Pressure-control apparatuses for testing systems, and related methods

Abstract

Pressure-control apparatuses for applying pressure to test specimens during testing, such as cycle testing of secondary battery cells and material-property testing of various materials. In some embodiments, a pressure-control apparatus includes one or more of a screw-drive mechanism that is driven by a stepper motor, a flexible drive coupling located between the motor and the screw-drive mechanism, and limit-switch circuitry that includes a pull-down-resistor arrangement that uses components of the pressure-control apparatus as electrical contacts. In embodiments for battery-cell testing, a pressure-control apparatus includes an apparatus controller that receives information from a cycler and that controls operations of the stepper motor based on that information, at time in conjunction with pressure signals from a pressure-sensing system located onboard the pressure- control apparatus.

Description

PRESSURE-CONTROL APPARATUSES FOR TESTING SYSTEMS, AND RELATED METHODSFIELD

[0001] The present disclosure generally relates to the field of electrochemical cell testing. In particular, the present disclosure is directed to pressure-control apparatuses for testing systems, and related methods.BACKGROUND

[0002] Electrochemical cells for secondary batteries undergo rigorous charge-discharge cycle testing at various stages of research, design, and manufacturing. Cycle testing of lithium-metal and other types of cells often involves testing the cells under various pressure conditions in which pressure is applied to the cells in a direction parallel to the stacking direction of the internal layered components of the cell, such as the cathode(s), separator(s), and anode(s). For example, pressure conditions during cycle testing may include constant pressure during charging, variable pressure during charging (e.g., due to expansion of a cell within a constant-gap space), and no pressure during discharging. Testing apparatuses for controlling cell pressure during testing are often spring-loaded devices for constant-pressure testing and rigid devices for constant-gap testing. Each spring-loaded device typically includes a pair of spaced-apart pressure plates that apply pressure to a cell between the plates, with four or more threaded- fastener-and-spring mechanisms biasing the plates toward one another to apply a desired pressure to the cell therebetween. Typically the spring mechanisms of such spring-loaded devices are manually set and do not allow for adjustments during testing.SUMMARY

[0003] In one implementation, the present disclosure is directed to a pressure-control apparatus for controlling pressure externally applied to at least one electrochemical cell during chargedischarge cycle testing of the at least one electrochemical cell. The pressure-control apparatus includes a pair of pressure applicators defining a cell-receiving region therebetween that receives the at least one electrochemical cell during testing; a screw-drive mechanism engaged with at least one of the pressure applicators and configured to move the at least one of the pressure applicators so as to apply and remove pressure from the at least one electrochemical cell present in the cell-receiving region during testing; a stepper motor operatively coupled to the screw-drive mechanism so as to move the at least one of the pressure applicators during testing; a sensor system that generates pressure data corresponding to pressure that the pressure-control apparatus is applying to the at leastone electrochemical cell during testing; and an apparatus controller having: an input that, during testing, receives pressure-control information from a charge-discharge cycler; and an output that, during testing, output drive signals to the stepper motor; wherein the apparatus controller is in operative communication with the stepper motor and includes: machine memory containing the machine-executable instructions that include machine-executable instructions that, during testing, controls the stepper motor as a function of at least the pressure-control information from chargedischarge cycler; and a microprocessor in operative communication with the machine memory and configured to execute the machine-executable instructions.

[0004] In another implementation, the present disclosure is directed to a testing system for cycle testing at least one electrochemical cell. The testing system includes a charge-discharge cycler designed and configured to: cycle the at least one electrochemical cells through a plurality of charging cycles and a plurality of discharging cycles; and generate pressure-control information corresponding to testing conditions for cycling the at least one electrochemical cell through the pluralities of charging and discharging cycles; and a pressure control apparatus that includes: a pair of pressure applicators defining a cell-receiving region therebetween that receives the at least one electrochemical cell during testing; a screw-drive mechanism engaged with at least one of the pressure applicators and configured to move the at least one of the pressure applicators so as to apply and remove pressure from the at least one electrochemical cell present in the cell-receiving region during testing; a stepper motor operatively connected to the screw-drive mechanism so as to move the at least one of the pressure applicators during testing; at least one sensor system that generates pressure data corresponding to pressure that the pressure-control apparatus is applying to the at least one electrochemical cell during testing; and an apparatus controller in operative communication with the charge-discharge cycler and having: an input that, during testing, receives the pressure-control from the charge-discharge cycler; and an output that, during testing, output drive signals to the stepper motor; wherein the apparatus controller includes: machine memory containing the machineexecutable instructions that include machine-executable instructions that, during testing, determine the output drive signals as a function of at least the pressure-control information; and a microprocessor in operative communication with the machine memory and configured to execute the machine-executable instructions.

[0005] In yet another implementation, the present disclosure is directed to a method of performing charge-discharge cycle testing on at least one electrochemical cell. The method includes receiving pressure-control information from a charge-discharge cycler in conjunction with a testingphase; causing a pressure-control apparatus that holds the at least one electrochemical cell to adapt to the testing phase; and when the pressure-control apparatus is adapted to the testing phase, electrically controlling the at least one electrochemical cell in accordance with the testing phase.BRIEF DESCRIPTION OF THE DRAWINGS

[0006] For the purpose of illustration, the accompanying drawings show aspects of one or more embodiments made in accordance with the present disclosure. However, it should be understood that the scope of this disclosure is not limited to the precise arrangements and instrumentalities shown in the drawings, wherein:

[0007] FIG. 1A is a partial block diagram and partial elevational view of a pressure-control apparatus that can be used with a testing system of the present disclosure, such as the testing system of FIG. 1;

[0008] FIG. IB is an enlarged cross-sectional partial view of the pressure-control apparatus of FIG. 1A; and

[0009] FIG. 2 is a schematic diagram of electronic circuitry that can be used with a pressurecontrol apparatus of the present disclosure, such as the pressure-control apparatus of FIGS. 1A and IB.DETAILED DESCRIPTION

[0010] OVERVIEW

[0011] In some aspects, the present disclosure is directed to a pressure-control apparatus that can be used for, among other things, cycle-testing electrochemical cells or for testing physical properties of materials, depending generally on how the pressure-control apparatus is configured and controlled. For the sake of convenience, the following descriptions are focused on pressure-control apparatuses configured and controlled for use in a cycle-testing system for charge-discharge testing of electrochemical cells. However, those skilled in the art will readily understand any change that needs to be made to the cycle-testing-specific embodiments described below in order to adapt a pressure-control apparatus to another use.

[0012] As discussed in the Background section above, electrochemical cells (hereinafter simply “cells”), such as cells for secondary batteries, are subject to charge-discharge cycle testing under various pressure conditions. For example, cells having plating-type anodes on which dendrites / mossy lithium tends to form during cycling (e.g., lithium-metal cells, sodium cells, etc.) are routinelycycled under differing pressure conditions during both the research-and-design phase and during the manufacturing / quality control phase. When deployed in a cell-testing scenario, a pressure-control apparatus of the present disclosure receives signals from a charge-discharge cycler so that the pressures that the pressure-control apparatus applies can be precisely coordinated with the charging and discharging according to the relevant testing protocol. Consequently, in some aspects, the present disclosure is directed to cell-testing systems that each include a pressure-control apparatus and a charge-discharge cycler that communicates pressure-control information to the pressurecontrol apparatus so as to coordinate the application of pressure to one or more cells that the pressure-control apparatus applies in conjunction with the charging / discharging that the chargedischarge cycler drives.

[0013] The foregoing and other aspects of the present disclosure are described below in the context of several examples.

[0014] EXAMPLES

[0015] Referring now to the drawings, FIGS. 1 A and IB illustrate an example testing system 100 that includes a pressure-control apparatus 104 and a charge-discharge cycler 108 that is in operative communication with the pressure-control apparatus. At a general level, the chargedischarge cycler 108 provides pressure-control information 112, such as cycling-status data, testphase data and / or pressure-control instructions, etc., to the pressure-control apparatus 104 that the pressure-control apparatus responds to by adapting itself to the relevant phase of the testing scheme that the charge-discharge cycler is implementing. The pressure-control apparatus 104 may adapt to the test phase by, for example, applying a constant pressure to a test specimen 116, setting a constant gap in which the test specimen resides during the testing, and / or relieving pressure on the test specimen, among other things. As discussed below in more detail, depending on the type of testing system 100, the test specimen 116 will vary, as will the tester (here, the charge-discharge cycler 108) and possibly the configuration of the pressure-control apparatus 104. When the testing system 100 is configured for testing cells, the test specimen 116 may be one or more cells, for example, pouchtype cells. In some embodiments, the test specimen may be one or more individual cells or may be one or more cells integrated into a battery or battery module that includes other components in addition to the cell(s), such as a housing, internal electrical connections, electrical terminals, embedded sensors, among others, and any combination or subcombination thereof.

[0016] In the embodiment shown, the pressure-control apparatus 104 includes a pair of spacedapart first and second pressure applicators 120(1) and 120(2), respectively, that generally define a specimen region 124 therebetween. In this example, the first and second pressure applicators 120(1) and 120(2) each include a corresponding planar pressure-applying face 120F(l), 120F(2) because of the planar nature of the test specimen 116 in this testing scenario (pouch-type cell(s)). However, in other embodiments, the first and second pressure applicators 120(1) and 120(2) may have any other suitable configuration(s) / shape(s) to match the particular test specimen 116 at issue, for example, by contouring to a non-planar test specimen and / or by including discrete contact regions for contacting specific pressure points or pressure regions on the test specimen, etc. It is noted that in a fully operational configuration for testing one or more cells, the specimen region 124 may contain, as will be understood by those skilled in the art, various items (not shown) for carrying out the charge-discharge testing, such as, but not limited to, electrical connectors for making any or all necessary electrical connections to the charge-discharge cycler 108 and a holder for holding the cell(s) under test, among other things.

[0017] The pressure-control apparatus 104 also includes a screw-drive mechanism 128 for moving at least one of the first and second pressure applicators 120(1) and 120(2) during testing. In the example shown, the screw-drive mechanism 128 using a driven lead screw 132 to selectively move the first pressure applicator 120(1) toward and away from the second pressure applicator 120(2) while the second pressure applicator remains stationary relative to other components of the pressure-control apparatus 104. In this embodiment, a stepper motor 136 of a suitable size and torque controllably and directly drives the lead screw 132, with the stepper motor being fixedly coupled to a base 140 via a rigid frame 144 that comprises a rectangular motor-support plate 144SP and four guide members 144GM(1) through 144GM(4) located proximate to the four corners of the rectangular motor-support plate.

[0018] The first pressure applicator 120(1) comprises a sliding plate 120P(l) and a bracket 120B fixedly secured to the sliding plate, here by a set of threaded fasteners 120F. The sliding plate 120P(l) is slidably engaged with the four guide members 144GM(1) through 144GM(4), and the bracket 120B is threadedly engaged with the lead screw 132. Consequently, when the stepper motor 136 drives the lead screw 132, the lead screw moves the first pressure applicator 120(1) up or down relative to the orientation of the pressure-control apparatus 104 as shown in FIG. 1A. The pitch of the threads 132T on the lead screw 132 and the torque of the stepper motor 136 may be designed and / or selected to ensure that the pressure-controlapparatus 104 is able to either apply a maximum design pressure to the test specimen 116 or maintain a constant gap under a maximum pressure caused by expansion of the test specimen in the constant gap, or both, depending on the operating requirements for the pressure-testing apparatus for the relevant test(s). The lead screw 132 and a corresponding threaded receiver 120R on the bracket 120B may each be made from and / or coated with any suitable low-friction material that minimizes the risk of the first pressure applicator 120(1) binding in its sliding engagement with the guide members 144GM(1) through 144GM(4). It is noted that while four guide members 144GM(1) through 144GM(4) are present in this embodiment, other embodiments may have more or fewer (including zero) slide-type guide members. The second pressure applicator 120(2) includes a fixed plate 120P(2) that doubles as the base 140 in this example.

[0019] The stepper motor 136 includes a housing 136H, a drive shaft 136DS, a stator (not shown) fixedly supported by the housing, a rotor (not shown) rotatably supported within the housing and to which the drive shaft is fixedly attached, and a motor driver (not shown, but see motor driver 204 of FIG. 2), which may be located internally or externally to the housing. The housing 136H is secured to the motor-support plate 144SP via four threaded fasteners 144F (only two shown). The stepper motor 136 can provide one or more benefits to the pressure-side of the testing that the testing system 100 performs. For example, some tests require “constant-gap” testing in which the specimen 116 needs to be constrained from expanding by the pressure-control apparatus 104. In constant-gap testing, the specimen 116 is placed in a specimen region 124 between the first and second pressure applicators 120(1) and 120(2), and the pressure-control apparatus 104 maintains a constant desired gap, G (FIG. 1A), between the pressure-applying faces 120F(l) and 120F(2) of, respectively, the first and second pressure applicators. The motor driver can control, without any feedback control, the stepper motor 136 so that screw-drive mechanism 128 maintains the gap G at a constant value for as long as a test requires.

[0020] The motor driver does this by first energizing the stepper motor 136 in a manner that drives the lead screw 132 so that the first pressure applicator 120(1) moves to the location needed to create the dimensional value of the gap G and then energizing the stepper motor in a constant manner so that the rotor, and hence drive shaft 136DS, remain in a fixed rotational position relative to the stator. The initial energization to move the first pressure applicator 120(1) to a location that creates the constant gap G can be done in any of a variety of ways, either without or with feedback control external to the stepper motor 136. For example, the motor driver can control the stepper motor 136 without any external feedback control by simply counting and controlling the number ofsteps of the stepper motor when the position of the pressure-applying face 120F(l) of the first pressure applicator 120(1) is calibrated to the stepper motor or with automated or manual feedback. Automated feedback can be provided, for example, using a position sensor, camera, etc., and manual feedback can be provided, for example, by an operator, the operator’s sight, and / or a manual motor control (not shown), such as a rheostat, among others.

[0021] Regarding holding the gap G at a constant value, as long as any pressure that an expanding specimen 116 within the gap G asserts on the first pressure applicator 120(1) when the stepper motor 136 is energized in a constant, i.e., non-changing, manner to hold the gap G at a constant value does not cause an opposing torque that exceeds the stepper motor’s maximum torque, the stepper motor can hold that constant gap as long as the motor driver continues the constant energization. For clarity and using a simple two-pole (N-S) permanent-bar-magnet rotor and a two- coil stator with the coils 180° apart from one another as an example, constant energization means that the stator is unchangingly energized so that one coil continuously remains an N pole and the other coil continuously remains an S pole so that the rotor remains fixed with the pole arrangement being S-[N-S]-N (stator coil[rotor]stator coil) the entire time while maintaining the constant value of the gap G. Of course, real- world stepper motors suitable for use as the stepper motor 136 are much more complex, but the underlying constant energization scheme is essentially the same.

[0022] Other benefits exist with utilizing the stepper motor 136. For example, with the stepper motor 136, it is a simple matter to control the stepper motor for testing in which the pressure-control apparatus 104 applies one or more constant pressures and / or one or more varying pressure profiles that vary over time in one manner or another. Generally, all that is needed are one or more pressure sensors and / or one or more force sensors, appropriately located, that provide measurements relating to pressure that the pressure-control apparatus 104 is either actively applying or actively resisting. For example, a 2D pressure sensor 148 may be provided between the test specimen 116 and the pressure-applying face 120F(2) of the second pressure applicator to measure a pressure proportional to the pressure being applied to or by the pressure-control apparatus 104. Of course, other sensors can be used, and each sensor used can be located elsewhere, as those skilled in the art will readily appreciate. One or more apparatus-control algorithms 152 that, for example, use measurement data from the pressure-sensor 148 or one or more other suitable sensors, can be provided in a suitable apparatus controller 156, so as to instruct the motor driver to energize the stepper motor 136 so that the pressure-control apparatus 104 applies or resists the requisite pressure(s). Those skilled in the art will readily appreciate not only the technical benefits of using a stepper motor — as opposed to aservo motor — for the pressure-control apparatus 104 of the present disclosure, but also the corresponding cost-saving benefits that flow from some of the technical benefits. For example, the stepper motor 136 avoids more complex feedback control systems that a servo motor would require, saving design time, programming time, and costs of certain components not needed for the stepper motor.

[0023] The lead screw 132 in this embodiment is coupled to the drive shaft 136DS of the stepper motor 136 via a flexible coupling 160. In some embodiments, the presence of the flexible coupling 160 provides a spring-like behavior when applying and relieving pressure to the test specimen 116 during testing. This behavior assists the screw-drive mechanism 128 in providing a more gradual pressure change to the test specimen 116, which, when the test specimen includes one or more cells of a certain type, such as lithium-metal cells, may prevent short circuiting within the cell(s) that could otherwise be induced by a particular testing regime. Other benefits of the flexible coupling 160 can include, but not be limited to, achieving a desired torque without slippage, permitting flexibility to inhibit motor wear, and compensating for misalignment, among others, and any relevant combination thereof. In other embodiments, the flexible coupling 160 is not provided.

[0024] In the embodiment of FIGS. 1A and IB, the pressure-control apparatus 104 includes a limit-switch circuit 164 that causes the apparatus controller 156 to turn off the stepper motor 136 when the first pressure applicator 120(1) reaches its limit of travel in a direction away from the second pressure applicator 120(2). In this example, the limit-switch circuit 164 is configured as a pull-down-resistor (PDR) circuit (not shown, but see pull-down-resistor circuit 228 of FIG. 2) that relies on contact between the free end 132E (FIG. IB) of the lead screw 132 and the opposing surface 120PS(l) (FIG. IB) of the plate 120P(l) of the first pressure applicator 120(1) to cause a change in state of the PDR circuit 228 (FIG. 2) that triggers the apparatus controller 156 to stop the stepper motor 136. In other embodiments, the limit-switch circuit 164 may optionally include a physical switch 164S in lieu of the PDR circuit 228 (FIG. 2). In this example, the physical switch 164S is located on one of the guide members 144GM, but it can be located elsewhere, such as on the surface 120PS(l) of the plate 120P(l). Implementing the limit-switch circuit 164 as the PDR circuit 228 (FIG. 2), however, simplifies the construction of the pressure-control apparatus 104 and can prevent damage if the physical switch 164S were to fail.

[0025] One example instantiation of the pressure-control apparatus 104 has the following characteristics and features. The stepper motor 136 has a standardized size, such as a standardizedsize under a National Electrical Manufacturers Association (NEMA) classification. For example, the stepper motor 136 may be a NEMA 34 stepper motor. Standardizing the size of the stepper motor 136 can provide the benefit of being able to change the operating characteristics by selecting a stepper motor having different performance characteristics in the same size class. For example, in a given size class, multiple stepper motors may have different torque and / or speed characteristics, with one set of characteristics being suitable for a certain pressure-application / pressure-resistance range, whereas another set of characteristics is suitable for a different pressure-application / pressureresistance range, among others.

[0026] In the example instantiation, the lead screw 132 is made of 1018 carbon steel and is a precision ACME lead screw that engages a corresponding precision ACME nut (threaded receiver 120R) on the plate 120P(l). The nut 120R is made of bronze for controlling the frictional forces between itself and the lead screw 132. The bracket 120B in this instantiation is a precision ACME flange. The guide members 144GM and the sliding plate 120P(l) that engages the guide members are PTFE anodized and have specific tolerances to allow proper sliding, pressure distribution, and use of pressure-rated lubricant therebetween. The plate 120P(2) is an anodized aluminum plate that allows for high pressures without damage while providing a dielectric barrier relative to the test specimen 116, which is particularly important when the test specimen is one or more cells. The foregoing characteristics and features are merely illustrative, and those skilled in the art will readily appreciate that many other instantiations of the pressure-control apparatus 104 can be made by changing any one or more of these characteristics and features as needed to suit a particular design and / or a particular instantiation without undue experimentation.

[0027] FIG. 2 illustrates an example electronics system 200 that can be deployed in a testing system of the present disclosure, such as the testing system 100 of FIGS. 1 A and IB. For ease of explanation, the electronics system 200 of FIG. 2 is illustrated in the context of the testing system 100 of FIGS. 1A and IB. Referring to FIG. 2, the electronics system 200 includes the stepper motor 136, the motor driver 204, the apparatus controller 156, a pressure-sensor board 208, and a power supply 212.

[0028] The apparatus controller 156 in this example is a self-contained computing device, such as a RASPBERRY PI® single-board computer, among others. The apparatus controller 156 includes a multi-terminal connector 156MTC, which in this example is a multi-terminal connector ofa current generation RASPBERRY PI® 40-terminal connector that those skilled in the art can readily use.

[0029] In this example, the stepper motor 136 is a commercial off-the-shelf (COTS) National Electrical Manufacturers Association (NEMA) 34 stepper motor and, correspondingly, the motor driver 204 is a compatible COTS motor driver that those skilled in the art will readily understand and / or be familiar with. The motor driver 204 is powered by the power supply 212, which in this example receives electrical power from a power source 216, such as a conventional wall outlet. The motor driver 204 is electrically connected to appropriate ones of the terminals of the multi-terminal connector 156MTC of the apparatus controller 156, including via DC-DC converters 220 as needed to handle the voltages of the corresponding signals appropriately.

[0030] The pressure-sensor board 208 carries the 2-D pressure sensor 148 (not shown in FIG. 2; see FIG. 1A). In this example, the pressure-sensor board 208 is powered by the power source 216 and provides an analog output signal to an analog drive system (ADS) 224, which in turn is connected to the appropriate terminals of the multi-terminal connector 156MTC of the apparatus controller 156.

[0031] As mentioned above, the limit-switch circuit 164 (FIG. 1A) is implemented as the PDR circuit 228. In this example, the PDR circuit 228 includes a first wire 228W(1) electrically connected to the lead screw 132 (FIGS. 1A and IB) and a second wire 228 W(2) electrically connected to the plate 120P(l) of the first pressure applicator 120(1). The first wire 228W(1) is electrically connected through parallel-connected first and second resistors 228R(1) and 228R(2) to appropriate terminals of the multi-terminal connector 156MTC of the apparatus controller 156. In this example, the first resistor 228R(1) is a lOk resistor and the second resistor 228R(2) is a 100Q resistor. The second wire 228W(2) is electrically connected directly to an appropriate terminal of the multi-terminal connector 156MTC of the apparatus controller.

[0032] In some embodiments and referring to FIG. 1A, the apparatus controller 156 controls the pressure-control apparatus 104 based on the pressure-control information 112 it receives from the charge-discharge cycler 108 that, for example, indicates the phase or status of testing scheme that the charge-discharge cycler is implementing during testing. In this example and as mentioned above, the apparatus controller 156 includes one or more apparatus-control algorithms (singly and collectively called “apparatus-control algorithm 152”) that use the pressure-control information 112 and, as needed, pressure-measurement signals (not illustrated) from the pressure sensor(s) 148 (seealso pressure sensor board 208 of FIG. 2) as inputs and that output in response thereto motor-control signals 168 (FIG. 1A) that cause the motor driver 204 (FIG. 2) to appropriately drive the stepper motor 136. In one nonlimiting example the apparatus-control algorithm 152 may be implemented using the Python programming language, among many others. Following is a nonlimiting example of functions that the apparatus-control algorithm 152 may provide in two example charge-discharge testing scenarios, namely, a constant-pressure-during-charging scenario and a constant-gap scenario. Those skilled in the art will readily appreciate that the below functions are merely illustrative and that many other functions can be added and / or substituted to suit a particular application and chargedischarge testing scenario without undue experimentation knowing the operating principles of the pressure-control apparatus 104.

[0033] The apparatus-control algorithm 152, other algorithms, data needed to operate the pressure-control apparatus 104, and / or data collected by the pressure-control apparatus, among other information, may be stored in one or more hardware storage memories 156M (single and collectively referred to as “machine memory”) that may be onboard the apparatus controller 156 and / or provided at one or more other locations. The machine memory 156M may be any one or more suitable types of hardware memory as is well-known in the art. It is noted that the term “machine memory” and “hardware storage memory” excludes transient signals, including pulsed signals and carrier-wave signals. The apparatus-control algorithm 152 and any other algorithms for operating the pressurecontrol apparatus 104 and / or communicating with the charge-discharge cycler 108 may be embodied in any suitable machine-executable instructions appropriate for the instantiation of the pressurecontrol apparatus. The apparatus-controller 156 may also include any suitable hardware 156H, such as microprocessors, input-output ports, signal converters, power converters, power supplies, etc., needed.

[0034] In this example of a constant-pressure-during-charging scenario, the apparatus controller 156 checks the testing phase of the test specimen 116 with the charge-discharge cycler 108 and goes into a 60-second loop depending on the testing phase (60 seconds as to not overload the charge-discharge cycler when requesting testing-phase status). Example testing-phases and corresponding functions of the apparatus-control algorithm 152 are as follows:• If the testing-phase is “rest cycle before charging” the specimen 116, then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to drive the stepper motor 136 to move the first pressure applicator 120(1) until the pressure-control apparatus 104 is applying a pressure of 150 psi (-1.034 MPa) to the specimen.• If the testing phase is “charging” the specimen 116, then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to drive the stepper motor 136 to periodically adjust the pressure that the pres sure- control apparatus 104 is applying to the specimen depending on the pressure-measurement signal.• If the testing phase is “rest cycle after charging” the specimen 116, then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to drive the stepper motor 136 to slowly release the pressure on the specimen until either there is no applied pressure or the first pressure applicator 120(1) reaches its movement limit (as sensed in this example by a pull-down-resistor circuit 228 (FIG. 2)).• If the testing phase is “discharging” the specimen 116, then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to cause the stepper motor 136 to rotate so that the pressure-control apparatus 104 does not apply any pressure to the specimen.• If the testing-phase is that the test schedule has reached a loop step, which tells the chargedischarge cycler 108 to repeat from a previous step, such as the above “rest cycle before charging” or the above “charging” status) then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to constantly energize the stepper motor 136 so as to hold the drive shaft 136DS and the lead screw 132 motionless.• Once the test schedule reaches an end status, then the apparatus controller 156 instructs the motor driver 204 (FIG. 2) to deenergize the stepper motor 136. The pressure-control apparatus 104 may then be turned off if desired.• The above schedule is adaptive.

[0035] In a specific, nonlimiting, example in which the signal from the pressure sensor 148 is a voltage signal that varies with pressure and a voltage of 2.03 V corresponds to a pressure of about 150 psi (-1.034 MPa), the algorithm 152 may include the following algorithm for a constantpressure testing scheme:• monitor voltage of the pressure sensor;• cause the stepper motor 136 to turn until pressure sensor reaches 2.03V or higher; o turns fast at first; o turns slower as the voltage signal approaches 2.03 V;• check voltage every 20 seconds and cause the stepper motor to tighten / loosen motor accordingly.

[0036] In a specific, nonlimiting, example in which the signal from the pressure sensor 148 is a voltage signal that varies with pressure and a voltage of 2.03 V corresponds to a pressure of about 150 psi (-1.034 MPa) and a voltage of -0.5V corresponds to a pressure of 0 psi (0 MPa), the algorithm 152 may include the following algorithm for a high-pressure-charge, low-pressure- discharge testing scheme:• Determine the step number of the cycler 108;• Depending on the step number, go into: o a “rest_cycle_before_charge” routine:■ cause the stepper motor 136 to turn until the voltage signal from the pressure sensor reaches 2.03 V or higher;■ periodically check the pressure-sensor voltage signal and cause the stepper motor to turn so as to tighten / loosen accordingly so that the pressure sensor outputs a voltage of 2.03 V;■ check the cycler step number every 60 seconds and exit the loop of this routine when the step number changes; o a “charge_cycle” routine:■ periodically check the pressure-sensor voltage signal and cause the stepper motor to turn so as to tighten / loosen motor accordingly so that the pressure sensor outputs a voltage of 2.03 V;■ check the cycler step number every 60 seconds and exit the loop of this routine when the step number changes; o a “rest_cycle_after_charge” routine:■ cause the stepper motor to turn so as to slowly release pressure;• turns slow at first;• turns faster as the pressure-sensor voltage signal approaches 1.0V (It is noted that the 1.0V value in this example was selected because it is between 0.5V and 2.03V (corresponding to 0 psi and 150 psi, respectively. In this example, the voltage output of the voltage sensor does not vary linearly with the pressure. In this example, it is not necessary to measure pressures between 0 psi and 150 psi; all that is required is that the pressure be above 0 psi and below 150 psi. In this example, since the 0 psi output (i.e., 0.5 V) has some moderate fluctuation, the pressure is lowered to cause a sensor-output voltage of1.0V and then the stepper motor turns the lead screw a set number of times known to release the remaining pressure. This voltage of 1.0 V was chosen in this example to not stop loosening too early and to make sure the pressure-control apparatus loosens enough to not apply pressure to the cell. If needed, a curve relating sensor output voltage and pressure can be created through testing using techniques well known in the art.);■ once the pressure-sensor voltage signal reaches 1.0V, cause the stepper motor to turn a set amount of times so as to release remaining pressure;■ check the cycler step number every 60 seconds and exit the loop of this routine when the step number changes; o a “nothing cycle” routine:■ perform discharge steps + miscellaneous direct-current internal resistance (DCIR) measurement steps;■ pause for 60 seconds and then continue (In this example, after the 60 second pause the algorithm will continue and come out of this "nothing cycle". The next piece of code that would execute after this step checks to see if the step loop number is equal to the step number (it will not be the first time since the loop hasn't repeated yet and the step number has not been updated). It would then check if "end cycle" is equal to the step number (which it also would not be the first time) and the cycle would be repeated. The step number is updated (whether this be the same number or a new number) and the algorithm will then continue down the list again.); o a “step_loop” routine:■ loops back to previous steps (this step rarely occurs and happens for a few seconds);■ pause for 15 seconds and then continue (See the explanation above for the 60- second pause that also applies to this 15-second pause.); o an “end_cycle” routine:■ the last step of the algorithm; exit the entire algorithm.

[0037] In this example of a constant-gap scenario, at the beginning of a test schedule, the charge-discharge cycler 108 may provide a set-gap signal to the apparatus controller 156 to cause thepressure-control apparatus 104 to set a constant value for the gap G. As discussed above, the apparatus-control algorithm 152 may do this by simply counting steps of the stepper motor 136 or using some sort of feedback control based on position of the first pressure applicator 120(1). When the apparatus controller 156 has set the gap G to the desired constant value, the apparatus-control algorithm 152 instructs the motor driver 204 (FIG. 2) to constantly energize the stepper motor 136 so as to hold the drive shaft 136DS and lead screw 132 motionless, so as to maintain the constant value of the gap. At this point, the charge-discharge cycler 108 may continue with the charge-discharge testing schedule while the apparatus controller 156 holds the constant value of the gap G by continuing to constantly energize the stepper motor 136. The test schedule may involve any number of charge cycles, discharge cycles, partial charge cycles, partial discharge cycles, rest cycles and in any logical combination while the pressure-control apparatus 104 holds the gap G at the desired constant value. Other functions that the testing system 100 may perform in connection with constant-gap cycle testing include, but are not limited to, changing the constant value of the gap G to differing values during the test schedule and controlling the motor driver 204 (FIG. 2) to open the gap G if the pressure that the 2D pressure sensor 148 senses exceeds a certain threshold that could result in damage to the test specimen 116 or the pressure-control apparatus 104, among other things. At the end of the test schedule, the charge-discharge cycler 108 may signal the apparatus controller 156 with a “test ended” status signal that causes the apparatus controller to signal the motor driver 204 (FIG. 2) to open the gap G and stop energizing the stepper motor 136.

[0038] In an illustrative, but nonlimiting example of communications between the apparatus controller 156 and the cycler(s) 108 over a suitable network (not shown), the apparatus controller requests a connection with a cycler computer (not shown, but part of the testing system) collecting data from the cycler. In an example, the apparatus controller 156 requests and establishes the connection using Python and MySQL connectors by identifying the cycler computer through a workgroup name / computer name so as to avoid the inconvenience of respecifying the IP address every time routers (not shown) on the network are rebooted.

[0039] In a case wherein the cycler 108 and the apparatus controller 156 cannot be connected to the same network, the connection can be established by IP address. Specifying a static / dedicated IP address for every cycler’s computer is required for this method. Note that the cycler computer must have access to the Internet. However, this method also works for local connections and communication if both the apparatus controller 156 and the cycler computer are connected to the same network.

[0040] Once connection is approved by the MySQL database on the cycler computer, the apparatus controller 156 proceeds to request information 112 from the cycler 108 for the cell(s) under test, such as the cycling state / step and voltage of a cycler’s cycling schedule. Such a process requires a user to specify the cycler and channel number. This process is repeated every 10 seconds in a nonlimiting example.

[0041] The foregoing example can be adapted to a wide variety of cyclers, such as cyclers available from Neware Technology LLC (Milpitas, California) and Arbin Instruments (College Station, Texas), among others. It is noted that differing cyclers may require differing request messages for requesting the information 112 from the corresponding database(s) when the design / structure of the databases are different. Other communications schemes and / or protocols may be implemented in the alternative.

[0042] Referring again to FIGS. 1 A and IB, while the foregoing example testing system 100 is configured as a cell-testing system to test electrochemical cells under various and / or varying cellpressure conditions, in other embodiments, the testing system may be configured for a different application. For example, the testing system 100 can be configured as a material-property testing system, with the test specimen 116 being a sample of a particular material desired to be tested, such as a viscoelastic material that recovers its strength after being compressed for some time. When the testing system 100 is configured as a material-property testing system, the pressure-control apparatus 104 may be used as shown and described above or may be modified to accommodate any special conditions needed for the testing that are different from the testing conditions of cells. However, the charge-discharge cycler 108 would be replaced by a materials-testing controller (not shown) that sends signals to the apparatus controller 156 that are appropriate to the particular materials-testing scheme implemented. In some embodiments, a materials-testing controller may be integrated into the apparatus controller.

[0043] Various modifications and additions can be made without departing from the spirit and scope of this invention. Features of each of the various embodiments described above may be combined with features of other described embodiments as appropriate in order to provide a multiplicity of feature combinations in associated new embodiments. Furthermore, while the foregoing describes a number of separate embodiments, what has been described herein is merely illustrative of the application of the principles of the present invention. Additionally, although particular methods herein may be illustrated and / or described as being performed in a specific order,the ordering is highly variable within ordinary skill to achieve aspects of the present disclosure. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.

[0044] Exemplary embodiments have been disclosed above and illustrated in the accompanying drawings. It will be understood by those skilled in the art that various changes, omissions and additions may be made to that which is specifically disclosed herein without departing from the spirit and scope of the present invention.

Claims

What is claimed is:

1. A pressure-control apparatus for controlling pressure externally applied to at least one electrochemical cell during charge-discharge cycle testing of the at least one electrochemical cell, the pressure-control apparatus comprising: a pair of pressure applicators defining a cell-receiving region therebetween that receives the at least one electrochemical cell during testing; a screw-drive mechanism engaged with at least one of the pressure applicators and configured to move the at least one of the pressure applicators so as to apply and remove pressure from the at least one electrochemical cell present in the cell-receiving region during testing; a stepper motor operatively coupled to the screw-drive mechanism so as to move the at least one of the pressure applicators during testing; a sensor system that generates pressure data corresponding to pressure that the pressure-control apparatus is applying to the at least one electrochemical cell during testing; and an apparatus controller having: an input that, during testing, receives pressure-control information from a chargedischarge cycler; and an output that, during testing, output drive signals to the stepper motor; wherein the apparatus controller is in operative communication with the stepper motor and includes: machine memory containing the machine-executable instructions that include machine-executable instructions that, during testing, controls the stepper motor as a function of at least the pressure-control information from charge-discharge cycler; and a microprocessor in operative communication with the machine memory and configured to execute the machine-executable instructions.

2. The pressure-control apparatus of claim 1, wherein the screw-drive mechanism comprises: a lead screw that the stepper motor drives during testing, the lead screw having a longitudinal axis; a coupling secured to one of the pressure applicators so that coupling and the pressure applicator move in unison in a direction parallel to the longitudinal axis of the lead screw when the stepper motor is driving the lead screw, the coupling threadedly engaging the lead screw; anda flexible drive coupling coupled between the stepper motor and the lead screw.

3. The pressure-control apparatus of claim 2, wherein: the pressure applicators provide a maximum opening therebetween; the lead screw has an end distal from the stepper motor; and the screw-drive mechanism further comprises: a lead-screw-end contact region that the end of the lead screw contacts when the pressure applicators are providing the maximum opening; and limit-switch circuitry designed and configured to detect when the end of the lead screw has contacted the lead-screw-end contact region and to generate a stop-motor signal to signal the apparatus controller to deenergize the stepper motor.

4. The pressure-control apparatus of claim 3, wherein the limit-switch circuitry comprises a pulldown-resistor circuit.

5. The pressure-control apparatus of any one of claims 1 through 4, wherein: the stepper motor includes a stator and a rotor; during testing, the pressure-control information indicates constant-gap testing; and the machine-executable instructions include machine-executable instructions that, in response to the indication of the constant-gap testing, cause the drive signal to constantly energize the stepper motor so as to hold the stator in a fixed rotational position relative to the stator during a charging cycle.

6. The pressure-control apparatus of claim 5, wherein the pressure-control information comprises a cycle status.

7. The pressure-control apparatus of any one of claims 1 through 4, wherein: the stepper motor includes a stator and a rotor; during testing, the pressure-control information indicates constant-pressure testing at a testpressure value; and the machine-executable instructions include machine-executable instructions that, in response to the indication of the constant-pressure testing, the test-pressure value, and the pressure data, cause the drive signal to energize the stepper motor so as to move the stator until the pressure data indicates a pressure substantially equal to the test-pressure value and thencontinue to energize the stator so as to maintain the pressure at substantially the test pressure value during a charging cycle.

8. The pressure-control apparatus of claim 7, wherein the pressure-control information comprises a cycle status.

9. A testing system for cycle testing at least one electrochemical cell, the testing system comprising: a charge-discharge cycler designed and configured to: cycle the at least one electrochemical cells through a plurality of charging cycles and a plurality of discharging cycles; and generate pressure-control information corresponding to testing conditions for cycling the at least one electrochemical cell through the pluralities of charging and discharging cycles; and a pressure control apparatus that includes: a pair of pressure applicators defining a cell-receiving region therebetween that receives the at least one electrochemical cell during testing; a screw-drive mechanism engaged with at least one of the pressure applicators and configured to move the at least one of the pressure applicators so as to apply and remove pressure from the at least one electrochemical cell present in the cellreceiving region during testing; a stepper motor operatively connected to the screw-drive mechanism so as to move the at least one of the pressure applicators during testing; at least one sensor system that generates pressure data corresponding to pressure that the pressure-control apparatus is applying to the at least one electrochemical cell during testing; and an apparatus controller in operative communication with the charge-discharge cycler and having: an input that, during testing, receives the pressure-control from the chargedischarge cycler; and an output that, during testing, output drive signals to the stepper motor; wherein the apparatus controller includes:machine memory containing the machine-executable instructions that include machine-executable instructions that, during testing, determine the output drive signals as a function of at least the pressure-control information; and a microprocessor in operative communication with the machine memory and configured to execute the machine-executable instructions.

10. The testing system of claim 9, wherein the screw-drive mechanism comprises: a lead screw that the stepper motor drives during testing, the lead screw having a longitudinal axis; a coupling secured to one of the pressure applicators so that coupling and the pressure applicator move in unison in a direction parallel to the longitudinal axis of the lead screw when the stepper motor is driving the lead screw, the coupling threadedly engaging the lead screw; and a flexible drive coupling coupled between the stepper motor and the lead screw.

11. The testing system of claim 10, wherein: the pressure applicators provide a maximum opening therebetween; the lead screw has an end distal from the stepper motor; and the screw-drive mechanism further comprises: a lead-screw-end contact region that the end of the lead screw contacts when the pressure applicators are providing the maximum opening; and opening-limiter circuitry designed and configured to detect when the end of the lead screw has contacted the lead-screw-end contact region and to generate a stop-motor signal to signal the apparatus controller to deenergize the stepper motor.

12. The testing system of claim 11, wherein the opening-limiter circuitry comprises a pull-down- resistor circuit.

13. The testing system of any one of claims 9 through 12, wherein: the stepper motor includes a stator and a rotor; during testing, the pressure-control information indicates constant-gap testing; and the machine-executable instructions include machine-executable instructions that, in response to the indication of the constant-gap testing, cause the drive signal to energize the stepper motor so as to hold the stator in a fixed rotational position relative to the stator during a charging cycle.

14. The testing system of claim 13, wherein the pressure-control information comprises a cycle status.

15. The testing system of any one of claims 9 through 12, wherein: the stepper motor includes a stator and a rotor; during testing, the pressure-control information indicates constant-pressure testing at a testpressure value; and the machine-executable instructions include machine-executable instructions that, in response to the indication of the constant-pressure testing, the test-pressure value, and the pressure data, cause the drive signal to energize the stepper motor so as to move the stator until the pressure data indicates a pressure substantially equal to the test-pressure value and then continue to energize the stator so as to maintain the pressure at substantially the test pressure value during a charging cycle.

16. The testing system of claim 15, wherein the pressure-control information comprises a cycle status.

17. A method of performing charge-discharge cycle testing on at least one electrochemical cell, the method comprising: receiving pressure-control information from a charge-discharge cycler in conjunction with a testing phase; causing a pressure-control apparatus that holds the at least one electrochemical cell to adapt to the testing phase; and when the pressure-control apparatus is adapted to the testing phase, electrically controlling the at least one electrochemical cell in accordance with the testing phase.

18. The method of claim 17, wherein the testing phase requires a constant gap, and causing the pressure control apparatus to adapt to the testing phase includes causing the pressure-control apparatus to constantly energize a stepper motor to hold the constant gap.

19. The method of claim 18, wherein the testing phase requires charging the at least one electrochemical cell, and electrically controlling the at least one electrochemical cell including charging the at least one electrochemical cell.

120. The method of claim 17, wherein the testing phase requires a constant pressure, and causing the pressure control apparatus to adapt to the testing phase includes causing the pressure-control apparatus to energize a stepper motor to maintain the at least one electrochemical cell at the constant pressure.

21. The method of claim 20, wherein the testing phase requires charging the at least one electrochemical cell, and electrically controlling the at least one electrochemical cell including charging the at least one electrochemical cell.

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