Title of Invention: Systems, methods, and devices for health monitoring of an energy storage device Abstract: A monitoring device for a battery pack, which includes a plurality of battery cells, has at least one ultrasound source and at least one ultrasound sensor. The ultrasound source can be configured to generate and direct ultrasound at one or more battery cells of the battery pack. The ultrasound sensor can be configured to detect ultrasound reflected from or transmitted through one or more cells of the battery pack. A battery management unit receives one or more signals from the ultrasound sensor responsive to the detected ultrasound. The battery management unit can be configured to determine a state of the battery pack based at least in part on the detected ultrasound. Detailed Description: Part general_description_paragraphs: Part CROSS-REFERENCE TO RELATED APPLICATIONS: The present application is a continuation of U.S. application Ser. No. 14/912,113, filed Feb. 15, 2016, which is a national stage entry of International Application No. PCT/US2014/051013, filed Aug. 14, 2014, which claims the benefit of U.S. Provisional Application No. 61/866,300, filed Aug. 15, 2013, all of which are hereby incorporated by reference herein in their entireties. Part FIELD: The present disclosure relates generally to health monitoring of an energy storage device, and, more particularly, to ultrasonic assessment of lithium-ion battery cells to monitor a state of health. Part SUMMARY: Systems, methods, and devices for monitoring a state of health of an energy storage device, such as a lithium-ion battery cell, are disclosed herein. In general, an ultrasonic acoustic source and sensor can be disposed proximal to a surface of a battery cell, which may be part of a larger battery pack. The ultrasonic source and sensor can be used to nondestructively assess the internal condition of vital interfaces inside the battery cell. These interfaces can include the interface between the anode active material, the cathode material, and the respective current collector (e.g., a metallic current collector). Alternatively or additionally, the ultrasonic source and sensor can be used to monitor battery swelling, electrode expansion, and/or electrode ruffling among other things. The resulting information can used to determine a state of health of the battery cell and/or the battery pack. The information about the extent of degradation can be used for predicting the reliability and/or the remaining useful life of the battery cell and/or battery pack. In one or more embodiments of the disclosed subject matter, a health monitoring device comprises an ultrasound source and an ultrasound sensor. The ultrasound source is configured to generate and direct ultrasound at an energy storage device. The ultrasound sensor is configured to detect ultrasound reflected from or transmitted through the energy storage device and to generate a signal responsive to the detected ultrasound from the energy storage device. In one or more embodiments of the disclosed subject matter, a method of monitoring an energy storage device comprises applying ultrasound to an energy storage device and detecting ultrasound reflected from or transmitted through the energy storage device. The method further comprises generating a signal indicative of the detected ultrasound. In one or more embodiments of the disclosed subject matter, a battery system with state of health monitoring comprises a battery pack, one or more ultrasonic health monitoring devices, and a battery management system. The battery pack comprises a plurality of individual lithium-ion battery cells. Each ultrasonic health monitoring device is arranged to assess one of the lithium-ion battery cells and includes an ultrasound source that directs ultrasound at the respective lithium-ion battery cell. Each ultrasonic health monitoring device further includes an ultrasound sensor that detects ultrasound reflected from or transmitted through the respective lithium-ion battery cell and generates a signal responsive thereto. The battery management system is configured to receive the signal from each ultrasound sensor and to determine a state of health of the battery pack based at least in part on said signal. Objects and advantages of embodiments of the disclosed subject matter will become apparent from the following description when considered in conjunction with the accompanying drawings. Part DETAILED DESCRIPTION: In one or more embodiments of the disclosed subject matter, an energy storage device, such as a battery cell (e.g., a lithium-ion battery cell), can be non-destructively assessed using ultrasound in order to determine a state of health or other information regarding the interior structure of the energy storage device. In some embodiments, the ultrasonic assessment may occur while the energy storage device is in use (e.g., during charging or discharging of the battery cell) so as to provide real-time information regarding the state of health of the energy storage device in the field. Control or use of the energy storage device may be altered in response to the real-time information, for example, to take corrective action to address imminent failure of the energy storage device. Alternatively or additionally, the information can be used to predict reliability or determine the remaining useful life of a system incorporating the energy storage device, for example, a battery pack with multiple battery cells. In other embodiments, the ultrasonic assessment may occur when the energy storage device is not yet in service, for example, as part of a field return evaluation or manufacturing quality control. In any of the embodiments, health monitoring can be accomplished by monitoring confidence values computed by applying statistical pattern recognition techniques to the transient behavior of battery cells, transient responses, and correlation of the responses with models and validated with experimental data. To perform the ultrasonic assessment of the energy storage device, ultrasonic pulses generated by an ultrasound source (e.g., an ultrasound pulser or transducer) can be focused at specific depths within the energy storage device to be assessed. As the acoustic wave approaches an interface within the energy storage device, the acoustic wave may be partially or totally reflected. Such interfaces may be associated with changes in the internal volume of the energy storage device caused by delamination, voiding, or other phenomena. The intensity of the reflected wave and/or transmitted wave is a function of the acoustic impedance of the interface. The reflected and/or transmitted waves can thus provide a measure of changes in the internal structure of the energy storage device that may be indicative of imminent failure or increasing degradation. Lithium Ion Batteries In one or more embodiments of the disclosed subject matter, the energy storage device is a battery cell, for example, a lithium-ion battery cell. Lithium-ion battery cells are free of many of the deficiencies from which other rechargeable battery cells suffer, such as high self-discharge rates and memory effects due to partial charge and discharge. In addition, because of their high energy density, long cycle life, and battery cell voltage, lithium-ion cells have been adopted for use in portable electronics as well as automotive applications, for example, as an energy storage device for all-electric or hybrid vehicles. FIGS. 1A-1B are schematic diagrams of discharging and charging configurations, respectively, to illustrate various structures associated with a lithium-ion battery cell 100. In general, a lithium-ion battery cell 100 can include one or more cathode layers 104, one or more anode layers 102, respective current collectors on which the layers 102, 104 are disposed, a separator 106, and electrolytes 108 filling the interior volume of the battery cell 100. The electrolytes 108 can include a mixture of organic carbonate solvents (e.g., ethylene carbonate and dimethyl carbonate) and polymer salts (e.g., LiPF6), which provide conductivity for the transport of lithium ions 110 between the electrodes 102, 104. Electrical contact between the internal electrodes 102, 104 is made via anode terminal 112 and cathode terminal 114, respectively, which are disposed external to the interior volume of the battery cell. During the charging process (FIG. 1B), a current 118 is supplied to the cathode terminal 114 via a charging power source 126. Electron flow 120 is from the cathode terminal 114 to the charging power source 126. The cathode 104 has a high standard redox potential. As a result the current 118 and electron flow 120, the transition metal of the cathode 104 is oxidized and lithium ions 110b diffuse through the separator 106 to the anode 102, where they are intercalated into layers of, for example, carbon graphite to form LixC6. During the discharging process (FIG. 1A), a load 116 is connected between the cathode terminal 114 and the anode terminal 112. As a result, the electron flow 120 is from the anode terminal 112 to the cathode terminal 114 while the current 118 is in the opposite direction. As a result, the transition metal of the cathode 104 is reduced. In addition, lithium ions 110a are deintercalated from the anode 102 and move though the electrolyte 108 and the separator 106 back to the cathode 104. It is to be appreciated that FIGS. 1A-1B are simplified illustrations of the inner workings of a lithium-ion battery cell and that practical embodiments of a lithium-ion battery cell will include more complex arrangements than those illustrated. For example, the cathode and electrode layers can be arranged in an interdigitated fashion, with alternating layers of anode and cathode electrodes in a thickness direction of the battery cell. Such a battery cell 200 is illustrated schematically in FIG. 2A. Thus, the anode layers 202 are arranged between adjacent cathode layers 204, and vice versa. Each anode layer 202 and each cathode layer 204 may be connected (in parallel or in series) to the anode terminal 212 and the cathode terminal 214, respectively, which provides electrical connection to a load or charging device located external to the battery cell. A separator layer (not shown) is provided between each adjacent cathode 204 and anode 202. The multi-layered electrode separator structure 220 sits in an electrolyte solution within an interior volume of the battery cell 200 and operates in a similar manner as described above with respect to FIGS. 1A-1B. For simplicity of illustration and explanation, the electrodes and separator (including their arrangement and number) in the following drawings have been simplified as a number of parallel lines and referred to generally as 220. However, other arrangements and configurations for the structure of the battery cell beyond those specifically illustrated and discussed are also possible according to one or more contemplated embodiments. For example, the battery cell may have a so-called button configuration. In the button configuration, the battery cell may be substantially cylindrical with a top surface of the cylinder serving as one electrode terminal and a bottom surface of the cylinder serving as the other electrode terminal. The electrode layers within the button cell can be arranged perpendicular to an axis of the button cell, as annular layers extending along the axis of the button cell, or in any other arrangement. In another contemplated embodiment, the battery cell need not have clearly delineated electrode layers within the interior volume thereof. For example, the interior volume of the battery cell may be filled with a slurry and electrode terminals can extend into the interior volume to provide electrical contact thereto. In another example, the interior volume of the battery cell may comprise lumps of material rather than planar electrodes. Such configurations may suffer from similar degradation as the planar electrode configurations discussed above. One of ordinary skill in the art will appreciate that other battery cell configurations are also possible and will benefit from assessment using the disclosed ultrasonic health monitoring devices and techniques. Despite advances in materials, packaging technologies and state monitoring solutions, many challenges regarding reliable use of lithium-ion battery cells remain. Over the lifecycle of a lithium-ion battery cell, various thermal, mechanical, and electrochemical processes contribute to the degradation of the cell's performance. Lithium-ion batteries generally begin to degrade almost immediately after completion of manufacturing and continue to degrade during storage and use. Degradation due to self-discharge, which occurs during storage as well as during charge/discharge cycling, may depend on the ambient temperature, storage time, and the state of charge of the cell (e.g., fully charged, partially charged, fully discharged, etc.). Additional degradation during charge/discharge cycles can be accelerated based on high-temperature exposure, frequent charge/discharge cycles, deep discharge (i.e., approaching fully discharged before recharging), and overcharge (i.e., charging beyond a designated capacity of the battery cell). Vital interfaces where degradation may occur inside a lithium-ion battery cell include the interface between the metallic current collector and the active material for both the anode and cathode. Internal resistance can increase with complex chemical reactions between the active materials, electrodes, and the electrolyte. Battery materials may also be susceptible to expansion during charging. As a result, the anode or cathode layers within the battery cell may delaminate from their respective current collector, thereby causing a shift in charge and discharge properties of the battery. FIG. 2B depicts a battery cell 200a in an as-manufactured state. Battery cell 200a thus has a set initial thickness and an ordered arrangement of electrode layers 220 within the internal volume of the battery cell. However, with continued charge and discharge cycles, swelling, delamination, or other degradation can occur. FIG. 2C shows a battery cell 200b that has degraded after multiple charging/discharging cycles. In particular, the electrode layers 220 have deformed resulting in electrode ruffling. Volumetric expansion of the electrode particles can cause localized stress concentrations that ruffle the electrode. This can cause a loss of connectivity between the electrode active material particles and the electrically conductive particles included in the electrode matrix. Separation or delamination of the electrode material and the current collector can occur. As a result, the useful capacity of the battery cell decreases due to its reduced charge-transfer capabilities. FIG. 2D shows another battery cell 200c that has degraded after multiple charging/discharging cycles. For example, localized heating and abusive operating conditions can result in the release of gas species that can cause volumetric expansion and/or venting of the cell to relieve internal pressure. If the battery cell is overcharged, the cathode can become unstable and the electrolyte can decompose. Alternatively or additionally, if the battery cell is overdischarged, the current collector (e.g., made of copper) can dissolve and cause internal short circuiting. As a result, local hotspots within the cell may be created that cause a variety of chemical reactions that release gas as a by-product. The gas release can cause ruffling of the electrode layers 220, similar to that illustrated in FIG. 2C, and may further cause a swelling of a housing of the battery cell 200c, thereby resulting a change in thickness of the battery cell 200c and/or localized deformation of one or more surfaces of the housing of the battery cell 200c. In some cases, swelling of the housing of the battery cell 200d may be present without significant ruffling of the electrode layer 220, as illustrated schematically in FIG. 2E. In worst case scenarios, rapidly increasing temperatures and excessive gas generation can cause the cell to explode and catch fire. However, many cells exhibit less severe levels of gas generation over their lifetime. This gas generation contributes to internal structural changes to the cell that can degrade the battery over its life cycle. For example, gas pockets in cycled cells can lead to a degradation due to displacement of the electrodes, thereby making it more difficult to transport ions through the electrolyte. Additionally, porosity in the electrode can increase thereby lowering connectivity between adjacent electrode material particles. A significant consequence of this degradation is a drop in the capacity of the battery cell as it is charged and discharged. As used herein, capacity of a battery cell refers to the maximum current that a battery cell can supply over a given time period and is commonly expressed in ampere-hours (Ah). For example, if a battery cell is rated for 1000 mAh, then it should be capable of supplying 1000 mA over a one-hour period before it needs recharging. While capacity rating provides a basis for what type of battery can best meet the needs of a particular system, it only provides a measure of the battery's initial capabilities. Any decrease in capacity due to degradation of the battery cell during storage and/or use will compromise the battery's ability to deliver effectively store and deliver energy. Given the chemical, mechanical and thermo-dynamic processes that occur within the battery cell and contribute to the degradation, the battery cell can be monitored to provide real-time information. For example, metrics of interest for real-time monitoring include amount of degradation in battery capacity as well as, but not limited to, amount of remaining charge in a battery and remaining useful battery life. Knowledge of the internal state of the battery cell can help determine charging times, appropriate discharge strategies, balancing between different cells in a battery pack, and/or thermal management within a battery pack. The current capacity of a battery cell over the as-manufactured or initial capability can be used to define one metric for a battery cell's state of health. The state of health metric reflects the degradation of the battery and/or the battery pack and can be based on a decrease in the available capacity that a battery can deliver or an increase in the internal resistance thereof. The state of health metric can be determined using data obtained by measuring the voltage and current during the charge and discharge stages and estimating, for example, the decay in capacity and state of health based on current, voltage, and temperature measurements. In general, a 20% decrease in deliverable capacity can represent a threshold beyond which the battery performance begins to deteriorate rapidly. While a decrease in the deliverable capacity or an increase in internal resistance may reflect degradation in a lithium-ion battery system, this only relates to reduced performance and does not address safety. Gas generation and changes to the structure of the cell also capture performance-related information as well as information related to unsafe conditions that could be exacerbated as the battery cell is further stressed. Thus, investigation of the internal cell structure can help provide a more complete state of health evaluation that includes decreases in both performance and safety. Battery Health Monitoring Device Embodiments of the disclosed subject matter can use ultrasonic assessment of the internal structure of an energy storage device, for example, a battery cell, in order to provide information regarding a state of health of the assessed battery cell. Such information can be used alone or in conjunction with other state of health metrics to provide a more complete picture of the state of health of a battery cell or a battery pack including multiple battery cells. Ultrasonic assessment detects changes in acoustic impedance, such as an interface between two materials, through measurement of reflected and/or transmitted acoustic signals. Modes of assessment can include a pulse-echo mode, a through-transmission mode, or both. In the pulse-echo mode, a sensor is arranged to detect ultrasound reflected from the interior of the battery cell. In the through-transmission mode, a sensor is arranged to detect ultrasound transmitted through the interior of the battery cell (e.g., by being located opposite the ultrasonic source or on a side of the battery cell opposite the ultrasonic source). In either mode, the source and sensor are configured to generate and detect, respectively, sound having a frequency in the ultrasound range, for example, greater than 1 MHz. These assessment modes can be used to assess, among other things, swelling, electrode expansion, electrode delamination, voiding, and/or electrode ruffling within an assessed battery cell. These degradation mechanisms may be related to degradation resulting from, for example, typical charge/discharge cycling, intermittent operation at an elevated temperature that may be within or above specified operating limits, or mechanical and thermomechanical stresses acting on the cell during its operation. Based on the detected ultrasound, a metric can be provided for the degradation within the battery cell. For example, the amplitude of the reflected pulse and/or transmitted pulse can be used as a metric to assign a degradation level to the electrodes within the battery. Alternatively or additionally, a controller can make a determination about the state of health of the battery cell based on the detected ultrasound alone or along with other information regarding operating characteristics of the battery cell. The ultrasonic source (e.g., a pulser or transducer) can emit pulses of ultrasonic energy at a specific frequency. Selection of the appropriate ultrasonic source and the corresponding assessment frequency can be based on the battery cell to be investigated, including among other things, the thickness of the battery cell, the geometry of the battery cell, and the temperature of assessment. Generally, a lower frequency transducer can be used to penetration into thick, more attenuating, and/or highly scattering battery cell materials, and a higher frequency transducer can be used for thinner, lower attenuating, and/or lower scattering battery cell materials. The ultrasonic source can be provided adjacent to an external surface of the battery cell and arranged to direct the ultrasonic energy into the interior of the battery cell. For example, an emission direction of the ultrasonic energy may be perpendicular to the plane of one or more electrode layers within the interior of the battery cell. The ultrasonic sensor (e.g., a transducer) can detect ultrasonic energy in a broad range of ultrasound frequencies or limited to the specific frequency emitted by the ultrasonic source. As with the ultrasonic source, the ultrasonic sensor can be provided adjacent to an external surface of the battery cell and arranged to detect ultrasonic energy coming from the interior of the battery cell, e.g., reflected or transmitted ultrasound. In some embodiments, the ultrasonic source and the ultrasonic sensor can be parts of a single transducer, for example, for use in a pulse-echo mode configuration. In other embodiments, the source and sensor can be separate components disposed at different portions on the battery cell. The ultrasonic source and/or the ultrasonic sensor can be disposed on the battery cell through a respective couplant. For example, the couplant may be disposed between and in contact with an external surface of the battery cell and a corresponding active surface of the ultrasonic source and/or the ultrasonic sensor. Thus, ultrasound traveling to or from the battery cell would pass through the couplant. The couplant provides a pathway to/from the battery cell for the ultrasound in order to avoid attenuation due to exposure of the ultrasound to air or other high attenuation mediums, which may otherwise compromise assessment of the battery cell. The couplant may be a separate component, for example, an encapsulated gel or gel pad, that is placed between the battery cell and the source or sensor, or attached to the source, sensor, or battery cell surface. Alternatively, the couplant may be integrated with the source or the sensor, e.g., as the material of an emission or detection face thereof. Appropriate couplants can be selected based on acoustic velocity, impedance, and attenuation, as well as other factors, for example, as discussed in “Approximate Material Properties in Isotropic Materials,” published in IEEE Transactions on Sonics and Ultrasonics, May 1985, SU-32(3): pp. 381-94, which is hereby incorporated by reference herein. In some embodiments, the couplant is a hydrocarbon grease. In other embodiments, the couplant is a pad of encapsulated gel. For example, the gel pad includes one or more polymers having an attenuation with respect to the applied ultrasonic frequencies similar to or approaching that of water. The gel can be a dry couplant elastomer comprising a blend of isomers of branched homopolymers with an attenuation of 5 dB relative to water, for example, as described in “Ultrasonic Properties of a New Low Attenuation Dry Couplant Elastomer,” by Ginzel et al., April 1994, which is also incorporated by reference herein in its entirety. Other examples of couplants include but are not limited to the Water Gel Ultrasound Solid Gel Pad by BlueMTech (BlueMTech, Korea) and the AquaFlex® Ultrasound Gel Pad (Parker Laboratories, USA). Other couplants can also be used according to one or more contemplated embodiments. The detected ultrasound from the battery cell may be evaluated as either an A-scan or C-scan. In general, A-scans can provide a determination of the state of health of the battery cell, and C-scan can be used to image an interior of the battery cell, for example, to visualize and locate regions of degradation. As used herein, A-scan refers to an amplitude modulation scan, i.e., the actual waveform of the acoustic signal obtained by the sensor. After application of an ultrasonic pulse to the battery cell, the resulting detected signal can be graphed where the horizontal axis is time and the vertical axis is amplitude. In contrast, C-scan refers to scanning the transducer in one or two dimensions, e.g., raster-scanning the source/sensor over the entire surface area of the battery cell to produce a digitized image. After application of an ultrasonic pulse at each scanned position, the resulting detected signal at a particular time (corresponding to a particular depth in the battery cell, for example, as determined by placement of the data gate) is graphed to provide a map of the interface at that depth. The data gate targets an interface of interest within the thickness of the sample through the assessment of a portion of the corresponding A-scan waveform. For example, the interface of interest can be defined by positioning a rectangular frame over the portion of the A-scan that corresponding with the interface of interest using appropriate image processing software. The larger the time value associated with the data gate on the time axis of the A-scan, the greater the depth of interface of interest within the battery cell. By moving the gate position in time on the A-scan, different depths within the sample can be imaged. If air, gas, or another medium is present at a particular interface, all of the ultrasonic signal from that particular region may be reflected back, which results in detectable areas on a C-scan. The presence of air or gas pockets due to inner delaminated regions or voids will also cause the shape of the A-scan waveforms, which are taken at different points over the interface of interest, to be different in the data-gate region. In cases of extreme delamination or separation between active material and corresponding current collector, a phase inversion of the A-scan signal occurs at the data-gate region. In one or more embodiments, a battery health monitoring device uses transmitted ultrasound to assess the internal volume of a battery cell, as described above, to make a determination regarding the state of health of the battery. For example, the battery health monitoring device 300 can be configured in a through-transmission mode for interrogating battery cell 200, as shown in FIG. 3A and FIG. 3B. The battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. An ultrasound source 304 is disposed on a first side of the battery cell 200 with a couplant 306 between the battery cell 200 and the source 304. For example, an ultrasonic pulse 308 from the source 304 may be directed substantially perpendicular to the plane of one or all electrode layers 220 within the interior of the battery cell. Alternatively or additionally, at least an emission face of the source 304 is arranged substantially parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200. The ultrasound sensor 310 can be disposed on a second side of the battery cell 200 opposite to the first side and arranged to receive the ultrasonic pulse 308 transmitted through the interior volume of the battery cell 200. Although not shown, the sensor 310 may also be disposed with a couplant between the battery cell 200 and the sensor 310. The sensor 310 can be arranged directly opposite to the source 304 so as to receive ultrasound 308 traveling in a straight line through the thickness of the battery cell 200, i.e., from a first side of the battery cell 200 facing the source 304 to a second side of the battery cell 200 facing the sensor 310. A controller 312 (i.e., control unit) can be provided to control operation of the ultrasound source 304 and the ultrasound sensor 310 and to determine a state of health of the battery cell 200 based on signals from the ultrasound sensor 310. For example, the controller 312 may command the ultrasound source 304 to apply an ultrasonic pulse to the battery cell 200. The ultrasound sensor 310 can generate a signal based on detected ultrasound and convey the signal to the controller 312, which may use the signal to compose an A-scan. The resulting A-scan can be evaluated based on timing and/or amplitude of the detected pulse, for example, to make a determination regarding state of health of the battery cell 200. Such evaluation can include, but is not limited to, a comparison of the resulting A-scan with a previously obtained A-scan, which may be an A-scan of the battery cell 200 that was taken when the battery cell was in an as-manufacture or as-delivered non-cycled state. The controller 312 can also be configured to control the battery cell 200, for example, to alter charging, discharging, or other operations of the battery cell based on its determined state of health. The source 304 and the sensor 310 can be disposed to assess one portion of the interior of the battery cell 200, for example, where structures within the interior of the battery cell 200 may be especially susceptible to degradation. Alternatively or additionally, the source 304 (and couplant 306) and the sensor 310 can move along a length (i.e., from left to right in FIG. 3A) and/or a width (i.e., into or out of the page in FIG. 3A) of the battery cell 200 to assess different portions of the battery cell 200. For example, the source 304 and the sensor 310 can move in order to obtain a C-scan of the battery cell 200 in order to image a particular defect or degradation. Controller 312 may control the source 304 and/or the sensor 310, for example, through an appropriate displacement mechanism, to provide the desired movement. In one or more additional embodiments, a battery health monitoring device uses reflected ultrasound to assess the internal volume of a battery cell, as described above, to make a determination regarding the state of health of the battery. For example, the battery health monitoring device 400 can be configured in a pulse-echo mode for interrogating battery cell 200, as shown in FIG. 4. As with the previously described embodiment, the battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. A transducer 402 is disposed on a first side of the battery cell 200 with a couplant 306 between the battery cell 200 and the transducer 402. The transducer 402 includes both an ultrasound source portion 404 and an ultrasound sensing portion 410. Although shown as separate portions, it is contemplated that the source portion 404 and the sensing portion 410 can be the same structure, for example, an active portion of the transducer 402 that serves an emitter when the ultrasound is emitted and then serves as a sensor after the ultrasound pulse is emitted. For example, the ultrasound 308 (e.g., an ultrasonic pulse) from the source portion 404 may be directed substantially perpendicular to the plane of one or all electrode layers 220 within the interior of the battery cell. Alternatively or additionally, at least an emission/detection face of the transducer 402 is arranged substantially parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200. The sensing portion 310 receives ultrasound 408 reflected from structures (e.g., electrode layers 220) within the interior volume of the battery cell 200. A controller 312 can be provided to control operation of the transducer 402 and to determine a state of health of the battery cell 200 based on signals from the transducer 402. For example, the controller 312 may command the transducer 402 to apply an ultrasound 308 to the battery cell 200. The transducer 402 can generate a signal based on detected ultrasound and convey the signal to the controller 312, which may use the signal to compose an A-scan. The resulting A-scan can be evaluated based on timing and/or amplitude of the detected energy, for example, to make a determination regarding state of health of the battery cell 200. Such evaluation can include, but is not limited to, a comparison of the resulting A-scan with a previously obtained A-scan, which may be an A-scan of the battery cell 200 that was taken when the battery cell was in an as-manufacture or as-delivered non-cycled state. The controller 312 can also be configured to control the battery cell 200, for example, to alter charging, discharging, or other operations of the battery cell based on its determined state of health. The transducer 402 can be disposed to assess one portion of the interior of the battery cell 200, for example, where structures within the interior of the battery cell 200 may be especially susceptible to degradation. Alternatively or additionally, the transducer 402 (and couplant 306) can move along a length (i.e., from left to right in FIG. 4) and/or a width (i.e., into or out of the page in FIG. 4) of the battery cell 200 to assess different portions of the battery cell 200. For example, the transducer 402 can move in order to obtain a C-scan of the battery cell 200 in order to image a particular defect or degradation. Controller 312 may control the transducer 402, for example, through an appropriate displacement mechanism, to provide the desired movement. Alternatively or additionally, the transducer 402 may be fixed while the battery cell 200 is moved with respect to the transducer 402 to assess different portions of the battery cell 200. For example, the transducer can include a roller or wheel-shaped contact portion, such as but not limited to the Olympus Roller Ultrasonic Transducer (e.g., part number RT-0105-16SY by Olympus Corporation). In one or more additional embodiments, a battery health monitoring device can use transmitted and reflected ultrasound, either simultaneously or sequentially, to assess the internal volume of the battery cell to make a determination regarding the state of health of the battery cell. For example, the battery health monitoring device 500, as shown in FIG. 5, can combine the through-transmission assessment features of the embodiment of FIGS. 3A-3B and the pulse-echo assessment features of the embodiment of FIG. 4. As with the previously described embodiments, the battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. In addition, as with the previously described embodiments, the device 500 can be disposed to assess a single portion of the battery cell 200, or the device 500 and/or the battery cell 200 can be moveable to assess different portions of the battery cell 200, for example, to obtain a C-scan. The controller 312 controls operation of the transducer 402 and sensor 310 and determines a state of health of the battery cell 200 based on signals from the transducer 402 and sensor 310. For example, the controller 312 may command the transducer 402 to apply an ultrasonic pulse 308 to the battery cell 200. Transducer 402 generates a signal based on detected, reflected ultrasound 408 and conveys a first signal to the controller 312, while sensor 310 generates a signal based on detected, transmitted ultrasound 308 and conveys a second signal to the controller 312. The controller 312 may use the first and second signals to determine a state of health of the battery cell, for example, by evaluating timing and/or amplitude in the detected signals and/or by comparison to previously obtained A-scans. For example, the controller 312 can use reflected ultrasound signals to localize degradation planes within the battery cell 200 while the transmitted ultrasound signals are used to measure the degree of degradation within the battery cell 200. The controller 312 can also be configured to control the battery cell 200, for example, to alter charging, discharging, or other operations of the battery cell based on its determined state of health. In one or more additional embodiments, a battery health monitoring device 600 uses reflected ultrasound to assess the internal volume of a battery cell 200, as shown in FIG. 6. Similar to the embodiment of FIG. 4, battery health monitoring device 600 is configured in a pulse-echo mode for interrogating battery cell 200. However, the ultrasound source 604 and the ultrasound sensor 610 are separate from each other and spaced on a first side of the battery cell 200. The ultrasound source 604 is disposed with an angled couplant 606 between the battery cell 200 and the source 604. The couplant 606 supports the source 604 in an angled configuration with respect to the surface of the battery cell 200 and/or the electrode layers 220 therein. Thus, the ultrasonic pulse 308 from the source 604 may be directed at an angle (i.e., not perpendicular or parallel) with respect to one or all electrode layers 220 within the interior of the battery cell. Alternatively or additionally, at least an emission face of the source 604 is arranged at angle with respect to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200. The ultrasound sensor 310 can be arranged to receive ultrasound 608 reflected from structures (e.g., electrode layers 220) within the interior volume of the battery cell 200. The ultrasound sensor 310 can be arranged with an active face thereof parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200, as shown in FIG. 6. Alternatively, the ultrasound sensor 310 may have an angled configuration similar to that of ultrasound source 604, but shifted to be aligned with a direction of the reflected ultrasound 608. As with the previously described embodiments, controller 312 can be provided to control operation of the source 604 and the sensor 610 and to determine a state of health of the battery cell 200 based on signals from the sensor 610. The battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. The source 604 and the sensor 610 can be disposed to assess one portion of the interior of the battery cell 200, for example, where structures within the interior of the battery cell 200 may be especially susceptible to degradation. Alternatively or additionally, the source 604 (and couplant 606) and the sensor 610 can move along a length (i.e., from left to right in FIG. 6) and/or a width (i.e., into or out of the page in FIG. 6) of the battery cell 200 to assess different portions of the battery cell 200. For example, the source 604 and the sensor 610 can move in order to obtain a C-scan of the battery cell 200 in order to image a particular defect or degradation. Alternatively or additionally, the angle of the source 604 (or the angle of the sensor 610, when angled) can be varied to assess different portions of battery cell 200. Controller 312 may control the source 604 and/or the sensor 610, for example, through an appropriate angling and displacement mechanism, to provide these desired movements. In one or more additional embodiments, a battery health monitoring device 700 uses transmitted ultrasound to assess the internal volume of a battery cell 200, as shown in FIG. 7. Similar to the embodiment of FIG. 3A, battery health monitoring device 700 is configured in a through-transmission mode for interrogating battery cell 200. However, the ultrasound source 604 and the ultrasound sensor 710 are spaced from each other in a length direction of the battery cell. The ultrasound source 604 is disposed with an angled couplant 606 between the battery cell 200 and the source 604. The couplant 606 supports the source 604 in an angled configuration with respect to the surface of the battery cell 200 and/or the electrode layers 220 therein. Thus, the ultrasonic pulse 308 from the source 604 may be directed at an angle (i.e., not perpendicular or parallel) with respect to one or all electrode layers 220 within the interior of the battery cell. Alternatively or additionally, at least an emission face of the source 604 is arranged at angle with respect to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200. The ultrasound sensor 710 can be arranged to receive ultrasound 308 transmitted through the interior volume of the battery cell 200. The ultrasound sensor 710 can be arranged with an active face thereof parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200, as shown in FIG. 7. Alternatively, the ultrasound sensor 710 may have an angled configuration parallel to that of ultrasound source 604 so as to be aligned with a direction of the transmitted ultrasound 608. As with the previously described embodiments, controller 312 can be provided to control operation of the source 604 and the sensor 710 and to determine a state of health of the battery cell 200 based on signals from the sensor 710. The battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. The source 604 and the sensor 710 can be disposed to assess one portion of the interior of the battery cell 200, for example, where structures within the interior of the battery cell 200 may be especially susceptible to degradation. Alternatively or additionally, the source 604 (and couplant 606) and the sensor 710 can move along a length (i.e., from left to right in FIG. 7) and/or a width (i.e., into or out of the page in FIG. 7) of the battery cell 200 to assess different portions of the battery cell 200. For example, the source 604 and the sensor 710 can move in order to obtain a C-scan of the battery cell 200 in order to image a particular defect or degradation. Alternatively or additionally, the angle of the source 604 (or the angle of the sensor 710, when angled) can be varied to assess different portions of battery cell 200. Controller 312 may control the source 604 and/or the sensor 710, for example, through an appropriate angling and displacement mechanism, to provide these desired movements. In one or more additional embodiments, a battery health monitoring device 800 uses transmitted ultrasound to assess the internal volume of a battery cell 200, as shown in FIG. 8. Similar to the embodiment of FIG. 3A, battery health monitoring device 800 is configured in a through-transmission mode for interrogating battery cell 200. However, an array 810 of ultrasound sensors 310 is provided on the opposite side of the battery cell 200 from the ultrasound source 304. For example, the ultrasonic pulse 308 from the source 304 may be directed substantially perpendicular to the plane of one or all electrode layers 220 within the interior of the battery cell. Alternatively or additionally, at least an emission face of the source 304 is arranged substantially parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200. An ultrasound sensor 310 can be arranged to directly opposite the ultrasound source 304 so as to receive the ultrasound pulse 308 transmitted through the interior volume of the battery cell 200. The remaining ultrasound sensors 310 of the array 810 can be arranged to receive any spreading 808 of the ultrasound 308, for example, due to expansion of the ultrasound wave in the interior of the battery cell 200 and/or scattering or deflection by internal structures (e.g., electrode layers 220) of the battery cell. Each ultrasound sensor 310 can be arranged with an active face thereof parallel to an external surface of the battery cell 200 and/or the plane of one or all electrode layers 220 within the interior of the battery cell 200, as shown in FIG. 8. As with the previously described embodiments, controller 312 can be provided to control operation of the source 304 and the sensors 310 and to determine a state of health of the battery cell 200 based on signals from the sensors 310. The battery cell 200 may be connected to a load or charger 302 via terminals 212, 214 such that the battery cell 200 may be assessed while the battery cell 200 is in use, for example, during discharging or charging. The source 304 can be disposed to assess one portion of the interior of the battery cell 200, for example, where structures within the interior of the battery cell 200 may be especially susceptible to degradation. Alternatively or additionally, the source 304 (and couplant 306) and, optionally one or more of sensors 310 of the array, can move along a length (i.e., from left to right in FIG. 8) and/or a width (i.e., into or out of the page in FIG. 8) of the battery cell 200 to assess different portions of the battery cell 200. For example, the source 304 can move with respect to the sensor array 810, with different sensors 310 of the array serving as the sensor directly opposite the source 304 as the source 304 moves, in order to obtain a C-scan of the battery cell 200 and to image a particular defect or degradation. Controller 312 may control the source 304 and/or the sensor array 810, for example, through an appropriate displacement mechanism, to provide these desired movements. In an alternative embodiment, multiple sources 304 can be provided as an array 904 similar to the array 810 of sensors 310, as illustrated in the battery health monitoring device 900 of FIG. 9. In such a configuration, each source 304 of the source array 904 may be arranged opposite to and correspond to a particular sensor 310 of the sensor array 810. To prevent cross-talk between adjacent sensors 310, each source 304 may be activated separately such that the corresponding through pulse 308 is detected by the corresponding sensor 310 before the next source 304 in the array is activated. Alternatively, sources 304 with sufficient spacing between each other may be activated at the same time, where the spacing minimizes the amount of cross-talk that may be detected by the corresponding sensors 310. For example, every other source 304 in array 810 may be actuated at the same time. In yet another alternative, sources 304 may be simultaneously activated and the sensors 310 of the array 810 simultaneously sampled and the resulting signals used in combination by the controller 312 to determine a state of health. In still another alternative embodiment, multiple sources can be provided as a source array similar to that illustrated FIG. 9, but with multiple sensors corresponding to each source of the source array. Thus, the number of sensors in the sensor array may be more than the number of sources in the source array. For example, each source can have a primary sensor disposed directly opposite thereto and secondary sensors with the primary sensor therebetween, but the secondary sensors do not have a source disposed directly opposite thereto. Activation of each source may be sequential or simultaneous, for example, as described above with respect to FIG. 9. In one or more additional embodiments, a battery health monitoring device 1000 uses reflected ultrasound to assess the internal volume of a battery cell 200, as shown in FIG. 10. Similar to the embodiment of FIG. 4, battery health monitoring device 1000 is configured in a pulse-echo mode for interrogating battery cell 200. However, a first array 1002a of ultrasound transducers 402 is provided on a first side of the battery cell 200, and optionally, a second array 1002b of transducers 402 can be provided on a second side opposite to the first side. Each transducer 402 may emit a pulse 308 into the interior of the battery cell 200 and can detect the resulting reflection from internal structures (e.g., electrode layers 220) within the battery cell 200. To prevent
{'bibliographic_information': "{'country': 'US', 'doc-number': '15996442', 'kind': 'B2', 'date': '20180602', 'extension': '3', 'disclaimer_text': 'This patent is subject to a terminal disclaimer.', 'invention_title': 'Systems, methods, and devices for health monitoring of an energy storage device'}", 'source_file': './grant/2020/ipg200602.xml', 'source_data': 'USPTO-Grant'}