New Multilayer All Solid Lithium Ion Battery Consisting of Electric Conduction Path for Inner Parallel Connection

Introduction

All solid litium ion battery that consist of inorganic solid material is expected as secondary battery of next generation, because the risk of liquid leakage and fire is low.Practical use of the lithium-ion secondary battery, which already used a polymer as the electrolyte, is progressing. The parallel multilayering of a battery is one of the subjects to increase the capacity of all solid litium ion battery. In this work, we prepared New Multilayer all solid litium ion battery that was produced by sheet processing. Anode layer and cathode layer has electric conduction path for inner parallel connection in the battery.

Experimental

LiFePO₄, Li₂O-P₂O₅-Al₂O₃ glass, Li_1.7Al_0.4Zr_1.5Y_0.1Si_0.2P_0.8O₁₂, and acetylene black were mixed, 1-propanol, the binder, the plasticizer, and the dispersing agent were added, and it was made the cathode slurry. The Cathode layer sheet was producedby tape cast of cathode slurry. Li₄Ti₅O₁₂, Li₂O-P₂O₅-Al₂O₃ glass, Li_1.2Al_0.1Zr_1.9Si_0.1P_2.9O₁₂, and acetylene black were mixed, 1-propanol, the binder, the plasticizer, and the dispersing agent were added, and it was made the anode slurry. The Anode layer sheet was producedby tape cast of anode slurry. Li₂O-P₂O₅-Al₂O₃ glass, Li_1.2Al_0.1Zr_1.9Si_0.1P_2.9O₁₂, and acetylene black were mixed, 1-propanol, the binder, the plasticizer, and the dispersing agent were added, and it was made the electrolyte slurry. The electrolyte layer sheet was producedby tape cast of electrolyte slurry. The holes were bored in the sheet with the fiber laser (FAYb) markers. The holes diameter of the anode and the cathode were 0.8 mm and that of the electrolyte were 0.4 mm. The arrangement pattern of a holes is seven kinds. It produced so that electrode might join through an electrolyte hole and counter electrode. There are eight layers of the cathode and the anode each other. The laminated sheet was cut at 11 mm in diameter. Degreasing was performed at 350 °C. The hotpress of the sample after degreasing was carried out at 600 °C and 196 MPa. The sample was grounded in diameter of 9.5 mm. Vacuum-drying temperature was 100 °C. The vacuum packing of the sample was carried out in the dry room. The cathode current collector was aluminum foil. The anode current collector was copper foil. Measurement temperature was set at 60 °C and charging rate were set at 1/20 C constant current charge, and cut-off voltage was set in 3300 mV.  Discharging rate was set at 1/100 C constant current discharge, and cut-off voltage was set in 10 mV.

Results and Discussion

The cross-sectional secondary electron image of the cathode side electric parallel conduction path is shown in a figure. The anode layer was coated by electlyte layer around Cathode electric conduction path. The thickness of the anode layer was 35 micrometers. The cathode layer was 40 micrometers. The electrolyte layer was 15 micrometers. The electrolyte layer was reduced to half thickness anode layer and cathode layer. The diameter of the cell was 9.5 mm, thickness was 0.95 mm, weight was 0.16 g, and density was 2.4 g/cm³. The discharge capacity of the cell was 93 mAh/g, average operating voltage was 1.5 V, and energy density was 20 Wh/kg. In experiment, Multilayer all solid litium ion battery consisting of electric parallel conduction path can be made by sheet processing. Electric discharge capacity was lower than the theoretical capacity. The reason guessed that The dispersion of LiFePO₄ was not enough.