  We report the electrochemical investigation of 5% Al doped MoS$_2$@rGO
composite as a high-performance anode for sodium (Na)-ion batteries. The x-ray
diffraction (XRD), Raman spectroscopy and high-resolution transmission electron
microscopy characterizations reveal that the Al doping increase the interlayer
spacing of (002) plane of MoS$_2$ nanosheets and form a stable 1T phase. The
galvanostatic charge-discharge measurements show the specific capacity stable
around 450, 400, 350, 300 and 200 mAhg$^{-1}$ at current densities of 0.05,
0.1, 0.3, 0.5 and 1~Ag$^{-1}$, respectively. Also, we observe the capacity
retentions of 86% and 66% at 0.1 and 0.3 Ag$^{-1}$, respectively, over 200
cycles with a consistent Coulombic efficiency of nearly 100%. The cyclic
voltammetry, galvanostatic intermittent titration technique, and
electrochemical impedance spectroscopy are used to find the kinetic behavior
and the obtained value of diffusion coefficient falls in the range of
10$^{-10}$ to 10$^{-12}$ cm$^2$s$^{-1}$. Intriguingly, the in-situ EIS also
explains the electrochemical kinetics of the electrode at different
charge-discharge states with the variation of charge transfer resistance.
Moreover, the post cycling investigation using ex-situ XRD and photoemission
spectroscopy indicate the coexistence of 1T/2H phase and field-emission
scanning electron microscopy confirm the stable morphology after 500 cycles.
Also, the Na-ion transport properties are calculated for 1T Al--MoS$_2$@rGO
interface and Al--MoS$_2$--MoS$_2$ interlayer host structure by theoretical
calculations using density functional theory.
