The research on aqueous zinc ion batteries (AZIB) is getting more attention as the energy transition continues to develop and the need for inexpensive and safe stationary storage batteries is growing. As the detailed reaction mechanisms are not conclusively revealed, we want to take an alternative approach to investigate the importance of pH value changes during cycling. By adding a pH-indicator to the electrolyte (2 M ZnSO 4 + 0.1 M MnSO 4 ), the local pH-value change during operation is visualized in operando. The overall pH value was found to increase during cycling whereas a major temporary pH drop in close proximity of the manganese dioxide electrode surface occurs. Additionally, this pH value change was quantified locally by in operando measurements with a pH micro electrode. Different electrolyte compositions with additives (sodium dodecyl sulfate (SDS), sulfuric acid (H 2 SO 4 )) and operation voltages were tested. The pH-potential-diagrams of manganese and zinc reveal pH value and potential limits, leading to active material dissolution at lower pH values and oxygen gas evolution at higher potentials >1.7 V. The procedure of combining a pH indicator, pH microelectrode measurements and pH-potential diagrams can be seen as an appropriate method to determine the recommendable working window of aqueous batteries.

The enthalpy and entropy of activation for the decomposition reaction of seven tetra-alkylammonium iodides in chloroform solution have been measured. All the salts contained the benzyl group attached to the nitrogen atom and decomposed to yield benzyl iodide and a tertiary amine as the only products.A Hammett free energy correlation is made and used to deduce the nature of the transition state, and a rationalization of the variation of the enthalpy and entropy of activation with the structure of the substrate is given.

A novel methodology for calculating the surface energy of a disordered material was developed and is described here. The method was used to calculate the range of surface energies for {100}, {110}, {111}, and {112} type facets of the disordered rock salt (DRX) cathode material Li 2 MnO 2 F, as a function of surface cation and anion decoration. Boltzmann averaging was used to determine average surface energies for each facet which were then used to calculate the equilibrium particle shape. It was found that Li 2 MnO 2 F displays predominantly {100} type lithium/fluorine-rich facets favoring a cubic particle shape. The density of states along with electronic structure-based bonding analyses are calculated to rationalize differences observed in surface energy. Importantly, it is found that surface lithium and fluorine lower the surface energy of the majority facets, suggesting that surfaces of Li 2 MnO 2 F are likely enriched in lithium and fluorine and display less oxygen and manganese, which has implications for capacity and rate retention.

The role of nanoscale chemomechanical behavior in macroscopic performance of functional materials is well recognized. For lithium-ion battery cathodes, tremendous effort has been devoted to the development of new chemistry and structure, yet fundamental understanding in the correlation between redox processes and mechanical properties of the novel materials lags 1 behind. In the present study, we prepare large discrete single-grains of Li-excess cationdisordered rocksalts (DRX) and investigate their chemomechanical behavior at the particle-level, using nano-resolution X-ray and electron-based spectro-imaging and chemical mapping techniques. While irregular cracking upon lithium extraction leads to the eventual breakdown of the baseline DRX oxide (Li 1.2 Ti 0.4 Mn 0.4 O 2 ) particles at high delithiation state, the fluorinated-DRX (Li 1.3 Ti 0.3 Mn 0.4 O 1.7 F 0.3 ) clearly displays aligned cracking along the <001> direction. The resulting periodicity in the cracking pattern enables the particles to retain their integrity and consequently, improved electrochemical stability. Density functional theory (DFT) calculations showed that fluorination leads to increased concentration of Li + on the (001) planes and preferential Li movements along the <001>-family directions, revealing the underlying mechanism for directional cracking. Our study demonstrates the unique role of fluorine in modulating nanoscale chemomechanics, which in turn influences the evolution of charge and strain heterogeneity at the particle level. These insights provide important design guidelines in further improving DRX cathode materials.