation - dependent variable in regression equation     

Polyethylene battery separator with auto‐shutdown ability,thermal stability of 220°C,and hydrophilic surface via solid‐state ultraviolet irradiation

To assure the safety of the lithium‐ion battery, the separator is required to have good thermal stability. Because the single‐layer polyethylene (PE) separator can only tolerate a temperature of 130°C, it is seldom employed currently by lithium‐ion battery manufacturers although its cost is low. In this article, we modified PE separator chain structure through solid‐state ultraviolet (UV) irradiation method to achieve a separator with composite structure of ～40% crystallized PE and ～70% gel content. Approximately 40% crystallized PE chains fulfill the task of auto‐shutdown at 130°C through melting and filling the pores. At the same time, the PE separator can maintain integrity till 220°C because of its highly cross‐linked chain structure. Besides, the modified PE separator is hydrophilic with a water contact angle of 33° after UV treatment and is able to absorb more electrolyte. However, the tensile strength and elongation at the break decreased because the cross‐linking network increased the rigidity. Nevertheless, these values still meet the requirements as the separator for lithium‐ion battery. Considering the low cost and easy preparation, current cross‐linked PE separator has potential to be used in lithium‐ion batteries for various applications, including electric vehicles and energy storage purpose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42169.     

Bifunctional poly(ethylene glycol) based crosslinked network polymers as electrolytes for all‐solid‐state lithium ion batteries

Polymer electrolyte based lithium ion batteries represent a revolution in the battery community due to their intrinsic enhanced safety, and as a result polymer electrolytes have been proposed as a replacement for conventional liquid electrolytes. Herein, the preparation of a family of crosslinked network polymers as electrolytes via the ‘click‐chemistry’ technique involving thiol‐ene or thiol‐epoxy is reported. These network polymer electrolytes comprise bifunctional poly(ethylene glycol) as the lithium ion solvating polymer, pentaerythritol tetrakis (3‐mercaptopropionate) as the crosslinker and lithium bis(trifluoromethane)sulfonimide as the lithium salt. The crosslinked network polymer electrolytes obtained show low T_g, high ionic conductivity and a good lithium ion transference number (ca 0.56). In addition, the membrane demonstrated sterling mechanical robustness and high thermal stability. The advantages of the network polymer electrolytes in this study are their harmonious characteristics as solid electrolytes and the potential adaptability to improve performance by combining with inorganic fillers, ionic liquids or other materials. In addition, the simple formation of the network structures without high temperatures or light irradiation has enabled the practical large‐area fabrication and in situ fabrication on cathode electrodes. As a preliminary study, the prepared crosslinked network polymer materials were used as solid electrolytes in the elaboration of all‐solid‐state lithium metal battery prototypes with moderate charge–discharge profiles at different current densities leaving a good platform for further improvement. © 2018 Society of Chemical Industry     

Electrochemical performance and thermal stability of the electrospun PTFE nanofiber separator for lithium‐ion batteries

Separator is a very important set of lithium‐ion batteries. At present, low porosity and poor thermal stability are two major disadvantages of separator. In this work, we first apply electrospinning method to prepare the Polytetrafluoroethylene (PTFE) nanofiber separator, which has the advantages of electrospinning method and PTFE materials. The effect of the PTFE nanofiber separator is investigated by scanning electron microscope, Capillary Flow Porometer, thermogravimetric–differential scanning calorimeter, linear sweep voltammeter, AC impedance, and charge/discharge cycling tests. The results demonstrate that the PTFE nanofiber separator has a special fiber structure made from PTFE particles gathering one by one along the fibers. Moreover, the PTFE nanofiber separator exhibits several advantages, including suitable pore diameter, uniform pore size distribution, high porosity, and electrolyte uptake, which enhance the ionic conductivity. The thermal stability of the PTFE nanofiber separator is much better than that of the conventional polyolefin separator. The Li/LiCoO₂ cell equipped with PTFE nanofiber separator exhibits excellent rate performance and first charge–discharge specific capacity of 142 and 131 mA h g^?1, respectively, accompanied by relatively stable cycle performance at 0.2 C rate. It is supposed to be a candidate for application in lithium‐ion batteries. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46508.     

微孔碳材料修饰的隔膜用于高性能锂硫电池

锂硫电池具有较高的能量密度,是有发展前景的能量存储体系之一。但“穿梭效应”严重制约了锂硫电池的实际应用,为解决该问题,本文通过简单的一步热解法合成了孔径均匀的微孔碳材料,探究了微孔碳材料修饰隔膜后对锂硫电池性能的影响。结果表明,制备的微孔碳材料孔径集中在0.56nm左右,修饰隔膜后不仅能够有效抑制“穿梭效应”的产生,还有利于加快锂离子的传输,确保正极一侧溶解的多硫化物的再次利用。在0.1C的电流密度下,采用微孔碳材料修饰隔膜的电池首次放电比容量为1359mAh/g,循环100次之后容量能保持在966mAh/g,而修饰之前的传统聚丙烯隔膜,循环100次之后的比容量仅为409mAh/g;在1C的电流密度下循环500圈后,采用微孔碳材料修饰隔膜的电池容量保持率为88%,表现出优异的循环稳定性。     

The Enhanced Performance of Polyethylene Composite Separators by the Modification of Lithium Salt@SiO2 Nanoparticles

Improving the dimensional thermal stability and electrochemical performance of polyethylene (PE) membrane is critical to enhance the safety performance of lithium-ion battery. In this paper, PE membranes are modified by lithium bis(trifuoromethanesulfonyl)imide (LiTFSI) solution and then coated with nano-SiO₂/polyvinyl alcohol solution to obtain composite membranes (PE@LnSiO₂, where n represents the concentration of LiTFSI solution). The obtained PE@L4SiO₂ (LiTFSI solution concentration is 4%) composite membrane possesses a thermal shrinkage rate of only 17% at 150 °C, which is far superior to that of the PE separator. The ionic conductivity of the composite membrane is 16.9 × 10⁻⁴ S cm⁻¹ at room temperature (RT), and the battery impedance decreases to 154 Ω, which is remarkably better than that of the PE membrane (188 Ω). The battery delivers a reversible discharge capacity of 164 mAh g⁻¹ at 0.2 C under RT after 250 cycles, and the coulomb efficiency remains above 99%. The battery also has a high discharge capacity of 132 mAh g⁻¹ at 2 C, which indicates that it has excellent rate performance. Therefore, this research successfully explores a simple method to effectively improve the dimensional thermal stability of PE separator, as well as the electrochemical and safety performance of lithium battery.     

Electrospun Polyacrylonitrile/Polyvinylidene Fluoride/Boehmite Separator and Gel Polymer Electrolyte Polyethylene Oxide/Polyvinylidene Fluoride-hexafluoropropylene/Lithium Bis(trifluoromethanesulfonyl)imide/Boehmite Composite Separator Are Used for Fast Charging

With the increasing popularity of electric vehicles, the fast charging of lithium (Li) batteries is attracting increasing attention. However, the rapid decline in battery capacity caused by fast charging and accidents caused by Li dendrites piercing the separator greatly restrict fast-charging applications. Herein, an electrospun polyacrylonitrile/polyvinylidene fluoride/boehmite (PAN/PVDF/12 wt.% AlO(OH)) and gel polymer polyethylene oxide/polyvinylidene fluoride-hexafluoropropylene/lithium bis(trifluoromethanesulfonyl)imide/boehmite (PEO/PVDF-HFP/12.6 wt.% LiTFSI /10 wt.% AlO(OH)) pressed together to form a two-layer functional separator is designed. The electrospun separator improves the high-temperature resistance of the entire separator due to its special structure. After the 1 h heat treatment at 220 °C, the thermal shrinkage rate of the double-layer separator reaches 10.1%, showing good thermal stability. At 0.2 C, the discharge capacity retention rate is 99.4% after 100 cycles. After 1000 cycles at a rate of 10 C, the discharge capacity remains at 88% of the initial value. The two-layer separator exhibits better capacity retention and superior rate performance than PP, providing an effective approach for commercializing fast-charging functional separators.     

低共熔混合锂盐合成Co和Al共掺杂的LiNiO2

在空气中,采用低共熔混合物L iNO3-L iOH为锂盐,制备了Co和A l共掺杂锂离子电池正极材料L iN i0.8Co0.15A l0.05O2。XRD分析表明,制得的正极材料具有完整的层状结构。电性能测试表明:在0.5 mA/cm2的放电电流密度和2.7—4.2 V的电压范围内,L iN i0.8Co0.15A l0.05O2首次放电比容量达147.6 mA.h/g,库仑效率达84.3%,第20次的放电比容量为133.8 mA.h/g。该合成新工艺,能制备出电化学性能良好的Co和A l共掺杂的L iN iO2正极材料。     

Cellulose acetate-based separators prepared by a reversible acetylation process for high-performance lithium-ion batteries

Lithium-ion batteries (LIBs) are one of the most widely used technologies for various applications. However, polyolefin separators can hardly meet the needs of the development of LIBs due to the poor heat shrinkage and bad wettability with the electrolyte. Herein, a cellulose acetate (CA)-based separator is developed by blending with cellulose nanocrystals (CNCs) using a simple reversible acetylation process. This separator exhibits inherent thermal stability and improved ionic conductivity due to the finger-like and sponge-like porous structure. Moreover, the discharge capacity of the separator with a CNC loading of 3% remains at 132.9 mA h g⁻¹ when the rate reverts to 0.2 C and the capacity retention reaches 89.5% after 50 cycles. Therefore, the obtained CA-based separators can be a competitive candidate for high-performance LIBs and point the way to sustainable development.     

蔗糖基炭材料的制备及其电化学性能研究

在蔗糖中按不同比例掺入膨胀石墨（EG）,在800qC和1000℃炭化制得蔗糖基炭材料。通过扫描电子显微镜（SEM）,透射电子显微镜（TEM）,X射线电子衍射（XRD）,对蔗糖基炭材料的表面形态和内部结构进行表征。采用循环伏安（cv）和恒流充放电表征其电化学性能,并分析其储锂机理。电化学实验结果表明：掺入3％质量比的EG在800℃下炭化得到的蔗糖基炭材料具有最优的大电流充放电性能,其在100mA／g的电流密度下,可逆放电容量为210mAh／g,容量保持率为85．5％;在200rnA／g的电流密度下,可逆放电容量为178．6mAh／g,容量保持率为72．5％。     

Li-LiFePO4 rechargeable polymer battery using dual composite polymer electrolytes

A composite polymer electrolyte, formed by dispersing into a poly(ethylene oxide)-lithium salt matrix two additives, i.e. calyx(6)pyrrole, (CP) acting as an anion trapper and superacid zirconia, S-ZrO₂ acting as a conductivity promoter, has been tested as a separator in a new type of rechargeable lithium battery using lithium iron phosphate as the cathode. The choice of the electrolyte was motivated by its favourable transport properties both in terms of lithium ion transference number and of total ionic conductivity. The choice of the cathode was motivated by the value of its operating voltage which falls within the stability window of the electrolyte. The performance of the battery was determined by cycling tests carried out at various rates and at various temperatures. The results demonstrate the good rate capability of the battery which can operate at high charge-discharge efficiency even at 1 C rate and that it can be cycled at 90 °C with a satisfactory initial capacity of the order of 90 mAh g⁻¹. These values outline the practical relevance of the composite electrolyte membrane and of its use as separator in a lithium battery. H. H. Sumathipala—On leave from Department of Physics University of Kelaniya, Kelaniya, Sri Lanka.     

Electrospun nanofiber polyacrylonitrile coated separators to suppress the shuttle effect for long-life lithium–sulfur battery

Polymeric coating on the separator with effective polysulfides diffusion inhibition can provide intimate contact between intermediate polysulfides and conductive layer of separator for high-energy lithium–sulfur (Li–S) batteries. Herein, polyacrylonitrile–poly(1,5-diaminoanthraquinone) (PAN/PDAAQ) and PAN-potassium functionalized graphene (PAN/K-FGF) nanofibers are synthesized via electrospinning method and act as effective separators for Li–S batteries to minimize polysulfides diffusion toward the anode. PAN/K-FGF coated separator shows capacity retention of 768 mAh g⁻¹ after 100 cycles at 1C. The capacity maintains at 419 mAh g⁻¹ after 500 cycles. PAN/PDAAQ nanofibers are coated on glass fiber separator functions as physical and chemical barrier for polysulfides diffusion. Therefore, the cell with PAN/PDAAQ coating on the separator demonstrates capacity retention of 881 mAh g⁻¹ after 100 cycles at 1C and small capacity decay rate of 0.11% per cycle resulted in 800 cycles at 1C. PAN/PDAAQ could define as an ideal separator material for Li–S batteries. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48606.     

Enhanced Thermal Stability and Electrochemical Performance of Polyacrylonitrile/Cellulose Acetate-Electrospun Fiber Membrane by Boehmite Nanoparticles: Application to High-Performance Lithium-Ion Batteries

In this study, polyacrylonitrile/cellulose acetate (PAN/CA) composite nanofiber membranes with different boehmite contents are prepared by electrospinning. The physical and electrochemical properties of the composite nanofiber membrane as a separator in lithium batteries are investigated. In contrast to commercial polypropylene membrane (PP), the nanocomposite fiber membrane has a 3D network structure, higher porosity, higher thermal stability, higher electrolyte absorptivity, higher ionic conductivity, and better cycling performance. The PAN/CA composite membrane with 12 wt% boehmite has the highest ionic conductivity (1.694 mS cm⁻¹); the specific discharge capacity is 160 mAh g⁻¹ at 0.2 C discharge density and the highest capacity retention rate is 99.3% after 100 cycles. The cycle rate at 2 C has a higher capacity retention rate (88.75%). These results indicate that the PAN/CA/AlOOH composite nanofiber membrane can be expected to replace the commercial polyolefin membrane and behave as a high-performance separator for lithium-ion batteries.     

A methodology for equation-based analysis of large chemical processes using the functional matrix

The equation-based approach to process analysis is necessary for efficient optimization of large and complex processes, and involves the problem of solving a large number of equations. To complement this approach, an improved equation-solving system using the functional matrix suggested by Mattione, Meir and Book was developed, and its capacity for the process analysis was demonstrated by case studies. The equation-solving system developed in this work reads equations, stores them in the functional matrix, rearranges them, and, if they have degrees of freedom, selects design variables which make each partition the easiest to solve. Given the values of the design variables, the system solves the equations as it manipulates the functional matrix. The developed equation-solving system was proved to be efficient for solving a large number of equations which involve degrees of freedom. Case studies show that the methodology established in this work is an appropriate basis for the equation-based analysis of large chemical processes.     

Flow Parameter Profiles in the Crossflow of a Two-Component Fluid through Semipermeable Membranes

Abstract

The analytical solution for spiral-wound module performance is a useful tool for developing explicit equations for the local values of variables like effective pressure, water flux, salt wall concentration, and velocities for seawater feed solutions. Depending on the operating conditions, knowledge of the local values of these variables could be useful to predict possible areas on the membrane surface where scale formation or fouling is likely to occur. Reasonable values for all variables have been found by using the developed equations at any point in the permeate and the feed side of the membrane. Although the method has been applied for spiral wound reverse osmosis membranes, it is believed that the same method could be used in similar hydrodynamic situations where flow through porous media is taking place.     

低共熔混合锂盐合成LiNi_(0.8)Co_(0.2)O_2的研究

在空气气氛中,采用低共熔混合物L iNO3-L iOH为锂盐,制备出了锂离子电池正极材料L iN i0.8Co0.2O2。XRD分析表明:此工艺制得的正极材料具有完整的层状结构。电性能测试表明:在0.5 mA/cm2的充放电电流密度和2.7~4.2 V的电压范围内,L iN i0.8Co0.2O2首次放电比容量为145.2 mA.h/g,充放电库仑效率为83.8%;循环20次后,放电比容量为124.8 mA.h/g。该方法能制备出电化学性能良好的L iN i0.8Co0.2O2正极材料。     

锂硫电池中抑制穿梭效应和锂枝晶的近期进展

锂硫电池具有突出的高比容量、环境友好、原材料廉价易得等特点,是未来新能源的一个选择方向。首先介绍了锂硫电池的研究背景以及放电原理,然后分别在电池的隔膜和负极2个方面叙述了抑制穿梭作用和抑制锂枝晶的最近进展,并且对未来锂硫电池的发展进行了展望。