Electrolytes and interphases in Li-ion batteries and beyond.

Energy-storage technologies, including electrical double-layer capacitors and rechargeable batteries, have attracted significant attention for applications in portable electronic devices, electric vehicles, bulk electricity storage at power stations, and “load leveling” of renewable sources, such as solar energy and wind power. Transforming lithium batteries and electric double-layer capacitors requires a step change in the science underpinning these devices, including the discovery of new materials, new electrochemistry, and an increased understanding of the processes on which the devices depend. The Review will consider some of the current scientific issues underpinning lithium batteries and electric double-layer capacitors.

Challenges Facing Lithium Batteries and Electrical Double‐Layer Capacitors

Haegyeom Kim,†,∥ Jihyun Hong,†,∥ Kyu-Young Park,†,∥ Hyungsub Kim,†,∥ Sung-Wook Kim, and Kisuk Kang*,†,‡ †Department of Materials Science and Engineering, Research Institute of Advanced Materials (RIAM), Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea ‡Center for Nanoparticle Research, Institute for Basic Science (IBS), Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul 151-742, Republic of Korea Nuclear Fuel Cycle Development Group, Korea Atomic Energy Research Institute, 989-111 Daedeok-daero, Yuseong-gu, Daejeon 305-353, Republic of Korea

Aqueous Rechargeable Li and Na Ion Batteries

Lithium-excess manganese layered oxides, which are commonly described by the chemical formula zLi2MnO3−(1 − z)LiMeO2 (Me = Co, Ni, Mn, etc.), are of great importance as positive electrode materials for rechargeable lithium batteries. In this Article, LixCo0.13Ni0.13Mn0.54O2−δ samples are prepared from Li1.2Ni0.13Co0.13Mn0.54O2 (or 0.5Li2MnO3−0.5LiCo1/3Ni1/3Mn1/3O2) by an electrochemical oxidation/reduction process in an electrochemical cell to study a reaction mechanism in detail before and after charging across a voltage plateau at 4.5 V vs Li/Li+. Changes of the bulk and surface structures are examined by synchrotron X-ray diffraction (SXRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), and time-of-flight secondary ion mass spectroscopy (SIMS). SXRD data show that simultaneous oxygen and lithium removal at the voltage plateau upon initial charge causes the structural rearrangement, including a cation migration process from metal to lithium layers, which is also supported ...

Detailed Studies of a High-Capacity Electrode Material for Rechargeable Batteries, Li2MnO3−LiCo1/3Ni1/3Mn1/3O2

Understanding reactions at the electrode/electrolyte interface (EEI) is essential to developing strategies to enhance cycle life and safety of lithium batteries. Despite research in the past four decades, there is still limited understanding by what means different components are formed at the EEI and how they influence EEI layer properties. We review findings used to establish the well-known mosaic structure model for the EEI (often referred to as solid electrolyte interphase or SEI) on negative electrodes including lithium, graphite, tin, and silicon. Much less understanding exists for EEI layers for positive electrodes. High-capacity Li-rich layered oxides yLi2–xMnO3·(1–y)Li1–xMO2, which can generate highly reactive species toward the electrolyte via oxygen anion redox, highlight the critical need to understand reactions with the electrolyte and EEI layers for advanced positive electrodes. Recent advances in in situ characterization of well-defined electrode surfaces can provide mechanistic insights an...

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Electrode–Electrolyte Interface in Li-Ion Batteries: Current Understanding and New Insights

The effect of vinylene carbonate (VC) as electrolyte additive on the formation mechanisms of passivation films covering both electrodes in lithium-ion batteries was investigated by X-ray photoelectron spectroscopy (XPS). LiCo O2 /graphite coin cells using a LiP F6 /ethylene carbonate:diethyl carbonate:dimethyl carbonate liquid electrolyte with or without VC were charged at 20 and 60°C. The identification of VC-derived products formed at the surface of the electrodes was carried out by a dual experimental/theoretical approach. From a classical XPS core peak analysis completed by a detailed interpretation and simulation of valence spectra supported by ab initio calculations, and through direct synthesis of the VC polymer, we could evidence the formation of the radical poly(VC) at the electrode/electrolyte interfaces. We showed that the radical polymerization is the main reaction mechanism of VC contributing to the formation of the passivation layers at the surface of both electrodes. © 2008 The Electrochemical Society.

The Effect of Vinylene Carbonate Additive on Surface Film Formation on Both Electrodes in Li-Ion Batteries

The impact of aluminum oxide coatings on LiCoO2 materials for commercial lithium ion batteries has been investigated by X-ray photoelectron spectroscopy (XPS). A low binding energy component in the Al 2p core peak spectra was observed and attributed to the formation of a LiAlx Co(1-x) O2 solid solution interphase for both Al2 O3 - and AlPO4 -coated LiCoO2. The surface chemistry of pristine and Al2 O3 -coated LiCoO2 cathodes and graphite anodes have been investigated after cycling up to 4.2 V or 4.4 V cutoff voltage and after various levels of capacity fade. The Al2 O3 coating enhances the capacity retention at both 4.2 V and 4.4 V cutoff voltages. XPS analyses provided evidence of the inhibition of cobalt dissolution from the LiCoO2 positive electrode by the aluminum coatings. Moreover, the Al2 O3 coating lowers the kinetics of degradation of electrolyte species, especially the LiPF6 salt. © 2007 The Electrochemical Society.

XPS Study on Al2O3- and AlPO4-Coated LiCoO2 Cathode Material for High-Capacity Li Ion Batteries

Vinylene carbonate (VC) is a commonly used electrolyte additive in Li-ion batteries because of its beneficial role on the formation of the solid electrolyte interphase. It was shown to contribute to surface film formation on both electrodes of LiCoO 2 /C cells via its radical polymerization mechanism. In this paper, we carried out a comparative study of the role of VC on electrode/electrolyte interfaces in LiCoO 2 /C, LiFePO 4 /C, and L'CoO 2 /Li 4 Ti 5 O 12 systems, in which the potential and the chemical nature of each electrode are changed. Coin-cells were charged at different potentials using a LiPF 6 /ethylene carbonate: diethyl carbonate: dimethyl carbonate liquid electrolyte with or without VC, and the electrodes were analyzed by X-ray photoelectron spectroscopy. We showed there is no interaction between the negative and positive electrodes in the VC polymerization mechanisms, for example, by exchange of chemical species from one electrode to the other, during the first charge. Separate mechanisms occur, although the same VC polymer is deposited at the surface of both electrodes.

L. El Ouatani

Papers

The Effect of Vinylene Carbonate Additive on Surface Film Formation on Both Electrodes in Li-Ion Batteries

XPS Study on Al2O3- and AlPO4-Coated LiCoO2 Cathode Material for High-Capacity Li Ion Batteries

Effect of Vinylene Carbonate Additive in Li-Ion Batteries: Comparison of LiCoO2 ∕ C , LiFePO4 ∕ C , and LiCoO2 ∕ Li4Ti5O12 Systems