Switching from an organic polymer-based Li ion electrolyte to a ceramic Li ion electrolyte is expected to allow for the higher energy density, improve the safety and cycle lifetime. These, all solid state Li ion batteries can also be miniaturized, which will streamline the packing design. Among studied Li ion conductive solid electrolyte (1, 2) garnet family have recently gained lots of attention due to the high ionic conductivity and electrochemical stability at ambient temperature. Garnet-like structure, Li₇La₃Zr₂O₁₂ (LLZO) has shown comparable Li ion conductivity with the current Li ion electrolytes (3). However, the reported ionic conductivity of a thin film LLZO was three orders of magnitude lower compared to bulk phase (4). The main goal of the current research is to develop thin film solid electrolyte on the LiCoO₂ electrode and investigate the interface. For this purpose, LLZO was fabricated using a liquid precursor technique. The Li-La-Zr nitrate solution was coated on the top surface of the LiCoO₂ substrate for several times until the appropriate thickness (300 nm – 1 µm) is obtained. After each step of coating, the deposited precursor is dried and decomposed at 450 °C. Figure 1 shows cross section image of crack-free, flat, dense and homogenous solid electrolyte layer deposited on the surface of the LiCoO₂. X-ray photoelectron spectroscopy (XPS) coupled with ion etching is used to understand the interface composition and thickness. Electrochemical impedance spectroscopy (EIS) was used to analyze and understand the electrolyte and interfacial resistance. 

References

1.            S. Teng, J. Tan and A. Tiwari, Current Opinion in Solid State and Materials Science, 18, 29 (2014).

2.            V. Thangadurai, D. Pinzaru, S. Narayanan and A. K. Baral, The Journal of Physical Chemistry Letters, 6, 292 (2015).

3.            R. Murugan, V. Thangadurai and W. Weppner, Angewandte Chemie International Edition, 46, 7778 (2007).

4.            K. Tadanaga, H. Egawa, A. Hayashi, M. Tatsumisago, J. Mosa, M. Aparicio and A. Duran, Journal of Power Sources, 273, 844 (2015).