bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Electrochemical Performance of Hydrogenated Li4Ti5O12 As Anode Materials for High-Power Li-Ion Batteries
Authors: Eom Ji-Yong , Yun Ju-Ho , Yoo Seung-Eul
Published: February 2020

Li4Ti5O12 (LTO) with a spinel structure has received much attention as the most promising alternative to the conventional graphite anode material of Li-ion batteries for hybrid electric vehicle, electric vehicle, and large-scale energy storage applications, due primarily to its advantageous material properties, such as enhanced safety, good capacity retention during cycling, and high power density. Also, LTO is a zero-strain insertion material, which has excellent Li+ insertion/extraction reversibility with no volume change. In spite of these advantages, LTO presents a relatively poor rate capability due to its low electrical conductivity and Li+ diffusion coefficient. Recently, the nanostructured LTO materials coated with carbon-based materials have been extensively studied in the hope of achieving further improvement in the rate capability due to both good electrical conductivity and short Li+ diffusion length. However, these nanomaterials present relatively low volumetric energy density and difficulty in the electrode coating process, and also high production cost. Therefore, it is very important to develop a novel method to achieve simultaneously the enhanced electrical conductivity and volumetric energy density of LTO material.

In this work, we suggest a facile method to achieve the improved electrochemical performance of LTO anode material composed of the micro-sized primary particles for high-power Li-ion batteries. The electrochemical performances of the micro-sized LTO particles, including the rate capability and cycling stability were significantly improved by hydrogenation. The hydrogenated LTO (denoted as H-LTO) particles were obtained by thermal annealing of the P-LTO (denoted as P-LTO) particles at 800 °C for 2~7 h in hydrogen atmosphere. Thermal annealing was performed in a quartz tube furnace filled with ultrahigh purity hydrogen gas. The H-LTO particles exhibited vastly superior the rate capability and capacity retention property during cycling to the P-LTO particles at high current density, since the insertion and extraction of Li+ through the H-LTO particles were preferable to those through the P-LTO particles, which were probably attributed to the short diffusion length for Li+, innumerable reaction sites, and relatively high electrical conductivity.
Synthesis and Electrochemical Characteristics of LiMnPO4/C Composite Materials for Lithium Ion Batteries
Authors: Kang Byeong Su , Kim Kyeong-Joon , Choi Seung-Woo , Kim Min-Young , Yang Seung-Hoon , Lim Jinsub , Lee Moo Sung , Kim Ho-Sung
Published: February 2020

Olivine-structured LiMnPO4 has attracted broad attention as a potential cathode material of Li-ion battery for EV application [1-2], which has some advantage with a higher energy density, higher redox potential and lower cost, etc. However, this material showed a poor electrochemical performance due to the low electronic conductivity [3-4]. Therefore, many researches have been performed to improve the electrochemical properties of LiMnPO4 material by the particle size reduction, cation doping and carbon coating, etc. [5-6]. In here, we studied nano-sized LiMnPO4/C composite materials with a high crystallization prepared using a modified co-precipitation method including a grinding mill and heat treatment process. As a result, the cell showed a good discharge capacity of 145mAh/g and a discharge potential of 3.8V. Furthermore, as the LiMnPO4/C material was combined with Li2MnO3-based material, the LiMnPO4/C composite materials showed a better electrochemical characteristic of above 200mAh/g at 0.05C. In summary, the nano-sized LiMnO4 material with a high crystallization shows good electrochemical properties at room temperature.

References

[1] J.N. Reimers, J.R. Dahn, J. Electrochem. Soc. 139 (1992) 209.

[2] D.K. Kim, P. Muralidharan, H.-W. Lee, R. Ruffo, Y. Yang, C.K. Chan, H.

Peng, R.A. Huggins, Y. Cui, Nano Letter 8 (11) (2008) 3948–3952.

[3] N.N. Bramnik, H. Ehrenberg, Journal of Alloys and Compounds 464 (2008) 259–264.4)

[4] J. Yang, J.J, Journal of The Electrochemical Society 153 (4) (2006) A716–A723

[5] T. Drezen, N.-H. Kwon, P. Bowen, I. Teerlinck, M. Isono, I. Exnar, Journal of Power Sources 174 (2007) 949–953.

[6] A.V. Murugan, T. Muraliganth, A. Manthiram, Journal of The Electrochemical Society 156 (2) (2009) A79–A83
Thin Film Coatings on Multiwalled Carbon Nanotubes for Lithium-Oxygen Battery Cathodes: Eliminating the Carbon Surface
Authors: Yilmaz Eda , Okur Faruk , Sagkal Sagnak , Eren Hamit , Biyikli Necmi
Published: February 2020

Energy storage is one of the biggest challenges in our way before switching to sustainable energy resources. Batteries can be a viable solution to this challenge if “better” batteries with higher energy density, improved stability and cheap price can be realized. Lithium-oxygen batteries have become popular recently as they can theoretically offer much higher energy densities compared the widely used Li-ion or Ni-Mh batteries. However, realizing Li-O2 batteries is no easy task, because of the electrolyte decomposition, cathode degradation and anode related problems which were intensively studied in recent years.1,2 These aforementioned problems come together to complicate the electrochemistry taking place inside the cell, consecutively over-potential, low cycling life and poor current rate responses are observed.

In this study thin film coatings of TiO2 are fabricated using atomic layer deposition technique (ALD) on multiwalled carbon nanotubes (MWCNT) and these composites were used as cathode for Li-O2 battery. (Fig.1) Such a structure eliminates the direct interaction of carbon surface with electrolyte molecules and prevents the degradation of carbon cathode without sacrificing the high energy density carbon provides. TiO2 was chosen as the coating material, since in a recent study by Thotiyl et. al. a thin surface film of TiO2 was shown to increase the oxygen reduction and evolution reactions activity of the TiC cathodes.3 The electrochemical properties of the prepared composites and the comprehensive analysis of their effect on degradation mechanisms will be discussed in this presentation.

References

Thotiyl, M. M. O., Freunberger, S. A., Peng, Z., Bruce, P. G., J. Am. Chem. Soc. 2013, 135, 494.

McCloskey, B. D., Speidel, A., Scheffler, R., Miller, D. C., Viswanathan, V., Hummelshøj, J. S., Nørskov, J. K., Luntz, A. C., J. Phys. Chem. Lett., 2012, 3, 997.

Thotiyl, M. M. O., Freunberger, S. A., Peng Z., Chen, Y., Liu, Z., Bruce, P. G., Nat. Mater. 2013, 12, 1050.

Figure 1
Polyethylene Oxide (PEO)-Based Electrolyte for Lithium Sulfur Polymer Battery
Authors: Carbone Lorenzo , Hassoun Jusef
Published: February 2020

Recently, innovations in the field of energy storage, requiring high capacity and efficiency triggered large number of studies on new systems such as batteries lithium-air and lithium sulfur. These new technologies may lead to significant advances and application as power sources in hybrid electric vehicles (HEVs), plugged-in hybrid vehicles (PHEVs), full electric vehicles (EVs) [1]. Lithium sulfur battery represents the most suitable candidate due to its promising characteristics in terms of specific capacity (1675 mAh g-1) and energy density (3500 Wh kg-1).

However, the Li-S electrochemical process leads to the formation of various polysulfide, i.e. species soluble in the common electrolytes, thus causing parasitic reaction and shuttle effects [2]. Furthermore, electrolytes such as carbonate have low thermal stability and flammability issues [3]. Hence, the study of electrolytes capable of supporting the high performance of the new electrode materials and the associated problems is necessary to optimize the cell performances. In this scenario, the ideal candidate for the use in the new generation of batteries is the polyethylene oxide-based electrolyte [4]. Herein, we report the characterization of a PEO-based membrane using LiCF3SO3 as the lithium-ion salt. The electrolyte, considered as suitable media for lithium-sulfur battery and characterized by high safety level, has been studied in terms of thermal properties (TGA, DSC), lithium ion conductivity, lithium interface stability, lithium transference number and cyclic voltammetry. Finally, a lithium-sulfur cell using the selected electrolyte has been efficiently investigated, by galvanostatic charge-discharge test, evidencing promising results in terms of delivered capacity and stability (see figure below reporting a typical charge discharge cycling profile of the studied lithium-sulfur polymer cell).

(Figure reports typical charge discharge cycling profile of the studied lithium-sulfur polymer cell)

Acknowledgements

This work was supported by Sapienza University-Volkswagen AG joint project

References

[1] R. Bernhard, A.Latini, S. Panero, B.Scrosati, J. Hassoun.   Journal of Power Sources 226 (2013) 329-333

[2] Sheng S. Zhang Journal of Power Sources 231 (2013) 153e162

 [3] Nagasubramanian, G. , Fenton, K. 101 (2013) 3-10

[4] F. Croce, R. Curini, A. Martinelli , L Persi , F. Ronci e B. Scrosati J. Phys. Chem. B 1999, 103, 10632-10638

Figure 1
Electrochemical Characteristics of Si/C/CNT Composites for Anode Material of Lithium Ion Battery
Authors: Lee Jong Dae , Jung Min Zy
Published: February 2020

In recent years, lithium ion battery has been widely used on portable electronic devices and electric/hybrid vehicles because of its high energy density and cycling stability. As an anode material for the lithium ion battery, Silicon(Si) is getting attention for its high theoretical specific capacity (about 4200mAh/g) and its proper potential range for lithium insertion and extraction. However, Si has properties that could be obstacles for its practical use as the lithium ion battery anode. Si not only has a low intrinsic electric conductivity but also undergoes severe volume changes during the lithium ion insertion/extraction process which results in pulverization of the electrode materials, causing the capacity to fade. To overcome these problems and enhance the electric conductivity, we synthesized Silicon/Carbon/CNT composites as an anode material. Si/C/CNT composites were prepared by the fabrication processes including the synthesis of SBA-15, magnesiothermic reduction of SBA-15 to obtain Si/MgO by ball milling, carbonization of phenolic resin with CNT and HCl etching. The prepared Si/C/CNT composites were analysed by BET, XRD, FE-SEM and TGA. Among the SBA-15 samples synthesized with reaction temperatures between 50°C and 70°C, the SBA-15 of 60°C showed the largest specific surface area. Also the electrochemical performances of Si/C/CNT composites as the anode electrode were investigated by constant current charge/discharge test, cyclic voltammetry and leakage tests in the electrolyte of LiPF6 dissolved in organic solvents(EC:DMC:EMC=1:1:1 vol%). The coin cell using Si/C/CNT composite(Si:CNT=97 :3 in weight) has better capacity(1,440 mAh/g) than that of other composition coin cells. Also, it is found that Si/C/CNT composite(Si:CNT=97:3 in weight) electrode shows improved cycling performance and electric conductivity.
Evaluation of the Electrochemical Properties of Copper Hydroxide and Related Copper Oxides in Sodium-Ion Batteries
Authors: Mamiya Mikito , Akimoto Junji
Published: February 2020

Recently, CuO shows high charge and discharge capacity in Na-ion battery. The number of electrode materials for Na-ion battery is much less than that for Li-ion battery.  Copper oxide and related materials are candidate for the high potential electrode materials for Na-ion battery. The theoretical capacity of CuO is 674 mAh g-1. When the charge-discharge reaction evaluated the range between 0 and 3.0 V, the discharge capacity shows 600 mAh g-1 at 1st.  However, the discharge capacity in 2nd cycle is decreased to near 300 mAh g-1. The low cycle performance is one of the week points.  In order to improve the cycle performance, we evaluate the properties in various voltage ranges and research the best performance condition. The charge-discharge reaction evaluated using a 2032 type coin cells.  The working electrode was prepared by mixing the samples, acetylene black (AB) and plytetrafluoroethylene (PTFE) in a 70:20:10 weight ratio. Na metal was used as a counter electrode. The 1M NaClO4 in EC:DMC(1:1) solution was used as the electrolyte. The current density was 10 mA g-1. When we set it between 1.0 and 4.0 V, which is 1.0 V higher than before, CuO shows reversible charge-discharge reaction up to 20 cycles.  The maximum discharge capacity is nearly 150 mAh g-1. Cu2O was also evaluated the properties, however the material did not show reversible reaction. The maximum discharge capacity is below 10 mAh g-1. Cu(OH)2 is a novel material as an electrode of Na-ion battery. The charge-discharge reaction was also evaluated. Figure 1 shows the charge-discharge profiles up to 10 cycles. The maximum discharge capacity is 247 mAh g-1.  There is a plateau around 1.3 V, which is corresponded to the redox reaction of Cu2+ to Cu+ (vs Na+/Na).    When the voltage range expands to 0 V, the redox reaction of Cu+ to Cu would increase the capacities.  However, the redox reaction makes disadvantage effect of the cycle performance.  Figure 2 shows the cycling performances of Cu(OH)2 in the voltage range of 1.0 to 4.0 V.  The reversible charge-discharge reaction is observed, although the discharge capacities above 200  mAh g-1 show only first 4 cycles.  The cycling performance is not good.  We are investigating the best matching of the measurement ranges and the electrolytes.  Furthermore, we develop an in-situ measurement of X-ray diffraction and charge-discharge reaction.  It will clear the mechanism of the reaction from the view of changing crystal structures.

Figure 1
Materials, Technologies, Equipment for Production and Non-Destructive Testing of High Energy, Safe and Low Cost Solid State Li-Ion Batteries
Authors: Shembel Elena M , Redko Vlad I , Klyui Nikolai I , Markevich Alexandr V , Maksyuta Irina M , Tutyk Valeriy A , Nosenko Alexander V , Kolomoyet Olga
Published: February 2020

Enerize achievements in the development the high energy solid state Li-ion batteries are based on the synergetic effect of our innovations in the areas of new materials, technologies and equipment for thin film deposition. Key materials and technologies include: vitreous high ionic conductivity solid inorganic electrolytes; high energy silicon – graphite composite binder free anodes with the structure, which ensures the high level of the adhesion between composition and current collector, cohesion between the particles of silicon and graphite, and high level stability during cycling. Key innovating methods and equipment are based on the Gas Discharge Electron Gun with a Cold Cathode, and Gas Detonation Deposition, which provide the high rate deposition of thin layers of electrode materials and solid electrolytes with predetermined properties. Breakthrough is resulting reducing the costs, increases productivity of battery fabrication, and provides reliability and high performance of batteries. Areas of applications for Li-ion batteries with solid inorganic electrolyte include: oil & gas drilling companies, hot environments and/or high loads, e.g. vehicle running uphill, military, power tools, deep mining, aerospace, and petrochemicals. Enerize owns 4 US patents and 4 US patent applications in the area of the solid state batteries
Sulphur Substitution As an Effective Way to Promote the Structural and Electrochemical Performance of the LiMn2O4 Cathode Material
Authors: Bakierska Monika , Molenda Marcin , Dziembaj Roman
Published: February 2020

The lithium-ion batteries are considered as the most dominant technology in the field of energy storage due to their high energy density [1]. Since they were introduced into market, the application targets have expanded from small portable devices to large-scale applications including hybrid electric vehicles (HEV), electric vehicles (EV) and stationary energy storage systems [2,3]. Lithium manganese oxide spinel has been recognized as a potential alternative cathode material. In comparison with LiCoO2, LiNiO2 and related systems, LiMn2O4 spinel possesses many advantages, e.g. high abundance, non-toxicity, low cost and great safety characteristics [4]. Nevertheless, it is well known that stoichiometric lithium manganese spinel suffers from significant capacity fade during the electrochemical cycling which is generally attributed to structural changes caused by Jahn Teller distortion of Mn3+ ions [5]. One of the various approaches to achieve better structural stability and hence, improve capacity retention is modification of oxygen sublattice in the LiMn2O4spinel by partial substitution with sulphur [6].

The aim of this work was to investigate how sulphur substitution affect the structural and electrochemical properties of LiMn2O4-ySyspinel materials.

Nanosized LiMn2O4-ySy (y = 0 or 0.01) spinel materials were obtained by a modified sol-gel method based on the hydrolysis and condensation processes. The prepared Li-Mn-O-S spinel systems were investigated with regard to the physicochemical properties using X-ray powder diffraction (XRD), elemental analysis (EA), nuclear magnetic resonance (NMR), low-temperature nitrogen adsorption-desorption measurements (N2-BET), differential scanning calorimetry (DSC) and electrical conductivity (EC) studies. The electrochemical performance of Li/Li+/LiMn2O4-ySycells was examined by galvanostatic charge/discharge tests (CELL TEST) and electrochemical impedance spectroscopy (EIS).

It was established that the introduction of a small amount of sulphur leads to the stabilization of the spinel structure and consequently, the enhancement of the cycling behavior what confirmed that sulphur substitution is an efficient way to advance the structural and electrochemical properties of the LiMn2O4spinel.

References:

[1] J. M. Tarascon, M. Armand, Nature 414 (2001) 359-367.

[2] K. Amine, J. Liu, I. Belharouak, S. H. Kang, I. Bloom, D. Vissers, G. Henriksen, Journal of Power Sources 146 (2005) 111-115.

[3] R. Mukherjee, R. Krishnan, T. M. Lu, N. Koratkar, Nano Energy 1 (2012) 518-533.

[4] J. W. Fergus, Journal of Power Sources 195 (2010) 939-954.

[5] L. Yang, M. Takahashi, B. Wang, Electrochimica Acta 51 (2006) 3228-3234.

[6] M. Molenda, R. Dziembaj, D. Majda, M. Dudek, Solid State Ionics 176 (2005) 1705-1709.
A Novel CNT Anode Material for Li Battery Applications
Authors: Riehl Bill , Riehl Bonnie , Banks Craig
Published: February 2020

Carbon nanotubes hold excellent promise for lithium based energy storage and conversion applications. The use of typical nanophase sp2 carbon as a host material has two principal disadvantages, chief of which is the substantial presence of electrochemical impurities and low lithium storage ability when compared with metallic lithium. A process is shown that produces electrochemically clean, high defect rate carbon nanotubes through the corrosion of silicon carbide fibers to produce a low internal resistance, high activity anode material for Li battery applications. This material is shown to be superior to conventional chemical vapor deposition grown CNTs electrochemically and physically. Residual material present in carbide derived CNTs are electrochemically inert carbides and oxides. The resulting CNT bundles are more consistent in chirality, as well as defect rate and physical dimension than the CVD grown counterparts.

Under optimal conditions Li intercalates into graphitic material in the form of LiC6, which leads to a specific capacity reduction from 3860 mAh/g for metallic Li to 372 mAh/g for the graphitic anodes. We describe a process, carbothermal carbide conversion, for the production of a uniquely valuable carbon nanotube material for electrochemical applications comprised of bundles of SWCNTs of high defect rate. As carbide conversion nanotubes form, the CNTs aggregate into bundles which consist of single-wall nanotubes held together by van der Waals forces roughly equivalent to graphitic sheet spacing, approximately 5 angstrom. These ropes display increased energy storage capabilities as Li ions can intercalate both into the channels between the nanotubes, and into the interior of the nanotubes themselves. This gives an anode stoichiometry of approximately LiC2, which is considerably higher than the value of conventional Li-graphite anodes. Studies have shown that the entry of Li ions preferentially enter through defects such as kinks or open ends of nanotubes. We show higher edge plane character of carbide derived CNTs via Raman spectroscopy, transmission electron microscopy and electrochemical deposition of nickel.

Figure 1
Microwave-Assisted Synthesis of Tin Sulfide/Reduced Graphene Oxide Nanocomposites As Anode Material for High-Performance Lithium-Ion Batteries
Authors: Lin Jeng-Yu , Ho Hsin-Ping
Published: February 2020

Rechargeable Lithium ion batteries (LIBs), as a great promise power source for next generation electric vehicles such as electric vehicles (EVs). Demands for batteries with higher energy density, better cycle performance, lower cost and more safety are increasing. Graphite is mostly used as anode material for the commercial Lithium ion batteries with the theoretical specific capacity 372 mAh g-1 only. However, in order to overcome the lower capacity problem, many alternatives as anode materials are concerned including metals or metal sulfides.

Recently, tin-based materials (e.g. Sn, SnO2, SnS) have been widely studied as anode materials because they have relatively high theoretical capacities, less toxic and low cost. In particular, tin sulfides has such as high theoretical capacity 782 mAhg1.However, the great volume expansion and the agglomeration of particles for the tin sulfides during the charge/discharge process could possibly result in pulverization of the electrode and thus to lead to rapid decrease in capacity and poor cycle life.

Graphene or reduced graphene oxide (RGO), as one of the highly potential materials in lithium-ion batteries, is also used to be decorated with metal oxides or metal sulfides due to their high specific surface area, excellent electronic conductivity and porous structure. Therefore, an improved electrochemical performance can be achieved. More recently. Lots works have demonstrated that the incorporation of graphene within tin sulfide-graphene nanocomposites can provide a large area contact for tin sulfide particles and inhibit the volume change of tin sulfides, thus enhancing the electrochemical performance of tin sulfide-graphene nanocomposites.

Thus, in this work, SnS/RGO nanocomposites was synthesized via a facile microwave-assisted method. The physical and electrochemical properties of the as-prepared nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, cyclic voltammetry, galvanostatic charge/discharge tests and electrochemical impedance analysis. Indeed, the SnS nanoparticles were successfully decorated on the surface of RGO, and the resultant SnS/RGO nanocomposite demonstrated an improved electrochemical performance because the incorporation of RGO provided a large area contact for SnS nanoparticles and inhibited the volume change of SnS during charge/discharge process.
Li-Ion Nanotubes for Li-Ion and Li-Sulphur Batteries
Authors: Yokota Nanami , Alfredsson Maria
Published: February 2020

Rechargeable lithium-ion batteries are considered to be the most promising energy storage due to their long cycle life and high specific capacity.[i] However, existing lithium-ion batteries use graphite as anode material and this is not efficient enough to reach market level to be employed in vehicles. There are still some challenges  to develop more in anode material to enhance their performance to meet the requirements for efficient energy storage. [ii] Silicon has been regarded as the most promising candidate to replace graphite anode material due to its excellent merits in high theoretical electrochemical capacity. It is safe to use in high-power applications due to its low discharge potential. [iii] However, the commercial application of Silicon in the battery is still not progressed due to severe mechanical damage because of volume expansion and contraction of Si electrodes during cycling operation. This could cause pulverisation and loss of capacity[iv] An effective way to solve this problem is the employment of nanostructure which are capable of minimising the volume change due to small size and available surrounding free space.[v]

The aim is to synthesise and lithiate silicon nanotubes, then employ the lithiated nanotubes as an anode material in both Li-ion as well as Li-sulphur batteries. This would improve the electrochemical performance by enhancing the cycling performance and higher reversible specific capacity may be achieved.

 

[i]  M.Rosa Palacin, Chemical Society Reviews, 2009, 38, 2565-2575.

[ii] S. Flandrois, B.Simon, Carbon, 1999, 37, 165-180.

[iii] J. Cho, Journal of Materials Chemistry, 2010, 20, 4009-4014.

[iv] D. Billaud, E. Mcrae and A. Herold, Mater. Res. Bull., 1979, 14, 857–864.

[v] J. Bae, J. Solid State Chemistry, 2011, 184, 1749–1755.
Towards High-Capacity Silicon Anodes for Lithium-Ion Batteries: On the Influence of Loading and Surface Coating on the Cyclability
Authors: Breitung Ben , Schneider Artur , Baumann Roelf-Peter , Sommer Heino , Brezesinski Torsten , Janek Jürgen
Published: February 2020

The development of efficient energy storage systems is of great importance in view of the increasing demand in electrical energy both for stationary and mobile applications. Silicon (Si) is an abundant and nontoxic material and provides one of the highest theoretical specific capacities (approx. 4000 mAh/g) of all known anode active materials. However, severe mechanical stresses, low coulombic efficiencies and irreversible capacity losses during cycling of silicon anodes are critical issues that need to be addressed.

For “real world” applications, it is indispensable to increase the gravimetric and volumetric energy densities of Li-ion batteries (e.g., by tailoring the areal loading of electrodes). Low active material loadings lead to high rate capability and good cyclability but result in low practical energy densities (and areal capacities). In this work, we show that systematic investigations of Si-based anodes with different silicon loadings help finding the optimum between cycling stability and areal capacity. Furthermore, we describe a straightforward pyrolysis process that allows for carbon encapsulation of silicon nanoparticles, which thus enhances the electrode stability, including rate capability and capacity retention. Batteries using the silicon/carbon nanocomposite demonstrate specific capacities of >2000 mAh/g and areal capacities of approx. 2 mAh/cm² over 200 cycles. The different materials employed were analyzed in detail via TEM, REM, Raman- and IR-spectroscopy, and galvanostatic charge/discharge measurements. In addition, we present results on the volume changes (cell “breathing”) and SEI formation upon cycling from in operando AFM measurements.
Studies of Anomalous Diffusion in Composite Silicon Anodes
Authors: Lain Michael J , Beattie Shane D , Loveridge Melanie J , Bhagat Rohit , Dashwood Richard
Published: February 2020

1.            Introduction

The diffusion coefficient is an important parameter of active materials for lithium ion batteries, particularly in higher rate applications like electric vehicles. It is useful to know the diffusion coefficient as a function of state of charge, and other parameters like temperature. Silicon has a very high lithiation capacity (3579 mA hr g-1), but a correspondingly large expansion when fully lithiated (> 270 %). On the first charge, crystalline silicon is converted to amorphous LixSi, and then to crystalline Li15Si4 at full lithiation. The diffusion coefficient in a-LixSi will have an important influence on the movement of these two phase boundaries, which in turn will impact upon the performance and operating life of the electrode. The two main techniques used to measure diffusion coefficients are a. c. impedance, via the Warburg coefficient, and galvanostatic intermittent titration technique (GITT). This report describes the use of both of these methods on composite silicon anodes.

 2.            Results

Electrodes were prepared using 3 µm silicon powder, with partially neutralised poly acrylic acid as binder and conductive carbon. Following a slow formation cycle (C/20), impedance spectra were recorded in two electrode half cells, at different states of charge. Figure 1 shows typical results at lithiation capacities of 300, 600, 900 and 1200 mA hr g-1. The data was fitted to equivalent circuits, with a series resistance, two resistor // CPE parallel combinations, and a low frequency constant phase element (CPE) tail. Apart from the fully delithiated anode, the tail was always at a much steeper angle than the standard Warburg value of 45o (power term = 0.5). Figure 2 shows plots of the fitted power term {n in Z = (iw)-n C-1}, at three different states of charge, during cycling.

 3.            Discussion

One explanation for the steeper gradient is that the diffusion is anomalous or non-Fickian [1]. This can occur for charge carrier movement in amorphous solids, like LixSi. After each hop, the charge carrier can wait “for a period drawn from a broad power law distribution” [1], reducing the overall rate of diffusion. Interestingly, a recent theoretical study has calculated a wide range of activation energies for lithium hopping in amorphous silicon (0.1 to 2.4 eV [2]). The difference in the power term at 600 mA hr g-1 during lithiation and delithiation implies a structural hysteresis, which may match the voltage hysteresis observed with silicon anodes.

 Further results, including GITT experimental data and analysis, will be presented at the conference.

 References

[1]          J. Electroanal. Chem. 499 (2001) p. 112          J. Bisquert & A. Compte

[2]          J. Phys. Chem. C 116 (2012) p. 22212              G. A. Tritsaris, K. Zhao, O. U. Okeke & E. Kaxiras

Figure 1
Structural Defects and the Impact of Battery Ageing - How Sensitive Are Entropy Profile Measurements, and What Do They Show?
Authors: Schlueter Steffen , Osswald Patrick J , Hoster Harry Ernst , Ghasemi Shahnaz , Maher Kenza , Yazami Rachid
Published: February 2020

We report on entropy profile measurements at lithium ion full and half cells.1 Those profiles are derived from voltage responses on temperature variations for various states of charge. For LiCoO2 cathodes, measured in half cells, we demonstrate that the entropy profiles are sensitive to particle sizes as varied through the synthesis method, including calcination (Fig. 1). The origin of those variations is further elucidated by in-situ XRD studies and thermodynamic calculations. We discuss, in how far those variations reflect an impact of the particle sizes on the stability of ordered and disordered phases, or rather are related to defects in the crystal structure. The density of such defects may as much depend on the synthesis route as the particle sizes do.

Furthermore, we demonstrate that entropy profile measurements are suitable to track the impact of cycle and thermal ageing2 on full cells. We show how full cell entropy profiles of new and aged cells can be calculated based on the half cell profiles of the fresh electrode materials. As confirmed by in-situ XRD measurements of new and aged cathodes (here: NMC and NCA), the changes observed in the entropy profiles can be explained without considering changes in the crystal structure of anode or cathode.

1 P. J. Osswald, M. del Rosario, J. Garche, A. Jossen, H. E. Hoster, Electrochimica Acta, DOI: 10.1016/j.electacta.2015.01.191

2 K. Maher, R. Yazami, J. Power Sources 261 (2014) 389

Figure 1
Degradation Diagnostics for Commercial Lithium-Ion Batteries
Authors: Birkl Christoph Robert , McTurk Euan , Roberts Matthew , Bruce Peter G , Howey David Alastair
Published: February 2020

We present a method to diagnose electrode-specific degradation in commercial lithium ion (Li-ion) cells. The method is used to estimate the loss of active electrode material and lithium inventory resulting from long-term cycling of commercial cells.

Li-ion cells degrade due to a complex interplay of physical and chemical processes [1, 2], which lead to performance deterioration and, ultimately, cell failure. The various degradation mechanisms progress at different rates and have distinct effects on cell performance and lifetime. Some mechanisms, for instance lithium plating and dendrite formation, can result in internal short circuits and, in the worst case, fires or explosions [3]. The ability to identify the prevalent degradation mechanisms at any point in time is therefore crucial in order to anticipate the remaining lifetime of a cell accurately and to warn against imminent cell failure.

Many degradation mechanisms have a noticeable effect on the cell’s open circuit voltage (OCV) [4, 5]. The proposed method is designed to harness the information contained in the OCV by fitting a phenomenological OCV model [6] to the OCV of cells measured at different stages of their cycle life. The OCV model consists of parametric electrode sub-models and a full cell model, which combines the electrode OCVs by adjusting the loading ratio (the ratio of anode versus cathode capacity) and the offset (the portion of un-utilized cathode capacity), see Figure 1. Fitting the loading ratio and offset at various stages in the cell’s life allows estimation of the loss of active electrode material as well as the loss of lithium inventory. By tracking the rates of loss of active material and cyclable lithium, projections about the cell’s end-of-life can be made. Moreover, registering the loss of a critical amount of active anode material might prevent lithium plating and associated risks of cell failure.

The OCV model has been fitted to experimental data recorded on a 4 Ah, LiCoO2 pouch cell, which was cycled at 2C and 45°C, with pseudo OCV curves (C/20 charge and discharge) recorded every 100 cycles. Initial results have shown high accuracies of OCV model fits, with RMS errors < 15 mV (see Figure 2). In order to validate identified degradation mechanisms, the diagnostic procedure is repeated on commercial LiNiMnCoO2cells, which are subjected to post mortem analyses including electrochemical analyses on 3-electrode cells, scanning electron microscopy and XRD.

[1]
J. Vetter et al. , J. Power Sources, vol. 147, pp. 269-281, 2005.

[2]
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[3]
Q. Wang et al., J. Power Sources, vol. 208, pp210-224, 2012.

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[5]
M. Dubarry et al., J. Power Sources, vol. 219, pp.204-216, 2012.

[6]
C. R. Birkl et al., Abstract no. 63, 227th ECS Meeting, 2015.

Figure 1
Diagnosis Method to Detect the Incorporation of Metallic Particles in a Lithium Ion Battery
Authors: Nakajima Hironori , Kitahara Tatsumi
Published: February 2020

Lithium ion batteries have the issue of internal short circuiting by the electrodeposition of metal at the negative electrode. This deposition follows the dissolution of metal particles incorporated into the positive electrode in manufacturing process. Thus, we have investigated the dissolution-deposition behavior of metals such as iron and copper using cyclic voltammetry and SEM/EDX. We have also addressed diagnosis method for the incorporation of the metal particles by electrochemical impedance spectroscopy. 

Test cells were assembled with positive electrodes of LiCoO2 mixed with acetylene black as conductive filler and PVDF binder, electrolyte solution of ethylene carbonate (EC)/diethylcarbonate (DEC) (1:1 vol.) containing 1 M LiPF6, and negative electrodes of graphite mixed with PVDF binder. Lithium metal was used as a reference electrode.

Cyclic voltammetry was carried out with positive electrodes of iron plate and copper foil as working electrodes. Current onset potentials originating in the anodic dissolution of iron and copper were around 2.4 V and 3.6 V (vs. Li+/Li), respectively[1]. Hence those metal dissolve during charging of a cell. The anodic current for copper was larger than that for iron．

Iron particle with a diameter of 150 μm, and copper particle with a diameter of 100 μm were adhered to the positive electrode surface. The fully charged cell by 1C with the iron particle exhibited no rapid voltage drop for one week whereas the cell with the copper particle showed rapid voltage drop before full charge, resulting in the short circuit much earlier than iron in agreement with the larger anodic dissolution current shown by the cyclic voltammetry. SEM and EDX observations of the surface of the negative electrode after charging showed iron and copper depositions in torus-shape.

We also repeatedly maintained the cells with those metal particles under fully charged state (SOC:100%) for 24 hours before a discharging/charging cycle to assess the time variation of impedance spectra. As a result, we find characteristic change of the Bode plot for the negative electrode in the case of iron particles between 10-1 Hz as shown in Fig. 1. Since time variation in the impedance spectra was detected, electrochemical impedance spectroscopy is effective diagnosis method to detect the metal particle incorporation.

[1] C. Iwakura, Y. Fukumoto, H. Inoue, S. Ohashi, S. Kobayashi, H. Tada, and M. Abe, J. Power Sources, 68, pp. 301-303 (1997).

Fig. 1 Bode plots for the negative electrode (a) with and (b) without the Fe particles.

Figure 1
Determining Performance-Limiting Mechanisms in Fluorophosphate Sodium-Ion Battery Cathodes Via Transition-Metal Mixing
Authors: Matts Ian L , Dacek Stephen , Pietrzak Tomasz Karol , Malik Rahul , Ceder Gerbrand
Published: February 2020

Motivated by the potential for new intercalation chemistries, sodium-ion batteries have received renewed interest as a possible replacement technology for lithium-ion batteries. To date, fluorophosphates, particularly Na3V2(PO4)2F3, are among the most promising sodium-ion cathodes studied. Fluorophosphates exhibit redox activity near 4V due to the strong inductive effect of phosphates and fluorine, and have been shown to reversibly cycle near their single-electron capacity of 128mAh/g, yielding energy densities close to 480Wh/kg1,2. However, efforts to further improve the capacity of these materials have achieved very little success.

            This work reports on our efforts to determine the mechanism by which fluorophosphate cathodes appear to be limited to their single-electron capacity. Our method is to examine systems that decouple previously observed Na+extraction limits from redox limits. We will discuss the electrochemical characterization of novel mixed-transition metal fluorophosphate systems, from which we can conclude that fluorophosphate cathodes’ capacities are not redox-limited. We demonstrate reversible capacity exceeding the single-electron theoretical capacity during a single charge/discharge. In addition, computational examination of limiting behaviors will be elaborated on. Specifically, possible site-limiting and diffusion-limiting mechanisms in fluorophosphate cathodes will be presented.

References:

[1]  R. A. Shakoor, D. H. Seo, H Kim, Y. Park, J. Kim, S. Kim, H. Gwon, S. Lee, and K. Kang. J. Mater. Chem., 22,20535–20541 (2012).

[2]  K. Chihara, A. Kitajou, I. Gocheva, S. Okada, and J. Yamaki. J. Power Soources., 227, 80 – 85 (2013).
Understanding the Oxygen Activities in High Voltage Cathode Materials in Lithium and Sodium Ion Battieres
Authors: Meng Shirley
Published: February 2020

Among all candidates of positive electrode materials for lithium ion batteries, the lithium-excess layered oxides have gained growing research interest in recent years. They can reach more than 290mAh/g capacity with an average voltage of 4 V, making them the positive electrode material with highest energy density among all known intercalation compounds for cathode materials. Being the source of major capacity improvement, the extra lithium ions, on the other hand, also cause unexplained phenomena in lithium-excess layered oxides. The rate performances of these materials are usually poor, and electron sources for the extra capacities have been under intense debate for years. In classical layered oxides, the transition metal (TM) oxide host TMO2 should retain its host structure during initial discharging–charging, while lithium ions are intercalated–de-intercalated from the host. In contrast, recent studies suggested that in lithium-excess manganese rich layered oxides, certain amounts of transition metal ions migrate from the transition metal layers to lithium layers during the very first charging–discharging cycle. Our previous work has suggested that the migration may be assisted by oxygen vacancies generated in the late charging states of the first cycle, but three critical questions remain unanswered: (1) how can we visualize and quantify the change in structure and chemical content at the atomic level (2) what is the energy required for oxygen vacancies formation upon cycling and how do they assist transition metal migration and (3) are the oxygen loss reversible or partially reversible. A similar phenomena could be observed in sodium intercalation compounds. The oxygen activiites in the intercalation compounds at high voltage will be discuced in details.
Influence of Synthesis Parameters on the Electrochemical and Interfacial Properties of Na2Ti3O7 As Anode for Na Ion Batteries
Authors: Zarrabeitia Maider , Castillo-Martínez Elizabeth , Eguía Aitor , Muñoz Márquez Miguel Ángel , López del Amo Juan Miguel , Rojo Teófilo , Casas-Cabanas Montserrat
Published: February 2020

Sodium ion batteries (SIBs) are becoming an attractive alternative for stationary applications because of their low cost: sodium is more abundant and easier to obtain than lithium and cheaper current collectors made of aluminium instead of copper can be used.

While for cathode materials many lithium analogues can be successfully used in SIB [1], the challenge is to find alternative anode materials [2], the reasons being the impossibility of sodium insertion into graphite and the formation of a stable SEI layer (Solid Electrolyte Interphase).

Na2Ti3O7 has been reported as the oxide with the lowest sodium insertion/deinsertion voltage at 0.3 V vs . Na+/Na and a capacity close to 200 mAh/g [3], becoming a very promising anode candidate both in terms of energy density and cost. However the reported capacity retention needs to be improved [4, 5] and the formation of a stable SEI layer remains to be proved.

Here we present a study were the role of several synthesis parameters, such as the sodium source precursor and the atmosphere during the cooling process, is correlated with the electrochemical properties of the sodium titanate, in particular, with the capacity retention which has been dramatically improved [6]. The composition of the SEI layer has also been studied at different points of galvanostatic curve by means of XPS (X-ray photoelectron spectroscopy) combined in some cases with ion bombardment depth profiling.

 

[1] V. Palomares, M. Casas-Cabanas, E. Castillo-Martínez, M.H. Man, T. Rojo, Energy Environ. Sci., 2013, 6, 2312-2337.

[2] M. Dahbi, N. Yabuuchi, K. Kubota, S. Komaba, Phys. Chem. Chem. Phys., 2014, 16, 15007-15028.

[3] P. Senguttuvan, G. Rousse, V. Seznec, J.M. Tarascon, M.R. Palacín, Chem. Mater., 2011, 23, 4109-4111.

[4] H. Pan, X. Lu, X. Yu, Y.S. Hu, H. Li, X.Q. Yang, L. Chen, Adv. Energy Mater., 2013, 3, 1186-1194.

[5] A. Rudola, K. Saravanan, C.W Mason, P. Balaya, J. Mater. Chem.
A, 2013, 1, 2653-2662.

[6] M. Zarrabeitia, E. Castillo-Martínez, J.M López del Amo, A. Eguía-Barrio, M.A. Muñoz-Márquez, T. Rojo, M. Casas-Cabanas (submitted)
Method for Dimensioning Battery and Thermal Management Systems for Heavy-Duty Vehicle Applications Using Aged Battery Experimental Data and Advanced Modelling Techniques
Authors: Kukkonen Samu
Published: February 2020

When a battery degrades, capacity and power capability fade while losses in battery cells increase. Despite from fading capacity, an electric vehicle battery needs to deliver designed performance until battery end-of-life. To dimension sufficient margin for battery power capability and thermal management, comprehension of battery performance degradation is required. This paper proposes battery cell and module level laboratory testing combined with advanced modelling techniques to obtain design specifications from aged batteries. Extensive laboratory cell aging and characterization tests are performed to parametrise customised Simulink based dynamic electrical battery models with aged battery data at different degradation levels. Furthermore, a finite element thermal model implemented with COMSOL Multiphysics is used to model heat transfer in battery pack structure and thermal management system. This model is validated using experimental data from a prototype battery module. The Simulink model is used to check and validate electrical performance using measured drive cycle data and to provide data on battery losses as an input for the COMSOL model. The latter model is then used to check the performance of a thermal management system. This paper provides an example of this design approach by dimensioning a battery for an opportunity charged electric city bus. The dimensioning is made by using real drive cycle and energy consumption data from an electric bus operating in the city of Espoo, Finland. The chosen cells are then characterized and aged to near end-of-life. Simulations on electrical and thermal performance are then conducted using Simulink and COMSOL with parametrisations representing fresh and aged cells at different levels of degradation. These results are then compared with each other. This gives an indication on how much margin should be designed for power capability and thermal management and tells the performance based end-of-life criteria for the battery system. The results are discussed and recommendations made on battery dimensioning using specifications of aged batteries.