In the OSTI Collections: Lithium-ion Batteries
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| Article Acknowledgement: Dr. William N. Watson, Physicist DOE Office of Scientific and Technical Information |
Reports available through OSTI's SciTech Connect
Patent available through OSTI's DOepatents
An electric battery of any kind has two electrodes made of different materials, each in contact with a material through which electrically charged atoms can pass. Chemical reactions at one electrode (the anode[Wikipedia]) turn some of the atoms or molecules there into positive ions by removing negatively charged electrons from them; in complementary reactions at the other electrode (the cathode[Wikipedia]), positive ions combine with electrons and neutralize. When the electrodes are connected outside the battery, electrons can flow from the anode electrode to the cathode through the connection, thus making an electric current. If devices that run on electric current are part of this connection, they can be powered as the current goes through them.
As the battery’s current-producing reactions proceed, positive ions formed at the anode proceed from its surface or interior into the surrounding battery material (the electrolyte), through which they can migrate to the cathode, where they combine with electrons arriving through the outside connection and become neutral again. These reactions can continue while the electrodes remain connected outside the battery; electrons that enter the outer circuit from the anode keep replacing the electrons taken up at the cathode by the positive ions that migrate to it. The battery will supply current through the outside connection as long as nothing stops the reactions, such as the anode running out of ionizable atoms or molecules, for instance.
In some batteries of this general type, the reactions can be reversed by connecting them to a device that drives current in the opposite direction. Electrons at the cathode will then be removed from atoms that had migrated to it, and the atoms, again ionized, will move back through the electrolyte toward the anode, where they will absorb electrons driven into it by the current-reversing device. The whole process thus recharges the battery to the extent that the original chemical reactions do get reversed.
Current-producing reactions that involve ions of lithium[Wikipedia] are particularly reversible. Lithium-ion batteries have high energy per unit of volume and mass, and other chemical reactions that compete with their current-generating reactions are minimal, so they don’t lose much charge when they’re not being used. This makes lithium-ion batteries popular for portable electronic devices and electric vehicles.[Wikipedia] However, lithium-ion batteries are still less than ideal. Reports available from OSTI’s SciTech Connect and DOepatents describe numerous diverse efforts being made to improve them.
While lithium-ion batteries don’t lose their charge very quickly when they’re not in use, over time they do lose their capacity for charge—a significant problem for batteries used in hybrid electric vehicles. According to a report by researchers at the University of Rhode Island (“Novel Electrolytes for Lithium Ion Batteries”[SciTech Connect]), this capacity loss in currently available lithium-ion batteries keeps their “calendar life” below 10-15 years, and the most frequently reported limitation on their calendar life is chemical reactions occurring where their electrodes are in contact with the surrounding electrolyte. The same reactions also limit the batteries’ thermal stability. The researchers investigated both the thermal stability of new electrolyte materials and the effects on calendar life of new electrolyte additives, finding promise in the salt lithium difluoro(oxalato) borate as an alternative to lithium hexafluorophosphate, and propylene carbonate as an alternative solvent to ethylene carbonate. Among other things, they found that when lithium-ion batteries are charged and discharged at 60 °C (140 °F, ?333 K), the batteries’ charge capacity can be retained by adding 1%-2% concentrations of methylene ethylene carbonate to 1 mole/liter lithium hexafluorophosphate in a 3:7 mixture of ethylene carbonate and ethyl methyl carbonate.
While the lithium in many lithium-ion batteries comes from a electrode made of both lithium and other kinds of atoms, the Rhode Island group examined one type of battery in which the lithium ions came from a electrode made of solid lithium. Pure lithium is, in fact, the lightest and most energy-efficient material for the lithium-source electrode, but its use requires suitable components in the rest of the battery. One possibility for such a component is a solid polymer electrolyte that remains stable against lithium metal. This type of electrolyte, initially developed at Lawrence Berkeley National Laboratory, has been developed further by Seeo, Inc. to produce a new class of high-energy lithium-ion batteries. The Department of Energy’s Vehicle Technologies Office sponsored a three-year project by Seeo to safely achieve even higher energy densities in lithium-ion batteries without high cost.
If a battery’s electrolyte is solid instead of liquid, the electrolyte in contact with the battery electrodes need not be homogeneous. As long as the lithium ions can flow all the way from one electrode to the other, different solid electrolytes can be in contact with each electrode and the battery would still work. If the solid electrolytes are optimally selected to remain stable at the different voltages of the two electrodes, the battery might work even better than a battery with a single liquid electrolyte surrounding both electrodes that can’t be optimized for both. Seeo thus focused on developing a dual electrolyte system, along with coating techniques for electrodes that receive lithium ions, various types of additives, and different electrolyte salts. By the end of the project, they had made lithium-ion batteries that produced 350 watt-hours of energy per kilogram at an energy density of 600 watt-hours per liter and a power density of 790 watts per liter. Details of their work were reported for the National Energy Technology Laboratory in “High-Voltage Solid Polymer Batteries for Electric Drive Vehicles”[SciTech Connect].
In addition to limiting a lithium-ion battery’s calendar life, the chemical reactions at its electrodes affect how easily the lithium ions get in and out of the electrodes. Since an understanding of these effects could inform efforts to optimize lithium-ion batteries’ performance, researchers at Lawrence Livermore National Laboratory and Pennsylvania State University ran molecular dynamics simulations of a battery. Their results were presented in “Molecular Structure and Ion Transport near Electrode-Electrolyte Interfaces in Lithium-Ion Batteries”[SciTech Connect] for presentation at the 249th National Meeting and Exposition of the American Chemical Society. The simulated battery had graphite electrodes and an electrolyte composed of 1 mole/liter lithium hexafluorophosphate salt in ethylene carbonate. One graphite electrode’s outermost carbon atoms were bonded to hydrogen, the other electrode’s to hydroxyl (see Figure 1). In the simulation, it was easy for the lithium ions to exit the graphite, even when an applied electric field opposed the ions’ motion, but the graphite was hard for the ions to enter, more so when the graphite surface was bonded to hydroxyl. The lithium ions also settled into more or less evenly-spaced layers between the electrodes, with the spacing largely determined by the concentration of lithium hexafluorophosphate salt. Furthermore, each lithium ion tended to be surrounded by four ethylene carbonate molecules whose hydrogen-atom ends pointed outward from the lithium. Top
 | Figure 1. Schematic of portion of a lithium-ion battery with graphite electrodes separated by an electrolyte made of lithium hexafluorophosphate salt (LiPF6) in ethylene carbonate (EC). Carbon-atom rings (represented by green hexagons) near the surface of the upper electrode are bonded to hydrogen atoms (depicted in gray), while some rings near the lower electrode’s surface are also bonded to hydroxyl groups (OH, oxygen atoms represented as red). The electrodes are 13 angstrom units (13 Å) thick and separated by a 33 angstrom-unit (33 Å) thickness of electrolyte. (From “Molecular Structure and Ion Transport near Electrode-Electrolyte Interfaces in Lithium-Ion Batteries”[SciTech Connect], page 3 of 4.) |
The arrangement of electrolyte molecules around the lithium ions partly depends on what electrolyte the ions are dissolved in. Findings from a project to examine this dependence are reported in “Final Progress Report for Linking Ion Solvation and Lithium Battery Electrolyte Properties”[SciTech Connect] from North Carolina State University. The molecules around the dissolved ions will respond to light waves of one frequency that they absorb from an outside source by emitting light waves of other frequencies. The frequency differences, whether positive or negative, depend on what ways the surrounding molecules are able to vibrate given their arrangement around the ions. The technique of measuring the frequency differences to get information about such motions is known as Raman spectroscopy[Wikipedia], after the discoverer of the frequency-change process that it’s based on. If the molecules’ arrangement is correctly associated with their possible vibrational modes, the arrangement can be deduced from the differences in frequency between the emitted and absorbed light.
The North Carolina researchers analyzed a wide variety of crystalline solvent and ion combinations by this method, and in the process corrected a large amount of inaccurate electrolyte-interaction information found in earlier published sources. One relevant finding was that the particular solvents examined tended not to be the only molecules surrounding the lithium ions: the portion of lithium salt molecules that the lithium ions dissociated from tended to stay close to the lithium ions also, instead of going past the first layer of solvent molecules and leaving them to surround the lithium ions by themselves. Another finding was that the very different solvation traits of the solvents studied were not reflected by great differences in certain electrochemical parameters, contrary to conventional assumptions. The group’s studies of the conditions at which various mixtures of solvents and lithium salts change their phase, solvate crystal structures, and electrolyte properties led to mechanistic explanations for the wide variability of several electrolytes’ viscosities and electrical conductivities, in keeping with the project’s goal of directly correlating electrolytes’ properties with their structure and composition. “This is a notable advance,” according to their report, “as no current theories exist which aptly explain the properties of concentrated electrolytes.”
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Figure 2. Varying modes of coordination of lithium ions with ions of CF3SO3-. The different arrangements allow the CF3SO3- ions to vibrate in different ways in response to light waves; analysis of how the CF3SO3- ions respond provides information about how they’re arranged around the lithium ions. (From “Final Progress Report for Linking Ion Solvation and Lithium Battery Electrolyte Properties”[SciTech Connect], page 5/11.) |
Atomic-level mechanistic explanations of how battery electrodes degrade, thus reducing the batteries’ energy-storage capacity over time, were the goal of a project carried out at Sandia National Laboratories to develop new experimental and theoretical techniques for exploring the phenomenon. According to the project report “The Science of Battery Degradation”[SciTech Connect],
Without this understanding, many models of battery degradation simply invoke a continuous loss of Li [lithium] through side reactions, mostly at the anode, which are presumed to be a result of the continuous formation of the solid electrolyte interphase, SEI. While it is certainly true that SEI formation will spontaneously occur on a Li-ion battery anode when lithiated, this layer should self-limit as the electron transport rate decreases. Experimental or theoretical techniques that permit detailed understanding or direct experimental observation of the formation and continuous growth and/or dissolution of the SEI with battery cycling is an important goal.
The techniques developed include:
· Making cross-sections as thin as 40 nanometers of commercial-scale battery electrodes
· Scanning transmission x-ray microscopy to probe lithium transport mechanisms in lithium-ion battery electrodes
· Construction of in situ liquid cells to observe electrochemical reactions in real time with transmission electron microscopy and scanning transmission x-ray microscopy
· Construction of in situ optical cells to analyze redox flow batteries by Raman spectroscopy
· Ab initio simulation (i.e., simulation calculated from physical laws and no other empirical data) of electrochemical reactions with controlled electrical potential, to study electrolyte degradation
· Combination of an electrochemical entropy-measuring technique with x-ray based measurements of electrodes’ atomic arrangements
Using these techniques led to several discoveries:
Scanning transmission x-ray microscopy showed that lithium transport in battery electrodes made of lithium iron phosphate is unexpectedly controlled by initial deposition of lithium, which leads to high heterogeneity in lithium content at each of the electrode material’s particles, and a surprising lack of variance in local current density with variation in the overall electrode charging current
In situ transmission electron microscopy showed that a size limit exists to lithium deposition of silicon anode particles, and that above this limit, particle fracture controls electrode degradation.
Electrochemical measurements of the potential difference between an unconnected battery’s electrodes, and the rate at which the difference changes with temperature, showed that a lithium-ion battery’s entropy, which depends on this rate, changes little with degradation, and that lower charge-discharge cycling rates recovers lost battery capacity.
Modeling of the interfaces between the battery electrodes and the electrolyte indicated that electrolyte degeneration may occur by either a single or double electron transfer process, depending on thickness of the solid-electrolyte-interphase layer, and that the crossover between single or double electron transfer can be modeled and predicted.
Battery lifetime models were also developed at the National Renewable Energy Laboratory with collaborators from Texas A&M University, the University of Colorado at Boulder, Colorado School of Mines, Eaton Corporation, Utah State University, and Ford Motor Company. Their work is described by the slide presentation “Predictive Models of Li-ion Battery Lifetime”[SciTech Connect] which was prepared for the 2014 IEEE Conference on Reliability Science for Advanced Materials and Devices. The presentation indicates that, while system design and control can be adequately guided by a combination of incomplete models and experimental data, detailed models of the relevant physical processes are needed to reduce test time and to guide future battery design. Such models are described after an introduction to lithium-ion batteries’ working principles and degradation mechanisms. The presentation states that thermal and electrochemical processes are well understood while their coupling to mechanical processes at various length scales between atom size to complete-battery size is still being worked out. Studies of automotive battery life are also presented, and a concluding summary says that the main factors controlling battery lifetime are the amount of time the battery spends at high temperature and high state of charge, and whether the battery undergoes charge-recharge cycles with a high depth of discharge and discharge rate.
Lithium-ion batteries for cars and stationary applications have high up-front costs. The batteries’ degradation with use means that optimizing them requires evaluating many years of operation. Several reports describe mathematical models of lithium-ion batteries intended to provide insight into the economics of batteries as well as their physics.
“Battery Lifetime Analysis and Simulation Tool (BLAST) Documentation” [SciTech Connect] describes a suite of models that was developed for this purpose by the National Renewable Energy Laboratory. The tools described combine the lab’s high-fidelity battery degradation model with a model of thermal and electrical battery performance, application-specific performance models of the larger system (such as an electric car), application-specific use data (e.g., travel patterns and driving data), and historic climate data from U.S. cities. The model suite thus provides “highly realistic long-term predictions of battery response” to enable comparisons of battery-use strategies. To keep the simulations of long-term use efficient, some aspects of battery performance, such as fast transient voltage response, aren’t accounted for, but the models do account for enough detail to allow long-term performance assessment.
Researchers at Argonne National Laboratory and Michigan State University expanded an existing mathematical model of resource use and productivity to permit analyses of vehicle batteries that use graphite anodes and four new types of cathode. The material and energy flows that occur from the extraction of the raw materials to their preparation for use as anodes and cathodes are documented in the report “Material and Energy Flows in the Production of Cathode and Anode Materials for Lithium Ion Batteries”[SciTech Connect]. The authors also used Argonne National Laboratory’s Battery Performance and Cost model to determine battery composition when different cathode materials were used in the battery. They concluded that compounds containing cobalt and nickel are the most energy-intensive to produce.
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Figure 3. Top: table of capacities, advantages, and drawbacks of different cathode materials for lithium-ion batteries. Bottom: flows of material and energy when lithium iron phosphate (LiFePO4) is produced using a hydrothermal (left) and a solid-state (right) preparation step. (From “Material and Energy Flows in the Production of Cathode and Anode Materials for Lithium Ion Batteries”[SciTech Connect], pp. 5, 13, 15.)
The high cost of batteries restricts both the salability of plug-in electric vehicles (“PEVs”) and the deployment of grid-connected energy storage systems, according to the National Renewable Energy Laboratory report “Identifying and Overcoming Critical Barriers to Widespread Second Use of PEV Batteries”[SciTech Connect]. The report, informed by data from the Center for Sustainable Energy, notes that a strategy of redeploying batteries into a secondary market after first using them in plug-in vehicles could help address both issues. Recognizing that “[b]y extracting additional services and revenue from the battery in a post-vehicle application, the total lifetime value of the battery is increased, and the cost of the battery can be reduced to both the primary and secondary users”, the Energy Department’s Vehicle Technologies Office funded the National Renewable Energy Lab to investigate this strategy’s feasibility and major barriers for lithium-ion batteries. The Lab’s analyses suggested that battery reuse had little ability to reduce upfront costs, but it could eliminate end-of-service costs to the vehicle owner and reduce costs, fossil-fuel use, and emissions for electric utilities.
The researchers found little incentive to replace a plug-in vehicle’s battery while the vehicle itself is useable (approximately 15 years), after which the battery would still have about 70% of its original capacity. How long the battery would last in its second use would depend greatly on its new duty cycle, climate, battery thermal management, and other factors, but could under favorable conditions exceed 10 years. Battery repurposing businesses could be dedicated to single vehicle models and operate efficiently within a less-than-nationwide region, thus avoiding complexities of repurposing heterogeneous batteries and nationwide battery collection. From consideration of repurposed-battery costs, battery supply, and demand and value of service, the researchers also found that the potential supply of second-use batteries could overwhelm the depth of many markets for them by at least an order of magnitude. The most promising applications they found were replacement of combustion-turbine plants for delivering grid power during demand peaks and provision of peak-shaving services.
While these findings suggest that second use of plug-in vehicle batteries would be valuable, the often-small economic margins make its economic viability dependent on several factors, particularly the availability of onboard diagnostics data and accurate assessments of battery degradation from primary and secondary use. The researchers thus recommended various specific practices by car and battery manufacturers, systems integrators and installers, utilities, regulators, and various third parties to support the viability of secondary battery use.
Plug-in vehicles use less fuel than conventional internal-combustion vehicles—not necessarily zero fuel, since fuel may be consumed at the power station that charges up the plug-in vehicles. Hybrid electric vehicles (“HEVs”) use batteries to assist onboard internal-combustion engines, but their batteries still have high enough upfront costs to make them less saleable than purely internal-combustion cars. Making hybrid batteries cheaper or more effective can reduce the cost difference, leading to more hybrid sales and greater total fuel savings. Approaches to improving hybrid batteries’ performance, and reducing their costs through methods other than battery reuse, are described in another National Renewable Energy Lab report, “Lower-Energy Energy Storage System (LEESS) Component Evaluation”[SciTech Connect], which describes work done in collaboration with the United States Advanced Battery Consortium and sponsored by the Energy Department’s Vehicle Technologies Office. It was found that cars whose energy-storage systems met much lower energy requirements than the existing standard for hybrids would still save significant amounts of fuel. The report describes a vehicle built to allow installing and testing of alternate energy-storage systems, and the vehicle’s use for testing lithium-ion capacitor modules. These modules had one lithiated graphite electrode with battery-type characteristics and a carbon electrode with ultracapacitor-type[Wikipedia] characteristics. Tests of different modules indicated that “as long as critical attributes such as engine start under worst case conditions can be retained, considerable ESS [energy-storage system] downsizing may minimally impact HEV fuel savings. … However, some combination of systems optimization to best leverage LEESS capabilities and cost reductions on the part of suppliers will be necessary to move LEESS technology from mere technical viability to having a compelling business case for broad use in HEV energy storage.”
Numerous patents have been issued for national-lab inventions to advance lithium-ion batteries beyond the technical limitations of earlier designs. Four examples issued in April and May of 2015 are described below, two primarily addressing anodes and two primarily addressing electrolytes. One of the anode patents is for an invention from Pacific Northwest National Laboratory; the rest are for Argonne National Lab inventions.
The problem addressed by the Pacific Northwest patent, “Methods for making anodes for lithium ion batteries”[DOepatents], is to surpass certain limitations of lithium-ion batteries. Most such batteries use carbonaceous anodes such as graphite, which has a theoretical charge capacity of 372 milliamp-hours per gram. In other lithium-ion batteries, the anodes are based on lithium-metal alloys, which “often exhibit poor cycle life and fast capacity fade” because they crack and turn to powder as lithium ions pass out of and into them during repeated discharge-recharge cycles. The anodes described in the patent are composite materials that have higher charge capacity than graphite and little tendency for lithium atoms to electroplate[Wikipedia] onto them. The patent itself is for methods of making such anodes, some of which are macroporous (having pores larger than 50 nanometers) to allow lithium ions to get in and out of them without the ions cracking or otherwise damaging them.
When some lithium-ion batteries are first used, part of their electrolyte decomposes and forms a solid on the anode while other interactions occur between the anode and lithium. These processes don’t reverse during recharging, so the batteries have much less capacity, and some useless mass, after their first cycle of use. The reactions also consume lithium from cathode materials that contain it. Making a battery that has a given capacity after its first cycle is thus more expensive to manufacture than it would otherwise be. The capacity loss can be between 10% and 30% for carbon-based anode materials, and substantially higher for materials based on materials like tin, selenium, or silicon. Non-lithiated cathodes can be used with lithium anodes, but this presents a different problem: with use, lithium anodes can form branches that lead to short circuits in the battery. There are treatments that can prevent this problem but they aren’t easy to implement on an industrial scale of battery fabrication. The recent anode patent by Argonne National Laboratory researchers, “Electroactive compositions with poly(arylene oxide) and stabilized lithium metal particles”[DOepatents], addresses these problems with partially or fully lithiated anodes in lithium-ion batteries that can diminish their first-cycle capacity loss and enable their use of non-lithiated cathodes.
Although electrodes are mentioned in the title of “Long life lithium batteries with stabilized electrodes”[DOepatents], the patent actually deals with electrolyte additives that protect the cathodes from unwanted chemical reactions. The patent notes that lithium-ion batteries whose electrodes and electrolytes are suitable for small electronic devices present various problems for electric-powered and hybrid-powered vehicles regarding safety, calendar life, cost, high-rate power assist and regenerative braking. The patent notes further that replacing the cobalt and nickel of commercial lithium-ion batteries’ electrodes with manganese would be cheaper, provide more power, improve safety, and not be detrimental to the environment, but existing batteries that use electrodes based on lithium manganese oxide spinel[Wikipedia] deteriorate over time in their electrochemical performance—more severely at temperatures above 40-50 °C (104-122 °F, ?313-323 K), which can easily be reached in electronic devices or vehicles. While several factors have been reported to be responsible for this deterioration, it’s generally attributed to the instability of manganese spinel; according to the patent, “[t]his degradation likely results from the formation and dissolution of manganese ions in the organic based electrolyte”. The patented solution is lithium-ion batteries containing nonaqueous electrolytes with one or more additives to protect the cathode surfaces from unwanted reactions, and methods of making the electrolytes. These electrolytes enhance the performance of lithium-ion batteries whose electrodes are based on minerals of the spinel and olivine[Wikipedia] groups, and on lithium cobalt oxide, lithium nickel cobalt oxide, lithium vanadium oxide, &c.
While the preceding electrolyte patent addressed battery performance, the last electrolyte patent, “Functional electrolyte for lithium-ion batteries”[DOepatents], addresses a different problem: safety, particularly the danger of charging the battery past the point of its capacity. According to the patent, overcharge “is one of the more common factors that could lead to serious safety issues in lithium-ion batteries” and is most likely to occur
… during the charging of a battery pack. Due to the manufacturing processes, there will always be a weakest cell with the lowest capacity in one battery pack. During charging, the weak cell will always reach its full capacity before the other cells and without triggering the voltage monitor of the charger because the voltage of the full pack is still within the normal range. But the weak cell is none-the-less in a state of overcharge. As a result, extra electricity will build up on the surface of the electrodes instead of being stored, thereby dramatically increasing the potential of the cathode. As the charging is continued, the potential will go beyond the electrochemical window of the electrolyte and cause various reactions of the electrolyte. For example, oxidation of the electrolyte may occur and thereby trigger other reactions. The cell may end up in a thermal runaway, or even result in an explosion.
The patent describes electrolytes that react differently when the battery, or a portion of it, begins to be charged beyond its capacity, thus keeping the electrodes from reaching potentials that will drive harmful electrolyte reactions. The electrolytes described would provide overcharge protection in lithium-ion batteries, electrical double-layer capacitors[Wikipedia], and other electrochemical devices.
Wikipedia
· Anode
· Cathode
· Lithium
· Supercapacitor (also referred to as “ultracapacitor”)
· Olivine
· Electric double-layer capacitor
· Lawrence Berkeley National Laboratory
· Seeo, Inc. for National Energy Technology Laboratory
· Lawrence Livermore National Laboratory
· Pennsylvania State University
· North Carolina State University
· Sandia National Laboratories
· National Renewable Energy Laboratory
· University of Colorado at Boulder
· Center for Sustainable Energy
· United States Advanced Battery Consortium
· Pacific Northwest National Laboratory
Reports available through OSTI’s SciTech Connect
· “Novel Electrolytes for Lithium Ion Batteries” [Metadata]
· “High-Voltage Solid Polymer Batteries for Electric Drive Vehicles” [Metadata]
· “Molecular Structure and Ion Transport near Electrode-Electrolyte Interfaces in Lithium-Ion Batteries” [Metadata]
· “Final Progress Report for Linking Ion Solvation and Lithium Battery Electrolyte Properties” [Metadata]
· “The Science of Battery Degradation.” [Metadata]
· “Predictive Models of Li-ion Battery Lifetime (Presentation)” [Metadata]
· “Battery Lifetime Analysis and Simulation Tool (BLAST) Documentation” [Metadata]
· “Material and Energy Flows in the Production of Cathode and Anode Materials for Lithium Ion Batteries” [Metadata]
· “Identifying and Overcoming Critical Barriers to Widespread Second Use of PEV Batteries” [Metadata]
· “Lower-Energy Energy Storage System (LEESS) Component Evaluation” [Metadata]
Reports available through DOepatents
· “Methods for making anodes for lithium ion batteries” [Metadata]
· “Electroactive compositions with poly(arylene oxide) and stabilized lithium metal particles” [Metadata]
· “Long life lithium batteries with stabilized electrodes” [Metadata]
· “Functional electrolyte for lithium-ion batteries” [Metadata]
· Vehicle Technologies Office, Office of Energy Efficiency & Renewable Energy, US Department of Energy
· American Chemical Society’s 249th ACS National Meeting & Exposition, Denver, CO, United States, Mar 22 - Mar 26, 2015 (“Molecular Structure and Ion Transport near Electrode-Electrolyte Interfaces in Lithium-Ion Batteries”)
· IEEE 2014 IEEE Conference on Reliability Science for Advanced Materials and Devices, 7-9 September 2014, Golden, Colorado [at CO School of Mines] (“Predictive Models of Li-ion Battery Lifetime (Presentation)”)
