High dielectric single-ion conducting interphase enables fast-charging lithium metal batteries

The poor stability and slow lithium ion (Li⁺) transfer kinetics of solid electrolyte interphase (SEI) pose significant challenges to lithium (Li) metal batteries. Although various SEI-related strategies have been developed, the Li⁺ transport properties and uniform Li deposition still require substantial improvement for fast-charging applications. Herein, we introduce a dielectric, single-ion-conductive artificial SEI (DS-SEI) composed of lithiated Nafion and BaTiO₃ (BTO) nanoceramics to address these issues. The lithiated Nafion stabilizes the Li anode with its elastic F-rich components and facilitates fast, single Li⁺ conduction through its anion-anchored structure. The high-dielectric BTO dynamically homogenizes the electric field (E-field) to promote uniform Li deposition, synergistically enhancing intrinsic single Li⁺ conductivity and Li⁺ desolvation/diffusion kinetics, thereby enabling fast charging of the Li anode. Consequently, the DS-SEI protected Li anode can cycle over 6800 h in a Li||Li cell at 10 mA cm⁻²/5 mAh cm⁻², over 400 cycles in a 2.75 mAh cm⁻² Li||LiFePO₄ cell at 1C, with 83.0 % capacity retention at 6C (16.5 mA cm⁻²), and maintain stable cycling in a 5.62 mAh cm⁻² Li||Li₆PS₅Cl|| LiNi_0.8Co_0.1Mn_0.1O₂ all solid-state cell. Our findings provide insights into the interfacial regulation of Li anode, paving the way for fast-charging Li metal batteries.