Li~+-Doping-lnduced Changes of Phase Composition in Electrodeposited Manganese(Ⅳ) Oxide Materials

摘要

The impact of Li~+ dopant-ions in fluorine-containing electrolytes on electrodeposited manganese(IV) oxide materialwas under investigation in this paper. The dependence of phase composition of this material at Li~+-concentration range in the electrolyte below the stoichiometric content of lithium in hollandite Li_2Mn_8O_(16) (Mn:Li ≈ 4:1) was established. The hollandite phase stabilization as a template effect caused by Li~+-ions is gradually reduced with the Li~+ concentration growth from 0.025 to 0.15 mol-L~(-1) LiOH concentration range. The hollandite content sharply drops at close to the stoichiometric Mn:Li ratio for this phase. In contrary, the concentration of cation-deficient E-MnO_2 becomes significant. Thus, the template effect of Li~+ cations at electrolytic doping from fluorine-containing electrolytes consists of stabilization of the hollandite tunnels at longer distance with the size of coherent scattering regions of this phase more than of about 20—50 A comparing with undoped materials. It is supposed that Li~+-ions presence makes tunnel space unavailable unlike water molecules or ammonium cations. Therefore, to realise molecular sieves based onmanganese(IV) oxides the availability of tunnels should be taken into account.