bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Individual Nanowire/Sheet Devices for Electrocatalysis
Authors: Yan Mengyu , Yang Jihui , Mai Liqiang 
Published: February 2020

Nowadays, substantial works have been devoted to electrochemical energy storage and conversion due to the increasing global energy demand. The individual nanowire/sheet electrochemical devices can establish an intrinsic relationship between the electrochemical performance and electronic transport. Meanwhile, it is a fantastic platform to tune the electrochemical behavior (including electrochemical energy storage and electrocatalytic) with external fields, which is meaningful on understanding the reaction mechanism and further developing new optimize strategy. Here, we highlight the recent developments of individual nanowire-sheet electrochemical devices in energy storage and catalysis.1

In the electrocatalytic field, we designed an in-situ testing platform with individual Ni-graphene nanosheet based oxygen evolution reaction devices.2 It is demonstrated that the oxygen acts as a barrier to significantly reduce the concentration of OH− ions at catalyst surface, slowing down the charge transfer process and OER kinetics. By removing oxygen in the electrolyte, a significant decrease in Tafel slope of over 20% and an early onset potential of 1.344 V vs. RHE have been achieved. Afterwards, the individual electrocatalytic devices were applied to understand how does the external electric field tune the hydrogen evolution reaction (HER) behavior. Increasing the back gate voltage from 0 to 5 V, the overpotential of individual MoS2 nanosheet decreases from 240 to 38 mV.3 Such strategy is further extended to VSe2 nanosheet.4 Our results indicate that HER performance improves along with the increasing of the negative back gate voltage. Besides, charge transfer resistance and high-frequency time constant drop dramatically, which demonstrates a much faster charge transfer process.
Reference

Mai L*, Yan M, Zhao Y. Track batteries degrading in real time.
Nature
2017, 546(7659): 469.

Wang P, Yan M*, Meng J, Jiang G, Qu L, Pan X, Mai L*, et al. Oxygen evolution reaction dynamics monitored by an individual nanosheet-based electronic circuit.
Nature Communications
2017, 8.

Wang J, Yan M*, Zhao K, Liao X, Wang P, Pan X, Mai L*, et al. Field Effect Enhanced Hydrogen Evolution Reaction of MoS2 Nanosheets.
Advanced Materials
2017, 29(7).

Yan M, Pan X, Wang P, Chen F, He L, Jiang G, et al. Field-effect tuned adsorption-dynamics of VSe2 nanosheet for enhanced hydrogen evolution reaction.
Nano Letters 17(7): 4109.
Improving Hydrogen Evolution Reaction Activity of Palladium By Ruthenium
Authors: Zhang Lulu , Feng Chenkai , Shao Minhua 
Published: February 2020

Hydrogen is one of the cleanest and most promising energy carriers that has all criteria considered for an alternative energy source. The hydrogen evolution reaction (HER) has been widely studied on noble metal catalysts, such as Pt and Pd owing to their extremely high activity in acid.1 However, these catalysts exhibit unexplained sluggish kinetics in alkaline media by orders of magnitude slower than that in acidic solutions.2-3 Here, we demonstrated that by conjunction with additional transition metal Ru, the activity of pure Pd can be enhanced.
In this study, PdRu alloys with different composition ratios were synthesized by impregnation method and were heat treated under different temperatures in Ar atmosphere. Their HER activities were investigated in both 0.5M H2SO4 and 1M KOH solutions. By comparison, the surface-modified Pd with Ru adatoms (Pd@Ru) was also prepared. The alloy showed excellent catalytic activities for HER than Pd@Ru and Pd. In acid (Figure 1a), Pd3Ru exhibited 32 mV shift at 10 mA cm-2 compared with Pd. In an alkaline solution (Figure 1b), it showed even more remarkable enhancement, with 120 mV improvement at 10 mA cm-2. At high pH, it was even more active than Pt. Based on these observations, alloying with Ru can increase the HER activity significantly, especially in alkaline solutions. In this talk, the results of density functional theory (DFT) calculations will be also discussed.

References

(1) Durst, J.; Siebel, A.; Simon, C.; Hasche, F.; Herranz, J.; Gasteiger, H., Energy Environ. Sci.
2014,
7, 2255-2260.
(2) Zheng, J.; Sheng, W.; Zhuang, Z.; Xu, B.; Yan, Y., Science advances
2016,
2, e1501602.
(3) Strmcnik, D.; Uchimura, M.; Wang, C.; Subbaraman, R.; Danilovic, N.; van der Vliet, D.; Paulikas, A. P.; Stamenkovic, V. R.; Markovic, N. M., Nat. Chem.
2013,
5, 300-306.

Figure 1
(Invited) Electrocatalytic Hydrogen Evolution in Neutral Solution
Authors: Shao Yuyan 
Published: February 2020

Electrocatalytic hydrogen evolution reaction (HER) has been intensively studied. Materials innovation and device engineering for HER has been focused on both acidic and alkaline systems, for which great progress has been made. However, there has been very limited studies for neutral solution. Generating H2 from water of intermediate pH (e.g., wastewater, seawater) has advantages of being less corrosive, environmentally benign, and potentially low cost. It also provides an efficient way for environmental cleanup, for example, H2 production using a microbial electrolysis cell (MEC) cleans wastewater. HER electrocatalysts based on earth abundant materials for operation in neutral conditions, which has been rarely explored, is thus highly attractive but remains a grand challenge.
Here we report our recent materials research and fundamental understanding on HER electrocatalysis in neutral solution. We have developed a new pseudo in situ synthesis method for the preparation of HER electrocatalysts molybdenum phosphide (MoP). The surface structure and chemistry can be easily controlled which enables us to study the structure-property relationship. Our MoP electrocatalyst demonstrates HER activity comparable to that of benchmark Pt in neutral solutions including natural sea water and phosphate buffered saline solution. It also demonstrates high stability with no performance fading in 4000 cycles. MoP electrocatalyst was further tested in an MEC, which is able to produce a 2X HER current density in comparison to the state-of-art MEC in literature. The high performance MEC with the new HER catalyst presents a promising technology approach for low cost hydrogen production.
Understanding the Improved Kinetics of the Hydrogen Evolution/Oxidation Reactions of the Platinum-Oxophilic Metal Systems in Alkaline Media
Authors: Jia Qingying , Li Jingkun , Mukerjee Sanjeev 
Published: February 2020

Realization of the hydrogen economy relies on effective hydrogen production, storage, and utilization. The slow kinetics of hydrogen evolution and oxidation reaction (HER/HOR) in alkaline media limits many practical applications involving hydrogen generation and utilization, and how to overcome this fundamental limitation remains debatable. Herein, we report that a wide broad of PtM (M represents oxophilic metals such as Ni, Nb, Ru, etc.) systems exhibit superior HER/HOR activity to Pt in alkaline media. Combined electrochemical and in situ spectroscopic data show that the improved HER/HOR kinetics is not attributable to the M-induced weakening of the Pt-H hydrogen binding energy, or the negative shift of the underpotential deposited hydrogen HUPD stripping peak, but rather related to the surface hydroxide species at the HER/HOR potential region accommodated by the surface M that is in the form of oxides. The possible beneficial role of the surface hydroxide, either reorienting the water molecules in the interface, and/or facilitating the removal of hydrogen adsorbates on Pt sites via the bifunctional mechanism will be discussed in the context of new electrochemical and spectroscopic data.
Acknowledgements
Current financial support from ARPA-E ((DE-AR0000688)) lead by Pajarito Powders is deeply appreciated. Use of the Stanford Synchrotron Radiation Lightsource, SLAC National Accelerator Laboratory, is supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Contract No. DE-AC02-76SF00515. Use of Beamline 2-2 at SSRL and ISS 8-ID of the NSLS II was supported by the National Synchrotron Light Source (NSLS) II, Brookhaven National Laboratory, under U.S. DOE Contract No. DE-SC0012704.

Figure 1
Comprehensive Study on Unusual Polarization Behaviors of the LiFePO4 Electrode Using Mathematical Modeling
Authors: Kondo Hiroki , Sasaki Tsuyoshi , Barai Pallab , Srinivasan Venkat 
Published: February 2020

LiFePO4 has been commercialized as a cathode material for high-power lithium-ion batteries for power-tools and hybrid-vehicles because of its low cost, high power, and thermal stability. The behavior of LiFePO4 electrodes, consisting of fine nanoparticles (30-150 nm), are influenced by the interactions between the constituent particles. In addition, the non-monotone potential profile of LiFePO4 single particles, which is characteristic of a many-particle model and originates from two-phase reactions, complicates the polarization behavior of the electrode's charge/discharge profile. One of the unique polarization behaviors of the LiFePO4 electrode is path-dependence[1], wherein the polarization during charge and discharge is influenced by the previous charge and discharge. In addition, the so-called memory-effect was recently reported as an unique polarization behavior of LiFePO4 electrode[2]. Here, an extra polarization bump appears in the (dis)charging profiles at around the SOC at which the previous partial (dis)charge was stopped. These unique polarization behaviors have been investigated in the past using mathematical simulations[3]. However, the detailed cause for the polarization has not been clarified yet. In this study, we investigated the polarization behavior of a LiFePO4 electrode by mathematical simulations using a many-particle model and deciphered the behavior using an active population[4].
It was clarified that the polarization of the memory-effect was caused by the reduction of the active population by relaxation during a previous rest. Through this mechanism, we suggested a new polarization behavior, so-called relaxation-induced-polarization (RIP), which affects the polarization in the (dis)charging profile after the rest. The RIP can be triggered by only the last rest, whereas the appearance of the memory-effect needs specific processes with at least three steps. We also investigated path-dependence behavior, which is a well-known but unusual polarization behavior of LiFePO4 electrodes, and suggested a mechanism for this behavior. Unlike the former two polarizations, the path-dependence was considered to be caused by kinetically inhomogeneous reactions for each particle. Using mathematical simulations incorporating a many-particle model, we further predicted that narrowing the particle size distribution was effective to reduce this polarization, but it cannot be fully erased. The comprehensive understanding of the three polarization behaviors by our model can give us more accurate estimation of the state-of-charge of Li-ion batteries with the LiFePO4 electrode.
References:
[1] V. Srinivasan and J. Newman, Electrochemical and Solid-State Letters, 9, A110 (2006).
[2] T. Sasaki et al., Nat Mater, 12, 569 (2013).
[3] M. Farkhondeh et al., Phys Chem Chem Phys, 16, 22555 (2014).
[4] P. Bai and G. Tian, Electrochimica Acta, 89, 644 (2013).
(Invited) High Energy Dry Electrode Technology
Authors: Duong Hieu , Shin Joon , Yudi Yudi 
Published: February 2020

Within this decade, there has been immense effort focused on reducing the cost of energy storage devices. The goal towards energy independence through electrification of automobiles for widespread adoption has greatly incentivized this endeavor. Strategies ranging from novel materials investigation to advanced device manufacturing development span the cost reduction effort. Maxwell Technologies is actively engaged in this global effort from the direction of dry electrode fabrication technology. Maxwell dry electrode technology offers manufacturing cost and performance competitiveness, and novel battery chemistry enablement. This paper provides the initial foundation and validation for the application of dry coated electrode in lithium-ion batteries.
Maxwell Technologies is a San Diego based ultracapacitor manufacturer that uses a proprietary liquid-free electrode production process. Advanced process development without the need for solvents has enabled Maxwell’s dry electrode production lines to operate at high throughput using a minimal manufacturing footprint. This unique electrode manufacturing process does not introduce any volatile waste products into the atmosphere or require complex manufacturing plant arrangement. It begins with dry raw materials compounding and maintains its liquid-free state throughout the subsequent processing steps to ultimately produce a robust high-performance ultracapacitor electrode.
Maxwell is currently engaged in research and development efforts to expand the application space of its dry electrode process technology to include battery electrode manufacturing. Cell performance using prototype dry coated lithium-ion battery electrodes has been demonstrated. Electrode configuration with various architectures using a wide range of materials can be produced at thicknesses ranging from about 50 microns to about 1 millimeter. In addition to manufacturing flexibility, the cohesion and adhesion properties of electrodes derived from the dry process are superior in the presence of electrolyte at high temperatures compared to those produced using the wet coating technology.
This unique electrode process technology offers significant saving in manufacturing cost and helps curb CO2 pollution during the battery electrode manufacturing process. By eliminating the use of any liquids/solvents, and the associated coating and drying complexity inherent in wet processing, the dry electrode process is environmentally friendly, and can be readily installed and commissioned with a much lower start-up capital investment. Thus, dry electrode manufacturing is economically attractive and socially responsible.
This paper will provide recent progress in high energy dry electrode coating technology and its capacity for the enablement of advanced battery chemistries, and cell performance results derived from dry coated lithium-ion battery electrodes.
Examining and Controlling the Behavior of Thermal Runaway in Multi Cell Systems
Authors: Lamb Joshua , Torres-Castro Loraine , Steele Leigh Anna M 
Published: February 2020

Abusive battery testing has most typically dealt with the behavior of single cell failure. However, large and complex battery systems require the consideration of how a single cell failure may lead to a more serious failure that consumes a large portion of a pack or module. Initial failure that leads to the thermal runaway of other cells within the system creates a much more serious condition than the failure of a single cell. Figure 1 shows how a single cell failure may not be indicative of multi-cell performance. Figure 1 (left) shows the results of the nail penetration of a single LiFePO4­-graphite 26650 cell. This failure resulted in a temperature increase to a peak of 100 °C along with venting of the cell. Figure 1 (right) shows a single cell failure within a 10 cell parallel string of the same cells. The initially observed failure is first more severe, with a peak observed temperature of ~250 °C immediately after the single cell failure. This then develops into a failure of the entire string 10 minutes later. This is significantly more severe than the single cell failure as well, with all cells peaking above 200 °C and the central cell seeing 370 °C.
This work examines the behavior of small modules of cylindrical and stacked pouch cells after thermal runaway is induced in a single cell. The limits of cell-to-cell failure propagation are explored by initiating failure on cells with reduced states of charge, packs with air gaps between cells, and packs with physical separation between cells. This data shows both how thermal failure propagation may be mitigated as well as demonstrating the behavior of a propagating cell failure under these conditions. Some data shows how a propagating failure of even a small pack may stretch over several minutes as the latent heat available causes the cells impacted to slowly reach critical points where thermal runaway occurs. This work also provides a better understanding of how cell failure propagates through a system, providing a fundamental basis for modeling work presented elsewhere. Establishing this basic understanding is crucial for the informed design of battery packs as well as predicting the effectiveness of failure mitigation strategies.
Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia LLC, a wholly owned subsidiary of Honeywell International Inc. for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Figure 1
Mathematical Modeling of the Charging Process of Li-S Batteries By Incorporating the Size-Dependent Li2s Dissolution
Authors: Xiong Cheng , Ren Yuxun , Jiang Haoran , Zeng Lin , Xu Jianbo , Zhao Tianshou 
Published: February 2020

Abstract

Lithium-sulfur (Li-S) batteries give rise to the further development of long-driving electric vehicles [1]. During the discharge process of lithium-sulfur batteries, the nucleation and growth of Li2S precipitates result in a non-uniform Li2S particle size distribution, significantly affecting the charging process [2,3]. However, a uniform Li2S distribution at the initial state of the charging process of the batteries is assumed in the models reported in the literature, leading to an unrealistic simulation of the charging process [3,4]. To address this issue, we propose a one-dimensional transient mathematical model, which incorporates the size-dependent Li2S dissolution and redox mediation reaction between dissolved polysulfides and Li2S particles into the charging process. Simulation results show that the dissolution rate of large Li2S particles is suppressed at a lower potential due to the small specific surface area, while the smaller Li2S particles are electrochemically oxidized into dissolved polysulfides first, which further act as the redox mediators to promote the oxidation of larger Li2S particles. Capturing these effects enables an excellent agreement between the predicted and measured charging voltage profiles. Moreover, the effects of particle sizes and redox mediation reaction rates are studied. It is revealed that the optimal amount of smaller-sized Li2S particles and suitable redox mediation reaction rate allow for a lower charging over-potential. Furthermore, it is shown that the effect of redox mediation rates on the dissolution of Li2S large particles exerts a significant influence on the charging process.

Key words: lithium-sulfur battery; mathematical model; dissolution kinetics; size effect; redox mediation

Acknowledgment: The work described in this paper was fully supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China (Project No. T23-601/17-R)

Reference

[1] A. Manthiram, Y. Fu, S.-H. Chung, C. Zu, Y.-S. Su, Rechargeable Lithium–Sulfur Batteries, Chem. Rev. 114 (2014) 11751–11787. doi:10.1021/cr500062v.
[2] F.Y. Fan, W.C. Carter, Y. Chiang, Mechanism and Kinetics of Li2S Precipitation in Lithium–Sulfur Batteries, Adv. Mater. 27 (2015) 5203–5209.
[3] Y.X. Ren, T.S. Zhao, M. Liu, P. Tan, Y.K. Zeng, Modeling of lithium-sulfur batteries incorporating the effect of Li 2 S precipitation, J. Power Sources. 336 (2016) 115–125.
[4] M. Ghaznavi, P. Chen, Sensitivity analysis of a mathematical model of lithium–sulfur cells: Part II: Precipitation reaction kinetics and sulfur content, J. Power Sources. 257 (2014) 402–411.
Advanced Electrolyte and Electrode Enabling High Energy Lithium Sulfur Batteries
Authors: Pan Huilin , Shao Yuyan , Liu Jun 
Published: February 2020

Currently, sulfur encapsulation in high surface area, nanoporous conducting carbon is the most widely studied approach to improve the cycling stability of Li-S batteries. However, the relatively large amount of high surface area carbon results in two fundamental problems with this approach. First, a large amount of electrolyte volume to sulfur (E/S) ratio (typically > 20 mlE/gs) is needed to fully wet the porous sulfur cathode. Second, the large amount use of high surface area carbon greatly decreases the overall energy density in the system, especially for volumetric energy density, and makes it difficult to compete with other battery technologies.
Here, we found the E/S ratio plays a critical role in the cycling stability of Li-S batteries. Owing to the insulating nature of S/Li2S, lowering E/S ratio increases the charge carrier transfer resistance on the interface, causing poor rechargeability and sustainability of sulfur cathode. An ammonium-based electrolyte additive is identified to effectively address the passivation issue of Li2S under low E/S ratio. To further solve the critical passivation issue of cathode especially under lean electrolyte condition, we proposed a new approach that does not depend on the conventional sulfur encapsulation with high surface area carbon was proposed to reduce electrolyte absorption. The new approach generates a large spherical porous agglomerated particles with self-sustaining structures to avoid cathode passivation, leading ~100% sulfur utilization with good cycling (Nature Energy 2, 813, 2017).
Interfacial Interactions of Lithium Polysulfide and Carbon Nanotubes
Authors: Han Kee Sung , Murugesan Vijayakumar , Mueller Karl T 
Published: February 2020

Lithium-Sulfur (Li-S) battery is a promising next-generation energy storage device which has the potential to replace the traditional Li-ion battery systems, primarily due to their higher specific capacity (1672 mAh/g) and the low cost of sulfur. However, the sulfur cathode is beset with technical challenges such as poor conductivity and high solubility, resulting in poor capacity retention upon cycling1-4. Encapsulation of sulfur with carbon allotropes is widely reported as a key strategy to decrease polysulfide solubility and enhance conductivity, with varying degrees of success. The unpredictable performance of carbon allotropes arises from poorly understood interactions with various lithium polysulfide species (Li2S
n
, 2 ≤ n ≤ 8). Multiwall carbon nanotubes (MWCNTs) are a widely used carbon allotrope in sulfur/carbon-based cathodes for Li-S batteries due to their superior electronic conductivity and enhanced diffusivity for Li+ cations. In an effort to understand the interaction between highly soluble lithium polysulfides (Li2S4, Li2S6, and Li2S8) and MWCNTs, we performed multimodal spectroscopic analyses including X-ray photoemission spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and 7Li nuclear magnetic resonance (NMR) based relaxation (T
1 and T
2) measurements (see Figure 1). This presentation will discuss the multimodal analyses which provide unique access to structural and chemical environments at the polysulfide-MWCNT interfacial region from then atomic to mesoscale level.
References:

J. Chen, K. S. Han, W. A. Henderson, K. C. Lau, M. Vijayakumar, T. Dzwiniel, H. Pan, L. A. Curtiss, J. Xiao and K. T. Mueller, Advanced Energy Materials 6 (11) (2016).

H. Pan, K. S. Han, M. Vijayakumar, J. Xiao, R. Cao, J. Chen, J. Zhang, K. T. Mueller, Y. Shao and J. Liu, ACS Applied Materials & Interfaces 9 (5), 4290-4295 (2017).

N. N. Rajput, V. Murugesan, Y. Shin, K. S. Han, K. C. Lau, J. Chen, J. Liu, L. A. Curtiss, K. T. Mueller and K. A. Persson, Chemistry of Materials 29 (8), 3375-3379 (2017).

M. Vijayakumar, N. Govind, E. Walter, S. D. Burton, A. Shukla, A. Devaraj, J. Xiao, J. Liu, C. Wang, A. Karim and S. Thevuthasan, Physical Chemistry Chemical Physics 16 (22), 10923-10932 (2014).

Figure 1