Reaction Mechanism and Kinetic Analysis of the Solid-State Reaction to Synthesize Single-Phase Li₂Co₂O₄Spinel

Lithium cobalt oxide has two polymorphs that display different electrochemical properties despite their identical redox reactions: a high-temperature phase having a layered structure (LiCoO 2; HT-LCO) and a low-temperature phase with a spinel framework (Li 2 Co 2 O 4; LT-LCO). The synthetic conditions of the single-phase LT-LCO were determined by thermogravimetric analysis performed on the solid-state reaction of Li 2 CO 3 and Co 3 O 4 . The results revealed that LCO synthesis was a second-order reaction with an activation energy of E a = 150 kJ mol –1 and a pre-exponential factor of A = 9.2 × 10 7 s –1 . XRD studies indicated that low-temperature synthesis below 350 °C is necessary to obtain the single-phase LT phase because the HT phase fraction increased with increasing synthesis temperature. Virtually single-phase LT-LCO obtained by calcining at 325 °C for 240 h exhibited zero-strain lithium insertion. These results contribute toward the establishment of a synthetic method for novel materials with reduced spinel structure.