bluuebunny/crossref_metadata_2025 huggingface dataset:
Multi-Directional 3D Laser Scanning of Lithium-Ion Cells to Detect Inhomogeneity during Cycling and Aging
Authors: Rieger Bernhard , Erhard Simon Vincent , Keil Peter , Jossen Andreas
Published: February 2020

Introduction

Measuring the thickness of lithium-ion batteries is a reliable method to detect the intercalation stages of the electrodes, the state of charge and irreversible effects during aging [1]. When using tactile high-precision displacement sensors, the measurement is limited to only a few positions of the cell at the same time [2].

Experimental

In this work, we developed a test stand, which enables simultaneous precise thickness measurement at 100 positions of the cell. This allows for investigations of the homogeneity of mechanical expansion during charging and discharging, as well as non-destructive state-of-health (SOH) mapping. In a first step, inhomogeneity of mechanical expansion during cycling is studied. In a second step, the effects of expansion inhomogeneity during cycling on the aging behavior of the cells are investigated by determining the irreversible and reversible thickness change at each of the 100 positions every 100th cycle.

Results

We found that the cell contracts homogeneously during discharge, whereas a significant overshoot in the thickness increase during high-rate charging at the current collector tabs is observed at 25 °C. When the ambient temperature is increased to 40 °C, this inhomogeneity is no longer observable. This effect has been ascribed in literature to non-homogeneous intercalation of Li-ions due to the interplay of fast and slow Li ion diffusion processes [3]. The SOH distributions reveal a homogeneous aging of the cells cycled at low charging rate and high charging rate at 40 °C.  Compared to that, the cells cycled at high charging rate at 25 °C show inhomogeneous degradation in areas close to the current collector tabs which show the largest degradation.

Literature

[1]       J. Cannarella, C.B. Arnold, Journal of Power Sources 269 (2014) 7–14.

[2]       K.-Y. Oh, J.B. Siegel, L. Secondo, S.U. Kim, N.A. Samad, J. Qin, D. Anderson, K. Garikipati, A. Knobloch, B.I. Epureanu, C.W. Monroe, A. Stefanopoulou, Journal of Power Sources (2014).

[3]       L.W. Sommer, P. Kiesel, A. Ganguli, A. Lochbaum, B. Saha, J. Schwartz, C.-J. Bae, M. Alamgir, A. Raghavan, Journal of Power Sources 296 (2015) 46–52.

Figure 1
Design of a Comprehensive Battery Pack Simulator for Hardware-in-the-Loop Testing of the Hybrid Electric Vehicle Control Unit
Authors: Nehzati Hassan , Safarabadi Majid , Esfahanian Mohsen , Esfandyari Mohammad Javad , Pourbafarani Zeinab
Published: February 2020

Application of electric drive systems in road transportation are appealing to become practical because they offer the affordable technology that reduces vehicle emissions and fuel use, increases efficiency and enhances performance. The performance and life-cycle costs of electric vehicles (EV) and hybrid electric vehicles (HEV) depend inherently on batteries. Battery pack performance directly affects the all-electric (zero-emission) range, power for acceleration, fuel economy, and charge acceptance during energy recovery from regenerative braking. Although Li-Ion rechargeable cells have the highest energy density, and among the highest power densities, of any cell commercially available today, they are much more unforgiving of abuse than other chemistries of batteries. Safety and reliability are the top concerns of the users of electric and hybrid electric vehicles which are both subject to not only the battery technology but also the management system for the battery. For the former, battery electrical and thermal simulation models can greatly help evaluating its charge/discharge and thermal behavior and for the latter, the Battery Management System (BMS) and its cooperation with vehicle control unit should be investigated to ensure the batteries safe operation. This paper presents the design of a comprehensive battery pack simulator which consists of the electrical, thermal and the BMS models. The designed simulator results were shown to have a good agreement with real test results and therefore it can be used for predicting the battery pack dynamic charge/discharge and thermal behavior. The designed battery pack simulator has been used for Hardware-in-the-Loop (HiL) testing of the Hybrid Control Unit (HCU) in a hybrid electric vehicle. Using HiL simulations, the HCU algorithms concerning the energy storage system management are investigated. The BMS functionalities and its cooperation with HCU can also be evaluated using the designed test bench.
Development of an Li2FeSiO4 Vs. Graphite Lib for Sustainable Energy Storage
Authors: Thomas Josh , Cai Jingjing , Eriksson Henrik , Fredin Kristofer , Liivat Anti , Gustafsson Torbjörn , Skårman Björn , Vidarsson Hilmar
Published: February 2020

The development of larger, more efficient, cheaper, safer and necessarily “greener” Li-ion batteries (LIBs) for electric vehicle (EV) and especially stationary energy-storage applications continues to present a major challenge to battery researchers and developers the World over. There are several underlying reasons for this; not least, the availability and cost of appropriate raw materials.  For example, several millions of tons/year of active cathode material will be needed if we are to achieve the long-term goal of a worldwide transition from ICEs to EVs – and to realistically cheap LIBs for use in large-scale sustainable-energy storage applications.    

     In this context, the absence of an ideal CATHODE material with a sufficiently high energy-density is arguably the most serious bottleneck facing us. A significant breakthrough has come with the development of polyanion-based cathode materials; typically, phosphates and silicates: e.g., LiFePO4 [1] and Li2FeSiO4 [2]. These materials are expected to be both cheaper and safer than conventional LIB transition-metal oxide cathode materials. A negative feature of these materials is, however, their poor electronic conductivity – a problem which is normally addressed by reducing particle-size into the nano-range and promoting ion conductivity through the use of various particle-surface coatings. Arguably the most promising cathode materials for large-scale applications involve the Li-M-SiO4 family of silicates, typically Li2FeSiO4.

    We present here an account of our recent advances in addressing the challenge of scaling up our successes on a lab-scale to produce well-functioning Li2FeSiO4 vs. graphite full-cell prototypes suitable for the sustainable energy storage market.

Keywords: lithium-ion battery, cathode material, scale-up, EV, sustainable-energy storage

REFERENCES                                                                            

[1]  A.K. Padhi et al., J. Electrochem. Soc., 144, 1609 (1997).

[2]  A. Nytén et al., Electrochem. Commun., 7, 156 (2005).

ACKNOWLEDGEMENTS

This work has been supported by the Global Climate and Energy Project of Stanford (GCEP), the
Swedish Energy Agency (STEM), VINNOVA and the Swedish Science Research Council (VR).
How Mixing Tetraglyme with Ionic Liquid Changes Volumetric and Transport Properties: An Experimental and Computational Study
Authors: Zhang Yong , Maginn Edward J.
Published: February 2020

Ionic liquids (ILs) are salts possessing many properties that make them attractive for use in a wide range of applications including batteries. One of the biggest drawbacks of ILs is that they tend to be more viscous than conventional solvents, which means low ionic conductivity when used as electrolytes in batteries. One effective way to lower the viscosities is to mix ILs with low viscosity additives such as molecular solvents. An obvious disadvantage of mixing molecular solvents with ILs is that the extremely low volatility of the IL is compromised by the finite vapor pressure of the diluent. One strategy to overcome this is to mix ILs with molecular solvents that are themselves of very low volatility. One such class of compounds are the glymes, which are oligoethers having a CH3O-(CH2CH2O)n-CH3 structure. In addition to having low volatility, glymes are effective at dissociating salts because of the electron donating nature of their ether oxygen groups. They also tend to have high thermal and electrochemical stability, which has led many groups to investigate mixing glymes with alkali metal salts (most commonly Li+ [NTf2]) for use as electrolytes in batteries. The alkali metal cation tends to coordinate with the oxygen atoms of the glyme, which can significantly lower the melting point of the salt.  Such systems usually retain the attractive properties of pure ILs but the transport properties are improved. They are considered a new class of ILs and have been termed “solvate ILs”. Tetraethylene glycol dimethyl ether (tetraglyme or G4) is a particularly promising glyme.

While there are many studies devoted to the properties of Li-based solvate ILs, much less work has been done investigating the properties of mixtures containing glymes and more conventional ionic liquids. In the current work, the density and viscosity of the IL [C6mim][NTf2]) and its mixtures with tetraglyme were measured at different temperatures and concentrations. Molecular dynamics (MD) simulations were also carried out on the mixtures in order to compute the density, self-diffusivity, viscosity, ideal ionic conductivity and liquid structure. We find that both the density and viscosity drop with increasing temperature and G4 concentration. Detailed analysis of the simulation results suggests that G4 preferentially solvates the cations, thereby weakening the interactions with the anions and resulting in faster dynamics, particularly for the anions. Such behavior was previously observed in solvate ionic liquids. Based on the simulation results of a model G4 system, it was further revealed that the localized negative charges on the oxygen atoms of G4 are primarily responsible for the preferential solvation of cations. If G4 (or a similar solvent) instead had large localized positive charges, it would tend to preferentially solvate the anions, resulting in increased cation mobility. This suggests a strategy for selecting molecular solvents that will selectively enhance cation dynamics.
Modelling of Li+ and Na+ Conduction Under Electric Fields in Organic Ionic Plastic Crystals
Authors: Jónsson Erlendur , Chen Fangfang , Forsyth Maria
Published: February 2020

Solid electrolytes are a promising topic, which could replace the flammable solvents currently used for both Li-ion battery electrolytes, and their Na-counterpart (still under development). Thus the transport properties of such solid electrolytes must be understood. Here, we studied the effect of applying an external electric field to an organic ionic plastic crystal, P1224PF6, previously reported to have interesting alkali-ion transport properties[i]. The study employed molecular dynamics (using a previously reported force field[ii]).

The roles of electric field strength and Li+/Na+ concentration were explored. Furthermore, system polarisation was explored by adding a surface/electrode to the system. This was done both on the basis of an external electric field and one due to electrode charge.

[i] Chen, F., Pringle, J.M., Forsyth, M. Chem. Mater.
2015, 27, 2666-2672.

[ii] Chen, F., Jin, L., de Leeuw, S.W., Pringle, J.M., Forsyth, M. J. Chem. Phys.
2013, 138, 244503.
Cycle Properties Improvement of "Li[Ni0.5Co0.2Mn0.3]O2/LiPON/Li" All-Solid-State Thin Film Batteries with Low Surface Ni Content
Authors: Tong Jun
Published: February 2020

Thin films of Li[Ni0.5Co0.2Mn0.3]O2 (NCM-523) were deposited on Au coated Si substrate by RF co-sputtering. The component ratio of Ni : [Co+ Mn] at the surface of NCM was modified through changing the power densities of each targets during deposition process. With decreasing the Ni content, a more stable surface structure of NCM has been obtained. After the all-solid-state thin film batteries with a structure of "Si/Au/NCM/LiPON/Li/Au" has been fabricated, and the electrochemical impedance spectroscopy (EIS) was taken to compare the interface resistance of "NCM/Li" with different Ni content. Systematic relationship between surface Ni content and interface resistance was established. Batteries with lower surface Ni content was with better cycle properties, showing capacity above 60 μAh*cm-2 *μm-1 under 0.5 C.
Electrode Degradation Analysis in Li-Ion Batteries
Authors: Malik Romeo , Finegan Donal P , Huang Qianye , Loveridge Melanie , Shearing Paul R. , Bhagat Rohit
Published: February 2020

This study investigates modes of degradation in composite silicon (Si) anodes for Li-ion batteries, with emphasis on the electrode architecture. In recent years, considerable studies have shown that crystalline Si is a promising negative electrode candidate, with a specific capacity of 3579 mAh/g which is ca. 10 times the specific capacity of graphite. However, Si still has major performance issues associated with it, predominantly the volume expansion (up to 280%) which can result in cracking and pulverisation of active particles. Additionally the surface of the Si reacts with the electrolyte at lower voltages to form the solid-electrolyte interphase (SEI) – a major source of continued irreversible Li loss. Subsequent charge-discharge cycling causes repeated disruption of the SEI layer where it continues to form and grow. These phenomena culminate in conductivity loss and capacity fade. Despite the numerous studies and evolution of sophisticated in-situ characterisation techniques, relatively little is understood still about the microstructural evolution and its impact and relation to the cell performance during operation and failure. Therefore, a more detailed study is required to fully characterise types of crystalline Si as well as the importance of electrode architectures for high capacity lithium-ion storage materials. 

It is imperative to comprehensively understand the fundamental degradation mechanisms inside anode microstructures and at their interfaces. X-ray computed tomography (CT), in conjunction with impedance spectroscopy and associated physical characterization, will be employed to capture and quantify key aspects of the evolution of internal morphology and resistance build up. This includes characterisation of SEI growth, porosity changes and conductive network breakdown during charge-discharge operation. The study will also include in-situ and operando tomography, and diffraction experiments for clearer insights into key degradation processes, such as delamination, initiation and propagation of particle cracking as well as time-resolved identification of phase transformations. X-ray CT has been proven to be an effective tool to explore the hierarchical structure of battery electrodes and for diagnosing battery failure mechanisms at multiple- length scales. This approach will enable us to observe and quantify failures in Li-ion batteries at the electrode level, and thus facilitate construction of better electrode architectures.

This study aims to characterise electrode structures to be able to develop and compare microstructural architecture with performance. It is anticipated that this study will influence major improvements in the design of Li-ion battery materials and their processing which in turn positively impact cell performance.

Figure 1
Feeling the Strain: Enhancing Ionic Transport in LiFePO4 and NaFePO4 Cathodes through Strain Effects
Authors: Heath Jennifer , Tealdi Cristina , Islam M. Saiful
Published: February 2020

Olivine-type phosphates LiFePO4 and NaFePO4 are among the most widely studied cathode materials for rechargeable batteries. To improve their rate behaviour for future electronic and vehicle applications, it is vital that the Li+ and Na+ conductivities be enhanced. In this study atomistic simulation methods are used to investigate the effect of lattice strain on ion transport and defect formation in olivine-type LiFePO4 and NaFePO4, as these properties are directly related to their intercalation behaviour. The results suggest that lattice strain can have a remarkable effect on the rate performance of cathode materials, with a major increase in the ionic conductivity and decrease in blocking defects at room temperature. Such understanding is important for the future optimization of high-rate cathodes, and is relevant to the growing interest in developing thin film solid-state batteries. In addition, complementary simulation work was carried out to compare the olivine and maricite forms of NaFePO4, specifically their defect and Na-ion conduction properties.
Investigation of Reaction Kinetics in Oxide Nanostructures for Li Ion Battery Conversion Electrodes
Authors: Kim Jae Jin , Fister Timothy T , Emery Jonathan D , Suh Hyo Seon , Elam Jeffrey W , Martinson Alex B. F. , Nealey Paul F. , Fenter Paul
Published: February 2020

As one of promising candidates for achieving a higher capacity Li ion battery electrode, transition metal oxides can electrochemically react with lithium to form lithium oxide and reduced metal phases as a so-called conversion reaction. Despite its higher energy density and use of cheaper materials than conventional intercalation materials, conversion materials have been commercially limited by several factors, including its slow, diffusion-limited kinetics, poor cycling performance driven by substantial structural re-organization and corresponding large volume changes, and Coulombic inefficiency—especially in the first cycle. In addition, there are substantial deviations in redox potentials for conversion reactions in oxides with respect to the thermodynamically expected values (Etherm~ 2 V). It is obvious that the interfacial processes play a critical role in the overall conversion reaction which enlists charge/mass transport through a complex network of metal-rich and lithia-rich domains and consequent nucleation/growth.

To understand and control the reaction kinetics, we have studied nanoscale model electrodes that take advantage of a geometrically well-defined, simple and reproducible structure, which enables us to investigate more readily the correlation between electrochemical reactivity and electrode microstructure. Using epitaxial thin films, we explore the role of strain and initial metal oxide surface structure on the potential for lithiation. To control transport and phase-separation, we have also examined various nanoscale oxide structures including spheres, cylinders and lamellae structures. These electrodes are prepared by combining the rich phase-space of self-assembled block copolymers with sequential infiltration synthesis via atomic layer deposition. Traditional scanning probe methods are combined with both in situ x-ray diffraction and small angle scattering to investigate the controlled phase separation of a conversion reaction. These results provide deeper knowledge of the reaction kinetics and new perspective on the energy loss mechanisms in conversion reaction while helping develop strategies for improving the viability of conversion materials.
Improved Cycling Stability of Conversion and Alloying Anodes through the Use of Nanomaterials
Authors: Rehnlund David , Lindgren Fredrik , Böhme Solveig , Nordh Tim , Zou Yiming , Pettersson Jean , Bexell Ulf , Edström Kristina , Nyholm Leif
Published: February 2020

In order to meet the growing need for portable energy storage future batteries need to provide improved energy densities. One major problem lies in the current use of intercalation based electrode materials which are typically limited to storing one lithium ion per formula unit. Improved energy storage can be achieved through the use of conversion and alloying reactions where it is possible to store multiple lithium ions per formula unit. Even though impressive energy densities can be obtained through the use of conversion and alloying anode materials, only surpassed by the use of lithium metal itself, these systems are typically plagued by capacity fading during cycling. The origin is generally ascribed to irreversible reactions with the electrolyte amplified by major volume expansion, causing the growth of a solid electrolyte interphase (i.e. SEI). One promising strategy to address this issue is through the use of nanosized electrode materials (e.g. Si nanoparticles), as it has been shown that nanoparticles and nanowires show better cycling stability than their bulk counterparts [1, 2]. Large particles (i.e micrometer sized) form cracks during cycling as opposed to smaller particles (i.e. < 150 nm) [3]. Even though the use of nanoparticles can reduce crack formation and the accompanied SEI growth, capacity fading is still observed for these systems. Our work has focused on studying freestanding nanostructured conversion materials (e.g. Cu2O nanowires), which offer in depth analyses of the conversion reactions without disturbance from binders or conducting additives. Contrary to previous understanding nanosized Cu2O thin films and multi-layered nanostructures show an increase in capacity during cycling [4, 5]. This behaviour is caused by improved access to the entire material when using the nanomaterials. The system has also shown improved performance during cycling likely caused by electrochemical milling of the particles thereby consistently reducing the particle size and thus allowing more of the material to be accessible. With the successful use of nanosized conversion materials our research is now focused on addressing the stability problems of alloying materials by studying the effect of nanomaterials. 

References:

1.         A. Magasinski, et al.. Nat. Mater., 2010. 22: p. 353-358

2.         C.K. Chan, et al.. Nat. Nanotechnol., 2008. 3: p. 31-35

3.         X. H. Liu, et al.. Adv. En. Mater., 2012. 2: p. 722-741

4.         M Valvo, et al.. J. Mat. Chem. A., 2014. 2: p. 9574-9586

5.         D. Rehnlund, et al.. Nanoscale, 2015. 7: p. 13591-13604

Figure 1
Thin Films of Organic Electrode Materials for All-Solid-State 3D-Microbattery Applications
Authors: Nisula Mikko , Karppinen Maarit
Published: February 2020

The miniaturization of electronic devices demands for energy storage systems of equal size. As the conventional liquid electrolyte cells do not scale well enough, the current focus is on all-solid-state thin film batteries. In order to increase the energy density while preserving the power density of the cells, nanostructuring of the substrate to increase the effective surface area is seen as a viable option. Such an approach places an apparent need for a thin-film deposition method capable of manufacturing the electrode and electrolyte materials on high aspect ratio substrates. A strong candidate for the task is the atomic layer deposition (ALD) technique which is based on sequential surface reactions of gaseous precursors. The surface saturation limited growth results in excellent conformality over complex surface features. However, the availability of ALD processes for Li-ion battery materials is severely lacking.

By utilizing combined atomic/molecular layer deposition (ALD/MLD) technique, we broaden the range of available electrode materials to those based on conjugated carbonyl systems. These organic electrode materials combine the high gravimetric energy density with abundant and environmentally benign constituents. We present demonstrative ALD/MLD processes for both anode and cathode materials and verify the electrochemical activity of the as-deposited thin films. Also shown is that the nanoscaling of the materials can be utilized to overcome the inherently poor kinetics of organic electrode materials without relying on any conductive additives. As the ALD/MLD method allows for making the cathode material directly in the fully-lithiated reduced state, the as-deposited pair can be combined into a full cell without an additional lithiation step.
Enhanced High Temperature and Rate Capability Performance of Nanoscale Lithium Titanate (Li4Ti5O12) Anode
Authors: Alaboina Pankaj Kumar , Ge Yeqian , Liu Yang , Uddin Md-Jamal , Park Seiung , Zhang Xiangwu , Cho Sung-Jin
Published: February 2020

Lithium titanate, Li4Ti5O12 (hereafter denoted as LTO) is an attractive anode material for high rate lithium-ion batteries. However, at high temperatures (above 50°C), LTO suffers from surface phase transitions that lead to severe gas generation issue. In this work, nanoscale LTO material was synthesized by water-based spray drying method followed by a high-temperature calcination to enhance the overall electrochemical performance. The synthesized material were found to be consisted of round shaped secondary particles which were formed by the association of large number of LTO primary particles (< 200 nm size). The nanoscale LTO anode material exhibited very stable electrochemical performance at high temperature (50°C) and high rate (5C) which can be attributed to the shortened lithium-ion diffusion lengths. Rate capability and impedance spectroscopy were also performed to further study the electrochemical properties. To better understand the structural behavior, cells were torn down after 1 cycle and 500 cycles. High resolution transmission electron microscope and selective area electron diffraction results revealed that the thickness of the LTO phase transitions layer after 500 cycles is almost the same as that after 1 cycle, around 3-5 nm.
Carbon Nanotube@MnO2 Hybrid Catalysts for Li-O2 Batteries
Authors: Wang Fan , Wen Zhaoyin , Shen Chen , Wu Xiangwei
Published: February 2020

Rechargeable lithium-oxygen (Li-O2) battery has attracted enormous research attention due to its remarkably high theoretical energy capacity. However, the sluggish oxygen reduction and oxygen evolution reaction (ORR and OER) kinetics cause the high over potential, poor electrolyte stability and short cycling life.[1] Thus, the development of eﬃcient catalysts are required to effectively improve the Li-O2 battery performance.

The materials based on MnO2 are recognized as low-cost and eﬃcient catalysts for Li-O2 battery cathodes.[2] Here, in-situ growth of branched MnO2 nanosheets on multi-walled carbon nanotubes (MWCNTs) were generated through a one-pot reaction process and applied as cathode catalyst in a rechargeable Li-O2 battery. The MnO2 with the morphology of curved petal-like walls (about 50 nm in thickness) were homogeneously coated outside the CNT (about 40 nm in diameter) to form a core–shell nanowires.[3] The CNT@MnO2 hybrid showed excellent catalytic activity for both ORR and OER processes in Li-O2 batteries. Owing to its ultra-high specific surface area, it delivered a high reversible capacity of 1500 mAh·g-1 based on the mass of the hybrid. This core-shell structure can effectively prevent direct contact between the CNT and the discharge product Li2O2, thus avoiding or reducing the decomposition of CNT and the formation of Li2CO3 during charge process, which can also improve the conductivity of the cathode and increase the cycling performance of Li-O2 batteries. As a promising cathode catalyst in Li-O2 batteries, the branched CNT@MnO2 nanocomposite cathode exhibits a stable full discharge and charge cycling performance. As shown in figure 1b, about 250 cycles were achieved with a fixed capacity of 500 mAh·g-1 at a current of 100 mA·g-1.

The results shown that such a design of a core-shell architecture with a high conductive carbon nanotube in the center and MnO2 nanosheets uniformly coated on its surface both achieved the high conductivity and excellent catalytic activity in Li-O2 batteries.

Figure 1. Schematic illustrations of the transfer of electrons in CNT@MnO2 cathode (a). discharging and charging profiles (b) and cycle performance of Li-O2 battery with CNT@MnO2 cathode(c).  

References:

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

[2] A. Debart, A. J. Paterson, J. Bao and P. G. Bruce, Angew. Chem. Int. Edit., 2008, 47, 4521-4524.

[3] Y. Chen, Y. Zhang, D. Geng, R. Li, H. Hong, J. Chen and X. Sun, Carbon, 2011, 49, 4434-4442.

Figure 1
Nickel-Rich Cathode Precursor Synthesis By Taylor Vortex Reactor
Authors: Kahvecioglu Feridun Ozgenur , Shin Youngho , Krumdick Gregory
Published: February 2020

Progresses in lithium ion battery (LIB) materials are increasing by the development of new synthesis methods where the production of materials in a scalable and continuous route is very critical when the process development transfers to large scale quantities. In a LIB, one of the most performance limiting components is the cathode, which also limits the overall performance of the battery. Among the other synthesis methods, co-precipitation from aqueous processes is known to yield the best cation mixing within the structure, in particular for the synthesis of cathode precursors for batteries. Continuous stirred tank reactor (CSTR) is by far the most widely used systems utilized in battery industry, yet have low reproducibility, product efficiency, and undergo from very long stabilization times due to low mass transfer rate.

Here, we report a new emerging technology, Taylor Vortex Reactor (TVR), for the cathode precursor synthesis which overcomes many complexities encountered in CSTRs. As current research in the field is trending towards exploring nickel-rich compositions, we produced Ni0.6Mn0.2Co0.2 (OH)2 precursors employing a continuous hydroxide route in a TVR which were then lithiated to form active cathode particles. The effect of rotation speed on the morphology, and particle size and distribution of the precursors were investigated and reported.  In general, higher rotation speed favored spherical particle formation with a smooth surface morphology along with a narrow particle size distribution. Tap densities of 1.77 – 1.98 g/cc for the precursor and 2.02 – 2.24 g/cc for the active materials were achieved, delivering 173 – 186 mAh/g discharge capacities at the first cycle with a C-rate of 0.1C when cycled between 4.3 - 3.0V.
Electrochemical Stiffness in Electrodes for Lithium Ion Batteries
Authors: Gewirth Andrew A. , Tavassol Hadi , Jones Elizabeth M. C. , Sottos Nancy R.
Published: February 2020

Higher power and charging rates are essential for large scale adoption of lithium-ion batteries in transportation applications. While lithium-ion batteries are ubiquitous in portable electronics, their performance and lifetime suffer during high rate charging and high power discharging. In such extreme electrochemical conditions, the mechanical response of electrode materials governs their degradation behavior. Here, we present a new technique to probe the electrochemically-induced mechanics of electrodes by calculating the electrochemical stiffness of electrodes via coordinated in situ stress and strain measurements.  Through the electrochemical stiffness, we elucidate inherent and rate-dependent mechanical responses of graphitic battery electrodes. We find that stress and strain are asynchronous as shown in the figure.  In particular, stress development is found to lead strain development as different graphite-lithium intercalation compounds are formed. Additionally, our analysis reveals inversely scaled rate-dependent behaviors for stress and strain responses. Stress scales as scan rate while strain scales with charge (or, equivalently, capacity).  These measurements provide a new paradigm for understanding mechanical effects in intercalation systems, such as batteries.  Stress arises as resistance to lithiation, while strain arises as a consequence of lithiation.  Electrochemical stiffness measurements provide new insights into the origin of the rate-dependent chemo-mechanical degradations, and provide a probe to evaluate advanced battery electrodes.

Electrochemical stress measurements are also utilized to interrogate diverse processes in Li ion battery materials, among them the response of Sn materials to lithiation and delithiation.
Investigation of Aluminum Environments in Li-Ion Cathode NCA and Al-Doped NMC Via 27al MAS NMR Spectroscopy
Authors: Dogan Fulya , Key Baris , Iddir Hakim , Vaughey John T.
Published: February 2020

Application of aluminum based coatings and partial aluminum substitution for transition metals (doping) are commonly used in lithium ion batteries to improve electrochemical performance and chemical stability of the cathode systems by modifying the surface of cathode materials, increasing the operating voltages, enhancing  thermal stability of the material, and reducing metal dissolution. However understanding the nature of surface and lattice aluminum environments  or understanding possible aluminum diffusion in to the interphase have been a challenge for aluminum bearing Li-ion battery materials such as LiNi1-y-zCoyAlzO2 (NCA), aluminum doped LiNixMnyCozO2 (NMC) and coated layered metal oxides. 27Al magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy is one of the few structural probes currently available that can qualitatively and quantitatively characterize lattice and non-lattice (i.e. surface, coatings, segregation, secondary phase etc.) aluminum coordinations. In the present study, we use NMR to gain new insights into transition metal (TM)-O-Al coordiations and evolution of lattice aluminum sites upon cycling. In each case, aluminum coordination of paramagnetic (lattice) and diamagnetic (non-lattice) nature have been investigated and their respective evolutions upon cycling reported.
New Polymeric Materials for Li-Ion Batteries: Poly(phenoxy-ketimine)s
Authors: Demir Haci O. , Berkem Ali S. , Bas Gamze , Cakmak Mukerrem
Published: February 2020

Lithium-ion batteries (LIBs) are in great demand as energy sources for many applications and research towards finding new materials to improve the performance is underway. Advances in active chemistry are left to the solid-state chemists’ creativity and innovation in the design and elaboration of new intercalation electrodes. Many of the organic compounds are limited by their thermal stability, rate capability, cycle life and low energy density values. Tarascon and co-workers have rekindled interest in the area of organic electrodes by proposing highly conjugated carboxylates, pyromellitic diimides, benzoquinone derivatives, oxocarbonyls, etc. as electrodes for Li-ion batteries.1In the case of poly(phenoxy-ketimine)s, they have been recognized that molecules with hydroxyl and ketimine pendant groups in conjugation with aromatic systems may be efficient organic electrodes. In this study, we report the usage of poly(phenoxy-ketimine)s, a potentially low-cost, eco-friendly, simple synthesis process, as organic electrode materials in Li-ion batteries (Scheme 1).

References:

1. M. Armand, S. Grugeon, H. Vezin, S. Laruelle, P. Ribiere, P. Poizot and J. M. Tarascon, Nat. Mater., 2009, 8, 120.

Scheme 1.The structure of the poly(phenoxy-ketimine)s

Figure 1
Performance and Safety Characteristics of Si-Based Anode Materials for Li-Ion Batteries
Authors: Yanagida Masahiro , Mukai Takashi , Ikeuchi Yuuta , Sakamoto Taichi , Yamashita Naoto , Tanaka Hideaki
Published: February 2020

Silicon is one of promising active materials for Li-ion batteries for its high capacity.  In order to utilize silicon-based materials as alternative anode, the composite electrodes were prepared from silicon-based materials with various binders (such as acrylic acid, polyimide), conducting materials (AB, CB) and current collecting materials.  Pouch cells were composed with the electrode and various separator.  To investigate the electrochemical properties of the silicon-based materials anode, an electrochemical test was conducted.  From the view point of the safety characterization compared with electrode resistance, the results of nail insertion test for pouch cells were also carried out.  In this study cycle performance was heavily dependent on the binder.
Effects of Biopolymer-Binder Crosslinking on Silicon Anode Performance
Authors: Dufficy Martin K , Dennis Kimberly A , Khan Saad A , Fedkiw Peter S
Published: February 2020

Silicon-based electrodes offer charge capacities much greater than graphite, however, short-cycle life stymies commercialization of Si in Li-ion batteries (LIBs). Binding agents plays a crucial role in Si-electrode performance; binder composition induces interactions/reactions with Si and electrolytes that greatly influence cycling performance of Si-based systems. Thus, elucidation of such interactions and reactions is paramount to extend cycle life and increase capacity. We previously reported on usage of guar gum (GG) as a novel binding agent for Si nanoparticle (SiNP) electrodes [1]. Electrodes using GG binders retain >70% capacity after 250 cycles and outperform carboxymethyl-bound Si electrodes. Nevertheless, shortcomings in SiNP/GG system include 1) low ionic and electronic conductivity and 2) fractured, and possibly delaminated, composite electrodes. To overcome these shortcomings, we developed a novel gel binder in which a conductive additive was reinforced within the binder.

The novel gel binder comprises crosslinked GG/carbon black (CB) dispersions. We first probed network formation via dynamic rheology, which revealed greater moduli for the GG/CB system than in the absence of CB, and suggests that CB particles enhance network strength through physical crosslinks (Figure 1a). In attempt to elucidate the role of the binder in Si-based electrodes, we investigated the influence of reaction time (or crosslinking density) on physical properties such as elasticity, electrolyte uptake, ionic conductivity, and adhesion. Physical properties could then be correlated with electrochemical performance in Li-ion half-cells. We found that marginally-crosslinked GG/CB binders in SiNP electrodes led to enhanced cycling performance, whereas capacity was limited in SiNP electrodes using densely-crosslinked GG/CB binders. Symmetrical charge/discharge cycling at 3.6 A g-1 revealed SiNP electrodes with marginally-crosslinked GG/CB binders have larger capacities than non-crosslinked binders (Figure 1b), which may be attributed to electronically conductive networks of CB. Additionally, capacity retention increased with crosslinking of binders (Figure 1b), which may be attributed to preservation of initial electrode microstructure. In attempt to enhance Si electrode feasibility in commercial LIBs, the ensuing study provides fundamental relations between crosslinked-biopolymer binders and SiNP electrode performance.

Figure 1. (a) Evolution of storage modulus, G’, in GG systems with CB (blue) and without (black) using measurements from dynamic stress sweeps; (b) Capacities over 200 cycles of SiNP electrodes using various GG/CB-binder crosslinking densities at 3.6 A g-1

Reference

[1] J. Mater. Chem. A, 2015, 3, 12023-12030

Figure 1
In Situ EXAFS Study of Tin Phosphide/Graphite Composite Anodes for Lithium-Ion Batteries
Authors: Ding Yujia , Li Zhe-Fei , Segre Carlo U , Wang Yuxuan , Botte Gerardine G
Published: February 2020

Lithium-ion batteries (LIBs) have become the primary power source for portable electronics and hybrid and electric vehicles. The rapid growth applications of LIBs require significant improvement in their capacity, energy density and cycle life. Sn-based materials are alternatives to replace the traditional most widely used anode material, graphite, which only offers a capacity of 372 mAh/g. Metallic tin or tin oxide can achieve initial capacities over 1000 mAh/g. However, these materials suffer from volume expansion and formation of irreversible phases during lithiation that degrade the capacity and battery performance rapidly. A layered structure material tin phosphide (Sn4P3) is a promising anode material with a high initial capacity of over 1200 mAh/g. Lithiation of Sn4P3 starts with a conversion reaction that forms metallic tin and lithium phosphide, followed by a lithium-tin alloying reaction. Although Li3P is a better lithium-ion conductor than Li2O, Sn4P3 still suffers from a large volume change during the initial lithiation and the irreversible formation of Li3P.

This study focuses on the characterization of Sn4P3 and Sn4P3/graphite composites synthesized by high-energy ball milling using red phosphorus and tin nanoparticles under Ar atmosphere. The capacity of pure Sn4P3 rapidly decreases to around 200 mAh/g after 15 cycles. In contrast, Sn4P3/graphite composites exhibit excellent electrochemical performance and durability with a capacity of 610 mAh/g at 0.4 C after 100 cycles. In addition, the coulombic efficiency was also much higher in the Sn4P3/graphite composites, indicating a reversible lithiation/delithiation behavior and more stable SEI layer formation.

In situ extended x-ray absorption fine structure (EXAFS) measurements were performed to study the local environment changes around Sn atoms during the lithiation/delithiation process. EXAFS scans of the cell were taken continuously and were analyzed as a function of different charged and discharged states. It is evident that the local Sn environment in the Sn4P3/graphite composite is fully reversible on lithiation/delithiation while the local Sn environment of pure Sn4P3 changes irreversibly after several cycles consistent with the electrochemical results. A mechanism for performance degradation of Sn4P3 and cycling durability of Sn4P3/graphite composites is proposed based on modeling of the EXAFS data.
Versatile Polymer-Template Method of Transition Metal Oxides for Lithium-Ion Battery Electrodes: Synthesis, Characterization and Electrochemical Properties
Authors: Lim Hyung-Seok , Suh Kyung-Do , Sun Yang-Kook
Published: February 2020

Transition metal oxides have been studied as positive- and negative-electrode materials for high-energy lithium-ion batteries (LIBs). The performance of LIBs depends on the characteristics of active materials such as crystal structure, matter composition, morphologies and electrical properties because of the insertion/extraction kinetics of Li ions and electron transfer. In this study, we report the strategic synthesis methods of tailored active materials for high performance LIBs using external-stimuli responsive polymer particles. Since the three-dimensional cross-linked polymer spheres can accommodate the introduction of various metal ions and polar molecules by diffusion from the aqueous and non-aqueous solutions, the hierarchically structured hybrid metal oxide spheres can be synthesized easily. The medium pH is most important factor in determining the morphologies of metal oxide particles because the mesh size of the cross-linked polymer network and the size of the diffuse polar species depend greatly on the pH of medium. Besides, the polymer phase remains the carbon residues on the surface of primary metal oxide grains during calcination process at certain heating condition. These carbon residues can accommodate the volume variation of metal oxides reacted with lithium ions as well as increasing the electrical conductivity of electrodes. We have fabricated various kinds of transition metal oxide particles and also investigated their electrochemical performances as positive- and negative-electrodes for LIBs.
Monitoring Structural Changes in LixNi0.8Co0.15Al0.05O2 Using Ex Situ
7li/ 27al NMR
Authors: Trease Nicole M. , Seymour Ieuan David , Radin Maxwell , Liu Haodong , Hy Sunny , Chernova Natasha A. , Whittingham M. Stanley , Meng Ying Shirley , Van der Ven Anton , Grey Clare P.
Published: February 2020

Although layered transition metal oxides are the most commercially available battery materials, they suffer from capacity fading over time due to transition metal (TM) and Li layer mixing that can lead to decreased Li diffusion and phase segregation due to oxygen loss. We have implemented 7Li and 27Al NMR to study the structural changes in LixNi0.8Co0.15Al0.05O2 (NCA) during electrochemical cycling. Using an optimized DFT calculated structure, the predicted NMR shifts are calculated using the spin-flipping method of Middlemiss et al.1 In the pristine materials, the 7Li and 27Al spectra indicate a dynamic Jahn-Teller distortion, as expected for LiNiO2, and the absence of Li in the TM layer. 27Al NMR also indicates that Al has a preference to be surrounded by six Ni3+ compared to a random solution model structure. 7Li NMR has been widely used to monitor local changes in the Li environment arising from Li/ TM layer mixing and the formation of defects and/or other phases.  Here we show that the 27Al NMR shift of the Al environment is highly sensitive to its proximity to Ni3+, allowing for the indirect monitoring of Ni migration out of the TM layer after multiple cycles. Both 7Li and 27Al NMR can be utilized to indicate the mechanisms leading to capacity fade in NCA and other Al-substituted layered transition metal oxides over multiple cycles.

Reference

1.         D. S. Middlemiss, A. J. Ilott, R. J. Clément, F. C. Strobridge and C. P. Grey, Chem Mater, 2013, 25, 1723-1734.
Insights into Microwave-Enhanced Cycling Performance of Nickel-Doped LiMn2O4 spinel Cathode Material at Elevated Temperature
Authors: Ozoemena Kenneth I. , Raju Kumar , Nkosi Funeka Phumzile , Mathe Mkhulu K.
Published: February 2020

Lithium manganese oxide (LMO) is a state-of-the-art cathode material for lithium-ion batteries. LMO works well at ambient temperature; however, it undergoes rapid capacity-fading during cycling at elevated temperatures (~55 oC) due to the manganese-dissolution. The last two decades have witnessed a number of strategies reported in the literature (including patents) to mitigate this problem and allow the LMO for large-scale applications. Unfortunately, most of the proposed strategies are either time-consuming or involve extensive use of materials that add to the cost of the final product, and/or require the use of less environmentally-friendly chemicals including very harsh acids that must be handled with utmost caution. There is need therefore to explore the use of simpler, fast, less expensive and ‘greener’ synthesis strategy.

In our work, microwave-assisted solid-state reaction has been used to dope LMO with very low amount of nickel (i.e., LiNi0.2Mn1.8O4, herein abbreviated as LMNO) for lithium-ion battery from Mn3O4 prepared from electrolytic manganese oxide (EMD, g-MnO2). To establish the impact of microwave irradiation on the electrochemical cycling performance at elevated temperature (60 oC), the Mn3+ concentration in the pristine and microwave-treated LMNO samples was independently confirmed by XRD, XPS, 6LiMAS-NMR and electrochemical studies including electrochemical impedance spectroscopy (EIS). In this presentation, we will show that microwave-treated sample (LMNOmic) allowed for the clear exposure of the {111} facets of the spinel, optimized the Mn3+ content, promoting structural and cycle stability at elevated temperature. Importantly, at elevated temperature (60 oC), the LMNOmic gave an improved cycling stability (> 80% capacity retention and ca. 90 % coulombic efficiency after 100 consecutive cycling) compared to the LMNO. For the first time, the impact of microwave irradiation on tuning the average manganese redox state of the spinel material to enhance the cycling performance of the LiNi0.2Mn1.8O4 at elevated temperature and lithium-ion diffusion kinetics have been clearly demonstrated.
Toward a High Temperature V6O13 Based Lithium-Ion Battery
Authors: Meng Wei , Bayley Paul M. , Pecher Oliver , Gaultois Michael , Grey Clare P.
Published: February 2020

V6O13 is a promising Li-ion battery cathode material for application in the high temperature oil field environment. The material exhibits a high capacity, and the voltage profile contains several plateaus due to complex and still unresolved transformations.1 The mechanisms behind the transformations that take place during these voltage plateaus are central to understanding and improving battery performance. In this study we present in situ X-ray diffraction data that highlight an asymmetric six-step discharge and five-step charge process (Figure 1). The LixV6O13 unit cell expands sequentially in c, b, and a directions during discharge and reversely shrinks back during charge. This result sheds light on the high specific capacity of V6O13 and lays the foundation for this material to be used as a cathode for secondary lithium batteries both at ambient and high temperature.

Figure 1