THIN FILM BATTERY DEVICE AND METHOD OF FORMATION
A thin film battery may include: a cathode current collector, the cathode current collector being disposed in a first plane; a device stack disposed on the cathode current collector, the device stack comprising an anode current collector, the anode current collector being disposed in a second plane, above the first plane; and a thin film encapsulant, the thin film encapsulant disposed above the device stack, wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a plurality of sides of the device stack, wherein the cathode current collector extends under the second portion of the thin film encapsulant and outside of the thin film encapsulant; and wherein the anode current collector extends under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
This Application claims priority to U.S. provisional patent application No. 62/322,415, filed Apr. 14, 2016, entitled “Volume Change Accommodating TFE Materials,” and incorporated by reference herein in its entirety.
FIELDThe present embodiments relate to thin film encapsulation (TFE) technology used to protect active devices, and more particularly to encapsulating thin film battery devices.
BACKGROUNDIn the fabrication of thin film batteries, patterning of device structures remains a challenge, for forming active regions of a device, or front-end, and for forming encapsulation portions of a device, or back-end.
In particular, for seamless integration into systems incorporating thin film batteries, a large benefit is the ability to form very thin batteries. To this end, reduction of non-active materials such as encapsulation material is useful, so non-active portions of a thin film battery add minimally to the overall size of the battery. Known methods of packaging energy storage devices, such as thin film batteries, include pouching, lamination, and the like. These methods add an undesirable amount of weight and volume to the device being packaged, or encapsulated. Thin film encapsulation (TFE) approaches for protecting active components of a thin film battery offer a potentially simplified manner of encapsulation, with minimum material and volume addition to the system. Notably, TFE approaches for these types of devices, such as thin film batteries, are far more challenging for several reasons. Firstly, accommodation of volume changes is useful, adding potential stress to a thin film encapsulant region during device operation. Secondly, a main function of the TFE is to provide good oxidant permeation barrier properties. Moreover, a TFE may be used encapsulate device structures including a larger topography variation. At the present, good TFE fabrication methods and the resulting device architectures are lacking for providing robust and consistent long-term operation of these devices.
With respect to these and other considerations the present disclosure is provided.
BRIEF SUMMARYIn one embodiment, a thin film battery may include a cathode current collector, the cathode current collector being disposed in a first plane; a device stack disposed on the cathode current collector, where the device stack comprises an anode current collector, where the anode current collector is disposed in a second plane, above the first plane. The thin film battery may further include a thin film encapsulant, where the thin film encapsulant is disposed above the device stack, wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a plurality of sides of the device stack. The cathode current collector may extend under the second portion of the thin film encapsulant and outside of the thin film encapsulant, and the anode current collector may extend under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
In another embodiment, a method of forming a thin film battery may include depositing a cathode current collector on a substrate in a first plane and forming a device stack on the cathode current collector, where the device stack comprises an anode current collector. The anode current collector may be disposed in a second plane above the first plane. The method may include forming a thin film encapsulant above the device stack, wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a side of the device stack. The cathode current collector may extend under the device stack, under the second portion of the thin film encapsulant and outside of the thin film encapsulant. The anode current collector may extend under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
In another embodiment, a method of encapsulating a thin film battery may include providing an active device region on a substrate base, wherein the active device region comprises a cathode current collector and a device stack. The device stack may be disposed on a portion of the cathode current collector and include an anode current collector. The method may also include forming a thin film encapsulant above the device stack, wherein the thin film encapsulant comprises a first portion extends along a surface of the anode current collector and a second portion extending along a side of the device stack. The cathode current collector may extend under the device stack, under the second portion of the thin film encapsulant and outside of the thin film encapsulant, and the anode current collector may extend under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
The present embodiments will now be described more fully hereinafter with reference to the accompanying drawings, where some embodiments are shown. The subject matter of the present disclosure may be embodied in many different forms and are not to be construed as limited to the embodiments set forth herein. These embodiments are provided so this disclosure will be thorough and complete, and will fully convey the scope of the subject matter to those skilled in the art. In the drawings, like numbers refer to like elements throughout.
The present embodiments are related to thin film encapsulant structures and methods, where the thin film encapsulant is used to minimize ambient exposure of active devices. The present embodiments provide novel structures and materials combinations for thin film devices encapsulated using thin film encapsulation.
Examples of active devices include electrochemical devices include electrochromic windows and thin film batteries wherein the active component materials are highly sensitive/reactive to moisture or other ambient materials. To this end, known electrochemical devices such as thin film batteries may be provided with encapsulation to protect the active component materials.
In various embodiments, a thin film device such as a thin film battery and techniques for forming a thin film battery are provided with a novel architecture including an encapsulant material. The thin film battery may include a layer stack composed of active layers, as well as the thin film encapsulant, where the thin film encapsulate also constitutes a multilayer structure.
In various embodiments novel combinations of thin film deposition and patterning operations is established, for formation of an active device region, a thin film encapsulant, or a combination of active device region and thin film encapsulant.
According to various embodiments, techniques are provided for forming thin film batteries exhibiting an improvement in the structure, the ease of manufacturing, performance, or a combination of these factors, as compared to known thin film batteries. Various considerations may affect the design of a thin film battery. A non-exhaustive list of factors includes the ability of the battery to accommodate local volume changes within specific regions of the thin film battery taking place during operation of a battery; protection from oxidative permeation; and ability to form a device accounting for large variations in topography. Further factors include the ability to limit the non-active material in a thin film battery to an acceptable level; the ability to form a thin film battery having an acceptable portion of non-active material within the device regions; and ability to manufacture a thin film battery using cost-effective techniques. In particular embodiments disclosed herein, the formation of thin film encapsulation is integrated with the formation of active device regions of a thin film battery in a novel manner enabling a more robust architecture for operation and stability of the thin film battery.
As shown in
In various embodiments, the thin film encapsulant 110 may be arranged as a thin film encapsulant including a first portion extending along a surface of the anode current collector 108 and a second portion extending along a side of the device stack 105. In particular, as shown in
Turning now to
The thin film encapsulant 110 may further act to accommodate volume changes occurring in the device stack 105 when the thin film battery 100 is charged and discharged. For example, in embodiments where the thin film battery is a lithium battery, the cathode 152 may be a LiCoO2 material including lithium, where the lithium diffuses back and forth between the cathode 152 and the anode current collector 108 during charging and discharging. The lithium may diffuse through the solid state electrolyte 154, where the solid state electrolyte 154 may be a known lithium phosphorous oxynitride (LiPON) material conducting the lithium between the cathode 152 and an anode region (not specifically shown) in the device stack 105. As such the lithium may tend to accumulate in a layer in the anode region during charging or to evacuate the anode region during discharging, where an effective layer thickness in the anode region may change by several micrometers or more during the charging and discharging.
At least one of the layers of the thin film encapsulant 110 in the embodiment of
More particularly, as used herein, a “soft and pliable” material may refer to a material having an elastic (Young's) modulus less than 20 GPa, for example, while a “rigid material.” such as a rigid metal layer or rigid dielectric layer, may have an elastic modulus greater than 20 GPa. Other characteristic properties associated with a soft and pliable material include a relatively high elongation to break, such as 70% or greater for at least one polymer layer of the thin film encapsulant. In some examples, such as silicone, a soft and pliable material may have an elongation to break up to 200% or greater.
As an example, the layer 160 may be a soft and pliable polymer, while the layer 162 may be a rigid material, such as a rigid metal or a rigid dielectric, such as silicon nitride. The layer 162 may serve the function of preventing oxygen and water diffusion into the device stack 105. The sequence layers of a polymer layer and a rigid dielectric layer may be repeated through the thin film encapsulant 110. In other words, the thin film encapsulant 110 may include at least one dyad, wherein a given dyad includes a soft and pliable polymer layer, and a rigid dielectric layer disposed adjacent the polymer layer. In particular embodiments, the layer 164 may be a polymer layer such as a soft and pliable polymer layer, the layer 166 a rigid dielectric layer or rigid metal layer, the layer 168 a soft and pliable polymer layer, and the layer 170 a rigid dielectric layer or rigid metal layer. While the thin film encapsulant 110 of
As further illustrated in
Turning now to
In some embodiments, the individual layers may be deposited using any combination of physical vapor deposition, chemical vapor deposition, and liquid deposition techniques. The layer thickness of these layers may be in accordance with thicknesses for known thin film batteries.
Turning now to
In various embodiments, the formation of a thin film encapsulant such as the thin film encapsulant 110 may take place in a series of operations, as detailed in
In various embodiments, the layer 160 may include a plurality of sub-layers, where different sub-layers are arranged to favor conformality or planarization effects. The choice of materials and deposition methods for different sub-layers may be tailored to induce either planarization or conformality. For example, a first sub-layer may be more conformal to promote sidewall coverage in a given topography—such as Parylene. The second sub-layer may be more planarizing for better next-layer deposition, e.g., spin/dip coating method. The use of multiple sub-layers within a layer 160, as well as the use of additional layers in a thin film encapsulant (see layer 162 as discussed below), may generate additional benefits including improved adhesion and mechanical properties, as well as limiting reactions in active regions of a thin film battery.
Turning now to
An advantage of using a maskless patterning process, such as laser etching, is the avoidance of complexity and costs associated with known masked patterning processes involving lithography and dry etching or wet etching. In this manner the complexities of lithography and etching, the consumable costs, and device effects are eliminated. In addition, laser based patterning allows device shape/design to be software recipe based, not depending upon physical masks, facilitating more rapid, flexible and simpler design changes.
In various embodiments, laser patterning may be accomplished primarily in two ways: using diffractive optics employing relatively high power to spread the laser beam over larger areas. This approach may be especially suitable for simple, easily repeated patterns not having fine pattern details. Another type of laser patterning especially useful for patterning thin film batteries according to the present embodiment is direct laser ablation using a rastering approach. Simple and advanced galvanometer based scanners may raster the laser beam to form more complex patterns, and are less limited by feature size and dimensions. To minimize patterning times, high repetition rate lasers (>1 MHz) may be used in combination with polygon mirrors to accomplish high volume production rates.
Pulse durations of picosecond and femtoseconds have been shown to be effective for thin film ablation. The use of radiation wavelengths in the ultraviolet (UV) range, green visible range, as well as infrared range, including wavelengths ranging from 157 nm to 1024 nm, may be effectively employed for patterning via laser ablation the layers of thin film batteries of the present embodiments, including polymer layers, rigid dielectric layers, and metal layers. While thin film encapsulant materials are often transparent or semi-transparent, usable wavelengths may be more appropriate in the UV or green visible range. Most of the aforementioned short pulse lasers are DPSS (Diode pumped solid state) while some fiber based lasers are also contemplated for use in embodiments of the disclosure.
In various embodiments, the material of layer 160, such as a flexible polymer material, and the thickness of the layer 160 may be arranged to provide benefits, such as accommodating deformation in the device stack 105 taking place due to transport of lithium during charging and discharging of a thin film battery to be formed. Turning now to
In the particular example of
Turning now to
After performing a patterned dyad process, this process may be repeated at least one time to generate a plurality of patterned dyads, according to some embodiments of the disclosure. Turning now to
In the particular example of
Turning now to
Turning now to
In various embodiments, the formation of a thin film encapsulant such as the thin film encapsulant 110 may take place in a series of operations, as detailed in
Turning now to
While not explicitly shown in
In addition, and in accordance with embodiments of the disclosure, a contacting metal may be deposited on the region 210 to form a cathode contact, as well as in the region 122 as shown in
Turning now to
There are multiple advantages provided by the present embodiments, including the ability to protect a device stack of a thin film battery while maximizing available substrate area, and the additional advantage of the ability to encapsulate a device stack in a manner accommodating changes in volume during operation of the thin film battery.
The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, while those of ordinary skill in the art will recognize the usefulness is not limited thereto and the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Thus, the claims set forth below are to be construed in view of the full breadth and spirit of the present disclosure as described herein.
Claims
1. A thin film battery, comprising:
- a cathode current collector, the cathode current collector being disposed in a first plane;
- a device stack disposed on the cathode current collector, the device stack comprising an anode current collector, the anode current collector being disposed in a second plane, above the first plane; and
- a thin film encapsulant, the thin film encapsulant disposed above the device stack,
- wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a plurality of sides of the device stack,
- wherein the cathode current collector extends under the second portion of the thin film encapsulant and outside of the thin film encapsulant, and
- wherein the anode current collector extends under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
2. The thin film battery of claim 1, wherein the thin film encapsulant comprises at least one dyad, wherein a dyad of the at least one dyad comprises:
- a soft and pliable polymer layer; and
- a rigid dielectric layer or a rigid metal layer, the soft and pliable polymer layer being disposed adjacent the rigid dielectric layer or rigid metal layer.
3. The thin film battery of claim 1, wherein the device stack further comprises:
- a cathode, the cathode being disposed on the cathode current collector; and
- a solid state electrolyte, the solid state electrolyte disposed on the cathode and under the anode current collector.
4. The thin film battery of claim 3, wherein the thin film encapsulant encapsulates the cathode, the solid state electrolyte and the anode current collector on a side of the device stack.
5. The thin film battery of claim 4, wherein the thin film encapsulant comprises a polymer layer and a rigid dielectric layer, the rigid dielectric layer being disposed adjacent the polymer layer, wherein the polymer layer and the rigid dielectric layer extend in a non-planar fashion along the surface of the anode current collector and along the side of the device stack.
6. The thin film battery of claim 2, wherein the thin film encapsulant comprises a plurality of dyads, wherein the thin film encapsulant further comprises a third region, wherein in the third region, in at least one dyad of the plurality of dyads the soft and pliable polymer layer and the rigid dielectric layer extend in a non-planar fashion above the surface of the anode current collector.
7. The thin film battery of claim 1 further comprising a substrate base, the substrate base disposed adjacent the cathode current collector.
8. A method of forming a thin film battery, comprising:
- depositing a cathode current collector on a substrate in a first plane;
- forming a device stack on the cathode current collector, the device stack comprising an anode current collector, the anode current collector being disposed in a second plane above the first plane; and
- forming a thin film encapsulant above the device stack,
- wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a side of the device stack,
- wherein the cathode current collector extends under the device stack, under the second portion of the thin film encapsulant and outside of the thin film encapsulant, and
- wherein the anode current collector extends under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
9. The method of claim 8, wherein the forming the device stack comprises:
- depositing a cathode layer on the cathode current collector;
- annealing the substrate after the depositing the cathode layer;
- depositing a solid state electrolyte layer on the cathode layer;
- depositing the anode current collector on the solid state electrolyte layer; and
- before the forming the thin film encapsulant, patterning the cathode layer, the solid state electrolyte layer, and the anode current collector to form the device stack and to expose the cathode current collector in a first region.
10. The method of claim 9, further comprising depositing a lithium anode layer after the depositing the solid state electrolyte layer and before the depositing the anode current collector.
11. The method of claim 9, wherein the patterning the cathode layer, the solid state electrolyte layer, and the anode current collector comprises etching the cathode layer, the solid state electrolyte layer, and the anode current collector over the first region using laser ablation to selectively remove a portion of the cathode layer, the solid state electrolyte layer, and the anode current collector.
12. The method of claim 9, wherein the forming the thin film encapsulant comprises forming a plurality of patterned dyads on the anode current collector, wherein a given patterned dyad of the plurality of patterned dyads comprises a soft and pliable polymer layer and a rigid dielectric layer.
13. The method of claim 9, wherein the forming the thin film encapsulant comprises:
- depositing a plurality of layers, wherein at least one layer comprises a soft and pliable polymer and at least one layer comprises a rigid dielectric layer; and
- etching the plurality of layers using a plurality of etch operations.
14. The method of claim 9, wherein the forming the thin film encapsulant comprises depositing an initial polymer layer in blanket form directly on the anode current collector and on the first region of the cathode current collector, wherein the initial polymer layer comprises a soft and pliable polymer.
15. The method of claim 14, further comprising: after the depositing the initial polymer layer: patterning the initial polymer layer to form a patterned polymer layer over the device stack and to expose the cathode current collector in a second region, the second region being disposed in the first region.
16. The method of claim 15, further comprising performing, at least once, a patterned dyad process me, the patterned dyad process comprising:
- depositing a blanket dyad comprising a rigid dielectric layer and a polymer layer on the device stack and on the cathode current collector; and
- patterning the blanket dyad to form a patterned thin film encapsulant over the device stack and to expose the cathode current collector in a new region, the new region being disposed in the second region.
17. The method of claim 16, further comprising:
- depositing a final rigid dielectric layer in blanket form on the patterned thin film encapsulant and on the new region of the cathode current collector; and
- patterning the final rigid dielectric layer to form the thin film encapsulant, the thin film encapsulant being disposed over the device stack and exposing the cathode current collector in a new region, the new region being disposed in the second region.
18. A method of encapsulating a thin film battery, comprising:
- providing an active device region on a substrate base, wherein the active device region comprises a cathode current collector and a device stack, the device stack being disposed on a portion of the cathode current collector and including an anode current collector; and
- forming a thin film encapsulant above the device stack,
- wherein the thin film encapsulant comprises a first portion extending along a surface of the anode current collector and a second portion extending along a side of the device stack,
- wherein the cathode current collector extends under the device stack, under the second portion of the thin film encapsulant and outside of the thin film encapsulant, and
- wherein the anode current collector extends under the first portion of the thin film encapsulant and outside of the thin film encapsulant.
19. The method of claim 18, wherein the active device region further comprises a cathode and a solid state electrolyte, wherein the providing the active device region comprises:
- depositing in blanket form the cathode current collector, the cathode, the solid state electrolyte, and the anode current collector; and
- patterning the anode current collector, the solid state electrolyte, and the cathode, wherein a portion of the cathode current collector is exposed.
Type: Application
Filed: Oct 31, 2016
Publication Date: Oct 19, 2017
Inventors: Byung-Sung Kwak (Portland, OR), Lizhong Sun (San Jose, CA), Giback Park (San Jose, CA), Dimitrios Argyris (Los Altos, CA), Michael Yu-Tak Young (Cupertino, CA), Jeffrey L. Franklin (Albuquerque, NM)
Application Number: 15/338,969