Enhanced cycling stability and thermal stability of YPO4-coated LiMn2O4 cathode materials for lithium ion batteries

Abstract

Abstract LiMn 2 O 4 cathode materials synthesized by a sol–gel method are coated by YPO 4 via wet coating strategy. The phase structures, components and morphologies of as-synthesized LiMn 2 O 4 and YPO 4 -coated LiMn 2 O 4 are characterized by X-ray diffraction, Raman spectroscopy and field emission scanning electron microscopy. The cycling performances are thoroughly investigated and compared at room temperature and 55 °C. The YPO 4 -coated LiMn 2 O 4 displays much enhanced cycling properties than pristine LiMn 2 O 4 . The optimal coating amount is determined to be 3 wt.%. The 3 wt.% YPO 4 -coated LiMn 2 O 4 exhibits capacity losses of only 15.9% after 200 cycles at room temperature and 19.7% after 100 cycles at 55 °C, much better than those of the pristine electrodes, 60% and 59.8%. Cyclic voltammetry confirms that YPO 4 coating effectively improves the structure stability of spinel LiMn 2 O 4 . Electrochemical impedance spectroscopy data further demonstrates that YPO 4 surface coating suppresses the undesirable growth of thick SEI (solid electrolyte interfacial) layer. Differential scanning calorimetry tests show that the existence of YPO 4 helps to enhance the thermal stability of LiMn 2 O 4 cathode.