Synthesis and electrochemical properties of LiNi0.375Co0.25Mn0.375−xCrxO2−xFx cathode materials prepared by sol–gel method

Layer-structured cathode material for lithium ion batteries LiNi0.375Co0.25Mn0.375−xCrxO2−xFx (0 ≤ x < 0.1) has been synthesized from sol–gel precursors. Its structure and electrochemical properties were investigated by X-ray diffraction (XRD) and a variety of electrochemical techniques. The XRD results reveal that LiNi0.375Co0.25Mn0.375−xCrxO2−xFx has typical hexagonal structure without impurity. The Cr–F co-doped materials show higher specific discharge capacity and improved cycling performance compared with the raw materials as x in the range of 0.00–0.06. LiNi0.375Co0.25Mn0.315Cr0.06O1.94F0.06 demonstrates an initial discharge capacity of 168.5 mAh g−1 with 20th capacity retention about 93.7%. It has been confirmed that the improved cycling performance is derived from the little increase of electrochemical impedance during the cycling.