bluuebunny/crossref_metadata_2025 huggingface dataset:
Incremental Interface Surface Potential Measured with a Nano-Gap Coplanar Device Structure and Its Applications
Authors: Hsueh Hsiao-Ting , Chen Po-Han , Chen Fan-En , Tsai Ming-Sheu , Wu Ting-Wei , Lin Chih-Ting
Published: February 2020

Because of detection characteristics in traditional capacitive-based biomolecular sensing technologies, it is important to have a uniform and defect-free interface layers. However, efforts to achieve the interface layer are tedious and labor intensive. To conquer this problem and enhance the sensing characteristics of capacitive-based biomolecular sensing device, in our report, we use co-planar electrode with nano-gap structure and placed the sensing element on the gap surface, which is different from traditional capacitive putting antigen/antibody on the electrode surface. This arrangement leads to gap-surface charge changes as molecular binding occurring. And the altered gap-surface charges modulate the electric double layer (EDL) of electrode sidewalls and result in the change of nano-gap capacitance. Utilizing surface modification with amine-terminated and aldehyde-terminated groups, we demonstrates the proposed electrode sidewall EDL contraction phenomena induced by gap-surface ion redistribution. Based on our experimental results of surface modifications, the capacitance variance of 1 µm and 100 nm gap width are 8% and 17%, respectively. In addition, we show that both gap width and detection environment play important roles in sensitivity and detection limit of the developed nano-gap device. With a demonstration of cTnT detection, a demonstrated detection dynamic range of the proposed method is from 10 pg/ml to 1 µg/ml, which is around 100 fold higher than that of traditional capacitive biosensors. The limit of detection is 10 pg/ml, which is the cut-off level in clinical examinations.
(Invited) Nanowire-Modified Electrode Enabling Low-Voltage Electroporation for Cell Inactivation
Authors: Xie Xing
Published: February 2020

Cell inactivation is a general process that has broad applications in food, water and medical industry. Electroporation is a promising alternative to traditional cell inactivation methods (e.g., thermal, chlorine, and ultraviolet radiation), attributed to its high throughput, free chemicals usage, and outstanding efficacy to all pathogens. However, concerns of high energy consumption (>10 kJ per liter of liquid sample treated) and safety issues to generate a strong field (~107 V/m) have been the major obstacles to the large-scale implementation of electroporation for cell inactivation. To overcome these limitations, conductive one-dimensional (1D) nanostructures have been placed on electrode surfaces to generate high electric field strength near the tip of the 1D structures with low applied voltages (<20 V). Taking advantage of this phenomenon, low-voltage electroporation devices have been introduced to achieve high efficiency with low energy consumption and high throughput. For example, we have developed a new copper-oxide nanowire (CuONW)-modified 3D copper foam electrode using a facile thermal oxidation approach. An electroporation disinfection cell (EDC) equipped with two such electrodes has achieved superior water disinfection performance (>7-log removal and no detectable bacteria in the effluent). The inactivation mechanism of electroporation guarantees an exceedingly low operation voltage (1 V) and energy consumption (25 J/L) with a short contact time (7 s). Low operation voltage avoids chlorine generation, thus reduces the potential of disinfection by-products (DBPs) formation. In addition, due to irreversible electroporation damage on cell membranes, no bacteria re-growth/reactivation occurs during storage after EDC treatment.
Nylon-Graphene Composite Nonwovens As Monolithic Conductive or Capacitive Fabrics
Authors: Gao Wei
Published: February 2020

Here we describe a nylon-graphene nonwoven (NGN) composite, prepared via dip-coating of nylon-6 nonwovens with graphen oxide (GO) in aqueous dispersions, which is later chemically reduced to introduce electrical conductivity. The correlation between the conductivity and the graphene loading is described by the percolation scaling law, with an exponent  of 1.2 and a critical concentration of 0.005 wt.%, the lowest among all the reported nylon systems. Monolithic supercapacitors have been further developed on the nylon-GO nonwoven composite (NGO), via a CO2-laser patterning process. The nylon nonwoven works as the sorbent matrix, leading to the high GO loadings that ensure sufficient coating thicknesses for the subsequent laser patterning. Deep electrodes were thus easily generated by the laser beam, and our best monolithic supercapacitors exhited an areal capacitance of 10.37 mF/cm2 , much higher than the 1~3 mF/cm2 reported for typical microsupercapacitors in PVA-H2SO4 electrolyte. Moreover, our supercapacitors were able to retain a capacitance density of 5.07 mF/cm2 at a higher scan rate (1.0 V/s), probably due to the facilitated ion migration within the highly porous and interconnected nonwoven framework. This is the first report of NGN with fascinating conductive and capacitive behaviors, demonstrating great potential for applications in wearable electronics and disposable energy storage systems.
He-Ion Induced Defect Generation and Doping of 2D MoS2 Monolayers
Authors: Aryeetey Frederick , Singh Dilbagh , Nowlin Kyle , Aravamudhan Shyam
Published: February 2020

In recent years, two-dimensional Transition Metal Dichalcogenide (TMDC) materials such as MoS2 have drawn considerable interest due to their intriguing electrical, optical, sensing, and catalytic properties [Castellanos-Gomez et al. 2012]. While Graphene-based devices have shown high carrier mobility up to ~ 105 cm2/Vs [Bolotin et al. 2008] and cut-off frequency higher than ~ 100 GHz [Liao et al., 2010], the inherent zero – band gap electronic structure of graphene results in high OFF state current. On the other hand, monolayer MoS2 is a semiconductor with a direct band gap of ~1.9eV [Mak et al. 2010]. MoS2 transistors are a promising alternative for the semiconductor industry due to their large ON/OFF current ratio (> 10e10) [Yoon et al., 2011], immunity to short channel effects, and abrupt switching. However, realization of practical mono/few layer MoS2 devices is limited by the free charge density in intrinsic MoS2 (10e10/cm2) [Rastogi et al. 2014]. The objective of this work is to utilize He-ion beam patterning to write pattern of vacancies (< 10 nm) onto CVD synthesized 2D MoS2. The vacancies thus generated are then doped via molecular doping technique to improve upon the intrinsic free carrier concentration in 2D MoS2. Briefly, the method is as follows. (a) First, highly crystalline 2D MoS2 are synthesized on SiO2/Si substrate using MoO3 and S powder as the precursors in a CVD furnace. (b) Next, He-ion beam patterning is used to generate vacancies in only the very top S layer. The shorter de Broglie wavelength of He-ions allows for milling at higher resolution than other charged particle microscopes. (c) Next, solution-based molecular doping method is used to realize non-degenerate n-type doping in 2D MoS2. This is accomplished by soaking the patterned 2D layers in 1, 2-dichloroethane (DCE) solution at room temperature for about 12 hours. As a result, the patterned vacancies are occupied by Cl atoms which donate the extra electrons to the MoS2 system. The electronic properties are tuned by varying the MoS2 layer thickness and solution concentration. Post-doping, the electrostatic properties are measured by using PL measurements and different modes of AFM, including Kelvin force microscopy (KFM) and Scanning microwave microscopy (SMM). An important contribution of this work is the presentation of optimized He-ion beam conditions, including the accelerating voltage and the effects of defect generation on the sub-surface layers. He-ion beam based defect generation creates a shallow penetration depth, which makes them more suitable for single S vacancies. Finally, the changes in the surface potential and a quantitative analysis of the dopant density were measured suing KFM and SMM respectively, indicating that doping is in the non-degenerate regime.
(Invited) Piezoelectric and Triboelectric Properties in 2D Materials for Energy Harvesting and Sensor Applications
Authors: Kim Sang-Woo
Published: February 2020

As the first issue, transition-metal dichalcogenides (TMDs) have reported on the piezoresponse of the materials as an external force is applied due to their broken inversion symmetry. TMD materials exhibit a strong piezoelectricity in their monolayer configuration, but the piezoelectric effect disappears or is significantly reduced when more than two layers are present. Piezoelectric devices employing monolayer TMD materials are not practically feasible because they lack the mechanical durability that is needed, and such mechanical robustness is crucial to develop useful piezoelectric devices that can be engineered using a multilayered structure. However, multilayered TMDs have a greatly reduced or absent piezoelectricity since the continuous growth of multilayered TMD leads to a stable stacking structure with alternating polarization directions in neighboring layers. We report on a simulation and experimental observation of piezoelectricity in mono/bilayer WSe2 synthesized via CVD and turbostratic stacking. The piezoelectricity and mechanical durability of the mono/bilayer WSe2 were assessed by conducting PFM measurements, a DFT simulation, and fabricating and characterizing the piezoelectric energy harvesters. As the second issue, I will present about the demonstration of large electric power generation from a single moving water droplet on a monolayer graphene, producing an output power of about 1.9 μW, which is about 100 times larger than the power output achieved in previous reports. This result is explained to be a result of the change in triboelectrification-induced pseudocapacitance between a water droplet and the monolayer graphene on polytetrafluoroethylene (PTFE). Positive and negative charges were found to respectively accumulate at the bottom and top surfaces of graphene on PTFE by the triboelectric potential generated during the graphene transfer process. The negative charges accumulate onto the top surface of the graphene and are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet. As the third topic, I am going to introduce a graphene tribotronic touch sensor which is based on coplanar coupling of a single electrode mode triboelectric nanogenerator (S-TENG) and a graphene FET. When any object (e.g. human finger) comes into contact with friction layer of the S-TENG, the charges are produced due to well-known triboelectric effect. The triboelectric charges act as a gate bias to the graphene FET and modulate its current transport. The tribotronic transistor therefore does not require any external gate voltage as in traditional metal oxide field effect transistors. The tribotronic sensors have displayed a sensitivity of ~2% kPa-1, a limit of detection <1 kPa, and a response time of ~30 ms.
(Invited) Design Two-Dimensional Layered Materials for Rechargeable Magnesium Batteries
Authors: Yao Yan
Published: February 2020

In the past few years, magnesium rechargeable batteries (MRBs) have attracted significant interest because of dendrite-free deposition and earth-abundant Mg resources. Despite the recent progress, the development of practical MRBs remains hindered largely due to the limited choices of Mg-intercalation electrodes. I will present our methods to overcome the large Mg2+ ion diffusion barrier to enhance the Mg diffusivity in two-dimensinoal materials. Theory, synthesis, electrochemical measurements, and kinetic analysis are combined to improve Mg diffusion behavior in MoS2, which is a poor Mg transporting material in its pristine form. I will also report a MgCl+ storage mechanism based on activated two-dimensional materials which enables high reversible capacity and excellent cycling stability.
In Situ investigation of Interfacial Transformations Between Oriented Transition Metal Dichalcogenides and Metals
Authors: Kondekar Neha , McDowell Matthew T
Published: February 2020

Layered materials, such as transition metal dichalcogenides (TMDCs), are attractive for energy storage, nanoelectronics, and electrochromic devices. Layered TMDC materials feature a strongly anisotropic crystal structure, with basal planes and edge sites within the structure exhibiting divergent chemical and bonding properties. The interaction of external metals and ions with TMDCs is critical for their use in batteries and electronic devices; metal ions are reversibly intercalated between TMDC layers when used as battery electrodes, and thin film metal electrical contacts must be interfaced with TMDCs in next-generation electronics. In both cases, the crystallographic orientation of the TMDC likely influences the interfacial reaction and/or ion intercalation pathways and kinetics, but the effect of crystallography on these phenomena is not well understood. Here, we use in situ x-ray photoelectron spectroscopy (XPS) to determine how the crystallography and structure of TMDCs (MoS2 and TaS2) influence interfacial transformation pathways and kinetics when interacting with different metals of interest for energy storage and electronic contacts. This work is enabled by the synthesis of MoS2 and TaS2 with controllably aligned crystal structure: thin films with vertically aligned layers are grown via a sulfidation process, and single crystals with horizontally aligned layers are also utilized. In situ XPS is carried out by sputter depositing thin metal films (lithium, silver, or gold) onto the oriented TMDC material within an XPS instrument, and photoelectron spectra are acquired at different times to probe near-surface chemical changes and reaction kinetics in the TMDC material. The results show that lithium reacts with both edge planes and basal planes in MoS2 at similar rates to form reduced Mo and S species. This indicates that the conversion reaction of MoS2 in Li-ion batteries is not strongly dependent on the crystalline anisotropy of the lattice. In contrast, less reactive metals (silver and gold) were observed to intercalate in low concentrations, and this intercalation behavior is strongly dependent on the orientation of MoS2­ and TaS2. Interestingly, despite the relatively unreactive nature of Ag and Au, these materials also induce slight chemical reduction at the TMDC interface. This study emphasizes the importance of using in situ experiments for understanding interfacial reaction mechanisms and kinetics, which are generally difficult to study in buried interfaces. Future work will focus on tuning interfacial interactions via crystallographic control.
Effect of Electrolyte Composition on Capacity Fading of Ni Rich Lithium Transition Metal Oxide Cathode for High Energy Density Lithium Ion Batteries
Authors: Kang Yoon-Sok , Choi Byungjin , Park Insun , Chung Yeonji , Koh Meiten , Ito Kimihiko , Kubo Yoshimi
Published: February 2020

The lithium-ion battery has been widely employed in mobile applications because of its advantages, such as high energy density, insignificant self-discharge rate, and reasonable price. While it is also the most promising candidate power source for advanced automobiles, it needs further development to meet the specifications of electric vehicles1,2. For example, the driving distance of an electric vehicle on a single charge is becoming more and more important, which requires batteries with ever higher energy density. One of the main strategies to enhance the energy density is to raise the average potential and specific capacity of the cathode materials3. For this purpose, Ni rich lithium transition metal oxides have been developed for promising cathode materials4,5. Nevertheless, there are several limitations that need to be surmounted before the mass production of high energy density batteries containing Ni rich lithium transition metal oxides. In particular, significant capacity fading has been observed with lithium ion battery using Ni rich lithium transition metal oxides6,7.

In this study, we found that cathode (Ni-rich LiNi0.8Co0.1Mn0.1O2) surface modification – phase transformation from a layered structure to a cubic phase – exerted a significant influence on battery performance. Such cubic phase hindered ionic and electronic conductivity of cathode particles. The kind of the cubic phase was different by changing the composition of the electrolyte. As a result, the resistance of the cylindrical cells after 300 cycles using different electrolyte showed a large gap, especially on cathode side.

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

[2] M. Armand, J.-M. Tarascon, Nature, 2008, 451, 652

[3] J. B. Goodenough, Y. Kim, Chem. Mater., 2010, 22, 587

[4] W. Liu et al, Angew. Chem. Int. Ed. Engl. 2015, 54, 4440

[5] A. Manthiram et al, Adv. Energy Mater, 2016, 6, 1501010

[6] D.P. Abraham et al, Electrochem. Comm., 2002, 4, 620

[7] S. Watanabe et al, J. Power Sources, 2014, 258, 210
Infrared Optical Measurements of Thermal Breakdown in Battery Electrolytes
Authors: Porter Jason Morgan , Wheeler Jeffrey Lee
Published: February 2020

Electrolyte thermal stability is critical for both battery safety and extending battery life. Battery fires are often the result of thermal breakdown of the liquid electrolyte leading to a flammable mixture of volatile products. Even in the absence of fire, electrolyte decomposition leads to battery swelling, harmful precipitates, reduced ion conductivities, and undesirable battery chemistry.

Current methods of determining electrolyte stability using ex-situ techniques, such as thermal gravimetric analysis or differential scanning calorimetry, can over predict thermal stability, do not address materials compatibility within batteries, and cannot identify chemical decomposition mechanisms. Infrared optical detection of thermal stability offers an in-situ approach providing: speciation, identification of chemical bonds involved in decomposition, real-time detection, and chemical kinetics.

In this work, the thermal stability of the room temperature ionic liquid 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO4]) is investigated using infrared (IR) spectroscopy. Quantitative IR absorption spectral data are measured for the heated ionic liquid. Spectra have been collected between 25°C and 100°C using a heated optical cell. Multiple samples and cell path lengths were used to determine quantitative values of the absorption coefficient. These results were compared to previous computational models of the ion pair to identify each absorption band with corresponding chemical bonds. The quantitative spectra were then used to measure the rate of thermal decomposition at elevated temperatures revealing the onset of breakdown above 75°C.
Matching Electrolyte Formulation with Cathode Chemistry
Authors: Pupek Krzysztof Z. , Dzwiniel Trevor L , Abraham Daniel P , Krumdick Gregory
Published: February 2020

Ethylene carbonate (EC) based electrolytes, e.g. Gen2 (1.2 M LiPF6 in EC/EMC 3/7) are commonly used as a baseline electrolyte for various cathode chemistries. Is EC the best choice for all active materials? Streich [1] investigated several cathodes (NCM111, NCM622 and NCM811) using a 1M LiPF6in EC/DEM 3/7 electrolyte and reached the conclusion that there is a strong correlation between the Ni content in the active material and the amount of carbon dioxide produced in a first cycle over 4.3V. The study suggests that tailoring electrolyte formulation for the specific electrodes chemistries may be a way of improving performance of the cells. Interestingly, Dahn [2] demonstrated that it is possible to improve the performance of NCM424//graphite pouch cells by completely eliminating EC from the electrolyte formulation. While EC-reach electrolytes proved to be a good choice for some electrode chemistries they may not be the best option in all cases.

We conducted a systematic study of several cathode chemistries in full cells (CR2032) with various electrolyte formulations, with and without EC.

Figure 1 shows the effect of electrolyte formulation on cycle life of NCM523 and NCA based cells. It is clear that for cells with NCA cathode electrolytes containing EC have an adverse effect on performance whereas this effect is not observed with NCM523 cells.

Comprehensive data from cycle life and cell impedance study of several cathode materials (NCM523, NCM622, NCM811, NCA and HE5050) in various electrolyte formulations will be presented and discussed. Our study will help researchers chose electrolyte formulation for the electrode material they investigate.

[1] Daniel Streich et al., Impact of Ni content on interface reactions at NCM electrodes, GRS/GRC Ventura CA, USA, 2016, Poster 160217

[2] J. R. Dahn et al, Electrolyte System for High Voltage Li-Ion Cells, Journal of The Electrochemical Society, 163 (13) A2571-A2578 (2016)

Figure 1
(Invited) Liquid and Solid State NMR Investigations of Electrolytes for Beyond Lithium Ion Applications
Authors: Greenbaum Steve , Gobet Mallory , Peng Jing , Munoz Stephen , Cresce Arthur v. , Russell Selena M. , Borodin Oleg , Xu Kang , Zimmerman Michael , Leising Randy
Published: February 2020

Nuclear magnetic resonance (NMR) has been productively employed to investigate ion transport and solvation in standard carbonate-based Li ion battery electrolytes and in solid polymer electrolytes based on poly(ethylene oxide) (PEO). Future electrochemical power sources require new electrolytes to adapt to disruptive changes in the basic working chemistry, such as moving from Li ion to Na ion, or to Li metal electrodes. We highlight two recent collaborative activities on electrolytes in our group (i) Na ion; (ii) Li metal polymer.

 Using a combination of 23Na, 19F and natural abundance 17O NMR, and pulsed field gradient diffusion in a collaboration with the U.S. Army Research Lab, we have examined NaPF6 solutions in binary solvent mixtures ethylene carbonate (EC) and ethylmethyl carbonate (EMC) for possible cation solvation preference as a function of EC/EMC ratio. Spectroscopic evidence demonstrate that the Li+ and Na+ cations share a number of similar ion–solvent and ion-ion interaction trends, such as a preference for a solvation shell rich in cyclic carbonates over linear carbonates and fluorinated carbonates. However some differences are noted, in particular a somewhat weaker ion-solvent interaction for Na+. Ionic Materials, Inc. has invented a novel polymer with extremely high ionic conductivity over a range of temperatures, even surpassing that of a commercial porous separator containing the standard liquid carbonate-based electrolyte at room temperature. This solid polymer can be reliably extruded into very thin films, is non-flammable, has attractive mechanical properties for lithium dendrite suppression, is electrochemically stable against Li, and is compatible with a variety of different anodes and cathodes. The polymer electrolyte is based on an inexpensive semicrystalline commercially available polymer such as polyether ether ketone or polyphenylene sulfide and Li salts familiar to the battery and polymer electrolyte communities. The ionic transport mechanism is unlike that which characterizes the PEO salt complexes – that is ion mobility is completely decoupled from polymer host motion, as verified by differential scanning calorimetry and NMR. In fact NMR pulsed gradient measurements reveal Li self-diffusion coefficients at room temperature that are an order of magnitude higher than in the ceramic ion conductors of the Li10GeP2S12 class and thus the highest in any known solid. Furthermore, the Li+ transference number determined electrochemically and by NMR is > 0.6.
All-Solid-State Lithium Batteries Based on Semi-Interpenetrating Network Solid Polymer Electrolyte and Composite Electrode
Authors: Kim Do Youb , Chang Ho Young , Suk Jungdon , KIM Dong Wook , Kang Yongku
Published: February 2020

Poly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have been considered as promising candidates for solid-state Li-ion battery (LIB) electrolyte that can replace current liquid electrolyte system.[1] However, PEO-based SPEs have critical problems for practical use in that the ionic conductivity is relatively low at an ambient temperature, and the high interfacial resistance between the SPE and electrode is relatively high. For better performance of solid-state batteries, SPEs should improve the ionic conductivity, strengthen the mechanical properties, and reduce the interfacial resistance between SPE and electrode as well.[2]

In this study, we report highly promising SPEs for all-solid-state LIBs based on a novel cross-linker having poly(ethylene oxide) (PEO) branches with very high ionic conductivity, improved mechanical stability, and good electrochemical stability. In order to reduce the interfacial resistance between SPE and electrode, we introduced a semi-interpenetrating network system through an in-situ polymerization of SPE precursor solution, and a composite electrode that contained an ionic conducting component. In addition, we also introduced Li-ion conducting powders into the SPE to increase ionic conductivity and mechanical strength of the SPE. As prepared SPEs had relatively high ionic conductivities of ca. 5~7 x 10-4 S/cm at an ambient temperature, good mechanical strengths, and electrochemically stable up to 5.2 V vs. Li/Li+. A cell composed of LiFePO4 composite cathode, Li metal anode, and SPE showed good specific capacity of 140 mAh/g at 0.5 C, cycle stability, and rate capability (95 mAh/g at 2 C). Specially, when the ionic conducting powder introduced into the SPE, Li+ transference number rose by 50 %, and thus the cell exhibited improved rate capability and mechanical strength. Finally, all-solid-state pouch-type cells were assembled with the SPEs exhibited stable electrochemical performance, even under a severely bent and folded state. 

[1] A. Ghosh, C.S. Wang, P. Kofinasb, J. Electrochem. Soc.
2010, 157, A846.

[2] K. Xu, Chem. Rev.
2004, 104, 4303.
Figure of Merit Approach for Evaluating L.I.B. Electrolyte Additives in a Combinatorial Study
Authors: Peebles Cameron , Gilbert James A , Tornheim Adam , Sahore Ritu , Garcia Juan , Lu Wenquan , Iddir Hakim , Zhang Zhengcheng , Bareno Javier , Abraham Daniel P , Liao Chen
Published: February 2020

In order to extend the lifetime and performance of lithium ion battery systems, the use of electrolyte additives continues to be one of the most effective and economical approaches currently under investigation. Common metrics used to measure the relative performance enhancement of these electrolyte additives include capacity retention and impedance rise. This study details efforts to 1) perform a combinatorial analysis of electrolyte additives for use in high voltage lithium ion battery systems, and 2) evaluate the performance of the tested electrolyte systems using two figures of merit (FOM) which address both capacity (energy) and impedance (power). Eight known additives were used throughout the course of the test: three additives known to work on the positive (cathode) electrode (TMSPi, TEPi, LiDFOB) and five additives known to work on the negative (anode) electrode (LiBOB, VC, tVCBO, PBE, PES). Electrochemical testing was performed on LiNi0.5Mn0.3Co0.2O2 /graphite full cells operating between 3.0-4.4 V. The cycling protocol combines several C rates (C/1, C/3, C/10) for capacity and rate information and intermittent hybrid pulse power characterization (HPPC) tests from which area specific impedance (ASI) values are calculated. Results from extensive testing reveal interesting trends in the electrolyte systems. In general, TMSPi performed well as an additive while a structurally analogous molecule, TEPi, performed poorly. Other trends, such as the effects of LiBOB on energy fade and VC on power fade, were found. Capacity, impedance and other electrochemical data will be presented to give a comprehensive overview of performance effects of the tested electrolyte additives. This work underscores the importance of developing evaluation methodologies in order to objectively view the performance of electrolyte systems and identify trends in electrolyte additive behavior.
New Material Routes to Polymeric Solid Electrolytes
Authors: Janietz Silvia , Meyer Wolfdietrich , Asaftei Simona
Published: February 2020

In our work photocurable liquid ionic compounds (PLICs) [1] and oxygen rich crosslinkers (ORCs) with carboxy- and ethoxygroups build the base of a monomer blend system [2] to obtain thin films on electrode surfaces of new polyionic polyacrylates as polymeric solid electrolytes (PESs) in a battery buildup [3].

The aim of our study is to show that the low ionic forces in an ionic liquid is preserved when the cation of the PLIC is fixed covalently bonded into a polymer network and turns into a PES after curing process. With similar intention ORC are designed to achieve a fixation of carboxy groups as an ideal chelator for lithium ions within a polymeric solid electrolyte.

The synthesis of PLICs and ORCs is described and characterized by NMR, IR and melting points. Formulation of PLICs, ORCs and lithium salts has been bladed and UV cured direct on Li foils as electrode material and the ionic conductivity in a half cell setup were determined by impedance spectroscopy. The free foils of PES show high temperature stability and the absents of crystallinity in DSC measurements.

Secondly a polymer design concept is presented that combine ion conductivity and mechanical stability in a block-co-polymer consisting of a PEG unit and a rigid rod aromatic unit aiming as a new material basis for battery separators.
(Invited) Decoupling Effective Li+ Ion Conductivity from Electrolyte Viscosity for Improved Room-Temperature Cell Performance
Authors: Moretti Arianna , Giffin Guinevere A , Passerini Stefano
Published: February 2020

Ionic liquids are attractive materials for alternative electrolytes to combat the safety issues associated with conventional organic carbonate-based electrolytes. However, the performance of ionic liquid-based cells is generally not competitive as the high viscosity and low conductivity limits the rate performance. The work presented here demonstrates that the drawbacks in terms of rate capability can be overcome through the use of the high lithium concentration Pyr12O1FTFSI0.6LiFTFSI0.4 electrolyte. Despite an order of magnitude difference in the conductivity and viscosity, this high concentration electrolyte outperforms the lithium-dilute electrolyte with the same components in terms of rate capability in LTO and LFP half and full cells. The results suggest that the effective Li ion transport in the concentrated electrolyte is higher than in the dilute solution.
Sulfur-Based SEI-Forming Additives for Lithium-Ion Batteries
Authors: Jankowski Piotr , Wieczorek Wladyslaw , Johansson Patrik
Published: February 2020

Due to the increasingly growing demands for reliable and high capacity energy storage in mobile devices and electric vehicles, tremendous efforts are being made to improve life-length, performance, and safety of lithium-ion batteries (LIBs). For LIBs the solid electrolyte interphase (SEI), formed by electrolyte reduction on the anode surface, is a key element and one way to improve LIBs is to control the process of SEI formation, rather than relying on spontaneous formation by electrolyte decomposition. Application of special molecules, SEI-forming additives, is a viable approach.

We here present a systematic study of several different sulfonyl compounds, as SEI-forming additives for a standard LP30 battery electrolyte. Electrochemical analysis of the resulting electrolytes shows a notable difference in reduction ability. The compositions of the formed SEI-layers were examined and all experimental data confronted with DFT calculations to better understand the influence of the chemical structure of the additives on the reduction properties. Finally, the electrolytes were cycled in graphite/LFP full cells to study the long-term stabilization properties of the SEI-layers formed.
Ionic Liquid Based Electrolytes for Electrical Storage
Authors: von Czarnecki Peter , Ahrens Maria , Iliev Boyan , Schubert Thomas J. S.
Published: February 2020

Ionic liquids (ILs) – salts that are liquid at temperatures below 100°C – have gained big popularity over the past years and have become products of industrial interest, instead of just being lab curiosities. Ionic Liquids show interesting combination of physical and chemical properties, such as tunable viscosity and conductivity, chemical and thermal stability as well as large electrochemical windows and incombustibility at temperatures below their decomposition point. Especially the last two allows their use as safe electrolytes in batteries, supercapacitors and other energy devices.[1-4]

Figure 1: Temperature-dependent viscosity of IL-mixtures.

One of the main disadvantages of ILs - their high viscosity - can be overcome by using mixtures (Figure 1). In this talk we will present our latest results and developments in the field of ionic liquid based electrolytes for batteries and supercapacitors. In the latter cycling stability over 8 000 000 cycles has been achieved. The use of mixtures of ionic liquids and suitable additives in order to enhance performance and safety of zinc - air, aluminum - air and silicon - air batteries will also be discussed.

 

Literature:

[1] M. A. Taige, D. Hilbert, T. J. S. Schubert, Z. Phys.
Chem. 226 (2012) 129-139.

[2] D. Aradilla, P. Gentile, V. Ruiz, P. Gómez-Romero, J. Wimberg, B. Iliev, T. Schubert, S. Sadki and G. Bidan, Adv. Nat. Sci.: Nanosci.
Nanotechnol., 2015, 6, 015004-015010.

[3] D. Gelman, B. Shvartsev, Y. Ein-Eli,
J. Mater. Chem. A

2(
2014)20237-20242.

[4] M. Kar, B. Winther-Jensen, M. Forsyth, D. R. MacFarlane, Phys.
Chem. Chem. Phys.

15 (2013) 7191-7197.

Figure 1
Evaluating Fluorinated Electrolyte Stabilities on Charged Ncm Cathode Surfaces with Potentiostatic Holds
Authors: Tornheim Adam , He Meinan , Peebles Cameron , Garcia Juan , Sahore Ritu , Dogan Fulya , Liao Chen , Iddir Hakim , Bareno Javier , Bloom Ira , Zhang Zhengcheng
Published: February 2020

Organic carbonate electrolytes are commonly used in lithium ion batteries due to their wide electrochemical stability window and high lithium salt solubility. However, the high voltage of some cathode materials is above the stability of these conventional carbonate electrolytes (>4.5V vs. Li+/Li). One method of increasing the anodic stability of the organic carbonates is through substitution of the solvents with a fluorinated carbonates. In this work, we evaluate the stability of electrolyte formulations comprising combinations of either ethylene carbonate, fluoroethylene carbonate, or difluoroethylene carbonate as cyclic carbonates, and ethyl methyl carbonate or hexafluorodiethyl carbonate as linear carbonates. Stability of these electrolytes at both positive and negative electrodes was determined by lithium/graphite half cell tests, as well as 60 hour potentiostatic hold tests at 4.6 V vs. Li+/Li with NMC (LiNi0.5Mn0.3 Co0.2O2) cathodes and either graphite or LTO (Li4Ti5O12) anodes. In potentiostatic holds with NMC cathodes, the fluorinated electrolytes show enhanced stability (lower oxidation current) with the graphite anodes, while fluorethylene carbonate containing formulations show higher oxidation currents with the LTO anodes. These results indicate the feasibility of fluorinated electrolytes in enabling high voltage cathodes through stability of the cathode/electrolyte interface.

Acknowledgements

The work at Argonne National Laboratory was performed under the auspices of the U.S. Department of Energy (DOE), Office of Vehicle Technologies, under Contract No.

DE-AC02-06CH11357.

The submitted issue has been created by the University of Chicago as Operator of Argonne National Laboratory (“Argonne”) under Contract No. W-31-109-Eng-38 with the U.S. Department of Energy. The U.S. Government retains for itself, and others acting on its behalf, a paid-up, non-exclusive, irrevocable, worldwide license in said article to reproduce, prepare derivative works, distribute copies to the public, and perform publicly and display publicly, by or on behalf of the Government.
Li-Metal/Solid Electrolyte Interfacial Stability Elucidated Via in Situ Electron Microscopy
Authors: Chi Miaofang , Sharafi Asma , Cheng Yongqiang , Sakamoto Jeff , Dudney Nancy J , Ma Cheng
Published: February 2020

Despite their different chemistries, novel energy-storage systems, e.g. Li-air, Li-S, all-solid-state Li batteries, etc., face one critical challenge of forming a conductive and stable interface between Li metal and a solid electrolyte. An accurate understanding of the formation mechanism and the exact structure/chemistry of the rarely existing benign interfaces, such as the Li/cubic-Li7-3x
Al
x
La3Zr2O12 (c-LLZO) interface, is crucial towards enabling the use of Li metal anodes. Due to spatial confinement and structural/chemical complications, current investigations are largely limited to theoretical calculations. Here, through an in situ formation of Li/c-LLZO interfaces inside an aberration corrected scanning transmission electron microscope, we successfully reveal the interfacial chemical and structural progression. Upon contact with Li metal, the surface of the c-LLZO is slightly reduced, and simultaneously receives Li+ from the Li metal, thereby maintaining the charge balance. Instead of triggering decomposition reactions, a localized phase transition occurs leading to the formation of a 6 nm thick interfacial tetragonal LLZO phase that is stable over time (Figure 1). Although this interphase is ultra-thin and can be easily overlooked, it may effectively prevent further interfacial reactions without compromising the ionic conductivity. Although the cubic-to-tetragonal transition is typically undesired during LLZO synthesis, the similar structural change was found to be the likely key to the observed benign interface. These insights provide a new viewpoint for designing Li/solid electrolyte interfaces that can enable the use of Li metal anodes in next-generation batteries.

Figure 1
Suppressing the Dendrite Growth on Li Metal Anode Via Manipulating the Solid Electrolyte Interface (SEI) Formation
Authors: Liu Haodong , Zhou Hongyao , Xing Xing , Lee Byoung-Sun , Liu Ping
Published: February 2020

The progressive advancements in communication and transportation has changed human daily life to a great extent. While important advancements in battery technology has come since its first demonstration, the high energy demands needed to electrify the automotive industry have not yet been met with the current technology. One possible anode is the Li metal, which has several distinct advantages over other anode materials. For example, it possesses extremely high theoretical specific capacity of 3860 mA h g-
1, and the lowest negative electrochemical potential.1 However, the uncontrollable Li dendrite growth on the Li metal during electrochemical cycling will cause serious safety problem, which brings up challenges in broadening the application of Li metal for Li batteries.

In this work, we successfully suppressed the Li dendrite growth on the Li anode by designing novel electrolyte systems. We observed an uniform solid electrolyte interface (SEI) layer was coated on the surface of Li metal anode through the scanning electron microscopy, this SEI layer helps to prevent the Li dendrite formation. Fig.1 compares the morphologies of deposited Li using different electrolytes. We also manipulated the composition of SEI by using different combinations of electrolyte solvents and Li salts. The chemical composition and structural information of the SEIs are investigated by X-ray Photoelectron Spectroscopy, X-ray diffraction, and Infrared Spectroscopy. Furthermore, this work demonstrates a new strategy of manipulating beneficial SEI formation, which shed light on the application of Li metal anode in high energy density batteries.

 

Reference

1. W. Xu, J. L. Wang, F. Ding, X. L. Chen, E. Nasybutin, Y. H. Zhang and J. G. Zhang, Energy & Environmental Science, 2014, 7, 513-537.

Figure 1
Detection and Influence of Residual Water Content on Electrochemical Performance of Solid State Polymer PEO-Litfsi Electrolytes
Authors: Graebe Heiko , Netz Andreas , Kwade Arno
Published: February 2020

All solid state lithium-ion batteries are one of the promising candidates to power future electric and hybrid electric vehicles due to their outstanding potential for safety improvement and power density. Typically all solid state battery concepts require a lithium-metal (Li-metal) anode to achieve higher energy density. For reasons of processability, polymer based solid electrolytes are often a preferred material class to form the separator and cathode. However, maximum attention has to be paid on the interface of solid polymer electrolyte (SPE) and Li-metal due to the extreme reactivity. Side reactions at the interface cause an increase of the contact resistance and a rapid drop of the cell performance.

Generally solid polymer electrolytes consist of at least two components: a polymeric host and a lithium salt. A well-known combination is polyethylenoxide (PEO) and lithium bis(trifluoromethanesulfone)imide (LiTFSI), which can be prepared by dissolving the two components in a suitable organic solvent which is subsequently removed during a drying step. Although this process appears rather simple, the details of this procedure have a significant impact on the functionality and stability of the SPE. This impact comes from the residual water content, solvents and impurities which as a result react with the Li-metal and cause undesired aging effects.

We studied the drying time of PEO and LiTFSI in-depth based on different variations applying the Karl Fischer titration technique. Commonly for the SPE preparation, solvents like n-methyl-2-pyrrolidion (NMP), acetonitrile, methanol etc. are used which also contain certain amounts of water depending on the purity grade. The interface between Li-metal and SPE was characterized by impedance spectroscopy in symmetrical cells (Li|SPE|Li) at 80°C. The work in our laboratory demonstrates a non-damaging approach to produce water-free PEO and LiTFSI. The results show that the Karl Fischer titration technique is a useful method to determine the residual water content of the PEO and LiTFSI independent of different drying time periods and methods. Moreover, it could be demonstrated, that there is an impact of the residual water on the interface resistance between the Li-metal and the SPE.

Figure 1
Development and Mechanism Investigation of Novel Fluorinated Ethers As Secondary Solvent in Electrolyte for Lithium-Sulfur Batteries
Authors: Zhang Shuo , Lee Chang Wook , Lal Jyotsana , Hu Bin , Zhang Jingjing , Zhang Lu , Lau Ka-Cheong , Liao Chen , Zhang Zhengcheng
Published: February 2020

Sulfur (S) has been identified as one of the most promising cathode material due to its high theoretical specific capacity (1675 mAh/g), good environment compatibility, and low cost. These features make lithium-sulfur battery a potential candidate for the next-generation battery, especially in electric vehicles and portable devices. However, the application of lithium-sulfur (Li-S) battery is still impeded by some limitations, including the low electrical and ionic conductivity of the elemental sulfur and the discharge product (Li2S), and the shuttle effect due to the presence the dissolved polysulfide (PS) species in electrolyte.

1,1,2,2-Tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE) has been identified as an effective secondary solvent in electrolyte for lithium sulfur batteries. In this study, fluorinated ethers (FEs) other than TTE were attempted in 1,3-dioxolane (DOL) based electrolyte, and comparison was made over cell performance, viscosity/conductivity of electrolyte, and aggregation states of lithium PS species.

1,1,2,2-Tetrafluoroethyl 2,2,2-trifluoroethyl Ether (HFE), ethyl 1,1,2,2-tetrafluoroethyl ether (ETE), and 1,1,2,3,3,3-hexafluoropropyl ethyl ether (HEE) were identified as promising alternatives to TTE to accommodate wider range of applications of Li-S batteries. However, amphiphilic FEs, like 1,1,1,2,2,3,3,4,4-Nonafluoro-6-(pentyloxy)hexane (NHPE) and 1,1,1,2,2,3,3,4,4,5,5,6,6-tridecafluoro-8-(pentyloxy)octane (TDPE) were not effective at all.

Depending on formula weight, viscosity and conductivity, cell performance of Li-S batteries containing electrolytes with different FEs also varied. And FEs with coulombic efficiency higher than that of TTE were discovered. In DOL/FE based electrolyte, the aggregation states of lithium PS species were investigated via small-angle X-ray scattering (SAXS), and revealed a variation in dimension of assemblies of lithium PS species in the presence of different FEs. The difference of cell performance can therefore be concluded as the variation in transport behavior of lithium PS species in electrolyte. In addition, this would offer some insights into the failure mechanisms of Li-S batteries, and promote further development of electrolyte for Li-S batteries.

Figure 1
Modeling Na2s Based Glassy Electrolytes for High Performance Solid State Sodium Ion Batteries
Authors: Dive Aniruddha , King Clarence C , Beckman Scott P , Martin Steve W , Banerjee Soumik
Published: February 2020

Limited availability of lithium and safety concerns due to flammability of liquid electrolytes pose significant challenges to commercial lithium-ion batteries. To overcome these limitations, it is essential to explore technologies beyond conventional lithium ion batteries, particularly for electric power grid applications. Sodium ion batteries, particularly those employing solid electrolytes, are being explored as potential candidates. Solid state electrolytes are typically non – toxic and more environmental friendly, which provides them an edge over their liquid counterparts. However, obtaining relatively high ionic conductivity at room temperatures is challenging. In this work, we studied sodium sulfide (Na2S) based glasses as electrolytes for solid state sodium ion batteries. More specifically, sodium sulfide – silicon sulfide [0.5Na2S – 0.5SiS2] glass was explored. These glassy electrolytes were modeled using classical molecular dynamics (MD) approach. The interactions between various ions in the glass were defined using Buckingham type potential. All the glasses were formed using a typical melt – quench technique. Due to amorphous nature of the glass, a large number of initial glass structures were studied to obtain statistically reasonable model. The density of glass obtained through MD was observed to match quite well to the experimentally reported value. Further structural validation of the molecular model was performed by comparing the pair distribution function (PDF) for different pairs of ions for actual glass to those obtained from MD simulations. The ionic conductivity values for these glasses at room temperature have been observed to be in the range of ~ 10-5S/cm, which agreed well with the values obtained from the molecular simulations. Furthermore, the activation energy for ion hopping within the glass was obtained through MD and compared well with experimental data. A KMC site model was developed, based on inputs from MD, to evaluate the ionic conductivity of these glasses at a much larger length scale and the results agreed well with experimental measurements.

Interactions at the anode – electrolyte interface play a key role in determining the performance of sodium ion batteries. Ab initio MD simulations of pure sodium metal and glassy electrolyte interface were performed. Structural configuration of the sodium anode – glass interface was estimated by calculating the density distribution and PDF’s for various ion pairs. Additionally, Na+ ion transport near the interface was studied carefully to determine specific metallic sites that accommodate Na+ ions. The distribution of these favorable sites along with their respective site energies were calculated and provided as inputs to KMC site model that simulated actual battery charging – discharging cycles based on the above inputs from ab initio MD.