Eliminating Charge\nTransfer at Cathode-Electrolyte\nInterface for Ultrafast Kinetics in Na-Ion Batteries

Sodium-ion batteries suffer from kinetic problems stemming\nfrom\nsluggish ion transport across the electrode–electrolyte interface,\ncausing rapid energy decay during fast-charging or low-temperature\noperation. One exciting prospect to enhance kinetics is constructing\nneuron-like electrodes that emulate fast signal transmission in a\nnervous system. It has been considered that these bioinspired designs\nenhance electron/ion transport of the electrodes through carbon networks.\nHowever, whether they can avoid sluggish charge transfer at the electrode–electrolyte\ninterface remains unknown. By connecting the openings of carbon nanotubes\nwith the surface of carbon-coated Na<sub>3</sub>V<sub>2</sub>O<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F cathode nanoparticles, here\nwe use carbon nanotubes to trap Na<sup>+</sup> ions released from\nthe nanoparticles during charge. Therefore, Na<sup>+</sup> movement\nis confined only inside the neuron-like cathode, eliminating ion transport\nbetween the electrolyte and cathode, which has been scarcely achieved\nin conventional batteries. As a result, a 14-fold reduction in interfacial\ncharge transfer resistance is achieved when compared to unmodified\ncathodes, leading to superior fast-charging performance and excellent\ncyclability up to 200C, and surprisingly, reversible operation at\nlow temperatures down to −60 °C without electrolyte modification,\nsurpassing other Na<sub>3</sub>V<sub>2</sub>O<sub>2</sub>(PO<sub>4</sub>)<sub>2</sub>F-based batteries reported to date. As battery operation\nhas relied on charge transfer at the electrode–electrolyte\ninterface for over 200 years, our approach departs from this traditional\nion transport paradigm, paving the way for building better batteries\nthat work under harsh conditions.