bluuebunny/crossref_metadata_2025_split huggingface dataset:
Through-Mask Electrochemical Etching of Micropillar Array with Megasonic Agitation
Authors: Du Liqun , Zhai Ke , Wang Shuxuan , Wen Yikui 
Published: February 2020

Micropillar array is widely used in bionics, thermodynamics and biomedicine because of its advantages in improving surface tribological properties and enhancing heat transfer [1, 2]. Through-mask electrochemical etching is one of the main methods to fabricate metal micropillar array in large scale [3].
In this study, we studied the etching effect of micropillar array with the method of megasonic assisted through-mask electrochemical etching. An anode vibrating type megasonic source at 1MHz was set up. Micropillar arrays were etched at megasionc intensity of 2W/cm^2. Fig. 1(a) shows the fabrication process of the micropillar array. The mask is prepared by photolithography. During the etching process, anode acts as an acoustic source and radiates megasonic waves simultaneously. Fig. 1(b) shows the micropillar arrays which were etched without megasonic and with megasonic agitation. Uniform micropillars were achieved with megasonic agitation compared to without megasonic agitation. Fig. 1(c) and Fig. 1(d) shows the measured height and diameter of the micropillars. Higher micro columns were obtained with megasonic agitation when the diameters of the micro columns are almost identical. Micropillars with an average diameter of 116.95μm and an average height of 11.31μm were obtained with megasonic agitation. Fig. 1(e) shows the etching factor of the micropillars. Average etching factor of the micropillars etched without megasonic agitation and with megasonic are 2.07 and 2.87, respectively. The method of megasonic assisted through-mask electrochemical etching can achieve much higher etching factor than without megasonic agitation. This work opens new promising fields for development of extensive fabrication methods of micropillar array.
Reference
[1] R. Xiao, R. Enright, E. N. Wang. Langmuir, 26(19) 15070-15075 (2010)
[2] M. Shojaeian, A. Koşar. Exp. Thermal Fluid Sci., 63 45-73 (2015)
[3] T. Baldhoff, V. Nock, A. T. Marshall, J. Electrochem. Soc., 165 (16) E841-E855 (2018)

Figure 1
Revealing Hidden Chemistry of Anode-Free Lithium Metal Battery
Authors: Huang Chen-Jui , Thirumalraj Balamurugan , Sutiono Hogiartha , Kuo Li-Ming , Su Wei -Nien , Hwang Bing-Joe 
Published: February 2020

Lithium metal batteries (LMBs) has been studied extensively over the past four decades and regained great attention then lithium-ion batteries (LIBs) recently due to its higher energy density and volumetric capacity. However, the inevitable formation of high surface area lithium (HSAL) [1,2], also known as dendrites, during the plating/stripping processes among cycling leads to poor capacity retention, low coulombic efficiency (CE), and potential safety concern. One of the major reasons causing serious dendrite formation is the usage of lithium foil as an anode electrode, owing to its soft texture and easily roughened surface. In addition, even if the lithium foil used is ultra-thin, the A/C ratio is still large than 1, which leads to unnecessary excess lithium and sacrifice of higher cathode loading within the cell.
Anode-free lithium metal batteries (AFLMBs), using no excess metallic lithium at the initial state, enable potentially higher energy density than LMBs [3,4]. Nevertheless, the configuration possesses lowest safety risk among the cells with the involvement of metallic lithium due to fewest amount of plated lithium in the charged state. However, low plating/stripping efficiency of AFLMBs leads to rapid capacity decay and very short cycle life. Thus, AFLMBs are often considered having less potential than LMBs or recognized as a failure for this type of cell configuration.
Here in, we fundamentally investigate different parameters which affect the performance of AFLMBs, comparing with LMBs, the hidden chemistry of AFLMBs is unveiled. Base on the obtained results, we tailor down different intrinsic reasons causing irreversible capacity and low CE, and the metallic lithium plating/stripping behavior. Thus, AFLMBs is able to provide extensive cycling performance evaluation, cycle life prediction of LMBs, and approaches to improve reversible lithium metal plating/stripping and suppress of dendrite formation.
Reference:
[1]: J.H. Cheng, A.A. Assegie, C.J. Huang, M.H. Lin, A.M. Tripathi, C.C. Wang, M.T. Tang, Y.F. Song, W.N. Su, and B.J. Hwang, J. Phys. Chem. C, 121, 7761–7766 (2017). [2]: A.M. Tripathi, W.N. Su and B.J. Hwang, Chem. Soc. Rev., 47, 736–851 (2018).
In-Situ Formation of Surface Coatings on Silicon Anodes
Authors: Vaughey John T. , Key Baris , Han Binghong , Dogan Fulya , Lapidus Saul , Liao Chen 
Published: February 2020

Silicon anodes have generated significant interest for their exceptional high capacities, relative low cost, and good operating voltage window. For may silicon electrode materials the inhomogeneous nature of the charged electrode yields a highly reduced surface and a less reduced bulk. Using single phase model compounds of the predominant electrodes structures at various states of charge we have examined the role of surface charge on the stability of the electrode to binder, electrolyte, and various salts. In our presentation we have taken these concepts and devised additives that react with the charged surface to coat the material with a more stable interfacial material that extends cycle life and improves performance versus baseline samples.
Notable examples include the synthesis of Li7Si3, a model compound for a 300mV Li-Si electrode. This material contains simple silicon dimers surrounded by lithium cations. Previous modeling has noted these dimers show double bond character, increasing their reactivity with the components of an electrochemical cell. In our studies crystalline samples were synthesized in Ta tubes and exposed to various solvents. Reactivity, as seen by XRD, NMR, and FTIR, confirmed the oxidation of the dimer species to a more oxidized compound (Li12Si7) and ring opening of EC-type solvents.
High Performance Silicon Anodes Enabled By Nonflammable Localized High Concentration Electrolytes
Authors: Jia Haiping , Zhang Ji-Guang , Xu Wu 
Published: February 2020

High performance silicon anodes enabled by nonflammable localized high concentration electrolyte

Haiping Jia, Ji-Guang Zhang, Wu Xu
Pacific Northwest National Laboratory, Richland, WA, United States.
Silicon (Si) anode is regarded as one of the most promising alternatives to graphite for high energy-density lithium-ion batteries (LIBs), but their practical applications have been hindered by high volume change, limited cycle life and safety concerns. In this work we developed nonflammable localized high concentration electrolytes (LHCEs) for Si-based anodes. The LHCEs enabled the Si anodes with significantly enhanced electrochemical performances comparing to conventional carbonate electrolytes with high content of fluoroethylene carbonate (FEC). The LHCE with only 1.2 wt% FEC can further improve the long-term cycling stability of Si-based anodes. When coupled with a LiNi0.3Mn0.3Co0.3O2 cathode, the full cells using this nonflammable LHCE could maintain >90% capacity after 600 cycles at C/2 rate, demonstrating excellent rate capability and cycling stability at elevated temperatures and high loadings. This work casts new insights in electrolyte development from the perspective of in-situ Si/electrolyte interphase protection for high energy-density LIBs with Si anodes.
The Effects of Cycling on Ionic and Electronic Conductivities of 18650 Li-Ion Cells
Authors: Thompson Andrea I , Pouraghajan Fezzeh , Mazzeo Brian A , Wheeler Dean 
Published: February 2020

During cycling or other aging processes, the capacity of lithium-ion batteries decreases and it is also observed that cell impedance increases. In order to better understand these processes, we are investigating the electronic conductivity and ionic conductivity of electrodes harvested from 18650 cells that have been cycled by different amounts.
Effective ionic conductivity of a porous electrode film is sometimes expressed in terms of tortuosity, which is correlated by a Bruggeman-type relationship [1]. A reasonably accurate method of measuring tortuosity is using the previously developed blocking electrolyte method [2]. As for effective electronic conductivity of electrodes, our group has developed experimental methods for accurately making this measurement as well [3].
In this work, the effects of cycling on both ionic and electronic conductivities are examined. We investigate different commercially made 18650 (cylindrical) cells, including those with iron phosphate and cobalt oxide cathodes. Each cell was charged and discharged for a different number of cycles, leading to increasing capacity losses. After certain number of cycles, each cell was cut open and the electrodes were harvested for testing. We will provide details on this experimental method as well as the conductivity results.
[1] Zacharias et al, Electrochem. Soc. 160, A306 (2013).
[2] Pouraghajan et al., Electrochem. Soc. 165, A2644, (2018).
[3] Lanterman et al., Electrochem. Soc. 162, A2145, (2015).

Figure 1
The Impact of Particle Size on Cycle Life and Stress Evolution in Silicon-Based Composite Electrodes
Authors: Jin Mok Yun , Guo Kai , Zhang Wei , Xiao Xingcheng , Gao Huajian , Sheldon Brian W. 
Published: February 2020

In practical silicon electrodes the coupled mechanical and chemical degradation of the solid electrolyte interphase (SEI) is a critical issue. During electrochemical cycling, the extremely large mechanical strains that are applied to the SEI on Si are a primary factor that limits cycle life. However, the effect of particle size on these strains has not been investigated in prior work.
To address this, we have integrated measurements on silicon nanoparticle composite electrodes with an in situ method for applying controlled mechanical strains to SEI during electrochemical cycling and a finite element model (FEM). Comparisons of electrodes with different particle sizes show lower capacity loss with smaller particles. This finding is explained with the FEM. Variations in the SEI formation were also investigated, using different cycling conditions and electrolyte additives.
Instrument for Measuring Local Ionic Conductivity of Porous Electrodes
Authors: Liu Baichuan , Nielsen Kayci , Mazzeo Brian , Wheeler Dean 
Published: February 2020

Due to the nature of how porous battery electrodes are fabricated, their microstructure is not uniform. For instance, there are variations in composition, effective electronic transport, and effective ionic transport. Such heterogeneity has been associated with several battery application issues. For example, variability in transport of ions can lead to a tendency for localized plating of lithium on anodes during fast charging [1-2].
Studying the heterogeneity of electrodes is a growing research topic. Our research group has previously developed a micro-four-line probe that successfully measured the variation of electronic conductivity of electrodes [3]. Another method to study the microstructure of electrodes is by means of SEM and X-ray tomography, and the variation of tortuosity (effective ionic resistance) in electrodes was computed by analyzing the tomographic data of microstructure [4].
We report here on a new technique to measure the local ionic resistance on a sub-mm length scale. A probe was made to detect the local transport of ions through a small aperture. The probe is scanned across the surface of a porous thin-film electrode in order to create maps of tortuosity or MacMullin number. The measurement was performed using electrochemical impedance spectroscopy, and an associated model is needed to invert the experimental results.
[1] Harris et al., The Journal of Physical Chemistry C 117, 6481 (2013).
[2] Vogel et al., Electrochimica Acta 297, 820 (2019).
[3] Lanterman et al., Journal of the Electrochemical Society 162, A2145 (2015).
[4] Kehrwald et al. Journal of The Electrochemical Society 158, A1393 (2011).

Figure 1
Large Batch Coating Process for Improving Thermal Stability of NCM622 Cathode
Authors: Durham Jessica L , Fister Timothy T , Murphy Michael J. , Wang Lixin , Zhou Fu , Lu Lei , Kim Kitae , Johnson Derek C , Lipson Albert L. 
Published: February 2020

Nickel-rich cathodes such as LiNi0.6Co0.2Mn0.2O2 (NCM622) have received considerable attention as a result of their high delivered capacity. However, owing to high nickel content, NCM622 cathodes suffer from reduced cycle life and thermal stability compared to lower nickel content NCM523 and NCM333 cathodes. (1) Traditional approaches to coating and doping, including exploration of various coating (Al2O3, AlF3, SiO2) and dopant (Al3+, Mg2+, F-) species which either act as a passivating layer between the cathode surface and reactive electrolyte or to stabilize the structure of the material, have been employed in the past to improve the performance of Ni-rich cathodes. (2-9)
This presentation demonstrates the effectiveness of a large batch (i.e. 500 grams) coating process to deposit either AlF3 or ZnO on NCM622 cathode material. The process is a dry mixing technique wherein the coating is applied using powerful mechanical energy to induce mechano-chemical reactions between the surface of NCM622 and AlF3 or ZnO. SEM imaging and EDX mapping illustrate that the size or morphology of the secondary particles is not affected by the process and the coating species is well-distributed among the bulk. Differential scanning calorimetry (DSC) and temperature-depending X-ray diffraction (XRD) were conducted to monitor the thermal stability of AlF3 and ZnO coated NCM622. Temperature-dependent XRD shows the structural degradation of the layered NCM622 structure to a non-layered rock-salt structure as a function of temperature. The peak positions in the DSC correspond directly to the c lattice parameter decreasing, which is caused by oxygen release, and the conversion to a rock-salt phase. These results indicate how AlF3 and ZnO coatings alter the collapse and phase transition of the delithiated NCM622 during heating.

References

(1) Liu, W.; Oh, P.; Liu, X.; Lee, M.-J.; Cho, W.; Chae, S.; Kim, Y.; Cho, J. Chem. Int. Ed.
2015, 54, 4440-4457.
(2) Mohanty, D.; Dahlberg, K.; King, D. M.; David, L. A.; Sefat, A. S.; Wood, D. L.; Daniel, C.; Dhar, S.; Mahajan, V.; Lee, M.; Albano, F. Reports
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(3) Han, B.; Paulauskas, T.; Key, B.; Peebles, C.; Park, J. S.; Klie, R. F.; Vaughey, J. T.; Dogan, F. ACS Appl. Mater. Interfaces
2017, 9, 14769-14778.
(4) Liao, J.-Y.; Manthiram, A. Power Sources
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(5) Du, K.; Xie, H.; Hu, G.; Peng, Z.; Cao, Y.; Yu, F. ACS Appl. Mater. Interfaces
2016, 8, 17713-17720.
(6) Zhou, P.; Zhang, Z.; Meng, H.; Lu, Y.; Cao, J.; Cheng, F.; Tao, Z.; Chen, J. Nanoscale
2016, 8, 19263-19269.
(7) Woo, S.-U.; Yoon, C. S.; Amine, K.; Belharouak, I.; Sun, Y.-K. Electrochem. Soc.
2007, 154, A1005-A1009.
(8) Hu, G.; Zhang, M.; Liang, L.; Peng, Z.; Du, K.; Cao, Y. Electrochimica Acta
2016, 190, 264-275.
(9) Krishna Kumar, S.; Ghosh, S.; Ghosal, P.; Martha, S. K. Power Sources
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Melt-Process for the Preparation of Porous Composite Electrodes for Battery Application
Authors: Verdier Nina , El Khakani Soumia , Lepage David , Prébé Arnaud , Dollé Mickael , Rochefort Dominic 
Published: February 2020

Lithium-ion batteries have become the dominant technology for electrochemical energy storage. They have been used in electronic portable devices for decades and now taking the lead in the transportation sector in electrical vehicles. As it has long been known, the release of CO2 from combustion engine-powered constituted a significant proportion of our global emission of greenhouse gases. In order to reduce this proportion, efforts are being deployed to increase the market penetration of electric vehicles which puts a growing pressure on the production of lithium-ion batteries. As a result, this production is predicted to rapidly and sharply grow in the next few years.
This fast development raises novel issues regarding the electrode production process and its impact on the environment. Currently, most of the electrode fabrication processes require organic solvent such as N-methyl-2-pyrrolidone (NMP), which is toxic and costly. It is therefore essential to find an alternative which is more sustainable that the solvent process yet that meets requirements of scalability, cost and productivity. In this context, we propose a new approach to electrodes fabrication process developed by our industrial partner Hutchinson (Patent US20130244098A1). It consists of a melt process which is well-known in the polymer industry to make composites. As such, our process does not require any solvent. In our study, we optimised the electrode formulation for power applications.
In this presentation, we will report the different steps of the new melt process. The active materials and the conductive carbons used are the same as in the conventional wet process, but the binder needs to be chosen with care. Indeed, due to constraints in terms of temperature, shear forces and of the mixing process itself, the binder must be a heat-tolerant elastomer, to allow good mixing properties to the blend and flexibility to the resulting electrode. As an alternative to the most commonly-used binder, PVdF, a lower-cost commercial elastomer, Hydrogenated Nitrile Butadiene Rubber (HNBR), was used as the binder. To evaluate its compatibility and performance in lithium-ion battery composite electrodes, it was first compared to PVdF with the common wet process to make electrodes. After the validation of HNBR as a binder, it was used with the melt-process. Power testing and cycling performances of electrodes made with different active materials will be presented, showing the feasibility of electrodes and the versatility of the melt-process.
The Structural Stabilization Effect of Tungsten Doping on Layered LiNiO2 Cathodes for High-Energy-Density Lithium-Ion Batteries
Authors: Ryu Hoon-Hee , Nam Gyeong Won , Sun Yang-Kook 
Published: February 2020

Ni-rich layered transition-metal (TM) oxides, e.g., Li[Ni
x
Co
y
Mn1-x-y]O2 (NCM) and Li[Ni
x
Co
y
Al1-x-y]O2 (NCA), have attracted considerable attention as cathode materials for Li-ion batteries (LIBs) and have been deployed in commercial EVs.1 In order to increase the energy density and satisfy the target driving range, the Ni content in NCM and NCA cathodes has been progressively increased, from 33% to 85%.2,3 At the end of this strategy lies LiNiO2 (LNO), in which all of the Co and Mn is replaced by Ni, yielding a high specific capacity of 250 mAh g-1 at a relatively low material cost.3 However, it was notoriously difficult to use in practice because LNO undergoes several phase transition during Li+ intercalation and deintercalation, which can lead to severe capacity fading.4 In addition to the detrimental phase transition occurring in the deeply charged state and the parasitic reactions of reactive Ni4+ at the surface cause the capacity fading of cathode materials.
In the present study, we investigated the effect of W doping on the structural stabilization during the electrochemical process. To systematically investigate the effect of W doping, a series of W-doped LNO cathodes with 1.0, 1.5, and 2.0 mol% W were synthesized using an optimized co-precipitation process. The structural behavior observed via in situ X-ray diffraction (XRD) was correlated to the electrochemical performance of the W-doped cathodes.

References

S.-T. Myung, F. Maglia, K.-J. Park, C. S. Yoon, P. Lamp, S.-J. Kim, Y.-K. Sun, ACS Energy Lett.
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H.-J. Noh, S. Youn, C. S. Yoon, Y.-K. Sun, J. Power Sources
2013, 233, 121.

H.-H. Sun, W. Choi, J. K. Lee, I.-H. Oh, H.-G. Jung, J. Power Sources
2015, 275, 877.

C. S. Yoon, D.-W. Jun, S.-T. Myung, Y.-K. Sun, ACS Energy Lett.
2017, 2, 1150.
(Invited) Low-Cobalt and Cobalt-Free Cathodes for Next-Generation Lithium-Ion Batteries
Authors: Manthiram Arumugam 
Published: February 2020

Lithium-ion batteries have become an integral part of our daily life with an exponential growth in portable electronics during the past couple of decades. They are now being intensively developed for the electrification of the transportation sector. They also have the potential to penetrate into the utility industry for the grid storage of electricity produced from renewable sources like solar and wind. As we move from small batteries used in portable devices to large batteries used in electric vehicles and grid storage, cost becomes a major factor in addition to other factors like cycle life, safety, energy density, charge-discharge rate, and environmental impact. Lithium-ion batteries for portable devices and electric vehicles currently employ layered LiNi1-x-yMnxCoyO2 cathodes with a significant amount of cobalt. Unfortunately, cobalt has limited abundance and is expensive, which could pose serious problems for a widespread deployment of lithium-ion batteries for electric vehicles and grid storage. Therefore, it is critical to develop cathodes with low-cobalt content or no-cobalt. Accordingly, the presentation will focus on the design and development of low-cobalt and cobalt-free layered oxide cathodes for next-generation lithium-ion batteries.
Layered LiNi1-x-yMnxCoyO2 cathodes with cobalt content as low as 6% for M in LiMO2 or no cobalt are synthesized with a desired optimum particle size by a coprecipitation of the hydroxide precursors employing a tank reactor. The hydroxide precursors are then fired at desired temperatures with lithium hydroxide with or without appropriate dopants to obtain the layered LiMO2 oxides. After an in-depth characterization, the oxide cathodes are evaluated by pairing with graphite anodes in full lithium-ion cells. Both the oxide cathodes and graphite anodes are characterized with a suite of analytical techniques before and after cycling the full cells for thousands of cycles to develop a fundamental understanding of the factors that lead to performance degradation. The analytical techniques include in-situ X-ray diffraction, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectrometry, scanning electron microscopy, and high-resolution transmission electron microscopy. Extensive data on cathode compositions, such as LiNi0.94Co0.06O2 and LiNiO2 with and without doping will be presented. Furthermore, the thermal stability and air-stability of the samples and the effects of doping on them will be discussed. Stabilized cathode compositions with capacities as high as 220 mA h g-1 and long cycle life will be presented.