Lithium deposition detection method, equipment and system

Abstract

The present invention discloses a lithium plating detection method, device and system, including: the battery to be tested first sleeps for a preset time in each discharge cycle and then discharges a preset capacity at a constant current, wherein each discharge cycle refers to the period from the start of the current sleep to the start of the next sleep; an internal resistance change curve is obtained according to the DC internal resistance, and the internal resistance change curve represents the relationship between the DC internal resistance and the corresponding voltage; the internal resistance change rate is obtained according to the internal resistance change curve, and an internal resistance polarization response curve is constructed in a pre-established plane coordinate system, and the internal resistance polarization response curve represents the relationship between the internal resistance change rate and the corresponding voltage. Among them, the internal resistance polarization response curve is obtained by discharging the battery to be tested in an intermittent sleep mode, and the internal resistance polarization response curve is determined according to the lithium plating threshold of the internal resistance polarization response curve to determine whether lithium plating occurs in the battery to be tested, so as to efficiently and simply identify the lithium plating of the battery.

Description

Technical Field

[0001] The present invention relates to the field of battery technology, and in particular to a lithium deposition detection method, device and system. Background Art

[0002] The safety of lithium-ion batteries has always been a hot topic in the development of new energy. Among them, lithium plating at the negative electrode is the key to directly or indirectly causing internal short circuits in batteries. Lithium plating has a great impact on the life and safety of lithium-ion batteries: on the one hand, since some of the precipitated lithium metal cannot be oxidized to lithium ions during discharge, the battery capacity decays; on the other hand, the precipitated lithium metal will form dendrites, and the continuous growth of dendrites may pierce the diaphragm, induce internal short circuits in the battery, and lead to dangerous accidents.

[0003] In related technologies, the detection dimension is single, and it is analyzed only from the voltage perspective, ignoring the changes in polarization and lithium concentration rebalance caused by deep lithium deposition; the detection steps are cumbersome, and it is difficult to obtain the detection parameters (voltage, internal resistance, thermodynamic capacity, decay rate, etc.). Since lithium metal is very active and reacts when it comes into contact with air, it is difficult to detect it using non-destructive methods, and thus it is impossible to effectively detect the lithium deposition state of the battery. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the present invention proposes a lithium plating detection method, which discharges the battery to be tested in an intermittent dormant manner, obtains the lithium plating threshold of the internal resistance polarization response curve, determines whether the battery to be tested has lithium plating, and efficiently and simply identifies the lithium plating of the battery.

[0005] The present invention further proposes a lithium precipitation detection device.

[0006] The present invention further proposes a lithium deposition detection system.

[0007] According to the first aspect of the present invention, the lithium plating detection method includes: the battery to be tested is first put to sleep and then discharges a preset capacity at a constant current in each discharge cycle, wherein each discharge cycle refers to the period from the start of the current sleep period to the start of the next sleep period, and the sleep period of the battery to be tested is a preset time; the DC internal resistance and the corresponding voltage of each discharge cycle are obtained; an internal resistance change curve is obtained according to the DC internal resistance, and the internal resistance change curve characterizes the relationship between the DC internal resistance and the corresponding voltage; the internal resistance change rate is obtained according to the internal resistance change curve, and an internal resistance polarization response curve is constructed in a pre-established plane coordinate system, and the internal resistance polarization response curve characterizes the relationship between the change rate of the internal resistance and the corresponding voltage; according to the lithium plating threshold of the internal resistance polarization response curve, whether lithium plating occurs in the battery to be tested; wherein each discharge cycle refers to the period from the start of the current sleep period to the start of the next sleep period.

[0008] According to the lithium plating detection method of the embodiment of the present invention, the battery to be tested is discharged in an intermittent dormant manner to obtain an internal resistance polarization response curve. According to the lithium plating threshold of the internal resistance polarization response curve, it is determined whether lithium plating occurs in the battery to be tested, thereby efficiently and simply identifying lithium plating of the battery.

[0009] According to some embodiments of the present invention, detecting whether lithium deposition occurs in the battery to be tested comprises: obtaining the vertical coordinate L of the first trough of the internal resistance polarization response curve after the battery to be tested starts to discharge; if L satisfies the relationship: L<0, determining that the battery to be tested is a lithium deposition battery; if L satisfies the relationship: L≥0, determining that the battery to be tested is a non-lithium deposition battery.

[0010] According to some embodiments of the present invention, the initial voltage V of the current discharge cycle is obtained. t1 and the corresponding voltage V of the current discharge cycle t2 ; The constant current is I, the DC internal resistance is DCIR, the DCIR, V t1 、V t2 and I satisfy the relationship: .

[0011] According to some embodiments of the present invention, acquiring the internal resistance variation curve according to the DC internal resistance includes: the abscissa of the internal resistance variation curve is the corresponding voltage of each discharge cycle, and the ordinate is the DC internal resistance of each discharge cycle.

[0012] According to some embodiments of the present invention, constructing an internal resistance polarization response curve in a pre-established plane coordinate system includes: the abscissa of the internal resistance polarization response curve is the corresponding voltage of each discharge cycle, and the ordinate is the internal resistance change rate of each discharge cycle.

[0013] According to some embodiments of the present invention, the DC internal resistance is the sum of ohmic internal resistance and one or more of concentration polarization internal resistance, electrochemical polarization internal resistance, ohmic polarization internal resistance, etc.

[0014] According to some embodiments of the present invention, the preset time of the discharge cycle is assumed to be T, and T satisfies the relationship: 3s≤T≤3600s.

[0015] According to the second aspect of the present invention, a lithium plating detection device includes: at least one processor; a memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method.

[0016] According to some embodiments of the present invention, the lithium plating detection equipment is deployed in the cloud.

[0017] According to a third aspect of the present invention, a lithium deposition detection system includes: a vehicle, the vehicle includes a battery; and the lithium deposition detection device is used to determine a lithium deposition detection result of the battery to be tested according to the method.

[0018] According to some embodiments of the present invention, the vehicle further includes: a domain controller, communicating with the battery and the lithium deposition detection device, the domain controller being used to obtain discharge data of the battery to be tested and send the discharge data of the battery to be tested to the lithium deposition detection device.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0021] Figure 1 is a schematic flow chart of a lithium deposition detection method according to an embodiment of the present invention;

[0022] Figure 2 It is a curve chart of voltage and actual capacity in non-interrupted sleep mode;

[0023] Figure 3 It is the internal resistance polarization response curve of the battery under test and the non-lithium-precipitated battery in the intermittent dormant discharge mode. DETAILED DESCRIPTION

[0024] Embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. Embodiments of the present invention are described in detail below.

[0025] Reference below Figure 1-Figure 3 A lithium deposition detection method according to an embodiment of the present invention is described, a lithium deposition detection device is proposed, and a lithium deposition detection system is proposed.

[0026] like Figure 1 As shown, the lithium precipitation detection method may include:

[0027] S1: The battery to be tested first sleeps in each discharge cycle and then discharges the preset capacity at a constant current until it is discharged to the discharge cut-off voltage. Each discharge cycle refers to the period from the start of the battery to be tested to the start of the next sleep period. The sleep time of each cycle is the same, and the sleep time is the preset time. In other words, the preset time is a constant value, and the battery to be tested is discharged from a full state to a discharge cut-off voltage in this way. That is, each time a certain value of the preset capacity is discharged, it sleeps for a certain period of time until it is discharged to the discharge cut-off voltage, that is, intermittent sleep. During the discharge process of the battery, the discharge current remains constant.

[0028] It should be noted that "battery capacity" in this application refers to the state of charge (SOC) of the battery, which is used to reflect the remaining capacity of the battery. Its numerical value is defined as the ratio of the remaining capacity to the fully charged capacity, expressed as a percentage. The value range of battery capacity SOC is 0-1. When SOC=0, it means that the battery is fully discharged, and when SOC=1, it means that the battery is fully charged.

[0029] For example, the preset capacity is 1% SOC, the preset time is 5s, and the constant current is 0.5C. The battery is disconnected and left to stand for 5 seconds every time 1% SOC is discharged, and the battery is discharged at a constant current of 0.5C (C is used to indicate the battery charge and discharge capacity ratio. 0.5C indicates the current intensity when the battery is fully discharged in two hours) to the discharge cut-off voltage.

[0030] During the specific experiment, the preset capacity of each discharge remains consistent, but the preset capacity can be set according to the actual situation, for example, it can be 0.5% SOC, 2% SOC or 3% SOC.

[0031] Assume that the preset time is T, and T satisfies the relationship: 3s≤T≤3600s. That is to say, the sleep time of each discharge cycle is not limited, and can be 4s, 6s, 7s, etc., or 60s, 180s, etc., and a specific value is selected according to the actual situation.

[0032] The size of the constant current is also not limited, and can be 0.2C, 0.4C, 1C, etc. A specific value is selected according to actual conditions.

[0033] Exemplarily, a vehicle such as a new energy vehicle may have a battery pack. The battery pack may include a battery management system (BMS) and a plurality of batteries. The battery to be tested may be any one of the plurality of batteries.

[0034] S2: Obtain the corresponding voltage and DC internal resistance of each discharge cycle.

[0035] If the preset capacity of each discharge is 1%SOC and the sleep time is 5s, then each discharge cycle refers to the process of starting to sleep, then discharging 1%SOC after 5s of sleep. The corresponding voltage of each discharge cycle is the terminal voltage after each discharge of 1%SOC is completed, the initial voltage is the voltage at the beginning of the discharge cycle sleep, and the DC internal resistance of each discharge cycle is the value of the terminal voltage of each discharge cycle minus the initial voltage of each discharge cycle divided by the constant current to obtain the DC internal resistance of each discharge cycle. According to the ratio of the voltage difference to the current difference of the battery under test at two adjacent discharge cycles, the DC internal resistance of the battery under test in each discharge cycle in the intermittent sleep charging mode can be obtained.

[0036] S3: Obtain an internal resistance change curve based on the DC internal resistance, where the internal resistance change curve represents the relationship between the DC internal resistance and the corresponding voltage. A coordinate system is recommended, and the internal resistance change curve is drawn in the coordinate system based on the DC internal resistance of each discharge cycle of the battery to be tested, where the two coordinate axes of the coordinate system are the DC internal resistance and the voltage. Specifically, the horizontal axis of the internal resistance change curve is the corresponding voltage of each discharge cycle, and the vertical axis is the DC internal resistance of each discharge cycle.

[0037] Get the initial voltage V of the current discharge cycle t1 and the corresponding voltage V of the current discharge cycle t2 ; Constant current is I, DC internal resistance is DCIR, DCIR, V t1 , 2V t2 and I satisfy the relationship: .

[0038] Measure the initial voltage V of each discharge cycle t1 And the corresponding voltage V t2 , according to the relation The DC internal resistance of each discharge cycle is obtained, and the corresponding points are plotted in the coordinate system. The points of the DC internal resistance of multiple discharge cycles are connected to form an internal resistance change curve.

[0039] In some embodiments, the DC internal resistance is the sum of the ohmic internal resistance and one or more of the concentration polarization internal resistance, electrochemical polarization internal resistance, and ohmic polarization internal resistance. That is, due to the different internal structures of different batteries, according to the relationship The obtained DC internal resistance may be the sum of one or more of the ohmic internal resistance and the concentration polarization internal resistance, the electrochemical polarization internal resistance, the ohmic polarization internal resistance, and the like.

[0040] S4: Obtain the internal resistance change rate according to the internal resistance change curve, and construct an internal resistance polarization response curve in a pre-established plane coordinate system. The internal resistance polarization response curve characterizes the relationship between the internal resistance change rate and the corresponding voltage. Specifically, the internal resistance change curve is differentiated to obtain the internal resistance change rate of the DC internal resistance. The internal resistance change rate corresponding to the corresponding voltage is the slope of the internal resistance change curve at the corresponding voltage. Construct the internal resistance polarization response curve in the second coordinate system, and the two coordinate axes of the second coordinate axis are the internal resistance change rate and the voltage.

[0041] The horizontal axis of the internal resistance polarization response curve is the corresponding voltage of each discharge cycle, and the vertical axis is the internal resistance change rate of each discharge cycle.

[0042] Among them, V is the corresponding voltage of each discharge cycle, and the vertical axis is , that is, the internal resistance change rate of the DC internal resistance corresponding to each corresponding voltage, that is, Figure 3 The internal resistance polarization response in .

[0043] S5: Detect whether lithium deposition occurs in the battery to be tested according to the lithium deposition threshold of the internal resistance polarization response curve. Specifically, detect whether lithium deposition occurs in the battery to be tested according to the lithium deposition threshold of the internal resistance polarization response curve of the battery to be tested. After the discharge starts, in some embodiments, the internal resistance polarization response curve of the lithium deposition battery has an internal resistance change rate peak and an internal resistance change rate trough in the initial stage of discharge. The ordinate of the trough can be used as a lithium deposition threshold to determine whether lithium deposition occurs.

[0044] Therefore, according to the change rate of the DC internal resistance of the lithium-ion battery during lithium dissolution, an internal resistance polarization response curve is drawn. The lithium-ion detection method in the present application can still significantly identify the lithium dissolution signal when the battery has a high discharge rate, thereby reducing the time of lithium-ion detection, improving the recognition efficiency, and efficiently and easily identifying the lithium-ion of the battery. It can quickly and intuitively reflect the situation of lithium-ion generation inside the battery through the polarization of the internal resistance caused by lithium dissolution inside the battery, thereby improving the universality of lithium-ion detection.

[0045] Furthermore, the ordinate L of the first trough of the internal resistance polarization response curve after the battery to be tested starts to discharge is obtained.

[0046] If L<0, the battery to be tested is determined to be a lithium deposition battery. That is, when the ordinate of the first trough after the battery to be tested starts to discharge is a negative value, that is, when the internal resistance change rate after the battery to be tested starts to discharge changes significantly, it can be determined that the battery to be tested is a lithium deposition battery.

[0047] If L≥0, it is determined that the battery to be tested is a non-lithium-separated battery.

[0048] That is to say, the ordinate L of the first trough after the battery to be tested starts to discharge can be used as the lithium deposition threshold, and whether lithium deposition occurs in the battery to be tested can be determined based on whether L is greater than 0.

[0049] For example, Figure 2 and Figure 3 The example a shows that the initial voltage of the lithium-ion battery discharge a is 3.2V, and the discharge cut-off voltage is 2.2V. Figure 2 and Figure 3 The example b represents a non-lithium-precipitated battery b. The other parameters of the non-lithium-precipitated battery b are consistent with those of the battery a, with an initial voltage of 3.2V and a discharge cut-off voltage of 2.2V.

[0050] like Figure 2 As shown, both a and b are discharged in the same non-sleep discharge mode (discharged at a constant current of 0.5C to the discharge cut-off voltage). The horizontal axis is the actual capacity, and the vertical axis is the discharge voltage. The curve characteristics of the discharge voltage and actual capacity of battery a and battery b are not obvious, and it is impossible to directly determine whether lithium plating occurs from the curve.

[0051] like Figure 3 As shown, the same intermittent dormant discharge method is used for both a and b, and the other parameters in the discharge process are the same. The internal resistance polarization response curve of battery a shows an internal resistance change rate trough less than 0 near 3.13-3.16V, and an internal resistance change rate peak and internal resistance change rate trough appear in the initial stage of discharge, and the difference between the peak and the trough is large, so it can be judged that battery a is a lithium deposition battery.

[0052] According to the second aspect of the present invention, the lithium plating detection device includes: at least one processor; a memory connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, and the instructions are executed by the at least one processor so that the at least one processor can execute the method.

[0053] The lithium deposition detection device includes: a memory and a processor, and the memory stores instructions that can be run on the processor. When the processor executes the instructions, the battery lithium deposition detection method in the above embodiment is implemented. The number of memories and processors can be one or more. The lithium deposition detection device adopts the above battery lithium deposition detection method, and draws an internal resistance polarization response curve according to the polarization change rate of the DC internal resistance of the lithium deposition battery when lithium dissolves, which can efficiently and easily identify the lithium deposition of the battery.

[0054] The lithium analysis detection device is intended to represent various forms of digital computers, such as laptop computers, desktop computers, workbenches, personal digital assistants, servers, blade servers, mainframe computers, and other suitable computers. The lithium analysis detection device can also represent various forms of mobile devices, such as personal digital processing, cellular phones, smart phones, wearable devices, and other similar computing devices. The components shown herein, their connections and relationships, and their functions are only examples, and are not intended to limit the implementation of the present application described herein and / or required.

[0055] In some embodiments, the lithium plating detection device can be deployed in the cloud.

[0056] According to the third aspect of the present invention, the lithium deposition detection system comprises: a vehicle, the vehicle comprises a battery; and a lithium deposition detection device according to the method, which is used to determine the lithium deposition detection result of the battery to be tested. According to the third aspect of the present application, the lithium deposition detection system comprises a vehicle and a lithium deposition detection device according to the second aspect of the present application. Among them, the vehicle comprises a battery lithium deposition detection device for determining the lithium deposition detection result of the battery according to the lithium deposition detection method of any embodiment of the first aspect of the present application.

[0057] According to the lithium deposition detection system of the embodiment of the present application, the lithium deposition status of each battery can be detected during the discharge process of the battery, thereby avoiding the risk of thermal runaway.

[0058] According to some embodiments of the present invention, the vehicle further includes: a domain controller, communicating with the battery and the lithium deposition detection device, the domain controller being used to obtain discharge data of the battery to be tested and send the discharge data of the battery to be tested to the lithium deposition detection device.

[0059] Exemplarily, the battery management unit sends status information such as battery voltage, battery current and battery temperature to the domain controller in real time through the controller area network (CAN). The domain controller converts the CAN signal into an Ethernet signal and sends it to the telematics box (T-Box), which is finally uploaded by the T-Box to the cloud-based lithium plating detection equipment.

[0060] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0061] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0062] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A lithium precipitation detection method, characterized in that: include: The battery under test first sleeps and then discharges a preset capacity at a constant current in each discharge cycle, wherein each discharge cycle refers to the period from the start of the current sleep period to the start of the next sleep period, and the sleep period of the battery under test is the preset time; Obtain the DC internal resistance and corresponding voltage of each discharge cycle; Acquire an internal resistance variation curve according to the DC internal resistance, wherein the internal resistance variation curve represents a relationship between the DC internal resistance and the corresponding voltage; Acquiring an internal resistance change rate according to the internal resistance change curve, and constructing an internal resistance polarization response curve in a pre-established plane coordinate system, wherein the internal resistance polarization response curve represents a relationship between the internal resistance change rate and the corresponding voltage; Detecting whether lithium deposition occurs in the battery to be tested according to the lithium deposition threshold of the internal resistance polarization response curve; The detecting whether lithium deposition occurs in the battery to be tested comprises: obtaining the vertical coordinate L of the first trough of the internal resistance polarization response curve after the battery to be tested starts to discharge; If L<0, it is determined that the battery to be tested is a lithium deposition battery; If L≥0, it is determined that the battery to be tested is a non-lithium-separated battery.

2. The lithium precipitation detection method according to claim 1, characterized in that: Obtain the corresponding voltage and DC internal resistance of each discharge cycle, including: Obtain the initial voltage V of the current discharge cycle t1 and the corresponding voltage V of the current discharge cycle t2 ; The constant current is I, the DC internal resistance is DCIR, and the DCIR, V t1 、V t2 and I satisfy the relationship: 。 3. The lithium precipitation detection method according to claim 1, characterized in that: The step of obtaining an internal resistance variation curve according to the DC internal resistance includes: the abscissa of the internal resistance variation curve is the corresponding voltage of each discharge cycle, and the ordinate is the DC internal resistance of each discharge cycle.

4. The lithium precipitation detection method according to claim 1, characterized in that: The constructing of the internal resistance polarization response curve in the pre-established plane coordinate system includes: the abscissa of the internal resistance polarization response curve is the corresponding voltage of each discharge cycle, and the ordinate is the internal resistance change rate of each discharge cycle.

5. The lithium precipitation detection method according to claim 1, characterized in that: The DC internal resistance is the sum of the ohmic internal resistance and one or more of the concentration polarization internal resistance, the electrochemical polarization internal resistance and the ohmic polarization internal resistance.

6. The lithium precipitation detection method according to claim 1, characterized in that: Assume that the preset time of the discharge cycle is T, and T satisfies the relationship: 3s≤T≤3600s.

7. A lithium deposition detection device, characterized in that: include: at least one processor; A memory communicatively connected to the at least one processor; wherein the memory stores instructions executable by the at least one processor, the instructions being executed by the at least one processor so that the at least one processor can execute the method of any one of claims 1-6.

8. The lithium deposition detection device according to claim 7, characterized in that: The lithium plating detection equipment is deployed in the cloud.

9. A lithium deposition detection system, characterized in that: include: A vehicle, the vehicle comprising a battery; The lithium deposition detection device according to claim 7 is used to determine the lithium deposition detection result of the battery to be tested according to the method according to any one of claims 1 to 6.

10. The lithium deposition detection system according to claim 9, characterized in that: The vehicle further includes: a domain controller, communicating with the battery and the lithium deposition detection device, wherein the domain controller is used to obtain discharge data of the battery to be tested and send the discharge data of the battery to be tested to the lithium deposition detection device.

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