bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) A New Type of Ni-Doped LiCoO2 with Enhanced Structural and Electrochemical Reversibility at High Voltage
Authors: Cho Woongrae , Cho Jaephil 
Published: February 2020

Li1-xCoO2 is the first commercialized and the most common active material in Li-ion cathodes, owing to its stable electrochemical performance in terms of cycle and rate capability. However, despite its high theoretical energy density (1070 Wh kg-1), LiCoO2 has only achieved relatively low gravimetric energy density (< 630 Wh kg-1) due to an irreversible phase transition after Li extraction of more than x = 0.6 (into Li1-xCoO2). On the other hand, Ni-rich layered materials (LiNixM1-xO2, M = Co or Mn, x > 0.6) have higher gravimetric energy density (> 720 Wh kg-1) than LiCoO2, in spite of the same Rm structure and similar theoretical capacity, because of their reversible Li extraction up to more than x = 0.7. However, the Ni-rich materials still have similar volumetric energy densities (< 2300 Wh L-1) with LiCoO2, due to their lower electrode densities (< 3.0 g cm-3, compared to < 4.0 g cm-3 for LiCoO2). Therefore, a better way to achieve high volumetric energy density is increasing the electrochemical reversibility of LiCoO2 to levels comparable to that of Ni-rich materials.
Previous studies about layered-structured materials mainly focused on improving their electrochemical reversibility, but fundamental investigation regarding different electrochemical reversibility between LiCoO2 and Ni-rich material was not a main issue and related studies are conducted base upon only chemical de-lithiation and simulation data.
Herein, we directly examine the two materials' structural changes and different irreversible deterioration mechanisms during cycling. In-situ X-ray diffraction patterns and theoretical calculation suggest that the phase transition of LiCoO2 from O3 oxygen stacking to O1 or O2 oxygen stacking is caused by increased oxygen-oxygen electrostatic repulsion during the charge process. Furthermore, we investigated a critical role of cations in lithium sites in layered-structured cathode materials. In case of Ni-rich materials, migration of Ni ions into the Li vacancies in Ni-rich materials during charge, a process called as 'cation mixing', screens the oxygen-oxygen repulsion that arises from lithium vacancies. This suppresses lattice parameter expansion along the c-axis, and therefore delays the phase transition although the cation mixing is cause of structural failure in Ni-rich material upon further Li extraction. As a result, LiCoO2 with 10% nickel-doped (LiCo0.9Ni0.1O2) displayed much enhanced electrochemical reversibility, which was increased by 0.1 mol lithium ion extraction with maintaining its electrode density of ~ 4.0 g cm-3.
Structural Evolution and Electrochemical Properties of O3-Type Layered Oxide with a Quaternary Transition Metal Composition
Authors: Kim Jae Chul , Kwon Deok-Hwang , Shi Tan , Wang Jingyang , Kim Haegyeom , Bianchini Matteo , Ceder Gerbrand 
Published: February 2020

To meet growing need for large-scale energy storage, rechargeable batteries that reversibly cycle sodium ions are an attractive alternative to the Li-based technology. In particular, Na-intercalating oxides favorably form energy-dense layered structures with almost all transition metals, allowing a wide selection of redox centers to obtain desirable electrochemical activities. However, desodiation in the layered materials is often limited by structural instability due to transition metal migration at high voltage. To address this issue, we formulate a quaternary-mixed transition metal system with the O3-type layered structure.
We propose Ti as a structural stabilizer and report a composition of NaTi0.25Fe0.25Co0.25Ni0.25O2 in this work. Synthesized by a solid-state reaction, the compound obtained is phase-pure with the R-3m symmetry. X-ray absorption spectroscopy reveals that transition metal oxidation states are Ti4+, Fe3+, Co3+, and Ni2+, suggesting that Ti remains electrochemically inert while others are redox-active. Our results highlight promising electrochemical performance of the material; 504 Wh kg-1 at C/20 and 200 Wh kg-1 at 30C at room temperature. According to in situ X-ray diffraction, the structural evolution upon desodiation differs from that upon resodiation. Interestingly, compared with the pristine O3 structure, we find that the discharged structure at 2 V after cycle is unchanged, leading to respectable cyclability. We will discuss the possible origin of this path-dependency of desodiated structures and its implication on electrochemical properties. Also, perspectives on the multi-transition metal system for layered cathode materials will be provided in this talk.
(Invited) Charge Compensation By Cationic/Anionic Redox for High-Capacity Positive Electrode Materials
Authors: Yabuuchi Naoaki 
Published: February 2020

In the past decade, lithium-enriched compounds, Li2MeO3 (Me = Mn4+, Ru4+ etc.), have been extensively studied for high-capacity positive electrode materials of lithium batteries. Although the origin of high reversible capacities was a debatable subject for a long time, recently it has been evidenced that charge compensation is partly achieved by solid-state redox of non-metal anions, i.e., oxide ions (anionic redox),[1] coupled with solid-state redox of transition metal ions (cationic redox), which is the basic theory used for classical lithium/sodium insertion materials. Competition between cationic and anionic redox reactions is often evidenced for the lithium-enriched materials because the energy level of oxygen 2p band is lowered by the presence of excess lithium ions with high ionic characters in the crystal lattice. Reversibility of anionic redox reactions is also influenced by ionic and covalent characters for chemical bonds of transition metal ions.[2, 3] In contrast, when the energy of metal 3d band is low enough than that of oxygen 2p, pure cationic redox is realized even for the lithium-excess system.[4, 5] Moreover, this concept is further extended to sodium battery applications.[6] From these findings, we discuss the stabilization and destabilization mechanisms and material design strategy with the concept of cationic and anionic redox reactions to develop new high-capacity lithium/sodium insertion materials for battery applications.
References
[1] M. Sathiya et al, and J.-M. Tarascon, Nature Materials, 12, 827 (2013).
[2] N. Yabuuchi et al., PNAS, 112, 7650 (2015).
[3] N. Yabuuchi et al., Nature Communications, 7, 13814 (2016).
[4] S. Hoshino, et al., and N. Yabuuchi, ACS Energy Letters, 2, 733 (2017).
[5] M. Nakajima and N. Yabuuchi, Chemistry of Materials, 29, 6927 (2017).
[6] K. Sato et al., and N. Yabuuchi., Chemistry of Materials, 29, 5043 (2017).
(A03 Best Poster Winner) Electrochemical and Microstructural Analysis of Cu6Sn5 Alloy Electrodes
Authors: Juarez-Robles Daniel , Gonzalez-Malabet Hernando J. , Ausderau Logan , Xiao Xianghui , Nelson George J. , Mukherjee Partha P. 
Published: February 2020

In recent years, copper-tin has risen as one of the most promising anode materials. It possesses a higher energy density than the conventional graphitic anode electrodes. And, the binary copper-tin alloy seems to mitigate the drastic volume changes, exhibited by other high capacity alloy electrodes (e.g., silicon, tin), during cycling. In order to take the next step, and implement this material in commercial applications (e.g., transport and portable electronics), it’s necessary to have a comprehensive understanding of its electrochemical performance.
In a conventional lithium-ion cell, the electrode consists of a porous intricate composite of three main components: active material, conductive additive and a polymeric binder. Electrochemical performance of these electrodes depends upon not only on the components but also on the electrode microstructure defined by the particle size, electrode thickness, porosity, and composition. The electrode microstructure also evolves according to the cycling condition; hence, the cell performance is affected by these changes.
In the present work, the microstructural-electrochemical interaction on Cu6Sn5 composite electrodes is studied. The electrode microstructure is modified by varying the composition and the drying temperature. The effect of the voltage window and its correlation with the copper expulsion phenomena is also analyzed. The former is accomplished through charge/discharge cycling of Cu6Sn5 half cells. Morphological changes are studied by removing the electrode from the cell and analyzing it using micrographic (SEM) techniques. Results will show how the mechanical degradation of the electrode impact the long term cycling performance.
Fundamental Chemistry Behind Rechargeable Li-Based Batteries and Beyond: Theoretical and Computational Chemistry Approach
Authors: Dubey Satya Prakash , Widanage Widanalage Dhammika , McGordon Andrew , Marco James 
Published: February 2020

Abstract: Motivated by energy security and environmental concerns, policymakers around the world are directing attention to electrified vehicles as a partial solution to reducing fossil fuel consumption and carbon emissions. In recent years, rechargeable Li-ion batteries emerge as an important power source, and their performance highlights the adoption into the automobile electrical vehicles (EV) sector as viable alternatives to combustion engines. The success of market penetration of these environmental-friendly vehicles strongly depends on the industrialization of new energy-storage technologies that must meet at the same time, performances, security, durability and cost requirements. However, the performance of today's battery chemistries relative to the battery weight is a limiting factor – there is a gap to close between today's technology and the requirements of future battery vehicles. The next-generation energy storage systems may be based on novel chemistries, such as all-solid-state, Li-ion, Li-S, and metal-oxygen, to achieve significantly higher energy density. Materials and their interfaces in these batteries are often the key limiting factors and origins of failures. For example, the degradation at the electrolyte-electrode interfaces causes poor cyclability, low capacitance, and premature failure in these new battery systems. It is crucial to focus on research which aligned towards, robust reaction kinetics modelling and its possible validation through experiments and discovering future advanced (Li, Si, Na-ion) batteries based on material chemistry and electrolyte design. To reveal such details, a fuller understanding of how the materials composition interact at the molecular level, which is not investigated in great detail so far is highly recommended by considering cost-effective computational chemistry tools (DFT, MD). Interaction of decomposed electrolyte/salt components with Li-ion is the key source of formation of SEI layer at the anode surfac such as LiF, Li2CO3, LiO, etc. To understand the stability and chemistry of SEI layer which is in general very complex, atomic level molecular chemistry simulation were performed. The perfect SEI would be a fast forming, flexible, stable and insoluble species with minimum electronic and maximum ionic conductivity. We use computational techniques to understand the limiting factors- such as reaction kinetics and chemistry involved for solid electrolyte interphase (SEI) growth and failure mechanisms at the interfaces, for the improvement of capacity and power fade to the new energy-storage technologies Fig. 1 [1].
[1] M. Datt Bhatt and C. O’Dwyer, “Recent progress in theoretical and computational investigations of Li-ion battery materials and electrolytes,” Phys. Chem. Chem. Phys., vol. 17, no. 7, pp. 4799–4844, 2015.

Figure 1
UV Photopolymerization of Vinyl Ether Based Polymer Electrolytes for Solid-State Lithium Batteries
Authors: Becker Melissa , Tenhaeff Wyatt 
Published: February 2020

The utilization of solid lithium metal in lithium ion batteries increases performance and capacities but introduces safety issues when combined with liquid electrolytes. This prevents its use in practical energy dense electrochemical cells, like those required for electric vehicles or consumer electronics. Safety can be increased by using polymer or gel electrolytes which are less flammable and provide a more formidable barrier to dendrite formation. However, the production of polymer electrolytes can often be complicated and involve several stages, making the processing time-consuming and expensive to apply on the industrial scale.
In this work we developed a simple bulk polymerization method in the presence of lithium salt to produce quick-curing vinyl ether based polymer electrolytes in a one-step cationic UV photopolymerization. These electrolytes are composed of ethyl vinyl ether (EVE) monomer and poly(ethylene glycol) divinyl ether (DVEp) crosslinker with triarylsulfonium hexafluorophosphate salt photoinitiator and bis(trifluoromethane) sulfonimide (LiTFSI) lithium salt. Systems with varying crosslinker to monomer (DVEp:EVE) volume ratios and lithium salt concentration ratios were produced to see the effects of crosslinking density and [O]:[Li] ratio on electrolyte properties. Attenuated Total Reflectance Fourier-transform Infrared spectroscopy (ATR-FTIR) was used to quantify polymer composition and verify complete polymerization. Ionic conductivities were measured from 0 to 80 °C using electrochemical impedance spectroscopy. The highest ionic conductivities were seen in samples with the lowest crosslinker concentrations and the highest lithium salt concentrations. The most conductive sample produced had composition 10:1 [O]:[Li] and 15% crosslinker by volume and reached an ionic conductivity of 1.2x10-6 S/cm at 20°C. Glass transition temperatures (Tg) were measured with differential scanning calorimetry (DSC) for various salt-free DVEp:EVE ratios; Tg was determined to be -15°C for composition with 15% crosslinker in the absence of salt. Investigation of the effect of salt on Tg’s and the electrochemical stability of these compositions is currently underway and will be reported.
Effect of Formation Rates on Performance of Lithium Metal Batteries
Authors: Nagpure Shrikant C. , Wood Sean M. , Dufek Eric J. , Dickerson Charles C , Liaw Bor Yann , Hu Victor Waiman 
Published: February 2020

Lithium metal rechargeable batteries (LRBs) have the potential to meet the 500 Wh·kg-1 energy density goal set by the US Department of Energy for high energy density batteries [1]. However, two issues need to be addressed in these batteries before their widespread commercialization: (1) safety concerns arising from dendritic growth and (2) limited cycle life due to low Coulombic efficiency and loss of active Li. Since organic solvents are thermodynamically unstable in the presence of highly-reducing Li, significant side reactions take place, the products of which form a solid electrolyte interphase (SEI) on the Li surface.
During the production process, Li-ion batteries undergo formation cycling to form a stable SEI and to evaluate the condition of the cell. However, the advantages of early cycle conditioning or formation are not well understood for LRBs, because new SEI forms on the Li surface during each cycle. The present study was undertaken to better understand how early cycling impacts interfacial processes in LRBs and ultimately how variation in the initial cycles impacts the life of the battery.
Cycling conditions, which include both charging (deposition) and discharging (stripping), affects the Li anode morphology [2, 3]. Build-up of a stable SEI layer and formation of a uniform Li surface during initial cycling of LRBs helps limit dendritic growth, and cell impedance in subsequent cycling. A stable initial SEI is also necessary to prevent corrosion of the Li metal electrode and to prolong the cycle and calendar life of the cells by limiting side reactions with the new Li surface. Using a high-Ni NMC cathode and a Li metal anode, an assortment of different cycling conditions which impact the dynamics of the Li-electrolyte interface were investigated. Performance was characterized with electrochemical diagnostic tools and surface morphology analysis. Both the deposition and stripping rate affected the impedance of the cell, surface kinetics, and interfacial mass transport, all of which impact the cycle life of LRBs.
References:
[1] Battery500 Consortium to Spark EV Innovations: Pacific Northwest National Laboratory-led, 5-year $50M effort seeks to almost triple energy stored in electric car batteries, in Office of Technology Transitions Energy.gov (2016).
[2] Hongfa Xiang, Pengcheng Shi, Priyanka Bhattacharya, Xilin Chen, Donghai Mei, Mark E. Bowden, Jianming Zheng, Ji-Guang Zhang, and Wu Xu, “Enhanced charging capability of lithium metal batteries based on Lithium bis(trifluoromethanesulfonyl)imide-lithium bis(oxalato) borate dual-salt electrolytes,” J Power Sources, 318, 170 (2016).
[3] Jiangfeng Qian, Wesley A. Henderson, Wu Xu, Priyanka Bhattacharya, Mark Engelhard, Oleg Borodin, and Ji-Guang Zhang, “High rate and stable cycling of lithium metal anode,” Nat Comm, 6, 6362 (2015).
Soldering a Gas Diffusion Layer Onto Stainless Steel Bipolar Plates Using Tin and Tin Alloys
Authors: McCay Katie , Kongstein Ole Edvard , Barnett Alejandro Oyarce , Seland Frode 
Published: February 2020

Bipolar plates are a key component within a PEM fuel cell stack, with roles such as electron transfer, fuel and waste transport, and stack support. However, stainless steel as a bipolar plate material suffers from poor corrosion properties, with increasing interfacial ohmic resistances across the cell and stack due to the formation of non-conductive oxide layers reducing voltage efficiency over time. These increases in resistance can be mitigated by coating the steel with a conductive and corrosion resistant material.
In this work, we electrodeposited a thin layer of Sn onto a stainless steel bipolar plate (BPP) and joined (soldered) it with a gas diffusion layer (GDL) material through hot-pressing at a temperature just below the melting point of tin. This process solders the GDL to the BPP through the Sn, providing an uninhibited conduction pathway and a drastically reduced interfacial contact resistance. In addition, the Sn layer forms a passive oxide upon exposure to a PEM environment, preventing further corrosion whilst maintaining conductivity through GDL fibres that have infiltrated the Sn layer during hot-pressing (see figure 1). We have optimised the electrodeposition and hot-pressing procedure, with promising in-situ results even after 200 hours of operation in a working fuel cell. This confirms that the novel idea is successful in producing a coating with low contact resistance and promising longevity.
However, accelerated ex-situ testing in dilute sulfuric acid solution (pH 5.5) revealed instability of the SnO2 layer. We propose that introducing alloying elements, such as Bi and In, will increase the stability of the oxide formed and thus impede the degradation of the Sn coating. This work investigates that claim, by depositing Sn alloys containing up to 10 wt % Bi and In onto a stainless steel bipolar plate. Conventional electrochemical measurements such as chronoamperometry and cyclic voltammetry, as well as interfacial contact resistance were performed to investigate the performance of this system.

Figure 1
Interfacial Characteristics of Graphene Containing Novel Microporous Layers for PEM FCs
Authors: Leeuwner Magrieta Jeanette , Wilkinson David P. , Gyenge Elod L. 
Published: February 2020

The cathodic microporous layer (MPL) provides many beneficial properties for performance improvement of the H2 PEM FC, particularly with respect to water management and oxygen transport to the catalyst layer [1,2]. The MPL performance is highly dependent on its in-operando material properties such as morphology, porosity and electrical conductivity (in-plane and through-plane, respectively). Furthermore, the interfacial interconnectivity of the MPL material properties with the nano-scale features of the catalyst layer (CL) and the macro-scale characteristics of the gas diffusion layer (GDL) are essential, yet difficult to study, elements in the optimal operation of the fuel cell cathode. In this study diverse graphene based MPLs were investigated by comparison with conventional carbon black and graphite materials. The graphene MPLs were composed of: stand-alone graphene foam [3], electrochemically exfoliated graphene micro-flakes [4] and reduced graphene oxide [5]. The general performance trends revealed lower overpotentials for the graphene MPLs in the electrode kinetic and ohmic controlled regions. In the electrode kinetic region, the improvement was attributed to the unique stacked flake morphology of the graphene assuring excellent interfacial adhesion with the catalyst layer combined with graphene’s high electronic conductivity. The lower ohmic polarization resistance on the other hand, is due to the compact and tortuous morphology of graphene MPLs exhibiting a higher tendency for water retention and inducing, thereby, superior membrane humidification. The enhanced water retention of the graphene MPL, however, can cause catalyst layer flooding at current densities greater than 1000 mA cm-2. To overcome this limitation, composite MPLs containing graphene flakes and carbon black (e.g., Vulcan XC-72) in a 1:1 weight ratio were manufactured and investigated. The graphene – carbon black composite MPLs, demonstrated lower overpotentials throughout the entire polarization curve with maximum power densities 81% and 28% higher compared with the carbon black only MPL at 20% and 100% cathode relative humidity, respectively. In addition, the graphene composite MPLs showed vastly superior durability at 20% cathode humidity in 5 h galvanostatic polarization experiments at 1000 mA cm-2.
References:

M. Blanco, D.P. Wilkinson, Int. J. Hydrogen Energy, 39, 16390-16404 (2014).

T. Swamy, E.C. Kumbur, M.M. Mench, J. Electrochem. Soc., 157, B77-B85 (2010).

M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, Fuel Cells, 6, 790-801 (2015).

A.T. Najafabadi, M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, ChemSusChem, 9, 1689-1697 (2016).

M.J. Leeuwner, D.P. Wilkinson, E. Gyenge, manuscript in preparation (2017).