Miaojun Wang

Enthalpy of Formation of Li x CoO2 ( 0.5 ⩽ x ⩽ 1.0 )

Single-phase 03-type Li x CoO 2 (0.5 ≤ x ≤ 1.0) samples were synthesized by chemically extracting lithium from LiCoO 2 with an oxidizer, NO 2 BF 4 , in acetonitrile medium under an argon atmosphere. The enthalpy of formationof Li x CoO 2 at 298 K was determined by high-temperature oxide melt solution calorimetry. The enthalpy of formation from binary oxides plus oxygen for Li x CoO 2 at 298 K varies linearly with x, and Li x CoO 2 becomes energetically less stable with decreasing x. From the linear trend, the enthalpies of formation for 03-type CoO 2 and monoclinic Li 0 . 5 CoO 2 were estimated. Monoclinic Li 0 . 5 CoO 2 is energetically more stable than the undistorted 03-type Li 0 . 5 CoO 2 . For CoO 2 , the energetic stability decreases in the order O1 > P3 > 03.