Lithium-ion (Li-ion) batteries as one of the most popular energy storage systems have been widely used in laptops, mobile phones, cameras, electric tools, and cars. However, the commercial Li-ion batteries employing Ni-and Co-based intercalation-type cathodes with limited capacities and energy densities cannot meet the rapidly rising market demands in Metal fluoride-lithium batteries with potentially high energy densities, even higher than lithium-sulfur batteries, are viewed as very promising candidates for next-generation lightweight and low-cost rechargeable batteries. However, so far, metal fluoride cathodes have suffered from poor electronic conductivity, sluggish reaction kinetics and side reactions causing high voltage hysteresis, poor rate capability, and rapid capacity degradation upon cycling. Herein, it is reported that an FeF 3 @C composite having a 3D honeycomb architecture synthesized by a simple method may overcome these issues. The FeF 3 nanoparticles (10-50 nm) are uniformly embedded in the 3D honeycomb carbon framework where the honeycomb walls and hexagonal-like channels provide sufficient pathways for the fast electron and Li-ion diffusion, respectively. As a result, the as-produced 3D honeycomb FeF 3 @C composite cathodes even with high areal FeF 3 loadings of 2.2 and 5.3 mg cm −2 offer unprecedented rate capability up to 100 C and remarkable cycle stability within 1000 cycles, displaying capacity retentions of 95%-100% within 200 cycles at various C rates, and ≈85% at 2C within 1000 cycles. The reported results demonstrate that the 3D honeycomb architecture is a powerful composite design for conversion-type metal fluorides to achieve excellent electrochemical performance in metal fluoride-lithium batteries.

Lithium oxide (Li 2 O) is a highly relevant material for battery applications, and as a binary antifluorite compound of first-row elements, it is equally interesting for basic science. This work investigates the behavior of ionic and electronic charge carriers in Li 2 O. The predominantly ionic conductivity is shown to be well-explained by a defect chemical model based on Frenkel disorder, vacancy migration, and vacancy-dopant association. The enthalpies and entropies of these three processes are derived, and good agreement is seen to isostructural Li 2 S, SrF 2 , and BaF 2 . An upper bound is determined for the electronic conductivity of Li 2 O, which is very low. These results provide more reliable thermodynamic and kinetic parameters for future rigorous treatments of Li 2 O in batteries. For example, even under favorable doping conditions, the ionic conductivity of bulk crystalline Li 2 O (with no higher-dimensional defects or interfacial effects) is multiple orders of magnitude too slow to account for the resistance of typical solid-electrolyte interface (SEI) layers.

Lithium sulfide is a functional material of great importance for battery research, since it is the discharge product in Li–S cathodes and a frequent component of anode passivation layers. In both cases, transport of charge carriers in Li2S is critical for performance. The exploration of charge carrier chemistry in such a simple binary compound is also of fundamental scientific interest. For that purpose, impedance spectroscopy and electromotive force measurements are performed over a broad range of temperatures and doping conditions. The results indicate predominant ion conduction and can be quantitatively explained by a defect chemical model based on Frenkel disorder and vacancy‐dopant association. Mobilities and migration barriers for both vacancy and interstitial defects are deduced. The thermodynamic and kinetic parameters derived for Li+ transport in antifluorite Li2S show remarkable agreement with the analogous parameters for F− transport in fluorite compounds such as BaF2, thereby improving the structural understanding of charge carrier chemistry in such compounds. An application of these results to passivation layers in solid state batteries is also discussed.

We demonstrate a novel synthetic route to fabricate a one-dimensional peapod-like Sb@C structure with disperse Sb submicron-particles encapsulated in carbon submicron-tubes. The synthetic route may well serve as a general methodology for fabricating carbon/metallic fine structures by thermally reducing their carbon-coated metal oxide composites.

Lithium–sulfur batteries with potentially high specific energy are viewed as very promising candidates for next‐generation lightweight and low‐cost rechargeable batteries. However, sulfur‐based cathodes suffer from dissolution of polysulfides causing shuttle effects. Here, in order to confine elemental sulfur and anchor the polysulfides, a novel host that is an inexpensive natural clay mineral, viz., vermiculite is proposed. When compared to regular carbon–sulfur composites, vermiculite–sulfur composites offer promising rate capability and much better cycling stabilities, displaying capacity retentions of ≈89 and ≈93% within 200 cycles at C/2 and 1 C, respectively, and ≈60 % at C/5 within 1000 cycles. Postmortem studies, advanced adsorption tests, density functional theory calculations, and zeta potential measurements in combination with intrinsic characteristics of the natural vermiculite provide insights into the new mechanism. The vermiculite contains naturally present surface cations which show a strong tendency to adsorb Sn2− anions, hence protecting them from dissolution. The excess surface charge is most probably compensated by excess Li+ in the space charge zones which is beneficial for charge transfer and local conductivity. The reported results show that natural clay‐minerals are promising sulfur hosts being able to fixate sulfides via electrical double layer effects, thus enabling high‐performance in lithium–chalcogen batteries.