Positive lithium supplement capsule, preparation method and positive plate

Abstract

The invention relates to a positive electrode lithium supplement capsule, a preparation method and a positive plate in the technical field of lithium batteries. The method comprises the following steps: S1, dissolving a high-molecular polymer into dichloromethane to obtain an organic dispersion solution; s2, mixing a lithium supplement agent, gelatin and distilled water to form an aqueous solution; s3, mixing the organic dispersion solution and the aqueous solution to form an O / W emulsion; s4, carrying out drying treatment on the O / W emulsion; and washing the product in the step S4 to obtain the lithium supplementing capsule. The positive electrode lithium supplement capsule prepared by the invention can effectively carry out first charge lithium supplement in the lithium ion battery containing the lithium manganate positive electrode plate, and slowly releases lithium ions in the early stage of battery circulation, so that the cycle performance of the lithium ion battery containing the lithium manganate positive electrode plate is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a positive electrode lithium supplementing gel capsule and a preparation method thereof, and a positive electrode sheet. Background Art

[0002] Rechargeable lithium-ion batteries are widely used in portable electronic devices, hybrid electric vehicles, and renewable energy storage systems. Lithium-ion batteries are usually composed of a transition metal oxide positive electrode and a graphite negative electrode. During the charge and discharge process, lithium ions migrate between the positive and negative electrodes, but during the first charge process, 5-20% of the Li+ forms a solid electrolyte interface (SEI) at the negative electrode and is consumed, resulting in high irreversible capacity loss and low first cycle coulombic efficiency. On the other hand, during the cycle of the battery, lithium ions are slowly and continuously consumed due to various reasons, affecting the capacity retention rate and cycle performance of the battery. Based on the lithium ion consumption problem caused by the first charge and cycle mentioned above, the current common solution is to replenish lithium to the positive electrode alone or to the negative electrode alone.

[0003] The applicant has found through research that the overall operating trend of spinel lithium manganese oxide shows a trend of first decreasing and then flattening. Therefore, the demand for lithium replenishment during the operation of lithium manganese oxide is different from that of other materials. It requires both rapid lithium replenishment in the early stage of the cycle to make up for the loss of active lithium in the SEI layer (the same as the prior art), and uninterrupted lithium replenishment in the early stage of the cycle to maintain balance. After the cycle stabilizes, the demand for lithium replenishment is no longer strong.

[0004] Based on the above findings, the applicant proposed a technical solution that is particularly suitable for lithium replenishment of lithium manganese oxide positive electrode sheets. Summary of the invention

[0005] In order to solve the above technical problems, the present invention discloses a positive electrode lithium supplement capsule and a preparation method, and a positive electrode sheet. The technical solution of the present invention is implemented as follows:

[0006] The first aspect of the present invention is to provide a method for preparing a positive electrode lithium supplement capsule, the method comprising the following steps:

[0007] S1, dissolving a high molecular weight polymer in dichloromethane to obtain an organic dispersion solution;

[0008] S2, mixing the first lithium supplement, gelatin and distilled water to form an aqueous solution;

[0009] S3, mixing the organic dispersion solution and the aqueous solution to form an O / W emulsion;

[0010] S4, drying the O / W emulsion;

[0011] S5, washing the product of S4 to obtain lithium supplement capsules.

[0012] In view of the fact that the lithium replenishment demand of lithium manganese oxide positive electrode sheets during operation is different from that of other materials, the lithium replenishment capsules proposed by the present invention can effectively perform the initial lithium replenishment in lithium ion batteries containing lithium manganese oxide positive electrode sheets, and slowly release lithium ions in the early stage of battery cycle (generally the first 100 cycles), thereby greatly improving the cycle performance of lithium ion batteries containing lithium manganese oxide positive electrode sheets.

[0013] Preferably, in S1, the high molecular polymer is polyethylene and / or polystyrene.

[0014] In specific applications, the high molecular polymer may be polyethylene only, polystyrene only, or a mixture of polyethylene and polystyrene, and the present invention does not impose any limitation on this.

[0015] Preferably, in S1, the mass ratio of the high molecular weight polymer to dichloromethane is 1:9.

[0016] Preferably, in S2, the first lithium supplement is selected from at least one of lithium oxide, lithium nitride, lithium sulfide, lithium-rich lithium ferrite, lithium oxalate, and lithium nickelate.

[0017] It should be noted that the term "at least one" in the present invention means that one of the above materials can be selected, or a mixture of two or more of the above materials can be selected. The above materials are all common lithium supplements in the field. Within the scope of understanding of those skilled in the art, the selection of lithium supplements in the present invention can be arbitrarily implemented as long as the implementation can meet the demand for positive electrode lithium supplementation.

[0018] Preferably, in the aqueous solution, the mass ratio of the lithium supplement is 4%-6%, the mass ratio of the gelatin is 0.4%-0.6%, and the mass ratio of the distilled water is 94%-96%.

[0019] Preferably, the mass ratio of the organic dispersion solution to the aqueous solution is 1:4.

[0020] Preferably, the average diameter of the lithium supplement capsule is 1 μm.

[0021] The second aspect of the present invention discloses a positive electrode lithium replenishing capsule, which is prepared by the method disclosed in the first aspect of the present invention.

[0022] The third aspect of the present invention discloses a positive electrode sheet, which includes the positive electrode lithium supplement capsule proposed in the second aspect of the present invention, and also includes a positive electrode active material, a conductive agent and a binder;

[0023] The positive electrode active material is lithium manganate.

[0024] The positive electrode sheet also includes a second lithium replenisher, which is completely consumed in the first three cycles.

[0025] The mass ratio of the first lithium replenisher to the positive electrode lithium replenisher capsule is (1-2): (8-9).

[0026] The first lithium supplement and the second lithium supplement are the same or different.

[0027] It is understood that the binder is a substance used to bind the positive electrode active material, the conductive agent and other components together. Without violating the inventive concept of the present application, the present application also has no special requirements on the type of binder, and any known type of binder can be used in the present application.

[0028] The binder includes any one of polytetrafluoroethylene, polyvinylidene fluoride, polypropylene, polyethylene, styrene-butadiene rubber, nitrile rubber, sodium hydroxymethyl cellulose, polyacrylic acid, polyacrylonitrile or sodium alginate, or a combination of at least two thereof.

[0029] It is understood that the conductive agent is mainly used to assist and improve the conductivity in the secondary battery. There is no particular limitation on the conductive agent in the present application, as long as it has electronic conductivity without causing chemical changes. Specifically, the conductive agent includes any one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene or carbon nanofibers, or a combination of at least two thereof.

[0030] The positive electrode lithium replenishing capsule prepared by the present invention can effectively perform the first lithium replenishment in the lithium ion battery containing lithium manganese oxide, and slowly release lithium ions in the early stage of the battery cycle, greatly improving the cycle performance of the lithium ion battery containing lithium manganese oxide. DETAILED DESCRIPTION

[0031] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Unless otherwise defined, all technical and scientific terms used in the present invention have the same meanings as those commonly understood by technicians in the technical field to which the present invention belongs; the terms used in the specific implementation methods are only for the purpose of describing specific embodiments and are not intended to limit the present invention; the terms "including" and "having" in the specification and claims of the present invention and the above description and any variations thereof are intended to cover non-exclusive inclusions.

[0033] In the description of the specific implementation methods of the present invention, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present invention, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0034] Reference to "embodiments" in the present invention means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described in the present invention may be combined with other embodiments.

[0035] In the description of the embodiments of the present invention, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects before and after are in an "or" relationship.

[0036] Throughout the present invention, numerical values ​​represent approximate measures or limits of ranges to cover minor deviations from given values ​​as well as embodiments with about the values ​​mentioned and embodiments with the exact values ​​mentioned. Except for the working examples provided at the end of the detailed description, all numerical values ​​of parameters (e.g., amounts or conditions) in this specification (including the appended claims) should be understood to be modified by the term "about" in all cases, regardless of whether "about" actually appears before the numerical value. "About" indicates that the stated numerical value allows some minor imprecision (close to the exact value of the value to some extent; approximately or reasonably close to the value; almost). If the imprecision provided by "about" is not otherwise understood in this ordinary sense in the art, "about" as used in the present invention at least indicates the variation that can be produced by the ordinary methods of measuring and using such parameters. For example, "about" may include a variation of less than or equal to 5%, optionally less than or equal to 4%, optionally less than or equal to 3%, optionally less than or equal to 2%, optionally less than or equal to 1%, optionally less than or equal to 0.5%, and in some aspects, optionally less than or equal to 0.1%.

[0037] Additionally, disclosure of ranges includes disclosure of all values ​​within the entire range and further divided ranges, including endpoints and sub-ranges given for such ranges.

[0038] Research has found that the overall operating trend of spinel lithium manganese oxide shows a trend of first decreasing and then flattening. Therefore, the demand for lithium replenishment during the operation of lithium manganese oxide is different from that of other materials. It requires both rapid lithium replenishment in the early stage of the cycle to make up for the loss of active lithium in the SEI layer (the same as the existing technology), and uninterrupted lithium replenishment in the early stage of the cycle to maintain balance. After the cycle stabilizes, the demand for lithium replenishment is no longer strong.

[0039] Based on the above findings, the present invention proposes a technical solution, which prepares the positive electrode lithium replenisher into a lithium replenisher capsule so that it can play the role of the first charging lithium replenisher in the first charging cycle of the lithium manganese oxide positive electrode sheet, and can also continuously replenish lithium in the early stage of the cycle of the lithium manganese oxide positive electrode sheet to maintain the balance of active lithium, thereby improving the cycle performance of the lithium manganese oxide positive electrode sheet. The lithium replenisher capsule of the present invention is particularly suitable for replenishing lithium of the lithium manganese oxide positive electrode sheet.

[0040] The embodiments of the present invention will be described in more detail below through examples and comparative examples. It should be noted that the embodiments of the present invention are not limited to these examples.

[0041] Example 1

[0042] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0043] 1. Preparation of lithium supplement capsules

[0044] Dissolve 10 g of polyethylene in 90 g of dichloromethane to obtain a dispersion solution A;

[0045] Mix 5 g of the first lithium supplement lithium oxalate, 0.5 g of gelatin, and 94.5 g of distilled water to form an aqueous solution B;

[0046] The dispersed solution A and the aqueous solution B were mixed at a ratio of 1:4 to form an O / W emulsion;

[0047] Drying and removing dichloromethane in the O / W emulsion to obtain polyethylene capsules containing the lithium supplement;

[0048] The capsules were washed with distilled water, and the average diameter of the prepared lithium supplement capsules was 1 micron.

[0049] 2. Preparation of positive electrode

[0050] The lithium supplement capsule prepared in step 1, the positive electrode active material lithium manganese oxide (LiMn2O4), the binder (PVDF), and the conductive agent (super-P) are mixed in a mass ratio of 10:85:2:3 to form a positive electrode slurry, which is applied to the surface of the aluminum foil and dried to form a positive electrode sheet.

[0051] 3. Preparation of negative electrode sheet

[0052] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0053] 4. Preparation of lithium-ion batteries

[0054] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0055] Example 2

[0056] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0057] 1. Preparation of lithium supplement capsules

[0058] 10 g of polystyrene (PS) was dissolved in 90 g of dichloromethane to obtain a dispersion solution A;

[0059] Mix 5 g of the first lithium supplement lithium oxalate, 0.5 g of gelatin, and 94.5 g of distilled water to form an aqueous solution B;

[0060] The dispersed solution A and the aqueous solution B were mixed at a ratio of 1:4 to form an O / W emulsion;

[0061] The dichloromethane in the O / W emulsion is dried to obtain polystyrene capsules containing the lithium supplement;

[0062] The capsules were washed with distilled water, and the average diameter of the prepared lithium supplement capsules was 1 micron.

[0063] 2. Preparation of positive electrode

[0064] The lithium supplement capsule prepared in step 1, the positive electrode active material lithium manganese oxide (LiMn2O4), the binder (PVDF), and the conductive agent (super-P) are mixed in a mass ratio of 10:85:2:3 to form a positive electrode slurry, which is applied to the surface of the aluminum foil and dried to form a positive electrode sheet.

[0065] 3. Preparation of negative electrode sheet

[0066] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0067] 4. Preparation of lithium-ion batteries

[0068] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0069] Example 3

[0070] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0071] 1. Preparation of lithium supplement capsules

[0072] 10 g of polystyrene (PS) was dissolved in 90 g of dichloromethane to obtain a dispersion solution A;

[0073] 4 g of the first lithium supplement lithium oxalate, 0.5 g of gelatin, and 95.5 g of distilled water were mixed to form aqueous solution B;

[0074] The dispersed solution A and the aqueous solution B were mixed at a ratio of 1:4 to form an O / W emulsion;

[0075] Drying and removing dichloromethane in the O / W emulsion to obtain polystyrene capsules containing a lithium supplement;

[0076] The capsules were washed with distilled water, and the average diameter of the prepared lithium supplement capsules was 1 micron.

[0077] 2. Preparation of positive electrode

[0078] The lithium supplement capsule prepared in step 1, the positive electrode active material lithium manganese oxide (LiMn2O4), the binder (PVDF), and the conductive agent (super-P) are mixed in a mass ratio of 10:85:2:3 to form a positive electrode slurry, which is applied to the surface of the aluminum foil and dried to form a positive electrode sheet.

[0079] 3. Preparation of negative electrode sheet

[0080] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0081] 4. Preparation of lithium-ion batteries

[0082] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0083] Example 4

[0084] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0085] 1. Preparation of lithium supplement capsules

[0086] Dissolve 10 g of polyethylene in 90 g of dichloromethane to obtain a dispersion solution A;

[0087] Mix 5 g of the first lithium supplement lithium oxalate, 0.5 g of gelatin, and 94.5 g of distilled water to form an aqueous solution B;

[0088] The dispersed solution A and the aqueous solution B were mixed at a ratio of 1:4 to form an O / W emulsion;

[0089] The dichloromethane in the O / W emulsion is dried to obtain polyethylene capsules containing the lithium supplement;

[0090] The capsules were washed with distilled water, and the average diameter of the prepared lithium supplement capsules was 1 micron.

[0091] 2. Preparation of positive electrode

[0092] Lithium oxalate, the lithium supplement capsule prepared in step 1, the positive electrode active material lithium manganese oxide (LiMn2O4), the binder (PVDF), and the conductive agent (super-P) are mixed in a mass ratio of 1:9:85:2:3 to form a positive electrode slurry, which is applied to the surface of the aluminum foil and dried to form a positive electrode sheet.

[0093] 3. Preparation of negative electrode sheet

[0094] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0095] 4. Preparation of lithium-ion batteries

[0096] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0097] Example 5

[0098] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0099] 1. Preparation of lithium supplement capsules

[0100] Dissolve 10 g of polyethylene in 90 g of dichloromethane to obtain a dispersion solution A;

[0101] Mix 5 g of the first lithium supplement lithium oxalate, 0.5 g of gelatin, and 94.5 g of distilled water to form an aqueous solution B;

[0102] The dispersed solution A and the aqueous solution B were mixed at a ratio of 1:4 to form an O / W emulsion;

[0103] Drying and removing dichloromethane in the O / W emulsion to obtain polyethylene capsules containing the lithium supplement;

[0104] The capsules were washed with distilled water, and the average diameter of the prepared lithium supplement capsules was 1 micron.

[0105] 2. Preparation of positive electrode

[0106] Lithium oxalate, the lithium supplement capsule prepared in step 1, the positive electrode active material lithium manganese oxide (LiMn2O4), the binder (PVDF), and the conductive agent (super-P) are mixed in a mass ratio of 2:8:85:2:3 to form a positive electrode slurry, which is applied to the surface of the aluminum foil and dried to form a positive electrode sheet.

[0107] 3. Preparation of negative electrode sheet

[0108] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0109] 4. Preparation of lithium-ion batteries

[0110] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0111] Comparative Example

[0112] A lithium-ion battery comprises alternating positive and negative electrodes and a separator arranged between the two electrodes, wherein the separator is made of conventional materials. The preparation method of the lithium-ion battery is as follows:

[0113] 1. Preparation of positive electrode

[0114] Lithium oxalate, positive electrode active material lithium manganese oxide (LiMn2O4), binder (PVDF), and conductive agent (super-P) are mixed in a mass ratio of 6.5:88.5:2:3 to form a positive electrode slurry, which is then coated on the surface of aluminum foil and dried to form a positive electrode sheet.

[0115] 3. Preparation of negative electrode sheet

[0116] Graphite, CMC+SBR, and super-P are mixed in a mass ratio of 94:4:2 to form a negative electrode slurry, which is then coated on the surface of the copper foil and dried to form a negative electrode sheet.

[0117] 4. Preparation of lithium-ion batteries

[0118] The positive electrode sheet prepared in step 2, the separator, and the negative electrode sheet prepared in step 3 are stacked and placed, and after liquid injection and formation, a lithium-ion battery is obtained.

[0119] Comparative experiment:

[0120] Take six groups of samples from Examples 1-5 and Comparative Examples, each group has 20 samples, and perform the following tests respectively:

[0121] 1. Test the first cycle capacity retention rate of each group of samples

[0122] (1) Charge at 1C or specified current to the final voltage, cut-off current 0.05C, and let stand for 30 minutes;

[0123] (2) Discharge at 1C to the final discharge voltage, record the discharge capacity, and let it stand for 30 minutes. The percentage of the discharge capacity in the first cycle to the initial capacity is the first cycle capacity retention rate.

[0124] 2. Test the 100-cycle capacity retention rate of each group of samples

[0125] (1) Charge at 1C or specified current to the final voltage, cut-off current 0.05C, and let stand for 30 minutes;

[0126] (2) Discharge at 1C to the final discharge voltage, record the discharge capacity, and let it stand for 30 minutes. The percentage of the discharge capacity at the 100th cycle to the initial capacity is the capacity retention rate at the 100th cycle.

[0127] 3. Test the number of cycles at which the discharge capacity of each group of samples decreases to 80% of the initial capacity.

[0128] (1) Charge at 1C or specified current to the final voltage, cut-off current 0.05C, and let stand for 30 minutes;

[0129] (2) Discharge at 1C to the final discharge voltage, record the discharge capacity, let it stand for 30 minutes, and record the number of cycles until the percentage of discharge capacity to initial capacity is 80%.

[0130] The average value of each test result is taken, and the test results are shown in the following table.

[0131]

[0132] According to the above table:

[0133] Compared with the comparative example, the first cycle capacity retention rate of Examples 1-3 is almost unchanged, which shows that preparing lithium oxalate into capsules does not affect the effect of the first lithium replenishment. In addition, the 100-cycle capacity retention rate and the number of cycles @ 80% SOC of Examples 1-3 are significantly higher than those of the comparative example, which shows that the cycle performance of Examples 1-3 is better than that of the comparative example.

[0134] Compared with Example 1, the proportion of lithium supplement capsules in the positive electrode sheet in Example 4 is reduced, and the reduced part is replaced by lithium oxalate. On this basis, the 100-cycle capacity retention rate and the number of cycles @80% SOC of Example 4 are improved compared with those of Example 1. This shows that the combined use of slow-release lithium supplement and traditional lithium supplement is helpful to improve the cycle performance of lithium manganate.

[0135] Example 5 further verifies the above argument. Compared with Example 4, the proportion of the components of the lithium supplement capsule in Example 5 is further reduced, and the proportion of the lithium oxalate component directly added to the positive electrode sheet is increased. On this basis, the 100-cycle capacity retention rate and the number of cycles @ 80% SOC of Example 5 are further reduced, which further illustrates that there needs to be an appropriate range for sustained-release lithium supplementation and direct addition of lithium supplementation, which is determined by the characteristics of lithium manganate materials.

[0136] It should be pointed out that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a positive electrode lithium supplement capsule, characterized in that: The steps include: S1. dissolving the polymer in dichloromethane to obtain an organic dispersion solution; S2. The first lithium supplement, gelatin and distilled water are mixed to form an aqueous solution; S3. The organic dispersion solution and the aqueous solution are mixed to form an O / W emulsion; S4. Drying the O / W emulsion; S5. Wash the product of S4 to obtain lithium supplement capsules.

2. The method according to claim 1, characterized in that In S1, the high molecular polymer is polyethylene and / or polystyrene.

3. The method according to claim 1, characterized in that In S2, the first lithium supplement is selected from at least one of lithium oxide, lithium nitride, lithium sulfide, lithium-rich lithium ferrite, lithium oxalate, and lithium nickelate.

4. The method according to claim 1, characterized in that The average diameter of the lithium supplement capsule is 1 μm.

5. A positive electrode lithium supplement capsule, characterized in that: Prepared by the method according to any one of claims 1 to 4.

6. A positive electrode sheet, comprising the positive electrode lithium supplement capsule according to claim 5, characterized in that: It also includes a positive electrode active material, a conductive agent and a binder; The positive electrode active material is lithium manganate.

7. The positive electrode sheet according to claim 6, characterized in that: The positive electrode sheet also includes a second lithium replenisher, which is completely consumed in the first three cycles.

8. The positive electrode sheet according to claim 7, characterized in that: The mass ratio of the second lithium replenisher to the positive electrode lithium replenishing capsule according to claim 5 is (1-2): (8-9).

9. The positive electrode sheet according to any one of claims 6 to 8, characterized in that: The first lithium supplement and the second lithium supplement are the same or different.

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