Investigation on Electrode/Electrolyte Interfaces through Impedance Spectroscopy

Abstract

In the present paper, impedance measurements of the battery configuration, Anode│lithium borophosphate glass electrolyte│LiCoO₂ cathode, has been carried out to throw some light on the electrochemical interfacial behavior between the chosen electrodes and electrolyte. The cathode material, lithium cobalt oxide (LiCoO₂) has been prepared by three different techniques and characterized. Sol-gel synthesized LiCoO₂ showed uniformly distributed spherical shape particles with an average size of 500 nm and also exhibited better electrochemical performance. Charging and discharging (2–3 cycles) of the battery indicated an OCV of 2 V. However, the theoretical OCV of 4 V could not be achieved. The poor performance of the battery could be attributed to the electrochemical processes and SEI film formation at the electrode/electrolyte interfaces. Impedance spectroscopy shows that the major contributions to the impedance of the battery are the electrolyte resistance and the electrode/electrolyte interfacial resistance. With each recharging cycle, the value of electrolyte resistance remains almost constant; however, the interface resistance increases, during the passage of current, due to the interfacial passive layer formation.

Keywords:

• Cathode
• interfaces
• solid electrolyte interface (SEI)