Mahmut Dirican

Carbon-Confined SnO2-Electrodeposited Porous Carbon Nanofiber Composite as High-Capacity Sodium-Ion Battery Anode Material.

Sodium resources are inexpensive and abundant, and hence, sodium-ion batteries are promising alternative to lithium-ion batteries. However, lower energy density and poor cycling stability of current sodium-ion batteries prevent their practical implementation for future smart power grid and stationary storage applications. Tin oxides (SnO2) can be potentially used as a high-capacity anode material for future sodium-ion batteries, and they have the advantages of high sodium storage capacity, high abundance, and low toxicity. However, SnO2-based anodes still cannot be used in practical sodium-ion batteries because they experience large volume changes during repetitive charge and discharge cycles. Such large volume changes lead to severe pulverization of the active material and loss of electrical contact between the SnO2 and carbon conductor, which in turn result in rapid capacity loss during cycling. Here, we introduce a new amorphous carbon-coated SnO2-electrodeposited porous carbon nanofiber (PCNF@SnO2@C) composite that not only has high sodium storage capability, but also maintains its structural integrity while ongoing repetitive cycles. Electrochemical results revealed that this SnO2-containing nanofiber composite anode had excellent electrochemical performance including high-capacity (374 mAh g(-1)), good capacity retention (82.7%), and large Coulombic efficiency (98.9% after 100th cycle).

Free-standing polyaniline–porous carbon nanofiber electrodes for symmetric and asymmetric supercapacitors

Polyaniline (PANI)–porous carbon nanofiber (PCNF) composites were generated by in situ polymerization of aniline on PCNFs for use as flexible, binder-less electrodes for high-performance supercapacitors. The effect of polymerization time on the electrode performance was studied by using symmetric cell configuration. Because of the high faradic current and good charge transfer between PCNFs and PANI, a maximum specific capacitance of 296 F g−1 and excellent rate performance were achieved for PANI–PCNF electrodes. PANI–PCNF electrodes also showed good capacitance retention (98%) after 1000 charge–discharge cycles. Furthermore, an asymmetric cell was successfully fabricated by using PANI–PCNF as the positive electrode and PCNFs as the negative electrode. Energy density and power density were improved significantly by using the asymmetric cell configuration. The resultant PANI–PCNF//PCNF asymmetric supercapacitor exhibited an energy density of 353 W h kg−1 with the power density of 609 W kg−1 at a current density of 1 A g−1.

A novel bi-functional double-layer rGO–PVDF/PVDF composite nanofiber membrane separator with enhanced thermal stability and effective polysulfide inhibition for high-performance lithium–sulfur batteries

A novel, bi-functional double-layer reduced graphene oxide (rGO)–polyvinylidene fluoride (PVDF)/PVDF membrane was fabricated by a simple electrospinning technique and was used as a promising separator for lithium–sulfur batteries. This double-layer membrane separator delivers two different functionalities: (i) the porous PVDF nanofiber framework in both rGO–PVDF and PVDF layers provides good thermal stability and maintains the structural integrity of the separator; and (ii) the conductive rGO–PVDF layer serves as a polysulfide inhibitor and ensures the fast transfer of lithium ions. Compared to conventional polypropylene membrane separators, this new separator design can significantly enhance the cycling stability and rate capability of the incorporated lithium–sulfur batteries. Overall, it is demonstrated that this new double-layer rGO–PVDF/PVDF composite membrane separator opens an alternate avenue in the structural design of high-performance lithium–sulfur batteries in dealing with multiple challenges.

SiO2-confined silicon/carbon nanofiber composites as an anode for lithium-ion batteries

Because of its ultra-high theoretical capacity (4200 mA h g−1), Si is considered as the most promising anode material candidate for next-generation high-energy lithium-ion batteries. However, the practical use of Si based anodes is constrained by the high volume change (up to 400%) of the Si active material during cycling. Intensive volume change of Si causes severe pulverization, loss of electrical contact between Si particles and the carbon current collector, and unstable SEI formation on the electrode surface. Herein, we introduce nanoscale silica-coated silicon/carbon (Si@C–SiO2) nanofiber composites that can maintain their structural stability during repeated cycling. Results indicated that nanoscale SiO2 coating of Si@C nanofibers helped preserve the Si particles within the nanofiber structure, resulting in stable solid electrolyte interphase formation and improved cycling performance. Electrochemical performance results showed that the Si@C–SiO2 nanofiber composite anodes had good capacity retention of 89.8% and high coulombic efficiency of 97.2% at the 50th cycle. It is, therefore, demonstrated that nanoscale SiO2 coating is an effective method to improve the electrochemical performance of Si@C nanofiber composite anodes.

Li0.33La0.557TiO3 ceramic nanofiber-enhanced polyethylene oxide-based composite polymer electrolytes for all-solid-state lithium batteries

A polyethylene oxide (PEO)-based composite solid polymer electrolyte filled with one-dimensional (1D) ceramic Li0.33La0.557TiO3 (LLTO) nanofibers was designed and prepared. It exhibits a high ionic conductivity of 2.4 × 10−4 S cm−1 at room temperature and a large electrochemical stability window of up to 5.0 V vs. Li/Li+, and is a promising electrolyte candidate for all solid-state lithium batteries.

Biomass derived porous carbon modified glass fiber separator as polysulfide reservoir for Li-S batteries

Biomass-derived porous carbon has been considered as a promising sulfur host material for lithium-sulfur batteries because of its high conductive nature and large porosity. The present study explored biomass-derived porous carbon as polysulfide reservoir to modify the surface of glass fiber (GF) separator. Two different carbons were prepared from Oak Tree fruit shells by carbonization with and without KOH activation. The KOH activated porous carbon (AC) provides a much higher surface area (796 m2 g-1) than pyrolized carbon (PC) (334 m2 g-1). The R factor value, calculated from the X-ray diffraction pattern, revealed that the activated porous carbon contains more single-layer sheets with a lower degree of graphitization. Raman spectra also confirmed the presence of sp3-hybridized carbon in the activated carbon structure. The COH functional group was identified through X-ray photoelectron spectroscopy for the polysulfide capture. Simple and straightforward coating of biomass-derived porous carbon onto the GF separator led to an improved electrochemical performance in Li-S cells. The Li-S cell assembled with porous carbon modified GF separator (ACGF) demonstrated an initial capacity of 1324 mAh g-1 at 0.2 C, which was 875 mAh g-1 for uncoated GF separator (calculated based on the 2nd cycle). Charge transfer resistance (Rct) values further confirmed the high ionic conductivity nature of porous carbon modified separators. Overall, the biomass-derived activated porous carbon can be considered as a promising alternative material for the polysulfide inhibition in Li-S batteries.

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.