Advancements in semiconductor technology have led to the production of large scale integrated circuits which have brought about a revolution in the electronics industry. Microelectronic components are now widely used in the production of a variety of electronic devices (i.e. computers, calculators, watches). Development of such miniature electronic instruments has demanded the evolution of batteries as miniature power supplies. This new generation of batteries must produce higher energy per unit volume and superior discharge characteristics as compared to traditional batteries.
Miniature batteries based on aqueous, non-aqueous and solid electrolytes are manufactured as power sources for microelectronic and portable electronic equipment. As an example, thin solid state batteries are often constructed with an anode formed of solid lithium and a cathode constructed of a solid electrolyte. The lithium is typically in the form of a thin lithium foil. Other types of metal foil are also utilized to form the anode (i.e. nickel). This type of battery has a long shelf life and operates efficiently over a wide temperature range.
An important design consideration in the manufacture of thin batteries is the packaging arrangement for sealing the active components of the battery. Thin batteries are typically assembled in a controlled environment and then sealed with some type of a case structure. Typically the cases are formed of a welded metal enclosure. A case may also be constructed as a foil pouch.
In general, the case must hermetically seal the active components of the battery from corrosive agents, such as moisture and oxygen, in the operating environment of the battery. Lithium foil in particular, and most metal foils commonly used in thin batteries in general, cannot survive more than a few hours or days in a high permeability or wet environment. For this reason, metal cases for batteries are typically formed using glass-to-metal or ceramic-to-metal seals. Foil pouch cases are typically assembled using sealed metal/polymer laminates.
These types of battery packaging arrangements are relatively expensive because the materials are expensive and the manufacturing requirements for forming the packages are complicated. In addition, battery cases or packages constructed with metal or metal/polymer laminates may be heavy and exhibit high electrical conductivity. A battery with a high metal mass and high conductivity may produce interference when utilized in radio frequency transmitter or receiver devices. Moreover, metal battery packages cannot be constructed with curved or irregular surface geometries. Finally, these types of metal battery packages may not satisfy the permeability and chemical resistance requirements of some demanding applications (i.e. high temperature and corrosive environments).
There is then, a need in the art for a thin battery packaging arrangement that overcomes the aforementioned limitations of prior art battery packaging arrangements. Accordingly, it is an object of the present invention to provide a battery package for thin batteries that is inexpensive and easy to manufacture yet offers a high level of protection for the internal components of the battery. It is a further object of the present invention to provide a battery package for thin batteries that is light weight and flexible and which is formed of a nonconductive highly impermeable material. It is yet another object of the present invention to provide a battery package for thin batteries that may be formed with a curved surface geometry. It is a further object of the present invention to provide a novel method for manufacturing a battery package in which a flexible base film is constructed to cover the battery and a flexible layer of an inorganic material such as silicon nitride, aluminum nitride, or aluminum oxide is deposited on the base film to encapsulate and seal the assembly.