Design of Pore and Matter Architectures in Manganese Oxide Charge-Storage Materials

Abstract

We describe the preparation of a manganese oxide polymorph in which the solid‐pore architecture of the material is controllably varied. All gels derived from a sol‐gel synthesis and annealed to crystallize in the 2×2 tunnel structure of cryptomelane , but exhibit markedly different final pore structures based on how the pore fluid is removed from the wet gel. The mesoporous structure of the initial gel is maintained by removing pore fluid under conditions where the capillary forces that result from extraction are either low (to form an ambigel) or nonexistent (to form an aerogel). These nanoscale mesoporous materials have higher capacities at high cycling rates than can be obtained for bulk cryptomelane. Finite‐diffusion processes describe the electrochemical association of with the networked, nanoscale crystallites. Controlling both the pore and solid architecture on the nanoscale offers a strategy for the design of new battery and charge‐storage materials. ©2000 The Electrochemical Society