Rechargeable lithium batteries

Much of materials electrochemistry represents a fusion of solid-state chemistry and electrochemistry. The commercial success of the world's first rechargeable lithium battery, introduced recently by Sony, is a triumph of materials electrochemistry. By developing radically new anodes, cathodes and electrolytes, a cell has been produced which can store three times the energy per unit weight and volume compared with conventional systems. This represents a revolution in battery technology. The Sony cell was developed in response to a demand from consumer electronic products such as camcorders. The future development of such products, e.g. mobile telephones and lap-top computers, of biomedical devices, such as the artificial heart, and of electric vehicles, is crucially dependent on developing advanced batteries. The markets for many of these devices are vast. The Sony cell is based on the rocking-chair concept and is composed of a carbon anode, LiCoO2 cathode and non-aqueous electrolyte. The advantages and disadvantages of the rocking-chair battery will be compared with those of the rechargeable lithium battery based on a lithium-metal anode. The Sony cell represents merely a first-generation lithium system. Future substantial improvements in performance will also rely on innovative materials electrochemistry. The search for new intercalation cathodes which can offer advantages compared with LiCoO2 are discussed. In particular, the development of new 3 and 4 V cathodes, based on LiMn2O4 spinel materials, is presented. These materials have a number of important advantages which make them attractive as the basis for a new generation of rechargeable lithium batteries. The new synthetic routes to the spinel materials are described, as are the structures, microstructures and electrochemical performance of these materials.