bluuebunny/crossref_metadata_2025_split huggingface dataset:
Composite Graphene/Blended Polymer of PEO/PVDF-HFP As Solid Polymer Electrolyte for Sodium Batteries
Authors: Le Phung My Loan , Vo Thanh Duy , Do Nguyen Hoang , Nguyen Hanh Thi Tuyet , Phung Trung Minh , Man Tran Van 
Published: February 2020

Solid polymer electrolytes (SPEs) are promising candidates for their application in electrochemical devices owing to its thermal and mechanical stability for application purposes [1-3]. The ionic conduction in polymer electrolytes occurs in amorphous phase where the ionic motion is coupled with the segmental motion above glass transition temperature. Among various polymers, the polyethylene oxide (PEO) has been studied extensively so far due to its high mechanical property and low barriers to bond rotation with ion efficiency [4,5]. Recently, the poly (vinylidene fluoride-hexafluoropropylene) (PVDF-HFP) has also greatly attracted as a polymer matrix with which provides mechanical stability (by PVdF) and improves ionic conductivity (by HFP component) [6-8]. In this work, we employed the blending polymer of PEO and PVdF-HFP to create a SPEs for sodium-ion battery application. Graphene addition aims to enhance ionic conductivity and mechanic properties of SPEs. Structure and morphology of polymer electrolytes were characterized by X-rays diffraction (XRD) and Scanning Electron Microscopy (SEM). The thermal properties of membrane were analyzed using Differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA). Ionic conductivity and electrochemical stability of polymer membranes were also studied using Electrochemical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CV). The battery performance was evaluated based on charge/discharge curve and sodium intercalation/deintercalation process. A comparison between Na-ion and Li-ion battery using SPEs was also performed.
References:
[1]. F. M. Gray F M (ed), Solid Polymer Electrolytes–Fundamentals and Technological Applications (New York: VCH), 1991.
[2] G. Mao, R.F. Perea, W.S. Howells, D. L. Priceand, M.L. Saboungi, Nature, 405 (2000), 163.
[3] J.Y. Song, Y. Y. Wang, C.C. Wan, J. Power Sources, 77 (1999),183.
[4] G.S. MacGlashan, Y.G. Andreev, P.G. Bruce P G, Nature 398 (1999), 792–794.
[5] S. Das, A. Ghosh, Electrochim. Acta 171 (2015), 59–65.
[6] R. Miao, B. Liu, Z. Zhu, Y. Liu, J. Li, X. Wang, Q. Li, J. Sources 184 (2008), 420–426
[7] S. Ramesh, S-C. Lu, I. Vankelecom, J. Phys. Chem. Solids 74 (2013), 1380.
[8] S. Ramesh, S-C. Lu, J. Mol. Liq. 177 (2013), 73
Acknowledgements:
This research is funded by VietNam National Foundation for Science and Technology Development supported (NAFOSTED) under grant number 104.03-2012.46 and Viet Nam National University of Ho Chi Minh city through.
Solid Electrolyte Interphase and Nitrogen Doping Effect on Potassium Storage Mechanism in Graphite
Authors: Wang Huanhuan , Liu Jilei , Shen Zexiang 
Published: February 2020

The inferior cycling stability critically impedes the development of potassium-ion batteries (KIBs). The solid electrolyte interface (SEI) for nitrogen doped graphite foam (NGF) was studied in both KPF6 and KN(SO2F)2 (KFSI)-based organic electrolytes, aiming to unravel the SEI effect on K+ ion storage mechanism. Electrochemical characterizations disclose that the KN(SO2F)2-based cells deliver improved electrochemical performance in terms of reversibility and cycling stability, compared to KPF6 based cells. Experimental results including depth-profiling XPS and FTIR spectra, together with the theoretical calculations, reveal that (CH2OCO2K)2, C2H5OCO2K, KF and K2CO3 are the dominant components of SEI layers in both electrolytes. Particularly, the amount of K2CO3 in KPF6-based electrolyte is much more than that in KFSI-based electrolyte, resulting in inferior stability. Moreover, the depth-profile XPS results indicate that the SEI formed in KFSI based electrolyte is much more stable, compact and thinner than that in KPF6 based electrolyte. All these features, together, ensure good stability and high reversibility in KFSI-based electrolyte.
The nitrogen doping effect on K+ ion storage was also explored. Enhanced electrochemical performance was identified upon increasing the nitrogen content, due to i) the enrichment of active sites for K+ ion storage and ii) the improved electronic conductivity. Moreover, the electrochemical performance is strongly dependent on N-doping types. Specifically, the pyridinic nitrogen dominates the reversible capacity, as identified by the presence of critical point at 4.29 at. %. In which, the atomic ratio of pyridinic N in NGF is 2.53 at. %, which is higher than that of 7.03 at. %, with only 2.16 at. % pyridinic N. The result is consistent with the theoretical study, which verifies that the charge transferred from K ions to NGF increases with the pyridinic nitrogen doping. Our results promote better understanding of K+ ion storage mechanism in graphite and provide invaluable guidance for optimized carbon-based electrode design for high-performance KIBs.
Fluoroethylene Carbonate-Based Organic Electrolyte Solution for Very Stable Lithium Metal Stripping−Plating at a High Rate and High Areal Capacity
Authors: Aurbach Doron , Markevich Elena , Salitra Gregory 
Published: February 2020

High theoretical specific capacity (3860 mAh g−1) and low negative redox potential make lithium metal an ideal anode for high-energy-density Li batteries. However, dendrite growth and side-electrolyte solution reactions limit the cycling life of the batteries with Li metal anode and cause severe safety problems, hindering practical use of these anodes. Many efforts have been made to stabilize Li metal anodes, including modification of the
Li surface by various mechanical, physical, and chemical techniques, increase of the effective Li-electrode surface by use of an anode matrix with a very large surface area, the use of solid electrolytes, the addition of selected cations (such as cesium or rubidium) which protect the Li surface from dendrite formation according to the self-healing electrostatic shield mechanism and the use of functional electrolyte additives for the in situ formation of a protective SEI. We demonstrate excellent cycling performance of Li metal anodes in EC-free FEC based organic carbonate electrolyte solutions, which were shown to be the most promising electrolyte solutions for high energy-density and high-voltage rechargeable Li batteries. Symmetric Li|Li cells demonstrated an extremely long cycle life and a stable voltage profile for more than 1100 cycles at a current density up to 2 mA cm−2 and an areal capacity of 3.3 mAh cm−2 with a minimal amount of electrolyte solution, sufficient for wetting the separator in coin cells (50 μl/cell or 22 μl cm−2). An increase in areal capacity up to 6 mA h cm−2 does not affect the shape of the voltage profile of the symmetric Li|Li cells. The use of the FEC-based electrolyte made it possible to obtain stable cycling of Li|NMC cells for hundreds of cycles with high loading of active cathode material with areal capacity of 3.3 mAh cm−2. We attribute the high performance of the Li anodes to the formation of a stable and efficient SEI on the surface of the Li metal electrodes cycled in FEC-based electrolyte solutions. The composition of the SEI is analyzed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.
Si Anode Materials for Li-Ion Batteries
Authors: Carroll Kyler J. , Li Bin , Strand Dee 
Published: February 2020

Silicon is regarded as one of the most promising anode materials because of its theoretical specific capacity (4200mAh/g) compared to commercially available graphite anodes (370mAh/g). However, Si electrodes suffer considerable volume expansion of up to 300% during electrochemical lithiation, leading to electrode cracking and pulverization of the Si, causing rapid capacity degradation. Various approaches had been used for using nanostructured Si materials have been applied to solve this problem, since the interval distance between nano structures and internal spaces in them can act as structural buffer space to accommodate the volume expansion of Si. Although some of the nanostructured Si materials achieved considerably high capacity and cyclability, they are usually prepared by complicate and high cost synthetic process which are difficult to extend to large scale. The other approach is using active/inactive alloys as an efficient way to reduce volume expansion and improve cycling performance. The volume expansion of Si can be suppressed by the presence of inactive components, resulting in the maximum energy density at a given volume expansion. Literature has also shown commercially available and low-cost Si alloys can serve as high capacity Li-storage anodic host materials with certain cyclability. If such Si alloy compounds can be made with required chemical stoichiometry and structural architecture though a simple mechanochemical process.
Wildcat Discovery Technologies is developing facile synthesis pathway to prepare Si-alloy active/inactive material. Our approach utilized high-throughput combinatorial research to optimize synthesis process, Si-alloy composition and electrode component to improve the cycling performance of the anode material. Here we demonstrate that with optimized synthesis process, varied active Si and inactive alloy composition reveal a strong correlation between capacity and cyclability.
Characterization of the Intrinsic Thermal and High-Voltage Stability of Organosilicon-Containing Electrolytes
Authors: Guillot Sarah Lucienne , Usrey Monica Lee , Peña Hueso Adrián , Hamers Robert J 
Published: February 2020

Lithium-ion batteries are increasingly used as energy storage devices today due to their excellent energy capacity and voltage characteristics. However, the limited window of electrochemical stability for lithium-ion battery electrolytes constrains the development of devices with higher voltages and longer lifetimes. Conventional carbonate electrolytes degrade under conditions of high heat or voltage to form electrode surface films, leading to capacity fade, impedance increase, and reduced performance over time. Additionally, these electrolytes present a safety risk due to degradation at high temperatures. Therefore, the development of electrolyte systems with increased thermal and electrochemical stability is a relevant issue in battery development.
Organosilicon solvents for battery electrolytes, developed by Silatronix, Inc. with the University of Wisconsin-Madison, have demonstrated improved oxidative stability, reduced gassing, and increased thermal stability. Our work characterizes the thermal and electrochemical behavior of these organosilicon electrolytes by accelerated aging with high heat and extreme potentials. We show evidence of inhibited thermal degradation and propose mechanisms for protection of the lithium salt in organosilicon electrolytes. We identify mechanisms of electrochemical stability and degradation at high voltages against model platinum electrodes. Electroanalytical voltammetry shows increased oxidative stability of the organosilicon electrolytes compared with carbonates. Multinuclear NMR is used to identify and quantify the soluble post-mortem electrochemical products. Voltage and electrolyte composition dependence of surface film product are tracked by x-ray photoelectron spectroscopy. These investigations of solvent-mediated mechanisms of enhanced electrochemical stability enable the future development of advanced high stability electrolytes.
Lithium-Oxygen Batteries with Ultrahigh Areal Capacities: Critical Roles of Air Cathode Architecture
Authors: Lin Yi , Kim Jae-Woo , Connell John W. 
Published: February 2020

Lithium-oxygen (Li-O2) battery systems are known to have a high theoretical energy density that surpasses that of lithium ion batteries. If successfully developed, these batteries could find uses in applications with high energy demand such as future electric aircraft. However, many challenges still remain, including the air cathode’s intrinsically sluggish discharge and charge reaction rates that limit performance, round trip efficiency, and Coulombic efficiency, as well as many problems associated with the lithium anode (such as dendrite formation) and the electrolyte (such as instability at high voltage).
Most research on the air cathode of non-aqueous Li-O2 batteries has focused on the choice of materials or catalysts that would improve the battery performance. However, the total capacities (best reflected by areal values) of the air cathodes are often low, typically limited by the areal mass loading, mostly less than 0.5 mg/cm2, making it inefficient for practical applications. However, with the increase of the mass loading, the mass transport through the cathode thickness becomes more limited. Therefore, the cathode architecture to enable optimal battery reactions across the entire thickness is critical. Here we present an ultrahigh areal capacity air cathode platform based on holey graphene’s unique dry compressibility, which circumvents the mass loading limitation of current cathode architecture. The facileness in the solvent-free fabrication process of the cathode allows many different designs of the dense, but breathable air cathode architectures with ultrahigh areal loadings (on the order of 10 mg/cm2) and excellent battery performance in capacity, round trip efficiency, and cyclability.
Li Storage in a Low Intercalation Potential Li2TiSiO5
Authors: Xia Yong-Yao 
Published: February 2020

Today’s anode for lithium ion batteries is dominated by graphite, with a low operate voltage at 0.1 V vs. Li+/Li, easy to format lithium dendrite and cause to safety risk. As an alternative anode material, the “zero-strain” spinel structure Li4Ti5O12 could avoid Li plating with a relative high intercalation potential (1.55 V vs. Li+/Li) and exhibits an excellent cycling stability. However, the slightly low capacity and high voltage of Li4Ti5O12 result in low energy density. Therefore, it is very important, but nevertheless a challenge, to develop a negative electrode material with a large capacity and an intercalation potential below 1 V, but not close to the Li plating potential, to ensure the safety of batteries. Herein, we report a new anode material of Li2TiSiO5 as anode material for LIBs. The electrochemical profile, structure and Li storage mechanism were extensively studied.
The crystal structure of Li2TiSiO5 is illustrated as a layered structure with infinite sheets of distorted TiO6 octahedra and SiO4 tetrahedra, linked by Li atoms. The distorted TiO6 octahedral and SiO4 tetrahedral networks are thought to be the origin of the structural stability of this material. The crystal structure is depicted in Fig. 1b (left) and the details are summarized in Table 1. Along with the refined structure of Li2TiSiO5, the nuclear-density difference (Fourier) map in Fig. 1b (middle) reveals negative nuclear density only at the 4d, 4e, and Ti (2c) sites, implying that lithium can only reside at these sites. The 4e sites are indicated by the yellow balls in Fig. 1b (right). Figure 2 give the typical charge/discharge curve of Li
2TiSiO5 at between 0 and 3 V (vs. Li+/Li), delivers a reversible charge capacity (Li-ion extraction) of 308 mAh/g, with a voltage plateau below 1.0 V.
Fig. 1 (a) Crystal structure characterization of Li2TiSiO5 and (b) typical charge/discharge curve of Li2TiSiO5

Figure 1
New Ion-Exchange Membranes Derived from Polyketone
Authors: Di Noto Vito , Nawn Graeme , Vezzù Keti , Bertasi Federico , Negro Enrico , Cavinato Gianni , Pace Giuseppe 
Published: February 2020

The centre piece at the heart of numerous energy storage and conversion devices, such as fuel cells and redox flow batteries, is the ion-exchange membrane (IEM). This typically polymeric material is responsible for the migration of ionic species, separation of fuel stocks and for providing additional support to the electrode assemblies. As a result, IEMs are required to possess excellent stability (both thermal and chemical), long lifetimes, electrical insulation, and high ionic conductivity and specificity. Current state-of-the-art polymer electrolytes possessing the more desirable properties tend to come with a price tag that can render their use in energy storage/conversion technologies somewhat cost prohibitive [1]. This has created a strong driving force aimed towards new, cheaper but still high performing materials, for use in energy storage/exchange systems.
The copolymerization of carbon monoxide and ethylene (two readily available and cheap feedstocks) leads to the formation of polyketone, a high performance thermoplastic that has found many applications resulting in its global production of thousands of tonnes per annum. The alternating 1,4-dicarbonyl functionality of aliphatic polyketone enables access, via classic Paal-Knorr chemistry, to a variety of new functionalized polymers [2]. Here we present a new ion conducting polymeric material derived from polyketone, that possess N-functionalized pyrrole units in the backbone (FPK) [3]. Ion-conductivities on the order of 10.6 and 8.6 mScm-1 for the hydroxide and iodide forms of methylated FPKs have been achieved at 80 oC, with the hydroxide FPK demonstrating high resistance towards alkaline conditions for over 20 hours at 80 oC.
The flexibility in the choice of the N-substituent renders these new materials higher tailorable and potentially useful in a range of energy storage/conversion technologies as either proton or anion exchange membranes.

Acknowledgements

The authors wish to thank the Strategic Project of the University of Padova “Materials for Membrane-Electrode Assemblies to Electric Energy Conversion and Storage Devices (MAESTRA)” for funding. V.D.N. thanks the University Carlo III of Madrid for granting him the “Catedra de Excelentia” (Chair of Excellence).

References

[1] S. Eckroad in Handbook of Energy Storage for Transmission or Distribution Applictions, Electric Power Research Institute Report 1007189, California, USA (2002)
[2] A. Sen et al., Macromolecules, 22, (1989), 2012, A.A. Broekhuis et al., J. Apply. Polm. Sci., (2016), 42924, A.A. Broekhuis et al., J. Appl. Polym. Sci., 107, (2008), 107, 262, A.A. Broekhuis, Dyes and Pigments, 98, (2013), 51
[3] N. Ataollahi, K. Vezzù, G. Nawn, G. Pace, G. Cavinato, F. Girardi, P. Scardi, V. Di Noto, R. Di Maggio, Electrochimica Acta., 226 (2017) 148-157.
Synthesis and Properties of s-PBI/2OH-PBI Random Copolymer for High Temperature PEM Fuel Cells
Authors: Lee Ju Sung , Lee Min Jae , Lee So Young , Jang Jong Hyun , Kim Hyoung-Juhn 
Published: February 2020

High temperature polymer electrolyte membrane fuel cell (HT PEMFC), which has the advantages of high tolerance to fuel impurities and simplified system according to no humidification, is currently being studied extensively. The phosphoric acid (PA) with proton conductivity at high temperature (150℃) is used as an electrolyte in HT PEMFC. Therefore, the affinity between membrane material and phosphoric acid and membrane durability are very important. At present, membrane material for HT PEMFC is mainly used the polymer based on polybenzimidazole (PBI). However, the PBI has the problems such as low molecular weight, low PA doping level, PA leakage during operation, and membrane durability. According to some studies, sulfonic acid groups and hydroxyl groups have high affinity for phosphoric acid. Therefore, PBI-based polymer electrolyte prepared from each monomer showed improved doping level, proton conductivity and performance. In this study, we tried to fabricate electrolyte membrane for HT PEMFC with improved properties and cell performance by simultaneously introducing these two functional groups.
For the synthesis of s-PBI/2OH-PBI random copolymer, monosodium salt of 2-sulphoterephthalic acid (STA), 2,5-dihydroxyterephthalic acid (2OH-TA) and 3,3'- diaminobenzidine were prepared with ratio of 1:0:1 (10:0), 0.5:0.5:1 (5:5), 0.4:0.6:1 (4:6). The condensation reaction was used for synthesis of copolymer. The polymer membranes were fabricated by direct casting method. The polymer membrane of the fabricated film type was placed in the humidity chamber at each hydrolysis condition. The degree of polymerization of s-PBI/2OH-PBI random copolymer was confirmed by measuring the torque of the polymer solution in real time. The characteristics of the prepared copolymer were analyzed by FT-IR and doping level. Finally, single cell performance according to monomer ratio and hydrolysis condition was evaluated by IV curve measurement.
The IV curves of s-PBI/2OH-PBI random copolymer were affected by monomer ratio and hydrolysis condition. First, the IV curves showed better performance as the monomer ratio of 2OH-TA increased in hydrolysis conditions of 50℃ and RH 50%. Despite the lowest doping level in the 4:6 monomer ratio, the highest cell performance in 4:6 was attributed to the improvement of the mechanical properties with the increase of polymerization degree. On the other hand, the IV curve at 4: 6 monomer ratio showed the best performance in RH 80% and 70% phosphoric acid bath condition. This confirmed that the polyphosphoric acid was only partially hydrolyzed in the RH 50% condition.

Figure 1
Diffusion Layers with Localized Hydrophilic Domains: Influence of Electron Energy on Spatial Resolution
Authors: Forner-Cuenca Antoni , Manzi-Orezzoli Victoria , Gubler Lorenz , Schmidt Thomas J. , Boillat Pierre 
Published: February 2020

The development of advanced water management strategies for polymer electrolyte fuel cells (PEFCs) could enable further improvements in power density, and therefore decrease the cost. A recently developed approach, consisting on electron radiation grafting using masks, has been utilized to fabricate gas diffusion layers with patterned wettability [1]. These novel materials feature hydrophilic, straightforward pathways for the transport of liquid water; and hydrophobic, low-resistance domains for the transport of reactant gases [2]. It has been recently demonstrated that PEFCs performance can be improved by employing the modified gas diffusion layers on the cathode side, due to the segregated distribution of liquid water that leads to reduced mass transport overpotentials [3].
However, further improvements in resolution are required to fabricate advanced porous materials with localized properties for various applications [4]. Pursuant to this goal, simulations can be used, in tandem with experiments, to elucidate the dominating parameters that influence the resolution (e.g. electron energy, mask-to-sample separation). Moreover, simulations can be utilized in a predictive fashion to calculate the electron beam parameters required to fabricate a given material. In this presentation, we will discuss the influence of electron beam energy on the spatial resolution of porous materials typically used in PEFCs. A combination of experiments and Monte-Carlo simulations was employed to advance the fundamental understanding of mask-assisted through-volume modifications of thick porous substrates. Interestingly, we found that an energy of, at least, 140 keV was required to modify throughout the complete thickness and that the use of energies lower than 300 keV results in a blurring in the adjacent regions. Additionally, we will discuss the influence of housing materials on the back-scattered radiation. Finally, and due to its practical relevance, we will discuss the possibility of selectively modifying one layer out of a bi-layered material (i.e. GDL-MPL arrangement).
[1] Forner-Cuenca, A. et al., Adv. Mater. 27, 6317–6322 (2015).
[2] Forner-Cuenca, A. et al., J. Electrochem. Soc. 163, F1038–F1048 (2016).
[3] Forner-Cuenca, A. et al., J. Electrochem. Soc. 163, F1389–F1398 (2016).
[4] Forner Cuenca, A. et al., Radiat. Phys. Chem. 135, 133–141 (2017).

Acknowledgments

AFC gratefully acknowledges the financial support of the Swiss National Science Foundation (P2EZP2_172183).