bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Side Reactions and Cycling Efficiency with Silicon Electrode Surfaces
Authors: Vaughey John T. , Dogan Fulya , Hubaud Aude A. , Schroeder David J. 
Published: February 2020

Energy storage materials – lithium-based portable energy storage technologies are an area of research that was born in the late 1960s / early 1970s, went global in the 1990s with portable consumer electronics, and is now being adapted to a variety of markets including electrification of vehicles, space flight, and grid storage. While showing promise, these new applications may have different requirements (e.g. power, cost, volume) than ones optimized for consumer markets.
To increase energy density, many researchers are exploring ways to incorporate silicon into a battery. Elemental silicon has many properties that make it a top candidate to replace graphitic carbon in next generation lithium-ion batteries. It has (1) very high gravimetric capacity (~3600 mAh/g), (2) high volumetric capacity (~7400 mAh/L), and (3) low insertion cell voltage. It also has many problems that must be overcome including (1) high volume expansion on lithiation, (2) an unstable SEI layer, and (3) instability of the fully charged anode to the electrolyte. Although significant effort has been focused on silicon-based electrodes, e.g. understanding the role of morphology, particle size, or local structure – our work has been concentrated on electrode level interactions. Using the knowledge gained from the materials level studies we are addressing what happens when the silicon is made into an electrode and exposed to the contents of an electrochemical cell [1-3].
Previous work by the Edstrom group [4-5] has shown that the normal passivation layer of silicon, namely silica, is in fact electrochemically active on the first charging cycle. On first lithiation it reacts to form Li4SiO4. This phase does not directly participate in the electrochemistry after this point, but does interact chemically with its environment to effect cycle efficiency and SEI stability [6]. In this talk we will discuss how, upon formation, it interacts with its environment and track these changes by FTIR, 29Si NMR, 7Li NMR, and PXRD with eventual formation of Li6Si2O7 and Li2SiO3.
[1] C. Joyce, L.Trahey, S.A. Bauer, F. Dogan, and J, T. Vaughey Journal of The Electrochemical Society, 159,A909-A914 (2012).
[2] F. Dogan, C. Joyce, and J. T. Vaughey Journal of The Electrochemical Society, 160, A312-A319 (2013).
[3] F. R. Brushett, L.Trahey, X. Xiao, J. T. Vaughey ACS Appl. Mater. Interfaces , 6, 4524−4534 (2014).
[4] B. Philippe, R. DedryveÌre, M. Gorgoi, H. Rensmo, D. Gonbeau, K. Edström

J. Am. Chem. Soc.,
135, 9829−9842 (2013).
[5] ] B. Philippe, R. DedryveÌre, M. Gorgoi, H. Rensmo, D. Gonbeau, K. Edström
Chem. Mater.,
25,394−404 (2013).
[6] A. A. Hubaud, Z. Z. Yang , D. J. Schroeder, F. Dogan, L. Trahey, J. T. Vaughey Journal of Power Sources
282, 639-644 (2015)

Figure 1
Interfacial Effects of Electrochemical Lithiation of Epsilon-VOPO4 and Evolution of the Electronic Structure
Authors: Quackenbush Nicholas F. , Wangoh Linda , Wen Bohua , Zhang Ruibo , Chung Youngmin , Chernova Natasha , Chen Zehua , Sallis Shawn , Lin Yuh-Chieh , Ong Shyue Ping , Whittingham M. Stanley , Piper Louis F.J. 
Published: February 2020

The epsilon polymorph of vanadyl phosphate ε-VOPO4 is a promising cathode material for high-capacity Li ion batteries, owing to its demonstrated ability to reversibly incorporate more than one lithium per redox center, with a total theoretical capacity of 331 mAh/g. As in the case of the olivines, the problem of the inherently low electronic conductivity of ε-VOPO4 is overcome by the use of nano-sized particles within the cathode. At these dimensions the electrochemical reaction can be largely affected by the interfacial chemistry at the nanoparticle surface. An investigation of these surface reactions is critical for obtaining a complete understanding of the mechanism by which lithium intercalates and how it relates to the electrochemical performance.
We performed x-ray photoelectron spectroscopy using both soft (XPS) and hard (HAXPES) x-rays to chemically distinguish and depth-resolve the interfacial phase transitions as a function of electrochemical discharge. Core level analysis supports a straightforward two-phase reaction as the first lithium is intercalated. In contrast, the insertion of the second lithium is more complicated with evidence of a significant radial lithium gradient, due to a possible to a disruption of the kinetics. From inspection of the valence band region, we were able to monitor the reversible evolution of ε-VOPO4 to Li2VOPO4 at the surface of our nanoparticles. These assignments were supported by hybrid density functional theory of the three phases. The origin of the radial gradient is likely associated with the presence of stable intermediate phases during the second reaction and warrants further attention. This work was supported as part of NECCES, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001294.

Figure 1
The Use of Reduced Cost and Purity Precursors in the Melt Preparation of LiFePO4
Authors: Talebi-Esfandarani Majid , Rousselot Steeve , Gauthier Michel , Sauriol Pierre , Liang Guoxian , Dollé Mickeal 
Published: February 2020

Different synthetic routes, such as solid state, sol-gel, hydrothermal, co-precipitation, and microwave preparations, have been used for preparing LiFePO4; (LFP) a key cathode material in lithium-ion battery applications. Usually it is necessary to use costly precursors with a high purity, such as FePO4 or FeC2O4, for the synthesis of LFP. In most methods secondary phases formed during synthesis, give rise to lower subsequent electrochemical capacities in the final product. The melt synthesis is an alternative, rapid and low-cost process proposed by Gauthier et
al., and can be a promising method for the large scale preparation of LFP. This process combines ideal-liquid phase reaction with short dwell times and fast reaction kinetics in a reducing atmosphere. Our team made an effort to reduce the high manufacturing cost of LFP by using a melt synthesis, enabling the utilisation of lower purity and lower cost raw materials; namely iron ore concentrate as a source of iron. In this work, different synthesis conditions (such as iron precursors, stoichiometric ratios, and solidification processes) are optimized to obtain a low cost carbon-coated LFP with a high purity and excellent electrochemical properties.
(Invited) Mechano-Electro-Chemical Coupling in Lithium Intercalation Compounds
Authors: Qi Yue , James Christine 
Published: February 2020

Mechano-Electro-Chemical (MEC) Coupling in intercalation compounds can be considered in multiple ways. Large stresses caused by electrochemically induced stoichiometry changes can lead to local stress and mechanical degradation. On the other hand, MEC coupling may also provide new opportunities to characterize materials by measuring the stress/strain generated by the stoichiometry change.
One typical challenge in modeling the MEC coupling is the lack of proper material properties as a function of the state of charge (SOC). To address this challenge, we developed “atomically informed” battery mechanics models by integrating density functional theory (DFT) predicted mechanical properties into continuum models to predict diffusion induced deformation and stress evolution and make direct comparisons with experiments. It was found that lithiation induced stiffening occurs in layered compounds, however the averaged Young’s moduli change very minimally at a function of SOC in the spinel and olivine structures. Depends on the tendency of Li to segregate to or deplete from the fractured surface, the work of decohesion of electrodes can decrease or increase with SOC, and crack instability may also occur due to phase transitions within the decohering region.
Measuring the strain due to stoichiometry change can be further complicated by the coupling of different vacancy species. For example, in Li-excess layered compounds (xLi2MnO3∙(1-x)LiMO2, where M=Ni, Co and/or Mn), it is widely agreed that oxygen vacancies can be introduced to the Li2MnO3 phase during the initial charging cycles. With DFT and Ab initio molecular dynamics calculations, we demonstrate that correlations exist between oxygen vacancy and the formation and migration of Li vacancies. As Li vacancies tend to form and cluster around oxygen vacancies, the oxygen vacancies hinder the diffusion of the Li ions. On the other hand, the nonstoichiometry strains are correlated between the two species, making the MEC coupling analysis more complex in these intercalation compounds.
Bulk Structure and Surface Properties of Lithium- and Manganese-Rich Layered Oxides and Their Impact on Electrochemical Performance
Authors: Chen Guoying , Kuppan Saravanan , Shukla Alpesh Khushalchand 
Published: February 2020

Lithium- and manganese-rich layered oxides, Li1+x
M1-x
O2 (M=Mn, Ni, Co), are promising cathode materials for lithium-ion batteries due to their high capacities, typically more than 250 mAh/g. Despite the intense research and development in the past decade, their commercial adoption remains hindered by severe shortcomings including a large first-cycle irreversible capacity loss, [1] voltage and capacity fade, [2] DC resistance rise at low state of charge (SOC) and transition metal dissolution. [3] Studies have attributed these issues to the structural changes occurring during first-cycle activation and prolonged cycling, yet the crystal structure of the pristine oxides is still a matter of debate. Fundamental studies on the conventionally synthesized, aggregated secondary particles often lead to ambiguous results due to the structural complexity in this class of materials. In this presentation, we report the synthesis of well-formed, discrete layered Li1+x
M1-x
O2 crystals with various morphologies and surface properties using a molten salt method. Complementary microscopy and spectroscopy techniques at multi-length scale, including aberration corrected (scanning) transmission electron microscopy, electron energy loss spectroscopy and X-ray energy dispersive spectroscopy, were used to reveal the structural make-up of the bulk as well as the surface of the primary particles. Surface sensitive soft X-ray absorption spectroscopy was further used to reveal the roles of key surface properties, particularly surface composition, surface area and surface crystalline orientation, in the material challenges facing Li1+x
M1-x
O2 cathodes. Future directions and research to enable this class of materials will also be discussed.

References:

1. Z. Lua and J. R. Dahn, Understanding the Anomalous Capacity of Li/Li[Ni
x
Li(1/3-2x/3)Mn(2/3-x/3)]O2 Cells Using In Situ X-Ray Diffraction and Electrochemical Studies, J. Electrochem. Soc., 149, A815 (2002).
2. J. R. Croy, S.-H. Kang, M. Balasubramanian, and M. M. Thackeray, Li2MnO3-Based Composite Cathodes for Lithium Batteries: A Novel Synthesis Approach and New Structures, Electrochem. Communications, 13, 1063 (2011).
3. S.-H. Kang and M. M. Thackeray, Enhancing The Rate Capability of High Capacity xLi2MnO3 .(1-x)LiMO2 (M = Mn, Ni, Co) Electrodes by Li–Ni–PO4 Treatment, Electrochem. Communications, 11, 748 (2009).

Acknowledgment

This work was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231.
Impact of Electrolyte on the Cycling of Si-Based Materials
Authors: Chevrier Vincent L , Aiken Connor , Petibon Remi , Ma Xiaohua , Le Dinh Ba , Dahn Jeff R , Eberman Kevin W , Krause Larry J 
Published: February 2020

Alloy-based negative electrodes have been considered the “next-generation negative electrode” expected to replace graphite for many years. However, few exist in the marketplace. Manufacturing alloy-based cells with acceptable cycling poses a major challenge, indeed many components of the cell must be adapted in order to obtain successful cycling. 3M has a long history of alloy research for negative electrodes and has developed commercially viable Si-based alloys.
Si-based negative electrode materials undergo massive volume changes during cycling. Pure Si expands by approximately 280% while 3M’s active/inactive Si alloys expand on the order of 135%. The expansion and contraction of the particles has important consequences on the surface stability of these materials. Furthermore, the choice of electrolyte has profound impacts on the cycling of cells containing Si-based materials. In this presentation we will show the impact of electrolyte reactivity on the physical and chemical characteristics of the particles, the composition of the electrolyte and the cycling performance of the cells.
Cross section SEM studies of cycled 3M Si alloy and pure Si show the dimensional changes occurring in Si-based materials with cycling due to electrolyte reactivity. After 100 cycles, an SEI is found on the 3M active/inactive alloy, while the pure nano Silicon dramatically increases in size. Figure 1 shows cross section images of the electrodes containing only binder and either 3M Si alloy or pure Si. While electrolyte reactivity can occur with minimal fade in half cells, capacity fade will occur in full cells.
Fluoroethylene carbonate (FEC) has long been known to be an important electrolyte for Si-based materials. Furthermore, full cells containing Si-based materials can sometimes undergo sudden failure with cycling. GC/MS studies of electrolytes from cycled full cells containing Si-based materials will be presented showing the relationship between electrolyte composition and sudden failure. These results highlight the importance of full cell design optimization for the implementation of Si-based materials in commercially-relevant full cells.

Figure 1
Failure Mechanisms of Siox- Vs. Sife- Graphite Composite Anodes in Li-Ion Batteries
Authors: Sim Soojin , Cho Jaephil 
Published: February 2020

Mobile IT battery market is encountered to development of anode materials with high capacity and long cycle life due to increasing consumers’ demands for longer operation time. To meet this requirement, change of cathode material can be considered at first, but any candidates cannot beat LiCoO2. Accordingly, it is natural to consider the capacity increase of the anode materials beyond 390mAh/g. To achieve this target, the mixture of graphite and Si materials should be modulated with controllable volume expansion of the composite.
Herein, we assembled full lithium ion cells containing SiOx- and SiFe- graphite (SiOx-G, SiFe-G) composite anodes with reversible capacity of 450mAh/g. Using these two materials, we carried out further experiments to elucidate the capacity fading mechanisms using XPS, XRD, HR-TEM, EDS etc. Preliminary result showed that electrolyte decomposition degree with each anode materials upon increasing cycle number significantly affected its structural stability.
Pre-Lithiated Silicon As the Anode Material for the Next Generation of Lithium Ion Batteries
Authors: Yang Yongan , Li Xuemin 
Published: February 2020

It is widely believed that next generation of lithium ion batteries (LIBs) needs non-graphite anodes. Among all anode materials scrutinized to date, silicon (Si) is one of the most promising ones, because of its exceptionally high charge capacity, earth abundance, low cost, and well-developed industrial infrastructure. However, silicon suffers from a poor cyclability due to the volume fluctuation induced electrode damage during the lithiation/delithiation cycles. To date, many strategies have been attempted to tackle this problem. Pre-lithiated silicon (lithium silicide, LixSi) holds the promise for alleviating the poor-cyclability problem, as the pre-occupied space by Li can provide adequate volume for the subsequent lithiation/delithiation processes. However, LixSi has high reactivity, the challenge in electrode fabrication is to prevent surface damage prior to battery assembly.
In this presentation, we will report our tactics of overcoming the challenge, starting from materials synthesis, structural characterizations, surface modification, and performance assessments. Compared with the un-lithiated Si electrodes, the LixSi electrodes show much better charge capacity, cyclability, and rate capability.
Proton-Conducting Polymer Electrolytes for Solid Flexible Supercapacitors
Authors: Gao Han , Lian Keryn 
Published: February 2020

Polymer electrolytes, acting as separator and ionic conductor, are key enablers for the next generation flexible supercapacitors. An ideal high-performance polymer electrolyte should exhibit: (i) high ionic conductivity; (ii) good ion accessibility at the electrode\electrolyte interface; (iii) wide electrochemical stability window; and (iv) high environmental and temperature stability. Although the conductivity of polymer electrolytes is typically a few orders of magnitude lower than that of their liquid counterparts, deploying them in the form of thin film can mitigate this issue and provide high rate and power performance in a supercapacitor device.
A typical solid polymer electrolyte consists of an ionic conductor, a polymer matrix, and additives. Heteropolyacids (HPAs) are excellent solid-state proton conductors at room temperature [1]. One of the common HPAs is silicotungstic acid (SiWA, H4SiW12O40•nH2O).
We have developed a polymer-in-salt electrolyte system for supercapacitors using SiWA and polyvinyl alcohol (PVA). A systematic approach has been used to improve the performance of SiWA-PVA polymer electrolytes through additives and polymer structural modifications. The electrolytes showed excellent proton conductivity, stability, and film flexibility that enables thin and light weight solid supercapacitors (Fig. 1). They also outperformed Nafion® in terms of environmental stability at ambient conditions [2].
These SiWA-based polymer electrolytes have demonstrated high rate performance in both electrochemical double layer capacitors and pseudo-capacitors [3-5]. The solid polymer electrolyte-based devices were able to charge and discharge up to 100 Vs-1, with a time constant of 10 ms [3-5]. To further expand the potential window of the SiWA-based electrolyte, and thus increase the energy density, alternative HPAs have been synthesized. In this talk, proton conductivity and structural properties of the developed polymer electrolytes will be discussed. Device performance of different HPA-based solid supercapacitors will be presented and compared.

References:

U. B. Mioè et al., Solid State Ionics, 176, 3005-3017 (2005).

H. Gao et al., Electrochem. Commun., 17, 48-51 (2012).

H. Gao and K. Lian, J. Mater. Chem., 22, 21272-21278 (2012).

H. Gao and K. Lian, J. Power Sources, 196, 8855-8857 (2011).

H. Gao et al., J. Power Sources, 222, 301-304 (2013).

Fig. 1. Photographs of (a) a HPA-based polymer electrolyte film and (b) an assembled flexible solid supercapacitor.

Figure 1
Bio-Templated and Bio-Tethered Materials for a Flexible Lithium Ion Battery
Authors: Allen Mark A , Riley Scott J. , Barannikova Evgenia , Winton Alexander 
Published: February 2020

Nature has a diverse toolkit that can be utilized to address a broad array of important chemistry related problems. These tools include DNA, lipids, polysaccharides, and proteins, each of which have been used for direct applications from sensors to electronics. Proteins represent nature’s most diverse polymer with a range of functionality determined by 20 naturally encoded amino acids. The structure and chemical functionality of each amino acid determine the properties of the polypeptide that they compose. In this presentation I will discuss the use of biomolecules in order to self-organize flexible electrodes for lithium ion batteries.
The focus of my group is to identify functional polypeptides for the purpose of improving technologically relevant materials. Our lab uses a technique called phage display in order to identify solid binding polypeptides that are specific for binding to and the mineralization of electroactive materials and use these materials to prepare new lithium ion batteries. Peptides that are identified are then genetically combined with other polypeptides in order to generate multi-functional polypeptides that can then be used to lash together myriad materials into a hierarchically assembled structure. This current work focuses on making these materials more flexible through the addition of bio-molecules.
The Cycling Behaviour of MnO2 as Investigated By Synchrotron XRD, Stepped Potential Electrochemical Spectroscopy (SPECS) and Cycling on the Electrochemical Quartz Crystal Microbalance (EQCM)
Authors: Donne Scott W , Gibson Andrew J , Wood Ross , Dupont Madeleine F 
Published: February 2020

Manganese oxides are promising materials for supercapacitor applications due to their low cost and relatively low toxicity, coupled with their high electrochemical activity [1]. MnO2 comes in many structural forms, with two main structural types to be discussed in this presentation. The first being the layer structure which is favoured by many researchers as it is believed to be able to undergo repeated cycling. Layer structures involve the arrangement of component [MnO6] octahedra such that they form a coherent flat plane. These flat planes are separated by charged species, with the number being dependent on the average oxidation state of the Mn in the layer. Birnessite is a layered form of MnO2 with either sodium, potassium or water in the interlayer spacing. Tunnel structures involve the arrangement of component [MnO6] octahedra in such a manner as to generate tunnels that run in one direction through the structure, with width and height equal to between one and three octahedra; the width and height do not need to be equal. Ramsdellite and Pyrolusite are both tunnel structures, with tunnel dimensions being 2 x 1 and 1 x 1 respectively [2].
One possible problem with the long term utilisation of pseudo capacitors, such as metal oxides, is that they can undergo structural change during cycling. This presentation will cover the cycling behaviour of Birnessite, Ramsdellite and Pyrolusite as examined by a number of different techniques. SPECS experiments performed in-situ at the Australian Synchrotron to map structural changes with respect to the state of charge of a manganese oxide material. In addition, data obtained on the mass changes during SPECS cycling of the three phases on the EQCM will be presented. The mass change, when corroborated with the amount of charge passed, gives information about the type of ions being inserted into the structure. In the case of these experiments, % values of K+ and H+ insertion have been obtained. In addition, values for retention of these ions during repeated cycling have been elucidated, which will provide valuable information for researchers engaging in the intelligent design of electrochemical capacitors utilising MnO2.
References
1. Wei, W., et al., Manganese oxide-based materials as electrochemical supercapacitor electrodes. Chemical Society Reviews, 2011(40): p. 1697 - 1721.
2. Post, J.E., Manganese oxide minerals: crystal structures and economic and environmental significance. Proceedings of the National Academy of Science, USA, 1999: p. 3477.