High Energy Density Rechargeable Batteries Research Articles

A facile approach using MgCl2 to formulate high performance Mg2+ electrolytes for rechargeable Mg batteries

Rechargeable Mg batteries have been regarded as a viable battery technology for grid scale energy storage and transportation applications. However, the limited performance of Mg2+ electrolytes has been a primary technical hurdle to develop high energy density rechargeable Mg batteries. In this study, MgCl2 is demonstrated as a non-nucleophilic and cheap Mg2+ source in combination with Al Lewis acids (AlCl3, AlPh3 and AlEtCl2) to formulate a series of Mg2+ electrolytes, representing the simplest method to prepare Mg2+ conductive electrolytes (no precursor synthesis, free of recrystallization and giving quantitative yield). These electrolytes are characterized by high oxidation stability (up to 3.4 V vs. Mg), improved electrophile compatibility and electrochemical reversibility (up to 100% coulombic efficiency). Three electrolyte systems (MgCl2–AlCl3, MgCl2–AlPh3, and MgCl2–AlEtCl2) were fully characterized by multinuclear NMR (1H, 27Al{1H} and 25Mg{1H}) spectroscopies and electrochemical analysis. Single crystal X-ray diffraction and NMR studies consistently established molecular structures of the three electrolytes sharing a common Mg2+-dimer mono-cation, [(μ-Cl)3Mg2(THF)6]+, along with an anion (AlCl4−, AlPh3Cl− and AlEtCl3− respectively). Clean and dendrite free Mg bulk plating and viable battery performance were validated through representative studies using the MgCl2–AlEtCl2 electrolyte. The reaction mechanism of MgCl2 and the Al Lewis acids in THF is discussed to highlight the formation of the electrochemically active [(μ-Cl)3Mg2(THF)6]+ dimer mono-cation in these electrolytes and their improved performance compared to reported electrolytes using nucleophilic Mg2+ sources.

A High Energy Density Rechargeable Zinc-Air Battery for Automotive Application

not Available.

The electrochemistry of activated carbonaceous materials: past, present, and future

Carbonaceous materials are widely used in electrochemistry. All allotropic forms of carbons—graphite, glassy carbon, amorphous carbon, fullerenes, nanotubes, and doped diamond—are used as important electrode materials in all fields of modern electrochemistry. Examples include graphite and amorphous carbons as anode materials in high-energy density rechargeable Li batteries, porous carbon electrodes in sensors and fuel cells, nano-amorphous carbon as a conducting agent in many kinds of composite electrodes (e.g., cathodes based on intercalation inorganic host materials for batteries), glassy carbon and doped diamond as stable robust and high stability electrode materials for all aspects of basic electrochemical studies, and more. Amorphous carbons can be activated to form very high specific surface area (yet stable) electrode materials which can be used for electrostatic energy storage and conversion [electrical double-layer capacitors (EDLC)] and separation techniques based on electro-adsorption, such as water desalination by capacitive de-ionization (CDI). Apart from the many practical aspects of activated carbon electrodes, there are many highly interesting and important basic aspects related to their study, including transport phenomena, molecular sieving behavior, correlation between electrochemical behavior and surface chemistry, and more. In this article, we review several important aspects related to these electrode materials, in a time perspective (past, present, and future), with the emphasis on their importance to EDLC devices and CDI processes.

Structural Analysis of Electrolyte Solutions for Rechargeable Mg Batteries by Stereoscopic Means and DFT Calculations

We present a rigorous analysis of unique, wide electrochemical window solutions for rechargeable magnesium batteries, based on aromatic ligands containing organometallic complexes. These solutions are comprised of the transmetalation reaction products of Ph(x)MgCl(2-x) and Ph(y)AlCl(3-y) in different proportions, in THF. In principle, these reactions involve the exchange of ligands between the magnesium and the aluminum based compounds, forming ionic species and neutral molecules, such as Mg(2)Cl(3)(+)·6THF, MgCl(2)·4THF, and Ph(y)AlCl(4-y)(-) (y = 0-4). The identification of the equilibrium species in the solutions is carried out by a combination of Raman spectroscopy, multinuclear NMR, and single-crystal XRD analyses. The association of the spectroscopic results with explicit identifiable species is supported by spectral analyses of specially synthesized reference compounds and DFT quantum-mechanical calculations. The correlation between the identified solution equilibrium species and the electrochemical anodic stability window is investigated. This study advances both development of new nonaqueous solution chemistry and possible development of high-energy density rechargeable Mg batteries.

A Novel High Energy Density Rechargeable Lithium-Air Battery

not Available.

Nanocomposite electrode materials for high energy density rechargeable lithium batteries

The manganese and chromium oxide nanocomposite electrode materials were synthesized by redox reactions using transition metal powders in solutions. The layered Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)] O2 (x= 0.054, 0.0142, 0.147 and 0.311) materials having α-NaFeO2 (R-3 m) structure were prepared by solid-state reactions with LiOH and the pre-prepared manganese and chromium precursors. The amount of chromium, after removing the traces of Li2CrO4 from the prepared samples, is found to increase with temperature. The Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)] O2 material with x = 0.147 exhibits a high discharge capacity of 280 mAh g− 1 in the first cycle and a good reversible capacity of about 250 mAh g− 1 when cycled in the voltage range 2.0–4.9 V. Whereas, the Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)]O2 material with x = 0.311 delivers a very low initial discharge capacity of 98 mAh g−1, which is found to be increased up to a discharge capacity of about 260 mAh g− 1 at the 30th cycling. This drastic increase in capacity is attributed to the redox couples of Cr+ 4/Cr+ 6 and Cr+3/Cr+4.

On the thermal behavior of Li bis(oxalato)borate LiBOB

The lithium salt, bis(oxalato)borate, LiBC 4O 8 (LiBOB), is one of the most important Li salts which are explored today in connection with R & D of novel, high energy density rechargeable Li batteries. The thermal stability of this salt in the temperature range of 40–350 °C was rigorously studied by accelerating rate calorimetry (ARC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). XRD, FTIR, SEM, and ICP were used to analyze the products of its thermal decomposition reactions. Studies by DSC and pressure measurements during ARC experiments with LiBOB detected an endothermic reaction with an onset at ∼293 °C, involving a complete irreversible decomposition of the LiBOB in which gaseous products are formed. In the first stage, Li 2C 2O 4 (crystalline), B 2O 3 (glass), CO and CO 2 gases are formed in both confined and open volumes. The next (final) stage in the thermal reactions is an irreversible formation of lithium triborate LiB 3O 5 (glass).

Gel polymer electrolyte lithium-ion cells with improved low temperature performance

For a number of NASA's future planetary and terrestrial applications, high energy density rechargeable lithium batteries that can operate at very low temperature are desired. In the pursuit of developing Li-ion batteries with improved low temperature performance, we have also focused on assessing the viability of using gel polymer systems, due to their desirable form factor and enhanced safety characteristics. In the present study we have evaluated three classes of promising liquid low-temperature electrolytes that have been impregnated into gel polymer electrolyte carbon-LiMn 2O 4-based Li-ion cells (manufactured by LG Chem. Inc.), consisting of: (a) binary EC + EMC mixtures with very low EC-content (10%), (b) quaternary carbonate mixtures with low EC-content (16–20%), and (c) ternary electrolytes with very low EC-content (10%) and high proportions of ester co-solvents (i.e., 80%). These electrolytes have been compared with a baseline formulation (i.e., 1.0 M LiPF 6 in EC + DEC + DMC (1:1:1%, v/v/v), where EC, ethylene carbonate, DEC, diethyl carbonate, and DMC, dimethyl carbonate). We have performed a number of characterization tests on these cells, including: determining the rate capacity as a function of temperature (with preceding charge at room temperature and also at low temperature), the cycle life performance (both 100% DOD and 30% DOD low earth orbit cycling), the pulse capability, and the impedance characteristics at different temperatures. We have obtained excellent performance at low temperatures with ester-based electrolytes, including the demonstration of >80% of the room temperature capacity at −60 °C using a C/20 discharge rate with cells containing 1.0 M LiPF 6 in EC + EMC + MB (1:1:8%, v/v/v) (MB, methyl butyrate) and 1.0 M LiPF 6 in EC + EMC + EB (1:1:8%, v/v/v) (EB, ethyl butyrate) electrolytes. In addition, cells containing the ester-based electrolytes were observed to support 5 C pulses at −40 °C, while still maintaining a voltage >2.5 V at 100 and 80% state-of-charge (SOC).

Improved low-temperature performance of lithium-ion cells with quaternary carbonate-based electrolytes

In order to enable future missions involving the exploration of the surface of Mars with Landers, and Rovers, NASA desires long life, high energy density rechargeable batteries which can operate well at very low temperature (down to −40 °C). Lithium-ion technology has been identified as being the most promising chemistry, due to high gravimetric and volumetric energy densities, as well as, long life characteristics. However, the state-of-art (SOA) technology is not sufficient to meet the needs of many applications that require excellent low-temperature capabilities. To further improve this technology, work at JPL has been focused upon developing electrolytes that result in lithium-ion cells with wider temperature ranges of operation. These efforts have led to the identification of a number of ternary and quaternary, all carbonate-based electrolytes that have been demonstrated to result in improved low-temperature performance in experimental three-electrode MCMB–carbon/LiNi 0.8Co 0.2O 2 cells. A number of electrochemical characterization techniques were performed on these cells (i.e. Tafel polarization measurements, linear polarization measurements, and electrochemical impedance spectroscopy (EIS)) to further enhance our understanding of the performance limitations at low temperature. The most promising electrolyte formulations, namely 1.0 M LiPF 6 EC+DEC+DMC+EMC (1:1:1:2 v/v) and 1.0 M LiPF 6 EC+DEC+DMC+EMC (1:1:1:3 v/v), were incorporated into SAFT prototype DD-size (9 Ah) lithium-ion cells for evaluation. A number of electrical tests were performed on these cells, including rate characterization as a function of temperature, cycle life characterization at different temperatures, as well as, many mission specific characterization tests to determine their viability to enable future missions to Mars. Excellent performance was observed with the prototype DD-size cells over a wide temperature range (−50 to 40 °C), with high specific energy being delivered at very low temperatures (i.e. over 95 Wh/kg being delivered at −40 °C using a C/10 discharge rate).

COLLOID CHEMICAL APPROACH TO THE CONSTRUCTION OF HIGH ENERGY DENSITY RECHARGEABLE LITHIUM - ION BATTERIES

The layer-by-layer self-assembly of poly(diallyldimethyl-ammonium) chloride, PDDA; graphite oxide, G, nanoplatelets; and polyethylene oxide, PEO, onto transparent indium tin oxide substrates, S, have provided cationic working electrodes which, with lithium wires as reference and counter electrodes, functioned as high energy density rechargeable lithium-ion batteries. Specifically, very high specific capacities (1232 and 1134 mAh.g−1) have been determined for batteries which had positive electrodes of ten sandwich layers of self-assembled films: S-(PDDA/GO/PEO)10 and S-(PDDA/PEO)10. The importance of the exfoliating GO into nanoplatelets and the colloid chemistry of self-assembly are discussed.

D-Electrons and two active thin film devices for achieving a solar energy economy

Abstract In this paper, the marriage of condensed matter science and solar energy technologies will be illustrated by two closely related active thin film devices, a variable reflectivity electrochromic window and a high energy density rechargeable (or secondary) thin film battery. Each device can significantly assist in achieving a solar energy economy. The primary focus of this paper is the important role of d-electrons in two candidate thin film materials, tungsten oxide and lithium cobalt oxide, that could be utilized in one or in both the devices, respectively.

Advanced rechargeable sodium batteries with novel cathodes

Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium-sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 W h kg −1 theoretical). Energy densities in excess of 180 W h kg −1 have been realized in practical batteries. More recently, cathodes other than sulfur are being evaluated. We, at JPL, are evaluating various new cathode materials for use in high energy density sodium batteries for advanced space applications. Our approach is to carry out basic electrochemical studies of these materials in a sodium cell configuration in order to understand their fundamental behaviors. Thus far, our studies have focussed on alternative metal chlorides such as CuCl 2 and organic cathode materials such as TCNE.