Professor Wang Pengfei and Professor Shi Le's research team from the Center of Nanomaterials for Renewable Energy, State Key Laboratory of Electrical Insulation and Power Equipment at Xi'an Jiaotong University (XJTU), has published a research paper titled ‌Potential-dependent interfacial specific adsorption accelerates charge transfer in sodium-ion batteries‌ in Nature Communications.

Sodium-ion batteries (SIBs) demonstrate significant potential for large-scale energy storage due to the abundance of sodium resources and low cost. Among cathode materials, P2-type layered oxides are considered highly promising for fast-charging SIBs owing to their open sodium-ion diffusion channels.

However, deep desodiation (high-voltage) triggers detrimental phase transitions (from P2 to O2) and irreversible lattice oxygen redox reactions, leading to severe kinetic polarization and thermodynamic hysteresis. Crucially, interfacial charge transfer resistance during cycling severely limits high-current-rate performance. Thus, resolving bulk structural stability and interfacial charge transfer issues is essential for developing fast-charging SIB cathodes.

The team investigated bulk evolution and interfacial electrochemistry in high-rate P2-type cathodes. Using a Ni/Mn-based P2 cathode (NMCFT, Na0.7Ni0.27Mn0.53Cu0.04Fe0.08Ti0.08O2), they revealed a ‌potential-dependent competitive adsorption mechanism‌ between anions and solvent molecules within the inner Helmholtz plane (IHP).

 At deep desodiation, NMCFT forms an intermediate Z-phase coexistence structure, preventing complete P2-to-O2 transformation. Triggering reversible anion redox reactions dominated by transition metal-oxygen (TM-O) hybridization significantly reduces kinetic polarization and hysteresis.

Optimized anion-specific adsorption increases the potential difference between the electrode and IHP, accelerating interfacial charge transfer. A fluorine-rich cathode electrolyte interphase (CEI) suppresses transition-metal dissolution and surface lattice collapse, ensuring long-term cyclability.

Synergistic optimization of bulk ion diffusion and interfacial charge transfer enables NMCFT to deliver exceptional fast-charging capability, extended cycle life, and industrial validation‌.

The team scaled up material synthesis to the kilogram level and assembled Ah-grade pouch full-cells with hard-carbon anodes (without pre-sodiation). Results show that the high specific energy was ‌156 Wh kg⁻¹‌ and the capacity retention was ‌about 80 percent after 300 cycles‌.

This work elucidates the long-neglected impact of interfacial adsorption on charge-transfer kinetics. establishing a dual-perspective (bulk/interface) design strategy for high-rate SIB cathodes with predictable kinetic properties.