Method for coating carbon on lithium titanium oxide-based anode active material nanoparticles and carbon-coated lithium titanium oxide-based anode active material nanoparticles produced by the method

A method for forming a carbon coating on lithium titanium oxide-based anode active material nanoparticles, the method comprising the steps of:

• (a) providing a solution comprising a lithium precursor, a titanium precursor, a surface modifier and a solvent, wherein the surface modifier comprises at least any one of a carboxylic acid, an aldehyde, and an amine, and the surface modifier is at a concentration of between 0.001 mol/L to 5 mol/L, wherein the solvent comprises an alcohol or a plurality of alcohols,
• (b) feeding the provided solution into a reactor, and reacting the provided solution under supercritical fluid conditions to form a reacted solution comprising nanoparticles of an anode active material represented by Li4Ti5O12,
• (c) separating the anode active material nanoparticles from the reacted solution prepared in (b), and
• (d) calcining the anode active material nanoparticles to coat the surface of the nanoparticles with carbon whereby to form the carbon coating anode active material nanoparticles that have an average diameter between 5 nm to less than 30 nm,
• wherein the surface modifier is dissolvable in the solvent and reacts with hydroxyl groups on a surface of the nanoparticles to form —CH2- and CH3- groups on the surface of the nanoparticles in the reacting in step (b), the surface modifier being present in the solution in step (a) in an amount effective for causing the carbon to coat the surface of the nanoparticles more uniformly and with less aggregation of the nanoparticles than if the surface modifier were omitted from the solution in step (a).

A method for preparing carbon coated Li4Ti5O12 nanoparticles, the method comprising:

• mixing together an alcohol solvent, a lithium precursor, a titanium precursor, and a surface modifier into a mixed solution, wherein the surface modifier is selected from the group consisting of a carboxylic acid, an aldehyde, an amine and a combination therein and wherein the surface modifier is at a concentration range between 0.001 mol/L to 5 mol/L;
• reacting the mixed solution under supercritical fluid conditions to prepare a Li4Ti5O12 nanoparticle solution;
• separating Li4Ti5O12 nanoparticles from the Li4Ti5O12 nanoparticle solution;
• and
• calcining the Li4Ti5O12 nanoparticles to form the carbon coated Li4Ti5O12 nanoparticles that have an average particle diameter between 5 nm to less than 30 nm.