CN115312769A

CN115312769A - Lithium supplement additive and particle size control method and application thereof

Info

Publication number: CN115312769A
Application number: CN202111681198.0A
Authority: CN
Inventors: 钟文; 万远鑫; 孔令涌; 朱成奔
Original assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Current assignee: Shenzhen Dynanonic Innovazone New Energy Technology Co Ltd
Priority date: 2021-12-30
Filing date: 2021-12-30
Publication date: 2022-11-08

Abstract

The application discloses a lithium supplement additive, and a particle size control method and application thereof. The variation coefficient CV value of the particle size distribution of the lithium supplement additive is less than 0.5. The particle size control method of the lithium supplement additive comprises the following steps: screening the prepared lithium supplement additive; and (3) measuring or calculating the CV value of the particle size distribution variation coefficient of the screened lithium supplement additive, and collecting the lithium supplement additive with the CV value of the variation coefficient less than 0.5. The lithium supplement additive has uniform particle size, on one hand, the difference of lithium ion removal rates in the first charging process is small, and the high-efficiency and stable lithium supplement effect can be realized; on the other hand, the electrode plate used for preparing the electrode plate has high surface quality, can be uniformly dispersed in an active layer of the electrode plate, and improves the quality and the electrochemical performance of the electrode plate. The particle size control method can ensure that the obtained lithium supplement additive has uniform particle size, is high in efficiency and saves control cost.

Description

Lithium supplement additive and particle size control method and application thereof

Technical Field

The application belongs to the field of secondary batteries, and particularly relates to a lithium supplement additive, and a particle size control method and application thereof.

Background

The oil energy crisis problems in the 60 and 70 th 20 th century forced people to find new alternative new energy sources, with the increasing awareness of environmental protection and energy crisis. Lithium ion batteries are considered to be one of the most promising energy sources because of their advantages of high operating voltage and energy density, relatively small self-discharge level, no memory effect, no pollution from heavy metal elements such as lead and cadmium, and ultra-long cycle life.

In the first charging process of the lithium ion battery, the surface of the negative electrode is usually accompanied by the formation of a solid electrolyte film SEI (solid electrolyte film), and the process consumes a large amount of Li ⁺ Meaning Li extracted from the cathode material ⁺ Part of the energy is irreversibly consumed, and the reversible specific capacity of the corresponding battery core is reduced. The cathode material, especially silicon-based cathode material, further consumes Li ⁺ Causing lithium loss of the anode material and reducing the first coulombic efficiency and the battery capacity of the battery. As in lithium ion battery systems using graphite cathodes, the first charge consumes about 10% of the lithium source. The depletion of the positive lithium source is further exacerbated when high specific capacity anode materials are employed, such as alloys (silicon, tin, etc.), oxides (silicon oxide, tin oxide) and amorphous carbon anodes.

In order to solve the problem of low coulombic efficiency caused by irreversible loss of the negative electrode, the requirement of high energy density can be met by supplementing lithium to the positive electrode besides pre-lithiating the negative electrode material and the pole piece. As the theoretical capacity of the lithium-rich iron-based material reported at present is up to 867mAh/g, the working voltage window is consistent with that of the conventional lithium ion battery, and the lithium-rich iron-based material does not participate in the electrochemical process at the later stage, so that the lithium-rich iron-based material is a lithium supplement additive with wide prospect.

However, in practical application, the existing lithium supplement additive has some defects, specifically, the performance of lithium supplement is unstable, and salient points or uneven aggregation and dispersion of particles are easy to generate when a pole piece is formed by coating. Or further there are particles in which the thickness of the coating layer is excessively different, thereby affecting the extraction and conduction of lithium ions.

Disclosure of Invention

The application aims to overcome the defects in the prior art, and provides a lithium supplement additive and a particle size control method thereof, so as to solve the technical problems that the lithium supplement performance of the existing lithium supplement additive is unstable, and agglomeration is caused or salient points exist in a pole piece.

Another object of the present application is to provide an electrode tab and a secondary battery including the same, so as to solve the technical problem that the electrochemical performance of the existing secondary battery, such as the first coulombic efficiency, is not ideal.

In order to achieve the above object, in a first aspect of the present application, a lithium supplement additive is provided. The CV value of the particle size distribution variation coefficient of the lithium supplement additive is less than 0.5.

Further, the coefficient of variation CV value is 0.4 or less.

Further, the lithium supplement additive is of a core-shell structure, a core body of the lithium supplement additive comprises a lithium supplement material, and a shell layer of the lithium supplement additive is a hydrophobic packaging layer.

Further, the lithium-supplementing material is L _x M _y N _z O _q 、Li _w At least one of A, wherein L in the molecular formula is Li or/and a mixed alkali metal element of Li and not more than 30% of at least one of K, na; m comprises at least one of Fe, co, ni, mn, V, fe-Co, cu, mo, al, ti and Mg; n comprises at least one of Fe, co, mn, ni, si, al or other equivalent or aliovalent metal elements; o is oxygen element; a is at least one element of C, N, O, P, S, F, B, se, x is 4-6,y is 0.7-1.0, z is 0.01-0.3, q is 4-5,0 < w ≦ 5.

Further, the hydrophobic encapsulation layer includes at least one of an ion conductor encapsulation layer and an electron conductor encapsulation layer.

Furthermore, the capacity of the electrode plate prepared from the lithium supplement additive, the conductive agent and the binder is not more than 30% when the electrode plate is stored for 20 hours under the environment humidity of 25% relative to the capacity decay rate when the electrode plate is stored for 0.5 hour; wherein, the lithium supplement additive is in the core-shell structure.

Furthermore, the capacity of the electrode plate prepared from the lithium supplement additive, the conductive agent and the binder when the electrode plate is stored for 20 hours under the environment humidity of 10 percent is not more than 20 percent relative to the capacity decay rate when the electrode plate is stored for 0.5 hour; wherein, the lithium supplement additive is in the core-shell structure.

In a second aspect of the present application, a method of controlling the particle size of a lithium supplement additive of the present application is provided. The particle size control method of the lithium supplement additive comprises the following steps:

screening the prepared lithium supplement additive;

and (3) measuring or calculating the CV value of the particle size distribution variation coefficient of the screened lithium supplement additive, and collecting the lithium supplement additive with the CV value of the variation coefficient less than 0.5.

Further, the method for calculating the variation coefficient CV value of the particle size distribution of the lithium supplement additive after screening treatment comprises the following steps:

carrying out particle size determination treatment on the screened lithium supplement additive, and calculating a particle size distribution variation coefficient CV value according to detected particle size data;

the method for measuring the particle size of the screened lithium supplement additive comprises the following steps:

and obtaining a field emission scanning electron microscope picture of the screened lithium supplement additive, selecting a plurality of sample particles in the field emission scanning electron microscope picture, and measuring the particle sizes of the sample particles.

Further, the step of measuring the particle size of several sample particles is preceded by a step of magnifying a field emission scanning electron microscope photograph.

Further, the CV value of the particle size distribution calculated from the measured particle size data is calculated according to the following formula:

wherein N represents the total number of sample particles, X _i Indicates the particle size of the ith sample particle,

to representAverage of particle sizes of all samples.

Further, the screening treatment is multi-stage screening treatment, and the lithium supplement additive obtained by screening treatment at each stage is respectively subjected to particle size measurement treatment and calculation of a CV (coefficient of variation) value of particle size distribution.

In a third aspect of the present application, an electrode sheet is provided. The electrode plate comprises a current collector and an electrode active layer combined on the surface of the current collector, wherein the electrode active layer is doped with the lithium supplement additive or the lithium supplement additive obtained by the particle size control method of the lithium supplement additive.

In a fourth aspect of the present application, a secondary battery is provided. The electrode plate comprises a positive plate and a negative plate, wherein the positive plate and/or the negative plate are electrode plates.

Compared with the prior art, the method has the following technical effects:

the variation coefficient CV value of the particle size distribution of the lithium supplement additive is controlled to be below 0.5 or further below 0.4, so that the lithium supplement additive has uniform particle size, on one hand, the difference of the lithium ion extraction rate in the first charging process is small, and the efficient and stable lithium supplement effect can be realized; on the other hand, the electrode plate used for preparing the electrode plate has high surface quality, can be uniformly dispersed in an active layer of the electrode plate, and improves the quality and the electrochemical performance of the electrode plate.

The particle size control method of the lithium supplement additive can effectively enable the particle size of the lithium supplement additive to be uniform, and enables the lithium supplement additive to have the effect of the lithium supplement additive applied in the text. Meanwhile, on the premise of ensuring the uniform particle size of the lithium supplement additive, the lithium supplement additive with different particle size gradients can be obtained through screening treatment, and the application requirements of the lithium supplement additive with different particle sizes are met. In addition, the particle size control method of the lithium supplement additive can ensure that the obtained lithium supplement additive has uniform particle size, is high in efficiency and saves control cost.

The electrode slice of the application is provided with the lithium supplement additive, so that the components contained in the electrode active layer of the electrode slice of the application are uniformly dispersed, the film layer is high in quality, the adverse phenomenon that the salient points and the effective components are gathered can be effectively avoided, and the electrode slice of the application is endowed with excellent electrochemical performance. In the process of charging and discharging, the difference of lithium removal rates of the lithium supplement additive contained in the lithium supplement additive is small, and lithium ions can be efficiently provided, so that the first effect and the whole electrochemical performance of the battery are improved.

The secondary battery comprises the electrode plate, so that the lithium ion battery has excellent first coulombic efficiency, battery capacity and cycle performance, long service life and stable electrochemical performance.

Drawings

In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings used in the detailed description or the prior art description will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is an SEM image at 1000 times magnification of the lithium supplement additive provided in example 1 of the present application.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application more clearly apparent, the present application is further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

In this application, the term "and/or" describes an association relationship of associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a is present alone, A and B are present simultaneously, and B is present alone. Wherein A and B can be singular or plural. The character "/" generally indicates that the former and latter associated objects are in an "or" relationship.

In the present application, "at least one" means one or more, "a plurality" means two or more. "at least one of the following" or similar expressions refer to any combination of these items, including any combination of the singular or plural items. For example, "at least one (a), b, or c", or "at least one (a), b, and c", may each represent: a, b, c, a-b (i.e., a and b), a-c, b-c, or a-b-c, wherein a, b, and c may be single or plural, respectively.

It should be understood that, in various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, some or all of the steps may be executed in parallel or executed sequentially, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.

The terminology used in the embodiments of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. As used in the examples of this application and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

The weight of the related components mentioned in the description of the embodiments of the present application may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present application as long as it is scaled up or down according to the description of the embodiments of the present application. Specifically, the mass described in the specification of the embodiments of the present application may be a mass unit known in the chemical industry field such as μ g, mg, g, kg, etc.

The terms "first" and "second" are used for descriptive purposes only and are used for distinguishing purposes such as substances from one another, and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. For example, a first XX may also be referred to as a second XX, and similarly, a second XX may also be referred to as a first XX, without departing from the scope of embodiments of the present application. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

The inventor of the application finds that the particle size of the existing lithium supplement additive has obvious influence and obvious correlation on the lithium supplement effect, the quality of an electrode plate and the electrochemical performance. The embodiment of the application provides a lithium supplement additive and a particle size control method.

In a first aspect, the present embodiments provide a lithium supplement additive. The coefficient of variation CV value of the particle size distribution of the lithium supplement additive in the examples of the present application is 0.5 or less, and more preferably 0.4 or less. In this way, the coefficient of variation CV of the particle size distribution of the lithium supplement additive in the examples of the present application was 0.5 or less, or further controlled to 0.4 or less, and therefore, the particle size distribution width was narrow and the particle size was uniform. Due to the uniform particle size and the small difference of the removal rate of the contained lithium ions, the lithium ions can be removed in the first circle of the charging process, a large amount of lithium ions are provided, and all the lithium ions are released concentratedly as much as possible to supplement the irreversible lithium ions consumed by the SEI film formed on the negative electrode, so that the high first effect is given to the lithium ion battery, and the large particles and the small particles can be avoided because of the Li ⁺ The difference in the dissolution rate causes the phenomenon that the lithium supplementing performance is unstable. On the other hand, the particle size is uniform, so that the surface quality of the formed electrode active layer is high, the surface quality of the electrode plate is ensured, the components in the electrode active layer can be uniformly dispersed, and the quality and the electrochemical performance of the electrode plate are improved.

The lithium supplement additive in the embodiment of the application can be an existing lithium supplement additive, can also be a lithium supplement additive improved or modified according to the existing lithium supplement additive, and can also be a newly developed lithium supplement additive. No matter what kind of lithium supplement additive is, the CV value of the particle size distribution of the lithium supplement additive in the examples of the present invention is 0.5 or less, and further 0.4 or less.

In the examples, the lithium supplement additive of the examples is a core-shell structure, the core body of which includes a lithium supplement material, and the shell layer of which is a hydrophobic encapsulation layer.

When the lithium supplement additive in the embodiment of the present application has the core-shell structure, in the embodiment, the core body including the lithium supplement material may include L _x M _y N _z O _q 、Li _w At least one of A. Wherein L is _x M _y N _z O _q L in the molecular formula is Li or/and Li and does not exceed30% excess of at least one mixed alkali metal element of K, na; m comprises at least one of Fe, co, ni, mn, V, fe-Co, cu, mo, al, ti and Mg; n comprises at least one of Fe, co, mn, ni, si, al or other equivalent or aliovalent metal elements; o is oxygen element; x is 4-6,y of 0.7-1.0, z is 0.01-0.3, and q is 4-5. Therefore, the lithium supplement material may be at least one of an iron-based lithium supplement material, a manganese-based lithium supplement material, a nickel-based lithium supplement material, and the like, depending on the kind of element M. In a particular embodiment, L _x M _y N _z O _q Wherein M is Fe and N is Al. At this time, L _x M _y N _z O _q The lithium-rich lithium-supplementing material shown may be Li ₅ Fe _0.98 Al _0.02 O ₄ . But not exclusively Li ₂ NiO ₂ 、Li ₅ FeO ₄ 、LiCoO ₂ 、LiMn ₂ O ₄ 、LiFePO ₄ And the like. The lithium supplement materials are rich in lithium, and can release lithium ions in the first circle of charging process to play an effective lithium supplement role. When this mend lithium material for anti fluorite structure, can also improve and mend lithium material one-way capacity characteristic to guarantee this application and mend lithium additive and mend lithium effect. When the lithium supplement material contains aluminum element doping, al atoms exist in a form of replacing iron atom lattices, the Al atoms existing in the form can widen the transmission channel of lithium ions, and can improve the extraction rate of the lithium ions.

In Li _w In A, A comprises C, N, O, P, S, F, B, se and at least one element, w is more than 0 and less than or equal to 5. The Li _w The precursor of the lithium supplement material A is a binary precursor of the lithium supplement material, and specifically can be but not only is Li ₃ N、Li ₂ S、Li ₂ O、Li ₂ O ₂ And the like.

When this application embodiment mend the lithium additive for above-mentioned nuclear shell structure, the hydrophobic encapsulation layer wraps the nuclear body, and like this, the fine and close encapsulation layer can effectively wrap the benefit lithium material that the nuclear body contained for the nuclear body is kept apart with the external world, avoids in the external world like the contact of moisture and carbon dioxide with the nuclear body, thereby guarantees the stability of nuclear body and guarantees to mend lithium additive's the benefit lithium effect and the stability of mending lithium.

Wherein, compact encapsulation layer can be the layer structure that can effectively isolate adverse factor such as steam or carbon dioxide in the environment, so its material can form compact hydrophobic coating and effectively guarantee to mend the material of lithium material stability in the nuclear body, on this basis, this compact encapsulation layer's material can also be the ion conductor encapsulated layer that can do benefit to ionic conduction, also can be the electron conductor encapsulated layer that does benefit to and improve electric conductivity, also can be the composite layer structure of ion conductor encapsulated layer and electron conductor encapsulated layer certainly. The ion conductor packaging layer can improve the lithium ion insertion and extraction effect of the lithium supplement material and the ion conductivity of lithium ions. The electronic conductor packaging layer can improve the electronic conductivity of the lithium supplement material, improve the conductivity of the lithium supplement material, stimulate the gram capacity of the lithium supplement additive to play, and realize the high-efficiency lithium supplement in the true sense.

When the hydrophobic encapsulation layer includes an ion conductor encapsulation layer, the material of the ion conductor encapsulation layer may be a material favorable for the increase of the ion conductivity, such as may include, but not limited to, at least one of perovskite type, NASICON type, garnet type. In a specific embodiment, the perovskite type comprises Li _3x La _2/3-x TiO ₃ (LLTO), in particular Li _0.5 La _0.5 TiO ₃ 、Li _0.33 La _0.57 TiO ₃ 、Li _0.29 La _0.57 TiO ₃ 、Li _0.33 Ba _0.25 La _0.39 TiO ₃ 、(Li _0.33 La _0.56 ) _1.005 Ti _0.99 Al _0.01 O ₃ 、Li _0.5 La _0.5 Ti _0.95 Zr _0.05 O ₃ Etc., of the NASICON type such as but not limited to Li _1.4 Al _0.4 Ti _1.6 (PO ₄ ) ₃ (LATP), garnet type comprising Li ₇ La ₃ Zr ₂ O ₁₂ (LLZO)、Li _6·4 La ₃ Zr _1·4 Ta _0·6 O ₁₂ ，Li _6.5 La ₃ Zr _1.5 Ta _0.5 O ₁₂ At least one of (1). By selecting the material of the ion conductor packaging layer, the ion conductivity of the ion conductor packaging layer can be further improved。

When the hydrophobic packaging layer comprises the electronic conductor packaging layer, the electronic conductor packaging layer can enhance the electronic conductivity of the compact packaging layer, so that the electronic conductivity of the lithium supplement additive is enhanced, and the internal impedance of the electrode is favorably reduced; meanwhile, the electronic conductor packaging layer can be secondarily utilized in the releasing process of the core body as a sacrificial product and after releasing is finished, and the auxiliary effect of the conductive agent is played in the electrode. And the electron conductor packaging layer or the electron conductor packaging layer and the ion conductor packaging layer further play a role in synergy of compactness, and the compactness of the compact packaging layer is improved, so that the lithium supplementing stability and the lithium supplementing effect of the lithium supplementing additive are improved. Based on the function of the electronic conductor packaging layer, the electronic conductor packaging layer can be fully coated or partially coated. In an embodiment, the material of the electronic conductor encapsulation layer comprises at least one of a carbon material, a conductive oxide, and a conductive organic. In a specific embodiment, when the material of the electronic conductor encapsulation layer is a carbon material, the carbon material includes at least one of amorphous carbon, carbon nanotube, graphite, carbon black, graphene, and the like. In other embodiments, when the material of the electronic conductor encapsulation layer is a conductive oxide, the conductive oxide may include In ₂ O ₃ 、ZnO、SnO ₂ At least one of (1). The conductive organic may be a conductive polymer or the like. The electronic conductivity can be further improved by adjusting the content and the material of the electronic conductor packaging layer.

In a further embodiment, the hydrophobic encapsulation layer has a thickness of 1-200nm. In other embodiments, the hydrophobic encapsulation layer comprises 1wt% to 5wt% of the total mass of the lithium supplement additive. The thickness and the content of the hydrophobic packaging layer are controlled within the range, so that the compactness of the hydrophobic packaging layer can be improved, the residual alkali content on the surface layer of the lithium supplement material is reduced, the storage stability and the processing stability of the lithium-iron-rich lithium supplement additive are further improved, and the ion and/or electron conductivity of the lithium supplement material is improved.

In addition, the hydrophobic packaging layer can also comprise other functional layers according to the needs, and the types of the other functional layers can be flexibly selected according to the needs.

Secondly, based on the CV value of the particle size distribution variation coefficient of the lithium supplement additive in the embodiment of the application, the core-shell structure, such as the core-shell structure containing the hydrophobic encapsulation layer, endows the lithium supplement additive of the application with excellent storage property and processability and stable electrochemical performance. As detected, the capacity decay rate of the electrode sheet directly prepared from the lithium supplement additive of the embodiment of the present application, such as the positive electrode sheet, for example, the electrode sheet (without the electrode active material) prepared from the lithium supplement additive, the binder and the conductive agent, when stored at an ambient humidity of 25% for 20 hours is not more than 30%, further not more than 18%, and when stored at an ambient humidity of 10% for 20 hours is not more than 20%, further not more than 6%, relative to the capacity when stored for 0.5 hours. Therefore, the lithium supplement additive provided by the embodiment of the invention and having the core-shell structure has excellent storage property, high lithium supplement effect and lithium supplement stability, and on the basis that the variation coefficient CV value of the particle size distribution of the lithium supplement additive provided by the embodiment of the invention is less than 0.5 and further less than 0.4, the hydrophobic encapsulation layer of the lithium supplement additive provided by the embodiment of the invention can be completely coated and effectively plays a role in hydrophobic isolation, so that the storage property of the lithium supplement additive provided by the embodiment of the invention is improved, such as the humidity resistance of the lithium supplement additive is improved. Ideally, the lithium supplement additive is stored in a dry and oxygen-free favorable environment such as a vacuum environment, so that the lithium supplement additive can exert the electrochemical performance to the maximum extent.

In a second aspect, the present application also provides a method for controlling the particle size of the above lithium supplement additive. The particle size control method of the lithium supplement additive comprises the following steps:

s01: screening the prepared lithium supplement additive;

s02: and (3) measuring or calculating the CV value of the particle size distribution variation coefficient of the screened lithium supplement additive, and collecting the lithium supplement additive with the CV value of the variation coefficient less than 0.5.

The lithium supplement additive in step S01 is a lithium supplement additive whose particle size needs to be controlled, such as a lithium supplement additive that can be prepared according to an existing lithium supplement additive preparation method, or a lithium supplement additive that is prepared according to an improved method of an existing lithium supplement additive preparation method, or a lithium supplement additive that is prepared by a newly proposed lithium supplement additive preparation method. In particular a lithium supplementing additive of the kind or structure as hereinbefore described.

The screening treatment in step S01 is to classify the lithium supplement additive to be treated according to particle size. In an embodiment, the screening process may be performed by adopting an existing screening manner, and the screening is performed as needed to realize screening of the lithium supplement additive to be processed, so as to obtain the lithium supplement additive with the target particle size distribution required in the embodiment of the present application, specifically, the lithium supplement additive with the particle size distribution coefficient of variation CV value of 0.5 or less, and further 0.4 or less is obtained. In a further embodiment, the screening process is a multi-stage screening process. By adopting multi-stage screening treatment, the lithium supplement additives with a plurality of gradient particle size sizes can be obtained at the same time, so that the screening treatment efficiency is improved, and the lithium supplement additives with different particle sizes and specifications can be obtained after the treatment in the step S02.

In the example, when the screening treatment is performed by the multi-stage screening treatment and the mesh numbers of the upper and lower adjacent layers are 500 meshes or less, the mesh number of the upper layer to the mesh number of the lower layer is 100 meshes or less, more preferably 50 meshes or less, and still more preferably 20 meshes or less. When the mesh number of the adjacent upper and lower layers is more than 500 meshes, the mesh number of the upper layer-the lower layer is less than or equal to 300 meshes, more preferably less than or equal to 200 meshes, and even more preferably less than or equal to 100 meshes. The screening grade number is more than or equal to 2, preferably more than or equal to 3. Through setting up such as different levels screen cloth mesh to this multistage screening processing, can improve the efficiency of screening processing to improve the particle diameter homogeneity of the benefit lithium additive that screening was collected at different levels.

In step S02, the CV value of the particle size distribution variation coefficient of the lithium supplement additive subjected to the screening process in step S01 is measured or calculated to obtain the lithium supplement additive in the predetermined target particle size distribution range. In the embodiment of the present application, the predetermined target particle size distribution range is the above-mentioned lithium supplement additive with particle size distribution having a coefficient of variation CV value of particle size distribution of less than 0.5 or further less than 0.4, and the lithium supplement additive in the specific particle size distribution range has the effects of the lithium supplement additive and specific electrochemical properties as described in the above application, such as uniform particle size, small difference in lithium ion extraction rate during the first charge cycle, high surface quality of the electrode sheet for production, and uniform dispersion in the active layer of the electrode sheet.

When the direct measurement of the coefficient of variation CV value is adopted, the measurement can be carried out by adopting corresponding particle size distribution coefficient of variation CV value test equipment.

When the CV value of the coefficient of variation is calculated by using a calculation method, in an embodiment, the method for calculating the CV value of the particle size distribution of the lithium supplement additive after the screening treatment includes the following steps:

and (4) carrying out particle size measurement treatment on the screened lithium supplement additive, and calculating a particle size distribution Coefficient of Variation (CV) value according to the detected particle size data.

In the embodiment of the present application, the method for determining the particle size of the lithium supplement additive after being screened may be implemented by using methods such as national standard or enterprise standard, and the method for determining the particle size of the lithium supplement additive after being screened includes the following steps:

The electron microscope (SEM) picture of the screened lithium supplement additive is obtained by adopting a field emission scanning electron microscope, so that the detection rate of the particle size can be effectively improved, and the efficiency of calculating the Coefficient of Variation (CV) value is improved. The number of the plurality of sample particles in the SEM picture is understood to be multiple, and the larger the number is, the more the CV value can be obtained, which represents the actual particle size distribution of the lithium supplement additive obtained by screening treatment. The number of sample particles may be, but is not limited to, 50. In order to improve the accuracy of the particle size measurement of the sample particles, in the embodiment, before the step of measuring the particle sizes of a plurality of sample particles, the field emission scanning electron microscope photograph is magnified, such as but not limited to 1000 times, for clarity and to improve the accuracy of the particle size measurement.

The particle size of the particles of the plurality of samples can be measured by using image analysis software and the like, so that the accuracy, precision and efficiency of particle size measurement are improved.

The CV value of the particle size distribution variation coefficient calculated according to the detected particle size data is calculated according to the following formula:

wherein N in the formula for calculating CV value represents the total number of particles of several samples, X _i Indicates the particle size of the ith sample particle,

the average value of the particle sizes of all samples is shown.

Based on the particle size control method of the lithium supplement additive in the embodiment of the application, the particle size of the lithium supplement additive can be effectively uniform, so that the lithium supplement additive has the effect of the lithium supplement additive in the above application. If the lithium ion battery has small lithium ion extraction rate difference, lithium ions can be extracted and released in a centralized manner in the first-circle charging process, and the first effect is improved. In the process of preparing the electrode, the surface quality of the electrode plate can be improved, the uniform dispersion degree in the active layer is improved, and the quality and the electrochemical performance of the electrode plate are improved. Meanwhile, on the premise of ensuring the uniform particle size of the lithium supplement additive, the lithium supplement additive with different particle size gradients can be obtained through screening treatment such as multi-stage screening treatment, and the application requirements of the lithium supplement additive with different particle sizes are met.

In addition, step S01 and step S02 of the method for controlling the particle size of the lithium supplement additive according to the embodiment of the present application are preferably performed in a protective atmosphere, such as a protective atmosphere of nitrogen or an inert gas, to improve the stability of the lithium supplement additive. When the lithium supplement additive is the above lithium supplement additive without the dense encapsulation layer, it is more desirable to perform the lithium supplement in a protective atmosphere to ensure the lithium supplement performance of the lithium supplement additive and the stability of the lithium supplement. The lithium supplement additive can ensure that the obtained lithium supplement additive has uniform particle size, high efficiency and strong correlation, and saves the control cost.

When the lithium supplement additive in steps S01 and S02 is the above lithium supplement additive without the dense encapsulation layer, and the variation coefficient CV value of the variation coefficient obtained by the particle size control method of the lithium supplement additive in the embodiment of the present application is less than 0.5, when the above dense encapsulation layer is coated, because the variation coefficient CV value of the particle size distribution of the lithium supplement additive is less than 0.5, the thickness of the above dense encapsulation layer formed on the surface of the lithium supplement additive is more uniform, the thickness of the dense encapsulation layer contained in each particle is more consistent, the yield of the coating process is high, and the electrochemical properties such as the lithium supplement effect of the coated lithium supplement additive are improved.

Of course, based on the particle size control method of the lithium supplement additive in the embodiment of the present application, the particle size control method of the lithium supplement additive in the embodiment of the present application is also suitable for controlling the particle size of the precursor particle of the lithium supplement additive. If the particle size of each source compound raw material of the lithium supplement additive is controlled by the particle size control method of the embodiment of the application, so that the particle size of each source compound raw material is uniform, in the thermal reaction, for example, when each source compound raw material is thermally treated by a microwave heating mode, the microwave heating mode is to convert the raw material into heat energy by absorbing microwave energy by a reactant, so that the whole body of each source compound raw material is heated at the same time, the heating is very uniform, the problems of inconsistent reaction rate, inconsistent crystal growth rate and the like caused by local temperature difference of a reaction system are avoided, and the lithium supplement additive precursor particles with consistent chemical composition and uniform particle size are favorably obtained. At this time, because the particle size of the precursor particle of the lithium supplement additive is uniform, in the subsequent process of generating the lithium supplement additive, because the particle size of the precursor particle of the lithium supplement additive is uniform, the crystal form and the electrochemical performance of the generated lithium supplement additive also have high consistency, and the particle size uniformity of the particles is higher.

In a third aspect, an embodiment of the present application further provides an electrode sheet. The electrode plate of the embodiment of the application comprises a current collector and an electrode active layer combined on the surface of the current collector. Wherein, the electrode active layer contains the lithium supplement additive in the embodiment of the application. Since the electrode plate according to the embodiment of the present invention contains the lithium supplement additive according to the embodiment of the present invention, the lithium supplement additive contained in the electrode plate plays the above role during charging and discharging, and can be consumed as a lithium source first as a "sacrificial agent" during the first cycle of charging to supplement irreversible lithium ions consumed by the negative electrode forming an SEI film, so as to maintain the lithium ion abundance in the battery system, and the lithium supplement additive contained in the electrode plate has a small lithium removal rate difference, so that the lithium ions can be efficiently provided, thereby improving the first efficiency and the overall electrochemical performance of the battery. And the electrode plate has high surface quality, has low or completely avoided adverse phenomena such as salient points and the like, and can effectively avoid the problem of unsatisfactory electrochemical performance of the electrode plate caused by aggregation because components in an electrode active layer, such as electrode active ingredients, particularly lithium supplement additives, are uniformly dispersed.

If the lithium supplement additive is a positive electrode lithium supplement additive or a negative electrode lithium supplement additive according to the types of the lithium supplement additives, the corresponding electrode slice is a positive electrode slice or a negative electrode slice.

In the embodiment, when the lithium supplement additive is a positive electrode lithium supplement additive, the mass content of the lithium supplement additive in the positive electrode active layer in the positive electrode sheet in the embodiment of the present application may be 1% to 10%, and further 1.0% to 5.0%. The positive active layer comprises a positive active material, a binder and a conductive agent besides the lithium supplement additive, wherein the binder can be a common electrode binder, such as one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene butadiene rubber, hydroxypropyl methyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivative. In the embodiment of the present application, the conductive agent may be a commonly used conductive agent, such as one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60, and carbon nanotube. The positive active material may include one or more of lithium cobaltate, lithium manganate, lithium iron phosphate, lithium manganese phosphate, lithium vanadium phosphate, lithium vanadyl fluorophosphate, lithium titanate, lithium nickel cobalt manganate, and lithium nickel cobalt aluminate.

In an embodiment, the electrode sheet preparation process may be: mixing an electrode active material, a lithium supplement additive, a conductive agent and a binder to obtain electrode slurry, coating the electrode slurry on a current collector, and drying, rolling, die cutting and the like to obtain the electrode slice.

In a fourth aspect, embodiments of the present application also provide a secondary battery. The secondary battery of the embodiment of the present application includes necessary components such as a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, and of course, includes other necessary or auxiliary components. When the positive electrode sheet is the positive electrode sheet in the embodiment of the present application, that is, the positive electrode active layer contained in the positive electrode sheet contains the lithium supplement additive in the embodiment of the present application. When the negative electrode sheet is the negative electrode sheet of the embodiment of the present application, that is, the negative electrode active layer contained in the negative electrode sheet contains the lithium supplement additive of the embodiment of the present application. Of course, the secondary battery may be a battery in which the positive electrode sheet is the positive electrode sheet containing the lithium supplement additive (positive electrode lithium supplement additive) and the negative electrode sheet is the negative electrode sheet containing the lithium supplement additive (negative electrode lithium supplement additive).

Because the secondary battery in the embodiment of the application contains the lithium supplement additive in the embodiment of the application, based on the excellent lithium supplement performance of the lithium supplement additive in the embodiment of the application, the secondary battery in the embodiment of the application has excellent first coulombic efficiency, battery capacity and cycle performance, long service life and stable electrochemical performance. More importantly, the secondary battery in the embodiment of the application does not need to be repeatedly assembled for lithium supplement additive performance evaluation, and has high timeliness and strong correlation.

The lithium supplement additive, the preparation method and the application thereof in the examples of the present application are illustrated by a plurality of specific examples.

1. The lithium supplement additive and the particle size control method thereof comprise the following steps:

example 1

The embodiment provides a lithium supplement additive and a particle size control method thereof. The lithium supplement additive comprises Li ₅ FeO ₄ The core and the carbon layer coating the core, that is, the carbon layer constitutes a dense encapsulation layer. And the CV value of the variation coefficient of the particle size distribution of the lithium supplement additive is 0.34.

The control method of the lithium supplement additive comprises the following steps:

S1.Li ₅ FeO ₄ the synthesis method comprises the following steps:

fully mixing a lithium source, a complexing agent, an iron source and a solvent, performing microwave heating and stirring treatment to obtain a precursor solution, and performing drying treatment and sintering treatment to obtain Li ₅ FeO ₄ Core material of Li under inert atmosphere ₅ FeO ₄ Carrying out multi-layer grading sieve treatment on the core material to obtain the core material with uniform particle size;

s2. In Li ₅ FeO ₄ The formation of a carbon dense hydrophobic layer on the surface of the inner core is also the formation of carbon coating:

taking polyvinyl chloride as a carbon source, and mixing the polyvinyl chloride and Li ₅ FeO ₄ Uniformly mixing the core material and N-methyl pyrrolidone, drying in vacuum, calcining for 4h at 400 ℃ under the protection of inert atmosphere to obtain Li serving as the core ₅ FeO ₄ The inner core material and the shell are carbon coating layers;

s3, screening the lithium supplement additive and determining a Coefficient of Variation (CV) value:

carrying out multilayer grading sieve treatment on the lithium supplement additive obtained in the step S2 under inert atmosphere, wherein the mesh number of adjacent upper and lower layers of screens in the multilayer grading sieve treatment is below 500 meshes, and the mesh number of the upper layer-the mesh number of the lower layer is not more than 20 meshes; taking a sample at regular time, taking an SEM picture, magnifying the SEM picture to 1000 times, randomly selecting 50 sample particles in the SEM picture as shown in figure 1, measuring the particle size data of the 50 sample particles by using software, counting the particle sizes of the 50 sample particles, calculating the coefficient of variation CV (coefficient of variation) according to the formula (1), discharging when the coefficient of variation is less than 0.5, and actually measuring the CV to be 0.34.

Example 2

The embodiment provides a lithium supplement additive and a particle size control method thereof. The lithium supplement additive comprises Li ₂ NiO ₂ The core and the carbon layer coating the core, that is, the carbon layer constitutes a dense encapsulation layer. And the CV value of the variation coefficient of the particle size distribution of the lithium supplement additive is 0.31.

S1.Li ₂ NiO ₂ the synthesis method comprises the following steps:

fully mixing a lithium source, a complexing agent, a nickel source and a solvent, carrying out microwave heating and stirring treatment to obtain a precursor solution, and carrying out drying treatment and sintering treatment to obtain Li ₂ NiO ₂ Core material of Li under inert atmosphere ₂ NiO ₂ Carrying out multi-layer grading sieve treatment on the core material to obtain the core material with uniform particle size;

s2. In Li ₂ NiO ₂ The formation of a carbon dense hydrophobic layer on the surface of the inner core is also the formation of carbon coating:

taking polyvinyl chloride as a carbon source, and mixing the polyvinyl chloride and Li ₂ NiO ₂ Uniformly mixing the core material and N-methyl pyrrolidone, drying in vacuum, calcining for 4h at 400 ℃ under the protection of inert atmosphere to obtain Li serving as the core ₂ NiO ₂ The inner core material and the shell are carbon coating layers;

carrying out multilayer grading sieve treatment on the lithium supplement additive obtained in the step S2 under inert atmosphere, wherein the mesh number of adjacent upper and lower layers of screens in the multilayer grading sieve treatment is more than 500 meshes, and the mesh number of the upper layer-the mesh number of the lower layer is less than or equal to 10 meshes; sampling at regular time, taking an SEM picture, magnifying the SEM picture to 1000 times, randomly selecting 50 sample particles in the SEM picture, measuring the particle size data of the 50 sample particles by using software, counting the particle sizes of the 50 sample particles, calculating the coefficient of variation CV (coefficient of variation) according to the formula (1), discharging when the coefficient of variation is less than 0.5, and actually measuring the CV value to be 0.31.

Comparative example 1

The present comparative example provides a lithium supplement additive. The lithium supplement additive comprises Li ₅ FeO ₄ The core and the carbon layer coating the core, that is, the carbon layer, constitute a dense encapsulating layer. And the CV value of the variation coefficient of the particle size distribution of the lithium supplement additive is 0.93.

The preparation method of the lithium supplement additive of the comparative example comprises the following steps:

S1.Li ₅ FeO ₄ the synthesis method comprises the following steps:

lithium source, complexing agent, iron source,Fully mixing the solvents, heating by a heating plate, stirring to obtain a precursor solution, drying, and sintering to obtain Li ₅ FeO ₄ A core material;

taking polyvinyl chloride as a carbon source, and mixing the polyvinyl chloride and Li ₅ FeO ₄ Uniformly mixing the core material and N-methyl pyrrolidone, drying in vacuum, calcining for 4h at 400 ℃ under the protection of inert atmosphere to obtain Li serving as the core ₅ FeO ₄ The inner core material and the shell are carbon coating layers.

And (3) taking a sample of the lithium supplement additive obtained in the step (S2) by taking an SEM photograph, magnifying the SEM to 1000 times, randomly selecting 50 sample particles in the SEM photograph, measuring the particle size data of the 50 sample particles by using software, counting the particle sizes of the 50 sample particles, and calculating the coefficient of variation CV value according to the formula (1) to be 0.93.

Comparative example 2

The present comparative example provides a lithium supplement additive. The lithium supplement additive comprises Li ₂ NiO ₂ The core and the carbon layer coating the core, that is, the carbon layer constitutes a dense encapsulation layer. And the CV value of the variation coefficient of the particle size distribution of the lithium supplement additive is 0.87.

S1.Li ₂ NiO ₂ the synthesis method comprises the following steps:

fully mixing a lithium source, a complexing agent, an iron source and a solvent, heating by a heating plate, stirring to obtain a precursor solution, drying, and sintering to obtain Li ₂ NiO ₂ A core material;

taking polyvinyl chloride as a carbon source, and mixing the polyvinyl chloride and Li ₂ NiO ₂ Uniformly mixing the core material and N-methyl pyrrolidone, drying in vacuum, calcining for 4h at 400 ℃ under the protection of inert atmosphere to obtain Li serving as the core ₂ NiO ₂ The inner core material and the shell are carbon coating layers.

And (3) taking a sample of the lithium supplement additive obtained in the step (S2) by taking an SEM photograph, magnifying the SEM to 1000 times, randomly selecting 50 sample particles in the SEM photograph, measuring the particle size data of the 50 sample particles by using software, counting the particle sizes of the 50 sample particles, and calculating the coefficient of variation CV value according to the formula (1) to be 0.87.

2. Lithium ion battery embodiment:

the lithium supplement additives provided in the above examples 1 to 2 and the lithium supplement additive provided in the comparative example were assembled into a positive electrode and a lithium ion battery, respectively, as follows:

positive electrode: under the same conditions, according to NMP: liFePO ₄ : lithium supplement additive: super P: PVDF, the four are mixed according to the mass ratio of 100; the rotating speed is set to be 30HZ; homogenizing, coating, drying and cutting into pieces to prepare a positive plate, and baking the positive plate in a vacuum oven at 100 ℃ to remove trace water; wherein, the lithium supplement additives are the lithium supplement additives provided in the above examples 1 to 2 and the lithium supplement additives provided in the comparative examples;

a negative electrode: the lithium metal sheet is a lithium metal sheet with the diameter of 16mm which can be produced in the lithium industry in Tianjin;

electrolyte solution: liPF with electrolyte of 1mol/L ₆ A solution, wherein the solvent consists of EC (ethylene carbonate) and DEC (diethyl carbonate) according to a volume ratio of 1:1;

diaphragm: PE diaphragms produced by Shanghai Enjie;

a battery case: the model number of the anode comprises a cathode shell, a stainless steel gasket and an anode shell and is CR2032

Assembling the lithium ion battery: the assembly sequence of the negative electrode shell, the stainless steel elastic sheet, the stainless steel gasket, the lithium metal sheet, the diaphragm, the electrolyte, the positive electrode sheet and the positive electrode shell is assembled into the button lithium ion battery in an inert atmosphere glove box.

3. Correlation performance testing

3.1 humidity resistance test of lithium supplement additive:

to further evaluate the moisture resistance of the lithium supplement material, we prepared a pole piece (without adding a positive electrode material) by separately mixing the lithium supplement material, a conductive agent and a binder, and we used example 1 as an example to test the specific capacity of the corresponding pole piece at different humidity (25%, 10%) for different time periods, and the related results are shown in table 1 and table 2 respectively. As can be seen from tables 1 and 2, although the specific capacity of the positive electrode sheet prepared by the positive electrode lithium supplement additive in example 1 of the present application stored the battery under different humidities varies, the variation is not large, especially when the humidity is 10%, the specific capacity after being placed for 20h is relatively small in attenuation amplitude of 0.5h, that is, the attenuation rate is only 3.4% (note: attenuation rate = (1-specific capacity placed for 20 h/specific capacity placed for 0.5 h) = 100%).

TABLE 1

TABLE 2

3.2 testing the electrochemical performance of the lithium ion battery:

the relevant electrochemical performance of each lithium ion battery assembled in the embodiment and the comparative example of the lithium ion battery is tested, and the testing process steps of constant-current constant-voltage charging-constant-current discharging are adopted, wherein the voltage range is 2.0V-3.75V, and the cut-off current is 0.1C. The relevant electrochemical properties of the lithium ion battery are shown in table 3 below:

TABLE 3

Wherein, the first charge refers to the first charge specific capacity (unit: mAh/g), the first discharge refers to the first discharge specific capacity (unit: mAh/g), and the first effect refers to the first coulombic efficiency.

As can be seen from the results in Table 1, in the charging obtained in example 1 (CV value: 0.34), the first charging specific capacity is 172.1mAh/g to 174.7mAh/g (mean value: 173.44 mAh/g), and the first coulombic efficiency is 95.99% to 97.42% (mean value: 96.75%); in contrast, in the charging obtained in comparative example 1 (CV value: 0.93), the first charge specific capacity was 166.9mAh/g to 173.7mAh/g (average: 170.44 mAh/g), and the first coulombic efficiency was 91.21% to 96.24% (average: 92.72%). In the charging obtained in example 2 (CV value: 0.31), the first charging specific capacity is 166.4 mAh/g-169.4 mAh/g (mean value: 167.78 mAh/g), and the first coulombic efficiency is 96.33% -97.58% (mean value: 96.62%); in the charging obtained in comparative example 2 (CV value: 0.87), the first charge specific capacity was 160.3mAh/g to 170.1mAh/g (average value: 165.44 mAh/g), and the first coulombic efficiency was 90.35% to 95.30% (average value: 92.20%). Comparing the embodiment with the comparative example, it is obvious that when the CV value of the added particle size variation coefficient of lithium supplement is less than 0.5, the specific capacity and the first effect are higher, and meanwhile, the deviation range is small and the performance is stable. The result shows that the lithium supplement additive provided by the application can realize efficient and stable lithium supplement effect, and the electrochemical performance of the secondary battery manufactured by using the lithium supplement additive is more stable.

The above examples only express several embodiments of the present application, and the description thereof is more specific and detailed, but not to be construed as limiting the scope of the present application. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, which falls within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.

Claims

1. A lithium supplement additive, which is characterized in that: the CV value of the variation coefficient of the particle size distribution of the lithium supplement additive is less than 0.5.

2. The lithium supplement additive of claim 1, wherein: the coefficient of variation CV value is less than 0.4; and/or

The lithium supplement additive is of a core-shell structure, a core body of the lithium supplement additive comprises a lithium supplement material, and a shell layer of the lithium supplement additive is a hydrophobic packaging layer.

3. The lithium supplement additive of claim 2, wherein: the hydrophobic packaging layer comprises at least one of an ion conductor packaging layer and an electronic conductor packaging layer; and/or

The lithium supplement material comprises L _x M _y N _z O _q 、Li _w At least one of A, wherein L in the molecular formula is Li or/and a mixed alkali metal element of Li and not more than 30% of at least one of K, na; m comprises at least one of Fe, co, ni, mn, V, fe-Co, cu, mo, al, ti and Mg; n comprises at least one of Fe, co, mn, ni, si, al or other equivalent or aliovalent metal elements; o is oxygen element; a comprises C, N, O, P, S, F, B, se, x is 4-6,y is 0.7-1.0, z is 0.01-0.3, q is 4-5,0 < w ≦ 5.

4. The lithium supplement additive according to any one of claims 2 to 3, wherein the capacity of an electrode sheet prepared from the lithium supplement additive, a conductive agent and a binder when stored for 20 hours at an ambient humidity of 25% has a capacity fade rate of not more than 30% relative to 0.5 hours of storage; and/or

The capacity of the electrode plate prepared from the lithium supplement additive, the conductive agent and the binder is stored for 20 hours under the environment humidity of 10 percent, and the capacity fading rate of the electrode plate stored for 0.5 hour is not more than 20 percent;

wherein, the lithium supplement additive is in the core-shell structure.

5. A method for controlling the particle size of a lithium supplement additive comprises the following steps:

screening the prepared lithium supplement additive;

and measuring or calculating the CV value of the particle size distribution variation coefficient of the lithium supplement additive subjected to screening treatment, and collecting the lithium supplement additive with the CV value of the variation coefficient less than 0.5.

6. The particle size control method according to claim 5, characterized in that: the method for calculating the particle size distribution Coefficient of Variation (CV) value of the lithium supplement additive after screening treatment comprises the following steps:

carrying out particle size determination treatment on the screened lithium supplement additive, and calculating a particle size distribution Coefficient of Variation (CV) value according to detected particle size data;

the method for measuring the particle size of the lithium supplement additive subjected to screening treatment comprises the following steps:

and obtaining a field emission scanning electron microscope picture of the lithium supplement additive after screening treatment, selecting a plurality of sample particles in the field emission scanning electron microscope picture, and measuring the particle sizes of the sample particles.

7. The method of controlling particle size according to claim 6, wherein: and before the step of measuring the particle sizes of a plurality of sample particles, amplifying the field emission scanning electron microscope picture.

8. The particle size control method according to any one of claims 6 to 7, wherein: calculating the CV value of the particle size distribution variation coefficient according to the detected particle size data according to the following formula:

coefficient of variation

Wherein N represents the total number of sample particles, X _i Denotes the particle size of the ith sample particle,

represents the average of all the sample particle sizes.

9. The particle size control method according to any one of claims 5 to 7, wherein: and the screening treatment is multi-stage screening treatment, and the particle size determination treatment and the calculation of the CV value of the particle size distribution variation coefficient are respectively carried out on the lithium supplement additive obtained by the screening treatment at each stage.

10. The utility model provides an electrode slice, includes the mass flow body and combines the electrode active layer on the mass flow body surface, its characterized in that: the electrode active layer contains the lithium supplement additive according to any one of claims 1 to 4 or the lithium supplement additive obtained by the particle size control method according to any one of claims 5 to 9.

11. A secondary battery comprises a positive plate and a negative plate, and is characterized in that: the positive electrode sheet and/or the negative electrode sheet is the positive electrode sheet according to claim 10.