bluuebunny/crossref_metadata_2025_split huggingface dataset:
Preventing Gas Formation in Dual Carbon Battery By Using Mixed Supporting Salt of LiPF6-LiBF4
Authors: Ishihara Tatsumi , Inda Keisuke , Kurihara Takuya 
Published: February 2020

Rechargeable battery with large energy capacity as well as superior rate property is strongly required for electric vehicle and hybrid vehicle. Dual carbon battery which is expected as a post Li ion battery with superior rate property, is based on intercalation of anion and cation into graphitic carbon and advantages on cycle stability and high discharge potential (>4V), however, low coulomb efficiency by gas formation is the most serious issue for this battery. In this study, gas formation mechanism was analyzed based on LiPF6/ethylene carbonate (EC) and diethylene carbonate (DMC).
Mass analysis of the formed gas suggests that the main species in gas was C2H6, C2H4, CO, and CH4 and the formation of these gas may be assigned to the electrochemical decomposition of EC during charge step. In the initial charge step, gas formation was observed from anode side at initial period and from cathode side at final period. Therefore gas formation from anode side could be assigned to the formation of SEI and that from cathode side could be oxidation of EC in electrolyte. Therefore, by using simple DMC electrolyte, amount of gas formation can be decreased. Among the examined electrolyte, gas formation amount became smallest when DMC was used for electrolyte. In addition, it was found that amount of gas formation was significantly suppressed by using LiBF4-DMC electrolyte, however, discharge capacity became smaller (ca. 40mAh/g). Therefore, mixing LiPF6 with LiBF4 in DEC shows the reasonable large discharge capacity (ca. 87 mAh/g) and the amount of gas was also suppressed. The optimized ratio for mixing was LiPF6:LiBF4=3:1 and gas amount formed became smaller by an order of magnitude. Although low coulomb efficiency was observed at the fist cycle, high coulomb efficiency was sustained over 300 cycles examined.
Preparation and Characterization of Polyethylene Oxide and Polycarbonate Based Composite Cathodes
Authors: Tessmer Britta , Buchheit Annika , Wiemhöfer Hans-Dieter 
Published: February 2020

In the last years, the attention on all solid-state batteries increased due to safety reasons. In current lithium ion batteries, organic solvents are used which can penetrate porous cathodes to ensure a good ion conductive contact with the active material. The advantage of these solvents is the good penetration in the porous cathodes. Major drawbacks are possible leakage and high flammability of the liquid electrolyte. Due to this reason, one approach is to replace the liquid by non-volatile solid electrolytes. A change in the state of aggregation causes some adjustments relative to the cathode. Solid electrolytes, which can be ceramics, glasses or polymers, are not able to penetrate the cathode as a liquid electrolyte can do. Therefore, the electrode has to consist of an additional lithium ion conductive compound. Possible polymeric materials are polyethylene oxide (PEO), polyethylene- and polypropylene carbonate (PEC/PPC) in combination with a lithium salt [1-3], for example lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).
The choice of the materials for the electrolyte was done by the means of conductivity, transference number of Li+, as well as processability and availability. As the starting point and for comparison, the well investigated system PEO/ LiTFSI [4] was used. In the second part, PEO was replaced by PEC or PPC. To optimize these electrolyte systems, different compositions were prepared using the hot press method and characterized regarding the conductivity and electrochemical stability.
The electrolytes with the highest conductivity were used to prepare composite cathodes using carbon black as electronically conducting additive as well as lithium iron phosphate (LFP) as active cathode material. The aim is to produce stable composite cathodes containing the solid polymeric electrolyte, active LFP particles and carbon black, which perform in a sufficient way. Also additionally additives, e.g. plasticizers, can be used to improve the performance of the whole cathode. Here, the hot press method was used again to obtain compact composites. The subsequent characterization was done with electrochemical impedance spectroscopy (EIS) and scanning electron microscopy (SEM). Also cycling tests were performed finally, which show moderate capacities. Further improvements are planned to achieve a higher capacity.

Acknowledgements

The authors acknowledge funding by the German Federal Ministry for Economic Affairs and Energy (BMWi) within the project FesKaBat (03ET6092E).

References

[1] P. Knauth, Solid State Ionics, 180, 911-916 (2009).
[2] W. Gorecki, M. Jeannin, E. Belorizky, C. Roux, M. Armand, J. Phys.: Condens. Matter, 7, 6823-6932 (1995).
[3] Z.-J. He, L.-Z. Fan, Rare Met., 37(6), 488-496 (2018).
[4] M. Hiller, M. Joost, H.J. Gores, S. Passerini, H.-D. Wiemhöfer, Electrochim. Acta, 114, 21-29 (2013).
Increased Cycle Stability of Dual Carbon Batteries By Using LiPF6 – LiTFSI Mixed Salt Electrolyte
Authors: Nakamura Kotaro , Akbay Taner , Madrid Jose , Inda Keisuke , Takagaki Atsushi , Ishihara Tatsumi 
Published: February 2020

Rechargeable battery with large energy capacity as well as superior rate property is strongly required for electric vehicle and hybrid vehicle. Dual carbon battery which is expected as a post Li ion battery, is based on intercalation of anion and cation into graphitic carbon and advantages on cycle stability and high discharge potential (> 4 V). However, low coulomb efficiency by gas formation is the most serious issue for this battery. In this study, effects of mixing LiPF6-LiTFSI in dimethyl carbonate (DMC) for electrolyte of DCB were studied.
For electrochemical measurements, graphitic carbon of KS6 (TIMCAL) and MAGD (Hitachi Kase) were used for the positive and negative electrode, respectively. For the charge/discharge investigations, a constant current rate of 0.5 mA cm−2 was applied for both charge and discharge steps, and the potential windows of 3.0 V to 5.2 V was used. LiPF6, LiTFSI and DMC of lithium battery grade (Kishida Chemical Co., Ltd., Japan) were used. The LiPF6-LiTFSI/DMC electrolyte was prepared by dissolving LiPF6, LiTFSI (battery grade) in DMC in a dry argon-filled glove box without further purification. Coin type cell was assembled in a glove box filled with a dry argon atmosphere.
It was found that mixing LiPF6 and lithium bis(trifluoro methanesulfonyl)imide (LiTFSI) at 1:1 for a support salt was highly effective for increasing coulomb efficiency and cycle stability. When LiPF6-LiTFSI in DMC was used, the discharge capacity of 90 mAh/g-cathode was sustained over 300 cycles without almost no degradation. Coulomb efficiency higher than 98% was achieved after 10 cycles suggesting a decreased gas formation, and it was also found that corrosion of Al current corrector was prevented by using LiPF6-LiTFSI mixed salt. DFT calculation and NMR measurement suggests that the complex anion of (PF5-TFSI)- and F- was formed resulting in the increased stability of intercalated anion and preventing Al current collector corrosion. It was also suggested that PF5-TFSI anion shows fast diffusivity in graphitic carbon which is in good agreement with superior rate property.
Synthesis and Electrochemical Performances of the High Nickel Content Layer-Structured Cathode Materials for High-Energy Libs
Authors: Kim Hyun-Soo , Lee Seung-Hwan , Lee Seul , Jin Bong-Soo 
Published: February 2020

Among the various cathode candidate, layer structured Li(Ni,Co,Mn)O2 (NCM) has been regarded as the most attractive alternative to LIBs owing to relatively modest volume change (LiCoO2), high specific capacity (LiNiO2) and good thermal stability (LiMn2O4). Although Li(Ni1/3Co1/3Mn1/3)O2 has been successfully commercialized as a battery cathode, researches on Ni-rich NCM (LiNixCoyMn1−x−yO2, x > 0.5) have been spotlighted due to its superior capacity (> 200 mAh/g, at 4.6 V vs. Li/Li+) [10]. Therefore, the future of NCM for high energy LIBs strongly depends on Ni-rich NCM materials.
It is reported that crystallinity and morphology, influenced by the sintering temperatures, all play important roles in the electrochemical performances. In this paper, we report the synthesis of LiNi0.91Co0.06Mn0.03O2 cathode materials with different sintering temperatures. Also the relationship between the sintering temperatures and the electrochemical performances is investigated. The sintering temperatures affect a crystallinity and morphology, which play an important role in electrochemical performances of LiNi0.91Co0.06Mn0.03O2. The electrochemical performances have improved with increasing sintering temperatures. The LiNi0.91Co0.06Mn0.03O2 sintered at 720 oC shows remarkably excellent performance: initial discharge capacity: 100 mAh/g, cycle performance: 98 % retention after 100 cycles (at 0.5 C) and rate capability: 88 % (at 2 C). These results indicate that LiNi0.91Co0.06Mn0.03O2 can be regarded as a next generation cathode for high-performance lithium ion batteries.
(Invited) Mitigation of Electrode Swelling of Pure Si Nano-Flake Anode for Advanced Lithium-Ion Batteries
Authors: Inaba Minoru , Haruta Masakazu , Doi Takayuki 
Published: February 2020

The poor cyclability of pure Si electrodes is attributed to crack formation and pulverization of Si active material due to a large volume expansion and contraction during charging and discharging, respectively. It is thus important to suppress the physical stress induced by the large volume changes to improve the cyclability of Si electrodes. We designed a Si powder with a flake shape (Si LeafPowder®, Si-LP, OIKE & Co., LTD.) with 100 nm in thickness and 3-5 mm in lateral dimension, and have reported that Si-LP electrodes have a high initial discharge capacity (ca. 2,500 mAh g-1) and good cycleability (Fig. 1) [1]. Another serious problem of Si anode is a swelling of the electrode owing to irreversible microstructural changes of Si nano-flakes upon cycling (Fig. 2) [2]. The Si-LP sheets in a composite electrode were substantially deformed during alloying/de-alloying cycling and formed the multi-folded layered structure on repeated cycling. Furthermore, many voids, which could accommodate volume changes of Si, were formed on repeated cycling. The multi-folded layered structure with many voids enabled the stable battery operation of the Si-LP electrodes.
Though good cycleability is obtained, the observed electrode swelling during cycling (Fig. 3) is not affordable for practical use. In this talk, we present some mitigation methods developed for suppression of electrode swelling of Si-LP anode and Si thin film anode, including the effects of additives (VC, FEC in Fig.4) [2], the effects of particle size, the effects of oxide content [3], the effects of pre-film formation [4], the effects of artificial SEI film [5], etc.
This research was supported by Japan Science and Technology Agency (JST) ALCA-SPRING and Japan Society for the Promotion of Science (JSPS) KAKENHI Grant Number 16H04649.
References
[1] M. Saito, et al., J. Power Sources, 196(16), 6637–6643 (2011). Doi:10.1016/j.jpowsour.2011.02.042
[2] M. Haruta et al., Electrochim. Acta, 267, 94-101 (2018). DOI: 10.1016/j.electacta.2018.02.062
[3] M. Haruta, et al, J. Electrochem. Soc., accepted for publication.
[4] M. Haruta, et al., J. Electrochem. Soc., 165 (9) A1874-A1879 (2018). DOI: 10.1149/2.1291809jes
[5] M. Haruta, et al., Nanoscale, 10(36), 17257-17264 (2018). DOI: 10.1039/c8nr05354e

Figure 1
Flexible Electrochromic Materials
Authors: Kim Haekyoung 
Published: February 2020

Electrochromic devices (ECDs) containing electroactive materials can reversibly change their optical absorbance and transmittance according to applied voltage, and this property is utilized in a variety of applications such as reflective displays, antiglare mirrors, smart windows and sensors. Electrochromic devices (EC), which dynamically change colour under applied potential, are widely studied for use in energy-efficient smart windows. To improve the viability of smart windows, many researchers are utilizing nanomaterials, which can provide electrochromic devices with improved coloration efficiencies, faster switching times, longer cycle lives, and potentially reduced costs. The flexible electrochromic films are promising film for applications in automobiles, buildings, etc.
Solution processed tungsten trioxide (WO3)-based electrochromic devices (ECDs) are successfully demonstrated. The thin layers with nanostructured materials of WO3 inks were coated on flexible substrate at room temperature, solution-processed method. In contrast to conventional ECDs based on metal oxides, we controlled the substrate to perform flexible ECDs. The performances of flexible transparent conductive electrodes (TCEs) will be presented. The performances and reliability of with flexible TCE will be presented.
Novel L AGP − PEI Composite Electrolyte
Authors: Lifshitz Moran , Greenbaum (Gutina) Anna , Feldman Yuri , Greenbaum Steve , Golodnitsky Diana 
Published: February 2020

Solid electrolytes (SE) have major advantages as an alternative to liquid electrolytes, in terms of reliability, safety, and easy design. SEs are generally defined as electronically insulating solid materials with high mobility and selective transport of charged ionic species within their structure. In general, they can be divided into two main categories: polymeric and inorganic. In this study we focus on the development of a novel composite Li1.5Al0.5Ge1.5(PO4)3 – Polyethyleneimine (LAGP−PEI) polymer-in-ceramic electrolyte, which contains high concentrations of ionic charge carriers with a minimal polymer concentration. Commercial nanoparticles of lithium aluminum germanium phosphate (Li1.5Al0.5Ge1.5(PO4)3, LAGP) were used as a ceramic matrix. Polyethyleneimine (PEI) was tested as a binder and lithium-ion-conducting medium. The combination of nanosize LAGP glass ceramics and PEI polymer was chosen to provide mechanical flexibility with the benefit of the high ionic conductivity of LAGP. The composite electrolytes were prepared by electrophoretic deposition (EPD). TGA, DSC, XRD, ESEM, NMR and EIS tests were used for the characterization of the samples. The dielectric properties of pristine LAGP and LAGP-based quasi-solid electrolytes, containing different concentrations of LiTFSI-based Pyr14 ionic liquid ions, were studied with the use of the BDS 80 (NOVOCONTROL) with automatic temperature control by a QUATRO Cryosystem.
The complex, non-Debye dielectric response of the composite electrolyte has been described in terms of several distributed relaxation processes separated by different frequency and temperature ranges. While at low temperatures, the main contribution is from LAGP, at the middle- and high-temperature regions, the superposition of a few non-Arrhenius processes is observed. 7Li diffusion of the composite electrolyte measured by NMR at 90°C was about 6±2 E-11 m2/s. The correlation of ion-transport phenomena with XRD, DSC and ESEM data will be presented in detail.

Acknowledgements

The research was funded by the Israel Ministry of Science and Technology, grant 53886 and by the Israel Science Foundation (INREP project).
Structure and Dynamics Property of Li-Ion Electrolyte in High Concentration Solution
Authors: Tong Jiahuan , Liang Xiaodong , Solms Nicolas von , Huo Feng , Zhang Suojiang 
Published: February 2020

Electrolyte is an indispensable composition in energy storage since the positive and negative electrodes are interconnected by electrolytes that determines the charge transport during the charging/discharging process. Ideal electrolytes should satisfy the following requirements: i.e., excellent electrochemical stability, wide voltage window, high conductivity, environmental friendliness and easy availability with high purity.[
1
,2] In this work, molecular dynamics simulations have been carried out on two organic solvents (dimethyl carbonate, diethyl carbonate) and four imidazolium-based ionic liquids ([Cnmim][X], n=2,4, X=[BF4]- and [TFSI]-) doped with 2 mol/L LiTFSI salt at 298 K and 313 K. Physicochemical properties, including density, viscosity, self-diffusion coefficient and conductivity are investigated. The contribution and influence of independent conductivity type for uncorrelated and correlated ion on the total conductivity are explored. In parallel, the structure of all electrolytes were further analyzed by the radial distribution functions and the ion coordination numbers. Among them, the structures of solute (LiTFSI) were analyzed in details and the effects of different solvents as well as anion and cation of ionic liquids on the interaction of Li+ were explored. The results indicate that the organic solvents restrict the free motion of the ions, reducing the conductivity of the electrolytes, on the contrary, solute is more stable due to the ionic structure of ionic liquids, especially the [C4mim][BF4] with the highest conductivity among the ILs-based electrolytes. More interesting, two conformations of TFSI- (cis and trans) of solute coexist in all electrolytes. Meanwhile, it was found that the effect of Li+ coordination is mainly determined by anion of ionic liquids and the interaction between Li+ and anion of ionic liquids is directly proportional to the length of the side chain of cation for ionic liquids. In this study, the properties and structures of the electrolytes of organic solvents and ionic liquids were compared thoroughly. The advantages of ionic liquid electrolytes are explained in detail and it is helpful to design higher conductive and more stable ionic liquid electrolytes at molecular level.

References

[1] Wang LL, Ye YS, Chen N, Huang YX, Li L, Wu F, Chen RJ. Development and Challenges of Functional Electrolytes for High-Performance Lithium–Sulfur Batteries. Advanced Functional Materials. 2018; 28.
[2] Chen W, Lei TY, Wu CY, Deng M, Gong CH, Hu K, Ma YC, Dai LP, Lv WQ, He WD, Liu XJ, Xiong J. Designing Safe Electrolyte Systems for a High‐Stability Lithium–Sulfur Battery. Advanced Energy Materials. 2018; 8.

Figure 1
Comparison of the Catalytic Activity of Pt(111) with Mononitride Surfaces in Hydrogen Evolution Reaction
Authors: Abghoui Younes , Skulason Egill 
Published: February 2020

The outcome of a comprehensive density functional theory (DFT) calculations on the surface of mononitrides in the (100) facets of the rocksalt structure reveals that earlier transition metal nitrides should enable hydrogen evolution reaction (HER) via a Tafel mechanism. To achieve this conclusion, H coverage on the surface was calculated as a function of the applied potential. Activation energies of H2 formation via the Tafel mechanism were also calculated at varying applied potentials. According to these computational results, TaN, HfN, MoN, and ScN are predicted to be capable of catalyzing HER at low overpotentials of −0.09 to −0.34 V versus a reversible hydrogen electrode (RHE)1,2. The interesting point to note here is that the activation energies of the Tafel mechanism on these nitrides were found relatively similar to those reported on Pt(111). Therefore, these materials are interesting for further experimental investigations.

References:

1) Y. Abghoui, E. Skúlason, Hydrogen Evolution Reaction Catalyzed by Transition-Metal Nitrides.J. Phys. Chem. C,
2017
, 121 (43), pp 24036–24045.
2) Y. Abghoui, “Novel electrocatalysts for sustainable ammonia production at ambient conditions”, Ph.D.dissertation, Faculty of Physical Sciences, University of Iceland, 2017, ISBN: 9789935934420.
Surface Characterization of Commercial Li-Ion Battery Electrodes Using Scanning Probe Microscopy
Authors: Mitta Saisameera , Stimming Ulrich 
Published: February 2020

Electrochemical energy storage is of high importance, as these systems constitute in the development of sustainable energy technologies. Structural changes of a battery electrode upon ion-intercalation were visualized for Li1 and Na2 batteries using STM on the atomic scale in real time. The important properties of a battery is to have a high energy density, high power density, low cost and long cycle life. The state of art choice of one of the cathode materials is NMC for high capacity Li-ion batteries in the electric vehicle applications3,4.However, the structural and interfacial changes of the material during battery operation have not been fully investigated. Hence, it would be interesting to understand the structure of NMC from a fundamental point of view in order to improve its performance.
Within this work, we investigate the commercial cylindrical NMC electrodes with a different degrees of loading using Atomic Force Microscope inside inert gas filled glove box (see Fig). We will also present the atomic resolution of this commercial NMC electrode using Scanning Tunneling Microscope.
Acknowledgements:
This work is partially supported by Faraday Institution and North-East Centre of Energy Materials (EP/R021503/1) funded by EPSRC.
References:

L.Seidl, S.Martens, J. Ma, U.Stimming and O.Schneider, Nanoscale, 2016, 8, 14004.

L. Seidl, N. Bucher, E. Chu, S.Hartung, S. Martens, O. Schneider and U.Stimming, Energy & Environmental Science, 2017, 7.

H. Sun and K. Zhao, The Journal of Physical Chemistry C, 2017, 121, 6002-6010.

S. Bak, E. Hu, Y.Zhou, X.Yu, S.D. Senanayake, S. Cho, K. Kim, K.Y. Chung, X. Q. Yang and K. W. Nam, ACS Applied Materials &Interfaces, 2014, 6, 22594-22601.

Figure 1