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

${\mathrm{CuBiSCl}}_{2}$ exhibits strongly contrasting anisotropies in charge and phonon transport, showing superior electron mobility (138 ${\mathrm{cm}}^{2}/\mathrm{V}\phantom{\rule{0.16em}{0ex}}\mathrm{s}$) 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 ${[{\mathrm{BiSCl}}_{2}]}_{n}$ 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/${\mathrm{mK}}^{2}$ at 700 K) and peak $ZT$ of 1.57 establish ${\mathrm{CuBiSCl}}_{2}$ as a paradigm for realizing the ``phonon glass-electron crystal'' concept through crystallographic engineering.