A new setup for in situ experiments with up to eight electrochemical cells, especially battery coin cells, and the corresponding custom‐made in situ cells are presented. The setup is primarily optimized for synchrotron powder diffraction measurements. As a newly constructed experimental setup, the in situ coin cell holder was tested for positional errors of the cells and the reliability of the diffraction as well as electrochemical measurements. The overall performance characteristics of the sample holder are illustrated by measurements on LiMn2O4 and LiNi0.35Fe0.3Mn1.35O4 spinel‐based positive electrode materials.

1 Introduction The magnetocaloric effect [1,2] is the basis of an energy-efficient refrigeration technology, which has the potential to reduce the energy consumption of air conditioners, refrigerators and other domestic and industrial cooling applications [3]. The most promising magnetocaloric materials exhibit first-order magnetostructural or magnetovolume transitions, which lead to high adiabatic temperature changes in response to a changing external magnetic field. The transition temperatures of these firstorder transitions can be shifted towards room temperature by means of hydrogenation or doping [4]. However, large entropy and temperature changes can only be maintained if the first-order nature of the transition is kept [4].However, it has been shown for first-order-type magnetocaloric La(Fe,Si) 13 that when measuring the adiabatic temperature change ΔT ad , one needs to carefully distinguish between the first field cycle, which delivers a high adiabatic temperature change of ΔT ad = 7 K, and following cycles, in which it is reduced to ΔT ad = 5.8 K [5]. Similar findings have been reported for magnetocaloric Heuslers

A brief review of in situ powder diffraction methods for battery materials is given. Furthermore, it is demonstrated that the new beamline P02.1 at the synchrotron source PETRA III (DESY, Hamburg), equipped with a new electrochemical test cell design and a fast two‐dimensional area detector, enables outstanding conditions for in situ diffraction studies on battery materials with complex crystal structures. For instance, the time necessary to measure a pattern can be reduced to the region of milliseconds accompanied by an excellent pattern quality. It is shown that even at medium detector distances the instrumental resolution is suitable for crystallite size refinements. Additional crucial issues like contributions to the background and available q range are determined.

A sustainable synthesis procedure of a rational-designed silicon−carbon electrode for a high-performance rechargeable Li-based battery has been developed. It was realized by an economical approach using low-cost trichlorosilane as feedstock and without special equipment. The synthesis strategy includes polycondensation of trichlorosilane in the presence of a surfactant to selectively form spheric silicon@silica particles via a hydrogen silsesquioxane (HSQ) intermediate. After subsequent carbonization of a sucrose shell and etching the composite, we obtained an anode material based on silicon nanoparticles with 2−5-nm average diameter inside a porous carbon scaffold. The active material exhibits a high rate capability of 2000 mAh/g at a current rate of 0.5 A/g with exceptional cycle stability. After almost 1000 times of deep discharge galvanostatic cycling at 2.5 A/g current rate the capacity is still 60% of the initial 1200 mAh/g. The excellent electrochemical performance is attributed to an interaction of a stabilized solid electrolyte interface on extreme small silicon particles and a well-designed porous carbon cage which serves as efficient charge conductor.

X-ray photoelectron spectroscopy (XPS) is a key method for studying (electro-)chemical changes in metal-ion battery electrode materials. In a recent publication, we pointed out a conflict in binding energy (BE) scale referencing at alkali metal samples, which is manifested in systematic deviations of the BEs up to several eV due to a specific interaction between the highly reactive alkali metal in contact with non-conducting surrounding species. The consequences of this phenomenon for XPS data interpretation are discussed in the present manuscript. Investigations of phenomena at surface-electrolyte interphase regions for a wide range of materials for both lithium and sodium-based applications are explained, ranging from oxide-based cathode materials via alloys and carbon-based anodes including appropriate reference chemicals. Depending on material class and alkaline content, specific solutions are proposed for choosing the correct reference BE to accurately define the BE scale. In conclusion, the different approaches for the use of reference elements, such as aliphatic carbon, implanted noble gas or surface metals, partially lack practicability and can lead to misinterpretation for application in battery materials. Thus, this manuscript provides exemplary alternative solutions.

Layered Li(M,Li)O2 (where M is a transition metal) ordered rock-salt-type structures are used in advanced metal-ion batteries as one of the best hosts for the reversible intercalation of Li ions. Besides the conventional redox reaction involving oxidation/reduction of the M cation upon Li extraction/insertion, creating oxygen-located holes because of the partial oxygen oxidation increases capacity while maintaining the oxidized oxygen species in the lattice through high covalency of the M-O bonding. Typical degradation mechanism of the Li(M,Li)O2 electrodes involves partially irreversible M cation migration toward the Li positions, resulting in gradual capacity/voltage fade. Here, using LiRhO2 as a model system (isostructural and isoelectronic to LiCoO2), for the first time, we demonstrate an intimate coupling between the oxygen redox and M cation migration. A formation of the oxidized oxygen species upon electrochemical Li extraction coincides with transformation of the layered Li1-xRhO2 structure into the γ-MnO2-type rutile-ramsdellite intergrowth LiyRh3O6 structure with rutile-like [1 × 1] channels along with bigger ramsdellite-like [2 × 1] tunnels through massive and concerted Rh migration toward the empty positions in the Li layers. The oxidized oxygen dimers with the O-O distances as short as 2.26 Å are stabilized in this structure via the local Rh-O configuration reminiscent to that in the μ-peroxo-μ-hydroxo Rh complexes. The LiyRh3O6 structure is remarkably stable upon electrochemical cycling illustrating that proper structural implementation of the oxidized oxygen species can open a pathway toward deliberate employment of the anion redox chemistry in high-capacity/high-voltage positive electrodes for metal-ion batteries.

Along the quasi‐binary section Li3PO4 ‐ CuI3PO4 three different phases Li3–xCuIxPO4 each with extended homogeneity range occur under equilibrium conditions (650 ≤ ; ≤ 700 °C). According to single‐crystal X‐ray structure analyses Phase 1 (0 < x ≤ 0.7) adopts the HT‐ or β‐Li3PO4 structure type [Li2.6CuI0.4PO4, Pnma (no. 62), Z = 4, a = 10.4612(2) Å, b = 6.1690(3) Å, c = 4.9854(2) Å, R1 = 0.023, wR2 = 0.062, Goof = 1.12] and Phase 2 (0.9 ≤ x ≤ 1.8) is isotypic to LT‐ or α‐Li3PO4 [Li2.05CuI0.95PO4, Pnm21 (no. 31), Z = 2, a = 6.2113(8) Å, b = 5.2597(7) Å, c = 4.9904(5) Å, R1 = 0.040, wR2 = 0.108, Goof = 0.98]. A preliminary structure model for the copper‐rich Phase 3 (2.1 ≤ x ≤ 2.8) [“Li0.6CuI2.4PO4”, P$\bar{3}$ (no. 147), a = 6.223(1) Å, c = 5.3629(5) Å] could be refined to R1 = 0.07. Sharp 31P‐MAS‐NMR resonances observed in the spectra of Li2.6CuI0.4PO4 (δiso = 10.4 ppm), Li2.05CuI0.95PO4 (δiso = 12.4 ppm), and Li0.84CuI2.16PO4 (δiso = 10.9 ppm) provide evidence for the absence of paramagnetic Cu2+ ions. Pure copper(I) orthophosphate CuI3(PO4) exists as a homogeneous melt ( ≥ 800 °C) and can be obtained as thermodynamically metastable solid by quenching. It is isotypic to Phase 3 [a = 6.284(3) Å, c = 5.408(5) Å]. Electrochemical delithiation of Li2.05CuI0.95PO4 (C/10, C/30) indicates two partially reversible oxidation processes between 3.75 V and 4.80 V (vs. Li0/Li+).

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