bluuebunny/crossref_metadata_2025 huggingface dataset:
Suitable Position of Reference Electrode in Three-Electrode Cell for Impedance Measurements in Lithium-Ion Rechargeable Battery Investigated By Finite Element Method
Authors: Hoshi Yoshinao , Narita Yuki , Honda Keiichiro , Ohtaki Tomomi , Shitanda Isao , Itagaki Masayuki
Published: February 2020

Our group [1] determined the suitable position of the reference electrode for impedance measurements in lithiumion rechargeable batteries (LIRBs) with a three-electrode cell by finite element method (FEM). Electrochemical impedance spectroscopy (EIS) is a powerful method to investigate the performance of batteries [2-7]. It is important to obtain the electrochemical paramters of the positive and negative electrodes in LIRBs. In order to measure the impedance spectra of both electrodes in LIRBs cell, a three-electrode cell is used for the impedace measurement. Although the electrochemical properties of the positive and negative electrodes in LIRBs cell were investigated using the three-electrode cell by EIS [8-11], the position of the reference electrode was yet to be established for the impedance measurement. As the measured impedance spectra are affected by the current distribution between electrodes, it is important to determine the suitable position of the reference electrode in the LIRBs cell.

In the present study, we proposed the best position of the reference electrode for measurement of the impedance spectra of the positive and negative electrodes in the LIRB cell by using a three-electrode cell. A symmetrical model for the LIRB cell is used for the FEM simulation. The simulations of the current and potential distributions for both electrodes are performed by FEM. The impedance spectra of both electrodes were also calculated by FEM to discuss the effect of the position of the reference electrode on the current distribution between both electrodes.

References:

[1] Y. Hoshi, Y. Narita, K. Honda, T. Ohtaki, I. Shitanda, M. Itagaki, Journal of Power Sources, 288 (2015) 168-175.

[2] N. Takami, A. Satoh, M. Hara, I. Ohsaki, Journal of the Electrochemical Society, 142 (1995) 371-379.

[3] K. Chung, M.W. Chung, W.S. Kim, S.K. Kim, Y.E. Sung, Y.K. Choi, Bulletin of the Korean Chemical Society, 22 (2001) 189-193.

[4] C.S. Wang, A.J. Appleby, F.E. Little, Electrochimica Acta, 46 (2001) 1793-1813.

[5] S.S. Zhang, M.S. Ding, K. Xu, J. Allen, T.R. Jow, Electrochemical and Solid State Letters, 4 (2001) A206-A208.

[6] M. Itagaki, N. Kobari, S. Yotsuda, K. Watanabe, S. Kinoshita, M. Ue, Journal of Power Sources, 135 (2004) 255-261.

[7] M. Itagaki, N. Kobari, S. Yotsuda, K. Watanabe, S. Kinoshita, M. Ue, Journal of Power Sources, 148 (2005) 78-84.

[8] D.P. Abraham, S.D. Poppen, A.N. Jansen, J. Liu, D.W. Dees, Electrochimica Acta, 49 (2004) 4763-4775.

[9] J. Zhou, P.H.L. Notten, Journal of the Electrochemical Society, 151 (2004) A2173-A2179.

[10] C.H. Huang, S.X. Zhuang, F.Y. Tu, Journal of the Electrochemical Society, 160 (2013) A376-A382.

[11] O.S. Mendoza-Hernandez, H. Ishikawa, Y. Nishikawa, Y. Maruyama, Y. Sone, M. Umeda, Electrochimica Acta, 131 (2014) 168-173.
Time Domain Analysis on Current Response of Equivalent Circuit Involving Constant Phase Element
Authors: Itagaki Masayuki , Suzuki Suguru , Hoshi Yoshinao , Shitanda Isao
Published: February 2020

Electrochemical impedance spectroscopy (EIS) is powerful method to investigate electrolyte/electrode interface of various energy devices and electrochemical phenomena. The electrolyte/electrode interface is simply represented by a parallel circuit of charge transfer resistance (R
ct) and double-layer capacitance (C
dl), and its impedance spectrum describes a true semicircle on the Nyquist plane theoretically. However, the depressed semicircle is often observed in the experimental result of the impedance spectrum. The depressed semicircle has been explained by distribution of various relaxations at electrolyte/electrode interface [1, 2]. Burg and co-workers [3] reported the relation between constant phase element (CPE) and distribution of time constants and proposed the calculation method of a capacitance from CPE parameters on the basis of ladder equivalent circuit. In the present paper, a time domain data of current response by parallel circuit of CPE and resistance were calculated by the following algorithm in order to attempt the separation of time constants in the current response in the time domain.

(1) The pulse voltage V (t) in the time domain including the data of the 2N unit is converted into the voltage V (ω) in the frequency domain by a fast Fourier transform (FFT).

(2) The impedance Z (ω) is calculated as a complex number at each frequency from the equivalent circuit involving CPE.

(3) The current I (ω) in the frequency domain is calculated by dividing Z (ω) by V (ω) in the frequency domain.

(4) I (ω) is converted into the time domain current I (t) by an inverse fast Fourier transform (IFFT)

(5) The number and value of the time constant of I (t) are determined by curve fitting of the ladder equivalent circuit.

(6) The impedance spectrum calculated by (5) is compared with that by the equivalent circuit involving CPE.

The calculated results indicate that the current response by the equivalent circuit involving CPE is a sum of those with plural time constants. It was found that the distribution of time constants is concerned with the CPE index (p) remarkably. In addition, the relation between the CPE constant (T
CPE) and C
dl was discussed.

References

[1] Z. Kener, T. Pajkossy, J. Electroanal. Chem.
448 (1998) 139.

[2] C. A. Schiller, W. Strunz, Electrochim. Acta
46 (2001) 3619.

[3] G. J. Burg, V. D. Eeden, M. Sluyters-Rehbach, J. H. Sluyters, J. Electroanal Chem., 176 (1984) 275.
In-Situ TEM Observation of Solid Electrolyte Interface Evolution during Li-Ion Battery Opeeration
Authors: Kushima Akihiro , Kuriyama Nariaki , Maebashi Takanori , Fujiwara Yoshiya , Li Ju
Published: February 2020

Solid electrolyte interface (SEI) plays a critical role in the Li-ion battery. The formation of the SEI passivates the electrode surface and prevents excessive decomposition of the electrolyte. On the other hand, it can degrade the electrolyte and cause a battery to fail if the electrolyte continues to decompose due to insufficient passivation of the electrode. This can be severe for the high capacity anode with large volume changes during charge/discharge cycles. With the expansion and the contraction of the electrode, SEI formed on the surface can crack or delaminate exposing a fresh surface to the electrolyte and cause poor cyclability of the battery. Understanding how does the SEI response to the volume change of the electrode is important to design the electrode structure to improve the cycle performance. The thickness of the SEI is in the nano-meter scale. Therefore, high-resolution imaging using electron microscopy is essential for observing the reaction process.

In this work we present the in-situ transmission electro microscopy observation of the structural evolution of the SEI formed on a Si anode during lithium ion battery operations. Here, we developed a liquid confining cell to prevent electrolyte from evaporating into the high vacuum inside the TEM. We observed the formation of a SEI layer on the Si film during charge along with the volume expansion of the film. Upon discharge, the contraction of the film was observed. The shrinking of the film was not uniform across the film and the strain gradient caused a tension on the SEI layer resulting in the crack formation. New SEI will form on the freshly exposed Si surface on the following charge. This can cause continuous decomposition of the electrolyte and eventual failure due to the electrolyte consumption. The in-situ TEM experiment in this work shows the breaking of the SEI can take place during the discharge after it was formed on charging. Various combinations of the electrolyte, electrode, and the applied potential or current density are necessary to obtain the optimum battery design for producing adequate SEI layer or prevent them from forming. However, out observation provides important information toward designing a battery structure with improved performance.

Figure caption: Sequential TEM image of the SEI cracking on Si anode discharged at 0.0 V vs. LiCoO2.

Figure 1
Measuring Dynamic Changes in Si SEI Chemistry
Authors: Veith Gabriel M , Browning James F , Sacci Robert L , Fears Tyler , Doucet Matthieu
Published: February 2020

In this presentation we will present experimental in situ measurements of the thickness and chemistry of the SEI layer that forms over amorphous silicon electrodes as a function of state-of-charge and cycle.  These measurements were performed using neutron reflectometry which was supported by XPS, IR and electrochemical measurements.  We will show the thickness of the Si SEI layer changes as a function of state-of-charge becoming thicker with lower states of lithiation and thinner with greater lithiation.  Furthermore, the chemistry changes with cycle from more LiF rich at higher states-of-charge to more polymeric when delithiated.  The thickness and the chemistry of the SEI layer changes with the addition of electrolyte additives, like fluorinated ethylene carbonate. Together these results help develop an understanding of additive chemistry and will direct the development of new additives.

This research was supported by the Materials Sciences and Engineering Division, Office of Basic Energy Sciences, U.S. Department of Energy under contract with UT-Battelle, LLC (GMV, TF, RLS – XPS, NR data collection, electrochemistry). Neutron reflectometry measurements were carried out on the Liquids Reflectometer at the Spallation Neutron Source which is sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy (JFB, MD – Data collection and analysis).
Chemical, Electrochemical and Physical Properties of the Solid Electrolyte Interphase on HOPG Surface: Mechanisms of Formation and Transition Metal Deposition
Authors: Antonopoulos Byron Konstantinos , Kirdar Cansu , Maglia Filippo , Schmidt-Stein Felix , Hoster Harry Ernst
Published: February 2020

Both the reaction pathways that lead to the formation of the solid electrolyte interphase (SEI) on the negative electrode of a lithium ion battery and the chemical, electrochemical and physical properties of the SEI are not well understood. Consequently, a full control of the SEI composition and properties through the selection of appropriate formation conditions is far from being achieved. In this contribution we present the influence of the formation potential on the chemical and electrochemical properties of SEIs formed on model carbon electrodes. Our results show that, on HOPG, SEI is formed via a two-step process, where the step occurs at respectively ~700 and ~400 mV vs. Li/Li+. The SEIs that are formed at potentials corresponding to the first or the second potential step exhibit drastically different characteristics in terms of chemical composition, thickness and transport properties. Our results are consistent with electrochemical investigations that are performed on commercial composite carbon electrodes. The SEI formed at higher potentials appears to be disadvantageous for Li+ ion intercalation. A further reduction of the SEI at lower potential is required to improve the intercalation.

The still debated mechanism of transition metal deposition on the anode of Li-ion batteries was also investigated on model HOPG electrode surfaces exposed to contaminated electrolyte after completion of the SEI formation. Our results indicate, that the deposition of transition metals is strongly affected by the nature of the SEI, in particular by its thickness. By introducing transition metal cations in our model system we demonstrate, that the respective deposition takes place at the SEI compact layer surface via an electron tunneling mechanism.

Figure 1
Study of the Interface Layer Between Lithium Metal and a Single Ion Conductor Ceramic, Based on Block Copolymer, for Lithium Air Batteries
Authors: Frenck Louise , Bouchet Renaud , Stevens Philippe , Balsara Nitash P.
Published: February 2020

The electrification of transport is a formidable challenge, however the energy storage possible in Li ion batteries is not sufficient to this purpose. A potential option is Lithium-air battery, first because of their very high energy densities and second because of their low costs. Two different approaches to the development of these batteries are possible: the anhydrous system which uses an organic electrolyte, and the aqueous system which uses an aqueous electrolyte [1]. An advantage of the aqueous system is its safety since toxic or inflammable solvents are not used. In order to protect the negative lithium electrode from the aqueous electrolyte, a thin ceramic water and gas tight membrane is used. The interface between the lithium metal and the ceramic membrane plays an important role in the cycling performance of the aqueous lithium air cell. Nonetheless, the poor or non-chemical stability of most ceramic electrolytes in contact with lithium metal limits the performance. A possible strategy to improve the interface between ceramic electrolyte and lithium metal might be by the use of polymer membranes [2].

               This study reports the effect of a polymer membrane between a ceramic electrolyte and lithium metal. Block copolymer electrolytes, such as polystyrene-block-poly (ethylene oxide) copolymer electrolyte (SEO) mixed with lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) salt, were used. The single ion conductor ceramic electrolyte was a Lithium Ion Conducting Glass Ceramic (LICGC) purchased from Ohara Corporation (1 inch X 1 inch 150µm thick). Impedance spectroscopy has been used, so as to study the lithium ion - lithium metal transfer from a lithium ion conducting polymer interface. Furthermore, in order to know if the sandwich polymer-ceramic cell showed an additional interfacial resistance, ionic conductivity experiments using electrochemical impedance spectroscopy were performed. Besides, polarization loss quantification at a lithium ion conducting polymer/single ion conductor interface was studied by DC current measurement by the Srinivasan et al method [3]. Finally, in order to confirm the intimacy of the ceramic and the polymer, the interface between the ceramic and the polymer was studied by synchrotron hard X-Ray micro tomography experiments on symmetric lithium-sandwich polymer-ceramic cells.

                                                                                                                         

P.G. Bruce, S. A. Freunberger, L. J. Hardwick, J-M. Tarascon, Nature Materials, 11, 19-29 (2012)

G.M. Stone, S.A. Mullin, A.A. Teran, D.T. Hallinan, A.M. Minor, A. Hexemer, N.P. Balsara, Journal of the Electrochemical Society 159(3) A222-A227 (2012)

Mehrotra, P. N. Ross, V. Srinivasan, Journal of the Electrochemical Society, 161 (10) A1681-A1690 (2014)
Speciation of Haloaluminate Electrolytes in Mg-Ion Batteries: A Combined Study of ab Initio Molecular Dynamics and Simulated X-Ray Absorption Spectroscopy
Authors: Wan Liwen , Prendergast David
Published: February 2020

Since the development of prototype Mg-ion battery system [Aurbach et al., Nature 407, 724 (2000)] that employs organohaloaluminate (Mg(AlCl2BuEt)2) in tetrahydrofuran (THF) as the electrolyte, the exact solvation structure of Mg2+ in solution is still under debate. For further development of divalent Mg-ion batteries, a molecular-scale understanding of how Mg ion is solvated in such complex solution is vital to understand and improve ion transport properties in the electrolyte and dissolution/deposition processes at the electrolyte/electrode interfaces.

In this work, we aim to resolve the controversy of the exact solvation structure of Mg2+ by performing ab initio molecular dynamics (AIMD) simulations. To validate our AIMD predicated Mg solvation structures, we also simulate the corresponding Mg and Cl K-edge X-ray absorption spectra and compare with existing literature. We conclude that in the dilute limit of salt concentration, Mg ion is always tetracoordinated. This corrects a long-standing bias that Mg ions should be hexacoordinated in THF solution. By comparing with various experimental measurements, our results also imply that the solvation structure of Mg ion in haloaluminate solution is very sensitive to local salt concentration, relative Mg/Al ratio and bias-dependent electric filed during cycles.

This work is supported as part of the Joint Center for Energy Storage Research (JCESR), an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
Composition Optimization of the Lithium-Rich Li3OCl1-X
Br
x
Anti-Perovskite Superionic Conductors
Authors: Deng Zhi , Radhakrishnan Balachandran , Ong Shyue Ping
Published: February 2020

The newly discovered lithium rich anti-perovskite (LRAP) superionic conductors are an extremely interesting class of materials with potential applications as solid electrolytes in Li-ion batteries. Here we present a rational composition optimization strategy for maximizing the Li+ conductivity in the LRAP guided by a combination of first principles calculations and percolation theory. Using nudged elastic band (NEB) calculations, we show that a Cl-rich channel with Br-rich endpoints configuration leads to low vacancy migration barriers in the LRAP structure. By incorporating the halide-environment-dependent NEB barriers in a bond percolation model, we predict that there are potentially higher conductivity Li3OCl1-x
Br
x
structures near 0.235 ≤ x ≤ 0.395. This prediction is confirmed by AIMD simulation that finds Li3OCl0.75Br0.25 to have a higher Li+ conductivity than Li3OCl0.5Br0.5, the highest conductivity LRAP identified experimentally thus far. These results highlight that there is scope for further enhancing the conductivity in the LRAP chemistry. The general approach developed can potentially be extended to other ion-conducting systems, such as the structurally similar perovskite oxygen-ion conductors of interest in solid-oxide fuel cells as well as other superionic conductors.
Nucleation and Growth Behavior of Electrodeposited Lithium in Ionic Liquid
Authors: Sano Hikaru , Sakaebe Hikari , Senoh Hiroshi , Matsumoto Hajime
Published: February 2020

Metallic lithium is a promising anode candidate for rechargeable battery; however, the dendrite formation during charging should be suppressed to improve safety and cycleability.  Many researches have been reported from the viewpoint of the control of the surface film on lithium metal1.  Ionic liquids nowadays attract much attention from electrochemists, some of which have excellent stability at highly cathodic states (such as Li/Li+).  Our group has focused on their unique features and utilized these ionic liquids as electrolyte with lithium metal anodes.  In the present study, in order to determine the condition for the non-dendritic lithium deposition, we investigated the electrodeposition behavior during nucleation and growth state in ionic liquids based on overpotential and Li-ion diffusion.

   10 wt.% of Li[Tf2N] was added to [C3mpip][Tf2N], [C4mpyr][Tf2N], and [N6,1,1,1][Tf2N] as the electrolytes.  Lithium metal was electrodeposited on nickel substrates at current densities ranging from 5 to 200 μA cm-2 for total charge amount of 0.1 and 3 C cm-2.  The morphology of electrodeposited lithium was observed by SEM.

   For the nucleation state, we focused on the case with charge amount of 0.1 C cm-2.  The deposits were better distributed when the current density was increased (Figure 1).  Additionally, the deposits were better distributed when the electrolyte viscosity was increased.  In these conditions, an increased overpotential was confirmed.  This is believed to lead to a wide distribution of nucleation sites due to decreased critical radii of the nuclei2.  On the contrary, for the growth state, we focused on the case with the charge amount of 3 C cm-2.  More deposits were more dendritic when the current density was increased (Figure 2) and also when the electrolyte viscosity was increased.  This result can be rationalized by considering that the lithium ion concentration extremely decreased at the electrode surface, since Li-ion diffusion is slower than the decrement in the concentration of Li-ion at the electrode surface3.  These tendency is common for noble-metal electrodeposition.  The reason why these tendency is also observed for less noble metals such as lithium is considered to be that the ionic liquid used in this study is very stable at the highly cathodic state and therefore less effect of native film formation on the deposition.

1.  D. Aurbach, E. Zinigrad, Y. Cohen, H. Teller , Solid State Ionics, 148, 405 (2002).

2.  H. Sano, H. Sakaebe, H. Senoh, H. Matsumoto, J. Electrochem. Soc., Submitted.

3.  H. Sano, H. Sakaebe, H. Senoh, H. Matsumoto, J. Electrochem. Soc., 161, A1236 (2014).

Figure 1
Electrochemical Energy Summit Plenary Address
Authors: Orr Franklin M.
Published: February 2020

The Electrochemical Energy Summit Plenary Address will be given by the U.S. Under Secretary for Science and Energy, Dr. Franklin (Lynn) M. Orr Jr.
Overcoming Key Challenges for a Viable Lithium-Sulfur Transportation Battery
Authors: Zavadil Kevin R
Published: February 2020

The lithium-sulfur electrochemistry is viewed as an attractive electrical energy storage system for transportation applications because of projections of system level energy density and specific energy in excess of state-of-the-art lithium ion technology. The current lack of a low cost ($100/kWh), high performance (400 Wh/L, 1000 cycle) Li-S battery technology is the consequence of limits imposed by several key materials science challenges that must be overcome to move this technology forward. A recent material-to-system analysis demonstrates that the most direct path to increased energy density and low cost is through the reduction of the electrolyte volume fraction (with respect to sulfur) and a reduction in excess metallic lithium [1]. Reduced electrolyte volume fraction requires developing knowledge of how sulfur redox chemistry is altered under lean or starved electrolyte conditions; including electrochemical limits to capacity, the spatial distribution and properties of solid discharge products, and occlusion of sulfur. Reduced Li metal excess requires science informed strategies for protecting the anode against parasitic reaction and maintaining dimensional control during Li electrodeposition and dissolution. The Joint Center for Energy Storage Research (JCESR) has assembled a multidisciplinary team to conduct the necessary science, translate this knowledge to test platforms, develop data fed performance models, and demonstrate progress through cell prototypes [2]. The goal of this presentation is to communicate JCESR’s current progress on these challenges and to provide perspective on where achievable performance will likely be pinned by select fundamental limits.

This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. Sandia is a multiprogram laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. DOE’s NNSA under contract DE-AC04-94AL85000.

 

D. Eroglu, K.R. Zavadil, K.G. Gallagher, “Critical Link between Materials Chemistry and Cell-Level Design for High Energy Density and Low Cost Lithium-Sulfur Transportation Battery,” J. Electrochem. Soc., 2015, 162 (6), A982-A990.

G. Crabtree, “The Joint Center for Energy Storage Research: A New Paradigm for Battery Research and Development”, AIP Conf. Proc., 2015, 1652, 112-128.
New Advances in Stabilizing High-Efficiency Semiconductors for Use in Solar Fuels Applications
Authors: McDowell Matthew T. , Sun Ke , Hu Shu , Lichterman Michael Frankston , Zhou Xinghao , Shaner Matthew , Verlage Erik , Brunschwig Bruce , Lewis Nathan S.
Published: February 2020

The photoelectrochemical conversion of sunlight into gaseous hydrogen or liquid hydrocarbon fuels can be an efficient method for renewable energy production, but significant materials challenges hinder the fabrication of integrated devices that are both efficient and stable. In particular, many moderate band gap semiconductors (Eg
= 1-2 eV) photocorrode rapidly (within seconds or minutes) during electrochemical operation in aqueous solution. This process is exacerbated in water oxidation photoanodes that operate at high potentials in acidic or alkaline environments. The stable and reliable use of moderate band gap semiconductors is integral to JCAP’s mission of creating efficient solar-to-fuels devices. As such, recent work at JCAP has focused on developing thin films that protect a number of high-efficiency semiconductors, including Si, CdTe, and GaP. Such protection layers need to satisfy a number of requirements: they must resist corrosion in alkaline or acidic environments, they must be transparent, and they must allow for the transport of photogenerated carriers from the semiconductor to the electrolyte interface. Research at JCAP has led to the development of thin film protection layers based on TiO2 and NiOx that fulfill these requirements and have enabled stable operation of Si-based photoanodes for >1000 h during water oxidation in corrosive alkaline electrolytes (Fig. 1). The NiOx and TiO2 layers are prepared via atomic layer deposition (ALD) or reactive sputtering over large areas, and the effects of composition, crystal structure, morphology, and electronic properties on photoelectrochemical performance have been studied in detail. Heterojunctions between TiO2 or NiOx protection layers and n-type photoactive semiconductors (n-Si, n-CdTe, n-GaP) are rectifying and yield photovoltages in the range of 0.3-0.6 V. Strategies to increase photovoltage via tailoring the interfacial chemistry/structure, as well as by utilizing buried homojunctions, have been successfully pursued. Furthermore, band alignments at various interfaces (semiconductor/protective layer and protective layer/electrolyte) have been investigated and must be controlled for optimal performance. Overall, this presentation will address both the fundamental scientific issues related to the development of these protective layers, as well as the application of these materials towards stabilizing planar and structured electrodes for solar fuels applications.

Figure 1. Long-term photocurrent stability test of Si-NiOx photoanodes for water oxidation.

Figure 1
Industry Invited Talks: "The Future of Battery and Fuel Cell Powered Cars: Challenges and Opportunities"
Authors: TBD x
Published: February 2020

This event will involve participation from representatives of the auto industry who will provide their perspective on the future of this exciting technology.
Advancing Operando Tools to Probe Multiscale Complexity in Chemical Energy Storage
Authors: Chapman Karena W , Grey Clare P , Chupas Peter J , Batson Philip , Cosandey Frederic , Cabana Jordi , Meng Shirley , Zhou Guangwen
Published: February 2020

Electrochemical energy storage is a rapidly expanding area of study, driven by critical applications in alternative energy technologies (e.g. for grid storage coupled to intermittent solar/wind energy sources) and improved efficiency (e.g. in vehicle technology). Batteries, by their nature, do not operate under equilibrium conditions. Accordingly, there is a growing need for operando characterization tools to understand the dynamic mechanisms and kinetics of the electrochemical reactions which govern energy storage. Within the NorthEast Center for Chemical Energy Storage (NECCES) EFRC, we are developing and applying a series of complementary operando tools to probe and decouple the structural, chemical, and electronic changes in operating batteries at the atomic-, particle- and electrode-levels. This will allow us to develop a comprehensive understanding of the fundamental processes that underlie performance limitations and failure. Methodologies span hard and soft X-ray scattering, spectroscopy and imaging, electron microscopies, and NMR-based spectroscopy and imaging.
Electrochemical Stiffness in Anodes and Cathodes for Lithium Ion Batteries
Authors: Gewirth Andrew A. , Tavassol Hadi , Jones Elizabeth M. C. , Esbenshade Jennifer , Sottos Nancy R.
Published: February 2020

Higher power and charging rates are essential for large scale adoption of lithium-ion batteries in transportation applications. While lithium-ion batteries are ubiquitous in portable electronics, their performance and lifetime suffer during high rate charging and high power discharging. In such extreme electrochemical conditions, the mechanical response of electrode materials governs their degradation behavior. Here, we present a new technique to probe the electrochemically-induced mechanics of electrodes by calculating the electrochemical stiffness of electrodes via coordinated in situ stress and strain measurements.  Through the electrochemical stiffness, we elucidate inherent and rate-dependent mechanical responses of graphitic battery electrodes. We find that stress and strain are asynchronous as shown in the figure.  In particular, stress development is found to lead strain development as different graphite-lithium intercalation compounds are formed. Additionally, our analysis reveals inversely scaled rate-dependent behaviors for stress and strain responses. Stress scales as scan rate while strain scales with charge (or, equivalently, capacity).  These measurements provide a new paradigm for understanding mechanical effects in intercalation systems, such as batteries.  Stress arises as resistance to lithiation, while strain arises as a consequence of lithiation.  Electrochemical stiffness measurements provide new insights into the origin of the rate-dependent chemo-mechanical degradations, and provide a probe to evaluate advanced battery electrodes.

We also report on our efforts to stabilize LiMn2O4 (LMO)  -- a low cost cathode material for a Li-ion battery  These cathodes suffer from significant capacity fade with cycling.  This capacity fade is in part associated with the dissolution of Mn from the cathode material. To prevent this dissolution, we coated LMO particles with a Au shell by a simple and scalable electroless deposition.  Characterization by SEM, TEM, EELS, and AFM showed that the Au shell was approximately 3 nm thick.  The Au shell prevented much of the Mn from dissolving in the electrolyte with 82% and 88% less dissolved Mn in the electrolyte at room temperature and 65 ºC, respectively, as compared to the uncoated LMO.  These Au coated cathode materials show great improvement in reducing Mn dissolution and extending electrochemical performance through hundreds of cycles over uncoated LMO.

Figure 1
The Evolution of a High Capacity Electrode
Authors: Wang YuHuang , Sun Chuan-Fu
Published: February 2020

Silicon can store Li+ at a capacity 10 times as high as that of graphite anodes. However, to harness this remarkable potential for electrical energy storage, one must address the multifaceted challenge of volume change inherent to high capacity electrode materials. In this talk, we present novel chemical strategies to address this challenge. Based on fundamental understanding of nanostructure interface, we have synthesized non-cracking silicon-carbon nanotube composite electrodes that electrically connect amorphous silicon beads. This synthesis is made possible by a propagative chemistry which creates regular bands of alkylcarboxyl groups along the nanotubes. The functional bands anchor the beads such that they exhibit a symmetric “radial breathing” around the CNT string, remaining crack-free and electrically connected throughout lithiation-delithiation cycling. We further show that, solely by chemical tailoring of the Si-C interface with atomic oxygen, the cycle life of the electrodes can be substantially improved, by 300%, even at high mass loadings. The evolution of this work culminates in the design and fabrication of a high capacity composite electrode that is weavable. The engineered andoe simultaneously attains high areal capacity (3.86 mAh/cm2), high specific capacity (922 mAh/g based on the mass of the entire electrode), and excellent cyclability (80% retention of capacity after 160 cycles), which are among the highest reported.

This work was mainly supported as part of Nanostructures for Electrical Energy Storage (NEES), an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DESC0001160. We acknowledge cumulative contributions from many collaborators particularly K. Karki, M. Okada, H. Liao, H. Zhu, Z. Jia, E. Baker, Y. Zhang, K. Gaskell, A. Ghemes, P. Wang, J. Cumings, L. Hu, Y. Inoue, T. Li, Y. Qi, and G. W. Rubloff.
Studies on Dielectric Properties of Annealed RF-Sputtered ZrO2 Thin Films
Authors: Mendoza Raul R. , Skaria Giji , Prakash Adithya , Velez Victor H. , Sundaram Kalpathy B
Published: February 2020

Dielectrics play an important role in semiconductor devices when it is used as gate insulator MOS transistors or in memory applications [1]. SiO2 has been one of the most typically used dielectrics due to its good properties like electrical and thermodynamic stability. It provides a great Si-SiO2 interface used in MOS transistors, and has high quality isolation electrical characteristic. Despite its benefits, there comes a point where continuous device scaling sets a limit to what materials can be used. Therefore, other high-k gate dielectric materials have to be found in order to go below 1.5nm thickness when SiO2 is used for the 45nm node technology. ZrO2 is one of the high-k materials that can be used as a possible solution [2].

ZrO2 possesses some interesting characteristics like relatively high-k and wide bandgap. In addition, its crystal structure changes at different temperatures, going from monoclinic to tetragonal and then to cubic as the temperature raises. Even though the monoclinic structure is stable and occurs at room temperature, the other two are not. This presents some problems, which create phase instability leading to stresses and cracking of the material. However, by introducing certain rare earth oxide based dopants as for example Yttria (Y2O3), stable phases for the tetragonal and cubic structures can be achieved, as well as increasing the permittivity constant of the dielectric [3,4].

In this work, ZrO2 thin films are deposited on glass substrates to find various properties. The films are prepared in an RF magnetron sputtering system using a 99.5% pure yttria-stabilized zirconium oxide target. ZrO2 based metal/insulator/metal (MIM) structures are fabricated using Aluminum as the top and bottom electrodes. Various electrical properties are investigated for the ZrO2 films prepared under different deposition and annealing conditions.

REFERENCES

[1] G. D. Wilk, R. M. Wallace, J. M. Anthony, “High-κ gate dielectrics: Current status and materials properties considerations” Journal of Applied Physics, Vol 89, 2001

[2] M. K. Bera, C. K. Maiti, "Reliability of Ultra-thin Zirconium Dioxide (ZrO2) Films on Strained-Si" Physical and Failure Analysis of Integrated Circuits, 2006.

[3] S. M. Hwang, S. M. Lee, K. Park, M. S. Lee, J. Joo, J. H. Lim, H. Kim, J. J. Yoon, Y. D. Kim “Effect of annealing temperature on microstructural evolution and electrical properties of sol-gel processed ZrO2 /Si films” Applied Physics Letters 98, 2011

[4] H. García, H. Castán, S. Dueñas, E. Pérez, L. Bailón, “Electrical characterization of MIS capacitors based on DY203-doped Zr02 dielectrics”, Electron Devices (CDE), 2015
(Invited) Li Rich FCC Materials As High Capacity Cathodes
Authors: Ren Shuhua , Chen Ruiyong , Fichtner Maximilian
Published: February 2020

In 2014, we developed a new type of compound based on lithium-rich metal oxyfluoride of Li2MO2F.[1] The novel material exhibits an outstandingly high capacity of 420 mAh g-1 with small lattice expansion and shrinkage of only 3% upon cycling owing to its stable rock salt host structure. Lithium, occupying 2/3 of the cation sites, is highly mobile. The structure stabilizes well after nearly two Li+ depletion. The flexibility of the host structure means a paradigm change in the Li+ storage, which opens new possibilities for obtaining higher storage capabilities both gravimetrically and volumetrically. Particularly, high volumetric energy densities up to 4600 Wh L-1were achieved.

The first generation of materials (M=V) [2] has recently been expanded by Cr as an alternative transition metal.[3] This presentation will address the first and the second generation of materials, where pure V and Cr compounds as well as systems with mixtures of the two metals have been synthesized and tested. It will be shown that Cr leads to higher discharge potentials, which are about 0.5 V above those of the pure V compounds. Moreover, the smaller cation enables higher packing densities of Li so that the theoretical gravimetric and volumetric energy densities of the respective Li rich fcc compound are high at average 2.8 V.

References

[1] (a) R. Chen, et al. EP patent application EP 14160894.3 (2014); (b) R. Chen et al., 226th ECS Meeting Cancun, Mexico (2014).

[2] R. Chen et al., Disordered lithium-rich oxyfluoride as a stable host for enhanced Li+ intercalation storage, Advanced Energy Materials (2015) 5, 1401814.

[3] S. Ren et al., Improved voltage and cycling for Li+intercalation in high-capacity disordered oxyfluoride cathodes, (2015) submitted.

 [MF1]

Figure 1
Re-Entrant Lithium Local Environments and Defect Driven Electrochemistry of Li- and Mn-Rich Li-Ion Battery Cathodes
Authors: Key Baris , Dogan Fulya , Long Brandon R. , Croy Jason R. , Gallagher Kevin G. , Iddir Hakim , Russell John , Balasubramanian Mahalingam
Published: February 2020

6Li NMR spectroscopy is used to quantitatively characterize local lithium environments that dominate the free energy for site occupation and to monitor the evolution of local order and low concentration defect formation with the goal of correlating local structural changes with hysteresis and voltage fade phenomena observed in layered lithium and manganese rich TM oxide cathode structures. We have undertaken an isotopic enrichment strategy coupled with very long acquisition times to obtain unprecedented, and quantitative, high-resolution data for cycled electrodes using fully enriched cell components. This strategy has allowed the determination of structure-activity relationships and monitoring the evolution of local order and low concentration defect formation with the goal of correlating local structural changes with hysteresis and voltage fade phenomena. We report new 6Li resonances centered at ~1600ppm that are assigned to LiMn6-TMtet sites, specifically, a hyperfine shift related to a small fraction of reentrant tetrahedral transition metals (Mntet), located above or below lithium layers, coordinated to LiMn6 units. The intensity of the TM layer lithium sites correlated with tetrahedral TMs loses intensity after cycling, indicating limited reversibility of TM migrations upon cycling. These findings reveal that defect sites, even in dilute concentrations, can have a profound effect on the overall electrochemical behavior.
Layered Cathode Materials with Controlled Particle Assembly for High Energy Lithium-Ion Batteries
Authors: Lin Feng , Li Yuyi , Nordlund Dennis , Liu Yijin , Weng Tsu-Chien , Xin Huolin , Doeff Marca
Published: February 2020

Stoichiometric layered lithium transition metal oxides (LiNi1-x-yMnxCoyO2) represent a family of cathode materials suitable for high-energy lithium ion batteries. However, their structural instability (e.g., surface reconstruction from the layered structure to a rock-salt/spinel mixed structure) when charged to high voltages impedes efforts to improve their energy densities. Here, we report on a study of LiNi1-x-yMnxCoyO2 materials prepared by a spray pyrolysis technique to provide improved cycling performance.

The as-prepared LiNi1-x-yMnxCoyO2 materials assemble into spherical structures that consist of nanosized primary particles. Revealed by transmission electron microscopy, these primary particles are “fused” together to form atomically disordered interfaces that may allow for lithium and electron diffusion. LiNi1-x-yMnxCoyO2 materials with different ratios of transition metals were synthesized, i.e., LiNi1/3Mn1/3Co1/3O2, LiNi0.4Mn0.4Co0.2O2, LiNi0.5Mn0.3Co0.2O2, LiNi0.6Mn0.2Co0.2O2, most of which show improved electrochemical performance (i.e., discharge capacity, capacity retention) compared to the counterparts synthesized by the conventional co-precipitation method, although different thermal treatment protocols are needed after the spray pyrolysis process. Surface reconstruction was quantified by soft X-ray absorption spectroscopy to investigate the surface phase transition of the LiNi1-x-yMnxCoyO2 materials after electrochemical cycling, and it is found that the materials prepared by spray pyrolysis have thinner surface passivation layers (a rock-salt/spinel mixed structure), which accounts for better capacity retention. This study suggests that morphological engineering by spray pyrolysis may offer an efficient pathway towards stable high-energy layered cathode materials.
(Invited) Understanding Surface and Structural Changes in High Energy Density Electrodes By NMR and Computational Studies
Authors: Grey Clare P , Michan Alison , Leskes Michal , Seymour Ieuan
Published: February 2020

This talk will focus on two different topics.  The first involves the use of NMR spectroscopy to characterize the SEI formed on silicon and carbon electrodes.  By using a multinuclear NMR approach in combination with a series of double resonance and two-dimensional NMR experiments, we identify many of the organic and inorganic components that are formed on silicon anodes.  Preliminary comparisons with the SEI on carbons will be made.  The second topic involves a study of layered materials by using a combination of NMR spectroscopy and DFT methods.  The use of DFT methods to calculate NMR shifts for these materials is challenging, particularly for partially delithiated (disordered) materials.  Our strategies in this area will be discussed, along with computational approaches to explore structural transformations.
(Invited) Effects of Crystalline Structure on the Electrochemical Properties of High Voltage Spinel Cathode Materials
Authors: Wu She-huang , Su Shou-Huang , Shiu Je-Jang
Published: February 2020

LiNi0.5Mn1.5O4 powders were prepared via a spraying-dry method followed by heating at temperatures between 600 and 1000oC for 8 hours in air with oven cooling. In order to eliminate the particle size effects, 900oC samples were annealed at 700oC under air for various durations. The crystalline structure of the prepared samples were investigated from their high resolution neutron powder diffraction data collected with Echidna at ANSTO and refined with Rietica Ver. 1.77. The results of Rietveld refinement for the NPD patterns manifest that the 700oC prepared sample contains 85% of ordered P4332 and 15% of disordered Fd
m phases whereas the powders prepared at temperatures higher than 800oC prevailed with disordered Fd
m phase (72`75%) with amount of rock-salt LixNi1-xO increases from 1 to 4% with heating temperature. For the annealed samples, the molar fraction of the ordered phase increases with increasing duration of annealing and converts completely into ordered phase after annealing for 60 hours. It suggests that the phase conversion and LixNi1-xO evolution/dissolution are reversible [1]. From the results of capacity retention study of the cells comprised with the prepared powders, it was found that sample prepared at 900oC with oven cooling exhibits the most promising performance among the prepared powders. These results are different from those reported by Fang et al. [2], however, they are similar to those reported previously that the disordered phase has better electrochemical properties than the ordered phase [3-5]. Though various reasons had been suggested [3, 6-7], the effects of crystalline structure on the cycling performance of high voltage spinel are still not clear. In this study, the effects are hope to reveal from the results of dissolution study for transition metals upon storage and cycling, linear sweep voltammetry for electrolyte oxidation on high voltage spinel, cyclic voltammetry for Li+ ion diffusivity, and the phase evolution detected by high resolution TEM for the fresh and cycled electrodes and in-situ NPD study.

Reference:

[1] L. Cai, Z. Liu, K. An, and C. Liang, J. Mater. Chem. A, 1,6908 (2013).

[2] H. Fang, Z. Wang, B. Zhang, X. Li and G. Li, Electrochem. Commun., 9, 1077 (2007).

[3] J. H. Kim, S. T. Myung, C. S. Yoon, S. G. Kang and Y. K. Sun, Chem. Mater., 16, 906 (2004).

[4] A. Bhaskar, N. N. Bramnik, A. Senyshyn, H. Fuess and H. Ehrenberg, J. Electrochem. Soc., 157, A689 (2010).

[5] K. Takahashi, M. Saitoh, M. Sano, M. Fujita and K. Kifune, J. Electrochem. Soc., 151, A173 (2004).

[6] M. Kunduraci, J. F. Al-Sharab and G. G. Amatucci, Chem. Mater., 18, 3585 (2006).

[7] X. H. Ma, B. Kang and G. Ceder, J. Electrochem. Soc., 157, (2010).
The Effect on Electrochemical Properties By the Content of Mn3+ of High-Voltage Spinel LiNi0.5Mn1.5O4 Cathode Material for Highly Stable Lithium-Ion Batteries
Authors: Li Jie , Liu Haidong , Wang Jun
Published: February 2020

High voltage spinel LiNi0.5Mn1.5O4 (LNMO) is considered as one of the most promising cathode material for next generation lithium ion batteries, which can greatly meet the rapid increasing demand of power sources applied into portable electronic devices and electric vehicles. The electrochemical performance of LNMO is greatly affected by the morphology and lattice structure. In order to improve the long-term cycling stability, particularly at elevated temperature, one of effective methods is to tune the amount of Mn3+ in LNMO for controlling the stability of spinel lattice structure due to complex interactions on the interface of electrode material and the electrolyte on the high operating voltage.

In this work, the influence of different content of Mn3+ in LNMO on electrochemical properties is displayed by truncated octahedral LNMO obtained by controlling synthetic conditions of heating atmosphere and temperature cooling rate. Superior truncated octahedral LNMO materials were synthesized with tuned Mn3+ content through heating under oxygen atmosphere and controlling the cooling conditions of natural cooling and a cooling rate of 5 oC/min, respectively. The material synthesized under O2 shows the smallest amout of Mn3+, while the one with natural cooling has the highest amount. The LNMO material obtained under O2 shows the best electrochemical stability with about 96% capacity retention after 500 cycles at 0.5C (1C = 147 mA/g). The material obtained at 5 oC/min shows about 90% of capacity retention after 2000 C cycles at 1C, while the one obtained with natural cooling can reach up to 88% of capacity retention after 500 cycles at 0.5C at 60 oC. Therefore, the Ni-Mn disordering intrinsically related to the Mn3+ amount has a great effect on the electrochemical performance of LNMO. More experimental details and measurement results will be exhibited later.

Reference:

1. Xiao, J., Chen, X., Sushko, P., et al, Adv. Mater. 2012, 24, 2109.

2. Chemelewski, K. R.; Lee, E.; Li, W.; Manthiram, A. Chem. Mater. 2013, 25, 2890.