bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Room Temperature Wafer Bonding of Wide Bandgap Semiconductors
Authors: Mu Fengwen , Wang Yinghui , Suga Tadatomo
Published: February 2020

Si power devices are quickly approaching their limits due to the intrinsic material properties. Wide bandgap semiconductors with the potential to allow significant performance improvement of power devices became very promising. With numerous studies and successive breakthroughs in recent years, wide bandgap semiconductors in term of material and device fabrication technologies have achieved huge advances. For example, large-size single crystalline substrate, high-quality epitaxial layer on hetero/homo substrate, and various power devices have been commercially available [1]. However, it is still very far to make the best use of the devices’ potential at low cost due to the difficult fabrication process and the expensive substrate. New innovative fabrication technologies are urgently desired. Wafer bonding, as one key technology capable of novel structure formation, efficient fabrication, device integration and cost reduction, is expected to be able to solve many problems in the fabrication of next-generation power device [2].

However, most of the previous wafer bonding of wide bandgap semiconductors need an annealing process at high temperature, even higher than 1000oC, which would limit its application in device fabrication. A well-developed low temperature wafer bonding method for wide bandgap semiconductors is still absent [3]. In this paper, our recent progress on the wafer bonding of wide bandgap semiconductors at room temperature would be introduced.

References

H. Okumura, MRS Bull., Vol. 40, pp. 439-444, 2015.

S. H. Christiansen, R. Singh, and U. Gosele, Proc. IEEE, Vol. 94, No. 12, pp. 2060-2106, 2006.

F. Mu, K. Iguchi, H. Nakazawa, Y. Takahashi, M. Fujino, R. He, and T. Suga, Appl. Phys. Express, Vol. 9, pp. 081302:1-4, 2016.
Ion Sieving Effect of Pillared Graphene Materials in Electrochemical Capacitors
Authors: Banda Harish , Daffos Barbara , Dubois Lionel , Taberna Pierre-Louis , Simon Patrice , Crosnier Olivier , Duclairoir Florence
Published: February 2020

Electrical double-layer capacitors (EDLCs), commonly known as supercapacitors, store energy through reversible adsorption of electrolytic ions on the charged electrode surfaces.1 Extensive work on carbide-derived carbons (CDCs), ACs and templated carbons revealed that the sub-micro pores (< 1 nm) contribute significantly to the overall charge storage.2
,
3 Carbon materials with uni-modal pore size distribution curves (PSD) are essential for such a focused analysis.4 However, the difficulties in synthesizing such carbon materials and obtaining their PSDs reliably through gas sorption have hampered the progress.5 Meanwhile, research on graphene derivatives for charge storage in SCs has shown promising advances owing to good surface areas and electrical conductivities. However, much of the current research is devoted to improving the material porosity with a focus on PSDs, similar to the research on ACs.6 Surprisingly, little attention has been devoted towards exploring the possible confinement of the electrolytic ions into the unique layered structures of graphitic materials. An analysis of materials with varied inter-graphene sheets distance (d-spacing) in SCs would assess the possibility of such confinement.

In this context, this study is aimed at understanding the consequences of interlayer spacing on electrochemical charge storage. A class of graphene-like materials with varying d-spacing have been synthesized using alkyl diamines cross-linking and are characterized for their application in SCs. Electrochemical analysis of the materials in SCs using electrolytes containing tetraalkylammonium cations of different sizes (alkyl: ethyl, propyl, butyl and hexyl) showed limitations of ion adsorption in different materials. The PSD curves of the materials show no presence of sub-micro pores (< 1 nm) and thus relate the observed ion limitation to d-spacing. Hence, this work demonstrates that the inter-layer galleries in graphene like materials indeed confine electrolyte ions based on the size constrictions. A correlation between the d-spacing and the electrolyte ion sizes is established and a condition for maximum capacitances versus d-spacing for a specific electrolyte is being investigated.

[1] Simon, P.; Gogotsi, Y. Nat Mater 2008, 7 (11), 845–854.

[2] Merlet, C.; Péan, C.; Rotenberg, B.; Madden, P. A.; Daffos, B.; Taberna, P.-L.; Simon, P.; Salanne, M. Nat. Commun. 2013, 4, 3701-3707.

[3] Raymundo-Piñero, E.; Kierzek, K.; Machnikowski, J.; Béguin, F. Carbon 2006, 44 (12), 2498–2507.

[4] Kondrat, S.; Pérez, C. R.; Presser, V.; Gogotsi, Y.; Kornyshev, A. A. Energy Environ.
Sci. 2012, 5 (4), 6474–6479.

[5] Béguin, F.; Presser, V.; Balducci, A.; Frackowiak, E. Adv. Mater. 2014, 26 (14), 2219–2251.

[6] Li, C.; Shi, G. Adv. Mater. 2014, 26 (24), 3992–4012.
Nano-Engineering of 2D Materials for Supercapacitors
Authors: Zhu Yachao , Simon Patrice , Favier Frederic
Published: February 2020

Exfoliation/restacking of 2D materials has recently been considered for the preparation of nanostructured electrode materials for supercapacitors. This approach consists in rebuilding new electrode materials from exfoliated layers of 2D materials either by restacking layers of different materials, by wrapping 3D materials with exfoliated layers, after chemical/morphological modification of those layers... with the aim of taking advantages of synergistic effects from distinct but complementary intrinsic behaviors together with the specific morphology of the resulting material. This can be, for example, to associate a 2D conductive material with a 2D pseudocapacitive material, eventually resulting in a more powerful nanocomposite electrode material [1]. This can also be about associating Faradaic layered double hydroxides (LDHs), for energy density, to more stable and powerful pseudocapacitive MnO2 [2], or opening a new macro/meso -porosity in Mxene layers for enhanced diffusion of electrolytic moieties in the reconstructed material.

This paper will present our most recent results gained while exploring these various approaches.

References

[1] Z. J. Fan , J. Yan , T. Wei, L. J. Zhi, G. Q. Ning , T. Y. Li, F. Wei, Adv. Funct. Mater. 211, 2011, 2366

[2] W. Quan, C. Jiang, S. Wang, Y. Li, Z. Zhang, Z. Tang, F. Favier, Electrochimica Acta, 2017, 247, 1072
Volumetric Electrochemical Performance of in-Plane and out-of-Plane Structured Multilayer Graphene Supercapacitors
Authors: Yoo Jungjoon , Kim Yong-Il , Lee Chan-Woo , Baek Jeong-Hun , Kim Jong-Huy
Published: February 2020

A graphene electrode with a novel in-plane structure is proposed and successfully adopted for use in supercapacitor applications. The in-plane structure allows the electrolyte ions to interact with all of the graphene layers in the electrode, thereby maximizing the utilization of the electrochemical surface area. This novel structure contrasts with the conventional out-of-plane stacked structure for such supercapacitors. We herein compare the volumetric capacitances of in-plane and out-of-plane structured devices with reduced multi-layer graphene oxide films as electrodes. The in-plane structured device exhibits a 2.5-times higher capacitance than the out-of-plane structured devices. Therefore, this study demonstrates the potential of in-plane structured supercapacitors with high volumetric performances as ultra-small energy storage devices.
Reliability of Silicon Avalanche Photodetector in Geiger Mode
Authors: Zuo Yuhua , Liu Taoran , Zhou Lin , Zheng Jun , Li Chuanbo , Cheng Buwen , Wang Qiming
Published: February 2020

APDs are high-gain semiconductor diodes that produce an avalanche effect at reverse bias voltage, also known as impact ionization. When APDs work in the Geiger mode, due to the theoretically infinite magnification factor, APD can detect single-photon signal. However, compared with the design progress of APDs, life and reliability tests are rarely reported. In this paper, a method for assessing the reliability of silicon APDs is proposed, including the rapid estimation of APD fault activation energy (Ea), the analysis of APD failure mechanisms and assessment of lifetime. The operating life of the APDs is expected to be tens of thousands of hours. For such long-life devices, accelerated life testing is suitable for APDs. In a temperature stress test, in order to maintain the unity of the failure mechanism, temperature limit should be determined by monitoring dark current through a progressive stress test at first. Then another set of samples of the same structure was selected for step stress experiments.The test time and temperature interval were optimized using Arrhenius formula according to the stress limit and failure activation energy. Compared to 15,000h, the expected lifetime of our samples, the test time is greatly shortened, proving the high efficiency of our method. Fail occurs when extending the test time. The main cause of fail is the increase of surface leakage current, which will be verified in subsequent tests. Failure rate increases with time in wear out phase, and strongly depends on the structure of the device. Therefore, in addition to the assessment of lifetime, it is of great significance to improve the device design.
Selective Silicon for Raised Extrinsic Base in PA Applications
Authors: Dongmo Pernell , Luce Cameron , Jain Vibhor , Liu Qizhi , Raman Ajay , Adkisson Jim
Published: February 2020

Selectively-grown silicon deposited via reduced pressure chemical vapor deposition is a well-known epitaxial technique that is used in academia and industry. During a selective Si deposition process, epitaxial silicon is grown on single-crystal Si or poly Si seed layer while suppressing nucleation on dielectric surfaces. This technique is advantageous for BiCMOS development and cost reduction in SiGe manufacturing. GlobalFoundries has leadership in SiGe PA technologies for high-volume WiFi and cellular markets, and also in high performance SiGe technologies. For next generation SiGe PA, p+ selective silicon, or highly-boron-doped silicon, is one of the leading candidates to improve device performance to meet challenging customer demands. Optimizing this process, however, is a non-trivial task. The latest data for p+ selective silicon is discussed.
(Invited) Patterning of Embedded STT-MRAM Devices: Challenges and Solutions
Authors: Berry Ivan , Park Jongchul , Kim Jongkyu , Min Benjamin , Lill Thorsten , Vahedi Vahid
Published: February 2020

Ion Beam Etching (IBE) is emerging as the technology of choice for patterning of advanced embedded MRAM devices (<40nm CD, <1:1 aspect ratio) for 28nm logic integrated circuits. Experimental and simulated etch data, for a representative STT-RAM structure with 38 to 45 nm CD and 150 to 200 nm pitch, show a reduction in the sidewall re-deposition when operating at high angle and high ion energy. Ion energies above 1000eV provide best profile performance in the main etch. However, this leads to intermixing of stack materials and device shorts. Ion energies below 100eV are used in an overetch step to remove the intermixed layer. Excellent beam divergence and energy spread over the entire ion energy range are paramount and requires co-optimization of of the ion beam source and grid. To avoid damage of patterned MgO by air exposure, IBE and encapsulation PECVD must be integrated on one vacuum platform.

Sub 1ppm short fail patterning results have been obtained with optimized IBE and encapsulation processes.
Chromium(III) Sensor Using Ion Selective Membrane Immobilized on FET for Ground Water Pollution
Authors: Shahim Suman , Sukesan Revathi , Hsieh Ching-Yen , Wang Shin-Li , Wang Yu-Lin
Published: February 2020

Anthropogenic industrialization related activities contribute to rising concentrations of heavy metal in the environment. This unprecedented deterioration of water quality by industrial effluents raises severe global health concern to both humanity and the ecosystem. Chromium, the 21st most abundant element on the earth’s crust, is extensively used in steel manufacturing, leather tanning, electroplating, paint and alloy manufacturing industries. The effluents released pollute water with Cr(III); classified as a group III carcinogen causing genotoxicity to flora and fauna. Hence water quality monitoring by detecting heavy metal concentration in tap water, canned liquid food items, etc will be of immense application if the sensor is affordable and equipped with simple user interface. Conventional methods like ICP-MS and AAS demand time, expense and complex equipments which are beyond the scope of daily use.

This work reports detection of Cr(III) employing Field Effect Transistor with Ion Selective Membrane on the gate electrode.The gate metal is extended and terminates in a two sensing electrode configuration modified with Poly Vinyl Chloride based sensing material.It is composed of an ionophore which binds with target analyte; consequently leading to a change in the transistor drain current. High sensitivity, selectivity and fast response time were observed in the pH range 3- 5 beyond which Cr forms hydroxyl complexes.The effective voltage at gate dielectric is a function of the concentration of Cr(III) ions in the test solution dropped on the sensing membrane. The device exhibits increasing trend of current gain with increase in concentration of the target ion as depicted in the plot. Hence, our simple novel biosensor can be calibrated to realize a cost effective, portable device to measure concentration of Cr(III) in real time drinking water quality monitoring or be integrated into food processing systems or even in medical diagnostics.

Figure 1
(Invited) Advanced Crystallization Using Blue Laser-Diode Annealing for Low Temperature Poly Si TFTs
Authors: Noguchi Takashi , Okada Tatsuya
Published: February 2020

Laser Crystallizations using Blue Laser-Diodes Annealing (BLDA) as well as conventional Excimer Laser Annealing (ELA) are discussed for mounting the TFTs on flexible panels.

On glass, high crystallinity of Si films can be obtained by using multi-shots ELA as well as CW laser scanning [1, 2]. There are some issues for Si film after ELA, such as rough Si surface or shots MURA including the fabrication cost. As a result of scanning BLDA for thin Si films, remarkable crystallization occurs with keeping the surface smooth not only for CVD film but also for sputtered Si film [3]. By changing the laser power of 445 nm beam, the grain size can be controlled from micro-grains to large grains as well as to anisotropic long crystal grains [4]. For the Si films of heavily phosphorus doped condition, the resistivity decreased drastically due to the increase in the carrier mobility with high carrier concentration after BLDA of single beam scanning as well as after multi-shots ELA [5].

To realize high performance poly Si films directly not only on flexible glass [6] but also on flexible plastic sheet, effective laser annealing for high quality Si film by low temperature deposition is expected and a design for the thermal buffer layers on flexible sheet is effective [7]. To perform ultra-low temperature TFT process, metal source/drain structure without using ion implantation is also proposed.

High performance poly Si TFTs with low fabrication cost on flexible panel should be possible not only for n-channel but also for p-channel [8, 9].

References

M. Tai, M. Hatano, S. Yamaguchi, S. K. Park, T. Noda, M. Hongo, T. Shiba and M. Ohkura, Proc. of AM-LCD, TFT3-3, p.231 (2002)

T. Noguchi, Mat. Res. Soc. Symp. Proc., 557, p.213 (1993),

T. Okada, K, Sugihara, S. Chinen and T. Noguchi, J. Korean Phys. Soc., 66, No.8, pp.1266-1269 (2015). .

T. Noguchi, J. Inf. Display, 11, No.1, p.12 (2010).

T. Noguchi and T. Okada, J. of Inf. Display, 15, No.1, p.47 (2014).

T. Harada, F. Gakiya, Y. Ishiki, T. Okada, T. Noguchi, K. Noda, A. Suwa and H. Ikenoue, Proc. of IDW, AMDp2-11L, p.444 (2016).

T. Okada, J.D. Mugiraneza, K. Shirai, T. Suzuki, T. Noguchi, H. Matsushima, T. Hashimoto, Y. Ogino and E. Sahota, Jap. J. Appl. Phys. 51, 03CA02 (2012).

K. Sugihara, K. Shimoda, T. Okada and T. Noguchi, J. Inf. Display, 18, No.4, 173-176 (2017).

T. Ashitomi, T. Harada, T. Okada, T. Noguchi, O. Nishikata and A. Ota, J. Inf. Display, 18, No.4, 185-189 (2017).
(Invited) Organic-Inorganic Hybrid Perovskite Tfts with MoO3 Modified Electrodes
Authors: Li Juan , Xu Jian , Tang Linlin , Ze Pengyu , Zhou Zhou , Zhang Jianjun
Published: February 2020

Abstract: Organic-inorganic hybrid perovskites have attracted substantial attention because of their excellent physical properties, which enable them to serve as the active material in emerging hybrid solar cells. Here, we proposed a new type of thin-film field-effect transistor (TFT) with an organic-inorganic hybrid perovskite channel layer. The organic-inorganic hybrid perovskite material has advantages of a high mobility like that of an inorganic semiconductor and the easy process like an organic layer. A TFT using CH3NH3PbI3 as the semiconducting channel was demonstrated. The effect of the evaporation amount of PbI2 on the crystallization and thickness of CH3NH3PbI3 films was studied. The organic-inorganic hybrid perovskite thin film with an average grain size of 1µm and a smooth surface has been achieved . The MoO3 was adopted as a buffer layer between metal electrodes and the active layer, which remarkably reduced the contact resistance from 705 kΩ·cm to 0.164 kΩ·cm, resulting in the improvement of the interface characteristics and performance of devices. The organic-inorganic hybrid perovskite TFT with the field effect mobility of 3.88cm2/V.s and the subthreshold slope of 1.6 V/dec. was achieved. Fig. 1 shows its transfer curves. This kind of TFT can be processed by cheap, low-temperature techniques, which suggest that it may be suitable for applications that require low cost, a large area, and the flexibility. Molecular engineering of the organic and inorganic components of the hybrids perovskite is expected to further improve device performance for high speed application.

Figure 1
(Invited) Thin Film Transistor Response to Terahertz Radiation
Authors: Shur Michael
Published: February 2020

Increasing sophistication, improved performance, and application of new material systems ranging from wide band gap oxides to van der Waals materials make testing Thin Film Transistor (TFT devices and circuits a growing challenge. We recently developed a new testing technique using the sub-terahertz (sub-THz) and THz radiation for testing electronic components, including transistors, Microwave Monolithic Integrated Circuits (MMIC) and Very Large Scale Integrated (VLSI) circuits. The THz radiation impinging on the transistors couples via contacts or interconnects and excites overdamped waves of the electron density – plasma waves - that are rectified by the transistor nonlinearities. This rectification results in the induced DC signal between the transistor contacts. The impinging THz modulation is modulated at a low frequency and a lock-in amplifier amplifies the resulting slowly modulated DC response. The resolution of this technique is better than the device feature size and scanning the beam allows to record the response images. The transistor response is sensitive to the applied bias voltage. The comparison of the responses between good and defective devices or circuits allows for developing the defect signatures. To analyze the application of this technique to TFTs, we introduce and analyze the TFT current dispersion length that determines the penetration of the radiation induced signals into the device channel and calculate the responsivity as a function of frequency for different TFT feature sizes using TFT Unified Charge Control Model. We also analyze the effect of the contact resistances and fringing parasitic capacitances on the response. Our results demonstrate the applicability of this new testing technique for the TFT testing.
(Invited) Oxide Heteroepitaxy for Soft Technology
Authors: Chu Ying-Hao
Published: February 2020

A new world is being formed based on the technologies composed of artificial intelligence, Internet of Things (IoT), and robot systems. Especially, in the research fields of IoT and robot systems, a device with mechanical flexibility can deliver more degrees of freedom on design of the systems. Therefore, the development of soft and flexible electronics becomes an important research direction for wearable and IoT devices. Due to the mechanical flexibility, polymers materials and thin foils made of metals are commonly used in the fabrication of flexible electronic systems. However, the reliability issue under practical operation hinders the applications of these flexible electronics, especially those on polymer substrates. This is attributed to a mismatch of thermal expansion coefficient between substrate and functional materials or low thermal and chemical endurance of polymers and organic materials. A lot of researchers are working hard and together to expand the applicability of current flexible devices. However, new pathway to flexible electronics can also be developed in parallel to provide more subtle solutions, thus needing new platform to integrate functional materials with good thermal and chemical stabilities together with mechanical flexibility. Recently, due to the quick rise of growth facilities, various techniques are employed to acquire flexible oxide heteroepitaxy. In this talk, I will highlight the methods to develop oxide heteroepitaxy with mechanical flexibility, including direct and indirect approaches. I will also provide an overview that classifies the application fields where flexible oxide heteroepitaxy have been adopted and the approach which has been used to develop particular oxide with the emphasis on electronic and photonic devices.
(Invited) Ion Transport in Low-Dimensional Ionic Conductors
Authors: Battaglia Corsin
Published: February 2020

We discuss ionic transport in fast lithium and sodium ion conductors, which receive renewed attention as solid-state electrolytes for all-solid-state batteries. Because transport of ions across interfaces can differ strongly from that in the bulk, the DC conductivity relevant for battery operation cannot be measured directly by impedance spectroscopy. We discuss models that accurately describe the impedance spectra of prototypical solid-state electrolyte materials including the effect of grain boundaries and ion-ion correlations.
(Invited) Molybdenum Sources Containing Alkali-Metals for the Low Temperature Growth of Optical Grade Monolayer MoS2
Authors: Medina Henry , Tong Shi Wun , Yang Weifeng , Manzano Carlos , Tan Lee Kheng , Wong Swee Liang , Tjiu Weng Weei , Chi DongZhi
Published: February 2020

Two dimensional (2D) transition metal dichalcogenides (TMDCs) based on molybdenum (Mo) and tungsten (W) are optimum building blocks for low power optoelectronic devices due to their particular electrical and optical properties when approaching to the monolayer. Unfortunately, those outstanding properties are usually associated with the synthesis of highly crystalline films at high temperature on specific substrates. In particular, for the synthesis of molybdenum disulphide (MoS2), temperatures over 650 °C are usually required to reach the sublimation point of the commonly used Molybdenum (VI) Oxide (MoO3). Different approaches such as plasma have demonstrated the possibility of the formation of MoS2 at low temperature at expenses of poor crystallinity displaying poor electrical and optical properties reflected in low mobility devices and decreased photoluminescence (PL). Here, we show that using alkali-metal containing sources mixed with MoO3, the sublimation point can be further decreased below 500 °C. The reactive Mo source sublimated at this temperature allows the formation of highly crystalline monolayer films with a PL comparable to those films synthesized at high temperature. Thermogravimetric measurements support the decrease of the sublimation point of Mo using alkali containing sources compared to the sublimation point of pure MoO3. In addition, Raman and PL mappings supported by X-ray Photoelectron Spectroscopy and TEM observations, confirm the quality and crystallinity of the synthesized films. More important, by using a low temperature process, the range of substrates used for synthesis can be further increased. As a proof of concept MoS2 was grown on low cost commercial borosilicate glass suitable for TFT applications.
Introduction of Coherent X-Ray Diffraction Microscopy to Analyze Manganese-Based Olivine Cathode Materials in Lithium-Ion Batteries
Authors: Park Jungjin , Sung Yung-Eun , Kim Chunjoong , Shapiro David
Published: February 2020

The carbon-coated LiMn0.8Fe0.2PO4 (LMFP) mesocrystals were designed to be favorable for kinetics of electron and lithium-ion conductivity due to its well-developed internal path composed of ~50-nm-sized nanocrystallites. The carbon-coated LMFP mesocrystals exhibited reasonable electrochemical cycle performance as well as superior rate capability, ensuring a proper model material to systematic study of reaction mechanism upon battery cycling. In order to investigate the reversibility of charge/discharge reaction on carbon-coated LMFP mesocrystals, we performed coherent x-ray diffraction microscopy to confirm the electronic-structure effects of each transition metal (Mn and Fe) and morphological changes. In addition, the electrochemical impedance spectroscopy at quasi-steady state has been analyzed as a supplementary tool. We believe that our systematic approaches as well as complementary analyses can provide clear experimental inspection on the origin of homogeneity/ inhomogeneity of charge/ discharge in LMFP electrodes via coherent x-ray diffraction microscopy and electrochemical impedance spectroscopy.
Molybdenum Doped Li2RuO3 As New Cathodes for Lithium Ion Batteries
Authors: Cui Yanhua , Cui Yixiu , Wang Jiali , Zhao Yu
Published: February 2020

Lithium-ion batteries have become the most widely used power source for the energy storage device , such as portableelectronic devices, long range electric vehicles andsmart grids. However, the energy densities of the state-of-the-art lithium-ionbatteries still cannot meet the increasing demand. As one of the most promising alternative electrochemical battery cathode materials, the lithium-rich layered oxides exhibit high specific capacities (230-250 mAh g−1) among all the cathode materials. The main drawback including voltage fade, large initial capacity loss, poor rate capability and limited cycle life hinder its practical applications. Approach strategies such as ionic doping and surface modification have been developed to improve the electrochemical performance and understand the origins of its high capacity, voltage decay and capacity fade in recent years. Herein, we successfully synthesized Mo-Doped Li2RuO3 through a solid-state reaction and systematically investigated the electrochemical performance of Li2Ru1-xMoxO3 (x = 0, 0.01, 0.02, 0.05) series. The results indicate this series materials show an enhanced electrochemical lithium reversibility than the pristine Li2RuO3 ， and Li2Ru0.98Mo0.02O3 exhibits the best performance in terms of specific capacity. Low content of Mo doping could realize an enhanced performance that originated mainly from the improved reversible anionic redox chemistry and charge transfer kinetics. It provide another choice for cathode materials for high performance LIBs.

Figure 1
(Invited) Understanding the Oxygen Release at High Potential for Transition Metal Oxides
Authors: Grimaud Alexis
Published: February 2020

The design of new materials is a pivotal question for the development of the next generation of electrochemical energy storage and conversion devices. Recently, triggering the redox activity of oxygen ions in transition metal oxides used as positive electrodes for Li-ion batteries was proposed as a promising strategy to develop Li-rich compounds with reversible capacity exceeding those of classical insertion layered compounds. Nevertheless, the science at play must be rationalized in order to control this phenomenon and assess the potential applications of such Li-rich electrodes. Indeed, following this discovery, fundamental questions remain. Among them, the exact nature of the oxygen species formed upon oxidation is critical since it governs not only its redox potential but also the discharge behavior for which sluggish kinetics and hysteresis were observed. Using recent examples, the different types of oxygen species will be discussed and their electrochemical behavior compared. Moreover, while early measurements suggested gaseous oxygen to be produced for these Li-rich at potentials above 4.3 V vs. Li+/Li, recent observations point toward oxygen evolution within a potential range that can span from 3.5 to 4.5 V vs. Li+/Li. This observation asks for 1) the development of new analytical tools in order to accurately detect and quantify these gaseous species and 2) to rationalize the standard potential for the evolution of lattice oxygen from the transition metal oxides. These two points will be discussed and strategies to circumvent this detrimental phenomenon will be proposed.
(Invited) Chemical Phenomena at Interfaces between Battery Cathodes and Electrolytes
Authors: Cabana Jordi
Published: February 2020

Controlling the reactions occurring at electrode-electrolyte interfaces is key to long-lasting energy storage technologies, such as Li-ion batteries, especially when pushing voltages of operation to increase their energy density. Extreme potentials reached at the electrodes in a fully charged battery render them too reactive toward the electrolyte, triggering deleterious decomposition reactions. While the description of products resulting from electrolyte decomposition has been an object of study for decades, the definition of reactions at the cathode side of the interface is less extensive. The cathodes in a battery are composed of transition metal oxides, which are known to present a rich redox chemistry. During this talk, tools employed to track the structure and chemistry of the surface of cathode particles vis-à-vis their electrochemical properties will be presented. Particular emphasis will be placed on X-ray absorption spectroscopy, a technique with surface specificity that probes redox chemistry. The results revealed that side reactions on the electrolyte are synchronized with the redox processes at the oxide surface, which ultimately lead to the dissolution of transition metal ions into the electrolyte.

Classical strategies to prevent these undesired reactions and increase electrode durability generally involved post-synthetic coatings of the cathode powders or the use of electrolyte additives. More recently, new effective options have been added through the demonstration, in our group, of core-(epitaxial) shell architectures at the level of primary particles. Yet the description of the exact modes of degradation and the means by which these strategies are effective remains elusive. The use of objects of study designed at the highest definition and fidelity, in the form of highly dispersed nanocrystals with conformal shells, enhances the understanding of these interfacial phenomena. The high fidelity ensures coherence in the data and the representative character of the characterization methods, especially when highly local probes are employed. The interplay between understanding of electrode-electrolyte processes and the design of novel cathode architectures will be discussed.
Enhanced Reversibility of ZIF-8-Derived Carbon-Coated ZnO Anode in the Presence of Fluoroethlyene Carbonate
Authors: Park Junghoon , Kim Sang-Ok
Published: February 2020

Development of advanced electrode materials is considered essential for achieving high-performance rechargeable batteries for the fast-growing electric vehicle and grid energy storage applications. Herein, a core-shell structured nitrogen-doped carbon-coated ZnO is prepared via the growth of zeolitic imidazolate frameworks (ZIF–8) on the ZnO surface followed by thermal decomposition under inert atmosphere. The microstructural characterization of the composite shows that ZnO particles are encapsulated within a highly conductive carbon nanolayer. By forming a LiF-rich solid electrolyte interphase (SEI) in the presence of the fluoroethylene carbonate additive, the ZnO-based composite exhibits a high specific capacity of 798 mA h g-1 with an initial Coulombic efficiency of 81%, good capacity retention of over 300 cycles at 1 A g-1, and improved rate performance up to 2 A g-1. These results demonstrate that the combination of the multifunctional ZIF–8-derived carbon coating and the introduction of electrolyte additive as a SEI modifier significantly improves the electrochemical performance of high-capacity ZnO anode.
Thermally Treated Sodium Carboxymethyl Cellulose Binder for Si Alloy Anodes
Authors: Yan Zilai , Obrovac Mark N
Published: February 2020

Binder is a key component for enabling good cycle life of Si and Si-based negative electrode materials in Li-ion cells, despite comprising only 2-10 wt% of the electrode coating. In previous research, thermal carbonization of polymer binders, e.g. polyvinylidene fluoride (PVDF),1 cyclized polyacrylonitrile (PAN),2 and poly(amide imide),3 was shown to enhance the cycling performance of high energy density alloy anodes greatly. For instance, sintered Si electrodes with PVDF binder can maintain a reversible capacity of 1150 mA h g-1 over 500 cycles at 1C rate.1 Among various binders, sodium carboxymethyl cellulose (Na-CMC) has some favorable characteristics: abundance, low cost, high water solubility, good thickening properties, and a high carboxmethyl group content, which is responsible for surface binding interactions with Si.4,5 To our best knowledge, the effect of heat treatment on Na-CMC binder for Si-alloy containing anodes has not been explored yet.6

Here, electrodes were composed of 60 wt% Si alloy, 28 wt% graphite, 2 wt% carbon black (CB), and 10 wt% Na-CMC. Some of electrodes were sintered under Ar flow by heating up to 300 or 600 °C at a rate at 10 ºC/min, and then held at 300 or 600 °C for three hours. Figure 1(a) shows the TGA curve of Na-CMC polymer in the temperature range of 25-800 ºC under Ar gas. After being heated at 600 ºC in Ar, Na-CMC has a mass residue of 38.6 wt.%. The pyrolysis product consists of amorphous carbon (42 wt.%) and Na2CO3 (58 wt.%). The cycling capacity retention of Si-alloy/graphite electrodes with Na-CMC binder is shown in Figure 1(b). The unheated electrodes suffer from significant capacity fade, having only 78% capacity left after 100 cycles. The capacity retention is improved when the thermal treatment is applied. After heating at 300 ºC, the capacity retention after 100 cycles was improved to 87%. A significant improvement of capacity retention results when 600 ºC thermal treatment is applied: over 95% capacity is retained. The formation of Na2CO3 in a network of amorphous carbon contributes to this high capacity retention.

Reference

F. M. Hassan, V. Chabot, A. R. Elsayed, X. Xiao, and Z. Chen, Nano Lett., 14, 277–283 (2014).

F. M. Hassan, R. Batmaz, J. Li, X. Wang, X. Xiao, A. Yu, and Z. Chen, Nat. Commun., 6, 8597 (2015).

H. S. Yang, S. H. Kim, A. G. Kannan, S. K. Kim, C. Park, and D. W. Kim, Langmuir, 32, 3300–3307 (2016).

U. S. Vogl, P. K. Das, A. Z. Weber, M. Winter, R. Kostecki, and S. F. Lux, Langmuir, 30, 10299–10307 (2014).

C. C. Nguyen, T. Yoon, D. M. Seo, P. Guduru, and B. L. Lucht, ACS Appl. Mater. Interfaces, 8, 12211–12220 (2016).

R. Petibon, V. L. Chevrier, C. P. Aiken, D. S. Hall, S. R. Hyatt, R. Shunmugasundaram, and J. R. Dahn, J. Electrochem. Soc., 163, A1146–A1156 (2016).

Figure
1 (a)TGA curves of Na-CMC collected at a heating rate of 5 ºC/min under Ar gas. (b) Capacity retention of three V6/SFG6L/CB/Na-CMC electrodes: untreated, heated at 300 ºC in Ar, and heated at 600 ºC in Ar.

Figure 1
Effect of RGO Coating of Li-Rich Cathode Material on Electrochemical Performance
Authors: Lim Sung Nam , Kim Kiyoung , Song Shin Ae
Published: February 2020

Li-rich, xLi2MnO3∙(1-x)LiMO2 (M = Ni, Co and Mn), cathode material have attracted interest due to their high capacity (>250 mAh g-1), which is a key characteristic required for a power supply to meet the energy demands of electric vehicles. However, they still were hard to use commercial cathode material, because their poor rate capability and inferior cycle performance caused by low electronic conductivity of active material and phase transformation induced from side reaction. To solve these critical problems, many groups have suggested coating the cathode material with a more stable material such as Al2O3, TiO2, and Li4Ti5O12. However, these coating materials lead to poor rate capability owing to their electronic insulated property, although they enhance cycle performance.

In this study, we prepared RGO costed Li-rich cathode material by using self-assembly to enhance rate capability as well as cycle performance. We investigated the effect of RGO coating on physical properties of cathode material such as structure, morphology and surface property. And we also investigated effect on the electrochemical performance.
Structural Effect of Conductive Carbons on the Adhesion and Electrochemical Behavior of NMC-442 Cathode for Lithium Ion Battery
Authors: Latifatu Mohammed , Yoon Choong Sup , Ko Jang Myoun
Published: February 2020

The adhesion strength as well as the electrochemical properties of LiNi0.4Mn0.4Co0.2O2 electrodes containing fiber-like carbon; vapor grown carbon fiber (VGCF), carbon nanotube (CNT) and particle-like carbon; super P (SP), ketjen black (KB) were compared. The morphological properties revealing the interaction between the different conductive carbons (CCs) and the active material was investigated using scanning electron microscope. The adhesion strength between the aluminum current collector and the composite film (AC/Al), and the adhesion strength between the active material and the CCs (Amid) of the electrodes were measured using surface and interfacial cutting analysis system (SAICAS). The results obtained from the measured adhesion strength points to the fact that, the structure and the particle size of conductive additives have tremendous influence on the binding property of the composite electrodes and this in turn affects the electrochemical property of the configured electrodes.
Electrochemical Performance of Uspld Prepared Silicon Anode Electrodes
Authors: Valikangas Juho Pekka , Lassi Ulla , Hu Tao
Published: February 2020

Introduction

Secondary battery materials are in great demand of research and new high energy density materials are required for higher quality of batteries1. Silicon based anode is one of the most promising anode material for Li-ion batteries, because it has high theoretical capacity (4200 mAh/g, lithiated to Li4.4Si) and low operating voltage (~0.3V versus Li/Li+) 2,3 Challenges for silicon based anode are the capacity fading during the first cycle and the poor cycle performance.

Experimental

Si layers on copper foil were produced by Picodeon’s ultra-short pulsed laser deposition (USPLD) technology. This technology utilizes pulsed lasers with pulse lengths in the picosecond range and high pulse repetition rates (MHz). The pulsed laser beam is delivered to the surface of the target, which is placed inside a vacuum chamber, through a scanner and a telecentric lens. With this beam delivery approach a focused scan line can be produced on the target. Material is removed by the laser pulses from the target material, and movement of the substrate through the material cloud generated by this line source enables straightforward deposition of uniform layers even on larger surface areas.

Cells with USPLD prepared Silicon anode and LiNi0.5Co0.2Mn0.3O2 cathode were prepared in the humidity controlled dry room. Cathode thicknesses were controlled to have different specific capacities for the silicon anode material. Different type of electrolytes and testing parameters were used to achieve better electrochemical results for USPLD silicon anodes.

Results and discussion

Results showed that electrochemical testing parameter and materials used in the tests have great influence on the electrochemical performance of silicon anode materials. Especially, additives used in the electrolyte seems to have a great influence on the cycle performance of silicon based anode material. Results also showed that silicon material should not charge full, instead 1500 mAh/g show much better electrochemical properties. Results also clarified some problems with half-cell and full-cell tests.

We have demonstrated that the 10µm thick 100% silicon anode layer prepared by USPLD can replace 50µm graphite layer in the Li-ion cell. Total energy density is higher for silicon-NCM cell than for graphite-NCM cell after hundred cycles. Still challenge is the poor cycle performance compared to graphite anode; however, results showed that it is possible to improve cycling properties by electrolyte additives and limiting charging capacity. Silicon based anode material is a good candidate for the next generation Li-ion battery.

Reference
s
:

W Choi and D. Aurbach (2016) Nature rewiew materials 1. (2016) 16013

A Huggins (1999) Journal of Power Sources, Vol 81-82, pp.13-19

Hui Wu, Yi Cui (2012) Nanotoday, Vol 7, issue 5, pp 414-429
(Invited) Synthesis of 3D Network Graphene Based on Physical Metallurgy
Authors: Zhao Naiqin , Ma Liying , He Chunnian , Sha Junwei
Published: February 2020

As a new nanocarbon material with excellent mechanical, physical and chemical performances, graphene has been attracted wide attentions for the applications in many field, especially for the electrode materials of energy storage devices. The high quality, controllable and effective synthesis of GN are main issues for its application. A 3D network structural graphene is promising for increase the electrochemical properties. We report a synthesis strategy by combining chemical method with physical metallurgy，achieving high quality and effective synthesis of 3D network graphene from powder, sheet to bulk foam. Chemical vapor deposition, de-alloying and powder metallurgy methods have been successfully used for the synthesis. Furthermore, carbon nanotubes(CNTs) was introduced in the 3D graphene for increasing the strength and conductivity. The processes and effects of chemical and physical process on the graphene structure are introduced and investigated, and the performance of the 3D-GN as the electrode materials in supercapacitor and lithium ion battery are explored. Without any current collectors and binder employed, a lithium ion capacitor (LIC) was assembled by 3D graphene reinforced by CNTs, which can achieve a high active materials mass loading per area, a large operating voltage window (0.01-4.2 V), current density per area (> 3 mA cm-2) and comparable energy density per mass (32 Wh kg-1), as well as excellent long cycling performance. Therefore, the 3D graphene are expected to be ideal electrode materials in high-performance electrochemical energy storage devices.
Application of Carbon Nanotubes Doped with Silicon As the Anode Electrode for Lithium Ion Battery
Authors: Zeferino González Isaias , Chiu Hsien-Chieh , Gauvin Raynald , Demopoulos George P. , Verde Gómez Ysmael
Published: February 2020

It is well known that the structural modification of carbon nanotubes (CNT) with heteroatoms, could modify their physical and chemical properties. These modifications open the possibilities to improve the electrochemical performance of CNT thus enhancing their application in batteries for storage of lithium ions. However, to achieve such characteristics it is important to control its structure, morphology and chemical composition during synthesis. In this work, the CNT were modified in situ by the intercalation of silicon (CNT-Si) in the graphitic carbon network to be used as an anode electrode in lithium ion battery. CNT-Si were synthesized by a modified chemical vapor deposition; toluene, ferrocene and triphenylsilane were used as carbon source, metal catalyst and silicon precursor, respectively. The effect of doping and temperature was investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X ray photoelectron spectroscopy (XPS). The microscopy results showed that the CNT-Si were structurally modified with various forms of roughness, distortions and defects not only in the inner walls but also on outer walls. The elevated synthesis temperature had the most significant effect in the graphitic carbon network. According to the Raman scattering, the CNT-Si presented greater structural disorder due to the integration of silicon atoms in the carbon, which increased the disorder in hexagonal network. Elemental analysis composition by XPS indicated that the silicon was intercalated preferably at a higher temperature with a concentration of 0.76±10 at. %, clearly showing that silicon was successfully linked in the carbon network as Si-C. In order to examine the electrochemical properties of the materials, CNT-Si were used as an anode electrode for galvanostatic charge and discharge tests, as well as for cyclic votammetry curves. The results highlighted that temperature played a very important role on the electrocatalytic characteristics of materials and the insertion of the silicon in the carbon structure provided more sites for the diffusion and storage of lithium. The processes of alloying and de-alloying lithium in the CNT-Si matrix, charge and discharge capacity, as well as its cyclic performance will be discussed.
Ammonia for Proton Conducting Medium in Metal-Organic Frameowkrs
Authors: Lim Daewoon , Kitagawa Hiroshi
Published: February 2020

Proton transport is essential and critical in a biological system and electrochemical devices. In particular, the fundamental understanding of proton conduction mechanism in conducting medium is important to design the efficient proton conductor. The overwhelming majority of proton conducting medium is water (H2O) which was intensively investigated because water can form the efficient hydrogen bonding networks by symmetric two proton donor and two acceptor sites resulting in degenerated proton conduction system (H3O++H2O ⇔ H2O+H3O+). In this point of view, we believe that ammonia (NH3) can be a next promising conducting medium due to its similar molecular system to water. Specifically, it shows a small molecular size (2.60 Å), three proton donor sites/ one acceptor site, and degenerated proton conduction system (NH4
++NH3 ⇔ NH3+NH4
+). Considering the fluid phase of NH3, a confined environment should be required to achieve NH3 proton conductor. The porous crystalline metal-organic frameworks (MOFs), tunable solid, are emerging as a new class of solid electrolyte because of a considerable porosity and versatile sorptivity. In particular, the pore of MOFs is a suitable platform to confine the guest molecules. In addition, a simultaneous proton donation from framework to NH3 can induce the conjugated acid-base system in the pores.

Here, we show, for the first time, proton conductivity through the simultaneously confined NH3 in MOFs by NH3 adsorption. We choose highly stable Al-based MOFs consisting of one-dimensional channel and MO4(OH)2 secondary building units (SBUs) interconnected by dicarboxylate groups. Fuethermore, we can tune the pore environment by using the different fuctionla groups of ligand. We found cooperative ammonia adsorption with simultaneous ammonium formation and the highly enhanced proton conductivity as NH3 pressure increases. Tthe structure analysis of MOFs incorporating NH3 by Rietveld refinement and dynamic motion study of confined NH3 by 2H solide-state NMR help to understand proton conduction mechanism. These results clearly support the Grotthuss mechanism not seen in bulk NH3 system. We believe that this research may provide a design strategy for material using NH3 as a conducting media as well as an energy carrier.