Method and device for detecting lithium content of battery

Abstract

The invention discloses a method and a device for detecting the lithium content of a battery. The detection method comprises the following steps: acquiring a unit cell index of a positive electrode active material of a target battery; and determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content. According to the embodiment of the invention, the unit cell index of the positive electrode active material of the target battery is obtained, and then the lithium content of the positive electrode active material of the target battery is obtained according to the relationship between the unit cell index of the positive electrode active material and the lithium content, so that the method is simple, convenient, rapid and relatively high in accuracy, and rapid detection of the lithium content of the battery is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a method and device for detecting the lithium content of a battery. Background Art

[0002] The information provided in this section is only background information related to the present application, and it is not necessarily prior art.

[0003] In the existing technical means, it is difficult to quickly and accurately obtain the lithium content of a battery under test or a battery component under test. For example, in some technologies, by disassembling the battery under test or the battery component under test, the positive electrode active material of the battery under test or the battery component under test is peeled off, and the lithium content of the battery or the battery component is obtained through means such as elemental analysis. However, the detection process of this method takes a lot of time and has low detection efficiency. Summary of the Invention

[0004] In view of the technical problems in the background art, the present application provides a method and device for detecting the lithium content of a battery, aiming to achieve rapid detection of the lithium content of the battery.

[0005] To achieve the above object, a first aspect of the present application provides a method for detecting the lithium content of a battery, including:

[0006] Obtaining the unit cell index of the positive electrode active material of the target battery;

[0007] Determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content.

[0008] In the embodiments of the present application, by obtaining the unit cell index of the positive electrode active material of the target battery, and then according to the relationship between the unit cell index of the positive electrode active material and the lithium content, the lithium content of the positive electrode active material of the target battery is obtained. This method is simple, convenient, fast, and has a high accuracy rate, realizing rapid detection of the lithium content of the battery.

[0009] In some embodiments, the step of obtaining the unit cell index of the positive electrode active material of the target battery includes:

[0010] Obtaining an X-ray diffraction pattern, a neutron diffraction pattern, or a high-resolution transmission electron microscope image of the positive electrode active material;

[0011] Determining the unit cell index of the positive electrode active material of the target battery according to the obtained X-ray diffraction pattern, neutron diffraction pattern, or high-resolution transmission electron microscope image.

[0012] Embodiments of the present application obtain the unit cell parameters of the positive electrode active material of a target battery through three provided methods, namely, the X-ray diffraction pattern, neutron diffraction pattern, or high-resolution transmission electron microscope image of the positive electrode active material, and the method is simple and convenient.

[0013] In some embodiments, the steps of determining the unit cell parameters of the positive electrode active material of a target battery include:

[0014] Select a plurality of characteristic peaks from the obtained X-ray diffraction pattern or neutron diffraction pattern;

[0015] Determine the interplanar spacing of the positive electrode active material of the target battery according to the diffraction angles of the plurality of characteristic peaks;

[0016] Determine the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

[0017] Embodiments of the present application do not require disassembling the battery. By analyzing the X-ray diffraction pattern or neutron diffraction pattern, the unit cell parameters of the positive electrode active material of the target battery can be obtained. This method simply, conveniently, and efficiently realizes non-destructive detection of the unit cell parameters of the target battery, and the battery after detection can still be used normally, saving battery costs.

[0018] In some embodiments, the steps of determining the unit cell parameters of the positive electrode active material of a target battery include:

[0019] Select two adjacent lattice fringes from the obtained high-resolution transmission electron microscope image;

[0020] Determine the interplanar spacing of the positive electrode active material of the target battery according to the spacing between the two adjacent lattice fringes;

[0021] Determine the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

[0022] Embodiments of the present application obtain the unit cell parameters of the positive electrode active material of the target battery by analyzing the high-resolution transmission electron microscope image, which is beneficial to making the detection of the unit cell parameters of the target battery have higher accuracy.

[0023] In some embodiments, the steps of determining the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery include:

[0024] Determine the relationship between the unit cell parameters and the interplanar spacing of the positive electrode active material according to the crystal system to which the positive electrode active material of the target battery belongs;

[0025] Determine the unit cell parameters of the positive electrode active material based on the interplanar spacing of the positive electrode active material of the determined target battery and the relationship between the unit cell parameters and the interplanar spacing of the positive electrode active material;

[0026] Determine the unit cell indices of the positive electrode active material of the target battery according to the relationship between the unit cell parameters and the unit cell indices of the positive electrode active material.

[0027] The embodiments of the present application obtain the unit cell indices of the positive electrode active material through the interplanar spacing, and the implementation method is simple, convenient and fast.

[0028] In some embodiments, the unit cell indices include one or more of unit cell parameters, unit cell volume or transition metal layer spacing.

[0029] The embodiments of the present application provide some specific unit cell indices. According to the relationship between the unit cell indices of the positive electrode active material and the lithium content, on the one hand, the lithium content of the battery can be detected, and on the other hand, the influence of lithium insertion / extraction during charge and discharge on the anisotropy of unit cell shrinkage and expansion can be quantitatively analyzed at the microscopic level, and / or the influence of lithium insertion / extraction during charge and discharge on the shrinkage and expansion of the unit cell volume can be quantitatively analyzed at the microscopic level, and / or the influence of the transition metal layer spacing on the crystal structure stability can be quantitatively analyzed at the microscopic level.

[0030] In some embodiments, the steps for constructing the relationship between the unit cell indices of the positive electrode active material and the lithium content include:

[0031] Obtain a number of X-ray diffraction patterns of the reference battery at several states of charge; the positive electrode active material of the reference battery and the positive electrode active material of the target battery are of the same positive electrode active material system;

[0032] Obtain the unit cell indices of the positive electrode active material at any state of charge according to the diffraction peak angles of the X-ray diffraction pattern obtained at any state of charge;

[0033] Obtain the relationship between the unit cell indices and the lithium content of the positive electrode active material at any state of charge according to the unit cell indices of the positive electrode active material obtained at any state of charge;

[0034] Collect the relationships between the unit cell indices and the lithium content of the positive electrode active material at several states of charge, and construct the relationship between the unit cell indices and the lithium content of the positive electrode active material.

[0035] Embodiments of the present application obtain a series of pairs of unit cell parameters and lithium content data of the positive electrode active material of a reference battery by performing X-ray scanning analysis on the same area position of the reference battery under different states of charge, so as to obtain the lithium content curve of the positive electrode active material of the reference battery under different unit cell parameters according to the obtained multiple sets of data groups. This curve serves as a database of the battery lithium content of this positive electrode active material system. In the future, when a battery under test or a battery component under test needs to obtain the battery lithium content, the battery lithium content can be directly obtained, and the method is simple, fast, and non-destructive.

[0036] In some embodiments, the step of obtaining the relationship between the unit cell index and the lithium content of the positive electrode active material under any state of charge includes:

[0037] Performing full-spectrum fitting on the obtained X-ray diffraction pattern under any state of charge to obtain the relationship between the unit cell index and the lithium content of the positive electrode active material under any state of charge.

[0038] Embodiments of the present application construct the relationship between the unit cell index and the lithium content of the positive electrode active material through the method of full-spectrum fitting. When it is necessary to obtain the battery lithium content of a battery under test or a battery component under test, only the battery under test or the battery component under test needs to be irradiated with X-rays to obtain the corresponding X-ray diffraction pattern, and the unit cell index of the positive electrode active material of the battery under test or the battery component under test can be determined. Then, substituting this unit cell index into the relationship between the unit cell index and the lithium content of the positive electrode active material of the same crystal system, the obtained lithium content is the battery lithium content of the battery under test or the battery component under test. This method is fast, convenient, and has a high accuracy rate.

[0039] In some embodiments, the step of performing full-spectrum fitting on the obtained X-ray diffraction pattern under any state of charge includes:

[0040] Selecting the measured X-ray diffraction pattern of the positive electrode active material of the reference battery under any state of charge;

[0041] Presetting the parameters of the influencing factors of the unit cell structure of the positive electrode active material to obtain the theoretical X-ray diffraction pattern of the positive electrode active material;

[0042] By adjusting the parameters of the influencing factors, making the residual between the diffraction peak data of the theoretical X-ray diffraction pattern and the diffraction peak data of the measured X-ray diffraction pattern less than or equal to the threshold, and defining the unit cell parameters and lithium content corresponding to the adjusted theoretical X-ray diffraction pattern as the unit cell parameters and lithium content of the positive electrode active material of the reference battery.

[0043] Embodiments of the present application facilitate obtaining the lithium content corresponding to the reference battery under multiple unit cell indices through the provided full-spectrum fitting method, and the obtained results have high accuracy and are easy to implement.

[0044] In some embodiments, the step of determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content includes:

[0045] In a database having the relationship between the unit cell index of several positive electrode active materials and the lithium content, find the relationship between the unit cell index of the positive electrode active material corresponding to the positive electrode active material of the target battery and the lithium content;

[0046] Substitute the unit cell index of the positive electrode active material of the target battery into the corresponding relationship between the unit cell index of the positive electrode active material and the lithium content to obtain the lithium content of the positive electrode active material of the target battery.

[0047] The embodiments of the present application construct a database containing the relationship between the unit cell index and the lithium content of various positive electrode active materials. In the future, when it is necessary to obtain the lithium content of the target battery, as long as the unit cell index of the positive electrode active material of the target battery is obtained, the lithium content of the target battery can be obtained simply and quickly, which has a high application prospect for the testing of the lithium content of a large number of target batteries.

[0048] In a second aspect, the embodiments of the present application provide a device for detecting the lithium content of a battery. The device for detecting the lithium content of a battery includes:

[0049] An acquisition module, which is used to acquire the crystal index of the positive electrode active material of the target battery;

[0050] A processing module, which is used to determine the lithium content of the positive electrode active material of the target battery according to the crystal index of the positive electrode active material of the target battery and the relationship between the crystal index of the positive electrode active material and the lithium content.

[0051] The device for detecting the lithium content of a battery has at least the same advantages as the method for detecting the lithium content of a battery, and can realize the rapid detection of the lithium content of a battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0053] Figure 1 is a schematic flowchart of the method for detecting the lithium content of a battery provided by the embodiments of the present application;

[0054] Figure 2 are several X-ray diffraction patterns of the reference battery in different states of charge in Embodiment 1 of the present application;

[0055] Figure 3 The relationship between the unit cell parameters and the lithium content of the positive electrode active material of the reference battery in Example 1 of the present application;

[0056] Figure 4 The X-ray diffraction pattern of the positive electrode active material of the target battery in Example 1 of the present application;

[0057] Figure 5 The X-ray diffraction pattern of the positive electrode active material of the target battery in Example 8 of the present application. Detailed Description of the Invention

[0058] The present application will be further described below in conjunction with specific embodiments. It should be understood that these specific embodiments are only used to illustrate the present application and not to limit the scope of the present application.

[0059] For the sake of brevity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form a range not explicitly recited; and any lower limit can be combined with other lower limits to form a range not explicitly recited, and similarly any upper limit can be combined with any other upper limit to form a range not explicitly recited. In addition, each separately disclosed point or single numerical value itself can be used as a lower limit or an upper limit and combined with any other point or single numerical value or combined with other lower limits or upper limits to form a range not explicitly recited.

[0060] In the description herein, unless otherwise specified, the term "or" is inclusive. That is, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0061] In the description herein, it should be noted that unless otherwise specified, "above" and "below" include the recited number, and "one or several" means two or more for "several".

[0062] Unless otherwise specified, the terms used in the present application have the well-known meanings commonly understood by those skilled in the art. Unless otherwise specified, the numerical values of the various parameters mentioned in the present application can be measured by various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the embodiments of the present application).

[0063] There are also some techniques that infer the change in the lithium content of the positive electrode active material based on the change in the diffraction peak intensity and / or peak height of the X-ray diffraction pattern or neutron diffraction pattern of the positive electrode active material. However, since lithium is inside the octahedron of the unit cell, when the lithium content is low, its change has a relatively small impact on the change in the characteristic peak intensity and / or peak height. Then, in the above method, there may be a significant change in the lithium content, but the change in the diffraction peak intensity and / or peak height is not obvious, which may lead to a relatively large lithium content error.

[0064] The technical solutions described in the embodiments of the present application are applicable to the detection method of the lithium content of the battery. The detection method of the lithium content of the battery disclosed in the present application can be used for lithium-ion batteries and can also be used for lithium-ion battery components, and the present application does not make any restrictions.

[0065] Please refer to Figure 1 , Figure 1 which is a schematic flow chart of the detection method of the lithium content of the battery provided by the embodiment of the present application.

[0066] See Figure 1 , the first aspect of the present application provides a detection method for the lithium content of a battery, including:

[0067] S1, obtaining the unit cell index of the positive electrode active material of the target battery.

[0068] S2, determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content.

[0069] Among them, the battery lithium content refers to the occupancy rate of lithium in the unit cell of the positive electrode active material of the lithium-ion battery. The occupancy rate of lithium refers to the probability that lithium statistically occupies a certain position in the unit cell. In the chemical formula, the battery lithium content refers to the subscript of lithium in the chemical formula of the positive electrode active material.

[0070] For example, the stoichiometric ratio is Li:TM (transition metal ion):O = 1:1:2 of LiNi 0.8 Co 0.1 Mn 0.1 O2 ternary positive electrode active material, belonging to the α-NaFeO2-type layered crystal structure of the hexagonal crystal system R-3m space group. In the crystal structure, lithium occupies the 3a(0 0 0) position. If all the 3a(0 0 0) positions in the crystal structure are occupied by lithium, the occupancy rate of lithium is 1, and its chemical formula is LiNi 0.8 Co 0.1 Mn 0.1O2, where the subscript of lithium is 1. If 80% of the 3a(00 0) positions in the crystal structure are occupied by lithium and 20% of the 3a(0 0 0) positions are not occupied by lithium (e.g., in the case of vacancies), then the occupancy rate of lithium is 0.8, and its chemical formula is Li 0.8 Ni 0.8 Co 0.1 Mn 0.1 O2, where the subscript of lithium is 0.8. It can be seen from this that the content of lithium in the positive electrode active material can be inferred through the occupancy rate of lithium.

[0071] The target battery refers to the battery or battery component for which the lithium content is to be detected. The positive electrode active material of the target battery refers to the active material in the positive electrode plate of the target battery.

[0072] The unit cell index of the positive electrode active material of the target battery refers to the parameter characterizing the unit cell information of the positive electrode active material of the target battery. For example, the parameter characterizing the shape and size of the unit cell of the positive electrode active material of the target battery.

[0073] Although lithium atoms are inside the octahedron of the unit cell, changes in its content will directly affect changes in the unit cell structure, and changes in the unit cell structure will directly affect changes in the unit cell index. Therefore, in this application, the change in the battery lithium content is obtained based on the degree of change in the unit cell index of the positive electrode active material, with a high accuracy rate.

[0074] The relationship between the unit cell index of the positive electrode active material and the lithium content refers to the corresponding relationship between the unit cell index of the positive electrode active material and the lithium content. In some embodiments, the relationship between the unit cell index of the positive electrode active material and the lithium content is a functional relationship, where the independent variable of the functional relationship is the unit cell index and the dependent variable is the lithium content.

[0075] In the embodiments of this application, the unit cell index of the positive electrode active material of the reference battery is changed through experiments, the corresponding battery lithium content under different unit cell indexes of the positive electrode active material is obtained, and then the relationship between the unit cell index of the positive electrode active material and the battery lithium content is constructed.

[0076] It is difficult to directly obtain the unit cell index of the material. In the embodiments of this application, according to the diffraction peak angle or the lattice fringes in the high-resolution transmission electron microscope pattern, the interplanar spacing of the positive electrode active material of the target battery is determined. According to the relationship between the interplanar spacing and the unit cell index, the unit cell index of the positive electrode active material is determined. Based on the determined unit cell index of the positive electrode active material, the lithium content of the positive electrode active material can be obtained quickly, simply, and accurately.

[0077] Exemplarily, taking the positive electrode active material of the target battery as LiNi 0.8 Co 0.1 Mn 0.1Taking O2 as an example, the first unit cell parameter a of the positive electrode active material is The relationship between the unit cell index of the positive electrode active material and the lithium content is as Figure 3 shown by the relational expression Occ(Li) = 19.972×a - 56.169, where Occ(Li) represents the lithium content of the positive electrode active material, and a represents the first unit cell parameter. Substituting the first unit cell parameter a as into the above relationship, the lithium content of the positive electrode active material of the target battery is determined to be 0.4257. At this time, the chemical formula of the positive electrode active material of the target battery is Li 0.4257 Ni 0.8 Co 0.1 Mn 0.1 O2, and the subscript of the lithium element is 0.4257, indicating that 42.57% of the 3a(0 0 0) positions in the unit cell of the positive electrode active material of the target battery at this time are occupied by lithium elements, and 57.43% of the 3a(0 0 0) positions are not occupied by lithium elements (such as the case of vacancies).

[0078] In the embodiments of the present application, by obtaining the unit cell index of the positive electrode active material of the target battery, and then according to the relationship between the unit cell index of the positive electrode active material and the lithium content, the lithium content of the positive electrode active material of the target battery is obtained. This method is simple, convenient, fast, has a high accuracy rate, and realizes the rapid detection of the lithium content of the battery.

[0079] In some embodiments, in S1, the step of obtaining the unit cell index of the positive electrode active material of the target battery includes:

[0080] S11, obtaining the X-ray diffraction pattern, neutron diffraction pattern or high-resolution transmission electron microscope pattern of the positive electrode active material.

[0081] Among them, the X-ray diffraction pattern refers to the spectrum recorded when the sample crystal diffracts X-rays at different angles. This spectrum includes multiple peaks with relatively high intensities and obvious characteristics. These peaks are related to the lattice parameters, structure types, crystal orientations, material properties, etc. of the crystal. By analyzing information such as the position, intensity and shape of the characteristic diffraction peaks, the crystallographic information of the crystal and the structural characteristics of the material can be determined.

[0082] The principle of the neutron diffraction pattern is similar to that of the X-ray diffraction pattern. The main differences include that the diffraction source of the X-ray diffraction pattern is X-rays, and the diffraction source of the neutron diffraction pattern is neutrons.

[0083] The high-resolution transmission electron microscope is Transmission Electron Microscope, abbreviated as TEM. The high-resolution transmission electron microscope pattern refers to the sub-microscopic or ultra-microscopic structure image of the sample obtained through TEM.

[0084] S12. Determine the unit cell parameters of the positive electrode active material of the target battery based on the obtained X-ray diffraction pattern, neutron diffraction pattern, or high-resolution transmission electron microscope image.

[0085] Among them, there are index parameters related to the unit cell parameters of the positive electrode active material of the target battery in the X-ray diffraction pattern, neutron diffraction pattern, or high-resolution transmission electron microscope image of the positive electrode active material of the target battery. The unit cell parameters of the positive electrode active material of the target battery can be easily obtained through the above three methods.

[0086] In the embodiments of the present application, through the three methods provided, that is, through the X-ray diffraction pattern, neutron diffraction pattern, or high-resolution transmission electron microscope image of the positive electrode active material, the unit cell parameters of the positive electrode active material of the target battery are obtained, and the method is simple and convenient.

[0087] In some embodiments, in S12, the steps of determining the unit cell parameters of the positive electrode active material of the target battery include:

[0088] S1211. Select several characteristic peaks in the obtained X-ray diffraction pattern or neutron diffraction pattern.

[0089] Among them, the characteristic peak refers to the diffraction peak for identifying the phase in the X-ray diffraction pattern or neutron diffraction pattern.

[0090] S1212. Determine the interplanar spacing of the positive electrode active material of the target battery according to the diffraction angles of the several characteristic peaks.

[0091] Among them, the diffraction angle refers to the position where the characteristic peak appears in the X-ray diffraction pattern or neutron diffraction pattern. The diffraction angle is usually represented by 2θ, that is, the angle between the incident light and the scattered light. The value of the diffraction angle can provide structural information of the relevant crystal, such as interplanar spacing and other information. The interplanar spacing refers to the distance between two adjacent crystal planes in a set of parallel crystal planes, and the size of the distance directly affects the properties and behaviors of substances.

[0092] S1213. Determine the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

[0093] Among them, since the interplanar spacing of the crystal is related to other indexes affecting the unit cell structure, therefore, the corresponding unit cell parameters can be obtained according to the value of the interplanar spacing of the crystal.

[0094] Exemplarily, the unit cell parameter is any unit cell parameter. Select a characteristic peak in the obtained X-ray diffraction pattern; substitute the diffraction angle of the obtained characteristic peak into the Bragg equation to obtain the interplanar spacing, and substitute the interplanar spacing into the relational formula between the unit cell parameter and the interplanar spacing to obtain the unit cell parameter.

[0095] Embodiments of the present application do not require disassembling the battery. By analyzing the X-ray diffraction pattern or neutron diffraction pattern, the unit cell parameters of the positive electrode active material of the target battery can be obtained. This method simply, conveniently, and efficiently realizes the non-destructive detection of the unit cell parameters of the target battery, and the battery after detection can still be used normally, saving battery costs.

[0096] In some embodiments, in S12, the steps of determining the unit cell parameters of the positive electrode active material of the target battery include:

[0097] S1221, select two adjacent lattice fringes in the obtained high-resolution transmission electron microscope image.

[0098] Among them, the lattice fringes appear as a series of parallel bright and dark fringes in the high-resolution transmission electron microscope image. According to diffraction theory, there is a definite relationship between the spacing of the lattice fringes and the lattice parameters. In the high-resolution transmission electron microscope image, by measuring the spacing of the lattice fringes, the interplanar spacing can be calculated.

[0099] In some embodiments, select a section of lattice fringes in the high-resolution transmission electron microscope image, then use a software tool such as a ruler measurement tool to measure the pixel spacing of the lattice fringes, and then calculate an approximate value of the spacing of the lattice fringes according to the proportional relationship between the pixels of the image and the actual distance. It should be noted that the measurement results of the lattice fringes are affected by various factors, such as the morphology of the sample, the crystallization quality, and the instrument performance. Therefore, in order to improve the measurement accuracy of the spacing of the lattice fringes, it is necessary to measure the spacing of the lattice fringes multiple times and perform statistical analysis on the results.

[0100] S1222, determine the interplanar spacing of the positive electrode active material of the target battery according to the spacing of the two adjacent lattice fringes.

[0101] S1223, determine the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

[0102] Embodiments of the present application obtain the unit cell parameters of the positive electrode active material of the target battery by analyzing the high-resolution transmission electron microscope image, which is beneficial to making the detection of the unit cell parameters of the target battery have high accuracy.

[0103] In some embodiments, in S1213 or S1223, the steps of determining the unit cell parameters of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery include:

[0104] S1231, determine the relationship between the unit cell parameters and the interplanar spacing of the positive electrode active material according to the crystal system to which the positive electrode active material of the target battery belongs.

[0105] Among them, the unit cell parameters include the edge lengths of the unit cell and the angles between the edge lengths. The relationship between the unit cell parameters of the crystal system and the interplanar spacing refers to the functional relationship between the unit cell parameters and the interplanar spacing. For those skilled in the art, information such as the relationship between the unit cell parameters of the crystal system and the interplanar spacing belongs to the prior art. After determining the crystal system to which the positive electrode active material of the target battery belongs, the relationship between the unit cell parameters and the interplanar spacing of this crystal system can be quickly queried.

[0106] S1232. Determine the unit cell parameters of the positive electrode active material according to the interplanar spacing of the positive electrode active material of the determined target battery and the relationship between the unit cell parameters of the positive electrode active material and the interplanar spacing.

[0107] S1233. Determine the unit cell index of the positive electrode active material of the target battery according to the relationship between the unit cell parameters of the positive electrode active material and the unit cell index.

[0108] Among them, the relationship between the unit cell parameters of the positive electrode active material and the unit cell index refers to the functional relationship formula between the unit cell parameters of the positive electrode active material and the unit cell index. In some embodiments, the independent variable of this functional relationship formula is the unit cell parameter, and the dependent variable is the unit cell index.

[0109] The embodiments of the present application obtain the unit cell index of the positive electrode active material through the interplanar spacing, and the implementation method is simple, convenient, and fast.

[0110] In some embodiments, in S1, the unit cell index includes one or more of unit cell parameters, unit cell volume, or transition metal layer spacing.

[0111] Among them, the unit cell parameter is a parameter describing the size and shape of the unit cell, and it includes indicators such as the edge length of the unit cell and the angles between the edge lengths.

[0112] The unit cell volume describes the arrangement of atoms or molecules in the crystal and is the basic unit of the crystal structure.

[0113] When calculating the unit cell volume, it is necessary to know the shape and size of the unit cell, that is, it is necessary to know the unit cell parameters. For different crystal structures, the unit cell parameters are also different. For example, for a cubic crystal structure, the unit cell is a cube, and for a hexagonal crystal structure, the unit cell is a hexahedron. After knowing the unit cell parameters of the unit cell, the unit cell parameters can be used to calculate the unit cell volume. For example, for a cubic crystal structure, the edge lengths of each side in its unit cell structure are equal, and the angles between the edge lengths are all 90°. It can be known that the unit cell volume of this crystal structure is the cube of the edge length of the unit cell. That is to say, after obtaining the edge length of the unit cell of this crystal structure, its unit cell volume can be calculated. In addition to the cubic crystal structure, there are many other crystal structures, such as face-centered cubic, body-centered cubic, etc. The calculation methods of the unit cell volume of each crystal structure are different, but all require obtaining the unit cell parameters.

[0114] The transition metal layer spacing refers to the interlayer distance formed by the arrangement of transition metal ions in the lattice in the ternary cathode active material. Transition metals refer to the elements in Groups 4 to 12 of the periodic table. In the ternary cathode active material, transition metals usually exist in the form of oxides, such as oxides of elements like nickel, cobalt, and manganese.

[0115] When calculating the transition metal layer spacing, the shape and size of the unit cell need to be known, that is, the unit cell parameters need to be known. For different crystal structures, the unit cell parameters are also different. For example, taking the cathode active material of the target battery as LiNi 0.8 Co 0.1 Mn 0.1 O2 as an example, it has a hexagonal crystal structure, and its transition metal layer spacing is one-third of the first unit cell parameter a. Therefore, after obtaining the first unit cell parameter a of this crystal structure, its transition metal layer spacing can be calculated.

[0116] The embodiments of the present application provide some specific unit cell indicators. According to the relationship between the unit cell indicators of the cathode active material and the lithium content, on the one hand, the lithium content of the battery can be detected, and on the other hand, the influence of lithium deintercalation / insertion during charge / discharge on the anisotropy of unit cell shrinkage / expansion can be quantitatively analyzed at the microscopic level, and / or the influence of lithium deintercalation / insertion during charge / discharge on the shrinkage / expansion of the unit cell volume can be quantitatively analyzed at the microscopic level, and / or the influence of the transition metal layer spacing on the crystal structure stability can be quantitatively analyzed at the microscopic level.

[0117] In some embodiments, in S2, the steps for constructing the relationship between the unit cell indicators of the cathode active material and the lithium content include:

[0118] S21, obtaining a plurality of X-ray diffraction patterns of the reference battery under a plurality of state of charge; the cathode active material of the reference battery and the cathode active material of the target battery are of the same cathode active material system.

[0119] Among them, the reference battery refers to the experimental battery used in the process of constructing the relationship between the unit cell parameters of the cathode active material and the lithium content of the cathode active material.

[0120] In some embodiments, by performing in-situ X-ray diffraction scanning on the reference battery, a plurality of X-ray diffraction patterns of the reference battery under a plurality of state of charge are obtained. In-situ X-ray diffraction refers to performing X-ray scanning analysis on the same area position of the same battery.

[0121] The State of Charge (SOC) refers to the ratio between the current charge of the battery and the full charge, usually expressed as a percentage. For example, 50% SOC means the current charge of the battery is half of the full charge. Taking the discharge process of the battery as an example, the positive electrode active material of the battery is in the process of lithium intercalation, and the lithium content of the battery changes from low to high. Taking the charging process of the battery as an example, the positive electrode active material of the battery is in the process of lithium deintercalation, and the lithium content of the battery changes from high to low. That is to say, the lithium content of the battery is different with different reference battery SOCs.

[0122] Taking the positive electrode active material of the target battery as LiNi 0.8 Co 0.1 Mn 0.1 O2 as an example, the positive electrode active material in the reference battery is also LiNi 0.8 Co 0.1 Mn 0.1 O2.

[0123] S22. Obtain the unit cell index of the positive electrode active material at any state of charge according to the diffraction peak angle of the X-ray diffraction pattern at any state of charge.

[0124] S23. Obtain the relationship between the unit cell index of the positive electrode active material and the lithium content at any state of charge according to the unit cell index of the positive electrode active material at any state of charge.

[0125] S24. Collect the relationships between the unit cell indices and lithium contents of the positive electrode active materials at several states of charge, and construct the relationship between the unit cell index of the positive electrode active material and the lithium content.

[0126] In the embodiments of the present application, by performing X-ray scanning analysis on the same area position of the reference battery at different states of charge, a series of data pairs of the unit cell parameters and lithium content of the positive electrode active material of the reference battery are obtained. Thus, according to the obtained multiple data sets, the lithium content curve of the positive electrode active material of the reference battery under different unit cell parameters is obtained. This curve serves as a database of the battery lithium content of this positive electrode active material system. In the future, when a battery under test or a battery component under test needs to obtain the battery lithium content, the battery lithium content can be directly obtained, and the method is simple, fast, and non-destructive.

[0127] In the embodiments of the present application, in-situ X-ray diffraction is performed on the reference battery, and the obtained data has high comparability. For non-in-situ X-ray diffraction of the reference battery, due to the influence of operations such as disassembling the battery, washing the electrode sheet, and transferring, it is often impossible to well restore the true state of the positive electrode active material of the battery during the charge and discharge process, and it will also lead to the obtained information not having good comparability.

[0128] In some embodiments, in S22, the step of obtaining the relationship between the unit cell index and the lithium content of the positive electrode active material in any state of charge includes:

[0129] S221, perform a full-profile fitting on the obtained X-ray diffraction pattern in any state of charge to obtain the relationship between the unit cell index and the lithium content of the positive electrode active material in any state of charge.

[0130] Full-profile fitting refers to a method of presetting structural parameters on a hypothetical crystal structure model to calculate the theoretical X-ray diffraction spectrum of the crystal, adjusting the preset structural parameters to make the calculated theoretical X-ray diffraction spectrum of the crystal coincide with the experimental spectrum, so as to obtain the unit cell index of the actual crystal. In the embodiments of the present application, through full-profile fitting, through continuous refinement and fitting of the calculated spectrum and the measured spectrum of the crystal structure, the lithium content of the measured crystal is obtained.

[0131] In the embodiments of the present application, the relationship between the unit cell index and the lithium content of the positive electrode active material is constructed by the method of full-profile fitting. When it is necessary to obtain the battery lithium content of the battery under test or the battery component under test, only need to irradiate the battery under test or the battery component under test with X-rays, obtain the corresponding X-ray diffraction pattern, and then the unit cell index of the positive electrode active material of the battery under test or the battery component under test can be determined. Then substitute the unit cell index into the relationship between the unit cell index and the lithium content of the positive electrode active material of the same crystal system, and the obtained lithium content is the battery lithium content of the battery under test or the battery component under test. This method is fast, convenient and has high accuracy.

[0132] In some embodiments, in S221, the step of performing a full-profile fitting on the obtained X-ray diffraction pattern in any state of charge includes:

[0133] S2211, select the measured X-ray diffraction pattern of the positive electrode active material of the reference battery in any state of charge.

[0134] S2212, preset the parameters of the influence factors of the unit cell structure of the positive electrode active material to obtain the theoretical X-ray diffraction pattern of the positive electrode active material.

[0135] Among them, the influence factor of the unit cell structure refers to the index that affects the unit cell structure. In some embodiments, the parameters of the influence factor of the unit cell structure include the unit cell parameters of the phase, space group, each element in the crystal, valence state of each element, number of each element and occupancy situation, isotropic factor and other indexes.

[0136] S2213, by adjusting the parameters of the influence factor, make the residual between the diffraction peak data of the theoretical X-ray diffraction pattern and the diffraction peak data of the measured X-ray diffraction pattern less than or equal to the threshold value, and the unit cell parameters and lithium content corresponding to the adjusted theoretical X-ray diffraction pattern are defined as the unit cell parameters and lithium content of the reference battery.

[0137] Among them, the measured X-ray diffraction pattern obtained by S2211 corresponds to a set of measured diffraction peak data, but the crystal structure of the measured diffraction pattern is unknown. It is difficult to directly detect the crystal structure of the measured diffraction pattern and it is not easy to implement.

[0138] S2212 and S2213 make the theoretical X-ray diffraction pattern of the preset crystal structure continuously approach the measured X-ray diffraction pattern obtained by S2211 through the method of full-spectrum fitting, and obtain the data pair of the unit cell parameters and the lithium content according to the data of the obtained theoretical X-ray diffraction pattern.

[0139] The embodiment of the present application is convenient for obtaining the lithium content corresponding to the reference battery under multiple unit cell indexes through the provided full-spectrum fitting method, and the accuracy of the obtained result is high and it is easy to implement.

[0140] In some embodiments, in S2, the step of determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content includes:

[0141] Step S01, in a database with the relationship between the unit cell indexes and lithium content of several positive electrode active materials, search for the relationship between the unit cell indexes and lithium content of the positive electrode active material corresponding to the positive electrode active material of the target battery.

[0142] Step S02, substitute the unit cell index of the positive electrode active material of the target battery into the corresponding relationship between the unit cell index of the positive electrode active material and the lithium content to obtain the lithium content of the positive electrode active material of the target battery.

[0143] The embodiment of the present application constructs a database containing the relationship between the unit cell indexes and lithium content of various positive electrode active materials. In the future, when it is necessary to obtain the lithium content of the target battery, as long as the unit cell index of the positive electrode active material of the target battery is obtained, the lithium content of the target battery can be obtained simply and quickly, which has a high application prospect for the testing of the lithium content of a large number of target batteries.

[0144] In some embodiments, the positive electrode active material of the target battery has a layered crystal structure.

[0145] Among them, the layered crystal structure refers to a crystal structure in which, inside the crystal, atomic, molecular or ionic groups form a two-dimensional extended layered structure, with strong short-range forces within the layer and a two-dimensional period matching the crystal structure, and weak long-range forces between the layers.

[0146] In a second aspect, the embodiment of the present application provides a device for detecting the lithium content of a battery. The device for detecting the lithium content of a battery includes:

[0147] An acquisition module, which is used to acquire the crystal index of the positive electrode active material of a target battery;

[0148] A processing module, which is used to determine the lithium content of the positive electrode active material of the target battery according to the crystal index of the positive electrode active material of the target battery and the relationship between the crystal index of the positive electrode active material and the lithium content.

[0149] The detection device for the lithium content of the battery has at least the same advantages as the detection method for the lithium content of the battery, and can realize the rapid detection of the lithium content of the battery.

[0150] In order to make the technical problems, technical solutions and beneficial effects solved by the embodiments of the present application clearer, the following will be further described in detail with reference to the embodiments and the drawings. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present application and its application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present application.

[0151] Embodiment 1

[0152] First, construct the relationship between the unit cell parameters of the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O2 and the lithium content:

[0153] (1) Select a reference battery, and the chemical formula of the positive electrode active material of the reference battery is LiNi 0.8 Co 0.1 Mn 0.1 O2; put the reference battery into a charge-discharge instrument, and while discharging (in some other embodiments, it can also be charging) at a constant current, perform in-situ X-ray diffraction scanning on the reference battery. Specifically, control the reference battery to release the same amount of electricity per unit time, and collect the X-ray diffraction pattern of the reference battery once, and obtain several X-ray diffraction patterns of the reference battery as shown in Figure 2 shown.

[0154] (2) Select the measured X-ray diffraction pattern of the positive electrode active material of the reference battery at a certain state of charge from several X-ray diffraction patterns of the reference battery shown in Figure 2 shown.

[0155] (3)Perform a full-spectrum fitting on the obtained measured X-ray diffraction pattern. Specifically, preset the parameters of the influencing factors of the unit cell structure of the positive electrode active material to obtain the theoretical X-ray diffraction pattern of the positive electrode active material. Adjust the parameters of the influencing factors so that the residual between the diffraction peak data of the theoretical X-ray diffraction pattern and the diffraction peak data of the measured X-ray diffraction pattern is less than or equal to the threshold. The unit cell parameters and lithium content corresponding to the adjusted theoretical X-ray diffraction pattern are defined as the unit cell parameters and lithium content of the positive electrode active material of the reference battery at this state of charge.

[0156] (4)Collect the data pairs of the unit cell parameters and lithium content of the positive electrode active material of the reference battery at several states of charge. Take the unit cell parameters as the independent variable and the lithium content as the dependent variable to obtain the relationship between the unit cell index and lithium content of the positive electrode active material of the reference battery as shown in Figure 3 .

[0157] (5)The slope of the obtained lithium content curve is 19.972 and the intercept is -56.169. Determine the relationship between the unit cell parameters and lithium content of the positive electrode active material, specifically Occ(Li) = 19.972×a - 56.169.

[0158] Secondly, detect the battery lithium content of the target battery. The detection method includes:

[0159] (6)Use X-rays to penetrate the target battery to obtain the X-ray diffraction pattern of the positive electrode active material of the target battery as shown in Figure 4 .

[0160] (7)Select the first characteristic peak (003) and the second characteristic peak (101) from the obtained X-ray diffraction pattern. It can be seen from the X-ray diffraction pattern that the diffraction peak angle 2θ1 of the first characteristic peak (003) is 18.502°, and the diffraction peak angle 2θ2 of the second characteristic peak (101) is 37.238°.

[0161] (8)Substitute the diffraction peak angle 2θ1 of the first characteristic peak and the diffraction peak angle 2θ2 of the second characteristic peak into the Bragg equation 2d (hkl) sinθ = nλ, where d (hkl) represents the interplanar spacing, θ represents half of the diffraction peak angle of the characteristic peak, and λ represents the wavelength of the X-ray, respectively, to obtain the first interplanar spacing and the second interplanar spacing of the positive electrode active material of the target battery. Among them, the X-ray is CuKα ray, and the wavelength λ is

[0162] (9) It is determined that the positive electrode active material of the target battery has a layered crystal structure of hexagonal crystal system; the crystal structure of the hexagonal crystal system includes 6 lattice parameters, namely: three edge length parameters and three face angle parameters of the unit cell; among them, the three edge length parameters are the first lattice parameter a, the second lattice parameter b, and the third lattice parameter c respectively; the three face angle parameters are the first face angle parameter α, the second face angle parameter β, and the third face angle parameter γ respectively. Among them, the three face angle parameters α, β, and γ are fixed values, which are 90°, 90°, and 120° in sequence. The first lattice parameter a is equal to the second lattice parameter b.

[0163] The relationship between the interplanar spacing and the lattice parameters is where d (hkl) represents the interplanar spacing, h represents the first Miller index, k represents the second Miller index, l represents the third Miller index, a represents the first lattice parameter, and c represents the third lattice parameter.

[0164] Among them, the first lattice parameter a, the second lattice parameter b, and the third lattice parameter c are converted into three smallest integers in the same proportion, that is, the least common multiple m of a, b, and c is taken, the first Miller index h = m * 1 / a, the second Miller index k = m * 1 / b, and the third Miller index l = m * 1 / c.

[0165] (10) Substitute the first interplanar spacing and the second interplanar spacing into the relationship between the interplanar spacing and the lattice parameters to obtain two functional expressions of the first lattice parameter a and the third lattice parameter c, and analyze these two functional expressions to obtain the specific values of the first lattice parameter a and the third lattice parameter c, where the first lattice parameter The third lattice parameter

[0166] (11) In the database of the relationship between the lattice parameters and the lithium content of several positive electrode active materials, find that the relationship between the lattice parameters and the lithium content of the positive electrode active material corresponding to the positive electrode active material of the target battery is Occ(Li) = 19.972×a - 56.169.

[0167] (12) Substitute the obtained first lattice parameter of the positive electrode active material of the target battery into the corresponding relationship formula Occ(Li) = 19.972×a - 56.169 between the lattice parameters and the lithium content of the positive electrode active material, where Occ(Li) represents the lithium content of the positive electrode active material, and a represents the lattice parameter, and analyze that the lithium content of the positive electrode active material in the target battery is 0.4257.

[0168] Examples 2 to 4 are similar to Example 1, the difference is that the first lattice parameters a analyzed in step (10) of Examples 2 to 4 are respectively

[0169] Example 5 is similar to Example 1, except that in Example 5, the unit cell index is the unit cell volume, and the relationship between the unit cell volume of the positive electrode active material determined in step (5) and the lithium content is Step (10) further includes calculating the unit cell volume, and the specific value is

[0170] Example 6 is similar to Example 1, except that in Example 6, the unit cell index is the transition metal layer spacing, and the relationship between the transition metal layer spacing of the positive electrode active material determined in step (5) and the lithium content is Occ(Li) = 11.7615×d M -56.169, d M represents the transition metal layer spacing; step (10) further includes calculating the transition metal layer spacing, and the specific value is

[0171] Example 7 is similar to Example 1, except that in step (1), the chemical formula of the positive electrode active material of the reference battery is LiMn2O4; the relationship between the unit cell parameters of the positive electrode active material determined in step (5) and the lithium content of the positive electrode active material is Occ(Li) = -3.7856×a + 31.424, as Figure 5 shown; in step (7), only the first characteristic peak (111) is selected, and its diffraction peak angle 2θ1 is 18.8°; in step (8), only the diffraction peak angle of the first characteristic peak (111) needs to be substituted into the Bragg equation; in step (9), it is determined that the positive electrode active material of the target battery is a layered crystal structure of a cubic crystal system; in this cubic crystal structure, the first unit cell parameter a, the second unit cell parameter b, and the third unit cell parameter c are all equal, and the three face angle parameters α, β, and γ are fixed values, all being 90°; the specific value of the first unit cell parameter a obtained by analysis in step (10) is In step (11), the relationship between the unit cell parameters of the positive electrode active material and the lithium content is Occ(Li) = -3.7856×a + 31.424; in step (12), the lithium content of the positive electrode active material in the battery to be tested is analyzed as 0.5714.

[0172] The positive electrode plate of the target battery in each example is disassembled, and an inductively coupled plasma emission spectrometer (ICP) is used to test the molar ratio of various elements in the positive electrode active material of the positive electrode plate, and in this way, the lithium content of the positive electrode active material is obtained.

[0173] For the specific values of the lithium content of the target batteries in Examples 1 to 7 obtained by the battery lithium content detection method provided by the present application and the lithium content of the target batteries in each example tested by an inductively coupled plasma emission spectrometer, please refer to Table 1.

[0174] Table 1 Lithium content of the target battery in Examples 1-7 obtained by the lithium content detection method provided by this application and the lithium content tested by inductively coupled plasma optical emission spectrometer

[0175]

[0176] As can be seen from Table 1, in each example, the lithium content obtained by the lithium content detection method provided by this application is relatively close to the lithium content tested by inductively coupled plasma optical emission spectrometer, indicating that the lithium content detection method provided by the examples of this application is relatively accurate, and the detection is fast, easy to implement, and has good application prospects.

[0177] In several embodiments provided by this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. For example, the device embodiments described above are only illustrative. For example, the division of units is only a logical function division. In actual implementation, there may be other division methods. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Another point, the displayed or discussed mutual coupling or direct coupling or communication connection can be through some interfaces, indirect coupling or communication connection of devices or units, and can be in electrical, mechanical or other forms.

[0178] In addition, in each embodiment of this application, each functional unit can be integrated in a processing unit, or each unit can exist physically alone, or two or more units can be integrated in one unit. The above integrated unit can be implemented in the form of hardware or in the form of a software functional unit.

[0179] The above is only the implementation manner of this application, and does not limit the patent scope of this application. All equivalent structure or equivalent process transformations made by using the content of the specification and drawings of this application, or directly or indirectly applied in other related technical fields, are equally included in the patent protection scope of this application.

Claims

1. A method for detecting the lithium content of a battery, characterized in that, Including: Obtaining the unit cell index of the positive electrode active material of the target battery; Determining the lithium content of the positive electrode active material of the target battery according to the unit cell index of the positive electrode active material of the target battery and the relationship between the unit cell index of the positive electrode active material and the lithium content.

2. The method for detecting the lithium content of the battery according to claim 1, wherein, The step of obtaining the unit cell index of the positive electrode active material of the target battery includes: Obtaining an X-ray diffraction pattern, a neutron diffraction pattern or a high-resolution transmission electron microscope pattern of the positive electrode active material; Determining the unit cell index of the positive electrode active material of the target battery according to the obtained X-ray diffraction pattern, neutron diffraction pattern or high-resolution transmission electron microscope pattern.

3. The method for detecting the lithium content of the battery according to claim 2, wherein The step of determining the unit cell index of the positive electrode active material of the target battery includes: Selecting a plurality of characteristic peaks in the obtained X-ray diffraction pattern or neutron diffraction pattern; Determining the interplanar spacing of the positive electrode active material of the target battery according to the diffraction peak angles of the plurality of characteristic peaks; Determining the unit cell index of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

4. The detection method of lithium content in the battery according to claim 2, characterized in that The step of determining the unit cell index of the positive electrode active material of the target battery includes: Selecting two adjacent lattice fringes in the obtained high-resolution transmission electron microscope pattern; Determining the interplanar spacing of the positive electrode active material of the target battery according to the spacing between the two adjacent lattice fringes; Determining the unit cell index of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery.

5. The method for detecting the lithium content of the battery according to claim 3 or 4, characterized in that, The step of determining the unit cell index of the positive electrode active material of the target battery according to the interplanar spacing of the positive electrode active material of the target battery includes: Determining the relationship between the unit cell parameters and the interplanar spacing of the positive electrode active material according to the crystal system to which the positive electrode active material of the target battery belongs; Determining the unit cell parameters of the positive electrode active material according to the determined interplanar spacing of the positive electrode active material of the target battery and the relationship between the unit cell parameters and the interplanar spacing of the positive electrode active material; Determining the unit cell index of the positive electrode active material of the target battery according to the relationship between the unit cell parameters of the positive electrode active material and the unit cell index.

6. The method for detecting the lithium content of the battery according to any one of claims 1 to 5, characterized in that, The unit cell index includes one or more of unit cell parameters, unit cell volume or transition metal layer spacing.

7. The detection method for the lithium content of the battery according to any one of claims 1 to 6, characterized in that, The construction step of the relationship between the unit cell index of the positive electrode active material and the lithium content includes: Obtaining a plurality of X-ray diffraction patterns of the reference battery under a plurality of state of charge; the positive electrode active material of the reference battery and the positive electrode active material of the target battery are of the same positive electrode active material system; Obtaining the unit cell index of the positive electrode active material under any state of charge according to the diffraction peak angle of the X-ray diffraction pattern obtained under any state of charge; Obtaining the relationship between the unit cell index of the positive electrode active material and the lithium content under any state of charge according to the unit cell index of the positive electrode active material obtained under any state of charge; Collecting the relationships between the unit cell index of the positive electrode active material and the lithium content under a plurality of states of charge, and constructing the relationship between the unit cell index of the positive electrode active material and the lithium content.

8. The detection method of the lithium content of the battery according to claim 7, characterized in that, The step of obtaining the relationship between the unit cell index of the positive electrode active material and the lithium content under any state of charge includes: Perform a full-spectrum fitting on the obtained X-ray diffraction pattern at any state of charge to obtain the relationship between the unit cell parameters and lithium content of the cathode active material at any state of charge.

9. The detection method of the lithium content of the battery according to claim 8, wherein The step of performing a full-spectrum fitting on the obtained X-ray diffraction pattern at any state of charge includes: Select the measured X-ray diffraction pattern of the cathode active material of the reference battery at any state of charge; Preset the parameters of the influencing factors of the unit cell structure of the cathode active material to obtain the theoretical X-ray diffraction pattern of the cathode active material; By adjusting the parameters of the influencing factors, make the residual between the diffraction peak data of the theoretical X-ray diffraction pattern and the diffraction peak data of the measured X-ray diffraction pattern less than or equal to the threshold. The unit cell parameters and lithium content corresponding to the adjusted theoretical X-ray diffraction pattern are defined as the unit cell parameters and lithium content of the cathode active material of the reference battery.

10. The method for detecting the lithium content of the battery according to claim 1, wherein The step of determining the lithium content of the cathode active material of the target battery according to the unit cell parameters of the cathode active material of the target battery and the relationship between the unit cell parameters of the cathode active material and the lithium content includes: In a database with the relationship between the unit cell parameters and lithium content of several cathode active materials, search for the relationship between the unit cell parameters and lithium content of the cathode active material corresponding to the target battery; Substitute the unit cell index of the cathode active material of the target battery into the corresponding relationship between the unit cell parameters of the cathode active material and the lithium content to obtain the lithium content of the cathode active material of the target battery.

11. A detection device for the lithium content of a battery, characterized in that, The detection device for the lithium content of the battery includes: An acquisition module for acquiring the crystal parameters of the cathode active material of the target battery; A processing module for determining the lithium content of the cathode active material of the target battery according to the crystal parameters of the cathode active material of the target battery and the relationship between the crystal parameters of the cathode active material and the lithium content.

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