Countering the Voltage Decay in High Capacity xLi2MnO3•(1-x)LiMO2 Electrodes (M=Mn, Ni, Co) for Li+-Ion Batteries

A new approach to synthesizing high capacity lithium-metal-oxide cathodes for lithium-ion batteries from a Li2MnO3 precursor is described. The technique, which is simple and versatile, can be used to prepare a variety of integrated 'composite' electrode structures, such as 'layered-layered' xLi(2)MnO(3)center dot(1-x)LiMO2, 'layered-spinel' xLi(2)MnO(3)center dot(1-x)LiM2O4, 'layered-rocksalt' xLi(2)MnO(3)center dot(1-x)MO and more complex arrangements, in which M is typically Mn, Ni, and/or Co. Early indications are that electrodes prepared by this method are effective in 1) countering the voltage decay that occurs on cycling 'layered-layered' xLi(2)MnO(3)center dot(1-x)LiMO2 electrodes without compromising capacity, and 2) reducing the extent of electrochemical activation required above 4.5 V on the initial charge. In particular, a 0.5Li(2)MnO(3)center dot 0.5LiMn(0.5)Ni(0.5)O(2) electrode, after activation at 4.6 V, delivers a steady capacity of 245 mAh/g between 4.4 and 2.5 V at 15 mA/g (similar to C/15 rate) with little change to the voltage profile; a first cycle capacity loss of 12%, which is significantly less than usually observed for 'layered-layered' electrodes, has been achieved with a manganese-rich 0.1Li(2)MnO(3)center dot 0.9LiMn(0.50)Ni(0.37)Co(0.13)O(2) electrode. These results have implications for enhancing the performance of the next generation of high-energy lithium-ion batteries. The flexibility of the method and the variation in electrochemical properties of various composite electrode structures and compositions are demonstrated. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.080206jes] All rights reserved.