Electrochemical energy conversion devices and cells, and positive electrode-side materials for them

An electrochemical energy conversion device comprising a stack of solid oxide electrochemical cells alternating with gas separators, wherein each electrochemical cell comprises a layer of solid oxide electrolyte, a negative electrode-side structure on one side of the electrolyte layer and comprising one or more porous layers including a functional layer of negative electrode material having an interface with the one side of the electrolyte layer, and a positive electrode-side structure on the opposite side of the electrolyte layer and comprising one or more porous layers including a layer of positive electrode material having an interface with the opposite side of the electrolyte layer, wherein said electrochemical cell and a first of the gas separators on the negative electrode side of the electrochemical cell at least partly form therebetween a negative electrode-side chamber and said electrochemical cell and a second of the gas separators on the positive electrode side of the electrochemical cell at least partly form therebetween a positive electrode-side chamber, and wherein scavenger material selected from one or both of free alkali metal oxygen-containing compounds and free alkaline earth metal oxygen-containing compounds is provided in or on one or more of the positive electrode-side structure, the second gas separator and any other structure of the electrochemical energy conversion device forming the positive electrode-side chamber, the scavenger material being accessible to poisons in the atmosphere in the positive electrode-side chamber during use of the electrochemical energy conversion device and being more reactive with the poisons than is the positive electrode material, and wherein if the scavenger material is provided in the layer of positive electrode material there is no scavenger material present at the interface of that layer with the electrolyte layer.