bluuebunny/crossref_metadata_2025 huggingface dataset:
Li2MnO3/Graphene Composite Anode Material for Lithium Ion Battery
Authors: Luo Hongze , Wen Lei
Published: February 2020

Lithium ion batteries have been popularly used as the rechargeable power sources in consumer electronics due to their high energy storage density since the first commercial lithium ion battery launched by Sony in 1991. Graphite is still commonly used as anode material for commercial Lithium ion batteries due to its low redox potential close to Li+/Li, good cycling stability, low cost, and environmental friendliness.[1] However, the performance of current lithium ion batteries, which use graphite as the anode material, cannot satisfy requirements of fast charge Lithium ion batteries. The volume expansion/contraction of the graphite associated with the lithium insertion and extraction process, which results in loss of inter-particle electronic contract, consequently, lead to poor cycling stability. Another consideration of graphite is their safety caused from lithium dendrite formation due to its low Lithium intercalation potential at about 0 V (vs. Li/Li+). [2]

The search for new anode materials for lithium ion batteries has been an important way to satisfy the ever-growing demands for better performance with higher energy/power densities, improved safety and longer cycle life. Recently, Li2MnO3
was investigated as an anode material for lithium ion battery.[3] Li2MnO3 exhibits much higher capacity than conventional carbon-based materials and a very stable cycling performance.

In this work, as-prepared Li2MnO3/graphene composite material shows the enhanced reversible specific capacity and the rate performance compared with that of pristine Li2MnO3
. It was found that the conductivity of Li2MnO3/graphene was significantly improved by forming a conductive graphene network throughout the insulating Li2MnO3.

 References

1. Peled, E., D. Golodnitsky, and G. Ardel, Advanced model for solid electrolyte interphase electrodes in liquid and polymer electrolytes. Journal of the Electrochemical Society, 1997. 144(8): p. L208-L210.

2. Zheng, G.Y., et al., Interconnected hollow carbon nanospheres for stable lithium metal anodes. Nature Nanotechnology, 2014. 9(8): p. 618-623.

3. Wang, D.D., et al., Novel Li2MnO3 nanowire anode with internal Li-enrichment for use in a Li-ion battery. Nanoscale, 2014. 6(14): p. 8124-8129.
Towards Following SEI Formation in-Situ Using Ambient Pressure Photoelectron Spectroscopy
Authors: Maibach Julia , Maripuu Rein , Andersson Margit , Urpelainen Samuli , Schnadt Joachim , Gustafsson Torbjörn , Rensmo Hakan , Edstrom Kristina , Siegbahn Hans , Hahlin Maria
Published: February 2020

Despite the large number of studies targeting surfaces, (buried) interfaces and chemical gradients in battery electrodes, the processes leading to the formation of the solid electrolyte interphase (SEI) are not yet fully understood. Fundamental research on the SEI’s formation process is necessary for controlled design of chemistries that lead to long term stable and functional solid/liquid interfaces in Li-ion batteries. Many of the components suggested to form within the SEI are highly reactive, and may directly upon formation further react with the surrounding components. Since most studies are performed post-mortem meaning after the battery has been taken apart, a missing key point is the study of the SEI formation process in real time. Ambient pressure photoelectron spectroscopy (AP-PES) offers the possibility to obtain more realistic information about the formation of these sensitive interfaces as experiments can be conducted at elevated pressures and with liquids present.

We will present results from our recent advances within the field of characterizing battery materials using AP-PES. This includes a new AP-PES instrumentation developed in Uppsala [1] together with a novel methodology for the direct investigation of the interface between the solid electrode and liquid electrolyte [2]. The latter technique was demonstrated with a Li-ion battery and for the first time enabled the study of the SEI in the Si|LiClO4in PC|Li battery system with the electrolyte present. The results show that the SEI composition for the wet electrode is stable within the probing time and generally agrees well with traditional UHV studies.

Using advanced near ambient pressure cell design at the SPECIES beamline at MAX-lab [3], we have studied Li metal in presence of PC vapor and for the first time in contact to a droplet of liquid PC (see Figure 1). The results from these studies concerning PC adsorption, stability during measurement conditions and radiation exposure are the basis for further electrolyte characterizations and the development of an in-situ electrochemistry cell, which will enable battery electrode cycling directly in the AP-PES setup.

References

[1] S. K. Ericsson et al., Rev. Sci. Inst. 85 (2014), 075111/1

[2] J. Maibach et al., Rev. Sci. Inst. 86 (2015), 044101

[3] J. Schnadt et al., J. Synchrotron Rad. 19 (2012), 701-704

Figure 1
Mechanism of Capacity Fading of Li-Rich Layer-Structured Cathode Materials Based on TEM/Electrochemical Analyses
Authors: Fung Kuan-Zong , Tsai Shu-Yi , Ni Chung-Ta , Huang Bo-Yuan
Published: February 2020

Recently, Li-rich layer-structured cathode formulated as xLi2MnO3 -(1-x)LiMO2(M = Mn, Ni, Co, etc.) exhibit high reversible capacity for Li-ion battery applications. Although Li-rich layer-structured cathode material show a reversible capacity as high as 250 mAh/g, its electrochemical properties such as capacity loss at first cycle, rate capability and capacity fading upon cycling still need to be investigated. A systematic study on crystal structures and electrochemical testing is employed.

In this study, various compositions of xLi2MnO3 -(1-x)LiMO2 (M = Mn, Ni, Co, etc.) were investigated. The electron diffraction pattern of spinel structure was observed from a cycled layer-structured cathode particle. The transition from layered structure to spinel structure may induce a large lattice distortion resulting in lattice breakdown and capacity. Furthermore, the phase transition may be caused by the redox reaction of transition metal ions through repeated cycling tests. Discussion will be carried out based on the results of XRD, SEM, TEM analyses on cycled cathode materials
Fluorine Passivation Layer Generation on Ncm Cathode Powder By Atmospheric Pressure Plasma
Authors: Jeong Hyeon Yeong , You Seungryul , Jung Yong Ho
Published: February 2020

NCM (Ni, Co, Mn Oxide) cathode powder was treated by the gas containing fluorine that is activated by the DBD (Dielectric Barrier Discharge) plasma. Up to 80% of the residual impurities (LiOH, Li2CO3) in NCM powder were removed and a thin film was newly formed on each powder surface at the same time. The major component of the film was identified as fluorine atom by the XPS and SEM-EDX analysis results and the DSC analysis showed that the treatment enhanced the thermal stability of the cathode powder. At the early stage of the treatment, a lot of film seeds were formed on the powder surface. As the treatment time went on, the seeds grew to a complete film and was getting thicker. After the 20 minutes of excessive treatment, the film surface was getting rougher and the thermal stability was getting worse at high temperature range. The reduced charge/discharge capacities of the treated cathode powder was less than about 1.6%, regardless of the treatment time.

Figure 1
Investigation on the Anode Surface of High Specific Energy Li-Ion Batteries
Authors: Chao-xiang Xie , Xin-bin Zhou , De-Chao Jian , Hai-tao Gu , Ke Wang
Published: February 2020

Lithium-ion batteries have become the most popular secondary battery of electric cars, electronic products and power grids with high specific energy and cycle life. Currently, the specific energy density of commercial lithium-ion battery is less than 250Wh / kg, with the continuous development of lithium-ion batteries, the indicator of the next generation of lithium-ion batteries energy density have reached 300Wh / kg. Lithium-ion batteries show good electrical performance advantages, are also facing a number of security issues and challenges, including the thermal decomposition of cathode electrodes , the decomposition reaction of the electrolyte, the surface of the anode electrode and aggregation effect, etc. which have become main factors affecting the security and stability of the cycle.

At present, the carbon materials dominate the anode materials of lithium ion batteries, and high specific energy Li-ion batteries mainly use graphite as the anode material, which enhances the specific energy density due to the high-capacity, long cycle life and high press density. However, this material tends to form lithium deposition in conditions of high C rate, charging at low temperature and higher polarization, and the deposited lithium becomes thicker to form the dendrite, which may penetrate through the separator, causing internal short circuit, even the safety issue.

In this paper, we investigate the mechanism of lithium deposited on the anode surface of high specific energy li-ion batteries(with NCA as the cathode，graphite as the anode) by the  electrochemical method combined with the physical characteristics analysis. From the potential of the battery, measured by three-electrodes and electrochemical analysis tools, the results show that, the lithium deposited on the anode electrode surface is mainly owing to the polarization of cathode and anode. For the charging process, if the polarization is higher enough, the potential of the anode electrode constantly is reduced, even to 0V or less, i.e., the lithium will be deposited on the anode surface. The investigation also shows that, using the method of pre-charge can maintain the anode potential above 0V, and it can effectively suppress the deposition of metal lithium on the anode electrode surface.

Figure 1
In-Situ Fabrication of MS (M = Co and Ni) Nanomaterials Anchored on Graphene for Reversible Lithium Storage
Authors: Tan Yingbin
Published: February 2020

We report a facile method to synthesize highly dispersive MS (M = Co and Ni) nanomaterials anchored on graphene sheets as an advanced anode material for reversible lithium storage. The obtained MS (M = Co and Ni) nanomaterials and graphene formed a sheet-on-sheet composite structure (Figure 1), which can not only facilitate ions/electrons transport along the interfaces, but also effectively prevent MS nanomaterials aggregation during the lithium storage processes. As a result, the graphene-supported CoS nanofibers and NiS nanosheets exhibit a high reversible capacity of 939 and 521 mA h g-1, respectively, with a Coulombic efficiency of over 98 % after 100 cycles at a current density of 100 mA g-1(Figure 2).

The excellent lithium storage properties of the MS-graphene composites can be attributed to the layered structure of the MS-graphene composites possessing the larger electrode-electrolyte contact area, the shorter ionic diffusion length and the easier transportation of lithium ions. This strategy of generating the composite structure can be extended to synthesize other metal sulfides-graphene nanomaterials for lithium-ion batteries.

Figure 1
Silyl and Silyl/Carbonate Blend Electrolytes for Lithium-Ion Battery Applications
Authors: Lyons Leslie J. , Peña Hueso Adrián , Johnson Tobias , West Robert
Published: February 2020

Novel silyl solvents as components of electrolytes for lithium-ion batteries have improved lithium ion transport and safety in comparison to the conventional carbonate solvents most in use in lithium-ion electronic devices.1 This presentation will explore the ion transport of a variety of electrolytes composed of the silyl solvent families (generic structures shown in Figure 1): silyl glycol molecules where the number of ethylene oxide chain units on the silyl fragment has been varied as well as the number of carbons bonding the ethylene oxide chain to the silicon, and silyl nitrile molecules where the salt solvating moiety is a nitrile functionality instead of a glycol.  Electrolytes of the silyl solvents with the salts LiPF6, LiTFSA, and LiBOB have been prepared and their variable temperature ionic conductivities measured by impedance spectroscopy.  Ionic conductivities of electrolytes at 25°C range from 1.1 to 2.5 mScm-1 for salt concentrations at 0.8 M or 1 M.  Based on these promising ionic conductivities, we have prepared a variety of solvent blend electrolytes in which the silyl solvent is mixed with conventional battery solvents such as the cyclic carbonates ethylene carbonate (EC) or propylene carbonate (PC), linear carbonates ethyl methyl carbonate or diethyl carbonate, and γ-valerolactone or methyl butyrate.  In general, ionic conductivities of the silyl solvent/carbonate blend electrolytes increase in comparison to the comparable electrolyte of the pure silyl solvent achieving ionic conductivities at 25°C of 5-6 mScm-1.  We have also measured variable temperature lithium and anion diffusion in PFG-STE NMR experiments which yield lithium and anion transference numbers.  Lithium transference numbers in silyl electrolytes are higher than those in analogous cyclic carbonate electrolytes.  From both the ionic conductivity and NMR diffusion measurements, we have calculated the extent of ion dissociation in these electrolytes.  We will report on the trend for lithium transference numbers and ion dissociation over the temperature range of 300 to 330 K for a number of electrolyte blends.  We also report the viscosities, glass transition temperatures, and dielectric constants of the silyl solvents which impact the variations in ion transport we find for the lithium salt electrolytes.  Full carbon/lithium cells of some of these electrolytes have been prepared and cycle well. 

1L. Zhang, L. Lyons, J. Newhouse, Z.
 
Zhang, M.

Straughan, Z. Chen, K. Amine,

R. Hamers,

and R. West J. Mater. Chem., 2010, 20, 8224-8226.

Figure 1
Organosilicon-Based Electrolytes with Superior Thermal and Electrochemical Stability to Enable High Energy Lithium Ion Batteries
Authors: Usrey Monica Lee , Peña Hueso Adrián , Du Peng , Zhou Liu , Johnson Tobias , Hamers Robert J , West Robert
Published: February 2020

Organosilicon (OS) electrolytes have been developed as a viable alternative to conventional carbonate electrolytes for lithium ion batteries. A recent trend in the Li-ion industry toward adoption of new materials, including electrolytes, is driven by the desire to deploy larger capacity batteries under broader operating conditions.  In addition, the development of new advanced Li-ion chemistries to meet these requirements often require electrolytes with enhanced thermal and electrochemical stability that provide performance across a wide temperature range. This novel organosilicon chemistry involves the merging of a silane with a lithium coordinating functionality. This combination results in solvents comprised of low molecular-weight molecules and having unique properties including high thermal stability, high flash point, low vapor pressure and relatively low viscosities. 

Recently, Silatronix has developed an entirely new class of OS molecules to provide new (patent pending) “Gen-3” solvents whose thermal, chemical, and electrochemical properties greatly surpass those of the earlier suite of OS compounds. Multiple structural variations from the “Gen-3” OS family showcase greatly enhanced stability and performance attributes. Specific examples of performance improvement include higher conductivity and lower viscosity while concomitantly providing superior thermal stability with LiPF6 and reduced gassing. 

In this work, we demonstrate the superior stability and performance attributes of the “Gen-3” family of molecules. For this we have evaluated the physical properties, thermal and electrochemical stability, and performance in coin and pouch cells across a wide temperature range with a variety of electrode materials. This work focuses on exploring the fundamental mechanisms underlying the enhanced stability, including a unique solvation sphere which provides salt stabilization and enhances the stability of all electrolyte components.
Understanding the Roles of Electrolyte Additives on the Surface Modification Mechanism of Silicon-Based Anodes in Lithium-Ion Batteries
Authors: Xu Chao , Lindgren Fredrik , Dupre Nicolas , Lestriez Bernard , Guyomard Dominique , Edström Kristina , Gustafsson Torbjörn
Published: February 2020

Silicon is considered as a promising candidate of the anode material for the next generation lithium-ion batteries, due to its substantially higher gravimetric and volumetric capacity compared to conventionally used graphite. Electrolyte additives, fluoroethylene carbonate (FEC) and vinylene carbonate (VC) particularly, are usually applied for silicon-based lithium-ion batteries to tackle the problems such as poor capacity retention and low coulombic efficiency.1-3 In the present work, the decomposition mechanism of FEC as well as the surface modification of Si electrodes were investigated.4 It was observed that the FEC additive degrades at a higher reduction potential prior to the other carbonate solvents. A conformal solid electrolyte interphase (SEI), which consists of the decomposition products of FEC, is instantaneously formed on the silicon electrode as a result. This stable SEI layer sufficiently limits the emergence of cracks and suppresses the additional SEI formation from the decomposition of other electrolyte components. Both of these effects lead to a slower increase in polarization, thus a slower capacity fading, for the FEC containing cell. The differences in the SEI layer, formed with or without the presence of FEC, are schematically demonstrated in Fig 1. Besides, it was also observed that the LiPF6 decomposition can be influenced with the presence of FEC, and this was further studied with a combination of X-ray photoelectron spectroscopy (XPS) and solid-state nuclear magnetic resonance (NMR) techniques.

We also demonstrated that by forming an effective SEI layer with the FEC and VC electrolyte additives, the silicon electrodes can be equally well functioning with a novel lithium 4,5-dicyano-2-(trifluoromethyl)imidazolide (LiTDI)-based electrolyte as with the state-of-art LiPF6-based electrolyte.5

Figure 1
Microwave Sintered Cubic Si-Doped Li7La3Zr2O12 with Improved Li-Ion Conductivity and High Density
Authors: Xu Dinghao , Wu Yongmin , Tian Wensheng , Tang Weiping
Published: February 2020

Microwave Sintered Cubic Si-Doped Li7La3Zr2O12 with Improved Li-Ion Conductivity and High Density

XU Ding-hao, WU Yong-min, TIAN Wen-sheng, TANG Wei-ping

(Shanghai Institute of Space Power-Sources,
Shanghai 200245, China)

High energy density and high security batteries have been widely used in intelligent has been widely used in intelligent devices and power and energy areas. With significant advantages on the specific energy and safety by using a solid electrolyte, all solid state lithium batteries are the future direction of development. Among all solid electrolytes which are suitable for all solid state lithium battery, Li7La3Zr2O12(LLZO) with its high theoretical density, small grain boundary impedance and low interfacial reaction dendrite probability has become an extremely promising material. In order to obtain a high density of Li7La3Zr2O12, calcinations is the primarily preparation method. The sintering temperature is higher than 1200℃ and sintering time is more than 30 hours. The calcinations can be repeated to reduce porosity. At the same time, in order to improve the ion conductivity of the interface and reduce grain boundary surface of the lithium-ion overflow barrier, it generally doped zirconium-bit or lanthanum-bit types of metal elements such as Ta, Nb, Hf, Al, etc, so as to reduce the structural barriers and improve ion transmission capacity. Microwave reaction is particularly suitable for the manufacture of high density material because of its high efficiency high heating rate and high reaction uniformity. Therefore, we chose to use the microwave sintering method, the auxiliary powder tab letting process, at a temperature of 900℃ and no more than 12 hours, to obtain high purity cubic Li7La3Zr2O12. This method greatly improves the efficiency of the reaction. At the same time, an amount of Al, Si oxide is adding to the powder through ball mill. These oxides adjust the microwave absorption rate of each micro region, thereby improving reaction uniformity. On the basis of improve the density of the solid electrolyte film, doping at the A-bit and C-bit can increase lattice size, improve cell symmetry, increase vacancy concentration and improve lithium ion transport kinetics rate of the solid electrolyte. The results show that the doped Li7La3Zr2O12 prepared by microwave method oxygen, its room temperature ionic conductivity is about 0.7ms/cm. this method with advantages of low energy consumption, high reaction efficiency can not only promote the all solid-state lithium battery technology, but also be applied to the preparation of Li1.4Al0.4Ti1.6(PO4)3, Li10GeP2S12 and other types of solid electrolyte so as to broaden the research and development ideas of the solid electrolyte material.
Novel Ionic-Liquid Type of Polymer Electrolytes for Lithium Batteries
Authors: Zhang Chaofu
Published: February 2020

The rapid growing market of electric transportation i.e. electric vehicles, laptop and cellular phones, has raised a large interest in safety of lithium batteries in the recent years. So, much attention has currently been paid to the solvent-free batteries, especially the case of solid-state batteries, which are made of inorganic solid components, and of batteries using solvent-free polymer electrolytes. In lithium battery field, solvate lithium ionic liquids are a new class of room-temperature ionic liquids (ILs), who exhibit desirable properties, including high lithium transport, high Li+ capacity and improved oxidative stability. Lithium ILs type solid polymer electrolyte which improve the performance is attributed to the weak static interaction between Li+ and the counter ion, and the immobilized anions  therefore might lead to a favored cationic charge transport.
Is Succinic Anhydride a Successful Additive for Graphite/Lmno Cells?
Authors: Charton Christopher , Santos Pena Jesus , Biller Agnès , LE Digabel Matthieu , Lemordant Daniel , Galiano Hervé
Published: February 2020

Nowadays lithium-ion batteries (LIBs) are widely used in nomad applications and electric vehicles. There are a lot of developments focused on electrode materials to improve the energy density. Lithium nickel manganese oxide (LMNO) is currently considered as one of the most promising cathode material for future 5 V lithium ion batteries. Nevertheless common electrolytes which are based on mixtures of alkylcarbonates containing LiPF6 as salt are strongly oxidized at the LMNO cathode [1]. As a result, battery performances are very limited. To improve the high voltage tolerance of the electrolyte, various formulations have been developed. Electrolyte additives can affect the reactions of decomposition of the electrolyte leading to the formation of a protective passive layer on the surface of the active material. Succinic anhydride (SA) seems to have a beneficial effect in LMNO based cells, lowering significantly capacity losses (or enhance capacity retention) and improving battery cycling life and the coulombic efficiency [2]. However, the role of SA on electrode/electrolyte interfacial mechanisms isn’t fully understood in graphite/LMNO cells. In this communication, the influence of SA as electrolyte additive is studied in various type of cells (half, full or symmetrical cells) based on LMNO and graphite electrodes. Preliminary results showed that SA does not operate efficiently at 20°C in EC:EMC – LiPF61 M mixture (see figure 1) in Li/Gr and Gr/Gr symmetrical cells. This study is completed by identifying the nature of electrolyte degradation products formed upon cycling (GC-MS analysis) and characterizing the protective layer on the surface of electrodes (X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS)).

[1] J. Demeaux, E. De Vito, M. Le Digabel, H. Galiano, D. Lemordant and B. Claude-Montigny, ECS Transactions
2013, 53, 5-21.

[2] V. Tarnopolskiy, J. Kalhoff, M. Nádherná, D. Bresser, L. Picard, F. Fabre, M. Rey and S. Passerini, Journal of Power Sources
2013, 236, 39-46.

Figure 1
One-Pot Synthesis of Chemically Bonded NaTi2(PO4)3/rGO 2D Nanocomposite for Sodium-Ion Batteries
Authors: Roh Ha-Kyung , Kim Myeong-Seong , Lee Geon-Woo , Kim Kwang-Bum
Published: February 2020

Abstract

NASICON-structured NaTi2(PO4)3 has been considered as  an outstanding potential cathode material for Na-ion batteries (NIBs) because of its good Na-ion intercalation reversibility and extremely small structural changes during charge/discharge cycling.1 Despite these advantages, NaTi2(PO4)3 suffers from intrinsically poor electronic conductivity, which leads to poor charging/discharging rate performance of NIBs. Up to now, several effective ways have been proposed to improve the electrochemical properties such as specific capacity and cycling stability, including reduction of the particle size to nanoscale, the addition of a surface coating and the synthesis of composite materials with conductive carbons.2

In particular, the composites of NASICON-structured materials with carbonaceous materials such as mesoporous carbon and graphene of reduced graphene oxide (rGO) has been recently proposed to enhance electronic conductivity of the electrode for improving the cycling performance.3 Graphene acts as a template due to its high specific surface area not only to deposite nano-sized metal oxide but also to connect the nano particles along a 2-dimensional conduction path. Furthermore, graphene can provide a void space against the volume changes of the metal oxide particles during lithium ion insertion/extraction process, which can improve the cycling performance. However, previously reported methods to fabricate of these composites require multistep, time-consuming processes, and complicated.4 Moreover, in this multistep method, the sodiation and heat treatment steps unfavorably affect the size, morphology and homogeneity of the resulting NaTi2(PO4)3 particles. Accordingly, their electrochemical properties showed only a marginal improvement compared with the bare NaTi2(PO4)3.

In this study, we have developed a phase-pure NaTi2(PO4)3/rGO nanocomposite through a facile one-pot synthesis based on microwave-assisted solvothermal synthesis, in which rGO was used to selectively heat the substrate to facilitate the preferential precipitation of NaTi2(PO4)3 nanoparticles (30-40 nm). Ti-O-C bonds formed during the synthesis process, which could efficiently transfer the electrons from the NaTi2(PO4)3 nanoparticles to rGO substrates. The strongly bonded NaTi2(PO4)3/rGO nanocomposite prepared in this study exhibited an excellent rate capability and good cyclability as an anode material for SIBs.

References

1. Il Park et al, J Electrochem Soc
2011,
158, A1067.

2. Pang, G. et al, J Mater Chem A
2014,
2, 20659.

3. Li et al,J Electrochem Soc
2014,
161, A1181.

4. Pang, G. et al, Nanoscale
2014,
6, 6328.

Figure 1
Silicon Nanowires-Based 3D Anodes for High-Capacity Lithium Ion Batteries
Authors: Schneier Dan , Peled Emanuel , Patolsky Fernando , Golodnitsky Diana , Freedman Kathrin , Davidi Guy
Published: February 2020

We report on the scalable synthesis and characterization of novel architecture three-dimensional high-capacity amorphous SiNWs-based anodes, with focus on studying their electrochemical degradation mechanisms. We achieved an unprecedented combination of remarkable performance characteristics, high loadings of 3-25 mAh/cm2, a very low irreversible capacity (10% for the 3-4 mAh/cm2 anodes), current efficiency greater than 99.5%, cycle stability both in half cells and a LiFePO4 battery and fast charge–discharge rates (up to 2.7C at 20mA/cm2). These SiNWs-based binder-free 3D anodes have been cycled for over 500 cycles, exhibiting a stable cycle life. Notably, it was found that the growth of the continuous SEI layer thickness, and its concomitant increase in resistivity, represents the major reason for the observed capacity loss of the SiNWs-based anodes, as we demonstrate by cleaning and reusing cycled anodes. We also demonstrate the effects of different types of coatings on SEI and cycling stability. Our data reveal that NWs-based anodes of novel architecture are expected to meet the requirements of lithium-ion batteries for both portable and electric-vehicle applications.
Dynamic Study of (De)Sodiation in Tunnel-Based Manganese Oxides and the Capacity Retention Via Voltage Control
Authors: Yuan Yifei , Ma Lu , He Kun , Yao Wentao , Nie Anmin , Bi Xuanxuan , Wu Tianpin , Lu Jun , Amine Khalil , Shahbazian-Yassar Reza
Published: February 2020

Developing advanced cathode materials for sodium ion batteries (NaIBs) with stable host structure and reliable capacity performance during cycling is crucial for the commercialization of NaIBs.[1] Nanostructured MnO2 is one competitive cathode candidate due to its low cost, environmental friendliness, and various open-framed polymorphs to facilitate cation insertion and extraction.[2] α-MnO2, which features 2×2 tunnels with 4.6×4.6 Å2 cavity, has recently become one research focus as such a tunneled structure in nanoscale was reported to be suitable for Na+ transport.[3] However, α-MnO2 suffers from structure instability, low coulombic efficiency and quick capacity decay during cycling, which prevent its further application to a large extent. The causes of these problems should be directly related to the repetitive tunnel-Na+interactions during (de)sodiation, which is currently poorly understood.

In this work, the (de)sodiation of α-MnO2 nanowires is dynamically studied and well understood using in situ TEM with an open cell design. The morphology, phase and structure of the electrode are characterized and recorded in real time. It is found that the sodiation starts with Na+ intercalation into the 2×2 tunnels without tunnel degradation up to Na/Mn equaling 0.5 (Mn3.5+). Then α-MnO2 phase gradually evolves into an intermediate Na0.5MnO2 phase. Upon deep sodiation to Na/Mn equaling 1 (Mn3+), the structure totally collapses and degrades to polycrystalline Mn2O3 and Na2O. The following (de)sodiation cycles confirm that the tunneled structure, once destroyed, can not be recovered, and the following cycles are dominated by the conversion reaction between Na0.5MnO2 and Mn2O3, whose reversibility is poor. 

The galvanostatic voltage profile at bulk level coin cells shows that the intercalation reaction featuring a slope profile happens between 4-1.4 V, while the conversion reaction featuring a plateau region is below 1.4 V. Based on this, the cycling voltage windows of the Na/MnO2 coin cells are set to above 1.5 V to maintain the original tunneled structures of α-MnO2 for reversible Na+(de)intercalation. This voltage control results in the prominent capacity retention of the batteries compared to those cycled below 1.5 V, whose capacity decays very fast. The coulombic efficiency is also obviously improved when the cells are cycled above 1.5 V.

References:

[1] Chem. Rev., 2014, 114, 11636–11682

[2] Nano Lett., 2015, 15, 2998–3007

[3] Nano Energy, 2016, 19, 382-390.

Figure 1
Tuning the Polysulfides Chemistry in Li-S Batteries Via Electrolyte Salt Selection
Authors: Chen Junzheng , Han Keesung , Henderson Wesley A , Vijayakumar Murugesan , Lau Kah Chun , Dzwiniel Trevor L , Pan Huilin , Curtiss Larry A , Xiao Jie , Mueller Karl T , Shao Yuyan , Liu Jun
Published: February 2020

Fast capacity fading due to polysulfide dissolution is a significant challenge for Li-S batteries. Porous carbon is widely studied for physically trapping polysulfide species. Here, we report a different chemical approach through suppressing polysulide dissolution using lithium 2-trifluoromethyl-4,5-dicyanoimidazole (LiTDI) as a supporting salt in electrolytes. The electrolyte to sulfur ratio(E/S) is carefully controlled and the results show that under the optimized E/S ratio the cycling stability of the lithium sulfur cell is improved in the LiTDI supported electrolyte. The  Combined experimental and simulation results reveal the dissolution mechanism of lithium polysulfides and suggest that the dominating disproportionation product of Li2S8 is Li2S4 in the LiTDI electrolyte due to a coordination between Li+ and TDI anion, rather than separated Li2S3 and Li2S5 as in the LiTFSI electrolyte. The Li2S4 would continuously form a Li4S8 dimer and precipitate out. Detailed DFT calculation and Li NMR results suggest lithium ion cation has a higher solvation level in the TDI based electrolyte. Furthermore, the Li-S cells with LiTDI based electrolyte with optimized sulfur to electrolyte ratio was firstly applied into a high loading cathode and achieve a stable cycling. The use of the electrolyte with the LiTDI salt (with polysulfide and LiNO3 additives) enables a cell with a high sulfur loading (3 mg-S cm-2) to deliver a 1.67 mAh cm-2 areal capacity after 300 stable cycles at a high current (2.4 mA cm-2) density. The fading of Li metal anode is also suppressed. 

Figure 1 Capacity retention of cells with (a) 1M LiTFSI and (b) 1M LiTDI in DOL/DME electrolytes (no additives) with different sulfur to electrolyte (S/E) ratios at a C/5 rate. 1C = 1675 mA g-1 of S and the cathode was prepared with 64 wt% S (i.e., S8), 16 wt% MWCNTs, 10 wt% Super P carbon additive and 10 wt% PVDF binder.

Figure 1
Effects of Cell Construction Parameters on the Performance of Lithium-Air (Li-O2) Batteries
Authors: Lee Jung-In , Song Min-Kyu
Published: February 2020

Lithium ion batteries (LIB) are widely used in small portable devices and still represent one of the best options available for large-scale power sources such as electric vehicles (EVs) and renewable energy storage systems (ESS). The low theoretical specific energy (~400 Wh Kg-1) of current LIB is insufficient for emerging technologies, thus many researchers have investigated novel battery systems with high specific energy to replace current LIB. Among various candidates, lithium-air (Li-O2) batteries have received much attention due to the very high theoretical specific energy (~3500 Wh kg-1, Li2O2), abundant oxygen source and simple reaction chemistry (2Li+ O2 + 2e- à Li2O2, Eo = 2.96V vs. Li/Li+). Although the advantages of Li-O2 batteries are attractive, the practical adoption of Li-O2 batteries has been restricted by a large irreversible capacity, poor cycle retention characteristics, and low energy efficiency due to the large hysteresis of charge/discharge and side reactions between battery components.

 Here, we report our recent findings in exploration of new electrolytes and oxygen cathodes in order to develop Li-Air batteries with sustainable, high-energy density. We investigated the performance of Li-O2 batteries using various porous carbon materials, electrolytes based on both organic and ionic liquids, and additives such as redox mediators. Various carbon substrates (such as Super-P, CNT, graphene and Ketjen black, Figure 1) were used to construct a porous cathode structure. It appears that their electrochemical properties (relevant to Li-Air batteries) are different due to their dissimilar morphology and surface area. We also conducted experiments with various electrolytes including some additives (LiNO3, LiI, etc.) as shown in Figure 2. Ionic liquids are promising electrolytes owing to relatively high electrochemical and chemical stabilities, along with safety benefits and environmental friendliness. Recently, the use of redox mediators has been identified as a promising route for reducing the overpotentials of the charge process. Based on these studies, we also investigated the effects (nature and concentration) of solvents (ionic liquids, ethers, and their mixtures) and redox mediators in electrolytes on the charging potential and reversibility of oxygen cathodes. Furthermore, we have used different porous carbon fiber papers as both a current collector and gas diffusion media. It appears that the physical oxygen diffusion property is closely linked to the capacity and cycling performance of Li-Air batteries due to the different sizes and connectivity of pores in different gas diffusion media. Electrochemical characterization techniques were combined with microanalysis (SEM, XRD) to optimize the electrode structures and performance. It is hoped that this study will provide some useful insights to the design criteria for high-performance Li-Air batteries.

Figure 1
Flexible Fibrous Substrates for Li-S Battery Cathodes
Authors: Musameh Mustafa , Chew Narelle , Truong Yen , Barghamadi Marzi , Ruether Thomas , Bhatt Anand , Hollenkamp Anthony F. , Best Adam Samuel , Kyratzis Illias Louis
Published: February 2020

Electrically and non-electrically conductive fibrous substrates have been investigated for the preparation of S cathodes. For nonconductive substrates such as wool and glass membranes, cathodes were prepared by spraying a mixture containing sulfur, carbon black and a polymer such as polyacrylic acid or PVDF. The preparation process is fast and well suited for large scale production of large cathodes with uniform coating and good adhesion. High sulfur loading of 55% or higher was possible by using this process. Cathodes prepared by spraying were assembled into 2032 coin cells with a Li anode, Solupor separator and an ionic liquid based electrolyte. Cycling of cells at the C/10 rate showed high initial discharge capacities, close to 1500 mAh g-1, with good stability.

Sulfur cathodes were also prepared by electropolymerisation with electrically conductive substrates such as carbon fibre cloth and fine stainless steel mesh. For electropolymerisation, a solution containing sulfur, carbon black, Nafion, pyrrole monomer and a dopant like sulfate is prepared. Cathodes were readily prepared by applying a potential for a certain period of time while mixing the solution. The loading of sulfur can reach up to 30% based on the amount of sulfur in the starting solution. The prepared cathodes showed high initial discharge capacities of 1500 mAh/g along with a coulombic efficiency of 97%.   

The use of such fibrous substrates adds another dimension to sulfur cathode technology by providing more control over the content and nature of active functional groups, surface porosity, and morphology. Each of these factors can be employed to counter the problem of polysulfide shuttling by enhancing the retention of sulfur reduction products within the cathode. In addition substrates which are electrically non-conductive can act both as a cathode and separator at the same time, without the need for an additional physical separator, by simple re-arrangement of the cell’s active components.
Research on Cell Chemistry of Sodium-Oxygen Battery for Improved Electrochemical Performance
Authors: Zhao Ning , Guo Xiangxin
Published: February 2020

Developing sodium-oxygen (Na-O2) batteries with high energy efficiency depends on identifying stable solvents resistant to decomposition. Here, we focus on the solvent stability against Hydrogen-abstraction by superoxide radicals during discharge. Using a detailed quantitative analysis, we show that the solvent’s resistance to H-abstraction is determined by its acid dissociation constant, pKa. The ether (TEGDME)-based electrolyte with a larger pK
a value (i.e. 46-52) leads to form a much larger percentage of NaO2 among the discharge products than the carbonate (EC/PC with pK
a of 20.9) and the ionic liquid (PP13TFSI with pK
a of 30.0)-based ones. It is indicated that the larger value of pK
a corresponds to the better electrolyte stability, beneficial to high round-trip efficiency of the Na-O2 battery.

Based on these results, the cyclability and rate-capability of Na-O2 batteries with TEGDME-based electrolyte have been optimized under various operation conditions. Under static O2/Ar atmosphere, they exhibit high energy storage (i.e. capacity of 4200 mAh g-1 at 0.1 mA cm-2), excellent cyclability (i.e. the batteries cycle 130 times with 750 mAh g-1 depth of discharge at 0.1 mA cm-2) and good rate performance (i.e. ~1500 mAh g-1 at 1.0 mA cm-2 with pre-deposition of a NaO2 nucleus layer). Such high performance indicates the importance of stable electrolyte and operating condition for high performance Na-O2 batteries. Further, the fundamental issues associated with the phase transformation from NaO2 to Na2O2·2H2O will be discussed in this presentation.
Improved Electrochemical Performance By Templating Carbon-Sulfur Composite Electrodes for Lithium-Sulfur Batteries
Authors: Robledo Carla Belen , Cámara Osvaldo Raúl , Thomas Jorge , Leiva Ezequiel Pedro Marcos , Harks Peter-Paul , Mulder Fokko M. , Visintin Arnaldo
Published: February 2020

Replacing fossil energy sources by renewable and clean energies is of large importance for decades to come. The mainly electric and intermittent renewables energies require proper electricity storage systems that must be: clean, economical, efficient, long life, safe and have high specific capacities (mass and volume). For Argentina, with its significant reserves of lithium in the north west of the country, developments on lithium-ion battery technology are of paramount importance. Current research in Argentina is carried out to improve future lithium battery prospects. Focus is on development and characterization of new active materials for Li-ion battery electrodes, and on systems beyond Li-ion. Li-S batteries are promising candidates to replace current Li-ion technology. In the case of C-S composite cathodes, there are several factors regarding the composition and structure that affect the performance of the battery. Nonetheless, little is known on how the architecture of the composite electrode influences the electrochemical performance of the battery. The present work consists of a systematic investigation of the influence of two very important factors regarding composite electrode fabrication and cell assembly. The factors that are considered are the electrode architecture, modified by templating, and the electrolyte to sulfur ratio. A full factorial two-by-three experimental design is employed, considering five response variables: the initial and final specific capacity of the sulfur cathode, the specific capacity loss per cycle, as well as the initial and final cell energy density. All battery cells are tested for 100 cycles galvanostatically with a C/10 current. Statistically significant factors and their interactions are identified.
3D-Printed Cathodes of LiMn1-XFexPO4nanocrystals Achieve Both Ultrahigh Rate and High Capacity for Advanced Lithium-Ion Battery
Authors: Hu Jiangtao , Jiang Yi , Cui Suihan , Duan Yandong , Liu Tongchao , Guo Hua , Lin Yuan , Zheng Jiaxin , Amine Khalil , Pan Feng
Published: February 2020

We developed a 3D-printing technology and printed 3D lithium-ion batteries (LIBs) based on LiFe0.79Mn0.21PO4@C nanocrystal cathodes to achieve both ultrahigh rate and high capacity. Coin cells with 3D-printedcathodes showed impressive electrochemical performance: a capacity of 108.45mAh g-1 at 100C, and reversible capacities of 150.21and 140.67 mAh g-1at 10Cand 20C after 1000cycles.APseudo Two-Dimensional Hidden Markov Model (P2D-HMM) was employed to clarify the relationship between layer number (i.e., thickness) and efficiency porosity of the electrode material and the rate performance and to better understand the mechanism behind both ultrahigh rate and high capacityperformance. The calculations indicate that factors such assolution intrinsic diffusion coefficient, efficiency porosity, and electrode thickness play a dominant role in the equivalent diffusion coefficient with the electrode beyond a certain thickness, which determines the whole kinetic process in LIBs. This fundamental studyshould provide helpful guidance forfuture design of LIBs with both high capacity and rate capability.
New Procedures to Improve Tap Density of Li-Rich Layered Cathode Materials for Li-Ion Batteries
Authors: Zhang Lianqi
Published: February 2020

A significant drawback for Li-rich layered materials is the low tap and compaction density in contrast to layered LiMO2[1]. Thus, improving tap density is an important issue for Li-rich layered materials. In our work, some efforts are contributed to addressing the issue. On one hand, a new pre-heat treatment procedure of carbonate precursors firstly using N2 and then O2 is adopted to separate processes of CO2 emission and O2 absorption, which presumably can reduce porosity of materials and then result in an improved tap density. The remarkably improved tap density of metal oxide (2.20 g cm–1) and cathode material (2.20 g cm–1) is observed with the procedure. However, it is at a cost of capacity. On the other hand, the dual chelating agents, ammonia and oxalate, which have a synergistic action on chelating transition-metal ion, are successfully introduced to prepare high tap density hydroxide precursors (1.67 g cm–3) and Li-rich cathode (2.28 g cm–3) with atomic level uniformity of elemental distribution.

From Fig.1 (b) and (c), it is obviously found that the two-steps procedure is indeed beneficial for obtaining the dense morphology with less pores, resulting in a higher tap density. From Fig.2, with the function of the dual chelating agents, the spherical secondary particles with dense morphology, which are closely aggregated from nano-sized primary particles, are demonstrated to be obtained. 

References

[1] P.Oh, S. Myeong, W. Cho, M.-J. Lee, M. Ko, H.Y. Jeong, J. Cho, Nano Lett. 14 (2014) 5965−5972.

Figure 1