Active electrode material

A method of making an active electrode material, the method comprising:

• providing a mixed niobium oxide having a Wadsley-Roth or Tetragonal Tungsten Bronze crystal structure, wherein the mixed niobium oxide is expressed by the formula MNbbOc, wherein M represents one or more cations, b satisfies 0.13≤b≤49, and c satisfies 3.3≤c≤124;
• combining the mixed niobium oxide with a carbon precursor to form an intermediate material, wherein the carbon precursor comprises polyaromatic sp2 carbon and is selected from pitch carbons wherein the intermediate material comprises the carbon precursor in an amount of 0.1-25 wt %;
• and
• heating the intermediate material under reducing conditions to pyrolyse the carbon precursor forming a carbon coating on the mixed niobium oxide and introducing oxygen vacancies into the mixed niobium oxide, thereby forming the active electrode material;
• wherein the step of heating the intermediate material under reducing conditions is performed at a temperature in the range of 400-1,200° C. under an inert gas;
• or under a mixture of an inert gas and hydrogen;
• or under vacuum;
• and
• wherein the active electrode material has an Ip/IG ratio as observed by Raman spectroscopy within the range of 0.90-1.15.