  We investigated the effect of Ni doping in a recently proposed quantum spin
liquid (QSL) candidate Li$_4$CuTeO$_6$. We performed a comprehensive study on
the structural and magnetic properties. We find that the anti-site disorder
between Li$^+$ and Cu$^{2+}$ persists until 50\% Ni doping in which Ni and Cu
occupy different crystallographic sites. As a result, while Cu sits in both
triangular and honeycomb layers in Li$_4$CuTeO$_6$, Ni forms only honeycomb
layer in Li$_4$NiTeO$_6$ and Li$_4$Cu$_{0.5}$Ni$_{0.5}$TeO$_6$. Our magnetic
susceptibility measurements show that the Weiss temperature decreases from
-145.68 K in Li$_4$CuTeO$_6$ to -6.15 K in Li$_4$NiTeO$_6$ as Ni doping
increases, and find no hint of magnetic ordering or freezing down to 1.8 K. Our
analysis implies the existence of abundant low energy excitations in these
materials.
