The conductivity of this vertically aligned structure (Figure 2) reaches 0.52 × 10 –4 S/cm, which is about 3.6 times higher than that of a composite electrolyte with randomly dispersed LATP NPs. The composite electrolyte also shows improved thermal and electrochemical stability compared to the pure PEO electrolyte. [Conductivity (Siemens/cm) is measured using the standard electrochemical impedance spectroscopy (EIS) technique - Refs. 3 & 4]
Figure 2. A schematic of the ceramic-based polymer electrolyte and a microphotograph show that the resultant material matrix is straight, which enables faster ion transport and thus increased conductivity. (Source: ACS Publications)
Researchers in earlier studies used either randomly dispersed ceramic particles in polymer electrolyte or fibre-like ceramic electrolytes that were not vertically aligned, and the randomly dispersed ceramic particles in the polymer matrix blocked the ion transport.
“We thought that if we combined the vertically aligned structure of the ceramic electrolyte with the polymer electrolyte, we would be able to provide a fast highway for lithium ions and thus enhance the conductivity,” says PhD student Haowei Zhai, the paper’s lead author. He adds, “We believe this is the first time anyone has used the ice-templating method to make flexible solid electrolyte, which is nonflammable and nontoxic, in lithium batteries.”
In addition, this technique could – in principle – enhance the energy density of batteries. By using the solid electrolyte, the lithium battery’s negative electrode, which is currently a graphite layer, could be replaced by lithium metal, and thus could improve the battery’s specific energy by 60% to 70%.
Student Zhai and project leader Yuan Yang, an assistant professor of materials science and engineering,