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• 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]

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]

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]

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/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]

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]

In this study, nickel plated silicon powders were produced using an electroless deposition process. The nickel content on the surface of silicon powders was changed by using different concentrations of NiCl 2 in the plating bath. The surface morphology of the produced Ni plated composite powders was characterized using scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) was used to determine the elemental surface composition of the composites. X-ray diffraction (XRD) analysis was performed to investigate the structure of the nickel plated silicon powders. Electrochemical cycling test of the nickel plated silicon electrodes were performed at a constant current of 100 mA/g in CR2016 test cells. In order to investigate electrochemical reactions of the nickel plated silicon powders with electrolyte, cyclic voltammetry test was performed at a scan rate of 0.1 mV/s. Among the used concentrations, the nickel plated silicon electrode produced using 40 g/L NiCl 2 had a 246 mAh/g discharge capacity after 30 cycles. [ABSTRACT FROM AUTHOR]

We perform ab initio calculations on the shear deformation response of the interdiffused Li?Si?Cu phase structure existing between a lithiated Si electrode and a Cu current collector. We show that the formation of well-delineated and weakly bonded Si?Cu and Li?Cu crystalline atomic layers within this phase structure facilitates interface sliding. However, sliding can be terminated by the formation of LiSi3 compounds across these atomic layers, which causes the abrupt capacity fade of the electrode after repeated cycling. [ABSTRACT FROM AUTHOR]

Abstract: The understanding of volume change mechanism of silicon electrode is necessary to design a new negative electrode using silicon-based active materials. Here, the drastic volume expansion of one silicon secondary particle with μm-size was in-situ observed in order to find apparent volume expansion ratio during the first charging by using single particle measurement technique. The apparent volume expansion accompanied with the first lithiation is much larger than theoretical expectation due to the agglutination state and anisotropic property. The importance of direct observation with the single particle measurement has been affirmed for understanding the characteristics of silicon electrodes. [Copyright &y& Elsevier]

Abstract: Few studies relate that the failure mechanism of silicon-based electrodes is the SEI formation. In this work, we used quantitative solid-state high-resolution nuclear magnetic resonance to show that main cause of irreversible capacity is not the decomposition of lithium salt but the degradation of electrolyte solvent with the formation of non lithiated carbon species as polymer or oligomers. [Copyright &y& Elsevier]

A novel hydroquinone (HQ) sensor was developed by depositing a film of copper hexacyanoferrate (CuHCF) on silicon electrode coated by a platinum layer. The stable film of CuHCF was electrochemically deposited onto a phosphorus heavy doped silicon (n+-Si) with 9μm epitaxial layer (n-n+-Si) wafers coated with about 40nm platinum layer (Pt/n-n+-Si). Scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) were used to characterize the morphology, composition and photo-electrochemical behavior of the CuHCF film. A two-electrode cell based on CuHCF/Pt/n-n+-Si electrode was used as sensor for HQ determination by photocurrent measurements at a zero bias. The sensor showed good photocurrent responses by adding different concentrations of HQ with a good stability. The linear range for the detection of HQ was 1.0×10−5 to 2.0×10−4 M, with a detection limit (S/N=3) of 2.2×10−6 M. This provides a facile way of detecting HQ and succeeds in averting from an inconvenient reference electrode. [ABSTRACT FROM AUTHOR]

Abstract: The local composition of negative silicon electrodes is studied by ex situ electron energy-loss spectroscopy along the first delithiation in a lithium battery. By measuring dozens of sample areas for over a dozen compositions, the local and overall inhomogeneities in these practical electrodes are evaluated. The statistical treatment of the data highlights the existence of larger inhomogeneities at the beginning of the delithiation as well as at a 100nm scale. It is also shown that, even if incremental capacity curves are different, the compositional changes during delithiation are identical for nano- and micro-Si. Namely, an initial Li15Si4 phase is replaced by a Li2±0.3Si amorphous phase in a biphasic process, the latter compound being further delithiated to amorphous silicon in single phase process. Results also show that the electrochemical irreversibility associated with the liquid electrolyte reduction/degradation is generated during the lithiation process, not the delithiation process. [Copyright &y& Elsevier]

A prussian blue (PB) film has been deposited on the surface of platinum (Pt) coated n-type epitaxial silicon (Pt/n-n+-Si) wafer. The electro-deposition of PB was achieved by a cyclic scan in a potential range of −0.2 to +0.60V (vs SCE) at 50 mV/s for 5 cycles in a solution containing 2.5 mM FeCl3, 2.5 mM K3Fe(CN)6, 0.1 M KCl and 0.1 M HCl with an illumination from 50 W bromine-tungsten lamp. The emphasis is laid on that this modified silicon electrode can be used as a sensor for the photocurrent determination of hydrogen peroxide at a zero bias by a two-electrode system without reference electrode. The use of the PB modified Pt/n-n+-Si electrode as a hydrogen peroxide sensor was demonstrated with good stability and selectivity. The PB film was characterized by cyclic voltammetry measurements and scanning electronic microscopy (SEM). A new photo-electrochemical sensor based on two-electrode system has been developed for determination of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

Abstract: Electrodes on planar type microelectromechanical system (MEMS) microprobes mainly record neurons on the top-side of probe shaft (called a top-side electrode). However, it is often necessary to record neurons other than those on the top-side of the probe shaft. This study uses the glass reflowing technique to embed silicon-vias in a glass probe to implement a microprobe capable of recording neurons around the shaft. The proposed technology makes it possible to fabricate, distribute, and integrate four types of electrodes on the shaft: top-side, back-side, double-side, and sidewall electrodes. These electrodes have different recording characteristics. The in vitro and in vivo (using crayfish and rat brain) experiments in this study shows that the top-side and back-side electrodes are respectively more sensitive to neurons on the top-side and back-side of the probe shaft. In contrast, signals recorded by double-side electrode and sidewall electrode are equally sensitive to neurons around the probe shaft. This study enables the implementation and integration of these four types of electrodes, meeting the requirements of various neural applications. [Copyright &y& Elsevier]

Abstract: The nature of Li–Si alloy phases that are generated in electrochemical lithiation is examined as a function of temperature. The electrochemical lithiation is performed at 0.0V (vs. Li/Li+) by short-circuiting an amorphous Si thin-film electrode with a Li metal counter electrode. At 25–85°C, the well-known Li15Si4 phase (theoretical specific capacity=3580mAhg−1) forms. At 100–120°C, however, Li21Si5 (4008mAhg−1) that is known to be the most Li-rich phase in Li–Si system is generated. The crystallization into Li21Si5 is, however, so kinetically slow that it does not appear in the transient cycling experiment. The Li21Si5 phase is converted to amorphous Si upon de-lithiation, but the restoration back to the initial phase is only observed at 100–120°C after a prolonged lithiation at 0.0V. The cycleability of this phase is poor due to a successive Li trapping inside the Si matrix, which is caused by the formation of electrically isolated Si islands. [ABSTRACT FROM AUTHOR]

This work shows the results obtained for the silicon modification with redox molecules derived from ferrocene. The effect of the crystallographic orientation of silicon on the electron-transfer rates was studied. For this study, silicon electrodes (p-type) with two different crystallographic orientations were employed: p-Si (100) and p-Si (111). The redox molecules employed were alkyl ferrocenes with 3, 5 and 10 carbon atoms (propyl, pentyl and decyl ferrocene, respectively). The results showed that the electron-transfer process is not influenced by the crystallographic orientation of silicon and that this process is determinate by electron hopping in a regime of bonded diffusion. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical cycling properties of a Si electrode were drastically improved by the introduction of an ethylene carbonate (EC)-rich electrolyte solution. Cross-sectional morphologies of fully charged Si electrodes were observed with scanning electron microscopy (SEM). The increment of EC in the electrolyte solution showed a tendency to prohibit the deterioration of the Si electrode during Li+ ion insertion. We analyzed the surface films formed on a Si electrode through Fourier transform infrared (FT-IR) spectroscopy. The solvation shell structures of Li+ ions in electrolyte solutions were studied with FT-IR spectroscopy, and the apparent solvation numbers for Li+ ions by EC molecules were calculated. [Copyright &y& Elsevier]

The mechanical behavior of an electrode during implantation into neural tissue can have a profound effect on the neural connections and signaling that takes place within the tissue. The objective of the present work was to investigate the in vivo implant mechanics of flexible, silicon-based ACREO microelectrode arrays recently developed by the VSAMUEL consortium (European Union, grant #IST-1999-10073). We have previously reported on both the electrical [1]-[3] and mechanical [4], [5] properties of the ACREO electrodes. In this paper, the tensile and compression forces were measured during a series of in vivo electrode insertions into the cerebral cortex of rats (7 acute experiments, 2-mm implant depth, 2-mm/s insertion velocity). We compared the ACREO silicon electrodes (40 opening angle, 1-8 shafts) to single-shaft tungsten electrodes (3° and 100 opening angles). The penetration force and dimpling increased with the cross-sectional area (statistical difference between the largest and the smallest electrode) and with the number of shafts (no statistical difference). We consistently observed tensile (drag) forces during the retraction phase, which indicates the brain tissue sticks to the electrode within a short time period. Treating the electrodes prior to insertion with silane (hydrophobic) or piranha (hydrophilic) significantly decreased the penetration force. In conclusion, our findings suggest that reusable electrodes for acute animal experiments must not only be strong enough to survive a maximal force that exceeded the penetration force, but must also be able to withstand high tension forces during retraction. Careful cleaning is not only important to avoid foreign body response, but can also reduce the stress applied to the electrode while penetrating the brain tissue. [ABSTRACT FROM AUTHOR]

In-situ infrared spectroscopy is an especially powerful technique when applied to semiconducting electrodes. The use of a multiple-internal-reflection geometry brings an important improvement in sensitivity. Also, it is compatible with a cell geometry featuring low series resistance and allowing for quantitative studies in the presence of a Faradaic reaction and a fast modulation of potential. Additional interests include the possibility of analysing the changes in electronic absorption associated with the space-charge layer and/or electronic surface states, and the possibility of varying the polarisation of the infrared beam, giving extra information on the absorbing species. Here the potentialities of the technique are illustrated through an in-situ study of the modification of the hydrogenated silicon surface by anodic substitution of methyl groups in a Grignard electrolyte. This irreversible reaction is analysed by using a current pulse method. The electrochemical character of the reaction is demonstrated, and unambiguous indications on the reaction mechanism are obtained from the kinetics of modification. The electronic quality of the modified silicon surface is seen to depend on the halogen involved in the Grignard, which can be rationalised in terms of the reaction mechanism. [Copyright &y& Elsevier]

• Effective coverage ratio (ECR) were introduced to mimic the different degrees of pre-existing interface defects. • Battery capacity would have a rapider loss when the ECR reduced below a threshold (about 55%). • Pre-existing defects would "boost" interfacial delamination during subsequent cycles in full discharge condition. Interfacial degradation is one of the root causes of the poor performance of Si-based lithium-ion batteries. Only figure out the role of interfacial degradation in cycling can we optimize electrodes to improve the battery robustness and durability. Here, we performed reactive force field (ReaxFF) atomistic simulations to investigate the "natural" delithiation responses of a-Si-core/a-Al 2 O 3 -coating electrode with different degrees of pre-existing interfacial defects. Effective coverage ratio (ECR) was introduced to mimic different degrees of the pre-existing defects on the a-Li x Si/a-Li x Al 2 O 3 interface. The simulation quantitatively showed that, in any ECR samples, the delithiation could be characterized as two stages: a steady stage with a higher discharge rate and a lower nanoporosity, and an unsteady stage with a lower discharge rate and a larger aggregates of nanopores. The deterioration of ECR caused the steady stage shortened and unsteady stage prolonged. Consequently, further interfacial delamination was easier to form in lower ECR samples in full discharge condition, and the pre-existing defects would "boost" interfacial delamination during subsequent cycles. Besides, the battery capacity would have a rapid loss when the ECR reduced below a threshold (about 55%). This work provides a fundamental understanding of delithiation-induced interfacial degradation mechanism of Si electrodes at atomic-level. [ABSTRACT FROM AUTHOR]

• We first demonstrate the path-independence of Ĵ -integral under chemomechanical loading. • The path-independence of Ĵ -integral for active materials with concentration-dependent material properties is validated. • We developed an incremental constitutive model accounting for the lithiation-induced plastic deformation. • The effect of the crack size and the influx on the Ĵ-integral for a cylindrical Si-electrode with a central-slit crack is examined. The cracking of the active materials in a lithium-ion battery as an adverse consequence of lithiation-induced deformation can significantly cause the capacity loss and likely result in catastrophic failure of the lithium-ion battery. Following the work by Kishimoto et al. [1] , we introduce the Ĵ -integral for the elastoplastic deformation of an active material with a slit-type crack under chemomechanical loading in this work and prove that the Ĵ -integral is path-independent. We also demonstrate that the classical J -integral is path-dependent and is not appropriate for the fracture analysis of the lithiation-induced cracking of the active materials in lithium-ion batteries. Using the incremental constitutive model developed in this work, we numerically analyze the size dependence of the Ĵ -integral under a constant influx for a cylindrical Si-electrode with a central-slit crack. The numerical results reveal that the value of the Ĵ -integral increases with the increase of the crack size and the influx at the same lithiation time, and there exists a maximum value of the Ĵ -integral for a given physical-geometrical configuration. The lithiation-induced softening has a limited effect on the value of the Ĵ -integral. All of these results suggest that the Ĵ -integral can be used to analyze the lithiation-induced propagation of cracks in active materials. [ABSTRACT FROM AUTHOR]

• The volume expansion of thin film amorphous silicon electrodes was investigated during potentiostatic lithiation. • Neutron reflectometry was used for an in-operando study. • A strongly non-linear correlation between volume and state-of-charge is found. 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. [ABSTRACT FROM AUTHOR]