Nanostructured Lithium Nickel Manganese Oxides for Lithium-Ion Batteries

Nanostructured lithium nickel manganese oxides were investigated as advanced positive electrode materials for lithium-ion batteries designated to power plug-in hybrid electric vehicles and all-electric vehicles. The investigation included material characterization and electrochemical testing. In cell tests, the Li_1.375Ni_0.25Mn_0.75O_2.4375 composition achieved high capacity (210  mAh  g⁻¹) at an elevated rate (230  mA  g⁻¹), which makes this material a promising candidate for high energy density Li-ion batteries, as does its being cobalt-free and uncoated. The material has spherical morphology with nanoprimary particles embedded in micrometer-sized secondary particles, possesses a multiphase character (spinel and layered), and exhibits a high packing density (over 2  g  cm⁻³) that is essential for the design of high energy density positive electrodes. When combined with the Li₄Ti₅O₁₂ stable anode, the cell showed a capacity of 225  mAh  g⁻¹ at the C/3 rate (73  mA  g⁻¹) with no capacity fading for 200 cycles. Other chemical compositions, Li_(1+x)Ni_0.25Mn_0.75O_(2.25+x/2) (0.32x0.65), were also studied, and the relationships among their structural, morphological, and electrochemical properties are reported. ©2010 The Electrochemical Society