Functional Interface Modifier with Visualizations of Dendrite Growth and Heat Evolution in Lithium Metal Batteries

For high-energy-density batteries, the lithium-metal anode remains the ultimate choice. However, lithium dendrites pose a serious safety concern for the practical use of lithium anodes. Here, a multipurpose artificial passivation is fashioned on the lithium-metal interface via a facile, versatile approach using stannic chloride as a sacrificial agent. Bilayered structure, rich in LiCl, coupled with a Li-Sn alloy, reinforces uniform lithium flux and suppresses electrolyte decomposition. The structure promotes uniform deposition and dendrite-free lithium growth. The protected anode operated at a high current density of 5 mA cm^-2/5 mAh cm^-2 and demonstrated cycling for more than 600 h. Operando confocal OM-based visualization of lithium growth phenomena and heat evolution measurements at the molecular level reveal dendrite-free lithium deposition and electrolyte decomposition, respectively. An in situ EIS measurement shows mitigation of the interfacial reaction. Moreover, the electrochemical performance of the battery achieves capacity retention of 97.1% (after 360 cycles at 0.5 mA cm^-2), 100.3% (after 410 cycles at 3 mA cm^-2), and 93.8% (after 480 cycles at 5 mA cm^-2), respectively, with a LiFePO₄ cathode for Sn-Li metal anode. This approach demonstrates a solvent- and binder-free method for stabilizing the lithium surface, enabling guided lithium growth for safe, high-performance lithium-metal anodes.