New mixed transition metal oxysalts as negative electrode materials for lithium-ion batteries

Different solid solutions in the MxM´1-xC2O4 ·2H2O (MM′: FeMn, CoMn; 0 ≤ x ≤ 1) system have been prepared in the form of nanoribbons by a reverse micelles method. The resulting di-hydrated oxalates form solid solutions that crystallize in two forms: the α monoclinic form with space group C2/c and the β orthorhombic form with space group Cccm. Anhydrous mixed oxalates are used as high-capacity (ca. 600 mA h g− 1) lithium storage materials, with good capacity retention after 75 cycles. The lithium storage mechanism is complex and involves conversion reactions together with double layer charge storage and reversible reactions with the electrolyte. The low temperature synthesis of these materials makes them attractive materials for low-cost Li-ion electrodes.