bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Layer Deposition of Zn(O, S) Buffer Layer on CIGS Solar Cell
Authors: Yu Yu-Hsuan , Kei Chi-Chung , Li Wen-Chieh , Wu Cheng-Han , Liang Shih-Chang , Ni Cuo-Yo , Shiao Ming-Hua
Published: February 2020

Deposition of Zn(O, S) thin film as the Cd-free buffer layer is an important topic in Copper Indium Gallium Diselenide (CIGS) solar cells since it offers the potential enhancements for low cost and good for our environment. For CIGS buffer layer deposition, chemical bath deposition is the most common method in use. However, the incompatibility with in-line vacuum-based production methods is an issue of concerned.

In this study, the buffer layer of Zn(O, S) thin films were fabricated by atomic layer deposition (ALD) method with alternately depositing of ZnS and ZnO thin films, using diethyl Zinc((C2H5)2Zn, DEZ), dimethyl sulfide((CH3)2S, DMS), and H2O as the precursors. As the alternative layers were deposited, atomic layer deposition technique exhibits good step-coverage, uniformity and accurate control of layer thickness. By changing the cycle ratios (m/n) of ZnS and ZnO, the oxygen (O)/sulfide(S) composition can be controlled in the Zn(O, S) buffer layer thin film as shown in Fig. 1. Various O/S composition ratios of Zn(O, S) thin films were deposited on the CIGS absorber. The optical properties, microstructure and chemical analyses of the deposited Zn(O, S) buffer layer thin films were carried out by ellipsometry, scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The CIGS device performances were measured by current-voltage (I-V) measurements.

Keywords: CIGS, Zn(O, S) buffer layer, atomic layer deposition (ALD)

References

[1] U. P. Singh, S. P. Patra. International Journal of Photoenergy, 2010, 311–330.

[2] N. Naghavi, S. Spiering, M. Powalla, B. Cavana, D. Lincot. Progress in Photovoltaics: Research and Applications, 2003, 11, 437-443

[3] U. Zimmermann, M. Ruth, M. Edoff. Proceedings of the 21st European Photovoltaic Solar Energy Conference, Dresden, 2006, 1831–1834.

[4] A. Hultqvist, C. Platzer-Björkman, J. Pettersson, T.Törndahl, M. Edoff. Thin Solid Films, 2009, 517, 2305–2308.

[5]J. Lindahl, J. T. Wätjen, A. Hultqvist, T. Ericson, M. Edoff and T. Törndahl. Progress in Photovoltaics: Research and Applications, 2013, 1588-1597.

Figure 1
Behavior of La0.6sr 0.4Co0.2Fe0.2O3-δ Cathode Powders Surface Modified by Atomic Layer Deposition for Solid Oxide Fuel Cells
Authors: Roeder Jeffrey F. , Zeberoff Anthony F , Van Buskirk Peter C , Torabi Alireza , Barton Joseph , Willman Carl , Ghezel-Ayagh Hossein , Huang Kevin
Published: February 2020

Atomic layer deposition (ALD) has been used to modify the surfaces of La0.6Sr0.4Co0.2Fe0.2O3-
d (LSCF) cathode powders with gadolinium doped ceria (GDC) and cobalt doped zirconia (CDZ). Cyclopentadienyl based Gd and Ce sources were used for GDC, while amidinate and amide sources were used for Co and Zr, respectively. ALD was carried out between 240-260°C. Transmission electron microscopy indicated uniform coating on selected samples, depending on process recipe. Coated powders were pressed into pellets and sintered at 1000°C in air. Microstructural analysis by scanning electron microscopy (SEM) revealed good sintering behavior. Similar sintering was observed for both GDC and CDZ treated powders. Pycnometry showed porosities in the range of approximately 41% for uncoated LSCF and in the range of 37-39% for surface modified powders and mercury probe analysis showed similar pore size distributions. Symmetrical electrochemical cells were prepared from pastes of uncoated and surface modified powders using a scandium stabilized zirconia electrolyte. Electrical impedance spectroscopy showed marked improvements in polarization for the surface modified powders (Fig. 1). ZrO2 and GDC coatings decreased polarization by a factor of 2. CDZ coatings decreased polarization by a factor of up to 4. Equivalent circuit modeling suggested little effect on gas diffusion through the porous structure, consistent with similar porosity values. Intermediate and high frequency contributions were significantly affected, suggesting a strong positive impact of the surface modification on both non-charge-transfer properties and charge-transfer properties, respectively. A pre-fabricated symmetrical cell treated with GDC via ALD showed very similar behavior to a symmetrical cell fabricated from surface modified GDC. This suggests that ALD may be used in alternate ways to improve cathode performance: on a fully sintered cathode or on the powder prior to sintering.

Figure 1
(Keynote) Reactions in Lithium Ion Batteries - Focusing on Interfacial Li+ Transfer -
Authors: Ogumi Zempachi
Published: February 2020

Lithium ion batteries (LIBs) can be defined as

Rechargeable batteries based on rocking-char type reactions of Li+

Batteries are prepared at a discharged state.

In this rocking-chair type batteries, insertion & extraction of Li+play a main role of battery reactions and electron transfer takes place between active materials and current collectors. The reaction seems simple compared with traditional batteries like lead-acid battery but not so simple.

In discharge of LiC6 / LiPF6, EC-DEC / Li1-xCoO2, Li+ inside graphite diffuses to the surface area and jumps out to electrolyte and solvated mostly with EC. The solvated lithium ion diffuses to the interface area between Li1-xCoO2 and electrolyte. Solvated Li+ removes their solvent shell and jump into Li1-xCoO2. The Li+ moves to inner of Li1-xCoO2.

The slowest step determines the reaction rate of the system. Under conditions that diffusion path is short and electronic conduction of the active materials is high and ionic conduction of electrolyte is high, de-solvation process become the slowest step. The activation energy of the step reaches Ca. 60 kJ/mol that depends slightly on electrolyte and is almost independent of host lattice.

Extraction of Li+ from C6Li cause the decrease in valence of carbon (graphene layer) and insertion into Li1-xCoO2 decreases the valence of cobalt forming host lattice. The valence change must cause atomic distance of host lattice, interlayer contraction of graphene forming graphite and elongation of Co-O length, i. e., phase transition must occur in solid phase. No information is available on the rate of this phase transition and we can consider that only oxide and other materials that can change the phase smoothly at the valence change are useful as active materials of lithium ion batteries.

Figure 1
Vanadium and Chromium Molecular Cluster Batteries (MCB): Li- Storage in Transition Metal Complexes
Authors: Rinck Julia , Das Bijoy , Fichtner Maximilian
Published: February 2020

Increasing energy demands and the requirement to reduce carbon dioxide emissions at the same time accelerated the world-wide research on renewable energy sources and energy storage. However, for future applications in personal electronics, electro-mobility and decentralised energy storage, new LIB electrode materials based on light-weight and earth abundant components with superior redox activity, long-term stability and high energy density are urgently required.

The concept of using molecular transition metal clusters as active electrode materials for reversible Li ion shuttling opens up a new direction for energy storage.[1] These metal complexes are interesting electrode materials due to the ability of the transition metal ions to exist in several oxidation states and reversibly reacting with Li.[2,3]

In this study we introduce LIBs based on molecular cluster systems of the early transition metal ions vanadium and chromium as the cathode active material, in a so-called molecular cluster battery (MCB).

Transition metal complexes of different ligand systems were characterised by IR, XRD and SEM techniques. Their Li cycling behaviour was investigated by galvanostatic cycling and cyclic voltammetry (CV). High reversible specific capacities with low capacity loss were found and multi-step redox processes were observed reflecting the various oxidation states of these metal ions. The 2D channels of the crystalline compounds, which are revealed in their crystal packing diagram, are suitable for an easy Li ion transportation trough the structure. The Li ion diffusion coefficients were determined by various electrochemical techniques, such as GITT, CV and EIS to understand the Li ion kinetics of these molecular metal clusters.

The various oxidation steps of molecular cluster compounds allow multi-step redox changes making these materials interesting compounds with potentially high specific capacities and allow a study of the kinetics of the lithium ion diffusion pathway.

References:

[1] H. Yoshikawa, C. Kazama, K. Awaga, M. Satoh, J. Wada, Chem. Commun. 2007, 3169-3170.

[2] H. Wang, Z. Zeng, N. Kawasaki, H. Eckert, H. Yoshikawa, K. Awaga, Chemistry, 2013, 19, 34, 11235-40.

[3] H. Yoshikawa, S. Hamanaka, Y. Miyoshi, Y. Kondo, S. Shigematsu, N. Akutagawa, M. Sato, T. Yokoyama, K. Awaga, Inorg. Chem., 2009, 48, 19, 9057-9059.
High-Voltage Lithium Metal Phospho-Olivines for Li-Ion Batteries
Authors: Allen Jan L. , Allen Joshua L. , Delp Samuel A. , Wolfenstine Jeff , Jow T. Richard
Published: February 2020

There is an ever-growing need for higher energy Li-ion batteries. Lithium metal phospho-olivines based on LiCoPO4 are promising cathode materials to help fulfill this need owing to their relatively high discharge capacity of up to 167 mAh g-1 at a discharge potential of 4.8V [1]. However, LiCoPO4 based Li-ion cells show a severe loss of discharge capacity upon multiple charge – discharge cycles owing to structure deterioration and electrolyte decomposition [2]. Partial substitution of Co by Fe significantly improves the cycle life [3] and increases Li+ ion and electrical transport [4]. Our most recent studies show that multi-element substitution for Co in LiCoPO4 further reduces capacity fade, substantially improves discharge capacity and reduces reactivity of the cathode with the electrolyte. Currently, we have achieved an energy storage capacity of 670 Wh kg-1 of cathode material (84% of LiCoPO4 theoretical) which can be compared to a maximum theoretical 576 Wh kg-1 for commercialized LiFePO4. The capacity fade of Li / LiCo1-xMxPO4 half cells over 500 cycles is less than 6%. This paper will report on our most recent results. We will discuss synthesis methods, transport measurements, electronic structure[5], the most promising substitutional chemistry and the structure of substituted LiCoPO4 as well as performance enhancements that result from improving the electrolyte high voltage stability [6].

References

K. Amine, H. Yasuda, M. Yamachi, “Olivine LiCoPO4 as 4.8 V electrode material for lithium batteries,” Electrochem. and Solid State Letters, 3 (2000) 178.

J. Wolfenstine, U. Lee, B. Poese, J.L. Allen, “Effect of oxygen partial pressure on the discharge capacity of LiCoPO4,” J. Power Sources
144 (2005) 226.

J.L. Allen, T.R. Jow, J. Wolfenstine, “Improved cycle life of Fe-substituted LiCoPO4,” J. Power Sources
196 (2011) 8656.

J.L. Allen, T. Thompson, J. Sakamoto, C.R. Becker, T.R. Jow, J. Wolfenstine, “Transport Properties of LiCoPO4 and Fe-substituted LiCoPO4,” J. Power Sources
254 (2014) 204.

M.D. Johannes, K. Hoang, J.L. Allen, K. Gaskell, “Hole polaron formation and migration in olivine phosphate materials,” Phys. Rev. B 85 (2012) 115106.

J.L. Allen, J.L. Allen, S.A. Delp, T.R. Jow, “Electrolyte additives for reducing the irreversible capacity loss, impedance and polarization of a doped LiCoPO4 cathode,” ECS Transactions
66 (2015) 149.

Figure 1
Li Storage in Olivine Structure LiFexMn1-XPO4
Authors: Xia Yong-Yao , Wang Ke
Published: February 2020

LiMnPO4 shows higher specific energy than that of LiFePO4, but suffers from poor kinetics. The mixed-cation olivine material LiFexMn(1-x)PO4 combined the good rate capability of LiFePO4 and high potential of LiMnPO4. Commonly, LiFe0.5Mn0.5PO4 is considered to exhibit two pairs of plateau in charge-discharge curves associated with MnPO4/LiMnPO4 and FePO4/LiFePO4 phase transformation. We prepared carbon coated LiFe0.5Mn0.5PO4 solid solution material by solvothermal method. This material delivers typical two plateaus in charge/discharge curves at low current rate, but a third plateau appears only during discharge at relative high current rate. The discharge capacity in the addition medium plateau increases with the current rate increases. LiFe0.5Mn0.5PO4 discharge mainly proceeds via the medium plateau at high current rate. Electrochemical measurements demonstrate that the additional discharge plateau can still be attributed to Mn3+ reduction, but with a different mechanism than in pure LiMnPO4 due to the presence of Fe in LiMnPO4 framework that gives the conditions for better kinetics.

Also the battery performance of a full battery consisting of LiFe0.2Mn0.8PO4 and layered transition-metal oxides (NMC) composite cathode and graphite anode was extensively studied. The addition of LMP in NMC greatly improved the battery safety.
Micro-Sized Bulk Porous Si from Fe-Si and Al-Si Alloys As High Performance Anodes for Li-Ion Batteries
Authors: Han Weiqiang , Tian Huajun , He Wei
Published: February 2020

Silicon has been perceived as one of the most promising anodes in the next generation lithium-ion batteries (LIBs) due to its superior theoretical capacity. However, bulk silicon experiences an enormous volume expansion during the lithiation/delithiation process, resulting in rapid capacity fading. And, its high-cost and low coulombic efficiency also present significant challenges for applications. We prepared micro-sized porous Si materials from the abundant and low-cost Fe–Si and Al-Si alloys via a facile process of ball-milling and acid etching. The method of the synthesis was simple, low-cost and industrially scalable. For example, The pure micro sized porous silicon anode from Fe-Si alloy showed a fantastic first-cycle coulombic efficiency of 88.1% and exhibited an excellent cycling stability of 1250 mA h g-1 at 500 mA g-1 after 100 charge/discharge cycles. An excellent rate capability was also demonstrated for the unique well-organized porous structure silicon Even at a high current density of 5 A g-1, the excellent discharge capacity was 558 mA h g-1. The unique well-organized micro sized porous structure could alleviate the volume change of the Si anode during the lithiation/delithiation process resulting in good long-term cycling stability. It is demonstrated that the low cost micro-sized porous Si material is very promising for scalable production of high-performance porous Si anode materials for high-energy lithium-ion batteries.
Novel Method of Contrast Improvement Applied to Lithium Ion Battery Electrode Materials Enabling Multi Modal and High Resolution 3D Imaging and Advanced Quantification
Authors: Biton Moshiel , Yufit Vladimir , Tariq Farid , Kishimoto Masashi , Brandon Nigel P.
Published: February 2020

The authors present for the first time a new methodology of contrast enhancement for multi modal 3D imaging, including novel advanced quantification, on a commercial Lithium Iron Phosphate (LFP) LiFePO4 cathode. The aim of this work is to improve the quality of the 3D imaging of challenging battery materials by developing methods to increase contrast between otherwise previously poorly differentiated phases. This is necessary to enable capture of the real geometry of electrode microstructures, which allows measurement of a wide range of microstructural properties such as pore/particle size distributions, surface area, tortuosity and porosity. These properties play vital roles in determining the performance of battery electrodes. In this study we present a novel method of sample preparation with a new type of epoxy impregnation, brominated (Br) epoxy, which is introduced here for the first time for this purpose and found suitable for multi modal imaging, for both focused ion beam scanning electron microscope (FIB-SEM) tomography and X-ray micro tomography. The Br epoxy improves image contrast, which enables higher FIB-SEM resolution (3D imaging), which is amongst the highest ever reported for composite LFP cathodes using FIB-SEM. In turn it means that the particles are well defined and the size distribution of each phase can be analysed accurately from the complex 3D electrode microstructure using advanced quantification algorithms.

Figure 1: High resolution 3D image of (a) LFP particle size distribution (b) Carbon particle size distribution (each colour represent a different particle size) 

Figure 1
Delithiation Mechanisms and the Surface Morphology of Lithium-Excess Li2MnO3 Material
Authors: Shin Yongwoo , Persson Kristin A
Published: February 2020

One of the most promising avenues for future high energy Li-ion batteries originate from the family of Li-rich, Mn-rich layered composite/solid solution cathodes. However, while it is known that high Li as well as Mn content contributes to the high capacity it also correlates with the chemical and structural degradation of the material. Despite the recent interest in the Li excess materials, and in particular the end member Li2MnO3, the inherent ionic conductivity of the material has not been clarified. Here we present the Li mobility in LixMnO3 (1 < x < 2), involving coherent Li migration from the two Li-containing layers by first-principles density functional theory. Surprisingly, and contrary to expectations from available electrode-level experimental results, we find that the pristine material exhibits excellent Li mobility enabling facile Li extraction from both the transition metal layer and Li-layer. Hence, we deduce that the observed inferior rate behavior of this class of Li cathode materials is not due to intrinsic poor bulk ionic mobility, but more likely due to surface-passivation, structural deterioration, and/or particle-particle electrode-level transport limitations. Speculating that the observed poor Li mobility in Li2MnO3 may be due to first charge release of oxygen which in turn leads to structural and chemical surface densification and poor electron and/or ion transport we investigate the surface oxygen loss as a function of facet and Li content. In the second part of this work, we systematically elucidate all possible low miller index surfaces with various cation ordering on each surface. We find spontaneous surface reconstruction rules that depend on the local environment and finally we show that while all Li2MnO3 surfaces are vulnerable towards oxygen release, some are more resistant than others which provides a design metric for more stable particle morphologies.
Population Balance Model of Formation and Growth of Solid Electrode Interphase in Lithium Ion Batteries
Authors: Tahmasbi Amir Abbas , Kadyk Thomas , Eikerling Michael
Published: February 2020

We develop a physical-statistical model for formation and growth of the solid electrolyte interphase (SEI) in the negative electrode of Li ion batteries. During charging/discharging cycles, the SEI layer forms via a reaction between lithium ions, electrons and solvent molecules. The growth of the SEI layer leads to capacity fade and an increase of the ion transport resistance. In addition, SEI growth decreases the total porosity. Our statistical modeling framework employs the Fokker-Planck theory and it uses a statistical particle density distribution function as input. Structure-changing processes at the particle level transform this statistical distribution, causing changes in battery performance, e.g. capacity fade and power fade. The present study focuses on the impact of SEI formation, explored within this modeling framework. To this end, we have formulated a set of kinetic and transport equations. The solution of the statistical model reveals a broadening of the initial statistical distribution of SEI thicknesses and a growth of the average thickness of SEI increases from 47 nm to 80 nm at 25 oC and C/2 charge rate after 1000 cycles. This results in a 5% reduction of the battery capacity as shown in Fig.1. The statistical model of SEI formation is used to perform a multi-objective optimization to find a set of optimized battery design parameters, which lead to minimizing the capacity loss and maximizing the power density. In this optimization, the weight between capacity loss minimization and power density maximization can be adjusted as desired, as shown in Fig. 2.

Figure 1
Electrochemical Performance of Carbon-Coated Cauliflower-like WO3 for Li-Ion Batteries
Authors: Kammari Sasidharachari , Yoon Sukeun
Published: February 2020

Metal oxides have been considered and investigated as alternative anodes for use in lithium ion batteries. The research focus is on two different mechanism groups: intercalation–deintercalation reaction and conversion (redox) reaction. The intercalation–deintercalation mechanism is that transition metal oxides and other compounds with a multidimensional layer structure can reversibly intercalate lithium ions into the lattice without destroying their crystal structure. While conversion mechanism usually produces metallic nanoparticles embedded in an insulating Li2O matrix and the shows generally much higher theoretical capacity than that of already-commercialized graphite.

Among the metal oxides, tungsten oxides (WO2, WO3, and WO3-x
H2O) as one of the important metal oxides with respect to physicochemical properties, have been extensively investigated for such applications as gas sensors, photocatalysis, electrochromic devices, electronic devices, dye-sensitized solar cells, supercapacitors, and lithium ion batteries. Interestingly, the tungsten oxides have better electronic conductivity (10–10-6 S cm-1) than some of the other oxides; in addition, they also rely on designing a nanostructured particle with a small radius and right crystalline phase for fast lithium-ion insertion and superior electrochemical performance. From this point of view, a wide variety of approaches have been pursued over the years for the synthesis of tungsten oxides, such as nanoparticles, nanowires, nanorods, and nanoflowers using various approaches which include a hydrothermal reaction, combustion process, sol–gel process, solution-phase reaction, template directed method, mechanochemical activation, and hot-wire chemical vapor deposition (HWCVD) method. However, most of the previous approaches led to the formation of monoclinic W18O49, hexagonal WO3, and WO3-xH2O nanostructures. There have been very few studies on nanostructured monoclinic WO3 (m-WO3).

In this study, we will present a facile hydrothermal process that obtains cauliflower-like carbon-coated WO3 oxide with a high rate-capability and good cycling performance for lithium-ion batteries. The motivation in this study is to explore the possibility of using m-WO3 as an anode material for lithium-ion batteries and to elucidate its reaction mechanism with lithium during the charge–discharge process.
Probing the Interfacial Parasitic Reactions Kinetics in Lithium-Ion Battery
Authors: Zeng Xiaoqiao , Chen Zonghai , Amine Khalil
Published: February 2020

The global R&D effort has been driven by the growing application of high energy-density lithium-ion batteries to electrify the transportation system and achieve significant reduction on non-renewable fuels consumption and greenhouse gas emission. However, high initial energy-density is still generally obtained with the price of a reduction on battery safety and life, which are fundamentally connected to the parasitic reactions in the cell at various temperatures. The practical high energy-density lithium-ion chemistry needs to be carefully balanced between energy-density and safety/lifetime of the chosen chemistry. The electrochemical validation of the effectiveness of those approaches for improving battery life is practically trivial, but extremely time-consuming, especially for those chemistries that have already been demonstrated capable of being charged/discharged for more than thousand cycles. Therefore, the fundamental understanding/measurement of parasitic reactions not only helps to select a proper life improving strategy, but also substantially shortens the lengthy electrochemical validating process.

In this work, a home-built high-precision leakage current measuring system was deployed to investigate the parasitic reaction kinetics between lithium transition metal oxide cathode (LiNi0.6Mn0.2Co0.2O2) and conventional carbonate electrolyte (1.0 M LiPF6 EC/EMC 3:7). The working electrode was held at a specific potential using the source meter, presuming that the state of the charge or the lithium concentration in the working electrode will reach an equilibrium state after the constant-voltage charge/discharge. During this process, the electron obtained from the environment by oxidizing the solvent, will be electrochemically monitored by the external circuit. The kinetic study revealed a strong dependence of parasitic reactions on the practical upper cutoff potential in terms of both the reaction mechanism and the reaction rate. The kinetic data also indicated a significant change of reaction mode at ~4.5 V vs. Li+/Li. The study implies that a different strategy might be needed for effective mitigation of the parasitic reactions for materials targeted for operation at a potential higher than 4.5 V vs. Li+/Li. It demonstrated that the kinetic study could be crucial in developing advanced electrode materials with a fundamental balance between energy density and battery life.

Figure 1
Biogenous Iron Oxide(BIOX)-As a High-Capacity Anode Material for Lithium Ion Batteries
Authors: Furusawa Homare , Takeda Yasuo , Imanishi Nobuyuki , Takada Jun
Published: February 2020

1.Introduction

Biogenous iron oxide(BIOX) is produced by Leptothrix ochracea, aquatic bacteria living in the world. BIOX is amorphous Fe3+-based oxide containing Si and P, and takes tube-formed structure. In recent years, lithium-ion batteries have been widely used and intensively studied to meet an increasing variety of application in the future. Especially exploitation of high-capacity lithium-ion batteries is very important. The capacity of BIOX is approximately three times larger than that of graphite, so that BIOX is expected as a new high-capacity anode material for lithium ion batteries. BIOX belongs to the category of conversion anode materials and shows superior cycle and rate performance beyond normal conversion anode; however, the large first irreversible capacity remains in disadvantage for the practical use. In this study, we applied lithium pre-doping to BIOX electrode to eliminate the first irreversible capacity, and succeeded to provide the lithium ion battery with high capacity and high cycle performance.<

2.Experimental

The BIOX cultured in Okayama university was firstly mixed with CNF (Carbon nanofiber) as a conductive agent, SBR (styrene-butadiene rubber) / CMC (carboxymethyl acid) as a binder (80:10:10 wt%) and water as a viscosity adjustor in an agate mortar. The slurry was coated on a copper foil, dried in air at 80ºC and vacuum-dried at 120ºC for 3h. The punched out electrode was pressed under the pressure of 2t.

The first irreversible capacity was eliminated by contacting a lithium metal sheet to the electrode in an electrolyte (LiPF6in EC / DEC (1:1)). The charge-discharge behavior was measured in a coin type cell (2025) with Li metal as a counter electrode. The current rate was 0.1 C (the theoretical capacity of BIOX: 666mAh / g) and the voltage range was set between 50 and 3000mV

3.Results

Figure 1 shows the voltage profiles of the first cycle for the as-prepared and Li- contacted electrodes. The former showed the first discharge capacity of 984mAh/g, and the following charged one of 712mAh/g. The first irreversible capacity is considerably large; the coulomb efficiency is only 72.0%. After the second cycle, almost 100% efficiency was obtained. On the other hand, the Li pre-doping by the contact of Li metal brought the high coulomb efficiency. The electrode of 30 s contacting of Li metal showed discharged capacity of 972mAh/g and charged one of 818mAh/g(coulomb efficiency:84.1% ).

The first irreversible capacity due to the SEI formation on the nano-particles in BIOX may be compensable with the reaction of Li metal in advance.

Figure 1
Electrochemical Performance of Graphite-Silicon Alloy Composite Anodes Using Cross-Linked Poly(vinyl alcohol) Binder for Lithium-Ion Batteries
Authors: Yook Seung Hyun , Kim Sang-Hyung , Kim Dong-Won , Kim Seon-Kyong , Park Cheol-Ho
Published: February 2020

The growing demand for rechargeable batteries requires a great improvement in the energy density of current lithium-ion batteries. In order to increase the energy density of lithium-ion batteries, silicon anode materials have been actively studied, because they exhibit a high theoretical capacity, a low reduction potential, are environmentally benign and are low cost.1 However, they suffer from substantial volume changes during cycling, which are highly detrimental to the cycling stability of lithium-ion batteries. The mechanical stresses caused by repeated volume changes can fracture the electrode, which results in poor electrical contacts between the active materials, electronic conductors and current collector. To solve these problems, many studies have been carried out by different approaches such as controlling the particle size and morphology, alloying with inert metals, embedding silicon in a conductive material, and applying several functional binders. In order to obtain the silicon-based composite anodes with high capacity and good cycling stability, we synthesized silicon alloy that was composed of silicon nanoparticles embedded in Al-Fe-Ti-Ni matrix phases. Using these silicon alloy material, we prepared the composite electrodes composed of graphite powder and silicon alloy particles. In these composite anodes, poly(vinyl alcohol) (PVA)s with different degree of cross-linking were employed as polymer binders. The effect of degree of cross-linking on interfacial adhesion and cycling performance of the composite electrodes was investigated to identify optimum processing condition. A systematic study demonstrated that the appropriate cross-linking of PVA made the electrodes mechanically strong and remarkably improved the cycling stability of the electrodes.

References

1. B. Liang, Y. Liu and Y. Xu, J. Power Sources, 267, 469–490 (2014).
Development of the Next Generation Anode Materials for Super-Efficient Lithium-Ion Batteries
Authors: Bakenov Zhumabay , Molkenova Anara , Zhexembekova Anar , Moldabayeva Azhar , Moldabayeva Marzhan , Kuanyshev Aidyn , Tayuekelev Medet , Beisbayeva Zhuldyz
Published: February 2020

The global environmental and energy challenges demand for an immediate response through decarbonization of the energy sources by technological advances and implementation of renewable sources. From this point of view, the development of super-efficient battery technology has received an extensive attention for electrification of vehicles and grid integration of renewables [1]. Silicon materials have not only overwhelmed the electronics industry, but also can be nominated as a key technology towards achieving such super-efficiency in batteries due to its appealing features associated with the highest-known specific capacity (~4200 mAh g-1), profusion, and attractive cost. However, its promotion in the global market is impeded by low-conductive nature and high structural instability during cycling. The abovementioned restrictions can be surmounted through involvement of stable spinel Li4Ti5O12 (LTO) structure [2] and polyacrylonitrile (PAN) polymer conductive network [3] in the preparation of Si-based anode material with superior electrochemical properties. PAN is considered to be a carbon source with sufficiently large electrical conductivity, while LTO possesses extremely safe “zero-strain” Li-ion insertion/extraction properties. High energy ball milling and heat treatment procedures were employed in the solid-state synthesis of Si/LTO/PAN ternary composite. This presentation will discuss a systematic study on the effect of precursor nature, versatility of components ratios in the composite electrode structure and highlight the process parameters, which play an important role in overcoming problems of Si anode and improving its physical and electrochemical properties.

Acknowledgements

This work was supported by the project grant 5097/GF4 “Development of a novel quartz (SiO2) based anode material for Li-ion batteries” from the Ministry of Education and Science of the Republic of Kazakhstan.

References:

[1] S. Goriparti, C. Capiglia, J. Power Sources 257 (2014) 421-443.

[2] S. Jing, Y. Liang, L. Li, Y. Peng, H. Yang. Electrochimic. Acta 155 (2015) 125-131.

[3] W. Yuping, S. Fang, Y.Jiang. J. Power Sources 75 (1998) 201-206.
Three-Dimensional Phase-Field Simulation of Li Diffusion and Stress Evolution in a Polycrystalline LiCoO2 Cathode
Authors: Tsuyuki Chisa , Yamanaka Akinori , Suzuki Yushi , Asari Yusuke , Iwasaki Tomio
Published: February 2020

The evolutions of stress and strain caused by Li-extraction and -insertion in a LiCoO2 (LCO) is one of the most important phenomena which affect performance of a Li-ion battery (LIB) with the LCO cathode. However, because experimental measurement of the stress and strain evolutions in the LCO is very difficult, numerical simulation models that enable us to investigate mechanical behaviors and electrochemical reactions in LIBs have been actively studied. Recently, the phase-field method, which has been originally developed for simulating microstructure evolutions during solidification and phase transformation in various materials, is used for investigating electrochemical reactions in various electrode materials used in LIBs. In this study, three-dimensional (3D) phase-field simulations of the Li diffusion and the stress evolution in a polycrystalline LCO cathode were performed. In order to perform the 3D simulations efficiently, the stress evolution in the LCO was calculated on the basis of the phase-field microelasticity theory that employes the fast Fourier transform algorithm to solve the mechanical equilibrium equation. As an example of the simulation results, the calculated distributions of Li concentration and the von Mises stress in a polycrystalline LCO cathode are shown in Fig. 1. Through the 3D simulations, the effects of microstructural factor of the LCO cathode, such as crystal orientation and grain size, and external mechanical boundary conditions on the Li diffusion and the stress evolution in the cathode were investigated.

Figure 1
Preparation of Highly Porous Silicon As an Anode for Lithium Ion Batteries
Authors: Ngo Duc Tung , Kim Young-Jae , Park Chan-Jin
Published: February 2020

The mobile world depends on lithium ion batteries (LIBs), which provide portable power for variety of applications, ranging from personal electronic devices such as laptops, mobile phones, digital cameras to electric vehicles due to the high energy density, low self-discharge and long cycle life of LIBs.

Nevertheless, current LIBs cannot still meet recent increased needs for higher energy density batteries from industries. Nowadays, LIBs can store more than double (200 Wh kg-1) energy density compared with the first commercial LIB. However, this value is still far from the goal in energy density of battery (400 Wh kg-1). Basically, this limitation of LIBs originates from their electrode materials; graphite as an anode and LiCoO2 as a cathode. Accordingly, to improve the energy and power densities of the LIBs, one of the easiest ways is to replace the conventional anode and cathode materials by other advanced materials with better capacity, rate capability, etc. In this context, Li alloys have emerged as a promising alternative candidate to replace graphite anode for LIBs due to the high specific capacity of the Li alloys. Although issues related to poor capacity retention of Li alloys caused by the large volume change during the lithiation/delithiation process have been addressed using new binders and electrolyte additives, the practical application of Li alloys as an anode is still a challenge, especially due to the limited rate capability of the Li alloys. Among the Li alloy based materials, silicon (Si) is considered the most suitable anode for LIBs due to the high theoretical capacity of 4200 mAh g-1 and low cost of Si.

In this work, we report the synthesis of highly monodisperse porous Si using a simple and scalable method. The porous nature of the Si enabled the homogeneous stress distribution within the structure during lithiation and delithiation, leading to the dramatic improvement in electrochemical stability. In particular, the high porosity offered the large electrolyte accessible surface area, the short Li-ion diffusion path, and the void spaces necessary for volume expansion. The porous silicon demonstrated the excellent reversible capacity and the minimal capacity fading for longer than 100 cycles at the high rate of C/10 (80% capacity retention with ~100% Coulombic efficiency). Further, this material exhibited the potential as an anode material for lithium-sulfur analogous battery.
Graphene Coated LiNi0.5Mn1.5O4 for High Power Positive Electrode Material of Lithium Batteries
Authors: Lee Chang-Woo , Kim Jun-Ho , Lee Hyun-Ju , Kim Jeom-Soo
Published: February 2020

Recently, high power rechargeable lithium-ion batteries have become the dominant power source for xEVs (HEV, PHEV, and BEV). LiMn2O4 (LMO) is well known cathode material and adopted in the field required high power. However, the application of LMO is somewhat limited due to the low energy compared to other positive materials. One of strategies to improve the energy density is increasing their operation voltage by using high voltage positive material. Fortunately, a spinel LMO can be modified by replacing Mn with some portion of Ni to realize the high operation voltage, which is LiNi0.5Mn1.5O4. Ni-substituted spinel, LiNi0.5Mn1.5O4, has a voltage plateau around 4.7 V (vs. Li/Li+) which is 0.7 V higher than LMO has. One of the restrictions for LiNi0.5Mn1.5O4 as the positive electrode material is its relatively low electronic conductivity (~10-5 S/cm) which exerts negative effects on the power performance.

In this study, it has been attempted to improve the power capability of LiNi0.5Mn1.5O4 by enhancing surface conductivity. The homogeneous LiNi0.5Mn1.5O4 powder was obtained through the alcohol-assisted hydrothermal process followed by surface coating with the graphene. Two different process has been applied for graphene coating such as solution and mechanical method respectively. It will be discussed that the effect of graphene coating on the physical and electrochemical properties of LiNi0.5Mn1.5O4.

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Interface Design with Conducting Polypyrrole Thin Film for Improving the Storage Property of Ni-Rich Materials
Authors: Cao Jingchao , Xiao Kesong
Published: February 2020

Layered high nickel composites, such as LiNi0.9Co0.1O2, LiNi0.85Co0.1Al0.05O2 and LiNi0.8Co0.1Al0.1O2, are considered to be the most promising materials for hybrid electric vehicles, plus-in bybrid vehicles, and electric vehicles due to their large capacity, good C-rate capacity and long cycle life. However, the characteristics of rapidly moisture absorbing and residual alkaline substance such as Li2CO3 and LiOH limited their practical applications. Considered the long life of the cathode material is an important factor during its application, the storage property of Ni-rich materials has attracted much attention. It is obviously known that the Ni-rich composites easily absorbed H2O and CO2 after being exposed to air, and Li2CO3, LiOH and NiO-like species were identified to the major species formed on the surface. These impurities are believed to be responsible for storage loss.

Meanwhile, attempts have been made to reduce the storage loss by two approaches, ie.: (1) decreasing the nickel content on the surface of the compound, such as coating, core-shell structural design and gradient structural design; (2)storing the materials in an atmosphere without H2O and CO2. As a result, a marked improvement in storage properties is achieved. In our study, surface design with conducting polypyrrole thin film, which is just like a capsule shell, can avoid the indirect contact with atmosphere and protect the core materials form corrosion causing by HF attacking.

The PPy-coated cathode materials were prepared by the chemical polymerization with and p-toluenesulfonate as the dopant. H2O2 was chosen as the oxidant in order to avoid the introduction of other impurity ions. X-ray diffraction (XRD) was employed to identify the crystalline phase of the products. The surface species on the materials surface were identified through Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectroscopy (EDXS). Transmission electron microscope (TEM) was used to identify the thickness of the thin film. To quantify the amount of the conducting thin film, thermogravimetric analysis (TGA) was carried on. Exposure test was carried out to determine the storage properties of pure and treatment composites. In order to measure the amount of residual alkaline substance on the surface, powders were soaked in water and the LiOH/Li2CO3were measured using titration method. All electrochemical properties of the composites were investigated by using coin cells (2016 type).

The results indicates that the Ni-rich composites designed with conducting thin film on the surface can effectively improve their storage properties. The amount of residual alkaline substance on the surface of powders coated with conducting thin film are greatly reduced after being exposed in air, compared with un-treatment powders. The thin film on the surface builds a conductive network, which is beneficial to improve their electrochemical properties as well.
Kraft Lignin - an Alternative Sustainable Binder Material for Green Li-Ion Batteries
Authors: Lu Huiran , Cornell Ann , Alvarado Fernando , Behm Mårten , Leijonmarck Simon , Li Jiebing , Tomani Per , Lindbergh Göran
Published: February 2020

The binder material plays an important role in the electrodes for Li-ion batteries, keeping good electrochemical stability and adhesion with the current collectors. The conventional binder for the commercial Li-ion batteries is poly vinylidene fluoride (PVDF). However, it requires dissolving in an organic solvent, typically N-methyl-2-pyrrolidione (NMP), which is toxic and expensive.

Kraft lignin is a byproduct which is extracted from pulp and paper industries by the LignoBoost process [1]. Its utilization has gained considerable attention due to its reasonable cost, relatively high purity and being renewable. In this work, kraft lignin was used for the first time as a binder material in Li-ion batteries [2]. It is more environmental friendly and potentially less expensive compared to the PVDF binder. Electrodes, LiFePO4 positive and graphite negative electrodes bound by kraft lignin, were characterized using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and galvanostatic charge-discharge cycles. Results show that the electrodes have good reversible capacities about 150 mAh g-1 for positive electrode and 300 mAh g-1 for negative electrode cycled at C/10, and fairly good rate capabilities. The negatives have a very high cycling stability with about 98% retention after 50 cycles cycled at C/4. It illustrates that lignin is a promising alternative sustainable binder material for green Li-ion batteries.

Reference

1. Tomani, P., The lignoboost process. Cellulose Chemistry & Technology, 2010. 44(1): p. 53.

2. Lu, H., et al., Lignin as a Binder Material for Eco-Friendly Li-Ion Batteries. Materials, 2016. 9(3): p. 127.

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Sonication-Induced Colloidal Nanocrystals of High-Capacity Cathode Material for Advanced Lithium-Ion Batteries
Authors: Zhao Jianqing , Huang Ruiming , Gao Lijun , He Huixin , Wang Ying
Published: February 2020

In this work, a facile surfactant-free sonication-induced route is developed to prepare colloidal nanocrystals of lithium-excess transition metal oxide (Li1.2Mn0.54Ni0.13Co0.13O2, hereafter marked as LMNCO) which is an emerging lithium-ion battery cathode material having very high theoretical capacity. The sonication process plays a critical role in forming LMNCO nanocrystals in ethanol (ethanol molecules marked as EtOHs) and inducing the interaction between LMNCO and ethanol molecules. The formation mechanism of LMNCO-EtOHs supramolecules in the colloidal dispersion system is proposed and examined by fluorescence spectra, theoretical simulation and Zeta potential measurements. It is suggested that the as-formed supramolecule is composed of numerous ethanol molecules capping at the surface of LMNCO nanocrystal core via hydrogen bonding. Such chemisorption gives rise to dielectric polarization of the absorbed ethanol molecules, resulting in a negative surface charge of LMNCO colloids. Additionally, diverse superstructures are resulted from self-assembly of LMNCO colloids during evaporation of ethanol. These self-assembly behaviors of colloidal LMNCO nanocrystals are then investigated by tuning the solvent evaporation condition. The assembled LMNCO architecture exhibits remarkably improved capacity and cycleability as compared to the original LMNCO particles, demonstrating a very promising cathode material for next-generation lithium-ion batteries. This work thus provides new insight into the formation and self-assembly of multiple-element complex inorganic colloids in common and surfactant-free solvents for enhanced performance in device applications.