Yaser Abu-Lebdeh

High capacity anode materials for Li-ion batteries based on spinel metal oxides AMn2O4 (A = Co, Ni, and Zn)

Manganites of transition and/or post-transition metals, AMn2O4 (where A was Co, Ni or Zn), were synthesized by a simple and easily scalable co-precipitation route and were evaluated as anode materials for Li-ion batteries. The obtained powders were characterized by SEM, TEM, and XRD techniques. Battery cycling showed that ZnMn2O4 exhibited the best performance (discharge capacity, cycling, and rate capability) compared to the two other manganites and their corresponding simple oxides. Further studies on the effect of different sintering temperatures (from 400 to 1000 °C) on particle size were performed, and it is found that the size of the particles had a significant effect on the performance of the batteries. The optimum particle size for ZnMn2O4 is found to be 75–150 nm. In addition, the use of water-soluble and environmentally friendly binders, such as lithium and sodium salts of carboxymethlycellulose, greatly improved the performance of the batteries compared to the conventional binder, PVDF. Finally, ZnMn2O4 powder sintered at 800 °C (<150 nm) and the use of the in-house synthesized lithium salt of carboxymethlycellulose (LiCMC) binder gave the best battery performance: a capacity of 690 mA h g−1 (3450 mA h mL−1) at C/10, along with good rate capability and excellent capacity retention (88%).

High-Voltage Electrolytes Based on Adiponitrile for Li-Ion Batteries

Adiponitrile, CN CH2 4CN, ADN, was evaluated as both a solvent and cosolvent in safer and more electrochemically stable electrolytes suitable for high energy and power density Li-ion batteries. An electrochemical investigation of its electrolyte solution with the Li CF3SO2 2N, LiTFSI, salt showed a wide electrochemical window of 6 V vs Li+/Li. The high melting point and the incompatibility of ADN with graphite anode required the use of ethylene carbonate EC as a cosolvent. The resultant EC:ADN electrolyte solutions showed ionic conductivities reaching 3.4 mS/cm, viscosities of 9.2 cP, and an improved resistance to aluminum corrosion up to 4.4 V, all at 20°C. Li-ion batteries incorporating graphite/LiCoO2 electrodes were assembled using EC:ADN electrolyte mixture containing 1 M LiTFSI and 0.1 M LiBOB as a cosalt, and discharge capacities of 108 mAh/g with very good capacity retention were obtained. AC impedance spectra of the batteries recorded as a function of charging and cycling indicated the presence of a stable solid electrolyte interface.

Study of the LiMn1.5Ni0.5O4/Electrolyte Interface at Room Temperature and 60°C

The surface layer (Cathode-Electrolyte Interface; CEI) on LiMn 1.5 Ni 0.5 O 4 , a promising, high voltage positive electrode for Li-ion batteries, was studied by XPS, AC impedance spectroscopy and FTIR spectroscopy. Half cells and full cells with LiMn 1.5 Ni 0.5 O 4 as positive electrode material and Li 4 Ti 5 O 12 as a negative electrode material were assembled in conventional carbonate-based electrolytes with LiPF 6 or LiBF 4 as the salt, and the effect of cycling at different operating conditions (short and long storage time, state of charge and temperature) on the surface layer composition was assessed. Capacities reaching near the theoretical value of 140 mAh g -1 were obtained in half cells cycled at C/2 and room temperature, with 85% of the capacity being retained after 100 cycles. Cycling at 60°C leads to a decrease in capacity and coulombic efficiency. The surface analysis by XPS revealed that the CEI is composed of inorganic species such as LiF and Li x PFyO z or Li x BF y O z as well as organic species such as polyethers and carbonates. Generally, it was found that cycling or storing the material at 60°C with an electrolyte using LiPF 6 as a salt yield more organic species and less LiF at the surface than the one with LiBF 4 .

A high capacity silicon–graphite composite as anode for lithium-ion batteries using low content amorphous silicon and compatible binders

In this study, silicon–graphite composites were prepared and investigated as anode materials for Li-ion batteries with small amounts of silicon and different binders. The silicon powders were prepared by ball-milling crystalline silicon for 100 h and 200 h. After 200 h, an average silicon particle size of 0.73 μm was obtained and XRD measurements confirmed the formation of an amorphous powder embedded within nanocrystalline regions. XPS analysis of the silicon samples showed that silicon particles were covered with a native silicon oxide layer that grows during ball-milling. Battery cycling of the silicon powders in half cells showed that the powder ball milled for 200 h gave the lowest first-cycle irreversible capacity and the highest reversible capacity reaching over 500 mA h g−1 after 50 cycles at C/12. Composites were made using graphite and only 5 wt% silicon powders. The silicon was found to be uniformly dispersed into the composites as evidenced by X-ray mapping and SEM. When tested in half cells using different binders, it was found that the polyetherimide binder showed the highest capacity reaching 514 mA h g−1 after 350 cycles at C/12, which is 1.6 times greater than commercial graphite anode. High rate cycling showed good capacity retention reaching half the capacity at 5 C.

Preparation of mesoporous silica with poly(oxyethylene)/(oxybutylene)/poly(oxyethylene) triblock copolymers as templates

The phase behaviour in neutral and acid aqueous solution is reported for two poly(oxyethylene)/poly(oxybutylene)/(oxyethylene) (EBE) triblock copolymers, of composition E33B10E33 and E43B14E43. Micellar solutions of both copolymers were utilised for templated-silica synthesis under acidic conditions. Calcination of the silica products gave mesoporous materials. The E33B10E33-templated silica exhibited a spherical morphology, whilst the E43B14E43-templated silica comprised irregularly shaped particles.

Effect of Nanoparticles on Electrolytes and Electrode/Electrolyte Interface

The addition of nano-sized inorganic fillers such as SiO2 to solid and liquid electrolytes to enhance their electrochemical and physical properties has been recently the focus of great deal of research. In this chapter, we review the work done in this area where various types of nanoparticles including ceramics and clay were used as additives to electrolytes commonly used in lithium-ion batteries research such as polymer electrolytes (gel and solid form), ionic and organic liquid electrolytes and plastic crystals.

Tin-Based Anode Materials for Lithium-Ion Batteries

Tin and its compounds constitute a new class of high-capacity anode materials that can replace graphitic carbon in current lithium-ion batteries. In the case of the two most studied, tin metal and tin oxide, it was shown that the inevitable volume expansion during electrochemical alloying with lithium can be mitigated using many strategies including formation of nanofilms, nanoparticles, nanocomposites, and nanostructures. It was demonstrated that high reversible capacities can be obtained and this was highlighted by the successful commercialization of a lithium-ion battery with a Sn/Co/C nanocomposite (NexelionTM).

An all-solid-state electrochemical double-layer capacitor based on a plastic crystal electrolyte

A plastic crystal, solid electrolyte was prepared by mixing tetrabutylammonium hexafluorophosphate salt, (C4H9)4NPF6, (10 molar %) with succinonitrile, SCN, (N C−CH2−CH2−C N), [SCN-10%TBA-PF6]. The resultant waxy material shows a plastic crystalline phase that extend from -36 °C up to its melting at 23 °C. It shows a high ionic conductivity reaching 4 × 10−5 S/cm in the plastic crystal phase (15 °C) and ~ 3 × 10−3 S/cm in the molten state (25 °C). These properties along with the high electrochemical stability rendered the use of this material as an electrolyte in an electrochemical double-layer capacitor (EDLC). The EDLC was assembled and its performance was tested by cyclic voltammetry, AC impedance spectroscopy and galvanostatic charge-discharge methods. Specific capacitance values in the range of 4-7 F/g. (of electrode active material) were obtained in the plastic crystal phase at 15 °C, that although compare well with those reported for some polymer electrolytes, can be still enhanced with further development of the device and its components, and only demonstrate their great potential use for capacitors as a new application.

Beyond Intercalation: Nanoscale-Enabled Conversion Anode Materials for Lithium-Ion Batteries

The use of transition metal oxides as anode materials in lithium-ion batteries offers great advantages over graphitic carbon due to their ability to deliver much higher specific capacities. The mechanism with which they electrochemically react with lithium was found to be peculiar and termed “conversion” to distinguish it from other mechanisms such as intercalation, insertion, and alloying. In this chapter, we have reviewed the behavior of a wide variety of transition metal oxides in lithium-ion batteries and the effect of structure/property relationship on their performance. It was found that a key enabler to the electrochemical reactivity of transition metal oxides is the nanosize effect and essentially the formation of nanoparticles and nanocomposites.

Graphene-Based Composite Anodes for Lithium-Ion Batteries

Graphene has emerged as a novel, highly promising material with exceptional properties and potential application in a wide range of technologies. As an anode material for lithium-ion batteries, it was shown that it cannot be used in the pure form due to its large irreversible capacity but as part of a composite with other active materials. Transition metal oxides, silicon, and tin have been explored as active anode materials to replace graphite because of their high theoretical capacities. However, these materials have large volume changes during cycling that leads to the failure of the batteries. To resolve this problem, additives have been added to these materials to mitigate this volume change. In recent years, graphene has been employed as an encapsulating agent for these materials. In this chapter, an overview of the work exploring composites made of graphene as a novel support for nanoscale materials that react with lithium and provide high capacities will be presented.