Method For Evaluating Battery Safety Under Internal Short-circuit Condition, Battery And Battery Pack Whose Safety Is Identified By Internal Short-circuit Safety Evaluation Method, And Method For Producing The Same

Patent Publication Number: US 8444717 B2

Title: Method for evaluating battery safety under internal short-circuit condition, battery and battery pack whose safety is identified by internal short-circuit safety evaluation method, and method for producing the same

Filing Date: April 22, 2008

Priority Date: April 24, 2007

Inventor(s): Shinji Kasamatsu, Mikinari Shimada, Masayuki Nagamine, Yasuo Fukase, Masatoshi Takahashi, Masato Iwanaga

Original Assignee / Applicant(s): Panasonic Corporation, Sony Corporation, Sanyo Electric Co., Ltd.

Link to Patent: US8444717B2

Summary:

This invention provides a method for evaluating the safety of a battery under an internal short-circuit condition, which is reliable and unlikely to yield false results. This method is said to accurately identify the quantum of heat generated in cases of internal short circuits, thereby guiding the battery manufacturers in providing additional security features like external insulation to protect the consumer. Typically, a battery contains an electrode group, which comprises a positive electrode and a negative electrode separated by an insulating material layer. According to the disclosed method, an internal short circuit is created by placing a foreign object at a location inside the battery between the positive electrode and the negative electrode; and applying pressure at the location ising a pressing tool to locally crush the insulating layer between the positive and negative electrodes. A rise in temperature due to heat generation confirms the short circuit. In this invention, the color-changing pressure-sensitive Fujifilm Prescale®, extreme low pressure type, was used to ascertain the contact area between the pressing tool and the electrode group.