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Beyond its Li‐ion conductivity, the solid electrolyte lithium thiophosphate (β‐Li3PS4) exhibits redox activity when its electrochemical stability window is exceeded. As this redox activity can be (partially) reversible, thiophosphates may be used as cathode active materials (CAM). Silver thiophosphate (Ag3PS4) is a well‐known Ag‐ion conductor, which has the same crystal structure and similar chemical composition as β‐Li3PS4. Here, Ag3PS4 is selected and studied as the CAM for Li solid‐state batteries (Li‐SSBs) with the configuration (In/InLi| β‐Li3PS4| Ag3PS4: β‐Li3PS4: C65 = 40: 50: 10 wt%). The cells provide a discharge capacity of 325 mAh g−1 at 10 mA g−1, but suffer from continuous capacity fading during cycling with an average Coulomb efficiency of 97% at 50 mA g−1. The reaction mechanism is studied using X‐ray diffraction, X‐ray photoelectron spectroscopy, Raman spectroscopy, and impedance spectroscopy. Overall, the reaction of Li with Ag3PS4 is found to be initially partially reversible, but over cycling Ag2S and S8 become the active materials along with the formation of other byproducts such as Ag2P2S6 and Li2P2S6. [ABSTRACT FROM AUTHOR]

Lithium thiophosphate (β‐Li3PS4) is a promising solid electrolyte (SE) for solid‐state batteries (SSBs). A major limitation is its very narrow electrochemical stability window which is caused by redox reactions involving sulfur and phosphorous. As these redox processes can be reversible, thiophosphates can be also studied as electrode materials. Herein, the use of Cu3PS4 as an active electrode material for Li SSBs with β‐Li3PS4 as the SE is explored. Both compounds exhibit similarities in crystal structure and composition which may benefit their compatibility. An In/InLi alloy is used as the counter electrode. The influence of electrode composition and temperature (room temperature and 60 °C) on the cell behavior is investigated. For an electrode composition of Cu3PS4: β–Li3PS4: C65 = 40: 50: 10 wt%, the initial discharge capacity at 60 °C is 776 mAh g−1 which fades over 60 cycles to 508 mAh g−1 when cycled between 0.8 and 2.8 V (vs. Li+/Li) at 50 mA g−1 (254.8 μA cm−2). Analysis by X‐ray diffraction and X‐ray photoelectron spectroscopy shows that Cu3PS4 irreversibly decomposes during lithiation. During cycling, the redox activity is found to be due to Cu2S and S8 redox. [ABSTRACT FROM AUTHOR]

Hydrogen‐doped In2O3 (In2O3:H) is highly conductive while maintaining extraordinary transparency, thus making it a very attractive material for applications in optoelectronic devices such as (multijunction) solar cells or light‐emitting devices. However, the corresponding metal/In2O3:H contacts may exhibit undesirably high resistances, significantly deteriorating device performance. To gain insight into the underlying efficiency‐limiting mechanism, hard X‐ray photoelectron spectroscopy is employed to in‐situ monitor annealing‐induced changes in the chemical structure of the Ag/In2O3:H interface system that is further complemented by ex‐situ electron microscopy analyses and contact resistance measurements. The observed evolution of the Ag‐ and In‐related photoelectron line intensities can be explained by significant intermixing across the Ag/In2O3:H interface. The corresponding lineshape broadening of the Ag 3d spectra is attributed to the formation of Ag2O and AgO, which becomes significant at temperatures above approximately 160 °C. However, after annealing to 300 °C, instead of the formation of an insulating AgOx interfacial layer, it is found i) In to be rather homogeneously distributed in the complete Ag/In2O3:H stack, ii) Ag diffusing into the In2O3:H, and iii) an improvement of the contact resistance rather than its often‐reported deterioration. [ABSTRACT FROM AUTHOR]

Copper sulfide shows some unique physico‐chemical properties that make it appealing as a cathode active material (CAM) for solid‐state batteries (SSBs). The most peculiar feature of the electrode reaction is the reversible formation of µm‐sized Cu crystals during cycling, despite its large theoretical volume change (75%). Here, the dynamic microstructural evolution of CuS cathodes in SSBs is studied using in situ synchrotron X‐ray tomography. The formation of µm‐sized Cu within the CAM particles can be clearly followed. This process is accompanied by crack formation that can be prevented by increasing the stack pressure from 26 to 40 MPa. Both the Cu inclusions and cracks show a preferential orientation perpendicular to the cell stack pressure, which can be a result of a z‐oriented expansion of the CAM particles during lithiation. In addition, cycling leads to a z‐oriented reversible displacement of the cathode pellet, which is linked to the plating/stripping of the Li counter electrode. The pronounced structural changes cause pressure changes of up to 6 MPa within the cell, as determined by operando stack pressure measurements. Reasons for the reversibility of the electrode reaction are discussed and are attributed to the favorable combination of soft materials. [ABSTRACT FROM AUTHOR]

The co‐intercalation of solvent molecules along with Na+ into the crystal lattice of electrode materials is an undesired process in sodium batteries. An exception is the intercalation of ether solvated alkali ions into graphite, a fast and highly reversible process. Here, reversible co‐intercalation is shown to also be possible for other layered materials, namely titanium disulfide. Operando X‐ray diffraction and dilatometry are used to demonstrate different storage mechanisms for different electrolyte solvents. Diglyme is found to co‐intercalate into the TiS2 leading to a change in the voltage profile and an increase in the interlayer spacing (≈150%). This behavior is different compared to other solvents, which expand much less during Na storage (24% for tetrahydrofuran [THF] and for a carbonate mixture). For all solvents, specific capacities (2nd cycle) exceed 250 mAh g−1 whereas THF exhibited the best stability after 100 cycles. The solvent co‐intercalation is rationalized by density functional theory and linked to the stability of the solvation shells, which is largest for diglyme. Finally, the TiS2 electrode with diglyme electrolyte is paired with a graphite electrode to realize the first proof‐of‐concept solvent co‐intercalation battery, that is, a battery with two electrodes that both rely on reversible co‐intercalation of solvent molecules. [ABSTRACT FROM AUTHOR]

A known strategy for improving the properties of layered oxide electrodes in sodium‐ion batteries is the partial substitution of transition metals by Li. Herein, the role of Li as a defect and its impact on sodium storage in P2‐Na0.67Mn0.6Ni0.2Li0.2O2 is discussed. In tandem with electrochemical studies, the electronic and atomic structure are studied using solid‐state NMR, operando XRD, and density functional theory (DFT). For the as‐synthesized material, Li is located in comparable amounts within the sodium and the transition metal oxide (TMO) layers. Desodiation leads to a redistribution of Li ions within the crystal lattice. During charging, Li ions from the Na layer first migrate to the TMO layer before reversing their course at low Na contents. There is little change in the lattice parameters during charging/discharging, indicating stabilization of the P2 structure. This leads to a solid‐solution type storage mechanism (sloping voltage profile) and hence excellent cycle life with a capacity of 110 mAh g‐1 after 100 cycles. In contrast, the Li‐free compositions Na0.67Mn0.6Ni0.4O2 and Na0.67Mn0.8Ni0.2O2 show phase transitions and a stair‐case voltage profile. The capacity is found to originate from mainly Ni3+/Ni4+ and O2‐/O2‐δ redox processes by DFT, although a small contribution from Mn4+/Mn5+ to the capacity cannot be excluded. [ABSTRACT FROM AUTHOR]

Organic-inorganic nanoparticle molecular hybrid materials are interesting candidates for improving exciton separation in organic solar cells. The orbital alignment at the internal interface of cadmium selenide (ArS-CdSe) hybrid materials functionalized with covalently attached arylthiolate moieties was investigated through X-ray photoemission spectroscopy (XPS) and ultraviolet photoemission spectroscopy (UPS). A physisorbed interface between arylthiol (ArSH) ligands and CdSe nanoparticles was also investigated for comparison. This interface was created via a multi-step thin film deposition procedure in-vacuo, where the surface was characterized after each experimental step. This enabled the direct comparison of ArSH/CdSe interfaces produced via physisorption and ArSCdSe covalently attached hybrid materials, which rely on a chemical reaction for their synthesis. All material depositions were performed using an electrospray deposition, which enabled the direct injection of solution-originating molecular species into the vacuum system. This method allows XPS and UPS measurements to be performed immediately after deposition without exposure to the atmosphere. Transmission electron microscopy was used to determine the morphology and particle size of the deposited materials. Ultraviolet-visible spectroscopy was used to estimate the optical band gap of the CdSe nanoparticles and the HOMO-LUMO gap of the ArSH ligands. These experiments showed that hybridization via covalent bonds results in an orbital realignment at the ArSH/ CdSe interface in comparison to the physisorbed interface. The orbital alignment within the hybrid caused a favorable electron injection barrier, which likely facilitates exciton-dissociation while preventing charge-recombination. [ABSTRACT FROM AUTHOR]