Na and Nb co-doped LiNi0.85Co0.15Al0.05O2 cathode materials for enhanced electrochemical performance upon 4.5 V application

Abstract High nickel cathode material LiNi0.85Co0.10Al0.05O2 (NCA) has attracted public attention because of its high energy density and low cost in production, but the material also faces the problem of rapid capacity decay due to the phase transition upon redox process. In this study, the co-modification with Na and Nb cations is employed to stabilize the lattice and promote the electrochemical behavior of the NCA material upon the application at 4.5 V. X-ray diffraction (XRD) investigations show that the co-modification of Na and Nb in the lattice reduces the disordering of the lattice and suppresses the volume change during the redox process, thereby increasing the specific capacity and the cyclic performance for the NCA material upon 4.5 V application. The Co-doped sample presents a specific capacity of 212.5 mAh/g when cycled 0.1 C, together with a capacity retention of 94.3% at 0.5 C after 100 cycles. This shows an obvious promotion when compared to that of undoped one (208.7 mAh/g and 78.2%). Furthermore, at a current density of 5 C, the Co-doped sample displays a high specific capacity of 152.2 mAh/g, while the value for the pristine NCA is only 129 mAh/g. Such improvement in rate performance can be attributed to the increased diffusion coefficient (from 7.57 × 10−13 to 3.27 × 10−12 cm2 s−1) due to the expanded space of lithium slab after co-doping of Na and Nb. The Na–Nb co-doping approach in this report offers a simple route to provide cathode materials with improved cyclability and enhanced rate behavior, demonstrating high potential for commercial application.