Improving sodium adsorption and diffusion at black phosphorus-NaZr₂(PO₄)₃interface based on a strong anisotropic...

The interface structure of the electrode-electrolyte plays a crucial role in the electrochemical performance of sodium-ion batteries (SIBs). In this study, two black phosphorus-NaZr₂(PO₄)₃heterojunctions (BP-NZP) with parallel stacking (PS) and vertical stacking (VS) configurations are constructed. The adsorption and diffusion behaviors of sodium (Na) at both BP-NZP heterojunctions are investigated by first-principles calculations. Binding energies indicate that both BP-NZP heterostructures are energetically stable, with the VS BP-NZP more stable. The PS BP-NZP has large interlayer barriers hindering ion diffusion into BP layers. While the VS BP-NZP contains wide channels with low barriers, which facilitate ion diffusion from interface into the BP. Furthermore, it is found that for the two BP-NZP heterostructures, Na atoms prefer to be adsorbed in the interfacial region, and these adsorptions have little effect on the dielectric properties of NZP and the electronic properties of BP, which is required for high-performance SIBs. The climbing image-nudged elastic band calculation and electrostatic potential distribution analysis further confirm that the wide channels in VS BP-NZP significantly improve Na migration from the interface into BP layers, whereas such migration of Na encounters greater difficulty in PS BP-NZP. In addition, our results show that trapping Na atoms at the interface of the VS BP-NZP can improve Na migration, which reveals that interface structure of electrode-electrolyte has a critical impact on the migration behavior of Na to traverse this interface. These findings suggest that an optimized heterostructure design strategy for the electrode-electrolyte can significantly improve the performance of SIBs.