Effects of architecture on the electrochemistry of binder-free inverse opal carbons as Li–air cathodes in an ionic liquid-based electrolyte

Abstract

In this work, different electrodes consisting of a layer of nanostructured binderless carbon supported on a stainless steel (SS) mesh have been developed and tested as cathodes for Li-air batteries. Inverse opal (IO) carbons were developed using poly(styrene-co-methacrylic acid) (PS-MAA) spheres of different sizes as templates via a resorcinol-formaldehyde sol-gel process. The resulting electrodes, which were mechanically stable and easy to manipulate, were electrochemically tested at both 25 and 60 C by galvanostatic cycling in an ionic liquid-based electrolyte (0.3 M LiTFSI in PYR14TFSI). Different ratios of co-monomers used in the preparation of the template polymeric spheres to control their size significantly influenced the resulting surface area, pore volume and pore distribution in IO carbons of different macropore size. From the electrochemical characterisation, transverse trends in reversibility and rate capability were identified depending on the macropore size of the inverse opal carbon. Smaller pores favor a better charge-discharge reversibility. Large pores contribute to an improved rate capability and large capacity, which are likely due, respectively, to deeper oxygen diffusion into the electrode, and to larger pore bottlenecks.

Mass‐transport Control on the Discharge Mechanism in Li–O2 Batteries Using Carbon Cathodes with Varied Porosity

“…Figure presents schematic representations of the two cells employed in this study. The still‐electrolyte cell was a homemade design, which is described in detail elsewhere, with electrodes and a separator stacked together similar to a coin‐ or Swagelok‐type cell. The stirred‐electrolyte cell was a bulk electrolysis cell made using a hermetically sealed three‐neck flask.…”

“…However, because of their high viscosity, they suffer from low conductivity. They are often used at higher temperature (40–60 °C), which decreases their viscosity and increases their conductivity, resulting in significantly higher capacities . By comparing the effect on different pore‐size distributions, we reported previously that an increased capacity at higher temperature results from improved precipitation in small pores .…”

Recent Progress on Stability Enhancement for Cathode in Rechargeable Non‐Aqueous Lithium‐Oxygen Battery

“…By providing triple phase (solid-electrolyte-gas) to sustain the Li-O 2 reactions and void space to house the generated Li 2 O 2 , the properties such as surface area and porosity of carbon cathode are seen to exert a prominent effect on the performances of Li-O 2 cells. [56][57][58][59] Central to these properties, the stability, which can be classifi ed into the mechanical stability and chemical stability according to established results, of carbon cathode is a factor of particular importance. Principally, the architecture of carbon cathode should be well-maintained and the components of carbon cathode should be stable towards the oxidative species generated during the oxygen reduction reaction (ORR)/oxygen evolution reaction (OER) processes, so as to provide a stable chemistry for the Li-O 2 reactions to occur.…”

Tailoring oxygen redox reactions in ionic liquid based Li/O2 batteries by means of the Li+ dopant concentration

“…A detailed description of the cell is reported in a previous work. 31 The electrodes consisted of a layer of commercial used as a current collector. All lithium-oxygen cells were assembled in an argon-filled glove box.…”