Development of Lithium Batteries for Powering Sensor Arrays SFR Workshop May 24, 2001 Nelson Chong, James Lim, Jeff Sakamoto and Bruce Dunn Los Angeles, CA 2001 GOAL: (a) to develop thermally robust inorganic electrolyte; (b) incorporate silicon lid into battery encapsulation scheme by 9/30/2001. 5/24/2001

Major Components of a Lithium Battery 5/24/2001

Project Direction In order to power SMART wafers, a low profile, thermally stable, high energy density battery must be used. Lithium-V2O5 thick film batteries are used to power SMART wafers. Advanced fabrication and encapsulation methods are needed to enhance battery performance under vacuum and high temperature conditions. 5/24/2001

New Inorganic/Organic Electrolyte 72.5 wt.% 0.9 M Li Imide LiN(CF3SO2)2 in propylene carbonate 21.7 wt.% PMMA Fumed Silica R805 particles/aggregates 5.8 wt.% (12nm) Silica Network in PMMA framework van der Waals electrostatic interactions hydrogen bonding Mixed by hand and heated 100-120oC 10 – 15 mins Li+ conduction Interconnected pore network provides a continuous ionic path. Fumed Silica Colloidal particles added to improve mechanical and thermal stability. Thermal stability >125 oC 5/24/2001

Improved Electrolyte Thermal Stability and Electrochemical Stability Stable thermal cycling between room temperature and 125oC. Stability window exists between 2.5 and 4.0 volts. Peaks are associated with stainless steel characteristics. Well behaved conductivity characteristics to > 125oC 5/24/2001

Thermal Cycling Characteristics of Battery with Nanocomposite Electrolyte Thermal tests at lower current density operation at 125oC cycling between RT and 125oC Batteries discharge nicely at 125oC. No capacity loss when alternate between RT and 125oC. 5/24/2001

Battery Encapsulated with Silicon Lid Discharge Characteristics for Silicon Lid Attached Battery 2mA discharge 5/24/2001

Lid Attachment Using Plasma Assisted Bonding (with N. Cheung) 5/24/2001

2002 and 2003 Goals 2002 Integrate new electrolyte into battery structure Develop in-situ lithium formation process 2003 Battery operation between RT and 150oC Battery survivability to sensor soldering operation 5/24/2001