Influence of the cathode porosity on the discharge performance of the lithium–oxygen battery

By varying the ratio between the amount of carbon and Kynar binder in the cathode of a lithium–oxygen battery, it could be shown that an increasing amount of binder resulted in a decrease in the discharge capacity, mainly as a result of the decrease in the cathode porosity. It was shown that the Kynar binder blocked the majority of the pores with a width below 300 Å as determined by studying the pore volume and pore size distribution by nitrogen adsorption. Three carbonate based electrolytes (PC, PC:DEC (1:1), and EC:DEC (2:1) with 1 M LiPF6) were tested with the various cathode film compositions. Generally, the PC:DEC and EC:DEC based electrolytes provided higher capacities than PC. The results indicated that the air electrode composition and its effect on the porosity of the cathode, as well as electrolyte properties, are important when optimizing the discharge capacity.

► The amount of binder in cast cathode films influenced the porosity of the cathode.
► Addition of more binder (Kynar) resulted in a decreased surface area and pore volume.
► The discharge capacity of the Li–O2 cell decreased by increasing the amount of Kynar.
► The Kynar blocked the majority of the pores with a width below 300 Å.
► The discharge capacity was very much dependent on the electrolyte properties as well.