The growing number of industrial applications requiring thin-film materials is prompting the development of new characterization methods. We demonstrate that laser-induced breakdown spectroscopy (LIBS) enables the verification of the spatial homogeneity of LiF films deposited by atomic layer deposition (ALD), and the quantification of the lithium amount in LiF thin films. In our experimental conditions, we obtained a limit of detection (LOD) of 0.7-4.1 fg.ng-1for the Li I line at 670.8 nm and for single-shot LIBS analysis. Then, an estimate of LOD in the range 0.17-0.93 fg.ng-1 (i.e. 170-930 ppb) was obtained with other acquisition parameters. Given the 100 Hz repetition rate of the laser shots, the LOD decreases by a factor of 10 in one second leading to 0.012-0.065 fg/root Hz. Such level of detection limit paves the way for future utilization of LIBS for the chemical characterization of thin films.

All-solid-state lithium batteries (ASSBs) are among the most promising energy storage technologies, particularly for electric vehicles, due to their enhanced safety. However, performances of these systems are still hindered by interfacial side reactions at electrode/electrolyte interfaces, especially when sulfide electrolytes are used, and additional issues of mechanical nature. In this work, an ASSB system composed of an argyrodite (Li5.7PS4.7Cl1.3) electrolyte, a lithium-rich sulfide cathode (Li1.2Ti0.8S2) operating at moderate voltage, and a lithium metal anode is investigated. The positive electrode/electrolyte interface is scrutinized during several battery cycles using X-ray photoelectron spectroscopy (XPS) via two complementary approaches (ex situ and in situ). We show that both titanium and sulfur species contribute to the electrochemical process without any detectable degradation of the electrolyte after 20 cycles and without the use of any protective coating. These results suggest that the electrochemical performances of such an all-sulfide system are not limited by the cathode/electrolyte reactivity, opening a promising route for the development of specific cathode materials adapted to sulfide electrolytes.

Li-Ni-Mn-O spinel cathode materials operating at similar to 5 V vs Li+/Li appear to be very interesting alternatives to Co-containing layered materials in terms of rate capability, energy and power densities, and sustainability of material resources. Nevertheless, their high operating voltage, which has been an asset to date, does not allow them to be used with conventional carbonate-based electrolytes. The latter undergoes spontaneous oxidation when in contact with the charged electrode, resulting in a reduction of the cathode material, an imbalance in the Li-ion system, and a subsequent rapid loss of capacity. This incompatibility could be overcome by creating a stable, electronically insulating solid interphase at the surface of the composite electrode. Here, we report the direct deposition of lithium fluoride (LiF) on LNMO electrodes by atomic layer deposition (ALD). LiF prepared with a specific combination of precursors (lithium bis(trimethylsilyl)amide and titanium tetrafluoride) has a total impurity content of less than 2% in the bulk. In addition, to enable direct coating by ALD on the positive electrode, a commonly used binder (polyvinylidene fluoride) was replaced with polyimide (PI), a more thermally stable and nonfluorinated polymer. Using X-ray photoelectron spectroscopy (XPS) and electrochemical analysis, we demonstrate the excellent thermal stability of this LNMO/PI electrode up to 300 degrees C as well as its electrochemical and chemical stability in a standard carbonate electrolyte. Electrochemical data show that LiF extends the cycle life of the LNMO/PI half-cell at a high C-rate (1C). The LiF layer has been proven to be stable on the pristine electrode upon prolonged exposure to the electrolyte. However, when charged at a low C-rate, the layer exhibits a tendency to disappear. The reasons for this behavior are not yet clear but could be linked to the degradation reactions in the electrolyte or to the local concentration changes.

Amorphous thin film materials in the LiPON ( 1 ) or LiSiPON ( 2 ) systems have been prepared for the first time in the early 1990s using magnetron sputtering. Since then, LiPON materials have been used as state-of-the-art solid electrolytes into all-solid-state thin film micro-batteries thanks to their outstanding properties (electrochemical stability vs Li°, wide electrochemical stability window of ~[4-0] V vs. Li + /Li 0 , isotropic and homogeneous medium, beneficial mechanical properties (3) , very low electronic conductivity). The ionic conductivity of LiPON prepared from Li 3 PO 4 targets remains rather moderate, reaching a maximum of 3.10 -6 S.cm -1 at room temperature. However, it has recently been demonstrated that the introduction of SiO 2 as a second glass former can increase this value up to 2.10 -5 S.cm -1 , and also that the ionic conductivity of these compounds does not increase steadily with their Li content. (4) This highlights the convoluted effects of mixed formers ( 5 ) (Si, P, B...), mixed anions (6) (O, N, S...) and Li concentration on the ionic conductivity. Nevertheless, the latter are usually observed on limited series of compositions, and barely not studied on large sets of samples, which can limit the understanding of composition-structure-conductivity relationships. In this context the aim of our work was to build a High Throughput Screening (HTS) approach to explore the Li x Si y P z O u N w system as a case study (Fig.1). Indeed, HTS approaches aim to accelerate material breakthrough discovery, and to understand beyond the material mechanisms. In material science, the goal is to accelerate the discovery of new keys organic, inorganic or composite materials. It may also bring beyond ‘classical’ iterative method regarding the study of complex systems (ternary, quaternary...) ( 7 ) . To do so, wide ranges of material libraries are synthesized, prior to be tested through an automated characterization workflow. Our specific approach starts with the preparation of material libraries by combinatorial synthesis using magnetron co-sputtering with tilted targets, then goes through automated and fast characterizations targeting specific properties, relevant to its application as ionic conductor. Deposition of thin films displaying composition and thickness gradients at the surface of a 4’’ silicon substrate is achieved by co-sputtering three target materials in a pure Ar or N 2 atmosphere. Deposition through a shadow mask allows to discretize the continuum and to prepare a library of 76 separate Li x Si y P z O u N w samples in one experiment. Then, by tuning the sputtering parameters (i.e discharge gas, gas pressure, incident power, target tilt, target-to-substrate distance,...) different compositional domains can be explored. Relevant automated characterization techniques are then applied to the material library spread on the 4’’ substrate. For the assessment of these amorphous ionic conducting films, dimensional (thickness), physical-chemical (composition & local structure) and functional properties (ionic/electronic conductivities) are studied.In this sequence, determining the composition of the thin film is a real challenge due to a number of requirements :(i) light elements analysis, especially lithium; (ii) need of localized analysis (mapping) on few mm² over large substrate (4” wafer); (iii) scarce material quantity available (~ μg) and finally (iv) fast analysis. Over lab-scale techniques available, only Laser Induced Breakdown Spectroscopy technique (LIBS) seems to fulfil all these requirements. To this purpose, LIBS is developed as a HTS mapping technique for chemical analysis. A sample calibration approach is implemented through coupling with robust chemical analysis techniques (RBS, NRA, ICP-OES, SEM-EDS). In short, this specific HTS procedure will be discussed and results about composition-structure-conductivity relationships in the LiSiPON system will be presented (Fig.2). References J. B. Bates et al. , J. Power Sources . 43 , 103–110 (1993). N. J. Dudney, J. B. Bates, J. D. Robertson, J. Vac. Sci. Technol. A . 11 , 377–389 (1993). A. S. Westover et al. , Chem. Mater. 35 , 2730–2739 (2023). T. Famprikis, J. Galipaud, O. Clemens, B. Pecquenard, F. Le Cras, ACS Appl. Energy Mater. 2 , 4782–4791 (2019). Y. Su et al. , Phys. Status Solidi B . 254 , 1600088 (2017). N. Mascaraque, J. L. G. Fierro, A. Durán, F. Muñoz, Solid State Ion. 233 , 73–79 (2013). E. J. Amis, X.-D. Xiang, J.-C. Zhao, MRS Bull. 27 , 295–300 (2002). Figure 1

Elemental analysis is a challenge for the development of High Throughput Experimentation (HTE) on thin film materials, and an even greater one when it comes to screening lithium-containing battery materials. In this regard, Laser-Induced Breakdown Spectroscopy has been evaluated here for the quantitative analysis of lithium in libraries of Li 2.3 PO 3.65 amorphous solid electrolyte films. The LIBS analysis of multiple samples with the same composition, but with thicknesses ranging from 50 to 700 nm, has revealed a linear trend in the intensity ratio of the Li I 610.35 nm and P I 214.91 nm emission lines, opening the way to rapid quantitative analysis of material libraries. The sensitivity of the technique finally allowed the detection of the Li I 670.79 nm emission line for film thicknesses down to 4 nm, corresponding to 0.2% of the ablated volume, or about 0.15 pg of Li.

A high-throughput experimental approach is developed to assess the correlations between chemical composition, structure and conduction properties of inorganic solid ionic conductors. This approach covers the preparation of a large number of samples by combinatorial synthesis, followed by fast characterization of the material library. The approach is primarily based on combinatorial synthesis by magnetron co-sputtering and the characterization of thin film samples where lithium phosphorus oxynitride (LiPON) is chosen as a case study. A library of 76 LiPON materials is prepared in one experiment from the reactive co-sputtering of LiPO3 and Li3PO4 in a N2 atmosphere. A specific sample design allows conducting thickness and impedance measurements, Raman spectroscopy, then fast and spatially-resolved chemical analysis by Laser-Induced Breakdown Spectroscopy (LIBS) on each material. Particular developments are devoted to this technique to achieve quantitative analysis of lithium in thin films. The materials cover a wide range of compositions with 0.95<Li/P<2.03 and a high N/P nitrogen content of approximate to 1.0-1.2. Two distinct compositional ranges can be distinguished. For 0.95<Li/P<1.2, conductivity increases and the PO3- chains gradually disappear, whereas for 1.2<Li/P<2.03, conductivity stabilizes despite continuous structural evolution, in parallel with an increase in charge carrier concentration. A high-throughput experimental approach, based on combinatorial synthesis by magnetron co-sputtering, is developed to assess correlations between chemical composition, structure and conduction properties of inorganic solid ionic conductors. Laser-Induced Breakdown Spectroscopy (LIBS) is introduced in particular to achieve fast quantitative chemical mapping that includes Li. This method is applied to study LiPON solid electrolytes over an extended composition range (0.95<Li/P<2.03, 1.0<N/P<1.2). image

Currently, amorphous LiPON prepared by magnetron sputtering is the most employed thin film electrolyte due to its ionic conductivity (similar to 10(-6) S.cm(-1)), negligible electronic conductivity, absence of grain boundaries and ability to passivate Li metal. Despite the outstanding cycling performance that this combination of properties enables, its moderate conductivity hinders the use microbatteries in Internet of Things applications due to the need for short but high current pulses during communication phases. To better meet this requirement, LiSiPON thin films with ionic conductivities more than ten times greater than that of LiPON have been synthesized, while encountering some challenges in controlling the composition and the reproducibility of the synthesis. Herein, we have synthesized LiSiPON thin films from a set of precursor targets having distinct lithium concentrations. The main results indicate that an increase in the lithium content in the target material significantly enhances its ionic conductivity. Curiously, the most conductive target results in lithium-deficient and poorly conductive thin films that are not particularly reproducible in terms of composition and electrical properties. Our results suggest that lithium migration away from the sputtered area (or racetrack), favored by the high ionic conductivity of the target, is the origin of the resulting Li-deficient films. Finally, we have succeeded in preparing LiSiPO targets with sufficiently low Li-ion conductivity that enable the reproducible deposition of highly conductive LiSiPON solid electrolytes.

SiOx electrodes are promising for high-energy-density lithium-ion batteries (LIBs) due to their ability to mitigate volume expansion-induced degradation. Here, we investigate the surface dynamics of SiOx thin-film electrodes cycled in different carbonate-based electrolytes using a combination of ex situ X-ray photoelectron spectroscopy (XPS) and operando synchrotron X-ray reflectivity analyses. The thin-film geometry allows us to probe the depth-dependent chemical composition and electron density from surface to current collector through the solid electrolyte interphase (SEI), the active material, and the thickness evolution during cycling. Results reveal that SiOx lithiation initiates below 0.4 V vs Li+/Li and indicate a close relationship between SEI formation and SiOx electrode lithiation, likely due to the high resistivity of SiOx. We find similar chemical compositions for the SEI in FEC-containing and FEC-free electrolytes but observe a reduced thickness in the former case. In both cases, the SEI thickness decreases during delithiation due to the removal or dissolution of some carbonate species. These findings give insights into the (de)lithiation of SiOx, in particular, during the formation stage, and the effect of the presence of FEC in the electrolyte on the evolution of the SEI during cycling.

Silicon materials are expected as a high-capacity anode material for lithium-ion batteries. However, the life of the cell with such silicon materials tends to be short due to the pulverization of silicon associated with its large volume change, and electrolyte consumptions associated with the continuous growth of solid electrolyte interphase (SEI). Compared to pure silicon anodes, silicon oxide (SiOx) has been reported to mitigate such issues and extend the life of the battery1,2. In this study, we combined ex situ XPS (X-ray photoemission spectroscopy) and operando XRR (X-ray reflectivity) methods to investigate the phase transformations in the thin-film SiOx and the nature of SEI during the first lithiation/delithiation cycle to obtain the insights to improve the cycle performances. Using ex situ XPS, we examined the depth profile of the thin-film SiOx sample (Figure 1) at some representative potentials during the first cycle. This elucidated the evolution of chemical nature and thickness of the SEI, and simultaneously the irreversible phase changes in the SiOx. In recent years, the operando XRR method has been successfully applied to the pure silicon thin films3,4, revealing the nature (like thickness and electron density) of top and bottom SEI layers in early cycles. In this study, XRR was applied to thin-film SiOx for the first time. The insight from XPS and that from XRR were integrated for a comprehensive understanding on the evolution of the SEI layer and the SiOx electrode. A systematic comparison was made using the electrolytes with FEC and without FEC to better understand the importance of FEC. It was found out that the SEIs in both systems commonly show breathing behaviors, but the thickness of the SEI is almost always smaller in the FEC containing system. These findings can be a foundation for the high-performance batteries. 1. Chen, T.; Wu, J.; Zhang, Q.; Su, X. Recent Advancement of SiOx Based Anodes for Lithium-Ion Batteries. J Power Sources 2017, 363, 126–144. 2. Hsu, C.-H.; Chen, H.-Y.; Tsai, C.-J. Stoichiometry Dependence of Electrochemical Behavior of Silicon Oxide Thin Film for Lithium Ion Batteries. J Power Sources 2019, 438, 226943. 3. Cao, C.; Steinrück, H.-G.; Shyam, B.; Stone, K. H.; Toney, M. F. In Situ Study of Silicon Electrode Lithiation with X-Ray Reflectivity. Nano Lett 2016, 16 (12), 7394–7401. 4. Cao, C.; Steinrück, H.; Shyam, B.; Toney, M. F. The Atomic Scale Electrochemical Lithiation and Delithiation Process of Silicon. Adv Mater Interfaces 2017, 4 (22), 1700771. Figure 1

Depuis leur mise sur le marche en 1991, les accumulateurs lithium-ion ont envahi notre quotidien : ils alimentent en energie nos smart phones, ordinateurs portables, tablettes, velos electriques, etc ; tandis que vehicules electriques et hybrides se repandent dans les rues. Comment cette technologie s’est-elle, en quelques annees, substituee aux filieres etablies depuis des decennies? Comment l’industrie asiatique a-t-elle reussi a occuper dans ce domaine une position dominante? Quelles seront les prochaines etapes du developpement de ces systemes de stockage electrique? En replacant cette problematique dans un contexte historique, cet permet de comprendre l’enchainement des decouvertes et des evolutions dans ce domaine, et apporte un eclairage sur les developpements en cours

Lithium phosphorus oxynitride, having an amorphous structure, has enabled all-solid-state thin film batteries with lithium metal anodes and high-voltage cathodes since the nineties. Nevertheless, the origins of its outstanding ionic conductivity compared to its crystalline counterparts, as well as the interplay between structure and ionic transport in this electrolyte, have remained elusive. Herein, we have applied a compelling methodology based on impedance spectroscopy analyses to isolate the distinct energetic contributions for the ionic conduction process, namely, the enthalpies for defect formation and migration. The variations of these enthalpies with the nitrogen content are correlated with structural aspects unveiled by solid-state nuclear magnetic resonance (NMR) and depth profiling X-ray photoelectron spectroscopies. The main findings indicate that the amorphous structure, inherent to radiofrequency magnetron sputtering synthesis, is the root of a striking decrease of the enthalpy related to defect formation, while the nitrogen incorporation plays a crucial role in Li+ ion mobility by forming bridging species, which tend to lower the enthalpy of migration.

Amorphous lithium phosphorus oxynitrides (LiPON), prepared by reactive magnetron sputtering, have become the electrolytes of choice for all-solid-state thin film microbatteries since its discovery in early 1990s. Nevertheless, there is still a lack of understanding of their atomic-level structure and its influence on ionic conductivity. Solid-state NMR spectroscopy represents a promising technique to determine the atomic-level structure of LiPON glasses but is challenging owing to its low sensitivity in the case of thin film materials. Recently, 31P solid-state NMR spectra of LiPON thin films were acquired under magic-angle spinning (MAS) conditions and assigned with the help of density functional theory (DFT) calculations of NMR parameters. However, the identification of the different P local environments in these materials is still a challenge owing to their amorphous structure and the lack of resolution of the 31P MAS NMR spectra. We show herein how the NMR observation of internuclear proximities helps to establish the nature of P sites in LiPON thin films. The 31P-14N proximities are probed by a transfer of population in double resonance (TRAPDOR) experiment, whereas 31P-31P proximities are observed using one-dimensional (1D) 31P double-quantum (DQ)-filtered and two-dimensional (2D) 31P homonuclear correlation spectra as well as dipolar dephasing experiments using DQ-DRENAR (DQ-based dipolar-recoupling effects nuclear alignment reduction) technique. The obtained NMR data further support the recently proposed assignment of 31P NMR signals of LiPON thin films. With the help of this assignment, the simulation of the quantitative 1D 31P NMR spectrum indicates that PO43- orthophosphate anions prevail in LiPON thin films and N atoms are mainly incorporated in [O3PNPO3]5- dimeric anions. PO3N4- isolated tetrahedra and [O3POPO3]4- anions are also present but in smaller amounts.

The timely arrival of novel materials plays a key role in bringing advances to society, as the pace at which major technological breakthroughs take place is usually dictated by the discovery rate at which novel materials are identified within chemical space. High-throughput experimentation and computation strategy, now widely considered as a watershed in accelerating the discovery and optimization of novel materials in virtually every field, enables simultaneous screening, synthesis and characterization of large arrays of different material classes toward identification of the lead candidates for given system and targeted application. However, the ability to acquire data, through the continued advancement of automation platforms and workflows especially in the field of battery research and development, often outpaces the ability to optimally leverage obtained data for improved decision-making. Closing this gap inevitably calls for adapted algorithms, development of reliable predictive models and enhanced integration with machine learning, deep learning, and artificial intelligence. This Review aims to highlight state-of-the-art achievements along with an assessment of current and future challenges as well as resulting perspectives toward accelerated development of advanced battery electrolytes and their interfaces.