Detection of trapped molecular O2 in a charged Li-rich cathode by Neutron PDF

Oxidation and reduction of the oxide ions in the bulk of cathode materials is a potential route towards increasing the energy density of Li-ion batteries. Here, we present neutron PDF...

Fast-ion conduction and local environments in BIMEVOX

The energy landscape of the fast-ion conductor Bi 4 V 2 O 11 is studied using density functional theory. There are a large number of energy minima, dominated by low-lying thermally accessible configurations in which there are equal numbers of oxygen vacancies in each vanadium–oxygen layer, a range of vanadium coordinations and a large variation in Bi–O and V–O distances. By dividing local minima in the energy landscape into sets of configurations, we then examine diffusion in each different layer using ab initio molecular dynamics. These simulations show that the diffusion mechanism mainly takes place in the 〈110〉 directions in the vanadium layers, involving the cooperative motion of the oxide ions between the O(2) and O(3) sites in these layers, but not O(1) in the Bi–O layers, in agreement with experiment. O(1) vacancies in the Bi–O layers are readily filled by the migration of oxygens from the V–O layers. The calculated ionic conductivity is in reasonable agreement with the experiment. We compare ion conduction in δ-Bi 4 V 2 O 11 with that in δ-Bi 2 O 3 . This article is part of the Theo Murphy meeting issue ‘Understanding fast-ion conduction in solid electrolytes’.

The fascinating world of mayenite (Ca12Al14O33) and its derivatives

Mayenite (12CaO·7Al2O3) is a mesoporous calcium aluminum oxide, with a characteristic crystalline structure. The framework of mayenite is composed of interconnected cages with a positive electric charge per unit cell that includes two molecules [Ca24Al28O64]4+, and the remaining two oxide ions O2−, often labelled “free oxygen”, are trapped in the cages defined by the framework. Starting from mayenite structure several derivatives have been prepared through advanced synthetic protocols by free oxygen substitution with various anions. Mayenite and its derivates have been intensively investigated in many applications which include catalysis (oxidation and reduction, ammonia synthesis, pinacol coupling), environmental sensors and CO2 sorbent materials. In this review, we summarize our recent results on the main applications of mayenite and its derivatives.

Crossover of positive and negative magnetoconductance in composites of nanosilica glass containing dual transition metal oxides

Magnetoconductance swithching phenomenon in nanosilica glass containing dual transition metal oxide ions.

Anode Effect Prediction in Hall-Héroult Cells Using Time Series Characteristics

In aluminium production, anode effects occur when the alumina content in the bath is so low that normal fused salt electrolysis cannot be maintained. This is followed by a rapid increase of pot voltage from about 4.3 V to values in the range from 10 to 80 V. As a result of a local depletion of oxide ions, the cryolite decomposes and forms climate-relevant perfluorocarbon (PFC) gases. The high pot voltage also causes a high energy input, which dissipates as heat. In order to ensure energy-efficient and climate-friendly operation, it is important to predict anode effects in advance so that they can be prevented by prophylactic actions like alumina feeding or beam downward movements. In this paper a classification model is trained with aggregated time series data from TRIMET Aluminium SE Essen (TAE) that is able to predict anode effects at least 1 min in advance. Due to a high imbalance in the class distribution of normal state and labeled anode effect state as well as possible model’s weaknesses the final F1 score of 32.4% is comparatively low. Nevertheless, the prediction provides an indication of possible anode effects and the process control system may react on it. Consequent practical implications will be discussed.

Synthesis and Structure of [Fe(TPA)Cl2](ClO4) and [{Fe(TPA)Cl}2O](ClO4)2 Where TPA = Tris-(2-pyridylmethyl)amine

[Fe(TPA)Cl2](ClO4), where TPA is tris-(2-pyridylmethyl)amine, crystallizes in the orthorhombic space group P212121 with Z = 4, a = 8.6264(10) Å, b = 15.459(3) Å, and c = 16.008(3) Å. The structure was determined at 110 K from 4333 reflections (3520 observed) with R = 0.041 (Rw = 0.082). The iron is pseudo-octahedral with the two chloride ions cis. The Fe-Cl bond trans to the tertiary amine is shorter. [{Fe(TPA)Cl}2O](ClO4)2 exhibits two polymorphic monoclinic forms, and the monohydrate also crystallizes in a monoclinic form. For the P21/c polymorph, Z = 2, a = 10.839(2) Å, b = 15.956(3) Å, c = 12.416(2) Å, β = 107.024(10)°, and the structure was determined at 95 K from 6514 reflections (3974 observed) with R = 0.052 (Rw = 0.099). For the C2/c polymorph, Z = 4, a = 20.5023(17) Å, b = 15.2711(13) Å, c = 16.1069(11) Å, β = 124.465(4)°, and the structure was determined at 161 K from 6250 reflections (3130 observed) with R = 0.0632 (Rw = 0.1229). For the hydrate, P21/n, Z = 4, a = 16.201(2) Å, b = 16.980(3), c = 16.451(3), β = 112.234(5)°, and the structure was determined at 100 K from 12,745 reflections (6600 observed) with R = 0.097 (Rw = 0.190). In each of the [{Fe(TPA)Cl}2O]2+ units, each iron is pseudo-octahedral with the chloride and oxide ions cis. The oxide bridge is linear, and the two chlorides are anti. The Fe-N distance for the pyridyl ring trans to the oxide bridge is quite long due to the trans influence of the oxide. Graphic Abstract The X-ray structures of [Fe(TPA)Cl2](ClO4), where TPA is tris-(2-pyridylmethyl)amine, and three polymorphs of dimeric [{Fe(TPA)Cl}2O](ClO4)2 are presented and discussed.