bluuebunny/crossref_metadata_2025 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.
Investigating the Doping Effect of Single Transition Metal Atoms on Basal Planes of MoS2 Monolayer Nanosheets for Electrochemical Hydrogen Evolution Reaction
Authors: Lau Hiu Ming , Lu Xiao Wei , Kulhavý Jiří , Wu Simson , Lu Lu Lin , Wu Tai Sing , Kato Ryuichi , Foord John S. , Soo Yun Liang , Kazu Suenaga , Tsang Shik Chi Edman
Published: February 2020

Surface sites of extensive exposed basal planes of MoS2 nanosheets for the first time have been doped with isolated transition metal atoms as 2D monolayer catalysts for the electrochemical hydrogen evolution reaction (HER). Our HAADF-STEM images clearly show that single transition metal atoms are situated on these multiple surface basal sites that subtly modify the electro-catalytic activities of the monolayer MoS2 dependent on the electronic and stereospecific properties. From the results of DFT calculations, it is found that these dopers play important roles in tuning the hydrogen adsorption enthalpies on exposed surface S atoms and Mo atoms in HER. Our electrochemical testing, characterization and computational modelling demonstrate that Co can significantly enhance the HER activity by the dominant Co-S interaction whereas Ni substantially lowers the HER rate due to the Ni-Mo interaction on the same basal site despite the two transition metal elements are neighbored to each other in the periodic table. We believe that both the geometric and electronic factors exerted by transition metal dopants are important parameters in further tuning the 2D MoS2 structure for rational design of the composite materials for more efficient electrochemical hydrogen production from water.
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.
Analyzing the Importance of Particle Morphology and Heterogeneity in Li-Ion Battery Electrodes
Authors: Mistry Aashutosh N , Mukherjee Partha P.
Published: February 2020

Experimental characterization of electrode microstructure continues to pose interest to the scientific community. Such imaging studies provide information about the arrangement of different constituting phases – a static information. On the other hand, correlation among electrode microstructure and system dynamics (e.g., cell performance) is still quite elusive. Specifically, how microstructural arrangement affects pore-scale transition events like intercalation and ionic transport is poorly understood, mostly since in operando experiments probing system dynamics are challenging. The present work attempts to elucidate this connection using direct numerical simulation of electrochemical transitions. An often overlooked concept in electrode performance is particle geometry. Tomography revealed particle geometries are used to study resulting electrochemical complexations during electrode operation (charge and discharge). Additionally, presence of secondary phase (binder at anode, while carbon-binder domains at cathode) gives rise to partial blockage of electrode electrolyte interface. Implications of this particle surface heterogeneity are also explored for different secondary phase arrangements. Particle morphology and heterogeneity jointly define the maximum particle utilization and in turn finite rate capacity. Interestingly C-rate dependence of (dimensionless) lithium intercalation map also changes qualitatively with particle morphology and surface heterogeneity, thus revealing the importance of accurate characterization of particle scale geometrical features.
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
Microscopic Structure and Electrolyte Nature Effects on Discharge Products of C-S Cathodes in Li-S Batteries
Authors: Balbuena Perla B , Perez-Beltran Saul , Kamphaus Ethan P , Torres Ana E , Soto Fernando Antonio
Published: February 2020

Intermediate and final discharge products of the lithiation of sulfur in C-S cathodes of Li-S batteries are extremely dependent on cathode morphology. When the cathode is a composite of carbon and sulfur, such morphology is in turn a function of the synthesis method. In spite of these complexities, some basic ideas can be formulated to prepare a model able to describe the C-S cathode characteristics and evolution. Here we use classical molecular dynamics with a reactive force-field to evaluate the cathode morphology and its evolution during lithiation in contact with a liquid (with or without S-containing additives) or with a solid electrolyte. The interfacial chemistry is examined with density functional theory and ab initio molecular dynamics. The same methods are used to o study the electronic conductivity of the potential insoluble products.
Effective Inhibition of the Polysulfide Shuttle Effect in Lithium–Sulfur Batteries By Rgo-PEDOT:PSS Coated Separators Via Air-Controlled Electrospray
Authors: Lee Jin Hong , Kim Seung Wan , Joo Yong Lak
Published: February 2020

Lithium-sulfur batteries are promising battery systems for becoming the next-generation energy storage devices. However, realizing their practical application is greatly challenged by the limitation of exhibiting poor cycling performances owing to the low electrical conductivity of sulfur active material and polysulfide shuttling effects during cycling. To solve these issues, a hybrid structure of reduced graphene oxide and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) was fabricated and coated onto the surface of the conventional separator using the air-controlled electrospraying method in this work. By applying these separators to the lithium-sulfur batteries, lower polarization ensued and a combination of chemical, physical, and electrostatic interactions mitigated the polysulfide shuttling effect. Hence, using these bi-functional coatings led to high initial capacity and improved cycling performances, resulting from to the higher utilization of active material and less loss of active material. Overall, this investigation demonstrates the potential for this coating material being adopted to improve lithium-sulfur battery technology.
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
Exploring the Electrochemistry of Organosulfides As High Capacity Cathode for Lithium Batteries
Authors: Ackerson Joseph , Fu Yongzhu , Ma Ying
Published: February 2020

Sulfur is a promising cathode material that offers exceptionally high capacity, however, it suffers from limited cyclability and a number of other serious issues. Recently, some organic sulfur-containing materials has been demonstrated to be promising alternatives with relatively high capacity while maintaining good cyclability. These materials often dissolve in the electrolyte forming a catholyte solution. In this work, the electrochemistry of various organosulfide molcules in the catholyte is explored using computational techniques. The equilibrium structures and the associated reaction mechanism upon lithiation are determined. It is found that the polysulfide shuttle effect can be greatly suppressed through an on-site trapping mechanism. The electrochemistry can also be tuned by a careful selection of the functional groups that attach to the sulfur chain. These observations help to improve our understanding of the electrochemical behavior of these organosulfides.
Effective Strategies for Improving the Cycle Life of Ni-Rich LiNixMnyCozO2 Cathodes for Lithium-Ion Batteries
Authors: Zheng Jianming , Zhao Wengao , Zou Lianfeng , Wang Chongmin , Zhang Jason
Published: February 2020

Lithium ion battery (LIB) is considered the most promising energy storage system for applications in electrical vehicles (EVs). However, the large-scale market penetration of EVs has been impeded by several challenges, particularly the limited energy density, high cost and safety concern of cathodes in LIB. Conventional layered oxide LiCoO2 (LCO) has been widely used in LIBs developed for consumer electronics, but the high cost of cobalt, low lithium utilization (~0.5 Li) has limited its application for EVs. To increase the driving range of EVs to over 300 miles at a single charge and promote the massive market penetration of EVs, low-cost electrode materials with high tap density, high-energy density, good rate capability, and long-term cycle life must be developed. Recently, Ni-rich layered structure cathode materials LiNixMnyCozO2 (NMC, x ≥ 0.6) have been receiving much attention as one of the most promising cathode materials for large scale applications owing to their high discharge capacity (200~220 mAh g-1) and energy density (~800 Wh kg-1) as compared to traditional LiCoO2 (~570 Wh kg-1). However, several technical challenges still exist with these Ni-rich NMCs due to their structural/interfacial instability and poor thermal stability. In this presentation, we will discuss several effective approaches, including lattice doping, grain boundary engineering, and use of novel electrolytes that enhance the structural/interfacial stability of Ni-rich NMC cathodes and significantly improved their long-term cycle life.
Deciphering the Voltage Increase Code in V2O5 Cathode for Li-Ion Battery
Authors: Liu Chaofeng , Cao Guozhong
Published: February 2020

Vanadium pentoxide (V2O5) delivers a highly reversible specific capacity of 294 mAh/g corresponding to two Li ions inserted into the host layered spaces. More attention, in the past decades, has been focused on the cycling stability and capacity enhancement through microstructure design and surface modification and layer spacing regulation. However, the change on the discharging voltage of vanadium pentoxide was ignored, especially, the remarkable increase happens in the first cycles. Herein, the phase structures and the chemical bonds of V2O5 were monitored by X-ray diffractometer and Raman spectroscopy at different charging/discharging states. The recorded patterns revealed the irreversible phase transition stemmed from γ-LixV2O5 that was partially transformed to γ’ -V2O5 rather than the completely pristine α-V2O5. The coexisted phases mutually changed their bond lengths that induced the changes on crystal field and electron cloud distribution, resulting in the decrease of electrons energy level in 3d orbitals and site energy for Li ion occupation. The revealed relationship between electrochemical potential and phase structures can provide a new sight to study and design high-voltage cathode that makes sure the possible full battery with a higher energy density.
(Invited) Fundamental Challenges to Develop High Energy Lithium Sulfur Pouch Cells
Authors: Xiao Jie , Lu Dongping , Shi Lili , Niu Chaojiang , Liu Jun
Published: February 2020

The renaissance of Li-S battery technology is evidenced by the intensive research efforts in recent years. Although the theoretical capacity and energy of a Li-S battery is theoretically very high, the projected usable energy is expected to be no more than twice that of state-of-the-art Li-ion batteries, or 500 Wh/kg. The recent “sulfur fever” has certainly gathered new knowledge on sulfur chemistry and electrochemistry, electrolytes, lithium metal, and their interactions in this “old” system; however, a real advance toward a practical Li-S battery is still missing. One of the main reasons is the lacking of fundamental understanding of Li-S batteries at cell levels. The surface/carbon composite, their particle size, sulfur electrode porosity and density critically dictate the deliverable energy from Li-S chemistry, whereas the parasitic reactions on Li metal anode determines the cycling life of the cell. This talk will briefly overviews the recent research progress on Li− S batteries, followed by a discussion of the scientific gap between lab research and realistic conditions of cell fabrication. The future work in Li-S battery research is also explored to propel relevant research efforts to accelerate the market penetration of Li-S batteries.
Graphene Induced Growth of Single Crystalline Sb2MoO6 Sheets and the Sodium Storage Performance
Authors: Liu Qing
Published: February 2020

Ternary oxides have been widely investigated as excellent anode candidates for LIBs with good cycling and rate capability. In the initial lithiation process, the ternary oxides decompose into Li-alloying metal particles distributed in the matrix of the second inert metal nanoparticles and Li2O. The matrix can act as effective buffer layer and alleviate the aggregation of nanoparticles. Therefore, some ternary oxide anodes for LIBs show greatly improved cyclability and rate performance.

Meanwhile, according to some reported publications, single crystalline materials, which has crystallographically oriented structure with few grain boundaries, can facilitate electron and ion transport compared with the amorphous or polycrystalline counterpart.

Inspired by the above strategies, we reported here a single crystalline Sb2MoO6/reduced graphene oxides composite as anode for SIBs. Interestingly, the Sb2MoO6 particles grow into large single crystalline sheets with the induction of graphene oxide in the hydrothermal process, and the obtained Sb2MoO6/RGO composites exhibit excellent electrochemical performance, delivering a high capacity of 430 mAh g-1 at 0.05 A g-1 and maintains 270 mAh g-1 at high current density of 4 A g-1. A capacity retention of 93.2% can be acquired after 220 cycles at 0.2 A g-1. To the best of our knowledge, the single crystalline Sb2MoO6/RGO composites is investigated as anode for SIBs for the first time.

Figure 1
Highly Durable Sulfur Impregnated Distorted Carbon Nanotubes for Sodium Ion Battery
Authors: Ramaprabhu Prof S , Ajay Piriya Vijaya kumar Saroja , Seshadhri Garapati Meenakshi , Chandrabhan Shende Rashmi , Dharavath Ravindar , Biswas Sanjay , Loganathan S , Balasubramanian T S , Rambabu K
Published: February 2020

Electrical energy storage systems are essential for storing energy produced from renewable energy resources. The increasing demand and price make it difficult for the large scale industrial production of energy storage devices. Therefore, it is necessary to find low cost energy storage devices for large-scale applications. Sodium is an alternative to lithium because it is the fourth abundant element in the Earth’s crust. The similar intercalation chemistry of sodium ions is comparable to lithium, which makes sodium ion battery (NIB) as an alternative to existing energy storage systems. The size of Na+ ions is about 1.02 Å and that of Li+ ions is 0.76 Å. The increased size of sodium ions causes instability of the electrode due to which volume expansion and slow reaction kinetics occur thereby lowering the specific capacity and cycle life. Carbon based nanomaterials have high cyclic stability with low specific capacity. To enhance the specific capacity the carbon based materials are coupled with materials, which undergo conversion or alloying reaction with sodium. During the process of conversion or alloying, the intake of number of sodium ions by the material is more enhancing the storage capacity. But due to the phase change of the material the volume gets expanded up to 420% (Sn). The repeated cycling causes pulverization of the electrode leading to capacity fading. The conversion-based materials have high specific capacity with comparatively low volume expansion. The combination of carbon-based material with conversion type of materials has a synergistic effect of both long cycle life and energy density. Among the carbon-based material, multiwalled carbon nanotubes (MWNTs) have good electrical conductivity but the intercalation of sodium ions into MWNTs is very less limiting the storage capacity. Partially oxidized multiwalled carbon nanotubes (PONTs) have disordered structure and large interlayer spacing, which can enhance the storage capacity with high electrical conductivity. Sulfur is a conversion based material which has high theoretical capacity of 1675 mA h/g is used mainly an active material in metal sulfur battery. Incorporation of sulfur into PONTs gives high specific capacity contributed by the sulfur and PONTs. The layers of PONTs provide cushion effect to accommodate the volume expansion caused by the conversion reaction of sulfur with sodium. In this present work, the results of sulfur incorporated PONTs as an anode material has been discussed for the achievement of high specific capacity and cycle life.
Bio-Inspired Surface Layer for the Cathode Material of High-Energy Density Sodium-Ion Batteries
Authors: Jo Chang Heum , Myung Seung-Taek
Published: February 2020

P2-Cathode materials for sodium battery are usually active in the range of 2–4.3 V, but the decomposition of the electrolytic salt above 4 V versus Na+/Na is common. Arguably, the one of the concerns is the formation of HF after the reaction of the salts with water molecules, which are present as an impurity in the electrolyte. This HF ceaselessly attacks the active materials and gradually causes the failure of the electrode via electric isolation of the active materials. In this study, we report a bio-inspired b-NaCaPO4 nanolayer on a P2-type layered Na2/3[Ni1/3Mn2/3]O2 cathode material. The coating layers successfully scavenge HF and H2O, and excellent capacity retention was achieved with the b-NaCaPO4-coated Na2/3[Ni1/3 Mn2/3]O2 electrode. This retention was possible because a less acidic environment was produced in the Na cells during prolonged cycling. The intrinsic stability of the coating layer also assisted in delaying the exothermic decomposition reaction of the de-sodiated electrodes. We suggest formation and reaction mechanisms for the coating layers responsible for the excellent electrode performance. The suggested technology is promising for use with cathode materials in rechargeable sodium batteries to mitigate the effects of acidic conditions in Na cells.

P2-type layered Na2/3[Ni1/3Mn2/3]O2 powders were synthesized by a conventional solid-state method. Na2CO3, Mn2O3, and NiO were thoroughly mixed. And then it was calcined at 1,000 °C for 12 h in air and then quenched, after which the pellet was immediately transferred into an Ar-filled glove box to minimize the adsorption of water and exposure to the CO2 in the air. Calcium nitrate and phosphoric acid were first dissolved in anhydrous ethanol at room temperature, and the as-synthesized active materials were added slowly to the solution. Then, the solution containing the active material was stirred continuously at 80 °C in a dry room, accompanied by the slow evaporation of the solvent. The as-prepared and bare Na2/3[Ni1/3Mn2/3]O2 powders were heated at 700 °C for 2 h in air. Also, the coated powders were characterized by XRD, SEM, and HR-TEM. Electrochemical properties of coated powders were examined by galvanostatic cycle test and electrochemical impedance spectroscopy.

b-NaCaPO4
coatings shows uniform coating layers, as observed by TEM. Thickness of coating layer is of about 10nm. Electrochemical test with half cells in voltage range of 2.5 - 4.3 V at 25 oC indicates that coated materials have better capacity retention and coulombic efficiency, rate capability, and low resistance. Thin coating layers seem to effective to improve the electrochemical properties. Also, b-NaCaPO4 coatings give decrease of residual sodium and byproduct on the surface of particle, as confirmed by ToF-SIMS. Details will be mentioned at the conference site.

Figure 1
Abstract Withdrawn
Authors: Debela Tekalign Terfa
Published: February 2020

This abstract has been withdrawn by the request of the author.
Applications of Carbon Nanotubes in Developing High Performance Lithium Sulfur Batteries
Authors: Wang Jiaping
Published: February 2020

Carbon nanotubes (CNTs) play very important roles in the field of lithium batteries. In this talk, research progress on the applications of CNTs as conductive additives and polysulfide barriers will be presented. In one aspect, CNTs are used as conductive additives and growth template for synthesis of nano sulfur−CNT composite material. The conductive CNT matrix not only avoids self-aggregation and ensures dispersive distribution of the sulfur nanocrystals, but also offers three-dimensional continuous electron pathway, provides sufficient porosity in the matrix to benefit electrolyte infiltration, confines the sulfur/polysulfides, and accommodates the volume variations of sulfur during cycling. Furthermore, abundant mesopores are introduced to CNTs through controlled oxidation in the air to obtain porous carbon nanotubes (PCNTs) that demonstrate improved dispersive behavior, enhanced conductivity, and higher mechanical strength. Large surface area and abundant adsorption points on tubes are introduced, which allow high sulfur loading, provide dual protection to sulfur cathode materials, and consequently alleviate the capacity fade especially during slow charge/discharge processes. Electrodes with a high sulfur loading of 70wt% demonstrate excellent reversible capacities and improved high-rate capability, revealing efficient suppression of polysulfide dissolution. In another aspect, ultrathin and lightweight interlayers based on CNT film and metal oxides/ sulfides/phosphides are developed as efficient polysulfide-trapping shields for high-performance Li–S batteries. A simple layer-by-layer procedure is used to construct a sandwiched vein-membrane interlayer by loading MnO2/MoS2/MoP2 nanoparticles on cross-stacked CNT films. The CNT film acts as a skeleton to support the MnO2/MoS2/MoP2 nanoparticles and to ensure their uniform distribution, and also physically hinders the polysulfide migration. The conductive CNT film also serves as a current collector and provides abundant electron pathways. Chemical adsorption of polysulfides is achieved by MnO2, MoS2, and MoP2 nanoparticles on the CNT film. The synergetic effect of the CNT film and the MnO2/MoS2/MoP2 nanoparticles enables the production of Li–S cells with high sulfur loadings, low capacity decay rate, high rate performance, and low self-discharge rate. In-situ Raman spectra, X-ray photoelectron spectroscopy results, electrochemical impedance spectroscopy results, and density functional theory calculations demonstrate the strong interaction between metal oxides/sulfides/phosphides and polysulfides and confirm the polysulfide-trapping ability of the CNT based interlayer. These results demonstrate the great potential of CNTs in developing high-performance Li–S batteries.
A New Generation of Rechargeable Aluminum Ion Battery Technology
Authors: Ng Kok Long , Malik Monu , Azimi Gisele
Published: February 2020

Among available energy storage technologies, rechargeable batteries rank at the top, as they offer the required energy and power density and on-demand response. Although there are several battery technologies available in the market – including lead-acid and Li-ion batteries – the future of these technologies, is of concern, because in addition to cost and safety related challenges, we may face material deficits due to the increasingly high demand and geopolitically restricted abundance. Therefore, it is imperative to develop efficient and economically viable battery technologies that rely on more earth abundant elements. Among potential candidates, aluminum ranks high because of low cost, high abundance, high volumetric capacity, and ability to exchange three electrons. Despite positive attributes, some previous studies on aluminum ion batteries have faced several challenges, including anode passivation, cathode degradation, low voltage, and lack of a stable electrolyte. Here we present a new generation of aluminum ion batteries made of an alloy of aluminum as the anode and a nanotextured activated graphitic sheet as the cathode. The electrolyte is composed of an organic solvent containing aluminum ions. Charge-discharge cycling indicates that cells are stable with minimal capacity decay and they show high discharge voltage and specific capacity. To elucidate the mechanism of electrochemical reactions within the cell, we utilized various microscopy and spectroscopy techniques including X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), scanning electron microscopy energy dispersive spectroscopy (SEM-EDS), transmission electron microscopy (TEM) before and after charge-discharge cycles. This research is ongoing to further develop and refine this innovative battery technology, which could enable sustainable generation and efficient utilization of electric energy.