Enhancing Quasi-Solid-State Lithium-Metal Battery Performance: Multi-Interlayer, Melt-Infused Lithium and Lithiophilic Coating Strategies for Interfacial Stability in Li||VS₂-DSGNS-LATP|PEO–PVDF||NMC622-Al₂O₃ Systems

The development of quasi-solid-state lithium metal batteries (QSSLMBs) is hindered by inadequate interfacial contact, poor wettability between electrodes and quasi-solid-state electrolytes, and significant volume changes during long-term cycling, leading to safety risks and cataclysmic failures. Here, we report an innovative approach to enhance interfacial properties through the in situ construction of QSSLMBs. A multilayer design integrates a microwave-synthesized Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) ceramic electrolyte, which is surface-coated with a lithiophilic conductive ink comprising VS 2 and disulfonated functionalized graphene nanosheets (VS 2 -DSGNS) using a low-cost nail-polish binder. Subsequently, a few drops of LiPF 6 in EC/DMC liquid electrolyte (LE) are impregnated into the uncoated side of the LATP surface. The quasi-solid-state electrolyte pellet of LATP-VS 2 -DSGNS surface was allowed to be in contact with the molten Li and held until Li flowed into the LATP-VS 2 -DSGNS surface completely via a “melt-infusion strategy” as an anode side. Additionally, a heterogeneous polymer matrix consisting of poly(ethylene oxide) (PEO) and poly(vinylidene difluoride) (PVDF) as a polymer interlayer is fabricated using a solution casting technique for improving the wettability between the LE impregnated side of LATP and cathode, to enhance overall charge transfer kinetics. The assembled symmetric cells, Li||LATP-VS 2 -DSGNS||Li and Li||PEO–PVDF/LE-LATP||Li, demonstrate high lithium-ion conductivities of 3.69 × 10 –4 and 1.02 × 10 –3 S cm –1, respectively, with impressive lithium-ion transfer numbers of 0.84 and 0.93 at 25 °C. Both cells exhibit a highly reversible lithium stripping/plating cycling process for over 600 h, with minimal voltage polarization of 10 and 31.6 mV, across a broad redox window (−1 to 6 V), effectively inhibiting lithium dendrite formation. Furthermore, the combination of a surface-modified Al 2 O 3 dry-coated, high-nickel NMC622 cathode with the PEO–PVDF|LATP-VS 2 -DSGNS||Molten-Li architecture in a CR2032 coin-type full-cell delivers a galvanostatic discharge capacity of 130.6 mAh g –1 at a 1C rate after 200 cycles, achieving 84.3% capacity retention, thereby demonstrating substantial reduction in interfacial resistance and enhanced stable battery performance of QSSLMBs.