Computer modelling of advanced materials for renewable energy devices

The price of oil continues to increase and there is no end in sight. Therefore it is important to increase production of alternative, sustainable, energy and to be able to store this energy. This proposal tries to develop rules for the design of new materials for advanced (lithium) batteries, solar_ cells and for storage of hydrogen. This is done by performing computer simulations of these materials using advanced simulation techniques, such as ab initio simulation and molecular dynamics, in which the motion of atoms and molecules is followed in the computer. These simulations provide a detailed understanding of the behaviour of materials and how this can be changed for example by adding small amounts of atoms or molecules (this is called heteroion doping). They give precise information on the atomistic structure of a material and how atoms are transported (migrate) through the structure. Using this we can obtain an understanding of the relation between structure of a material and its performance. This in turn allows us to suggest new structures with desirable properties and ways of producing these materials.In batteries the electrode materials have to be able to take up lithium ions and release these again a large number of times as the battery gets charged and decharged. For the battery performance the following factors are important: the voltage difference between the electrodes, how many lithium ions go into and out of the electrodes, how fast can they go in and out and how often. With computer simulations we can monitor and learn to understand how these properties are affected as we change the materials. Using this we can obtain an understanding of the relation between structure of a material and its performance. Examples of new materials are nanosheets and nanotubes of titanium dioxide. Nanotubes are tubular molecules with properties that makes them potentially extremely useful for many applications, particularly in small scale electric and mechanical devices. Nanosheets are extremely thin layers composed of atoms or molecules, such as titanium dioxide. Using our simulations we will study how these new materials perform in batteries, solar cells and as materials for the storage of hydrogen.Such studies will be carried out for a number of materials, such as ceramic oxides and nanocomposites, that is materials which are made of dissimilar components and mixed at an extremely fine (nano-)meter scale.To carry out these studies we also need to develop some new methods for simulating these materials. In particular when defects, such as missing or extra ions, are present new techniques for calculating their properties will be designed.