Li-ion batteries have transformed portable electronics and will play a key role in the electrification of transport. However, the highest energy storage possible for Li-ion batteries is insufficient for the long-term needs of society, for example, extended-range electric vehicles. To go beyond the horizon of Li-ion batteries is a formidable challenge; there are few options. Here we consider two: Li-air (O(2)) and Li-S. The energy that can be stored in Li-air (based on aqueous or non-aqueous electrolytes) and Li-S cells is compared with Li-ion; the operation of the cells is discussed, as are the significant hurdles that will have to be overcome if such batteries are to succeed. Fundamental scientific advances in understanding the reactions occurring in the cells as well as new materials are key to overcoming these obstacles. The potential benefits of Li-air and Li-S justify the continued research effort that will be needed.

Li-O2 and Li-S batteries with high energy storage.

Each cell of a battery stores electrical energy as chemical energy in two electrodes, a reductant (anode) and an oxidant (cathode), separated by an electrolyte that transfers the ionic component of the chemical reaction inside the cell and forces the electronic component outside the battery. The output on discharge is an external electronic current I at a voltage V for a time Δt. The chemical reaction of a rechargeable battery must be reversible on the application of a charging I and V. Critical parameters of a rechargeable battery are safety, density of energy that can be stored at a specific power input and retrieved at a specific power output, cycle and shelf life, storage efficiency, and cost of fabrication. Conventional ambient-temperature rechargeable batteries have solid electrodes and a liquid electrolyte. The positive electrode (cathode) consists of a host framework into which the mobile (working) cation is inserted reversibly over a finite solid–solution range. The solid–solution range, which is...

The Li-ion rechargeable battery: a perspective.

2.1. Solvents 4307 2.1.1. Propylene Carbonate (PC) 4308 2.1.2. Ethers 4308 2.1.3. Ethylene Carbonate (EC) 4309 2.1.4. Linear Dialkyl Carbonates 4310 2.2. Lithium Salts 4310 2.2.1. Lithium Perchlorate (LiClO4) 4311 2.2.2. Lithium Hexafluoroarsenate (LiAsF6) 4312 2.2.3. Lithium Tetrafluoroborate (LiBF4) 4312 2.2.4. Lithium Trifluoromethanesulfonate (LiTf) 4312 2.2.5. Lithium Bis(trifluoromethanesulfonyl)imide (LiIm) and Its Derivatives 4313

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Nonaqueous liquid electrolytes for lithium-based rechargeable batteries.

Li-ion battery technology has become very important in recent years as these batteries show great promise as power sources that can lead us to the electric vehicle (EV) revolution. The development of new materials for Li-ion batteries is the focus of research in prominent groups in the field of materials science throughout the world. Li-ion batteries can be considered to be the most impressive success story of modern electrochemistry in the last two decades. They power most of today's portable devices, and seem to overcome the psychological barriers against the use of such high energy density devices on a larger scale for more demanding applications, such as EV. Since this field is advancing rapidly and attracting an increasing number of researchers, it is important to provide current and timely updates of this constantly changing technology. In this review, we describe the key aspects of Li-ion batteries: the basic science behind their operation, the most relevant components, anodes, cathodes, electrolyte solutions, as well as important future directions for R&D of advanced Li-ion batteries for demanding use, such as EV and load-leveling applications.

Challenges in the development of advanced Li-ion batteries: a review

Energy storage is more important today than at any time in human history. Future generations of rechargeable lithium batteries are required to power portable electronic devices (cellphones, laptop computers etc.), store electricity from renewable sources, and as a vital component in new hybrid electric vehicles. To achieve the increase in energy and power density essential to meet the future challenges of energy storage, new materials chemistry, and especially new nanomaterials chemistry, is essential. We must find ways of synthesizing new nanomaterials with new properties or combinations of properties, for use as electrodes and electrolytes in lithium batteries. Herein we review some of the recent scientific advances in nanomaterials, and especially in nanostructured materials, for rechargeable lithium-ion batteries.

Nanomaterials for rechargeable lithium batteries

It is suggested that in practical nonaqueous battery systems the alkali and alkaline earth metals are always covered by a surface layer which is instantly formed by the reaction of the metal with the electrolyte. This layer, which acts as an interphase between the metal and the solution, has the properties of a solid electrolyte. The corrosion rate of the metal, the mechanism of the deposition‐dissolution process, the kinetic parameters, the quality of the metal deposit, and the half‐cell potential depend on the character of the solid electrolyte interphase (SEI).

https://iopscience.iop.org/article/10.1149/1.2128859/pdf

The Electrochemical Behavior of Alkali and Alkaline Earth Metals in Nonaqueous Battery Systems—The Solid Electrolyte Interphase Model

https://iopscience.iop.org/article/10.1149/2.1441707jes/pdf

Review—SEI: Past, Present and Future

Recent studies show that the SEI on lithium and on anodes in liquid nonaqueous solutions consists of many different materials including , LiF, LiCl, , alkoxides, and nonconducting polymers. The equivalent circuit for such a mosaic‐type SEI electrode is extremely complex. It is shown that near room temperature the grain‐boundary resistance (Rgb) for polyparticle solid electrolytes is larger than the bulk ionic resistance. Up to now, all models of SEI electrodes ignored the contribution of Rgb to the overall SEI resistance. We show here that this neglect has no justification. On the basis of recent results, we propose here for SEI electrodes equivalent circuits which take into account the contribution of grain‐boundary and other interfacial impedance terms. This model accounts for a variety of different types of Nyquist plots reported for lithium and electrodes in liquid nonaqueous and polymer electrolytes.

https://iopscience.iop.org/article/10.1149/1.1837858/pdf

Advanced Model for Solid Electrolyte Interphase Electrodes in Liquid and Polymer Electrolytes

The redox processes of at a glassy carbon electrode in THF was studied by programmed cyclic voltammetry in the range of +1300 to −2000 mV (vs. polysulfide reference electrode) at sweep rates of 2–200 mV/s. One anodic and up to three cathodic peaks were detected. The anodic peak seems to result from the oxidation of all PS's through the same intermediate to elemental sulfur. The first cathodic peak is caused by the reduction of all PS to in a diffusion controlled reaction. The second reduction peak most likely arises from the reduction of to . This is apparently preceded by a chemical step. The third reduction peak is caused by the reduction of to or S2− or a mixture of both in a diffusion‐controlled reaction. The high Tafel slope of the third peak apparently results from passivation of the electrode by the precipitation of and .

https://iopscience.iop.org/article/10.1149/1.2095868/pdf

Lithium Sulfur Battery Oxidation/Reduction Mechanisms of Polysulfides in THF Solutions

The effects of mild oxidation (burning) of 2 synthetic graphites on the reversible (Q{sub R}) and irreversible (Q{sub IR}) capacities, anode-degradation rate (on cycling) in three different electrolytes and graphite-surface topology have been studied. STM images of both modified graphites show nanochannels having an opening of a few nanometers and up to tens of nanometers. It is believed that these nanochannels are formed at the zigzag and armchair faces between two adjacent crystallites and in the vicinity of defects and impurities. Mild burn-off was found to improve performance in Li/Li{sub x}C cells: Q{sub R} is increased by 10--30%, Q{sub IR} is generally decreased (for less than 6% burn-off) and Li{sub x}C{sub 6} anode degradation rate is much lower. Performance improvement is attributed to the formation of a solid electrolyte interface (SEI) chemically bonded to the surface carboxylic groups at the zigzag and armchair faces, and to accommodation of extra lithium at the zigzag, armchair, and other edge sites and nanovoids.

Emanuel Peled

Papers

The Electrochemical Behavior of Alkali and Alkaline Earth Metals in Nonaqueous Battery Systems—The Solid Electrolyte Interphase Model

Review—SEI: Past, Present and Future

Advanced Model for Solid Electrolyte Interphase Electrodes in Liquid and Polymer Electrolytes

Lithium Sulfur Battery Oxidation/Reduction Mechanisms of Polysulfides in THF Solutions

Improved Graphite Anode for Lithium‐Ion Batteries Chemically Bonded Solid Electrolyte Interface and Nanochannel Formation