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To investigate electrochemical performances of an amorphous lithium tungsten oxide (LWO) layer, an amorphous LWO-modified LiCoO 2 (LCO) thin film electrode is fabricated by pulsed laser deposition and is exposed under a humid environment. The amorphous LWO-modified LCO exhibits high capacity retention of 80% at a rapid charge-discharge rate of 20 C. Conversely, the bare LCO exhibits capacity retention of 0% at the rates of 20 C. Electrochemical impedance spectroscopy demonstrates that the LWO-modified LCO maintains a low interfacial resistance after the cycling test compared with the bare LCO. X-ray photoemission spectroscopy (XPS), scanning transmission microscopy (STEM), and electron energy loss spectroscopy (EELS) indicate the presence of Li 2 CO 3 on the surface of the bare LCO electrode and a thick degraded surface layer of CoO structure on the surface of LCO primary particle after electrochemical tests. XPS, STEM, and EELS indicate the presence of low amounts of Li 2 CO 3 on the surface of the LWO-modified LCO, the LCO layer remains in a normal state, and LWO layer maintains the amorphous LWO state after the tests. Thus, the amorphous LWO protective layer contributes to suppressing the degradation of LCO and maintaining an amorphous LWO state with a lithium ion conductor, resulting in high-power durability. [ABSTRACT FROM AUTHOR]

Room-temperature rechargeable sodium-ion batteries (SIBs), in view of the large availability and low cost of sodium raw materials, represent an important class of electrochemical systems suitable for application in large-scale energy storage. In this work, we report a novel, high power SIB formed by coupling the layered P2-Na 0.7 CoO 2 cathode with the graphite anode in an optimized ether-based electrolyte. The study firstly addresses the electrochemical optimization of the two electrode materials and then the realization and characterization of the novel SIB based on their combination. The cell represents an original sodium rocking chair battery obtained combining the intercalation/de-intercalation processes of sodium within the cathode and anode layers. We show herein that this battery, favored by suitable electrode/electrolyte combination, offers unique performance in terms of cycle life, efficiency and, especially, power capability. [ABSTRACT FROM AUTHOR]

Here we present a high-power all-solid-state supercapacitor based on a novel structure of MnO 2 @KCu 7 S 4 NWs. The electrodes exhibit excellent electrochemical performance with large specific capacitance of 533 F g −1 and the maximum power density 2.02 kW kg −1 , still hold 85% of the capacitance over 6000 cycles. Besides, we also explored the effect of temperature on the capacitance. When compared with capacitance at different temperatures, the specific capacity at 80 °C demonstrates significantly higher. Moreover, two supercapacitors in series can power 41 light-emitting diodes (LEDs) about 4 min. These results suggest that such MnO 2 @KCu 7 S 4 hybrid composite is promising for next generation high-performance supercapacitors. [ABSTRACT FROM AUTHOR]

Lithium-ion batteries with a combination of a lithium titanium oxide (LTO, Li4/3Ti5/3O4) anode and 4-volt-class cathodes, namely, LiMn2O4 (LMO) and LiNixCoyMn1-x-yO2 (NCM) cathode, have been developed for automotive and stationary power applications. The 3 Ah-class LTO/LMO cell for high-power applications had a high output power density of 3600 W kg−1 for 10 s pulse. High-rate full cycling tests at 10 C rate exhibited a high capacity retention of 95% after 30000 cycles. The capacity retention after 15 years at 35 °C in the calendar life tests is predicted to be 93%. Such a high-power and long-life performance of LTO/LMO cell is suitable for not only hybrid electric vehicle (HEV) but also idling-stop system (ISS) applications. The 20 Ah-class LTO/NCM cell with an energy density of 90 Wh kg−1 exhibited a power density of 2200 W kg−1. The storage life for floating charge at 100% state of charge (SOC) and the full cycle-life at 3 C rate are predicted to be 10 years at 45 °C and 10,000 cycles, respectively. It was demonstrated that the LTO/NCM cells have an excellent balance of high-power, high-energy, low-temperature, and long-life performance for not only electric vehicle (EV) but also plug-in hybrid electric vehicle (PHEV) and stationary power applications. [ABSTRACT FROM AUTHOR]

Abstract: Porous Mn3O4 nanoparticles with tunable microstructures are synthesized from Mn(AcO)2·4H2O with Pluronic F127 as a dispersant. The amount of copolymer served as the surfactant in the precursor solution is varied to change/tune the specific surface area/porosity of Mn3O4. The textural and electrochemical properties of porous Mn3O4 nanoparticle are systematically characterized by means of the N2 adsorption/desorption isotherms, scanning electron microscopic (SEM), transmission electron microscopic (TEM), X-ray diffraction (XRD), and voltammetric analyses. The interactions between manganese precursor and triblock copolymer can be used to control the microstructures of resultant oxides. Mn3O4 nanoparticles with tunable porosity and high surface area achieve the excellent capacitive performances (e.g., high-power characteristics and impressive capacitance retention) for next generation supercapacitors. The specific surface area indicating the electrochemically active sites for charge storage/delivery as well as the pore structure indexed by the BJH pore volume, which affects the ion transportation and electrolyte permeation, have been demonstrated to be the key factors determining the capacitive performances of Mn3O4 in the low-rate and high-rate processes, respectively. [Copyright &y& Elsevier]

Abstract: In an endeavor to improve the discharge C-rate performance of lithium-ion polymer batteries targeting high-power applications, we develop a novel gel polymer electrolyte-coated separator, which is based on introduction of close-packed poly(methyl methacrylate) (PMMA) nanoparticle arrays onto a polyethylene (PE) separator. In contrast to a conventional PMMA dense coating layer, a noticeable feature of the PMMA nanoparticle array coating layer is its highly ordered nanoporous structure, i.e. well-connected interstitial voids formed between the close-packed PMMA nanoparticles. This unique morphology allows for not only favorable liquid electrolyte wettability but also facile ionic conduction of the PMMA nanoparticle arrays-coated separator, both of which play crucial roles in improving the discharge C-rate performance of cells assembled with the separator. [Copyright &y& Elsevier]

Abstract: Layered LiNi1/3Co1/3Mn1/3O2 has been synthesized by heating its precursor of Ni1/3Co1/3Mn1/3(OH)2 and Li2CO3 at the temperature around of 900°C in air, and applied in high-power lithium-ion secondary cells by mixed with LiCoO2 in mass ratios of 1:1 and 1:2. The lithium-ion secondary cells with mixture of LiNi1/3Co1/3Mn1/3O2 and LiCoO2 showed a potential change similar to that of cell with pure LiCoO2 under low-rate discharge condition. The ICR18650 LIB with the mixed positive electrode is capable of discharge at 15C current rate with a better electrochemical performance compared to that of pure LiNi1/3Co1/3Mn1/3O2. Especially, the ICR18650 LIB with the mixed positive electrode exhibits improved safety performance during overcharge period compared to LiCoO2. Therefore, the mixture of LiNi1/3Co1/3Mn1/3O2 and LiCoO2 is a promising alternative material to LiCoO2 for high-power LIB. [Copyright &y& Elsevier]

Abstract: The performance of 18650-type high-power lithium-ion cells is being evaluated as part of the U.S. Department of Energy''s (DOEs) Advanced Technology Development (ATD) program. In this article, we present accelerated aging data acquired on 18650-cells containing LiNi0.8Co0.15Al0.05O2- or LiNi0.8Co0.1Al0.1O2-based positive electrodes, MAG-10 graphite-based negative electrodes, and 1.2-M LiPF6 in EC:EMC (3:7 by wt.) electrolyte. Capacity and impedance data acquired on electrodes harvested from these cells highlight the contributions of the positive and negative electrodes to the degradation of cell performance. We also describe test methodologies used to examine the electrochemical characteristics of the harvested electrodes. Identifying and optimizing cell components responsible for performance degradation should enable the development of new lithium-ion cell chemistries that will meet the 15-year cell calendar life goal established by DOEs FreedomCar initiative. [Copyright &y& Elsevier]

Cells were life-cycled cells using profiles with a 3, 6, or 9% change in state of charge (ΔSOC) at 40, 50, 60, and 70 °C. From the voltage response of the cells to the life-cycle profile at each temperature, we separated the overall impedance rise into two simpler terms, Ro (ohmic) and Rp (polarization), using an equivalent circuit model. The Ro data tend to follow the expected trends (40>50>60>70 °C). Although the Rp data trends show that Rp can either decrease or increase asymptotically with time, the overall temperature-dependent behavior is similar to that of Ro. We illustrate the types of processes that can occur in one lithium-ion cell chemistry. Based on the initial rates, the processes are complex. The Ro term dominates the observable cell impedance, but Rp adds a non-trivial contribution. [Copyright &y& Elsevier]

The new automotive architectures will require high-voltage, high-power batteries that are completely different from existing 12 V flooded lead–acid products. Battery requirements for these applications are reviewed first from the standpoint of the vehicle, and then from an electrochemical/thermal performance perspective. Design and performance characteristics are then critically evaluated for the three major candidates for the new 36/42 V systems, namely: valve-regulated lead–acid (VRLA), nickel–metal-hydride (Ni–MH), and lithium-ion (Li-ion). Design and manufacturing requirements, performance strengths and weaknesses, reliability issues, markets and pricing are then examined for the VRLA battery, which appears to be the leading candidate at this time. [Copyright &y& Elsevier]

To increase the user acceptance and to push electric mobility towards mass suitability, the energy and power density of Li-ion batteries for electric vehicles are among the most crucial features to be improved. The two major approaches to increase the energy density are the development of improved active materials and favorable cell designs. However, the identification of an optimal cell design is a sophisticated challenge due to the large number of interdependent factors influencing the different performance parameters. In the present study, a straightforward model based on the concept of diffusion-limited C-rate is proposed to optimize the energy density of Li-ion battery cells with specified rate performance. The model is introduced and the underlying assumptions are verified by comprehensive experimental investigations. The model is used to identify optimal design parameters of anode and cathode regarding maximum volumetric and gravimetric energy for specified rate performance. A sensitivity analysis is carried out to quantify optimization potentials of cell components and their properties. The results are discussed regarding promising improvement strategies and the practical limits of Li-ion batteries. Image 1 • Development of an application-oriented modeling tool for Li-ion battery design. • Optimizing design parameters regarding max. energy for specified rate performance. • Quantification of optimization potentials of cell components and their properties. • Optimization of cells using state-of-the-art design and material parameters. • Determination of practical limits of Li-ion batteries using a best-case scenario. [ABSTRACT FROM AUTHOR]

Partial electrification of vehicle drive trains, for example by the usage of 48 V systems, require high-power batteries with extreme robustness to temperatures, current rates and energy throughputs. In this study, the application-relevant lifetime performance of 33 state-of-the-art high-power lithium titanate oxide nickel manganese cobalt oxide (LTO|NMC) cells is measured under cyclic, calendar, and drive cyclic aging regimes. Regular extended check-ups reveal the cell performance in terms of capacity loss and internal resistance increase, which allows for the identification of critical operating conditions. For the first time a passive electrode effect is identified in calendar aging tests of LTO cells in which the cathode is geometrically and capacitively oversized. Passive electrode areas lead to a change in cell balancing, which can be illustrated by the shift of the half-cell voltage curves. Generally, the investigated cells show an excellent cycle stability for shallow cycles, even at high ambient temperatures and high current rates. Only large cycle depths greater than 70% at elevated temperatures reduce the battery life significantly. Furthermore, the results show that cells cycled in areas of low state of charge age faster than in areas of high state of charge. The rise in internal resistance under calendar aging has the most detrimental influence on lifetime in a 48 V battery. Image 1 • Observation of passive electrode effect for LTO-based cells with cathode overhang. • Change in cell balancing causes reversible variations in extractable capacity. • Outstanding cycle stability for small cycle depths even at high temperatures. • Both high and low states of charge trigger accelerated cell aging. • Internal resistance increase as lifetime defining criteria in 48V application. [ABSTRACT FROM AUTHOR]

Sulphur-doped spinel LiMn 2 O 3.99 S 0.01 is a promising cathode material for lithium-ion batteries. It can be obtained in a form of nanocrystals by a facile, eco-friendly and water-based sol-gel synthesis. In this work, LMOS was successfully coated with a 2–3 nm conductive carbon layer fabricated from pyrolysis of modified poly(N-vinylformamide) - water-soluble polymer precursor. Carbon coated material exhibits greatly increased performance under high currents and improved cyclability in long-term charge-discharge tests. Pristine and carbon-coated samples are characterized by X-ray diffraction, thermogravimetric analysis, elemental analysis, transmission electron microscopy and X-ray photoelectron spectroscopy. Electrochemical performance of the materials is examined by galvanostatic charge-discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. Carbon coated sample present a highly enhanced rate capability, withstanding up to 100C rate and maintaining up to 67.5% of initial 1C discharge capacity at 50C rate (1C - 148 mA g−1 – current required to fully charge a cell in time of 1 h). Li+ ion apparent diffusion coefficient in carbon coated sample is approximately twice increased. Electrochemical impedance spectroscopy has shown, that carbon coating decreases internal resistances of the cell caused by material passivation and charge-transfer reactions. Image 1 • Carbon coating on doped spinel nanomaterial through pyrolysis of water-soluble polymer. • Modified cathode material maintaining up to 100C rate of charge and discharge. • Multi-functional carbon nanocoating for high power and durable Li-ion batteries. • Improvement in lithium ion diffusion coefficient. [ABSTRACT FROM AUTHOR]