Systems and methods for detecting lithium plating to optimize dc fast charging and battery aging

Abstract

The present disclosure provides "Systems and methods of detecting lithium plating to optimize DC fast charging and battery aging." Systems and methods for charging a battery cell of a battery are described. A cutoff voltage for a charging rate to the battery cell can be adjusted so that the likelihood of lithium plating to an anode of the battery cell can be reduced. The charging rate of the battery cell can be adjusted according to a reference voltage that can eliminate material phase transition voltage fluctuations.

Description

Technical Field

[0001] This specification relates to methods and systems for detecting lithium plating on the anode of a battery cell. In one example, material phase transition voltage fluctuations are eliminated from battery cell voltage measurements, allowing the voltage limits to be accurately updated over cell life or changing environmental conditions, thereby reducing lithium plating during DC fast charging. Background Technology

[0002] Vehicles may include traction batteries for propulsion. Traction batteries may include lithium (Li) chemistry to increase charge density and improve battery efficiency. Additionally, Li batteries may have a longer lifespan and can be charged at higher rates than batteries with other chemistry. However, Li batteries can also undergo lithium plating at the battery anode. Specifically, when a Li-ion battery is charged at a higher C-rate (e.g., a measure of the battery charging current relative to the total cell capacity) or at a lower temperature, Li ions may deposit on the surface of the anode rather than embed into the graphite particles. Therefore, it is desirable to determine when lithium plating can begin in the battery cell, making it possible to reduce the likelihood of lithium plating by updating various charging parameters within the battery control system as the battery cell ages. Summary of the Invention

[0003] According to the present invention, a method for charging a battery cell includes: adjusting the charging rate of the battery cell via one or more controllers in response to a voltage or pressure that causes the lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage is based on a reference voltage level, or the pressure is based on a reference pressure level.

[0004] In one aspect of the invention, it is anticipated that the lithium plating rate of the anode is less than the threshold lithium plating rate of the anode at a reference voltage level.

[0005] In one aspect of the invention, adjusting the charging rate includes reducing the charging rate of the battery cells.

[0006] In one aspect of the invention, the voltage or pressure is further based on the derivative of a quantity including the reference voltage level or the reference pressure level.

[0007] In one aspect of the invention, the battery cell is a lithium-ion battery cell.

[0008] In one aspect of the invention, the charging rate is adjusted via a DC fast charger.

[0009] In one aspect of the invention, the lithium plating rate is based on lithium ions deposited on the anode but not embedded in the graphite or other particles of the anode.

[0010] In one aspect of the invention, the reference voltage level is not constant relative to time.

[0011] According to the present invention, a system for charging a battery cell is provided, the system comprising: a power source for charging the battery cell; and one or more controllers, the one or more controllers including executable instructions stored in a controller memory, the executable instructions causing the one or more controllers to adjust the charging rate of the battery cell via the power source in response to a voltage level, the voltage level being referenced from a table or function via the C-rate of the battery cell and the temperature of the battery cell, the voltage level being based on a reference voltage, wherein the reference voltage is a voltage at which lithium plating of the battery cell is not expected to occur.

[0012] According to one embodiment, the invention is further characterized by additional instructions for performing the following operation: replacing the voltage level in a table or function with a second voltage level based on the amount of current flowing into the battery cell.

[0013] According to one embodiment, the invention is further characterized by additional instructions for performing the following operation: determining a second voltage level based on the second derivative of the battery cell voltage with respect to the battery cell charge.

[0014] According to one embodiment, the voltage at which lithium plating is not expected to occur in the battery cell is based on experimental results of charging the battery cell.

[0015] According to one embodiment, the invention is further characterized by additional instructions for performing the following operations: replacing multiple voltage levels, including voltage levels in a table or function.

[0016] According to one embodiment, the invention is further characterized by additional instructions for performing the following operation: determining the derivative of the battery cell voltage with respect to the charge capacity of the battery cell.

[0017] According to one embodiment, the power source is a power converter.

[0018] According to the present invention, a method for charging a battery cell includes: adjusting the charging rate of the battery cell via one or more controllers in response to a voltage value that causes the lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage value is stored in a table or function and is based on a reference voltage level; and updating the voltage value in the table or function in response to an amount of time since the most recent update of the value in the table or function.

[0019] In one aspect of the invention, the method includes updating a plurality of other voltage values, which serve as the basis for adjusting the charging rate of the battery cells, in response to the amount of time.

[0020] In one aspect of the invention, the method includes adjusting the temperature of the battery cell while updating a plurality of other voltage values ​​that serve as the basis for adjusting the charging rate of the battery cell.

[0021] In one aspect of the invention, the method includes adjusting the C-rate of the battery cell while updating a plurality of other voltage values ​​that serve as the basis for adjusting the charging rate of the battery cell.

[0022] In one aspect of the invention, the time measure is since the most recent voltage update. Attached Figure Description

[0023] The advantages described herein will be more fully understood when read, either alone or with reference to the accompanying drawings, by reading examples of embodiments referred to herein as specific implementations, in which: Figure 1 This is a schematic diagram of an example electric vehicle; Figure 2 This is a schematic diagram of an example Li-ion battery cell; Figure 3 The graphs showing dV / dQ and dP / dQ versus the battery cell charge capacity are presented. Figure 4 It shows and A graph showing the relationship between the battery cell charge capacity and the actual charge capacity. Figure 5 It shows d 2 V / dQ 2 and d 2 P / dQ 2 A graph showing the relationship between the battery cell charge capacity and the actual charge capacity. Figure 6 A graph showing the lithium plating threshold is provided. Figure 7 An image of a Li-ion battery electrode without lithium plating is shown; Figure 8 An image of a Li-ion battery electrode with lithium plating is shown; and Figure 9 and Figure 10 A flowchart is shown for a method for determining the start and update of lithium plating thresholds. Detailed Implementation

[0024] This specification relates to estimating the voltage of a battery or battery cell when lithium plating occurs at one or more electrodes, such that charging of the battery and / or battery cell can occur at a voltage lower than the voltage at which lithium plating occurs at the electrodes or battery electrodes under a given set of conditions. In this way, the lifespan of the battery cell and the battery can be extended. The battery cell can be combined with... Figure 1 In vehicles of the type shown. Figure 2 An example Li-ion battery cell is shown in the image. Figure 4 The graph shows the differential voltage and pressure versus battery capacity when the phase change effect is eliminated. Figure 5 The figure shows the curves of second-derivative differential voltage and pressure versus battery capacity when the phase change effect is eliminated. Figure 6 The graph shows the lithium plating voltage and capacity threshold. Figure 7 and Figure 8 The image shown is of the battery electrodes. Figure 9 and Figure 10 The document illustrates a method for detecting and reducing lithium plating in battery cells.

[0025] Battery cells can be charged within a continuous range between low and high C-rate conditions. Furthermore, differential capacity analysis of the full cell voltage can be applied as a non-invasive method to detect lithium plating during constant current battery cell charging conditions. At higher C-rates, a sudden decrease in dV / dQ at a given capacity, compared to all other lower C-rates, is used to indicate the onset of lithium plating. Figure 3 Furthermore, for C-rates greater than 1.5, any reduction in dV / dQ due to lithium plating is confounded by material phase transition effects. To minimize battery charging time (a crucial factor for electric vehicle adoption), it is desirable to be able to charge the battery cell at a wide range of C-rates throughout its entire lifespan.

[0026] The inventors of this document have recognized the above-mentioned problems and have developed a method for charging a battery cell, the method comprising: adjusting the charging rate of the battery cell via one or more controllers in response to a voltage or pressure that causes the lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage or pressure is based on a reference voltage level.

[0027] By applying a reference level voltage to determine the voltage at which lithium plating can be indicated at the anode of the battery cell, it is possible to provide technical results that enable differential capacity analysis for lower charging rates, allowing the determination of a threshold voltage for lower battery cell charging rates. When the battery cell is charged at a lower charging rate, the threshold voltage can allow the determination or estimation of the likelihood of lithium plating onto the anode of the battery cell.

[0028] This specification offers several advantages. Specifically, the method provides a way to mitigate the likelihood of lithium plating on the anode of a battery cell at lower charging rates and / or during charging of the anode based on the cell's lifespan or health status. Furthermore, the method can provide a way to adjust the voltage used as the basis for detecting the likelihood of lithium plating on the anode of a battery cell, allowing the battery cell to be charged closer to its capacity without initiating lithium plating on the anode. Additionally, the method provides a way to increase the signal-to-noise ratio for identifying the likelihood of lithium plating on the anode of a battery cell.

[0029] The above and other advantages and features of this specification will become readily apparent when understood alone or in conjunction with the accompanying drawings, based on the following detailed description.

[0030] It is understood that the above description of the invention is provided to present a series of concepts further described in the detailed embodiments in a simplified form. This is not intended to identify key features of the claimed subject matter, the scope of which is uniquely defined by the claims appended to the detailed embodiments. Furthermore, the claimed subject matter is not limited to solutions to any of the shortcomings mentioned above or in any part of this disclosure.

[0031] Figure 1 A block diagram of an example vehicle propulsion system 100 for vehicle 121 is shown. The front portion of vehicle 121 is indicated by 110, and the rear portion of vehicle 121 is indicated by 111. The vehicle propulsion system 100 includes a motor 126. The motor 126 may consume or generate electricity depending on its operating mode. (Through) Figure 1 Mechanical connections between various components are shown as solid lines, while electrical connections between various components are shown as dashed lines.

[0032] The vehicle propulsion system 100 includes a rear axle 122. In some examples, the rear axle 122 may include two half-shafts, such as a first half-shaft 122a and a second half-shaft 122b. The vehicle propulsion system 100 further has front wheels 130 and rear wheels 131. The rear wheels 131 can be driven via a motor 126.

[0033] The rear axle 122 is coupled to the motor 126. The rear drive unit 136 transmits power from the motor 126 to the axle 122, causing rotation of the rear wheels 131. The rear drive unit 136 may include a low gear 175 and a high gear 177 coupled to the motor 126 via the output shaft 126a of the motor 126. The low gear 175 may be engaged via a fully engaged low gear clutch 176. The high gear 177 may be engaged via a fully engaged high gear clutch 178. The high gear clutch 178 and the low gear clutch 176 may be engaged and disengaged via commands received by the rear drive unit 136 via a controller area network (CAN) 199. Alternatively, the high gear clutch 178 and the low gear clutch 176 may be engaged and disengaged via a digital output or pulse width provided by the control system 114. The rear drive unit 136 may include a differential gear 128 such that torque can be supplied to the first half-shaft 122a and the second half-shaft 122b. In some examples, an electronically controlled differential clutch (not shown) may be included in the rear drive unit 136.

[0034] Motor 126 can receive power from an on-board energy storage device (e.g., a traction battery) 132. Additionally, motor 126 can provide generator functionality to convert the vehicle's kinetic energy into electrical energy, which can be stored in energy storage device 132 for later use by motor 126. Inverter system controller 134 (ISC1) can convert the alternating current generated by motor 126 into direct current for storage in energy storage device 132, and vice versa. Electric drive system 135 includes motor 126 and inverter system controller 134. Energy storage device 132 can be a battery, capacitor, inductor, or other energy storage device. Power flowing into electric drive system 135 can be monitored via current sensor 145 and voltage sensor 146. The position and rotational speed of motor 126 can be monitored via position sensor 147. Torque generated by motor 126 can be monitored via torque sensor 148.

[0035] Motor 126 can propel vehicle 121 in the forward or reverse direction in response to the position of shift selector 159. In addition, vehicle 121 can be put into parking gear (e.g., when no vehicle is moving with the wheels locked) or neutral gear in response to the position of shift selector 159.

[0036] In some examples, energy storage device 132 may be configured to store electrical energy that can be supplied via a high-voltage bus 195 (e.g., a component such as a conductor carrying current and high voltage (e.g., a voltage greater than 60 volts)). The high-voltage bus 195 may be connected to a high-voltage vehicle accessory (e.g., a heat pump, air conditioner, heater, etc.) 186 and a power converter 191 (e.g., a direct current (DC) to DC converter or an alternating current (AC) to DC converter). The power converter 191 is electrically coupled to an electrical socket 190, and the electrical socket 190 may be electrically coupled to an external charging station 198 (e.g., a DC fast charger (DCFC), a Level 2 charger (e.g., a 240-volt AC charger), or a Level 1 charger (e.g., a 120-volt AC charger)) via a wire 193. The external charging station 198 includes a non-transitory (e.g., read-only memory) 198a, random access memory 198b, digital input / output 198c, and a microcontroller 198d. Power converter 191 can control the current flow and voltage supplied to energy storage device 132. Power converter 191 may include non-transitory (e.g., read-only memory) 191a, random access memory 191b, digital input / output 191c, and microcontroller 191d. Socket sensor 197 provides indication of whether vehicle 121 is plugged into external charging station 198. External charging station 198 resides outside the vehicle (e.g., not part of the vehicle). High-voltage bus 195 may also be electrically coupled to DC / DC converter 184, which allows power to be transferred from high-voltage bus 195 to low-voltage bus 196 (e.g., conductors, terminals, and other conductive links). Thus, power can be exchanged between energy storage device 132 and low-voltage battery 182 (e.g., battery voltage less than 20 volts). Low-voltage battery switch 185 can be selectively disconnected to prevent power supply (e.g., 12 volts DC) from low-voltage bus 196 to low-voltage battery 182. The low-voltage bus 196 can distribute low-voltage power to low-voltage electrical loads 183 (e.g., power-consuming devices such as infotainment systems, windshield wipers, blowers, etc.).

[0037] return Figure 1The energy storage device 132 includes a plurality of battery cells 137, an energy storage device controller 139, and a power distribution module 138. The energy storage device controller 139 can provide charge balancing among the energy storage elements (e.g., battery cells) and communication with other vehicle controllers (e.g., controller 112). The power distribution module 138 controls the inflow and outflow of power into the energy storage device 132. A contactor 133 can selectively couple and decouple the energy storage device 132 from the high-voltage bus 195 and the inverter system controller (ISC1) 134. The inverter system controller 134 includes a non-transitory memory microcontroller 134a (e.g., read-only memory), a random access memory 134b, digital input / output 134c, and a microcontroller 134d. In some examples, the contactor 133 may be located external to the energy storage device 132. The power distribution module 138 is also shown as being directly electrically coupled to a protected DC / DC converter 169.

[0038] The energy storage device temperature control system 163 (e.g., a heat pump or heat exchanger) may include a temperature control actuator 164 (e.g., a pump, valve, electrical switch, etc.) to adjust the temperature of the energy storage device. The energy storage device temperature control system 163 may receive a requested energy storage device temperature via a controller coupled to CAN 199.

[0039] The control system 114 can communicate with the motor 126, energy storage device 132, navigation system 187, etc. The control system 114 can receive sensor feedback information from the electric drive system 135 and energy storage device 132, etc. Furthermore, the control system 114 can send control signals to the electric drive system 135 and energy storage device 132, etc., in response to this sensor feedback. The control system 114 can receive instructions from the human operator 102 or the autonomous controller regarding operator requests for output from the vehicle propulsion system. For example, the control system 114 can receive sensor feedback from a pedal position sensor 194 communicating with pedal 192. Pedal 192 can schematically represent a pedal requested by the driver. Similarly, the control system 114 can receive instructions from the operator (e.g., user) requesting vehicle deceleration via the human operator 102 or the autonomous controller. For example, the control system 114 can receive sensor feedback from a pedal position sensor 157 communicating with the vehicle brake caliper control pedal 156.

[0040] One or more wheel speed sensors (WSS) 123 may be coupled to one or more wheels of the vehicle propulsion system 100. The wheel speed sensors can detect the rotational speed of each wheel. Such an example of a WSS may include a permanent magnet type sensor.

[0041] Controller 112 may form part of control system 114. In some examples, controller 112 may be a single controller for the vehicle. Control system 114 is shown receiving information from multiple sensors 116 (various examples of which are described herein) and sending control signals to multiple actuators 181 (various examples of which are described herein). As an example, sensor 116 may include a tire pressure sensor (not shown), wheel speed sensor 123, etc. In some examples, sensors associated with motor 126, wheel speed sensor 123, etc., may transmit information to controller 112 about various states of motor operation. Controller 112 includes non-transitory (e.g., read-only memory) 165, random access memory 166, digital input / output 168, and microcontroller 167. Controller 112 may receive input data via CAN 199 and provide the data to human / machine interface 140. Additionally, controller 112 can transmit vehicle data and receive commands (e.g., a request to prepare the vehicle for long-term storage) via transceiver 160 and remote device 161 (e.g., a cellular phone, tablet, or other remote wireless device). Remote device 161 can transmit commands and receive data via cellular or satellite network 162.

[0042] Now for reference Figure 2 The diagram shows an exploded view of a portion of an exemplary battery cell 137. Battery cell 137 includes a cathode electrode 218 and an anode electrode 220 for connection to a busbar (not shown). The anode electrode 220 may comprise graphite. The busbar transfers charge from one battery cell to another. Battery cell 137 can be combined with other battery cells in series and / or in parallel. When battery cells are combined in parallel, the busbar (not shown) is coupled like the battery cell electrodes. For example, the positive electrode of a first battery cell is coupled to the positive electrode of a second battery cell to combine the battery cells in parallel. The busbar also couples the positive and negative electrodes of the battery cells when it is desired to increase the voltage of the battery pack. In this example, battery cell 137 also includes a pouch cell 224 containing an electrolyte compound. However, it is understood that battery cell 137 can have different shapes (e.g., cylindrical or prismatic).

[0043] Figure 1 and Figure 2The system provides a system for charging a battery cell, the system comprising: a power source for charging the battery cell; and one or more controllers, the one or more controllers including executable instructions stored in a controller memory, the executable instructions causing the one or more controllers to adjust the charging rate of the battery cell via the power source in response to a voltage level, the voltage level being referenced from a table or function via the C-rate of the battery cell and the temperature of the battery cell, the voltage level being based on a reference voltage, wherein the reference voltage is a voltage at which lithium plating of the battery cell is not expected to occur. In a first example, the system further includes additional instructions for performing the following: replacing the voltage level in the table or function with a second voltage level based on the amount of current flowing into the battery cell. In a second example that may include the first example, the system further includes additional instructions for performing the following: determining the second voltage level based on the second derivative of the battery cell voltage with respect to the battery cell charge. In a third example that may include one or both of the first and second examples, the system includes: wherein the voltage at which lithium plating is expected to not occur in the battery cell is based on experimental results of charging the battery cell. In a fourth example, which may include one or more of the first to third examples, the system further includes additional instructions for performing the following operations: replacing multiple voltage levels including voltage levels in the table or function. In a fifth example, which may include one or more of the first to fourth examples, the system further includes additional instructions for performing the following operations: determining the derivative of the battery cell voltage with respect to the charge capacity of the battery cell. In a sixth example, which may include one or more of the first to fifth examples, the system includes a power converter in which the power source is stated.

[0044] Now for reference Figure 3 The graphs show the rate of change of battery cell pressure with battery cell charge capacity and the battery cell charge capacity, as well as the rate of change of battery cell voltage with battery cell charge capacity and the battery cell charge capacity.

[0045] from Figure 3The first graph, starting at the top, is a graph of the rate of change of battery cell pressure with battery cell charge capacity (dP / dQ) versus battery cell charge capacity. The vertical axis represents the rate of change of pressure with battery cell charge capacity, in kilonewtons per ampere-hour. The horizontal axis represents battery cell charge capacity, in ampere-hours. The first graph includes multiple traces 302-316. Each trace represents a constant charging current for different battery cells at a fixed ambient temperature, and each trace is identified by a specific numerical identifier. Trace 302 represents a charging rate of 2.25C, trace 304 represents a charging rate of 2C, trace 306 represents a charging rate of 1.75C, trace 308 represents a charging rate of 1.5C, trace 310 represents a charging rate of 1.25C, trace 312 represents a charging rate of 1C, trace 314 represents a charging rate of 0.75C, and trace 316 represents a charging rate of C / 3.

[0046] From Figure 3 The second graph at the top is a graph of the rate of change of battery cell voltage with battery cell charge capacity (dV / dQ) versus battery cell charge capacity. The vertical axis represents the rate of change of battery cell voltage with battery cell charge capacity, in volts per ampere-hour. The horizontal axis represents battery cell charge capacity, in ampere-hours. The second graph includes multiple traces 320-334. Each trace represents a constant charging current for a different battery cell, and each trace is identified by a specific numerical identifier. Trace 320 represents a charging rate of 2.25C, trace 322 represents a charging rate of 2C, trace 324 represents a charging rate of 1.75C, trace 326 represents a charging rate of 1.5C, trace 328 represents a charging rate of 1.25C, trace 330 represents a charging rate of 1C, trace 332 represents a charging rate of 0.75C, and trace 334 represents a charging rate of C / 3.

[0047] Included Figure 3 The curves in the two graphs fluctuate due to three main reasons: 1) material phase transition effect, 2) polarization effect, and 3) effect caused by lithium plating. As shown in the figure, material phase transition and polarization effects can complicate the detection of the initiation of lithium plating. Figure 3 The second curve at the top shows that for charging rates less than or equal to 1.5C, no discernible pattern is visible in the battery cell voltage data. Additionally, pressure measurements within the battery cell can increase the resources available for battery arrays or packs. Therefore, the rate of change of pressure with respect to battery cell charge capacity, and the rate of change of voltage with respect to battery cell charge capacity, can be disregarded when estimating lithium plating within the battery cell.

[0048] Now for reference Figure 4The graphs show the reference pressure compensation rate of change of battery cell pressure with battery cell charge capacity and the battery cell charge capacity, as well as the reference pressure compensation rate of change of battery cell voltage with battery cell charge capacity and the battery cell charge capacity.

[0049] From Figure 4 The first graph at the top is a graph of the rate of change of battery cell pressure with battery cell charge capacity (dP / dQ) versus battery cell charge capacity. The vertical axis represents the rate of change of pressure with battery cell charge capacity, with reference pressure compensation, in kilonewtons per ampere-hour. The horizontal axis represents battery cell charge capacity, in ampere-hours. The first graph includes multiple traces 402-414. Each trace represents a constant charging current for a different battery cell, and each trace is identified by a specific numerical identifier. Trace 402 represents a charging rate of 2.25C, trace 404 represents a charging rate of 2C, trace 406 represents a charging rate of 1.75C, trace 408 represents a charging rate of 1.5C, trace 410 represents a charging rate of 1.25C, trace 412 represents a charging rate of 1C, and trace 414 represents a charging rate of 0.75C.

[0050] From Figure 4 The second graph at the top is a graph of the reference voltage compensation rate of change (dV / dQ) of the battery cell voltage versus the battery cell charge capacity. The vertical axis represents the reference voltage compensation rate of change of the battery cell voltage versus the battery cell charge capacity, in volts per ampere-hour. The horizontal axis represents the battery cell charge capacity, in ampere-hours. The second graph includes multiple traces 420-432. Each trace represents a different constant charging current for a different battery cell, and each trace is identified by a specific numerical identifier. Trace 420 represents a charging rate of 2.25C, trace 422 represents a charging rate of 2C, trace 424 represents a charging rate of 1.75C, trace 426 represents a charging rate of 1.5C, trace 428 represents a charging rate of 1.25C, trace 430 represents a charging rate of 1C, and trace 432 represents a charging rate of 0.75C.

[0051] To overcome the limitations of dV / dQ analysis, the voltage change rate is compensated via a reference voltage, and the evaluation is performed. ,in , where V is the measured cell voltage across the cell electrodes of a standard two-electrode cell during constant current cell charging. Vref is a variable representing the voltage during a constant current charging rate, where lithium plating at the cell anode is not expected to occur at a given temperature (e.g., at a relatively slow charging rate, such as C / 3), and Q is the cell charge capacity. The Vref variable is not constant over time (e.g., it varies over time) and / or may vary with the cell state of charge (SOC) or cell charge capacity. In one example, Vref can be determined for a specific cell C-rate and temperature by charging the cell at a specific C-rate and temperature and then checking for lithium plating after charging. If lithium plating at the cell anode is not detected due to the C-rate at a specific temperature, then the C-rate and the cell voltage at the specific temperature can be chosen as Vref. The battery cell voltage is also monitored, and if lithium plating is observed after charging, the battery cell voltage during charging can be determined as a threshold voltage to reduce the likelihood of lithium plating in the battery cell. The battery cell voltage value is interpolated into a function or table that can be referenced by C-rate and battery cell temperature. Vref being the maximum C-rate at which lithium plating at the battery cell anode is not expected can be beneficial. This is because the closer the C-rate at which Vref is obtained is to the actual C-rate at which lithium plating occurs at the battery cell anode, the closer the polarization in the battery cell voltage data will be. This can increase signal sensitivity and improve the signal-to-noise ratio of the measurement technique. By introducing... This term can eliminate material phase transition voltage fluctuations from dV / dQ, making The curves or traces vary primarily due to polarization and lithium plating, thereby increasing the likelihood of detecting lithium plating at the anode of the battery cell.

[0052] From Figure 4 In the first and second curves at the top, for a specific trace, the start of lithium plating at the anode of the battery cell is indicated by a circular mark (e.g., 402a) placed above the specific trace, as indicated for each trace. Additionally, it can be observed that for battery cell capacities exceeding the threshold battery cell charge capacity, The curve includes ratio Figure 3 The larger negative slope of the dV / dQ curve shown can help to more robustly determine the lithium plating of the battery cell anode. Furthermore, compared to... Figure 3 Compared to the dV / dQ curves shown, after assuming a negative slope for battery cell capacities greater than the threshold capacity, The curve has a small tendency to become a positive slope. Therefore, by monitoring... The curves make it easier to identify the condition of lithium plating.

[0053] Now for reference Figure 5 The graphs show the second derivative of the change in battery cell pressure with reference pressure compensation for battery cell charge capacity and the battery cell charge capacity, as well as the second derivative of the rate of change of battery cell voltage with reference voltage compensation for battery cell charge capacity and the battery cell charge capacity.

[0054] From Figure 5 The first curve at the top is the second derivative (d) of the reference pressure compensation change of the battery cell pressure as a function of the battery cell charge capacity. 2 P / dQ 2 This is a graph showing the relationship between the battery cell pressure and its charge capacity. The vertical axis represents the second derivative of the reference pressure compensation for changes in battery cell pressure with varying charge capacity, expressed in kilonewtons per ampere-hour. The horizontal axis represents the battery cell charge capacity, expressed in ampere-hours. The first graph includes multiple traces 502-512. Each trace represents a constant charging current for a different battery cell, and each trace is identified by a specific numerical identifier. Trace 502 represents a charging rate of 2.25C, trace 504 represents a charging rate of 2C, trace 506 represents a charging rate of 1.75C, trace 508 represents a charging rate of 1.5C, trace 510 represents a charging rate of 1.25C, and trace 512 represents a charging rate of 1C.

[0055] From Figure 5 The second curve at the top is the second derivative (d) of the reference voltage compensation change of the battery cell voltage as the battery cell charge capacity changes. 2 V / dQ) 2 The graph shows the relationship between the battery cell charge capacity and the reference voltage. The vertical axis represents the derivative of the reference voltage-compensated battery cell voltage with respect to the battery cell charge capacity, in volts per ampere-hour. The horizontal axis represents the battery cell charge capacity, in ampere-hours. The second graph includes multiple traces 520-530. Each trace represents a constant charging current for a different battery cell, and each trace is identified by a specific numerical identifier. Trace 520 represents a charging rate of 2.25C, trace 522 represents a charging rate of 2C, trace 524 represents a charging rate of 1.75C, trace 526 represents a charging rate of 1.5C, trace 528 represents a charging rate of 1.25C, and trace 530 represents a charging rate of 1C.

[0056] From Figure 5 In the first curve at the top, it can be seen via The threshold level of the battery cell's charge capacity exceeding the threshold charge capacity is used to determine the start of lithium plating at the anode of the battery cell. Different threshold levels may exist for each battery cell's C-rate.

[0057] From Figure 5In the second curve at the top, it can be seen via A threshold level (e.g., ε) for the charge capacity of a battery cell exceeding a threshold charge capacity (e.g., δ) is used to determine the start of lithium plating at the anode of the battery cell. Different threshold levels may exist for each battery cell's C-rate or temperature. The threshold level is indicated by ε. In this example, the threshold charge capacity of the battery cell is indicated by a vertical line marked δ.

[0058] The second derivative with respect to the battery cell charge can be used to determine at what battery cell voltage and C-rate the anode lithium plating begins, because the second derivative increases the signal-to-noise ratio of the voltage, which can serve as the basis for determining the likelihood of lithium plating on the battery cell anode electrode. Furthermore, this method provides a simple algorithmic approach for detecting the onset of lithium plating.

[0059] Now for reference Figure 6 The image shows two graphs. (Source: [Insert Source Here]) Figure 6 The first graph at the top is a graph showing the battery cell voltage versus the battery cell's C-rate. The vertical axis represents the battery cell voltage and the horizontal axis represents the battery cell's C-rate. (Source: [Original Source Name]) Figure 6 The first curve at the top of the graph shows hollow points (e.g., 602) and shaded points (e.g., 604). Hollow points represent points based on... Figure 4 and Figure 5 The detection method shown estimates or anticipates the cell voltage at which Li electroplating occurs to the anode of the battery cell. The shaded dots indicate the voltage based on... Estimate or anticipate the cell voltage at which Li plating occurs at the anode of the battery cell. The voltage, represented by hollow dots and shaded dots, is determined via the two electrodes of the battery cell, one of which is the positive electrode and the other is the negative electrode.

[0060] Hollow dots and shaded dots indicate that, for the start of lithium plating at a given ambient temperature, the cell voltage increases as the C-rate of the cell decreases. Hollow dots and shaded dots exhibit a similar relationship between cell voltage and C-rate.

[0061] From Figure 6 The second graph at the top is a graph showing the battery cell's charge capacity versus its C-rate. The vertical axis represents the battery cell's charge capacity, and the horizontal axis represents the battery cell's C-rate. (Source: [Original Source Name]) Figure 6 The first curve at the top of the graph shows hollow points (e.g., 610) and shaded points (e.g., 612). Hollow points represent points based on... Figure 4 and Figure 5 The detection method shown estimates or anticipates the battery cell capacitance when Li electroplating occurs at the anode of the battery cell. The shaded dots indicate the capacitance based on... Estimate or anticipate the battery cell charge capacity when Li electroplating occurs at the anode of the battery cell. The battery cell charge capacity, represented by hollow dots and shaded dots, is determined via a two-electrode battery cell, one of which is the positive electrode and the other is the negative electrode.

[0062] Now for reference Figure 7 The image shows a photographic image of the anode of a battery cell without lithium plating. It can be... Figure 7 The images in Figure 8 The images were compared to distinguish between anode electrodes without lithium plating and anode electrodes including lithium plating.

[0063] Now for reference Figure 8 The image shows a photographic image of the anode of a battery cell, including lithium plating. Some of the lithium plating is indicated by arrows. This lithium plating reduces the available lithium within the battery cell, increases the likelihood of micro-short circuits, leads to gas generation within the battery cell, and increases the resistance of the anode surface. Figure 8 It is more than and An example of lithium plating in a battery cell, indicating the voltage at which lithium plating occurs.

[0064] Now for reference Figure 9 and Figure 10 This paper illustrates a method for detecting the initiation of lithium plating on the anode electrode of a battery cell and for updating the battery cell voltage for which lithium plating is expected to occur. At least a portion of method 900 may be included as executable instructions stored in a non-transitory memory of one or more controllers. Furthermore, some portions of method 900 may be actions performed in the physical world via one or more controllers and one or more actuators.

[0065] Figure 9 The method describes monitoring battery cell voltage and adjusting the battery cell voltage to a level that must not be exceeded during charging. However, it is understood that... Figure 9 and Figure 10 In this method, battery cell pressure can replace battery cell voltage to achieve essentially the same result as reducing the likelihood of lithium plating on the battery cell anode.

[0066] At 902, method 900 determines the battery cell operating conditions to determine the battery cell's operating state. Battery cell operating conditions may include, but are not limited to, battery cell voltage, battery cell temperature, battery cell pressure, and the current flowing into or out of the battery cell. Method 900 proceeds to 904.

[0067] At 904, method 900 determines whether the traction battery is being charged. The traction battery and its individual battery cells can be charged via a DC fast charger (DCFC), alternating current (AC), or regenerative current. If the traction battery is charged via a stationary power source, the vehicle charger can supply current to the battery at a constant rate. If the traction battery is charged via the vehicle's propulsion power source, the inverter can supply current to the battery and battery cells at a constant rate. Method 900 can determine whether the traction battery is being charged based on the operating state of the vehicle's power converter or the operating state of the inverter electrically coupled to the traction battery. If method 900 determines that the traction battery is being charged, the answer is yes, and method 900 proceeds to 904. Otherwise, the answer is no, and method 900 proceeds to 910.

[0068] At 906, method 900 determines the C-rate of the battery cell, where the C-rate is the amount of current that the battery receives during charging or discharging over a specific duration. The C-rate can be defined as the charge capacity of the battery cell divided by one hour. The current C-rate of the battery can be determined by dividing the current flowing through the battery cell by the rated energy storage (Ah (ampere-hours)) of the battery cell. The battery is charged using a constant charging current. Method 900 proceeds to 908.

[0069] At 908, method 900 determines a battery cell voltage threshold or alternatively, battery cell pressure, based on the current battery cell C-rate and current battery cell temperature. Specifically, method 900 indexes or references a table or function that outputs voltage thresholds in response to the battery's current C-rate and current temperature. After the voltage values ​​have been determined via vehicle and battery testing, the voltage values ​​in the table or function are stored. Battery testing may include charging the battery cells at the C-rate and temperature, and then checking the lithium plating on the anode electrode of the battery cells after the charging phase. This process can be repeated for multiple C-rates and temperatures. The battery cell voltage or pressure at the start of lithium plating is stored in the table or function such that the charger or charging device does not supply charging current for voltages higher than the threshold voltage at the current C-rate and battery cell temperature. Method 900 may transmit voltage thresholds to inverter system controller 134, power converter 191, external charging station 198, and / or other devices such that no charging current is supplied to the battery cells when the battery cell voltage is higher than these voltages or when the battery cell pressure is greater than the threshold pressure. Method 900 proceeds to 910.

[0070] At 910, method 900 begins charging the battery cells of the traction battery. In one example, the external charging station can initiate the charging process by starting charging the battery cells at a higher C-rate (e.g., 3C) and incrementally reducing the charging current to a lower C-rate (e.g., C / 3) in response to the battery cell voltage. For example, DCFC can begin charging the battery cells at 3C, and if the battery cell voltage reaches a voltage threshold as determined in step 908 (e.g., a voltage threshold based on the 3C charging rate), DCFC reduces the charging current to the battery cells to 2.5C and continues charging the battery cells to a threshold charge amount or to a second voltage threshold as determined in step 908. This process can be repeated multiple times until the battery cells are fully charged, requiring a switch to a constant voltage mode, or the user stops the charger from charging the battery cells. In other examples, the battery cells can be charged via a traction inverter or power converter through a similar procedure, such that the traction inverter or power converter adjusts the charging rate of the battery cells. Method 900 proceeds to 912.

[0071] At 912, method 900 determines whether to update the lithium-ion battery cell voltage threshold or pressure threshold. In one example, method 900 may determine to update the lithium-ion battery cell voltage threshold in response to the cumulative amount of current entering and leaving the battery cell exceeding a threshold. Alternatively, method 900 may determine to update the lithium-ion battery cell voltage threshold based on the amount of time since the most recent update of the lithium-ion battery cell voltage threshold or the amount of time since the most recent update of the lithium-ion battery cell pressure threshold. If method 900 determines that the lithium-ion battery cell voltage threshold (e.g., a value in the table or function mentioned at step 908) or the lithium-ion battery cell pressure threshold needs to be updated, the answer is yes, and method 900 proceeds to 914. Otherwise, the answer is no, and method 900 proceeds to exit.

[0072] At 914, method 900 selects an initial C-rate for the current temperature of the battery cell. In one example, the method begins with a value of 2C. However, before performing steps after step 914, method 900 may charge or discharge the battery cell to a predetermined state of charge (SOC) value from which a constant current assessment of the battery cell can be performed. For example, method 900 may adjust the SOC of the battery cell to a specific state (e.g., 10% SOC) before performing steps after step 914. Therefore, performing at least part of method 900 may be advantageous when the battery cell has already been discharged and when user operation allows for slower charging (e.g., overnight). Method 900 proceeds to 916.

[0073] At 916, method 900 begins charging the battery cell at the C-rate selected in step 914. The battery cell is charged at a constant current level. Method 900 proceeds to 918.

[0074] At 918, method 900 measures the battery cell voltage or pressure. The battery cell voltage can be measured between the anode (-) and cathode (+) of the battery cell. The battery cell pressure can be measured via a pressure sensor. Method 900 can continuously monitor the battery cell voltage. Method 900 proceeds to 920.

[0075] At position 920, method 900 is determined. The value is generated over a period of time. A vector of values. In a continuous-time example, it can be determined And via (V(t)-Vref(t) and Sure Therefore, dQ / dt is I(t), therefore Vref can be determined as described above. If the battery cell pressure is an observed control parameter, then determine... And it can be determined via P(t)-Pref(t). Where Pref is the reference pressure, and lithium plating at the anode of the battery cell is undesirable. Method 900 proceeds to 922.

[0076] At position 922, method 900 is determined. The derivative, or Alternatively, method 900 can determine... The derivative of . Method 900 proceeds to 924.

[0077] At position 924, method 900 determines the battery cell charge capacity for battery cells exceeding a threshold charge capacity. The first instance where the second derivative is less than the threshold. Method 900 can evaluate the battery cell's charging duration. The second derivative is used to determine the first instance. Alternatively, method 900 can determine the battery cell charge capacity for battery cells with a charge capacity greater than the threshold. The first instance where the second derivative is greater than the threshold. Method 900 proceeds to 926.

[0078] At position 926, method 900 will correspond to where The battery cell voltage whose second derivative is greater than the value of the first instance of battery change determined in step 922 is stored in the controller memory (or a slightly smaller voltage used to reduce or terminate lithium plating). Based on the C-rate and battery cell temperature to which the first instance value is determined, the battery cell voltage value is stored in a table or function. Therefore, method 900 stores the values ​​therein. The second derivative of the cell voltage v(t) at the same time t is less than the threshold. Alternatively, method 900 will correspond to the cell voltage v(t) at the same time t. The cell pressure of the battery cell, whose second derivative is greater than the value of the first instance of the threshold battery change determined in step 922, is stored in the controller memory (or used to completely reduce or terminate lithium plating at a slightly smaller voltage). Method 900 proceeds to 928.

[0079] At 928, method 900 determines whether the memory locations in the associated lookup table have been updated as expected or requested (e.g., all memory locations in the lookup table are updated completely or partially). If method 900 determines that the requested update for each of the controller memory cells corresponding to various C-multipliers has been updated, the answer is yes, and method 900 proceeds to exit. Otherwise, the answer is no, and method 900 proceeds to 930.

[0080] At 930, method 900 selects a new C-rate. In one example, method 900 may reduce the most recent previous C-rate to determine the new C-rate. For example, method 900 may reduce the most recent C-rate from 2C to 1.5C. Method 900 may also adjust the battery cell temperature by adjusting a battery cell temperature control device (e.g., heat pump, resistance heater, temperature control valve, etc.) to produce a new C-rate for a specific, predetermined battery cell temperature. Note that before performing step 930, method 900 may charge or discharge the battery cell to a predetermined state of charge (SOC) value from which a constant current assessment of the battery cell can be performed. If discharging the battery cell is unavailable, method 900 may wait until the battery cell discharges or becomes available for discharge. Method 900 then returns to 916.

[0081] Therefore, method 900 can charge the battery cell from a lower charge level to a charge level where the voltage of the battery cell is just below or at the voltage at which Li begins to plate at the anode of the battery cell. Furthermore, method 900 can modify the voltage threshold indicating that lithium plating is about to occur, thereby reducing the likelihood of lithium plating at the anode of the battery cell. Additionally, it is understood that although method 900 is described for a single battery cell, the method can be applied to an entire battery array or battery pack formed by multiple battery cells that can be arranged in parallel and series.

[0082] Figure 9 and Figure 10 The method provides a way to charge a battery cell, the method comprising: adjusting the charging rate of the battery cell via one or more controllers in response to a voltage or pressure that causes a lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage is based on a reference voltage level, or wherein the pressure is based on a reference pressure level. In a first example, the method comprises: wherein the lithium plating rate of the anode is expected to be less than a threshold lithium plating rate of the anode at a reference voltage level. In a second example that may include the first example, the method comprises: wherein adjusting the charging rate includes reducing the charging rate of the battery cell. In a third example that includes one or both of the first and second examples, the method comprises: wherein the voltage or pressure is further based on a derivative of an amount including the reference voltage level or the reference pressure level. In a fourth example that may include one or more of the first to third examples, the method comprises: wherein the battery cell is a lithium-ion battery cell. In a fifth example that may include one or more of the first to fourth examples, the method comprises: wherein the charging rate is adjusted via a DC fast charger. In a sixth example, which may include one or more of the first to fifth examples, the method includes: wherein the lithium plating rate is based on Li ions deposited on the anode without being embedded in graphite or other particles. In a seventh example, which may include one or more of the first to sixth examples, the method includes: wherein the reference voltage level is not constant relative to time.

[0083] Figure 9 and Figure 10The method also provides a method for charging a battery cell, the method comprising: adjusting the charging rate of the battery cell via one or more controllers in response to a voltage value that causes the lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage value is in a table or function stored in a controller memory (e.g., read-only memory) and is based on a reference voltage level; and updating the voltage value in the table or function in the controller memory in response to an amount of time since the value in the table or function was last updated. In a first example, the method further comprises updating a plurality of other voltage values ​​as a basis for adjusting the charging rate of the battery cell in response to the amount of time. In a second example that may include the first example, the method further comprises adjusting the temperature of the battery cell while updating the plurality of other voltage values ​​as a basis for adjusting the charging rate of the battery cell. In a third example that may include one or both of the first and second examples, the method comprises adjusting the C-rate of the battery cell while updating the plurality of other voltage values ​​as a basis for adjusting the charging rate of the battery cell. In a fourth example that may include one or more of the first to third examples, the method comprises: wherein the amount of time is since the voltage was last updated.

[0084] The methods and routines disclosed herein can be stored as executable instructions in non-transitory memory and can be implemented by a system including a controller in conjunction with various sensors and actuators. Furthermore, parts of the methods can be physical actions taken in the real world to change the state of a device. The specific routines described herein can represent one or more of any number of processing strategies (such as event-driven, interrupt-driven, multitasking, multithreading, etc.). Therefore, the various actions, operations, and / or functions shown can be performed in the shown sequence, in parallel, or in some cases omitted. Similarly, the processing order is not necessarily necessary to achieve the features and advantages of the examples described herein, but is provided for ease of illustration and description. One or more of the actions, operations, and / or functions shown can be repeatedly performed according to the specific strategy used. Furthermore, the described actions, operations, and / or functions can be graphically represented as code programmed into a non-transitory memory of a computer-readable storage medium in the system, wherein the described actions are implemented by executing instructions in a system including various hardware components in conjunction with an electronic controller. One or more of the method steps described herein can be omitted if desired.

[0085] While various embodiments have been described above, it is understood that these embodiments are presented by way of example rather than limitation or constraint. It should be understood that the configurations and routines disclosed herein are exemplary in nature, and these specific examples should not be considered limiting, as numerous variations are possible. For example, the above-described techniques can be applied to powertrain systems including different types of propulsion sources, such as different types of electric motors, internal combustion engines, and / or transmissions. The techniques can be used independently or in combination with other powertrain systems, which, as examples, are not limited to mechanical and propulsion systems for tandem axles, electric support axles, P4 axles, HEVs, BEVs, agricultural vehicles, marine vehicles, motorcycles, recreational vehicles, and on-road and off-road vehicles. The subject matter of this disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations disclosed herein, as well as other features, functions, and / or properties. It will be apparent to those skilled in the art that the disclosed subject matter may be embodied in other specific forms without departing from the spirit of this subject matter.

[0086] The appended claims specifically point to certain combinations and sub-combinations considered novel and non-obvious. These claims may refer to an “a” element or a “first” element or its equivalent. Such claims are to be understood as including a combination of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and / or properties may be claimed by amending these claims or by setting new claims in this application or related applications. Such claims, whether broader, narrower, equivalent, or different in scope from the original claims, are also considered to be included within the subject matter of this disclosure. As used herein, unless otherwise specified, the term “about” is interpreted as representing ±5% of the stated scope.

Claims

1. A method for charging a battery cell, comprising: The charging rate of the battery cell is adjusted via one or more controllers in response to a voltage or pressure that causes the lithium plating rate of the anode of the battery cell to be greater than a threshold amount, wherein the voltage is based on a reference voltage level or the pressure is based on a reference pressure level.

2. The method of claim 1, wherein the lithium plating rate of the anode is expected to be less than the threshold lithium plating rate of the anode at the reference voltage level.

3. The method of claim 1, wherein adjusting the charging rate includes reducing the charging rate of the battery cell.

4. The method of claim 1, wherein the voltage or pressure is further based on the derivative of a quantity including the reference voltage level or the reference pressure level.

5. The method of claim 1, wherein the battery cell is a lithium-ion battery cell.

6. The method of claim 1, wherein the charging rate is adjusted via a DC fast charger.

7. The method of claim 1, wherein the lithium plating rate is based on lithium ions deposited on the anode without being embedded in the graphite or other particles of the anode.

8. The method of claim 1, wherein the reference voltage level is not constant with respect to time.

9. A system for charging battery cells, the system comprising: A power source, used to charge the battery cells; as well as One or more controllers, the one or more controllers including executable instructions stored in a controller memory, the executable instructions causing the one or more controllers to adjust the charging rate of the battery cell via the power source in response to a voltage level, the voltage level being referenced from a table or function via the C-rate of the battery cell and the temperature of the battery cell, the voltage level being based on a reference voltage, wherein the reference voltage is a voltage at which lithium plating of the battery cell is not expected to occur.

10. The system of claim 9, further comprising additional instructions for performing the following operation: replacing the voltage level in the table or function with a second voltage level based on the amount of current flowing into the battery cell.

11. The system of claim 10, further comprising additional instructions for performing the following operation: determining the second voltage level based on the second derivative of the battery cell voltage with respect to the battery cell charge.

12. The system of claim 9, wherein the voltage at which lithium plating is not expected to occur in the battery cell is based on experimental results of charging the battery cell.

13. The system of claim 9, further comprising additional instructions for performing the following operations: replacing a plurality of voltage levels including the voltage level in the table or function.

14. The system of claim 9, further comprising additional instructions for performing the following operation: determining the derivative of the battery cell voltage with respect to the charge capacity of the battery cell.

15. The system of claim 9, wherein the power source is a power converter.

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