bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Explosion Synthesis of Si/C Nanocomposites for Li Secondary Batteries
Authors: Kim Doohun , Ha Yoon-Cheol , Cho Chuhyun , Lee Won-Jae , Doh Chil-Hoon
Published: February 2020

A novel technique of electrical explosion has been used for nanomaterial synthesis by a single-step process [1-5]. However, it was known that in principle the electrical explosion of Si is not possible due to the fact that applying a high voltage on Si wire having relatively high electrical resistance leads to a current flow through surface plasma formed along the wire which disables the resistive heating of Si. In this presentation, we will show the successful application of electrical explosion to silicon nanoparticle synthesis and the electrochemical properties of Si/C nanocomposites derived from the nanoparticles.

The electrical explosion of Si was successfully applied using a liquid media to suppress the unfavorable surface plasma generation. The physical and chemical properties of the produced materials were analyzed by XRD, FE-SEM, HR-TEM and the performances of the Si/C composites as an anode for Li ion batteries were investigated by electrochemical charge/discharge measurements. The Si/C composites obtained under the explosion in hexane and ethanol consist of a core-shell structure with a compact graphitic carbon on the Si particle surface which cause detrimental effects against Li ion diffusion. However, we found that Si explosion in methanol minimized the formation of the carbon phase on the surface of nano-sized Si. The Si/C nanocomposite after a simple pyrolysis with carbon precursor showed a high capacity with an excellent cycle performance.

[1] Cho, C., Choi, Y.W., Kang, C., Lee, G.W. Effects of the medium on synthesis of nanopowders by wire explosion process (2007) Applied Physics Letters, 91 (14), p. 141501.

[2] Cho, C., Ha, Y.-C., Kang, C., Jin, Y.-S., Rim, G.-H. Preparation of a nickel nanopowder by wire explosion in liquid media (2010) Journal of the Korean Physical Society, 57 (61), pp. 1807-1810.

[3] Ha, Y.-C., Cho, C. Production of highly-dispersed nano-sized Sn powders in a liquid medium by using a high-energy electrical explosion (2010) Journal of the Korean Physical Society, 57 (61), pp. 1574-1576.

[4] Cho, C., Ha, Y.-C., Kang, C., Jin, Y.-S., Rim, G.-H. Electrical explosion of silicon rod in distilled water (2011) Japanese Journal of Applied Physics, 50 (10 PART 1).

[5] Ha, Y.-C., Kang, C., Cho, C., Kim, Y.-U., Park, C.-M., Sohn, H.-J. Wire explosion synthesis of a Sn/C nanocomposite as an anode material for Li secondary batteries (2011) Journal of the Korean Physical Society, 59 (61), pp. 3458-3462.
High Voltage Na3V2O2x(PO4)2F3-2x (0≤x≤1) Positive Electrode Materials for Na-Ion Batteries
Authors: Serras Paula , Palomares Veronica , Alonso Javier , Sharma Neeraj , Lopez del Amo Juan Miguel , Kubiak Pierre , Fernandez-Gubieda María Luisa , Rojo Teofilo
Published: February 2020

Sodium-ion batteries have arisen as good candidates to become alternative systems that could complement commercial Li-ion systems [1]. The use of Na instead of Li in rocking chair batteries could mitigate the possible shortage of lithium in an economical way. For this purpose, the search for commercially viable Na-ion batteries demands finding and optimizing new electrode materials and electrolytes.

Among the possible cathodic materials, the family of compounds Na3V2O2x(PO4)2F3-x (Fig. 1) presents high operating voltages and specific capacity values, which are key parameters to get a high energy density battery [2]. In this study, two sodium-vanadium fluorophosphate materials were prepared:

- Carbon-free and carbon-coated Na3V2O2(PO4)2F phase (x = 1), where vanadium oxidation state is V4+.

- A mixed valence V3+/V4+ carbon-coated material belonging to the Na3V2O2x(PO4)2F3-2x family where 0 ≤ x ≤ 1.

Structural characterization of the composites was performed by powder X-ray diffraction (XRD). A double titration method as well as 23Na and 19F NMR measurements were necessary for the determination of the oxidation state of the vanadium. The morphology of the materials was analyzed by Scanning Electron Microscopy (SEM). The electrochemical measurements were conducted using Swagelok-type cells versus a metallic sodium anode. Ex-situ XRD and XANES data of electrodes charged and discharged at selected voltages allowed to deeper study the structural evolution of the material during cycling.

The two investigated compounds show similar electrochemical features such as high operating voltages (3.6 and 4.1 V vs. Na/Na+) and a high theoretical specific capacity (about 130 mAh/g). However, some differences can be observed in the potential vs. capacity curves (Fig. 2). A comparison between the up-to-date literature data [3,4] and the electrochemical data obtained from both the mixed valence and V4+materials will be established. The relationships composition-structure-electrochemical behaviour will be presented in detail and discussed.

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

[2] P. Serras, V. Palomares, A. Goñi, I. Gil de Muro, P. Kubiak, L. Lezama and T. Rojo J. Mater. Chem. 22 (2012) 22301.

[3] K. Chihara, A. Kitajou, I. D. Gocheva, S. Okada, J-I Yamaki J Power Sources, (2012) doi: 10.1016/j.jpowsour.2012.10.034.

[4] R. A. Shakoor, D-H Seo, H. Kim, Y-U Park, J. Kim, S-W Kim, H. Gwon, S. Leec and K. Kang .J. Mater. Chem. 22 (2012) 20535.
Preparation and Electrochemical Performance of Mo6V9O40 Nanorods as Cathode Materials for Li-Ion Batteries
Authors: Hu Meng , Wei Jinping , Zhou Zhen
Published: February 2020

Searching for cathode materials for Li ions batteries with high energy density is a key mission in recent years [1]. Among various candidates, vanadium and molybdenum oxides have been intensively studied due to their high capacity, easy preparation, and low cost. For example, Li ions can reversibly intercalate/deintercalate into the lattice layers of V2O5 and MoO3. Their hybrid oxides, molybdenum-vanadium based oxides, have been reported to be more sustainable to over discharge (to 1.5 V vs. Li/Li+), including solid solution (V1
-
yMoy)2O5 (0≤y≤0.3) and Mo6V9O40 [2]. Introduction of Mo into the structure increases the M-O bond length, and the structure is more flexible for Li ion intercalation/deintercalation. In addition, substituting Mo6+ for V5+increases the electronic conductivity [3].

Pure-phase molybdenum and vanadium mixed oxides are difficult to be obtained due to the multiphase equilibrium. Extremely long annealing time at high temperatures (above 600ºC) is needed to eliminate the impurity phases (such as V2O5 and MoO3). However, long time at high temperatures results in large particles, which degrades the electrochemical performance and is unfavorable for large-scale production. In this work, Mo6V9O40 nanorods with the diameters of ~200 nm were prepared through a sol-gel route, and the calcining time decreased to 2 h. The Mo6V9O40 nanorods exhibited an initial discharge capacity of 369 mA h g-1 at a current density of 100 mA g–1, and Li+ intercalation is partly irreversible, which is similar to V2O5. The discharge capacities of the second cycle were 276.2 and 212 mA h g-1 at 100 mA g–1 and 1 A g–1, and retained 214.8 and 181.8 mA h g-1after 50 cycles, exhibiting good cyclic stability and rate performance.

Figure 1. (a) SEM, (b) TEM, (c) charge/discharge curves at 100 mA g–1, and (d) cyclic performance at 100 mA g–1 and 1 A g–1 of Mo6V9O40nanorods.

References

[1] M. Hu, X. Pang, Z. Zhou, J. Power Sources 237 (2013) 229-242.

[2] A. Tranchant, R. Messina, J. Power Sources 24 (1988) 85-93.

[3] M. Uchiyama, S. Slane, E. Plichta, M. Salomon, J. Electrochem. Soc. 136 (1989) 36-42.
Flexible, Free Standing Integrated Conductive Network/Current Collector Organic Radical Polymer Electrode
Authors: Xie Jingying , Dai Yang , Cai Sendan , Yang Weijing
Published: February 2020

Organic radical batteries (ORBs) are emerging as high-rate capable, designable, environmentally friendly, and promising power for thin film batery. An ORB is composed of at least one of its electrodes based on radical polymer or organic radical as the active material. The first report of ORB was by Nakahara et al. in 20021.The n-type radical polymer can serve as the anode active material, while the p-type radical polymer, which usually bearing repeating units of nitroxide radicals, can be employed as the cathode active material. The charging process of the p-type radical polymer based cathode corresponds to the one-electron oxidation of the nitroxide radicals to the oxoammonium cations, with electrolyte anions providing the counter-charge. Upon discharge, the reverse processes occur.

However, the organic radical polymer electrode suffers from low energy density because of the low electronic conductive of the active polymer material, leading to require a lot of conductive carbon (>60 wt%) should be added to the electrode fabrication. In order to improve the energy density of the radical polymer electrode, we develop a new conducting network/current collector integrated electrode.

The electrode possesses higher energy density (active material > 50 wt%), flexible and free standing, that is quite promising for thin film battery application. The results and details will be presented in the meeting.

This work was supported by National Natural Science Foundation of China (No. 21103109, No. 21373137), Shanghai Science and Technology Talent Program(No. 12XD1421900).

Reference

K. Nakahara et al Chem. Phys. Lett. 359, 351 (2002).

T. Katsumata et al Macromolecules 41,1175 (2008).
Layered Sodium Cobalt Oxides Anchored on Graphene for Improvement of Capacity Retention in Sodium Ion Batteries
Authors: Lim HaetSal , Pyo Myoungho
Published: February 2020

NaxCoO2 is a well-known material for a promising cathode in sodium ion batteries. The crystal structures of NaxCoO2 have been reported to have four different phases. Each phase is built up by sheets of edge-sharing CoO6 octahedra, allowing Na+ ions to be intercalated with octahedral and/or trigonal prismatic surroundings. According to the stacking sequence of the oxygen layers, two or three repeating CoO2 sheets per unit cell can be present. Two-layer structure has γ phase in 0.6≤x≤0.75 and three-layer structure has β phase in 0.55≤x≤0.6, α phase in 1≤x≤0.9, and α’ phase at x=0.75. In this study, stoichiometric NaCoO2 (NCO) was anchored on graphene oxide (GO) and used as a cathode for sodium ion batteries. Co3O4 was first prepared on GO and thermally converted to NCO in an inert atmosphere (to minimize the loss of GO). During this process, GO was simultaneously reduced to graphene to provide NCO with a conducting network and possibly structural stability. Since the stoichiometric NCO, which has an O3-type layered structure, is in an electronically semiconducting state in contrast to non-stoichiometric NCO (metallic), the improvement of electrochemical property of NCO could be expected by incorporating graphene. Preliminary study showed that the capacity retention of NCO anchored on graphene was substantially better than the pristine NCO. Multi-step phase transition was not altered, but the capacity fading was negligible during 50 cycles. We are currently focusing on the synthesis of phase-pure NCO in an inert atmosphere.
Amorphous FeVO4/Mesoporous Carbon Composite: A Novel Cathode Material of Lithium-Ion batteries
Authors: Yu Zhongbao , Qiu Jingyi , Li Meng , Si Yuchang
Published: February 2020

Lithium ion batteries have been considered as one of the best candidates of the new environmental-friendly energy storage devices. However the low specific capacity of cathode materials becomes the main bottle-neck issue that lithium ion batteries face. Therefore it is imperative to develop new cathode materials to solve this problem. Vanadium-based cathode material such as FeVO4 with double valences change has important theoretical significance and practical utility for the development of high capacity lithium ion batteries. As everyone knows, the low electronic conductivity of FeVO4 results in the poor cycle stability and rate performance. To improve the electronic conductivity of FeVO4, herein amorphous FeVO4/mesoporous carbon composite was synthesized via an in-situ method. The FeVO4 was successfully filled in the hole of the carbon. Mesoporous carbon has many advantages in favor of the improved electrochemical properties of FeVO4 such as the high conductivity of mesoporous carbon has high specific surface, large pore volum can loading more FeVO4, the transfer distance ions and electrons is confined inside the mesoporous, and the amorphous state of FeVO4 is kept during cycling due to the confinement of the mesoporous carbon. The discharge capacity of the first cycle were as high as 249 mAh/g. The discharge capacity was kept 228 mAh/g after 40 cycles.
Substitution Chemistry of Li2MSiO4: A Highly Flexible Framework
Authors: Armstrong Anthony Robert , Billaud Juliette Marie , Adamson Paul , Eames Christopher , Islam M. Saiful , Bruce Peter G.
Published: February 2020

Lithium transition metal silicates, Li2MSiO4(M=Fe, Mn, Co)[1], have attracted a lot of interest recently as positive electrodes for Li-ion batteries due to their potentially high theoretical capacities and to their rich crystal chemistry as they undergo complex polymorphism. One of the drawbacks of the silicates is their modest rate capability, particularly at room temperature. The present work addressed this problem.

The polymorphs of Li2MSiO4can be classified into low (β) and high (γ) temperature forms, which differ in the ordering/distribution of cations within tetrahedral sites of an hcp based packing of oxygen. β forms exhibit only corner sharing and γ polymorphs both corner and edge sharing. It has been shown by us and by others that Li2FeSiO4 exists in at least 3 different polymorphic forms and that. in the case of Li2MnSiO4two stable polymorphs are observed [1-3].

The silicates are analogous to the LISICON materials (Lithium SuperIonic Conductors), of the form Li2+2xZn1-xGeO4, which adopt the γ structure with interstitial and highly mobile lithium. Therefore, stabilization of the γ polymorph to room temperature represents a potentially attractive route to enhancing the rate performance thus overcoming one of the major barriers to adoption of Li2MSiO4 cathodes.

With appropriate substitutions we have been able to stabilise the γ polymorph for both Li2FeSiO4 and Li2MnSiO4systems. We will report the effects on structure and electrochemistry of the various substitutions. In the iron system good cycling stability and improved rate capability are observed (fig. 2).

References

[1] a) A. Nytén, A. Abouimrane, M. Armand, T. Gustafsson and J.O. Thomas, Electrochem. Comm., 7, (2005) 156; b) M. S. Islam, R. Dominko, C. Masquelier, C. Sirisopanaporn, A. R. Armstrong and P. G. Bruce, J. Mater. Chem., 21 (2011) 9811.

[2] S. I. Nishimura, S. Hayase, R. Kanno, M. Yashima, N. Nakayama, A. Yamada, J. Am. Chem. Soc., 130 (2008) 13212.

[3] C. Sirisopanaporn, A. Boulineau, D. Hanzel, R. Dominko, B. Budic, A. R. Armstrong, P. G. Bruce, C. Masquelier, Inorg. Chem., 49 (2010) 7446.
Synthesis of Nanostructured TiNb2O7 Anode: High Capacity and Improved Rate Performance for Lithium Ion Battery Applications
Authors: Jo Changshin , Chun Jinyoung , Lee Jinwoo
Published: February 2020

Titanium-based materials have been regarded as promising alternatives to carbon-based electrode materials due to their high-voltage lithium insertion processes using a Ti4+/Ti3+ redox couple (~1.5 V vs. Li/Li+). Within this high voltage region (> 1V), the electrode is safe from the formation of solid-electrolyte interphase (SEI) and a lithium dendrite formation, thus guaranteeing a stable cycle performance and fast charging/discharge performance. However, the most negative point of the anode using the Ti4+/Ti3+ redox couple is their theoretically low charge capacities (Li4Ti5O12: 175 mA h g-1 and anatase TiO2: 168 mA h g-1).

As a new electrode material, TiNb2O7 (TNO) was reported by Goodenough’s group in 2011. This material can insert 5 Li ions due to the multiple redox couples (Ti4+/Ti3+, Nb5+/Nb4+, and Nb4+/Nb3+), corresponding to a high theoretical capacity of 387.6 mA h g-1. This value is much higher than that of other Ti- and Nb-based electrodes. However, due to the high formation temperature of monoclinic TNO phase, it was hard to synthesize nano-sized or nano-structured TNO materials. Above 900 °C, primary particles grow to a large size, in the order of 100 nm. Therefore, an effective fabrication method for the nanosized TNO crystals is necessary in order to achieve rapid Li storage, as in the case of other electrode studies.

In this presentation, we report the synthesis of an ordered mesoporous structured TiNb2O7 (OM-TNO) and its high capacity and rapid rate performance as an anode in LIB. The OM-TNO was synthesized using block-copolymer-assisted, one pot synthesis. As a structure-directing agent, Poly (ethylene oxide-b-styrene) interacts with the hydrolyzed Ti- and Nb-sol, resulting in a segregation of PS blocks and PEO/precursors. After heat-treatment at 900 °C, nano-sized TNO crystals are formed inside the pore walls. As an anode, OM-TNO electrode exhibited high reversible capacity of 289 mA h g-1 at a 0.1 C rate, and high rate capability; 40% capacity retention at a 50 C rate (= 19.35 A g-1). The enhanced electrochemical performance is attributed to the OM-TNO’s unique features, such as the small crystallites, large mesopores, and high surface area.
A Study of the Effect of Graphite Surface Properties on the Cycle Life of Lithium Ion Battery By the Analysis of SEI Layer
Authors: Kwon Se Man , Oh Seh Min , Park Yong Tae , Kim Byoung Ju , Kang Sung , Park Sei Min
Published: February 2020

Much work has described the influence of anodic SEI (Solid Electrolyte Interphase) on the cycle stability of a lithium secondary battery. Especially, it was reported that the characteristics of SEI Layer were greatly affected by the crystallographic and chemical properties of graphite. The purpose of this study was the identification of the effect of functional groups of graphite on the chemical composition and distribution of SEI Layer. Also the correlation between the SEI film properties and cycle life of battery was investigated through the analysis of composition and distribution of the components that constitute the SEI film.

Two kinds of commercial natural graphite active materials prepared by different surface modification process were used for the comparison of the functional groups. These active materials were manufactured as powders by POSCO-Chemtech (PCT-H, PCT-3). The PCT-H was modified by surface reforming process, and PCT-3 was fabricated from the graphitization of natural graphite with carbon layer of surface.

With these anode materials, the cyclic test was performed using 2032 - typed coin cell.

After 300th cycle, the anode was isolated from coin cell to inhibit the chemical change of SEI layer. XPS and TEM-EELS analyses on the anode were followed for the comparison of the characteristics under inert atmosphere.

In this work, It was found that the modification method of graphite strongly Influenced on the SEI layer. Therefore, this result can be utilized to improve the compatibility of the anode to the electrolytes.
Electrolytes Beyond the State of the Art for Rechargeable Magnesium Batteries
Authors: Mohtadi Rana , Mizuno Fuminori , Arthur Timothy S.
Published: February 2020

Recently, rechargeable magnesium batteries have been attracting an increased attention as a candidate for a post Li-ion battery owing to a high volumetric capacity (3833 mAh cm-3 vs. 2046 mAh mAh cm-3 for Li) , absence of dendrites formation and the lower cost of Mg metal (about 10 times cheaper than Li). Nonetheless, current Mg battery technologies suffer from several drawbacks which hamper reaching its full potential. For example, the absence of robust and practical high voltage/high capacity cathodes currently limits the energy density which could be harnessed using these batteries.[1] Another major challenge relates to the electrolytes used in magnesium batteries. Current state of the art electrolytes use Grignard/organohalo magnesium reagents and complexes since electrolytes based on conventional inorganic and ionic Mg salts were found to passivate the Mg metal surface. [1] These organohalo reagents, while possessing an impressive electrochemical performance, were found to cause corrosion to the metallic battery parts such as current collectors. This corrosive nature has been linked to the presence of the chloride ion which is an integral part of the electrolytes’ make. Therefore, a new strategy for designing electrolytes for magnesium batteries is highly desired. We have been pioneering the development of a new class of electrolytes that are based on borohydrides salts. These represent the first and only example of an inorganic, relatively ionic and halide free salts reported to date that are compatible with Mg metal. [2] These electrolytes were used in the first rechargeable Mg battery utilizing an inorganic salt leading to opening a new dimension in the design space of magnesium battery electrolytes. Here, we will explain our design strategies, discuss fundamental properties obtained from systematic spectroscopic and electrochemical studies and share up-to-date results related to these new promising systems.

References

[1] H. D. Yoo, I. Shterenberg, Y. Gofer, G. Gershinsky, N. Pour, D. Aurbach, Energy Environ. Sci. 2013, 6, 2265-2279.

[2] R. Mohtadi, M. Matsui, T. S. Arthur, S.-J. Hwang, Angew. Chem. Int. Ed. 2012, 51, 9780 –9783.
Enhanced Performance of Li-S Battery with Self-Assembled Polypyrrole Film As a Functional Interlayer
Authors: Ma Guoqiang , Wen Zhaoyin , Jin Jun , Wang Qingsong
Published: February 2020

Lithium sulfur batteries are attracting increasing attentions in recent years due to their high theoretical capacity of 1675 mAh.g-1, low cost, natural abundance and environmental friendliness. However, a rapid capacity fading hinders their practical application, which is attributed to the high insulating nature of sulfur, the dissolution of lithium polysulfides and volume expansion[1, 2]. In this work, as schematically illustrated in Fig.1a, a self-assembled polypyrrole (PPy) films composing of PPy nano-wires and PPy nano-tubes are sandwiched between sulfur cathode and separator of Li-S cell to act as functional interlayer in attempt to alleviate the polarization of sulfur cathode and to suppress the shuttle effect.

Fig.1 TEM images of PPy nano-wires and PPy nano-tubes, and a schematic cell configuration of rechargeable Li-S batteries with PPy interlayer (a). Initial charge/discharge profiles (b), Nyquist plots measured before cycling (above) and after 100cycles at 0.2C (below) (c), cycle performance and coulombic efficiency of Li-S batteries with PPy nano-wire interlayer, PPy nanotube interlayer and without interlayer(d).

As shown in Fig.1b, the Li-S battery with PPy interlayers shows higher discharge plateaus and lower charge plateaus than the cell without interlayer, indicating a decreased polarization. Moreover, both the typical valley at the end of the first discharge plateaus and a peak at the beginning of the charge profile for Li-S cell disappear for the cell with PPy interlayers. Fig.1c shows evidently decreased resistance of the cells with PPy interlayer, indicating that the interlayer acts as a pseudo-upper current collector which reduces the effective resistance of the highly insulating sulfur cathodes and enhances the utilization rate of the active material. Furthermore, the cycle performance and coulombic efficiency of the cells with PPy nano-wire and PPy nano-tube interlayers are much better than the cell without interlayer. The positive effect of PPy interlayer could be ascribed to the strong adsorption effect between PPy and lithium polysulfides[3] which can inhibit the migration of lithium polysulfides effectively and thus improve the coulombic efficiency and cycling stability. As seen in Fig.1d, the discharge capacities of Li-S batteries with PPy nano-wires interlayer and PPy nano-tube interlayer are maintained at 782mAh.g-1 and 687.5mAh.g-1 after 200 cycles respectively, which are much higher than the cell without interlayer (476mAh.g-1after 100 cycles).

References

[1] S.A.F. Peter G. Bruce, Laurence J. Hardwick and Jean-Marie Tarascon, Nat Mater, (2012) 11,19-29.

[2] Y. Yang, G. Zheng, Y. Cui, Chem Soc Rev, 42 (2013) 3018-3032.

[3] W. Li, Q. Zhang, G. Zheng, Z.W. Seh, H. Yao, Y. Cui, Nano Lett, 13 (2013) 5534-5540.
Nitrogen-Enriched, Nanostructured Carbon Materials for Application in High-Loading Lithium-Sulfur Cathodes
Authors: Schneider Artur , Brezesinski Torsten , Sommer Heino , Janek Jürgen
Published: February 2020

The development of efficient energy storage systems is of exceptional importance considering the increasing demand in electrical energy for both, stationary and mobile applications. Among a wide range of possible cathode materials elemental sulfur has the highest theoretical capacity of 1675 mAh/g which makes it a promising candidate as a positive electrode material.[1] However, the poor cycle life and rate capability of sulfur cathodes have limited the practical application of this attractive technology. Sulfur is highly electronically and ionically insulating which makes the use of conductive additives such as carbon black inevitable. Polysulfides, being generated during cyclization, dissolve in the liquid electrolyte and shuttle between the anode and cathode to react chemically and cause a loss of active material. Furthermore, the final product of the sulfur reduction, Li2S, is highly insulating and partially responsible for the rising electrode resistance during cycling. Precipitation of solid lithium sulfide is assumed to proceed both, on cathode and on anode side.

Different carbon materials are widely used as cathode additives as they offer a high electronic conductivity coupled with low mass and a high surface area.[2] Recently, significant progress has been achieved using structured meso- and microporous carbons as host materials for sulfur. In order to prevent the loss of active material by dissolution, the conductive matrix is assumed to constrain the highly soluble polysulfide inside the cathode by chemical or physical interactions. Therefore, the parasitic polysulfide shuttle and undesired side reactions with the lithium anode can be mitigated. Moreover, structured carbons have a stabilizing impact on the structural integrity of the cathode matrix, as they are able to compensate the mechanical stress arising from the volume expansion during the chemical conversion of sulfur into lithium sulfide. [3]

Here, we present novel, nitrogen-enriched, nanostructured carbons (MPC) as cathode materials for lithium-sulfur batteries. Synthesized via hard-template approach, the obtained materials exhibit a well-defined mesoporous structure with a nitrogen content of approx. 10 %, enabling the possibility of sulfur infiltration. Due to a high specific surface area (400 – 500 m2/g), enhanced polysulfide adsorption and good mechanical stability, cathodes with a high active material loading (above 2 mg/cm2) and improved cycling performance can be fabricated.

Significantly improved specific and areal capacities were achieved over 200 cycles with an increased sulfur loading. It can be shown that the synergetic effects of sulfur confinement and carbon modification can crucially improve the performance of lithium-sulfur batteries.

References

[1] Manthiram, A., Acc. Chem. Res., 2013, 46, 1125–1134

[2] Ji, X. L.; Nazar, L. F. Nat. Mater. 2009, 8, 500–506.

[3] Sun, F. ACS Appl. Mater. Interfaces, 2013, 5, 5630–5638
Doping and Defect Chemistry in LiCoO2 By First-Principles Calculation
Authors: Koyama Yukinori , Arai Hajime , Tanaka Isao , Uchimoto Yoshiharu , Ogumi Zempachi
Published: February 2020

Introduction

In order to improve the performance of lithium-ion batteries, doping to electrode active materials is often carried out. The doped ions are extrinsic point defects in the active materials, and thus the doping exerts an influence on native point defects in the materials. Since the point defects are associated with many properties of the active materials, information on the doped ions as well as the native defects is of importance to control the materials. In this study, we made comprehensive first-principles calculations to estimate solubility of various species doped into LiCoO2and to discuss effects of the doping on the defect chemistry.

Computation method

As the doped species to LiCoO2, several metals such as Na, Mg, and Al, were selected. Both the Li and Co sites were considered as the substitution positions of the doped ions. Vacancies, interstitial cations and antisite cations were examined as the native defects. Defect formation energy was evaluated by first-principles calculations using a supercell consisting of 144 atoms with a single defect. The first-principles calculations were carried out using the plain-wave basis PAW method and the GGA+U exchange correlation functional. Equilibrium defect concentrations were estimated by the Boltzmann distribution under given chemical conditions and charge neutrality.

Results and discussion

Figure 1(a) illustrates equilibrium defect concentrations in Al-doped LiCoO2 as a function of temperature when LiCoO2 coexists with LiAlO2 and Li5AlO4 under an oxygen pressure of 0.2 atm. Al preferentially substitutes for Co (AlCo) as shown in the figure, and thus this condition can be considered as a nominal composition of Li(Al
x
Co1-x
)O2 with a small amount of excess Li. At this chemical condition, one can expect high Al solubility of ~50% with low concentrations (<1%) of the native defects such as CoLi under usual synthetic conditions (800-900 °C in air). Since defect formation energy and equilibrium defect concentration depend on the chemical condition, more Li-rich and Al-rich conditions were also examined. Figure 1(b) illustrates equilibrium defect concentrations at the more Li-rich condition, where LiCoO2 coexists with Li2O and Li5AlO4. At this condition, the concentration of AlCo is less than 10%. This is because excess Li reacts with Al, resulting in suppression of the Al-doping to LiCoO2. On the other hand, when LiCoO2 coexists with LiAlO2 and CoAl2O4 as the Al-rich condition, the concentration of CoLi becomes ~6% at 1100 K as shown in Fig. 1(c). The Al-rich condition means Li-poor condition, and thus Li deficiency in LiCoO2 is increased. These calculations suggest that the chemical conditions are of great importance to achieve both the increase in the Al solubility and the suppression of the Li deficiency. The solubility and effects on the defect chemistry of other species are discussed at the meeting.

Acknowledgement

This work was supported by RISING project of NEDO.
Thermodynamic Analysis of Lithium Storage at Abrupt Junctions: Modeling and Experimental Evidence
Authors: Chen Chia-Chin , Fu Lijun , Samuelis Dominik , Maier Joachim
Published: February 2020

Besides conventional lithium storage mechanisms, a novel interfacial storage mode was predicted to occur in M/LiX nanocomposites (M stands for any electron conductor, e.g. metal, which does not alloy with Li). According to this mechanism, the individual charges (Li+, e-) are stored in the space charge layers, i.e., Li+ is accommodated at the Li2O side of the boundary, while the e- is restricted to the metal side. As neither of the composites could store Li by itself, this is called ‘job-sharing’ mechanism [1]. Recently, a thermodynamic model for interfacial storage was developed, which describes both semi-infinite and mesoscopic boundary conditions [2]. In this contribution, we present that the predicted power law for the Li-activity dependence of the capacity for a semi-infinite model can be reproduced, in both Li2O-Ru and LiF-Ni composites systems. Further exploitation of the interfacial storage mechanism may provide interesting information as to better compromise power and energy density for Li-ion batteries. Moreover, the correlations allow for a generalized storage picture of nanocrystals.

Reference:

[1] J. Jamnik and J. Maier, Phys. Chem. Chem. Phys., 5, 5215-5220 (2003).

[2] J. Maier, Angew. Chem. Int. Ed., 52(19), 4998-5026 (2013).
Investigation of Ether-Based Ionic Liquid Electrolytes for Lithium-O2 Batteries
Authors: Ferrari Stefania , Quartarone Eliana , Bini Marcella , Tomasi Corrado , Capsoni Doretta , Mustarelli Piercarlo
Published: February 2020

The growing global energy demand of modern society is urging to find large-scale sources, which are more sustainable and environmentally friendly than the oil-based ones. At present, the capacity of the state-of-the-art lithium ion battery is limited and therefore, radically different approaches are required in order to fulfil the very demanding requests of energy storage. Rechargeable Li-O2/air batteries can potentially represent an interesting solution because they theoretically can store more energy than Li-ion batteries. At present numerous aspects of Li-O2 batteries deserve to be carefully investigated before becoming a commercial reality and among them the electrolyte is one of the main challenges.1 Ether based electrolytes have attracted a lot of interest because they combine several beneficial attributes; they are safe, low cost, stable up to 4.5V and they are of low volatility. Tetra(ethylene) glycol dimethyl ether (TEGDME) has been recently employed in Li-O2 batteries and with very good electrochemical performances.2 Hydrophobic ionic liquids (ILs) have been largely employed in case of the conventional Li-ion cells, however a few details on their behaviour in Li-O2batteries are still available.

In this work, we investigated the potential use as electrolytes of mixtures of TEGDME and ether functionalized ionic liquids (ILs). We show the results of the characterization of mixtures having different ratio TEGDME-ILs and containing LiCF3SO3 or LiTFSI salt by means of thermal analysis, conductivity and electrochemical stability measurements. In addition, their application in Li-O2 batteries has been assessed, investigating Li/TEGDME-IL/O2 cells by means of cycling voltammetry (CV) and galvanostatic charge-discharge tests. Oxygen reduction and evolution reactions (ORR and OER) have been studied in TEGDME-ILs mixtures to address the mechanism and reversibility of ORR and OER. Our results demonstrate that oxygen reduction and evolution take place in a reversible way and that ether-based electrolytes containing ionic liquids worthwhile of being further investigated for rechargeable Li-O2cells.

[1] D. Capsoni, M. Bini, S. Ferrari, E. Quartarone, P. Mustarelli J. Power Sources(2012) 220, 253.

[2] H.-G. Jung, J. Hassoun, J.-B. Park, Y.-K. Sun, B. Scrosati Nat. Chem. (2012) 4, 579
Construction of Direct-Growth in Situ Doped Polypyrrole/CNT Core Shell Composite on Carbon Cloth As a High Performance Flexible Supercapacitor
Authors: Yesi Yesi , Shown Indrajit , Ganguly Abhijit , Chen Li-Chyong , Chen Kuei-Hsien
Published: February 2020

In the 21st century, the growing demand of the smart portable electronic gadgets, such as roll-up display, electric paper and wearable systems for smart electronics need to develop the flexible super capacitor with both high-power density and large energy density. Conducting polymers (CPs) are one of the most potential pseudo-capacitor materials for foundation of flexible-supercapacitors, motivating the existing energy storage devices towards the future advanced flexible electronic applications due to their high redox active specific capacitance and inherent elastic polymeric nature [1,2]. To the best of our knowledge, among CPs, polypyrrole (PPy) have shown better elasticity and conductivity than the polyaniline. However, a key weakness of the PPy based supercapacitor electrode is mechanical instability due to the considerable volume change during the repeated charge-discharge process. Consecutively binary composites of PPy with CNTs on flexible substrate have been explored on the traditional slurry process. A major limitation of the traditional slurry derived electrode consists in the sluggish rate of ion transport during the faradic reactions in electrode due to the high internal resistance of binders. To solve this problem in this work, polypyrrole/CNT core shell composite directly grown on flexible carbon cloth (CC). The CNTs were directly grown on the CC by microwave plasma-enhanced chemical vapor deposition in order to obtain a strong adhesion of CNT on CC, and then the in situ doped well uniform PPy/CNT core-shell composite was synthesized via oxidative electropolymerisation. The PPy/CNT/CC electrode fabricated by direct growth process with optimum thickness of PPy possesses the low interfacial resistance, and shows high gravimetric capacitance of 486.1 F/g with a mass loading around 6 mg/cm2 at a current density of 0.9 A/g. Furthermore, this PPy/CNT/CC electrode delivers remarkably a very high cycle stability (17% capacitance loss after 10000 cycles) and high flexibility.  The detail core shell electrode fabrication process of PPy/CNT on flexible CC and their electrochemical pseudo-capacitance with stability performance will be discussed. These results clearly present a cost-effective and simple fabrication method of the PPy/CNT composite with enormous potential in flexible energy storage device applications.

 

References

[1]    Y.Y. Horng, Y.C. Lu, Y.K. Hsu, C.C. Chen, L.C. Chen, K.H. Chen, Journal of Power Sources. , 2010, 195, 4418.

[2]    I. Shown, A. Ganguly, L. C. Chen, K. H. Chen, Energy Science & Engineering, 2014, DOI: 10.1002/ese3.50.
A Novel Flow Battery Using Quinoxaline Derivatives As Redox Couple
Authors: Li Xue , Zhao Yang , Pan Jianxin , Xie Xiaofeng , Ramani Vijay K
Published: February 2020

New and renewable energy resources are being developed to reduce the use of fossil fuels and decrease the greenhouse gas emission. Energy storage is now seen as the opportunity for improve energy efficiency and utilize discontinuous clear energy like the wind and solar power. Redox flow battery is now leading the way in electrochemical energy storage system for its low cost, flexibility and high efficiency. Flow batteries are almost metal based of which the most widely used is all vanadium redox flow battery. A breakthrough by using metal-free organic-inorganic redox couples as active materials. 9,10-anthraquinone-2,7-disulphonic acid (AQDS) undergoes extremely rapid and reversible two-electron two proton reduction on a glassy carbon electrode in sulphuric acid had made[1]. And a quinoxaline-derivatives as initial low-potential materials had employed and showed good columbic and energy efficiency[2].

Quinoxaline is a promising active material for flow batteries due to its low molecular weight, high solubility and ability to transfer two electrons per pyrazine ring. In this study, quinoxaline-derivatives were studied, and the reduction potentials including hydroxyquinoxaline and methylquinoxaline are calculated with DFT, while solvation free energies calculated by COSMO model. A better reversibility as well as rapid kinetics have been observed. The most of the derivatives are highly soluble in aqueous or non-aqueous solutions and the reduction potentials are relatively low (~-0.3V) indicate that can be combined with the Br2/Br- couple, which would show high energy efficiency. Electrochemical properties of quinoxaline-derivatives with various concentration, different additions, in different solvents will be tested which would involving Cyclic Voltammetry (CV), Electrochemical Impedance Spectroscopy (EIS), Rotating Disk Electrode and Rotating Ring-Disk Electrode (RDE and RRDE). The battery performance will be tested employing quinoxaline-derivatives and Br2/Br-as cathode and anode redox couples, respectively.

Key words:flow battery, redox couple, quinoxaline

Acknowledgment:This work was supported by the National High Technology R&D Program of China (2012AA053401)

References

[1] B. Huskinson, M.P. Marshak, et al. A metal-free organic––inorganic aqueous flow battery. [J] Nature. 2014, 505: 195-198.

[2] Fikile R. Brushett, John T. Vaughey, and Andrew N. Jansen. An All-Organic Non-aqueous Lithium-Ion Redox Flow Battery. [J] Adv. Energy Mater. 2012, 2, 1390–1396.
Operando X-Ray Diffraction As a Tool to Monitor Compositional Gradients in Battery Electrodes
Authors: May Brian M , Kim Cheon Jung , Yu Young-Sang , Cabana Jordi
Published: February 2020

Batteries are a crucial technology for a society to move away from fossil fuels. The amount of energy a battery can store is proportional to the amount of charge transferred by the cathode and anode [1]. To maximize this energy, electrode thickness is maximized. These electrodes are made of a porous active material which allows for lithium transport in and out of the materials. Inhomogeneities will be observed due to the non-uniformity of the pores, as well as the conductive additive within the cell. Therefore, the rate of lithium insertion/removal is dependent on the location within the electrode. As the electrode thickens, the inhomogeneities will increase as a function of the distance from the anode, resulting in gradients normal to the electrode. The development of these gradients is also associated with transport within the active material.

X-ray diffraction (XRD) is a powerful technique that can provide structural information on the unit cell [2]. Performing operando experiments can reveal information on the dynamic composition of the electrode. The materials of interest are various compositions of LiMO2 (M=Ni, Mn, Co, Al), crystallizing in a layered α-NaFeO2-type structure. These materials have high theoretical charge capacities, yet can only stably cycle at a fraction of them during operation [3]. During each charge cycle, the material transforms following a second-order phase transition involving continuous miscibility between end states, which is easily followed by diffraction. In the presence of chemical gradients that take place during the transformation, the XRD peaks would progressively broaden. These gradients will vanish when the circuit is open. We validated this hypothesis with LiNi0.33Co0.33Mn0.33O2 (NCM111) electrodes. Peaks broadened during the reaction and faded during relaxation, especially at high rates. Figure 1 demonstrates this phenomenon when charging to 4.3V at a 1C rate (60 minutes for full charge). We leveraged the high penetration enabled by the 115 keV beam in beamline 11-ID-C at Advanced Photon Source to do the measurements in coin cells without thin windows, to ensure constant isostatic pressure and avoid undesired sources of chemical gradients. In this presentation, we will summarize the results obtained in a variety of experimental conditions, such as rate, voltage window and electrode porosity. The observations help explain how gradients are formed within positive electrodes based on layered oxides and can provide information on why the theoretical capacity has yet to be achieved in application.

References

1. A. Van der Ven, J. Bhattacharya, A. A. Belak, Accounts of Chemical Research 46, 1216-1225 (2012)

2. He, B. Two-dimensional X-ray Diffraction. 2009.

3. Goodenough, J. B.; Kim, Y. Chem. Mater. 2010, 22, 587-603.

Figure 1
Studies on Kinetics and Mechanism for Rechargeable-Iron Electrodes Using in Situ x-Ray Diffraction Technique in Conjunction with Electrochemistry
Authors: Ravikumar Musuwathi Krishnamoorthy , Sundar Rajan Aravamudan , Shukla Ashok Kumar
Published: February 2020

Iron is the fourth most abundant element on the earth’s crust. It is cost effective, has large theoretical specific capacity and is non-toxic. Iron-based accumulators are both mechanically and electrically rugged. Besides, iron electrodes are also environmentally benign unlike other battery electrode materials, such as cadmium and lead.1 Open-circuit potential of a charged alkaline-iron electrode is always negative to hydrogen evolution reaction. Consequently, iron is thermodynamically unstable and suffers corrosion through concomitant evolution of hydrogen. Hydrogen evolution also occurs while charging alkaline iron electrodes bringing about a decrease in their charge acceptance. Several sulfide additives, like FeS, PbS and Bi2S3, have been used to increase hydrogen over-potential to mitigate this problem. Recently, we reported a carbon-grafted alkaline iron electrode for iron-based accumulators with specific capacity values in excess of 400 mAh g-1 with faradaic efficiency of about 80%.2 In this study, we report in situ x-ray diffraction investigations on charge and discharge products of carbon-grafted iron electrodes with and without Bi2S3 additive to throw light on a feasible charge and discharge mechanism in these electrodes. When iron electrodes with Bi2S3 additives are subjected to formation cycle Fe3O4 is reduced to metallic α-Fe. Interestingly, carbon-grafted iron electrodes with Bi2S3 exhibit complete conversion of Fe3O4 to α-Fe at the end of formation cycles and, consequently, it is surmised that carbon grafting into the iron active material promotes utilization of active material.

 References:

S.R. Narayanan, G.K. Surya Prakash, A. Manohar, Bo. Yang, S. Malkhandi and Andrew Kindler, Solid State Ionics, 216, 105 (2012).

A. Sundar Rajan, S. Sampath and A.K. Shukla, Energy Environ. Sci.,
7, 1110 (2014).
Chemiacl Potential and Degradation of Solid Electrolyte for SOFCs
Authors: Lim Hyung-Tae , Jung Myung Geun , Park Mi-Young
Published: February 2020

The stability of a solid oxide fuel cell (SOFC) stack is strongly dependent on the magnitude and profile of the internal chemical potential of the solid electrolyte. If the internal partial pressure is too high, the electrolyte can be delaminated from the electrodes. The formation of high internal pressure is attributed to a negative cell voltage, and this phenomenon can occur in a bad cell (with higher resistance) in a stack. This fact implies that the internal chemical potential plays an important role in determining the lifetime of a stack. In the present work, we fabricate two kinds of electrolyte, oxygen ion conductor (YSZ) and proton conductor (BCY), for solid oxide fuel cells and conduct degradation tests under a negative voltage condition, as a function of electrolyte structure and composition. Results indicate that the addition of electronic conduction in the electrolyte with bi-layer structure can effectively enhance the cell stability, especially under severe operating conditions.
Electrochemical Study on the Impact of Metallization on Si Particles for Li-Ion Negative Electrode
Authors: Spreafico Marco Alberto , Cojocaru Paula , Oriani Andrea Vittorio , Triulzi Francesco , Magagnin Luca , Apostolo Marco , Biso Maurizio
Published: February 2020

Li-ion batteries are widely used in a large number of devices that are used in everyday life, from Smart Devices to Hybrd Electric Vehicles (HEVs). The research is prompted towards the development of innovative materials that can further enhance the performances of batteries1,2.

Research on anodic materials is of crucial importance to meet the requirements for cited applications in terms of power and energy density. On this side, Silicon is considered to be the most promising material in terms of deliverable theoretical specific capacity, 4200 mAh/g.  However, cycling performances of Silicon are jeopardized by the structural instability suffered from the material upon charge/discharge cycling. To address this issue, different solutions have been tested3
,
4. The approach developed in this work is to apply a metallic coating to the Si particles by electrochemical techniques, i.e. electroless deposition and galvanic displacement.

In this work, a study of the electrochemical impact of the coating on the behavior of the electrode will be done in two steps. First, an assessment of the growth mechanism of metallic coating on Si particles will be carried out by means of SEM analysis. Then, the electrochemical characterization of electrodes containing metallized particles will be carried out by means of electrochemical impedance spectroscopy, SEM analysis and coin cell cycling.

References:

1. J. B. Goodenough and Y. Kim, Chem. Mater., 22, 587–603 (2010)

 2. Y. Sun et al., Nat. Mater., 11, 942–947 (2012)

 3. C. K. Chan et al., Nat. Nanotechnol., 3, 31–5 (2008)

 4. B. A. Boukamp, J. Electrochem.
Soc., 128, 725 (1981)