Electrochemical cell unit for a secondary battery

The present invention relates to an electric cell unit for a secondary battery as well as to such a secondary battery module. The electric cell unit comprises: - a first electric cell (12) enclosed by a first casing (13), - a second electric cell (14) enclosed a second casing (15), wherein at least one of first and second casings (13, 15) comprises a recessed portion (16, 18) extending along a side edge (11) thereof to form a receptacle (30), which is adapted to receive at least one thermal transfer element (28).