Metallic Anode Materials Research Articles

Open the Window to Lithium Detection and Nanostructure Analysis

Abstract The features and benefits of a new cutting-edge windowless energy-dispersive detector (EDS) detector are introduced. This innovative technology provides fast results at high signal-to-noise with ultra-high analytical spatial resolution. The benefits are demonstrated through examples of nanostructures from various nanoscale devices including lithium metal anode specimens. Using windowless EDS detector technology allows for the efficient collection of EDS data under the same conditions used for high-resolution imaging (low accelerating voltage, low probe current, and short working distance). Examples include cross sections of lithium metal anode materials prepared with a broad argon ion beam and using an air-isolated workflow. The analyses of the cycled and pristine lithium-ion battery (LIB) materials are shown, along with the contrast results of crystal-shaped impurities found within these materials.

A high-capacity Sn metal anode for aqueous acidic batteries

•Sn metal with high capacity and low potential as qualified anode for acidic battery •“Dead Sn” issue during Sn anode cycling has been identified and solved •Interfacial alloying regulation improves deposition uniformity and reversibility •Sn anode can be matched with various cathodes and delivers good performances Aqueous acidic batteries are a good choice to respond to battery diversity, delivering safety, cost, environmental friendliness, and high-power necessary for renewable energy storage. However, the practical adoption is greatly challenged by low voltage and energy density due to the inadequate metal anode materials. Here, we report an interfacial regulated Sn metal anode as the solution of the last piece of the puzzle. The ease of recycling, low potential, fast redox kinetics, and high capacity of Sn perfectly fit the battery system, and the Sn metal shedding critical issue is successfully suppressed by promoting uniform deposition for added interaction from alloying. Consequently, this reversible Sn anode with 442 mAh g−1 matches well to different types of cathodes. The as-assembled acidic batteries also demonstrate sufficient output voltage (up to 1.7 V), energy density (up to 312 Wh kg−1 based on both electrodes), kinetics (up to 24 C), and stability (up to 2,400 cycles). Aqueous acidic batteries are a good choice to respond to battery diversity, delivering safety, cost, environmental friendliness, and high-power necessary for renewable energy storage. However, the practical adoption is greatly challenged by low voltage and energy density due to the inadequate metal anode materials. Here, we report an interfacial regulated Sn metal anode as the solution of the last piece of the puzzle. The ease of recycling, low potential, fast redox kinetics, and high capacity of Sn perfectly fit the battery system, and the Sn metal shedding critical issue is successfully suppressed by promoting uniform deposition for added interaction from alloying. Consequently, this reversible Sn anode with 442 mAh g−1 matches well to different types of cathodes. The as-assembled acidic batteries also demonstrate sufficient output voltage (up to 1.7 V), energy density (up to 312 Wh kg−1 based on both electrodes), kinetics (up to 24 C), and stability (up to 2,400 cycles).

Facile design of alloy-based hybrid layer to stabilize lithium metal anode

Lithium (Li) metal has been considered a promising anode candidate for next-generation energy-storage applications due to its ultrahigh capacity. However, the uncontrolled dendrite growth and continuous side reactions challenge the cycle life and practical application. Herein, by a facile and mild solution method, we build a compact LiZn alloy-based hybrid layer on the Li-metal surface. This hybrid layer exhibits favorable chemical stability, excellent wettability to electrolyte, and enhanced thermodynamic affinity to Li. As a result, the hybrid layer modified lihtium metal anode (HL-Li) enables accelerated Li-ion diffusion kinetics and dense Li deposition. Through the operando cell evaluation, moreover, we demonstrate that the hybrid layer restricts the Li dendrite growth of Li metal anodes effectively by reducing the volume expansion to half. Endowed with both thermodynamic and kinetic superiority, HL-Li exhibits low overpotential and prolonged cycles in both symmetric cells and full cells. Our work confirms the lithiophilic hybrid layer obtained by a facile solution process to enable dendrite-free deposition, providing a guidance for the synthesis of high-performance Li metal anode materials.

Lithium Silicates in Anode Materials for Li-Ion and Li Metal Batteries

The structural and interfacial stability of silicon-based and lithium metal anode materials is essential to their battery performance. Scientists are looking for a better inactive material to buffer strong volume change and suppress unwanted surface reactions of these anodes during cycling. Lithium silicates formed in situ during the formation cycle of silicon monoxide anode not only manage anode swelling but also avoid undesired interfacial interactions, contributing to the successful commercialization of silicon monoxide anode materials. Additionally, lithium silicates have been further utilized in the design of advanced silicon and lithium metal anodes, and the results have shown significant promise in the past few years. In this review article, we summarize the structures, electrochemical properties, and formation conditions of lithium silicates. Their applications in advanced silicon and lithium metal anode materials are also introduced.

Recent advances of non-lithium metal anode materials for solid-state lithium-ion batteries

This review, for the first time, systematically summarizes the application of C, Si, Sn, Bi, metal hydrides and lithium titanate as anode materials in solid-state lithium batteries.

Lithium Metal Deposition and Stripping in Porous Hosts Coupled with Viscous Polymer Electrolytes

High energy density rechargeable batteries are desired to meet global goals of increased use of renewable energy and vehicle electrification. Higher energy densities can be achieved by replacing graphite anodes with metal anodes. Among metal anode materials, lithium metal anodes are promising due to their high theoretical capacity and low reduction potential. However, obstacles such as dendrite growth and continuous electrolyte decomposition need to be addressed for successful commercialization of rechargeable batteries with lithium metal anodes. It is widely reported that porous 3D lithium metal hosts can mitigate dendrite growth by accommodating lithium deposition uniformly within the hosts during cycling. Continuous electrolyte decomposition can also be mitigated by replacing liquid electrolytes with solvent-free electrolytes. We incorporate both strategies in this work to address the critical issues described above by demonstrating lithium deposition/stripping cycling on 3D electrode hosts with viscous polymer electrolytes. First, lithium metal deposition/stripping cycling within non-conductive and conductive hosts were compared, where zinc oxide (ZnO) coated polyacrylonitrile (PAN) nanofibers was used as the non-conductive lithium metal host and ZnO coated copper nanowires were prepared as the conductive lithium metal host. The non-conductive host showed successful cycling of 5 mAh/cm2(25 µm thickness) of lithium metal without short circuiting. Further, deposition/stripping cycling with viscous star polymers (polystyrene-co-poly(polyethylene glycol) methyl ether acrylate (PS-co-PPEGMA)) and a linear oligomer polyethylene glycol dimethyl ether (PEGDME) were compared. The effects of the physical and electrochemical properties of the polymer electrolytes on lithium deposition and interfacial impedance will be discussed.

Electrochemically Engineering Antimony Interspersed on Graphene toward Advanced Sodium-Storage Anodes.

Nanoengineering of metal anode materials shows great potential for energy storage with high capacity. Zero-dimensional nanoparticles are conducive to acquire remarkable electrochemical properties in sodium-ion batteries (SIBs) because of their enlarged surface active sites. However, it is still difficult to fulfill the requirements of practical applications in batteries owing to the deficiency of efficient and scalable preparation approaches of high-performance metal electrode materials. Herein, an electrochemical cathodic corrosion method is proposed for the tunable preparation of nanostructured antimony (Sb) by the introduction of a surfactant, which can efficiently avoid the agglomeration of Sb atom clusters generated from the Zintl compound and further stacking into bulk during the electrochemical process. Subsequently, graphene as the support and conductive matrix is uniformly interspersed by generating Sb nanoparticles (Sb/Gr). Moreover, the reversible crystalline-phase evolution of Sb ⇋ NaSb ⇋Na3Sb for Sb/Gr was studied by in situ X-ray diffraction (XRD). Benefiting from the interconnection of the conductive network, Sb/Gr anodes deliver a high capacity of 635.34 mAh g-1, a retained capacity of 507.2 mAh g-1 after 150 cycles at 0.1 C (1 C = 660 mAh g-1), and excellent rate performance with the capacities of 473.41 and 405.09 mAh g-1 at 2 and 5 C, respectively. The superior cycle stability with a capacity of 346.26 mAh g-1 is achieved after 500 cycles at 2 C. This electrochemical approach offers a new route toward developing metal anodes with designed nanostructures for high-performance SIBs.

A stable carbon host engineering surface defects for room-temperature liquid Na[sbnd]K anode

Alkali metal anode (Li, Na, K) are promising anodes for high-energy-density batteries because of high theoretical capacities and low redox potentials. While dendrite growth still restricts practical applications of alkali metal batteries. In contrast, liquid metal anode materials can avoid the problem of dendrite formation. But the poor wettability of liquid metal on most of hosts makes it difficult to assemble cell for the strong surface tension. Herein, we report a treated carbon cloth (denoted TCC) that can fast absorbs liquid NaK alloy at room temperature owing to the enhancing wettability by engineered surface defects of oxygenic groups and nanoscale cracks. When assembled in a symmetric cell with NaK alloy, it renders long cycle life over 1800 h and low voltage polarization below 300 mV compared with Na symmetric cell. When cycling with Na3V2(PO4)3 cathode as full cell, it also exhibits excellent capacity and capacity retention of 87.58% after 1000 cycles at 10 C.

(Invited) Multiscale Analysis of Battery Materials Using X-Ray Microscopy

Battery electrodes are inherently multiscale, functional material systems that provide sites for chemical reactions and pathways for charge and reactant transport. A greater understanding of the interaction between transport phenomena, electrochemistry, and electrode structures is critical to advance battery performance and reliability. Direct microstructural imaging methods provide a unique capability for the multiscale observation of electrode structures and the material changes that occur during battery operation. The microstructural image data produced by these methods also facilitates physics-based simulation informed by real device structures. Applications of X-ray microscopy to battery electrodes at multiple scales are presented. X-ray nanotomography (XNT) and microtomography (µCT) of battery electrode materials are presented for high capacity metallic anode materials and transition metal oxide cathode materials. First, X-ray imaging is presented as a means of assessing the impact of processing methods on electrode structure at nano- and micro-scales. Ex situ and in operando spectroscopic imaging using µCT and nano-scale X-ray absorption near edge structure (XANES) are then presented as a means of assessing multiscale chemical and structural changes in electrodes during cycling. The data obtained through these imaging efforts facilitates modeling of real electrode structures. Modeling efforts informed by the microstructural data obtained are discussed with a focus on Li-ion cathode materials. Observations from modeling are complemented by microstructural analysis that permits description of cathode performance in terms of dimensionless parameters.

Integrated, Flexible Lithium Metal Battery with Improved Mechanical and Electrochemical Cycling Stability

The success of beyond lithium-ion battery (LIB) technologies, i.e., Li oxygen and Li–S cells, depends in large part on the use of metallic anode materials. Metallic lithium, however, tends to grow parasitic dendrites, which would penetrate the separator to cause safety concerns. Moreover, the dendrites are highly reactive to carbonate electrolytes and invariably render a reduced Coulombic efficiency. Here, we propose our design of a dendrite blocking layer with size-tunable Ag nanoparticles (NPs) decorated on the mesoporous SiO2 nanospheres. The synergistic coupling of these complementary components enables the effective regulation of the lithium nucleation behavior via a protected Li–Ag alloying process. The Li plating/stripping process of a symmetric Ag NPs@SiO2-coated Li–metal cell exhibits a reduced voltage hysteresis, facile lithium nucleation process, and enhanced Coulombic efficiencies at various current densities. When the Ag NPs@SiO2-coated copper foil anode was integrated with lithium manganese ...

Toward High Performance Lithium–Sulfur Batteries Based on Li2S Cathodes and Beyond: Status, Challenges, and Perspectives

AbstractLithium sulfur (Li–S) batteries are attracting ever‐increasing interests as a new generation rechargeable battery system with high energy density and low cost. Li–S batteries will fulfill their theoretical potential if the problem of polysulfides shuttle effect can be solved. Therefore, tremendous efforts have been devoted to overcoming this problem from the aspects of physical confinement and chemisorption of polysulfides. Recently, it is discovered that replacing sulfur cathodes with lithium sulfide (Li2S) can not only largely avoid the volume expansion issue during cycling, but it can also work with anode materials other than lithium metal to eliminate serious safety concerns for traditional Li–S batteries. However, there are many challenges for developing practical Li metal‐free Li–S battery systems, because Li2S‐based cathode materials are moisture‐sensitive and prelithiation of the non‐Li metal anode materials is usually required for practical applications. This study reviews the recent advances of Li‐S batteries based on Li2S cathode with features of improved safety, high Coulombic efficiency, and high energy density. The electrode activation processes are also discussed, which is critical for achieving high performances. It is anticipated that the extensive efforts will lead to breakthroughs for the development of Li2S cathode ‐based Li‐S batteries.

Low‐Cost Metallic Anode Materials for High Performance Rechargeable Batteries

AbstractThe ever‐growing market of portable electronic devices and electric vehicles has significantly stimulated research interests on new‐generation rechargeable battery systems with high energy density, satisfying safety and low cost. With unique potentials to achieve high energy density and low cost, rechargeable batteries based on metal anodes are capable of storing more energy via an alloying/de‐alloying process, in comparison to traditional graphite anodes via an intercalation/de‐intercalation process. However, the drawbacks of metal anodes such as high initial capacity loss and short cycling life need to be solved before commercialization. Herein, we mainly dedicate the attention on recent progresses in the metallic materials (e.g., Al, Sn, Mg, Zn, Sb and Bi) which have the best likelihood of being applied in commercial batteries and the advanced modification strategies including nanosizing, composite design, and alloy/intermetallic construction for better battery performance. In addition, the investigations of such metal anodes in some new battery systems such as sodium‐ion batteries, aluminum‐ion batteries, zinc‐ion batteries, magnesium‐ion batteries, and dual‐ion batteries are further briefly reviewed.

Microbial fuel cells: From fundamentals to applications. A review

In the past 10–15 years, the microbial fuel cell (MFC) technology has captured the attention of the scientific community for the possibility of transforming organic waste directly into electricity through microbially catalyzed anodic, and microbial/enzymatic/abiotic cathodic electrochemical reactions. In this review, several aspects of the technology are considered. Firstly, a brief history of abiotic to biological fuel cells and subsequently, microbial fuel cells is presented. Secondly, the development of the concept of microbial fuel cell into a wider range of derivative technologies, called bioelectrochemical systems, is described introducing briefly microbial electrolysis cells, microbial desalination cells and microbial electrosynthesis cells. The focus is then shifted to electroactive biofilms and electron transfer mechanisms involved with solid electrodes. Carbonaceous and metallic anode materials are then introduced, followed by an explanation of the electro catalysis of the oxygen reduction reaction and its behavior in neutral media, from recent studies. Cathode catalysts based on carbonaceous, platinum-group metal and platinum-group-metal-free materials are presented, along with membrane materials with a view to future directions. Finally, microbial fuel cell practical implementation, through the utilization of energy output for practical applications, is described.

In-Situ Monitoring of Stress Development and Electrochemical Behaviour of Metallic Thin Film Anode Materials for Li-Ion Batteries

Due to their high specific capacities and higher (safer) operating potentials, metallic materials such as Sn and Al are among the promising alternatives to graphitic carbon as anode materials for Li-ion batteries. However, the metallic anode materials undergo huge volumetric changes during lithiation/delithiation which leads to the development of stresses that result in severe mechanical degradation and concomitant drastic capacity fade. Furthermore, the stresses affect the thermodynamics of the lithiation/delithiation ‘reactions’ and exert influences on the various electrochemical behaviour. In order to develop better understanding of the origins, magnitudes and resulting effects of such stress developments, in correlation with the initial stress states, crystallographic orientations, stages of lithiation/delithiation, associated phase transformations and surface reactions, we have monitored the stress developments in-situ during lithiation/delithiation. Sn and Al have been selected for the present studies, with the concerned electrodes possessing simple thin film architectures, without binder/additive/porosity. The active electrode films of ~100 nm in thickness have been deposited via e-beam deposition on different current collector films (~100 nm thick), such as Cu (for both Sn and Al), Ni (for Sn) or Ti (for Sn) on thicker (~0.5 mm) quartz substrates (stiff substrate) for allowing monitoring of the in-plane stress developments via substrate curvature technique using multi-beam optical stress sensor (MOSS) in-situ during electrochemical cycling against Li metal in custom-made electrochemical cell [1]. In addition to the expected developments of compressive stresses during lithiation and reverse during delithiation, we focus on some of the finer features of the stress developments, which involves the stress evolution during the first order phase transformations that take place during the Li-alloying reactions (i.e. formation of the various Li-Sn and Li-Al intermetallic) [2]. To develop better understanding, attempt has also been made to mathematically model the observed in-plane stress developments at the different stages (single and two-phase regimes). As will be demonstrated, our observations suggest occurrences of mechanical degradation mainly during the phase transformations, with the electrode materials being fairly stable during the single phase (solid solution) regimes. In order to explore a possible route towards improving the mechanical integrity and cyclic stability upon lithiation/delithiation, the effects of inducing pre-cycling residual stresses via simple annealing treatments have been investigated. Carefully planned experiments with films possessing different residual stress states, aided with in-situ monitoring of the stress developments during lithiation/delithiation, have highlighted the importance of such initial conditions on aspects related to cyclic stability and overpotentials. The use of Sn and Al based electrodes, where the molar volume change associated with the phase transformations are considerably higher compared to other electrode materials, have further strengthened the understanding. On a different note, the influences of different current collectors (Cu, Ni and Ti) on the crystallographic orientations, and concomitantly on the various electrochemical behaviour and stress developments will also be highlighted. Our in-situ observations also suggest the development of stresses due to SEI formation, similar to the case of graphitic carbon [3]. It is believed that the understandings developed as part of the present work will contribute towards successful developments of electrode materials based on alloying reactions. Keywords: anode materials, Sn, Al, stress development

Insights into the Li-Storage Mechanisms and Mechanical Integrities of the Next Generation Anode Materials for Li-Ion Batteries

The issues concerning safety and relatively inferior Li-capacities of graphitic carbon based anodes for Li-ion batteries have motivated researchers world-wide to look at alternative anode materials such as metals, graphenic carbon and also metal/carbon composites. Despite extensive research efforts, some of the major issues and behavioral patterns associated with these anode materials are either yet to be resolved, or better understood in scientific terms. For instance, the metallic anode materials still suffer from drastic capacity fades due to mechanical degradation arising from huge volumetric changes upon lithiation/delithiation [1]. Furthermore, still lacking is the understanding of the correlations between the potential, state-of-charge, phase transformations and stress developments in such electrode materials. With respect to graphenic carbon based anodes, even though recent reports suggest significantly enhanced Li-capacities, the Li-storage mechanisms leading to such capacities are still under debate [2,3]. Furthermore, the mechanical integrity of graphenic carbon upon repeated lithiation/delithiation has not yet been established. Here it is interesting to note that, even though as per the common belief graphene may be used to buffer the stresses in the metallic anode materials [4], this possible role of graphene is yet to be understood in scientific terms, especially in terms of quantifying the stress developments in the presence or absence of graphene. Against these backdrops, in order to develop better fundamental understandings on these issues we are using thin films of Sn, Si, few layer graphene (FLG) and Si-FLG multi-layered films as model electrode materials/architectures. The Sn and Si films are deposited via e-beam deposition, while the FLG (~ 6 layers) films are deposited via chemical vapor deposition on Cu foil/film (using methane; at 1000oC). In addition to studying the electrochemical behaviour using different current densities and potential/current steps against Li-foil, real-time monitoring of the in-plane stress developments have been performed using multi-beam optical stress sensor during electrochemical cycling [1,5]. Such in-situ investigations have allowed quantitative determinations of the stress developments and provided us with deeper insights into the various unresolved aspects; for eventually establishing correlations between the potentials, surface phenomena, state-of-charges, Li-storage mechanisms, phase/stage transformations, dimensional changes and stress developments. With respect to lithiation/delithiation of Sn, we have observed for the first time that the stress developments remain elastic in the single phase (solid solution) regimes, whereas plastic deformation and/or fracture occur just during the first order phase transformations between the different Sn-Li intermetallics during Li-alloying/dealloying [5]. It has been hypothesized that the huge stresses associated with the eigenstrains related to the formation of the new intermetallics with significantly different molar volumes than the parent phases are responsible for this behaviour. Our work with few layer graphene based thin films has allowed us to develop better insights into the respective contributions from the classical Li-intercalation mechanism and Li-storage in defect sites towards the overall Li-capacity, which we re-confirm as being significantly higher compared to that for bulk graphitic carbon. Additionally, our in-situstress measurements reveal that mechanical degradation do occur in each electrochemical cycle during the initial stages of lithiation and later stages of delithiation; more specifically, during the co-existences of dilute stage I and stage IV Li-GICs. As will be presented, our analysis correlates such structural degradation with the Li-distribution near the edge sites and differential inter-planar spacing in FLG during these stages. Our work with graphene (FLG)/Si multi-layered films has revealed that just the presence of graphene may not be successful in improving the structural integrity of the composite anode for enhancing cycle life. The behavioral patterns and overall stress magnitudes obtained in real-time during electrochemical cycling allow better understanding on the influence of the graphene layer and highlights the need for careful optimization of the relative thicknesses of the Si and graphene films and the lateral dimensions of the Si islands (in case of patterned Si films) for improving the effectiveness of graphene as a ‘buffer layer’. Acknowledgements: The contributions from Ravi Kali, Farjana J. Sonia, Manoj K. Jangid, Dr. M. Aslam (IIT Bombay, India); and Anton Tokranov and Prof. Brian W. Sheldon (Brown University, USA) are duly acknowledged. Financial assistances from IRCC, IIT Bombay and DST & CSIR, Government of India are duly acknowledged. References A. Mukhopadhyay, B.W. Sheldon; Prog. Mater. Sci. 63 (2014) 58.D. Datta J. Li, N. Koratkar, V.B. Shenoy; Carbon 80 (2014) 305.E. Lee, K.A. Persson; Nano. Lett. 12 (2012) 4624.V. Chabot, K. Feng, H.W. Park, F.M. Hassana, A.R. Elsayed, A. Yu, X. Xiao, Z. Chen; Electrochim. Acta 130 (2014) 127.A. Mukhopadhyay, R. Kali, S. Badjate, A. Tokranov, B.W. Sheldon; Scripta. Mater. 92 (2014) 47.

Facile synthesis of sandwiched Zn2GeO4–graphene oxide nanocomposite as a stable and high-capacity anode for lithium-ion batteries

Traditional metal anode materials in lithium-ion batteries are plagued by instability upon discharge-charge cycling. We report that a unique sandwiched Zn2GeO4-graphene oxide nanocomposite has been synthesized on a large scale through a simple ion-exchange reaction, whereby Zn2GeO4 nanorods with lengths of 600 nm and widths of 40 nm are homogeneously sandwiched into the graphene oxide matrix. Compared with bare Zn2GeO4 nanorods, a dramatic improvement in the electrochemical performance of the resulting nanocomposite has been achieved. In the voltage window of 0.001-3 V, the electrode of the Zn2GeO4-graphene oxide nanocomposite delivers a specific capacity as high as 1150 mA h g(-1) at 200 mA g(-1) after 100 discharge-charge cycles. Even at a high current density of 3.2 A g(-1), a capacity of 522 mA h g(-1) can be retained. The unusual electrochemical performance including highly reversible capacity and excellent rate capability arise from synergetic chemical coupling effects between Zn2GeO4 and graphene oxide.

Metallic anodes for next generation secondary batteries

Li-air(O2) and Li-S batteries have gained much attention recently and most relevant research has aimed to improve the electrochemical performance of air(O2) or sulfur cathode materials. However, many technical problems associated with the Li metal anode have yet to be overcome. This review mainly focuses on the electrochemical behaviors and technical issues related to metallic Li anode materials as well as other metallic anode materials such as alkali (Na) and alkaline earth (Mg) metals, including Zn and Al when these metal anodes were employed for various types of secondary batteries.

Intense Ion Beam Flux of Adsorbed Gases and Metallic Anode Materials in the “Point Pinch Diode” Measured with Thomson-Parabola Ion Spectrometer

An intense flux of ion beams was observed in a “Point Pinch Diode” which consists of concentric elliptic or spherical electrodes and a slender magnetically insulated transmission line. The ion beam had an energy of about 380 keV, which was equivalent to the supplied diode voltage. The peak current density of the ion beam ranged from 5 to 7.5 kA/cm2 in spite of a small input energy (less than about 1 kJ). Measurements with a Thomson-parabola ion spectrometer show that the major components were hydrogen, carbon, and oxygen, the origins of which were oil and water adsorbed on the surface of the metallic anodes. A significant flux of the metallic ion beams was also detected in the cases of aluminium, copper and gold anodes.