PIEZOELECTRIC MECHANISM FOR ACTIVE PRESSURE CONTROL FOR IMPROVED BATTERY PERFORMANCE

Abstract

A vehicle, a pressure control device, and a method for controlling the pressure in a vehicle battery. The pressure control device comprises a carrier plate, a pressure plate, and an actuator. The pressure plate is configured to move relative to the carrier plate. The battery is positioned between the carrier plate and the pressure plate. The actuator alternates between a first form and a second form to move the pressure plate relative to the carrier plate and control the pressure in the battery.

Description

INITIATIONThe present disclosure relates to increasing the performance of a battery, and more particularly to controlling the pressure applied to a battery operating under high pressure conditions to increase its performance.A lithium metal battery (LMB) may be used for the power supply of an electric vehicle. When the LMB is operated under low pressure conditions, dimers may grow between the anode and the cathode of the battery. These dendrimers limit the life and effectiveness of the LMB. However, the dendritic growth may be reduced by operating the LMB under high pressure conditions. Accordingly, it is desirable to provide a method and apparatus for pressurizing the battery during operation.SUMMARYIn an exemplary embodiment, a pressure control device for controlling pressure in a battery is disclosed. The pressure control device includes a backing plate, a pressure plate, and an actuator. The pressure plate is configured to move with respect to the support plate. The battery is disposed between the support plate and the pressure plate. The actuator is configured to switch between a first shape and a second shape to move the pressure plate relative to the backing plate and control the pressure in the battery.In addition to one or more of the features described herein, the actuator includes a piezoelectric material ribbon extending from a first end to a second end, the piezoelectric material ribbon coupled to a control plate at the first end by a first carrier and to the control plate at the second end by a second carrier.In addition to one or more of the features described herein, one of: the first end is fixed to the first carrier and the second end is fixed to the second carrier, the first end is fixed to the first carrier and the second end is slidable with respect to the second carrier, and the first end is slidable with respect to the first carrier and the second end is slidable with respect to the second carrier.In addition to one or more of the features described herein, the actuator further comprises a steel strip coupled to the piezoelectric material.In addition to one or more of the features described herein, the steel strip is biased toward one of the first and second dies.In addition to one or more of the features described herein, the control plate is fixed with respect to the carrier plate.In addition to one or more of the features described herein, the pressure control device further comprises a pressure sensor configured to measure a pressure within the battery and a controller configured to control a current through the actuator based on the pressure.In another embodiment, a method of controlling pressure in a battery is disclosed. The method includes disposing the battery between a carrier plate and a pressure plate configured to move relative to the carrier plate, and energizing an actuator to transition between a first shape and a second shape to move the pressure plate relative to the carrier plate to control pressure within the battery.In addition to one or more of the features described herein, the actuator includes a piezoelectric material ribbon extending from a first end to a second end, the piezoelectric material ribbon coupled to a control plate at the first end by a first carrier and to the control plate at the second end by a second carrier.In addition to one or more of the features described herein, one of: the first end is fixed to the first carrier and the second end is fixed to the second carrier, the first end is fixed to the first carrier and the second end is slidable with respect to the second carrier, and the first end is slidable with respect to the first carrier and the second end is slidable with respect to the second carrier.In addition to one or more of the features described herein, the actuator further comprises a steel strip coupled to the piezoelectric material.In addition to one or more of the features described herein, the steel strip is biased toward one of the first and second dies.In addition to one or more of the features described herein, the control plate is fixed with respect to the carrier plate.In addition to one or more of the features described herein, the method further comprises measuring a pressure within the battery using a pressure sensor and controlling a current through the actuator based on the pressure.In yet another embodiment, a vehicle is disclosed. The vehicle includes a battery and a pressure control device. The pressure control device includes a backing plate, a pressure plate configured to move relative to the backing plate, the battery disposed between the backing plate and the pressure plate, and an actuator configured to switch between a first shape and a second shape to move the pressure plate relative to the backing plate to control pressure in the battery.In addition to one or more of the features described herein, the actuator includes a piezoelectric material ribbon extending from a first end to a second end, the piezoelectric material ribbon coupled to a control plate at the first end by a first carrier and to the control plate at the second end by a second carrier.In addition to one or more of the features described herein, one of: the first end is fixed to the first carrier and the second end is fixed to the second carrier, the first end is fixed to the first carrier and the second end is slidable with respect to the second carrier, and the first end is slidable with respect to the first carrier and the second end is slidable with respect to the second carrier.In addition to one or more of the features described herein, the actuator further comprises a steel strip coupled to the piezoelectric material.In addition to one or more of the features described herein, the steel strip is biased toward one of the first and second dies.In addition to one or more of the features described herein, the vehicle further comprises a pressure sensor configured to measure a pressure within the battery and a controller configured to control a current through the actuator based on the pressure.The above features and advantages, as well as other features and advantages of the disclosure, will be readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGSOther features, advantages and details are included, by way of example only, in the following detailed description, which relates to the drawings, in which: FIG. 1 shows an electric vehicle according to an example embodiment; FIG. 2 shows a battery system for a battery in an example embodiment; FIG. 3 is a close-up side view of the actuator in the non-energized state; FIG. 4 is a close-up side view of the actuator in an energized state; FIG. 5 is a perspective view of the actuator in a non-energized state in a first embodiment; FIG. 5A shows a second carrier and a slot of the actuator; FIG. 6 is a perspective view of the actuator in an excited state in the first embodiment; FIG. 7 is a perspective view of the actuator in a second embodiment; FIG. 8 is a side view of the pressure control device in another embodiment.DETAILED DESCRIPTIONThe following description is merely exemplary in nature and is not intended to limit the present disclosure, its application, or its use. It should be understood that throughout the drawings, corresponding reference numerals designate like or corresponding parts and features.According to an example embodiment, FIG. 1 shows an electric vehicle 100. The electric vehicle 100 includes an electric motor 102, a battery system 104, and a controller 106. The battery system 104 includes a battery 108 having anodes 110 and cathodes 112 that tend to form dimers during operation at standard pressure or ambient pressure. The dimers degrade the performance of the battery 108. In various embodiments, the battery 108 is any battery that requires high pressure conditions for operation, such as a lithium metal battery (LMB). The battery system 104 includes a device that applies pressure to the battery 108 and is capable of adjusting or controlling the pressure as desired.The controller 106 may include processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group), and memory that executes one or more software or firmware programs, combinatorial logic circuitry, and / or other suitable components that provide the described functions. The controller 106 may include a non-transitory computer readable medium having instructions stored therein that, when processed by one or more processors of the controller 106, implement a method of operating the battery system 104 to pressurize the battery 108 to a desired pressure.FIG. 2 shows a battery system 200 for a battery 108 in an example embodiment. The battery system 200 includes a housing 202 in which the battery 108 is housed. The housing 202 may include a bottom surface 204, a top surface 206, and sidewalls 208. Inside the housing 202, a pressure control device 210 for the battery 108 is disposed.The pressure control device 210 includes a support plate 212 on which the battery 108 is disposed, a pressure plate 214 movable relative to the support plate, and posts 216 that guide movement of the pressure plate in a direction either toward or away from the support plate. The support plate 212 may be identical to the bottom surface of the housing 202. The backing plate 212 abuts a first side of the battery 108, and the pressure plate 214 abuts a second side of the battery 108 that is opposite the first side. The pressure plate 214 may be moved toward the support plate 212 to increase the pressure applied to the battery 108. The pressure plate 214 may be moved away from the support plate 212 to reduce the pressure applied to the battery 108.An actuator 218 is disposed at a position above the pressure plate 214. The actuator 218 includes a piezoelectric material that changes shape when electric current is applied. The piezoelectric material may transition between a first shape (when no current is applied to the piezoelectric material) and a second shape (when full current is applied to the piezoelectric material). The piezoelectric material may be referred to as being energized when current is applied and not energized when current is not applied. The current may be provided by a voltage source (not shown) that applies a voltage to the ends of the piezoelectric material. The first shape may be a planar shape, while the second shape is a curved shape that occupies a larger space than the first shape. The actuator 218 may be coupled to or fixed to a control plate 220 that is held in a fixed location with respect to the support plate 212. In various embodiments, the control plate 220 may be the top surface 206 of the housing 202. In the first shape (i.e., in the planar shape), the actuator 218 exerts little or no force on the pressure plate 214. When the piezoelectric material is energized and assumes the second shape (i.e., the curved shape), it expands out of plane to apply a force to the pressure plate 214 and thereby increase the pressure in the battery 108.A pressure sensor 240 is configured to measure the pressure within the battery 108. The pressure may be sent to the controller 106 or another suitable processor. The controller 106 may control the operation of the motor based on the sensed pressure in the battery 108 by controlling the amount of current flowing through the piezoelectric material.FIG. 3 shows a close-up side view 300 of the actuator 218 in the non-energized state. The actuator 218 includes a band 302 of piezoelectric material extending from a first end 304 to a second end 306. The first end 304 is coupled to a first carrier 308 and the second end 306 is coupled to a second carrier 310. The first carrier 308 is coupled to the control plate 220 at a first location and the second carrier 310 is coupled to the control plate at a second location. The first end 304 may be fixed in place by the first bracket 308 and the second end 306 may be fixed in place by the second bracket 310. When no current flows through the piezoelectric material, the band 302 forms a first planar shape.In one embodiment, the band 302 comprises a bimorph layer comprising two layers of different piezoelectric materials that expand differently when energized by current, thereby creating a bend or arc in the band 302. Additionally, the band 302 may include a layer of steel or steel band or a layer of another material that forms a spring that enhances deflection of the band 302 upon energization. The steel layer may be prestressed into an arcuate shape.In another embodiment, the band 302 may comprise a layer of steel or other material forming a spring biased toward a flat or planar shape. In this embodiment, the band 302 is inherently arcuate in shape (i.e., when no current is applied). The piezoelectric material, when energized, retracts the spring.FIG. 4 shows a close-up side view 400 of the actuator 218 in the energized state. When a current flows through the piezoelectric material, the band 302 takes a second shape. The second shape includes an arc in which a central portion of the material flexes away from the control plate 220 and toward the pressure plate 214. In this form, the belt 302 exerts a force on the pressure plate 214 causing the pressure plate 214 to move away from the control plate 220 and toward the support plate 212. The amount of current flowing through the piezoelectric material ribbon 302 may be controlled to adjust the strength of the arc generated in the ribbon 302, and thus the force applied to the pressure plate 214.FIG. 5 shows a perspective view 500 of the actuator 218 in a non-excited state in a first embodiment. The first end 304 of the strap 302 is fixed in place by the first carrier 308. The second support 310 includes a slot 502 through which the second end 306 of the band 302 is freely movable or can slide. FIG. 5A shows the second carrier 310 and the slot 502. When the band 302 is in the planar shape, the second end 306 is fully extended through the slot 502. The second end 306 may include a flanged portion 504.FIG. 6 shows a perspective view 600 of the actuator 218 in the excited state in the first embodiment. When the band 302 assumes an arcuate shape, the second end 306 is pulled inward through the slot 502. The flange portion 504 limits the extent to which the second end 306 is pulled through the slot 502.FIG. 7 shows a perspective view 700 of the actuator 218 in a second embodiment. The first support 308 includes a first slot 702 through which the first end 304 of the band 302 can freely move or slide. The second support 310 includes a second slot 704 through which the second end 306 of the belt 302 is freely movable or can slide. When the band 302 is in the planar shape, the first end 304 extends through the first slot 702 and the second end 306 extends through the second slot 704. When the band 302 assumes an arcuate shape, the first end 304 is pulled inward through the first slot 702 and the second end 306 is pulled inward through the second slot 704. The first end 304 may include a first flanged portion 706 and the second end 306 may include a second flanged portion 708, each limiting the extent to which its respective ends may be pulled through their respective slots.FIG. 8 shows a side view 800 of the pressure control device 210 in another embodiment. The pressure control device 210 includes a plurality of actuators. Three actuators 218a, 218b, 218c are shown for illustration. Each actuator can be independently energized with independently controlled currents. In this way, different forces may be applied at different locations on the surface of the pressure plate 214, causing differential pressure to be present within the battery 108.The terms "a" and "an" do not mean a quantity limitation, but rather denote the presence of at least one of the elements mentioned. The term "or" means "and / or" unless the context clearly indicates otherwise. Throughout this specification, when "one aspect" is mentioned, it means that a particular element (e.g., feature, structure, step, or characteristic) described in connection with the aspect is included in at least one of the aspects described herein and may or may not be present in other aspects. It is understood that the described elements may be combined in any suitable manner in the various aspects.When an element such as a layer, film, region or substrate is referred to as being "on" another element, it may be directly on the other element or intervening elements may also be present. In contrast, there are no intervening elements when an element is referred to as being "directly on" another element.Unless otherwise specified herein, all testing standards are the latest standard in effect on the filing date of this application or, if a priority is claimed, on the filing date of the earliest priority application in which the testing standard appears.Unless defined otherwise, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure pertains.Although the above disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes may be made and equivalent elements may be substituted without departing from the scope thereof. Moreover, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from its essential scope. Therefore, it is intended that the present disclosure not be limited to the particular embodiments disclosed, but include all embodiments that are within its scope.

Claims

A pressure control device for controlling pressure in a battery, comprising: a backing plate; a pressure plate configured to move with respect to the backing plate, the battery being disposed between the backing plate and the pressure plate; and an actuator configured to switch between a first shape and a second shape to move the pressure plate with respect to the backing plate and control pressure in the battery.The pressure control device of claim 1, wherein the actuator comprises a piezoelectric material ribbon extending from a first end to a second end, the piezoelectric material ribbon being coupled to a control plate at the first end by a first carrier and to the control plate at the second end by a second carrier.The pressure control device of claim 2, wherein one of: (i) the first end is fixed to the first support and the second end is fixed to the second support; (ii) the first end is fixed to the first support and the second end is slidable with respect to the second support; and (iii) the first end is slidable with respect to the first support and the second end is slidable with respect to the second support.The pressure control device of claim 2, wherein the actuator further comprises a steel strip coupled to the piezoelectric material.The pressure control apparatus of claim 1, further comprising a pressure sensor configured to measure a pressure within the battery, and a controller configured to control a current through the actuator based on the pressure.A method of controlling pressure within a battery, comprising: disposing the battery between a backing plate and a pressure plate configured to move relative to the backing plate; and energizing an actuator to transition between a first shape and a second shape to move the pressure plate relative to the backing plate and control pressure in the battery.The method of claim 6, wherein the actuator comprises a band of piezoelectric material extending from a first end to a second end, the band of piezoelectric material coupled to a control plate at the first end by a first carrier and to the control plate at the second end by a second carrier.The method of claim 7, wherein one of: (i) the first end is fixed to the first support and the second end is fixed to the second support; (ii) the first end is fixed to the first support and the second end is slidable with respect to the second support; and (iii) the first end is slidable with respect to the first support and the second end is slidable with respect to the second support.The method of claim 7, wherein the actuator further comprises a steel strip coupled to the piezoelectric material.The method of claim 6, further comprising measuring a pressure within the battery using a pressure sensor and controlling a current through the actuator based on the pressure.

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