bluuebunny/crossref_metadata_2025 huggingface dataset:
Relating Structure to Electrochemistry: I
n-Situ Studies of Fe[Fe(CN)6] As Cathode Materials for Rechargeable Li- and Na-Ion Batteries
Authors: Godfrey Thomas , Schmid Siegbert
Published: February 2020

The Prussian blue type compound Fe[Fe(CN)6] is investigated as a cathode material for use in rechargeable Li- and Na-ion batteries. The structural changes following electrochemical Li+ and Na+ ion insertion during charge-discharge cycles were followed using in-situ X-ray and neutron powder diffraction techniques.1-3

The electrochemical performance of Fe[Fe(CN)6] has been investigated for both Li+ and Na+ ions with capacities of 100 and 115 mA h g-1 respectively. Further investigations of the Na-ion cells for Fe[Fe(CN)6] show the capacity to depend on the heating temperature used in preparing the cathode material. Fe[Fe(CN)6] heated at 110 °C shows the highest capacity of 115 mA h g-1, with capacity fading to 75 mA h g-1 when the framework is heated at 150 °C. Cells containing samples of Fe[Fe(CN)6] heated at 110 °C show excellent capacity retention of more than 99% after 50 cycles.

In-situ synchrotron X-ray diffraction has been performed for the Na-ion cells, while in-situneutron diffraction studies were carried out on Li-ion cells. In both cases, these allow for the direct correlation of structural changes to the cathode material and the observed electrochemical properties, as both are collected simultaneously.

(1) Roberts, M.; Biendicho, J. J.; Hull, S.; Beran, P.; Gustafsson, T.; Svensson, G.; Edström, K. Journal of Power Sources
2013, 226, 249.

(2) Sharma, N.; Peterson, V. J. Solid State Electrochem.
2012, 16, 1849.

(3) Bergstöm, Ö.; Andersson, A. M.; Edström, K.; Gustafsson, T. J. Appl. Crystallogr.
1998, 31, 823.
Phosphorus-Based Negative Electrode Materials for Na-Ion Batteries
Authors: Kim Youngjin , Oh Seung M. , Choi Aram , Lee Kyu Tae
Published: February 2020

Introduction

Na-ion batteries have recently received a lot of attention as a next-generation battery, because Na resources are inexhaustible and cheaper than Li resources. However, although Na-ion batteries have shown promising electrochemical performance including stable cycle performance and good rate performance, it should be mentioned that it is not easy for Na-ion batteries to replace Li-ion batteries owing to the critical issue of Na-ion batteries having slightly lower energy density than Li-ion batteries. Therefore, in order to successfully replace Li-ion batteries by Na-ion batteries, new anode materials having a high reversible capacity should be introduced. In this presentation, phosphorus-based negative electrode materials are introduced for Na-ion batteries. Phosphorus-based electrodes showed excellent electrochemical performance including a high reversible capacity (>700 mAh/g), excellent cycle performance, and an ideal redox potential (< 0.4 V vs. Na/Na+), thus making it a promising candidate for Na ion batteries.

Experimental

Two types of phosphorus-based active materials were prepared as follows. For red phosphorus/carbon composites, phosphorus powder and Super P carbon were mixed in a 7:3 weight ratio using a high energy mechanical ball-milling method. For the synthesis of tin phosphide, phosphorus and Sn powders were mixed using the same ball-milling method.

Samples of active materials were mixed with carbon black (Super P) and polyacrylic acid (PAA) in a 7:1:2 weight ratio. The electrochemical performance was evaluated using 2032 coin cells with a Na metal anode and 1 M NaClO4in ethylene carbonate and diethyl carbonate (1:1 v/v) with or without the addition of 5% fluoroethylene carbonate (FEC).

For the analysis of the reaction mechanism, ex-situ X-ray diffraction (ex-situXRD), high resolution transmission electron microscope (HR-TEM) and X-ray absorption spectroscopy (XAS) analysis were performed.

Results and Discussion

The amorphous red phosphorus/carbon composite exhibited promising electrochemical performance including i) high reversible capacity of 1890 mA h g-1 (equivalent to 2.18 mol of Na alloyed with one mole of P); ii) good cycle performance over 30 cycles; and iii) appropriate redox potential of ca.0.4 V vs. Na/Na+.

Also, tin phosphide electrode showed excellent electrochemical performance including i) high reversible capacity of about 718 mA h g-1; ii) negligible capacity fading over 100 cycles in spite of the large particle size (> a few micrometer).

Finally, the reaction and failure mechanisms of both electrodes were studied using ex situ instrumental analysis.

References

[1] Y.Kim, Y. Park, A. Choi, N.S. Choi, J. Kim, J. Lee, J.H. Ryu, S.M. Oh, K.T.Lee, Adv. Mater.
25(22) 3045 (2013).
In Situ XRD Investigations on Structural Change of P2-Layered Materials during Electrochemical Sodiation/Desodiation
Authors: Jung Young Hwa , Johnsen Rune E. , Christiansen Ane Sælland , Norby Poul , Kim Do Kyung
Published: February 2020

Sodium layered oxides (NaxMO2) are attractive as positive electrode materials for rechargeable sodium-ion batteries (SIBs) due to high capacity, fast ionic diffusion and simple synthetic process. O3-layered lithium compounds have led successful commercialization of current lithium-ion batteries; as a result, rich experiences for structural studies of O3-layered compounds have been accumulated over the past decades. For sodium layered oxides, however, P2-layered compounds have been reported for better cyclability and structural stability during electrochemical reactions than O3-structure. Therefore, systematic studies on P2-layered materials for SIBs are highly required. In this study, we report the structural and electrochemical property of P2-NaxFeyMnyCo1-2yO2 synthesized by simple solid state reaction. The X-ray diffraction pattern of as-synthesized powder is indexed as a hexagonal lattice (P63/mmc, No.194), which is identical to P2-layered structure. The structural changes in hexagonal P2-layered oxides have been investigated during electrochemical sodiation/desodiation by in-situ synchrotron X-ray diffractions of a capillary based micro battery cell. From the result of in-situ studies, the initial layered structure is maintained from 2.0 to 4.0 V vs. Na+/Na during first desodiation. The phase transformation is observed over the 4.0 V, but the original P2 structure is completely restored at the following sodiation process. The relationship between structural and electrochemical properties of this P2-layered material will be discussed.
A Silicon/Graphene Composite Anode for High-Efficiency Lithium Batteries
Authors: Nobili Francesco , Maroni Fabio , Raccichini Rinaldo , Tossici Roberto , Marassi Roberto
Published: February 2020

Composite anodes based on Si and reduced graphene oxide (RGO) have been prepared using commercial Si nanopowder, graphene oxide (GO) and polyacrilic acid (PAA) as starting materials. A double reduction step, consisting in microwave irradiation at mild power followed by thermal annealing in reducing atmosphere, yielded the composite powder made of Si:reduced graphene oxide (RGO) in the approximate mass ratio 30:70. The charge/discharge properties of the anode materials are determined by the homogeneous dispersion of Si grains between RGO nanosheets, that act as structural buffer for volume changes related to Li-Si reversible alloying and as improved electrical conductor. Electrodes have been prepared using high-molecular weight PAA as binder, which promises better mechanical stability towards silicon volume changes. The electrochemical behavior of the composite anode material has been characterized by galvanostatic cyclations and electrochemical impedance spectroscopy, using LiPF61M in EC:DMC 1:1 electrolyte, also modified by the addition of 5% vinylene carbonate (VC).

Several anodes have been investigated, consistently delivering reversible capacities higher than 1000 mAhg-1, with a mechanism that, after initial lithiation of crystalline Si, mainly involves reversible Li-Si alloying/dealloying between amorphous a-Li and a-LixSi phases. Particularly, when cycled in VC-modified electrolyte the anode exhibits a remarkable cycle life, resulting in a residual capacity of more than 900 mAhg-1 after 60 cycles at 500 mAg-1 and efficiency values close to unity. Several factors concur in determining this behavior, namely: (i) the efficient Si dispersion in RGO carbonaceous matrix; (ii) the good mechanical properties of PAA binder; (iii) the formation of a stabilized SEI by VC additive in the electrolyte.
Monodisperse Porous Alluaudite NaFePO4 Nanocomposites for Sodium Ion Battery
Authors: Huang Weifeng , Zhou Jing , Li Biao , An Li , Cui Peixin , Xia Wei , Xia Dingguo , Chu Wangsheng , Wu Ziyu
Published: February 2020

Looking for a new promising cathode material of sodium ion batteries (SIBs) is a challenge for large energy storage systems. Here we present a study of a novel alluaudite NaFePO4 and NaFePO4/CNT nano-composites for SIBs application. The new monodisperse porous NaFePO4 microspheres and their nano-composites consist of nanorods with an open three-dimensional framework. First principles calculations identify two fast one-dimensional paths for Na+ insertion and extraction. Moreover, the electrochemical characterization demonstrates that up to 0.9 Na+ can be intercalated/deintercalated reversibly even for 50 cycles using this novel NaFePO4/CNT nano-composite.
Amorphous Columnar Silicon Anodes with Excellent Cycling Stability for Advanced High Voltage Lithium Ion Full Cells: Dominant Factors Governing Cycling Performance
Authors: Aurbach Doron , Markevich Elena , Salitra Gregory , Fridman Katia , Elazari Ran , Sharabi Ronit , Garsuch Arnd , Lampert Jordan
Published: February 2020

An excellent cycling stability of monolithic amorphous columnar silicon electrodes with the loqading of 1.3 mg/cm2 in fluoroethylene carbonate (FEC)-based electrolyte solutions was demonstrated. The effect of the electrolyte solution composition and the cycling protocol on the long-term cycling performance and surface chemistry of amorphous silicon electrodes was investigated using electrochemical tools, XPS, SEM and EDS. It relates to the ability of FEC to form polyenes, as well as to a high rate of HF formation in its water contaminated LiPF6 solutions, measured by 19F NMR spectroscopy. We found that excellent passivation in FEC solutions related to a low content of oxygen containing moieties species (e.g. organic and inorganic carbonates, alkoxides, oxygen-containing organic polymers) in surface films.

Galvanostatic tests and spectroscopic analyses revealed also a strong dependence of the composition and properties of the surface films on amorphous Si electrodes on the cycling procedure. Charge limited galvanostatic cycling procedure including repeated deep discharge of Si electrodes down to 10 mV vs. Li/Li+in every cycle from the very beginning of the electrodes life, ensures the formation of thin and highly passivating surface films on their surface and good cycling performance. To the contrary, when a limited portion of the capacity of Si electrodes during cycling relates to the higher potential range (discharge limited protocol), surface films enriched with oxygen containing species are formed. Their passivating properties are less effective compared to the other composition discussed above (polyenes + LiF).

Cycling stability of Si electrodes in LiPF6solutions decreases in the following order FEC/DMC > 3,4-trans-difluoroethylene carbonate (DFEC)/DMC > ethylene carbonate (EC)/DMC > propylene carbonate (PC).

Amorphous columnar silicon electrodes were combined with high voltage LiNi0.5Mn1.5O4 spinel and LiCoPO4/C composite cathodes and high specific capacity xLi2MnO3
.(1-x)LiNiyMnzCo1-y-zO2 cathodes. These batteries demonstrated excellent performance in term of cycle life, charge-discharge efficiency and good rate capability.
Calcium-Doping for Structure Stabilization of Sodium Transition Metal Oxide Cathodes in Sodium Ion Batteries
Authors: Bae Eun Gyoung , Jeong Jaehyang , Han Su cheol , Kwak Joon Seop , Pyo Myoungho
Published: February 2020

NaNi0.5Mn0.5O2 (NNMO), which has a layered structure, is a promising cathode material for sodium ion batteries. The stack of Mn(Ni)O2 slabs in a layered structure of NaiNi0.5Mn0.5O2, are composed of edge-shared Mn(Ni)O6 octahedra, forming metal-occupied octahedral sites and empty tetrahedral sites. The octahedral sites in Na slabs are also occupied by Na+ ions, which are sandwiched by edge-sharing with Mn(Ni)O2 slabs. In this work, O3-CaxNa1-2x[Ni0.5Mn0.5]O2 (0 < x ≤ 0.1) was synthesized by incorporating Ca2+ into NaO6 layer of Na[Ni0.5Mn0.5]O2. Both the significant difference in ionic radii between Ca2+ (1.12Å) and Ni2+ (0.69Å) or Mn4+ (0.53 Å) and the reduction of Na+ content allowed the preparation of phase-pure and cation-mixing-free (i.e., absence of Ca2+ in transition metal oxide layers) CaxNa1-2x[Ni0.5Mn0.5]O2 up to x = 0.05. It was expected that, while no noticeable change was observed in a dimension of MnO6 octahedron, NaO6 octahedron continuously shrank as the increase of Ca2+ content. The latter effect was expected to prevent the structural degradation during repeated charge-discharge, eventually contributing to the improvement of capacity retention. Preliminary study indicated that, while pristine Na[Ni0.5Mn0.5]O2 showed a continuous decrease in discharge capacity, Ca0.05Na0.90[Ni0.5Mn0.5]O2 maintained a significant fraction of an initial capacity with a small capacity fading during 50 cycles. The excellent capacity retention of Ca2+-doped one is believed because the strong interaction of immobile Ca2+ with O2- helps restore of the initial O3 structure, which leads to the maintenance of distinctive phase transition steps on discharge profiles after repeated cycles in contrast to pristine one.
A New, Rapid Approach for the Synthesis of Germanium Nanowire Based Li-Ion Battery Anodes and Their Excellent Performance over Extended Cycles
Authors: Mullane Emma , Kennedy Tadhg , Ryan Kevin M
Published: February 2020

Ge nanowires (NWs) have recently been highlighted as active materials for Li battery anodes.1,2 Ge NWs (along with Si NWs2,3) are well placed as anode materials for Li-ion storage due to their high theoretical capacity of 1384 mAhg-1. The diffusion of Li within Ge is some 400 times faster than in Si1 meaning that Ge is particularly suited to high power rate anodes. To maximize the capacity of NW based Li-ion anodes, they should be grown in high density directly on the metal current collector to allow for efficient current transport. Ancillary materials such as inactive catalyst seeds, binders and conductive additives should also be minimised as they diminish capacity by adding mass to the final device. Herein we present the development of a rapid pyrolysis route4 allowing the formation of high density Ge NW mats grown directly on stainless steel current collector substrates with reactions taking < 30 seconds (Figure 1 a). The growth system exploits the in-situ formation of discrete Cu3Ge catalyst seeds from a thermally evaporated Cu layer producing centimetre scale NW coverage on device integrable substrates. Electrochemical testing of the NW covered substrates yielded capacity measurements greater than 1000 mAhr-1g after 1000 cycles with a Coulombic efficiency of 99.7 % (Figure 1 b). The NW based anodes showed high-rate stability with discharge capacities of 800 mAhg-1cycled at a rate of 10C. The method represents a rapid scalable approach for the formation of highly promising Li-ion anode materials.

1. Candace K. Chan, Xiaou Feng Zhang, Yi Cui, Nano Letters
2007, 8, 307-309

2. Mullane, E.; Kennedy, T.; Geaney, H.; Dickinson, C.; Ryan, K. M. Chemistry of Materials
2013, 25, 1816.

3. Candace K. Chan, Peng Hailin, Gao Liu, Kevin McIlwrath, Xiao Feng Zhang, Robert A. Huggins, Yi Cui, Nature Nanotechnology
2008, 3 (1), 31-35

4. Mullane, E.; Geaney, H.; Ryan, K. M. Chemical Communications
2012, 48, 5446.
Influences of Dopants on the Properties of LiMnO2 and Li2MnO3 in OLO Cathode for Li Ion Batteries
Authors: Kong Fantai , Longo Roberto C , Park Min-Sik , Yoon Jaegu , Yeon Dong-Hee , Park Jin-Hwan , Wang Weihua , KC Santosh , Doo Seok-Kwang , Cho Kyeongjae
Published: February 2020

The over-lithiated-oxides (OLOs), a composite of layered structures of Li2MnO3 and LiMO2 (M = Mn, Fe, Co, Ni), have shown much higher storage capacity than the traditional layered oxides for Li ion battery cathode because of the Li2MnO3 phase. However, Li2MnO3 is not stable after the 1st charge-discharge cycle and will partly transform into layered LiMnO2, which indicates that the practically used phase is a mixture of both Li2MnO3 and LiMnO2. During the subsequent cycles, the OLO voltage decreases due to the phase transition of layered LiMnO2 into spinel. Experimentally, the effective dopants satisfying multiple cathode materials requirements of thermodynamic stability, optimized voltage and improved kinetics based on ionic and electronic conductivities are investigated to overcome the voltage degradation and to improve the power capacity. In this work, redox potential, lithium ion diffusion and charge carrier transportation of both phases are examined in details using the ab initio density-functional theory (DFT) simulations. The calculations find, due to the Jahn-Teller effect of Mn3+ atoms, Li vacancy migration in LiMnO2 has special behaviors and hole polaron and electron polaron will form in LiMnO2 and Li2MnO3 phases, respectively. Based on the understanding of the pure phase properties, the effects of 10 cationic (Mg, Ti, V, Nb, Fe, Ru, Co, Ni, Cu, Al) and 2 anionic (N, F) dopants on the redox potential, ionic and electronic conductivity are investigated. These DFT findings could provide conceptual guidance in the experimental search for the effective dopants enabling the practical application of OLO cathodes.

This work was supported by Samsung GRO project.
Effect of Particle Morphology on the Cycle Life of LiNixCoyMn1-x-YO2 Electrode in Li-Ion Cell
Authors: Valikangas Juho Pekka , Lassi Ulla , Hu Tao , Rasanen Samuli
Published: February 2020

LiCoO2 is one of the widely used cathode material in portable Li-ion batteries. Cobalt is expensive metal, therefore it is substituted with cheaper metals such as nickel, but the delithiated structure of LixNiO2 is not thermally stable in the presence of organic electrolyte. However, as a result of partial substitution of cobalt with nickel and manganese, LiNixCoyMn1-x-yO2 has high thermal stability and is widely investigated as positive electrode material for the Li-ion batteries.

The aim of this research was to understand how metal substitutions and particle morphology effect on the electrode cycle life in the Li-ion cell. Electrode materials LiCoO2 and LiNixCoyMn1-x-yO2 were prepared from a several of precursors under different synthesis conditions to achieve optimal crystal sizes and morphologies for Li-ion cell. Phase purities and crystal sizes were studied by XRD and morphologies of particles were investigated by FESEM from the electrode foil cross-sections. After electrochemical cycle tests, the morphologies of particles were re-investigated to see how the testing affect to the different morphologies and chemistries of samples.

Results indicate that crystal size and morphology has big influence on the electrochemical cycling properties of LiNixCoyMn1-x-yO2 electrode material in the Li-ion cells. The optimum particle size and morphology were obtained from the experiments and discussed.
Toward a Lithium-‘air’ Battery: The Effect of CO2 on the Chemistry of a Lithium-Oxygen Cell
Authors: Lim Hee-Dae , Lim Hyung-Kyu , Park Kyu-Young , Gwon Hyeokjo , Kim Jinsoo , Kang Kisuk
Published: February 2020

Lithium-oxygen chemistry offers the highest energy density for a rechargeable system; such a system is known as a “lithium-air battery”. Most studies of lithium-air batteries have focused on demonstrating battery operations in an environment of pure oxygen; such a battery should technically be described as a “lithium-dioxygen (O2) battery”. Consequently, the next step for the lithium-“air” battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO2 is of particular interest because its solubility in organic solvents is about fifty times higher than that of O2, and it can react actively with O2
-
·, which is the key intermediate species in Li-O2 battery reactions. In this work, we investigated the reaction mechanisms in the Li-O2/CO2 cell under various electrolyte conditions using quantum mechanical simulations combined with experimental verification. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect. Thus, a low dielectric electrolyte tends to primarily form Li2O2, while a high dielectric electrolyte is effective in electrochemically activating CO2, yielding only Li2CO3. Most surprisingly, we further discovered that a high dielectric medium such as DMSO can result in the reversible reaction of Li2CO3 within a Li-air cell (contrary to conventional belief) over multiple cycles. We believe that the current mechanistic understanding of the chemistry of CO2 in a Li-air cell and the interplay of CO2 with electrolyte solvation will provide an important guideline for developing Li-air batteries. Furthermore, the newly discovered possibility for a rechargeable Li-O2/CO2 battery based on Li2CO3 formation chemistry may have merits in enhancing cyclability by minimizing side reactions.
Electrochemical Properties of Lithiated Silicon/Sulfur Battery
Authors: Kim Hyung-Sun , Jeong Tae-Kyung
Published: February 2020

The lithium sulfur battery has much higher specific capacity of 1675 mAh/g and energy density of 2600 Wh/kg than conventional lithium ion battery [1]. However, the lithium sulfur battery is difficult to commercialize because a lithium metal used as anode has dendrite growth and explosiveness. Traditional graphite anodes that are applicable for rechargeable Li-ion batteries may not be suitable for rechargeable sulfur batteries since they have low capacity and poor passivation in ethereal solutions. Therefore alternative anodes for sulfur cathode are required. Silicon anode material, which exhibits very high specific capacity of 4200 mAh/g (for a stoichiometry of Li4.4Si) is one of the most attractive candidates for Li-ion batteries [2, 3]. Combining pre-lithiated silicon anode with sulfur cathode may promote the commercialization. However, both sulfur cathode and silicon anode have drawbacks. The most serious drawback in sulfur cathode that the capacity is rapidly decreased with cycling, because the lithium polysulfide, an intermediate product in the sulfur redox reaction is readily dissolved out into the electrolyte during cycling. Silicon as an anode material is hampered by its large volume expansion (>300%), causing pulverization, loss of electrical contact and consequently early capacity fading. Therefore, various approaches to solve such problems have been suggested [4].

In this work, we suggest an advanced lithium metal free, pre-lithiated silicon-sulfur battery. In our previous research, carbon mesh was inserted between the sulfur cathode and the separator [5]. Sulfur cathode with carbon mesh was inhibited polysulfide dissolved in an electrolyte and was enhanced a utilization of sulfur. In the silicon anode, carbon coating on silicon surface has been conducted. Silicon properties such as electrical conductivity and Li-ion conductivity can be enhanced by carbon coating. Prior to use in the silicon/sulfur battery, the silicon was lithiated by direct contact with a lithium metal in a 1M LiTFSI solution with 1, 2-dimethoxyethane (DME) and 1, 3-dioxolane (DOL) at volume ratio of 1:1. The results show that lithiated silicon-sulfur battery exhibits increased capacity and good cyclability.

[1] Y. Yang, M. T. McDowell, A. Jackson, J. J. Cha, S. S. Hong and Y. Cui, Nano let., 10 (2010) 1486-1491.

[2] N. Liu, L. Hu, M. T. McDowell, A. Jackson and Y. Cui, Acs Nano, 5 (2011) 6487-6493

[3] I. Hong, B. Scrosati, F. Croce, Solid State Ionics, 232 (2013) 24-28

[4] M. Green, E. Fielder, B. Scrosati, M. Wachtler, J. S. Moreno, Electrochemical and Solid-State Letters, 6 (2003) A75-A79

[5] T. G. Jeong, Y. H. Moon, H. H. Chun, H. S. Kim, B. W. Cho and Y. T. Kim, Chem. Commun., 49 (2013) 11107-11109
Porous Perovskite LaNiO3 Nanocubes As Cathode Catalysts for Li-O2 Batteries with Low Charge Potential
Authors: Zhang Jian , Chen Wei
Published: February 2020

In recent years, rechargeable lithium-O2 batteries with remarkably high theoretical energy storage capacity have attracted significant attention for applications in electric vehicles and energy storage of smart grids. However, for practical applications they still suffer from substantial challenges especially high charge overpotential caused by the sluggish oxygen evolution reaction(OER). Up to now, the most efficient OER catalysts are noble metals with high price and scarce quantity. Therefore, developing efficient OER catalysts with low price is essential for rechargeable Li-O2 battery. In our work, porous LaNiO3 nanocubes with porous structure and large specific surface area were employed as electrocatalyst in a Li-O2 battery cell. This catalyst showed high OER activity that could reduce the charge potential low to 3.40 V. The synergistic effect of porous structure, large specific surface area and high electrocatalytical activity ensures the Li-O2battery with enchanced capacity and good cycle stability. Furthermore, it is found that corrosion of lithium anode is also responsible for the capacity fading of Li-O2 battery, in addition to the passivation of oxygen cathode. Our finding indicated that porous LaNiO3 nanocubes can be recognized as a promising cathode catalyst for Li-O2 battery. Our work provided a perspective for the improvement of electrocatalyst performance in Li-O2 battery by tuning the structure of perovskite oxide.
3D Hyperbranched Hollow Carbon Nanorod Encapsulated Sulfur Composites for Lithium-Sulfur Batteries with Superior Electrochemical Performance
Authors: Chen Shuangqiang , Huang Xiaodan , Liu Hao , Sun Bing , Yeoh Waikong , Li Kefei , Zhang Jinqiang , Wang Guoxiu
Published: February 2020

Lithium-sulfur batteries have been plagued for a long time by the low Coulombic efficiency, fast capacity loss and poor high rate performance. Herein, we report the synthesis of graphitic hyperbranched hollow carbon nanorods encapsulated sulfur composites as cathode materials for lithium-sulfur batteries. The sulfur composite cathodes, approximate 1 mg for each electrode, deliver a high specific capacity of 1378 mAh/g at 0.1C current rate and exhibit stable cycling performance. The as-prepared cathode materials also achieve excellent high rate capacities and cyclability, such as 990 mAh/g at 1C, 861 mAh/g at 5C and 663 mAh/g at 10C, extending to more than 500 cycles. The superior electrochemical performances could be ascribed to the unique graphitic hyperbranched hollow carbon nanorods architecture and high length/radius aspect ratio of carbon nanorods, which can effectively prevent the dissolution of polysulfides, decrease self-discharge and confine the volume expansion on cycling. High capacity, excellent high-rate performance and long cycle life render the as-developed sulfur/carbon nanorod composites as a promising cathode material for lithium-sulfur batteries.
Organo Metallic Free Electrolytes for Magnesium Rechargeable Batteries
Authors: Shterenberg Ivgeni , Salama Michael , Gofer Yosef , Aurbach Doron
Published: February 2020

Developing an organo-metallic free electrolytic solution is crucial step towards a practical magnesium battery system. Implementing Grignard reagents in a commercial battery would pose a great impediment owing to the material’s high cost, its hazardous nature, and high susceptibility towards oxidation. The Magnesium Aluminum Chloro Complex (MACC) solutions, developed at the Bar Ilan University in conjunction with its allies at Pellion, Cambridge, MA, consist of solely inorganic salts; MACC is the reaction products of the acid base reaction between MgCl2 and AlCl3 in the right proportion in THF. MACC solutions are endowed with high Mg deposition/stripping cycling efficiency, upwards of 99%, low over-potential for magnesium deposition and a wide electrochemical window of 3.1V. Reversible intercalation/de-intercalation of Mg ions into Chevrel-phase Mo6S8, from a MACC solution has also been demonstrated. Normally, freshly synthesized MACC solution exhibits very poor magnesium deposition/dissolution reversibility. However, it was discovered serendipitously that by an electrochemical process, coined “conditioning”, it is possible to significantly enhance the electrochemical characteristics of such electrolyte solutions. The electrochemical “conditioning” consist of slowly electrochemically cycling the solutions in a sealed cell, using Pt as WE and Mg foil as CE in the potential range of -1.2V and 2.8V. This study is an important step forward, eliminating the need for Grignard/organo-metallic based electrolytes with their intrinsic disadvantages, and towards a more “simple salt” based system.
High-Capacity Characteristics of Li-S Rechargeable Battery Using CNT Electrode
Authors: Tsukahara Naoki , Fukuda Yoshiaki , Nozue Tatsuhiro , Murakami Hirohiko
Published: February 2020

Carbon nanotubes (CNTs) are good electronic conductors and have a high chemical stability. We have synthesized vertically aligned CNTs directly on nickel foils and applied them to a cathode of a lithium-sulfur (Li-S) rechargeable battery [1, 2]. The CNTs grown by our thermal CVD process have characteristically a spiral structure. CNT/S composite cathodes were fabricated by impregnating the CNT films with molten S. Figure 1 shows cycle performance and Columbic efficiency of the CNT/S composite cathode containing 8 mg cm-2 with S content of 86 wt% in a 2032 type cell. LiTFSI (0.86 M) dissolved in DME/DOL (9:1 vol %) with LiNO3 (3 wt%) additives was used as electrolyte. The high S loading cell retained a specific capacity of 1000 mAh g-1 even after 50 cycles. This good performance is considered to be attributed by the spiral CNT structure which can hold the electrolyte containing the dissolved polysulfides with a little loss.

Reference

[1] T. Nozue, presented at the 2012 MRS Spring Meeting, San Francisco, 2012 (unpublished)

[2] T. Nozue, presented at The 54th Battery Symposium, Osaka, 2013 (unpublished)
Size Effect of Sulfur Nanoparticles in Lithium Sulfur Batteries
Authors: Lu Wei , Wang Changhong , Wu Xiaodong , Chen Liwei
Published: February 2020

Here we report size-dependent specific capacities and rate performances of lithium sulfur batteries on the basis of sulfur nanoparticles (SNPs) with different sizes adhering on the surface of reduced graphene oxide (RGO).Uniform SNPs with a tunable particle size from 150 to 10 nm were synthesized via sulfur-amine chemistry based synthesis method with S loading >75% (wt%). Our results clearly demonstrate that sulfur utilization and rate performance are dramatically increased with SNPs size down, due to prominent improvement of electron mobility and enlarging of active region for electrochemical reaction at the interface of sulfur and RGO. Furthermore, SNPs with size of 4 nm were also prepared, whose sulfur utilization can reach up to 100% at the current density of 0.2 A/g. Moreover, the capacity remains at 1254 mAh/g after 200 cycles under the rate of 0.5 C. The initial capacity of 1574 mAh/g remains at 963 mAh/g after 500 cycles under the rate of 1 C rate. Here represents the highest initial capacity and the best capacity retention so far.
Hierarchical Nanostructured Carbon/Sulfur Hybrid Cathode for High-Performance Lithium-Sulfur Battery
Authors: Peng Hong-Jie , Huang Jia-Qi , Zhao Meng-Qiang , Zhang Qiang , Liu Xin-Yan , Wei Fei
Published: February 2020

Among various energy storage/conversion systems, lithium-sulfur batteries are considered as one of the most promising candidate due to not only very high theoretical energy density of 2600 Wh kg-1 (based on lithium-sulfur redox couple) and wide operating temperature range benefiting from its unique multiple-electron-transfer chemistry, but also abundant reserves and environmental friendliness of sulfur. However, several intrinsic obstacles should be overcome for its applicably extension, including the ultra-low electrical conductivity of sulfur and its lithiated products, huge volumetric changes during charge and discharge, and the shuttling mechanism of soluble intermediate polysulfides.

Here, a hierarchical nanostructured carbon/sulfur hybrid in which the porous carbon was in situ integrated into graphene/single-walled carbon nanotube (SWCNT) hybrid matrix with small cyclo-S8 molecule clusters was fabricated as advanced cathode material for lithium-sulfur battery application. The sp2 graphene/SWCNT hybrid interlinked framework was served as robust conductive scaffold with good electrical conductivity and structure stability, while the micro-/mesoporous carbon accommodated sulfur and lithium polysulfides, provided accessibility for liquid electrolyte to active material, and suppress the shuttle behavior due to the spacial confinement. Therefore, such hierarchical all-carbon nanostructure hybridized with small cyclo-S8 molecule clusters obtained an excellent electrochemical performance including an ultrahigh specific capacity of 1121 mAh g-1 at 0.5 C, a favorable high-rate capability of 809 mAh g-1 at 10 C, a very low capacity decay of 0.12 % per cycle, and an impressive cycling stability of 877 mAh g-1 after 150 cycles at 1 C. As sulfur loading increasing from 50 wt % to 77 wt %, high capacities of 970, 914, and 613 mAh g-1 were still available at current densities of 0.5, 1, and 5 C respectively. Based on the total mass of packaged devices, gravimetric energy density of GSH@APC-S//Li cell was expected to be 400 Wh kg-1 at a power density of 10000 W kg-1, matching the level of engine driven systems.

Reference:

[1] HJ Peng, et al. Adv. Funct. Mater., 2014, DOI: 10.1002/adfm.201303296
Solvate Ionic Liquids as Electrolyte for Li-Oxygen Battery
Authors: Tatara Ryoichi , Kwon Hoi-min , Ueno Kazuhide , Tachikawa Naoki , Dokko Kaoru , Watanabe Masayoshi
Published: February 2020

Rechargeable Li-air (Li-O2) batteries have recently attracted enormous attention due to their prospective high energy density. To realize reversible and stable operation of Li-air batteries, however, many serious problems, such as volatilization of electrolyte and electrolyte decomposition by O2
- radical, have to be solved.[1]

Our group recently reported that equimolar mixtures of glymes and Li salts behave as ionic liquids (ILs) rather than as ordinary concentrated electrolyte solutions.[2] For instance, as shown in Fig. 1, triglyme (G3) can coordinate to a Li+ ion, forming a 1:1 complex cation, [Li(G3)1]+; it can also behave as an independent cation similar to the cations of typical ILs. Thus, the glyme-Li salt complex has been categorized as a new subclass of ILs called “solvate ILs”.[3] The solvate ILs have many desirable properties as lithium conducting electrolyte[4]-[5] as well as low volatility and thermal- and electrochemical stabilities, which are crucial for Li-air batteries. In the present study, we applied solvate ILs to electrolyte of Li-air battery.[6]

The solvate IL, [Li(G3)1][TFSA], was prepared by simply mixing purified triglyme (G3) and lithiumbis(trifluoromethanesulfonyl)amide (LiTFSA) in a 1:1 molar ratio. The electrochemical properties of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the solvate ILs were investigated by cyclic voltammetry (CV), rotating ring-disk electrode voltammetry (RRDE) and galvanostatic charge-discharge measurement.

Fig. 2 shows CVs for a glassy carbon (GC) electrode in [Li(G3)1][TFSA] saturated with O2 or Ar (as background). A large reduction peak emerges when the electrode is polarized to negative potential under the O2 atmosphere, and a clear anodic peak can be seen on reversing the sweep from 1.5 to 4.2 V, although no appreciable current is observed under the Ar atmosphere. It suggests that reversible ORR-OER takes place on the GC electrode in [Li(G3)1][TFSA]. The results of RRDE and charge-discharge test in this solvate ILs will also be reported.

Acknowledgement

This study was partly supported by RISING program from the New Energy and Industrial Technology Development Organization (NEDO) of Japan, for which the authors are grateful.

References

[1] P. G. Bruce et al. Nat. Mater. 11 (2012) 19. [2] T. Tamura et al. Chem. Lett. 39 (2010) 753. [3]C. A. Angell et al. Faraday Discuss. 2012, 154, 9. [4] K. Yoshida et al. J. Am. Chem. Soc. 133 (2011) 13121. [5] K. Dokko et al. J. Electrochem. Soc. 160 (2013) A1304. [6] R. Tatara et al. Chem. Lett. 42, (2013) 1053.
Advanced Cathode, Electrolyte and Separator materials to Improve the Energy Density and Cycle Stability of Soft-Package Lithium-Sulfur Battery
Authors: Zhang Hongzhang , Zhang Huamin , Zhang Yining
Published: February 2020

The lithium/sulfur battery has been attracting increasing attention due to their higher theoretical specific energy density (2,600 Wh kg−1), almost ten times greater than that of commercially used lithium ion batteries. However the practical energy density of the Li/S battery (soft package) is still too low (<450Wh/kg), accompanied other unsolved problems as poor cycle life, low safety as well as worse rate capability. In order to solve these problems, we need to develop better cathode materials, better electrolyte composition, better anode protect mechanism and ect.

In our lab, we mainly focus on the study of cathode materials (carbon/sulfur), cathode structure, electrolyte and separators, which combined together to improve the battery performance. For one thing, by improving the cathode (including the carbon surface area, C/S ratio, porous distribution), the energy density of the Li/S battery has been improved to 500 Wh/kg and 600 Wh/L (discharge to 1.5V) in our lab. For another thing, by improving the electrolyte and separator, the Li/S coin cell could cycle 100 cycles (0.1 C) with capacity retention of 70% (still over 800mAh/g (S)) with 3.0 mg/cm2(S) cathode.

In this presentation, the development of Li/S battery in the energy storage department of DICP will be introduced, including materials design (cathode, electrolyte, and separator), preparation and soft package design. Battery performance with different carbon materials combined with different electrolyte and separators series will be summarized and discussed in detail.
Electrochemical Reaction Mechanism of Li2S Active Material in All-Solid-State Lithium-Sulfur Batteries
Authors: Hayashi Akitoshi , Hakari Takashi , Nagao Motohiro , Tatsumisago Masahiro , Ichinose Takahiro , Ozaki Tomoatsu , Togawa Yoshihiko , Mori Shigeo
Published: February 2020

Rechargeable lithium-ion batteries have been widely used in portable electronic devices such as cellular phones and personal computers. Increasingly they are also being scaled up for using large applications in electric vehicles and smart grids. However, due to limited capacity in both cathodes and anodes, the specific energy density of lithium-ion batteries needs to improve remarkably to meet the requirements for practical applications. Current cathode materials have an actual capacity less than half that of anode materials such as graphite and silicon. Therefore, high-capacity cathode materials are required to realize lithium-ion batteries with higher-energy densities. Lithium sulfide, Li2S, is a high-capacity positive electrode material with the theoretical capacity of 1168 mAh g-1. However, there are two major issues to be solved. One is that its low electronic conductivity restricts its actual capacity to much lower values than that theoretically predicted. The other is capacity fading which arises from high dissolution of lithium polysulfide into the liquid electrolyte during the electrochemical reaction of Li2S electrode. The use of inorganic solid electrolyte (SE) is expected to inhibit the polysulfides dissolution. We reported that a Li2S–Cu composite electrode prepared by mechanical milling retained the reversible capacity of 350 mA h g-1 for 20 cycles in all-solid-state cells using Li2S-P2S5 SEs [1]. Recently it is found that Li2S electrode prepared by milling with carbon materials exhibited excellent cycling stability with high capacity of 700 mAh g-1 in the all-solid-state cells [2]. However, the origin of excellent reversibility has not been understood. In this study, reversible structural and morphological changes at the nanoscale during the full-electrochemical cycles in all-solid-state lithium-sulfur batteries have been revealed by high-resolution TEM, electron diffraction, and energy-dispersed X-ray spectroscopy experiments. The smooth and adhesive interface among Li2S active material, Li2S-P2S5 electrolyte, and acetylene black in Li2S composite electrodes is realized at the nanoscale, which is fabricated by mechanical milling technique. Reversible variations during cycles between crystallization and amorphization of sulfur-based active nanoparticles are responsible for the feasibility of the high capacity and excellent cycling stability.

References

[1] A. Hayashi, R. Ohtsubo, T. Ohtomo, F. Mizuno, M. Tatsumisago, J. Power Sources, 183 (2008) 422.

[2] M. Nagao, A. Hayashi, M. Tatsumisago, J. Mater. Chem., 22 (2012) 10015.
The Morphological Effect of Cobalt Oxide Nanocatalysts on the Electrochemical Performance of Lithium-Air Battery
Authors: Song Kyeongse , Cho Eunbi , Jung Jaepyeong , Kang Yong-Mook
Published: February 2020

Next generation rechargeable batteries are required to have higher energy density compared to the state-of-art battery. The energy density of the commercial lithium ion battery cannot meet the stringent requirements, whereas the lithium-air battery has high theoretical specific energy coming up to 11700 Wh/kg because lithium–air battery is based on discharge reaction between Li and oxygen to yield Li2O2. However, very little is known about the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in the cathode of lithium-air battery. Moreover, lithium oxides like Li2O and Li2O2 are formed in cathode, which are thermodynamically difficult to decompose finally leading to an enormous irreversible reaction. Therefore, many efforts to overcome this problem have focused on finding proper catalysts having significantly improved ORR and OER. As reported previously, because versatile nanomaterials such as nanowires, nanocubes or nanosheet have shown unique chemical or physical properties due to the change of surface area, size confinement effects and etc., their electrochemical properties or catalytic effects were quite different from bulk counterparts when they were applied to various energy devices like fuel cell, lithium ion battery and solar cells. So, we judged that the morphological change of nanomaterial-based catalysts can be one of the main keys for controlling ORR and OER activities of lithium-air battery.

In this study, diverse cobalt oxide-based nanocatalysts in the form of nanocubes and so forth were synthesized, and their catalytic activities were compared in the morphological or structural viewpoint.
Lithium-Sulfur Cells: State of the Art, Electrolyte/Sulfur Ratio, Silicon Anodes and Safety Tests
Authors: Hagen Markus , Quiroga-González Enrique , Dörfler Susanne , Tübke Jens , Fanz Patrik , Althues Holger , Krampfert Matthias , Frohberg Jens
Published: February 2020

Lithium-sulfur cells are potential high gravimetric energy density cells with 200-500 Wh/kg. Unfortunately typical used ether based electrolytes are not stable towards Li and degrade during cycling next to a decreasing active Li mass. Typical Li-S publications therefore work with an excess of electrolyte and Li combined with relatively low sulfur loads allowing high cycle numbers at the cost of low practical relevance.

High cell energy densities can only be obtained with a low electrolyte/sulfur ratio (ml/g) next to high sulfur utilization, fraction and load. Unfortunately low amounts of electrolyte typically decrease the sulfur utilization negatively and most sulfur cathodes need electrolyte/sulfur ratios between 5:1 and 10:1 to deliver maximum sulfur utilization. Unfortunately these ratios are too high to surpass the energy density of commercialized Li-Ion technology. We therefore suggest that the reserach focus should be switched away from maximizing only the sulfur utilization to optimization of the whole electrode capacity incl. the electrolytes weight. But even with such electrodes the obtainable cycle number will be low because of the electrolyte degradation. Since no superior, stable electrolytes exist up to now a good strategy might be the use of (lithiated) Si anodes instead of Li metal anodes. Si anodes face severe volume changes during cycling but are at least not completely converted like Li metal anodes. Thus, the electrolyte degradation might be slowlier with Si anodes and allow higher cycle numbers and also higher safety compared to Li metal anodes.

In the talk we would like to give a short overview about state of the art Li-S research, discuss the impact of the electrolyte/sulfur ratio on cell energy density, show some S8-LixSiy full cell results with very high active material loads (Si > 2mg/cm²!) and conlude with safety test results of small Li-S multi layer pouch cells.
New Cell Configuration with Carbon Interlayers for High Cycle Stability Lithium Sulfur Batteries
Authors: Chen Biao , Guo Rui , Li Yong , Liu Wen , Pei Hai Juan , Xie Jingying
Published: February 2020

Lithium sulfur batteries are the most promising next-generation energy storage system due to their high energy density and low cost[1]. Although the studies on Li-S batteries have been ongoing over many years, commercialization of Li-S battery has not been successful due to many problems including the significant capacity fading.

The diffusion of polysulfides causes fast capacity decay of Li-S battery[2]. In this work, a well-designed carbon interlayer was used between the separator and the sulfur electrode for accommodating the migration of polysulfides during cycling. This Li-S cell configuration delivers excellent cycle stability, retaining a reversible discharge capacity of 850.7mAh·g-1 after 50 cycles with a retention rate of 80.5% when the sulfur loading of the cathode is 5.2mg·cm-2(Figure 1). The result indicates that this configuration is highly practical for the lithium sulfur batteries.

References:

[1]P.G.Bruce, S.A.Freunberger, L.J.Hardwick, and J.M.Tarascon, Nature materials., 11, 19(2011).

[2] Y. Yang, G. Zheng, and Y. Cui, Chemical Society Reviews
.,42, 3018(2013).