Despite the imminent commercial introduction of Li-ion batteries in electric drive vehicles and their proposed use as enablers of smart grids based on renewable energy technologies, an intensive quest for new electrode materials that bring about improvements in energy density, cycle life, cost, and safety is still underway. This Progress Report highlights the recent developments and the future prospects of the use of phases that react through conversion reactions as both positive and negative electrode materials in Li-ion batteries. By moving beyond classical intercalation reactions, a variety of low cost compounds with gravimetric specific capacities that are two-to-five times larger than those attained with currently used materials, such as graphite and LiCoO(2), can be achieved. Nonetheless, several factors currently handicap the applicability of electrode materials entailing conversion reactions. These factors, together with the scientific breakthroughs that are necessary to fully assess the practicality of this concept, are reviewed in this report.

Beyond Intercalation-Based Li-Ion Batteries: The State of the Art and Challenges of Electrode Materials Reacting Through Conversion Reactions

Quest for Nonaqueous Multivalent Secondary Batteries: Magnesium and Beyond

The lithium/sulfur battery is a promising electrochemical system that has a high theoretical capacity of 1675 mAh g–1, but its discharge mechanism is well-known to be a complex multistep process. As the active material dissolves during cycling, this discharge mechanism was investigated through the electrolyte characterization. Using high-performance liquid chromatography, UV–visible absorption, and electron spin resonance spectroscopies, we investigated the electrolyte composition at different discharge potentials in a TEGDME-based electrolyte. In this study, we propose a possible mechanism for sulfur reduction consisting of three steps. Long polysulfide chains are produced during the first reduction step (2.4–2.2 V vs Li+/Li), such as S82– and S62–, as evidenced by UV and HPLC data. The S3•– radical can also be found in solution because of a disproportionation reaction. S42– is produced during the second reduction step (2.15–2.1 V vs Li+/Li), thus pointing out the gradual decrease of the polysulfide chai...

Lithium/Sulfur Cell Discharge Mechanism: An Original Approach for Intermediate Species Identification

Publisher Summary This chapter discusses the reduction potentials involving inorganic free radicals in aqueous solution. Because free radicals are usually transients, knowing their thermodynamic properties is primarily useful in mechanistic studies. Thus, the useful redox couples associated with a given free radical correspond to plausible elementary steps in reaction mechanisms. All potentials are expressed against the normal hydrogen electrode (NHE). Apart from the NHE, the standard state for all solutes is the unit molar solution at 25 °C. This violates the usual convention for species, such as O 2 that occur as gases, but because the rates of bimolecular reactions in solution are significant, the unit molar standard state is most convenient. The emphasis is on electron transfer reactions in which no bonds are formed or broken, electron transfer reactions in which concerted electron transfer and bond cleavage could occur, and certain atom transfer reactions. The chapter also presents a tabulation of ∆ f G ° values for all the radicals. A common approach in estimating the thermochemistry of aqueous free radicals is to use gas-phase data with approximations of solvation energies.

Reduction potentials involving inorganic free radicals in aqueous solution

Aluminum as anode for energy storage and conversion: a review

The electrochemistry of the , , and electrode phases in molten electrolyte at 400°C was studied using cyclic voltammetry at sweep rates of 0.02–1 mV/sec. Emf's, polarization characteristics, and nucleation overpotentials were obtained for each major electrode reaction; the anodic nucleation overpotentials increased with emf for all three electrodes. The disulfide electrodes lost sulfur during the extended cyclic‐voltammetry tests. These losses appear to be associated with a nonequilibrium species that is involved in the electrochemical formation of the disulfides from their precursors.

Reactions of FeS2, CoS2, and NiS2 Electrodes in Molten LiCl ‐ KCl Electrolytes

Syntheses are described for the isostructural 1T-M/sub 2/Cl/sub 2/C, M = Sc, Y, Zr, 1T-ml/sub 2/Cl/sub 2/N, M = Sc, Zr, and 1T-Zr/sub 2/Br/sub 2/C from normal-valent halide, metal, and either graphite, N/sub 2/, NaN/sub 3/, or ..beta..-ZrNCl at 750-1000 /sup 0/C in sealed Nb or Ta containers. All are formed in virtually quantitative yield save for Zr/sub 2/Cl/sub 2/N. The 1T-type structure, consisting of slabs of hcp layers sequenced X-M-M-X with C or N in trigonal-antiprismatic interstices between the double-metal layers, is related to that of ZrCl and ZrBr and is isostructural with Ta/sub 2/S/sub 2/C. The details of the structure were established from single-crystal studies of 1T-Sc/sub 2/Cl/sub 2/C and 1T-Sc/sub 2/Cl/sub 2/N (nitride:P3 m1, Z = 1, a = 3.3495 (4) A, C = 8.808 (1) A, R = 0.050 and R/sub w/ = 0.050 and R/sub w/ = 0.060 for 76 independent reflections, 2 theta < 50/sup 0/). Sc/sub 2/Cl/sub 2/C also occurs in a 3R-type arrangement of the same slabs. Alkali-metal intercalation of the scandium or zirconium chloride carbides was not successful. Reasons for the reordering of the ZrX host on bonding of interstitial C or N and XPS evidence for both the carbidic naturemore » of carbon and a large M-C covalency in Sc/sub 2/Cl/sub 2/C and Zr/sub 2/X/sub 2/C are presented. 33 references, 1 figure, 4 tables.« less

Synthesis and structure of double-metal-layered scandium, yttrium, and zirconium chloride carbides and nitrides, M2Cl2C and M2Cl2N

A new, inorganic low melting electrolyte with the composition LiAlCl/sub 4/-NaAlCl/sub 4/-NaAlBr/sub 4/-KAlCl/sub 4/ (3:2:3:2) (or equivalently LiAlBr/sub 4/-NaAlCl/sub 4/-KAlCl/sub 4/ (3:5:2)) has been developed. The melting point for this neutral melt is 86/sup 0/C; the decomposition potential is approximately 2.0V; the ionic conductivity is measured in the range 97/sup 0/-401/sup 0/C and is 0.142s cm/sup -1/ at 100/sup 0/C, and the density is 2.07g cm/sup -3/. The conductivity seems to be an almost linear combination of the conductivities of the four individual halo salts which form the melt. Other examined higher melting mixtures exhibit conductivities deviating less than +-10% from their combination expectations. The low melting electrolyte is employed in the rechargeable battery system Al/electrolyte/Ni/sub 3/S/sub 2/ at 100/sup 0/C. The open-circuit voltage of this system is from 0.82 to 1.0V. Dendrite-free aluminum deposits are obtained. The cycling behavior of the battery system is reported.

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A Novel Inorganic Low Melting Electrolyte for Secondary-Aluminum-Nickel Sulfide Batteries

Negative oxidation states of chalcogens in molten salts. 2. Raman spectroscopic, spectrophotometric, and electron spin resonance studies on chloroaluminate solutions containing an S3-entity

S. Von Winbush

Papers

Reactions of FeS2, CoS2, and NiS2 Electrodes in Molten LiCl ‐ KCl Electrolytes

Synthesis and structure of double-metal-layered scandium, yttrium, and zirconium chloride carbides and nitrides, M2Cl2C and M2Cl2N

A Novel Inorganic Low Melting Electrolyte for Secondary-Aluminum-Nickel Sulfide Batteries

Negative oxidation states of chalcogens in molten salts. 2. Raman spectroscopic, spectrophotometric, and electron spin resonance studies on chloroaluminate solutions containing an S3-entity

Resonance raman spectra of S3− in molten salts