A Structurally Flexible Halide Solid Electrolyte with High Ionic Conductivity and Air Processability

In this work, a structurally revivable, chloride-ion conducting solid electrolyte (SE), CsSn$_{0.9}$In$_{0.067}$Cl$_3$, with a high ionic conductivity of 3.45 × 10$^{−4}$ S cm$^{−1}$ at 25 °C is investigated. The impedance spectroscopy, density functional theory, solid-state $^{35}$Cl NMR, and electron paramagnetic resonance studies collectively reveal that the high Cl$^−$ ionic mobility originates in the flexibility of the structural building blocks, Sn/InCl$_6$ octahedra. The vacancy-dominated Cl$^−$ ion diffusion encompasses co-ordinated Sn/In(Cl) site displacements that depend on the exact stoichiometry, and are accompanied by changes in the local magnetic moments. Owing to these promising properties, the suitability of the CsSn$_{0.9}$In$_{0.067}$Cl$_3$, as an electrolyte is demonstrated by designing all-solid-state batteries, with different anodes and cathodes. The comparative investigation of interphases with Li, Li–In, Mg, and Ca anodes reveals different levels of reactivity and interphase formation. The CsSn$_{0.9}$In$_{0.067}$Cl$_3$ demonstrates an excellent humidity tolerance (up to 50% relative humidity) in ambient air, maintaining high structural integrity without compromises in ionic conductivity, which stands in contrast to commercial halide-based lithium conductors. The discovery of a halide perovskite conductor, with air processability and structure revival ability paves the way for the development of advanced air processable SEs, for next-generation batteries

Studies on the design and the development of novel Co-free cathode materials for rechargeable Li-ion batteries

The ever-increasing demand for Li-ion batteries coupled with concerns regarding raw material supply, availability and cost, drives the research towards cobalt-free battery materials. Currently, cobalt is a critical constituent of conventional layered electrode materials. Great efforts have been devoted to the development of potential alternatives. In this context, the polyanionic LiFeBO3 and disordered rock-salts oxides/oxyfluoride with NaCl structure were investigated. Until recently, these materials were not considered suitable as cathode materials owing to the poor Li mobility in these frameworks. The recent discovery of facile Li transport in disordered rock-salts enabled by a percolating network of Li-rich environments has expanded the structural space of materials that can be used as Li-ion electrodes. It has been shown that the reversible capacity of disordered rock-salts increases considerably with Li-excess, which can be accommodated either by using a combination low-valence transition metal and a high-valent d0-cation or the substitution of O2- by F-. Moreover, the structurally stabilizing yet redox-inactive d0-cations such as Ti4+ and Zr4+ could be replaced by the redox-active d1-V4+, which led to significant improvements in reversible capacity. The choice of the redox-active transition metal is critical and plays a determinant role in the performance. For the studied Ni-based disordered rock-salts, which exhibit comparably high average discharge voltages, the introduction of Li-excess leads to a competition between Ni and O for charge-compensation with Ni being oxidized to Ni3+ on the average as revealed by XAS and DEMS. The O oxidation results in O2 gas loss, which manifests itself in pronounced voltage hysteresis for the discharge and significant capacity fade. Combining Li-excess with O2-/F- substitution in Li2VO2F increases Li content and unlocks a multi-electron V3+/V5+ redox, exhibiting extraordinary capacity. In contrast to Li-excess Ni-based systems, no evident oxygen loss has been found for Li2VO2F. The effect of cation substitution on the electrochemical performance has been explored in nano-sized LiM0.5V0.5O2 (M=Mn, Fe, Co). It has been found that compounds which have relied on (V3+/V+4/V+5) redox couples exhibited comparably low average voltages between 2.2-2.6 V vs. Li/Li+. Overall, the gain of higher capacity in disordered rock-salts comes at the expense of higher capacity fading that progressively worsens with oxidation to higher potentials and cycle numbers. In this regard, the use of concentrated electrolytes and cathode surface coatings turned out to be a promising approach to alleviate surface degradation. It is shown that both Li-stochiometric disordered rock-salts and LiFeBO3, which are perceived to be inactive in the micro-size, can function well when they are sufficiently nano-sized

Interface in Solid-State Lithium Battery: Challenges, Progress, and Outlook

All-solid-state batteries (ASSBs) based on inorganic solid electrolytes promise improved safety, higher energy density, longer cycle life, and lower cost than conventional Li-ion batteries. However, their practical application is hampered by the high resistance arising at the solid-solid electrode-electrolyte interface. Although the exact mechanism of this interface resistance has not been fully understood, various chemical, electrochemical, and chemo-mechanical processes govern the charge transfer phenomenon at the interface. This paper reports the interfacial behavior of the lithium and the cathode in oxide and sulfide inorganic solid-electrolytes and how that affects the overall battery performance. An overview of the recent reports dealing with high resistance at the anodic and cathodic interfaces is presented and the scientific and engineering aspects of the approaches adopted to solve the issue are summarized.</p

Design of small hobby CNC milling machine with fixed table

The topic of this work is the design of a small model CNC milling machine with a fixed table for machining wood, plastic, or light alloys (Al, Zn, etc.). It also includes a calculation report and drawing documentation of selected nodes. The beginning of this work consists of an introduction to the issue of milling machines, their distribution and subsequent market analysis. Subsequently, the input parameters are designed on the basis of market analysis and in the last part there is a calculation report, the design of the milling machine itself and a short economic evaluation

Oxygen Activity in Li-Rich Disordered Rock-Salt Oxide and the Influence of LiNbO3LiNbO_{3} Surface Modification on the Electrochemical Performance

Li-rich disordered rock-salt oxides such as Li1.2Ni1/3Ti1/3Mo2/15O2 are receiving increasing attention as high-capacity cathodes due to their potential as high-energy materials with variable elemental composition. However, the first-cycle oxygen release lowers the cycling performance due to cation densification and structural reconstruction on the surface region. This work explores the influence of lithium excess on the charge compensation mechanism and the effect of surface modification with LiNbO3 on the cycling performance. Moving from a stoichiometric LiNi0.5Ti0.5O2 composition toward Li-rich Li1.2Ni1/3Ti1/3Mo2/15O2, oxygen redox is accompanied by oxygen release. Thereby, cationic charge compensation is governed by the Ni2+/3+ and Mo3+/6+ redox reaction. Contrary to the bulk oxidation state of Mo6+ in the charged state, a mixed Mo valence on the surface is found by XPS. Furthermore, it is observed that smaller particle sizes result in higher specific capacities. Tailoring the surface properties of Li1.2Ni1/3Ti1/3Mo2/15O2 with a solid electrolyte layer of LiNbO3 altered the voltage profile, resulting in a higher average discharge voltage as compared to the unmodified material. The results hint at the interdiffusion of cations from the metal oxide surface coating into the electrode material, leading to bulk composition changes (doping) and a segregated Nb-rich surface. The main finding of this work is the enhanced cycling stability and lower impedance of the surface-modified compound. We argue that surface densification is mitigated by the Nb doping/surface modification

Vanadium Oxyfluoride/Few-Layer Graphene Composite as a High-Performance Cathode Material for Lithium Batteries

Metal oxyfluoride compounds are gathering significant interest as cathode materials for lithium ion batteries at the moment because of their high theoretical capacity and resulting high energy density. In this regard, a new and direct approach is presented to synthesize phase-pure vanadium oxyfluoride (VO₂F). The structure of VO₂F was identified by Rietveld refinement of the powder X-ray diffraction (XRD) pattern. It crystallizes in a perovskite-type structure with disorder of the oxide and fluoride ions. The as-synthesized VO₂F was tested as a cathode material for lithium ion batteries after being surface-coated with few-layer graphene. The VO₂F delivered a first discharge capacity of 254 mA h g^–1 and a reversible capacity of 208 mA h g^–1 at a rate of C/20 for the first 20 cycles with an average discharge voltage of 2.84 V, yielding an energy density of 591 W h kg^–1. Improved rate capability that outperforms the previous report has been achieved, showing a discharge capacity of 150 mA h g^–1 for 1 C. The structural changes during lithium insertion and extraction were monitored by ex-situ XRD analysis of the electrodes discharged and charged to various stages. Lithium insertion results in an irreversible structural change of the anion lattice from ³/₄ cubic close packing to hexagonal close packing to accommodate the inserted lithium ions while keeping the overall space-group symmetry. For the first time we have revealed a structural change for the ReO₃-type structure of as-prepared VO₂F to the RhF₃ structure after lithiation/delithiation, with structural changes that have not been observed in previous reports. Furthermore, the new synthetic approach described here would be a platform for the synthesis of new oxyfluoride compounds