bluuebunny/crossref_metadata_2025 huggingface dataset:
Thermal Conductivity of Ultrananocrystalline Diamond/Nonhydrogenated Amorphous Carbon Composite Films Prepared By Coaxial Arc Plasma Deposition
Authors: Takeichi Satoshi , Nishiyama Takashi , Kohno Masamichi , Takahashi Koji , Katamune Yuki , Yoshitake Tsuyoshi
Published: February 2020

Diamond possesses the highest thermal conductivity (2 × 103 Wm-1K-1) in all bulk materials, owing to low phonon scattering in diamond. Since phonon scattering is drastically enhanced by grain boundaries, the thermal conductivity of polycrystalline diamond films is strongly dependent on the grain size. The thermal conductivity of ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite (UNCD/a-C:H) films comprising a large number of UNCD grains with diameters of less than 10 nm and an a-C:H matrix have been prepared mainly by chemical vapor deposition (CVD). The highest thermal conductivity reported so far is 12 Wm-
1K-
1, which is comparable with that of sp3-rich non-hydrogenated amorphous carbon (a-C). It has been reported for a-C:H and UNCD/a-C:H films that the thermal conductivity is degraded by the incorporation of H atoms in the films.

Recently we have realized the formation of UNCD/a-C films comprising UNCD grains and an a-C matrix, by coaxial arc plasma deposition (CAPD). CAPD does not necessarily require a hydrogen atmosphere during the deposition for the formation of diamond grains. So far, the thermal conductivity of hydrogen-free UNCD/a-C films has never been studied because H atoms are unintentionally incorporated into the films from source gases in CVD. In this study, UNCD/a-C films were deposited under a base pressure, and the thermal conductivity of the films were measured for the first time to our knowledge.

UNCD/a-C films were deposited on n-Si substrates at base pressures of less than 10-4 Pa and the substrate temperature of 550 °C using coaxial arc plasma gun equipped with a graphite target. Mo films with the thickness of 80 nm were deposited on the UNCD/a-C films by sputtering for the TDTR. The thermal conductivity of the UNCD/a-C films was measured by a time-domain thermoreflactance (TDTR) technique.

The thermal conductivity of the UNCD/a-C films was estimated to be 23.7 Wm-
1K-
1 by TDTR. The thermal conductivity is evidently higher than that of UNCD/a-C:H prepared by CVD. Two reasons for it are supposed. One is that an a-C in UNCD/a-C is probably advantageous for thermal conduction as compared with an a-C:H in UNCD/a-C:H, since it has been reported for a-C:H that the thermal conductivity decreases with increasing hydrogen content in a-C:H. The other is that UNCD/a-C does not contain hydrogen atoms that prevent from phonon scattering, whereas the preferential existence of hydrogen atoms at grain boundaries between UNCD grains and those between UNCD grains and an a-C:H matrix enhances phonon scattering for UNCD/a-C:H films prepared by CVD, which results in a decrease in the thermal conductivity. Further details will be presented in the conference.
Field Emission from Titanium-Coated Carbon Nanotubes Grown on Micron-Sized Silicon Pillar Arrays
Authors: Uh Hyung Soo , Park Sangsik
Published: February 2020

Carbon nanotubes (CNTs) have attracted great attention because of their unique physical properties such as high mechanical strength, thermal stability and electrical properties[1]. Because CNTs have high electron emission efficiency at low voltage due to their high aspect ratio, CNTs have been regarded as the most efficient electron emitter among various materials such as metal, semiconductor. However, the electric-field-screening effect of the dense CNTs and relatively high work function of CNTs (~ 5 eV) degrades the emission performance significantly[2,3]. CNTs grown on uneven substrate can reduce electric-field-screening effect and coating of CNTs with lower work function leads to enhanced field emission. In particular, it is reported that the coating Titanium (Ti) on CNTs affects the work function and the substantial change in surface morphology of CNTs most significantly[4].

In this paper, we report the combined effect of suppression of electric-field-screening and lower work function on field emission characteristics by Ti-coated CNTs on micron-sized silicon (Si) pillar arrays. Micron-sized Si pillar arrays are formed using conventional photolithography process including reactive ion etching by mixture gas of SF6 and Ar. CNTs are grown on Invar(52% Fe-42% Ni-6% Co alloy) catalyst using C2H2 as a source gas by inductively-coupled plasma-enhanced chemical vapor deposition. Then, Ti with 5 nm thickness is optionally coated on CNTs by sputtering method and field emission behaviors are investigated in a diode configuration in the vacuum of ~10-7 Torr.

Field enhancement factor for CNTs on Si pillar arrays was higher by 15% compared with that of CNTs on Si. The application of Ti on CNT surface reduced turn-on field by 30% further compared with that of pristine CNTs. In addition, coating of CNTs also improved emission stability by strengthening the adhesion between CNTs and substrate. We expect that the Ti-coated CNTs grown on micron-sized silicon pillar arrays can be excellent electron sources, providing a very stable current at very low ﬁelds by reduction of electric-field-screening effect and effective work function of emitters..

 

References:

[1] M. S. Dresselhaus, G. Dresselhaus, P. Avouris, Carbon Nanotubes: Synthesis, Structure, and Application, Springer, Berlin (2001).

[2] M. Shiraishi, M. Ata, Carbon 39 (2001) 1913.

[3] L. Nilsson, O. Groening, C. Emmenegger, O. Kuettel, E. Schaller, L. Schlapbach, H. Kind, J. M. Bonard, K. Kern, Appl. Phys. Lett. 76 (2000) 2071.

[4] Y. Cho, C. Kim, H. Moon, Y. Choi, S. Park, C.K. Lee, S. Han, Nano Lett. 8 (2008) 81.

Figure 1
Observation of Ferromagnetic Semiconductor Behaviors from Graphene Doped with Manganese-Oxide By Electrochemical Method
Authors: Park Chang-Soo , Qiu Dongri , Shon Yoon , Kim Eun Kyu
Published: February 2020

Ferromagnetic semiconductors have attracted much attention in the field of spintronic application, because future electronic devices will have a switchable magnetic ordering in semiconductors for exploiting spin rather than charge. The key importance of the magnetic semiconductor is the Curie temperature to maintain the ferromagnetic ordering at room temperature. A high Curie temperature above room temperature has been shown in carbon-based materials. Recently, graphene which is an atomically monolayer graphite, has been an important issue for future spin electronic devices due to the high mobility and superb material properties. Especially, a theoretical result showed that graphene with defects behaves like a diluted magnetic semiconductor (DMS). In general, sp2 hybridized carbon atoms in graphene have an unsaturated dangling bond, which induces various surface modifications. Therefore, doping onto graphene easily leads to modification of the electronic structure, magnetic property, and carrier density.

In this work, we report an electrochemical doping of manganese-oxide onto graphene, and also investigate the ferromagnetic semiconductor behavior from the manganese-oxide doped graphene. We have doped a manganese-oxide onto graphene by an electrochemical method. Graphene showed a clear ferromagnetic semiconductor behavior after doping of manganese-oxide. The manganese-oxide doped graphene has a coercive field (Hc) of 232 Oe at 10 K, and has the Curie temperature of 270 K from the temperature-dependent resistivity using transport measurement. The ferromagnetism of manganese-oxide doped graphene attributes to the double-exchange from the coexistence of Mn3+ and Mn4+ on the surface of graphene. In addition, the semiconducting behavior is caused by the formation of manganese-oxide on graphene.
Chemical Etching and Transfer for Fabrication of Transparent Graphene Electrodes
Authors: Ishihara Masatou , Okigawa Yuki , Yamada Takatoshi , Hasegawa Masataka
Published: February 2020

Conventional transparent electrodes make use of indium tin oxide (ITO) and are commonly used in touch screens, ﬂat panel displays and solar cells. Nearly 90% of ITO film market is for the touch screen application, which is expected to grow more and more in the future. Graphene is potential candidates for transparent conductive films for electrical and optoelectronic devices and various other applications due to its high electrical conductivity, chemical and physical stability. High-quality graphene films have been synthesized by microwave plasma treatment of a copper substrate with Joule heating using low concentration carbon source.

 The copper foils with A4 (211 mm X 297 mm) size are used as substrate. Few-layer graphene was deposited on the copper foil for a few minutes. The transfer of the graphene films to a desired target substrate is enabled by the wet-etching of the underlying copper foil. This is carried out by treating the film with an aqueous (NH4)2S2O8 solution after a support material is covered on the graphene/copper surface, in our case a surface protective sheet. The graphene/sheet film is placed on the 188-mm thick polyethylene terephthalate (PET) substrate (graphene facing the surface). The surface protective sheet is removed from a sheet/graphene/PET film. We measured the transmittance and sheet resistance of the graphene/PET by using a haze meter and a four probe method, respectively.

 The transmittance was 96% (except PET substrate) and the sheet resistance was about 500 ohm. Subsequently, graphene/PET film was doped with gold (III) chloride solution to decrease its sheet resistance. After doping processes, the sheet resistance of the graphene/PET films decreases below 150 ohm.

 Acknowledgment: This work is mainly based on results obtained from a project supported by

New Energy and Industrial Technology Development Organization (NEDO).
Dominant Formation of Carbon Nano or Microcoils By the Manipulation of SF6 Injection Flow
Authors: Kim Dongchul , Kim Sung-Hoon , Lee Jae-Kyung
Published: February 2020

Carbon nano or microcoils were synthesized using C2H2 flow as a source gas along with an injection of SF6 flow as an incorporated additive gas under the thermal chemical vapour deposition (TCVD) system. These syntheses were carried in the reaction temperature range of 550―850°C. According to the different reaction temperature the ratio of SF6/C2H2 injection gases flows and the injection time of SF6 flow were varied respectively. At the lowest reaction temperature (550°C) in this work, the carbon microcoils could be formed within a relatively short initial injection time (less than 15min) of SF6 flow. With increasing the injection time of SF6 flow, the carbon nanocoils could be well-developed on the surface of the sample. At 750°C, the formation of the carbon microcoils was dominated on the whole surface of the sample, irrespective of the ratio of SF6/C2H2 injection gases flows and the injection time of SF6 flow. At the highest reaction temperature (850°C) in this work, any coil-like morphology could not be observed on the surface of the sample. Based on these results the optimal condition for the formation of the carbon nano or microcoils in the viewpoints of the reaction temperature, the ratio of SF6/C2H2 injection gases flows, and the injection time of SF6 flow were suggested. Furthermore, the cause for the formation of carbon nano or microcoils within a limited reaction condition was discussed.
Graphene Based Electronic Textiles Fabricated with Natural Materials
Authors: Jeon Jun Woo , Han Songlee , Shin Dong Seok , Kim Byung Hoon
Published: February 2020

High-performance carbon-based electronic textiles have recently been considered as the potential components for low-cost, multifunctional flexible and wearable electronics. Although many promising results have been reported to fabricate carbon textiles, they are not adoptable to the current textile industry, such as, nylon, cotton, polyester, and silk due to their chemical stability. Here, we report a facile way to prepare fully conductive, flexible, and stable reduced graphene oxide (RGO)-based textiles from yarns to fabrics using electrostatic interaction and hydrogen bonding.

The electronic textiles using graphene oxide (GO) was fabricated by two methods. First the currently used textiles such as nylon, cotton, and polyester were functionalized with bovine serum albumin (BSA) by soaking 0.5 wt% BSA solution for 10 min a room temperature. The prepared BSA-coated textiles were immersed in 1.0 mg/ml GO solution with mild shaking. As a result, GO-wrapped textiles were obtained. In order to endow the conducting property in these textiles, the GO-wrapped textiles were reduced by hydroiodic acid or thermal treatment. After reduction process, the conductivity reached up to 10 S/cm, which can light a LED lamp. This conducting textile fabricated with cotton, polyester, and nylon can be achieved by BSA through the hydrogen bonding between the protein (BSA) and graphene oxide. Using this property, we also synthesized the electronic textiles with cocoon silk and spider web. Since they already have proteins, the electronic textiles was fabricated without BSA, which was produced by simply dipping the silk and spider web into the GO solution. Its conductivity is comparable to that with BSA. These electronic textiles exhibit excellent electromechanical stability under severe mechanical deformation and a large number of repetitive bending cycles.

Figure 1
The Role of Graphene Nanostructures on Colloidal Quantum Dot Photovoltaic Devices
Authors: Tavakoli Mohammadmahdi , Tavakoli Razieh , Simchi Abdolreza , Fan Zhiyong
Published: February 2020

PbS quantum dots (QDs) have received considerable attention in the past decade due to their low-cast solution processing, bandgap tenability by control the size, and multiexciton generation make them particularly attractive as an active absorbing layer in optoelectronic devices such as solar cells. Recently, combining semiconductor quantum dots and graphene are a new strategy to improve the optoelectronic properties of photovoltaics devices. Herein, we have reviewed our recent works which are expolred the role of graphene as a passivation agent on the surface of PbS QDs and an interface layer between the electron transfer layer and absorber layer. First, we have demonstrated that the graphene can wrap the surface of PbS QDs and passivate the deep trap states by using a novel solution proces. Simulation by density functional theory of a prototypical model of a non-stoichiometric Pb-rich core (400 atoms) coated by graphene (20 atoms for each graphene sheet) indicates the possibility of surface passivation of (111) planes of PbS with graphene resulting in a decrease in trap states and recombination sites. The graphene coating of the PbS quantum dots decrease the exciton lifetime up to 0.78 µs as compared to 1.2 µs for the oleic acid passivated PbS quantum dots due to the fast extraction of carriers. We have employed PbS/graphene as well as Cd-doped PbS/graphene quantum dots as active layers of bulk heterojunction solar cells, and achieved solar power conversion efficiencies of 3.6% and 4.1%, respectively. In addition to the surface passivation role, a thin layer of graphene as an interface layer can increase the performance of PbS QDs device due to the improvement of carriers transfer and enhancement of current density. In our work, a simple and novel method is employed to synthesize a new structure of graphene, i.e. hollow graphene. In this regards., ZnO-Graphene QDs nanocomposite synthesized by a solution method and then ZnO QDs were dissolved from the structure using an acidic solution to obtain hollow graphene. Afterward, this structure was utilized in PbS QDs solar cell in order to improve the carriers transport. It is shown that holow graphene electrodes enhance electron extraction, yielding 30% improvement in performance compared with conventional device.

Figure 1
Semiconductive Behavior of Anodic Titanium Oxide Films with Different Thicknesses
Authors: Fujimura Eri , Fujioka Yuhei , Tsuchiya Hiroaki , Fujimoto Shinji
Published: February 2020

The high corrosion resistance of metal in aqueous environment depends on a thin oxide film formed on its surface. Oxide films on many metals and alloys exhibit the semiconductive property that is considered to be related to corrosion behavior. Therefore elucidating the semiconductive property of oxide film is necessary to understand corrosion resistance of metals and alloys. In order to discuss the semiconductive property of oxide film, in-situ analytical techniques are desired as the denature of the oxide film during evaluation is avoided. Photoelectrochemical response and electrochemical impedance spectroscopy have been applied to study the semiconductive property of oxide film in-situ. In the present work, the semiconductive property of anodic Ti oxide films with different thickness was analyzed using the techniques. Materials were pure Ti discs embedded into epoxy resin. Prior to experiments, its surface was mirror-finished, then ultrasonically cleaned in methanol, ethanol and deionized water for 5 min, successively. The mirror-finished Ti surface was anodized at various potentials ranged from 3 V to 7 V for 60 min in a 0.01 M Na2SO4 solution and phosphate buffer solution, then examined with electrochemical impedance spectroscopy and photoelectrochemical response.

For the electrochemical impedance spectroscopy, the capacitance of space charge region was measured and analyzed to estimate donor density and flat band potential. The donor density decreased and the flat band potential increased with increasing film formation potential for all samples. This result indicates that the electronic property of the oxide films is correlated with the film formation potential. In the photoelectrochemical response, a photocurrent exhibited similar transients under all conditions. A spectrum of the photocurrent was separated into two components; a spike photocurrent and a subsequent steady photocurrent. At high measuring potentials, spike charge estimated from the spike photocurrent and the steady photocurrent decrease with increasing the film formation potential. At lower potentials, on the other hand, the spike charge and the steady photocurrent increase with increasing the film formation potential. This result suggests that not only film formation conditions but also measurement conditions influence the photoelectrochemical response. In the presentation, the results will be discussed based on results for electrochemical impedance spectroscopy.
A Novel Ceramic-Polymer Composite Electrolyte for Lithium Batteries
Authors: Richter Felix Herrmann , Zekoll Stefanie , Marriner-Edwards Cassian , Hekselman Aleksandra K. , Kasemchainan Jitti , Cai Dongyu , Wallace Robert , Thijssen Job H. J. , Bruce Peter G.
Published: February 2020

Lithium metal is being intensively pursued as an anode due to its high specific capacity. However, dendrite formation, Li loss and short circuiting upon cell cycling presently impede its use. Furthermore, the flammability of liquid electrolytes poses a severe safety hazard. Replacement of organic liquids by solid electrolytes could pave the way for using lithium metal, simultaneously improving specific energy and battery safety.

Efforts continue on ceramic electrolytes. Challenges include the formation and manufacture at scale of sufficiently thin, highly dense, pinhole-free sheets of ceramic electrolytes, required for high power devices. Such electrolytes must also maintain contact with the solid electrodes while inhibiting Li dendrites and be durable towards volume changes of the electrodes as well as to external shock.

Polymer electrolytes have been developed for a number of years. They can exhibit good adhesion and contact to the electrodes, but typically have lower conductivity and limited capability of suppressing dendrite formation.[i]

To date, ceramic and polymer electrolytes remain a challenge. Composites of particulate ceramics embedded within polymer electrolytes have been investigated to improve the conductivity and mechanical properties.
[ii]
Our approach is to create ordered composite electrolytes, which allows modification of the mechanical properties of the composite while retaining good overall ionic conductivity.

The conductivity of the polymer-ceramic composite is 1.5E-4 S/cm at 25 °C. The results for different ceramic-polymer compositions indicate that the mechanical properties of the composite can be modified by the presented approach. Mechanical testing and the results of galvanostatic cycling will be reported.

[i] G. M. Stone, S. A. Mullin, A. A. Teran, D. T. Hallinan Jr., A. M. Minor, A. Hexemer, N. P. Balsara, J. Electrochem. Soc., 2012, 159, A222–A227.

[ii] Y.-C. Jung, S.-M. Lee, J.-H. Choi, S. S. Jang and D.-W. Kim, J. Electrochem. Soc., 2015, 162, A704–A710.
Influence of Used Carbons and Binders on Electrochemical Properties of Li-S Cathode
Authors: Kazda Tomáš , Sedlarikova Marie , Tichý Jiří , Cudek Pavel , Fafilek Günter
Published: February 2020

Lithium ion batteries play an important and indispensable role in the current technology thanks to the development of wearable electronics and also thanks to the increasing interest in electric vehicles. It will be necessary to replace the currently used electrode materials with new materials with higher capacity and energy density for further development in these areas, such as high-voltage batteries, lithium-sulphur batteries or Li-Air batteries. Lithium-sulphur batteries are very promising due to their high capacity and easy availability of materials. The theoretical capacity of sulphur is 1675 mAh/g and energy density is higher than 3200 Wh/kg. This system suffers by many problems. There is almost 80 % volumetric expansion during cycling on cathode or shuttle effect. Shuttle effect is probably the biggest problem of this system. Formation of polysulfides (Li2S8, Li2S6, Li2S4 etc.) takes place during charging and discharging. These polysulfides are soluble in the electrolyte and they are subsequently deposited on the anode. This process leads to the decrease of capacity and cycle life of the battery. There are many ways how to prevent this process as encapsulation of sulphur in carbon in the case of formation of the barriers on the surface of electrode or separator. Another possibility is using 3D structured cathodes. These 3D structures can keep polysulfides inside the electrode and prevent capacity decrease during cycling. A biological material with high porosity was used in this article to create a 3D structure into which sulphur was incorporated by different methods as coating or precipitation. These electrodes were cycled at various loads and compared with a standard electrode. 3D electrodes show higher stability than standard electrode and higher area capacity of more than 2 mAh/cm2.

This research has been carried out in the Centre for Research and Utilization of Renewable Energy (CVVOZE). Authors gratefully acknowledge the financial support from the Ministry of Education, Youth and Sports of the Czech Republic under NPU I programme (project No. LO1210), BUT specific research programme (project No. FEKT-S-14-2293) and in part financially supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project CEITEC 2020 (LQ1601).
Electronic Structure Changes As Source of Chemical and Interfacial Instability in LiCoPO4 As Positive Electrode for High Voltage Li-Ion Batteries
Authors: Lapping Jacob Grant , Allen Jan L. , Jow T. Richard , Allen Joshua L. , Johannes Michelle , Freeland John W , Cabana Jordi
Published: February 2020

The energy storage capability of a battery scales with the potential difference between its electrodes. Yet operation of positive electrode materials at high potentials introduces challenges of stabilization of charged states. As of today, no positive electrode material has been demonstrated to durably and safely operate above 4.5 V vs. Li+/Li0. LiCoPO4-based electrodes theoretically offer high specific capacity and high potentials of operation, around 4.8V vs. Li+/Li0, but these electrodes are prone to failure during cycling. Failure occurs through chemical and structural degradation in the bulk of the active material or at its interfaces with cell components, especially the electrolyte. The development of Li-ion battery electrodes operating at high potential is indispensable to meet the specific energy target of 250 kWh/kg at the packaged cell level.

Changes in the electronic structure and chemical stability of olivine-type LiCoPO4 and Fe-substituted LiCoPO4 were explored as both a function of ion substitution and oxidation state. Soft Ex situX-Ray absorption spectroscopy (XAS) made it possible to compare the changes in chemical bonding between electrode bulk and surface as a function of lithium content. This technique can probe the density of states at the transition metal and O levels. The evolution of these levels revealed changes in the metal-oxide covalence when lithium was deintercalated from the structure, and, thus, the material was oxidized. An increase in covalence can lead to the destabilization of the anions. If this process takes place in the bulk of the material, this destabilization can lead to thermal degradation via oxygen loss. At the surface, even small degrees of destabilization are sufficient to produce oxidizing species that attack the electron-rich solvent molecules in the electrolyte, leading to irreversible capacity loss.

Increased metal-oxygen covalence was universally observed in the spectroscopy in the form of a rising pre-O K-edge peak at ~530 eV as a function of lithium deintercalation in both bulk and surface. However, accompanying changes in the Co spectroscopy were only observed in the Fe-substituted sample. These changes are also indicative of increased hybridization between Co 3d and O 2p orbitals. Co K-edge XANES and EXAFS experiments further corroborated these findings, in which virtually no changes in the Co K-edge were observed upon oxidation of unsubstituted LiCoPO4. Fe doping appears to play a substantial role in getting Co to participate in redox chemistry, and the mechanism by which it occurs is currently being explored using Density Functional Theory. Fe-substituted LiCoPO4 is an exciting new positive electrode material that may prove useful in advancing Li-ion battery technology.
A123's High Power and High Energy Li-Ion Chemistry Development for Vehicle Electrification
Authors: Johnson Derek C , Hammoud Maha , Xu Charlie , Wang Jun , Campion Christopher , Iocco Rocco
Published: February 2020

A123 has traditionally been a lithium-ion phosphate (LFP) focused company, providing state-of-the-art, high power solutions with excellent safety for low voltage automotive applications.  This focus continues to result in the development of unique LFP synthesis and crystal structure doping processes to further enhance low temperature performance.  In an effort to produce safe, high-energy density cells utilizing nickel-rich NCM cathodes and large capacity anode materials, A123 is implementing the same crystal level doping and surface coating approach that has been effective for low voltage material development.  This presentation topic is therefore focused on the high power cathode material development that has resulted in Lithium Ion Starter Batteries (LiSBs) with cold crank capabilities that surpass lead acid batteries and high energy advancements at the material and cell levels in order to achieve energy densities approaching 300 Wh/kg and 600 Wh/L for EV applications.
Stabilizing the Solid Electrolyte Interphase on Silicon-Based Anode Materials for Lithium-Ion Batteries By in-Situ Reductive Electropolymerization
Authors: Moeremans Boaz , Zheng Yueming , Duarte Roberto Felix , Deduytsche Davy , Detavernier Christophe , Hahlin Maria , Boyen Hans-Gerd , Hardy An , Van Bael Marlies K , Renner Frank Uwe
Published: February 2020

Increasing the capacity of Li-ion batteries and making the involved interfaces much more stable is one of the crucial current challenges for sustainable energy use.1 Silicon anodes promise almost a 10-fold capacity increase with respect to conventional graphite anodes.2 The continuous degradation of the Solid Electrolyte Interphase (SEI) at the surface of silicon-based anode materials has been recognized as the key problem of these electrodes, currently preventing their commercial introduction.3 The effect of the addition of additives to the electrolyte has been investigated in the past on graphite anodes, resulting in the use of FEC and VC in commercial lithium-ion batteries. However, due to the severe volume expansion of silicon during battery cycling, the SEI is under much higher stresses compared to graphite. Hence the stabilization of the SEI on silicon is required to improve its battery performance.

Here we present a methodology to specifically introduce polymer species into the SEI. We analyzed the interfacial film using Hard X-ray Photoelectron Spectroscopy (HAXPES), Raman spectroscopy and electrochemical testing. HAXPES enabled us to address the full depth-dependent layer chemistry and allowed us to probe the interface of the solid-electrolyte interphase and the silicon-based electrode. Figure 1a shows the C1s spectrum of the SEI on a silicon based anode after cycling using a standard electrolyte and for Figure 1b an electrolyte with the monomer additive. A detailed analysis gives information on the SEI layer thickness and the distribution of the additive-based polymer formation. In particular Br2p3/2 HAXPES spectra reveal more details on the mechanism. The battery performance of the additives was investigated by coin-cell battery testing and provides a more detailed view into the influence of electrolyte additives on the SEI.

REFERENCES

1.   J. B. Goodenough and K.-S. Park, J. Am. Chem. Soc.
135, 1167-1176 (2013).

2.   M. N. Obravac and L. Christensen, Electrochemical and Solid-State Letters
7, A93-A96 (2004).

3.   B. Philippe, K. Edström et al., Chemistry of Materials
24, 1107-1115 (2012).

Figure 1
Unusual Na Storage Behavior of Ordered Mesoporous Carbon on Ether-Based Electrolyte System
Authors: Kim Yunok , Jeong Mihee , Lew Gil Hwan , Oh Woong , Jin Xing , Kim JI Man , Yoon Won-Sub
Published: February 2020

The Li-ion battery (LIB) market increases rapidly due to the development of portable electronic devices and energy storage systems (ESSs). By increasing the demand for commercialization of scale-up LIB, large amounts of accumulated lithium resources will be consumed in the near future. Recently, Na-ion battery (NIB) system is considered as an alternative to LIB system because sodium resources are abundant and distributed around the world as well as sodium storage mechanism is similar to that of lithium. In contrast to LIB, graphite is not suitable for NIB anode material due to the small interlayer for large ionic radius of Na+ ion. Therefore, previous studies have investigated that non-graphitic carbon materials can deliver reversible Na+ ion insertion and extraction with initial capacity up to 300mAh g-1, however, the cycle stability of non-graphitic carbon materials is very poor.

Ordered mesoporous carbon (OMC) has the advantage of large surface area due to the development of nano-sized pores inside a micron-sized particle, which results in large electrode/electrolyte interface, easy penetration of electrolyte, and fast diffusion of Li+/Na+ ion. The ordered hexagonal structure of the OMC was formed as an inverse replica of a mesoporous silica SBA-15 structure and started from phenanthrene as a carbon source. In carbonate-based electrolyte system, the first and second discharge capacities of the OMC were 800 mAh g-1 and 350 mAh g-1 at a current density of 100 mA g-1, respectively, which means a large irreversible capacity loss, whereas in ether-based electrolyte system, the first irreversible capacity decreased considerably, implying an enhanced reaction reversibility. Even though the first discharge capacity in the ether-based electrolyte was about 200 mAh g-1, the capacity in the ether-based electrolyte increased during repeated cycling and achieved 350 mAh g-1 after 100 cycles. In contrast, the cycle retention in carbonate-based electrolyte degraded down to 200mAh g-1 consistently during 100 cycles.

To elucidate the electrolyte system-dependent Na+ storage of the OMC, various electrochemical analyses and synchrotron X-ray based techniques were performed using two-type electrolytes of 1 M NaPF6 in EC/DMC=1/1 and 1 M NaPF6 in DEG/DME.
Scalable modified Solid-State Synthesis of Na2Ti3O7 Nanorods As Anodes for Sodium-Ion Batteries
Authors: Li Chi-Ying Vanessa , Ho Ching-Kit , Chan Kwong-Yu
Published: February 2020

Sodium-ion batteries are regarded as one of the potential candidates to substitute lithium ion batteries in large-scale electric energy storage applications in the near future. [1] Several forms of sodium titanates including Na2Ti3O7, Na2Ti6O13 and Na4Ti5O12have been recently applied as anode in sodium ion batteries. [2-4]

In this study, single-crystalline Na2Ti3O7 nanorods are successfully fabricated by solid-state method with the addition of some solid additives. The electrochemical performance of Na2Ti3O7 nanorods is compared to conventionally synthesized Na2Ti3O7 irregular particles. Na2Ti3O7 nanorods outperform Na2Ti3O7 irregular particles at all current rates in the range of 0.1 to 5 C. Without surface modification, the nanorods can still manifest a reversible discharge capacity of 70 mAhg-1at a high current rate of 5 C. The enhanced electrochemical performance can be attributed to the high surface area of the nanorods as well as efficient ion transport induced in highly uniform one-dimensional nanostructure.

References

H. Pan, Y.-S. Hu and L. Chen, Energy & Environmental Science, 2013, 6, 2338-2360.

P. Senguttuvan, G. Rousse, V. Seznec, J.-M. Tarascon and M. R. Palacín, Chemistry of Materials, 2011, 23, 4109-4111.

A. Rudola, K. Saravanan, S. Devaraj, H. Gong and P. Balaya, Chemical Communications, 2013, 49, 7451-7453.

P. J. P. Naeyaert, M. Avdeev, N. Sharma, H. B. Yahia and C. D. Ling, Chemistry of Materials, 2014, 26, 7067-7072.

Acknowledgements

This project is financially supported by Research Grants Council of Hong Kong (GRF 17300014), HKU Small Project Funding (201409176115), HKU Strategic Research Theme on Clean Energy, and University Development Fund for Initiative for Clean Energy and Environment.

Figure 1
Bifunctional Catholyte for Li Air Batteries
Authors: Arul Anupriya , Christy Maria , Park Hyosoek , Nahm Kee Suk
Published: February 2020

Lithium–air (O2) batteries still suffer from a relatively low practical energy density even though it far exceeds other energy storage systems with its extremely high theoretical energy density. The multiphase electrochemical reaction on the air–cathode of a Li–air battery has difficulty in proceeding when operated with solid catalysts. The battery reaction involves three-phase (solid–liquid–gas that is, catalyst–electrolyte–O2) electrochemical interface which landed in the investigation of a diffusive liquid phase electrocatalyst. Iron phthalocyanines (FePc) were dissolved in 1M LiTFSI (DMSO) electrolyte and employed as liquid catalysts in Li–air batteries. The dissolved FePc facilitated the cell reaction kinetics by acting as a transporter for superoxide species (O2)- and electrons between the cathode surface and discharge products, Li2O2. The electrochemical battery testing and impedance analyses exhibited better performance with liquid FePc catalysts than the solid catalysts. The proper formation and decomposition of Li2O2 without direct contact with carbon surface or blocking of pores were evident from the post characterization studies of the air cathode surfaces.

Figure 1
Development of Thin-Film Solid Electrolyte-Electrode System for All-Solid-State Application
Authors: Frech Florian , Lorrmann Henning , Sextl Gerhard
Published: February 2020

All-solid-state batteries have been shown as an innovative candidate for next-gen lithium-ion batteries. Thin-film technologies offer an approach to solve several inherent challenges. To achieve a complete thin-film all-solid-state battery all components, especially electrodes and solid electrolytes have to be prepared in a suitable combination. In contrast to conventional liquid-solid electrolyte-electrode systems, additional requirements arise from the fact that electrochemically active interfaces have to be formed while preparing.

Using cost efficient and upscalable sol-gel processes solid NASICON-type electrolytes (e. g. Li1+xAlxTi2-x(PO4)3, LATP) offer a high ionic conductivity at room temperature and a high anodic stability [1]. In previous work we presented a LATP solid electrolyte prepared by sol-gel methods on a current collector as substrate [2]. In a layer-by-layer setup (shown in Fig. 1) the substrate-anode system forms the underlying substrate for the electrolyte coating. Oxide-based electrodes indicate interfacial reactions in the presence of NASICON-type electrolytes at temperatures higher than 300 °C [3]. Therefore they turned out to be unstable in the coating-associated temperature treatment. Phosphate-based electrode materials provide a suitable approach.

This poster presents single- and multi-layer films a of phosphate-based anode material on conducting transparent oxides prepared by dip- and spin- coating method. The single- and multi-layer systems exhibited good electrochemical properties and appear suitable for the electrolyte coating process including the associated temperature treatment. Grazing incidence X-ray diffraction reveals no interface reaction and SEM investigation shows a good physical connection on the electrolyte-electrode interface. Furthermore, half-cell CV and cycling tests confirm a low charge transfer resistance at the interface. Future work will focus on the cathode/electrolyte interface and finally a working solid-state cell.

[1]   P. Knauth, Solid State Ionics
2009, 180, 911–916.

[2]   F. Frech et. al., Development of thin glass-ceramic electrolytes via a sol-gel route, Poster on IMLB 2014

[3]   A. Aboulaich et. al., Adv. Energy Mater.
2011, 1, 179–183

Figure 1
Graphite Phase Behavior during Lithium(de)Intercalation
Authors: Bazant Martin Z. , Smith Raymond B. , Guo Yinsheng , Yu Zhonghua , Efetov Dmitri , Wang Junpu , Kim Philip , Brus Louis
Published: February 2020

One of the processes limiting the rate of charging of lithium ion batteries is the possibility that lithium will plate onto the graphite anode at high charging currents, leading to safety hazards. Lithium can plate when the filling fraction of lithium within the graphite approaches unity near the particle surface, which occurs when transport into the particles is not fast enough compared to the intercalation current. Thus, models must correctly describe the transport of lithium within the graphite, a phenomenon complicated by the fact that graphite particles tend to phase separate, both by forming staged structures in which lithium is only located between every n'th layer of graphene, and also by forming high and low concentration domains within individual layers. The different stages correspond to plateaus in the open circuit voltage and are characterized by a distinct visual color change, allowing optical characterization of local state of charge of graphite electrodes and particles. We propose here a simple free energy model to explain the intralayer phase separation as well as the high filling fraction staging structures. Then, we apply this free energy to a phase field transport model which allows us to capture single-crystal experimental intercalation results and makes distinct predictions from Fickian diffusion models, which we describe here.
Has the Recycling of Lithium Ion Batteries Raw Materials Become Necessary?
Authors: Lifton Jack P
Published: February 2020

The total supply chain for the production of lithium ion batteries critically involves recycling, because either there isn't enough production of lithium, cobalt, and titanium or the supplies of them are geopolitically constrained or limited. The world base metal commodity glut has simultaneously slowed or stopped the production of the technology metals and materials necessary to produce lithium ion batteries. In fact without additonal or new supplies from existing mines the production of lithium ion batteries may need to be slowed and matched to the recycling of the critical materials. Finally the recycling of lithium ion batteries to recover the raw materials used in their construction is itself a step in more than one supply chain. Corodination among the separate supply chains for lithium salts; battery grade graphite; cobalt; and titanium will also be necessary. Has American industry recognized this problem? Even if so, can solutions be implemented in time to support the rapid build up of the electric vehicle ramp up now under way?
Identifying the Origin of Stability of Cathode Materials with Al3+-Based Surface Modifications: Amorphous Al2O3 or Crystalline LiAlxCo1-XO2?
Authors: Hu Linhua , Phillips Patrick J , Key Baris , Cabana Jordi
Published: February 2020

Chemical degradation at electrode/electrolyte interfaces in Li-ion batteries creates the challenge of designing stable cathode materials to avoid the loss of active cathode material at the interface of the cathode and electrolyte.  Surface modification with non-active oxide is regarded as a valid strategy to decrease such degradation based on their role as electronic insulator between cathode and electrolyte. Although different oxides have been reported to enhance stability against chemical degradation, the realization of stability and durability of surface modified cathode materials is not well understood owing to the inhomogeneity and complex morphology of typical cathode powders and the resulting difficulty in properly characterizing the surface structure. Indeed, the specific chemical identity of the non-active oxide on the surface of cathode materials can vary. For instance, Al3+ can incorporate as amorphous Al2O3 or crystalline LiAlxCo1-xO2, among others.

Herein, we directly synthesized well-defined LiCoO2 (LCO) nanocrystals with a hydrothermal process and employed as model cathode materials before coating 2nm uniform Al3+ oxide thin films on their surface and annealed at different temperatures. Phase analysis have confirmed that Al can be formed as Al2O3 at low temperature and as LiAlxCo1-xO2 at high temperature. Microscopy analysis presents direct proof of Al conformally coated on their surface. The electrochemical properties have demonstrated the different effect of coating with different Al-containing phases. Compared to bare LCO nanoplates, amorphous Al2O3 film coated on such nanoplates presents higher capacity and average stability whereas LiAlxCo1-xO2 coated film have much higher stability with average capacity. Data from atomic resolution TEM and solid state NMR will be discussed.
Evaluation and Thermal Analysis of LiCoO2/Graphite Battery during Cycling
Authors: Mao Ya , Bai Qingyou , Xie Jingying
Published: February 2020

Lithium ion batteries have been widely used as power source of 3C products, EV, HEV, PHEV and energy storage of green grid. However, as a solution to high energy density storage, lithium-ion batteries have been seriously plagued by the safety issues. In this Paper, the thermal runaway at full charged state and heat production of LiCoO2/graphite battery during charge and discharge with different current density was investigated during every 500 cycles. Results showed that the heat production increased with cycles and the regularity of heat rate was deviated at the end of life cycling. The temperature of heat production decreased and the heat rate was accelerated as the cycle number increased during thermal runaway.

Figure 1
Composite Polymer Electrolytes for Lithium Ion Batteries
Authors: Fan Li-Zhen , Wang Qiujun
Published: February 2020

Polymer electrolytes are expected to be the alternative electrolytes to satisfy the needs for power storage device because of several important factors, such as high ionic conductivities, reliable safety, easy fabrication, appropriate mechanical properties along with important technological issues related to electrochemical stability. Solid polymer electrolytes prepared by dissolving the salt into the polymer framework are still found to present low ionic conductivities at ambient temperature and dependence of temperature. The ionic conductivities can be enhanced by dissolving polymer matrices and lithium salts in organic solvents. However, liquid electrolytes will deteriorate mechanical properties. Here we have prepared a series of polymer electrolytes with excellent thermostability,well mechanical property, wide electrochemical window and high ionic conductivity, including trimethylolpropane trimethylacrylate (TMPTMA) based, triethylene glycol diacetate-2-propenoic acid butyl ester (TEGDA-BA) based, polyimide (PI) based and polyacrylonitrile (PAN) based polymer electrolytes using in situ thermal polymerization or polymer casting method [1-8]. The as prepared polymer electrolytes exhibit high ionic conductivities, electrochemical stability and excellent charge/discharge cycling performance. The excellent properties of polymer electrolytes make them significant potential materials for next generation lithium ion batteries.

References

[1]. Q.J. Wang, W.L. Song, L.Z. Fan, Q. Shi. J. power sources, 2015, 295: 139-148.

[2]. Q.J. Wang, W.L. Song, L.Z. Fan, Y. Song. J. Membrane Sci., 2015, 492: 490-496.

[3]. Q.J. Wang, W.L. Song, L.Z. Fan, Y. Song. J. Membrane Sci., 2015, 486: 21-28.

[4]. Q.J. Wang, W.L. Song, L.Z. Fan, Q. Shi. J. power sources, 2015, 279: 405-412.

[5]. Q.J. Wang, Z.X. Jian, W.L. Song, S.C. Zhang, L.Z. Fan. Electrochim. Acta, 2014, 149 (12): 176-185.

[6]. Q.J. Wang, W.L. Song, L.N. Wang, Y. Song, Q. Shi, L.Z. Fan. Electrochim. Acta, 2014, 132: 538–544.

[7]. H.H. Fan, H.X. Li, L.Z. Fan, Q. Shi. J. power sources, 2014, 249: 392-396.

[8]. D. Zhou, L.Z. Fan, H.H. Fan, Q. Shi. Electrochim. Acta, 2013, 89: 334-338.
A Lithium-Ion Battery Separator Based on Porous Poly (arylene ether ketone) Membranes
Authors: Mong Anh , Kim Dukjoon
Published: February 2020

Porous poly(arylene ether ketone) (PAEK) membranes are prepared by selective removal of poly(lactic acid) (PLA) molecules from self-assembled PAEK-PLA block copolymers. The pore size and porosity of the membranes are precisely controlled by adjusting PLA concentration. The synthesis of the PAEK-PLA copolymer is confirmed by FTIR and NMR spectroscopies and the morphology of the membrane is examined by scanning electron microscopy (SEM). Several important properties such as liquid electrolyte uptake, contact angle, thermal and mechanical stability, and lithium ion conductivity are measured and compared with those of commercial poly(propylene) (PP) membranes to investigate their application feasibility as a separator. The porous PAEK membrane shows improved thermal and dimensional stability compared to the PP membrane. The EC/DEC/EMC (1:1:1, v/v/v) soaked PAEK membrane with a pore diameter of 50 nm shows the highest lithium ion conductivity, higher than that of PP membrane. More importantly, the porous PAEK membranes show superior liquid electrolyte holding capacity to the PP membrane.
Processing of Aluminum-Doped Lithium Lanthanum Zirconate Garnet-Type Solid Electrolyte Materials
Authors: Fergus Jeffrey , Zhang Xingxing
Published: February 2020

Lithium lanthanum zirconate (LLZO) with the garnet crystal structure has high lithium ion conductivity and good electrochemical stability, so it is an attractive material for use as the solid electrolyte in lithium ion batteries.  One of the challenges in the application of LLZO is processing the material to obtain the desired composition, crystal structure and morphology.  In this paper, results on processing of LLZO materials for use in single-phase and composite solid electrolyte materials are presented.