Degradation Mechanism of Dimethyl Carbonate (DMC) Dissociation on the LiCoO₂Cathode Surface: A First-Principles Study

The degradation mechanism of dimethyl carbonate electrolyte dissociation on the (010) surfaces of LiCoO 2 and delithiated Li 1/3 CoO 2 were investigated by periodic density functional theory. The high-throughput Madelung matrix calculation was employed to screen possible Li 1/3 CoO 2 supercells for models of the charged state at 4.5 V. The result shows that the Li 1/3 CoO 2 (010) surface presents much stronger attraction toward dimethyl carbonate molecule with the adsorption energy of −1.98 eV than the LiCoO 2 (010) surface does. The C–H bond scission is the most possible dissociation mechanism of dimethyl carbonate on both surfaces, whereas the C–O bond scission of carboxyl is unlikely to occur. The energy barrier for the C–H bond scission is slightly lower on Li 1/3 CoO 2 (010) surface. The kinetic analysis further shows that the reaction rate of the C–H bond scission is much higher than that of the C–O bond scission of methoxyl by a factor of about 10 3 on both surfaces in the temperature range of 283–333 K, indicating that the C–H bond scission is the exclusive dimethyl carbonate dissociation mechanism on the cycled LiCoO 2 (010) surface. This study provides the basis to understand and develop novel cathodes or electrolytes for improving the cathode–electrolyte interface.