Conductive porous structures are favorable as active electrode materials for energy storage by boosting the active sites and specific surface area but have been rarely achieved in transition metal dichalcogenides. Here, we developed acid-assisted exfoliation for the first time, to successfully exfoliate TaS2 into very large-sized conductive monolayers with controllable in-plane sub-nanopores. By TaS, monolayer inducing both interlayer lattice expansion and basal in-plane etching, hydrogen ion, previously regarded disastrous in charged system, was creatively utilized as an efficient and easily accessible assistant in simultaneous exfoliation and controllable structural modification. Benefiting from pore size (similar to 0.95 nm) matching well with electrolyte ion size, coexistence of ultrahigh conductivity and fast ion transport was achieved in metallic large-sized monolayers. Notably, the as-produced TaS2-based electrode delivers large volumetric capacitance (508 F/cm(3) at scan rate of 10 mV/s) and high energy density (58.5 Wh/L) when fabricated into a micro-supercapacitor. We anticipate acid-assisted exfoliation to be a promising strategy in constructing 2D nanomaterials with novel structure for wide energy applications.