Spontaneous grain refinement induced by thiourea derivatives enables energy-efficient manganese production

The thiourea derivative promotes the uniform distribution of Mn 2+ and modulates the electric field for uniform Mn deposition. Efficient and energy-saving electrodeposition of manganese remains challenging due to inhomogeneous deposition and competing hydrogen evolution at cathodic interfaces. Here, we report a dynamic molecular adsorption strategy using trace thiourea derivatives to regulate interfacial ion transport and nucleation behavior, achieving spontaneous grain refinement within the electrodeposited layer. Combined computational and experimental analyses reveal that thiourea derivatives construct a dynamic adsorption layer at the electrode/electrolyte interface, increasing the nucleation overpotential. Meanwhile, the electron-donating coordination of thiourea derivatives regulates the solvation structure of Mn 2+ and reduces interfacial water activity. This approach achieves spatially uniform Mn nucleation and spontaneous phase transition from metastable γ-Mn to stable α-Mn with refined grains, accompanied by a reduction in average grain size to 1.129 μm. With the methylthiourea (MTU) additive, we achieve 86.87 % current efficiency (a 4.61 % improvement) at reduced energy consumption of 4328.47 kWh t −1 (a 6.28 % reduction). Application in aqueous all-manganese batteries demonstrates an average Coulombic efficiency of 80.85 % over 30 cycles. This work proposes a molecular-level interfacial engineering strategy that enables cleaner metal electrodeposition and sustainable aqueous energy-storage applications, offering a new design paradigm for Mn metal as a clean and sustainable material.