Encapsulation of Metal Oxide Nanocrystals into Porous Carbon with Ultrahigh Performances in Lithium-Ion Battery

A simple and industrial scalable approach was developed to encapsulate metal oxide nanocrystals into porous carbon (PC) with a high distribution. With this method, the composite of PC-metal oxide were prepared in a large amount with a low cost; particularly they exhibit ultrahigh performances in lithium-ion battery applications. For example, the PC-CoO_<i>x</i> and PC-FeO_<i>x</i> show a high capacity around 1021 mA h g^–1 and 1200 mA h g^–1 at the current density of 100 mA g^–1 respectively, together with an excellent cycling ability (>400 cycles) and rate capacity even at the high current densities of 3 A g^–1 and 5 A g^–1

Ruthenium-Based Electrocatalysts Supported on Reduced Graphene Oxide for Lithium-Air Batteries

Ruthenium-based nanomaterials supported on reduced graphene oxide (rGO) have been investigated as air cathodes in non-aqueous electrolyte Li-air cells using a TEGDME-LiCF₃SO₃ electrolyte. Homogeneously distributed metallic ruthenium and hydrated ruthenium oxide (RuO₂·0.64H₂O), deposited exclusively on rGO, have been synthesized with average size below 2.5 nm. The synthesized hybrid materials of Ru-based nanoparticles supported on rGO efficiently functioned as electrocatalysts for Li₂O₂ oxidation reactions, maintaining cycling stability for 30 cycles without sign of TEGDME-LiCF₃SO₃ electrolyte decomposition. Specifically, RuO₂·0.64H₂O-rGO hybrids were superior to Ru-rGO hybrids in catalyzing the OER reaction, significantly reducing the average charge potential to ∼3.7 V at the high current density of 500 mA g^–1 and high specific capacity of 5000 mAh g^–1

Improvement of Electrochemical Properties of Lithium–Oxygen Batteries Using a Silver Electrode

Silver (Ag) electrodes are prepared by an electrodeposition method at −0.25 V versus SCE. To evaluate the effect of particle size on Li–air cells, deposition times are 3, 10, 30, and 300 s. When cycled at a current density of 0.032 mA cm^–2, the Ag-deposited electrode for 300 s shows very low polarization corresponding to the oxygen evolution reaction potential at 3.6 V. X-ray diffraction studies confirm that the main discharge product is Li₂O₂, and the results of scanning electron microscopy and transmission electron microscopy of the discharged electrodes show lithium peroxides at different positions due to the limitation of active sites on silver particles

A Metal-Free, Lithium-Ion Oxygen Battery: A Step Forward to Safety in Lithium-Air Batteries

A preliminary study of the behavior of lithium-ion-air battery where the common, unsafe lithium metal anode is replaced by a lithiated silicon–carbon composite, is reported. The results, based on X-ray diffraction and galvanostatic charge–discharge analyses, demonstrate the basic reversibility of the electrochemical process of the battery that can be promisingly cycled with a rather high specific capacity

Influence of Temperature on Lithium–Oxygen Battery Behavior

In this Letter we report an electrochemical and morphological study of the response of lithium–oxygen cells cycled at various temperatures, that is, ranging from −10 to 70 °C. The results show that the electrochemical process of the cells is thermally influenced in an opposite way, that is, by a rate decrease, due to a reduced diffusion of the lithium ions from the electrolyte to the electrode interface, at low temperature and a rate enhancement, due to the decreased electrolyte viscosity and consequent increased oxygen mobility, at high temperature. In addition, we show that the temperature also influences the crystallinity of lithium peroxide, namely of the product formed during cell discharge

Study on the Catalytic Activity of Noble Metal Nanoparticles on Reduced Graphene Oxide for Oxygen Evolution Reactions in Lithium–Air Batteries

Among many challenges present in Li–air batteries, one of the main reasons of low efficiency is the high charge overpotential due to the slow oxygen evolution reaction (OER). Here, we present systematic evaluation of Pt, Pd, and Ru nanoparticles supported on rGO as OER electrocatalysts in Li–air cell cathodes with LiCF₃SO₃–tetra­(ethylene glycol) dimethyl ether (TEGDME) salt-electrolyte system. All of the noble metals explored could lower the charge overpotentials, and among them, Ru-rGO hybrids exhibited the most stable cycling performance and the lowest charge overpotentials. Role of Ru nanoparticles in boosting oxidation kinetics of the discharge products were investigated. Apparent behavior of Ru nanoparticles was different from the conventional electrocatalysts that lower activation barrier through electron transfer, because the major contribution of Ru nanoparticles in lowering charge overpotential is to control the nature of the discharge products. Ru nanoparticles facilitated thin film-like or nanoparticulate Li₂O₂ formation during oxygen reduction reaction (ORR), which decomposes at lower potentials during charge, although the conventional role as electrocatalysts during OER cannot be ruled out. Pt-and Pd-rGO hybrids showed fluctuating potential profiles during the cycling. Although Pt- and Pd-rGO decomposed the electrolyte after electrochemical cycling, no electrolyte instability was observed with Ru-rGO hybrids. This study provides the possibility of screening selective electrocatalysts for Li–air cells while maintaining electrolyte stability