SURFACE MODIFIED CATHODE WITH IMPROVED LITHIUM INTERCALATION BEHAVIOR

摘要

Surface modification of LiNi_0.4Mn_0.4Co_0.2O₂(442)compound with certain inert (M_xO_y) metal oxides viz., Al₂O₃, Bi₂O₃, In₂O₃, Cr₂O₃, ZrO₂, ZnO, MgO has been attempted with a view to improve the structural and cycling stability, especially upon high voltage and high rate cycling conditions. In addition to HF scavenging effect, the protective metal oxide inter-connect layer restricts the number of oxide ion vacancies eliminated during the initial cycling of cathode, resulting in the reduced irreversible capacity loss of the first cycle. Among the surface modified cathodes, Bi₂O₃ coated LiNi_0.4Mn_0.4Co_0.2O₂ cathode exhibits appreciable specific capacity values of 196 (Q_dc1) and 175 (Q_dc100) mAh g⁻¹ with 89% capacity retention, thus evidencing the superiority of Bi₂O₃ modifier in improving the electrochemical behavior of pristine LiNi_0.4Mn_0.4Co_0.2O₂ cathode. Further, suitability of Bi₂O₃ coated LiNi_0.4Mn_0.4Co_0.2O₂ cathode for high voltage (5.0 V) and high rate (3 C) lithium intercalation and de-intercalation applications has been demonstrated up to 100 cycles.