bluuebunny/crossref_metadata_2025 huggingface dataset:
High-Energy and High-Power Electrodes Screened by Microstructure Reconstruction and Model Simulation
Authors: Ender Moses , Illig Jörg , Weber André , Ivers-Tiffée Ellen
Published: February 2020

Even though it is well-known that high-power and high-energy lithium ion cells require different electrode design rules, conventional analysis methods fail to quantify the key properties of their microstructures. To shed light on the differences between commercial high-power and high-energy cells, their electrode microstructures are analyzed in detail using focused ion beam and micro X-ray tomography. The cells under investigation are a 18650 LiFePO4/graphite power cell and a 18500 LiCoO2/graphite energy cell.

A three-dimensional reconstruction of anodes and cathodes allows for specifying their tailor-made microstructural characteristics. Beside the basic structural parameters (a) volume fractions, (b) surface areas, (c) average particle sizes and (d) tortuosity, a more advanced analysis yields additional information such as: (e) particle size distributions, (f) space-resolved tortuosity values (g) a detailed analysis of different secondary-particle classes.

Based on this array of microstructural information, the specific characteristics of all electrodes are identified with respect to cell performance. This newly gained insight is backed up by model simulations. These are based on a refined homogenized porous electrode model, which is parameterized with the structural parameters extracted from the reconstructions.

This combined approach gives a high-definition picture of tailor-made electrodes and facilitates understanding of rate-limiting mechanisms in high-power and high-energy electrodes. During charging and discharging, the electrochemically active zone spreads out over the entire electrode thickness within the high-power cell. Contrary, it is spatially restricted in both electrodes of the high-energy cell and migrates from the separator towards the current collector. Model simulations show, that this behavior is caused by (i) the lower electrode porosity and (ii) the larger electrode thickness of the high-energy cell. Furthermore, model simulations show, that the maximum discharge current of both cathodes (16C and 4C) is restricted by a depletion limitation of the electrolyte.

Figure 1: Three-dimensional reconstructed microstructures of the high-power cell (a, c) and the high-energy cell (b, d). For the anodes (a, b), the graphite phase is shown in blue with the porosity appearing transparent. For the LiFePO4 cathode (c), the two different agglomerate classes are shown in different shades of green, the carbon additive is shown in gray. For the LiCoO2 cathode (d), the active material is also shown in green and the carbon in gray. The porosity in both cathodes appears transparent.
Role of Grain Size in Redox Induced Thin Film Stress in Ceria Systems
Authors: Sheth Jay , Chen Di , Bishop Sean R. , Sheldon Brian W. , Tuller Harry L.
Published: February 2020

Transitioning from the micro to nano morphology scale can result in dramatic changes in electrical and optical properties of films. Space charge effects and creation of a significantly greater fraction of interfaces/grain boundaries are believed to give rise to such size scale effects. While electrical properties have generally dominated research in this area, mechanical properties, such as film stress and strain, also exhibit scaling effects. In-situ wafer curvature measurements are employed to measure these stresses on pure and 10% Praseodymium doped ceria (PCO) thin films during oxidation-reduction cycling and over a range of temperatures and oxygen partial pressures. These measured stress values are compared to the values reported for the bulk PCO and also to the thin film defect equillibria model developed by some of the co-authors and was found to fit well with the predicted values. In both the pure ceria and PCO thin films, the compositional stresses increased with decreasing grain sizes thus corroborating the idea that the space charge effects near surfaces and interfaces has a significant impact on the compositional stresses.
Platinum Decorated Nafion Functionalized Single-Wall Carbon Nanohorns As Catalyst for Proton Exchange Membrane Fuel Cell Applications
Authors: Ebenezer D , Jagannatham M , Bhuneshwar Paswan , Prathap Haridoss
Published: February 2020

Electrode structure plays an important role in the performance of proton exchange membrane fuel cells. To get high electrochemical active area in the electrode, perfluorosulfonate-ionomer is loaded in stage wise. Single-wall carbon nanohorns (SWCNHs) are synthesized by DC arc-discharge method in Helium atmosphere and these synthesized SWCNHs were functionalized with Nafion. Platinum was reduced onto Nafion functionalized SWCNHs through colloidal method. Pt/Nafion-SWCNHs catalysts were prepared by varying deposition times. Detailed characterization of the catalyst was carried out using Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), infrared spectroscopy (IR), and Thermo Gravimetric Analysis (TGA). TEM of Pt decorated SWCNHs revealed uniformly dispersed Pt nano particles with an average particle size of 3 nm in the SWCNHs. IR studies of catalyst confirm the presence of Nafion on Pt/Nafion-SWCNHs. Nafion membrane and Pt/Nafion-SWCNHs catalyst were used to construct fuel cell in decal method and tested in fuel cell testing facility. Cyclic voltammetry tests of the catalyst also confirm the high electrochemical active area of the catalyst. Pt reduction onto Nafion functionalized SWCNHs leads to an increase in electrochemically active surface area. High platinum utilization due to increased electrochemical surface area with efficient SWCNHs support of Pt/Nafion-SWCNHs catalyst makes it a promising electrocatalyst for fuel cells.
Electrode Side Reactions, Capacity Loss and Mechanical Degradation in Lithium Ion Batteries
Authors: Xu Jiagang , Deshpande Rutooj , Pan Jie , Cheng Yang-Tse , Battaglia Vince
Published: February 2020

To further develop lithium ion batteries, it is important to improve the understanding of battery degradation mechanisms. In this presentation, we report the results of a series of experiments which helped establish a relationship between coulombic efficiency, side reactions, capacity loss, and mechanical degradation in lithium ion batteries. Graphite/Li(Ni1/3Mn1/3Co1/3)O2 (NMC) CR2325 full cells of two very different initial anode/cathode capacity ratios (R), both greater than 1, are assembled to investigate their electrochemical behavior. It is observed that, during electrochemical cycling, the cell with a higher R value displays a lower coulombic efficiency than that of a cell  with a smaller R value. The cell with the high R value is shown to have less initial capacity yet less capacity fade during cycling. This confirms the hypothesis that coulombic efficiency is not a perfect indicator of capacity fade. These experiments also show that electrolyte reactions on the anode affect the electrolyte reactions on the cathode and there is, thus, “cross talk” between the two electrodes. This work also supports the idea that capacity fade in graphite based cells is a result of the fracturing and repairing of the solid-electrolyte interphase (SEI) on the anode that leads to a lithium imbalance in full cells and that fracture is worse for cells where the anode particles are cycled to a greater percentage of the full capacity.
(Invited) Improved Performance of Lithium-Sulfur Battery with Fluorinated Electrolyte
Authors: Zhang Zhengcheng , Azimi Nasim , Xue Zheng , Takoudis Christos G
Published: February 2020

Despite the great promise, the Li-S battery poses several technological challenges, including fast capacity fading with cycling, high self-discharge rate, and low energy efficiency. Many of these issues are related to the internal “redox shuttle mechanism,” which results in parasitic reactions of dissolved lithium polysulfides (Li2Sx, x=4-8) with the lithium anode and the loss of sulfur active material.[1] A problem arises because of the dissolution of lithium polysulfide from the cathode into the electrolyte solvent¯typically a mixture of 1,3-dioxolane (DOL) and 1,2-dimethoxyethane (DME).

In this paper, we present a new electrolyte containing an organo-fluorine compound, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) for the first time for the lithium-sulfur battery. Fluoroether compound exhibits much higher hydrophobicity than its non-fluorinated counterpart, and as a result, its interaction with hydrophilic Li2Sx is quite weak. A solubility test clearly indicated that Li2S8 has very limited solubility in the mixture of Fluoroether 3 and DOL at a 1:1 or greater volume ratio, whereas it completely dissolves in the mixture of DOL/DME (1:1 ratio), a state-of-the-art (SOA) electrolyte for the Li-S battery (Fig. 1). The low solubility of lithium polysulfides in fluoroether solvent significantly affects their diffusion into the bulk electrolyte, mitigating the shuttle effect and enhancing the charging efficiency (Fig. 2).[2] The new fluorinated electrolyte suppressed the deleterious shuttling effect and improved the capacity retention and coulombic efficiency in cell tests. In addition, it was found to eliminate the self-discharge of the lithium-sulfur battery.

Figure 1
Sulfur Cathode for High Performance Lithium Sulfur Batteries
Authors: Ryu Hee-Yeon , Woo Hee Jin , Lee Yoon Ji , Park Sang Jin , Kim Dong Hee , Lee Ho-Teak
Published: February 2020

Over the last few decades, electric vehicles (HEV, PHEV, BEV) have been developed as one of the solution to the CO2emission problems. For the successful electric vehicles commercialization, batteries with high energy density are required. Among several kinds of batteries, the lithium sulfur battery is a very attractive candidate, because elemental sulfur has the highest theoretical capacity(1,672 mAh/g) and highest theoretical energy density(2,600 Wh/kg) of all known cathode materials. However, lithium sulfur battery has some problems about cycle life and sulfur utilization efficiency. Recently, a lot of researchers are focused on solving those problems.

In this research, electrochemical properties of lithium sulfur battery were investigated by applying mesoporous carbon and carbon fiber sheet to sulfur cathode. Mesoporous carbon with controllable pore sizes (4nm, 12nm, 25nm) was fabricated and the pores are filled with sulfur for mesoporous carbon/sulfur composites. The optimal pore size of mesoporous carbon was chosen by cell performance test. Carbon fiber sheet was also applied to cathode as a frame structure to have chemical reaction even higher thickness of electrode with maximum sulfur loading. Using those mesoporous carbon/sulfur composites and carbon fiber sheet, lithium sulfur pouch cell was designed, fabricated and tested.

As a result, the discharge capacity of lithium sulfur pouch cell shows 1,206 mAh/g_S with sulfur loading amount of 8.5mg/cm².

Figure 1
Sodium-Ion Battery Cathode Material Synthesized By Spray Pyrolysis
Authors: Shen Kuan-Yu , Lengyel Miklos , Wang Louis S. , Axelbaum Richard L.
Published: February 2020

Lithium-ion batteries have been the dominant choice for batteries for decades, however there are concerns related to the limited availability of lithium, which could potentially increase the cost and affect further implementation. As a promising alternative, sodium-ion batteries have attracted significant attention in recent years [1, 2]. The potential markets for sodium-ion batteries could range from devices where cycle life and cost are more prevailing factors than energy density, such as grid-scale energy storage for smart grid applications. A single-step, facile spray pyrolysis is being evaluated in this group for the synthesis of sodium-ion battery cathode materials.

In the current study, Na0.44MnO2 was selected due to its promising electrochemical performance, unique structure, and its similarity to transition metal oxides [3, 4]. Figure 1 shows the SEM image of Na0.44MnO2 annealed at 800 ºC. The material demonstrates a uniform, rod-like morphology. Figure 2 displays the XRD data of samples annealed at different temperatures for two hours. Na0.44MnO2 has an orthorhombic lattice cell (pbam space group) and is isostructural with Na4Mn4Ti5O18. The sample annealed at 700 ºC displays impurity peaks around the 30º 2θ. These impure phases may be related to the incomplete decomposition at this temperature. There are no additional phases observed in the 800 ºC and 900 ºC annealed samples. Figure 3 shows the first cycle voltage profile of the Na0.44MnO2 (annealed at 800 ºC) cell at C/10, where 1C equals to 120 mAg-1. The material demonstrates a discharge capacity of 100 mAhg-1, which is comparable to materials reported from other synthesis methods.

References:

1.      M.D. Slater, D. Kim, E. Lee, C.S. Johnson, Advanced Functional Materials, Sodium-Ion Batteries, 23(8), 2013, 947-958.

2.     V. Palomares, P. Serras, I. Villaluenga, K.B. Hueso, J. Carretero-Gonzalez, T. Rojo, Energy and Environmental Science, Na-ion batteries, recent advances and present challenges to become low cost energy storage systems, 5(3), 2012, 5884-5901.

3.      F. Sauvage, L. Laffont, J.M. Tarascon, E. Baudrin, Inorganic Chemistry, Study of the insertion/deinsertion mechanism of sodium into Na0.44MnO2, 46(8), 2007, 3289-3294.

4.      L.W. Zhao, J.F. Ni, H.B. Wang, L.J. Gao, RSC Advances, Na0.44MnO2-CNT electrodes for non-aqueous sodium batteries, 3(18), 2013, 6650-6655

Figure 1
Spinel LiMn2O4 Thin Films for 3 V Operating All-Solid-State Lithium Microbatteries
Authors: Bailly Nicolas , Mirvaux Boris , Boissel Jean-Marc , Porthault Hélène
Published: February 2020

Nowadays, all-solid-state microbatteries have become a choice of alternative power source for microelectronic devices such as secured smart cards, RFID tags, stand-alone sensors, etc. In this context, low potential lithium-based systems suitable for microelectronic requirements have to be developed. Here, spinel LiMn2O4material, known for operating in the 4 V region, was investigated in the 3 V region.

Thin films were prepared using physical vapor deposition (RF-magnetron sputtering). SEM micrographs reveal a dense microstructure and a typical columnar growth. The as-deposited material appears to crystallize in a cubic spinel structure according to X-ray diffractograms. Atomic absorption spectroscopy shows a slight over-lithiation of the samples. Process parameters such as Ar/O2ratio and total pressure were optimized to improve electrochemical performances of the material.

First results were obtained in a coin cell configuration with an organic liquid electrolyte. Low crystallinity thin films elaborated with optimized conditions led to a good specific capacity of about 60 µAh.cm-².µm-1. A large 3 V plateau, which corresponds to the structural transformation from cubic spinel to tetragonal phase, can be observed after a low temperature post deposition heat treatment at 300°C in air (Fig. 1a, red curve).

LiMn2O4 thin films were then integrated in all-solid-state microbatteries using LiPON as solid electrolyte (Fig. 1b). The microbatteries integrating LiMn2O4thin films exhibit a good cycle performance.

The authors acknowledge ST-Microelectronics for the financial support.

Figure 1
Activation with Li Enables Facile Sodium Storage in Germanium
Authors: Mitlin David
Published: February 2020

Germanium is a promising sodium ion battery (NIB, SIB) anode material that is held back by its extremely sluggish kinetics and poor cyclability. We are the first to demonstrate that activation by a single lithiation - delithiation cycle leads to a dramatic improvement in practically achievable capacity, in rate capability, and in cycling stability of Ge nanowires (GeNWs) and a Ge thin film (GeTF). TEM and time-of-flight secondary ion mass spectrometry (TOF-SIMS) analysis shows that without activation, the initially single crystal GeNWs are effectively Na inactive, while the 100 nm amorphous GeTF sodiates only partially. Activation with Li induces amorphization (in GeNWs) reducing the barrier for nucleation of the Na
x
Ge phase(s). Introducing a dense distribution of nanopores via activation with Li at slower cycling rate, e.g. 0.1C, reduces the Na solid-state diffusion length by lowering the effective Ge thickness, and leads to improvement in cycling performance by buffering the sodiation stresses. The resultant kinetics are promising: Tested at 0.15C (1C = 369 mA/g, i.e. Na:Ge 1:1) for 50 cycles the GeNWs and GeTF maintain a reversible (desodiation) capacity of 346 mAh/g and 418 mAh/g, respectively. They also demonstrate a capacity of 355 and 360 mAh/g at 1C and 284 and 310 mAh/g at 4C. Even at a very high rate of 10C the GeTF delivers 169 mAh/g.
Performance of a Mgs Battery Using Grignard Based Electrolytes
Authors: Perdue Brian Robert , Apblett Christopher Alan
Published: February 2020

The lithium ion battery has revolutionized energy storage since its introduction to the commercial market in the early 90’s.  Despite its impact, it can be argued that the lithium ion battery is reaching its limit in terms of energy density.  In order to advance energy storage and move beyond lithium ion, new strategies must be considered such as a multivalent ion or a chemical conversion the cathode.  One such system is the magnesium sulfur system which utilizes a chemically safe earth abundant multivalent magnesium metal anode with a high capacity (1675 mA/g) earth abundant sulfur cathode.  One of the promises of using multivalent chemistry with sulfur cathodes is that the formation of polysulfides may be suppressed or eliminated as the multivalent sulfides compounds have low solubility in the solvent systems.  In the current study full cells were constructed using a magnesium metal anode, a coated sulfur cathode, utilizing the well characterized Grignard based electrolytes (EtBuAlCl2)2- (dichloro complex, DCC) and second generation Mg(AlCl4-nPhn)2 (all phenyl complex, APC).  Full cells were subsequently analyzed with slow scanning cyclic voltammetry (SSCV), galvanostatic charge/discharge, and post mortem EDX.  SSCV results show electrochemical activity consistent with the formation of polysulfides for both  APC and DCC with slight variations in performance between the two.  Galvanostatic charge/discharge data shows an expected capacity loss between the first and second cycle, however an unexpected recovery of capacity as cycling continued with the capacity reaching 825 mAh/g at the 25th cycle.  Full cell testing also demonstrated kinetic limitations as well as variations in performance between the two electrolytes consistent with SSCV results.  Postmortem EDX was on each cell component and showed no evidence of polysulfides on the anode surface, and possible trace amounts of sulfur in the separator.  EDX of the cathode showed evidence of a precipitated magnesium sulfur compound previously unreported.  The absence of sulfur on the anode and separator coupled with the precipitated magnesium sulfur compound on the cathode suggests that polysulfides precipitate out in a magnesium system rather than shuttle as they do in the lithium system, presenting a possible solution to the issues of polysulfide formation.
Toward Practical Application of Functional Conductive Polymer Binder for a High-Energy Lithium-Ion Battery Design
Authors: Zhao Hui , Wang Zhihui , Lu Peng , Jiang Meng , Guerfi Abdelbast , Battaglia Vince , Xiao Xingcheng , Zaghib Karim , Liu Gao
Published: February 2020

Silicon alloys have the highest specific capacity when used as anode material for lithium-ion batteries; however, the drastic volume change inherent in their use causes formidable challenges toward achieving stable cycling performance. Large quantities of binders and conductive additives are typically necessary to maintain good cell performance. In this report, only 2% (by weight) functional conductive polymer binder without any conductive additives was successfully used with a micron-size silicon monoxide (SiO) anode material, demonstrating stable and high gravimetric capacity (>1000 mAh/g) for ∼500 cycles and more than 90% capacity retention. Prelithiation of this anode using stabilized lithium metal powder (SLMP) improves the first cycle Coulombic efficiency of a SiO/NMC full cell from ∼48% to ∼90%. The combination enables good capacity retention of more than 80% after 100 cycles at C/3 in a lithium-ion full cell.

Figure 1
Mesoporous Carbon Cathode in a Li-O2 Battery: Effect on Li2O2 Product Morphology and Recharge Potential
Authors: Dutta Arghya , Byon Hye Ryung
Published: February 2020

One of the major challenges of lithium-oxygen (Li-O2) battery is high recharging overpotential, which is responsible for low stability of both non-aqueous electrolyte and carbon electrode, leading to serious side reactions. The fundamental reason for the high overpotential is very poor conductivity of solid Li2O2 as a discharge product, which requires further energy to be electrochemically decomposed (Li2O2→2Li+ + O2 + 2e–). Interestingly, the crystallinity and morphology of the Li2O2 profoundly influence on its conductivity, thus affecting the charging overpotential.1,2 The amorphous Li2O2 has much higher ionic and electronic conductivities compared to the crystalline Li2O2.1 In addition, the small size of Li2O2 with large contact area to the carbon electrode can aid in its smooth decomposition at low charging potential.2 Such type of Li2O2, which has been clearly observed in the presence of some solid-state metal/metal oxide promoters,3,4 is possibly attributable to the high O2 adsorption affinity of the promoters. Unlike these reports, we herein present the unique structure of Li2O2 using a promoter-free mesoporous carbon electrode, which greatly lowers the recharge potential. The mesoporous carbon of CMK-3 consisting of cylindrical-shaped pores with a pore diameter of ~3.5 nm was employed to the cathode (positive electrode) in the Li-O2 cell using 0.5 M LiTFSI in TEGDME. Strikingly, the CMK-3 based Li-O2 cell shows a very low recharge potential below 3.5 V until ~75% of recharge process. The pivotal reason for the decreased overpotential may be associated with an amorphous and flake-shaped Li2O2 vertically formed on the surface of CMK-3 during discharge, which are almost completely decomposed at the low recharge potential. This result is very distinguished from other carbon electrodes such as ketjen black (KB) carbon particle, multi-walled carbon nanotube (MWCNT) and LPC-80 consisting of spherical pores with a diameter of ~80 nm, where higher recharge potentials shown can be correlated with typical structure of spherical and thick Li2O2 particles. We propose that the surface structure of mesoporous carbon electrode is key to implant the Li2O2 flake while the effect of cylindrical pores within the CMK-3 may be negligible when considering low capacity (~1100 mAh/gcarbon) associated with a high surface area (~1500 m2/g). A detailed morphological and electrochemical analysis will be discussed in the presentation.

References

(1)  Tian, F.; Radin, M. D.; Siegel, D. J. Chem. Mater. 2014, 26, 2952-2959.

(2)  Dunst, A.; Epp, V.; Hanzu, I.; Freunberger, S.; Wilkening, M. Energy Environ. Sci.
2014,
7, 2739-2752.

(3)  Yilmaz, E.; Yogi, C.; Yamanaka, K.; Ohta, T.; Byon, H. R. Nano Lett.
2013, 13, 4679-4684.

(4)  Xu, J. J.; Wang, Z. L.; Xu, D.; Zhang, L. L.; Zhang, X. B. Nat. Commun.
2013, 4, 2438-2447.

Figure 1
Alternatives for Magnesium Metal Anodes? Intercalation Materials As Negative Electrodes for Rechargeable Magnesium-Ion Batteries
Authors: God Colin , Burrell Anthony K. , Ingram Brian , Kapper Katja , Koller Stefan , Lenardt Christian , Vaughey John T.
Published: February 2020

The unabated demand of cost-effective and high performance battery systems compells research groups to look for further improvements of energy storage systems around the world. Lithium-ion batteries seem to be an appropriate solution for this energy issue, but on the other hand extraordinary breakthroughs within the next years are not to be anticipated. Furthermore, lithium-ion batteries still suffer from serious safety concerns. Considering properties such as a rather low reduction potential (-2.36 V vs. SHE), high specific capacity (3380 mAh/cc), low equivalent weight and moreover, sufficient safety due to a non-dendritic metal deposition, magnesium-ion batteries appear to be competitive to lithium-ion batteries [1].

Since organic, aprotic electrolyte systems create a passivation layer on the Mg metal surface preventing a reversible Mg-deposition and dissolution, corrosive electrolytes such as Grignard compounds have to be used [2]. However, research focuses on the development of Mg-battery systems with an operational voltage of 3V Grignard electrolytes do not provide. A strategy to achieve the ambitious 3V goal is the development of intercalation/insertion compounds such as tin or graphite and replacement of corrosive electrolytes by organic ones [3].

From literature it is well known that the Mg-intercalation into graphite is impossible showing even solvated intercalation [4, 5]. However, in this contribution we want to shed light on the intercalation behavior of Mg into graphite with a broad range of electrochemical and spectroscopical analysis methods showing a non destructive and reversible magnesiation and de-magnesiation of a common graphite electrode with organic, aprotic electrolytes (cf. figure 1, figure 2 and figure 3).

References:

[1] P. Saha, M.K. Datta, O.I. Velikokhatnyi, A. Manivannan, D. Alman, P.N. Kumta. Progress in Materials Science 66, 2014, 1-86.

[2] Z. Lu, A. Schechter, M. Moshkovich, D. Aurbach. Journal of Electroanalytical Chemistry, 1999, 203–217.

[3] N. Singh, T.S. Arthur, C. Ling, M. Matsui, F. Mizuno. ChemComm, 2012.

[4] M. Kawaguchi, A. Kurasaki. Chem. Commun., 2012, 48, 6897–6899.

[5] Y. Maeda, Ph. Touzain. Electrochimica Acta, 1988, 1493-1497.

Figure 1
Study on the Preparation of the Cathode Materials for Lithium-Ion Batteries By Multiphase Redox Method
Authors: Xi Xiao-ming , Liao Daqian , Hu Liu-quan , Huang Zhou-shu , Tang Mo-tang
Published: February 2020

We report a new method, which is called multiphase redox method, to prepare the cathode materials for lithium-ion batteries, such as LiCoO2 and LiMn2O4. Compared with other methods, multiphase redox method to prepare the cathode materials has greater advantages in both technology and cost. From a technical perspective, the reaction of embedding lithium was fulfilled in water solution and the ultrafine precursors with the structure of cathode materials could be obtained. In addition, the precursors were very uniform in chemical composition. Meanwhile, from a cost perspective, the raw materials to prepare cathode materials by multiphase redox method were the salts with relatively low price. This report studies the process conditions to prepare the precursors, the reaction mechanism, the sintering and the electrochemical performance of the sintered samples.
Highly Concentrated Catholyte Based on Solvate Ionic Liquid for Flow Battery
Authors: Takechi Kensuke , Kato Yuichi , Hase Yoko
Published: February 2020

Liquid based batteries, including a flow battery, have unique and significant benefits due to its simple structure and flexible handling of their liquid active materials as ‘electrochemical fuels’. In spite of this great ‘fueling’ capability, which may enable the rapid charging of electric vehicles, the energy density of the regular catholytes and anolytes is lower (<100 Wh/l) than that of the solid-state active materials used in regular batteries. A non-aqueous system is a simple and effective method of improving the discharging voltage more than 2 V, which is the limit of the aqueous system, coupling with highly negative anodes. The concentration of redox species in organic solvents is, however, generally lower than that in aqueous solutions and difficult to reach over 2 M with, at least, the same molar of supporting salt. It is important to note that stoichiometric couples of redox species and an appropriate salt is the minimum requirement for the liquid active materials because the valence of the redox species must be changed during discharging and charging and compensating ions must be present in the system. Moreover, the liquids should have a stable fluidic property without freezing or precipitation even in a low temperature range.

In this study, we report an innovative strategy to prepare the liquid active materials in order to increase their energy density. Our technology focuses on the
melting
of pure redox compounds to maximize their concentration instead of
dissolving
them in solvents. This simple yet challenging approach has been successfully realized using supercooled liquid technology by the combination of a specific plasticizing salt and a low melting point redox active compound. Such a supercooled liquid can be obtained by mixing of 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (4-methoxy-TEMPO, MT) and Li bis(trifluoromethanesulfonyl) imide (LiTFSI, LT) and stabilizing the mixture further below their melting points. The redox-active supercooled liquid exists in a highly stable liquid state over a wide temperature range that extends to below its normal melting points. The special properties of this supercooled liquid are due to the scientifically unique and rare solvation state known as a ‘solvate ionic liquid’, which is typified by a liquefied ion-pair stabilized by a neutral third compound. As a catholyte, the addition of an appropriate amount of solvent such as water helps to enhance the electrochemical advantage while maintaining the liquid’s supercooled nature, and a battery with a Li+ conducting architecture exhibits 93% electrochemical activity and 99% coulombic efficiency in the 1st cycle with an average discharge voltage of 3.6 V (Fig. 1). The catholyte also performed an energy density of 200 Wh/l, which is one of the highest values for catholytes reported to date with an organic redox compound.

Figure 1
Benchmarking Metal and Metal Oxide Promoters for Oxygen Evolution Reaction in Li-O2 Cells
Authors: Yang Chunzhen , Wong Raymond Albert , Dutta Arghya , O Minho , Hong Misun , Yamanaka Keisuke , Ohta Toshiaki , Byon Hye Ryung
Published: February 2020

Despite high theoretical capacity, a Li-O2 cell has suffered from huge oxidation potential polarization on carbon-based positive electrode for charge (>4.2 V vs. Li/Li+), due to sluggish decomposition of non-conductive discharge product, lithium peroxide (Li2O2 ↔ 2Li+ + O2 + 2e-) [1]. Such high potential triggers side reactions such as degradation of electrolyte and carbonaceous electrode, which results in poor cycle-ability [1]. To mitigate this problem during oxygen evolution reaction (OER), solid-state metal or metal oxide nanoparticles (indicated as promoters), which have been widely employed as catalysts in aqueous media, were introduced to the electrode [2]. However, the specific role of promoters in the Li-O2 battery is little known due to complication from accompanying parasitic side reactions [3]. In addition, reasonable comparison of promoters’ activities is not feasible under different performance conditions when various reports were referred [2]. Therefore, to gain a reasonable assessment of their activities in the Li-O2 cell and an understanding of the promoters’ role, it is necessary to examine Li-O2 cells with these promoters under the same condition and analyze their reaction processes in detail. Here I present diagnosis of the true role of promoters, representative of platinum (Pt), gold (Au), palladium (Pd) and cobalt oxide (Co3O4), for OER in Li-O2 cells. After preparation of comparable size and mass loading of promoters on carbon nanotube (CNT) electrode, the Li-O2 cells containing these promoter/CNT combinations were examined using galvanostatic mode under the same operating conditions. The promoter/CNT electrodes show reasonably lower charge potentials than the promoter-free electrode for the 1st charge. Through in situ gas analysis of online electrochemical mass spectroscopy (OEMS) and ex situ chemical analysis of X-ray near-edge fine structure (XANES) spectroscopy, the evolved gas amount and remaining product after charge could be correlated, which accounted for the true reaction occurring for each promoter.

References

[1] (a) G. Girishkumar, B. McCloskey, A. C. Luntz, S. Swanson and W. Wilcke, J. Phys. Chem. Lett., 2010, 1, 2193–2203; (b) P. G. Bruce, S. A. Freunberger, L. J. Hardwick and J.-M. Tarascon, Nature Mater., 2012, 11, 19–29.

[2] (a) Y. –C. Lu, H. A. Gasteiger and Y. Shao-Horn, J. Am. Chem. Soc., 2011, 133, 19048-19051; (b) Z. Peng, S. A. Freunberger, Y. Chen and P. G. Bruce, Science, 2012, 337, 563-566; (c) F. Li, D. –M. Tang, Y. Chen, D. Golberg, H. Kitaura, T. Zhang, A. Yamada and H. Zhou, Nano Lett., 2013, 13, 4702-4707; (d) R. Black, J.-H. Lee, B. Adams, C. A. Mims and L. F. Nazar, Angew. Chem. Int. Ed., 2013, 52, 392–396;

[3] B. D. McCloskey, R. Scheffler, A. Speidel, D. S. Bethune, R. M. Shelby and A. C. Luntz, J. Am. Chem. Soc., 2011, 133, 18038-18041.

Figure 1
Li15Si4 As Potential Charged Anode Material:Cycling Stability and Reactivity Towards Carbonate Electrolyte
Authors: Toffoletti Lorenzo , Meini Stefano , Tsiouvaras Nikolaos , Gasteiger Hubert A , Fässler Thomas F.
Published: February 2020

In the development of high energy density Li-ion batteries, two elements have drawn the interest of the scientific community due to their low cost and high specific capacity: silicon and sulfur. These two elements are considered next generation’s active materials for anode and cathode, respectively. In order to exploit the advantages given by both materials in terms of specific capacity (and thus specific energy), lithium has to be introduced at the time of manufacturing either on the cathode side (as Li2S/Si cell) or on the anode side (as LixSiy/S cell). The Li-Si system has been recently investigated as potential source of lithiated anode materials 1,2, however up to date little is known about their highly exothermal reaction with alkyl carbonate based electrolytes. In this work we address the latter point via in-situ Online Electrochemical Mass Spectrometry (OEMS)3. By monitoring the gas evolution (mainly ethylene) resulting from contacting the metastable phase Li15Si4 and the non-aqueous electrolyte during a simulated electrolyte filling experiment of a Li-ion cell (Fig. 1), it was possible to get fundamental understanding of the challenges that cell manufacturers will have to face when using lithiated anode materials. The cycling stability of Li15Si4 as well as the role played by the total electrode surface area were as well thoroughly investigated.

References: 1) Zeilinger M et al., Chem. Mater. 25 (2013), 4623-4632. 2) Ma R. et al., J. Phys. Chem. Lett. 3 (2012), 3555-3558. 3) Tsiouvaras et al., J. Electrochem. Soc. 160(3) (2013), A471-A477

Figure 1
Effect of AlF3 Surface Coating on High Energy Lmr-NMC Material
Authors: Shin Youngho , Kahvecioglu Feridun Ozgenur , Krumdick Gregory
Published: February 2020

In this study, we explore the effect of AlF3 surface coating on Li1.2Mn0.54Ni0.13Co0.13O2 to mitigate the voltage fade issue. The precursor of this high energy material was synthesized using carbonate co-precipitation method by a 20L continuous stirred tank reactor (CSTR). Then, the synthesized precursor was mixed with Li-source and calcined at 900°C to generate cathode material. This product was used as the base material for AlF3 surface coatings.

A customized wet coating system was used for surface modification of the pristine material with 0.5, 1.0, 1.5 and 2.0 wt.% AlF3. The morphology, surface area, particle size and its distribution of the pristine and coated materials were characterized by scanning electron microscopy (SEM), BET and particle size analysis. The composition and the structure of the materials were characterized by inductively coupled plasma mass spectroscopy (ICP-MS) and X-ray diffraction (XRD).

The coated and pristine cathode powders were electrochemically tested using Voltage Fade protocol of Argonne National Laboratory. We demonstrate that AlF3 coating shows improved capacity retention compared to its pristine material. As a key factor, uniform surface coating provides improved capacity retention and rate capability of Li1.2Mn0.54Ni0.13Co0.13O2.
Insight into the Lithiation of SiO2 As a New Energy Storage Anode Material for Li-Ion Batteries
Authors: Ostadhossein Alireza , van Duin Adri
Published: February 2020

Silica (SiO2) has been considered as a promising anode material of lithium ion batteries (LIBs) due to its similar advantages of storing a large quantity of lithium and low discharge potentials of Silicon (Si) electrodes. Besides, Atomic layer deposition of SiO2is a predominant coting material to mitigate the chemo-mechanical degradation of Si nanostructures anode. Si anodes coated with native oxide layer can sustain more than 6000 cycles with little capacity fade. Therefore, it is vital to determine the effect of the oxide layers on the volume expansion, lithium insertion and the morphology changes of Si anodes in LIBs. While the lithiation of Silicon (Si) has been extensively studied from both experimental and theoretical point of view, the underlying mechanism of lithium insertion in the silicon oxide has not yet been recognized well.

To better understand the lithiation behavior in SiO2 at the atomistic level we herein performed a series of reactive molecular dynamics simulation combining with the grand canonical montecarlo (GCMC) to demonstrate the lithiation behavior of SiO2. In addition, the Li transports throughout both crystalline and amorphous silica have been investigated. ReaxFF parameters are improved to account for the interaction of Li with Si and O atoms. We performed density functional theory calculations to examine the structural evolution, bonding mechanism, and voltage profile of lithiated c-SiO2 and a-SiO2. Both ReaxFF and DFT results indicate anisotropic long range Li-diffusion throughout the a-Quartz lattice. More specifically, Li should overcome 0.12 eV barrier heights when it transports along the c-axis of α-Quartz crystal, whereas the barrier of diffusion for Li moving perpendicular to the c-axis is calculated around 0.9 eV. Li transport throughout a-SiO2 bulk is also investigated and the results are compared with barriers obtained from DFT simulations.

Figure 1
Optimization of LiMnPO4 Using Solid State Processes
Authors: Oladimeji Charles F , Moss Pedro L.
Published: February 2020

The development of lithium ion battery over the years has been in leaps and bound. Research is still ongoing towards the development of better lithium ion batteries and utilization techniques to power devices and machines of the future ranging from hand tools to electric vehicle. Presently LiCoO2is one of the most commercially available secondary batteries in the market right now.

Among the olivine battery materials LiFePO4 is the most researched and understood material. Other olivine materials have higher energy density but some unfavorable characteristics hinder commercialization. LiCoPO4 and LiNiPo4 have really high voltages that is not in the operating range of presently usable electrolytes. LiMnPO4 is a very promising olivine material, its operating voltage is higher than that of LiFePO4 but still within the operating range of conventional electrolytes.

The low energy density of LiMnPO4 at high rate cycling is a major problem that must be solved before it can be commercialized. Studies have shown that this is due to the low electronic conductivity, large volume change between LiMnPO4 and MnPO4 and high activation resistance 1.

Many approaches have been applied to solve this problem. The poor electronic conductivity can be alleviated with the use of carbon coating. Using a one-step carbon coating process results in better coating and increased conductivity compared to two step coating as shown in figure 11. Isovalent co-doping has also been shown to increase the performance of the material. Some other interesting approach to the problem has also been employed. The use of grinding aid to reduce the size of the product has been shown to increase performance 3.  Use of oleic acid during fabrication reduces particle growth and agglomeration 4. Improved electrochemical performance was also gotten by the use of off stoichiometric mix of the precursor 2.

The goal of our research is to combine these various methods that has been shown to increase performance of the material then characterize and analysis the material to see if the resulting material would be of higher performance as whole.

REFERENCES

1. Electrochemical Performance of LiMnPO4 Synthesized with Off-Stoichiometry Byoungwoo Kang and Gerbrand Ceder

2. Rate Performance of LiMnPO4 Based Materials from Different Carbon Source Addition Process Haisheng Fang, Enrui Dai, Kun Yang, Bin Yang, Yaochun Yao, Wenhui Ma, Yongnian Dai

3. Grinding aid-assisted preparation of high-performancecarbon-LiMnPO4Lingbing Ran, Xiaoyan Liu, Qiwei Tang, Kunlei Zhu, Jianhua Tian,Jiangyong Du, Zhongqing Shan∗

4. Confined synthesis of hierarchical structured LiMnPO4/C granules by a facile surfactant-assisted solid-state method for high-performance lithiumion batteries Longfei Zhang, Qunting Qu, Li Zhang,* Jing Li and Honghe Zhen

Figure 1
High Energy Density Solid-State Lithium Battery
Authors: Thokchom Joykumar
Published: February 2020

This presentation seeks to present the science and technology of a safe all-solid-state, high-energy density, rechargeable lithium battery. The main breakthroughs in the solid-state battery technology will be summarized and will share our latest contributions in the advancement of the technology. The unit cell of the battery comprises lithium metal as the anode, a novel high performance lithium nickel manganese cobalt oxide based composite cathode and a lithium stable composite electrolyte as separator. At cell level we are able to achieve a very high energy density at moderate rate and elevated temperature. This achievement is made possible by adopting our proprietary composite cathode composition and processing. Another advantage is its ability to operate at high temperature up to 160oC compared to the commercially available lithium-ion batteries, which normally operate only up to 60oC. The targeted applications for the battery are for automobile and others like consumer electronics, power tools, medical, and oil exploration.

 Key Words: solid composite electrolyte, all-solid-state lithium battery, high-energy density, extended temperature range, and electric vehicles
Pulverization Strategy for Graphite-CoOx Composite Cathode of Lithium-Air Batteries
Authors: Kwak Won-Jin , Shin Chang Dae , Ming Jun , Lu Jun , Curtiss Larry , Amine Khalil , Sun Yang-Kook
Published: February 2020

The lithium-air battery has been attracted around the world owing to very high energy density, which could well satisfy the increased energy requirement from electronic devices, especially the electric vehicle.1-3

However, despite large R&D efforts devoted to its implementation, several issues have so far limited the performance of the lithium oxygen battery because of few discharge-charge cycles, large polarization and low rate capability.4, 5

Some researchers used many materials for cathode in lithium air batteries because inherent activation effect and morphology of each material had an effect to decrease polarization and increase capacity. Although carbon has been talked making by-product like Li2CO3, it is the mostly used material because of the advantage in the way that amount and cost. Some paper told that not only carbon but also electrolyte co-makes this side reaction problem in lithium oxygen battery system.

In this study, a new physical pulverization strategy has been developed to prepare a highly active composite of CoOx and crushed graphite (CG) for the cathode in lithium–air batteries. The effect of CoOx loading on the charge potential in the oxygen evolution reaction was investigated in coin cell tests. The CoOx (38.9 wt%)/CG composite showed a low charge potential of 3.92 V with a delivered capacity of 2 mAh/cm2 under a current density of 0.2 mA/cm2. The charge potential was 4.10 and 4.15 V at a capacity of 5 and 10 mAh/cm2, respectively, with a current density of 0.5 mA/cm2. The stability of the electrolyte and discharge product on the gas-diffusion layer after the cycling were preliminarily characterized by 1H nuclear magnetic resonance spectroscopy, scanning electron microscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The high activity of the composite was further analyzed by electrochemical impedance spectroscopy, cyclic voltammetry, and potential-step chronoamperometry. The results indicate that our near-dry milling method is an effective and green approach to preparing a nanocomposite cathode with high surface area and porosity, while using less solvent. Its relative simplicity compared with the traditional solution method could facilitate its widespread application in catalysis, energy storage, and materials science.

References

[1] K.M. Abraham Journal of The Electrochemical Society 1996, 143, 1.

[2] G. Girishkumar; B. McCloskey; A.C. Luntz; S. Swanson; W. Wilcke J Phys Chem Lett 2010, 1, 2193-2203.

[3] B. Scrosati; J. Hassoun; Y.K. Sun Energ Environ Sci 2011, 4, 3287-3295.

[4] S.A. Freunberger; Y. Chen; Z. Peng; J.M. Griffin; L. J. Hardwick; F. Bard; P. Novak; P. G. Bruce J. Am. Chem. Soc. 2011, 133, 8040-8047.

[5] G.R. Mettam; L.B. Adams; B.S. Jones; R.Z. Smith Introduction to the Electronic Age, E-Publishing Inc., New York, 2009, 281-304.
Stability of Hard Carbon Coated Low Purity Natural Graphite As a Lithium-Ion Battery Anode Material
Authors: Kim Byung-ryang , Hong Young Kyu , Kang Hye-Joung , Shin Sang-Yong , Lee Jong-hyuk , Kim Sun Ah , Lee Ki-Tae , Shin Jin-Koog
Published: February 2020

Natural graphite is widely used in commercialized batteries by virtue of low cost, high capacity and stable charge/discharge performance [1]. However, multi-level purification process for battery-grade natural graphite (>99.9%) accompanies high manufacturing cost, although the raw material price is low enough. Accordingly, if we can avoid some purification steps such as acid-based purification process without loss of battery performance, we can reduce the manufacturing costs as well as environmental budget. In order to use low-purity graphite as anode material, one needs a way to prevent potential side reactions.

In this study, we adopted carbon coating method which has been reported to effectively reduce the irreversible capacity and extend the cycle life of Li-ion battery [2]. The hard carbon coating on the low-purity graphite was expected to improve the reliability of Li-ion battery by blocking the impurity diffusion. For hard carbon coating, spherical graphite was blended with thermosetting polymer and then sintered in a nitrogen atmosphere at 1300℃. For electrochemical measurements, we assembled 2032 type coin half-cells. Characteristics of the half-cell were evaluated as a function of cycle number and with different C-rates. Structural and thermal stability of hard carbon coating layer was also evaluated. To examine the structural stability, microstructure of hard carbon layer before and after the repeated charge-discharge cycles was observed using TEM. Thermal stability was evaluated by measuring capacity fading of cells after the elevated temperature storage. Based on the measured results, we discussed the validity of the hard carbon coating for the practical use of low-purity graphite.

♦ Reference

[1] Y.P. Wu, C. Jiang, C. Wan, R. Holze, Solid State Ionics 156 (2003) 283.

[2] J.J. Li, X.M. He, C.Y. Jiang, C.R. Wan, J. New Mater. Electrochem. Syst. 9 (2006) 21.

♦ Acknowlgement

This research was financially supported by the Ministry of Trade, Industry and Energy(MOTIE) and Korea Institute for Advancement of Technology(KIAT) through the Promoting Regional specialized Industry

Figure 1