bluuebunny/crossref_metadata_2025 huggingface dataset:
Revealing the Thermodynamics of Magnesium and Lithium Ion Insertion Chemistry in Ultrafast Discharging Hybrid Rechargeable Batteries
Authors: Aykol Muratahan , Kim Soo , Cho Jae-Hyun , Ha Jung-Hoon , Chung Kyung Yoon , Kim Kwang-Bum , Cho Byung-Won , Wolverton Chris
Published: February 2020

We present a combined experimental and theoretical strategy to design dual-salt Mg2+/Li+ batteries with very high electrochemical performance.[1] In this work, we first investigate the (co)-insertion mechanisms of Mg2+ and Li+ ions into the Mo6S8 cathode by using density functional theory (DFT) calculations together with the Nernst relation. We show that there exists a threshold for the Li+ activity in the electrolyte above which lithiation is preferred instead of magnesiation. Based on the DFT results, to achieve high electrochemical performance, we suggest an approach to control the insertion chemistry by varying the Li salt content of the electrolyte. Using this approach, we have carefully revealed the ion insertion chemistry for the Mg-metal anode/Mo6S8cathode hybrid Mg/Li batteries with all-phenyl complex (APC) and LiCl electrolytes.

Our experimental results confirm that at low Li+ activities in the electrolyte, Mg2+ insertion dominates and the battery can cycle only below 80 mAh g-1, whereas at high Li+ activities, fast Li+ ionic transport in the entire intercalation range leads to higher voltage, capacity and rate capability. We find that the Mg/Li hybrid rechargeable battery with an APC 0.2 M and LiCl 0.5 M dual-salt electrolyte has a remarkable electrochemical performance. This hybrid battery with optimized insertion chemistry achieves 93.6% capacity retention at 20 C and 87.5% at 30 C at room temperature. Our combined computational and experimental study suggests an effective route to develop new dual-salt hybrid systems with controlled insertion chemistry.

Acknowledgement

This work has been supported by The Dow Chemical Company and Northwestern-Argonne Institute of Science and Engineering (NAISE).

References

[1] J.-H. Cho, M. Aykol, S. Kim, J.-H. Ha, C. Wolverton, K. Y. Chung, K.-B. Kim, and B. -W. Cho, J. Am. Chem. Soc.
2014, 136, 16116.
Does Pseudocapactive Charge Storage Take Place in Nanoparticulate TiO2 and Li4Ti5O12 Anodes?
Authors: Opitz Martin , Yue Junpei , Wallauer Jens , Smarsly Bernd , Roling Bernhard
Published: February 2020

Titanium oxide-based materials, such as TiO2 and Li4Ti5O12 (LTO), are considered as interesting alternative anode materials for lithium ion batteries. In order to increase the interfacial area between TiO2 particles and the battery electrolyte and in order to reduce the diffusion length for Li+ ions within the particles, both materials have been extensively studied. [1], [2] Thereby, indication has been found that the charge storage is not entirely due diffusion-controlled Faradaic charge storage, but also due to pseudocapacitive charge storage. [3], [4]

We studied nanoparticlate LTO electrodes and compared this to Li storage in Nb-doped TiO2 particles. Using scan rate-dependent cyclic voltammetry, we determined the amount of Faradaic and of pseudocapactive charge with the same method that was reported in the literature [1], [4]. Thereby, we discovered that the application of this method leads to unphysical results, which is originated in the iso-potential plots of the scan-rate dependent current density. We show that even for simple prototype Faradaic reactions, such iso-potential plots yield an apparent pseudocapacitance.

References

[1]   J. Wang, J. Polleux, J. Lim, B. Dunn, J. Phys. Chem. C 111 (2007) 14925–14931.

[2]   D. Wang, X. Wu, Y. Zhang, J. Wang, P. Yan, C. Zhang, D. He, Ceramics International 40 (2014) 3799–3804.

[3]   T. Brezesinski, J. Wang, J. Polleux, B. Dunn, S.H. Tolbert, Journal of the American Chemical Society 131 (2009) 1802–1809.

[4]   P. Yu, C. Li, X. Guo, J. Phys. Chem. C 118 (2014) 10616–10624.
Direct Synthesis of Non-Stoichometric Nanocrystalline Metal Oxides and Their Composites: Improving the Reversibility and Current Capability of Lithium-Ion Batteries
Authors: Takeuchi Kenneth J , Marschilok Amy C , Takeuchi Esther S
Published: February 2020

As the demand for large scale batteries grows, considerations such as earth abundance, cost, and toxicity gain increased significance.  Metal oxides are worthy of evaluation as active materials for electrochemical energy storage, particularly those utilizing earth abundant, low cost, environmentally benign metal centers.  However, to facilitate broader implementation of metal oxides in batteries, improvements to current capability and reversibility are needed. 

Some metal oxides adopt close-packed coordination environments, which optimize ion density.  However, ion and electron transfer are challenges which may or may not be exacerbated as a result of high ion density.  An emerging paradigm for the implementation of close-packed materials in higher current applications is the tuning of the materials crystallite dimensions, where the reduction of crystallite size should minimize the path length for ion transport upon discharge, resulting in a reduction of both internal cell resistance and the resultant structural strain associated with lithium insertion.  Significant improvements in current capability of metal oxides and their composites via direct crystallite size control and other strategies will be described.

The synthetic approaches described in this presentation will provide new strategies which may be applicable toward development of other new classes of materials and composites with energy or energy storage applications.
An Investigation of the Impact of Protic Impurities, Different Housing Materials and Silicon on the Thermal Aging of Electrolytes Used in Lithium-Ion Batteries
Authors: Handel Patricia , Fauler Gisela , Kapper Katja , Schmuck Martin , Stangl Christoph , Fischer Roland , Uhlig Frank , Koller Stefan
Published: February 2020

Concerning prospective energy storage, lithium-ion batteries (LIBs) are one of the most outstanding technologies due to their high energy density as well as great cycle stability. To increase their operational lifetime, thermal degradation of the most common conductive salt lithium hexafluorophosphate LiPF6 (1) should be avoided. Therefore, it’s crucial to minimize traces of protic impurities resulting from e.g. organic carbonates. In fact, the products of the endothermic equilibrium of LiPF6 are preferably formed at higher temperatures, leading to the formation of hydrofluoric acid (HF) and subsequently to further degradation of electrolyte components. (2) 

LiPF6 (s)  LiF (s) + PF5(g)                          [1]

PF5 (g) + H2O (l) → O=PF3(g) + 2 HF (l)           [2]

Lux et al. (3) followed the HF formation in LiPF6 containing electrolytes by spectroscopic ellipsometry of SiO2 layers. As we reported recently (4), SiO2 probably promotes the degradation of LiPF6 in organic carbonate based electrolytes.

Herein, we report about the decomposition of 1M LiPF6 in a binary mixture of ethylene carbonate and diethylene carbonate in a ratio of 40:60 (w/w) at ambient and elevated temperature (cf. table 1). Degradation products are studied by nuclear magnetic resonance spectroscopy (NMR, cf. figure 1), gas chromatography mass spectrometry (GC-MS) and headspace GC-MS (HS-GC-MS). Acid-base and coulometric titration are used to determine the total amount of acid and water content upon aging, respectively. Ultraviolet-visible (UV-Vis) spectroscopy is used to follow the color change of the electrolyte (cf. figure 2). The influence of protic contamination, different housing materials and added active materials on the electrolyte aging is shown.

Acknowledgement

VOLKSWAGEN VARTA Microbattery Forschungsgesellschaft and Herbert Quandt Foundation are gratefully acknowledged for funding.

References

1. K. Xu, Chem. Rev., 104, 10 (2004).

2. C. L. Campion, W. Li, B. L. Lucht, J. Electrochem. Soc., 152, A2327 (2005).

3. S. F. Lux, I.T. Lucas, E. Pollak, S. Passerini, M. Winter, R. Kostecki, Electrochem. Commun., 14, 47  (2012)

4. P. Handel, G. Fauler, K. Kapper, M. Schmuck, C. Stangl, F. Fischer, F. Uhlig, S. Koller, J. Power Sources, 267, 255 (2014).

Figure 1
Designing New Conductive Imidazole-Derived Salt for Lithium-Ion Battery Electrolytes: A Computational Approach
Authors: Leggesse Ermias Girma , Jiang Jyh-Chiang
Published: February 2020

Ever since the commercialization of the rechargeable Li-ion cell, LiPF6 is by far the most widely used electrolyte salt. It can produce electrolyte solutions with a superior ion conductivity, good electrochemical oxidation stability, and adequate thermal stability when dissolved in binary or ternary solvent systems of cyclic carbonates. However, LiPF6is also reported to have series problems that may lead to performance and safety issues (1). In order to circumvent these issues, researches have focused on designing new lithium salts which have thermal and electrochemical stability, high ionic conductivity and easy synthesis route (2-6).

In this work, we report designing of an alternative salt derived from bis(trifluoroborane)imidazolide (LiIm(BF3)2) by employing density functional theory (DFT) calculations. New anion structures were generated by considering substitution at the C5 position with electron withdrawing groups (-F, -CF3, -SO3H and -NO2) and electron donating groups (-NH2, -OCH3 and –CH3). By using the optimized anion structures, random lithium ion-pair configurations (around 130 structures for each) were generated and optimized to identify the most stable configurations.  The effects of different substituents were investigated with respect to ion dissociation energies, anion oxidative stability, and aromaticity of the molecules. Based on our calculations, we have found that, ion dissociation energies and intrinsic oxidative potentials of the anions were largely affected by the type of substituents introduced on the parent structure. Compared to –PF6 and -Im(BF3)2 (standard anions), –CF3 and  -NO2 substituted anions showed an increase in anion oxidation stability. Since, BF3 occupies the strong Lewis basic sites of the imidazole ring, the parent structure itself exhibit a charge delocalization over the aromatic ring, which results in a weak coordinating ability with Li+. With the exception of –F, -CF3 and –CH3, further introduction of substituents at C5 position led to a much lower cation–anion interaction. Among the possible anions studied, 5-nitro-bis(trifluoroborane)imidazolide, with oxidation potentials > 5.7 V vs. Li+/Li , can be considered as a good candidates for high voltage Li-ion battery applications. Moreover, we have also found that the ion-pair dissociation energy, and anion stability of the selected salt are much improved compared to experimentally reported LiIm(BF3)2 and LiPF6.

References

1. K. Xu, Chem. Rev., 104, 4303 (2004).

2. J. Scheers, E. Jonsson, P. Jacobsson and P. Johansson, Electrochemistry, 80, 18 (2012).

3. K. Angenendt and P. Johansson, J Phys Chem B, 115, 7808 (2011).

4. P. Johansson and P. Jacobsson, J Power Sources, 153, 336 (2006).

5. E. Jonsson and P. Johansson, Phys Chem Chem Phys, 14, 10774 (2012).

6. J. Scheers, L. Niedzicki, G. Z. Zukowska, P. Johansson, W. Wieczorek and P. Jacobsson, Phys Chem Chem Phys, 13, 11136 (2011).

Figure 1
A Roadmap to Design Robust Redox Shuttles for Lithium-Ion Batteries
Authors: Odom Susan A , Risko Chad , Casselman Matthew D , Elliott Corrine F , Ergun Selin , Kaur Aman Preet
Published: February 2020

In designing robust, effective redox shuttles for overcharge protection in lithium-ion batteries, a variety of factors are necessary to consider and evaluate. The stability and reactivity of the radical cation form of a redox shuttle candidate are critical to extensive overcharge performance. Radical cations are subject to a variety of reactions because of their unpaired electron and positive charge, making them subject to nucleophilic attack and dimerization, among other reactions including disproportionation or premature reduction. Equally as important is the stability of the neutral form of the redox shuttle, which may decompose through reaction with electrolyte, SEI, and/or be reduced at the anode/electrolyte interface. Neither stability nor reactivity is easy to predict, although an understanding of organic chemistry can lead to some general guidelines for the design of less reactive species. Density functional theory (DFT) calculations can be used to predict energies of reaction and have been employed by Curtiss, Dahn, and our group. DFT calculations can also be used to compute oxidation and reduction potentials, helping to identify promising candidates before synthesizing materials. This presentation focuses on our work using DFT calculations to help us identify promising redox shuttles and to gain a better understanding of their reactivity and includes experimental data in support of some of the proposed mechanisms of decomposition.
A Silicon-Graphene Electrode with Multilayered Structure for High Performance Lithium-Ion Batteries
Authors: Gao Xianfeng , Li Jiangyang , Xie Yuanyuan , Yuan Chirs
Published: February 2020

A silicon-graphene electrode composed of porous Si and reduced graphene oxide with multilayered structure was synthesized from bulk Si particles through inexpensive electroless etching and graphene self-encapsulating approach. The prepared composite electrode presents superior electrochemical performance with a discharge capacity of 1026 mAh/g tested at 1A/g and good retention rate. The columbic efficiencies are about 99% during the whole cycling process. The electrode was extensively characterized and it is found that the superior performance attributes to the novel multilayered structure with porous Si particles encapsulated, which effectively accommodate the large volume change during the lithiation/delithiation process and provide increased electrical conductivity. This facile approach offers an alternative route to construct promising low cost Si electrode for future industrial applications.
A Novel Surface Modified Nano-Silicon As Promising Anode Material Lithium-Ion Batteries
Authors: Han Joong-Hee , Hayati-Roodbari Nastaran , Elsaesser Michael S , Schodl Juergen , Gavrilovic Wohlmuther Aleksandra , Hans Philipp , Hradil Klaudia
Published: February 2020

Silicon has been considered as one of the most promising anode materials for LIBs in order to replace the conventional anode material (graphite). Investigations of the Li-Si binary system indicated at least theoretically, the highest specific capacity (4200 mAh/g), during the electrochemical lithium alloying (Li4.4Si) of silicon with lithium ions. Unfortunately, Si shows a very low mechanical elasticity during the battery cycling (lithiation/delithiation), which causes a contact loss in the electrode and subsequently lead to a shorter cycle life and finally fast capacity fading. This is the major drawback of Si as an anode material and the reason why a general distribution within the lithium ion battery market couldn´t be established up to now.

The first idea proposed to overcome this shortcoming, is a new approach concerning the binder materials. In the research of energy storage materials, a new technology named biomimetics has been adapted to breakthrough the serious technical problem. The use of bioinspired binders for the silicon anode materials represents one basic approach of our present study. Namely, potato starch, gelatine and alginic acid from brown algae were studied as a binder. It was found that the potato starch was the best binder, exhibiting 1500 mAh/g at the 20thcycle. This is due to the fact that amylopectin polysaccharides suppress the volume change of silicon and form a beneficial SEI film on the electrode during cycling.

The second idea proposed in this work is based on the formation of a nanoscale, 3D-connected mesoporous silicon by a magnesiothermic reduction process, providing short diffusion pathways for the lithium ions during lithiation / delithiation. The silicon-based cells were characterized by electrochemical investigations and the first results show that the mesoporous silicon-based cell exhibits a discharge capacity of 1200 mAh/g and a coulombic efficiency of 84% after the cycling precondition with 0.05C. The improvement of the electrical conductivity and the modification of the surface´s electrochemical properties is achieved by an adaption of a coating method, known as substrate-induced coagulation. The coating materials are distinguished between lithium reactive and nonreactive. Further, they can be subdivided, i.e. carbonaceous materials (nano-graphite, graphene), nano metals (Cu, Ni) and nano metal oxides [TiO2, In(OH)3, ITO(indium tin oxide)].
Significant Capacity Improvement and Long Cycle-Life of Lithium-Ion Battery through Thin Film Stabilized Cathode Particles
Authors: Patel Rajankumar L. , Liang Xinhua
Published: February 2020

Lithium-ion batteries (LIBs) have been implemented as a high energy and high power density source in numerous electronic devices, electrical vehicles, and space-crafts. A great deal of research has been carried out to improve the lifetime and capacity of LIBs. Thin film coatings on LIB electrode powders have proven to be an effective way to improve the capacity retention, rate capability, and thermal stability of electrode materials. Atomic layer deposition (ALD), as a thin film deposition technique, has been explored as a viable path to improve the performance of LIBs. However, a trade-off between the species transport (capacity) and protection (lifetime), resulting from the insulating properties of ALD films, is the key challenge in ALD technology. Here, we report a new strategy to overcome this trade-off by coating an ultra-thin conformal conductive ALD film on the surfaces of LiMn2O4 particles. The optimized conductive film coated particles exhibit a significant improvement in capacity and cycling performance compared to uncoated samples at room temperature and 55 °C for long cycling numbers. The initial capacity of the conductive film coated sample shows 24% increment compared to the capacity of the uncoated one, and 96% and 95% of the initial capacity is retained after 1,000 cycles with 1 C rate at room temperature and 55 °C, respectively.
Investigation of LiMn2O4-Li2NiF4 Solid Solutions As Electrode Materials for Lithium-Ion Batteries
Authors: Yi Tanghong , Kim Chunjoong , Plews Michael Rhys , Cabana Jordi
Published: February 2020

Lithium ion batteries play a very important role in consumer electronics as the component where energy stored. However, today’s lithium ion batteries are not suitable for widespread application in electric vehicles due to the high cost required to achieve desired levels of energy density and life.1 Improvements in energy density (cell voltage and/or storage capacity) are still sought for these applications. Given the high capacity of graphite-based negative electrodes, the focus is placed on increasing performance at the positive electrode. Today, the most popular positive electrode materials are layered LiMO2 (M = Co, Mn, Ni), spinel LiM
2O4 (M = Mn, Ni), and olivine LiMPO4 (M = Fe, Co, Mn).2, 3 LiM
2O4 and its derivatives are widely used in current electric vehicles mainly because of their robust framework with fast ionic diffusion and low cost. In this work, we explore the possibility of raising their voltage of operation by incorporating Li2NiF4 into the LiMn2O4 lattice to form a solid solution of LiMn2O4-Li2NiF4 by taking the advantage of their structural similarity. The reaction between the two components is complex. Apart from single phase samples, core-shell structures could also be obtained by varying the ratio of two components as well as reaction duration. An example of this competition is provided by LiMn2O4-20% Li2NiF4, as shown by the different elemental distributions from energy dispersive spectroscopy (EDS) elemental maps in Figure 1, indicating solid solution and core-shell structures, respectively. The local chemical environment change of oxygen, fluorine and transition metals has been investigated by X-ray absorption spectroscopy. The electrochemical performance of the phase-pure LiMn2O4-Li2NiF4solid solutions will also be presented. 

 ADDIN EN.REFLIST 1.            R. V. Noorden, Nature,
50726-28 (2014).

2.            J. M. Tarascon and M. Armand, Nature,
414359-367 (2001).

3.            B. L. Ellis, K. T. Lee, and L. F. Nazar, Chem. Mater.,
22691-714 (2010).

Figure 1
Improved Electrochemical Performances and Thermal Stability of LiNi0.6Co0.2Mn0.2 by Li3PO4 coating
Authors: Lee Suk Woo , Kim Myeongseong , Kim Kwang-Bum
Published: February 2020

LiCoO2 is the most commercialized in lithium ion batteries (LIBs) for portable electronics because of its high volumetric energy density compared to the other commercialized cathode materials. However, low specific capacity (145 mAh/g @ 4.3 V cut-off) hinders its application to emerging technologies, such as power tool and plug-in hybrid electric vehicles. As a result, layered Ni-rich LiNixCoyMn1
-
x
-
yO2 materials have attracted much attention as promising alternative cathode materials because of their high capacity and relatively low cost. However, Ni-rich layered cathode materials suffer from structural instability by direct contact with electrolyte at high voltage (>4.3V), resulting in poor cyclability, rate capability and thermal instability. To solve these problems, a lot of researches have been carried out to coat the surface of layered cathode materials using oxide or phosphate, such as TiO2, Al2O3, and Li3PO4.

Among these coating materials, Li3PO4 has attracted a great attention as coating material due to its high ionic conductivity and thermal stability due to strong P=O bonding. Recently, Zhao et al., reported on the Li3PO4 coating on LiFePO4 cathode material, but they used Li3PO4 nano particle as a coating material, resulting in non-uniform coating. Also, Xiong et el, tried to coat the Li3PO4 on LiNi0.8Co0.1Mn0.1O2 cathode material using the reaction between (NH4)2HPO4 and lithium residues, but the Li3PO4 coating layer is not confirmed.

In this study, we report on the synthesis of Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 using a citric acid assisted sol-gel method in which nm-thick Li3PO4 layer was uniformly coated on the LiNi0.6Co0.2Mn0.2O2. It exhibited improved cyclability at high voltage (4.7V) and rate capability than those of bare LiNi0.6Co0.2Mn0.2O2. In addition, Li3PO4-coated LiNi0.6Co0.2Mn0.2O2 showed improved thermal stability at elevated temperature.

More details on the synthetic procedure, electrochemical and physical properties will be presented at the meeting.
Effects of Fast Charging on Lithium-Ion Cells
Authors: Somerville Limhi , Jennings Paul , McGordon Andrew , Lyness Christopher , Prezas Panagiotis , Basco John , Bareno Javier , Duong Tien , Bloom Ira
Published: February 2020

As electrified vehicles become widely accepted, consumers expect the characteristics to be similar to those with a conventional, internal-combustion engine. Among these is the ability to ‘refuel’ quickly. For example, current lithium-ion battery technology takes an hour or more to recharge (refuel) whereas a conventional car can take 5 minutes or less. Some work has been does to understand the electrical effect fast charging lithium-ion cells has. However, no one understands what faster charging does to internal cell components.

We cycled commercially-available 18650 cells at four different charge C-rates (0.7, 2, 4, 6) and two different charge-returned windows (40% and 100%); the discharge rate was C/3. The cells were opened and both electrodes as well as separator were analysed in an argon-environment glove box using a range of surface-sensitive, analytical techniques.

The binder material at the negative electrode decomposed at higher C-rates causing delamination from the copper current collector. Surprisingly, cells cycled within a smaller charge-returned window completely delaminated irrespective of C-rate, suggesting there are at least two different mechanisms responsible for electrode delamination in the cells.

Analysis of surface film chemistry and thickness showed a dependence on C-rate. Cells cycled at higher C-rates had a thicker surface film and a more complex chemistry. Gel permeation - liquid chromatography showed that the surface film of the cells was extremely complex, with a large range of molecular weights (MW). As the C-rate increased, the average MW of the oligomers from the surface film also increased.

These findings indicate that an increased charging rate affects the negative electrodes surface film and its adhesion to the current collector. Although a smaller SoC window caused less resistance increase and capacity losses in 18650 cells it was detrimental to the lamination properties. This could have significant implications for unconstrained pouch cells.
Anisotropic Mechanical Deformation of Lithium-Ion Electrode Networks Using Reconstructed Microstructures
Authors: Mendoza Hector , Roberts Scott A. , Brunini Victor E. , Long Kevin N. , Grillet Anne M.
Published: February 2020

Lithium-ion batteries are attractive for consumer electronics because of their high energy density, low self-discharge rates, and no memory effect.  However, like all rechargeable batteries, lithium-ion batteries suffer from capacity fade.  Understanding the mechanisms that lead to capacity fade in lithium-ion batteries is crucial for the advancement of lithium-ion battery technologies and the electronics relying on them for operation.  We hypothesize that one of the mechanisms leading to capacity fade arises due to mechanical stresses and changes to the connectivity of the electron transport network, which results from lithium intercalation reactions as batteries are cycled through charges and discharges.  Based on our hypothesis, we analyze these changes to the network structure by performing three-dimensional simulations of the particles at the mesoscale using reconstructed microstructures from SEM/EDS images of actual electrode particles.   We model the anisotropic swelling using coupled multi-physics simulations with a finite element code that encompasses mechanical, electrochemical, species transport, and thermal effects.  By incorporating all the aforementioned effects into our model, we hope to provide insight on how degradation of lithium-ion batteries evolves as a result of changes in the electron transport network arising from swelling, deformation, and stress generation driven by lithium intercalation.
High Capacity and High Density Sio Anode for High-Energy Lithium-Ion Batteries
Authors: Yuca Neslihan , Zhao Hui , Zheng Ziyan , Battaglia Vince , Zaghib Karim , Liu Gao
Published: February 2020

High capacity and high density functional conductive polymer binder/SiO electrodes are fabricated and calendered to various porosities. The effect of calendering is investigated to the reduction of thickness and porosity, as well as the increase of density. SiO particle size

remains unchanged after calendaring. When compressed to an appropriate density, an improved cycling performance and increased energy density are shown compared to the uncalendered electrode and over-calendered electrode. The calendered electrode has a highdensity

of ~1.2 g/cm3. A high loading electrode with an areal capacity of ~3.5 mAh/cm2 at a C/10 rate is achieved using functional conductive polymer binder and simple and effective calendaring method.

Figure 1
Towards a Better Reversibility of the Electrochemical Li-Si Reaction through the Use of Partially Oxidized Silicon Particles and Alternative Electrolyte Salt/Additives
Authors: Touidijine Amina , Morcrette Mathieu , Courty Matthieu , Davoisne Carine , Lejeune Michael , Mariage Nicolas , Porcher Willy , Larcher Dominique
Published: February 2020

Silicon is one of the most promising candidates as anode material for Li-ion batteries because it offers the largest gravimetric and volumetric capacities
[1]
. However, the most challenging problem associated with the Li-Si reaction is the drastic particles swelling (up to + 300% in volume) which results in degradation of the electrode cohesion and in capacity loss upon cycling
[2]
. Accordingly, the choice of the binder is crucial as it dictates most of the performances of the Si-based electrode
[3]
and also drives the nature of the solvent used to dissolve it. CMC (Carboxy-Methyl-Cellulose) is known to be a very efficient binder to maintain electronic percolation and mechanical integrity of Si-based electrodes
[4]

. Also, CMC is water soluble hence environment friendly compared to other polymeric binders that could necessitate hazardous solvents, such as NMP.

However, the large-scale production of Si/CMC/C composite electrode is troublesome since it generally leads to a large H2 bubbling within the slurry, later making impossible the fabrication of uniform electrodes. This results from the oxidation of Si by water (Si + 2H2O à SiO2 + 2H2), and we will here show how we mastered and finally avoided this reaction through partial and controlled oxidation of Si by pre-reaction with either water (Siwater) or air at moderated temperatures (Siair).

By coupling volumetric, chemical, XRD, TEM/EELS, TGA/DSC, IR and gas adsorption data, the texture and chemistry of the resulting silica-based coating layers were found to be highly dependent on the oxidation path (Figure 1), while the level of oxidation is tuned by the time-temperature of the treatment. Although fully oxidized samples are totally inactive vs. Li., a mild oxidation (e.g. 10-15wt% SiO2) protects the Si core from water during the electrode processing, while ensuring very stable capacity upon extended cycling (Figure 2). 

The electrochemical properties of the various resulting oxidized materials will be here deeply discussed. In addition, we will describe the effects of 1) alternative salts (LiPF6 and LiTDI), 2) various additives (FEC and VC), and 3) different procedures for the electrode making (e.g. powder mixing, drying conditions) onto the reaction of these Si/SiO2composite materials with Li. 

[1] G. C. L. B.A. Boukamp, and R.A Huggins, J. Electrochem. Soc: Electrochem Sicence and Thechnology
1981, 128, 725-729.

[2] U. Kasavajjula, C. Wang and A. J. Appleby, Journal of Power Sources
2007, 163, 1003-1039.

[3] N. S. Hochgatterer, M. R. Schweiger, S. Koller, P. R. Raimann, T. Wöhrle, C. Wurm and M. Winter, Electrochemical and Solid-State Letters
2008, 11, A76.

[4] B. Lestriez, S. Bahri, I. Sandu, L. Roue and D. Guyomard, Electrochemistry Communications
2007, 9, 2801-2806.

Figure 1
High Energy and Power Density TiO2 Nanotube Electrodes By Conformal Electrodeposition of Polymer Electrolyte
Authors: Djenizian Thierry , Plylahan Nareerat
Published: February 2020

Due to high surface area and improved charge transport, self-supported nanostructured materials based on transition metal oxides can be used as electrode for Li-ion batteries (LIBs). Their use is particularly interesting when considering the miniaturization of energy storage systems and the development of micropower sources [1]. For example, it has been reported that self-organized titania nanotubes (TiO2NTs) are potential candidates as negative 3D self-supported electrodes for Li-ion microbatteries [2]. In the prospect of developing all-solid-state batteries, it has been also demonstrated that electrodeposition technique (EDP) is a viable approach to achieve the deposition of polymer electrolytes on nanostructured electrode materials [3,4].

In this work, we study the conformal electrodeposition of PMMA-(PEO)5 copolymer on TiO2NTs by electrochemical techniques. The physical and chemical analyses of the electrodeposited polymer carried out by SEM, TEM, XPS, TGA, and NMR will be discussed in order to understand the relationship existing between the EDP parameters and the properties of the polymers.

Then, the benefits of the conformal coating of polymer electrolyte on the electrochemical performance in terms of energy density and power density will be highlighted. Actually, due to better electrode/electrolyte interface, we show that the capacity of the half cell is improved by 45% at 1 C compared to bare TiO2NTs (Fig. 1). Furthermore, we report that the polymer-coated TiO2nts tested in the full cell deliver an average capacity of ∼30 μA h cm−2 (120 mA h g−1) with LiNi0.5M1.5O4, ∼25 μA h cm−2 (100 mA h g−1) with LiFePO4 and ∼23 μA h cm−2 (90 mA h g−1) with LiCoO2, respectively during 50 cycles (Fig. 2).

References

1. B. L. Ellis, P. Knauth, and T. Djenizian, Adv. Mater, 26, 3368, (2014).

2. T. Djenizian, I. Hanzu, P. Knauth, J. Mater. Chem.,  21, 9925, (2011).

3. N. A. Kyeremateng, F. Dumur, P. Knauth, B. Pecquenard, and T. Djenizian, Electrochem. Commun., 13, 894 (2011).

4. N. Plylahan, N.A. Kyeremateng, M. Eyraud, F. Dumur, H. Martinez, L. Santinacci, P. Knauth, T. Djenizian, Nanoscale Res. Lett., 7, 349, (2012).

Figure 1
Polymer-Assisted Solution Method to Metal Oxide Network Structures for Lithium-Ion Battery Electrodes
Authors: Luo Hongmei
Published: February 2020

Rechargeable lithium-ion batteries have been extensively investigated for their promising application in hybrid electric vehicles because of their high energy and power densities and long cycle lifetime. A great effort has been made to synthesize a variety of electrode materials to improve the energy density, rate capability, and cycling stability. Nanostructured materials have received much attention as electrodes due to the short transport lengths for both electrons and lithium ions, higher electrode-electrode contact area, and better accommodation of the strain of lithium insertion/extraction.

Here we report a facile polymer-assisted chemical solution method to grow cobalt oxide, nickel oxide, bismuth oxide, and vanadium oxide network structures for lithium-ion battery anodes and cathodes. The carbon left from the decomposition of polymers is an effective binder between metal oxides and the nickel foam. As compared to the metal oxide powders prepared in a conventional way by using polymer binder and carbon black, these one-step direct growth electrodes showed much better lithium storage properties with high capacities, stable cyclability, and rate capability. For example cobalt oxides on nickel foam gave a capacity of 900 mAh/g at a current density of 1 A/g and 600 mAh/g at 4 A/g. The good performances of these electrodes could be attributed to intimate contact between the active material and the nickel foam, the porosity of the current collector, and the network structure of the active materials.
Probing Ionic Transport in a Lithiated Carbon Anode with Electrochemical Strain Microscopy
Authors: Wang Peiqi , Li Jiangyu
Published: February 2020

Lithium ion batteries are the most widely used energy storage device in both portable electronics and electric vehicles due to its high energy density. However, there are still remaining issues unsolved. To further improve the Li-ion battery performance, it’s important to understand the lithium ion intercalation/de-intercalation process upon cycling. The development of a new scanning probe microscopy technique (SPM), electrochemical strain microscopy (ESM), in which a combination of AC bias and DC bias is applied to the sample surface, allows us to evaluate mobile ionic diffusivity and electrochemical reactivity on the nanoscale.

In this work, we will first discuss about using a series of strain-based SPM techniques to distinguish different microscopic mechanisms including electromechanical coupling, spontaneous polarization, induced dipole moment and electrostatics. Then we will demonstrate the localized probing of lithium ion transport property in a lithiated carbon anode using ESM. Pristine carbon anode is also studied as comparison. Also, we’ll investigate the lithium ion transport through the solid electrolyte interface (SEI) layer, which is formed on the carbon anode surface upon cycling.
Influence of Lithium Precursors and Calcination Atmospheres on Graphene Sheets-Modified Nano-Li4Ti5O12 Anode Material
Authors: Yuan Tao , Li Wenting , Zhang Weimin , Ma Jingjing , He Yu-Shi , Liao Xiao-Zhen , Ma Zi-Feng
Published: February 2020

With the advantageous features include suitable lithium insertion position and "zero strain" structure, Li4Ti5O12 has become one of the ideal anode materials for lithium-ion battery and battery-capacitor system. However, the obstacle of its poor electronic and Li+ conductivity restrict its rate capacity. Many researches proved that the one-pot preparation process, which is mixing the carbon precursor with lithium and titanium precursor and then thermal treating in an inert or reducing atmosphere together, not only can form a carbon coating layer to improve the electronic property of the materials easily, but also inhibits the particle size growth of LTO by a barrier effect of carbon. Among kinds of carbon source, graphene presents excellent unique properties, which has been considered as an ideal carbon source to improve the electrochemical performance of LTO and many other active materials. However, the intersheet π-π attractions of GS easily resulted in its restacking and agglomeration. Therefore, an oxygenated graphene (GO) with a special amphiphilic molecular structure is adopted as GS precursor to prepare GS modified composites. Due to the amphiphilic characteristic of GO, the choice of an appropriate Li precursor is extremely important to obtain a high quality product.

In this study, we systematically investigated the influence of lithium precursor and calcination atmosphere on the reaction mechanisms, phase formation, particulate morphology, surface properties and electrochemical performance of graphene sheets-modified nano-Li4Ti5O12 composite. The results shown that the lithium precursor containing carboxyl anion such as LiAc and Li2CO3 would connect with oxygen groups of GO by strong hydrogen bonds to restrict the morphology of composites and the phase formation of pure spinel Li4Ti5O12. Furthermore, the oxygen ratio in the molecular structure of lithium compound is proportional to the consumption of graphene. In addition, the reducing atmosphere facilitates the partial reduction of Ti4+ to promote the interfacial charge transfer kinetics of the product.

Through optimization the conditions of the reaction, the sample adopting LiOH precursor with adjustment GS ratio calcined under Ar/H2 (5 %) atmosphere delivers 172.8 mAh g-1 at 1 C and maintained a discharge capacity of 98.0 mAh g-1 at a high rate of 40 C. This sample also showed fairly stable cycling performance. After 800 deep cycles at a high charge/discharge rate of 40 C, the capacity can hold 97.7 % of its second discharge value. This study not only provides an optimization of Li precursor and calcination condition for GS modified LTO material, but also has significant reference value for any combination reaction with GO participation.
A Self-Promotion Effect during ORR Process in Lithium Oxygen Battery
Authors: Zhang Wang , Shen Yue , Huang Yunhui
Published: February 2020

Rechargeable lithium oxygen batteries have attracted enormous attention due to its high theoretical energy density which could fulfill the ever increased energy requirement for electrification of road transport. There are numerous significant problems hinder it moving from theory to practice, especially the fundamental understanding of ORR and OER processes. Great efforts have been paid on the fundamental mechanism of O2 reduction in nonaqueous electrolyte. In this study, by combining cyclic voltammetry (CV) with in-situ surface enhanced Raman spectroscopy (SERS), we show a self-promotion effect during ORR process in aprotic lithium oxygen battery, that is the residual lithium peroxide after charge can act as an effective nucleation site for subsequent discharge process, promoting the lithium peroxide precipitation. The promotion effect becomes more obvious as cycles continue, then recedes after dozens of cycles since the electrode surface is blocked by side reaction products. This self-promotion effect is strongly affected by the solvent, as reported previously, the pathway of O2 reduction to form Li2O2 is related to the solvent donor number (DN). We proved here the self-promotion effect of lithium peroxide is obviously observed in intermediate DN solvents in which lithium peroxide precipitation undergoes electrode surface and solution pathways simultaneously. As a result of the self-promotion effect, the discharge capacity increases as cycles continue during first dozens of cycles. In summary, this work provide more insights into the ORR process for further fundamental understanding of lithium oxygen battery.
Omc for Poorly Conductive Products in Rechargeable Sodium-Air Batteries
Authors: Shin Hyeon-Ji , Kwak Won-Jin , Chen Zonghai , Yoon Chong seung , Lee Joong-Kee , Amine Khalil , Sun Yang-Kook
Published: February 2020

Development of renewable energy resources requires high-efficiency energy conversion and large-scale, low-cost, high-density energy storage devices. The energy density of traditional Li ion batteries is inadequate to meet the increased requirements, especially for electric or hybrid electric vehicles. Metal air batteries1-5 have attracted a great deal of attention mainly because of the extremely high energy density of the metal-air battery system, which is close to the energy density of fossil fuels. One advantage of Na–air batteries over Li-ion or Li–air batteries is its low material cost and its natural abundance, as sodium is 30 times cheaper than lithium. Moreover, the energy density of a Na–air battery is similar to the maximum practical energy density of a Li–air battery (1600 Wh/kg).6 As a common challenge to be addressed for all air-based battery technologies, excessive discharge products can accumulate on the cathode surface; most of these have very low electrical conductivity, and thus tend to inactivate surface reaction sites and block oxygen diffusion channels. Hence, the over-accumulation of discharge products can lead to the increase in polarization during charging of the Na–air battery and eventual termination of the oxygen evolution reaction.7 To reduce the accumulation of discharge products for decreased charge potential and improved cycling performance, morphological properties of the cathode (e.g. surface area, pore volume, and pore size) need to be tailored while employing different catalysts. However, to the best of our knowledge, there have been no reports of research efforts to confine the size or arrangement of discharge products in the vicinity of the cathode to decrease the charge potential and improve the cycling behavior of Na–air batteries. In the present work, OMC having 2.7 nm size pore (OMC-2.7) was employed as a cathode material to control the formation and subsequent decomposition of discharge products, and thus to reduce polarization and improve cycling behavior.

 

References

[1] Abraham K. M., Jiang Z., J. Electrochem. Soc. 1996, 143, 1−5.

[2] A. Inoishi, S. Ida, S. Uratani, T. Okano, T. Ishihara, Phys. Chem. Chem. Phys. 2012, 14, 12818–12822.

[3] G. Cohn, Y. Ein-Eli, J. Power Sources 2010, 195, 4963–4970.

[4] J.-S. Lee, S.-T. Kim, R. Cao, N.-S. Choi, M. Liu, K. T. Lee, J. Cho, Adv. Energy Mater. 2011, 1, 34–50.

[5] S. Yang, H. Knickle, J. Power Sources 2002, 112, 162–173.

[6] Peled E., Golodnitsky D., Mazor H., Goor M., Avshalomov S., J. Power Sources 2011, 196, 6835-6840.

[7] Pascal Hartmann, Conrad L. Bender, Joachim Sann, Anna Katharina Du¨rr, Martin Jansen, Ju¨rgen Janek, Philipp Adelhelm, Phys. Chem. Chem. Phys. 2013, 15, 11661-11672.
Fast Assembly of Si-CNFs Anodes for High-Performance Lithium-Ion Batteries
Authors: Yao Meng , Liu Xingbo , Zhang Hui
Published: February 2020

A hybrid lithium-ion anode material, made of acid-functionalized carbon nanofibers (CNFs) and amino modified Si nanoparticles (SiNPs), was synthesized by fast homogeneous electrophoretic deposition (EPD). Regular distribution of SiNPs in the three dimensional electro-active frameworks with the help of the interactions of surface functional groups can effectively improve the electron transport and restrict volume expansion during Li insertion/extraction. The as-deposited composite film exhibits a stable capacity of 790 mAh g-1 for 100 cycles at a current density of 400 mA g-1. The stability of suspension and weight ratio of Si to CNFs plays the key roles in the electrochemical performance.  It provides a possible environmentally friendly and cost-effective preparation method for future high-performance Li-ion battery applications.
Geometric Characteristics of Three-Phase Porous Microstructures for All Solid-State Lithium Ion Batteries
Authors: Lim Cheolwoong , Penumaka Rani V , Murakami Sho , Song Zhibin , De Andrade Vincent , De Carlo Francesco , Kim Youngsik , Zhu Likun
Published: February 2020

Fast lithium ion conducting inorganic solid materials are considered superior candidates for lithium ion batteries (LIBs) to overcome flammable characteristics, leakage, and tight electrochemical window issues of organic liquid electrolytes. Besides high ion conductivities of the inorganic materials, their wide electrochemical window and good chemical stability with electrode materials are great advantages as an electrolyte [1]. However, there are remained challenges to utilize the inorganic solid-state electrolytes for LIBs because of a low specific capacity, rate capability, and cycle life. Our previous study [2] showed a large capacity decay after the first charge and poor cycle life of an all solid-state LIB (Li1+xMn2O2 + Li1.3Ti1.7Al0.3(PO4)3 | Li1.3Ti1.7Al0.3(PO4)3  | Li1-xMn2O2 + Li1.3Ti1.7Al0.3(PO4)3). We concluded that the large capacity decay was caused by dismantled ion and electron pathway due to the structural change after the first charge. The electrochemical impedance spectroscopy results showed that the internal resistance of the solid-state cell has reduced by applying higher pressing pressure. Therefore, it is necessary to investigate the realistic microstructure to understand the capacity decay and poor cycle life of the all solid-state LIB.

By using synchrotron nano-computed tomography (nano-CT) at Argonne National Lab, we implemented quantitative study of the microstructures of all solid-state LIBs. The three-phase electrode was fabricated from a 47:47:6 (wt%) mixture of Li(Ni1/3 Mn1/3 Co1/3)O2 as active material (NMC), Li1.3Ti1.7Al0.3(PO4)3as Li-ion conductor (LTAP), and Super P carbon as electron conductor. The electrodes were packed under two different pressures (700 psi and 1300 psi) to control the volume fractions of void phase. To obtain the morphology data of the electrodes, TXM measurements were carried out adjusting energy levels of a synchrotron x-ray source. The x-ray generated images of solid-state electrodes with a 60 nm of spatial resolution at 8 keV are shown in Fig. 1. The gray-scaled intensity values of the images indicate the x-ray absorption rate of the materials. From the Fig. 1 (a) and (b), NMC particles, LTAP particles, and pores can be distinguished due to their different intensity values. Based on the reconstructed microstructure, the geometric characteristics will be presented to understand the lithium ion and electron pathways in all solid-state LIBs.

Acknowledgments: This work was supported by US National Science Foundation under Grant No. 1335850.

References

1. P. Knauth, Solid State Ionics, 180, 911 (2009).

2. N. M. Asl, J. Keith, C. Lim, L. Zhu, and Y. Kim, Electrochimica Acta, 79, 8 (2012).

Figure 1. Nano-CT images of solid-state electrode (NMC+LTAP) by full-field TXM measurements at an 8 keV of x-ray under packing pressures (a) 700 psi and (b) 1300 psi

Figure 1