Three-dimensionally ordered macroporous Li ₄Ti ₅O ₁₂: Effect of wall structure on electrochemical properties

Three-dimensionally ordered macroporous (3DOM) Li ₄Ti ₅O ₁₂ was synthesized using poly(methyl methacrylate) colloidal crystal templates and metal organic aqueous precursors. 3DOM structures of various filling fractions and wall thicknesses were synthesized, and the materials evaluated in lithium ion battery cells. The 3DOM architecture was found to markedly improve the rate capability of Li ₄Ti ₅O ₁₂ when the voids of the template were underfilled or perfectly filled. When the template voids were overfilled, the performance of the electrode was similar to that of nonporous Li ₄Ti ₅O ₁₂. We believe the enhanced rate capability results from the interconnected network of nanometer scale walls, which create short lithium diffusion distances and better contact with the electrolyte. SEM and TEM micrographs reveal that the nature of the wall structure forms low angle grain boundaries in 3DOM Li ₄Ti ₅O ₁₂, which enhances conduction pathways in the particle, especially at high rates.