## 1 Introduction  
Over the past few decades, the depletion of fossil fuels and a significant increase in energy consumption have driven the development of efficient high-performance energy storage systems. Supercapacitors or electrochemical capacitors are the most promising and efficient energy storage devices owing to their long cycle life, high power density, fast charging/discharging and better safety tolerance compared to batteries [1; 2; 3; 4]. Supercapacitors are classified broadly into two categories: pseudocapacitors and electrical double layer capacitors (EDLCs). The EDLCs possess a higher power density and excellent cycle stability. The charge storage mechanism in EDLCs follow the non-Faradaic reaction where the accumulation of electrostatic charge takes place at the interface of the porous electrode/electrolyte within a few angstroms. Carbon-structured materials, such as carbon nanotubes (CNTs), graphene and activated carbon (AC), are the most commonly used materials in the development of EDLC-based supercapacitors [5; 6; 7; 8; 9]. However, binary EDLC materials, such as CNT/graphene, AC/CNT and carbon black/graphene, are widely used, owing to their better electrochemical and cycling stability performance. Though, binary EDLC materials have shown improved electrochemical performance but still the reported performance of these materials remains insufficient for the development of high-performance supercapacitors. [PERSON] et al. fabricated an electrospun carbon nanofiber/graphene composite electrode material for a supercapacitor and reported a specific capacitance of 183 F g\({}^{-1}\)[10]. [PERSON] et al. reported a unique poly(3,4-ethylenedioxythiophene)/g-C\({}_{3}\)N\({}_{4}\) binary electrode material with an electrochemical performance of 137 F g\({}^{-1}\)[11]. A self-assembled graphene/CNTsbinary composite was prepared by [PERSON] et al. [12] and the reported electrochemical performance of the respective binary material was 120 F g\({}^{-1}\). [PERSON] et al. focused on the development of a three-dimensional nitrogen-doped graphene/CNT framework for supercapacitor applications [13]. The three-dimensional N-doped CNT/graphene framework delivered a specific capacitance of 180 F g\({}^{-1}\) at a current density of 0.5 A g\({}^{-1}\). The poor electrochemical performance of binary EDLC electrode materials can degrade the energy density and power density performances of designed symmetric or asymmetric supercapacitor devices. To overcome the inferior electrochemical performance of binary EDLC materials, such as multiwalled carbon nanotubes/activated carbon (MWCNTs/AC), it is an ideal solution to develop ternary composite electrode materials. Boron nitride nanotubes (BNNTs) can be a suitable candidate to modify MWCNTs/AC EDLC-based materials. Recently, [PERSON] et al. tested the electrochemical performance of a BNNT-modified, polymer-derived silicon oxycarbide composite electrode material with a maximum specific capacitance of 78.93 F. g\({}^{-1}\)[14]. Furthermore, [PERSON] et al. designed and fabricated a SWCNTs/BNNT composite electrode material with an electrochemical performance of 82 F g\({}^{-1}\)[15]. There are various binary and ternary EDLC composite electrode materials reported for supercapacitor applications; however, according to our literature survey, the printed EDLC materials based on the unique combination of MWCNTs/AC/BNNTs with excellent electrochemical properties have not yet been reported. The printing process, which is cost effective, rapid prototyping, easy customization and environmentally friendly due to the simplified processes, has shown great potential to design and fabricate high-performance energy storage devices, with the following enlisted advantages: First, it provides outstanding printing flexibility and precise geometry controllability with a wide range of bulk and nanomaterial materials in any form (powders, liquids and metals) [16].