Dual‐Function Air Cathode for Metal–Air Batteries with Pulse‐Power Capability

Wiring zinc in three dimensions re-writes battery performance—dendrite-free cycling

“…This all-Zn two-electrode cell functions as an electroanalytical tool that allows one to put the 3D structure through its paces-we can force the inherent Zn dissolution/ deposition reactions at rates one would rarely attempt in a battery. In addition to permitting high rates of chargedischarge, the symmetric cell circumvents the need for a complementary electrode that might otherwise limit performance at demanding current loads-e.g., a bifunctionally catalyzed air cathode that can reduce and evolve O 2 in the case of a rechargeable Zn-air cell [37][38][39] or a Ag/Ag x O cathode that can sustain high-rate charging. 40 Symmetric test cells are commonly employed in battery science for fundamental exploration of reversibility, interfacial characteristics, and the effect of additives on Li performance; 41,42 note that symmetric cells (e.g., Li vs. Li or Zn vs. Zn) are not meant to attain voltages of relevance for practical batteries.…”

Retaining the 3D Framework of Zinc Sponge Anodes upon Deep Discharge in Zn–Air Cells

“…The long-term goal for a redesigned Zn electrode is its implementation into rechargeable Zn–air cells. The Zn sponge electrodes described herein, along with our concurrent efforts on pulse-power–enabled carbon nanofoam air cathodes, , are but two breakthroughs en route to that goal. We have demonstrated dendrite-free charge–discharge cycling to modest DOD (20% of theoretical Zn utilization) in symmetric Zn/ZnO and Ag–Zn cells, and ongoing experiments are focused on incorporating efficient oxygen-evolution catalysts into air cathodes and constructing prototype rechargeable Zn–air cells.…”

Carbon Nanofoam-Based Cathodes for Li–O2Batteries: Correlation of Pore–Solid Architecture and Electrochemical Performance

“…22 Some researchers anticipate that diminishing returns with respect to capacity will be reached when pores approach tens of nanometers because the accumulation of electrically insulating solids (e.g., Li oxides and Li carbonates) will self-limit as electroactive cathode surfaces passivate. [23][24][25] In this work, we leverage our ongoing efforts to optimize freestanding, three-dimensional (3D) porous carbon nanofoam papers 26 as air-breathing cathodes for Zn-air batteries [27][28][29][30] by exploring the relationship between the nature of the free volume of the nanofoam structure-both the size of the pores therein and the size distribution of those pores-and the specific capacity of a Li-O 2 cell constructed with a nanofoam paper cathode. The well-characterized mesopore-to-macropore size regime of the nanofoam-based air cathodes (10s to 100s of nanometers) spans a range unrepresented in the literature for Li-O 2 cathodes, where the conductive component toggles between conventional microporous-to-mesoporous-carbons and nonconventional architectures such as nanotube/nanofiber assemblies (e.g., "buckypaper") or freestanding metal foams, metal oxides, or carbon, where voids are typically on the order of micrometers.…”