bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Oil and Water – the Challenge of Developing Separators for Ionic Liquid Electrolytes
Authors: Francis Candice , Sammut Karl , Lammas Andrew , Best Adam Samuel
Published: February 2020

Ionic liquids are without doubt one of the most interesting materials for the replacement of organic solvent based electrolytes for both lithium-ion and lithium metal batteries [1]. Their improved physico-chemical properties, such as negligible vapour pressure, high thermal decomposition temperatures and wide electrochemical window, as compared to traditional battery electrolytes, make them attractive for these devices. However, their relatively high viscosities due to their elevated melting points and lower conductivity at sub-ambient temperatures have proven difficult to overcome without blending them with other organic-based materials.

A further challenge has appeared in recent times as researchers and companies try prototyping devices incorporating ionic liquid electrolytes – suitable separators [2, 3]. Due to the varying hydrophobic / hydrophilic nature and rapidly changing viscosity (as a function of temperature) of ionic liquid electrolytes, the choice of a suitable separator is extremely challenging. Traditional polyethylene and polypropylene separators are typically difficult to “wet” and as such, lead to relatively high internal resistance and low initial capacities as the cell components wet out. In most instances, researchers revert to Whatman glass fibre separators due to the ease of wetting because of the very open pores within the structure.

In this presentation, we will detail some of the approaches to developing separator materials specifically for ionic liquid electrolytes by previous workers and contrast and compare this with our own efforts. We will detail the impact of the choice of base separator material on wettability and device performance and then examine various methodologies used to enhance separator performance.

References

1. A. Lewandowski and A. Swiderska-Mocek, Journal of Power Sources
194: 601-609 (2009)

2. C. S. Stefan, D. Lemordant, B. Claude-Montigny and D. Violleau, Journal of Power Sources
189(2): 1174-1178 (2009)

3. M. Kirchhöfer, J. von Zamory, E. Paillard and S. Passerini, International Journal of Molecular Sciences
15(8): 14868-14890 (2014)

Acknowledgements

The authors acknowledge funding support provided by the ARC Research Training Centre for Naval Design and Manufacturing and the CSIRO Manufacturing High Performance Metal Industries Program.
Design and Syntheses of New Dipolar Organic Aprotic Solvents for 5V Lithium-Ion Batteries
Authors: Flamme Benjamin , Haddad Mansour , Phansavath Phannarath , Vidal Virginie , Chagnes Alexandre
Published: February 2020

The development of new technologies for electrochemical energy storage is one of the main challenge of the next decades. Many hopes now rely on lithium-ion batteries (LiBs) that have invaded the market of laptops and which appear to be the best choice with the short time for electric vehicles, and perhaps for network applications (electricity storage from wind turbines or solar cells for example). Many works concern the search for cathodes with high-energy density but only few studies focus their research on the synthesis of new dipolar aprotic organic solvents for LiBs electrolytes. Thus, there is a need to deviate from traditional approaches for identifying new electrolytes stable to high voltage that are based on "Trial and Errors" approaches. To alleviate this issue, a collaborative project funded by the French Research Agency (ANR) and reuniting multidisciplinary research groups that combines highly and specific complementary skills in organic chemistry, electrochemistry, solution chemistry, thermodynamics and theoretical chemistry was launched in October 2014. The present paper aims at presenting recent advances from this group on the design of new electrolytes for high-voltage batteries.

After a brief critical review of literature data about physicochemical and electrochemical properties of electrolytes for lithium-ion batteries in order to highlight the lack of homogeneity, new data will present data in order to get a homogenized database for performing QSPR calculations. In particular, this database will include a set of 20 new dipolar aprotic organic solvents synthesized and characterized in the present work. Based on the trend between the chemical structure of solvents and their physicochemical and electrochemical properties deduces from the above-mentioned database, the formulation of new electrolytes for 5V lithium-ion batteries will be presented. A particular attention will be paid on the anodic stability of these electrolytes at a NMC electrode and their behavior at a graphite electrode.
Numerical Study of Striped Diffusion during Lithiation of Tin Oxide Anodes
Authors: Ramasubramanian Ajaykrishna , Yurkiv Vitaliy , Najafi Ali , Nie Anmin , Khounsary Ali , Shahbazian-Yassar Reza , Mashayek Farzad
Published: February 2020

Tin oxide (SnO2) is widely recognized as a promising negative electrode material for high capacity lithium (Li)-ion batteries due to its high-energy density. Recent experiments1–3 using high-resolution Transmission Electron Microscopy (TEM) show that the lithiation process in SnO2 nanowires occurs in two stages. Initially, rapid Li diffusion occurs from one end of the nanowire to the other through narrow stripes along the electrode. This stage is followed by a second stage where Li diffuses through the bulk at a much lower speed throughout the electrode leading to amorphization. In order to understand this complex phenomenon we have employed a finite element (FE) modeling in conjunction with previous in-situ TEM experiments3 to study the lithiation of SnO2 nanoelectrodes. In the experimental work, SnO2 nanowire lithiation process was characterized using in-situ TEM where the SnO2 nanowire was placed on the negative side of the in-situ setup and was brought in direct contact with the Li source.1

The idea behind FE in this context is to formulate the lithiation process using physical models which provide results consistent with experimental observations. The model is based on the understanding that in SnO2 nanowire a slip plane is created due to non-perfect contact of the source or defects and the stress at the slip planes leads to significantly higher diffusion coefficient.1

The developed constitutive model which has been implemented in FE, captures the formation of striped diffusion regime and corresponding electrode’s expansion during the lithiation of SnO2. In particular, the model incorporates the formation of stripes by using a variable nonlinear diffusivity coefficient which is a function of the concentration-dependent stress. The structural changes associated with the Li diffusion/intercalation in the electrode geometry are modeled using a 2D plane strain assumption and linear elastic material. The results from the model show a clear formation of striped diffusion regime due to the induced stresses, at low concentrations of Li. This results in a small strain of 10% within the nanowire and is followed by a bulk diffusion and expansion at higher concentrations. Thus, the simulations allow for the spatiotemporally resolved prediction and analysis of Li diffusion/intercalation and its influence on the electrode performance under the realistic operation conditions.

References

1. A. Nie, L. Y. Gan, Y. Cheng, H. Asayesh-Ardakani, Q. Li, C. Dong, R. Tao, F. Mashayek, H. T. Wang, U. Schwingenschlgl, R. F. Klie, and R. S. Yassar, ACS Nano, 7, 6203–6211 (2013).

2. L. Q. Zhang, X. H. Liu, Y. C. Perng, J. Cho, J. P. Chang, S. X. Mao, Z. Z. Ye, and J. Y. Huang, Micron, 43, 1127–1133 (2012).

3. J. Y. Huang, L. Zhong, C. M. Wang, J. P. Sullivan, W. Xu, L. Q. Zhang, S. X. Mao, N. S. Hudak, X. H. Liu, A. Subramanian, H. Fan, L. Qi, A. Kushima, and J. Li, 330, 1515 LP – 1520 (2010).
PEDOT/PSS-Coated Porous Silicon as anode of lithium-Ion Batteries
Authors: Wang Yadong , Zhang Yue
Published: February 2020

Silicon (Si) has been regarded as the most promising anode material of lithium-ion batteries (LIBs) because of its super-high theoretical capacity. However, dramatic volume variations during cycling of lithiation/de-lithiation will trigger electrode pulverization, disruption and structural failure of solid electrolyte interface (SEI), and the according poor cycling performance as well. 

Nanolization, composite with buffer material and special microstructure design of silicon based materialsare the most common strategy to alleviate the volume change effects[1-2]. The given electrode material design are usually with high-cost, complicated process and low volume specific capacity. 

In this work, the porous Si in the size of several micrometers are synthesized by Metal-assisted chemical etching(MaCE) method, in which micro-sized Si particles is locally etched in the isopropyl alcohol solution containing AgNO3 and HF[3]. The resulting porous Si is subsequently coated with a thin PEDOT/PSS layer. PSS is used in dispersing porous Si particles well into an aqueous solution and then tethering EDOT monomer onto the surface of porous Si particles to facilitate the formation of a uniform PEDOT coating [4].

Fig. 1. SEM image of porous Si (a) and porous Si@PEDOT/PSS(b).

Figure 1 shows that the pore size in the as synthesized silicon particles is below 200nm, and the PEDOT/PSS is uniformed coated on the silicon particle surface. This unique micron sized core-shell structure is considered to contribute to cycle stability and rate capability. The micron size silicon particles will help the realization of favorable volume specific capacity. The suitable sized pores in the silicon will be enough to accommodate the volume change resulting from lithiation. And the PEDOT/PSS coating is used to shield the silicon from the direct contact to electrolyte and inhabit the repeated rupture and reconstruction of SEI during volume change charge/discharge cycling. The detailed electrochemical performance of this silicon electrode material will be reported in meeting poster session. 

Acknowledgement Financial support by the National Science Foundation of China (21473128 and 21373154) is gratefully acknowledged.

References

[1] J. Zhang, C. Zhang, et al., Nanoscale Res. Lett.10 (2015)395.

[2] B. Wang, X. Li, et al.,Nano Lett. 13 (2013) 5578.

[3] Chang C, Liu Y, Chen C. Surface and Coatings Technology, 303, 232, 2016.

[4] Chen L, Yuan C, Dou H, et al. Electrochim. Acta, 54, 2335(2009).

Figure 1
Analysis of the Synergic Effects in LiFePO4/Li2CuO2 Cathode Blends for Li Ion Batteries Via Electrochemical and EPR Experiments
Authors: Juarez-Yescas Carlos , Guzmán Gregorio , Ramos-Sánchez Guadalupe , Aguilar-Eseiza Noe , Ramirez-Rosales Daniel , González I.
Published: February 2020

Much of the focus in improving the specific energy in Li-ion batteries is centered on the cathode, specifically designing new active materials; moreover, a promising alternative is the use of ‘blended’ electrodes, which are comprised of at least two different active materials working synergically. Although the principle behind these collaborative properties is not yet fully understood, the reasoning behind this proposal is based on the correlation of property-function of each component. Blending two or more cathode materials can result in a cathode with fewer of the drawbacks than the parent materials, allowing for an optimized performance compared to what would be possible with the individual materials. LiFePO4 and LiCoO2 are two of the most commercial cathode materials because of their high stability and adequate specific capacities, but are unable to meet the higher capacity demands of newer technologies. Li2CuO2 is a promising cathode material with a specific capacity of 490 mAh/g, notwithstanding it undergoes irreversible phase changes during cycling, resulting in poor cyclability and a specific capacity far lower than its theoretical capacity1. The objective of this study is to take advantage of the stability of commercial active materials, such as LiFePO4 and LiCoO2 to stabilize the high capacity Li2CuO2 phase for practical use. Preliminary results of the Li2CuO2/LiFePO4 blends have shown an improved capacity, albeit still below the theoretical capacity of Li2CuO2, and a slight improvement with respect to the cyclability. The method used to blend these materials as well as the inclusion of the conductive and binding additives and the order of addition during the blending have all shown to affect the battery’s performance. Electron Paramagnetic Resonance (EPR) experiments have shown that electrodes blended with a ball mill presumably lead to the formation of stable oxygen vacancies which have an effect on the synergy which is not observable in pure Li2CuO2 blended cathodes or physical mixtures. Additionally, the presence of the conductive and binding additives during the blending process appear to result in a more homogenous mixture, preventing the reversion of Li2CuO2 into its precursors during the blending process, thus promoting higher specific capacities. The authors thank CONACyT-SENER- 416 Sustentabilidad No. 245754 for the financial support.

1. G. Ramos-Sanchez et al., Solid State Ionics, 303, 89–96 (2017).
Understanding the Solution Chemistry of Coprecipitation and the Homogeneity of the Precipitated Particle to Achieve Excellent Electrochemical Performance of Transition Metal Oxide Cathode Materials for Lithium-Ion Batteries
Authors: Dong Hongxu , Koenig Gary , Wang Anny , Barron Alexandra
Published: February 2020

Coprecipitation is a widely used method to synthesize multicomponent transition metal cathode materials for lithium-ion batteries. The major advantages of the coprecipitation method are the homogeneity of different transition metal ions within the precipitated particles, and the tunability of the particle morphology through control of the reaction conditions. In this poster, we will show our recent results related to the coprecipitation of precursors for lithium-ion active materials, as well as their conversion to cathode materials. Solution chemistry was chosen to achieve explicit control over particle composition, and a variety of characterization methods including electrochemical evaluation were utilized to demonstrate the structure and performance of the synthesized materials. As an example material, we will use high voltage spinel LiMn1.5Ni0.5O4 synthesized from manganese and nickel blend oxalate precursor. We will present insights into nucleation and particle growth processes during particle formation in the coprecipitation reaction. We will also demonstrate the level of homogeneity that coprecipitation is able to achieve relative to traditional solid-state methods.
Stabilizing High-Voltage and High-Capacity Cathode-Electrolyte Interface Using Functional Electrolyte Component
Authors: Lee Hee-Yeol , Pham Hieu Quang , Kwon Young-Gil , Hwang Eui-Hyung , Song Seung-Wan
Published: February 2020

Li- and Mn-rich xLi2MnO3
∙(1−x)LiMO2 (M = Mn, Ni, Co) layered oxides cathode materials are known to exhibit high specific capacities ≥ 250 mAhg−1 on the high-voltage operation above 4.6 V vs. Li/Li+,1,2 which are considered as promising cathode materials for achieving advanced high-energy density lithium-ion batteries. The capacity of these cathode materials can increase by increasing the charge cut-off voltage. However, the limited anodic instability of the conventional carbonate-based organic electrolytes above 4.2 V vs. Li/Li+ makes the attainment of high capacity from Li-rich layered oxide cathode material difficult. In order to mitigate the electrolyte issue, we have been developing new functional electrolyte components with high anodic stability above 4.6 V to stabilize high-voltage interface between Li-rich layered oxide cathode and electrolyte.1,2 High-voltage electrochemical and cathode-electrolyte interfacial studies and their correlation to high-voltage cycling performance would be presented in the meeting.

Acknowledgements

This research was supported by Ministry of Trade, Industry & Energy (R0004645) and Creative Human Resource Development Consortium for Fusion Technology of Functional Chemical/ Bio Materials of BK Plus program by Ministry of Education of Korea.

References

1. H. Q. Pham, K.-M. Nam, E.-H. Hwang, Y.-G. Kwon, H.-M. Jung, S.-W. Song, J. Electrochem. Soc., 161, A2002 (2014).

2. H. Q. Pham, E.-H. Hwang, Y.-G. Kwon, S.-W. Song, J. Power Sources, 323, 220, (2016).
Micron-sized Secondary Silicon Spherical Composite for Practical Li-ion Batteries
Authors: Feng Kun , Liu Wenwen , Li Matthew , Zhang Yining , Chen Zhongwei
Published: February 2020

The ever-growing demand for smaller batteries with higher energy density and longer life cycle has triggered research interest on metal alloy materials as an anode for Li-ion batteries (LIBs) in broad applications such as electric vehicle and portable electronics, because metal alloys usually possess much higher theoretical gravimetric and volumetric capacities than those of graphite. Si has been considered as potential candidate due to its highest capacity (4200 mAh/g, according to a state of Li4.4Si), low price and high abundancy. However, progressively large volume change during the charge and discharge reactions hinders Si from being commercially used. We have successfully developed a micron-szied secondary Si-based composite (MSC), with Si nanoparticles (diameter ~70 nm, commercial) embedded in a porous conductive network constructed with conductive carbon and binder materials. Si NPs were purchased in bulk and used as received. The MSC anode exhibited an initial CE of 81%, and >99.8% thereafter. The volume expansion of Si has been effectively limited inside the secondary particle, avoiding damage to the structure of electrode. As a result, the MSC electrode delivered excellent cycling stability with 8% loss over 500 cycles at a rate of 0.5C. Considering the advantages of micron-sized composite, this material could be of interest in the application of real-life LIBs.
Recovering Lost Capacity of Aged LiMn2O4 from Commercial Aqueous Battery By Direct Relithiation through Hydrothermal Treatment
Authors: Wang Han , Whitacre Jay
Published: February 2020

So far, most industrial Li-ion battery recycling processes are conducted using the following two methods: hydrometallurgical method and pyrometallurgical method that completely decompose the electrodes to elemental constituents. Although improvements in term of product quality and process complexity have been made over the industrial Li-ion battery recycling processes, they are still considered to be process-intensive and energy-consuming, while also wasting the initial energy embodied during the production of the cathode materials system. 1-2

In this work, we demonstrate a novel approach to recycle LiMn2O4 as used in aqueous electrolyte batteries. LiMn2O4 cathode material was extracted from commercial aqueous battery that was cycled over several thousand cycles.3 The aged LiMn2O4 cathode material showed lower specific capacity than its uncycled counterpart. The material was then recycled by reacting it with a lithium source through two different methods: (a) solid-state reaction and (b) hydrothermal reaction. We recycled LiMn2O4 cathode material by directly relithiating the aged LiMn2O4 with a lithium source and without breaking it down into elemental form and re-synthesizing it. The advantages of this method are three folds: (1) it reduces usage of high temperature process to break down cathode materials into element form or other compound, (2) it decreases complexity of chemical process, and (3) it reduces usage of different chemicals for element refinement. This study shows the feasibility of recycling aged LiMn2O4through a simple and energy-efficient approach and recovering its lost capacity.

The outcomes of the using these two recycling methods are compared in term of phase purity, morphology, and electrochemical capacity. Our results show that the hydrothermally recycled product had superior phase purity and electrochemical capacity, and compared favorably even with uncycled material

The effect of process parameters in the hydrothermal process such as molar ratio of reactants, reaction temperature and reaction time is discussed and rated. The results show that by adjusting these process parameters, we are able to regenerate aged LiMn2O4through a simple hydrothermal reaction.

Reference:

1. Xu, J.; Thomas, H. R.; Francis, R. W.; Lum, K. R.; Wang, J.; Liang, B., A review of processes and technologies for the recycling of lithium-ion secondary batteries. J Power Sources
2008,
177(2), 512-527.

2. Georgi-Maschler, T.; Friedrich, B.; Weyhe, R.; Heegn, H.; Rutz, M., Development of a recycling process for Li-ion batteries. J Power Sources
2012,
207, 173-182.

3. Whitacre, J. F.; Shanbhag, S.; Mohamed, A.; Polonsky, A.; Carlisle, K.; Gulakowski, J.; Wu, W.; Smith, C.; Cooney, L.; Blackwood, D.; Dandrea, J. C.; Truchot, C., A Polyionic, Large-Format Energy Storage Device Using an Aqueous Electrolyte and Thick-Format Composite NaTi2(PO4)(3)/Activated Carbon Negative Electrodes (vol 3, pg 20, 2015). Energy Technol-Ger
2015,
3 (8), 796-798.

Figure 1
Cycling Porous Silicon with Lithium Iron Phosphate for High Performance Li-Ion Batteries
Authors: Song Farren Botao , Dhanabalan Abirami , Karulkar Mohan , Biswal Sibani Lisa
Published: February 2020

Silicon has drawn significant attention as an anode material for lithium ion batteries due to it significant capacity over carbon anode materials. Much of the literature as focused on cycling silicon with lithium-metal as the counter-electrode, which serves as an infinite source of lithium ions. We have recently shown that porous silicon is able to cycle at 1000 mAh/g at 1C for 600+ cycles against a lithium-metal counter-electrode. Here we will present the practical applicability and cycling performance of porous silicon with commercially available lithium-iron phosphate (LFP) cathodes. Having excess anode capacity is the standard widely used in industry with graphite-based lithium ion batteries to prevent lithium plating issue. However, we have observed that our porous silicon exhibits longer cycle life when the cathode capacity is in excess. This is likely due to the large consumption of lithium-ions during the formation of solid-electrolyte interface (SEI) layer. Our experiments will show that two different cycle performance based on either the anode or cathode in excess for the purpose of assembling a full-cell battery. Furthermore, a three-electrode test cell is used to monitor the I-V curves for each electrode independently to determine if lithium plating or other electrode degradation mechanisms occur.
Single-Frequency Battery State-of-Health Diagnostic for LiFePO4 Cells in 4P1S Array
Authors: Huhman Brett
Published: February 2020

The determination of the state of health of a battery cell is of critical importance when high discharge rates are necessary (>10C). The US Naval Research Laboratory (NRL) has performed work previously to determine a single frequency using Electrochemical Impedance Spectroscopy (EIS) that can describe the state of health for a single LiFePO4 cell. However, a battery system that can be used in the field requires multiple cells in parallel. Thus, NRL has expanded the previous work to evaluate four cells connected in parallel. The first array was constructed of cells carefully selected for the same equivalent series resistance (ESR) at 1 kHz, the same capacity to within 25 mAH, and nearly identical EIS spectra from 1 kHz – 1 Hz. Four replicant arrays were subsequently constructed of cells with identical ESR and capacity to represent the battery pack construction by a manufacturer. Each array will be pulse discharged at 10C (26 A) using a discharge profile identical to a pulsed power system at NRL. Results from the lifetime testing will be presented, with an electrochemical model and a post-mortem analysis of the battery film surfaces.
The Influence of Surface Morphology of Copper Foils on the Efficiency of Lithium Ion Batteries
Authors: Yen Chih-Han , Dow Wei-Ping
Published: February 2020

For the increasing demand of portable electronic devices and electric vehicles, lithium-ion batteries (LIBs) become a fast-growing and crucial technology because of high power density and light weight. To manufacture LIBs with good performance and appropriate cost, the components constituting LIBs should not only possess excellent quality and reliability but also be cost-effective. The current collector in the negative electrode of LIBs is an indispensable material, and the most commonly used material is copper foil with optimal quality. Currently, the mainstream copper foil adopted in LIBs is manufactured by rolling, since the rolled copper foil provides smooth surfaces on double sides (Rz < 1 μm), which ensure good capacity retention rate. However, the rolled copper foil is much more expensive than electrodeposited (ED) copper foil, especially for ultra-thin one (< 8 μm), since it requires more times of rolling and annealing. Consequently, the manufacture of thin ED copper foil with optimal properties is a critical issue to lower the cost of LIBs. Unfortunately, the ED copper foil produced by conventional method is not applicable in LIBs industry, and the main reason is that the surface roughness of the ED copper foil on both sides is remarkably different, which affects the capacity retention rate of LIBs [1]. In addition, the actual mechanism of how the surface morphology influencing the performance of LIBs has been not studied yet. In this work, we produced an 8 μm thick ED copper foil with different surface morphology by adding specific additives in the plating bath, including very low profile copper foil (Rz < 0.1 μm) or copper foil with pinholes on the surface, and comparing the performance of these ED copper foils with a conventional ED copper foil and a commercial rolled copper foil. The surface morphology and structure of each copper foil was examined by SEM, AFM, and XRD. Most importantly, carbon based material would be coated on these copper foils and then sealed in coin cells to examine the electrochemical behavior and efficiency of lithium ion coin cells. Accordingly, the relationship of the active carbon material and the surface morphology of the negative current collector was clarified.

Reference

:

1. Kazuo Kondo, Rohan N. Akolkar, Dale P. Barkey, Masayuki Yokoi, Copper Electrodeposition for Nanofabrication of Electronics Devices, p. 243, Springer-Verlag New York (2014).
(Invited) Interface Engineering and Characterization in Lithium-Garnet Batteries
Authors: Hu Liangbing
Published: February 2020

Solid state electrolytes are known for non-flammability, dendrite blocking, and stability over large potential windows. Garnet-based solid-state electrolytes have attracted much attention for their high ionic conductivities and stability with lithium metal anodes. However, high interface resistance with lithium anodes hinders their application to lithium metal batteries. In this talk, I will discuss various interface engineering materials for Li metal and Garnet, including ALD Al2O3, PECVD Si, metals and alloys (Nature Materials 2016; JACS 2016; Advanced Materials 2017; Science Advances 2017).

I will also discuss our recent progress on cathode-garnet interface engineering. I will also discuss our recent achievement on in-situ neutron depth profiling technique in understanding Li-garnet and CNT-garnet interfaces.
Titanium Dioxide Coated Graphite Anode Materials with Fast Charging Capability for Lithium-Ion Battery
Authors: Kim Dae Sik , Yoo Hyundong , Jeong Goojin , Kim Hansu
Published: February 2020

Along with the rapid growth in robots, mobile electronics and electric vehicles (EVs) technology, lithium ion batteries (LIBs) are facing several technical challenges such as higher energy density and fast charging capability. Graphite, currently used anode materials for LIBs, has technical limitations to be used for robots, mobile electronics and EVs in terms of energy density and fast charging capability. To solve these problems, various anode materials have been suggested for alternative graphite anode material. In this work, titanium dioxide coated graphite was investigated as an anode material with fast charging capability for LIBs. The proposed core-shell structure, titanium dioxide coated graphite anode electrode exhibited an excellent rate capability of 96.4 % of the capacity retention at a rate of 10 C compare to that tested at a rate of 0.2 C without any degradation of reversible capacity and long-term cycle performance. The characterization, microstructure and electrochemical properties of the titanium dioxide coated graphite will be discussed in more detail.
(Battery Division Technology Award Address) Progress in High-Capacity Gradient Layered Li[NixCoyMnz]O2 Cathodes for Lithium-ion Batteries
Authors: Sun Yang-Kook
Published: February 2020

Rechargeable lithium-ion batteries have great potential as a new large-scale power source for electric vehicles (EVs) due to their high energy density, high voltage, and long cycle life. However, commercialization of these batteries for the automobile industry requires further improvements in energy density and safety. Meeting this challenge has centered on finding new high-capacity electrode materials, especially cathode materials. A layered lithium transition metal oxide, Li[NixCoyMnz]O2 (x+y+z = 1) have been extensively utilized and studied as cathode materials for lithium-ion batteries due to their high capacity [1]. It is well known that an increase of the Ni content in the Li[NixCoyMnz]O2 results in an increase of capacity and total residual lithium content, but a decrease in capacity retention and safety [2]. To resolve the aforementioned drawbacks and to overcome the inherent chemical instability of Ni-rich layered cathodes and to improve capacity retention, we have hybridized Ni-rich and Ni-deficient Li[NixCoyMnz]O2 cathodes at the particle level by establishing concentration profiles within a single particle such that the Ni-rich center maximizes the capacity while the Ni-deficient particle surface ensures high thermal and structural stability in the form of a core-shell (with gradient) [3], full concentration gradient (FCG) [4], and two-slope full concentration gradient (TSFCG) lithium nickel-cobalt-manganese oxide [5]. In addition to increasing the structural stability, Al was incorporated into the FCG and TSFCG cathodes [6]. All the hybridized Li[NixCoyMnz]O2 cathodes demonstrated better electrochemical and thermal properties than their corresponding convention Li[NixCoyMnz]O2 cathodes without concentration (Figure 1).

Reference
s

J. Katana Ngala, et al, J. Mater. Chem. 14, 214-220, 2004.

H.-J. Noh, et al, J. Power Sources, 233, 121-130, 2013.

Y.-K. Sun, et al, Nat. Mater. 8, 320-324, 2009.

Y.-K. Sun, et al, Nat. Mater. 11, 942-947, 2012.

B.-B. Lim, et al, Adv. Fun. Mater. 25, 4673-4680, 2015.

U.-H. Kim, et al, Adv. Energy Mater. 6, 1601417, 2016.

Figure 1. SEM and TEM images of hybridized Li[NixCoyMnz]O2 cathodes and their cell performances.

Figure 1
Low-Platinum Electrocatalysts for the Oxygen Reduction Reaction at Fuel Cell Cathodes
Authors: Yusuf Maha
Published: February 2020

Low-Platinum electrocatalysts for the Oxygen Reduction Reaction at fuel cell cathodes

Maha Yusuf+, Drew Christopher Higgins+, John Xu++, Yongmin Kim++, Tanja Graf+++, Thomas D. Schladt+++, Thomas F. Jaramillo+, Friedich B. Prinz++

+

Department of Chemical Engineering, Stanford University, Stanford, California, 94305, USA

++

Department of Mechanical Engineering, Stanford University, Stanford, California, 94305, USA

+++

Volkswagen Group Research, Wolfsburg, 38436, Germany
 

Low-temperature fuel cells are a promising technology that converts clean and sustainable carbon-free fuels to electrical power. They are suitable for a wide-range of applications including in the transportation sector to grid-scale power generation. One of the major limitations in fuel cell technologies is the efficiency loss at the cathode due to the kinetically sluggish oxygen reduction reaction (ORR).[1] Currently, Pt-based electrocatalysts are the most commonly used catalysts at the fuel cell cathode. However, the scarcity, high cost, and the sluggish ORR kinetics on Pt catalysts drive the need to develop alternative catalytic Pt-based electrocatalysts with better mass activity, and durability to improve the performance and lower the cost of fuel cells.[2-3]

We have developed sputter deposition techniques to fabricate Pt and Pt-alloy based electrocatalysts with reduced precious metal contents. We particularly aim to engineer the structure, surface chemistry, and catalyst-support interactions to achieve high Pt-based mass activities and catalyst durability. In this study, we focus on leveraging the ability of sputter deposition to achieve low-loadings of Pt, with the ability to achieve control over their thicknesses and compositions [4-5]. The sputter deposited Pt-based catalysts are characterized by various techniques such as X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and inductively coupled plasma mass spectrometry. The catalysts are rigorously evaluated for both electrochemical oxygen reduction reaction activity, and durability using the rotating-disk electrode (RDE) technique. Our initial electrochemical testing results are promising, and show mass activities that already exceed the DOE’s 2020 target criteria of 0.44 A/mgPt
6.

References:

Adina Morozan, Bruno Jousselme, Serge Palacin, Energy Environ. Sci., 2011
, 4 (1238-1254).

2. A. Brouzgou, S.Q. Song, P. Tsiakaras, Appl. Catal., B, 2012, 127 (371-388).

Haifeng Lv, Dongguo Li, Dusan Strmcnik, Arvydas P. Paulikas, Nenad M. Markovic, Vojislav R. Stamenkovic, Nano Energy, 2016
, 29 (149-165).

Ryan O’Hayre, Sang-Joon Lee , Suk-Won Cha , Fritz.B Prinz, J. Power Sources,
2002
, 109 (483-493).

Ikwhang Chang, Seunghee Woo, Min Hwan Lee, Joon Hyung Shim, Yuanzhe Piao, Suk Won Cha, Appl. Surf. Sci.,
2013
, 282 (463-466).

U.S. Department of Energy’s Multi-Year Research, Development, and Demonstration Plan 2016. Source: https://energy.gov/sites/prod/files/2016/10/f33/fcto_myrdd_fuel_cells.pdf
Electrochemical Oxidation of Methane on Metal Catalysts
Authors: Ataee-Esfahani Hamed , Chen Dejun , Tong YuYe
Published: February 2020

Methane is the major component of natural gas and it is considered as an important feedstock in petrochemical industry for producing value-added chemicals. The current industrial processes have low selectivity and require conditions of high temperature and pressure for production of synthesis gas. Therefore, developing new methods for direct conversion of methane to methanol or higher hydrocarbons is necessary. Among the possible game-changing new chemistries, the electrochemical approach has its own advantages for both practical applications and fundamental studies and therefore represents emerging alternative opportunities to the conventional steam reforming and combustion of methane. This is because as electrochemical reactions are driven by either potential or current, they can most likely take place at room or mildly high temperature (<100 °C). Moreover, as the potential or current can be precisely controlled, so can be the electrochemical reactions, which is ideal for in situ mechanistic studies.

Here, we examined several metal-based materials as electrocatalysts for methane electro-oxidation in CH4-saturated aqueous solution using Cyclic Voltammetry and Chronoamperometry methods. The in situ SEIRAS (Surface Enhanced IR Reflection Absorption Spectroscopy) spectra recorded during the Chronoamperometry measurement of CH4 oxidation was used to investigate the intermediates and products on catalyst surface. Our findings confirms that redox chemistry of metals with more than one oxidation state can be utilized to generate active oxygen species (e.g. O2
-, O-, O2
2-) on the surface and facilitate efficient oxidation of methane. We will also compare the electrochemical oxidation of methane on these metal-based catalysts.

References

1. J. Baltrusaitis, I. Jansenc, J. D. Schuttlefield Christus, Catal. Sci. Technol., 2014, 4, 2397-2411.

2. K. Ogura and K. Takamagari, Nature, 1986, 319, 308–308.

3. B. Lee, Y. Sakamoto, D. Hirabayashi, K. Suzuki, T. Hibino, Journal of Catalysis, 2010, 271, 195–200.
Composition Dependence of Physical Constants of Binary Solvent Mixtures
Authors: Nambu Noritoshi
Published: February 2020

The relative permittivity is a measure of the solvent’s ability to insulate opposite charges from each other and has a very significant effect on the strength of the interactions between ions. We have investigated the relative permittivities, ε
r sln, and excess relative permittivities, ε
r sln
E, of aqueous and nonaqueous mixtures as a function of the composition at 25 ºC. Experimental data were fitted with the Redlich-Kister equation. We found the values of three coefficients (a
0, a
1, and a
2) in the Redlich-Kister equation. We explained the deviation from the ideal solution in terms of the magnitude of the coefficient a
0. a
0 is a dominant factor governing the Redlich-Kister equation. The decrease in a
0 made a plot of ε
r sln vs. x
2 close to a straight line, which might correspond to the ideal solution. The cohesive forces between dissimilar components might result in the increased effective dipole moment and, consequently, in the small negative value of a
0. The amount of the cooperative orientation polarization of a water (W)−2,2,2-trifluoroethanol (TFE) binary mixture was larger than that found for a W−ethanol (EtOH) binary mixture. The effective dipole moment of an ethylene carbonate (EC)−dimethyl carbonate (DMC) binary mixture was increased as compared to those found for EC−ethyl methyl carbonate (EMC) and EC−diethyl carbonate (DEC) binary mixtures.
(Invited) New Photoanode Materials for Photoelectrochemical Water Splitting
Authors: Yan Yanfa
Published: February 2020

The direct photoelectrochemical (PEC) splitting of water into hydrogen and oxygen remains a promising route for producing sustainable and renewable hydrogen fuel. PEC devices use both photocathodes for the hydrogen generation (p-type semiconductors) and photoanodes for the oxygen evolution (n-type semiconductors), respectively. From chemical stability concerns, n-type metal oxides and p-type non-metal oxides are the desirable photoelectrodes. Unfortunately, none of the current existing metal oxides have demonstrated high solar-to-hydrogen conversion efficiencies under visible light irradiation, due largely to the fact that most metal oxides have too large bandgaps to effectively absorb the main portion of the sunlight spectrum, i.e., visible light. It is essential to engineer the bandgaps of metal oxides for the applications of PEC water splitting. For p-type photocathodes, most considered materials such as CuInS2, Cu(In,Ga)Se2, CuZnSnS4 (CZTS) and WSe2 have bandgap not wide enough or have poor performance when their bandgaps are widened. In this talk, I will present our recent results on two new PEC materials, one metal oxide (barium bismuth niobate) and one non-metal oxide (copper barium tin sulfide). Through density-functional theory (DFT) and experimental synthesis, we demonstrate a new approach to effectively engineer the bandgap of barium bismuth niobate double perovskites (Ba2Bi1+xNb1-xO6), i.e, varying the composition. We find that the film with the composition of Ba2Bi1.4Nb0.6O6 forms single pure phase and exhibits a nearly direct bandgap of about 1.64 eV, which is small enough to absorb visible light at wavelengths below 756 nm. For copper barium tin sulfide (CBTS), our DFT calculations indicate that it exhibits much better defect tolerance than CZTS. Our preliminary results show a saturated photocurrent of ~11 mA cm-2 were reached at -0.55 V vs RHE in a neutral electrolyte.
(Europe Section Heinz Gerischer Award Address) TiO2-Based Visible Light Photocatalysts Based on Interfacial Charge Transfer Process
Authors: Hashimoto Kazuhito
Published: February 2020

TiO2 is known as an efficient photocatalyst and is well studied aiming for environmental and energy application. However, TiO2 absorbs only UV light and thus its application had been limited. We recently demonstrated that the surface modification of TiO2 with Cu(II) or Fe(III) nanoclusters produced a new optical absorption in the visible light region. We also found that those surface modified TiO2s show an efficient visible-light-sensitivity in photocatalysis under ambient conditions. Its reaction mechanism can be explained as follows. In the case of Cu(II) nanocluster-grafted TiO2 (Cu(II)-TiO2) for example, electrons in the valence band (VB) of TiO2 are excited to the Cu(II) nanoclusters under visible-light irradiation through an interfacial charge transfer (IFCT) process. The introduction of excited electrons into the Cu(II) nanoclusters leads to the formation of Cu(I) species, which efficiently reduce oxygen molecule through two-electron process. In other words, Cu(II) nanocluster serves as a multi-electron catalyst for molecular oxygen reduction reaction. In addition, during the IFCT process, holes are generated in the deep VB of TiO2 and are used for the decomposition of organic compounds. Thus, these nanocluster-modified TiO2s show very strong oxidation power even under visible light excitation and are promising materials for visible-light-sensitive photocatalytic applications under ambient conditions.

In this lecture, I will review our studies on these IFCT-based TiO2 visible light sensitive photocatalysts, and also show the results of their demonstration tests obtained in some public spaces such as airports and hospitals towards anti-bacterial and anti-virus building material application..

References

1. J. Am. Chem. Soc. 2007, 129, 9596. 2. Chem. Phys. Lett., 2008, 457, 202. 3. J. Phys. Chem. C., 2009, 113, 10761. 4. J. Am. Chem. Soc. 2010, 132, 6899. 5. J. Am. Chem. Soc. 2010, 132, 15259. 6. Chem. Mater. 2011, 23, 5282. 7. J. Phys. Chem. C 2009, 113, 10761. 8. J. Hazard. Mater. 2012, 235-236, 265. 9. ACS Nano 2012, 6, 1609. 10. J. Am. Chem. Soc. 2013, 135, 10064. 11. J. Mater. Chem. A 2014, 2, 13571. 12. ACS Nano 2014, 8, 7229. 13. J. Mater. Chem. A 2015, 3, 17312. 14. J. Phys. Chem. Lett. 2016, 7, 75.
Photoelectrochemical Water Splitting of Metal Oxide Photoanode Enhanced with a Cerium(III/IV) Redox Mediator
Authors: Bright Joeseph , Wu Nianqiang
Published: February 2020

Photoelectrochemical (PEC) water-splitting remains a promising sustainable technique for hydrogen generation. However, existing photoanode materials for PEC water-splitting suffer from sluggish water oxidation kinetics. Cerium (IV) compounds have historically been used as oxidizers in chemical and are thermodynamically able to oxidize water without additional energy input. In this project, Cerium(III/IV) is used as a regenerable redox mediator for water oxidation. A rutile TiO2 nanorod array (TiO2 NRA) is employed as a photoanode in an acidic electrolyte containing varying concentrations of Ce(III). This presentation demonstrates the roles of Ce(III) in improving the photoelectrochemical performance of TiO2 NRA.
Ag-Loaded Bi5O7I/Sr2TiO4 p-n Junction Photocatalysts for Photocatalytic Degradation of Methyl Orange Under Visible Light Illumination
Authors: Hu Chechia , Huang Hui-Xin , Chen Tzu-Hsin
Published: February 2020

Ag-loaded n-type Sr2TiO4 and p-type Bi5O7I heterostructure photocatalyst was prepared in this work. Scanning electron microscopy, UV-Vis optical absorption spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were performed. Bismuth ions are easily to substitute on titanium sites by adjusting the pH value because Sr2TiO4 and Bi5O7I exhibit identical orthorhombic layered structure, thus shifting the optical absorption edge of the Bi5O7I/Sr2TiO4 composite toward long wavelength region and reducing the band gap energy. After Ag loading as a cocatalyst, Ag-Bi5O7I/Sr2TiO4 composite showed high photocatalytic activity to degrade methyl orange dye under visible light irradiation. This result can be attributed to the high electron-hole separation resulting from the strong electron-withdrawing ability of Ag and the p-n junction formed at the Bi5O7I/Sr2TiO4 interface. In summary, a facile Ag-loaded Bi5O7I/Sr2TiO4 heterojunction presented an improved photocatalytic activity and can be served as a promising photocatalyst.
Free Carrier Absorption Assisted Photoelectrochemistry of Silicon
Authors: Lee Benjamin T. -H. , Chiang C. -C. , Hwang Yean-Ren
Published: February 2020

Free-carrier absorption (FCA) in semiconductor is a process which carriers within conduction or valence band absorbs near-bandgap photon energies to transfer themselves into a higher energy state without generating electron-hole pairs. The energy absorption activates phonon scattering and is generally considered to have undesirable impact on the performance of electronic or optical devices. Here we find, in an electrochemical processing of silicon, the FCA not only has a significate impact on chemical reaction but also contributed to the formation of nanocrystals. By the effect of FCA, nanocrystals form directly on the bulk surface via a rate-limited photo-electrochemistry processing. The formation mechanism of silicon quantum dots as follows: phonon scattering is generated at the photo-absorption site with its nearby atoms from absorbing laser as an hole-countercurrent to reduce redox reaction for dissolving silicon and caused amphoteric defects around the point. To proving the concept, we employed a 0.9 W/cm2, 1310 nm laser that can penetrate through silicon but be absorbed by free-carriers. After anodizing, a brilliant non-etching spot irradiated by the laser appeared on the black surface of P++
silicon substrate. Under He-Cd laser photoexcitation, we found the photoluminescence in the spot was enhanced to 450% than the around porous silicon forming in dark in the vicinity of the spot.
Cuprous Oxide Photocathode with Carbon-Based Protective and Electrocatalytic Layers for Efficient Water Splitting
Authors: Yu Chunlin , Jia Qing , Zhang Xingwang
Published: February 2020

Enormous efforts have been made to search suitable photocathode materials for photoelectrochemical (PEC) system, because it is a promising way to directly convert solar energy to H2, to meet the urgent demand for global energy. Among common photocathode materials, earth abundant p-type Cu2O is one of the most promising candidate due to its bandgap (2 eV), which facilitates visible light absorption, and its suitable conduction band (0.7 eV) which is negative of hydrogen evolution potential. But its poor stability in aqueous solution severely restricts its application in PEC system. To solve this problem, we adopt a simple and convenient method to form the ultrathin carbon film which has the outstanding electrical conductivity to transfer photogenerated electron from semiconductor into electrolyte solution to protect Cu2O from self-photocorrosion. It was found that carbon based catalyst with ultra-high hydrogen evolution reaction catalytic activity serves as an important role to enhance photocurrent density. This work provided a low cost and simple synthetic method for improving the stability of Cu2O planar film and efficiency of water splitting. This available strategy could expand to design many other materials which endure stability problem in PEC system, and the carbon based catalyst/carbon film/Cu2O multilayer structure might be the model system for basic research of designing other high-performance photocathode materials.