Rechargeable lithium batteries, also known as lithium-ion batteries or lithium secondary batteries, are among the most popular rechargeable batteries for portable electronic devices. Beyond consumer electronics, rechargeable lithium batteries also become popular for military, electronic vehicle, and aerospace applications. One major safety concern with the current commercial rechargeable lithium batteries is that the batteries may suffer thermal runaway and cell rupture if overheated or overcharged. Spotnitz and Franklin, J. Power Sources 2003, 113, 81-100. In extreme cases, this can lead to combustion. In 2006, for example, Sony recalled about 6 millions notebook computer batteries after a number of instances where the batteries overheat or caught fire. To reduce the risks, rechargeable lithium batteries are commonly equipped with various safety devices, such as an external positive temperature coefficient (PTC) resistor. However, such an external PTC device may not respond adequately when a hazardous reaction occurs in very high rate, e.g., when an internal short circuit occurs. Thus, there is a great demand for rechargeable lithium batteries with an improved safety profile, especially rechargeable lithium batteries with high energy capacity. Therefore, there is a need for a PTC electrode for developing a rechargeable lithium battery with an improved safety profile.
USPTO Backgrounds
USPTO Backgrounds