Method for preparing a crystalline solid material of formula (LiCl) x.2Al 3,nH 2 O, wherein n is between 0.01 and 10, x is between 0.4 and 1, and wherein the method comprises at least the following steps: a) a step of precipitating boehmite, in an aqueous medium, comprising bringing into contact at least one basic precursor preferably selected from among sodium aluminate, potassium aluminate, ammonia, hydroxide, sodium and potassium hydroxide; and at least one acidic precursor, aluminum chloride, and hydrochloric acid, wherein at least one of the basic or acidic precursors comprises aluminum, in order to obtain a boehmite suspension, wherein step a) is carried out at a temperature of between 5 and 35°C, and the amount of the basic precursor is chosen in order to obtain a pH of the end of precipitation in the reaction medium of between 7.5 and 9.5, b) a step of bringing into contact the precipitate obtained in step a) with at least lithium chloride (LiCI) as lithium source, c) a filtration step of the suspension obtained in step b) to obtain a paste, d) a step of drying the paste obtained at the end of step c) at a temperature between 20 and 80°C, preferably for a duration of between 5 minutes and 12 hours, e) a step of shaping the paste dried by acid extrusion-kneading, wherein the dried paste resulting from step d) is kneaded in the presence of an amount of acid of between 0.05 and 5% by weight relative to the dry material, wherein the dry material is the weight of the paste resulting from step d) dried in an autoclave at 200°C, preferably for 6 hours, wherein the acid is an organic or inorganic acid, and wherein the paste is then subjected to in an extrusion step, the step e) of shaping by acid extrusion-kneading that is carried out in the absence of a binder or in the presence of a binder except for a binder chosen from solid precursors of alumina chosen from among aluminum oxides, aluminum hydroxides and aluminum oxyhydroxides which are soluble or dispersible in a solution of phosphoric acid, f) a step of drying the shaped material obtained at the end of step e) at a temperature between 20 and 200°C, preferably for a period between 5 minutes and 20 hours. a) a step of precipitating boehmite, in an aqueous medium, comprising bringing into contact at least one basic precursor preferably selected from among sodium aluminate, potassium aluminate, ammonia, hydroxide, sodium and potassium hydroxide; and at least one acidic precursor, aluminum chloride, and hydrochloric acid, wherein at least one of the basic or acidic precursors comprises aluminum, in order to obtain a boehmite suspension, wherein step a) is carried out at a temperature of between 5 and 35°C, and the amount of the basic precursor is chosen in order to obtain a pH of the end of precipitation in the reaction medium of between 7.5 and 9.5, b) a step of bringing into contact the precipitate obtained in step a) with at least lithium chloride (LiCI) as lithium source, c) a filtration step of the suspension obtained in step b) to obtain a paste, d) a step of drying the paste obtained at the end of step c) at a temperature between 20 and 80°C, preferably for a duration of between 5 minutes and 12 hours, e) a step of shaping the paste dried by acid extrusion-kneading, wherein the dried paste resulting from step d) is kneaded in the presence of an amount of acid of between 0.05 and 5% by weight relative to the dry material, wherein the dry material is the weight of the paste resulting from step d) dried in an autoclave at 200°C, preferably for 6 hours, wherein the acid is an organic or inorganic acid, and wherein the paste is then subjected to in an extrusion step, the step e) of shaping by acid extrusion-kneading that is carried out in the absence of a binder or in the presence of a binder except for a binder chosen from solid precursors of alumina chosen from among aluminum oxides, aluminum hydroxides and aluminum oxyhydroxides which are soluble or dispersible in a solution of phosphoric acid, f) a step of drying the shaped material obtained at the end of step e) at a temperature between 20 and 200°C, preferably for a period between 5 minutes and 20 hours.