Coated metal oxide materials and method, process, and apparatus for making the same

A method for making a coated metal oxide, comprising:

• mixing a first metal-containing solution and a first supercritical fluid to facilitate formation of a metal oxide,
• wherein the metal oxide is formed in a closed-loop continuous hydrothermal process;
• forming a coating in the closed-loop continuous hydrothermal process by mixing an additional solution to facilitate formation of a coating on the metal oxide, or forming the coating by depositing one or more atomic layers on a surface of the metal oxide using a first metal-containing compound and an oxidizing gas, wherein the coating comprises at least one of a metal, a polymer, or a conductive material;
• separating the metal oxide or coated metal oxide formed from a waste fluid, where the waste fluid contains unreacted components from the first metal-containing solution and the first supercritical fluid;
• and
• extracting one or more metals from the waste fluid, wherein the one or metals comprise lithium wherein the first metal-containing solution and the first supercritical fluid are recycled in the closed-loop hydrothermal process prior to the separation of the metal oxide or coated metal oxide from the waste fluid.