Chemically modified Ba6Mn24O48 tunnel manganite as a lithium insertion host

The electrochemical behavior of chemically modified tunnel — type Ba6Mn24O48 powder and whiskers has been examined in terms of the lithium intercalation/deintercalation. A maximum overall specific capacity of 136 mAh/g was achieved for the nanostructured form of the proton-exchanged Ba6Mn24O48 phase. This phase is formed by Ba2+/H+ exchange, a process which is also accompanied by Mn dissolution, a commensurate increase in the Mn oxidation state, and an anisotropic shrinkage of the unit cell. Three types of lithium ions were detected in the Li NMR spectra of the chemically and electrochemically lithiated materials. Li resonances at ∼ 380 and 280 ppm, due to sites nearby both Mn3+/Mn4+ ions in the large tunnels were seen in the ion-exchanged samples, while resonances at similar locations and at ∼ 100 ppm (due to Li near Mn3+), were observed in the electrochemically lithiated materials. The investigated materials show potential as “electrochemically-active-and-reinforcing” components, and open up strategy with which to produce composite flexible electrodes for lithium-ion batteries.