Ion Solvation and the Search for a Correlation with Electrode Passivation

2015 ◽  
Vol 1740 ◽  
Author(s):  
Arthur von Wald Cresce ◽  
Selena M. Russell ◽  
Adele Fu ◽  
Emily Wikner ◽  
Kang Xu ◽  
...  
Keyword(s):  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Lithium Ion ◽  
Solvent System ◽  
Raw Material ◽  
Binary Solvent ◽  
Ionization Mass ◽  
Electrochemical Testing ◽  
Solvent Molecules ◽  
Electrode Passivation

ABSTRACTThe solvation of cations and anions in a lithium-containing electrolyte was studied using electrospray ionization mass spectrometry (ESI-MS) combined with nuclear magnetic resonance (NMR) and electrochemical testing. The purpose of these experiments was to develop an understanding of the solvation of the small, hard Li+ cation and the more cryptic nature of the solvation of poorly-coordinating anions such as PF6- and BF4-. It has long been held that the passivation of graphitic anodes in lithium ion batteries is a solvation-driven process, meaning that whatever solvent molecules surround the Li+ cation will provide the raw material for the formation of the solid electrolyte interphase (SEI) layer. Because the SEI is a critical component, and because a binary solvent system is normally used in lithium batteries, it is necessary to understand the competitive nature of lithium solvation. Conversely, the anion can be chemically active even if poorly coordinating; therefore, it was desired to see if a competitive solvation condition exists for the anion as well. Results indicate that Li+ has a strong preference for cyclic carbonates like ethylene carbonate (EC) over linear carbonates, where the anions had a mixed preference. It is thought that anion solvent preference might dictate oxidative chemistry that occurs on the cathode, while the anion also significantly participates in the formation of SEI on the anode.

Fabrication of 1D Nanometer Tungsten Trioxide under Different Solvent System

2019 ◽  
Vol 944 ◽  
pp. 1144-1151
Author(s):  
Lin Yan Zhao ◽  
Yue Gang Shen ◽  
You Shu Fan ◽  
Li Wen Ma ◽  
Xiao Li Xi
Keyword(s):  
Tungsten Trioxide ◽  
Dye Sensitized Solar Cells ◽  
Chemical Properties ◽  
Lithium Ion ◽  
Solvent System ◽  
Raw Material ◽  
Solvent Type ◽  
Photocatalytic Activities ◽  
Size And Morphology ◽  
Physical And Chemical

As a cheap and stable transition metal oxide, tungsten trioxide (WO3) has received extensive attentions due to superior physical and chemical properties that could be used in electronic devices, lithium-ion batteries, gas sensors, dye sensitized solar cells, catalysts. In this study, the well-designed 1D architecture of nanowires and nanorods was successfully synthesized via a simple and facile solvethermal method with no template or additives. It is found that both solvent type and concentration of W raw material can affect the size and morphology of WO3significantly in a regular way. Different products showed distinct photocatalytic activities during the processing of degradation methylene blue under visible light, and the underlying reasons for the different photocatalytic activities were discussed.

scholarly journals Physico-chemical Properties of Solutions of Lithium Bis(fluorosulfonyl)imide (LiFSI) in Dimethyl Carbonate, Ethylene Carbonate, and Propylene Carbonate

2021 ◽  
Author(s):  
Johannes Neuhaus ◽  
Erik von Harbou ◽  
Hans Hasse
Keyword(s):  
Experimental Data ◽  
Electrical Conductivity ◽  
Propylene Carbonate ◽  
Dimethyl Carbonate ◽  
Ethylene Carbonate ◽  
Chemical Properties ◽  
Lithium Ion ◽  
Solvent System ◽  
Empirical Correlations ◽  
Physico Chemical

Battery performance strongly depends on the choice of the electrolyte-solvent system. Lithium bis(fluorosulfonyl)imide (LiFSI) is a highly interesting novel electrolyte. Information on physico-chemical properties of solutions of LiFSI, however, is scarce. Therefore, the density, shear viscosity, and electrical conductivity of solutions of LiFSI in three pure solvents that are interesting for battery applications: dimethyl carbonate (DMC), ethylene carbonate (EC), and propylene carbonate (PC), were studied experimentally at temperatures between 273 K and 333 K at 1 bar and concentrations of LiFSI up to 0.45 mol mol−1 in the present work. Empirical correlations of the experimental data are provided. The comparison of the data of this work with the corresponding LiPF6 data underpins the attractiveness of LiFSI as an electrolyte in lithium ion batteries.

The Effect of Solvent on the Capacity Retention in a Germanium Anode for Lithium Ion Batteries

2018 ◽  
Vol 15 (4) ◽  
Author(s):  
Kuber Mishra ◽  
Wu Xu ◽  
Mark H. Engelhard ◽  
Ruiguo Cao ◽  
Jie Xiao ◽  
...  
Keyword(s):  
Electrochemical Performance ◽  
Photoelectron Spectroscopy ◽  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Lithium Ion ◽  
Capacity Retention ◽  
Sei Layer ◽  
Capacity Degradation ◽  
Fluoroethylene Carbonate

A thin and mechanically stable solid electrolyte interphase (SEI) is desirable for a stable cyclic performance in a lithium ion battery. For the electrodes that undergo a large volume expansion, such as Si, Ge, and Sn, the presence of a robust SEI layer can improve the capacity retention. In this work, the role of solvent choice on the electrochemical performance of Ge electrode is presented by a systematic comparison of the SEI layers in ethylene carbonate (EC)-based and fluoroethylene carbonate (FEC)-based electrolytes. The results show that the presence of FEC as a cosolvent in a binary or ternary solvent electrolyte results in an excellent capacity retention of ∼85% after 200 cycles at the current density of 500 mA g−1; while EC-based electrode suffers a rapid capacity degradation with a capacity retention of just 17% at the end of 200 cycles. Post analysis by an extensive use of X-ray photoelectron spectroscopy (XPS) was carried out, which showed that the presence of Li2O in FEC-based SEIs was the origin for the improved electrochemical performance.

scholarly journals Butyronitrile-Based Electrolytes for Fast Charging of Lithium-Ion Batteries

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2869 ◽  
Author(s):  
Peter Hilbig ◽  
Lukas Ibing ◽  
Martin Winter ◽  
Isidora Cekic-Laskovic
Keyword(s):  
Ionic Conductivity ◽  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Depth Profiling ◽  
Lithium Ion ◽  
Cycling Performance ◽  
Fast Charging ◽  
Fluoroethylene Carbonate ◽  
Solvent Additive

After determining the optimum composition of the butyronitrile: ethylene carbonate: fluoroethylene carbonate (BN:EC:FEC) solvent/co-solvent/additive mixture, the resulting electrolyte formulation (1M LiPF6 in BN:EC (9:1) + 3% FEC) was evaluated in terms of ionic conductivity and the electrochemical stability window, as well as galvanostatic cycling performance in NMC/graphite cells. This cell chemistry results in remarkable fast charging, required, for instance, for automotive applications. In addition, a good long-term cycling behavior lasts for 1000 charge/discharge cycles and improved ionic conductivity compared to the benchmark counterpart was achieved. XPS sputter depth profiling analysis proved the beneficial behavior of the tuned BN-based electrolyte on the graphite surface, by confirming the formation of an effective solid electrolyte interphase (SEI).

scholarly journals CO2-based atomic/molecular layer deposition of lithium ethylene carbonate thin films

2020 ◽  
Vol 2 (6) ◽  
pp. 2441-2447
Author(s):  
Juho Heiska ◽  
Milad Madadi ◽  
Maarit Karppinen
Keyword(s):  
Thin Films ◽  
Solid Electrolyte ◽  
Lithium Ion Battery ◽  
Ethylene Carbonate ◽  
Molecular Layer ◽  
Solid Electrolyte Interphase ◽  
Lithium Ion ◽  
Molecular Layer Deposition ◽  
Organic Species ◽  
Layer Deposition

CO2 is used as a precursor in atomic/molecular layer deposition (ALD/MLD) for the fabrication of lithium ethylene carbonates, which are the organic species that naturally form in the solid electrolyte interphase of a typical lithium-ion battery.

scholarly journals Study of decomposition products by gas chromatography-mass spectrometry and ion chromatography-electrospray ionization-mass spectrometry in thermally decomposed lithium hexafluorophosphate-based lithium ion battery electrolytes

RSC Advances ◽  
2015 ◽  
Vol 5 (98) ◽  
pp. 80150-80157 ◽  
Author(s):  
Vadim Kraft ◽  
Waldemar Weber ◽  
Martin Grützke ◽  
Martin Winter ◽  
Sascha Nowak
Keyword(s):  
Mass Spectrometry ◽  
Lithium Ion Battery ◽  
Ethylene Carbonate ◽  
Lithium Ion ◽  
Gas Chromatography Mass Spectrometry ◽  
Ionization Mass ◽  
Decomposition Products ◽  
Ethyl Methyl ◽  
Ethyl Methyl Carbonate ◽  
Methyl Carbonate

In this work, the thermal decomposition of a lithium ion battery electrolyte (1 M LiPF6 in ethylene carbonate/ethyl methyl carbonate, 50/50 wt%) with a focus on the formation of organophosphates was systematically studied.

scholarly journals Effect of Fluoroethylene Carbonate Additive on the Initial Formation of Solid Electrolyte Interphase on Oxygen Functionalized Graphitic Anode in Lithium Ion Batteries

2020 ◽  
Author(s):  
Nadia Intan ◽  
Jim Pfaendtner
Keyword(s):  
Solid Electrolyte ◽  
Lithium Ion Batteries ◽  
Density Functional ◽  
Reaction Pathway ◽  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Lithium Ion ◽  
Cell Decomposition ◽  
Ab Initio Molecular Dynamics ◽  
Fluoroethylene Carbonate

The formation of a solid electrolyte interphase (SEI) at the electrode/electrolyte interface substantially affects the stability and lifetime of lithium-ion batteries (LIBs). One of the methods to improve the lifetime of LIBs is by the inclusion of additive molecules to stabilize the SEI. To understand the effect of additive molecules on the initial stage of SEI formation, we compare the decomposition and oligomerization reactions of a fluoroethylene carbonate (FEC) additive on a range of oxygen functionalized graphitic anode to those of an ethylene carbonate (EC) organic electrolyte. A series of density functional theory (DFT) calculations augmented by ab-initio molecular dynamics (AIMD) simulations reveal that EC decomposition on an oxygen functionalized graphitic (1120) edge facet through an SN2 mechanism is spontaneous, even in an uncharged cell. Decomposition of EC through an SN2 reaction pathway results in alkoxide species regeneration which is responsible for continual oligomerization along the graphitic surface. In contrast, FEC prefers to decompose through an SN1 pathway, which does not promote alkoxide regeneration. The ability of FEC as an additive to suppress alkoxide regeneration results in a smaller and thinner SEI layer that is more flexible towards lithium intercalation during the charging/discharging process. In addition, the presence of different oxygen functional groups at the surface of graphite dictates the oligomerization products and LiF formation in the SEI.

scholarly journals Effect of FSI Based Ionic Liquid on High Voltage Li-Ion Batteries

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2879
Author(s):  
Wenlin Zhang ◽  
Yongqi Zhao ◽  
Yu Huo
Keyword(s):  
Ionic Liquid ◽  
Molecular Orbital ◽  
High Voltage ◽  
Electrode Materials ◽  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Specific Capacity ◽  
Lithium Ion ◽  
Voltage Range ◽  
Discharge Specific Capacity

In this manuscript, a functionalized ionic liquid 1-cyanoethyl-2-methyl-3-allylimidazolium bis (trifluoromethanesulfonimide) salt (CEMAImTFSI) was synthesized and explored as an electrolyte component to improve the oxidation resistance of the electrolyte in high-voltage lithium-ion batteries. Based on the calculation by Gaussian 09, CEMAImTFSI has a higher highest occupied molecular orbital (HOMO) value than the organic solvents ethylene carbonate (EC) and dimethyl carbonate (DMC), suggesting that CEMAImTFSI is more susceptible to oxidation than EC and DMC. Moreover, a low Li+ binding energy value of –3.71 eV and the lower lowest unoccupied molecular orbital (LUMO) enable CEMAImTFSI to migrate easily to the surface of the LiNi0.5Mn1.5O4 cathode and participate in the formation of the SEI (solid electrolyte interphase) film, protecting the electrode materials. Electrochemical studies showed that the LiNi0.5Mn1.5O4/Li cell with 1.0 mol/L LiPF6-EC/DMC/10 vol% has the best cycling stability in the voltage range of 3–5 V. The initial discharge specific capacity of the cells was 131.03 mAh·g−1 at 0.2 C, and even after 50 cycles the discharge specific capacity value of 126.06 mAhg−1 was observed, with the cell showing a capacity retention as high as 96.2%. Even at the rate of 5 C, the average discharge specific capacity of the cell was still 109.30 mAh·g−1, which was 1.95 times higher than the cell without the CEMAImTFSI addition. The ionic liquid molecules adsorption on the cell electrode surface was confirmed by X-ray photoelectron spectroscopic (XPS) analysis after charge–discharge measurements.

Research on Pollution-Free Separation of Wheat Straw Cellulose by Ethanol/Acetic Acid Solvent System

2011 ◽  
Vol 284-286 ◽  
pp. 786-790 ◽  
Author(s):  
Jin Bao Li ◽  
Mei Yun Zhang ◽  
Ya Ling Yang ◽  
Ling Ying Jia
Keyword(s):  
Acetic Acid ◽  
Wheat Straw ◽  
Solvent System ◽  
Kappa Number ◽  
Raw Material ◽  
Binary Solvent ◽  
Cellulose Content ◽  
Pure Cellulose ◽  
Ethanol Acetic Acid ◽  
Hemicellulose Degradation

Agriculture wastes-- wheat straw is used as raw material to take place of cotton and wood pulp in this research. In order to separating of the crude cellulose, non-polluting ethanol/acetic acid binary solvent system is utilized to dissolve lignin. Then pure cellulose is obtained by refining processing. Finally, microcrystalline cellulose is obtained by acid hydrolysis, grinding and the subsequent process. The paper focuses on the effect of the dosage of acetic acid in the binary solvent system on separating efficiency of wheat straw cellulose, and analyzing the effects of acetic acid dosage on kappa number, yield, α-cellulose content and crystallinity of the wheat straw crude cellulose. The results indicated that acetic acid can promote the removal of lignin and hemicellulose degradation, and is conducive to improve the purity of crude fiber. The lignin removed mainly adsorbed and deposited onto the surface of crude cellulose. The optimum dosage of acetic acid in the thermal decomposition system of wheat straw is 2%. Under the optimum condition, the crystallinity of crude cellulose is the highest, the yield and α-cellulose content are both rather high, but a low Kappa number.

scholarly journals Experimental and Modeling Analysis of Holey Graphene Electrodes for High-Power-Density Li-Ion Batteries

Crystals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1063
Author(s):  
Yu-Ren Huang ◽  
Cheng-Lung Chen ◽  
Nen-Wen Pu ◽  
Chia-Hung Wu ◽  
Yih-Ming Liu ◽  
...  
Keyword(s):  
Ion Transport ◽  
Ethylene Carbonate ◽  
Solid Electrolyte Interphase ◽  
Specific Capacity ◽  
Rate Capability ◽  
Lithium Ion ◽  
Md Simulations ◽  
Sei Layer ◽  
Uniform Dispersion ◽  
Li Ion

The performances of lithium-ion batteries (LIBs) using holey graphene (HGNS) as the anode material are compared with those using non-holey graphene (GNS). The effects of graphene holes on ion transport are analyzed with a combined experiment/modeling approach involving molecular dynamics (MD) simulations. The large aspect ratio of GNS leads to long transport paths for Li ions, and hence a poor rate capability. We demonstrate by both experiments and simulations that the holey structure can effectively improve the rate capability of LIBs by providing shortcuts for Li ion diffusion through the holes in fast charge/discharge processes. The HGNS anode exhibits a high specific capacity of 745 mAh/g at 0.1 A/g (after 80 cycles) and 141 mAh/g at a large current density of 10 A/g, which are higher than the capacity values of the GNS counterpart by 75% and 130%, respectively. MD simulations also reveal the difference in lithium ion transport between GNS and HGNS anodes. The calculations indicate that the HGNS system has a higher diffusion coefficient for lithium ions than the GNS system. In addition, it shows that the holey structure can improve the uniformity and quality of the solid electrolyte interphase (SEI) layer, which is important for Li ion conduction across this layer to access the electrode surface. Moreover, quantum chemistry (QC) computations show that ethylene carbonate (EC), a cyclic carbonate electrolyte with five-membered-ring molecules, has the lowest electron binding energy of 1.32 eV and is the most favorable for lithium-ion transport through the SEI layer. A holey structure facilitates uniform dispersion of EC on graphene sheets and thus enhances the Li ion transport kinetics.

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