Cellulose nanocrystals (CNCs) have attracted a great interest for various industrial applications due to their wide range of characteristics including compatibility, recyclability, and reproducibility. The efficient preparation of the quality cellulose nanocrystals (CNCs) from microcrystalline cellulose (MCC) utilizing ionic liquid (IL) 1-butyl-3-methylimidazoluim hydrogen sulfate (BmimHSO4) and dimethyl sulfoxide (DMSO) binary mixture was investigated and compared the results with those obtained from the pure IL. The produced CNCs were characterized using atomic force microscopy (AFM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and x-ray diffractometry (XRD). It was observed that the average diameter of CNCs obtained with IL-cosolvent (C-CNCs), and pure IL (P-CNCs) were 50 nm and 0.77 µm, respectively, whereas the length of C-CNCs and P-CNCs were found to be 757 nm and 2.11 µm, respectively. The non-isothermal Coats-Redfern model with numerous mechanisms were used to model the thermal degradation kinetics of CNCs. The C-CNCs and P-CNCs exhibited lower activation energies of 86.45 and 19.10 KJ/mol respectively, than that of MCC 386.8 KJ/mol. The role of DMSO in the production of CNCs was discussed. The proposed IL based binary mixture could be an effective for the production of high quality CNCs for different applications. © 2021 Elsevier B.V.