In spite of intrinsic limitations, neutron powder diffraction is, and will still be in the future, the primary and most straightforward technique for magnetic structure determination. In this paper some recent improvements in the analysis of magnetic neutron powder diffraction data are discussed. After an introduction to the subject, the main formulas governing the analysis of the Bragg magnetic scattering are summarized and shortly discussed. Next, we discuss the method of profile fitting without a structural model to get precise integrated intensities and refine the propagation vector(s) of the magnetic structure. The simulated annealing approach for magnetic structure determination is briefly discussed and, finally, some features of the program FullProf concerning the magnetic structure refinement are presented and discussed. The different themes are illustrated with simple examples.

Recent advances in magnetic structure determination by neutron powder diffraction

In the previous paper Ralph Brodd and Martin Winter described the different kinds of batteries and fuel cells. In this paper I will describe lithium batteries in more detail, building an overall foundation for the papers that follow which describe specific components in some depth and usually with an emphasis on the materials behavior. The lithium battery industry is undergoing rapid expansion, now representing the largest segment of the portable battery industry and dominating the computer, cell phone, and camera power source industry. However, the present secondary batteries use expensive components, which are not in sufficient supply to allow the industry to grow at the same rate in the next decade. Moreover, the safety of the system is questionable for the large-scale batteries needed for hybrid electric vehicles (HEV). Another battery need is for a high-power system that can be used for power tools, where only the environmentally hazardous Ni/ Cd battery presently meets the requirements. A battery is a transducer that converts chemical energy into electrical energy and vice versa. It contains an anode, a cathode, and an electrolyte. The anode, in the case of a lithium battery, is the source of lithium ions. The cathode is the sink for the lithium ions and is chosen to optimize a number of parameters, discussed below. The electrolyte provides for the separation of ionic transport and electronic transport, and in a perfect battery the lithium ion transport number will be unity in the electrolyte. The cell potential is determined by the difference between the chemical potential of the lithium in the anode and cathode, ∆G ) -EF. As noted above, the lithium ions flow through the electrolyte whereas the electrons generated from the reaction, Li ) Li+ + e-, go through the external circuit to do work. Thus, the electrode system must allow for the flow of both lithium ions and electrons. That is, it must be both a good ionic conductor and an electronic conductor. As discussed below, many electrochemically active materials are not good electronic conductors, so it is necessary to add an electronically conductive material such as carbon * To whom correspondence should be addressed. Phone and fax: (607) 777-4623. E-mail: stanwhit@binghamton.edu. 4271 Chem. Rev. 2004, 104, 4271−4301

http://www.chemie.uni-regensburg.de/Anorganische_Chemie/Vortrag/StudentenWS06-07/Vortrag_Amereller.pdf

Lithium Batteries and Cathode Materials

Li-ion battery materials: present and future

Electrolytes and interphases in Li-ion batteries and beyond.

Graphene has attracted tremendous research interest in recent years, owing to its exceptional properties. The scaled-up and reliable production of graphene derivatives, such as graphene oxide (GO) and reduced graphene oxide (rGO), offers a wide range of possibilities to synthesize graphene-based functional materials for various applications. This critical review presents and discusses the current development of graphene-based composites. After introduction of the synthesis methods for graphene and its derivatives as well as their properties, we focus on the description of various methods to synthesize graphene-based composites, especially those with functional polymers and inorganic nanostructures. Particular emphasis is placed on strategies for the optimization of composite properties. Lastly, the advantages of graphene-based composites in applications such as the Li-ion batteries, supercapacitors, fuel cells, photovoltaic devices, photocatalysis, as well as Raman enhancement are described (279 references).

/pdf/graphene-based-composites-540z2xd3o0.pdf

Graphene-based composites

Electrochemical properties of are studied as Li is deintercalated from . High precision voltage measurements and in situ x‐ray diffraction indicate a sequence of three distinct phase transitions as varies from 1 to 0.4. Two of the transitions are situated slightly above and below and are caused by an order/disorder transition of the lithium ions. The order/disorder transition is studied as a function of temperature allowing the determination of an order/disorder phase diagram. In situ x‐ray diffraction measurements facilitate a direct observation of the effects of deintercalation on the host lattice crystal structure. The other phase transition is shown to be first order (coexisting phases are observed for ) involving a significant expansion of the parameter of the hexagonal unit cell. We report the variation of the lattice constants of with and show that the phase transition to the lithium ordered phase near is accompanied by a lattice distortion to a monoclinic unit cell with , , and . Finally we report an overall phase diagram for and .

https://iopscience.iop.org/article/10.1149/1.2221184/pdf

Electrochemical and In Situ X‐Ray Diffraction Studies of Lithium Intercalation in Li x CoO2

The electrolyte plays an important role in governing the high-current performance of Li-ion batteries. Nonnally, battery electrolytes are optimized for maximum conductivity. In order to gain a more profound understanding of the role of the electrolyte, properties such as the Li salt diffusion coefficient, the Li + transference number, and the Li salt activity all need to be measured in addition to the conductivity. The situation is further complicated by the fact that high currents change the cell temperature and also create strong concentration gradients in the electrolyte. A full set of transport properties for LiPF 6 in a propylene carbonate/ ethylene carbonate/dimethyl/carbonate mixture were measured as a function of temperature and LiPF 6 concentration. The Li + transference number was found to be fairly constant with concentration. The activity and diffusion coefficient were both found to vary strongly with temperature and concentration. The temperature dependence of the transport properties is shown to be crucial for making predictions of cell performance at high currents.

https://iopscience.iop.org/article/10.1149/1.1872737/pdf

Jan N. Reimers

Papers

Electrochemical and In Situ X‐Ray Diffraction Studies of Lithium Intercalation in Li x CoO2

Transport Properties of LiPF6-Based Li-Ion Battery Electrolytes

In situ x-ray diffraction and electrochemical studies of Li1−xNiO2

Dependence of the electrochemical intercalation of lithium in carbons on the crystal structure of the carbon

Structure and Electrochemistry of Lixfeyni1-Yo2