Enhanced Electrochemical Performance of the Cathode for a Lithium Ion Secondary Battery Using Lithium Ion Conductive Glass-Ceramics

Abstract

Ceramics powder such as SiO2 and Al2O3 are incorporated in to the polymer electrolyte to form the composite film for the sake of improving ionic conductivity, mechanical and thermal properties. Though these filler enhanced ionic conductivity of gel electrolyte due to the disruption of polymer matrix and increasing micro pores, these are not ionic conductive material. We found that the gel electrolyte film (Pvdf based polymer) was enhanced ionic conductivity by adding LICGCTM. We have developed lithium ion conducting glass-ceramics LICGCTM with a NASICON type structure for solid lithium ion electrolyte.1- 3) The ionic conductivity of the glass ceramics with a Li1+x+yAlxTi2-yGeyPO4 composition shows over 1×10-4 Scm-1 at room temperature. Such ceramics have a very stable in ionic conduction. In addition, the ionic conductivity does not decrease, even if it was soaked in an aqueous of Li salt solution4-5), and does not lose the weight in boiling distilled-water for 1 h. The glass-ceramics with the crystalline form of Li1+x+yAlxTi2–xSiyP3–yO12 with a NASICON-type structure by heat-treated glass with a specific composition1-2). This glass-ceramics has a high lithium-ion conductivity that is equal to or more than 10–3 Scm–1at room temperature. Furthermore, because it is very stable in the atmosphere and even to exposure to moist air, it is possible to use this material to apply a solid-electrolyte for a lithium ion secondary battery using organic liquid electrolyte. In this work, the effect of LICGCTM as additive for a lithium ion secondary battery was investigated. We synthesized LiCoO2 cathode with 5wt.% LICGCTM filler and evaluated it the charge and discharge property using a half cell. We confirm the rate performance at room temperature is enhanced at 0.2-3.0C comparing pristine LiCoO2 cathode. The rate performance was indicated 20 percent increasing at 2.0C rate as compared to pristine LiCoO2 cathode. The charging performance was also enhanced at higher rate at room temperature.