Lithium ion battery capacity matching evaluation method
Through the three-electrode synchronous measurement technology, the capacity of the positive and negative electrodes is directly tested in lithium-ion batteries, solving the problems of cumbersome and large errors in traditional methods, and achieving more efficient and accurate capacity matching evaluation.
Patent Information
- Application Number
- CN202411852902.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-04-15
AI Technical Summary
When verifying the excess capacity of the negative electrode capacity of lithium-ion batteries, traditional methods require additional assembly of standard buckle batteries for separate testing. The process is cumbersome and prone to errors, resulting in reduced evaluation accuracy.
The three-electrode synchronous measurement technology is used to obtain the local equilibrium potential curves of the positive electrode and the negative electrode and compare them with the pre-acquisition standard curves, and calculate the actual capacity of the positive electrode and the negative electrode in the lithium-ion battery, thereby verifying the actual capacity excess rate of the negative electrode.
It improves the efficiency and accuracy of battery capacity matching evaluation, simplifies the verification steps, and reduces the error caused by individual tests of positive and negative electrode capacity.
Smart Images
Figure CN119828015A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for evaluating the capacity matching of lithium ion batteries. Background Art
[0002] Lithium-ion batteries are widely used in electric vehicles, power storage, digital products, aerospace and other fields due to their advantages such as high specific energy, high power and low self-discharge. In recent years, in order to improve the energy density of lithium-ion batteries, battery systems with high-nickel ternary materials as positive electrodes and silicon-based composite materials as negative electrodes have become a hot topic of research.
[0003] Lithium-ion battery is a secondary battery. Its working principle is: during the charging process, lithium ions (Li + ) is released from the positive electrode lattice under the action of the electric field, migrates to the negative electrode through the electrolyte, and then is embedded in the lattice structure of the negative electrode material; during the discharge process, the lithium ions in the negative electrode material are released from the negative electrode lattice under the action of the electric field, migrate to the positive electrode through the electrolyte, and then are embedded in the lattice structure of the positive electrode material, releasing the electrical energy stored during the charging process. It can be seen that the working process of the lithium-ion battery is accompanied by the process of lithium ions being inserted and deinserted back and forth between the positive and negative electrodes. Therefore, ensuring the capacity matching of the positive and negative electrodes of the lithium-ion battery is a key factor in achieving the design optimization of the lithium-ion battery. Usually, the negative electrode capacity of the lithium-ion battery is designed to be higher than the positive electrode capacity. This is because the potential of the silicon-based composite negative electrode is close to the potential of the lithium metal electrode. Designing an excessive negative electrode capacity can avoid problems such as electrode lithium precipitation and reduce the consumption of active lithium, thereby improving the cycle stability and safety of high-energy-density batteries.
[0004] However, traditionally, the verification of the excess capacity design of the negative electrode is to make the materials of the positive and negative electrodes of the high-energy-density battery into standard button cells, and then test the positive and negative electrode capacities separately, so as to calculate the excess capacity rate of the negative electrode. This method requires additional assembly of standard button cells for separate testing, which is a cumbersome process, and the separate testing of the positive and negative electrode capacities is prone to errors, resulting in reduced accuracy in the assessment of the excess capacity rate of the negative electrode. Therefore, it is urgent to develop an in-situ lithium-ion battery capacity matching evaluation method to verify the actual excess capacity rate of the lithium-ion battery negative electrode, thereby guiding the optimization of battery design and development processes. Summary of the invention
[0005] The purpose of the present invention is to provide an in-situ high specific energy lithium ion battery capacity matching evaluation method to improve the real-time and accuracy of battery capacity matching evaluation.
[0006] In order to achieve the above object, the present invention provides a lithium ion battery capacity matching evaluation method, characterized in that it includes:
[0007] Step 1, respectively providing a standard curve of a positive electrode material and a standard curve of a negative electrode material; obtaining a standard specific capacity value of the positive electrode on the standard curve of the positive electrode material; and obtaining a standard specific capacity value of the negative electrode on the standard curve of the negative electrode material;
[0008] Step 2, providing a reference electrode, and assembling the reference electrode, a positive electrode sheet composed of the positive electrode material, and a negative electrode sheet composed of the negative electrode material into a three-electrode battery;
[0009] Step 3, performing a three-electrode synchronous measurement test on the three-electrode battery to obtain a positive electrode local equilibrium potential curve and a negative electrode local equilibrium potential curve;
[0010] Step 4, after reading the charge cut-off potential value in the positive electrode local equilibrium potential curve, read the specific capacity value corresponding to the charge cut-off potential value in the standard curve of the positive electrode material to obtain the positive electrode specific capacity measurement value; after reading the discharge cut-off potential value in the negative electrode local equilibrium potential curve, read the specific capacity value corresponding to the discharge cut-off potential value in the standard curve of the negative electrode material to obtain the negative electrode specific capacity measurement value;
[0011] Step 5, calculating the excess capacity rate of the negative electrode of the three-electrode battery to evaluate the capacity matching of the three-electrode battery.
[0012] Furthermore, the step 1 comprises:
[0013] Providing a positive electrode material and a negative electrode material of a lithium-ion battery respectively;
[0014] Using the positive electrode material and the negative electrode material to respectively manufacture a positive electrode standard battery and a negative electrode standard battery;
[0015] Obtaining a complete charging equilibrium potential curve of the positive electrode material by performing a charging test on the positive electrode standard battery;
[0016] By performing a discharge test on the negative electrode standard battery, a complete discharge equilibrium potential curve of the negative electrode material is obtained.
[0017] Furthermore, the complete charge equilibrium potential curve of the positive electrode material and the complete discharge equilibrium potential curve of the negative electrode material are both relationship curves between specific capacity and voltage.
[0018] Furthermore, the complete charge equilibrium potential curve of the positive electrode material includes a charge voltage platform, and the charge voltage platform is an inclined platform; the complete discharge equilibrium potential curve of the negative electrode material includes a discharge voltage platform, and the discharge voltage platform is an inclined platform.
[0019] Furthermore, the charging mode of the charging test includes any one of current titration charging, voltage titration charging or small rate constant current charging; the discharging mode of the discharging test includes any one of current titration discharge, voltage titration discharge or small rate constant current discharge.
[0020] Furthermore, the charging method is small rate constant current charging; the discharging method is small rate constant current discharging;
[0021] The small ratio has a value range of 0.01C to 0.1C.
[0022] Furthermore, the step 5 comprises:
[0023] Calculate the ratio M of the positive electrode standard specific capacity value obtained in step 1 to the positive electrode specific capacity measurement value obtained in step 4;
[0024] Calculate the ratio m of the negative electrode standard specific capacity value obtained in step 1 to the negative electrode specific capacity measurement value obtained in step 4;
[0025] The excess capacity rate of the negative electrode of the three-electrode battery is calculated by the formula: (m / M-1)×100%.
[0026] Furthermore, the positive electrode local equilibrium potential curve and the negative electrode local equilibrium potential curve are relationship curves between time and voltage.
[0027] Furthermore, the positive electrode material includes at least any one of nickel cobalt manganese, lithium cobalt oxide, nickel cobalt aluminum, and lithium manganese oxide.
[0028] Furthermore, the negative electrode material includes at least one of silicon, silicon monoxide, a silicon-carbon composite material, and a mixed material of a silicon-containing material and graphite.
[0029] Compared with the prior art, the beneficial effects of the present invention at least include:
[0030] The present invention provides an in-situ lithium-ion battery capacity matching evaluation method, which adopts a three-electrode synchronous measurement technology, can simultaneously test and obtain the local equilibrium potential curves of the positive electrode and the negative electrode in the lithium-ion battery, and then compare the local equilibrium potential curves of the positive electrode and the negative electrode with the standard curves (complete equilibrium potential curves) of the positive electrode material and the negative electrode material obtained in advance, so as to obtain the actual capacity used by the positive electrode and the actual capacity used by the negative electrode in the lithium-ion battery, thereby calculating and verifying the actual excess capacity rate of the negative electrode in the lithium-ion battery. On the one hand, the evaluation method improves the efficiency of battery capacity matching evaluation, especially for lithium-ion batteries of different manufacturing batches but using the same materials, there is no need to assemble standard button batteries for verification, which simplifies the verification steps; on the other hand, the evaluation method reduces the errors that may be caused by testing the positive and negative electrode capacities separately, thereby improving the accuracy of evaluating the excess capacity rate of the battery negative electrode. BRIEF DESCRIPTION OF THE DRAWINGS
[0031] Figure 1 The present invention is a flow chart of a lithium-ion battery capacity matching evaluation method.
[0032] Figure 2 1 is a complete charge equilibrium potential curve of the positive electrode material of an embodiment of the present invention.
[0033] Figure 3 1 is a complete charge equilibrium potential curve of the negative electrode material of an embodiment of the present invention.
[0034] Figure 4 1 is a local equilibrium potential curve of the positive electrode and the negative electrode of the three-electrode battery according to an embodiment of the present invention. DETAILED DESCRIPTION
[0035] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0036] The “high specific energy lithium-ion battery” described herein refers to a lithium-ion battery with an energy density greater than 260Wh / kg.
[0037] The "SOC" (State of Charge) mentioned in this article refers to the percentage of the current remaining power of the lithium-ion battery.
[0038] The “positive electrode specific capacity measurement value” and “negative electrode specific capacity measurement value” mentioned in this article refer to the specific capacity values used by the positive electrode and the negative electrode during the actual operation of the lithium-ion battery.
[0039] As described in the background technology, in the existing evaluation method of the excess capacity rate of the negative electrode of the lithium-ion battery, the positive electrode and the negative electrode need to be tested separately. The process is cumbersome and prone to cause large test errors, and cannot accurately reflect the capacity matching of the positive and negative electrodes of the lithium-ion battery during actual operation.
[0040] To solve the above problems, the present invention proposes for the first time an in-situ capacity matching evaluation method for lithium-ion batteries. Through the three-electrode synchronous measurement technology, the local equilibrium potential curves of the positive and negative electrodes in the lithium-ion battery are compared with the complete equilibrium potential curves of the positive and negative electrode materials obtained in advance, so as to obtain the actual utilized capacity of the positive electrode and the actual utilized capacity of the negative electrode in the lithium-ion battery, thereby calculating and verifying the actual excess capacity rate of the negative electrode in the lithium-ion battery, and improving the evaluation accuracy.
[0041] See also Figure 1 The present invention provides a method for evaluating the capacity matching of a lithium-ion battery, comprising the following steps:
[0042] Step 1, respectively providing a standard curve of a positive electrode material and a standard curve of a negative electrode material; obtaining a standard specific capacity value of the positive electrode on the standard curve of the positive electrode material; and obtaining a standard specific capacity value of the negative electrode on the standard curve of the negative electrode material.
[0043] In some embodiments, step 1 comprises:
[0044] Step 1.1, respectively provide a positive electrode material and a negative electrode material of a lithium-ion battery.
[0045] The lithium-ion battery is a high-energy lithium-ion battery. The positive electrode material includes at least one of nickel-cobalt-manganese, lithium cobalt oxide, nickel-cobalt-aluminum, and lithium manganese oxide. The negative electrode material includes at least one of silicon, silicon oxide, silicon-carbon composite material, and a mixed material of silicon-containing material and graphite.
[0046] Step 1.2, using the positive electrode material and the negative electrode material to respectively make a positive electrode standard battery and a negative electrode standard battery.
[0047] The positive electrode standard battery and the negative electrode standard battery are both 2016 standard button batteries. In some embodiments, the manufacturing method of the 2016 standard button battery includes:
[0048] Step 1.2.1, weigh the working material: conductive agent: binder in a mass ratio of 8:1:1, add the weighed working material, conductive agent, and binder into a polar solvent and mix them evenly to obtain a working electrode slurry. For the positive electrode standard battery, the working material is a positive electrode material; for the negative electrode standard battery, the working material is a negative electrode material. The conductive agent can be any one of carbon black, acetylene black, carbon nanotubes, and reduced graphene oxide. As an example, the conductive agent is carbon black; the binder can be any one of polyvinylidene fluoride, carboxymethyl cellulose, and styrene-butadiene rubber. As an example, the binder is polyvinylidene fluoride; the polar solvent can be any one of N-methylpyrrolidone, ethanol, and acetone. As an example, the polar solvent is N-methylpyrrolidone.
[0049] Step 1.2.2, coating the working electrode slurry on a metal foil current collector, drying, rolling, and punching into discs with a diameter ranging from 10 mm to 14 mm to obtain the working electrode sheet of the 2016-type standard button cell.
[0050] Step 1.2.3, using the working electrode sheet as the positive electrode sheet and the lithium metal sheet as the negative electrode sheet, in a glove box, assembling the working electrode sheet and the lithium metal sheet into the 2016-type standard button battery.
[0051] Step 1.3, obtaining a complete charging equilibrium potential curve of the positive electrode material by performing a charging test on the positive electrode standard battery.
[0052] After the positive electrode standard battery is activated (for example, by performing a small current charge and discharge cycle), a charging test is performed. The positive electrode standard battery is charged from 0% SOC to 100% SOC to obtain a complete charging equilibrium potential curve of the positive electrode material, that is, the standard curve of the positive electrode material. The charging method of the positive electrode standard battery includes any one of current titration charging, voltage titration charging, or small rate constant current charging. In some implementations, the charging method is small rate constant current charging, and the value range of the small rate is 0.01C to 0.1C (that is, the current is 1% to 10% of the rated capacity of the standard battery).
[0053] Step 1.4, obtaining a complete discharge equilibrium potential curve of the negative electrode material by performing a discharge test on the negative electrode standard battery.
[0054] After activating the negative electrode standard battery (for example, performing a small current charge and discharge cycle), a discharge test is performed. The negative electrode standard battery is discharged from 0% SOC to 100% SOC to obtain a complete discharge equilibrium potential curve of the negative electrode material, that is, the standard curve of the negative electrode material. The discharge method of the negative electrode standard battery includes any one of current titration discharge, voltage titration discharge or small rate constant current discharge. In some embodiments, the discharge method is small rate constant current discharge, and the value range of the small rate is 0.01C to 0.1C.
[0055] In some embodiments, the complete charge equilibrium potential curve of the positive electrode material and the complete discharge equilibrium potential curve of the negative electrode material are both curves of the relationship between specific capacity and voltage. The complete charge equilibrium potential curve of the positive electrode material includes a charge voltage platform, and the charge voltage platform is an inclined platform; the complete discharge equilibrium potential curve of the negative electrode material includes a discharge voltage platform, and the discharge voltage platform is an inclined platform.
[0056] Step 2, providing a reference electrode, and assembling the reference electrode, a positive electrode sheet composed of the positive electrode material, and a negative electrode sheet composed of the negative electrode material into a three-electrode battery.
[0057] In some embodiments, the reference electrode is any one of lithium-plated copper wire and lithium metal wire, and the reference electrode is implanted between the positive electrode and the negative electrode of the lithium-ion battery to form a three-electrode battery.
[0058] Step 3, performing a three-electrode synchronous measurement test on the three-electrode battery to obtain a positive electrode local equilibrium potential curve and a negative electrode local equilibrium potential curve.
[0059] In some embodiments, the three-electrode synchronous measurement test includes using a parameter acquisition instrument to simultaneously test the potential difference between the positive electrode and the reference electrode, and between the negative electrode and the reference electrode during the charging process of the three-electrode battery, so as to monitor the response changes of the positive electrode and the negative electrode to the reference electrode in real time.
[0060] In some embodiments, the positive electrode local equilibrium potential curve and the negative electrode local equilibrium potential curve are relationship curves between time and voltage.
[0061] Step 4, after reading the charge cut-off potential value in the local equilibrium potential curve of the positive electrode, read the specific capacity value corresponding to the charge cut-off potential value in the complete charge equilibrium potential curve of the positive electrode material to obtain the positive electrode specific capacity measurement value; after reading the discharge cut-off potential value in the local equilibrium potential curve of the negative electrode, read the specific capacity value corresponding to the discharge cut-off potential value in the complete discharge equilibrium potential curve of the negative electrode material to obtain the negative electrode specific capacity measurement value.
[0062] Step 5, calculating the excess capacity rate of the negative electrode of the three-electrode battery to evaluate the capacity matching of the three-electrode battery.
[0063] In some embodiments, step 5 comprises:
[0064] Step 5.1, calculate the ratio of the positive electrode standard specific capacity value obtained in step 1 to the positive electrode specific capacity measurement value obtained in step 4, denoted as M.
[0065] Step 5.2, calculate the ratio of the negative electrode standard specific capacity value obtained in step 1 to the negative electrode specific capacity measurement value obtained in step 4, denoted as m.
[0066] Step 5.3, calculate the excess capacity rate of the negative electrode of the three-electrode battery by the formula: (m / M-1)×100%.
[0067] When the negative electrode capacity excess rate is 0-20%, the three-electrode battery has a good capacity matching. Preferably, when the negative electrode capacity excess rate is 0-15%, the capacity matching of the three-electrode battery is better. If the negative electrode capacity excess rate is too high, that is, the negative electrode capacity of the three-electrode battery is too high, it will cause the initial charge and discharge efficiency of the three-electrode battery to decrease, which is not conducive to improving the energy density of the three-electrode battery. If the negative electrode capacity excess rate is too low, that is, the negative electrode capacity of the three-electrode battery is too low, it will cause the potential of the negative electrode to be close to the lithium metal deposition potential under the charging cut-off condition, thereby causing uneven deposition of lithium metal on the negative electrode, and even lithium dendrites in severe cases, causing safety problems.
[0068] The technical solution of the present invention is further described in detail below in conjunction with the embodiments and drawings.
[0069] Example
[0070] This embodiment provides a method for evaluating the capacity matching of a lithium-ion battery, comprising the following steps:
[0071] In step S101, a positive electrode material and a negative electrode material of a high specific energy lithium-ion battery are provided respectively: the positive electrode material is a nickel cobalt manganese oxide material; and the negative electrode material is a mixed material of a silicon-containing material and graphite.
[0072] Step S102, using the positive electrode material and the negative electrode material to respectively manufacture a positive electrode standard battery and a negative electrode standard battery. The positive electrode standard battery and the negative electrode standard battery are both 2016 standard button batteries.
[0073] The method for making the positive electrode standard battery includes: weighing the nickel cobalt manganese oxide lithium material: carbon black: polyvinylidene fluoride in a mass ratio of 8:1:1, using N-methyl pyrrolidone as a solvent, adding the weighed nickel cobalt manganese oxide lithium material, carbon black, and polyvinylidene fluoride into N-methyl pyrrolidone and mixing evenly to obtain a first working electrode slurry. The first working electrode slurry is coated on a metal foil current collector, dried, rolled, and punched into a disc with a diameter of 10 mm to obtain the first working electrode sheet of the positive electrode standard battery. The first working electrode sheet is used as the positive electrode sheet and the lithium metal sheet is used as the negative electrode sheet. In a glove box with an argon atmosphere, the first working electrode sheet and the lithium metal sheet are assembled into the positive electrode standard battery.
[0074] The method for making the negative electrode standard battery includes: weighing the mixed material of silicon-containing material and graphite: carbon black: polyvinylidene fluoride in a mass ratio of 8:1:1, using N-methylpyrrolidone as a solvent, adding the weighed mixed material of silicon-containing material and graphite, carbon black, and polyvinylidene fluoride into N-methylpyrrolidone and mixing evenly to obtain a second working electrode slurry. The second working electrode slurry is coated on a metal foil current collector, dried, rolled, and punched into a disc with a diameter of 10 mm to obtain the second working electrode sheet of the negative electrode standard battery. The second working electrode sheet is used as the positive electrode sheet and the lithium metal sheet is used as the negative electrode sheet. In a glove box with an argon atmosphere, the second working electrode sheet and the lithium metal sheet are assembled into the negative electrode standard battery.
[0075] Step S103, performing a charging test on the positive electrode standard battery to obtain a complete charging equilibrium potential curve of the positive electrode material and obtain a positive electrode standard specific capacity value.
[0076] After the positive electrode standard battery is activated, the positive electrode standard battery is charged at a constant current of 0.05C from 0% SOC to 100% SOC. The voltage range of the positive electrode standard battery is 2.6V to 4.3V. The complete charge equilibrium potential curve of the positive electrode material is obtained. Figure 2 According to the complete charge equilibrium potential curve of the positive electrode material, the standard specific capacity value of the positive electrode is 236.2 mAh / g.
[0077] Step S104, performing a discharge test on the negative electrode standard battery to obtain a complete discharge equilibrium potential curve of the negative electrode material and obtain a negative electrode standard specific capacity value.
[0078] After the negative electrode standard battery is activated, the negative electrode standard battery is discharged at a constant current of 0.05C from 0% SOC to 100% SOC. The voltage range of the negative electrode standard battery is 0.001V to 1.5V. The complete discharge equilibrium potential curve of the negative electrode material is obtained. Figure 3According to the complete discharge equilibrium potential curve of the negative electrode material, the standard specific capacity value of the negative electrode is 777.8 mAh / g.
[0079] Step S105, providing a reference electrode, wherein the reference electrode is a lithium-plated copper wire, and assembling the lithium-plated copper wire, a positive electrode sheet composed of the positive electrode material, and a negative electrode sheet composed of the negative electrode material into a three-electrode battery.
[0080] Step S106, performing a three-electrode synchronous measurement test on the three-electrode battery to obtain a positive electrode local equilibrium potential curve and a negative electrode local equilibrium potential curve.
[0081] The parameter acquisition instrument is used to simultaneously test the time-voltage relationship curves of the reference electrode and the positive electrode, and the reference electrode and the negative electrode during the charging process of the three-electrode battery, and the local equilibrium potential curve of the positive electrode and the local equilibrium potential curve of the negative electrode are obtained in situ. The charging method of the charging process is: constant current charging from 0% SOC to 100% SOC at a rate of 0.05C, and the voltage range is 2.5V to 4.2V. The local equilibrium potential curve of the positive electrode and the local equilibrium potential curve of the negative electrode are as follows Figure 4 shown.
[0082] Step S107, according to Figure 4 In the local equilibrium potential curve of the positive electrode, the charge cut-off potential value is read as 4.25V, and the specific capacity value corresponding to the charge cut-off potential value (4.25V) is read in the complete charge equilibrium potential curve of the positive electrode material obtained in step S103, thereby obtaining a positive electrode specific capacity measurement value of 231.9mAh / g in the three-electrode battery; in the local equilibrium potential curve of the negative electrode, the discharge cut-off potential value is read as 0.05V, and the specific capacity value corresponding to the discharge cut-off potential value (0.05V) is read in the complete discharge equilibrium potential curve of the negative electrode material obtained in step S104, thereby obtaining a negative electrode specific capacity measurement value of 694.12mAh / g in the three-electrode battery.
[0083] Step S108, calculate the ratio of the positive electrode standard specific capacity value (236.2 mAh / g) obtained in step S103 to the positive electrode specific capacity measurement value (231.9 mAh / g) obtained in step S107, and obtain M as 1.018. Calculate the ratio of the negative electrode standard specific capacity value (777.8 mAh / g) obtained in step S104 to the negative electrode specific capacity measurement value (694.12 mAh / g) obtained in step S107, and obtain m as 1.121. By formula: (m / M-1)×100%, the excess capacity rate of the negative electrode of the three-electrode battery is calculated to be 10.12%. The excess capacity rate of the negative electrode is within the positive and negative electrode capacity matching range (0-15%) of the lithium-ion battery, indicating that the three-electrode battery has good capacity matching.
[0084] In summary, the present invention utilizes three-electrode synchronous measurement technology, and through in-situ testing, can quickly obtain the capacity utilized by the positive and negative electrodes of a high-energy-density lithium-ion battery, thereby calculating the actual excess capacity rate of the negative electrode of the high-energy-density lithium-ion battery, and achieving rapid and accurate evaluation of the capacity matching of the positive and negative electrodes of the battery, which is beneficial to guiding and optimizing the preparation process of high-energy-density lithium-ion batteries.
[0085] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.
Claims
1. A method for evaluating the capacity matching of a lithium-ion battery, characterized in that: include: Step 1, respectively providing a standard curve of a positive electrode material and a standard curve of a negative electrode material; obtaining a standard specific capacity value of the positive electrode on the standard curve of the positive electrode material; and obtaining a standard specific capacity value of the negative electrode on the standard curve of the negative electrode material; Step 2, providing a reference electrode, and assembling the reference electrode, a positive electrode sheet composed of the positive electrode material, and a negative electrode sheet composed of the negative electrode material into a three-electrode battery; Step 3, performing a three-electrode synchronous measurement test on the three-electrode battery to obtain a positive electrode local equilibrium potential curve and a negative electrode local equilibrium potential curve; Step 4, after reading the charge cut-off potential value in the positive electrode local equilibrium potential curve, read the specific capacity value corresponding to the charge cut-off potential value in the standard curve of the positive electrode material to obtain the positive electrode specific capacity measurement value; after reading the discharge cut-off potential value in the negative electrode local equilibrium potential curve, read the specific capacity value corresponding to the discharge cut-off potential value in the standard curve of the negative electrode material to obtain the negative electrode specific capacity measurement value; Step 5, calculating the excess capacity rate of the negative electrode of the three-electrode battery to evaluate the capacity matching of the three-electrode battery.
2. The lithium-ion battery capacity matching evaluation method according to claim 1, characterized in that: The step 1 comprises: Providing a positive electrode material and a negative electrode material of a lithium-ion battery respectively; Using the positive electrode material and the negative electrode material to respectively manufacture a positive electrode standard battery and a negative electrode standard battery; Obtaining a complete charging equilibrium potential curve of the positive electrode material by performing a charging test on the positive electrode standard battery; By performing a discharge test on the negative electrode standard battery, a complete discharge equilibrium potential curve of the negative electrode material is obtained.
3. The lithium-ion battery capacity matching evaluation method according to claim 2, characterized in that: The complete charge equilibrium potential curve of the positive electrode material and the complete discharge equilibrium potential curve of the negative electrode material are both relationship curves between specific capacity and voltage.
4. The lithium-ion battery capacity matching evaluation method according to claim 2, characterized in that: The complete charge equilibrium potential curve of the positive electrode material includes a charge voltage platform, and the charge voltage platform is an inclined platform; the complete discharge equilibrium potential curve of the negative electrode material includes a discharge voltage platform, and the discharge voltage platform is an inclined platform.
5. The lithium-ion battery capacity matching evaluation method according to claim 2, characterized in that: The charging mode of the charging test includes any one of current titration charging, voltage titration charging or small rate constant current charging; the discharging mode of the discharging test includes any one of current titration discharge, voltage titration discharge or small rate constant current discharge.
6. The lithium-ion battery capacity matching evaluation method according to claim 5, characterized in that: The charging method is low-rate constant-current charging; the discharging method is low-rate constant-current discharging; The small ratio has a value range of 0.01C to 0.1C.
7. The lithium-ion battery capacity matching evaluation method according to claim 1, characterized in that: The step 5 comprises: Calculate the ratio M of the positive electrode standard specific capacity value obtained in step 1 to the positive electrode specific capacity measurement value obtained in step 4; Calculate the ratio m of the negative electrode standard specific capacity value obtained in step 1 to the negative electrode specific capacity measurement value obtained in step 4; The excess capacity rate of the negative electrode of the three-electrode battery is calculated by the formula: (m / M-1)×100%.
8. The lithium-ion battery capacity matching evaluation method according to claim 1, characterized in that: The positive electrode local equilibrium potential curve and the negative electrode local equilibrium potential curve are relationship curves between time and voltage.
9. The lithium-ion battery capacity matching evaluation method according to claim 1, characterized in that: The positive electrode material includes at least one of nickel cobalt manganese, lithium cobalt oxide, nickel cobalt aluminum and lithium manganese oxide.
10. The lithium-ion battery capacity matching evaluation method according to claim 1, characterized in that: The negative electrode material includes at least one of silicon, silicon monoxide, a silicon-carbon composite material, and a mixed material of a silicon-containing material and graphite.