Fast Li-ion insertion into nanosized LiMn₂O₄ without domain boundaries

The effect of crystallite size on Li-ion insertion in electrode materials is of great interest recently because of the need for nanoelectrodes in higher-power Li-ion rechargeable batteries. We present a systematic study of the effect of size on the electrochemical properties of LiMn₂O ₄. Accurate size control of nanocrystalline LiMn₂O ₄, which is realized by a hydrothermal method, significantly alters the phase diagram as well as Li-ion insertion voltage. Nanocrystalline LiMn ₂O₄ with extremely small crystallite size of 15 nm cannot accommodate domain boundaries between Li-rich and Li-poor phases due to interface energy, and therefore lithiation proceeds via solid solution state without domain boundaries, enabling fast Li-ion insertion during the entire discharge process.