: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Aqueous Zn batteries are promising energy storage devices for large-scale energy-storage due to low cost and high energy density. However, their lifespan is limited by the water decomposition and Zn dendrite growth. Here, we suppress water reduction and Zn dendrite growth in dilute aqueous electrolyte by adding dimethyl sulfoxide (DMSO) into ZnCl2-H2O, in which DMSO replaces the H2O in Zn2+ solvation sheath due to a higher Gutmann donor number (29.8) of DMSO than that (18) of H2O. The preferential solvation of DMSO with Zn2+ and strong H2O-DMSO interaction inhibit the decomposition of solvated H2O. In addition, the decomposition of solvated DMSO forms Zn12(SO4)3Cl3(OH)15·5H2O, ZnSO3, and ZnS enriched-solid electrolyte interphase (SEI) preventing Zn dendrite and further suppressing water decomposition. The ZnCl2-H2O-DMSO electrolyte enables Zn anodes in Zn||Ti half-cell to achieve a high average Coulombic efficiency of 99.5% for 400 cycles (400 h), and the Zn||MnO2 full cell with a low capacity ratio of Zn:MnO2 at 2:1 to deliver a high energy density of 212 Wh/kg (based on both cathode and anode) and maitain 95.3% of the capacity over 500 cycles at 8 C.

Solvation Structure Design for Aqueous Zn Metal Batteries.

The development of low-cost and high-safety zinc-ion batteries (ZIBs) has been extensively discussed and reviewed in recent years, but the work on the comprehensive discussion and perspectives in developing zinc-ion electrolytes is still relatively lacking. Faced with critical challenges and bottlenecks practically, the viability of ZIBs critically depends on the development of suitable electrolytes and their practical considerations. In this review, a systematic summary with regard to the basic characteristics of zinc-ion electrolytes facing different issues from optimization strategies to the fundamental science of electrolyte/electrode interfaces (EEIs), particularly in the feasible modifications and advanced characterizations of EEIs, has been put forward. Due to the lack of consideration of the practical issues in major academic studies, we have particularly highlighted aspects that mainly focus on the choice of the electrolyte system, dosage of liquid and fluid electrolytes, status of gel and all-solid electrolytes, together with other concerns related to the electrolytes. The final section proposes significant perspectives to guide and promote the development of zinc-ion electrolytes.

Fundamentals and perspectives in developing zinc-ion battery electrolytes: a comprehensive review

Rechargeable aqueous batteries are an up-and-coming system for potential large-scale energy storage due to their high safety and low cost. However, the freeze of aqueous electrolyte limits the low-temperature operation of such batteries. Here, we report the breakage of original hydrogen-bond network in ZnCl2 solution by modulating electrolyte structure, and thus suppressing the freeze of water and depressing the solid-liquid transition temperature of the aqueous electrolyte from 0 to –114 °C. This ZnCl2-based low-temperature electrolyte renders polyaniline||Zn batteries available to operate in an ultra-wide temperature range from –90 to +60 °C, which covers the earth surface temperature in record. Such polyaniline||Zn batteries are robust at –70 °C (84.9 mA h g−1) and stable during over 2000 cycles with ~100% capacity retention. This work significantly provides an effective strategy to propel low-temperature aqueous batteries via tuning the electrolyte structure and widens the application range of temperature adaptation of aqueous batteries. Rechargeable aqueous batteries are promising for potential large-scale energy storage due to their high safety and low cost. Here the authors analyse a zinc chloride based low-temperature electrolyte for improving practicability of the aqueous batteries.

/pdf/modulating-electrolyte-structure-for-ultralow-temperature-4pi49b1dpd.pdf

Modulating electrolyte structure for ultralow temperature aqueous zinc batteries.

In contemporary years, the increasing demand for high-capacity and safe energy storage has spurred wide attentions in zinc batteries featuring either high voltage, high capacity or both. Despite the extensive research progress, achieving high-energy-density zinc batteries is still challenging and requires a synergy of the multiple factors including reaction mechanisms, electrodes, and electrolytes. In this Review, we comprehensively summarize the rational design strategies, and critically analyze the positive effects and potential issues in optimizing the electrochemistry, cathode materials, electrolytes and device architecture. At the end, the challenges and prospects for the further development of high-energy-density zinc batteries are outlined to guide the research towards new-generation batteries for household appliance, low-speed electric vehicles and large-scale energy storage system.

Design Strategies for High-Energy-Density Aqueous Zinc Batteries.

Insufficient ionic conductivity and freezing of the electrolyte are considered the main problems for electrochemical energy storage at low temperatures (low T). Here, an electrolyte with a freezing point lower than -130 °C is developed by using dimethyl sulfoxide (DMSO) as an additive with molar fraction of 0.3 to an aqueous solution of 2 m NaClO4 (2M-0.3 electrolyte). The 2M-0.3 electrolyte exhibits sufficient ionic conductivity of 0.11 mS cm-1 at -50 °C. The combination of spectroscopic investigations and molecular dynamics (MD) simulations reveal that hydrogen bonds are stably formed between DMSO and water molecules, facilitating the operation of the electrolyte at ultra-low T. Using DMSO as the electrolyte additive, the aqueous rechargeable alkali-ion batteries (AABs) can work well even at -50 °C. This work provides a simple and effective strategy to develop low T AABs.

Aqueous Batteries Operated at −50 °C

Aqueous zinc-ion batteries are promising candidates for grid-scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc-ion batteries. Here, a nanoflake-self-assembled nanorod structure of Ca0.28 MnO2 ·0.5H2 O as Zn-insertion cathode material is designed. The Ca0.28 MnO2 ·0.5H2 O exhibits a reversible capacity of 298 mAh g-1 at 175 mA g-1 and long-term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per-insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn2+ in Mn-based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca0.28 MnO2 ·0.5H2 O cathode and facilitate the following insertion of Zn2+ in 1 m ZnSO4 /0.1 m MnSO4 electrolyte. This work can enlighten and promote the development of high-performance rechargeable aqueous zinc-ion batteries.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/smll.202002852

Layered Ca 0.28 MnO 2 ·0.5H 2 O as a High Performance Cathode for Aqueous Zinc-Ion Battery

/pdf/designing-electrolyte-structure-to-suppress-hydrogen-303p2xo63p.pdf

Tianjiang Sun

Papers

Aqueous Batteries Operated at −50 °C

Layered Ca 0.28 MnO 2 ·0.5H 2 O as a High Performance Cathode for Aqueous Zinc-Ion Battery

Designing electrolyte structure to suppress hydrogen evolution reaction in aqueous batteries

“Water-in-Deep Eutectic Solvent” Electrolytes for High-Performance Aqueous Zn-Ion Batteries

High Power and Energy Density Aqueous Proton Battery Operated at −90 °C