Performance evaluation of printed LiCoO2 cathodes with PVDF-HFP gel electrolyte for lithium ion microbatteries

• Published in: Electrochimica acta 2008-07, Vol.53 (17), p.5523-5527
• Main Authors: Park, Moon-Soo, Hyun, Sang-Hoon, Nam, Sang-Cheol, Cho, Sung Back
• Format: Article
• Language: English
• ISSN: 0013-4686
• DOI: 10.1016/j.electacta.2008.03.007

In order to improve the discharge capacity in lithium ion microbatteries, a thick-film cathode was fabricated by a screen printing using LiCoO2 pastes. The printed cathode showed a different discharge curves when the cell was tested using various (liquid, gel and solid-state) electrolytes. When a cell test was performed with organic liquid electrolyte, the maximum discharge capacity was 200 muAh cm-2, which corresponded to approximately 133 mAh g-1 when the loading weight of LiCoO2 was calculated. An all-solid-state microbattery could be assembled using sputtered LiPON electrolyte, an evaporated Li anode, and printed LiCoO2 cathode films without delamination or electrical problems. However, the highest discharge capacity showed a very small value (7 muAh cm-2). This problem could be improved using a poly(vinylidene fluoride-hexafluoro propylene) (PVDF-HFP) gel electrolyte, which enhanced the contact area and adhesion force between cathode and electrolyte. The discharge value of this cell was measured as approximately 164 muAh cm-2 (approx 110 mAh g-1). As the PVDF-HFP electrolyte had a relatively soft contact property with higher ionic conductance, the cell performance was improved. In addition, the cell can be fabricated in a leakage-free process, which can resolve many safety problems. According to these results, there is a significant possibility that a film prepared using the aforementioned paste with screen printing and PVDF-HFP gel electrolyte is feasible for a microbattery.