The Effects of AlF[sub3] Coating on the Performance of Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] Positive Electrode Material for Lithium-Ion Battery.

AIF[sub3]-coated Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] materials have been synthesized as positive electrode materials for lithium-ion batteries. The pristine and AIF3-coated Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] materials were characterized by X-ray diffraction, scanning electron microscopy, differential scanning calorimetry, and charge-discharge techniques. The electrochemical studies indicated that the AIF[sub3]-coated Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] showed initial irreversible capacity loss of only 47 mA h/g compared to 75.5 mA h/g for pristine material. Meanwhile, the coated material also exhibited better rate capability and cyclic performance, which has higher capacity retention of 87.9% after 80 cycles at 0.5 C rate at room temperature in comparison with only 67.8% for the pristine one. The functional mechanism of AIF[sub3] coating on the performance of Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] was also investigated by electrochemical impedance spectroscopy (EIS) and in situ differential electrochemical mass spectrometry (DEMS). ETS analysis indicated that AIF[sub3]-coated Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2] had stable charge transfer resistance (R[subet]). In situ DEMS results revealed that the activity of extracted oxygen species from layered positive electrode material was greatly reduced and the decomposition of the electrolyte was significantly suppressed for AIF[sub3]-coated Li[Li[sub0.2]Mn[sub0.54]Ni[sub0.13]Co[sub0.13]]O[sub2]. Therefore, more oxygen molecules rather than carbon dioxide were observed in the coated material system. It is demonstrated again that the AIF[sub3] coating layer played an important role in the stabilization of the electrode/electrolyte interface for the coated material. [ABSTRACT FROM AUTHOR]