High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

High-performance supercapacitors of carboxylate-modified hollow carbon nanospheres coated on flexible carbon fibre paper: Effects of oxygen-containing group contents, electrolytes and operating temperature

Although carbon black nanoparticles (CBs) at ca. 10 wt.% are widely used as a conductive additives for energy storage electrodes for lithium ion batteries and supercapacitors, they are not extensively used as the active materials for such devices due to their poor ionic conductivity and wettability. In this work, CBs were oxidized by a process of refluxing with conc. HNO3 for 6-72 h, providing oxidized CBs (OCBs) with different oxygen-containing groups (i.e., carboxyl, hydroxyl, and carbonyl) and contents. The OCBs refluxed for 12 h have ca. 2.0-fold higher accessible active surface area than that of the pristine CBs. The as-fabricated symmetric supercapacitor using OCBs refluxed for 12 h with a [BMP][DCA] ionic liquid electrolyte exhibits specific energy and maximum specific power of 88 Wh kg-1 and 8429 W kg-1, respectively with the capacitance retention over 97% after 6000 cycles. A single coin-cell supercapacitor prototype fully charged can supply electrical power to a red LED over 24 min. This device may be practically used as a battery replacement in high power applications

Polysulfide Filter and Dendrite Inhibitor: Highly Graphitized Wood Framework Inhibits Polysulfide Shuttle and Lithium Dendrites in Li–S Batteries

The design and manufacture of advanced materials based on biomaterials provide new opportunities to solve many technological challenges. In this work, a highly graphitized wood framework (GWF) with a porous tunnel structure and microvilli is constructed as a multifunctional interlayer to improve the electrochemical performance of lithium–sulfur (Li–S) batteries. The GWF not only retains the 3D transport network of wood, but also offers increased deposition sites for polysulfides through the microvilli which grow on the inner surfaces of the carbon tunnels. Electrochemical tests show that GWF effectively enhances the initial discharge capacity of the Li–S battery to 1593 mAh g−1 at 0.05 C, with a low capacity decline of 0.06% per cycle at 1 C. Besides, the GWF interlayer also effectively protects lithium anodes from corrosion by Sx2−, thus they still keep their metallic luster and clean surface even after long charge-discharge cycles. These enhancements are attributed to the high conductivity, abundant microvilli, and tunnel confinement effects of GWF, which effectively inhibit the shuttle effect of polysulfides by the same principle as nose hairs filtering the air. This work presents a new understanding of bionic/biomaterials and a new strategy to improve the performance of Li–S batteries