A process for preparing lithium carbonate wherein said process is carried out in a three-compartment membrane electrolysis cell, said process comprising: submitting an aqueous composition comprising a lithium compound which comprises lithium sulphate to an electrolysis or an electrodialysis under conditions suitable for converting at least a portion of said lithium sulphate into lithium hydroxide, wherein said process is carried out by introducing said aqueous composition comprising said lithium sulphate into a central compartment, an aqueous composition comprising lithium hydroxide into a cathodic compartment, and an aqueous composition comprising NH3 into an anodic compartment, and converting said lithium hydroxide into lithium carbonate wherein converting said lithium hydroxide into lithium carbonate is carried out by: reacting an aqueous composition comprising said lithium hydroxide with CO2 by sparging said CO2 into said composition, said sparging being carried out while pH is at least maintained at a value of 10 to 12.5, thereby obtaining a slurry comprising said lithium carbonate; inserting at least a portion of said slurry into a clarifier and obtaining a supernatant comprising lithium bicarbonate and a solid comprising said lithium carbonate; separating said solid from said supernatant; and heating said supernatant at a temperature of at least 85 °C so as to at least partially convert said lithium bicarbonate into lithium carbonate. submitting an aqueous composition comprising a lithium compound which comprises lithium sulphate to an electrolysis or an electrodialysis under conditions suitable for converting at least a portion of said lithium sulphate into lithium hydroxide, wherein said process is carried out by introducing said aqueous composition comprising said lithium sulphate into a central compartment, an aqueous composition comprising lithium hydroxide into a cathodic compartment, and an aqueous composition comprising NH3 into an anodic compartment, and converting said lithium hydroxide into lithium carbonate wherein converting said lithium hydroxide into lithium carbonate is carried out by: reacting an aqueous composition comprising said lithium hydroxide with CO2 by sparging said CO2 into said composition, said sparging being carried out while pH is at least maintained at a value of 10 to 12.5, thereby obtaining a slurry comprising said lithium carbonate; inserting at least a portion of said slurry into a clarifier and obtaining a supernatant comprising lithium bicarbonate and a solid comprising said lithium carbonate; separating said solid from said supernatant; and heating said supernatant at a temperature of at least 85 °C so as to at least partially convert said lithium bicarbonate into lithium carbonate. reacting an aqueous composition comprising said lithium hydroxide with CO2 by sparging said CO2 into said composition, said sparging being carried out while pH is at least maintained at a value of 10 to 12.5, thereby obtaining a slurry comprising said lithium carbonate; inserting at least a portion of said slurry into a clarifier and obtaining a supernatant comprising lithium bicarbonate and a solid comprising said lithium carbonate; separating said solid from said supernatant; and heating said supernatant at a temperature of at least 85 °C so as to at least partially convert said lithium bicarbonate into lithium carbonate.