bluuebunny/crossref_metadata_2025 huggingface dataset:
Chasing Protons in Lithium Batteries
Authors: Chen Zonghai
Published: February 2020

Nickel-rich lithium transition metal oxides have been recently considered as one of most promising cathode materials for high energy density lithium-ion batteries. However, the instability of the cathode electrolyte interface has been the major technological barrier for the development of nickel-rich cathodes. The early research has simply assigned this interfacial instability to the electrochemical oxidation of the commonly used carbonate solvents without much discussion on the nature of the parasitic reactions. To shed light on the chemical insight of the parasitic reaction, a proprietary high precision electrochemical system was built in-house to quantitatively measure the rate and kinetics of the side reactions between the delithiated cathode and the non-aqueous electrolyte. Our results clearly indicated the dominant chemical reaction within the working potential window is the chemical, not electrochemical, reaction between the intermediate phase of cathode and the electrolyte, generating locally concentrated protons at the surface of the cathode materials. Detailed investigation demonstrates that the generated proton is the chemical connection between the interfacial stability and the electrochemical performance of the then cathode material.
Diffraction Signal from Sodium Cluster in Hard Carbon: A Combined Experimental and Computational Study
Authors: Morikawa Yusuke , Nishimura Shinichi , Watanabe Eriko , Yamada Atsuo
Published: February 2020

Na-ion batteries have attracted increasing attention as large-scale energy storage devices. Hard carbon is a standard anode material owing to its large capacity and good cycling stability1, 2. However, sodium storage mechanism of hard carbon has not been fully understood due to its low crystallinity and diversity of microstructure. This study aimed to systematic understanding of the relationship between microstructure and sodium storage behavior with special attention to the diffraction signal from sodium cluster confined in nanopores.

Hard carbons were synthesized by hydrothermal treatment of sucrose and subsequent high-temperature carbonizations at T = 1000-1900 °C (denoted as HC-T). The charge-discharge tests were carried out using half-cells. As the heat-treatment temperature increased, the capacity of the high potential region (> 0.2 V) decreased while the plateau region (< 0.2 V) become dominant. HC-1400 showed the highest overall capacity (347 mAh g-1) and initial coulombic efficiency (95.2%). Reaction mechanism analyses were performed on three representative samples, HC-1000, HC-1400, and HC-1900.

Ex-situ small angle X-ray scattering (SAXS) measurements revealed (i) the nanopores become larger with decreasing their number for higher annealing temperatures, (ii) insertion of sodium into the nanopores proceeded under ca. 0.07 V. When electrodes were overcharged exceeding the sodium deposition voltage (ca. –0.01 V), the sodium density in the nanopores became comparable to that of bulk bcc sodium. Besides, apparent smaller capacity of HC-1900 was analyzed to be a kinetic observation with larger cathodic polarization.

Careful ex-situ X-ray diffraction measurements have detected smaller mean interlayer distances in order of HC-1900 < HC-1400 < HC-1000. Expansion of interlayer distance upon sodium insertion was observed for HC-1000 and HC-1400, but not at all for HC-1900, suggesting the existence of a threshold interlayer distance to allow sodium insertion. Importantly, for the first time, we have succeeded to detect a broad peak appeared around 29° as a signature of sodium insertion into the nanopores, and its origin was analyzed to be diffraction from sodium clusters in the nanopores using DFT-MD simulations.

Based on these analyses, criteria for better hard carbon will be discussed in the poster.

Figure 1
Failure Analysis of the Rechargeable Porous Zinc Electrode in Alkaline Electrolyte
Authors: D'Ambrose Michael Joseph , Yadav Gautam Ganapati , Turney Damon , Gallaway Joshua W. , Nyce Michael , Messinger Robert J. , Banerjee Sanjoy
Published: February 2020

Metallic zinc (Zn) is an attractive negative electrode material for rechargeable batteries because it is a non-toxic, earth abundant metal. It has a low equilibrium potential of -1.35 V vs. mercury-mercuric oxide (Hg/HgO) in concentrated alkaline electrolyte and a high gravimetric discharge capacity of 820 mAh/g. During discharge, Zn oxidizes and forms a dissolved complex known as the zincate ion, Zn(OH)4
2-, from which zinc oxide (ZnO) precipitates as a solid. On charge, Zn(OH)4
2- is reduced to metallic Zn. Motivation to study the Zn electrode in rechargeable batteries is driven by a target overall battery energy density of 200 Wh/L that is sustainable for 500 or more charge-discharge cycles. This corresponds to a Zn electrode discharge density in the range of 650 mAh/mL.

The cycle life of the porous Zn electrode in concentrated alkaline electrolyte is observed to decrease with increasing percentage of discharge capacity of Zn accessed. The percentage of discharge capacity of Zn accessed is known as the depth of discharge (DOD). Zn electrodes were cycled in the range of 1% to 15% Zn DOD in zinc-manganese dioxide (Zn-MnO2) batteries and in the range of 15% to 30% Zn DOD for zinc-nickel (Zn-Ni) batteries. Additives were incorporated into the zinc electrodes for the tests done on Zn-Ni batteries. Additives used were surfactant cetyltrimethylammonium bromide (CTAB), bismuth oxide (Bi2O3), synthetic layered silicate Laponite, and calcium hydroxide (Ca(OH)2). The potential values of the Zn electrodes vs. Hg/HgO reference electrodes were recorded.

During healthy galvanostatic discharge, Zn electrodes displayed a nearly constant potential vs. Hg/HgO at approximately -1.35 V. Tests that failed due to Zn exhibited a shift from this equilibrium potential that corresponded to a loss of cell voltage. This shift may be attributed to concentration overpotential as ZnO is precipitated, thereby inhibiting the hydroxide ions from reaching the reacting metal interface. The shift may also be due to formation of a passivated layer on the electrode which effectively blocks the remaining active material. There are generally two regimes observed in the potential curves of the Zn electrode vs. Hg/HgO prior to cell failure. Beyond the healthy plateau at -1.35 V, the first regime consists of a sloping potential while the second regime is an additional plateau. The second plateau shifts with increasing cycle number and corresponds to cell death. See the attached figure for discharge curves of a Zn electrode cycled at 5% Zn DOD. The second plateau is believed to be due to passivation of the Zn electrode. The additives were observed to modify the discharge potential curve of the Zn electrode vs. Hg/HgO.

Figure 1
Suppressing Reactivity of Sulfides in Solution Processing Enables Scalable Manufacturing of Thin, Flexible and Stable Solid-State Electrolytes
Authors: Tan Darren Huan Shen , Banerjee Ahbik , Deng Zhi , Wu Erik , Nguyen Han , Doux Jean-Marie , Wang Xuefeng , Cheng Ju-hsiang , Ong Shyue Ping , Meng Shirley , Chen Zheng
Published: February 2020

All solid-state batteries (ASSBs) have the potential to deliver higher energy densities, wider operating temperature range and improved safety compared with today’s liquid electrolyte-based batteries. However, they still face challenges that limit their commercialization resulting from thick solid-state electrolytes (SSEs), and poor processability due to their unstable chemistries. Existing studies on solvent-binder based casting methods to reduce SSE thickness and improve processability still lack crucial fundamental understanding of the behavior and selection criteria for different SSE-binder-solvent systems. In this work, we attempt to isolate various SSE-binder-solvent system behaviors and study their chemical and electrochemical compatibilities using both bulk and surface sensitive characterization tools. With these findings, we introduce a novel binder-solvent combination that significantly reduces SSE thickness (~50 µm) and improves processability of ASSBs while maintaining high ionic conductivity (0.7 mS cm-1). The resulting organic/inorganic composite SSE was found to be stable against lithium metal by plating and stripping over 2000 hours at 0.11 mA cm-2 and 1.1 mAh cm-2. This study suggests the importance of understanding fundamental SSE-binder-solvent interactions and provides a potential design strategy for scalable production of ASSBs.
A First-Principles Study on Sodium Superionic Conductor Na11Sn2PS12
Authors: Oh Kyungbae , Chang Donghee , Park Inchul , Kang Kisuk
Published: February 2020

Sodium superionic conductors are key components for solid-state sodium batteries which are regarded as promising energy storage devices for large-scale application due to their safety, possibility of increasing energy density, and design flexibility. Recently, a new crystalline sodium superionic conductor Na11Sn2PS12 was reported with a high ionic conductivity over 1 mS/cm at room temperature. Herein, we present first-principles investigations on the new sodium superionic conductor. Our ab initio molecular dynamics (AIMD) simulations confirm the isotropic diffusion of Na11Sn2PS12 and show that all Na sites participate in the diffusion comparably. This study also reveals that the presence of Na vacancy/interstitial does not affect the ionic conductivity, while isovalent substitutions of Sn site by Si or Ge significantly impede the diffusion by reducing free volumes of Na diffusion path as demonstrated by our systematic AIMD simulations. Thermodynamic calculations based on phase diagram analyses indicate that Na11Sn2PS12 phase is stable even at zero kelvin but possesses relatively narrow electrochemical window of 1.16–1.92 V. It is predicted that Na11Sn2PS12 forms a compatible interface with TiS2 but reacts with Na metal to produce undesirable byproducts. We believe that our theoretical study provides a broader understanding on Na11Sn2PS12 and helps guide the optimal design for application in solid-state batteries.
The Influence of Inactive Mn4+ Cation on the Redox Behavior of Active Co3+ Cation and O2- anion in Cathode Material.
Authors: Wang Xue-Long , Xiao Ruijuan , Fan Xiulin , Yu Xiqian , Hu Enyuan , Yang Xiao-Qing
Published: February 2020

Co3+/Co4+ redox has been widely utilized in layer structured cathode material for Lithium ion batteries due to its relatively high potential (vs Li+/Li) and good stability during cycling. In comparison, Mn4+ cation is proven to stay inactive for a wide potential range while it activates anionic oxygen redox in Li2MnO3. With introduction of Mn into LiCoO2 system, our experimental results showed that crystal structure had changed into spinel structure with Fd-3m symmetry and the redox behavior of Co3+ and O2- changed dramatically. The redox potential of Co3+/Co4+ increased much from c.a. 3.8V vs Li+/Li in layer structured LiCoO2 to over 5V vs Li+/Li in spinel LiCoMnO4. Meanwhile, the hard X-ray absorption spectroscopy results implied that less oxygen contribution to charge compensation during delithiaion process with Mn substituion. Through careful DFT calculations we revealed that the differences are mainly caused by the inactive dopant Mn elements rather than the transformation of crystal structure. More ionic-like Mn-O bonds induces stronger electron localization in Li-Mn-Co-O system compared with Li-Co-O system and, therefore, changes redox behaviors of Co3+/Co4+ and oxygen participation in charge compensation. Combined with soft X-ray absorption spectroscopy technique, the effects of Mn substitution on electronic hybridization status in Li-Co-O system was verified.

Acknowledgement

This project was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies through Advanced Battery Material Research (BMR) program (Battery 500 consortium) under Contract No. DESC0012704
Three-Dimensional Structural Analysis of All-Solid-State Electrode with Oxide-Based Solid Electrolyte
Authors: Park Joonam , Kim Dohwan , Appiah Williams Agyei , Song Jihun , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

All-solid-state batteries (ASSBs) are promising secondary batteries which have been studied for high energy density and safety. However, ASSBs have not had excellent electrochemical performance owing to using solid electrolyte instead of liquid electrolyte. Two main reasons are very low ion conduction property due to complex pathway made with the solid electrolytes and the large decline of the contact area between active materials and the solid electrolytes. In spite of distinct faults were already recognized, there have hardly been the studies because of the difficulty of obtaining the value by using the experiment.

In this study, we tried to gain the values from the simulation technics, which helped us draw the three-dimension electrode structure and check essential properties such as the contact area, tortuosity, and conductivity etc. with the variable electrochemical performance. In order to verify the appropriacy of our computational approach, the component ratio experiment that had been rudimentary for the electrode design was simulated under condition changing the ratio of natural graphite as the active material and LSTP (Li2O-SiO2-TiO2-P2O5) as the oxide-based solid electrolyte and then were compared and discussed with the data that anyone could confirm as the experiment.
Development of Virtual Integrated Battery Environment for Coupled Multiscale Modeling of Li-Ion Batteries
Authors: Allu Srikanth
Published: February 2020

The demand for high energy and power density of Lithium-ion batteries due to increasing acceptance into mobility and transportation sector has pushed wide spectrum of developments from materials to processing/packaging technologies. The design considerations at the cell level are primarily the performance and safety aspects as the batteries could degrade over cycle life in capacity or could lead to thermal runaway under extreme operating conditions. To understand the implications of any new development a comprehensive predictive modeling framework is developed that could model multiple spatial/temporal scales and could seamlessly integrate multiple physics. In this poster we introduce a new release of virtual integrated battery environment (vibe) that model variations of electrode materials and associated physical processes within full length cell simulations. As a demonstration, couple of electrochemical-thermal-mechanical simulationsbased on the upscaled properties are presented that help us understand the underlying mechanisms that battery undergoes during extreme conditions.
Aqueous Alkali Metal-Ion Battery with Hexacyanometallate Electrodes and Concentrated Electrolyte
Authors: Nakamoto Kosuke , Sakamoto Ryo , Sawada Yuki , Zhao Liwei , Ito Masato , Okada Shigeto
Published: February 2020

Aqueous alkali metal-ion batteries have attracted much attention, because they have three major advantages, namely non-flammability, high ionic conductivity and low cost. In addition, water can dissolve various salts in large amounts to provide a variety of electrolytic solutions. On the other hand, the 1.2 V theoretical electrochemical window of water restricts the selection of the cathode and anode active materials. However, three years ago, this issue was first addressed by U.S. Army Research Laboratory [1]. They successfully expanded the cell voltage of the aqueous Li-ion battery more than 2 V by introducing highly concentrated electrolytes, which effectively suppressed undesired electrolysis of water. To confirm the electrochemical window expansion of the concentrated electrolyte even in Na system, we also tried to realize a high voltage aqueous Na-ion battery by concentrated aqueous electrolyte. In preliminary measurement, 1.4 V average discharge voltage was obtained in the combination of Prussian blue-type Na2Mn[Fe(CN)6] (NMHCF) cathode and NASICON-type NaTi2(PO4)3 (NTP) anode with concentrated (17 mol/kg) NaClO4 aqueous electrolyte [2]. However, according to a CV measurement, the electrochemical window was almost 2.8 V [2]. Therefore, in order to further raise the cell voltage, instead of NTP anode based on Ti4+/Ti3+ redox, Prussian blue-type KMn[Cr(CN)6] (potassium manganese hexacyanochromate; KMHCC) anode based on Cr3+/Cr2+ redox was adopted. Then, 2 V class aqueous Na-ion battery was successfully obtained [3].

As this analogy, we have newly found the rechargeable operation of the aqueous K-ion battery in the combination of Prussian blue-type K2Mn[Fe(CN)6] (potassium manganese hexacyanoferrate; KMHCF) cathode and KMHCC anode with highly concentrated potassium triflate (19 mol/kg KSO3CF3; KOTf) aqueous electrolyte. The average cell voltage was approximately 1.5 V and the specific capacity was 118 mAh/g-KMHCF and 60 mAh/g-KMHCC, respectively. However, the two similar full cells suffered from capacity fading caused by degradation of Prussian blue-type structure induced by side reaction such as electrolysis of water solvent or electrolyte salt decomposition. The mechanism of degradation and our trial to improve the cyclability by changing the condition such as charging rate, cell configuration, electrolyte or its additives will be discussed in presentation.

References

[1] L. Suo, O. Borodin, T. Gao, M. Olguin, J. Ho, X. Fan, C. Luo, C. Wang, and K. Xu, Science, 350 (2015) 938-943.

[2] K. Nakamoto, R. Sakamoto, M. Ito, A. Kitajou, and S. Okada, Electrochemistry, 85(4) (2017) 179-185.

[3] K. Nakamoto, R. Sakamoto, Y. Sawada, M. Ito, and S. Okada, Small Methods, (2018) 1800220.
All Organic Interface Layer Formed from Vinylene Carbonate and Stable Plating of Lithium Metal
Authors: Zhou Hongyao , Liu Haodong , Liu Ping
Published: February 2020

Prevailing demand for lithium-ion batteries with higher energy density draws more researcher's attentions on the use of lithium metal as the anode material. An order of magnitude higher specific capacity and much lower reduction potential of lithium metal compared to graphite makes lithium metal suitable anode for the next-generation lithium-sulfur and lithium-air batteries. However, nonuniform plating or dendrite formation of lithium metal is a major issue for shorting batteries. Stable interface between lithium metal and electrolyte is the key to the uniform growth of lithium. Vinylene carbonate (VC) is a widely used additive in commercial electrolyte for lithium-ion batteries, and the effect of VC on stabilizing lithium metal has been reported. VC is proposed to polymerize on lithium surface to form flexible thin coating layer, which regulates the lithium-ion flux at the interface and put a mechanical pressure on the growing lithium dendrite. The interface layer is composed of multiple decomposition products from organic solvents and fluorinated salt and extremely complex to analyze.

Here we propose a gel electrolyte composed of vinylene carbonate and lithium iodide (LiI) to form polymer coating layer on the lithium surface. FTIR, NMR, and GC-FID analysis confirm polymerization of vinylene carbonate is triggered by lithium iodide through decarboxylation and forms poly(vinylene catbonate). Because iodide is electrochemically irreducible anion, no decomposition occurs on the lithium surface and simplifies the interface composition. Without the formation of inorganic compounds in VC-LiI gel electrolyte, Li//Li symmetric cell cycles for 1000 hours at 1 mA cm-2 and 1 mAh cm-2, with a practical electrolyte thickness of 25 μm (separator free). Coulombic efficiency of lithium plating/stripping in VC-LiI gel electrolyte is 98.6%, which is significantly higher than conventional carbonate-based electrolyte. Cross-sectional SEM image of cycled lithium metal reveals dense polymer coating and dendrite free morphology. Therefore, the simple all-organic interface, differing from conventional heterogeneous inorganic/organic mixture, can stabilize the lithium surface. We present a new perspective on the design of electrolyte and lithium interface.
Understanding the Impact of Composition and Processing on Tortuosity and Electrochemical Performance for Li-Ion Battery Electrodes
Authors: Seeba Jann , Reuber Sebastian , Wolter Mareike , Michaelis Alexander
Published: February 2020

Li-ion batteries (LIBs) are considered as the suitable technology for electric vehicles, as they offer a combination of power and energy density.

Research principally aims to improve the energy density, e.g. by increasing the specific energy density of the active material. Another approach to enhance the cells energy density is to increase the ratio of active material to inactive parts, for example by increasing the electrodes coating thickness. However, by enhancing the thickness the diffusion length of Li-ions extends which impairs the cells rate capability significantly. To tackle this problem the electrode design has to be optimized

The diffusion path in electrodes is described by the tortuosity parameter, which is defined by the deviation from the shortest diffusion path. By knowing the electrodes tortuosity, the rate capability of thicker electrodes can be optimized within the production process.

In the past the tortuosity was only accessible by tomographic measurements, which are time consuming and have a boundary in resolution or sample size. Newly developed electrochemical methods have been described in the literature, that allow a simple measurement of tortuosity, enabling comprehensive analysis of influences on tortuosity

We present a systematic study of the influence of composition and processing on the tortuosity. For the composition different active materials and conductive additives are evaluated. Furthermore, the impact of different processing of materials is evaluated, for example a change from tape casting with low viscosity slurries to an extrusion based coating process with high viscosity pastes.

Main aim is to improve the rate capability of thick electrodes. This is done by comparing the acquired tortuosity with the measured electrochemical test. Results show small changes in composition can lead to better rate capability with minimal sacrifice of capacity. Lastly, potential impact on the cycle life will be considered, to avoid a sacrifice in cycle life time.
Working Toward Faster Charging Lithium-Ion Cells through Electrolyte Chemistry
Authors: Hall David S , Logan Eric R. , Eldesoky Ahmed , Tonita Erin M. , Ma Xiaowei , Dahn Jeff R
Published: February 2020

As the adoption of electric vehicles continues to increase, there is a growing demand for faster charging lithium-ion cells to compete with the convenience of fuel-powered vehicles. Yet even for modern designs, rapidly charging lithium-ion cells can cause a decrease in cycle and calendar lifetimes. This is largely attributable to the large overpotentials required to apply large currents, which can lead to unwanted lithium metal plating at the graphite electrode surface. Moreover, as electrode thickness increases for higher energy density cells, lithium-ion transport in the electrolyte becomes limited, leading to even larger overpotentials. This work will present novel electrolytes with improved lithium-ion transport properties. Several co-solvent systems were identified based on the viscosity, permittivity (dielectric constant), and DFT-calculated electrochemical stability windows of the pure compounds. Several formate, nitrile, ketone, and amide co-solvents will be shown to increase the ionic conductivity of LiPF6 in conventional organic-carbonate-based solutions (Figure 1). Based on gas production during the first formation cycle in Li[Ni1-x-yCoxAly])2/graphite-SiO pouch cells, five candidates were identified: methyl formate (MF), ethyl formate (EF), propionitrile (PN), isobutyronitrile (iBN), and dimethyl formamide (DMF). High temperature storage (60°C), ultrahigh-precision coulometry (UHPC), and long-term cycling results will be presented showing that MF offers the greatest balance between conductivity increase and cell lifetime. PN may prove useful for low temperature (< 40°C) applications.

Figure 1 – a) Ionic conductivity of 1.2 mol L−1 LiPF6 solutions prepared with 20% of co-solvent and 80% of a 25:5:70 mixture by weight of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate, respectively. b) Solution conductivities relative to control solution, i.e., no co-solvent. Co-solvents include isobutyl acetate (iBA), methyl propionate (MP), methyl butyrate (MB), methyl formate (MF), ethyl formate (EF), n-propyl formate (nPF), isobutyl formate (iBF), propionitrile (PN), isobutyl nitrile (iBN), methyl ethyl ketone (MEK), and dimethyl formamide (DMF).

Figure 1
Analysis of Transport Properties of Polycarbonate-Based Polymer Electrolytes Containing Lithium (perfluoroalkylsulfonyl)Imides for Possible Application in Lithium-Ion Batteries
Authors: Gerlitz Anna Isabella , Buchheit Annika , Grünebaum Mariano , Wiemhöfer Hans-Dieter
Published: February 2020

The search for safe electrolytes for the use in lithium metal batteries and high energy density batteries has driven the interest in alternative polymer electrolytes with enhanced performance. The central interest focuses on transport properties as good ionic conductivities and on high electrochemical stability towards lithium metal anodes and cathodes for high voltage batteries. To gain insight in the Li-ion movement in polycarbonates, as dry or gel electrolyte, is necessary for understanding how to improve these systems and achieve better performances. In this context, we present a critical study on polycarbonates as alternative to polyethylene oxide (PEO) in salt-in-polymer electrolytes. [1]

Polymer electrolytes based on PEO as well as some related with grafted PEO side chains along polymer backbones such as polyphosphazenes, polysiloxanes and others are known to reach ionic conductivities in the range of 10-3 - 10-4 S·cm-1 in a favourable temperature range and typical Li+ transference numbers around 0.2.[2,3] In contrast to that, polycarbonates were reported to exhibit transference numbers up to about 0.5 as well as higher ionic conductivities and electrochemical stability.[4]

In this work, the commercially available polycarbonates polyethylene carbonate (PEC) and polypropylene carbonate (PPC) were prepared as flexible self-standing membranes with dissolved fluorinated lithium salts such as LiTFSI and others. With the use of propylene carbonate (PC) novel gel-polymer electrolytes have been fabricated. The ion conducting polymer membranes were examined regarding their electrochemical and transport characteristics with respect to possible battery applications. We studied ionic conductivity and Li-ion transference number as well as the coordination of lithium with different dissolved lithium salts on carefully purified polycarbonate samples. We obtained ionic conductivities in dry state around 10-6 S·cm-1 at room temperature and up to 10-3 in gelled systems. The novel gel systems based on PEC and PPC perform significantly better than the dry alternatives.

Acknowledgements

The authors acknowledge the funding within the project BenchBatt (03XP0047A) by the German Ministry of education and research. We are also grateful for the support by the Helmholtz Association within the Helmholtz Institute Münster (HI MS).

[1] P. Knauth, Solid State Ionics, 180 (2009) 911-916.

[2] M. Grünebaum, M.M. Hiller et al., Prog. Solid State Chem. 42 (2014) 85–105.

[3] M. Hiller, M. Joost et al., Electrochim. Acta 114 (2013) 21-29.

[4] Y. Tominaga, K. Yamazaki, Chem. Commun. 50 (2014) 4448-4450.
Electrochemical Behavior of TiO2 Coating on Ncm Cathode Material for All-Solid State Batteries
Authors: Ban Hee-Jung , Jung Ha-Young , Ryu Hye-Min , Park Sang-Jun , Kim Min-Young , Song Young-Woong , Jeon Se-Hyeon , Nam Su-jeong , Kim Ho-Sung , Kim Yoong-Ahm
Published: February 2020

Recently, the demand for the middle- or large-sized lithium batteries with safety has increased. To solve this problem, all-solid state batteries (ASSBs) are actively researched. However, it is known that the ASSBs has a higher interfacial resistance than the conventional lithium batteries. Also, the ASSBs are operated at a high temperature of 60 to 80 °C, resulting in the degradation of the cycle performance due to the collapse of the structure of the active material.

In this study, NCM materials were coated with TiO2 via sol-gel process. The crystal structure and surface morphology were observed according to TiO2 content and calcination temperature using X-ray diffraction (XRD), Scanning electron microscope (SEM), and Transmission electron microscope (TEM). Moreover, ASSBs were fabricated by using the TiO2-coated NCM as cathode, composite electrolyte (CE) and lithium metal as anode. Electrochemical characteristics were evaluated on the all-solid cells at 70°C, 0.1C. As a result, it has been found that the lattice parameters and crystal size of the NCM bulk are affected by the sintering temperature and the TiO2 coating content, which also affects the discharge capacity and cycle characteristics of the cells. We describe about the electrochemical behavior of NCM coatings by TiO2 in ASSBs in more detail.
Improving the Cycling Stability of Ni-Rich Layered Cathode Material By Introducing Redox Shuttle Electrolyte Additives
Authors: Zhu Xinhua , Revilla Reynier I. , Bheemireddy Narendraprasad Reddy , Hubin Annick
Published: February 2020

A systematic post-mortem analysis on a batch of power-optimized commercial LiNi0.80Co0.15Al0.05O2 (NCA) electrodes with different aging conditions was conducted. This aging study provides direct evidence that the intrinsic surface heterogeneity, resulting in locally overcharge reactions, plays a critical role in the degradation of NCA electrodes.

Accordingly, we propose a counter measure, adding redox shuttle electrolyte additive (RSA), to improve the cycling stability of Ni-rich layered cathode materials. The RSA can effectively balance the inhomogeneously distributed state-of-charge by shuttling excess charges between overcharged particles and normal charged particles. The unfavorably local overcharging reactions are thus inhibited. As indicated in the experimental results, with a small amount (0.025 M) of RSA 1,4-di-tert-Butyl-2,5-bis(2,2,2-trifluoroethoxy)benzene, the cycling performance of the commercial Nickel-rich cathode materials is improved about 30% in practical utilizing conditions as shown in the figure. There is a great potential for exploiting this approach in all kinds of commercial lithium-ion battery systems containing a liquid electrolyte. Furthermore, the remarkable effectiveness of the RSA approach further justifies the crucial role that the surface inhomogeneity plays in the cycling aging. Therefore, this issue deserves more attention in future aging studies of lithium-ion batteries.

Figure 1
Development of Foam-Based 3D-Electrodes for High Power All-Solid State Batteries
Authors: Bardenhagen Ingo , Glenneberg Jens , Gräfenstein Alexander , Speckmann Björn , Stenzel Volkmar , Schwenzel Julian
Published: February 2020

Conventional lithium ion battery concepts are based on two-dimensional electrode structures. They usually comprise electrodes consisting of active material layers deposited on metallic foils that are stacked together with polymer-based separators and soaked with liquid electrolyte.

The concept presented here in contrast makes use of three-dimensional, foam-based structures as substrates for the deposition of the active material layers. The large inner surface of the foams allows for a drastical increase of the available surface area for ion exchange. This allows for high power applications, even when the ionic conductivity of the electrolyte is limited, as is the case for many solid-state electrolytes. Because of the high porosity of the foams of 95% and above, the volumetric energy density can still be kept at a high level in this concept.

The research presented here reports the development of novel three-dimensional, foam-based electrodes for application in lithium ion batteries with liquid or all-solid state electrolytes. By their specialized design, these electrodes are capable of delivering both high power and high energy. Requirements for the foam design are derived from application demands. Next, the foam substrates are coated with active material layers and assembled into cells for proof of concept. Different coating concepts and the impact of pore size and foam material are evaluated. And outlook on all-solid state battery concepts extending the liquid-electrolyte approach is given as well.

The work presented here is part of the project ‘Batt3D’. Financial support by the German Federal Ministry of Economic Affairs and Energy is gratefully acknowledged.

Figure 1
Characterization of Battery Material Interfaces By Time-of-Flight Secondary Ion Mass Spectrometry
Authors: Walther Felix , Koerver Raimund , Fuchs Till , Ohno Saneyuki , Sann Joachim , Rohnke Marcus , Zeier Wolfgang G. , Janek Jürgen
Published: February 2020

Energy storage is one of the key issues in the context of renewable energy. Fluctuations in energy production due to the dependence on external conditions, such as the weather, complicate the predictability in the energy supply and the progress in the transition to renewable energy. In this context, batteries based on Li ions are one of the most promising candidates to solve this problem. Also the application in the automotive sector is of general interest, but suffers from limited acceptance in society due to the relatively short range of electric vehicles and long battery charging times.[1]

Progress in the field of Li ion based batteries requires a better understanding of the underlying degradation mechanisms to further increase the battery performance. Therefore, cycling stability needs to be improved and related issues, such as capacity fading, must be solved in order to reduce costs and resource consumption. Investigations regarding the degradation on the interface between the electrodes and the electrolyte are challenging since several materials are contributed in low concentrations and a high lateral resolution is required to determine the local material distribution. Typically, such investigations are based on electrochemical studies, diffraction methods, microscopic investigations and computational methods.[2-4] In contrast, the measuring possibilities of analytical methods such as time-of-flight secondary ion mass spectrometry (ToF-SIMS) are yet not fully exploited.

In this work, we demonstrate that ToF-SIMS can make a significant contribution to the elucidation of degradation processes in batteries. This includes the establishment of ToF-SIMS in optimization processes of individual battery components and the characterization of degradation. Next to surface analysis and conventional depth profiling, we used surface imaging with delayed extraction combined with sputtering to enable analytical 3D tomography of coated particles with simultaneously high lateral resolution up to 100 nm and high mass resolution (m/∆m = ~ 5000). FIB-SIMS tomography was applied to check the particle morphology. The samples examined include cathode and anode materials, such as coated Li[Ni
x
Co
y
Mn
z
]O2 particles (NCM with x + y + z = 1) and graphite.

In summary, we demonstrate that ToF-SIMS is a valuable tool for the tomographic study of battery materials. In combination with delayed extraction, ToF-SIMS can be used to reveal structural information in batteries in the nm range that are not easily accessible by other techniques.

[1] E. Dütschke et al., Technologie-Roadmapping am Fraunhofer ISI: Konzepte - Methoden - Praxisbeispiele, 3, 2012.

[2] B. Wu et al., J. Mater. Chem. A Mater. energy Sustain., 2016, 4, 15266–15280.

[3] A. O. Kondrakov et al., J. Phys. Chem. C., 2017, 121 (6), 3286–3294.

[4] Y. Zhu et al., J. Mater. Chem. A., 2016, 4, 3253-3266.
Vanadium-Based Polyoxometalate As Anode Materials for Lithium–Ion Capacitors
Authors: Huang Shao Chu , Lin Chia Ching , Chen Han Yi
Published: February 2020

Because of the increasing demand for portable devices, renewable energy systems, and electric vehicles, energy storage system has been developed intensively over the past decade. Researchers have intensively studied low-cost, high energy density, high power density, and high-safety energy storage devices. Lithium-ion batteries (LIBs) have advantages of high energy density and no memory effect. However, the power density is relatively low. In contrast to LIBs, supercapacitors (SCs) exhibit high power density and long cycling life, but low energy density. Therefore, lithium ion capacitors (LICs) which combine the superiorities of LIBs and SCs has been announced recently in order to achieve both high energy density and power density.

Polyoxometalates (POMs) are a class of anionic polynuclear transition metal oxides, and they possess multiple redox reactions which can store many charges per molecule. Hence, POMs have been employed as electrode materials for energy storage devices, such as LIBs, sodium-ion batteries (NIBs), and SCs, and most of them exhibit high capacity.

In this work, a vanadium-based POM (V-POM) was utilized as anode material for LICs. V-POM exhibited high specific capacities as well as good cycling stability. A full cell comprised with V-POM anode and porous carbon cathode were assembled, and it showed high energy density and high power density. These results demonstrated that V-POM anode material is suitable for LIC applications. Furthermore, we also utilized several in operando techniques to investigate the charge storage mechanisms of this V-POM anode including X-ray Absorption Spectroscopy and X-ray diffraction.
Synchrotron Operando x-Ray Computed Tomography of Battery Pouch Cells
Authors: Zenyuk Iryna V. , DeBari Annalisa , Lim Wei Han , Parkinson Dilworth Y. , Xiao Xianghui
Published: February 2020

X-ray computed tomography (CT) is a promising technique for three-dimensional imaging of batteries. Synchrotrons feature bright x-ray sources that enable micro-scale imaging at a minute time-scale. With hard x-rays the field-of-view is 3 x 3 mm and the x-rays are mostly attenuated by metal current collectors and metal-oxides in the cathode of a battery. Conventional coin cells are not fit for x-ray tomography due to stainless steel being highly x-ray attenuating, even at high energy when it is possible to obtain significant percentage of transmission, view within the coin cell is limited. We demonstrate a design of coin cell with a 5 mm cutout imaging window to enable limited angles x-ray tomography but the resulting images contained high signal-to-noise ratio and the modified coin cells are difficult to handle having electrolyte leaching, electric conductivity and other issues. Several groups have developed a Swagelok cell or an alternative to it, however the design does not allow for high throughput and the compression levels, as well as air-tight sealing present an issue. The current collectors in Swagelok cells have to have graphite inserts, else the alignment of the cell presents an issue because stainless-steel current collector can block the x-ray beam, if the alignment is not perfect. This horizontal configuration is also challenging, as the size of the imaged area is restricted to 3 mm, else the transmission can be an issue, especially for the cathode side because in this horizontal configuration X-rays penetrate 3 mm or more of material from every angle of rotation.

We have developed a high throughput pouch cell design for x-ray CT imaging featuring 1 cm diameter active area. The design enables imaging of lithium metal and lithium dendrites, as well as, interfaces in symmetric and actual pouch cells. The pouch cell design does not require precise alignment as imaging is done in a vertical configuration. The pouch is processed in a similar manner as it would, if designed for electrochemical testing. The time-resolved imaging shows the time-sequence of Li plating and stripping as a function of cycling rate. Unlike optical microscopes, that use large distance between the anode and cathode and have limited field-of-view, the pouch cell features micron-scale thicknesses of components and separation distances that are more representative for actual battery design.
High Voltage Activation of the Nasicon-Type Na4mnv(PO4)3 Cathode Studied By Operando X-Ray Diffraction
Authors: Zakharkin Maxim V. , Drozhzhin Oleg A. , Tereshchenko Ivan V. , Abakumov Artem M. , Antipov Evgeny V. , Stevenson Keith J.
Published: February 2020

NASICON-type Na3V2(PO4)3 delivers a highly reversible capacity of more than 110 mAh/g, showing a voltage plateau at 3.4 V corresponding to the V4+/V3+ redox couple [1]. In Na3+xMnxV2-x(PO4)3, introduction of Mn(II) lowers the cost of the material and enhances the operation voltage compared to that in Na3V2(PO4)3 [2]. Here, we studied the phase transformation behavior of Na4MnV(PO4)3 upon charge and discharge within different voltage limits.

In Na4MnV(PO4)3 two well-defined steps are observed when charged to 3.8 V [2]. After the increase of the cut-off voltage on charge up to 4.0V the electrochemical behavior on discharge changes, namely instead of two steps as in the case of cut-off at 3.8V a gradual slope is observed [3].

By operando synchrotron X-ray powder diffraction we’ve found that symmetry reduction from rhombohedral to monoclinic occurs immediately after the start of the electrochemical desodiation, with restoring of the rhombohedral phase at 3.8 V [4]. Cycling within 2.5-3.8 V potential range proceeds through both solid solution (Na4MnV(PO4)3↔ Na3MnV(PO4)3) and two-phase (Na3MnV(PO4)3↔ Na2MnV(PO4)3) processes. An additional voltage plateau at ~3.8-4.0 V vs. Na/Na+ is observed, associated with re-distribution of Na cations over available crystallographic positions and “unlocking” of the Na1 site in the rhombohedral phase. Reverse insertion of Na+ cations proceeds via a complete solid solution region. The experimentally observed reversible electrochemical capacity increases by ≈14% after raising cut-off voltage.

This work was supported by the Russian Science Foundation (Grant No. 17-73-30006).

Reference
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[1] K. Saravanan; C. W. Mason; A. Rudola; K. H. Wong; P. Balaya. The First Report on Excellent Cycling Stability and Superior Rate Capability of Na3V2(PO4)3 for Sodium Ion Batteries. Adv. Energy Mater. 2013, 3, 444−450.

[2] W. Zhou; L. Xue; X. Lü; H. Gao; Y. Li; S. Xin; G. Fu; Z. Cui; Y. Zhu; J.B. Goodenough. NaxMV(PO4)3 (M = Mn, Fe, Ni) Structure and Properties for Sodium Extraction. Nano Letters, 2016, 16 (12), 7836-7841

[3] F. Chen; V. M. Kovrugin; R. David; O. Mentré; F. Fauth; J.-N. Chotard; C. Masquelier. A NASICON-Type Positive Electrode for Na Batteries with High Energy Density: Na4MnV(PO4)3. Small Methods, 2018, 2, 1800218

[4] M.V. Zakharkin; O.A. Drozhzhin; I.V. Tereshchenko; D. Chernyshov; A.M. Abakumov; E.V. Antipov; K.J. Stevenson. Enhancing Na+ Extraction Limit through High Voltage Activation of the NASICON-Type Na4MnV(PO4)3 Cathode. ACS Applied Energy Materials, 2018, 11 (1), 5842-5846

Figure 1
Comparing Operando XRD and Dems to Investigate Metal-Substituted LiNiO2
Authors: Bianchini Matteo , Schweidler Simon , Schiele Alexander , Hartmann Pascal , Brezesinski Torsten , Janek Jürgen
Published: February 2020

LiNiO₂ (LNO) has been introduced as cathode active material for Li‐ion batteries in 1990 [1]. After years of intensive research, it emerged that several instability issues plague the material, so that it was abandoned in favor of isostructural metal‐substituted compounds called NCA (for lithium nickel cobalt aluminum oxide) and NCM (lithium nickel cobalt manganese oxide). These sacrifice a certain amount of specific energy in exchange for stability, durability and safety [2]. With few exceptions, NCA and NCM are nowadays the industrial standard when it comes to automotive applications. However, the continuous push towards electric cars with longer driving range is synonym, for these compounds, with increasing the nickel content (which is already beyond 80%), eventually leading back again to LiNiO₂. For this reason, we synthesized a series of LiNiO2 samples, where Ni is substituted by low amounts of other elements (< 5%). We implement a characterization strategy based on operando XRD, differential electrochemical mass spectrometry (DEMS) and ex situ TEM, enabling us to track, in real time upon battery charge and discharge (i.e., as Li is extracted/inserted from/into LNO, respectively), the evolution of the material´s crystal structure, the transformation of its surface and the evolution of gaseous products. We place particular emphasis on the behavior of LNO at high state of charge (> 4.1 V), where the transition between the hexagonal phases H2 and H3, whose unit cell volume is very different, induces significant mechanical strain in the material [3]. The H2 and H3 phases are also thermodynamically metastable [4] and decompose towards off-stoichiometric Li1-zNi1+zO2, with release of O2[5], a reaction we can observe by DEMS and TEM. With this combined strategy, we aim at understanding which element, if any, can sufficiently stabilize LNO in the charged state.

Bibliography

Dahn, J.R., U. Vonsacken, and C.A. Michal, Structure and Electrochemistry of Li1+-yNiO2 and a New Li2NiO2 Phase with the Ni(OH)2 Structure. Solid State Ionics, 1990. 44(1-2): p. 87-97.

Myung, S.-T., et al., Nickel-Rich Layered Cathode Materials for Automotive Lithium-Ion Batteries: Achievements and Perspectives. ACS Energy Letters, 2017. 2(1): p. 196-223.

Yoon, C.S., et al., Structural Stability of LiNiO2 Cycled above 4.2 V. ACS Energy Letters, 2017. 2(5): p. 1150-1155.

Das, H., et al., First-Principles Simulation of the (Li–Ni–Vacancy)O Phase Diagram and Its Relevance for the Surface Phases in Ni-Rich Li-Ion Cathode Materials. Chemistry of Materials, 2017. 29(18): p. 7840-7851.

Bianchini, M., et al., There and back again - The journey of LiNiO2 as cathode active material. Angew Chem Int Ed Engl, 2018: p. 10.1002/anie.201812472.
Distinguishing Slow Charge Transfer from Slow Desolvation Rate-Determining Step in Ion Intercalation Processes
Authors: Nikitina Victoria A , Stevenson Keith J.
Published: February 2020

The elucidation of the reaction rate-determining step nature in intercalation processes is essential for the development of approaches for a precise control of rate-limiting factors. Earlier work in the field of the lithium-ion intercalation kinetics has led to the establishment of a general pattern of Butler-Volmer type of charge transfer rate control for a wide range of intercalation materials. However, further research in the field of the development of aqueous Li-ion batteries, as well as alternative to Li+ battery chemistries (Na+, K+, Mg2+ intercalation) resulted in the accumulation of valuable experimental information on the electrochemical intercalation processes for a much wider range of solvents (aqueous solutions, glymes, nitriles, etc.), cations and electrode materials, which suggests that Butler-Volmer type potential dependence of the charge transfer rates is not characteristic for the intercalation processes in solvents, where surface layers formation is not observed, e.g. in aqueous solutions.

In this work, we explore the kinetic patterns of lithium-ion intercalation into two model cathode materials (LiCoO2 and LiMn2O4) and develop criteria for distinguishing between Butler-Volmer slow charge transfer and slow chemical steps. A numerical model for the rate-limiting ion desolvation step is developed and the predictions of the model are compared with the experimental voltammetric and electrochemical impedance spectroscopy data. We show that slow desolvation step results in essential changes in the shape of both cyclic voltammetry and impedance responses with the kinetic resistance vs. potential dependencies being highly informative for the reaction rate control diagnostics. The consideration of the intercalation kinetics in four solvents (water, propylene carbonate, acetonitrile and dimethyl sulfoxide) allows concluding on the influence of the resistivity of surface layer/electrode material interface on the reaction slow step nature.

Figure 1