Ion-Specific Storage and Diffusion Mechanisms in Cross-Linked Layered Phosphorus Electrodes: From Clustering to Correlated Dynamics

Understanding ion intercalation at high state-of-charge is vital for designing high-capacity, fast-charging electrodes. Conventional graphite and alloy-based anodes face limitations─either low capacity or poor reversibility due to structural degradation. Black phosphorus (BP) offers high theoretical capacity but suffers from large volume changes and metal–phosphorus alloy formation that hinder reversibility. Here, using first-principles calculations and molecular dynamics simulations, we investigate Li, Na, and Mg intercalation in a cross-linked layered black phosphorus framework (BPL) engineered with the expanded interlayer spacing of BP. Unlike BP, BPL enables high-capacity intercalation while preserving host integrity. Notably, Na exhibits nonclustering, fast diffusion even at high concentrations, whereas Li and Mg form diffusion-limiting aggregates. These distinct behaviors arise from differences in ion–host coupling and charge transfer. Our findings establish that equilibrium structural dynamics can serve as a predictive descriptor for ion mobility and capacity, highlighting the potential of phosphorus-based architectures for high-rate, high-density Na-ion storage.