A non-stoichiometric spinel phase (Li 1.02 Mn 1.90 Y 0.02 O 4−y F 0.08 ) 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 LiBO 2 , and the effects of the LiBO 2 coating on Li 1.02 Mn 1.90 Y 0.02 O 4−y F 0.08 spinel phase were investigated. The results showed that pure Li 1.02 Mn 1.90 Y 0.02 O 4−y F 0.08 had good electrochemical properties, however, the non-stoichiometric spinel coated with LiBO 2 showed better electrochemical performance at both room temperature and high temperature (50°C) than pure Li 1.02 Mn 1.90 Y 0.02 O 4−y F 0.08 . The initial discharge capacity of the LiBO 2 -coated non-stoichiometric spinel was 118mAhg −1 at a current density of 1mAcm −2 over the voltage range from 3.0 to 4.4V. 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 LiBO 2 effectively improved the electrochemical properties of non-stoichiometric spinel as a cathode material.