Ozan Toprakci

A review of recent developments in membrane separators for rechargeable lithium-ion batteries

In this paper, the recent developments and the characteristics of membrane separators for lithium-ion batteries are reviewed. In recent years, there have been intensive efforts to develop advanced battery separators for rechargeable lithium-ion batteries for different applications such as portable electronics, electric vehicles, and energy storage for power grids. The separator is a critical component of lithium-ion batteries since it provides a physical barrier between the positive and negative electrodes in order to prevent electrical short circuits. The separator also serves as the electrolyte reservoir for the transport of ions during the charging and discharging cycles of a battery. The performance of lithium-ion batteries is greatly affected by the materials and structure of the separators. This paper introduces the requirements of battery separators and the structure and properties of five important types of membrane separators which are microporous membranes, modified microporous membranes, non-woven mats, composite membranes and electrolyte membranes. Each separator type has inherent advantages and disadvantages which influence the performance of lithium-ion batteries. The structures, characteristics, manufacturing, modification, and performance of separators are described in this review paper. The outlook and future directions in this research field are also given.

α-Fe2O3 Nanoparticle-Loaded Carbon Nanofibers as Stable and High-Capacity Anodes for Rechargeable Lithium-Ion Batteries

α-Fe(2)O(3) nanoparticle-loaded carbon nanofiber composites were fabricated via electrospinning FeCl(3)·6H(2)O salt-polyacrylonitrile precursors in N,N-dimethylformamide solvent and the subsequent carbonization in inert gas. Scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and elemental analysis were used to study the morphology and composition of α-Fe(2)O(3)-carbon nanofiber composites. It was indicated that α-Fe(2)O(3) nanoparticles with an average size of about 20 nm have a homogeneous dispersion along the carbon nanofiber surface. The resultant α-Fe(2)O(3)-carbon nanofiber composites were used directly as the anode material in rechargeable lithium half cells, and their electrochemical performance was evaluated. The results indicated that these α-Fe(2)O(3)-carbon nanofiber composites have high reversible capacity, good capacity retention, and acceptable rate capability when used as anode materials for rechargeable lithium-ion batteries.

Carbon Nanotube-Loaded Electrospun LiFePO4/Carbon Composite Nanofibers As Stable and Binder-Free Cathodes for Rechargeable Lithium-Ion Batteries

LiFePO(4)/CNT/C composite nanofibers were synthesized by using a combination of electrospinning and sol-gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and carbon source. Functionalized CNTs were used to increase the conductivity of the composite. LiFePO(4) precursor materials, PAN and functionalized CNTs were dissolved or dispersed in N,N-dimethylformamide separately and they were mixed before electrospinning. LiFePO(4) precursor/CNT/PAN composite nanofibers were then heat-treated to obtain LiFePO(4)/CNT/C composite nanofibers. Fourier transform infrared spectroscopy measurements were done to demonstrate the functionalization of CNTs. The structure of LiFePO(4)/CNT/C composite nanofibers was determined by X-ray diffraction analysis. The surface morphology and microstructure of LiFePO(4)/CNT/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO(4)/CNT/C composite nanofibers was evaluated in coin-type cells. Functionalized CNTs were found to be well-dispersed in the carbonaceous matrix and increased the electrochemical performance of the composite nanofibers. As a result, cells using LiFePO(4)/CNT/C composite nanofibers have good performance, in terms of large capacity, extended cycle life, and good rate capability.

Electrospun Nanofiber-Based Anodes, Cathodes, and Separators for Advanced Lithium-Ion Batteries

Novel nanofiber technologies present the opportunity to design new materials for advanced rechargeable lithium-ion batteries. Among the various existing energy storage technologies, rechargeable lithium-ion batteries are considered as effective solution to the increasing need for high-energy electrochemical power sources. This review addresses using electrospinning technology to develop novel composite nanofibers which can be used as anodes, cathodes, and separators for lithium-ion batteries. The discussion focuses on the preparation, structure, and performance of silicon/carbon (Si/C) nanofiber anodes, lithium iron phosphate/carbon (LiFePO4/C) nanofiber cathodes, and lithium lanthanum titanate oxide/polyacrylonitrile (LLTO/PAN) nanofiber separators. Si/C nanofiber anodes have the advantages of both carbon (long cycle life) and Si (high lithium-storage capacity). LiFePO4/C nanofiber cathodes show good electrochemical performance including satisfactory capacity and good cycling stability. LLTO/PAN nanofiber separators have large electrolyte uptake, high ionic conductivity, and low interfacial resistance with lithium, which increase the capacity and improve the cycling stability of lithium-ion cells. These results demonstrate that electrospinning is a promising approach to prepare high-performance nanofiber anodes, nanofiber cathodes, and nanofiber separators that can potentially replace currently-used lithium-ion battery materials.

Electrospun carbon nanofibers decorated with various amounts of electrochemically-inert nickel nanoparticles for use as high-performance energy storage materials

Carbon nanofibers decorated with various amounts of electrochemically-inert metallic nickel nanoparticles are synthesized through electrospinning and carbonization processes. The morphology and composition of Ni nanoparticles in carbon nanofibers are controlled by preparing different nanofiber precursors. The lithium-ion battery performance evaluations indicated that the content of electrochemically-inert Ni nanoparticles in carbon nanofibers has a great influence on the final electrochemical performance. For example, at certain Ni contents, these composite nanofibers display excellent electrochemical performance, such as high reversible capacities, good capacity retention, and excellent rate performance, when directly used as binder-free anodes for rechargeable lithium-ion batteries. However, when the Ni content is too low or too high, the corresponding electrodes show low reversible capacities although they still have good reversibility and rate performance.

LiFePO4 nanoparticles encapsulated in graphene-containing carbon nanofibers for use as energy storage materials

LiFePO4/graphene/C composite nanofibers, in which LiFePO4 nanoparticles were encapsulated in graphene-containing carbon nanofiber matrix, were synthesized by using a combination of electrospinning and sol-gel techniques. Polyacrylonitrile (PAN) was used as the electrospinning media and the carbon source. Graphene was incorporated in order to increase the conductivity of the composite. PAN was dissolved in N,N–dimethylformamide (DMF). LiFePO4 precursor and graphene were dispersed in DMF separately and were mixed with PAN solution before electrospinning. Electrospun fibers were heat-treated to obtain LiFePO4/graphene/C composite nanofibers. The structure of LiFePO4/graphene/C composite nanofibers was determined by X–ray diffraction analysis. The surface morphology and microstructure of LiFePO4/graphene/C composite nanofibers were characterized using scanning electron microscopy and transmission electron microscopy. Electrochemical performance of LiFePO4/graphene/C composite nanofibers was evaluated in coin-...

Electrospun carbon nanofiber-supported Pt―Pd alloy composites for oxygen reduction

Carbon nanofiber-supported Pt–Pd alloy composites were prepared by co-electrodepositing Pt–Pd alloy nanoparticles directly onto electrospun carbon nanofibers. The morphology and size of Pt–Pd alloy nanoparticles were controlled by the surface treatment of carbon nanofibers and the electrodeposition duration time. Scanning electron microscopy/energy dispersive spectrometer (SEM)/(EDS) and x-ray photoelectron spectroscopy (XPS) were used to study the composition of Pt–Pd alloy on the composites, and the co-electrodeposition mechanism of Pt–Pd alloy was investigated. The resultant Pt–Pd/carbon nanofiber composites were characterized by running cyclic voltammograms in oxygen-saturated 0.1 M HClO 4 at 25 °C to study their electrocatalytic ability to reduce oxygen. Results show that Pt–Pd/carbon nanofiber composites possess good performance in the electrocatalytic reduction of oxygen. Among all Pt–Pd/carbon nanofibers prepared, the nanofiber composite with a Pt–Pd loading of 0.90 mg/cm 2 has the highest electrocatalytic activity by catalyst mass.

Comparison of high-volume instrument and advanced fiber information systems based on prediction performance of yarn properties using a radial basis function neural network:

In this study, an artificial neural network (ANN) model is presented in order to predict the tenacity and hairiness of carded cotton yarns. Fiber measurement values generated by using a high-volume instrument (HVI) and an advanced fiber information system (AFIS) were used in the ANN model as input parameters. The radial basis function neural network (RBFNN) was used as ANN structure. The best RBFNN model was determined by analyzing the effect of epochs and the number of neurons on prediction performance. By using this ANN structure, the comparison between the performance of predicting yarn properties from HVIs and from AFISs was carried out. In the study, four different yarn counts (Ne20, Ne24, Ne30, and Ne40) for 10 different blends were applied. Each yarn count was spun at 4.34αe twist factor. In this study, the model presented a good rate of accuracy for predicting yarn tenacity and hairiness by using HVI and AFIS fiber values. The study showed that there was no significant difference between the accuracy of predicting these yarn properties from HVI fiber measurement results and those from an AFIS by using the RBF. From the results, it was noted that the performance of predicting yarn hairiness was better than that of predicting yarn tenacity. Also, this study could provide researchers with exclusive information on how to select the most appropriate ANN architecture and how to evolve the model for testing.

13 – Conductive textiles

With the rapid development of flexible electronics, conductive textiles are becoming important building blocks for wearables in broad applications. Different from conventional textiles, conductive textiles require fabrics to have a basic wearable function as well as electrical conductivity. Conductive textiles have been used in applications such as antistatic, electromagnetic (EM) shielding, and e-textiles. In this chapter, we introduce the fundamental principles of conductive textiles and review recent developments of advanced conductive coating technologies and their applications in antistatic, EM shielding, and e-textiles.