New materials hold the key to fundamental advances in energy conversion and storage, both of which are vital in order to meet the challenge of global warming and the finite nature of fossil fuels. Nanomaterials in particular offer unique properties or combinations of properties as electrodes and electrolytes in a range of energy devices. This review describes some recent developments in the discovery of nanoelectrolytes and nanoelectrodes for lithium batteries, fuel cells and supercapacitors. The advantages and disadvantages of the nanoscale in materials design for such devices are highlighted.

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Nanostructured materials for advanced energy conversion and storage devices

Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li-air (O(2)) and Li-S. The energy that can be stored in Li-air (based on aqueous or non-aqueous electrolytes) and Li-S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li-air and Li-S justify the continued research effort that will be needed.

Li-O2 and Li-S batteries with high energy storage.

There is great interest in developing rechargeable lithium batteries with higher energy capacity and longer cycle life for applications in portable electronic devices, electric vehicles and implantable medical devices. Silicon is an attractive anode material for lithium batteries because it has a low discharge potential and the highest known theoretical charge capacity (4,200 mAh g(-1); ref. 2). Although this is more than ten times higher than existing graphite anodes and much larger than various nitride and oxide materials, silicon anodes have limited applications because silicon's volume changes by 400% upon insertion and extraction of lithium which results in pulverization and capacity fading. Here, we show that silicon nanowire battery electrodes circumvent these issues as they can accommodate large strain without pulverization, provide good electronic contact and conduction, and display short lithium insertion distances. We achieved the theoretical charge capacity for silicon anodes and maintained a discharge capacity close to 75% of this maximum, with little fading during cycling.

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High-performance lithium battery anodes using silicon nanowires

2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

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Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

Li-ion battery materials: present and future

A hydrogen storage and release material is provided in the form of a supportive host component that carries or contains a hydrogen absorbing guest material. Metal compounds, such as oxides, carbides, nitrides, or the like, are prepared to carry polyaromatic molecules that absorb hydrogen in conjugated double bonds. Examples of suitable guest-host materials include layers of vanadium oxide with interacted layers of polyaniline or polythiophene. Dopant elements, like nickel, in the host oxide can enhance hydrogen absorption and de-sorption in the host material.

Guest-host hydrogen storage material

http://absimage.aps.org/image/MAR12/MWS_MAR12-2011-004375.pdf

Effect of Iron-based Impurities on the performance of nanostructured C-LiFePO$_{4}$ cathode materials for Li ion Batteries

The purpose of this chapter is to give a general overview of the properties of compounds such as electrode materials in lithium batteries, particularly those in which there is an appreciable amount of ionic transport within solid components.

Materials for Electrodes: Crystalline Compounds

Hydrogen storage alloys, especially as newly formed, have often required high temperature (e.g., >700°C) activation before the solids will absorb an amount of hydrogen normally storable by the composition. Now, such alloys may be activated by a low temperature (typically below zero degrees Celsius) soak in pressurized hydrogen followed by desorption of the hydrogen at a temperature above about 1000C. Such low temperature hydrogen absorption and higher temperature hydrogen desorption may be repeated a few times until the hydrogen storage alloy material readily absorbs and holds hydrogen for release on demand, and subsequent hydrogen refilling.

Low temperature activation of metal hydrides

Polymer electrolytes are attracting interest because of potential use in ‘solid state’ batteries and electrochromic windows. In this work the nature of the chemical bonds and ion association in polymer-salt complexes were studied. The fundamental vibrational frequencies of LiClO4 − were calculated using valence force constants which are obtained from the ClO4 − anion. The calculated frequencies and the band assignments agree quite well with the observed frequencies. Raman and IR spectroscopy were used to investigate the interaction of Li+ and ClO4 − with the PEO chains. Lithium ion interacted with the negatively charged oxygen of PEO and C104 interacted electro- statically with the positively charged hydrogens. The strong electrostatic interactions induced changes in the intensity of the Raman bands and IR absorption bands of the polymer. The Raman and IR spectra of the polymer-salt complexes clearly show the existence of ‘free’ ions, ionpairs and salt clusters at various concentrations of the lithium salt. The maximum concentration of “free” ions deduced from the spectroscopy is in excellent agreement with the salt concentration required to obtain maximum ionic conductivity.

Gholam-Abbas Nazri

Papers

Guest-host hydrogen storage material

Effect of Iron-based Impurities on the performance of nanostructured C-LiFePO$_{4}$ cathode materials for Li ion Batteries

Materials for Electrodes: Crystalline Compounds

Low temperature activation of metal hydrides

Nature of the Chemical Bonds in Polymer-Salt Complexes: Raman and IR Studies