The solid lithium-ion electrolyte “Li₇La₃Zr₂O₁₂” (LLZO) with a garnet-type structure has been prepared in the cubic and tetragonal modification following conventional ceramic syntheses routes. Without aluminium doping tetragonal LLZO was obtained, which shows a two orders of magnitude lower room temperature conductivity than the cubic modification. Small concentrations of Al in the order of 1 wt% were sufficient to stabilize the cubic phase, which is known as a fast lithium-ion conductor. The structure and ion dynamics of Al-doped cubic LLZO were studied by impedance spectroscopy, dc conductivity measurements, ⁶Li and ⁷Li NMR, XRD, neutron powder diffraction, and TEM precession electron diffraction. From the results we conclude that aluminium is incorporated in the garnet lattice on the tetrahedral 24dLi site, thus stabilizing the cubic LLZO modification. Simulations based on diffraction data show that even at the low temperature of 4 K the Li ions are blurred over various crystallographic sites. This strong Li ion disorder in cubic Al-stabilized LLZO contributes to the high conductivity observed. The Li jump rates and the activation energy probed by NMR are in very good agreement with the transport parameters obtained from electrical conductivity measurements. The activation energy E_a characterizing long-range ion transport in the Al-stabilized cubic LLZO amounts to 0.34 eV. Total electric conductivities determined by ac impedance and a four point dc technique also agree very well and range from 1 × 10⁻⁴ Scm⁻¹ to 4 × 10⁻⁴ Scm⁻¹ depending on the Al content of the samples. The room temperature conductivity of Al-free tetragonal LLZO is about two orders of magnitude lower (2 × 10⁻⁶ Scm⁻¹, E_a = 0.49 eV activation energy). The electronic partial conductivity of cubic LLZO was measured using the Hebb–Wagner polarization technique. The electronic transference number t_{e −} is of the order of 10⁻⁷. Thus, cubic LLZO is an almost exclusive lithium ion conductor at ambient temperature.

Tuning porosity with electric fields: Many metal-organic framework (MOF) compounds exhibit soft porosity—i.e., their lattices can undergo considerable deformation. Knebel et al. formed membrane layers of the MOF ZIF-8 and found that it was converted into a polar polymorph with a stiffer lattice in response to an applied electric field (see the Perspective by Gascon). This change reduced gas transport but, for certain gas mixtures such as propane and propene, also improved their separation factor. Science , this issue p. 347 ; see also p. 303

In the present work, a new class of high entropy materials for energy storage applications is introduced. Multi-anionic and -cationic compounds are prepared by facile mechanochemistry using a recently designed multi-cationic transition-metal-based high entropy oxide as the precursor and LiF or NaCl as the reactant, leading to formation of lithiated or sodiated materials. Notably, the Li-containing entropy-stabilized oxyfluoride described herein (Li_x(Co_0.2Cu_0.2Mg_0.2Ni_0.2Zn_0.2)OF_x) exhibits a working potential of 3.4 V vs. Li⁺/Li, enabling its use as a cathode active material. Unlike conventional (non-entropy-stabilized) oxyfluorides, this new material shows enhanced Li storage properties due to entropy stabilization, which, in general, facilitates tailoring the cycling performance by varying the constituent elements in yet unprecedented ways. In addition, we demonstrate that the concept of entropy stabilization is also applicable to Na-containing oxychlorides with a rock-salt structure, thus paving the way toward development of (next-generation) post-Li battery technologies.

Technological and scientific challenges coupled with environmental considerations have prompted a search for simple and energy-efficient syntheses and processing routes of materials. This tutorial review provides an overview of recent research efforts in non-conventional reactions and syntheses of oxides induced by mechanical action. It starts with a brief account of the history of mechanochemistry. Ensuing discussions will review the progress in homogeneous and heterogeneous mechanochemical reactions in oxides of various structures. The review demonstrates that the event of mechanically induced reactions provides novel opportunities for the non-thermal manipulation of materials and for the tailoring of their properties.