bluuebunny/crossref_metadata_2025 huggingface dataset:
Lithium-Rich Core-Shell Cathodes with Low Irreversible Capacity and Mitigated Voltage Fade
Authors: Li Jing , Camardese John , Shunmugasundaram Ramesh , Glazier Stephen , Lu Zhonghua , Dahn Jeff R
Published: February 2020

Lithium-rich layered Ni-Mn-Co oxide materials have been intensely studied in the last decade.  Mn-rich materials have serious voltage fade issues and the Ni-rich materials have poor thermal stability and readily oxidize the organic carbonate-based electrolyte.1  Core-shell (CS) strategies that use Ni-rich material as the core and Mn-rich materials as the shell can balance the pros and cons of these materials in a hybrid system.2  The lithium-rich CS materials synthesized through co-precipitation method introduced here showed much improved overall electrochemical performance compared to the core-only (Ni-rich) and shell-only (Mn-rich) samples.

In this work, CS samples with 67 mol% of core with the composition Li1+x(Ni0.67Mn0.33)1-xO2  (C) and  33 mol% of shell with the compositions Li1+x(Ni0.2Mn0.6Co0.2)1-xO2  (S1) or Li1+x(Ni0.4Mn0.5Co0.1)1-xO2  (S2) with varied lithium content were synthesized and  studied.

Figure 1 shows the energy dispersive spectroscopy results of the CS precursor and lithiated samples. Figure 1 shows that there was diffusion of transition metals between the core and shell phases after sintering at 900oC compared to the prepared hydroxide precursors.  A Mn-rich shell was still maintained whereas the Co which was only in the shell in the precursor was approximately homogeneous throughout the particles.

The CS samples with optimal lithium content showed low irreversible capacity (IRC), as well as high capacity and excellent capacity retention. Sample CS2-3 had a reversible capacity of ~218 mAh/g with 12.3% (~30 mAh/g) IRC and 98% capacity retention after 40 cycles to 4.6 V at 30oC at a rate of ~C/20. 

Figure 2 shows the average discharge potential (a) and the difference between the average charge and discharge potentials, delta V (b), of cells with the core-only (C), CS and shell-only (S) samples. Figure 2 shows that cells of the CS samples have stable impedance (delta V is stable) as well as a very stable average voltage as compared to cells of the core-only and shell-only samples. Ultra-high precision coulometry (UHPC) measurements confirmed that the CS samples with optimal lithium content had distinctively better columbic efficiency.

Apparently, the Mn-rich shell can effectively protect the Ni-rich core from reactions with the electrolyte while the Ni-rich core renders a high and stable average voltage.

Reference

1. E.-J. Lee, H.-J. Noh, C. S. Yoon, and Y.-K. Sun, J. Power Sources, 273, 663–669 (2015).

2. J. Camardese, J. Li, D. W. Abarbanel, a. T. B. Wright, and J. R. Dahn, J. Electrochem. Soc., 162, A269–A277 (2014).

Figure 1
Effects of K-Ion Doping on Electrochemical Performance of Na3V2(PO4)3 Cathode Materials for Na-Ion Batteries
Authors: Eom Ji-Yong
Published: February 2020

Lithium ion batteries have been widely studied due to their superior energy and power densities to utilize large scale applications such as electric vehicles and energy storage systems. In spite of extensive researches to overcome the problem of the lithium ion battery price, the large scale battery market has been sluggishly extended primarily due to the lack of lithium resources. Alternatively, sodium ion batteries are illuminated for the energy sources of the large scale energy storage system because of sufficient sodium sources.

As a class of the sodium ion battery cathode materials, phosphate-based Na-insertion hosts (NaVPO4F, NaMPO4, Na1.5VOPO4F0.5, Na2FePO4F, NaTi2(PO4)3, etc.) with strong polyanion networks have received great attention due to their excellent structural and thermal stabilities. NASICON-Na3V2(PO4)3 is the one of the promising cathode materials for the sodium ion batteries. Na3V2(PO4)3 shows 117.6 mAh·g-1 theoretical capacity at 3.4 V vs. Na/Na+ in V4+/V3+ redox couple. It has strong PO4 polyanion networks which improve the safety of the large scale applications. Unfortunately, Na3V2(PO4)3 shows severe capacity fading at high rate because of the low electrical conductivity and ion diffusivity. In the phosphate-based active materials for Li or Na ion batteries, the addition of conductive materials and the substitution of transition metal or alkali metal with alien ions have been conducted to overcome these problems. Especially the substitution of Li ion with Na ion or K ion for the Li ion batteries shows better electrochemical performances due to the lattice expansion and narrowing the band gap.

In this work, NASICON-Na3-xKxV2(PO4)3/C (x=0, 0.05, 0.10, and 0.15) are synthesized by a solid state reaction. By the doped K ion which is larger than Na ion (rK+ (1.52 Å) > rNa+ (1.16 Å)), the structure becomes enlarged and it makes Na ion migrate easily. Moreover the doped K ion in the structure even after charging contributes to the structural stability by reducing volume changes during cycling.
Conductivity Enhancement and Thin-Film Processing of Li4Ti5O12(LTO) Spinel for Li Battery Applications
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta
Published: February 2020

Lithium titanium oxide spinel Li4Ti5O12 has been reported to be a zero-strain lithium insertion host material because it exhibits extremely small variations of the lattice parameters during the charge and discharge processes. In general, Poor adhesion between thin-film electrode and substrates is the common cause for performance degradation of thin-film electrode during repeated charge/discharge tests. Thus, Li4Ti5O12 spinel may be the ideal candidate for the anode of thin-film Li ion battery for long cycle applications. 

However, unmodified Li4Ti5O12 usually exhibits poor rate performance, which mainly results from its low electronic conductivity (ca. 10-13 S·cm-1) and moderate Li+ diffusion coefficient (10-8cm2·s-1). 

In addition, different electrochemical behaviors will be expected when Li4Ti5O12 spinel is prepared in thin-film compared to that in power forms. Therefore, the objective of this work is (1) to enhance the conductivity of  Li4Ti5O12 spinel by substitution of aliovalent dopants for Ti ions, (2) to fabricate thin film of Li4Ti5O12spinel by using RF-sputtering technique, (2) to investigate the effect of annealing temperature/atmospheres on the electrical/electrochemical properties of thin film Li4Ti5O12, (3) to evaluate the feasibility of using thin film of Li4Ti5O12 as anode for Li microbattery applications.

In this study, the Li4Ti5O12 thin film was deposited on either the Si substrate or glass substrate by sputtering technique. The crystallization of deposited Li4Ti5O12 thin film will be enhanced by annealing at various atmospheres and temperatures. The single phase Li4Ti5O12 was finally obtained after co-sputtering of Li-containg and Ti-containing targets. The crystal structure and crystallization will be examined by glancing XRD. The resistivity of Li4Ti5O12 thin film will be evaluated by four probe technique and our novel micromeaurement system. The capacity of Li4Ti5O12 thin film will be evaluated from charge/discharge tests.
A Comparative Study of Layered Transition Metal Oxide Cathodes for Application in Sodium-Ion Battery
Authors: Hasa Ivana , Buchholz Daniel , Passerini Stefano , Hassoun Jusef
Published: February 2020

Nowadays, efficient, safe, low cost and environmentally friendly storage systems are required in response to the modern society needs. Li-ion batteries (LIBs), considered one of the promising systems to fulfill these requirements, represent the most widespread secondary battery for consumer and portable electronics and possibly for power hybrid and electric vehicles.[1]  Stationary energy storage, in contrast to high energy density applications, is principally driven by cost rather than high performances in terms of energy density. Therefore, batteries with alternative chemistry, complementary to and not competing with the lithium-ion battery technology are necessary.[2,3]

Recently, sodium-ion batteries have attracted large attention since, in principle, suitable to match the economic and environmental issues due to the high abundance and low cost of the employed materials.[4,5]Herein, we report a study on P-type layered sodium transition metal-based oxides, of the composition NaxMO2 (M=Ni, Fe, Mn), used as cathode materials for sodium-ion batteries employing a 1M NaPF6 in propylene carbonate (PC) as electrolyte solution.[6] Indeed, P-type layered oxides appear to be very promising in terms of high delivered capacity. [7,8] We synthesize the materials via co-precipitation method followed by an annealing step in air and a water rinsing process. Following, we fully investigate the effect of Ni to Fe ratio, annealing temperature and sodium content on the electrochemical performances of the electrodes. The impact of these parameters on the structural and electrochemical properties of the materials is revealed by X-ray diffraction, scanning electron microscopy and cyclic voltammetry, respectively. The suitability of this class of P-type materials for sodium battery application is finally demonstrated by cycling tests revealing an excellent electrochemical performance, with a delivered capacity of about 200 mA h g-1and charge-discharge efficiency approaching 100 %.

[1] J.-M. Tarascon, M. Armand, Nature,414, 359 (2001);

[2] J.-M. Tarascon, Nat. Chem., 2, 510 (2010) ;

[3] B. W. Jaskula , Lithium, in Mineral Commodity Summaries 2012 , U. S. Geological Survey , Reston, VA 2012 , p. 94;

[4] V. Palomares, P. Serras, I. Villaluenga, K.B. Hueso, J. Carretero-Gonzalez, T. Rojo, Energy Environ. Sci., 5, 5884 (2012);

[5] S.-W. Kim, D.-H. Seo, X. Ma, G. Ceder, K. Kang, Adv. Energy Mater., 2, 710 (2012);

[6] I. Hasa, D. Buchholz, S. Passerini, J. Hassoun, ACS Appl. Mater. Inte., (2015) in press;  

[7] I. Hasa, D. Buchholz, S. Passerini, B. Scrosati, J. Hassoun, Adv. Energy Mater. 2014, doi:10.1002/aenm.201400083;

[8] N. Yabuuchi, M. Kajiyama, J. Iwatate, H. Nishikawa, S. Hitomi, R. Okuyama, R. Usui,Y. Yamada, S. Komaba, Nature Mater., 11, 512 (2012);

Figure 1
Iron Doping Effects in NiMn2O4 Structures with Hierarchical Porosity: Stabilization of the Cubic Spinel Phase and Kinetics Activation for Li Storage
Authors: Ma Yue , Tai Cheuk-Wai
Published: February 2020

Spinel-type mixed oxides possess richer redox reactions for Li+ storage and at least two orders of magnitude higher electrical conductivity than binary metal oxides. This talk demonstrates the synthesis of  NiMn2O4 composite with three-dimensional macro/mesoporous network and various iron doping amount via a facile and scalable nanocasting method. Multi-scale pores were integrated in the structure through the structural engineering: interconnected macropores were reverse-replicated by employing the polymeric sacrificial template; whereas mesopores were formed upon the pyrolysis of the polymer during heat treatment. Through tailoring the metal precursor ratio, the tetragonal sites of divalent nickel could be preferentially substituted by iron, resulted in the stabilized cubic phase of quaternary oxide FexNi1-xMn2O4. Combining the elemental analysis from XPS and EELS techniques as well as crystal field theory, we concluded the stabilization mechanism of iron doping in our spinel structure system. Electrochemical characterizations exhibited the best of the composites prepared as such was capable to deliver high specific capacity, remarkable rate capability (2 A.g-1) and very good cycle life for Li+ storage (600 cycles).
The Role of Carbon on the Discharge Product and Cell Performance of the Sodium Superoxide (NaO2) Battery
Authors: Bender Conrad L. , Schwab Matthias Georg , Adelhelm Philipp , Janek Jürgen
Published: February 2020

Batteries based on the cell reaction between alkali metals and atmospheric oxygen are highly attractive energy stores due to their superior theoretical energy densities. However, despite continuous progress fundamental challenges in further developing these cell systems remain. Understanding the oxygen electrode reaction and improving cycle life while at the same time maximizing the practical energy capacity are some of the most important issues that have to be tackled. Here, we focus on the aprotic sodium-oxygen battery and the role of the carbon electrode on product formation and cell performance (cycle life and capacity)[1-2].

Two different discharge product have recently been reported in literature for the sodium-oxygen battery, one leading to either sodium peroxide or hydrated sodium peroxide and the other to sodium superoxide. [3-8] The thermodynamic driving force is quite similar for both cases and it remains unclear whether only kinetics or also nano-effects [9] determine the reaction route. One important aim of our current study therefore was to explain the discrepancy reported in literature. [1] We investigated whether the electrode material, the structure or the local current density have any influence on the product stoichiometry or the cell performance. Therefore, we tested several types of carbon materials with a broad range in properties. As important finding, we always found phase-pure NaO2 as discharge product irrespective of the type of carbon used. But at the same time, the achievable capacities range from 300 to values as high as 4000 mAh∙g(C)-
1. We further studied the impact of electrolyte composition on the cell chemistry and found significant differences depending on the type of solvent used. At last, we demonstrate that the cycle life of Na/O2 cells can be largely improved by using carbon nanotubes based electrodes yielding capacities of 231 mAh∙g(C)-
1 / 0.64 mAh∙cm-
2 for at least 140 cycles. [2]

Acknowledgment: The research was supported by the BASF scientific network of electrochemistry and batteries. C.L. Bender is grateful to Fonds der chemischen Industrie (FCI) for a scholarship.

Literature:

[1] C.L. Bender, Adv. Energy Mater., 2014, doi: 10.1002/aenm.201301863. [2] C.L. Bender, Energy Technol., 2015, doi: 10.1002/ente.201402208 [3] Q. Sun, Electrochem. Commun., 2012, 16, 22–25. [4] W. Liu, Chem. Commun., 2013, 49,1951-1953. [5] J. Kim, Phys. Chem. Chem. Phys., 2013, 15, 3623-3629. [6] Z. Jian, J. Power Sources, 2014, 251, 466-469. [7] P. Hartmann, Nat. Mater. 2013, 12, 228-232. [8] N. Zhao,  Phys. Chem. Chem. Phys., 2014, 16,15646-15652. [9] S. Kang, Nano Lett., 2014, 14, 1016- 1020.
The Electrolyte Transport in a Porous Electrode of Lib Using Lbm
Authors: Jeon Dong Hyup
Published: February 2020

LBM for multi-phase fluid mixture is applied to the problem of electrolyte transport phenomena in two-dimensional porous electrode structure of LIBs. LB model successfully simulates the complicated microscopic behaviors of liquid electrolyte in porous electrode providing the mechanism of liquid electrolyte transport in LIBs. It is shown that LBM approach is an effective tool to investigate electrolyte transport phenomena in porous electrode with wettability taken into consideration. The results indicate that the wettability in porous electrode is strongly influenced by two-phase (electrolyte and air) transport and thus removal of existing air can be a bottleneck for the enhancement of wettability. Improving the wettability can be attained by controlling the material properties such as porosity, particle size and contact angle to assist in an efficient distribution of liquid electrolyte.
Cathodes for Lithium Sulfur Batteries
Authors: Nitze Florian , Fossum Kjell , Andersson Simon , Xiong Shizhao , Palmqvist Anders , Matic Aleksandar
Published: February 2020

Lithium sulfur (Li-S) batteries are a promising candidate to replace state-of-the-art lithium-ion batteries with an expected 3-5 fold increased capacity. Even though they have been studied for decades the final breakthrough to make the system feasible for application for example in the transportation sector has not yet been achieved. However, many improvements have been made during the last years. One of many obstacles that needs to be overcome is the design of suitable cathodes, efficiently preventing capacity fading.

Here, different carbon nanostructures have been tested as sulfur containing matrices in Li-S batteries. Examples are sulfur-doped ordered mesoporous carbons (S-doped OMC) or helical carbon nanofibers (HCNFs). With both materials we achieve high sulfur utilization and good capacity retention. Sulfur-doping of the carbon matrix shows positive effects on cyclability and capacity per cathode mass. We find that the doping also influences the electrochemical behavior of the whole system and conclude that there exists a strong interaction between dopant and loaded sulfur utilized during charge and discharge of the battery. In the system using helical nanofibers we find that the performance of HCNFs is substantially better compared to straight fibers or nanotubes. We explain this with the specific properties of HCNFs making activation efficient without major deterioration of the overall structure. All materials have been extensively characterized using a variety of methods such as electron microscopy and electrochemical testing.
A Low Cost and High Capacity Synthesis of Lithium Iron Phosphate Using a Pulse Combustion Reactor System
Authors: Krizan Gregor , Dominko Robert , Gaberscek Miran
Published: February 2020

We have developed a reactor for continuous synthesis of various metal oxide materials in oxidizing or reducing atmosphere. The capacity of the current pilot reactor version is 2 L of precursor per hour. In the case of synthesis of lithium iron phosphate this corresponds to 100 grams per hour and the procedure is scalable to 100 kilograms per hour. The apparatus is comprised of a pulse combustion type burner, which operates at a frequency of 150 – 240 Hz and a temperature above 1000 °C, a two fluid nozzle for spraying the precursors, and a reactor pipe, where the reaction takes place. The oxidizing and reducing atmosphere is controlled by setting a fuel rich or fuel lean burning. When working with reducing atmosphere the spraying gas is nitrogen, otherwise air or oxygen can be used. The particles are cooled down with air to about 150 °C and collected with an electrostatic precipitator.

Here we demonstrate the functioning of the reactor on the example of lithium iron phosphate. The two precursors used consisted of iron nitrate and lithium carbonate, dissolved in nitric acid. The phosphorus source in one case was ammonium dihydrogen phosphate and triethyl phosphate in the other. As the fuel we used either urea combined with sucrose or glycine. All compounds were dissolved in deionized water. When the precursor is heated up, the water evaporates, and the remaining nitrates and organics react. This process is equivalent to solution combustion synthesis. However, changing the composition of the precursor strongly affects the morphology of the produced materials, which means that the reaction in the precursor is as important as the conditions in the reactor.

By spraying such precursors into the hot zone of the reactor, which is held at about 800 °C, the formed droplets are each its own microreactor. The water from the droplets evaporates very fast because of the high temperature and good heat transfer in pulse combustion burners; the temperature in the reactor drops to about 700 °C. This leads to a precipitation of precursor salts and hinders the coalescence of droplets. After the salts reach a high enough temperature, the reaction starts so that a lot of gaseous products are produced. In the case of urea precursor, porous spheres with a diameter of 3 – 15 μm are formed; in the case of glycine precursor agglomerates of particles from 50 to 300 nm are formed. The particles in both cases are carbon coated, either due to carbonization of sucrose or an excess of glycine fuel.

As synthesized lithium iron phosphate is partly amorphous, mainly because of the very short residence time at a temperature above 500 °C. Heat treatment in an Ar atmosphere at 700 °C for 3 hours yielded phase pure lithium iron phosphate. The as prepared and heat treated materials have been investigated using XRD, SEM, CHNS elemental analysis and ICP. The electrochemical behavior of as prepared and thermally treated materials has been investigated in a lithium half cell.
Flash Solution Oxidation in the Preparation of Cathode Materials for Mg and Li Ion Power Sources
Authors: Sutto Thomas Edward
Published: February 2020

Using a previously described approach towards preparing oxide nanoparticles via the use of potassium superoxide, we have explored the preparation of cathode materials such as LiCoO2, LiMn2O4 or Mg(M1,M2)O2.  From solutions of LiI, or Magnesium Acetate with various transition metals, it is possible to prepare a wide host of potential nanopoarticulate cathode materials in solution.  Initial preparation typically yields an amorphous blend of the material, but subsequent oxygen annealing at relatively low temperatures (100-200 oC) results in the formation of nanometer sized cathode materials, such as shown in the accompanying figure for 2.5 nM sized LiCoO2 prepared via this solution method.

Figure 1
Origin of High Areal Capacitances of Low Apparent Surface Area Carbons
Authors: Gao Xiuli , Wu Xiaozhong , Xing Wei
Published: February 2020

The energy storage mechanism of low apparent specific surface carbons derived from direct pyrolysis of biomass or N-rich polymers has puzzled the researchers in the supercapacitor field in recently years. In order to explore this scientific problem, such carbon materials were prepared through pyrolysis of seaweed and nitrogen-rich polymers such as melamine formaldehyde resin and polyaniline. The chemical and physical properties of these carbons were investigated intensively by nitrogen sorption analysis, CO2 sorption analysis, X-ray photoelectron spectroscopy and X-ray diffraction. Besides, the capacitive properties of these carbon materials were investigated by galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that all the carbons derived from direct pyrolysis of seaweed or polymers possess low apparent specific surface areas of no more than 60 m2 g-1, and their areal capacitance could reach up to an abnormally high value of 252 μF cm-2. Combining the results of systematical pore structure analyses and electrochemical measurements, it was found that these carbons contain numerous ultramicpores which could not be detected by the adsorbate of N2 but are accessible to CO2 and electrolyte ions. These ultramicropores play dominant roles in the charge storage process for these low apparent surface area carbons. We concluded that the energy storage mechanism of these carbons is mainly electric double layer capacitance and that the contribution of pseudocapacitance to the total capacitance is less than 15 %. This finding challenges the widely accepted viewpoint that the high capacitance of O-rich or N-doped carbon is mainly attributed to the pseudocapacitance generated from the faradic reactions between oxygen or nitrogen functionalities and electrolyte.
Lithium-Titanate Thin Films By Solid State Reaction As Electrode Material for Thin-Film Lithium-Ion Batteries
Authors: Labyedh Nouha , Put Brecht , Hardy An , Van Bael Marlies K , Vereecken Philippe M.
Published: February 2020

Lithium titanate (Li4Ti5O12) or LTO continues to attract great interest as anode for lithium ion because of its safety and the potential high power for the nanoparticle form. Its spinel structure allows a reversible three lithium ions intercalation at 1.55V vs Li+/Li which is well above the potential for the reduction of most electrolytes including solid electrolytes. The high voltage of lithium ion insertion/extraction in/from Li4Ti5O12 also prevents the formation of dendritic lithium which can happen due to overcharging for anodes which have low potentials close lithium deposition (0V vs Li+/Li). Such metallic lithium filaments  can cause a short circuit between the battery anode and cathode with potential overheating and rupture. Moreover, LTO shows a negligible volume change during battery charging and discharging. Despite all these advantages, LTO has a poor electronic conductivity that leads to a limitation in the rate capability of this electrode.

In this talk we will report on a novel and low cost fabrication method of lithium titanate thin film electrodes for thin-film lithium ion batteries. The process is based on a solid state reaction occurring between TiO2 and Li2CO3 stacked-layers upon thermal annealing. The TiO2 layer was prepared by thermal oxidation of a sputtered Ti film and the Li2CO3 layer was deposited by spin-coating. LTO thin films were prepared on both Pt and TiN current collectors.

The phase and morphology of the prepared LTO films were investigated using a X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD patterns display intense characteristic diffraction LTO peaks and SEM micrographs show a close and continuous 70 nm thick LTO film.

Furthermore, the stoichiometry of the fabricated LTO films was evaluated by X-ray photoelectron spectroscopy (surface spectra and depth profile analyses) and elastic recoil detection (ERD) analyses. Films with composition the spinel Li4Ti5O12 composition were fabricated, proving that the thermal treatment causes elements intermixing leading to the formation of a Li4Ti5O12 material.

The electrochemical activity of the films was studied by cyclic voltammetry and galvanostatic charge/discharge experiments. The cyclic voltammogram reveals redox peaks around 1.55V (vs. Li+/Li) corresponding to the Li-ion insertion/extraction in/from the spinel Li4Ti5O12 upon reduction/oxidation of Ti4+/Ti3+. The lithiation and delithiation curves show extremely flat plateaus at 1.55 V (vs. Li+/Li) characteristic of Li4Ti5O12. A 100% of the LTO theoretical capacity was reached at 0.1 C.  A difference between the lithiation and delithiation capacities at the same C-rate was detected. This discrepancy will be explained by the difference in Li-ion diffusion kinetics during Li-ion insertion and extraction processes.
Efficient Synthesis of Hierarchical Porous Carbons for Application in Li-S Cells
Authors: Strubel Patrick , Thieme Sören , Althues Holger , Kaskel Stefan
Published: February 2020

The Li-S battery is a promising candidate to meet the demands on future generation mobile power supplies due to the high theoretical gravimetrical energy density and low price of sulfur. Unfortunately, the active material sulfur exhibits a very low conductivity, which limits the performance. A nanostructured carbon matrix is required. Up to date, large numbers of novel, elaborate host structures have been explored. However, in particular, suitable and effective production processes need to be established.

To overcome the existing drawbacks we focus on the development of a scalable and efficient approach for the synthesis of nanostructured porous carbon materials by using of inexpensive, commercially available ZnO nanoparticles as hard template.[1] One major benefit of the process is the in-situ removal of all pore building components through carbothermal reduction. Thus, no toxic/reactive gases are required and purification of the as-prepared porous carbon is not necessary. Adjusting the ZnO-NP template size, porous carbons with internal pore volumes as high as 3.9 cm3 g-1 and tailored pore sizes reaching from 20 nm to 200 nm with ideal template replication are obtained. The carbothermal reduction process, furthermore, facilitates the access of a hierarchical pore system with distinctive microporosity leading to very high specific surface areas even exceeding 3000 m-2 g-1. The synergetic advantage of that bimodal porosity renders them particularly suitable for the application in high energy density lithium-sulfur batteries. A high capacity of > 1200 mAh g-1-sulfur (> 750 mAh g-1-electrode) at a high sulfur loading of ≥ 3 mg cm-2 and good cycle stability was achieved even using a low amount of electrolyte. This allows for further weight reductions and maintenance of high energy density on cell level.

[1] Strubel et al., Adv. Funct. Mater. 2015, 25, 287–297. doi: 10.1002/adfm.201402768.
Solid-State Lithium Polymer Secondary Batteries
Authors: Hogan Matteo , Wilson James , Holder Simon , Browning Darren , Alfredsson Maria
Published: February 2020

Energy storage plays a vital role in everyday life. As the worlds need for energy has increased so has the demand for better performing batteries, batteries that can defy conventional constraints and batteries that have improved safety. Currently Lithium ion batteries dominates this sector due to their high specific energy and high specific power.

However they are currently not without faults, improving on their design and construction would be greatly beneficial in certain industries. For example, non-metallic batteries could be useful when a reduction in interference with an antennae signal is desired, another possibility is to create a polymer which is both ionic and electrically conducting as this allows the removal of current collectors from a conventional design again reducing interference and also the number of interfaces in the battery construction. In addition to this, polymer electrolytes could offer a viable design solution for when irregularly shaped batteries are necessary and this would also remove the issue of combustible electrolytes. The objectives are to synthesise mixed conducting polymers and electrochemically test them, then assemble a solid-state Lithium polymer battery. Results based on these systems will be presented are the battery cycles giving both individual polymer performance and again with the full solid state assembly.
Thermal Runaway of a Commercial 18650 Li-Ion Battery with a NCA Cathode - Impact of SOC and Overcharge
Authors: Golubkov Andrey , Scheikl Sebastian , Planteu Rene , Voitic Gernot , Thaler Alexander , Hacker Viktor
Published: February 2020

Li-ion batteries excel in energy density and cycle life. Unfortunately those benefits come with a price: When Li-ion batteries are mistreated with high over-temperature or strong overcharge, they can transit into a so-called thermal runaway(TR). During the TR, exothermic reactions increase the temperature. In turn, the increased temperature accelerates those reactions and the system destabilizes. At the end of the TR, battery temperatures higher than 900°C can be reached and high amounts of burnable and harmful gases are released.

We examined the TR characteristics of a commercially available 18650 cell made by a well known manufacturer. This cell is based on Lix(Ni0.80Co0.15Al0.05)O2cathode and has energy density of 254Wh/kg. Destructive temperature-ramp experiments with discharged, partially charged as well as fully charged and over-charged cells were done. Additionally, we dismantled one cell to make a mass split and to identify the compositions of the cell components.

In the presentation correlations between SOC and the TR parameters (onset temperature, max. temperature, amount of produced vent-gas, vent-gas composition) will be shown. An attempt will be made to rationalise the amount and composition of the vent-gas with a simplified chemical reaction system.

We hope that the results of this work can aid the industry to enhance the safety of battery driven devices and to find appropriate mitigation measures for some of the battery abuse scenarios.

Figure 1
Graphite As Anode Material for Sodium-Ion Batteries: Making an Inactive Electrode Active to Compete with Li-Ion Batteries
Authors: Jache Birte , Adelhelm Philipp
Published: February 2020

Being the standard anode material in lithium-ion batteries (LIBs), graphite is considered to fail application in sodium-ion batteries (NIBs) because no suitable binary intercalation compounds (b-GICs) exist. In this study, we demonstrate that this limitation can be successfully circumvented by using co-intercalation phenomena in a diglyme-based electrolyte. Results have been published in Angewandte Chemie International Edition: B. Jache, P. Adelhelm, Angew. Chemie
2014, 53, 10169–10173. The resulting compound is a stage-I ternary intercalation compound
(t-GICs) with an estimated stoichiometry of Na(diglyme)2C20.

Beneficial properties of the electrode reaction are its low overpotentials and stable capacities of around 100 mAh/g for more than 1000 cycles. The initial irreversible capacity of around 10 % is, to the best of our knowledge, the smallest one reported so far for NIB negative electrodes. The overall coulomb efficiency exceeds > 99.87 %. The intercalation process proceeds over several intermediated stages and occurs in narrow potential window below 1 V vs. Na/Na+. A one-to-one comparison with the analogue lithium system shows the more suitable performance of the sodium based system. X-ray diffraction was used to study the electrode reaction during different stages of sodiation/lithiation. The reversible formation of ternary GICs is unequivocally proven by the shift in the (002) diffraction line and the appearance of additional reflexes.

The peculiar properties of ternary GICs combined with the advantage of using relatively low cost substances might make this electrode reaction attractive for stationary applications. As t-GICs are also formed with other solvents, our approach provides an alternative route to search for new electrode reactions for NIBs.

Figure 1
Investigating the Effects of Transport and Mixing on Dendrite Growth in High Energy Density Lithium Batteries
Authors: Tan Jinwang , Tartakovsky Alexandre , Ryan Emily M
Published: February 2020

High Energy density lithium (Li) batteries are promising advanced energy technologies for applications in the automotive and portable power markets. Advanced Li batteries have several design and operational challenges to overcome before becoming commercially viable. One of these challenges is the formation of dendrites on the anode surface of the Li-air battery over multiple charge and discharge cycles. Dendrite formation decreases cell performance and causes safety concerns due to short circuiting. In this research computational methods are adopted to investigate the physics of dendrite formation in Li-air batteries and to develop strategies to suppress dendrite growth.

The effects of convection and anisotropic transport properties in the electrolyte on the morphology and growth rate of dendrites are investigated using a two-dimensional (2D) smoothed particle hydrodynamics (SPH) model. SPH is a mesh-free Lagrangian computational fluid dynamics method, which allows for easy implementation of complex physics at the dendrite surface.

Anisotropic diffusion is modeled to study the effects of mixing near the anode-electrolyte interface on dendrite growth. The simulation results suggest that high anisotropy in the electrolyte promotes a robust, compact dendrite structure versus isotropic diffusion cases. Convection effects are also considered to study the electro-osmosis effect on dendrite growth. Circulating flows are included in the model to simulate electro-osmotic flows near the anode-electrolyte interface. The simulation results reveal that the convection effect will increase the mixing near the dendrite and lead to significant changes in dendrite morphology.

The results of these computational studies are being used to develop mitigation strategies for dendrite growth in Li-air batteries. These strategies include the use of novel electrolyte solutions and hybrid electrolyte designs, which allow for the tuning of transport properties through the electrolyte. The computational models are being used to investigate these designs and optimize material properties to increase battery performance and lifetime.

Figure 1
Finding Stable Solid Electrolyte-Cathode Interfaces for Li7La3Zr2O12 Garnet - a DFT Study
Authors: Miara Lincoln J. , Richards William Davidson , Wang Yan , Ceder Gerbrand
Published: February 2020

Lithium garnets with the general formula Li7La3Zr2O12 (LLZO) have many properties of an ideal electrolyte in all-solid state lithium batteries. However, internal resistance in batteries utilizing these electrolytes remains high. For widespread adoption, performance must be improved by improving bulk conductivity, reducing grain boundary resistance, and/or pairing LLZO with an appropriate cathode to minimize interfacial resistance. 

Despite high bulk conductivity, any electrolyte is impractical if a large interfacial resistance is present, arising either from decomposition products formed between cathode and electrolyte at high sintering temperatures or from electrochemical decomposition at the interface during cycling. The origin of the observed interfacial resistance in all solid state batteries is currently a matter of some debate. There are usually two explanations given in the literatures: the buildup of a space-charge layer at the interface, and interfacial phase-decomposition1–5

In this work we use first principles calculations to identify the thermodynamic driving forces for reactions between the electrolyte and electrode across the lithium chemical potential range experienced during operation. We examine LLZO and the similar material Li5La3Ta2O12(LLTO) against common cathodes.  We perform a careful thermodynamic assessment of the interface equilibrium using a grand canonical ensemble. We also provide valuable information when choosing a system for all-solid-state battery construction using LLZO or LLTO as an electrolyte.

References

(1)       Takada, K.; Ohta, N.; Zhang, L.; Xu, X.; Hang, B. T.; Ohnishi, T.; Osada, M.; Sasaki, T. Solid State Ionics
2012, 225, 594–597.

(2)       Maier, J. Nat. Mater.
2005, 4, 805–815.

(3)       Takada, K.; Ohta, N.; Zhang, L.; Fukuda, K.; Sakaguchi, I.; Ma, R.; Osada, M.; Sasaki, T. Solid State Ionics
2008, 179, 1333–1337.

(4)       Takada, K. Langmuir
2013, 29, 7538–7541.

(5)       Haruyama, J.; Sodeyama, K.; Han, L.; Takada, K.; Tateyama, Y. Chem. Mater.
2014, 26, 4248–4255.
Theory and Modeling of Platinum Surface Reactions
Authors: Baroody Heather , Rinaldo Steven , Eikerling Michael
Published: February 2020

The formation and reduction of surface oxide species determine both the electrocatalytic activity of Pt towards the oxygen reduction reaction as well as the rate of corrosive Pt dissolution [1]. We perform theory and modeling work to rationalize the various stages of oxide formation and reduction at Pt. Our mechanistic models establish relations between metal phase potential and surface oxidation state that govern the transient current response of the electrode, as probed for instance in cyclic voltammetry. In the first part, we will discuss a recently developed kinetic model for oxide formation and reduction at Pt in the voltage range of 0.65–1.15 V [2]. The model is evaluated against electrochemical [3], spectroscopic [4] and computational studies [5]. In the second part, we will present a kinetic model of oxide growth on platinum in the high voltage regime, above 1.15 V. The governing equations of the oxide growth model account for mass and charge conservation, species migration, and electric field effects. As the outcome, we will obtain a generalized oxide growth law of platinum. The results will be compared to experimental cyclic voltammetry data to extract rates of kinetic and transport processes. Moreover, the model incorporates a mechanism of platinum dissolution. Using this model, we strive to explain the dramatically enhanced rate of Pt dissolution at extended surfaces and in nanoparticle systems, observed in experimental studies that involved voltage cycling through the high voltage regime [6,7,8]. Knowledge of the mechanisms of growth and reduction of oxides on platinum will allow us to refine our theory of platinum dissolution in polymer electrolyte fuel cells [9].

References

[1] A. Seyeux, V. Maurice, and P. Marcus, J. Electrochem. Soc.
160, C189 (2013).  

[2] S. G. Rinaldo, W. Lee, J. Stumper, and M. Eikerling, Electrocatalysis
5, 262 (2014).

[3] A.M. Gómez-Marín, J. Clavilier, J.M. Feliu, J. Electroanal. Chem.
688, 360 (2013)

[4] M. Wakisaka, H. Suzuki, S. Mitsui, H. Uchida, M. Watanabe, Langmuir
25, 1897 (2009)

[5] L. Wang, A. Roudgar, M. Eikerling, J. Phys. Chem.
C
113, 17989 (2009)

[6] S. G. Rinaldo, P. Urchaga, J. Hu, W. Lee, J. Stumper, C. Rice, and M. Eikerling, Phys. Chem. Chem. Phys., submitted.

[7] A. A. Topalov, S. Cherevko, A. R. Zeradjanin, J. C. Meier, I. Katsounaros, and K. J. J. Mayrhofer, Chemical Science
5, 631 (2014).

[8] L. Xing, M. A. Hossain, M. Tian, D. Beauchemin, K. T. Adjemian, and G. Jerkiewicz, Electrocatalysis
5, 96 (2014).

[9] S. G. Rinaldo, W. Lee, J. Stumper, and M. Eikerling, Physical Review E
86, 041601 (2012).
Quinone Redox Flow Battery Electrode Testing
Authors: Brezovec Paul , Kennedy Timothy , Markiewicz Daniel , McCluskey Michel
Published: February 2020

The efficiency and cost of a redox flow battery (RFB) can be significantly affected by the electrode selected for scale-up.  Carbon felt has traditionally been used as the electrode in flow batteries, but flow battery design requires it to be highly compressed thereby requiring high pumping power and causing battery leakage problems.  Additionally, by compressing the felt, the electrolyte must be pumped through the felt at enough pressure to ensure uniform flow through the felt. Carbon felt has a high specific surface area and good electrical conductivity. Any replacement must meet the needs of the flow battery system in terms of specific surface area and electrical conductivity. Prototype alternatives to the homogeneous carbon felt were screening tested, indicating that configurations of foam and felt composite were useful to lower pressure drop through the cell while providing the necessary electrical continuity for RFB operation.

Quinone electrolytes were employed in each half-cell to test the charge/discharge performance of the RFB. A design of experiment methodology was used for a composite electrode, while varying current and electrolyte flow. Interesting delayed double-electron transfer effects were noted from the redox of the quinone electrolytes. Testing has shown that the composite electrode has advantages over the felt. The testing confirmed that the composite electrode has the potential of increasing the efficiency of the flow battery. Testing results to date will be reported indicating the redox of the quinone electrolytes when the composite electrode configuration is changed.
Performance Characteristics of the Zn-Ce Hybrid Redox Flow Battery
Authors: Berlouis Leonard , Nikiforidis Georgios
Published: February 2020

Redox flow batteries (RFB) offer a potential solution to the implementation of medium to large scale energy storage (10 kWh - 10 MWh) since they have the advantage of cost, flexibility, rapid response and safety over other alternatives such as the lithium ion and sodium-sulfur batteries. The zinc-cerium hybrid RFB is one of the most promising RFB systems due to its high open circuit cell voltage (Ecell
= 2.4 V) and moderately high energy density (20 – 35 kWh dm-3). The investigations here examined the impact of operating parameters such as charging/discharge current density, electrolyte composition, flow velocity, temperature and the use of different carbon composite electrodes on the performance of the Zn-Ce RFB.  The chemical stability of the positive electrode material in the strongly oxidising Ce(III)/Ce(IV) is an issue here and although certain treated carbon surfaces have shown some promise, long term electrode stability has only been achieved so far with Pt or Pt/Ir coatings on titanium. On the negative electrode side, the impact of charging current density (0.5 mA cm-2 to 100 mA cm-2) and temperature (25°C to 60°C) on the nature and morphology of the zinc deposit from concentrated (~2.5 M) Zn2+ solutions in methanesulfonic acid (MSA) were initially investigated using an electrochemical Hull cell. The measurements revealed that on a number of carbon composite electrodes (BMA5, PPG86 and BPP4) from the SGL Group, the best compact and adherent deposits were produced over a narrow current density range. Flow cell investigations were then carried out to evaluate the influence of these parameters on the cell performance.  The RFB used here comprised the carbon composite electrode (100 cm2) as the negative terminal in contact with the Zn2+/MSA solution. A Pt/Ti mesh served as the positive electrode in contact with an electrolyte containing 0.8 M total cerium content in 3.5 M MSA. A Nafion® 117 cation exchange membrane separated the two electrolytes in the flow cell. The reservoirs containing the two electrolytes were immersed in a water bath whose temperature was maintained constant through a Gallenkamp water circulator.  Consistently, high (>90%) coulombic efficiencies (ηC) were obtained from the charge-discharge cycles. High zinc concentrations yielded energy efficiencies of ~64% at currents of 1 A over the temperature range 45°C - 60°C. Under these conditions, the duration of the charging cycles, from 10 min to 2 hours, had little impact on the energy efficiency. Nevertheless, variations in ηC and in particularly, the voltage efficiency (ηV) were observed on charging at different current densities although flow velocity had little impact on these efficiencies.  Investigations are also currently under way to examine the kinetics of the cerium half-cell so that the cell capacity can be improved by using additives as well as mixed anion electrolytes.
Relating Anode Gaps to the Positioning of the Reference Electrode in PEM Fuel Cells
Authors: Berg Peter , Kulikovsky Andrei
Published: February 2020

We present analytical solutions for the potential and current density distributions in the vicinity of inactive (“dead”) regions inside a PEM fuel cell anode. For simplicity, the dead region is modeled as a step function for the anode exchange current density, representing membrane gaps or delamination. The solutions exhibit a large peak of the anode current density just outside the dead region. This overshoot can substantially exceed the average current density, thereby accelerating membrane degradation. In the limit of large gap sizes, we demonstrate how these findings relate to the positioning of a reference electrode which can independently measure the anode and cathode overpotential, respectively.   

[1] A. A. Kulikovsky and P. Berg, Analytical description of a dead spot in a PEM fuel cell anode, ECS Electrochem. Lett., 2, pp. F64-F67 (2013)

[2] P. Berg and A. A. Kulikovsky, A model for a crack or a delaminated region in a PEM fuel cell anode: Analytical solutions, Electrochim. Acta, submitted.