Lithium intercalation in two-dimensional penta-NiN₂: insights from NiN₂/NiN₂ homostructure and G/NiN₂ heterostructure

High-energy-density lithium-ion batteries (LIBs) are essential to meet the requirements of emerging technologies for advanced power storage and enhanced device performance. The next generation of LIBs will require high-capacity anode materials that move beyond the lithium intercalation chemistry of conventional graphite electrodes. The use of two-dimensional (2D) bilayer structures offers immediate advantages in the development of LIBs. Herein, motivated by the recently synthesized 2D Cairo pentagon nickel diazenide (NiN₂) material, we conduct a scrutiny of the intercalation process of lithium atoms in the interlayer gap of NiN₂/NiN₂ homostructure. Based on density functional theory (DFT), we demonstrate that the diffusion energy barrier of lithium move across the NiN₂/NiN₂ anode is relatively low, ranging from 0.058 to 0.52 eV, and the corresponding reversible capacity reaches a remarkable value of 499.0927 mA h g^-1 per formula unit, surpassing that of graphite (372 mA h g^-1). Furthermore, we investigate a 2D van der Waals (vdW) heterostructure composed of pre-strained structures of graphene and NiN₂ for use as an anode material in LIBs. It is found that the introduction of graphene leads to improvements in both electrochemical activity and deformation characteristics. The presented results provide theoretical support for the potential of bilayer structures combining NiN₂, suggesting them as promising candidates for the development of high-performance anode materials.