Preparation And Electrochemical Performanceof Manganese Oxide/Carbon Composites

As an ideal electrode material, nitrogen-doped porous carbon draws increasing attention due to its high surface area, special pore structure and large pore volume. However, the shortages of poor electronic conductivity, low energy density and power density restrict its applications in practice. In this paper, the main study is to prepare nitrogen-enriched porous carbons with novel morphologies by using different methods and investigate its electrochemical performances in detail.Nitrogen-included porous carbons with plum-branch structure were synthesized by sol-gel method. Melamine-700 sample presents the largest nitrogen content of 4.4% and the highest surface area of 308.5 m2·g-1 of all. Moreover, Melamine-700 electrode material reveals the optimal electrochemical properties, including large capacitance(ca.254.5 F·g-1 at 0.3 A·g-1), excellent rate capability(201.5 F·g-1 at 10.0 A·g-1,ca.79.2% capacitance retention) as well as remarkable cycle stability(194.5 F·g-1 after 3300 cycles, up to 96.5% capacitance retention).Three-dimensional(3D) nitrogen-doped porous carbons(NPC) cellular foams with different levels of pore structure were prepared by a template method in room temperature. NPC-750 sample prepared at optimum pyrolysis temperature of 750 °C exhibits high surface area of 424.941 m2·g-1, moderate nitrogen content of 1.22% and favorable pore size distribution in the range about 3-4 nm. Furthermore, NPC-750 demonstrates the best capacitance performance: a high specific capacitance of about 239.30 F·g-1 at 0.5 A·g-1; outstanding rate capability that the specific capacitance reaches to 212.90 F·g-1 at 10.0 A·g-1(up to 88.97% capacitance retention); excellent cycling stability(~10% capacitance loss after 5000 cycles) tested in 6 M KOH aqueous solution.Three-dimensional(3D) interconnected N-enriched porous lamellar carbons(NPLCs) were prepared by carbonization using mantis-shrimp shell. NPLC-750 synthesized at optimum calcination temperature of 750 °C shows large surface area of 1276 cm2·g-1 hierarchical porous structure analyzed and suitable nitrogen content of 1.78 %. NPLC-750 sample exhibits ultra-high specific capacitance of 312.62 F·g-1 at 0.3 A·g-1, excellent rate capability with the specific capacitance of 278.65 F·g-1 at 20.0 A·g-1 and outstanding cycling stability of around 93.97% capacitance retention after 10000 cycles at a high current density of 20.0 A·g-1. Tested as a symmetrical total cell, NPLC-750 presents a high energy density of 15.05 Wh·Kg-1 at 270 W·Kg-1, and still retain 10.12 Wh·Kg-1 even at a large power density of 14580 W·Kg-1.