Lithium insertion into manganese dioxide polymorphs in aqueous electrolytes

The electrochemical behaviour of the spinel-like LiMn2O4 was studied in non-aqueous and aqueous saturated alkali nitrate electrolytes in comparison with the layered manganese dioxide delta-MnO2. The results obtained by galvanostatic and cyclic voltammetry techniques showed that the insertion of Li+/e(-) or H+/e(-) depends on both the host lattice and the type of electrolyte. The spinel-like LiMn2O4 preferably allowed the insertion of Li+/e(-) in non-aqueous and aqueous saturated LiNO3 electrolytes, as observed from the similarity of the electrochemical behaviour in these electrolytes and the stability of the structure. This was explained by the presence of a three-dimensional network of vacant tetrahedral and half-filled octahedral sites in LiMn2O4, which guarantee high mobility of Li+ ions. The layered manganese dioxide could be inserted by Li+/e(-) only in non-aqueous electrolytes.