| 摘要 |
PROBLEM TO BE SOLVED: To obtain excellent charging and discharging characteristics by using a lithium vanadium phosphate composite compound as a positive electrode material. SOLUTION: A lithium vanadium composite compound Liy(V1-xMx)2(PO4)3 is used as the positive electrode material of a lithium ion secondary cell. In the formula, M is at least one kind of bi or more-valent cation selected from Al, Ti and Zr, x ranges 0<x<=0.2, y is 3 when M is Al and is 3-2x when M is Ti or Zr. The compound is prepared by mixing a Li compd., V compd., phosphate compd., Ti compd., Zr compd., and/or Al compound in a specified mixing ratio according to the chemical compsn. of the objective composite compound, thermally decomposing the mixture at 200 to 400 deg.C and 1 atmospheric pressure in air for 1 to 5 hours. Then the decomposed material is compacted into a circular pellet of 15 mm diameter under 30 MPa pressure, and fired at 700 to 1100 deg.C in an inert atmosphere such as argon to obtain the lithium vanadium phosphate composite compound as a sintered body. |
