Physics-based control of battery temperature

Abstract

In one embodiment, an electrochemical cell system includes at least one electrochemical cell unit, a thermal control system operably connected to the at least one electrochemical cell unit, a memory in which is stored a physics-based model of the at least one electrochemical cell unit and in which are stored program instructions, and a controller operably connected to the at least one electrochemical cell unit, the thermal control system, and the memory. The controller is configured to execute the program instructions to identify a first requested operation, obtain a first generated target temperature of the physics-based model and the identified first requested operation, and control the thermal control system based on the obtained first target temperature while controlling the at least one electrochemical cell unit based on the identified first requested operation.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to batteries, and more particularly to a method for controlling a lithium-ion battery. BACKGROUND

[0002] The trend towards electrification of automobiles is increasing and most automobile manufacturers have announced plans to produce plug-in hybrid electric vehicles (PHEVs) and electric vehicles (EVs). Currently, lithium-ion based batteries are considered the most promising battery system for hybrid electric vehicle (HEV), PHEV, and EV applications due to their high energy density, lack of hysteresis, and low self-discharge current.

[0003] However, there are still some technical challenges in integrating lithium-ion based batteries into vehicle devices. One technical challenge is the time required to recharge a battery pack. Although fast charging is desirable for user convenience, there are daunting challenges in fast charging of lithium-ion batteries, where standard charging techniques such as constant current-constant voltage (CC-CV) can cause damage to the battery due to large current passing through the battery if used for fast charging. These large currents result in overpotential and mechanical stress in the battery, which can accelerate the aging process of the battery and result in reduced life.

[0004] Another important aspect is that the power required from the battery varies significantly while in use. For example, the demand during acceleration and while driving uphill typically exceeds the power demand of the vehicle while cruising or driving downhill.

[0005] To optimally operate the battery under these varying conditions, advanced battery management systems (BMS) have been incorporated into vehicles. The BMS is configured to provide appropriate charging strategies for replenishing the battery pack in a fast and reliable manner. The BMS is also used to regulate power output and consumption. However, the incorporation of the BMS is complex because the above conditions are not the only variable that must be handled.

[0006] For example, the performance of a lithium-ion battery decreases with use and time. The energy and power storage capability decreases due to a variety of mechanisms, including (but not limited to) 1) loss of available lithium, 2) loss of electrode host material, and / or 3) increase in cell internal resistance. Lithium can be lost in a solid-electrolyte interphase (SEI) or through lithium deposits (e.g., dendrites). The electrode host material also degrades over time. For example, manganese oxide materials can undergo manganese dissolution. Thus, the physical properties of a particular battery cell change during the life of the battery cell.

[0007] However, the physical property changes in the battery cell are not linear with time for each battery cell. The battery's temperature rise affects the rate of these degradation mechanisms. For example, at elevated temperatures, the rate of side reactions increases, which prematurely ages the battery cell by creating capacity fade and increased internal resistance. High energy battery cells, such as those incorporating lithium, can be more sensitive to temperature effects due to higher electrode loading, lower electrode porosity, and less amount of electrolyte. The reason for the electrolyte reduction is because as the battery cell cycles and the materials expand / contract, the electrolyte can be squeezed out of the battery cell electrode.

[0008] However, higher temperatures are not entirely detrimental to the battery. Thus, while higher temperatures increase the rate of SEI growth, higher temperatures can also decrease the risk of dendrite formation. Furthermore, raising the battery cell temperature can accelerate the diffusion of electrolyte back into the battery cell electrode. Increased temperature also accelerates ion diffusion between electrodes, as well as transport / dynamics when lithium ions intercalate / deintercalate. Thus, the internal resistance of a lithium ion battery generally decreases with increasing temperature (within a specified operating range), thereby increasing the battery power and energy density. Additionally, with the decrease in internal resistance, less voltage is needed as a driving force during charging (less resistance). Thus, for a given voltage, the charging rate increases.

[0009] Therefore, the upper temperature limit associated with battery cells, particularly lithium ion battery cells, is typically set at a temperature that balances the over-aging with the benefits of a warmer temperature. However, the temperature limit is based on nominal battery cells, not on the specific physical properties of a particular battery cell at a particular time. Thus, the temperature limit is typically overly conservative in order to protect non-nominal battery cells. Furthermore, some temperature limits are established without regard to the actual life of the battery cell.

[0010] The deficiency of simply using nominal battery cell data is illustrated by reference to the rate of detrimental side reactions. The rate of side reactions, while related to temperature, is also related to the state of charge (SOC) of the battery cell. As the SOC of the battery cell increases for a given temperature, the rate of side reactions increases over a given life time. Thus, a single temperature limit unnecessarily restricts the operation of the battery during charging events and discharging events.

[0011] Furthermore, in addition to the battery cell considerations, actual system (e.g., vehicle) embodiments must also consider operational requirements. For example, a user who infrequently takes trips that require recharging during the trip can determine that the convenience of fast charging in order to continue a particular trip outweighs the cost of increased battery aging due to fast charging, as such fast charging is infrequently used. Thus, the loss of battery life is offset by the convenience of faster charging.

[0012] Accordingly, a BMS that better balances the operational requirements of a battery while minimizing the effects of, for example, battery aging would be beneficial. It would be even more beneficial if the user of the system could influence the way the BMS controls battery operation to take into account the user's operational expectations for the overall system. SUMMARY

[0013] In one embodiment, an electrochemical cell system includes at least one electrochemical cell unit, a thermal control system operably connected to the at least one electrochemical cell unit, a memory having stored therein a physics-based model of the at least one electrochemical cell unit and program instructions, and a controller operably connected to the at least one electrochemical cell unit, the thermal control system, and the memory. The controller is configured to execute the program instructions to identify a first requested operation, obtain a first generated target temperature based on the physics-based model and the identified first requested operation, and control the thermal control system based on the obtained first target temperature while controlling the at least one electrochemical cell unit based on the identified first requested operation.

[0014] In one or more embodiments, obtaining a first generated target temperature based on the physics-based model and the identified first requested operation includes obtaining at least one cell unit first parameter of the at least one cell unit using a sensor suite associated with the at least one cell unit. The system then sets a model target temperature to a predetermined temperature associated with the first requested operation and a model target current to a maximum current associated with the first requested operation. The first future at least one cell unit second parameter of the at least one cell unit is then predicted using the physics-based model based on the obtained at least one cell unit first parameter using the model target temperature and the model target current. The predicted first future at least one cell unit second parameter is then compared to a threshold value and, if satisfactory, the model target temperature and current are set as the generated target temperature and current for controlling the cell unit.

[0015] In one or more embodiments, the controller is further configured to execute the program instructions to identify any additional requested operations different from the first requested operation. The system then obtains a different generated target temperature based on the physics-based model and the identified second requested operation and controls the thermal control system based on the different generated target temperature while controlling the at least one electrochemical cell unit based on the identified second requested operation.

[0016] In one or more embodiments, the controller receives itinerary data from a user input / output device, identifies a required charging operation based on the itinerary data, and sets the required charging operation as the requested operation.

[0017] In one or more embodiments, the controller further identifies the required charging operation as a fast charging operation and uses the input / output device to alert the user of this fact. The user is then asked to authorize the controller to perform the fast charging through the input / output device.

[0018] In one or more embodiments, the controller obtains mileage data associated with the route data from a database associated with the trip. By providing the route data including the trip start time, the controller identifies the first required charging operation as a fast charging based on the obtained mileage data and the trip start time.

[0019] In one or more embodiments, obtaining the first generated target temperature based on the physics-based model and the identified requested operation includes: generating a modified model target temperature based on the model target temperature; generating a modified model target current based on the model target current; using the physics-based model, the modified model target temperature, and the modified model target current, predicting a second future at least one battery cell second parameter of the at least one battery cell based on the obtained at least one battery cell first parameter; setting the model target temperature to the modified model target temperature; setting the model target current to the modified model target current; and comparing the second future at least one battery cell second parameter to a second threshold. If the comparison criterion(s) is / are satisfied, the model target temperature / current is used as the generated target temperature and current. Otherwise, the above steps are repeated.

[0020] According to one embodiment, a method of operating an electrochemical cell system includes utilizing a controller operably connected to at least one electrochemical cell, a thermal control system, and a memory to identify a first requested operation by executing program instructions stored in the memory. The method further includes utilizing the controller to obtain a first generated target temperature, the first generated target temperature based on a physics-based model stored in the memory and the identified first requested operation. The controller then controls the thermal control system based on the obtained first target temperature while controlling the at least one electrochemical cell based on the identified first requested operation using the controller.

[0021] In one or more embodiments, obtaining the first generated target temperature includes obtaining, using a sensor suite associated with the at least one battery cell, at least one battery cell first parameter of the at least one battery cell. The controller then sets the model target temperature to a predetermined temperature associated with the first requested operation and sets the model target current to a maximum current associated with the first requested operation. The method includes predicting, using the physics-based model, the model target temperature, and the model target current, a first future at least one battery cell second parameter of the at least one battery cell based on the obtained at least one battery cell first parameter, and comparing, with the controller, the first future at least one battery cell second parameter to a first threshold.

[0022] In one or more embodiments, the method further includes identifying, with the controller, a second requested operation, the second requested operation being different from the first requested operation; obtaining, with the controller, a second generated target temperature, the second generated target temperature being based on the physics-based model and the identified second requested operation, the second generated target temperature being different from the first generated target temperature; and controlling, with the controller, the thermal control system based on the obtained second generated target temperature while controlling the at least one electrochemical cell based on the identified second requested operation.

[0023] In one or more embodiments, the method includes receiving, with the controller, at least one route data from a user input / output device; identifying, with the controller, the first required charging operation based on the at least one route data; and setting the first required charging operation as the first required operation.

[0024] In one or more embodiments, the method includes identifying, with the controller, the first required charging operation as a fast charging operation; controlling, based on identifying the first required charging operation as the fast charging operation, the user input / output device to alert a user that the fast charging operation is required; and receiving, with the controller, authorization from the user to perform the fast charging via the input / output device.

[0025] In one or more embodiments, the at least one route data includes a trip start time, and the method further includes obtaining, with the controller, mileage data associated with the at least one route data from a database associated with the at least one route. In the method, identifying, with the controller, the first required charging operation as the fast charging operation includes using the obtained mileage data and the trip start time to identify the first required charging operation as the fast charging operation.

[0026] In one or more embodiments, obtaining the first generated target temperature further comprises generating a modified model target temperature based on the model target temperature and generating a modified model target current based on the model target current. Then, using the physics-based model, the modified model target temperature, and the modified model target current, a second future at least one battery cell second parameter of the at least one battery cell is predicted based on the obtained at least one battery cell first parameter. The method comprises setting the model target temperature to the modified model target temperature, setting the model target current to the modified model target current, and comparing the second future at least one battery cell second parameter to a second threshold. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a schematic diagram of a battery pack in accordance with the present disclosure.

[0028] Figure 2 is a schematic diagram of a system comprising a battery management system for a battery pack. Figure 1

[0029] Figure 3 is a schematic diagram of a battery cell of a battery pack of Figure 1

[0030] Figure 4 depicts a process used by a battery management system of Figure 2 to control thermal conditions in a battery pack of Figure 1 using a physics-based model of one or more battery cells of the battery pack.

[0031] Figure 5 depicts a process used by a battery management system of Figure 2 when executing a physics-based model.

[0032] Figure 6 depicts a process for identifying an intended route and verifying the ability of a system of Figure 2 to implement the route without violating battery parameter constraints.

[0033] Figure 7 depicts a plot of exemplary simulation results using a physics-based model. DETAILED DESCRIPTION

[0034] To facilitate an understanding of the principles of the embodiments described herein, reference is made to the appended drawings and description thereof. Reference to the drawings is not intended to limit the scope of the subject matter. The present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the described embodiments as would occur to one ordinarily skilled in the art to which the document pertains.

[0035] ​​Various operations can be described as multiple discrete actions or operations, in turn, that are performed in succession with each other. However, the ordering of descriptions should not be understood as implying that these operations are necessarily performed in the recited order. In some embodiments, additional operations are performed in addition to those described, or in place of those described. In some embodiments, the operations are performed in an order different from that described.

[0036] The terms "comprises", "comprising", "includes", "including", "has", "having" and the like as used herein are synonymous. The word "about" when used in relation to a number is meant to encompass at least ten percent of the number, preferably five percent of the number, and most preferably two percent of the number.

[0037] Embodiments of the present disclosure discussed below are applicable to any desired battery chemistry that exhibits temperature-dependent changes in internal resistance and / or temperature-dependent differences in internal aging processes. For illustrative purposes, some examples relate to lithium-ion batteries. As used herein, the term "lithium-ion battery" refers to any battery that includes lithium as an active material. In particular, lithium-ion batteries include, but are not limited to, lithium-based liquid electrolyte, solid electrolyte, gel electrolyte, and batteries commonly referred to as lithium polymer batteries or lithium-ion polymer batteries. As used herein, the term "gel electrolyte" refers to a polymer infused with a liquid electrolyte.

[0038] Furthermore, while described with respect to vehicle embodiments, the present disclosure is applicable to any use of a battery in an operational setting in which it is desirable to balance operational requirements with battery life loss.

[0039] Reference is now made to Figure 1 The battery pack 100 includes a plurality of battery cells 102 arranged in a battery pack housing 104. Each battery cell 102 includes a cell housing 106 from which a positive terminal 108 and a negative terminal 110 are exposed. In one embodiment of a parallel arrangement, the positive terminals 108 are connected to one another by a current collector 112, and the negative terminals 110 are connected to one another by a different current collector 114. In another embodiment, one or more of the positive terminals 108 are connected by a current collector to an adjacent negative terminal 110 to provide a series connection. The current collectors 112 / 114 are connected to respective positive and negative battery pack terminals 116, 118, which are connected to an external circuit 120.

[0040] In one embodiment, the external circuit 120 includes the electrical system of the vehicle in which the battery pack is located. The vehicle electrical system includes typical loads such as motors, lights, navigation systems, vehicle information and entertainment systems, etc. In addition, the external circuit provides charging of the battery pack 100. To this end, in some embodiments, the motor is configured as a regenerative braking system. In some embodiments, the external circuit 120 additionally / alternatively includes an external charging connection.

[0041] In Figure 1 In embodiments of the battery pack 100, a battery management system (BMS) 128 is included. The BMS 128 is operably connected to each battery cell 102 by control lines 130. Reference is made to Figure 2 The BMS 128 is described in further detail, Figure 2 The BMS 128 is shown incorporated into a system 132, which in some embodiments is an automobile. The BMS 128 includes a controller 134, a memory 136, and a communication module 138. The controller 134 is implemented in various embodiments with a general purpose or special purpose programmable processor that executes programmed instructions stored in the memory 136. In some embodiments, at least some of the functionality of the controller 134 is additionally / alternatively provided by the vehicle control system 142 and / or provided remotely from the system 132, such as by a remote controller located at a charging station, service center, manufacturing center, etc. Thus, in some embodiments, the controller 134 is implemented as multiple controllers located at the battery and / or remote from the battery cells 102 and / or the system 132.

[0042] The instructions / commands and data required to perform the programmed functions are stored in the memory 136 along with a physics-based model of the battery pack 100 and / or the battery cells 102. In some embodiments, the memory 136 is implemented as multiple memories, which in some embodiments include one or more memories remote from the BMS 128. The processor, memory, and communication module 138 or other interface circuitry configure the controller 134 to operate the battery pack 100 to charge and discharge the battery cells at desired charge and discharge rates. In various embodiments, the processor, memory, and interface circuitry components are provided on a printed circuit card or as circuitry in an application specific integrated circuit (ASIC). In some embodiments, the circuitry is implemented with discrete components or circuitry provided in a VLSI circuit. The circuitry described herein is also implemented with a combination of processors, ASICs, discrete components, or VLSI circuits. Further discussion of BMSs can be found, for example, in U.S. Patent No. 8,188,715, issued May 29, 2012, the contents of which are incorporated by reference herein in their entirety.

[0043] In addition to the battery cells 102, the controller 134 is operatively connected to a sensor suite 140. The sensor suite 140 includes various sensors for determining operating conditions of the battery cells 102. In one embodiment, one or more of the sensors are temperature sensors, voltage sensors, pressure sensors, and / or current / coulomb sensors. In some embodiments, each battery cell 102 is associated with a respective dedicated sensor suite 140 operatively connected to the battery cell 102. The sensor suite 140 in these embodiments includes one or more temperature sensors, voltage sensors, and / or current / coulomb sensors configured to obtain data for each individual battery cell.

[0044] Figure 2 The controller 134 in embodiments is also operatively connected to a vehicle control system 142, an input / output device 144 including, in one embodiment, a touchscreen, and an on-board diagnostic port 146 via a communication module 138. In various embodiments, the communication module 138 is configured to communicate wirelessly with or through one or more of the vehicle control system 142, the input / output device 144, and the on-board diagnostic port 146.

[0045] The controller 134 is also operatively connected to a temperature control system 148. The temperature control system 148 in different embodiments includes one or more of a fan, a vehicle cooling system, a heater, and the like. In some embodiments, a liquid coolant is circulated through tubes positioned proximate to the battery cells to heat / cool the battery cells. In some embodiments, air is used to heat / cool the battery cells with or without tubes. The temperature control system 148 is configured to provide heating and / or cooling to the battery pack 100 and / or the battery cells 102 under the control of the controller 134 in order to achieve a target battery cell temperature.

[0046] The controller 124 is also operatively connected to a trip-associated database 149. While depicted in Figure 2 FIG. 1 as being remote from the system 132, in some embodiments, the trip-associated database 149 is at least partially located within the memory 136. The trip-associated database includes data associated with travel. Thus, in one or more embodiments, the trip-associated database 149 includes road maps, elevation data, weather data, traffic data, and the like.

[0047] As Figure 3As shown in FIG. 1, in one embodiment, each battery cell 102 includes a positive current collector 150, a layer of positive electrode 152, and in some embodiments, a layer of separator 154, which is omitted, a negative electrode 156, and a negative current collector 158. In some embodiments, the multiple layers of battery cell 102 are stacked on top of one another so as to form an electrode stack. In other embodiments, the battery cell 102 is wound around itself in a spiral shape so as to form a so-called “jelly-roll” or “Swiss-roll” configuration. In some embodiments, additional layers are provided, such as a protective layer.

[0048] The positive current collector 150 electrically connects the positive terminal 108 of the battery cell 102 with the positive electrode 152 so as to enable electrons to flow between the external circuit 120 and the positive electrode 152. Likewise, the negative current collector 158 electrically connects the negative terminal 110 with the layer of negative electrode 156.

[0049] When the battery pack 100 is connected to an external circuit 120 powered by the battery pack 100, lithium ions separate from electrons in the negative electrode 156. The lithium ions travel through the separator 154 and into the positive electrode 152. Free electrons in the battery pack 100 flow from the negative electrode 156 through the negative current collector 158 to the negative terminal 110 of the battery cell 102. The electrons are then collected by the battery pack current collector 114 and transmitted to the battery pack terminal 118. The electrons flow through the external circuit 120 to provide power and then through the positive battery pack terminal 116 and back into the battery cell 102 via the positive terminal 108. Connecting the battery pack 100 to an external circuit that charges the battery pack 100 causes the opposite flow of electrons and lithium ions.

[0050] As noted above, a physics-based model is stored within the memory 136. In embodiments that include multiple memories 136, a simplified physics-based model is stored within the local memory 136 of the BMS 128, while a more comprehensive physics-based model is stored in a memory 136 remote from the BMS 128, such as in the vehicle control system 142, a service facility, a manufacturer’s facility, etc. Any desired physics-based model can be incorporated. Such physics-based models include those described in M. Doyle, T. F. Fuller, J. Newman, “Modeling of galvanostatic charge and discharge of the lithium / polymer / insertion cell,” J. Electrochem. Soc., 142, 5, 1505-1513 (1995); and M. Doyle, G. Newman, H. Bloom, T. F. Fuller, and Z. Liu, “Electrochemical Impedance Spectroscopy of Lithium-Ion Batteries,” J. Power Sources, 81-82, 1-8 (2000). J. Electrochem. SocT. F. Fuller, M. Doyle, J. Newman, "Simulation and optimization of the dual lithium ion insertion cell", J. Electrochem. Soc, vol. 140, no. 6, pp. 1526-1533, (1993), J. Electrochem. Soc T. F. Fuller, M. Doyle, J. Newman, "Simulation and optimization of the dual lithium ion insertion cell", J. Electrochem. Soc, vol. 140, no. 6, pp. 1526-1533, (1993), IEEE Control Systems Magazine T. F. Fuller, M. Doyle, J. Newman, "Simulation and optimization of the dual lithium ion insertion cell", J. Electrochem. Soc, vol. 140, no. 6, pp. 1526-1533, (1993), Electrochemical and Solid State Letters T. F. Fuller, M. Doyle, J. Newman, "Simulation and optimization of the dual lithium ion insertion cell", J. Electrochem. Soc, vol. 140, no. 6, pp. 1526-1533, (1993).

[0051] Side reaction loss rate limit data is also stored within the memory 136. The side reaction loss rate limit data included in the physics-based model in some embodiments identifies a limit associated with an allowable side reaction loss rate for each defined battery cell operation. In some embodiments, one or more side loss rate limit data is expressed as an associated operational limit. As an example, during "rapid charging" in general, a battery cell is initially charged at a high current for a period of time in which the voltage of the battery cell changes. Once the battery cell reaches a particular voltage, the current is reduced and the battery cell is charged at a constant voltage at the end of the charge. In some embodiments, multiple constant voltage segments are used during charging, each having a different voltage. During the segments in which the voltage remains constant, the current varies. The initial constant current and varying voltage applied to the battery cell during rapid charging is defined based on a desired maximum side loss rate, and thus is side reaction loss rate limit data. The initial constant current and varying voltage is also referred to as a "battery cell operation".

[0052] Similarly, each segment during the constant voltage segment of fast charging, where the voltage remains constant while the current is allowed to vary, is a different "cell operation." Thus, a "cell operation" includes a predefined current and voltage relationship (or a predefined current / voltage range relationship) and a "power type." The "power type" is a classification of the operation that is further used to correlate limits on the rate of side reaction loss allowed. Exemplary "power types" include normal charging, normal discharging, high power discharging, constant current charging, pulsed current charging, constant voltage charging, etc. The specific manner in which the power types are segregated varies between embodiments.

[0053] In general, normal charging and normal discharging are assigned side reaction loss rate limits that are lower than the side reaction loss rate limits associated with fast charging because the driving force for side reactions is higher during fast charging. Likewise, the side reaction loss rate limits assigned to "normal" charging are generally lower than the side reaction loss rate limits associated with at least the constant current portion of fast charging. However, side reaction loss is also a function of the time taken to perform the charging. Thus, at very slow charging rates, the cumulative side reaction loss can exceed that of normal charging. These relationships are captured within the physics-based model. Thus, when the time / current demand (or supply) is not critical to the performance of the system (e.g., vehicle) in which the battery is located, the battery is controlled by the physics-based model to minimize the impact on battery life.

[0054] As noted above, the cell temperature has a significant impact on the operational characteristics of the cell and on the impact of particular operations on the life of the cell. Thus, the controller 134 executes program instructions stored in the memory 136 to perform a process 170 of Figure 4 FIG. 17 to control the cell temperature so as to optimize the power and energy delivered to / from the battery pack 100 / cell 102. The process 170 is described with respect to a single cell 102, but in some embodiments, the process 170 is performed simultaneously or nearly simultaneously for the battery pack 100 as a whole and / or for all of the cells 102.

[0055] At block 172, the controller 134 identifies the requested operation. The requested operation can be a requested normal discharge, a requested fast discharge, a requested normal charge, a requested fast charge, etc. In some embodiments, the identification of the requested operation is based on user input and / or sensed characteristics. For example, in some embodiments, the controller 134 uses the sensor suite 140 to determine that power has been made available to charge the battery pack 100. In some embodiments, the controller 134 additionally or alternatively receives input from the input / output device 144, as discussed more fully below. In other embodiments, all criteria for determining between normal charge and fast charge are stored in the memory 136.

[0056] Once the controller 134 identifies the requested operation at block 172, the controller 134 obtains the generated target temperature for the requested operation at block 174. As discussed in further detail below, in some embodiments, a physics-based model is used to generate and store a table in the memory 136 that identifies predetermined target temperatures for a plurality of battery cell SOC ranges and / or state of health (SOH) ranges for predefined current / voltage / power types. In some embodiments, the physics-based model stored within the memory 136 and / or BMS is used to generate target temperatures based on current battery conditions in response to a request from the controller 134.

[0057] In any case, once the controller 134 obtains the target temperature, the controller 134 controls the temperature control system 148 based on the target temperature in order to heat / cool the battery cells 102 as needed to achieve the target temperature. (Block 176). At block 178, the requested operation is performed under the control of the controller 134. In some embodiments, the operation is started before the battery cells reach the desired temperature. As an example, when the battery cell temperature is to be raised, in some embodiments, the battery cells are used as resistors in order to self-heat during the initial stages of charging or discharging.

[0058] At block 180, the controller 134 determines whether the identified operation has completed. If so, the process returns to block 172 and a new operation is identified / waited for. If there is no power demand on the battery cells, the new operation can be, for example, “disconnect battery cells,” “trickle discharge,” a subsequent charge segment, etc.

[0059] If the operation has not completed at block 180, then at block 182 the controller 134 determines whether a subsequent operation has been requested. If so, the process returns to block 172. If there is no subsequent request, then the process returns to block 174 in some embodiments and the generated target temperature is again obtained. By repeatedly querying the physics-based model (or data table), the target temperature is modified as the battery condition changes during operation. In some embodiments, a single target temperature is used for the entire operation. Energy savings in certain cases can be achieved in this way, as sometimes the battery pack can not need to be thermally controlled.

[0060] In some embodiments, the generated target temperature obtained at block 174 is generated using a process 190 such as Figure 5 The process 190 uses a physics-based model stored within the memory 136. The physics-based model parameters stored within the memory 136 include parameters corresponding to the physical and chemical configuration of the battery pack 100 / cell 102 and include constraints for (e j ) current, voltage, temperature, and internal battery / cell state, which are used to limit the current level applied to the battery based on feedback from the current state of the battery and predictions from the physics-based model of the future state of the battery when a given current level is applied to the battery during a charging process. Thus, during the process 170, the controller 134 adjusts the controlled temperature at block 176 of the process 170 and the current applied to the battery for the next time increment at block 178 of the process 170 based on the process 190.

[0061] Returning to Figure 5 At block 192, the physics-based model stored in the memory 136 is initialized by the controller 134. At block 194, the controller 134 obtains battery parameters using the sensor suite 140 and / or data stored in the memory 136. To generate real-time target temperatures, the battery data including temperature, SOC, SOH, charge current, charge voltage, etc. for each cell or cell block is preferably obtained using the sensor suite 140 and / or data stored in the memory 136. To generate target temperatures for use in a lookup table, in some embodiments, nominal values of the battery data are obtained from values stored in the memory 136. Such battery data in different embodiments is generated from previous runs of the physics-based model and / or historical operation data of similar batteries / cells.

[0062] The process continues to block 196 and the controller 134 dynamically selects the maximum current level (I max), with time increments (t) during the charging operation. k During this period, the target current (I) of the model is used as the target current. k (This is provided to the battery / battery cell. For discharge operations, the maximum current is the current obtainable from the battery under the current assumed conditions for a given battery cell.) Controller 134 will also provide the model target temperature (T...) k ) is set to be equal to the previously determined optimal temperature (T) for a specific operation. opt ).

[0063] The obtained battery parameters are compared with the constraint limits stored in memory 136 to identify any constraints on operation (e j (Box 198). In Figure 5 In the example, when e j When the value of is less than zero, the individual constraint is satisfied, when e j When the value of is essentially zero, the constraint is at its maximum limit, and when e j When the value is greater than zero, the constraint is exceeded. Therefore, if there is no constraint violation at box 198, then it is based on I. k and T k To execute a physics-based model (box 200) to generate estimates for each battery parameter, and for each battery parameter, the associated e j It exists within a physics-based model.

[0064] At box 202, the estimated battery parameters are compared with the stored thresholds. If all constraints are met... j If the value is less than or equal to zero, the process continues to box 204, and I k and T k It is sent to or received by controller 134 for use in controlling the charging for the next increment (see box 174 of process 170).

[0065] If constraint e is applied at box 198... j Any one of them equal to or greater than zero, or if constraint e is applied at box 202 j If any of them is greater than zero, the process continues to box 206, and I k and T k One or more modifications in the function are to be the following: I k and T k I used for previous iterations k and T k The value (I) k-1 and T k-1 ), and current or temperature (or other parameters) exceeding the constraint (e respectively). j I and e jT ) to generate modified I k and T k , respectively, of I k + and T k + ) to the extent that the constraints e k + and T k + A physics-based model is executed to generate an estimated value for each battery parameter for which there is an associated e j at block 210. I k and T k are set to I k + and T k + .

[0066] The process then returns to block 202 and compares the estimated battery parameters from block 208 to the stored thresholds. If all of the constraints e j are less than or equal to zero, the process continues to block 204 and I k and T k are sent to the controller 134 for use in controlling charging (see block 174 of process 170). If any of the constraints e j at block 202 are greater than zero, the process returns to block 206 and one or more of I k and T k are again modified as a function of I k and T k , the values of I k and T k for the previous iteration (I k-1 and T k-1 ), and the current or temperature exceeding the constraints (e j I and e j T ) to generate new modified I k and T k (I k + and T k + ) to the extent that the constraints e

[0067] During the charging process or other operations described in Figure 4 , the process 190 is performed for each of the K time increments to select the target temperature and / or maximum current level, which also enables the battery operations to satisfy the constraints ej The optimization provided by process 170 enables recharging of the battery pack 100, for example, in a shorter time than existing CC / CV charging processes, while also reducing or eliminating accelerated aging or degradation of the battery by meeting selected constraints, such as maximum allowed internal state values, battery current, voltage, and temperature levels.

[0068] Thus, process 170 uses battery pack / cell temperature as a variable that can be increased until a side reaction loss rate limit value associated with the power type (i.e., operation) is reached. Thus, the target temperature is the maximum cell temperature that can be targeted by the controller 134 without exceeding the side reaction loss rate limit value associated with the power type.

[0069] For some embodiments that incorporate one or more lookup tables, process 190 is performed for different SOC and SOH combinations and ranges over the expected lifetime of the battery cell / battery. The resulting current and temperature parameters (I k and T k ) are stored in the lookup table for use in process 170.

[0070] As noted above, T k , also referred to herein as the“model target temperature,” is initially set to T opt for the particular operation at block 196. The“optimal” temperature is a function of a number of considerations, including, in different embodiments, one or more of the following: 1) minimizing battery cell degradation for the particular operation, 2) minimizing operation time, e.g., charging time, 3) maximum power and energy demand / availability, and 4) maximizing energy efficiency. Thus, while it is generally known that longer charging times can be less energy efficient, there is a point at which efficiency starts to decrease. This point is identified using a physics-based model in order to maximize efficiency.

[0071] In some embodiments, process 170 / 190 is further used to parameterize an aging model of the battery cell / battery. By observing many battery packs over time (e.g., in electric vehicles), the variation in cell parameters and aging behavior can be correlated. For example, the loss of recyclable lithium can be correlated with time at different temperatures and voltages, and the optimal temperature for the battery pack can be appropriately modified. Thus, the system is made informed by both the physics-based model and the parameters collected from machine learning as the battery pack ages.

[0072] As noted above, in some embodiments, the identification of the requested operation at block 172 includes user input through input / output devices 144. For example, the user can request "quick charging" or be asked to select between "quick charging" and "normal charging." In one embodiment, since there is some increased aging of battery pack 100 during quick charging as compared to normal charging, the user is allowed to control when such quick charging occurs.

[0073] In one embodiment, the user interface of input / output devices 144 allows the user to provide input for identifying the requested operation by providing details regarding future operation of the battery pack, as described with respect to process 220 of Figure 6 At block 222, the user inputs route data, which in different embodiments includes the mileage to be traveled in the next segment and the time of departure. In one embodiment, the user input includes route data of one or more of a destination, way points, a desired time of arrival, a desired time of departure, etc. In any case, controller 134 then accesses one or more journey-associated databases as needed to identify one or more of the route mileage, the mileage between way points, elevation changes, the speed / speed profile of the route, weather, typical traffic patterns, etc. (block 224). In some embodiments, the journey-associated databases are stored within memory 136. In some embodiments, at least some of the journey-associated databases are located remotely from the vehicle.

[0074] At block 226, the controller obtains battery parameters including SOC, SOH, current temperature, etc. using sensor suite 140, and at block 228, controller 134 executes a physics-based model in conjunction with the route data and the battery parameter data. In embodiments where the user has identified multiple destinations / way points and times of arrival / departure, the physics-based model is configured to determine the SOC at the end of each segment, as well as the start SOC of the next segment with normal charging between the termination of the first segment and the start of the second segment.

[0075] The results of the executed model provide an estimate of system 100 to achieve the input route associated with the route data without violating any constraints (block 230). In addition to SOC and temperature constraints, the constraints in various embodiments also include speed constraints, charging time constraints, quick charging constraints, etc. If there are no system constraints, process 220 continues to block 232 and informs the user using input / output devices 144 that the system is available for the journey. In some embodiments, the heat profile generated during process 220 is made available to the user at block 232. At block 232, the user is further informed of any actions necessary to perform the route (e.g., billing).

[0076] In some embodiments, the data generated at block 232 is further used to identify the requested operation at block 172 of process 170. As an example, for simplicity, using a single input, when the only input to process 220 is a predetermined departure time, once the constraints at block 230 are passed, at block 232, the start time is passed to process 170 as the requested warm-up / cool-down operation. The system then determines at block 176 the most efficient method for controlling the battery to the nominal drive temperature at the predetermined departure time, such as by keeping the battery warm, allowing a certain amount of cooling before heating, etc.

[0077] Returning to Figure 6 If at block 230, all of the constraints are not satisfied, the system proceeds to block 234 and issues an alert using input / output device 144. In some embodiments, in addition to the alert, controller 134 provides suggestions as to how to modify the route to complete the desired trip. Such modifications in various embodiments include: performing one or more fast charges, modifying the arrival time to provide a more efficient vehicle speed, modifying the departure time to allow for additional charging, etc. In some embodiments, the constraints include a lower SOC limit for activating the thermal control system. Thus, the alert is issued informing the user that the temperature will not be controlled to the optimal temperature due to the low SOC, and the thermal control system is placed in the energy saving mode.

[0078] Process 220 then returns to block 222 where the user modifies the route data. Such modifications can include modified authorizations, including fast charge authorizations, modified waypoints, modified arrival / departure times, etc. The process then continues as described above until there are no constraints violated at block 230.

[0079] Thus, in some embodiments, controller 134 provides feedback to the user based on the physics-based model performed and the database associated with the trip. In some embodiments, the feedback includes a warning that a fast charge will be needed at a particular waypoint in order to have sufficient power for the next trip segment. The user then authorizes the fast charge, or modifies the route such as by extending the stay at a particular location. In some embodiments, controller 134 provides suggestions for route modifications based on the physics-based model and data obtained from the trip-related database to avoid one or more fast charges during the trip. In some embodiments, controller 134 identifies the number of fast charges remaining that are allowed, and controls input / output device 144 to display the number of fast charges remaining that are available.

[0080] In some embodiments, the controller 134 provides feedback in the form of a warning that the particular leg cannot be provided with sufficient battery power even with one or more fast charges. In such cases, the controller 13 identifies modifications in some embodiments that will enable the trip to be completed. Such modifications include extending the time at particular waypoints, adding new waypoints, etc.

[0081] In some embodiments particularly useful in rental vehicles, the controller 134 provides feedback in the form of a warning that the planned route will require one or more fast charges, which will incur one or more additional charges.

[0082] In some embodiments, the process 220 is modified by using input from the controller 134 as "user" input. In certain such embodiments, the controller "learns" the driving habits of the user. For example, the controller 134 identifies the paths that the user typically takes for particular days, and / or identifies the times associated with particular sites for particular paths. Thus, when the vehicle stops at a known location (e.g., home, work, school, store, etc.), the controller 134 inputs route data and performs the process 220 based on prior history at block 222. For example, when the vehicle arrives at home on a Sunday evening, the controller identifies the departure time for Monday associated with going to the work site. If all conditions pass at block 232, the process in some embodiments further includes alerting the user that the vehicle will be prepared for the predicted event. The user can confirm or override the event. If the event is confirmed, the controller proceeds to the process 170.

[0083] Figure 7 Curves depicting exemplary simulation results using a physics-based model are plotted. During the simulation, the battery was held isothermally at 40°C until the prescribed SOC was reached. At that SOC, the battery cell was cooled to 20°C and held isothermally at 20°C for the remainder of the charge.

[0084] Figure 7 Curve 240 depicts the total charge lost to side reactions on the cathode (eldη sr in mol / cm 2 vs. battery SOC (positive current), Figure 7 Curve 242 depicts the total charge lost to side reactions in the anode (eldη sr in mol / cm 2 vs. battery SOC (negative current), and curve 244 depicts the charge duration in seconds vs. battery SOC.

[0085] The longer the battery is at higher temperatures, the more total charge lost to side reactions in the battery (mol / cm 2) is larger, so the side reaction losses are minimized by shifting to lower temperatures at higher SOC. Figure 7 It was determined that for an exemplary battery cell design, the longer the battery cell is kept at 40°C, the shorter the charging duration. Therefore, to reduce the charging time, an acceptable side reaction rate was established and used to identify a target temperature for the battery (to increase the charging rate) until a SOC has been reached that corresponds to an acceptable side reaction rate. The target temperature of the battery / cell is then lowered, e.g., to 20°C, to prevent exceeding the maximum allowed rate of side reaction losses. While 40°C and 20°C are example identification temperatures, other temperatures are used in other embodiments. Moreover, in some embodiments, the selected temperature is not selected based on side reaction losses alone. In such embodiments, considerations such as heating / cooling efficiency are also used. Figure 7

[0086] The above-described systems and methods provide more precise details (informed in real-time by physics-based models or lookup tables) that allow for optimal control of the battery temperature that enables optimal power and energy transfer while minimizing battery cell aging. According to the above-described principles, when high power performance is desired (with respect to charging or discharging), the optimally controlled battery is heated (or cooled) as needed, as long as it will not age the battery beyond an acceptable rate determined based on the desired battery life, and the optimally controlled battery is cooled (or allowed to cool) when high power transfer is not needed or when the side reaction losses become too large when considering the desired battery life.

[0087] Therefore, when a user needs fast charging, e.g., in an electric vehicle on a relatively cold day, the battery pack is actively and / or passively heated at the beginning of charging (low to medium state of charge) in order to speed up charging, and then cooled to reduce the rate of aging at the highest level of charge (when the driving force for the degrading side reactions is highest).

[0088] The disclosed embodiments use real-time measurements of impedance (internal resistance) and / or predictions of internal states (e.g., individual electrode potentials and overpotentials) from physics-based battery cell performance models, aging models, and thermal models for predicting battery cell heating due to charging and discharging to provide adaptively controlled battery temperature. The above-described embodiments provide 1) the identification of the optimal temperature for minimal battery aging during all usage conditions using physics-based models and / or empirical models known from field data, and 2) the use of a control system to move the battery to the optimal temperature by using heating and cooling of the battery pack, and / or fast cycling of current in order to warm up the battery pack (e.g., pulsed charging / discharging or alternating current / voltage).

[0089] ​Thus, the described embodiments provide the ability to optimally control temperature at the point most critical to the underlying physics within the battery cell. This is a significant improvement over previously known approaches that relied on more empirical understanding of battery cell performance, which required extensive testing that was expensive and often inadequate. Applications of the above techniques include using a physics-based model to determine an optimal temperature for charging as a function of history and state of charge, then optimally influencing the temperature, including using battery current to internally heat the battery cell (e.g., setting the battery cell to discharge), intermittently varying the rate of charge throughout the charging process, and / or diverting energy to run auxiliary power units such as fans in order to reach a target temperature that optimizes power / energy transfer within the constraints of acceptable side reaction losses.

[0090] It should be appreciated that variations or alternatives to the above-described and other features and functions can be desirably combined into many other different systems, applications, or methods. Subsequently, various presently unforeseeable or unanticipated alternatives, modifications, variations, or improvements can be made by those skilled in the art using the above description and incorporating their knowledge and skills. These and other changes can be made to the above-described embodiments and functionality without departing from the scope of the application, which is defined by the appended claims.

Claims

1. An electrochemical cell system comprising: at least one electrochemical cell unit; a thermal control system operably connected to the at least one electrochemical cell unit; a memory in which is stored a physics-based model of the at least one electrochemical cell unit, and in which is stored program instructions; and a controller operably connected to the at least one electrochemical cell unit, the thermal control system, and the memory, the controller configured to execute the program instructions to: identify a first requested operation; obtain a first generated target temperature, the first generated target temperature based on the physics-based model and the identified first requested operation, and generated based on a current cell condition of the at least one electrochemical cell unit; and control the thermal control system based on the obtained first target temperature, while controlling the at least one electrochemical cell unit based on the identified first requested operation, wherein obtaining the first generated target temperature based on the physics-based model and the identified first requested operation comprises: obtaining at least one cell unit first parameter of the at least one electrochemical cell unit using a sensor suite associated with the at least one electrochemical cell unit; setting a model target temperature to a predetermined temperature associated with the first requested operation; setting a model target current to a maximum current associated with the first requested operation; using the physics-based model, the model target temperature, and the model target current, predicting a first future at least one cell unit second parameter of the at least one electrochemical cell unit based on the obtained at least one cell unit first parameter; and comparing the first future at least one cell unit second parameter to a first threshold.

2. The electrochemical cell system of claim 1, wherein the controller is further configured to execute the program instructions to: identify a second requested operation, the second requested operation different from the first requested operation; obtain a second generated target temperature, the second generated target temperature based on the physics-based model and the identified second requested operation, the second generated target temperature different from the first generated target temperature; and control the thermal control system based on the obtained second generated target temperature, while controlling the at least one electrochemical cell unit based on the identified second requested operation.

3. The electrochemical cell system of claim 2, further comprising: receiving, with the controller, at least one route data from a user input / output device; identifying, with the controller, a first required charging operation based on the at least one route data; and setting the first required charging operation as the first requested operation.

4. The electrochemical cell system of claim 3, further comprising: identifying, with the controller, the first required charging operation as a fast charging operation; based on identifying the first required charging operation as the fast charging operation, controlling the user input / output device to alert the user that the fast charging operation is required; and receiving, with the controller, authorization from the user to perform the fast charging via the input / output device.

5. The electrochemical cell system of claim 3, further comprising: obtaining, with the controller, mileage data associated with the at least one route data from a database associated with the at least one trip, wherein: the at least one route data comprises a trip start time; and identifying, with the controller, the first required charging operation as a fast charging operation comprises using the obtained mileage data and the trip start time to identify the first required charging operation as the fast charging operation.

6. The electrochemical cell system of claim 1, wherein obtaining the first generated target temperature based on the physics-based model and the identified first requested operation further comprises: generating a modified model target temperature based on the model target temperature; generating a modified model target current based on the model target current; using the physics-based model, the modified model target temperature, and the modified model target current, predicting a second future at least one cell second parameter of the at least one cell based on the obtained at least one cell first parameter; setting the model target temperature to the modified model target temperature; setting the model target current to the modified model target current; and comparing the second future at least one cell second parameter to a second threshold.

7. The electrochemical cell system of claim 6, wherein the controller is further configured to execute the program instructions to: identify a second requested operation, the second requested operation being different than the first requested operation; obtain a second generated target temperature, the second generated target temperature being based on the physics-based model and the identified second requested operation, the second generated target temperature being different than the first generated target temperature; and control the thermal control system based on the obtained second generated target temperature while controlling the at least one electrochemical cell based on the identified second requested operation.

8. The electrochemical cell system of claim 7, further comprising: receiving, with the controller, at least one route data from a user input / output device; based on the at least one route data, identifying, with the controller, a first required charging operation; and setting the first required charging operation as the first requested operation.

9. The electrochemical cell system of claim 8, further comprising: identifying, with the controller, the first required charging operation as a fast charging operation; based on identifying the first required charging operation as the fast charging operation, controlling the user input / output device to alert the user that the fast charging operation is required; and receiving, with the controller, authorization from the user to perform the fast charge via the input / output device.

10. The electrochemical cell system of claim 8, further comprising: obtaining, with the controller, trip data associated with the at least one route data from a database associated with the at least one trip, the at least one route data comprises a trip start time; and identifying, with the controller, the first required charging operation as a fast charging operation comprises using the obtained trip data and the trip start time to identify the first required charging operation as a fast charging operation.

11. A method of operating an electrochemical cell system, comprising: identifying, with a controller operably connected to at least one electrochemical cell unit, a thermal control system, and a memory, a first requested operation by executing program instructions stored in the memory; obtaining, with the controller, a first generated target temperature, the first generated target temperature based on a physics-based model stored in the memory and the identified first requested operation, and generated based on a current cell condition of the at least one electrochemical cell unit; and controlling, with the controller, the thermal control system based on the obtained first target temperature, while controlling, with the controller, the at least one electrochemical cell unit based on the identified first requested operation, wherein obtaining the first generated target temperature comprises: obtaining at least one cell unit first parameter of the at least one electrochemical cell unit using a sensor suite associated with the at least one electrochemical cell unit; setting, with the controller, a model target temperature to a predetermined temperature associated with the first requested operation; setting, with the controller, a model target current to a maximum current associated with the first requested operation; predicting, using the physics-based model, the model target temperature, and the model target current, a first future at least one cell unit second parameter of the at least one electrochemical cell unit based on the obtained at least one cell unit first parameter; and comparing, with the controller, the first future at least one cell unit second parameter to a first threshold.

12. The method of claim 11, further comprising: identifying, with the controller, a second requested operation, the second requested operation different from the first requested operation; obtaining, with the controller, a second generated target temperature, the second generated target temperature based on the physics-based model and the identified second requested operation, the second generated target temperature different from the first generated target temperature; and controlling, with the controller, the thermal control system based on the obtained second generated target temperature, while controlling the at least one electrochemical cell unit based on the identified second requested operation.

13. The method of claim 12, further comprising: receiving, with the controller, at least one route data from a user input / output device; identifying, with the controller, a first required charging operation based on the at least one route data; and setting the first required charging operation as the first requested operation.

14. The method of claim 13, further comprising: identifying, with the controller, the first required charging operation as a fast charging operation; controlling, with the controller, the user input / output device to alert a user that the fast charging operation is required based on identifying the first required charging operation as the fast charging operation; and receiving, with the controller, authorization from the user to perform the fast charging via the input / output device.

15. The method of claim 13, wherein the at least one route data comprises a trip start time, the method further comprising: obtaining, with the controller, mileage data associated with the at least one route data from a database associated with at least one trip, and wherein identifying, with the controller, the first required charging operation as a fast charging operation comprises using the obtained mileage data and the trip start time to identify the first required charging operation as the fast charging operation.

16. The method of claim 11, wherein, obtaining the first generated target temperature based on the physics-based model and the identified first requested operation further comprises: generating a modified model target temperature based on the model target temperature; generating a modified model target current based on the model target current; using the physics-based model, the modified model target temperature, and the modified model target current, predicting a second future at least one battery cell second parameter of the at least one battery cell based on the obtained at least one battery cell first parameter; setting the model target temperature as the modified model target temperature; setting the model target current as the modified model target current; and comparing the second future at least one battery cell second parameter to a second threshold.

17. The method of claim 16, further comprising: identifying, with the controller, a second requested operation, the second requested operation being different than the first requested operation; obtaining, with the controller, a second generated target temperature, the second generated target temperature being based on the physics-based model and the identified second requested operation, the second generated target temperature being different than the first generated target temperature; and controlling, with the controller, the thermal control system based on the obtained second generated target temperature while controlling the at least one electrochemical cell based on the identified second requested operation.

18. The method of claim 17, further comprising: receiving, with the controller, at least one route data from a user input / output device; identifying, with the controller, a first required charging operation based on the at least one route data; and setting the first required charging operation as the first requested operation.

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