Stabilizing Ni-rich high energy cathodes for advanced lithium-ion batteries: the case of LiNi0.9Co0.1O2

Abstract

Lithiated oxides like Li[Ni_xCo_yMn_z]O₂ (x + y + z = 1) with high nickel content (x ≥ 0.8) can possess high specific capacity ≥200 mA h g⁻¹ and have attracted extensive attention as perspective cathode materials for advanced lithium-ion batteries. In this work, we synthesized LiNi_0.9Co_0.1O₂ (NC90) materials and studied their structural characteristics, electrochemical performance, and thermal behavior in Li-cells. We developed modified cationic-doped NC90 samples with greatly improved properties due to doping with Mo⁶⁺ and B³⁺ and dual doping via simultaneous modification with these dopants. The main results of the current study are significantly higher capacity retention, greatly reduced voltage hysteresis, and considerably decreased charge-transfer resistance of the Mo and Mo–B doped electrodes compared to the undoped ones upon prolonged cycling. We also revealed remarkable microstructural stability of the Mo-doped electrodes, whereas the undoped samples were unstable and exhibited networks of cracks developed upon cycling. Using density functional theory, we modeled the electronic structure of the undoped, Mo, B single-doped, and Mo–B dual-doped samples and established that the Ni-site is preferred over Co and Li sites. Additionally, density functional theory-based bonding strength calculations suggest that the dopants form strong bonds with oxygen, possibly reducing oxygen release from the cathode. An important finding is that B-dopant tends to segregate to the surface of NC90 similarly to that in NCM85 materials, as shown in our previous reports. In conclusion, this study presents a general approach for effectively stabilizing high-energy Ni-rich layered cathodes charged up to 4.3 V.