Design and construction of organic-inorganic composite artificial solid electrolyte interface films with high ionic conductivity for lithium-metal batteries

Abstract

Artificial solid electrolyte interface (SEI) layers protect lithium (Li) anodes and minimize electrolyte side reactions. Composite SEI layers comprising inorganic and organic materials offer high Li⁺ conductivity, robust mechanical strength, and excellent flexibility. In this study, Li_1.3Al_0.3Ti_1.7(PO₄)₃(LATP) is integrated into a matrix of poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(ethylene oxide) (PEO), lithium bis(trifluoromethanesulfonyl)imide(LiTFSI), and succinonitrile (SN), resulting in the fabrication of composite artificial SEI membranes (PPSL-L16). These membranes consist of a robust inorganic layer (rich in LiF, Li₂CO₃, and Li₃N) and a flexible organic polymer layer. The membranes exhibit high ionic conductivity (σ: 1.40 × 10⁻³ S cm⁻¹), inhibit Li dendrite formation, and enhance capacity retention and cell cycling stability. After 400 cycles at 1 C, PPSL-L16/Li||LiFePO₄ (LFP) full cells retain 88.94 % of their initial capacity—5.64 times that of bare Li (15.77 %)—and the Li anode thickness increases by only 14.4 μm, which is 7 % of that observed in bare Li (205.6 μm), indicating significant suppression of Li dendrite growth. Symmetric PPSL-L16/Li cells achieve stable Li plating/stripping, maintaining a low overpotential (∼100 mV) for 2280 h 0.55 mA cm⁻² and 2.1 mA h cm⁻². The reduced crystallinity of the complexes and interfacial modulation by LATP enhance Li⁺ transport, thereby improving the σ of the composite SEI, broadening its electrochemical stability window (ESW), and further suppressing Li dendrite formation. These improvements contribute to superior battery safety, cycling performance, and rate capability. This strategy provides a feasible and effective approach for developing high-performance Li-metal batteries with long cycle life.