From metal to cathode material: in situ formation of LiCoO2 with enhanced cycling performance and suppressed phase transition

LiCoO2 (LCO) has attracted wide attention due to its high energy density, whose synthesis relies on the cobalt oxide precursor. The conventional synthetic method features a low yield. What is even worse, order–disorder phase transition of LCO occurs above 4.2 V, leading to structural instability and rapid capacity decay. To tackle these problems, a new synthetic method is proposed in this work, where LiCoO2 is in situ formed using cobalt metal as the precursor. M-LCO-850 °C (cobalt metal used as the precursor) exhibits a better cycle performance and faster Li+ diffusion rate than C-LCO (commercial synthesis method). The stable cycling performance is associated with the suppression of the order–disorder phase transition, which is attributed to the Co2+ “pillar” effect. Co2+ occupies the Li layer in the charge and discharge process, which acts as a “pillar” to support the CoO2 layer to inhibit order–disorder phase transition during the cycle, reducing the polarization and promoting the insertion/de-insertion reaction of Li+. Meanwhile, the synthesis yield and compacted density of M-LCO-850 °C are improved by 18.8% and 11.89%, respectively, compared to C-LCO. This method provides a new strategy for the in situ synthesis of cathode materials for lithium-ion batteries.