bluuebunny/crossref_metadata_2025_split huggingface dataset:
Controlled Release of Encapsulated Additives for Enhanced Performance of Lithium-Ion Batteries
Authors: Lim Taewook , White Scott R. , Sottos Nancy R. 
Published: February 2020

Autonomous strategies are developed for controlled release of encapsulated vinylene carbonate (VC) to promote beneficial interfacial reactions for SEI (Solid-Electrolyte Interphase) formation. Typically, VC is incorporated in a lithium-ion battery when it is manufactured but its initial concentration is usually limited to a maximum of a few wt% to avoid increased cell resistance due to a reaction of surplus VC. This initial concentration of VC is rapidly consumed during the initial charge and discharge cycles and cannot be utilized effectively for subsequent cycles. In our approach, microcapsules containing VC additive are designed for release of the additive into electrolyte over time. The diffusion-based release of VC from the microcapsules into electrolyte leads to a relatively low VC concentration during initial charge and discharge cycles, and additional VC is available for subsequent cycles.
The VC microcapsules are successfully prepared by a solvent-exchange method that allows VC to diffuse through the microcapsule shell-wall at elevated temperature. VC concentration profiles in electrolyte at three different environments (pouch cell with 2wt% VC, pouch cell with 5wt% VC microcapsules, and electrolyte with 5wt% VC microcapsules) were evaluated at room temperature by taking aliquots of electrolyte at fixed intervals and measuring the VC concentration by NMR. In pouch cells where 2wt% VC liquid was added directly to electrolyte (not encapsulated), the VC concentration decreased significantly after the first cycle at C/10 rate. In great contrast, in pouch cells that contained VC microcapsules, the VC concentration increased from 0 to 3wt% due to timed-release of encapsulated VC in electrolyte.
To evaluate the electrochemical performance for the additive release from microcapsules, we conducted EIS (Electrochemical Impedance Spectroscopy), cycling tests at various C-rates, as well as long-term cycling tests for pouch cells containing no VC (0wt%), VC liquid (5wt% not encapsulated) and VC microcapsules (5wt%). Comparison of the impedance spectra (Fig. 1a) showed that interfacial resistance for pouch cells with 5wt% VC microcapsules was much lower than pouch cells with same amount of VC liquid added directly, which results from lower initial VC concentration in pouch cell with VC microcapsules. In cycling tests at various C-rates, the pouch cell with 5wt% VC microcapsules has even better rate capability, where its discharge capacity was over 2.5 times higher at 5C-rate compared to pouch cell with 5wt% VC liquid. After 400 cycles at 1C-rate (Fig. 1b), the pouch cell with VC microcapsules showed similar capacity retention as the pouch cell including same amount of VC liquid (not encapsulated). This result provides preliminary evidence that the rate capability of lithium-ion batteries can be enhanced without trade-off for capacity retention through time release of microencapsulated additives.

Figure 1
Lithium-Ion Polymer Batteries Assembled with a Cross-Linked Composite Polymer Electrolyte Using a Vinyl-Functionalized SiO2 Nanoparticles
Authors: Shin Won-Kyung , Cho Jinhyun , Yoo Ji-Hyun , Lee Yoon-sung , Kim Dong-Won 
Published: February 2020

Recently, a safety of lithium-ion batteries has been a critical issue as the demand of high capacity batteries for electric vehicles and energy storage systems has increased. The electrolyte commonly used in current lithium-ion batteries is lithium salts (mostly LiPF6) in a mixture of carbonate-based organic solvents. However, the high flammability of the organic solvents in liquid electrolyte can lead to fires and explosions when short circuits or local overheating accidentally occurs [1]. Furthermore, HF can be generated by thermal decomposition and hydrolysis of LiPF6 by trace moisture in the electrolyte solution, which leads to degradation of the cycling performance of lithium-ion batteries at high temperature [2, 3]. Among the various electrolyte systems for lithium-ion batteries, the cross-linked polymer electrolyte is one of the promising candidates due to its high ionic conductivity, good interfacial properties and thermal safety with no electrolyte leakage. In this work, we synthesized the vinyl-functionalized SiO2 particles and coated them onto the fibrous polymer membrane or the microporous polyolefin separator. The SiO2 particles on polymer participated in free radical polymerization with tri(ethylene glycol) diacrylate in a gel electrolyte precursor to form a cross-linked composite polymer electrolyte. An in-situ cross-linking reaction using these reactive SiO2-coated separators promoted strong interfacial adhesion between electrodes and separator, and allowed effective encapsulation of liquid electrolyte, resulting in low interfacial resistances. In addition, the silica nanoparticles played a role as HF scavengers to reduce HF content in the electrolyte at high temperature. The lithium-ion polymer cells assembled with a SiO2-coated separator exhibited superior cycling performance to cell prepared with a conventional polyethylene separator due to the strong interfacial adhesion between the electrodes and separator, as well as suppression of deleterious reactions during cycling.

References

1. J.Wen, Y.Yu, C.Chen, Mater. Express, 2, 197 (2012).
2. E.Zinigrad, L.Larush-Asraf, J.S.Gnanaraj, M.Sprecher, D.Aurbach, Thermochim Acta, 438, 184 (2005).
3. S.F.Lux, I.T.Lucas, E.Pollak, S.Passerini, M.Winter, R.Kostecki, Electrochem. Commun., 14, 47 (2012).
Exceptionally Stable, Non-Aqueous, Sodium-Based Electrolytes for High Energy Electrochemical Capacitors
Authors: Sun Che-Nan , Ruther Rose Emily , Delnick Frank , Nanda Jagjit 
Published: February 2020

Current-generation, acetonitrile-based electrolytes for supercapacitors have a practical voltage window around only 2.7 V. Extending the electrochemical window can significantly increase energy density, since the energy stored in a capacitor increases quadratically with voltage. We report on electrolytes consisting of sodium salts in linear polyether (glyme) solvents which clearly show a 4 V electrochemical window. Electrolyte conductivities range between 1-10 mS/cm, which are comparable to ionic liquids or propylene carbonate-based electrolytes. Importantly, all salts and solvents are commercially available. This family of electrolytes has the potential to double the energy density of supercapacitors, while remaining as cost-effective and scalable as today’s commercial electrolytes.

Acknowledgement

This work is supported by Laboratory Directed Research and Development (LDRD) program of Oak Ridge National Laboratory under the seed project S12-056.
Degradation Behavior in Lithium Iron Phosphate Secondary Cells Under High Rate Pulsed Discharge
Authors: Wetz David Alan , Wong Derek Nathan 
Published: February 2020

LiFePO4 secondary cells cycled under a ultra-high rate pulsed discharge profile are dismantled to study the changes in surface chemistry in pulse power load systems. Three cells lost the ability to charge (0 Ahrs) in less than 50 cycles at 15C (40A) pulsed discharge/continuous recharge conditions. Electrode samples show varying levels of solid electrolyte interphase growth. However, x-ray absorption near edge structure analysis conducted on the cathode material shows minimal loss of active lithium. A cell cycled under the same conditions with a 60°C operating temperature limit showed more gradual capacity fade and a higher degree of shift in the photon energy of the XANES spectrum. XPS analysis shows thicker SEI formation in the 60°cells. This indicates that the additional thermal energy in the 75°C cells provide more favorable conditions for the evolution of a degradation mechanism that is more complex than lost active material. Increased concentration in oxygen at the anode surface indicates heavy reduction in the electrolyte salt forming LixPFy-Oz. The 0 Ahr cells showed higher concentration of Fluorine and an SEI that contains mostly LiF. Results suggests that high temperature, ultra-high rate pulsed cycling favors LiPF6 reduction into LiF and thus the concentration of Li2CO3 in the SEI is reduced creating a high impedance film.
Complementary Operando Investigations of Graphite Cycled in Ionic Liquids By XPS and Raman Spectroscopy
Authors: Streich Daniel , Novák Petr , El Kazzi Mario 
Published: February 2020

Stable electrochemical cycling of graphite in ionic liquid electrolytes has recently been achieved in presence of bis(fluorosulfonyl)imide ([FSI]-) [1]. To get a better understanding of how FSI enables stable cycling, Raman spectroscopy (Raman) [2] and x-ray photoelectron spectroscopy (XPS) [3] were employed as two complementary operando techniques to monitor changes in the bulk structure and the chemical surface composition of graphite particle and HOPG model electrodes, respectively. These electrodes were cycled in 1-ethyl-3-methylimidazolium / bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI] ionic liquid electrolyte containing either 1 M LiTFSI or 1 M LiFSI salt. The Raman experiments show that [EMIM]+ strongly competes with Li+ for intercalation sites in graphite and that Li+ intercalation only takes place at a detectable level in presence of [FSI]- (Figure 1.a). XPS at the IL/electrode interface suggests that both [TFSI]- and [EMIM]+ undergo reductive decomposition reactions resulting in the formation of a solid surface layer (Figure 1.b). A model describing the mechanism behind the cycling improvement in presence of FSI- will be presented based on these results.

[1] M. Ishikawa, et al, Journal of Power Sources
162, 658-662 (2006)

[2] P. Lanz, P. Novák, J. Electrochem.
Soc. 161, 10, A1555-A1563 (2014)

[3] D. Weingarth, A. Foelske-Schmitz, A. Wokaun, R. Kötz, Electrochem. Commun. 11, 619-622 (2011)

Figure 1
Elucidating the Interfacial Structure at the Ionic Liquid-Solid Interface Using Atomic Force Microscopy and Molecular Dynamics
Authors: Black Jennifer , Feng Guang , Zhang Yu , Okatan M. Baris , Zhang Pengfei , Dai Sheng , Kalinin Sergei V. , Cummings Peter T , Balke Nina 
Published: February 2020

The structure and properties of ionic liquids (ILs) at the solid-liquid interface will govern their performance in all applications including energy storage and catalysis. Although it is well known that the interfacial structure of ionic liquids is very different to that of classical dilute electrolytes, a comprehensive understanding of the ion structure within the electrical double layer for this class of electrolytes is still lacking. Therefore it is necessary to have experimental methods to elucidate the interfacial ion structure which can be related to electrochemical performance. Atomic force microscopy (AFM) force spectroscopy is capable of probing the layered ion structure formed at the interface, and offers advantages over other techniques (e.g. x-ray and neutron reflectivity, surface force apparatus) due to its high spatial resolution allowing for the ion structure to be examined in a spatially resolved manner. Although there are several studies demonstrating the impressive ability of AFM to probe the interfacial ion structure in ionic liquids, several questions remain regarding the measured AFM response. (e.g. what is the role of the AFM probe?, Do we measure cations or anions? Can we tune ion selectivity?)
In this work we examine the AFM force profiles of various ionic liquids at different substrates to examine how the substrate and ionic liquid properties affect the interfacial ion structure. We also use a series of different AFM probes of different geometry and chemistry to determine the effect on the measured force profiles. Our experimental results are compared directly with molecular dynamics simulations, and through a combination of experimental and theoretical approaches we are able to develop a better understanding of the measured force response and factors determining the interfacial structure at the ion-liquid solid interface.
High Capacity Li-Rich Cathode Materials
Authors: Luo Kun , Roberts Matthew , Hao Rong , Bruce Peter G 
Published: February 2020

The need for better batteries has never been greater. Many automotive manufacturers now believe that limitations in the performance of current lithium-ion batteries represent the greatest barrier to the electrification of transport. Lithium batteries may also play a critical role in de-carbonization of the electricity grid.
Lithium rich layered cathodes, which offer increased capacity, have, for several years, been regarded as the next major advance, but they are still challenged by problems such irreversible first cycle capacity, voltage fade on cycling related to changes in the structure. Recently important work has been carried out to better understand the origin of the high capacity and the voltage fade.
In this contribution we shall present a new sol-gel synthesis for compositions such as Li1.2Mn0.54Ni0.13Co0.13O2 and discuss their limitations and operation. In addition the mechanisms of charge compensation, oxygen loss vs oxygen redox, will be considered. The electrochemical performance is shown in Figure 1. The characteristic load cure is seen with a significant first cycle irreversible capacity; the implications of this will be discussed. The cycling stability of the material is good with a capacity of ~250 mAh g-1 maintained after 100 cycles.

Figure 1
Charging Voltage Limit Effects on the Electro-Chemical Behavior of High Capacity Manganese-Rich Cathode in Lithium Ion Batteries
Authors: Mao Wen-feng , Fu Yanbao , Ai Guo , Battaglia Vince 
Published: February 2020

Compared with normal cathode materials for lithium ion batteries (LIBs) (such as LiCoO2, LiMn2O4, Li[Ni1/3Co1/3Mn1/3]O2 and LiFePO4), the high capacity manganese rich cathode (HCMR) materials (xLi2MnO3• (1-x)LiMO2, M = Ni, Co, Mn) demonstrates the highest discharge capacity (~250 mAh g-1) along with cost reduction and safety enhancement. This material is therefore considered as a high promising cathode material for the next generation LIBs. However, the charging voltage limits effects on the electrochemical behavior have never been studied. And this material presents complex structural changes upon cycling that are still misunderstood. The purpose of this study is to investigate the charging voltage limit effects on the electrochemical performance and structure of HCMR cathode material.
HCMR electrodes were prepared with a composition of active material (85 wt%), acetylene black conductive additive (7%), and PVdF binder (8%). The loading is about 1.0 mAh/cm2. 2325 coin cells were assembled for electrochemical measurement with Celgard 2400 as separator and lithium metal as counter electrode. Electrochemical measurements were performed using a Maccor battery cycler.
The charge-discharge curves and corresponding cycling performances between 2.0 V and five different upper voltage limits are shown in Fig. 1 and Fig. 2. There is an obvious voltage plateau around 4.5 V during the first charge process, which may be responsible for the activation of the HCMR. The capacities of this material improved with an increase in upper voltage limit up to 4.8 V. For the upper voltage limit of 4.5 V, the capacity of HCMR increased for the first 60 cycles, which may be related to the gradual activation of the HCMR. When the upper voltage exceeds 4.8 V, electrolyte oxidation involving the cathode is believed to cause an increase in resistance that and worse capacity retention. Considering both the discharge capacity and capacity retention, 4.7 V seems to be the best charging voltage limit, which exhibits a discharge capacity of ~240 mAh g-1and capacity retention of 99.88% after 350 cycles. It is well known that the voltage decreases with cycling. The dQ/dV curves (Fig. 3) indicate that both peak voltage and peak area, which are highly related to the HCMR structure and electrochemical performance, change with cycling and upper voltage limit.
Although an increase in the upper voltage limit can improve capacity, 4.7 V is the best upper cut-off voltage for long life and high energy LIBs containing HCMR. The structure changes will be discussed in further work.

Figure 1
Origins of the DC-Resistance Increase in HCMRTM Cathodes
Authors: Kostecki Robert , Battaglia Vince , Chen Guoying , Chen Wei , Liu Gao , Membreno Daniel , Persson Kristin A , Shukla Alpesh Khushalchand , Terborg Lydia , Yi Tanghong 
Published: February 2020

High capacity manganese rich (HCMR™) materials are promising candidates for commercial Li-ion battery positive electrodes for applications in electric and plug-in hybrid electric vehicles.1 These oxides, also denoted as xLiMO2 - (1-x)LiMnO3 (M = Co, Mn, Ni), deliver a high discharge capacity (>240 mAh/g) at operating voltages exceeding 3.5 V vs. Li/Li+.2 However, these materials have significant limitations and suffer from high first cycle irreversible capacity loss, impedance rise and voltage fade during cycling.2-4 Extensive studies of HCMR™ electrodes indicated a structural modification/ rearrangement as one of the major reasons for the electrode/material degradation.
In this work three possible scenarios for the origin of the DC-R rise are presented:

Evidence of Structural Transformation with Cycling and Proposed Strategies Using Lithium and Transition Metal Substitutions
In this section first-principle studies of the structural stability of Li2-xAx(Mn1-yBy)O3 and the effect of doping as well as the structure and possible structural changes of the pristine and aged HTMRTM material are discussed. Preliminary evaluations of the material suggest a single phase, aperiodic crystal consisting of monoclinic domains.

Ionic and Electronic Barriers at Interphases and Interfaces

In situ Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and potentiostatic intermittent titration technique (PITT) provide information about structural changes of the surface, surface layer formation and Li+ diffusivity. Raman spectroscopy suggests transformation to a spinel like structure and FTIR spectroscopy indicates formation of a surface film composed of electrolyte decomposition products. The Li+ diffusivity in HCMRTM correlates strongly with the DC-R behavior within each cycle.

Loss of Mechanical Integrity in HCMRTM Material - Changes in Morphology and Topology

Discussion of how changes in morphology and topology during cycling correlate with long term impedance rise and changes in the unit cell parameters of the HCMRTM material.

Acknowledgements

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231, under the Applied Battery Research for Transportation (ABR) Program and Award Number DE-EE0006443.

References

1. M. M. Thackeray, S. H. Kang, C. S. Johnson, J. T. Vaughey, R. Benedek and S. A. Hackney, J Mater Chem, 17, 3112 (2007).
2. Y. Li, M. Bettge, B. Polzin, Y. Zhu, M. Balasubramanian and D. P. Abraham, J. Electrochem. Soc., 160, A3006 (2013).
3. K. J. Carroll, D. Qian, C. Fell, S. Calvin, G. M. Veith, M. F. Chi, L. Baggetto and Y. S. Meng, Phys Chem Chem Phys, 15, 11128 (2013).
4. D. Mohanty, A. S. Sefat, S. Kalnaus, J. L. Li, R. A. Meisner, E. A. Payzant, D. P. Abraham, D. L. Wood and C. Daniel, J Mater Chem A, 1, 6249 (2013).
(Invited) Advances in Cathode Materials for High Energy Density Lithium-Ion Batteries
Authors: Nanda Jagjit 
Published: February 2020

Advances in high energy density of lithium-ion technology hinges upon the development of next generation high capacity cathode materials. Current state-of-the-art cathodes like NMC have capacity in the range of 180 mAh/g within a voltage window of 2.5-4.2 V. This is a factor of two less than the capacity of the most commonly used anode material, carbon (372 mAh/g). Current high voltage cathode chemistries such as lithium-manganese rich NMC (LMR-NMC) cathodes though promise capacities > 270 mAh/g when cycled to 4.7 V but has a number of stability issues including phase transition and TM dissolution. Mn-Ni high voltage spinel although structurally stable and more robust has relatively lower capacity 147 mAh/g. More than anything these high voltage cathodes need to be cycled at voltages > 4.6 volts that is clearly above the electrochemical stability window for the most commonly used electrolytes (LiPF6 in carbonates).
The talk will review the research progress made in the area of high voltage cathodes for lithium-ion namely, lithium-magnanese rich NMC and high voltage spinel, and the remaining challenges there-in. Topics include other alternative high capacity, 4 V cathodes chemistries that utilize multiple redox states of the host transition metals and thereby intercalate two or more lithium ions per formula unit of the TM. To this effect, we report our recent work on solid-solution compositions of nickel-stabilized two lithium copper oxides having generic formula, Li2CuxNi1-xO2, where x = 0.4-0.6. Optimized composition of this family of cathodes show reversible capacities in excess of 200 mAh/g with good capacity retention but further work is needed to stablize the structure.
Synthesis of LiCoO2 and LiNi1/3Mn1/3Co1/3O2 2D Nanosheets By Osmotic Swelling for High Performance Lithium-Ion Batteries
Authors: Cheng Qian , Chan Candace K. 
Published: February 2020

2D materials have attracted a great deal of attention for their unique electrical and magnetic properties, but may also play important roles in energy storage applications. Lithium-ion batteries and supercapacitors are widely used to power mobile devices, but the energy and power densities of the electrode materials still need improvement. Many conventional battery materials have layered structures, and hence can be readily exfoliated into 2D nanosheet materials. The high surface area and short ionic diffusion distances in the 2D nanosheets may improve the charging/discharging rates and result in more lithium insertion or surface adsorption. Furthermore, hybrid electrode materials composed layers of different cathode materials may be possible by reassembling different nanosheets. These sandwich structures could potentially result in unique synergistic effects and novel redox behavior due to the interactions from different sheets. Finally, we can obtain better understanding of the structure of complex layered cathode materials through exfoliation and high resolution ex-situ microscopy studies.
Here we present our synthesis of 2D nanosheets of two common lithium-ion battery materials, LiCoO2 (LCO) and LiNi1/3Mn1/3Co1/3O2 (NMC). Nanosheets were obtained by exfoliation of LCO and NMC particles using traditional osmotic swelling with tetraethylammonium (TEA). TEM, SEM and AFM analysis showed that the particles were successfully exfoliated nanosheets with around 2 nm thickness. XRD and SADP[CKC1] analysis showed that these materials had hexagonal structures with good crystallization. A reassembly process was developed and applied to obtain LCO, NMC, and LCO/NMC hybrid particles. Electrochemical evaluation of the particles as electrodes for lithium-ion batteries and supercapacitors were performed. Our work is a firm step forward on improving understanding of osmotic swelling processes for the synthesis of nanosheets from complex metal oxides as well as the design and fabrication of high performance hybrid electrodes for energy storage applications.