An ultrathin and robust single-ion conducting interfacial layer for dendrite-free lithium metal batteries

The practical application of rechargeable lithium metal batteries (LMBs) encounters significant challenges due to the notorious dendrite growth triggered by uneven Li deposition behaviors. In this work, a mechanically robust and single-ion-conducting interfacial layer, fulfilled by the strategic integration of flexible cellulose acetate (CA) matrix with rigid graphene oxide (GO) and LiF fillers (termed the CGL layer), is rationally devised to serve as a stabilizer for dendrite-free lithium (Li) metal batteries. The GCL film exhibits favorable mechanical properties with high modulus and flexibility that help to relieve interface fluctuations. More crucially, the electron-donating carbonyl groups (C=O) enriched in GCL foster a strengthened correlation with Li⁺, which availably aids the Li⁺ desolvation process and expedites facile Li⁺ mobility, yielding exceptional Li⁺ transference number of 0.87. Such single-ion conductive properties regulate rapid and uniform interfacial transport kinetics, mitigating the growth of Li dendrites and the decomposition of electrolytes. Consequently, stable Li anode with prolonged cycle stabilities and flat deposition morphologies are realized. The Li||LiFePO₄ full cells with CGL protective layer render an outstanding cycling capability of 500 cycles at 3 C, and an ultrahigh capacity retention of 99.99% for over 220 cycles even under harsh conditions. This work affords valuable insights into the interfacial regulation for achieving high-performance LMBs.