A system and method for measuring current distribution in a power battery

Abstract

This invention discloses a system and method for measuring current distribution in a power battery. The system uses multiple surface electrodes to divide the battery electrode surface into several regions. A voltage acquisition module collects real-time voltage values ​​between adjacent surface electrodes and simultaneously collects the real-time voltage value between the last surface electrode and the battery tab. A time-voltage curve is obtained based on the collected real-time voltage values. A current analysis module is used to obtain real-time current values ​​for each region of the battery electrode surface based on the real-time voltage values. Then, based on the real-time current values ​​of each region of the battery electrode surface, the state of charge (SOC) value of each region and the current distribution density in the power battery are obtained, thereby determining the location of lithium-ion risk points in the power battery. This invention enables the measurement of current distribution on a power battery plane, identifying points with high current density distribution, and thus predicting lithium-ion risk points.

Description

Technical Field

[0001] This invention relates to the field of power batteries, specifically to a system and method for measuring the current distribution in a power battery. Background Technology

[0002] The rapid development of new energy vehicles has placed higher demands on the fast-charging capability and driving range of power batteries, leading to increasingly in-depth research into the electrochemical and thermal coupling mechanisms of large batteries. During operation, the insertion and extraction reactions, side reactions, and ohmic heat of the battery cause a significant temperature rise during charging and discharging. Uneven temperature distribution within the battery leads to uneven electrochemical impedance in different parts of the cell, resulting in uneven electrochemical reactions and further affecting the fast-charging capability and lifespan of the cell. Therefore, after determining the materials and structure of the cell in the early stages of cell design, it is crucial to study its electrochemical reaction characteristics. Currently, preliminary results can only be obtained through simulation. The simulation model is approximate, and some parameters use empirical values. To further improve the reliability of the simulation, further experimental data verification and input are needed to make the simulation results more credible. Measuring the current density distribution in lithium batteries remains an industry challenge, as there is no accurate experimental measurement method available.

[0003] An invention discloses a non-destructive testing device and method for fuel cell current density distribution, comprising three magnetic field acquisition units. The output terminals of each of the three magnetic field acquisition units are connected to one end of a data transmission module, and the other end of the data transmission module is connected to a computer. All three magnetic field acquisition units are arranged on the same plane as the MEA (Mean Interchange Air) of the fuel cell. Two magnetic field acquisition units are respectively located on both sides of the fuel cell, and the remaining magnetic field acquisition unit is located at the end of the fuel cell, away from the air inlet. This invention obtains the magnetic field strength at each location by setting magnetic field acquisition units on both sides and at the end of the fuel cell. The computer then calculates the current density distribution of the fuel cell based on the obtained magnetic field strength. The testing device has a simple structure, requires no external power supply, and requires no modification to the fuel cell. The current density distribution result calculated using the electromagnetic inversion algorithm has high accuracy. The core principle of this invention is to collect the magnetic fields from different regions and then convert the magnetic field signals into current signals according to Hall's law. However, current power batteries, whether they are wound square cells, stacked cells, or blade batteries, all use clamps in their production and installation. This is because the negative electrode graphite expands during fast charging, and only by using clamps to constrain the negative electrode graphite can its condition be the same as that in the battery pack. However, using clamps interferes with the magnetic field, leading to inaccurate magnetic field strength measurements, and consequently, inaccurate current calculations derived from the magnetic field. Furthermore, the conversion from magnetic field strength to current involves some approximations, further complicating the calculation's accuracy.

[0004] A fuel cell current measurement circuit is disclosed, wherein one electrode of the fuel cell is divided into at least two mutually insulated regions, each of the at least two regions being connected to a load module to form at least two branches, the discharge voltages of the at least two branches being adjustable, and the testing device measuring the discharge current of each of the at least two branches. By employing a multi-channel adjustable load, all regions of the fuel cell operate at the same potential, resulting in highly accurate measured current and fuel cell current density distribution.

[0005] In this design, one electrode is divided into two mutually insulated regions, a structural advantage of fuel cells. Furthermore, the adjustable load and voltage of the two paths are uncontrollable and equivalent to the impedance of each layer in the electrode thickness direction and the polarization voltage difference during charging and discharging in lithium batteries. Fuel cells are essentially equivalent to multiple electrodes connected in series, making the principle simpler. The adjustable load consists of a sliding rheostat and an electronic load circuit, combined with an operational amplifier and a field-effect transistor. This patent primarily measures the current distribution in the thickness direction of the fuel cell; it cannot measure the current density on the surface of the fuel cell, nor can it be used to measure the current density on the surface of a power battery. Summary of the Invention

[0006] The purpose of this invention is to provide a system and method for measuring the current distribution in a power battery, which can provide an accurate method for measuring the current distribution on the surface of battery electrodes.

[0007] To achieve this objective, the present invention provides a system for measuring the current distribution in a power battery, which includes multiple surface electrodes, a voltage acquisition module, and a current analysis module.

[0008] Multiple surface electrodes are laid side by side on the surface of the battery electrode sheet, and the multiple surface electrodes divide the surface of the battery electrode sheet into multiple regions. The battery electrode sheet between two adjacent surface electrodes is one region.

[0009] The voltage acquisition module is used to collect the real-time voltage value between two adjacent surface electrodes during the charging and discharging process of the power battery, and at the same time collect the real-time voltage value between the last surface electrode and the battery tab. Based on the real-time voltage value between two adjacent surface electrodes and the real-time voltage value between the last surface electrode and the battery tab, a time-voltage curve is obtained.

[0010] The current analysis module is used to convert the real-time voltage value into the real-time current value at each surface electrode based on the time-voltage curve. Based on the real-time current value at each surface electrode, the module obtains the real-time current value of each region on the surface of the battery electrode. Then, based on the real-time current value of each region on the surface of the battery electrode, the module obtains the state of charge value of each region on the surface of the battery electrode. At the same time, based on the real-time current value of each region on the surface of the battery electrode, the module obtains the current distribution density in the power battery. Based on the current distribution density in the power battery and the state of charge value of each region on the surface of the battery electrode, the module determines the location of the lithium risk point in the power battery.

[0011] Furthermore, the battery electrode is either the positive electrode or the negative electrode of the battery.

[0012] Furthermore, the surface electrode is made of a porous conductive material.

[0013] Furthermore, the plurality of surface electrodes divide the surface of the power battery into rectangular regions of equal area.

[0014] Furthermore, the method for acquiring the real-time voltage between two adjacent surface electrodes includes: welding copper wires to the tail of each surface electrode, connecting the copper wires to a data acquisition instrument, obtaining the real-time voltage between two adjacent surface electrodes by reading the data acquisition instrument, and recording the time-voltage curve.

[0015] Furthermore, the method for obtaining the real-time current value of each region on the surface of the battery electrode includes: calculating the real-time current at each surface electrode using Ohm's law based on the real-time voltage, and subtracting the real-time current at two adjacent surface electrodes to obtain the real-time current of each region on the surface of the battery electrode.

[0016] Furthermore, the method for obtaining the state of charge (SOC) values ​​of each region on the surface of the battery electrode includes: obtaining the capacitance value of each region on the surface of the battery electrode by integrating the real-time current value of each region on the surface of the battery electrode with time; and obtaining the SOC value of each region on the surface of the battery electrode by the ratio of the capacitance value of each region on the surface of the battery electrode to the theoretical capacitance value of the corresponding region on the surface of the battery electrode.

[0017] Furthermore, the method for obtaining the current distribution density in the power battery based on the real-time current values ​​of various regions on the surface of the battery electrode includes: the ratio of the real-time current value of each region on the surface of the battery electrode to the real-time total current of the power battery is used as the current distribution density parameter of each region on the surface of the battery electrode.

[0018] Furthermore, the method for determining the location of lithium risk points in a power battery based on the current density distribution in the power battery and the state of charge values ​​of various regions on the surface of the battery electrode includes: when a region has a state of charge value lower than a first state of charge threshold and a current density lower than a first current density threshold, and when a region has a state of charge value higher than a second state of charge threshold and a current density higher than a second current density threshold, this region is identified as a lithium risk point.

[0019] The method for measuring the current distribution in a power battery, based on the aforementioned system for measuring current distribution in a power battery, includes the following steps:

[0020] Multiple surface electrodes are laid side by side on the surface of the battery electrode sheet, and the multiple surface electrodes divide the surface of the battery electrode sheet into multiple regions. The battery electrode sheet between two adjacent surface electrodes is one region.

[0021] During the charging and discharging process of the power battery, the real-time voltage value between two adjacent surface electrodes is collected, and the real-time voltage value between the last surface electrode and the battery tab is also collected. Based on the real-time voltage value between two adjacent surface electrodes and the real-time voltage value between the last surface electrode and the battery tab, a time-voltage curve is obtained.

[0022] The real-time voltage value is converted into the real-time current value at each surface electrode based on the time-voltage curve. The real-time current value of each region on the surface electrode is obtained based on the real-time current value at each surface electrode. Then, the state of charge value of each region on the surface of the battery electrode is obtained based on the real-time current value of each region on the surface of the battery electrode. At the same time, the current distribution density in the power battery is obtained based on the real-time current value of each region on the surface of the battery electrode. Based on the current distribution density in the power battery and the state of charge value of each region on the surface of the battery electrode, the region where the lithium risk point of the power battery is located is determined.

[0023] The beneficial effects of this invention are as follows: By arranging surface electrodes in a power battery, the surface of the battery electrode can be divided into different regions. Then, by measuring the voltage between adjacent surface electrodes and knowing the resistance between adjacent surface electrodes, the current distribution on the surface of the power battery electrode can be obtained using Ohm's law. This method can monitor the temperature and current density distribution characteristics of different regions of the battery cell in real time, evaluate the characteristics of the current density distribution on the electrode surface, further identify the location of lithium plating risk points, and further guide the design of cell size and local coating process of the electrode sheets. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the structure of the present invention;

[0025] Figure 2 This is a schematic diagram showing the arrangement of multiple surface electrodes in the battery of the present invention;

[0026] Figure 3 This is a schematic diagram of the voltage collected by adjacent surface electrodes according to the present invention;

[0027] Figure 4 This is a schematic diagram showing the proportion of current distribution in the battery of the present invention under different SOCs;

[0028] Wherein, 1—surface electrode, 2—battery electrode sheet, 3—battery tab. Detailed Implementation

[0029] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0030] Example 1

[0031] like Figure 1 As shown, the present invention provides a system for measuring the current distribution in a power battery, which includes multiple surface electrodes 1, a voltage acquisition module, and a current analysis module.

[0032] Multiple surface electrodes 1 are laid side by side on the surface of battery electrode 2. The multiple surface electrodes 1 divide the surface of battery electrode 2 into multiple regions, and the battery electrode 2 between two adjacent surface electrodes 1 is one region.

[0033] The voltage acquisition module is used to collect the real-time voltage value between two adjacent surface electrodes 1 during the charging and discharging process of the power battery, and at the same time collect the real-time voltage value between the last surface electrode 1 and the battery tab 3. Based on the real-time voltage value between the two adjacent surface electrodes 1 and the real-time voltage value between the last surface electrode 1 and the battery tab 3, a time-voltage curve is obtained.

[0034] The current analysis module is used to convert the real-time voltage values ​​(the real-time voltage values ​​are the real-time voltage values ​​between two adjacent surface electrodes 1, and the real-time voltage values ​​between the last surface electrode 1 and the battery tab 3) into real-time current values ​​at each surface electrode 1 based on the time-voltage curve. Based on the real-time current values ​​at each surface electrode 1, the real-time current values ​​of each region on the surface of the battery electrode 2 are obtained. Then, based on the real-time current values ​​of each region on the surface of the battery electrode 2, the state of charge (SOC) values ​​of each region on the surface of the battery electrode 2 are obtained. Simultaneously, based on the real-time current values ​​of each region on the surface of the battery electrode 2, the current distribution density in the power battery is obtained. Based on the current density distribution in the power battery and the SOC values ​​of each region on the surface of the battery electrode 2, the location of lithium-ion risk points in the power battery is determined.

[0035] In the above technical solution, the battery electrode 2 is the positive electrode or negative electrode of the battery.

[0036] The battery electrode includes a positive electrode and a negative electrode. The principle of testing the current distribution on the surface of the electrode by arranging surface electrodes on the positive and negative electrodes is the same. The surface electrodes are made of the same current collector material as the battery electrode.

[0037] In the above technical solution, the surface electrode 1 is made of a porous conductive material.

[0038] Because surface electrodes cannot impede the lithium-ion insertion / extraction process, otherwise it would affect battery performance. Porous conductive materials, with their porous structure (typically 100-micrometer and 125-micrometer pore sizes), do not obstruct the transport of lithium ions between the positive and negative electrodes or their insertion / extraction into the graphite. The separator between the positive and negative electrodes in a normal lithium battery also has a porous structure. For example, if a porous surface electrode is placed on the surface of a graphite negative electrode, without hindering lithium-ion insertion / extraction, then after a full charge, lithium ions at the location of the surface electrode can be inserted into the graphite, meaning the graphite negative electrode surface will still appear golden yellow.

[0039] Furthermore, the surface electrode needs to be compatible with the chemical and electrochemical environment of the lithium battery, and the built-in surface electrode needs to be relatively thin for easy installation inside the power battery. Therefore, the preferred material for the surface electrode on the negative electrode surface is porous copper foil or porous copper mesh, while the preferred material for the surface electrode on the positive electrode surface is porous aluminum foil or porous aluminum mesh. Using copper foil on the negative electrode surface, consistent with the current collector material of the power battery's negative electrode, and using porous aluminum foil on the positive electrode surface, consistent with the current collector material of the power battery's positive electrode, results in better electrochemical and chemical stability.

[0040] In the above technical solution, the plurality of surface electrodes 1 divide the surface of the power battery into rectangular regions of equal area.

[0041] Dividing the surface of the power battery into equally sized rectangular regions ensures that the resistance of each region is basically the same, reducing variables in current density measurement.

[0042] In the above technical solution, the method for acquiring the real-time voltage between two adjacent surface electrodes 1 includes: welding copper wires to the tail of each surface electrode 1, connecting the copper wires to a data acquisition instrument, obtaining the real-time voltage between two adjacent surface electrodes 1 by reading the data acquisition instrument, and recording the time-voltage curve.

[0043] After welding copper wires to the tails of each surface electrode 1, the copper wires need to be led out through holes drilled in the battery cover to the outside of the power battery. When measuring real-time voltage, such as... Figure 2 As shown, n surface electrodes are arranged in the battery. Following the connection of Table 1 to the positive terminal of the data acquisition instrument and Table 2 to the negative terminal, the electrodes are sequentially connected to VTable1, VTable2, VTable2, VTable3...VTablen-1, and VTablen (negative terminal). The real-time voltage between two adjacent surface electrodes is obtained by reading the tables. Tables 1, 2...n represent surface electrode 1, surface electrode 2... surface electrode n.

[0044] In the above technical solution, the method for obtaining the real-time current value of each region on the surface of the battery electrode 2 includes: calculating the real-time current at each surface electrode 1 by using Ohm's law to calculate the real-time voltage, and subtracting the real-time current at two adjacent surface electrodes 1 to obtain the real-time current of each region on the surface of the battery electrode 2.

[0045] For the negative electrode, the current is greater closer to the battery tab and smaller further away from the tab. By arranging the surface electrodes, the current at different arrangement points can be known, and the local current can be known by subtracting the two currents.

[0046] according to Figure 2 As shown, the formulas for calculating the current through different nodes are:

[0047] Vmeter1 = 0.5 * Imeter2 * R1 (R1 is the resistance of the current collector in region 1, and Vmeter1 = Vmeter2 is the voltage between surface electrode 1 and surface electrode 2.)

[0048] Vmeter2 = 0.5 * Imeter3 * R2 (R2 is the resistance of the current collector in region 2, and Vmeter2 = Vmeter3 is the voltage between surface electrode 2 and surface electrode 3.) ...

[0050] Vmetern-1metern = 0.5 * Imetern * Rn-1 (Rn-1 is the resistance of the current collector in region n-1, and Vmetern-1metern is the voltage between surface electrode n-1 and surface electrode n.)

[0051] Vmeternnegative = 0.5 * Inegative * Rn (Rn is the resistance of the current collector in region n, and Vmeternnegative is the voltage between the surface electrode n and the negative electrode tab.)

[0052] Where R is the resistance, which is mainly determined by the copper foil current collector of the negative electrode when it is on the negative electrode surface. R = ρ*L / (T*W), where ρ is the conductivity of the copper foil, L is the distance between two adjacent surface electrodes, T is the thickness of the copper foil current collector of the negative electrode, which is generally 5um, 6um or 8um, and W is the width of the negative electrode sheet.

[0053] Calculations based on current in different planes:

[0054] I1 = Itable2 (Itable2 is the current at surface electrode 2, and the meanings of Itable3...Itablen follow the same pattern)

[0055] I2 = Table 3 - Table 2 ...

[0057] In-1=I table nI table n-1

[0058] In=I negative electrode-I table n

[0059] The current satisfies I1+I2+I3...+In=Itotal, where Itotal is the total charging and discharging current.

[0060] In the above technical solution, the method for obtaining the state of charge value of each region on the surface of the battery electrode 2 includes: obtaining the capacitance value of each region on the surface of the battery electrode 2 by integrating the real-time current value of each region on the surface of the battery electrode 2 with time; and obtaining the state of charge value of each region on the surface of the battery electrode 2 by the ratio of the capacitance value of each region on the surface of the battery electrode 2 to the theoretical capacitance value of the corresponding region on the surface of the battery electrode 2.

[0061] The battery capacity can be obtained by integrating the current and time in a specific part of the battery. Knowing the area and the load on the negative electrode, the weight of the battery can be obtained. Multiplying the weight by the specific capacity gives the theoretical capacity. Dividing the capacity charged by the actual charging current by the theoretical capacity gives the state of charge of the charging capacity.

[0062] The formula for obtaining the capacitance value is: ∫i(t)dt=c, where i(t) is the local current time curve detected in real time, t is the charging time, c is the charging capacity in the local negative electrode, and the local current measured in real time is integrated with time to obtain the capacity c. When c>c0 (c0 is the theoretical capacity that can be embedded according to the local coating of graphite), the part exceeding the theoretical embedding capacity can only be deposited in the form of lithium metal.

[0063] In the above technical solution, the method for obtaining the current distribution density in the power battery based on the real-time current value of each region on the surface of the battery electrode 2 includes: the ratio of the real-time current value of each region on the surface of the battery electrode 2 to the real-time total current of the power battery is used as the current distribution density parameter of each region on the surface of the battery electrode 2.

[0064] In the above technical solution, the method for determining the location of lithium risk points in the power battery based on the current distribution density in the power battery and the state of charge (SOC) values ​​of various regions on the surface of the battery electrode 2 includes: when the SOC values ​​of various regions on the surface of the battery electrode 2 change, the current density distribution of various regions on the surface of the battery electrode 2 also changes. When a region has an SOC value lower than a first SOC threshold, the current density is also lower than a first current density threshold; when an SOC value is higher than a second SOC threshold, the current density is also higher than a second current density threshold. This region is then identified as a lithium risk point.

[0065] like Figure 3 As shown, the process of determining the location of lithium risk points includes: dividing the surface of the negative electrode of the power battery into 5 equal regions; charging the power battery at a 1C rate between 2.0-3.65V; collecting voltage data from adjacent surface electrodes during charging; and calculating the percentage of current in different regions of the negative electrode surface at 10%, 30%, 50%, 70%, and 90% SOC, according to the current density measurement procedure. Figure 4 As shown, in region 4, the current percentage before the 50% SOC region is around 10%, a relatively small percentage. However, a reversal is observed in the current during the 70% to 90% SOC region, with the local current percentage increasing to around 40%. This area represents a high-risk point for lithium plating. This judgment is based on the following: Batteries generally exhibit higher polarization at high SOC levels. High polarization causes a rapid voltage increase during charging, meeting the lithium plating potential. Once lithium plating occurs, the lithium intercalation process in graphite ceases to be the primary charge storage mechanism and becomes the surface-based lithium plating kinetics. Due to the lower polarization at the lithium plating point and the relatively easy deposition of lithium on the metal surface, the lithium plating process may trigger an increase in local current, further exacerbating the lithium plating phenomenon. At low SOC levels, the battery voltage is relatively low, far below the lithium-ion deposition potential, thus lithium plating does not occur.

[0066] Currently, cooling for wound battery cells is generally located at the bottom of the core, with areas near the tabs experiencing the greatest temperature rise. This temperature difference between the bottom of the core and the tabs leads to uneven current distribution. Currently, the evaluation of full-tab or half-tab designs for wound cells relies primarily on thermal simulations and experimental measurements. However, the current distribution within the battery core provides better support for battery structure selection and design. Stacked blade battery designs also suffer from issues such as high temperature and current density near the tabs, and a tendency for lithium plating near the positive and negative tabs.

[0067] Identifying lithium risk points can guide the design of cell size and electrode local coating processes, as cell size distribution, electrode coating process, and current distribution are all interconnected. For example, cell size distribution affects cell heat generation and local temperature distribution within the battery. Temperature distribution influences the polarization of the cell surface, thus affecting the current distribution. Uneven electrode coating, with areas of high compaction or large particle accumulation, can slow down local electrode kinetics, leading to localized lithium deposition sites within the battery.

[0068] Example 2

[0069] The method for measuring the current distribution in a power battery, based on the aforementioned system for measuring current distribution in a power battery, includes the following steps:

[0070] Step 1: As Figure 2 As shown, multiple surface electrodes 1 are laid side by side on the surface of battery electrode 2. The multiple surface electrodes 1 divide the surface of battery electrode 2 into multiple regions, and the battery electrode 2 between two adjacent surface electrodes 1 is one region.

[0071] Step 2: During the charging and discharging process of the power battery, the real-time voltage value between two adjacent surface electrodes 1 is collected, and the real-time voltage value between the last surface electrode 1 and the battery tab 3 is collected. Based on the real-time voltage value between two adjacent surface electrodes 1 and the real-time voltage value between the last surface electrode 1 and the battery tab 3, a time-voltage curve is obtained.

[0072] Step 3: Convert the real-time voltage value into the real-time current value at each surface electrode 1 based on the time-voltage curve. Obtain the real-time current value of each region on the surface of the battery electrode 2 based on the real-time current value at each surface electrode 1. Then, obtain the state of charge value of each region on the surface of the battery electrode 2 based on the real-time current value of each region on the surface of the battery electrode 2. At the same time, obtain the current distribution density in the power battery based on the real-time current value of each region on the surface of the battery electrode 2. Determine the location of the lithium risk point in the power battery based on the current distribution density in the power battery and the state of charge value of each region on the surface of the battery electrode 2.

[0073] Example 3

[0074] The present invention also includes a computer program product comprising a computer program / instructions that, when executed by a processor, implement the steps of the method for measuring the current distribution in a power battery described above.

[0075] The contents not described in detail in this specification are existing technologies known to those skilled in the art.

Claims

1. A system for measuring the current distribution in a power battery, characterized in that: It includes multiple surface electrodes (1), a voltage acquisition module, and a current analysis module; Multiple surface electrodes (1) are laid side by side on the surface of the battery electrode (2). The multiple surface electrodes (1) divide the surface of the battery electrode (2) into multiple regions, and the battery electrode (2) between two adjacent surface electrodes (1) is one region. The voltage acquisition module is used to collect the real-time voltage value between two adjacent surface electrodes (1) during the charging and discharging process of the power battery, and at the same time collect the real-time voltage value between the last surface electrode (1) and the battery tab (3). Based on the real-time voltage value between two adjacent surface electrodes (1) and the real-time voltage value between the last surface electrode (1) and the battery tab (3), a time-voltage curve is obtained. The current analysis module is used to convert the real-time voltage value into the real-time current value at each surface electrode (1) based on the time-voltage curve. Based on the real-time current value at each surface electrode (1), the real-time current value of each region on the surface of the battery electrode (2) is obtained. Then, based on the real-time current value of each region on the surface of the battery electrode (2), the state of charge value of each region on the surface of the battery electrode (2) is obtained. At the same time, based on the real-time current value of each region on the surface of the battery electrode (2), the current distribution density in the power battery is obtained. Based on the current distribution density in the power battery and the state of charge value of each region on the surface of the battery electrode (2), the region where the lithium risk point of the power battery is located is determined: when the state of charge value of a region is lower than the first state of charge threshold, the current density is also lower than the first current density threshold; when the state of charge value is higher than the second state of charge threshold, the current density is also higher than the second current density threshold. This region is determined to be a lithium risk point.

2. The system for measuring current distribution in a power battery according to claim 1, characterized in that: The battery electrode (2) is either the positive electrode or the negative electrode of the battery.

3. The system for measuring current distribution in a power battery according to claim 1, characterized in that: The surface electrode (1) is made of a porous conductive material.

4. The system for measuring current distribution in a power battery according to claim 1, characterized in that: The plurality of surface electrodes (1) divide the surface of the power battery into rectangular regions of equal area.

5. The system for measuring current distribution in a power battery according to claim 1, characterized in that: The method for acquiring the real-time voltage between two adjacent surface electrodes (1) includes: welding copper wires to the tail of each surface electrode (1), connecting the copper wires to a data acquisition instrument, obtaining the real-time voltage between two adjacent surface electrodes (1) by reading the data acquisition instrument, and recording the time-voltage curve.

6. The system for measuring current distribution in a power battery according to claim 1, characterized in that: The method for obtaining the real-time current value of each region on the surface of the battery electrode (2) includes: calculating the real-time current at each surface electrode (1) by using Ohm's law to calculate the real-time voltage, and subtracting the real-time current at two adjacent surface electrodes (1) to obtain the real-time current of each region on the surface of the battery electrode (2).

7. A system for measuring current distribution in a power battery according to claim 1 or 6, characterized in that: The method for obtaining the state of charge values ​​of each region on the surface of the battery electrode (2) includes: obtaining the capacitance value of each region on the surface of the battery electrode (2) by integrating the real-time current value of each region on the surface of the battery electrode (2) with time; and obtaining the state of charge value of each region on the surface of the battery electrode (2) by the ratio of the capacitance value of each region on the surface of the battery electrode (2) to the theoretical capacitance value of the corresponding region on the surface of the battery electrode (2).

8. A system for measuring current distribution in a power battery according to claim 1 or 6, characterized in that: The method for obtaining the current distribution density in the power battery based on the real-time current value of each region on the surface of the battery electrode (2) includes: the ratio of the real-time current value of each region on the surface of the battery electrode (2) to the real-time total current of the power battery as the current density distribution parameter of each region on the surface of the battery electrode (2).

9. A method for measuring the current distribution in a power battery based on the system of claim 1, comprising the following steps: Multiple surface electrodes (1) are laid side by side on the surface of the battery electrode (2). The multiple surface electrodes (1) divide the surface of the battery electrode (2) into multiple regions, and the battery electrode (2) between two adjacent surface electrodes (1) is one region. During the charging and discharging process of the power battery, the real-time voltage value between two adjacent surface electrodes (1) is collected, and the real-time voltage value between the last surface electrode (1) and the battery tab (3) is collected. Based on the real-time voltage value between two adjacent surface electrodes (1) and the real-time voltage value between the last surface electrode (1) and the battery tab (3), a time-voltage curve is obtained. The real-time voltage value is converted into the real-time current value at each surface electrode (1) according to the time-voltage curve. The real-time current value of each region on the surface of the battery electrode (2) is obtained according to the real-time current value at each surface electrode (1). Then, the state of charge value of each region on the surface of the battery electrode (2) is obtained according to the real-time current value of each region on the surface of the battery electrode (2). At the same time, the current distribution density in the power battery is obtained according to the real-time current value of each region on the surface of the battery electrode (2). The lithium risk point of the power battery is determined according to the current distribution density in the power battery and the state of charge value of each region on the surface of the battery electrode (2).

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