bluuebunny/crossref_metadata_2025 huggingface dataset:
Impact of Iron Elusion on the Capacity Degradation of FeF3 –Two-Compartment Cell Study–
Authors: Yoshii Kazuki , Taguchi Noboru , Miyazaki Takeshi , Shikano Masahiro , Sakaebe Hikari
Published: May 2020

Iron trifluoride (FeF3) has been attracted as one of the promising candidates for the positive electrode material of lithium secondary batteries due to their high theoretical capacity (712 mA g–1) and high energy density (1949 Wh kg–1). However, its poor cyclability and a large hysteresis of the voltage during charge and discharge still remain the problem to solve for the commercialization. The cycling performance of FeF3-based lithium secondary battery has been improved by various strategies, such as the addition of anion receptor, coating by other metals and tuning of electrolyte composition so far [1-3], but the suppression of degradation and the elucidation of its mechanism have not accomplished completely. In the present study, we investigated the charge and discharge behavior of the FeF3 positive electrode using a designed two-compartment type cell which has lithium ion-conducting ceramics as a separator to prevent the cross-talk of the electrolyte between the positive and negative electrode.

A charge/discharge test was performed using a coin cell and two-compartment type cell using 1.0 mol dm–3 LiPF6 in 1:1 ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) as the electrolyte. Disassembling analysis of both cells including SEM observation and X-ray fluorescence analysis revealed that the elution of Fe is more responsible for the degradation of the FeF3 electrode than a thick film formation on the electrode due to the cross-talk in the coin cell. Furthermore, the cyclability was improved using the electrolyte with LiDFOB as an additive for only the positive electrode side of the two-compartment type cell, whereas the improvement of the cyclability was not found when the additive was applied to a coin cell. After the cycling tests, various analyses, such as electrochemical impedance, X-ray photoelectron spectroscopy, and transmission electron microscopy, were also conducted for the electrode with and without additives in the electrolyte to examine the degradation mechanism of FeF3 positive electrode. The obtained results were considered useful for the improvement of the cycling performance of FeF3-based lithium ion batteries.

References

[1] K. Kumagae, K.-I. Okazaki, K. Matsui, H. Horino, T. Hirai, J.-I. Yamaki and Z. Ogumi, J. Electrochem. Soc., 163, A1633 (2016).

[2] Y. Li, X. Zhou, Y. Bai, G. Chen, Z. Wang, H. Li, F. Wu and C. Wu, ACS Appl. Mater. Interfaces, 9, 19852 (2017).

[3] H. Senoh, K. Matsui, M. Shikano, T. Okumura, H. Kiuchi, K. Shimoda, K. Yamanaka, T. Ohta, T. Fukunaga, H. Sakaebe and E. Matsubara, ACS Appl. Mater. Interfaces, 11, 30959 (2019).

Acknowledgement

This work was supported by the New Energy and Industrial Technology Development Organization (NEDO) under the “Research and Development Initiative for Scientific Innovation of New Generation Batteries 2 (RISING2)”
Application of a Holed Cathode and Anode Preparedwith a Picosecond Pulsed Laser for Lithium Ion Batteries (1)~ Performance of Holed Cathodes with Solid-State Electrolytes ~
Authors: Watanabe Tatsuya , Gunji Takao , Suzuki Kei , Ando Nobuo , Nakamura Susumu , Hayashi Narumi , Soma Naohiko , Matsumoto Futoshi
Published: May 2020

Recently, we have reported that the porous current collector could be produced with a pico-second pulse laser system and that graphite electrodes prepared with porous Cu current collectors improved the rate of Li+-pre-doping reaction in the laminated graphite electrodes [1-3]. In this study, in order to speed up the rate of the pre-doping reaction more, the porous graphite electrodes were prepared by directly opening the holes on the surface of graphite electrodes with a picosecond laser (Fig. 1). In the cell composed of laminated porous graphite electrodes (Fig. 2) and a lithium metal, the Li+-doping reaction proceeded much faster than in the cells of the graphite electrodes prepared with porous current collectors and a Li metal. In addition, the results of electrochemical impedance spectroscopy suggested that the transfer of Li+ ions though the holes on the graphite electrodes was a rate determining step of the doping reaction of Li+ to laminated graphite electrodes and that the decrease in the hole diameter at the constant of opening rate of holes on the graphite electrodes cased the reduction of resistance for Li+ ions, resulting in shortening the time for completing the doping reaction of Li+ ions.

Figure 1
(Invited) Chemical Manipulation for High Performance Li-S Battery
Authors: Xie Jia
Published: May 2020

Lithium-sulfur batteries have been regarded as one of the most promising new battery technologies due to high theoretical energy density (2600 Wh kg-1) , the abundant resource and low cost of sulfur. However, both sulfur cathodes and lithium metal anodes can’t meet the design requirements for high specific energy batteries. In this talk we will introduce a new reaction pathway and by using Se or Te as eutectic accelerator to boost reaction kinetics, it is possible to eliminate polysulfide dissolution while under the dissolution deposition mechanism and obtain high performance sulfur cathode compatible with both ether and carbonate electrolytes. Meanwhile, for lithium metal anode, we have developed an polymer/alloy hybrid layer through a facile reaction. The hybrid layer is not only beneficial for uniform deposition of lithium and inhibiting the formation of lithium dendrites, but also greatly improves the stability to moisture and obtains relatively stable cycle performance. With the newly developed anode and cathode materials, a high specific energy lithium-sulfur secondary battery with significantly improved performance is obtained, and the energy density and cycle life are expected to show breakthrough in large batteries.

References

Zhipeng Jiang, Liu Jin, Zhilong Han, Wei Hu, Ziqi Zeng, Yulong Sun, Jia Xie*, Angew.
Chem. Int. Ed., 2019, 58, 11374-11378

Xin Chen, Linfeng Peng, Bin Shan, et al and Lixia Yuan* & Jia Xie
*, Nat.
Commun.
2019, 10, 1021

Shuping Li, Zhilong Han, Bin Shan, et al and Jia Xie*, Nano Energy
, 2019, 60,153-161

Shuping Li, Ziqi Zeng, Bin Shan, et al, and Jia Xie
*, ACS Appl. Energy Mater.
2019, 2, 4, 2956-2964

Yunyang Zhang, Yulong Sun, Bin Shan, et al and Jia Xie*, Energy Storage Mater., 2019, 21, 287-296
Compatibility of Porous Silicon with Lithium Polysulfides for Full Cell Lithium Ion Battery Applications with Sulfur Cathodes
Authors: Cavers Heather , Krüger Helge , Polonskyi Oleksandr , Adelung Rainer , Nöhren Sandra
Published: May 2020

Crystalline silicon is an ideal anode candidate for lithium ion batteries as it offers a high Li+ ion storage capacity, direct current pathway and is a stable and earth abundant element. In order to match the high theoretical energy density of silicon in lithium ion batteries a suitable cathode material is required. Sulfur based cathodes have a high theoretical storage capacity for application in lithium ion batteries, based on the conversion reaction of the cyclic S8 molecule with lithium to form smaller lithium polysulfides up to Li2S, and are also cheap and earth abundant. One of the major drawbacks of lithium sulfur cathode materials is the tendency of lithium polysulfides to be dissolved by the electrolyte, which causes the polysulfides to migrate away from the cathode, leading to an overall capacity loss. For application of porous silicon in a full cell lithium ion battery with sulfur it is important to understand the impact the presence of lithium polysulfides can have on the functionality of porous silicon as an anode. In this study porous silicon anodes with thicknesses of 6 µm and 12 µm were cycled in a half cell in the presence of varying concentrations of Li2S6 (0 M, 0.017 M and 0.083 M). For the electrolyte with 0.017 M Li2S6 the cycling behavior was comparable, or better, than the electrolyte with no polysulfides. The SEI layer formed on the surface of the porous silicon anodes was investigated ex situ with X-ray photoelectron spectroscopy, Raman spectroscopy and scanning electron microscopy after one, five and ten cycles. It was seen that in the first cycle lithium polysulfides are contained in the SEI and undergo an oxidation reaction to form sulfates over the following cycles. This leads to a more inorganic SEI layer in the presence of polysulfides, especially in the case of the 12 µm porous silicon, and long term cycling stability. The 12 µm porous silicon anode cycled in the presence of 0.083 M Li2S6 showed stable cycling behavior over one hundred cycles, with limited capacity loss and coulombic efficiencies of 96.2 % after one hundred cycles.
Ultra-Microporous Carbon Aerogel Encapsulating Sulfur As Cathode for Lithium-Sulfur Batteries
Authors: Nojabaee Maryam , Schwan Marina , Sievert Brigitta , Schettler Jessica , Wagner Norbert , Milow Barbara , Friedrich Andreas K
Published: May 2020

The operating range and cost effectivity of electric vehicles are significantly compromised by the low energy density of state-of-the-art lithium-ion batteries. For the realization of electro-mobility, chemistries beyond Li-ion such as lithium-sulfur batteries offering high gravimetric energy density are requisite. However, the commercialization of Li-S batteries faces challenges such as severe capacity fade induced by the so-called polysulfide shuttle effect. Encapsulating and trapping the active material in the cathode matrix are among many approaches inhibiting polysulfide dissolution and shuttle effect [1-3].

Herein, we synthesized and investigated highly porous carbon aerogels (CA) as conductive matrix embedding sulfur for cathode in Li-S batteries [4]. Resulting from organic resorcinol-formaldehyde aerogels, the synthesised carbon aerogels exhibit highly porous structure with porosity up to 97%, high surface area of 500-2000 m²·g-1 and large micropore volume of 0.1-0.6 cm³·g-1. The gas-phase sulfur infiltration of the carbon aerogels and the resulting confinement of the short-chain sulfur in the micropores are demonstrated using complementary characterization techniques including TGA, XRD, and XPS. It is shown that S-infiltrated microporous carbon aerogel cathodes are able to suppress the polysulfide shuttle effect, maintaining 80% (1100 mAh/g(S)) of initial discharge capacity after 100 cycles at 0.3C in carbonate-based electrolyte. The cyclability and compatibility of the ether and carbonate-based electrolyte with such composite cathode are explicitly discussed. Additionally, the influence of chemical and physical properties of different synthesized carbon aerogels including pore density, size and morphology on the electrochemical behavior of the cell is investigated in detail.

1. S. Evers, & L. F. Nazar, New approaches for high energy density lithium–sulfur battery cathodes. Acc. Chem. Res. 46, 1135–1143 (2012).

2. Y. Yang, G. Zheng, Y. Cui, Nanostructured sulfur cathodes. Chem. Soc. Rev. 42, 3018–3032 (2013).

3. R. Fang, K. Chen. L. Yin, Z. Sun, F. Li, HM Cheng, The regulating role of carbon nanotubes and graphene in lithium-ion and Lithium-sulfur batteries, Advanced Materials, 31(9) 1800863 (2019)

4. Schwan und L. Ratke, "Flexible Carbon Aerogels" J. Carbon Res. 2, 22 (2016).
First-Principles Investigation of Anchoring Behavior of Tungsten Dichalcogenides for Lithium-Sulfur Batteries
Authors: Islam Mahbubul , Jayan Rahul
Published: May 2020

The commercialization of lithium-sulfur (Li-S) batteries is crippled due to lithium polysulfides (LiPSs) dissolution into the electrolyte and the poor kinetics of their reversible conversions. The graphene-based materials have been widely used as a conductive matrix, however, the apolar nature of the graphene provides insufficient binding required for the containment of the LiPSs within the cathode material. In this regard, the transition metal dichalcogenides exhibit great promise as anchoring materials (AMs) due to their capability of strong adsorption to LiPSs thus suppression of the polysulfides shuttles. In this study, we used first-principles based density functional theory (DFT) calculations to investigate the chemical interactions such as binding energies and catalytic activities between AMs such as tungsten dichalcogenides, WX2 (X=S, Se, and Te) and the LiPSs. We found that the WX2 possesses moderate binding strength to the LiPSs which is desired for effective anchoring. We perform an in-depth analysis of charge transfer and the electronic density of states to elucidate the underlying mechanisms that dictate the binding behavior of LiPSs and WX2. The catalytic activity of WX2 for the delithiation of the lower-order polysulfides are demonstrated through the reduction of the reaction barriers compared to the apolar AMs. Overall, our simulation results provide detailed insight into the behavior of WX2 as AMs to suppress the LiPSs migration and increase the kinetics of LiPSs conversion reactions, henceforth paves the way towards the development of high-performance Li-S batteries.
(Invited) Current Status and Bottlenecks of the Intercalation of Mg into Spinel Oxides
Authors: Cabana Jordi
Published: May 2020

Electrochemical energy storage was an important enabler of the wireless revolution and it is touted as a key component of a society that shifts away from its dependence on fossil fuels. Li-ion batteries are the primary technology when high energy devices are required. However, despite their improved functionality over older systems (e.g. lead-acid car batteries), they do not quite yet meet the emerging energy demands in transportation and grid markets. This roadblock sparked interest in the development of batteries that utilize Mg2+ as ionic carrier. Theoretical predictions indicate that couples exist between a Mg metal negative electrode and oxide positive electrodes that could surpass the current practical limits of current devices. However, severe practical challenges have limited the study of the electrochemical properties of oxides to the simple elucidation of the viability and reversibility of the fundamental reactions of intercalation of Mg2+. Among the candidate oxides, the general family of spinel-type M2O4 (M=transition metal) are considered as leading contenders [1, 2]. In this talk, we will present the most up-to-date insight into the ability of spinel oxides to diffuse Mg2+. These observations will be paired with the outcomes of electrochemical reactions in non-aqueous electrolytes, since the use of Mg metal requires rigorously anhydrous environments. We will discuss the evidence supporting intercalation of Mg2+, and describe changes that correlate with both the identity of M and the existence of defects in the spinel structure [2, 3]. Critical to the endeavor is the ability to synthesize particles at small dimensions, as is the characterization of chemical and physical phenomena using a combination of tools providing information at different scales. The discussion will naturally lead us to reveal foundational bottlenecks that must be overcome to make Mg electrochemistry viable for energy storage.

1. Liu et al., Energy Environ. Sci.
2015, 8, 964.

2. Kim et al., Adv. Mater.
2015, 27, 3377.

3. Hu et al., Nanoscale
2019, 11, 639.
Developing Common Descriptors for Plating/Stripping of Divalent Metals in Organic Electrolytes
Authors: Connell Justin G. , Zorko Milena , Agarwal Garvit , Assary Rajeev , Liao Chen , Strmcnik Dusan , Markovic Nenad M.
Published: May 2020

A significant challenge facing the development of new chemistries for multivalent batteries is the fact that many of the most promising electrolytes are incompatible with either metallic anodes or high voltage cathodes, both of which are required in order for such systems to compete with existing Li-ion batteries. For example, many Mg electrolytes rely on the presence of significant concentrations of Cl- to enable reversible metal plating/stripping at the anode, which is incompatible with oxide cathode materials due to parasitic reactions (e.g. oxide dissolution, Cl2 gas evolution) that take place at high voltage. More broadly speaking, investigations of multivalent anode chemistry are generally focused on a single working cation, making it difficult to identify and understand trends that may extend beyond individual systems and point to general design principles for developing new multivalent electrolyte chemistries. Focusing on the specific role of Cl- in promoting reversibility in multivalent systems, systematic rotating disk and ring-disk electrode (RDE and RRDE) investigations of metal plating/stripping were performed utilizing a variety of divalent cations (i.e., Mg2+, Zn2+ and Cu2+) and the bis-(trifluoromethane sulfonyl) imide (TFSI-) anion. By introducing varying concentrations of Cl-, a cooperative effect is observed between TFSI- and Cl- that yields the overall more reversible behavior of mixed electrolytes relative to electrolytes containing only TFSI-. This effect is shown to be general for Mg, Zn and Cu electrodeposition, and mechanistic understanding of the role of Cl- in improving reversibility of TFSI-based electrolytes is provided through the combination of R(R)DE experimental results with computational evaluation of the activity and stability of various TFSI- and Cl-based solution complexes. The cooperative anion effect can be further generalized to other electrolyte systems, pointing to the presence of common descriptors for the activity of divalent metal anodes and suggesting a set of general design principles for developing new multivalent electrolytes.
Electrolytes for Magnesium Batteries: Which Way to Go?
Authors: Jankowski Piotr , Garcia Lastra Juan Maria , Vegge Tejs
Published: May 2020

Magnesium battery technology is one of the promising post-lithium technology, that has potential to reduce our lithium dependence, and at the same time outperform current Li-ion technology. Magnesium is more abundant, hence cheaper, and comes with promises of higher energy density and lower tendency to dendrite formation – possibility of metallic anode application. Higher capacity of such battery comes from double charge of magnesium ion, that also causes battery chemistry more difficult. Especially electrode/electrolyte interface becomes tricky, and simple transfer of electrolyte concept from lithium technology is not possible. Reversible plating/stripping of magnesium has been demonstrated many times, however in most of the cases from highly reactive and/or aggressive electrolytes. That put some obstacles on the way for future commercialization and a key challenge on the road to a rechargeable magnesium batteries is the development of non-corrosive magnesium electrolytes.

For some time, role of chloride in electrode process was considered to be essential for reduction of magnesium ions. However new studies show possible operation of magnesium battery with Cl-free electrolyte. Conditions for that are not completely clear, and here we are going to put some light on the processes occurring at electrode/electrolyte interfaces. DFT calculations are used to understand desolvation of magnesium ion, which is a key step prior to reduction at the electrode. Comparison of both systems, with standard and Cl-free electrolytes, shows the possibility to tune electrode process by changes in electrolyte composition, indicating the way towards the less reactive, and less corrosive systems.

Presented results were obtained within E-MAGIC project, which received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 824066.
Quest for Nanocrystal Spinel Oxides As Prospective Cathodes for Next-Generation Magnesium Batteries
Authors: Hu Linhua , Cabana Jordi
Published: May 2020

Rechargeable batteries based on the intercalation of multivalent cations are a promising energy storage technology to overcome the limitations of safety, cost, and energy density of state-of-the-art Li-ion batteries. However, functionality of cathodes in Mg batteries has only been realized with a few of S-containing compounds, which possess limited capacity and operate at low potential, hindering competitive energy densities. Spinel oxides have been predicted to improve both voltage and capacity. However, the strong electronic interaction between these cations and the corresponding frameworks impose the challenge of Mg2+ low mobility and sluggish kinetics.

Herein, a series of spinel oxides with designed sizes and defects have been evaluated as possible cathodes, studying their fundamental ability to intercalate Mg2+ by using different temperatures. Mg2+ deintercalation at high voltage was achieved at 110oC, and, under certain conditions, even at room temperature. In addition, the capabilities of Mg2+ reversible intercalation are correlated to particle size. Our results demonstrate that the design of nanosized spinel oxides could enable an efficient pathway to improve Mg2+ reaction kinetics, thus advancing the ability to develop new multivalent cathode protypes with high energy density.

References:

1. Liu, M., Rong Z., Malik, R., Canepa P., Jain A., Ceder G., Persson K. Spinel compounds as multivalent battery cathodes: a systematic evaluation based on ab initio calculations. Energy Environ. Sci. 2015, 8, 964.

2. Kim C., Phillips P. J., Key B., Yi T., Nordlund D., Yu Y.-S., Bayliss R. D., Han S., He M., Zhang Z., Burrell A. K., Klie R. F., Cabana J. Direct Observation of Reversible Magnesium Ion Intercalation into a Spinel Oxide Host. Adv. Mater. 2015, 27, 3377.

3. Hu, L., Johnson I.D., Kim S., Nolis G.M., Freeland J.W., Yoo H.D., Fister T., McCafferty L., Ashton T., Darr J., Cabana J. Tailoring the electrochemical activity of magnesium chromium oxide towards Mg batteries through control of size and crystal structure. Nanoscale 2019, 11, 639.
Enhanced Stability at the Electrode-Electrolyte Interface in Ionic Liquid Electrolyte for 5 V Lithium-Ion Rechargeable Batteries
Authors: Lee Hyeon Jeong , Pasta Mauro
Published: May 2020

Lithium nickel manganese oxide (LiNi0.5Mn1.5O4) is a promising cathode material for next-generation lithium-ion rechargeable batteries due to its high operating voltage of 4.7 V vs. Li/Li+. However, there are lots of drawbacks in using LNMO as a cathode material because of the liquid electrolyte instability. When carbonate-based electrolytes are decomposed at high cut-off voltage, they generate a hydrofluoric acid which attacks the surface of LNMO. This unwanted parasitic reaction at the electrode-electrolyte interface accelerates the decay in cycle life. In this work, Ionic liquid (1M LiFSI in Pyr13FSI) is adopted as an electrolyte for LNMO cathode material. Highly stable ionic liquid mitigates dissolution of Ni and Mn even in the high cut-off voltage of 5.1 V vs. Li/Li+. X-ray fluorescence mapping analysis confirmed the mitigation of dissolution by building up a 2D image of the varying composition of a sample.
Transient Behavior in Phase-Transforming Electrodes Revealed By Operando X-Ray Diffraction
Authors: Deng Haitao , Jin Norman , Zhao Hongbo , Lim Kipil , Lomeli Eder , Takacs Christopher J , Bazant Martin Z. , Chueh William C.
Published: May 2020

Solid state phase transformation triggered by lithium insertion is ubiquitous in many commercially available battery electrodes such as LiXFePO4 (LFP), LiXCoO2 and graphite. Understanding the kinetics of phase transformation, in particular the nucleation and growth of a second phase due to the Li compositional changes is key to achieving high cycling rates in these phase separating materials. LFP is a model phase transforming material with a large miscibility gap that thermodynamically favors phase separation (segregation into Li-rich and Li-poor phases) in bulk crystals of sizes larger than 50 nm.

It’s commonly accepted that phase transformation at constant current happens via two major pathways: (1) particle-by-particle transformation with a moving interface and (2) concurrent transformation, mediated by a kinetically stabilized solid solution[1-4]. However, realistic battery operation involves erratic charging and discharging behavior such as brief pulses, rests, etc, wherein our current understanding is still lacking. Primarily the relationship between particle dynamics (i.e. the solid solution fraction, active particle population) in an electrode and applied overpotential remains unclear. We herein combine operando X-ray diffraction and numerical phase field simulation to track and understand the transient response of the battery particles during non-constant current conditions. This work highlights the importance of particle dynamics for phase separating electrodes in operation and inspires general battery operating principles that prolong cycle life.

References

[1] Li, Yiyang, et al. Nature materials 13.12 (2014): 1149.

[2] Liu, Hao, et al. Science. 344.6191 (2014): 1252817.

[3] Li, Yiyang, et al. Nature materials 17.10 (2018): 915.

[4] Bazant, Martin Z, et al. Acc. Chem. Res. 46.5 (2013): 1144-1160.
Solving the Solvation Structure of Ions: X-Ray Absorption Studies on Multivalent Cations in Solution
Authors: Driscoll Darren M , Balasubramanian Mahalingam
Published: May 2020

X-ray absorption fine structure (XAFS) studies of liquid electrolytes have been performed to identify the elemental and geometric coordination around multivalent cations. Progress has been made in the characterization of first- and second-coordination shells around multivalent cations such as Ca2+ and Zn2+ in a multitude of organic and aqueous systems. Through careful fitting, using optimized coordination geometries and photoelectron scattering pathways, we elucidate the local structure around multivalent cations. Multi-anion experiments including a variety of solvent molecules, from weakly coordinating to strongly chelating species and an extensive list of coordinating anions have shed light on ion paring formation in these electrolytic solutions. All of these material exhibit pronounced changes in the extended X-ray absorption fine structure (EXAFS) and the X-ray absorption near edge structure (XANES) of the cation as a result of ion-pairing. These studies suggest the contact-ion pairing in certain cation-anion systems may impact the overall viability of certain cation-anion-solvent compilations in electrochemical systems.
(Invited) Heterogeneous Integration Packaging Challenges for Artificial Intelligence
Authors: Sikka Kamal
Published: May 2020

As semiconductor and system scaling has saturated, heterogeneous integration of disparate components in a singular electronic package has become increasingly important. A variety of new packaging techniques are being developed for heterogeneous integration. These techniques include multiple-chip packages incorporating high-density laminated substrates, inter-chip bridges, silicon interposers, and three-dimensional chip stacking. This talk will compare and contrast these varied techniques and identify the associated challenges. These challenges include fine-pitch interconnects, new materials, complex assembly, thermal management, and test and reworkability, among others. Implications to tool development, test protocols, and simulation techniques will also be discussed.
Electronic and Optical Properties of Short-Period Si/Sige Superlattices: Effects of Interfacial Atomic-Scale Roughness
Authors: Fettu Gabriel , Attiaoui Anis , Samik Mukherjee , Bauer Matthias , Moutanabbir Oussama
Published: May 2020

SiGe/Si superlattice (SL) are currently a central building block of nanosheet transistors proposed for the 7 nm technology nodes and beyond [1], where elective wet-etching of the SiGe layers has been used to release the Si layers and form a vertically stacked channels architecture [2]. Consequently, the interfacial abruptness and uniformity in heterostructures are critical to control their electronic and optical properties. Recently, we demonstrated a 3-D atomistic-level mapping of the roughness and uniformity of buried epitaxial interfaces in Si/SiGe SLs with a layer thickness in the 1.5-7.5 nm range [3]. This direct quantification of the abruptness of buried interfaces enabled a direct evaluation of interfacial effects on electronic and optical properties of epitaxial heterostructures. For instance, spectroscopic ellipsometry indicated the first observation of a new superlattice-related optical transition between 2.2 and 2.7 eV. However, the interpretation of this new transition can only be achieved using a theoretical framework considering atomic-level details of the interfacial roughness. To that end, we have been carrying out theoretical investigations to build a correct quantum mechanical model that incorporates the effect of the interface, directly measured from atom probe tomography (APT), to interpret the possible SL-related optical transition. Thus, an 8-band k⋅p formalism was developed and validated for group IV semiconductors [4], where a quantum mechanical incorporation of the interface width is highly coveted because the microscopic interface asymmetry (MIA) effect can greatly influence the electronic and optical properties of short-period SLs, induce strong interactions between different SL subbands, and enhance the absorption strength considerably [5]. It has been shown that the nature of the SL interfaces can have a significative impact on the optical confinement properties of other group IV heterostructures [6]. To test this model, experimental optical characterization of four different SLs (the mean Ge concentration of the layers within the SLs is in the 25 to 30 at. % range and is the periodicity of the SLs) will be presented and discussed. Then, by simulating the SL optical properties with the developed 8-band k⋅p method, the effect of the interface will be investigated to try and explain the observed spectroscopic transition.

[1] G. Hellings, et al, in 2018 IEEE Symp. VLSI Technol. (IEEE, 2018), pp. 85–86.

[2] K. Komori, et al, Solid State Phenom. 282, 107 (2018).

[3] S. Mukherjee, et al, ArXiv: Cond-Mat 1908.00874, 1 (2019).

[4] T. B. Bahder, Phys. Rev. B 41, 11992 (1990).

[5] H. M. Dong, et al, Thin Solid Films 589, 388 (2015).

[6] F. Szmulowicz, et al, Phys. Rev. B - Condens. Matter Mater. Phys. 69, 155321 (2004).
Static Negative Capacitance Response in Ferroelectric/Paraelectric Superlattices
Authors: Gharbi Mariem , Sylvestre Alain , Dellis Jean-Luc , Le Marrec Françoise , Karkut Mickael , Lemee Nathalie
Published: May 2020

Recently Zubko et al.(1) reported a negative capacitance effect in PbTiO3/SrTiO3 superlattices. The negative capacitance of ferroelectrics is proposed as a solution to overcome the “Boltzmann tyranny” that holds back the process of miniaturization. Nowadays, the transistors are becoming too small, which increased the energy dissipation hence the self-heating of the electronic chips. The phenomenon of negative capacitance is gaining a great interest since it has been proposed as a way to reduce the power consumption of field-effect transistors(2), by replacing the conventional SiO2 gate insulator by an insulator that provides a negative capacitance effect.

Actually, in ferroelectrics, “the negative capacitance state” takes place at the frontier between the two stable polarization states, during the transient processes of switching, and therefore is intrinsically thermodynamically unstable

Hence, negative capacitance cannot be evidenced for single layer ferroelectrics but should be stabilized in a series capacitance system. The ferroelectric capacitance can be stabilized in the negative regime, when a paraelectric capacitor and a ferroelectric capacitor are connected in series. Hence, the paraelectric/ferroelectric superlattices provide a model system to investigate the negative capacitance effect.

The negative capacitance was shown to be strongly related to the existence of a 180° stripe domain structure. In fact, the depolarization field inside such structure is very strong and induces 180° stripe nanodomains formation in order to screen this field and to maintain the ferroelectric state. This nanodomains, in particularly, the domain wall motion greatly influences the dielectric properties of the heterostructure.

Here we report an experimental study on a series of Pb(Zr0.2Ti0.8)O3 /SrTiO3 superlattices in which we evidenced 180° stripe nanodomains. The investigation of such system is motivated by the fact that leakage currents are reduced in PZT compared to the ferroelectric PbTiO3, investigated by Zubko et al.,and also by the possibility to vary the misfit strain related to PbTiO3 /SrTiO3 superlattices . For this study the thickness of the ferroelectric layers was fixed to 4 unit cells and those of the paraelectric layer was varied from 3 to 10 unit cells. The domain’s electrostatic effect in the superlattice is confirmed by a noticeable reduction of the Curie temperature. We will present an in-depth analysis of the dielectric response of these superlattices by impedance spectroscopy. The temperature dependent dielectric measurements will be presented and will emphasize a negative capacitance effect in these superlattices.

References

- Zubko et al., Nature, 2016, 534, 524–528.

- S. Salahuddin and S. Datta, Nano Lett.8, 405 (2008)
Electrical Characterization of Sputter Deposited AlxSc1-XN Thin Films
Authors: Tsai SungLin , Kusafuka Kazuki , Hoshii Takuya , Wakabayashi Hitoshi , Tsutsui Kazuo , Kakushima Kuniyuki
Published: May 2020

Ferroelectric materials have been utilized for non-volatile memory applications [1]. Beside extensive works on ferroelectric HfO2 thin film [2, 3], recent works on nitride-based materials have proven that AlxSc1-xN (ASN) also shows ferroelectricity with a box-like characteristic [4]. Commonly Pt electrodes with a large Schottky barrier are utilized to overcome the small bandgap of ASN. However, a high remnant polarization of over 100 µC/cm2 is attractive for future non-volatile memory applications. The purpose of this study is to measure the basic electrical properties of ASN films deposited by sputtering with W electrodes.

50-, 75-, and 100-nm-thick ASN films were deposited by DC reactive sputtering with an Al0.57Sc0.43 target in Ar and N2 ambient at a substrate temperature of 400oC. Both top and bottom electrodes were deposited at room temperature.

Leakage current characteristics of the fabricated metal-insulator-metal (MIM) capacitors indicate a breakdown field of 3 MV/cm. Temperature-dependent leakage current measurement has indicated a Schottky barrier height of 1.0 eV at W/ASN interface, which is rather small for memory application and needs to be engineered. Hysteresis in the polarization-voltage measurements can be hardly observed due to excess leakage current. However, ferroelectric hysteresis curves were obtained from capacitance-voltage (CV) measurements at 100 kHz for all the samples with different thicknesses. The coercive field taken from the hump in the CV curves was 0.9 MV/cm for 50-nm-thick sample and 1.4 MV/cm for 75 and 100 nm-thick samples, which are lower than the reported thick ASN samples [4], implying thickness-dependent properties of ASN films.

In conclusion, JV and CV characteristics of sputter-deposited ASN films on W electrode were performed. Relatively low energy offset at metal/ASN interface was extracted. Ferroelectric hysteresis was obtained from CV measurement even for a film as thin as 50 nm.

References

[1] T. S. Böscke, et al., Appl. Phys. Lett., 99, 102903 (2011). [2] S. Kundu, et al., Nature Scientific Reports, 5, 8494 (2015). [3] M. Kobayashi, et al., IEEE J. Electron Dev. Soc., 7, 134 (2018). [4] S. Fichtner, et al., J. Appl. Phys., 125, 114103 (2019).

Figure 1
(Invited) Atomic-Layer-Deposition of in-Situ Crystallized Ge2Sb2Te5 Alloy and Gete/Sb2Te3 Superlattice, and Their Phase-Change Performances
Authors: Hwang Cheol Seong
Published: May 2020

This paper introduces a new atomic layer deposition process for highly conformal, nanocrystalline-as-deposited GeTe-Sb2Te3 pseudo-binary film growth at a deposition temperature of 130 °C. The process utilizes Ge(II)-guanidinate, Te(Si(CH3)3)2, and Sb(OC2H5)3 with the NH3 co-reagent. The alternative GeTe and Sb2Te3 subcycles produced various film compositions, all consistent with the GeTe-Sb2Te3 tie lines, owing to the stoichiometric reactions between the precursors without involvement of undesirable side reactions. The density of the nanocrystalline Ge2Sb2Te5 (GST225) films was 6.2 g/cm3, similar to the density of the bulk crystalline material. The crystallization behaviors indicated that the distribution of the constituent elements of the GST225 films was highly uniform at the atomic level, as opposed to the case of the low-temperature (100 °C)-deposited films. The cubic to hexagonal transition at 350 °C upon post-annealing produced (0001) hexagonal planes highly aligned along the substrate. The demonstration of the phase change memory device achieved high cycling endurance (>107).

The same ALD process was further exploited to grow the GeTe/Sb2Te3 superlattice structure, which might be an even more energy-efficient phase change material. It was found that the Sb2Te3 layer could be grown in highly c-axis oriented manner on SiO2 surface, which then can be used as the template layer for the subsequent growth of also highly c-axis oriented GeTe layer. Direct growth of the GeTe layer on SiO2 did not result in the similar optimal results. However, a certain intermixing occurs during the alternating growth of the Sb2Te3 and GeTe layers, of which details are dependent on the thickness ratio of the two layers. Interestingly, the intermixed layers still showed a certain type of layered structure, which appeared to be related to the van der Waals nature of the Sb2Te3 layer. However, such a layered structure could hardly be achieved on metallic surface such as TiN. This might be related with the highly interacting chemical nature of the TiN surface as well as the relatively rough surface topography. Adopting graphene or ultra-thin SiO2 layer on the TiN recovered the highly c-axis aligned growth behavior.
Understanding the Formation of Soluble Bases in Nickel-Rich Layered Materials and Their Reactivity Towards Electrolyte
Authors: Martinez Ana Cristina , Grugeon Sylvie , Cailleu Dominique , Courty Matthieu , Tran-Van Pierre , Delobel Bruno , Laruelle Stephane
Published: May 2020

In the last years, LiNixMnyCozO2 (x+y+z = 1) layered materials have been widely used as positive electrode materials in lithium-ion batteries for electric car applications, because of their high energy density given by the nickel content. Unfortunately, their stability towards H2O and CO2 is compromised when x>0.5, favoring the formation of surface species commonly called soluble bases (SB). The presence of SB has shown to increase the cell’s impedance, decrease the capacity retention and evolve gas during functioning1-4. Therefore, in this work, accurate SB quantification methods were implemented on four high-nickel layered materials with the aim of further deciphering their formation mechanisms and reactivity towards electrolyte.

The optimization of a procedure that allows the quantification of SB in the as-received and after H2O/CO2storage of the NMC532, 622, 811 and LiNi0.9Co0.1O2, will be shown through the complementary use of acid-base titration and inductively coupled plasma (ICP) techniques. We unveiled the presence and quantified different lithium and sodium salts. Moreover, thanks to additional TGA/MS analysis, we propose a novel NMC surface degradation mechanism upon H2O/CO2 storage that involves the presence of lithium and nickel-based surface species. Finally, through nuclear magnetic resonance technique (19F and 31P NMR), the chemical reactivity of these surface species towards a commercial LiPF6-based liquid electrolyte was studied at room and at high temperature, evidencing the presence of lithium fluorophosphate as major decomposition product.

1. Liu, H. S., et al. (2006). "Investigation and improvement on the storage property of LiNi0.8Co0.2O2 as a cathode material for lithium-ion batteries." Journal of Power Sources 162(1): 644-650.

2. Bi, Y. J., et al. (2016). "Stability of Li2CO3 in cathode of lithium ion battery and its influence on electrochemical performance." Rsc Advances 6(23): 19233-19237.

3. Renfrew, S. E. and B. D. McCloskey (2017). "Residual Lithium Carbonate Predominantly Accounts for First Cycle CO2 and CO Outgassing of Li-Stoichiometric and Li-Rich Layered Transition-Metal Oxides." Journal of the American Chemical Society 139(49): 17853-17860.

4. Mahne, N., et al. (2018). "Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen." Angewandte Chemie-International Edition 57(19): 5529-5533.
Origins of Capacity Fade and Material Degradation in Ni-Rich NMC Li-Ion Batteries
Authors: Dose Wesley M , Mahadevegowda Amoghavarsha , Morzy Jędrzej K , Ducati Caterina , Grey Clare P. , De Volder Michael F. L.
Published: May 2020

Nickel-rich layered oxide cathode materials are promising candidates for automotive lithium-ion batteries due to their low cost and high reversible capacity.1 However, paired with graphite anodes these materials exhibit faster voltage and capacity fading compared to isostructural LiNixMnyCozO2 (NMC) cathodes with lower nickel content.2 In this work we will explore the origins of capacity fade and material degradation in graphite/LiNi0.8Mn0.1Co0.1O2 (NMC811) full cells. With a focus on strategically designed electrochemical protocols (see Fig. 1), the role of several key cycling parameters (e.g. upper cut-off voltage, time at high voltage, phase transitions) on the degradation are decoupled. The ageing processes are quantified in terms of the full cell capacity retention, impedance rise, electrode slippage, and NMC cathode deterioration. We find that most full cell capacity loss and impedance rise is caused by increasing the upper cut-off voltage to >4.2 V, with the impedance increase largely driven by concomitant full state-of-charge (SOC) cycling. Time spent at high voltage (voltage holds) has less impact on these parameters. These findings are supported by electron microscopy and spectroscopy experiments (SEM, high-resolution TEM, and STEM-EELS) on cycled electrodes, which show clear evidence for cycle history dependent degradation including particle cracking, shearing, and surface reconstruction.

References

1. Schipper, E. M. Erickson, C. Erk, J.-Y. Shin, F. F. Chesneau, and D. Aurbach, J. Electrochem. Soc., 164, A6220, 2017.

2. Jung, M. Metzger, F. Maglia, C. Stinner, H. A. Gasteiger, J. Electrochem. Soc., 164, A1361, 2017.

Figure 1
Ultra-Stable Performance of Ni-Rich Layered Oxide Cathodes for Lithium-Ion Batteries Using Ionic Liquid Electrolyte
Authors: Wu Fanglin , Kuenzel Matthias , Kim Guk-Tae , Passerini Stefano
Published: May 2020

High energy density lithium-ion batteries (LIBs) have continually been of great research interest amplified by the exponentially growing demand for electric vehicles.[1] Among the investigated systems, nickel-rich transition metal oxides appear very promising owing to their high specific capacity,[2] and low cobalt content, according to necessity of reducing the cobalt proportion in LIB cathodes due to its severe shortage and strong environmental and ecological concerns.[3] However, the increased nickel content also introduces previously overcome challenges of poor capacity retention and thermal stability due to the vulnerability of the nickel rich oxide towards interfacial side reactions.[4] Herein, a low volatility and non-flammable ionic liquid-based (IL) electrolyte[5] consisting of 0.8Pyr14FSI-0.2LiTFSI is employed to overcome those challenges faced by a Ni-rich LiNi0.8Co0.1Mn0.1O2 positive electrode. The cathode exhibits remarkable electrochemical performance in half-cell configuration, delivering a specific capacity of approximately 200 mAh g-1 and practically no capacity fading after 100 cycles at 0.1C at room temperature. After 600 cycles at 0.5C the cathode has an outstanding capacity retention of 97%, which is substantially higher than with the conventional organic carbonate-based electrolyte used for reference, attributed to a much more stable electrode-electrolyte interfacial layer. Even at elevated temperature (40 °C) the LiNi0.8Co0.1Mn0.1O2 in combination with the IL electrolyte offers a specific capacity of more than 200 mAh g-1 as well as a capacity retention around 99% after 100 cycles at 0.5C. To the best of our knowledge these results exceed the state-of-the-art performance reported for any Ni-rich positive electrode.

Reference

[1] W. Liu, P. Oh, X. Liu, M. J. Lee, W. Cho, S. Chae, Y. Kim, J. Cho, Angewandte
Chemie
2015, 54, 4440.

[2] S. H. A. Heist, and S. H. Lee, J
. Electrochem
. Soc
2019, 166 (6) A873-A879.

[3] C.Vaalma, D. Buchholz, M. Weil, S. Passerini, Nature Review Materials
2018, 3, 18013.

[4] U.-H. Kim, L.-Y. Kuo, P. Kaghazchi, C. S. Yoon, Y.-K. Sun, ACS Energy Letters
2019, 4, 576.

[5] G. A. Elia, U. Ulissi, S. Jeong, S. Passerini, J. Hassoun, Energy & Environmental Science
2016, 9, 3210.
A Thin-Layer Carbon Nanosphere Coating on Ni-Rich NMC811 Core-Shell Cathode Via Solvent-Free Mechanofusion Process: In Operando Investigation and Highly Stable 18650 Li-Ion Battery
Authors: Phattharasupakun Nutthaphon , Wutthiprom Juthaporn , Sarawutanukul Sangchai , Tomon Chanikarn , Duangdangchote Salatan , Duriyasart Farkfun , Sawangphruk Montree
Published: May 2020

In the past decades, rechargeable Li-ion batteries (LIB) are of interest and become the most essential device for the storage of electric energy in many applications, especially for electric vehicles (EVs). To date, only Ni-rich cathode materials, especially the NMC811, could enhance the energy density of the LIB up to 250 Wh kg-1 suitable for long-range EVs. However, the practical application of the NMC811 has not yet been fully developed because of many issues, i.e. (i) the formation of high-valence state Ni4+ causes several parasitic reactions with continuous consumption of electrolyte, (ii) the formation of microcrack during the lattice changes leading to fast capacity decay, (iii) Li+/Ni2+ cation mixing causing the formation of inactive phase on the surface, and (iv) poor electron and ionic conductivities of the materials limiting its use at high rates. To solve these problems, the surface coating approach is utilized in which a thin layer of carbon nanosphere with a thickness of ca. 50-80 nm was coated on the surface of Ni-rich NMC811 cathode using a solvent-free mechanofusion process. It was found that carbon nanoparticles were mechanically fused into the NMC811 altering the surface property of the material. The improved performance was fundamentally investigated by several techniques, i.e. GITT, in operando XRD, and in situ DEMS. The NMC811cs exhibits faster Li-ion diffusivity, higher lattice parameter changes, and less gas formation at the high charging potential as expected from the uniformly coated carbon shell. In addition, to demonstrate the practical feasibility of this process, 18650 Li-ion batteries of NMC811cs cathode coupled with graphite anode were also fabricate in a dry room compared to the conventional NMC811 cell. The NMC811cs 18650 cell with a capacity of 2.5 Ah per cell exhibits excellent cycling retention after tested at a high rate of 1.0 C. This work provides a novel and economical strategy for highly stable practical 18650 Li-ion battery.