• Mn7O8SiO4 with the braunite used as an anode material for Li-ion batteries. • Long flat plateaus at 0.6 V and capacity up to 800 mAh.g−1 on first discharge. • Mn3+/Mn2+ redox couple confirmed by XRD, XPS, and EIS results during cycling.
• Novel deep eutectic solvent based on LiTFSI and EG was formed at the molar ratio about 1:3. • DES 1:4 exhibiting the highest conductivity value as a potential electrolyte for carbon-based EDLC • Significant enlargement of the operating voltage of supercapacitor (up to 3.0 V vs NHE)