METHOD FOR PROTECTING A BATTERY SYSTEM BASED ON AN ESTIMATE OF THE QUANTITY OF LITHIUM DEPOSIT

Abstract

The present invention relates to a method for protecting a battery system (1) comprising an energy storage element (10). The method comprises a charging phase including the determination of a setpoint for the maximum permissible charging current (CC1) and the measurement of an instantaneous charging current (I(t)) of the battery system (1), monitoring whether the measured current (I(t)) is greater than the setpoint (CC1), and, according to the invention, upon detection that the measured current (I(t)) is greater than the setpoint (CC1), the calculation of a first parameter representing the amount of lithium deposition (QDL1) on the surface of an electrode of the storage element (10) of the battery (1) during the detection period, and the control of a protection dependent on the first parameter (QDL1). The invention is applicable to electrified vehicles. Figure 1.

Description

Title of the invention: METHOD FOR PROTECTING A BATTERY SYSTEM BASED ON AN ESTIMATE OF A QUANTITY OF LITHIUM DEPOSITION

[0001] The field of the invention relates to a method for controlling the current of an electrochemical cell battery system.

[0002] The battery systems of electrified vehicles are currently mainly equipped with lithium-ion electrochemical cells. In operation, these cells are likely to deteriorate if they are not used under nominal operating conditions, i.e. within the thermal, current and voltage limits defined by the cell manufacturers. Indeed, in the event of excessively low temperatures or excessively high currents being driven, the electrodes of a cell can become saturated with lithium atoms on the surface, which can lead to the formation of dendrites causing internal short circuits. The management of the charging and discharging currents of the cells must be carried out under safe conditions while ensuring optimal energy management and the least restrictive use of the battery possible, particularly in terms of charging time and driving range.

[0003] Lithium transport in a negative graphite electrode is generally slower than in positive electrodes and, consequently, is the limiting phenomenon of the charging current. This phenomenon is called lithium deposition or lithium plating, also referred to as "Lithium Plating" in English. Too high a lithium concentration can lead to the formation of dendrites and cause an increase in internal resistance, or even a short circuit. During charging, lithium ions are reduced to lithium metal on the surface of the graphite structure during the exchange of electrons. The rate of reduction of lithium ions is proportional to the current and diffusion in the graphite structure follows the diffusion laws. The diffusion rate depends on the lithium metal concentration gradient and a diffusion coefficient, which depends on the state of charge, temperature and aging of a cell.Fick's law governs the diffusion of lithium ions into the various components of the battery, such as the electrolyte and electrodes.

[0004] We can cite patent document EP-A1-2266181 describing a charging method adaptive based on a technique for estimating a diffusion time and a lithium concentration on the surface from the diffusion time, the cell capacity and the measured charging current. Then, from the concentration, a charging current is calculated. This document teaches how to measure the diffusion time during a relaxation phase from the measurement of an open-circuit voltage depending on the application of a direct current for a fixed duration. This technique for estimating the surface lithium concentration concerns charges connected to a terminal, commonly called "Plug-in" charges. This technique is therefore not applicable to regenerative braking due to the driving dynamics and the impossibility of imposing cell relaxation, particularly in the case of a vehicle with an entirely electric motor.

[0005] Document WO-A1-2022237476 is known from the state of the art, which teaches a solution for calibrating charging current pulse tables from electrochemical and thermal models established experimentally. These electrochemical models also include a law of diffusion coefficient of lithium ions at the electrodes. This document teaches a principle of control by current pulse of a given duration, for example 10 seconds, of which a stopping condition can be dependent on the cell voltage relative to a high voltage threshold, an electrode potential value between the negative electrode and the separator or a cell temperature. These pulse tables are intended to control maximum currents respecting the electrochemical constraints of the cells, in particular with regard to the lithium deposition.

[0006] Patent document WO-A 1-2022032460 is also known, describing a solution comprising a method for detecting lithium plating on a battery cell electrode comprising determining a potential value in real time of the negative electrode and in which, if this potential becomes less than or equal to a threshold of zero volts, the method detects lithium plating. This document teaches the use of a model embedded in a vehicle to determine this potential as a function of the charging current, state of charge and temperature. This document teaches a principle for controlling the charging current aimed at reducing the current value as a function of this potential. The disadvantage of a real-time calculation model is that it is particularly energy-intensive.

[0007] The problem with current solutions lies in the difficulty of estimating a state of damage over the duration of use of a vehicle. In particular, the calibration of current thresholds and confirmation time to trigger an electrical protection is particularly complex because these protections must not lead to performance limitations due to the necessary safety margin. For example, it may not be a problem to occasionally remain at 106% of the maximum current limit for 10 seconds, but if the confirmation is set to 10 seconds, there may be many exceedances of 105% for less than 10 seconds, which may become a problem over a prolonged period. Conversely, reducing the confirmation time would tend to increase the risk of false detections.

[0008] There is therefore a need to overcome the aforementioned problems. One objective of the invention is to propose a function for estimating the surface state of lithium deposition in the electrochemical cells of a battery, making it possible to improve the protection of the batteries and to reduce the limitations of electrical performance.

[0009] More specifically, the invention relates to a method for protecting a battery system comprising an energy storage element, the method being implemented by a control unit of said battery system and comprising the following steps:

[0010] - a charging phase comprising the determination of a current setpoint of maximum permitted charge and measurement of an instantaneous charging current of the battery system,

[0011] - monitoring if the measured current is greater than the setpoint,

[0012] - in case of detection that the measured current is greater than the setpoint, the calculation of a first parameter representative of a quantity of lithium deposition on the surface of an electrode of the storage element of the battery during the detection period,

[0013] - the control of a protection dependent on the first parameter.

[0014] The method according to the invention may include the following additional characteristics, alone or in combination:

[0015] - The first parameter is calculated from an estimation function based on Faraday's law and a current value corresponding to the difference between the measured current and the setpoint during the detection time.

[0016] - The estimation function includes a parameterizable diffusion coefficient applied to the setpoint value.

[0017] - The calculation of a second parameter representative of the quantity of deposition of cumulative lithium and which is calculated from the sum of values ​​of the first parameter calculated during several charging phases.

[0018] - The control of a protection comprises at least a first control for limit the charging current setpoint when the second parameter crosses a first deposit threshold.

[0019] - The control of a protection includes a second control for opening a switch of the battery system charging line when the second parameter is greater than a second maximum deposition threshold.

[0020] - The control of a protection includes a third control for opening definitive opening of a switch of the charging line of the battery system when the second parameter is greater than a third deposition threshold, the third definitive opening command prohibiting subsequent use of the storage element.

[0021] - The instruction is delivered by a first direct current table taking into account input of the electrical parameters measured during the charging phase, the first table delivering values ​​of the setpoint applicable during a first fixed duration from a reference state of the storage element corresponding to the measured electrical parameters.

[0022] According to the invention, there is provided a battery system comprising an energy storage element and a control unit configured specifically for implementing the protection method according to any one of the preceding embodiments.

[0023] An electrified vehicle comprising such a system is further provided.

[0024] According to the invention, there is provided a battery system comprising an element of energy storage and a control unit specifically configured for implementing the protection method according to any of the preceding embodiments.

[0025] A computer program is provided comprising instructions which, when the program is executed by a control unit of a battery system, cause the latter to implement any one of the embodiments of the protection method according to the invention.

[0026] A computer-readable recording medium is provided comprising instructions which, when executed by a computer, cause the computer to implement any one of the embodiments of the protection method according to the invention.

[0027] The invention implements a parameter for estimating a quantity of lithium deposition improving the diagnosis and protection of battery systems. The invention makes it possible to improve the monitoring of battery damage in order to prevent excessive deposition preventing the recycling of cells.

[0028] Other characteristics and advantages of the present invention will appear more clearly on reading the detailed description which follows, comprising embodiments of the invention given as non-limiting examples and illustrated by the appended drawings, in which:

[0029] [Fig-1] schematically represents a battery system according to the invention.

[0030] [Fig.2] schematically represents a negative electrode structure illustrating the principle of diffusion of lithium atoms in a graphite particle structure.

[0031] [Fig.3] represents a block diagram of an embodiment of the protection method according to the invention.

[0032] [Fig.4] represents an electrified vehicle intended for the implementation of the invention.

[0033] The invention applies to energy storage systems with electro-cells. chemicals, in particular of the lithium-ion type. The method according to the invention aims to provide an estimate of a lithium deposition on the surface of a battery cell electrode and to control protection dependent on this estimate. The invention relates to any type of electrified vehicle, i.e. comprising an electric motor machine and power electronics, 100% electric or hybrid, preferably motor vehicles, but not only, such as an aircraft, tractor, electric bicycle, ships, truck.

[0034] [Fig.l] schematically represents a battery system 1 comprising an energy storage element 10 comprising at least one electrochemical cell 11 in accordance with the invention. The storage element 10 may comprise a plurality of cells 11 or group of cells (also called a cell cluster) electrically connected in parallel and / or in series.

[0035] An electrochemical cell is an electrical energy accumulator having two terminals, a positive electrode and a negative electrode, and having a voltage of a few volts, most often between 2.3V and 4.2V, approximately. The cells can be of the lithium-ion type. More precisely, a lithium-ion cell is composed mainly of a porous positive electrode, a porous negative electrode, a separator and an electrolyte (which can be liquid, polymeric or solid). A lithium Nickel Manganese Cobalt oxide NMC or a lithium iron phosphate LFP can be cited as examples of positive electrode active materials, Nickel Cadmium (Ni-cd), or Nickel-Metal-Hydride (Ni-MH) for example. The negative electrode can be a graphite structure or a metal alloy, for example. The operating principle of a lithium-ion cell is based on the reversible exchange of lithium ions between the two porous electrodes.

[0036] The battery system 1 further comprises means for measuring, estimating or sensing electrical parameters, including at least one current sensor 12 capable of measuring or estimating a current value passing through the storage element 10, a voltage sensor and a temperature sensor for cells 11 or each cell 11 of the energy storage element 10. The battery system 1 further comprises switching means 14 for opening and closing the current line. These power switching means are, for example, power relays or controllable transistors suitable for electrically connecting and disconnecting the storage elements of the battery from a charging interface or from an electrical network powered by the battery. In an electrified vehicle application, the switching means comprise the switch(es) connecting the battery to the charging socket box, for example.

[0037] The battery system 1 further comprises a control unit 13 (also called ECU for “Electronic Control Unit” or BMS for “Battery Management System”). The control unit 13 is provided with an integrated circuit computer and electronic memories, the computer and the memories being configured to execute the protection method according to the invention. But this is not obligatory. Indeed, the calculator could be external to the battery control unit, while being coupled to the latter. The control unit 13, according to the invention, can be produced in the form of software modules (or computer modules (or even "software")), or electronic circuits (or "hardware"), or even a combination of electronic circuits and software modules.

[0038] The invention proposes a method for protecting the battery based on the physical properties of lithium diffusion on the surface of an electrode and on Faraday's law making it possible to estimate a quantity of lithium deposition during charging as a function of a difference between the charging current and a maximum authorized current setpoint.

[0039] To illustrate the lithium deposition phenomenon, in [Fig.2], a graphite negative electrode structure is shown schematically for different charging rates. Diagram 2a shows the zero-current electrode where the surface concentration is uniform to the internal concentration of the graphite structure. Diagram 2b shows the electrode for moderate charging current where the surface concentration is higher than the internal concentration but remains below a saturation level. Diagram 2c shows the electrode for high charging current where lithium deposits form on the surface of the electrode. The reduced lithium is proportional to the current and cannot be fully inserted. Lithium deposit appears, represented by the oval-shaped patterns.

[0040] From these observations, calibration information for direct current tables is obtained either by numerical modeling or by experimental means for a fixed duration, taking as input electrical parameters including the state of charge (SOC) and the temperature of an energy storage element, a cell or a group of cells. These direct current tables deliver current values ​​applicable during the fixed duration. An experimental protocol carried out on cells under controlled conditions can be a numerical modeling from the lithium concentration equations described above. Another experimental protocol can be the measurement of a reference potential of the negative electrode corresponding to a voltage measured between the negative electrode and a so-called reference electrode, generally made of lithium, connected to the electrolyte.During charging, when this voltage reaches 0 volts, this condition indicates that the saturation level has been reached.

[0041] A first table provides values ​​of a first continuous charging current applicable for the first duration at most as a function of measured electrical parameters. The current values ​​are applicable until a saturation level of lithium deposition is reached on the surface of a negative electrode of said storage element at the end of the first duration. The measured parameters include the state of charge SOC and the temperature of a storage element, for a range of [0%, 100%] in SOC and for a temperature range [-20°C, 60°C] for example. We plan to obtain several first tables for different applicable durations, for example durations between 1 second and 180 seconds, for example a table for a duration of 10 seconds, another table for a duration of 30 seconds and another table for a duration of 180 seconds. These are current tables intended for a dynamic load situation while a vehicle is running, such as regenerative braking for example.

[0042] A second table, for controlling a direct current for a second given duration, differs from the first table in that the second applicable duration of the current is greater than that of the first table or tables, i.e. greater than several minutes, between several minutes and possibly several hours. The direct current value delivered by the second table corresponds to a lithium reduction rate close to that of the diffusion of atoms in the core of the electrode structure. This second current can be controlled constantly, i.e. until the voltage limit of a cell corresponding to the so-called “Cut-off voltage” is reached without the lithium deposition phenomenon appearing. These are current values ​​suitable for charging at a terminal, for example.The second table provides current values ​​applicable without risk of lithium deposition depending on the SOC state of charge and temperature parameters of a storage element, for a range of [0%, 100%] in SOC and for a range of [-20°C, 60°C] for example. It is envisaged to obtain several second tables for durations of 180 seconds or more.

[0043] The control unit 13 comprises, stored in memory, at least a first direct current table 151 and a second direct current table 152. The control unit may comprise a plurality of tables 151 and a plurality of tables 152 for different durations. For example, first tables 151 are stored for direct currents IDC1 of duration 10 seconds, 30 seconds and 180 seconds. Second tables 152 are stored for direct currents IDC2 of greater durations, for example, 360 seconds or more. First tables and second tables specific to charging currents or discharging currents may also be provided. The control unit 13 is configured to deliver maximum current values ​​applicable during the first and second durations specific to each table as a function of instantaneous electrical parameters including the state of charge and the temperature of the storage element.

[0044] Conventionally, the control unit 13 of the battery system further comprises an estimator of the aging state of the cells providing an SOH parameter representative of the aging state. The estimator 15 further comprises a table delivering a current correction factor as a function of the parameter of SOH aging. The current correction factor is intended to correct a current value delivered by the first and second tables 151 and 152.

[0045] The control unit 13 comprises a current controller 16 comprising a control function 161 delivering current control information CCI, which may be a current setpoint value, a maximum current setpoint authorized at the given instant or an authorized electrical power in charge or discharge. The function 161 takes as input information comprising at least the current values ​​IDC1 and IDC2 delivered by the first and second direct current tables 151 and 152. The information CCI is delivered via communication means to other electrical systems consuming and / or generating energy, for example a voltage converter, an electric motor, a charger.

[0046] The current controller 16 comprises an estimation function 162 configured to monitor the current I(t) flowing through the storage element with respect to the current control information CCI. The function 162 is capable of detecting whether the current I(t) is greater than the information CCI and when this situation occurs, it calculates a first parameter QDL1 representative of a first quantity of lithium deposition and a second parameter QDL2 representative of a second cumulative quantity of lithium deposition during the use of the battery system 1.

[0047] The consumer and generator electrical systems control currents calculated on the basis of the CCI information and on the basis of power estimators and resistance parameters. These estimators sometimes have calibrations that are distorted or unsuitable for a particular situation or faulty, which can generate the control of a charging current higher than the setpoint determined by the battery system. Nevertheless, a protection mechanism is provided configured so that in the event of detection of a current I(t) which is higher than a critical threshold, the control unit immediately actuates the power cut-off switches.

[0048] In a variant, the estimation function 162 is based on Faraday's law and a current value corresponding to the difference between the measured current and the setpoint during the duration of the charge according to the relationship below expressed in moles. The calculation is carried out only when the current I(t) is greater than the maximum current setpoint, because in this situation for the value of the remaining current difference, the lithium deposition is greater than the diffusion in the graphite structure. This technique for estimating the deposition thus makes it possible to set up a damage counter for the surface of the electrode.

[0049] QDL\ = (Z(t)-Œl)*At *(^), QDL1 being the quantity of lithium expressed in grams, I(t) being the instantaneous charging current expressed in Amperes, At being the calculation time expressed in seconds, CCI being the charging current setpoint expressed in Amperes, F being the Faraday constant 96485 Coulomb per mole of electron. The first quantity of lithium deposition can also be expressed in grams based on the lithium molar mass parameter Mli according to the following relationship: QDL 1=(1(t)-CCl) *At *(1 / F) *Mli. Alternatively, the first quantity of deposition can also be estimated by a parameter representative of a quantity of energy expressed in ampere-hours.

[0050] The invention provides a variant of the estimation function 162 using a parameterizable diffusion coefficient Kdiff applied to the value of the CCI setpoint implemented according to the following relationship where Kdiff is between [0,1]: QDLl=(I(t)-Kdiff*CCl)*At*(1 / F). In an optimistic calibration, for Kdiff equal to 1, the hypothesis is that only the current deviation value between the measured current and the CCI setpoint generates lithium deposition. In a pessimistic calibration, for Kdiff equal to 0, as soon as the measured current exceeds the maximum current setpoint, then the electrode no longer diffuses lithium into the internal structure and the entire measured current generates lithium deposition on the surface of the electrode. The diffusion coefficient makes it possible to calibrate the estimator 162.

[0051] In the application of an electrified vehicle, it will be noted that the values ​​of the QDL1 parameters are calculated during the charging phase in a regenerative braking situation or during the charging phase in a charging situation at terminals.

[0052] Furthermore, the estimation function 162 performs the calculation of a second parameter representative of a second cumulative lithium deposition quantity QDL2 which is calculated from the sum of the first deposition quantities QLD1 calculated during several charging phases. The second quantity performs the role of a lithium deposition damage counter monitoring the deposition phenomenon over the lifetime of the battery system. In particular, the parameter QDL2 has the function of monitoring the damage to the cells with respect to one or more predetermined deposition thresholds in order to generate protective corrections during the lifetime of the vehicle or to generate a diagnosis of the state of damage to the cells, or even trigger a disconnection command and signal a diagnosis of recycling or irreversible damage to the cells.

[0053] Furthermore, the current controller 16 may comprise a protection function 163 configured to determine a protection command as a function of the cumulative lithium deposition quantity QDL2. The protection function is capable of generating CPI commands for limiting the current setpoint CCI as a function of the value of the parameter QDL2 relative to one or more predetermined deposition thresholds, CP2 commands for opening switches of the current line of the battery system or CP3 definitive opening commands.

[0054] In [Fig.3], the protection method according to the invention is represented by a block diagram. The method is implemented by a battery system control unit. The method is intended, for example, for an electrified motor vehicle application.

[0055] In a first step 61, the battery system is started and in nominal operation. Charging and discharging phases can be controlled.

[0056] The method comprises a second step 62 of controlling a charging phase of the storage elements of the battery. A charging current is controlled and for this purpose, the control unit determines the current setpoint CCI and transmits the current setpoint CCI to a charging device, for example a charger, an AC / DC or DC / DC current converter, to a charging station, or to a generator such as an electrical machine. The current setpoint CCI may be a maximum authorized current determining a limit beyond which lithium deposition is likely to occur. The current setpoint CCI is provided by the first direct current table 151 or the second direct current table 152, with reference to [Fig.l]. Alternatively, the current setpoint CCI may be a maximum power. During the recharging phase, the control unit continuously measures the charging current i(t) flowing through the energy storage elements.

[0057] The method comprises a monitoring step 63 if the measured current (I(t)) is greater than the CCI setpoint. Conventionally, the control unit implements protection commands in the event of an overshoot, generally further conditioned by a validation by a time delay of the overshoot. If the overshoot has a duration less than the time delay, the protection is not triggered. However, the invention makes it possible to assess damage even for cases where the validation is not confirmed.

[0058] According to the invention, the protection method comprises, in the event of detection that the measured current (i(t) is greater than the CCI setpoint, the calculation 64 of a first parameter representative of a quantity of lithium deposition QDL1 on the surface of an electrode of the storage element of the battery during the detection period. This calculation is triggered immediately at the instant of excess of the current and for the entire duration of excess.

[0059] This first parameter QLD1 makes it possible to estimate damage to the cells in this situation in order to determine the cell protection measures, or even the possibility of recycling the cells or not. Conventional protections trigger an opening of switches as soon as the current i(t) exceeds the maximum current setpoint, after confirmation of the exceedance. The invention has the advantage of providing information concerning the damage to the cells and of evaluating a possibility of restarting the battery system or recycling the cells.

[0060] In one embodiment, the first parameter QDL1 is calculated from the estimation function based on Faraday's law and a current value corresponding to the difference between the measured current and the setpoint during the duration of the charge in accordance with the following relationship:

[0061] QDL1 = (Z( / )-Œl)*At*(^)-

[0062] The first parameter QLD1 can be expressed in moles or grams depending on the molar mass of lithium, or alternatively by a quantity of charged energy expressed in ampere-hours.

[0063] In another variant of the method of calculating the first parameter QLD1, the estimation function includes the configurable diffusion coefficient Kdiff applied to the value of the CCI setpoint. The diffusion coefficient makes it possible to adjust the calibration of the deposition phenomenon according to hypotheses or observations determined experimentally. The diffusion coefficient makes it possible to calibrate a protection margin empirically.

[0064] Furthermore, the protection method comprises the calculation 65 of the second parameter QLD2 representative of a quantity of cumulative lithium deposition during the use of the battery system, during several charging phases. This parameter QLD2 ensures the monitoring of the deposition throughout the lifetime of use of the battery system. It makes it possible to establish protection measures. It aims in particular to monitor the phenomenon of slow deposition. The parameter QLD2 is calculated according to the following relationship:

[0065] QDL2(t) = QDL2 ( t -1 ) + QDL l(f), t being a time calculation step in seconds.

[0066] The method further comprises a step of controlling a protection 66 of pending the first lithium deposition quantity QDL1 and the second parameter QLD2. More specifically, the protection 66 comprises at least a first command to limit the charging current setpoint when the second parameter QLD2 crosses a first deposition threshold. This step provides several deposition thresholds each triggering a specific current limitation configured gradually so as to progressively reduce the current setpoint if the setpoint overshoot phenomenon persists. This corrective action makes it possible to deal with the persistent overshoot phenomenon likely to cause deposition and having a fleeting duration preventing their detection by the protection mechanisms subject to validation by time delay. Each threshold is expressed in a lithium deposition quantity, in moles or grams, or in quantity of energy.The thresholds are determined experimentally and recorded in the control unit's memory.

[0067] Current limitations can be configured to reduce the setpoint of CCI current of a value between 100% and 50% of the setpoint value, for example, progressively, depending on the value of the QDL2 parameter between 0% and 100% of the value of a maximum deposition threshold. A current limitation table stored in the memory of the control unit taking the QDL2 parameter as input delivers a limitation value.

[0068] Furthermore, the protection command 66 may comprise a second command for opening a switch of the charging line of the battery system when the second parameter QLD2 is greater than a second maximum deposition threshold. The second threshold corresponds to a maximum deposition quantity calibrated to end the use of the battery and signal to the user the performance of a maintenance diagnosis in order to evaluate the possibility of recycling or not.

[0069] Optionally, the method comprises the command for the definitive opening of a switch of the charging line of the battery system when the second parameter QLD2 is greater than a third deposition threshold, the third definitive opening command prohibiting subsequent use of the storage element. This third threshold is equal to or greater than the second threshold. It corresponds to a critical deposition level for which the cells must be replaced.

[0070] When the current i(t) returns to a value lower than the CCI setpoint, the charging phase 62 is controlled in nominal operation. The parameters QDL1 and QDL2 are no longer incremented.

[0071] In [Fig.4], an electrified vehicle 80 comprising a battery system 83 according to the invention is shown schematically. The vehicle may be a hybrid or all-electric vehicle. The vehicle 80 includes an electric prime mover 81 for moving the vehicle and powered by the battery system 83. Some or all of the functions of the vehicle 80 are controlled by a control unit 82. The control unit 82 may include at least one processor that executes instructions stored in a computer-readable medium such as non-volatile memory. The control unit 82 may also be multiple computing devices that control individual components or subsystems of the vehicle 80 in a distributed manner. The processor may be any conventional processor, such as a commercially available central processing unit. Alternatively, the processor may be a dedicated device such as an application-specific integrated circuit (ASIC) or other hardware processor.

[0072] The prime mover 81 and the battery system 83 can be controlled in regenerative braking operation. The battery system comprises a control unit 84 comprising a computer and memories configured for implementing the protection method according to the invention. In particular, the memories have a recorded program comprising instructions which, when the program is executed by the battery system control unit, cause the latter to implement any one of the embodiments of the control method according to the invention. In addition, the control unit 84 is connected in communication with the vehicle's computers by means of an on-board communication bus 88, for example of the CAN (Control Area Network) type, to deliver the protection and / or diagnostic command determined from the method according to the invention. The vehicle further comprises a voltage converter 85 of the DC / DC or AC / DC type. The vehicle further comprises an electrical relay or switch 86 provided for selectively disconnecting and connecting the battery system 83 from the vehicle's electrical systems and, possibly, from a charging box 87.The charging box is an interface allowing the connection of a charging cable 89 to an external energy source 90 connected to an extended electrical supply network 91 operating at alternating voltage. The protection commands generated by the method according to the invention comprise the opening of one or more relays 86 and the command to limit the current setpoint to the current control function of the battery system.

[0073] The invention is described in the above by way of example. It is understood that the person skilled in the art is able to produce different variant embodiments of the invention by associating, for example, the different characteristics above taken alone or in combination, without departing from the scope of the invention.

Claims

Claims

1. Method for protecting a battery system (1) comprising an energy storage element (10), the method being implemented by a control unit (13) of said battery system (1) and comprising the following steps: - a charging phase comprising the determination (62) of a setpoint of the maximum authorized charging current (CCI) and the measurement of an instantaneous charging current (I(t)) of the battery system (1), - monitoring (63) whether the measured current (I(t)) is greater than the setpoint (CCI), characterized in that it further comprises the following steps: - in the event of detection that the measured current (i(t)) is greater than the setpoint (CCI), the calculation (64) of a first parameter representative of a quantity of lithium deposition (QDL1) on the surface of an electrode of the storage element (10) of the battery (1) during the detection period, - the control (66) of a protection dependent on the first parameter (QDL1).

2. Method according to claim 1, in which the first parameter (QDL1) is calculated from an estimation function based on Faraday's law and a current value corresponding to the difference between the measured current (i(t)) and the setpoint (CCI) during the detection duration.

3. Method according to claim 2, in which the estimation function comprises a parameterizable diffusion coefficient (Kdiff) applied to the setpoint value (CCI).

4. Method according to any one of claims 1 to 3, further comprising the calculation (65) of a second parameter (QDL2) representative of the cumulative lithium deposition quantity and which is calculated from the sum of values ​​of the first parameter (QLD1) calculated during several charging phases.

5. Method according to claim 4, in which the control (66) of a protection comprises at least a first control (CPI) for limiting the charging current setpoint (CCI) when the second parameter (QDL2) crosses a first deposition threshold.

6. Method according to claim 4 or 5, in which the control (66) of a protection comprises a second control (CP2) for opening a switch (14) of the charging line of the battery system (1) when the second parameter (QDL2) is greater than a second maximum deposition threshold.

7. Method according to any one of claims 4 to 6, in which the control (66) of a protection comprises a third control (CP3) for the definitive opening of a switch (14) of the charging line of the battery system (1) when the second parameter (QDL2) is greater than a third deposition threshold, the third definitive opening control prohibiting subsequent use of the storage element.

8. Method according to any one of claims 1 to 7, in which the setpoint (CCI) is delivered by a first direct current table (151) taking as input measured electrical parameters (P) during the charging phase, the first table (151) delivering values ​​of the setpoint applicable during a first fixed duration (Dl) from a reference state of the storage element (10) corresponding to the measured electrical parameters (P).

9. Battery system (1) comprising an energy storage element (10) and a control unit (13) configured specifically for implementing the protection method according to any one of claims 1 to 8.

10. An electrified vehicle (80) comprising a battery system (83) according to claim 9.

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