This invention relates broadly to a Li-ion thin film microbattery and method of fabricating the same, and to a microbattery array and a method of fabricating the same.
Technological advances in microelectronics have reduced the power requirements of electronic circuitry and micro-electro-mechanical systems, enabling the use of on-chip Li-ion thin film microbatteries for applications such as environmental sensing [1,2], RFID [3], smart cards [4], Internet of Things (IoT) [5], and even micro-spacecraft [6]. Many more applications can be made possible when microbatteries are directly integrated with electronic circuitry rather than placed separately on a printed circuit board (PCB).
Microbatteries can be fabricated using thin film technologies commonly used for manufacture of other microsystems [7,8]. Li-ion thin film microbatteries (TFMs) typically include a cathode comprising a Li-containing transition metal oxide or the like, an anode typically made by Lithium metal and a solid electrolyte made by Lithium Phosphorus Oxynitride (LiPON).
In order to meet the increasing demands on capacity and performance, new concepts for Li-ion microbatteries that can be manufactured in a simple manner are desirable. The critical issues inhibiting the large-scale commercial adoption of Li-ion microbatteries to-date are: (i) relatively low capacity of Li-containing cathode materials; (ii) safety concerns when using pure Li metal as the anode; (iii) reduced reliability when using high capacity anode (Si); and (iv) integrability with CMOS processes and platforms.
Embodiments of the present invention seek to address one or more of the above-mentioned needs.
In accordance with a first aspect of the present invention there is provided a Li-ion thin film microbattery comprising a Li-free cathode comprising a transition metal oxide thin film; an anode comprising a lithiated Ge or Si thin film; and an electrolyte film disposed between the cathode and the anode; wherein a Li-source of the Li-ion thin film microbattery is provided by means of the lithiated Ge or Si thin film.
In accordance with a second aspect of the present invention there is provided a microbattery array comprising two or more of the Li-ion thin film microbattery of the first aspect.
In accordance with a third aspect of the present invention there is provided a method of fabricating a Li-ion thin film microbattery, comprising the steps of providing a Li-free cathode comprising a transition metal oxide thin film; providing an anode comprising a lithiated Ge or Si thin film; and providing an electrolyte film disposed between the cathode and the anode; wherein a Li-source of the Li-ion thin film microbattery is provided by means of the lithiated Ge or Si thin film
In accordance with a fourth aspect of the present invention there is provided a method of fabricating a microbattery array, comprising fabricating two or more Li-ion thin film microbatteries using the method of the third aspect.
The invention will be better understood with reference to the detailed description when considered in conjunction with the non-limiting examples and the accompanying drawings, in which:
Example embodiment of the present invention can provide for a Li-ion thin film microbattery that can be easily integrated into microelectronic or other microsystems fabrication processes.
Example embodiment of the present invention can provide for a high capacity cathode material (Li-free transition metal oxides such as V2O5, CrO3, RuO2) implementation into Li-ion microbatteries.
Example embodiment of the present invention can provide for a high capacity, improved cyclability and safety anode material (Si and Ge) implementation into Li-ion microbatteries.
Example embodiment of the present invention can provide for Li-source implementation (in the anode side) into Li-ion microbatteries (referred as pre-lithiation technique).
Example embodiment of the present invention can also provide new design and process fabrication for integrable Li-ion thin film microbattery arrays characterized by customizable output power and improved reliability.
In energy storage field, one of the key parameters widely used to compare different electrode active materials is gravimetric specific capacity measured by [mAh/g] or [Ah/Kg] metrics. However, microbatteries are restricted in terms of the amount of areal footprint the microbattery stack can occupy. Therefore, the areal specific capacity of electrodes is a far more important metric measured by [mAh/cm2] or [μAh/cm2] units. Moreover, since areal specific capacity is a function of the volumetric specific capacity, the key parameter in the Li-ion thin film microbatteries field is the volumetric specific capacity measured by rescaling the areal specific capacity over the thickness of the electrode [mAh/cm2μm] or [μAh/cm2μm].
Considering the volumetric specific capacity a list of possible cathode materials can be found in Table 1. Among them it is possible to identify two different classes: the first one made by cathodes containing Li in their stoichiometry while the second one is characterized by Li-free transition metal oxides cathode materials.
The increasing demand on capacity might be solved by introducing Li-free transition metal oxide cathodes such as CrO3, V2O5 and RuO2 that are characterized by a very high volumetric specific capacity. A drawback of such cathodes is the absence of Li-ions within their structure, which makes them unusable in current state-of-the-art Li-ion microbatteries, where cathodes act as the Li-ion source. Indeed the state-of-the-art for Li-ion thin film microbattery cathode is typically restricted to LiMxOy stoichiometries where M is a transition metal such as Co, Mn, Ni or a mixture of transition metals). Li containing cathode materials act as the Li-source for the full microbattery, and in the first charge cycle the Li is transferred to the anode materials. The advantages of this family of materials are (i) good cyclability, (ii) safety, and (iii) reasonable rate performance. However, as a class, these materials have limited volumetric specific capacity for storage of Li (the highest is LiNi0.5Mn0.5O2˜65.1 μAh/cm2μm). To this stage the overall energy capacity of a microbattery is generally limited by the capacity of the cathode, as higher capacity anode materials are available and implemented.
In example embodiments of the present invention, Li-free transition metal oxides are instead implemented as cathode active materials for Li-ion thin film microbatteries. For example RuO2 is characterized by a very high volumetric specific capacity [561.8 μAh/cm2μm], due to its ability to incorporate up to 4 mol Li atoms per mol of RuO2 during the discharge phase via the following reaction:
RuO2+4e−+4Li+→Ru+2Li2O
RuO2 thin film can be deposited through a variety of techniques such as, but not limited to: chemical vapor deposition, electrodeposition, physical vapor deposition. In example embodiments sputtering deposition of a RuO2 target in Ar, O2 and a mixture Ar:O2 plasma environment is used. Electrochemical performance of as synthesized RuO2 thin film in Ar (curves 100) and O2 (curves 102) are shown in
RuO2 can provide an overall volumetric specific energy of about 1014.2 mWh/cm2μm, which is 5 times greater with respect to the state-of-the-art LiCoO2 volumetric specific energy (248.5 mWh/cm2μm). While Li-free transition metal oxide cathodes have a relatively large voltage dispersion as a function of charge state (i.e. the absence of a voltage plateau), with respect to state-of-the-art (LiCoO2 and LiFePO4), this can preferably be addressed in example embodiments by developing an integrated/CMOS compatible fabrication process and/or the fabrication of a Li-ion thin film microbatteries array, as will be described in more detail below. The output voltage and power can be appropriately fine-tuned in example embodiment by integrating the microbattery with a suitable CMOS driver circuit such as amplifiers and/or by coupling different Li-ion thin film microbatteries in an array.
RuOx thin films were deposited on several types of substrates, including stainless steel (SS) discs, and Ti/Pd layers deposited on SiO2-coated Si wafers. Deposition of RuOx layers on Ti/Pd films on oxidized Si wafers were well suited for scanning electron microscopy (SEM), transmission electron microscopy (TEM) and x-ray diffraction (XRD) characterization. Electrochemical performance was investigated using SS discs, which acted both as current collectors and non-reactive substrates. SS discs of 1.2 cm in diameter and 0.5 mm in thickness were cut from an AISI 316 L sheet and mechanically polished to create a mirror-like smooth surface, avoiding roughness effects on the electrochemical characterization. The mechanical polishing involved three different steps: (i) use of P800 (3M Imperial Sandpaper) SiC polishing paper, (ii) followed by P1600 (3M Imperial Sandpaper) SiC polishing paper and (iii) finally a 0.1 μm Al2O3 powder dispersion. Sonication in DI water and acetone was used to remove organic and inorganic compounds from the SS surface.
RuOx thin films were deposited using sputter deposition from a stoichiometric RuO2 target (3 inch, 99.995% purity, ALB Materials) in an RF magnetron sputtering system (ANELVA®) at room temperature with an Ar/O2 plasma. The target was pre-sputtered at 50 W for 10 minutes, which was followed by deposition for five hours at the same power. During the deposition, the sample stage was rotated at 40 rpm to ensure uniform deposition. The background pressure was in the range ˜2×10−6 Torr. The flow rates of Ar and O2 were adjusted to vary the composition of Ar and O2 in the mixed plasma (Table 2). Depositions were carried out at 4.00 mPa.
All samples were weighed before and after sputter deposition using a RADWAG-MYA/2Y microbalance (resolution: 0.001 mg) to determine the mass of the deposited RuOx. Surface morphologies and cross-sections were observed using a field-emission scanning electron microscope (FE-SEM, FEI Inspect F50) equipped with an Energy Dispersive X-ray spectrometer (EDX, Oxford PentaFET) used for chemical analysis (performed at 10 KeV).
The crystal structure of the sample was characterized using X-ray diffraction (XRD, Bruker D8 Advance) with Cu Kα1 radiation at a scan rate of 1° min−1 for 2Ø between 20 and 90 (both powder diffraction and single crystal XRD were carried out), as well as high-resolution selected area electron diffraction (SAED) using a JEOL 2100F transmission electron microscope (TEM) operating at 200 keV. Cross-sectional samples were prepared for TEM characterization by depositing 50 nm of carbon and 150 nm of platinum followed by ion milling using a focus ion beam in a system also equipped for scanning electron microscopy (FEI Nova 600i Nanolab).
Electrochemical tests were conducted in a half-cell setup using a tom cell. Half-cells consisting of as-prepared RuOx cathodes, lithium metal anodes and lithium reference electrodes were characterized using a 1 M LiPF6 in ethylene carbonate/diethyl carbonate (V/V=1:1) electrolyte, and a Celgard poly-propylene separator. Cells were assembled in an Ar-filled glove box with H2O and O2 levels less than 0.1 ppm. Investigations of the electrochemical performance were performed outside the glove box at room temperature. Cyclic Voltammetry (CV) and galvanostatic cycling were carried out from 0.75 to 3.6 V with respect to the Li/Li+ electrode using a BioLogic VMP3 station and NEWARE High Precision Battery Testing System. The charge and discharge cycles refer to the lithiation and delithiation of the RuOx electrode, respectively. Charge/discharge cycles were performed at a current density of 30 μA/cm2 (corresponding to ˜75 mA/g, ˜0.1 C).
Cross-sectional SEM images were used to evaluate thin film thickness, which, in turn, was used to evaluate the specific volumetric capacity. Thickness measurements also allow determination of an average growth rate under different plasma conditions (Table 2). As the O2 mole fraction in the plasma was increased, the total mass and thickness of the deposited material decreased. The calculated mass density and growth rate decreased accordingly, from 9.18 to 6.17 g/cm3 and from 2.6 to 1.2 nm/min, respectively. The density of the as-deposited RuO1.92 is slightly lower than the theoretical density of crystalline RuO2 (6.97 g/cm3). The differences in the film density shown in Table 2 can be attributed to an increase in the weight percentage of oxygen within the RuOx films with increasing oxygen partial pressure in the O2/Ar plasma. This has also been confirmed using EDX and Rutherford backscattering spectrometry (RBS) measurements, which indicated the weight percentage of the different elements in the films (Table 2): the ruthenium-to-oxygen ratio of the films increased with the mole fraction of O2 in the sputtering gas. A 26.4% oxygen plasma (which corresponds to a pO2 of about 1.056 mPa) leads to an oxygen content close to the ruthenium oxide stoichiometric value (RuO1.92).
RuOx films can provide an overall volumetric energy of about 1014.2 mWh/cm2μm, which is 5 times greater than that of LiCoO2 films volumetric specific energy (˜248.5 mWh/cm2μm). Considering only active material, our results for both specific capacity and energy density are in good agreement with previous results given by Kim et al. [29] for RuO2 powders. That the high capacity of RuOx electrodes can be obtained in as-deposited thin films demonstrates their great potential for use in high performance TFMs
While RuOx films can exhibit a relatively large voltage variation as a function of the state of charge (i.e. the absence of a voltage plateaus), compared to materials such as LiCoO2 and LiFePO4, for TFMs, this limitation can be overcome by developing an integrated control circuit. Electronic circuits typically require a stable (constant voltage) and clean (low noise) power supply voltage as many parameters that define their performance depend on the supply voltage. In general, any battery is only partially able to supply a sufficiently stable clean voltage because its output voltage reduces and its output impedance increases as the energy capacity diminishes, and its output voltage dips when a large current is drawn. To circumvent these limitations, a power management circuit is routinely employed embodying a DC-DC converter [34-37] to provide a stable supply voltage from a poorly defined output battery voltage—a Boost DC-DC converter [37] to step-up (increase) the output voltage or Buck DC-DC [34] to step-down (reduce) the output voltage. If a very stable or low-noise output voltage is required, a Low-DropOut (LDO) voltage regulator is applied to the output of the DC-DC converter. In general both the DC-DC converter and LDO feature low output impedance. In other words, power management can be employed to provide a stable and clean supply voltage despite the high variation in the voltage supplied by a RuOx-based thin film microbattery according to example embodiments.
The stoichiometry of the films was found to depend strongly on the O2 content of the Ar/O2 sputtering gas. Use of plasmas with low oxygen contents leads to lower oxygen contents in the films. Experimental results also showed that the Ru to O ratio in the thin film has a significant effect on the electrochemical performance, both the volumetric specific capacity (see curve 600 in
In view of e.g. safety issues when using pure Li metal as the anode and the reduced reliability when using high capacity anode (Si), example embodiments advantageously use Ge based anode material for Li-ion thin film microbatteries. In microbatteries traditional anode materials are pure Li and Si thin film. Although Si is known as the material characterized by the highest gravimetric specific capacity (˜4.4 Li atoms per Si atom, ˜0.83 mAh/cm2μm), it suffers from a very high volume expansion while cycling (˜420%). In the thin film forms, this volume expansion leads to a very high stress evolution resulting in a very low cyclability of the electrode.
The advantages of Ge thin film anodes when used in Li-ion microbatteries according to example embodiments can include: (i) higher reliable areal capacity compared to Si, in spite of Ge having a lower volumetric specific capacity compared to Si; (ii) the rate of charge and discharge for Ge is higher than for Si; (iii) Ge has improved safety compared to pure Li.
While Ge has a higher volumetric specific capacity than conventional anode materials like carbon, it is only about 90% (˜0.74 mAh/cm2μm) that of Si. However, it has been recognized by the inventors that volumetric specific capacity is not the only one key parameter to be taken in account: cycle life is also a very important feature of Li-ion microbatteries. Cycle life is defined by the number of charge/discharge cycles that a battery can lasts before starts to reduce visibly (conventionally 80/85% of the initial capacity) its performance.
As mentioned above, lithiated Si suffers from a large volume expansion of about 420%, whereas Ge only has a volume expansion of about 270% [10]. It has been recognized by the inventors that this difference in volume expansion causes different reliable areal specific capacities for Si and Ge in the thin film form. From experiments with example embodiments of the present invention, it was found that Ge, curves 200a-c, can cycle well at higher thin film thickness compared to Si, curves 202a-c, as shown in
In the half-cell configuration (i.e. a configuration with a Ti/Pd current collector and Ge/Si thin film, a solid electrolyte (LiPON), a liquid electrolyte (LiPF6) and a Li foil as a counter electrode), a cycle life of about 42 and 247 cycles for 487 nm Si and 548 nm Ge thickness respectively.
The reason for the difference in cycling performance between Si and Ge is believed to be evident from comparative in-situ stress evolution studies during lithiation/delithiation. It was found that Ge inelastically deforms at much lower stresses than Si. Ge (see curves 700, 702 in
It has been reported that the diffusivity of Li-ions in Ge is 400 times higher than in Si at room temperature [12,13]. Here, Li-ions diffusivity is taken to be a measure of the lithiation and delithiation rates. Enhanced diffusivity of Li-ions in Ge compared to Si, is an added advantage to using Ge as a Li-ion anode, according to example embodiments. This advantageously enhances the rate performance of Ge anodes, curve 800, compared to Si anodes, curve 802 (
Pure Li-metal can be used as a high capacity (0.206 mAh/cm2μm) anode material which also serves as Li-ions source in a microbattery. However, safety concerns limit the use of Li-metal as an anode. Potential Li dendrite formation resulting in a short circuit of electrodes, or exposure of Li-metal (in the event of encapsulation failure) to atmospheric ambient resulting in explosive combustion, make it an unsafe anode to be used in commercial Li-ion batteries. Use of Ge anodes in Li-ion microbatteries according to example embodiments advantageously eliminates the need for having Li in its pure metallic phase. Moreover, the theoretical volumetric capacity of Ge anodes (˜0.74 mAh/cm2μm) is higher than that of Li metal, resulting in a volumetric capacity advantage of example embodiments of the present invention as well.
Ge thin-films can be deposited through a variety of techniques such as, but not limited to: chemical vapor deposition [16], electrodeposition [17] and physical vapor deposition [18]. Specifically, Ge anodes can be deposited through sputtering, a physical vapor deposition technique according to an example embodiment. In the following, implementation of Ge thin films in a full microbattery stack according to example embodiments will be described.
The advantages of using a pre-lithiation technique according to example embodiments described herein can include: (i) it makes possible to use Li-free cathode materials; (ii) it leads to improved cyclability/reliability; (iii) it can provide the ability to tailor the amount of Li incorporation to better manage performance vs. cyclability trade-offs; (iv) it can provide improved safety when compared to the use of pure Li-metal; and (v) it can ensure that the Li is never in the form of metallic Li, thereby arresting any stray motion of Li-ions, advantageously making the microbattery stack CMOS compatible when integrated with electronic circuitry.
Li-ion thin film microbatteries can be deposited through a variety of techniques such as, but not limited to: the sol-gel method [19], chemical vapor deposition [20], electrodeposition [21], ALD [22] or physical vapor deposition [8]. Sputtering deposition is a physical vapor deposition technique. Several examples of how sputter deposition can be used to create pre-lithiated thin films according to example embodiments are described herein. Similar strategies would apply for other film formation techniques in different embodiments. Pre-lithiation of anodes (such as Si or Ge) can be achieved by at least three different sputtering process: (i) sputtering of a pre-lithiated target, (ii) bi-layer, (iii) co-sputtering or (iv) multi-layer deposition.
In the sputtering of a pre-lithiated target according to example embodiments, Li is present within the stoichiometric structure of the target material such as LixSiy, LixGey. The fabrication process of the target material may involve chemical methods, electrochemical methods, solid-state reactions, sol-gel preparations. Optimal Li-loading of the electrode can be achieved by engineering the stoichiometry of the target material.
In the Bi-layer process (
In the Multi-layer process (
In the Co-sputtering process (
In the three processes described above with reference to
All the four different sputtering processes described above have been investigated according to example embodiments. Presently, the best results have been achieved following the bi-layer process. However, it is believed that by e.g. using an adequate sputtering tools, which allows several depositions without breaking the vacuum (i.e. without exposing target materials and samples to atmosphere), all the four different sputtering processes described above can result in a complete pre-lithiation electrode synthesis.
High areal/volumetric specific capacity and microbattery cyclability according to example embodiments can enable complex integrated circuits (ICs) with tight (i.e. CMOS-level) integration between the electronic circuits and the microbatteries. The microbatteries can preferably have the required energy capacity to power the selected parts of the ICs, and preferably have sufficient reliability to last for the useful life of the ICs. This can advantageously lead to an overall miniaturization of the size of ICs, due to the optimal use of the available areal footprint.
Additionally, integrable microbattery arrays, when paired with CMOS power management circuits according to example embodiments, can allow for customizable and controllable power output, which would allow the optimal use of a microbattery's stored charge, regardless of its output voltage as a function of its charge state (which would address potential challenges faced by microbatteries with large output voltage variation such as the RuO2 cathode microbatteries described earlier). Smart integrated power management circuits can also be expected to enhance the reliability of the microbatteries (and therefore the entire IC) due to their ability to properly regulate charging and discharging operations for maximal circuit life and efficiency.
Integration of Li-ion thin film microbatteries makes a Li-ions barrier layer and the use of a CMOS compatible processes desirable to fabricate the microbattery.
A critical issue in integrated microbatteries is the possibility of contamination of the electronic circuitry by Li-ions. This can affect the electronic circuitry's operation. To prevent Li-ions diffusion and other possible contamination, the right choice of protective insulators is important. A Li-ion barrier layer of Si3N4 (also referred as SiN) and/or SiO2 thin films are used in example embodiments which can be deposited by several methods such as, but not limited to, chemical vapor deposition, ALD, physical vapor deposition or thermal oxidation. By using a Li-barrier layer it is preferably possible to stop any stray motion of Li-ions, making the microbattery stack CMOS compatible. A protective/passivation/encapsulation layer of the microbattery is also desirable to protect the microbattery from the exposure to atmosphere. A Parylene C thin film as passivation layer deposited by a room-temperature CVD process is used according to an example embodiment, advantageously improving the overall compatibility with CMOS processes.
CMOS compatible processes to fabricate the microbattery can be classified in two different families: (i) separate fabrication of electronic circuitry and microbatteries on silicon substrates, followed by wafer-bonding; or (ii) direct deposition of the microbattery on the top/bottom of the fabricated electronic circuitry. The techniques and advantages of both these routes according to example embodiments are discussed below.
Wafer-bonding is an established technology for SOI wafers [23], MEMS [24] and strained-Si [25] fabrication. This technique can also be used to integrate microbatteries with electronic circuitry. In this case, the electronic circuitry 1000 (i.e. one or more electronic circuitry layers) is first fabricated on a Si substrate 1002 with appropriate protective insulation layers 1004 and vias 1006 for current conduction (
Microbattery integration through wafer-bonding is believed to be preferred when high temperature annealing processes are essential to the fabrication of the microbattery stack.
When no annealing is required for the microbattery stack fabrication, the stack can be directly deposited on the electronic circuitry's (i.e. one or more electronic circuitry layers) substrate. One specific example in this case is RuO2, a Li-ion cathode material. RuO2 does not require annealing as it interacts with Li-ions chemically to form a new phase, rather than through intercalation (LiCoO2) mechanism which requires that the material be crystalline and therefore generally requires high temperature annealing. An example of a microbattery stack fabricated completely at room temperature is composed by RuO2 (cathode), LiPON (electrolyte) and pre-lithiated LixSiy (anode) [28]. In this approach, there is no need for wafer-bonding as the entire fabrication takes place on a single Si substrate. The microbattery stack 1100 can be deposited on top of the electronic circuitry 1102 (
In both integration processes, the thin-films of the microbattery can be deposited through a variety of techniques such as, but not limited to: the sol-gel method [19], chemical vapor deposition [20], electrodeposition [21], atomic layer deposition [22] or physical vapor deposition [8]. Sputtering is a physical vapor deposition technique and unlike chemical vapor deposition does not require complex precursor and ambient chemistries. Also, to deposit patterned microbattery thin-films such as those shown in
Integrable microbatteries can be fabricated to include more than one individual battery cell.
Microbattery arrays can have the following advantages: (i) customizable power output, and (ii) improved reliability.
The amount of current and voltage drawn from the microbattery array can be customized. Using the same active battery materials, different current and voltage performance can be achieved. In the equivalent circuit shown in
Additionally, arrays are more reliable compared to individual cells. A single cell might fail due to material failure during operation. As an example, consider when two cells are connected in parallel. Even when one of the cells fails, the same voltage can be drawn albeit at half of the current. To further improve reliability, the battery array can be designed in such a way that the non-functioning cells can be by-passed.
As can be seen from
According to one embodiments, a Li-ion thin film microbattery is provided comprising a Li-free cathode comprising a transition metal oxide thin film; an anode comprising a lithiated Ge or Si thin film; and an electrolyte film disposed between the cathode and the anode; wherein a Li-source of the Li-ion thin film microbattery is provided by means of the lithiated Ge or Si thin film.
The transition metal oxide may comprise V2O5, CrO3, and/or RuO2. The electrolyte film may comprise LiPON. The Li-ion thin film microbattery may further comprise one or more power management electronic circuitry layers electrically coupled to the cathode and the anode. The management electronic circuitry layers may be formed on a first substrate and a microbattery stack comprising the Li-free cathode, the anode, and the electrolyte film are formed on a second substrate, and wherein the first and second substrates are bonded to each other on respective tops surfaces thereof. The power management electronic circuitry layers and a microbattery stack comprising the Li-free cathode, the anode, and the electrolyte film may be formed on the same substrate. The electronic circuitry layers and the microbattery stack may be formed on the same side of the substrate. The electronic circuitry layers and the microbattery stack are formed on opposite sides of the substrate. The Li-ion thin film microbattery may comprise current collection contacts for the Li-free cathode and the anode, respectively, arranged at the same level.
In one embodiment, a microbattery array comprising two or more of the Li-ion thin film microbattery of the above described embodiment is provided.
The transition metal oxide may comprise V2O5, CrO3, and/or RuO2. The electrolyte film may comprise LiPON. The method may further comprise providing one or more power management electronic circuitry layers electrically coupled to the cathode and the anode. The power management electronic circuitry layers may be formed on a first substrate and a microbattery stack comprising the Li-free cathode, the anode, and the electrolyte film are formed on a second substrate, and wherein the first and second substrates are bonded to each other on respective tops surfaces thereof. The method may comprise forming the power management electronic circuitry layers and a microbattery stack comprising the Li-free cathode, the anode, and the electrolyte film on the same substrate. The method may comprise forming the electronic circuitry layers and the microbattery stack on the same side of the substrate. The method may comprise forming the electronic circuitry layers and the microbattery stack on opposite sides of the substrate. The method may comprise arranging current collection contacts for the Li-free cathode and the anode, respectively, at the same level. Providing the anode may comprise a bi-layer deposition of the semiconductor material and Li, respectively, and controlling a reaction between the semiconductor material and the Li for the lithiation. Providing the anode may comprise a multi-layer deposition of multiple layers of the semiconductor material and Li, respectively, and controlling a reaction between the semiconductor material and the Li for the lithiation. Providing the anode may comprise a co-deposition of the semiconductor material and Li for the lithiation.
In one embodiment, a method of fabricating a microbattery array is provided, comprising fabricating two or more Li-ion thin film microbatteries using the method of fabricating a Li-ion thin film microbattery of the above embodiment.
It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive. Also, the invention includes any combination of features, in particular any combination of features in the patent claims, even if the feature or combination of features is not explicitly specified in the patent claims or the present embodiments.
This application claims the benefit of priority of U.S. Provisional Application No. 62/368,231 filed on Jul. 29, 2016, the content of which is incorporated herein by reference in its entirety for all purposes.
Filing Document | Filing Date | Country | Kind |
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PCT/US2017/044351 | 7/28/2017 | WO | 00 |
Number | Date | Country | |
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62368231 | Jul 2016 | US |