Method for manufacturing room-temperature sodium halide-based solid electrolyte and solid electrolyte manufactured thereby

Orthorhombic NaAlCl4 solid electrolyte with Na2 sites formed via non-heat-treated ball milling synthesis

This technology creates an orthorhombic NaAlCl4 compound by mixing sodium chloride (NaCl) and aluminum chloride (AlCl3) through a ball milling process, forming new sodium sites (Na2) to enhance ionic conductivity and electrochemical stability.

Existing sodium solid electrolytes suffer from high costs and low room-temperature ionic conductivity. Furthermore, they face limitations such as severe decomposition reactions when operated at high voltages of 3–4V or higher, leading to instability at the interface between the cathode and the electrolyte.

This technology synthesizes a NaAlCl4 solid electrolyte with artificially created Na2 sites within the crystal structure using only a 600–650 rpm ball milling process for 10–11 hours, without heat treatment. It enables the implementation of all-solid-state batteries operating at 3–4V or higher by incorporating this material into the cathode, anode, or electrolyte layer. Suitable for large-scale sodium-based ESS and low-cost all-solid-state cells that reduce reliance on lithium, this technology provides high-voltage-compatible electrolytes using inexpensive chloride raw materials and a single grinding process.

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Key Features:

• A step of mixing sodium chloride (NaCl) and aluminum chloride (AlCl3), which are solid electrolyte raw materials, in a 1:1 molar ratio
• A step of ball-milling the mixture under argon gas using 10 to 13 mm diameter balls at 600 to 650 rpm for 10 to 11 hours
• A room-temperature solid electrolyte containing an orthorhombic NaAlCl4 compound with a 30 °C ionic conductivity of 3.0 x 10-6 to 9.0 x 10-5 S/cm
• A room-temperature operating all-solid-state battery containing the NaAlCl4 solid electrolyte in at least one of the cathode layer, anode layer, or the solid electrolyte layer between them

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This invention was developed with support from the Ministry of Economy and Finance for the development of 600Wh/L-class large-area all-solid-state battery bridge technology for EVs.

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