Synthesis and modification of non-stoichiometric spinel (Li1.02Mn1.90Y0.02O4−yF0.08) for lithium-ion batteries

A non-stoichiometric spinel phase (Li1.02Mn1.90Y0.02O4−yF0.08) was synthesized using a natural polymer sol–gel method. It was characterized by X-ray diffraction. The particle size and shape of the as-prepared compounds were observed by scanning electron microscope. The new compound was coated with LiBO2, and the effects of the LiBO2 coating on Li1.02Mn1.90Y0.02O4−yF0.08 spinel phase were investigated. The results showed that pure Li1.02Mn1.90Y0.02O4−yF0.08 had good electrochemical properties, however, the non-stoichiometric spinel coated with LiBO2 showed better electrochemical performance at both room temperature and high temperature (50 °C) than pure Li1.02Mn1.90Y0.02O4−yF0.08. The initial discharge capacity of the LiBO2-coated non-stoichiometric spinel was 118 mAh g−1 at a current density of 1 mA cm−2 over the voltage range from 3.0 to 4.4 V. The discharge capacity was about 99.2% of the initial capacity after 100 cycles at room temperature and about 95.2% after 50 cycles at high temperature (50 °C). The modification of spinel with LiBO2 effectively improved the electrochemical properties of non-stoichiometric spinel as a cathode material.