A Facile Synthesis of 2d Bimetallic Solid Solution Nitrides for Robust Stability in Lithium-Ion Battery

Nanostructured transition metal nitrides (TMNs) demonstrate immense promise for lithium-ion battery applications owing to their outstanding conductivity and high theoretical capacity. However, issues such as volume expansion, aggregation, and rapid capacity decay remain to be addressed. Although two-dimensional (2D) TMNs offer enhanced structural stability, effectively synthesizing them becomes a challenge, necessitating the exploration of suitable 2D templates. Herein, a facile synthesis of 2D nitrides, including TiVN, NbVN and TiNbN, is achieved through nitriding their corresponding MXenes. The distinct 2D layered structure enables them fast lithium-ion transport and inhibits volume variation, thereby improving rate performance and stability. Moreover, the incorporation of bimetallic elements in solid solution TiVN, NbVN and TiNbN induces lattice distortion, creating lattice vacancies and increasing lithium storage capacity. Atomic-level interactions within solid solutions, as confirmed by the shifts of binding energy, contribute to improved structural stability and accelerated charge transfer. The theoretical calculation further proves that the bimetallic solid solution structure elevates the d-band center and increases the Li+ adsorption energy. Consequently, the synthesized TiVN, NbVN and TiNbN demonstrate remarkable lithium storage performance. Especially, NbVN stands out by achieving a specific capacity of 216.6 mAh g-1 after 1,400 cycles at 1 A g-1, significantly outperforming Nb4N5 and VN. Our investigation into the lithium storage variations between TiVN, NbVN and TiNbN reveals that the presence of Nb promotes a porous morphology and provides channels for rapid lithium diffusion, leading to superior electrochemical stability and discharge capacity in NbVN.