Doron Aurbach

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

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 todays 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.

Prototype systems for rechargeable magnesium batteries.

The thermodynamic properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries, because it may provide a considerably higher energy density than the commonly used lead–acid and nickel–cadmium systems. Moreover, in contrast to lead and cadmium, magnesium is inexpensive, environmentally friendly and safe to handle. But the development of Mg batteries has been hindered by two problems. First, owing to the chemical activity of Mg, only solutions that neither donate nor accept protons are suitable as electrolytes; but most of these solutions allow the growth of passivating surface films, which inhibit any electrochemical reaction. Second, the choice of cathode materials has been limited by the difficulty of intercalating Mg ions in many hosts. Following previous studies of the electrochemistry of Mg electrodes in various non-aqueous solutions, and of a variety of intercalation electrodes, we have now developed rechargeable Mg battery systems that show promise for applications. The systems comprise electrolyte solutions based on Mg organohaloaluminate salts, and MgxMo 3S4 cathodes, into which Mg ions can be intercalated reversibly, and with relatively fast kinetics. We expect that further improvements in the energy density will make these batteries a viable alternative to existing systems.

A short review of failure mechanisms of lithium metal and lithiated graphite anodes in liquid electrolyte solutions

Abstract Li electrodes in any relevant electrolyte solution (i.e., polar aprotic) are covered by surface films of a very complicated structure. It was found that even in cases where the surface films formed on lithium contain elastomers, or where the lithium metal reactivity is reduced by doping with elements such as N, As, Al, Mg, Ca, etc., it is impossible to achieve sufficient passivation with lithium electrodes and liquid solutions. Passivation is considerably worsened when Li electrodes are operated at high rates (especially at high charging, Li deposition rates). Thus, there is no way that rechargeable Li batteries can compete with Li-ion batteries in any application that requires high charging rates (e.g., in powering portable electronic devices). The electrochemical behavior of lithiated graphite electrodes also depends on passivation phenomena. The surface films formed on lithiated graphite are similar to those formed on Li metal in the same solutions. The volume changes of graphite electrodes during Li insertion–deinsertion are small enough to enable their reasonable passivation in a variety of electrolyte solutions. A critical factor that determines the stability of graphite electrodes is their morphology. It was found that the shape of graphite particles plays a key role in their application as active mass in anodes for Li-ion batteries.

On the Surface Chemical Aspects of Very High Energy Density, Rechargeable Li–Sulfur Batteries

Li(metal)-sulfur (Li-S) systems are among the rechargeable batteries of the highest possible energy density due to the high capacity of both electrodes. The surface chemistry developed on Li electrodes in electrolyte solutions for Li-S batteries was rigorously studied using Fourier transform infrared and X-ray photoelectron spectroscopies. A special methodology was developed for handling the highly reactive Li samples. It was possible to analyze the contribution of solvents such as 1-3 dioxolane, the electrolyte LiN(SO 2 CF 3 ) 2 , polysulfide (Li 2 S n ), and LiNO 3 additives to protective surface films that are formed on the Li electrodes. The role of LiNO 3 as a critical component whose presence in solutions prevents a shuttle mechanism that limits the capacity of the sulfur electrodes is discussed and explained herein.

On the correlation between surface chemistry and performance of graphite negative electrodes for Li ion batteries

This paper discusses some important aspects of the correlation between surface chemistry, 3D structure, and the electrochemical behavior of lithiated graphite electrodes. By reviewing results obtained with diAerent electrolyte solutions (e.g. ethylene carbonate-based solutions, propylene carbonate solutions, and ether-based systems), we describe the stabilization and capacity fading mechanisms of graphite electrodes. One of the failure mechanisms occurs at potentials >0.5 V Li/Li + , and relates to an increase in the electrode’s impedance due to improper passivation and a simultaneous change in the electrode’s morphology, probably due to gas formation. At low potentials (depending on the electrolyte solution involved), phenomena such as exfoliation and amorphization of the graphite electrodes can be observed. Stabilization mechanisms are also discussed. In general, surface stabilization of the graphite is essential for obtaining reversible lithiation and a long electrode cycle life. The latter usually relates to precipitation of highly compact and insoluble surface species, which adhere well, and irreversibly, to the active surface. Hence, the choice of appropriate electrolyte solutions in terms of solvents, salts and additives is very critical for the use of graphite anodes in Li batteries. The major analytical tools for this study included FTIR and impedance spectroscopies, XPS, and in situ and ex situ XRD in conjunction with standard electrochemical techniques. # 1999 Elsevier Science Ltd. All rights reserved.

Sulfur‐Impregnated Activated Carbon Fiber Cloth as a Binder‐Free Cathode for Rechargeable Li‐S Batteries

A route for the preparation of binder-free sulfur-carbon cathodes is developed for lithium sulfur batteries. The method is based on the impregnation of elemental sulfur into the micropores of activated carbon fibers. These electrodes demonstrate good electrochemical performance at high current density attributed to the uniform dispersion of sulfur inside the carbon fiber.

On the use of vinylene carbonate (VC) as an additive to electrolyte solutions for Li-ion batteries

Vinylene carbonate (VC) was tested as an additive to electrolyte solutions for Li-ion batteries. For the model electrodes, synthetic graphite was chosen as the anode material, while LiMn2O4 spinel and LiNiO2 were chosen as the cathode materials. The test solution was 1 M LiAsF6 in a 1:1 mixture of ethylene and dimethyl carbonates (EC–DMC). Cyclic voltammetry (CV), chronopotentiometry, impedance spectroscopy, electrochemical quartz crystal microbalance (EQCM), FTIR and X-ray photoelectron spectroscopies have been used in this study. It was found that VC is a reactive additive that reacts on both the anode and the cathode surfaces. The influence of this additive on the behavior of Li–graphite anodes is very positive, since it improves their cyclability, especially at elevated temperatures, and reduces the irreversible capacity. The spectroscopic studies indicate that VC polymerizes on the lithiated graphite surfaces, thus forming poly alkyl Li-carbonate species that suppress both solvent and salt anion reduction. The presence of VC in solutions reduces the impedance of the LiMn2O4 and LiNiO2 cathodes at room temperature. However, we have not yet found any pronounced impact of VC on the cycling behavior of the cathodes, either at room temperature or at elevated temperatures. Thus, VC can be considered as a desirable additive for the anode side in Li-ion batteries, one which has no adverse effect on the cathode side.

Common electroanalytical behavior of Li intercalation processes into graphite and transition metal oxides

This paper compares the electroanalytical behavior of lithiated graphite, Li x CoO 2 , Li x NiO 2 , and Li x Mn 2 O 4 spinel electrodes. Slow scan rate cyclic voltammetry (SSCV), potentiostatic intermittent titration (PITT), and electrochemical impedance spectroscopy (EIS) were applied in order to study the potentiodynamic behavior, the variation of the solid-state diffusion coefficient, and the impedance of these electrodes. In addition, X-ray diffractometry and Fourier transform infrared (FTIR) spectroscopy were used in order to follow structural and surface chemical changes of these electrodes upon cycling. It was found that all four types of electrodes behave very similarly. Their SSCV are characterized by narrow peaks which may reflect phase transition between intercalation stages, and the potential-dependent Li chemical diffusion coefficient is a function with sharp minima in the vicinity of the CV peak potentials, in which the differential electrode capacity is maximal. The impedance spectra of these electrodes reflect an overall process of various steps in series. These include Li + ion migration through surface films, charge transfer which depends strongly on the potential, solid-state diffusion and, finally, accumulation of the intercalants in their sites in the bulk of the active mass, which appears as a strongly potential-dependent, low-frequency capacitive element. It is demonstrated that the above electroanalytical response, which can be considered as the electrochemical fingerprint of these electrodes, may serve as a good in situ tool for the study of capacity fading mechanisms.

A review of advanced and practical lithium battery materials

Presented herein is a discussion of the forefront in research and development of advanced electrode materials and electrolyte solutions for the next generation of lithium ion batteries. The main challenge of the field today is in meeting the demands necessary to make the electric vehicle fully commercially viable. This requires high energy and power densities with no compromise in safety. Three families of advanced cathode materials (the limiting factor for energy density in the Li battery systems) are discussed in detail: LiMn1.5Ni0.5O4 high voltage spinel compounds, Li2MnO3–LiMO2 high capacity composite layered compounds, and LiMPO4, where M = Fe, Mn. Graphite, Si, LixTOy, and MO (conversion reactions) are discussed as anode materials. The electrolyte is a key component that determines the ability to use high voltage cathodes and low voltage anodes in the same system. Electrode–solution interactions and passivation phenomena on both electrodes in Li-ion batteries also play significant roles in determining stability, cycle life and safety features. This presentation is aimed at providing an overall picture of the road map necessary for the future development of advanced high energy density Li-ion batteries for EV applications.

Solid‐State Electrochemical Kinetics of Li‐Ion Intercalation into Li1 − x CoO2: Simultaneous Application of Electroanalytical Techniques SSCV, PITT, and EIS

The electroanalytical behavior of thin electrodes is elucidated by the simultaneous application of three electroanalytical techniques: slow‐scan‐rate cyclic voltammetry (SSCV), potentiostatic intermittent titration technique, and electrochemical impedance spectroscopy. The data were treated within the framework of a simple model expressed by a Frumkin‐type sorption isotherm. The experimental SSCV curves were well described by an equation combining such an isotherm with the Butler‐Volmer equation for slow interfacial Li‐ion transfer. The apparent attraction constant was −4.2, which is characteristic of a quasi‐equilibrium, first‐order phase transition. Impedance spectra reflected a process with the following steps: ion migration in solution, ion migration through surface films, strongly potential‐dependent charge‐transfer resistance, solid‐state diffusion, and accumulation of the intercalants into the host materials. An excellent fit was found between these spectra and an equivalent circuit, including a Voigt‐type analog ( migration through multilayer surface films and charge transfer) in series with a finite‐length Warburg‐type element ( solid‐state diffusion), and a capacitor (Li accumulation). In this paper, we compare the solid‐state diffusion time constants and the differential intercalation capacities obtained by the three electroanalytical techniques.