bluuebunny/crossref_metadata_2025 huggingface dataset:
Study on Cycle Life of Lithium-Ion Batteries Using in Situ
7li Solid-State Nuclear Magnetic Resonanc
Authors: Arai Juichi , Nakahigashi Rie , Sugiyama Teruyasu
Published: February 2020

The life of the lithium-ion batteries (LIBs) used as power sources for electrically powered vehicles, such as e-scooters, e-bikes, and electrically assisted wheel chairs, is critical for the stable operation of these products throughout their lifetime. Understanding the battery life may help in improving the performance of the vehicles powered by LIBs. However, examining the degradation mechanism without disassembling the cell is not easy. Thus, the cell life of the same cell cannot be tracked. Hence, in situ measurements are required.

We have developed an in situ
7Li solid-state nuclear magnetic resonance (NMR) measurement and studied the reaction inside the LIBs without decomposition [1,2]. We applied this technique to the analysis of the battery cycle life. The Li intercalation in carbon (graphite intercalation compound, GIC) was monitored every 100 cycles during cycle tests that were performed at 10 and 25 °C with 0.5 and 1 C discharge rates, respectively. The cell was composed of a LiCoO2 positive electrode, a carbon negative electrode, and an organic electrolyte (ethylene carbonate (EC)/ethyl methyl carbonate (EMC) with 1 M LiPF6). Fig. 1 shows the spectra measured at 100% state of charge (SOC), a fully charged mode at 0.2 C constant-current and constant-voltage (CCCV), every 100 cycles at 25 °C.

K. Gotoh, M. Izuka, J. Arai, Y. Okada, T. Sugiyama, K. Takeda, H. Ishida, Carbon, 79, 380 (2014).

J. Arai, Y. Okada, T. Sugiyama, K. Gotoh, M. Izuka, K. Takeda, ECS Trans. 62(1), 159 (2014).

Figure. 1. Spectra measured at 100% state of charge (SOC) (a) before the cycle test, (b) after 100 cycles, (c) after 200 cycles, and (d) after 300 cycles.

Figure 1
Scalable Synthesis of Composite As Cathode in Li-S Batteries with Improved Performance
Authors: Niu Junjie
Published: February 2020

On the demand of large-scale energy storage, the secondary lithium-ion batteries (LIBs) are attracting more attentions on portable devices and electric vehicles. Numerous efforts are being taken into finding new electrode materials which have folds higher capacity with respect to the traditional materials over the last decade. In particular, scientists have explored silicon shows a 7-10 times higher capacity of >2000 mAh/g than the commercial graphite. However, on the cathode side, substantial capacity improvement in comparison of silicon anode is lacking, which largely restrict the commercialization of high energy density batteries. Sulfur has been identified as one of most promising cathode materials for its high theoretical capacity (1675 mAh/g, 8-10x times higher than LiCoO2) and the theoretical specific energy (~2600 Wh/kg, 5x times higher than LiCoO2/graphite) of Li-S battery. Nevertheless, researchers remain stagnant in pushing this high power-density battery into industrial applications. The major barrier is from the rapid capacity decay, which is due to the low electrical conductivity, volume expansion and the shuttling effect. Averting chemomechanical degradation thus poses as one of the primary challenges in exploiting sulfur cathodes in the development of next-generation batteries.

       Here we present a scalable synthesis of lithium-sulfur composite cathode with improved performance. An open network of conductive carbon black nanoparticles (Cnet) is infused with sulfur (Snet) to form sponge-like interpenetrating, doubly percolating random networks (Cnet + Snet). A >750 mAh/g discharge specific capacity of this sulfur nanosponge cathode was received after 100 cycles under a rate of 0.2 C. A >500 mAh/g discharge capacity was attained after 300 cycles, making this cathode material attractive for powering portable electronic devices.
A Multi-Scale Electrochemical Modeling of Amorphous Silicon Thin Film in a Lithium Ion Batteries
Authors: Gwak Yunki , Moon Janghyuk , Cho Maenghyo
Published: February 2020

The electrochemical performance of Li-ion batteries strongly depends on the interaction between atomic scale and micro scale phenomena in particular, within the electrodes. Therefore, we propose a multi-scale model to characterize the electrochemical and mechanical response of amorphous silicon thin film with discharge-charge cycling.In multiscale frameworks, we analyze the lithium kinetics and the thermodynamics such as lithium migration energy barriers and excess gibsss free energy of lithium silicon alloys using density functional theory calculation. With the calculated results, the lithiation behavior in silicon thin film anode shows the large deviation compared to the simulated results based on an ideal solution model. We identify that these effects account for nonlinear lithium diffusion behavior using continuum based numerical simulation. We also consider the coupled diffusion and mechanical model for the cell scale,and determine non equilibrium cell potential as function of surface lithium concentration using Bulter-Volmer kinetics. Our simulation results are shown to be well consistent with known experimental observation at different C-rates and thicknesses.This multi-scale approach in lithium ion battery can provide essential guidance in the interpretation of lithiation and delithiation phenomena and is enable of predicting battery performance before experiments are ever performed.

Figure 1
Structurally Stabilized Fe Oxides through Conversion Reactions with Li+ By Embedment in a Li4Ti5O12 Matrix
Authors: Jo Mi Ru , Jung Jaepyeong , Song Kyeongse , Yang JungHoon , Lee Gi-Hyeok , Kang Yong-Mook
Published: February 2020

Transition metal oxides are promising electrode materials for lithium-ion batteries that operate through conversion reactions. Energy densities for conversion reactions are higher than for intercalation reactions, but most transition metal oxides show poor cycling performance and reversibility due to pulverization of active materials and subsequent volume changes. We report a facile, scalable, electrospinning synthesis for fabrication of Li4Ti5O12-coated Fe/Fe3O4 nanocomposites into one-dimensional hybrid nanofibers (C@Fe-Fe3O4/Li4Ti5O12 hybrid NFs). This is a new class of highly-reversible and safe anode material that significantly reduces the lithium-ion diffusion length and improves strain tolerance caused by lithium-ion insertion/extraction. Oxidation state is also impressively controlled through a carbothermal reaction during annealing. The precise oxidation state control of C@Fe-Fe3O4/Li4Ti5O12 hybrid NFs provided high capacity due to the Fe oxide conversion reaction and substantial reversibility and stability resulting from zero-strain characteristics and superb kinetics of Li4Ti5O12. This new electrode material appears promising for future energy systems.
Analysis of All-Solid Li-Ion Batteries By Photoelectron Spectroscopy: Experimental Procedures, Interpretation and Results
Authors: Fingerle Mathias , Schwöbel André , Precht Ruben , Jaegermann Wolfram , Hausbrand René
Published: February 2020

Electrochemical devices such as lithium-ion secondary batteries consist of complex layer systems with interfaces and interphases that play a crucial role in cell performance and degradation. The understanding of the energy level alignment and double layer formation especially at electrode-electrolyte interfaces is therefore mandatory. Photoelectron Spectroscopy (PES) is a reliant tool and widely accepted method in surface science to probe the electronic structure of thin, electronically conducting layer systems on a nanometer scale, e.g. of semiconductor devices.  For such systems, an aligned Fermi level (i.e. electrochemical potential of electrons) can usually be presumed resulting in well-defined experimental conditions for PES. For ionic systems involving (solid) electrolytes, the experimental conditions are less clear due to the lack of sufficient electronic conductivity. Nevertheless, also in such cases PES proofs to be a useful tool, i.e. for analysis of solid electrolytes or characterization of full cells and interfaces [1].

In this contribution, we focus on the different electrolyte- and ionic-interface related effects, such as charging and Fermi level misalignment, and discuss experimental strategies and interpretation of PES measurements. By example of a LiCoO2|LiPON|Li thin film battery, we demonstrate how interface experiments and analysis of the top electrode of a layer stack can be performed and interpreted. Key factors taken into consideration are the electrochemical equilibrium of the lithium ions at the interfaces as well as the ability of the electrolyte to sustain an electric (ionic) current, given corresponding (de)intercalation reactions are triggered.  Next to information on electron energy level alignment and double layer formation, information on ion energy levels, ionic and electronic contribution to cell voltage, formation of reaction layers as well as electronic structure of intercalation electrodes can be obtained from suitable experiments (see e.g.[1-3]).

1.            Hausbrand, R., D. Becker, and W. Jaegermann, A surface science approach to cathode/electrolyte interfaces in Li-ion batteries: Contact properties, charge transfer and reactions. Progress in Solid State Chemistry, 2014. 42(4): p. 175-183.

2.            Tonti, D., C. Pettenkofer, and W. Jaegermann, In-Situ Photoelectron Spectroscopy Study of a TiS2 Thin Film Cathode in an Operating Na Intercalation Electrochemical Cell. Ionics, 2000. 6(3-4): p. 196-202.

3.            Schwöbel, A., R. Hausbrand, and W. Jaegermann, Interface reactions between LiPON and lithium studied by in-situ X-ray photoemission. Solid State Ionics, in press.
Development of a Novel Manganese Dioxide/Nickel Oxyhydroxide Fibrous Positive Electrode for Fuel Cell/Battery (FCB) Systems
Authors: Shimizu Hiroki , Choi Bokkyu , Panthi Dhruba , Musil Mike , Tsutsumi Atsushi
Published: February 2020

A novel MnO2/NiOOH fibrous positive electrode for Fuel Cell/Battery (FCB) systems has been proposed. FCB systems containing manganese dioxide and metal hydride (MH) as active materials for the positive and negative electrodes, respectively, have been found to be attractive energy storage and power generation systems because they can function as both fuel cells and secondary batteries with high energy and power density. Moreover, they can also be chemically charged by gaseous hydrogen and oxygen supply. However, the chemical charging rate of the positive electrode of the FCB systems is relatively low compared to the negative electrode. In our previous study, highly dissolved oxygen in an electrolyte was used in order to improve the chemical reaction rate of oxygen charging on a manganese dioxide electrode. The study showed that the charge rate will be 3.45 mAh/(g･min) if the oxygen is supplied with the limiting pressure. This result implies that the proton diffusion in the crystalline structure of the manganese dioxide or the dissociation of oxygen molecule on the manganese dioxide surface is the rate determining step in the oxygen charging. In the current study, therefore, we suggest two approaches for the fabrication of FCB positive electrodes to improve the oxygen charging rate: i) enlargement of active surface area by an electrodeposition method of active materials on carbon fibers, and ii) introduction of small amount of nickel oxyhydroxide to fibrous manganese dioxide electrodes in order to enhance the electrical conductivity of the positive electrode. Nickel oxyhydroxide is a well known positive electrode material of Ni-MH batteries and has higher electrical conductivity than manganese dioxide. Thus, the combination of nickel oxyhydroxide with manganese dioxide is expected to lead to a higher electrical conductivity of the FCB positive electrode. In the present paper, the characteristics of the proposed fibrous electrode will be studied by using galvanostatic measurement, electrochemical impedance spectroscopy, scanning electron microscopy analysis, and X-ray diffraction measurement.
Using Nanostructured Materials to Develop Anodes for Lithium-Ion Batteries and Increase the Efficiency of Photovoltaic Cells.
Authors: Stewart Jimmel , Alfredsson Maria
Published: February 2020

Renewable energy resources have become one of the most important challenges of the 21st century. One way to tackle the problem of the growing need for a low cost and environmentally friendly storage system is to invest and develop in new research. One solution is to build on the advancements of silicon solar cells and silicon electrode materials for lithium-ion batteries and to consider using nanostructured materials to develop hybrid functional energy materials. This research looks at the use of atomistic simulations to design silicon nanotubes and particles with an enhanced energy harvesting and storage properties. As for carbon, nanotubes with different structures and properties can be created by rolling a layer of graphene in different directions. For silicon, it is found that independent of the way the tubes are created they show metallic behaviour, as opposed to carbon nanotubes which demonstrate both semi-conducting as well as metallic properties. Contrary silicon nanoparticles are insulating in agreement with previous studies. This finding is important for applications in high energy density storage applications, where metallic silicon can be employed both as the anode and the cathode material. It could also improve the efficiency of photovoltaic cells.
Embroidered 3D Porous Structures As Current Collectors for Li-Ion Batteries
Authors: Aguiló-Aguayo Noemí , Pena Espiñeira Pablo , Bechtold Thomas
Published: February 2020

There is a need to improve battery designs to maximise energy and power densities. Standard planar current collectors present some limitations in electronic conductivity due to a thickness of the active mass, problems with the uniformity of thermal conductivity at high current densities, as well as difficulties with the handling of the batteries. Here, we present embroidered 3D porous structures fabricated by technical embroidery as an alternative to be used as current collectors for LiFePO4 batteries. X-ray computed micro tomography was used to provide the appropriate morphological characterisation of the 3D structures. The electrochemical behaviour of the electrodes was also investigated using charge and discharge cycles. Specific capacities as a function of the mass loading and the increase of the current densities are presented.

Figure 1
High-Index Faceted Pt Nanoflower Catalysts with Ultra-Low Overpotential and Superb Cyclic Retention for Rechargeable Li-O2 Batteries
Authors: Song Kyeongse , Jung Jaepyeong , Cho Eunbi , Park Mihui , Agyeman Daniel Adjei , Kang Yong-Mook
Published: February 2020

Surface structure of noble metal catalysts has been regarded as an important factor to determine the catalytic activities in various applications. For oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the cathode of Li-O2 batteries, however, the structure sensitive catalytic activities are still poorly understood. We here report the preparation of anisotropic structure of Pt nanoflowers and its catalytic properties in rechargeable Li-O2 batteries. As for the ORR properties, the Pt nanoflowers exhibit high capacity (12,985 mAh/gcarbon), excellent rate capability and a good cycle performance up to 70 cycles (with a curtaining capacity of 1,000 mAh/gcarbon). In addition, the Pt nanoflowers demonstrate a low OER potential of 3.1 V, providing the highest round trip efficiency of ~87% at a current density of 200 mA/gcarbon. These greatly enhanced ORR and OER performances of the Pt nanoflower-incorporated cathode compared to that of commercial Pt/C catalyst can be attributed to the exposed high-index {411} facets on their anisotropic structure.
Nickel Sulfide/Carbon Nanotube Nanocomposites As High Performance Cathode Materials for Asymmetric Supercapacitors
Authors: Lin Jeng-Yu , Chou Shu-Wei
Published: February 2020

Recently, supercapacitors have attracted extensive attention due to their unique properties of long cycling life, low maintenance cost, and high power density. Furthermore, supercapacitors show great potential applications for energy-storage systems in portable electronic devices and hybrid electric vehicles. Typically, supercapacitors have two mechanisms of the charge storage/delivery, namely the electric double-layer capacitors (EDLC) and psuedocapacitors. The pseudocapacitor usually shows a higher value of specific capacitance (Cm) than EDLC due to the presence of the Faradaic process. However, both EDLC and the pseudocapacitor show lower specific energy densities than batteries. Therefore, the development of the supercapacitors with high power and energy densities is still a challenge.

In this study, the Ni3S2/carbon nanotube composites were successfully developed by means of the glucose-assisted hydrothermal method. The composite electrode shows a high specific capacitance of 800 F/g and great cycling stability at a current density of 3.2 A/g. Furthermore, an asymmetric supercapacitor device was fabricated by using the composite of Ni3S2 and MWCNTs as the cathode and activated carbon as the anode. The fabricated device can be operated reversibly between 0 and 1.6 V, and obtain a high specific capacitance of 55.8 F/g at 1 A/g. It also delivers a maximum energy density of 19.8 Wh/kg with a power density of 798 W/kg. As a result, the asymmetric supercapacitor device based on the Ni3S2/MWCNTs cathode can be considered as a promising energy storage device.
Low Voltage Anodes for Lithium-Ion Batteries
Authors: Clark Steve , Armstrong Anthony Robert , Bruce Peter G
Published: February 2020

Graphite has proved a highly successful anode for lithium ion batteries; however it is not without its limitations. There is intensive research to perfect silicon based anodes but important challenges still remain in the quest for high cycling efficiency and high cycle numbers. As a result, there remains much need for investigation of alternative anodes for lithium-ion batteries. Recently we investigated anodes based on LiVO2
1,2.  Intercalation into this compound, which is isostructural with LiCoO2, occurs in a two phase process with the formation of hexagonal Li close packed Li2VO2.1 We have now extended these studies to related compounds, and solid solutions, and have identified anodes with a capacity of over 205 mAh/g at C rate, Fig. 1. The density of these materials is 3.34 g/cm3 resulting in a volumetric capacity of 718 mAh/cm3 at 1C. Volumetric capacity is important for applications such as electric vehicle.  Detailed results of these investigations will be presented in the meeting.

References:

1) A.R. Armstrong, C. Lyness, P.M. Panchmatia, M.S. Islam, P.G. Bruce, Nat. Mater. 10 (2011) 223-228.

2) F.d.r. Pourpoint, X. Hua, D.S. Middlemiss, P Adamson, D Wang, P.G  Bruce, C.P. Grey, Chem. Mater. 2012, 24, 2880−2893.

Figure 1
Correlation Between Microstructure Parameters and Performance Characteristics of Lithium-Ion Cathodes
Authors: Costard Janina , Raumer Michael , IJsselstein Tim , Gerthsen Dagmar , Ivers-Tiffée Ellen
Published: February 2020

Lithium-Ion Batteries receive growing attention because of their potentially high energy and power density, which are important requirements for automobile applications. Reports agreed that the positive electrode is hereby the performance limiting cell component.

NxMyCz (nickel manganese cobalt spinel) is one of the most promising cathode materials, both due to its rather high operating voltage and to either high power or energy density [1]. Hereby, a compromise between high power (thin layers and, i.e., high porosity) and high energy density (thick layers and, i.e., low porosity) has to be reached, in particular for automotive applications. This demands for an extended understanding of the interplay between microstructure parameters and chemical stoichiometry of NMC cathodes on cell performance characteristics.

In this study, two NMC - cathodes recovered from commercial high energy and high power cells are analyzed (i) by SEM and X-ray tomography and (ii) by Electrochemical Impedance spectroscopy (EIS). By evaluating the impedance spectra measured at 0 to 40°C and at SOC 0 to SOC 100 by the distribution function of relaxation times (DRT) [2], a physically motivated transition line model [3] was established. The microstructure parameters required for a quantitative analysis of the electrochemical loss processes were obtained by X-ray tomography data. Additionally, the exact composition is determined by energy dispersive X-ray spectroscopy (EDX) investigations

The results confirm, that a NMC electrode custom tailored for high energy density is rather thick (70 µm) and made of large low-porous agglomerates of primary particles, as described in [4]. The significant difference between the NMC cathode of a high energy and a high power cell however is not, as expected, a significantly higher porosity, but a sophisticated combination of small carbon black particles and elongated carbon black fibers, enabling high discharge currents. The tortuosity of the electrode pores, which represent the transport pathways for the liquid electrolyte, is low for the high power cell, which raises the effective electrolyte conductivity significantly, when compared to the high energy cell [4]. Furthermore the high power cell features a special compound of two different NxMyCz active materials. By including all the results from EIS, DRT, X-ray tomography and EDX, an evaluation of the influence of composition and microstructure on performance characteristics of the NxMyCz cathodes will be presented.

References

 

[1] K.C. Kam, A. Mehta, J.T. Heron, M.M. Doeff, Journal of the Electrochemical Society 159 (2012) A1383–A1392.

[2] J. Illig, Physically based Impedance Modelling of Lithium-Ion Cells (2014)

[3] J. Euler, W. Nonnenmacher, Electrochimica Acta 2 (1960) 268–286.

[4] M. Ender, J. Joos, A. Weber, E. Ivers-Tiffée, Journal of Power Sources 269 (2014) 912–919.
Identification of Failure Mechanisms in Si Electrodes for Li-Ion Batteries
Authors: Beattie Shane D , Loveridge Melanie
Published: February 2020

Introduction:

Silicon anodes are studied as a high capacity alternative to graphite for Lithium-ion batteries.  Unfortunately, when silicon anodes are paired with commercially relevant cathodes the cell suffers from rapid capacity fade.  Failure mechanisms resulting in rapid capacity fade are identified using three techniques: i) study of voltage-capacity profiles from three-electrode cells, ii) the effect of upper cut-off voltage on capacity retention, and iii) ex-situ X-ray diffraction.

Discussion:

Most commercial Li-ion cells are cycled using a constant-current, constant-voltage profile.  Voltage limits are typically set between 3 and 4.2 V.  When using novel cell chemistries it is important to understand how industry standard cycling profiles affect the evolution of the voltage–capacity profile.  Anode/cathode voltage is tracked in a three electrode cell to understand how the voltage profile of each electrode evolves over time/cycle number.  Data shows that as silicon electrodes are cycled they lose capacity/active lithium inventory (Figure 1).  Silicon electrodes have a sloping voltage profile.  When lithium inventory is depleted the end of charge voltage at the anode will increase; correspondingly, the end of charge voltage at the cathode will increase (> 4.4 V vs. Li).  This rise in voltage at the end of charge will liberate more lithium from the cathode, replenishing some of the lost lithium inventory.  This has short term gains by replenishing the lost lithium inventory, but long term consequences as cathodes do not cycle well at higher voltages (Figure 2).  

Ex-situ XRD data shows that when silicon electrodes are cycled to less than their theoretical capacity, the conversion from crystalline to amorphous silicon is continuous (Figure 3).  This suggests that previously amorphized silicon is not preferentially lithiatied, contrary to voltage considerations.  The data suggests that crystalline particles continue to crack during cycling, exposing fresh crystalline silicon surfaces.  Lithium reacts at the newly formed crystalline silicon surface due to its close proximity to the electrolyte, rather than diffusing through the bulk to reach previously amorphized Si.  This process results in continued decomposition of electrolyte, and formation of excessive SEI.  XRD and electrochemical data show that the conversion from crystalline to amorphous silicon stops above ~ 180 mV. 

Conclusion:

Results from three-electrode cells clearly show an increase in end of charge voltage at the anode/cathode as a function of time/cycle number.  The end of charge voltage at the cathode reaches above 4.4 V, which is beyond the recommended cycling regime of the cathode and electrolyte.  This rise in end of charge voltage results in decreased cycling efficiency and rapid loss of capacity.  XRD data shows that when Si electrodes are cycled to less than their theoretical capacity the conversion of crystalline Si to amorphous Si is continuous below a voltage of ~ 180 mV.

Figure 1
Characterization of Structure and Electronic States of La0.5Ca0.25MnO3 surface By First-Principles Simulation
Authors: Ando Yasunobu , Nakamura Sunya , Minamitani Emi , Shimizu Ryota , Iwaya Katsuya , Ohsawa Takeo , Hitosugi Taro , Watanabe Satoshi
Published: February 2020

Perovskite oxides (perovskites) are promising candidates for oxidation catalysis in solid-state fuel cells because of their high chemical activity on the surface and variety in composition. However, direct observation of their surface structures and properties has been difficult due to the lack of easy-cleavage plane. Research on the clean surfaces of perovskites has been demanded.

Recently, some of the coauthors of this presentation have succeeded in epitaxial growth of La0.75Ca0.25MnO3 (LCMO) thin films and their scanning tunneling microscope (STM) obsearvation at low temperature (see Fig. 1). They found that the LCMO surface is reconstructed and shows a zigzag pattern with √2×√2 periodicity. They also revealed via scanning tunneling spectroscopy that the surface is insulating. In order to identify its atomic structure and mechanism of its insulating nature, we have carried out first-principle simulations with the LCMO slab models.

We use the Vienna ab-initio simulation package (VASP). The strong Coulomb interaction among 3d electrons in Mn ions is taken into acount by local spin density approximation (LSDA) + U method. We adopted 28 doping models of the La0.75Ca0.25MnO3 four-layered slab and analyzed atomic and electronic strucutres of 3 typical models (see Fig. 2). Since the samples are made on SrTiO3(100) substrate in the experiments, we fixed the lattice constants and atomic positions of undermost layer to those determined by experiments. STM images were simulated using the local density of states (LDOS) at 1.5eV below the Fermi level and at 2 Å from the surface.

Simulated STM image for the most stable model (See Fig. 3) shows the same zigzag tendency as the experimental ones. This trend can be understood by the reconstruction of the coordinated O atoms around Mn. Some of the unstable doping models do not show the zigzag tendency because of large surface distortion due to the Ca dopant near the surface.

The stable doping model also reproduces the insulating nature of surface. On the other hand, layer projected density of states show no band gap for the inner layers of the slabs. Structural analysis together with the charge analysis suggests that this difference is led by the surface reconstruction around the Mn atoms.

Figure 1
The Aprotic Lithium-Air Battery: New Insights into Materials and Reactions
Authors: Mahne Nika , Müller Tobias , Breuer Stefan , Chen Yuhui , Johnson Lee , Fontaine Olivier , Bruce Peter G , Freunberger Stefan A
Published: February 2020

In the long term high-volume applications such as electric vehicles and the storage of electricity from renewables require a step change in energy density, material sustainability and cost that stepwise improvement of current Li-ion technology based on intercalation electrodes cannot hope to deliver. Radical new approaches are required, motivating ambitious and potentially game-changing research ‘beyond intercalation chemistries’. One such alternative is the Li-air(O2) battery; its theoretical specific energy exceeds that of Li-ion, but many hurdles face its realization.[1-3] First, the processes that occur in the cell on discharge and charge need to be understood to use such knowledge to address the hurdles.

The discharge reaction in the cathode of the nonaqueous Li-O2 cell involves reduction of O2 and the formation of solid Li2O2; the process is reversed on charge, O2 + 2 Li+ + 2 e– « Li2O2. It is now understood that parasitic reactions are a major cause for overpotentials on discharge and charge and limited cycle life. These are both caused by decomposition of many electrolytes and the cathode. Poor electron transport in Li2O2 is recognized as a major factor limiting its achievable amount during discharge (that is, achievable capacity) and the rate and overpotentials at which it can be formed and decomposed during cycling[4-6]. A further major challenge is extended cyclability at desirable deep discharge. We will discuss recent insights into the mechanism of Li2O2 formation and decomposition, of parasitic reactions and novel electrode and electrolyte materials.

[1]                 P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nature Mater.
11 (2012) 19.

[2]                 J. Christensen, P. Albertus, R.S. Sanchez-Carrera et al., J. Electrochem. Soc.
159 (2012) R1.

[3]                 Y.-C. Lu, B.M. Gallant, D.G. Kwabi et al., Energy Environ. Sci.
6 (2013) 750.

[4]                 Y. Chen, S.A. Freunberger, Z. Peng, O. Fontaine, P.G. Bruce, Nature Chem.
5 (2013) 489.

[5]                 A. Dunst, V. Epp, I. Hanzu, S.A. Freunberger, M. Wilkening, Energy Environ. Sci.
7 (2014) 2739.

[6]                 L. Johnson, C. Li, Z. Liu et al., Nature Chem.
6 (2014) 1091
A Spectroelectrochemical Study of Oxygen Electrode Reactions in Dimethyl Sulfoxide Electrolyte for Aprotic Li-O2 Batteries
Authors: Peng Zhangquan , Zhang Xinmin , Zhang Yelong , Bruce Peter G
Published: February 2020

Due to their high theoretical energy density, Li-O2 systems based on aprotic electrolytes have attracted a great deal of interest in the past few years.1-3 Operation of an aprotic Li-O2 battery critically relies on the reversible and efficient oxygen electrode reactions occuring in the positive electrode.4,5 Therefore, it is important to understand the oxygen reaction mechanisms at the positive electrode/Li+ electrolyte interface. Here, we report a mechanistic study of a model system, i.e., oxygen reactions on an Au electrode in a Li+dimethyl sulfoxide (DMSO) electrolyte with a range of complementary techniques. By spectroscopically identifying the reaction products and intermediates, coupled with electrochemical measurements under well-defined conditions, oxygen reaction pathways and the rate limiting steps were depicted.

References

[1] Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nat. Mater.
2012, 11,  19-29.

[2] Lu, J.; Li, L.; Park, J.-B.; Sun, Y. -K.; Wu, F.; Amine, K. Chem. Rev.
2014, 114, 5611-5640.

[3] Luntz, A. C.; McCloskey, B. D. Chem. Rev.
2014, 114, 11721–11750.

[4] Peng, Z.Q.; Freunberger, S. A.; Chen, Y.; Bruce, P. G. Science
2012, 337, 563-566.

[5] Peng, Z.Q.; Zhang, X.M.; Zhang, Y.L.; Bruce, P.G.  manscirpt in preparation.
Revealing Conduction Mechanisms in Lithium-Rich Garnets Using Aliovalent Dopants
Authors: Brugge Rowena Helen , Aguadero Ainara , Kilner John A.
Published: February 2020

Lithium stuffed garnets such as Li7La3Zr2O12  (LLZO) show promise as solid state lithium ion conductors for use in high energy density storage applications due to their chemical and thermal stability and electrochemical performance versus current technology electrolytes. Much work has focused on improving the conductivity of these systems by optimizing the lithium content in the cubic garnet phase rather than the less conducting tetragonal polymorph1.

Despite extensive studies on these materials, there is uncertainty as to the preferred migration of Li; whether the ions move from one octahedral (Oh) site to another via a neighbouring tetrahedron (Oh-Td-Oh path), or hop directly across Oh sites, bypassing the Td site (Oh-Oh path), is still up for debate2,3.

We seek to confirm the lattice site occupancy of the mobile lithium ions and their associated conduction pathways by varying the lithium-substituted dopant species (Ga, Zn, Ge), thereby blocking Li movement through one of the two paths. The effect of dopant charge and ionic radius on cubic phase stabilization (as a result of Li concentration) and lattice strain is studied.

Moreover, the moisture sensitivity of Li-conductor ceramics has been recently associated with a deterioration of Li transport4 and density of the material, of great importance in battery applications5. In this study, we use an argon-supplied glove box coupled to a furnace for processing and synthesis, preventing proton exchange with Li, thus avoiding the creation of proton charge carriers and improving the densification to above 90% relative density. This is fundamental to analyze the real Li-conduction mechanism and optimize the Li conductivity in garnets. To study the degradation process of lithium displacement by protons in moisture, and the effect of the protons on the ionic conductivity, we conduct isotopic exchange experiments on the samples using H2O and D2O followed by secondary ion mass spectroscopy. The total conductivity of the samples is found by AC impedance in a range of humidities and temperatures. X-ray diffraction and neutron diffraction are employed to determine the structural features, specifically to localize the dopants, Li and protons and to analyse the conduction pathways as a function of the dopant.

References

1J. Awaka et al.(2009)  J. Solid State Chem. 182, 2046-2052

2 Han, J. et al. (2012) Chem. Commun., 48 (79), 9840–9842

3 Xu, M. et al. (2012) Phys .Rev. B, 85, 052301

4Aguesse, F. et al. (2014) Adv. Mater. Interfaces, 1 (7), 1300143

5 Bernuy-Lopez, C. et al. (2014) Chem. Mater., 26 (12), 3610-3617

Figure 1
Non-Aqueous Ionic Liquid Energy Storage Systems
Authors: Sutto Thomas Edward
Published: February 2020

Our research has focused on the use of ionic liquids based on acetate, trifluoroacetate, hydrogen sulfate and oxalate as new types of electrolytes for non-aqueous energy storage systems.  Electrodes studied have included MnO2, Ag2O, as well as Zn and Sn.  Additionally, work has begun on studying the interactions of VOx electrolytes for a rechargeable V-O battery.  Results will show progress towads making not only simple primary batteries, but also re chargeable systems as well.

Figure 1
New Oxide Catalyst Support Generation for PEFC - Application in Meas, Performance and Stability Issues
Authors: Patru Alexandra , Fabbri Emiliana , Kötz Ruediger , Schmidt Thomas J.
Published: February 2020

The stability of fuel cell performance still remains a significant challenge for polymer electrolyte fuel cell (PEFC) technology. The well-known carbon corrosion degradation process [1] leads to an intense research for an alternative catalyst support materials. One of the actual trends in this field is focused on conductive metal oxide development, as they can exhibit a high electrochemical stability when used in their highest oxidation states, and can be tailored with a high specific surface compatible with the targeted PEFC application.

Up to date, the literature reports stability studies for new oxide catalyst supports but the degradation protocols are realised at the laboratory level (typically room temperature, high potential range, non-optimised catalytic layer) [2].  Only few data are available regarding the processing of these new alternative supports for Pt in a PEFC and their stability under real working conditions of the derived MEAs.

For this purpose Pt/IrTiO2 and Pt/Sb-doped SnO2 (SbSnO2) catalysts were studied. Pt/IrTiO2 provided by Umicore® was used as a model catalyst, whereas Pt/SbSnO2 catalyst was synthesized in our laboratories. For this purpose, a SbSnO2 powder was first synthesized by a modified sol-gel method. Platinum nanoparticles obtained by the polyol method [4] were further deposited on this oxide support. Different cathodes were prepared by direct spraying of optimised suspensions of Pt/IrTiO2 and Pt/SbSnO2 catalyst nanoparticles on a Nafion® XL-100 membrane.

The fuel cell performances and stabilities of the various membrane-electrode assemblies are examined in details. The results are compared with the MEAs based on the state of the art Pt/C (46%wt on High surface area carbon, Tanaka) catalyst and prepared by the same spraying procedure.

Acknowledgement

The authors thank Umicore AG & Co KG and the Competence Center for Energy and Mobility (CCEM) Switzerland for their financial support within the project DuraCat.

References

[1] F.N. Buchi, M. Inaba, T.J. Schmidt, editors. Polymer Electrolyte Fuel Cell Durability, Springer(2009).

[2] Y. Takabatake, Z. Noda, S.M. Hayashi, K. Sasaki, International Journal of Hydrogen Energy 39,   5074-5082 (2014).

[3] E. Fabbri, A. Rabis, R. Kötz, T. J. Schmidt, Physical Chemistry Chemical Physics 16, 13672-13681 (2014).

[4] E. Fabbri, A. Patru, A. Rabis, R. Kötz, T. J. Schmidt, Chimia 68, 217–220 (2014).
Thin, Robust, Stable, High Performance Anion Exchnage Membranes for Elecrochemical Energy Conversion Applications
Authors: Herring Andrew M , Maes Ashley M , Sarode Himanshu N , Liu Ye , Pandey Tara P , Caire Benjamin R , Liberatore Matthew W , Coughlin E. Bryan , Di Noto Vito
Published: February 2020

The potential of anion exchange membrane (AEM) fuel cells to provide inexpensive compact power from a wider variety of fuels than is possible with a proton exchange membrane (PEM) fuel cell, has continued to drive the research interest in this area.  Alkaline catalysis in fuel cells has been demonstrated with non-precious metal catalysts, and with a variety of fuels beyond H2 and methanol. Alkaline fuel cells (AFCs), based on aqueous solutions of KOH, have serious drawbacks associated with system complexity and carbonate formation. Anion exchange membrane (AEMs) fuel cells have a number of advantages over both PEM fuel cells and traditional AFCs; however, although anionic conductivity in AEMs can be comparable to PEMs the chemical stability of membrane attached cations in hydroxide is still not always sufficient for practical applications.  The real issue is water transport; water is both a product and a reactant in these systems and wet cations are much more stable than dry.  Wetted cations are alos much more stable than dry cations.  So an understanding of water in these membranes is essential.

Here we discuss water and anion transport in a series of thin mechanically robust state of the rt experimental anion exchange membranes.  The membranes are generally constructed from an isoprene block and a vinyl benzyl bromide block,  either randomly or in di-, tri- or penta- block configurations.  Post quaterniaztion leads to functionalized AEMs.  We use electrochemical impedance spectroscopy to measure anion conductivity, multi-nuclear pulse field gradient spin echo NMR to measure self-diffusion, and broadband electric spectroscopy to measure the relaxation processes in these polymers.  This information is coupled with microscopy and SAXS to explore the polymer morphology.  Putting transport and morphology together allows us to describe a complete picture of water and anion transport in these systems.

We have begun to build direct fueled AEM fuel cells and electrolyzers for hydrogen and ammonia production from these membranes and their related ionomers.  We will alos show a few examples of the AEMs practical uses in single cell devices in this talk.
Spinel MnO2 As a Rapidly Oxidizing Cathode Material for Fuel Cell/Battery Systems
Authors: Musil Mike , Choi Bokkyu , Panthi Dhruba , Tsutsumi Atsushi
Published: February 2020

The fuel cell/battery (FCB) system combines the working principle of an alkaline battery with an alkaline fuel cell. As anode material, a metal hydride is chosen, which is also found in nickel-metal hydride batteries. This mischmetal can be charged both electrochemically and under hydrogen atmosphere. As a cathode material, manganese dioxide (MnO2) is utilized. We have shown previously that MnO2can, under the right conditions, be cycled electrochemically and recharged from its discharged form (MnOOH) via oxidation in an oxygen saturated alkaline solution.

MnO2 can have different crystalloid structures, depending on the allocation of the MnO6 octahedra. In previous work, we have mostly focused on electrolytic manganese dioxide (EMD), also called γ-MnO2, in which the MnO6 octahedra are aligned to create a combination of 2x1 and 1x1 tunnel structures. In this work, however, we investigated the possibility of utilizing spinel MnO2, also known as λ-MnO2, as an alternative

To obtain λ-MnO2, we first synthesized LiMn2O4 via a solid state reaction of EMD with LiOH. The result was a spinel structure with Li+ ions occupying the tetrahedral sites. The lithium ions can then be removed chemically in a diluted acid, thereby leaving the solid in a spinel structure. We then analyzed the performance of λ-MnO2 for the application in FCB and compared it with γ-MnO2. For this, we manufactured half-cells, cycled the samples electrochemically and recharged MnOOH in an oxygen-saturated alkaline solution in an autoclave.

The cathodes were manufactured through a pasting method with a slurry consisting of  MnO2, carbon black (CB) and ethylene-vinyl acetate (EVA) in a weight ratio of 100:15:10 dissolved in xylene. Half-cells were assembled with nickel foam and Hg/HgO as counter and reference electrode, respectively, polypropylene as separator and a 6M KOH solution as electrolyte.

Compared with γ-MnO2, λ-MnO2 shows a similar capacity during the first discharge, but loses a high capacity between the first and second discharge. Afterwards, capacity loss is considerably lower and at around the same rate as for γ-MnO2. However, in terms of rechargeability with oxygen, λ-MnO2 shows superior results. In an oxygen-saturated 6M KOH solution under 1MPa pressure, after 1 hour, the fully discharged λ-MnO2 recharged to 15% of its maximum theoretical capacity, compared to 10% of γ-MnO2.

These are very promising results on our target of combining the advantages of fuel cells with batteries. Further research is thus being conducted, mainly focusing on improving rechargeability of λ-MnO2.
Water-Splitting for Solar Fuel Devices
Authors: Haro Marta , Guerrero Antonio , Gimenez Sixto , Bisquert Juan
Published: February 2020

Social environmental concerns about global warming and CO2 emissions provide the stimulus to find the way to replace fossil fuels by solar fuels. In this context, sustainable energetic schemes should be based on the conversion of abundant energy-poor molecules (such as H2O) into energy-rich molecules (as for example H2) using sunlight as the energy source. This solar fuel can be easily stored, transported and used upon demand in fuel cells, where the reverse reaction takes place to convert chemical energy into electricity. This is one of the key challenges of the twenty-first century and multidisciplinary work is needed to succeed in transforming the theory into practice.To achieve a practical technology, low-cost materials and earth-abundant catalysts are required to be used for both reactions (water splitting and H2 oxidation into water). In the present talk, we report the production of solar fuels with low-cost materials based on organic chemistry (3). The synthetic versatility of these materials and understanding of the energetic aspects provides the design rules to extract the generated photocurrent in the organic blend to the electrolyte solution in the scale of mA·cm-2. For technological application, the rational design of the harvesting light material (the organic blend), the interfacial selective layers (hole and electron selective layers) and the catalyst are equally important. Herein, the study of the electron selective layer and catalyst (noble-metal free) are researched towards optimising both H2 production rate and stability in these devices.

References:

[1] H. B. Gray, Nature Chem. 1, 7 (2009)

[2] S. W. Cha, W. Colella, F. B. Prinz, Fuel cell fundamentals New York: John Wiley & Sons (2006)

[3] A. Guerrero, M. Haro, S. Bellani, M. R. Antognazza, L. Meda, S. Gimenez, J. Bisquert, Energ. Environ. Sci. 7, 3666 (2014)
Beyond Li-Ion: Utilization of the High Energy Density of Silver-Zinc in Secondary Button and Coin Cell Miniature Battery Sizes
Authors: Ortega Jeffrey Vincent , Dueber Ross Eugene
Published: February 2020

The performance data for rechargeable silver-zinc (AgZn) button cells are compared with the published performance data for commercially available rechargeable Li-ion and Li-polymer cells.  The results show that silver-zinc cells offer greater capacity and energy densities over the equivalently sized rechargeable Li-ion and Li-polymer batteries.   Additionally, for the two smallest sized silver-zinc batteries, there are no equivalently sized Li-ion solutions currently available.  In comparison with the smallest Li-ion available, the silver-zinc cell has a 57% greater energy density, while the largest silver-zinc cell is shown to be greater by 20% over the best performing Li-ion option available.  How the subcomponents and the construction of the AgZn cell affect this enhanced performance will be discussed.
X-ray tomographic investigation of water distribution in polymer electrolyte membrane fuel cells with different gas diffusion media
Authors: Alrwashdeh Saad Sabe' , Markötter Henning , Haußmann Jan , Scholta Joachim , Hilger André , Manke Ingo
Published: February 2020

Water transport in polymer electrolyte membrane fuel cells (PEMFCs) is investigated by synchrotron X-ray imaging as a non-destructive testing method. Two different measurement techniques, namely in-situ radiography and quasi-in-situ tomography were combined to reveal the relationship between the structure of the microporous layer (MPL) and the water flow at different operation temperatures. It is shown how water distribution and transport are quantified and visualized. With this method, investigations of different cell materials at different operating parameters such as cell current, gas humidity, gas flow, etc. are conducted.