Replacement of nickel by aluminium in the brucite-type Ni(OH), layers leads to layered double hydroxides (LDH), which can be used as active materials for nickel hydroxide electrodes. Ni/AI LDH compounds [O< AI/(Ni + Al) 6 0.251 were synthesized by precipitation with ammonia from mixed Ni/AI nitrate solutions and characterized by X-ray powder diffraction, infrared spectroscopy, chemical analysis and transmission electron microscopy. X-Ray powder diffractograms of fresh precipitates are characteristic of turbostratic layered double hydroxides. A structural model describing the turbostratic layered double hydroxides is proposed on the basis of the experimental results. The brucite-type layers are non-stoichiometric and present hydroxide vacancies: their chemical composition can be written as [Ni:?, Ali+ (OH-), -,,+,,-x,] and the interlamellar layers as [(NO,), (CO;-);nH,O] with xGO.25. The interlamellar anions (NO; or COZ-) play two roles: those in DJh symmetry, compensate for the positive-charge excess of A13+ ions, while those in C,, symmetry, compensate for that of hydroxide vacancies. When aged, mixed turbostratic Ni/Al hydroxides with the higher aluminium content (x>0,18) change into synthetic takovites (crystallized Ni-AI-CO, double hydroxides) through a dissolution-recrystallization process.