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 <i>in situ</i> construction of QSSLMBs. A multilayer design integrates a microwave-synthesized Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) ceramic electrolyte, which is surface-coated with a lithiophilic conductive ink comprising VS₂ and disulfonated functionalized graphene nanosheets (VS₂-DSGNS) using a low-cost nail-polish binder. Subsequently, a few drops of LiPF₆ in EC/DMC liquid electrolyte (LE) are impregnated into the uncoated side of the LATP surface. The quasi-solid-state electrolyte pellet of LATP-VS₂-DSGNS surface was allowed to be in contact with the molten Li and held until Li flowed into the LATP-VS₂-DSGNS surface completely <i>via</i> 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-VS₂-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 Al₂O₃ dry-coated, high-nickel NMC622 cathode with the PEO-PVDF|LATP-VS₂-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.