Abstract: A method for producing high purity lithium hydroxide monohydrate from materials containing a lithium salt selected from Li2SO4, LiCl, Li2CO3 or mixtures thereof is provided. The method includes membrane electrolysis of an aqueous solution of the indicated lithium salt using a cation exchange membrane and a nickel-plated stainless steel cathode. The catholyte is withdrawn from the circulating stream and evaporated to give crystals of lithium hydroxide monohydrate, which are separated from the mother liquor, washed with water and dried to give the final high purity lithium hydroxide monohydrate. Part of the spent washing solution is fed into the catholyte evaporation process. Part of the mother liquor formed after the separation of crystals of lithium hydroxide monohydrate is returned to the catholyte evaporation process. The reverse flow of the anolyte is replenished with a concentrated lithium salt solution prepared from the original lithium salt.