Batteries/Thin Film 060405
(April 2006) Oak Ridge Micro-Energy Inc. - OKME
Patent Number 6,994,933 B1
Long Life Thin Film Battery and Method Therefore
Asignee: Oak Ridge Micro-Energy, Inc.
Summarized by Donald Georgi
This patent relates to extending the life of thin film primary and rechargeable micro-batteries. The method is to add coatings which are both impenetrable to oxygen and water plus other coatings which are sacrificial in that they chemically combine with oxygen and water to form an oxide or hydroxide which limits migration.
The thin film battery is structured according to prior art and employs a common solid electrolyte with the sulfide addition described in a previous Oak Ridge Micro-Energy (Stock symbol, OKME) patent # 6,818,356 B1.
If the oxygen and water can be limited, there is a possibility that thin film batteries can suitably perform for 20 years. Based on scientific principles, it has been determined that the maximum oxygen penetration can be no more than 1.6 micromoles/m2 per day and a maximum of 3.3 micromoles/m2 per day of water.
Past patented processes have defined multilayer paralyne and metallization layers without success because of the pin holes and asperities which provide contaminant pathways.
In this patent, the surface conditions are corrected with a planarization layer made up of a polymeric film with superior flatness which then allows for metallization, ceramic and/or sacrificial layers to be built up over the battery components to seal it from the contaminants. A number of layer possibilities are described and fundamental coating processes are included.
There are four fundamental claims:
Claim 1 describes the method for improving the life of a thin film rechargeable with steps of applying the planarization layer over the anode layer followed by coatings of metal, ceramic and polymeric materials. Claims 2-8 expand on the basic concept by defining a lithium or lithium-ion anode. The polarization material can be acrylates, diacrylates, triacylates and polyolefing which do not contain an organic acid. Polarization flatness is less than 0,005 cm/in. Provision for placing a metallization layer on the anode prior to placing the planarization is allowed as long as it does not alloy with the anode. Adding a coating of lithium-phosphorus oxynitride and/or a sacrificial layer of magnesium is provided for.
Claim 9 is similar to claim 1 except that it describes the structure of the rechargeable battery which is placed on a substrate. A description of the cathode, electrolyte and anode are covered before the layers of planarization and coatings are added. In claims 10-15 identical coatings descriptions to those of claims 1-8 are restated.
Claim 16 describes the thin film rechargeable battery improvements consisting of the planarization and other layers, with claims 17-20 listing details of the layers as previously described.
Claim 21 specifically identifies the solid electrolyte as the one using the sulfide ion dopant as described in patent 6,818,356 B1.
The patent is very specific about applicability to thin-film batteries. (BD note: but is there any part of it which is applicable to other lithium/Lithium-ion chemistries?)