A new surface phase of Al2Ti7O15 to enhance the electronic conductivity and interfacial stability of LiCoO2 cathode materials

LiCoO2 (LCO) is one of the most commonly used cathodes for lithium ion batteries applied in consumer electronics products. However, higher upper cutoff voltage (greater than4.2 V vs Li/Li+) is necessary for LCO in pursuit of higher energy density, which comes along with structural and interfacial instability of LCO. Herein, the combined modification of Al-Mg-Ti co-doping and Al2O3 coating of LCO is employed to improve the stability of LCO under 4.5 V (vs Li/Li+). As a result, the electrochemical performance, kinetic performance and the storage performance evaluated at both coin cell and pouch cell levels are promoted after the modification. Further analysis proves that the suppression of phase transition from order to disorder, and the retarded side reaction between LCO and the electrolyte are the main reasons for the enhanced performances of modified LCO. Interestingly, a new phase, Al2Ti7O15 (ATO), is discovered near the surface of the modified LCO, which is beneficial to elevating the electron conductivity and transmission property of lithium ions as demonstrated by the DFT calculation and conductivity measurement. This work provides new insights into the effect of Al-Mg-Ti co-doping on LCO materials.