Crystals of κ-[(BEDT-TTF)2][Cu(N(CN)2)Br] were available with good quality and high reproducibility from the BEDT-TTF electro-oxidation with an electrolyte molar ratio [Ph4P][N(CN)2]:CuBr of 1:1 in a mixture of THF and ethylene glycol. Surprisingly, by varying the electrolyte molar ratio from 1:1 to 1:8 a novel type of BEDT-TTF salt, [BEDT-TTF]2[Cu2Br3], was formed. The solid-state structure of [BEDT-TTF]2[Cu2Br3] consists of stacks of non-coordinated BEDT-TTF molecules and stacks of the contact ions [BEDT-TTF][Cu2Br3] (triclinic space group, P1). The two crystallographically independent [BEDT-TTF][Cu2Br3] contact ions in the second stack are related by a pseudo-inversion center. Resistivity measurements on single crystals reveal that [BEDT-TTF]2[Cu2Br3] possesses a semiconductor-like behavior under normal pressure from room temperature down to at least 10 K.