bluuebunny/crossref_metadata_2025 huggingface dataset:
Study of Li Metal/C Paper Electrodes for Li/S Batteries By Operando Dilatometry
Authors: Fatahine Mohamed , Guay Daniel , Roue Lionel
Published: December 2020

The use of Li metal anode in rechargeable batteries such as Li-S and Li-air is challenging due to the uncontrolled formation of lithium dendrites during repeated charge/discharge cycling, which induces various issues such as cell short circuit, aggravated adverse reactions, dead Li formation, polarization increase and large volume changes, resulting in safety concerns and low coulombic efficiencies [1]. Different characterization techniques have been used to study Li metal electrode morphological changes associated with Li dendrite formation such as scanning electron microscopy, transmission electron microscopy, atomic force microscopy and optical microscopy [2]. A large part of these characterizations were performed ex situ or in situ but under static conditions (no cycling) or operando using open cell requiring none volatile electrolyte, giving limited information on the Li growth dynamics in real systems. Recently, operando synchrotron X-ray tomography has been used to visualize the morphological evolution of Li metal electrodes in various cell configurations (e.g. Li-S cell [3]). However, the limited access to beamtime at synchrotron X-ray sources and challenges with data processing (image segmentation, volume reconstruction, artefact minimization, etc.) are major drawbacks.

In the present study, a simple and low-cost method is used to monitor the electrode thickness variation associated with the Li plating/stripping process. This technique, named ‘’electrochemical dilatometry’’, consists in integrating a gap sensor or a displacement transducer within the electrochemical cell for measuring the vertical displacement of the working electrode during its cycling. It has been successfully applied for studying the volume expansion/contraction of Si-based electrodes for Li-ion batteries [4]. To the best of our knowledge, electrochemical dilatometry has never been applied to the study of Li metal electrodes. In the present study, this technique is used for studying the expansion/contraction behavior of electrodes integrating commercial porous C papers as 3D matrices for Li electrodeposition and compared to what is observed on a 2D Cu foil substrate (Figure 1).

References

[1] X.B. Cheng, R. Zhang, C.Z. Zhao, Q. Zhang, Toward safe lithium metal anode in rechargeable batteries: a review, Chem. Rev 117 (2017) 10403-10473.

[2] D. Lin, Y. Liu, Y. Cui, Reviving the lithium metal anode for high-energy batteries, Nat. Nanotechnol. 12 (2017) 194-206.

[3] G. Torin, G. Vaughan, R. Boucher, F. Alloin, M. Di Michiel, L. Boutafa, J.F. Colin, C. Barchasz, Multiscale characterization of lithium/sulfur battery coupling operando X-ray tomography and spatially-resolved diffraction, Sci. Rep. 7 (2017) 2755.

[4] A. Tranchot, P-X. Thivel, H. Idrissi, L. Roué, Impact of the slurry pH on the expansion/contraction behavior of silicon/carbon/carboxymethylcellulose electrodes for Li-ion batteries. J. Electrochem. Soc. 163 (2016).

Figure 1
New Class of Electrodes to Minimize Tortuosity and Enable Fast Charging
Authors: Roumi Farshid
Published: December 2020

The major problem with fast charging is that high charge rates are restricted by ionic transport and polarization, addressed today by thinner electrodes at the expense of energy density. The goal is to increase electrode utilization such that a thicker electrode can deliver both high energy density and high charge rates.

We are developing a novel electrode design, called PLE, which enables up to double the rate of electrode utilization, at high charge/discharge rates. It is chemistry agnostic and applicable to today’s anode and cathode chemistries such as Graphite and lithium oxide materials, as well to future chemistries such as silicon and sulfur materials. PLE enables 2X higher rate of discharge, compared to conventional electrodes, at 5m Ah/cm2 at C/3. Originally developed by our team at Caltech in 2015, PLE is a laminated electrode structure, based on laminating 2 layers of unit electrodes to make a thicker electrode

Figure 1
Study of Supercapacitor Performance Degradation Depending on Oxide Layer of Aluminum Current Collector
Authors: Kim Hyeonjin , Oh Mihyun , Yun Hyun , Shin Dalwoo
Published: December 2020

Supercapacitor performance comparison depending on the various oxide film thickness of aluminum foil was studied. The study was focused on the anodic behavior of organic solvent based cylindrical supercapacitor.

The study aimed to see correlation between the active material current collector interface changes and the performance of the supercapacitor such as capacitance, ESR or gas generation depending on varying Al current collector oxidation pre-treatment. The results of performance test showed that electrode degradation of the interface between active material coating layer and the Al current collector are influenced by the oxidation pre-treatment process. Furthermore, the supercapacitor performance test by using long time period stored Al foil as a current collector (which is naturally oxidized at room temperature) was conducted to see how long the Al foil for supercapacitor can be stored without notable performance degradation.
Ternary Cross-Linked Multi-Functional Blended Polymers for High-Performance Silicon Anodes in Lithium-Ion Batteries
Authors: Attia Elhadi , Hassan Fathy , Elkamel Ali , Chen Zhongwei
Published: December 2020

Silicon (Si) based anode material is highly attractive for next-generation lithium‐ion batteries (LIBs) due to its unparalleled

theoretical capacity and abundance. However, a severe problem of Si is the significant volume change associated with the

lithiation processes, resulting in reduced capacity retention. Researchers have traditionally considered the roles of

interactive binders and conductive additives as separate entities. These two components often lead to remarkably

decreased mass ratio of Si to nonactive material, which inevitably limits the electrode capacity. To achieve an enhance

utilization efficiency, herein, we have developed a multifunctional nanocomposite binder for high capacity nano-size Sibased

material through a cross-linked polymer of carboxymethylcellulose (CMC), polyacrylic acid (PAA) spine with

graphenized polyacrylonitrile (PAN) through a gradual carbonizing route. This nanocomposite strongly interacts with Si

material, providing a robust nanoarchitecture with abundant conductive pathways for Li-ion transport. CMC and PAA with a

large number of carboxyl groups provide binding ability by sturdy three-dimensional (3D) cross-linked network with relatively

a thin SiO2 mechanical binding film on the surface of Si nanoparticles onto a highly porous carbon and forming a stable

solid electrolyte interface (SEI) layer. Meanwhile, graphenized PAN provides a highly interconnected conductive

nanoarchitecture of a nitrogen-doped graphenized-like structure (NG), which provides enhanced pathways for lithium ion

diffusion. Without any conductive additives, this nanocomposite material not only shows a high superior 1st discharge

capacity of 3473 mAh g-1, high initial Coulombic efficiency of 89%, excellent rate capability, and remarkable cycling life for

more 600 cycles when cycled at high current density of 3000 mA g-1, but also maintaining good cyclability with a constant

high areal capacity of ~ 2.7 mAh cm-2. Together with the ease of fabrication, this provides a promising avenue for

commercial LIBs.

Figure 1
Controlling the Lithium Intercalation Voltage in the Li(Mn1-x
Ni
x
)2O4 Spinel Via Tuning of the Ni Concentration: A Density Functional Theory Study.
Authors: Malatji Kemeridge Tumelo , Santos-Carballal David , Terranova Umberto , Ngoepe Phuti , de Leeuw Nora
Published: December 2020

LiMn2O4 spinel is a promising cathode material for secondary lithium-ion batteries. However, although showing a high average voltage of lithium intercalation, the material is structurally unstable, suffering lowering of the crystal symmetry lowering due to Jahn-Teller distortion of the six-fold Mn3+ cations. Although Ni has been proposed as a suitable substitutional dopant to improve the structural stability of LiMn2O4 and enhance the average lithium intercalation voltage, the thermodynamics of the Ni incorporation and its effect on the electrochemical properties of this spinel material are not yet known. In this work, we have employed density functional theory calculations with a Hubbard Hamiltonian (DFT+U) to investigate the thermodynamics of mixing of the Li(Mn1-x
Ni
x
)2O4 solid solution. Our results suggest that LiMn1.5Ni0.5O4 is the most stable composition from room temperature up to at least 1000K, which is in excellent agreement with experiment. We also found that the configurational entropy is much lower than the maximum entropy at 1000K, indicating that higher temperatures are required to reach a fully disordered solid solution. A maximum average lithium intercalation voltage of 4.8 eV was calculated for the LiMn1.5Ni0.5O4 composition, which is very close to the experimental value. The temperature was found to have a negligible effect on the Li intercalation voltage of the most stable composition. The findings reported here support the application of LiMn1.5Ni0.5O4 as a suitable cathode material for lithium-ion batteries with a highly stable voltage of intercalation under a wide range of temperatures.
Prussian Blue Derived Vertical Graphene Structure for High Frequency Electrochemical Capacitors
Authors: Li Wenyue , Fan Zhaoyang
Published: December 2020

High frequency electrochemical capacitors (HF-ECs), which have large capacitance density and therefore reduced device size in substitution of the bulky aluminum electrolytic capacitors, are of increasing interest. To produce HF-ECs that can respond at hundreds and even kilo hertz range, the tortuous mesoporous electrode of a conventional EC must be replaced with a relatively straightforward and large pore-based structure, and the whole electrode resistance must be small. Various electrode structures have been investigated but very few can deliver an adequate capacitance density at 120 Hz.

In this study, Prussian blue (PB) cubes, as a metal organic framework, are used as building blocks of a 3D scaffold for the vertical graphene (VG) nanosheets growth. In a rapid plasma enhanced chemical evaporation deposition (PECVD) process, a 3D conductive porous network comprised of VG and PB-derived carbon cages was successfully fabricated, and this material structure has a seamless interface with the current collector. Benefiting from the unique electrode material structure, the fabricated HF-ECs exhibited an equivalent series resistance (ESR)as low as 40 mΩ cm-2, 120 Hz phase angle (F

120
) of 85.9o and 120 Hz electrode areal capacitance (CA
120
) of 1.02 mF cm-2, or F

120
= -80.6o and CA
120
= 2.34 mF cm-2 for a thicker electrode, which are among the best reported overall performances thus far for HF-ECs. Integrated cell was assembled to work at 2.7 V for line frequency filtering of different waveforms, demonstrating excellent performance.

Figure 1. (a) SEM and (b) TEM images of PB derived vertical graphene structure. (c) CV curves recorded at 100 V s-1,(d) complex-plane-impedance plotswith inset displaying the high-frequency region, and (e) the derived specific capacitance versus frequency (red line: 3 mg, yellow line: 5 mg and purple line: 7 mg of PB precursor treated in PECVD for 5 min).

Figure 1
Evaluation of Amorphous Oxide Coatings for High-Voltage Li-Ion Battery Applications Using a First-Principles Framework
Authors: Cheng Jianli , Sivonxay Eric , Persson Kristin A.
Published: December 2020

Surface coatings can effectively suppress cathode degradation and enhance electrochemical performance of lithium-ion batteries. To improve our understanding and rational design of amorphous cathode coating materials, here, we present a framework to explore transport mechanisms and thermodynamic stability in such materials. The framework includes series of ab-initio molecular dynamics (AIMD) simulations to obtain amorphous structures and diffusion trajectories, the analysis of the change in coordinating environments during diffusion, the estimation of room temperature diffusivities and the evaluation of the material's suitability in terms of its ability to facilitate Li+ transport while blocking O2- transport. We apply this framework to two commonly used amorphous coating materials: ZnO and Al2O3. We find that (1) Li+ and O2- diffuse much faster in ZnO than in Al2O3. (2) At a state of high charge, neither Al2O3 nor ZnO is expected to retain a significant amount of Li+. (3) Al2O3 provides a better conformal cathode coating than ZnO. We believe this framework can be productively used to evaluate other amorphous materials for different performance metrics and facilitate the development of optimal cathode coatings.
Using Scanning Micro X-Ray Fluorescence (µXRF) to Visualize, Understand and Quantify Transition Metal Dissolution in Li-Ion Cells
Authors: Eldesoky Ahmed , Logan Eric R. , Johnson Michel , McFarlane Chris , Dahn Jeff R.
Published: December 2020

State-of-the-art Li-ion batteries (LIBs) typically consist of a graphite anode with a capacity of 372 mAh g-1 and a cathode material consisting of a layered transition metal oxide in the form of LiMO2
, where M = Ni, Mn, Co or Al (NMC and NCA material), or olivine-type material in the form of LMPO4
, where M = Fe, such as LiFePO4 (LFP). Proposed degradation mechanisms for the cathode material in LIBs include transition metal dissolution (TMD), particle cracking and phase transformation, which are believed to contribute to significant capacity fade due to the loss of cathode active material1.

Here, we report the use of scanning Micro X-Ray Fluorescence (µXRF) to investigate the effects of cell drying conditions and VC additive on the extent of TMD in LFP type cells and its subsequent deposition on the anode surface. For quantitative analysis, we prepared a calibration wedge made up of a pristine graphite anode with a known linear gradient of sputtered Fe. Figure 1a shows the µXRF images of the calibration sample and blank, from which we were able to correlate known TM concentrations to an observed signal intensity in the form of net count per area to facilitate accurate quantification, schematically shown in Fig. 1b. Unlike previous reports of XRF use in TMD analysis2, our approach allows us to quantify TM concentration deposited on our anodes without having to alter the surface by DMC washing, or through ball-milling, which preserves the nature of the sample and allows us to extract both quantitative and qualitative information (such as element distribution) from our aged cells using matrix-matched calibrants.

In this work, we demonstrate how our scanning µXRF approach enabled us to visualize the distribution of TMs and other elements present on the anode surface and quantify TMD in LFP Li-ion cells. We show that Fe dissolution can be greatly reduced with rigorous cell drying and appropriate choice of additives. Additionally, we report the presence of locally high TM concentration spots on the anode which we believe are due to non-uniformities in cell stack pressure. Finally, we observe that the extent of TMD is normally not significant enough to be responsible for cell capacity fade due to active material loss, and propose how Fe dissolution might be contributing to a more complicated cell failure mechanism which will be important to investigate in future work to understand its impact on cycle life.

References:

Börner, M. et al. Degradation effects on the surface of commercial LiNi0.5Co0.2Mn0.3O2 electrodes. J. Power Sources
335, 45–55 (2016).

Evertz, M., Lürenbaum, C., Vortmann, B., Winter, M. & Nowak, S. Development of a method for direct elemental analysis of lithium ion battery degradation products by means of total reflection X-ray fluorescence. Spectrochim. Acta - Part B At. Spectrosc.
112, 34–39 (2015).

Figure 1
Impact of Water on the Properties of Superconcentrated Electrolytes
Authors: Genereux Simon , Gariépy Valérie , Rochefort Dominic
Published: December 2020

Superconcentrated electrolytes are a new class of electrolyte that is of interest to the scientific community for battery applications. These electrolytes consist of an amount of salt greater than the amount of solvent, while remaining liquid. It is currently accepted that the reduction of the solvation sphere under these conditions results in a greater electrochemical stability of the solvent and a higher Li+ transport number. These properties, are widely used in the literature For instance, superconcentrated electrolytes employing acetonitrile as the solvent have been applied in lithium metal batteries while acetonitrile with moderate salt concentration decomposes on lithium. Despite the attractiveness of the field to these electrolytes, their properties are still poorly understood, and the methods of analysis used vary between different studies. There is no standard protocol for their use and it becomes difficult to establish correlations between different studies. Our goal is to establish the required methods to standardize the methodology and fill the gaps in the field.

To do so, we firstly studied superconcentrated electrolytes based on LiTFSI and acetonitrile. The approach taken highlights the factors that have a significant impact on the properties of electrolytes. One of these factors is the water content. The results demonstrate that the presence of water in the solutions has a limited impact on the physical properties of viscosity and density of the mixtures as long at the concentration remains at and below 1000 ppm. The water content has a significant impact on the electrochemical window of stability of the electrolyte, reducing it to less than 2 V at 1000 ppm. The solvating structure of superconcentrated electrolytes is also studied via the electrochemistry of the Ferrocene/Ferrocenium couple to probe the impact of the electrolyte properties on electron transfer reactions. These results highlight the importance of structure and composition in the development of superconcentrated electrolytes.
Full Cell Understanding of Solvents in Battery Systems
Authors: Usrey Monica Lee , Guillot Sarah Lucienne , Johnson Tobias , Peña Hueso Adrián , Zhou Liu , Kerber Brian , Du Peng
Published: December 2020

Lithium ion batteries are complex systems with multiple components that can be optimized to obtain desired performance capability. These components include electrolyte salts, solvents, and additives, as well as electrode active materials and coatings. Rational optimization of battery components requires an understanding of the fundamental science driving the observed performance. Silatronix® has developed a suite of analytical tools and methods using a combination of full format batteries, lab R&D cells, and model systems to construct a complete understanding of the battery from the cell level performance to the fundamental chemistry. This process includes the recovery and analysis of all parts of a full format pouch cell, including liquid electrolyte, generated gas, and electrode surface layers (Fig. 1).

Using this process, Silatronix® has evaluated several battery components, including organosilicon solvents for Li-ion electrolytes, to acquire a comprehensive picture of how these components provide observed performance benefits. For example, OS3®, a novel organosilicon chemistry that merges a silane with a Li+ coordinating nitrile functionality, has provided multiple performance benefits in various advanced Li-ion chemistries. Key experimental results include improved high temperature cycling stability in full format graphite/NMC622 pouch cells with 1%, 2%, or 3% OS3® (Fig. 2a), and using a model system of electrolyte in NMR tubes, we show that enhanced thermal stability of the bulk electrolyte results from HF scavenging and LiPF6 salt stabilization when 2-16% OS3® is present (Fig. 2b). Reduction of gas generation during high temperature testing in pouch cells with a commercial Si-based anode is also shown with 2% OS3® (Fig. 2c), and gas product identification and quantification is determined by GC-TCD for mechanistic analyses. In addition, OS materials change the reactivity of other electrolyte components, particularly at the electrolyte/electrode interfaces that govern critical performance attributes in Li-ion cells such as gas generation and interfacial impedance. These key performance benefits serve to enable several next generation battery chemistries, including a strong synergy with Si-based anodes.

Figure 1
Effect of Ion Species on the Electrochemical Characteristics of Liquid Electrolytes for High Performance EDLCs
Authors: Park Tae hyun , Park Myung-Soo , Kim Sang-Gil , Lee Byung Jun , Kim Dong-Won
Published: December 2020

Electric double layer capacitors (EDLCs) have been considered one of the most promising electrochemical energy storage devices with high specific power and long cycle life. They are being used in power sources for hybrid electric vehicles and other energy storage systems. An electrolyte with high ionic conductivity and wide electrochemical window is one of the vital constituents of EDLCs and it plays an important role in EDLC performance. In particular, acetonitrile (ACN) has been widely used as an electrolyte solvent in EDLCs, because it can dissolve salts effectively and thus has high ionic conductivity.However, there are few reports on systematic studies of ion species in salt for EDLC. In this respect, we studied the correlation between ion species and electrochemical properties of ACN-based electrolytes. In this work, ammonium, pyrrolidinium and piperidinium-based salts were employed to achieve high ionic conductivity. Ionic conductivity of electrolyte consisting of smaller ions exhibited higher ionic conductivity. Among the various salts, 1-ethyl-2-methylpyrrolidinium tetrafluoroborate, N-trimethyl-N-propylammonium bis(fluorosulfonyl)imide and 1,1-dimethyl piperidinium bis(fluorosulfonyl) imide exhibited high ionic conductivity and wide electrochemical stability window.
Improvement of High Voltage Cycling Performance of Lithium-Ion Cells By Employing a Functional Additive
Authors: Hong Seung-Bo , Han Dong-Kwan , Kim Dong-Won
Published: December 2020

Lithium-ion batteries (LIBs) are being widely used in many applications such as mobile electronic devices, electric vehicles and energy storage systems because of their high energy density and excellent cycle life. As there is always need for increasing the battery capacity, high voltage operating is essential. However, there are several issues in high voltage operation of LIBs; dissolution of transition metal from the active cathode material and oxidative decomposition of liquid electrolyte. Among the strategies for improving the high-voltage cycling performance, an addition of functional additive is one of the most promising methods. Functional additives can form cathode electrolyte interphase (CEI) on the cathode surface during cycling, which suppress the oxidative electrolyte decomposition and the dissolution of transition metal from cathode. In our study, we investigated effective additives for forming the uniform CEI layer and applied them to the LIB composed of graphite anode and NCM cathode. Electrochemical characterization and performance evaluation were performed to examine how these additives could improve the high-voltage cycling performance of LIBs.
Degradation of Carbon Electrodes in the Vanadium Redox Flow Battery
Authors: Singh Ashutosh Kumar , Pahlevaninezhad Maedeh , Yasri Nael , Roberts Edward P.L.
Published: December 2020

The Vanadium Redox Flow Battery (VRFB) is a promising candidate for large scale energy storage. These systems are expected to operate for long cycle life ~ 10 years of lifetime (~ 500 - 2000 charge – discharge cycles).1 The VRFB’s system includes an posolyte (VO2
+/VO2+) and negolyte (V2+/V3+) compartments with carbon electrodes, and uses acidic electrolytes (usually 3M H2SO4). The carbon electrodes in VRFB need to perform in a harsh and corrosive environment associated with the charge/discharge cycling. In this study, we used polyacrylonitrile (PAN) based carbon papers as model carbon electrodes to study changes in the electrodes during cycling operation. The carbon papers were pre-treated according to the conventional approach by heating them in air at 500 ⁰C to incorporate oxygen functional groups on their surfaces.2,3 These pre-treated electrodes were then used in flow battery for 100-cycles at a current density of 80 mA/cm2. At the single cell level, the performance of these electrodes following the operation indicated a slight decrease in voltage efficiency (from 60 % to 52 %). This decrease in performance may be attributed to the electrode degradation during operation. Characterization of the electrode prior and following 100-cycles was performed using Raman spectroscopy, XPS analysis as well as electrochemical studies. Raman analysis showed differences between the fresh and the degraded carbon electrodes, including increasing defect and electronic density distribution. XPS analysis of the degraded electrodes suggest an alteration in the amount of oxygen functional groups. Electrochemical studies showed an decrease in the electron transfer kinetics after degradation, coupled with noticeable difference between the electrodes exposed to the posolyte (VO2
+/VO2+) and negolyte (V2+/V3+). The results provide insight into the stability of the oxygen functional groups during cycling operation which could assist in developing pre-treatment methods to functionalize the VRFB’s electrodes and for other similar electrochemical systems.

References:

(1) Soloveichik, G. L. Flow Batteries: Current Status and Trends. Chem. Rev.
2015, 115, 11533–11558.

(2) Singh, A.; Yasri, N.; Karan, K.; Roberts, E. P. L. Electrocatalytic Activity of Functionalized Carbon Paper Electrodes and Their Correlation to the Fermi Level Derived from Raman Spectra. ACS Appl. Energy Mater.
2019, acsaem.9b00180.

(3) Singh, A. K.; Yasri, N.; Karan, K.; Roberts, E. P. L. Effect of Pretreatment on Carbon Materials. Meeting. Abstract.
2018, MA2018-01, 2391.
(A04 Best Poster Award Winner) Magnetic Resonance Imaging of Sodium-Ion Batteries - The Quest for Quasimetallic Nanoparticles
Authors: Doswell Claire , Bray Joshua M , Pavlovskaya Galina E , Chen Lin , Kishore Brij , Kendrick Emma , Titirici Magda , Britton Melanie
Published: December 2020

An increase in the demand for clean energy generation has brought about a need for improved energy storage devices to distribute the power generated by renewable sources. Sodium-ion batteries have been proposed as a lower cost and more sustainable solution. In order to commercialise this emerging technology, new materials and characterisation techniques are required. Magnetic resonance imaging (MRI) is able to characterise both the electrode and electrolyte materials non-invasively, providing a more holistic view of battery chemistry. Furthermore, MRI can spatially resolve electrochemical processes, in real-time, within cells.(1-4) In this study, 23Na and 1H nuclear magnetic resonance (NMR) spectroscopy and MRI experiments have been performed, in operando, on sodium metal cells. At high cycle rates, the growth of dendrites is observed during galvanostatic plating. Operando
23Na NMR experiments on sodium full cells have also been performed, which provide unprecedented insight into the sodiation mechanisms within a hard carbon anode. The formation of metallic and quasimetallic sodium species are observed during the first charge cycle.(5)

M. M. Britton, Prog. Nucl. Magn. Reson. Spectrosc., 101, 51 (2017).

M. M. Britton, ChemPhysChem, 15, 1731 (2014).

A. J. Davenport, M. Forsyth and M. M. Britton, Electrochem. Commun., 12, 44 (2010).

J. M. Stratford, P. K. Allan, O. Pecher, P. A. Chater and C. P. Grey, Chem. Commun. (Cambridge, U.K.), 52, 12430 (2016).

J. M. Bray, C. L. Doswell, G. E. Pavlovskaya, L. Chen, B. Kishore, H. Au, H. Alptekin, E. Kendrick, M. M. Titirici, T. Meersmann and M. M. Britton, Nat. Commun., 11, 2083 (2020).

Figure 1
Using Flow to Control Lithium-Ion Battery Crosstalk for Better Lifetime Predictions
Authors: Siboonruang Tana , Tang Maureen
Published: December 2020

High-voltage lithium-ion batteries suffer from accelerated capacity fade due to crosstalk reactions between their electrodes. For example, while the battery is operating at a high voltage, transition metals from cathode active material dissolve into the electrolyte and diffuse to the anode. These metals disrupt the formation, growth, and performance of the solid-electrolyte interface (SEI), causing accelerated capacity fade. Although the effects of crosstalk reactions on battery lifetime and coulombic efficiency are well documented in full-cell studies, the mechanism by which accelerated capacity fade occurs is currently poorly understood.

In this study, we show that a combination of collector-generator experiments and single particle battery modeling can be used to better understand the effects and mechanisms of crosstalk reactions on capacity fade. Using a microfluidic flow cell, lined with commercial high-voltage lithium-ion battery electrodes and filled with commercial lithium-ion battery electrolyte, we are able to replicate commercial battery conditions while studying crosstalk reaction fundamentals. Because of forced convection in the cell, crosstalk species generated at the upstream electrode react at the downstream electrode and do not diffuse back to the upstream electrode. This allows us to isolate effects of crosstalk reactions on the downstream electrode and more clearly determine their role in capacity fade.

From this study, we present a series of proof-of-concept experiments, in which we show that the charge/discharge behavior of each electrode will clearly depend on flow rate and direction. In addition, we also demonstrate that, using electroanalytical techniques, crosstalk reaction thermodynamic and kinetic parameters can be determined. These parameters are then implemented into a single particle model to elucidate the effects of crosstalk on battery lifetime. This application highlights the novelty of the microfluidic flow cell in deconvoluting crosstalk reactions for generating meaningful inputs in physics-based battery lifetime models.
Scaling While Shorting: Lessons Learned When Non-Unity Coulombic Efficiency Is Independent of Cycle Life
Authors: Steingart Daniel A. , La O' Gj , Mohr Robert
Published: December 2020

The modern lithium ion battery has been engineered to impressive standards, with coulomibic efficiency approaching 99.999% and a safety record for well manufactured cells of less that on incident in 10,000,000 cell given the correct environmental and cycling standards. But the ion-shuttle mechanism within the the battery sets up the relationship

Cremaining
= Cinitial ηc
cycles

Over the past few years we have redesigned a zinc bromine battery that decouples this relationship almost completely, with the goal of

Cremaining
≠ Cinitial ηc
cycles

In this approach we purposefully trade entropy management for cycle life, but it is not without its cost and challenges. In this presentation I will review the progress and challenges of a battery that does not fail critically under internal short circuit conditions, and discuss pathways and pitfalls we have discovered along the way.

We will discuss:

The extent to which side reactions can be "self-cancelling"

The associated impact of heat generated by "guided" side reaction

The scaling behavior and functional and spatial heterogeneity encountered when one allows significant latitude in the reaction space within a cell.
(Invited) Zombie Lithium: Consequences of Remainder Lithium Metal in Lithium Ion Batteries
Authors: Steingart Daniel A. , Chang Wesley
Published: December 2020

It is well understood that lithium metal should not exist in lithium ion batteries, but high energy/high rate lithium ion cells did not seem to have gotten this memorandum. Dissection of commercial cells often indicates direct and indirect evidence of metallic lithium present in the battery. This lithium is often called "dead" lithium as it is considered no longer active. In this presentation we motivate the nomenclature zombie lithium because it is, in this construction, truly undead. Lithium metal that is present in lithium ion batteries is never completely isolated from the other activities of the cell, and as the cell ages, without proper understanding, the "dead" lithium can suddenly arise and impact the cell is decidedly negative ways.

In this presentation we will review and (try to) understand behavior of zombie lithium generated during the operation of a lithium ion battery and time scale and length scales of its impact across the cell and the system.
Gelation of Cathode Electrolytes for Improved Structural Integrity and Enhanced Electrochemical Performance of Li-O2 Batteries
Authors: Tamate Ryota , Matsuda Shoichi
Published: December 2020

Due to the significantly high theoretical energy density, lithium-oxygen (Li-O2) batteries have been attracting much attention as next generation lithium secondary batteries. Nevertheless, there remain a lot of fundamental challenges to be solved for commercialization of Li-O2 batteries, and the cycling performance of currently reported state-of-the-art Li-O2 batteries is still very poor compared to commercially available Li-ion batteries.[1,2] One of the critical problems for the Li-O2 batteries is the leakage of excess liquid electrolytes from the cathode.[3] During the cell operation, Li2O2 is deposited onto the surface of carbon electrodes, which forces the liquid electrolyte out of the cathode. As a result, the deficiency of liquid electrolytes induces deterioration of the cycling performance. Moreover, the formation of Li2O2 causes serious volume expansion of the carbon cathode, which leads to the structural disintegration of electrodes.[4]

To suppress the leakage of electrolytes and disintegration of cathode structures, we are aiming to gelate electrolytes inside the carbon nanotube (CNT) cathodes. Although some gel polymer electrolytes have been reported for Li-O2 batteries so far,[5] gelation of electrolytes inside the cathode has been little investigated. In this study, several types of multi-functional cross-linkers are evaluated to gelate the cathode electrolytes via thermally or UV light-initiated in situ polymerization. By tuning the chemical structure and composition of gelling agents, viscoelastic properties of gels can be broadly controlled. We investigate the effect of gel viscoelasticity and cell restraint pressure on the leakage of electrolyte and mechanical integrity of the CNT cathode, as well as battery performance of the Li-O2 cells. In addition, as another strategy to fabricate CNT-based gel cathodes, solvent-mediated technique is exploited: CNTs, electrolytes, gelling polymers, and volatile solvents are kneaded to form paste films. After evaporation of the solvent, CNT-based gel cathodes were obtained. The relationship between composition and preparation process of the gel cathode and resultant electrochemical performance of Li-O2 cells are studied in detail. We also explore the possibility to reduce the electrolyte amount inside cathodes by gelation toward practically high energy density Li-O2 batteries.

References

[1] N. Imanishi, O. Yamamoto, Mater. Today
2014, 17, 24.

[2] L. Grande, E. Paillard, J. Hassoun, J.-B. Park, Y.-J. Lee, Y.-K. Sun, S. Passerini, B. Scrosati, Adv. Mater.
2015, 27, 784.

[3] H. Lee, D. J. Lee, M. Kim, H. Kim, Y. S. Cho, H. J. Kwon, H. C. Lee, C. R. Park, D. Im, ACS Appl. Mater. Interfaces
2020, 12, 17385.

[4] F. Li, J. Chen, Adv. Energy Mater.
2017, 7, 1602934.

[5] T. Liu, Z. Chang, Y. Yin, K. Chen, Y. Zhang, X. Zhang, Solid State Ionics
2018, 318, 88.
Investigating the Chemical SEI of New and Aged Commercial Li Primary Batteries
Authors: Deichmann Eric J. , Cammack Claudina X. , Merrill Laura C. , Harrison Katharine , Rosenberg Samantha G. , Jungjohann Katherine L , Anderson Travis M.
Published: December 2020

Li primary batteries have been used in commercial and military applications for decades due to their unrivaled energy density and long shelf-life. For years, the impressive shelf-life of these batteries has been primarily attributed to a stable solid electrolyte interphase (SEI), which hinders parasitic reactions at the anode/electrolyte interface. However, few published studies have probed electrode/electrolyte composition in commercial cells, and no previous studies have isolated contributions of the cathode and the electrolyte to SEI stability. To fill this knowledge gap, the present study attempts to de-convolute contributions from each entity by determining component compositions and unveiling the effect each constituent has on SEI stability. In this study, we investigate SEI compositions of three common Li primary chemistries - Li/MnO2, Li/FeS2 and Li/CFx, all of which display exceptional shelf-life. Additionally, due to the dynamic nature of the SEI, cells exposed to varying extents of ageing have been investigated to understand how the SEIs physical and chemical characteristics vary with time. Techniques such as X-ray Photoelectron Spectroscopy (XPS) and Energy-Dispersive Spectroscopy (EDS) are used to conduct chemical analysis of the SEI, while Scanning Electron Microscopy (SEM) is used to elucidate morphological changes in anode and SEI behavior as a function of extent of ageing and cathode/electrolyte chemistry.

This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-program laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA-0003525.
Fabrication and Characterization of Electrospun Pvam/TEOS Based Gel Polymer Electrolyte
Authors: Mentbayeva Almagul , Kassenova Nazym , Kalybekkyzy Sandugash , Bakenov Zhumabay , Kahraman Vezir
Published: December 2020

Gel polymer electrolyte (GPE) is a promising alternative for the toxic and flammable liquid electrolyte in lithium ion batteries because of leak proof, longer shelf life and safety concerns. GPE consists of a porous polymer host and liquid electrolyte saturated within and combines the advantages of both the liquid and solid components [1].

In this study, a novel three-dimensional network GPE based on poly(vinyl alcohol)/maleic anhydride/tetraethyl orthosilicate (PVA/MA/TEOS) with polymer fibers were developed. Crosslinked nanofibrous polymer membranes for GPE of various composition were fabricated by UV-electrospinning method. The dual crosslink polymer membranes were obtained after heat treatment of as-prepared polymer nanofibers, due to the condensation of hydrolyzed TEOS. The morphology of the electrospun membranes was studied using scanning electron microscopy as shown in Figure 1. The uniform and well cross-linked nanofibers were formed with addition of 5 and 10% of TEOS.

The excellent thermal properties of the membranes were proven using thermal gravimetric analysis. The membranes have an improved porosity and exhibit high uptake when activated with the liquid electrolyte of lithium salt in a mixture of organic solvents, and also show high liquid retention properties. Electrochemical impedance spectroscopy and linear sweep voltammetry testes showed a high conductivity and vide range (up to 5.5 V) electrochemical stability of prepared GPE. Electrochemical performance of the polymer gel electrolyte is evaluated in Li/polymer electrolyte/LiFePO4coin cell with various current density and showed promising results.

Figure 1. SEM image of PVA/MA/TEOS fibers with (a) 5% and (b) 10% TEOS

Acknowledgements

This research was supported by Faculty-development competitive research grant “Development of composite anion exchange membranes with improved chemical and mechanical stability” from Nazarbayev University.

Reference
s:

[1] M. Zhu, J. Wu, Y. Wang, M. Song, L. Long, S.H. Siyal, X. Yang, G. Sui, Journal of Energy Chemistry 37 (2019) 126-142.

Figure 1
(Invited) Visualizing Live-Formation of Interphase at Atomic Scale
Authors: Lu Jun
Published: December 2020

The solid-electrolyte-interphase (SEI) in Li-ion battery has been considered one of the most important but least understood and elusive component. In this work, its live-formation was visualized quantitatively at atomistic level with unique combination of in-situ/operando techniques. For the first time, the precise weighing of graphitic anode during its initial lithiation process was realized with electrochemical quartz crystal microbalance, which unequivocally identifies lithium fluoride (LiF) and lithium alkylcarbonates as the main chemical components of the interphase at different potentials. In-situ gas analysis confirmed the preferential reduction of cyclic over acyclic carbonate molecules, making lithium ethylene dicarbonate (LEDC) the major product contributed from solvent. This lithium alkylcarbonate, at least in its nascent form, was revealed to be re-oxidizable, despite general belief that interphase is electrochemically inert and its formation irreversible. Meanwhile, atomic force microscope found that the presence of LEDC on graphitic surface started at edge sites, which does not seem to occur in an obvious staging manner as the intercalation of Li+ does. These atomistic and quantitative observations shed new light on the formation chemistry, mechanism and properties of SEI. Such in-depth understanding will serve as guiding principles for the tailor-design of ideal interphases in future battery chemistries.
Nucleation, Growth, and Properties of the Solid Electrolyte Interphase – a Multimodal Approach Using a Model System
Authors: Cao Chuntian , Steinrück Hans-Georg , Borodin Oleg , Mars Julian Emanuel , Takacs Christopher J , Tsao Yuchi , Lukatskaya Maria R. , Schroeder Marshall , Xu Kang , Toney Michael F
Published: December 2020

Due to the low potentials on anode materials in lithium-ion batteries, the electrolyte decomposes on the anode forming a passivation layer, termed solid electrolyte interphase (SEI). The SEI plays an essential role in battery performance since it is a major source of capacity loss and dictates cell kinetics. Nevertheless, the properties of the SEI are not yet well-understood.

Here, we present the utilization of a simple and well-defined model system to understand the atomic level SEI nucleation and growth, as well as structural and chemical properties. Experiments were performed in a half-cell configuration with N-doped silicon carbide (N-SiC) wafer working electrode, Li metal counter/reference electrode, and LP30 electrolyte (1M LiPF6 in 1:1 wt% ethylene carbonate:dimethyl carbonate). N-SiC has the advantage of being electrically conductive but electrochemically inactive, allowing for a straightforward interpretation of electrochemical and structural measurements, and provides information on the intrinsic electrolyte reactivity.

We used a multimodal approach combining in-situ X-ray reflectivity (XRR), precision electrochemistry at slow rates (e.g. 0.16 mV/s cyclic voltammetry), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). We obtained the evolution of the SEI’s thickness, electron density, and roughness through quantitative operando XRR measurements during the first two cyclic voltammetry (CV) cycles. Further, we found via complementary XPS experiment that the SEI was mainly composed of LiF, and we tracked the crystalline LiF growth with in-situ XRD. LiF can be formed via two reaction pathways. One is the direct reduction of PF6
-, the other is the electrocatalytic hydrogen evolution reaction of the trace amount of HF in the electrolyte, forming LiF and H2. In order to elucidate the formation mechanism of LiF, we combined the electrochemical and structural/chemical results for LP30 with precise electrochemistry using several baseline LiPF6 and/or HF containing electrolytes. The results indicate that the direct reduction of PF6
- contributes to LiF formed at ~ 1.5 V versus Li/Li+, consistent with our quantum chemistry calculations. Finally, we revealed that the ratio between organic and inorganic compounds in SEI could be tuned by changing the cycling rate.

We envision that this methodology and the use of well-defined model systems can be applied to other electrolyte-electrode systems. Our results are essential in understanding the formation mechanism and properties of SEI and can aid future experimental and computational works.
Quantifying Immobile Lithium at the Graphite Anode Surface from Formation to Fast Charging
Authors: Chebuske Matthew , Higashiya Seiichiro , Flottman Spencer , Bakhru Hassaram , Antonopoulos Konstantinos Byron , Paschos Odysseas , Gittleson Forrest S , Efstathiadis Harry
Published: December 2020

Engineering the solid electrolyte interphase (SEI) at the surface of graphite anodes in Li-ion batteries is crucial to optimizing the rate capability, cycle life, and calendar life of commercial cells. It has been reported that fast-forming SEIs on composite graphite electrodes in a high-potential region (~0.24 V vs. Li/Li+) has a positive influence on rate capability in half cell formats [1]. Potentiostatic EIS modulation applied during formation has shown similar results to the fast formation method. In this work, we evaluated the efficacy of various SEI formation methods on the rate and cycle life of full cell Li-ion batteries, and then analyzed electrode surfaces ex situ to locate and quantify immobile lithium. Lithium nuclear reaction analysis (Li-NRA) provided an effective non-destructive method to correlate irreversible electrochemistry with physical surface phenomena [2].

It is well established that high current charging can induce Li plating on the graphite anode, leading to accelerated capacity fade. Several methods have been used to quantify this phenomena including titration and secondary ion mass spectroscopy (SIMS). Here, we employ Li-NRA and a suite of complementary techniques (i.e. XPS and SIMS) to show how the amount of immobile Li and its depth profile varies with charge rate (up to 5C) and cycle number.

[1] B. K. Antonopoulos, C. Stock, F. Maglia, H. E. Hoster, Electrochim. Acta, 269 (2018), 331-339.

[2] A. Schulz, D. DeRosa, S. Higashiya, M. Rane-Fondacaro, H. Bakhru, P. Haldar, J. Energy Storage 14 (2017), 106-111. A. Schulz, D. DeRosa, S. Higashiya, M. Rane-Fondacaro, H. Bakhru, P. Haldar, J. Power Sources 360 (2017), 129-135.