Method and system for acquiring lithium precipitation amount of battery

Abstract

The invention discloses a method and system for obtaining the lithium precipitation amount of a battery, and belongs to the technical field of batteries, and the method comprises the steps: carrying out the charging test of a reference battery, and obtaining a first resistance curve and a second resistance curve of the reference battery; obtaining a negative electrode resistance curve and a lithium precipitation resistance curve based on a preset lithium precipitation boundary potential and the first resistance curve; fitting a first function based on the negative electrode resistance curve, and fitting a second function based on the lithium precipitation resistance curve; acquiring a first resistance and a terminal charge state of the to-be-tested battery at the lithium precipitation state charging terminal, and acquiring a second resistance based on the terminal charge state and the second resistance curve; and based on the first function, the second function, the first resistance, the terminal charge state and the second resistance, obtaining the lithium precipitation amount of the to-be-measured battery. The reference battery is arranged to obtain the total battery voltage and the cathode voltage signal of the to-be-detected battery, and the lithium precipitation amount can be accurately obtained without damaging the to-be-detected battery, so that the prediction accuracy of the performance and the service life of the battery is improved, and the safety of the battery is guaranteed.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of battery technology, and in particular to a method and system for obtaining the amount of lithium deposition in a battery. Background Art

[0002] Lithium deposition will occur during the use of the battery. The deposited lithium is still electrochemically active and has a low potential. It can be embedded in graphite and the positive electrode when stationary or discharged, gradually causing battery degradation and affecting battery safety.

[0003] Since short-term or small amounts of lithium deposition do not have a significant impact on battery safety, it is necessary to accurately obtain the amount of lithium deposition. Currently, the lithium deposition amount is usually obtained by disassembling and observing the battery, or by element characterization. However, the above methods cannot accurately obtain the amount of lithium deposition, which affects the use of the battery. Summary of the invention

[0004] The embodiments of the present application provide a method for obtaining the amount of lithium precipitated from a battery to solve the technical problem in the prior art that the amount of lithium precipitated cannot be accurately obtained, which affects the use of the battery; the embodiments of the present application also provide a system for obtaining the amount of lithium precipitated from a battery.

[0005] In order to solve the above technical problems, the embodiments of the present application disclose the following technical solutions:

[0006] In a first aspect, a method for obtaining the amount of lithium deposition in a battery is provided, comprising:

[0007] A charging test is performed on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested; the first resistance curve is configured as a change curve of the negative electrode resistance of the reference battery at each state of charge, and the second resistance curve is configured as a change curve of the full battery resistance of the reference battery at each state of charge.

[0008] Based on the preset lithium deposition boundary potential and the first resistance curve, obtaining a negative electrode resistance curve and a lithium deposition resistance curve;

[0009] Fitting a first function based on the negative electrode resistance curve, and fitting a second function based on the lithium deposition resistance curve;

[0010] Acquire a first resistance and a terminal state of charge of the battery under test at a charging terminal in a lithium deposition state, and acquire a second resistance based on the terminal state of charge and the second resistance curve;

[0011] The amount of lithium deposition of the battery to be tested is obtained based on the first function, the second function, the first resistor, the terminal state of charge, and the second resistor.

[0012] In combination with the first aspect, the step of performing a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery includes:

[0013] Performing a charging test on the reference battery based on a preset rate to obtain the full battery voltage, negative electrode voltage, negative electrode resistance and full battery resistance of the reference battery at different states of charge;

[0014] Acquire the first resistance curve based on the negative electrode voltage, the full battery state of charge, the charging current and the negative electrode resistance;

[0015] The second resistance curve is acquired based on the full-battery voltage, the full-battery state of charge, the charging current and the full-battery resistance.

[0016] In combination with the first aspect, the step of performing a charging test on the reference battery based on a preset rate to obtain the negative electrode resistance and the full battery resistance of the reference battery at different states of charge includes:

[0017] Charging the reference battery based on a preset rate, and recording the negative electrode potential during the charging process;

[0018] In response to charging into a preset amount of electricity, suspending charging, and placing the reference battery on hold for a preset time to complete stage charging;

[0019] Performing the stage charging for a plurality of times on the reference battery until the battery is charged to a cut-off power level, thereby completing the charging of the reference battery;

[0020] In each stage of charging, the negative electrode resistance and the full battery resistance corresponding to the current charging state are obtained based on the first voltage of the reference battery when charging is suspended, the second voltage of the reference battery when the standby is completed, and the charging current of the reference battery.

[0021] In combination with the first aspect, the cut-off power meets: 80% SOC≤A≤200% SOC, wherein A is the cut-off power, and SOC is the rated state of charge of the reference battery;

[0022] The preset time satisfies: 0.001s≤t≤600s, where t is the preset time.

[0023] In combination with the first aspect, the first function is fitted as follows:

[0024] f(y)=a1y 2 +a2y+a3;

[0025] Wherein, y is the charge state of lithium insertion, and a1, a2 and a3 are the first fitting constants.

[0026] In combination with the first aspect, the second function is fitted as follows:

[0027]

[0028] Wherein, x is the charge state of lithium deposition, and b1, b2, b3 and b4 are the second fitting constants.

[0029] In combination with the first aspect, the lithium precipitation amount is obtained based on the following formula:

[0030] R0-R1=f(S L-end )-f(S L-end -SoC Li )+|g(SoC Li )|;

[0031] Wherein, R1 is the first resistor, S L-end is the terminal state of charge, R0 is the second resistor, SoC Li is the lithium deposition amount, f() is the first function, and g() is the second function.

[0032] In combination with the first aspect, the step of obtaining the negative electrode resistance curve and the lithium deposition resistance curve based on the preset lithium deposition boundary potential and the first resistance curve includes:

[0033] Determine a portion of the first resistance curve where the negative electrode potential is higher than the lithium deposition boundary potential as the negative electrode resistance curve;

[0034] The portion of the first resistance curve where the negative electrode potential is lower than the lithium deposition boundary potential is determined as the lithium deposition resistance curve.

[0035] In combination with the first aspect, the lithium deposition boundary potential satisfies: -20mV≤b≤0mV, wherein b is the lithium deposition boundary potential.

[0036] In a second aspect, a system for obtaining the amount of lithium deposition in a battery is provided, characterized in that it includes:

[0037] A first acquisition module is configured to perform a charging test on a reference battery to acquire a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery having the same system and capacity as the battery to be tested;

[0038] A second acquisition module is configured to acquire a negative electrode resistance curve and a lithium deposition resistance curve based on a preset lithium deposition boundary potential and the first resistance curve;

[0039] A fitting module, configured to fit a first function based on the negative electrode resistance curve, and to fit a second function based on the lithium deposition resistance curve;

[0040] A third acquisition module is configured to acquire a first resistance and a terminal state of charge of the battery under test at a charging terminal in a lithium deposition state, and acquire a second resistance based on the terminal state of charge and the second resistance curve;

[0041] The fourth acquisition module is configured to acquire the lithium deposition amount of the battery to be tested based on the first function, the second function, the first resistor, the terminal state of charge, and the second resistor.

[0042] One of the above technical solutions has the following advantages or beneficial effects:

[0043] Compared with the prior art, the method for obtaining the amount of lithium deposition in a battery provided by the present application includes: performing a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested; obtaining a negative electrode resistance curve and a lithium deposition resistance curve based on a preset lithium deposition boundary potential and a first resistance curve; fitting a first function based on the negative electrode resistance curve, and fitting a second function based on the lithium deposition resistance curve; obtaining a first resistance and a terminal state of charge of the battery to be tested at the end of the lithium deposition state charging, and obtaining a second resistance based on the terminal state of charge and the second resistance curve; obtaining the amount of lithium deposition of the battery to be tested based on the first function, the second function, the first resistance, the terminal state of charge, and the second resistance. In this way, by setting a reference battery, obtaining the full battery voltage signal and the negative electrode voltage signal of the battery to be tested, it is possible to accurately obtain the amount of lithium deposition without destroying the battery to be tested, thereby improving the accuracy of predicting battery performance and life, and ensuring battery safety.

[0044] The battery lithium deposition amount acquisition system provided in the present application has all the technical features and beneficial effects of the battery lithium deposition amount acquisition method described above, which will not be described in detail here. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The technical solution and other beneficial effects of the present application will be made apparent by describing in detail the specific implementation methods of the present application in conjunction with the accompanying drawings.

[0046] Figure 1 A schematic diagram of a process for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application;

[0047] Figure 2 A schematic diagram of a charging test of a reference battery in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application;

[0048] Figure 3 A schematic diagram of the calculation and fitting results of the negative electrode resistance in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application;

[0049] Figure 4A schematic diagram of the calculation and fitting results of the lithium deposition resistance in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application;

[0050] Figure 5 A schematic diagram of the test results of the resistance of the full battery in a non-lithium deposition state in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application;

[0051] Figure 6 The voltage curve of the battery to be tested with 2C charging in the method for obtaining the amount of lithium deposition in the battery provided in the embodiment of the present application;

[0052] Figure 7 A schematic diagram of the structure of a system for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application. DETAILED DESCRIPTION

[0053] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. In the description of the present application, it is necessary to understand that the orientation or position relationship indicated by the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0054] The applicant found that disassembly and observation is a destructive experiment, and disassembly and observation is highly subjective, and it is impossible to accurately obtain the amount of lithium precipitated; and element characterization methods, such as inductively coupled plasma (ICP), cannot distinguish between the lithium embedded in the negative electrode and the lithium compounds and the precipitated lithium, and cannot accurately obtain the amount of lithium precipitated.

[0055] To this end, the present application sets up a reference battery to obtain the full-battery voltage signal and the negative electrode voltage signal of the battery to be tested, so as to accurately obtain the amount of lithium plating without destroying the battery to be tested, thereby improving the accuracy of prediction of battery performance and life and ensuring battery safety.

[0056] The specific implementation methods of the present application are described below by way of examples:

[0057] See also Figure 1 and Figure 2 , Figure 1 The flowchart of the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application is shown. Figure 2 The charging test schematic diagram of the reference battery in the method for obtaining the amount of lithium deposition in the battery provided in the embodiment of the present application is illustrated. The present application provides a method for obtaining the amount of lithium deposition in the battery, comprising the following steps 101 to 105.

[0058] Step 101, perform a charging test on the reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested, the first resistance curve is configured as a change curve of the negative electrode resistance of the reference battery at each state of charge, and the second resistance curve is configured as a change curve of the full battery resistance of the reference battery at each state of charge. Specifically, the reference battery, as a three-electrode battery with the same system and capacity as the battery to be tested, can be used as a test standard for the battery to be tested. Then, the first resistance curve and the second resistance curve are used to evaluate the relevant performance of the battery to be tested in the charging test, so that the amount of lithium deposition can be obtained without disassembling the battery to be tested. In addition, by monitoring the change curves of the negative electrode resistance and the full battery resistance of the reference battery, the resistance change of the reference battery at different states of charge can be obtained, so as to evaluate the health of the battery to be tested, the capacity attenuation, and the dynamic characteristics of the internal reaction of the battery to be tested. It should be noted that the conditions for lithium deposition in the reference battery and the battery to be tested are the same. For example, the reference battery and the battery to be tested do not deposit lithium when they are normally charged at 1C and 25°C, but deposit lithium when they are normally charged at 2C and 25°C. It is understandable that the above conditions are only used as examples and are not specific limitations on the reference battery and the battery to be tested.

[0059] In one embodiment, step 101 performs a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery, including: performing a charging test on the reference battery based on a preset rate to obtain the full-cell voltage, negative electrode voltage, negative electrode resistance and full-cell resistance of the reference battery at different states of charge; obtaining a first resistance curve based on the negative electrode voltage, full-cell state of charge, charging current and negative electrode resistance; obtaining a second resistance curve based on the full-cell voltage, full-cell state of charge, charging current and full-cell resistance. Specifically, the preset rate refers to a rate that is similar to the rate of the battery to be tested, but will not cause lithium deposition; the full-cell state of charge refers to all different states of charge of the reference battery. In this way, the reference battery is charged and tested at a preset rate to obtain the curves of the full-cell voltage, negative electrode voltage, negative electrode resistance and full-cell resistance of the reference battery as the state of charge changes, thereby obtaining the internal electrochemical reaction and resistance characteristics of the reference battery; at the same time, the present application also obtains the resistance change of the reference battery during the charging process by analyzing the first resistance curve and the second resistance curve.

[0060] In one embodiment, a reference battery is charged and tested based on a preset rate, and the steps of obtaining the negative electrode resistance and the full battery resistance of the reference battery at different states of charge include: charging the reference battery based on a preset rate and recording the negative electrode potential during the charging process; suspending charging in response to charging a preset amount of electricity, and placing the reference battery on hold for a preset time to complete the stage charging; charging the reference battery in multiple stages until it is charged to a cutoff amount of electricity, and the charging of the reference battery is completed; in each stage of charging, based on the first voltage of the reference battery when charging is suspended, the second voltage of the reference battery when the standby is completed, and the charging current of the reference battery, the negative electrode resistance and the full battery resistance corresponding to the current state of charge are obtained. The embodiment of the present application can monitor the resistance change of the reference battery at different states of charge in real time by charging in multiple stages and recording the negative electrode resistance and the full battery resistance, thereby continuously recording the capacity change and internal resistance change of the reference battery. Specifically, after obtaining the first voltage V1 and the second voltage V2, the negative electrode resistance or the full battery resistance can be obtained according to R=|(V1-V2) / I|, where R is the negative electrode resistance or the full battery resistance, I is the charging current, and || represents the absolute value. Specifically, the steps for obtaining the resistance of the whole battery are as follows: in each stage of charging, the first voltage of the battery voltage when the reference battery suspends charging, the second voltage of the battery voltage when the reference battery is put on standby, and the charging current of the reference battery are obtained, the first voltage is subtracted from the second voltage, and the result is divided by the charging current to obtain the resistance of the whole battery, on this basis, the values ​​of the resistance of the whole battery at different charge states are calculated respectively to obtain the second resistance curve; the steps for obtaining the negative electrode resistance are as follows: the first negative electrode voltage when the reference battery suspends charging, the second negative electrode voltage when the reference battery is put on standby, and the charging current of the reference battery are obtained, the first negative electrode voltage is subtracted from the second negative electrode voltage, and the result is divided by the charging current to obtain the negative electrode resistance, on this basis, the values ​​of the negative electrode resistance at different charge states are calculated respectively to obtain the first resistance curve.

[0061] In one embodiment, the cut-off power meets: 80% SOC ≤ A ≤ 200% SOC, where A is the cut-off power and SOC is the rated state of charge of the reference battery; the preset time meets: 0.001s ≤ t ≤ 600s, where t is the preset time. Specifically, the cut-off power A can be any value among 80% SOC, 90% SOC, 100% SOC, 110% SOC, 120% SOC, 130% SOC, 140% SOC, 150% SOC, 160% SOC, 170% SOC, 180% SOC, 190% SOC, 200% SOC, or a range between any two values, preferably 140% SOC. The preset time t can be 0.001s, 0.002s, 0.003s, 0.004s, 0.005s, 0.006s, 0.007s, 0.008s, 0.009s, 0.01s, 0.02s, 0.03s, 0.04s, 0.05s, 0.06s, 0.07s, 0.08s, 0.09s, 0.1s, 0.2s, 0.3s, 0.4s, 0.5 t is any value among s, 0.6s, 0.7s, 0.8s, 0.9s, 1s, 2s, 3s, 4s, 5s, 6s, 7s, 8s, 9s, 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 200s, 300s, 400s, 500s, and 600s, or a range value between any two values, preferably 0.01s≤t≤10s.

[0062] Step 102, based on the preset lithium deposition boundary potential and the first resistance curve, obtain the negative electrode resistance curve and the lithium deposition resistance curve. Specifically, the lithium deposition boundary potential is the negative electrode potential of the reference battery where lithium deposition occurs, and the negative electrode resistance curve reflects the migration characteristics of lithium ions in the reference battery during the charge and discharge process. The present application analyzes the negative electrode resistance curve by the lithium deposition boundary potential, evaluates the stability and cycle life of the reference battery, and provides a reference for the battery to be tested.

[0063] In some embodiments, step 102 is based on a preset lithium deposition boundary potential and a first resistance curve, and the step of obtaining a negative electrode resistance curve and a lithium deposition resistance curve includes: determining the portion of the first resistance curve where the negative electrode potential is higher than the lithium deposition boundary potential as the negative electrode resistance curve; determining the portion of the first resistance curve where the negative electrode potential is lower than the lithium deposition boundary potential as the lithium deposition resistance curve. Specifically, after obtaining the curve of the change of the negative electrode resistance of the reference battery during the charging process with the state of charge SOC, i.e., the first resistance curve, the line where the negative electrode potential is the lithium deposition boundary potential is the lithium deposition boundary line, the first resistance curve where the negative electrode potential is higher than the lithium deposition boundary potential is determined as the negative electrode resistance curve, the first resistance curve where the negative electrode potential is lower than the lithium deposition boundary potential is determined as the lithium deposition resistance curve, and the first curve is divided into a negative electrode resistance curve and a lithium deposition resistance curve, so as to distinguish the lithium insertion state and the lithium deposition state of the reference battery, and serve as a basis for the subsequent calculation of the lithium deposition amount of the battery to be tested. It should be noted that the state of charge SOC in the lithium deposition resistance curve in the present application is calculated starting from the SOC corresponding to the lithium deposition boundary potential of 0, and the resistance R is calculated starting from the Rx corresponding to the lithium deposition boundary potential of 0.

[0064] In one embodiment, the lithium separation boundary potential satisfies: -20mV≤b≤0mV, where b is the lithium separation boundary potential. Specifically, the lithium separation boundary potential b can be any value among -20mV, -19mV, -18mV, -17mV, -16mV, -15mV, -14mV, -13mV, -12mV, -11mV, -10mV, -9mV, -8mV, -7mV, -6mV, -5mV, -4mV, -3mV, -2mV, -1mV, 0mV, or a range value between any two values.

[0065] Step 103, fit the first function based on the negative electrode resistance curve, and fit the second function based on the lithium deposition resistance curve. Specifically, the present application obtains the mathematical model of the first function and the second function by fitting the negative electrode resistance curve and the lithium deposition resistance curve, and then describes the resistance characteristics and lithium ion loss inside the reference battery through the first function and the second function. Thus, as a reference for the battery to be tested, by controlling the resistance and lithium ion loss inside the battery to be tested, the charge and discharge process of the battery to be tested is optimized, and the efficiency and cycle life of the battery to be tested are improved.

[0066] In one embodiment, the first function is fitted as:

[0067] f(y)=a1y 2 +a2y+a3 (1);

[0068] Wherein, y is the state of charge of lithium insertion, a1, a2 and a3 are first fitting constants, and the first fitting constants can be obtained by fitting the test data of the charging test of the above reference battery.

[0069] In one embodiment, the second function is fitted as:

[0070]

[0071] Wherein, x is the state of charge of lithium deposition, b1, b2, b3 and b4 are second fitting constants, and the second fitting constants can be obtained by fitting the test data of the charging test of the above reference battery.

[0072] Step 104, obtain the first resistance and terminal state of charge of the battery to be tested at the end of the lithium deposition state charging, and obtain the second resistance based on the terminal state of charge and the second resistance curve. Specifically, the first resistance and the second resistance are similar to the process of obtaining the negative electrode resistance or the full battery resistance. The battery to be tested is charged at the lithium deposition rate, and the voltage of the battery to be tested at the end of the lithium deposition state charging during the stage charging process is recorded as V3, and the voltage of the battery to be tested after being left for a preset time is recorded as V4. The formula R1=|V3-V4 / I| is used to obtain the first resistance R1, where I is the charging current of the battery to be tested, and || represents the absolute value. The terminal state of charge at the end of the lithium deposition state charging is then recorded as S L-end , and based on the second resistance curve, find the terminal state of charge S L-end The corresponding resistor is the second resistor R0.

[0073] Step 105, based on the first function, the second function, the first resistor, the terminal state of charge, and the second resistor, the amount of lithium deposition of the battery to be tested is obtained. Specifically, after the amount of lithium deposition is obtained, the amount of lithium deposition can be converted into the lithium deposition capacity, i.e., SoC, by the capacity C of the battery to be tested. Li ×C.

[0074] In one embodiment, the amount of lithium deposition is obtained based on the following formula:

[0075] R0-R1=f(S L-end )-f(S L-end -SoC Li )+|g(SoC Li )| (3);

[0076] Among them, R1 is the first resistor, S L-end is the terminal charge state, R0 is the second resistor, SoC Li is the amount of lithium precipitation, f() is the first function, and g() is the second function.

[0077] The following is a specific example to illustrate the method for obtaining the amount of lithium deposition in the battery of the present application. It is known that the capacity of the battery C to be tested is 4Ah, and the battery C to be tested will not deposit lithium at 1C and 25°C, but will deposit lithium when charged at 2C and 25°C. It is necessary to calculate the amount of lithium deposition when charged at 2C. It is understandable that whether lithium deposition occurs in the battery C to be tested is determined by the negative electrode potential. Please refer to Figures 3 to 6 , Figure 3 A schematic diagram illustrating calculation and fitting results of negative electrode resistance in a method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application; Figure 4 A schematic diagram illustrating the calculation and fitting results of the lithium deposition resistance in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application; Figure 5 A schematic diagram illustrating the test results of the resistance of the full battery in a non-lithium deposition state in the method for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application; Figure 6 The voltage curve of the battery to be tested with 2C charging in the method for obtaining the amount of lithium deposition in the battery provided in the embodiment of the present application is illustrated.

[0078] A reference battery is made using a three-electrode battery with the same battery system and capacity as the battery C to be tested. The reference battery is charged at a preset rate of 1C (no lithium deposition occurs in the battery C to be tested and the reference battery during normal charging at 1C), and the negative electrode potential is recorded. The reference battery is left for 10 seconds after each charge of 3.3% SOC until it reaches the cutoff capacity of the reference battery, i.e. 140% SoC. The first resistance curve is divided by 0V as the lithium deposition boundary potential, and the full battery resistance, negative electrode resistance curve, and lithium deposition resistance curve are calculated using the formula R = |V1-V2 / I|. The calculation results are shown in the figure. Figure 3 , Figure 4 and Figure 5 As shown in the figure, the SOC in the lithium deposition resistance curve is calculated starting from the SOC corresponding to the lithium deposition boundary potential as 0, and the resistance R is calculated starting from the Rx corresponding to the lithium deposition boundary potential as 0.

[0079] Use functions f(y) and g(x) to fit the two curves respectively. The fitting results are as follows: Figure 3 , Figure 4 and Figure 5 As shown, the first fitting constant and the second fitting constant are shown in Table 1.

[0080] Table 1

[0081]

[0082] Perform a 2C charge test on the battery to be tested and record the voltage change of the battery to be tested within 10 seconds after the charging is completed. Figure 6 The first resistance R1 = 0.00427 of the battery under test at the end of 2C charging is calculated by the formula R1 = |V3-V4 / I|, and the corresponding terminal state of charge is S L-end=0.86. Pass Figure 5 The second curve in finds R0=Rc(0.86)=0.0056.

[0083] By formula: R0-R1=f(S L-end )-f(S L-end -SoC Li )+|g(SoC Li )|, substituting the known quantity into:

[0084]

[0085] Solving SoC Li =0.06835, which is converted into the lithium plating capacity of the battery C to be tested: 0.06835×4Ah=0.2734Ah.

[0086] The method for obtaining the amount of lithium deposition in a battery provided by the present application includes: performing a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested; obtaining a negative electrode resistance curve and a lithium deposition resistance curve based on a preset lithium deposition boundary potential and a first resistance curve; fitting a first function based on the negative electrode resistance curve, and fitting a second function based on the lithium deposition resistance curve; obtaining a first resistance and a terminal state of charge at the end of the battery to be tested in the lithium deposition state charging, and obtaining a second resistance based on the terminal state of charge and the second resistance curve; obtaining the amount of lithium deposition of the battery to be tested based on the first function, the second function, the first resistance, the terminal state of charge, and the second resistance. In this way, by setting a reference battery, obtaining the full battery voltage signal and the negative electrode voltage signal of the battery to be tested, it is possible to accurately obtain the amount of lithium deposition without destroying the battery to be tested, thereby improving the accuracy of predicting battery performance and life, and ensuring battery safety.

[0087] Accordingly, see Figure 7 , Figure 7The structural schematic diagram of the battery lithium deposition amount acquisition system provided by the embodiment of the present application is illustrated. The embodiment of the present application provides a battery lithium deposition amount acquisition system, including a first acquisition module, a second acquisition module, a fitting module, a third acquisition module and a fourth acquisition module; wherein the first acquisition module is configured to perform a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested; the second acquisition module is configured to obtain a negative electrode resistance curve and a lithium deposition resistance curve based on a preset lithium deposition boundary potential and a first resistance curve; the fitting module is configured to fit a first function based on the negative electrode resistance curve, and fit a second function based on the lithium deposition resistance curve; the third acquisition module is configured to obtain a first resistance and a terminal state of charge of the battery to be tested at the end of the lithium deposition state charging, and obtain a second resistance based on the terminal state of charge and the second resistance curve; the fourth acquisition module is configured to obtain the lithium deposition amount of the battery to be tested based on the first function, the second function, the first resistance, the terminal state of charge, and the second resistance.

[0088] The battery lithium deposition amount acquisition system provided in the present application has all the technical features and beneficial effects of the battery lithium deposition amount acquisition method described above, which will not be described in detail here.

[0089] The above is a detailed introduction to a method and system for obtaining the amount of lithium deposition in a battery provided in an embodiment of the present application. Specific examples are used in this article to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solution and core idea of ​​the present application. Ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some of the technical features therein with equivalents; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for obtaining the amount of lithium deposition in a battery, characterized in that: include: Performing a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery with the same system and capacity as the battery to be tested; the first resistance curve is configured as a change curve of the negative electrode resistance of the reference battery at each state of charge, and the second resistance curve is configured as a change curve of the full battery resistance of the reference battery at each state of charge; Based on the preset lithium deposition boundary potential and the first resistance curve, obtaining a negative electrode resistance curve and a lithium deposition resistance curve; Fitting a first function based on the negative electrode resistance curve, and fitting a second function based on the lithium deposition resistance curve; Acquire a first resistance and a terminal state of charge of the battery under test at a charging terminal in a lithium deposition state, and acquire a second resistance based on the terminal state of charge and the second resistance curve; The amount of lithium deposition of the battery to be tested is obtained based on the first function, the second function, the first resistor, the terminal state of charge, and the second resistor.

2. The method for obtaining the amount of lithium deposition in a battery according to claim 1, characterized in that: The step of performing a charging test on a reference battery to obtain a first resistance curve and a second resistance curve of the reference battery includes: Performing a charging test on the reference battery based on a preset rate to obtain the full battery voltage, negative electrode voltage, negative electrode resistance and full battery resistance of the reference battery at different states of charge; Acquire the first resistance curve based on the negative electrode voltage, the full battery state of charge, the charging current and the negative electrode resistance; The second resistance curve is acquired based on the full-battery voltage, the full-battery state of charge, the charging current and the full-battery resistance.

3. The method for obtaining the amount of lithium deposition in a battery according to claim 2, characterized in that: The step of performing a charging test on the reference battery based on a preset rate to obtain the negative electrode resistance and the full battery resistance of the reference battery at different states of charge includes: Charging the reference battery based on a preset rate, and recording the negative electrode potential during the charging process; In response to charging into a preset amount of electricity, suspending charging, and placing the reference battery on hold for a preset time to complete stage charging; The reference battery is charged in the above-mentioned stages for a plurality of times until it is charged to a cut-off power level, thereby completing the charging of the reference battery; In each stage of charging, the negative electrode resistance and the full battery resistance corresponding to the current charging state are obtained based on the first voltage of the reference battery when charging is suspended, the second voltage of the reference battery when the standby is completed, and the charging current of the reference battery.

4. The method for obtaining the amount of lithium deposition in a battery according to claim 3, characterized in that: The cut-off power meets the following conditions: 80% SOC≤A≤200% SOC, where A is the cut-off power and SOC is the rated state of charge of the reference battery; The preset time satisfies: 0.001s≤t≤600s, where t is the preset time.

5. The method for obtaining the amount of lithium deposition in a battery according to claim 1, characterized in that: The first function is fitted as: <h2 style=";text-align:left;direction:ltr">f(y) = a1y<h2 style=";text-align:left;direction:ltr"> 2 <h2 style=";text-align:left;direction:ltr"> +a2y+a3; Wherein, y is the charge state of lithium insertion, and a1, a2 and a3 are the first fitting constants.

6. The method for obtaining the amount of lithium deposition in a battery according to claim 5, characterized in that: The second function is fitted as: Wherein, x is the charge state of lithium deposition, and b1, b2, b3 and b4 are the second fitting constants.

7. The method for obtaining the amount of lithium deposition in a battery according to claim 6, characterized in that: The lithium precipitation amount is obtained based on the following formula: R0-R1=f(S L-end )-f(S L-end -SoC Li )+|g(SoC Li )|; Wherein, R1 is the first resistor, S L-end is the terminal state of charge, R0 is the second resistor, Soc Li is the lithium deposition amount, f() is the first function, and g() is the second function.

8. The method for obtaining the amount of lithium deposition in a battery according to claim 1, characterized in that: The step of obtaining the negative electrode resistance curve and the lithium deposition resistance curve based on the preset lithium deposition boundary potential and the first resistance curve includes: Determine a portion of the first resistance curve where the negative electrode potential is higher than the lithium deposition boundary potential as the negative electrode resistance curve; The portion of the first resistance curve where the negative electrode potential is lower than the lithium deposition boundary potential is determined as the lithium deposition resistance curve.

9. The method for obtaining the amount of lithium deposition in a battery according to claim 1, characterized in that: The lithium deposition boundary potential satisfies: -20mV≤b≤0mV, wherein b is the lithium deposition boundary potential.

10. A system for obtaining the amount of lithium deposition in a battery, characterized in that: include: A first acquisition module is configured to perform a charging test on a reference battery to acquire a first resistance curve and a second resistance curve of the reference battery; wherein the reference battery is configured as a three-electrode battery having the same system and capacity as the battery to be tested; A second acquisition module is configured to acquire a negative electrode resistance curve and a lithium deposition resistance curve based on a preset lithium deposition boundary potential and the first resistance curve; A fitting module, configured to fit a first function based on the negative electrode resistance curve, and to fit a second function based on the lithium deposition resistance curve; A third acquisition module is configured to acquire a first resistance and a terminal state of charge of the battery under test at a charging terminal in a lithium deposition state, and acquire a second resistance based on the terminal state of charge and the second resistance curve; The fourth acquisition module is configured to acquire the lithium deposition amount of the battery to be tested based on the first function, the second function, the first resistor, the terminal state of charge, and the second resistor.

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