Here we provide a detailed X-ray photoelectron spectroscopy (XPS) study of the electrode/electrolyte interface of a graphite anode from commercial NMC/graphite cells by intense sputter depth profiling using a polyatomic ion gun. The uniqueness of this method lies in the approach using 13-step sputter depth profiling (SDP) to obtain a detailed model of the film structure, which forms at the electrode/electrolyte interface often noted as the solid electrolyte interphase (SEI). In addition to the 13-step SDP, several reference experiments of the untreated anode before formation with and without electrolyte were carried out to support the interpretation. Within this work, it is shown that through charging effects during X-ray beam exposure chemical components cannot be determined by the binding energy (BE) values only, and in addition, that quantification by sputter rates is complicated for composite electrodes. A rough estimation of the SEI thickness was carried out by using the LiF and graphite signals as internal references.

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Solid electrolyte interphase (SEI) forming electrolyte additives are able to improve the performance of lithium ion and lithium metal batteries. In this work, the electrochemical performance of graphite and lithium metal, when using 1 M LiTFSI (lithium bis(trifluoro-methanesulfonyl)imide) in tetraethylene glycol dimethyl ether (TEGDME) with and without the addition of different amounts of fluoroethylene carbonate (FEC), is compared. It is shown that 1 M LiTFSI in TEGDME without additive is not able to form an effective SEI on graphite and that this electrolyte is also continuously decomposing on lithium metal. By the addition of > 2 wt% FEC, an effective SEI is formed on both, lithium metal and graphite, enabling good cycling stability. Furthermore, 1 M LiTFSI in TEGDME with FEC as additive is a suitable electrolyte for lithium iron phosphate (LFP) based lithium ion batteries.In analogy to metallic lithium and lithium-rich "lithium-alloys", lithiated (charged) graphite/carbon is thermodynamically unstable in the typically used organic solvent-based electrolytes. 1 Therefore, the carbon surfaces, which are exposed to the electrolyte, have to be kinetically protected by an solid electrolyte interphase (SEI). 2 Nevertheless, there are significant differences in the SEI formation process between metallic lithium and graphite/carbon. 3 Film formation on metallic lithium takes place right upon contact with the electrolyte. The various electrolyte components decompose spontaneously with low selectivity on the Li metal surface and parts of the decomposition products form the SEI. Due to an increase in IR drop across the SEI, with SEI growth, the reactivity of metallic lithium electrode vs. electrolyte decreases. As a consequence, the reduction of the electrolyte becomes more and more selective. The number of electrolyte components, which are still sensitive to reduction vs. the (now partially electronically "passivated") lithium electrode are limited. On the contrary, SEI formation on carbonaceous lithium storage materials takes place as a charge consuming side reaction in the first few cycles, especially during the first reduction (charge reaction). The electrolyte components, which are the least stable toward reduction, selectively react first. This makes SEI forming electrolyte additives particularly attractive for the use with carbonaceous anodes. When the electrolyte additive forms an effective SEI and is sensitive to reduction, the additive is reduced first and forms an initial SEI before reduction reactions of the other (main) electrolyte components takes place. 4 With the addition of suitable electrolyte additives, the initial SEI can be tailored and appropriate cell formation can be achieved. As a result of the different SEI formation processes, the SEI compositions on lithium metal and on carbonaceous anodes are different. 3,5 In addition to the above mentioned differences, the surface of metallic lithium is periodically renewed during cycling, causing formation of a new SEI in each following cycle (Figure 1). ...

We report the synthesis of new NHC gold(I) and NHC gold(III) halide, amino acid and dipeptide complexes. Transmetallation of the N-phenylalanine-substituted NHC silver complex 3 with Me2SAuCl yields the phenylalanine-NHC gold(I) conjugate 4a. Halide exchange with LiBr and oxidation of 4a with Br2 in CH2Cl2 yields the phenylalanine-NHC Au(I) and Au(III) bromides 4b and 4c, respectively. Reaction of N-Boc protected cysteine methyl ester (Boc-Cys-OMe) or the dipeptide N-Boc-Leu-Cys-OMe with the NHC gold chloride 6a yields the (NHC)Au-S complexed amino acid and dipeptide derivatives 8 and 9. The NHC gold(III) complexes 4c and 6c were characterised by single crystal X-ray analysis. All of the tested gold carbene complexes showed significant anti-tumor activity on the HeLa, HepG2 and HT-29 cancer cell lines. The best compounds show activity comparable to the well-known anti-cancer drug cisplatin. There seems to be no clear cut structure-activity relationship in the compounds tested, nor did we observe a dependence on the metal oxidation state or the different halide substituents. Given the ease of preparation, stability and high activity of the compounds described herein, it may be possible to design tumor-specific anti-cancer agents based on NHC gold amino acid conjugates in the future.

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A detailed X-ray photoelectron spectroscopy (XPS) study of the surface and electrolyte decomposition layer of a LixNi1/3Mn1/3Co1/3O2 (NMC) cathode from commercial NMC/graphite cells by intense sputter depth profiling (SDP) using a polyatomic ion gun is provided. Cathodes of a cell after electrochemical formation and a cell at a state of initial capacity (SOIC) of 80%, which was reached after 2500 full cycles at 30 °C, are investigated.

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Micron-sized truncated octahedral LiNi 0.5 Mn 1.5 O 4 (LNMO) samples with different degrees of Ni/Mn disordering have been obtained by controlling the synthesis conditions, such as calcination atmosphere (O 2 and air), cooling rate or additional annealing step. The influences of Ni/Mn disordering on the physical properties and electrochemical performance of the truncated octahedral LNMO samples have been systematically investigated. The analyses of thermogravimetry, X-ray photoelectron spectroscopy, X-ray diffraction, powder neutron diffraction, Raman spectroscopy and X-ray absorption spectroscopy reveal that the occurrence and degree of Ni/Mn disordering are closely related with the formation of oxygen vacancies and presence of Mn 3+ . Slow cooling rate and post-annealing can result in low degrees of Ni/Mn disordering and oxygen vacancies. Electrochemical measurements show that Ni/Mn disordering and oxygen vacancies have no obvious effect on the rate capability since all LNMO samples share a truncated octahedral morphology with the exposed {100} surfaces. However, they play significant roles in improving long-term cycling stability, especially at the elevated temperature of 60 • C. This work suggests that the electrochemical performance of LNMO with optimized truncated morphology can be further enhanced through tuning the degrees of Ni/Mn disordering and oxygen vacancies.