A mechanism study of M3B2O6 (with M = Co, Ni and Cu) towards Li

The electrochemical reactivity mechanism of M3B 2O6 (with M = Co, Ni and Cu) powders towards Li was studied by a combination of Transmission Electron Microscopy (TEM), infrared spectroscopy (IR), 11B Magic Angle Spinning Nuclear Magnetic Resonance (MAS NMR). The electrochemical properties of these materials as anode for Li batteries were investigated, and found to be similar to those of 3d-metal oxides. In fact, the reduction process of 3d-metal borates involves their decomposition in metal nanograins dispersed into a lithia matrix surrounded by an organic layer responsible for the observed extra capacity. The lithia matrix consists of a mixture of lithium oxide (Li2O) and lithium orthoborate (Li3BO3). During the subsequent charge, the organic layer vanishes and the metal grains are partially or fully oxidized with the concomitant decomposition of Li2O