Electrochemical energy storage is attractive, having very high storage efficiencies typically exceeding 90 %, as well as relatively-high energy densities. Li-ion battery technology provides the highest energy densities of commercialized battery-tech­nologies and has found widespread use in portable electronic applications. Appli­cation of Li-ion batteries in electrical vehicles and as static storage media is emerging, however, improved performance and reduced cost, combined with safety

N. Sharma (H)

School of Chemistry, The University of New South Wales, Sydney, NSW 2052, Australia e-mail: neeraj. sharma@unsw. edu. au

M. Wagemaker

Faculty of Applied Sciences, Radiation, Science and Technology Department, Delft University of Technology, Mekelweg 15, 2629 JB Delft, The Netherlands e-mail: m. wagemaker@tudelft. nl

© Springer International Publishing Switzerland 2015 139

G. J. Kearley and V. K. Peterson (eds.), Neutron Applications in Materials for Energy, Neutron Scattering Applications and Techniques,

DOI 10.1007/978-3-319-06656-1_7

Electronic conductor

•• Lithium storage material Binder

enhancements, are required. This has initiated a worldwide research effort for Li-ion electrode and electrolyte materials that combine desirable properties such as high energy and power density, low cost, high abundance of component elements, and electrochemical stability [1—4]. In the current generation of Li-ion batteries, insertion materials that reversibly host Li in the crystal structure form the most important class of electrodes. Although the future of Li-ion batteries looks bright, it should be noted that the availability of a number of relevant transition metals and possibly Li itself is a topic of interest [2].

In a Li-ion battery two insertion-capable electrodes[11] with a difference in Li chemical potential (change in free energy upon Li addition) are in contact through an electrolyte (an ionic conductor and electronic insulator) and a separating membrane, see Fig. 7.1. The Li will flow from the insertion material in which Li has a high chemical-potential towards the electrode in which Li has a low chemical-potential. Only Li-ions can flow through the electrolyte and the charge compensation requires electrons to follow via the external circuit which can be used to power an application. By applying a higher electrical potential than the spontaneous equilibrium open circuit polarization the process can be reversed. High energy-density requires a large
specific-capacity of ions in both electrodes and a large difference in chemical potential. High power (and fast insertion/extraction) requires both electrons and Li-ions to be highly mobile throughout the electrode materials and electrolyte.