A New Three‐Volt Spinel Li1 + x Mn1.5Ni0.5 O 4 for Secondary Lithium Batteries

The spinel has been prepared at low temperature using a new sol‐gel process. X‐ray diffraction analysis reveals that the obtained material presents a cubic spinel structure with a unit cell parameter lower than that of stoichiometric . X‐ray photoelectron spectroscopy confirms the divalent state of doped nickel in the material. Furthermore, compound can intercalate a second lithium both chemically and electrochemically, leading to the formation of a new material with the same cubic spinel structure. This material presents only one plateau at around 3 V vs. with a large discharge capacity of 160 mAh/g and fairly good cyclability. This result is in contrast to the undoped , where two plateaus at 4 and 3 V are observed because of the occurrence of a structural transition caused by the Jahn‐Teller effect. The structure and the electrochemical behavior of are investigated and compared to those of material prepared by the same sol‐gel process.