Co-MnO2 Nanorods for High-Performance Sodium/Potassium-Ion Batteries and Highly Conductive Gel-Type Supercapacitors

Abstract

Manganese dioxide (MnO2) is considered as a strong candidate in the field of new-generation electronic equipment. Herein, Co-MnO2 has excellent electrochemical properties in tests as the cathode electrode of sodium-ion batteries and potassium-ion batteries. The rate performance remains at 50.2 mAh g−1 at 200 mA g−1 for sodium-ion batteries. X-ray diffraction (XRD) is utilized to evaluate the crystal structure transition from Co0.2-MnO2 to NaMnO2 with discharge to 1 V, proving that Co-doping does indeed facilitate the acceleration of ion transport and support layer spacing to stabilize the structure of MnO2. Subsequently, highly conductive (0.0848 S cm−1) gel-type supercapacitors are prepared by combining Co0.2-MnO2, potassium hydroxide (KOH), and poly(vinyl alcohol) (PVA) together. Co0.2-MnO2 provides capacitive behavior and strengthens the hydrogen bonds between molecules. KOH acts as an ion crosslinker to enhance hydrogen bond and as electrolyte to transport ions. 5 wt% Co0.2-MnO2@KOH/PVA has superb mechanical endurance, appreciable electrical conductivity, and ideal capacitive behavior. The quasi-solid-state supercapacitor demonstrates stabilized longevity (86.5% at 0.2 mA cm−3 after 500 cycles), which can greatly promote the integration of flexible energy storage fabric devices.