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At least 1,333 records · Page 74

Fast Charging of Li-Ion Cells: Part III. Relaxation Dynamics and Trap-Controlled Lithium Ion Transport

Fast charging of Li-ion batteries would ease consumer concerns regarding refueling time of electric vehicles. In this series of articles, we are systematically examining the effects of high currents flowing through the cell. Here we consider open-circuit relaxation dynamics for cell voltage and individual electrode potentials after abrupt termination of steady-state charging currents (1-6C) or short current pulses (< 30 s) of either polarity (to 16C). We demonstrate that dispersive kinetics observed after these current perturbations become faster for higher currents applied before the rest period. Our observations indicate that the voltage relaxation behaviors (i) depend on the current during charge, and less so on the state of charge, (ii) display universal stretched-exponential kinetics, (iii) can be induced by a short current pulse, (iv) require a minimum amount of charge transfer during the pulse, and (v) originate mainly from the oxide cathode. Trap controlled Li + ion transport through a partially disordered oxygen-depleted subsurface layer in the cathode is suggested as a possible origin for the relaxation behavior. The slow multidecadal responses to high currents can cause the nonlinearities observed during rapid charging of the electrochemical cells, reported in Part 2 of this series.

25 ENERGY STORAGE↗

Ion Association Constants for Lithium Ion Battery Electrolytes from First-Principles Quantum Chemistry

We provide a quantum chemical computational framework to calculate ion association constants relevant to lithium ion battery electrolytes. We compare our method to reported experimental values as the solvent, cation, and anion are varied. For solvent, anion, and cation variations, the standard errors are respectively 0.2 eV, 0.12 eV, and 0.11 eV for the chosen data set, where Pearson correlation values are all above 0.92.

25 ENERGY STORAGE↗

A layered nonstoichiometric lepidocrocite-type sodium titanate anode material for sodium-ion batteries

A lepidocrocite-structured sodium titanate prepared by ion-exchange of a Cs-containing precursor shows promise as an anode material for sodium ion batteries, with a discharge capacity of up to 229 mAh g -1 at an average potential of about 0.6 V vs. Na + /Na. Titanium vacancies in the metal oxide layers provide additional sites for sodium intercalation in addition to interlayer sites, which accounts for the higher capacity compared to other previously reported lepidocrocite-structured titanates. By screening a series of electrolyte formulations and binders, we were able to improve the first-cycle coulombic efficiency to 81.8% and 94.7% respectively using CMC/SBR-based and binder-free electrodes in ether electrolytes. Finally, the electrochemical consequences of short-term air-exposure on the electrodes are also discussed.

25 ENERGY STORAGE↗

Design Status Update of the Electron-Ion Collider

The design of the electron-ion collider EIC to be constructed at Brookhaven National Laboratory has been continuously evolving towards a realistic and robust design that meets all the requirements set forth by the nuclear physics community in the White Paper. Over the past year activities have been focused on maturing the design, and on developing alternatives to mitigate risk. These include improvements of the interaction region design as well as modifications of the hadron ring vacuum system to accommodate the high average and peak beam currents. Beam dynamics studies have been performed to determine and optimize the dynamic aperture in the two collider rings and the beam-beam performance. We will present the EIC design with a focus on recent developments.

43 PARTICLE ACCELERATORS↗

High-Field Design Concept for Second Interaction Region of the Electron-Ion Collider

Efficient realization of the scientific potential of the Electron Ion Collider (EIC) calls for addition of a future second Interaction Region (2nd IR) and a detector in the RHIC IR8 region after the EIC project completion. The second IR and detector are needed to independently cross-check the results of the first detector, and to provide measurements with complementary acceptance. The available space in the existing RHIC IR8 and maximum fields achievable with NbTi superconducting magnet technology impose constraints on the 2nd IR performance. Since commissioning of the 2nd IR is envisioned in a few years after the first IR, such a long time frame allows for more R&D on the Nb₃Sn magnet technology. Thus, it could provide a potential alternative technology choice for the 2nd IR magnets. Presently, we are exploring its potential benefits for the 2nd IR performance, such as improvement of the luminosity and acceptance, and are also assessing the technical risks associated with use of Nb₃Sn magnets. In this paper, we present the current progress of this work.

43 PARTICLE ACCELERATORS↗

Tagged Short-Range Correlations for Medium to Heavy Ions at an Electron Ion Collider

Understanding short-range correlations between pairs of nucleons in the nucleus is an important nuclear physics topic that can address longstanding mysteries in nuclear physics such as the behavior of dense nuclear systems and the modification of parton distributions. As a collider and with a large acceptance detector, the Jefferson Lab version of the Electron Ion Collider has unique capabilities that are complementary to previous short-range correlation studies, most notably the ability to more fully reconstruct the final state. Optimization of the collider’s detector to maximally exploit these capabilities called for important extensions of existing simulation tools. For this one year laboratory directed research and development project, we upgraded the benchmark electron-nucleon event generator for lepto-production simulation code Benchmark eA Generator for LEptoproduction (BeAGLE) to be able to handle tagged medium-to-heavy nucleons. This included updating the code to correctly handle Fermi motion of nucleons in the nucleus as well as the large momentum caused by short-range correlations. In addition, we also investigated the possibility of improved kinematic reconstruction methods for electron nucleon collisions and looked at pair-spectator tagging of short-range correlations with the Jefferson Lab electron ion collider design. The project progressed very much as planned.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

Efficient Leaching of Metal Ions from Spent Li-Ion Battery Combined Electrode Coatings Using Hydroxy Acid Mixtures and Regeneration of Lithium Nickel Manganese Cobalt Oxide

Extensive use of Li-ion batteries in electric vehicles, electronics, and other energy storage applications has resulted in a need to recycle valuable metals Li, Mn, Ni, and Co in these devices. In this work, an aqueous mixture of glycolic and lactic acid is shown as an excellent leaching agent to recover these critical metals from spent Li-ion laptop batteries combined with cathode and anode coatings without adding hydrogen peroxide or other reducing agents. An aqueous acid mixture of 0.15 M in glycolic and 0.35 M in lactic acid showed the highest leaching efficiencies of 100, 100, 100, and 89% for Li, Ni, Mn, and Co, respectively, in an experiment at 120 °C for 6 h. Subsequently, the chelate solution was evaporated to give a mixed metal-hydroxy acid chelate gel. Pyrolysis of the dried chelate gel at 800 °C for 15 h could be used to burn off hydroxy acids, regenerating lithium nickel manganese cobalt oxide, and the novel method presented to avoid the precipitation of metals as hydroxide or carbonates. The Li, Ni, Mn, and Co ratio of regenerated lithium nickel manganese cobalt oxide is comparable to this metal ratio in pyrolyzed electrode coating and showed similar powder X-ray diffractograms, suggesting the suitability of α-hydroxy carboxylic acid mixtures as leaching agents and ligands in regeneration of mixed metal oxide via pyrolysis of the dried chelate gel.

Electrochemistry↗

Laboratory measurements of the K-shell transition energies in L-shell ions of Si and S [Energy measurements of K-shell transitions in L-shell ions of Si and S]

We have measured the energies of the strongest 1s–2${\ell }\ ({\ell }={\rm{s}},{\rm{p}})$ transitions in He- through Ne-like silicon and sulfur ions to an accuracy of $\lt 1\,\mathrm{eV}$ using the Lawrence Livermore National Laboratory's electron beam ion traps, EBIT-I and SuperEBIT, and the NASA/GSFC EBIT Calorimeter Spectrometer (ECS). We identify and measure the energies of 18 and 21 X-ray features from silicon and sulfur, respectively. The results are compared to new Flexible Atomic Code calculations and to semi-relativistic Hartree–Fock calculations by Palmeri et al. (2008). These results will be especially useful for wind diagnostics in high-mass X-ray binaries, such as Vela X-1 and Cygnus X-1, where high-resolution spectral measurements using Chandra's high-energy transmission grating has made it possible to measure Doppler shifts of $100\,\mathrm{km}\,{{\rm{s}}}^{-1}$. The accuracy of our measurements is consistent with that needed to analyze Chandra observations, exceeding Chandra's $100\,\mathrm{km}\,{{\rm{s}}}^{-1}$ limit. Hence, the results presented here not only provide benchmarks for theory, but also accurate rest energies that can be used to determine the bulk motion of material in astrophysical sources. Finally, we show the usefulness of our results by applying them to redetermine Doppler shifts from Chandra observations of Vela X-1.

74 ATOMIC AND MOLECULAR PHYSICS↗