Anode-supported planar solid oxide fuel cells (SOFCs) have been developed at Tokyo Gas. Recently, to achieve a tight gas seals and sufficient electrical contacts between each cell, a new method for stacking the cells has been evolved. The former system was assembled by stacking planar cells and rigid planar interconnectors alternately. This study reports a new system, in which constituent units with an envelope configuration are piled vertically. Each cell is wrapped in a thin electrically conductive alloy and connected to the next cell through a flexible metal interconnector. Thus, the assembly is called an envelope-type SOFC stack. By using a thin alloy foil and a flexible metal interconnector, tight gas seals and sufficient electrical contact between each cell are achieved. Tests are conducted on 7- and 20-cell stacks and an improvement in performance is obtained. (c) 2006 Elsevier B.V. All rights reserved.