|United States Patent
,   et al.
March 1, 2005
Volumetric micro batteries
A microelectronic battery is formed from Zn/Air technology as a volumetric
energy storage device from soft lithography techniques. The microelectric
battery includes an anode and a cathode disposed in an electrolyte tank
having a volume <1 mm.sup.3 that is filled with an electrolyte.
Lewis, Jr.; David H. (Irvine, CA);
Waypa; John J. (Rancho Palos Verdes, CA);
Antonsson; Erik K. (Pasadena, CA);
Lakeman; Charles D. E. (Albuquerque, NM)
Northrop Grumman Corporation (Los Angeles, CA);
TPL, Inc. (Albuquerque, NM);
California Institute of Technology (Pasadena, CA)
September 5, 2001|
|Current U.S. Class:
||429/27; 429/42; 429/44; 429/163 |
||H01M 006//04; H01M 012//06|
|Field of Search:
References Cited [Referenced By]
U.S. Patent Documents
|3787240||Jan., 1974||Gillman et al.
|4842963||Jun., 1989||Ross, Jr.
|5338625||Aug., 1994||Bates et al.
|5567210||Oct., 1996||Bates et al.
|5587259||Dec., 1996||Dopp et al.||429/233.
|2003/0152815||Aug., 2003||LaFollette et al.||429/7.
Pique et al. ("Laser Direct Writing of Microbatteries for Integrated Power
Electronics", SPIE's LASE '2001, Jan. 20-26th, 2001, San Jose, CA,
Proceedings preprint (4274-39)).*
Salmon et al. ("Fabrication of rechargeable microbatteries for
microelectrochemical system (MEMS) applications", Proceedings of the
Intersociety Energy Conversion Engineering Conference (1998), 33rd), no
Primary Examiner: Tsang-Foster; Susy
Attorney, Agent or Firm: Katten Muchin Zavis Rosenman, Paniaguas; John S.
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
The present invention is related to commonly-owned patent application Ser.
No. 09/948,033, entitled "Micro Supercapacitors", filed on Sep. 5, 2001,
now U.S. Pat. No. 6,621,687B2.
1. A microelectronic battery comprising:
an air cathode;
a zinc anode; and
an electrolyte tank for carrying an electrolyte disposed in communication
with said cathode and said anode, wherein said cathode, anode and
electrolyte tank form a microelectronic volumetric storage device having a
volume <1 mm.sup.3, wherein said cathode is an air cathode and said
anode is formed with a Zn electrode forming a microelectronic Zn/Air
2. The microelectronic battery as recited in claim 1, wherein said
microelectronic battery is formed as a generally cubic device defining a
footprint (length (L).times.width (W)) and a height (H).
3. The microelectronic battery as recited in claim 2, wherein said L, W and
H dimensions are approximately equal.
4. The microelectronic battery as recited in claim 1, wherein the cathode
includes a first substrate and at least one cathode carried by said
5. The microelectronic battery as recited in claim 4, further including at
least one first bond pad for connection to an external electrical circuit,
said at least one first bond pad electrically coupled to said at least one
6. The microelectronic battery as recited in claim 4, wherein said first
substrate is formed from silicon.
7. The microelectronic battery as recited in claim 5, wherein said at least
one cathode is formed from a composite device.
8. The microelectronic battery as recited in claim 7, wherein said
composite includes a Ni electrode with a carbon black/MnO.sub.2 /PTFE
composite disposed thereupon.
9. The microelectronic battery as recited in claim 4, further including a
gas permeable membrane formed over said cathode.
10. The microelectronic battery as recited in claim 9, wherein said
membrane is formed from a carbon black/PTFE composite.
11. The microelectronic battery as recited in claim 9, wherein said
membrane is formed from a polymeric perfluoroalkylene oxide membrane.
12. The microelectronic battery as recited in claim 1, wherein said anode
is formed on a second substrate.
13. The microelectronic battery as recited in claim 12, wherein said second
substrate is glass.
14. The microelectronic battery as recited in claim 13, further including
at least one second bond pad formed on said second substrate and
electrically coupled to said zinc electrode.
15. The microelectronic battery as recited in claim 1, wherein said
electrolyte tank is formed from a polymer material.
16. The microelectronic battery as recited in claim 15, wherein said
polymer material is polyethylene.
17. The microelectronic battery as recited in claim 15, wherein said
polymer material is polytetrafluoroethylene.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a microelectronic battery and more
particularly to a microelectronic battery formed as a volume energy
storage device from soft lithography techniques which provides increased
capacity relative to so-called thin film batteries or area energy storage
2. Description of the Prior Art
Thin film microelectronic batteries are known. Examples of such batteries
are disclosed in U.S. Pat. Nos. 5,338,625 and 5,567,210. Such thin film
batteries are formed by depositing an anode, such as vanadium on a
substrate. A cathode, such as amorphous vanadium oxide, VO.sub.x, is
deposited on a portion of the anode. An amorphous oxynitride lithium
electrolyte film is deposited on top of the cathode to form a Li--VO.sub.x
The footprint of the Li--VO.sub.x battery cell is about one square
centimeter and about 8 microns thick. Such a configuration provides about
130 microamp hours of battery capacity. In order to increase the capacity
of such a thin film battery, the area dimensions are increased. As such,
such thin film batteries are known as area energy storage devices.
Unfortunately, applications exist in which the area or footprint is limited
and increased capacity is required. Examples of such applications include
high speed electronics applications and certain military applications. In
particular, high speed electronics applications are known in which the
processing speed is so fast that on-chip/on-board power supplies are
required to prevent local current starvation. Military applications are
also known with space constraints and relatively high capacity
requirements. Examples of such military applications include sensor
applications used in covert applications. Due to the capacity or
requirements and space limitations, thin film power supplies are
In order to increase the battery capacity for use in such applications
without increasing the footprint, one possible solution is to utilize a
different battery technology which provides a higher capacity. For
example, Zn/Air batteries are known to have the highest volumetric energy
storage (36 J/mm.sup.3) of any known battery technology. In addition to
having a high capacity, Zn/Air batteries provide other advantages. For
example, Zn/Air batteries are also known to have a relatively flat
discharge curve with a relatively long storage life. Moreover, such Zn/Air
batteries have already been demonstrated to be environmentally safe and
are amenable for use in medical applications. Examples of such Zn/Air
batteries are disclosed in U.S. Pat. Nos. Des. 427,144 and 4,842,963.
Unfortunately, such Zn/Air batteries have heretofore only been known to be
formed on a macroscale, thus making them unsuitable for use in various
microelectronic applications as discussed above. Thus, there is a need for
a microelectronic battery having increased capacity relative to known thin
film batteries for use in applications which require relatively high
capacity in a relatively small area or footprint.
SUMMARY OF THE INVENTION
Briefly, the present invention relates to a microelectronic battery which
provides increased battery capacity relative to known thin film batteries
without the need for increasing the footprint. In order to provide
increased capacity, the microelectronic battery in accordance with the
present invention is formed from Zn/Air technology as a volumetric energy
storage device. As a volumetric energy storage device, the height
dimension of the device may be increased relative to known thin film
batteries to provide increased battery capacity without the need to
increase the footprint dimensions. As such, the microelectronic battery in
accordance with the present invention is suitable for various applications
which require a relatively high capacity power supply with a relatively
DESCRIPTION OF THE DRAWINGS
These and other advantages of the present invention will be readily
understood with reference to the following specification and attached
FIG. 1 is an elevational view of a microelectronic battery in accordance
with the present invention.
FIG. 2 is a process diagram which illustrates the fabrication of an array
of microelectronic batteries as described in FIG. 1.
The present invention relates to a microelectronic battery, generally
identified with the reference numeral 20, formed from Zn/Air technology.
The microelectronic battery 20 is formed as a volume energy storage device
and provides increased battery capacity relative to known thin film
batteries, for example, as discussed above, without increasing the
dimensions of the footprint. For example, the microelectronic battery 20
formed, for example, as a 1 mm cube, can provide around 600 microamp hours
of capacity as compared to the 130 microamp hour capacity of the
Li--VO.sub.x thin film battery discussed above. In addition to increased
capacity and small footprint relative to thin film batteries, the
microelectronic battery 20 is amenable to being fabricated utilizing micro
electromechanical systems (MEMS) fabrication processes, such as soft
lithography manufacturing processes, used for non-silicon materials, such
as ceramics, polymers and plastics. In addition, the microelectronic
battery 20 is volume scalable which enables its volume (rather than area)
to be increased or decreased depending on the application.
Turning to FIG. 1, the microelectronic battery 20 may include three parts:
an air cathode 22, a Zn anode 24 and an electrolyte tank or insulator 26.
As will be discussed in more detail below, the air cathode 22 is formed
with a membrane with one or more access holes, generally identified with
the reference numeral 28. The air access holes 28 allow air to enter the
air cathode 22 where oxygen in the air is reduced and discharge is
Electrochemical reactions for Zn/Air batteries are well known and are
Anode: Zn+2OH⇄ZnO+H.sub.2 O+2e
Cathode: O.sub.2 +2H.sub.2 O+4e⇄4O
Overall Reaction: 2Zn+O.sub.2 ⇄2ZnO.fwdarw.1.4-1.65 volts
A diagram for forming an array of microelectronic battery cells 20 is
illustrated in FIG. 2. As mentioned above, each microelectronic battery
cell can be formed utilizing soft lithography techniques. In particular,
the air cathode 22 is formed on a substrate 30, for example, a silicon
substrate. A plurality of Ni electrodes, generally identified with the
reference numeral 32, are deposited on the substrate 30 utilizing known
metal deposition techniques, such as RF or DC magnetron or diode
sputtering techniques or other metal deposition techniques. In addition, a
number of bond pads, generally identified with the reference numeral 34,
are deposited by known metal deposition techniques on the substrate 30. As
shown in FIG. 2, each of the bond pads 34 are disposed along an edge of
the substrate 30 and connected to the electrodes by way of electrical
conductors or leads, generally identified with the reference numeral 36.
The bond pads 34 and the electrical conductors 36 may be formed from Ni by
known metal deposition. Once the electrodes 32, bond pads 24 and
electrical conductors 31 are formed on the substrate 30, a catalytic
composite 36 is deposited over each electrode 32 by known techniques. The
catalytic composite may be, for example, carbon black/MnO2/PTFE. Other
catalytic composites may also be suitable, such as carbon
fibers/M(OH)x/PTFE, where M(OH)x represents metal hydroxides including:
nickel hydroxide, iron hydroxide, manganese hydroxide and chromium
In order to limit the influx of water and protect the substrate 30 from the
electrolyte, a hydrophobic membrane 38, which acts as a separator, is
deposited over the assembly. The hydrophobic membrane 38 is a gas
permeable membrane formed from, a carbon black/PTFE composite or polymeric
perfluoropolyalkylene oxide membrane, for example, that allows air to pass
while limiting the diffusive influx of water.
As mentioned above, air access holes 28 are provided to enable air to enter
into the battery cells. These air access holes 28 are formed in the
substrate 30. A membrane, formed from, for example, Si.sub.3 N.sub.4 is
deposited on an exposed side of the substrate 30 to isolate the battery
from oxygen in the atmosphere until it is desired to put the battery in
The Zn anode includes a glass substrate 42. A plurality of Zn electrodes 44
are deposited upon the glass substrate 42 by known techniques. As shown, a
number of bond pads, generally identified with the reference numeral 46,
are formed along one edge of the substrate 42. In addition, a number of
electrical conductors or leads 48 are formed on the substrate 42 to
connect each of the Zn electrodes 44 to each of the bond pads 46.
The electrolyte tank 26 acts as an insulator to insulate the anode 24 and
cathode 22 as shown in FIG. 1. The electrolyte tank 26 may also form a
tank for holding an electrolyte as shown in FIG. 2. The electrolyte tank
26 may be formed in a generally rectangular shape as shown having a number
of cells commensurate with the number of Zn electrodes 44. The electrolyte
tank 26 may be formed from a polymer material, such as polyethylene (PE)
or polytetrafluoro ethylene (PTFE) or other solution processable polymer.
The electrolyte tank 26 is aligned over the Zn electrodes 44. The tank is
then filled with an electrolyte such as KOH gel mixed with Zn powder,
fibers or granules in order to maximize the surface area of the Zn
available for oxidation. Additional organic components, such as binders
and corrosion inhibitors, can be added to improve battery performance, if
As shown in FIG. 2, the glass substrate 42 closes one end of the battery
cell 20. The Zn anode 24 including the electrolyte tank 26 with
electrolyte forms a base of the microelectronic battery cell 20. The air
cathode 22 is disposed on top of the anode 24 such that the electrodes 32
are aligned with the cells of the electrolyte 26. Once assembled, the
substrate 30 closes the other end of the microelectronic battery 20. As
mentioned above, the air access holes 28 are provided in the substrate 30
and covered with a gas permeable membrane 40.
Many modifications and variations of the present invention are possible in
light of the above teachings. For example, thus, it is to be understood
that, within the scope of the appended claims, the invention may be
practiced otherwise than as specifically described above.
What is claimed and desired to be secured by Letters Patent of the United
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