Heteroelement-containing vanadium sulfide

A method for predicting performance of a lithium ion secondary battery comprising, as an electrode active material for the lithium ion secondary battery, a foreign element-containing vanadium sulfide that comprises vanadium, sulfur, and an element other than vanadium and sulfur (foreign element) as constituent elements, the method comprising

• calculating the relative energy of a cluster molecule by first-principles calculation, the cluster molecule having a structure in which one or more vanadium atoms in a cluster composed of vanadium sulfide unit cells are replaced by a specific foreign element;
• and
• evaluating the lithium ion secondary battery as having excellent cycle characteristics when the calculated relative energy is equal to or lower than that of vanadium sulfide not containing the foreign element.

A method for predicting performance of a lithium ion secondary battery comprising, as an electrode active material for the lithium ion secondary battery, a foreign element-containing vanadium sulfide that comprises vanadium, sulfur, and an element other than vanadium and sulfur (foreign element) as constituent elements, the method comprising

• calculating at least one parameter of a cluster molecule by first-principles calculation, the cluster molecule having a structure in which one or more vanadium atoms in a cluster composed of vanadium sulfide unit cells are replaced by a specific foreign element, the parameter being at least one member selected from the group consisting of electron density of states, band gap, and relationship between the valence band maximum (VBM) and the conduction band minimum (CBM) of the cluster molecule;
• and
• evaluating the lithium ion secondary battery as having excellent electrochemical performance when the electronic conductivity of the foreign element-containing vanadium sulfide obtained from the calculation result is equal to or higher than that of vanadium sulfide not containing the foreign element.

A performance prediction method that is a method for selecting a foreign element to be present in a foreign element-containing vanadium sulfide that comprises, as constituent elements, vanadium, sulfur, and an element other than vanadium and sulfur (foreign element), the method comprising

• calculating the relative energy of a cluster molecule by first-principles calculation, the cluster molecule having a structure in which one or more vanadium atoms in a cluster composed of vanadium sulfide unit cells are replaced by a specific foreign element;
• and
• selecting the foreign element when the calculated relative energy is equal to or lower than that of vanadium sulfide not containing the foreign element.

A performance prediction method that is a method for selecting a foreign element to be present in a foreign element-containing vanadium sulfide that comprises, as constituent elements, vanadium, sulfur, and an element other than vanadium and sulfur (foreign element), the method comprising

• calculating at least one parameter of a cluster molecule by first-principles calculation, the cluster molecule having a structure in which one or more vanadium atoms in a cluster composed of vanadium sulfide unit cells are replaced by a specific foreign element, the parameter being at least one member selected from the group consisting of electron density of states, band gap, and relationship between the valence band maximum (VBM) and the conduction band minimum (CBM) of the cluster molecule;
• and
• selecting the foreign element when the electronic conductivity of the foreign element-containing vanadium sulfide obtained from the calculation result is equal to or higher than that of vanadium sulfide not containing the foreign element.