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In the search for high energy density cathodes for next-generation lithium-ion batteries, the disordered rocksalt oxyfluorides are receiving significant attention due to their high capacity and lower voltage hysteresis compared with ordered Li-rich layered compounds. However, a deep understanding of these phenomena and their redox chemistry remains incomplete. Using the archetypal oxyfluoride, Li 2 MnO 2 F, we show that the oxygen redox process in such materials involves the formation of molecular O 2 trapped in the bulk structure of the charged cathode, which is reduced on discharge. The molecular O 2 is trapped rigidly within vacancy clusters and exhibits minimal mobility unlike free gaseous O 2 , making it more characteristic of a solid-like environment. The Mn redox process occurs between octahedral Mn 3+ and Mn 4+ with no evidence of tetrahedral Mn 5+ or Mn 7+ . We furthermore derive the relationship between local coordination environment and redox potential; this gives rise to the observed overlap in Mn and O redox couples and reveals that the onset potential of oxide ion oxidation is determined by the degree of ionicity around oxygen, which extends models based on linear Li–O–Li configurations. This study advances our fundamental understanding of redox mechanisms in disordered rocksalt oxyfluorides, highlighting their promise as high capacity cathodes.

Amid the growing interest in rechargeable aqueous zinc-based batteries, tunnel-structured α-MnO2 has emerged as a promising cathode material owing to its low cost, high capacity and high safety.However, the precise charge storage mechanism, possibly involving proton and/or Zn ion insertion, has not been fully characterized especially at the atomistic level. Here, we report new insights through a combined investigation of atomic-scale electron microscopy, electrochemical analysis and ab initio simulations. We find that reversible Zn 2+ insertion into α-MnO2 framework is unlikely in the aqueous system, and that the charge storage process is dominated by H + insertion into the tunnel structures which are maintained upon discharging to HMnO2. Furthermore, we identify the local lattice positions for the hydroxyl (OH) groups in HxMnO2 as a function of H content. We reveal the consequent anisotropic structural change proceeding from the particle surface into the bulk, and thus account for the structural failure and capacity decay of the electrode upon cycling.Future work should consider optimizing proton insertion kinetics with enhanced host stability.

The oxygen evolution complex (OEC) of photosystem II (PSII) is intrinsically more active than any synthetic alternative for the oxygen evolution reaction (OER). A crucial question to solve for the progress of artificial photosynthesis is to understand the influential interactions during water oxidation in PSII. We study the principles of interatomic electron transfer steps in OER, with emphasis on exchange interactions, revealing the influence of delocalizing ferromagnetic spin potentials during the catalytic process. The OEC is found to be an exchange coupled mixed-valence electron-spin acceptor where its orbital physics determine the unique activity of PSII. The two unpaired electrons needed in the triplet O molecule interact with the high spin state of the catalyst via exchange interactions; the optimal ferromagnetic catalyst and the resulting radical intermediates are spin paired. As a result, the active center of the CaMnO cofactor, stimulated by the driving potential provided by photons, works as a spin valve to accelerate the formation and release of O from diamagnetic HO.

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The kinetics of surface 'explosions' on single-crystal surfaces has been explored by mathematical modelling of a number of possible kinetic models and examining the quality offit to a wide range of experimeitd data. Secondorder autocatalysis has been the previously preferred model. However, this model is inconsistent since if assumes a random distribution of adsorbates on the surface and yet islanding is known to occur in a number of 'explosive' adsorbate systems. Indeed. it is found to be necessary to assume a high loco1 coverage (practically independent of the global coverage) near initiation sites to fit the data well. Hence, a new approach that takes into account the effect of intemtions between neighbouring adsorbates is required. A circular island model is developed which incorporates the effects of asynchronous initiation and the reduced yield caused by island merging using simple assumptions. This is found to be capable of producing fits to 'explosive' desorption dara as gwd as those obtained by the second-order model.

We have studied, by using ab initio calculations, the electronic properties of electro‐catalysts for the oxygen evolution reaction (OER) with polarised density of states caused by localised spins in the d shell. Oxygen is a molecule in the triplet state (i.e., the outer electrons have parallel spins), which means that the spins localised in the p shell (↑O=O↑), the d shell and the conduction band electrons (t2gnegm) will couple through exchange interactions, which we think will provide favourable conditions for the OER. We compare the perovskites CaCu3Fe4O12 (CCF) and Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with RuO2. CCF and BSCF both have fluctuating electronic structures accessible at room temperature that are linked to conducting spin‐polarised density of states, equivalent to the paramagnetic state of covalent transition metal oxides with fine charge conductivity. CCF and BSCF both possess a considerable number of unpaired electrons localised in the inner d shell, high‐spin configurations and competing inter‐atomic exchange interactions. As a first approximation, the average fluctuation of the magnetisation in the metal atoms correlates linearly with the OER onset potential for the studied compositions. By linking the dynamics of the localised inner‐electron spins to the conduction spins through exchange interactions, we can predict that other perovskites, such as Sr2Fe0.75Co0.25MoO6, will be OER active at room temperature, as they have similar electronic properties to CCF and BSCF.