MXene and silk fibroin peptide team up to build a 1+1>2 in situ SEI film

The utilization of solid-state lithium-ion batteries (SLIBs) is envisaged for the next generation of energy storage devices due to their exceptional energy density. Nonetheless, for practical applications of SLIBs, it is crucial to address the challenges associated with unstable interfaces and poor electrochemical performance. By employing silk fibroin peptide (SFP) and MXene, we successfully achieved the in-situ generation of uniform solid electrolyte interphase (SEI) films through the design of modified interfaces. The incorporation of -NH2 groups from SFP and the -F terminus from MXene facilitated the formation of Li3N and LiF, thereby enabling selective localization and controlled SEI film growth as confirmed by the time-of-flight secondary-ion mass spectrometry (TOF-SIMS) analysis. The Derjaguin-Müller-Toporov (DMT) modulus demonstrated the robustness of the SEI film. This phenomenon enhances interfacial stability, promotes lithium-ion nucleation, suppresses dendrite growth, and improves overall electrochemical performance during battery operation. The presence of -NH2 possessing a lone pair of electrons exhibited excellent lithophile properties that facilitated micro-complexes formation with lithium ions, thereby promoting lithium salt dissociation and facilitating the lithium-ion migration within systems. Furthermore, the interface-modified polymer electrolytes (PEs) demonstrated an impressive ionic conductivity of up to 1.16 × 10−3 S cm−1, along with a favorable transference number of lithium ions (tLi+) of 0.57. Notably, the modified PEs significantly contributed to stable battery operation at room temperature (RT), exhibiting an initial discharge capacity of 117.6 mAh g−1 at 5 C. This innovative strategy involving modification at the interface level represents a significant advancement towards achieving stable operation in high-energy SLIBs.