Electrode Materials for Lithium Ion Batteries: A Review

Electrochemical energy storage systems are categorized into different types, according to their mechanisms, including capacitors, supercapacitors, batteries and fuel cells. All battery systems include some main components: anode, cathode, an aqueous/non-aqueous electrolyte and a membrane that separates anode and cathode while being permeable to ions. Being one of the key parts of any new electronic device or electric vehicles, lithium ion batteries have gained great attention in recent years. Lithium ion batteries store/provide energy by insertion/extraction of lithium ions in/from the structure of the electrode materials in successive charge/discharge cycles. The energy and power densities, determine the batteries performance. In order to improve the energy/power density and cyclic life of a lithium ion battery, its electrode materials and electrolyte must be properly chosen. Cathode materials store energy through intercalation or conversion reactions, while the energy storage mechanism in anode materials are intercalation, conversion reactions or alloying/dealloying. Depending on the electrode material, one or more of the aforementioned mechanisms may take place which directly affect the battery performance. Each group of electrode materials have their own advantages and shortcomings; therefore, proper selection of the electrode material is an important issue in applicability of a lithium ion battery. This review covers the principles of energy storage in lithium ion batteries, anode and cathode materials and the related mechanisms, recent advancements and finally the challenges associated with enhancement of lithium ion batteries

Synthesis and characterization of porous zinc oxide nano-flakes film in alkaline media

In this study, porous zinc oxide nano-flakes were successfully synthesized by anodization method on zinc substrate in a 0.025 M NaOH and 0.05 M NH4Cl solution with the voltage of 10 V at room temperature. The field emission scanning electron microscopy’s (FESEM) images show the structural evolution during 90 min of the anodization process. They also demonstrate the dependency of growth of ZnO flakes on the grains of the zinc substrate. Regarding FESEM images and possible chemical reactions taking place during the anodization process, a growth mechanism and sequences for the formation of ZnO have proposed. The Pourbaix diagram also confirmed this possible mechanism. The elemental  and phase analysis conducted on films proved the formation of the ZnO after the anodization process. The cyclic voltammetry showed the oxidation of zinc into zinc oxide is related to the -1.28 V peak and the peak of zinc oxide reduction is situated at -1.48 V.  The band gap of anodized zinc foil was calculated to be 3.24 eV. The photocatalytic activity of synthesized thin films also was studied and the ImageJ software analysis showed a strong correlation between the photocatalytic activity and the portion of porosity in the synthesized films

Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

© 2018, The Author(s). High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing

Surface Alloying of Cupronickel Alloy with Aluminum using Tungsten Inert Gas Process

Surface melting and alloying of Copper-Nickel (Cupronickel) alloy by preplacing aluminum powder and using tungsten inert gas process (TIG) in shielded atmosphere of argon gas were investigated. Surface melting resulted in the formation of a fairly porous dendritic microstructure. Surface alloying with aluminum resulted in the formation of Al2Cu and Al4Cu9 intermetallic compounds along with Cu-rich matrix and unstable martensitic structure. Surface melting reduced the hardness from 140 HV0.1 (substrate) to 70 HV0.1, mainly due to the loss of cold work effect of the initial substrate. On the other hand, surface alloyed zone showed a hardness of 300 HV0.1, mainly due to the formation of intermetallic compound. Tafel polarization results indicated improvement in corrosion resistance of cupronickel alloy after surface melting and alloying

Oxidation resistance of the nanostructured YSZ coating on the IN-738 superalloy

Conventional and nanostructured YSZ coatings were deposited on the IN-738 Ni super alloy by the atmospheric plasma spray technique. The oxidation was measured at 1100°C in an atmospheric electrical furnace. According to the experimental results the nanostructured coatings showed a better oxidation resistance than the conventional ones. The improved oxidation resistance of the nanocoating could be explained by the change in structure to a dense and more packed structure in this coating. The mechanical properties of the coatings were tested using the thermal cyclic, nanoindentation and bond strength tests, during which the nanostructured YSZ coating showed a better performance by structural stability

Synthesis and Characterization of ZnO Nanostructures Grown via a Novel Atmospheric Pressure Solution Evaporation Method

In this study, a novel method called “atmospheric pressure solution evaporation (APSE)” wasdeveloped for growing of Zinc Oxide (ZnO) nanostructures on Al2O3 surface. Zinc acetate dihydrate,Polyvinyl Pyrrolidone, and deionized water were used as precursor, capping, and solvent, respectively.The growth of ZnO nanostructures from evaporated solution was performed at three temperatures of300, 400, and 500°C. Field emission scanning electron microscopy (FESEM) demonstrated that ZnOnanostructures formed in nanorods or cauliflower-like rods based on the growth temperature. X-raydiffraction patterns of ZnO nanostructures prepared at different growth temperatures were indexed ashexagonal Wurtzite structure without any impurity. The optical band gap energy evaluated by diffusereflectance spectroscopy (DRS) was 3.22∼3.29 eV. Optical properties of the ZnO nanostructures areinvestigated by UV–Vis spectroscopy. There is a blue shift in the band edge with changing of thegrowth temperature. The degradation of Methylene Blue (MB) dye demonstrated that ZnO nanorodsgrown at the growth temperature of 300°C showed better photodegradation compared to othernanostructures. Antifungal properties of ZnO nanorods against Candida albicans were much higherthan that of the other nanostructures. This method, compared to other synthesis methods of ZnOnanostructures, offers several advantages, such as simplicity, cost-effectiveness, low-temperature,atmospheric pressure, and large area deposition. Such a low-temperature growth method may exposegreat opportunities for synthesis of ZnO nanorods onto various low-temperature-endurance substratesand extend the field of ZnO-based nanoscale devices

Effect of processing parameters on the electrochemical performance of graphene/ nickel ferrite (G-NF) nanocomposite

Fuel cells, secondary batteries and capacitors are among many promising energy storage devices. In particular, supercapacitors have attracted much attention because of their long life cycle and high power density. Graphene/nickel ferrite(G-NF) based supercapacitors were successfully fabricated through a one-step facile solvothermal route. Effects of synthesis conditions i.e. solvothermal time and temperature, on the powder particle characteristics were evaluated using x-ray photoelectron spectroscopy (XPS), powder x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Fast Fourier transformation (FFT) patterns were also recorded on the HRTEM microscope to determine the lattice and crystallinity of the nanocomposites. Structural and chemical studies proved that increasing the solvothermal duration and temperature leads to improved crystallinity of NiFe2O4phase as well as higher degree of reduction of graphene oxide to graphene. The electrochemical measurements showed that solvothermal conditions of 180°C and 10h produces the highest specific capacity of 312 and 196 F g-1 at current densities of 1 and 5 A g-1, respectively calculated from charge-discharge test. This G-NF electrode material, also showed a capacity of 105 F g-1 after 1500 cycles at current density of 10 A g-1 which makes it an outstanding supercapacitor material with promising long cycle electrochemical stability and performance

Characteristics of electrospun chitosan/carbon nanotube coatings deposited on AZ31 magnesium alloy

Abstract Mg-based biomaterials are commonly used as biodegradable orthopedic implants (e.g., bone regeneration applications). However, achieving high biocompatibility and corrosion resistance has remained a challenge to be tackled. In this work, to investigate various fabricated coatings (with and without pre- anodizing), five categories of samples are considered: (a) bare Mg alloy (Mg), (b) Anodized Mg alloy (Mg-A), (c) CS-coated Mg alloy (Mg-C), (d) CS-coated anodized Mg alloy (Mg-AC), and (e) CS-CNT-coated anodized Mg alloy (Mg-ACC). These samples were characterized by using Field Emission Scanning Electron Microscopes (FE-SEM), Energy Dispersive Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FT-IR), and Raman Spectroscopy. The adhesion within the coated samples was compared. Then, the effects of the coatings were evaluated by comparing wettability, corrosion behavior, and biocompatibility for bare and coated samples. The adhesion test showed that the coatings exhibited higher adhesion for Mg-AC and Mg-ACC compared to Mg-C. Desired wettability was achieved as the contact angles of coated samples were in the range of 55°– 65°. Electrochemical impedance and polarization as well as immersion tests showed higher corrosion resistance for coated samples. The composite coated sample showed improved cell adhesion since the osteoblast cells covered almost the entire surface of the sample. Moreover, osteoblast cell viability for the sample was around 40% higher than that of the bare sample. Graphical abstrac

Effect of high-pressure torsion on microstructure, mechanical properties and corrosion resistance of cast pure Mg

Abstract High-pressure torsion (HPT) processing was applied to cast pure magnesium, and the effects of the deformation on the microstructure, hardness, tensile properties and corrosion resistance were evaluated. The microstructures of the processed samples were examined by electron backscatter diffraction, and the mechanical properties were determined by Vickers hardness and tensile testing. The corrosion resistance was studied using electrochemical impedance spectroscopy in a 3.5% NaCl solution. The results show that HPT processing effectively refines the grain size of Mg from millimeters in the cast structure to a few micrometers after processing and also creates a basal texture on the surface. It was found that one or five turns of HPT produced no significant difference in the grain size of the processed Mg and the hardness was a maximum after one turn due to recovery in some grains. Measurements showed that the yield strength of the cast Mg increased by about seven times whereas the corrosion resistance was not significantly affected by the HPT processing