Tuning anion solvation energetics enhances potassium–oxygen battery performance

Abstract

The oxygen reduction reaction (ORR) is a critical reaction in secondary batteries based on alkali metal chemistries. The nonaqueous electrolyte mediates ion and oxygen transport and determines the heterogeneous charge transfer rates by controlling the nature and degree of solvation. This study shows that the solvent reorganization energy (λ) correlates well with the oxygen diffusion coefficient (DO2) and with the ORR rate constant (k) in nonaqueous Li–, Na–, and K–O2 cells, thereby elucidating the impact of variations in the solvation shell on the ORR. Increasing cation size (from Li+ to K+) doubled k/λ, indicating an increased sensitivity of k to the choice of anion, while variations in DO2were minimal over this cation size range. At the level of a symmetric K–O2 cell, both the formation of solvent-separated ion pairs [K+–(DMSO)n–ClO4− + (DMSO)m–ClO4−] and the anions being unsolvated (in case of PF6−) lowered ORR activation barriers with a 200-mV lower overpotential for the PF6− and ClO4− electrolytes compared with OTf− and TFSI− electrolytes with partial anion solvation [predominantly K+–(DMSO)n–OTf−]. Balancing transport and kinetic requirements, KPF6 in DMSO is identified as a promising electrolyte for K–O2 batteries.

An Aqueous, Electrode-Decoupled Redox-Flow Battery for Long Duration Energy Storage

“…60 Diffusion coe cients were higher for Ce species as compared to Ti species, and higher diffusion coe cients in CH 3 SO 3 H-supported electrolytes suggested reduced complexation with both Ti and Ce following Pearson's hard-soft acid-base theory. 61,62 The rst electron transfer rate constants (k ) for both the Ce and Ti redox couples were also calculated from the CVs using the method of Kochi and Klingler as detailed in Supplementary Materials Section S3.3. 63 Reduced complexation in CH 3 SO 3 H-supported electrolytes led to higher k 0 values in these electrolytes.…”

Fuel and oxygen harvesting from Martian regolithic brine

“…S7), exhibiting a similar trend as that seen in O 2 -saturated SMRB. As detailed in SI Appendix, section S6.3, Pb 2 Ru 2 O 7−δ was found to exhibit greater bifunctional oxygen reduction reaction (ORR)/OER activity as compared to RuO 2 in near-neutral media by applying the Marcus-Hush kinetic formulation to the Tafel analysis of the LSVs (22)(23)(24). This provides a pathway for the utilization of the H 2 produced by our Martian electrolyzer in a fuel cell with a Pb 2 Ru 2 O 7-δ cathode and for the eventual development of a unitized regenerative fuel cell for the use in Mars-like conditions.…”

Prospects for Anion-Exchange Membranes in Alkali Metal–Air Batteries

“…The thermal runaway of the cell, which leads to whole battery pack failure, is believed to be caused by mechanical, electrical, or thermal abuses [11]. Moreover, Li-ion batteries' energy density is only about 100-200 Wh/Kg, which Among several potential candidates, metal-air batteries are a promising and competitive highenergy alternative to Li-ion batteries [13]. Metal-air batteries are high energy density electrochemical cells that use air at the cathode (+ve) and metal as the anode (−ve) with an aqueous electrolyte [14].…”

“…Similarly, there is an intense interest in rechargeable Zn-air batteries, since Zn is the most active metal (less passive) that can be plated from an aqueous electrolyte [18]. Fe-air Among several potential candidates, metal-air batteries are a promising and competitive high-energy alternative to Li-ion batteries [13]. Metal-air batteries are high energy density electrochemical cells that use air at the cathode (+ve) and metal as the anode (−ve) with an aqueous electrolyte [14].…”

“…Figure 1 shows the chemistries and principal components of lead-acid and Liion batteries. Among several potential candidates, metal-air batteries are a promising and competitive highenergy alternative to Li-ion batteries [13]. Metal-air batteries are high energy density electrochemical cells that use air at the cathode (+ve) and metal as the anode (−ve) with an aqueous electrolyte [14].…”