Jin-Bum Park

Aprotic and Aqueous Li–O2 Batteries

Li−O2 Batteries Jun Lu,† Li Li,‡ Jin-Bum Park, Yang-Kook Sun,* Feng Wu,*,‡ and Khalil Amine*,†,∥ †Chemical Sciences and Engineering Division, Argonne National Laboratory, 9700 South Cass Avenue, Lemont, Illinois 60439, United States ‡Beijing Key Laboratory of Environmental Science and Engineering, School of Chemical Engineering and the Environment, Beijing Institute of Technology, Beijing 100081, China Department of Energy Engineering, Hanyang University, Seoul 133-791, South Korea Chemistry Department, Faculty of Science, King Abdulaziz University, 80203 Jeddah, Saudi Arabia

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).

Understanding the behavior of Li–oxygen cells containing LiI

Mankind has been in an unending search for efficient sources of energy. The coupling of lithium and oxygen in aprotic solvents would seem to be a most promising direction for electrochemistry. Indeed, if successful, this system could compete with technologies such as the internal combustion engine and provide an energy density that would accommodate the demands of electric vehicles. All this promise has not yet reached fruition because of a plethora of practical barriers and challenges. These include solvent and electrode stability, pronounced overvoltage for oxygen evolution reactions, limited cycle life and rate capability. One of the approaches suggested to facilitate the oxygen evolution reactions and improve rate capability is the use of redox mediators such as iodine for the fast oxidation of lithium peroxide. In this paper we have examined LiI as an electrolyte and additive in Li oxygen cells with ethereal electrolyte solutions. At high concentrations of LiI, the presence of the salt promotes a side reaction that forms LiOH as a major product. In turn, the presence of oxygen facilitates the reduction of I3− to 3I− in these systems. At very low concentrations of LiI, oxygen is reduced to Li2O2. The iodine formed in the anodic reaction serves as a redox mediator for Li2O2 oxidation.

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.

Ordered Mesoporous Carbon Electrodes for Li–O2 Batteries

Ordered mesoporous carbon (OMC) with highly ordered pore channels was applied as an oxygen-side electrode for a Li-O2 battery. To evaluate the effect of the pore channel size on battery performance, we employed OMCs possessing two different pore sizes (6 and 17 nm). When cycled at a current density of 200 mA g(-1)carbon, the OMC electrodes reduced polarization in the oxygen evolution reaction by 0.1 V compared to those consisting of conventional super P carbon electrode. X-ray diffraction and transmission electron microscopy of the discharged oxygen electrodes provided evidence for the formation of amorphous Li2O2, a product of the oxygen reduction reaction, inside the OMC pores rather than on the electrode surface as in the case of the super P electrode. The OMC electrodes were also effective at high current densities (500 mA g(-1)carbon and 1000 mA g(-1)carbon).

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-CoOx and PC-FeOx 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).

Assembling metal oxide nanocrystals into dense, hollow, porous nanoparticles for lithium-ion and lithium–oxygen battery application

New dense hollow porous (DHP) metal oxide nanoparticles that are smaller than 100 nm and composed of Co3O4, FeOx, NiO and MnOx were prepared by densely assembling metal oxide nanocrystals based on the hard-template method using a carbon colloid as a sacrificial core. These nanoparticles are quite different from the traditional particles as their hollow interior originates from the stacking of nanocrystals rather than a spherical shell. The DHP nanoparticles preserve the intriguing properties of nanocrystals and possess desirable surface area and pore volume that enhance the active surface, which ultimately benefits applications such as lithium-ion batteries. The DHP Co3O4 nanoparticles demonstrated an enhanced capacity of 1168 mA h g(-1) at 100 mA g(-1)vs. 590 mA h g(-1) of powders and stable cycling performance greater than 250 cycles when used as an anode material. Most importantly, the electrochemical performance of DHP Co3O4 nanoparticles in a lithium-O2 battery was also investigated for the first time. A low charge potential of ∼4.0 V, a high discharge voltage near 2.74 V and a long cycle ability greater than 100 cycles at a delivered capacity of 2000 mA h g(-1) (current density, 200 mA g(-1)) were observed. The performances were considerably improved compared to recent results of mesoporous Co3O4, Co3O4 nanoparticles and a composite of Co3O4/RGO and Co3O4/Pd. Therefore, it would be promising to investigate such properties of DHP nanoparticles or other hollow metal (oxide) particles for the popular lithium-air battery.

Sodium salt effect on hydrothermal carbonization of biomass: a catalyst for carbon-based nanostructured materials for lithium-ion battery applications

The salt effect of NaxA (A = SO42−, Cl−, NO3−, etc.) on the hydrothermal carbonization of biomass is reported. It is a new catalyst and recyclable template to more simply and effectively prepare carbon-based materials, such as porous carbon-coated anode materials (e.g., Fe3O4@porous-C) in lithium-ion battery applications with enhanced performance.

A sustainable iron-based sodium ion battery of porous carbon–Fe3O4/Na2FeP2O7 with high performance

A type of porous carbon–Fe3O4 (e.g., PC–Fe3O4) composite with an industrially scalable production was introduced in the sodium ion battery application for the first time. The PC–Fe3O4 composite, consisting of highly dispersed Fe3O4 nanocrystals within the porous carbon with a relatively low weight percent of 45.5 wt%, could efficiently demonstrate high capacities of 225, 168, 127, 103, 98 and 90 mA h g−1 under the current densities of 50, 100, 200, 300, 400 and 500 mA g−1 with a good stability over 400 cycles. The utilization co-efficient of Fe3O4 nanocrystals was proven to be much higher than most of the Fe3O4 nanoparticles reported recently via the study of the capacity contribution of carbon originally. In addition, the robustness of electrode during the charge–discharge was well characterized by ex situ XRD and emission scanning electron microscopy (SEM). More importantly, a new concept of an elemental iron-based sodium ion battery of PC–Fe3O4/Na2FeP2O7 is presented. This is the first example to introduce an element-rich configuration in the sodium ion battery from the viewpoint of sustainability. The full battery demonstrated a superior capacity of 93 mA h g−1, high capacity retention of 93.3% over 100 cycles and work voltage around 2.28 V with the energy density of 203 W h kg−1. Such configuration of an iron-based sodium battery would be highly promising and sustainable owing to its low cost and high stability in grid storage.

Redox Mediators for Li–O2 Batteries: Status and Perspectives

Li-O2 batteries have received much attention due to their extremely large theoretical energy density. However, the high overpotentials required for charging Li-O2 batteries lower their energy efficiency and degrade the electrolytes and carbon electrodes. This problem is one of the main obstacles in developing practical Li-O2 batteries. To solve this problem, it is important to facilitate the oxidation of Li2 O2 upon charging by using effective electrocatalysis. Using solid catalysts is not too effective for oxidizing the electronically isolating Li-peroxide layers. In turn, for soluble catalysts, red-ox mediators (RMs) are homogeneously dissolved in the electrolyte solutions and can effectively oxidize all of the Li2 O2 precipitated during discharge. RMs can decompose solid Li2 O2 species no matter their size, morphology, or thickness and thus dramatically increase energy efficiency. However, some negative side effects, such as the shuttle reactions of RMs and deterioration of the Li-metal occur. Therefore, it is necessary to study the activity and stability of RMs in Li-O2 batteries in detail. Herein, recent studies related to redox mediators are reviewed and the mechanisms of redox reactions are illustrated. The development opportunities of RMs for this important battery technology are discussed and future directions are suggested.