bluuebunny/crossref_metadata_2025 huggingface dataset:
High Sensitivity Bimetallic Electrode Generation through the Study of Copper Electrocrystallisation on Metallic Substrates (Md/Ms) in Acidic Media
Authors: Abed Sherif , Gibilaro Mathieu , Chamelot Pierre , David Arnaud , Barus Carole , Abed Sherif
Published: July 2022

The electrochemical nucleation of copper on metallic substrates in acidic media was investigated using cyclic voltammetry and chronoamperometry. The purpose is to optimize the operating conditions for preparing a high sensitivity bimetallic electrode. Indeed, optimizing the electrodeposition parameters whereby two different metals are present: deposited metal Md and substrate metal Ms, allows the generation of a large number of microelectrodes, correspondingly, yield the largest active surface, and so, increasing the electrode sensitivity.

The aim of this study is to highlight the positive impact of controlling the electrodeposition process of a metal on a substrate and determining the operation conditions towards the augmentation of the active surface area of an electrode.

This work is focused on studying the first instance of copper nuclei formation on the electrode surface and the growth of these nuclei over time. Factors influencing deposit quality and allow to yield the highest specific surface area were considered, principally the overvoltage and the deposit cutoff charge. The nucleation phenomena and the initial growth of the copper nuclei on three different metallic substrates was studied. The plot of the experimental results were compared to theoretical models for the two possible nucleation modes: instantaneous and progressive. The nucleation phenomena was overseen on cyclic voltammetry recorded and the electrodeposition overvoltage were determined for each couple (Md/Ms). Chronoamperometric measurements evidenced that copper electrodeposition process involves progressive nucleation on the substrates, which was confirmed by scanning electron microscopy (SEM). Afterward, the germination rates were determined.

The optimum theoretical cutoff charges were calculated from chronoamperograms using Faraday’s law and were experimentally verified.

Optimal operating conditions were determined for the preparation of bimetallic electrodes with the largest active surface area. Subsequently, copper deposition runs were carried out on the three electrode substrates. The formed bimetallic electrodes were tested using square wave voltammetry for their ability to detect species requiring high sensitivity identification tools such as nitrates in seawater. In open ocean, the concentration of nitrates can drop from few dozens of micromolars to as littles as few nanomolars.

The copper nuclei fount out to be unstable on the substrate in maritime area due to corrosion and attack by dissolved oxygen. A cathodic polarization by applying a direct current was applied to protect the deposited copper.
Streamlined Derivations and Explanations of the Scharifker-Hills Model
Authors: Sun Yunkai , Zangari Giovanni
Published: July 2022

Despite being very popular in the analysis of experimentally measured potentiostatic transients during the initial stage of electrodeposition of metallic single-element coatings, the derivations and the assumptions of the Scharifker-Hills (S-H) model are not well understood. Important details and assumptions are scattered in different original papers. Meanwhile, some of the simplifications in derivations are somewhat intuitive, rather than being rigorously derived from a set of governing equations.

It is important to understand the derivations, the assumptions, and the successfulness of the S-H model first before moving forward to an advanced model for the potentiostatic transient at the initial stage of metal or alloy electrodeposition. In this presentation, we will provide rigorous derivation for each step and each assumption, thus achieving a complete demonstration of the physics of the S-H model.

References:

[1] G.J. Hills, D.J. Schiffrin, J. Thompson, Electrochemical nucleation from molten salts—I. Diffusion controlled electrodeposition of silver from alkali molten nitrates, Electrochim. Acta, 19 (1974) 657-670.

[2] B. Scharifker, G. Hills, Theoretical and experimental studies of multiple nucleation, Electrochim. Acta, 28 (1983) 879-889.

[3] G. Gunawardena, G. Hills, I. Montenegro, B. Scharifker, Electrochemical nucleation: Part I. General considerations, J. Electroanal. Chem., 138 (1982) 225-239.

[4] B.R. Scharifker, J. Mostany, Three-dimensional nucleation with diffusion controlled growth: Part I. Number density of active sites and nucleation rates per site, J. Electroanal. Chem., 177 (1984) 13-23.

[5] B.R. Scharifker, J. Mostany, Electrochemical Nucleation and Growth, in: A.J. Bard (Ed.) Encyclopedia of Electrochemistry2007, pp. 512-539.

[6] M. Sluyters-Rehbach, J.H.O.J. Wijenberg, E. Bosco, J.H. Sluyters, The theory of chronoamperometry for the investigation of electrocrystallization: Mathematical description and analysis in the case of diffusion-controlled growth, J. Electroanal. Chem., 236 (1987) 1-20.
Comparative Studies of Electrochemical Behavior of Silicon Anode Active Materials for High-Energy Lithium-Ion Batteries
Authors: Lim Guntae , Kwak Sehyun , Park Seong Jun , Song Seung-Wan
Published: July 2022

Longer driving range electric vehicles require higher energy lithium-ion battery (LIB) than that of state-of-the-art LIBs. Therefore, the development of high capacity cathode and anode active materials beyond conventional ones is highly encouraged. Silicon (Si) as a high-capacity anode material has been studied for decades. However, still its fraction used in Si-graphite composite anode is limited to a few wt%, due to a large volume change, low electrical conductivity and unstable interface to electrolyte. Ever since the advent of the Si anode, numerous challenges such as size control, surface coating, active/inactive alloy, void space engineering, and composites have been conducted. In this presentation, we report comparative studies of electrochemical cycle behavior along with interfacial resistance changes of various silicon anode active materials and interfacial reaction behavior with electrolyte components.

Acknowledgements

This research was supported by the National Research Foundation grant funded by the Ministry of Science and ICT (No. 2021M3H4A3A02086211).
State-of-Charge Dependent Change of the Young’s Modulus in Lithium-Ion Batteries
Authors: Daubinger Philip , Feiler Simon , Gold Lukas , Hartmann Sarah , Giffin Guinevere A.
Published: July 2022

One way to increase the sustainability of lithium-ion batteries (LIB) is to extend the cycle life, e.g., in electric vehicles. To do this, the effects within a LIB must be understood and tracked over its lifetime. In addition to electrical (e.g. IR-drop) and thermal measurements (e.g. temperature inhomogeneities), a new approach for such studies is the use of ultrasound to investigate the mechanical changes inside a LIB [1]. With this low-cost technology, it is possible to detect mechanical degradation (e.g. local thickness change due to lithium plating) or Young’s moduli changes over lifetime and possibly counteract them by the battery management system.

In this work a self-built device containing a LIB between two opposing transducers is used to study the impact of state-of-charge (SOC), current rate and frequency on the ultrasound signal inside the LIB. Based on the time the ultrasound signal takes to pass through the LIB (time-of-flight (TOF)), the speed of sound and the Young’s moduli can be determined. The influence of the applied current rate and the frequency of the transducer to the TOF/ speed of sound in the LIB is relatively small. However, the SOC has an impact on the TOF/ speed of sound, where the speed of sound is around 4.5% higher in the fully charged state with ~1740 m s-1 compared to the discharged state with ~1660 m s-1 (see Figure 1 (a)). One explanation for this phenomenon is the change in the lithium staging within the graphite anode. In a charged battery, the graphite anode is filled with lithium ions, which enhances the transmission properties of ultrasound. By knowing speed of sound, the Young’s modulus of the whole battery can be estimated as ~4.2 GPa in discharged state and ~5.6 GPa in the charged state (Figure 1 (b)). This significant increase can also be explained with the lithiation stages of the graphite anode, as the graphite particles themselves exhibit a threefold increase of the Young’s modulus during lithiation [2]. Additionally, the evolution of the speed of sound and Young’s moduli is studied during aging of the LIB.

References:

[1] Gold, L., Bach, T., Virsik, W., Schmitt, A., Müller, J., Staab, T. E., & Sextl, G. (2017). Probing lithium-ion batteries' state-of-charge using ultrasonic transmission–Concept and laboratory testing. Journal of Power Sources, 343, 536-544.

[2] Qi, Y., Guo, H., Hector Jr, L. G., & Timmons, A. (2010). Threefold increase in the Young’s modulus of graphite negative electrode during lithium intercalation. Journal of The Electrochemical Society, 157(5), A558.

Figure 1
Chemical and Morphological Changes of Graphite Electrodes at Low Cathodic Potentials and Its Relevance to Li-Ion Batteries
Authors: Wong Raymond , Yokota Yasuyuki , Kazuma Emiko , Oniki Motoyuki , Kim Yousoo
Published: July 2022

Lithium-ion (Li-ion) batteries have become ubiquitous to modern-day electronics and electric vehicles. A detailed understanding regarding the reversible and irreversible nature of Li-ion electrode processes is a prerequisite to rationally delineate the factors affecting device performance and clarify degradation mechanisms. This includes, for instance, the role of electrode cracking and solid solid-electrolyte-interphase (SEI) formation which can contribute toward irreversible capacity loss. In terms of experimental approaches, aside from the high surface area electrodes used in practical systems, one powerful approach is to incorporate the study of well-defined electrodes and surface science techniques.1

Herein, we employ highly oriented pyrolytic graphite (HOPG) as a well-defined model anode in Li-ion batteries and reveal the chemical and morphological changes at low cathodic potentials prior to the potentials of bulk SEI formation.2 To achieve this, we employ the use of X-ray photoelectron spectroscopy (XPS) and ultrahigh vacuum scanning tunneling microscopy (UHV-STM). We utilize a so-called UHV-EC setup to provide a snapshot-like analysis of the electrode surface without the involvement of electrode washing or exposure to air.

Upon cathodic polarization at ca. 1.75V (Figure 1), STM imaging shows the onset and occurrence of graphite exfoliation which can originate from the intercalation of solvated Li+ ions. Meanwhile, XPS shows a minimal amount of residual electrolyte along with the observation of LiF indicating the decomposition of the Li salt (LiPF6). The future extensions of our methodology and additional details will be provided at the presentation.

Figure 1. (a) Cathodic linear sweep voltammogram in 1.1 M LiPF6 EC/DMC. Following polarization at ca. 1.75 V (b) STM imaging, and (c) XPS F 1s and Li 1s spectra.

References

[1] T. Minato, T. Abe, Prog. Surf. Sci.
92, 240-280 (2017).

[2] R. A. Wong, Y. Yokota, E. Kazuma, M. Oniki, Y. Kim, J. Phys. Chem. C
125, 21093-21100 (2021).

Figure 1
Ultra-Fast Synthesis of Single Atoms for All-Solid-State Lithium-Sulfur Batteries
Authors: Zheng Xueli
Published: July 2022

All-solid-state lithium-sulfur (Li-S) battery has attracted the most attention in the past decades due to its high theoretical energy density (2600 Wh kg-1), high safety, low cost, and environmentally friendly feature. However, several issues need to be addressed before commercializing all-solid-state Li-S battery. The insulating nature of charged product sulfur and discharged product lithium sulfide results in low active material utilization. The dissolution of polysulfides intermediate and shuttling effect leads to fast capacity decay. Incorporating catalysts into the cathode or separator has proven to be very effective for promoting the sluggish Li-S reaction kinetics, suppress the shuttling effect of polysulfides, thus achieving superior cycling performance of Li-S battery using the liquid electrolyte. Single atom catalyst with the maximum atom utilization, unique coordination environment attracted particular attention. Whether single atom sites are feasible in the solid-state electrolyte is still unexplored. Herein, we synthesized single atom catalysts using ultra-fast approach. High-angle annular dark-field aberration corrected scanning transmission electron microscopy image and extended X-ray absorption fine spectroscopy verified the presence of single atoms on the support. The optimized absorption sites of single atoms were further studied with density functional theories. Using polyethylene oxide and lithium bis(trifluoromethanesulfonyl)imide infiltrated polyimide as the solid polymer electrolyte, we evaluated the cycling performance of all-solid-state Li-S battery. Single atoms incorporated sulfur cathodes exhibits higher cycling performance than the bare sulfur cathodes due to the significantly enhance lithium-sulfur redox reaction kinetics. The fast Li-S redox reaction kinetics were also revealed by calculating the energy barrier from sulfur to lithium sulfide using density functional theories. The formation of lithium sulfide from lithium disulfide was found to be the rate-limiting step for discharging sulfur. With the help of single atoms, the energy barrier of the rate-limiting step is significantly reduced. Our work provides new insights to improve the capacity and cycling life of all-solid-state Li-S batteries for commercializing Li-S technology.
Understanding of Structural, Dynamic and Ionic Diffusion Characteristics of Li6(PS4)SCl Superionic Conductor from Classical Molecular Dynamics
Authors: Das Tridip , Merinov Boris V , Yang MoonYoung , Goddard William
Published: July 2022

Solid-state batteries are preferred over commercial Li-ion batteries, due to their higher thermochemical stability, higher safety, and longer cycle life. Successful applications of solid-state batteries largely depends on electrode-electrolyte interfacial stability and fast Li-ion transport in the electrolyte.1 Among different electrolyte candidates from polysulfide, oxide, argyrodite, perovskite families - Li6(PS4)SCl looks very promising due to its lithium superionic conductivity at room temperature and very wide electrochemical stability window (0−7 V versus Li/Li+).2

We report here our results on molecular dynamics simulations with applied electric fields (LAMMPS+UFF)8 to explain both cationic and anionic diffusion mechanisms leading to the Li-superionic conductivity of a Li6(PS4)SCl single crystal. Charges on ionic species were scaled from DDEC6 calculated charges and the Li-ion charge is comparable to that calculated for Li-ions in Li-P-S systems using ReaxFF. We find that Li migration occurs via conjugated substitutional type diffusion involving rearrangements of three or more Li-ions in a 3D matrix of anions that are essentially stationary around room temperature. Figure 1 shows mean-square displacements (MSDs) of the ions in Li6(PS4)SCl in our 20 ns MD simulation. The MSD of the Li-ions reaches the Fickian regime for Li-diffusion after 1 ns of the simulation.

The predicted Li-ion diffusivity (4x10-12 m2/s) and conductivity for single phase Li6(PS4)SCl is 6.7 mS/cm is in good agreement with solid state NMR measurements of 5.7 mS/cm.4 Our calculated activation energy of 0.26 eV is within experimentally reported range. 0.27 – 0.29 eV, from NMR measurements (Figure 2).3–6 We further used the two phase thermodynamic (2PT) method7 to predict the melting point. Also, a detailed study was performed to examine the directional electric field effect of different field strengths on the Li-ion diffusion in Li6(PS4)SCl.

Financial support of this research from the Centre of Hong Kong Quantum AI Lab Ltd established by the University of Hong Kong (the InnoHK initiative) is gratefully acknowledged.

References:

L. Ye and X. Li, Nature, 593, 218–222 (2021).

J. C. Bachman et al., Chem. Rev., 116, 140–162 (2016).

C. Yu, L. van Eijck, S. Ganapathy, and M. Wagemaker, Electrochimica Acta, 215, 93–99 (2016).

R. Schlenker et al., Chem. Mater., 32, 8420–8430 (2020).

S. Ganapathy, C. Yu, E. R. H. van Eck, and M. Wagemaker, ACS Energy Lett., 4, 1092–1097 (2019).

I. Hanghofer, B. Gadermaier, and H. M. R. Wilkening, Chem. Mater., 31, 4591–4597 (2019).

S.-T. Lin, M. Blanco, and W. A. Goddard, J. Chem. Phys., 119, 11792–11805 (2003)

A. K. Rappe et al., J. Am. Chem. Soc.
114, 10024–10035 (1992)

Figure 1
The Correlation between Structure, Surface, and Performance in Fe- and Mg-Substituted LiNi0.5Mn1.5O4 Cathodes
Authors: Murdock Beth , Zhang Li , Pérez Gabriel , Tapia Ruiz Nuria
Published: July 2022

A need for lithium-ion cathodes that have a reduced dependence on scarce elements, such as cobalt, has been prompted by surge in eco-consciousness over the past decade. The spinel-type LiNi0.5Mn1.5O4 (LNMO) cathodes, with high operating voltages (ca. 4.7V vs Li+/Li) and energy densities (ca. 650 Wh kg-1), have received particular attention for this reason.1 Poor cycling stability, however, which arises from structural instabilities, electrolyte degradation, surface densification and loss of active material through transition metal dissolution, limits their widespread adoption.2 Elemental substitution has been employed to overcome such limitations, in which improved cycling stability has been observed. In such samples, the segregation of substituents to the cathode surface has been reported, yet the effect of surface segregation on the local atomic structure and surficial reactivity of the cathodes is under-researched.3

To further explore these areas, Fe- and Mg-substituted LNMO samples have been synthesised. Despite lower initial capacity, Mg-substituted LNMO exhibits significantly improved cycling stability over 300 cycles at 50°C. A combination of x-ray and neutron diffraction, neutron pair distribution function analysis, and x-ray absorption and photoelectron spectroscopy are used to explore the complex relationships between bulk structure, local structure, surface reactivity and performance in Fe- and Mg-substituted LNMO cathodes.

References

Liang, G., Peterson, V.K., See, K.W., Guo, Z., and Pang, W.K. (2020). Developing high-voltage spinel LiNi 0.5 Mn 1.5 O 4 cathodes for high-energy-density lithium-ion batteries: current achievements and future prospects . J. Mater. Chem. A.

Ma, J., Hu, P., Cui, G., and Chen, L. (2016). Surface and Interface Issues in Spinel LiNi0.5Mn1.5O4: Insights into a Potential Cathode Material for High Energy Density Lithium Ion Batteries. Chem. Mater. 28, 3578–3606.

Shin, D.W., Bridges, C.A., Huq, A., Paranthaman, M.P., and Manthiram, A. (2012). Role of Cation Ordering and Surface Segregation in High-Voltage Spinel LiMn LiMn 1.5Ni 0.5-xM xO 4(M = Cr, Fe, and Ga) Cathodes for Lithium-Ion Batteries. Chem. Mater. 24, 3720–3731.

Figure 1
Two Electrolyte Decomposition Pathways at NMC Electrodes in Lithium-Ion Batteries
Authors: Rinkel Bernardine L. D. , Vivek J. Padmanabhan , Garcia-Araez Nuria , Grey Clare P.
Published: July 2022

Preventing the decomposition reactions of electrolyte solutions is essential for extending the lifetime of lithium-ion batteries. However, the exact mechanism(s) for electrolyte decomposition at the positive electrode, and particularly the soluble decomposition products that form and initiate further reactions at the negative electrode, are still unknown. In this work, a combination of operando gas measurements and solution NMR was used to study decomposition reactions of the electrolyte solution at NMC (LiNixMnyCo1-x-yO2) and LCO (LiCoO2) electrodes. A partially delithiated LFP (LixFePO4) counter electrode was used to selectively identify the products formed through processes at the positive electrode. Based on the detected soluble and gaseous products, two distinct routes with different onset potentials are proposed for the decomposition of the electrolyte solution at NMC electrodes. At low potentials (<80% state-of-charge, SOC), ethylene carbonate (EC) is dehydrogenated to form vinylene carbonate (VC) at the NMC surface, whereas at high potentials (>80% SOC), 1O2 released from the transition metal oxide chemically oxidises the electrolyte solvent (EC) to CO2, CO and H2O. The formation of water via this mechanism was confirmed by reacting 17O-labelled 1O2 with EC and characterising the reaction products via 1H and 17O NMR spectroscopy. The water that is produced initiates secondary reactions, leading to the formation of the various products identified by NMR spectroscopy. Noticeably fewer decomposition products were detected in NMC/graphite cells compared to NMC/LixFePO4 cells, which is ascribed to the consumption of water (from the reaction of 1O2 and EC) at the graphite electrode, preventing secondary decomposition reactions. The insights on electrolyte decomposition mechanisms at the positive electrode, and the consumption of decomposition products at the negative electrode contribute to understanding the origin of capacity loss in NMC/graphite cells, and are hoped to support the development of strategies to mitigate the degradation of NMC-based cells.
Effect of Post-Grinding and Heat Treatment on the Electrochemical Performance of NMC622 Li-Ion Battery Cathode Materials
Authors: Tahmasebi Mohammad Hossein , Obrovac Mark
Published: July 2022

Given the increasing demands for high energy density lithium-ion batteries (LIBs), all cell components, particularly cathode materials, will need significant improvement in the future. Among the possible cathode materials for LIBs, NMC-based materials (LiNixMnyCozO2) have been receiving more attention due to their high energy density and low price. However, NMC-based cathode materials still suffer from degradation and capacity fading due to polarization and structural change over charge-discharge cycling which may be associated with, for example, cation mixing and particle morphology. Among these, the particle size of NMC-base cathodes plays an important role in degradation mechanism during long-term electrochemical cycling [1,2].

The present study comprehensively highlights the effect of post-grinding methods and re-heating on electrochemical performance of Li-NMC622 cathode materials. For this purpose, NMC622 samples were synthesized using commercial precursors and different grinding methods were employed to break up the agglomerated secondary particles into smaller sizes. Accordingly, the microstructural, morphological, and electrochemical evolution of unground and ground samples were studied. Microscopy observations, along with electrochemical data, suggest that marked performance improvements can be achieved by controlling the particle size of NMC622 through post-grinding and heat treatment.

References

B. Huang et al., Solid State Ionics, 345, 115200 (2020).

A. Liu et al., J. Electrochem. Soc., 168, 050506 (2021).
(Digital Presentation) Mapping of Degradation Processes in Ni-Rich Layered Oxide Cathode Materials in State-of-the-Art Commercial Li-Ion Cells Based on Battery Usage Conditions
Authors: Mikheenkova Anastasiia , Roy Chowdhury Niladri , Smith Alexander James , Tesfamhret Yonas , Pay Gómez Cesar , Wreland Lindström Rakel , Thiringer Torbjörn , Berg Erik J. , Lacey Matthew , Hahlin Maria
Published: July 2022

Ni-rich oxide cathode active materials are today key components in Li-ion batteries used for electric vehicles (EV). The high capacity of LiNixCoyMnzO2 and LiNixCoyAlzO2 (NCA) with x≥0.6 has enabled a continued increase in energy density and decrease in cost at the pack level, enabling the rapid growth of the EV market in recent years. Despite a wide use, rather fast material ageing results in the batteries being a source of considerable environmental impact [1]. Various degradation sources are highlighted in the literature, these include transition metal dissolution, surface layer reconstruction, particle cracking, etc [2]. However, when extrapolating the knowledge from a model cell to a commercial battery the relevance and the degree of degradation impact can drastically change [3]. The importance of approaching real conditions is a key to a full understanding of the ageing processes occurring in commercial cells. In the given work, we analyse commercial state-of-art 2170 cylindrical cells. The cells were aged at various temperatures and state of charge windows, targeting divergent usage scenarios. The degradation processes were accessed with a wide range of analytical techniques applied to extracted electrodes (x-ray diffraction, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, cycling voltammetry, incremental capacity analysis, electrochemical impedance spectroscopy and intermittent current interruption). In the current work we show that depending on the operating conditions, influence of ageing sources varies. Additionally, ageing mapping within cell geometry is presented highlighting “hot spots” of the cell [4].

References

[1] W. Liu et al., “Nickel-Rich Layered Lithium Transition-Metal Oxide for High-Energy Lithium-Ion Batteries,” Angew. Chemie Int. Ed., vol. 54, no. 15, pp. 4440–4457, Apr. 2015.

[2] T. Li, X.-Z. Yuan, L. Zhang, D. Song, K. Shi, and C. Bock, Degradation Mechanisms and Mitigation Strategies of Nickel-Rich NMC-Based Lithium-Ion Batteries, vol. 2018, no. January 2017. Springer Singapore, 2019.

[3] M. Lucu et al., “Data-driven nonparametric Li-ion battery ageing model aiming at learning from real operation data – Part A: Storage operation,” J. Energy Storage, vol. 30, p. 101409, Aug. 2020.

[4] Mikheenkova et al., in manuscript.
(Invited) Understanding the Coupled Electrochemical-Mechanical Behavior of Materials for Improving the Performance and Durability of Lithium-Ion Batteries
Authors: Cheng Yang-Tse
Published: July 2022

With an increasing demand for higher energy and power density of lithium-ion batteries (LIBs), the coupled electrochemical-mechanical degradation of electrode materials becomes a more pressing problem. In particular, fracture and delamination of electrodes can occur during repeated charging and discharging of LIBs. An improved understanding of the mechanical behavior of electrode materials, which often evolves with the state-of-charge and cycle number, is therefore necessary for improving the performance and durability of LIBs and other types of batteries. In this presentation, I will provide an overview of our recent work on using four complementary measurement techniques: (1) electrochemical nanoindentation, (2) scanning probe microscopy, (3) peel adhesion and cohesion test, and (4) electrode curvature measurement to help understand several coupled effects between mechanical and electrochemical behavior of materials on the performance and durability of high capacity electrodes. Examples include silicon/polymer porous composite electrodes, polymeric binders, lithium metal electrodes, and ceramic materials for the positive electrode and solid-state electrolyte. These characterization techniques may also be used to investigate the coupled electrochemical-mechanical behavior of a wide range of materials for lithium-ion batteries and beyond.
Impact of Ni Content on the Structure and Electrochemical Performance of the Co-Free, Li/Mn-Rich Layered Cathode Materials
Authors: Qi Gongshin , Hu Jiazhi , Balogh Michael P , Wang Lei , Nageswaran Shubha , Pieczonka Nicholas , Li Wei
Published: July 2022

Since early 1990s lithium-ion batteries (LIBs) have become the most important secondary/rechargeable battery technology for portable electronic devices; and more recently for battery powered vehicles. Extensive research has been conducted on high-capacity electrode materials for LIBs due to the emerging demands for high energy density batteries for electric vehicles. Compared with the conventional cationic redox-based cathode materials, such as NMC, LMO and LFP, Li-excess, Manganese rich layered cathode (LLC) materials containing cationic and anionic redox process, show great potential as the next generation cathode materials because of their higher theoretical specific capacity and lower raw material cost.

Our work has shown that Ni content of the Co-free, LLC materials, Li1.2NixMn0.8-xO2 (x = 0.12, 0.24, 0.30 and 0.36) prepared by a citric acid method, has a significant impact on the material structure, electrochemical performance, and thermal stabilities. Generally, the primary particle size increased as the Ni content increased with a primary particle size distribution in the range of 200–600 nm for the samples investigated. Monoclinic phase (C2/m) and spinel (Fd3m) phase depending on the content of Ni have been identified by XRD. With increasing Ni content, the fraction of the spinel phase decreased and eventually the pure layered structure was obtained on the samples at x = 0.30 and 0.36. Our work demonstrates that the charging and discharging capacities are determined by the Ni or Mn content. The highest charging and discharging capacities were achieved when x = 0.24. As Ni content increased, the first cycle coulombic efficiency decreased, and the thermal stability deteriorated. But, an increase in Ni content results in an increase in average discharge voltage, higher electrochemical stability of the layered structure, fast Li ions diffusivity. Li1.2Ni0.12Mn0.68O2 sample exhibited the best capacity retention and thermal stability among the tested samples. However, its specific energy density was limited due to the lowest average discharge voltage. The Li1.2Ni0.36Mn0.44O2 sample which contained the highest Ni content exhibited the worst thermal stability, but relatively higher specific energy density due to the highest average discharge voltage.
(Invited) Thermal Properties of NMC Cathode Materials
Authors: Doeff Marca M.
Published: July 2022

NMC (LiNixMnyCozO2; x+y+z»1) materials deliver high capacity and excellent performance when used as cathodes in lithium-ion batteries. Increasing demand for higher energy density and concerns about the cost and ethics of using cobalt have prompted battery manufacturers to use Ni-rich formulations such as LiNi0.6Mn0.2Co0.2O2 (NMC622) and LiNi0.8Mn0.1Co0.1O2 (NMC811). The thermal stability of (partially) delithiated NMCs is known to decrease with increasing Ni content, however, so that scenarios of fires and other safety events become more distinct possibilities. To investigate the thermal properties of Ni-rich NMCs, we prepared partially and fully delithiated Ni-rich NMCs corresponding to various states-of-charge by chemical methods. We then studied the bulk and surface properties of these materials as they were heated or after they were heated, using a variety of ex situ and in situ synchrotron methods to understand the chemical changes that occur. Of particular concern are reactions that result in release of oxygen. Heated materials progress through a series of bulk structural changes from layered to spinel to rock salt as temperatures rise. Transition temperatures depend on both lithium and nickel content, with bulk changes evident at temperatures as low as 150°C. Surface-sensitive techniques such as soft X-ray absorption spectroscopy (sXAS) indicate that subtle changes that lead to oxygen release can happen well below these temperatures. The thermal behavior of the Ni-rich materials is very complex, and involves lattice transformation, transition metal migration and valence change and lithium redistribution. Moreover, these changes are dependent upon primary particle size, with smaller particles reacting at lower temperatures than larger ones. These observations suggest that materials can be engineered (through primary particle size manipulation, for example) to improve thermal robustness, and therefore, safety and reliability of lithium-ion batteries.
Binder-Free Cathode Enabling High Capacity Li-Ion Battery
Authors: Brahim Sean , Maat Stefan
Published: July 2022

Li-ion batteries have polymeric binder in their electrodes resulting in high internal resistance and hence long charge times and compromised product lifetime. We have developed Li-ion batteries utilizing binder-free NMC cathodes containing carbon nanotube (CNT). Our proprietary processing of CNT into viscous organic or water-based slurry without surfactant or dispersant reduces or eliminates the need for organic binder and carbon black additives in these cathodes. The benefits of incorporating our processed CNT slurry into NMC cathode electrodes are realized by significant gains in specific energy and power. When the organic binder in the cathode is completely removed, our Li-ion batteries retain superior performance metrics over conventional binder-containing cells, including significantly reduced impedance (-31%) and increased capacity (5%). Li-ion pouch cells containing these binder-free NMC/CNT cathodes show 2.5% higher specific energy. Our cells with binder-free cathode complete 500 cycles with 50% less capacity fade than cells with binder, and display more than 2x improvement in capacity at 10C rate discharge. A processing advantage of eliminating the polymeric binder from the formulation mix was demonstrated by the use of IPA as dispersing solvent in place of the costlier and toxic NMP solvent. Li-ion cells containing binder-free NMC/CNT cathodes from IPA mix preserved their performance advantages over conventional NMP-based binder-containing cells.

Figure 1
(Digital Presentation) Lithiation/De-Lithiation of a Unique C-S Species in Amorphous FeS4/C Cathodes for Li Batteries
Authors: Wygant Bryan R. , Kolesnichenko Igor V. , Schorr Noah B. , Lambert Timothy N.
Published: July 2022

When paired with Li metal anodes, Fe-based conversion cathodes like iron sulfide present a promising material for creating energy dense rechargeable batteries for energy storage. While iron sulfide cathodes (e.g. FeS2) typically suffer from deleterious polysulfide formation, recent work with a class of amorphous iron sulfide-carbon composites (e.g. FeS4/C) has shown minimal evidence of polysulfide formation during lithiation and de-lithiation, and thus it may represent a pathway to stable, polysulfide-free iron sulfide batteries. Prior reports indicate that the active component of the composite is the FeS4 and that the amorphous carbon does not exhibit any electrochemical response. While studying this material, however, we have found evidence to suggest that the cycling of FeS4 alone does not fully explain the electrochemical and chemical behavior observed for the FeS4/C cathode, and that the carbon plays a significant role in the overall electrochemistry of the composite.

In this presentation, we will present a study of this amorphous FeS4/C composite as a cathode for use in Li batteries and provide evidence of the electrochemical lithiation and de-lithiation of a previously unstudied and unreported C-S compound found in the composite material. Our results indicate that this C-S species is amorphous and is (electro)chemically similar to sulfurized poly(acrylonitrile) (SPAN) and carbyne polysulfide (C-PS). By coupling ex situ Raman and X-ray photoelectron spectroscopy (XPS) to galvanostatic battery cycling, we show how chemical changes in the FeS4/C cathode correspond to electrochemical features associated with the lithiation and de-lithiation of both iron sulfide and the C-S species. Our results indicate that the C-S species is electrochemically active at all stages of cycling, while the FeS4 loses activity within approximately 15-20 cycles. This differs significantly from earlier reports and suggests that the lack of polysulfide formation when testing the FeS4/C composite may in fact be due to the cycling of this C-S species rather than iron sulfide. These results serve as an initial foray into the electrochemistry of this new material and should provide a basis for additional study of this new and promising C-S based cathode material for Li batteries.

This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-mission 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. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.
Organofluorophosphates As Electrochemical Aging Products in Lithium Ion Battery Electrolytes
Authors: Kubot Maximilian , Nowak Sascha , Winter Martin
Published: July 2022

The lithium ion battery (LIB) electrolyte is a delicate system susceptible to a manifold of influences both from the outside and inside. Thermal stress and overcharging of the LIB can result in unwanted side reactions such as rapid electrolyte degradation and the so-called thermal runaway, respectively. Here, the degradation of the conducting salt, namely lithium hexafluorophosphate (LiPF6 )poses many risks to the LIB and the environment. Hydrolysis of LiPF6 leads to the formation of hydrofluoric acid (HF) and POF3 which can react with the organic compounds within the electrolyte to form highly toxic organofluorophosphates (OFPs). The formation of OFPs in LIBs due to thermal stress has been covered in literature. In this study the electrochemically induced formation of OFPs is discussed. Electrolytes containing fluoroethylene carbonate (FEC) as a film-forming additive indicated the presence of OFPs forming at operation voltages of 4.8 V in self-assembled LIB coin cells. Cycling of the coin cells with cut-off voltages of 4.8 V gave rise to 15 non-acidic and two acidic OFPs after 10 charge/discharge steps. The quantity of FEC had an impact on the amount of OFPs formed which gives reason to incorporate FEC in the formation pathways proposed in this study. The formation pathway of OFPs through EC-polymerization proposed in literature is evaluated and an alternative mechanism with FEC as the carbonyl-carbon donor is presented. Structure elucidation and separation of the formed OFPs is achieved by utilization of a) hydrophilic interaction liquid chromatography (HILIC) for acidic OFPs and b) reversed-phase (RP) chromatography for non-acidic OFPs hyphenated to a high-resolution ion trap time-of-flight mass spectrometer (IT-TOF-MS). Based on the findings in this study and due to the highly toxic nature of OFPs further investigation of the formation of OFPs in FEC-containing electrolytes is necessary. Further, the impact of the operation voltages needs to be assessed to ensure for safe and efficient LIBs.
Lithium-Ion Battery Degradation: How to Diagnose It
Authors: O'Kane Simon E. J. , Kirkaldy Niall , Offer Gregory James , Marinescu Monica
Published: July 2022

Many different degradation mechanisms occur in lithium-ion batteries, all of which interact with one another [1]. However, there are few fewer observable consequences of degradation than there are mechanisms [2]. It is possible to measure the different degradation modes: loss of lithium inventory (LLI), loss of active material (LAM), impedance change and stoichiometric drift [3].

It is not always possible to link these observable consequences of degradation to any particular mechanism or combination of mechanisms. Many models of degradation exist [4], but these models have many parameters that cannot be measured directly. A recent modelling study [5] found the number of parameters that the model is sensitive to is greater than the number of observable degradation modes.

However, the same model [5], despite including just four degradation mechanisms, found five possible degradation pathways a battery can follow. The model was built so that more mechanisms can easily be added later, so more pathways will be found.

In this work, a new approach to diagnosing battery degradation is proposed, based on these pathways. Experimental data for the degradation modes can be identified as being consistent with a particular pathway. Once the correct pathway is found, the parameters that particular pathway is sensitive to can be fit to the data, feeding back into the model.

[1] Jacqueline Edge et al., Phys. Chem.: Chem. Phys. vol. 23, pp. 8200-8221, 2021.

[2] Christoph Birkl et al., Journal of Power Sources vol. 341, pp. 373-386, 2017.

[3] Matthieu Dubarry et al., J. Electrochem. En. Conv. Stor. vol. 17, pp. 044701, 2020.

[4] Jorn Reniers et al., J. Electrochem. Soc. vol. 166 pp. A3189-A3200, 2019.

[5] Simon O’Kane et al., Phys. Chem.: Chem. Phys., submitted, 2022. https://arxiv.org/abs/2112.02037
(Digital Presentation) Systematic Cycle and Calendar Aging of Commercial 18650 LFP Lithium-Ion Cells
Authors: Wittman Reed M , Fresquez Armando , Chalamala Babu , Preger Yuliya
Published: July 2022

In recent years lithium-ion (Li-ion) batteries with a lithium iron phosphate (LFP) cathode have become popular for grid storage and electric vehicle applications. To address uncertainty in their performance and lifetime, we initiated a multi-year cycle and calendar aging study of commercial LFP cells under systematically varied conditions. Here, we present an update of cycling data from these cells at their current state where most have reached 80% capacity retention. Cells were cycled at different state of charge (SOC) ranges (0-100%, 20-80%, and 40-60%), temperatures (15, 25, and 35 °C) and discharge rates (0.5C, 1C, 2C, and 3C). Additionally, we present data from a concurrent calendar aging study at different temperatures (15, 25, and 35 °C) and SOCs (25, 50, and 90%).

To date, higher ambient temperatures have most significantly reduced the cycle and calendar life of LFP cells. A higher SOC range or single SOC value during cycle and calendar aging, respectively, also increased the capacity fade rate, but to a lesser extent. The rate of discharge during cycling showed a mixed influence on capacity fade, with the highest and lowest rates producing the most rapid fade. This data provides a foundation to identify the distinct contributions of calendar and cycle aging. We will also discuss changes in other metrics that are of interest to system integrators, such as round-trip efficiency, cell skin temperature during cycling and discharge energy throughput. Finally, we will discuss future work that will center around materials cycling of cells disassembled at 80% capacity and cycling the remaining cells down to an end of life of 40% capacity, at which point materials characterization will be conducted again. This will help determine why capacity fade varies in the cells and what is their useful life under these aging conditions.

This work was funded by the DOE Office of Electricity under the direction of Dr. Imre Gyuk.

Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & 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-NA0003525. SAND2021-15833 A
(Invited) In-Situ Nanoscale Coatings on Silicon Anodes
Authors: Li Xiang , Han Binghong , Uppuluri Ritesh , Dogan Fulya , Key Baris , Vaughey John T.
Published: July 2022

One of the directions being pursued for next generation electrochemical cells is the incorporation of elemental silicon into a lithium-ion battery anode. Silicon's high storage capacity and abundance make it an appealing material for lithium-ion cells. While many studies revolve around its mechanical issues (high volume expansion) and coulombic efficiency on cycling, a major roadblock to its use is its poor calendar life. On standing while charged, silicon based electrodes are observed to lose capacity (active lithium). Since this type of test does not involve particle breakdown, losses due to issues associated with parasitic currents are in part derived from the high reactivity of charged silicon anodes with the surrounding electrolyte and electrode binder. In this talk we will be discussing a new concept that deactivates the redox activity of the silicon surface while maintaining the high lithium-ion conductivity of the highly charged surface phases. We have found that by selectively adding alkaline earth cations to the surface, a more electron precise phase (i.e. Li14MgSi4 vs Li15Si4) forms that acts to change the phase evolution moving away from phases formed by gradual one-electron oxidation in the binary lithium-silicon system. Various studies show that the parasitic currents are seen to drop with addition and cycling with extended calendar life observed. Mechanistic studies will be presented that highlight magnesium addition to the electrolyte and electrode and the role of time on the surface phases.
Electrode Drying Metrology Via Light Microscopy with Supporting Techniques
Authors: Morrison Andrew R T , Dawson Will , Kendrick Emma , Shearing Paul R , Brett Dan
Published: July 2022

An important way to improve the performance of mass-produced lithium-ion batteries is to develop a better understanding of the manufacturing process’s effects on the electrode structure, and thereby its performance. Drying of the electrode slurry is a key step in that process. The parameters that affect drying electrodes have been mainly studied through ex-situ methods. There are far fewer examples of in-line metrologies of drying electrode properties, with notable exceptions including stress measurement by bending beam and dynamic mechanical analyzer, and ultrasonic measurements revealing the evolution of acoustic reflecting surfaces in the electrode (1). With so few in-line metrologies having been investigated, the possibilities are quite wide. However, it is striking that perhaps the most obvious of in-line metrologies has not been systematically investigated in the literature – that of simple visual observation of the drying surface (specifically with a microscope).

Light microscopy can reveal a surprising amount of detail about the drying electrode. In Figure 1 micrographs of a drying electrode under two different lighting conditions – with ring lighting and with coaxial lighting – are shown. In the coaxial lighting condition, the surface of the drying solvent can be seen. In freshly coated electrode slurry, the surface of the drying solvent is uniform and unremarkable, then holes appear as the solvent evaporates eventually leading to a honeycomb-like structure. In the ring lit images, the active material particles themselves are visible directly, and their movement while drying can be tracked. Here, we will examine how microscopy supported by other techniques which yield averaged properties to complement microscopy’s local measurements, such as film stress, can elucidate the drying electrode more fully.

1. Y. S. Zhang, N. E. Courtier, Z. Zhang, K. Liu, J. J. Bailey, A. M. Boyce, G. Richardson, P. R. Shearing, E. Kendrick and D. J. L. Brett, Advanced Energy Materials, 2102233 (2021).

Figure 1