bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrolyte Additives for Mg Stripping Reaction in Lithium-Magnesium Hybrid Batteries
Authors: Kim Haebeen , Kim Duri , Ryu Ji Heon
Published: February 2020

Rechargeable magnesium batteries have the advantages of low cost and high theoretical capacity without dendrite formation. However, the Mg batteries have critical problem of sluggish kinetic by the slow solid-state diffusion of highly polarizing divalent Mg-ions in most intercalation hosts. This problem can be overcome by hybrid batteries combining a Mg-metal negative electrode and fast lithium intercalation hosts when the Li+ ions are used with Mg2+ ions. Although two kinds of cations exist in the electrolyte, the Li ions can be easily intercalated into the host positive electrode materials and the Mg ion can be electroplated and stripped at the negative electrode because of its relatively higher standard reduction potential. However, the Mg metal electrode still have problem of the formation of the blocking layer between the magnesium metal surface and electrolyte. In case of using the Mg(TFSI)2 and glyme-based electrolyte, the huge overpotential occurs in the Mg stripping reaction during discharging process. We found that the electrolyte additives containing the halogen anion such as Cl- and Br- reduced the overpotential of the Mg stripping reaction.

The Li4Ti5O12 (LTO) and mechanically polished Mg disk were used the electrode materials and the 1.50 M LiTFSI and 0.15 M Mg(TFSI)2 in glyme:diglyme=1:1 solution (standard electrolyte) was used as dual salt electrolyte. This cell showed a negative discharging voltage (about -1.0 V) due to the huge Mg stripping overpotential while the charging reaction occurs at 0.8 V. After the addition of 0.1 M LiCl, 0.1 M LiBr, or 0.5 M MgCl2, the discharging voltage increased to +0.5 V from the 2nd cycle after activation process during 1st cycle while the charging voltage was almost close to the halogen-free electrolyte. In spite of the increase of the halogen anion concentration, the further improvement was not detected.

When the HMDS (hexamethyldisilazane) was added to the electrolyte with the LiCl, the overpotential of Mg stripping reaction was sharply decreased from the first cycle without activation process. But the overpotential did not decrease in case of the HMDS addition to the standard electrolyte composition (halogen-free).

Therefore, the Mg/LTO hybrid cell with dual salt electrolyte containing halogen anion and HMDS showed good electrochemical performances with low polarization from the initial cycle.
Directing Mg Storage Chemistry in Organic Polymers Towards High Energy Mg Batteries
Authors: Dong Hui , Liang Yanliang , Tutusaus Oscar , Mohtadi Rana , Yao Yan
Published: February 2020

Magnesium batteries could offer high energy density without compromising safety due to the use of non­dendritic Mg metal anode. However, the charge­ dense divalent Mg2+ also makes cation ingress into and diffusion within cathode materials kinetically sluggish. It is therefore intriguing that recently organic cathodes were reported to deliver high energy and power even at room temperature. Herein we reveal that previous organic cathodes likely all operate on an MgCl ­storage chemistry sustained by a large amount of electrolyte that significantly reduces cell­ level energy. We go on to demonstrate Mg batteries featuring an Mg2+­ storage chemistry using quinone polymer cathode, Cl­ free electrolytes, and Mg metal anode. Under lean electrolyte conditions, the organic cathode in cells on Mg ­storage chemistry deliver the same energy while using ca. one tenth of the amount of electrolyte needed for the MgCl ­based counterparts. With the right combination of organic cathodes and chloride ­free electrolytes, the observed specific energy (up to 243 Wh kg­-1), power (up to 3.4 kW kg-
­1), and cycling stability (up to 87%@2500 cycles) of Mg ­storage cells consolidate organic polymers as promising cathode candidates for high­ energy Mg batteries.
Solution-Based Synthesis of Li3PS4 Solid Electrolytes
Authors: Lim Hee-Dae , Xing Xing , Liu Ping
Published: February 2020

Sulfide-based solid electrolytes have attracted much attention due to their high conductivities, which are far beyond those of oxide-based solid electrolytes.[1,2] However, They (Li2S-P2S5 system, i.e., LPS) have been normally synthesized by solid state synthesis such as mechanical ball milling. These methods require rigorous control of reaction environment as well as high temperature heat treatment and repeated pelletizing steps. In contrast, solution-based synthesis methods can induce chemical reaction among precursor particles (Li2S and P2S5) at low temperatures resulting in the formation of conductive phases of β-Li3PS4 and Li3P7S11 with only moderate thermal treatment.[3,4] The method deserves great attention since it simplifies synthesis process, yields products of great purity, and may facilitate the fabrication of composite electrodes with improved interfaces.

In this work, we have developed an efficient method to form a thin solid electrolyte layer directly on Li metal using the liquid coating techniques. The formation of LPS (Li2S-P2S5) based electrolyte is achieved by rational design of the solvent and the Li, P, and S precursor ratios. The solution electrolyte can be directly coated and formed on Li metal through the in-situ formation of the solid electrolyte layer, which does not require the complex synthesis process and high temperature sintering step. Layers of thickness of < 50 mm can be fabricated and electrochemical cycling of lithium is achieved. This liquid-phase coating is a simple and straightforward technique for making a thin solid electrolyte and can be applicable to anode surface with complex contours. The new liquid coating technique holds the promise to overcome the limitations of current state solid electrolytes.

[1] Kamaya, N. et al. A lithium superionic conductor. Nature Mater. 10, 682-686 (2011).

[2] Yamane, H. et al. Crystal structure of a superionic conductor, Li7P3S11. Solid State Ion. 178, 1163-1167 (2007).

[3] Ito, S. et al. A synthesis of crystalline Li7P3S11 solid electrolyte from 1,2-dimethoxyethane solvent. J. Power Sources 271, 342-345 (2014).

[4] Liu, Z. et al. Anomalous High Ionic Conductivity of Nanoporous β-Li3PS4. J. Am. Chem. Soc. 135, 975-978 (2013).
Investigation of Effect of Zinc Powder Modification for the Zinc-Bromine Flow Battery
Authors: Lee Je-Nam , Do Eunbyul , Kim Youngkwon
Published: February 2020

The increasing deployment of intermittent energy source such as solar and wind has raised the need of large storage device to improve grid reliability and power quality. Redox flow batteries (RFBs) are regarded as one of the most promising candidates, because of simple design, good scalability, good cycle efficiency, and reliable long lifespan. Among them, zinc-bromine flow battery (ZBB) is considered as one of the most promising candidates for large-scale energy storage due to the high solubility of Zn ion and low cost which is attributed to the abundance of zinc compounds. Combined with high cell voltage (1.84V), ZBB shows up to 440Wh/kg with a practical energy density of around 65-75 Wh/kg. However, widespread application of ZBB has been impeded due to its low power density, zinc dendrite, or hydrogen evolution. In this work, we investigate the effect of zinc powder-based anode modification on the electrochemical characteristics of zinc-bromine flow battery.
Understanding the Role of Lithium Ions and Electron Transport in a Multi-Electrode System Designed for Lithium-Oxygen Batteries
Authors: Tamakloe Wilson , Adjei Agyeman Daniel , Park Mihui , Kang Yong-Mook
Published: February 2020

The formation and decomposition of the discharge products (Li2O2) during the charging and discharging processes in Li-oxygen batteries are the main reactions that drive this technology, initiated at a solid-liquid-gas phase boundary involving Li+, O2 and e- in the cathode compartment. However the mechanistic contribution of each of these component to the electrochemical reactions in a given cell remains unknown.

In this study, we seek to understand the role of Li+ and e- at the phase boundary by developing a dual-cathode system containing a lithium conducting electrode(Li3N) and an electron conducting electrode(LiI) separated by nickel mesh. It was observed that, the LiI has the tendency to form reduced oxygens on the electrode surface via I-/I3
- redox couple, while Li-ions migrate to the electrode surface by the Li-ion conductive effect of the Li3N in the reactions leading to the discharge product formation. The discharge products on the Li3N electrode were found to be oxygen-rich, while those on the LiI electrode surface were found to be oxygen-deficient.

Electrochemical analyses revealed that the cells could discharge up to a capacity of 3.74mAh/cm2 at a current density of 0.1mA/cm2 with an over potential of 0.59V upon charging. At the same current density the cells were able to discharge-charge up to 184 cycles at a cut-off capacity of 0.2mAh/cm2.
Phosphorus-Based Two-Dimensional Anode Composites Enabling High Rate Capability and Long Life for Sodium Ion Batteries
Authors: Wang Ting , Zhang Kai , Park Mihui , Kang Yong-Mook
Published: February 2020

Over the past decade, sodium ion batteries (SIBs) as a highly promising candidate for alternative battery technologies beyond Li-ion batteries (LIBs), have raised much attention for grid-level applications considering the sustainability of SIBs. However, compared with the multitudinous choices of anode materials for LIBs, their sodium counterparts are relative rare, which makes the electrochemical reactions in SIBs more difficult. In this work, we have investigated GeP3 with two-step protection as an anode material for SIBs. Through involving conductive carbon and graphene nano-sheets , GeP3/C@rGO possesses high electrical conductivity (5.89*10−1 S·cm−1 ) and high specific area (167.85 m2
g−1). Severing as a novel anode for SIBs, GeP3/C@rGO delivers an unprecedented reversible capacity of 800 mAh g−1 with repeating 400 cycles at 0.2 A g−1. Furthermore, the two-step protection sample (i.e., GeP3/C@rGO) could maintain a high discharge capacity of 473 mAh g−1 even at a high current density of 5 A g−1, which is higher than those of both pure GeP3 and one-step protection samples (i.e., GeP3/C, GeP3@rGO). Ex-situ XRD and XPS tests demonstrate that GeP3/C@rGO exhibits the highest reaction activation and highest composition stabilization to resists the damages from huge volume change and electrolyte corrosion with co-contribution of both conductive carbon and graphene nano-sheets components. All these properties suggest GeP3/C@rGO could sever as a promising anode material for SIBs, and the strategy of two-step protection is meaningful for other alloying-type anodes in the next-generation energy storage applications.
Degradation Phenomena in Silicon-Carbon Composite Anodes from Industrial Battery Grade Silicon
Authors: Ulvestad Asbjørn , Foss Carl Erik Lie , Andersen Hanne Flåten , Vullum Per Erik , Voje Jorunn , Maehlen Jan Petter
Published: February 2020

Graphitic carbon is the anode of choice in lithium ion (Li-ion) batteries due to its low cost, availability and cyclability. However, silicon is emerging as a promising candidate to replace/complement conventionally used anodes with a potential to store ten times more lithium (3579 mAh/g) compared to graphitic carbons (372 mAh/g) [1]. But, as is often the case, great performance in one parameter comes with great costs in other parameters. The large lithiation capacity of silicon comes with extreme volume change during lithiation and delithiation, which severely impacts the materials cyclability. Typical mitigation methods for this involve using nanostructured silicon [2-3] , optimisation of binders [4] and adding appropriate SEI forming electrolyte additives [5].

Silicon as anode material has now grown to a mature field, and many degradation phenomena has been explored in detail, in particular on nanostructured silicon using powerful in-situ TEM studies [6]. For current Li-ion batteries, improvement of the anode capacity beyond approximately 1200 mAh/g has negligible impact on the overall capacity cell. Thus, composite anodes containing both silicon and a conventional anode material such as graphite, are sufficient for most batteries. While degradation mechanisms of pure nano-silicon structures have been studied in detail, similar phenomena specific to composite silicon-carbon electrodes have not. In our work we have performed post-mortem FIB-SEM and TEM studies to investigate degradation occurring over a large number of cycles, examining the effect and interplay between the graphite and the silicon in composite anodes. In this work, we have explored different degradation phenomena observed in silicon-carbon composite, including electrode thickening, silicon migration, electrochemical sintering, dendritic surface formation, inhomogeneous lithiation and dependence of electrode thickness on lithiation level. Electrochemical performance of silicon-carbon composite and graphitic carbons have also been studied for comparison.

The composite silicon-carbon and graphite anodes are based on industrial battery grade silicon and carbon produced at Elkem, a world leading company for environment-friendly production of silicon and carbon. The electrochemical performance was cycled in half cells where the working electrode was made by mixing a silicon-carbon composite /graphitic carbon powder with an organic binder in an aqueous slurry and coated on a dendritic Cu-foil. Structural properties and degradation mechanisms were examined by electron microscopy (SEM, FIB-SEM, TEM) and XRD. Support for this work was provided through the ENERGIX program of the Research Council of Norway.
Effect of Ti-Mesh Interlayer on the Negative Electrode for Zinc-Bromine Flow Batteries
Authors: Lee Je-Nam , Do Eunbyul , Kim Youngkwon
Published: February 2020

Redox flow batteries (RFBs) are regarded as one of the most attractive systems for large-scale electrochemical energy storage because of simple design, good scalability, and good cycle efficiency. Among various flow batteries, zinc-bromine flow battery (ZBB) has a lot of benefits due to the high solubility of Zn, which enables high practical energy density of around 65~75 Wh/kg. Additionally, low cost which comes from the abundance of zinc compounds has thrown light on the popularization of ZBB. Until now, however, widespread application of ZBB has not been realized due ot its drawback.

Zinc dendrite growth has negative effect on Zn/Br performance because of membrane damage, which allows self-discharge. Therefore, to get rid of dendrite formation after prolonged cycling, zinc dendrite strip cycling should run in the process of cycling.

In this work, we introduced Ti-mesh interlayer on the negative electrode to suppress the formation of zinc dendrite. We compared the effect of mesh interlayer using strip cycling during cycling.
Problem and Simple Solutions of Layered Cathode Materials
Authors: Zhang Sheng S.
Published: February 2020

Layered cathode materials, including Ni-rich and Li-rich lithium transition metal oxides, are one class of the most promising cathode materials for high energy density Li-ion batteries because of their high capacity and low cost. However, the Ni-rich and Li-rich cathode materials face two same problems of (1) oxygen evolution at high potentials, and (2) significant amount of Li residues in the forms of Li2O, LiOH, and Li2CO3 on the particle surface. Most of known concerns with these two types of cathode materials can be attributed to these two problems, such as irreversible phase transition from hexagonal to cubic phase, intergranular cracking with repeated cycling, transition metal ion dissolution, as well as electrolyte degradation that consequently results in impedance increase and volumetric swelling of the batteries. Since these two problems are the intrinsic properties of the layered lithium transition metal oxides, there are no perfect solutions that can completely solve these two problems. What one can do is to minimize the negative effects caused by these two problems. By selecting Ni-rich LiNi0.80Mn0.10Co0.10O2 (NMC811) as an example, in this presentation we demonstrate two simple strategies: (1) removing Li residues in the cathode slurry-coating step, and (2) in-situ eliminating the released active oxygen in the battery. Both strategies are simple without need of changing the existing procedures, and show different degree improvements on the cycling stability and rate capability of the Li/NMC811 cells. Our presented strategies are believed to be applicable to all other Ni-rich and Li-rich layered cathode materials.
Lithium Plating–a Life-Limiting and Safety Issue in a Li-Ion Cell
Authors: Ratnakumar Bugga V. , Smart Marshall C. , Jones John-Paul , Krause Frederick C.
Published: February 2020

Despite their advances and widespread use in various applications for the last two decades, Li-ion batteries continue to exhibit occasional failures from Li plating on the anode. Li plating can have immediate effects on performance and more devastating effects upon the safety, if the Li plating occurs in a dendritic form that could pierce through the separator causing an internal short. Even in a benign form, plated Li—lacking the protective SEI that protects the carbon anode —tends to react with electrolyte which results in a rapid growth in interfacial impedance and capacity loss during cycling. Li plating will manifest whenever intercalation kinetics (into carbon) are slower compared to lithium plating over carbon, despite the lower reversible potential of the latter. Poor cell design factors, i.e., improper matching of anode and cathode in terms of electrochemical capacities and geometric aspects with localized hotspots in current distribution, and inappropriate electrolyte, can cause Li plating on the anode. The nature of the anode, electrolyte and SEI are among the most important factors that can influence Li plating.1

Apart from the design/chemical abnormalities, lithium plating is also triggered by the operational conditions, such as fast charge rates and low operating temperatures relevant to planetary space missions. In our earlier study, we have demonstrated that the choice of the electrolyte is critical in determining the propensity towards lithium plating.2 Specifically, these studies indicate that the Li intercalation kinetics are mainly dictated by the anode surface films (SEI), which in turn could be controlled by a judicious selection of electrolyte solution, i.e., both solvent and salt. We have established a correlation between the poor lithium intercalation kinetics and the propensity towards lithium plating using different electrolytes with different solvent blends and different electrolyte additives.

Recently, Li plating was observed in cells upon extended cycling at ambient temperature in a Low Earth Orbit (LEO) satellite simulation condition, involving 30 minutes of discharge and 60 minutes of charge continuously, possibly due to impeded intercalation kinetics at the anode. Likewise, exposure to high intensity radiation environments may have led to Li plating in prototype 18650 cells upon subsequent cycling. In this paper, we will discuss the Li plating phenomenon in these specific examples, and with reference to anode/cathode interfacial kinetics at low temperatures in different electrolytes.

ACKNOWLEDGEMENT

The work described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration (NASA).

REFERENCES

B. V. Ratnakumar and M. C. Smart, ECS Trans. 25 (36), 241 (2010).

M. C. Smart and B. V. Ratnakumar, J. Electrochem. Soc.
2011, 158 (4), A379.
Effects of Separators on Lithium Metal Batteries
Authors: Xu Wu , Li Xing , Zhang Ji-Guang
Published: February 2020

The separator is an essential inactive component in liquid-electrolyte based batteries, with the function of separating the positive electrode from the negative electrode to avoid the electronic flow but enable the free ionic transport. The major commercial separators are thin, porous polymeric membranes with single layer or multilayers, and the polymer materials are typically polyolefins, polyesters, and so on. In recent years, separators with surface modifications have also been reported and produced for lithium (Li)-ion batteries, with the purposes of improving the mechanical strength, wettability, cell performance and safety tolerance under various abuse conditions. A lot of positive results have been achieved in Li-ion batteries. In recent years, with the demand for higher energy density than that from the state-of-the-art Li-ion batteries, the research and development of rechargeable Li metal batteries has been revived. However, the effects of the separators on the stability of Li metal anode and the performance of Li metal batteries have seldom reported. In this work, we have comprehensively studied the chemical and electrochemical stabilities of commercially available separators with Li metal anode in two kinds of liquid electrolytes, and found that the separators do have different stabilities with Li metal anode especially in conventional LiPF6-based electrolytes. The details of the investigations will be reported at the presentation.
Sulfone-Based Electrolytes for Next Generation Lithium Batteries
Authors: Schroeder Marshall A. , Alvarado Judith , Zhang Minghao , Olguin Marco , Ding Michael S , Borodin Oleg , Meng Ying Shirley , Xu Kang C.
Published: February 2020

An electrolyte system based on a sulfone solvent will be presented, outlining a newly discovered synergy between solvent and salt that simultaneously addresses the interfacial requirements of coupling a graphitic anode with a high voltage spinel cathode (LNMO). At the anode, a LiF-rich interphase generated by early-onset reduction of the salt anion effectively suppresses solvent co-intercalation and subsequent graphite exfoliation, enabling unprecedented and highly reversible graphite cycling in a pure sulfone system. Under aggressively oxidative conditions, QC calculations predict that high salt concentration promotes formation of complexes/aggregates which slow the decomposition of the solvent and leads to polymerizable rather than gaseous byproducts--a fundamental improvement over conventional electrolytes. These predictions are corroborated by an in-depth analysis of these functional interphases, as well as stable, long term operation of high voltage (4.85V) LNMO-graphite full cells.
Degradation Mechanism of Ni-Rich Layered Cathode Materials during High Voltage Cycling Revealed By Multi-Model Synchrotron X-Ray Imaging and Spectroscopy Techniques
Authors: Shadike Zulipiya , Bak Seong-Min , Hu Enyuan , Lin Ruoqian , Lee Hung-Sui , Yang Xiao-Qing
Published: February 2020

Ni-rich layered cathode materials are important candidates for lithium-ion batteries used for high energy density applications, such as electric vehicles. However, these materials are suffering severe capacity fade caused by surface reconstruction, unstable cathode-electrolyte interface (CEI) formation and micro crack formation during cycling, especially when a high cut off charge voltage is applied (such as 4.6 and 4.8V). To understand the origin of this capacity fade, state-of-the-art diagnostic tools are applied to understand their structure, chemical and morphological properties of LiNi0.94Co0.06O2 (NC) and LiNi0.92Co0.06Al0.02O2 (NCA) cathode materials during cycling. Electrochemical measurement results show that the NCA cathode delivered higher capacity and stable cyclic performance even cycled at a high cut of voltage of 4.8V. In situ X-ray absorption spectroscopy (XAS) results of NC and NCA electrodes measured during the first and 51st charge/discharge cycling between the voltage range of 2.8-4.4V showed that both Ni and Co contribute to the capacity by going through the Ni3+/Ni4+ and Co3+/Co4+ redox couples. The Ni-K edge XAS spectra of NC cathode charged to 4.8V showed slightly reduction of Ni4+ during the high voltage charging. While, XAS spectra of NCA cathode did not showed reduction of Ni4+ when the cell charged to the higher voltage. More interestingly, C, F, O, Ni and Co soft XAS spectroscopy of NC and NCA electrodes at the different state of charge provided more comprehensive insight into surface and bulk chemical properties. The results showed that much thicker CEI layer formed on the NC surface compared with the NCA cathode, indicated that Al-doping effectively reduced the side reaction of cathode materials with the electrolyte. We have also compared the morphological and chemical evolution of NC and NCA secondary particles using full-filed in-situ transmission X-ray microscopy (TXM) during the initial cycle. Results will be presented at the meeting.

Acknowledgement

This project was supported by the U.S. Department of Energy, the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies through Advanced Battery Material Research (BMR) program (Battery500 consortium) under Contract No. DESC0012704.
Effect of Binder on the Formation and Depth Distribution of SEI in Silicon Anodes
Authors: Parikh Pritesh , Sina Mahsa , Banerjee Abhik , Wang Xuefeng , D'Souza Macwin Savio , Zhou Qian , Snyder Kent , Meng Shirley
Published: February 2020

Silicon alloying anodes form an attractive technology in the ongoing evolution of Li-ion batteries. Their easy of availability, low cost, large theoretical specific capacities and low alloying potentials versus lithium (Li) would allow easy commercial adoption with ~10-15 wt% silicon already in use in the industry. To increase the available areal energy density, the mass loading of silicon needs to be increased. In this respect, the volume expansion in silicon (of ~ 300%) during cycling needs to be mitigated, to prevent mechanical failure and loss of electrical contact, both of which severely impede the capacity retention. While traditional techniques such as the use of intermetallics, conformal carbon coatings and tailoring the morphology, shape and size of the silicon anodes have attained reasonable success, polymeric organic binders and ionic liquid electrolyte have recently gained popularity. Polyacrylic acid-based binders (PAA) are ideal due to their high mechanical flexibility while ionic liquids form more stable SEI species compared to carbonate-based electrolytes. However, interactions between the binder and the ionic liquid salts as well as its influence on the SEI has not been considered, due to the traditional held view of the binder being a soft backbone matrix. Herein we report on the effect of PAA and CMC binder on the rate, composition and depth distribution of the SEI species in silicon anodes. We use STEM-EDX (scanning transmission electron microscope-energy dispersive x-ray spectroscopy), EELS (electron energy loss spectroscopy) amd XPS (X-ray photoelectron spectroscopy), to study and observe the distribution of LiF and sulphides/sulphates in the SEI. Based on our observations we propose a mechanism for better capacity retention in electrodes with PAA binder, due to formation of passivating sulphides close to the silicon surface which is a direct consequence of faster LiFSI decomposition to LiF in presence of PAA binder.
Stability and Functionality for PEDOT-Coated LiFeSO4F
Authors: Gustafsson Torbjörn , Blidberg Andreas , Björefors Fredrik , Alfredsson Maria , Tengstedt Carl , Valvo Mario
Published: February 2020

LiFeSO4F can be synthesised in two different polymorphs, tavorite- and triplite-type, depending on the synthesis conditions1. We have used a solvothermal route to synthesise the tavorite-type, which offers a decent energy storage capacity with an open crystal framework providing fast solid-state Li-ion transport2. It’s functionality is strongly affected by surface modification. It shows minimal polarization during electrochemical cycling when coated with p-doped PEDOT3. This coating alleviates a kinetic barrier for its lithium insertion/extraction reactions4. The redox activity of this material has been studied with S and Fe K-edge X-ray Absorption Near Edge Spectroscopy (XANES) together with Raman and 57Fe Mössbauer spectroscopies. The results indicated a stable p-doping of the PEDOT coating in the entire potential window for the electrochemical cycling. The iron-ligand electronic interaction increased during delithiation.

Fig. 1. Linear combination fit of S K-edge XANES spectrum for LiFeSO4F-PEDOT conditioned at 2.5 V vs. Li+/Li.

Ref: 1. N. Recham et al. Nat. Mater. 9 (2010) 68–74. 2. R. Tripathi et al. Chem.
Mater. 23 (2011) 2278–2284. 3. A. Sobkowiak, et al., Chem. Mater. 25 (2013) 3020–3029. A. Blidberg, et al. ChemElectroChem 4 (2017) 1896–1907.

Figure 1
New Insights in the Prolonged Cycle Life of Si Electrodes Prepared in Aqueous Buffered Media at Low pH
Authors: Jeschull Fabian , Trabesinger Sigita
Published: February 2020

Silicon as an anode material in lithium-ion batteries (LIB) has the 10-fold storage capacity of lithium ions than graphite and is thus an interesting candidate for next generation LIB.[1] However, due to the sever volume expansion during the alloying reaction of Si with Li, the physical inter-particle connections mediated by the electrode binder are broken. As a result the electrode disintegrates and its capacity fades rapidly.

The mechanical and interfacial properties can be enhanced when the Si electrodes are prepared in an aqueous solution of a citric acid buffer at pH=3, instead of neutral pH, such as water.[2] This behavior was previously ascribed to the acid-catalyzed formation of a silyl ester between binder and the native silicon oxide surface.[3] However, many questions still remain unanswered, e.g. what is the impact of the pH or how does the type of acid affect the surface functionalization? Additionally, recent results suggest that citric acid itself interacts strongly with the Si surface, thus forming an artificial SEI layer.[3]

In our study we are providing a deeper insight in the role of the carboxylic acids by examining a series of different carboxylic acids, namely glycolic acid (GlyAc), malic acid (MalAc) and citric acid (CitAc) (Figure 1). The carboxylic acids carry a different number of functional groups, which helps to interpret the rather complex FTIR spectra (Fig. 1a) of these silicon:acid:binder composites. The impact of the carboxylic acid on other cell components (e.g. electrolyte salt or current collectors) was investigated by on-line mass spectroscopy, electron microscopy and electrochemical techniques (e.g. Fig. 1b). Our aim is to evaluate how the capacity retention of acid-treated Si electrodes could be further improved by rational choice of the buffer chemistry and to identify the key control parameters in the functionalization process and during slurry preparation (e.g. pH and acid strength) in order to advance the slurry fabrication process and the performance of Si-containing electrodes.

References

[1] Obrovac, M. N.; Chevrier, V. L. Alloy Negative Electrodes for Li-Ion Batteries. Chem. Rev. 2014, 114 (23), 11444–11502.

[2] Mazouzi, D.; Lestriez, B.; Roué, L.; Guyomard, D.; Electrochem. Solid-State Lett. 2009, 12 (11), A215–A218.

[3] Chandrasiri, K.W., C. C. Nguyen, B. S. Parimalam, S. Jurng, B. L. Lucht, J. Electrochem. Soc.
2018, 165, A1991–A1996

Figure 1
Effect of Current Density and Deposition Time on Lithium Metal and Its Solid Electrolyte Interphases Via Cryogenic TEM
Authors: Wang Xuefeng , Lu Bingyu , Zhang Minghao , Li Yejing , Nguyen Han , Meng Ying Shirley
Published: February 2020

Li metal is an ideal, yet problematic anode for rechargeable batteries. Although it has been used for decades, little is known about its structure and solid electrolyte interphase (SEI), especially at the nanoscale. It is crucial to correlate the nanostructure change of the electrochemically deposited Li metal (EDLi) at different deposition conditions with the anode performance. By means of the powerful cryogenic transmission electron microscope (cryo-TEM), this work unravels the effect of the current density and deposition time on the nanostructure of the EDLi. It is shown that current density has a great influence on both the Li crystallinity and the SEI components. Methyl lithium (CH3Li) is identified as a new SEI component. The heterogeneous characteristics of the EDLi is highlighted in a single EDLi ribbon. Based on the cryo-TEM observations, the mosaic model for SEI structure is further modified. These findings increase the knowledge base of the growth behavior of EDLi, provide important new insights on the SEI properties and highlight the connection between the nanostructure, performance and strategies.
In-Depth Understanding of Battery Interfaces by Nanoscale Chemical Imaging
Authors: Zhou Jigang
Published: February 2020

Deeper understanding of the interface (chemical and electronic structure) between components within hybrid active electrode materials and the interface between active electrode materials and the electrolyte is crucial for developing better performance batteries. Element specific X-ray absorption near-edge structures (XANES) spectroscopy, explores detailed information on the local chemistry and electronic states of the absorbing atom which makes it an excellent tool for battery interface investigation to understand chemical bonding, electronic structure, and surface and bulk chemistry difference. XANES with nano-focused X-ray beam (STXM) and surface sensitive field-imaging X-PEEM can collect chemical imaging of high chemical sensitivity and spatial resolution. In this talk I will show nanoscale chemical imaging studies of battery materials by STXM and X-PEEM at CLS SM beamline. The emphasize is novel STXM with yield signal detection (XRF and TEY) and exploratory X-PEEM for surface imaging. Correlative chemical imaging of interface in a commercial like electrode without sample preparation was obtained by X-PEEM. This approach maintains the nature of the interface which is an interplay of local environment, morphology and facet orientation of electrode active materials. That information will lead new insights on battery material surface engineering in and/or out of battery cell toward a battery with high performance and long serve life.
Modeling Transport Properties in Concentrated Systems Considering Species Association
Authors: Li Guanchen , Monroe Charles W
Published: February 2020

Species association – including effects such as ion pairing and solvent complexation – can complicate electrochemical transport dynamics. As a liquid electrolyte becomes more concentrated, driving forces for association become stronger and may profoundly impact system performance. Ion pairing has been proposed to explain the extended diffuse double layers observed at ionic-liquid/electrode interfaces [1]. Researchers also have justified the low or negative cation transference numbers observed for many lithium electrolytes by suggesting that ions associate [2]. These discussions motivated our systematic study of species association effects in concentrated electrolytes.

The Nernst–Planck theory has been used to study reactive multi-species liquid electrolytes [3], but it ignores solute/solute interactions, limiting applicability to dilute solutions [4]. In concentrated solutions, such interactions can alter transport dynamics substantially, even when species concentrations are relatively low. Monroe has illustrated that interactions between lithium salts and dissolved oxygen can manifest diffusion potentials that change open-circuit voltages of metal-air batteries considerably [5]. Accordingly, even the minor species produced by weak association should not be ignored in concentrated electrolytes. A multi-species concentrated-solution model considering species association will provide a more general and comprehensive interpretation of experimental transport-property data.

Monroe and Delacourt derived flux-explicit transport laws from Onsager–Stefan–Maxwell equations, and emphasized the need for thermodynamic rigor in multi-species transport characterization [6]. The present research advances their framework further, by accounting for species association. In systems were species associate, the Onsager–Stefan–Maxwell transport equations are further constrained by local association equilibria and kinetics. Thus some transport properties may be intrinsically correlated. We will present reformed flux-explicit transport equations and clarify how locally equilibrated association affects apparent transport dynamics.

Three systems, namely, doped ion-conductive ceramics, ionic liquids, and binary solutions, will be analyzed: we will investigate carrier/carrier interaction in doped solid electrolytes, and illustrate how defects or doped elements induce diffusion polarization; we will model the ionic-liquid double layer in cases where ions can combine to form a neutral pair; and we will discuss how the association of solutes affects transference-number measurements in liquid binary solutions.

[1] M.A. Gebbie, et al., PNAS. 110, 9674-9679 (2013)

[2] G. Richardson, et al., J. Electrochem. Soc., 165(9), H561-H567 (2018)

[3] S. Clark, et al., ChemSusChem,10, 4735 – 4747 (2017)

[4] A.M. Bizeray, et al., J. Electrochem. Soc., 163(8), E223-E229

[5] C. W. Monroe, J. Electrochem. Soc., 164(11), E3547-E3551 (2017)

[6] C. W. Monroe and C. Delacourt, Electrochimica Acta, 114, 649–657 (2013)
Tuning the Electrochemistry of Magnesium Electrode
Authors: Yuwono Jodie A
Published: February 2020

Magnesium (Mg) metal is a promising electrode material for batteries application considering its high volumetric capacity, low cost, safety and environmentally benignity. This translates into the fact that Mg-based batteries can be manufactured in small dimensions (without decreasing the capacity) with a lower cost over the current state-of-art lithium (Li-) based batteries. In the recent years, this is evidenced from a growing number of prototype, showing the capability of Mg-based battery in producing a large current density with a high reversible capacity. However, the reliability of Mg electrode is critical as Mg metal undergoes a rapid Mg dissolution reaction, causing a short lifetime of the electrode and battery. The details of Mg electrochemistry is very complex and unique compared to other alkali and alkali earth metals. For instance, during anodic polarisation Mg has a capability to support hydrogen evolution reaction at a high rate. An understanding of reaction mechanisms at the interface can provide significant information on obtaining a desirable electrochemical performance for Mg electrode, which is beneficial for the development of stable and consistent performance of Mg-based batteries.

In this study, we recently investigated the electrode/ electrolyte interactions of Mg-based electrodes in aqueous electrolytes using a first-principles approach combined with the electrochemical characterisations. The classical description of the Mg electrochemical reaction is complicated by the formation of passive layer, dissolution of Mg and evolution of hydrogen gas. These reactions occur simultaneously and are often associated with the decreasing Coulombic efficiency and parasitic discharge that could lead to the premature battery failure. By recognising the importance of each individual reaction at the interface, we can selectively control the reactions; thus, providing a practical approach to engineer the electrochemical performance of Mg electrode and battery. With this knowledge, it is expected that a viable approach to optimise the use of Mg electrode can be achieved in both primary and secondary batteries, regardless of the electrolyte.

Figure 1
Design and Development of 21700 Type Cells for Electric Vehicle Applications
Authors: Yang Gang , Huang Chien-po , Huang Bryant , Mao Chengyu , Liu Ying
Published: February 2020

The world’s transition to sustainable energy has been largely accelerated from the transportation field. Thanks to the increasingly wide deployment of charging station and government incentives, electric vehicles are seeing a fast growth in sales over years. Most of them are completely or partially powered by Li-ion batteries, which store and distribute the energy whenever is the needed for the operation of the vehicle. The battery pack consists of tens, hundreds, or thousands of individual cells, depending on the size (kWh) of the pack and cell as well as the form factor of the cell.

As an EV start up, SF Motors is trying to produce the intelligent EV for everyone. One prominent feature of EV is their fast acceleration. A high power is delivered during fast acceleration, which requires the cell to be discharged at extreme high rates. Simultaneously, extensive heat is generated during fast acceleration, causing cell temperature increase and stimulating safety concerns. Here, we’re developing 21700-type cylindrical cells which can deliver extreme high power safely in a short time without compromising its high energy density. Each factor affecting cell rate capabilities like electrode materials, areal loadings, electrode architecture and electrolytes are individually investigated by various electrochemical techniques such as symmetric cells and three-electrode cells. By integrating state-of-art electrode materials, advanced cell design and processing, we’re able to build cells with high energy density, high power, and long cycling life while keeping a high standard for safety. The successful implementation of this extreme high power cell will enable advanced electric vehicles with long drive range (> 300 miles) and top performance driving experiences.
Engineering Transport Pathways and Interfaces in Hybrid Solid Electrolytes at Roll-to-Roll Manufacturing Scales
Authors: Hatzell Kelsey , Dixit Marm
Published: February 2020

Recently, there has been a push toward all solid-state batteries to eliminate flammability issues in portable electronics. Several solid conductors exist and broadly fall into two material categories: (1) polymers and (2) ceramics. Polymer ionic conductors are advantageous because they can be manufactured easily into thin films, are mechanically robust, and flexible. However, polymer conductors have lower ionic conductivities when compared with their ceramic counterpart. Ceramic conductors boast outstanding ionic conductivities (>10 mS/cm) but processing the electrolyte into thin films (50-100 micrometer) for efficient device integration still remains a challenge because of the brittle nature of the ceramic. There have been a few studies which have investigated a hybrid approach which combines the polymer and ceramic into a composite electrolyte to achieve both processing and performance requirements. A grand challenge with solid state batteries, independent of ion conductor composition, is transport at interfaces. There are both intrinsic interfaces formed within a material by grain, vacancies, and material junctions (composite). Furthermore, there are extrinsic interfaces formed when integrated with an electrode. There is a significant need to understand how we can tailor these interfaces during processing using state of the art manufacturing techniques.

Slot die coaters are extensively used in roll-to-roll processing industrially[2]. However, some challenges remain that deter realization of the full potential of this technique for scalable manufacturing of functional materials. Some of these challenges are multi-material coating ability, active control and feedback, coating intermittently and enhancing resolution among others[3]. Herein, we study a system of colloidal inks with a custom-made benchtop slot-die system. Initial results have shown that the nano-scale interactions in the ink phase impact the macroscopic ink properties and the coating structure [4,5]. This work focuses on demonstrating functional gradation capabilities in slot-die coating system through a novel multi-layer design and understanding how pathways can be engineered for efficient transport.

[1] Hatzell, Kelsey B., et al. "Understanding inks for porous-electrode formation." Journal of Materials Chemistry A 5.39 (2017): 20527-20533. [2] Department of Energy. Roll to Roll Processing Technology Assessment. Technical report, 2015. [3] Corie L Cobb and Christine C Ho. Additive Manufacturing: Rethinking Battery Design. Interface, 3–6, 2016 [4] Dixit, Marm B., et al. "Catalyst Layer Ink Interactions That Affect Coatability." Journal of The Electrochemical Society165.5 (2018): F264-F271. [5] Dixit, Marm, and Kelsey B. Hatzell. "Understanding Binary Interactions and Aging Effects in Catalyst Layer Inks for Controlled Manufacturing." ECS Transactions 80.8 (2017): 301-307.
Two-Dimensional SnS2 Nanosheets on Prussian Blue Template for High Performance Sodium Ion Batteries
Authors: Sim Glenn Joey
Published: February 2020

SnS2/PB anode material was synthesized via two steps. First, three-dimensional Prussian Blue (PB) nanostructures were derived from a simple hydrothermal synthesis. After etching with hydrochloric acid (HCl), the PB nanocubes were used as a template for the next step. Two-dimensional SnS2 nanosheets were grown on the PB nanocubes through a facile hydrothermal synthesis, giving rise SnS2/PB hybrid nanoarchitecture. The as prepared SnS2/PB is further employed as the anode of sodium ion batteries (SIBs). The SnS2/PB nanoarchitecture exhibits high capacity, long cycle life and exceptional rate capabilities as an anode of SIBs. In specific, it delivers a capacity of 725.7 mA h g-1 at 50 mA g-1. When cycled through 200 cycles, it achieved a stable cycling capacity of 400 mAh g-1 at 200mA g-1 This enhanced SIB performance further proves that SnS2 has the capabilities and potential as an anode material for SIBs. The stable Na+ storage properties of SnS2/PB was attributed to the synergistic effect among the conductive PB carbon, used as the template in this work. These results obtained potentially paves the way for the development of excellent electrochemical performance with stable performance of SIBs.

Keywords: Prussian Blue, Carbon Nanocubes, Tin disulfide, Sodium ion batteries

Figure 1
Iron Sulfide Embedded Nanostructured Carbon Materials for High-Performance Lithium and Sodium-Ion Batteries
Authors: Ahn Jou-Hyeon , Haridas Anupriya K. , Heo Jungwon
Published: February 2020

The development of high energy density lithium and sodium ion batteries (LIBs) with stable cycle performance is of significant importance, recently, due to the emerging energy demands like energy storage systems and electric vehicles. The low theoretical capacities offered by commercialized intercalation based cathode materials (such as LiFePO4 and LiCoO2) limit the high energy density applications of the present era, substantially. However, the transition metal based conversion materials (MX, X=oxides, fluorides and sulfides, M= Fe, Co, Mn, Cu, Ni) can store more than one Li or Na ion per transition metal leading to high theoretical capacities with moderate operating potentials. Iron sulfide (FeS) is an inexpensive and environmentally benign material, with a high theoretical capacity of 609 mAh/g. Nevertheless, the FeS based electrodes suffer from limited cycle life because of the large volume changes (up to 200 %) encountered upon cycling, which eventually destroys the electrode structure. The generation of polysulfide intermediates during the cycling process further accelerates the capacity decay. The present work investigates in detail, the lithium or sodium ion storage in iron sulfide embedded nanostructured carbon materials synthesized. The presence of nano-sized FeS particles in the composites improves the sluggish reaction kinetics whereas the one-dimensional morphology of the conductive carbon matrix encapsulating them shortens the lithium or sodium-ion diffusion pathway and promotes rapid electron transfer. The carbon matrix encapsulating the FeS nanoparticles can effectively accommodate the volume changes and associated strains encountered during the cycling process. The electrochemical performances of the synthesized FeS nanoparticle loaded nanostructured carbon composite confirm the superior reversibility of the electrode with superior cycling stability and specific capacity.