Built-in hybrid intercalation cations facilitated fast lithium-ion conduction of lamellar montmorillonite for safety lithium-metal batteries

Solid-state lithium-metal batteries have good prospects such as high theoretical energy density and excellent safety while available solid-state electrolytes cannot meet the electrochemical requirements. In this study, hybrid cations are built-in intercalated in lamellar montmorillonite to facilitate fast lithium-ion conduction, and a stable and safe lithium-metal battery is achieved. The hybrid intercalation cation of the large-size organic molecule cetyltrimethylammonium bromide (CTAB) broadens the insertion space as well as the Li⁺ insertion ensuring the concentration of interlayer conduction carriers. Based on hybrid intercalated montmorillonite, a 35 μm-thick high inorganic content solid-state electrolyte with excellent flexibility, superior hardness, and heat resistance has been prepared by the solution casting method. This electrolyte possesses high ionic conductivity (7.64 × 10⁻⁴ S·cm⁻¹ at 25 °C), low ionic mobility energy (0.16 eV), and a wide window of electrochemical stabilization (4.92 V). With such a high-performance electrolyte, Li symmetric cells are stably cycled over 2000 h at 25 °C with a low overpotential of 30 mV. The Li||LiFePO₄ solid-state battery exhibits excellent cycling stability with 94.1 % capacity retention for 200 cycles at 25 °C. This interface regulation and interlayer ion transfer strategy may provide a new method for high-performance solid-state batteries.