bluuebunny/crossref_metadata_2025 huggingface dataset:
Understanding the Degradation Mechanism of Lithium Nickel Oxide Cathode for Li-Ion Batteries
Authors: Tong Wei , Xu Jing
Published: February 2020

Nowadays, Li-ion battery technology has become one of the best performing energy storage devices and holds the best promise to power the upcoming electrical vehicles (EV).1 Continuous search of cathode materials with even better performance and lower cost ($/Wh) led to numerous layered lithium transition metal oxides, such as LiNixMnyCozO2 and LiNixCoyAlzO2 (0 < x, y, z <1). Recently, there is an emerging interest on developing Ni-rich cathode materials because a higher level of Ni incorporation can lead to a higher practical capacity.2 This is resulted from the electronic configuration of Ni3+ (3d7), allowing the removal of electrons only from the eg band, therefore, the loss of oxygen occurs at a higher charge state.3 On the other hand, a higher Ni content may result in a severe capacity fade during cycling, likely due to the structural transformation in the bulk and at the surface.4, 5 A combination of different transition metals in these LiNixMnyCozO2 or LiNixCoyAlzO2 further increases the complexity of the problem because of the phase separations and side reactions with electrolyte resulting from the difference in chemical and electrochemical reactivity of the transition metals. We have reported the synthesis of high-performance LiNiO2
6, here, we will use it as a model system to reveal the intrinsic performance degradation mechanism originating from the high Ni content for those complex R-3m layered oxides.

The phase transition, charge compensation and local chemical environment of Ni in the bulk and at the surface of LiNiO2 were investigated by a variety of bulk and surface characterization techniques for different terms of cycling. We revealed the phase transition from original hexagonal (H1) phase to another two hexagonal (H2+H3) phases and observed a gradual loss of H3 phase features over the extended charges. The reduction in Ni redox activity occurred in both charge and discharge states, and it appeared both in the bulk and at the surface over the extended cycles. The destruction in crystal structure, and Ni redox activity simultaneously contributed to the cycling performance decay of LiNiO2.

Reference

1. M. S. Whittingham, Chemical Reviews, 2004, 104, 4271-4301.

2. M. H. Choi, C. S. Yoon, S. T. Myung, B. B. Lim, S. Komaba and Y. K. Sun, Journal of the Electrochemical Society, 2015, 162, A2313-A2318.

3. M. Balasubramanian, X. Sun, X. Q. Yang and J. McBreen, Journal of Power Sources, 2001, 92, 1-8.

4. P. F. Yan, J. M. Zheng, D. P. Lv, Y. Wei, J. X. Zheng, Z. G. Wang, S. Kuppan, J. G. Yu, L. L. Luo, D. Edwards, M. Olszta, K. Amine, J. Liu, J. Xiao, F. Pan, G. Y. Chen, J. G. Zhang and C. M. Wang, Chemistry of Materials, 2015, 27, 5393-5401.

5. J. M. Zheng, W. H. Kan and A. Manthiram, Acs Applied Materials & Interfaces, 2015, 7, 6926-6934.

6. J. Xu, F. Lin, D. Nordlund, E. J. Crumlin, F. Wang, J. Bai, M. M. Doeff and W. Tong, Chemical Communications, 2016, 52, 4239-4242.
Comparative Study of Fluorinated and Non-Fluorinated Electrolytes in Li[NixMnyCoz]O2/Graphite Pouch Cells
Authors: Ma Lin , Xia Jian , Dahn Jeff R
Published: February 2020

The fluorinated electrolyte system, fluoroethylene carbonate (FEC)/bis (2,2,2-trifluoroethyl) carbonate (TFEC) (1/1 w/w), has shown promising performance when Li[Ni0.42Mn0.42Co0.16]O2(NMC442)/graphite pouch cells were operated at 4.5 V.1 Therefore Li[Ni1/3Mn1/3Co1/3]O2(NMC111), NMC442, Li[Ni0.5Mn0.3Co0.2]O2(NMC532), Li[Ni0.6Mn0.2Co0.2O2](NMC622), Al2O3 coated NMC532 and Al2O3 coated NMC622/graphite pouch cells were examined using the FEC/TFEC electrolyte system and compared to cells made with the traditional electrolyte solvent system: ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3/7 w/w). Both electrolyte systems contained 1M LiPF6 and 2% prop-1-ene-1,3-sultone (PES) plus 0.5% methylene methane disulfonate (MMDS) as electrolyte additives.2,3

This systematic study was performed using the ultra high precision charger (UHPC) at Dalhousie University, electrochemical impedance spectroscopy (EIS), gas evolution measurements and long term cycling tests. A wide upper cut-off voltage window was explored during extensive UHPC testing (from 4.1 V to 4.6 V). The charge end-point capacity slippage, capacity fade, columbic efficiency (CE), impedance change during cycling and gas evolution were compared to measure the effects of different electrolyte solvents on different NMC/graphite pouch cells.

Figures 1(a-d) show that the coulombic efficiency (CE) of the FEC/TFEC system is higher than that of the EC/EMC system for all uncoated NMC grades except for NMC622 when the upper cut-off voltage is 4.5 V. This suggests better long term cycling performance at high voltage when FEC/TFEC is used, except for NMC622. The reactions between charged NMC grades (4.5 V) and these two electrolyte systems at elevated temperatures were also investigated by accelerating rate calorimetry (ARC). Figures 1(g-h) show that FEC/TFEC does not affect the thermal performance of NMC532 and NMC622 compared to EC/EMC. However, the self-heating rate of charged NMC111 or charged NMC442 reaction with FEC/TFEC is higher than that of EC/EMC after a temperature greater than 150°C. This means that cell designers will need to may close attention to the impact of fluorinated solvents on cell safety.

References:

1. J. Xia, M. Nie, J. C. Burns, A. Xiao, W. M. Lamanna, and J. R. Dahn, J. Power Sources. 307 (2016) 340–350.

2. K.J. Nelson, Jian Xia and J.R. Dahn, J. Electrochem. Soc. 161 (2014) A1884-A1889.

3. J. Xia, N. N. Sinha, L. P. Chen, G. Y. Kim, D. J. Xiong and J. R. Dahn, J. Electrochem. Soc. 161 (2014) A84-A88.

4. J. Xia, M. Nie, L. Ma and J. R. Dahn, J. Power Sources. 306 (2016) 233–240.

Figure 1
Phase-Field Simulation of Li Intercalation-Induced Stress Evolution in an Elastically Imhomogeneous LiCoO2 Polycrystals
Authors: Yamanaka Akinori , Suzuki Yushi , Tsuyuki Chisa , Asari Yusuke , Iwasaki Tomio
Published: February 2020

The phase-field method, which has been originally developed for simulating microstructure evolutions during solidification and phase transformation in metallic materials, is actively used for simulating electrochemical reactions and microstructure evolutions in lithium ion batteries (LIBs). Recently, Yamakawa et al. [S. Yamakawa et al., Solid State Ionics, Vol. 262 (2014), pp. 56-60.] proposed a two-dimensional phase-field (PF) model for simulating the Li diffusion and the stress evolution in a polycrystalline LiCoO2 (LCO) electrode. Wu et al. [L. Wu et al., Journal of Power Sources, Vol. 299 (2015), pp. 57-65.] extended the PF model proposed by Yamakawa et al. in order to simulate the Li intercalation-induced stress evolution in three-dimensions. However, these previous studies assumed the LCO was elastically isotropic material, and moreover, the electrolyte that filled between the LCO grains was not taken into account directly. In this study, in order to consider a realistic situation of the LCO electrode in the LIB, a three-dimensional PF model of the Li diffusion and the stress evolution in the LCO was developed on the basis of the phase-field microelasticity theory for an elastically inhomogeneous system. In order to accelerate the calculation of the stress evolution, we employed parallel computing technique using a graphic processing unit (GPU). Using the developed PF model, we investigated the effect of pores and electrolyte in a polycrystalline LCO electrode on the Li diffusion and the stress evolution in the LIB.
Lithium Transport in High-Capacity Encapsulated Silicon-Vacnt Electrodes
Authors: Fan Juichin , Harb John N. , Davis Robert C. , Vanfleet Richard R.
Published: February 2020

Si-based anodes are being explored for use in advanced lithium ion batteries due to their capacity and energy density, which exceeds that of current graphite anodes. However, there are several important factors that influence and often limit the cycling performance of these electrodes including large silicon volume changes and extensive SEI formation. Nanostructured electrodes have been shown to effectively reduce the negative impact of volume expansion; however, the use of nanostructures can greatly increase the electrode/electrolyte surface area and lead to greater SEI formation. Consequently, several strategies have been developed to reduce the area available for SEI formation while maintaining the benefits of a nanostructured material. In this study, we use silicon-coated vertically aligned carbon nanotube (Si-VACNT) electrodes to examine the role of Li transport in a system where encapsulation has been used to reduce the surface area of the nanostructured electrode that is exposed to the electrolyte. This system is ideal for studying the impact of an electrolyte-blocking layer due to its well-defined geometry and high aspect ratio. Since transport plays an essential role in the cycling performance of these electrodes, it is desirable to understand the factors that govern the transport of Li into and out of the silicon anode in the absence of electrolyte. Two different transport directions and length scales are relevant—1) radial transport of Li in/out of each silicon-coated nanotube (~50nm diameter) and 2) lithium transport along the length of the nanotubes (~100 micron height). Experimental results indicate that the height of the Si-VACNT electrodes does not appear to limit Li transport, even though that height was orders of magnitude greater than the diameter of the tubes. This result has important implications for a variety of encapsulation strategies. Additional tests were performed to characterize transport in the radial direction, which appeared to be a limiting factor. These tests included GITT (galvanostatic intermittent titration technique) measurements and EIS measurements on differently sized electrodes at different conditions. Hysteresis was also examined. Finally, a model was developed to help explain the experimental observations.
Understanding the Heat Signature from Charging and Discharging of Li-Ion Batteries
Authors: Ralbovsky Peter Joseph
Published: February 2020

Recently the development of new calorimetric tools to measure lithium-ion batteries during the cycling process has allowed researchers and engineers to better understand how the battery operates, determine efficiency at different temperatures and power levels, design appropriate thermal management systems, as well as to look at entropy changes and parasitic reactions. Also heat output and entropic changes to the cells can be used for aging studies or to determine the State-of-Health (SOH) of a cell. 

An example of a heat signature measured for an 18650 lithium ion cell is provided. The current and heat signal measured from three consecutive charge and discharge cycles are shown. In this example an 18650 cell was charged and discharged at a constant current (500 mA or C/5) for 150 minutes. The heat measured by the calorimeter shows good repeatability for the three cycles both in general size and shape but also in some finer details where there is some smaller mechanism occurring within the cell in a repeatable manner. The heat signal which is measured is the sum of the reversible (entropic) heat and the irreversible heat (ohmic and polarization). The irreversible heat is always exothermic while the reversible heat is endothermic on the charge and exothermic on the discharge. Therefore the total heat measured from the discharge (exothermic) will always be larger than the total heat measured from the charge (endothermic). This can clearly be seen in the example provided.

From monitoring the voltage and current, the total efficiency of the battery can be measured by looking at the differences in the total charge from 0-100% SOC. Measuring the open cell voltage (OCV) at different SOC and temperatures can be used to calculate entropy. The addition of accurately measuring heat during these cycles provides a direct measurement of wasted energy and the calculation of efficiency can done between any two different SOC. Entropy can be measured both using OCV and through low current heat measurements. The combination of the approaches can provide insight into the fine details of the heat signatures that are measured for specific cell chemistries. Such an approach is detailed in this paper.

Figure 1
Hybrid Separator Composed of Pvdf-HFP/Exfoliated Graphene Oxide Nanosheets for Li-Ion Batteries
Authors: Choi Yunah , Park Jong Hyeok
Published: February 2020

We report novel poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP)/ graphene oxide (GO) nanocomposite separators for lithium secondary batteries. During phase inversion of PVdF-HFP which is the origin of pore generation, GO nanosheets can be incorporated into the PVdF-HFP skeleton. The battery performances of the cells with the PVdF-HFP/GO nanocomposite separators were greatly improved compared to pure PVdF-HFP based one. In addition, the thermal stability of the nanocomposite separators is also greatly enhanced by the addition of GO, in which the battery cells with composite separators that are thermally annealed at 150 and 180 °C function well. The inclusion of 2-dimensional GO nanosheets could also enhance the tensile strength of neat PVdF-HFP separators, leading to mechanically stable polymer separators.
Correlation of Local Conductivity to Microstructure for Li-Ion Battery Electrodes By Use of a Contact Probe and SEM/FIB
Authors: Vogel John E , Lange William , Clement Derek V , Mazzeo Brian A , Wheeler Dean R
Published: February 2020

Electron transport in lithium-ion battery structures is a key factor in overall battery performance, but the cause of localized high and low electron transport values, or conductivity, has not been well-studied or understood. Factors that may affect such heterogeneity include high-level variables such as film composition and porosity, as well as manufacturing steps such as film drying and calendering [2].

Here we report on our efforts to correlate battery film structure to measured conductivity values, to better understand the causes of observed film heterogeneity. A modified micro 4-line probe [1] was installed in a high resolution stage with a microscope attached for localization on a µm scale. Using the associated theory, electrical conductivity of commercially manufactured battery films was mapped. Subsequently, particularly “hot” or “cold” conductivity locations were additionally investigated by scanning electron microscope (SEM) combined with focused ion beam (FIB) milling to produce planar cross sections.

SEM/FIB images are segmented into 3 domains: carbon, active material, and pores. Each image is characterized using key metrics. These key metrics are then compared to mapped conductivity values in order to determine possible causes of high and low conductivity. This contributes to the goal of this work, namely to increase the uniformity of electrodes by improved control of the manufacturing process.

Figure 1: Measured electrical resistivity of commercial anode (top) with SEM/FIB cross section of region with high conductivity (bottom).

References

[1]

B. Lanterman et al. "Micro-four-line probe to measure electronic conductivity and contact resistance of thin-film battery electrodes," J. Electhrochem. Soc., vol. 162, pp. A2145-A2151, 2015.

[2]

M. Forouzan et al. “Experiment and simulation of the fabrication process of lithium-ion battery cathodes for determining microstructure and mechanical properties,” J. Power Sources, vol. 312, pp. 172-183, 2016.

Acknowledgements

This research is supported by the US Department of Energy through the Advanced Battery Material Research Program.

Figure 1
Towards a Better Understanding of Batteries: Manufacturing and Modeling Using Comsol
Authors: Moss Pedro L. , Chepyala Seshuteja , Weatherspoon Mark H.
Published: February 2020

High energy lithium (Li) batteries are fast becoming a promising energy market for applications in the automotive and portable power markets. In the search for better specific energy and lower cost to manufacture the batteries, novel methods are being researched to overcome the design and operational entices before becoming commercially viable. One of these methods to achieve the above said goals is to manufacture the cells and compare the manufactured cell with its model using COMSOL Multiphysics.

This paper proposes battery cell manufacturing and laboratory level testing combined with advance modeling techniques to obtain a correlation for the cell life and stability characteristics data obtained by both simulation and manufactured cell. The batteries are made in the laboratory using the proven and tested methods and the cells are assembled after performing detailed analysis on the surface area and BET analysis of the electrodes. The cells are modeled in COMSOL Multiphysics to estimate the cycle life and stability and to check whether the simulated data is the same as the estimated data. This latter model is then used to check the performance of the cell. The COMSOL simulations are done for different cells and the data is compared with their respective manufactured cell data. The cells are prepared using various available electrode materials and extensive study is carried out regarding the assembly and manufacturing.

Preliminary tests of cathode electrode half cells using lithium iron phosphate (LFP) have achieved good results and the theoretical and practical specific capacities are similar as shown in Figure 1. We are able to achieve the specific capacity of LFP half-cell close to 135mAh (densified) as compared to the theoretical capacity of 155mAh. The cells should show similar charge discharge performance when modeled in COMSOL and achieve the similar results when the cells are tested. The results are discussed and recommendations made on battery dimensioning using the specifications observed.

Figure1:

Figure 1
Hetero-Nanonet Mediated Paper Batteries with Origami Foldability
Authors: Yoo JongTae , Cho Sung-Ju , Choi Keun-Ho , Lee Sang-Young
Published: February 2020

Advent of new smart energy era including electric vehicles, grid scale energy storage systems, and flexible/wearable electronics indispensably requires full-fledged rechargeable power sources with reliable electrochemical performances and versatile form factors as a key enabling technology. Here, as a naturally abundant and environmentally friendly paper-mediated material/architecture strategy to address the challenges of conventional battery technologies, we demonstrate a new calss of hetero-nanonet (HN) paper batteries based on one-dimensional (1D) building blocks of cellulose nanofibrils (CNFs)/multiwall carbon nanotubes (MWNTs). The HN paper batteries consist of CNF/MWNT-intermingled geteronets embracing electrode active powders and microporous CNF separator membranes. The CNFs and MWNTs are well intermingled, producing the hetero-nanonets embracing LiFePO4 powders. The CNF/MWNT-intermingled heteronets allow the formation of highly-reticulated CNT networks and also interstitial voids, thus creating 3D bicontinuous electron/ion conduction pathways that can boost redox reaction kinetics of the HN electrodes. Also, the HN electrodes can be knotted in the form of a ribbon without mechanical rupture.

Over a wide range of discharge current densities the HN cathode shows significant improvement in the discharge capacities than the conventional one, demonstrating the electrochemical superiority of the HN cathode in the rate capability of cells. The HN cathode can be folded at an interval of 5 mm. Such excellent flexibility of the HN cathode is due to the CNF/MWNT heteronet-mediated structural tolerance/compliance. Finally, we fabricated the paper crane HN full cell. Over a wide range of bending radius the HN paper cells showed the superiority in areal capacity than the previous works.

In summary, we present a new class of hetro-nanonet paper batteries based on one-dimensional building blocks of CNFs/MWNTs. The CNF/MWNT heteronanonet-mediated material/structural uniqueness enables the realization of three-dimensional bicontinuous electron/ion transport pathways and also exceptional mechanical compliance.
Accelerating Rate Calorimetry Tests of 18650 Li-Ion Cells before and after Storage Degradation at High Temperature
Authors: Konakawa Kotaro , Mendoza-Hernandez Omar S. , Sone Yoshitsugu , Ishikawa Hiroaki , Umeda Minoru
Published: February 2020

The use of Li-ion cells has been growing globally with a large number of cells powering a wide range of applications in variety of environments, and there have been several reported incidents raising safety concerns. Some of the cases have been related to overheating (thermal runaway) of Li-ion cells. Thermal runaway occurs when the exothermic reactions go out of control, thus the self-heating rate of the cell increase to the point that it begins to generate more heat than what can be dissipated. Understanding the behavior of Li-ion cells during thermal runaway is critical to evaluate the safety of these energy storage devices under outstanding conditions. In this work we analyze the thermal runaway behavior of 18650 Li-ion cells before and after storage degradation at high temperatures. The thermal behavior of the cells is analyzed using accelerating rate calorimetry.

Non-degraded and degraded commercial available 18650 Li-ion secondary cells were tested. The nominal capacity of the cells is 2550 mAh anode and cathode materials are graphite and LiCoO2 + additives, respectively. In order to degrade the cells, these were stored at 80°C and at different state of charges. The cells were tested inside an accelerating rate calorimeter (ARC, 2000TM Columbia Scientific Industries) to record exothermic and thermal runaway reactions under adiabatic conditions. The cells were charged/discharged using a battery tester (KIKUSUI, PFX2011).

Figure 1 shows the exothermic degree of non-degraded and degraded Li-ion cells as a function of state of charge. The data were generated from the self-heating rates of the cells obtained during the ARC tests at 180°C, where the self-heating rates of the cells were normalized based on the highest self-heating rate. This plot is useful to compare the exothermic behavior of the Li-ion cells at different state of charges. The non-degraded cell exhibited the largest exothermic degree at 100% SOC and the lowest degree at 0% SOC. The degraded cells presented lower exothermic degrees than that of the non-degraded cell at 100% SOC but higher exothermic degrees at 0% SOC.

Figure 1
Molecular Modeling of Energy Barrier of Li Ion Transport from Negative to Positive Electrodes
Authors: Saito Shuhei , Alam Md. Khorshed , Takaba Hiromitsu
Published: February 2020

Lithium ion battery is used as a main power supply of a small portable device and large power supplies for electric cars. For further applications, however, an improvement in battery performance from materials level based on rational design of Li ion transport in the battery is needed. In this study, we carried out systematic analysis of energy barrier of Li ion transport from anode to cathode materials using first-principles molecular dynamics and classical molecular dynamics. First, we calculated the energy barrier of diffusion of Li ion through several kinds of electrolyte. To validate the accuracy of calculated transport properties, diffusion coefficients and activation energies for diffusion of ions in LiPF6-DEC-EC at different temperature (-20 ℃ – 20 ℃) and ratio of DEC/EC are compared with experimental data and confirmed the reasonable agreement. Furthermore, the solvation energy of Li ion in electrolytes as well as the salvation structure were investigated by density functional theory and classical molecular dynamics. First principles molecular dynamics and density functional theory were used to calculate the adsorption energy and activation energy fir diffusion of Li ion in cathode materials such as LiCoO2. From these analysis, we conclude that the solvation energy, which is more than 50 kcal/mol for EC/DEC system, is the highest energy barrier for transport of Li ion of which would be the limited step for Li ion transport although it depends on the condition. We also investigated the influence of these transport properties to the battery performance (I-V curve). We will present more concrete data regarding Li ion transport at the conference.
Carbon Fiber Coated MnO2 As Sulfur Carrier for Lithium Sulfur Battery
Authors: Zhang Yun , Guo Yi , Wu Nai Teng
Published: February 2020

Carbon fiber derived from bacterial cellulose is used to load sulfur for lithium sulfur battery, when it is coated by MnO2(C-MnO2). The composite material is characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and thermogravimetric analysis (TG), while its electrochemical performance tests are carried out at different current density. Compared to samples without MnO2, the as-designed material deliver much better electrochemical performance. The initial specific capacity of as-prepared C-MnO2/sulfur composite is 1154mAh g-1 at 0.05C. After 200 cycles at 2C, the sample also delivers the discharge capacity of 376 mAh g-1. Besides, the sample also shows an improved rate performance than its counterpart. Three dimensional network carbon fiber derived from bacterial cellulose can improve conductivity of electrode material. Moreover, MnO2 plays a role to adsorb polysulfide chemically. The special design can effectively alleviate shuttle effects of polysulfide.
LiVxFeyPO4f Nanostructure Cathodes for Lithium Ion Batteries
Authors: Channu V. S. Reddy , Thanedar Shri
Published: February 2020

Fluorophosphates, like LiVPO4F, are expected to show high operating voltage (4.2V), long term cycle life (~1260 cycles) and low capacity fade behavior compared to the currently favorables LiCoO2 (4.0V), LiFePO4 (3.5V), and LiFePO4F or LiFeSO4F, or NaFeSO4F. The LiVPO4F could replace the current cathode technology to enable the commercial production of low cost, high energy density and safe Li -ion batteries for EV and PHEV applications. However, electrolyte oxidation at higher potential and the formation of poly-vanadate compounds like Li3V2(PO4)3 as an impurity during the two step synthesis process must be controlled. By adopting appropriate surface modification, preferably by various ceramic oxides, carbon and phosphate (FePO4 and AlPO4 etc.) based coatings would be employed to reduce activity towards electrolyte.

Soft-chemical synthesis offers numerous advantages for the formation of novel or advanced material forms including control over morphology (i.e., nanomaterials, coatings), phase, and composition. The controlled synthesis of nanomaterials and coatings, in particular, is imperative for the development of optical and electrical devices with ever-shrinking dimensions.

Substitution of environmental friendly transition metal cations, such as Co or Mn or Fe or Mg, in between vanadium site using soft-chemical or precipitation methods, could lead towards reducing the toxicity and the cost. In brief description, on the synthesis of LiVxFeyPO4F, V2O5, NH4H2PO4, LiOH.H2O, Fe(NO3)2.9H2O,NH4F and oxalic acid were used as-received to prepare the precursor solution. Oxalic acid used as a chelating agent and a reducing agent. First, V2O5 and oxalic acid in a stoichiometric ratio of 1:3 dissolved in deionized water under magnetic stirring at room temperature until forms a clear solution. Second, a mixture of stoichiometricNH4H2PO4, Fe(NO3)2.9H2O, NH4F and LiOH. H2O were added to the solution, followed by vigorously stirred using a magnetic stirrer for 1 h. The mixture solution was heated to 80 °C under active stirring to evaporate the water for several hours until homogenous slurry formed. Finally, the slurry was kept in an oven at 120 °C overnight. The prepared material was pressed into pellets and calcinate at 650 °C for 8 h under a gas flow of 90% Ar and 10 % H2.
MoO2/Mo2c Hybrid Nanowires As High Performance Anode Materials for Lithium Ion Batteries
Authors: Yang Lichun
Published: February 2020

Molybdenum oxides, mainly including MoO3 and MoO2, are attractive materials with potential applications in catalysis, sensors and energy storage. Owing to the good electronic conductivity, high stability and density, MoO2 was proposed as a host material for lithium ions. However, the application of MoO2 as anode material for lithium ion batteries was limited in the early research, due to the low capacity and poor cycling stability resulting from the bulky dimensions, the consequential slow kinetics and huge volume changes during the charge/discharge process. To improve the performance of MoO2, a most promising way is to design and construct nanostructured composites [1-3].

Here we report on MoO2/Mo2C hybrid nanowires synthesized through simple calcination using MoOx/amine nanowires as a precursor. The small diameters of the nanowires ensure fast lithium ion insertion and extraction, while the long dimensions benefit good electron transport between wires. Besides, Mo2C with a high specific conductance distinctly increases the structural stability and electronic conductivity of the hybrid nanowires. As a result, the cycling and rate performance of the hybrid nanowires is remarkably enhanced. At a current density of 1000 mA/g, a discharge capacity of ~700 mAh/g is still retained after 300 cycles, which indicates the MoO2/Mo2C hybrid nanowires a promising anode material for high performance lithium ion batteries.

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (Nos. 51402110, and 51231003).

[1] Q.S. Gao, L. C. Yang, X. C. Lu, J. J. Mao, Y. H. Zhang, Y. P. Wu, Y. Tang, J. Mater. Chem., 2010, 20, 2807.

[2] L.C. Yang, L. L. Liu, Y. S. Zhu, X. J. Wang, Y. P. Wu, J. Mater. Chem., 2012, 22, 13148.

[3] H. J. Zhang, K. X. Wang, X. Y. Wu, Y. M. Jiang, Y. B. Zhai, C. Wang, X. Wei, J. S. Chen, Adv. Funct. Mater., 2014, 24, 3399.
Facile Preparation of Nanoflake Covered-Hollow NiCo2O4 and the Study of Electrochemical and Structural Properties As an Anode Material in Lithium Ion Batteries
Authors: Yoo Jaeseung , Venugopal Nulu , Son Suhan , Oh Woong , Lew Gil Hwan , Palanisamy Kowsalya , Yoon Won-Sub
Published: February 2020

Transition metal oxide materials such as NiO, CoO and Co3O4 have been studying as attracting anode materials for lithium ion batteries and currently binary metal oxide systems are considered as promising material because of a great advantage to overcome the drawbacks like poor reversible capacity, conductivity and so on. For example, NiCo2O4 is one of binary metal oxide materials and has advantages such as low cost and toxicity because of low Co content in the material compared with Co3O4. Also electrochemical performance of NiCo2O4 is similar with that of Co3O4. The other strategy to enhance the performance is to make nanostructures such as nanoparticle, nanorod, nanoflake and hollow structure because of their high surface area. In this study, we report a facile preparation to synthesize nanoflake covered hollow NiCo2O4 by precipitation and annealing in air atmosphere. The surface area of the synthesized hollow NiCo2O4 is determined to be about 134 m2g-1 having pore size of 3-4 nm by N2 absorption method. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations reveal that hollow NiCo2O4 ­has unique porous morphology with nanoflakes of about 50 nm appeared on the surface of each hollow particle. The coin cell test with hollow NiCo2O4 electrode shows good electrochemical performance that the NiCo2O4 cell showed 440 mAh g-1 of discharge capacity at a current density of 5000 mA g-1 and was recovered 1519 mAh g-1 at a current density of 100 mA g-1 after fast C-rate. Also, the NiCo2O4 cell has excellent cycle life with above 1500 mAh g-1 at a current density of 100 mA g-1 after 30 cycles. Moreover, we investigated the structural change during the lithiation/delithiation by ex-situ X-ray diffraction (ex-situ XRD) technique based on synchrotron X-ray source. Detailed results will be presented at the meeting.
Improvement of the Electrochemical Performance of Si Anodes By Use of Ultrathin Polydopamine Coating upon Conductive Carbon Particles
Authors: Song Danoh , Jung Dae Soo , Cho Inseong , Lee Yong Min , Ryou Myung-Hyun
Published: February 2020

Although silicon (Si) have received worldwide attention as a promising anode candidate because they are not only able to provide high theoretical capacity ~3500 mAh g-1 but also cheap and environmentally friendly source, a successful implementation of Si anode based lithium-ion batteries (LIBs) has been hindered thus far. This is because Si anodes suffer from huge volume change (c.a. 300%) during cycling. To improve cycle performance of Si anode based LIBs, the mechanical stress should be efficiently alleviated.

In this study, we developed surface modified conductive additive by use a mussel-inspired polymeric material: polydopamine (PD). Due to hydrophilic moiety of PD coating layer, PD-treated Super-P was well dispersed in the water, thus we could use poly(acrylic acid) (PAA) as a polymeric binder. PD-treated Super-P achieved highly improved cycle performance of Si anodes. Using FT-IR, we verified that the improved cycle performance is attributable to the newly formed covalent bonds between the amine group in PD-treated Super-P and the hydroxyl group in PAA. Furthermore, we evaluated adhesion property of anode composite using a Surface And Interfacial Cutting Analysis System (SAICAS). PD-treated Super-P showed the highest adhesion value compared to bare Super-P.

 

Acknowledgements

This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT & Future Planning (2014R1A1A1005861).
Rice Husk-Derived Porous Silicon with High Purity As Anode for Lithium Ion Batteries
Authors: Jung Dae Soo
Published: February 2020

Recently, social concerns and the importance of ‘green growth’ and ‘renewed energy technology’ have increased, which resulted from the increase in the cost of fossil fuels and climate change. One of the critical technologies for accomplishing ‘green growth’ is the recycle of waste products generated through manufacturing processes. One of the largest wastes is rice husks, which are generated from the production of rice. Rice is cultivated in more than 75 countries in the world and the worldwide annual rice production amounts to approx. 422 million metric tons, of which about 20% is rice husk. However, its utilization has been limited to low-value applications in the agriculture area, such as stockbreeding rugs, bed soil, fertilization and lagging materials etc., which is the case because of their tough, woody and abrasive properties.

Thus, many researchers have attempted to increase their added value, including the development of rice husks activated carbon, rice husk gasification and electricity generation. Some research groups have studied the potential of using rice husks as a fiber resource. Ah et al. reported the preparation of packing materials and Lee et al. developed a rice husk board. Rice husks contain approximately 20 wt% silica and because of ‘natural selectivity’ of rice plants, it has a lower level of metallic impurities than other representative silica sources, such as quartz, bentonite and diatomaceous earth etc.. Therefore, a significant effort has been directed at the production of high purity silicon-based materials from rice husks, such as SiC, Si3N4, SiO2 and high grade silicon. However, most of these studies are based on using rice husk ash (RHA), which is generated after the combustion of rice husk and very few studies have examined the potential of using the organic part of rice husks.

Thus, we developed a refinery process to integrate the use of rice husks and increase of the value of rice husks. This process has the combined benefit of producing valuable silicon-based materials and cellulose-based materials. The rice husks are divided into fiber and inorganic components during the refinery process. In this work, we investigated the chemical composition and morphological characteristics of the rice-husk derived silica obtained from the refinery process. The conditions for preparing SiO2 with high purity and high surface area were optimized and highly porous nano-structured silicon (Si) with high purity was prepared from rice husk-derived silica. We also examined the potential of using the rice husk derived silicon as an anode material in Li-ion batteries.
A Novel Adhesion Map Correlating Adhesion Properties to the Electrode Design Parameters in Lithium-Ion Battery Electrode
Authors: Kim Kyuman , Byun Seoungwoo , Cho Inseong , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Fabricating the electrodes satisfying the targeted energy density, power density, and loading level is not a simple task to achieve because there are interrelated electrode design parameters such as loading level, density, thickness, composition, etc., affecting on the electrode property. Thus far, the time-consuming repetitive trials have been an only answer to achieve this goal.

To determine the optimized binder content and the electrode density have been also a difficult question because there has been few systematic research on adhesion properties for LIB electrodes. For instance, the conventional peel test with adhesive tape (3M Scotch tape) has been widely utilized to compare adhesion properties in electrode as a measuring tool.

Our group have introduced the Surface and Interfacial Cutting and Analysis System (SAICAS), which are able to measure the shear stress as well as adhesion strength at the interfaces in the LIB electrodes [1-4]. Here in, we utilized the SAICAS to correlate the adhesion property and the typical electrode design parameters–the loading level and the density–by utilizing a SAICAS technique. First, we measured the adhesion properties of LiCoO2 electrodes, having four different electrode densities (2.0, 2.5, 3.0, and 3.5 g cm-3) and three different loading levels (5, 10, and 15 mg cm-2), at the interface between current collector and electrode coating layer and at the middle of the electrode coating layer. Second, from the obtained data, we draw an empirical equation to predict adhesion strength as a function of electrode density and loading level. Third, we verified our attempt was reasonable by predicting the adhesion strength of the LiCoO2electrode randomly chosen in a random loading level and a random density.

Acknowledgements

This work was supported by the Human Resource Training Program for Regional Innovation and Creativity through the Ministry of Education and National Research Foundation of Korea (NRF-2014H1C1A1066977).

 

References

[1] Son, B.; Ryou, M.-H.; Choi, J.; Lee, T.; Yu, H. K.; Kim, J. H.; Lee, Y. M., Measurement and Analysis of Adhesion Property of Lithium-Ion Battery Electrodes with SAICAS. ACS Appl. Mater. Interfaces 2013, 6, 526-531.

[2] Choi, J.; Ryou, M.-H.; Son, B.; Song, J.; Park, J.-K.; Cho, K. Y.; Lee, Y. M., Improved High Temperature Performance of Lithium-Ion Batteries through Use of a Thermally Stable Co-Polyimide-Based Cathode Binder. J. Power Soures 2014, 252, 138-143.

[3] Choi, J.; Kim, K.; Jeong, J; Cho, K. Y.; Ryou, M.-H.; Lee, Y. M., Highly Adhesive and Soluble Co-polyimide Binder: Improving the Long-Term Cycle Life of Silicon Anodes in Lithium-Ion Batteries, ACS Appl. Mater. Interfaces, 2015, 7, 14851-14858

[4] Song, D.; Lee, S. H.; Kim, K.; Ryou, M.-H.; Park, W. H.; Lee, Y. M., Soluble Polyimide Binder for Silicon Electrodes in Lithium Secondary Batteries, Appl. Chem. Eng, 2015, 26, 674-680
Heat-Resisting and Flame-Retarding Difunctional Separators for Safe Lithium-Ion Battery
Authors: Hwang Suyeon , Jeon Hyunkyu , Lee Taejoo , Ryou Myung-Hyun , Lee Yong Min
Published: February 2020

Considering the ever increasing demands for the large-scale lithium-ion batteries (LIBs) targeting for the electric vehicles (EVs) and energy storage systems (ESSs), safety of LIBs is the primary issue to be solved for the successful implementation in a market. Although various types of heat-resisting separators have been suggested by introducing heat-resisting ceramic fillers, the main purpose of them is to improve dimensional stability of polyolefin-based microporous separator at high temperature [1,2]. If the separators are able to prevent not only short-circuit, but also retard flammability of organic liquid electrolytes at an abnormal condition, they can significantly improve the safety of LIBs.

To achieve this goal, here in, we introduced ammonium phosphate, a typical flame-retardant, in the ceramic-coated separators. We optimized the coating process and evaluated physical properties of the surface-coated separators such as morphology, permeability, wettability, ionic conductivity etc. Furthermore, we investigated the heat-resistance using hot electric iron tips and the combustion behavior of surface-coated separators by measuring self-extinguish time. The effect of surface-coated separators on the electrochemical properties of LIBs is also evaluated using 2032-type coin cells.

Reference

[1] Taejoo Lee et al. Effect of Al2O3coatings prepared by RF sputtering on polyethylene separators for high-power lithium ion batteries, Macromolecular Research, 22, 1190-1195 (2014)

[2] Myung-Hyun Ryou et al, Mussel-Inspired Polydopamine-Treated Polyethylene Separators for High-Power Li-Ion Batteries, Adv. Mater., 23, 3066–3070 (2011)

Acknowledgements

This research was supported by the Ministry of Trade, Industry & Energy(MOTIE), Korea Institute for Advancement of Technology(KIAT) through the Encouragement Program for The Industries of Economic Cooperation Region (G02A01280032701)
The Effects of Surface Polyanions on the Lithium-Excess Layered Cathode
Authors: Xu Guofeng , Li Jianling , Wang Xindong
Published: February 2020

The lithium-excess layered cathode materials Li1+xM1-xO2 or xLi2MnO3·(1-x)LiMO2 (M is a transition metal or a mixture of transition metals) are quite promising due to the reversible capacity of up to 280 mAh g-1 and the wide working voltage range and low cost. There are some drawbacks to overcome for the further application of lithium-rich cathode although extensive researches have been carried out. The large irreversible capacity loss during the initial cycle has a significant impact on the subsequent charge and discharge capacity. The mechanisms of lithium transference and structure evolution during the initial and succeeding cycles require further investigation. The cathode exhibits awful rate capability because of the existence of the low electronic conductivity ingredient Li2MnO3. In addition, the cathode also presents a gradual capacity drop by reason of local phase transformation during cycling.

The high capacity of ＞250 mAh g-1 only occurs when the voltage exceed 4.5 V and the 4.5 V platform is related to the oxidation of lattice O. The gas phase oxidation product releases from the material along with the migration of transition metal element and the resulted evolution of crystal structure. Considering the oxygen release and ion migration happened firstly at the surface of the material particles, the polyanions contains F are adopted to treat the surface of Li1.2Co0.13Ni0.13Mn0.54O2 in order to stabilize the crystal lattice. The treated materials show better electrochemical performance and the mechanism is analyzed in detail.
Study of the Structural and Thermal Stabilities of Chemically Deintercalated Phases of NMC Type Positive Electrode Materials for Lithium Ion Batteries
Authors: El Mofid Wassima , Ivanov Svetlozar , Bund Andreas
Published: February 2020

Given the importance attributed to safety aspects of advanced lithium ion batteries [1-4], the structural and thermal stabilities of the active materials are of great importance. The main focus of our work is a double substituted Ni-rich NMC material LiNi0.6Mn0.2Co0.15Al0.025Fe0.025O2 (NMCAF), which has been recently reported as a material with good electrochemical performance, improved cycleability and capacity retention [5]. For comparison we also studied a pristine NMC material with the stoichiometry LiNi0.6Mn0.2Co0.2O2.

The materials chosen for this study were synthesized by the self-combustion method. The preservation of the α-NaFeO2 type layered structure after metal substitution was confirmed by X-ray diffraction.

In order to study the structural effects at different lithiation states a chemical deintercalation at room temperature based on a non-aqueous NO2BF4 / acetonitrile solution has been performed..

The X-ray patterns of the deintercalated phases showed a continuous displacement of the diffraction lines with the extraction of lithium ions, accompanied by broadening of the diffraction peaks. Both systems have been subsequently the object of thermal characterisation by means of thermogravimetric analysis (TGA), in order to assess the heating effect on the structural stability. .The results displayed continuous mass losses between 100 ° C and 600 ° C for both materials, most probably corresponding to oxygen release. The observed thermal instability can cause a serious safety issues due to exothermic reaction of the released oxygen with the electrolyte. This process can affect the cycle life and even the safety of the battery [6].

Comparing TGA results for both materials, the non-substituted NMC displayed higher weight loss related to pronounced thermal instability. These results evidenced once more the stabilizing effect of the double substitution of Co with Al and Fe in the pristine NMC material.

References

[1] Dan Doughty, E. Peter Roth, The electrochemical society interface (2012) 37-44.

[2] E.P Roth, D.H Doughty, J. Power Sources 128 (2004) 308-318

[3] Diego Lisbona, Timothy Snee, Process Safety and Environmental Protection 89 (2011) 434-442.

[4] P.G. Balakrishnan, R. Ramesh, T. Prem Kumar, J. Power Sources 155 (2006) 401-414

[5] W. El Mofid, S. Ivanov, A. Konkin, A. Bund, J. Power Sources 268 (2014) 414-422.

[6] J. R. Dahn, E. W. Fuller, M. Obrovac, U. Von Sacken, Solid State Ionics 69 (1994) 265-270.
Understanding of the Polyacrylic Acid Role As Efficient Binder in Silicon Based Electrode for Li-Ion Battery
Authors: Porcher Willy , Chazelle Sophie , Mariage Nicolas , Boulineau Adrien , Haon Cédric , Bridel Jean-Sébastien , Van Rompaey Tim
Published: February 2020

Silicon is a promising material at the negative electrode due to its huge specific capacity and its low potential. Nevertheless, silicon undergoes also huge volume changes upon alloying and de-alloying with lithium; up to +300%. Among the material design or the electrolyte composition, the role of the binder is also critical to obtain a good cycle life.

Several studies have reported that polyacrylic acid (PAA) would be a suitable binder for silicon composite electrode [1-3]. However, little is known about its behavior.

In this study, we have evaluated firstly in the framework of a design of experiments (DOE), silicon based electrodes integrating PAA binder with different molecular weights, proportions and pH. The first irreversible capacity and the mean coulombic efficiency upon cycling were the parameters studied in this DOE. We have confirmed in fact that PAA, when appropriately used, was an efficient binder in silicon based electrode compared to other binders as carboxymethyl cellulose (CMC) or polyether imide (PEI).

In addition, we have tried to understand PAA behavior, compared to CMC and PEI, based on the interactions of binder/silicon into the slurries, the binders distributions into the electrodes (Figure 1), the binders mechanical properties and electrodes thickness measurements at different states of charge after different cycles. All these characterizations allow better understanding of the binder role in silicon electrodes.

Figure 1: a) c) TEM images and b) d) STEM EELS mapping (Si: green; C: red) of Si based electrodes coated with a) b) PAA and c) d) CMC as binder

[1]: A. Magasinski, B. Zdyrko, I. Kovlaneko, B. Hertzberg, R. Burtovyy, C. F. Huebner, T. F. Fuller, I. Luzinov and G. Yushin, ACS Appl. Mater Interfaces, 2, 3004 (2010).

[2]: V. L. Chevrier, L. Liu, D. Ba Le, J. Lund, B. Molla, K. Reimer, L. J. Krause, L. D. Jensen, E. Figgemeier and K. W. Eberman, J. Electrochem. Soc., 161, A783 (2014).

[3]: Z.-J. Han, K. Yamagiwa, N. Yabuuchi, J.-Y. Son, Y.-T. Cui, H. Oji, A. Kogure, T. Harada, S. Ishikawa, Y. Aokid and S. Komaba, Phys.Chem.Chem.Phys., 17, 3783 (2015).

Figure 1