NEGATIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM ION SECONDARY BATTERIES, METHOD FOR PRODUCING SAME, AND LITHIUM ION SECONDARY BATTERY

摘要

The present invention provides: a negative electrode active material for lithium ion secondary batteries, which has high capacity, high energy density and high safety; and a lithium ion secondary battery which uses the negative electrode active material for lithium ion secondary batteries. This negative electrode active material for lithium ion secondary batteries is characterized by being an oxide containing Li and Fe, and is also characterized in that the oxide has an LiFeO2 crystalline phase and an amorphous phase and the oxide has a peak ratio of the peak value of the (200) plane of LiFeO2 relative to the peak value of the amorphous phase as calculated by formula (1) of from 13.2 to 100. This method for producing a negative electrode active material for lithium ion secondary batteries is characterized in that a compound obtained by mixing LiOH·H2O and FeOOH at a predetermined ratio and distilled water are hermetically sealed in a pressure-resistant container and the pressure-resistant container is held at 180-200°C for 10-20 hours, thereby obtaining an oxide that has an LiFeO2 crystalline phase and an amorphous phase, or alternatively a crystalline phase of LiFeO2 and LiFe5O8 and an amorphous phase.