Engineering oxygen-deficient NiCo2O4 nanorods by nitrogen plasma treatment for superior lithium storage

The development of high-capacity and durable anode materials is crucial for next-generation lithium-ion batteries (LIBs). Although spinel-type NiCo 2 O 4 has attracted considerable attention due to high theoretical capacity, its practical application is hindered by poor electronic conductivity and structural degradation during cycling. Herein, we propose a controlled N 2 plasma treatment as an effective post-synthesis strategy to engineer oxygen vacancies into NiCo 2 O 4 without altering its bulk crystal structure. The introduced oxygen vacancies significantly enhance electronic conduction and Li + transport kinetics, as confirmed by systematic electrochemical and kinetic analyses. The optimized NiCo 2 O 4 -P5 electrode delivers a high initial discharge capacity of 1423.5 mAh g −1 with a stable and extended voltage plateau at 0.1 A g −1 , exceptional rate performance (421.2 mAh g −1 at 2 A g −1 ), and outstanding cycling stability with 94.1% capacity retention over 700 cycles at 1 A g −1 . These significant improvements are attributed to the oxygen-deficient structure that facilitates charge transfer and stabilizes the electrode interface. This work provides a generalizable and scalable approach for defect engineering in transition metal oxide anodes, offering new insights into the design of high-performance energy storage materials.