bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of Commercially Available SiC Power Mosfets
Authors: Lelis Aivars , Green Ron , El Mooro , Habersat Dan
Published: February 2020

With the introduction of SiC power MOSFETs into the commercial market place, it is critically important to determine the reliability of these devices. A number of potential issues need to be addressed, including the stability of the device threshold voltage, and the reliability of both the body diode and the gate oxide.

An ideal switch has minimal leakage current in the OFF state and very low resistance in the ON state. But an excess negative shift of the threshold voltage under high-temperature reverse-bias (HTRB) conditions can lead to a critical increase in OFF-state leakage current and potential device failure [1]. In a similar fashion, a large positive shift of the threshold voltage may occur under high-temperature gate-bias (HTGB) conditions, wherein a positive bias-temperature stress is applied. This can lead to a significant increase in the ON-state resistance.

This work focuses on the stability of the device threshold voltage when subject to bias-temperature stressing, although the reliability of the body diode will also be discussed in the full paper. The primary defects that contribute to shifts in the threshold voltage are near-interfacial oxide traps [2, 3]. A certain number of defect states become activated during device processing. This can vary depending on the details of the processing steps, or may be a function of device design. Typical instabilities of the threshold voltage at room temperature are about 0.25 V. Much larger threshold-voltage instabilities are observed following bias-temperature gate-bias stressing. This is very likely due to the activation of additional oxide traps, which can then participate in the oxide-trap charging process [3]. Since this activation is a function of time at temperature (and bias), more stressful processing conditions can quicken the onset of significant shifts in the threshold voltage during bias-temperature stressing. (Similarly, stressing at higher temperatures also leads to an earlier onset of significant increases in threshold-voltage instability.)

As a result, we have observed a marked difference in the onset of significant increases in threshold-voltage instability between different commercial vendors. This difference in bias-temperature stress time can vary in some cases by two orders of magnitude. Detailed results will be provided in the full paper.

References

1. Lelis, et al., Mater. Sci. Forum, vols. 679-680, p. 599 (2011).

2. Lelis, et al., IEEE Trans. Elec. Dev., 55:8, 1835 (2008).

3. Lelis, et al., ECS Transactions, Vols. 41(8), p. 203 (2011).
Studies of Relaxation Processes and Basal Plane Dislocations in CVD Grown Homoepitaxial Layers of 4H-SiC
Authors: Dudley Michael , Wang Huanhuan , Wu Fangzhen , Yang Yu , Guo Jianqiu , Chung Gil , Zhang Jie , Thomas Berndt , Sanchez Edward K , Mueller Stephan , Hansen Darren , Loboda Mark
Published: February 2020

It is well known that basal plane dislocations (BPDs) that are replicated from Physical Vapor Transport (PVT) grown 4H-SiC substrates into Chemical Vapor Deposition (CVD) grown homoepitaxial layers can have a detrimental effect on device performance by inducing the expansion of Shockley faults in the epilayer which cause forward voltage drop. As a result, significant advances have been made in engineering the processes by which BPDs are replicated into the epilayer. For example, the conversion of BPDs into less harmful threading edge dislocations (TEDs) at the substrate/epi interface can be enhanced by direct etching of the substrate surface intersections of the BPDs or by growth interrupts which induce etching. Conversion rates of BPDs into TEDs during epilayer growth have been studied in this paper. Secondly, the behavior of BPDs which are replicated into the epilayer has been studied using Synchrotron White Beam X-ray Topography (SWBXT), Monochromatic Beam X-ray Topography (SMBXT), KOH etching and other techniques on pre- and after- epilayer growth of the same substrate. It is observed that dislocation loops inside substrate can move towards interface and then produce interfacial dislocations (IDs) and half-loop arrays (HLAs) under certain growth conditions during homoepitaxy growth of 4H-SiC on off-cut substrates. The HLAs and IDs are observed to form from pairs of opposite sign screw oriented basal plane dislocations in the substrate which replicate into the epilayer and glide opposite directions once critical thickness has been exceeded. Thirdly, we report on both interfacial dislocations and HLA’s generated from: (a) surface sources of BPDs; (b) micropipes; (c) 3C inclusions; and (d) substrate/epilayer interface scratches.It is also observed that some dislocations glide past the interface and into the substrate. This will also be discussed.
Work Force Development Challenges in the Wide Band Gap Supply Chain Industry
Authors: Ruland Gary , Wessel Tom
Published: February 2020

Reduced Research, Development, and Engineering cycle times in new product development efforts have increased pressure in all three disciplines causing management teams to seek the most productive paths to success. Of these three, the development effort, in particular process development is the most challenged. Workforce requirements to close this gap are a working knowledge of semiconductor processing with practical expertise of WBG material properties and processing in one of the four following supply chain elements: substrate, epi, device, and packaging, and a working knowledge of the remainder. To solve specific problems, a solid foundation in Applied Engineering with strong skills in Design of Experiments, Statistics, and Process Control are required. Finally, barriers created by non-compete agreements and IP issues are increasing.
Control of Metal-Insulator Transition of Vanadium Dioxide Thin Film Grown by Excimer Laser Assisted Metal Organic Deposition
Authors: Tsuchiya Tetsuo , Nakajima Tomohiko , Shinoda Kentaro , Takako Nakamura
Published: February 2020

In order to fabricate the new devices for the next generation, it is necessary to develop new materials, nanostructured thin films, low temperature processing. To achieve these aims, we have developed the photo-induced chemical solution deposition such as excimer laser-assisted metal organic deposition (ELAMOD) and photo reaction of nano-particle method (PRNP) for the preparation of the patterned metal oxide thin film on organic, glass and single crystalline substrates. In this presentation, we will talk about epitaxial VO2 thin film with nanostructure by using the photo-induced chemical solution deposition, and its excellent properties of the thin film for new uncooled IR sensor.
Towards Highly Transparent and Flexible Field Emission Displays Based on Low-Dimensional Nanocarbon
Authors: Tanemura Masaki
Published: February 2020

Transparency and flexibility are key words required for the devices of next generation. This is also the case for displays, for example, highly intelligent information displays for the upcoming ubiquitous world. To realize the transparent and flexible devices, nanocarbon, such as carbon nanotubes (CNTs), carbon nanofibers (CNFs) and graphene, are promising. In the present talk, nanocarbon-based highly transparent and flexible displays will be dealt with.

Field emission displays (FEDs) offer promising advantages such as high brightness, low power consumption, wider viewing angle, etc. Recently some groups have demonstrated the fabrication of nanocarbon based flexible (opaque) FEDs [1, 2]. The next step is the realization of transparency. To achieve this, we are tackling several approaches based on single-walled CNTs, ion-induced conical nanocarbons and their hybrid structures formed on transparent and flexible polymer substrates [3-8]. In addition, in situ transmission electron microscope (TEM) observation of graphene and CNT formation from amorphous carbon-based nanofibers by solid phase reaction during field emission process will be demonstrated [9].

1. H. S. Sim, et al., Appl. Phys. Lett., 90 (2007) 143103-143105.

2. B-J. Yoon, et al., J. Am. Chem. Soc., 127 (2005) 8234-8235.

3. P. Ghosh, et al., J. Am. Chem. Soc., 132 (2010) 4034-4035.

4. D. Ghosh, et al., Chem. Commun., 47 (2011) 4980-4982.

5. M. Tanemura and S. P. Lau: "Flexible Field Emitters: Carbon Nanofibers" in "Carbon Nanotube and Related Field Emitters: Fundamentals and Applications" Edited by Y. Saitoh, Wiley-VCH (Weinheim) (2010), Chapt. 15.

6. D. Ghosh, et al., Phys. Status Solidi RRL 6 (2012) 303–305.

7. D. Ghosh, et al., Phys. Status Solidi RRL 7 (2013) 1080–1083.

8. P. Ghosh, et al., J. Nanoscience and Nanotechnology, 13 (2013) 5767-5772.

9. M. Zamri, M. Tanemura, et al., ASC Nano, 6 (2012) 9567-9573.
Study on Oxide Thickness Dependence of Current-Voltage Characteristics for HfOx Based ReRAM Device
Authors: Hamada Yoshifumi , Otsuka Shintaro , Shimizu Tomohiro , Shingubara Shoso
Published: February 2020

A resistance random access memory (ReRAM) is expected to be a next-generation nonvolatile memory because of its fast switching speed, and low power consumption. The device structure is composed of an oxide layer sandwiched with two metal electrodes. ReRAM exhibits repetitive transition between high resistance state (HRS) and low resistance state (LRS). It is considered that resistive switching phenomenon is caused by the formation and rupture of the conductive filament formed in the oxide layer. In this study, we investigated HfOx thickness dependence of current-voltage characteristics for Ni/HfOx/Pt ReRAM device. We fabricated Ni/HfOx/Pt devices with a simple crossbar structure. HfOx layer was deposited on the Pt bottom electrode by DC reactive sputtering. The I-Vcharacteristics were measured by two-probe method at room temperature.

Red line in Figure 1 shows I-V characteristics of the Ni/ HfOx/Pt device with oxide thickness of 5.6 nm. Initial state of resistance is HRS. SET process (from HRS to LRS) took place at 2.4 V with a current compliance of 0.1 mA. RESET process (from LRS to HRS) occurred at -1.6 V. The resistance ratio of HRS to LRS is about 107 with 0.1 V readout bias. On the other hand, blue line shows the I-V characteristics of the Ni/ HfO2/Pt device with oxide thickness of 4.0 nm. Initial state of resistance is LRS. Forming process was not observed in this device. SET process took place at 1.0 V. RESET process was observed at -0.6 V. Switching voltage of this device is smaller than the former device with the thicker oxide layer. The resistance ratio of HRS/LRS is about 101 with 0.1 V readout bias. There was a significant difference in switching properties between these devices whose oxide thicknesses differ only 1.6 nm.

It is suggested that leakage current increases when the oxide thickness decreases, thereby the on-state occurred initially for the device with 4.0 nm oxide. It should be noted that I-V characteristic is symmetrical for the device with 4.0 nm oxide, while it is asymmetrical for the device with 5.6 nm oxide. This suggests the mechanism of conductive filament formation and rupture is completely different between these devices. Further discussions and analysis will be presented in the symposium.
Single-Grain Si Tfts Fabricated on a Precursor from Doctor-Blade Coated Liquid-Si
Authors: Zhang Jin , Trifunovic Miki , van der Zwan Michiel , Takagishi Hideyuki , Shimoda Tatsuya , Ishihara Ryoichi
Published: February 2020

In the application of display, Si TFTs is superior than organic TFTs and metal oxide TFTs in the sense of carrier mobility, reliability and traditional IC process compatibility. However, the difficulty of achieving single crystalline Si limits the application of Si TFTs. In this paper, we would like to present a low-temperature approach for manufacturing single-grain Si TFTs on a precursor from doctor-blade coated liquid-Si on flexible polyimide substrate, with the carrier mobility of 460 cm2/Vs and 121 cm2/Vs, for electrons and holes respectively.

Pure cyclopentasilane is used as liquid-Si, and it was coated using doctor-blade method, and polymerized under the UV lamp. According to [1], polysilane was formed after polymerizing the solution of cyclopentasilane and toluene. After an annealing process at 350 °C, an a-Si precursor was formed (see Fig. 1). A XeCl laser with the wavelength of 308 nm was used for the crystallization of the a-Si precursor, and thanks to the special cavity structures called the grain-filters, which are 110 nm width by 700 nm depth, underneath the a-Si layer, Si single grains were formed[2] (see Fig.2). A top-gated transistor was fabricated using the IC-compatible process of ICP gate oxide growth (250 °C), PECVD TEOS oxide (350 °C), Al gate and contact pads formation, self-aligned source-drain dopant ion-implantation and laser activation of the dopants (room temperature). The process temperature was so low that the devices were fabricated on top of flexible polyimide substrate. At the end of the process, all the devices were peeled off from the supporting Si wafer to a PEN foil and become flexible (Fig. 5).

The devices show transfer characteristics with high on-off ratio and high carrier mobility, 420 cm2/Vs for electrons and 121 cm2/Vs for the holes (Fig. 3). After peeling off from the Si wafer, the devices could function until a bending diameter of 6 mm (Fig.4). To restrain the mobility degradation during the bending, a double-sided polyimide structure was investigated.

[1] T. Shimoda, Y. Matsuki, M. Furusawa, T. Aoki, I, Yudasaka, H. Tanaka, H. Iwasawa, D. Wang, M. Miyasaka and Y. Takeuchi, Nature 440, 6, 2006, 783-786

[2] R. Ishihara, P.C. van der Wilt , B.D. van Dijk , A. Burtsev , J.W. Metselaar and C.I.M. Beenakker, Thin Solid Film 427, 2003, 77-85
High Temperature Performance of MoS2 Thin Film Transistors
Authors: Shur Michael , Rumyantsev Sergey , Samnakay Rameez , Jiang Chenglong , Goli Pradyumna , Balandin Alexander
Published: February 2020

We report on the characteristics of long channel (1 to 2 micron MoS2 thin film transistors) measured in the temperature range from 25 oC to 200 oC. Using the long channel allowed us minimizing the effect of the contact resistance for a more accurate extraction of the effective field effect mobility in the channel. The extracted field effect mobility, see Fig.1, (varying from 5 to 7 cm2/V-s in different samples) was only a very weak function of temperature. The on-to-off ratio was ~ 104 at room temperature decreasing to 103 at 220 oC. The devices had the threshold voltage varying from 80 V to 40 V when temperature increased from 25 oC to 220 oC, see Fig. 2. A very large subthreshold slope of nearly 11 V corresponded to the density of states in the energy gap of approximately 3x1013 cm-2 or approximately 3 x1012 1/(eVcm2) at the band edge. The low frequency noise measurements in the range from 1 Hz to 100 Hz revealed 1/f noise with no recombination-generation bulges. The density of traps extracted from the noise data using the McWhorter model was close to that extracted from the temperature measurement. Our results show that MoS2 TFTs can compete with a-Si TFTs and a-Si sensors for high temperature applications.
Interpretation of Defect States in Sputtered IGZO Devices Using I-V and C-V Analysis
Authors: Mudgal Tarun , Walsh Nathaniel , Edwards Nicholas , Manley Robert G. , Hirschman Karl D
Published: February 2020

There has been significant progress in advancing the performance of IGZO TFTs; however device stability still remains a challenge. While traditional materials and techniques used for silicon-based TFTs may not be applicable, the influence of defect states can be reduced by annealing. The interpretation of non-ideal current-voltage (I-V) characteristics is not always unambiguous due to issues that may be related to carrier injection. Capacitance-voltage (C-V) analysis provides complementary information that is valuable in separating the influence of material and interface defects from other factors that influence transistor operation.

In this work, bottom-gate, top-contact TFT structures and interdigitated capacitors fabricated using sputtered IGZO have been investigated. Interdigitated capacitors, unlike one-dimensional capacitors, are much more representative of the actual TFT structure; specifically the channel region. Annealing was performed at 300 - 400 °C in O2, N2and air ambient conditions. Silicon dioxide, aluminum oxide, and B-staged bisbenzocyclobutene-based (BCB) resins were applied as materials for back-channel passivation. Analytical measurements and both I-V and C-V results were used to refine a material model developed for TCAD device simulation [1]. The correlation between I-V and C-V characteristics will be presented.

[1] T. C. Fung, C. S. Chuang, C. Chen, K. Abe, R. Cottle, M. Townsend, et al., "Two-dimensional numerical simulation of radio frequency sputter amorphous In-Ga-Zn-O thin-film transistors," Journal of Applied Physics, vol. 106, p. 084511, 2009.
Improvement of Electrical Properties and Bias Stability of InGaZnO Thin-Film Transistors by Fluorinated Silicon Nitride Passivation
Authors: Jiang Jingxin , Tatsuya Toda , Tatsuoka Gengo , Wang Dapeng , Furuta Mamoru
Published: February 2020

Recently, oxide-based thin-film transistors (TFTs) have attracted considerable attention for applications such as active-matrix flat panel displays. Among oxide semiconductors, amorphous InGaZnO (a-IGZO) is widely accepted as a promising channel material for TFT application [1]. However, the bias induced instability is a remained issue to be solved. Ambient atmosphere includes oxygen and water, which easily absorb on the exposed a-IGZO surface and influence TFT properties; therefore, a suitable passivation layer is an essential to improve the reliability of the oxide TFTs. In this study, electrical properties of the IGZO TFTs with SiOx, fluorinated SiNx (SiNX:F) passivation were investigated.

Bottom-gate IGZO TFT with SiOX etch-stopper was used for this experiment, and a SiOX or SiNX:F was deposited on the TFT as a passivation [2]. The experimental transfer characteristics (IDS-VGS) of the IGZO TFTs with SiOX and SiNX:F passivation are shown in Fig. 1(a) and 1(b), respectively. The IGZO TFT with SiNX:F passivation showed steep subthrehold swing, low threshold voltage (Vth), and small hysteresis as compared with the SiOX passivation. Fig. 2 shows the comparison of positive bias temperature stress (PBTS) reliability of the IGZO TFTs with SiOX and SiNX:F passivation. It was found that positive threshold voltage shift is significantly suppressed by SiNX:F passivation. Influence of SiNX:F passivation on reliability of the IGZO TFT will be presented at the conference.

Authors would like to thank Tokyo Electron Co., Ltd. for their experimental supports on SiNx:F film.

[1] K. Nomura, H. Ohta, A. Takagi, T. Kamiya, M. Hirano, and H. Hosono, Nature. 432, 488 (2004).

[2] M. Furuta, M. P. Hung, and J. Jiang, D. Wang, S. Tomai, H. Hayasaka, and K. Yano, ECS Trans., 54 (2013).
Nano-Crystalline Oxide Semiconductor Materials for Display and Semiconductor Device Applications
Authors: Jeon Sanghun
Published: February 2020

Ever evolving advances in oxide semiconductor materials and devices continue to fuel leading edge developments in display technology, and transparent electronics, thanks to new integration processes, enabling large area processing on rigid and flexible substrates. Nanocrystalline oxide semiconductor offer a host of advantages such as low cost and high scalability, in addition to seamless heterogeneous integration with a host of other inorganic and organic materials in view of its low thermal budget in processing which provides integration flexibility. This has spawned a wealth of applications ranging from high frame rate interactive displays with embedded imaging to flexible electronics, where speed and transparency are essential requirements Therefore, transparent electronic systems, which have been once viewed as science fiction, can now become a reality. In semiconductor device applications, interest in oxide semiconductors stem from a number of attributes primarily their ease of processing, and high field effect mobility, resulting in stackable process nature on silicon circuits. In this talk, various semiconductor device applications via nanocrystalline oxide semiconductor materials will be presented.

In the first part of our presentation, as seen in Figure 1, we present a photo-transistor embedded in a display pixel, in which gate operation is used to accelerate recovery from photocurrent level to the dark state. We describe the origin of ultra-high quantum efficiencies in photo-sensors based on nanocrystalline oxide hetero-junction thin film transistor (TFT). In order to understand the origin of high photocurrent of a device, we evaluated the influence of a light spot from source to drain side on the photoconductive gain of photosensor array. This work here demonstrates high sensitivity image sensor along with quantitative analysis of the quantum efficiency in the hetero-junction TFT taking into account the optical absorption, electron lifetime, and transit time.

The integration of electronically active oxide components onto silicon circuits represents an innovative approach to improving the functionality of novel devices. Like most semiconductor devices, complementary-metal-oxide-semiconductor image sensors (CISs) (see Figure 2) and memory devices have physical limitations when progressively scaled down to extremely small dimensions. In the 2nd part of presentation, we propose a novel hybrid CIS architecture and memory architectures that are based on the combination of nanometer-scale oxide thin-film transistors (TFTs) and a conventional Si device. The results demonstrate how our stacked hybrid device could be the starting point for new device strategies in image sensor architectures. Furthermore, we expect the proposed approach to be applicable to a wide range of micro- and nanoelectronic devices and systems.
Electrodeposition and Evaluation of Ruthenium Film from Divalent Ruthenium Electrolyte
Authors: Chiba Shintarou , Fujinami Tomoyuki , Arai Susumu
Published: February 2020

Introduction

Ruthenium is a platinum-group element with properties similar to those of rhodium, which also is a platinum-group element. Compared to rhodium, ruthenium is considerably cheaper and its industrial applications have gradually been increasing. Ruthenium plating films are expected to be used for electrical contact parts due to their low contact resistance, abrasion resistance, and corrosion resistance. However, very few studies on ruthenium plating have been reported thus far. As ruthenium has a small hydrogen overpotential, the generation of hydrogen gas during electrodeposition should occur easily. Therefore, electrodeposition of ruthenium from ionic liquids instead of aqueous solutions has been investigated.1,2) In addition, ruthenium plating baths containing trivalent ruthenium ions are often used for electrodeposition. We have examined the electrodeposition of ruthenium films from a bath containing divalent ruthenium ions.3)

In the present study, the electrodeposition behavior and microstructure of these films were studied.

Experimental

An electroplating bath containing 0.1 M RuCl3•nH2O and 0.5 M L (+)-ascorbic acid was prepared. Trivalent ruthenium ions were changed to divalent ions by the addition of ascorbic acid. Copper plates were used as substrates. Plating was performed at 80°C with aeration under galvanostatic conditions (current density; 5 A dm-2, electrical charge; 50 C cm-1). A phase structure analysis of the deposits was performed using X-ray diffraction (XRD). The surface morphology and cross-sectional texture were observed using field–emission scanning electron microscopy (FE-SEM). Elemental mapping was carried out using electron probe X-ray micro-analysis (EPMA). Wear testing was performed using a scratch tester. The surface hardness was measured using a micro-Vickers hardness tester.

Results and Discussion

Figure 1 shows an SEM image of the ruthenium plating film surface. Some cracks are seen on the surface of the film. Figure 2 shows a cross-sectional SEM image of the film, which has a thickness of about 2 µm. Although a crack is seen, there are no voids in the film. It was found that the film had a low degree of crystallinity and contained a certain amount of chlorine, by XRD analysis and EPMA analysis, respectively.

Properties of the ruthenium film will be discussed at the meeting.

References

1) O. Mann, W. Freyland, O. Raz, Y. Ein-Eli, Chem. Phys. Lett., 460, 178 (2008).

2) O. Raz, G. Cohn, W. Freyland, O. Mann, Y. Ein-Eli, Electrochim. Acta, 54, 6042 (2009).

3) Y. Miyagawa, S. Arai, M. Endo, Abstract of the Electrochemical Society Japan Fall Meeting 2006, p.271 (2006).

4) S. Chiba, S, Arai, T, Fujinami, Abstract of The Surface Finishing Society of Japan 128th Meeting, p.27 (2013).
Effect of Annealing Temperature on Electrochemical and Mechanical Properties of STS with Titanium Carbonitride Composites Synthesized By Spark Plasma Sintering
Authors: Allabergenov Bunyod , Abidov Amir , Jeong Soon-Wook , Kim Sungjin
Published: February 2020

Stainless steel-titanium carbonitride based composites were fabricated and analyzed to utilize for bipolar plate in fuel cells. In order to study the size effect of the titanium carbonitride on mechanical and corrosion resistance properties of the composites, micro and nanosize titanium carbonitride powders were used. Stainless steel-carbonitride composites were prepared by spark plasma sintering and subsequently annealed at different temperatures up to 1100 °C to improve the morphological and mechanical properties. Various properties of the obtained samples were compared before and after annealing. It was shown that after the heat treatment, mechanical properties of the stainless steel-carbonitride composites were improved due to the diffusion of titanium carbonitride particles into stainless steel. Addition of microsized titanium carbonitride powders was found to be effective to improve the mechanical properties of the composite such as microhardness and compressive strength. However, addition of nanosized titanium carbonitride powders led to increasing of corrosion resistivity of the composite. Physical properties, such as thermal and chemical stability of the obtained composite samples were investigated by microhardness tester, potentiostat, field emission-scanning electron microscope, EDX and X-ray diffraction.
A Theory of Li Percolation in Rocksalts and Demonstration as Capacity Cathode Materials with Substantial Cation Disorder
Authors: Ceder Gerbrand , Urban Alex , Li Xin , Lee Jinhyuk
Published: February 2020

There is a clear need to develop dense, lithium intercalation oxides with > 200 mAh/g practical capacity. Today, nearly all high energy density cathodes for rechargeable lithium batteries are well-ordered materials where lithium and other cations occupy distinct sites. Cation-disordered materials are generally disregarded because lithium diffusion tends to be limited in them. The recently demonstrated performance of Li1.211Mo0.467Cr0.3O2, achieving close to 300 mAh/g, shows that lithium diffusion can be facile in disordered materials [1] and made us revisit the question of how Li diffuses through rocksalt-like materials. We have combined ab initio computations of local Li migration barriers with percolation modeling to develop a unified understanding of Li diffusion in close-packed oxides. The theory explains the high capacity of layered and spinel-like materials, and the lack of reversible capacity in γ-LiFeO2. More surprisingly, the new percolation theory also clearly supports that Li-excess is needed to achieve high capacity in partially or fully disordered materials. We can now give very specific guidelines for the amount of Li-excess needed in order to achieve a particular reversible capacity, and open up a new direction for finding very high capacity cathodes.

[1] J. Lee, A. Urban, X. Li, D. Su, G. Hautier, G. Ceder, Unlocking the Potential of Cation-Disordered Oxides for Rechargeable Lithium Batteries, Science, 343 (6170), 519-522 (2014)
Fabrication of Well-Aligned, Multi-Layered Cu/Si Nanorods Array and Its Use As Anode for Lithium Ion Batteries
Authors: Polat Deniz Billur , Keles Ozgul
Published: February 2020

Two multilayered Cu/Si thin films (flat and well-aligned structured) were prepared by using an electron-beam evaporation deposition. An oblique angle deposition was used to form a well aligned, multi-layered Cu/Si nanorods array in the thin film. Galvanostatic half-cell measurement showed that the well aligned multi-layered Cu/Si nanorods containing thin film anode exhibited a moderate capacity for 100 cycles due the particularities in its structure and morphology: The structural analysis demonstrated that Cu in the films buffered the mechanical stress occurred during lithiation and enhanced the electrical conductivity in the film. The morphological observation revealed the importance of the inclined nanorods since they increased the contact area of the anode with Li, decreased the polarization and enhanced the mechanical tolerance against the volumetric changes due to the homogenously distributed nanosized interspaces among them.
Evaluating Si-Based Materials for Commercially Relevant Li-Ion Batteries
Authors: Chevrier Vincent L , Liu Li , Le Dinh Ba , Krause Larry J , Jensen Lowell , Figgemeier Egbert , Eberman Kevin W
Published: February 2020

Methods and criteria for assessing the commercial viability of Si-based materials are discussed and demonstrated with the 3M V6 alloy and 60 nm nano Si powder. These materials are firstly evaluated through the cycling of neat electrodes containing only alloy and binder to characterize the capacity, first cycle efficiency, binder compatibility, and microstructure stability of the material. The alloy displays higher first cycle efficiency, lower fade, and a more stable amorphous microstructure compared to the nano Si, which displays a variable microstructure with a rate dependent presence of crystalline Li15Si4.

Figure 1 shows the dQ/dV of neat electrodes containing (a) only nano Si and LiPAA binder for which the Li15Si4 peak gradually decreases, and (b) Si-based alloy (V6Neat) and LiPAA binder with a dQ/dV characteristic of amorphous Si.

The materials are then evaluated in graphite-containing composite electrodes having high areal capacities (> 2 mAh/cm2). In a well designed composite electrode including carbon nanotubes, 3M V6 material was found to cycle with little fade and high coulombic efficiency (~99.8%) while maintaining a stable dQ/dV. A composite electrode of equivalent volumetric capacity with nano Si powder shows similar capacity retention over 50 cycles but an unacceptably low coulombic efficiency (~99.2%). High precision coulometry and calorimetry results show surface area as the dominant factor in levels of parasitic reactions with Si based materials.

A review of failure modes for various Si implementations and their impact on full cell cycling will also be presented.
Thermal and Structural Behavior of Surface-Modified Li[Ni0.7Co0.2Mn0.1]O2 As a Positive Electrode for Rechargeable Lithium Batteries
Authors: Jo Chang Heum , Myung Seung-Taek
Published: February 2020

Lithium secondary battery is promising as a power backup for energy storage system. In this respect, studies towards improvement in performances of electrode are being progressed to assure long cycling performances, thermal stability, safety, and so on. In particular, positive electrode materials are need to be further investigated to accomplish the above- mentioned properties. Several kinds of 4 V class positive electrode materials are commercially available. Among them, LiCoO2 is one of the most common electrode materials in rechargeable lithium batteries. Although the LiCoO2 has many advantages, this material has poor capacity retention because of dissolution of Co and structural instability at deeply charged state. To improve the nature of active material, surface modification is effective to overcome those limited properties of active materials. Actually, Metal oxides as coating materials have been extensively studied. In this study, Metal phosphate coatings are applied on the surface of Li[Ni0.7Co0.2Mn0.1]O2. We, here, report the resulting structural, electrochemical and thermal properties of the surface-modified Li[Ni0.7Co0.2Mn0.1]O2.

H3PO4 and metal salts were selected as starting materials for surface modification of Li[Ni0.7Co0.2 Mn0.1]O2. A solution anhydrous ethanol containing metal phosphates was stirred at 30 oC for 5 hours. Then, active materials were added into the solution. And the solution was evaporized at 80 oC in air and the resulting precipitates were then heated at 500 oC in air. Also, the coated powders were characterized by XRD, SEM, and HR-TEM. Electrochemical properties of coated powders were examined by galvanostatic cycle test and electrochemical impedance spectroscopy.

Metal phosphates coatings shows uniform coating layers, as observed by TEM. TG and DSC analyses were conducted for the materials. Electrochemical test with half cells in voltage range of 3 - 4.3 V at 25 oC indicates that coated materials have better capacity retention and coulombic efficiency, rate capability and thermal properties. Thin coating layers were effective in improvement of the electrochemical, structural and thermal properties. Also, metal phosphates coatings give decrease in the residual lithium content and byproduct on the surfaces of particles, as confirmed by ToF-SIMS. And the materials were analyzed into XPS and ToF-SIMS to confirm surface byproducts of the materials itself at high temperature. Details will be mentioned at the conference site.
A High Rate Lithium-Rich Layered MNC Cathode with Low Capacity Fade for Li-Ion Batteries
Authors: Ates Mehmet Nurullah , Mukerjee Sanjeev , Abraham K.M.
Published: February 2020

We report a new synthesis method, termed self-sustaining combustion reaction, that resulted in a lithium-rich MNC (LLMNC) cathode material with high rate capability and excellent capacity maintenance during cycling compared to the lithium-rich metal oxide cathode materials previously reported in the literature (
1-4
). This porous, sponge-like composite metal oxide of the composition, 0.5Li2MnO3. 0.5LiMn0.5Ni0.35Co0.15O2, was characterized by means of its X-ray diffraction (XRD) pattern, FESEM (Field Emission Scanning Electron Microscopy) images and electrochemical data. The interconnected pore structure of the material with enhanced surface properties (figure 1, inset) compared to its previously known counterpart synthesized from the co-precipitation method provides higher rate capability with low capacity fade during long-term cycling.

The XRD pattern of the material, with the Li2MnO3 region magnified, presented in Figure 1, perfectly matches with the literature data(
3
) for the layered Li-rich MNC material of similar composition. We obtained discharge capacities of approximately 300, 250, 200 and 150 mAh/g at C/20, C/4, and C and 2C discharge rates for electrodes having an active material loading of approximately 7 mg/cm2. Remarkably, excellent capacities with practically zero capacity fade has been observed for hundreds of cycles at the C discharge rate as shown in Figure 2 for a Li half-cell cycling between 2-4.9V at room temperature. Detailed structural and electrochemical properties of the material characterized using cyclic voltammetry (CV), XRD, X-ray Absorption Spectrometry (XAS), FESEM and High Resolution Transmission Electron Microscopy (HRTEM) will be discussed.

References:

1. M. N. Ates, Q. Jia, A. Shah, A. Busnaina, S. Mukerjee and K. M. Abraham, Journal of The Electrochemical Society, 161, A290 (2014).

2. Y. Chen, G. Xu, J. Li, Y. Zhang, Z. Chen and F. Kang, Electrochimica Acta, 87, 686 (2013).

3. A. Ito, D. Li, Y. Ohsawa and Y. Sato, Journal of Power Sources, 183, 344 (2008).

4. F. Amalraj, D. Kovacheva, M. Talianker, L. Zeiri, J. Grinblat, N. Leifer, G. Goobes, B. Markovsky and D. Aurbach, Journal of The Electrochemical Society, 157, A1121 (2010).
Polycarbonate-Based Solid Polymer Electrolytes for Li-Ion Batteries
Authors: Sun Bing , Mindemark Jonas , Edström Kristina , Brandell Daniel
Published: February 2020

Conventional Li-ion batteries containing flammable and volatile liquid electrolytes are challenged to deliver safe and stable performance for practical energy storage applications. Alternatively, solid polymer electrolytes (SPEs), which intrinsically eliminate the use of organic solvents, display good mechanical stability and flexibility against physical deformation of battery pack and volume retention of electrode materials. The use of SPEs with high thermal and electrochemical stability would contribute to the design and manufacture of safe and cost-effective Li-ion batteries, especially for large-scale applications under elevated temperatures [1].

Host materials for most SPEs have yet been dominated by polyethers with ethylene oxide (EO) and propylene oxide (PO) as repeating units. As an interesting replacement to the low-molecular-weight cyclic and linear carbonates, a new class of polymer hosts based on polycarbonates has been considered as Li+-conducting electrolytes [2]. The incorporation of polar carbonate units in the polymer host could effectively facilitate the separation of ion clusters and allow high salt doping in SPEs.

In this work, we have developed and explored poly(trimethylene carbonate) (PTMC) as a polymer host alternative for all solid-state Li-ion batteries. High-molecular-weight PTMC was synthesized via bulk ring-opening polymerization. Electrochemical and thermal properties of the PTMC/LiTFSI complexes with varied salt concentration were systematically investigated using electrochemical impedance spectroscopy (EIS) and thermal analysis (DSC/TGA). The as-prepared SPEs are amorphous materials and thermally stable up to 200 °C. The best-performing electrolyte could display useful ionic conductivity at elevated temperatures and was also found electrochemically stable towards 5.0 V vs. Li+/Li. The cycling performance of Li | SPE | LiFePO4 half cells has been tested at elevated temperatures and the cells display long-term cycling stability with retained high capacity up to 153 mAh/g. The gradual increase in capacity might be due to improved interfacial contacts during cycling and storage [3].

Acknowledgements

This work has been supported by the STandUP for Energy project and KIC InnoEnergy.

References

[1] B. Scrosati, J. Garche, J. Power Sources, 195 (2010) 2419.

[2] a) Smith, M. J. et al. Solid State Ionics, 140 (2001) 345; b) Silva, M. M. et al. J. Power Sources, 111 (2002) 52; c) Silva, M. M. et al. Electrochim. Acta, 49 (2004) 1887; d) Silva, M. M. et al. Solid State Sci., 8 (2006) 1318; e) Barbosa, P. C. et al. Solid State Ionics, 193 (2011) 39.

[3] B. Sun, J. Mindemark, K. Edström, D. Brandell, Solid State Ionics (2013), DOI: 10.1016/j.ssi.2013.08.014.
The Delithiation Behavior of LiFePO4 Particles with Broad Particle Size Distribution during Chemically Delithiation
Authors: Yoo Sunyoung , Kang Byoungwoo
Published: February 2020

LiFePO4 is the most promising cathode material, especially for electric vehicle (EV) because of its inexpensive cost, superior thermal and structural safety, and non-toxicity. Although LiFePO4 has been believed to be poor conductor due to its low electronic conductivity and 1D lithium diffusion, nano-sized LiFePO4 shows the fastest electrochemical reaction during charge and discharge.

To understand these intriguing behaviors, we have to consider delithiation behavior of particles in the electrode which consists of 1010 ~ 1017 particles in addition to the transport properties in the material because a particle has a non-monotonic chemical potential[1]. The non-monotonic chemical potential of single particle in multi-particle electrode leads to characteristic electrochemical behaviors such as a flat potential in voltage curve of the electrode and a sequential phase transformation between particles. Thus, delithiation behaviors in a particle in the electrode should be understood.

In this study, we will explore delithiation behaviors of LiFePO4 with broad particle size distribution. For this purpose, chemical delithiation and followed centrifuge method were applied to understand the delithiation behavior of LiFePO4 depending on particle size. This simple method shows phase transformation behaviors more directly. We synthesized LiFePO4 with broad particle size distribution by solid state reaction. And then, we can easily separate chemically delithiated small and large particles by centrifuge method. In this talk, we will introduce simple centrifuge method and will discuss about delithiation behavior of LiFePO4 with broad particle size distribution during chemical delithiation.

[1] W. Dreyer et al 2010 The thermodynamic origin of hysteresis in insertion batteries Nature Mat.
9, 448.
Fine-Grained Si Alloy Prepared By Melt Spinning and Its Electrochemical Performance for Li Ion Battery Anode
Authors: Kaburagi Tomohiro , Miki Fumihiro , Watanabe Manabu , Chiba Nobutaka , Hatano Masaharu , Inoda Kento , Tanimoto Hisanori
Published: February 2020

Silicon is candidate as an anode material for high energy Li ion batteries. Among Si materials, Si alloys attract great interests from a viewpoint of high durability and high coulombic efficiency. We found that sputter-deposited some of amorphous Si alloys (ex. Si-Sn-Ti ternary alloy) showed high electrochemical performance from the combinatorial study. In the present study, we synthesized amorphous Si alloys by using a Melt Spinning process and investigated the potential toward volume production as well as the electrochemical performance.To obtain amorphous Si alloys, the ease of mixing between Si and added metals or the chemical mixing enthalpy is an important factor. In the case of Si-Sn-Ti alloy, the mixing enthalpy decreases by increasing Ti/(Ti+Sn) ratio and it is expected for easier preparation of the amorphous alloys at higher Ti/(Ti+Sn) ratios (Fig. 1). The SEM/EPMA elemental mapping of several Si-Sn-Ti alloy indicated that the Si atoms in Ti rich composition alloy (Si/Sn/Ti=60/10/30 wt%) is more uniformly and finely dispersed than Sn rich composition alloy (Fig. 2). The electrochemical performance will be reported in the presentation. This work was partially supported by the project “Research and Development of Lithium ion Battery Application / Research and Development of High Capacity Si-based Alloy Anode” of the New Energy and Industrial Technology (NEDO).
Structual and Electrochemical Effects of Sn Addition on Si-Based Alloy Anod for Lithium Ion Batteries
Authors: Kim Min-Hyun , Choi Young-Pil , Kim Seon-Kyong , Park Cheol-Ho , Kim Yoon-Keun
Published: February 2020

Various portable electronic devices are wildly used in the world due to the remarkable progress of information technology since 2000. It leads to the increasing demand for rechargeable batteries. As a result, Lithium Ion batteries (LIB) are intensively investigated by many researchers. Currently graphite-based anode materials have widely used. In order to extend to rapidly increasing demand and wider applications as electric vehicles, we have to develop a new anode material. Si-based alloy anode material is one of the strongest candidates because it has many advantageous properties such as high capacity, high safety, good electrochemical stability, and low production cost. M. Kim. et al.[1] has developed a good Si-base alloy anode material and they reported the structural and electrochemical properties[1]. The Si-base alloy is consisted of finely dispersed active silicon crystals and surrounding inactive metal matrix. The main role of inactive-matrix in Si-based alloy is suppressing the volume change and it helps the Si-based alloy maintain good cycle performance.

In this study, in order to enhance the cycle performance, we have added Sn metal which has theoretical capacity of 972mAh/g. Si and Sn nanocrystallites embedded in Si-Ti-Fe matrix were developed using arc melting followed by a rapid quenching method which could produce a large scale at one time. To identify the reaction mechanism, the ex-situ XRD, SEM, TEM, analyses were employed. Si and Sn nanocrystallites of approximately 100nm were dispersed in matrix composed of Si2TiFe. Consequently the Si/Sn/Si2TiFe composite showed a good cycle performance with 1000mAh/g over 50 cycles.

[1]Journal of electroanalytical Chemistry 687 (2012)84-88
New Synthesis Approach for High-Voltage Spinel LiNi0.5Mn1.5O4 a High Performance Positive Material for Lithium-Ion Batteries
Authors: Liu Haidong , Li Jie
Published: February 2020

With the demand for increasing the energy and power, a lot of attention has been attracted by the LiNi0.5Mn1.5O4 (LNMO) spinel cathode material for lithium ion batteries, as it can be operated at a high voltage of ~ 4.7 V (versus Li+/Li) with offering 3-dimensional lithium-ion diffusion channels, allowing fast intercalation/deintercalation of lithium ions. However, it still remains challenging to get excellent rate capacity and cycling stability for LNMO material, especially at elevated temperature, due to the complex influencing factors and the undesired side reactions with the electrolytes. [1-5]

Various synthesis techniques, material modifications, and morphology control for high-voltage spinel LNMO have been reported to improve the electrochemical performance.[4-7] Such as cation doping, surface coating, and creating nanostructures. Meanwhile, the particle morphology of the material, especially the surface crystallographic planes, can also have an obvious influence on the electrochemical properties of material itself.

Herein, a new synthesis approach, allowing shorter material processing, will be presented, which leads to an achievement of special morphology of LNMO cathode material. The obtained LNMO material was characterized by means of X-rays diffractions (XRD), Raman spectrum, electron microscopy (SEM), and electrochemical measurements (CV, EIS, and galvanostatic charge-discharge test). The special morphology enables high-rate performance and cycle life simultaneously. The electrochemical performance was improved remarkably. Detailed discussion will be presented.

References

[1] Goodenough, J. B.; Park, K. S. J. Am. Chem. Soc. 2013, 135, 1167.

[2] Xiao, J.; Chen, X.; Sushko, P. V.; Sushko, M. L.; Kovarik, L.; Feng, J.; Deng, Z.; Zheng, J.; Graff, G. L.; Nie, Z.; Choi, d.; Liu, J.; Zhang, J. G.; Whittingham, M. S. Adv. Mater. 2012, 24, 2109.

[3] Duncan, H.; Duguay, D.; Abu-Leddeh, Y.; Davidson. I. J. J. Elecrochem. Soc.2011, 158, A537.

[4] Chemelewski, K. R.; Lee, E.; Li, W.; Manthiram, A. Chem. Mater.2013, 25, 2890.

[5] Zhang, X.; Cheng, F.; Yang, J.; Chen, J. Nano Lett. 2013, 13, 2822.

[6] Shaju, K. M.; Bruce, P. G. Dalton Trans.2008, 5471.

[7] Zhou, L.; Zhao, D.; Lou, X. Angew. Chem., Int. Ed. 2012, 51, 239.