The invention relates to batteries.
Batteries are commonly used electrical energy sources. A battery contains a negative electrode, typically called the anode, and a positive electrode, typically called the cathode. The anode contains an active material that can be oxidized; the cathode contains or consumes an active material that can be reduced. The anode active material is capable of reducing the cathode active material.
When a battery is used as an electrical energy source in a device, electrical contact is made to the anode and the cathode, allowing electrons to flow through the device and permitting the respective oxidation and reduction reactions to occur to provide electrical power. An electrolyte in contact with the anode and the cathode contains ions that flow through the separator between the electrodes to maintain charge balance throughout the battery during discharge.
A battery typically includes a housing and a seal assembly that contain the active materials, the electrolyte and the separator. In some embodiments, the seal assembly includes a cover and a conductor connected to the cover. The conductor may contact one of the active materials and serve as an electrical terminal of the battery. The cover can be connected to the housing by crimping or welding to provide a liquid-tight seal.
In one aspect of the invention, a battery has a housing, a cover, and a seal engaged with the cover. The cover has an outer edge and is connected to the housing at the outer edge. The cover includes at least one portion of reduced thickness between the outer edge of the cover and the seal.
The portion of reduced thickness can be a groove in the cover. The groove can have a triangular cross-section. In other embodiments, the groove has a semi-circular cross-section.
The portion of reduced thickness of the cover can be between about 5 and about 90 percent of a thickness of the cover. The portion of reduced thickness of the cover can be between about 10 and about 50 percent of a thickness of the cover.
The cover can have two portions of reduced thickness located on opposing sides of the seal. In some embodiments, a semicircular portion of reduced thickness extends around the seal to connect the two straight portions of reduced thickness. In some embodiments, the portion of reduced thickness encircles the seal entirely. In some embodiments, the portion of reduced thickness contacts the seal.
The battery may also have a conductor extending through the cover with the seal being between the conductor and an inner edge of the cover. The conductor may be a rivet. In some embodiments, the rivet defines an opening that extends through the rivet that can be used as a hole for filling the battery.
In another aspect, a battery has a housing, a cover, and a seal. The cover has an outer edge at which the cover is connected to the housing. The cover includes at least a portion of reduced thickness between the outer edge of the cover and the seal, the portion of reduced thickness comprising two grooves in the cover located on opposing sides of the seal. The seal is engaged with the cover.
In some embodiments, the grooves have triangular cross-sections. In other embodiments, the grooves have semi-circular cross-sections.
In another aspect, a method of manufacturing a battery includes placing an anode and a cathode into a housing and welding a cover to the housing. The cover has an outer edge, is sized to engage with the housing, and has a hole sized to receive a conductor. The cover also includes at least a portion of reduced cross-section between the outer edge of the cover and the hole.
Batteries can incorporate seals to electrically isolate a conductor, placed through the battery cover and into the battery housing, from the battery cover. Including portions of reduced thickness in the battery cover, between the outer edge of a battery cover and the seal around the conductor, may limit heat transfer from the outer edge to the seal. Allowing higher temperature welding processes to be used without damaging heat-sensitive seals can enable faster, more efficient manufacturing processes as well as providing better attachment between the battery housing and the cover. This may be particularly useful in the manufacture of prismatic batteries whose flat sides make it difficult to get a good weld between the battery housing and the cover without damaging the seal due to the seal's proximity to the outer edge of the cover. In addition, by limiting heat transfer from the outer edge of the cover to the seal, including these portions of reduced thickness in the battery cover enables the use of inexpensive plastics as a material to form the conductor seal. As a result, batteries can be made less expensively and have fewer heat-induced failures caused by welding during the manufacturing process.
The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other aspects, features, and advantages of the invention will be apparent from the description and drawings, and from the claims.
Referring also to
Still referring to
Other embodiments of portions 30 are possible. For example, referring to
Portions 30 can be formed in a variety of cross sections. For example,
Although portions 30 are shown on the top surface of cover 18, in some embodiments, portions 30 are formed on a bottom surface of the cover, alternatively or additionally to the portion(s) formed on the top surface.
Portions 30 can be made according to conventional production techniques. For example, portions 30 can stamped (e.g., with a die set) on cover 18 when the cover is made. Other methods include, for example, laser machining, coining, chemical etching, and milling. The methods may be performed during or after manufacture of cover 18.
Battery 10 can be made by placing an anode material, a cathode material, an electrolyte, and a separator into housing 14, and placing seal assembly 15 in the open end of the housing. Cover 18 can then be welded to housing 14 to seal battery 10.
While a number of embodiments have been described, the invention is not so limited. For example, in some embodiments, multiple heat chokes may be formed in the cover between a given edge of the cover and the seal.
In other embodiments, rivet 26 is hollow and can be used to fill battery 10 with electrolyte, rather than, for example, using fill hole 42.
Vent 38 provides a pressure relief mechanism that is closed under normal conditions but will open if the gasses produced within a battery exceed a predetermined pressure. As described above, battery 10 includes both vent 38 and portions 30, but in other embodiments (not shown), portions 30 can be configured to perform as a vent, i.e., to fail open when a predetermined internal pressure is exceeded.
Other embodiments are within the scope of the following claims.