Architecting versatile NiFe2O4 coating for enhancing structural stability and rate capability of layered Ni-rich cathodes

Nickel-rich layered oxides are considered one of the most promising cathode materials for efficient lithium-ion batteries due to their high energy density and reasonable cost. However, at high cut-off voltage, the interfacial instability and structural degradation lead to severe capacity attenuation and poor thermal stability, which greatly hinder their large-scale applications. Herein, a multifunctional antispinel NiFe2O4 coated LiNi0.6Co0.2Mn0.2O2 (NCM@NFO) material is in-situ induced by co-precipitation and subsequent sintering, boosting the cycling stability of Ni-rich materials. Coupling in-depth characterizations (in-situ X-ray diffraction, etc.) with density functional theory calculations, the versatility of the NFO coating has been revealed. Including suppressing the transition metal dissolution, preventing the unwanted phase transition, inhibiting the oxygen vacancy generation, and stabilizing the crystal structure of the NCM by forming an M-O-N bonding network. More importantly, attributing to the high ion/electron conductivity of the NFO layer, the Li+ transport kinetics between NCM@NFO particles have been facilitated. Benefitting from the collaborative effect of the protective NFO coating, the optimized 2 wt% NFO@NCM (NCM@NFO-2) sample achieves higher capacity retention (81.25 vs 67.88% after 200 cycles) at high voltages (2.75 similar to 4.5 V@0.5C) and more excellent rate capabilities (109.86 vs 49.52 mAh center dot g(-1) at 10C), as well as impressive capacity retention of 81.72% after 100 cycles (at 60 degrees C@1C). Constructing a versatile bimetallic oxide protective layer at the secondary particle surface of layered oxides provides an effective strategy for Ni-rich cathodes towards high-energy, long-duration, and safe lithium ion batteries.

Automated summary

Nickel-rich layered oxides are highly promising cathode materials for efficient lithium-ion batteries, but their interfacial instability and structural degradation limit their large-scale applications. In this study, a multifunctional antispinel NiFe2O4 coated LiNi0.6Co0.2Mn0.2O2 material is synthesized, which improves the cycling stability of the Ni-rich material. The NiFe2O4 coating suppresses transition metal dissolution, prevents unwanted phase transitions, inhibits oxygen vacancy generation, and stabilizes the crystal structure. Additionally, it facilitates Li+ transport kinetics between particles. The optimized 2 wt% NiFe2O4@LiNi0.6Co0.2Mn0.2O2 sample shows higher capacity retention at high voltages and excellent rate capabilities, demonstrating the effectiveness of constructing a versatile bimetallic oxide protective layer for high-energy and safe lithium-ion batteries.