Acoustic wave-driven mixing for suppression of dendrite formation and ion depletion in batteries

Abstract

To provide a battery capable of suppressing dendrite formation and ion depletion. A battery may include a first electrode, a second electrode, an electrolyte, and at least one acoustic wave device configured to generate acoustic streaming during charging and / or discharging of the battery. Charging of the battery can be triggered to cause cations from the first electrode to migrate through the electrolyte and deposit on the second electrode, and discharging can be triggered to cause cations from the second electrode to migrate through the electrolyte and deposit on the first electrode. The acoustic streaming can drive mixing and / or turbulence in the electrolyte, which can increase the charge and / or discharge rates of the battery by increasing the diffusion rate of cations and / or anions. The mixing and / or turbulence can further prevent the formation of dendrites on the first electrode and / or second electrode by at least homogenizing the distribution of cations and / or anions in the electrolyte.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 882,450, filed August 2, 2019, and entitled "CHEMISTRY-AGNOSTIC PREVENTION OF ION DEPLETION AND DENDRITE FORMATION IN A LIQUID ELECTROLYTE," and U.S. Provisional Patent Application No. 62 / 968,556, filed January 31, 2020, and entitled "CHEMISTRY-AGNOSTIC PREVENTION OF ION DEPLETION AND DENDRITE FORMATION IN A LIQUID ELECTROLYTE," the disclosures of which are incorporated herein by reference in their entireties.

[0002] (Statement of Federally Funded Support) This invention was made with government support under Grant No. EE008363 awarded by the Department of Energy. The government has certain rights in this invention.

[0003] The subject matter disclosed herein relates generally to battery technology, and more particularly to suppressing dendrite formation and ion depletion in rechargeable batteries. [Background technology]

[0004] Batteries can convert chemical energy into electrical energy, and vice versa, through oxidation and reduction. For example, during battery discharge, atoms at the battery's anode (e.g., negative electrode) can oxidize to form cations (e.g., positively charged ions) and free electrons. The free electrons can migrate from the battery's anode to its cathode (e.g., positive electrode), thereby generating an electric current through an external circuit that includes the battery's electrical load. The cations can also migrate to the cathode through an electrolyte interposed between the anode and cathode. Meanwhile, to charge the battery, an electric current can be applied to the battery to oxidize atoms at the cathode, forming both cations and free electrons. The free electrons can return to the anode through the external circuit, while the cations can migrate through the electrolyte to return to the anode. Summary of the Invention

[0005]

[0003] In one aspect, a battery includes a first electrode, a second electrode, an electrolyte interposed between the first and second electrodes, and at least one acoustic wave device configured to generate acoustic streaming during charging and / or discharging of the battery, wherein charging of the battery triggers cations from the first electrode to migrate through the electrolyte and deposit on the second electrode, discharging of the battery triggers cations from the second electrode to migrate through the electrolyte and deposit on the first electrode, the acoustic streaming drives mixing and / or turbulence in the electrolyte, the mixing and / or turbulence increasing the charge and / or discharge rates of the battery by at least increasing the diffusion rate of cations and / or anions, and the mixing and / or turbulence further preventing dendrite formation on the first electrode and / or the second electrode by at least homogenizing the distribution of cations and / or anions in the electrolyte.

[0006] In some variations, one or more of the features disclosed herein may be optionally included in any workable combination, including the following features: Homogenization may prevent the formation of dendrites by at least reducing the concentration gradient of cations and / or anions in the electrolyte.

[0007] In some variations, homogenization may prevent the formation of dendrites by at least increasing the uniformity of the distribution of cations and anions in the electrolyte.

[0008] In some variations, homogenization may prevent the formation of dendrites by at least increasing the uniformity of the deposition of cations on the first electrode and / or the second electrode.

[0009] In some variations, the mixed flow of electrolyte may further maximize the transport of cations and / or anions to replace cations and / or anions depleted from the electrolyte during charging and / or discharging of the battery.

[0010] In some variations, the electrolyte may include a liquid electrolyte including one or more of water, carbonate-based electrolytes, ester-based electrolytes, ether-based electrolytes, ionic liquids, nitrile-based electrolytes, phosphate-based electrolytes, sulfur-based electrolytes, and sulfone-based electrolytes.

[0011] In some variations, the electrolyte may include polymer-based electrolytes, organic electrolytes, solid electrolytes, non-aqueous organic solvent electrolytes, and gas electrolytes.

[0012] In some variations, the first electrode may be the anode of the battery.

[0013] In some variations, the battery anode may be formed from a metal including at least one of lithium (Li), potassium (K), magnesium (Mg), copper (Cu), zinc (Zn), sodium (Na), and lead (Pb).

[0014] In some variations, the battery anode may be formed from an intercalation material including at least one of graphite, graphene, and / or titanium dioxide (TiO2).

[0015] In some variations, the battery anode may be formed from an alloy including at least one of silicon (Si), aluminum (Al), and tin (Sn).

[0016] In some variations, the battery anode may be formed from a conversion material including copper peroxide (CuO2).

[0017] In some variations, the second electrode may be the cathode of the battery.

[0018] In some variations, the cathode of the battery may be an intercalation type electrode including at least one of a lithium intercalation carbon electrode, a lithium intercalation silicone electrode, a vanadium oxide electrode, a lithium overload electrode, a graphite electrode, and a graphene electrode.

[0019] In some variations, the cathode of the battery may be an alloy-type electrode that includes tin (Sn).

[0020] In some variations, the cathode of the battery may be an air electrode containing at least one of oxygen (O) and air.

[0021] In some variations, the at least one acoustic wave device may be a transducer deposited on a substrate. The transducer may be configured to respond to an electrical input signal by at least applying tension and compression in and / or on the substrate. The substrate may respond to the tension and compression by at least oscillating to generate a plurality of acoustic waves.

[0022] In some variations, the plurality of acoustic waves may include surface acoustic waves, Lamb waves, bending waves, thickness mode vibrations, mixed mode waves, longitudinal waves, shear mode vibrations, and / or bulk wave vibrations.

[0023] In some variations, at least one acoustic wave device may include one or more pairs of integrated transducers, a layer of conductive material, and / or one or more contact pins.

[0024] In some variations, the substrate may be formed from at least a piezoelectric material.

[0025] In some variations, the piezoelectric material is lithium niobate (LiNbO), lithium titanate (LiTiO), barium titanate (BaTiO), lead zirconate titanate (Pb(Zr x Ti 1-x )O3, where (0≦x≦1)), quartz, aluminum nitride (AlN), langasite, lead magnesium niobate-lead titanate (PMN-PT), lead-free potassium sodium niobate (K 0.5 Na 0.5 NbO3 or KNN), doped derivatives of lead-free potassium sodium niobate, and / or polyvinylidene fluoride (PVDF).

[0026] In some variations, the at least one acoustic wave device can be configured to generate a plurality of acoustic waves having frequencies corresponding to decay lengths of the plurality of acoustic waves, which can correspond to a first length of the first electrode, a second length of the second electrode, and / or a distance between the first and second electrodes.

[0027] In some variations, at least one acoustic wave device may be integrated within and / or onto the case of the battery.

[0028] In some variations, the battery may be a coin cell, a pouch cell, or a cylindrical cell.

[0029] In some variations, the battery may be coupled to a circuit configured to drive the at least one acoustic wave device, and the circuit may include an integrated battery charging circuit and an automatic resonance seeking function.

[0030] In some variations, the method may include receiving a feedback signal in response to one or more acoustic waves, the one or more acoustic waves being generated by at least one acoustic wave device comprising a battery, and the feedback signal corresponding to at least a partial reflection of the one or more acoustic waves formed by one or more components internal to the battery; determining an internal morphology of the battery based at least on the feedback signal; and controlling operation of the battery based at least on the internal morphology of the battery.

[0031] In some variations, controlling the operation of the battery may include terminating the operation of the battery in response to a feedback signal indicating the presence of dendrites and / or gas bubbles on the surface of the first electrode and / or the second electrode.

[0032] In some variations, controlling operation of the battery may include terminating operation of the battery in response to a feedback signal indicating the presence of a detached dendrite on the at least one acoustic wave device, a break in the solid electrolyte interfacial layer, and / or the formation of a protective polymer layer.

[0033] In some variations, operation of a battery may be terminated by electrically isolating the battery from its electrical load and / or from other batteries in the same battery array.

[0034] Details of one or more variations of the subject matter described herein are set forth in the accompanying drawings and the description below. Other features and advantages of the subject matter described herein will be apparent from the description and drawings, and from the claims. While certain features of the presently disclosed subject matter have been described for illustrative purposes in connection with rechargeable batteries, it should be readily understood that such features are not intended to be limiting. The claims following this disclosure are intended to define the scope of the protected subject matter.

[0035] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the subject matter disclosed herein and, together with the description, serve to explain some of the principles associated with the subject matter disclosed herein. [Brief explanation of the drawings]

[0036] [Figure 1] 1A-1C illustrate a comparison between a conventional lithium metal battery and a lithium metal battery with an integrated surface acoustic wave device, according to some exemplary embodiments. [Figure 2] FIG. 10 illustrates a comparison of lithium deposition morphology on a copper substrate with and without the presence of surface acoustic waves, according to some example embodiments. [Figure 3] FIG. 10 illustrates a comparison of Coulombic efficiency with and without the presence of surface acoustic waves at various deposition and stripping rates, according to some example embodiments. [Figure 4] FIG. 10 illustrates a comparison of galvanostatic cycling performance of a lithium iron phosphate battery with and without the presence of surface acoustic waves, according to some exemplary embodiments. [Figure 5] FIG. 10 illustrates a comparison of cycling performance of a full battery cell with and without the presence of surface acoustic waves, according to some exemplary embodiments. [Figure 6] FIG. 10 illustrates a comparison of lithium deposition morphology for a lithium anode with and without the presence of surface acoustic waves, according to some exemplary embodiments. [Figure 7]10A-10C illustrate flow velocity distributions within a battery with an integrated surface acoustic wave device, according to some exemplary embodiments. [Figure 8] FIG. 1 illustrates an example of a battery cell with an integrated surface acoustic wave (SAW) device, according to some exemplary embodiments. [Figure 9] 1A-1C illustrate a comparison of different states of a surface acoustic wave device immersed in a carbonate-based electrolyte with and without a parylene coating, according to some exemplary embodiments. [Figure 10] FIG. 10 illustrates a comparison of first cycle deposition performance of lithium copper batteries with and without surface acoustic waves, according to some exemplary embodiments. [Figure 11] 1A-1C show scanning electron microscope (SEM) images illustrating operations for achieving lithium electrode porosity, according to some exemplary embodiments. [Figure 12] FIG. 10 illustrates a comparison of the change in concentration gradient with and without surface acoustic waves at different state of charge (SOC) statuses, according to some exemplary embodiments. [Figure 13A] FIG. 10 illustrates a comparison of the electrochemical performance of a pouch cell with an outer integrated surface acoustic wave device and a baseline cell, according to some exemplary embodiments. [Figure 13B] FIG. 10 illustrates a comparison of the electrochemical performance of a pouch cell with an inner integrated surface acoustic wave device and a baseline cell, according to some exemplary embodiments. [Figure 14] FIG. 1 is a block diagram illustrating an example of a surface acoustic wave battery system, according to some exemplary embodiments. [Figure 15] FIG. 2 illustrates a top-level description of the circuit blocks that form a surface acoustic wave battery system, according to some exemplary embodiments. [Figure 16] FIG. 1 is a circuit diagram illustrating an example of a microcontroller, according to some exemplary embodiments. [Figure 17] FIG. 2 is a circuit diagram illustrating an example of a surface acoustic wave driver, according to some exemplary embodiments. [Figure 18A]FIG. 1 is a circuit diagram illustrating an example of a battery cycler, according to some exemplary embodiments. [Figure 18B] FIG. 1 is a circuit diagram illustrating an example of a battery cycler control circuit, according to some exemplary embodiments. [Figure 19] FIG. 2 is a circuit diagram illustrating an example of a power management circuit, according to some exemplary embodiments. [Figure 20] FIG. 1 is a block diagram illustrating an example of an electrical driver system for a surface acoustic wave device, according to some exemplary embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0037] In practice, like reference numbers indicate like structures, features, or elements.

[0038] Charging a battery can cause dendrite formation. For example, lithium (Li) metal batteries can cause lithium dendrite formation at the battery anode when lithium ions returning from the cathode to the anode form irregular, moss-like deposits on the anode. Dendrite formation can gradually reduce the battery's discharge capacity. Furthermore, dendrites forming on the anode can eventually penetrate the separator to contact the cathode, causing an internal short circuit within the battery. Therefore, dendrite formation can compromise the safety, rechargeability, capacity, and lifespan of conventional lithium metal batteries. The risk of dendrite formation in lithium metal batteries can be particularly high at high current densities, making them unsuitable for applications requiring high charging rates.

[0039] In some exemplary embodiments, a lithium metal battery can include an integrated surface acoustic wave (SAW) device that can operate to suppress the formation of lithium dendrites in the lithium metal battery during charging of the lithium metal battery. The surface acoustic wave device can generate acoustic streaming, which can drive rapid submicron boundary layer mixing flow of the electrolyte adjacent to the anode of the lithium metal battery. This surface acoustic wave-driven mixing flow can increase the uniformity of lithium deposits on the anode of the lithium metal battery, including by reducing the lithium concentration gradient that exists during charging of the lithium metal battery, even when the lithium metal battery undergoes rapid charging. Notably, this surface acoustic wave-driven mixing flow can suppress the formation of lithium dendrites even when the chemical composition of the lithium metal battery, such as the inclusion of a carbonate-based electrolyte (e.g., ethylene carbonate (EC) and diethyl carbonate (DEC)), makes the lithium metal battery particularly vulnerable to dendrite formation. The surface acoustic wave device also provides minimal power consumption (e.g., approximately 10 mWh / cm), particularly with respect to the power consumed to charge the lithium metal battery. 2 ) may act to inhibit dendrite formation.

[0040] FIG. 1 illustrates a comparison between a conventional lithium metal battery and a lithium metal battery with an integrated surface acoustic wave device, according to some exemplary embodiments. Referring to FIG. 1(a), a surface acoustic wave (SAW) device 100 can generate acoustic streaming, driving the flow of electrolyte 110 within the gap between electrodes 120. FIG. 1(b) illustrates the fluid flow, ion distribution, and dendrite formation present in a conventional lithium metal battery, and FIG. 1(c) illustrates the fluid flow, ion distribution, and dendrite formation present in a lithium metal battery with an integrated surface acoustic wave device. As shown in FIGS. 1(b)-(c), the solid electrolyte in a conventional lithium metal battery allows high ion concentration gradients to develop during charging, which leads to lithium dendrites, dead lithium, lithium metal volume expansion, a non-uniform solid electrolyte interface (SEI), and ultimately, short circuits within the lithium metal battery. In contrast, in a lithium metal battery with an integrated surface acoustic wave device, the acoustic streaming generated by the surface acoustic wave device during charging can recirculate the electrolyte to create a homogenous ion distribution and uniform lithium deposition (e.g., on the anode of the lithium metal battery) during charging.

[0041] In some exemplary embodiments, acoustic streaming generated by a surface acoustic wave device can suppress lithium dendrite formation in a lithium metal battery, even if the battery's chemical composition, such as the inclusion of a carbonate-based electrolyte (e.g., EC / DEC), makes the lithium metal battery particularly susceptible to dendrite formation. Figure 2 shows a comparison of lithium deposition morphology on a copper substrate with and without the presence of surface acoustic waves, according to some exemplary embodiments. A baseline lithium-copper battery without a surface acoustic wave device and a lithium-copper battery with an integrated surface acoustic wave device may be formed to contain a carbonate electrolyte (e.g., EC / DEC in 1 M LiPF), which is known to trigger dendrite formation even at low current density rates. Dendrite formation can be detected based on the respective voltage profiles of the baseline battery and the battery cell with the integrated surface acoustic wave device. Thus, an increase in the voltage of the baseline cell may be indicative of dendrite formation, while the constant voltage exhibited by the lithium-copper battery with the integrated surface acoustic wave device at high current densities may indicate uniform lithium deposition. The presence of surface acoustic waves can even prevent the sudden voltage drop that the baseline cell exhibits at the beginning of deposition, as the surface acoustic waves can minimize the inhomogeneous nucleation barrier present in the baseline cell.

[0042] Figure 2 shows scanning electron microscope (SEM) images of electrodes from a baseline cell and a cell with an integrated surface acoustic wave device following one deposition cycle. Figure 2(a)-(d) show the results for an areal capacity of 1 mAh cm. -2 until it reaches 1 mAcm -2 Figures 2(e)-(h)d show the baseline cell after lithium plating on the copper substrate at a current density of (1 C). -2 until it reaches 1 mAcm -2 Figures 2(i)-(l) show the battery with the integrated surface acoustic wave device after lithium was plated onto the copper substrate at a current density of (1 C) 1 mAh / cm. 2 until an areal capacitance of 6 mA / cm is achieved 2Figures 2(m)-(p) show the baseline battery after lithium was plated onto the copper substrate at a current density of 1 mAh / cm. 2 until an areal capacitance of 6 mA / cm is achieved 2 Figure 2 shows a battery with an integrated surface acoustic wave device after lithium plating on a copper substrate at a current density of 1000 Ω / s. It should be understood that Figures 2(a), (b), (e), (f), (i), (j), (m), and (n) show cross-sectional views, and Figures 2(b), (f), (j), and (n) are enlarged views of Figures 2(a), (e), (j), and (m), respectively. Meanwhile, Figures 2(c), (d), (g), (h), (k), (l), (o), and (p) show top views, and Figures 2(d), (h), (l), and (p) are enlarged views of Figures 2(c), (g), (k), and (o), respectively.

[0043] Referring to FIG. 2, a baseline cell charged without surface acoustic waves and a cell charged with surface acoustic waves can show the resulting difference in electrode thickness (e.g., 1 mA cm -2 The thickness of the lithium deposits was 9.1 μm when cycled without surface acoustic waves at a current density of 1000 s, compared with 5.3 μm when cycled with surface acoustic waves. This difference may correspond to the density of the lithium deposits. Theoretically, if lithium were deposited without any porosity or dendrites, a 4.85 μm-thick lithium deposit could be achieved. Thus, the density of the lithium deposits achieved in the presence of surface acoustic waves indicates that surface acoustic waves can improve the behavior and morphology of the deposits. This difference in deposition morphology can also be observed in the top views of the baseline cell and the cell with the integrated surface acoustic wave device. For example, Figures 2(g)-(h) show that the deposit morphology of the cell with the integrated surface acoustic wave device may be dense and devoid of dendrites, whereas Figures 2(c)-(d) show that the deposit morphology of the baseline cell may exhibit porosity as well as dendrites.

[0044] The difference in electrode thickness between a baseline cell charged without surface acoustic waves and a cell charged with surface acoustic waves is significant at higher current densities (e.g., 6 mA cm -2) may be even more pronounced. In the battery with the integrated surface acoustic wave device, the deposition thickness increased slightly to 6 μm, while the deposition thickness of the baseline cell increased dramatically to 27 μm. This significant change in thickness of the baseline battery may be an indication of dendrite formation and loose lithium deposition. From a top view, the lithium dendrites may appear thinner and more porous when the baseline battery is exposed to higher current densities. In contrast, the battery with the integrated surface acoustic wave device may exhibit a more homogeneous morphology, including the presence of lithium agglomerates, indicating the formation of a homogeneous and stable solid electrolyte interface (SEI).

[0045] Figure 3 shows a comparison of Coulombic efficiency with and without the presence of surface acoustic waves at various deposition and stripping rates, according to some exemplary embodiments. A baseline cell and a cell with an integrated surface acoustic wave device were tested at 1 mAhcm -2 While increasing the current density (for example, 1 mA cm), the capacitance is increased until the area capacitance is reached and the current returns to 1 volt. -2 Starting with 2, 3, 4, 5, 6 mAcm -2 The cells were cycled (increasingly). Figure 3(a) shows the resulting electrochemical profile of the cell with the integrated surface acoustic wave device, and Figure 3(b) shows the electrochemical profile of the baseline cell. As shown in Figure 3, the baseline cell was cycled at 2 mAcm -2 The cells may begin to exhibit unstable electrochemical profiles starting at the third cycle when exposed to current densities of 1000 mAh. Figure 3(c) shows the average coulombic efficiency of the baseline cell (black dots) and the cell with the integrated surface acoustic wave device (green dots) along with error bars as a function of current density, summarized from Figures 3(a)-(b).

[0046] The cyclability of the battery with the integrated surface acoustic wave device can be investigated at different cycle rates using a carbonate-based electrolyte (e.g., 1 M LiPF in EC / DEC). The battery with the integrated surface acoustic wave device can be cycled at 1 mA cm -2 The cells exhibit an average coulombic efficiency of 91.5% at 2 mAcm, while the baseline cells exhibit a coulombic efficiency of 88%.-2 When cycled at a current density of 2 mA cm, after the first two cycles, the cell with the integrated surface acoustic wave device maintains a coulombic efficiency of 89%, while the baseline cell can exhibit a coulombic efficiency of 87%. -2 In contrast, batteries with integrated surface acoustic wave devices can maintain optimal cycling performance throughout, including by continuing to exhibit stable electrochemical profiles. For example, batteries with integrated surface acoustic wave devices can maintain >80% coulombic efficiency throughout cycling, even at high charge rates, while the coulombic efficiency of baseline batteries can degrade even at relatively low charge rates.

[0047] 4 shows a comparison of galvanostatic cycling performance of lithium iron phosphate batteries with and without the presence of surface acoustic waves, according to some exemplary embodiments. Figure 4 shows the galvanostatic cycling performance of a baseline lithium iron phosphate (LiFePO4) battery without an integrated surface acoustic wave device and a lithium iron phosphate battery with an integrated surface acoustic wave device, each with a carbonate-based electrolyte (e.g., EC / DEC, etc.), at different cycling rates. Specifically, Figure 4(a) shows the galvanostatic cycling performance of a baseline lithium iron phosphate (LiFePO4) battery without an integrated surface acoustic wave device and a lithium iron phosphate battery with an integrated surface acoustic wave device, each with a carbonate-based electrolyte (e.g., EC / DEC, etc.), at different cycling rates. Specifically, Figure 4(b) shows the galvanostatic cycling performance of a baseline lithium iron phosphate (LiFePO4) battery without an integrated surface acoustic wave device and a lithium iron phosphate battery with an integrated surface acoustic wave device, each with a carbonate-based electrolyte (e.g., EC / DEC, etc.), at different cycling rates. -2 (1mAcm -2 Figure 4(b) and (c) show a comparison of the discharge capacities of the baseline battery and the battery with the integrated surface acoustic wave device at charge densities back to 1 C. Meanwhile, the charge and discharge profiles at the last cycle (10th, 15th, 20th, 25th, 30th, 35th, 40th, and 45th cycles) of the baseline battery and the battery with the integrated surface acoustic wave device at each current density are shown, respectively.

[0048] As shown in FIG. 4, the baseline battery and the lithium iron phosphate battery with an integrated surface acoustic wave device exhibited excellent cycling performance at low cycling rates (e.g., 0.5 mA cm−1). 2or 0.5C), they can exhibit similar discharge capacities (e.g., 137 mAh / g). This may be due to the existence of a small lithium ion concentration gradient at low current densities even in the baseline cell without an integrated surface acoustic wave device. However, differences in discharge capacity may begin to appear at higher current densities (e.g., above 1 mAcm). Therefore, -2 can be considered a critical value at which dendrites may begin to form and surface acoustic waves may begin to affect the cycling performance of the battery cell.

[0049] For example, a lithium iron phosphate battery with an integrated surface acoustic wave device can deliver 1 mAcm -2 can deliver 130 mAh / g at a current density of 1 mAcm, while the baseline cell can deliver 130 mAh / g at a current density of 1 mAcm -2 At a current density of 120mAcm -2 Also, the decrease in discharge capacity may be more rapid for the baseline cell when the induced current density increases. For example, the baseline cell may be -2 to 6mAcm -2 In contrast, the battery with the integrated surface acoustic wave device delivered 8.3% discharge capacity when the current density was increased to 1 mA cm. -2 to 6mAcm -2 When the temperature was increased to 1000 saturation, the discharge capacity increased by 42%.

[0050] Referring again to Figure 4, the lithium iron phosphate battery with the integrated surface acoustic wave device can recover to a higher discharge capacity when the current density is substantially reduced. For example, the baseline battery also recovered some of its discharge capacity when returned to a lower current density, but the recovered discharge capacity of the baseline battery is lower. The fact that the battery recovered its discharge capacity may indicate rapid charge and discharge due to the lack of permanent damage. Nevertheless, the low discharge capacity of the baseline battery at high charge rates may result from the low diffusion rate and high lithium concentration gradient present within the baseline battery. In contrast, the higher discharge capacity of the battery with the integrated surface acoustic wave device may be primarily due to lithium ions being closer to full charge due to acoustic streaming in the charged state. This phenomenon is again demonstrated in the charge and discharge profiles shown in Figures 4(b) and 4(c). Referring to Figures 4(b) and 4(c), voltage hysteresis increases dramatically relative to the baseline battery at high cycling rates. The voltage hysteresis is greater than 6 mA cm. -2 The voltage increased to 1.02 V at a current density of 100%, which is 100% greater than the cell with the integrated surface acoustic wave device. The large voltage hysteresis relative to the baseline cell may indicate poor lithium ion diffusivity in the absence of surface acoustic waves.

[0051] Figure 5 shows a comparison of cycling performance of a full battery cell with and without the presence of surface acoustic waves, according to some exemplary embodiments. Figure 5 shows a comparison of cycling performance of a full battery cell with and without the presence of surface acoustic waves, according to some exemplary embodiments, at 2 mA cm over 200 cycles. -2Figure 5(a) shows the cycling performance of a full battery with a lithium anode and a lithium iron phosphate (LFP) cathode exposed to a current density of 100 mAh / g (corresponding to 2 C). The full LFP battery with an integrated surface acoustic wave device can deliver an initial discharge capacity of 110 mAh / g, while the baseline LFP battery can deliver an initial discharge capacity of 90 mAh / g. Figure 5(a) also shows that the battery with the integrated surface acoustic wave device can maintain 80% of its discharge capacity over 200 cycles, while the baseline battery can maintain 53% of its initial discharge capacity. The galvanostatic profiles of the baseline LFP battery at 10, 50, 100, 150, and 200 cycles are shown in Figure 5(b), and the galvanostatic profiles of the battery cell with the integrated surface acoustic wave device at 10, 50, 100, 150, and 200 cycles are shown in Figure 5(c).

[0052] Referring again to FIG. 5(a), cycling performance can be improved by the presence of surface acoustic waves. For example, as shown in FIG. 5(a), the discharge capacity of the battery with the integrated surface acoustic wave device may be higher through 200 cycles, and the initial discharge capacity of the battery is 20% higher than that of the baseline battery without the integrated surface acoustic wave device. The battery with the integrated surface acoustic wave device may also maintain its discharge capacity better than the baseline battery. For example, FIG. 5(a) shows that after 200 cycles, the battery with the integrated surface acoustic wave device maintains 82% of its initial discharge capacity, while the baseline battery can only maintain 51% of its initial discharge capacity.

[0053] The difference in discharge capacity and its maintenance can be observed in the voltage profile of the baseline battery shown in Figure 5(b) and the battery with the integrated surface acoustic wave device shown in Figure 5(c). Figure 5(b) shows an increase in cell polarization with each successive cycle. Specifically, there is a 63% increase in polarization voltage between the 10th (0.28 V) and 200th cycle (0.77 V) of the baseline battery. This increase in polarization may indicate the presence of lithium dendrites and therefore may be related to the decrease in discharge capacity over successive cycles. In contrast, Figure 5(c) shows a stabilization of polarization in the voltage profile of the battery with the integrated surface acoustic wave device. Notably, the polarization voltage at the 10th cycle is 0.266 V and remains at 0.298 V at the 200th cycle. This minimal 10% increase in polarization voltage over 200 cycles may indicate stable cycling performance.

[0054] Figure 6 shows a comparison of lithium deposition on a lithium anode with and without the presence of surface acoustic waves, according to some exemplary embodiments. For example, Figure 6(a) shows a scanning electron microscope (SEM) image of the lithium electrode of a baseline battery, which shows loose lithium deposition and the presence of lithium dendrites. In contrast, Figure 6(c) shows a scanning electron microscope image of the lithium electrode of a battery with an integrated surface acoustic wave device, which shows denser and smoother lithium deposition.

[0055] When the porosity of the lithium deposits was quantified, the lithium electrode from the baseline battery exhibited a porosity of 0.541 μm, while the porosity of the lithium electrode in the battery with the integrated surface acoustic wave device was significantly lower at 0.0367 μm. The difference in the porosity and morphology of the lithium deposits can also be observed in the cross-sectional views in Figures 6(b) and 6(d). For example, the baseline battery had a 165 μm-thick lithium deposit, indicating that 66% of the battery's lithium was consumed due to dendrite formation and electrolyte depletion. In contrast, the battery with the integrated surface acoustic wave device consumed only 10% of its lithium due to dendrite formation and electrolyte depletion after 200 cycles.

[0056] The performance of a lithium metal battery can depend on its diffusion characteristics, which directly affect the charge and discharge rate, capacity, and cycle stability of the lithium metal battery. In most batteries, the fluid velocity u in the electrolyte is negligible. Therefore, the depleted lithium ions (Li) from the electrolyte into the anode due to ion migration that causes charging. + ) can be replaced through diffusion. However, in lithium metal batteries undergoing fast charging, diffusion may be too slow to overcome ion depletion of the electrolyte. Thus, the charge rate of lithium metal batteries can be maximized by recirculating the electrolyte to improve ion transport. For example, electrolyte recirculation can be achieved by introducing a surface acoustic wave-driven flow, which can increase the electrolyte fluid velocity, u, from zero to approximately 1 m / s, for example. Nevertheless, in some exemplary embodiments, a surface acoustic wave device can be configured to generate surface acoustic waves that maximize ion transport while suppressing the formation of lithium dendrites.

[0057] Conventional models of dendrite formation in electrochemical cells typically characterize dendrite formation as a spatially one-dimensional diffusion problem, storing a large number of ions in an electrolyte exposed to a given current flowing through the cell. The current may be a function of the potential difference between the electrodes. In contrast, according to some exemplary embodiments, electrolyte flow, particularly impinging currents, can inhibit the early growth of small dendrites. Therefore, convective and diffusive transport of ions within an electrochemical cell can be modeled transversely and parallel to the electrodes. The cell can be considered to be near a critical current density, and slight morphological defects along the electrodes form "hot spots" that locally enhance the rate at which metal ions adsorb onto the electrodes, enabling the initial growth of dendrites. Additionally, acoustically driven flow within the cell can be considered to affect the distribution of ions along the electrodes near these hot spots.

[0058] 7 shows the distribution of flow velocity in a battery with an integrated surface acoustic wave device, according to some exemplary embodiments. Referring to FIG. 7, the surface acoustic wave device is operating at 474 mW, while the average fluid velocity in the battery can be 5 mm / s.

[0059] The attenuation length of the acoustic wave in the electrolyte after leakage from the surface acoustic wave device is 4π in the electrolyte solution. 2 f 2 / c 3 sound )x(4μ / 3p) -1 ≒1cm, f, c sound , μ, and p are 1.22 g / cm 3 represent the frequency, sound speed, viscosity, and density of the electrolyte solution. Acoustic waves can propagate in the fluid electrolyte over length scales roughly corresponding to the size of the battery electrodes, a consequence of choosing an operating frequency of 100 MHz for the surface acoustic wave device when the size of the prototype battery was known. Acoustic streaming can be most similar to Eckart streaming due to the presence of lateral confinement and acoustic attenuation through the bulk of the fluid. The experimental flow field is characterized by the characteristic length and velocity δ and u, respectively. cBased on experimental data, the characteristic streaming velocity is u c ≈5 mm / s, and the thickness of each electrolyte chamber in the cell, i.e., L = 50 μm, can be considered as the characteristic length. For 1 M LiPF6 in EC:DEC electrolyte, the Reynolds number is Re = pu c L / μ≈0.2-2, indicating laminar, approximately viscous flow, as expected from the dimensions of the structure.

[0060] However, if the diffusion coefficient of the ion is 10 -9 m 2 / s, this could indicate strong ion convection and potentially an ion transport boundary layer with a thickness of ≈ 0.1-1 μm. This conclusion follows from the requirement that the higher-order convective and diffusive components in the transport equations must be of comparable magnitude within the boundary layer, which implies that the corresponding Péclet number within the boundary layer is u c This is satisfied by requiring that l / D≈1.

[0061] The analysis is based on the characteristic speed u c This can be simplified by assuming simple shear flow. The small thickness of the boundary layer compared to the gap between the electrodes, and the lack of excess pressure therein, at least locally, supports the assumption of simple shear flow.

[0062] Assuming that the electric field in the battery is effectively screened by the high electrolyte concentration, the stable mass transport of ions is governed by equation (1) below:

number

[0063] The problem can be simplified by further assuming a 2D problem, where the x coordinate is along the flow in the boundary layer and the y coordinate is across the electrodes, which are considered to be flat and parallel (prior to physical dendrite growth). As shown in equations (2) and (3) below, the problem can be solved subject to the conservation of mass of metal ions in the electrolyte and harmonic variations in ion concentration along the surface of the lithium electrode, which are associated with localized ion depletion regions near hotspots for dendrite growth.

number

number

[0064] These equations allow for a localized minimum along the lithium electrode, where the ion concentration vanishes completely, thus favoring a hot spot. The velocity field within the boundary layer is given by u = βye x and v=0e y where u and v are the e associated with the x and y coordinates, respectively. x and e y is the component of the velocity field along the unit vector direction, and β ≒ u cwhere / δ is the shear rate along the y-coordinate and δ is the characteristic length of the flow in the boundary layer. The solution to this problem, subject to δ = 0 (no flow) and δ > 0 (simple shear flow in the boundary layer), is provided in the Supporting Information.

[0065] In the absence of flow, the diffusion-limited flux of ions to the electrode, −i, can be given by equation (4) below:

number

[0066] The presence of a flow near the lithium electrode is 1 / 3 The advection of lithium ions into the electrode can be enhanced as proportional to Pe≡u c l / D is the Peclet number. In addition, the flow is 1 / 3 This can further enhance the local transport of lithium ions to the hot spots, proportional to . This result is consistent with the observation that enhanced convection of ions along the electrode to the hot spots reduces the fluctuations in ion concentration that would otherwise occur. The overall rate of lithium ion adsorption to the electrode can be given by the following equation (5):

number

[0067] The first term on the right can represent the spatially monotonic convective contribution to ion flux for a flat, homogeneous electrode, and the second term represents a correction for the spatially non-monotonic convective contribution to ion flux due to the presence of hot spots. The third term, given simply as O(∈), is an additional convective contribution to ion flux, which is spatially monotonic and can be obtained numerically. The first and third terms can be a product of similarity analysis and are therefore mathematically singular at the origin x=0; therefore, the current expression in equation (5) can remain physically valid away from the origin.

[0068] The mechanism by which flow inhibits dendrite growth may seem counterintuitive. Flow is the transport of lithium ions (Li) to the electrode, particularly to hot spots where dendrites can grow, as given independently by the first and second terms on the right side of equation (5), respectively. + ) flux. The ion flux is spatially perturbed by ion depletion adjacent to the hotspot for dendrite growth, which is given by the second term in the equation. However, along the electrode, x -1 / 3 The decaying higher-order convection term, such as , eliminates the localized ion flux maximum and is therefore key to the inhibition of dendrite growth. The combined contribution of both terms eliminates the localized ion transport maximum to the electrode and therefore eliminates the spatially localized growth spot on the electrode—the dendrite.

[0069] However, this suppression of dendrite growth occurs from x = 0 to x where the shear flow (or alternatively the electrode) begins. <x crit As x increases, the second of the two terms in equation (5) can become dominant, and x ≥ x critHot spots at θ begin to allow dendrite growth. To determine this critical length, we require the gradient of the ion flux to not change sign with x along the electrode, such that d(-i) / dx<0, avoiding localized ion flux maxima along the electrode. Substituting equation (5) into the inequality, replacing the spatial derivative of the term sin(kx)-√3cos(kx)ny by its numerical upper bound of 2, ignoring the quadratic (O(∈)) spatially monotonic contribution to the ion flux along the electrode surface, and thus comparing the higher-order spatially monotonic ion flux contributions with the higher-order (harmonic) contributions to the ion flux from the presence of dendrites, gives the following equation:

number

[0070] (5), and the corresponding estimate of the dendrite-free length of the electrode, x crit The corrections to the ion flux due to the presence of hot spots at are qualitative results. These quantitative magnitudes suggest that the contribution of ion depletion (adjacent to the hot spots) to the ion flux is proportional to the magnitude of the high-order (O(1)) convective effect (∈≒Pe -2 / 3 Therefore, x crit have shown that excitation of currents near the electrode inhibits dendrite growth, but only up to a limited electrode length that depends on the electrode properties. crit can increase when the density of hot spots and their intensity decrease, i.e., when reducing the excess of ion depletion adjacent to the hot spots. Alternatively, increasing the flow intensity can increase x crit It is clear that further increases. An interesting result here is that this length is independent of the details of the flow, but only if the Péclet number is significantly larger than 1. Here, a means of ensuring that the Péclet number is sufficiently large may be acoustic streaming.

[0071] Thus, in some exemplary embodiments, the frequency of the surface acoustic wave device can be selected to ensure that the length scale of acoustic wave attenuation matches the distance along the interelectrode gap (e.g., the length of the electrodes, the distance between the electrodes, etc.) over which flow needs to be driven. The integration of a small, high-frequency ultrasonic generator to drive electrolyte flow within the interelectrode gap can result in an ion flux distribution that stabilizes the potential location of dendrite growth within a specific distance from the ultrasonic source. The distance can be independent of the details of the flow, as long as the Peclet number is sufficiently large. This configuration may be feasible with acoustic streaming induced by the surface acoustic wave device, even with rapid charging rates and electrode material choices that would normally be considered impractical. As an example, a lithium-copper battery can be used at 6 mA cm while maintaining a coulombic efficiency of over 80% throughout. -2 Similarly, a lithium iron phosphate (LiFePO4) configuration can provide a discharge capacity of 95 mAh / g after 100 cycles at a charge and discharge rate of 2C.

[0072] As mentioned above, in some exemplary embodiments, batteries may be fabricated to include an integrated surface acoustic wave device. For example, to fabricate the lithium-copper battery described in connection with FIGS. 2-3, a 10 μm-thick copper electrode may be rinsed with acetone to remove surface impurities and oxides before use as an electrode, while a 100 μm-thick lithium anode may be discarded to remove the oxide layer before functioning as an electrode. A lithium iron phosphate (LFP) electrode may be prepared by mixing lithium iron phosphate powder, polyvinylidene fluoride (PVDF), and carbon black (C) in a ratio of 75%, 10%, and 15%, respectively. The powder is mixed with N-methyl-2-pyrrolidone (NMP) as a solvent to form a slurry, which is then cast onto aluminum foil and dried in a vacuum oven for 12 hours. The average mass loading is approximately 3.1 mg cm. -2The electrolyte used may be a commercial grade 1M solution of lithium hexafluorophosphate (LiPF6) (BASF) in a 1:1 (w / w) mixture of ethylene carbonate (EC) and diethyl carbonate (DEC). Finally, a Celgard 480 separator (Celgard Incorporation) may be interposed between the cathode and anode.

[0073] The surface acoustic wave device is a 500 μm thick 127.68 o A Y-rotated, X-propagated cut lithium niobate substrate (LiNbO3 (LN), Roditi) can be fabricated through a lift-off lithography process to deposit, for example, 28 pairs of unweighted gold-chromium (Au / Cr) fingers to form an integrated transducer (IDT). The surface acoustic wave device can be coated with Parylene C using chemical vapor deposition to prevent reaction with the electrolyte present in the battery. The baseline battery, as well as the battery with the integrated surface acoustic wave device, can be assembled in an argon-filled glove box, where moisture and oxygen levels are maintained at <1 ppm. The battery housing can include a nut, back ferrule, front ferrule, and body to seal the electrolyte and electrodes from exposure to air. The current collectors used in the battery can also be formed from stainless steel rods.

[0074] 8 illustrates an example of a battery cell 800 having an integrated surface acoustic wave (SAW) device 810. As shown in FIG. 8, the battery cell 800 may also include a first electrode 820a (e.g., a cathode), a second electrode 820b (e.g., an anode), and an electrolyte 830. The surface acoustic wave device 810, the first electrode 820a (e.g., a cathode), the second electrode 820b (e.g., an anode), and the electrolyte 830 may be provided inside a housing 840 of the battery cell 800. It should be understood that the battery cell 800 may be a lithium (Li) battery, a lithium-ion battery, a potassium (K) battery, a magnesium (Mg) battery, a copper (Cu) battery, a zinc (Zn) battery, a sodium (Na) battery, a potassium (K) battery, or the like. Each of the first electrode 820a and the second electrode 820b may be a metal electrode, a cation-intercalated composite electrode, an air electrode, a graphite electrode, a graphene electrode, a lithium-intercalated carbon electrode, a lithium-intercalated silicone electrode, a sulfur electrode, a tungsten electrode, a silicon electrode, a nitride electrode, a vanadium oxide electrode, a lithium-excess electrode, or the like.

[0075] In some exemplary embodiments, the surface acoustic wave device 810 may be configured to generate surface acoustic waves. However, it should be understood that the surface acoustic wave device 810 may also generate other types of acoustic waves, including, for example, Lamb waves, bending waves, thickness mode vibrations, mixed mode waves, longitudinal waves, shear mode vibrations, and / or bulk wave vibrations. The surface acoustic wave device 810 may include a transducer deposited on a substrate. The transducer may be configured to respond to an electrical input signal by applying at least tension and compression in and / or on the substrate. The substrate may respond to tension and compression by at least oscillating to generate a plurality of surface acoustic waves. The transducer may include one or more pairs of integrated transducers, a layer of conductive material, and / or one or more contact pins. The substrate may be made of, for example, lithium niobate (LiNbO), lithium titanate (LiTiO), barium titanate (BaTiO), lead zirconate titanate (Pb(Zr)), or other suitable materials. x Ti1-x )O3, where (0≦x≦1)), may be formed from piezoelectric materials including quartz, aluminum nitride (AlN), polyvinylidene fluoride (PVDF), and the like.

[0076] In some exemplary embodiments, a surface acoustic wave device, such as surface acoustic wave device 810, may be integrated inside or outside the battery case. When the surface acoustic wave device is integrated outside the battery case, one or more solvents may be used to couple the surface acoustic wave to the battery. It should be understood that the surface acoustic wave device may be integrated in a variety of different ways into various different types of battery cells. For example, in a pouch cell, the surface acoustic wave device may be attached to any surface of the pouch cell. In a cylindrical cell, the surface acoustic wave device may be positioned from the bottom and / or top flat surface or along the edge of the cylinder roll. In a coin cell, the surface acoustic wave device may be positioned on the flat surface or circular edge of the coin cell.

[0077] FIG. 13A shows a comparison of the electrochemical performance of a pouch cell with an externally integrated surface acoustic wave device and a baseline battery according to some exemplary embodiments. Referring to FIG. 13A, the electrochemical performance of a pouch cell, in this case a lithium-ion battery, having a surface acoustic wave device integrated into its outer casing, e.g., packing surface, can be compared to that of a baseline cell without an integrated surface acoustic wave device. Surface acoustic waves can be coupled into the battery through ultrasound gel to generate acoustic streaming within the battery. The battery can be tested with a 10-minute charge time and a 3-hour discharge time. FIG. 13B shows a clear improvement in energy density and capacity retention in the battery with the externally integrated surface acoustic wave device. The externally integrated surface acoustic wave device can enable the lithium-ion battery to deliver an energy density of 140 Wh / kg with 33% capacity retention over 100 cycles, while the baseline battery could only deliver an energy density of 110 Wh / kg with 20% capacity retention over 100 cycles. This improvement in cycling performance can be attributed to the acoustic flow of the electrolyte provided by the external integrated surface acoustic wave device.

[0078] FIG. 13B shows a comparison of the electrochemical performance of a pouch cell with an internal integrated surface acoustic wave device and a baseline battery according to some exemplary embodiments. Referring to FIG. 13B, the lithium-ion pouch cell with an internal integrated surface acoustic wave device and the baseline battery without an integrated surface acoustic wave device can be cycled with a 10-minute recharge time. FIG. 13B shows that compared to the baseline battery without an integrated surface acoustic wave device, the lithium-ion pouch cell with an internal integrated surface acoustic wave device exhibits superior cycling performance, including a 100% higher energy density (e.g., 100 Wh / kg with surface acoustic waves versus 55 Wh / kg for the baseline battery) and extended cycle life (2000 cycles with 80% capacity retention with surface acoustic waves versus nearly zero capacity retention after 200 cycles for the baseline battery).

[0079] In some exemplary embodiments, the internal morphology of a battery having an integrated surface acoustic wave device can be determined based on at least a feedback signal formed by reflection of one or more surface acoustic waves reflected from the surfaces of the battery's electrodes. For example, the surface acoustic wave device can generate one or more surface acoustic waves while the battery is being charged and / or discharged. These surface acoustic waves can propagate through an electrolyte filling the interior of the battery toward one or more electrodes of the battery before being reflected from the surfaces of the one or more electrodes. The surface acoustic wave device can be further configured to detect the feedback signal formed by reflection of these acoustic waves from the surfaces of the one or more electrodes.

[0080] A surface acoustic wave device can exhibit piezoelectric properties. For example, a surface acoustic wave device can include a transducer (e.g., one or more pairs of metallic integrated transducers, a layer of conductive material, contact pins, etc.) deposited on a substrate formed from a piezoelectric material. Thus, a surface acoustic wave device can generate multiple acoustic waves by converting at least an electrical signal into mechanical energy embodied by the acoustic waves. Furthermore, a surface acoustic wave device can detect a feedback signal by converting at least the mechanical energy of the feedback signal into an electrical signal. However, it should be understood that a different detector can be used to detect the feedback signal instead of and / or in addition to a surface acoustic wave device.

[0081] In some exemplary embodiments, a battery with an integrated surface acoustic wave device may be coupled with a controller configured to determine an internal morphology of the battery based at least on the feedback signal and to control operation of the battery based at least on the morphology. The controller may be configured to terminate operation of the battery in response to the feedback signal indicating an adverse morphology, including, for example, the presence of dendrites and / or bubbles on the surface of the first electrode and / or the second electrode. In response to detecting the presence of an adverse morphology, the controller may terminate operation of the battery by at least electrically isolating the battery from the battery's electrical load and / or other batteries in the same battery array.

[0082] FIG. 14 shows a block diagram illustrating an example of a surface acoustic wave battery system 1400, according to some exemplary embodiments. A top-level description of the circuit blocks of the surface acoustic wave battery system 1400 is shown in FIG. 15. Referring to FIGS. 14-15, the surface acoustic wave battery system 1400 may include a software control board for simultaneously performing interactive battery cycling and surface acoustic waveform generation. For example, the example surface acoustic wave battery system 1400 shown in FIGS. 14-15 may include a surface acoustic wave driver 1420 and a battery cycler 1430 coupled to a battery with an integrated surface acoustic wave device 1410 and controlled by a microcontroller 1440. Different portions of this circuit may require different power supply voltages. This may be provided, for example, by a power management block 1450 that receives a 12 VDC input from a wall outlet. The microcontroller 1430 shown in FIG. 16 may be designed similarly to an Arduino Nano and may be programmed using Arduino software. The microcontroller 1430 may be powered through a USB connection to a computer. To facilitate control using I2C, several IO expanders may be used.

[0083] FIG. 17 shows a circuit diagram illustrating an example of a surface acoustic wave driver 1420, according to some exemplary embodiments. In some exemplary embodiments, the surface acoustic wave driver 1420 can be configured to output a high-frequency signal in the range of 2.5 kHz to 200 MHz, which can be generated using a CMOS clock IC (Si5351). The surface acoustic wave driver 1420 can use an external 27 MHz crystal oscillator and a 3.3 V DC power supply. This high-frequency surface acoustic wave (SAW) signal can be fed to a clock buffer (CDCLVC11) with four outputs, and a square-wave modulation (PWM) signal from the microcontroller 1440 can be applied to the buffer's enable signal. An attenuator is used to control the power of this surface acoustic wave signal. The attenuation, ranging from 0.5 to 31.5 dB, can be adjusted using a 6-bit digital input, which has a 5 V power supply. Finally, the surface acoustic wave signal can be fed through a two-stage amplifier using an operational amplifier with a power supply "VDRV" ranging from 12 V to 37 V. If necessary, a matching network may be placed before the tuning SMA connector.

[0084] FIG. 18A shows a circuit diagram illustrating an example of a battery cycler 1430, according to some exemplary embodiments. In some exemplary embodiments, the battery cycler 1430 can use two power FETs (Q1, Q2): a p-channel for charging and an n-channel for discharging. These power FETs have a maximum rated drain current of 32 A and can operate from a 5 V power supply. To enable the charge or discharge function, switching transistors (Q4, Q5, Q16) may be used, as shown in FIG. 18A. The primary function of the battery cycler 1430 may be to generate a user-defined constant current for charging / discharging, which can be achieved using feedback control. The power FET drain current (Isen) can be sensed using an instrumentation amplifier (AD623). The output of this amplifier (Vref+Isen*Rsen*gain) may be fed back to the non-inverting side of an operational amplifier. On the inverting side, a DAC-generated voltage of (Vref+Ichg*Rsen*gain) may be applied, where Ichg is the required current. This feedback loop can adjust Isen to match Ichg. An ADC (ADS7924) can be used to read one or more essential values ​​such as battery voltage, battery current, temperature, etc.

[0085] FIG. 18B shows a circuit diagram illustrating an example of a battery cycler control circuit 1800, according to some exemplary embodiments. Referring to FIGS. 18A-18B, the battery cycler 1830 can include a control circuit 1800 configured to hard set fault conditions, such as over-discharge, over-charge, and over-temperature. When the battery voltage reaches 4.2V, MAX_CHGn can go high to prevent further charging. Similarly, when the battery voltage reaches 2.5V, MIN_CHGn can go high to prevent further discharging. If the thermistor attached to the battery 1410 reads 45C, TEMP_HIGHn goes high to prevent further charging and / or discharging. If a fault condition (e.g., CLEAR_FAULTSn) is falsely indicated, an external push button can be used to clear these fault conditions.

[0086] FIG. 19 shows a circuit diagram illustrating an example of a power management circuit 1450, according to some exemplary embodiments. Different DC power supply voltages may be used by different components throughout the circuit. All of these power supply voltages may be generated on-board from a 12VDC input. A step-down (12V to 5V) buck converter may be used to obtain the "5V0_BATT" power supply for the FETs in the battery cycler 1430. The "VDRV" voltage can be generated using a controllable boost converter to achieve a voltage between 12V and 37V. The remaining voltages (e.g., 5V0_CH, 5V0_SIG, 6.5V, 3.3V, etc.) can be generated using LDOs, as these voltages do not require high current.

[0087] 20 shows a block diagram illustrating an example of an electrical driver system 2000 for a surface acoustic wave device, according to some exemplary embodiments. Referring to FIG. 20, despite differences in required stimulation frequencies and power levels, electrical driver systems for various surface acoustic wave devices may include blocks for stimulus generation, amplification, power management, control, and user interface, as well as sensing and feedback.

[0088] In some exemplary embodiments, stimulus generation can be achieved by a class of semiconductor circuits known as "phase-locked loops" (PLLs) or "frequency synthesizers." This low-cost solution uses a reference crystal oscillator to generate very accurate and stable tones. The frequency is programmable over a specified range with very fine (<0.01 MHz) resolution. However, unlike the benchtop RF signal generators or arbitrary waveform generators (AWGs) that it replaces, the output amplitude of a phase-locked loop is typically fixed. Also, phase-locked loops may not be able to generate the output power required to drive acoustic surface wave devices, thus requiring an amplification block.

[0089] In some exemplary embodiments, a chain of amplifiers may be used to couple the output of the phase-locked loop to the input of the surface acoustic wave device, achieving increasingly higher voltage swings as needed (at the expense of higher supply or power consumption). Additionally, duty cycle control may be added using a clock buffer enable signal, an attenuator (using a dedicated chip or a simple resistor divider) may be used to fine-tune the signal amplitude, and a power amplifier with a push-pull output stage may be employed to efficiently deliver high current (power) to the surface acoustic wave device. The surface acoustic wave device itself may be modeled as a low-impedance load at the resonant frequency.

[0090] In some exemplary embodiments, a power management unit (PMU) can generate all of the voltage supplies (3.3V, 5V, 24V, etc.) required by the various semiconductor chips on a printed circuit board from a single battery or outlet. These circuits are commonly known as "DC-DC converters." A "boost converter" can be used to step up the voltage from input to output, and a "low dropout" (LDO) regulator can be used to step down the voltage. If greater efficiency is required, a "buck converter" can also be used to achieve the step-down function. This unit can replace a benchtop power supply.

[0091] In some exemplary embodiments, a microcontroller unit (MCU) such as an Arduino Nano can serve as the interface between the electronic driver system and the end user. Through a general-purpose I2C IO expander, the microcontroller can translate user input and send low-level digital signals to control all components on the printed circuit board (PCB). The microcontroller may be connected to a laptop through a USB connection for maximum programming and testing flexibility. It may also be pre-programmed with several options (e.g., power on / off, frequency up / down, etc.) selected by pushbuttons. Thus, the resulting surface acoustic wave battery system can be a completely self-contained, easy-to-use device.

[0092] While the electronics described above may be sufficient to drive a surface acoustic wave device, value-added features are still possible. For example, in some exemplary embodiments, the electrical driver system 2000 may include a thermistor to monitor the temperature of specific portions of the substrate. Once digitized and read by a microcontroller, the measurement data may be used to monitor operating conditions or within a feedback loop, for example, to automatically shut down a given component when it overheats. The electrical driver system 2000 may also incorporate a current sensor in the surface acoustic wave device itself to automatically detect the optimal resonant frequency to account for variations in boundary conditions against inevitable device-to-device variations, especially when liquid may be present on the surface of the surface acoustic wave device. These factors often shift the resonant frequency by 100 kHz or more, which may be enough to significantly degrade the performance of acoustic transducers with high Q factors.

[0093] For example, a phase-locked loop frequency range may be swept by a microcontroller, and the output current to the surface acoustic wave device may be measured, digitized, and recorded for each stimulation frequency. The range may be specified in an algorithm to minimize the time required to perform the sweep and to enable the selection of higher harmonics that may be useful in the transducer. The voltage amplitude V at the driver amplifier, the final stage of the signal chain, may be constant through a resistor feedback architecture. Therefore, the higher the output current amplitude I, the higher the power P delivered to the surface acoustic wave device (e.g., P = VI). Therefore, the frequency at which the measured current amplitude is maximized may correspond to the resonant frequency of the transducer.

[0094] In some exemplary embodiments, two-dimensional calculations can be performed to aid in the analysis of various battery cells, particularly to determine the change in concentration gradients within a lithium metal battery with or without acoustic streaming, as shown in Figure 1. For lithium metal batteries without an integrated surface acoustic wave device, the Electrochemistry Module was used with a physically controlled mesh, cubic current distribution, and Nernst-Planck interface. This interface describes the current and potential distribution within an electrochemical cell by considering the individual transport of charged and uncharged species (ions) in the electrolyte by diffusion, migration, and convection using the following Nernst-Planck equations:

number

[0095] For lithium metal batteries with integrated surface acoustic wave devices, the simulation is more complex and requires the sequential use of the electrochemistry module for acoustic pressure, creeping flow, and frequency and time domain calculations. The body force term (F i ) can be first obtained from the damped acoustic waves propagating in the electrolyte via the acoustic pressure module,

number

[0096] Wave attenuation in COMSOL can be modeled relative to the wave power (P) as follows:

number

[0097] The body force F obtained from this calculation i can be used in the creeping flow module, represented by a time-averaged derived equation from mass and momentum conservation to second order,

number

[0098] In some exemplary embodiments, a thin, electrochemically compatible, durable, and acoustically compatible material can be used to protect a surface acoustic wave device from corrosion from the electrolyte present in a lithium metal battery cell. Figure 9 shows scanning electron microscope (SEM) images of a lithium niobate (LN) substrate immersed in a carbonate-based electrolyte (e.g., EC / DEC). The initial morphology of the optically polished lithium niobate surface shown in Figures 9(a)-9(b) can be corroded after 7 days of immersion in the electrolyte, resulting in 100 μm-long fractal dendritic structures across the entire surface, as shown in Figures 9(c)-9(d). Therefore, to prevent corrosion caused by reaction with the electrolyte, the surface of the surface acoustic wave device can be coated with a protective material, such as a film of parylene.

[0099] Table 1 below shows the effect of parylene film on the performance of surface acoustic wave devices. As shown, the effect of 200 nm parylene coating is weak, and can reduce displacement, velocity, and acceleration by 2%. Therefore, parylene film can protect surface acoustic wave devices in harsh environments while having a negligible effect (e.g., <1%) on the performance of the surface acoustic wave device.

[0100] [Table 1]

[0101] Figures 9(e) and 9(f) show the longer-term effects of a carbonate-based electrolyte (e.g., ED / DEC) on a parylene-coated surface acoustic wave device that had been immersed in the electrolyte for two months. As shown, the surface morphology of the lithium niobate substrate and aluminum integrated transducer remains pristine. Figures 9(g) and 9(h) show the morphology of the parylene-coated surface acoustic wave device after 280 cycles. As shown, even after long-term cycling, the parylene coating remains stable on the surface of the surface acoustic wave device.

[0102] 10 shows a comparison of first cycle deposition performance of a lithium copper battery with and without surface acoustic waves, according to some exemplary embodiments. The lithium copper battery shown in FIG. 10 has a current of 1 mA / cm 2 and 6mA / cm 2 Figure 10(a) shows the current density of 1 mA / cm with (green) and without (black) the presence of surface acoustic waves. 2 Figure 10(b) shows a comparison of electrodeposition curves at a current density of 6 mA / cm with (green) and without (black) surface acoustic waves. 2 Electrodeposition curves at different current densities are compared.

[0103] FIG. 11 shows scanning electron microscope (SEM) images illustrating operations for obtaining lithium electrode porosity, according to some exemplary embodiments. Porosity can be determined for electrodes of a baseline battery (e.g., without an integrated surface acoustic wave device) shown in FIGS. 11(a)-11(c) as well as for batteries with integrated surface acoustic wave devices shown in FIGS. 11(d)-11(f). For each type of battery, FIGS. 11(a) and 11(c) can show top-down scanning electron microscope images of the lithium electrode that, when thresholded on the binary images shown in FIGS. 11(b) and 11(d), provide depth images suitable for determining porosity, shown in FIGS. 11(c) and 11(e).

[0104] In some exemplary embodiments, to overcome the difficulties associated with observing surface acoustic wave-induced electrolyte acoustic streaming, a "dummy" battery assembly made of transparent acrylic plates with water and polystyrene particles bound together may be employed to mimic the conditions in a real battery in an observable manner for a set of simple experiments designed to partially validate the COMSOL calculations and analytical results, particularly the induced fluid flow.

[0105] Because acoustic streaming is based on the presence of viscosity and compressibility in fluid flow, the typical assumption of incompressible Stokes flow at small scales or in batteries may be inappropriate. Instead, the full Navier-Stokes equations with conservation of momentum are used. Through knowledge of the amplitude distribution of surface acoustic wave sources in a representative setup using a laser Doppler vibrometer, velocity boundary conditions can be defined at the electrolyte boundary adjacent to the surface acoustic wave device.

[0106] Within the fluid domain, the prototype battery's configuration dimensions and 6 mAcm -2 The lithium ions (Li) present in the electrolyte under the action of insertion on the anode and extraction from the cathode according to the charging rate (equivalent to 6 C) + ) species, a convection-diffusion equation can be included. As shown in Figure 12, the analysis lacks the initial "hot spot" assumed to exist for the analysis, but still demonstrates the benefit of surface acoustic wave-driven acoustic streaming in reducing the non-uniform lithium ion distribution in the inter-electrode gap. At the beginning of charging, all lithium ions are shown to be in the anode (as shown in the top layer of the setup) for the baseline cell without surface acoustic waves and the cell with the integrated surface acoustic wave device (e.g., Figures 12(a) and 12(d)).

[0107] Returning again to FIG. 12, FIGS. 12(a)-12(c) can show the change in lithium ion concentration at 0%, 50%, and 100% state of charge (SOC) due to acoustic streaming. As shown, the concentration gradient can remain uniform throughout the charging process. In contrast, the concentration gradient of lithium ions in a baseline battery without surface acoustic waves at 0%, 50%, and 100% SOC is shown in FIGS. 12(d)-12(f), respectively. Here, the absence of surface acoustic waves is shown to be associated with a large change in the concentration gradient.

[0108] Referring again to equations (1)-(3), the problem associated with these equations is the transformation TIFF2026004293000016.tif9150, which can be made dimensionless and therefore simplified, to obtain the following equations (10) to (12).

number

[0109] Equations (10)-(12) can support the ion transport boundary layer and are therefore related to the unique asymptotic expansion of the concentration c in 1 / Pe. Thus, there is an outer concentration field away from the lithium electrode described by C, and an inner (boundary layer) concentration filed near the electrode described by c. To solve the inner (boundary layer) problem, we can change the coordinate y to y=YPe, so that the higher-order diffusion terms satisfy the convection. -n Both concentration fields may be rescaled in the form TIFF2026004293000018.tif7162 must be satisfied. Higher order concentration fields can be expressed as series expansions C=C0+∈C1+... and c=∈C 1+...can be expanded in powers of ∈ according to

[0110] For higher orders, the problem related to equations (10)-(12) in the external field can be solved as a system of equations.

number

number

number

number

[0111] This system of equations is satisfied by:

number

[0112] Taking the y-derivative of the higher order concentrations near the surface of the lithium electrode at Y=ζ=0 gives:

number

[0113] Therefore, the dimensional flux of ions to the electrode is

number

[0114] Since C0 is a constant, the next order problem shown in equations (10) to (12) in the external field can satisfy the following simultaneous equations:

number

[0115] The next order problem equations (10) to (12) in the inner field are

number

number

number

number

[0116] Therefore, the corresponding dimensional flux of the ions is

number

[0117] From equation (16) TIFF2026004293000034.tif8168 Omitting, Equation (17) is expressed as c 1,2 By replacing it with =coskx, c 1,2 The problem can be further stated as follows:

number

number

number

[0118] (21)~923) Conversion formula c 1,2 =f(Y)e ikx Using this gives the following alternative system of equations:

number

number

[0119] c 1,2 The real component of the Y derivative of is given by:

number

[0120] Therefore, the corresponding dimensional flux of the ions is

number

[0121] Finally, using equation (16), equation (17) is calculated as c 1,3 =0, and c 1,2 c) Be able to describe the problem. 1,3 The problem gives a spatially monotonic solution and requires a numerical solution. However, this solution does not lend itself to higher-order solutions for the dendrite-free length of the electrode. Therefore, in the following, we refer to solutions of this problem in terms of O(ε) orders of magnitude.

[0122] The total ion flux to the Li electrode is i=i0+ε(i 1,1 +i 1,2 +i 1,3 ), which transforms to:

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[0123] The subject matter described herein may be embodied in systems, devices, methods, and / or products, depending on the desired configuration. The implementations described in the foregoing description do not represent all implementations consistent with the subject matter described herein. Instead, they are merely some examples consistent with aspects related to the described subject matter. While several variations have been described in detail above, other modifications or additions are possible. In particular, additional features and / or variations may be provided in addition to those described herein. For example, the implementations described above may be directed to various combinations and subcombinations of the disclosed features and / or combinations and subcombinations of several additional features described above. Additionally, the logic flow illustrated in the accompanying drawings and / or described herein does not necessarily require the particular order shown, or sequential order, to achieve desired results. Other implementations may also be within the scope of the following claims.

Claims

1. The first electrode and The second electrode and An ion-containing electrolyte interposed between the first electrode and the second electrode, A housing that houses the first electrode, the second electrode, and the electrolyte, An elastic wave device is disposed on the outside of the housing and bonded to the housing using a binder, A battery equipped with, The electrolyte generates the flow of ions between the first electrode and the second electrode during charging and discharging of the battery. The binder is configured to bond the elastic waves generated by the elastic wave device to the housing, thereby transferring the elastic wave energy to the electrolyte via the acoustic flow passing through the housing, A battery in which the electrolyte is stirred by the acoustic current, and as a result the diffusion rate of the ions moving through the electrolyte increases, and the ion distribution in the electrolyte becomes uniform.

2. The battery according to claim 1, wherein the electrolyte is a liquid electrolyte comprising one or more of the following: water, carbonate-based electrolytes, ester-based electrolytes, ether-based electrolytes, ionic liquids, nitrile-based electrolytes, phosphate-based electrolytes, sulfur-based electrolytes, and sulfone-based electrolytes.

3. The battery according to claim 1, wherein the electrolyte is a polymer electrolyte or a solid electrolyte.

4. The elastic wave device includes a transducer disposed on a substrate, The transducer is configured to apply tension and compression within the substrate in response to an electrical input signal, The substrate generates the elastic wave by oscillating in response to the tension and compression. The battery according to claim 1.

5. The substrate is lithium niobate (LiNbO ３ ), lithium titanate (Li ２ TiO ３ ), barium titanate (BaTiO ３ ), lead zirconate titanate (Pb(Zr ｘ Ti １－ｘ )O ３ , where (0 ≤ x ≤ 1)), quartz, aluminum nitride (AlN), langasite, lead magnesium niobate-lead titanate (PMN-PT), lead-free potassium sodium niobate (K ０．５ Na ０．５ NbO ３ or KNN), a doped derivative of lead-free potassium sodium niobate, and a piezoelectric material selected from the group consisting of polyvinylidene fluoride (PVDF), the battery according to claim 4.

6. The elastic wave includes one or more of the following: surface elastic waves, Lamb waves, bending waves, thickness mode vibrations, mixed mode vibrations, longitudinal waves, shear mode vibrations, and bulk wave vibrations, as described in claim 1.

7. The battery according to claim 1, wherein the attenuation length of the elastic wave corresponds to at least one of the first length of the first electrode, the second length of the second electrode, and the distance between the first electrode and the second electrode.

8. The battery is connected to a circuit configured to drive the elastic wave device, The circuit includes a built-in battery charging circuit and an automatic resonance search function. The battery according to claim 1.

9. The battery according to claim 1, wherein the binder comprises an ultrasonic gel or a polymer layer configured to match the impedance between the elastic wave device and the housing.

10. The battery according to claim 1, wherein the elastic wave device is configured to selectively generate the elastic wave during charging or discharging of the battery.

11. The battery according to claim 1, wherein the frequency of the elastic wave is selected such that the Peclet number due to the acoustic flow is greater than 1 in the boundary layer adjacent to at least one surface of the first electrode and the second electrode.

12. The battery according to claim 1, wherein the elastic wave device has one or more pairs of integrated transducers.

13. The battery according to claim 1, wherein the battery comprises one of a lithium battery, a lithium-ion battery, a sodium battery, a potassium battery, a magnesium battery, a copper battery, or a zinc battery.

14. A method for operating a battery comprising a first electrode, a second electrode, an electrolyte, a housing, and an elastic wave device, The steps include generating elastic waves using the elastic wave device, A step of receiving a feedback signal in response to the elastic wave, The elastic wave is generated by the elastic wave device, The feedback signal corresponds to the reflection of at least a portion of the elastic waves generated by one or more components inside the battery. The housing forms the interior of the battery and houses the first electrode, the second electrode, and the electrolyte inside; The steps include determining the internal shape of the battery based on at least the feedback signal, A step of controlling the operation of the battery based at least on the shape inside the battery, Methods that include...

15. The method according to claim 14, wherein the control of the operation includes stopping the operation of the battery in response to a feedback signal indicating the presence of one or more of (a) a dendrite, (b) a bubble on the first electrode, or (c) a bubble on the second electrode.

16. The method according to claim 14, wherein the control of the operation includes stopping the operation of the battery in response to a feedback signal corresponding to one or more of the following: (a) the presence of detached dendrites, (b) damage to the solid electrolyte interface layer, and (c) the formation of a protective polymer layer on the elastic wave device.

17. The method according to claim 14, wherein the control of the operation includes electrically disconnecting the battery from an electrical load or another battery.

18. The method according to claim 14, wherein the control of the operation includes adjusting at least one of the frequency, amplitude, or duty cycle of the elastic wave generated by the elastic wave device.

19. The method according to claim 14, wherein the control of the operation includes temporarily suspending charging while maintaining the operation of the elastic wave device.

20. The method according to claim 14, wherein the feedback signal is generated by the reflection of elastic waves from the electrode surface.

21. The method according to claim 14, wherein the feedback signal is generated during the discharge of the battery.

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