Advances In Battery Technology Research Articles

Investigate the lithium Dynamics in Li-Rich Layered Oxide Cathode Material Via Operando Neutron Diffraction

The progressive advancements in communication and transportation has changed human daily life to a great extent. While important advancements in battery technology has come since its first demonstration, the high energy demands needed to electrify the automotive industry have not yet been met with the current technology. One possible cathode material are the Li-rich layered oxide compounds xLi2MnO3.(1-x)LiMO2 (M= Ni, Mn, Co) (0.5=<x=<1.0) that exhibit capacities over 280 mAh g-1. In this class of compounds, lithium ions can reside in both lithium layer and transition metal layer of close packed oxygen framework, typical from O3 type layered oxides like LiCoO2.1-3 Large irreversible capacities are often observed in these materials due to irreversible oxygen loss or side reactions stemming for the electrolyte. It has been also observed using ex-situ NMR that lithium reinsertion back into the transition metal layer is little to none. However, these studies have not revealed the dynamic process of lithium migration for the Li-rich material under operando electrochemical cycling conditions. In order to gain more in-depth insights about the lithium (de-)intercalation mechanisms in Li-rich layered oxides, track particularly the lithium ions in transition metal layer, operando neutron diffraction experiments were designed to quantitatively observe lithium migration in this type of oxides during the electrochemical process. In this study, we use amorphous silicon as an anode for the neutron diffraction battery design in order to avoid any overlap of signal that may be associated with the anode material. We perform operando neutron diffraction to probe lithium and oxygen for a high Li-rich (HLR), Li[Lix/3Ni(3/8-3x/8)Co(1/4-x/4)Mn(3/8+7x/24)O2 (x = 0.6) material, and low Li-rich (LLR), Li[Lix/3Ni(1/3-x/3)Co(1/3-x/3)Mn(1/3+x/3)O2 (x = 0.24) material with varying degrees of the high voltage plateau. In conjunction with the operando neutron diffraction, density functional theory (DFT) calculations were used to explore the incorporation of dilute oxygen vacancy, its affect on the lattice mechanics and oxygen positions. We also observe site-dependent lithium migration taking place during different stage of charging/discharge processes. Furthermore, this work demonstrates the potential of investigating dynamic changes of light elements in large format (10-100 times larger format than the typical operando cells for synchrotron X-ray diffraction) prismatic and cylindrical batteries under realistic cycling condition via operando neutron diffraction method. Acknowledgements UCSD’s efforts are supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231, Subcontract No. 7073923, under the Advanced Battery Materials Research (BMR) Program. The neutron experiments benefited from the SNS user facility, sponsored by the office of Basic Energy Sciences (BES), the Office of Science of the DOE. H.L. acknowledges the financial support from the China Scholarship Council under Award No. 2011631005. Y.C. acknowledge the support from U.S. DOE’s Office of Basic Energy Sciences, Material Science and Engineering Division. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Reference 1. H. Liu, D. Qian, M. G. Verde, M. Zhang, L. Baggetto, K. An, Y. Chen, K. J. Carroll, D. Lau, M. Chi, G. M. Veith and Y. S. Meng, Acs Appl Mater Inter, 2015, 7, 19189-19200. 2. M. G. Verde, H. D. Liu, K. J. Carroll, L. Baggetto, G. M. Veith and Y. S. Meng, Acs Appl Mater Inter, 2014, 6, 18868-18877. 3. H. D. Liu, C. R. Fell, K. An, L. Cai and Y. S. Meng, J Power Sources, 2013, 240, 772-778.

Improved Electrochemical Performance in Advanced Lithium-Ion Batteries with Porocarb® As Functional Additive

Electric vehicles face significant battery related challenges such as driving range, recharge time, durability, and cycle life. New concepts for improved and advanced battery technologies are required in order to increase driving range and durability, while simultaneously decreasing recharging time, weight, and cost. In recent years, new cell designs have been developed specifically for large scale applications in the automotive and stationary storage sectors. A new electrode concept is to supplement with Heraeus Porocarb® porous particles as a functional additive to assure optimal mass transport of lithium ions by locally enhancing the effective diffusivity in the volume of the calendared electrode. Thereby achieving higher energy densities with improved cycle life and durability. Heraeus Porocarb is an electrochemically inert carbon with low specific surface with a unique porosity profile with distinct pore size regime. Its fully interconnected macropores allow for rapid ion transport, while the mesopores locally store electrolyte promoting mass transport and the pulse response of the cell. Heraeus Porocarb can be implemented into lithium-ion battery electrodes in two different ways. More conventionally, a percolation-type approach can be taken for Porocarb particles which are smaller than the active material particles. Due to the interconnected and surface-accessible pore network in Porocarb, ionic percolation sets in at the same time as electronic transport, and local improvement of the porosity evolves into a globally interconnected transport pathway of Li+ions with low tortuosity. The second electrode concept is an imprinting-type approach where the Porocarb particles used are larger and the active material is not only slightly imprinted but to a certain degree embedded in the Porocarb after calendaring. Due to the large contact area, very low resistances can be achieved in between the carbon and the active material, which alleviates contact resistance degradation and delamination, thereby extending cycle lifetime of the electrode. The properties of Heraeus Porocarb will be presented with electrochemical data showing the enhanced performance and the so-called “Porocarb effect.” This effect can be seen in lithium ion full cells by adding Porocarb in small quantities to the cathode. Therefore a representative cathode recipe were used, with an active material (NMC-111) content of 93 wt.%, 3 wt.% PVDF binder, 2.5 wt.% carbon black and 1.5 wt.% Porocarb. Reference cells were using a graphite instead of Porocarb. Two different cathode loadings were chosen: 120 g/m2 and 240 g/m2representing high-power and high-energy cell designs, respectively. The unique porous structure of Porocarb increases significantly the kinetics in the electrode and overcomes easily the drawbacks of the low rate capability of high energy cell. Figure 1

Operando Lithium Dynamics in the Li-Rich Layered Oxide Cathode Material Via Neutron Diffraction

The progressive advancements in communication and transportation has changed human daily life to a great extent. While important advancements in battery technology has come since its first demonstration, the high energy demands needed to electrify the automotive industry have not yet been met with the current technology. One possible cathode material are the Li-rich layered oxide compounds xLi2MnO3.(1-x)LiMO2 (M= Ni, Mn, Co) (0.5=<x=<1.0) that exhibit capacities over 280 mAh g-1. In this class of compounds, lithium ions reside in both lithium layer and transition metal layer of close packed oxygen framework, typical from O3 type layered oxides like LiCoO2.1 , 2 Large irreversible capacities are often observed in these materials due to irreversible oxygen loss or side reactions stemming for the electrolyte. It has been also observed using ex-situ NMR that lithium reinsertion back into the transition metal layer is little to none. However, these studies have not revealed the dynamic process of lithium migration for the Li-rich material under operandoelectrochemical cycling conditions. Neutron scattering has several distinct advantages for battery studies: 1) The sensitivity of neutron to light elements such as lithium and oxygen are significant in order to determine their position in the crystal structure; 2) Compares to the X-ray, the neutron shows larger scattering contrast between neighboring elements in the periodic table specifically the scattering lengths; and 3) The deep penetration capability of neutron allows simultaneous observation of the cathode and anode.3 However, challenges exist in broadening the application of operando neutron diffraction for Li-ion batteries research. First, limited by the generation reactions of neutrons, the neutron flux is usually several orders of magntitude lower than X-rays. In another words, longer acquisition times as well as larger amounts of samples are required for neutron diffraction experiments. In addition, the existence of hydrogen, which has a large incoherent neutron-scattering cross-section, is detrimental to the signal-to-noise ratio of neutron diffraction pattern. Separators (polyethylene based porous membrane) and poly carbonate based electrolyte solutions contain a considerate amount of hydrogen. These two major reasons pose significant challenges to operando neutron diffraction for lithium ion battery research although it is such a powerful technique for light elements like lithium. In order to gain more in-depth insights about the lithium (de-)intercalation mechanisms in Li-rich layered oxides, track particularly the lithium ions in transition metal layer, operando neutron diffraction experiments were designed to quantitatively observe lithium migration in this type of oxides during the electrochemical process. In this study, we use amorphous silicon as an anode for the neutron diffraction battery design in order to avoid any overlap of signal that may be associated with the anode material. We perform operando neutron diffraction to probe lithium and oxygen for a high Li-rich (HLR), Li[Lix/3Ni(3/8-3x/8)Co(1/4-x/4)Mn(3/8+7x/24)O2 (x = 0.6) material, and low Li-rich (LLR), Li[Lix/3Ni(1/3-x/3)Co(1/3-x/3)Mn(1/3+x/3)O2 (x = 0.24) material with varying degrees of the high voltage plateau. In conjunction with the operando neutron diffraction, density functional theory (DFT) calculations were used to explore the incorporation of dilute oxygen vacancy, its affect on the lattice mechanics and oxygen positions. We also observe site-dependent lithium migration taking place during different stage of charging/discharge processes. Furthermore, this work demonstrates the potential of investigating dynamic changes of light elements in large format (10-100 times larger format than the typical operando cells for synchrotron X-ray diffraction) prismatic and cylindrical batteries under realistic cycling condition via operando neutron diffraction method. Acknowledgements UCSD’s efforts are supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the U.S. Department of Energy (DOE) under Contract No. DE-AC02-05CH11231, Subcontract No. 7073923, under the Advanced Battery Materials Research (BMR) Program. The neutron experiments benefited from the SNS user facility, sponsored by the office of Basic Energy Sciences (BES), the Office of Science of the DOE. H.L. acknowledges the financial support from the China Scholarship Council under Award No. 2011631005. This work used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation grant number ACI-1053575. Reference 1. H. Liu, D. Qian, M. G. Verde, M. Zhang, L. Baggetto, K. An, Y. Chen, K. J. Carroll, D. Lau, M. Chi, G. M. Veith and Y. S. Meng, Acs Appl Mater Inter, 2015, 7, 19189-19200. 2. M. G. Verde, H. D. Liu, K. J. Carroll, L. Baggetto, G. M. Veith and Y. S. Meng, Acs Appl Mater Inter, 2014, 6, 18868-18877. 3. H. D. Liu, C. R. Fell, K. An, L. Cai and Y. S. Meng, J Power Sources, 2013, 240, 772-778. Figure 1

DVT prophylaxis strategies following total joint arthroplasty

Routine prophylaxis against venous thromboembolism is indicated following total joint arthroplasty. Prophylactic strategies differ in efficacy and safety, and variable risk exists among patients. Many strategies have been successfully used for chemoprophylaxis as well as mechanical prophylaxis with the use of pneumatic compression. Advances in battery technology and pump miniaturization have expanded the use of pneumatic compression in the post-discharge setting with mobile devices. Pneumatic compression is contraindicated in certain patients, and not all patients tolerate the devices. Mobile pneumatic compression is a valuable adjunct to venous thromboembolic risk mitigation strategies, but does not eliminate the need for pharmacologic agents.

Economic Solutions to Nuclear Energy's Financial Challenges

This Note presents a legal, economic, and regulatory roadmap to drive long-term innovation in sustainable energy generation. Next-generation nuclear power, which fundamentally mitigates many safety and nuclear waste issues, is the focus of this Note; however, the economic concepts can be applied to encourage solar, wind, advanced battery, and other sustainable technologies with high upfront costs and low long-term variable costs. Advanced nuclear energy generation is economically competitive on a long-term levelized cost basis, but suffers from a timing issue—a large amount of capital is needed upfront, with repayment over several decades, during which time significant capital costs can accrue (e.g., compounding interest, often at unfavorably high interest rates). This Note offers solutions to offset capital costs in both regulated and deregulated energy markets, including tools to accelerate recognition of future revenue and to reduce interest rates.

Power system balancing for deep decarbonization of the electricity sector

We explore the operations, balancing requirements, and costs of the Western Electricity Coordinating Council power system under a stringent greenhouse gas emission reduction target. We include sensitivities for technology costs and availability, fuel prices and emissions, and demand profile. Meeting an emissions target of 85% below 1990 levels is feasible across a range of assumptions, but the cost of achieving the goal and the technology mix are uncertain. Deployment of solar photovoltaics is the main driver of storage deployment: the diurnal periodicity of solar energy availability results in opportunities for daily arbitrage that storage technologies with several hours of duration are well suited to provide. Wind output exhibits seasonal variations and requires storage with a large energy subcomponent to avoid curtailment. The combination of low-cost solar technology and advanced battery technology can provide substantial savings through 2050, greatly mitigating the cost of climate change mitigation. Policy goals for storage deployment should be based on the function storage will play on the grid and therefore incorporate both the power rating and duration of the storage system. These goals should be set as part of overall portfolio development, as system flexibility needs will vary with the grid mix.

New Methods for Personal Exposure Monitoring for Airborne Particles.

Airborne particles have been associated with a range of adverse cardiopulmonary outcomes, which has driven its monitoring at stationary central sites throughout the world. Individual exposures, however, can differ substantially from concentrations measured at central sites due to spatial variability across a region and sources unique to the individual, such as cooking or cleaning in homes, traffic emissions during commutes, and widely varying sources encountered at work. Personal monitoring with small, battery-powered instruments enables the measurement of an individual's exposure as they go about their daily activities. Personal monitoring can substantially reduce exposure misclassification and improve the power to detect relationships between particulate pollution and adverse health outcomes. By partitioning exposures to known locations and sources, it may be possible to account for variable toxicity of different sources. This review outlines recent advances in the field of personal exposure assessment for particulate pollution. Advances in battery technology have improved the feasibility of 24-h monitoring, providing the ability to more completely attribute exposures to microenvironment (e.g., work, home, commute). New metrics to evaluate the relationship between particulate matter and health are also being considered, including particle number concentration, particle composition measures, and particle oxidative load. Such metrics provide opportunities to develop more precise associations between airborne particles and health and may provide opportunities for more effective regulations.

Recent Advances in Graphene-Based Materials for Lithium Batteries

Energy production and storage have become key issues due to the ever increasing demand of electricity in modern days. Rechargeable batteries are recognized as the primary power sources for applications from portable electronic devices to electric vehicles. Recently, there has been a growing interest in investigating graphene nanocomposite materials for various energy storage applications, such as electrodes in lithium batteries. With its unique structural, mechanical, and electrical properties, graphene can be a critical component in nanostructured electrode materials with improved capacity and cyclability, enabling the development of advanced batteries and new battery technologies. This paper reviews the recent achievements in graphene utilization in negative electrodes for Li-ion batteries and introduces the latest progress of flexible graphene-based Li-ion batteries. A survey of the scientific advances achieved thanks to the use of graphene in the so called “beyond Li-ion” technologies, namely Li-sulphur and Li-O2 batteries, is also presented. Keywords: Energy storage, lithium battery, graphene, nanocomposites, Li-O2, Li-sulphur.

Wearable sensor-based objective assessment of motor symptoms in Parkinson's disease.

Effective management and development of new treatment strategies of motor symptoms in Parkinson's disease (PD) largely depend on clinical rating instruments like the Unified PD rating scale (UPDRS) and the modified abnormal involuntary movement scale (mAIMS). Regarding inter-rater variability and continuous monitoring, clinical rating scales have various limitations. Patient-administered questionnaires such as the PD home diary to assess motor stages and fluctuations in late-stage PD are frequently used in clinical routine and as clinical trial endpoints, but diary/questionnaire are tiring, and recall bias impacts on data quality, particularly in patients with cognitive dysfunction or depression. Consequently, there is a strong need for continuous and objective monitoring of motor symptoms in PD for improving therapeutic regimen and for usage in clinical trials. Recent advances in battery technology, movement sensors such as gyroscopes, accelerometers and information technology boosted the field of objective measurement of movement in everyday life and medicine using wearable sensors allowing continuous (long-term) monitoring. This systematic review summarizes the current wearable sensor-based devices to objectively assess the various motor symptoms of PD.

Recent Progress in the Fundamental Understanding of Garnet-Based Superionic Conductors and Fabrication of Solid-State Cells for Advanced Lithium Batteries

In recent years, the push to move past conventional Li – ion battery technology has grown. Several advanced battery technologies and cell chemistries have been identified as promising candidates including i) solid-state batteries with Li metal anodes, ii) Li – S, and iii) flow batteries. Although an engineered solution using liquids may be possible for some of these options, a solid electrolyte is an enabling technology for each of these beyond Li – ion alternatives. Li7La3Zr2O12 (LLZO) with the cubic garnet structure is a promising solid electrolyte for advanced battery concepts such as solid state Li-ion batteries. Cubic LLZO is a fast ion conductor and is chemically and electrochemically stable between 0 and 6V vs. Li/Li+. This presentation will show recent advances 1) in the understanding of the conduction mechanism and 2) towards fabrication of solid-state device. First, neutron diffraction was used to successfully determine the Li site occupancy for a series of cubic LLZO compositions stabilized by Tantalum. Furthermore, the Li site occupancy has been related to the bulk ionic conductivity and activation energy as measured by Electrochemical Impedance Spectroscopy (EIS) with equivalent circuit modelling as a function of temperature. It was found that the maximum in the conductivity coincides with the cubic-to-tetragonal phase transition. The cubic-to-tetragonal transitional point also represents the maximum in octahedrally coordinated Li site occupancy and shortest Li-Li separation distances. Determination of the carrier concentration from results of the neutron diffraction and conductivity measurements support the earlier suggestion by Ohta et al. that not all the Li-ions are participating in conduction. Second, recent results towards bonding of electrodes to a cubic LLZO membrane will be presented. The ability to form electrochemically active solid/solid interfaces will allow for fundamental investigation of the charge transfer mechanism from one crystalline solid to another. Overall, the purpose of this work is to establish a fundamental knowledge base to assess the feasibility of large-format solid-state batteries.

(Invited) Atomic Layer Deposition of Nanophase Materials for Electrical Energy Storage

Batteries, as one of the most successful electrochemical electrical energy storage (EES) devices, hold great promise to boost widely implementation of renewable clean energies such as wind and solar power in three major domains: portable electronics, transport, and smart grids. To date, state-of-the-art lithium-ion batteries (LIBs) are dominant in consumer electronics, but still not applicable for electrical vehicles and smart grids in terms of energy density, cost, safety, and stability. In this context, huge research effort has been undergoing in pursuing cost-effective, high-energy, and robust batteries as next-generation EES devices. In the past few years, atomic layer deposition (ALD), a traditional thin film technique in semiconductor industries, has been identified as a new thrust for advanced EES and demonstrated powerful capabilities in addressing existing difficulties with various advanced battery technologies. Benefited from its unique mechanism, ALD now has become a versatile and irreplaceable tool for developing a large range of novel nanophase materials. The resultant nanoscale materials are playing more and more important roles in seeking new clean energy solutions. In the first place, ALD enables to provide a large variety of high-efficient electrodes (anodes and cathodes) by nanoarchitecturing energy-related materials. Secondly, ALD is particularly capable of finely tailoring battery interfaces for improved battery safety and stability, distinguishing its unrivalled quality from other methods in accurately controlling sub-nano to nanoscale ultrathin films with the most desired properties. In addition, ALD shows notable potential in constructing superionic lithium conductors as solid-state electrolytes for reliable battery safety, featuring its exceptional ability in tuning materials composition and crystallinity of complex compounds. In this invited talk, we will summarize and illustrate the various demonstrable strategies of ALD for next-generation LIBs and beyond Li-ion technologies (e.g., lithium-sulfur, lithium-oxygen, and sodium-based batteries), and highlight the most successful accomplishments of ALD in batteries. We will also give some outlooks on ALD future research trends and its opportunities in helping accomplish our energy missions.

Next-Generation Redox Flow Battery Technologies

In order to enable the large-scale adoption of the redox flow battery technology for grid-scale energy storage, the cost of a redox flow battery system needs to further reduced. Here we report a new redox flow battery chemistry based on soluble commodity redox active materials, which eliminate the need for expensive metal-based redox couples. Compared with other reports in this area, our new redox flow battery technology demonstrated higher voltage, energy density, rate capability, and improved cycling stability (Figure 1). Recent progress of the advanced redox flow battery technologies research at PNNL will also be discussed, such as new developments on the high energy density electrolyte, high selective membrane, catalytic electrode, as well as nonaqueous redox flow battery technologies. Acknowledgements The authors would like to acknowledge financial support from the U.S. Department of Energy’s (DOE’s) Office of Electricity Delivery and Energy Reliability (OE) (under Contract No. 57558). Pacific Northwest National Laboratory is a multi-program national laboratory operated by Battelle for DOE under Contract DE-AC05-76RL01830. Figure 1. Voltage profile and the cyclic capacity behavior of the new redox flow battery technology. Figure 1

Simultaneous Neutron and x-Ray Tomography for Advanced Battery Research

The current demand of high powered portable electronics and electric vehicles has put significant strain on current battery technology. To improve performance of advanced battery technologies, such as lithium-air, it is critical to understand how reactive species transport and distribute throughout the cell at varying states of charge. Neutron and x-ray imaging techniques allow in-situ visualization of reactants within the battery. X-ray attenuation increases with increasing atomic number while neutron attenuation is more random with strong attenuation by lithium. These techniques can provide complementary data by providing critical microstructure information. To provide access to both techniques, NIST is developing a simultaneous neutron and x-ray imaging facility. The new system orients a 90 keV microfocus x-ray source 90° to the neutron beam to allow for simultaneous tomography as shown in Figure 1. This x-ray system will allow for variable energy, brilliance, and magnification while matching the neutron spatial resolution of 15-50 micron. Matching image resolution of the two beams will allow the overlaying of the two tomograms. Simultaneously imaging batteries will allow reaction species, such as lithium, and solid structure to be resolved at identical conditions which can’t be guaranteed for serial imaging (possibly at different facilities). This presentation will describe the new simultaneous imaging system and evaluate its measurement uncertainties while assessing its abilities using an assortment of batteries including alkaline, Ni-Cd, and Li-ion. Figure 1

CNFET-Based 0.1- to 1.2-V DC/DC Boost Converter With Voltage Regulation for Energy Harvesting Applications

With the wide-scale adoption of various low-voltage power hungry wearable and portable electronic devices, researchers are compelled to focus on alternate sources of energy. This problem further demands attention as advancements in battery technology have failed to match the growth in power consumption of such devices. Energy harvesting has been widely debated and studied as an alternative of batteries in such devices. Adoption of such techniques requires an efficient dc/dc step-up conversion to boost ultralow-voltages scavenged from the environment. This paper presents a carbon nanotubes-FETs-based architecture for harvesting ambient energy from the surroundings (typical voltage $\sim$ 100 mV) and boosting it to useful voltage levels (1.2 V). Such a converter is capable of sourcing sufficient current ( $120 \;\mu$ A) to supply modern low-power CMOS devices and exhibits an efficiency of $27\%$ . In addition, a voltage regulation circuit is also proposed to minimize the fluctuations in output due to unreliable supply of input voltage. The design is modeled using extensive simulations in experimentally verified Stanford CNFET model that has been calibrated for $90\%$ accuracy. This paper concludes the discussion with a comparison between the proposed architecture and other CMOS-based designs.

Social, economic, technological, and environmental impacts of the development and implementation of solar‐powered charge stations

This work focuses on aspects related to the development and implementation of solar‐powered charge stations (SPCS), analyzing specifically the social, economic, and technological challenges associated with increasing the use of electric vehicles (EVs) and the availability of SPCS. Greenhouse gas emissions can be reduced by the electrification of transportation and the generation of electricity with sustainable energy, including solar energy at SPCS. The charging infrastructure for EVs can be improved by adding SPCS to many parking lots so that EV owners can plug in at work, shopping centers, events, and home. Results from a Kansas State University survey indicate that the limited charging infrastructure is a present concern when considering a purchase of an EV. Smart grid developments with real time prices for electricity have many positive features that support SPCS installations and EV sales, including higher values for the electricity generated at SPCS and reduced cost for night time charging of EVs. There is the potential to improve urban air quality by replacing internal combustion vehicles that have emissions with EVs that do not have carbon emissions. When all costs are considered, SPCS and EVs have a favorable outlook, and advances in battery technology have the potential to reduce EV costs and increase their range. © 2015 American Institute of Chemical Engineers Environ Prog, 34: 1808–1813, 2015

Further advances in battery technologies are needed for smart grid

Lithium-ion batteries are improving too slowly to revolutionize the storage of electricity.

Decoder-Complexity-Aware Encoding of Motion Compensation for Multiple Heterogeneous Receivers

For mobile multimedia systems, advances in battery technology have been much slower than those in memory, graphics, and processing power, making power consumption a major concern in mobile systems. The computational complexity of video codecs, which consists of CPU operations and memory accesses, is one of the main factors affecting power consumption. In this article, we propose a method that achieves near-optimal video quality while respecting user-defined bounds on the complexity needed to decode a video. We specifically focus on the motion compensation process, including motion vector prediction and interpolation, because it is the single largest component of computation-based power consumption. We start by formulating a scenario with a single receiver as a rate-distortion optimization problem and we develop an efficient decoder-complexity-aware video encoding method to solve it. Then we extend our approach to handle multiple heterogeneous receivers, each with a different complexity requirement. We test our method experimentally using the H.264 standard for the single receiver scenario and the H.264 SVC extension for the multiple receiver scenario. Our experimental results show that our method can achieve up to 97% of the optimal solution value in the single receiver scenario, and an average of 97% of the optimal solution value in the multiple receiver scenario. Furthermore, our tests with actual power measurements show a power saving of up to 23% at the decoder when the complexity threshold is halved in the encoder.

Review—Superconcentrated Electrolytes for Lithium Batteries

Ever-increasing demand for better batteries has set extraordinarily high standards for electrolyte materials, which are far beyond the realm of a conventional nonaqueous electrolyte design. Superconcentrated (or highly concentrated) solutions are emerging as a new class of liquid electrolytes with various unusual functionalities beneficial for advanced lithium (Li) battery applications. This article reviews unique features, as well as basic physicochemical properties, of highly concentrated electrolytes from the viewpoint of their peculiar solution structure, and discusses their future contributions to advanced battery technologies.

Towards high-energy and durable lithium-ion batteries via atomic layer deposition: elegantly atomic-scale material design and surface modification

Targeted at fueling future transportation and sustaining smart grids, lithium-ion batteries (LIBs) are undergoing intensive investigation for improved durability and energy density. Atomic layer deposition (ALD), enabling uniform and conformal nanofilms, has recently made possible many new advances for superior LIBs. The progress was summarized by Liu and Sun in their latest review [], offering many insightful views, covering the design of nanostructured battery components (i.e., electrodes and solid electrolytes), and nanoscale modification of electrode/electrolyte interfaces. This work well informs peers of interesting research conducted and it will also further help boost the applications of ALD in next-generation LIBs and other advanced battery technologies.

Photo-Oxidation of Hydrogenated Fullerene (Fullerane) in Water

Hydrogenated fullerenes (termed fulleranes) have been demonstrated to be key material components in advanced hydrogen storage and lithium battery technologies, among other applications; however, their potential environmental reactivity has not been evaluated to date. Here, for the first time, photoinduced oxidation and corresponding dissolution of solid fulleranes (C60Hx, where x = 39.9–45.5) into water are demonstrated to occur rapidly under attenuated sunlight, UV-A irradiation, and even dark conditions, albeit more slowly as long as oxygen is present. Through a series of batch experiments, reaction kinetics demonstrate that both light and oxygen play critical roles in the solvation process as reaction rates were a function of both irradiation intensity and wavelength along with dissolved oxygen concentration. Resulting products, which were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet–visible spectroscopy, total organic carbon analysis, and dynamic light scattering, showed significant loss of hydrogenation and extensive oxygen-based functional group addition(s). Hydroxyl radical was identified as one of the major reactive oxygen species involved in the reaction. The increased hydrophilicity of product materials was quantified through classic octanol–water partition experiments (Kow).