The improving conductivity of LiFePO4 by optimizing the calendaring process

Abstract

Lithium ion batteries have important applications in various electronic devices. The use of battery components such as LiFePO4 cathodes determines battery performance. However, the electronic conductivity of LiFePO4 is low; therefore, increasing the conductivity of the LiFePO4 cathode sheet is very important. The aim of this research is to obtain the conductivity of LiFePO4 cathode sheet which can be applied as lithium ion battery cathode through calendaring process optimization. LiFePO4 cathode sheet preparation begins with LiFePO4 slurry (LiFePO4 + Carbon Black and PVDF / NMP) slurry, followed by coating it on Al foil surface, resulting in a sample denoted as C0. The calendaring process was then carried out to the cathode sheet, at 100°C by repeating once, twice, and three times, producing samples hereinafter referred to as C1, C2, and C3 respectively. LiFePO4 cathode sheet products are characterized with X-ray diffractometer (XRD) and scanning electron microscopy (SEM) combined with energy-dispersive spectrophotometer (EDS) and LCR-meter. The XRD pattern shows that the LiFePO4 cathode sheet consists of LiFePO4 and carbon crystal phases. The cross-sectional microstructure of the LiFePO4 cathode sheet shows that the sheets becomes denser and thinner as the number of calendaring increases. The thickness of the LiFePO4 cathode sheet decreases with increasing calendaring process. The LiFePO4 cathode sheet for the C0 sample was about 160μm in thick, and decreased gradually to 140, 130 and 120μm for the C1, C2 and C3 samples, respectively. The conductivity of the sample was improved from 9.9 × 10−5 to 2.9 × 10−5, 3.0 × 10−4, and 5.5 × 10−4 S.cm−1. The density also was improved from 2.359 to 2.516 and to 2.638 g.cm−1 with increasing calendaring process. It can be concluded that the optimizing calendaring process of the LiFePO4 cathode sheet with the LiFePO4 cathode sheet is important to improve the performance of batteries.