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.

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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Lithium-and manganese-rich layered electrode materials, represented by the general formula xLi 2 MnO 3 • (1x)LiMO 2 in which M is Mn, Ni, and Co, are of interest for both high-power and highcapacity lithium ion cells. In this paper, the synthesis, structural and electrochemical characterization of xLi 2 MnO 3 • (1x)LiMn 0.333 Ni 0.333 Co 0.333 O 2 electrodes over a wide compositional range (0 e x e 0.7) is explored. Changes that occur to the compositional, structural, and electrochemical properties of the electrodes as a function of x and the importance of using a relatively high manganese content and a high charging potential (>4.4 V) to generate high capacity (>200 mAh/g) electrodes are highlighted. Particular attention is given to the electrode composition 0.3Li 2 MnO 3 • 0.7LiMn 0.333 Ni 0.333 Co 0.333 O 2 (x ) 0.3) which, if completely delithiated during charge, yields Mn 0.533 Ni 0.233 Co 0.233 O 2 , in which the manganese ions are tetravalent and, when fully discharged, LiMn 0.533 Ni 0.233 Co 0.233 O 2 , in which the average manganese oxidation state (3.44) is marginally below that expected for a potentially damaging Jahn-Teller distortion (3.5). Acid treatment of 0.3Li 2 MnO 3 • 0.7LiMn 0.333 Ni 0.333 Co 0.333 O 2 composite electrode structures with 0.1 M HNO 3 chemically activates the Li 2 MnO 3 component and essentially eliminates the first cycle capacity loss but damages electrochemical behavior, consistent with earlier reports for Li 2 MnO 3 -stabilized electrodes. Differences between electrochemical and chemical activation of the Li 2 MnO 3 component are discussed. Electrochemical charge/discharge profiles and cyclic voltammogram data suggest that small spinel-like regions, generated in cycled manganese-rich electrodes, serve to stabilize the electrodes, particularly at low lithium loadings (high potentials). The study emphasizes that, for high values of x, a relatively small LiMO 2 concentration stabilizes a layered Li 2 MnO 3 electrode to reversible lithium insertion and extraction when charged to a high potential.

A non-aqueous lithium-ion redox fl ow battery employing organic molecules is proposed and investigated. 2,5-Di-tert-butyl-1,4-bis(2-methoxyethoxy)benzene and a variety of molecules derived from quinoxaline are employed as initial high-potential and low-potential active materials, respectively. Electrochemical measurements highlight that the choice of electrolyte and of substituent groups can have a signifi cant impact on redox species performance. The charge-discharge characteristics are investigated in a modifi ed coin-cell confi guration. After an initial break-in period, coulombic and energy effi ciencies for this unoptimized system are ∼ 70% and ∼ 37%, respectively, with major charge and discharge plateaus between 1.8-2.4 V and 1.7-1.3 V, respectively, for 30 cycles. Performance enhancements are expected with improvements in cell design and materials processing.