Secondary battery voltage measurement method and apparatus

Abstract

This invention relates to a method and apparatus for measuring the voltage of a secondary battery. Existing methods for assessing the state of charge (SOC) of a battery can only be performed when the battery is not in operation, and therefore cannot reflect the battery's true SOC. This method involves connecting the positive and negative electrodes of the secondary battery to a first voltmeter to measure a first voltage; placing a positive-side voltage measuring probe on the positive electrode side of the secondary battery, and symmetrically, placing a negative-side voltage measuring probe on the negative electrode side; connecting the positive and negative-side voltage measuring probes to a second voltmeter to measure a second voltage; and taking the average of the first and second voltages as the measured voltage value of the secondary battery for assessing its remaining capacity. This invention enables rapid, accurate, and effective measurement of the secondary battery voltage while it is in operation, thereby allowing for more precise management of the energy storage of the secondary battery.

Description

Technical Field

[0001] This invention relates to the field of battery performance testing technology, specifically to a method and device for measuring the voltage of a secondary battery. Background Technology

[0002] The state of charge (SOC) of a battery, also known as remaining capacity or stored capacity, reflects the amount of charge a secondary battery has when fully charged. This parameter reflects the battery's maximum capacity. The capacity of a battery at different charging levels can be expressed as "%SOC". For example, when a battery is charged to half its total capacity, it can be expressed as 50% SOC. Storage batteries, power batteries, and energy storage stacks all belong to the category of secondary batteries. During use, the capacity of a secondary battery will irreversibly decrease due to changes in charging and discharging current, the number of charge / discharge cycles, operating temperature, and usage conditions. In practical applications of secondary batteries, such as accurately assessing the remaining capacity of power batteries to determine the driving range and charging time of electric vehicles, and accurately assessing the capacity of energy storage stacks for rapid charge / discharge scheduling, the precise measurement of battery state of charge demonstrates its extremely important practical significance and value.

[0003] Currently, traditional methods for measuring the state of charge (SOC) of secondary batteries include the open-circuit voltage method. The open-circuit voltage method estimates the SOC by using the correlation between the battery's open-circuit voltage (OCV) in its non-operating state; it cannot be used when the battery is operating. However, in applications such as electric vehicles and energy storage stacks, it is more important to obtain accurate real-time battery voltage under operating conditions. But whether it's a lithium-ion battery with solid-state active materials or a flow battery with active materials dissolved in solution, traditional battery voltage is obtained by measuring the voltage between the positive and negative current collectors (called electrodes). However, due to the diffusion of active materials, the concentration of active materials is inconsistent throughout the battery, causing the battery voltage obtained by the above method to deviate from the true state of the battery. In practical applications of secondary batteries, since the active materials are stored in a three-dimensional structure, such as a cuboid or cylinder, the electrodes for collecting current and measuring voltage are often combined, using sheet-like, rod-like, or mesh-like metal electrodes. The electrode surface is the site of charge-discharge chemical reactions. Active materials must diffuse to the electrode surface to achieve these reactions. Because the charge-discharge chemical reactions occur very quickly, while the diffusion rate of active materials within the battery is often slow, the measured voltage cannot reflect the true state of charge of the battery's active materials.

[0004] Therefore, it is necessary to improve existing battery voltage measurement methods to address the problems of large distances between electrodes and separators and large differences between the voltage measured by the voltmeter and the actual average voltage in batteries, power batteries, and energy storage stacks. Summary of the Invention

[0005] The purpose of this invention is to provide a method and device for measuring the voltage of a secondary battery, so as to solve the problems that existing measurement methods can only be implemented when the battery is not in operation and cannot reflect the true energy storage state of the battery.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for measuring the voltage of a secondary battery, the method comprising:

[0008] The first voltage is measured after connecting the positive and negative electrodes of the secondary battery to the first voltmeter.

[0009] A positive electrode voltage measuring probe is placed on the positive electrode side of the secondary battery, and symmetrically, a negative electrode voltage measuring probe is placed on the negative electrode side of the secondary battery.

[0010] After connecting the positive side voltage measurement probe and the negative side voltage measurement probe to the second voltmeter, the second voltage is measured.

[0011] The average of the first voltage and the second voltage is taken as the voltage measurement value of the secondary battery, which is used to assess the remaining capacity of the secondary battery.

[0012] Furthermore, when the active material of the secondary battery is located between the secondary battery electrode and the battery separator:

[0013] The first voltage is measured after connecting the positive and negative electrodes of the secondary battery to the first voltmeter.

[0014] n positive electrode voltage measurement probes, n≥2, are placed on the positive electrode side of the secondary battery. The first positive electrode voltage measurement probe is placed on the surface of the battery separator on the positive electrode side of the secondary battery, and the nth positive electrode voltage measurement probe is placed inside the positive electrode active material. Symmetrically, n negative electrode voltage measurement probes, n≥2, are placed on the negative electrode side of the secondary battery. The first negative electrode voltage measurement probe is placed on the surface of the battery separator on the negative electrode side of the secondary battery, and the nth negative electrode voltage measurement probe is placed inside the negative electrode active material.

[0015] After connecting the first positive side voltage measurement probe and the first negative side voltage measurement probe to the second voltmeter, the second voltage is measured.

[0016] Connect the voltage measuring probe on the positive side of the nth electrode and the voltage measuring probe on the negative side of the nth electrode to the (n+1)th voltmeter respectively, and then measure the (n+1)th voltage.

[0017] The average value of all voltages is taken as the voltage measurement value of the secondary battery, which is used to assess the remaining capacity of the secondary battery.

[0018] Alternatively, when the secondary battery electrodes are located within the active material of the secondary battery:

[0019] The first voltage is measured after connecting the positive and negative electrodes of the secondary battery to the first voltmeter.

[0020] n positive electrode voltage measurement probes, n≥2, are placed on the positive electrode side of the secondary battery. The first positive electrode voltage measurement probe is placed on the surface of the battery separator on the positive electrode side of the secondary battery, and the nth positive electrode voltage measurement probe is placed inside the positive electrode active material outside the positive electrode. Symmetrically, n negative electrode voltage measurement probes, n≥2, are placed on the negative electrode side of the secondary battery. The first negative electrode voltage measurement probe is placed on the surface of the battery separator on the negative electrode side of the secondary battery, and the nth negative electrode voltage measurement probe is placed inside the negative electrode active material outside the negative electrode.

[0021] After connecting the first positive side voltage measurement probe and the first negative side voltage measurement probe to the second voltmeter, the second voltage is measured.

[0022] Connect the voltage measuring probe on the positive side of the nth electrode and the voltage measuring probe on the negative side of the nth electrode to the (n+1)th voltmeter respectively, and then measure the (n+1)th voltage.

[0023] The average value of all voltages is taken as the voltage measurement value of the secondary battery, which is used to assess the remaining capacity of the secondary battery.

[0024] Alternatively, when the secondary battery electrodes are located on the surface of the battery separator:

[0025] The first voltage is measured after connecting the positive and negative electrodes of the secondary battery to the first voltmeter.

[0026] n positive electrode voltage measurement probes, n≥2, are placed inside the positive electrode active material of the secondary battery, including a first positive electrode voltage measurement probe and an nth positive electrode voltage measurement probe; symmetrically, n negative electrode voltage measurement probes, n≥2, are placed inside the negative electrode active material of the secondary battery, including a first negative electrode voltage measurement probe and an nth negative electrode voltage measurement probe.

[0027] After connecting the first positive side voltage measurement probe and the first negative side voltage measurement probe to the second voltmeter, the second voltage is measured.

[0028] Connect the voltage measuring probe on the positive side of the nth electrode and the voltage measuring probe on the negative side of the nth electrode to the (n+1)th voltmeter respectively, and then measure the (n+1)th voltage.

[0029] The average value of all voltages is taken as the voltage measurement value of the secondary battery, which is used to assess the remaining capacity of the secondary battery.

[0030] On the other hand, a secondary battery voltage measuring device is provided, the device being used to implement the method, including:

[0031] Voltage measuring probe and voltmeter;

[0032] The voltage measurement probes are set on the surface of the battery separator of the secondary battery or in the active material of the secondary battery, with at least two probes symmetrically arranged on both sides along the battery separator.

[0033] The voltmeter is connected between the positive and negative electrodes of the secondary battery and between the symmetrical voltage measuring probes on both sides.

[0034] Furthermore, the voltage measurement probe is made of a conductive material, selected from metallic materials, carbon materials, and conductive polymer materials.

[0035] Furthermore, the voltage measurement probe is needle-shaped or cylindrical, with a diameter ranging from 1 nanometer to 100 millimeters.

[0036] Furthermore, the voltage measurement probe is sheet-shaped with a thickness of 1 nanometer to 100 millimeters.

[0037] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0038] The method of the present invention, by configuring one or more pairs of voltage measurement probes, can achieve rapid, accurate and effective measurement of battery voltage in the working state, thereby enabling more precise management of energy storage of secondary batteries such as storage batteries, power batteries, and energy storage stacks. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the concentration distribution of the positive and negative active materials during the charging of a secondary battery.

[0041] Figure 2 This is a schematic diagram of the concentration distribution of the positive and negative active materials during the discharge of a secondary battery.

[0042] Figure 3 This is a schematic diagram of the probe position when the active material of the secondary battery is located between the electrode and the separator of the secondary battery.

[0043] Figure 4 This is a schematic diagram of the probe position when the electrode of the secondary battery is located in the active material of the secondary battery.

[0044] Figure 5 This is a schematic diagram of the probe position when the electrode of the secondary battery is located on the surface of the secondary battery separator. Detailed Implementation

[0045] To facilitate understanding of the present invention, a more complete description will be given below with reference to the accompanying drawings. Preferred embodiments of the invention are shown in the drawings. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the invention.

[0046] In the description of this patent, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "setting" should be interpreted broadly. For example, they can refer to a fixed connection or setting, a detachable connection or setting, or an integral connection or setting. Those skilled in the art can understand the specific meaning of the above terms in this patent according to the specific circumstances.

[0047] In the description of this patent, it should be understood that all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which this patent pertains. In case of any contradiction, the definitions in this specification shall prevail. Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art, the reagents used in the embodiments are commercially available products, and the devices used in the embodiments are existing devices. The limitation on the means, reagents, or devices shall not be construed as a limitation on this patent, and means, reagents, or devices of the same type that solve the same technical problem are all within the protection scope of this patent.

[0048] In the description of this patent, it should be understood that when the amount of substance, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether such range is disclosed individually. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0049] In the description of this patent, it should be understood that the method involves multiple steps, which should not be interpreted as a limitation on the order of the steps. Technical solutions obtained by changing the order of steps when solving the same technical problem are also within the scope of protection of this patent.

[0050] This invention provides a method for measuring the voltage of a secondary battery, which solves the problems of existing measurement methods, which can only be performed when the battery is in operation and cannot reflect the true state of energy storage. Due to the diffusion of active materials in the battery, the concentration of active materials is not uniform throughout the battery. This causes the battery voltage obtained by existing methods to deviate from the true state of the battery, which can be explained by the Nernst equation.

[0051] Assume the redox couple of the positive electrode active material of the battery is P. + / P - (P + The oxidation state of the positive electrode active material, P - (The positive electrode active material is in its reduced state), and the negative electrode active material has a redox couple of N0. + / N - (N + The oxidation state of the negative electrode active material, N - (The active material at the negative electrode is in its reduced state). During battery charging and discharging, the active material gains or loses only one electron each time. The resulting reaction can be represented as:

[0052] Charging state: Positive P - -e→P + negative electrode N + +e→N -

[0053] The battery reaction is: P - +N + →P + +N -

[0054] Discharge state: Positive P + +e→P - negative electrode N - -e→N +

[0055] The battery reaction is: P - +N + ←P + +N -

[0056] At this point, the Nernst equation for the battery voltage is expressed as:

[0057] U = U(standard) - [(RT) / (nF)]ln[([P] + ] / [P - ])·([N - ] / [N + ])]

[0058] U is the instantaneous voltage of the battery; U(standard) is the voltage of the battery under standard conditions, which can be calculated from thermodynamic parameters; R is the gas constant; T is the absolute temperature of the battery at this time; n is the number of transferred charges of the battery; F is the Faraday constant; [P + [P] represents the concentration of the positive electrode active material in its oxidized state; - [N] represents the concentration of the positive electrode active material in the reduced state; + [N] represents the concentration of the negative electrode active material in its oxidized state; - [ ] represents the concentration of the negative electrode active material in the reduced state.

[0059] The Nernst equation for battery voltage is the fundamental principle and basis for measuring battery voltage. According to the Nernst equation, there are five parameters that determine battery voltage: T, [P], [T ... + ]、[P - ]、[N + ] and [N - ], where [P + ] and [P - Interrelated, [P] + ]+[P - [P] is a constant, equal to the concentration of the positive electrode active material, therefore [P] + If it's high [P] - [N] is lower; - ] and [N + Interrelated, [N] + ]+[N - [N] is a constant, equal to the concentration of the negative electrode active material. - If it's high [N] + [P] is low. This also shows that [P] + ] / [P - ] and [N - ] / [N + These two ratios determine the size of U.

[0060] During battery charging, from an overall perspective, the [P] on the positive side... + [P] is getting bigger and bigger. - [P] gets smaller and smaller, therefore [P] + ] / [P - The size also increases, and as the battery approaches full charge, the positive electrode active material is essentially in the form of P. + Existence; [N] on the negative side - [N] is getting bigger and bigger. + [N] gets smaller and smaller, therefore [N] - ] / [N + The voltage U also increases; the final result is that the battery voltage U increases, and as the battery approaches full charge, the negative electrode active material is basically in the form of N. -It exists. The process of discharging is the opposite.

[0061] In practical applications of secondary batteries, the active materials are stored in a three-dimensional structure, such as a cuboid or cylinder, while the electrodes for collecting current and measuring voltage are often combined into one, using sheet-like, rod-like, or mesh-like metal electrodes. The electrode surface is the site of charge-discharge chemical reactions; the active materials must diffuse to the electrode surface to achieve these reactions. Because the charge-discharge chemical reactions occur very quickly, while the diffusion rate of the active materials within the battery is often slow, the collected voltage cannot reflect the true state of charge of the battery's active materials.

[0062] Therefore, from a microscopic perspective, during the charging process, [P] + ]、[P - ]、[N + ] and [N - A gradient will form along the direction away from the electrode surface, such as... Figure 1 As shown. Therefore, [P] + ] / [P - ] and [N - ] / [N + A gradient will also be formed, that is, the direction away from the electrode surface [P]. + ] / [P - The ratio of ] and [N] - ] / [N + The ratio of [voltage] gradually decreases. Therefore, the value measured by the voltmeter from the two electrodes will be higher than the actual average voltage of the battery, thus affecting the actual charging effect.

[0063] During the discharge process, [P] + ]、[P - ]、[N + ] and [N - A gradient will also form along the direction away from the electrode surface, such as... Figure 2 As shown. Therefore, [P] + ] / [P - ] and [N - ] / [N + A gradient will also be formed, that is, the direction away from the electrode surface [P]. + ] / [P - The ratio of ] and [N] - ] / [N + As the ratio of the two electrodes gradually increases, the value measured by the voltmeter from the two electrodes will be lower than the actual average voltage of the battery, thus causing a deviation in the estimation of the actual remaining capacity.

[0064] Combining the electrodes for collecting current and measuring voltage results in the following consequences: during charging, the voltmeter detects that the charging cutoff voltage has been reached, but the battery is not actually fully charged; during discharging, the voltmeter detects that the discharging cutoff voltage has been reached, but the battery still has discharge capacity. Regardless of the method used, it's essentially impossible to avoid measuring battery voltage. If the measurement results deviate significantly from the actual situation, it will cause problems with battery energy storage management and affect its use.

[0065] This method can effectively solve the problems caused by the above reasons, and specifically includes the following steps:

[0066] S1: After connecting the positive and negative electrodes of the secondary battery to the first voltmeter, the first voltage is measured;

[0067] S2: Place a positive electrode voltage measuring probe on the positive electrode side of the secondary battery, and symmetrically place a negative electrode voltage measuring probe on the negative electrode side of the secondary battery.

[0068] S3: Connect the positive side voltage measurement probe and the negative side voltage measurement probe to the second voltmeter and measure the second voltage;

[0069] S4: Take the average of the first voltage and the second voltage as the voltage measurement value of the secondary battery, which is used to assess the remaining capacity of the secondary battery.

[0070] Depending on the structure of the secondary battery, the number of probes can be increased. The above method can be implemented in the following three ways:

[0071] Example 1:

[0072] like Figure 3 When the active material of a secondary battery is located between the battery electrode and the battery separator:

[0073] S1: After connecting the positive and negative electrodes of the secondary battery to the first voltmeter V1, the first voltage U1 is measured.

[0074] S2: Place n positive electrode voltage measurement probes on the positive electrode side of the secondary battery, n≥2, in this embodiment, n=3, wherein the first positive electrode voltage measurement probe T1 is placed on the surface of the battery separator on the positive electrode side of the secondary battery, and the second positive electrode voltage measurement probe T2 and the third positive electrode voltage measurement probe T3 are placed inside the positive electrode active material; symmetrically, place n negative electrode voltage measurement probes on the negative electrode side of the secondary battery, n≥2, in this embodiment, n=3, wherein the first negative electrode voltage measurement probe T1' is placed on the surface of the battery separator on the negative electrode side of the secondary battery, and the second negative electrode voltage measurement probe T2' and the third negative electrode voltage measurement probe T3' are placed inside the negative electrode active material;

[0075] S3: Connect the first positive side voltage measuring probe T1 and the first negative side voltage measuring probe T1' to the second voltmeter V2 and then measure the second voltage U2;

[0076] S4: Connect the second positive side voltage measuring probe T2 and the second negative side voltage measuring probe T2' to the third voltmeter V3 respectively and measure the third voltage U3. Connect the third positive side voltage measuring probe T3 and the third negative side voltage measuring probe T3' to the fourth voltmeter V4 respectively and measure the third voltage U4.

[0077] S5: Take the average value of U1, U2, U3, and U4 as the voltage measurement value of the secondary battery, which is used to assess the remaining power of the secondary battery.

[0078] Example 2:

[0079] like Figure 4 When the electrodes of a secondary battery are located within the active material of the secondary battery:

[0080] S1: After connecting the positive and negative electrodes of the secondary battery to the first voltmeter V1, the first voltage U1 is measured.

[0081] S2: Place n positive electrode voltage measurement probes on the positive electrode side of the secondary battery, n≥2, in this embodiment, n=3, wherein the first positive electrode voltage measurement probe T1 is placed on the surface of the battery separator on the positive electrode side of the secondary battery, and the second positive electrode voltage measurement probe T2 and the third positive electrode voltage measurement probe T3 are placed inside the positive electrode active material outside the positive electrode; symmetrically, place n negative electrode voltage measurement probes on the negative electrode side of the secondary battery, n≥2, in this embodiment, n=3, wherein the first negative electrode voltage measurement probe T1' is placed on the surface of the battery separator on the negative electrode side of the secondary battery, and the second negative electrode voltage measurement probe T2' and the third negative electrode voltage measurement probe T3' are placed inside the negative electrode active material outside the negative electrode;

[0082] S3: Connect the first positive side voltage measuring probe T1 and the first negative side voltage measuring probe T1' to the second voltmeter V2 and then measure the second voltage U2;

[0083] S4: Connect the second positive side voltage measuring probe T2 and the second negative side voltage measuring probe T2' to the third voltmeter V3 respectively and measure the third voltage U3. Connect the third positive side voltage measuring probe T3 and the third negative side voltage measuring probe T3' to the fourth voltmeter V4 respectively and measure the third voltage U4.

[0084] S5: Take the average value of U1, U2, U3, and U4 as the voltage measurement value of the secondary battery, which is used to assess the remaining power of the secondary battery.

[0085] Example 3:

[0086] like Figure 5 When the secondary battery electrodes are located on the surface of the battery separator:

[0087] S1: After connecting the positive and negative electrodes of the secondary battery to the first voltmeter V1, the first voltage U1 is measured.

[0088] S2: Place n positive electrode side voltage measurement probes, n≥2, in this embodiment, n=3, including a first positive electrode side voltage measurement probe T1, a second positive electrode side voltage measurement probe T2, and a third positive electrode side voltage measurement probe T3; symmetrically, place n negative electrode side voltage measurement probes, n≥2, in this embodiment, n=3, including a first negative electrode side voltage measurement probe T1', a second negative electrode side voltage measurement probe T2', and a third negative electrode side voltage measurement probe T3';

[0089] S3: Connect the first positive side voltage measuring probe T1 and the first negative side voltage measuring probe T1' to the second voltmeter V2 and then measure the second voltage U2;

[0090] S4: Connect the second positive side voltage measuring probe T2 and the second negative side voltage measuring probe T2' to the third voltmeter V3 respectively and measure the third voltage U3. Connect the third positive side voltage measuring probe T3 and the third negative side voltage measuring probe T3' to the fourth voltmeter V4 respectively and measure the third voltage U4.

[0091] S5: Take the average value of U1, U2, U3, and U4 as the voltage measurement value of the secondary battery, which is used to assess the remaining power of the secondary battery.

[0092] To implement the above method, the present invention provides corresponding measuring devices including a voltage measuring probe and a voltmeter. For example... Figure 3-5 The voltage measuring probes are disposed on the surface of the battery separator of the secondary battery or in the active material of the secondary battery, with at least two probes symmetrically arranged on both sides along the battery separator; the voltmeter is connected between the positive electrode and the negative electrode of the secondary battery and between the symmetrical voltage measuring probes on both sides.

[0093] The voltage measurement probe is made of a conductive material, selectable from metallic materials (such as alloys, stainless steel, gold, platinum, nickel, carbon steel, copper, aluminum, etc.), carbon materials (graphite, charcoal, carbon nanotubes, graphene, etc.), and conductive polymer materials (such as polyacetylene, polypyrrole, polythiophene, polyaniline, etc.). The voltage measurement probe is needle-shaped or cylindrical, with a diameter ranging from 1 nanometer to 100 millimeters. The voltage measurement probe can also be sheet-shaped, with a thickness ranging from 1 nanometer to 100 millimeters.

[0094] For example, a lithium-ion battery with a nominal voltage of 3.7 volts, discharged at a discharge rate of 1C to a certain point, such as... Figure 1 The voltage measured during conventional voltage measurement is 3.553 volts. (As shown) Figure 3 Voltage measuring probes were set up, and the measured voltages were 3.625 V for voltage 2, 3.606 V for voltage 3, 3.582 V for voltage 4, and 3.553 V for voltage 1. Therefore, the overall average battery voltage was 3.592 V. The voltage measured using this invention is higher than that measured using traditional methods, indicating that the remaining battery capacity calculated using traditional voltage measurement methods is underestimated.

[0095] For example, in a vanadium redox flow battery with an open-circuit voltage of 1.5 volts, at a certain moment during constant current charging and discharging, such as... Figure 1 The voltage measured during conventional voltage measurement is 1.626 volts. Figure 5 Voltage measuring probes were set up, and the measured voltages were 1.626 V, 1.585 V, 1.528 V, and 1.435 V, respectively. The overall average battery voltage was 1.544 V. The voltage measured using this invention is lower than that measured using traditional methods, indicating that the remaining battery capacity calculated using traditional voltage measurement methods is too high.

[0096] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A method of measuring voltage of a secondary battery, characterized in that: the method comprises: measuring a first voltage after connecting a positive electrode and a negative electrode of the secondary battery to a first voltmeter; placing a positive-side voltage measurement probe on a positive side of the secondary battery, and symmetrically, placing a negative-side voltage measurement probe on a negative side of the secondary battery; measuring a second voltage after connecting the positive-side voltage measurement probe and the negative-side voltage measurement probe to a second voltmeter; taking an average of the first voltage and the second voltage as a voltage measurement value of the secondary battery, which is used for remaining capacity estimation of the secondary battery; when active material of the secondary battery is located between the secondary battery electrode and the battery separator: measuring a first voltage after connecting a positive electrode and a negative electrode of the secondary battery to a first voltmeter; placing n positive-side voltage measurement probes on a positive side of the secondary battery, n≥2, wherein a first positive-side voltage measurement probe is placed on a positive-side battery separator surface of the secondary battery, and an n-th positive-side voltage measurement probe is placed inside positive active material; symmetrically, placing n negative-side voltage measurement probes on a negative side of the secondary battery, n≥2, wherein a first negative-side voltage measurement probe is placed on a negative-side battery separator surface of the secondary battery, and an n-th negative-side voltage measurement probe is placed inside negative active material; measuring a second voltage after connecting the first positive-side voltage measurement probe and the first negative-side voltage measurement probe to a second voltmeter; measuring an n+1-th voltage after connecting the n-th positive-side voltage measurement probe and the n-th negative-side voltage measurement probe to an n+1-th voltmeter, respectively; taking an average of all the voltages as a voltage measurement value of the secondary battery, which is used for remaining capacity estimation of the secondary battery; when the secondary battery electrode is located inside the active material of the secondary battery: measuring a first voltage after connecting a positive electrode and a negative electrode of the secondary battery to a first voltmeter; placing n positive-side voltage measurement probes on a positive side of the secondary battery, n≥2, wherein a first positive-side voltage measurement probe is placed on a positive-side battery separator surface of the secondary battery, and an n-th positive-side voltage measurement probe is placed inside positive active material outside the positive electrode; symmetrically, placing n negative-side voltage measurement probes on a negative side of the secondary battery, n≥2, wherein a first negative-side voltage measurement probe is placed on a negative-side battery separator surface of the secondary battery, and an n-th negative-side voltage measurement probe is placed inside negative active material outside the negative electrode; measuring a second voltage after connecting the first positive-side voltage measurement probe and the first negative-side voltage measurement probe to a second voltmeter; measuring an n+1-th voltage after connecting the n-th positive-side voltage measurement probe and the n-th negative-side voltage measurement probe to an n+1-th voltmeter, respectively; taking an average of all the voltages as a voltage measurement value of the secondary battery, which is used for remaining capacity estimation of the secondary battery; when the secondary battery electrode is located on the battery separator surface: measuring a first voltage after connecting a positive electrode and a negative electrode of the secondary battery to a first voltmeter; n positive electrode side voltage measurement probes, n≥2, including a first positive electrode side voltage measurement probe and an n-th positive electrode side voltage measurement probe, are placed in the positive electrode active material of the secondary battery; symmetrically, n negative electrode side voltage measurement probes, n≥2, including a first negative electrode side voltage measurement probe and an n-th negative electrode side voltage measurement probe, are placed in the negative electrode active material of the secondary battery; The first positive electrode side voltage measurement probe and the first negative electrode side voltage measurement probe are connected to the second voltmeter to measure the second voltage; The n-th positive electrode side voltage measurement probe and the n-th negative electrode side voltage measurement probe are connected to the n+1-th voltmeter to measure the n+1-th voltage; The average of all voltages is taken as the voltage measurement value of the secondary battery, which is used for the remaining capacity evaluation of the secondary battery.

2. A secondary battery voltage measurement device, characterized in that: The device is used to implement the method of any one of claims 1, comprising: Voltage measurement probes and voltmeters; The voltage measurement probes are placed on the surface of the battery separator of the secondary battery or in the active material of the secondary battery, and at least two are symmetrically placed on both sides along the battery separator; The voltmeter is connected between the positive electrode and the negative electrode of the secondary battery and between the symmetrically placed voltage measurement probes on both sides.

3. The device of claim 2, characterized in that: The voltage measurement probe is made of conductive material, selected from metal material, carbon material, and conductive polymer material.

4. The device of claim 3, characterized in that: The voltage measurement probe is needle-shaped or cylindrical, with a diameter of 1 nanometer to 100 millimeters.

5. The device of claim 4, characterized in that: The voltage measurement probe is sheet-shaped, with a thickness of 1 nanometer to 100 millimeters.

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