A strategy used to design high capacity (.200 mAh g 21 ), Li 2 MnO 3 -stabilized LiMO 2 (M = Mn, Ni, Co) electrodes for lithium-ion batteries is discussed. The advantages of the Li 2 MnO 3 component and its influence on the structural stability and electrochemical properties of these layered xLi 2 MnO 3 ?(1 2 x)LiMO 2 electrodes are highlighted. Structural, chemical, electrochemical and thermal properties of xLi 2 MnO 3 ?(1 2 x)LiMO 2 electrodes are considered in the context of other commercially exploited electrode systems, such as LiCoO 2 , LiNi 0.8 Co 0.15 Al 0.05 O 2 , Li 1+x Mn 22x O 4 and LiFePO 4 . G o o d e n o u g h a t O x f o r d University, UK. After spending twenty years at the Council for Scientific and Industrial Research (CSIR), Pretoria, South Africa (1973-1994) on battery-related research, he moved to the United States where he is currently an Argonne Distinguished Fellow and Group Leader at Argonne National Laboratory outside Chicago. His primary research interest is determining the structure-electrochemical properties of solid electrolyte and electrode materials for electrochemical applications.Sun-Ho Kang received his B.S. (1992), M.S. (1994), a n d P h . D . ( 1 9 9 8 ) i n M a t e r i a l s S c i e n c e a n d Engineering from Seoul National University, South Korea. After studying as a postdoctoral fellow with P r o f e s s o r J o h n B . Goodenough at the University of Texas at Austin (1999)(2000), he joined the Chemical Engineering Division at A r g o n n e N a t i o n a l Laboratory. His primary research interests include synthesis, electrochemical and transport properties, and structure-property relationships of electrode materials for energy storage and conversion systems.

The escalating and unpredictable cost of oil, the concentration of major oil resources in the hands of a few politically sensitive nations, and the long-term impact of CO 2 emissions on global climate constitute a major challenge for the 21 st century. They also constitute a major incentive to harness alternative sources of energy and means of vehicle propulsion. Today's lithium-ion batteries, although suitable for small-scale devices, do not yet have sufficient energy or life for use in vehicles that would match the performance of internal combustion vehicles. Energy densities 2 and 5 times greater are required to meet the performance goals of a future generation of plug-in hybrid-electric vehicles (PHEVs) with a 40-80 mile all-electric range, and all-electric vehicles (EVs) with a 300-400 mile range, respectively. Major advances have been made in lithium-battery technology over the past two decades by the discovery of new materials and designs through intuitive approaches, experimental and predictive reasoning, and meticulous control of surface structures and chemical reactions. Further improvements in energy density of factors of two to three may yet be achievable for current day lithiumion systems; factors of five or more may be possible for lithium-oxygen systems, ultimately leading to our ability to confine extremely high potential energy in a small volume without compromising safety, but only if daunting technological barriers can be overcome.

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Recent advances to develop manganese-rich electrodes derived from 'composite' structures in which a Li 2 MnO 3 (layered) component is structurally integrated with either a layered LiMO 2 component or a spinel LiM 2 O 4 component, in which M is predominantly Mn and Ni, are reviewed. The electrodes, which can be represented in two-component notation as xLi 2 MnO 3 ?(1 2 x)LiMO 2 and xLi 2 MnO 3 ?(1 2 x)LiM 2 O 4 , are activated by lithia (Li 2 O) and/or lithium removal from the Li 2 MnO 3 , LiMO 2 and LiM 2 O 4 components. The electrodes provide an initial capacity .250 mAh g 21 when discharged between 5 and 2.0 V vs. Li 0 and a rechargeable capacity up to 250 mAh g 21 over the same potential window. Electrochemical charge and discharge reactions are followed on compositional phase diagrams. The data bode well for the development and exploitation of high capacity electrodes for the next generation of lithium-ion batteries.

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