Enhanced stability and electrochemical properties of lanthanum and cerium co-modified LiVOPO4 cathode materials for Li-ion batteries

A facile and efficient ball-milling assisted sol–gel synthesis route was developed to prepare triclinic ε-LiVOPO4 (LVOP) material with lanthanum (La) and cerium (Ce) modification individually as well as simultaneously. An LVOP/LaPO4/CePO4 composite cathode material was successfully synthesized and results show that La and Ce co-modification noticeably improves the electrochemical performance by enhancing the high voltage capacity upon cycling, which indicates contributions from the good ionic conductors LaPO4 and CePO4. The simultaneous La and Ce modification improves the high voltage performance significantly with an increase of 50% in high voltage capacity after 20 cycles compared to pure LVOP. It also shows stabilized cycling performance with 91% capacity retention after 50 cycles at 0.1C rate, along with high-rate capability with a capacity of 83.1 mAh/g compared to the pristine sample showing the capacity of 51. 6 mAh/g at a high rate of 5C. This can be attributed to the good conductivity of LaPO4 and CePO4. In addition, the LVOP/LaPO4/CePO4 composite and the pristine LVOP give a charge transfer resistance of ∼105 and ∼212 Ω, respectively, showing much lower impedance due to a combination of La and Ce addition.