bluuebunny/crossref_metadata_2025_split huggingface dataset:
In-Situ TEM Investigation on Thermal Stability and Oxygen Release Behavior of Charged and Discharged LiCoO2
Authors: Sharifi-Asl Soroosh , Yuan Yifei , Asayesh-Ardakani Hasti , Nie Anmin , Shahbazian-Yassar Reza 
Published: February 2020

Since the first discovery of Li ion batteries (LIBs), enormous research has been dedicated to improve their electrochemical performance such as energy density, power density and lifetime. Yet not much research has been focused on the safety issues and thermal stability of these systems.
LiCoO2is one of the most widely used cathode materials in LIBs. High energy density and light weight cell has made it a good candidate for first generation electric vehicles (Tesla roadster) and even airplanes (Boeing 787 Dreamliner). However, due to the poor thermal stability, its application has been limited to the consumer electronics now. It is well known that Charged LCO when exposed to higher temperatures, as in a case of a mechanical impact or overcharge, releases a portion of its oxygen. Released oxygen can react with electrolyte exothermically and trigger a hazardous thermal runaway. In order to hinder this process we need to gain more in-depth knowledge about underlying mechanisms of this harmful reaction and phase/structural transitions.
In-Situ TEM is known to be a powerful method for studying materials in dynamic conditions such as high temperatures. In this study we utilized transmission electron microscopy to study Li1-xCoO2 (0.5<x<1) in different temperatures. High resolution imaging integrated with electron energy loss spectroscopy (EELS) reveals that cobalt valance changes from 4+ to 3+ at less than 300°C and from 3+ to 2+ at about 450°C showing a two-step oxygen release mechanism in charged LCO Simultaneously, selected area diffraction pattern (SADP) suggests formation of Li vacancy super-lattice and defects such as twins at about 300°C. Going further in temperature results in increase in density of defects and formation of grain boundaries. These findings can be helpful in improving the structural stability of these materials.
Evaluation of Additive Performance on Charged Ncm Surface through Potentiostatic Holds
Authors: Tornheim Adam , Sahore Ritu , Bareno Javier , Bloom Ira , Zhang Zhengcheng 
Published: February 2020

In an effort to achieve higher energy density batteries, many higher voltage cathodes are being investigated. However, at high voltage (V>4.5 vs. Li/Li+), conventional carbonate electrolytes are unstable, leading to electrolyte oxidation and subsequent drop in battery performance. Two possible methods for mitigating electrolyte oxidation are through the use of intrinsically stable electrolytes at the elevated cathode voltage, or through the use of electrolyte additives that sacrificially decompose on the charged cathode surface, impeding further oxidation of the electrolyte. Evaluation of electrolyte or additive performance is traditionally accomplished by cycling tests or through voltammetry with platinum or carbon working electrodes, however each of these methods has intrinsic gaps. Capacity retention can be affected by electrode ‘slippage’ as well as electrode-electrode effects, and voltammetry on inert working electrodes is not evaluating reaction rates on a representative surface. Determining oxidation rates at the cathode surface is of great value in the design of passivating additives.
In this work, stability of electrolytes was assessed using high voltage potentiostatic holds (4.6V vs. Li/Li+, for at least 60 hours) at elevated temperature with a NCM (LiNi0.5Co0.2Mn0.3O2
) electrode as the working electrode and an LTO (Li4Ti5O12) electrode as a counter and reference. A 60 hour potentiostatic hold allows for the relaxation of electrode polarization such that the dominant contributor to external current is oxidation reactions, allowing a quantitative measure of electrolyte decomposition rate. Within this protocol, the passivating effect of various additives can be evaluated both during and after the potentiostatic hold by comparing oxidation current for an additive-containing electrolyte to the baseline. Upon completion of the potentiostatic hold, the capacity and impedance are measured, and cells were disassembled with components characterized by XPS, LC-MS, and IR.

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.
Optimising the Concentration of LiNO3 in C4mpyr-Tfsi-Based Electrolyte in Li-S Batteries
Authors: Musameh Mustafa , Barghamadi Marzi , Best Adam Samuel , Hollenkamp Anthony F. , Mahon Peter , Ruether Thomas 
Published: February 2020

In the lithium-sulfur (Li-S) context, LiNO3 is known to improve the battery performance by forming efficient SEI layer on the lithium anode and consequently prevent or minimise chemical and electrochemical reduction of polysulfides on the anode and suppress the associated lithium polysulfides shuttle effect during cycling. Mikhaylik, from Sion Power Corp. [1], has patented, for the first time, a method that employs N-O bond containing additives, such as LiNO3, in the electrolyte to suppress the PS shuttle effect. Herein, the modification of LiNO3 additive concentration (0.05 to 0.4 mol kg-1) in a C4mpyr-TFSI electrolyte-based Li-S system, for the first time with the best of our knowledge, is investigated in which 0.1 mol kg-1 was determined to be the optimum concentration in the blended IL-organic electrolyte as a result of higher conductivity and higher ion mobility.
Similar performance of cells with different nitrate additive concentrations at 50 oC confirms the correlation between ionic conductivity/viscosity and cell performance. Pulsed field gradient-NMR (PFG-NMR) is utilized to measure diffusion coefficients for cations and anion the electrolytes. The data shows higher diffusion coefficients (therefore higher mobility) for anion and cations in electrolyte containing 0.1 mol kg-1 compared to electrolytes with higher or lower LiNO3 additive at room temperature. Furthermore, the lower D values for TFSI- and Li+ compared to pyrrolydinium cation confirms the transportation of Li+ in the form of [Li(TFSI)n](n-1)- complex in the electrolyte.
1. Mikhaylik, Y.V., Electrolytes for lithium sulfur cells. 2008, SION POWER CORPORATION: US.
Functional Ionic Liquid Based Electrolytes
Authors: Moganty Surya 
Published: February 2020

NOHMs Technologies is developing functional ionic liquid based hybrid electrolytes for high energy density, high voltage, and high power batteries for EV and military applications. The composition of electrolytes greatly affects the cell performance from rate capability, lithium cycling efficiency, and capacity retention at various temperatures to tolerance against electrical, mechanical and thermal abuses. Ionic liquids offer a host of attractive properties, including ultralow vapor pressure, high thermal stability, high ionic conductivity and wide electrochemical stability, which make them attractive as electrolytes. However, there are some physical property limitations that to-date has made them unattractive for lithium battery applications. High viscosity and the fraction of the ionic conductivity of the electrolyte arising from mobile lithium ions (i.e. the so-called lithium transference numbers) are typically low for these materials, which make cells assembled using ionic liquid electrolytes prone to large polarization during operation of the cell. These limitations can be easily overcome by blending ionic liquids with appropriate co-solvents. These hybrid electrolytes simultaneously overcome the poor thermal & electrochemical stability and safety problems that have plagued lithium battery electrolytes for years while still maintaining high conductivity. They provide a platform for engineering electrolytes with both chemical and interfacial tunability that beyond improving safety, expand the range of available battery form factors.
During the presentation, we will show how the ionic liquid functionality affects the SEI formation on the graphite anode and high voltage stability. We intend to answer the following questions: 1) functional ionic liquid and co-solvent formulations to achieve a >4.5V electrolyte, 2) is the capacity fade dependent on the upper voltage cut-off, and 3) how the electrolyte formulations improve the capacity retention of at high voltages and elevated temperatures using 200 mAh pouch cells.

Figure 1
Investigation of Electrolytes for Sio/Graphite Anode Based High Energy Cells
Authors: Wang Jun , Campion Christopher , Vurgaropulos Adam , Pinnell Leslie , Johnson Derek C 
Published: February 2020

High energy cells with SiO/graphite composite anode tend to demonstrate fast capacity fade and gas generation during long term cycling test, due primarily to large volume expansion of Si particles and continuous SEI formation which consumes electrolyte components quickly. As a result, loss of accessible anode material and depletion of electrolyte are common failure mechanisms. Overcoming those challenges requires careful electrolyte formulation to create a stable anode SEI layer with the goal of extending cycle life and reducing cell gas generation.
In this study, a commercial grade small-format pouch cell with SiO/graphite and NCM 523 was selected as an electrochemical test vehicle to screen various electrolyte formulations. A baseline was obtained with commercial electrolytes, which revealed fluoroethylene carbonate (FEC) as a key enabling additive for cycle life. Unfortunately severe cell gassing is often observed with cells that exhibited superior cycle life. A rigorous electrolyte formation matrix was then constructed by varying FEC content, solvent type and ratio, introducing anti-gassing additives and mixed salts. Subsequent testing of these formulations demonstrated that up to 2% 1,3-propane sultone (PS) could effectively reduce cell gassing, but the associated higher cell impedance also adversely impacted cycle life. Formulations with lithium bis(oxalato)borate (LiBOB) as a secondary salt had little influence on cell cyclability but significantly increased cell gassing. The culpability of the additive was confirmed via gas composition analysis. Other variables such as solvent ratio and additives commonly used in graphite based cells appeared to be much less effective for Si containing anodes. Through composition modification, an optimal electrolyte formulation was identified with long cycle life and low gas generation.
Enhanced Electrochemical Performance of Li4Ti5O12 Anode for Lithium Ion Batteries with Titanate Coupling Reagent As Electrolyte Additive
Authors: Zhang Yixiao , Han Guangshuai , Lv Taolin , Xie Jingying , Yan Liqin , Cui Xiaoli , Liu Hui , Shao Leijun 
Published: February 2020

With the increasing applications of lithium ion batteries in energy storage, electric vehicles and hybrid electric vehicles, it’s required to improve the energy density, safety, rate capability and cycling stability of the batteries. Spinel Li4Ti5O12 is a promising anode material for lithium-ion batteries which possesses good Li+ insertion and de-insertion reversibility with negligible structure change, high safety and rate capability, excellent cycle stability1-2. While the theoretical capacity of it, 175 mAh g-1, is slightly low. Meanwhile, it’s observed gassing during storage or cycling3, limitting its application.It was found that the surface coating could be an effective method to solve the swelling problem and be beneficial to the electrochemical performance4.
In this paper, we investigated the effect of titanate coupling reagent TCA-K38S as electrolyte additive on the performance of Li4Ti5O12. TCA-K38S, isopropyl tri-(dioctylpyrophosphate) titanate, is a liquid monoalkoxy pyrophosphate titanate, usually used as coupling agent not only finorganic fillers with resins, but also fnon-polar materials with polar materials, the structural formula is shown in Fig.1. The electrolyte used in this work are 1.2 mol LiPF6 in EC/ EMC solvents ((3:7 by volume), the TCA-K38S was added at 1wt.% and 3 wt.% to the electrolyte solution. Fig.2 shows the cycling performance of Li4Ti5O12 batteries with different amounts of the TCA-K38S additive at various rates. It can be seen that the specific capacity of batteries with 1wt.% additive is 180 mAh g-1 at the first discharge and stable in 170mAh g-1 at 0.2 C, comparied to 162mAh g-1 and 158mAh g-1 at 0.2 C when it’s without additives.

Acknowledgements

The project was supported by the National High Technology Research and Development Program of China (863) (2013AA050902) and Shanghai Science and Technology Development Fund (15DZ2282000, 14JC1491800) .

References

[1]. Z. Huang, D. Wang, Y. Lin, X.Y. Wu, P. Yan, C.M. Zhang, D.N. He, J. Power Sources, 266 (2014) 60-65.
[2]. E. Pohjalainen , J. Kallioinen , T. Kallio, J. Power Sources, 279 (2015) 481-486.
[3]. K. Wu, J. Yang, Y. Liu, Y. Zhang, C. Y. Wang, J.M. Xu, F. Ning, D.Y. Wang, J. Power Sources, 237 (2013) 285-290.
[4]. Z.J. Ding, L. Zhao, L.M. Suo, Y. Jiao, S. Meng, Y.S. Hu, Z.X. Wang, L.Q. Chen, Phys. Chem. Chem. Phys., 2011, 13, 15127–15133.

Figure 1
In Situ Gas Analysis of Li-Ion NixCoyMnz Cathode Interface Reactivity
Authors: Berg Erik J. , Bolli Christoph , Guéguen Aurélie , He Minglong , Streich Daniel , Novák Petr 
Published: February 2020

Li-ion cathode materials based on xLi2MnO3·(1–x)(NiyCozMn1-y-z)O2 (NCM), including both the stoichiometric (x = 0) as well as the Li-rich derivatives (x > 0), are currently under intensive research and development to be implemented in the next-generation batteries because of their high specific charge and operating potential [1, 2]. By tuning the transition metal composition, the cathode properties can be tailored according to application specific requirements: specific charge, rate capability and cycle life. However, compositions offering higher cell energies (e.g. Li- and Ni-rich) generally display increased reactivity towards the electrolyte that may unfavorably influence the thermal stability, impedance and capacity retention of the cells [3]. We demonstrate in situ gas analysis to be a powerful tool to both characterize and in turn mitigate performance limiting interface side-reactions of NCM cathodes and carbonate based electrolytes.
Online electrochemical mass spectrometry (OEMS) enables the in situ analysis of gases evolving inside the electrochemical cell during cycling [4]. The nature, onset, and extent of evolving volatile species provide crucial mechanistic understanding of transformation/decomposition reactions of both the electrode and electrolyte. Side-reaction products associated with the electrolyte LiPF6 salt (e.g. POF3, …), solvent (H2, C2H4, …), and electrode (O2, CO2,…) are readily discernable with high sensitivity and correlated to the electrochemical response during the charge/discharge process. We demonstrate the initiation of a continuous LiPF6mediated electrolyte decomposition cycle at high cell voltages, which drastically increases acidity of the electrolyte and dissolution of the active materials [5]. The influence of the transition metal composition of the active material [6], electrolyte solvents [7], and additives [8] (EC, FEC, VC, …) with respect to the anodic electrolyte decomposition is demonstrated.
[1] P. Rozier, J.M. Tarascon, Journal of The Electrochemical Society, 162 (2015) A2490-A2499.
[2] E.J. Berg, C. Villevieille, D. Streich, S. Trabesinger, P. Novák, Journal of The Electrochemical Society, 162 (2015) A2468-A2475.
[3] H.-J. Noh, S. Youn, C.S. Yoon, Y.-K. Sun, Journal of Power Sources, 233 (2013) 121-130.
[4] E. Castel, E.J. Berg, M. El Kazzi, P. Novák, C. Villevieille, Chemistry of Materials, 26 (2014) 5051-5057.
[5] A. Guéguen, D. Streich, M. He, M. Mendez, F. Chesneau, P. Novák, E. J. Berg, Submitted.

[6] D. Streich, J-Y. Shin, F. Chesneau, P. Novák, E. J. Berg, Submitted.

[7] D. Streich, A. Guéguen, M. Mendez, F. Chesneau, P. Novák, E. J. Berg, Submitted.

[8] A. Guéguen, C. Bolli, M. Mendez, F. Chesneau, P. Novák, E. J. Berg, Submitted
Improvement of Electrode/ Electrolyte Interfaces in Graphite/LiNi0.5Mn1.5O4 Batteries at High Voltage and Elevated Temperature By Using New Family of Lithium Pyridal Trimethyl Borates
Authors: Dong Yingnan , Lucht Brett L , Xu Mengqing , Zhou Liu , Chen Yanjing , Demeaux Julien , Mac Intosh Alex , Meini Stefano , Garsuch Arnd 
Published: February 2020

A novel series or lithium alkyl trimethyl borates and lithium aryl trimethyl borates have been prepared and investigated as cathode film forming additives. The borates are prepared via the reaction of lithium alkoxides or lithium phenoxides with trimethyl borate. Incorporation of 0.5-2.0 % (wt) of the lithium borates to a baseline electrolyte (1.0 M LiPF6 in 3:7 (EC/EMC)) results in improved capacity retention and efficiency of high voltage graphite / LiNi0.5Mn1.5O4 cells especially upon cycling at elevated temperature (55 oC). The improved performance results from the sacrificial oxidation of the lithium borate on the cathode surface to generate a cathode passivation film. The lithium borates can be readily structurally modified to act as a functional group delivery agent to modify the cathode surface. Ex-situ surface analysis of the electrodes after cycling confirms that the lithium borates modify the cathode surface and generate a borate rich surface film which inhibits electrolyte oxidation and Mn dissolution.
Solvent, Lithium Salt and Temperature Influence on Stability of Carbonate Based Electrolytes for 5 V LiNi0.5Mn1.5O4
Authors: He Minglong , Boulet-Roblin Lucien , Borel Philippe , Tessier Cécile , Novák Petr , Villevieille Claire , Berg Erik J. 
Published: February 2020

Spinel LiNi0.5Mn1.5O4 (LNMO) is one of the most promising next-generation cathode candidates for Li-ion batteries because of its reversible specific charge of 147 mAh/g and a high operating potential of 4.7 V.[1] However, the cycling performance of high-voltage cathodes is limited by the poor anodic stability of the most commonly employed alkyl carbonate electrolytes, e.g. ethylene carbonate (EC) and dimethyl carbonate (DMC).[2] Increasing attention is paid to alkyl carbonate based electrolytes for high-voltage applications, including the selection of co-solvents, additives, the role of lithium salt and possible catalytic effect from the electrode components.
The presented work focuses on the investigation of electrolyte decomposition mechanisms and consequent gas evolutions from LNMO cathode by applying in situ gas analysis techniques, i.e. in situ pressure characterization and online electrochemical mass spectrometry (OEMS).[3] The major detected volatile species include H2, CO, CH3F, CO2, and POF3 (only with LiPF6 salt), which present gas evolution profiles depending on the electrochemical potential and electrolyte composition. Enhanced gas evolution rates are observed by increasing DMC content, exchanging LiPF6 salt to LiClO4 or increasing the cell temperature.[4] Ni cations with different oxidation states on the LNMO surface preliminarily exhibit dissimilar catalytic efficiency towards electrolyte decomposition. Our in situ gas analysis provides valuable insights into electrolyte degradation processes on LNMO cathodes, thus further assisting intensive efforts to enhance both performance and safety of high-voltage Li-ion batteries.
[1] C. M. Julien and A. Mauger, Ionics, 19, 951 (2013).
[2] D. Aurbach, B. Markovsky, Y. Talyossef, G. Salitra, H.-J. Kim and S. Choi, Journal of Power Sources, 162, 780 (2006).
[3] M. He, E. Castel, A. Laumann, G. Nuspl, P. Novák and E. J. Berg, Journal of The Electrochemical Society, 162, A870 (2015).
[4] M. He, L. Boulet-Roblin, P. Borel, C. Tessier, P. Novák, C. Villevieille and E. J. Berg, Journal of The Electrochemical Society, 163, A83 (2016).
Wide Temperature Range Electrolyte Development for Start-Stop Vehicle Application
Authors: Cheng Gang , Zhu Ye , Strand Dee 
Published: February 2020

Over the last decade, many governments have implemented more stringent regulations on vehicle fuel economy and CO2 emissions. For example, European targets for new passenger cars reduce emissions to 130g CO2 per kilometer by 2015, with further reduction to 95g by 2021. Start-stop technology reduces CO2 emissions by shutting off the engine when the vehicle is at a stop, such as traffic lights, and restarts the engine instantly when the driver accelerates the vehicle to proceed. Fuel consumption is also reduced, which is desirable from the vehicle owner’s perspective. Start-stop technology is not new, with initial usage traced back to 1980’s by VW in Fiat. However, this application has been greatly limited by the low energy density and poor cycle life of lead acid batteries, which have been primarily used for this application. Batteries intended for start-stop applications must start the engine a high number of times, must survive limited or extended engine-off periods, and must be able to operate over a wide temperature range (-40° C to 60 °C).
Start-stop automobiles have gained momentum recently because of more stringent carbon emission regulations, but also due to technology enhancements achieved in lithium ion batteries. Compared to lead acid, lithium ion batteries have higher energy density as well as longer cycle life. However, the power performance of lithium ion batteries is limited at the low temperatures required for automotive applications due to low conductivities of the electrolyte and the solid electrolyte interphase (SEI). Solutions to the low temperature problem generally consist of adding solvents with very low melting points and/or low viscosities to the formulation which keep the electrolyte from freezing or reduce the viscosity at low temperature. However, these solvents tend to be detrimental to high temperature stability required to meet the lifetime requirements of the vehicle batteries.
Using its unique High Throughput Battery Workflow, Wildcat has developed promising electrolyte formulations with significantly improved low temperature power performance while improving or maintaining high temperature stability relative to a baseline electrolyte formulation. Wide temperature range formulations were developed for both NMC//graphite and NMC//LTO electrode chemistries and over 30% improvement on both low temperature power performance as well as high temperature stability has been successfully achieved.
Figure 1. Solvent composition has strong effect on reducing low temperature impedance (blue/purple is best result, gray/red is worst)

Figure 1