Rechargeable Li-ion full batteries based on one-dimensional Li-rich Li1.13Mn0.26Ni0.61O2 cathode and nitrogen-doped carbon-coated NiO anode materials.

To meet the increasing requirements of lithium-ion batteries (LIBs) as energy sources for mobile electronic devices and electric vehicles, great efforts are being made to develop cathode and anode materials with high specific capacity and lifetime stability. Herein, we report a Li-rich one-dimensional (1D) Li1.13Mn0.26Ni0.61O2 (0.3Li2MnO3·0.7LiNiO2, LMO@LNO) cathode and a nitrogen-doped carbon-decorated NiO (NC@NiO) anode material prepared from 1D Ni(OH)2 nanowires (NWs) for application in full LIBs. The as-prepared 1D Li-rich LMO@LNO cathode displays a high discharge capacity (184.4 mA h g-1), high coulombic efficiency (73.9%), long-term cyclability, and good rate performance in comparison with pristine LiNiO2 (LNO). Moreover, the 1D NC@NiO composite anode exhibits a high discharge capacity (914.5 mA h g-1), high coulombic efficiency (76.8%), long cycling life, and better rate performance, as compared with bare NiO. A full LIB consisting of the nanostructured Li-rich LMO@LNO cathode and the NC@NiO anode delivers a high capacity of over 167.9 mA h g-1 between 4.0 and 0.1 V. These enhanced electrochemical characteristics suggest that the full LIB configuration with 1D Li-rich LMO@LNO and NC@NiO composites holds promise as a next-generation secondary battery platform.

An N-doped porous carbon network with a multidirectional structure as a highly efficient metal-free catalyst for the oxygen reduction reaction.

Metal-free catalysts have gained substantial attention as a promising candidate to replace the expensive platinum (Pt) catalysts for the oxygen reduction reaction (ORR) which is a key process in low temperature fuel cells. Development of highly efficient and mass-producible N-doped carbon catalysts, however, remains to be a great challenge. In this study, N-doped porous carbon (NPC) materials were synthesized via a simple, cost-effective and scalable method for mass production by using the d-gluconic acid sodium salt, pyrrole, Triton X-100 and KOH. The resulting NPC possessed a multidirectional porous carbon network (SBET: 1026.6 m2 g-1, Vt: 1.046 cm3 g-1) with hierarchical porosity and plenty of graphitic N species (49.1%). Electrochemical tests showed that the NPC itself was highly active for the ORR under alkaline and acidic conditions via a four electron pathway for the complete reduction of O2 in water. More importantly, this NPC catalyst demonstrated better performance than commercial Pt/C catalysts in terms of long-term durability and methanol tolerance under both conditions.

Honeycomb-Like Nitrogen-Doped Carbon 3D Nanoweb@Li2 S Cathode Material for Use in Lithium Sulfur Batteries.

Current lithium-ion batteries have a low theoretical capacity that is insufficient for use in emerging electric vehicles and energy-storage systems. The development of lithium-sulfur batteries utilizing Li2 S cathodes would be a promising option to overcome the capacity limitation. In this work, new three-dimensional (3D) honeycomb-like N-doped carbon nanowebs (HCNs) have been synthesized through a facile aqueous solution route for use as a cathode material in lithium-sulfur batteries. The Li2 S@HCNs cathode delivers a high discharge capacity of approximately 815 mAh g-1 after 65 cycles at 0.1 C, along with a superior rate capacity of approximately 568 mAh g-1 even at 2 C. The outstanding electrochemical rate performance is ascribed to their unique 3D honeycomb-like nanoweb structure, consisting of nanowires derived from polypyrrole. These properties greatly enhance the electrochemical reaction kinetics by providing efficient electron pathways and hollow channels for electrolyte transport. Nitrogen doping in the carbon nanowebs also considerably improves the chemisorption properties by tuning affinity between sulfur and oxygen functional groups on the carbon framework. The simple synthesis strategy and the resulting unique electrode structure could present a new avenue in nanostructure research for high-performance lithium-sulfur batteries.

Bifunctional Hybrid Catalysts with Perovskite LaCo0.8Fe0.2O3 Nanowires and Reduced Graphene Oxide Sheets for an Efficient Li-O2 Battery Cathode.

In this paper, bifunctional catalysts consisting of perovskite LaCo0.8Fe0.2O3 nanowires (LCFO NWs) with reduced graphene oxide (rGO) sheets were prepared for use in lithium-oxygen (Li-O2) battery cathodes. The prepared LCFO@rGO composite was explored as a cathode catalyst for Li-O2 batteries, resulting in an outstanding discharge capacity (ca. 7088.2 mAh g-1) at the first cycle. Moreover, a high stability of the O2-cathode with the LCFO@rGO catalyst was achieved over 56 cycles under the capacity limit of 500 mAh g-1 with a rate of 200 mA g-1, as compared to the Ketjenblack carbon and LCFO NWs. The enhanced electrochemical performance suggests that these hybrid composites of perovskite LCFO NWs with rGO nanosheets could be a perspective bifunctional catalyst for the cathode oxygen reduction and oxygen evolution reactions in the development of next-generation Li-O2 battery cathodes.

Fabrication of three-dimensional ordered macroporous spinel CoFe2O4 as efficient bifunctional catalysts for the positive electrode of lithium-oxygen batteries.

Three-dimensionally ordered macroporous (3DOM) CoFe2O4 (CFO) catalysts were prepared by using the colloidal crystal templating method to be used as bifunctional catalysts of Li-O2 battery positive electrodes. In order to study the relationship between the macropore diameter and charge/discharge behavior, 3DOM CFO catalysts with two different pore diameters of 140 and 60 nm were prepared. The physicochemical properties of the 3DOM CFO catalysts were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. When the 3DOM CFO catalyst with a pore diameter of 140 nm (CFO@140) was used in the O2-electrode of Li-O2 batteries, it exhibited a substantially enhanced discharge capacity (ca. 11 658.5 mA h g-1) in the first cycle. Moreover, the Li-O2 cells with the CFO@140 catalyst showed cycling stability over 47 cycles at a limited capacity of 500 mA h g-1 with a reduced potential polarization of 1.13 V, as compared with that with Ketjen Black carbon and the 3DOM CFO of 60 nm pore diameter (CFO@60). Their high cycling stability, low overpotential, high round-trip efficiency, and high rate performance suggest that these 3DOM CFO catalysts could be promising O2-electrode catalysts for next-generation lithium-oxygen batteries.

Ultrathin amorphous α-Co(OH)2 nanosheets grown on Ag nanowire surfaces as a highly active and durable electrocatalyst for oxygen evolution reaction.

Ultrathin α-Co(OH)2 nanosheets, prepared via simple hydrolysis at room temperature, were directly grown on Ag nanowires. The catalyst exhibited improved activity for the oxygen evolution reaction, with a reduced onset overpotential (220 mV) and superior durability because of the enhanced electron conductivity and stability of Ag nanowires in alkaline media.

Exploring the effects of the size of reduced graphene oxide nanosheets for Pt-catalyzed electrode reactions.

Pt-supported reduced graphene oxide (Pt/RGO) catalysts were prepared over the RGO sheets with different sizes for methanol oxidation and oxygen reduction reactions in acidic media. The Pt on the smaller RGO presented higher catalytic activities than the Pt on the larger RGO and the commercial Pt/C catalyst.

MnCo2O4 nanowires anchored on reduced graphene oxide sheets as effective bifunctional catalysts for Li-O2 battery cathodes.

A hybrid composite system of MnCo2 O4 nanowires (MCO NWs) anchored on reduced graphene oxide (RGO) nanosheets was prepared as the bifunctional catalyst of a Li-O2 battery cathode. The catalysts can be obtained from the hybridization of one-dimensional MCO NWs and two-dimensional RGO nanosheets. As O2 -cathode catalysts for Li-O2 cells, the MCO@RGO composites showed a high initial discharge capacity (ca. 11092.1 mAh gcarbon (-1) ) with a high rate performance. The Li-O2 cells could run for more than 35 cycles with high reversibility under a limited specific capacity of 1000 mAh gcarbon (-1) with a low potential polarization of 1.36 V, as compared with those of pure Ketjenblack and MCO NWs. The high cycling stability, low potential polarization, and rate capability suggest that the MCO@RGO composites prepared here are promising catalyst candidates for highly reversible Li-O2 battery cathodes.