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Given the inherent performance limitations of intercalation‐based lithium‐ion batteries, solid‐state conversion batteries are promising systems for future energy storage. A high specific capacity and natural abundancy make iron disulfide (FeS2) a promising cathode‐active material. In this work, FeS2 nanoparticles were prepared solvothermally. By adjusting the synthesis conditions, samples with average particle diameters between 10 nm and 35 nm were synthesized. The electrochemical performance was evaluated in solid‐state cells with a Li‐argyrodite solid electrolyte. While the reduction of FeS2 was found to be irreversible in the initial discharge, a stable cycling of the reduced species was observed subsequently. A positive effect of smaller particle dimensions on FeS2 utilization was identified, which can be attributed to a higher interfacial contact area and shortened diffusion pathways inside the FeS2 particles. These results highlight the general importance of morphological design to exploit the promising theoretical capacity of conversion electrodes in solid‐state batteries., Particle‐size reduction of iron sulfide nanoparticles improves its performance as an active material in solid‐state conversion cathodes: For reduced particle dimensions, the electrochemical utilization of FeS2 is increased. The potential of FeS2 as an electrode in solid‐state batteries is highlighted and the importance of the morphological design of battery materials is underscored.

Owing to high ionic conductivity and good oxidation stability, halide‐based solid electrolytes regain interest for application in solid‐state batteries. While stability at the cathode interface seems to be given, the stability against the lithium metal anode has not been explored yet. Herein, the formation of a reaction layer between Li3InCl6 (Li3YCl6) and lithium is studied by sputter deposition of lithium metal and subsequent in situ X‐ray photoelectron spectroscopy as well as by impedance spectroscopy. The interface is thermodynamically unstable and results in a continuously growing interphase resistance. Additionally, the interface between Li3InCl6 and Li6PS5Cl is characterized by impedance spectroscopy to discern whether a combined use as cathode electrolyte and separator electrolyte, respectively, might enable long‐term stable and low impedance operation. In fact, oxidation stable halide‐based lithium superionic conductors cannot be used against Li, but may be promising candidates as cathode electrolytes., Superionic halide solid electrolytes show excellent cathodic electrolyte properties in solid state batteries, but they are unstable in contact with the lithium metal anode. The forming solid electrolyte interphase is analyzed herein, using X‐ray photoelectron spectroscopy and impedance spectroscopy. Additionally, the hetero‐interface between Li3InCl6 and Li6PS5Cl is analyzed to highlight the concept of hybrid electrolyte cells.

The demand for lithium-ion batteries has risen dramatically over the years. Unfortunately, many of the essential component materials, such as cobalt and lithium, are both costly and of limited abundance. For this reason, the recycling of lithium-ion battery electrodes is crucial to ensuring the availability of such resources and protecting the environment. Herein, a simple and scalable recycling process was developed for the prototypical cathode active material Li1.02 (Ni0.8 Co0.1 Mn0.1 )0.98 O2 (NCM-811). By a combination of thermal decomposition and dissolution steps, spent NCM could be converted into Li2 CO3 and a transition metal oxalate blend, which served as precursors for new NCM. Importantly, it was also possible to individually separate each transition metal during the recycling process, thereby extending the utility of this method to a wide variety of NCM compositions. Each intermediate in the process was investigated by scanning electron microscopy and X-ray diffraction. Additionally, the elemental composition of the recycled NCM-811 was confirmed using inductively coupled plasma optical emission spectroscopy and energy-dispersive X-ray spectroscopy. The electrochemical performance of the recycled NCM-811 exhibited up to 80 % of the initial capacity of pristine NCM-811. The method presented herein serves as an efficient and environmentally benign alternative to existing recycling methods for lithium-ion battery electrode materials.

Halide-based solid electrolytes are currently growing in interest in solid-state batteries due to their high electrochemical stability window compared to sulfide electrolytes. However, often a bilayer separator of a sulfide and a halide is used and it is unclear why such setup is necessary, besides the instability of the halides against lithium metal. It is shown that an electrolyte bilayer improves the capacity retention as it suppresses interfacial resistance growth monitored by impedance spectroscopy. By using in-depth analytical characterization of buried interphases by time-of-flight secondary ion mass spectrometry and focused ion beam scanning electron microscopy analyses, an indium-sulfide rich region is detected at the halide and sulfide contact area, visualizing the chemical incompatibility of these two electrolytes. The results highlight the need to consider more than just the electrochemical stability of electrolyte materials, showing that chemical compatibility of all components may be paramount when using halide-based solid electrolytes in solid-state batteries.

A diode requires the combination of p- and n-type semiconductors or at least the defined formation of such areas within a given compound. This is a prerequisite for any IT application, energy conversion technology, and electronic semiconductor devices. Since the discovery of the pnp-switchable compound Ag

Inspired by the recent interest in fast ionic conducting solids for electrolytes, the ionic conductivity of a novel ionic conductor Na1+x Ti2-x Gax (PS4 )3 has been investigated. Using X-ray diffraction and impedance spectroscopy the sodium ionic conductivity in this compound was demonstrated, in which bond valence sum analysis suggests a tunnel diffusion for Na+ . Substitution with Ga3+ leads to an increasing Na+ content, an expansion of the lattice and an increasing conductivity with increasing x in Na1+x Ti2-x Gax (PS4 )3 . Given the relation to the NASICON family, upon replacement of the phosphate by a thiophosphate group, a rich structural chemistry can be expected in this class of materials. This work demonstrates the potential for making NaTi2 (PS4 )3 an ideal system to study structure-property relationships in ionic conductors.

Effiziente thermoelektrische Materialien werden durch ein Zusammenspiel von stark voneinander abhangenden Transporteigenschaften erreicht. Um diese wissentlich zu beeinflussen, wird ein tieferes Verstandnis der Chemie und Physik in Festkorpern benotigt. Auf der Grundlage von Molekulorbitaldiagrammen, der “Tight‐Binding”‐Methode und dem klassischem Verstandnis von Bindungsstarken betrachten wir das gezielte Design thermoelektrischer Materialien. Hierbei werden Parameter wie Elektronegativitat, Bandbreite, Orbitaluberlappung sowie Bindungsenergie und ‐lange herangezogen, um Trends der elektronischen Eigenschaften wie Grose und Temperaturabhangigkeit von Bandlucken, effektive Masse der Ladungstrager sowie Bandentartung und Bandkonvergenz zu erklaren. Gitterwarmeleitfahigkeiten werden in Bezug auf die Kristallstruktur und Bindungsstarke behandelt, um den Einfluss von Bindungslangen zu verdeutlichen. Wir zeigen, wie Symmetrie und Starke von Bindungen den Transport von Elektronen und Phononen beeinflussen und wie gezielte Strategien zu Veranderungen und zur Verbesserung thermoelektrischer Effizienz fuhren konnen.

Experimentally, AZn_2Sb_2 samples (A=Ca, Sr, Eu, Yb) are found to have large charge carrier concentrations that increase with increasing electronegativity of A. Using density functional theory (DFT) calculations, we show that this trend can be explained by stable cation vacancies and the corresponding finite phase width in A1−xZn_2Sb_2 compounds.

ZnxSb1–x systems are one of the most promising materials for thermoelectric applications due to their low cost, low toxicity, and high thermoelectric figure of merit. We report the discovery and characterization of novel ZnSb polymorphs with improved thermoelectric properties from a systematic ab initio structural search. The putative ground state at low temperature is a structure with Pbca symmetry. Corresponding electron and phonon transport properties are computed, where the lattice thermal conductivity was accurately obtained through third-order interatomic force constants. At 500 K, both the reduced figure of merit S2/L as well as the lattice thermal conductivity are superior to any previously reported numbers on ZnSb polymorphs, rendering the Pbca phase a promising candidate for an exceptionally good thermoelectric material.

Thermoelektrische Materialien bieten die Moglichkeit, thermische Gradienten in elektrische Energie umzuwandeln um somit Abwarme aus verschiedensten Prozessen zur Energieerzeugung zu nutzen. In diesem Artikel werden die physikalischen Hintergrunde der thermoelektrischen Effekte beschrieben sowie Aufbau und Wirkungsgrad thermoelektrischer Generatoren erlautert. Um eine Brucke zwischen der Physik und Chemie in Festkorpern zu schlagen, werden die unterschiedlichen physikalischen Transportprozesse in Festkorpern mit Hilfe chemischer Konzepte erlautert. Anhand von Beispielen fur thermoelektrische Materialien werden die Ansatze zur Maximierung des thermoelektrischen Wirkungsgrades und der Einfluss der chemischen und strukturellen Faktoren beschrieben. Thermoelectric materials directly convert heat gradients into electrical energy, useful for the recovery of wasted heat generated by different processes. This article describes the thermoelectric effects, the physics of their origin, and the design and efficiency of thermoelectric generators. The different transport properties of solid state materials will be illustrated with basic chemical concepts to connect the physics and chemistry in solids. State of the art thermoelectric materials will be introduced to demonstrate the typical approaches and the influence of chemical and structural influences for a maximum thermoelectric efficiency.

The title nanowires are hydrothermally synthesized with a yield of several hundred milligrams from aqueous mixtures of Fe(NO3)3, SiO2, and NaOH (autoclave, 160—220 °C, 14 h).

The copper ion conducting argyorite-type title compound is synthesized from the elements (evacuated quartz ampule, 1323 K, 3 h, and 773 K, 72 h) and its thermoelectric transport properties are studied.

Quaternary chalcopyrites have shown to exhibit tunable band gaps with changing anion composition. Inspired by these observations, the underlying structural and electronic considerations are investigated using a combination of experimentally obtained structural data, molecular orbital considerations, and density functional theory. Within the solid solution Cu2ZnGeS4-x Se x , the anion bond alteration parameter changes, showing larger bond lengths for metal-selenium than for metal-sulfur bonds. The changing bonding interaction directly influences the valence and conduction band edges, which result from antibonding Cu-anion and Ge-anion interactions, respectively. The knowledge of the underlying bonding interactions at the band edges can help design properties of these quaternary chalcopyrites for photovoltaic and thermoelectric applications.

Single crystals of Ln 3 GaO 6 (Ln = Nd, Sm, Eu, Gd) were grown out of a reactive high temperature hydroxide melt. The structures were solved by single-crystal X-ray diffraction. These gallium oxides crystallize in the polar space group Cmc 2 1 where the orientation of the GaO 4 tetrahedra determines the polarity of the structure. The atomic positions along with the determination of the absolute structure are reported. The lanthanide atoms are located in a seven-fold coordination environment forming edge-sharing zigzag-chains. The photoluminescence was investigated and the europium and gadolinium members of this series exhibit intense luminescence in the visible portion of the spectrum.

Single crystals of LnKNaNbO5 (Ln = La, Pr, Nd, Sm, Eu, Gd, Tb) were grown out of a reactive high temperature hydroxide melt. The structures were solved by single crystal X-ray diffraction. All compounds of the series LnKNaNbO5 crystallize in the space group P4/nmm. The niobium is located in a rare square pyramidal coordination environment in this layered structure. EuKNaNbO5, GdKNaNbO5, and TbKNaNbO5 exhibit room temperature photoluminescence with bright orange-red, pink-purple, and green emissions, respectively. Unlike in many oxide structures, the photoluminescence is not quenched, although the rare earth elements fully occupy a position in the crystal structure.

Ge and Sn in (GeTe)nSb2Te3 (GST) and (SnTe)nSb2Te3 compounds, respectively, are partially substituted by Cd. These layered compounds (n = 1) consist of NaCl-type slabs that are separated by van der Waals gaps. Resonant X-ray diffraction yields different Cd-atom distributions in Cd0.2Ge0.8Sb2Te4 and Cd0.2Sn0.8Sb2Te4, which indicate how van der Waals gaps in metastable cubic GeTe-rich or SnTe-rich compounds (n ≥ 7) are surrounded. The latter exhibit promising thermoelectric properties with figures of merit ZT ≈ 0.8 at 450 °C. Alloying with Sb2Te3 increases the ZT value of SnTe by a factor of up to two because of an increased Seebeck coefficient and a reduced thermal conductivity; the hole concentration is significantly reduced. A further improvement in ZT by ≈20% is possible by Cd-doping, most likely due to a more covalent bonding character, yielding a ZT of ≈1.1 at 450 °C for Cd1.2Sn10.8Sb2Te15. In order to understand the electronic transport properties of these p-type semiconductors, the single parabolic band model is applied. By contrast, Cd doping in GST materials reduces the Hall mobility and therefore decreases the power factor compared to undoped GST materials.

Taking La- and I-doped PbTe as an example, the current work shows the effects of optimizing the thermoelectric figure of merit, zT, by controlling the doping level. The high doping effectiveness allows the carrier concentration to be precisely designed and prepared to control the Fermi level. In addition to the Fermi energy tuning, La-doping modifies the conduction band, leading to an increase in the density of states effective mass that is confirmed by transport, infrared reflectance and hard X-ray photoelectron spectroscopy measurements. Taking such a band structure modification effect into account, the electrical transport properties can then be well-described by a self-consistent single non-parabolic Kane band model that yields an approximate (m*T)^(1.5) dependence of the optimal carrier concentration for a peak power factor in both doping cases. Such a simple temperature dependence also provides an effective approximation of carrier concentration for a peak zT and helps to explain, the effects of other strategies such as lowering the lattice thermal conductivity by nanostructuring or alloying in n-PbTe, which demonstrates a practical guide for fully optimizing thermoelectric materials in the entire temperature range. The principles used here should be equally applicable to other thermoelectric materials.