High n -type thermoelectric performance due to anisotropic charge-phonon transport in CuBiSCl2

CuBiSCl₂ exhibits strongly contrasting anisotropies in charge and phonon transport, showing superior electron mobility (138 cm²/V0.16em0exs) yet ultralow lattice thermal conductivity (0.40 W/mK) along the a axis at 300 K. This exceptional combination arises from the anisotropic bonding hierarchy where [BiSCl₂]ₙ ribbons facilitate efficient charge conduction through delocalized Bi-$6p$/S-$3p$ networks, while soft Cu-dominated vibrations strongly scatter heat-carrying phonons in the same direction. The resulting high-power factor (1.71 mW/mK² at 700 K) and peak $ZT$ of 1.57 establish CuBiSCl₂ as a paradigm for realizing the ``phonon glass-electron crystal'' concept through crystallographic engineering.