Tin (Sn) alloy electrodes show great potential for advancing battery performance due to the high capacity of tin. To realize this potential, the volumetric expansion during the lithiation process must be mitigated. One means of mitigating volumetric expansion of tin is to alloy it with copper to create Cu 6 Sn 5 . Such alloy electrodes retain some of the high capacity of tin, while attempting to accommodate volumetric changes with the addition of the malleable copper. Lithiation and delithiation tests were conducted with the Cu 6 Sn 5 pellet electrodes to produce microstructural changes at the electrode surface. To observe and quantify these microstructural changes, x-ray microtomography was performed on electrode samples after electrochemical testing. The microtomography data was reconstructed into a 3D image, segmented, and the continuous phase size distribution (PSD) of each electrode sample was analyzed. The electrodes lithiated to 0 V vs Li/Li + and then delithiated to 0.2 V vs. Li/Li + showed the most substantial reduction in overall PSD compared to the other samples. This suggests that full lithiation of the Sn present in the alloy electrodes followed by partial delithiation of the Li 4.4 Sn to Li 2 CuSn can cause substantial microstructural changes related to volume expansion on lithiation and structural collapse upon delithiation. The electrodes fully lithiated to 0 V vs Li/Li+ and not delithiated show a higher overall phase size distribution, including all solid phases, than the pristine sample and the electrode samples that were partially lithiated to 0.2 V vs. Li/Li + and delithiated to 1.5 V vs. Li/Li + . The higher overall phase size distribution that is shown by the sample that was fully lithiated and not delithiated is evidence of the significant volumetric expansion of the Cu 6 Sn 5 compound due to lithiation. During this process of volumetric expansion, the phase size distribution of the Cu 6 Sn 5 /Sn phase is shown to decrease. When the volumetric expansion of the lithiated electrode samples and the volumetric contraction of the delithiated electrode sample are considered together, it can be inferred that the microstructural changes that are observed, such as the decrease in phase size distribution of the Cu 6 Sn 5 /Sn phase, can be attributed to the volumetric expansion and contraction of the compound during the lithiation and delithiation process.

Flexible Li-ion batteries (LIBs) have a strong oncoming consumer market demand for use in wearable electronic devices, flexible smart electronics, roll-up displays, electronic shelf labels, active radio-frequency identification tags, and implantable medical devices. This market demand necessitates research and development of flexible LIBs in order to fulfill the power requirements of these next-generation devices. This study investigated the performance of quasi-solid anode — the active and conductive additive materials suspended in liquid electrolyte — for flexible lithium-ion batteries (LIB). A quasi-solid graphite anode was fabricated and tested using different material ratios and compositions, showing an acceptable performance. Furthermore, this study looked into the effect of graphite powder ratios in battery performance. A ratio of over 65% of the specific discharge capacity to the theoretical capacity was achieved maintaining the capacity retention of more than 74% after the second cycle.

We propose the concept of Multifunctional-Energy-Storage Composites (MES Composites) which highlights a unique integration technique for embedding lithium-ion battery materials in structural carbon-fiber-reinforced-polymers (CFRP). Unlike standard lithium-ion pouch cells, the MES Composites maximizes material utilization by using CFRP facesheets to house the electrochemistry. Through-thickness polymer reinforcements are implemented to allow load transfer between the two facesheets, analogous to the sandwich structure construction. In this work, the design rationale, materials and fabrication techniques, experimental evaluation, and performance of the first-generation MES Composites will be presented. MES Composite cells with a nominal capacity of approximately 4 Ah, with various reinforcements-array configurations, were fabricated and first tested through a series of electrochemical reference performance tests (RPT) under a strain-free condition. The MES Composite cells then underwent a mechanical-electrical-coupling test, where a quasi-static three-point-bending load was applied at increasing increments. Mechanical testing was interrupted after each increment to perform a sequential RPT to quantify any non-catastrophic degradation in the electrochemical performance. The obtained results verify the feasibility of the concept showing that the electrochemical performance of the MES Composites can be maintained at the same level as the regular lithium-ion battery. The reinforcement architecture of the MES Composite constrains the relative motion of the battery electrodes and increases the bending rigidity, resulting in a higher load carrying capacity and inhibiting non-fatal injury of the cell under mechanical loads. This multifunctional material system can also be scaled up and ultimately provide considerable weight and volume saving at the system level.

Internal short-circuiting is the most dangerous abuse scenario for lithium ion batteries. A nail penetration test simulates the internal short circuit process by penetrating a test cell/pack with an electrically conductive nail. Pass or failure of the cell and/or chemistry is determined by the presence of smoke or flame following penetration. To understand and eliminate the safety concerns arising from the internal shorts, it is important to fully understand the cell/pack dynamics during the shorting process. Gathering useful data at the point of penetration during nail penetration tests is very challenging due to the inherent destructive nature of the test. This paper presents an intelligent nail (iNail) design consisting of four parts where multiple sensors (thermo-couples, strain gauges, etc.) can be conveniently placed for reliable and efficient data collection. The time history of temperature distributions through the cell/pack thickness can be recorded with the iNail without position control of the nail penetration tester, greatly simplifying the test. A prototype stainless steel iNail is manufactured with three embedded thermocouples. Nail penetration tests are conducted on fully charged 4 Ah gr/NCM pouch cells. The iNail successfully recorded the temperature time history at the penetration point during the tests. Pack level nail penetration tests (three pouch cells in parallel) were also performed with iNail temperature measurements.

The success of grid scale energy storage hinges on our ability to solve real problems economically. By mapping energy storage physics to application economics, this paper offers a technology neutral look at how energy storage can solve real problems. A value analytics methodology was developed that combines the physics of energy storage, application power commands, and market-specific economic constructs. This approach evaluates and optimizes the value of energy storage for specific projects by providing insight into the tradeoffs between the lifecycle costs and revenues. These analytics calculate the net present value (NPV) and internal rate of return (IRR) of select energy storage assets, markets, and applications by considering these key factors: • Duty profiles and control strategies • Market economics and revenue streams • Asset performance at cell, module, and system levels • Price projections including balance of plant (BOP) • Cycle and calendar life • Project length and financing terms The value analytics methodology combines three model streams. The first takes a high fidelity load profile (for example, the power output of a building, wind turbine, or solar farm), imposes a specific control strategy, and calculates revenue streams in a selected market. From this first model stream a storage power command is generated. This power command is fed into the second model stream that calculates the required size and price of a given storage type. Finally, a third model stream uses empirical life models to calculate degradation rates, replacement intervals, and maintenance costs. These are rolled up into a project specific financial analysis that forecasts project NPV and IRR. The underlying engine for this methodology is a large performance and price database of over 100 commercial and emerging energy storage assets that spans a wide range of technologies from ultracapacitors and flywheels to lead acid and lithium-ion batteries. The physics based performance of each asset is captured as an equivalent circuit model. These models are exercised to create performance envelops that describe the rate dependent power capability as a function of the type, amount, and age of installed storage. The energy storage value analytics described in this paper can be used to test key sensitivities. This methodology has been applied to standalone energy storage systems as well as the combination of energy storage with renewables and distributed power generation. As shown, the methodology is relevant for an even wider range of applications. Several solution maps will be shared that reveal, by market segment, the energy storage type, amount, and application that create the greatest customer value. This type of informed design and dispatch will solve real problems, create new value streams, and open new markets for grid scale energy storage.

Currently there are nearly 750 million ground vehicles in service worldwide. They are responsible for 50% of petroleum (oil) consumption and 60% of all greenhouse gas (GHG) emissions worldwide. The number of vehicles is forecasted to double by 2050. Therefore the environmental issues such as noise, emissions and fuel burn have become important for energy and environmental sustainability. This paper provides an overview of specific energy and environmental issues related to ground transportation. The technologies related to reduction in energy requirements such as reducing the vehicle mass by using the high strength low weight materials and reducing the viscous drag by active flow control and smoothing the operational profile, and reducing the contact friction by special tire materials are discussed along with the portable energy sources for reducing the GHG emissions such as low carbon fuels (biofuels), Lithium-ion batteries with high energy density and stability, and fuel cells. The technological challenges and opportunities for innovations are discussed.

Portable energy storage will be a key challenge if electric vehicles become a large part of our future transportation system. A big limiting factor is vehicle range. Range can be further limited if heating and air conditioning systems are powered by the electric vehicle’s batteries. The use of electricity for HVAC can be minimized if a thermal battery can be substituted as the energy source to provide sufficient cabin heating and cooling. The aim of this project was to model, design, and fabricate a thermal storage battery for electric vehicles. Since cost and weight are the main considerations for a vehicular application — every attempt was made to minimize them in this design. Thus, the final thermal battery consists of a phase change material Erythritol (a sugar alcohol commonly used as artificial sweetener) as the storage medium sealed in an insulated, stainless steel cooking pot. Heat exchange to the thermal battery is accomplished via water (or low viscosity engine oil) which is pushed through a copper coil winding. A CFD model was used to determine the geometry (winding radius and number of coils) and flow conditions necessary to create adequate heat transfer. Testing of the fabricated design indicates that the prototype thermal battery module losses less than 5% per day and can provide enough heat to meet the demand of cruising passenger vehicle for up to 1 hour of full heating on a cold day. Other metrics, such as $/kJ and kJ/kg, are competitive with Lithium ion batteries for our prototype.

Lithium-ion (Li-ion) batteries are favored in hybrid-electric vehicles and electric vehicles for their outstanding power characteristics. In this paper the energy loss due to electrical contact resistance (ECR) at the interface of electrodes and current-collector bars in Li-ion battery assemblies is investigated for the first time. ECR is a direct result of contact surface imperfections and acts as an ohmic resistance at the electrode-collector joints. ECR is measured at electrode connections of a sample Li-ion battery, and a straightforward analysis is presented to evaluate the relevant energy loss. Through the experiments, it is observed that ECR is an important issue in energy management of Li-ion batteries. Effects of surface imperfection, contact pressure, joint type, collector bar material, and interfacial materials on ECR are highlighted. The obtained data show that in the considered battery, the energy loss due to ECR can be as high as 20% of the total energy flow in and out of the battery under normal operating conditions. However, ECR loss can be reduced to 6% when proper joint pressure and/or surface treatment are used. A poor connection at the electrode-collector interface can lead to a significant battery energy loss as heat generated at the interface. At sever conditions, heat generation due to ECR might cause serious safety issues, thermal runaway, sparks, and even melting of the electrodes.

This paper presents a numerical study on heat generation in a lithium-ion (LiC 6 /LiPF 6 /Li y Mn 2 O 4 ) battery cell. The numerical model considered multi-physics including battery kinetics, diffusion, and thermal analysis. The heat generation rate was determined by a local heat generation model. This model enables the investigation of the effects of battery parameters on different heat generation mechanisms and the overall heat generation rate in the battery. The effects of the thickness of the battery components and the size of the electrode particles at different discharge rates were evaluated. The results revealed the relationships between these parameters. A battery with a low heat generation rate and efficient battery utilization may be achieved through parameter optimization.

The levelized costs of delivered energy from the leading technologies for grid-scale energy storage are calculated using a model that considers likely number of cycles per year, application-specific expected lifetime, discount rate, duty cycle, and likely trends in the markets. The expected capital costs of the various options evaluated — pumped hydrostorage, underground pumped hydrostorage (UPHS), hydrogen fuel cells, carbon-lead-acid batteries, advanced adiabatic compressed air energy storage (AA-CAES), lead-acid batteries, lithium-ion batteries, flywheels, sodium sulfur batteries, ultra capacitors, and superconducting magnetic energy storage (SMES) — are based on recent installation cost data to the extent possible. The marginal value of the delivered stored energy is analyzed using recent grid-energy prices from regions of high wind-energy penetration. Grid-scale energy storage is expected to lead to significant reductions in greenhouse gas (GHG) emissions only in regions where the off-peak energy is very clean. These areas will be characterized by a high level of wind energy with cheap off-peak and peak prices. At the expected price differentials, the only conventional options expected to be commercially viable in most cases are hydro storage, especially via dam up-rating, and UPHS. The market value of energy storage for short periods of time (under a few hours) is expected to be minimal for grid-scale purposes. Only low-cost daily storage is easily justified both from an economic and environmental perspective.

Three major challenges — grid stability, domestic oil limitations, and climate change — could all be addressed simultaneously by using off-peak electrical energy to recycle CO 2 into liquid fuels (such as gasoline, jet fuel, and diesel). Simulations have shown that recent innovations should make it practical to reduce CO 2 to CO at over 66% of theoretical efficiency limits. When combined with other process advances, it would then be possible to synthesize most hydrocarbons and alcohols from point-source CO 2 and clean off-peak grid energy (wind or nuclear) at system efficiencies in the range of 51–61%. Energy storage density in renewable, carbon-neutral kerosene is 44 MJ/kg, compared to ∼0.4 MJ/kg for Li-ion batteries. This process begins by electrolyzing water using clean energy to get the hydrogen required by the Reverse Water Gas Shift (RWGS) reactor and by a novel Renewable Fischer Tropsch Synthesis (RFTS) process. Off-peak grid energy averaged only $13/MWhr in the Minnesota hub in 2009. At such prices, the synthesized liquid fuels ( “WindFuels” ) should compete even when petroleum is only $50/bbl. Considerable effort over the past decade has been put into exploring high-temperature (HT) paths toward the production of renewable syngas (H 2 + CO) that could lead to sustainable synthesis of liquid fuels; but competitive fuel production from these HT thermo-chemical routes still appears to be decades away. An alternative path — the RWGS reaction — utilizes much less aggressive conditions and should be much more practical. With low-cost hydrogen becoming available from off-peak wind and nuclear, efficient reduction of CO 2 to CO becomes viable at moderate temperatures (750–1000 K) via the RWGS reaction. Challenges arise because of equilibrium limits imposed by the reaction thermodynamics below 800 K and because of competing methanation and coking reactions above 800 K to 1000 K, depending on the catalysts. Several promising sets of conditions and catalysts are being evaluated. To drive the reaction to the right, a multi-stage process is required with efficient separation processes. This in turn depends on advances in cost-effective gas-to-gas recuperators for relatively low pressures to limit parasitic methanation reactions. Another challenge may be passivation of the recuperator surfaces to minimize hydrogenation of the CO during the heat recovery. Preliminary simulations indicate reduction of CO 2 to CO with about 2.2 MJ/kg-CO should be practical at commercial scale.