System and method for measuring current distribution in power battery

Abstract

The invention discloses a system and a method for measuring current distribution in a power battery. The surface of a battery pole piece is divided into a plurality of areas by a plurality of surface electrodes; the voltage acquisition module acquires a real-time voltage value between two adjacent surface electrodes, acquires a real-time voltage value between the last surface electrode and a battery tab, and obtains a time-voltage curve according to the acquired real-time voltage values; the current analysis module is used for obtaining the real-time current value of each area on the surface of the battery pole piece according to the real-time voltage value, and then obtaining the charge state value of each area on the surface of the battery pole piece and the current distribution density in the power battery according to the real-time current value of each area on the surface of the battery pole piece; and judging the area of the lithium risk point of the power battery. According to the invention, current distribution based on a power battery plane can be measured, and points with relatively large current density distribution can be identified, so that lithium precipitation risk points can be pre-judged.

Description

Technical Field

[0001] The present invention relates to the field of power batteries, and in particular to a system and method for measuring current distribution in a power battery. Background Art

[0002] The rapid development of new energy vehicles has put forward higher requirements for the fast charging capability and endurance of power batteries, and the research on the mechanism of electrochemical and thermal coupling of large batteries has become more and more in-depth. During the operation of power batteries, the battery's insertion and extraction reactions, as well as the battery's side reactions and battery ohmic heat, lead to a significant temperature rise effect during the battery's charging and discharging process. The uneven temperature distribution inside the battery will lead to uneven electrochemical impedance in different parts of the battery cell, and thus uneven electrochemical reactions in different parts, which will further affect the fast charging capability evaluation of the battery cell and the life of the battery cell. Therefore, in the early stage of battery cell design, it is urgent to study its electrochemical reaction characteristics after determining the material and structure of the battery cell. At present, preliminary results can only be obtained through simulation. The model in the simulation process is approximated, and some parameters also use empirical values. In order to further improve the credibility of the simulation, further experimental data verification and input are also required to make the simulation results more credible. At present, measuring the current density distribution in lithium batteries is an industry problem, and there is no accurate method for actual measurement.

[0003] An invention discloses a nondestructive detection device and method for the current density distribution of a fuel cell, including three magnetic field acquisition units, the output ends 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; the three magnetic field acquisition units are arranged in the same plane as the MEA of the fuel cell, two of which are arranged on both sides of the fuel cell; the remaining magnetic field acquisition unit is arranged at the end of the fuel cell and away from the air inlet end of the fuel cell; the present invention arranges magnetic field acquisition units on both sides and the end of the fuel cell, uses the magnetic field acquisition units to obtain the magnetic field strength at the location, and then uses a computer to calculate the current density distribution result of the fuel cell according to the obtained magnetic field strength; the detection device has a simple structure, does not require an external power supply, and does not require the fuel cell to be modified; the current density distribution result calculated by the electromagnetic inversion algorithm has a high accuracy. The core principle of this invention is to collect magnetic fields in different regions and then convert the magnetic field signal into a current signal according to the Hall law. However, current power batteries, whether they are wound square cells, laminated batteries or blade batteries, require fixtures for production and installation, because the negative electrode graphite will expand during fast charging. Only by using fixtures to constrain the negative electrode graphite can the negative electrode graphite be the same as in the battery pack. The use of fixtures will interfere with the magnetic field, resulting in inaccurate magnetic field strength during testing, and therefore inaccurate current converted from the magnetic field. In addition, there are some approximate processing in the process of converting magnetic field strength to current, so there are also certain problems with the accuracy of the calculation.

[0004] A fuel cell current measurement circuit, wherein one pole of the fuel cell is required to be divided into at least two mutually insulated regions, the at least two regions are respectively connected to a load module to form at least two branches, the discharge voltages of the at least two branches are respectively adjustable, and the test device measures the discharge current of the at least two branches respectively. By using a multi-channel adjustable load, each region of the fuel cell works at the same potential, and the measured current and the obtained fuel cell current density distribution have a high authenticity.

[0005] In this scheme, a pole piece is divided into two mutually insulated areas, which is the advantage of the stack electrode structure of the fuel cell. In addition, the load and voltage of the two paths are adjustable respectively. The impedance of each layer in the thickness direction of the pole piece in the lithium battery and the polarization pressure difference during the charging and discharging process are uncontrollable and equivalent. The fuel cell is essentially an equivalent circuit diagram of multiple electrodes in series, which is simpler in principle. The adjustable load is a sliding rheostat and an electronic load circuit, which must be combined with an operational amplifier and a field effect transistor. This patent mainly measures the current distribution in the thickness direction of the fuel cell. It cannot measure the current density of the fuel cell on the battery surface, nor can it be used to measure the current density on the surface of the power battery. Summary of the invention

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

[0007] To achieve this purpose, the present invention is designed to provide a system for measuring current distribution in a power battery, which includes a plurality of 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 pole piece, and the multiple surface electrodes divide the surface of the battery pole piece into multiple areas, and the battery pole piece between two adjacent surface electrodes is one area;

[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 surface electrode of the last sheet and the battery tab, and obtain the time-voltage curve according to the real-time voltage value between the two adjacent surface electrodes and the real-time voltage value between the surface electrode of the last sheet and the battery tab;

[0010] The current analysis module is used to convert the real-time voltage value into a real-time current value at each surface electrode according to the time-voltage curve, obtain the real-time current value of each area on the surface of the battery electrode according to the real-time current value at each surface electrode, and then obtain the state of charge value of each area on the surface of the battery electrode according to the real-time current value of each area on the surface of the battery electrode; at the same time, obtain the current distribution density in the power battery according to the real-time current value of each area on the surface of the battery electrode, and judge the area where the lithium risk point of the power battery is located according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery electrode.

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

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

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

[0014] Furthermore, the method for collecting the real-time voltage between two adjacent surface electrodes includes: welding a copper wire at the tail of each surface electrode, connecting it to a data acquisition instrument through the copper wire, obtaining the real-time voltage between the two adjacent surface electrodes through the readings of the data acquisition instrument, and recording a time-voltage curve.

[0015] Furthermore, the method for obtaining the real-time current value of each area 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 currents at two adjacent surface electrodes to obtain the real-time current of each area on the surface of the battery electrode.

[0016] Furthermore, the method for obtaining the state of charge value of each area on the surface of the battery electrode includes: obtaining the capacitance value of each area on the surface of the battery electrode according to the integral of the real-time current value of each area on the surface of the battery electrode over time, and obtaining the state of charge value of each area on the surface of the battery electrode according to the ratio of the capacitance value of each area on the surface of the battery electrode to the theoretical capacitance value of the corresponding area on the surface of the battery electrode.

[0017] Furthermore, the method for obtaining the current distribution density in the power battery according to the real-time current value of each area on the surface of the battery electrode includes: taking the ratio of the real-time current value of each area on the surface of the battery electrode to the real-time total current of the power battery as the current distribution density parameter of each area on the surface of the battery electrode.

[0018] Furthermore, the method for judging the area where the lithium risk point of the power battery is located according to the current density distribution in the power battery and the state of charge values ​​of various areas on the surface of the battery electrode includes: when the state of charge value of an area is lower than a first state of charge threshold, the current density is also lower than the first current density threshold, and when the state of charge value is higher than a second state of charge threshold, the current density is also higher than the second current density threshold, and this area is determined to be a lithium risk point.

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

[0020] Multiple surface electrodes are laid side by side on the surface of the battery pole piece, and the multiple surface electrodes divide the surface of the battery pole piece into multiple areas, and the battery pole piece between two adjacent surface electrodes is one area;

[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 surface electrode of the last sheet and the battery tab is collected at the same time, and a time-voltage curve is obtained according to the real-time voltage value between the two adjacent surface electrodes and the real-time voltage value between the surface electrode of the last sheet and the battery tab;

[0022] According to the time-voltage curve, the real-time voltage value is converted into the real-time current value at each surface electrode, and the real-time current value of each area on the surface of the battery electrode is obtained according to the real-time current value at each surface electrode. Then, the state of charge value of each area on the surface of the battery electrode is obtained according to the real-time current value of each area on the surface of the battery electrode; at the same time, the current distribution density in the power battery is obtained according to the real-time current value of each area on the surface of the battery electrode, and the area where the lithium risk point of the power battery is located is judged according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery electrode.

[0023] Beneficial effects of the present invention: The present invention can divide the surface of the power battery electrode into different areas by arranging the surface electrodes in the power battery, and then measure the voltage between adjacent surface electrodes, and obtain the current distribution on the surface of the power battery electrode by Ohm's law when the resistance between adjacent surface electrodes is known. This method can monitor the temperature and current density distribution characteristics of different areas of the battery cell in real time, evaluate the characteristics of the current density distribution on the electrode surface, further identify the location of the lithium deposition risk point, and further guide the design of the battery cell size and the local coating process of the pole piece. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the present invention;

[0025] Figure 2 A schematic diagram of arranging multiple surface electrodes in a battery of the present invention;

[0026] Figure 3 A schematic diagram of voltage collection by adjacent surface electrodes of the present invention;

[0027] Figure 4 It is a schematic diagram of the current distribution ratio of the battery of the present invention at different SOCs;

[0028] Among them, 1 is the surface electrode, 2 is the battery electrode, and 3 is the battery ear. DETAILED DESCRIPTION

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

[0030] Example 1

[0031] like Figure 1 As shown, the system designed by the present invention for measuring current distribution in a power battery comprises a plurality of 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 the battery pole piece 2. The multiple surface electrodes 1 divide the surface of the battery pole piece 2 into multiple areas. The battery pole piece 2 between two adjacent surface electrodes 1 is one area.

[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 surface electrode 1 of the last sheet and the battery tab 3, and obtain the time-voltage curve according to the real-time voltage value between the two adjacent surface electrodes 1 and the real-time voltage value between the surface electrode 1 of the last sheet and the battery tab 3;

[0034] The current analysis module is used to convert the real-time voltage value (the real-time voltage value is the real-time voltage value between two adjacent surface electrodes 1, and the real-time voltage value between the surface electrode 1 of the last sheet and the battery tab 3) into the real-time current value at each surface electrode 1 according to the time-voltage curve, and obtain the real-time current value of each area on the surface of the battery electrode 2 according to the real-time current value at each surface electrode 1, and then obtain the state of charge value of each area on the surface of the battery electrode 2 according to the real-time current value of each area 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 area on the surface of the battery electrode 2, and the area where the lithium risk point of the power battery is located is judged according to the current density distribution in the power battery and the state of charge value of each area on the surface of the battery electrode 2.

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

[0036] The battery pole piece includes a positive pole piece and a negative pole piece. The principle of testing the current distribution on the surface of the pole piece by arranging surface electrodes on the positive and negative pole pieces is the same. The surface electrode is consistent with the current collector material of the battery pole piece.

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

[0038] Because the surface electrode cannot resist the deintercalation process of lithium ions, otherwise it will affect the battery performance. The porous conductive material has a porous structure, generally with a pore size of 100 microns and a pore size of 125 microns, which will not block the transmission and deintercalation of lithium ions between the positive and negative electrodes into the graphite. The separator between the positive and negative electrodes in a normal lithium battery also has a porous structure. For example, if the porous surface electrode is arranged on the surface of the graphite negative electrode and does not hinder the deintercalation of lithium ions, then after being fully charged, the lithium ions at the location where the surface electrode is arranged can be embedded in the graphite, that is, the surface of the graphite negative electrode is still golden yellow.

[0039] In addition, the surface electrode needs to be compatible with the chemical and electrochemical environment of the lithium battery. At the same time, the built-in surface electrode needs to be relatively thin and easy to install inside the power battery. Therefore, on the surface of the negative electrode, the preferred material for the surface electrode can be porous copper foil or porous copper mesh, and on the surface of the positive electrode, the preferred material for the surface electrode can be porous aluminum foil or porous aluminum mesh. The copper foil used on the negative electrode surface is consistent with the current collector material of the negative electrode of the power battery, and the porous aluminum foil is used on the positive electrode surface, which is consistent with the current collector material of the positive electrode of the power battery, so it has good electrochemical and chemical stability.

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

[0041] Dividing the surface of the power battery into equal rectangular areas can ensure that the resistance of each area is basically the same, reducing the variables in the current density measurement.

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

[0043] After welding the copper wires at the tail of each surface electrode 1, it is necessary to punch holes in the battery cover to lead the copper wires out to the outside of the power battery. Figure 2 As shown, n surface electrodes are arranged in the battery, and V1, V2, V3, Vn-1, Vn-1, Vn-2 are connected to the positive electrode of the data acquisition instrument and V1, V2, V3, Vn-1, Vn-1, Vn-2 are connected to the negative electrode in sequence, and the real-time voltage between two adjacent surface electrodes is obtained by reading the meter. The table 1, table 2, ... table n represent surface electrode 1, surface electrode 2, ... surface electrode n.

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

[0045] For the negative electrode, the closer to the battery ear, the greater the current, and the farther away from the ear, the smaller the current. By arranging the surface electrodes, we can know the current at different arrangement points, and by subtracting the two currents, we can know the local current.

[0046] according to Figure 2 As shown, the current calculation formula passing through different nodes is:

[0047] Vtable1table2=0.5*Itable2*R1 (R1 is the resistance of the current collector in region 1, Vtable1table2 is the voltage between surface electrode 1 and surface electrode 2.)

[0048] Vtable2table3=0.5*Itable3*R2 (R2 is the resistance of the current collector in region 2, and Vtable2table3 is the voltage between surface electrode 2 and surface electrode 3.) ...

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

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

[0052] Where R is the resistance, which is mainly determined by the copper foil of the current collector 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 of the negative electrode current collector, generally 5um, 6um or 8um, and W is the width of the negative electrode plate.

[0053] Calculated by the current in different in-plane directions:

[0054] I1 = I_table2 (I_table2 is the current at surface electrode 2, and the meanings of I_table3... I_tablen are类推)

[0055] I2 = I_table3 - I_table2 ...

[0057] In-1 = I_tablen - I_tablen-1

[0058] In = I_negative - I_tablen

[0059] Where the currents satisfy I1 + I2 + I3... + In = I_total, and I_total is the total current of charge and discharge.

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

[0061] The integration of the current of a battery part with respect to time can obtain the battery capacity. After knowing the area and the loading of the negative electrode plate of the battery part, the weight of the battery part can be obtained. Multiplying the weight by the specific capacity utilization can obtain the theoretical capacity. Dividing the capacity charged by the actual charging current by the theoretical capacity can obtain 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 measured in real time, t is the charging time, and c is the charging capacity in the local negative electrode. Integrating the local current measured in real time with respect to time gives 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 precipitated in the form of lithium metal.

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

[0064] In the above technical solution, the method for determining the area where the lithium risk point of the power battery is located according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery pole piece 2 includes: when the state of charge value of each area on the surface of the battery pole piece 2 changes, the current density distribution of each area on the surface of the battery pole piece 2 will also change. 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, and 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, and this region is determined to be a lithium risk point.

[0065] like Figure 3 As shown in the figure, the process of determining the area where the lithium risk point is located includes: dividing the negative electrode surface of the power battery into 5 equal areas, charging the power battery at a rate of 1C between 2.0-3.65V, collecting the voltage of two adjacent surface electrodes during the charging process, and calculating the current percentage of different areas of the negative electrode surface at 10%, 30%, 50%, 70% and 90% SOC according to the process of measuring the current density. Figure 4 As shown, the current proportion of region 4 before the 50% SOC region is about 10%, and the current proportion is relatively small. In the 70% to 90% SOC region, the current is reversed, and the local current proportion increases to about 40%, which means this is a high-risk point for lithium deposition. This judgment is made because: Generally, the battery has a high degree of polarization under high SOC conditions. High polarization will cause the battery voltage to rise rapidly during charging, satisfying the battery's lithium deposition potential conditions. Once lithium deposition occurs, the lithium insertion process of graphite is no longer the main charge storage mechanism, but is transformed into surface lithium deposition dynamics. Since the polarization at the lithium deposition site is small and lithium deposition on the metal surface is relatively easy, the lithium deposition process may cause an increase in local current, further exacerbating the lithium deposition phenomenon. At low SOC, the battery voltage is relatively low, far below the deposition potential of lithium ions, so lithium deposition does not occur.

[0066] For current wound cells, cooling is generally done at the bottom of the core, and the area near the tabs is generally where the temperature rises the most. Therefore, the temperatures at the bottom of the core and the tabs of the wound cell are different, which will lead to uneven current distribution at the bottom of the core and the tabs. Currently, the evaluation of the full-tab or half-tab design of the core is mainly based on thermal simulation and experimental results, but the current distribution of the battery core can better support the selection and design of the battery structure. The blade battery design of the stacked battery also has problems such as high temperature near the tabs, high current density, and easy lithium precipitation near the positive and negative tabs.

[0067] The lithium risk points can guide the design of the cell size and the local coating process of the pole piece, because the cell size distribution and the pole piece coating process and the current distribution all affect each other. For example, the cell size distribution will affect the heat generation of the cell and the local temperature distribution of the battery. The temperature distribution will affect the polarization of the cell surface, thereby affecting the current distribution therein; the pole piece coating process has uneven coating on the pole piece surface, and the high compaction or accumulation of large particles in the unevenly coated areas will cause the local dynamics of the electrode to slow down, causing the local part of the battery to become a lithium deposition site.

[0068] Example 2

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

[0070] Step 1: Figure 2 As shown, multiple surface electrodes 1 are laid side by side on the surface of the battery pole piece 2, and the multiple surface electrodes 1 divide the surface of the battery pole piece 2 into multiple areas, and the battery pole piece 2 between two adjacent surface electrodes 1 is one area;

[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 surface electrode 1 of the last sheet and the battery tab 3 is collected at the same time, and a time-voltage curve is obtained according to the real-time voltage value between the two adjacent surface electrodes 1 and the real-time voltage value between the surface electrode 1 of the last sheet and the battery tab 3;

[0072] Step 3: Convert the real-time voltage value into the real-time current value at each surface electrode 1 according to the time-voltage curve, obtain the real-time current value of each area on the surface of the battery electrode 2 according to the real-time current value at each surface electrode 1, and then obtain the state of charge value of each area on the surface of the battery electrode 2 according to the real-time current value of each area on the surface of the battery electrode 2; at the same time, obtain the current distribution density in the power battery according to the real-time current value of each area on the surface of the battery electrode 2, and judge the area where the lithium risk point of the power battery is located according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery electrode 2.

[0073] Example 3

[0074] The present invention also includes a computer program product, including a computer program / instruction, which, when executed by a processor, implements the steps of the above-mentioned method for measuring current distribution in a power battery.

[0075] The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field.

Claims

1. A system for measuring current distribution in a power battery, characterized in that: It includes a plurality of surface electrodes (1), a voltage acquisition module and a current analysis module; A plurality of surface electrodes (1) are laid side by side on the surface of a battery electrode sheet (2), and the plurality of surface electrodes (1) divide the surface of the battery electrode sheet (2) into a plurality of regions, wherein the battery electrode sheet (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 simultaneously collect the real-time voltage value between the last surface electrode (1) and the battery tab (3), and obtain a time-voltage curve 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); The current analysis module is used to convert the real-time voltage value into a real-time current value at each surface electrode (1) according to the time-voltage curve, obtain the real-time current value of each area on the surface of the battery electrode (2) according to the real-time current value at each surface electrode (1), and then obtain the state of charge value of each area on the surface of the battery electrode (2) according to the real-time current value of each area on the surface of the battery electrode (2); at the same time, obtain the current distribution density in the power battery according to the real-time current value of each area on the surface of the battery electrode (2), and judge the area where the lithium risk point of the power battery is located according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery electrode (2).

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

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

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

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

6. A 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 area on the surface of the battery electrode (2) comprises: 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 currents at two adjacent surface electrodes (1) to obtain the real-time current of each area 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 value of each area on the surface of a battery electrode piece (2) comprises: obtaining the capacitance value of each area on the surface of the battery electrode piece (2) based on the integration of the real-time current value of each area on the surface of the battery electrode piece (2) over time, and obtaining the state of charge value of each area on the surface of the battery electrode piece (2) based on the ratio of the capacitance value of each area on the surface of the battery electrode piece (2) to the theoretical capacitance value of the corresponding area on the surface of the battery electrode piece (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 a power battery according to the real-time current value of each area on the surface of a battery pole piece (2) comprises: taking the ratio of the real-time current value of each area on the surface of the battery pole piece (2) to the real-time total current of the power battery as the current density distribution parameter of each area on the surface of the battery pole piece (2).

9. A system for measuring current distribution in a power battery according to claim 1, characterized in that: The method for determining the area where the lithium risk point of a power battery is located based on the current distribution density in the power battery and the state of charge values ​​of various areas on the surface of the battery pole piece (2) comprises: when the state of charge value of an area is lower than a first state of charge threshold, the current density is also lower than the first current density threshold, and when the state of charge value is higher than a second state of charge threshold, the current density is also higher than the second current density threshold, and this area is determined as a lithium risk point.

10. A method for measuring current distribution in a power battery, comprising the following steps: A plurality of surface electrodes (1) are laid side by side on the surface of a battery electrode sheet (2), and the plurality of surface electrodes (1) divide the surface of the battery electrode sheet (2) into a plurality of regions, wherein the battery electrode sheet (2) between two adjacent surface electrodes (1) is one region; During the charging and discharging process of the power battery, a real-time voltage value between two adjacent surface electrodes (1) is collected, and at the same time, a real-time voltage value between the last surface electrode (1) and the battery tab (3) is collected, and a time-voltage curve is obtained 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); The real-time voltage value is converted into a real-time current value at each surface electrode (1) according to the time-voltage curve, and the real-time current value of each area on the surface of the battery electrode (2) is obtained according to the real-time current value at each surface electrode (1), and then the state of charge value of each area on the surface of the battery electrode (2) is obtained according to the real-time current value of each area 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 area on the surface of the battery electrode (2), and the area where the lithium risk point of the power battery is located is judged according to the current distribution density in the power battery and the state of charge value of each area on the surface of the battery electrode (2).

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