Effects of Nonaqueous Electrolytes on the Performance of Lithium/Air Batteries

Abstract

The effects of various properties of nonaqueous electrolytes on the performance of lithium/air batteries are investigated. The performance of a lithium/air battery is determined by the number of triphase regions formed by oxygen, electrolyte, and active carbons (with catalyst). The oxygen diffusion rate through the open channels (strongly related to the polarity of the electrolyte) is several orders of magnitude larger than that through the liquid electrolyte; therefore, the electrolyte polarity is the most important factor on the performance of lithium/air batteries compared with other properties of the electrolyte, such as oxygen solubility, viscosity, and ionic conductivity. The quantity of the electrolyte added to a cell also significantly affects the discharge performance of the lithium/air battery, and a clear maximum in capacity is observed as a function of the electrolyte amount. The addition of tris(pentafluorophenyl)borane as a functional additive and cosolvent in electrolytes can help dissolve partial Li 2 O and Li 2 O 2 formed during the battery discharge process, which is beneficial to increasing the discharge capacity. However, this addition also largely reduces the contact angle and increases the electrolyte viscosity, thus decreasing the discharge capacity of the lithium/air battery.