The recovery of valuable metals from spent lithium iron phosphate (LFP) black mass has garnered significant attention, with hydrometallurgy serving as the dominant recycling strategy. The leachate derived from hydrometallurgical processes typically contains impurity ions such as copper, aluminum, and fluoride, necessitating purification prior to the recovery of valuable metals. In particular, the efficient removal of aluminum ions while minimizing lithium loss via physical adsorption and chemical co-precipitation remains a critical challenge. While neutralization precipitation is a conventional method for aluminum removal, the resulting precipitate exhibits non-negligible lithium adsorption. Alternatively, cryolite precipitation can be employed in more acidic environments to produce highly crystalline aluminum-bearing precipitates with lower lithium adsorption; however, in lithium-rich solutions, it tends to form lithium-containing cryolite (Na_1.5Li_1.5AlF₆), leading to significant lithium losses. To address this limitation, this study proposes a novel hydrometallurgical approach to recover lithium from Na_1.5Li_1.5AlF₆. The process involves converting Na_1.5Li_1.5AlF₆ into a solid mixture of Na₃AlF₆ and LiF in a NaF solution, followed by selective dissolution. Specifically, a sulfuric acid medium containing sodium sulfate was developed to selectively dissolve LiF while inhibiting Na₃AlF₆ dissolution via the common ion effect. Experimental results demonstrated that complete conversion of Na_1.5Li_1.5AlF₆ was achieved under the following conditions: NaF concentration of 45 g/L, 70 ℃, liquid-to-solid (L/S) ratio of 15 mL/g, and a reaction time of 3 h. The resulting filtrate could be recycled after NaF replenishment. Subsequently, selective leaching of LiF was achieved with an initial sulfuric acid concentration of 90 g/L, Na⁺ concentration ≥ 8 g/L, 20–30 ℃, L/S ratio of 15 mL/g, and a duration of 1 h. Through this two-step process, effective aluminum-lithium separation was realized, with aluminum enriched in the solid Na₃AlF₆ phase and lithium transferred to the liquid phase for subsequent recovery. This work provides a viable strategy for the efficient extraction of lithium from cryolite precipitates in spent battery recycling.