No abstract

The new perovskite PbVO 3 was synthesized under high-temperature and high-pressure conditions. Its crystal structure (a ) 3.80005(6) Å, c ) 4.6703(1) Å, Z ) 1, S.G. P4mm) contains isolated layers of corner-shared VO 5 pyramids, which are formed instead of octahedra due to a strong tetragonal distortion (c/a ) 1.23). The lead atom is shifted out of the center of the unit cell toward one of two [VO 2 ]-layers due to the influence of the lone pair. This new perovskite exhibits a semiconductor-like F(T) dependence down to 2 K. This behavior can be qualitatively explained by taking into account strong electron correlations in electronic structure calculations.

The crystal structure of the Sr 2 Fe 2 O 5 brownmillerite has been investigated using electron diffraction and high resolution electron microscopy. The Sr 2 Fe 2 O 5 structure demonstrates two-dimensional order: the tetrahedral chains with two mirror-related configurations (L and R) are arranged within the tetrahedral layers according to the -L-R-L-Rsequence, and the layers themselves are displaced with respect to each other over 1/2[111] or 1/2[111 j ] vectors of the brownmillerite unit cell, resulting in different ordered stacking variants. A unified superspace model is constructed for ordered stacking sequences in brownmillerites based on the average brownmillerite structure with a ) 5.5298(4)Å, b ) 15.5875(12)Å, c ) 5.6687(4)Å, and (3 + 1)-dimensional superspace group I2/m(0βγ)0s, q ) βb* + γc*, 0 e β e 1/2, 0 e γ e 1.

Metal-ion batteries are key enablers in today’s transition from fossil fuels to renewable energy for a better planet with ingeniously designed materials being the technology driver. A central question remains how to wisely manipulate atoms to build attractive structural frameworks of better electrodes and electrolytes for the next generation of batteries. This review explains the underlying chemical principles and discusses progresses made in the rational design of electrodes/solid electrolytes by thoroughly exploiting the interplay between composition, crystal structure and electrochemical properties. We highlight the crucial role of advanced diffraction, imaging and spectroscopic characterization techniques coupled with solid state chemistry approaches for improving functionality of battery materials opening emergent directions for further studies.

No abstract

Sodium (de)intercalation in the Na 4 MnV-(PO 4 ) 3 NASICON-type cathode has been studied with operando synchrotron X-ray powder diffraction and galvanostatic cycling up to 3.8 and 4.0 V cutoff voltages. Symmetry reduction from rhombohedral to monoclinic was observed immediately after the start of the electrochemical desodiation, with restoring of the rhombohedral phase at 3.8 V. Cycling within the 2.5−3.8 V potential range proceeds through both solid-solution and two-phase processes. An additional voltage plateau at ∼3.9 V is observed, associated with "unlocking" of the Na1 site in the rhombohedral phase. Reverse insertion of Na + cations proceeds via the entire solid-solution region. The experimentally observed discharge capacity increases by ≈14% after raising cutoff voltage. KEYWORDS: sodium-ion battery, NASICON, Na 4 MnV(PO 4 ) 3 , phase transitions, operando XRD

No abstract

For Abstract see ChemInform Abstract in Full Text.