Moreover, the S -doped graphene achieved a augmented capacitance retention of 83% after 10000 cycles at 3 mA cm -2 . An increased energy storage performance by the S-doped graphene over desulphurised graphene is attributed to the couple of factors in which the Rct value for Sdoped graphene was found to be 9.55 Ω which is appreciably lower than desulphurised form of graphene . On contrary, the SBET of former was found to be 418 m 2 g -1 which is slightly higher than the latter (406 m 2 g -1 ). [614]. The specific capacitance for S doped graphene with DMSO as the solvent was found to be 240.2 F g -1 at 3.3 A g -1 in 1 M Na2SO4 and higher than that prepared with water as the solvent (141.0 F g -1 ) and depicted in Fig. . The augmented energy storage performance in DMSO solvent over water is attributed to the fact that the sulphur doping content as well as the SBET of former case were found to be 7.02 at. % and 693.3 m 2 g -1 and these values are greater than those of latter having the values of 3.81 at. % and 522.77 m 2 g -1 , respectively. Finally, they proposed that the enhanced content of C-S in the S-doped graphene prepared using DMSO exhibits the EDLC behaviour which is better than that obtained using water owing to the fact that the sulphide bridge formed at the edge of the layer in the former case that permits the quick transport of ions without encouraging the undesirable side reactions. and pyridine (Py), respectively . It was found that the electrical conductivity diminishes with increase of fluorine content. The fluorine content of the F-doped graphene synthesized using DCM from XPS and the electrical conductivity for the flexible F-doped graphene film were found to be 6 at% and 218.2 S m -1 , respectively. Among the various solvents, the F-doped graphene obtained using DCM has got the high specific capacitance of 104.8 F g -1 at 0.5 A g - 1 with 88% retention of original capacitance after 10000 cycles in sodium sulphate based solidstate electrolyte. In another study, Bulusheva et al. reported the fabrication of few layered Fluorinated graphene by the fluorination of bromine intercalated graphite with BrF3 by solution assisted method followed by the thermal exfoliation at 800 °C . The atomic content of fluorine for the as-prepared material evaluated from XPS found to be 1.4 at%. The capacitance of Fluorinated graphene was found to be 21 F g -1 in 1 M H2SO4 electrolyte and the substantial 7.5 times increment in the capacitance (158 F g -1 at 2 mV s -1 ) was observed after the mild oxidation with mixture of concentrated H2SO4 and HNO3 3:1 vol.) at 60 °C for 30 minutes. The low capacitance prior to acid treatment in acidic electrolyte was due to the hydrophobic nature experienced by the C-F bonds and the increment in capacitance was attributed to the improved wettability as well as the faradaic interaction between oxygen functionalities in acidic electrolyte after subjecting the oxidation of the as-prepared samples with the mixture of acids. Interestingly, An et al. prepared the fluorinated graphene hydrogel using HF as the precursor by hydrothermal at different temperatures . Among the various temperatures, the fluorinated graphene prepared at 150 °C about 24 h has attained the maximum fluorine content of 4.52 at. % as well as the highest capacitance of 227 F g -1 at 1 A g -1 in 6 M KOH solution and greater than RGO (150 F g -1 ). It has been explained that the significant difference in electronegativity between fluorine and carbon generates the positive charge on the neighbouring carbon atoms that promotes the transportation of negatively charged ions during electrochemical cycling. Besides, the positively charged carbon atoms behave as electrochemically active sites which contribute to the pseudocapacitance. Kakaei et al. prepared the chlorine doped RGO by ultrasonic assisted method using NaClO4 as the precursor . The chlorine doped RGO exhibits the specific capacitance of 178.4 F g -1 at 1 A g -1 in 1M H2SO4 solution which is greater than RGO (100. 5 F g -1 ). This is also evidenced as a result of Rct calculated from Nyquist plot for Cl doped RGO was found to be 3.44 Ω which is relatively lesser compared to RGO (6.2 Ω) suggesting that the conductivity of the Cl doped RGO electrode is higher than RGO. It was also observed that the Rct value increased from 3.44 to 5.12 and 6. The areal capacitance of F-doped graphene based microsupercapacitor found to be 14.2 mF cm -2 at 1 mV s -1 which is comparatively higher than those of exfoliated graphene (9.3 mF cm -2 ) and hydrothermally treated graphene based microsupercapacitor (7.4 mF cm -2 ), respectively in EMIMBF4 electrolyte. From Fig. , the prepared F-doped graphene based allsolid-state microsupercapacitor powered the red LED for more than 60 s upon charging to 3.5 V at 0.5 A cm -3 along with the high volumetric energy density of 59 mWh cm -3 in PVDF-HFP/EMIMBF4 based gel electrolyte with 93% of capacitance retention after 5000 cycles proposing that highly beneficial for wearable electronics. Yucan Zhu et al. produced the I-doped RGO by the incorporation of certain amount of iodine into frees-standing GO film in the autoclave heated at 150, 200 and 250 °C for 3 h [620]. On incrementing the mass loading, the gravimetric capacitance of the symmetric cell derived from the optimised ratio of iodine and GO (3:1) in I-doped RGO films remains unchanged around 150 F g -1 at 0.2 A g -1 while the areal capacitance experienced the linear increment and attained the maximum upto 524 mF cm -2 and shown in Fig. and, respectively. It was observed that the Rct diminishes with increase of mass loading. Moreover, the I-doped RGO based flexible solid-state device achieved the areal capacitance of 450 mF cm -2 at 1 mAcm -2 in PVA-KOH gel electrolyte and 96.5% of capacitance retained after 5000 cycles at 300 mV s -1 . Xingke ye et al. prepared the iodine doped fluffy reduced graphene oxide by heat-pressing technique with HI as the precursor . Because of efficient hot-pressing technology, the van der Waals interactions between the graphene sheets and the restacking also reduced. The conductivity of the material is found to be 3000-3300 Sm - 1 because of iodine doping by chemical reduction. Thus, the obtained material with 0.51 at% of iodine has achieved the specific capacitance of 238.4 F g -1 at 0.5 A g -1 in 1 M H2SO4 solution.