Abstract: <SPAN lang=EN-US style="FONT-SIZE: 10.5pt; FONT-FAMILY: "Times New Roman"; mso-bidi-font-size: 12.0pt; mso-font-kerning: 1.0pt; mso-ansi-language: EN-US; mso-fareast-language: ZH-CN; mso-bidi-language: AR-SA; mso-fareast-font-family: 宋体">A stable and uniform MgO layer was coated on the surface of spinel type LiMn<SUB>2</SUB>O<SUB>4</SUB> cathode material by solution method with Mg-polyacrylic acid (PAA) as raw material. Structure and performances of the coated and uncoated LiMn<SUB>2</SUB>O<SUB>4</SUB> were characterized by means of SEM and AES.Results showed that LiMn2<SUB>-x</SUB>Mg<SUB>x</SUB>O<SUB>4</SUB> solid solution was formed on the surface of spinel type LiMn<SUB>2</SUB>O<SUB>4</SUB>.This solid solution protective layer can reduce the direct contact between LiMn<SUB>2</SUB>O<SUB>4</SUB> and electrolyte,and thus effectively suppress the interaction between them.After surface modification treatment,stability and electrochemical properties of LiMn<SUB>2</SUB>O<SUB>4</SUB> cathode material all had been obviously improved.There was only about 20% capacity fading after 450 cycles of the battery made from the coated LiMn<SUB>2</SUB>O<SUB>4</SUB> cathode material.</SPAN>