Dendrite-Free Lithium Metal Batteries Enabled by Coordination Chemistry in Polymer-Ceramic Modified Separators

Issues with lithium dendrite growth and dead lithium formation limit the practical application of lithium metal batteries, especially under high current conditions where uneven temperature distribution leads to serious safety concerns. Herein, In situ assembly of polydopamine (PDA) and aluminum nitride (AlN) coatings on polypropylene (PP) separator is introduced to address these challenges. The AlN particles are encapsulated by PDA, and the functional groups in PDA form Al-O coordination bonds with Al³⁺, which promote uniform Li⁺ flux and reduce the migration barrier of Li⁺, thereby enabling dendrite-free lithium deposition. In addition, the designed PDA@AlN@PP separator exhibits excellent electrolyte wettability, enhanced mechanical performance, and stable thermal resistance, providing a uniform thermal distribution and serving as a robust barrier against dendrite penetration. As a result, symmetric Li||Li cells (over 1800 h at 1 mA cm⁻² and 1 mAh cm⁻²) and Li||Cu cells (over 600 cycles at 0.5 mA cm⁻² and 0.5 mAh cm⁻², coulombic efficiency over 98%) demonstrate outstanding long cycle performance and high coulombic efficiency. Moreover, the corresponding Li||LiFePO₄ cells exhibit a high specific capacity of 91.3 mAh g⁻¹ at 5 C. This work provides a new approach for designing functionalized separators for high-performance lithium metal batteries.