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Silicon is considered one of the most promising anode materials owing to its high theoretical energy density, however, the volume expansion/contraction during electrochemical lithiation/delithiation cycles leads to instability of the solid electrolyte interphase (SEI), which ultimately results in capacity degradation. Herein, the local stress and deformation evolution status of an SEI layer on an anode particle are investigated through a quantitative electrochemical-mechanical model. The impacts of structural uniformity, mechanical strength, and operating conditions on the stability of the SEI layer are investigated in detail. The simulation results demonstrate that when the silicon particle radius decreases from 800 nm to 600 and 400 nm, the failure time increases by 29% and 65%, respectively, of the original failure time; When the structural defect depth ratio is reduced from 0.6 to 0.4 and 0.2, the failure time increases by 72% and 132%, respectively; For the discharge rate, the condition at 0.1 C has 34% and 139% longer time to failure than that at 0.2 C and 0.3 C, respectively. This work provides insight into the rational design of stable SEI layers and sheds light on possible methods for constructing silicon-based lithium-ion batteries with longer cycling lives. [ABSTRACT FROM AUTHOR]

Silicon-based anodes are widely expected to vastly improve the performance of lithium-ion batteries (LIBs). However, the silicon anode interface is well-known to be unstable and reactive, leading to various electrolyte side reactions that would ultimately lower the battery performance. Consequently, it is critically important to rationally design the silicon anode to stabilize its interface. The Langmuir-Blodgett (LB) technique is a well-established, versatile, and powerful method for fabricating ultrathin films over solid substrates. Here, we utilize LB approach to generate thin films composed of small organic molecules over silicon electrodes as protective layers. Such molecular layers were found capable of mediating the electrochemical behavior of silicon electrodes in both aqueous and organic carbonate electrolytes. This study illustrates the applicability of small-molecule LB films in electrode interface engineering for LIB technology development.

Historically, lithium cobalt oxide and graphite have been the positive and negative electrode active materials of choice for commercial lithium-ion cells. It has only been over the past ~15 years in which alternate positive electrode materials have been used. As new positive and negative active materials, such as NMC811 and silicon-based electrodes, are being developed, it is crucial to evaluate the potential of these materials at a stack or cell level to fully understand the possible increases in energy density which can be achieved. Comparisons were made between electrode stack volumetric energy densities for designs containing either LCO or NMC811 positive electrode and silicon-graphite negative electrodes, where the weight percentages of silicon were evaluated between zero and ninety percent. Positive electrode areal loadings were evaluated between 2.00 and 5.00 mAh cm−2. NMC811 at 200 mAh g−1 has the ability to increase stack energy density between 11% and 20% over LCO depending on percentage silicon and areal loading. At a stack level, the percentage of silicon added results in large increases in energy density but delivers a diminishing return, with the greatest increase observed as the percentage of silicon is increased from zero percent to approximately 25–30%. [ABSTRACT FROM AUTHOR]

This work aims to review and understand the behavior of the electrochemical lithiation onset of amorphous silicon (a-Si) films as electrochemically active material for new generation lithium-ion batteries. The article includes (i) a review on the lithiation onset of silicon films and (ii) a mechanochemical model with numerical results on the depth-resolved mechanical stress during the lithiation onset of silicon films. Recent experimental studies have revealed that the electrochemical lithiation onset of a-Si films involves the formation of a Li-poor phase (Li0.3Si alloy) and the propagation of a reaction front in the films. The literature review performed reveals peculiarities in the lithiation onset of a-Si films, such as (i) the build-up of the highest mechanical stress (up to 1.2 GPa) during lithiation, (ii) a linear increase in the mechanical stress with lithiation which mimics the characteristics of linear elastic deformation, (iii) only a minute volume increase during Li incorporation, which is lower than expected from the number of Li ions entering the silicon electrode, (iv) the largest heat generation appearing during cycling with only a minor degree of parasitic heat contribution, and (v) an unexpected enhanced brittleness. The literature review points to the important role of mechanical stresses in the formation of the Li-poor phase and the propagation of the reaction front. Consequently, a mechanochemical model consisting of two stages for the lithiation onset of a-Si film is developed. The numerical results calculated from the mechanochemical model are in good accord with the corresponding experimental data for the variations in the volumetric change with state of charge and for the moving speed of the reaction front for the lithiation of an a-Si film of 230 nm thickness under a total C-rate of C/18. An increase in the total C-rate increases the moving speed of the reaction front, and a Li-rich phase is likely formed prior to the end of the growth of the Li-poor phase at a high total C-rate. The stress-induced phase formation of the Li-poor phase likely occurs during the lithiation onset of silicon electrodes in lithium-ion battery. [ABSTRACT FROM AUTHOR]

To meet the demand of flexible devices, it was urgent to develop flexible high-capacity electrodes for lithium-ion batteries (LIBs). Silicon (Si) as an active material would effectively elevate the specific capacity of LIBs, but the drastic volume changes and low intrinsic conductivity seriously affected its electrochemical performance during the charge-discharge process. In this research, a new type of composite was designed using two-dimensional reduced graphene oxide (rGO), one-dimensional carbon nanotubes (CNTs), and silicon nanoparticles (Si NPs) as raw materials. The prepared rGO/Si/CNTs composite had an intricate and intersecting porous network structure inside, with rGO as the substrate, CNTs as a bridge, and Si NPs as the active material. The rGO would provide abundant attachment sites for Si NPs, improve electrode conductivity, and alleviate the volume change of electrode. CNTs can effectively suppress the stacking of rGO layers and generate more voids for the reaction, and also serve as a bridge for electron transfer between rGO layers. Furthermore, the interaction between each other also heightened the flexibility and strength of electrodes. Compared to the other composites, rGO/Si/CNTs=2:2:1 electrodes presented the superior electrochemical performance. When cycled at 200 mA g−1, its discharge capacity was 2217.2 mAh g−1 after 200 cycles. As the current density increasing to 1000 and 5000 mA g−1, the discharge capacity maintained at 1877.2 and 534.8 mAh g−1 for 1000th cycle, and it also demonstrated superior rate performance. Besides, the assembled flexible battery maintained a good current output under various bending conditions, and was expected to be widely used in the flexible wearable energy storage devices. [Display omitted] • An intricate and intersecting porous network structure was prepared to fix Si NPs. • The rGO and CNTs were applied to increase conductivity and heighten the flexibility and stability of electrodes. • The rGO/Si/CNTs=2:2:1 anode exhibited 534.8 mAh g−1 at the high current density of 5000 mA g−1 after 1000 cycles. • The assembled flexible battery of rGO/Si/CNTs=2:2:1 maintained a good current output under various bending conditions. [ABSTRACT FROM AUTHOR]

For the coupling problems of lithium-ion batteries, a key issue at hand is that it is still unclear which mechanical failures can cause degradation and how, which is particularly salient at the electrode level. In this work, the correlation between electrode-level cracks and cycling capacity of silicon electrodes is investigated. Unexpectedly, for cracks in active layers, the capacity decreases with the increase of crack width, while the connection of other crack features to the capacity is weaker or even absent. Meanwhile, the modeling results, however, suggest that the increase in crack width cannot directly cause the capacity fading. To explain these results, the relationship between electrode debonding and active layer crack opening is also described quantitatively. By combining the debonding model and the porous electrode model, the connection between crack widths of active layers and capacity fading is clarified, and accurate predictions are obtained. These results indicate that the easily measurable width of active layer cracks is qualified to evaluate degradation, while the electrode debonding is in fact the direct cause of capacity fading. The findings in this work provide a more precise understanding of the degradation mechanism in lithium-ion battery electrodes.

Historically, lithium cobalt oxide and graphite have been the positive and negative electrode active materials of choice for commercial lithium-ion cells. It has only been over the past ~15 years in which alternate positive electrode materials have been used. As new positive and negative active materials, such as NMC811 and silicon-based electrodes, are being developed, it is crucial to evaluate the potential of these materials at a stack or cell level to fully understand the possible increases in energy density which can be achieved. Comparisons were made between electrode stack volumetric energy densities for designs containing either LCO or NMC811 positive electrode and silicon-graphite negative electrodes, where the weight percentages of silicon were evaluated between zero and ninety percent. Positive electrode areal loadings were evaluated between 2.00 and 5.00 mAh cm−2. NMC811 at 200 mAh g−1 has the ability to increase stack energy density between 11% and 20% over LCO depending on percentage silicon and areal loading. At a stack level, the percentage of silicon added results in large increases in energy density but delivers a diminishing return, with the greatest increase observed as the percentage of silicon is increased from zero percent to approximately 25–30%.

The object of research is the process of obtaining silicon nanomaterials for lithium-ion batteries of energy storage devices, and the subject of research is the technology of gas-phase plasma-chemical synthesis for the production of Si-nanoparticles. In the course of the study, numerical simulation methods were used, which made it possible to determine the parameters of temperature fields, velocities and concentrations. To study the processes of synthesis of nanopowders, a plasma reactor with an electric arc plasma torch of a linear scheme and using an argon-hydrogen mixture as a plasma-forming gas was developed. To analyze the influence of an external magnetic field on the control of the plasma jet parameters, a series of experiments was carried out using an electric arc plasma torch on plasma laboratory facilities with a power of 30 and 150 kW. The influence of a magnetic field on the process of formation and evaporation of a gas-powder flow in a plasma jet was studied by determining the configuration, geometric dimensions, and structure of the initial section of the jet. In this case, the dispersed material – silicon powder was fed to the plasma torch nozzle section according to the radial scheme. Experimental confirmation of the phenomenon of elongation of the high-temperature initial section of the plasma jet in a longitudinal magnetic field has been obtained. The experimental results indicate that the creation of a peripheral gas curtain significantly changes the characteristics of heat and mass transfer in the reactor. It should be expected that for optimization it is possible to exclude the deposition of nanosilicon particles on the walls of the reactor and provide conditions for continuous operation. The effect of two-phase flow, heat transfer, and mass flow of nanoparticles, including the surface of a plasma reactor with limited jet flow, in the processes of obtaining silicon nanopowders has been studied. This made it possible to correct a number of technological characteristics of the process of constructive design of the actions of plasma synthesis of nanopowders. The patterns obtained can be used for constructive and technological design in the creation and development of a pilot plant for high-performance production of nanosilicon powders. [ABSTRACT FROM AUTHOR]

• Characteristics like electrode thickness and electrolyte volume affect performance. • Large electrolyte to electrode volume (20:1) significantly improves capacity. • Relationship between electrolyte and electrode volume needs to be understood. Silicon electrodes are being investigated as potential high-capacity replacements for graphite electrodes in lithium-ion batteries. Various factors affecting silicon electrodes need to be understood to maintain increased capacity and high performance at subzero temperatures. This work investigates electrode thickness and volume of electrolyte used that can affect performance of a copper modified silicon electrode at −20 °C. When electrolyte volume is large compared to electrode volume (20:1 ratio), the performance of these cells at low temperature is noticeably improved, retaining approximately 400 mAh/g capacity at −20 °C after 50 cycles. [ABSTRACT FROM AUTHOR]

As the demand for mobile energy storage devices has steadily increased during the past decades due to the rising popularity of portable electronics as well as the continued implementation of electromobility, energy density has become a crucial metric in the development of modern batteries. It was realized early on that the successful utilization of silicon as negative electrode material in lithium‐ion batteries would be a quantum leap in improving achievable energy densities due to the roughly ten‐fold increase in specific capacity compared to the state‐of‐the‐art graphite material. However, being an alloying type material rather than an intercalation/insertion type, silicon poses numerous obstacles that need to be overcome for its successful implementation as a negative electrode material with the most prominent one being its extreme volume changes on (de‐)lithiation. While, as of today, a plethora of different types of Si‐based electrodes have been reported, a universally common feature is the interface between Si‐based electrode and electrolyte. This review focuses on the knowledge gained thus far on the impact of different liquid electrolyte components/formulations on the interfaces and interphases encountered at Si‐based electrodes. [ABSTRACT FROM AUTHOR]

Over the past decade, there has been a significant advancement in understanding the mechanics of silicon (Si) electrodes in lithium (Li)-ion batteries. Much of this interest in Si electrodes as ideal anode materials for high-capacity Li-ion batteries stems from its theoretical specific capacity of 4200 mAh gâˆ'1, which is an order-of-magnitude higher than that of conventional graphite electrodes (372 mAh gâˆ'1). However, the high capacity of Li ions is also accompanied by a ∼300% volume expansion of the Si electrode during Li intercalation, which results in massive cracking of the electrode and capacity fade. In this review article, we summarize recent progress in elucidating the underlying fracture and failure mechanics of Si electrodes using multiscale computations and experiments, spanning the quantum, atomistic, microscopic, and macroscopic length scales. We focus on four fundamental mechanics issues: (i) the mechanical properties and fracture behavior of lithiated Si electrodes; (ii) the interfacial mechanics between Si thin-film electrodes and current collectors; (iii) the deformation and failure mechanics of the solid electrolyte interphase; and (iv) the design of Si electrodes for improved mechanical performance. Current challenges and possible future directions for the field of mechanics of materials in pursuit of high-capacity rechargeable batteries are also discussed. [ABSTRACT FROM AUTHOR]

This work aims to review and understand the behavior of the electrochemical lithiation onset of amorphous silicon (a-Si) films as electrochemically active material for new generation lithium-ion batteries. The article includes (i) a review on the lithiation onset of silicon films and (ii) a mechanochemical model with numerical results on the depth-resolved mechanical stress during the lithiation onset of silicon films. Recent experimental studies have revealed that the electrochemical lithiation onset of a-Si films involves the formation of a Li-poor phase (Li0.3Si alloy) and the propagation of a reaction front in the films. The literature review performed reveals peculiarities in the lithiation onset of a-Si films, such as (i) the build-up of the highest mechanical stress (up to 1.2 GPa) during lithiation, (ii) a linear increase in the mechanical stress with lithiation which mimics the characteristics of linear elastic deformation, (iii) only a minute volume increase during Li incorporation, which is lower than expected from the number of Li ions entering the silicon electrode, (iv) the largest heat generation appearing during cycling with only a minor degree of parasitic heat contribution, and (v) an unexpected enhanced brittleness. The literature review points to the important role of mechanical stresses in the formation of the Li-poor phase and the propagation of the reaction front. Consequently, a mechanochemical model consisting of two stages for the lithiation onset of a-Si film is developed. The numerical results calculated from the mechanochemical model are in good accord with the corresponding experimental data for the variations in the volumetric change with state of charge and for the moving speed of the reaction front for the lithiation of an a-Si film of 230 nm thickness under a total C-rate of C/18. An increase in the total C-rate increases the moving speed of the reaction front, and a Li-rich phase is likely formed prior to the end of the growth of the Li-poor phase at a high total C-rate. The stress-induced phase formation of the Li-poor phase likely occurs during the lithiation onset of silicon electrodes in lithium-ion battery.

Silicon electrodes are widely used in semiconductor etching machines. The periodic consumption of silicon electrodes has become an important consumable in wafer manufacturing. Due to the limited number of silicon electrode manufacturers and the increasing demand for silicon electrodes in global market, the newly processed silicon electrodes need to be immediately delivered to wafer manufacturers to ensure uninterrupted production. Driven by this, this paper introduces a new integrated scheduling problem called the silicon electrode production and transportation integrated scheduling problem (SEPTISP), whose criterion is to minimize the makespan. This problem is modeled as a combination of the production scheduling subproblem (PSS) and the transportation scheduling subproblem (TSS). These two subproblems are coupled with each other. Considering the SEPTISP's NP-hard and coupling properties, a novel collaborative Q-learning hyper-heuristic evolutionary algorithm integrated with reinforcement learning scheme (CQHEA_RLS) is proposed to handle them. In the CQHEA_RLS, the production agent and the transportation agent are focused on executing exploitation in the reduced but promising regions via their specific search actions, while the joint agent is centered on performing exploration in the whole solution space through its joint search actions and determining the suitable search regions for the other two agents. Meanwhile, the joint agent also integrates the historical performance information of its own and the other two agents' search actions to dynamically choose its subsequent search actions. Moreover, each agent is devised as an effective Q-learning hyper-heuristic evolutionary algorithm. This new collaborative framework ensures that the CQHEA_RLS can continuously search downwards to obtain truly high-quality solutions in a relatively short runtime. The experimental results demonstrate that the designed algorithm can achieve better performance than the existing state-of-the-art algorithms. [ABSTRACT FROM AUTHOR]

We propose a novel mathematical model for predicting the effective modulus of Si electrodes in Li-ion batteries by considering the large volume expansion of Si during lithiation and porosity variation, as well as the influence of change in Li-ion concentration and Poisson's ratio, assuming the Si electrode as a particulate composite material. Though previous studies considered the Li-ion concentration and Poisson's ratio in their models, they rarely considered the porosity and a large change in the volume of silicon, which degrade the performance of Li-ion batteries with Si electrodes. The proposed model is formulated on the basis of a three-phase particulate composite material composed of silicon particles, pores, and binders. Through parametric studies, it is found that the Li-ion concentration in silicon increases nonlinearly and the Poisson's ratio decreases during charging, regardless of the structure (crystalline or amorphous) of the silicon particles. The effective modulus of the three-phase particulate composite electrode decreases during charging as a result of the changes in the Li-ion concentration, Si and binder volumes, pores, and Poisson's ratio. The accuracy of the developed model is validated by comparing the predicted moduli of this model with other 3 experimental data and 2 model predictions. [ABSTRACT FROM AUTHOR]

Summary: In situ growing conductive polyaniline (PANi) has been regarded as a functional binder to enhance the performance of silicon based anodes in half cells, while few papers discussing the influence of Mn2+ from cathode on full cells. In this paper, the effects of Mn2+ on NSi@PANi electrodes in both half and full cells are investigated, and the mechanism for the fast capacity fade of LiMn2O4/NSi@PANi full cell is elucidated. Results reveal that the full cell will significant accelerate the capacity fade of NSi@PANi anode, and the extra consumption of active Li+ and electrolytes caused by the deposited Mn2+ on silicon anodes in lithium manganate (LMO)/NSi@PANi full cells is confirmed as the main reason of the capacity fade and lower coulombic efficiency for the excessive growth of solid electrolyte interphase. [ABSTRACT FROM AUTHOR]

Large volume modifications during electrochemical cycling of electrodes in Li-ion batteries often limit successful applications due to stress formation, electrode fracture and delamination from the current collector. In this study, we carried out investigations on the volume changes taking place during potentiostatic lithiation of the high capacity electrode material amorphous silicon. Thin film electrodes were investigated at potentials of 0.45, 0.28, 0.19 und 0.06 V vs Li/Li+ during lithiation using in-operando neutron reflectometry. We found a strongly non-linear correlation between volume and state-of-charge for each potential applied in strong contrast to the results of galvanostatic lithiation. A possible explanation might be that for high current densities occurring at the beginning of each potentiostatic lithiation step free volumes are created in the electrode material leading to disproportionate volume expansion.

Silicon carbon nanoparticles (SCNPs) coated with reduced graphene oxide (rGO) were fabricated by a hydrothermal method and subsequently by a simple heat treatment process. SCNPs/rGO exhibit excellent electrochemical performance which not only attributes the rGO layer to inhibit the volumetric expansion of silicon and reduce the impedance between the active material and lithium ions during the electrochemical process, but also improves the electrical conductivity of SCNPs/rGO. The as-prepared compound was cyclically tested at a current density of 150 mA/g, with the first charge and discharge capacities of 3152.2 mAh/g and 3342.7 mAh/g, respectively. Moreover, the electrochemical performance of SCNPs/rGO was better than SCNPs. The R CT values for fresh battery, after 1 cycle and 100 cycles, are 120.9 Ω , 120.5 Ω and 104 Ω. Thus, compared with SCNPs, SCNPs/rGO exhibited lower overall impedance values. These results indicate that the addition of graphene layer significantly improved the electrochemical performance of SCNPs electrodes and reduced the internal resistance of the battery. Silicon carbon nanoparticles coated with rGO were obtained by hydrothermal method. The use of rGO to improve the electrical conductivity of the material can also act as a carbon matrix material to inhibit the volume expansion effect. The results showed that the addition of rGO improved the conductivity of lithium ions and played a positive role in the diffusion of lithium ions. [ABSTRACT FROM AUTHOR]

The plastic flow in a silicon electrode during lithiation can alter the stress state in the silicon electrode and retard the fracture of the silicon electrode. In this work, we develop a rate-dependent model to investigate the plastic flow and phase transformation, which concurrently occur during the lithiation of a cylindrical silicon electrode. Using a power law for the plastic-flow potential and neglecting elastic deformation, we obtain analytical solutions of the stresses in the silicon electrode, which are dependent on the temporal evolution of the interface between lithiated phase and un-lithiated phase. A simplified diffusion model, which captures the temporal evolution of the interface, is proposed in the framework of the Cahn-Hilliard phase-field theory. The numerical results are in good accord with the results from the phase-field model with finite deformation. Under galvanostatic operation, the stresses are dependent on the lithiation rate, and the stresses on the surface of the silicon electrode are independent of initial radius and lithiation time. Under potentiostatic operation, the stresses in a silicon electrode of a smaller radius is larger than that in a silicon electrode of a larger radius. The magnitudes of the stresses on the surface decrease with the increase of both initial radius and the lithiation time. [ABSTRACT FROM AUTHOR]

Stray corrosion and electrolytic products deposition in the machining gap are major influence factors seriously restricting the application of micro electrochemical machining (ECM). Currently, one technical bottleneck is preparing thin and durable insulating films on electrode sidewall to restrain the stray corrosion. In previous work, we proposed an anisotropically-etched silicon electrode for micro ECM, on which silicon dioxide and silicon nitride are deposited as insulating films. The heavily doped silicon electrode body has good electrical conductivity, and the silicon-based films have excellent insulating property. The anisotropically-etched silicon electrode on (1 0 0) crystal plane has an isosceles trapezoid cross section. To get better machining performance compared with cylindrical electrode, the silicon electrode is rapidly rotated on a spindle in micro ECM process. The periodically varying lateral gap has a special effect on the electrolyte flow characteristics. A simulation model of electrolyte flow and discrete phase distribution is established by Fluent software. Simulation results indicate that the normal flow rate of electrolyte with silicon electrode is 50 times higher than that with cylindrical electrode, which is benefit for removing solid electrolytic products smoothly. The maximum concentration and residual ratio of solid electrolytic products are decreased with the rotating speed increasing. When the rotating speed is higher than 1200 rpm, the residual ratio is reduced to 13%. ECM experimental results indicate that electrolytic products on the workpiece machined by a silicon electrode are much fewer than that by cylindrical electrode. Silicon electrodes with trapezoidal cross section have a distinct advantage for reducing electrolytic products deposition. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to analyze a 70% Si/C/perfluorooctene-carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping (CAMP) Facility, Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.83 401 nm). A survey spectrum together with O 1s, C 1s, and Si 2p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor sodium, copper, calcium, and lithium signals and show the expected silicon-carbon, carbon-fluorine, and silicon-fluorine species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to analyze a 70% Si/C-carbon black/polyethylene glycol/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.834 01 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey scan was collected to ascertain the amount of beam-induced damage, which appears to be minimal. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor copper and lithium signals and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well as contributions related to the binder material. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to analyze a 70% Si/C/polyvinylidine difluoride/carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.834 01 nm). A survey spectrum together with O 1s, C 1s, and Si 2p are presented. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor copper and lithium signals and show the expected silicon-carbon and silicon-fluorine species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy (XPS) was used to analyze a 70% Si/C-carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.834 01 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey spectrum was collected to ascertain the amount of beam-induced damage, which appears to be minimal. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor copper, nitrogen, calcium, and lithium signals and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well contributions related to the binder material. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to analyze a 90% Si/C-lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.834 01 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey spectrum was collected to ascertain the amount of beam-induced damage, which appears to be minimal. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor lithium signal and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well contributions related to the binder material. [ABSTRACT FROM AUTHOR]

X-ray photoelectron spectroscopy was used to analyze a 15%Si/C-graphite/carbon black/lithiated polyacrylic acid electrode fabricated at the Cell Analysis, Modeling, and Prototyping Facility (CAMP), Argonne National Laboratory. The spectra were obtained using incident monochromatic Al Kα radiation at 1486.6 eV (0.83 401 nm). An initial survey spectrum together with O 1s, C 1s, and Si 2p are presented. A final survey spectrum was collected to ascertain the amount of beam-induced damage, which appears to be minimal. The spectra indicate the principal core level photoelectron and Auger electron signals with only minor nitrogen and lithium signals and show the expected silicon-carbon species related to the surface modification process in addition to oxidized carbon and silicon due to atmospheric exposure as well contributions related to the binder material. [ABSTRACT FROM AUTHOR]

Polymeric binders are a critical component to enhance mechanical integrity, maintain electronic conductivity, and achieve long durability of silicon (Si)-based electrodes. A fundamental understanding of the relationship between binder properties and mechanical degradation of Si electrodes is indispensable to developing durable Si-based electrodes. Using an environmental nanoindentation system, we measured the mechanical properties of Si composite electrodes made with different binders, including polyvinylidene fluoride (PVDF), Nafion, sodium-carboxymethyl cellulose (Na-CMC), and sodium-alginate (SA), as a function of the state-of-charge and cycle numbers under both dry and wet conditions. In contrast to electrodes made of Si alone, both elastic modulus (E) and hardness (H) of Si composite electrodes increase with lithium concentration within each cycle. E and H continuously decrease during long-term cycling. The mechanical property evolution of Si composite electrodes can be correlated with the porosity and irreversible thickness changes, which are largely determined by the mechanical properties of binders, instead of the adhesion between binders and Si. Electrodes under wet conditions have smaller E and H values than those under dry conditions because binders soften in the electrolyte. These findings not only provide useful mechanical parameters for battery modeling, but also may help design high performance and durable Si-based electrodes. • Elastic modulus and hardness of Si electrodes as a function of the state of charge. • Mechanical properties of binders and the adhesion strength between binders and Si. • Binder-dependent porosity and irreversible volume changes of Si composite electrodes. [ABSTRACT FROM AUTHOR]

To understand the effect of a polydopamine interlayer between a copper current collector and a silicon composite electrode, a physics‐based model is used to analyze the cycle performance of silicon‐based lithium‐ion half‐cells with bare and polydopamine‐treated copper current collectors. We investigate the capacity‐fading mechanisms of the two cell configurations by analyzing the model parameters that change with cycling. The major capacity‐fading mechanisms in the silicon‐based anodes are the increase in film resistance (solid electrolyte interphase resistance and contact resistance) and the isolation of silicon active material. The polydopamine interlayer reduced the contribution of the film resistance and isolation of the silicon active material to the capacity fade by 22 % and 10 %, respectively. The insulating‐nature of the polydopamine interlayer resulted in an increase in the charge transfer resistance contributing to 15 % reduction in the capacity retention. The efficacy of the physics‐based model is validated with experimental data obtained from silicon‐based half‐cells with bare and polydopamine‐treated copper current collectors. [ABSTRACT FROM AUTHOR]

To develop feasible probes for heavy metal ions has been considered as one of the most important research topics, due to the significance in monitoring and evaluating the toxicity of environmental water system, especially for the drinking water. This work provided a probe for Pb(II) ion detection in purified drinking water. Nickel hexacyanoferrate (NiHCF) films were prepared by vacuum evaporating nickel fine wire and transforming in a potassium ferricyanide solution on the front surface of platinum coated n-silicon. The transformed NiHCF film shows a reversible insertion electrochemistry and possesses electrocatalytic activity under illumination. The NiHCF-modified electrode was used as photoelectrode and dihydroxybenzene as photocurrent mediators to make up photoelectrochemical (PEC) sensor for Pb(II) ion detection in purified drinking water based on a two-electrode cell in absence of reference electrode and operated at zero working voltage. We have investigated the effects of Pb(II) ions on the photocurrent of hydroquinone or catechol in the purified water. The assay demonstrated good photocurrent responses by adding different concentrations of Pb(II) ion into purified drinking water with a linear range of 20-1560 nM and the limit of determination (based on S/N = 3) is 4.8 nM and 5.3 nM for the presence of hydroquinone and catechol, respectively. [ABSTRACT FROM AUTHOR]

Cycling number, crystal orientation, temperature and electric field strength play key roles in affecting the capacity and cycling ability of Li-ion battery. However, the detailed dynamic and continuous process of capacity decline mechanism from above factors need to be further understood at nanoscale. Herein, we report deformation behavior and microstructure evolution of Si anode under electric field using molecular dynamics simulations. The results show larger cycling number and electric field strength cause larger volume expansion of Si electrode, leading to the capacity loss and the reducing cycling ability as well as the decreasing structural stability. The phase transformation from diamond cubic structure to body-centred tetragonal structure and the amorphous formation depend on lithiated and delithiated depths. The crystal orientation [100] Si anode produces the volume expansion owing to a large number of nanoscale void. The various temperatures strongly affect the number and radius of nanovoid. The associated transition in the nanovoid nucleation due to the involuntary diffusion process is driven by larger cycling number or electric field strength, resulting in the irreversible capacity loss of Li-ion battery. An established analytical model suggests that diffusion-induced stress not only relies on the position of Si anode but depends upon the cycling time. [ABSTRACT FROM AUTHOR]

The microstructural degradation of a composite silicon electrode at different stages in its cycle life was investigated in 3D using X-ray nano-computed tomography. A reconstructed volume of 36 μm × 27 μm × 26 μm from the composite electrode was imaged in its pristine state and after 1, 10 and 100 cycles. Particle fracturing and phase transformation was observed within the electrode with increased cycling. In addition, a distinct, lower X-ray attenuating phase was clearly resolved, which can be associated with surface film formation resulting from electrolyte breakdown and with silicon particle phase transformation. Changes in quantified microstructural properties such as phase volume fraction and particle specific surface area were tracked. Electrode performance loss is associated with loss of active silicon. These imaging results further highlight the capability of high resolution X-ray tomography to investigate the role of electrode microstructure in battery degradation and failure. [ABSTRACT FROM AUTHOR]

Amorphous silicon is a promising high-capacity anode material for application in lithium-ion batteries. However, a huge drawback of the material is that the large capacity losses taking place during cycling lead to an unstable performance. In this study we investigate the capacity losses occurring during galvanostatic lithiation of amorphous silicon thin film electrodes by in-situ neutron reflectometry experiments for the first ten cycles. As determined from the analysis of the neutron scattering length density and of the film thickness, the capacity losses are due to irreversible storage of lithium in the electrode. The amount of stored lithium increases during cycling to 20% of the maximum theoretical capacity after the 10th cycle. Possible explanations are discussed. [ABSTRACT FROM AUTHOR]

Due to their high theoretical capacity compared to that of state-of-the-art graphite-based electrodes, silicon electrodes have gained much research focus for use in the development of next generation lithium-ion batteries. However, a major drawback of silicon as an electrode material is that it suffers from particle fracturing due to huge volume expansion during electrochemical cycling, thus limiting commercialization of such electrodes. Understanding the role of material microstructure in electrode degradation will be instrumental in the design of stable silicon electrodes. Here, we demonstrate the application of synchrotron-based X-ray tomographic microscopy to capture and track microstructural evolution, phase transformation and fracturing within a silicon-based electrode during electrochemical lithiation. [ABSTRACT FROM AUTHOR]

The application of silicon (Si) substrate as photoelectrode in light-addressable electrochemistry (LAE) is severely limited due to its ease of surface oxidation. The resulted silicon oxide (SiO x) layer is electronically insulating and blocks charge transfer between the electrode and electrolyte. Keeping the Si from being oxidized is a key challenge for its practical use as a semiconductor electrode. In this work, we find that by developing a thin layer of polydopamine film on the surface of Si substrate, followed by carbonization at 550 °C, the natural oxidation of Si substrate can be successfully forestalled. When applied as an electrode, it is further found that the carbonized polydopamine (cPDA) layer can also prevent anodic oxidation of Si. The cPDA layer-modified Si substrate exhibits good photoelectrochemical performance and great stability, with no obvious signal decrease under ambient environment over 32 h. Our work here provides a new modification strategy for anti-oxidation of Si substrate and it is promising in the application of light-addressable electrochemical sensing and imaging. [Display omitted] • A thin layer of c-PDA was successfully coated on Si surface to protect it from both natural and anodic oxidation. • The cPDA layer-protected Si presents good charge transfer ability and stability. • The cPDA layer-protected Si shows great potential in application of light-addressable electrochemical sensing and imaging. [ABSTRACT FROM AUTHOR]

Silicon is a promising candidate to substitute or complement graphite as anode material in Li-ion batteries due, mainly, to its high energy density. However, the lithiation/delithiation processes of silicon particles are inherently related to drastic volume changes which, within a battery's physically constrained case, can induce significant deformation of the fundamental components of the battery that can eventually cause it to fail. In this work, we use non-destructive time-lapse X-ray imaging techniques to study the coupled electrochemo-mechanical phenomena in Li-ion batteries. We present X-ray computed tomography data acquired at different times during the first lithiation of custom-built silicon-lithium battery cells. Microstructural volume changes have been quantified using full 3D strain field measurements from digital volume correlation analysis. Furthermore, the extent of lithiation of silicon particles has been quantified in 3D from the grey-scale of the tomography images. Correlation of the volume expansion and grey-scale changes over the silicon-based electrode volume indicates that the process of lithiation is kinetically affected by the reaction at the Si/Li x Si interface. [ABSTRACT FROM AUTHOR]

A platinum (Pt) film coated n-silicon (Pt/n-n-Si) was modified with nickel(II)-potassium hexacyanoferrate (NiHCF)-graphene sheets (GS) hybrid and used as a photo-electrochemical (PEC) sensor for non-enzyme hydrogen peroxide (HO) detection. A NiHCF film was deposited on the surface of GS/Pt/n-n-Si electrode by chemical method. The structure and composition of the NiHCF film was characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). PEC behavior of the NiHCF-GS/Pt/n-n-Si electrode was investigated using cyclic voltammetry (CV) under illumination. The modified electrode has been used as PEC sensor for HO detection with a linear range of 2.0 × 10-2.9 × 10 M and a detection limit of 1.0 × 10 M at a signal-to-noise ratio of 3 in a two-electrode cell with a Pt plate as counter electrode. The characteristics of GS layer have been discussed in both the improvement of sensibility and selectivity. [ABSTRACT FROM AUTHOR]