Grow carbon nanotubes inside manganese dioxide nanotubes and you’ve got high-capacity, potentially inexpensive electrodes for lithium-ion batteries.

The electrodes are made by forming manganese dioxide nanotubes in a template, then growing carbon nanotubes inside the manganese dioxide nanotubes. Manganese dioxide is an abundant material, but researchers have had difficulty making efficient electrodes from it. The carbon nanotubes help the manganese dioxide withstand repeated charging and discharging, and they increase the electrical conductivity of the electrodes.

The nanotubes have a relatively high capacity because both the manganese dioxide and carbon nanotubes hold lithium ions. The coaxial nanotube electrodes hold about 500 milliamp hours per gram. The graphite electrodes used in today’s lithium-ion batteries hold less than 400 milliamp hours per gram.

The coaxial nanotubes could be used in high-capacity lithium-ion batteries that power vehicles and store electricity generated by renewable sources.

Research paper:
Coaxial MnO2/Carbon Nanotube Array Electrodes for High-Performance Lithium Batteries
Nano Letters, published online February 2, 2009