Growth Of Electrodeposits Research Articles

Bio-inspired self-cleaning carbon cloth based on flower-like Ag nanoparticles and leaf-like MOF: A high-performance and reusable substrate for SERS detection of azo dyes in soft drinks

Surface-enhanced Raman scattering (SERS) enables azo dye monitoring become rapid and efficient. However, the high cost, low efficiency and poor recyclability of SERS substrate limit its practical application. Herein, we propose a facile strategy to develop self-cleaning carbon cloth as a high-performance and reusable SERS substrate through in-situ growth of leaf-like metal-organic framework (L-MOF) and one-step electro-deposition of flower-like Ag nanoparticles (CC-L-MOF@F-Ag) followed by chemical modification for SERS detection of congo red (CR), chrysoidine (CYD) and acid orange II (AO II) in soft drinks. Taking advantages of superhydrophobicity and SERS-active F-Ag, the prepared self-cleaning CC-L-MOF@F-Ag not only avoids the diffusion-random problem and further boosts sensitivity, but also yields excellent self-cleaning property through facile washing with water, endowing its good reusability and stability. Furthermore, this substrate can realize quantitative detection of CR, CYD and AO II with low limits of detection (0.013 μM for CR, 0.017 μM for CYD and 0.0067 μM for AO II) and wide linear detection range (0.1 – 1000 μM for CR, 0.1 – 1000 μM for CYD and 0.01 – 100 μM for AO II). Meanwhile, CR, CYD and AO II in six soft drinks were also successfully detected with satisfactory recoveries. This method provides a potential and cost-effective strategy to develop advanced SERS sensing device for effective monitoring azo dyes in soft drinks.

Three-dimensional carbon nanotubes/iron oxyhydroxide shell/core hybrid as a binder-free electrode for the flexible supercapacitor

Carbon nanotubes/iron oxyhydroxide (CNTs/FeOOH) three-dimensional hybrid with shell/core nanostructure is designed as a binder-free electrode for the flexible supercapacitor (SC) application. The coiled and dense CNT forest is preferentially fabricated on flexible carbon fiber cloth (CC) by chemical vapor deposition (CVD) and employed as a highly conductive carrier for electrodeposition growth of FeOOH. The average diameter and length of the single CNT are 30–60 nm and 2–3 μm. The shell/core structured CNTs/FeOOH three-dimensional hybrid maintains the consistent interconnecting network morphology, contributing to overcoming the problem of poor conductivity of FeOOH and the transmission of electron channels and the diffusion of electrolyte ions. The CNTs/FeOOH hybrid exhibits a high mass-specific capacitance of 824 F g−1 (or 0.59 F cm−2) in 1 M Na2SO4 electrolyte at 0.5 mA cm−2. By increasing the FeOOH deposition weight, the enhanced area-specific capacitance of 0.892 F cm−2 (or 564 F g−1) is obtained at 0.5 mA cm−2, and the enhanced capacitance retention can reach 96% after 3000 charge/discharge cycles. Besides, a flexible SC is fabricated using the CNTs/FeOOH hybrid electrode and carboxymethyl cellulose (CMC)/Na2SO4 gel electrolyte. The SC displays an energy density as high as 13.33 Wh kg−1 at a power density of 1000 W kg−1. The SC device shows large bending deformation, and these SC devices pack can drive a red diode to work. These results provide such a shell/core structured CNTs/FeOOH three-dimensional hybrid that can be used as potential and low-cost electrode material for flexible SC.

Grain-Boundary-Rich Copper for Efficient Solar-Driven Electrochemical CO2 Reduction to Ethylene and Ethanol.

The grain boundary in copper-based electrocatalysts has been demonstrated to improve the selectivity of solar-driven electrochemical CO2 reduction toward multicarbon products. However, the approach to form grain boundaries in copper is still limited. This paper describes a controllable grain growth of copper electrodeposition via poly(vinylpyrrolidone) used as an additive. A grain-boundary-rich metallic copper could be obtained to convert CO2 into ethylene and ethanol with a high selectivity of 70% over a wide potential range. In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy unveils that the existence of grain boundaries enhances the adsorption of the key intermediate (*CO) on the copper surface to boost the further CO2 reduction. When coupling with a commercially available Si solar cell, the device achieves a remarkable solar-to-C2-products conversion efficiency of 3.88% at a large current density of 52 mA·cm-2. This low-cost and efficient device is promising for large-scale application of solar-driven CO2 reduction.

Regulating the growth of aluminum electrodeposits: towards anode-free Al batteries

2-D Au coatings enable stable and uniform deposition of Aluminum.

A hybrid composed of MoS2, reduced graphene oxide and gold nanoparticles for voltammetric determination of hydroquinone, catechol, and resorcinol.

A ternary hybrid composed of molybdenum disulfide (MoS2), reduced graphene oxide (rGO) and gold nanoparticles (AuNPs@MoS2-rGO) was prepared and used for voltammetric detection of hydroquinone (HQ), catechol (CC) or resorcinol (RC). The composition and structure of the hybrid were characterized in detail. The electrochemical behaviors of a glassy carbon electrode (GCE) modified with the hybrid towards the oxidation of HQ, CC, and RC were investigated using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The results revealed 3D MoS2 is active for the catalytic oxidation of these isomers. Additional integration with rGO and AuNPs further improves catalysis due to their synergistic interaction. The enhanced catalysis leads to oxidation of HQ, CC and RC at 0.074V, 0.178V, and 0.527V (vs. Ag/AgCl; by CV) with reduced overpotential (20-100mV) and 8-fold or 3-fold increased peak current compared to those obtained on MoS2/GCE, or MoS2-rGO/GCE, respectively. Selective detection of one isomer in the presence of the other two was realized by DPV. The linear ranges are 0.1-950μM, 3-560μM, and 40-960μM for HQ, CC, and RC, and the detection limits are 0.04μM, 0.95μM, and 14.6μM, respectively. The sensor also shows good selectivity and displays satisfactory recovery for real sample analysis. Graphical abstract Schematic illustration of the preparation of AuNPs@MoS2-rGO hybrid by hydrothermal growth of MoS2-rGO and subsequent electrodeposition of gold nanoparticles (AuNPs), and its application for selective detection of hydroquinone, catechol and resorcinol by voltammetry.

Nucleation and Early Stage Growth of Li Electrodeposits.

The morphologies that metal electrodeposits form during the earliest stages of electrodeposition are known to play a critical role in the recharge of electrochemical cells that use metals as anodes. Here we report results from a combined theoretical and experimental study of the early stage nucleation and growth of electrodeposited lithium at liquid-solid interfaces. The spatial characteristics of lithium electrodeposits are studied via scanning electron microscopy (SEM)in tandem with image analysis. Comparisons of Li nucleation and growth in multiple electrolytes provide a comprehensive picture of the initial nucleation and growth dynamics. We report that ion diffusion in the bulk electrolyte and through the solid electrolyte interphase (SEI) formed spontaneously on the metal play equally important roles in regulating Li nucleation and growth. We show further that the underlying physics dictating bulk and surface diffusion are similar across a range of electrolyte chemistries and measurement conditions, and that fluorinated electrolytes produce a distinct flattening of Li electrodeposits at low rates. These observations are rationalized using X-ray photoelectron spectroscopy(XPS), electrochemical impedance spectroscopy (EIS), and contact angle goniometry to probe the interfacial chemistry and dynamics. Our results show that high interfacial energy and high surface ion diffusivity are necessary for uniform Li plating.

Surface Engineering of 3D Gas Diffusion Electrodes for High‐Performance H2 Production with Nonprecious Metal Catalysts

AbstractIn this work, a methodology is demonstrated to engineer gas diffusion electrodes for nonprecious metal catalysts. Highly active transition metal phosphides are prepared on carbon‐based gas diffusion electrodes with low catalyst loadings by modifying the O/C ratio at the surface of the electrode. These nonprecious metal catalysts yield extraordinary performance as measured by low overpotentials (51 mV at −10 mA cm−2), unprecedented mass activities (>800 A g−1 at 100 mV overpotential), high turnover frequencies (6.96 H2 s−1 at 100 mV overpotential), and high durability for a precious metal‐free catalyst in acidic media. It is found that a high O/C ratio induces a more hydrophilic surface directly impacting the morphology of the CoP catalyst. The improved hydrophilicity, stemming from introduced oxyl groups on the carbon electrode, creates an electrode surface that yields a well‐distributed growth of cobalt electrodeposits and thus a well‐dispersed catalyst layer with high surface area upon phosphidation. This report demonstrates the high‐performance achievable by CoP at low loadings which facilitates further cost reduction, an important part of enabling the large‐scale commercialization of non‐platinum group metal catalysts. The fabrication strategies described herein offer a pathway to lower catalyst loading while achieving high efficiency and promising stability on a 3D electrode.

Electrodeposition stability of metal electrodes

Rechargeable battery chemistries, with high energy densities, are particularly desirable in order to meet the burgeoning demand for energy storage. In this regard, metal electrodes have recently drawn extensive research interest due to the intrinsic energy density boost, while a fundamental study is needed to reveal the underlying mechanisms governing the electrodeposition stability. Here, we explore the mesoscale interactions in nucleation and growth of electrodeposition, with a focus on the competition of ion transport in the electrolyte, electrochemical reactions at the electrolyte-electrode interface, and surface self-diffusion. It is found that lithium (Li) and sodium (Na) metal anodes have the tendency to form dendrites at high local reaction rates, whereas magnesium (Mg) and aluminum (Al) do not, because of the low intrinsic self-diffusion barriers. Nonuniform electrodeposition at low reaction rates is observed, which could be attributed to the spatial inhomogeneities due to separator wetting, solid electrolyte interphase (SEI) formation, and electrode surface roughness. This work provides a fundamental understanding of the mesoscale underpinnings on the electrodeposition stability of various metal electrodes, especially shedding light on pathways toward potentially dendrite-free electrodeposition morphology.

In-Situ Imaging of Electrochemical Polymerization of Functionalized Thiophenes Using Transmission Electron Microscopy

There is considerable continuing interest in developing conjugated polymer materials like the functionalized thiophene poly(3,4-ethylenedioxythiophene) (PEDOT) to interface ionically conducting living tissue with electronically conducting metallic or semiconducting biomedical devices. These versatile conjugated polymers can also be used in organic solar cells, anti-static coatings and flexible organic electronic devices. Electrochemical polymerization can be used to synthesize thin-films of conjugated polymers. Typically, a 3-electrode system comprising of a working, counter and reference electrodes is used for this process. It is initiated by the electrochemical oxidization of the monomers, followed by the formation of higher molecular weight products that precipitate from solution, forming a thin-film of the conjugated polymer on the working electrode (anode). The reaction can be controlled either potentiostatically (constant voltage) or galvanostatically (constant current).This technique has several advantages over vapor-phase and chemical polymerization such as the facile control of polymer morphology (rough and bumpy under normal conditions) and the ability to coat patterned surfaces. However, the factors that determine the development of these structures during electrodeposition are not yet well established. This makes it difficult to design new systems and optimize device performance. Considering that the morphology of electrochemically-polymerized thin-films can be fine-tuned by controlling the early stage nucleation and growth of the oligomeric clusters, we have used in-situ, low dose Transmission Electron Microscopy to image and obtain a detailed understanding of the fundamental processes occurring at the electrode-solution interface, especially the evolution of the mobile oligomers that precede solid polymer film formation. The observation and quantification of these electrochemical reactions are made possible using a commercial holder designed by Protochips, Inc. The liquid (monomer solution) is sandwiched between a top chip and a spacer chip. The spacer chip is used to control the amount of liquid to be imaged (typically 500 nm – 1000 nm). This system can either be used in a static mode (no flow) or flowing mode depending on the requirements. The top chip is equipped with the electrical connections required to perform electrochemical reactions and watch the process in-situ. During the experiments, we observed individual nuclei forming, merging and growing in size and thickness with increasing charge density. These droplets correspond to more mobile, oligomer-rich clusters which further react with the monomers in the solution to form the solid polymer (PEDOT) deposit. This mechanism of precipitation and solidification provides a reasonable explanation for the usual bumpy morphology of the electrochemically polymerized films. We observed that the deposition occurs in 2 regimes. The first regime corresponds to an increase in nucleation density (the nucleation regime) and the second (the growth regime) where the clusters start to merge and increase in size causing a decrease in the nucleation density. During the deposition, certain droplets were found to gradually decrease in size and mass thickness, indicating some degree of reversibility of the process which was not previously appreciated. In addition to this, we have found substantial variations when the chemistry of the monomer is changed, including a dramatic increase in the nucleation density when a more hydrophilic, carboxylic acid substituted EDOT was used as a comonomer. The total electron doses we used for these experiments were around 10-20 mC/cm2. These were well below the critical dose for electron damage of the PEDOT, which is about 0.1 C/cm2. Further, using a macromolecular counter-ion, poly(acrylic acid) (PAA) during the electrodeposition facilitates the formation of highly anisotropic nano-fibrils of PEDOT thereby reducing the overall impedances due to increase in the effective surface area. The basic understanding is that PAA prevents the lateral growth of PEDOT which results in the nano-fibrillar morphology. Using operando electron microscopy, we have observed the nucleation and growth of these fibrils in an oriented, dendritic manner at the solution-electrode interface, allowing us to better understand the nano-fibril formation mechanisms. These experiments have presented us with unprecedented insights about the processes occurring at the nanoscale during the early stage nucleation and growth of electrodeposition of PEDOT and PEDOT copolymers. Figure 1

RGB video electrochemistry of copper electrodeposition/electrodissolution in acid media on a ternary graphite:copper:polypropylene composite electrode

Galvanostatic copper electrodeposition and electrodissolution on graphite:copper:polypropylene composite electrodes in acidic media have been investigated to extend the technological applicability of ternary composites. Both electrochemical processes were monitored by RGB video electrochemistry. The analysis of digital images allowed the color changes on the electrode surface to be investigated. We estimate the growth rate of the copper layer in two different electrode geometries. The relatively high resistance of this composite causes a gradient of the electric resistance along the electrode involving a non-homogeneous electrodeposit growth in CuSO4/H2SO4 aqueous solutions. Copper electrodissolution was studied in HCl and H2SO4 aqueous solutions. Whereas chloride anions stabilized cuprous cation, the electrodissolution process in HCl takes place apparently by a more complicated mechanism. Dispersion of color estimated from the standard deviation of the RGB color images was also analyzed and it has been postulated as a tool for identifying possible intermediate species on the electrode surface.

Liquid Cell Transmission Electron Microscopy Sheds Light on The Mechanism of Palladium Electrodeposition.

Electrodeposition is widely used to fabricate tunable nanostructured materials in applications ranging from biosensing to energy conversion. A model based on 3D island growth is widely accepted in the explanation of the initial stages of nucleation and growth in electrodeposition. However, there are regions in the electrodeposition parameter space where this model becomes inapplicable. We use liquid cell transmission electron microscopy along with post situ scanning electron microscopy to investigate electrodeposition in this parameter space, focusing on the effect of the supporting electrolyte, and to shed light on the nucleation and growth of palladium. Using a collection of electron microscopy images and current time transients recorded during electrodeposition, we discover that electrochemical aggregative growth, rather than 3D island growth, best describes the electrodeposition process. We then use this model to explain the change in the morphology of palladium electrodeposits from spherical to open clusters with nonspherical morphology when HCl is added to the electrolyte solution. The enhanced understanding of the early stages of palladium nucleation and growth and the role of electrolyte in this process provides a systematic route toward the electrochemical fabrication of nanostructured materials.

Towards a 3D GeSbTe phase change memory with integrated selector by non-aqueous electrodeposition.

We have recently reported a new method for the electrodeposition of thin film and nanostructured phase change memory (PCM) devices from a single, highly tuneable, non-aqueous electrolyte. The quality of the material was confirmed by phase cycling via electrical pulsed switching of both 100 nm nano-cells and thin film devices. This method potentially allows deposition into extremely small confined cells down to less than 5 nm, 3D lay-outs that require non-line-of-sight techniques, and seamless integration of selector devices. As electrodeposition requires a conducting substrate, the key condition for electronic applications based on this method is the use of patterned metal lines as the working electrode during the electrodeposition process. In this paper, we show the design and fabrication of a 2D passive memory matrix in which the word lines act as the working electrode and nucleation site for the growth of confined cells of Ge-Sb-Te. We will discuss the precursor requirement for deposition from non-aqueous, weakly coordinating solvents, show the transmission electron microscopy analysis of the electrodeposition growth process and elemental distribution in the deposits, and show the fabrication and characterisation of the Ge-Sb-Te memory matrix.

Electrodeposition: Electrocarving during Electrodeposition Growth (Adv. Mater. 51/2018)

The controllable electrochemical fabrication of well-defined silver-oxide clathrate micro-/nanostructures is realized by Shikuan Yang and co-workers in article number 1805686 by intentionally manipulating the previously neglected electrocarving process during electrodeposition growth (MEDEG). The dominance of the electrocarving and the electrodeposition growth process can be immediately manipulated by varying the deposition voltage and/or the composition of the electrolyte, enabling controllable synthesis of micro-/nanostructures of various materials directly on a substrate.

Electrocarving during Electrodeposition Growth

Shape- and size-controlled synthesis of micro/nanostructures is of fundamental importance in many applications of physics and chemistry. Wet chemical growth methods have achieved shape- and size-controlled synthesis of colloidal nanocrystals of various compositions. Compared with wet chemical methods, electrochemical deposition (ECD) yields micro/nanostructures affixed to a substrate, but the resulting structures are poorly controlled. Herein, the controllable electrochemical fabrication of well-defined silver-oxide clathrate micro/nanostructures is realized by intentionally manipulating the previously neglected electrocarving process during electrodeposition growth (MEDEG). Most importantly, the dominance of the electrocarving and the electrodeposition growth process can be immediately manipulated by varying the deposition voltage and/or the composition of the electrolyte. Unique delta-wing-, arrowhead-, and butterfly-like silver-oxide clathrate structures are created using the MEDEG method. MEDEG complements the capability of ECD for controllable synthesis of micro/nanostructures of various materials directly on a substrate. The study details the mechanisms that may enable MEDEG to become a competitive alternative to traditional wet chemical methods in the controllable synthesis of micro/nanostructures. This understanding of MEDEG should motivate applications in fields which demand well-defined micro/nanostructures affixed to a substrate.

(Invited) Rational Design of Nanoporous Polymer Electrolytes and Solid-Liquid Interphases for Lithium Metal Batteries

Advances in the basic science and engineering principles of electrochemical energy storage is imperative for significant progress in portable electronic devices. In this regard, metal based batteries comprising of a reactive metal (like Li, Na, Al) as anode have attracted remarkable attention due to their promise of improving the anode-specific capacity by as much as 10-fold, compared to the current state-of-art Li-ion battery that uses a graphitic anode. Perhaps their greatest advantage lies in the possibility of using of a Li-free high-capacity cathode like Oxygen that can improve the gravimetric energy density of batteries from ~0.3kWh/kg to ~12kWh/kg (i.e. comparable to the useful energy available from combustion of hydrocarbons). A persistent challenge with batteries based on metallic anodes, concerns their propensity to fail by short-circuits produced by dendrite growth during battery recharge, as well as by runaway of the cell resistance due to internal side reactions with liquid electrolytes. In this talk, I will discuss my research that utilizes multiscale transport modeling and experiments to fundamentally understand and to thereby develop rational designs for polymer electrolytes and electrode-electrolyte interphases that overcome these challenges (Tikekar, Choudhury et al. Nat. Energy 2016). There have been several studies in literature dedicated to the prevention of dendrite growth by means of a high modulus physical barrier. However, electrolytes/separators with high mechanical strength tend to have low ionic conductivity, thus limiting their practical use. A recent theoretical study from our group reported a linear stability analysis of dendrite growth (Tikekar et al., Sci Adv. 2016) of metal electrodeposition and showed that the length-scale on which transport occurs near the electrodes could be as important as electrolyte modulus in stabilizing metals against dendrite formation. In a nutshell, this study concluded that dendrites can be prevented from crossing over to the counter electrode using battery separators with pore-diameter lower than critical (smallest) size of the dendritic nucleate. To evaluate this proposal, we designed cross-linked nanoparticle-polymer composite electrolytes with tunable pore size and quantified the stability of metal electrodeposition in these systems. In contrast to most previously reported polymer electrolytes, the crosslinked membrane simultaneously showed good mechanical strength (~1MPa) and high ionic conductivity at room temperature (~5mS/cm), which is a consequence of the high crosslinking node points in these membranes (Choudhury et al. Nat. Commn. 2015). Direct visualization experiments were performed to understand the effect of pore-size on dendrite growth, which showed remarkable agreement with the theoretical predictions. Furthermore, when operated in a battery, the crosslinked membrane showed the highest short circuit time compared to similar electrolytes reported in the literature. Importantly, these studies showed that while the tendency for battery failure by dendrite-induced short-circuits can be reduced in polymer electrolytes, the issue of capacity-fading as a result of continuous reactions of the metal with liquid electrolyte persists. An additional striking fact in the electrodeposition literature not addressed by the linear stability analysis is that certain metals, including Magnesium, do not form dendrites. In the second part of my talk, I will show how multiscale analysis of transport at electrochemical interfaces enables design of stable solid-liquid interphases for reactive metal batteries. Recently, we used Density Functional Theory (DFT) calculations to quantify the diffusion energy barrier of ions on Mg, Li, Na surfaces and interestingly it seen that the diffusion barrier of Mg (0.02eV/atom) is several fold lower than Li (0.14eV/atom) or Na (0.16eV/atom) metals. In fact, the diffusion barrier of Li2CO3, Li2O (the commonly found compounds in lithium interface) is even higher, which is consistent with the dendritic electrodeposition in such batteries. However, in quest for finding stable interfaces, we observed that most metal halides (LiF, LiBr, NaF etc.) have much lower diffusion barrier. In other words, halide-rich interfaces on lithium or sodium can lead to stable electrodeposition similar to Mg deposition (Choudhury et al. Nat. Commn. 2017). We further utilize Classical Nucleation Theory (CNT) to understand implication of the ab-initio model in macroscopic metal deposition. The predictions from the coupled DFT-CNT model were validated using ex-situ scanning electron microscopy as well as in-situ optical microscopy. The nucleation pattern, indeed, showed a strike difference between usual (carbonate-rich) and halide-rich lithium interfaces. Based on these fundamental understanding, the solid electrolyte interphase in lithium metal batteries were artificially modified using organo-metallic reactions to enable enhanced reversibility in high energy density Lithium-Oxygen battery that demonstrated extended capacity retention and longer cycle life (Choudhury et al. Sci. Adv. 2017). Figure 1

Thermodynamic aspects of bis(3‑sulfopropyl) disulfide and 3‑mercapto‑1‑propanesulfonic acid in Cu electrodeposition

Organic additives play an important role in regulating film growth and properties in Cu electrodeposition. 3‑Mercapto‑1‑propane sulfonate (MPS) and its dimer bis(3‑sulfopropyl) disulfide (SPS) are representative accelerators that promote Cu electrodeposition rate. In this study, the formal reduction potential of SPS to MPS was determined by measuring the equilibrium constants of thiol–disulfide interchange reactions with the reference thiol/disulfide pairs by 1H nuclear magnetic resonance (1H NMR) spectroscopy. The calculated formal reduction potential of SPS to MPS was 0.153 V (vs. standard hydrogen electrode). Based on this calculation, the cell potentials of Cu(I)(thiolate) formation reaction with either SPS or MPS, which is a key reaction in accelerating mechanism, were also estimated by ultraviolet–visible absorption and 1H NMR spectroscopies: they were found to be 0.202 V and 0.214 V for SPS and MPS, respectively. The positive cell potential indicates that the formation of Cu(I)(thiolate) complexes is thermodynamically favorable in the presence of additives.

Nanoscale in situ detection of nucleation and growth of Li electrodeposition at various current densities

Transmission GISAXS shows the real-time evolution of sizes and structures of Li dendrites, from primary Li nanoparticles to fractal dimensions.

Understanding Morphology Evolution in Lithium Electrodeposition

Lithium-ion batteries are poised to play an important role in the push for electric vehicles. Electroplating and possible dendritic growth, however, have been a safety concern. Non-uniform electrodeposition and subsequent growth may cause short circuit. Apart from catastrophic failure, Li plating results in the battery performance decay as well. There is a need for a better understanding of the factors that are most critical in the nucleation and growth of Li electrodeposition and the morphology evolution thereof. The metal ion reaches the electrode surface where it is reduced. The metal atom can thereafter diffuse inside the bulk electrode or aggregate on the surface under some specific set of conditions and form a variety of structures on the electrode surface, like small islands, uniform film, mossy or filament like structure or dendrite (as schematically shown in Figure 1). Physicochemical determinants affecting electrodeposition include the adsorption energy of metal atom on electrode surface, diffusion barrier for metal atom in the bulk electrode compared to that on the electrode surface, the crystallographic nature of the electrode surface, the strength of cohesive metal-metal interaction. Beyond the nature of the electrode material, the operating temperature, current density and applied potential can also affect the electrodeposition rate, which consequently control the morphology evolution. In this study, a mesoscale interfacial modeling and analysis is presented in order to investigate the lithium electrodeposition regimes and morphology evolution. Figure 1

Thermodynamics and Kinetics of Lithium Dendrite Growth

Lithium metal anodes are a promising choice to achieve high energy density compared to current graphite anodes. However, lithium whisker growth (dendrites) during battery charging poses a major safety and performance concern for both lithium metal batteries, and overcharging of presently used graphite anodes in lithium-ion batteries. The present understanding of lithium electrodeposit growth is largely based on the Diffusion Limited Aggregation theory that results in a tip-controlled growth of fractal or dendritic structures. However, lithium electrodeposits have been reported in scientific literature to grow from the base at low current densities [1,2,3], that cannot be explained solely by electrodeposition kinetics. In this work, the mechanisms of lithium growth on anodes are analyzed assessing the combined contribution of electrochemical and mechanical driving forces. Physical mechanisms for tip-controlled and base-controlled growth modes are developed based on a thermodynamically consistent formulation, and have been validated based on the available scientific literature. Analytical and numerical solutions are discussed.

The Response and Limits of Fast Discharge and Charge Rates of Electrodeposited V2O5 Inverse Opal Networks in Lithium Batteries

Structurally stable electrodeposited vanadium pentoxide inverse opal networks on FTO-coated glass are electrochemically tested as a function of C-Rate (discharging and charging) in this study. Recent applications of IOs in electrochemical energy storage have proven that their open-worked structure promotes more stable Li-ion intercalation during cycling(1-3), exhibit improved rate capability due to increased surface area and decreased path lengths for Li+ insertion,(4-7). Rate limitations associated with standard Li-ion batteries can be improved in principle due to shorter diffusion lengths in the 3D architecture(8, 9), particularly important for charging in full cells. V2O5 has been widely investigated(10) as a cathode material for Li-ion batteries due to its high theoretical specific capacity and is useful for reversible Li-ion insertion and removal due to its mixed valance and layered structure.(11) The difference in open-topped versus overfilled (closed top) 3D inverse opal macroporous V2O5 networks, due to electrodeposition growth time, is examined by galvanostatic cycling, and both 3D structure are examined at C-rates in the range 0.5 – 30 C. Electrochemical analysis demonstrates how lithium phase changes increasing C-rate in both open and overfilled network cases, with capacity values investigated after 25 charge/discharge cycles. Raman scattering and X-ray diffraction is used to investigate the change in structure and phase in each case at each C-rate, along with SEM images to visual investigate the effect of C-rate on the V2O5 inverse opal networks.