Controlling the pore-solid architecture of mesoporous, high surface area manganese oxides with the birnessite structure

We describe the preparation of nanoscale, mesoporous manganese oxides with the birnessite structure. Although all dried gels derive from the same sol-gel chemistry, the final pore architectures are significantly different, being determined by the method employed for removal of the pore fluid. The high porosity of the initial wet gel is retained if the pore fluid is removed where capillary forces are either minimized (to form an ambigel) or zero (to form an aerogel). The higher porosities of ambigels and aerogels facilitate the insertion/de-insertion of Li cations, resulting in improved electrochemical performance at high charge/discharge rates as compared to the xerogel form. (C) 2001 Elsevier Science B.V. All rights reserved.