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_1.375 Ni_0.25 Mn_0.75 O _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 Li₄ Ti ₅ O₁₂ 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 _0.25 Mn_0.75 O_(2.25+x/2) (0.32 ≤ x ≤ 0.65), were also studied, and the relationships among their structural, morphological, and electrochemical properties are reported.