Jean-Marie Tarascon

Issues and challenges facing rechargeable lithium batteries.

Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges that remain regarding the synthesis, characterization, electrochemical performance and safety of these systems.

Building better batteries.

Researchers must find a sustainable way of providing the power our modern lifestyles demand.

Electrical Energy Storage for the Grid: A Battery of Choices

The increasing interest in energy storage for the grid can be attributed to multiple factors, including the capital costs of managing peak demands, the investments needed for grid reliability, and the integration of renewable energy sources. Although existing energy storage is dominated by pumped hydroelectric, there is the recognition that battery systems can offer a number of high-value opportunities, provided that lower costs can be obtained. The battery systems reviewed here include sodium-sulfur batteries that are commercially available for grid applications, redox-flow batteries that offer low cost, and lithium-ion batteries whose development for commercial electronics and electric vehicles is being applied to grid storage.

Nanomaterials for Rechargeable Lithium Batteries

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.

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

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.

On the Origin of the Extra Electrochemical Capacity Displayed by MO/Li Cells at Low Potential

and thegrowth of a polymer/gel-like film at high and low potentials, respectively, is extremely sensitive to cycling voltage ranges with thebest results obtained when the cells are fully discharged. The low-voltage process is quite reversible over the 0.02 to 1.8 V rangewith a sustained capacity of about 150 mAh/g over a few hundred cycles. Within such a range of potential the polymer/gel-like isbarely evolving while it vanishes as the oxidation potential is increased above 2 V. From the cyclic-voltammogram profiles weconclude that the origin of the low-voltage capacity is nested in the pseudocapacitive character of thein situ made polymeric/gelfilm. Tentative explanations based on comparisons with existing literature are made to explain such an unusual finding.© 2002 The Electrochemical Society. @DOI: 10.1149/1.1467947# All rights reserved.Manuscript submitted July 2, 2001; revised manuscript received November 14, 2001. Available electronically April 2, 2002.

Synthesis conditions and oxygen stoichiometry effects on Li insertion into the spinel LiMn[sub 2]O[sub 4]

Using a new electrolyte composition which is stable against oxidation up to 5 V, the full electrochemical deintercalation of lithium from the spinel LiMn[sub 2]O[sub 4], is studied. The origin of two new reversible oxidation-reduction peaks near 4.5 and 4.9 V are examined. The capacity associated with these peaks depends on both the nominal composition x in Li[sub x]Mn[sub 2]O[sub 4] and the synthesis conditions (annealing temperatures and cooling rates), and thereby can be used as an indicator for electrochemically optimized LiMn[sub 2]O[sub 4] powders. The authors present evidence that these peaks are related to local structural defects. Thermogravimetric measurements (TGA) on Li[sub x]Mn[sub 2]O[sub 4] powders show a reversible loss of oxygen that can reach 5% at 1,000 C. The authors find that some of this weight loss is associated with the conversion of cubic LiMn[sub 2]O[sub 4] to a new tetragonal spinel phase and then to the decomposition of this phase into the orthorhombic LiMnO[sub 2] phase plus other products. This new tetragonal LiMn[sub 2]O[sub 4] spinel is prepared as a single phase, and its electrochemical properties are reported.

CoO[sub 2], The End Member of the Li[sub x]CoO[sub 2] Solid Solution

While has been widely studied in the past 15 years as a promising positive electrode material in lithium‐ion batteries, suprisingly, many questions are still unanswered concerning the electrochemical characteristics of the lithium intercalation material. Among these is the existence of an end member phase on complete lithium deintercalation. The use of dry plastic lithium‐ion battery technology has allowed the construction of an in situ x‐ray diffraction cell which allows structural characterization of at x values at and close to 0 for the first time. Instead of the expected destruction of the core structure of by a drastic increase in structural disorder, an increase in crystallographic quality occurred as x approached 0. For the first time, the end member phase was isolated. This phase is a hexagonal single‐layered phase (O1) believed to be isostructural with and has lattice parameters of a = 2.822 A and c = 4.29 A. The phase converted immediately back to a three‐layer (O3) delithiated type phase on lithium reinsertion. Electrochemical studies show that 95% of lithium can be reinserted back into the structure on complete delithiation and reversible cycling properties are maintained when cycled back to 4.2 V.

Particle Size Effects on the Electrochemical Performance of Copper Oxides toward Lithium

The electrochemical reactivity of tailor-made Cu 2 O or CuO powders prepared according to the polyol process was tested in rechargeable Li cells. To our surprise, we demonstrated that CuO, a material well known for primary Li cells, and Cu 2 O could reversibly react with 1.1 Li and 2 Li ions per formula unit, respectively, leading to reversible capacities as high as 400 mAh/g in the 3-0.02 V range. The ability of copper oxide-based Li cells to retain their capacity upon numerous cycles was found to be strongly dependent on the particle size, and the best results (100% of the total capacity up to 70 cycles) were obtained with I μm Cu 2 O and CuO particles. Ex situ transmission electron microscopy data and in situ X-ray experiments show that the reduction mechanism of Cu 2 O by Li first involved the formation of Cu nanograins dispersed into a lithia (Li 2 O) matrix, followed by the growth of an organic coating that partially dissolved upon the subsequent charge while Cu converted hack to Cu 2 O nanograins. We believe that the key to the reversible reactivity mechanism of copper oxides or other transition metal oxides toward Li is the electrochemically driven formation of highly reactive metallic nanograins during the first discharge, which enables the formation-decomposition of Li 2 O upon subsequent cycles.

Conjugated dicarboxylate anodes for Li-ion batteries.

Present Li-ion batteries for portable electronics are based on inorganic electrodes. For upcoming large-scale applications the notion of materials sustainability produced by materials made through eco-efficient processes, such as renewable organic electrodes, is crucial. We here report on two organic salts, Li(2)C(8)H(4)O(4) (Li terephthalate) and Li(2)C(6)H(4)O(4)(Li trans-trans-muconate), with carboxylate groups conjugated within the molecular core, which are respectively capable of reacting with two and one extra Li per formula unit at potentials of 0.8 and 1.4 V, giving reversible capacities of 300 and 150 mA h g(-1). The activity is maintained at 80 degrees C with polyethyleneoxide-based electrolytes. A noteworthy advantage of the Li(2)C(8)H(4)O(4) and Li(2)C(6)H(4)O(4) negative electrodes is their enhanced thermal stability over carbon electrodes in 1 M LiPF(6) ethylene carbonate-dimethyl carbonate electrolytes, which should result in safer Li-ion cells. Moreover, as bio-inspired materials, both compounds are the metabolites of aromatic hydrocarbon oxidation, and terephthalic acid is available in abundance from the recycling of polyethylene terephthalate.