We describe the preparation of a manganese oxide polymorph in which the solid-pore architecture of the material is controllably varied. All MnO2 gels derived from a KMnO4-based sol-gel synthesis and annealed to 300 degrees C crystallize in the 2 x 2 tunnel structure of cryptomelane (KdeltaMnO2 or alpha-MnO2), 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 Li:MnO2 capacities at high cycling rates than can be obtained for bulk cryptomelane. Finite-diffusion processes describe the electrochemical association of Li+ with the networked, nanoscale MnO2 crystallites. Controlling both the pore and solid architecture on the nanoscale offers a strategy for the design of new battery and charge-storage materials.