bluuebunny/crossref_metadata_2025 huggingface dataset:
First Principles Investigations of Reactions Mechanisms of LixMO4 (M=Fe, Mn, Ni, Co) Electrodes/Electrocatalysts for Hybrid Li-Ion/Li-O2 Cells
Authors: Kinaci Alper , Trahey Lynn , Thackeray Michael M. , Kirklin Scott J. , Wolverton Chris , Chan Maria K. Y.
Published: February 2020

We recently proposed a vision for high energy, ‘all-in-one’ electrode/electrocatalyst materials for hybrid Li-ion/Li-O2 cells [1]. Electrochemical experiments with Li5FeO4, which has a defect antifluorite-type structure, have demonstrated a substantially smaller voltage polarization during charge and discharge and hence a higher energy efficiency compared to standard reactions between lithium and oxygen to form Li2O2 [2]. Other materials in this class include Li6MO4 (M=Mn, Ni, Co) that offer a theoretical capacity of ~1000 mAh/g at ~3 V. The mechanisms by which these materials delithiate and lose oxygen, however, is not well understood. The results of first principles density functional theory (DFT) calculations to establish the thermodynamic conditions for the extraction of Li/Li+O from Li5FeO4 and Li6MO4 compounds will be presented. A step-by-step, history-dependent, removal process is followed; the stability of Li and Li+O deficient samples is investigated on the basis of the extraction reaction energies. Various stages of Li/Li+O removal are identified. Structural changes and electronic structure evolution, as well as computed characterizations of the reactions will also be reported.

[1] M. M. Thackeray, M. K. Y. Chan, L. Trahey, S. Kirklin, and C. Wolverton, Journal of Physical Chemistry Letters, 4, 3607 (2013).

[2] L. Trahey, C. S. Johnson, J. T. Vaughey, S.-H. Kang, L. J. Hardwick, S. A. Freunberger, P. G. Bruce, M. M. Thackeray, Electrochemical and Solid-State Letters, 14, A64 (2011).
The Effect of Pore Size Controlled Carbon for Lithium Oxygen Batteries
Authors: Kwak Won Jin , Park Jin-Bum , Sun Yang-Kook
Published: February 2020

The lithium-oxygen battery has been attracting great attention around the world due to its extremely high energy density (i.e., 1-2 kWh kg-1), which could well satisfy the ever increased energy requirement from electronic devices, especially the electric vehicle and plug-in hybrid electric vehicle.1-3

This exceptional energy potentiality has trigged the worldwide interest in this super energy storage system. However, despite large R&D efforts devoted to its implementation, several issues, associated with both electrodes and electrolytes, have so far limited the performance of the lithium oxygen battery due to few discharge-charge cycles and low rate capability.4, 5

Many materials are used for cathode in lithium oxygen battery. Among them, carbon is the mostly used material because of the advantage in the way that amount and cost, although it has been talked making by-product like Li2CO3. (Some paper told that not only carbon but also electrolyte makes the problem in lithium oxygen battery system)

In this study, we show that Ordered mesoporous carbon (OMC) with highly ordered pore channels which was applied as an oxygen-side electrode for a lithium-oxygen battery.

To evaluate the effect of the pore channel size on battery performance, OMCs possessing two different pore sizes (6 and 17 nm) were employed. When cycled at a current density of 200 mA g-1carbon, the OMC electrodes reduced polarization in the oxygen evolution reaction by 0.1 V compared to those consisting of conventional super P carbon electrode. X-ray diffraction and transmission electron microscopy of the discharged oxygen electrodes provided evidence for the formation of amorphous Li2O2, a product of the oxygen reduction reaction, inside the OMC pores rather than on the electrode surface as in the case of the super P electrode. The OMC electrodes were also effective at high current densities (500 mA g-1carbon and 1000 mA g-1carbon).

References

[1] K.M. Abraham, Journal of The Electrochemical Society, 143 (1996) 1.

[2] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, and W. Wilcke, J Phys Chem Lett, 1 (2010) 2193-2203.

[3] B. Scrosati, J. Hassoun, and Y.K. Sun, Energ Environ Sci, 4 (2011) 3287-3295.

[4] S.A. Freunberger, Y. Chen, Z. Peng, J.M. Griffin, L. J. Hardwick, F. Bard, P. Novak, P. G. Bruce, J. Am. Chem. Soc. 133 (2011) 8040-8047.

[5] G.R. Mettam, L.B. Adams in: B.S. Jones, R.Z. Smith (Eds.), Introduction to the Electronic Age, E-Publishing Inc., New York, (2009), pp. 281–304.
High Sulfur Loading of Cathodes for Li-S Batteries
Authors: Liu Wen , Li Yong , Guo Gui , Pei Hai Juan , Fu Wen Zheng , Xie Jingying
Published: February 2020

Lithium sulfur batteries have attracted the most attention owing to their high energy density (2600Wh/kg), while the specific capacity and capacity retention of sulfur electrodes play a crucial role on increasing the energy density of lithium sulfur batteries. Many researches focus on the materials with very high specific capacity per gram of sulfur but very low sulfur content and cells with very low sulfur loading of cathodes [1-3]. In this work, the cells with much higher sulfur loading of electrodes (4.34mg S/cm2, named as S-L and 7.24mg S/cm2, named as S-H) show better electrochemical performance.

Fig. 1(a) shows the first discharge/charge potential curves of lithium sulfur batteries with S-L and S-H as cathodes. Two plateaus (about 2.35V and 2.10V) in the discharge curve and one plateaus (about 2.20-2.40V) in the charge curve are observed, which agree well with the previous work [4]. Comparison of cycling performance between S-L and S-H cathode was shown in Fig. 1(b). S-L cathode shows an initial specific capacity of 845mAh/g at 50mA/g between 1.50-2.80V, which exhibits a discharge capacity of 763mAh/g after 45 cycles with a capacity retention of 90.3%. Moreover, the cell with S-H cathode delivers 836mAh/g and 754mAh/g at the first cycle and the 25th cycle, respectively. The excellent electrochemical performance of high sulfur loading of electrodes makes the development of high energy Li-S batteries possible.

Fig. 1 (a) The first discharge/charge potential curves of lithium sulfur batteries with S-L and S-H as cathode between 1.50-2.80V; (b) Comparison of cycling performance between S-L and S-H cathode.

Reference:

[1] F. F. Zhang, X. B. Zhang, Y. H. Dong, L. M. Wang, J. Mater. Chem., 2012, 22, 11452.

[2] S. Evers, L. F. Nazar, Chem. Commun., 2012, 48, 1233.

[3] G. Zheng, Y. Yang, J.J. Cha, S. S. Hong, Yi Cui, Nano Lett., 2011, 11, 4462.

[4] L. Xiao, Y. Cao, J. Xiao, B. Schwenzer, M. H. Engelhard, L. V. Saraf, Z. Nie, G. J. Exarhos, J. Liu, Adv. Mater., 2012, 24, 1176.
a Novel Sulfur Electrode for the Lithium Ion/Sulfur Battery
Authors: Peled Emanuel , Alon Meital , Golodnitsky Diana
Published: February 2020

The lithium/sulfur battery has many attractive properties. In addition to a high theoretical energy density (about 2600 Wh/kg), it is made of relatively low-cost and non-poisonous materials. However, it has several disadvantages which result from the solubility of sulfur and of lithium polysulfides (PS) in the battery electrolyte. These include self-discharge, short cycle life and low Coulombic efficiency. In addition, the use of a metallic lithium anode poses safety and reversibility problems. The lithium-ion battery is assembled in the discharged state. Thus, in the case of the lithium ion/sulfur battery, lithium sulfide must be incorporated into the cathode prior to cell assembly. Up to now, a very limited number of papers have been published on the assembly of the lithium/sulfur battery in the discharged state (including: Scrosati, Cai, Hayash, Yang). Another problem related to this battery is the large volume changes of the cathode during cycling. The cathode material expands on discharge and contracts on charge. The molar volume of Li2S, is about 80% greater than that of sulfur. This leads to mechanical stress at the cathode and contributes to more rapid degradation of capacity. A novel strategy to overcome the degradation of the sulfur electrode will be described and discussed. Preliminary results collected from cycling of coin cells, having 1 to 4mAh/cm2 of sulfur, over a voltage range of 1.5 to 2.8V, show a very stable capacity and very high current efficiency - nearly 100%. The high current efficiency clearly Indicates a strong depression of the shuttle current resulting from the solubility of the polysulfides in common Li/S batteries.
Study of Cathode Materials for Li Ion Batteries with EPR and High Field EPR Spectroscopy
Authors: Jakes Peter
Published: February 2020

In this work we present EPR measurments done with electrode materials

from Li ion batteries. A comparison of different systems shows, why EPR is

useful studying cathode and anode materials as well as degradation. For the

interpretation of the EPR spectra, high filed measurements, measurments at

different temperatures and in situ measurements are very useful.
Nitrile-Assistant Eutectic Electrolytes for Cryogenic Operation of Lithium-Ion Batteries at Fast Charges and Discharges
Authors: Cho Yoon-Gyo , Hwang Chihyun , Kang Minsun , Song Hyun-Kon
Published: February 2020

The charge/discharge characteristics at low temperature (LT = -20 oC) are enhanced by using ethylene carbonate (EC)-based electrolytes with the help of assistant solvents of nitriles. Conventional liquid electrolytes (e.g. a mixture of EC and dimethyl carbonate (DMC), abbreviated by LED) cannot support satisfactory capacity at the low temperature as well as high rates even if electric vehicles require low temperature operation. Introducing propionitrile or butyronitrile (Pn or Bn) into LED (resulting in LEDPn or LEDBn) as a co-solvent increases significantly the high-rate capacities at -20 oC. For example, LEDPn delivers 62 % of available capacity at 1C and 46 % at 3C with 2.7 V cut-off while the control LED provides just 6 % and 4 % at the same rates. The successful operation at -20 oC with the nitrile-assistant electrolytes results from high ionic conductivity, low viscosity and freezing point depression caused by eutectic behavior of carbonates (EC/DMC) and Pn. Based on phase diagram of Pn with EC/DMC, we expect meaningful battery operation up to -110 oC, probably lower, at the eutectic composition.
Self-Limiting Lithiation and Viscoplasticity of Electrode Nanoparticles in Li-Ion Batteries
Authors: Drozdov Aleksey D , Sommer-Larsen Peter , Christiansen Jesper deClaville
Published: February 2020

A model is derived for the viscoplastic behavior of a host medium driven by stress-induced diffusion of guest atoms. The constitutive equations are applied to study development of stresses in a spherical electrode particle subjected to insertion of lithium. Numerical simulation demonstrates ability of the model to capture basic phenomena observed in anode nanoparticles under lithiation: formation of a sharp interphase between a Li-poor core and a Li-rich shell, slowing down of the interphase motion revealed as self-limiting lithiation, and growth of tensile hoop stresses at the outer surface of a particle leading to its fracture. Good agreement is demonstrated between observations on interphase propagation in silicon nanoparticles and predictions of the model.

Our approach is grounded on the following assumptions:

Electrochemical alloying of guest atoms with a host medium is treated as their (temporary or permanent) immobilization in an electrode particle.

Two types of guest atoms are distinguished: mobile and immobilized (trapped). Transport of mobile atoms is described by the diffusion equation with a reaction term (that accounts for their binding with host atoms) and diffusivity affected by concentration of immobilized atoms. The rate of immobilization is proportional to concentrations of mobile atoms and available traps.

A sharp boundary (interphase) between the domains rich and poor in guest atoms is formed when the rate of trapping exceeds the rate of diffusion.

To characterize development of stresses in a host medium, plastic flow is associated with evolution of its structure (each elementary act of plastic deformation reflects rearrangement of the host matrix induced by alloying with a guest atom).

Within the regular solution model, free energy of a mobile atom is treated as the sum of two (entropic and enthalpic) components. Self-limiting lithiation of electrode particles is described by presuming the Flory-Huggins parameter to be affected by pressure.

To reduce the number of adjustable parameters in the governing equations, simplifying assumption are introduced: (i) changes in elastic moduli with concentration of guest atoms are disregarded, (ii) transport of guest atoms through a host medium is considered within the concept of small strains, (iii) anisotropic volume expansion of electrode particles is not taken into account.

Ability of the model to describe self-limiting lithiation of silicon nanoparticles is illustrated in Figure 1 where dimensionless thickness of a Li-rich outer shell h is plotted versus dimensionless time t(symbols: experimental data (McDowell et al., 2012), filled circles: results of numerical simulation).

Acknowledgement: Financial support by the EU Commission through FP-7 Project Evolution-314744 is gratefully acknowledged.

References:

1. A.D. Drozdov, Int. J. Solids Struct. 2014 (in press).

2. A.D. Drozdov, P. Sommer-Larsen, J.deC. Christiansen, J. Appl. Phys. 2014 (in press).
Influence of LiFSI on Rate Capability of Lithium-Ion Battery
Authors: Xue Gang , Xie Jingying , Feng Yi
Published: February 2020

Lithium bis(fluorosulfonyl)imide (LiFSI) has been investigated as a conducting salt of liquid electrolytes for lithium-ion batteries (LIBs). It shows higher decomposition temperature and Li+ conductivity than LiPF6. LiNi1-x-yCoxAlyO2 (0<x,y<1) is one research focus on LIB cathode materials for its high discharge specific capacity and excellent cycle life. In this article, LiFSI is used as main salt in Li0.8Co0.15Al0.05O2 (NCA) /graphite LIBs to enhance rate capability. NCA/graphite LIBs with LiPF6-based organic electrolyte show 95.3% capacity retention at 1C discharge rate and 89.6% at 3C discharge rate, whereas discharge capacity retention of LiFSI-based ones is 96.7% at 3C.
Thermo-Electrochemical Simulation of Li-Ion Cells Under Abuse Condition
Authors: Tanaka Nanako , Bartsch Philipp , Danzer Michael A. , Döring Harry , Bessler Wolfgang G.
Published: February 2020

Safety of lithium-ion cells is one of the most important aspects of battery research [1]. As a pilot study preliminary to building an early-alert heat management system for lithium-ion cells, we present 1D multi-scale simulation of a single cell with exothermic reactions which induce thermal runaway. The thermo-electrochemical model used in this work includes electrochemical and thermochemical kinetics in range from micro to macro scales [2]. Lithium insertion and extraction in active materials are assumed to follow Butler-Volmer kinetics. The model cell in this study has mesocarbon microbeads (MCMB) in anode and a blended electrode of LiMn2O4 (LMO) and LiNi0.8Co0.15Al0.05O2 (NCA) in cathode. The thermodynamic properties of the pure electrode materials are obtained through published half-cell potentials [3,4,5]. The property of blend material is formulated based on an assumption observed through experiments by Tran et al [6].

To simulate runaway events, we take into account thermal degradation mechanisms both at anode and cathode sides at elevated temperature. At the anode, four exothermic reactions are considered; solid electrolyte interface (SEI) decomposition, SEI formation, ethylene oxidation and reaction of lithium with water. Similarly, oxygen release from NCA and oxidation of solvent (ethylene carbonate) are modeled at the cathode. The reactions are assumed to follow Arrhenius behavior and Tafel type expression for non-charge transfer reaction and charge transfer reaction, respectively. The pre-exponential factor and activation energies of the reactions are taken from either literature or fits with published differential scanning calorimetry (DSC) experiments.

Thermal simulations are used to predict the onset of runaway events under cycling from room temperature up to 333 K of ambient temperature. The cycles are tested under current rates of 1, 2, 3 and 4C. Figure 1 shows the heat resulting from cycling with 4C leading to a chain of exothermic reactions approximately at 350 K inducing thermal runaway.

Furthermore, predictions of temperature and kinetic behavior in case of short circuits are presented (Figure 2). The comparison with experimental measurement is discussed.

Acknowledgement

Financial support by the Volkswagen foundation is gratefully acknowledged.

References

[1] D. Doughty, E.P. Roth, ECS Interface, 2012.

[2] N. Tanaka, W. Bessler, Solid State Ionics, http://dx.doi.org/10.1016/j.ssi.2013.10.009 (2013).

[3] Y.F. Reynier, R.Yazami, B. Fultz, J. Electrochem. Soc., 151 (3) (2004) A422-A426.

[4] K.E. Thomas, C. Bogatu, J. Newman, J. Electrochem. Soc., 148 (6) (2001) A570-A575.

[5] H. Yang, J. Prakash, J. Electrochem. Soc., 151 (8) (2004) A1222-A1229.

[6] H.Y. Tran, C. Taubert, M. Fleischhammer, P. Axmann, L. Knuppers, M. Wohlfahrt-Mehrens, J. Electrochem. Soc., 158 (5) (2011) A556-A561.
Thin and Flexible Solid State Electrolytes for Ambient and Middle Temperature Storage Systems
Authors: Ahlbrecht Katharina , Hupbauer Cornelius , Tübke Jens , Hoffmann Michael J
Published: February 2020

Solid state electrolytes are generally used in high-temperature systems such as fuel cells or sodium/sulfur batteries. They are mostly found in stationary energy storage applications. On the one hand solid state electrolytes have a high ionic conductivity especially at elevated temperatures. On the other hand, they are very brittle and fragile because they are made of ceramic or glass-like materials. To use the solid state electrolyte in next generation systems, such as in Li/S, Li/Air or sodium-based systems at ambient or middle temperature, the solid state electrolyte is embedded in a flexible, ductile and non-metallic material by using a recently developed manufacturing process. The advantage of those materials is the possibility of their plastic deformation under stress.

By using adjusted and optimized electrolytes for each electrode in the Li/S battery, intrinsic parasitic effects like the polysulfide shuttle mechanism or electrolyte degradation at the side of the alkaline metal anode could be prevented. As an alternative to lithium today sodium-based systems have become an interesting subject for researchers. Due to the low melting temperature of sodium (about 100 °C), it is conceivable to use molten sodium as an anode separated with a thin, flexible and stable solid state electrolyte from a cathode. With this design a formation of dendrites and a reaction with a liquid electrolyte should be avoided and improved cycling stability can be obtained.
A Microscopic Safety Mechanism Study for Li Ion Battery
Authors: Chung Jaesik
Published: February 2020

As the large number of LiB has powering in wide ranges of devices in a variety of usage and environmental conditions, there were several LiB field incidents. Many LiB safety mechanisms studies were devoted to understand the safety hazard and to prevent field safety incidents. Many researches have focused on the inherent safety of the battery materials and on the simulation of the cell abuse conditions. The thermal behavior and stability of the LiB cell and its component were studies by the
DSC (Differential Scanning Calorimetry), ARC (Accelerating Rate Calorimeter) and other tools. Many LiB degradation and safety mechanisms were proposed from those results. Meanwhile, some LiB safety standard and approval test are in place to minimize hazard or to prevent field safety incidents, which simulate batteries in the thermal, electrical and mechanical abuse conditions.
However frequent LiB field incidents on the certified batteries have still causing big concerns on its safety.

Many field incident analysis reports identified that there are important difference between reported LiB safety mechanisms in papers, abuse testing in standards and the real field incidents. And those concluded the battery field incidents almost originated due to the cell internal short circuit that was not predictable at the point of cell manufacturing
process
and certifciation or approval testing process. There are many factors which can induce cell internal short circuit; -metal impurity in the electrode matrials, -metal particle during cell manufacturing process, -flaw in separator, - flaw in cell design and manufacturing, - defected by electric, mechanical and thermal impact and so on.

This paper studied a mechanism of the cell internal short circuit by using microscopic techniques. This technique checks the status of a cell design and manufacturing status of a cell model, which may cause a cell internal short circuit during in use if the cell has flaw.
We performed two types o
f the "Destructive Physical Analysis" testing to
identify a cell's latent possibility of inducing internal short circuit; 1) by measuring the gap between separator and anode and cathode in the jellyroll or cell stacking (sepertor shrinkage allowance at room/high teperatture and cell electrode geometry) by microscopic techniques; 2) by checking the position and status of insulation mechanism in the cell (Electrode tab insulation, Application of insulation, Supplementary Insulation, Internal short avoidance, Position of insulation material).

This paper shows the relationship between the status of a cell model and the simulation result of the cell abuse testing (Electric testing, and thermal testing and mechanical testing). This paper identifies the battery safety mechanism which is representing the real field failures and incidents.

Attached image file shows
relationships between cell design/manufacturing status of a LiB cell and cell abuse simulation testing result.
Physical Vapor Deposition of Li7La3Zr2O12 for All-Solid-State Thin Film Li Batteries
Authors: Lobe Sandra , Stemme Florian , Tsai Chih Long , Finsterbusch Martin , Dellen Christian , Uhlenbruck Sven , Buchkremer Hans Peter
Published: February 2020

The liquid solvents used as electrolytes in conventional Li ion batteries limit the operating temperature range and cause safety problems due to insufficient electrochemical stability. With purpose to avoid these disadvantages solid electrolytes, like lithium conducting oxides, sulfides or phosphates can be used. A promising oxide is the garnet-like Li7La3Zr2O12 that shows one of the highest total Li ion conductivities (about 10-4 S cm-1 at room temperature) in this class of materials. It also enables a wide application range due to its thermal stability and chemical resistance against possible electrode materials, e.g. metallic Lithium.

In order to compensate the lower Li ion conductivity compared to liquid electrolytes current work is focused on thin electrolyte layers. Hence, main research aspect of the presented work is the thin film processing of Li7La3Zr2O12 with physical vapor deposition methods, especially RF magnetron sputtering. The growth conditions are optimized with regard to synthesize stoichiometric, crack-free and smooth thin films. Deposition is followed by thermal treatment of the as-grown samples to improve the crystallinity which should in turn improve the Li ion conductivity. The composition, structure and the electrochemical behavior of the resulting thin films are analyzed in order to deposit all-solid-state thin film batteries.
Combined IR and Raman I
n Situ Microscopy on Single Particles - A New Tool for Interface Studies
Authors: Novak Petr , Lanz Patrick
Published: February 2020

Vibrational spectroscopy is well suited to the investigation of processes occurring in lithium-ion batteries during electrochemical cycling. The combined application of Raman and IR spectroscopy offers additional advantages connected to the complementary nature of the two methods. Whereas Raman spectroscopy is particularly sensitive to local structural changes of the electrode material, IR spectroscopy provides a good way of probing the interface with the organic electrolyte. Employing microscopic methods and a specially adapted cell allowed spatial resolution and the recording of in situ data, respectively.

In this contribution, we will describe the first application of these spectroscopic methods to the characterization of the same spot at a single working particle. Originally, combined Raman and IR microscopy was first developed by using glassy carbon, which offers the advantage of exhibiting excellent IR reflectivity. However, because glassy carbon is unable to intercalate lithium, the method was further developed and applied to a single, graphite particle. Unlike conventional compound electrodes consisting of microscopic graphite powders, this allows the measurement of IR spectra with good signal-to-noise ratios. This study is thus employed to showcase a powerful application of the combined same-spot spectroscopic method. The automated measurement of Raman and IR spectra provides an efficient way of correlating information on the electronic state of the electrode (intercalation) with effects related to the interface with the electrolyte (SEI). Corresponding results are presented and discussed in this contribution.
Enhanced Separator Properties By Thermal Curing of Poly(ethylene glycol)Diacrylate-Based Gel Polymer Electrolytes for Lithium-Ion Batteries
Authors: Kim Kwang Man , Lee Young-Gi , Ko Jang Myoun , Cho Won Il
Published: February 2020

Porous polyethylene (PE) or nonwoven poly(vinylidene fluoride) (PVdF) separator-supported gel polymer electrolytes are realized by thermal polymerization of a precursor solution consisting of poly(ethylene glycol)diacrylate (PEGDA) and an electrolyte solution (1 M LiPF6 in an equal-volume mixture of ethylene carbonate and dimethyl carbonate). The polymerization conditions are optimized to include a PEGDA content of 3 wt.% in the precursor solution and subsequent heat treatment at 80oC for 10 min. Even though the gelled PEGDA electrolyte has a lower ionic conductivity than the electrolyte solution, a Li
x
CoO2/graphite full-cell that has a gel electrolyte with optimized PEGDA content on the PVdF separator achieves a battery performance superior to the one with PE. The best battery performances achieved are a high discharge capacity (116 mAh g-1), a good high-rate capability (95 mAh g-1 at 5.0 C-rate), and a high capacity retention ratio (90%) after the 100th cycle. This enhancement is due to the incorporation of a polar electrolyte solution that is entrapped by the polar PEGDA matrix within the nonwoven PVdF separator, which is a more suitable host that is able to well absorb and preserve the gel electrolyte. Figures below are (left) a schematic diagram of gelation procedures from the full-cell fabrication to its heat treatment via a droplet insertion of the precursor solution and (right) cycle performance of the Li
x
CoO2/graphite full-cells at 1.0 C-rate, using the PEGDA-containing gel polymer electrolytes on PE and PVdF separators.
In-Situ Characterization of Si-Based Electrodes By Dilatometry and Acoustic Emission
Authors: Tranchot Alix , Etiemble Aurelien , Thivel Pierre-Xavier , Idrissi Hassane , Roué Lionel
Published: February 2020

The replacement of carbon by silicon as active material in negative electrodes of Li-ion batteries is very attractive since the gravimetric and volumetric capacities of silicon are much higher than those of carbon. However, silicon suffers from huge volume variation (up to ~300% versus 10% for C) upon cycling. This leads to the electrode pulverization inducing electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and coulombic efficiency. A precise evaluation of the volume variation and cracking processes is thus crucial to develop more efficient Si-based electrodes. For that purpose, in the present study, the volume change of Si-based anodes during cycling is monitored by in situ dilatometry. In addition, in situ acoustic emission (AE) measurements are performed to study the electrode pulverization process with cycling. For a better identification of the origin of the different populations of detected AE signals, a detailed study of their energetic and temporal characteristics (amplitude, rise time, frequency...) is conducted. The influence of the cycling conditions (discharge capacity, cycle number, C-rate), electrode formulation (Si particle size…) and processing (calendar pressure) and electrolyte composition on the electrode volume variation and cracking is highlighted and correlated to its electrochemical performance.
All Solid-State Lithium Batteries Assembled with Hybrid Solid Electrolytes
Authors: Jung Yun-Chae , Choi Jeong-Hee , Lee Sang-Min , Kim Dong-Won
Published: February 2020

Lithium-ion batteries have rapidly become the dominant power sources for portable electronic devices, electric vehicles and energy storage systems, due to their high energy density and long cycle life [1,2]. However, safety issues still prevent full utilization of these batteries. One of the most efficient methods to enhance the battery safety is to use solid electrolyte [3-5]. Solid inorganic electrolytes present potential advantages, such as a wide electrochemical stability window, enhanced thermal stability, absence of solvent leakage and high resistance to shocks, which are important safety assets. However, sheet manufacturing, especially using thin-film technologies for making large-scale batteries, is considered to be difficult because of brittle characteristics of ceramic materials. In this work, the hybrid solid electrolytes composed of lithium aluminum germanium phosphate (LAGP) and poly(ethylene oxide)(PEO) were prepared in the form of flexible thin film, and their electrochemical properties were investigated. Their morphological properties studied using SEM, EDS and XRD. The ionic conductivities and electrochemical stability of hybrid solid electrolytes were much higher than those of PEO-based polymer electrolyte. All solid-state lithium batteries assembled with hybrid solid electrolyte exhibited high discharge capacity and excellent capacity retention with a coulombic efficiency exceeding 99.5% at 55 oC.

References

[1] J. M. Tarascon, M. Armand, Nature 414 (2001) 359.

[2] P. G. Bruce, B. Scrosati, J. M. Tarascon, Angew. Chem. Int. Ed. 47 (2008) 2930.

[3] N. Kamaya, K. Homma, Y. Yamakawa, M. Hirayama, R. Kanno, M. Yonemura, T. Kimiyama, Y. Kato, S. Hama, K, Kawamoto and A. Mitsui, Nat. Mater. 10 (2013) 682.

[4] H. S. Jadhav, M.S Cho, R. S. Kalubrame, J. S. Lee, K. N. Jung, K. H. Shin, C. J. Park, J. Power Sources 241 (2013) 502.

[5] Y. Li, C. A. Wang, H. Xie, J. Cheng, J. B. Goodenough, Electrochem. Commun. 13 (2011) 1289.
Effect of Temperature and Tfsi Concentration on Lithium-Ion Diffusion in (PVDF-HFP)-PYR14 TFSI-LiTFSI Gel Electrolytes
Authors: Sobrados Isabel , Sanz Jesus , Amarilla Jose Manuel , del Rio C. , Morales Enrique
Published: February 2020

Lithium batteries have been considered as the most probably next generation of power sources for portable electronic devices and electric vehicles. However, safety risks related to the use of highly flammable liquid electrolytes in combination with high voltage electrodes are the main obstacle to their introduction into the market. Recently ionic liquids have emerged as potential materials to substitute the conventional organic carbonate-based liquid electrolytes. In this work we report on the effect of temperature and lithium salt molar concentration on lithium ion diffusion in (PVDF-HFP)-PYR14TFSI-LiTFSI gel electrolytes. TFSI molar ratios range from 0,05 to 1 mol%. The self-diffusion coefficient of lithium ions (D 7Li) was measured at temperatures from 20 to 100°C using the pulsed-field gradient NMR (PFG-NMR) method by using a Bruker 400MHz Avance NMR spectrometer with a magnetic field of 9.4 T. A stimulated echo pulse sequence with gradient pulses of duration (δ) of 1-2 ms and an observation time (Δ) equal to 20 ms was applied. The decay of the signal in dependence on the gradient strength g results in the diffusion coefficient by fitting the exponential decay function. A parallel analysis was made for PYR14TFSI/TFSI ionic liquid electrolytes.

The results obtained indicate that the value of D 7Li at high temperature for both liquid and gel electrolytes is practically independent on the LiTFSI molar concentration, while larger differences have been detected at low temperatures, in accordance with ionic conductivity data. The temperature dependence of the calculated self-diffusion coefficients fit the Arrhenius equation. The values of the activation energy Eac, calculated by plotting the shelf diffusion coefficient vs. 1/T, depends on the relative concentration of the lithium salt in the gel, increasing when TFSI molar ratio goes from 0,05 to 1 mol% for both liquid and gel electrolytes.
Thermodynamic Explanation of Orientation-Dependend Expansion of Lithiated Si Nanowires
Authors: Rohrer Jochen , Moradabadi Ashkan , Kaghazchi Payam , Albe Karsten
Published: February 2020

Due to its high mass-specific capacity Si is an attractive anode material for Li ion batteries.

The highest capacites have been achieved for Si nanowires, wires consisting of a crystalline core and an amorphous shell.

During first-cycle lithiation, both the amorphous shell and the crystalline core transform into amorphous LixSi where x may reach a maximum value of ~4.4 at full lithiation.

During first lithiation, it has been observed that Si nanowires expand differently into different directions [1].

In particular, expansion into <110> is largest while expansion into <111> is smallest.

It has been suggested that this behaviour is due to an orientation-dependent diffusion rate of the interface

between lithiated Si (amorphous LixSi) and the crystalline core [1,2].

In this work we use ab initio density functional theory calculations to study interfaces between lithiated Si and crystalline Si.

In particular we focus on interfaces between Si(100), Si(110) and Si(111) with amorphous Li2Si (a-Li2Si).

a-Li2Si is chosen as model for lithiated Si since it has recently been suggested to coexist with crystalline Si [3].

We find that a-Li2Si/Si{111} interfaces are energetically most favourable,

while a-Li2Si/Si{110} interfaces are the least favourable (among the three considered ones).

Since expansion along <111> generates a-Li2Si/Si{110} interfaces (<1-10> is orthogonal to <111>)

and expansion along <110> generates a-Li2Si/Si{111} interfaces,

our calculations naturally explain experimental observations on a thermodynamic basis.

For completeness, we also study the kinetics of Li across the interfaces.

Preliminary results indicate that Li diffusion barriers are independent of the orientation of the interface.

This implies in particular that kinetics does not hinder a thermodynamic evolution of the system.

References:

[1] H. Yang et al., Nano Lett.
12, 1953 (2012).

[2] M.K.Y. Chan, C. Wolverton and J.P. Greeley, J. Am. Chem. Soc.
134, 14362 (2012)

[3] J. Rohrer and K. Albe, J. Phys. Chem. C
117, 18796 (2013).
Effect of Silica and Tin Oxide Nanoparticles on Properties of Nanofibrous Electrospun Separators
Authors: Zaccaria Marco , Cannucciari Giorgia , Fabiani Davide , Gualandi Chiara , Focarete Maria Letizia
Published: February 2020

Recently the use of electrospun separators in lithium ion batteries has been studied due to the outstanding properties of the nanofibrous non-woven constructs [1]: high porosity, high pore interconnectivity and wide surface area that lead to a large electrolyte uptake with respect to a commercial microporous separator, e.g. Celgard. This behaviour makes electrospun mats suitable for high ionic conductivity applications in lithium cells. Further improvements in membrane properties can be achieved through dispersion of additives (such as oxides particles) inside nanofibers, aiming at increasing the mechanical, thermal and electrical properties of the polymeric separators, in order to satisfy lithium battery safety concerns and capacity requirements. The use of nanoadditive to improve the properties of electrospun membranes for polymer electrolyte batteries is a quite novel topic, not completely investigated in literature.

In this work Poly(vinylidene fluoride) (PVDF) solutions have been filled with fumed silica and tin oxide nanoparticles and electrospun to produce lithium battery separators. Membrane morphology characterization and energy dissipation spectroscopy have been carried out by means of a scanning electron microscope, in order to evaluate fiber quality, fiber diameter distribution and the presence of the additives inside the material. Thermogravimetric analysis, Differential Scanning Calorimetry, and tensile tests have been used to evaluate thermal stability, thermal and mechanical properties of the separators and to quantify the inorganic fraction. Electrical characteristics have been investigated through dielectric spectroscopy and conductivity measurements in order to ensure the very low electric conductivity of the membranes regarding electronic carriers. Nanoparticle dispersion inside the fibers has been evaluated by means of a transmission electron microscope. Finally, the electrospun separators have been soaked in electrolyte solution to estimate their uptake performance.

[1] F. Croce, M.L. Focarete, J. Hassoun, I. Meschini, B. Scrosati, A safe, high-rate and high-energy polymer lithium-ion battery based on gelled membrane prepared by electrospinning, Energy and Environmental Science, 2011, 4, 921–927.
Prediction of Volumetric, Specific Energy and Power Density of High-Capacity Thin Layer Battery Electrodes By Using a Novel Multi-Scale Modelling Framework
Authors: Kriston Akos , Pfrang Andreas , Popov Branko N
Published: February 2020

In this work, a novel modelling approach is presented, which is able to directly relate the microstructure of the active layer of thin-film batteries to the battery cell macroscopic behaviour. A general pore-scale model has been developed by mimicking the layer fabrication process. Five different electrode structures were reconstructed taking into account the interaction between the deposited particles during the layer formation. In each simulation 108particles were deposited with 5 different sticking rules. Fig.1. captures the beginning of the layer formation. Fig.1a) shows weak interaction between the particles, i.e. the layer is mainly governed by random deposition, and b) strong attractive forces, i.e. every particle sticks to the nearest neighbour. The different colours correspond to the deposition of 1000 particles, while white spaces correspond to open pores.

Instead of simulating each type of reconstructed layer, the renormalization group theory is applied to analyse the effect of thickness on the properties of the active layer. It is shown, that in spite of the very different morphology, all these reconstructed layers belong to the same universality class and can be described by a general non-linear scaling law. The simulation results imply that porosity and specific surface area depend on the thickness of the electrode, which is not commonly considered in battery models. The general expression derived is incorporated into a macrohomogeneous model and the charge-discharge performance is simulated. The volumetric and specific energy and power densities are calculated and finally, the simulation results are compared with measured data at different thicknesses.

The developed method offers an efficient tool not only to predict, but to design high power and high capacity batteries for automotive applications and/or scale down dimensions for microelectronics and MEMS. It can be used for fast screening of novel manufacturing technologies as well as for deeper understanding of the effect of microscale structure on the macroscopic behaviour of battery cells.
In Situ Electron Microscope Observations of Electrochemical Lithium Deposition/Dissolution with a Glassy Solid Electrolyte
Authors: Ejiri Makoto , Motoyama Munekazu , Iriyama Yasutoshi
Published: February 2020

Introduction

　The recent discoveries of inorganic solid electrolytes with large Li+ ionic conductivities have greatly propelled the research on all-solid-state lithium batteries. Solid electrolyte blocks Li dendrite growth toward the cathode if Li metal is used as the negative electrode. This is certainly attractive because the theoretical energy density of Li metal (2062 Ah L-1) is much greater than those of presently commercialized negative electrodes (e.g. graphite). It is hence important to understand how Li metal grows and dissolves through solid electrolyte interfaces in the charge-discharge processes [1]. This study reports in-situscanning electron microscope (SEM) observations of the initial stage of Li growth at electrode/amorphous solid electolyte interfaces.

Experimental

　The mojority of the electrolyte (1.25 cm × 1.25 cm) is a mirror-polished Li1.3Al0.3Ti1.7(PO4)3 (LATP) sheet (OHARA Co.) with a thickness of 150 μm. Its top and bottom surfaces were sputter-coated with lithium phosphorus oxynitride (LiPON) layers with thicknesses of 2.5 μm. The working electrode is a 30-nm-thick-Cu film onto a circular area with a diameter of 5.0 mm in the center of the top LiPON surface. The counter electrode is a 3-4-μm-thick-Li film on the bottom LiPON surface. Electrochemical Li deposition and dissolution were conducted in a Keyence VE-9800 SEM under galvanostatic conditions. Li deposition/dissolution are carried out at 50 μA cm-2 to 3 mA cm-2. The total charges are 180 mC cm-2 for all curent densities. This charge amount corresponds to a plating of a 242-nm-thick Li film if the plated film formed a contiguous solid thin film.

Results and discussion

　Figure 1 shows SEM images of the growth trajectories of different Li nuclei at 100 μA cm-2. Li nuclei under a Cu film eventually break the Cu film to grow Li rods. Li deposits break a Cu film at approximately 240 s. Once a Cu film is cracked, new Li nucleation no longer occurs. Thus, strain energies in Li and Cu are considered to influence the Li nucleation and growth under a Cu film. At 1.0 mA cm-2, the number of Li nucleation sites increases. Additionally, rapid agglomeration of Li nuclei under a Cu film is observed (Figure 2). In contrast to the case at 100 μA cm-2, Li rods do not grow through cracks of a Cu film.

　Li dissolution reactions were also observed by in-situ SEM, and Li self-diffusion in Li rods seems to dominate the stripped length within a rod. Morphological changes of a Cu film at the first cycle influence the preferential sites for Li growth at subsequent cycles. Li deposition/dissolution reactions will be further discussed in more detail with in-situ SEM movies.

Reference

[1] F. Sagane, K. Ikeda, K. Okita, H. Sano, H. Sakaebe, and Y. Iriyama, J. Power Sources, 233 (2013) 34.
Lithium Distribution in Monocrystalline Silicon-Based Lithium-Ion Batteries
Authors: Janski Rafael , Fugger Michael , Sternad Michael , Wilkening Martin
Published: February 2020

There is a growing demand on power sources for micro-system applications. Li-ion micro batteries (µ-batteries) with silicon-based anodes may fulfill the necessary requirements. Silicon shows superior properties as anode material in batteries such as a very high specific capacity [1]. Well-engineered manufacturing techniques allow a high level of integration into silicon-based semiconductor devices [2].

One challenging topic for the integration concerns lithium distribution inside the anode to understand the cyclability of silicon. Moreover, the prevention of loss of Li-ion in non-active areas of the battery is a key issue. Therefore, the introduction of a tight barrier layer is essential for such systems [3]. For these investigations analytical techniques are required, which can obtain information on the lateral as well as depth lithium distribution.

Surface structured silicon and sputtered diffusion barriers on silicon were tested as working electrodes in a half-cell Swagelok® design together with a EC: EMC, LiPF6-based electrolyte. Two mass spectrometry based techniques were applied to investigate the properties of structured silicon anodes together with the barrier characteristics of refectory metal materials: (i) ToF-SIMS was used as imaging technique for depth profiling the first micrometers and (ii) Laser ablation ICP-MS allowed to measure depth-profiles of up to hundreds of microns perfectly complementing the ToF-SIMS technique.

The presented study focuses on the non-uniform Li-distribution in silicon anodes with the aim to avoid structural weak hotspots due to locally unbalanced dilatation. Beside the detailed investigation of the native anode structures we tested different silicon-barrier combinations, e.g., Si – TiN, to clarify their potential as Li-inert material in future battery applications (see Fig. 1).

Acknowledgement

Financial support by the Federal Ministry of Economy, Family and Youth and the National Foundation for Research, Technology and Development is gratefully acknowledged. Moreover, we thank Infineon Technology Austria AG for financial and technical support.

References

[1] B.A. Boukamp, G.C. Lesh, R.A. Huggins, All-solid lithium electrodes with mixed-conductor matrix. J. Electrochem. Society, 1981, 128, 4, 725-729

[2] J.F.M Oudenhoven, L. Baggetto, P.H.L Notten, All-solid state lithium-ion microbatteries: A review of various 3D concepts. Adv. Energy Mater., 2011,1, 10-33

[3] J.E. Trevey, J. Wang, C.M. Deluca, K.K. Maute, M.L. Dunn, S-H Lee, V.M. Bright, Nanostructured electrodes for solid-state 3D rechargeable lithium batteries, Sensors and Actors A167, 2011, 139-145

Figure 1: ToF-SIMS profile of a sputtered titanium nitride barrier layer on a highly doped Si substrate after 10 cycles vs. a lithium counter electrode in EC:EMC (3:7), 1 M LiPF6.
Gel Polymer Electrolyte Based on Tetraethylene Glycol Dimethyl Ether Used As a Stable Electrolyte for Lithium Oxygen Batteries with Enhanced Cycling Performances
Authors: Zhang Jinqiang , Sun Bing , Chen Shuangqiang , Xie Xiuqiang , Huang Xiaodan , Wang Guoxiu
Published: February 2020

Free-standing gel polymer electrolytes with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) matrix plasticized with tetraethylene glycol dimethyl ether (TEGDME) were prepared and investigated. The as-prepared gel polymer electrolytes exhibited good reversibility of Li+ plating and striping, large operating window, and acceptable ionic conductivity. When applied in lithium-oxygen (Li-O2) batteries, the gel polymer electrolyte exhibited a high initial discharge capacity of 2,988 mAh g-1. Furthermore, the battery with gel polymer electrolyte can last at least 50 cycles in the fixed capacity cycling, displaying an excellent stability.Detailed study reveals that the gelling process is essential for the cycling stability enhancement. With excellent electrochemical properties, the free-standing gel polymer electrolyte presented in this investigation have great application potentials in long-life Li-O2 batteries.