Ali Abouimrane

A New Class of Lithium and Sodium Rechargeable Batteries Based on Selenium and Selenium–Sulfur as a Positive Electrode

A new class of selenium and selenium-sulfur (Se(x)S(y))-based cathode materials for room temperature lithium and sodium batteries is reported. The structural mechanisms for Li/Na insertion in these electrodes were investigated using pair distribution function (PDF) analysis. Not only does the Se electrode show promising electrochemical performance with both Li and Na anodes, but the additional potential for mixed Se(x)S(y) systems allows for tunable electrodes, combining the high capacities of S-rich systems with the high electrical conductivity of the d-electron containing Se. Unlike the widely studied Li/S system, both Se and Se(x)S(y) can be cycled to high voltages (up to 4.6 V) without failure. Their high densities and voltage output offer greater volumetric energy densities than S-based batteries, opening possibilities for new energy storage systems that can enable electric vehicles and smart grids.

Chemically active reduced graphene oxide with tunable C/O ratios

Organic dispersions of graphene oxide can be thermally reduced in polar organic solvents under reflux conditions to afford electrically conductive, chemically active reduced graphene oxide (CARGO) with tunable C/O ratios, dependent on the boiling point of the solvent. The reductions are achieved after only 1 h of reflux, and the corresponding C/O ratios do not change upon further thermal treatment. Hydroxyl and carboxyl groups can be removed when the reflux is carried out above 155 °C, while epoxides are removable only when the temperature is higher than 200 °C. The increasing hydrophobic nature of CARGO, as its C/O ratio increases, improves the dispersibility of the nanosheets in a polystyrene matrix, in contrast to the aggregates formed with CARGO having lower C/O ratios. The excellent processability of the obtained CARGO dispersions is demonstrated via free-standing CARGO papers that exhibit tunable electrical conductivity/chemical activity and can be used as lithium-ion battery anodes with enhanced Coulombic efficiency.

(De)Lithiation Mechanism of Li/SeSx (x = 0–7) Batteries Determined by in Situ Synchrotron X-ray Diffraction and X-ray Absorption Spectroscopy

Electrical energy storage for transportation has gone beyond the limit of converntional lithium ion batteries currently. New material or new battery system development is an alternative approach to achieve the goal of new high-energy storage system with energy densities 5 times or more greater. A series of SeSx-carbon (x = 0-7) composite materials has been prepared and evaluated as the positive electrodes in secondary lithium cells with ether-based electrolyte. In situ synchrotron high-energy X-ray diffraction was utilized to investigate the crystalline phase transition during cell cycling. Complementary, in situ Se K-edge X-ray absorption near edge structure analysis was used to track the evolution of the Se valence state for both crystalline and noncrystalline phases, including amorphous and electrolyte-dissolved phases in the (de)lithiation process. On the basis of these results, a mechanism for the (de)lithiation process is proposed, where Se is reduced to the polyselenides, Li2Sen (n ≥ 4), Li2Se2, and Li2Se sequentially during the lithiation and Li2Se is oxidized to Se through Li2Sen (n ≥ 4) during the delithiation. In addition, X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy demonstrated the reversibility of the Li/Se system in ether-based electrolyte and the presence of side products in the carbonate-based electrolytes. For Li/SeS2 and Li/SeS7 cells, Li2Se and Li2S are the discharged products with the presence of Se only as the crystalline phase in the end of charge.

Sodium insertion in carboxylate based materials and their application in 3.6 V full sodium cells

The sodium battery has the potential to be the next generation rechargeable system which utilizes cheaper and more abundant sodium material but affords nearly the same power as lithium batteries. One of the key barriers for the sodium battery is the lack of stable anode materials which can insert sodium ions reversibly at relatively low potential. This contribution reports the sodium insertion in a series of organic carboxylate based materials: (C8H4Na2O4), (C8H6O4), (C8H5NaO4), (C8Na2F4O4), (C10H2Na4O8), (C14H4O6) and (C14H4Na4O8) at low voltage (below 0.6 V vs. Na/Na+). These organic anode materials can insert reversibly up to 2 Na per molecule with good cycleability. The Na insertion mechanism was proposed and 3.6 V full sodium batteries were made and cycled reversibly at room temperature and at 55 °C.

Development of LiNi0.5Mn1.5O4 / Li4Ti5O12 System with Long Cycle Life

The electrochemical performance of LiNi{sub 0.5}Mn{sub 1.5}O{sub 4} (LNMO)/Li{sub 4}Ti{sub 5}O{sub 12} (LTO) cells with different designs, positive-electrode-limited, negative-electrode-limited, and positive/negative capacity ratio of {approx} (1) was investigated at different temperatures and current densities. Half-cells based on either LNMO/Li or LTO/Li exhibited an outstanding rate capability. When both electrodes were combined in a full cell configuration, the LNMO/LTO cells showed an excellent rate capability, with 86% discharge capacity retention at the 10C rate. Of the three designs, the negative-limited full cell showed the best cycling performance when discharged at the 2C rate in tests at room temperature: 98% capacity retention after 1000 cycles. The negative-limited full cell also exhibited excellent cycling characteristics in tests at 55 C: 95% discharge capacity retention after 200 cycles. These results clearly demonstrate that the LNMO/LTO system with a negative-limited design is attractive for plug-in hybrid electric vehicles, where a long cycle life and a reasonable power are needed.

Li–Se battery: absence of lithium polyselenides in carbonate based electrolyte

The lithiation mechanism of the Li-Se cell in a carbonate-based electrolyte is discussed. It is found that Se is directly reduced to Li2Se in discharge without intermediate phases detected by in situ X-ray diffraction or X-ray absorption spectroscopy. The reason is that the redox products Se and Li2Se, as well as lithium polyselenides are insoluble in the electrolyte.

Exfoliation and reassembly of cobalt oxide nanosheets into a reversible lithium-ion battery cathode

An exfoliation-reassembly-activation (ERA) approach to lithium-ion battery cathode fabrication is introduced, demonstrating that inactive HCoO(2) powder can be converted into a reversible Li(1-x) H(x) CoO(2) thin-film cathode. This strategy circumvents the inherent difficulties often associated with the powder processing of the layered solids typically employed as cathode materials. The delamination of HCoO(2) via a combination of chemical and mechanical exfoliation generates a highly processable aqueous dispersion of [CoO(2) ](-) nanosheets that is critical to the ERA approach. Following vacuum-assisted self-assembly to yield a thin-film cathode and ion exchange to activate this material, the generated cathodes exhibit excellent cyclability and discharge capacities approaching that of low-temperature-prepared LiCoO(2) (~83 mAh g(-1) ), with this good electrochemical performance attributable to the high degree of order in the reassembled cathode.

Electrically Conductive Ultrananocrystalline Diamond-Coated Natural Graphite-Copper Anode for New Long Life Lithium-Ion Battery

Y.-W. Cheng, C.-P. Liu Department of Materials Science and Engineering National Cheng Kung University No. 1, University Road Tainan 70101 , Taiwan C.-K. Lin, A. Abouimrane, Z. Chen Chemical Sciences and Engineering Division Argonne National Laboratory 9700 South Cass Avenue, Argonne IL 60439–4837 , USA Y.-C. Chu, Prof. Y. Tzeng Institute of Microelectronics Department of Electrical Engineering National Cheng Kung University No. 1, University Road Tainan 70101 , Taiwan E-mail: tzengyo@mail.ncku.edu.tw Y. Ren X-Ray Science Division Argonne National Laboratory 9700 South Cass Avenue, Argonne IL 60439–4837 , USA Orlando Auciello Materials Science & Eng Department and Bioengineering Department University of Texas-Dallas 800 W. Campbell Rd., RL10 Richardson , TX 75080–3021 , USA E-mail: orlando.auciello@utdallas.edu

Improved cyclability of a lithium–sulfur battery using POP–Sulfur composite materials

The microporous nature of the porous organic polymer (POP) successfully limits the crystallization of sulfur and hence restrains the dissolution and diffusion of lithium polysulfides formed during the repeated charge and discharge process of lithium–sulfur batteries. In this study, we demonstrated for the first time that a POP–sulfur nanocomposite can lead to high coulombic efficiency and superior reversibility in lithium–sulfur batteries.

Probing cation intermixing in Li2SnO3

Li2MnO3 holds great promise as a key component for lithium-manganese-rich oxides as high-capacity and high-energy-density cathode materials for lithium-ion batteries. However, its structural complexity remains an unresolved puzzle, hindering the further development of this class of cathode materials. In this work, the structure of Li2SnO3 was investigated as a model of Li2MnO3. Specifically, the structural evolution of materials during the solid-state synthesis of Li2SnO3 was studied using in situ high-energy X-ray diffraction. It was confirmed that Li2SnO3 with a C2/c structure was formed using the solid-state process. However, the severe intralayer intermixing between Li and Sn was found to lead to several weakening or vanishing reflection peaks.