bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Calcium-Ion Cathode Materials
Authors: Kim Sanghyeon , Yin Liang , Parajuli Prakash , Blanc Lauren , Fister Timothy T , Park Haesun , Kwon Bob Jin , Zapol Peter , Klie Robert F , Kang Kisuk , Nazar Linda F , Lapidus Saul H. , Ingram Brian J. , Vaughey John T.
Published: December 2020

Calcium-ion batteries (CIBs) could be an alternative to lithium-ion batteries (LIBs) for certain niche applications due to their theoretically high operating potentials and the high natural abundance of calcium. However, the development of CIBs has been limited by the lack of proper electrolytes and electrode materials due to the difficulties identifying Ca-ion insertion host materials. Previous efforts to develop CIB cathodes have been made mainly based on intercalation materials such as Prussian blue-based materials (1) , layered oxide materials (MoO3 (2), V2O5 (3), CaCo2O4 (4-5), and layered phosphates (VOPO4·2H2O) (6). In this discussion we will be reviewing the state of Ca-ion battery materials and delve into an analysis of several functional polyanionic materials that show promising properties and characteristics as CIB cathodes. The NASICON-type NaV2(PO4)3, derived from de-sodiation of Na3V2(PO4)3, has been shown to reversibly intercalate Ca2+ -ions (capacity 81 mA h g-1) above 3V (vs. Ca2+/Ca) with stable cycling performance. DFT calculations, XAS, XRD, and TEM studies were used to support the insertion of Ca-ions and give insights into the diffusion mechanism of the materials involved (7,8). The presentation will also provide insights into materials design aspects of CIB materials and note areas of need that would benefit the MV battery community.

References:

(1) Albert L. Lipson, Baofei Pan, Saul H. Lapidus, Chen Liao, John T. Vaughey,Brian J. Ingram “Odyssey of Rechargeable Ca-Ion Batteries: A New Energy Storage System”. Chem. Mat.
2015,
27
, 8442.

(2) Marta Cabello, Francisco Nacimiento, Ricardo Alcántara, Pedro Lavela, Carlos Pérez Vicente,José L. Tirado “Applicability of Molybdite as an Electrode Material in Calcium Batteries: A Structural Study of Layer-type CaxMoO3” Chem. Mat., 2018,
30, 5853−5861

(3) M. Bervas, L.C. Klein, G.G. Amatucci “Vanadium oxide–propylene carbonate composite as a host for theintercalation of polyvalent cations”. Solid State Ionics
2005
176, 2735–2747.

(4) A. Ponrouch, M.R. Palacin “On the road toward calcium-based batteries” Current Opinion in Electrochemistry
2018, 9, 1-7.

(5) Haesun Park, Yanjie Cui, Sanghyeon Kim, J. T. Vaughey, PeterZapol “Ca Cobaltites as Potential Cathode Materials for Rechargeable Ca-Ion Batteries: Theory and Experiment” J. Phys. Chem. C
2020,
124, 5902−5909

(6) J.J. Wang, S.S. Tan, F.Y. Xiong, R.H. Yu, P.H. Wu, L.M. Cui, Q.Y. An “VOPO4 2H(2)O as a new cathode material for rechargeable Ca-ion batteries” Chem Comm. 2020
56 3805.

(7) M.L. Mao, T. Gao, T, S.Y., Hou, C.S. Wang “A critical review of cathodes for rechargeable Mg batteries” Chem Soc Reviews
2018
47 8804.

(8) T.N. Chen, G.S. Gautam, W.X. Huang, G. Ceder, G “First-Principles Study of the Voltage Profile and Mobility of Mg Intercalation in a Chromium Oxide Spinel” Chem Mat
2018
30 152.
Charge-Storage Mechanism of Aluminum-Sulfur Batteries
Authors: Smajic Jasmin , Wee Shianlin , Fernandes Simoes Filipa R. , Hedhili Mohamed N. , Wehbe Nimer , Abou-Hamad Edy , Costa Pedro M.F.J.
Published: December 2020

The electrochemical performance of aluminum-sulfur batteries is beset by poor stability and sluggish charge-storage properties. To address these issues, carbon allotropes have been used as electrode fillers, but successful outcomes remain inexplicably elusive. Here, a composite of sulfur and small diameter single-walled carbon nanotubes is synthesized and used as a cathode for reversible aluminum-sulfur batteries. The assembled electrode delivers a high capacity of 1024 mAh/g and effectively reduces the cell polarization by 37%. Moreover, the use of small-diameter SWCNT helps in lowering the electrolyte-to-sulfur ratio down to 17 μg/ml, an important step toward lean electrolyte conditions. Despite that, the capacity fade of the Al-S battery cannot be fully reversed. As we show, the consequence of the interaction between the electrolyte and S is the buildup of insoluble and poorly conductive discharge products, which inhibit charge diffusion and progressively deactivate the electrode, ultimately causing capacity decay. Overall, this works clarifies the carbon–sulfur–electrolyte interactions and their role in the underlying charge-storage mechanism of Al-S batteries.
Unlocking Multiphysics Design Guidelines on Si/C Composite Nanostructures for Next Generation High-Energy-Density and Robust Lithium-Ion Battery Anode
Authors: Gao Xiang , Xu Jun
Published: December 2020

Lithium ion batteries (LIBs) have been one of the most popular energy storage devices in many fields. Along with the development of the LIBs, high energy density becomes one of the most urgent requests in the market. To achieve this goal, high capacity anode materials are attracting more and more research interests, among which the Si related material is one of the most promising candidates for next generation LIBs. The biggest problem of Si related materials is the tremendous volume change during the cycling. Thus, many strategies have been proposed to solve this problem, e.g. nano engineering, composites, etc. The Si/C composite material, is widely adopted because it has the advantage of nanomaterials as well as compensates the weakness of nano-properties. Current material fabrication guidance for novel designs of Si/C composite particle materials for anode only focuses on electrochemical behavior and redox reactions at the nano/micro level; however, they cannot provide detailed information for predicting mechanical deformations of the composite particles especially coupled with electrochemical and thermal fields. Herein, an electro-chemo-mechanical model is established and implemented to quantitatively analyze the multiphysics behavior of five representative Si/C composite nanostructures. Numerical simulation manifests that yolk-shell and dual-shell structures are more robust in terms of particle fractures. With the consideration of electrochemical performance, the yolk-shell structure is the most excellent type among the compared five Si/C composites. Finally, design guidance is mapped to further illustrate quantitative structure-property relations. This study provides novel insights on Si/C composite nanostructure anode material design and further powerful design tools for next-generation high-energy-density lithium-ion batteries.
Characterization and Optimization of Co-Doped SnO2 As Anode for Lithium-Ion Batteries
Authors: Birrozzi Adele , Asenbauer Jakob , Ashton Thomas , Groves Alexandra R. , Darr Jawwad , Bresser Dominic
Published: December 2020

Tin oxide-based materials have been intensively investigated as alternative anodes for lithium-ion batteries due to their high specific capacity, environmental friendliness, non-toxicity, and ease of handling.[1] However, the initial formation of Li2O upon lithiation is essentially irreversible, which has a severe effect on the first cycle coulombic efficiency and the reversibly achievable capacity in general.[2] It has been shown that the incorporation of transition metal dopants can address this issue, as it enables the reversible formation and reformation of Li2O.[3] The choice of the dopant, however, plays a critical role for the long-term cycling stability, rate capability, and eventual energy density of the resulting lithium-ion cells.[4]

Herein, we show that the addition of specific combination of different dopants allows for further tailoring the electrochemical properties. We also demonstrate the production of such materials using a scalable continuous hydrothermal flow method. The performance of the best composition (Sn0.9Co0.05Mn0.05O2, SCMO) was further improved by applying a carbonaceous coating. The electrochemical investigation of the coated anode material was conducted in half-cells and in high-energy full-cells using high-voltage LiNi0.5Mn1.5O4 (LNMO) as active material for the cathode (Figure 1).[5] The performance of the full-cells was further enhanced by carefully optimizing the anode composition and fine-tuning the full-cell design, considering electrolytes and different pre-lithiation degrees.

Reference
s
:

[1] F. Zoller, D. Böhm, T. Bein, D. Fattakhova-Rohlfing, ChemSusChem.,
1

2

, 4140 (2019)

[2] I.A. Courtney and J.R. Dahn, J Electrochemical Soc., 144
, 2045 (1997)

[3] D. Bresser, S. Passerini and B. Scrosati, Energy Environ. Sci.
,

9
, 3348 (2016)

[4] Y. Ma et al, Sustain. Energy Fuels,
2
, 2601 (2018)

[5] A. Birrozzi et al., Batter. Supercaps,
3
, 284 (2020).

Figure 1
Quenching Method and Performance of High Voltage Layered Lithium Rich Nickel Manganese Oxides
Authors: Burke Sven , Whitacre Jay
Published: December 2020

Due to their promise of high specific capacity layered lithium rich nickel manganese oxide materials have a large body of literature dedicated to their structure, and electrochemical behaviors[1–5]. Yet these materials have often been marred by significant capacity losses, rate capability limitations, and structural instability over the course of cycling. Several techniques involving surface and structural modifications have been used to mitigate these capacity losses[6–8]. In this work we used a hybrid acetate/nitrate precursors and sol-gel/combustion synthesis to conduct an unprecedented combined survey of the composition of Li(NixLi(1/3-2x/3)Mn(2/3-x/3))O2, and synthetic quench rates to elucidate the effects of these variables on electrochemical cycling behavior, bulk morphology, and surface morphology of the layered lithium rich manganese oxides. We find that the electrochemical behavior of these materials is dependent on both the nickel content as well as the quenching method, with a lower limit on the nickel content beyond which the effects of quenching are minimal. Despite XRD revealing loss of super lattice peaks indicating a loss of transition metal ordering, often associated with capacity loss, galvanostatic cycling of samples saw improved capacities over the course of cycling. SEM found bulk morphology of cathodes differs across nickel contents, yet it did not experience large changes over the course of cycling. The use of TEM found that the surfaces of Li(NixLi(1/3-2x/3)Mn(2/3-x/3))O2 powders is highly sensitive to quenching method, and comparison of surfaces over the course of cycling provided incites into the effects of quenching and nickel content on electrochemical cycling behaviors of the cathode materials. This investigation reveals that careful considerations in synthesis are required for the realization of high-performance layered lithium rich nickel manganese oxides.

[1] Y. J. Park, Y.-S. Hong, X. Wu, K. S. Ryu, S. H. Chang, J. Power Sources
2004, 129, 288.

[2] Z. Lu, L. Y. Beaulieu, R. A. Donaberger, C. L. Thomas, J. R. Dahn, J. Electrochem.
Soc.
2002, 149, A778.

[3] Z. Lu, J. R. Dahn, J. Electrochem. Soc.
2002, 149, A1454.

[4] M. Jiang, B. Key, Y. S. Meng, C. P. Grey, Chem.
Mater.
2009, 21, 2733.

[5] J. Bréger, N. Dupré, P. J. Chupas, P. L. Lee, T. Proffen, J. B. Parise, C. P. Grey, J. Am. Chem. Soc.
2005, 127, 7529.

[6] D. Eum, B. Kim, S. J. Kim, H. Park, J. Wu, S. P. Cho, G. Yoon, M. H. Lee, S. K. Jung, W. Yang, W. M. Seong, K. Ku, O. Tamwattana, S. K. Park, I. Hwang, K. Kang, Nat.
Mater.
2020, 19, 419.

[7] H. Z. Zhang, Q. Q. Qiao, G. R. Li, S. H. Ye, X. P. Gao, J. Mater. Chem.
2012, 22, 13104.

[8] Y. Wu, A. Manthiram, Solid State Ionics
2009, 180, 50.
A Maturation Process or Binders Based on Coordination Chemistry to Boost the Mechanical Strength and Cyclability of Si-Based Electrodes
Authors: Huet Lucas , Kana Nassima , Mazouzi Driss , Vanpeene Victor , Devic Thomas , Maire Eric , Roué Lionel , Lestriez Bernard
Published: December 2020

Silicon is attractive as negative electrode material for Li-ion batteries (LIBs) to increase their energy density [1]. The main challenge is to deal with the large silicon volume expansion induced by its lithiation, which damages the mechanical integrity of the electrode, and produces an unstable solid electrolyte interphase (SEI).

Recently, we have discovered a post-processing treatment, called maturation, which very significantly improves the mechanical and electrochemical stabilities of silicon-based electrodes made with polycarboxylic acid binders [2-4]. It consists of storing the electrode in a humid atmosphere for a few days before drying and cell assembly. We found that during maturation, the atmospheric-induced corrosion of the current collector releases oxidized copper species that migrate into the electrode to physically crosslink the binder phase, substantially modifying its resiliency to the silicon volume variation as shown by various in situ and operando characterizations. The pre-addition of a small amount of copper or zinc salt in the electrode slurry allows to reach similar improvement of electrochemical performance than maturation [5]. This reveals that there is great potential to explore coordination chemistry to design new, more efficient binders through the medium strength and dynamic nature of coordination bonds [6].

Acknowledgments

The authors thank the Natural Sciences and Engineering Research Council of Canada (NSERC) (grant RGPIN-2016-04524) and Transition Énergétique Québec (TEQ) (grant Techno-0040-0001) for financial support of this work.

References

[1] M.N. Obrovac, Si-alloy negative electrodes for Li-ion batteries. Current Opinion in Electrochemistr, 2018, 9, 8–17.

[2] Z. Karkar et al., How silicon electrodes can be calendered without altering their mechanical strength and cycle life J. Power Sources, 2017, 371, 136-147.

[3] C. Real Hernandez et al., A Facile and Very Effective Method to Enhance the Mechanical Strength and the Cyclability of Si-Based Electrodes for Li-Ion Batteries, Adv. Energy Mater, 2017, 1701787.

[4] V. Vanpenne et al., Adv. Energy Mater, Dynamics of the morphological degradation of Si-based anodes for Li-ion batteries characterized by in-situ synchrotron X-ray tomography, Adv. Energy Mater. 9, 2019, 1803947

[5] D. Mazouzi et al., CMC-citric acid Cu(II) cross-linked binder approach to improve the electrochemical performance of Si-based electrodes Electrochimica Acta, 2019, 304, 495-504.

[6] T. Devic, B. Lestriez, L. Roué, Silicon Electrodes for Li-Ion Batteries. Addressing the Challenges through Coordination Chemistry, ACS Energy Letters, ACS Energy Lett., 2019, 4, 550−557.
The Change in Strain in Silicon Anodes Due to the Formation of the Solid Electrolyte Interphase
Authors: McBrayer Josefine , Serkland Darwin , Fenton Kyle R , Apblett Christopher A. , Minteer Shelley
Published: December 2020

Silicon anodes are a promising choice to replace graphite anodes in lithium ion batteries for electric vehicle applications because they have a near 10-fold increase in theoretical energy density. Unfortunately, the solid electrolyte interphase (SEI) on silicon has been found to degrade both mechanically and chemically. The strain due to SEI formation versus the strain in the electrode due to lithiation and delithiation is not well understood. This work used in situ moiré microscopy to make in-plane strain measurements with an emphasis on the observed strain during SEI formation. A novel method was used to create smooth, 50 nm silicon thin films on 2 µm thick copper foil electrodes. A sample grating was patterned on the backside of the electrodes for use with an in-house moiré microscope (see figure). The reference grating was incorporated into the microscope and imaged onto the sample to form moiré patterns which were then used to calculate in-plane strain. Strain measurements were obtained in situ with constant current cycling and cyclic voltammetry. Special care was taken to try and deconvolute the different sources of strain. The changes in strain due to variations in electrolyte additives and the introduction of electrolyte were explored.

Figure 1
Abundant Natural Dye-Based Organic Molecule As Sole Redox Active Material for Symmetric Aqueous Redox Flow Battery
Authors: Nambafu Gabriel , Shao Minhua
Published: December 2020

Organic redox flow batteries (ORFBs) are considered potential substitutes to their traditional metal-based counterparts for application as large scale energy storage device[1] . This is in consideration to the merits offered by organic redox active materials i.e. inexpensive, environment friendly, high solubility and existence in diverse molecular structures that facilitates synthetic tunability to design molecules with the desired physicochemical properties[2] . However, capacity fade as result of cross-contamination has been one of the main challenges hindering development of this energy storage technology[3] . Symmetric redox flow batteries that employs a single redox active material in both electrolytes have the potential to address this challenge making them very attractive[4] .

In this work, a low-cost organic dye is coupled with a radical organic molecule to form a sole bifunctional redox active material that can be used as both negoyte (-0.71V) and posolyte (0.52V versus Hg/Hg2SO4) in an organic symmetric aqueous redox flow battery. Cyclic voltammetry studies of the combined bifunctional molecule reveal reversible redox reactions of the redox couples leading to a theoretical cell voltage of 1.23V. A symmetric pumped cell testing demonstrated over 100 consecutive charge/discharge cycles with nearly 85% coulombic efficiency at current density of 2.5 mAcm-2. The battery utilizes a pH neutral supporting electrolyte (NaCl in water) which is inexpensive, non-corrosive and non-flammable resulting to a low-cost, durable, safe and environmental-friendly redox flow battery.
(Invited) Surface Thermolysis of ALD Precursors and Its Implications for Deposition
Authors: Wang Xinwei
Published: December 2020

ALD is an important technology to fabricate thin film materials. The quality of the ALD films relies much on the surface chemistry reactions involved in the ALD process. Aiming to achieve high-quality ALD films, we carried out careful studies, based on an in situ XPS technique, to investigate the surface thermolysis of various ALD precursors. From the surface thermolysis behavior, a number of important implications can be revealed for engineering the associated ALD processes. Taking nickel amidinate as an example, we found that this precursor was reactive even at room temperature, which suggests a good suitability for low-temperature ALD; that the surface amidinate moiety decomposed at 250 °C, which suggests a limit for high-temperature ALD; and that the byproduct of the surface reaction, i.e. amidine, could be adsorbed on the surface at low temperature, which could be trapped in the ALD films causing C and N impurities. To further demonstrate the importance of these implications, an example of the ALD of NiO using this nickel amidinate precursor was experimentally investigated. Indeed, consistent experimental results about the deposition temperature and the trend of impurities were found. These results highlight the importance of the surface thermolysis approach for rational ALD process engineering.
Comparative Study of Titanium Nitride ALD using High Purity Hydrazine vs Ammonia
Authors: Alvarez Daniel , Andachi Keisuke , Tsuchibuchi Gaku , Suzuki Katsumasa , Spiegelman Jeffrey , Murata Hayato
Published: December 2020

Emerging devices (Logic and Advanced Memory) require high quality thin (5-20 Å) electrode and barrier films. Difficult thermal budget constraints are now being placed on well-known materials such as TiN and TaN. Deposition temperature limitations have reached 350°C and below while very low resistivity (<100 micro-ohm/cm) must be achieved. Novel Ti precursors are being explored.1 Our approach has focused on hydrazine (N2H4) as an alternative nitrogen source to NH3.

Hydrazine is generally difficult to handle from a safety perspective due to its flammability and toxicity. We have developed a novel method to store and generate hydrazine in situ as a high purity gas which is then delivered to ALD process chambers.2 In this study, we examine the effect that hydrazine has on low deposition temperature TiN ALD processes. We experimentally evaluate TiN ALD growth and film characteristics using TiCl4/ N2H4 in comparison to that using TiCl4/NH3.

Titanium Nitride films were deposited using the hot wall type tubular furnace and a sequential gas supply system. Deposition temperature was set to predetermined value in the range from 250°C to 400°C. In the case of TiCl4/NH3, GPC was 0.10-0.27 Å/cycle at 250-400°C, where a decrease is noted as the deposition temperature is reduced. With the use of hydrazine, an increase in GPC is observed at each deposition temperature vs NH3. Moreover, the temperature dependence of GPC moved in the opposite direction of TiCl4/NH3. Specifically, GPC of TiCl4/N2H4 ALD was 19% higher at 400°C while an increase of 310% was seen at 250°C versus NH3. In the case of TiCl4/N2H4, the ALD window appears in the range of 250-400°C, where TiCl4 adsorption saturation curves are observed at 250°C and 400°C. Refractive index (R.I.) of TiCl4/N2H4 ALD was about 1.68-1.73 at 250-400°C. These values were approximately equal to R.I. of typical sputtered TiN which was about 1.66. In contrast, R.I. of TiCl4/NH3 ALD was larger than 2.00 in the 250- 300°C range. Because of R.I. of typical titanium oxide is about 2.4-2.5, it is assumed that the TiCl4/NH3 ALD film is contaminated by oxygen. In the ammonia case, background contaminants in the reactor appear to compete with low reactivity NH3 for reaction sites on the ALD surface. In the TiCl4/N2H4 case, higher temperature is not required to form high quality TiN films compared to TiCl4/NH3 ALD.

From the above results, the use of high purity hydrazine is beneficial to maintaining high throughput and good film quality under the new constraints for emerging devices. Film composition by XPS and Resistivity measurements consistent with this conclusion will also be presented.

References

[1] Klesko J.P., Thrush C.M., Winter C.H., Chemistry of Materials. 27: 4918-4921, (2015).

[2] J. Spiegelman, Daniel Alvarez et al., 18th International Conference on Atomic Layer Deposition (2018) AMTuP2.

Figure 1
Atomic Layer Etching of Silicon Oxide with CF3I and O2 Plasma
Authors: Kim Seon Yong , Lee Taehoon , Park In-Sung , Ahn Jinho
Published: December 2020

Perfluorinated compounds (PFCs) such as CF4, C2F6, C3F8, and C4F8 have been widely used in plasma dry etching and in-situ deposition chamber cleaning processes.[1] More recently, the PFCs have been used in atomic layer etching (ALE), which is considered the promising etching technique that can control the etched thickness in atomic scale levels.[2] However, PFCs generally have a high global warming potential (GWP), which is a significant figure of merit concerned with global warming.

CF3I has been studied as a dry etching gas to replace PFCs because of its ultra-low GWP (GWP100=0.3). However, most of the results have been required at high plasma power over 1000 W, which made it difficult to commercialize.[3] Therefore, the feasibility of applying CF3I to ALE processed at low plasma power (400 W or less) is an important factor to replace PFCs.

In this study, ALE of SiO2 was performed with CF3I as an etchant gas. In the ALE process, one cycle involved two steps: surface modification and removal steps. In the first step, surface modification, CF3I plasma was treated on the SiO2 surface to deposit fluorocarbon polymer. In the second step, removal step, O2 plasma was used to remove the deposited polymer. When fluorocarbon polymer was removed by O2 plasma, SiO2 film was etched by the byproduct of volatile SiFx generated in the interlayer between fluorocarbon polymer and SiO2. The surface change in the respective modification and removal step was confirmed by X-ray photoelectron spectroscopy (XPS), and the etched thickness of SiO2 film during ALE process was measured by using ellipsometry and transmission electron microscopy (TEM).

As a result of SiO2 ALE using CF3I, etched thickness per cycle (EPC) saturation with both CF3I plasma treatment time and O2 plasma treatment time shows that etching was proceeding to atomic scale. When the plasma power is 300 W, the EPC is 0.93 nm/cycle. It means the fast etch rate enough to replace other PFCs at a low power condition.[2]

References

[1] C. J. Mogab, et. al., J. Appl. Phys. 49, 3796 (1978).

[2] D. Metzler, et. al., J. Vac. Sci. Technol. A 32, 020603 (2014).

[3] A. Misra, et. al., D. Rufin, Mat. Let. 34 415 (1998).
Thin Films of Layered-MoS2: ALD of Molybdenum and Sulfurization a Novel Approach
Authors: Mane Anil U. , Choudhury Devika , Elam Jeffrey W.
Published: December 2020

Thin layers of two dimensional (2D) materials mainly transition metal dichalcogenides (TMDs) and more specifically ultra-thin layered-MoS2 semiconductor possess exceptional properties such as electrical, optical, magnetic, mechanical and chemical properties. This allows the exploration of internal quantum degrees of freedom of electrons and their potential for use in semiconductor microelectronics, optoelectronic, energy, and sensor and detector applications. These exciting results are being achieved mostly by using exfoliation of flecks from bulk MoS2 crystal. However, the biggest challenge in realizing TMDs full potential has been the lack of scalable material synthesis methods for such films with high uniformity, conformality and interfacing with other materials such as oxides, metals and its process compatibility. Among the various thin film deposition methods, atomic layer deposition (ALD) offers the best combination of precisely controlled layer-by-layer thin film growth at low temperature with very high conformality on complex substrates. Here we will present the growth of layered-MoS2 thin films. To grow high quality layered–MoS2 thin films, we have developed an ALD-based two step processing approach: firstly the growth of well controlled ultra-thin layer of Mo metal using ALD followed by the sulfurization of the ALD Mo layer at various temperatures. This two-steps processing results in high quality layered-MoS2 thin films on large substrates. For the Mo ALD process we used molybdenum hexafluoride (MoF6) and Si2H6 precursors. We used in-situ QCM measurements to study interfacial and nucleation effects in the formation of continuous ultra-thin metal layer of Mo. The composition of both the ALD Mo and the layered MoS2 layers was determined by X-ray photoelectron spectroscopy (XPS). Further, cross-sectional transmission electron microscopy (TEM) was performed to confirm the formation of layered MoS2 on high aspect ratio trenches and Raman analysis to verify the signature of E12g blue shift and A1g red shift in the MoS2 structure. Here, we will discuss the details of the two-step thin film growth process for creating layered MoS2 layers via ALD Mo and subsequent sulfurization as well as the properties of the MoS2 films.
(Invited) Controlled Assembly of 3D Graphene Electrodes for Enhanced Alkali Metal Storage
Authors: Lee Michael J , Lee Hoyoung , Lee Kyungbin , Lee Byeongyong , Lee Seung Woo
Published: December 2020

Graphene has been intensively investigated as an electrode material for energy storage devices thanks to its large surface area and excellent electrical conductivity. However, the restacking of graphene sheets is inevitable during the solution process due to π–π and hydrophobic interactions, which reduces the available surface area. Recently, 3D structured crumpled graphene has emerged as an promising electrode material due to its aggregation-resistive property.

In this study, we will introduce our recent efforts to assemble 3D structured crumpled graphene anodes through the stacking engineering process for Li-, Na-, K-ion batteries. We reveal the role of defects in improving the charge storage performance through the surface-controlled charge storage mechanism. The crumpled graphene anodes exhibited high capacity with excellent rate-performance and cycling stability. We further evaluate the temperature-dependent performance of 3D graphene anodes, demonstrating their superior charge storage performance in extreme cold environments. Finally, we will discuss anodic electrochemical exfoliation of graphite for the fast production of graphene at low cost with moderate quality.
Layered Electrode Architectures Enabled By Holey Graphene Hosts
Authors: Lin Yi , Connell John W.
Published: December 2020

Battery electrodes are typically prepared using a slurry-based method, where high boiling point organic solvents are typically used with a polymer binder to disperse active electrode materials and conductive carbon additives followed by casting onto current collector sheets. In this process, the use of organic solvents are environmentally hazardous, energy intensive, and time-consuming, while polymeric binders add weight and can undergo parasitic reactions during battery cycling. Here we discuss the use of a unique conductive carbon nanomaterial, namely holey graphene, as a multifunctional host that can be processed via a facile, solvent-free, binder-free, cold pressing method to prepare electrodes with unique architectures. This approach can accommodate a broad range of battery chemistries, such as lithium oxygen/carbon dioxide (Li-O2/CO2), lithium sulfur/selenium (Li-S/Se), and various lithium ion chemistries. The successful use of dry, cold compression allows the convenient modification of electrode mass loading with unique architectures containing active materials randomly mixed or layered with single or multiple layers of one or more active materials. In the conventional slurry-based electrode fabrication method, it is difficult, if not impossible, to achieve such layered architectures. In particular, the layered electrode architectures from the dry, cold press approach are easy to fabricate without significantly sacrificing device performance, and are amenable to continuous roll-to-roll dry processing. In addition, these architectures offer unprecedented perspectives on the battery material loading vs. utilization efficiency, as well as enabling unique characterization opportunities to advance mechanistic understanding of various battery chemistries. Potential applications of this unique electrode fabrication approach for solid-state batteries will also be discussed.
Chemical Manipulation Towards High Performance Li-S Batteries
Authors: Xie Jia , Jiang Zhipeng , Zeng Ziqi , Zhang Wei , Li Shuping
Published: December 2020

Lithium-sulfur batteries have been regarded as one of the most promising new battery technologies due to their high theoretical energy density (2600 Wh kg-1) and the abundant resource as well as the low cost of sulfur. However, current sulfur cathodes and lithium metal anodes can’t meet the design requirements for high specific energy batteries. In this talk we will introduce several chemical manipulation methods for high performance Li-S batteries. On the sulfur cathode side, a new reaction pathway is proposed and Se or Te as eutectic accelerator is introduced to boost reaction kinetics. It is possible to eliminate polysulfide dissolution while under the dissolution deposition mechanism and obtain high performance sulfur cathodes compatible with both ether and carbonate electrolytes.[1-5] For lithium metal anodes, we have developed a couple of multifunctional artificial layers through simple and facile chemical methods. The multifunctional layers are beneficial not only for uniform deposition of lithium, but also for prolonged cycling performance.[6-7] With the newly developed anode and cathode materials, a high energy lithium-sulfur battery with significantly improved performance is obtained under the conditions of high areal capacity loading (> 10 mAh cm-2), lead electrolyte (3 ul/mgS) and low N/P ratio (~ 3: 1). The energy density and cycle life are expected to show breakthrough in large Li-S batteries.

References

Chen, L. Peng, L. Wang, K. Yuan, Y.H. Huang, B. Shan, L.X. Yuan*, and J. Xie*, Nature Communications, 2019, 10, 1021

Zhang, Y. Sun, H. Jia, Z. Zhang, B. Shan, and J. Xie*, Energy Storage Materials, 2019, 21, 287-296

Li, Z. Han, W. Hu, L. Peng, J. Yang, L. Wang, Y. Zhang, B. Shan and J. Xie*, Nano Energy, 2019, 60, 153-161

Li, Z. Zeng, J. Yang, Z. Han, W. Hu, L. Wang, J. Ma, B. Shan and J. Xie*, ACS Applied Energy Materials, 2019, 2(4), 2956-2964

Wang, X. Chen, S. Li, J. Yang, Y. Sun, L. Peng, B. Shan and J. Xie*, Journal of Materials Chemistry A, 2019, 7, 12732-12739

Jiang, J. Liu, Z. Han, W. Hu, Z. Zeng, Y. Sun and J. Xie*, Angewandte Chemie International Edition, 2019, 58(33), 11374-11378

Jiang, Z. Zeng, C. Yang, Z. Han, W. Hu, J. Lu, and J. Xie*, Nano Letters,
2019, DOI:10.1021/acs.nanolett.9b03562
Study on the Effect of Surface Area on the ORR Performance of Perovskite Catalyst for High Performance Lithium-Oxygen Batteries
Authors: Kim Jiyoun , Choi Yusong , Ahn Tae-Young , Cho Jang-Hyeon
Published: December 2020

Lithium oxygen(Li-O2) batteries have been recognized as one of the next-generation power sources, capable of supplying power for a long time even in an independent extreme environment. In spite of the theoretical advantage, Li-O2 batteries face technical and economical challenges that must be addressed to promote them as commercially variable techcologies for future energy system. Above all, battery performance largely depends on the activities of the cathode during discharge and charge, respectively. The undesirable overpotential caused by sluggish reaction kinetics assiciated with the ORR and OER greatly limit the current performance of Li-O2 batteries, which must be improved by efficient catalyzing the reactions. Among the numerous catalysts, perovskite oxides have attention for candidate electrocatalyst for Li-O2 batteries due to their high electronic/ionic conductivity, high electrochemical stability, and catalytic activity. Especially, La0.6Sr0.4Co0.2Fe0.8O3(LSCF) is considered as a typical catalyst for Li-O2 batteries, which and provide high oxygen surface exchange coefficient for fast kinetics at the gas/electrode interface. The surface area is significantly related on the ORR and OER performance, which influences on the active area for reactions. In this study, we have tried to utilize a simple high energy ball milling process to investigate the electrochemical properties of LSCF catalyst. Through the BET analysis, it was confirmed that the specific area significantly was increased after ball milling due to the reduced particle size, obtaining the optimized milling time with the higher ORR performance. The electrochemical activities have been measured with rotating disk electrode(RRDE) method. Well-ball milled LSCF catalyst has resulted in the enlargement of specific surface area and increased defective sites, which improve the catalytic activity.

To investigate the influence of LSCF oxides on the ORR process, the performance of composite electrode with LSCF catalyst in LITFSI in either solvents has been compared with a carbon based cathode(carbon nano tube(CM130)). From the discharge results, the composite electrode showed the superior performance as well as higher specific capacitance (more than 1.6 times) than carbon based electrode dye to the altered transport and reaction kinetics due to LSCF. In this study, we have proposed the processes of obtaining a catalyst with optimal electrochemical properties through a relatively simple process and applied it to electrode for lithium oxygen batteries.
Porous Si-C Composite As High-Performance Anode Material for Li-Ion Batteries
Authors: Yang Young Mo , Kim Jae-Hun
Published: December 2020

Li-ion batteries (LIBs) have received widespread recognition as power sources for various potable electronics, electric vehicles, and large-scale energy storage systems. To meet ever-increasing demand for energy storage, it is necessary to develop next generation anode materials with a high capacity. Carbon-based materials are widely used as anodes for LIB and however, the theoretical capacity for graphite (372 mAh g–1) is limited due to its intercalation chemistry. Si has been considered as one of the most promising next generation materials as LIB anodes to replace commercial graphite because of its outstanding theoretical gravimetric capacity of 3580 mAh g–1 (for Li15Si4 phase), which can be obtained through the electrochemical alloying reaction with Li ion. Currently, the main challenges for using Si-based active materials are structural transition, low electrical conductivity, and unstable solid electrolyte interphase (SEI) formation caused by the large volume change (~400%) during alloying and dealloying cycle and irreversible side reactions with electrolyte. The large volume changes lead to the pulverization of electrode materials, resulting in degradation of capacity upon cycling. To overcome these drawbacks, many researches have been performed and various strategies have been proposed in terms of structural aspects such as hollow sphere, core-shell structure, and porous structure. In this study, porous Si-C composites were prepared through a simple annealing method of commercial amorphous silica (a-SiO2) and magnesium silicide (Mg2Si). Then, a chemical wet etching process was performed to remove formed magnesium oxide (MgO) and a carbon layer coating was finally carried out. The prepared material exhibited high reversible capacity and good cycle performance with very high initial coulombic efficiency. The enhanced electrochemical properties can be attributed to the porous structure with thin carbon coating.
Porous Silicon-Cobalt Silicide-Carbon Composites for Reversible Lithium Storage
Authors: Seo Hyungeun , Kim Jae-Hun
Published: December 2020

With increasing use of portable electronic devices and electric vehicles, demand for development of high-energy density rechargeable batteries is rising. To meet the market demand for long-lasting rechargeable batteries, energy density of Li-ion batteries (LIBs) should be increased. The energy density of batteries is determined by the capacities of electrodes. Carbonaceous materials have been used as negative electrodes (anodes) in commercial LIBs because of their low operating potential and reasonable cycle life. However, the theoretical capacity of graphite anodes is relatively low, which is 372 mAh g-1 for the fully intercalated LiC6 phase. To increase the capacity, different types of materials using alloying or conversion reaction should be developed. Li-alloy-based materials can store several Li ions with an atom by electrochemical alloying reactions and therefore, high capacity can be obtained. In particular, Si has a high theoretical capacity of 3580 mAh g-1 for Li15Si4 and low operating potential. However, serious capacity fading usually occurs because of huge volume changes during cycling and their low electric conductivity. To address this problem, many strategies have been developed through changes in materials design. For example, incorporation of carbon is the most famous method to solve the capacity fading of Li-alloy-based materials upon cycling. The existence of carbon in Si matrix can buffer the volume expansion of Si materials with increased electric conductivity, thus simultaneously improving both cycling and rate performance. Porous structure can be another strategy to relieve the volume expansion by using the internal pores. However, the process is generally time and energy consuming. In this study, we report a simple preparation process of porous Si-CoSi2-C composites as anode materials for LIBs. The porous composite was synthesized through cheap starting materials and cost-effective methods. Si, magnesium silicide, and cobalt oxide were mixed using high energy mechanical milling (HEMM). Then, a carbon material was incorporated by HEMM. To produce porous structure, MgO formed by HEMM was removed by a wet etching process. As a result, porous Si-CoSi2-C composites were prepared. These composites exhibited a reversible capacity of 1100 mAh g-1 and good capacity retention after 100 cycles. The porous structure and the amorphous carbon matrix alleviated the volume change to allow the enhanced electrochemical performance.
(Invited) High Performance Ge/Si Photodetectors for Data Center and 5G Applications
Authors: Cai Pengfei , Pan Dong
Published: December 2020

Ge/Si optical devices have been in intense study for many years. In particular, they find themself as one of core optical devices in the Silicon Photonics technologies for high speed optical fiber communications. Among various silicon photonic devices, Germanium on Si photodectors have been widely commercialized in the application for 5G and data center. We have shipped more than millions pcs of Ge/Si optical devices from simple photodiodes to high performance avalanche photodiodes. These devices such as Ge/Si APDs have attracted tremendous attention due to their theoretical better performance than traditional III-V APDs and relatively low cost originally from CMOS foundry. In 2015, we start to ship 10G/25G Ge/Si photodiodes while developing a 10Gb/s APD with 1e-12 sensitivity equal to -29.5dBm at 1550nm; in 2016, we developed a 25Gb/s APD with world record 1e-12 sensitivity equal to -23.5dBm at 1310nm; in 2017, we developed a linear 28Gbaud APD receiver providing 5dB and 5.7dB improvement over PIN solutions for MMF and SMF PAM4 applications respectively; in 2019, we developed a 106 Gb/s (53GBaud PAM4) normal-incidence Ge/Si APDs with sensitivities of -16.8 dBm. Even with large defect density from lattice mismatch between Ge and Si substrate layer, Ge/Si optical devices demonstrate good reliability and passed all required qualification tests according to GR-468. In this paper, we reviewed the structure, materials, process, performance and reliability of the Ge/Si PIN and APD devices. To our knowledge, this is the best sensitivity reported for 100G APD.
Evaluation of Thermal Expansion Coefficient in Ge1-x
Sn
x
Nanowire Using Reciprocal Space Mapping
Authors: Ogasawara Gai , Yokogawa Ryo , Hirosawa Ichiro , Yoshioka Kazutoshi , Takahashi Yuki , Suda Kohei , Ogura Atsushi
Published: December 2020

Ge1-x
Sn
x
is expected to be a new material for next-generation electronic and thermoelectric device because it has higher carrier mobilities and lower thermal conductivity than pure Si and Ge. Here, strain is an important factor for designing electric and thermoelectric devices. It has been reported that there is a correlation between strain and thermal conductivity for group IV semiconductors [1]. In plane compressive strain is induced in epitaxially grown GeSn thin film on a Ge substrate due to the difference in lattice parameter. Anisotropic strain relaxation has been occurred in the GeSn nanowires. Anisotropic strain may cause anisotropic thermal expansion and thermal conductivity. In this study, we evaluated the thermal expansion of Ge1-x
Sn
x
nanowire fabricated on Ge substrate using reciprocal space mapping (RSM) by synchrotron radiation X-ray diffraction (XRD) measurement.

The Ge1-x
Sn
x
thin films were epitaxially grown on Ge (001) substrate for 34 and 45 nm by home-made metal organic chemical vapor deposition [2]. Sn concentrations (x) is 3.2% as confirmed by Rutherford backscattering spectrometry. Then, the nanowires were fabricated by electron beam lithography and dry etching as shown in Fig. 1. The major axis length (L) parallel to [110] were fixed at 10 µm while the minor axis width (W) parallel to [-110] were 200 or 500 nm. For the measurement of RSM, multi-axis diffractometer in BL19B2 of SPring-8 was used. The photon energy was 10 keV, which is just under the K-edge of Ge at 11 keV. We fabricated many nanowires to obtain sufficiently strong X-ray diffraction. The sample temperature was controlled using a heating stage (Anton Paar DHS1100).

Figure 2 shows the relationship between temperature and the lattice parameters in Ge0.968Sn0.032
nanowire with W=500 nm. Thermal expansion for the sample with W=200 nm showed an isotropic change. However, it was revealed that the thermal expansion between the in-plane minor axis [-110] and the out-of-plane [001] directions were different for the sample with W=500 nm. In the previous study, we have confirmed the uniaxial strain relaxation (minor axis direction [-110]) has been occurred with decreasing W for Ge1-x
Sn
x
nanowire [3]. Thus, it is considered that the thermal expansion become isotropic as the nanowire width gets shorter.

References

Xu et al., J. Appl. Phys. 106, 114302 (2009).

Suda et al., ECS Trans. 64 (6). 697 (2014).

K. Yoshioka et al., Thin Solid Films 697, 137797 (2020).

Figure 1
Towards the Development of Better Sodium Titanate Anodes
Authors: Yin Wei , Doeff Marca M
Published: December 2020

Sodium-ion batteries represent a drop-in replacement for lithium-ion batteries to meet our ever-growing energy demands. Advantages include the abundance and lower cost of sodium compared to lithium, and the possibility of using cheaper aluminum current collectors instead of the copper ones in lithium-ion cells. Among the many cell components, proper choice of electrode materials are essential for enabling proper functioning of sodium-ion batteries. Compared to the massive exploration of cathode materials, the development of anode materials remains challenging for sodium ion batteries as graphite does not intercalate sodium to an appreciable extent. Sodium titanates are among the few anode materials that can reversibly intercalate sodium ions at appropriately low potentials and moderate capacities1 although they have low first-cycle coulombic efficiency. Sodium titanates encompass a range of materials with different compositional and structural characteristics, which remain relatively unexplored for this application.2-4 There is a clear need to build a comprehensive knowledge scenario linking their compositional and structural characteristics and relevant performance metrics. Herein, we compare several sodium titanate compounds, ranging from sodium nonatitanate, lepidocrocite-structured titanates, and Na2Ti3O7. These materials all have stepped layered or corrugated structures, with sodium ions located between transition metal oxide layers, yet display distinctly different electrochemical behaviors. By coupling electrochemical characterization with an array of synchrotron techniques, we offer more insights into their sodium storage mechanisms and provide effective measures to improve their battery behaviors.

References:

M. Doeff, et al.
Journal of Inorganic and Organometallic Polymers and Materials
,
24, 5-14 (2014).

M. Shirpour, et al.
Energy
& Environmental Science, 6, 2538-2547 (2013).

P. Senguttuvan, et al.
Chemistry of
Materials, 23, 4109-4111 (2011).

M. Shirpour, et al.
Chemistry of
Materials
,
26, 2502-2512 (2014).