The electrochemical intercalation of silver into AgNiO2 resulting in the formation of Ag2NiO2 was studied for different temperatures (270-330 degrees C) and polytypes of the starting material (3R and 2H). Pure 3R-polytype samples of AgNiO2 can be prepared by deintercalation of Ag out of Ag2NiO2, proving reversibility of this reaction. The measured cell voltage during intercalation was used to derive the maximum intercalation current. It is dependent on temperature and thickness of the product layer and can be evaluated according to a parabolic rate law. At higher current densities additional silver deposition takes place. For a mixture of 3R and 2H polytype (2.2:1) of AgNiO2 the activation energy for intercalation was calculated as 36 kJ/mol. The pure 3R type has an increased reactivity that can be rationalized by crystallographic arguments. (c) 2007 The Electrochemical Society.