From High‐Capacity to Practical: Lean‐Tin Alloying Strategy in Borophene‐Encased Hard Carbon Hosts as Anodes for Scalable Sodium‐Ion Pouch Batteries

ABSTRACT Inspired by the “lean‐silicon” strategy used in practical high‐capacity lithium‐ion anodes, we report, for the first time, a sodium‐ion battery (SIB)‐compatible lean‐tin alloying‐type anode built on a borophene‐encased hard carbon (B/HC) framework. A series of B/HC hosts with varying borophene loadings was systematically screened, after which Sn nanoparticles were introduced through NaBH 4 ‐assisted wet‐chemical reduction to obtain a “lean‐tin” architecture. Electrochemical analysis shows that 15 wt% Sn loaded on a 10 wt% borophene‐hard carbon host (15Sn@10B/HC) exhibits a strongly diffusion‐dominated charge‐storage mechanism, with Na + diffusion coefficients nearly double that of pristine B/HC. The 15Sn@10B/HC anode delivers 399.8 mAh g– 1 and sustains long‐term cycling for up to 500 cycles at 0.25 C (∼167 days test duration) with 93.9% retention. In full‐pouch cell configuration with Na 3 V 2 (PO 4 ) 3 cathode, the 15Sn@10B/HC anode delivers a nominal discharge voltage of 3.0 V with 235.8 mAh g– 1 ANODE (61.5 mAh g ‒1 COMBINED ) reversible discharge capacity and 707.4 Wh kg −1 ANODE (184.5 Wh kg ‒1 COMBINED ) energy density at 0.25 C rate. DFT calculations further confirm the superior Na + adsorption behavior linked to this proposed “lean‐tin” architecture. Overall, this work demonstrates that lean‐tin loading on a borophene‐hard carbon scaffold provides a practical, scalable, and industry‐relevant pathway for developing high‐capacity SIB anodes.