bluuebunny/crossref_metadata_2025 huggingface dataset:
Controlled Formation of Li4Ti5O12-C Hollow Hybrid Microspheres for an Improved Battery Performance in Lithium Ion Batteries
Authors: Cao An-Min , Yang Li-Ping
Published: February 2020

The In this contribution, we reported our progress on the construction and optimization of the hybrid structure of Li4Ti5O12-Carbon (LTO-C) for their application as an anode material in lithium ion batteries. By means of a template-free process, uniform hollow hybrid microspheres (HHMs) of LTO-C has been prepared with delicate control on the central cavity and the nanocomposite wall, which was composed of a crystalline LTO matrix with conductive carbon well dispersed inside. The synthesis protocol for LTO-C was very convenient, low-cost, environmentally benign, and suitable for large-scale production. We identified that the hollowing process is induced by the gradual crystallization of solid microspheres whose crystallinity was relatively low at the beginning. The high temperature treatment initiated a progressively-inward crystallization starting from the particle surface: Crystallization firstly happened on the surface, and then marched into the core as evidenced by a steady encroachment of the crystallization frontline towards the center, resulting in the formation of the central cavity due to the increased tension inside. We demonstrated that such a synthetic platform for hollow microspheres were versatile and could be readily applicable for the synthesis of different kinds of metal oxides HHMs. By using the LTO-C as an anode material, we confirmed the advantage of the HHMs structure for their application in lithium ion batteries as revealed by the much higher discharge capacity and much improved rate capability.

Figure 1: a) SEM images of the TiO2-UF precursors which exist as uniform solid nanospheres. b) SEM image of the FIB-prepared cross section of the LTO-C HHMs sample, showing the hollow nature of the inner particles. c) The ﬁrst charge/discharge curves at 0.1 C for different samples tested, showing the advantage of the LTO-C HHMs one as compared to those control samples with either no cavity or no carbon matrix. d) Cyclablity test results for different samples.

Figure 1
Synthesis and Characterization of Gold Nanoparticles and Study of Their Interaction with Hydroxyl Radicals
Authors: Muñoz Eduardo Carlo , Milesi Renzo , Navarrete Emilio Alonso , Henríquez Rodrigo Gonzalo , Schrebler Ricardo Silvio
Published: February 2020

Nanoparticles have been extensively employed in different fields such as medicine, optics, physics, biology and chemistry, due to its optical, thermal, magnetic and reactivity properties can be controlled by changing the size of these particles without to vary the composition of the material. At present, they have made significant progress to synthesize high-quality nanostructures, mainly metal nanoparticles and semiconductor nanocrystals.

Gold nanoparticles (AuNPs) are of great interest because their chemical properties, i. e. molecular recognition, reactivity, biological properties i. e. DNA-AuNPs assemblies and physical properties, i. e. optical properties and electrochemical properties.

This work deals with the interaction of gold nanoparticles (AuNPs) with hydroxyl radicals. The results obtained in this research constitutes a first theoretical and experimental approach for to evaluate AuNPs as a sensor to free radicals.

In a first stage, the synthesis of gold nanoparticles was performed in aqueous media by reaction with tetrachloroauric acid (HAuCl4) and sodium citrate as reducing agent in a reflux system. The synthesis process was analyzed by using a factorial design experiment which considered different concentrations of reducing agent, temperature and stirring rate. In this analysis, the reducing agent concentration and temperature are significant variables and have a positive influence on AuNPs size, i. e. an increase of these produce an increase in the nanoparticle size.

Later, AuNPs were characterized by UV-Vis spectroscopy where the corresponding absorption spectrums were obtained. In addition, AuNPs were immobilized on a silicon surface by means of a electrostatic irreversible deposition. A potential difference of 40 V was applied at different times between the p-type silicon and a graphite electrode immersed in the colloidal media containing the AuNPs. Afterwards, the modified silicon surface was analyzed by Atomic Force Microscopy (AFM) where size and AuNPs distribution were analyzed .

Finally, the AuNPs were exposed to hydroxyl radicals coming from a Fenton reaction. During the interaction, the intensity and wavelenght of the absorption maximum was monitored as function of time. Additionally, the morphological change after interaction was analyzed. The results obtained in this conditions show slight changes in the AuNPs properties. However, this study can be extended to other radicals which can present a stronger interaction with these nanoparticles.

Figure 1
The Importance of Renewable Hydrogen in Decarbonization
Authors: Ayers Katherine E , Danilovic Nemanja
Published: February 2020

Hydrogen is an important industrial gas, representing a 10 million metric tons/year industry worth $100 billion. Currently over 95% of that hydrogen is made from fossil fuels: natural gas reforming or coal gasification. Close to 50% of the world’s annual hydrogen production is used for ammonia generation and oil refining, with the hydrogen generation being the highest energy and highest emission subcomponent of ammonia generation. In addition, 2% of U.S. energy currently goes through hydrogen as an intermediate, a number that will increase substantially when hydrogen fueled vehicles become widespread. In order to meet the Climate Action Plan goals of 80% reduction in greenhouse gas emissions by 2050, net zero carbon pathways for hydrogen production are therefore critical.

There are several pathways to generating hydrogen from renewable sources, but one of the most advanced is membrane-based water electrolysis powered by solar, wind, or hydropower. While electrolysis has been demonstrated at megawatt scale, there is still significant promise for further improvement. Several countries are already committed to advancing this technology, and are working on the critical materials issues that drive cost and efficiency. Longer term technologies such as photoelectrochemical water splitting or thermochemical routes may provide lower cost pathways in the end, but need to build from technologies that have already been developed at relevant scale.

The "perfect" technology to address the energy challenge will always be 20 years away. As new concepts moves from basic principles to bench scale experiments and beyond, the pitfalls become clearer. At the same time, dismissing existing commercial technologies on the basis of limitations which might become relevant at multi-gigawatt or terawatt scale prevents us from maximizing early impact on sustainability. This poster will focus on the need to leverage existing clean energy technologies in the near term to serve the megawatt and gigawatt scale, as building blocks and bridges to future technologies.
(Keynote) DOE's Efforts to Accelerate Federally-Funded Technology to the Marketplace
Authors: Dixon Robert K.
Published: February 2020

DOE's approach to technology transfer has evolved over the years. With a reinvigorated approach to commercializing technology developed with the National Laboratories, Universities, and other partners, DOE is improving its focus on getting taxpayer returns from federal energy R&D investments. Programs such as the Lab Impact Initiative, and new teams like the Office of Technology Transitions, demonstrate how the DOE approach has evolved, and provide opportunities for scientists and entrepreneurs to take their ideas from concept to market.
Effect of Zero Volt Storage on Commercial Lithium Titanate Cells
Authors: Brunell Michael , Hanauer Brad , Loveridge Melanie , Dashwood Richard , Bhagat Rohit
Published: February 2020

With the increase in usage of lithium ion batteries there has been an increased focus on the relative safety of the technology. One of the largest impacts has been the safety during shipping (air, marine and by road transport) with many passenger flights now banning the transport of all lithium ion batteries. In additional there are continued safety concerns that arise during the warehousing and storage of a large number of cells in system manufacturer’s facilities awaiting assembly into systems. Finally there has been an increase in the operating voltages of many vehicle and grid systems with transportation systems as high as 700 volts and grid systems reaching greater than 1,100 volts, as the voltage of the system increases the risks and safety concerns associated with assembly of the systems significantly increases.

This study examines the effect of reducing the terminal voltage of commercial 13 Ah lithium titanate cells to
zero volts
, well below the limits of traditional lithium ion batteries. [1,2] Prior to full cell testing, coin cells of lithium titanate versus lithium were manufactured to explore the behaviour of the lithium titanate under high voltage scenarios, as would be experienced by the electrode in a full cell stored at low voltages. The coin cells were characterized through cycling, storage and SEM imaging.

Following the half-cell testing commercial full cells were stored in multi-month intervals over the course of one year to simulate storage in a manufacturer’s warehouse. Following each storage period the cells health and performance were characterized through a number of techniques including standard cycling at various rates, capacity checks, incremental capacity analysis of low rate voltage curves, pulse power capability and EIS measurements at various states of charge.

A comparison to a set of control cells, stored under the same environmental conditions but at the manufacturers recommended voltages, is presented demonstrating that cells stored at zero volts suffer no appreciable change to capacity, cycling capability, voltage stability. Additionally it is shown that there has been no increase in impedance, high current rate performance for both charge and discharge remains unaffected, and no discernible damage has been done to the cell during long term storage. This work demonstrates that reducing a lithium titanate cell zero volts is a feasible method of storage and may provide a solution to increasing the safety of the cells in a number of scenarios.

 

[1] H.-F. Li, J.-K. Gao, S.-L. Zhang, Effect of Overdischarge on Swelling and Recharge Performance of Lithium Ion Cells, Chinese J. Chem. 26 (2008) 1585–1588. doi:10.1002/cjoc.200890286.

[2] H. Maleki, J.N. Howard, Effects of overdischarge on performance and thermal stability of a Li-ion cell, J. Power Sources. 160 (2006) 1395–1402. doi:10.1016/j.jpowsour.2006.03.043.

Figure 1
Investigation into Estimation of Battery Core Temperature Using Electrochemical Impedance Spectroscopy on a 4P1S Array of 26650 Cells
Authors: Huhman Brett , Love Corey T , Heinzel John M
Published: February 2020

Battery core temperature is a critical parameter necessary determining the safe operating area (SOA) of a battery cell and battery packs to avoid abuse and prevent failure and accidents. Prior work in the literature has demonstrated this method with single cells, while this work investigates the feasibility of expanding to cover a single series array of four cells in parallel (4P1S). A set of baseline experiments with thermal chamber was used to equilibrate a commercial cell to a specific temperature, in the range of 10°C – 70°C in 5°C increments to simulate the SOA. After a 24 hour rest period, an electrochemical impedance spectroscopy (EIS) spectra was recorded with a range of 10 kHz – 0.1 Hz, on eight LiFePO4 cells to identify a frequency range where the impedance response is directly related to the core temperature of the battery. To carry out a statistical analysis, the eight cells were selected to have closely matched impedance and capacities. The cells were used to generate an expected response based on the measured data. Two 4P1S arrays were constructed using the baselined cells, and the experiment repeated with EIS across each array in an open circuit configuration. Finally, each array was discharged into a load at the 0.5C, 1C, 2C, 5C, and 10C levels to evaluate the diagnostic under simulated operating conditions. Recorded in situ for discharging cells, this data set will allow us to develop more accurate models, which will lead to improved cell performance. This work will discuss experimental results to date.
Investigation of Anode/Cathode Electrolyte Interfaces at High Cell Voltages with and without Additives
Authors: Liu Dongqing
Published: February 2020

The electrodes electrolyte interfaces of lithium ion battery at high cell voltages were investigated by using in-situ electrochemical impedance spectroscopy (EIS) with three electrodes cell. NCM/C system electrodes were investigated separately in the electrolyte of LiPF6 in ethylene carbonate (EC) and dimethyl carbonate (DMC) with and without the most commonly used additives vinylene carbonate (VC), vinyl ethylene carbonate (VEC) and fluoroethylene carbonate (FEC). Fourier transform infrared (FTIR) and ultraviolet-visible (UV-vis) were carried out to examine the stability of additives at the electrodes electrolyte interfaces at high cell voltage. This work provides valuable information for lithium ion battery at high cell voltage especially in the choice of electrolyte additives.
Coupled Electrochemical, Electrical and Thermal Modeling of Li-Ion Battery Modules
Authors: Kalnaus Sergiy , Allu Srikanth , Pannala Sreekanth , Simunovic Srdjan , Elwasif Wael , Turner John A
Published: February 2020

Severe thermal gradients can develop in Li-ion battery packs and modules especially at high discharge rates and can affect the performance. We report the results of the coupled electrochemical, electrical, and thermal modeling of a lithium-ion battery module comprised of four pouch cells connected either in series or in parallel. Newly developed open architecture software was used to build the model and perform highly resolved multi-physics simulations [1]. The goal was to determine temperature variations across the cells within the module with different cooling scenarios as well as effects of such thermal gradients on potential variations. This was achieved by monitoring local state of charge within the cells. Cumulative effects of such gradients were estimated over number of cycles. NMC vs Graphite system was modeled. Aging scenarios leading to increased impedance in the cells were considered.

Allu, S., Kalnaus, S., Elwasif, W., Simunovic, S., Turner, J.A., Pannala, S., A new open computational framework for highly-resolved coupled three-dimensional multiphysics simulations of Li-ion cells, J. Power Sources 246 (2014), 876-886.
A Semi-Empirical Capacity Fade Model for Li-NCA Cathode
Authors: Basu Suman , Hariharan Krishnan S , Kolake Subramanyya Mayya , Song Taewon
Published: February 2020

Lithium Nickel-Cobalt-Aluminum (NCA) is a popular cathode material for Li-ion cells due to its high energy density and moderate cost. Cycling experiments confirmed that the cathode capacity fade is the dominant capacity fade mechanism [1] in such cells. Electron energy loss spectroscopy (EELS) and X-Ray Absorption Fine Structure (XAFS) analysis of the aged LiNCA particles exhibit the formation of a NiO type layer, which is inactive to Li intercalation, at the surface of the particles. Estimated amount of this inactive layer is found to match with the capacity loss of the cell. Therefore, a physics based model with one empirically determined parameter has been constructed for this reaction and it has been implemented on Li-ion battery electrochemical model [3]. The model predicts the relative capacity of a Li-NCA cell cycles at different temperatures with high accuracy (Fig.1). For constant current condition, a simple closed form solution for the capacity fade has been derived and validated. On extension this model can effectively predict the remaining useful life.

References:

Y. Zhang and C-Y. Wang, J. Electrochem. Soc.,
156, A527 (2009).

T. Sasaki, T. nonaka, H. Oka, C. Okuda, Y. Itou, Y. Kondo, Y. Takeuchi, Y. Ukyo, K. Tatsumi and S. Muto, J. Electrochem. Soc., 156, A289 (2009).

S. Basu, K.S. Hariharan, S.M. Kolake, T.Song, T. Yeo, S. Doo, J. Electrochem. Soc., Manuscript Accepted. 

Figure 1
Contribution of a Reference Electrode Inserted in a Commercial Cell in the Understanding of the Ageing Mechanisms of C/NMC Li-Ion Batteries at Low Temperatures
Authors: Pilipili Matadi Bramy , Geniès Sylvie , Delaille Arnaud , Bultel Yann
Published: February 2020

Lithium-ion batteries degrade over time, according to different parameters and among which the charge conditions have a major impact. For both understanding and modeling work, a study about various parameters related to the charge has been conducted, considering the charge C-rate, the temperature, and the start and end of charge criteria (also called state-of-charge window). On the sidelines of this work, the monitoring of the potential of each electrode during an electrical test has been realized successfully thanks to the introduction of 2 lithium metal reference electrodes in a commercial lithium-ion cell. The measurements carried out on the instrumented commercial cell with a reference electrode allow to follow the potential behavior of each electrode separately while the cell is subjected to a charge / discharge profile.

The comparison of the results obtained from these measurements to those from post-mortem analysis (SEM, GC-MS, XRD, DSC and coin cells) of the cells have also made it possible to question the theory of metallic lithium deposition mechanism on the graphite electrode at full cycling and at cold temperatures [1] as predominant mechanism in favor of a new hypothesis, namely the polymerization of an electrolyte component as the cause of the lithium ions blocking into the graphite or an abnormal growth of the SEI in these conditions. This ageing mechanism would have diverse backgrounds according to the battery usage conditions [2]. TOF-SIMS analyzes are planned shortly and are expected to understand the mechanism involved

[1] J. B. Goodenough and Y. Kim, « Challenges for rechargeable batteries », Journal of Power Sources, 196 (2011) 6688-6694.

[2] M. C. Smart and B. V. Ratnakumar, « Effects of Electrolyte Composition on Lithium Plating in Lithium-Ion Cells », Journal of the Electrochemical Society, 158 (4) A379-A389 (2011)

Figure 1
Study of the Aluminum Anode Oxide Film and Cathode Material Interface of Conductive Polymer Aluminum Solid Electrolytic Capacitor
Authors: Sekiguchi Masaki , Ito Tomohiro , Tachibana Kazuhiro , Nishina Tatsuo
Published: February 2020

Introduction

 In 1745, Lyden jar was invented by J.Sesaguliers and Peter Van Muchenbroek. In1855, It was discovered by Charles Weatstone capable of forming an insulating film on the surface of the electrode. (By this discovery, we can make the electrolytic capacitor.) Aluminum electrolytic capacitor, was made by GE, Inc in 1908. And about 1931, aluminum electrolytic capacitor has been commercialized in the United States.

 Current, aluminum electrolytic capacitor is used in a power supply and noise reduction and an inveter.

 Electrolytic capacitor has a large equivalent series resistance and electricity is wasted. So, having a small equivalent series resistance, conductive polymer aluminum solid electrolytic capacitors are in practical use.

 However, conductive polymer aluminum solid electrolytic capacitor, to the leakage current is larger, the withstand voltage is low. It is desirable that this drawback is eliminated. It should be made clear disadvantages mechanism.

 It seems to be difficult when using typical electrochemical cell. This study was carried out by devising the cell.

Experiments, Results and Discussion

 The anode oxide film even if contaminated with carbon in a conductive polymer was repaired. As a result, the conductive polymer has been shown that increasing the insulating film of the anode oxide film.

 A conductive polymer aluminum solid electrolytic capacitors made of aluminum foil and a separator, as compared with the electrolytic solution cathode electrolysis capacitance, equivalent series resistance decreases. equivalent series resistance was reduced, especially 10kHz ~ 100kHz.

 Anodic aluminum after being anode oxidation, affixed a reinforcement seal.

 It was added dropwise to the electrolyte solution into the hole of the reinforcement label. Put the counter electrode and measured cyclic voltammetry without separator. This experiment shows, the anode oxide film showed it to be damaged by a separator.
Polyaniline / Nickel Ferrite / Nitrogen Doped Graphene Ternary Composite for Supercapacitors
Authors: Xia Xifeng , Tong Luyou , Lei Wu , Hao Qingli
Published: February 2020

AbstractElectrode materials are the most important components which greatly affect the capacity, power density and energy density of electrochemical energy storage devices. Lithium ion capacitors combining the advantages of lithium ion battery and supercapacitor, have been widely investigated recently due to their high energy density and high power density [1,2]. Herein, polyaniline / nickel ferrite / nitrogen doped graphene (PNFNG) ternary composite material and nitrogen doped graphene material were prepared by hydrothermal method and in situ polymerization [3]. The specific capacitance of PNFNG is 667 F/g at 0.1A/g in a two-electrode symmetric system tested in KOH aqueous electrolyte. The capacitance loses only 5% after repeating test for 5,000 cycles at a high current density of 5A/g. The energy density of the symmetric supercapacitor can reach 23 Wh/kg at a power density of 28 W/kg. With comparison, a lithium ion hybrid capacitor was assembled with the ternary composite as an anode and activated carbon as a cathode, and the organic electrolyte. The energy density of the hybrid capacitor reaches 104.4 Wh/g when its power density is 300 W/kg at 0.3A/g, respectively. Meanwhile, the capacitance of the hybrid capacitor is 80.3 F/g. The capacitance can keep 72% after 700 cycles at 0.3A/g.

Acknowledgements

The work was supported by the National Natural Science Foundation of China (Nos. 21073092, 21103092), Program for NCET-12-0629, Ph.D. Program Foundation of Ministry of Education of China (No.20133219110018), the Science and Technology Support Plan (No. BE2013126).

References

[1] Ma Y, Chang H, Zhang M, et al. Graphene‐Based Materials for Lithium‐Ion Hybrid Supercapacitors[J]. Advanced Materials, 2015, 27(36): 5296-5308.

[2] Aravindan V, Gnanaraj J, Lee Y S, et al. Insertion-type electrodes for nonaqueous Li-ion capacitors[J]. Chemical reviews, 2014, 114(23): 11619-11635.

[3] Wang W, Hao Q, Lei W, Xia X, Wang X.Ternary nitrogen-doped graphene/nickel ferrite/polyaniline nanocomposites for high-performance supercapacitors. Journal of Power Source, 2014, 269, 250-259.
Simultaneous Production of High-Performance Flexible Textile Electrodes and Fiber Electrodes for Wearable Energy Storage
Authors: Xu Chengjun , Dong Liubing
Published: February 2020

Flexible supercapacitors are important energy storage devices used for wearable and smart electronics. Various flexible supercapacitors have been prepared, including fiber supercapacitors, paper-like supercapacitors, three-dimensional aerogel materials based supercapacitors and textile supercapacitors. During them, fiber supercapacitors can be utilized in micro-devices, while textile supercapacitors are suitable for large-sized energy storage. To fabricate the flexible supercapacitors, the key lies in the acquirement of flexible electrodes, e.g., flexible fiber electrodes and textile electrodes. In this text, an effective strategy was proposed for the simultaneous productions of high-performance flexible textile electrodes and fiber electrodes. The prepared textile electrodes are textile/CNTs and textile/MnO2/CNTs composite textiles. During them, textile/MnO2/CNTs textile electrode/supercapacitor displays outstanding areal capacitances up to 3 F cm-2 and energy densities, and highly conductive textile is suitable for fabricating thicker electrode for supercapacitors with the high power. Scalable preparation of fiber electrodes was easily realized by dismantling textiles. In addition, the textile electrodes and fiber electrodes possess a long operation life and outstanding flexibility. Electrochemical properties of the electrodes may be further improved by optimization of MnO2, CNTs and polymers on the textiles. Despite of this, the present work is promising to promote the development of flexible electrodes and flexible energy storage devices.ercapacitors.[1-4]

Reference

[1] L. Dong, C. Xu*, et al. Adv Mater, 2016, 28, 1675.

[2] L. Dong, C. Xu*, et al. J Mater Chem A, 2015, 3, 4729.

[3] L. Dong, C. Xu*, et al. J Mater Chem A, 2016, 4, 4659.

[4] L. Dong, C. Xu*, et al. Carbon, 2015, 90, 164

Acknowledgements: We thank the financial surppots from NSFC, 973, and Shenzhen Technical Plan Projects.
Pseudohalide-Based Electrolytes for High-Energy Electrochemical Capacitors
Authors: Fic Krzysztof , Gorska Barbara , Bujewska Paulina , Béguin François , Frackowiak Elzbieta
Published: February 2020

Redox-active electrolytes and additives offer a large selection of available species serving for supercapacitor energy enhancement. The first group refers to typical organic compounds like hydroquinone with isomeric forms. There are also several reports on methylene blue and indigo carmine compounds tested on multi-walled carbon nanotubes. Nevertheless, these organic admixtures have limited solubility in water, and/or their bulkiness restricts adsorption at the interface. Apart from organic molecules, another group of electroactive species includes halide ions. Initially, the iodide/iodine and bromine/bromide redox couples were introduced to supercapacitors. To the best of our knowledge, this is the first report on the employment of alkali metal and ammonium thiocyanates (SCN-) aqueous solutions serving as an electrolyte for supercapacitors. The investigation presents a comprehensive study including the effect of salt concentration, the impact of counter anion type (K+, Na+, Li+ and NH4
+), the influence of applied current collectors as well as the effectiveness of asymmetric configuration. Our research proves that symmetric AC/AC system can easily operate up to 1.6 V with high capacitance and great cyclability. The thiocyanate redox shuttle with formal redox potential at +0.77 V vs. SHE preserves the positive electrode against oxidation and contrarily to iodides or bromides, oxidized SCN- specimen (e.g. polythiocyanogen) in a polymeric form does not evaporate from the system (unlike I2 or Br2). A comparative study on the effect of salt concentration and dependence on the type of current collectors (gold, titanium, and stainless steel) was performed using the KSCN aqueous solutions at various concentrations (1-7 mol∙L-1). It has been demonstrated that the highest concentration of SCN- specimen (7 mol∙L-1) preserved the best performance whatever the current collector used. However, on Ti and stainless steel current collectors, the activity of SCN- seems to be slightly reduced and more ‘capacitive’ profile has been observed. More in-depth studies demonstrated that the system based on 7 mol∙L-1 KSCN aqueous solution preserved high capacitance values even at 10 A∙g-1 current load and retained high energy density (~30 Wh∙kg-1) up to 10 kW∙kg-1 of power rate. Furthermore, we observed that kind of current collector strongly influences the cycle life of the system. Although the gold current collectors provided the highest capacitance during first 1000 cycles, their cyclability is limited to 2 000 cycles. For stainless steel-based systems, the capacitance retention reached 10 000 cycles at 1.6V voltage range.
Activated Carbons By Nitrogen Doped Chemical Activation and Their Performance for Electrical Double Layer Capacitors
Authors: Yoshikawa Masaaki , Fujimoto Hiroyuki
Published: February 2020

Chemical activation by alkali such as KOH is well known for the making process of high surface area activated carbons, but sometimes it had difficulties because of generation of metallic potassium and H2. In comparison with KOH, K2CO3 activation is very inert and safe but it is also known that cannot generate high porosity carbons. A novel chemical activation method by K2CO3 with addition of nitrogen compounds to carbon raw materials was developed. We investigated the Australian Loy Yang Brown coal as carbon raw material and urea or melamine as nitrogen compound. We prepared activated carbon which has specific surface area of over 2,000m2/g and meso pore ratio of over 40% by additional ratio of 1:1:2 as Brown coal: Urea: K2CO3 and activation at 900 degree C. The performance of this carbon as electrical double layer capacitor gives the specific capacity of 36F/g and 18F/cc.
High Performance Supercapacitor with the Activated Carbon Particle/Polymer Composite
Authors: Jang Yunseok , Kim Kwang-Young
Published: February 2020

In recent years, supercapacitors are widely studied for memory backup systems, hybrid electric vehicles and fuel cell vehicles. Supercapacitor electrodes are usually made to coat the activated carbon sludge on the current collect electrodes. And the activated carbon sludge is composed of the activated carbon particle, polymer binder and high conductivity materials. Polyvinylidene fluoride (PVDF) is usually used as the polymer binder in the activated carbon based supercapacitors. The PVDF is an insulator material, but the activated carbon is a conducting material. The reduced conductivity as adding the PVDF is enhanced by adding other high conductivity materials such as conductive carbon black. In this presentation, we propose a composite system based on the activated carbon and the crosslinkable polymer binder for high performance supercapacitor electrodes. We used the crosslinkable polymer binder instead of the PVDF binder and conductive carbon black to form the activated carbon clusters. The crosslinkable polymer binder has a merit such as minimizing the binder contents. We minimized the crosslinkable polymer binder contents to overcome the reduced conductivity of activated carbon clusters. And we demonstrate the effects of the minimized crosslinkable polymer binder on the electrical properties of supercapacitor electrodes. Acknowledgments  This study was supported by the R&D program of the Korea Research Council for Industrial Science and Technology of Republic of Korea (Grant 2015K000217/ 10052802/ KM3710/ NK186C/ SC1130/ MO5970/ NM8270).
Comparative Study with Phenol and Furfural Resin-Based Active Carbon for High Density Electric Double Layer Capacitor
Authors: Nakazawa Takafumi , Nishimura Kouhei , Saito Takeyasu , Okamoto Naoki , Ide Isamu , Onishi Yoshikazu , Nishikawa Masanobu
Published: February 2020

Electric double layer capacitor (EDLC) has been attracted much attention as one of the most promising high power and durable energy storage devices. However, low energy density is the major drawback, therefore, the optimization of specific surface area, nanoscale and mesoscale pore volume should be necessary to improve electrostatic capacity and reliability.

In this study, we carburized thermosetting resin-based particles (phenol resin and furfural resin, 10 µm in diameter) in N2 atmosphere in three hour (temperature rising rate 1ºC /min) at 400 ºC or 600ºC. Then, we treated carburized particle by three kinds of methods, KOH activation (KOH: samples = 4: 1 in weight ratio), CO2 activation or a combination of KOH and CO2 activation (KOH+CO2 activation). All activation methods were performed for 30 minutes at 800ºC or 850ºC (temperature rising rate 10ºC /min). Also, some samples were treated in the acid solution (Sulfuric acid: nitric acid = 3:1 in volume ratio) for 30 minutes at 60 ºC before KOH activation. Specific surface area/pore size distribution measurement was performed by N2 adsorption method. Elemental analysis was done by using to determine CHNO fraction. We prepared coin shaped carbon electrode (12 mm in diameter, from 8:1:1 mixture of active carbon, carbon black, and PTFE), and investigated the electrostatic characteristics of the capacitors in 6M KOH to elucidate the relationship between characteristic structure properties and electrochemical.  

We obtained large specific surface area as 1253 m2/g and 1240 m2/g in phenol resin by KOH activation and KOH+CO2 activation, respectively, however, did 515 m2/g by CO2 activation. The mesopore volume to total pore volume ratio of (12.8 %) KOH+CO2 activation method is larger than KOH activated method (11.5 %), suggesting that CO2 activation after the KOH activation increase pore size. Electrostatic capacity was 125 F/g and 158 F/g KOH activation and KOH+CO2 activation, respectively, though specific surface area is almost the same with both cases. This same trend was also seen with furfural resin. Electrostatic capacity was 163 F/g with phenol resin and 119 F/g with furfural resin at 20mA/g.

The specific capacity became three times, from 45 F/g to 153 F/g by introducing acid-treatment before KOH activation with furfural resin. Oxygen contents by elemental analysis also became three times. The results suggested that active carbon surface having an oxygen containing functional groups enhance capacitor performances.
Insights into Fast Lithium and Sodium-Ion Conduction in Solid Electrolyte and Cathode Materials
Authors: Islam M. Saiful
Published: February 2020

Major advances in rechargeable batteries require the discovery and characterisation of new materials. It is clear that a complete understanding of the properties of electrode and electrolyte materials for both Li- and Na-ion batteries requires fundamental knowledge of their underlying structural, ion diffusion and surface properties on the atomic- and nano-scales. In this context, advanced materials modelling [1] combined with structural and electrochemical techniques are now powerful tools for investigating these properties. This talk will highlight recent studies [2,3] in the following areas: (i) structural and mechanistic insights into fast lithium-ion conduction in Li4SiO4-Li3PO4 solid electrolytes; (ii) ion diffusion pathways in polyanionic cathode materials such as Li-sulfates (e.g. LiFeSO4OH) and Na-phosphates (e.g. Na2FePO4F, NaFePO4).

References

[1] M.S. Islam; C.A.J. Fisher, Chem. Soc. Rev., 43, (2014) 185.

[2] Y. Deng et al., J. Amer. Chem. Soc., 137 (2015) 9136.

[3] S.M. Wood et al., J.
Phys. Chem. C., 119 (2015) 15935.
In Operando Studies for the Strategic Development of High Performance Lithium/Sulfur Batteries
Authors: Kim Chi-Su , Marceau Hugues , Hovington Pierre , Zhu Wen , Paolella Andrea , Guerfi Abdelbast , Vijh Ashok , Zaghib Karim
Published: February 2020

Li-S battery has attracted intensive attentions during the past decades as a strong candidate that may overcome the limit of current lithium-ion battery technology. In spite of its promises, a number of challenges still remain unsolved hindering the commercialization of Li-S batteries in near future, especially for the EV applications. It is generally accepted that the technical problems of Li-S battery are related with the intrinsic nature of conversion reactions, like low conductivity, poor diffusivity and significant morphology change, along with the unique properties of sulfur chemistry which include high solubility and strong reactivity of polysulphide species in organic solvents. However, fundamental mechanisms behind the limited performance of Li-S batteries are not fully understood and remain controversial according to the analytical methods and the specific experimental conditions. Since the charge-discharge electrochemical reaction in Li-S batteries involves complicated chemical reactions in bulk electrolyte, ex-situ analysis does not reflect the actual situation inside the battery, due to the rapid re-equilibrium of the reaction species during the sample preparation process and even during the observation period. Moreover, high volatility of elemental sulfur (S8) often leads to the misinterpretation of characterization results which are obtained in the vacuum condition or with high temperature treatment.

In this study, Li/S cells were investigated with operando techniques using Scanning Electron Microscope (SEM), Ultraviolet-Visible absorption spectroscopy (UV-Vis) and Raman spectroscopy. All-solid-state polymer electrolytes were employed to design the operando cells, which allowed a real time observation of SEM images and a speciation by UV-VIS and Raman without needs for the solvent dilution. The operando SEM successfully visualizes the cross-section of Li/S polymer cell and reveals the evolution of morphology changes with cycles, as well as the aging mechanism including the migration of sulfur species and irreversible loss of active materials out of the cathode electrode. Appearance of elemental sulfur is clearly observed beyond 2.3V in the middle of charge process. The non-destructive operando UV-VIS spectroscopy demonstrates the evolution of characteristic absorption bands with progress of discharge and charge, and shows the accumulation of soluble sulphides in the electrolyte, not only high order polysulfides but also less soluble Li2S, over cycling. The inverse relationship between the intensity of S4
2- and S6
2- bands in UV-VIS spectroscopy implies that the charge and discharge reactions take place through different pathways; the formation of S4
2- is prominent during discharge and shuttle reactions, while S6
2- is more prevailing during charge.
Fundamental Aspects of Lithium Ion Battery Materials Degradation Mechanisms
Authors: Gasteiger Hubert A.
Published: February 2020

Increasing cycle-life and energy density of lithium ion batteries requires the development of improved electrolyte additives and a detailed understanding of the stability of electrolyte and cathode electrode components, particularly at high anodic potentials. The fundamental decomposition/degradation mechanisms will be examined by on-line electrochemical mass spectrometry (OEMS), by AC impedance, and by ex-situ ATR-FTIR and NMR. In this presentation, we will discuss the following aspects:

anodic and cathodic decomposition mechanisms of electrolytes and electrolyte additives;

quantification of the anodic stability of conductive carbons and of conductive carbon coatings at potentials relevant for high-voltage cathode materials;

effect of water and hydroxide impurities on carbon and electrolyte stability.
Stabilization of High Energy Cathodes By Introducing Conformal Passivating Shells on the Surface
Authors: Kwon Bob Jin , Phillips Patrick J , Key Baris , Kim Chunjoong , Klie Robert F , Cabana Jordi
Published: February 2020

Combined cycling stability at high energy density is required for lithium ion battery to meet the criteria for use in electric vehicles. In generally, material utilization and rate capability are enhanced at small particle sizes. [1] Reduced size of electrode materials can enhance the rate of lithium ions because of shortened diffusion pathway and increases surface area to induces facile access by the electrolyte. In contrast, chemical degradation at electrode-electrolyte interface is also facilitated by large contact area with nanoparticle electrode. Unfavorable interfacial reactions such as dissolution of active materials and decomposition of electrolyte mainly occur because the surface of active materials is energetically unstable. [2] In order to minimize side reactions that can negatively affect to electrochemical performance, replacing electrochemically inactive ions on the surface of active materials can improve the interfacial stability. However, this substitution should take place as thin passivating layers on individual particles to preserve storage capacity. [3]

Herein, we demonstrate a strategy toward the stabilization of interfaces by introducing core-shell type of nanocrystals that is composed of electroactive transition metal oxide in core and ultra-thin inactive epitaxial oxide shell on the surface. To prove this concept, we introduce layered LixCoO2 nanocrystals as a core component, with Al-rich shells as passivation layer to minimize side reaction with electrolyte. The resulting materials shows stable cycling curves as well as higher capacity retention at high rate of charging and discharging reaction compared to bare LixCoO2.

References

1.         Isaac D. Scott, Yoon Seok Jung, Andrew S. Cavanagh, Yanfa Yan, Anne C. Dillon, Steven M. George, and Se-Hee Lee, Nano Letters, 414–418, 11 (2011).

2.         Peter G. Bruce, Bruno Scrosati, and Jean-Marie Tarascon, Angew. Chem. Int. Ed, 2930-2946, 47 (2008).

3.         Chunjoong Kim, Patrick J. Phillips, Linping Xu, Angang Dong, Raffaella Buonsanti, Robert F. Klie, and Jordi Cabana, Chem. Matter, 394-399, 27 (2014).

Figure. (a) Evolution of specific capacity (solid symbol) and coulombic efficiency (open symbol) in cycling at C/20, (b) electron microscopic image, (c) EELS for Al and (d) EELS for Co atom of LixCoO2 with Al rich shell nanocrystals.

Figure 1
Ultrathin Coating of Nitrogen and Sulfur Co-Doped Graphene Nanosheets on Polymer Separator for Suppressing Dendritic Lithium Growth in Lithium Metal Batteries
Authors: Cho Jinhyun , Shin Won-Kyung , G Kannan Aravindaraj , Kim Dong-Won
Published: February 2020

The advent of electric vehicles and other high energy density applications has intensified the research efforts on lithium metal-based batteries, as metallic lithium can provide a high specific capacity (~3,862 mAh g-1), enabling it as a promising negative electrode for next-generation battery systems [1,2]. However, the instability of lithium electrodes is one of the greatest challenges hindering the successful development of lithium metal batteries.  Lithium metal is unstable against nearly all chemical species and reacts with organic solvents and salts in liquid electrolytes.  Moreover, continuous deposition and stripping of lithium may induce uncontrollable dendritic Li growth, which in turn leads to internal short circuits, failure, and eventually explosions.

In this work, we demonstrated that an ultrathin nitrogen and sulfur co-doped graphene (NSG) layer deposited on a PE separator could effectively stabilize the lithium electrode surface, suppress dendrite formation, and improve the cycling stability of lithium metal batteries. The NSG coating layer is very thin as compared to other ceramic coatings in micrometer scales, which can provide higher energy density of the cell with NSG separator.  The incorporation of heteroatom dopants could induce structural deformations due to local strains induced in the carbon framework, thereby allowing for easy ionic migration while maintaining a uniform ionic flux on the Li metal surface.  Moreover, the lone pair electrons in the heteroatom dopants led to the generation of negative charge, resulting in enhanced interfacial interactions between the NSG-coated separator and the lithium electrode.  The NSG coating also imparted thermal stability to the PE separator, thus preventing thermal shrinkage of the separator at elevated temperature and enhancing battery safety.  The cycling performance of the lithium metal cell employing a NSG coated separator was remarkably improved as compared to the cell with a pristine PE separator.

 

References

[1]  J. -M. Tarascon, M. Armand, Nature
2001, 414, 359–367.

[2]  W. Xu, J. Wang, F. Ding, X. Chen, E. Nasybulin, Y. Zhang, J. G. Zhang,. Energy Environ. Sci.
2014, 7, 513–537.
Development of Novel Noncarbonate Electrolytes for Silicon Alloy Anodes
Authors: Zhu Ye , Cheng Gang , Strand Dee
Published: February 2020

Wildcat Discovery Technologies is developing novel electrolyte additives and noncarbonate solvent formulations that yield improved solid electrolyte interphase (SEI) layers on silicon alloy anodes. The large volumetric changes in silicon during charge/discharge cycles result in mechanical disruption of conventional SEI's leading to rapid capacity fade as the cell cycles. Novel additives that could help to form more mechanically robust SEI passivation layers, hence improving cycle life of silicon based materials are identified through the screening in propylene carbonate (PC) based electrolyte since PC is not expected to form an effective SEI layer. The additives are tested with PC to determine their efficacy. Wildcat's high throughput electrolyte formulation, cell assembly, and test capabilities enable the evaluation of hundreds of additives in a very short timeframe.

Once effective SEI additives are identified in a PC-based formulation, other non-SEI forming solvents can be evaluated. Since the additives are effective without solvent participation in SEI formation, solvents that may not be reductively stable on the anode can also be considered, opening the possibility to more oxidatively stable or less flammable solvents. Wildcat has evaluated hundreds of combinations of noncarbonate solvents with its initial silicon anode SEI additives, and identified a few very unique combinations that showed further improved cycle life over the state-of-the-art carbonate based electrolyte.

Finally, with the most promising noncarbonate solvents in hand, new electrolyte additives are screened for further improved cycle life. The new additives selection is based on the earlier additive screening in PC electrolyte. A thorough Structure Activity Relationship (SAR) study for those promising additives is carried out. This presentation will focus on the results of the additive improvement to cycle life in NMC//Si full cells, and illustrate the opportunities for novel solvent combinations. We will demonstrate the power of high throughput development of lithium ion battery advanced electrolytes within this presentation.
Observation of Li2s-P2S5 Crystalline Glass By Transmission Electron Microscopy
Authors: Mori Shigeo , Tsukasaki Hirofumi , Suginaka Yusuke , Mori Youta , Matsuyama Takuya , Hayashi Akitoshi , Tatsumisago Masahiro
Published: February 2020

Sulfide solid electrolytes are electrochemically stable in a wide potential window and exhibit high lithium ion conductivities of more than 10-4 S cm-1 at room temperature. In particular, the Li2S-P2S5 glasses, which are served as the solid electrolyte, have been reported to crystallize above 473 K in the heating process from room temperature. Noted that lithium ion conductivities depend strongly on precipitated crystalline phases [1, 2]. In this study we have investigated microstructures of the Li2S-P2S5 glasses by transmission electron microscopy (TEM). Figure 1 shows the high-resolution (HR) TEM image of the 75Li2S-25P2S5 glass at room temperature, together with the corresponding electron diffraction (ED) pattern. Although a halo pattern due to the amorphous structure was observed in the ED pattern, crystalline nanoparticles with approximately 5x5 nm2 were found to be randomly distributed in the amorphous state, as indicated by dotted circle regions (Fig. 1). Furthermore, in-situ TEM observation in the 75Li2S-25P2S5 glasses revealed that the crystallization started at approximately 473 K and gradually proceeded as temperature increased from 473 K.

[1] F. Mizuno et al, Adv. Mater. 17 (2005) 918-921. [2] F. Mizuno et al, Solid State Ionics 177 (2006) 2721-2725.

Figure 1