Flexible solid-state Ge – LiCoO2 battery: From materials to device application

¹CMEMS - UMINHO, University of Minho, Campus Azurem, Guimaraes, 4804 - 533, Portugal

²DEI, University of Minho, Campus Azurem, Guimaraes, 4804 -l533, Portugal

³Physics Center and Physics Department, University of Minho, Campus Gualtar, Braga, 4710- 057, Portugal

⁴Chemistry Center, University of Minho, Campus Gualtar, Braga, 4710 - 057, Portugal

Adv. Mater. Lett., 2017, 8 (8), pp 820-829

DOI: 10.5185/amlett.2017.1429

Publication Date (Web): May 23, 2017

Copyright © IAAM-VBRI Press

E-mail: evieira@dei.uminho.pt

Abstract

Design and fabrication of reliable materials with high capacity, cycling stability and good adhesion properties for flexible microbatteries remains a challenge. A 2 µm thick flexible solid-state Ge-LiCoO₂ battery was fabricated and the structure, composition, thermal, optical, electrical, and electrochemical properties of the materials that determine and influence its electrochemical potential were investigated. RF-sputtered lithium cobalt oxide (LiCoO₂) cathode and lithium phosphorus oxynitride (LiPON) electrolyte films were fabricated at 120 W and 100 W of power, respectively. A ~ 300 nm thick Ge anode was deposited by e-beam. The full-battery was fabricated using conventional and low-cost PVD processes. X-ray diffraction (XRD) and Raman spectroscopy confirms the hexagonal R͞3m phase of annealed LiCoO₂. Differential scanning calorimetry (DSC) technique was applied to investigate the thermal behaviour of the LiPON film with a moderate electrical resistivity of 10⁸ Ωcm and high optical transmission (> 75%) in the UV-Visible range. Bending experiments were also performed to evaluate thin-films adhesion and stability. Scanning electron microscopy (SEM) technique was used to evaluate the morphology of films surface and the layered structure of the full-battery. This detailed experimental study allows us to understand the discharge behavior of the fabricated Li-ion battery. 

Keywords

Flexible, thin-film, li-ion battery, bending, energy storage