Introduction to the Focus Issue of Selected Presentations from the International Meeting on Lithium Batteries (IMLB 2014)

The Electrochemical Society 2015 Journal of the Electrochemical Society Vol.162 No.2

Optimized Bicompartment Two Solution Cells for Effective and Stable Operation of Li-O₂ Batteries

Kwak, Won-Jin,Jung, Hun-Gi,Aurbach, Doron,Sun, Yang-Kook Wiley Blackwell (John Wiley Sons) 2017 ADVANCED ENERGY MATERIALS Vol.7 No.21

<P>Lithium-oxygen batteries are in fact the only rechargeable batteries that can rival internal combustion engines, in terms of high energy density. However, they are still under development due to low-efficiency and short lifetime issues. There are problems of side reactions on the cathode side, high reactivity of the Li anode with solution species, and consumption of redox mediators via reactions with metallic lithium. Therefore, efforts are made to protect/block the lithium metal anode in these cells, in order to mitigate side reactions. However, new approach is required in order to solve the problems mentioned above, especially the irreversible reactions of the redox mediators which are mandatory to these systems with the Li anode. Here, optimized bicompartment two solution cells are proposed, in which detrimental crossover between the cathode and anode is completely avoided. The Li metal anode is cycled in electrolyte solution containing fluorinated ethylene carbonate, in which its cycling efficiency is excellent. The cathode compartment contains ethereal solution with redox mediator that enables oxidation of Li2O2 at low potentials. The electrodes are separated by a solid electrolyte membrane, allowing free transport of Li ions. This approach increases cycle life of lithium oxygen cells and their energy efficiency.</P>

Sodium oxygen batteries: one step further with catalysis by ruthenium nanoparticles

Kang, Jin-Hyuk,Kwak, Won-Jin,Aurbach, Doron,Sun, Yang-Kook The Royal Society of Chemistry 2017 Journal of materials chemistry. A, Materials for e Vol.5 No.39

<▼1><P>A Ru catalyst exhibits a bifunctional catalytic effect for ORR and OER based on Na2−xO2 as the discharge product in Na–O2 batteries.</P></▼1><▼2><P>Sodium–oxygen batteries have received much attention recently due to their possible higher energy efficiency and lower cost than lithium–oxygen batteries. Na<SUP>+</SUP> ions are less electrophilic than Li<SUP>+</SUP> ions (softer Lewis bases). Thereby, oxygen reduction in the presence of Na<SUP>+</SUP> ions may undergo a highly reversible one electron process to form sodium superoxide as a main product. However, sodium superoxide may have adverse effects on the stability and cycle life of sodium–oxygen batteries because of its high reactivity towards all kinds of relevant solvents. Therefore, sodium–oxygen batteries, in which the major oxygen reduction products are sodium peroxide moieties, may have an advantage in terms of better stability. This paper reports for the first time on sodium–oxygen batteries in which the cathodes comprise carbon nanotubes (CNTs) decorated with nanoparticles of ruthenium serving as a stationary catalyst. With these cathodes both oxygen reduction and evolution reactions are effectively catalyzed. The main oxygen reduction product on these CNT/Ru containing cathodes was deficient sodium peroxide, analyzed by XRD, XPS and SEM. Sodium–oxygen cells with Ru decorated CNT cathodes exhibited stable cycling performance over 100 cycles, while similar cells having CNT based cathodes showed much lower stability. It was clear that the limiting factor in the sodium–oxygen batteries containing CNT/Ru cathodes was the sodium anodes. Thereby it is believed that the present study is a step forward in the efforts to develop sodium–oxygen batteries.</P></▼2>

Effect of nickel and iron on structural and electrochemical properties of O3 type layer cathode materials for sodium-ion batteries

Hwang, Jang-Yeon,Myung, Seung-Taek,Aurbach, Doron,Sun, Yang-Kook Elsevier 2016 Journal of Power Sources Vol.324 No.-

<P><B>Abstract</B></P> <P>We investigate that the effect of Ni and Fe contents on structural and electrochemical properties of O3-type layered Na[Ni<SUB>0.75−x</SUB>Fe<SUB>x</SUB>Mn<SUB>0.25</SUB>]O<SUB>2</SUB> (x = 0.4, 0.45, 0.5, and 0.55) in which Mn is fixed at 25%. As increasing the Ni contents, the capacities are gradually higher while the capacity retention and thermal properties are inferior. When Fe contents are increased, by contrast, the electrode exhibits stable capacity retention and satisfactory thermal stability although the resulting capacity slightly decreases. Structural investigation of post cycled electrodes indicate that lattice variation is greatly suppressed from x = 0.5 in Na[Ni<SUB>0.75−x</SUB>Fe<SUB>x</SUB>Mn<SUB>0.25</SUB>]O<SUB>2</SUB>. This indicates that an appropriate amount of Fe into the Na[Ni<SUB>0.75−x</SUB>Fe<SUB>x</SUB>Mn<SUB>0.25</SUB>]O<SUB>2</SUB> stabilizes the crystal structure and this leads to the good cycling performances. Also, the better structural stability obtained by Fe addition is responsible for the less heat generation at elevated temperature for the desodiated Na<SUB>1−δ</SUB>[Ni<SUB>0.75−x</SUB>Fe<SUB>x</SUB>Mn<SUB>0.25</SUB>]O<SUB>2</SUB> (x = 0.4, 0.45, 0.5, and 0.55) caused by less evaporation of oxygen from the crystal structure.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We investigate the effect of Ni and Fe contents on O3-type NFM cathode. </LI> <LI> The Ni contents contribute to a higher discharge capacity. </LI> <LI> An appropriate amount of Fe contents improves the electrochemical properties. </LI> <LI> The resulting demonstrates an appropriate balancing of the Ni and Fe contents. </LI> </UL> </P>

Critical Role of Crystal Water for a Layered Cathode Material in Sodium Ion Batteries

Nam, Kwan Woo,Kim, Sangryun,Yang, Eunjeong,Jung, Yousung,Levi, Elena,Aurbach, Doron,Choi, Jang Wook American Chemical Society 2015 Chemistry of materials Vol.27 No.10

<P>Layered transition metal oxides are considered promising cathodes for sodium ion batteries (SIBs) due to their superior specific capacities. However, they usually suffer from insufficient cycling and rate performance mainly from the structural instability during repeated cycles. We overcome these longstanding challenges by engaging crystal water in the interlayer space of sodium manganese oxide under the Birnessite framework. The crystal water enhances Na ion diffusion both in the crystal host and at the interface, suppresses fatal Mn<SUP>2+</SUP> dissolution, and improves long-term structural stability, leading to excellent performance in rate capability and cycle life. The current study suggests that many hydrated materials can be good candidates for electrode materials of emerging rechargeable batteries that need to deal with the large size or multivalent charge of their carrier ions.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-10/acs.chemmater.5b00869/production/images/medium/cm-2015-00869q_0003.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00869'>ACS Electronic Supporting Info</A></P>

NaCrO₂ cathode for high-rate sodium-ion batteries

Yu, Chan-Yeop,Park, Jae-Sang,Jung, Hun-Gi,Chung, Kyung-Yoon,Aurbach, Doron,Sun, Yang-Kook,Myung, Seung-Taek The Royal Society of Chemistry 2015 ENERGY AND ENVIRONMENTAL SCIENCE Vol.8 No.7

<P>Sodium-ion batteries offer a potential alternative or complementary system to lithium-ion batteries, which are widely used in many applications. For this purpose, layered O3-type NaCrO<SUB>2</SUB> for use as a cathode material in sodium-ion batteries was synthesized <I>via</I> an emulsion-drying method. The produced NaCrO<SUB>2</SUB> was modified using pitch as a carbon source and the products were tested in half and full cells using a NaPF<SUB>6</SUB>-based non-aqueous electrolyte solution. The carbon-coated NaCrO<SUB>2</SUB> cathode material exhibits excellent capacity retention with superior rate capability up to a rate of 150 C (99 mA h (g oxide)<SUP>−1</SUP>), which corresponds to full discharge during 27 s. The surface conducting carbon layer plays a critically important role in the excellent performance of this cathode material. We confirmed the reaction process with sodium using X-ray diffraction and X-ray absorption spectroscopy. Thermal analysis using time-resolved X-ray diffraction also demonstrated the structural stability of carbon-coated Na<SUB>0.5</SUB>CrO<SUB>2</SUB>. Due to the excellent performance of the cathode material described herein, this study has the potential to promote the accelerated development of sodium-ion batteries for a large number of applications.</P> <P>Graphic Abstract</P><P>Carbon-coated NaCrO<SUB>2</SUB> synthesized <I>via</I> an emulsion method exhibits excellent cyclability and ultrafast rate capability up to a rate of 150 C, demonstrating ideal properties for advanced sodium-ion batteries. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c5ee00695c'> </P>

Review—A Comparative Evaluation of Redox Mediators for Li-O₂ Batteries: A Critical Review

Kwak, Won-Jin,Kim, Hun,Jung, Hun-Gi,Aurbach, Doron,Sun, Yang-Kook The Electrochemical Society 2018 Journal of the Electrochemical Society Vol.165 No.10

<P>For resolving the low-energy efficiency issue of Li-O-2 batteries, many kinds of redox mediators (RMs) have been adapted. However, studies looking into the problems of RMs in these systems are insufficient. We compare herein effects and problems of RMs in Li-O-2 batteries by applying unique methodology, based on two types of cells, comparison between argon and oxygen atmospheres and combining electrochemistry in conjunction with spectroscopy. Using systematic electrochemical measurements, representative RMs in Li-O-2 battery prototypes were thoroughly explored with respect to oxygen presence, voltage ranges and scan rates. By this comparative, multi-parameters study we reached valuable insights. We identified possible routes for RMs degradation in Li-O-2 batteries related to the cathode side, using bi-compartments cells with solid electrolyte that blocks the crossover between the cathode and the Li metal sides. Based on comparative electrochemical and spectroscopic analyses, we confirmed that degradation of the RMs activity was caused by intrinsic decomposition of the RMs in the electrolyte solution at the cathode part, even before further reactions with reduced oxygen species. This work provides a realistic view of the role of important RMs in Li-oxygen cells and suggests guidelines for effective screening and selecting suitable RMs, mandatory components in Li-O-2 batteries. (C) The Author(s) 2018. Published by ECS.</P>

Electrochemical Performance of a Layered-Spinel Integrated Li[Ni_1/3Mn_2/3]O₂ as a High Capacity Cathode Material for Li-Ion Batteries

Nayak, Prasant Kumar,Grinblat, Judith,Levi, Mikhael D.,Haik, Ortal,Levi, Elena,Talianker, Michael,Markovsky, Boris,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2015 Chemistry of materials Vol.27 No.7

<P>Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> was synthesized by a self-combustion reaction (SCR), characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Raman spectroscopy, and studied as a cathode material for Li-ion batteries at 30 °C and 45 °C. The structural studies by XRD and TEM confirmed monoclinic Li[Li<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> phase as the major component, and rhombohedral (LiNiO<SUB>2</SUB>), spinel (LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB>), and rock salt Li<SUB>0.2</SUB>Mn<SUB>0.2</SUB>Ni<SUB>0.5</SUB>O as minor components. The content of the spinel phase increases upon cycling due to the layered-to-spinel phase transition occurring at high potentials. A high discharge capacity of about 220 mAh g<SUP>–1</SUP> is obtained at low rate (C/10) with good capacity retention upon cycling. However, LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> synthesized by SCR exhibits a discharge capacity of about 190 mAh g<SUP>–1</SUP> in the potential range of 2.4–4.9 V, which decreases to a value of 150 mAh g<SUP>–1</SUP> after 100 cycles. Because of the presence of the spinel component, Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> cathode material exhibits part of its capacity at potentials around 4.7 V. Thus, it can be considered as an interesting high-capacity and high-voltage cathode material for high-energy-density Li-ion batteries. Also, the Li[Ni<SUB>1/3</SUB>Mn<SUB>2/3</SUB>]O<SUB>2</SUB> electrodes exhibit better electrochemical stability than spinel LiNi<SUB>0.5</SUB>Mn<SUB>1.5</SUB>O<SUB>4</SUB> electrodes when cycled at 45 °C.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-7/acs.chemmater.5b00405/production/images/medium/cm-2015-00405w_0020.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b00405'>ACS Electronic Supporting Info</A></P>

Study of the Most Relevant Aspects Related to Hard Carbons as Anode Materials for Na-ion Batteries, Compared with Li-ion Systems

de-la-Llave, E.,Borgel, V.,Zinigrad, E.,Chesneau, F. F.,Hartmann, P.,Sun, Y. K.,Aurbach, D. LASER PAGES PUBLISHING LTD 2015 ISRAEL JOURNAL OF CHEMISTRY Vol.55 No.11

Feasibility of Full (Li-Ion)–O₂ Cells Comprised of Hard Carbon Anodes

Hirshberg, Daniel,Sharon, Daniel,De La Llave, Ezequiel,Afri, Michal,Frimer, Aryeh A.,Kwak, Won-Jin,Sun, Yang-Kook,Aurbach, Doron American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.5

<P>Aprotic Li-O-2 battery is an exciting concept. The enormous theoretical energy density and cell assembly simplicity make this technology very appealing. Nevertheless, the instability of the cell components, such as cathode, anode, and electrolyte solution during cycling, does not allow this technology to be fully commercialized. One of the intrinsic challenges facing researchers is the use of lithium metal as an anode in Li-O-2 cells. The high activity toward chemical moieties and lack of control of the dissolution/deposition processes of lithium metal makes this anode material unreliable. The safety issues accompanied by these processes intimidate battery manufacturers. The need for a reliable anode is crucial. In this work we have examined the replacement of metallic lithium anode in Li-O-2 cells with lithiated hard carbon (HC) electrodes. HC anodes have many benefits that are suitable for oxygen reduction in the presence of solvated lithium cations. In contrast to lithium metal, the insertion of lithium cations into the carbon host is much more systematic and safe. In addition, with HC anodes we can use aprotic solvents such as glymes that are suitable for oxygen reduction applications. By contrast, lithium cations fail to intercalate reversibly into ordered carbon such as graphite and soft carbons using ethereal electrolyte solutions, due to detrimental co-intercalation of solvent molecules with Li ions into ordered carbon structures. The hard carbon electrodes were prelithiated prior to being used as anodes in the Li-O-2 rechargeable battery systems. Full cells containing diglyme based solutions and a monolithic carbon cathode were measured by various electrochemical methods. To identify the products and surface films that were formed during cells operation, both the cathodes and anodes were examined ex situ by XRD, FTIR, and electron microscopy. The HC anodes were found to be a suitable material for (Li-ion) O-2 cell. Although there are still many challenges to tackle, this study offers a more practical direction for this promising battery technology and sets up a platform for further systematic optimization of its various components.</P>