bluuebunny/crossref_metadata_2025 huggingface dataset:
Silicon Nano Wires Anodes for High-Performance Lithium Ion Batteries
Authors: Peled Emanuel , Schneier Dan , Patolsky Fernando , Golodnitsky Diana , Menkin Svetlana , Davidi Guy , Harpak Nimrod , Mados Edna , Ardel Gilat
Published: February 2020

We report on the scalable synthesis and characterization of novel architecture three-dimensional high-capacity amorphous Silicon Nanowires (SiNWs)-based anodes, with a quarter of the thickness of common graphite anode. The SiNWs were grown in a novel, catalyst free process, on a thin stainless steel (SS) net. With the use of two and three electrodes coin cells we focus on studying their electrochemical performance and degradation mechanisms. By using our novel, low cost and high mass loading chemical vapor deposition (CVD) procedure we synthesized anodes that have shown stable cycle life for over 600 cycles and provided capacities of up to 6mAh/cm2, very low (<10%) irreversible capacity and good compatibility with commercial cathodes. Notably, it was found that the growth of the solid electrolyte interphase (SEI) thickness and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes. Our anodes have been coupled with commercial cathodes (LFP and NCA), and have the potential to increase the energy density of LIBs by over 40%. In order to prove the scalability of our anodes, they have been successfully incorporated in industrial hardware cylindrical cells, proving they are a viable candidate for anodes of the next generation lithium ion batteries for portable applications and electric vehicles. Most recently, these anodes have successfully been cycled in all solid state cells consisting of solid polymer electrolytes, paving the way for safer, more durable LIBs.
Tannic Acid As a Binder in Silicon Anodes for Lithium-Ion Batteries
Authors: Sarang Kasturi , Lutkenhaus Jodie L.
Published: February 2020

Increasing demand for portable electronic devices, electric vehicles, and grid scale energy storage has spurred interest in developing high capacity rechargeable lithium ion batteries (LIBs). Due to this interest, researchers have been extensively studying materials with high lithium ion storage capability, such as silicon, to replace the graphite anode in LIBs. Silicon is a non-toxic, abundantly available material and has a theoretical gravimetric capacity of 3500 mAh/g with a low operating potential of 0 to 1 V vs. Li/Li+. However, silicon has not yet been commercialized as an anode material due to large volume variation (>300 %) during lithiation and delithiation. This causes pulverization and loss of electrical contact between components, leading to capacity degradation and short battery cycle life. These problems can be overcome by using a binder that can hydrogen bond with the silicon particles. Here, we demonstrate utilization of tannic acid (TA), a natural polyphenol derived from wood, as a binder for silicon anode in lithium ion batteries. The resulting silicon electrodes demonstrate good cycling stability with a capacity of 1000 mAh/g for 200 cycles. This cycling stability can be attributed to the presence of the many hydroxyl (OH) groups (14.8 mM of -OH per g of TA) that hydrogen bond with the silicon particles’ OH groups. Additionally, water processability makes the electrode synthesis process environmentally friendly. This work demonstrates that a molecule with high hydrogen bonding capability can be used as a binder. Furthermore, future modifications of TA can further improve its performance as a binder for silicon anodes.
The Decoupling of Solid-Electrolyte Interphase Formation from the Mechanical Deformation of Silicon Electrodes
Authors: Yin Yanli , Cao Lei , Yoon Taeho , Wood Kevin N. , Arca Elisabetta , Stetson Caleb , Xiao Chuanxiao , Schnabel Manuel , Yang Guang , Teeter Glenn , Jiang Chunsheng , Nanda Jagjit , Ban Chunmei
Published: February 2020

The reduction of electrolyte is well known to result in the formation of the solid electrolyte interphase (SEI) at the interface of electrolyte and silicon electrodes which determines the reversibility of lithium ion battery chemistry. The SEI formation is usually coupled with the mechanical deformation of silicon electrode because of its large volume changing of about 300% during the cycling lithiation and delithiation. We may know more about the chemistry of SEI by decoupling it from the silicon mechanical deformation. In this talking, we will present a novel electrochemical methodology having achieved this decoupling which results in a special surface species - “early-stage SEI”. The chemistry of the early-stage SEI was well studied to distinguish the following challenging questions: Can the early-stage SEI passivate the silicon surface? How is the stability of the early-stage SEI during the long rest in the electrolyte? In comparison with the regular SEI coupled by the mechanical deformation of silicon, the early-stage SEI was found with a lot of new chemistry by using the characterization of X-ray Photoelectron Spectroscopy (XPS), Atomic Force Microscopes-Scanning Spreading Resistance Microscopy (AFM-SSRM). The composition of early-stage SEI was verified by XPS to include lithium ethylene dicarbonate (LiEDC) and lithium carbonate (Li2CO3). Meanwhile, the silicon was verified without lithiation behavior. The evolution of surface roughness and electrical conductivity of early-stage SEI was addressed by AFM-SSRM. This study may gain much attention due of the fundamental understanding of the silicon electrode surface chemistry with potential application in lithium ion battery of high energy density.
Multi-Textured Structure Cathode Materials to Accommodate the Fast Charging for Lithium Secondary Batteries
Authors: Min Byeong-Cheol , Lee Sang-Min , Kim Jeom-Soo
Published: February 2020

Small-sized portable electronic devices have been lead the lithium secondary battery industry to this day. In recent years, demands for lithium secondary batteries in the field of electrified vehicles have increased sharply, and this is about to overtake the demand from the conventional fields such as portable electronics. As the battery size gets larger, a charging time is getting more important especially in automobile sectors. The rapid kinetics must be satisfied at both electrodes simultaneously in a lithium secondary cell under increased charging current in order to reduce the charging time. Spinel and olivine materials were suggested as high rate materials for positive electrodes, however those materials have the limitation of lower energy density compared to layered structure one.

In this study, a specially designed hydroxide precursor with NCM chemistry was synthesized by using a conventional co-precipitation method. The hydroxide precursor has a multi-textured structure of a dense sphere encapsulated with a porous layer. The final product synthesized with this precursor was evaluated as an active material for a positive electrode under fast charging conditions. The details of results will be presented including physico-chemical and electrochemical properties of the precursor and final product at the meeting.
Recycling Spent Battery Cathode Materials Using Electrochemical Relithiation
Authors: Li Xuemin , Burrell Anthony , Ban Chunmei
Published: February 2020

Lithium ion batteries are composed of high-cost metals such as lithium, cobalt, nickel, and manganese. Limited resources of these raw materials motivate battery material recycling and reusing, which at the same time alleviates environmental pollution. Reuse of worn battery electrodes does not damage the original cathode materials and avoids multi-steps of chemical reactions. The strategy of battery electrode reusing should be developed based on the battery degradation mechanisms. Therefore, understanding the major degradation factors of the end-of-life batteries is helpful to develop an efficient way for cathode reusing. Layered transitional metal oxides with a general formula LiNixMnyCozO2 (x+y+z=1) have been well used as cathode materials in commercial lithium-ion batteries. In this work, the spent LiNi0.4Mn0.4Co0.2O2 has been selected to study the degradation mechanism under different cycling conditions. The results from the combined morphological and structural study suggest that lithium ion loss causes the performance degradation in such cathode materials. Then, we studied the electrochemical Li+ rejuvenation for the spent cathode materials by using electrochemical reactions and analysis. The results have enabled us to establish the electrochemical relithiation conditions and develop a systematic understanding of the impact of electrochemical relithiation on the properties of the recovered materials.

References:

C. R. Birkl, M. R. Roberts, E. McTurk, P. G. Bruce and D. A. Howey, Journal of Power Sources, 341, 373 (2017).

B. P. Matadi, S. Geniès, A. Delaille, C. Chabrol, E. de Vito, M. Bardet, J.-F. Martin, L. Daniel and Y. Bultel, Journal of The Electrochemical Society, 164, A2374 (2017).

E. Hu, S.-M. Bak, J. Liu, X. Yu, Y. Zhou, S. N. Ehrlich, X.-Q. Yang and K.-W. Nam, Chemistry of Materials, 26, 1108 (2014).

S.-M. Bak, E. Hu, Y. Zhou, X. Yu, S. D. Senanayake, S.-J. Cho, K.-B. Kim, K. Y. Chung, X.-Q. Yang and K.-W. Nam, ACS Applied Materials & Interfaces, 6, 22594 (2014).
Characterization of Chemical and Electrochemical Lithiation/ Delithiation of LiFePO4
Authors: Gupta Devanshi , Koenig Gary
Published: February 2020

Redox kinetics for the electroactive compounds used in a lithium-ion battery are a key indicator of their power density. The kinetics and phase transformation of these compounds can be studied using potentiostatic methods, which apply constant thermodynamic driving force while the material is dispersed within a composite electrode. The current response, in some cases, is interpreted as a phase transformation of the solid electroactive material. Most studies apply electrochemical potential on the fabricated electrode, which gives convoluted data as inactive carbon, binders, and current collectors play a significant role in charge transfer. In this work, chemical redox was investigated for LiFePO4 to study the chemical lithiation and delithiation process at different temperatures. The kinetics were analyzed using a Johnson-Mehl-Avrami-Kolmogerov model and compared to electrochemical kinetics determined using coin cells. It was found that different pathways were followed for chemical and electrochemical redox. The apparent activation energy was an order of magnitude larger for chemical redox relative to electrochemical redox.
Tunable LiAlO2/Al2O3 Coating to Improve the Specific Capacity and Cycle Stability of Nano-LiCoO2
Authors: Shaw Leon , Ashuri Maziar , He Qianran , Kaduk James A
Published: February 2020

A facile wet-chemical method to coat nano-LiCoO2 particles is investigated in this study. In this newly-developed wet-chemical method, Al(NO3)3 is used as the Al source to form Al2O3 and LiAlO2, whereas LiNO3 is used as a sacrificial agent to protect nano-LiCoO2 and at the same time to form LiAlO2 by reacting with Al2O3. Addition of LiNO3 into the Al(NO3)3 coating solution suppresses the unwanted formation of Co3O4 during the coating process and leads to a thin (5–10 nm) and continuous LiAlO2/Al2O3 coating on nano-LiCoO2 particles. 21 wt. % LiAlO2/Al2O3-coated nano-LiCoO2 exhibits an unusually high initial specific capacity of 225 mA h g-1, while micro-LiCoO2 can only deliver a specific capacity of 145 mA h g-1 even though the charge/discharge voltage windows are the same. Furthermore, 21 wt. % LiAlO2/Al2O3-coated nano-LiCoO2 offers 100% increase in the specific capacity over pristine nano-LiCoO2 after 5 cycles at 0.1C, 20 cycles at 1C and 20 cycles at 3C. Moreover, 21 wt. % LiAlO2/Al2O3-coated nano-LiCoO2 is able to charge/discharge for 425 cycles at 3C with only 18% capacity loss and maintain a final specific capacity of 128 mA h g-1. In contrast, the specific capacity of micro-LiCoO2 diminishes to 50 mA h g-1 after 200 cycles at 3C. The unusually high specific capacity and superior capacity retention for long cycle life at high rates of 21 wt. % LiAlO2/Al2O3-coated nano-LiCoO2 are attributed to its huge electrode/electrolyte interfacial area for charge/discharge with small polarization and the effectiveness of LiAlO2/Al2O3 coating in preventing capacity decay during soaking as well as during cycling. The principle and methodology of this newly-developed wet-chemical coating method are applicable to other layered transition metal oxide cathodes and can open up new opportunities to obtain superior electrochemical properties from these advanced cathodes in the future.
Transparent Conducting Oxides As Cathodes in Li-O2 batteries: A First Principles Computational Investigation
Authors: Radhakrishnan Balachandran , Lawson John W
Published: February 2020

Li-O2batteries have traditionally used carbon based electrodes (graphite, buckypaper) as the cathode of choice due to its good electrical conductivity, stability against non-aqueous electrolytes like dimethoxyethane (DME) and ease of handling. But, the carbon cathode also leads to formation of carbonate by-products that increase overpotentials during charging leading to degradation of the cathode and reduction of cyclability. Recent investigations have focused on using metal-oxides like SnO2, TiO2 as viable cathodes-alternatives in Li-O2 systems. In this paper, we investigate transparent conducting oxides (TCOs) as cathodes with focus on the interface between the TCO surfaces and the discharge product, Li2O2, in the Li-O2battery using first principles computations. TCOs have found use as electrodes in photovoltaic cells and other semi-conductor applications due to their tunable conductivity via defects/doping, ease of synthesis of preferred surfaces and stability to environmental factors. These properties, along with their stability against ethers, make them a promising class of cathodes in Li-O2 battery. Using DFT computations and thermodynamic arguments, we predict the chemical and electrochemical stability of some of the well-known TCOs in a Li-O2 battery. Further, surface adsorption computations show that not all oxides promote formation of Li2O2 and different surfaces of same cathode material can behave differently. We also explore the role dopants can play in achieving a stable electrically conducting cathode that promotes discharge of Li2O2. We extend the analysis to suggest possible oxide chemistries that should be investigated as cathodes in Li-O2batteries.
A Long Cycle-Life and High-Rate Magnesium-Ion Battery Anode Enabled through Self-Healing By Near-Room-Temperature Solid-Liquid Phase Transition
Authors: Wang Lin , Welborn Samuel S. , Detsi Eric
Published: February 2020

The growing popularity of lithium-ion batteries has raised a serious concern about the long-term supply of these batteries, since lithium and cobalt resources used are becoming more expensive due to demand, and the global cobalt market heavily depends on the supply from countries with high geopolitical risks. Therefore, scalable alternatives battery technologies are desirable to reduce the dependence on lithium and cobalt. Over the past few years, magnesium-ion batteries have been the subject of intense research as an alternative to lithium, owing to the various advantages of magnesium including the abundance of magnesium resources for large-scale applications. Nevertheless, progress toward practical magnesium-ion batteries has been impeded, partly by the absence of suitable electrolytes that are compatible with magnesium metal used as the negative electrode. Typically, common salts and organic solvents combinations similar to those used in lithium-ion batteries yield a magnesium-ion-blocking passive film on the magnesium metal negative electrode. A promising way to circumvent this electrolyte issue is through the use of alloy-type anodes as the negative electrode instead of magnesium metal. However, state-of-the-art alloy-type magnesium-ion battery anodes can only be reversibly cycled up to 200 times with acceptable capacity retention [1]. Such a cycle-life is far below the thousands of cycles required for practical battery applications. In this talk, I will present a novel high-performance alloy-type magnesium-ion battery anode which we have developed, which can be reversibly (de)magnesiated at the C-rate of 3C over 1000 cycles with excellent capacity retention. This exceptional performance is to thanks to the self-healing property of the active electrode material, which undergo solid-to-liquid phase transition when the cell operate around 30-40oC. Operando X-ray scattering techniques were used to demonstrate this self-healing property in real-time during magnesiation and demagnesiation.

Keywords: Mg-ion battery anode, self-healing, operando X-ray scattering, solid-liquid phase transition

[1] CHENG, Y., et al. 2015. Interface promoted reversible mg insertion in nanostructured tin-antimony alloys Adv. Mater. 27, 6598-6605.
Intercalation of Solvated Magnesium-Ions into Layered Transition Metal Sulfide for Fast Mg Storage
Authors: Li Zhenyou , Zhao-Karger Zhirong , Fichtner Maximilian
Published: February 2020

Rechargeable magnesium (Mg) batteries (RMBs) are potential candidates for new generation battery technologies due to the attractive properties of Mg as a metal anode, especially the intrinsic nature of homogeneous Mg deposition and abundant Mg reserves. Compared to the monovalent counterpart (e.g. Li+), the divalent Mg ions have a greater charge density and thus need to overcome much stronger electrostatic forces for insertion and diffusion inside the host structures. One of the strategies to enhance Mg2+ ion intercalation kinetics is to reduce its charge density.

Herein, we present the intercalation chemistry of the solvated ions [Mg(DME)3]2+, in which the improved ion mobility has been proven by various electrochemical and spectroscopic characterizations.1 The novel concept was realized with Mg[B(hfip)4]2/DME electrolyte2, 3 and a layered MoS2 cathode coupled with a Mg anode. The cell configuration exhibited a long-term cycling stability (>200 cycles) and high rate capability (47 mA h g-1 at 0.5 A g-1). In addition, the mechanism of Mg storage has been investigated in detail, revealing the reversible 2H to 1T MoS2 phase transition during Mg ions de-/intercalation. Compared to other reported intercalation with [Mg(H2O)x]2+ or MgCl-,4, 5 the DME molecules will neither passivate the anode nor corrode the cell components, which makes this approach more practical. Moreover, the concept of solvated Mg2+ ions can be potentially extended to other intercalation cathode materials and applied to other multivalent ions intercalation.

References

Z. Li, X. Mu, Z. Zhao-Karger, T. Diemant, R. J. Behm, C. Kübel and M. Fichtner, Nature Communications, 2018, 9, 5115.

Z. Zhao-Karger, M. E. Gil Bardaji, O. Fuhr and M. Fichtner, J. Mater. Chem. A, 2017, 5, 10815-10820.

Z. Zhao-Karger, R. Liu, W. Dai, Z. Li, T. Diemant, B. P. Vinayan, C. Bonatto Minella, X. Yu, A. Manthiram, R. J. Behm, M. Ruben and M. Fichtner, ACS Energy Letters, 2018, 3, 2005-2013.

K. W. Nam, S. Kim, S. Lee, M. Salama, I. Shterenberg, Y. Gofer, J.-S. Kim, E. Yang, C. S. Park, J.-S. Kim, S.-S. Lee, W.-S. Chang, S.-G. Doo, Y. N. Jo, Y. Jung, D. Aurbach and J. W. Choi, Nano Letters, 2015, 15, 4071-4079.

H. D. Yoo, Y. Liang, H. Dong, J. Lin, H. Wang, Y. Liu, L. Ma, T. Wu, Y. Li, Q. Ru, Y. Jing, Q. An, W. Zhou, J. Guo, J. Lu, S. T. Pantelides, X. Qian and Y. Yao, Nature Communications, 2017, 8, 339.
Elucidating Zn, Mg, and Ca Electrodeposition Mechanisms in Nonaqueous Electrolytes for Next-Generation Metal Batteries
Authors: Ta Kim , See Kimberly A , Zhang Ruixian , Shin Minjeong , Rooney Ryan , Neumann Elizabeth K. , Gewirth Andrew A.
Published: February 2020

Due to their significantly higher volumetric capacity, natural abundance, and decreased cost compared to Li metal, Zn, Mg, and Ca rechargeable metal batteries in nonaqueous electrolyte solutions have been the subject of extensive research and development. In this study, we employ the electrochemistry and computational simulation to examine the reversible electrodeposition processes of multivalent metals in nonaqueous electrolytes. Cyclic voltammetry (CV) obtained from Zn electroplating/stripping at an ultramicroelectrode (UME) shows that current density and scan rate are independent as predicted from a simple electron transfer process. However, CVs obtained from Mg and Ca deposition/stripping processes at an UME displays an inverse dependence between current density and scan rate. COMSOL simulations suggest that Zn deposition is governed by a one−step two−electron (E) transfer process while Mg and Ca plating requires a chemical step prior to electron transfer step, suggesting a chemical−electrochemical (CE) mechanism.
Incorporation of Aluminum into High-Nickel Layered Oxide Cathodes: An Interphase and Structural Study
Authors: Li Jianyu , Manthiram Arumugam
Published: February 2020

The rapidly growing energy market calls for advanced Li-ion batteries with high energy density and acceptable service life. Ni-rich layered oxides (LiNixM1
−xO2, x > 0.6, M = Mn, Ni, Co), especially those with ultrahigh Ni content (Ni > 0.9), are able to deliver a high capacity of > 200 mA h g−1 with a high average operating voltage of 3.8 V vs Li/Li+. They hold great promise to power a 300-mile electric vehicle and are being intensively studied in recent years. However, severe critical problems greatly hinder the widespread application of high-Ni layered oxides. First, during electrochemical cycling, the generation of monoclinic and hexagonal structures in the delithiated state induces large unit cell volume changes and anisotropic strains, which leads to microcrack formation and eventually secondary particle disintegration. Furthermore, this structural evolution process is worsened as Ni content increases due to the presence of the hexagonal 3 (H3) phase in the deeply delithiated state. Second, a high concentration of unstable Ni4+ in the highly delithiated high-nickel layered oxide tends to react aggressively with the carbonate electrolyte, resulting in the formation of cathode-electrolyte interphase (CEI). Furthermore, the unwanted reaction greatly expedites the irreversible transformation of the layered structure to a rock-salt (NiO) phase. Overall, these various degradation processes result in a high interfacial impedance and poor electrochemical performance. Herein, to tackle these issues, a trace amount of Al is substituted into a high-Ni layered oxide and the dual-function of Al cooperation is demonstrated. By substituting a small dose of Al (2 mol %) for Ni in LiNi0.92Co0.06Al0.02O2, the capacity retention of the full cells utilizing Al-doped LiNi0.92Co0.06Al0.02O2 cathode paired with graphite anode after 1000 cycles increases from 47% to 83% compared to that of Al-free LiNi0.94Co0.06O2. Through in-situ X-ray diffraction, we provide the operando evidence that Al dopant tunes the H2−H3 phase transition process from a two-phase reaction to a quasi-monophase reaction, minimizing the mechanical degradation. Furthermore, Al dopant facilities the formation of phosphate-enriched CEI on the cathode surface, which protects the cathode from severe electrolyte attack. Also, secondary-ion mass spectrometry reveals considerably suppressed transition-metal dissolution with Al doping, effectively preventing sustained parasitic reactions and active Li trapping due to chemical crossover on the graphite anodes. This work offers a viable approach for adopting high-Ni cathodes in Li-ion batteries.

Figure 1
A Simple Surface Modification Technique to Improve the Electrochemical Properties of NMC Family Cathode Materials
Authors: Ashuri Maziar , He Qianran , Shaw Leon
Published: February 2020

The facile phosphoric acid (H3PO4) surface modification of layered lithium transition metal oxide cathode materials has been proven to enhance the reversible capacity and rate capability of these materials. Here, we have investigated the effect of this treatment on two NMC cathode materials, Li(Ni1/3Mn1/3Co1/3)O2 (NMC333) and Li(Ni0.5Mn0.3Co0.2)O2 (NMC532). The thin nanolayer of Li3PO4 coating was formed after subjecting the NMCs to H3PO4 solution followed by heating at 500 °C for 5 h under air. The Li3PO4 coating formed is found to be very potent in enhancing the specific capacity of the first discharge as well as the rate capability and capacity retention in the subsequent charge/discharge cycles for both NMCs. The obtained results demonstrate that the H3PO4 treatment is a simple and general method to improve the electrochemical properties of NMCs with different compositions and have the potential for industrial applications.
Impedance Based Electrode Diagnostics of Charge-Discharge Kinetics in Li-Ion Pouch Cells
Authors: Perumaram Rangarajan Sobana , Barsukov Yevgen , Mukherjee Partha P.
Published: February 2020

The electrochemical reactions inside a Li-ion cell is a result of complex interplay among different physicochemical processes occurring at anode and cathode. In order to fundamentally understand the charge/discharge kinetics at each electrode, an impedance based in-situ diagnostics is presented within a three-electrode pouch cell configuration. This allows identifying the factors that influence the Li-ion cell performance at different temperatures over a range depths of discharge. The resistances and the activation energies of different processes, such as charge-transfer and diffusion, are determined for individual electrodes. It was found that at low temperatures, the effect of intercalation induced staging in a graphite anode affects the pore ionic resistance, diffusion resistance and the double layer capacitance.
An Experimental Analysis on the Impacts of Different Pulse Charging Frequencies on Lithium Ion Batteries
Authors: Rajagopalan Kannan Dhevathi Rajan , Moss Pedro L. , Weatherspoon Mark H.
Published: February 2020

Lithium ion batteries can be charged by different techniques. CCCV (constant current, constant voltage) charging is the conventional method that is predominantly employed for charging the lithium ion batteries. Pulsed current charging is seen as one of the promising techniques for fast charging and high energy efficiencies.1–3 However, the impacts on the batteries due to the variations in the frequency of pulses are seldom investigated on high energy batteries. The objective of this work is to experimentally investigate the impacts of current pulses at different frequencies on commercial LTO and NMC batteries. The results of charging time, overall cycle life and efficiency are then compared with the conventional charging method. In this experiment, pulsed current profile is controlled by varying the duty cycle and amplitude to maintain the average for effective comparison with CCCV charging. Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron Microscope (SEM) are used in analyzing the impacts of both the charging protocols on different lithium battery chemistries.

References

J. M. Amanor-Boadu, M. A. Abouzied, and E. Sanchez-Sinencio, IEEE Trans. Ind. Electron., 65, 7383–7394 (2018).

M. F. Hasan, C.-F. Chen, C. E. Shaffer, and P. P. Mukherjee, J. Electrochem. Soc., 162, A1382–A1395 (2015) http://jes.ecsdl.org/cgi/doi/10.1149/2.0871507jes.

H. Z. Z. Beh, G. A. Covic, and J. T. Boys, 2013 IEEE Energy Convers. Congr. Expo. ECCE 2013, 315–320 (2013).
(Invited) Hierarchy of Stochastic Scales in Intercalation Electrodes
Authors: Mukherjee Partha P. , Mistry Aashutosh N
Published: February 2020

Lithium-ion batteries, owing to their widespread application domains, are often subject to operation in extremes, e.g., fast charge and low temperatures. Porous electrodes in such systems exhibit stochasticity over hierarchy of scales. Analyzing and understanding electrode complexations across scales necessitate a data-driven framework. In this talk, we present the implications of stochastic features in electrodes, such as irregular particles, non-conformal pore network, inhomogeneity in separator microstructure and active particle aggregation. Especially, the effects of scale hierarchy are analyzed from the perspective of intercalation, thermal, and electrodeposition response under operational extremes based on a data-driven framework.
Multiscale Modeling of Multiphase Transport in PEM Water Electrolyzer
Authors: Zhou Jie , Johansen Hans , Danilovic Nemanja , Zenyuk Iryna V. , Weber Adam Z.
Published: February 2020

Understanding multiphase transport in proton-exchange-membrane water electrolyzer (PEMWE) is critical to improving electrolyzer performance and optimizing the material.1-4 Mathematical modeling is ideally suited to tackle such issues, especially due to the inherent divergent time and lengthscales involved during operation. In a PEMWE, the multiphase transport mainly involves: a) Liquid water transport in the porous electrode; b) Interaction between liquid water and product gas; and c) Gas transport, i.e., removing product gas in the liquid water through the porous transport layer (PTL) and into the channel. For a), as liquid water is the reactant, its distribution in the PTL and catalyst layer is of great importance to the reaction distribution. For b), the gas bubble formation on the electrochemically active surface area (ECSA) blocks the water access and leads to a dynamic redistribution of current, which affects the local and perhaps global cell performance and may lead to enhanced degradation. Lastly, understanding the mechanism of gas bubble detachment is necessary in order to minimize the loss of ECSA due to gas bubble coverage.

In this talk, a multiscale, multiphysics PEMWE model will be presented. The model includes a two-dimensional, nonisothermal, multiphase, macrohomogeneous model combined with a local microscale model that accounts for the fluid flow interaction between a gas bubble and liquid water. The bubble coverage is introduced as a function of current density,5 and its impact on current redistribution discussed in terms of allowable coverage and dynamic cycling gas evaluation at the local reaction site. The structural information such as pore-size distribution and tortuosity is obtained from X-ray computed tomography (CT) data, which is also used to validate some of the model predictions under operando conditions. Also, based on the X-ray data, the microstructure of the PTL has been reconstructed and two-phase fluid simulations have been carried out to predict effective transport properties that are incorporated into the marcoscale model. Lastly, the porous electrode parameter optimization such as wettability, porosity, and pore size, will be introduced to provide guidance in material and structural design for better electrolyzer performance.

M. Carmo, D. L. Fritz, J. Mergel and D. Stolten, International Journal of Hydrogen Energy, 2013, 38, 4901-4934.

U. Babic, M. Suermann, F. N. Büchi, L. Gubler and T. J. Schmidt, Journal of The Electrochemical Society, 2017, 164, F387-F399.

E. Leonard, A. D. Shum, S. Normile, D. C. Sabarirajan, D. G. Yared, X. Xiao and I. V. Zenyuk, Electrochimica Acta, 2018, 276, 424-433.

T. Kadyk, D. Bruce and M. Eikerling, Scientific reports, 2016, 6, 38780.

R. Balzer and H. Vogt, Journal of the Electrochemical Society, 2003, 150, E11-E16.
Combined Simulative and Experimental Multi-Scale Approach to Study the Microstructural Evolution of a Ni-Based SOFC Anode Under Operating Conditions
Authors: Marusczyk Anika , Haremski Patricia , Hoffrogge Paul Wilhelm , Schneider Daniel , Nestler Britta , Wieler Matthias , Lupetin Piero
Published: February 2020

The degradation mechanism of Ni-based solid oxide fuel cell (SOFC) anodes under operating conditions is dominated by an unfavorable microstructural evolution that involves the coarsening of nickel grains. The resulting reduction of the active triple-phase boundary leads to a significant loss of performance. In this work, we present a combined simulative and experimental multi-scale approach to predict the microstructural evolution, and therefore degradation, of the anode while avoiding time-consuming long-term experiments. To generate a fundamental understanding of the relevant mechanisms, all applicable material parameters, such as interfacial energies and diffusion constants, are considered and exploited in large-scale 3D phase-field simulations. For their non-trivial determination, we are following a combined simulative and experimental approach using atomistic simulation methods and thermal grooving experiments that is presented in this work. Our determined material parameters are discussed in a comparative way with a focus on the accuracy and capabilities of the used method. Their applicability and relevance to the phase field simulations is elaborated based on a sensitivity analysis.
(Invited) Intermediates in PEC Water Oxidation — How They Come and How They Go
Authors: Braun Artur
Published: February 2020

Atmospheric oxygen that we live on is the result of a fundamental evolutionary step in photosynthesis which occurred on Earth 2-3 billion years ago [Biello 2009]. The water oxidation in natural photosystem II accounts for 50% of this oxygen. The man-made analog to this natural process is water oxidation in photoelectrochemical cells - one of the most complex processes in physical chemistry. I will showcase how modern x-ray spectroscopy methods have assisted in the understanding of the molecular pro-cesses which occur in natural [Bora 2013, Ralston 2000, Visser 2001] and in man-made "photosystems". A most recent example is the element and orbital specific identification of transient electron holes in iron oxide [Braun 2012], chemical surface intermediates [Bora 2011] and changes in the water molecules in the electrochemical double layer during photoelectrochemical water oxidation [Braun 2016]. I will also demonstrate how the electronic structure evolution is quantitatively paralleled by the electric transport properties of the electrodes during operation.

[Biello 2009] Biello D: The Origin of Oxygen in Earth's Atmosphere. In Scientific American 2009.

[Bora 2011] Bora DK et al. Journal of Physical Chemistry C 2011, 115:5619-5625.

[Bora 2013] Bora DK et al. JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA 2013, 190:93-105.

[Braun 2012] Braun A et al. Journal of Physical Chemistry C 2012, 116:16870-16875.

[Braun 2016] Braun A et al. Catalysis Today 2016, 260:72-81.

[Ralston 2000] Ralston CY et al. Journal of the American Chemical Society 2000, 122:10553-10560.

[Visser 2001] Visser H et al. Journal of the American Chemical Society 2001, 123:7031-7039.
(Invited) Electrodeposition of Semiconductors: An Emerging and Hugely Popular Art
Authors: Rajeshwar Krishnan
Published: February 2020

This perspective talk focuses on the history and status of electrodeposition for preparing thin films of inorganic semiconductors, metal/semiconductor junctions, or even nanocomposite materials containing different phases. The use of light brings an added dimension and versatility to the preparative strategy. Variants on the basic cathodic or anodic deposition protocols will be elaborated as are approaches that rely on the initial deposition and stripping of a precursor layer. Another topic is operando compositional analysis of the depositing layers using a combination of electrochemical techniques with other complementary probes such as electrochemical quartz crystal microgravimetry (EQCM) and AC impedance spectroscopy. Finally, state-of-the art and future challenges will be identified using examples drawn from the author’s and collaborators’ laboratories as well as other works.
(Invited) Emerging Designs for Polymer-Based Energy Storage Devices and Sensors
Authors: Wang Kaiping , Wu Zhenghui , Azoulay Jason , Ng Tse Nga
Published: February 2020

Conducting polymers are an important class of Faradaic materials for energy storage, as they present opportunities to create energy dense supercapacitors. The vast majority of conducting polymers are p-type cathodes and already operating at or close to the upper voltage limit of non-aqueous electrolytes. On the other hand, it is generally safe for electrolytes to operate down to -2 V vs Standard Hydrogen Electrode. Therefore, extending the operational voltage in the negative range is an attractive route to increase energy density. Here we present promising n-type polymers that retained 90% of initial capacitance after 1000 charge-discharge cycles. We measure in operando the electronic and ionic transport in conducting polymers by current-voltage and spectroscopic measurements, where spatial variations of film absorption would be mapped to discern electronic versus ionic degradation. We infer the mechanisms that lead to capacitance fade and suggests structural and electrochemical strategies to realize high-endurance energy storage devices for wearable systems.

In addition, organic polymers responsive to the short wavelength infrared (SWIR) spectra are used to realize photodetectors that is relevant to a variety of applications including environmental monitoring and medical diagnosis. Here we show novel donor-acceptor polymers with narrow bandgap responsive in the SWIR region, and the polymers are processed into bulk heterojunction photodiodes with photoresponse up to wavelength of 1.7 micron. The performances of devices with different polymer structures were compared through metrics including detectivity, quantum efficiency, response time and rectification ratio. Example applications including hemodynamics and tissue composition measurements will be demonstrated.
A Kinetic Study of Cationic Polymer Chemical Vapor Deposition
Authors: Giambra Dominic James , Tenhaeff Wyatt
Published: February 2020

Chemical vapor deposition (CVD) is a critical processing technology in the semiconductor industry, and over the past several years, significant strides have been made in developing CVD technologies for the controlled synthesis of compositionally well-defined polymer thin films. CVD of polymers is attractive because it combines synthesis and thin film processing into a single step, while eliminating the use of solvent required in conventional solution-based processing. An important variant of polymer CVD is initiated chemical vapor deposition as it provides exquisite control over polymer chemistry and film morphology by essentially executing a heterogeneous free radical polymerization. Inspired by this iCVD approach, a novel polymer CVD approach has been developed based on classical cationic chain polymerization. This approach has been term catCVD.

In catCVD, coinitiation with a Lewis acid and a proton-donor is used to protonate vinyl bonds in surface-adsorbed monomer molecules, leading to the formation of carbenium ions. The thermodynamics and kinetics of catCVD are highly favorable, and the reaction proceeds spontaneously, eliminating the need for heated filaments as in iCVD or any other energy input. In initial proof-of-concept experiments, polystyrene films were synthesized by catCVD and iCVD. Fourier-transform infrared spectroscopy (FTIR) showed that the film compositions are nearly identical, while real-time interferometry showed that the deposition rate of catCVD enhanced almost 50X relative to iCVD.

The kinetics of catCVD were further analyzed to determine the functional dependence of the polymerization rate expression on deposition parameters, including precursor surface concentrations and substrate temperatures. It was shown that the rate of propagation is second order with respect to the monomer, which is in agreement with the accepted rate law for solution-based cationic polymerization. Size exclusion chromatography (SEC) of the deposited polymer films showed that polymer MW is invariant with respect to film thickness, indicating that the lifetime of the extending polymer chains is orders of magnitude shorter than the deposition time. We conclude that polymer initiation and termination are occurring continuously throughout the deposition process. Experiments are currently being executed to determine the activation energy for the polymerization rate constant. A comprehensive study of the polymer composition and film structure using various analytical techniques, including ellipsometry, x-ray photoelectron spectroscopy, and scanning electron microscopy will also be presented.
Surmofs and Ccncs As Novel Tuneable Metal-Organic Materials for Photonic, Electronic, Optoelectronic and Thermoelectric Applications
Authors: Redel Engelbert
Published: February 2020

Here we present a particularly interesting class of surface-anchored (metal-organic frameworks andcoordination network compounds) materials SURMOFs and (conductive coordination network compounds) CCNCs for the fabrication e.g. of 1D (Photonic Band Gap) PBG materials [1,2] as optical sensors, low-k dielectric thin films [3], optoelectronic/electrochromic switchable coatings/devices [4] microelectronic devices, e.g. RRAM devices (see Fig. 1) [5] or Hybrid-Materials NPs@SURMOFs for future artificial Light-Harnessing (LH) assemblies and photocatalysts.[6] Furthermore SURMOFs thin films demonstrates promising application potential of organic porous thin films in future thermoelectric devices.[7]

References:

[1] J. Liu, E. Redel, S. Walheim, Z. Wang, V. Oberst, J. Liu, S. Heissler, A. Welle, M. Moosmann, T. Scherer, M. Bruns, H. Gliemann, C. Woell Chemistry of Materials (ACS) 2015, 27, 1991-1996.

[2] J. P. Best, J. Michler, J. Liu, Z. Wang, M. Tsotsalas, X. Maeder, S. Roese, V. Oberst, J. Liu, S. Walheim, H. Gliemann, P. G. Weidler, E. Redel and C. Woell Appl. Phys. Lett. 2015, 107, 101902.

[3] E. Redel, Z. Wang, S. Walheim, J. Liu, H. Gliemann, C. Woell, App. Physics Lett. 2013, 103, 091903

[4] J. Liu, W. Zhou, S. Walheim, Z. Wang, P. Lindemann, S. Heissler, J. Liu, P. G. Weidler, T. Schimmel, C. Woell, E. Redel Optics Express (OSA) 2015, 23, 13725-13733.

[5] Z. Wang, D. Nminibapiel, P. Shrestha, J. Liu, K. P. Cheung, W. Guo, P. G. Weidler, H. Baumgart, C. Woell, E. Redel (Back Cover Issue 1/02 2016) ChemNanoMat (Wiley-VCH) 2016, 2, 67-73.

[6] W. Guo, C. Zhi, C. Yang, T. Neumann, C. Kuebel, W. Wenzel, A. Welle, W. Pfleging, O. Shekhah, C. Woell, E. Redel Nanoscale (RSC) 2016, 8, 6468-6472.

[7] J. Liu, W. Zhou, J. Liu, I. Howard, G. Kilibarda, S. Schlabach, D. Couprey, M. Addicoat, S. Yoneda, Y. Tsutsui, T. Sakurai, S. Seki, Z. Wang, P. Lindemann, E. Redel, T. Heine, C. Woell *VIP ≡ Very Important Paper (Angewandte Front Cover Issue 2015-54/25) Angewandte Chemie International Edition (Wiley-VCH) 2015, 54, 7441-7445.

[8] X. Chen, Z. Wang, Z. M. Hassan, P. Lin, K. Zhang, H. Baumgart, E. Redel, ECS Journal of Solid State Science and Technology, 6, P150-P153 (2017).
(Keynote) Exploration of Process Techniques for Ga2O3 Based Diodes
Authors: Ren Fan , Yang Jiancheng , Carey Patrick H , Pearton Stephen J. , Tadjer Marko J , Kuramata Akito
Published: February 2020

Monoclinic β-phase Ga2O3 has outstanding potential for power electronics, and high quality, large diameter bulk crystals and epitaxial layers of Ga2O3 are already available with a wide range of controllable n-type doping levels by edge-defined film-fed (EFG) growth using iridium crucibles, by Czochralski or by float zone. The direct energy bandgap of Ga2O3, ∼4.9 eV, yields a very high theoretical breakdown electric field (∼8 MV/cm). For power electronics, the Baliga figure-of-merit, proportional to carrier mobility, critical electric field and breakdown voltage, is almost four times higher for Ga2O3 than for GaN. Currently, the major limitation for Ga2O3 based device fabrication is the lack of low resistance Ohmic contacts, low damage dry etching process, and thermally stable Schottky contacts. In this work, we review the processing techniques of Ohmic and Shcottky metallizations, plasma etching, surface treatments, and dielectrics for gate oxides as well as diode edge terminations.
Temperature-Dependent Electrical Characteristics of β-Ga2O3 Diodes with W Schottky Contacts up to 500°C
Authors: Fares Chaker , Ren Fan , Pearton Stephen J.
Published: February 2020

There is a rapidly growing need for high performance power switching semiconductors in applications such as renewable energy systems, smart grids, transportation electrification, electric and hybrid electric vehicles, industrial machinery control, electricity production, and military systems. Interest in even more efficient, lightweight, and reliable power converters, based on ultra-wide-bandgap (WBG) semiconductors has led to Ga2O3 drawing significant attention due to its large breakdown field of around 8 MV.cm-1. Switches fabricated from wide bandgap semiconductors such as Ga2O3 have a higher power density, better efficiency, and thermal tolerance compared to Si, which can reduce the need for expensive bulky cooling systems. A major drawback of Ga2O3 is its low thermal conductivity. Thermally stable Schottky contacts for these rectifiers are also needed to ensure stability in power conversion systems.

In this study, we have measured the electrical characteristics of sputter-deposited W Schottky contacts with Au overlayers for reducing sheet resistance on n-type Ga2O3 before and after device operation up to 500°C. Assuming thermionic emission is dominant, the extracted barrier height decreases with measurement temperature from 0.97 eV (25°C) to 0.39 eV (500°C) while showing little change from its initial value of 0.97 eV after cooling down from each respective operation temperature. The room temperature value is comparable to that obtained by determining the energy difference between binding energy of the Ga 3d core level and the valence band of the Ga2O3 when W is present, 0.80 ± 0.2 eV in this case. The Richardson constant was 54.05 A.cm-2.K-2 for W and the effective Schottky barrier height at zero bias (eΦb0) was 0.92 eV from temperature-dependent current-voltage characteristics. The temperature coefficient for reverse breakdown voltage was 0.16 V/K for W/Au and 0.12 V/K for Ni/Au. The W-based contacts are more thermally stable than conventional Ni-based Schottkies on Ga2O3 but do have more reverse leakage current at higher operating temperatures.
Hydrogen Sensor for High Temperature and Humid Environment Applications
Authors: Jang Soohwan , Kim Mankyung , Shin Hoseong , Baik Kwang Hyeon
Published: February 2020

There are great interest in hydrogen as an alternative energy source and a viable energy carrier. Compared to conventional fossil fuels, it is an emission-free fuel that can produce larger heat of enthalpy when reacted with oxygen. Hydrogen gas is extremely reactive with oxygen, and has very low ignition energy of 0.019 mJ. Especially, leaking gas from pressurized container may induce spontaneous flammable ignition due to its negative Joule-Thomson coefficient. Therefore, hydrogen gas sensing systems are essential in various hydrogen related applications. GaN based material system is well-suited to hydrogen sensing because of its wide bandgap for high temperature operation, and mechanical and chemical robustness for device reliability. Many types of devices based on the GaN, including Schottky diodes, metal oxide semiconductor diodes, GaN nanowires and AlGaN/GaN high electron mobility transistors have been developed for fast and sensitive detection of hydrogen. In this presentation, hydrogen sensing characteristics of highly sensitive GaN based hydrogen sensors with various crystal planes will be explained. Also, as a dramatic approach to improve the sensitivity of the device, active platinum nanostructure and photo-chemically etched GaN will be discussed. In addition, nano-porous membrane will be introduced for the reliable operation of hydrogen sensor in humid ambient.