Capacity limiting electrode detection method of lithium ion battery

Abstract

The invention discloses a method for detecting a capacity-limiting electrode of a lithium ion battery, which is used for determining that the capacity-limiting electrode of the lithium ion battery is a positive electrode or a negative electrode, and comprises the following steps: S1, assembling the lithium ion battery with a reference electrode; s2, the lithium ion battery is charged, and in the charging process, local equilibrium potential curves of the positive electrode and the negative electrode of the lithium ion battery are obtained in situ through a three-electrode synchronous testing technology; s3, identifying whether a voltage platform inflection point appears in the local equilibrium potential curve of the positive electrode and the negative electrode so as to determine the capacity limiting electrode of the lithium ion battery; according to the scheme, the capacity limiting electrode can be identified without assembling the positive plate and the negative plate of the lithium ion battery into a button cell, the operation is convenient, and the detection is rapid.

Description

Technical Field

[0001] The present invention relates to the field of lithium - ion batteries, and particularly to a method for detecting the capacity - limiting electrode of a lithium - ion battery. Background Art

[0002] Due to advantages such as high specific energy, high power, and low self - discharge, lithium - ion batteries are widely used in fields such as electric vehicles, power energy storage, digital products, and aerospace. Since the lithium - intercalation potential of graphite is about 0.1V, close to the deposition potential of lithium metal, in traditional lithium - ion battery systems with graphite as the negative electrode, the positive electrode is usually used as the capacity - limiting electrode to avoid the deposition of metallic lithium caused by too low negative - electrode potential during charging, which may generate lithium dendrites and cause safety problems.

[0003] However, with the continuous development of new negative - electrode materials, negative - electrode materials with higher lithium - intercalation potentials are constantly being developed, such as lithium titanate, niobium oxide, niobium - titanium oxide, lithium yttrium titanate, etc. These materials also have higher safety and long - life characteristics. Using such negative - electrode materials as the capacity - limiting electrode will not cause the generation of lithium dendrites and can give play to the long - life characteristics of the materials. Therefore, it is necessary to detect the capacity - limiting electrode of a lithium - ion battery.

[0004] The traditional method for detecting the capacity - limiting electrode of a lithium - ion battery is to assemble the positive - electrode sheet and negative - electrode sheet of the assembled lithium - ion battery into standard coin - type batteries respectively, test to obtain the positive - electrode capacity and negative - electrode capacity respectively, and compare the positive - electrode and negative - electrode capacities; the electrode with the lower capacity is the capacity - limiting electrode. However, this method requires additional battery assembly for separate testing, and the process is cumbersome. Therefore, there is an urgent need to develop an in - situ method for detecting the capacity - limiting electrode of a lithium - ion battery to guide battery design and optimize the manufacturing process. Summary of the Invention

[0005] The object of the present invention is to propose a method for detecting the capacity - limiting electrode of a lithium - ion battery, which does not require assembling the positive - electrode sheet and negative - electrode sheet of the lithium - ion battery into coin - type batteries for detection respectively, and has the advantages of convenient operation and rapid detection.

[0006] To achieve the above object, the present invention proposes a method for detecting the capacity - limiting electrode of a lithium - ion battery, used to determine whether the capacity - limiting electrode of the lithium - ion battery is the positive electrode or the negative electrode, including the following steps:

[0007] S1. Assemble a lithium - ion battery with a reference electrode;

[0008] S2. Charge the lithium - ion battery, and during the charging process, in - situ obtain the local equilibrium potential curves of the positive electrode and the negative electrode of the lithium - ion battery through three - electrode synchronous testing technology;

[0009] S3. Identify whether there is a voltage plateau inflection point in the local equilibrium potential curves of the positive electrode and the negative electrode, so as to determine the capacity-limiting electrode of the lithium-ion battery.

[0010] Optionally, in step S1, the positive electrode and / or the negative electrode of the lithium-ion battery are made of materials with relatively stable charge and discharge voltage plateaus.

[0011] Optionally, the positive electrode of the lithium-ion battery is made of one or any combination of lithium nickel manganate and its derivative materials, lithium iron phosphate and its derivative materials.

[0012] Optionally, the negative electrode of the lithium-ion battery is made of one or any combination of lithium titanate and its derivative materials, graphite and its derivative materials.

[0013] Optionally, in step S2, any one of the charging methods of current titration charging, voltage titration charging, and small-rate constant current charging is used to charge the lithium-ion battery, so that the battery charge of the lithium-ion battery is charged from 0% SOC to 100% SOC.

[0014] Optionally, when charging the lithium-ion battery with the small-rate constant current charging, the small-rate value range is 0.01 - 0.2C.

[0015] Optionally, in step S1, a lithium-plated copper wire or lithium metal is used as the reference electrode for assembly.

[0016] Optionally, if only the positive electrode of the lithium-ion battery is made of materials with relatively stable charge and discharge voltage plateaus, then in step S3, identify whether there is a voltage plateau inflection point in the local equilibrium potential curve of the positive electrode. If there is a voltage plateau inflection point, the positive electrode is the capacity-limiting electrode; if there is no voltage plateau inflection point, the negative electrode is the capacity-limiting electrode.

[0017] Optionally, if only the negative electrode of the lithium-ion battery is made of materials with relatively stable charge and discharge voltage plateaus, then in step S3, identify whether there is a voltage plateau inflection point in the local equilibrium potential curve of the negative electrode. If there is a voltage plateau inflection point, the negative electrode is the capacity-limiting electrode; if there is no voltage plateau inflection point, the positive electrode is the capacity-limiting electrode.

[0018] Optionally, if both the positive electrode and the negative electrode of the lithium-ion battery are made of materials with relatively stable charge and discharge voltage plateaus, then in step S3, identify whether there is a voltage plateau inflection point in the local equilibrium potential curve of the positive electrode or the negative electrode. The electrode corresponding to the local equilibrium potential curve with a voltage plateau inflection point is the capacity-limiting electrode.

[0019] Compared with the prior art, a method for detecting the capacity-limiting electrode of a lithium-ion battery of the present invention has the following advantages and beneficial effects:

[0020] The present invention utilizes the characteristics that the potential curve of a material with a relatively stable charge-discharge voltage plateau has obvious voltage plateau inflection points at the end of charging or discharging. By using a three-electrode synchronous measurement technique, the local equilibrium potential curves of the positive and negative electrodes of a lithium-ion battery are obtained, and the limited-capacity electrode of the lithium-ion battery is determined by identifying the shapes of the local equilibrium potential curves. This method does not require assembling the positive and negative electrode sheets of the lithium-ion battery into button cells for detection respectively, is convenient to operate, and the detection is fast. Description of the Drawings

[0021] Figure 1 is a flowchart of a method for detecting the limited-capacity electrode of a lithium-ion battery according to an embodiment of the present invention;

[0022] Figure 2 are the local equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery in an embodiment of the present invention. Detailed Embodiments

[0023] The following will combine with the Figures 1 to 2 in the embodiments of the present invention to elaborate in detail on the technical solutions, structural features, achieved objectives, and effects in the embodiments of the present invention.

[0024] It should be noted that the drawings adopt a very simplified form and all use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention, and are not used to limit the limiting conditions for implementing the present invention. Therefore, they do not have technical essence. Any modification of the structure, change of the proportional relationship, or adjustment of the size, without affecting the effects that the present invention can produce and the objectives that can be achieved, should still fall within the scope covered by the technical content disclosed by the present invention.

[0025] It should be noted that in the present invention, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including", or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article, or device including a series of elements not only includes the clearly listed elements, but also includes other elements not clearly listed, or also includes elements inherent to such a process, method, article, or device.

[0026] Since the existing method for detecting the capacity-limiting electrode of a lithium-ion battery is to assemble the positive and negative electrodes of the lithium-ion battery into coin cells respectively for detection, and the operation is cumbersome. To solve this problem, the present invention discloses a method for detecting the capacity-limiting electrode of a lithium-ion battery, which is used to determine whether the capacity-limiting electrode of the lithium-ion battery is the positive electrode or the negative electrode. This method in-situ obtains the local equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery through a three-electrode synchronous testing technique, and identifies the voltage plateau inflection points in the local equilibrium potential curves of the positive and negative electrodes according to the different materials used for the positive and negative electrodes, so as to determine the capacity-limiting electrode.

[0027] The technical solution of the present invention will be described in detail below in conjunction with specific embodiments.

[0028] As Figure 1 shown, a method for detecting the capacity-limiting electrode of a lithium-ion battery according to an embodiment of the present invention includes the following steps:

[0029] S1. Assemble a lithium-ion battery with a reference electrode;

[0030] S2. Charge the lithium-ion battery, and in the charging process, in-situ obtain the local equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery through a three-electrode synchronous testing technique;

[0031] S3. Identify whether there are voltage plateau inflection points in the local equilibrium potential curves of the positive and negative electrodes, so as to determine the capacity-limiting electrode of the lithium-ion battery.

[0032] In step S1, the reference electrode is an electrode with a stable electrode potential, which can be used as a reference to measure the potential of other electrodes, so as to more accurately measure the potential changes of the positive and negative electrodes during the operation of the lithium-ion battery. In this embodiment, a lithium-plated copper wire is used as the reference electrode for assembly, and the reference electrode is correctly placed inside the battery. For example, the positive electrode, separator, reference electrode, separator, and negative electrode are stacked in sequence, so that there is a certain distance between the reference electrode and the positive or negative electrode to avoid mutual interference.

[0033] In addition, in other embodiments, lithium metal can also be used as the reference electrode.

[0034] Both the positive and negative electrodes of the lithium-ion battery are made of materials with relatively stable charge-discharge voltage plateaus. Such materials have good stability during charge and discharge, small voltage fluctuations during use, and stable output voltage, which is beneficial to improving the safety and stability of the battery.

[0035] At the same time, since this material is used as the positive and negative electrodes of the lithium-ion battery, the limited-capacity electrode can be determined according to the local equilibrium potential curves of the positive and negative electrodes in step S3. In this embodiment, the positive electrode of the lithium-ion battery is made of lithium nickel cobalt manganese oxide material, and the negative electrode of the lithium-ion battery is made of lithium titanate material.

[0036] In more embodiments, lithium nickel manganese oxide and its derivative materials, lithium iron phosphate and its derivative materials, or any combination thereof can also be used to make the positive electrode of the lithium-ion battery; lithium titanate and its derivative materials, graphite and its derivative materials, or any combination thereof can be used to make the negative electrode of the lithium-ion battery.

[0037] In step S2, the lithium-ion battery is charged by a constant current charging method at a low rate, so that the battery charge of the lithium-ion battery is charged from 0% SOC to 100% SOC. Among them, the low rate value range is 0.01-0.2C. SOC refers to the ratio of the current stored charge of the battery to the charge stored when the battery is fully charged, expressed as a percentage; 0% SOC means that the battery is in a fully discharged state, that is, there are almost no lithium ions available for external power supply in the battery; 100% SOC means that the battery is fully charged and the insertion of lithium ions in the electrode reaches a saturated state.

[0038] In other embodiments, the lithium-ion battery can also be charged by current titration charging or voltage titration charging.

[0039] During the charging process from 0% SOC to 100% SOC, the local equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery are in-situ obtained through a three-electrode synchronous test technology. The local equilibrium potential curve is a time-voltage curve, and the time is the time from 0% SOC to 100% SOC.

[0040] Among them, the local equilibrium potential curve is a concept relative to the complete equilibrium potential curve. The complete equilibrium potential curve refers to the potential curve corresponding to the situation where, under ideal conditions, lithium ions in the electrode material can be completely reversibly inserted and extracted, so that the capacity of the electrode is fully exerted. Due to the existence of the limited-capacity electrode, the potential change range of the positive or negative electrode is only a part of the complete equilibrium potential curve, that is, the so-called local equilibrium potential curve.

[0041] In step S3, according to the local equilibrium potential curves of the positive and negative electrodes measured in S2, it is identified whether there is a voltage plateau inflection point. If there is a voltage plateau inflection point, the corresponding electrode is the limited-capacity electrode.

[0042] In this embodiment, as Figure 2As shown, it is the partial equilibrium potential curve obtained in step S2. In this curve, a voltage plateau inflection point appears at the end of the partial equilibrium potential curve of the negative electrode, while no voltage plateau inflection point appears at the positive electrode. Thus, in this lithium-ion battery, the negative electrode is the capacity-limiting electrode.

[0043] In another embodiment, the difference from the above embodiment is that only the positive electrode of the lithium-ion battery is made of a material with a relatively stable charge-discharge voltage plateau. Correspondingly, in step S2, the partial equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery are still obtained. In step S3, it is identified whether a voltage plateau inflection point appears at the end of the partial equilibrium potential curve of the positive electrode. If a voltage plateau inflection point appears, the positive electrode is the capacity-limiting electrode; if no voltage plateau inflection point appears, the negative electrode is the capacity-limiting electrode.

[0044] In yet another embodiment, the difference from the above embodiment is that only the negative electrode of the lithium-ion battery is made of a material with a relatively stable charge-discharge voltage plateau. Correspondingly, in step S2, the partial equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery are still obtained. In step S3, it is identified whether a voltage plateau inflection point appears at the end of the partial equilibrium potential curve of the negative electrode. If a voltage plateau inflection point appears, the negative electrode is the capacity-limiting electrode; if no voltage plateau inflection point appears, the positive electrode is the capacity-limiting electrode.

[0045] In the solution of the present invention, by using the characteristic that the potential curve of the material with a relatively stable charge-discharge voltage plateau has an obvious voltage plateau inflection point at the end of charging or discharging, the partial equilibrium potential curves of the positive and negative electrodes of the lithium-ion battery are quickly obtained through the three-electrode synchronous measurement technology, and the capacity-limiting electrode of the lithium-ion battery is detected by identifying the shape of the partial equilibrium potential curve, which has the advantage of fast detection.

[0046] Although the content of the present invention has been introduced in detail through the above preferred embodiments, it should be recognized that the above description should not be considered as a limitation of the present invention. After those skilled in the art read the above content, various modifications and substitutions of the present invention will be obvious. Therefore, the protection scope of the present invention should be defined by the appended claims.

Claims

1. A method for detecting a capacity-limited electrode of a lithium-ion battery, for determining whether the capacity-limited electrode of a lithium-ion battery is a positive electrode or a negative electrode, characterized in that: The following steps are involved: S1. Assembling a lithium-ion battery with a reference electrode; S2. charging the lithium-ion battery, and during the charging process, obtaining in situ the local equilibrium potential curves of the positive electrode and the negative electrode of the lithium-ion battery by a three-electrode synchronous testing technology; S3. Identify whether a voltage platform inflection point appears in the local equilibrium potential curves of the positive electrode and the negative electrode, thereby determining the capacity-limiting electrode of the lithium-ion battery.

2. The method for detecting a limited capacity electrode of a lithium ion battery according to claim 1, characterized in that: In step S1, the positive electrode and / or negative electrode of the lithium-ion battery is made of a material having a relatively stable charge and discharge voltage platform.

3. The method for detecting a limited capacity electrode of a lithium ion battery as claimed in claim 2, characterized in that: The positive electrode of the lithium-ion battery is made of one or any combination of lithium nickel manganese oxide and its derivative materials, lithium iron phosphate and its derivative materials.

4. The method for detecting a limited capacity electrode of a lithium ion battery according to claim 2 or 3, characterized in that: The negative electrode of the lithium-ion battery is made of one or any combination of lithium titanate and its derivative materials, graphite and its derivative materials.

5. The method for detecting a limited capacity electrode of a lithium ion battery according to claim 1, characterized in that: In step S2, the lithium-ion battery is charged by any one of current titration charging, voltage titration charging and low-rate constant current charging, so that the power of the lithium-ion battery is charged from 0% SOC to 100% SOC.

6. The method for detecting a limited capacity electrode of a lithium ion battery as claimed in claim 5, characterized in that: When the lithium-ion battery is charged by the small-rate constant-current charging, the small-rate value ranges from 0.01C to 0.2C.

7. The method for detecting a limited capacity electrode of a lithium ion battery according to claim 1, wherein: In step S1, lithium-plated copper wire or lithium metal is used as the reference electrode for assembly.

8. The method for detecting a limited capacity electrode of a lithium ion battery as claimed in claim 2, characterized in that: If only the positive electrode of the lithium-ion battery is made of a material having a relatively stable charge and discharge voltage platform, then in step S3, it is identified whether a voltage platform inflection point appears in the local equilibrium potential curve of the positive electrode; if a voltage platform inflection point appears, the positive electrode is a limited capacity electrode; if no voltage platform inflection point appears, the negative electrode is a limited capacity electrode.

9. The method for detecting a limited capacity electrode of a lithium ion battery as claimed in claim 2, characterized in that: If only the negative electrode of the lithium-ion battery is made of a material having a relatively stable charge and discharge voltage platform, then in step S3, it is identified whether a voltage platform inflection point appears in the local equilibrium potential curve of the negative electrode; if a voltage platform inflection point appears, the negative electrode is a limited capacity electrode; if no voltage platform inflection point appears, the positive electrode is a limited capacity electrode.

10. The method for detecting a limited capacity electrode of a lithium ion battery according to claim 2, characterized in that: If the positive electrode and the negative electrode of the lithium-ion battery are both made of materials with a relatively stable charge and discharge voltage platform, then in step S3, it is identified whether a voltage platform inflection point appears in the local equilibrium potential curve of the positive electrode or the negative electrode, and the electrode corresponding to the local equilibrium potential curve having a voltage platform inflection point is a limited capacity electrode.

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