bluuebunny/crossref_metadata_2025 huggingface dataset:
Non-Prestonian Behavior Study and Development of Advanced Oxide Polish Slurry for Stop-In-Film Applications
Authors: Zhou Hongjun , Murella Krishna , Hughes John , O'Neill Mark
Published: February 2020

Non-Prestonian behavior is defined as a non-linear correlation between the removal rate and the polishing pressure. It is believed to be related to dishing, erosion and self-stopping behavior that is observed on pattern wafers.

Nojo et al. has reported that “self-stopping polishing” can be achieved when the non-Prestonian behavior was observed.  Significant research effort has been made in this field, following this initial report. For example, the effect of chemical additive concentrations and molecule weight of additives, along with abrasive concentration and size on non-Prestonian behavior have been studied.  Primarily, blanket wafer performance data has been presented in the majority of published work. Although some researchers had conducted modelling to calculate the effect of non-Prestonian behavior on pattern performance, a comparison between pattern and blanket wafer performance in not available.  This is needed to enable a more clear understanding of non-Prestonian behavior.

In this presentation, Prestonian behavior was modulated by adjusting chemical concentrations and / or formulation pH. Pattern performance, including oxide removal rate and step height reduction rate, were collected and evaluated.  It was determined that non-Prestonian behavior does not necessarily lead to good pattern performance. From the learnings of this systematic study, a high-performance, oxide-polish slurry for stop-in-film applications was successfully developed.
Material Removal Behavior of Nano-Sized Cerium Hydroxide Abrasive Slurry for Chemical Mechanical Polishing
Authors: Kim Hong Jin , Lee Tae Hoon , Ryan Anne
Published: February 2020

Microscratch induced by Chemical Mechanical Polishing (CMP) is a chronic problem to device yield-killing. In sub-14nm device, its criticality becomes more important due to its structural and process complexity. In order to mitigate scratching during CMP process, minimizing abrasive particle size without sacrificing removal rate is the most important parameter. Uniform size distribution of abrasive particles is critical to reduce scratching as well. For this purpose, less than 5nm sized (i.e., nano-sized) cerium hydroxide-based particle (NSC) is utilized as oxide CMP slurry. This size is much smaller than conventionally used calcined ceria slurry (100nm – 200nm in particle size). The slurry that is used in this experiment is designed to have high TEOS selectivity to polysilicon. And the effect of NSC on the microscratch generation is investigated with stop on polysilicon CMP process for so-called ‘dummy gate’ formation and experimental results show more than 80% microscratch reduction compared with process of record (POR) process. Moreover, microscratch size is much smaller than calcined ceria slurry induced microscratch. However, although dramatic microscratch reduction is obtained with NSC, its polishing behavior has not been well understood. In this study, material removal behavior with NSC is explored by a series of experiments involving tribological analysis. 300mm tetra-ethyl-ortho-silicate (TEOS) oxide is used for the experiments, and non-Prestonian TEOS removal behavior with respect to down pressure is observed. At low down force regime, TEOS removal rate is linearly proportional to down force, which is following Preston equation. However, after certain pressure is reached, TEOS material removal rate increases slowly and slope of removal rate becomes smaller. The effect of rotational speed, retainer ring down force, dilution and additive on the removal rate is also explored. TEOS removal rate increase as rotational speed increase is not as sensitive as down pressure effect, and TEOS removal rate is decreased at high retainer ring down force. Experimental results suggest that TEOS removal mechanism by nano-sized cerium hydroxide particle is different from conventionally used calcined ceria particle. Based on the experimental results, this study emphasizes surface reaction as a dominant parameter to determine removal rate rather than mechanical aspect of material removal.

Figure 1
Probing the Role of Slurry Chemistry on Nanoparticle-Media Adsorption Relevant to Cu CMP Filtration Applications
Authors: Wienck Richard A , Mlynarski Amy , Connor Patrick , Levy Patrick , Keleher Jason J
Published: February 2020

As the complexity of nanoparticle dispersions used in next-generation CMP slurries increases to meet stringent performance demands, it is necessary to develop polymeric filtration media that capture rouge particles in order to reduce overall surface defectivity without sacrificing planarization efficiency.  Therefore, it is essential to probe the molecular level interactions at the nanoparticle/slurry chemistry/polymer filtration media interface and in turn correlate this to the key performance metrics such as substrate removal rate, post CMP defects, planarization efficiency. More specifically, simulated Cu CMP slurries with a wide range of film formation chemistries for performance control were evaluated with respect to the filterability through various polymeric filtration media.  It was determined that a synergy exists between the structure of the additive (small organic molecule vs. surfactant-like additive) and the filter medias ability to regulate the dynamic adsorption processes of the slurry nanoparticles.  Utilizing atomic force microscopy (AFM), electrochemical quartz crystal nanobalance (EQCN), modified ATR-IR spectroscopy, and in-situ rotating disk electrode corrosion measurements the static and dynamic nanoparticle binding mechanisms can be determined and correlated to the filterability studies. Furthermore, monitoring the pre/post filtration zeta potential and particle size distributions, bulk copper removal rate, and corrosion current as a function of filtration pressure, the role of filtration media slurry chemistry health can be surveyed on CMP performance based scale.
(Invited) Critical Review of CMP Requirements in the Future
Authors: Banerjee Gautam
Published: February 2020

With the introduction of tri-gate at 22nm technology node by Intel, other logic chip manufacturing technology developers have steadily migrated from planar to 3 dimensional FinFET technology at the fron-end-of-line. Historically, at 0.8μm technology node, there was no CMP although 2-3 metal levels were used. At 0.35μm technology node, a CMP step was introduced. CMP became mainstream with multiple steps requiring CMP at 90nm technology node which continued until 2x nm technology node.  However, at 1x (e.g. 14nm) technology node, CMP began to transition from a ‘process simplifier’ to a ‘process enabler’ step. Expanding applications of CMP have made possible the integration of FinFET, RMG (Replacement Metal Gate) and TSV (Through-Silicon-Via)[1].

In sub 1x logic fabrication, the total number of CMP steps may reach 20 or more. Use of FinFET technology in 1x and sub 1x provides much better performance at the same power budget or equal performance at a much lower power budget compared to planar mode[2]. Further, III-V compounds are expected to be integrated at 5nm technology node. III-V materials enable Vdd scaling to address power without sacrificing performance due to the very high electron injection velocity at virtual source compared to Si[3]. These III-V films will require CMP with special care due to the probability of toxic gas release (AsH3/PH3).

Beyond 5nm, it is widely assumed that FinFET technology will not be able to provide the small scale features and therefore, gate-all-around technology will be used. To implement gate-all-around, one potential pathway may be to use 2D TMD (2 dimensional transition metal dichalogenide) films. 2D TMD gate-all-around film allows for increasing direct S/D (source/drain) tunneling[4].

With new types of films getting integrated in smaller features, it is necessary therefore to understand the type and nature of various films being used to fabricate devices using sub 1x nm features. In this paper, various US patent applications by leading device manufacturers within the past year will be reviewed to explore the most important CMP steps needed to fabricate new devices. Further, new slurry formulation efforts to enable new CMP requirements for the sub 1x nm devices will be reviewed for the same timeline.

References:

1) Y. Moon et al, CMPUG, July 2014, San Francisco, CA.

2) C. Surisetty et al, CAMP 2013, Lake Placid, NY.

3) T.W. Kim, IEDM 2012.

4) K. Majumdar et al, EDL, 35, p.402, 2014.
Planarization of GaN Using a FeIII-Ligand Based Catalyst in H2O2 Solution to Improve Its Removal Rate
Authors: Xu Li , Pan Guoshun
Published: February 2020

A large amount of attention has been given recently to gallium nitride (GaN) substrates which are considered to be a promising candidate for opto-, high power and high frequency electronic devices due to their wide bandgaps, high carrier mobility, high saturated electron drift velocity and high breakdown field . It is essential to provide a complete damage-free surface to realize the full potential of GaN devices. Chemical mechanism planarization (CMP) is applied to the surface as a final treatment to produce atomic level surface flatness by removing the damage on the surface. However, the removal rate of GaN in CMP with colloidal silica-abrasive-based slurry under acidic slurry pH condition presents a range of ten to a hundred nanometers per hour because of their high mechanical hardness, thermal stability and strong chemical inertness. Thus, improving the CMP removal rate for GaN will lead to an acceleration in the realization of next generation optoelectronics devices on GaN.

        In this work, a method for facilitating the removal rate as well as obtaining atomically smooth surface of GaN with a novel FeIII-Ligand-based catalyst in hydrogen peroxide (H2O2) solution is presented. Effect of process parameters, such as concentration of H2O2, the mass of FeIII-Ligand-based catalyst in slurry, pH of the slurry and concentration of abrasive particles on the material removal rate (MRR) as well as the surface quality have been studied in details.
(Invited) Plasma Modification of Graphene Based Materials and Its Applications in Water Treatment
Authors: Yang Hui Ying
Published: February 2020

The ion and other impurities in the seawater is a naturally distributed element in the environment. The seawater aqueous solution plays an important role in many application fields with proper ion removing and desalination process, e. g. in a middle-scale semiconductor factory, different manufacture process.  Therefore, it is necessary to control different ion concentrations within the limit.  In the desalination field, reverse osmotic membrane, capacitive desalination, and electro-dialysis desalination are the most popular technologies. However, none of them can efficiently remove smalll ions from seawater due to its small size and uncharged species  at pH 8.4. In this presentation, we will discuss different plasma treatment methods and their applications in the treatment of carbon based nanomaterials for water treatment and desalination.  We synthesize different carbon based nanomaterials graphene oxide, by simple two-step process in the aqueous solution and have extremly high efficiency as media for water treatment and desalination.
Production of N-Graphene By Microwave N2-Ar Plasmas (invited)
Authors: Henriques Julio , Tatarova Elena , Dias Ana , Dias Francisco , Bundaleski Nenad , Abrashev Miroslav , Felizardo Edgar , Cvelbar Uros
Published: February 2020

Nitrogen doped graphene sheets, have attracted much attention due to their exceptional performance as parts of fuel cells, lithium-ion batteries and supercapacitors. Free-standing Nitrogen-doped graphene sheets where produced in a low pressure microwave N2-Ar plasma. Graphene sheets were treated by plasma at different exposure times and doped with nitrogen atoms, which incorporated the hexagonal carbon lattice, mainly, in pyridinic, pyrrolic and quaternary functional groups. Optical emission spectroscopy were applied to monitor the nitrogen atoms, gas temperature and electron density at the substrate position. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) techniques were applied to characterize the produced N-graphene, along with transmission electron microscopy (TEM) to study the morphology and structure of the samples. Doping levels as high as 5.6 % were achieved and an increase in the sp2/sp3ratio was observed for a relatively short exposure times. This study shows that by incorporating nitrogen atoms into graphene, its physico-chemical properties are considerably altered.

Acknowledgements: This work was supported by Fundação para a Ciência e a Tecnologia, under Project Pest-OE/UID/FIS/50010/2013 and grant SFRH/BD/52413 (PD-F APPLAuSE) .
(Invited) Mechanisms of Plasma Therapy
Authors: Graves David B
Published: February 2020

In this talk, I address research directed towards biomedical applications of cold atmospheric pressure (CAP) plasma such as sterilization, surgery, wound healing and anti-cancer therapy. The field has seen remarkable growth in the last 3-5 years, but the mechanisms responsible for the biomedical effects have remained mostly mysterious. It is known that plasmas readily create reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS (or RONS), in addition to a suite of other radical and non-radical reactive species, are essential actors in an important sub-field of aerobic biology termed ‘redox’ (or oxidation-reduction) biology. These species clearly play some role, but the time- and space-dependence of observed plasma therapy argues for a more complex mechanism. It is postulated that CAP can trigger a therapeutic shielding response in tissue in part by creating a time- and space-localized, burst-like form of oxy-nitrosative stress on near-surface exposed cells through the flux of plasma-generated RONS. In some cases, electric fields appear to play a key role in assisting transport through membranes. RONS-exposed near-surface layers of cells communicate to the deeper levels of tissue via a form of ‘bystander effect,’ similar to responses to other forms of cell stress such as radiation. In this proposed model of CAP therapeutics, the plasma stimulates a cellular survival mechanism through which aerobic organisms shield themselves from infection and other challenges.
Improvement of Electron Injection by a Ramp-Shape N-Doped Architecture for High-Efficiency Organic Light Emitting Diodes
Authors: Tsai Chi-Ting , Chu Sheng-Yuan
Published: February 2020

Over the past decades, organic light-emitting diodes (OLEDs) have drawn a lot of attention due to its numerous advantages over light-emitting diodes (LEDs) and liquid crystal display (LCDs). These characteristics make OLED become one of the most promising candidates for commercial applications such as solid state lighting and active matrix organic light-emitting diode (AMOLED) display. However, device properties such as lifetime, efficiency, power consumption are still the main issues needed to overcome for their practical uses. In order to fulfill a highly power-efficient light source or display with OLEDs, the device energy loss during electron–photon conversion should be low. Recent years, there are plenty of approaches proposed to improve the electron or hole injection from the electrodes and reduce the ohmic losses. The most typical way is inserting a chemically p- or n-doped layer between the hole transporting layer (HTL) and anodes or between the electron transporting layer (ETL) and the cathodes, respectively.

In our work, we report OLED with a novel n-doped ramp-shape electron injection structure composed of rubidium carbonate (Rb2CO3) doped 2-methyl-9,10-di(2-naphthyl) anthracene (MADN) which is prepared by thermal co-evaporation. We increase the doping concentration from 17.5 mol% to 84 mol% while depositing the  electron injection materials approaching the cathode. By increasing the doping concentration, the activation energy of the material decreases as the Fermi level shifting toward the lowest unoccupied molecular orbital (LUMO). Under thermal equilibrium conditions, a ramp-shape architecture is formed and gradually distribute the energy barrier from cathode to electron transport layer in the device therefore achieve significant electron injection improvement. 

As a result, a OLED with the ramp-shape electron injection structure ITO/NPB (40nm)/Alq3 (40nm)/Rb2CO3:MADN (14nm, 17.5~84 mol%)/LiF (1nm)/Al (140nm) accomplished maximum luminance of 33370 cd/m2 and current efficiency of 5.292 cd/A. By contrast, the device without the ramp-shape architecture (the normal device) ITO/NPB (40nm)/Alq3 (40nm)/LiF (1nm)/Al (140nm) only achieved a maximum luminance of 17030 cd/m2 and current efficiency of 3.41 cd/A. The total improvement (55% by current efficiency and 95% by luminance) made by adding ramp-shape structure to device indicated a remarkable electron injection facilitation and its performance is much more efficient than the device with typical electron injection layer ITO/NPB (40nm)/Alq3 (40nm)/Rb2CO3:MADN (5nm, 64 mol%)/LiF (1nm)/Al (140nm).

Figure 1
Process-Structure-Properties Relationship of Electrodeposited Au Thin Film Used in Thermoelectric Power Generation Device
Authors: Banga Dhego
Published: February 2020

An effective thermoelectric (TE) power source consists of TE modules and thermal management device. The TE modules must be connected electrically in series on both the top and bottom surface with bridging metal interconnects that must maintain low contact resistance with high mechanical strength while operating at high current densities and temperature gradients. Due to its low emissivity, excellent electronic, and mechanical properties, Au coatings can be used for interconnect metallization and heat mitigation in TE modules and thermal management devices respectively.

In this study, we report on the successful synthesis of perfectly coherent and atomically sharp nanoscale growth twin boundaries (figure 1(e&f)) and the introduction of highly crystalline atomic structure (figure 1(f)) in the interior of each grain of Au electrodeposits using pulsed electrodeposition from an additive stable cyanide gold bath. The increase in sharpness of nanoscale twin boundaries resulted in improved mechanical and electronic properties in Au electrodeposits1. During the study of nucleation and growth mechanism of Au electrodeposition process, we established that both instantaneous and progressive nucleation modes could be achieved depending on the overpotential used during deposition. Instantaneous nucleation was observed at lower overpotentials (≥ -0.75 V vs Ag/AgCl) while progressive nucleation occurred at larger overpotentials (< -0.75 V vs Ag/AgCl). We then compared direct (DC) and pulse current (PC) electrodeposition modes and their effects on mechanical and electronic properties of the electrodeposits. We determined that the use of large overpotentials (≤ -0.9 V vs Ag/AgCl) successfully produced films with enhanced properties. Compared to films generated using DC electrodeposition, pulsed Au coatings had improved physical and electronic properties with emissivity as low as 0.006, contact resistance five times less, hardness and electrical conductivity twice as much. We also found that long pulse on-times (≥ 2ms) and a small duty cycle (10%) were needed to produce smooth, porous free(figure 1(b&c)), highly crystalline, strongly textured, low emissivity, reduced contact resistance, enhanced electrical conductivity, and mechanically strong Au electrodeposits.

Reference

1.            L. Lu, Y. F. Shen, X. H. Chen, L. H. Qian, and K. Lu, Science,
304 (5669), 422-426 (2004).

Figure 1
High Rate Li-S Batteries: Hollow TiO2 Webbed Carbon Nanotubes with Dual Functional Porous Carbon-Paper
Authors: Hwang Jang-Yeon , Abouimrane Ali , Khaleel Mohammad Ahmed , Belharouak Ilias , Manthiram Arumugam , Sun Yang-Kook
Published: February 2020

The Li–S batteries are becoming attractive due to the abundance of elemental sulfur and its environmental compatibility. In addition, sulfur undergoes a two-electron redox reaction with lithium and offers an extremely high theoretical speciﬁc capacity of 1675 mAh g−1 and a high energy density of 2600 Wh kg−1.1 Despite these advantages, several issues have hampered the practical use of Li–S batteries. For example, the insulating character of sulfur and lithium sulﬁde impede the full electrochemical utilization of sulfur. Moreover, the dissolution of lithium polysulﬁde inter-mediates in the electrolyte triggers undesirable shuttle reactions. Other issues such as low Coulombic efﬁciency, high self-discharge, and huge volume change remain unsolved. To overcome these drawbacks, several mitigation strategies have been explored by various research groups. One of the most followed routes deals with the mixing/impregnation/conﬁnement of sulfur within highly conducting carbons. carbon nanotube-based composites have been used for high sulfur loading amount. Another approach is the use of metal oxides. In particular, TiO2 is a promising host for sulfur containment owing to its high absorption ability2. Further enhancement in the capacity and cycle life of Li–S batteries has been realized by Manthiram’s group by employing a free-standing interlayer (between the sulfur cathode and the separator) that plays the bifunctional role as a trap for mobile polysulﬁdes and as an upper current collector for fast electron transport3.

Herein, we synthesized and characterized (i) a S-HMT@CNT sulfur cathode comprised of hollow, spherical, nanostructured TiO2 and carbon nanotubes and (ii) DF-PCW interlayer comprised of highly porous carbon spheres and carbon nanotubes. The pores of TiO2 allowed for high sulfur loadings and accommodation of the volume expansion at the electrode level. The CNT component provided an overlap-ping network that improved both the electronic conductivity and mechanical strength of the S-HMT@CNT and DF-PCW. The pores in the carbon interlayer played the role of a medium that scavenged the dissolved lithium polysulﬁdes, while improving Li-ion and electron transports. Owing to our cathode characteristics and cell design, the lithium–sulfur cell fabricated demonstrated good cycle life, high efﬁciency, and high rate capability. Of signiﬁcance, the excellent cycling realized at the 2C and 5C rates is appealing for utilizing the lithium–sulfur batteries in high power applications
In Situ Measurements of Solid Electrolyte Interphase Evolution on Silicon Electrodes
Authors: Yoon Insun , Abraham Daniel P , Lucht Brett L , Bower Allan F , Guduru Pradeep
Published: February 2020

We report in situ measurements of initial solid electrolyte interphase (SEI) evolution on silicon negative electrode and also the lithiation-induced silicon volume changes in lithium ion half-cells. Thin film amorphous silicon (a-Si) electrodes are designed to enable unambiguous measurement of SEI thickness evolution and silicon thickness evolution. The thin film electrode samples are assembled into a custom-designed electrochemical cell integrated with an atomic force microscope (AFM) to facilitate real time measurements. The films are subjected to two potentiostatic lithiation and delithiation cycles by applying a series of constant potential values against lithium metal, which serves as the counter and reference electrode. The thickness changes are measured after a state of equilibrium is reached at each potential value. Experiments are carried out with two electrolytes – 1.2M lithium hexafluoro-phosphate (LiPF6) in ethylene carbonate (EC) and 1.2M LiPF6 in propylene carbonate (PC) – to investigate the influence of electrolyte compositions on SEI formation and electrochemical performance. The results reveal that the predominant SEI thickness evolution occurs during the first cycle, and reaches steady values of approximately 17nm with EC electrolyte and 10nm with PC electrolyte. Despite the thinner SEI layer, capacity loss due to SEI formation is larger with PC electrolyte compared to that of EC electrolyte. Si volume change shows approximately 21% of irreversible volume expansion during the first cycle and no appreciable irreversible volume expansion was observed in the subsequent cycle. In addition, silicon volume expansion shows an approximate linear relationship with the state of charge. Volume change and capacity of silicon films show hysteresis as functions of equilibrium potential. We seek to explain such hysteretic behavior in terms of the stress-potential coupling in silicon, which shows both qualitative and quantitative agreement. Beyond the specific materials systems considered here, the in situ AFM based experimental technique developed in this work has broader applications to investigate the role of electrolyte composition in the SEI formation kinetics.

Figure 1
Determination of Individual Contributions to the Ionic Conduction in Litf/Pegdme-150 Liquid Electrolyte
Authors: Popovic Jelena , Maier Joachim
Published: February 2020

Current salt containing liquid lithium electrolytes show both cationic and anionic conductivity with lithium transference numbers below 50% leading to formation of the ion concentration gradients inside a lithium battery cell. Moreover, the possibility of indirect (vehicular) transport of lithium ions from one electrode to the other via ion pair diffusion is usually neglected when typical DC polarization measurements are performed.[1] If the concept of Conservative Ensembles [2] is employed, effective conductivity can be deconvoluted into transport contributions from free ions and ion pairs even when higher order aggregates are present.[3] We demonstrate experimentally that a combination of DC polarization, impedance spectroscopy and PFG-NMR can enable such analysis for an electrolyte composed of poly(ethylene glycol) dimethyl ether (PEGDME-150) and lithium trifluoromethanesulfonate (LiTf) salt at ambient temperature.[4] In this case, the influence of ion pairs is substantial at all concentrations with values exceeding pure lithium conductivity (in 1M LiTf/PEGDME-150, only 5% of the current is transported by solvated Li+ while 21% is transported via Li-Tf ion pair under applied voltage). By including IR spectroscopy in the arsenal of techniques, mobilities of all species as well as effective mass action constants are calculated for the first time.

 

J. Maier,
Advanced Functional Materials, 21, 1448, 2011.

J. Maier, Journal of the American Ceramic Society, 76, 1212, 1993.

J. Maier, Electrochimica Acta, 129, 21, 2014.

J. Popovic, C. Pfaffenhuber, J. Melchior, J. Maier, Electrochemistry Communications, 60, 195–198, 2015.
Improved Lithium-Sulfur Cell with a Thin Barrier Membrane
Authors: Moy Derek , Narayanan S. R.
Published: February 2020

The development of a high cycle life rechargeable lithium-sulfur battery is of substantial interest due to its high theoretical specific capacity of 1675 mAh/g and energy density of 2600 Wh/kg. These properties combined with the low cost and abundance of sulfur are attractive for practical and high performance lithium-sulfur batteries.  However, the realization of these lithium-sulfur batteries have been limited by performance issues relating to their poor cycle life and low energy efficiency. The typical lithium-sulfur cell loses 20-50% of its initial capacity within 100 cycles due to a parasitic reaction known as the polysulfide shuttle.

The polysulfide shuttle originates from the inherent solubility of the higher order polysulfides, S8
2-, S6
2-, and S4
2-, at the positive electrode. These polysulfides are capable of shuttling between the positive sulfur electrode and negative lithium electrode. When a polysulfide species contacts the negative electrode, it will be reduced to a lower order polysulfide species. If reduced to another soluble species such as S6
2- or S4
2-, it will shuttle back to the positive electrode where it must be reoxidized, resulting in charging inefficiency. If reduced to an insoluble species such as S2
2- or S2-, it will precipitate, resulting in irreversible capacity loss. Therefore, inhibiting the polysulfide shuttle is necessary to improving the energy efficiency and cycle life of lithium-sulfur batteries.

We herein present a method of inhibiting the polysulfide shuttle through use of a thin barrier membrane. The thin barrier membrane is non-porous and capable of conducting lithium ions. The non-porosity of the membrane allows for physical exclusion of polysulfide species from the lithium electrode while the ionic conductivity allows for transport of lithium ions necessary for charge and discharge processes. In a cell configuration, the thin barrier membrane is sandwiched between two porous separators to maintain electronic isolation and inserted between the sulfur and lithium electrode.

We have studied the effect of the thin barrier membrane in 2032-type coin cells consisting of sulfur-carbon composite positive electrodes, lithium foil negative electrodes, and 1 M LiTFSI electrolyte. The performance of the membrane was compared to cells of similar construction without the membrane and also to cells with 0.25 M lithium nitrate, the state-of-the-art polysulfide shuttle inhibiting additive. We have analyzed the performance of all cells using galvanostatic cycling, electrochemical impedance spectroscopy, and direct shuttle current measurements.1 We have found that the thin barrier membrane improves the energy efficiency and cycle life of lithium-sulfur cells by suppressing the polysulfide shuttle.

References:

1. D. Moy, A. Manivannan, and S. R. Narayanan, J. Electrochem. Soc., 2015, 162, A1-A7

Figure 1
Aqueous Ceramic Coating upon Hydrophobic Polyethylene Lithium-Ion Battery Separators through Use of an Anionic Surfactant
Authors: Jeon Hyunkyu , Yeon Daeyong , Lee Taejoo , Park Joonam , Hwang Suyeon , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Highly thermal stable and robust ceramic-coated separators (CCSs) should be included for large-format lithium-ion batteries (LIBs) to secure their safety even at various abnormal conditions such as automobile accident. However, the ceramic coating layer of a few micrometers needs additional coating and slitting processes, resulting in increasing the separator price. Moreover, the hydrophobicity of polyethylene separators requires non-polar organic solvent-based coating slurry consisting of ceramic particles and polymeric binders. In general, organic solvents started to be excluded in the industry field owing to their environmental pollution and additional recovery facility. That is why aqueous ceramic coating process should be developed while overcoming its wetting problem upon hydrophobic polyethylene separators.

Herein, we newly introduce an anionic surfactant, containing both hydrophobic and hydrophilic groups, to make the aqueous slurry be well-dispersed and easily wetted upon polyethylene separators. Due to the cationic property of Al2O3 surface in water, anionic surfactants are appropriate in this application. Among various them, we have chosen disodium laureth sulfosuccinate (DLSS) for this system. We optimized the water-based ceramic coating process using DLSS and investigated the physical properties of Al2O3 ceramic-coated separators. We also studied the electrochemical properties of cells containing the CCSs.

Acknowledges

This research was supported by the New Technology Convergency Type Growth Engine Project of the National Research Foundation (NRF) funded by the Ministry of Science, ICT & Future Planning (NRF-2014M3C1A8074768) and the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977)
Synthesis and Identification of Al-Based Ultrathin Films on Well-Defined Oxide Nanocrystals for Li-Ion Batteries
Authors: Hu Linhua , Cabana Jordi
Published: February 2020

Chemical degradation and capacity fading is one of challenge in LIBs due to the loss of active cathode material from interaction at the interface of the cathode and electrolyte.1 The use of coatings based on a non-active oxide, e.g. Al2O3, is a prevailing strategy to decrease such degradation based on their role as electronic insulator between cathode and electrolyte.2,3 Although many strategies have been reported using different synthetic methods, the surface coating is not well controlled owing to random deposition of precursor on powders of complex morphology, which results in inhomogeneities that leave active surfaces without proper passivation.  Therefore, the synthesis of uniform thin films based on aluminum oxides with controlled thickness, coated on each nanocrystal of an active oxide is an important prerequisite to improve the durability of cathode materials.

Herein, LiCoO2 (LCO) nanoplates were directly synthesized by a hydrothermal process and subsequent coating of aluminum oxide by precursor decomposition and thermal treatment. Figure 1(a) and (b) show TEM images of as-prepared bare LCO nanoplates and coated LCO nanoplates. The edge length and thickness of hexagonal nanoplates is about 50nm and 10~20nm. The exposed surfaces are (001) and (010). 1~2nm thick alumina were uniformly coated on LCO nanoplates. EDX mapping and line scan has confirmed the LCO core and alumina shell structure. The thermal treatments were performed at 400~600oC for 3hours. The size of LCO didn’t change after coating. The electrochemical properties have demonstrated the enhanced effect of alumina coating. The balance of capacity and cycling ability is dependent on different temperature and loading of alumina.

References:

Jonathon L. Tebbe, Aaron M. Holder, and Charles B. Musgrave. ACS Appl. Mater. Interfaces, 24265-24278, 7(2015). Mechanisms of LiCoO2 Cathode Degradation by Reaction with HF and Protection by Thin Oxide Coatings

Seung-Taek Myung, Kentarou Izumi, Shinichi Komaba, Hitoshi Yashiro, Hyun Joo Bang, Yang-Kook Sun, and Naoaki Kumagai J. Phys. Chem. C 2007, 111, 4061-4067, 111(2007). Functionality of Oxide Coating for Li[Li0.05Ni0.4Co0.15Mn 0.4]O2 as Positive Electrode Materials for Lithium-Ion Secondary Batteries

Jun Liu and Arumugam Manthiram. Chem. Mater.
1695-1707, 21 (2009). Understanding the Improvement in the Electrochemical Properties of Surface Modified 5 V LiMn1.42Ni 0.42Co0.16O4 Spinel Cathodes in Lithium-ion Cells

Figure 1
Stabilization of Cubic-Na3PS4 to Enhance Ionic Conductivity of Solid Electrolytes for All-Solid-State Sodium Sulfur Batteries
Authors: Kompella Christopher , Nguyen Han , Hy Sunny , Zhu Zhuoying , Chu Iek-Heng , Ong Shyue Ping , Meng Ying Shirley
Published: February 2020

Solid-state electrolytes (SSE’s) are crucial in realizing the potential of novel rechargeable batteries. All-solid-state batteries with inorganic solid electrolytes offer a number of advantages by improving safety, reliability, and cost [1]. Sulfide glasses are promising as a solid electrolyte due to their superionic ionic conductivity [3]. Na3PS4 is a glass-ceramic that is precipitated from the sulfide glass matrix, exhibiting ionic conductivities of 10-6 and 10-4 S/cm for the tetragonal and cubic phases, respectively [4]. Here we provide a simple synthesis process for stabilizing the cubic phase, which also reduces the activation energy to 330 meV. We also investigate anion doping, which can further improve upon this result by increasing Na vacancies, via a composition curve of Cl-doping to determine optimal concentration of (1-x)Na3PS4-xNaCl, for 0 > x > 0.0625.

Acknowledgements

This work was supported by National Science Foundation under grant number ACI-1053575.

References

[1]      Kamaya, Noriaki et al. “A Lithium Superionic Conductor.” Nature Materials10.9 (2011): 682–686. Web.

[2]      Hayashi, Akitoshi et al. “Superionic Glass-Ceramic Electrolytes for Room-Temperature Rechargeable Sodium Batteries.” Nature Communications 3.May (2012): 856. Web.Tatsumisago, Masahiro, and Akitoshi Hayashi. “Sulfide Glass-Ceramic Electrolytes for All-Solid-State Lithium and Sodium Batteries.” International Journal of Applied Glass Science10 (2014): 226–235. Web.

[3]      Ribes, M., B. Barrau, and J.L Souquet. “Sulfide Glasses: Glass Forming Region, Structure and Ionic Conduction of Glasses in Na2S-XS2 (X=Si, Ge), Na2S-P2S5, and Li2SGeS2 Systems.” Journal of Non-Crystalline Solids39 (1980): 271–276. Print.

[4]      Hayashi, Akitoshi et al. “Superionic Glass-Ceramic Electrolytes for Room-Temperature Rechargeable Sodium Batteries.” Nature Communications 3.May (2012): 856. Web.

Figure 1
Interconnected Ge/Cu Nanostructured Anodes for High Areal Capacity Li-Ion Microbatteries
Authors: Lee Gwang-Hee , Lee Seun , Mho Sun-Il , Kim Dong-Wan
Published: February 2020

Li-ion microbatteries (LIMBs) have been rapidly developed in integrated smart micro-systems for bio medical devices and wearable devices. To improve rapidly integrated micro-systems, it is important to develop LIMBs with high energy and power density per unit area. Therefore, areal (or volumetric) capacity is more important than gravimetric capacity. Specially, anode materials having high areal capacity can provide a more effective way to develop advanced high-performance LIMBs. Ge anode materials could also realize high volumetric capacities of approximately 8650 mA h cm-3, similar to volumetric capacities of Si anode materials. In addition, three-dimensional (3-D) conducting networks with Ge anode materials could provide synergistic effects. The 3-D conducting networks offers the opportunity to lead high areal capacity because of increasing mass loading of active materials per unit area, improving electronic and ionic pathways by interconnected open channel networks, and relaxing of the volume expansion during discharge/charge cycling.

Herein, we suggest to design newly 3-D network structures which could load massive Ge anode materials for high energy and power density per unit area. We fabricated highly ordered 3-D Ge nanoarrays loaded on Cu nanowire-network current collectors (Ge/Cu Nanowire-Networks). As the Cu nanowire-network current collector, the Cu nanonets were synthesized by MOCVD (metal-organic chemical vapor deposition) using a Cu(C2H3O2)2∙H2O powder. And then, the Ge nanowires as anode materials were deposited onto the as-prepared Cu nanonets using the thermal evaporation of Ge powder. Loading mass of the Ge nanowires is dependent on deposition time. To provide porous structures, the prepared samples removed spontaneous oxide layers by 0.2 vol% H2SO4 solution.

We performed electrochemical performance tests of the Ge/Cu Nanowire-Networks with various mass loadings (from 0.7 to 7.0 mg cm-2). The Ge/Cu Nanowire-Networks showed stable high areal capacity (> 2 mA h cm-2) at a current density of 1 mA cm-2 over 140 cycles and the excellent rate capability of 1.3 mA h cm-2 at a current density of 5 mA cm-2. The Ge/Cu Nanowire-Networks with a mass loading density 7.0 g cm-2 has been fabricated, achieving a high areal capacity of 6.4 mA h cm-2 after 40 cycles. Also, we performed EIS analysis to determine the relationship between the electrochemical performance and electrode kinetics. To investigate morphologies and phases of the Ge/Cu Nanowire-Networks, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were employed.
Influence of Excess Lithium on the Electrochemical Performance of Li1+Z
MnTiO4 Spinel Structure for High Capacity and Long Cycle Life
Authors: Vu Ngoc Hung , Im Won Bin
Published: February 2020

Spinel based lithium manganese oxide is the most attractive cathodes for lithium-ion battery due to high capacity, low cost, and non-toxic. This material has a theoretical high capacity of 296 mAh g-1 (2 Li+ ions) if Li+ ions are fully inserted/extracted into/from the spinel structure. However, it is well known that when LiMn2O4 is discharged to a low voltage, e.g., 2 V, high spin Mn3+ ions may induce severe Jahn-Teller distortion. Up to date, this material is only used in the 4 V region with a low capacity of 120 mAh g-1. [1, 2]

Much effort has been made to enhance the cycle stability of such cathode materials in a wide voltage window (e.g., 2.0-4.8 V). The substitution of titanium for manganese can improve the cycle life of cathode materials but with a decrease in the capacity of material which restrict its usage in a broad application. [2, 3]

In this paper, Li1+z
MnTiO4 (z = 0, 0.5, and 1) were developed to solve the problems of low capacity and short cycle life. Excess lithium material (z = 0.5 and 1) formed a solid-solution with notation (1-a)LiMn2-x
Ti
x
O4.aLi2Mn
y
Ti1-y
O3, which improve the capacity of material up to 218 mAh g-1, after 60 cycles with a capacity retention of 93 %. The structure and electrochemical properties were investigated carefully through X-ray diffraction, galvanostatic cycling, cyclic voltammetry (CV), galvanostatic intermittent titration technique (GITT) to understand the mechanism of the improvement in the capacity and cycle stability of material. We also analyzed the effect of impurity phase as a significant factor that affects the electrochemical performance of the cathodes.

References

Thackeray, M.M. Prog. Solid State Chem. 1997, 25 (1–2), 1-71

Wang, S.; Yang, J.; Wu, X.; Li, Y.; Gong, Z.; Wen, W.; Lin, M.; Yang, J.; Yang, Y. J. Power Sources. 2014, 245, 570-578.

Chen, R.; Knapp, M.; Yavuz, M.; Heinzmann, R.; Wang, D.; Ren, S.; Trouillet, V.; Lebedkin, S.; Doyle, S.; Hahn, H.; Ehrenberg, H.; Indris, S. J. Phys. Chem. C. 2014, 118 (24), 12608-12616.

Figure 1
High-Energy and Safe Positive Electrode Material with Two-Slope Concentration Gradient for Lithium-Ion Batteries
Authors: Lim Byung-Beom , Yoon Chong seung , Kim Sung-Jin , Lee Juhyon J. , Sun Yang-Kook , Kim Un-Hyuk
Published: February 2020

Li[Ni0.65Co0.13Mn0.22]O2 cathode with two-sloped full concentration gradient (TSFCG), maximizing the Ni content in the inner part of the particle and the Mn content near the particle surface, is synthesized via a specially designed batch-type reactor. The cathode delivers a discharge capacity of 200 mAh g−1 (4.3 V cutoff) with excellent capacity retention of 88% after 1500 cycles in a full-cell configuration. Overall electrochemical performance of the TSFCG cathode is benchmarked against conventional cathode (CC) with same composition and commercially available Li[Ni0.8Co0.15Al0.05]O2 (NCA). The TSFCG cathode exhibits the best cycling stability, rate capability, and thermal stability of the three electrodes. Transmission electron microscopy analysis of the cycled TSFCG, CC, and NCA cathodes shows that the TSFCG electrode maintains both its mechanical and structural integrity whereas the NCA electrode nearly pulverizes due to the strain during cycling.
Effect of Lithium in Transition Metal Layers of High-Ni Positive Electrode Materials on Electrochemical Properties
Authors: Lim Byung-Beom , Yoon Chong seung , Myung Seung-Taek , Komaba Shinichi , Sun Yang-Kook
Published: February 2020

Li was incorporated into transition metal layers of Ni-rich Li[Ni0.95Co0.05]O2 by formation of a solid solution with Li2MnO3 (layer notation: Li[Li0.33Mn0.67]O2), which can be denoted as (1-x)Li[Ni0.95Co0.05]O2 – xLi[Li0.33Mn0.67]O2, to understand the effect of Li on the structure, electrochemistry and thermal characteristic of the cathode. Structural analysis data obtained by Rietveld refinement of X-ray diffraction data indicate that the additional Li can be found in the transition metal layers of (1-x)Li[Ni0.95Co0.05]O2 – xLi[Li0.33Mn0.67]O2. An interesting feature is that the average oxidation states of Ni and Mn are 3+ and 4+, respectively, for (1-x)Li[Ni0.95Co0.05]O2 – xLi[Li0.33Mn0.67]O2 as demonstrated by X-ray absorption study. The first discharge capacity was approximately 217 mAh g−1, and the resulting retention was above 90% for 0.9Li[Ni0.95Co0.05]O2 – 0.1Li[Li0.33Mn0.67]O2 (Li[Li0.033Ni0.855Co0.045Mn0.067]O2) in the range of 2.7 to 4.5 V for 100 cycles, which is a surprising result for Ni-rich compounds. Moreover, the thermal stability of (1-x)Li[Ni0.95Co0.05]O2 – xLi[Li0.33Mn0.67]O2 was significantly improved over the cathodes with identical Ni fraction. These results highlight the role of tetravalent Mn ions, even in small amounts, in stabilizing the electrochemical performances and thermal properties in the Ni-rich layer cathodes.
Facile Reduction of Pseudo-Carbonates: Promoting Solid Electrolyte Interphases with Dicyanoketene Alkylene Acetals in Lithium-Ion Batteries
Authors: Forestier Coralie , Jankowski Piotr , Coser Laura , Gachot Grégory , Sannier Lucas , Johansson Patrik , Grugeon Sylvie , Laruelle Stéphane , Armand Michel
Published: February 2020

In recent years, greener transportation has become of major interest to limit air pollution and global warming. For this purpose, Li-ion batteries (LIBs) are considered as the most promising power source for electric vehicles (EV) and hybrid electric vehicles (HEV) due to their high energy density. The use of high-energy multi-cell battery packs imposes ever more stringent requirements on LIBs in term of safety and long-term cyclability.

The formation of an effective SEI passivation layer at the negative electrode / electrolyte interface was found to be of paramount importance in order to enable LIB long-life cycling and controlling the threshold for thermal runaway. This is why SEI-forming additives have been used in the electrolyte to reinforce these protective properties, with the most common additives being vinylene carbonate (VC) (1), fluoroethylene carbonate (FEC) (2), and vinyl ethylene carbonate (VEC) (3).

To our knowledge, the modification of EC and PC on the carbonyl group, rather than on the alkylene bridge as for VC, VEC, or FEC, has not previously been attempted.(4,5) It is known that the =C(CN)2 group is an “oxygen equivalent” being even slightly more electronegative than O itself and extending considerably the conjugation. Hence, we hypothesized that modified EC or PC, with C=C(CN)2 replacing the carbonyl groups, could lead to a more facile reduction at higher potentials and a stable SEI.

The dicyanoketene propylene (and ethylene) acetal, DCKPA (DCKEA), have both been synthesized according to a simple procedure.(6) The reduction process has been investigated for DCKPA by means of GC/MS and IR analysis and the efficiency as a SEI-reinforcing additive demonstrated by the analysis of the soluble products using liquid GC/MS.

The cycling tests using a pouch cell configuration at both 20 and 45°C were realized with only 0.5 wt.% of additive in the electrolyte and resulted in higher capacity retention.  Moreover, a post-mortem analysis by DSC revealed an improvement in term of safety due to an improved lithiated graphite/electrolyte interface.

[1] H.-H. Lee, Y.-Y. Wang, C.-C. Wan, M.-H. Yang, H.-C. Wu, D.-T. Shieh, Journal of Applied Electrochemistry. 35 (2005) 615–623.

[2] I.A. Profatilova, S.-S. Kim, N.-S. Choi, Electrochimica Acta. 54 (2009) 4445–4450.

[3] Y. Hu, W. Kong, H. Li, X. Huang, L. Chen, Electrochemistry Communications. 6 (2004) 126–131.

[4] C. Forestier, P. Jankowski, L. Coser, G. Gachot, L. Sannier, P. Johansson, et al., Journal of Power Sources. 303 (2016) 1–9.

[5] Pending patent

[6] W.J. Middleton, V.A. Engelhardt, Journal of the American Chemical Society. 80 (1958) 2788–2795.

 

Figure 1: Results of cycling tests at 45°C without and with 0.5 wt.% of DCKPA using a pouch cell configuration, and the post mortem DSC / liquid GC/MS analyses.

Figure 1