bluuebunny/crossref_metadata_2025 huggingface dataset:
Leveraging Reactivity Differences to Isolate the Less-Common Holmium Metallofullerenes
Authors: Tepper Katelyn R. , Stevenson Steven
Published: February 2020

This research focuses on the less-common Ho-based metallofullerenes. For their purification, we developed a two-stage separation. In the first step, we removed fullerene contaminants by selective reaction with aminopropanol. This initial stage is important because it simplifies the sample mixture for the second stage, HPLC. Subsequent injection and fraction collection permits the isolation of Ho endohedrals having less-common cages. UV-Vis spectra for purified species will be presented.
Improved Bending Fracture Behavior of Large-Scale Graphene Monolayer-Intervened Flexible Oxide Thin Films
Authors: Choi Hong Je , Kim Da Bin , Cho Yong Soo
Published: February 2020

This work describes for the first time the quantitative analyses of bending fracture resistance of a flexible transparent conducting oxide (TCO) thin film, here using Al-doped ZnO thin films, which are substantially improved by the intervention of a monolayer graphene layer. Most of the mechanical effects by graphene have focused on the graphene itself and particularly when only the stretched strains are applied. Excessive stretching stress induces buckling and/or flakes with the intervened graphene, which has been the issue for the actual evaluation of flexible cracking performance. This work focuses on the external effect of graphene, namely how the intervention of graphene can influence positively the fracture behaviour of inorganic thin films under bending operation on the basis of quantitative analyses of flexible fracture parameters including fracture energy, film strength and fracture toughness. A graphene monolayer of ~1 cm x 1 cm scale was transferred successfully to a polymer substrate prior to the sputter-deposition of Al-doped ZnO thin films with variable thickness of 50 to 200 nm. Cracking evolution of the ZnO:Al thin films depended largely on the applied bending strain and film thickness. The crack-initiating strain of ~1.64% with the graphene corresponds to a ~61% improvement compared to the reference sample without the graphene. The resultant mechanical parameters, fracture energy, film strength and fracture toughness, support well the enhanced fracture resistance under the bending operation. For example, the fracture energy was identified as enhanced by ~272% with the intervention of graphene.
(Invited) Metal Halide Perovskites at the Nanoscale: High Quality Optoelectronic Materials with Unique Phase Properties
Authors: Luther Joseph M.
Published: February 2020

The newly rediscovered perovskite semiconductor system has the potential to be extremely transformative for all optoelectronic devices, especially photovoltaics (PVs). Perovskite semiconductors of the form APbI3 where A is a large +1 charged cation, typically Cs, methylammonium, or formamidinium have had a huge resurgence among materials scientists for outstanding PV properties despite being overlooked for decades. Semiconductors containing the latter two A-site cations listed are hybrid organic-inorganic materials, and as such, are far less understood compared to conventional all inorganic or even organic material systems. Regardless of this spotty formal understanding, lead-halide perovskites have very rapidly been optimized to power conversion efficiency levels on par with all other materials even with extensive history of research. Perovskites show a unique tolerance to crystalline defects that cause trouble in most other semiconductors. Therefore the potential offered is that very high efficiency PVs can be fabricated in extremely fast and inexpensive ways, thus offering a revolution for the solar industry and a direct route toward producing the world’s energy with a simple and clean technology. Long-term durability of the devices is the critical remaining challenge to be solved.1 Two examples of major instabilities in device performance are the volatility of the organic cation and the specific crystal habit in which the material embodies.

Nanoscale versions (often termed quantum dots (QDs)) of the all-inorganic metal halide perovskite (CsPbI3) tend to retain the desired perovskite phase due to strain effects at the surface of the QDs whereas conventional films of the same material “relax” to an orthorhombic non-perovskite structure at room temperature. Therefore these QDs potentially solve both of the instability issues. The cubic CsPbI3 QD cells operate with a rather remarkable open-circuit voltage of >1.2 volts and have produced power conversion efficiencies over 13%.2,3 This customizable new nanomaterial system has incredible potential for many applications in optoelectronics, including photovoltaics, LEDs, displays and lasers. We describe the formation of perovskite phase-CsPbI3 QD films with long range electronic transport that retain the high temperature phase in ambient conditions making up the active layer in optoelectronic devices. Perspectives on how this technology can become transformative will be discussed.

References

A. Christians, P. Schulz, J.S. Tinkham, T.H. Schloemer, S.P. Harvey, B.J .Tremolet de Villers, A. Sellinger, J.J. Berry, J.M. Luther, Nature Energy, 2018, 3 (1), 68.

Swarnkar, A.R. Marshall, E.M. Sanehira, B.D. Chernomordik, D.T. Moore, J.A. Christians, T. Chakrabarti, J.M. Luther, Science, 2016, 354 (6308), 92-95.

M. Sanehira, A.R. Marshall, J.A. Christians, S.P. Harvey, P.N. Ciesielski, L.M. Wheeler, P. Schulz, L.Y. Lin, M.C. Beard, J.M. Luther, Science Advances, 2017, 3 (10), eaao4204.
Electrochemical and Chemical Reductions to Stable [Co(NO)]9 N-Confused Porphyrin Complexes for NO to Nitrous Oxide Conversion
Authors: Hung Chen-Hsiung
Published: February 2020

Stable [Co(NO)]9 complex is rare in literature. In this report, we present the synthesis of a [Co(NO)]8 N-confused porphyrin (NCP) complex from the reaction of a four coordinated cobalt complex with nitric oxide. In addition to the regular N-confused porphyrin ligand, the [Co(NO)]8 complexes with an inner carbon methylated NCP and inner carbon oxygenated NCP were also obtained. Reversible redox couples were observed from CV and IR spectroelectrochemical studies upon the electrochemical reduction or oxidation on the [Co(NO)]8 complexes. The distinctive differences on the shifting of ν(NO) suggest that the supporting ligand will control an either metal-based or a ligand-based redox process. Through a bulk electrolysis or treatment of cobaltocene, [Co(NO)]9 complexes were obtained. The obtain of the first single-crystal structure further demonstrates an unique stability of this NCP ligand supported [Co(NO)]9 complex. For the first time, we observed that the [Co(NO)]9 complex is active toward the hydrogen evolution reaction. More importantly, the addition of ethanol into the solution of [Co(NO)]9 observed the conversion of axial NO ligand to nitrous oxide. The potential mechanism of NO to N2O conversion and the spectroscopic information of the reaction intermediates will be discussed in this presentation.

Figure 1
Tuning up Redox and Photophysical Properties of Donor-Acceptor Dichromophoric Dyads and Triads Toward a Rational Design of New Light-Harvesting Materials
Authors: Nemykin Victor V. , Zatsikha Yuriy V. , Kovtun Yuriy P. , Blank David A.
Published: February 2020

Redox and photophysical properties of a large number of the porphyrins, phthalocyanines, BODIPY-, aza-BODIPY-, and BOPHY-based donor-acceptor dyads and triads have been investigated by the variety of spectroscopic and electrochemical methods as well as steady-state and time-resolved spectroscopic methods. The electronic structures of new compounds investigated by the Density Functional Theory (DFT) and Time-Dependent DFT (TD-DFT) methods.
Peripheral π-Extention of Carbazole-Based Porphyrins
Authors: Maeda Chihiro
Published: February 2020

We have explored the synthesis and functionalization of carbazole-based porphyrins. For example, compound 1 exhibited strong NIR absorption at 1087 nm due to the expanded conjugation by four benzo-fusion moieties. Here, we tried intramolecular cyclization of ethynyl-substituted compounds to form ethylene-fused compounds 2. Furthermore, additional benzo-fusion to carbazole moiety using benzocarbazole furnished 3. Thus newly synthesized porphyrins showed further red-shifted and broadened NIR absorption.

Figure 1
Effects of Amino Acids on Silicon Oxide for High Silicon Oxide Removal Rate Ceria Slurry
Authors: Kim Taesung
Published: February 2020

Chemical mechanical polishing (CMP) is a process for flattening a wafer, and its importance is increasing as design rules are shrunk. There are Inter Level Dielectric (ILD), Shallow Trench isolation (STI), and 3D-NAND CMP processes for polishing the oxide surface in the CMP process. In the case of 3D-NAND CMP, a high removal rate (RR) slurry is required because a thick oxide film must be polished in a short time. Generally, ceria or silica slurries are used in oxide CMP. Ceria slurry shows high RR by Ce-O-Si bonding. The slurry includes additives for purpose of dispersion of abrasive, pH adjustment, change of wafer surface properties. Amino acids have various functional groups depending on the pH. Depending on the activity of the functional groups, the amino acid has various effects on the surface of the slurry or silicon oxide. Amino acids were used additive in slurry and some amino acids increased the removal rate. We investigated the effect of some amino acids on the silicon oxide wafers and ceria slurry. The effect of amino acids on the removal rate was analyzed by zeta potential, contact angle and X-ray photoelectron spectroscopy analysis. Our results indicate that some amino acid adsorb on oxide surface and increase the values of absolute zeta potential. Differences in zeta potential values between slurry and wafer surface make high removal rate.

Figure 1
Simple but Highly-Efficient Polysulfide Trapping Strategy for Lithium-Sulfur Batteries
Authors: Yuan Yan , Zheng Dongdong , Fang Zhao , Lu Hai
Published: February 2020

Lithium-sulfur (Li-S) battery, as an attractive alternative to the state-of-the-art Li-ion battery by the merits of high energy density and abundant material sources, is expected to meet the urgent demand of next-generation electric vehicles. However, several challenges severely hinder its application process, including low conductivity of elemental sulfur and lithium sulfide, large volume expansion upon discharge, and unfavorable redox shuttle due to the soluble polysulfides (PSs). In order to increase sulfur utilization and cycle stability of the Li-S batteries, a variety of strategies on modifying sulfur cathode have been attempted, e.g. development of sulfur-carbon composite, introduction of extra surface coating and novel electrode component, etc.

It is worthy to note that many studies involving PS’ trapping material/structure always brought about significant improvement of cell performance. This is because that the active species loss and shuttle side effect were reduced. Recently our research group has reported the good chemical affinity of polyacrylamide (PAM) to PSs, coming from the strong binding of the amide group in the PAM with Li-S• species. Therefore, the polymer was successfully used in the surface coating on either sulfur cathode or porous separator [1, 2]. Poly(acrylic acid) (PAA), another water-soluble polymer, also can act as a favorable PS blocking layer because the COOH groups in the long chain can form strong hydrogen bonds with the PS anions [3].

This research demonstrates a simple but highly-efficient PS trapping strategy that employs PAA and PAM as a functional binder and additive for sulfur cathode, respectively. The synergistic action of these two distinctive agents contributes to higher reversible capacity and longer cycle life of Li-S batteries compared to conventional electrode. The mechanism of trapping PSs in the artificially-designed cathode framework was discussed, and the enhancement of hydrophilic nature of the cathode to the liquid electrolyte was also considered. It needs to be emphasized that the novel cathode can be easily fabricated on a large-scale without any additional procedures.

Fig. 1 Comparison of cycle performance of PAM/PAA-contained cathode and conventional sulfur cathode

Reference:

[1] T. Li, Y. Yuan, B. Hong, et al, Electrochim. Acta, 2017, 244, 192-198

[2] H. Lu, J. Wang, T. Li, et al, J Solid State Electrochem., 2018, 22, 953-958

[3] S. Zhang, D. Tran, Z Zhang, J. Mater. Chem. A, 2014, 2, 18288-18292

Acknowledgment:

This work was financially supported by National Natural Science Foundation of China (No.51704222, 51604221 and 51574191), Natural Science Basic Research Plan in Shaanxi Province of China (No.2016JQ5040), and Special Scientific Research Program of Education Department of Shaanxi in China (No.17JK0427).

Figure 1
Mxenes As Sulfur Host Material for Magnesium-Sulfur Batteries
Authors: Kaland Henning , Fagerli Frode Håskjold , Hadler-Jacobsen Jacob , Boge Lars-Arne , Schnell Sondre Kvalvaag , Vullum-Bruer Fride
Published: February 2020

Magnesium-sulfur batteries offer the possibility of combining highly abundant and cheap elements with high energy density. Despite recent significant improvements, critical aspects still in need of optimization include electrolyte and cathode design [1]. The latter involves finding a cathode composition that prevents the polysulfide shuttle mechanism, which deteriorates the capacity retention, while at the same time providing high electrical conductivity to the insulating sulfur. Since its invention in 2011 [2], the MXene family of materials has attracted much attention for a range of applications, mostly due to its high electrical conductivity combined with hydrophilicity and good mechanical strength [3]. Recently, MXene-based sulfur composite cathodes have demonstrated promising performance for lithium-sulfur batteries [4].

Here, titanium- and vanadium-based MXenes have been investigated as sulfur host material for magnesium-sulfur batteries. MXenes were obtained by leaching out the aluminum from the corresponding MAX phase, which was confirmed by XRD and EDS. After sulfur loading, the MXene-sulfur composite was tested as cathode with a Mg anode, glass fiber separator and different Mg electrolytes, showing promising electrochemical performance. Optimization of the MXene surface termination, the sulfur infiltration method and the electrolyte is currently being investigated, with an aim of lowering the overpotential, improving capacity retention and increasing the sulfur utilization.

Reference
s
:

[1] Z. Zhao-Karger, M. Fichtner, MRS Communications (2017), 7, 770–784.

[2] Naguib et al., Adv. Mater. 23 (2011) 4248-4253.

[3] B. Anasori, M. R. Lukatskaya, Y. Gogotsi, Nature Reviews Materials 2 (2017) 16098, 1-17.

[4] Gao et al., Small (2018), 14, 1802443.
Understanding of Failure Mechanism of High Energy Lithium-Sulfur Pouch Cells
Authors: Shi Lili , Lu Dongping , Niu Chaojiang , Ren Xiaodi , Xiao Jie , Liu Jun
Published: February 2020

Lithium sulfur (Li-S) battery is a promising next generation energy storage technology for vehicle electrification or large scale energy storage due to the high theoretical energy, low cost, and environmental friendliness of sulfur. 1 However, deployment of Li-S batteries in practical applications has been hindered by the low practical energy and limited cycle life. Extensive researches in Li-S batteries have been performed, and significant advances have been demonstrated in material development and fundamental understandings of the reaction mechanism. 2, 3 However, most of the previous studies are based on thin film sulfur electrodes, excess amount of electrolyte, or small size coin cell configuration. It has been reported that sulfur utilization and cycle life are both affected if using electrodes with elevated sulfur loading and under conditions of lean amount of electrolyte. 4 This indicates scientific gaps existing between the high loading electrodes and the reported thin film counterparts. The new understandings and knowledge linking the “theoretical” and “practical” are essential for the further maturing of the Li-S battery technology. In an attempt to fill such scientific gaps, high energy Li-S pouch cells were designed and fabricated in our research by using high loading electrodes and lean electrolyte. Practically high energy of 372 Wh kg-1 has been demonstrated in the Li-S pouch cells although cycle life is still limited. Systematic understanding of cell failure mechanism under practical conditions was carried out by using advanced characterization techniques. Electrolyte depletion and non-uniformity of electrochemical reactions of both cathode and anode were identified as dominant factors of cell capacity decay and internal short-circuit. Detailed postmortem analysis of the cycled Li-S pouch cell and failure mechanism understanding will be presented and discussed at the meeting.

References

A. Manthiram, Y. Z. Fu, S. H. Chung, C. X. Zu and Y. S. Su, Chem. Rev., 2014, 114, 11751-11787.

D. Aurbach, E. Pollak, R. Elazari, G. Salitra, C. S. Kelley and J. Affinito, J. Electrochem. Soc., 2009, 156, A694-A702.

X. L. Ji, K. T. Lee and L. F. Nazar, Nat. Mater., 2009, 8, 500-506.

D. P. Lv, J. M. Zheng, Q. Y. Li, X. Xie, S. Ferrara, Z. M. Nie, L. B. Mehdi, N. D. Browning, J. G. Zhang, G. L. Graff, J. Liu and J. Xiao, Adv. Energy Mater., 2015, 5, 8.
Highly Conductive PEO-Based Polymer Electrolyte for Na Battery Applications
Authors: Lu Xiaochuan , He Xinzi , Wang Hui , Reed David , Sprenkle Vincent
Published: February 2020

State-of-the-art Li- or Na-ion batteries typically use organic solvents in the electrolytes, which might cause serious safety issues. Replacing the liquid electrolytes with nonflammable, dense solid-state electrolytes can potentially solve this problem. Among all types of solid electrolytes, PEO-based polymer electrolytes (PBPEs) have attracted extensive attentions owing to their excellent flexibility, chemical stability, and easiness for processing. However, their relatively low ionic conductivities limit the applications in batteries. Here, we reported our recent progress to develop a class of highly conductive PBPEs for Na battery applications. Through addition of a moderate amount of ionic liquid (e.g., EMITFSI) to PEO, a significant amount of amorphous phase was detected in the polymer, which is critical to achieve high ionic conduction. Addition of 5~15 wt.% NaTFSI to the composite further increased the content of the amorphous phase and eventually led to a nearly 100% amorphous. The total ionic conductivities of the PBPE with 15 wt.% NaTFSI were as high as 0.59 and 2.07 x 10-3 S/cm at RT and 50oC, respectively, which is significantly higher than those of traditional PBPEs. In this study, the electrochemical, chemical, and mechanical properties and performance of the PBPEs have been thoroughly investigated, which indicated this type of PBPEs is very promising as a membrane for all-solid-state Na battery applications.
Current Collector Interface for Phase Changing Tin Anode in Sodium Ion Batteries: Insight from First Principles Calculations
Authors: Sharma Vidushi , Ghatak Kamalika , Datta Dibakar
Published: February 2020

Performance of an efficient and high capacity Lithium-ion battery (LIB) and Sodium-ion battery (NIB) greatly depends upon electrode-current collector interface. While copper (Cu) is most extensively used current collector at the anode end, it has been associated with numerous functional issues such as debonding, corrosion, strain accommodation, low flexibility, and high cost and weight. In this work, we investigate the comparative performance of Graphene with Cu as the current collector for NIB anode. Graphene not only provides the battery system much-needed flexibility, cost, and weight efficiency but also imparts mechanical stability to the system during the sodiation and de-sodiation cycles. Tin (Sn) has been taken up as model anode material owing to its potential and promising high theoretical specific capacity of 994 mAh/g. However, the anodic performance of Sn is limited by its high-volume expansion and multiple phase changes which leads to subsequent mechanical failure. Therefore, the effect of mechanical strains and phase transitions during battery performance on the interface has been investigated in detail. We have employed vdW inclusive GGA based Density Functional Theory (DFT) implemented in VASP to study the effect of sodiation and de-sodiation on the mechanical integrity of anode and current collector interface. We report that Graphene is more efficient in combatting mechanical stresses generated in the anode during the performance and also allows easy expansion to Sn. We hope that this work will throw more light on the mechanics and chemistry that are prominent at the interface of an anode and current collector.
Interfacial Stabilization for Improved Cycling Performance of Polymer-Based All-Solid-State Batteries Using Additive Combination
Authors: Yee Minha , Suk Jungdon , Song Seung-Wan
Published: February 2020

Recently, researchers are devoted to develop all-solid-state batteries based on solid electrolytes such as polymers, sulfides, oxide ceramics that can provide improved thermal stability and safety than conventional lithium-ion batteries based flammable organic liquid electrolyte. However, solid electrolytes faces to challenge lower ionic conductivity and interfacial contact problem between cathode and electrolyte, which causes large interfacial resistance. In this presentation, we report the fabrication of polymer-based all-solid-state batteries with high-nickel LiNi0.8Co0.1Mn0.1O2 cathode, attainment of high areal capacity ~1.5 mAhcm-2 and improvement of cycling performance using additive combination. Studies of the changes in the structure and morphology of cathode and surface composition and their correlation to the performance would be discussed in the meeting.

Acknowledgements

This research was supported by the Korean Ministry of Trade, Industry & Energy (10080025), and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/Bio Materials of BK Plus program by Ministry of Education of Korea.
Lithium-Ion Polymer Cells Fabricated Using in-Situ Cross-Linked Quasi-Solid-State Polymer Electrolyte
Authors: Park Sung-Guk , Jung Yun-Chae , Seo Yerin , Kim Dong-Won
Published: February 2020

Lithium-ion batteries (LIBs) have been actively developed and are being used nowadays in various applications. However, liquid electrolyte currently used in LIBs has critical drawbacks such as flammability and leakage problem. To enhance the safety of LIBs, intensive efforts have been devoted to replace liquid electrolyte to safer electrolytes. Among the various promising electrolyte systems, solid polymer electrolytes have received great attention due to enhanced safety, absence of leakage and design flexibility. However, their low ionic conductivities preclude their practical applications at ambient temperatures. Accordingly, most relevant research has focused on the preparation and characterization of plasticized polymer electrolytes that contain small amount of organic solvent. In this work, we report the preparation and electrochemical characteristics of quasi-solid-state polymer electrolytes synthesized from ion-conductive poly(propylene carbonate) (PPC), which were in-situ cross-linked in the presence of small amount of plasticizing solvent by click chemistry. The polymer electrolyte was applied to the lithium polymer cell composed a lithium anode and a LiNi0.6Co0.2Mn0.2O2
cathode. Our result demonstrate that the quasi-solid-state polymer electrolytes are very promising electrolytes for achieving high performance and enhancing battery safety.
Lithium Ion Intercalation into Graphite in so2-Based Inorganic Electrolyte Towards High-Rate Capable and Safe Lithium Ion Batteries
Authors: Lee Jiwhan , Kim Ayoung , Jung Hojae , Jeong Goojin , Kim Hansu
Published: February 2020

Lithium ion batteries (LIBs) have been used widely as power sources for portable electronic devices and regarded as promising power sources for next-generation secondary battery system. To meet the demands of these emerging applications, the safety, power density and energy density of Li batteries need to be further improved. In this presentation, we report the reversible lithium ion intercalation reaction into graphite anode in LiAlCl4-3SO2 non-flammable inorganic liquid electrolyte. Using ex situ x-ray diffraction analysis as well as electrochemical characterization techniques, we found that lithium ions could be reversibly intercalated into graphite anode materials with highly stable capacity retention up to 100 cycles. X-ray photoelectron spectroscopy on the reacted graphite electrode clearly showed that solid electrolyte interface(SEI) formed on the graphite was completely different from SEI formed on the graphite in the conventionally used organic electrolyte. Detailed electrochemical properties of graphite in SO2-based inorganic electrolyte will be discussed in this presentation.
One-Step Synergy of Coating and Doping By TiN Atomic Layer Deposition for Significant Improvement on Li-Ion Battery
Authors: Gao Yan , Park Jonghyun , Liang Xinhua
Published: February 2020

Atomic layer deposition (ALD) method has emerged as a promising technique to address the dissolution and poor conductivity of electrode materials of lithium ion batteries. In this work, synergic coating and doping on LiFePO4 (LFP) was carried out by titanium nitride (TiN) ALD. The composition of TiN layer on the surface of LFP particles was interpreted as a combination of TiN and titanium oxynitride (TiOxNy) by X-ray photoelectron spectroscopy (XPS). The Ti-doped phase was formed by reactions between TiCl4 precursor and LFP during ALD, and this phase was consistent with lithium titanium phosphate. Owing to the synergy of TiN coating and Ti doping, the specific capacity of modified LFP increased to ~159 mAh/g, which was ~93% of its theoretical capacity; after 1,000 cycles of charge-discharge at a 2C rate at room temperature, the modified LFP exhibited a super stable cyclic behavior with a capacity retention of ~89%, whereas the failure of uncoated LFP began after only 500 cycles. The electrochemical impedance spectra showed TiN ALD-modified LFP significantly lowered the film and charge-transfer resistances, and a restricted growth of solid permeable interface layer on the surface of cathode was confirmed by SEM.
Honeycomb-like Nitrogen-Doped Carbon 3D Nanoweb@Li2s Cathode Material for Use in Lithium Sulfur Batteries
Authors: Kim Yoongon , Noh Yuseong , Lee Seungjun , Bae Jaejin , Kim Yekyu , Ahn Hyunwoo , Kim Won Bae
Published: February 2020

Current lithium-ion batteries have a low theoretical capacity that is insufficient for use in emerging electric vehicles and energy storage systems. The development of lithium-sulfur batteries utilizing Li2S cathodes would be a promising option to overcome the capacity limitation. In this work, novel three-dimensional (3D) honeycomb-like N-doped carbon nanowebs (HCNs) have been synthesized through a facile aqueous solution route for use as a cathode material in lithium-sulfur batteries. The Li2S@HCNs cathode delivers a high discharge capacity of ca. 815 mAh g-1 after 65 cycles at 0.1 C, along with a superior rate capacity of ca. 568 mAh g-1 even at 2 C. The outstanding electrochemical rate performance is ascribed to their unique 3D honeycomb-like nanoweb structure, consisting of nanowires derived from polypyrrole. These properties greatly enhance the electrochemical reaction kinetics by providing efficient electron pathways and hollow channels for electrolyte transport. Nitrogen doping in the carbon nanowebs also considerably improves the chemisorption properties by tuning affinity between sulfur and oxygen functional groups on the carbon framework. The simple synthesis strategy and the resulting unique electrode structure could present a new avenue in nanostructure research for high performance lithium-sulfur batteries.
Electrolyte Effects on the Intercalation of PF6
- into Graphite Positive Electrode for Dual-Ion Batteries
Authors: Yu Denis , Wang Yao
Published: February 2020

Different from traditional lithium-ion batteries (LIBs) which rely on Li+ as the only charge carriers, dual-ion batteries (DIBs) which use both cations and anions as electroactive species have received increasing attention due to their high power- density and low cost. So far, graphite has been shown to accommodate anions such as PF6
- and BF4
- with a capacity of close to 100 mAh g-1 and a potential of above 4.5V vs. Li/Li+ on the positive electrode [1-3]. Since the anions originate from the electrolyte, the electrochemical performances of the graphite electrode depend highly on the type of solvent used.

Figure 1a shows the cyclic voltammograms of graphite (KS6, Timcal) electrodes in 3M LiPF6 dissolved in linear carbonate solvents of dimethyl carbonate (DMC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC). We can see that by changing the solvent, the reaction peaks are completely changed. In particular, the lower onset potential at around 4.39 V vs. Li/Li+ suggests that it is easier for PF6
- anions to intercalate into graphite with EMC than DMC and DEC. Rate performances of graphite electrodes in the three different solvents are shown in Figure 1b. Interestingly, electrolyte with EMC solvent also gives much better rate capability than those with DMC and DEC. This is attributed to the difference in chemical interaction between the PF6
- anions and the solvent molecules. Further works on understanding how solvents’ properties, solvation structure and charge transfer impedances etc. affect the observed performances are underway and will be presented at the meeting.

References

[1] J. A. Seel, J. R. Dahn, Electrochemical intercalation of PF6 into graphite, J. Electrochem. Soc. 147 (2000) 892-898.

[2] T. Ishihara, M. Koga, H. Matsumoto, M. Yoshio, Electrochemical intercalation of hexafluorophosphate anion into various carbons for cathode of dual-carbon rechargeable battery, Electrochem. Solid State Lett. 10 (2007) A74-76.

[3] G. Wang, M. Yu, J. Wang, D. Li, D.Tan, M. Loffler, X. Zhuang, K. Mullen, X. Feng, Self-Activating, Capacitive Anion Intercalation Enables High-Power Graphite Cathodes, Adv. Mater. 30 (2018) 1800533.

Figure 1
Electrochemical Performance of Artificial Graphite Coated By Petroleum Pitch for Anode Material in Li-Ion Battery
Authors: Lee Jong Dae , Jo Yoon Ji
Published: February 2020

In recent years, carbon-based materials have been extensively investigated as anode materials for Li-ion battery (LIB). Carbon materials have been considered as promising materials for LIB anodes in portable electronic devices and electric/hybrid vehicles for their low material cost, abundance, nontoxicity and high capacity. Despite these advantages, the practical application of the carbon-based materials is still limited by their poor electrochemical performances. To enhance the electrochemical performances, we have performed the surface coating of graphite with pitch based on pyrolyzed fuel oil (PFO) using solvent fraction method. As solvents, n-hexane, toluene, tetrahydrofuran (THF) and quinoline were used. The PFO was heat-treated at 420 °C for 3 h to prepare the pitch and the softening point of prepared pitch was 240 °C. In this study, the effects of the solvent agents and graphite/pitch ratios on electrochemical performances were investigated. The PFO-pitch-coated graphite was analyzed by TGA, FE-SEM, and TEM. The coating thickness of the prepared graphite was about 100-500 nm and the graphite coated with THF solvent had a smoother surface than that using other solvents. Also the electrochemical performances of the PFO-pitch-coated graphite as an anode were investigated by constant current charge/discharge, cyclic voltammetry and impedance tests in the electrolyte of LiPF6 dissolved in organic solvents (EC:DEC=1:1 vol%). The coin cell using the PFO-pitch-coated graphite (Graphite:pitch =9:1 in weight) had the better discharge capacity (382 mAh/g) than that of other composition coin cells. Also, PFO-pitch-coated graphite was observed to give lower irreversible capacity and resistance than pristine graphite.
Heterostructured Nanoporous Silicon Anode for High Energy Density Lithium Ion Battery
Authors: Pathak Anil Daliprasad , Pati Soobhankar , Sahu Kisor , Mandal Animesh
Published: February 2020

Silicon has been identified as the best candidate element for next generation lithium-ion batteries (LIB) anode material. It is widely available and capacity is more than ten times of conventional graphite. However, using silicon anode in LIB, still remains an unfinished agenda despite very sincere global research efforts1-3. The reasons for this are ~300% expansion in volume upon lithiation, causing fracture or pulverization of the anode structure and sluggish diffusion of lithium in bulk silicon. These challenges can be addressed by using porous silicon. The porosity in silicon can accommodate the majority of the volume expansion during repeated charge-discharge cycling of battery. Most of the under-development processes for porous silicon necessitate sourcing the material from electronic grade Si-wafers. Though this is overkill for many applications, the reason for using electronic grade silicon is due to lack of a cost effective processing route for porous silicon. Here we report a novel and industrially scalable route for production of heterostructured nanoporous silicon particles with a high specific area from low grade Si raw material. We demonstrate capacity retention of more than 1000mAh/gm and columbic efficiency in excess of 98% even after 300+ cycles of operation, using this porous silicon as anode material in a coin cell. This process can also be easily integrated with existing battery fabrication methods, without requiring major changes. Our proposed method is likely to ensure a promising, high throughput process for production porous silicon and its use in lithium ion batteries.

References:

Y. Jin, B. Zhu, Z. Lu, N. Liu, and J. Zhu, Adv. Energy Mater., 1700715, 1–17 (2017).

X. Zuo, J. Zhu, P. Müller-Buschbaum, and Y. J. Cheng, Nano Energy, 31, 113–143 (2017) http://dx.doi.org/10.1016/j.nanoen.2016.11.013.

Bloomberg, Nat. , 559, 467–471 (2018) https://www.nature.com/magazine-assets/d41586-018-05752-3/d41586-018-05752-3.pdf.
Fluorination of Mxene by Elemental F2 as Electrode for Lithium-Ion Batteries
Authors: Jafta Charl J , Thapaliya Bishnu , Lyu Hailong , Xia Jiexiang , Meyer Harry M , Paranthaman Mariappan Parans , Sun Xiao-Guang , Bridges Craig A. , Dai Sheng
Published: February 2020

Extensive research efforts have been devoted to the development of alternative materials as electrode materials, in particular, exfoliated transition metal carbides, called MXene due to their 2D layered structure. We have thus investigated how modifying the anion sublattice of MXene can be used to address this challenge.

In this presentation we will show the transformation of MXene sheets into TiOF2 2D sheets with superior electrochemical performance. MXene synthesized from Ti3AlC2 has been fluorinated for 3 - (FMX3), 6 - (FMX6), and 24 hours (FMX24), respectively by means of a direct fluorination process. Exposure of MXene powder to elemental fluorine for 3 hours induces the formation of CF2 groups and TiF3 on the surface, which have beneficial effects on the electrochemical performance. X-ray photoelectron spectroscopy suggests that after fluorinating the MXene sample for 6 hours, that 2+ and 3+ Ti oxidation states are not present on the surface, with only Ti4+ present indicating TiOF2. X-ray diffraction indicates that there is TiOF2 present after fluorinating for 3 hours and after 24 hours the MXene has transformed to TiOF2 with minor impurities remaining, while maintaining the 2D layer morphology. All the fluorinated materials have cycling stabilities superior to MXene with capacities of > 200 mAh/g, which already has a good cycling stability with a stable capacity of ~ 100 mAh/g over 120 cycles. The electrochemical performance of FMX3 and FMX24 are superior as compared to MXene and FMX6, with the latter fluorinated MXene having a comparatively inferior performance. FMX24 with its TiOF2 phase has good capacity that increases with cycle number. FMX24 has a better rate capability as compared to a non 2D layered TiOF2, indicating the advantage of the 2D layered morphology derived from the parent MXene phase. These transformed MXene materials, in addition to being utilized as anode material for lithium ion batteries, can also be used beneficially in other battery chemistries such as lithium sulfur batteries.
Carbon Nanospheres-Encapsulated Silicon Anode from Solvent-Free Mechanofusion Process for Ultrahigh Stable Lithium Silicon Batteries
Authors: Wutthiprom Juthaporn , Phattharasupakun Nutthaphon , Srimanon Krisara , Sawangphruk Montree
Published: February 2020

Silicon (Si) is one of the most promising anode materials due to its high theoretical capacity (~4200 mAh g-1 for Li22Si5) and volumetric capacity (~2400 mAh cm-3) which is almost 10-time higher than the conventional graphite. However. the drastic volume expansion of Si particles (up to 300%) during battery operation can cause the structural degradation and loss of electrical contact resulting in the rapid capacity decay. In addition, the formation of solid electrolyte interface (SEI) layer deposited on the anode surface due to the decomposition of the carbonate electrolyte will decrease the electrode’s electrochemical reactivity. Many approaches were introduced to address these issues especially Si encapsulation using carbon- or graphene-based materials. Herein, the carbon nanospheres (20-50 nm) are mechanically coated on SiO2 particles via a solvent-free mechanofusion process creating the core@shell structure. SiO2@C are further reduced using magnesiothermic reaction and Si@C was finally obtained. The carbon shell can act as the Si encapsulation layer protecting the crack of Si during charging/discharging as well as allow SEI film to form only at the outer surface of carbon. In addition, the generated voids during the reduction process can provide the space for Si expansion. In order to reduce the low coulombic efficiency between an initial and secondary discharge capacity, the pre-lithiated Si@C was used as the anode in LIB which can deliver the specific capacity of 1390 and 1227 mAh g-1 for the 1st and 2nd cycle (at 0.05C), respectively. Interestingly, the ultrahigh stability of Si@C was obviously seen even though the cell was tested for 1000 cycles. The ex-situ FE-SEM and TEM were investigated to confirm that Si@C can maintain its structure after long cycling. In addition, the ex-situ XPS was further experimented for the 1st discharge and after stability testing. The results show that there are no detected peaks of Si for both states indicating that carbon black shell can completely confine the Si particles within. The Si@C core@shell materials producing from mechanofusion process may become the promising anode for high performance LIB due to its low cost productive as well as the excellent electrochemical stability.
Li-Ion Cell Development with Advanced Anodes
Authors: Lang Christopher M. , Herb Jake T. , Moran Peter D.
Published: February 2020

Physical Sciences Inc. (PSI) has developed advanced cell construction techniques to produce high energy density batteries using advanced anode and cathode materials to power next generation technologies. Lithium metal and silicon based anode systems offer the potential to improve cell energy density and performance. However, efficient utilization of these anodes has not been achieved to date due to first cycle limitations and lithium consumption. PSI has developed a novel formation procedure that enables the full utilization of both anode and cathode electrodes. As a result, cells constructed with silicon or lithium metal anodes can realize greater energy density with improved cycle life. Test results from cells >2 Ah will highlight the scalability of PSI’s cell design and processing techniques.
Surface Modification for Suppressing Interfacial Parasitic Reactions of Nickel-Rich Lithium-Ion Cathode
Authors: Cai Jiyu , Gao Han , Xu Guiliang , Li Luxi , Ren Yang , Meng Xiangbo , Amine Khalil , Chen Zonghai
Published: February 2020

Ni-rich lithium nickel manganese cobalt oxides (LiNixMnyCo1-x-yO2, x≥ 0.5, NMCs) are low cost and high capacity cathode materials for Li-ion batteries. However, various issues (i.e. transition metal dissolution, structural disordering, particle cracking, surface film thickening, etc.) hinder their cycling stability under high cut-off potentials. The mechanisms of these performance degradations have already been investigated in the battery research community. Interestingly, these phenomena were primarily observed at the surface layer of the cathode material, implying that they may also be facilitated by some interfacial parasitic reactions between the delithiated NMC electrode and the non-aqueous electrolyte [1]. In this study, LiNi0.6Mn0.2Co0.2O2 (NMC 622) electrodes modified with TiO2 via atomic layer deposition (ALD) were used as a model system to demonstrate the criticalness of the interfacial parasitic reactions. The suppression of the interfacial parasitic reactions effectively reduced the resistance of cathodic surface films, inhibited the dissolution of transition metals, lowered the particle fragmentation, and mitigated the cation mixing of NMC 622. All these results demonstrated that minimizing the interfacial parasitic reactions is a key approach to improve the durability and stability of Ni-rich NMCs under high-voltage cycling.

Zeng, X.; Xu, G.-L.; Li, Y.; Luo, X.; Maglia, F.; Bauer, C.; Lux, S. F.; Paschos, O.; Kim, S.-J.; Lamp, P.; Lu, J.; Amine, K.; Chen, Z., Kinetic Study of Parasitic Reactions in Lithium-Ion Batteries: A Case Study on LiNi0.6Mn0.2Co0.2O2. ACS Appl. Mater. Interfaces
2016,
8 (5), 3446-3451.

Figure 1
Cooperating Effects of Conformal Iron Oxide ALD Coating and Post-Annealing on Li-Rich Layered Cathod
Authors: Gao Yan , Shang Zeyu , He Xiaoqing , Park Jonghyun , Liang Xinhua
Published: February 2020

Li-rich layered cathode materials draw a wide attention due to their superior Li-storage capability and high energy density, but they suffer capacity degradation and voltage decay due to phase transition and metal dissolution during cycling. To address these problems, iron oxide atomic layer deposition (ALD) was performed on Li-rich layered cathode powders in a fluidized bed reactor, followed by an annealing process for a further improvement. The annealing of iron oxide-coated particles led to the diffusion of iron cation into the structure and a higher structure ordering. After 100 cycles of charge-discharge at a 1C rate and 55 °C, the iron oxide-coated cathode material delivered an initial capacity of ~196 mAh g-1 with a capacity retention of ~49%, while the annealing process improved it to ~221 mAh g-1 and a capacity retention of ~73%. The Fe doping on the surface of cathode facilitated Li+ transport and stabilized cyclic behavior. On the surface, the annealed-coated cathodes suppressed decomposition of electrolyte salt and formed a more stable solid permeable interface layer. In the bulk, a stable spinel phase formed during cycling contributed to the stability of structure; metal dissolution was also suppressed due to the annealing plus coating. These effects enabled a stable- and high-performance Li-ion battery cathode.
Taking LCO to the Next Level: Atomic Layer Deposition for Enhanced Performance of Power Electronics Materials
Authors: Hughes Barbara K. , Herbert-Walters Meghan N. , Trevey James E , King David M.
Published: February 2020

ALD is a platform technology that has been widely demonstrated throughout the literature to impart significant processing and performance gains on lithium ion battery technologies, having notable impacts on surface stabilization of the positive electrode. At Forge Nano, we have elevated this predominantly research scale technique to production heights, making ALD a viable and affordable technology to meet a variety of materials enhancement needs. Our surface modification process allows for sub-nanometer thickness coatings to be tuned for optimal battery performance for battery chemistries relevant in both power electronics as well as vehicle technologies. In this work we will demonstrate the significant gains observed to commercially available LCO by way of increased cycle life, increased energy density and beyond state-of-the art fast charge capabilities. Alongside performance enhancements, we will explore the mechanisms of ALD protection at high voltage, during shelf-life aging and under strenuous test conditions including variable temperatures and c-rates.
Regulating Ca2+ Electrolyte Transport and Stability for Calcium Metal Deposition
Authors: Hahn Nathan T , Zavadil Kevin R , Self Julian , Seguin Trevor , Persson Kristin A
Published: February 2020

Beyond Li-ion electrochemical energy storage systems based on divalent metal cations occupy a new frontier of research and development efforts related to materials chemistry and design. High energy density batteries based on the promise of high capacity Mg or Ca metal anodes are yet to be realized due to problems associated with the stability and ion transport properties of organic electrolytes and insertion cathodes. Controlling the stability of Ca2+ electrolytes at calcium metal anodes has been a particularly challenging task, although a recent demonstration suggests a possible path forward for reversible calcium electrodeposition in ethereal electrolytes.1 The calcium system, then, represents an intriguing exemplar for understanding divalent metal electrodeposition under conditions that push the boundaries of organic electrolyte stability. In this presentation we will discuss how interactions among species within Ca2+ electrolytes such as Ca(BH4)2/THF and other recently developed systems facilitate transport and delivery of the working cation to the interface for deposition and how surface interactions influence the stability of supporting electrolyte species and direct the system toward inefficiency and byproduct formation as a function of species susceptibility. These studies utilize a combination of experimental spectroscopy, microscopy and electrochemistry along with computational simulation of Ca2+ coordination cluster structures and stabilities. We will discuss the impact of these factors on calcium metal morphology and composition providing new insight into the rules connecting Ca2+ electrolyte properties to interfaces for Ca metal deposition. These design principles will serve as a guide to the development of advanced electrolyte concepts capable of pushing the boundaries of reductive stability in divalent metal electrolytes toward higher voltage beyond Li-ion batteries.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

References

Wang, D.; Gao, X.; Chen, Y.; Jin, L.; Kuss, C.; Bruce, P. G., Plating and stripping calcium in an organic electrolyte. Nature Materials
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17, 16.