bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mo2c Nanoparticle-CNT Composite Electrode for Lithium-Oxygen Battery
Authors: Kwak Won-Jin , Curtiss Larry , Sun Yang-Kook , Lau Kah Chun , Amine Khalil 
Published: February 2020

The five times higher energy density compared to conventional Li-ion batteries and its environment friendly reaction system make Li–O2 batteries a promising energy storage system. In spite of their great prospect, practical use of Li−O2 batteries still suffer many challenges such as low energy efficiency, poor rate capability and a poor cycle life. These problems are mainly attributable to excessive accumulation of discharge products (Li2O2), which induce poor reversibility and high polarization when they decompose during charging.1,2 Consequently, the number of operating cycles for Li−O2 batteries cannot yet match those of Li-ion batteries. Moreover, the energy efficiency (< 80%) of the present Li−O2 battery system is also too low. To improve the performance of Li−O2 battery systems, a key factor is finding ways to enhance the catalytic activity of the cathode for formation and decomposition of Li2O2, which is critical to decrease the polarization and increase the reversibility.3,4 Herein, we introduce well dispersed molybdenum carbide nanoparticles onto carbon nanotubes (Mo2C/CNT) as a cathode material for Li−O2 batteries. Mo2C could be a good catalyst for the oxygen evolution reaction (OER) in Li−O2 batteries and the carbon nanotubes could help the Mo2C nanoparticles be an ORR catalyst due to its electrical conductivity. In this report, a Mo2C/carbon nanotube composite as a cathode is demonstrated to reduce high over potentials during charge and improve the cycling performance of Li−O2batteries.

References

(1) Lu, Y. C.; Shao-Horn, Y. Probing the Reaction Kinetics of the Charge Reactions of Nonaqueous Li–O2 Batteries J. Phys. Chem. Lett.
2013, 4, 93-99.
(2) Xu, J. J.; Wang, Z. L.; Xu, D.; Zhang, L. L.; Zhang, X. B. Tailoring deposition and morphology of discharge products towards high-rate and long-life lithium-oxygen batteries Nat. Commun. 2013, 4, 2438-2449.
(3) Lu, J.; Lei, Y.; Lau, K. C.; Luo, X.; Du, P.; Wen, J.; Assary, R. S.; Das, U.; Miller, D. J.; Elam, J. W. et al. A nanostructured cathode architecture for low charge overpotential in lithium-oxygen batteries Nat. Commun.
2014, 5, 2383-2391.
(4) Li, F.; Tang, D. M.; Chen, Y.; Golderg, D.; Kitaura, H.; Zhang, T.; Yamada, A.; Zhou, H. Ru/ITO: A Carbon-Free Cathode for Nonaqueous Li–O2 Battery Nano Lett.
2013, 13, 4702-4707.
High Efficient Charge of Li-O2 Batteries with TEMPO Derivatives
Authors: Hase Yoko , Shiga Tohru , Mizuno Fuminori , Nishikoori Hidetaka , Iba Hideki , Takechi Kensuke 
Published: February 2020

Li-O2 batteries, in which Li2O2 is formed and decomposed on the cathode during discharge and charge, respectively, have attracted considerable attention as one of the future energy storage devices demanding high energy density. Recently, we demonstrated the Li-O2 battery employing a ionic liquid, N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium bis(trifluoromethanesulfonyl)imide (DEME-TFSI), as the solvent of the electrolyte. In this battery, little amount of parasitic reaction products were obtained after discharge because of specific stability of DEME-TFSI against O2 radicals which is well known as one of the major causes decomposing electrolytes in Li-O2 batteries. In addition, relatively lower over potential in charging (< 3.5 V vs. Li/Li+) was observed, whereas the charge capacity was limited to approximately 80% of discharge. According to the quantification analysis, the major causes of the irreversible capacity is Li2O2 remained in the cathode even after charge and parasitic products accompanied by charge process.
We, therefore, focused on redox mediators in order to accelerate the charge reaction. Recently, several redox compounds dissolved in the electrolyte of Li-O2 batteries are reported as redox mediators which make formation or oxidation of Li2O2 more effectively. In this study, we applied 4-methoxy-2,2,6,6-tetramethylpiperidine-1-oxyl (MeO-TEMPO) as a mediator because its oxidized compound, MeO-TEMPO+, stoichiometorically oxidizes Li2O2. In charge process, dissolved MeO-TEMPO was oxidized to MeO-TEMPO+ on the cathode that encouraged the oxidation of Li2O2 and obviously improved the rechargeability (Fig. 1). However, during the detailed investigation, we found that the mediator itself was deactivated along with the deterioration of the carbon cathode during charging; therefore, it is essential to avoid electrochemical oxidation of Li2O2 on the carbon for more efficient battery system.
In order to solve these problems, we have developed new strategy to decouple discharge and charge by chemical regeneration mechanism with mediator. In our new Li-air battery system, the charging process is totally different from an ordinary Li-air battery, and is a replacement of its electrolyte by that containing MeO-TEMPO+ oxidized (charged) separately in advance. Li2O2 in the discharged cathode is stoichiometorically decomposed by the MeO-TEMPO+ (chemical regeneration of cathode), while MeO-TEMPO+ is recovered to the original MeO-TEMPO after the reaction. This indirect charging mechanism promotes the decomposition of Li2O2 without potential electrochemical parasitic reactions and provides a significant improvement of the cycle life. At the same time, the decoupled charge/discharge processes makes more flexibility for the usage of the Li-air battery.

Figure 1
Dynamic Modeling of the Reaction Mechanism in a Li/O2 Cell: Influence of a Redox-Mediator
Authors: Grübl Daniel , Bergner Benjamin , Janek Jürgen , Bessler Wolfgang G. 
Published: February 2020

Interest and research in metal-air batteries is ongoing on a high level due to their high theoretical energy density and potential low-cost materials. Most research activities are performed in the field of lithium-oxygen chemistry with organic electrolytes. This system suffers high overpotentials during charge, indicating asymmetrical charge/discharge reaction mechanisms. High charge overpotentials low the energy efficiency and can increase potential-driven side reactions (e.g., electrolyte decomposition). In order to reduce charge overpotentials, the use of redox mediators has been proposed. Different redox mediators have been demonstrated, such as, TTF [1], LiI [2] and FePc [3]. Bergner et al. introduced 2,2,6,6-tetramethylpiperidinyloxyl (TEMPO) as redox mediator [4], which will be further investigated in the present study.
In order to further understand the mechanism of redox mediators, we present a continuum modeling study of a lithium-oxygen cell. The one-dimensional computational domain consists of a gas reservoir filled with oxygen, a porous carbon cathode flooded with an organic electrolyte, a porous separator, and a lithium metal anode. The model includes a detailed description of the electrochemistry in the cathode. During discharge, gaseous oxygen dissolves at the interface between the closed gas reservoir and the cathode (O2,gas ⇄ O2,dissolved). Following, a multi-step mechanism is implemented involving lithium superoxide as intermediate (Li+ + O2 + e– ⇄ LiO2), followed by the formation Li2O2 by chemical disproportion of LiO2 (2LiO2 ⇄ Li2O2 + O2). In the anode the metallic lithium reacts to lithium ions (Li ⇄ Li+ + e–). This mechanism is complemented by charge-transfer of the TEMPO redox mediator (TEMPO ⇄ TEMPO+ + e–), allowing for direct reduction of the lithium peroxide upon charge (Li2O2 + 2 TEMPO+ ⇄ 2 Li+ + O2+ TEMPO). The model is parameterized using experimental data [1]. Galvanostatic discharge and charge simulations reveal the advantage of using a redox-mediator. The electrochemical reaction mechanism and the crystal growth of the sodium superoxide within the cathode is quantified.

Figure
1
: Discharge (left) and charge mechanism involving a redox-mediator (right) in a Li-O2 cathode.
[1] Y. Chen, S. A. Freunberger, Z. Peng, O. Fontaine, P. Bruce, Nature Chemistry 5, 489 (2013).
[2] H.-D. Lim, H. Song, J. Kim, H. Gwon, Y. Bae, K.-Y. Park, J. Hong, H. Kim, T. Kim, Y. H. Kim, X. Lepró, R. Ovalle-Robles, R. H. Baughman, and K. Kang, Angew. Chem. 126, 4007–4012 (2014).
[3] D. Sun, Y. Shen, W. Zhang, L. Yu, Z. Yi, W. Yin, D. Wang, Y. Huang, J. Wang, D. Wang, and J. B. Goodenough, J. Am. Chem. Soc. 136, 8941–8946 (2014).
[4] B. J. Bergner, A. Schürmann, K. Peppler, A. Garsuch, and J. Janek, “TEMPO: A Mobile Catalyst for Rechargeable Li-O2 Batteries,” J. Am. Chem. Soc. 136, 15054–15064 (2014).

Figure 1
Platinum-Nickel (Pt3Ni) Alloy Nanoparticles Decorated Graphene As a Catalyst of Oxygen Electrode in Li-O2 Cells
Authors: Munichandraiah N , Kumar Surender , Scanlon L G 
Published: February 2020

Development of an appropriate bi-functional catalyst for reversible O2 electrode in rechargeable Li-O2 cells is a challenging task. Graphene is an emerging material for several applications owing to its unique properties. In the present study, Pt3Ni alloy nanoparticles anchored onto reduced graphene oxide (RGO) are prepared and investigated as catalyst for Li-O2 cells. For the preparation of Pt3Ni-RGO, commercial graphite powder is oxidized and exfoliated to form graphene oxide (GO). The required quantities of chloroplatinic acid and nickel chloride are dissolved in an aqueous suspension of GO and then reduced by NaBH4 so that the mass ratio of Pt3Ni to RGO is unity. Pt4+ and Ni2+ ions adsorbed on GO sheets undergo reduction simultaneously with the reduction of GO to form Pt3Ni nanoparticles decorated RGO. The formation and morphology of Pt3Ni-RGO are studied by using powder XRD and TEM. The microscopy image (Fig. 1) indicates the presence of alloy nanoparticles distributed over RGO sheets.
The catalytic activity of Pt3Ni-RGO is investigated by cyclic voltammetry and rotating disk electrode (RDE) studies in a non-aqueous electrolyte containing tetrabutyl ammonium perchlorate. Cyclic voltammograms recorded at several sweep rates consist of O2 reduction current peaks as well as oxygen evolution current peaks. Both peak currents increase with square root of sweep rate following the Randles Sevcik equation. The RDE studies provide diffusion limited current at several speeds of RDE. The data follow Levich and Koutecky-Levich equations. The values of number of electrons and diffusion coefficient of O2 calculated using these equations are 0.93 and 1.75 x 10-5 cm2 s-1, respectively.
Several Li-O2 cells employing Pt3Ni-RGO as the O2 electrode bi-functional catalyst are assembled and subjected to charge-discharge studies. The discharge capacity obtained at a current density of 0.3 mA cm-2 is 9016 mAh g-1 (8.36 mAh cm-2). It is seen that there is a decrease in discharge capacity initially on repeated charge-discharge cycling. Nevertheless, the discharge capacity stabilizes in a few cycles. The capacity obtained at the end of 10 cycles is 3641 mAh g-1 (3.27 mAh cm-2). Results of these studies will be presented.

Figure 1
Study on the Application of Ailicon-Cobalt Oxide Anode Material in Lithium-Ion Batteries
Authors: Liu Wen-Long , Wang Dong-Xia , Wu Meng-Qiang 
Published: February 2020

Silicon (Si)-based materials have the highest capacity among the investigated anode materials and have been recognized as one of the most promising materials for lithium-ion batteries. However, it is still a significant challenge to obtain good performance for practical applications due to the huge volume change during the electrochemical process. To date, the most successful strategy is to introduce other components into Si to form composite or alloy materials.
In this paper, using the etching technology, porous silicon was prepared, and the silicon and porous silicon were modified by chemical precipitation method. The surface morphology of the obtained material was analyzed by SEM and TEM, the crystalline was characterized by XRD, BET was used to measure the specific surface area and pore size distribution. The charge-discharge properties of the battery, in which lithium as the anode and the prepared materials as the cathode, were analyzed. Then the electrical characteristics were studied by cyclic voltammetry and AC impedance analysis method.
In the program of charge and discharge experiments of the Li (without modified)/Si battery, the discharge capacity was 2281 mAh g-1 in the first circle, and it will decreased to 555 mAh g-1 in the second circle, indicating the rate of decline up to 75.7%. The results show that the discharge capacitance of the prepared lithium battery using silica, which modified by 12% CoO, as the cathode materials were 3269 mAh g-1 and 2021 mAh g-1 in the first and second circle, respectively, the rate of decline was 38.18%, which is superior than other sample. Using porous silicon modified by variety of weight percentage as cathode materials for lithium batteries, the charge and discharge results showed that when the weight percentage of cobalt oxide fixed at 12% showed the best results, and the first and second discharge capacity was 3590 mAh g-1 and 2679 mAh g-1, respectively, the rate of the discharge capacity decrease was only 25.4%.
The cyclic voltammetry results showed that the peak current density of Li/Si-CoO (12%) battery was corresponding to the Li/Si system. According to the AC impedance analysis, we inferred the main reason for the decline in silicon battery in the process of continuous charge-discharge is the increase of impedance capacitance of charge transfer (R
ct). The R
ct of the Li/Si battery increased from 9.02 to 13.98 Ω at the end of first and fifth charge and discharge, however, the R
ct of the Li/Si-CoO(12.0%) was 4.52Ω, which is lower than that of the Li/Si battery. The reason may be the volume of expansion and contraction of silicon can be effectively slow down due to the addition of the cobalt oxide. On the other hand, the conductivity may be increased because of the formation of cobalt metal in the process of charge and discharge, which will improve the utilization rate of silicon materials and slow its capacity decline.
Characterisation of Si-Based Anodes for Li-Ion Batteries By Operando Dilatometry and Acoustic Emission Measurements
Authors: Tranchot Alix , Thivel Pierre-Xavier , Idrissi Hassane , Roué Lionel 
Published: February 2020

The replacement of graphite by silicon as the active material in negative electrodes of Li-ion batteries is very attractive since the specific capacity of Si is 10 times higher than that of graphite. However, Si suffers from huge volume variation (up to ~300% vs 10% for C) during its lithiation. This leads to the electrode cracking which induces electrical disconnections in addition to cause an instability of the solid electrolyte interface (SEI), resulting in poor cycle life and low coulombic efficiency.
A precise evaluation of the electrode volume variation and cracking upon cycling is thus crucial to develop more efficient Si-based anodes. To date, the study of their morphological changes is usually limited to post mortemexaminations by microscopy. This does not allow a detailed analysis of the morphological degradation process, which can significantly vary depending on the electrode composition and processing, and the charge/discharge conditions.
In the present study, the volume change with cycling of Si-based anodes is monitored by operando dilatometry experiments. For that purpose, a specific displacement transducer is used, which allows measuring expansion or shrinkage of the electrode during cycling down to the sub-micrometer range. Operando acoustic emission (AE) measurements are also performed to study the electrode cracking [1]. The AE technique is based on the detection and analysis of transient elastics waves generated by stress events. The influence of the cycling conditions and electrode formulation on the volume variation and cracking of Si-based electrodes is highlighted, and correlated to their electrochemical performance.

[1] A. Tranchot, A. Etiemble, P-X. Thivel, H. Idrissi, L. Roué In-situ acoustic emission study of Si-based electrodes for Li-ion batteries, J. Power Sources 279 (2015) 259-266.
Mesocellular Carbon Foam (MCF)/Sulfur Composites for High Performance Lithium Sulfur Batteries
Authors: Kim Hyung Sun , Jeong Tae-Kyung , Kim Yong-tae 
Published: February 2020

In this study, we introduce a mesoporous carbon with large pore volume (1.72 cm3/g) and bimodal mesopore structure (4 nm and 30 nm). Mesocellular carbon foam (MCF) was first synthesized by employing mesocellular silica as a template. After that, MCF was improved hydrophobicity thorough acid treatment to form stronger bonding between carbon and sodium thiosulfate pentahydrate (sulfur precursor). MCF/S composite was prepared by solution chemical deposition method (Sol-method). By Sol-method, sulfur of 73 wt.% was loaded in mesopore channels. As a result, the composite exhibited enhanced cyclability and retained a stable capacity of 820 mAh/g after 50 cycles.
The Effect of Lithium Iodide in Li-O2 Batteries
Authors: Lee Seon-Hwa , Kim Hee Min , Hirshberg Daniel , Sharon Daniel , Shin Hyeon-Ji , Aurbach Doron , Sun Yang-Kook 
Published: February 2020

Non aqueous Li-O2 battery would seem to be a most promising energy storage and conversion battery system. However, it has practical challenges such as solvent and electrode stability, pronounced overvoltage for oxygen evolution reactions, limited cycle life and poor rate capability. One of the strategies is the use of electrocatalysts. These were used to facilitate oxygen reduction, and the oxidation of the Li2O2 precipitate.1-2 One of the approaches suggested to the fast oxidation of Li2O2 is the use of redox mediators such as iodine. Redox mediators in electrolyte can easily be electrochemically oxidized and transfer electrons to Li2O2. The latter step considerably reduces the high over-voltage required to oxidize solid Li2O2. One of the redox mediators recently studied in Li-O2 batteries was iodine.3 Iodine and its reduced forms I3- and I- are soluble in polar aprotic solvent. Considering that upon oxidation iodide forms iodine which oxidation, which in turn catalyzes the oxidation of Li-peroxide, the development of Li–oxygen cells with LiI as an additive would look quite promising.4 At very low concentrations of LiI, the iodine formed serves as a redox mediator for Li2O2 oxidation, oxygen is reduced to Li2O2. However, in high concentrations of LiI, the presence of the salt promotes a side reaction that forms LiOH as a major product.

References

1. B. D. McCloskey, R. Scheffler, A. Speidel, D. S. Bethune, R. M. Shelby, and A. C. Luntz, J. Am. Chem. Soc., 2011, 133, 18038–18041.`
2. S. A. Freunberger, Y. Chen, N. E. Drewett, L. J. Hardwick, F. Bardé, and P. G. Bruce, Angew. Chem. Int. Ed. Engl., 2011, 50, 8609–8613.
3. H.-D. Lim, H. Song, J. Kim, H. Gwon, Y. Bae, K.-Y. Park, J. Hong, H. Kim, T. Kim, Y. H. Kim, X. Lepró, R. Ovalle-Robles, R. H. Baughman, and K. Kang, Angew. Chem. Int. Ed. Engl., 2014, 53, 3926–3931.
4. S. Meini, N. Tsiouvaras, K. U. Schwenke, M. Piana, H. Beyer, L. Lange, and H. A. Gasteiger, Phys. Chem. Chem. Phys., 2013, 15, 11478–11493.
A Study of Mg Intercalation Mechanism of a Prospective Mg Full Cell Design
Authors: Sa Niya , Burrell Anthony K. , Kinnibrugh Tiffany L. , Wang Hao , Key Baris , Chapman Karena W , Vaughey John T. , Proffit Danielle L. , Chupas Peter J , Fister Timothy 
Published: February 2020

A preliminary prospective full cell design composed of V2O5·xH2O as cathode with a Mg metal as anode is constructed where insertion and de-insertion of magnesium into V2O5·xH2O is fully reversible. An in-depth understanding of the Mg intercalation mechanism is investigated by pair distribution function analysis, x-ray absorption near edge structure (XANES) and 25Mg magic angle spinning (MAS NMR) spectroscopy. Interestingly, Mg intercalation results in the formation of multiple phases with different interlayer spacings. Our findings showed that the interlayer spacing of V2O5·xH2O contracts upon Mg intercalation and expands for de-intercalation. An in-depth MAS NMR reveals the existence of two magnesium environments and more interestingly, magnesium intercalation induced a more well-defined Mg-O environment.
Novel Mg Electrolytes for Rechargeable Mg Batteries Based on [Mg2(Î¼-Cl)2]2+ Cation
Authors: Li Guosheng , Cheng Yingwen , Stolley Ryan M , Han Keesung , Shao Yuyan , Liu Jun , Sprenkle Vincent 
Published: February 2020

An attractive path to increase energy storage capacities, lower the material costs, and improve operation safety involves the use of multi-valent elements with low reduction potentials. Key benefits of multi-valent systems over mono-valent (i.e. Li, Na) include (1) Increased electrons available per molecule that significantly impacts energy density characteristics. Potential candidates include magnesium (Mg) that can lose two electrons and aluminum three electrons, coupled with increased abundance and decreased production cost makes them viable alternatives for low cost energy storage. In this presentation, a novel [Mg2(μ-Cl)2]2+ cation complex, which is highly active for reversible Mg electrodeposition, was identified for the first time in this work. This complex was found to present in electrolytes formulated in dimethoxyethane (DME) through dehalodimerization of non-nucleophilic MgCl2 by reacting with either Mg salts (such as Mg(TFSI)2, TFSI= bis(trifluoromethane)sulfonylimide) or Lewis acid salts (such as AlEtCl2 or AlCl3).The electrolyte synthesis and understandings developed in this work could be insightful for rational formulation of a family of electrolytes with the general formula [Mg2(μ-Cl)2(DME)4][anion]x, and provide new opportunities for developing cathode materials, and therefore could be significant for practical Mg batteries.
Understanding the Initial Stages of Reversible Mg Deposition and Stripping in Non-Aqueous Electrolytes
Authors: Canepa Pieremanuele , Gautam Gopalakrishnan Sai , Malik Rahul , Rong Ziqin , Zavadil Kevin R , Persson Kristin A , Jayaraman Saivenkataraman , Ceder Gerbrand 
Published: February 2020

Rechargeable Mg batteries have been identified as a candidate storage system for the next-generation high energy density rechargeable batteries because of the possibility of pairing a non-dendrite forming Mg metal anode (~2.37 V vs. SHE) with high theoretical specific capacity (2205 A h kg-1) [1] with a Mg intercalation-based cathode. However, several daunting problems still prevent the realization of Mg-battery: (i) the limited selectivity of electrolyte systems that display reversible Mg deposition, (ii) the narrow electrochemical window of the electrolyte, (iii) lack of high-voltage cathode materials, (iv) irremediable interruption of the battery functions by passivation of the anode material. While it is well established that Mg can be deposited reversibly from complex ethereal solutions of Mg-Chloro complex reagents, the stripping/deposition mechanism at the anode is still debated [2,3]. In this talk we present a detailed atomistic DFT study of the interaction of solvent molecules i.e. THF, and the salts (Mg-Chloro complex) when in contact with Mg-anode surfaces, focusing on the competitive absorption of these chemical species at the interface [4]. Ab initiomolecular dynamics results will complement adsorption calculations providing a better understanding of the morphology of the electrolyte/anode interface. These models are essential to clarify the challenging electron-transfer mechanism occurring at the electrode/solvent interface [4].
References:
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50, 243–245 (2014).
[4] P. Canepa, G. S. Gautam, R. Malik, S. Jayraman, Z. Rong, K. R. Zavadil, K. Persson, G. Ceder, Chem. Mater. 10.1021/acs.chemmater.5b00389