Regulating Li-ion flux with a high-dielectric hybrid artificial SEI for stable Li metal anodes

Abstract

The interface regulation of lithium metal anodes (LMAs) is considered one of the most critical issues in the pursuit of high energy density for lithium metal batteries. As a key physical characteristic, the dielectric feature of the interface overlayer decides the electric field and charge–current distribution within the interface region and directly influences the Li deposition behavior of LMAs. Herein, a high-dielectric artificial solid–electrolyte interface (SEI) is designed to regulate the electric field distribution and Li⁺ flux and stabilize the interface in LMAs. In the hybrid organic–inorganic polydopamine (PDA)-SiO₂ artificial SEI, the enhanced dielectric permittivity by inorganic SiO₂ has important effects in preventing current variation, guiding uniform current/potential distribution and homogenizing the Li⁺ flux within the SEI interface, thus achieving uniform Li plating, while the high elasticity, strong Li affinity and lithiophilic/hydrophilic property of PDA can suppress Li dendrite growth and stabilize the SEI structure over long cycles. These multi-functional properties of the artificial SEI for LMAs can achieve remarkable cycling in both the symmetric cell configuration (2800 h at 5 mA cm⁻² with 1 mA h cm⁻²) and LiCoO₂||Li full cells. Our work provides a physical point-of-view of the novel configuration of the artificial SEI for stable LMAs and can be extended to the protection of other alkali metal anodes.