Lithium-ion batteries are now widely used as energy storage devices for portable electronic devices such as laptop computers, cellular phones and digital cameras due to their high-energy density. Large-sized lithium-ion batteries and battery packs are also very attractive for electric vehicles (EV) and hybrid electric vehicle (HEV) applications. However, safety concerns have become the most important issue for the development of lithium-ion batteries because quite a few serious accidents of fire and explosi...