CROSS REFERENCE TO RELATED APPLICATIONS

The present invention application claims priority to Japanese Patent Application No. 2017-242269 filed in the Japan Patent Office on Dec. 19, 2017, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a secondary battery and a battery pack including the same.

Description of Related Art

Non-aqueous electrolyte secondary batteries are used as driving power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs, PHEVs), and as stationary storage battery systems, for example, for use in reducing the output fluctuations of solar power, wind power, and other resources, and for use in peak shift of grid-connected power to store power at night and use it for daytime. In these applications, secondary batteries connected in parallel are used.

For these secondary batteries, Japanese Published Unexamined Patent Application Nos. 2016-119210 and 2013-089592 (Patent Documents 1 and 2) disclose techniques for disposing a current interrupting mechanism or a fuse part in the conduction path between an electrode body and a terminal to improve reliability. The current interrupting mechanism operates in response to an increase in the internal pressure of the battery case.

The fuse part melts and breaks upon the flow of a large current.

BRIEF SUMMARY OF THE INVENTION

A secondary battery and a battery pack including the same need to ensure high reliability in case of a short circuit that may occur inside the secondary battery.

An object of the present invention is to provide a secondary battery having high reliability and a battery pack including the same.

A secondary battery according to an aspect of the present invention includes:

an electrode body that includes a positive electrode plate and a negative electrode plate;

an outer body that has an opening and houses the electrode body;

a sealing plate that is made of metal and seals the opening; and

a terminal that is electrically connected to the positive electrode plate or the negative electrode plate,

wherein

a conduction path between the positive electrode plate or the negative electrode plate and the terminal is provided with a current interrupting mechanism or a fuse part,

the terminal is attached to the sealing plate via an insulating member made of resin,

at least part of the terminal is disposed on the battery outer side with respect to the sealing plate, and

an electrically insulating, intermediate heat-resistant layer or an electrically insulating, intermediate heat-resistant member is disposed between the terminal and the sealing plate.

The inventors of the present invention have found that there is the following issue in a battery pack including secondary batteries that are connected in parallel and each have a current interrupting mechanism or a fuse part in a conduction path between the electrode body and the terminal.

In the case where secondary batteries are connected in parallel and a short circuit occurs between positive and negative electrodes in one secondary battery, a current flows into the secondary battery in which the short circuit has occurred from other secondary batteries connected in parallel. Thus, the secondary battery in which the short circuit has occurred in the case where secondary batteries are connected in parallel tends to reach a higher-temperature state than that in the case where secondary batteries are not connected in parallel. When the secondary battery reaches a high-temperature state, the electrolyte decomposes to increase the pressure of gas in the battery case, and the current interrupting mechanism operates. Since the operation of the current interrupting mechanism causes disconnection of the conduction path between the electrode body and the terminal, the current flow from other secondary batteries into the secondary battery in which the short circuit has occurred is terminated.

In the case where secondary batteries have a fuse part and a short circuit occurs between positive and negative electrodes in one secondary battery, the fuse part melts and breaks due to a short-circuit current to disconnect the conduction path between the electrode body and the terminal. Thus, the current flow from other secondary batteries into the secondary battery in which the short circuit has occurred is terminated.

However, even when the current flow from other secondary batteries into the secondary battery in which the short circuit has occurred is terminated, the chemical reaction inside the battery or the like may maintain the high-temperature state of the secondary battery in which the short circuit has occurred or may increase the temperature of the secondary battery in which the short circuit has occurred. In the case where the secondary battery reaches a high-temperature state, there is a possibility that an insulating member made of resin that insulates between the terminal and the sealing plate may melt. If an insulating member made of resin between a positive electrode terminal and the sealing plate and an insulating member made of resin between a negative electrode terminal and the sealing plate both melt, the positive electrode terminal and the negative electrode terminal are each electrically connected to the sealing plate. This forms a conduction path of positive electrode terminal-sealing plate-negative electrode terminal and thus forms a closed circuit with the secondary batteries connected in parallel. Then, a current flows in the secondary batteries connected in parallel, and a large current flows in the secondary batteries connected in parallel to the secondary battery in which the short circuit has occurred. As a result, an abnormal event may occur in the secondary batteries connected in parallel to the secondary battery in which the short circuit has occurred.

The secondary battery according to the aspect has a structure in which electrical connection between the terminal and the sealing plate is unlikely to occur even if the insulating member between the terminal and the sealing plate melts. Even if a short circuit occurs inside one of the secondary batteries connected in parallel, an abnormal event is unlikely to occur in secondary batteries different from the secondary battery in which the short circuit has occurred.

The electrically insulating, intermediate heat-resistant layer preferably has a resistivity of 1.0×104Ω·cm or higher at 25° C. The electrically insulating, intermediate heat-resistant layer preferably has a resistivity of 1.0×104Ω·cm or higher at 400° C. The electrically insulating, intermediate heat-resistant layer preferably has a higher melting point than the insulating member made of resin disposed between the terminal and the sealing plate. The electrically insulating, intermediate heat-resistant layer preferably has a melting point of 400° C. or higher. In the case where the electrically insulating, intermediate heat-resistant layer is made of two or more materials, at least one of the materials of the electrically insulating, intermediate heat-resistant layer preferably has a melting point of 400° C. or higher.

The electrically insulating, intermediate heat-resistant member preferably has a resistivity of 1.0×104Ω·cm or higher at 25° C. The electrically insulating, intermediate heat-resistant member preferably has a resistivity of 1.0×104Ω·cm or higher at 400° C. The electrically insulating, intermediate heat-resistant member preferably has a higher melting point than the insulating member made of resin disposed between the terminal and the sealing plate. The electrically insulating, intermediate heat-resistant member preferably has a melting point of 400° C. or higher. In the case where the electrically insulating, intermediate heat-resistant member is made of two or more materials, at least one of the materials of the electrically insulating, intermediate heat-resistant member preferably has a melting point of 400° C. or higher.

The present invention can provide a secondary battery with high reliability and a battery pack including the same.

