bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Performance of Graphite/ LiNi0.5Mn1.5O4 Cells Cycled to High Voltage (4.8 V) with Electrolyte Additives
Authors: Lucht Brett L. , Garsuch Arnd , Xu Mengqing , Dong Yingnan 
Published: February 2020

There is significant interest in the development of higher energy lithium ion batteries (LIB) for electric vehicles. One method of improving the energy density of lithium ion batteries is to increase the operating voltage of the cells by increasing the working potentials of positive electrode employing for example lithium nickel manganese spinel LiNi0.5Mn1.5O4as the active material. However, cycling of lithium-ion cells to high voltages (~5.0 V vs lithium reference electrode, LRE) proceeds with relatively low (99% and less) coulombic efficiency. Among the primary contributors to the poor cycling efficiency are the electrochemical oxidation reactions of the electrolytes at the high positive potentials of positive electrode.
The failure mechanism of graphite /LiNi0.5Mn1.5O4 cells cycled at 25 oC and 55 oC (1.2 M LiPF6 in 3:7 EC/EMC) have been analyzed by electrochemical methods and ex-situ surface analysis of the electrodes. Graphite /LiNi0.5Mn1.5O4 cells cycle well at 25 oC , but have rapid capacity fade upon cycling at 55 oC. Independent electrochemical analysis of anodes and cathodes extracted from cells cycled at 55 oC suggest that both electrodes have significant capacity loss, although the cathode capacity can be recovered with longer charging times. Ex-situ surface analysis of the cathode with SEM reveals that the bulk cathode particles and the cathode laminate are retained while XPS confirms the presence of a cathode electrolyte interface composed of the decomposition products of the electrolyte. Ex-situ analysis of the anode reveals a thick anode solid electrolyte interphase (SEI), anode delamination, and the presence of Mn. The results suggest that both the anode and the cathode contribute to performance loss in graphite/LiNi0.5Mn1.5O4cells.
We are using this mechanistic information about capacity fade in graphite/LiNi0.5Mn1.5O4 cells to develop novel additives to improve the performance of LiNi0.5Mn1.5O4 cycled to high voltage (4.8 V vs Li). The additives include Lewis basic species which inhibit the thermal decomposition of LiPF6 and cathode film forming additives. Preliminary investigations suggest that incorporation of the novel additives into graphite/ LiNi0.5Mn1.5O4 cells significantly improves the capacity retention upon cycling at high voltage (4.8 V vs Li) and moderately elevated temperature (55 oC). Ex-situ surface analysis of the electrodes after cycling suggest that the additives modify the surface of the LiNi0.5Mn1.5O4cathode via the formation of a stable cathode electrolyte interface (CEI). The presence of the CEI inhibits the oxidation of the electrolyte and dissolution of Mn and Ni from the surface of the cathode particles. The additives, also stabilize the SEI on the anode by preventing Mn deposition on the anode surface and damage of the anode SEI.
The details of our experimental results and our mechanistic interpretation will be presented.
Reversible H+/Li+ Ion Exchange and Structure Stability of Garnet-Type Nb-Doped Li7La3Zr2O12 in Water
Authors: Liu Cai , Wen Zhaoyin , Shen Chen , Zhang Gao xiao 
Published: February 2020

The lithium garnet-type oxide is considered as a promising candidate of solid electrolytes to be applied in all solid lithium batteries for its high ion conductivity, chemical stability vs. metal lithium and wide electrochemical potential window. In order to further improve the ion conductivity, dopants like Nb and Ta have been adopted and much progress has been achieved. The total lithium-ion conductivity of Nb-doped Li7La3Zr2O12 was as high as 0.8mS/cm. In this work, its reversible H+/Li+ion exchange reaction and the structural stability in aqueous solutions are systematically investigated.
Cubic garnet phase Li6.25La3Zr1.75Nb0.25O12 (LLNZO) was prepared by a conventional solid-state reaction process at 950oC. The H+/Li+ion exchange reaction of the LLNZO powder was performed in distilled water and the pH value was recorded simultaneously. The process was carried out continuously for 4 times. The lithium content and crystal structure of the garnet powder were measured by ICP and XRD.
The pH value of the distilled water increased quickly after the cubic garnet powder was added in it and finally reached a constant value. The garnet powder was then filtered and the dispersion was repeated with fresh water for deeper ion exchange. The products with different H+/Li+ ion exchange rate were obtained via this way for further dynamics analysis of ion exchange process. The remaining lithium content of the garnet powder was gradually declined after the ion exchange happened. FTIR spectra was tested to identify the ion exchange. It was found that the cubic garnet phase was maintained even the ion exchange rate of lithium ion was up to 74.8% and was confirmed by the high resolution lattice imaging and XRD analysis. The stoichiometry of garnet-type Li6.25-xHxLa3Zr1.75Nb0.25O12, as well as the crystal lattice parameters, was evolved with the H+/Li+ ion exchange reaction in aqueous solutions. It is noticeable that the reverse ion exchange of H+ by Li+was achieved by controlling the reaction temperature, pressure, the lithium concentration and the pH of the solutions. The successful re-exchange indicated the high stability of the Nb doped cubic garnet phase.
Fig.1 XRD results of Li6.25La3Zr1.75Nb0.25O12powder and products from distilled water treatment
Fig.2 The evolution of the constant pH value and remaining lithium content versus water treating stages
Fig.3 TEM and electron diffraction images of Li6.25La3Zr1.75Nb0.25O12with 74.8% lithium ion exchange

Reference

(1) Truong, L. and V. Thangadurai (2011). Chemistry of Materials 23(17): 3970-3977.

(2) Shimonishi, Y., A. Toda, et al. (2011). Solid State Ionics 183(1): 48-53

(3) Ishiguro, K., Y. Nakata, et al. (2013). Journal of the Electrochemical Society 160(10): A1690-A1693.
Electrolyte for Vanadium Redox Flow Batteries: The Role of Complexing Counter Ion
Authors: Roznyatovskaya Nataliya , Noack Jens , Fischer Peter , Tübke Jens , Pinkwart Karsten 
Published: February 2020

Flowable electrochemical systems, such as redox flow batteries are alternative technologies for grid-scale applications, although their high operational and initial costs, safety concerns and limited cycle-life still prevent them from free entrance to the market. All-vanadium redox flow battery (V-RFB) employs two redox couples of V(IV)/(V) and V(II)/(III) in highly acidic media with sulphate or mixed counter anions [1]. The operation of V-RFB based on sulphuric acid electrolyte is limited by low thermal stability of catholyte, i.e. by processes of dimerization or polymerization of V(V) species, which are poorly understood and low kinetics of vanadium electrode reactions at carbon electrodes.
The V(IV) and V(V) ions are known to be complexated by sulphate anions in acidic media [2], V(V) seems to be stabilized in concentrated sulphuric acid [3]. In this work the non-complexing perchlorate anion has been used to avoid the competition for vanadium ion coordination. Several catholytes including 0.5M of V(IV)/V(V) have been prepared in 1M sulphuric acid from vanadyl sulphate salt and in 1M perchloric acid by ion exchange reaction and electrooxidation at graphite felt electrode. The V(IV)/V(V) electrode reactions have been investigated by cyclic voltammetry at pre-oxidized glassy carbon electrode (Figure 1). The V(IV) oxidation and V(V) reduction are found to proceed more reversibly in sulphate-containing electrolyte. The oxidative conversion of V(IV) have been characterized in-situ in visible and near-infrared range during spectoelectrochemical measurement in three-electrode cell at reticulated glassy carbon electrode.
Both of the studied systems have been compared as electrolytes in the 40 cm2 cells using carbon felt electrodes and Nafion separator membrane. The charge-discharge tests performed at current densities from 25 to 50 mA/cm2 revealed that both systems have comparable power densities during charge, however the sulphate-containing electrolyte has higher power density during discharge.
The test of thermal stability revealed the higher stability of the 0.5 M V(V) in sulphuric acid compared to equimolar V(V) solution in perchloric acid.
The results can be useful for careful adjustment of vanadium ion coordination in electrolyte for improved V-RFB. Being impractical as a neat electrolyte solution the vanadium-perchlorate system can be used to study the effect of other, i.e. strongly complexing ligands and can serve as a reference system.
1. P. Leung et al. RSC Adv ,2, 10125 (2012)
2. N. Kausar, R. Howe, M. Skyllas-Kazacos, J. App. Electrochem
., 31, 1327 (2001)
3. J. Krakowiak, D. Lundberg, I. Persson, Inorg. Chem
., 51, 9598 (2012)
Figure 1: Cyclic voltammogramms in Vanadium (IV) and (V) solution with various counter ions.

Figure 1
N, N-Diethyltrimethylsilylamine (DETMSA) As Electrolyte Additive for Si Based High Energy Lithium-Ion Batteries
Authors: He Meinan , Hu Libo , Wang Yan , Xu Kang , Zhang Zhengcheng 
Published: February 2020

Silicon is a highly promising high capacity anode material for high energy lithium-ion batteries for electric vehicle application. Great progress has been made especially in the area of material level on the nano scale.1 However, the electrolyte research tailored to further improve the performance of the Si anode is limited.2 In this paper, we present a new electrolyte additive N, N-diethyltrimethylsilylamine (DETMSA) which showed great improvement over the conventional carbonate electrolyte using the fluoroethylene carbonate as additive. Our experiment data showed that with addition of 0.5 wt. % of DETMSA to the baseline electrolyte 1.2 M LiPF6 EC/EMC+10% FEC, the Li/Si-graphite cell gained a 10% improvement in capacity retention increase with high coulombic efficiency at room temperature. The functioning mechanism of the new electrolyte additive for Si anode was investigated by the XPS, SEM/EDX and FT-IR. 3

References:

He, M., Sa, Q., Liu, G., & Wang, Y. (2013). Caramel Popcorn Shaped Silicon Particle with Carbon Coating as a High Performance Anode Material for Li-Ion Batteries. ACS applied materials & interfaces, 5(21), 11152-11158.

Zhang, S. S. (2006). A review on electrolyte additives for lithium-ion batteries.Journal of Power Sources, 162(2), 1379-1394.

Zhang, S., Ding, M. S., Xu, K., Allen, J., & Jow, T. R. (2001). Understanding solid electrolyte interface film formation on graphite electrodes. Electrochemical and Solid-State Letters, 4(12), A206-A208.
Influence of CO2 on the Cathode Performance and Stability of La1-XSrxCo0.2Fe0.8O3-Î´ in Solid Oxide Fuel Cells
Authors: Cetin Deniz , Yu Yang , Luo Heng , Lin Xi , Pal Uday Bhanu , Basu Soumendra Nath , Gopalan Srikanth 
Published: February 2020

La1-xSrxCo0.2Fe0.8O3-δ is a high performance cathode material due to its mixed ionic and electronic conducting behavior that has widely been in used in solid oxide fuel cells (SOFCs). It has been shown that Sr segregates out of the lattice to the surface of the material and creates new phases in forms of SrO and SrCO3. Even though these surface phases are known to be insulators, their effects on oxygen surface exchange, oxygen transport, and on the overall cell performance remain as open questions.
In order to address the above issues, electrochemical impedance spectroscopy (EIS) was used to study cathode performance on cells of the configuration La1-xSrxCo0.2Fe0.8O3-δ (LSCF)/ gadolinium-doped ceria (GDC) barrier electrolyte layer/ yttria-stabilized zirconia (YSZ) electrolyte/porous (La0.8Sr0.2)0.95MnO3-YSZ counter electrode. LSCF performance was investigated in a dual atmosphere set up in CO2–free air and in the presence of CO2 at the intermediate operational temperature range of 600-800°C as a function of time.
Electrochemistry and Transport of Redox Active Polymers Across a Porous Separator: Towards a Size-Selective Strategy for Non-Aqueous Redox Flow Batteries
Authors: Gavvalapalli Nagarjuna , Hui Jingshu , Lichtenstein Timothy , Cheng Kevin , Moore Jeffrey S , Rodríguez-López Joaquín 
Published: February 2020

Non-aqueous redox flow batteries (NRFBs) are a potentially viable alternative to their aqueous counterparts. NRFBs offer a wider range of redox active species and electrolytes available for their design, thus increasing the chance that highly soluble and stable redox couples can be used. However, the lower ionic conductivity observed in NRFBs due to the use of organic electrolytes in combination with ion-exchange membranes, which are often not designed for these environments, have slowed down their wide-scale implementation. Separating the redox active species in the electrolyte compartments by size-exclusion without greatly impeding the transport of supporting electrolyte is a potentially powerful alternative to the use of poorly-performing ion-exchange membranes. We will present our advances towards implementing such strategy using viologen-based redox active polymers (RAPs) together with a commercial off-the-shelf porous separator such as Celgard™ [1]. These RAPs, with molecular weight between 21 and 318 kDa exhibited size-dependent transport across the porous separator, while retaining many of the attractive properties of a non-aqueous redox couple: high solubility (up to 2.7 M in acetonitrile), facile electron transfer even at high concentration, 94-99% charge/discharge efficiency, and cyclability without evidence of decomposition. Preliminary testing using a stirred cell showed the possibility of integrating RAPs and porous separators into a working device that achieved close to nominal open circuit voltage, stable charge/discharge over several hours and crossover on the order of only 2%. These characteristics, as well as size-dependent transport measurements strongly suggest that porous separators can be used to allow an unimpeded transfer of supporting electrolyte while discriminating the RAP component. Advances in the synthesis of RAPs with other functionalities and their evaluation in flow conditions will be presented.
[1] Gavvalapalli, N.; Hui, J.; Cheng, K.; Lichtenstein, T.; Shen, M.; Moore, J.S.; Rodríguez-López, J. J. Am. Chem. Soc. 2014, 136, 16309-16316
Fabrication and Study of All-Solid-State Li-Ion Batteries Based on Self-Organized Titania Nanotubes
Authors: Djenizian Thierry , Plylahan Nareerat , Letiche Manon , Barr Maissa 
Published: February 2020

The electrochemical storage performances of devices are seriously compromised when decreasing the size of the components down to the micrometer scale. This is particularly true for the development of microbatteries which are rapidly reaching their performance limit in terms of energy density and power density because of its two-dimensional geometry thin film technology impeding fast electron/ion transport in the electrodes and higher interfacial charge transfer resistances. To overcome these issues, all-solid-state 3D microbatteries have attracted interest while remaining a technological challenge since they require the marriage between materials science, electrochemistry, and microfabrication processes. In this context, titania nanotubes (TiO2NTs) have been extensively studied as a 3D negative electrode for lithium-ion batteries (LIBs). These self-supported nanostructured electrode show a suitable nanotubular morphology to fabricate microbatteries with high energy and power densities (1-4).
In this work, the Li+ insertion into anatase TiO2nts using PEO-based polymer as electrolyte has been studied by cyclic voltammetry (CV) and chronoamperometry (CA). The electrochemical characterizations reveal that that the Li+ storage is dominated by the bulk diffusion (into the lattice) with the contribution of the pseudo-capacitive effect at the surface. Beside the mechanistic investigations, we report the fabrication of the first all-solid-state Li-ion batteries based on titania nanotubes as negative electrode, PMMA-(PEO)5 as polymer electrolyte and LiNi0.5Mn1.5O4 as positive electrode (Fig. 1). The electrochemical performance of this new thin film microbattery will be presented and discussed (Fig. 2).
References
1. B. L. Ellis, P. Knauth, and T. Djenizian, Adv. Mater, 26, 3368, (2014).
2. T. Djenizian, I. Hanzu, P. Knauth, J. Mater. Chem., 21, 9925, (2011).
3. N. Plylahan, M. Letiche, M. Barr, and T. Djenizian, Electrochem. Commun., 43, 121 (2014).
4. N. Plylahan, M. Letiche, M. Barr, B. Ellis, S. Maria, T. Phan, E. Bloch, P. Knauth, and T. Djenizian, J. Power Sources, 273, 1182 (2015).

Figure 1
Polarization Analysis Based on Realistic Lithium Ion Battery Electrode Microstructure Using Numerical Simulation
Authors: Yan Bo , Lim Cheolwoong , Song Zhibin , Kim Youngsik , Zhu Likun 
Published: February 2020

The performance of lithium ion battery (LIB) is limited by the inner polarization and it is important to understand the factors that affect the polarization [1]. This study focuses on the polarization analysis based on realistic 3D electrode microstructures. A c++ software was developed to rebuild and mesh the microstructure of cathode and anode electrodes through Nano-CT and Micro-CT scanned images respectively. As a result, the LIB model was composed of electrolyte, cathode and anode active materials and current collectors. By employing 3D finite volume method (FVM), another c++ code was developed to simulate the discharge and charge processes by solving coupled model equations. The simulation revealed the distribution of physical and electrochemical variables such as concentration, voltage, current density, reaction rate, et al. In order to explore the correlation of local effects and electrode structural heterogeneity, the cathode electrode were divided equally into 8 sub-divisions, of which the porosity, tortuosity, specific surface area were calculated. We computed the polarizations in the sub-divisions due to different sub-processes, i.e., the activation of electrochemical reactions and charge transport of species. As shown in Fig. 1, the tortuosity is very irregular because of unevenly distributed cathode particle size and packing pattern with low porosity. There are no exact and direct relations among porosity, tortuosity and specific surface area. Fig. 2 shows that the polarizations are related to the porosity in sub-divisions. The knowledge from the study will help to figure out the mechanism of polarization and power loss in LIB, which could be useful to improve LIB design and manufacturing.
Acknowledgments: This work was supported by US National Science Foundation under Grant No. 1335850.

References:

1. A. Nyman, T. G. Zavalis, R. Elger, M. Behm and G. Lindbergh, Journal of The Electrochemical Society, 157, A1236 (2010).

Figure 1
(Invited) Improvement of Electron Transfer Rate at Metal/Organic Interfaces Using Pd Atomic Layers
Authors: Ikeda Katsuyoshi 
Published: February 2020

Chemical modification of a metal electrode is one of promising methods to realize various electrochemical functions. For example, photocurrent generation may be achieved by surface modification of a metal electrode with chromophores. Electrocatalytic activity may be enhanced by immobilization of catalyst molecules on a metal surface. However, these molecule-induced functionalities are strongly affected by metal/organic interface properties. In particular, the electronic conductance at metal/organic interfaces may be one of essential issues to limit the efficiency of the electrochemical functions. In this work, the electron transfer kinetics at metal/organic interfaces was experimentally investigated using Cobalt porphyrin (CoTPP) modified Au electrodes. To control the connection between Au and CoTPPs, bridge monolayers were formed on the electrode using various thiol- or isocyanide-molecules, and CoTPPs were then immobilized on top of the bridge layers. The electron transfer rate for oxygen reduction reaction (ORR) on CoTPPs was thoroughly investigated for various modified electrodes using the rotating disk electrode (RDE) method.
The interface structure between the Au electrode and the molecular layers was controlled with and without forming Pd monoatomic layers (Fig. (a)). The Pd overlayer on Au surface (Au/PdML) was prepared by the underpotential deposition (UPD) method. The Au and Au/PdML electrodes were self-assembly covered with various diisocyanide molecules such as TPDI (4,4’-terphenyl diisocyanide). CoTPPs were attached on these molecular layers. Figure (b) shows Tafel plots for ORR on CoTPPs on SAM-covered Au or Au/PdML electrode. Electron transfer rate on the Au/PdML was much faster than that on the Au while the Tafel slop was not affected by the presence of Pd overlayer. This result indicates that the performance of chemically functionalized electrodes can be improved by the metal/organic interface control.

Figure 1
New Push-Pull, Multicomponent Phthalocyanine-Based Photsensitizers for DSSCs
Authors: de la Torre Gema , Torres Tomas , Fazio Ettore , López-Pérez Ana 
Published: February 2020

In the last few years, phthalocyanines (Pcs) have attracted strong interest in the field of dye-sensitized solar cells (DSSCs).1 A3B phthalocyanines such as TT40,2 functionalized with non-aggregating bulky substituents at three isoindole rings (i.e. A) and a highly directional carboxylic acid linker at the other isoindole (i.e. B), have reached photovoltaic power conversion efficiencies over 6% in hybrid devices with mesoporous TiO2. Although Pcs are more stable and strongly absorbing than porphyrin (Por) analogues, the latter have shown much more efficient as dyes for DSSCs, especially those with a “push-pull” substitution pattern, such as SM315.3 In the search for new hints for the rational molecular design and optimization routes, we aim to explore if this “push-pull “ pattern also applies to Pcs as a tool to achieve efficient sensitization of TiO2. Therefore, we have synthesized donor-π-acceptor Zn(II)Pcs such as 2, holding one electron-donor, aminophenyl–type unit and a carboxyethynyl moiety as acceptor and anchoring group, starting from ABAB Pc 1 recently reported by us.4 This Pc consist of two opposite isoindoles functionalized with bulky bis(trifluoromethyl)phenyl groups, which afford solubility to the molecule and hamper its aggregation, and two faced isoindoles containing iodine atoms, which can be used for further chemical transformation into the target donor-π-acceptor system 2. Additionally, we have undertaken the preparation of Zn(II)Por-Zn(II)Pc dyads 3, which absorb a broad part of the visible spectrum and show cascade-charge transfer capabilities, for the sensitization of TiO2. In these ensembles, the Zn(II)Por unit, functionalized with three arylamino moieties, features as the ultimate electron donor unit, and the carboxy Zn(II)Pc is responsible of the direct injection of electrons to the semiconducting film.

1 Martinez-Diaz, M. V.; de la Torre, G.; Torres, T. Chem. Commun.
, 2010, 46, 7090.

2 Ragoussi, M.-E. ; Cid, J.-J. ; Yum, J.-H. ; de la Torre, G. ; Di Censo, D. ; Grätzel, M. ; Nazeeruddin, M. K.; Torres, T. Angew.
Chem. Int. Ed.
2012, 51, 4375.

3 Mathew, S.; Yella, A.; Gao, P.; Humphry-Baker, R.; Curchod, B. F. E.; Ashari-Astani, N.; Tavernelli, I.; Rothlisberger, U.; Nazeeruddin, M. K. ; Grätzel, M.; Nature Chem.
2014, 6, 242.

4 Fazio, E. Jaramillo-Garcia, J.; de la Torre, G.; Torres, T. Org. Lett., 2014, 16, 4706.

Figure 1