Potential-dependent interfacial specific adsorption accelerates charge transfer in sodium-ion batteries

Fast-charging capabilities of sodium-ion batteries have emerged as a pivotal objective within the energy storage fields. Sodium layered P2-type oxide cathodes have the most potential for fast charging due to their inherent fast Na ⁺ mobility. However, their electrochemical polarization and interfacial charge transfer especially at high state of charge are limiting factors in quick kinetic response for large current. Herein, we demonstrate that a typical P2-type cathode (Na _0.7 Ni _0.27 Mn _0.53 Cu _0.04 Fe _0.08 Ti _0.08 O ₂ ) achieves high-rate capacities through avoiding octahedral stacking faults, maintaining lattice oxygen activity and controlling anion-specific adsorption. The intermediate Z-phase intergrowth structure mitigate kinetic hysteresis and thermodynamic polarization by simultaneously suppressing the detrimental P2−O2 phase evolution and irreversible oxygen redox. The potential-dependent competitive adsorption mechanism between anions and solvent molecules is revealed within the inner Helmholtz plane (IHP), where optimized anion-specific adsorption elevates potential difference between cathodes and IHP, accelerating charge transfer across the electrode/electrolyte interface. Furthermore, the F-rich cathode/electrolyte interphase generated from IHP avoids transition metal dissolution and surface lattice collapse for stable long-term cycling. This study highlights the synergistic coupling interaction between bulk phase stability and interfacial environment optimization in ensuring fast Na ⁺ /charge transport kinetics for sodium-ion batteries.