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

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<sub>2</sub>MnO<sub>3</sub>•(1-x)LiMO<sub>2</sub>, `layered-spinel' xLi₂MnO₃•(1-x)LiM₂O₄, `layered-rocksalt' xLi<sub>2</sub>MnO<sub>3</sub>• (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' xLi₂MnO₃•(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 0.5Li₂MnO₃•0.5LiMn_0.5Ni_0.5O₂ 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 (~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 0.1Li₂MnO₃•0.9LiMn_0.50Ni_0.37Co_0.13O₂ 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. [ABSTRACT FROM AUTHOR]