Vibrational spectral studies of ion-ion and ion-solvent interactions. III. Zinc nitrate in water/acetonitrile mixtures

Enhanced reversibility and electrochemical window of Zn-ion batteries with an acetonitrile/water-in-salt electrolyte

An acetonitrile/water-in-salt (AWIS) hybrid electrolyte was developed for Zn-ion batteries. Compared to conventional aqueous electrolytes, the AWIS hybrid electrolyte prolonged the lifespan of Zn|Zn cells from 150 to 2500 h and increased the upper cut-off voltage from 1.8 to 2.2 V for Zn-MnO2 batteries. This new AWIS hybrid electrolyte is expected to enhance the energy and power density of Zn-based batteries for large-scale grid storage.

A four-electron Zn-I2 aqueous battery enabled by reversible I-/I2/I+ conversion

Electrochemically reversible redox couples that embrace more electron transfer at a higher potential are the eternal target for energy storage batteries. Here, we report a four-electron aqueous zinc-iodine battery by activating the highly reversible I₂/I⁺ couple (1.83 V vs. Zn/Zn²⁺) in addition to the typical I^-/I₂ couple (1.29 V). This is achieved by intensive solvation of the aqueous electrolyte to yield ICl inter-halogens and to suspend its hydrolysis. Experimental characterization and modelling reveal that limited water activity and sufficient free chloride ions in the electrolyte are crucial for the four-electron process. The merits of the electrolyte also afford to stabilize Zn anode, leading to a reliable Zn-I₂ aqueous battery of 6000 cycles. Owing to high operational voltage and capacity, energy density up to 750 Wh kg^-1 based on iodine mass was achieved (15-20 wt% iodine in electrode). It pushes the Zn-I₂ battery to a superior level among these available aqueous batteries.

Raman and DFT study of polar nu(CN) and non-polar nu(C-H) modes of acetonitrile in aqueous Ag nano-colloids

Raman spectra of acetonitrile (Acn) in different millimolar (mM) concentrations adsorbed on Ag nano-colloids were recorded in the region 2100-3300cm(-1). The nu(CN) and nu(C-H) modes show blue shifts of approximately 3 and approximately 1cm(-1), respectively, when the concentration of Acn in the mixture is increased from 2 to 8mM. The blue shift of nu(CN) and nu(C-H) modes is predominantly because of adsorption of Acn molecules on Ag nano-colloids. The wave number shift and variation of intensity of the nu(CN) and nu(C-H) bands have been discussed in terms of the adsorption geometry, which probably changes from flat-on configuration at lower concentration of Acn to an end-on configuration at higher concentration of Acn. The dephasing of nu(CN) oscillator becomes considerably slower at higher concentration of Acn. The adsorption of Acn molecules on the nano-colloids was simulated using the (B3LYP) method and the basis sets used for Acn molecules and Ag atoms were 6-311++G(d,p) and Lanl2dz, respectively.