Early stage decomposition of solid polymer electrolytes in Li metal batteries

Development of functional and stable solid polymer electrolytes SPEs for battery applications is an important step towards both safer batteries and for the realization of lithium based or anode less batteries. The interface between the lithium and the solid polymer electrolyte is one of the bottlenecks, where severe degradation is expected. Here, the stability of three different SPEs poly ethylene oxide PEO , poly amp; 949; caprolactone PCL and poly trimethylene carbonate PTMC together with lithium bis trifluoromethanesulfonyl imide LiTFSI salt, is investigated after they have been exposed to lithium metal under UHV conditions. Degradation compounds, e.g. Li O R, LiF and LixSyOz, are identified for all SPEs using soft X ray photoelectron spectroscopy. A competing degradation between polymer and salt is identified in the outermost surface region lt;7 nm , and is dependent on the polymer host. PTMC LiTFSI shows the most severe decomposition of both polymer and salt followed by PCL LiTFSI and PEO LiTFSI. In addition, the movement of lithium species through the decomposed interface shows large variation depending on the polymer electrolyte syste

The degree of electron itinerancy and shell closing in the core ionized state of transition metals probed by Auger photoelectron coincidence spectroscopy

Auger photoelectron coincidence spectroscopy APECS has been used to examine the electron correlation and itinerance effects in transition metals Cu, Ni and Co. It is shown that the LVV Auger, in coincidence with 2p photoelectrons, spectra can be represented using atomic multiplet positions if the 3d shell is localized atomic like and with a self convoluted valence band for band like itinerant materials as explained using the Cini Sawatzky model. For transition metals, the 3d band changes from band like to localized with increasing atomic number, with the possibility of a mixed behavior. Our result shows that the LVV spectra of Cu can be represented by atomic multiplet calculations, those of Co resemble the self convolution of the valence band and those of Ni are a mixture of both, consistent with the Cini Sawatzky mode

Thermal degradation of lead halide perovskite surfaces

Commercial use of lead halide perovskites requires improved ther mal stability and therefore a better understanding of their degrada tion mechanisms. The thermal degradation of three clean perovskite single crystal surfaces MAPbI3, MAPbBr3, FAPbBr3 was investigated using synchrotron based photoelectron spectroscopy. Central find ings are that the halide has a large impact on thermal stability and that the degradation of formamidnium results in the formation of a new organic species at the FAPbBr3 crystal surfac

Auger and photoelectron coincidences of molecular O2 adsorbed on Ag 111

The oxygen on Ag 111 system has been investigated with Auger electron photoelectron coincidence spectroscopy APECS . The coincidence spectra between O 1s core level photoelectrons and O KLL Auger electrons have been studied together with Ag3d AgM4,5NN coincidences. We also describe the electron electron coincidence spectrometer setup, CoESCA, consisting of two angle resolved time of flight spectrometers at a synchrotron light source. Contributions from molecular oxygen and chemisorbed oxygen are assigned using the coincidence data, conclusions are drawn primarily from the O 1s O KLL data. The data acquisition and treatment procedure are also outlined. The chemisorbed oxygen species observed are relevant for the catalytic ethylene oxidatio

Early-Stage Decomposition of Solid Polymer Electrolytes in Li-Metal Batteries

Development of functional and stable solid polymer electrolytes SPEs for battery applications is an important step towards both safer batteries and for the realization of lithium based or anode less batteries. The interface between the lithium and the solid polymer electrolyte is one of the bottlenecks, where severe degradation is expected. Here, the stability of three different SPEs poly ethylene oxide PEO , poly amp; 949; caprolactone PCL and poly trimethylene carbonate PTMC together with lithium bis trifluoromethanesulfonyl imide LiTFSI salt, is investigated after they have been exposed to lithium metal under UHV conditions. Degradation compounds, e.g. Li O R, LiF and LixSyOz, are identified for all SPEs using soft X ray photoelectron spectroscopy. A competing degradation between polymer and salt is identified in the outermost surface region lt;7 nm , and is dependent on the polymer host. PTMC LiTFSI shows the most severe decomposition of both polymer and salt followed by PCL LiTFSI and PEO LiTFSI. In addition, the movement of lithium species through the decomposed interface shows large variation depending on the polymer electrolyte syste

Probing and Controlling Surface Passivation of PbS Quantum Dot Solid for Improved Performance of Infrared Absorbing Solar Cells

Surface properties of colloidal quantum dots (CQDs) are critical for the transportation and recombination of the photoinduced charge carrier in CQD solar cells, therefore dominating the photovoltaic performance. Herein, PbS CQD passivated using liquid-state ligand exchange (LSLX) and solid-state ligand exchange (SSLX) strategies are in detail investigated using photoelectron spectroscopy (PES), and solar cell devices are prepared to understand the link between the CQD surface properties and the solar cell function. PES using different energies in the soft and hard X-ray regime is applied to study the surface and bulk properties of the CQDs, and the results show more effective surface passivation of the CQDs prepared with the LSLX strategy and less formation of lead-oxide. The CQD solar cells prepared with LSLX strategy show higher performance, and the photoelectric measurements suggest that the recombination of photoinduced charges is reduced for the solar cell prepared with the LSLX approach. Meanwhile, the fabricated solar cells exhibit good stability. This work provides important insights into how to fine-tune the CQD surface properties by improving the CQD passivation, and how this is linked to further improvements of the device photovoltaic performance

Hard x ray photoelectron spectroscopy A snapshot of the state of the art in 2020

Hard X-ray photoelectron spectroscopy (HAXPES) is establishing itself as an essential technique for the characterisation of materials. The number of specialised photoelectron spectroscopy techniques making use of hard X-rays is steadily increasing and ever more complex experimental designs enable truly transformative insights into the chemical, electronic, magnetic, and structural nature of materials. This paper begins with a short historic perspective of HAXPES and spans from developments in the early days of photoelectron spectroscopy to provide an understanding of the origin and initial development of the technique to state-of-the-art instrumentation and experimental capabilities. The main motivation for and focus of this paper is to provide a picture of the technique in 2020, including a detailed overview of available experimental systems worldwide and insights into a range of specific measurement modi and approaches. We also aim to provide a glimpse into the future of the technique including possible developments and opportunities