Materials Science

A Basic Deposit

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Science  05 Jun 2009:
Vol. 324, Issue 5932, pp. 1242
DOI: 10.1126/science.324_1242b
CREDIT: LIU ET AL., ADV. FUNCT. MATER. 19, 1015 (2009)

Manganese dioxide (MnO2) meets many of the requirements as an electrode in lithium (Li) batteries, but the bulk material exhibits low capacity and poor cycling because Li ion intercalation distorts the crystal lattice. Nanostructuring of the bulk material can alleviate some of the problems, but typical templating routes for creating mesoporous MnO2 have not been cost-effective. Liu et al. report on the deposition of mesoporous MnO2 films through a two-step cathodic deposition process driven by water electrolysis. Hydroxide ions generated at the cathode in a 0.1 M Mn2+ solution formed Mn(OH)2, which precipitated, and after exposure to air, formed MnO2·0.5 H2O. This material has a nanowall-array morphology (shown at left) with high surface area (96 m2 g−1) and an energy storage capacity with Li ions of 256 mA·hour g−1. The higher capacity and better cycle life of this material, relative to the material formed directly in an anodic version of the process (80 mA·hour g−1), were attributed to the mesoporous structure of the nanowalls.

Adv. Funct. Mater. 19, 1015 (2009).

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