bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrodes for Sodium-Ion Batteries with Excellent Rate Performance Using Porous Carbon Networks
Authors: Yu Yan , Fu Lijun , Zhu Changbao , Li Weihan , Maier Joachim
Published: February 2020

Recently, sodium ion batteries (NIBs) gained increasing attention, because of its abundant reserves and relatively even geological distribution. However, the development of NIBs is greatly hampered because of the lack of appropriate active materials for both cathodes and anodes. Since the Na ion is ca. 55% larger than the Li ion, finding suitable host materials with sufficiently large interstitial space to accommodate sodium ions and to allow reversible and rapid ion insertion and extraction is very difficult. NASICON-type Na3V2(PO4)3 has recently been considered as a prospective cathode material for NIBs, because of its highly covalent 3D framework crystalline structure, high energy density (~400 Wh/kg) and good thermal stability. For anode materials, disordered carbon is particularly attractive because of their large interlayer distance and disordered structure that could accommodate sodium ions.

Here, we briefly present porous carbon based electrodes for NIBs with excellent rate performance: (1) Carbon-coated nanosized Na3V2(PO4)3 embedded in the porous carbon matrix (abbreviated as CC-NVP@PCM); (2) Nitrogen-doped activated porous carbon fibers (ACFs); (3)Flexible free-standing porous carbon nanofibers (P-CNFs) with three-dimensional (3D) interconnected structure.

The CC-NVP@PCM was prepared by using a facile soft-chemistry based method with post heat-treatment. It shows high rate performance (44 mAhg-1at 200C ). This ultrahigh rate performance is comparable to that of supercapacitor, but with much higher energy density.

The ACFs were synthesized by pyrolysis of Ppy nanofiber precursor. It shows excellent capacity retention and extraordinary rate performance. The reversible capacity at 0.05 Ag-1 is 296 mAhg-1 and could still maintain as 72 mAg-1 at a current of 10 Ag-1.

In case of the P-CNFs electrode prepared by electrospinning, it delivers a reversible capacity of 266 mAh.g-1 after 100 cycles at 0.2C, corresponding to 80.3 % of the initial charge capacity. When cycled at a current density as high as 500 mAg-1 (2C), it still delivers a reversible capacity of ~140 mAh.g-1after 1000 cycles.

The improvement of electrochemical performance of these porous carbon based electrodes for NIBs is attributed to the special design and porous structure, which confined a variety of advantages: hierarchical porous channels enabling short transport length for ions and electrons, carbon coated structure resulting in low resistances, good mechanical properties leading to the excellent morphology stability.
Na-Ion Mobility in Layered Na2FePO4F and Olivine NaFePO4
Authors: Wood Stephen M , Tripathi Rajesh , Nazar Linda F , Islam M. Saiful
Published: February 2020

Materials for sodium-ion batteries are attracting renewed interest. Olivine NaFePO4 and layered Na2FePO4F are interesting materials that have been reported recently as possible positive electrodes. Here, we report their Na-ion conduction behaviour and intrinsic defect properties using atomistic simulation methods.[1,2] In the NaFePO4 olivine, Na ion migration is essentially restricted to the [010] direction along a curved trajectory, similar to that of LiFePO4, but with a lower migration energy. However, Na/Fe antisite defects are also predicted to have a lower formation energy: the higher probability of tunnel occupation with a relatively immobile Fe2+ cation – along with a greater volume change (17%) on redox cycling – contributes to the poor electrochemical performance of the Na olivine. Na+ ion conduction in Na2FePO4F is predicted to be two-dimensional (2D) in the interlayer plane with a similar low activation energy. The antisite formation energy is slightly higher; furthermore, antisite occupation would not impede transport significantly owing to the 2D pathway. This factor, along with the much lower volume change (3.7%) on redox cycling, is undoubtedly responsible for the better electrochemical performance of the layered structure.

[1] R. Tripathi, S.M. Wood, M.S. Islam and L.F. Nazar, Energy and Envrion. Sci., 2013, 6, 2257-2264

[2] M.S. Islam and C.A.J. Fisher, Chem. Soc. Rev., 2014, 43, 185-204
Improvement of High Voltage Cyclic Performance By Novel Binder for High Energy Lithium Ion Battery Application
Authors: Kaneko Mayumi
Published: February 2020

Introduction

Lithium-ion batteries (LIB) have been used as high density storage devices for several kinds of applications. Higher energy density and higher durability are required for use of high-performance energy devices. Among various attempts to improve energy density of LIB, technologies which increase battery voltage have emerged as a viable solution.

Binder affects electrochemical performance reaction directly because it exists near the active materials. In a previous report, Co-ion dissolution and Co3O4 formation were observed in the electrode with PVdF (Polyvinylidene fluoride) [1].

In this study, we clarified the degradation mechanism of cathode electrode that contain PVdF binder.

Experimental

The cathode electrodes consisted of LiCoO2, acetylene black, and PVdF. The performance tests were investigated in 40mAh laminate type lithium ion cells. The cycle life test was performed at 4.2V or 4.4V. Solid F-NMR of electrode was used for the analysis of binder degradation after cycle test.

Thin-film electrode of LiCoO2 was fabricated on Au substrate by rf-sputtering method [2]. X-ray diffraction pattern indicated that high crystalline LiCoO2 thin-film electrode was prepared. Binders were spin-coated on the thin-film electrode. Three-electrode cell was used for electrochemical measurements of LiCoO2 thin-film electrode. The electrochemical properties of LiCoO2 thin films were investigated by cyclic voltammetry (CV)

Results

Figure 1 shows cycle performance at each cut-off voltage. Cycle performance was dramatically decreased at high cut-off voltage. Figure 2 shows the cyclic voltammograms of LiCoO2 thin-film electrode coated with PVdF in LiClO4/EC/DEC at 60°C. Around 3.9 V, peaks of lithium-ion de-intercalation /intercalation were observed. With cycling, redox currentsgradually decreased and redox voltage shifted. This result suggested the degradation of LiCoO2.

We evaluated the structure change of LiCoO2 after cycle test by TEM spectroscopy. From the TEM spectroscopy, degradation of surface structure was observed at the electrode after cycle test. From the F-NMR, structure of PVdF was slightly changed after the cycle test. It is suggested that PVdF increased the reactivity of active material. From ICP measurements, the amount of metal precipitation on anode was also increased after cycle test. And adhesion strengths wassignificantly decreased after cycle test.

In our presentation, we will show a new type of water-based binder developed by Zeon which can contribute to improvement of cell performance, such as improved cycling performance.
P2 Structure Sodium Manganese Oxides for Na-Ion Batteries
Authors: Billaud Juliette Marie , Singh Gurpreet , Armstrong Anthony Robert , Gonzalo Elena Candida , Roddatis Vladimir , Armand Michel , Rojo Teofilo , Bruce Peter G.
Published: February 2020

Lithium ion batteries have dominated the world of portable electronic devices over the past two decades and are making their way into the electric vehicle market due to their high energy density. However, recently sodium ion batteries have regained the interest of the scientific community due to the high and uniform abundance of sodium across the world and consequent low cost compared to lithium, making them attractive for grid storage. Various electrode materials have been studied for sodium ion batteries. Layered oxides, NaMO2, where M is one or more transition metals, represent an attractive class of cathodes for Na batteries. Here we show that Na0.67MnO2 with the P2 structure, Fig 1, exhibits a high capacity (175 mAhg-1), close to the best reported for a Na cathode, and with good capacity retention, in contrast to previous studies of Na0.67MnO2 where the capacity faded rapidly.1 Due to the presence of Jahn–Teller active Mn3+ in Na0.67MnO2, the structure undergoes various structural transitions during sodiation/desodiation leading to many voltage steps in the charge/discharge profile.1-3 We have investigated reducing the phase transitions by substituting Mn3+ ions with electrochemically inactive dopant ions, which have a strong preference for octahedral sites in the layered oxide framework. This leads to the formation of a highly stable framework that shows a smooth charge/discharge profile with very low polarization even for a substitution level as low as 5%, Fig. 2, and a capacity of ~ 175 mAhg-1. Such an observation is significant for the future development of sodium ion battery cathode materials.

Lattice parameters of all the substituted compositions could be refined using hexagonal (P63/mcm) and orthorhombic (Cmcm) space group symmetries, whilst the situation pertaining to Na0.67MnO2 samples proved more complex.

References

[1] A. Caballero, L. Hernan, J. Morales, L. Sanchez, J. Santos Pena and M. A. G. Aranda, J. Mater. Chem., 2002, 12, 1142.

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

[3] X.F. Wang, M. Tamaru, M. Okubo and A. Yamada, J. Phys.
Chem. C, 2013, 117, 15545.
New Iron Sulfate Based Compounds as Positive Electrode Materials for Li-Ion Batteries
Authors: Rousse Gwenaelle , Lander Laura , Reynaud Marine , Tarascon Jean-Marie
Published: February 2020

Electrochemical storage has become an integral part of our mobile society and great hopes are being placed in Li-ion batteries to meet future demands dictated by the upcoming electric vehicle (EV) and grid application markets. Batteries with greater autonomy and built from materials having minimal environmental footprint need to be developed. This calls for both innovative chemistry and new concepts. Currently battery researchers are turning their attention to the design of polyanionic electrodes made of abundant elements. Sulfate chemistry has been a fertile ground with the recent discovery of many sulfates compounds such as AMSO4
X (A = Li, Na, K; M = Fe, Mn, Ni, Co; X = F, OH).1 Among them, the triplite form of LiFeSO4F presents an electrochemical activity at 3.9 V vs. Li+/Li, with a decent capacity. Inspired by minerals,2 we also reported a fluorine-free sulphate compound Li2Fe(SO4)2, whose structure was solved from powder diffraction data: the monoclinic marinite structure is built upon FeO6 octahedron and SO4 tetrahedron forming an open framework into which lithium ions can move. The redox voltage of Li2Fe(SO4)2 competes with the one of triplite: 3.83 V vs. Li+/Li.3

In this talk, we will report on a new polymorph of Li2Fe(SO4)2, whose structure is orthorhombic (Figure 1). This polymorph can be prepared at room temperature via a ball-milling route, and it transforms into the marinite monoclinic form on heating. This new form is also electrochemically active via two plateaus located at 3.85 V and 3.73 V vs. Li+/Li, as it will be reported in a publication we have submitted very recently. Although the capacity displayed by these sulfates is too low to be implemented in real applications, these materials constitute model compounds to understand the interplay between redox voltage and structural arrangement. They also give hints about the feasibility of using high-voltage Fe-based compounds as positive electrodes in secondary Li-ion batteries. Lastly, we will mention how and why these compounds, which wereinitially studied for their performances as electrode materials, can also be interesting for their physical properties, especially for the magnetic ones that we studied from neutron powder diffraction.4

1. Rousse, G. & Tarascon, J. M. Sulfate-Based Polyanionic Compounds for Li-Ion Batteries: Synthesis, Crystal Chemistry, and Electrochemistry Aspects. Chem. Mater.130919065413003 (2013). doi:10.1021/cm4022358

2. Reynaud, M. et al. Design of new electrode materials for Li-ion and Na-ion batteries from the Bloedite mineral Na2Mg(SO4)2•4H2O. J. Mater Chem A, asap (2014).

3. Reynaud, M. et al. Li2Fe(SO4)2 as a 3.83V positive electrode material. Electrochem. Commun.
21,77–80 (2012).

4. Reynaud, M., Rousse, G., Chotard, J. N., Rodriguez-Carvajal, J. & Tarascon, J. M. Marinite Li2M(SO4)2 (M = Co, Fe, Mn) and Li1Fe(SO4)2: model compounds for super−super exchange magnetic interactions. Inorg. Chem.
52, 10456–10466 (2013).
Cathode Powder Surface Treatment Using Atmospheric Pressure Plasma
Authors: Seok Dong Chan , Jeong Hyeon Yeong , Jung Yong Ho
Published: February 2020

LiOH, Li2CO3 impurities of NCM (8:1:1) Li ion battery cathode powder were removed by using atmospheric pressure plasma. Specially designed plasma reactor was used for the study. The mixed gas of N2, H2, CH4, SF6 and NF3 was used for dielectric barrier discharge plasma generation. N2-SF6 and N2-NF3 mixed gas plasma showed the best removal performance and when the SF6 or NF3 content was increased, the removal efficiency was also increased with a plateau. Addition of a small amount of hydrogen containing gas such as H2 and CH4 into the plasma enhanced the impurity removal efficiency but the proportional relationship with the content increment with these gases was not shown. It is well known that the fluorine containing gas extinguishes plasma, however the hydrogen containing gas seems attenuated the extinguishing effect of the fluorine containing gas for this case. In the early stage of the study, the cathode powder was treated by direct contact with the plasma, however, it was also observed that the same removal effect was shown by just mixing the powder with the gas passed through the plasma generator. The plasma treatment of 3kW applied power could remove more than 50% of impurities from the NCM powder at 13kg/hr of the treatment speed. In the same impurity removal treatment condition, it was observed that fluorine passivation layer was formed on the surface of the cathode particle at the same time. Other than the impurity removal and fluorine passivation on the cathode active material, the atmospheric pressure plasma powder treatment can offer the solution for enhancement of dispersion property in making powder slurry and carbon adsorption on the active material surface etc.
3D Nanostructured Binder Free Electrodes for Novel Energy Storage Devices
Authors: Zhou Haitao , Wang Xuehang , Sheridan Edel , Chen De
Published: February 2020

Energy-storage technologies, including supercapacitors with high power density and rechargeable batteries with high energy density, have attracted significant attention for applications in electric vehicles, power line conditioners, and load leveling of solar energy and wind power. However, for such applications, the demand for both high power density and energy density devices is becoming increasingly important. Thus, novel hybrid energy storage devices combining the advantages of supercapacitors and batteries is becoming a hotstopic in the energy storage research field. In previous work, the 3D nanostructured binder free electrodes have been shown to deliver high discharge capacity and excellent rate capability, which were assessed using Li-ion half cells [1-4], indicating that energy storage devices with high energy and power density may be achieved using such kinds of 3D electrodes. In this work, novel Li-ion full cells and supercapacitors were designed and fabricated using MnOx-based 3D electrodes, a manganese oxides based Li-ion full cell is shown in Figure 1a-c. The electrochemical performances of the different energy storage devices were assessed using a 3-electrode cell, as shown in Figure 1 d-f. The maximum energy density of the manganese oxides based Li-ion full cell is 223 Wh/kg at 146 W/kg. The Sn and Si based 3D anodes were also prepared and assessed using both Li-ion half cells and Li-ion full cells.

Figure 1 (a)
Figure 1 (b)
Figure 1 (c)

Figure 1 (d)
Figure 1 (e)

Figure 1: (a) Scheme of the manganese oxides based Li-ion full cell. S(T)EM images of the nanostructured LiMn2O4 cathode material (b) and the 3D C/MnOy/ACNTs anode materials (c). Two- and three-electrode charge (d) and discharge (e) voltage profiles of the manganese oxides based Li-ion full cell utilizing Li metal reference.

References

[1] Lou, F. et al. (2013) Journal of Materials Chemistry A, 1 (11), 3757-3767.

[2] Lou, F. et al. (2013) Journal of Energy Chemistry, 22 (1), 78-86.

[3] Lou, F. et al. Chemsuschem, accepted

[4] Zhou, H. et al. (2013) Nanotechnology, 24 (43), art. no. 435703.
Cycling Stability of Flexible Positive Electrodes for Li-Ion Batteries Using Nano-Fibrillated Cellulose As a Binder
Authors: Lu Huiran , Behm Mårten , Cornell Ann , Leijonmarck Simon , Lindbergh Göran
Published: February 2020

Li-ion batteries are the most important power source in the application of portable electronics. Flexible Li-ion batteries attract increasing interest and could be very useful in bendable and wearable electronic devices. Nano-fibrillated cellulose (NFC), a renewable material, is a promising candidate as a binder for flexible Li-ion batteries, with good mechanical properties. They can be produced using a water-based paper making process, avoiding the use of toxic solvents. Recent work has shown capacity fading during repeated cycling of the paper based Li-ion batteries, and the traces of moisture in the NFC may be the cause for this degradation[i],[ii]. In the present work, the cycling stability of flexible positive electrodes (Fig. 1) for Li-ion batteries using NFC as a binder is investigated and discussed as function of electrode drying conditions, mainly the time and temperature. Preliminary results show that the cells with longer drying time of the NFC-based electrode obtains a better cycling performance at C/10, as well as a higher coulombic efficiency.

[i] S.Leijonmarck, et al. Flexible nano-paper-based positive electrodes for Li-ion batteries-Preparation process and properties, Nano Energy, 2013, 2, 794–800.

[ii] S.Leijonmarck, et al. Single-paper flexible Li-ion battery cells through a paper-making process based on nano-fibrillated cellulose, Journal of Materials Chemistry A, 2013, 1, 4671-4677.
Effect of F-Doping on the Cycling and Structural Stability of li[Li0.2Mn0.534 Ni0.133Co0.133]O2 Cathode for Li-Ion Batteries
Authors: Gu Haitao , Wang Ke , Xie Jingying , Xie Chaoxiang , Zhou Xinbing , Jian Dechao
Published: February 2020

In recent studies, the layered composites with Li2MnO3 and LiMO2 have become as the promising cathode materials for lithium ion batteries due to the high capacity of around 250 mAh/g with a lower cost and better safety in comparison with LiCoO2.

In this study, a PAAM(Polyacrylamide)-assisted carbonate co-precipitation method was attempted to prepare the spherical Li[Li0.2Mn0.534 Ni0.133Co0.133]O2 cathode material. With the F-doping, the particle size of Li[Li0.2Mn0.534 Ni0.133Co0.133]O1.95F0.05 decreased, which was beneficial for the electrochemical properties. After 80cycles at 0.05C, the capacity was 259 mAh/g and the retention was 90% for Li[Li0.2Mn0.534 Ni0.133Co0.133]O1.95F0.05. After 200 cycles at 0.1C, 0.2C and 0.3C, the retention was 94%, 93% and 95%, respectively. The cycling properties was improved obviously with F-doping. From the results of synchrotron radiation XRD, the structures were changed with the temperature from the ambient temperature to 500 °C for Li[Li0.2Mn0.534 Ni0.133Co0.133]O2. But no structural changes were observed for Li[Li0.2Mn0.534 Ni0.133Co0.133]O1.95F0.05. Hence, the structural stability was improved further with F-doping.
Germanium Nanowire Based Lithium-Ion Anode Exhibiting a Stable and High Capacity Over 1000 Cycles
Authors: Kennedy Tadhg , Mullane Emma , Geaney Hugh , Osiak Michal , O'Dwyer Colm , Ryan Kevin M
Published: February 2020

Ge nanowire (NW) based materials have emerged as viable candidates for next generation rechargeable lithium-ion battery anodes with energy and power densities that are multiples of current graphitic based electrodes.1-3 The key advance is the capability of NWs to overcome the well-known pulverization problem that is detrimental to the cycle life and hence viability of their bulk counterparts. NWs also provide good electrical conductivity along their length, have a high interfacial area in contact with the electrolyte, have an optimal short diffusion distance for Li-ion transport and can be grown directly from current collectors, eliminating the need for binders and conductive additives 4,5 Here we demonstrate stable cycling over 1100 cycles of Sn seeded Ge NWs grown directly from a current collector via a solvent vapour growth system. We show by ex-situ high-resolution transmission electron microscopy and high-resolution scanning electron microscopy studies that the NW array transforms into a robust, porous network structure within the first 100 cycles.6 Once this network is formed it is highly stable, maintaining a capacity of ̴ 900 mAh/g over the following 1000 cycles. The electrolyte additive, vinylene carbonate (VC), was found to play an important role, facilitating the formation of this stable network morphology. The electrode material described here has several advantages as it is formed in a low energy, wet-chemical process with Ge NWs nucleating and growing from an evaporated Sn layer on stainless steel. Sn also has a high maximum theoretical capacity and we show both physically (HRTEM) and electrochemically (differential capacity plots) that the Sn seeds at the end of the NWs reversibly alloy with lithium and contribute to the electrodes overall specific capacity. The NW electrode architecture performed exceptionally well in rate capability tests achieving a discharge capacity of 435 mAh/g after 80 cycles at a discharge rate of 100C. Considering the low cost and low energy required, especially when compared with CVD systems, we believe our synthetic protocol to be an attractive and scalable synthesis approach for high-performance group IV nanowire based electrodes.

Chan, C. K.; Zhang, X. F.; Cui, Y. Nano Lett.
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Kennedy, T.; Mullane, E.; Geaney, H.; Osiak, M.; O’Dwyer, C.; Ryan, K.M. Nano Lett.
2013, DOI:10.1021/nl403979s
Enhanced Cycle Performance in a Binder Free Lithium Sulfur Battery Using Few-Layer Graphene Foam Scaffold
Authors: Xi Kai , Kidambi Piran R , Peng Xiaoyu , Ducati Caterina , Hofmann Stephan , Kumar Vasant R
Published: February 2020

A lithium-sulfur (Li-S) battery has a high theoretical specific capacity (1675 mAh g-1 of elemental sulfur) and a high nominal energy density (2500 Wh kg-1 of cell weight), which offers the prospect of a significant energy density improvement compared to the mainstream lithium-ion batteries (150 Wh kg-1). However, the development of Li-S battery technology has been plagued by problems arising from the highly insulating nature of sulfur (5×10-30 S cm-1 at 25 °C), the high solubility of lithium polysulfides in the electrolyte and volumetric expansion of sulfur during lithiation. Here, we demonstrate the design and preparation of few-layer graphene (FLG) foam scaffold for sulfur loading to fabricate cathode structures for lithium-sulfur batteries.

In this work, a free-standing FLG monolithic network foam was formed as a negative of a Ni metallic foam template by CVD followed by etching away of Ni. Then, a three-dimensional (3-D) cathode system for lithium sulfur (Li-S) batteries has been synthesised by loading sulfur on to this interconnected network of few-layered graphene (FLG) via a sulfur solution infiltration method. This cathode system did not require any additional binding agents, conductive additives or a separate metallic current collector thus decreasing the weight of the cathode by typically ~20-30 wt%. A Li-S battery with the sulfur/FLG foam cathode shows good electrochemical stability and high rate discharge capacity retention for up to 400 discharge/charge cycles at a high current density of 3200 mA g-1, which due to the FLG foam offers excellent electrical conductivity, an appropriate pore structure for containing the electro-active sulfur and facilitates rapid electron/ion transport. Even after 400 cycles the capacity decay is only ~0.064% per cycle relative to the early (e.g. the 5th cycle) discharge capacity, while yielding an average columbic efficiency of ~96.2%. To further understand the sulfur loading ability of FLG foam, the composites with high content (up to 72 wt %) were also investigated. The composite with high content of sulfur still presented good initial discharge capacity and good cycle stability after 200 cycles. Our results indicate the potential suitability of graphene foam for efficient and high-performance batteries.
Development of a High Temperature PEO-Based Li-O2 Battery
Authors: Balaish Moran , Ein-Eli Yair
Published: February 2020

Li-air battery has the potential of becoming the ultimate power source among all electrochemical energy conversion and storage configurations derived from lithium chemistry. Unfortunately, current configurations, mostly based on a non-aqueous organic liquid electrolyte, suffer from numerous challenges, namely high electrolyte volatility, electrolyte decomposition, low cycle-life, low discharge rates and high discharge/charge over-potential. A very appealing Li-air configuration is obviously one which sees the use of a solid, solvent-free, electrolyte, such as those formed by combining poly(ethylene oxide), PEO, and a lithium salt. Polymer electrolytes are well known promising materials for high energy density rechargeable batteries. Polymer electrolytes poses several advantages over liquid based electrolytes systems, in terms of high chemical, thermal and electrochemical stabilities, all of those are important factors for batteries in number of applications, ranging from portable electronics to electric vehicles. However, wide use of solid polymer electrolyte is still prevented by the decay in ionic conductivity (10-7 to 10-5 S cm-1 at room temperature), resulting from low ionic mobility, high degree of polymer matrix crystallinity, and low degree of charge separation in addition to ion association. We hereby offer a new Li-air battery configuration, based on the well-investigated PEO- lithium salt electrolyte system. The Li-air battery will be comprised of a lithium metal anode, a highly Li+ conductive, oxygen permeable PEO-based, lithium polymer electrolyte and a high surface area carbon air cathode. As opposed to current lithium polymer electrolytes, which operate at room temperature and suffer from low ionic conductivity, the new proposed configuration will operate at a high temperature of 80°c. Above 70°c PEO predominantly exists in the amorphous state, thus a practically useful conductivity is easily achievable in the temperature range of 70-95°c. Our Li-air cell is discharged/ charged at high temperature, thus enabling better kinetics, resulting in high current densities and lower over-potential. The system is studied by electrochemical methods as well as spectroscopic ones.

The results of this work will contribute to the development of practically viable Li-air batteries.
Graphene Quantum Dots (GQDs) Surface Functionalization to Enhance the Cycle Stability and Electron Path on Lithium Sulphur Batteries
Authors: Park Jungjin , Kim Kwi Ryong , Lee Kyung Jae , Yu Seong-Ho , Chung Dong Young , Sung Yung-Eun
Published: February 2020

Recently, sulphur has been considered as a promising material lithium rechargeable battery cathode due to a superior specific capacity of 1672 mAh/g to other traditional metal oxides/phosphates cathodes, abundant resources, low cost, and environmental friendliness. Despite these advantages, it has been faced with rapid capacity fading due to dissolution of polysulphides and precipitation of lithium sulphides. Furthermore, low electrical conductivity of sulphur leads to low utilization of the active materials as a sulphur electrode. To make up for the weak points of lithium sulphur batteries, many researchers have studied various methods to overcome these problems by controlling matrix and additive of liquid electrolyte. In this study, graphene quantum dots (GQDs) were used to surface functionalizer that were able to support electron path and alleviate polysulphides dissolution, which have a role in conducting agents and various functional additives, results in high specific capacity and good cycle ability in lithium sulphur batteries.
Functional, Water-Soluble Binders for Improved Capacity, Rate Capability and Stability of Lithium-Sulfur Batteries
Authors: Lacey Matthew , Jeschull Fabian , Edström Kristina , Brandell Daniel
Published: February 2020

In recent years, great strides forward have been made in increasing the practical capacity and cycle life of the lithium-sulfur system. Many of the strategies currently pursued involve optimisation of the conductive host structure, in order to maximise sulfur utilisation; coupled with some form of encapsulation of the active material, to mitigate capacity fade due to the well-explored reactions of polysulfide intermediates at the anode[1,2].

Recently, our group has investigated the use of functional polymers as binders in this system, particularly poly(ethylene oxide) (PEO)[3] and mixtures of PEO and poly(vinylpyrrolidone) (PVP)[4]. PVP has recently been similarly investigated elsewhere[5]. We have identified that a binder of 4:1 PEO:PVP can significantly improve the capacity, rate capability and stability of Li-S cells compared to conventional alternatives, e.g., PVdF. We have used galvanostatic cycling and impedance spectroscopy (IS) to determine that these improvements are most likely due to the influence of the polymer functionality on the chemistry of polysulfides in the electrolyte near the electrode surface.

These commodity polymers are inexpensive, water soluble, environmentally friendly and widely available, making them particularly interesting for mass production of Li-S cells. Through this simple approach we can demonstrate reversible capacities in excess of 1000 mAh g-1 for cathodes with total sulfur content of at least 58%.

Figure: comparison of different water-soluble binders: left) cycling of simple Li-S cells based on Super P host with 50% total sulfur loading at C/5; right) first discharge of Ketjen Black-based composites with 58% sulfur loading at C/50.

References:

[1] X. Ji, K. T. Lee, L. F. Nazar, Nat. Mater.
2009, 8, 500.

[2] X. L. Li, Y. L. Cao, W. Qi, L. V Saraf, J. Xiao, Z. M. Nie, J. Mietek, J. G. Zhang, B. Schwenzer, J. Liu, J. Mater.
Chem.
2011, 21, 16603.

[3] M. J. Lacey, F. Jeschull, K. Edström, D. Brandell, Chem. Commun.
2013, 49, 8531.

[4] M. J. Lacey, F. Jeschull, K. Edström, D. Brandell, submitted.

[5] Z. W. Seh, Q. Zhang, W. Li, G. Zheng, H. Yao, Y. Cui, Chem. Sci.
2013, 4, 3673.
Nickel(II)-1,4,8,11-Tetraazacyclotetradecane As a Single Electrolyte Component for Non-Aqueous Redox Flow Batteries
Authors: Kim Hyun-seung , Yoon Taeho , Jang Jihyun , Mun Junyoung , Hwang Hongseo , Ryu Ji Heon , Oh Seung M.
Published: February 2020

Energy storage systems (ESSs) are required for stable electricity supply from power plants and efficient usage of generated electricity. ESSs are also needed to accommodate fluctuations in renewable energy generation. Redox flow batteries (RFBs) are considered as one of the reliable choices for ESSs.

Since 1970s, RFB technologies have been developed mainly on the basis of aqueous electroytes, which show a critical drawback; limited working voltage (< 1.23 V) due to a narrow electrochemical stability window of water.1 This constraint can, however, be relieved if electrochemical stability window is widened by deliberately controlling the composition of non-aqueous electrolyte systems.

Redox couple is the core component in non-aqueous electrolyte systems, which should satisfy at least the following requirements; (i) high working voltage, (ii) high solubility in non-aqueous solvents, (iii) stability for high couloumbic efficiency and cycle retention, and (iv) facile molecular diffusion in solutions. It must be additionally beneficial if it can be used for both catholyte and anolyte. When such a single electrolyte component is used for RFBs, the loss of redox couple by side reactions can be greatly suppressed.

A metal-multidentate complex, (nickel(II)-1,4,8,11-tetracyclotetradecane, Ni(cyclam)2+) has been tested if or not it satisfies the above requirements.

The nickel complex is reduced and oxidized at -1.78 V and 0.74 V (vs. Fc/Fc+), respectively (Fig. 1). Hence, this redox couple can be used as a single electrolyte component for non-aqueous RFBs. The expected working voltage is as high as 2.52 V, which is much larger than those for conventional aqueous RFBs. The maximum solubility is ~0.4 M at room temperature. This value is again higher than those for the conventional metal-ligand complexes (0.1 M).2 A much enlarged energy density is thus expected with this RFB since it shows larger values for both cell voltage and capacity. This redox couple also exhibits a stable cycle performances. As seen in Fig. 1, the current profiles are not changed even after 50 cycles.

Galvanostatic charge-discharge cycling is carried out in a non-flowing static cell. The coulombic efficiency is ~ 75% after 3 cycles.

References

1. M. Skyllas-Kazacos, M.H. Chakrabarti, S.A. Hajimolana, F.S. Mjalli, and M. Saleem, J
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2. W. Wang, Q. Luo, B. Li, X. Wei, L. Li, and Z. Yang, Adv
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Fig. 1
. The 1st and 50th cyclic voltammograms of Ni(cyclam)2+
Atomic-Scale Structure of Intercalated/De-Intercalated Electrode Materials in Lithium/Sodium Ion Batteries Via Aberration-Corrected Annular-Bright-Field Electron Microscopy
Authors: Gu Lin
Published: February 2020

To satisfy ever-demanding inquires upon energy storage for applications in portable electronics, electric vehicles and smart grid etc., lithium ion batteries have been proved to be one of the ideal candidates in terms of energy density and power density. However, limited understanding for the structural evolution of electrode materials at atomic scale amid electrochemical process substantially hinders their further performance optimization. The recent success of annular-bright-field (ABF) imaging method erected on aberration-corrected scanning transmission electron microscopy (STEM) has been demonstrated to be a powerful technique to directly visualize individual light atoms, in particular the lithium ions, probing the nearly-equilibrated local structure of lithiated/delithiated electrodes under electrochemical cycling at atomic resolution. Compared to the high-angle annular-dark-field (HAADF) image, it is clearly demonstrated that not only heavy elements are revealed in ABF image, but also the atomic columns of O and Li. The ABF contrast tends to minimize the variance of the atomic number (Z) by following a Z1/3 dependency. With the unique ABF method, we have further studied possible electrochemical reaction mechanisms and detailed microstructure for (partially) lithiated/delithiated 1D-LiFePO4, 2D-LiCoO2, Li2MnO3 and 3D-Li4Ti5O12 and other lithium-based active materials with atomic resolution, which are essential for basic understanding and further performance optimization. These achievements provide new insight into the lithium/sodium storage mechanism in important cathode materials for lithium/sodium ion batteries.

References:

[1] Y. Sun, et al., Nature Commun. 4 (2013) 1870.

[2] R. Wang, et al. Adv. Energy Mater., in press.

[3] C. B. Zhu, et al. Adv. Func. Mater., in press.

[4] X. Lu, et al., Nano Lett. 12 (2012) 6192.

[5] S. Xin, et al., J. Am Chem. Soc. 134 (2012) 18510.

[6] X. Lu, et al., Adv. Mater. 24 (2012) 3233. (Editor’s Choice in Science 336 (2012) 1621.)

[7] Y. Q. Wang, et al., J. Am Chem. Soc. 134 (2012) 7874.

[8] X. Lu, et al., Energy Environ. Sci. 4 (2011) 2638.

[9] L. Gu, et al., J. Am Chem. Soc. 134 (2011) 4661.
Fluorinated High-Voltage Electrolyte: Synergetic Effect of Solvents and Additives
Authors: Xue Zheng , Hu Libo , Su Chi-Cheung , He Meinan , Zhang Zhengcheng
Published: February 2020

High-voltage electrolytes (HVEs) for Li-ion battery refer to the electrolytes that are intrinsically stable towards oxidative decomposition on the cathode at high charging potential. To develop HVEs that are compatible with 5 V spinel LiNi0.5Mn1.5O4 (LNMO), we focus on incorporating fluorinated solvents in the electrolyte formulation. In the meantime, we also take into account the stability of such electrolytes on the anode. A combination of cathode-compatible fluorinated solvents with anode-protecting additives is envisaged to be a promising solution for a successful HVE.

A new HVE containing fluorinated carbonates was evaluated against LNMO cathode and showed excellent oxidative stability. Several additives were found to form solid-electrolyte interphase (SEI) layers that effectively prevented significant decomposition of the HVE on the graphite anode. Cell performance was evaluated at both ambient and elevated temperatures. The fluorinated HVE exhibited much improved performance compared with conventional non-fluorinated carbonate-based electrolyte especially at high temperature. Cycling results and electrochemical impedance spectroscopy (EIS) data clearly demonstrated the synergetic effect of the fluorinated solvents and the SEI forming additives.
Study on the Synthesis and Application of Core-Shell Structured Nanoparticles of Fe3O4
Authors: Chin Chun-Yi , Chou Kan-Sen
Published: February 2020

This study addressed different materials to coat iron oxide, after using co-precipitation to synthesize. During synthesizing iron oxide, FeSO4•7H2O as a single raw material , was emphasized as a precursor salt. In advance, FeSO4•7H2O was oxidized into trivalence by using hydrogen peroxide, allocated Fe(Ⅱ)and Fe(Ⅲ) mole ratio as one to two, and synthesized ferric ferrous oxide nanoparticle by sodium hydroxide co-precipitation, which TX-100 was a protective agent to disperse uniformly.

Depend on the morphology of several nanopartical types through the processing, separation of precursor salt solution and NaOH solution in pump by adding TX-100 solution would get Fe3O4 ratio more evenly. Besides during the experiment, variety loading of NaOH and dispersant, using two- stage method to add NaOH as well, rod and particle mixure would obtain.

XRD, SQUID, HRTEM and SEM were used to analyze the particle size, uniformity, Magnetic, and Crystal structure. Also, intend to find the relation among synthesis and properties, and continue to work on electrodes for battery application to seek the optimal performance corresponded to synthesis conditions.

Preparation of Fe3O4@Ag was took AgNO3 and C6H12O6, the reductant, into Fe3O4 solution. Different mole ratio of AgNO3 and Fe3O4 were mix- coated. Through the process, surface modifier makes coating completely and uniformly. Later, same analysis entailed to Fe3O4@Ag product powder. The purpose was to examine its completely coating, thickness, and magnetism.
Nucleation and Growth of Lithium Peroxide in the Li/O2 Cell
Authors: Lau Sampson , Archer Lynden A.
Published: February 2020

The aprotic Li–O2 battery offers a vast improvement in theoretical energy density up to ten times that of current Li-ion batteries, but still suffers from shortcomings in cell and material design. Some of these shortcomings stem from the large gap in understanding between fundamental studies and cell cycling experiments. In particular, it is known from computational studies that the solid Li2O2 discharge product is an electronic insulator, but SEM images of discharged cathodes show particles of Li2O2 much larger than what electron conduction and tunneling would allow. In addition, the shape of the discharge curves does not match the expected exponential resistance rise of a cell limited by electron tunneling.

In order to bridge Li2O2 properties with experimental observations, we developed a model in which Li2O2 forms as discrete particles on the cathode surface by using a combination of Kolmogorov’s statistical phase transformation theory and the atomistic nucleation theory. Nucleation rate was modeled according to a two-step process involving formation of a LiO2 intermediate. Despite its relative simplicity, the proposed model provides a near-quantitative description of empirically observed discharge curves (Figure 1). We find that the sudden potential drop at the end of discharge is caused by the reduction in active surface area as Li2O2 covers the cathode surface. Thus, the extra overpotential gained during discharge is the kinetic overpotential of the ORR rather than an ohmic overpotential through the Li2O2 bulk.

This model can be used as a guide for cathode and electrolyte design, by maximizing the amount of Li2O2 that can be collected for a given amount of electrochemically active surface area. One strategy is to promote the growth of larger Li2O2 particles. For cathodes, this means reducing the rate of nucleation by having a higher nucleation energy barrier or a lower concentration of active sites. For electrolytes, this means solvating the LiO2 intermediate to promote the superoxide disproportionation pathway. In principle, the general form of this model is applicable to any electrochemical cell that produces a solid passivation layer.

Figure 1: (a) Empirically observed discharge curves (symbols), compared with fit of the nucleation and growth model (lines). (b) Analysis of model parameters shows that they are independent of operating conditions.

Figure 1
Modeling of Proton Conductivity through Perfluorosulfonate Acid Electrolyte Membranes
Authors: Zhang Bo , Edwards Brian Joseph
Published: February 2020

Proton conductivity (σ) through perfluorosulfonate acid (PFSA) polymer electrolyte membranes was modelled from the unsaturated hydraulic conductivity, which was described as a power-law function of water content; i.e.,λ
q
, where λ is the water content and the exponent q is a porosity factor. In this study, the membrane was modeled as a network of nanopores with the anionic groups (i.e., –SO3
–) assumed to be fixed along the pore wall according to an indeterminate distribution consistent with the material’s equivalent weight (EW) and dry membrane density. The transport of the hydronium ions inside the porous network was expressed using the extended Nernst-Einstein equation, which was modified using continuum percolation theory to reveal the relevant transport mechanisms at different water contents and temperatures. The power q in the modification was compatible with the critical path analysis simulation results; i.e., q=1.28±0.07 in two dimensions and q=1.86±0.19 in three dimensions, depending singularly on the dimensionality of the transport system. The average electrical conductivity of the membrane was deduced in terms of the following quantities: water content, equivalent weight, and the nature of the perfluorosulfonate acid polymer side chain.  Theoretical predictions of this model were compared against experimental data of conductivity for four different membranes: DuPont’s Nafion 117 (EW = 1100), Membrane C (EW = 900) of Chlorine Engineers Corp., Japan, Dow Chemical’s XUS 13204.10 (EW = 800), and a 3M membrane developed by 3M Corp. (EW = 1000) for different water contents and temperatures. The theoretical predictions of the model matched the experimental data with reasonable quantitative accuracy in most cases.
Ring-Expanded Phthalocyanines Fused with Fluorene Skeleton for Light-Harvesting in the Near-IR Region
Authors: Yamamoto Satoshi , Kimura Mutsumi
Published: February 2020

Organic photovoltaic devices (OPVs) based on thin films of organic semiconductors have been intensely investigated as a promising candidate for low-cost, lightweight, and scalable solar cells. While OPVs have achieved high conversion efficiencies, their organic semiconductors mainly absorb the light in visible range. To enhance their efficiency, the expansion of light-harvesting range is a key issue in this field.

Phthalocyanines (Pcs) and their metal complexes (MPcs), synthetic porphyrin analogues, have been widely investigated as near-IR absorbing dyes because of their intense Q band (600-700 nm), high molar extinction coefficients (e > 100000 M-1 cm-1), and excellent thermal, chemical, and photolytic stabilities. The electronic structure and properties of MPcs can be tailored by modifying the macrocyclic ligands and changing the central metals [1].

We present here designed and synthesized novel ring-expanded zinc phthalocyanine (ZnFc , Figure1), in which four fluorene rings were fused with porphyrazine ring. Fusing fluorene rings with the porphyrazine rings lead to red-shifting the Q band and tailoring of the HOMO and LUMO energy levels as well as an expansion of p-system. We demonstrated the expansion of the light-harvesting area in BHJ solar cells based on poly(3-hexylthiophen) (P3HT) and 1-(3-methoxycalbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) by co-sensitizing with ZnFc. When the ZnFc decorated with eight alkyl chains was added to P3HT/PCBM BHJ solar cells, the solar cells showed a higher device efficiency with 16 % enhancement of JSC
as compared with that of the reference P3HT/PCBM BHJ solar cells due to the expansion of light-harvesting range [2].

We also synthesized an asymmetrical fluorene-fused phthalocyanine (FcS1, Figure1), which containing three fused fluorene rings and one carboxylic acid. FcS1 indicated a potential for near-IR sensitizer in DSSCs. The absorption spectrum of FcS1 adsorbed onto a nano-crystalline TiO2 film suggested the formation of J-aggregation with tilted orientation of macrocyclic ligands. While the DSSC cells sensitized by FcS1 showed a modest efficiency of 3.2 % under simulated air mass 1.5 global sunlight, FcS1 could convert the red and near-IR light regions between 600 and 860 nm [3].

Reference

[1] J. Mack, N. Kobayashi, Chem. Rev.
2011, 111, 281-321.

[2] S. Yamamoto, M. Kimura, ACS Appl. Mater. Interfaces
2013, 5, 4367-4373.

[3] S. Yamamoto, T. Ikeuchi, S. Mori, M. Kimura, Asian J. Org. Chem.
2014, 10, 1083-1088.

Figure 1