Influences of surface Al concentration on the structure and electrochemical performance of core-shell LiNi0.8Co0.15Al0.05O2 cathode material

Abstract NCA cathode material is a promising cathode material for the lithium-ion batteries with high energy density. However, the drastic capacity fading and low thermal stability limit their practical applications. These issues are mainly attributed to the unstable interface between the electrode and electrolyte. Core-shell structure has been demonstrated as an effective method to achieve the combination of the high capacity, long cycle life and high thermal stability. However, the influence of the surface aluminum concentration on the structure and electrochemical performance of the core-shell NCA cathode material are still not clear. Herein, NCA is designed to four core-shell structures with different surface aluminum concentration. This study reveals that aluminum doping into the layered structure shrink the interatomic distance in the transition metal layer but expand the transition metal layers. Therefore, Al doping in the layered structure facilitates the migration of lithium-ions and benefits of the improving of the electrochemical performances of Ni-rich cathode materials. As expected, Li[(Ni0.85Co0.15)2/3(Ni0.7Co0.15Al0.15)1/3]O2 electrode delivers the high discharge capacity of 182.6 mAh g−1 with the capacity retention of 91.2% at 0.2C after 260 cycles. This study implies that the moderate shell thickness and surface aluminum content contribute to enhance the electrochemical properties of NCA cathode distinctly.