Positive active material for rechargeable lithium battery, method of preparing the same, and rechargeable lithium battery including the same

A positive active material for a rechargeable lithium battery comprises a compound represented by the following Chemical Formula 1 and has a peak at a 2θ value of between 40.0 degrees and 41.0 degrees in an X-ray diffraction (XRD) pattern. [Chemical Formula 1] LiMCoPO wherein, in the above Chemical Formula, 0≤x≤2, 0.98≤y≤1, 0