A mild one-step synthesis of sodium pre-intercalated 6-MnO2@CC for flexible high-performance supercapacitors with ultralong cycle life

Cation ion intercalated delta-MnO2 has been considered as a promising candidate for flexible energy storage devices. Herein, we fabricated Na ion pre-intercalated delta-MnO2 immobilized on flexible carbon cloth (CC) for symmetric supercapacitors via a mild one-step cyclic voltammetry (CV) electrodeposition method. Compared to that of NaxMnO2-32 without NH4+additive, NaxMnO2-32-N with NH4+ additive obtained a larger Cs (1208 mF center dot cm- 2) with a 40 % increase and a maintained Cm (208 F center dot g- 1 at 1 mA center dot cm- 2). In addition, NaxMnO2-32-N exhibited more remarkable capacitive behavior and better rate capability. Based on the XPS, BET, TEM and SEM results, the increase of specific surface area, Na+ ion pre-embedded content and deposition mass were deduced to be the dominant role in optimizing electrochemical properties of delta-MnO2. A flexible symmetric supercapacitor was assembled by NaxMnO2-32-N electrodes to evaluate its applications and demonstrated a high energy density of 117.74 mu W center dot h center dot cm- 2 (at a power density of 225 mu W center dot cm- 2) and power density of 3375 mu W center dot cm- 2 (at an energy density of 12.35 mu W center dot h center dot cm- 2) with good flexibility. Furthermore, it showed excellent capacity retention rate (97 %) and coulomb efficiency (105 %) after 80,000 long-term charging/recharging cycles.