Formulation of nanostructured V2O5 based screen printable ink: Toward fabrication of micro-supercapacitors

The continuous growth in flexible electronics evolution of flexible electronics demands equally adaptable energy storage solutions, pushing the boundaries beyond conventional sandwich-structured devices that suffer from safety concerns, limited energy density, and poor mechanical flexibility. In-plane micro-supercapacitors (MSCs) have emerged as a superior alternative, with printing technology offering a scalable and cost-effective fabrication approach. Here, we develop a screen-printable ink based on ultrasonically synthesized nanostructured V₂O₅ (usN-V₂O₅) to fabricate high-performance MSCs on both rigid alumina and flexible PET substrates, utilizing silver-printed current collectors for efficient charge transport. To tailor electrochemical performance, we employ two distinct electrolytes: polyacrylamide (PAM)-Li₂SO₄ gel for exceptional stability and 1-Ethyl-3-methylimidazolium tetra fluoroborate (EMIM BF₄) ionic liquid (IL) for an expanded electrochemical window and enhanced energy density. The PAM-Li₂SO₄ based MSC on alumina substrate delivers an outstanding specific capacitance of 49.9 F cm⁻³, maintaining 87.75 % retention over 10,000 cycles, while the IL-based MSC on PET achieves an impressive energy density of 2.25 mWh cm⁻³ at 1609.39 mW cm⁻³, significantly outperforming its PAM-Li₂SO₄ counterpart (1.70 mWh cm⁻³ at 1000 mW cm⁻³). Notably, it excels in mechanical flexibility, retaining charge storage performance even after 300 bending cycles, reinforcing its potential for wearable and stretchable electronics. These findings underscore the promise of usN-V₂O₅-based screen-printable MSCs as a game-changing solution for next-generation flexible and high-energy-density energy storage devices.