Characterization of Li2MnSiO4 and Li2FeSiO4 cathode materials synthesized via a citric acid assisted sol-gel method

Two members of the family of orthosilicate, Li2FeSiO4 and Li2MnSiO4, are prepared by a citric acid assisted sol-gel method. As cathode materials for lithium-ion batteries, their structural, morphological and electrochemical characteristics are investigated and compared. Both cathode materials have nanoparticles with similar lattice parameters. Li2FeSiO4 has a maximum discharge capacity of 152.8 mAh g-1, and 98.3% of its maximum discharge capacity is retained after fifty cycles. However, the discharge capacity of Li2MnSiO4 fades rapidly and stabilized at about 70 mAh g-1 after twenty cycles. The electrochemical impedance and differential capacity analysis indicate that Li2MnSiO4 has larger charge transfer impedance and higher electrochemical irreversibility than Li2FeSiO4, which makes its electrochemical behaviors seriously deteriorate and leads to difference between two silicate materials.