A study is made on the conditions and methods of preparation of LiNiO2 and their influence on lithium deficiency. A soft chemistry route by hydroxide precipitation and a classical ceramic method were used. In order to compensate the lithium deficiency in LiNiO2, we used a small excess of lithium precursor (never more than 10 mol%). The different samples were characterized by X-ray powder diffraction, followed by a Rietveld refinement. Optimized synthesis conditions lead to Li1-xNi1+xO2 quasistoichiometric materials with a lithium molar deficiency, x, less than 1%, confirmed by Rietveld refinement. Electron spin resonance (ESR) and magnetic measurements are in agreement with these very low x values. A spin-glasslike behavior is observed for the most stoichiometric sample. The susceptibility shows a maximum at 7.5 K on zero-field cooling and is almost constant below 7.5 K on field cooling. No anomaly of the susceptibility is observed at high temperature, indicating a good homogeneity of all samples. A strong influence of x in a narrow composition range (0.004-0.062) on the electrochemical cycling behavior of the corresponding samples is observed.