Engineering Heterogeneous Sn(II) Electrolytes for Durable and High-Performance Acidic Tin−Manganese Flow Battery

Acidic tin-based redox flow batteries (RFBs) represent a promising alternative to vanadium systems owing to their low cost, elemental abundance, and superior resistance to the hydrogen evolution reaction. However, nonuniform Sn electrodeposition and low active-material solubility severely impede their practical implementation. Herein, a heterogeneous nucleation strategy is proposed to regulate interfacial deposition by deliberately introducing dispersed SnSO 4 nanoparticles into concentrated sulfuric acid. Dynamic light scattering (DLS) confirms the formation of uniform colloidal seeds at an optimal precursor concentration of 0.3 M. Acting as in situ heterogeneous nucleation sites, such dispersed particles enable highly conformal and adherent Sn plating across carbon felt electrodes, strongly contrasting the localized agglomeration inherent to conventional homogeneous electrolytes. Coupled with a Mn 2+ /Mn 3+ posolyte, the resulting acidic Sn–Mn flow battery (TMFB) delivers exceptional stability, operating continuously for over 440 h at an areal capacity of 20 mAh cm −2 . Furthermore, the battery achieves an impressive average energy efficiency of 81.86% at 80 mA cm −2 alongside a remarkable peak power density of 346.05 mW cm −2 , outperforming most previously reported acidic RFBs. This work successfully transforms undissolved solid species into functional nucleates, establishing a general design principle for high-energy-density, cost-effective aqueous energy storage.