NOVELTY - Producing a nitrided lithium (Li)-titanium (Ti) compound oxide (I), comprises: preparing a raw material composite that has a raw material containing lithium, titanium, and oxygen and a nitriding agent, which is substituted amine compounds (1a) and is solid or liquid at room temperature (25 degrees C); and synthesizing the nitrided Li-Ti compound oxide by firing the raw material composite to nitride the raw material.    USE - (I) is useful as a negative electrode active material and in a lithium-ion battery (all claimed), which is useful in the field of information-related equipment, communication equipment and in the field of automobiles for developing electric vehicles and hybrid vehicles.    ADVANTAGE - (I): is low in reduction potential; has reversibility in insertion, higher Li ions extraction and highly stable battery voltage; and does not suffer from the occurrence of a detachment and a crack unlike a film, as it is a particulate, hence has excellent durability. (I) provides lithium-ion battery excellent: in high current operation, hence it is possible to shorten the time required to charge the battery to 90% of the capacity; in cycle characteristics; and in safety.    DETAILED DESCRIPTION - Method of producing a nitrided lithium (Li)-titanium (Ti) compound oxide (I), comprises: preparing a raw material composite that has a raw material containing lithium, titanium, and oxygen and a nitriding agent, which is substituted amine compounds of formula (N(R1)(R2)(R3)) (1a) and is solid or liquid at room temperature (25 degrees C); and synthesizing the nitrided Li-Ti compound oxide by firing the raw material composite to nitride the raw material.    R1-R3 = functional group having at least one of C, H, O or N.    INDEPENDENT CLAIMS are also included for:    (1) a nitrided Li-Ti compound oxide comprising lithium, titanium, oxygen, and nitrogen, where the nitrided Li-Ti compound oxide is crystalline; and    (2) a lithium-ion battery, comprising: a positive electrode active material layer (1) containing a positive electrode active material; a negative electrode active material layer (2) containing a negative electrode active material; and an electrolyte layer (3) formed between the positive electrode active material layer and the negative electrode active material layer, where the negative electrode active material is the nitrided Li-Ti compound oxide.    DESCRIPTION OF DRAWING(S) - The figure is a schematic sectional diagram showing an example of an electricity generating element of a lithium-ion battery.    Positive electrode active material layer (1)    Negative electrode active material layer (2)    Electrolyte layer (3)    Electricity generating element (10)