Showing papers by "Christian M. Julien published in 2016"

Carbon nanotubes in Li-ion batteries: A review

Abstract: Portable-electronics epitomizing technological breakthrough in history of mankind, are universal reality thanks to rechargeable batteries. LIBs, lithium-ion batteries, owing to high-reversible capacity, high-power capability, good-safety, long-life and zero-memory effects are at the heart of this revolution. Nonetheless, longer-battery-life, higher-current- and power-density, better-safety, and flexibility, crucial for portables and hybrid-electric-vehicles further fuel the research to better their electrochemistry. Electrode materials are vital for performance of batteries. Recent developments in nanoscience and nanotechnology offer potential prospects to devise novel-nanostructured electrode materials for next-generation better-performing LIBs. Nanostructured materials are pivotal to these progresses due to their manageable surface-area, stunted mass and charge-diffusion span, and volume change acclimatization during charging/discharging. CNTs, carbon-nanotubes, with distinct 1D-tubular structure, excellent electrical and thermal conductivities, mechanical flexibility and significantly large surface-area, are considered ideal additives to enrich electrodes’ chemistry. Here, we observe contemporary developments in synthesis and characterization of CNTs and CNTs-based nanostructured composite-electrodes for utilization in LIBs.

Optimization of Layered Cathode Materials for Lithium-Ion Batteries

Abstract: This review presents a survey of the literature on recent progress in lithium-ion batteries, with the active sub-micron-sized particles of the positive electrode chosen in the family of lamellar compounds LiMO2, where M stands for a mixture of Ni, Mn, Co elements, and in the family of yLi2MnO3•(1 − y)LiNi½Mn½O2 layered-layered integrated materials. The structural, physical, and chemical properties of these cathode elements are reported and discussed as a function of all the synthesis parameters, which include the choice of the precursors and of the chelating agent, and as a function of the relative concentrations of the M cations and composition y. Their electrochemical properties are also reported and discussed to determine the optimum compositions in order to obtain the best electrochemical performance while maintaining the structural integrity of the electrode lattice during cycling.

Smart materials for energy storage in Li-ion batteries

Abstract: The natural inhabitants of the gastrointestinal tract play a key role in the maintenance of human health. Over the last century, the changes on the behavior of our modern society have impacted the diversity of this gut microbiome. Among the strategies to restore gut microbial homeostasis, the use of probiotics has received a lot of attention. Probiotics are living microorganisms that promote the host health when administered in adequate amounts. Its popularity increase in the marketplace in the last decade draws the interest of scientists in finding suitable methods capable of delivering adequate amounts of viable cells into the gastrointestinal tract. Encapsulation comes into the scene as an approach to enhance the cells survival during processing, storage and consumption. This paper provides a comprehensive perspective of the probiotic field at present time focusing on the academia and industry scenarios in the past few years in terms of encapsulation technologies employed and research insights including patents. The analysis of the encapsulation technologies considering food processing costs and payload of viable bacteria reaching the gastrointestinal tract would result into successful market novelties. There is yet a necessity to bridge the gap between academia and industry.

Composite anodes for lithium-ion batteries: status and trends

Abstract: Presently, the negative electrodes of lithium-ion batteries (LIBs) is constituted by carbon-based materials that exhibit a limited specific capacity 372 mAh g−1 associated with the cycle between C and LiC6. Therefore, many efforts are currently made towards the technological development nanostructured materials in which the electrochemical processes occurs as intercalation, alloying or conversion reactions with a good accommodation of dilatation/contraction during cycling. In this review, attention is focused on advanced anode composite materials based on carbon, silicon, germanium, tin, titanium and conversion anode composite based on transition-metal oxides.

Olivine-Based Blended Compounds as Positive Electrodes for Lithium Batteries

Abstract: Blended cathode materials made by mixing LiFePO4 (LFP) with LiMnPO4 (LMP) or LiNi1/3Mn1/3Co1/3O2 (NMC) that exhibit either high specific energy and high rate capability were investigated. The layered blend LMP–LFP and the physically mixed blend NMC–LFP are evaluated in terms of particle morphology and electrochemical performance. Results indicate that the LMP–LFP (66:33) blend has a better discharge rate than the LiMn1−yFeyPO4 with the same composition (y = 0.33), and NMC–LFP (70:30) delivers a remarkable stable capacity over 125 cycles. Finally, in situ voltage measurement methods were applied for the evaluation of the phase evolution of blended cathodes and gradual changes in cell behavior upon cycling. We also discuss through these examples the promising development of blends as future electrodes for new generations of Li-ion batteries.

Anodes for Li-Ion Batteries

Abstract: The active elements for negative (anode) electrodes are reviewed here according to the following sequence. First, the carbon anode is considered, since almost all the Li-ion batteries on the market are presently equipped with graphitic carbon. Then the next elements of the Mendeleev table (Si, Ge, …) are considered. Then the metal oxides have been divided according to the three different Li insertion processes that determines their advantages and disadvantages: intercalation, alloying/de-alloying, conversion reaction. Only the promising elements for the next generations of Li-ion batteries have been selected. Emphasis is made on the progress achieved the last 5 years, since the reader is guided to other reviews for elder works.

Cathode Materials with Two-Dimensional Structure

Abstract: This chapter is devoted to the role of layered structured materials, since they have peculiar properties of mixed conduction for electrons and ions, so that redox reaction can be delocalized in their volume, so that they can be used as active materials of electrodes. We present the relationship between structure and electrochemical features with special attention for materials currently used as positive electrode in lithium batteries for their high capability to host foreign ions. Different crystal chemistries are examined from the basic lithiated metal dioxides structure to the very sophisticated solid solutions or composites.

Fluoro-polyanionic Compounds

Abstract: In this chapter, we present the progress that allows several lithium-intercalation compounds to become the active cathode element of a new generation of Li-ion batteries, namely the materials with a poly-anion-based structure M x (XO4) y (M is a transition-metal cation and X = P, S), which are promising to improve the technology of energy storage and electric transportation, and address the replacement of gasoline engine by meeting the increasing demand for green energy power sources. The electrode materials considered here are fluorine-containing compounds including fluorophosphates LiMPO4F (M = V, Fe, T), Li2 M′PO4F (M = Fe, Co, Ni), hybrid ion Li x Na1−x VPO4F, and fluorosulfates LiMSO4F; M = Fe, Co, Ni, Mn, Zn, Mg). The electrochemical performance of these materials as the active cathode element of Li-ion batteries is also discussed.

Challenges and Issues Facing Lithium Metal for Solid State Rechargeable Batteries

Abstract: The commercial use of lithium metal batteries was delayed because of dendrite formation on the surface of the lithium electrode, and the difficulty finding a suitable electrolyte that has both the mechanical strength and ionic conductivity required for solid electrolytes. Recently, strategies have developed to overcome these difficulties, so that these batteries are currently an option for different applications, including electric cars. In this work, we review these strategies, and discuss the different routes that are promising for progress in the near future.

Electrolytes and Separators for Lithium Batteries

Abstract: The current commercial Li-ion batteries are based on organic liquids, i.e., ethyl carbonates that have a high dielectric constant and thus are good solvents for salts. They also show a fairly large electrochemical window of stability. However, these organic solvents have high vapor pressures and in case of accidental battery shorts or thermal runaway, can lead to fires and explosions. The objective of the present chapter is to summarize the state of the art of nonaqueous electrolytes with development on control the SEI formation, safety concerns with Li salts, protection against overcharge and fire retardants.

Polyanionic Compounds as Cathode Materials

Abstract: Polyanionic compounds have emerged as novel lithium insertion compounds and considered as the most advanced positive electrodes for the next generation of Li-ion batteries owing to their advantages with regard to low cost, non-toxicity, environmental friendliness, and high safety. From the safety view point, compared to metal-oxide cathodes, these materials rank number one, with a remarkable thermal stability and tolerance to overcharge and over-discharge. This chapter outlines the structural, physical, and electrochemical properties of lithium-phosphate compounds. Several aspects that are important for applications are discussed such as morphology upon synthesis, residual impurities and surface state of particles. These impurities are identified and a quantitative estimate of their concentrations is deduced from the combination of analytical methods. LiFePO4 has won the challenge to be the active element for the positive electrode of Li-ion batteries for electro-mobility. An optimized preparation provides materials with carbon-coated particles free of any impurity phase, insuring structural stability and electrochemical performance that justify the use of this material as a cathode element in new generation of lithium secondary batteries operating for powering hybrid electric vehicles and full electric vehicles.

Safety Aspects of Li-Ion Batteries

Abstract: The carbon-coated LiFePO4 Li-ion oxide cathode was studied for its electrochemical, thermal, and safety performance. This electrode exhibited a reversible capacity corresponding to more than 89 % of the theoretical capacity when cycled between 2.5 and 4.0 V. Cylindrical 18650 cells with carbon-coated LiFePO4 also showed good capacity retention at higher discharge rates up to 5C rate with 99.3 % coulombic efficiency, implying that the carbon coating improves the electronic conductivity. Hybrid pulse power characterization (HPPC) test performed on LiFePO4 18650 cell indicated the suitability of this carbon-coated LiFePO4 for high power HEV applications. The heat generation during charge and discharge at 0.5C rate, studied using an isothermal microcalorimeter (IMC), indicated cell temperature is maintained in near ambient conditions in the absence of external cooling. Thermal studies were also investigated by Differential Scanning Calorimeter (DSC) and Accelerating Rate Calorimeter (ARC), which showed that LiFePO4 is safer, upon thermal and electrochemical abuse, than the commonly used lithium metal oxide cathodes with layered and spinel structures. Safety tests, such as nail penetration and crush test, were performed on LiFePO4 and LiCoO2 cathode based cells, to investigate on the safety hazards of the cells upon severe physical abuse and damage.

Basic Elements for Energy Storage and Conversion

Abstract: Major challenges of the twenty-first century will concern the global climate change and dwindling fossil energy reserves that motivate to develop sustainable solutions based on renewable sources of energy. Because they are intermittent systems, accumulators of electric power are required. This chapter provides basic concept for the energy storage and conversion systems. Basic elements of technologies are also given, which make an introduction of the topics.

Nanotechnology for Energy Storage

Abstract: While lithium-ion batteries are currently the workhorses of portable electronics and power tools, the technology is just beginning to move up for power density applications such as electric drive vehicles and future energy storage options such as smart grids and back-up power systems. The later requires much higher charge rates that can be achieved to some extend by the use of nanomaterials. Two main reasons for electrochemical improvement are commonly evoked by designing electrode materials into the nanoscale domain: (1) the shorter diffusion lengths for the lithium ion across the active particle and (2) the increasing contact area between electrode and electrolyte. The purpose of this chapter is to draw attention to the technologies involved in the synthesis, layout and optimization of nano materials used as active components in Li-ion batteries. We present several nanostructured compounds such as lamellar compounds, manganese oxides and iron phosphates. Functional nanomaterials are also examined such are nanofibers, nanorods, nanocomposites, and nanocrystals.

Principles of Intercalation

Abstract: In this chapter, we describe the basic concept of intercalation applied to electrode materials for batteries. This phenomenon has attracted considerable attention in electrochemistry because of the use of intercalation compounds (ICs) as ion and electron exchangers in energy storage and conversion devices. The need for more efficient electrical energy storage devices has prompted research on new electrode materials. In lithium-ion batteries, positive and negative electrodes are ICs with electronic and ionic properties. The different classes of mechanism that controls the electrochemical reactions in galvanic cells are presented and the relationship structure-energy is examined.

Cathode Materials with Monoatomic Ions in a Three-Dimensional Framework

Abstract: The relationships between structural and electrochemical properties are examined for materials having three-dimensional (3D) structure for the diffusion paths for Li+ ions. Among the 3D lithium insertion compounds with M = manganese and vanadium cations, namely, binary M x O y and ternary LiM x O y phases are the most popular. A special emphasis to the different forms of spinel structures that are normal-spinel, defect-spinel, and doped-spinel frameworks are currently used as positive electrodes in high-power batteries for EVs.

Reliability of the Rigid-Band Model in Lithium Intercalation Compounds

Abstract: Numerous layered structured compounds are interesting materials in which lithium intercalation occurs primarily without destruction of the host lattice. In many cases a rigid band model is a useful first approximation for describing the changes in electronic properties of the host material with intercalation. We observed, nevertheless, that the rigid-band model is not applicable to all of the layered compounds. One may argue that the applicability of the rigid-band model may be taken as a test for the properties most desirable in a good intercalation material. This needs yet to be more extensively documented for their promising applications as insertion electrode in rechargeable lithium batteries. This chapter presents the applicability of the rigid-band model on intercalation compounds with a layered structure namely the transition-metal chalcogenides MX 2 (X = S, Se) and the transition-metal oxides LiMO2 (M = Co, Ni) as well.

Technology of the Li-Ion Batteries

Abstract: As we have seen in different chapters of this book, the electrodes are usually tested from half-cells consisting of lithium metal as the counter-electrode. This is a convenient tool to determine the irreversible capacity loss during the first and eventually the second cycle, the reversible capacity at available at different rates, the operating voltage. The properties of the full cell can then be anticipated from these data. The design of the batteries is dictated by different parameters that are reviewed in this chapter. The first one is the compatibility between the materials that are chosen for the two electrodes, according to the rules concerning the relative positions of their chemical potentials. We have detailed and explained these rules in Chap. 2, so we start here with electrodes which satisfy these compatibility rules allowing for the formation of a protective solid-electrolyte interface (SEI) layer at the surface of the negative electrode. The second most important parameter concerns the capacity of the electrodes.