Ultra-high rate and long cycle life sodium-based dual-ion batteries enabled by Li₂TiO₃-modified cathode-electrolyte-interphase

Sodium-based dual-ion batteries (SDIBs) have received widespread attention due to their high voltage, low cost, safety, and eco-friendliness. Nevertheless, the irregular spherical graphite cathodes are limited by the mass transfer non-uniformity and sluggish reaction kinetics due to uneven anion migration through the highly tortuous pathways and the inductive anisotropic electric fields. Herein, we report a facile dissolution-precipitation-carbonation optimized modification strategy to synthesize a series of nano-Li₂TiO₃/C-modified graphite flake (GF-LTx, x = 1, 2.5, and 5) as cathode for SDIBs. The Li₂TiO₃-C-Cathode Electrolyte Interphase (Li₂TiO₃-C-CEI) trinity layer by in situ reactions shows good cycling performance. The intrinsic mechanism of Li₂TiO₃-C-CEI was further explored by DFT molecular orbital theory and distribution relaxation time (DRT) analysis. Notably, the GF-LT2.5 achieves 10,000 stable cycles at 3–5.2 V (vs. Na/Na⁺) with a initial capacity of 91.1 mAh g⁻¹ and a decay rate of only 0.00217 % per cycle. Furthermore, GF-LT2.5 demonstrates an ultra-high rate performance of 100C with only 30 s for a single charge and 86 % capacity for low current density. Infrared thermography confirms the good thermal stability and safety of the gel-based flexible pouch cells. This work provides new insights into the design of high-rate performance, long-cycle stability, and high-safety energy storage systems.