Synergistic Heterointerface Engineering of Ti 3 C 2 T x /g–C 3 N 4 Bilayers for Robust Sn‐Based Alloying‐Type Negatrodes for Sodium‐ion Pouch Batteries

ABSTRACT Futuristic sodium‐ion negatrode technologies with higher energy capabilities is critical for overcoming the bottlenecks in large‐scale commercialization of beyond‐coin‐cell battery formats. Therefore, this study reports a Ti 3 C 2 T x /g–C 3 N 4 bilayer hybrid strategy for supporting tin (Sn) nanostructures for pouch‐sized sodium‐ion battery negatrodes. Our results indicate that this bilayer hybrid approach solves the inherent issues of alloying‐type Sn‐based system. Initially, Ti 3 C 2 T x /g–C 3 N 4 bilayers with varying Ti 3 C 2 T x and g–C 3 N 4 ratios are optimized to obtain a stable, porous matrix, which is subsequently used to support Sn nanostructures. As a result, a homogeneous Sn distribution within a conductive Ti 3 C 2 T x scaffold and nitrogen‐rich g–C 3 N 4 framework is achieved. Structural and surface analyses confirm the formation of the robust Sn–Ti 3 C 2 T x /g–C 3 N 4 bilayer hybrid heterostructure with DFT simulations predicting strong interfacial interactions that enhance (de)sodiation processes. The final optimized Sn–Ti 3 C 2 T x /g–C 3 N 4 [1:2] bilayer hybrid nanocomposite negatrode delivers a reversible capacity of 511 mAh∙g −1 (0.5 C) with 89.12% retention (1500 cycles) in a 4.5 × 3 cm half‐pouch cells. Combined with a Na 2−x Ni[Fe(CN) 6 ] 1‐y positrode, the resulting full‐pouch cells deliver a reversible discharge capacity of 49.9 mAh∙g −1 (total mass, 1.0 C), translating to an energy density of 124.25 Wh∙kg −1 with 88.2% retention (1000 cycles).