bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Predictive Model of Lithium-Ion Electrode Fabrication, Including Mixing, Coating, Drying, and Calendering
Authors: Forouzan M. Mehdi , Gillespie Anthony , Lewis Nicholas , Mazzeo Brian A , Wheeler Dean R 
Published: February 2020

The microstructure of commercially made lithium-ion battery electrodes is not necessarily optimal for cell performance. In an attempt to optimize the performance, detailed understanding of the microstructure is necessary. Factors that influence electrode microstructure include high-level variables such as composition and porosity; as well as detailed fabrication conditions that are part of the film-making, drying, and calendering steps.
Here we report on continuing efforts to model the particle-level microstructure of porous electrodes and how this relates to fabrication conditions [1]. LAMMPS, a molecular simulation code, was adapted for these mesoscale particle simulations. In particular we simulate an NCM lithium-ion cathode using a superposition of spheres to imitate active particles, carbon, binder, and solvent. Equations of motion coupled to inter-particle forces are solved to simulate particle motion and subsequent immobilization during fabrication steps.
Our model is uniquely able to capture the essential physics in both the slurry and dried film. Model results are validated by comparing to experimental results for microstructure, tortuosity, and mechanical properties like viscosity and elasticity. Such simulations are a first step in allowing us to predict electrode microstructure and therefore battery performance from fundamental fabrication conditions. This contributes to the long-term goal of this work, namely to increase the performance of electrodes by improved control of the manufacturing process.
This work was supported by the U.S. Department of Energy through the BMR program.

References:

[1] M. Forouzan et al., J. Power Sources 312, 172-183 (2016).

Figure 1:

Sequence of images (top to bottom) showing simulated electrode coating process with slurry film (green) moving relative to blade (gray) at shear rate 250 s-1.

Figure 1
Investigation of the Conductivity Effect on Silicon Anode Performance for Lithium Ion Batteries
Authors: Yuca Neslihan , Doğdu Murat Ferhat , Cetintasoglu Mehmet Emre , Taskin Omer Suat , Avci Ipek 
Published: February 2020

The early development on rechargeable lithium battery began with lithium (Li) metal and Sony put into the market the first lithium ion batteries in 1991. Since that date the graphite has been used as commercial anode with the practiable capacity of 250 mAh/g and it has been yet reached the 290 mAh/g in 2015 [1]. In the development of high capacity anode materials for lithium ion batteries, silicon is apparently very promising as anode material due to its high theoretical capacity ~4200 mAh/g. However, the huge volume change (~300%) occurs during the cycling and it results breakdown of the conductive network of the composite electrode. This causes the electrical contact problem between conductive agent and the current collector, resulting low Coulombic efficiency and poor capacity retention for silicon-based lithium ion batteries (LIBs).
Polypyrene (Ppr) polymer has much concern recently not only the conductivity and other electrical properties but also thermal stability and mechanical properties. In this study, the aim is to enhance the conductivity of Si electrode which is crucial for charge-discharge rate of a battery. The high conductivity provides fast charge-discharge and that is very important for consumer electronics and electric vehicle applications. For this purpose, the conductive Ppr was synthesized through the free-radical polymerization of the acrylate backbone in the presence of an initiator. It was used as a conductive polymer for silicon anode in LIBs. The conductivity of anode was also studied with different carbonecous additives (carbon black, super p and carbon nanotube). The cells were fabricated as half and full cell. Li was used as the counter electrode for half-cell and NCA was used as the cathode for full cell.
Table 1. Experimental results for the conductivity study of Si anode

Experiment No
Composition Ratio
Active Material
Binder
Conductive additive

1
90:10
Si
Ppr
-

2
85:15
Si
Ppr
-

3
85:10:5
Si
Ppr
CB

4
85:10:5
Si
Ppr
SP

5
85:10:5
Si
Ppr
CNT

6
85:10:5
Si
PVDF
CB
Comparative Study of Si-Ti Thin Films and Alloys As Lithium Ion Anodes
Authors: Wang Yukun , Liu Hui , Zhu Min , Obrovac Mark N 
Published: February 2020

Si based materials have been intensively studied due to the high theoretical capacity of Si (2194 Ah/L, 3579 mAh/g [1, 2]) and applicable lithiation voltage (around 0.4 V [3]). To address the issues brought by severe volume change during the charge-discharge process, the concept of active-inactive Si based alloys has been developed. Si can form intermetallic compounds with some inactive (towards Li) metals, such as Fe, Co, Mn and Ni [4]. These inactive Si1-xMx phases dilute the expansion of Si and thereby improve electrode cycling performance. Recent reports suggested that the voltage curves of Si1-xMxalloys can be shifted by hundreds of millivolts, presumably due to the stress induced by the volume expansion of active Si while being bonded to the inactive phase [5].
In this work, Si1-xTix (0 ≤ x ≤ 0.4, Δx = 0.05) alloys were prepared both by ball milling and magnetron sputtering. The structure evolution of these alloys and their electrochemical performance as negative electrodes for lithium ion batteries were compared. The capacity dependence of the Si-Ti alloys on Ti content suggests that these alloys comprise an active Si phase and an inactive Si phase. A voltage shift was observed during the lithiation process of Si1-xTix thin-films. Increasing the Ti content (x ≤ 0.3) was found to gradually lower the lithiation voltage by a shift of up to 600 millivolts, while the average voltage during delithiation process remains constant. (Figure 1). The voltage shift during discharge suppresses the formation of the Li15Si4phase at full lithiation, resulting in improved cycling performance.
This presentation will discuss the structural and electrochemical characteristics of sputtered and ball-milled Si-Ti alloys and their relation to alloy reversible capacity and cycle life.

Acknowledgements

The authors acknowledge funding from NSERC and 3M Canada, Co. under the auspices of the Industrial Research Chair and Discovery grant programs. We also acknowledge the support of the Canada Foundation for Innovation, the Atlantic Innovation Fund and other partners that fund the Facilities for Materials Characterization managed by the Institute for Research in Materials. Yukun Wang acknowledges the support from SCUT Doctoral Student Short-term Overseas Visiting Study Funding Project.

References

[1] M.N. Obrovac and L. Christensen, Electrochem. Solid-State Lett., 7 (5) A93, (2004).
[2] M.N. Obrovac and L.J. Krause, J. Electrochem. Soc., 154(2) A103, (2007).
[3] L. Baggetto, R.A.H. Niessen, F. Roozeboom, and P.H.L. Notten, Adv. Funct. Mater., 18(7) 1057 (2008).
[4] Z. Du, T.D. Hatchard, R.A. Dunlap and M.N. Obrovac, J. Electrochem. Soc.,
162 (9) A1858, (2015).
[5] Z. Du, S.N. Ellis, R.A. Dunlap and M.N. Obrovac, J. Electrochem. Soc.,
163 (2) A13, (2016).

Figure 1
Investigation of Pristine Li1.2Ni0.13Mn0.56Co0.13O2 By Advanced TEM
Authors: Wiktor Christian , Liu Hanshuo , Jiang Meng , Wu Yan , Yang Xingyi , Botton Gianluigi A. 
Published: February 2020

Layered Li-transition metal (TM) oxides are very promising materials for new Li ion battery cathodes. Compounds with an increased content of Li and Mn are particularly interesting because they exhibit a high capacity of 200-300 mAhg-1 even after an initial drop in capacity during the first charging cycle.[1] The structure of such compounds and their capacity degradation over multiple cycles is not fully understood due to the complexity of the crystallographic phases, the ambiguities in the diffraction data and the presence of additional phases.
The investigated compound Li1.2Ni0.13Mn0.56Co0.13O2 is derived from LiNi0.33Mn0.33Co0.33O2, (NMC). Due to the higher capacity of the Li-rich compound, it will be referred to as high energy NMC (HENMC).[2] The chemical formula of HENMC can be rewritten as Li2MnO3 · LiNi0.33Mn0.33Co0.33O2 which implies that this compound is a mixture of trigonal NMC and monoclinic Li2MnO3. In NMC, there are two different cation layers which are exclusively occupied by Li and TM respectively. In Li2MnO3 one third of the TM sites are occupied by Li. HENMC must be either a phase mixture with distinct domains of the two oxides or a solid solution of the two, with “Li rich” positions in the TM layers and an overall reduced, monoclinic symmetry (Figure 1).[3] The exact nature of HENMC and similar materials is crucial to understand the de-lithiation processes during charging cycles.
The layered structure and its relation to other phases was investigated with a combination of electron diffraction in bright-field and scanning modes with high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning TEM (HAADF-STEM) imaging. Due to the high structural similarity of NMC and Li2MnO3, all lattice distances which can be found for NMC can also be found for Li2MnO3; as seen in the respective electron diffraction patterns (Figure 2). HAADF-STEM imaging reveals the presence of Li-rich positions in the TM layers as indicated by a lower intensity of the related atom columns (Figure 3). Due to the stacking faults of the TM layers, the interpretation of contrast in any other orientation becomes by far less intuitive as we will demonstrate. A LiTM2O4 spinel phase is found on the surface quite frequently. Its relation to the bulk phase was derived from high resolution images. STEM-EELS revealed the presence of surface reduction due to oxygen depletion in HENMC.
This work thus provides structural information about the synthesized material in its pristine state to facilitate understanding the changes the material undergoes during the (de-)lithiation segments of electrochemical cycling. Further investigations on such effects are currently being carried out and will be discussed.
[1] B. L. Ellis, K. T. Lee, L. F. Nazar, Chem.
Mater.
2010,
22, 691-714.
[2] C. S. Johnson, N. Li, C. Lefief, J. T. Vaughey, M. M. Thackeray, Chem. Mater.
2008,
20, 6095-6106.
[3] H. Yu, H. Zhou, J. Phys. Chem. Lett.
2013,
4, 1268−1280.

Figure 1
Understanding the Degradation Mechanism of Lithium Nickel Oxide Cathode for Li-Ion Batteries
Authors: Tong Wei , Xu Jing 
Published: February 2020

Nowadays, Li-ion battery technology has become one of the best performing energy storage devices and holds the best promise to power the upcoming electrical vehicles (EV).1 Continuous search of cathode materials with even better performance and lower cost ($/Wh) led to numerous layered lithium transition metal oxides, such as LiNixMnyCozO2 and LiNixCoyAlzO2 (0 < x, y, z <1). Recently, there is an emerging interest on developing Ni-rich cathode materials because a higher level of Ni incorporation can lead to a higher practical capacity.2 This is resulted from the electronic configuration of Ni3+ (3d7), allowing the removal of electrons only from the eg band, therefore, the loss of oxygen occurs at a higher charge state.3 On the other hand, a higher Ni content may result in a severe capacity fade during cycling, likely due to the structural transformation in the bulk and at the surface.4, 5 A combination of different transition metals in these LiNixMnyCozO2 or LiNixCoyAlzO2 further increases the complexity of the problem because of the phase separations and side reactions with electrolyte resulting from the difference in chemical and electrochemical reactivity of the transition metals. We have reported the synthesis of high-performance LiNiO2
6, here, we will use it as a model system to reveal the intrinsic performance degradation mechanism originating from the high Ni content for those complex R-3m layered oxides.
The phase transition, charge compensation and local chemical environment of Ni in the bulk and at the surface of LiNiO2 were investigated by a variety of bulk and surface characterization techniques for different terms of cycling. We revealed the phase transition from original hexagonal (H1) phase to another two hexagonal (H2+H3) phases and observed a gradual loss of H3 phase features over the extended charges. The reduction in Ni redox activity occurred in both charge and discharge states, and it appeared both in the bulk and at the surface over the extended cycles. The destruction in crystal structure, and Ni redox activity simultaneously contributed to the cycling performance decay of LiNiO2.
Reference
1. M. S. Whittingham, Chemical Reviews, 2004, 104, 4271-4301.
2. M. H. Choi, C. S. Yoon, S. T. Myung, B. B. Lim, S. Komaba and Y. K. Sun, Journal of the Electrochemical Society, 2015, 162, A2313-A2318.
3. M. Balasubramanian, X. Sun, X. Q. Yang and J. McBreen, Journal of Power Sources, 2001, 92, 1-8.
4. P. F. Yan, J. M. Zheng, D. P. Lv, Y. Wei, J. X. Zheng, Z. G. Wang, S. Kuppan, J. G. Yu, L. L. Luo, D. Edwards, M. Olszta, K. Amine, J. Liu, J. Xiao, F. Pan, G. Y. Chen, J. G. Zhang and C. M. Wang, Chemistry of Materials, 2015, 27, 5393-5401.
5. J. M. Zheng, W. H. Kan and A. Manthiram, Acs Applied Materials & Interfaces, 2015, 7, 6926-6934.
6. J. Xu, F. Lin, D. Nordlund, E. J. Crumlin, F. Wang, J. Bai, M. M. Doeff and W. Tong, Chemical Communications, 2016, 52, 4239-4242.
Comparative Study of Fluorinated and Non-Fluorinated Electrolytes in Li[NixMnyCoz]O2/Graphite Pouch Cells
Authors: Ma Lin , Xia Jian , Dahn Jeff R 
Published: February 2020

The fluorinated electrolyte system, fluoroethylene carbonate (FEC)/bis (2,2,2-trifluoroethyl) carbonate (TFEC) (1/1 w/w), has shown promising performance when Li[Ni0.42Mn0.42Co0.16]O2(NMC442)/graphite pouch cells were operated at 4.5 V.1 Therefore Li[Ni1/3Mn1/3Co1/3]O2(NMC111), NMC442, Li[Ni0.5Mn0.3Co0.2]O2(NMC532), Li[Ni0.6Mn0.2Co0.2O2](NMC622), Al2O3 coated NMC532 and Al2O3 coated NMC622/graphite pouch cells were examined using the FEC/TFEC electrolyte system and compared to cells made with the traditional electrolyte solvent system: ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3/7 w/w). Both electrolyte systems contained 1M LiPF6 and 2% prop-1-ene-1,3-sultone (PES) plus 0.5% methylene methane disulfonate (MMDS) as electrolyte additives.2,3

This systematic study was performed using the ultra high precision charger (UHPC) at Dalhousie University, electrochemical impedance spectroscopy (EIS), gas evolution measurements and long term cycling tests. A wide upper cut-off voltage window was explored during extensive UHPC testing (from 4.1 V to 4.6 V). The charge end-point capacity slippage, capacity fade, columbic efficiency (CE), impedance change during cycling and gas evolution were compared to measure the effects of different electrolyte solvents on different NMC/graphite pouch cells.
Figures 1(a-d) show that the coulombic efficiency (CE) of the FEC/TFEC system is higher than that of the EC/EMC system for all uncoated NMC grades except for NMC622 when the upper cut-off voltage is 4.5 V. This suggests better long term cycling performance at high voltage when FEC/TFEC is used, except for NMC622. The reactions between charged NMC grades (4.5 V) and these two electrolyte systems at elevated temperatures were also investigated by accelerating rate calorimetry (ARC). Figures 1(g-h) show that FEC/TFEC does not affect the thermal performance of NMC532 and NMC622 compared to EC/EMC. However, the self-heating rate of charged NMC111 or charged NMC442 reaction with FEC/TFEC is higher than that of EC/EMC after a temperature greater than 150°C. This means that cell designers will need to may close attention to the impact of fluorinated solvents on cell safety.
References:
1. J. Xia, M. Nie, J. C. Burns, A. Xiao, W. M. Lamanna, and J. R. Dahn, J. Power Sources. 307 (2016) 340–350.
2. K.J. Nelson, Jian Xia and J.R. Dahn, J. Electrochem. Soc. 161 (2014) A1884-A1889.
3. J. Xia, N. N. Sinha, L. P. Chen, G. Y. Kim, D. J. Xiong and J. R. Dahn, J. Electrochem. Soc. 161 (2014) A84-A88.
4. J. Xia, M. Nie, L. Ma and J. R. Dahn, J. Power Sources. 306 (2016) 233–240.

Figure 1
Lithium Transport in High-Capacity Encapsulated Silicon-Vacnt Electrodes
Authors: Fan Juichin , Harb John N. , Davis Robert C. , Vanfleet Richard R. 
Published: February 2020

Si-based anodes are being explored for use in advanced lithium ion batteries due to their capacity and energy density, which exceeds that of current graphite anodes. However, there are several important factors that influence and often limit the cycling performance of these electrodes including large silicon volume changes and extensive SEI formation. Nanostructured electrodes have been shown to effectively reduce the negative impact of volume expansion; however, the use of nanostructures can greatly increase the electrode/electrolyte surface area and lead to greater SEI formation. Consequently, several strategies have been developed to reduce the area available for SEI formation while maintaining the benefits of a nanostructured material. In this study, we use silicon-coated vertically aligned carbon nanotube (Si-VACNT) electrodes to examine the role of Li transport in a system where encapsulation has been used to reduce the surface area of the nanostructured electrode that is exposed to the electrolyte. This system is ideal for studying the impact of an electrolyte-blocking layer due to its well-defined geometry and high aspect ratio. Since transport plays an essential role in the cycling performance of these electrodes, it is desirable to understand the factors that govern the transport of Li into and out of the silicon anode in the absence of electrolyte. Two different transport directions and length scales are relevant—1) radial transport of Li in/out of each silicon-coated nanotube (~50nm diameter) and 2) lithium transport along the length of the nanotubes (~100 micron height). Experimental results indicate that the height of the Si-VACNT electrodes does not appear to limit Li transport, even though that height was orders of magnitude greater than the diameter of the tubes. This result has important implications for a variety of encapsulation strategies. Additional tests were performed to characterize transport in the radial direction, which appeared to be a limiting factor. These tests included GITT (galvanostatic intermittent titration technique) measurements and EIS measurements on differently sized electrodes at different conditions. Hysteresis was also examined. Finally, a model was developed to help explain the experimental observations.
Understanding the Heat Signature from Charging and Discharging of Li-Ion Batteries
Authors: Ralbovsky Peter Joseph 
Published: February 2020

Recently the development of new calorimetric tools to measure lithium-ion batteries during the cycling process has allowed researchers and engineers to better understand how the battery operates, determine efficiency at different temperatures and power levels, design appropriate thermal management systems, as well as to look at entropy changes and parasitic reactions. Also heat output and entropic changes to the cells can be used for aging studies or to determine the State-of-Health (SOH) of a cell.
An example of a heat signature measured for an 18650 lithium ion cell is provided. The current and heat signal measured from three consecutive charge and discharge cycles are shown. In this example an 18650 cell was charged and discharged at a constant current (500 mA or C/5) for 150 minutes. The heat measured by the calorimeter shows good repeatability for the three cycles both in general size and shape but also in some finer details where there is some smaller mechanism occurring within the cell in a repeatable manner. The heat signal which is measured is the sum of the reversible (entropic) heat and the irreversible heat (ohmic and polarization). The irreversible heat is always exothermic while the reversible heat is endothermic on the charge and exothermic on the discharge. Therefore the total heat measured from the discharge (exothermic) will always be larger than the total heat measured from the charge (endothermic). This can clearly be seen in the example provided.
From monitoring the voltage and current, the total efficiency of the battery can be measured by looking at the differences in the total charge from 0-100% SOC. Measuring the open cell voltage (OCV) at different SOC and temperatures can be used to calculate entropy. The addition of accurately measuring heat during these cycles provides a direct measurement of wasted energy and the calculation of efficiency can done between any two different SOC. Entropy can be measured both using OCV and through low current heat measurements. The combination of the approaches can provide insight into the fine details of the heat signatures that are measured for specific cell chemistries. Such an approach is detailed in this paper.

Figure 1
Correlation of Local Conductivity to Microstructure for Li-Ion Battery Electrodes By Use of a Contact Probe and SEM/FIB
Authors: Vogel John E , Lange William , Clement Derek V , Mazzeo Brian A , Wheeler Dean R 
Published: February 2020

Electron transport in lithium-ion battery structures is a key factor in overall battery performance, but the cause of localized high and low electron transport values, or conductivity, has not been well-studied or understood. Factors that may affect such heterogeneity include high-level variables such as film composition and porosity, as well as manufacturing steps such as film drying and calendering [2].
Here we report on our efforts to correlate battery film structure to measured conductivity values, to better understand the causes of observed film heterogeneity. A modified micro 4-line probe [1] was installed in a high resolution stage with a microscope attached for localization on a µm scale. Using the associated theory, electrical conductivity of commercially manufactured battery films was mapped. Subsequently, particularly “hot” or “cold” conductivity locations were additionally investigated by scanning electron microscope (SEM) combined with focused ion beam (FIB) milling to produce planar cross sections.

SEM/FIB images are segmented into 3 domains: carbon, active material, and pores. Each image is characterized using key metrics. These key metrics are then compared to mapped conductivity values in order to determine possible causes of high and low conductivity. This contributes to the goal of this work, namely to increase the uniformity of electrodes by improved control of the manufacturing process.

Figure 1: Measured electrical resistivity of commercial anode (top) with SEM/FIB cross section of region with high conductivity (bottom).

References

[1]
B. Lanterman et al. "Micro-four-line probe to measure electronic conductivity and contact resistance of thin-film battery electrodes," J. Electhrochem. Soc., vol. 162, pp. A2145-A2151, 2015.
[2]
M. Forouzan et al. “Experiment and simulation of the fabrication process of lithium-ion battery cathodes for determining microstructure and mechanical properties,” J. Power Sources, vol. 312, pp. 172-183, 2016.
Acknowledgements
This research is supported by the US Department of Energy through the Advanced Battery Material Research Program.

Figure 1