bluuebunny/crossref_metadata_2025_split huggingface dataset:
Li Storage Behavior of C-Coated Si/SiOx Nanospheres As a High Capacity Anode Material for Lithium-Ion Battery
Authors: Park Eunjun , Park Minsik , Lee Jaewoo , Kim Young-Jun , Kim Hansu 
Published: February 2020

Si has gained much attention as anode materials for lithium-ion battery due to its high theoretical capacity (3,580 mAhg-1) and low standard oxidation potential (0.4 V vs. Li/Li+). Despite these features, Si anode materials still have limits to commercial uses by poor cycle performance associated with their mechanical pulverization of Si due to severe volume change during alloying/dealloying with Li. To overcome this problem, various approaches have been suggested. In particular, the composites, which are composed of active Si and inactive buffer material, showed promising approaches for reducing the mechanical strain during cycles. On the other hand, nanostructuring of active materials would be helpful for further improvement of cycle performance. After heat treatment of Si/SiOx precursor at 1200 °C under inert atmosphere, we obtained Si nanocrystals embedded SiOx nanospheres with a size of 200 nm, in which about 10 nm sized Si nanocrystals are embedded in amorphous SiOx matrix. In order to improve electrical conductivity of Si/SiOx nanocomposites, carbon layer was coated on the surface of Si/SiOx nanocomposites.
The Si/SiOx nanospheres and C-coated Si/SiOx nanospheres were characterized by a field emission scanning electron microscope (FESEM), a high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD) patterns, solid state 29Si magnetic angle spinning nuclear magnetic resonance (MAS NMR) and X-ray photoelectron spectroscopy (XPS) analyses.
The C-coated Si/SiOx composites showed a reversible capacity of 950 mAh/g-1 at current density of 200 mAg-1 with stable cycle performance over 100 cycles and high rate capabilities. In this presentation, the electrochemical properties of the C-coated Si/SiOx nanocomposites will be discussed in more detail.
Degradation Studies on LiFePO4 cathode
Authors: Scipioni Roberto , Jørgensen Peter Stanley , Hjelm Johan , Norby Poul , Rasmussen Claus Nygaard , Jensen Søren Højgaard 
Published: February 2020

Lithium-ion batteries are a promising technology for automotive application, but limited performance and lifetime is still a big issue. The aim of this work is to study and address degradation processes which affect LiFePO4 (LFP) cathodes - one of the most common cathodes in commercial Li-ion batteries.
In order to evaluate how the LFP cathode is affected by C-rate a LFP working electrode, Lithium metal foil counter electrode and Lithium metal reference electrode was tested in a 3-electrode setup with a standard 1M LiPF6 in 1:1 EC/DMC electrolyte and glass fiber separator. The working electrode/counter electrode was subjected to several charge/discharge cycles between 3.0 V and 4.0 V at different discharge rates. Figure 1 shows the voltage profile of the LFP electrode (solid line) and full battery (dotted line) during charge/discharge process. It is seen that the higher the C-rate, the higher is the polarization furnished by the counter electrode which reduces the capacity.
In Figure 2, the discharge capacity [mAh/g] is plotted vs the number of charge/discharge cycles. Series of 10 cycles at a given C-rate was applied to the battery. Each series was followed by a C/10 cycle (green points). A linear fit has been applied to the first series (omitting first two cycles where instability of the system is observed), in order to calculate the degradation rates.
High C-rates are seen to affect the discharge capacity, but the capacity is almost completely recovered (green points) and only a limited degradation occurs.

Impedance spectroscopy has been also applied to investigate the LFP cathode degradation. Figure 3 shows the imaginary part of the impedance measured at 50% State-of-Charge after each series of cycles. The relative increase in the impedance arc around 1 KHz (assumed to be associated with charge transfer resistance at the LFP particle surfaces) is seen to gradually decrease with increasing number of series. This indicates that more cycles per series is needed to establish a convincing relation between C-rate and degradation.
The degradation studies will be coupled with FIB/SEM analysis in order to observe changes in the pore structure or micro cracks that would affect electronic percolation. Figure 4 displays an example of a fresh LFP cathode after FIB cutting. White particles are LFP grains while the black area contains carbon particles and pores, which are difficult to distinguish from each other. Substitution of the epoxy resin with a silicon resin increases the contrast between pores and carbon particles [1] and this will be used in the forthcoming FIB/SEM analysis.

References

[1] M. Ender et al, Journal of The Electrochemical Society, 159 (7) A972-A980 (2012)
Electrochemical Performance of Overlithiated Li1+XNi0.8Co0.2O2: Structural and Oxidation State Studies
Authors: Rusdi Roshidah , Kamarulzaman Norlida , Elong Kelimah , Rusdi Hashlina , Abd Rahman Azilah 
Published: February 2020

Pure layered compound of overlithiated Li1+xNi0.8Co0.2O2 (x=1,1.05,1.1) samples were successfully prepared by a combustion method. Structural studies of the XRD results showed that when lithium was doped into the LiNi0.8Co0.2O2 cathode materials, the structural parameters of the materials changed slightly when more lithium is doped, that is the cell parameter decreased. Scanning electron microscopy (SEM) revealed that the morphology of the particle c0.2hanged a little from rounded polyhedral-like particle to sharp edged polyhedral crystals when more lithium is doped. Energy dispersive X-ray spectroscopy (EDX) showed that the stoichiometries of Ni and Co agrees with calculated synthesized values. X-ray photoelectron spectroscopy (XPS) studies showed that the binding energy of Li 1s is decreased for the doped Li1.05Ni0.8Co0.2O2 compound followed by Li1.1Ni0.8Co0.2O2 and LiNi0.8Co0.2O2. This implies that the Li+ ions can be more easily extracted from Li1.05Ni0.8Co0.2O2 materials than the other stoichiometries. The XPS results are supported by the electrochemical performance of the samples. Li1.05Ni0.8Co0.2O2 showed the best results with a specific capacity of 113.29 mAh/g compared to Li1.1Ni0.8Co0.2O2 with a specific capacity of 112.32 mAh/g and LiNi0.8Co0.2O2 with a specific capacity of 94.71 mAh/g. Li1.05Ni0.8Co0.2O2 also showed the best capacity retention of 7.8 % over 10 cycles.
Reference
[1] R.Santhanam, B.Rambabu, "Improved High Rate Cycling of Li-rich Li1.1Ni1/3Co1/3Mn1/3O2

Cathode for Lithium Batteries" Int.J,Electrochem.Sci.,4 (2009) pp. 1770-1778
Hybrid Polyvinyl Alcohol/Silicon Nanofiber Anodes with High Concentrated Graphene Nanoribbons for Rechargeable Lithium-ion Batteries
Authors: Kim Yong Seok , Li Zhong , Patel Bharat , Chakrapani Srinivasan , Lee Sangho , Joo Yong Lak 
Published: February 2020

Despite the highest theoretical capacity of 3579 mAh/g in lithium–ion batteries,[1,2] silicon (Si) anodes have been still suffered from severe capacity fading, because of two kinds of drawbacks such as (i) dramatic volume expansion called pulverization leading to electrical disconnection as well as (ii) formation of solid–electrolyte interface on their surfaces.
Herein, we prepared an organic/inorganic hybrid anode of polyvinyl alcohol (PVA)/Si nanoparticles (NPs)/graphene nanoribbons (GNRs) nanofibers via electrospinning process. Since PVA polymer could be dissolved in water, our hybrid nanofibers have been made via water‒based electrospinning, which means that toxic solvents like N–Methyl–2–pyrrolidone (NMP) do not need to be used for preparing the electrodes. Furthermore, the PVA polymer as a good dispersant can effectively help to disperse high‒concentrated GNRs (20 mg/ml) under water, which are unzipped from multiwall carbon nanotubes for better dispersion ability. The battery cells using the hybrid PVA/Si/GNRs nanofibers exhibited an initial high discharge capacity of over 5000 mAh/g at 0.1C because of the contribution of well–dispersed GNRs and Si NPs, while only Si NPs have the first discharge capacity of ca. 2500 mAh/g. At even 1C (3.6 A/g), they showed a high reversible capacity of around 1800 mAh/g owing to highly–conductive GNRs within the hybrid nanofibers. Moreover, the nanofibers retained very stable cycle retention of over 90% during 200 cycles. Such excellent cycle retention should be attributed by cross–linked and stabilized PVA nanofibers covering Si NPs, available to not only prohibit the volume expansion but also alleviate the formation of SEI layers. In terms of electrochemical properties, the hybrid nanofibers represented much less charge transport resistance from electrochemical impedance spectroscopy and higher peak current density from cyclic voltammetry than only Si NPs, because the GNRs as electrical conductors in the electrodes must be well–distributed between Si NPs. As a result, we demonstrated an outstanding battery performance through a novel hybrid PVA/Si/GNRs nanofibers directly fabricated via water–based spinning.

References

[1] H. Wu, Y. Cui, Nano Today
2012,
7
, 414.
[2] Wu H.; Chan G.; Choi J. W.; Ryu I.; Yao Y.; McDowell M. T.; Lee S. W.; Jackson A.; Yang Y.; Hu L.; Cui Y. Nature Nanotech.
2012, 7, 310.
The Electrochemical Performances of Metal Ions and F- Co-Substituted Li4Ti5O12
Authors: Kim Jae Hyun , Park Jung Soo , Baek Seong-Ho 
Published: February 2020

The graphite is usually selected as anode material of commercial lithium-ion batteries, because of its large theoretical capacity (372 mAh g-1) and reversible charged-discharge for Li+, but the potential safety problem is dendritic lithium growth on the anode surface during the charging and discharging. Li4Ti5O12 has almost no formation of SEI layer and dendritic lithium growth on the electrode surface during charging/discharging because its high flat operating voltage of about 1.5 V. To overcome the demerit of insulating property of Li4Ti5O12, doping the structure with small amounts of various transition metal ions have been tried.
The investigation of electrochemical performances of Al3+ and F- co-substituted compounds was previously done. But, the electrochemical performance of co-substituted specimen was worse than the Al3+ substituted one.
The electrochemical perfomances of the eight kinds of F- and metal ions (Fe, Mg, Ag, Zn, Sr, Sn Mo, and Co ions) co-doped Li4Ti5O12 specimens were studied. Among them, the cycle retention was best in F- and Co ion co-doped sample. The capacity of F- and Mg ion co-substituted one was largest. The capacity of all the co-substituted samples was larger than pure Li4Ti5O12. The good cycle performance was explained by the relative bonding strength between metal ion and oxygen ion.
Improved Lithium Sulfur Battery Performance through Attaching Nanosilica on the Backside of Nickel Foam
Authors: Cho Sung Ho , Yoon Woo Young 
Published: February 2020

Lithium Sulfur (Li-S) battery has a theoretically high specific capacity of 1675 mAh g-1, which one of the most promising energy source for electric vehicles (EVs), hybrid electric vehicles (HEVs) and energy storage system (ESS). However, Li-S batteries have crucial problem resulting from the polysulfides dissolution which is called ‘Shuttle Effect’. This shuttle effect causes overpotential and lowers its Coulomb efficiency. Also, a loss of active material by dissolution makes capacity fading. So the prevention of the polysulfides dissolution is the main issue of sulfur batteries. To solve the polysulfides dissolution we use nanosilica material on the current collector of cathode. It is reported that nanosilica has a characteristics of absorbing polysulfides. Zhang. et. al reported that they could control the shuttle mechanism by using nanosilica on the separator. However, the polysulfides accumulated on the separator hinder Li ion transport, leading to low capacity values compared to pristine Li-S batteries. In our research, nickel foam based sulfur cathode with silica coated on backside is investigated. Silica on the backside absorbs polysulfides, eventually suppressing the shuttle effect and reducing the quantity of the polysulfides on the separator. As a result, the coulomb efficiency and the capacity of the Li-S battery has increased comparing the uncoated Li-S battery. The examination was conducted by comparing between the pristine and the silica coated sample. Cells were tested at the current densities of 0.1 C rate with limited voltage of 1.8 to 2.8V. The morphology of the samples was observed on a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). The structure of the samples was characterized by X-ray diffraction (XRD) spectroscopy. The result was analyzed by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV).
[1] S.S.Zhang, D.T.Tran, Electrochim. Acta, 114, 296 (2013).
Novel Design of Silicon Electrode Based on Stainless Steel Metal Fibril As Current Collector for Lithium-Ion Batteries
Authors: Song Seonghyun , Kim Chang-Hyeon , Choi Jaecheol , Yeon Subin , Ryou Myung-Hyun , Lee Yong Min 
Published: February 2020

Silicon (Si) has been one of the promising anode materials targeting for the next high capacity lithium-ion batteries (LIBs). Lithium ions are reversibly stored in Si based on an alloy mechanism, and thus Si can possess much higher level of theoretical capacity (4,200mAh/g), over 10 times, compared to that of commercial graphite (372mAh/g) [1]. Unfortunately, however, inherent low electric conductivity and poor cell performance has hindered commercialization of Si for a decade.
In order to solve these drawbacks, nano-sized and nano-structured silicon has been introduced. In this work, we developed novel design silicon electrode based on stainless steel metal fibril. In order to achieve this goal, we introduced 3-D current collectors based on stainless steel metal fibril (SF) to increase free volume within Si anodes [2] Subsequently, Si coated by radio frequency (RF) magnetron sputtering method. Coating thickness and loading amount of Si active material on SF was controlled around 1μm and 0.2mg/cm2, respectively. Electrochemical performance of as-prepared SF based Si anode was evaluated using charge-discharge machine (PNE, Koran). Surface changes of as-prepared Si anodes were monitored by Scanning Electron Microscope (TOPCOM, japan)-Energy Dispersive X-ray Spectroscopy (AMETEK, USA).

References

[1] D.J. Lee et al, Electrochemistry Communications, 34 (2013) 98-101
[2] D.J. Lee et al, Journal of Materials Chemistry A, 10 (2014) 1039

Acknowledgements

This work was supported by the IT R&D program of MKE/KEIT. [10041142, Electrolyte Additive for 200Wh/kg High LIB of High Cycle Life]
Alginate Nanofibers as a Binder in Lithium-Ion Cells
Authors: Dufficy Martin K , Khan Saad A , Fedkiw Peter S 
Published: February 2020

It is well known that the volume expansion upon Li-alloying, followed by pulverization, deleterious side reaction, and electronic isolation limits the commercial use of high-capacity anode materials such as silicon and tin. Despite these challenges, researchers aspire to discover means to integrate high-capacity materials into electrodes. The electrode binder, one of the least investigated components in a lithium-ion battery, is posited as a potential remedy to many of the issues that lead to cell failure. Manipulating the composition and morphology of the binder impacts the longevity of the cell as well as the capacity retention. Here we show that alginate nanofibers as an anode binder can be used to enhance the performance of Si anodes for lithium-ion batteries.
Alginate is an anionic polysaccharide derived from brown algae [1]. Although it has many industrial uses such as a textile processing and a thickening agent in foods, alginate has recently been reported [1] as an eco-friendly alternative to the conventional PVDF binder. Sodium alginate has been shown to protect the active material by forming an inert passivating layer with common organic carbonate electrolyte solvents while providing ample Li conductivity [1]. Recently, our group has shown that alginate nanofibers can be formed via electrospinning alginate-PEO blends [2]. PEO, albeit electrochemically stable, can be leached away to form porous alginate nanofibers (Figure 1). Electrospinning provides a desirable fiber extrusion technique because it allows for a continuous and facile method to produce multi-component nanofibers. The small size scale of these fibers can further enhance the electronic and ionic transport through the cell.
Here we report physical and electrochemical characteristics of alginate fibers as the binding component in both graphite and silicon anodes. X-ray diffractograms and energy-dispersive x-ray spectroscopy are used to determine the phase and location of the electrochemically active materials, respectively. Cyclic voltammetry test are employed to observe reversibility of the cell. Lithium diffusion rates into the anode materials are also determined. Charge and discharge curves demonstrate alginate fibers may be used in lieu of PVDF as a binding material in Li-ion cells.

Figure 1: SEM image showing alginate fibers. The fibers were not sputter-coated and slight charging effects are evident.
[1] I. Kovalenko et al., Science
334, 75 (2011)
[2] C. A. Bonino et al., Carbohydrate Polymers
85, 111(2011)
Synthesis and Electrochemical Performance of Low Surface Area Alloy Anodes for Lithium-Ion Battery
Authors: Zhao Xiuyun , Dunlap Richard A , Obrovac Mark N 
Published: February 2020

Introduction

Alloy negative-electrode materials could significantly increase the energy density of commercial Li-ion batteries [1]. From a practical point of view, alloys prepared by ball milling are inexpensive lithium hosts and easily scalable. However, such alloys typically have small particle sizes and high surface area, increasing their reactivity with electrolyte. Here, we describe a composite alloy material which has been post treated to significantly reduce surface area. The resulting composites have significantly reduced surface area and improved cycling performance over ball milled alloys of similar composition.

Experimental

Alloys were prepared ball milling stoichiometric amounts of Si and Fe. Post-treated alloys were ground and sieved to a 53 μm particle size. Electrodes comprising active material, carbon black and polyimide binder were cycled in 2325 coin-type cells with two Celgard 2300 separators, a lithium foil counter/reference electrode and 1M LiPF6 in EC/DEC/FEC 60/30/10 by volume electrolyte at 30 °C. Cells were cycled at a C/4 rate and trickled discharged to C/20 in a voltage range of 0.005 V-0.9 V. X-ray diffraction (XRD) measurements were collected using a Rigaku Ultima IV diffractometer with a Cu Kαsource. A Phenom G2-pro Scanning Electron Microscope (SEM, Nanoscience, Arizona) was used to study the particle size and morphology of the samples. Surface area was determined by single-point Brunauer, Emmett, and Teller (BET) method using a Micromeritics Flowsorb II 2300 surface area analyzer.

Results

Figure 1 shows the XRD pattern of ball-milled Si/Fe alloy, which consists of XRD peaks from Si, Fe and FeSi2 phases. Figure 2 shows the SEM images of the Si/Fe and post-treated alloy particles. For Si/Fe, many fine particles with a diameter less than 3 μm can be observed along with a few large particles. The particle size range for the post-treated particles is between 10 and 40 μm. BET surface area measurement shows that the post treated particles have a significantly reduced surface area compared to the Si/Fe ball milled alloy (2.6 m2/g for Si/Fe, 0.9 m2/g for post-treated particles), which is consistent with the SEM results.
Figure 3 shows the cycling performance of Si/Fe and the post-treated particles. The post-treated particles have a reversible capacity of 600 mAh/g after the first cycle and good capacity retention. By contrast, the capacity of the ball milled Si/Fe alloy electrode fades gradually during cycling.

Acknowledgements

The authors acknowledge funding from NSERC and 3M Canada, Co. Xiuyun Zhao acknowledges the support from the DREAMS program.

References

[1]. M.N. Obrovac, Leif Christensen, Dinh Ba Le and J.R. Dahn, J. Electrochem. Soc. 154, A849 (2007).
In-Situ Electrochemical Studies of Li-Ion Start-Stop Vehicle Batteries through a Novel Cell Design
Authors: Wang John , Sherman Elena , Soukiasian Souren , Graetz Jason , Tataria Harshad , Verbrugge Mark W 
Published: February 2020

Lithium ion batteries are now used extensively for vehicle traction applications. Because of their high specific power and long usage life, lithium ion batteries are very appealing for power assist vehicular applications. Implementation of Li-ion batteries for start-stop systems is one of the pragmatic approaches being considered for reducing vehicle fuel consumption. During start-stop operation, the engine automatically shuts down when the vehicle comes to stop and then quickly restarts when propulsion is desired by the operator. Such start-stop operations of the vehicle can effectively reduce the amount of engine idling time, leading to fuel savings.
One of the main challenges for start-stop applications is meeting the cold-cranking power requirements at -30oC. Due to the kinetic limitations, pulse power performance of Li-ion batteries drop dramatically at low temperatures. Given the requirement for starting the engine at low temperature, it is typical that the cold cranking power capability determines the module size needed for start-stop systems; and therefore directly impacts the system weight and cost. It is essential to understand the source of the kinetic limitations (e.g. electrolyte resistance, electrode-electrolyte interfacial resistance, or diffusion resistance) and design a system that can dramatically improve the cold cranking power.
In this talk, we demonstrate the implementation of a new cell design to investigate the pulse power performance of LiMn2O4 (LMO) / Li4Ti5O12 (LTO) batteries for start-stop applications. Figure 1 shows the schematic of the cell design; it is composed of four electrodes, with two LTO and two LMO electrodes adjacent to each other. The current collectors are porous, allowing the ions to pass through them. This type of design enables the in-situ investigation of LTO/LTO, LTO/LMO, LMO/LMO cells in a single cell while the neighboring electrodes are used for voltage monitoring. In this report, our focus is to investigate the kinetics of each individual electrode under low temperatures. Using EIS and linear voltage polarization studies, we provide insight on the source of resistance limiting the pulse power capability of the cell at low temperatures (-30oC). We found that electrolyte transport limitations control the cell performance at low temperatures, which directly impacts the cold cranking power.