bluuebunny/crossref_metadata_2025 huggingface dataset:
Investigating the Effect of Lewis Acid Base Interaction in Non-Stoichiometric Vanadium Oxide Based CNFs in Lithium – Sulfur Battery
Authors: Pai Rahul , Singh Arvinder , Kalra Vibha
Published: February 2020

Despite the potential of lithium-sulfur batteries to reach practical energy densities of 500–600 Wh/kg, there are still many problems plaguing their development. The sulfur cathode suffers from low electrochemical utilization and poor cycle life owing to the insulating nature of S and the Li2S discharge product, and the shuttling of lithium polysulfide species especially at high areal mass loadings. Enormous progress has been achieved in terms of capacity and static life during the past few years to overcome these issues, by employing various carbon and inorganic materials (metal oxides, metal-organic frameworks). Recently, non-stoichiometric metal oxides have been employed as sulfur host materials due to their high conductivity and ability to bind polysulfides chemically through unsaturated metal ion sites. However, the formation of metal-suboxides involves a high-temperature calcination process, which usually results in dense host materials with lower accessible surface area, and a reduced host/polysulfide interaction. Moreover, these studies are often reported with low sulfur loadings (1–2 mg/cm2) resulting in lower areal capacity.

Herein, we report the use of electrospun vanadium monoxide/carbon nanofibers (VCNFs) as cathode host in Li-S batteries, which provide high electrical conductivity for better sulfur utilization and strong Lewis acid-base interaction with polysulfides to suppress shuttle. The developed cathode possesses hierarchical micro-mesoporous architecture with inter-fiber spacing and a high surface area of 181 m2/g. The unique architecture overcomes the challenges associated with dense, low active surface area based powered oxide materials. The developed VCNFs-S cathodes with a high sulfur loading of 3 mg/cm2 exhibit initial discharge capacities of ∼1350, ∼1247, and ∼1113 mAh g–1 at 0.1, 0.2, and 0.5 C rates, respectively, with long-term cycling (Fig 1a) over 200 cycles at 0.5 C rate. Moreover, at ~7mg/cm2, Li-S cells exhibit high areal capacity of 8 mAh/cm2 at a current density of C/10 up to 50 cycles (Fig 1b). The high surface area results in active reaction sites spread throughout the VCNFs, improving the accessible reaction area for better binding of polysulfides, enabling the smooth operation at high-loading in Li-S system. Using postmortem X-ray photoelectron spectroscopy analysis, this study reveals the presence of strong Lewis acid–base interaction between VO (3d3) and Sx
2– through the coordinate covalent V–S bond formation. Additionally, freestanding nature of the cathodes eradicate the need of additional inactive elements, viz., binders, additional current collectors (Al-foil), and additives. Our results highlight the importance of developing high surface area metal-suboxides/monoxide-based conducting polar host materials for next-generation Li–S batteries.

Figure 1
Surface-Modified Si Nano-Particles as New Anode Materials
Authors: Jiang Sisi , Hu Bin , Neale Nathan , Zhao Bin , Zhang Zhengcheng
Published: February 2020

Silicon has been considered as one of the most promising anode materials for next generation high-energy lithium-ion battery due to its extremely high theoretical capacity. However, large volume expansion/contraction (~ 300%) during lithiation/delithiation process leads to rapid capacity fade during repeated cycling. The main contributor for the poor performance of Si anode is mainly due to the particle pulverization during the rapid Li+ insertion/extraction and the loss of electrical contact caused by the rearrangement of electrode structure. Nano Si material has shown positive impact on the cell performance. Compared with bulk Si, nanostructured Si (<150 nm) largely resolved the pulverization issue. However, the intrinsic electrolyte reactivity with the lithiated Si particles still exists resulting in the gradual active lithium loss and capacity degradation.

In this presentation, a novel approach attempting to stabilize the surface of the Si particles is reported. Plasma synthesized silicon nanocrystals with Si-H terminal groups were subject to hydrosilylation with various organic compounds containing an allyl group as shown in Figure 1. Preliminary results indicate that the surface functionalization could stabilize the Si/electrolyte interface affording much improved Coulombic efficiency and cycling performance. The latest progress will be presented.

Figure 1
A Discovery of an Unexpected Metal Dissolution of Thin-Coated Cathode Particles: Its Theoretical and Experimental Explanations
Authors: He Yufang , Sarkar Susmita , Liang Xinhua , Park Jonghyun
Published: February 2020

The degree of metal dissolution of cathode materials is a critical parameter in determining Li-ion battery performance. Ultra-thin coated LiMn2O4 (LMO) cathode particles via Atomic Layer Deposition (ALD) exhibit superior battery performance over bare LMO particles. However, we have observed that ultra-thin CeO2 coating intensifies Mn dissolution of LMO during cycling of lithium-ion battery, whereas ultra-thin Al2O3 coating tends to inhibit Mn dissolution. A detailed study of Density Functional Theory (DFT) has been carried out to illustrate the experimental observations. First, the manganese vacancy formation energy is calculated, along with the bonding strengths of Mn-O of uncoated, Al2O3 coated, and CeO2 coated particles via Crystal Orbital Overlap Population (COOP) calculations. Further, the projected density of state calculation of Mn is used to confirm the electronic occupancy of Mn atom for each case. Surprisingly, the atomic analysis is consistent with the experimental observations. This is the first report that coatings can accelerate metal dissolution, which can show new insights into ALD coatings and their impact on metal dissolution in cathode materials.
Dry Processed Nickel-Rich Layered Transition Metal Oxide Cathode Electrode
Authors: Shin Joon , Yudi Yudi , Magsino Prince , Wong Wilma , Duong Hieu
Published: February 2020

Lithium ion battery is a key driver for the proliferation of clean transportation. While its high energy density and operating life time are favorable, the overall cost is limiting widespread adoption. Since the first commercial lithium ion batteries produced by Sony in 1991 for consumer electronics, energy density and life time have gradually improved with the development of new electrode materials such as high capacity LiNixMnyCozO2, LiNi0.8Co0.15Al0.05O2 and silicon, and electrolyte additive such as vinylene carbonate1 and fluoroethylene carbonate2. Recently nickel-rich layered cathode and high capacity silicon anode have been incorporated into commercial lithium ion battery to further increase energy density. While electrode materials have advanced, electrode manufacturing process has largely remained the same, reaching a plateau in coating width, line speed, electrode energy density and production cost. To address these critical needs, Maxwell Technologies has developed a dry battery electrode coating technology with differentiating attributes.

Maxwell’s unique solvent-free coating process used to commercialize ultracapacitors can be adapted to produce electrodes using current state-of-the-art lithium ion battery chemistries and advanced materials3-5 with advantages over conventional wet coating process. The benefits are lower CO2 emission, lower capex and opex cost, improved energy density and the ability to process moisture sensitive or reactive materials. To demonstrate these attributes, we have advanced our dry electrode process development using nickel-rich layered cathode materials to improve energy density, increase cycle life and reduce cell manufacturing cost. We have produced dry electrodes using LiNi0.6Mn0.2Co0.2O2, LiNi0.8Mn0.1Co0.1O2 and LiNi0.8Co0.15Al0.05O2 in roll-to-roll format and characterized their electrochemical performances in small and large capacity pouch cells. Dry process demonstration for prelithiated materials has also been established.

This paper will report the physical properties of nickel-rich layered dry cathode film produced at the lab and pilot production level and their electrochemical performance with coating loading of 30-40mg/cm2 per coating side, which is significantly heavier than a typical wet cast electrode in the range of 20-24mg/cm2 per coating side in commercial high energy 18650 cell.

References:

Aurbach, D.; Gamolsky, K.; Markovsky, B.; Gofer, Y.; Schmidt, M.; Heider, U., Electrochim. Acta, 2002, 47, 1423-1439.

Sinha, N. N.; Burns, J. C.; Dahn, J. R.; J. Electrochem. Soc., 2013, 160, A709-A714.

Duong, H.; Suszko, A.; Feigenbaum, H., 229th ECS meeting, May 29-June 6, 2016, Abstr. #475.

Shin, J.; Duong, H., 233rd ECS meeting, May 13-17, 2018, Abstr. #A03-0365.

Duong, H.; Shin, J.; Yudi, Y., 48th Power Sources Conference, June 11-14, 2018, P34-37.
Binder-Induced Interface Stabilization and Performance Improvement of Nickel-Rich Cathode
Authors: Pham Hieu Quang , Lee Hee-Yeol , Jung Hyun Min , Song Seung-Wan
Published: February 2020

High-energy Li-ion batteries are well-suited for electric vehicle (EV) and energy storage applications. For the success of long-range energy storage systems, increasing the specific energy density of Li-ion batteries toward more than doubled compared to commercial batteries is on demand. Nickel (Ni)-rich multi-component layered oxide, represented by LiNi1−x−y
Co
x
Mn
y
O2 (NCM, x+y £ 0.5), is a promising high-capacity cathode material for high-energy batteries, whose capacity increases by increasing the amount of Ni and/or by increasing charge cut-off voltage above 4.2 V versus Li/Li+. Their long term performance and high-voltage cycling performance however are often limited, due to high reactivity at highly charged state, instable cathode-electrolyte interface, and the occurrence of metal-dissolution, particle cracking and structural degradation, particularly.1-3 In order to mitigate those problems, we have been designing and developing novel functional binder,4 which provides a solution to the degradation problems of the Ni-rich cathodes coated with conventional polyvinylidenefluoride (PVdF) binder, through superior binding ability to cathode surface and the formation of a robust cathode-electrolyte interface structure. Improved cycling performance and interfacial stabilization of Ni-rich cathodes by the effects of our functional binder would be discussed in the meeting.

Acknowledgements

This research was supported by Ministry of Trade, Industry & Energy (10080025), National Research Foundation (NRF-2015R1D1A1A01060838) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/ Bio Materials of BK Plus program by Ministry of Education of Korea.

References

Y.-M. Lee, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon, D.-H. Kang, S.-W. Song, J. Phys. Chem. C., 118, 10631 (2014).

H.Q. Pham, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon, H.M. Jung, S.-W. Song, J. Electrochem. Soc., 161 A2002 (2014).

D.-T. Nguyen, J. Kang, K.-M. Nam, Y. Paik, S.-W. Song, J. Power Sources, 303, 150 (2016).

H.Q. Pham, G. Kim, H.M. Jung, S.-W. Song, Adv. Funct. Mater., 28, 1704690 (2018).
Influence of Binder Coverage on Interfacial Chemistry of Thin Film LiNi0.6Mn0.2Co0.2O2 Cathodes
Authors: Phillip Nathan Dale , Veith Gabriel M.
Published: February 2020

Given the pervasive implementation of lithium ion batteries in portable electronics, focus has increased on improving energy density for transportation applications. One route to accomplish this is through the development of high capacity cathodes such as Ni-rich LiNixMnyCo1-x-yO2 (x > 0.5). When charged beyond 4.3 V vs. Li/Li+, however, these materials suffer from irreversible structural changes and gas evolution, accelerating electrolyte decomposition at the cathode/electrolyte interface (CEI). These reactions are convoluted in composite electrodes due to binder and carbon additives as well as porosity creating a poorly defined cathode/electrolyte contact area. To reduce this complexity, thin films comprised solely of active material can be used as a model system to study the interface with controlled quantities and chemistries of coatings such as binders found in standard slurry cast electrodes.

In this study, thin films of LiNi0.6Mn0.2Co0.2O2 were prepared by radio frequency magnetron sputtering to examine the effects of binder coverage morphology and chemistry on the CEI. Binder films were deposited atop the active material by spin coating, which provides a reliable means to cast uniform films down to a few nanometers. Spray coating was used to deposit a conglomerated binder morphology for comparison to the spun coating. These morphologies were repeated for three binders: polyvinylidene difluoride (PVDF), carboxymethyl cellulose (CMC), and lithium polyacrylate (LiPAA) for subsequent characterization. Scanning electron microscopy and atomic force microscopy examined the morphology and topology of the binder films, and samples were weighed with a microbalance to verify equivalent binder loadings across each sample. X-ray photoelectron spectroscopy results indicated that the amount of insulating species present at the interface varied with binder morphology and chemistry. The interfacial species evolved at different rates for each system during cycling, suggesting that binder selection has implications on the initial surface environment as well as over the lifetime of the cathode. These data will be presented alongside Raman, FTIR, and AC impedance spectroscopy to examine how the composition of the interface evolves with cycling and between systems. These results provide valuable insight into the influences of binders on the CEI of Ni-rich cathode materials.

Figure 1
Compact Lithium-Ion Battery Electrodes Fabricated with Lightweight Reduced Graphene Oxide-Based Aerogels
Authors: Pender Joshua Paul , Xiao Han , Dong Ziyue , Cavallaro Kelsey A , Weeks Jason A , Heller Adam , Ellison Christopher J. , Mullins Charles Buddie
Published: February 2020

We report here the synthesis and fabrication of reduced graphene oxide (rGO)-based aerogels as free-standing lithium-ion battery (LIB) electrodes and 3D scaffolds for supporting conventional LIB active materials (e.g., LiFePO4, Li4Ti5O12, LiNixCoyMnzO2). As a 3D replacement for conventional metal-foil current collectors, we demonstrate the fabrication of compact (2 – 3 g cm-3) electrodes via slurry-infiltrating the porous aerogels with controlled active-material loading (~3 – 30 mg cm-2) and compressing the resultant composites to a desired thickness (~30 – 130 μm from a starting thickness of 3.2 mm). The controlled loading and tunable thickness provide high composite electrode densities that are of essence for consideration in a practical application. Replacement of the usual copper foil (anode) and aluminum foil (cathode) current collectors with the lightweight, integrated rGO-based aerogels drastically reduces the weight and volume occupied by the current collector, thereby increasing the energy density per unit volume and mass at the electrode level.

We further demonstrate that the addition of poly (acrylic acid) (PAA) to the rGO scaffold (referred to as rGO-PAA) provides a versatile platform for exploring a diverse range of structure-function relationships that will guide our understanding of fabricating high-performance electrodes with the lightweight rGO aerogels. For example, due to the electrically-insulating nature of PAA, reducing its content is expected to lead to an increase in electrical conductivity of the aerogel; conversely, we show that the incorporation of PAA facilitates a more uniform pore structure that is expected to improve the ionic conductivity of Li+ ions in the electrolyte. We are exploring this versatility to identify requisite synthesis and processing conditions that optimize the trade-off between electrical conductivity, pore structure, and mechanical properties in the rGO-based aerogels.

Overall, the straightforward synthesis of the rGO-based aerogels starting from inexpensive precursors (graphite and poly (acrylic acid)) provides a scalable fabrication procedure, and the use of commercially-available and high tap-density LIB active materials with the lightweight aerogels enables fabrication of composite electrodes with practical active-material loadings and electrode densities. This approach is unique from that of many other 3D electrodes that use hydrothermal, chemical deposition, or co-precipitation methods to fabricate low tap-density nanomaterials tethered to a 3D substrate that often result in low mass loadings or low volumetric energy densities.
Processing, Fast Formation, and Performance of Aqueous-Processed Low-Co Cathodes for High-Energy Lithium-Ion Pouch Cells
Authors: Wood David L. , Wood Marissa , Mao Chengyu , Li Jianlin , Ruther Rose E. , Du Zhijia
Published: February 2020

Ni-rich, or low-Co, layered active materials are promising candidates for next-generation cathodes for lithium-ion batteries. However, these materials present processing and performance challenges such as compatibility with water during aqueous electrode formulation, unoptimized SEI/CEI formation conditions during cell assembly, and unstable capacity fade when cycled to upper cutoff voltages above 4.3 V vs. Li/Li+.

The DOE Battery Manufacturing R&D Facility at ORNL (BMF) has recently moved towards low-Co-containing and high-energy LiNi0.8Mn0.1Co0.1O2 (NMC 811) as a new internal cathode baseline and away from LiNi0.5Mn0.3Co0.2O2 NMC 532 for conducting cathode water stability and formation protocol studies. These XRD, Raman spectroscopy, XPS, and TEM studies verified that there was no change in bulk structure of the NMC 811 with long-term water exposure, and only small changes in the surface chemistry. Capacity retention under 0.33C/-0.33C USABC long-term cycling for NMC 811 aqueous-processed single-layer pouch cells was obtained and compared to: 1) the NMP/PVDF processed standard; and 2) NMC 811 exposed to water for 4 hours before processing with the standard NMP/PVDF formulation. The water exposed NMC 811 processed in NMP showed a similar capacity fade to the aqueous processed case. However, all three cases showed excellent capacity retention through 600 cycles, and the aqueous processed cells and NMP processed cells exhibited ~75% and ~80% capacity retention through 1000 cycles, respectively. It was also observed that the differences in capacity fade for all three cases occur within the first ~100 cycles, and the capacity fade slopes were similar from that point on. It is thought that this slight difference in early capacity retention is due to surface chemistry changes of the NMC 811 during aqueous processing and could be remedied with shorter mixing times or a surface protective coating.

To decrease the high manufacturing cost associated with long formation times for low-Co cathodes, five different formation protocols were studied using graphite anodes where the total formation time varied from 10 to 86 h. Electrochemical characterization and post mortem analysis showed that longer formation times do not necessarily improve long-term performance while extremely short formation protocols result in lithium plating and poorer electrochemical performance. It was found that the optimum formation protocol is intermediate in length to minimize impedance growth, improve capacity retention, and avoid lithium plating.

This presentation will focus on recent ORNL advancements in these areas, where aqueous processing conditions (mixing times, water exposure, binder type, etc.) and fast formation protocols are being developed for NMC 811 and that will be extended to other low-Co and Co-free cathodes.
Influence of Calcination Temperature on the Performance of Li and Mn Rich Li1.2Mn0.54Co0.13Ni0.13O2layered Electrode for Lithium Ion Battery
Authors: Piraman Shakkthivel , Alagar Srinivasan
Published: February 2020

The synthesis/calcination temperature playing a significant role on the performance, safety, and cycle life-time of lithium ion batteries (LiB). In this research work, we have reported the formation of homogeneously dispersed Li1.2Mn0.54Co0.13Ni0.13O2 (LMNCO) with sub-micron spheres architectures with good crystallinity through simple cost-effective precipitation further ball milling synthesis method to enhance the performance of the LIB energy storage system. The synthesized LMNCO cathode electrode materials were calcined at different temperature such as 800, 900 and 1000 °C to examine the influence of calcination temperature on the physiochemical and performance of the electrode. Synthesized LMNCO cathode electrode materials were characterized through TGA/DTA, XRD and SEM studies. The electrochemical characteristics of the synthesized materials were analyzed, the LMNCO prepared at 900 °C was exhibited a best electrochemical performance in LIBs while the charge-discharge profile was carried out in a voltage window of 2.0–4.8 V at 0.1 C rate compared with other materials synthesized at 800 and 1000°C. The first charge/discharge capacity of LMNCO synthesized at 900°C was found to be 259.6 mAh g-1 with the coulombic efficiency of 72.3 %. However, a well capacity retention (95%) of 183.0 mAh g-1 in the 100th cycle was obtained at 1 C rate. Other cathode materials LMNCO-800°C and LMNCO-1000°C were also performed well.

Figure (1) and Figure (2)

References

Leng, F. et al. Eﬀect of Temperature on the Aging rate of Li Ion Battery Operating above Room Temperature. Rep.
5, 12967; doi: 10.1038/srep12967 (2015).

Handel, P. et al. Termal aging of electrolytes used in lithium-ion batteries – An investigation of the impact of protic impurities and diﬀerent housing materials. Power Sources
267, 255–259 (2014)

Feng, L., Cher Ming, T., Rachid, Y. & Minh Duc, L. A practical framework of electrical based online state-of-charge estimation of lithium ion batteries. Power Sources
255, 423–430 (2014).

Keywords: Precipitation;LMNCOsub-microspheres; charge/discharge capacity; LIBs; XRD.

Figure 1
Review of Capacity Fade Models for Lithium-Ion Batteries
Authors: Teo Linnette , Pathak Manan , Crawford Alasdair J. , Viswanathan Vish , Schwartz D. T. , Subramanian Venkat R.
Published: February 2020

Degradation in lithium-ion batteries occur mainly due to the loss of cyclable lithium and loss of active material in the electrodes.1 The lifetime of a battery is limited by the reduction in capacity as the battery is cycled, which can occur through mechanisms such as formation and growth of the solid interface layer (SEI), electrolyte decomposition, dissolution of transition metals at the cathode, lithium deposition at the anode, and porosity changes.2
,
3 While there are many physics-based degradation models that exist in the literature, the ability to accurately predict capacity and power fade over many cycles is limited. This is because not all capacity fade mechanisms are well understood or incorporated in a single model, and a wide range of parameters and different operating conditions make it difficult to arrive at a consistent model.2
,
4

In this study, we look at SEI models in the literature such as Ramadass’ kinetically limited model,5 Ploehn’s diffusion limited model,6 and Safari’s mixed model,7 and apply them to the single particle model (SPM). Mechanisms proposed by Lin8 and Delacourt4 that model side reactions at the cathode will also be explored. We look at the effects of charging/discharging rates and depth of discharge on the degradation during cycling, and the effects of temperature and state of charge on degradation during storage. We will also analyze how predicted degradation changes for different parameter ranges. A rubric of qualitative trends that have been observed experimentally will be used to determine the consistency of existing models.

References

P. Arora, R. E. White, and M. Doyle, J. Electrochem. Soc., 145, 3647–3667 (1998).

V. Ramadesigan, K. Chen, N. A. Burns, V. Boovaragavan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 158, A1048–A1054 (2011).

X. G. Yang, Y. Leng, G. Zhang, S. Ge, and C. Y. Wang, J. Power Sources, 360, 28–40 (2017).

C. Delacourt and M. Safari, J. Electrochem. Soc., 159, A1283–A1291 (2012).

P. Ramadass, B. Haran, R. White, and B. N. Popov, J. Power Sources, 123, 230–240 (2003).

H. J. Ploehn, P. Ramadass, and R. E. White, J. Electrochem. Soc., 151, A456–A462 (2004).

M. Safari, M. Morcrette, A. Teyssot, and C. Delacourt, J. Electrochem. Soc., 156, A145–A153 (2009).

X. Lin, J. Park, L. Liu, Y. Lee, A. M. Sastry, and W. Lu, J. Electrochem. Soc., 160, A1701–A1710 (2013).
A Highly Hierarchical Hollow Sodium Sulfide Nanospheres Embedded in Spongy Carbon Composite As Cathode for High-Rate Performance Sodium-Sulfur Batteries
Authors: Wang Chuanlong , Wang Huan , Li Weiyang
Published: February 2020

Sodium-sulfur (Na-S) batteries have shown great promise as the next-generation energy storage systems owing to its high specific energy, low cost and high earth abundance of both Na and S. However, the low electronic conductivity and ionic conductivity of the active materials cause slow kinetics of Na-S chemistry and make high-rate performance impossible. Herein, a facile and scalable approach has been employed to synthesize hollow sodium sulfide (Na2S) nanospheres embedded in a highly hierarchical and spongy conductive carbon matrix, forming an intriguing architecture similar to the morphology of frogspawn coral, which has shown great potential as a cathode for high-rate performance Na-S batteries. The shortened Na-ion diffusion pathway benefited from the hollow structures together with the fast electron transfer from the carbon matrix contributes to high electrochemical reactivity, leading to high capacity and superior cycling performance at various current rates. At current densities of 1.4 and 2.1 A/g, high initial discharge capacities of 980 and 790 mAh/g (based on sulfur) can be achieved, respectively, with reversible capacities stabilized at 600 and 400 mAh/g (based on sulfur) after 100 cycles. As a proof of concept, we demonstrate Na-metal free Na-S batteries paired with Sn embedded in carbon as anode, which shows an exciting cycling performance of an initial capacity of 550 mAh/g (based on sulfur) with a capacity retention over 80% for over 50 cycles. Our work could provide guidance on rational materials design towards the success of room-temperature high-rate Na-S batteries.[1]

Reference:

[1] C.
Wang, H. Wang, X. Hu, E. Matios, J. Luo, Y. Zhang, X. Lu, W. Li, Adv. Energy Mater, 2018, 1803251.

Figure 1
Critical Safety Boundaries of Lithium Electrodeposition Against Nanoporous Ceramic Separators
Authors: Bai Peng
Published: February 2020

The growth mechanisms and morphology of lithium electrodeposits in liquid electrolyte are highly current-dependent [1]. While it was reported that diffusion-limited dendritic growths can easily penetrate, and reaction-limited whisker growths can be blocked by ceramic nanopores [2], the current densities that lead to the unsafe dendritic growths and safe whisker growths are disparate from each other. The penetration of lithium metal through nanopores can still occur at intermediate, yet under-limiting current densities [3]. In this study, operando experiments on transparent capillary cells and post-mortem analyses on realistic sandwich cells were performed to obtain insights on the safety-related growth mechanisms across a wide range of practical current densities. Our results suggest the existence of three growth modes of lithium, due to the competing reactions of lithium deposition and the solid electrolyte interphase (SEI) formation. A critical current density (6 mA cm-2), roughly 30% of the system-specific limiting current density, is identified as a practical safety boundary for battery design and operation, under which root growing lithium whiskers are the dominant structure of electrodeposition and can be blocked by commercial nanoporous ceramic separators. Our operando experiments of miniature junction cells also reveal that metal penetration of the separator does not lead to zero voltage immediately, but rather to sudden, small voltage drops, which should not be treated as benign soft shorts.

References

[1] W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang and J.-G. Zhang, Energy Environ. Sci., 2014, 7, 513–537

[2] P. Bai, J. Li, F. R. Brushett and M. Z. Bazant, Energy Environ. Sci., 2016, 9, 3221-3229

[3] P. Bai, J. Guo, M. Wang, A. Kushima, L. Su, J. Li, F. R. Brushett, M. Z. Bazant, Joule, 2018, 2, 2434-2449
(Invited) Equivalent Circuit Modeling for EIS on Structured Electrode in LIB
Authors: Osaka Tetsuya , Nara Hiroki
Published: February 2020

For realization of energy sustainable society, electric energy storages are essential to efficiently use energies generated by solar- and wind- power plants and to displace petrol-driven vehicles to electric-powered vehicles. Lithium-ion battery (LIB) is one of the promising electric energy storages because of high-power and high-energy density. For further improvement of LIBs on high-power and high-energy density, a structure of electrodes is important. Because there is a trade-off relationship between power-density and energy-density, which relates to electrode density. The electrode structure will change with degradation due to charge-discharge cycles. Therefore, non-destructive diagnosis is required for evaluation of the electrode structure. Electrochemical impedance spectroscopy (EIS) is powerful to analyze electrodes without disassembling the battery. However, the evaluation of the structural change of electrode is required to model a proper equivalent circuit. In this presentation, a case of an intricate electrode which has reaction distribution in depth direction and a case of an intricate electrode which has particle size distribution will be introduced. For modeling the reaction distribution in depth direction, transmission line model (TLM) is applied (shown in Fig. (a)). [1–3] For modeling the particle size distribution, a parallel circuit of R
ct­­–W (charge transfer resistance and Warburg impedance) is applied to model various particle size groups (shown in Fig. (b)). [4] In the model, diffusion length in solid is assumed to be various. Additionally, to verify the equivalent circuit, a case with different particle size distribution (Fig. (c)) was evaluated.

References

[1] H. Nara, D. Mukoyama, T. Yokoshima, T. Momma, T. Osaka, Impedance Analysis with Transmission Line Model for Reaction Distribution in a Pouch Type Lithium-Ion Battery by Using Micro Reference Electrode, J. Electrochem. Soc. 163 (2016) A434–A441. doi:10.1149/2.0341603jes.

[2] H. Nara, S. Tominaka, T. Momma, T. Osaka, Impedance Analysis Counting Reaction Distribution on Degradation of Cathode Catalyst Layer in PEFCs, J. Electrochem. Soc. 158 (2011) B1184. doi:10.1149/1.3610988.

[3] H. Nara, T. Momma, T. Osaka, Impedance analysis of the effect of flooding in the cathode catalyst layer of the polymer electrolyte fuel cell, Electrochim. Acta. 113 (2013) 720–729. doi:10.1016/j.electacta.2013.06.055.

[4] H. Nara, K. Morita, D. Mukoyama, T. Yokoshima, T. Momma, T. Osaka, Impedance Analysis of LiNi1/3Mn1/3Co1/3O2 Cathodes with Different Secondary-particle Size Distribution in Lithium-ion Battery, Electrochim. Acta. 241 (2017). doi:10.1016/j.electacta.2017.04.153.

Figure 1
(Invited) Lithium Metal Plating and Stripping Stability with a Solid Electrolyte Separator across Length Scales from the nm to the mm
Authors: Albertus Paul
Published: February 2020

Definitively understanding the stability of lithium metal plating and stripping over thousands of cycles, and at rates, loadings, and amounts of excess lithium of practical relevance is a challenge of great significance. Numerous modeling approaches to understand and predict stability have been proposed, across length scales and for different types of material systems. This talk will focus on lithium metal stability in solid electrolyte systems, highlighting several of the major classes of stability models that have been proposed, as well as the key experimental results that must be explained by any stability model. The talk will also emphasize the need for lithium stability models that treat physical aspects of separators and cell designs that span from the nm to the mm length scale, as well as practical operating conditions such as desired rates of plating and stripping of >10 mA/cm2. The critical need for property measurements and experimental model validation platforms will be emphasized.
(Invited) Ferroelectric Devices for Alternative, Non-Von Neumann Computing
Authors: Khan Asif
Published: February 2020

In the post-Moore era of electronics, significant interests are developing around new models of computation that overcome the bottlenecks of traditional von Neumann architectures, and draw features from the neuro-scientific principles of biological brains. In physically implementing those alternative kernels, emerging nanoelectronic materials and devices show great promise in terms of power efficiency and compactness due to their interesting features (such as hysteresis, non-volatility, plasticity, stochasticity, polymorphism)--features that are not readily available in CMOS platforms. The ferroelectric field-effect transistor (FeFET) is such an emerging device where a ferroelectric oxide is introduced into the gate oxide stack of a field-effect transistor. In this talk, we will present how the FeFET technology could be utilized for implementing non-von Neumann computing systems such as coupled neuro-oscillatory networks and spiking neural networks. The talks will include recent experimental results in tandem with theoretical calculations and simulations.
Study on Forming-Free Characteristic of Amorphous Carbon Oxide Reram By Controlling Cu-Filament Shape
Authors: Jin Soo-Min , Kwon Ki-Hyun , Kim Dong-Won , Kim Hea-Jee , Yang Hun-Mo , Kim Ji-Yeon , Park Jea-Gun
Published: February 2020

Resistive random access memory (ReRAM) is one of the most promising candidates for the next-generation memory due to its simple structure, high switching speed and low power consumption [1]. Recently, there has been large interests in using carbon-baed material as solid electrolyte to overcome the limit of conventional metal-oxide memory. It has remarkable advantages over past metal-oxide memory such as high memory margin (Ion/Ioff
> 100) and fast switching speed (20~50ns) [2]. However, the requirement of forming process to activate resisitive switching operation is one of the critical issues. Forming process may degrade the device switching characteristic and is not desirable for circuit design. In this study, forming-free characteristic of a-COx (amorphous carbon oxide) based ReRAM was observed by controlling the Cu-filament shape. To accurately control the Cu-atom concentration profile, insertion of Cu thin film was carried out in several ways. The first device, named A, was fabricated with the common ReRAM structure of Pt / Cu-doped a-COx / W. The second device, named B, was vertically stacked with the strcutrue of Pt / a-COx / Cu-doped a-COx / W. The third device, named C, was vertically stacked with the strcutrue of Pt / Cu-doped a-COx / a-COx / Cu-doped a-COx / W. The device was fabricated on W bottom electrode wafer patterned from 34 nm to 1921 nm by photo lithography process. The a-COx and other metals were deposited using dc magnetron sputter (PVD method). After the fabrication, the Cu-atom concentration profile was carefully examined using SIMS analysis to understand the correlation between forming-free chracteristic and Cu-filament shape. Forming-free characteristic device presented identical forming and set voltage of -0.85 V. Moreover, the result indicated that the high resistance state current of 2.41-7 A at 0.1 V, low resistance state current of 5.98-5 A at 0.1 V and the memory window margin (Ion/Ioff) of 2.48×102. In our study, we present that the precise design of the Cu-atom concentration profile of a-COx based ReRAM is the significant key to achieve the forming-free and stable non-volatile memory characteristic.

[1] Daniele Ielmini, Semicond. Sci. Technol. 31 (2016) 063002

[2] Claudia A. Santini et al, NAT COMMUN, 6:8600 (2015)

* This material is based upon work supported by the Ministry of Trade, Industry & Energy(MOTIE, Korea) under Industrial Technology Innovation Program (10068055).

Figure 1
Multilevel Resistive Switching in Hf-Based Rram
Authors: Jain Barsha , Huang Chia-sheng , Misra Durgamadhab , Tapily Kandabara , Clark Robert D. , Consiglio Steven , Wajda Cory S. , Leusink Gert J.
Published: February 2020

Resistive random-access memory (RRAM) device has attracted wide attention for next-generation nonvolatile memory (NVM) application due to simple structure, high cycling endurance, good retention, low power consumption and fast switching time (1, 2). In recent years, RRAM devices are extensively researched for multi-level data storage (3, 4). RRAM devices can be driven to various resistance states by applying suitable compliance current values during the switching operation.

In this work, multilevel resistive switching behaviors of RRAM devices with three different dielectric materials like HfO2, HfAlO2 and HfZrO2 are investigated with fixed top/bottom electrodes. To control the resistance state, a thin Al2O3 layer (1 nm) was inserted between the bottom electrode and switching dielectric (Ti/TiN/Al2O3/HfAlO2 or HfZrO2 or HfO2/Ti/TiN). The fabrication details of these devices are presented elasewhere (5). Fig. 1 shows DC endurance cycling on the LRS/HRS resistances of the three RRAM structures, (a) HfAlO2, (b) HfZrO2 and (c) HfO2 for different increasing compliance currents. The endurance cycling is performed with 20 cycles per compliance level. As can be seen from the figure, different low resistance states (LRS) and high resistance states (HRS) are well resolved after dc endurance cycling for HfAlO2 and HfZrO2 based RRAM devices. Devices with HfO2, on the other hand, does not show any multilevel LRS or HRS behavior for increase in compliance current. The reason is possibly due to the lack of oxygen vacancies available in the HfO2-RRAM structure.

When HfZrO2 was subjected to a post deposition annealing (PDA) in nitrogen environment, the resistance distribution of LRS and HRS was improved, possibly due to improvement of dielectric quality while the oxygen vacancy concentration remained the same. To further improve the resistance window an additional 2 nm thick TiN layer was added before the Ti layer on top electrode of HfZrO2 based RRAM. The cycle to cycle distribution of HRS/LRS resistance of HfZrO2 based RRAM was significantly improved while the compliance current for switching was increased.

In summary, process optimization and electrode selection with HfZrO2 as the switching layer can provide significant multilevel storage in RRAM devices.

References:

E. Ambrosi, A. Bricalli, M. Laudato and D. Ielmini, Faraday discussions DOI: 10.1039/c8fd00106e (2018).

A. Prakash and H. Hwang. Physical Sciences Reviews, vol. 1(6), (2016)

Chen, et al., Semiconductor Science and Technology7 (2015): 075002.

J. Jang and V. Subramanian. Thin Solid Films 625 (2017): 87-92.

D. Misra, S. Sultana, B. Jain, N. Bhat, K. Tapily, R.D. Clark, S. Consiglio, C.S. Wajda, and G.J. Leusink, ECS Trans., vol. 86(2), 77, 2018.

Figure 1
Perpendicular Spin-Transfer-Torque Magnetic Tunnel Junction Multi-Level Cell with Dual Free Layers and MgO Tunnel Barriers
Authors: Baek Jong Ung , Jun Han-Sol , Choi Jin-Young , Kondo Kei , Park Jea-Gun
Published: February 2020

Perpendicular spin-transfer-torque magnetic random access memory (p-STT-MRAM) is a promising candidate memory device for replacing dynamic random access memory (DRAM) facing with 10-nm sub scaling down. In addition to scaling down, p-STT MRAM has many advantages like fast write/read speed (~10ns) as DRAM, low power consumption (<1pJ), high endurance (>1014), and non-volatility (retention time > 10 years). But to replace DRAM, there are several challenges to be solved. First, high tunneling magneto-resistance (TMR) ratio for read sensing margin. Second, low critical current density(J
C) for low power consumption. Third, thermal stability(Δ) for long retention time to save data. And also these parameters should be achieved at 350oC annealing temperature of the back-end-of line (BEOL) to be commercialized. Among them, thermal stability is closely related with cell size. As a cell size of MTJ decreases to achieve a high density memory device, thermal stability decreases with retention time, thus it is not easy to implement both high density and non-volatile memory device simultaneously by decreasing the cell size of MTJ.

In our study to solve this issue, we propose the p-STT multi-level cell (MLC) magnetic tunnel junction (MTJ) because MLC MTJ can satisfy both high density and non-volatile memory device at the same time. In particular, we design the MTJ structure with dual free layers and MgO tunnel barriers, so that the MTJ can demonstrate four resistance states. In addition, we investigated the effect of the thickness of two free layers and MgO tunnel barriers on two magneto-resistance (MR) and switching voltage. In our experiments, the p-STT MTJ spin-valves were fabricated on 12-inch-diameter Si/ SiO2/W/TiN wafers by utilizing a 12-in. multi-chamber-cluster magnetron-sputtering system under a high vacuum (less than 110-8 Torr) without breaking the vacuum. Then, all samples were subject to ex-situ annealing at 350℃ at a back end of line (BEOL) for 30 minutes under a magnetic field of 3 tesla. In our presentation, we present how to optimize the thicknesses of two free layers and MgO tunnel barriers. In addition, we repot how the magnetic behavior and the resistance of MTJ is affected by magnetic and how the magneto-resistance of MTJ is closely related to the crystallinity of two MgO tunnel barriers.

Acknowledgements

This work was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2A1A05001285)
Ferroelectric Characteristics of Hf0.5Zr0.5O2-Based Mfis and Mfmis Capacitors for Steep-Slope Ferroelectric Field Effect Transistor Applications
Authors: Roh Jangho , Park Hyeon Woo , Lee Yong Bin , Hyun Seung Dam , Kim Keum Do , Moon Taehwan , Lee Young Hwan , Kim Baek Su , Kim Bum Yong , Kim Ho Hyeon , Hwang Cheol Seong
Published: February 2020

Research of hafnium oxide-based ferroelectric materials has attracted much attention in the community with superior advantages of their compatibility with silicon. Also, negative capacitance (NC) effect from ferroelectric films attracts a great deal of attention because it could be one of the solutions for the high power-consumption issue of field effect transistors (FET). However, since the non-linear Q-V response of semiconductor in the FET structure in conjunction with the domain formation in the ferroelectric layer resulted in complicated device behaviors, it is necessary to understand the physics of the ferroelectric characteristics related to the interactions among the layers such as the depolarization field and charge trapping/injection for sub-60mV/dec subthreshold swing (SS) operation.

In this study, the electrical properties of a Metal-Ferroelectric-Insulator-Semiconductor (MFIS) capacitor with a 7-10nm Hf0.5Zr0.5O2 (HZO) ferroelectric layer and an ultrathin interfacial oxide layer (SiO2) were examined in order to understand the underlying physics of the ferroelectric characteristics (Figure 1 (a)). These properties were compared with those of a Metal-Ferroelectric-Metal-Insulator-Semiconductor (MFMIS) capacitor to analyze the interactions among each layer in the two different structures by pulse measurement. In addition, the ferroelectric characteristics of HZO on semiconductor related to the charge injection through the interfacial oxide layer with different thicknesses and the non-linear Q-V response of semiconductor have been investigated (Figure 1 (b)). Lastly, the effects of different PMA temperatures and HZO thicknesses were also examined and the experimental data were verified by the charge injection-controlled simulation model which was used to simulate the transfer characteristics based on different experimental conditions. (Figure 2).

Figure 1
Study on Interface Engineering of TiN/SiO2 Layers to Reduce the Parasitic Capacitance in CMOS Circuits
Authors: Kim Suncheul , Bae Jong-yong , Park Miseok , Kwon Yong Il , Han Dong-Hoon , Lee Ui-Hyoung , Koo Yoonbon
Published: February 2020

Recent developments in CMOS (Complementary Metal-Oxide-Semiconductor) technology have heightened the need for high-quality interface between mold and metal line, in order to decrease the RC delay in CMOS circuit. This technical trend indicates that the understanding of the interface reaction between the silicon dioxide (SiO2) and the titanium nitride (TiN) is emerging as an important issue in the thin film deposition process. However, only few researchers have focused on the interface researches to investigate the formation of parasitic capacitance and its material properties of TiN/SiO2 layer.

In this work, we report the formation mechanism of Titanium dioxide (TiO2) on SiO2 surface during the TiN deposition process based on a Plasma Enhanced Chemical Vapor Deposition (PECVD) and Titanium tetrachloride (TiCl4) gas reactions. This research has explored the effects of the partial pressure of TiCl4 gas in the initial step of TiN deposition on the formation of the intermetallic compound of TiN/SiO2 interface layer. The results of atomic composition and the position of valance band of the composite material analyzed by X-ray photoelectron spectroscopy (XPS) reveals that the parasitic capacitance material is the TiO2. The high partial pressure of TiCl4 leads to an increased oxygen-titanium ratio (O/Ti ratio) and a decreased maximum position of valance band at the interface between TiN and SiO2, which is attributed to TiO2 formation. Furthermore, we investigated the effect of the thickness of TiO2 and its Oxygen intensity induced by TiCl4 gas treatment on the change of the parasitic capacitance using X-ray fluorescence (XRF) analysis and Secondary Ion mass spectrometry (SIMS).