MXene‐Induced Pseudocapacitive Transformation in Battery‐Type Metal Sulfide: A Paradigm for High‐Rate Sodium Storage

ABSTRACT High‐rate sodium‐ion storage is hindered by the sluggish kinetics of battery‐type materials. Here, we present a universal MXene‐enabled capacitive enhancement strategy, exemplified by interlayer‐confined SnS ₂ quantum dots (QDs) within Ti ₃ C ₂ T _x MXene to form a porous 0D/2D heterostructure. Strong interfacial electronic coupling generates built‐in electric fields, while quantum confinement shifts Na ⁺ storage from diffusion‐dominated to pseudocapacitive behavior (94% contribution at 2 mV s ⁻¹ ). MXene nanoconfinement buffers volume changes and ensures uniform QD dispersion, enabling ultrafast Na ⁺ /electron transport. The electrode delivers 348 mAh g ⁻¹ at 0.05 A g ⁻¹ , retains 88.8% capacity after 3000 cycles, and achieves Na ⁺ diffusion coefficients of 10 ⁻¹⁰ –10 ⁻¹¹ cm ² s ⁻¹ . This work elucidates interfacial modulation as a powerful design principle for transforming battery‐type materials into pseudocapacitive electrodes, providing a general pathway toward high‐rate, durable sodium‐ion energy storage.