Thin Co-Mn layered double hydroxide (LDH) nanoflakes and Activated carbon (AC) from cork raw material (Quercus Suber) with highly porous structure and good textural properties was synthesized by a facile solvothermal and two-step eco-friendly hydrothermal syntheses routes respectively. A hybrid device was successfully fabricated using Co-Mn LDH as the positive electrode and AC as negative electrode. The device exhibited a high energy density of 20.3 W h kg−1 and corresponding power density of up to 435 W kg−1 at 0.5 A g−1 current density in 1 M KOH aqueous electrolyte. The device also displayed a very high stability with 99.7% capacitance retention after 10,000 continuous charge-discharge cycles and negligible degradation after subsequently subjecting it to voltage holding test at its maximum operating voltage for 70 hours. These results showcase the potential use of this hybrid device as possible electrodes for high energy density supercapacitor application.