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In the present investigation, renewable kraft lignin-based nanofibers were synthesized by facile electrospinning technique and further converted into carbon nanofibers (CNFs) by heat treatment at different temperatures (600, 800 and 1000 °C). These different heat treated carbon nanofiber mats were characterized using SEM, Raman, FTIR, BET and electrochemical workstation. These CNFs were used as a free-standing electrode and characterized for electrochemical performance using a three-electrode system. Among different electrodes, the 800 °C heat treated CNF electrode shows higher specific capacitance (196.63 F/g @ 1 A/g) as compared to the 600 and 1000 °C heat treated CNF electrodes. Based on the electrochemical performance, 800 °C heat treated CNF electrode is selected to assemble two different types of symmetrical supercapacitor devices i.e., aqueous (using 1 M H 2 SO 4) and solid-state electrolyte using PVA-1M H 2 SO 4 polymer gel. The solid-state electrolyte device operating potential window of 0–2 V which is higher than that of an aqueous electrolyte based device. In addition to this, it delivers higher energy and power density as 62.6 Wh/kg and 1.25 kW/kg respectively with an efficiency of 99.5% after 10,000 cycles. These remarkable results of Kraft lignin-derived ribbon type CNF based solid-state symmetrical supercapacitor device opens new paths for the development of futuristic carbon-based free-standing mat as energy storage devices. • Lignin (90%) based carbon nanofibers synthesized by electrospinning and heat treatment at different temperatures. • Effect of heat treatment on microstructure, surface area and functional groups has been studied extensively. • The assembled symmetrical solid state supercapacitor device operates within a wide potential window of 0–2 V. • It shows superior long cycle life of 99.5% after 10,000 charge-discharge cycles. • The solid-state supercapacitor device shows high values of energy (62.6 Wh/kg) and power (1.25 kW/kg) density. [ABSTRACT FROM AUTHOR]