Depth Profiling Method Research Articles

(Invited) Neutrons as a Powerful Tool for Better Understanding Electrochemistry on Various Length and Time Scales

Today, sophisticated methods are applied to gain a deeper understanding of processes in in-situ electrochemistry. There are few ways to study electrochemically relevant processes on different length and/or time scales without affecting the processes themselves. Probes that cover a sufficient volume of the sample non-destructively and are sensitive to the important charge carriers are in great demand. For such purposes, neutrons are an ideal candidate to perform this task because they have relatively high sensitivity to the light chemical elements, can distinguish neighboring elements of the periodic table, have a large beam cross-section, and possess high penetration depth for many types of materials.Therefore, many open questions are addressed to unique neutron techniques tailored to solve the open problems. This article gives an overview of some examples to show the advantages of using neutrons for special questions on different length and time scales [1]. For surface investigations of electrodes, the neutron depth profiling method (NDP) is suitable for characterizing the Li distribution up to the nano range [2]. Neutron diffraction is a powerful tool to better understand cylindrical cells at the atomic level, e.g. during the intercalation process [3]. Another strong field of neutrons is the monitoring of the wetting process during the electrolyte filling of prismatic hard case cells on the macroscopic length scale using the neutron imaging technique [4].

Oxygen diffusion and surface exchange coefficients measurements under high pressure: Comparative behavior of oxygen deficient versus over‐stoichiometric air electrode materials

AbstractMixed ionic electronic conductors (MIECs) oxides are used as electrode materials for solid oxide cell (SOC) application, as they combine high electronic conductivity as well as high oxygen diffusivity and oxygen surface exchange coefficients. The ionic transport properties can be directly determined thanks to the isotopic exchange depth profiling (IEDP) method. To date, the reported measurements have been performed at ambient pressure and below. However, for a higher efficiency of hydrogen production at the system level, it is envisaged to operate the cell between 10 and 60 bar. To characterize the MIEC oxides properties in such conditions, an innovative setup able to operate up to a total pressure of 50 bar and 900°C has been developed. The main goal of this study was to compare the behavior of two types of reference materials: the oxygen deficient La‐Sr‐Fe‐Co perovskites, and the overstoichiometric lanthanide nickelates Ln2NiO4+δ (Ln = La, Pr, Nd). Diffusion and surface exchange coefficients obtained under 6.3 bar of oxygen are measured and their evolution discussed in light of the change in oxygen stoichiometries. This analysis allows better understanding of the dependency of the surface exchange coefficient with the oxygen partial pressure.

UV femtosecond single-pulse and collinear double-pulse laser-induced breakdown spectroscopy (LIBS) for depth-resolved characterization of nano-scaled films

In the current work, we demonstrate the UV femtosecond (248 nm, 450 fs) single-pulse and double-pulse laser-induced breakdown spectroscopy (LIBS) as an effective method for depth profiling of nanometer-thick multi-layered structures, including photovoltaic thin films. Femtosecond LIBS enabled selective detection of both organic and inorganic materials at different depths within nanometer-scale (10–250 nm) multi-layered samples having thicknesses comparable to the etching depth produced by a single laser shot ablation. To enhance the analytical capabilities of the method, we applied the collinear double-pulse LIBS technique, using a Michelson interferometer to split the laser pulse into two equal-energy pulses. Results obtained with Indium Tin Oxide (ITO) nanofilms (115 nm layer thickness) present a clear increase of the intensity emission by a factor of 3 to 10, depending on laser fluence, when the double-pulse approach is used. Single-pulse LIBS achieved an ablation rate of around 60 nm, while the double-pulse configuration achieved 40 nm/pulse, in a sequence of seven laser shots. Furthermore, via double-pulse LIBS spectra were recorded even at fluences as low as 150 mJ/cm2, compared to 250 mJ/cm2 required for capturing spectra, when the same total energy per pulse was maintained.

Dendrite Formation on the Poly(methyl methacrylate) Surface Reactively Sputtered with a Cesium Ion Beam.

The development of topography plays an important role when low-energy projectiles are used to modify the surface or analyze the properties of various materials. It can be a feature that allows one to create complex structures on the sputtered surface. It can also be a factor that limits depth resolution in ion-based depth profiling methods. In this work, we have studied the evolution of microdendrites on poly(methyl methacrylate) sputtered with a Cs 1 keV ion beam. Detailed analysis of the topography of the sputtered surface shows a sea of pillars with islands of densely packed pillars, which eventually evolve to fully formed dendrites. The development of the dendrites depends on the Cs fluence and temperature. Analysis of the sputtered surface by physicochemical methods shows that the mechanism responsible for the formation of the observed microstructures is reactive ion sputtering. It originates from the chemical reaction between the target material and primary projectile and is combined with mass transport induced by ion sputtering. The importance of chemical reaction for the formation of the described structures is shown directly by comparing the change in the surface morphology under the same dose of a nonreactive 1 keV xenon ion beam.

A‐site acceptor‐doping strategy to enhance oxygen transport in sodium–bismuth–titanate perovskite

AbstractSodium–bismuth–titanate (NBT) has recently been shown to contain high levels of oxide ion conductivity. Here we report the effect of A‐site monovalent ions, M+ = K+ and Li+, on the electrical conductivity of NBT. The partial replacement of Bi3+ with monovalent ions improved the ionic conductivity by over one order of magnitude without an apparent change of the conduction mechanism, which is attributed to an increase in the oxygen vacancy concentration based on an acceptor‐doping approach. The 18O tracer‐diffusion coefficient (D*) determined by the isotope exchange depth profile method in combination with secondary ion mass spectrometry confirmed that oxygen ions are the main charge carriers in the system. Among these acceptor‐doped samples, 4% Li doping provides the highest total conductivity, leading to a further discussion of doping strategies for NBT‐based materials to enhance the electrical behavior, is discussed. Comparisons with other oxide‐ion conductors and an oxygen‐vacancy diffusivity limit model in perovskite lattice suggested that the doped NBT‐based materials might already have achieved the optimization of the ionic conductivity.

Multiscale analysis of thermal degradation of polyamide 6,6 - Influence of temperature on oxygen diffusion-limited oxidation profiles

This paper is devoted to the impact of oxygen diffusion on thermal ageing of PA-6,6. Samples were subjected to ageing in air at temperatures ranging from 140°C to 200°C for different times. Depth profiling methods using AFM measurements were developed to characterise the heterogeneity of the thermal and mechanical properties of the oxidised polymer. A comparison of the results obtained with micro-FTIR profiles was performed to correlate the chemical and physical changes induced by oxidation (i.e., from molecular to macroscopic scales). As a result of diffusion-limited oxidation (DLO), it was shown that polymer oxidised much faster at the surface than in the bulk.

Analysis of Hydrogen in Inorganic Materials and Coatings: A Critical Review

The currently used bulk analysis and depth profiling methods for hydrogen in inorganic materials and inorganic coatings are reviewed. Bulk analysis of hydrogen is based on fusion of macroscopic samples in an inert gas and the detection of the thereby released gaseous H2 using inert gas fusion (IGF) and thermal desorption spectroscopy (TDS). They offer excellent accuracy and sensitivity. Depth profiling methods involve glow discharge optical emission spectroscopy and mass spectrometry (GDOES and GDMS), laser-induced breakdown spectroscopy (LIBS), secondary ion mass spectrometry (SIMS), nuclear reaction analysis (NRA), and elastic recoil detection analysis (ERDA). The principles of all these methods are explained in terms of the methodology, calibration procedures, analytical performance, and major application areas. The synergies and the complementarity of various methods of hydrogen analysis are described. The existing literature about these methods is critically evaluated, and major papers concerning each method are listed.

Melanin system composition analyzed by XPS depth profiling

The melanins are a class of natural pigments ubiquitous throughout the biosphere. These pigments are gaining significant attention as advanced materials due to their biocompatibility, optical and electrical properties. The most common form of melanin, eumelanin, has a well-known problem of insolubility in most common solvents. The insolubility has made standard chemical analysis challenging, leading to researchers opting to use X-Ray photoelectron spectroscopy (XPS). However, standard XPS used on melanins and related materials have been limited to being a surface technique, and hence reported values to date may not reflect the bulk. In this work, we have investigated with XPS depth-profiling method the chemical information of the surface and the bulk of powder and thin-films of eumelanin and several melanin derivatives. These latter derivatives are modified melanins designed to overcome the insolubility of the standard systems. Our result indicates that there are only few differences in the chemical composition of the melanin chemical structure between the surface and bulk, for either the powder of film samples. Our results show that a basic surface probe is sufficient to obtain an accurate elemental composition for basic melanin samples. As such, our analysis indicates that XPS characterization is an important characterization of polyindolequinone systems in general such as the melanins and polydopamines.

Preferential sputtering of metal oxide mixture thin films

Metal oxide mixture materials enable the production of dielectric multilayer coatings for highest power laser applications. During thin film deposition, when using sputtering techniques in combination with composite target materials, preferential sputtering occurs on the target surface. The quantitative analysis of the mixture thin film composition, usually performed by ion beam based depth profiling methods, is also affected by preferential sputtering. To gain a deeper understanding, the atomic composition variation of sputtered mixture material surfaces is calculated applying the Monte Carlo simulation program tridyn. The simulation results are compared to the atomic composition gradient measured via depth profiling x-ray photoelectron spectroscopy for mixture thin films composed of HfO2, Sc2O3, Al2O3, and SiO2. The deviations between the experimental and simulated data are discussed with respect to the different mixture material combinations.

ThinFilmsAnalysisMPEI – Software for XPS Analysis of Multilayer Multicomponent Films

The work presents ThinFilmsAnalysisMPEI software implementing the method of chemical and phase depth profiling based on photoelectron spectra interpretation, described in paper [1]. Efficiency and productivity of the software for the problem of chemical and depth profiling is shown on examples of synthetic and experimental spectra.

Operando Isotopic Exchange in Solid Oxide Fuel Cells: Oxygen-Transport Dependency on Applied Potential.

The oxygen isotopic exchange technique is a powerful tool to investigate the oxygen transport kinetics in an oxide solid. In a solid oxide fuel cell, isotopic surface exchange and diffusion coefficients are classically determined by using the Isotopic Exchange Depth Profiling method followed by ex situ SIMS characterizations. Despite its relevance, the utilization of in situ or operando techniques to measure the isotopic exchange under an electrical bias remains marginal. We developed here a set-up which enables operando monitoring of oxygen exchange in SOFC type cells under polarization. The system has been used for studying the oxygen mobility dependency upon polarization on a symmetrical Pt/YSZ/Pt cell (YSZ: yttria-stabilized zirconia). Homomolecular and heterolytic exchange reactions were undertaken to investigate the oxygen activation step and discriminate the limiting step among the sequence of elementary steps which constitute the oxygen transport process in the SOFC system. Oxygen ions incorporation into the dense ionic conductor was identified to be the rate determining step, and its first order rate constant dependency on applied potential was established.

Performance of in situ gamma-ray spectrometry in the assessment of radioactive cesium deposition around the Fukushima Daiichi nuclear power plant

In situ gamma-ray spectrometry using diverse survey platforms has been conducted in contaminated areas with various dose rate levels around the Fukushima Daiichi nuclear power plant (FDNPP). Six survey sites, including two evacuation zones around the FDNPP, were selected for ground-based gamma-ray spectrometry using HPGe (high purity Ge) and LaBr3(Ce) detectors to assess the radioactive cesium deposition in the ground. Laboratory analysis of soil samples taken by depth from the sites was performed to evaluate the depth profile of radioactive cesium. The diverse levels of radioactivity of 137Cs were then distributed to six survey sites from 30 to 3000 kBq·m−2 in the measurement period of October 2018. Finally, a method to directly calculate the depth profile using in situ measurement was introduced so as to have representation over a wide area, and the results were successfully compared with those of sample analysis at one point in the site. Except for the sites with relatively high lateral inhomogeneity of radioactive cesium, about 30% difference between two depth profiling methods using samples and in situ measurement was shown in the calculated radioactivity of 134Cs and 137Cs in the ground.

Tailoring Electric Field Standing Waves in Reflection–Absorption Infrared Spectroscopy to Enhance Absorbance in Buried Molecular Layers

Electric field standing waves (EFSW) that establish within thin films during their characterization by reflection–absorption infrared (RAIR) spectroscopy are shown to result in a >25-fold enhancement in the intensity of absorbance features in a molecularly thin methane (Me) layer buried within Argon (Ar) films. Using an all-optical depth profiling method and describing the interference effects responsible for these phenomena using a classical optics model, modulations in the EFSW amplitude at specific sample thicknesses are demonstrated to be responsible for these strong deviations from Beer–Lambert behavior. Tuning sample thickness is shown to enable the EFSW depth profile to be tailored, conferring greatly enhanced sensitivity and increased spatial selectivity to RAIR spectroscopy. These are highly desirable attributes for the characterization of interfacial structures and mesoscopic dynamic processes within complex buried multilayer assemblies and stratified composite films used to model and study a range of materials and life science phenomena.

Investigations on silver incorporated RF sputtered ZnO thin films

In this work, ZnO thin films were fabricated using RF Magnetron Sputtering technique on ITO substrates. The operating parameters time of deposition, Argon working pressure, distance between target and substrate, oxygen pressure, RF power etc. were optimized so as to get good quality ZnO thin films. The prepared films were characterised using various techniques like XPS, SEM, EDS etc. It was observed that the sheet resistance of the pristine ZnO film was around 200 MΩcm−1 even when coated on ITO substrates. For device level application the resistance of the film must be low. Therefore silver was incorporated by sputtering, and it served the purpose of reducing the sheet resistance of pristine ZnO film. The Ag incorporated films were also characterised by the above mentioned techniques. Detailed compositional analysis was done using depth profiling method of XPS. Resistance measurements were also done in these samples. The sheet resistance decreased (from ∼ 200 MΩcm−1) to a range of about 500 MΩcm−1 by silver incorporation.

Time-of-flight secondary ion tandem mass spectrometry depth profiling of organic light-emitting diode devices for elucidating the degradation process.

Organic light-emitting diode (OLED) products based on display applications have become popular in the past 10 years, and new products are being commercialized with rapid frequency. Despite the many advantages of OLEDs, these devices still have a problem concerning lifetime. To gain an understanding of the degradation process, the authors have investigated the molecular information for deteriorated OLED devices using time-of-flight secondary ion mass spectrometry (TOF-SIMS). TOF-SIMS depth profiling is an indispensable method for evaluating OLED devices. However, the depth profiles of OLEDs are generally difficult due to the mass interference among organic compounds, including degradation products. In this study, the tandem mass spectrometry (MS/MS) depth profiling method was used to characterize OLED devices. After degradation, defects comprised of small hydrocarbons were observed. Within the defect area, the diffusion of all OLED compounds was also observed. It is supposed that the source of the small hydrocarbons derives from decomposition of the OLED compounds and/or contaminants at the ITO interface. The true compound distributions have been determined using MS/MS depth profiling methods. The results suggest that luminance decay is mainly due to the decomposition and diffusion of OLED compounds, and that OLED decomposition may be accelerated by adventitious hydrocarbons present at the ITO surface.

Improvement of Hysteresis in Aluminum Doped Indium-Tin-Zinc-Oxide Thin Film Transistors By Modulating Intrinsic Film Stress of Mo S/D Electrodes

Since first novel report from Hosono’s research group in 2004, numerous studies have been conducted on amorphous oxide TFTs [1]. Because of their various advantages such as high electron mobility, large on-off ratio, and low fabrication temperature, oxide TFTs are expected to play an important role in the next generation display applications. Among several important parameters of oxide TFTs, hysteresis in the transfer curve can give us critical information about types and densities of defects in the TFTs. In the case of clockwise hysteresis, it is generally known that the hysteresis occurs when there are electron traps in the bulk region of the active layer, or interface between the active front channel and the gate insulator. Therefore, until now, studies have mainly focused on reducing the hysteresis by optimizing several engineering conditions such as deposition method, deposition temperature, post-annealing temperature. On the other hand, as far as we know, the intrinsic film stress, which is determined by the process conditions during the thin film deposition, has not been discussed much in terms of performance of oxide TFT. Especially in the large screen display applications, the intrinsic film stress of metal contacted with active layer, needs to be carefully handled because carrier trap sites may be generated due to high film stress , resulting in degradation of device performance. Nevertheless, there have been few studies about the change of device properties caused by the intrinsic film stress in the oxide TFT. Thus, in this study, we investigated the relationship between the intrinsic film stress of metal and the hysteresis phenomenon in the aluminum doped indium-tin-zinc-oxide (Al-ITZO) TFT. First, we fabricated molybdenum (Mo) thin films with different intrinsic film stress by intentionally controlling the argon working pressure during the sputtering process [2]. The intrinsic film stress values of Mo thin films were calculated by Stoney equation which uses the change of substrate curvature before and after the thin film deposition. According to the calculated results, high-stress Mo and low-stress Mo showed intrinsic tensile stress values of 1920.7 MPa and 143.9 MPa, respectively. Then, we fabricated back-channel-etched structured Al-ITZO TFTs by applying those molybdenum Mo thin films as source and drain (S/D) electrodes, and compared hysteresis of each TFT. It was confirmed that the modulation of the intrinsic film stress of S/D electrodes affected the clockwise hysteresis characteristics of the TFTs. As shown in Figure 1, in the case of TFT using high-stress S/D, hysteresis was about 1.4V larger than the TFT with low-stress S/D in both of short and long channel TFT. This result is interesting because the S/D electrodes with the same material but different film stress on the back surface of the active layer induced a change of the hysteresis. Therefore, we assumed that the stronger tensile stress of high-stress S/D induced larger hysteresis in the TFT, and X-ray photoelectron spectroscopy (XPS) depth profile method was used for further analysis. By analyzing the XPS results, it was possible to compare the difference of the chemical state at the front channel after depositing S/D electrodes with different film stress values, and consequently, hysteresis difference could be explained. Through this research, we expect new engineering perspective can be provided in display industries. [1] Nomura, Kenji, et al. "Room-temperature fabrication of transparent flexible thin-film transistors using amorphous oxide semiconductors." Nature 432.7016 (2004): 488. [2] Windischmann, Henry. "Intrinsic stress in sputter-deposited thin films." Critical Reviews in Solid State and Material Sciences 17.6 (1992): 547-596. This work has supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT)(2018R1A2A3075518). Figure 1

A New Method to Study Depth Profiles in Silicon/Carbon Composite Electrodes

Si as active material has become a prominent candidate as anode material for high-energy Li-ion cells. Unfortunately, Si in Si/C anodes is hard to quantify by established methods, e.g. with ICP-OES no depth profile can be obtained and HF is needed for digestion. Here, we present a semi-quantitative depth profiling method based on glow discharge optical emission spectroscopy (GD-OES). The GD-OES calibration covers Si contents in the range of 0-100 wt.-% in the anode. The results are validated with lab and pilot line coated anodes with known Si contents. The quantified depth profiles with different pristine anodes show a homogeneous distribution of Si and therefore the presented GD-OES method is capable of assessing the quality of composite active materials, from graphite dominant up to pure Si1. The GD-OES method is further applied to anodes obtained from Post-Mortem analysis of commercially available 18650 and 21700 cells. The measurements reveal that the anodes of state-of-the-art Li-ion cells contain up to 5% wt.-% Si. GD-OES depth profiles of anodes after formation (anodes coated in our labs as well as anodes from commercial cells) show a Si peak near the anode surface (near the anode | separator interface, see Figure 1a. This peak changes with aging and is decreased when the anodes are washed with DMC (see Figure 1b). The presence of this peak is further investigated by EDX of ion milling cross-sections. ICP-OES of the DMC washing solution indicates soluble Si species. This aging mechanism is further investigated by Raman spectroscopy. Acknowledgement: The research leading to these results has been performed within the project LIB.DE and received funding from the federal ministry for economics and energy Germany (BMWi) under contract n° 03ET6081A. Literature: K. Richter, T. Waldmann, M. Memm, M. Kasper, and M. Wohlfahrt-Mehrens, J. Electrochem. Soc., 165, A3602–A3604 (2018). Figure 1

Mitigating Measurement Artifacts in TOF-SIMS Analysis of Perovskite Solar Cells.

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is one of the few techniques that can specifically distinguish between organic cations such as methylammonium and formamidinium. Distinguishing between these two species can lead to specific insight into the origins and evolution of compositional inhomogeneity and chemical gradients in halide perovskite solar cells, which appears to be a key to advancing the technology. TOF-SIMS can obtain chemical information from hybrid organic-inorganic perovskite solar cells (PSCs) in up to three dimensions, while not simply splitting the organic components into their molecular constituents (C, H, and N for both methylammonium and formamidinium), unlike other characterization methods. Here, we report on the apparently ubiquitous A-site organic cation gradient measured when doing TOF-SIMS depth-profiling of PSC films. Using thermomechanical methods to cleave perovskite samples at the buried glass/transparent conducting oxide interface enables depth profiling in a reverse direction from normal depth profiling (backside depth profiling). When comparing the backside depth profiles to the traditional front side profiled devices, an identical slight gradient in the A-site organic cation signal is observed in each case. This indicates that the apparent A-site cation gradient is a measurement artifact due to beam damage from the primary ion beam causing a continually decreasing ion yield for secondary ions of methylammonium and formamidinium. This is due to subsurface implantation and bond breaking from the 30 keV bismuth primary ion beam impact when profiling with too high of a data density. Here, we show that the beam-generated artifact associated with this damage can mostly be mitigated by altering the measurement conditions. We also report on a new method of depth profiling applied to PSC films that enables enhanced sensitivity to halide ions in positive measurement polarity, which can eliminate the need for a second measurement in negative polarity in most cases.

Surface Film Formation and Dissolution in Si/C Anodes of Li-Ion Batteries: A Glow Discharge Optical Emission Spectroscopy Depth Profiling Study

Addition of a certain amount of Si to state of the art graphite anodes has become the most prominent option to increase the energy density of Li-ion cells. However, the distribution of Si in the depth of Si/C anodes is difficult to measure with established methods. In this paper, we present a semiquantitative depth profiling method based on glow discharge optical emission spectroscopy (GD-OES). The calibration of this method covers 0–100 wt % Si content in the anode and is validated by pilot-line-coated Si/C anodes with known Si contents. The quantified depth profiles with different pristine anodes show a homogeneous distribution of Si before contact with electrolyte. In contrast to that, pilot-line-coated electrodes after formation and long-term cycled cells with Si/C composite anodes from a commercially available 18650-type cell, as control measurement, reveal a peak near the anode surface, which corresponds to a new aging mechanism. This aging mechanism is verified by interrupted GD-OES sputtering. Raman spectroscopy and ICP-OES substantiate the dissolution of Si species in the electrolyte.

A Comparison of Electrode Surface Films Formed with Different Oxide Cathodes for Lithium-Ion Batteries

High-nickel, Li-rich, and high-voltage spinel electrodes are lithium-ion battery cathodes commonly considered as candidates for near-term commercialization. Each of these cathode materials can offer higher energy densities than conventional lithium cobalt oxide cathode materials, at least during initial cycles. High-Ni cathodes of the form LiNiaMnbCo1-a-bO2 have the same layered structure as current commercial cathodes with alternating transition metal and lithium layers between oxide slabs. With increasing Ni content, High-Ni cathode materials generally can provide higher discharge capacities, reaching upwards of 240 mAh g-1. Li-rich electrode materials (Li1+xMO) have a similar layered structure as High-Ni materials but include excess Li+ in the transition metal layer that can be accessed for much higher discharge capacities, even exceeding 300 mAh g-1. High-voltage spinel electrodes of the form LiMnaNi2-aO4 operate at high voltages providing high energy densities, though at much lower discharge capacities, ca. 140 mAh g-1. While all three of these electrode classes offer exciting possibilities for future lithium-ion battery development, they all suffer from the inherent instability of their surface reactivities. High-Ni cathodes suffer from high surface reactivity and a slow growth of the cubic rocksalt phase throughout cycling that impedes lithium intercalation. The activation of Li-rich electrodes involves a complex surface passivation involving the evolution of molecular oxygen and the formation of a spinel-like phase. High-voltage spinel electrodes operate outside the electrolyte stability region, so also suffer from rapid oxidative breakdown of electrolyte components and impedance growth. Aside from the cathode interphase, the solid electrolyte interphase formed at the anode can be affected by the surface chemistry of these various cathodes; for instance, transition-metal ions may dissolve from the cathode, migrate to the anode side where they are reduced, and act as a catalyst for further electrolyte reduction. This presentation describes our recent characterization of cathode and anode surface electrolyte interphases from cells with High-Ni, high-voltage spinel, and Li-rich electrodes. Half cells vs. lithium anodes, as well as full cells with up to 1,500 cycles are presented. For these studies, we employ time of flight – secondary ion mass spectrometry (TOF-SIMS), a powerful characterization technique pioneered by our group for characterization of battery materials. TOF-SIMS provides sub-nanometer depth resolution of specific chemical fragments over micron-sized image areas that can also be used in a depth profiling method, through layer-by-layer ablation of surface species to form a 3D image (Figure 1). TOF-SIMS is used in conjunction with standard characterization techniques, such as X-ray photoelectron spectroscopy (XPS), galvanostatic cycling data, and electrochemical impedance spectroscopy. Figure 1: A 3D TOF-SIMS image of cycled high-Ni cathode particles with transition metals indicated in green, as well as decomposed organics (C-, CH-, CH2 - ) indicated in red. Figure 1