A disclosure sacrificial positive electrode material with reduced gas generation and a method of preparing the same are disclosed herein. In some embodiments, a method includes calcining a mixture of lithium oxide (Li2O) and cobalt oxide (CoO) in an atmosphere containing an inert gas and oxygen gas and having a relative humidity of 20% or less, wherein the oxygen gas is at a partial pressure of 1% or less, to prepare a lithium cobalt metal oxide represented by Chemical Formula (1): LixCo(1-y)MyO4-zAz  [Chemical Formula 1] M is at least one selected from the group consisting of Ti, Al, Zn, Zr, Mn and Ni, A is a halogen, x, y and z are 5≤x≤7, 0≤y≤0.4, and 0≤z≤0.001. A battery having the sacrificial positive electrode material can have reduced gas generation in the electrode assembly at the time of charging the battery, and thus the stability and life of the battery are improved.