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Aqueous ammonium‐ion batteries (AAIBs) are considered as one of the most promising technologies for large scale energy storage applications, due to their intrinsic safety, environmental friendliness and low cost. Nevertheless, the practical application of AAIBs is impeded by hydrogen evolution reaction (HER) occurring in diluted aqueous electrolyte. Highly concentrated electrolytes can improve electrochemical stability but lead to higher costs and increased hydrolysis of NH4+. In this work ethylene glycol (EG) is proposed as co‐solvent, which can act as H‐bond modulating agent, to increase the stability of AAIBs with diluted electrolytes. The perturbation of water H‐bond network regulated by EG is proved by spectroscopic methods, while the suppressed HER is confirmed by differential electrochemical mass spectrometry (DEMS) results. As a result, full cells with 3,4,9,10‐perylenebis(dicarboximide) (PTCDI) anode and FeFe(CN)6 (FeHCF) cathode and EG‐added electrolyte exhibit stable cycling performance with capacity retention of 77% after 1950 cycles. [ABSTRACT FROM AUTHOR]

Aiming at a detailed understanding of the interaction between an ionic liquid, O2, and electrodes in Mg-air batteries, we performed a combined differential electrochemical mass spectrometry and in situ infrared spectroscopy model study on the interaction between the ionic liquid (IL) 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide (BMP-TFSI) and a gold film electrode in the presence and absence of O2 and Mg2+ ions in the potential range relevant for the oxygen reduction reaction (ORR) and evolution reaction. Detailed information on the dynamic exchange of adsorbed ions, on the stability/decomposition of the ionic liquid, and on the activity/selectivity/reversibility of the ORR is derived from measurements performed under potentiodynamic and potentiostatic conditions. In neat BMP-TFSI, we find the dynamics of the potential induced exchange of adsorbed ions to depend significantly on the exchange direction. In the presence of O2, the anions formed in the ORR distinctly affect the adsorption characteristics of the IL ions and the exchange dynamics. Furthermore, the ORR changes from reduction to superoxide anions at moderate potentials to reduction to peroxide anion at more negative potentials. In the additional presence of Mg2+ ions, dominant magnesium peroxide and oxide formation result in an irreversible ORR, in contrast to the requirements of an efficient re-chargeable Mg-air battery. In addition, these ions result in the increasing formation of a blocking adlayer, reducing the coverage of adsorbed IL species. [ABSTRACT FROM AUTHOR]

Li‐rich layered oxides (LRLO) with specific energies beyond 900 Wh kg−1 are one promising class of high‐energy cathode materials. Their high Mn‐content allows reducing both costs and the environmental footprint. In this work, Co‐free Li1.2Mn0.6Ni0.2O2 was investigated. A simple water and acid treatment step followed by a thermal treatment was applied to the LRLO to reduce surface impurities and to establish an artificial cathode electrolyte interface. Samples treated at 300 °C show an improved cycling behavior with specific first cycle capacities of up to 272 mAh g−1, whereas powders treated at 900 °C were electrochemically deactivated due to major structural changes of the active compounds. Surface sensitive analytical methods were used to characterize the structural and chemical changes compared to the bulk material. Online DEMS measurements were conducted to get a deeper understanding of the effect of the treatment strategy on O2 and CO2 evolution during electrochemical cycling. [ABSTRACT FROM AUTHOR]

Lithium‐rich layered oxides (LRLOs) exhibit specific capacities above 250 mAh g−1, i.e., higher than any of the commercially employed lithium‐ion‐positive electrode materials. Such high capacities result in high specific energies, meeting the tough requirements for electric vehicle applications. However, LRLOs generally suffer from severe capacity and voltage fading, originating from undesired structural transformations during cycling. Herein, the eco‐friendly, cobalt‐free Li1.2Ni0.2Mn0.6O2 (LRNM), offering a specific energy above 800 Wh kg−1 at 0.1 C, is investigated in combination with a lithium metal anode and a room temperature ionic liquid‐based electrolyte, i.e., lithium bis(trifluoromethanesulfonyl)imide and N‐butyl‐N‐methylpyrrolidinium bis(fluorosulfonyl)imide. As evidenced by electrochemical performance and high‐resolution transmission electron microscopy, X‐ray photoelectron spectroscopy, and online differential electrochemical mass spectrometry characterization, this electrolyte is capable of suppressing the structural transformation of the positive electrode material, resulting in enhanced cycling stability compared to conventional carbonate‐based electrolytes. Practically, the capacity and voltage fading are significantly limited to only 19% and 3% (i.e., lower than 0.2 mV per cycle), respectively, after 500 cycles. Finally, the beneficial effect of the ionic liquid‐based electrolyte is validated in lithium‐ion cells employing LRNM and Li4Ti5O12. These cells achieve a promising capacity retention of 80% after 500 cycles at 1 C. [ABSTRACT FROM AUTHOR]

A study conducted demonstrates the potential of in-situ Fourier transform infrared (FTIR) spectroscopy measurements in an attenuated total reflection configuration (ATR-FTIRS) for the evaluation of reaction pathways, elementary reaction steps, and their kinetics for formic acid electrooxidation on a Pt film electrode. With increasing temperature, the steady-state IR signal of C[O.sub.ad] increases, while that of formate decreases.