RAPID IODINATION OF THE ISOMERS OF AMINOBENZOIC ACID IN AQUEOUS MEDIUM BY IOD...EDITOR IJCRCPS
The rapid kinetics of the iodination of para-aminobenzoic acid and meta-aminobenzoic acid by iodine monochloride at 4.5 pH has
been studied by employing hydrodynamic voltammetry. The reactions were found to be of the second order and the specific
reaction rates for the two reactions were found to be 25 M-1s-1 and 10 M-1s-1 at 25.00C respectively. These data were
complemented with those for the iodination of ortho-aminobenzoic acid by ICl obtained earlier to quantitatively assess the relative
reactivity of the three isomers stemming from substituent regiospecificity.
Keywords: Iodine monochloride, hydrodynamic voltammetry, aminobenzoic acid isomers.
Electrochemical properties of myoglobin deposited on multi walled carbon nano...Expand_Lives
We report the direct electrochemical and electrocatalytic properties of myoglobin (MB) on a multi-walled
carbon nanotube/ciprofloxacin (MWCNT/CF) film-modified electrode. A highly homogeneous MWCNT
thin-film was prepared on an electrode surface using ciprofloxacin (CF) as a dispersing agent. MB was
then electrochemically deposited onto the MWCNT/CF-modified electrode. The MB/MWCNT/CF film was
characterized by scanning electron microscopy and UV–visible spectroscopy (UV–vis). UV–vis spectra
confirmed that MB retained its original state on the MWCNT/CF film. Direct electrochemical properties of MB on the MWCNT/CF film were investigated by cyclic voltammetry. The formal potential and
electron transfer rate constant were evaluated in pH 7.2 buffer solution as−0.327 V and 300 s
−1
, respectively. In addition, the MB/MWCNT/CF-modified electrode showed excellent electrocatalytic properties
for the reduction of hydrogen peroxide (H2O2). The MB/MWCNT/CF-modified electrode was used for the
detection of H2O2at concentrations from 1×10
−6
Mto7×10
−4
M in pH 7.2 buffer solution. Overall, the
MB/MWCNT/CF-modified electrode was very stable and has potential for development as a H2O2sensor.
RAPID IODINATION OF THE ISOMERS OF AMINOBENZOIC ACID IN AQUEOUS MEDIUM BY IOD...EDITOR IJCRCPS
The rapid kinetics of the iodination of para-aminobenzoic acid and meta-aminobenzoic acid by iodine monochloride at 4.5 pH has
been studied by employing hydrodynamic voltammetry. The reactions were found to be of the second order and the specific
reaction rates for the two reactions were found to be 25 M-1s-1 and 10 M-1s-1 at 25.00C respectively. These data were
complemented with those for the iodination of ortho-aminobenzoic acid by ICl obtained earlier to quantitatively assess the relative
reactivity of the three isomers stemming from substituent regiospecificity.
Keywords: Iodine monochloride, hydrodynamic voltammetry, aminobenzoic acid isomers.
Electrochemical properties of myoglobin deposited on multi walled carbon nano...Expand_Lives
We report the direct electrochemical and electrocatalytic properties of myoglobin (MB) on a multi-walled
carbon nanotube/ciprofloxacin (MWCNT/CF) film-modified electrode. A highly homogeneous MWCNT
thin-film was prepared on an electrode surface using ciprofloxacin (CF) as a dispersing agent. MB was
then electrochemically deposited onto the MWCNT/CF-modified electrode. The MB/MWCNT/CF film was
characterized by scanning electron microscopy and UV–visible spectroscopy (UV–vis). UV–vis spectra
confirmed that MB retained its original state on the MWCNT/CF film. Direct electrochemical properties of MB on the MWCNT/CF film were investigated by cyclic voltammetry. The formal potential and
electron transfer rate constant were evaluated in pH 7.2 buffer solution as−0.327 V and 300 s
−1
, respectively. In addition, the MB/MWCNT/CF-modified electrode showed excellent electrocatalytic properties
for the reduction of hydrogen peroxide (H2O2). The MB/MWCNT/CF-modified electrode was used for the
detection of H2O2at concentrations from 1×10
−6
Mto7×10
−4
M in pH 7.2 buffer solution. Overall, the
MB/MWCNT/CF-modified electrode was very stable and has potential for development as a H2O2sensor.
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
EDTA Titration
more chemistry contents are available
1. pdf file on Termmate: https://www.termmate.com/rabia.aziz
2. YouTube: https://www.youtube.com/channel/UCKxWnNdskGHnZFS0h1QRTEA
3. Facebook: https://web.facebook.com/Chemist.Rabia.Aziz/
4. Blogger: https://chemistry-academy.blogspot.com/
EDTA Titration
Effect of Chemically Treated Aluminum Nitrate: Its Dielectric Studies Of Sisa...paperpublications3
Abstract: Aluminum oxide synthesized through sintering route. The present research work deals with Alrrite composite prepared using chemical reactions. Aluminum nitrates and ammonium chloride doped with sisal fiber has been prepared. The comparative studies of aluminum oxide were examined through dielectric measurement.
Electrochemical Behavior of L-Tyrosine at Poly (Dicyclomine Hydrochloride) Fi...paperpublications3
Abstract: An electrochemical method for the determination of L-Tyrosine (LTY) using a dicyclomine hydrochloride (DICY) polymer film modified carbon paste electrode. The surface morphology of poly (DICY) modified carbon paste electrode was characterized by SEM. The modified electrode showed excellent electro catalytic activity towards the oxidation of LTY in 0.1 M phosphate buffer solution of pH 6.5. The effect of pH, concentration and scan rate were studied at the bare carbon paste electrode and poly (DICY) modified carbon paste electrode were investigated. Increase of LTY concentration shows linear increase in oxidation peak current. The linear relationship was obtained between the anodic peak current (Ipa) and concentration LTY in range 2×10-5 M to 1×10-3 M with correlation coefficient of 0.9984. The low detection limit (LOD) and low quantification limit (LOQ) of LTY were detected. The cyclic voltammetric studies indicated that the oxidation of LTY at the modified electrode surface was irreversible; adsorption controlled and undergoes a one electron transfer process at the poly (DICY) film modified carbon paste electrode. The modified electrode showed high sensitivity, detection limit, high reproducibility, easy preparation and regeneration of the electrode surface.
Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Productijtsrd
A condensation product CP was successfully synthesized from reaction of dimethyl amino benzaldehyde and aniline giving yields of 80 . The compound was characterized by Fourier Transform Infrared FTIR Spectroscopy. The corrosion inhibiting property of the CP on mild steel in HCl solution were investigated by the weight loss measurements, electrochemical impedance spectroscopy EIS and linear polarization resistance LPR . The concentrations of CP were varied from 1 x 10 3 M to 5 x 10 3 M. The inhibition efficiencies obtained from all the methods employed were in good agreement where the percentage of inhibition efficiencies increased with concentration of CP. Results showed that CP was the better inhibitor with inhibition efficiency of 90 at 5 x 10 3 M additive concentration. This is likely due to the effect of its large molecular size, higher number of electroactive heteroatoms and bigger p electron cloud of the conjugated double bond system. Ganesha Achary "Corrosion Inhibition of Mild Steel in HCl Medium by a Condensation Product" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-4 | Issue-4 , June 2020, URL: https://www.ijtsrd.com/papers/ijtsrd30869.pdf Paper Url :https://www.ijtsrd.com/chemistry/physical-chemistry/30869/corrosion-inhibition-of-mild-steel-in-hcl-medium-by-a-condensation-product/ganesha-achary
Role of the morphology and surface planes on the catalytic activity of spinel...Science Padayatchi
The electrocatalytic activity of the spinel oxide LiMn1.5Ni0.5O4 with
different morphologies (cubic, spherical, octahedral, and truncated octahedral) has been
investigated for the oxygen evolution reaction (OER) in alkaline solutions that is of
interest for metal−air batteries. The OER activity increases in the order truncated
octahedral < cubic < spherical < octahedral, despite a larger surface area (2.9 m2 g−1) for
the spherical sample compared to nearly similar surface areas (0.3−0.7 m2 g−1) for the
other three samples. The high activity of the octahedral sample is attributed to the
regular octahedral shape with low-energy {111} surface planes, whereas the lowest
activity of the truncated octahedral sample is attributed to the high-energy {001} surface
planes. The octahedral sample also exhibits the lowest Tafel slope of 70 mV dec−1 with
the highest durability whereas the truncated octahedral sample exhibits the highest Tafel
slope of 120 mV dec−1 with durability similar to the cubic and spherical samples. The
study demonstrates that the catalytic activities of oxide catalysts could be tuned and
optimized by controlling the surface morphologies/planes via novel synthesis approaches.
Recent Achievements with Alane (Aluminum Hydride, AlH3) and Fuel Cell Power S...chrisrobschu
Fuel cells have many advantages compared to conventional power sources including high efficiency and solid-state operation. Until now, a key shortcoming of fuel cell technology has been the fuel itself, as conventional methods for storing hydrogen were unsafe or impractical for portable use. This paper discusses a lightweight, energy-dense, non-toxic, recyclable, stable, and easy to transport solution for hydrogen storage. It is a material known as Alane that exists as powder and, when heated to the proper temperature, controllably releases hydrogen gas. Alane has near ideal attributes in terms of reactivity, stability, and safety - making it an excellent choice for several applications in need of a portable hydrogen supply. However, it has historically been difficult to produce efficiently. Through partnerships with leading industry experts in the government and private sector, Ardica Technologies has advanced the state of the art of Alane production. Ardica has developed a small-scale process which has been proven to yield high quality Alane that meets or exceeds the characteristics of the generally accepted gold standard reference material.
Power sources 2018_paper14-2
Underwater Sound Generation Using Carbon Nanotube Projectorschrisrobschu
The application of solid-state fabricated carbon nanotube sheets as thermoacoustic projectors is extended from air to
underwater applications, thereby providing surprising results. While the acoustic generation efficiency of a liquid immersed nanotube
sheet is profoundly degraded by nanotube wetting, the hydrophobicity of the nanotube sheets in water results in an air envelope
about the nanotubes that increases pressure generation efficiency a hundred-fold over that obtained by immersion in wetting alcohols.
Due to nonresonant sound generation, the emission spectrum of a liquid-immersed nanotube sheet varies smoothly over a wide
frequency range, 1-105 Hz. The sound projection efficiency of nanotube sheets substantially exceeds that of much heavier and thicker
ferroelectric acoustic projectors in the important region below about 4 kHz, and this performance advantage increases with decreasing
frequency. While increasing thickness by stacking sheets eventually degrades performance due to decreased ability to rapidly transform
thermal energy to acoustic pulses, use of tandem stacking of separated nanotube sheets (that are addressed with phase delay) eliminates
this problem. Encapsulating the nanotube sheet projectors in argon provided attractive performance at needed low frequencies, as
well as a realized energy conversion efficiency in air of 0.2%, which can be enhanced by increasing the modulation of temperature.
Thermophones using carbon nanotubes and alternative nanostructures for high p...chrisrobschu
There is a large promise for thermophones in high power sonar arrays, flexible loudspeakers and noise cancellation devices. The freestanding aerogel-like carbon nanotube sheet as a thermoacoustic (TA) heat source demonstrates so far the best performance. However, the limited accessibility of large size free standing carbon nanotube sheets and other even more exotic materials published recently, hampers the field. I present here new alternative materials for TA heat source with high energy conversion efficiency, additional functionalities, environmentally friendly and cost effective production technologies. I discuss the TA performance of alternative nanoscale materials and compare their spectral and power dependencies of sound pressure in air. The study presented here focuses on engineering of thermal gradients in the vicinity of nanostructures and subsequent heat dissipation processes from the interior of encapsulated thermoacoustic projectors. Applications of TA projectors for high power SONAR arrays, sound cancellation, and optimal thermal design, regarding enhanced energy conversion efficiency, are discussed.
Faceplate NOV 2012 Page 19, Vic Maroldachrisrobschu
See FacePlate NOV2012 Page 19 for retirement article on Vic Marolda and description of the Engineering and Dive Support Unit (EDSU) work and the Naval Undersea Warfare Center (NUWC)
Faceplate nov2012 marolda
Sonardyne International has sold and delivered additional Sentinel Intruder
Detection Sonar Systems for the US Navy. They will be used for the Integrated
Swimmer Detection Program managed by the Naval Underwater Warfare Center
(NUWC) in Newport RI. Ordered in October 2009, the systems were delivered and
commissioned within six weeks.
SRNL Acceptability Envelope metal hydrideschrisrobschu
The design and evaluation of media-based hydrogen storage systems requires the use of
detailed numerical models and experimental studies, with significant amount of time and
monetary investment. Thus a scoping tool, referred to as the Acceptability Envelope, was
developed to screen preliminary candidate media and storage vessel designs, identifying
the range of chemical, physical and geometrical parameters for the coupled media and
storage vessel system that allow it to meet performance targets. The model which
underpins the analysis allows simplifying the storage system, thus resulting in one inputone
output scheme, by grouping of selected quantities.
Two cases have been analyzed and results are presented here. In the first application
the DOE technical targets (Year 2010, Year 2015 and Ultimate) are used to determine the
range of parameters required for the metal hydride media and storage vessel. In the second
case the most promising metal hydrides available are compared, highlighting the potential
of storage systems, utilizing them, to achieve 40% of the 2010 DOE technical target. Results
show that systems based on LiMg media have the best potential to attain these performance
targets.
Srnl acceptability
envelope_metal_hydride_h2_int_j_hydrogen_energy_2012_37
Investigation of Metal and Chemical Hydrides for Hydrogen Storage in Novel Fu...chrisrobschu
DOE Funded Activities
Objectives:
•Use engineering analyses to screen H2 storage systems against DoD targets & requirements (FY15)
•Identify suitable hydrogen storage materials and suitable vehicle demonstration platforms
•Develop a preliminary design of an integrated UUV design with a solid hydrogen storage system
•Complete detailed design of the hydrogen storage system
•Complete integrated system design
ONR/NUWC Funded Activities
Objectives:
•
Design and build a small bench-scale, alane-based, hydrogen storage vessel
•
Perform preliminary testing on the bench-scale, storage system
•
Package and ship bench-scale vessel and alanematerial to the Navy NUWC
•
Provide technical support to Navy NUWC for their further testing and evaluation
Doe amr st134_motyka_2016_p
Investigation of Solid State Hydrides For Autonomous Fuel Cell Vehicleschrisrobschu
Joint Department of Energy Department of Navy
Hydrogen storage material aluminum hydride, or Alane, for Unmanned Undersea Vehicles
St134 teprovich 2017_o
US Undersea Warfare Science & Technology Objectives and US Unmanned Undersea ...chrisrobschu
US Undersea Warfare Science & Technology Objectives and US Unmanned Undersea Vehicles (UUV) Overview
The Naval Undersea Warfare Center Division Newport provides research, development, test and evaluation, engineering, analysis and assessment, as well as Fleet support capabilities for submarines, autonomous underwater systems, and offensive and defensive undersea weapon systems, and stewards existing and emerging technologies in support of undersea warfare.
•Power and Energy Science and Technology Objectives:
1.Develop safe reliable, affordable and high efficiency energy management, generation, transfer, shipment, deployment, and storage for undersea platforms;
2.Develop safe, reliable, affordable and efficient high pulse power management, generation, transfer and employment;
3.Develop the capability to reliably and safely harvest, obtain, store and transfer energy to undersea assets;
4.Develop capability to reliably characterize the failure effects and modes of power and energy sources.
Overview of The Naval Undersea Warfare Center (NUWC) Distro Achrisrobschu
The Naval Undersea Warfare Center (NUWC) has a proud heritage of providing superior
undersea warfare (USW) products and services to the U.S. Navy. Our mission is
enduring and our fundamental role of serving the Fleet is as vital today as it has ever
been since our predecessor was created in 1869.
Our role as a Navy Warfare Center is to support the Chief of Naval Operations’ (CNO)
“A Cooperative Strategy for 21st Century Seapower” by bringing cost-effective solutions
to the Fleet. In cooperation with our government, industry, and academic partners, we
do this by developing conceptual ideas, seizing technological opportunities, and bringing
these through product development, testing, sea-trial, acquisition, acceptance testing,
Fleet introduction, and on-going support.
Nuwc brochure distro_a
Presentation: DOE Stetsoon Hydrogen Storage technologieschrisrobschu
Hydrogen Storage Technologies –
A Tutorial
with Perspectives from the US National Program
Ned T. Stetson
U. S. Department of Energy
1000 Independence Ave., SW
Washington, DC 20585
Materials Challenges in Alternative and Renewable Energy
Cocoa Beach, FL
February 22, 2010
• Why do we need better hydrogen storage?
• Physical storage technologies
– Liquid
– Compressed
– Cryo-compressed
• Materials-based storage technologies
– Hydrogen sorbents
– Metal hydrides
– Complex hydrides
– Chemical hydrogen storage
Doe stetson hydrogen_storage_technologies_tutorial
Fuel Cells for Unmanned Undersea Vehicles (UUVs) 16MAR2016chrisrobschu
There is a naval need for an air-independent advanced electric power source with high energy storage for unmanned undersea vehicles (UUV).
Current battery systems can not meet mission requirements.
Proton exchange membrane fuel cells (PEMFC) and solid oxide fuel cells (SOFC) are being investigated due to higher efficiencies and energy densities.
System safety must meet requirements for approval.
PEMFC and SOFC have been identified to meet UUV requirements due to their high efficiency and improved energy density over current battery systems.
Many options for reactant storage, critical for system energy.
System safety is critical for approval.
ONR BAA objectives to deliver TRL-6 fuel cell system for UUVs.
Fuel cells for uu vs 16_mar2016
Presentation: Power & Eenrgy for Unmanned Undersea Vehicles (UUVs)chrisrobschu
UUV and UDNS Energy & Power Technology Challenges
Energy and power density plus:
• Air-independent operation
• Refuelability
• Multi-mission capability
• Stealth
• Safety
• Environmentally benign
• Endurance (high energy density)
• Weight/volume constraints
• Buoyancy
• Quick start-up
• Low/no signature
• Cost effective
Power and energy_sources_10-27-11
Interim Guidance for Adopting Fuel Cell Technology into the Navy Fleetchrisrobschu
Purpose: Disseminate Proposed SG270 Fuel Cell Interim Guidance
Hazard Assessment Process
Provide updates since guidance was published ~FY13
Goal: Solicit feedback from Stakeholders
Comments, Questions
Possible revisions to process
Develop approval process so early designs can be influenced to increase chance of approval
Sg270 fc brief_17_nov2016_01b_public_release
Lithium Ion Conductive Glass Ceramics:
Properties and Application
in Lithium Metal Batteries
Kousuke Nakajima a, Takashi Katoh a,
Yasushi Inda a, Brion Hoffman b
aOHARA-INC., 1-15-30 Oyama, Chuo-ku, Sagamihara-shi, Kanagawa 252-5286, Japan
bOHARA CORPORATION, 23141 Arroyo Vista,Suite 200,
Rancho Santa Margarita, CA 92688, United States
Symposium on Energy Storage Beyond Lithium Ion; Materials Perspective,
October 7-8, 2010 Oak Ridge National Laboratory
Kousuke Nakajima, OHARA INC.
8th October, 2010
Session8 240-nakajima
Lithium Ion Conductive
Glass Ceramic Electrolyte
Very high theoretical specific energy: 8572 Wh/kg of Li and 4578 Wh/L of Li
Quiet, Minimal Signature, Long shelf life (no self discharge)
Potentially safer to store than Li-ion (No Cathode in storage)
• External Attributes:
• Entire anode is surrounded by Seawater Environment
• Laminate Material cold formed to encase lithium slug
• Pouch designed to Collapse as lithium reservoir is depleted
Ø Pressure tolerant
Ø Minimal pressure differential across Ceramic Membrane
• Package assembled and heat sealed
4
• Internal Attributes:
• Lithium reservoir (Slug)
Ø Can be scaled for Mission Duration
• Typical Li Metal Disc
Ø 1.75” OD, 0.2” Thick
• Non Aqueous Electrolyte
• Nickel Current collector
Ø Cold Welded to Lithium Slug
• Ni Electrical Tabs
Electrochemical Performance Of Pressure Tolerant Anodes For A Li-seawater Ba...chrisrobschu
Electrochemical Society Meeting
Electrochemical Performance Of Pressure Tolerant Anodes For A Li-seawater Battery
Autonomous undersea systems are being developed for a variety of US Navy mission scenarios.
The mission duration of autonomous undersea vehicles and sensors is limited by the amount of onboard energy.
Objective:
Develop a novel energy source with increased energy density for increased mission duration.
Also must be:
Safe
Robust
Long shelf life
Pressure tolerant
Reasonable cost
Air independent
Very high theoretical specific energy:
8572 Wh/kg of Li and 4578 Wh/L of Li (seawater cathode)
Don't need to carry seawater or oxygen.
Practical battery energy density depends on efficient packaging of Li and voltage.
Primary (one use) battery
Reserve Battery
Long shelf life – no self discharge
Potentially safer to store than commercial Li batteries
Ecs spring meeting_2009
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Overview of the fundamental roles in Hydropower generation and the components involved in wider Electrical Engineering.
This paper presents the design and construction of hydroelectric dams from the hydrologist’s survey of the valley before construction, all aspects and involved disciplines, fluid dynamics, structural engineering, generation and mains frequency regulation to the very transmission of power through the network in the United Kingdom.
Author: Robbie Edward Sayers
Collaborators and co editors: Charlie Sims and Connor Healey.
(C) 2024 Robbie E. Sayers
Final project report on grocery store management system..pdfKamal Acharya
In today’s fast-changing business environment, it’s extremely important to be able to respond to client needs in the most effective and timely manner. If your customers wish to see your business online and have instant access to your products or services.
Online Grocery Store is an e-commerce website, which retails various grocery products. This project allows viewing various products available enables registered users to purchase desired products instantly using Paytm, UPI payment processor (Instant Pay) and also can place order by using Cash on Delivery (Pay Later) option. This project provides an easy access to Administrators and Managers to view orders placed using Pay Later and Instant Pay options.
In order to develop an e-commerce website, a number of Technologies must be studied and understood. These include multi-tiered architecture, server and client-side scripting techniques, implementation technologies, programming language (such as PHP, HTML, CSS, JavaScript) and MySQL relational databases. This is a project with the objective to develop a basic website where a consumer is provided with a shopping cart website and also to know about the technologies used to develop such a website.
This document will discuss each of the underlying technologies to create and implement an e- commerce website.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Hierarchical Digital Twin of a Naval Power SystemKerry Sado
A hierarchical digital twin of a Naval DC power system has been developed and experimentally verified. Similar to other state-of-the-art digital twins, this technology creates a digital replica of the physical system executed in real-time or faster, which can modify hardware controls. However, its advantage stems from distributing computational efforts by utilizing a hierarchical structure composed of lower-level digital twin blocks and a higher-level system digital twin. Each digital twin block is associated with a physical subsystem of the hardware and communicates with a singular system digital twin, which creates a system-level response. By extracting information from each level of the hierarchy, power system controls of the hardware were reconfigured autonomously. This hierarchical digital twin development offers several advantages over other digital twins, particularly in the field of naval power systems. The hierarchical structure allows for greater computational efficiency and scalability while the ability to autonomously reconfigure hardware controls offers increased flexibility and responsiveness. The hierarchical decomposition and models utilized were well aligned with the physical twin, as indicated by the maximum deviations between the developed digital twin hierarchy and the hardware.
2. 1360 L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366
Table 1
Electrolyte compositions and abbreviations used in this report.
1 LiPF6-1 1.0 M LiPF6–PC/DME (1:1), plus 1000 ppm DMAc
2 LiPF6-2 1.0 M LiPF6–PC/DME/1,3-dioxolane (1:1:1), plus 3000 ppm TBA
3 LiBOB-1 0.7 M LiBOB–PC:DME (1:1)
4 LiBOB-2 0.7 M LiBOB–PC:DME:1,3-dioxolane (1:1:1)
5 LiI 0.75 M LiI–DME:1,3-dioxolane (1:2)
6 LiTfSI 0.75 M LiTfSI–DME:1,3-dioxolane (1:2)
salts which introduces a high viscosity into the electrolyte as
concentration increases [3].
The conductivities of the electrolytes were measured with a
712 Conductometer from Metrohm Ltd. at several temperatures:
−20, 0, 20, and 40 ◦C. The physical properties of the solvents
are listed in Table 2. Two lithium/electrolyte/lithium coin cells
(NRC-ICPET, 23 mm in diameter) for each electrolyte were pre-
pared. The surface area of the counter/reference lithium foil is
2.3 cm2, while the working lithium foil has a surface area of
0.8 cm2. Cell to cell variation was less than 5%. Electrochem-
ical impedance spectroscopy (EIS) and linear (dc) polarization
analysis of the coin cells were performed using a 263A potentio-
stat/galvanostat (Princeton Applied Research). The EIS frequency
ranged from 100 kHz to 0.1 Hz in order to study the evolution
of the SEI without the risk of charge–discharge behavior dam-
aging the SEI film at lower frequencies. The EIS ac perturbation
amplitude was 2.5 mV for room temperature measurements and
5.0 mV for low temperature (−8 ◦C) measurements. Linear polar-
ization analysis was performed by cyclic voltammetry (CV) at a
scanning rate of 0.02 mV s−1 from the open circuit voltage – 0.0 mV
in the case of Li/Ele/Li – to 10.0 mV. The contribution of cell resis-
tances to polarization was determined as the slopes of the linear
plots.
Samples for NMR spectroscopy were prepared in an Ar-filled
glove box. NMR sample tubes were flame-sealed and stored for
set amounts of time at 80 ◦C. NMR spectroscopy was performed
using a JEOL 400 MHz NMR spectrometer. 13C NMR, 19F NMR and
11B NMR spectra were collected using a single pulse method. Spec-
tra references were 13C TMS at 0 ppm, 19F LiPF6 at 65.0 ppm and
11B LiBOB at 6.5 ppm. GC–MS analyses were obtained on an Agilent
Technologies 6890 GC with a 5973 Mass Selective Detector and a
HP-5MS Column. Helium was used as the carrier gas with a flow
rate of 3.3 mL min−1. Samples were ramped from 30 to 250 ◦C at
10 ◦C min−1. Scanning electron microscopy (SEM) analyses of the
soaked lithium metal electrodes were conducted on a JEOL-5900
Scanning Electron Microscope. Samples were rinsed by anhydrous
DME and dried under vacuum overnight and transferred from glove
box to SEM chamber in a sealed transport container filled with
argon.
3. Results and discussion
3.1. Conductivity of the electrolytes
The temperature dependence of LiPF6- and LiBOB-based elec-
trolytes have similar trends. There is a steady decrease in
conductivity with decreasing temperature (Fig. 1). The incorpo-
ration of the lower viscosity solvent, 1,3-dioxolane, increases the
Fig. 1. Conductivity of prepared electrolytes vs. temperature.
Fig. 2. Typical EIS Nyquist plot for Li/Ele/Li cell.
conductivity by 3–4 mS cm−1 for LiPF6-based electrolytes and by
∼1 mS cm−1 for LiBOB-based electrolytes.
The conductivity of the LiI-based electrolyte is largely tem-
perature independent with a slight trend toward increasing
conductivity with decreased temperature [2]. Similar trends have
been reported with alkali metal salts in ethereal solvents with low
dielectric constants [6]. LiTfSI has a slight decrease in conductivity
when temperature decreases. The high dissociation constant and
large size of the LiTfSI anion makes it suitable for solvents with
lower dielectric constants [3] which result in low viscosity.
3.2. EIS impedance
A typical Li/Ele/Li cell impedance spectrum and equivalent cir-
cuit are provided in Fig. 2. The semicircle in the high to intermediate
frequency range is attributed primarily to the SEI impedance, along
with some charge transfer resistance which is typically small in
comparison [7–9]. From 19.7 to 0.1 Hz, there is a curve approach-
ing Zim = 0. This has been associated with finite length diffusion
phenomena on a non-blocking electrode [10,11].
Impedance spectra for the anode SEI measured at 25 ◦C over
time are provided in Fig. 3. The initial impedances, RSEI, range from
about 125 for LiI to 325 for LiBOB-1. Upon storage of the cells at
room temperature for 15 days a small impedance rise was observed
Table 2
Physical properties of solvents [4].
Acronym Dielectric constant Viscosity (cP) Melting point (◦
C)
Propylene carbonate PC 64.95 2.51 −48.8
1,2-Dimethoxy ethane DME 7.075 0.407 −58
1,3-Dioxolane 7.13 0.589 −95
3. L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366 1361
Fig. 3. SEI impedance vs. time, all measured at 25 ◦
C.
for all electrolytes except LiTfSI. After storage at room temperature
for 15 days the cells were exposed to elevated temperature (50 ◦C)
for 3 days to simulate accelerated aging. After the accelerated aging
the cell containing LiI-based electrolyte had the lowest impedance.
Both the LiI and LiTFSI electrolytes had only small increases (15%
and 13%, respectively) in the impedance after storage at elevated
temperature.
A significant increase in impedance was observed for all of the
other electrolytes. The increase was greatest for LiBOB-1 (85%)
followed by LiPF6-2 (48%), LiBOB-2 (60%) and LiPF6-1 (45%). The
impedance increases suggest that there is a complex relationship
between the electrolyte composition (salt and solvent) and the
development of the SEI layer. The incorporation of 1,3-dioxolane
decreases the impedance for LiBOB-based electrolytes, LiBOB-1 vs.
LiBOB-2, but increases the impedance of LiPF6-based electrolytes,
LiPF6-2 vs. LiPF6-1. This suggests that both the salt and the solvent
are involved in surface film formation on lithium metal electrodes.
In the case of LiBOB electrolytes, the reaction of the 1,3-dioxolane
on the surface of Li may prevent further decomposition reactions of
the LiBOB salt. However, the Lewis acidity of LiPF6 (via generation of
PF5) may catalyze polymerization of 1,3-dioxolane thus increasing
the impedance [12].
Fig. 4. EIS spectra measure at −8 ◦
C, before and after storage at 50 ◦
C for 3 days.
Fig. 4 contains impedance measured at −8 ◦C, before and after
high temperature storage (50 ◦C for 3 days). The impedance spectra
for LiPF6-2 and LiBOB-1 after accelerated aging are not provided due
to the extremely high resistances. The impedance trend at −8 ◦C is
similar to that observed at 25 ◦C. The impedance of each cell at −8 ◦C
is roughly 10 times the impedance of the same cell at 25 ◦C. The SEI
film impedances are summarized in Fig. 5.
3.3. Linear (dc) polarization
In addition to EIS, linear (dc) polarization analysis provides
further information about SEI film resistance [13–15]. Represen-
tative data is provided in Fig. 6. The slope of the linear fit of the
data provides the cell resistance. The polarization resistances of
thermal abused cells determined by dc polarization are shown in
Fig. 7 and generally agree with those determined by EIS. The low-
temperature resistance is about 10 times of the resistance at 25 ◦C.
The cells show the following trend in resistance: LiI ≈ LiTfSI < LiPF6-
1 ≈ LiBOB-2 < LiPF6-2 < LiBOB-1.
Fig. 5. Summary of SEI impedance.
4. 1362 L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366
Fig. 6. Typical linear polarization data.
3.4. Thermal stability of the electrolytes
3.4.1. LiPF6-based electrolyte
The thermal instability of LiPF6 in carbonate and ethereal
solvents is well known [16–18]. Storage of LiPF6 at elevated temper-
ature (>75 ◦C) results in the thermal dissociation of LiPF6 to LiF and
PF5. The Lewis acidity of PF5 is largely responsible for the reaction
with solvent [16]. While the reactions of LiPF6 or PF5 with carbon-
ates and simple ethers have been previously reported [18], interest
in utilizing DME and 1,3-dioxolane in lithium battery electrolytes
prompted further investigation. Storage of 0.5 M LiPF6 in DME at
80 ◦C for 3 days results in discoloration of the electrolyte and the
appearance of new resonances by 13C and 19F NMR spectroscopy
(Figs. 8 and 9). The new 19F resonances are consistent with the gen-
eration of fluorophosphates (OPF2OR and OPF(OR)2). The new 13C
resonances are consistent with formation of diglyme and dimethyl
ether. The thermally abused electrolyte was analyzed by GC–MS
and structurally assigned through matching to the National Insti-
tutes of Standards (NIST) library (Fig. 10). Phosphorus oxyfluoride
along with dimethyl ether and diglyme are observed as expected
from solvent disproportionation reactions. Upon incorporation of
1 wt.% DMAc to 0.5 M LiPF6 in DME the thermal decomposition is
dramatically inhibited. Electrolytes with DMAc can be stored at
80 ◦C for 3 days with little evidence for decomposition [19].
The thermal stability of 1,3-dioxolane in LiPF6 is significantly
lower than DME. Preparation of a 0.5 M LiPF6 solution of 1,3-
dioxolane results in the generation of poly-dioxolane upon storage
at room temperature for 3 h, as evidenced by 13C NMR spectroscopy
(Fig. 11). Unfortunately, addition of the moderate Lewis basic addi-
tive DMAc does not suppress the polymerization of 1,3-dioxolane.
However, addition of the strong Lewis base tributylamine (TBA,
1 wt%) significantly reduced the polymerization reaction [20]. The
Fig. 7. Polarization resistance of thermal abused coin cells at 25 and −8 ◦
C, respectively.
Fig. 8. 13
C NMR of 0.5 M LiPF6 in DME without additives.
5. L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366 1363
Fig. 9. 19
F NMR of 0.5 M LiPF6 in DME.
Fig. 10. GC traces of 0.5 M LiPF6 in DME.
instability of LiPF6/1,3-dioxolane-based electrolytes is shown by
the higher impedances observed for LiPF6 electrolytes containing
1,3-dioxolane.
3.4.2. LiBOB-based electrolytes
Storage of LiBOB in PC at 80 ◦C for 5 days provides no evidence for
decomposition of either PC or LiBOB. This supports previous investi-
gations suggesting that LiBOB/carbonate electrolytes are thermally
stable [21]. A single resonance for LiBOB is observed at 6.5 ppm
in 11B NMR spectra. Storage of the 0.7 M LiBOB–PC:DME (1:1)-
based electrolyte at 80 ◦C for 5 days results in precipitation and
decomposition of LiBOB. A new 11B resonance at 4.2 ppm consistent
with the formation of a new tetravalent boron species is observed
[22].
Storage of the 0.7 M LiBOB–PC:DME:1,3-dioxolane (1:1:1) elec-
trolyte at 80 ◦C for 5 days resulted in decomposition of both LiBOB
and the solvent. Peaks characteristic of poly-dioxolane and other
ethereal side products are observed by 13C NMR spectroscopy. Two
new broad resonances (8.3 and 22.0 ppm) are observed in 11B NMR
spectra (Fig. 12), consistent with the formation of trivalent and
tetravalent borane species, respectively [22–25]. Related species
are observed upon reaction of LiBOB with methanol. LiBOB is
quantitatively converted to B(OMe)3 (17.7 ppm, 11B) and LiB(OMe)4
Fig. 11. 13
C NMR of 0.5 M LiPF6 in 1,3-dioxolane (25 ◦
C, without heating).
6. 1364 L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366
Fig. 12. 11
B spectra of 0.7 M LiBOB–PC:DME:1,3-dioxolane (1:1:1), stored at 80 ◦
C
for 5 days.
(4.3 ppm, 11B) upon storage in methanol at room temperature for
24 h.
3.4.3. LiI-based electrolytes
There is little spectroscopic evidence for the decomposition of
LiI in DME and 1,3-dioxolane. However, there is a slight yellowing of
the solution over time which probably results from the generation
of low concentrations of I2 in solution.
3.4.4. LiTfSI-based electrolytes
LiTfSI-based electrolytes are stable to thermal abuse by the NMR
analysis. There is no evidence for either solvent or salt decompo-
sition upon storage at 80 ◦C for 5 days. The outstanding thermal
stability of solid LiTfSI has been previously reported [26].
3.5. SEM of the electrodes
Changes to the surface of lithium metal upon exposure to the dif-
ferent electrolytes were analyzed by SEM. The lithium metal was
soaked in electrolyte for 2 weeks at room temperature followed by
SEM analysis. The pristine lithium metal has light uniform paral-
lel striations (Fig. 13). In addition, there are some faint irregular
features on the surface.
Fig. 13. SEM image of pristine lithium.
Storage of lithium metal in the presence of LiPF6 electrolytes
results in significant changes to the surface of the metal (Fig. 14).
The striations are significantly deeper and less uniform while the
irregular features are more pronounced. The changes to the surface
are consistent with either an etching of the surface by the elec-
trolyte or deposition of electrolyte decomposition products on the
surface of the lithium metal. The surface modification correlates
with the observed increase in impedance. However, the differ-
ences between LiPF6 electrolytes with and without 1,3-dioxolane
are small.
Changes to the surface of lithium metal are also observed upon
storage in the presence of LiBOB-based electrolytes (Fig. 15). Sam-
ples containing LiBOB have only small changes in both the light
uniform striations and faint irregular features, but there is a gen-
eration of new granular particles on the surface. The appearance
of the new particles suggests that the reactions of the LiBOB elec-
trolytes are either initiated by surface defects or that the initial
electrolyte decomposition products initiate localized degradation
of the electrolyte. Regardless, LiBOB electrolytes significantly mod-
ify the metal surface.
Samples of lithium soaked in 0.75 M LiI–DME:1,3-dioxolane
(1:2) provide similar results to the LiPF6 electrolytes (Fig. 16). The
depth of the striations is increased with little change in the irreg-
ular features. The surface of the lithium metal exposed to LiTfSI
electrolyte is very similar to the pristine lithium suggesting only
Fig. 14. SEM images of lithium–1.0 M LiPF6–PC/DME (1:1) (left) and 1.0 M LiPF6–PC/DME/1,3-dioxolane (1:1:1) (right).
7. L. Yang et al. / Journal of Power Sources 185 (2008) 1359–1366 1365
Fig. 15. SEM images of lithium–0.7 M LiBOB–PC:DME (1:1) (left) and 0.7 M LiBOB–PC:DME:1,3-dioxolane (1:1:1) (right).
Fig. 16. SEM images of lithium–0.75 M LiI–DME:1,3-dioxolane (1:2).
Fig. 17. SEM image of lithium–0.75 M LiTfSI–DME:1,3-dioxolane (1:2).
small changes to the surface, consistent with the impedance data
(Fig. 17).
4. Conclusion
Six electrolytes based on different lithium salts and solvents
were investigated by conductivity, EIS, linear polarization, NMR
spectroscopy, and SEM. Conductivities of the LiPF6- and LiBOB-
based electrolytes depend strongly on temperature, whereas the
LiTfSI- and LiI-based electrolytes have little temperature depen-
dence between −20 and +40 ◦C. EIS and linear polarization indicate
that the LiI-based electrolyte has the smallest surface film resis-
tance both at room temperature and at −8 ◦C, while 0.7 M
LiBOB–PC:DME (1:1) has highest resistance of all electrolytes. The
addition of 1,3-dioxolane greatly reduces the resistance of LiBOB-
based electrolytes but increases the resistance of LiPF6 electrolytes.
The thermal stability of the electrolytes was investigated by NMR
spectroscopy. LiI and LiTfSI electrolytes have very good stability
while the stability of LiBOB and LiPF6 is lower, especially in the pres-
ence of 1,3-dioxolane. SEM surface analysis generally supported
the EIS and linear polarization data, suggesting the modification
of the lithium metal surface is largely responsible for the changes
in resistance.
Acknowledgements
We thank the Partnership for Ocean Instrumentation (POI) at the
University of Rhode Island and the Naval Undersea Warfare Cen-
ter, Division Newport for partial support of this research. Yardney
Technical Products (Lithion) for assistance with conductivity mea-
surements. The sensor and Surface Technology Partnership at URI
for assistance with SEM. Chemetal for generous donation of LiBOB.
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