bluuebunny/crossref_metadata_2025_split huggingface dataset:
Does Spinel Serve As a Rigid Framework for Oxygen Redox?
Authors: Shi Xiang-Mei , Watanabe Eriko , Okubo Masashi , Yamada Atsuo 
Published: December 2020

A major challenge for the development of lithium-ion batteries with high energy densities is to discover a large-capacity cathode material, and an additional oxygen redox capacity has recently been regarded as a new impetus. From the electronic-structure viewpoint, the best-studied oxygen-redox cathode materials, lithium-rich layered oxides possess oxide ions with nonbonding O 2p states along the Li-O-Li coordination axis, which provide the oxygen redox activity. After oxygen oxidation, either a π-type M t
2g-O 2p interaction (M: transition metal) or an O-O bond formation stabilizes the oxidized oxide ions, allowing for reaction reversibility. However, the layered structure is generally unstable after extracting an excess amount of Li ions, leading to the degradation of both capacity and voltage during charge/discharge cycles. It is therefore particularly important to implement oxide ions with nonbonding O 2p states into a stable host framework against excess Li-ion extraction to achieve reversible oxygen-redox capacity. As spinel oxides have a stable three-dimensional framework, it is attractive to explore for spinel oxides capable of the oxygen-redox reactions.
Here, we theoretically diagnose the oxygen-redox activity of spinel oxides using density functional theory (DFT) calculations. LiMg0.5Mn1.5O4 is employed as a model material, as its spinel structure is expected to have oxide ions with nonbonding O 2p state owing to the existence of ionic Mg2+ in the framework. The electronic structure change during the oxygen-redox reaction of LiMg0.5Mn1.5O4 is compared with that of a typical Li-rich layered oxide (Li2MnO3), revealing the lability of oxidized oxide ions in a spinel oxide.
Introduction to Neocarbonix: Binderless Electrodes for Lithium-Ion Batteries
Authors: Brambilla Nicolo 
Published: December 2020

Energy storage electrodes are often limited in their electrochemical stability and electrical performance by polymer binders used in the active material layer. Binders are also used to adhere the active material to the current collector. Binders are usually polymeric resins used in electrodes to mechanically hold active material powders together. Active materials may be graphite, silicon-carbon, silicon oxides for anodes, and lithium metal oxides for cathodes in the case of lithium-ion batteries (LIBs). They can also be high surface area activated carbons, in the case of EDLCs. The binders are a passive component in energy storage electrodes and they carry limitations in terms of electrical conductivity, thermal stability and chemical stability.
Capacity and C-rate capabilities in LIBs and ESR in EDLCs suffer because electrically insulating inactive binder material takes up space within the electrode material. Meanwhile lifetime at temperature and voltage can suffer as the binder material interacts with the internal electrochemical system of the energy storage device. Additionally, thermal stability of the electrode can be limited both by the electrochemical activity of the binder material as well as phase transitions of the binder material. Performance of energy storage systems using conventional electrodes in particularly high power applications may be limited by the thermal stability of the binder as well. Internal heat dissipation in those applications can be a serious concern when combined with ambient temperatures, especially in space-constrained environments or in applications where thermal management is at a premium. Energy density is also limited by the thickness of active materials that a standard coating process with binder-containing slurry can yield. Finally, cost of electrode production is dramatically impacted by the slurry drying step, as strong solvents with high boiling point (e.g. NMP) must be used to dissolve polymer binders, and are difficult to evaporate.
Nanoramic has developed an alternate solution - Neocarbonix - an electrode platform technology that effectively replaces polymer binders and primers. Results have been demonstrated for both LIB cathodes and EDLC electrodes. Nanoramic's Neocarbonix electrodes have significantly lower ESR, better C-rate capabilities, greater active material thickness for improved energy density, while also retaining or improving specific capacity. Lifetime at high temperature is also significantly improved, because of the increased thermal and chemical stability of the electrodes.
Electrode production cost is also dramatically reduced, as the Neocarbonix process is solvent-agnostic. The solvent can be selected to speed up the drying process during coating, which dramatically improves the production throughput.
Improving Performance of Cation-Disordered Rocksalt Oxyfluoride Cathodes
Authors: Ahn Juhyeon , Chen Dongchang , Chen Guoying 
Published: December 2020

The development of next-generation rechargeable batteries requires cathode materials with elevated energy and power densities, increased lifespan and safety, as well as reduced cost. Lithium-rich cation-disordered rocksalt (DRX) compounds, composed of a redox-active transition-metal (TM) cation such as Mn3+ and a redox-inactive d
0 TM cation such as Ti4+, Nb5+ and Mo6+, are promising new cathode materials in meeting these requirements. The high capacity in this class of materials originates from the combined redox activities of Mn cations at lower voltages and oxygen anions at higher voltages, typically around 4.5 V. While the Mn redox process is fairly reversible, O redox often has limited reversibility which presents significant challenges in maintaining cathode cycling stability.
In this presentation, we report the excellent performance of a new Mn-rich DRX oxyfluoride cathode material based on the Li-Mn-Nb-O-F system. The phase-pure material was synthesized by using a fluoropolymer precursor in the solid-state reactions. The initial capacity contribution of the cathode was primarily attributed to Mn3+/Mn4+ redox with little O redox participation. The unique redox behavior, evidenced by the defined regions on the voltage profile (Figure 1a) and the dominating reduction peak near 3 V (Figure 1b), leads to a high discharge capacity and impressive cycling stability (Figure 1c). Stable cycling with a discharge capacity as high as 250 mAh g-1 was achieved. Combined with the high Mn content, the substitution of O anions with F likely increases the Mn migration barrier and consequently enhances overall stability.
Figure 1. Electrochemical performance of the Mn-rich DRX cathode: (a) charge and discharge voltage profile, (b) the corresponding differential capacity versus voltage profile, and (c) discharge capacity as a function of cycle number.

Figure 1
Silicon Nanoparticles in Li-Ion Batteries: Understanding the Role or Particle Size, Surface Oxidation, and Processing Conditions on Composite Electrode Longevity
Authors: Carroll Mike , Pach Gregory , Neale Nathan 
Published: December 2020

The high theoretical gravimetric charge density (4200 mAhr g-1), low lithium storage voltage (0 – 0.4 V vs Li metal), elemental abundance, and existing expertise in manufacturing make silicon a promising candidate as an anode material for next generation lithium ion battery (LIB) technology. However, broad adoption of silicon is limited by the rapid electrode failure associated with irreversible process related to repeated charge and discharging. Because of the extreme volume changes of the silicon active material with lithium alloying (~300% at Li3.75Si) the electrode experiences large mechanical stressors. In addition, the highly reducing environment upon lithium silicide formation forces chemical reactions between the active material and electrolyte and other electrode components which result in a heterogeneous interfacial layer called the silicon-electrolyte-interphase (SEI). The role and composition of the SEI is complex, however, the SEI is hypothesized to passivate the Si surface against additional parasitic reactions but is also prone to mechanical degradation from repeated cycling. These aspects of lithium storage in silicon slow the on-ramp of silicon in LIB anodes.
To begin to alleviate these irreversible processes in silicon-based electrodes we study the effect of silicon particle size, processing conditions, and electrolyte formulation on the electrode’s cycle stability, rate capability, and calendar life. We find that upon exposure to water, all silicon in our single-nanometer scale particles are oxidized to SiO2, which, we show, has no reversible lithiation capacity in the electrochemical potential window of normal silicon lithiation. We find a very strong relationship between the silicon particle size and the cycle stability, where, smaller silicon particles show a profound improvement on the capacity retention, but, due to the high surface area-to-volume ratio, also have an increased rate of reaction with the electrolyte. These results help to build a more comprehensive understanding on the role the electrode processing conditions and silicon particle size, and provide a foundation for additional work to improve the longevity of silicon in lithium ion battery devices.
(Invited) New Structural Design and Synthesis of Sulfur-Carbon Composite Materials for Lithium-Sulfur Batteries
Authors: Suk Jungdon 
Published: December 2020

The development of electric vehicles and smart grids necessitates the search for next-generation secondary batteries possessing increased energy densities, with the lithium-sulfur (Li-S) battery being one of the most promising candidates satisfying these demands. Specifically, Li-S batteries are promising energy storage and conversion systems owing to their high theoretical specific energy capacity (1675 mAh g-1) and energy density (2567 kWh kg-1) [1]. However, the practical use of Li-S batteries is hindered by their low specific capacity, low coulombic efficiency, poor rate capability, and poor cycling stability caused by the low conductivity of sulfur (5 x 10-30 S cm-1), dissolution of polysulfides (Li2Sx, 2≤ x ≤ 8) in the electrolyte and their redox shuttling/parasitic reactions and high volume expansion during discharge [2]. To overcome these drawbacks, many studies have focused on developing the design and materials of nanostructured host, electrolyte, interlayers, separators, additives, etc [3]. Interconnected three-dimensional frameworks comprising multi-walled carbon nanotubes, graphene, or carbon particles offer a combination of constituent advantages and can thus be used to achieve superior energy conversion and storage properties.
Herein, we designed and prepared various approaches for interconnected highly conductive carbon materials which enable to make sulfur composite materials for Li-S batteries. The resultant sulfur-carbon composite paper cathode exhibited high reversible specific capacity of 1386 mAhg-1, good rate capability up to 5C, and excellent cycling performance (a capacity retention 68% after 400 cycles), all of which are significantly improved from those of bare sulfur cathode or sulfur-GO composite only [5]. Rational design of cathode composition, structure, and a simple fabrication process can give insight into the development of various advanced cathode materials for high performance Li-S batteries.

References

[1] X. Ji, K.T. Lee, L.F. Nazar, Nat. Mater. 8 (2009) 500.
[2] Y. Yang, G.Y. Zheng, Y. Ciu, Chem. Soc. Rev. 42 (2013) 3018.
[3] Y.X. Yun, S. Xin, Y.G. Guo, L.J. Wan, Angew. Chem. Int. Ed. 52 (2013) 13186.
[4] H.J. Peng, J.Q. Huang, X.B. Cheng, Q. Zhang, Adv. Energy Mater. 7 (2017) 1700260
[5] J. Kim, Y. Kang, S.-W. Song, J. Suk, Electrochimica Acta 299 (2019) 27.
Improved Mass Transfer of Methyl Viologen By the Nitrate As Counter Anion for Aqueous Redox Flow
Authors: Jin Chang Soo , Jang Sang Soon , Park Se-Kook , Yeon Sun-Hwa , Jung Yoon Seok , Shin Kyoung Hee 
Published: December 2020

Among the redox active materials, viologen compounds are the most promising redox species, featuring the stable redox reaction MV2+/MV+ and the tunability of the substituents and counter anion, indicating that its electrochemical properties (i.e., diffusion coefficient and electron transfer rate constant) are significantly influenced by the substituents and counter anions[1-8]. Herein, we present the viologen compound employing nitrate as counter anion (MV2+*2NO3
-) as an aqueous redox active material. The MV2+ 2NO3
- was synthesized and characterized by elemental analysis, nuclear magnetic resonance (NMR) spectroscopy, and Raman spectroscopy, and then, the electrochemical properties were studied using cyclic voltammetry and rotating disk electrode techniques. Compared with MV2+ 2Cl- using chloride as the counter anion, which is commonly used an anolyte, it was demonstrated that MV2+ 2NO3
- featured fast mass transfer properties (D = 5.13 x 10-5 cm2 s-1) and comparable kinetics (Ket = 9.68 x 10-3 cms-1.

Reference

[1] B. Hu, Y. Tang, J. Luo, G. Grove, Y. Guo, T.L. Liu, Improved radical stability of viologen anolytes in aqueous organic redox flow batteries, Chemical communications 54(50) (2018) 6871-6874.
[2] B. Hu, C. DeBruler, Z. Rhodes, T.L. Liu, Long-cycling aqueous organic redox flow battery (AORFB) toward sustainable and safe energy storage, Journal of the American Chemical Society 139(3) (2017) 1207-1214.
[3] T. Liu, X. Wei, Z. Nie, V. Sprenkle, W. Wang, A total organic aqueous redox flow battery employing a low cost and sustainable methyl viologen anolyte and 4‐HO‐TEMPO catholyte, Advanced Energy Materials 6(3) (2016) 1501449.
[4] T. Janoschka, N. Martin, U. Martin, C. Friebe, S. Morgenstern, H. Hiller, M.D. Hager, U.S. Schubert, An aqueous, polymer-based redox-flow battery using non-corrosive, safe, and low-cost materials, Nature 527(7576) (2015) 78-81.
[5] B. Dunn, H. Kamath, J.-M. Tarascon, Electrical energy storage for the grid: a battery of choices, Science 334(6058) (2011) 928-935.
[6] P.M. Monk, N.M. Hodgkinson, Charge-transfer complexes of the viologens: effects of complexation and the rate of electron transfer to methyl viologen, Electrochimica acta 43(3-4) (1998) 245-255.
[7] P. Monk, viologens, Wiley1998.
[8] C. Bird, A. Kuhn, Electrochemistry of the viologens, Chemical Society Reviews 10(1) (1981) 49-82.
Synthesis and Electocatalytic Activity of MnO2/RuO2/Carbon Nanocomposites to Enhance Lithium-Oxygen Battery Performance
Authors: Nahm Kee Suk 
Published: December 2020

Lithium-oxygen battery has received much attention as a potential energy storage system because of its ultra-high theoretical energy density (5,200 Wh kg−1), which remains to be the most promising future technology. However, there are several scientific/technical hurdles that must be overcome in order for a rechargeable Li–air battery to be commercialized in the market. In particular, the incomplete decomposition of solid discharge products such as Li2O2 etc. formed during discharge process passivates the cathode surface by clogging pores of the porous carbon cathode, resulting in diminishing the overall performance of battery. In order to solve these issues, great effort has been devoted to designing and developing novel electrocatalysts. It has been reported that electrocatalysts play an important role in ORR and OER, and hence improve the kinetics and efficiency of the Li–air battery.
In this work, a suitable bifunctional catalyst was synthesized with MnO2 and RuO2, which are the well-known catalysts for oxygen reduction reaction(ORR) and oxygen evolution reaction(OER), respectively, by supporting on two different carbon supports such as graphite nanofiber(GNF) and graphene oxide(GO) for the application to oxygen cathode bifunctional catalysts of lithium-air batteries. MnO2/GNF was first prepared by a simple hydrothermal synthesis and was then decorated with various decorating ratios of RuO2 using a simple redox reaction technique. A good electrocatalytic performance was observed from a weight ratio of RuO2:MnO2/GNF=5:5. The Li-oxygen battery fabricated with the synthesized catalyst composition delivered a reduced overpotential with good cyclability and high specific capacity. In order to understand the effect of carbon, urchin-shaped α-MnO2/RuO2 nanostructures was first synthesized by a hydrothermal synthesis and was then loaded on GO with a weight ratio of 5:5 using a redox reaction technique. The synthesized α-MnO2/RuO2@GO (5:5) composite delivered high specific capacity with excellent electrocatalytic activity. Between the two different carbon supported composites, RuO2@MnO2/GNF showed excellent catalytic activity than α-MnO2/RuO2@GO. The increase in the surface area of carbon supports greatly influenced the performance of Li-air battery. Catalysts with carbon supports showed higher activity than without carbon. RuO2@MnO2/GNF was found to be the best catalyst which has two or tree times larger surface area than α-MnO2/RuO2@GO. Thus, RuO2@MnO2/GNF with 5:5 weight percentage was found to be the best electrocatalyst than all other synthesized catalysts.
Application of Stabilized Lithium Metal Powder (SLMP®) in Silicon Anodes for Advanced Lithium-Sulfur Batteries
Authors: Mahlendorf Falko , Meyer Thomas , Heinzel Angelika 
Published: December 2020

Silicon is a potential anode material for lithium-sulfur batteries. This future energy storage system has an essential higher energy density and significantly lower costs compared to lithium-ion batteries. However, a big problem by using silicon is the high volume expansion of 280 %. The volume expansion and contraction results in a break-up of the solid electrolyte interface (SEI). The SEI has to be reformed continuously during cycling, which leads to a continuous loss of lithium. One approach to compensate the lithium loss during cycling is the prelithiation of silicon anode with a stabilized lithium metal powder (SLMP
®
). SLMP can serve as an additional lithium source to mitigate the capacity loss during the first and the following cycles and improve the energy density significantly.
Adding SLMP directly into the slurry during electrode production is problematic because it is incompatible with many conventional electrode components. Therefore the application of SLMP on the finished electrode as an additional layer is advantageous. For this purpose, the SLMP can be mixed in a solvent and applied to the electrode. After drying, the SLMP must still be activated by a pressing process, since the protective carbonate shell must be broken open. One problem here is the rapid separation of SLMP and solvent. A possible solution is the addition of a binder, like styrene-butadiene rubber (SBR).
Here we present a silicon/graphene-based anode prelithiated with SLMP in the electrolyte systems 1 M LiTFSI, 0.2 M LiNO3 in dimethoxy ethane (DME) and 1,3-dioxolane (DOL). For this work, we used a commercially available Si/C composite material with a PAA binder. The silicon content of the electrode is 25 %. SLMP is loaded on the top of the electrode and activated by a pressing process. The advantage of a binder in the SLMP - solvent mixture will be shown, and also that the binder has no negative effect on the electrochemical properties. The electrodes are examined by galvanostatic cycling and show high coulomb efficiency of over 85 % in the first cycle. Also, the SLMP of the anode compensates the lithium loss over at least 300 cycles. We will show the improvements of the anode prelithiated with SLMP compared to pure Si/C anodes.
(Invited) Tensile Strain Engineering and Defects Management in GeSn Laser Cavities
Authors: EL Kurdi Moustafa , Elbaz Anas , Wang Binbin , Sakat Emilie , Herth Etienne , Patriarche Gilles , Pantzas Konstantinos , Sagnes Isabelle , Sauvage Sebastien , Checoury Xavier , Chelnokov Alexei , Reboud Vincent , Chretien Jeremie , Pauc Nicolas , Calvo Vincent , Boeuf Frédéric , Boucaud Philippe , von den Driesch Nils , Grützmacher Detlev , Hartmann Jean-Michel , Buca Dan 
Published: December 2020

We present GeSn material engineering to address both defect managements and band structure via tensile strain in laser cavities. We show that GeSnOI technologies allow to address both issues, with drastic reduction of power density thresholds in lasing devices at 2-3 µm wavelengths range.
First set of analysis were performed on GeSn micro-disks with removed defects from their active region. The GeSn layers, grown on Ge strain-relaxed-buffers (SRBs) on silicon, were etched into micro-disks cavities. A specific chemistry were used to remove the dense misfit dislocation array from the suspended area of the GeSn disk, which constitutes the laser gain media. We obtained reduced lasing thresholds from hundreds of kW/cm2, as commonly obtained in the literature at low temperature, to around 10 kW/cm2 in pulsed regime with Sn content as low as 7 % to 10.5 %.
In a second set of analysis we demonstrate a new approach relied on GeSn layers transfer on insulator, GeSnOI, with the aim to introduce SiNx stressor layers in an all-around geometry. [1,2] Tensile strain transfer from the stressor layers to GeSn micro-disks of 1.6% were reached, homogenously distributed in the disks volume. The defective interface were removed from the GeSn layer once it has been transferred on the host Si-substrate. This approach was applied to a GeSn layer with only 5.4% of Sn-content, which is nominally an indirect band gap semiconductor that cannot support lasing. The applied tensile strain transformed the Ge0.95Sn0.05 alloy into a direct-band gap material which support lasing with dramatically reduced thresholds, to 0.8 kW/cm2 at low temperature [3]. Tensile strain indeed yields to reduction of the valence band density of state by lifting the HH-LH degeneracy at the Γ-point, and thus contributes to reduce the lasing thresholds. The tensile strained GeSn lasers operate under continuous-wave-pumping up to 70 K thanks to further thermal management of the GeSnOI devices [3]. These results show the potential of new GeSn material engineering for future integration of laser sources on silicon platform using fully CMOS-compatible technology.
[1] M. El Kurdi, M. Prost, A. Ghrib, et.al. ACS Photonics 3, 443 (2016).
[2] A. Ghrib, M. El Kurdi, M. Prost, et. al. Adv. Opt. Mater. 3, 353 (2015).
[3] A. Elbaz et. al. Nature Photonics, March (2020) doi.org/10.1038/s41566-020-0601-5