Lithium supplement film and application thereof

Abstract

The invention discloses a lithium supplementing film and application thereof, and belongs to the field of energy storage. The lithium supplementing film is different from an existing lithium supplementing method of pulping or coating, the supporting layer based on specific components has excellent mechanical strength, meanwhile, the lithium supplementing film can be directly applied and attached to a positive pole piece of a lithium battery energy storage device to achieve lithium supplementing, the requirements for production and use conditions are low, and the lithium supplementing capacity is stable and can be accurately controlled during lithium supplementing.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery energy storage, and in particular to a lithium supplement film and application thereof. Background Art

[0002] During the first charge and discharge cycle, a solid electrolyte interface (SEI) film is formed on the negative electrode interface of a lithium battery energy storage device, which causes a portion of active lithium to be deactivated and causes irreversible capacity loss. Therefore, it is generally necessary to replenish lithium in the device. The common lithium replenishment process is to add a certain lithium-containing compound when preparing the positive electrode of the device, which will replenish a certain amount of lithium ions to the positive electrode during the charge and discharge process of the device.

[0003] However, lithium-containing compounds have poor air stability and are easily deteriorated by reaction due to exposure to air and contact with moisture and carbon dioxide in the air. Therefore, the prior art introduces lithium-containing compounds into lithium-ion energy storage devices in a non-pulping form. For example, CN116130807A uses a conductive polymer doped with metallic lithium to prepare a lithium-replenishing film, which is further pressed with a base film to prepare a diaphragm for lithium-ion batteries to achieve lithium replenishment. However, this method has extremely high requirements for the quality of the diaphragm and high requirements for production conditions, otherwise there may be a risk of battery short circuit explosion. CN115832468A discloses a lithium-replenishing pole piece, which improves the activity and stability of the lithium-replenishing agent near the active layer of the current collector by arranging two layers of active material with different porosities on the current collector. However, this method requires strict control of the porosity of the two coatings, which has high requirements for the process in the actual preparation process, and also makes it difficult to control the lithium-replenishing capacity of the lithium-replenishing agent. Summary of the invention

[0004] Based on the defects of the prior art, the purpose of the present invention is to provide a lithium replenishing film. The product has excellent mechanical strength based on a support layer of specific components. At the same time, it can be directly applied to the positive electrode plate of a lithium battery energy storage device to achieve lithium replenishment. It has low requirements on production and use conditions, and the lithium replenishment capacity during lithium replenishment is stable and can be precisely controlled.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A lithium supplement film comprises a support layer and a lithium supplement layer located on the surface of the support layer;

[0007] The lithium supplement layer includes a lithium-containing compound, and the support layer includes polyester fiber.

[0008] In the prior art, in order to avoid the oxidation and deterioration of lithium-containing compounds in the lithium supplement agent, the lithium supplement agent is set on the surface of the positive electrode plate or the diaphragm in the form of a coating. However, this practice has high requirements for the production and preparation of the positive electrode plate or the diaphragm and the conditions of use, and it is difficult to control the lithium supplement capacity and lithium supplement efficiency of the lithium supplement agent. To this end, the present invention is designed to provide a thin film product specifically for lithium supplementation. The product is obtained by compounding a lithium supplement layer containing lithium-containing compounds and a support layer. The product is completely separated from the positive electrode plate of the lithium battery energy storage device. Therefore, both can be prepared using conventional process conditions, and the thickness of the lithium supplement layer is also controllable. When the lithium supplement diaphragm is in use, it is only necessary to laminate and roll the lithium supplement film with the positive electrode plate, and then peel off the support layer, so that the lithium supplement layer can be laminated on the positive electrode plate and used for lithium supplementation during the charging and discharging process. In this process, the bonding tightness and bonding uniformity of the lithium supplement layer and the active material layer of the positive electrode plate can also be adjusted depending on the bonding and rolling process conditions. At the same time, since the support layer uses polyester fiber as a component, it has excellent mechanical properties. Therefore, this product can not only achieve industrial pressing and bonding with the positive electrode, but also has moderate connectivity with the lithium replenishment layer, which can ensure that the lithium replenishment layer will not fall off easily during the preparation and bonding process, and the bonding effect is good. After the support layer is peeled off, it can also ensure that the surface of the lithium replenishment layer bonded to the positive electrode is intact, which will not affect the lithium replenishment efficiency of the lithium replenishment layer. If other components are used as the main body of the support layer, it is difficult to achieve this technical effect.

[0009] Preferably, the support layer has a thickness of 2 to 50 μm.

[0010] According to the actual thickness requirement of the lithium replenishing layer and the processing conditions when the lithium replenishing film is used later, the support layer of the present invention can be set to different thicknesses, and generally 2 to 50 μm is the most suitable.

[0011] Preferably, the polyester fiber is at least one of polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polyethylene glycol block copolyester (PETG), polypropylene terephthalate, poly(1,4-cyclohexanedimethyl terephthalate) fiber, poly(ethylene 2,6-naphthalate) fiber, and polyether carbonate.

[0012] After screening, it was found that when the above-mentioned polyester fibers are used, the mechanical strength of the product is better and the protective effect on the lithium replenishing layer is better.

[0013] More preferably, the polyester fiber in the support layer is at least one of polyethylene terephthalate and polybutylene terephthalate, and the thickness of the support layer is 15 to 25 μm.

[0014] When the support layer of the lithium-replenishing film of the present invention has the above technical features, it has the best mechanical strength, which can ensure that the components in the lithium-replenishing layer will not break or fall off during the lamination rolling process of the lithium-replenishing film, and the final lamination effect is good.

[0015] Preferably, the lithium replenishing layer comprises a lithium-containing compound and a reducing agent.

[0016] When a reducing agent is introduced into a lithium-containing compound, it can reduce the potential of the lithium-containing compound during the lithium replenishment process, thereby improving the lithium replenishment performance of the lithium-containing compound.

[0017] More preferably, the lithium-containing compound is LiF, LiO2, Li2O, Li2O2, Li2S, Li3N, Li3P, Li2NiO2, Li2CuO2, Li2MoO3, Li2VO3, Li2RuO3, Li2MnO3, Li2SiO3, Li2Si2O5, Li3VO4, Li3NbO4, Li3RuO4, Li3PO4, Li4SiO4, Li4TiO4, Li 5FeO4, Li5NbO5, Li5TaO5, Li5ReO6, Li6CoO4, Li6MnO4, Li6NiO4, Li6WO6, Li6Zr2O7, Li7NbO6, Li 7VO6, Li7BiO6, Li7TaO6, Li8ZrO6, Li8SnO6, Li8SiO6, Li8CeO6, Li8MoO6, Li8MnO6, Li8Nb2O9, Li 12 Nb2O 11 At least one of;

[0018] More preferably, the lithium-containing compound is at least one of Li5FeO4, Li4SiO4, Li2NiO2, and Li2SiO3.

[0019] More preferably, the reducing agent is at least one of a boride, a sulfide, a phosphide, and a reducing element;

[0020] The boride is at least one of cobalt boride, molybdenum boride, calcium boride, aluminum boride, magnesium boride, titanium boride, zirconium boride, silicon boride, and lanthanum boride;

[0021] The sulfide is at least one of sodium sulfide, iron sulfide, cobalt sulfide, molybdenum sulfide, tungsten sulfide, titanium sulfide, magnesium sulfide, calcium sulfide, copper sulfide, lanthanum sulfide, zinc sulfide, tin sulfide, nickel sulfide, and silicon sulfide;

[0022] The phosphide is at least one of iron phosphide, boron phosphide, nickel phosphide, sodium phosphide and zinc phosphide;

[0023] The reducing element is at least one of elemental sulfur, elemental phosphorus, elemental boron, elemental silicon, elemental aluminum, elemental germanium, elemental arsenic, elemental iodine, elemental vanadium, elemental manganese, elemental iron, elemental cobalt, elemental nickel, and elemental tin;

[0024] More preferably, the reducing agent is at least one of molybdenum boride, lanthanum boride, molybdenum sulfide, copper sulfide, lanthanum sulfide, nickel phosphide, elemental sulfur, elemental boron, and elemental cobalt.

[0025] More preferably, the lithium replenishing layer further includes at least one of a binder and a conductive agent.

[0026] More preferably, the binder is at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), polyethylene (PE), and polypropylene (PP); the conductive agent is at least one of graphene, carbon nanotubes, conductive carbon black, and carbon nanofibers.

[0027] More preferably, the lithium supplementing layer comprises the following components in parts by weight: 75-95 parts of a lithium-containing compound and a reducing agent, 5-25 parts of a binder, and 0-10 parts of a conductive agent.

[0028] Preferably, the thickness of the lithium replenishing layer is 0.5-50 μm.

[0029] According to the thickness of the positive electrode plate of the device actually requiring lithium replenishment and the difference in the active material system, those skilled in the art can select lithium replenishment layers of different thicknesses to prepare the lithium replenishment film of the present invention.

[0030] Preferably, the lithium-replenishing film further comprises a conductive layer, and the supporting layer and the conductive layer are respectively located on both sides of the lithium-replenishing layer.

[0031] When the conductive layer is modified on the lithium replenishment layer, the lithium replenishment film of the present invention can further improve the electron transmission efficiency between the lithium replenishment layer and the positive electrode plate when used. At the same time, due to the presence of the conductive layer, there is no direct contact between the lithium replenishment layer and the positive electrode plate, which can further avoid the mutual physical and chemical influence between the two structures during the bonding and charging and discharging processes, thereby improving the lithium replenishment stability of the lithium replenishment layer.

[0032] More preferably, the conductive layer comprises a conductive agent and a solid electrolyte;

[0033] More preferably, the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers;

[0034] More preferably, the solid electrolyte is at least one of an oxide solid electrolyte, a chloride solid electrolyte, and a polymer solid electrolyte. More preferably, the solid electrolyte includes Li7La3Zr2O 12 , Li 1.5 Al0.5 Ti 1.5 (PO4), Li 1.5 Al 0.5 Ge 1.5 One or more of oxide solid electrolytes such as lithium phosphorus oxide (PO4), lithium phosphorus oxide nitrogen (LiPON) and chlorides such as Li3InCl6, Li3YCl6, Li2ZrCl6 and polymer solid electrolytes.

[0035] More preferably, the conductive layer further includes a binder.

[0036] Another object of the present invention is to provide a method for preparing the lithium supplement film, comprising the following steps:

[0037] The raw materials for preparing the lithium supplement layer are mixed and ground, coated on the surface of the support layer and pressed to obtain the lithium supplement film;

[0038] or

[0039] The raw materials for preparing the lithium replenishing layer are mixed and ground, coated on the surface of the supporting layer and pressed to form the lithium replenishing layer, and then the raw materials for preparing the conductive layer are mixed and ground, coated on the surface of the lithium replenishing layer and rolled to obtain the lithium replenishing film.

[0040] The lithium-replenishing film of the present invention adopts a pressing / rolling method to construct and combine various structural layers whether it contains a conductive layer or not. The operation steps are simple, and products with different thicknesses and lithium-replenishing efficiencies can be obtained directly by adjusting the processing conditions during pressing / rolling or the formula of the raw materials, thereby realizing industrial large-scale production.

[0041] Preferably, the pressure during pressing is 2-25t and the temperature is 10-80°C.

[0042] Preferably, the pressure during rolling is 2-25t and the temperature is 10-80°C.

[0043] Another object of the present invention is to provide a method for replenishing lithium in a lithium battery energy storage device, comprising the following steps:

[0044] (1) butting and laminating one side of the active material of the positive electrode sheet with the lithium replenishing layer or the conductive layer of the lithium replenishing film of the present invention and rolling them, and then peeling off the supporting layer of the lithium replenishing film to obtain a positive electrode sheet containing the lithium replenishing layer;

[0045] (2) The positive electrode plate is used to assemble a lithium-ion energy storage device, thereby completing the lithium replenishment of the lithium-ion energy storage device.

[0046] Compared with the existing conventional lithium replenishment process, the lithium replenishment method of the lithium battery energy storage device described in the present invention does not rely on the processing and preparation of the positive electrode plate, and can even use the existing commercially produced positive electrode plates. It only needs to combine the lithium replenishment film described in the present invention with the positive electrode plate by rolling, and then use the plate to prepare the lithium battery energy storage device, and the lithium replenishment of the device is completed. There is no need to consider the mutual influence between the lithium replenishment material and the positive electrode active material during the production and mixing process. This method is more suitable for semi-automatic / fully automatic factory production modes that require large production capacity and high yield. However, this lithium replenishment method can only achieve the ideal effect when the lithium replenishment layer of the lithium replenishment film contains lithium-containing compounds. If the active lithium replenisher in the lithium replenishment layer is of other types, it is difficult to guarantee the effect.

[0047] Preferably, the lithium energy storage device includes a lithium battery, a lithium ion battery, a semi-solid battery or a solid-state battery.

[0048] Preferably, the active material is at least one of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese phosphate, lithium cobalt oxide, lithium manganese oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0049] The lithium-supplementing film of the present invention is suitable for various lithium-ion energy storage devices and is also universal for positive electrode active materials of different systems.

[0050] Preferably, the roller pressing has a pressure of 2 to 25 t and a temperature of 10 to 80°C.

[0051] The beneficial effect of the present invention is that the present invention provides a lithium replenishing film. This product is different from the existing lithium replenishing methods of pulping or coating. The support layer based on the specific composition has excellent mechanical strength. At the same time, it can be directly applied to the positive electrode plate of the lithium battery energy storage device to achieve lithium replenishment. It has low requirements for production and use conditions. The lithium replenishment capacity during lithium replenishment is stable and can be precisely controlled. DETAILED DESCRIPTION

[0052] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments and comparative examples, the purpose of which is to understand the content of the present invention in detail, rather than to limit the present invention. All other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the protection scope of the present invention. The experimental reagents and instruments involved in the implementation of the present invention, unless otherwise specified, are all commonly used common reagents and instruments.

[0053] Examples 1 to 9

[0054] An embodiment of the lithium-replenishing film and its application according to the present invention, and a method for preparing the lithium-replenishing film according to this embodiment, comprises the following steps:

[0055] (1) mixing and grinding a commercially available lithium-containing compound, a reducing agent, a binder, and a conductive agent to obtain a lithium-replenishing layer slurry;

[0056] (2) After cutting the commercially available support layer into a suitable size, the lithium replenishing layer slurry is coated on one side, and then pressed at 40° C. and 15 MPa to obtain a lithium replenishing film.

[0057] The ratio and composition of each raw material are shown in Table 1.

[0058] Table 1

[0059]

[0060] In order to verify the performance of the lithium supplement film described in this embodiment, a positive electrode sheet for a lithium ion battery was prepared in advance, including the following steps: using NMP as a solvent, adding a certain amount of binder PVDF to NMP, stirring for 30 minutes until the binder is completely dissolved, then adding a certain amount of conductive agent Super P, stirring for 20 minutes until the conductive agent is completely dispersed, and adding different commercial positive active materials (LiFePO4, ternary NCM LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.5 Mn 1.5 O4), the mass ratio of positive electrode active material, binder and conductive agent is 94:3:3. After stirring for 30 minutes, the slurry is coated on aluminum foil with a certain thickness, and then dried and rolled to obtain a positive electrode sheet with a thickness of 100 μm. The sheets are marked as D1 (LiFePO4), D2 (ternary NCM) and D3 (LiNi 0.5 Mn 1.5 O4).

[0061] The lithium replenishing layer of the lithium replenishing film obtained in each embodiment is closely contacted with the active material layer of the corresponding positive electrode plate, and then the two are rolled and laminated at 25°C and 10MPa. Then the supporting layer of the lithium replenishing film is peeled off, and the positive electrode plate retaining the lithium replenishing layer is used as the positive electrode, the commercial silicon-carbon material is used as the negative electrode, and 1M LiPF6 is dissolved in EC / DMC (1:1, volume ratio) as the electrolyte, and assembled into a button battery of model CR2032 in a glove box filled with inert atmosphere.

[0062] After the prepared button cell was left to stand at room temperature for 10 hours, a charge and discharge cycle test was performed on the button cell prepared above using a Blue Electric Battery Charge and Discharge Tester. The theoretical specific capacity of lithium iron phosphate was calculated to be 160mAh / g, the theoretical specific capacity of NCM was calculated to be 210mAh / g, and the theoretical specific capacity of high-voltage nickel manganese oxide was calculated to be 140mAh / g. The specific test conditions of the battery are as follows: the charge and discharge current of lithium iron phosphate in the first week is 0.05C, and the voltage is 2.5~4.2V. From the second week, the charge and discharge current is 0.2C, and the voltage is 2.5~3.8V; the charge and discharge current of ternary NCM in the first week is 0.05C, and the voltage is 2.5~4.6V. From the second week, the charge and discharge current is 0.2C, and the voltage is 2.5~3.2V; the charge and discharge current of high-voltage nickel manganese oxide in the first week is 0.05C, and the voltage is 3.0~4.85V. From the second week, the charge and discharge current is 0.2C, and the voltage is 3.0~4.85V.

[0063] The test results are shown in Table 2.

[0064] At the same time, the electrodes D1 to D3 were directly assembled into batteries and tested according to the above method without composite lithium supplementation films, serving as a blank control group.

[0065] Finally, the lithium-containing compound and reducing agent in Example 2 were directly added to the positive electrode slurry of the blank group, mixed evenly and coated to obtain a positive electrode sheet containing lithium supplement material. The battery was directly assembled and tested according to the above method as a control group.

[0066] As can be seen from Table 2, after the lithium-replenishing film of the present invention is applied to lithium-ion batteries, compared with the blank groups of three different active material systems, the initial charging capacity and discharge capacity of the lithium-ion battery are improved, and the charging capacity after 100 cycles is still higher than that of the blank group, indicating that the lithium-replenishing film can achieve the expected lithium-replenishing effect. At the same time, compared with the control group, it can be seen that the performance of the lithium-replenishing battery prepared by the method provided by the present invention is better than that of the lithium-replenishing battery obtained by directly adding the lithium-replenishing material to the positive electrode slurry for coating. At the same time, this method can be directly applied to commercial positive electrode sheets that have been prepared, and has a wider range of applications.

[0067] Table 2

[0068]

[0069]

[0070] Embodiments 10 to 20

[0071] An embodiment of the lithium-replenishing film and its application according to the present invention, and a method for preparing the lithium-replenishing film according to this embodiment, comprises the following steps:

[0072] (1) mixing and grinding a commercially available lithium-containing compound, a reducing agent, and a binder to obtain a lithium-replenishing layer slurry;

[0073] (2) mixing and grinding the conductive agent, solid electrolyte, and binder to obtain a conductive layer slurry;

[0074] (3) After cutting the commercially available support layer into a suitable size, a lithium replenishing layer slurry is coated on one side, and then pressed at 40°C and 15 MPa to form a lithium replenishing layer on the support layer surface. Then, a conductive layer slurry is coated on the lithium replenishing layer and pressed at 25°C and 10 MPa to obtain a lithium replenishing film.

[0075] The ratio and composition of each raw material are shown in Table 3.

[0076] Table 3

[0077]

[0078]

[0079] In order to verify the performance of the lithium-replenishing film described in this example, a positive electrode sheet for a lithium-ion battery was prepared in the same manner as in Example 1 and the same test was performed.

[0080] The test results are shown in Table 4.

[0081] It can be seen from Table 4 that when the lithium-replenishing film of the present invention is further introduced into a conductive layer, the obtained product can further improve the initial charging capacity of the lithium-ion battery during lithium replenishment, and the electrochemical performance of the lithium-ion battery is further improved.

[0082] Table 4

[0083]

[0084]

[0085] Comparative Examples 1 to 3

[0086] A self-supporting lithium-replenishing film and its application, wherein the preparation method of the self-supporting lithium-replenishing film comprises the following steps:

[0087] (1) A commercially available lithium-containing compound, a reducing agent, a binder, and a conductive agent are mixed and ground evenly to obtain a lithium-replenishing layer slurry; the lithium-replenishing layer slurry formulas of the three comparative examples are the same as those of Example 2, Example 5, and Example 8, respectively;

[0088] (2) The lithium-replenishing layer slurry is coated on a solid plate, followed by pressing at 40° C. and 15 MPa, and the solidified film is separated from the solid plate to obtain a self-supporting lithium-replenishing film.

[0089] The respective supporting lithium supplement films were used to bond the positive electrode sheets and tested according to the method described in Example 1. The results are shown in Table 5.

[0090] It can be seen from Table 5 that compared with the lithium replenishing effect of the lithium replenishing film described in Example 1, the self-supporting lithium replenishing film did not show the expected lithium replenishing effect. This is mainly because without the support layer, the film does not have sufficient mechanical strength when compounded with the positive electrode plate, and is prone to breakage and falling off. The bonding effect with the active material layer of the positive electrode plate is poor, and the lithium replenishing effect of the lithium-containing compound cannot be exerted.

[0091] Table 5

[0092]

[0093] Comparative Examples 4 to 6

[0094] A self-supporting lithium-replenishing film and its application, wherein the preparation method of the self-supporting lithium-replenishing film comprises the following steps:

[0095] (1) mixing and grinding a commercially available lithium-containing compound, a reducing agent, a binder, and a conductive agent to obtain a lithium-replenishing layer slurry;

[0096] (2) mixing and grinding the conductive agent, solid electrolyte, and binder to obtain a conductive layer slurry;

[0097] (3) coating a lithium replenishing layer slurry on a solid plate, and then pressing at 40°C and 15 MPa to form the lithium replenishing layer, and then coating a conductive layer slurry on the lithium replenishing layer and pressing at 25°C and 10 MPa to separate the obtained composite film layer into a solid plate to obtain a self-supporting lithium replenishing film; the formulas of the lithium replenishing layer slurry and the conductive layer slurry in steps (1) and (2) of the three comparative examples are the same as those in Example 11, Example 15 and Example 20, respectively.

[0098] The respective supporting lithium-supplementing films were used to bond the positive electrode sheets and tested according to the method described in Example 1. The results are shown in Table 6.

[0099] Table 6

[0100]

[0101] Comparative Example 7

[0102] A lithium supplement film, which is different from Example 2 only in that the support layer is composed of polyethylene.

[0103] The product was used to bond positive electrode sheets and tested according to the method described in Example 1. The results are shown in Table 7.

[0104] Table 7

[0105]

[0106] Comparative Example 8

[0107] A lithium supplement film, which is different from Example 2 only in that the support layer is composed of polyvinyl chloride.

[0108] The product was used to bond positive electrode sheets and tested according to the method described in Example 1. The results are shown in Table 8.

[0109] Table 8

[0110]

[0111]

[0112] It can be seen from the lithium replenishment effects of Comparative Examples 7 and 8 and the corresponding example products that the material of the support layer of the lithium replenishment film of the present invention cannot be selected arbitrarily. If an inappropriate type is selected, it may cause the lithium replenishment layer to break and fall off during the process of bonding the product with the positive electrode sheet, and may also damage the lithium replenishment layer when the support layer is peeled off.

[0113] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A lithium supplement film, characterized in that: It includes a support layer and a lithium supplement layer located on the surface of the support layer; The lithium supplement layer includes a lithium-containing compound, and the support layer includes polyester fiber.

2. The lithium supplement film according to claim 1, characterized in that: The thickness of the support layer is 2-50 μm.

3. The lithium supplement film according to claim 1, characterized in that: The polyester fiber is at least one of polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyethylene glycol block copolyester, polypropylene terephthalate, poly(1,4-cyclohexanedimethyl terephthalate) fiber, poly(ethylene-2,6-naphthalate) fiber, and polyether ester carbonate.

4. The lithium supplement film according to claim 1, characterized in that: The lithium replenishing layer comprises a lithium-containing compound and a reducing agent; preferably, the lithium-containing compound is LiF, LiO2, Li2O, Li2O2, Li2S, Li3N, Li3P, Li2NiO2, Li2CuO2, Li2MoO3, Li2VO3, Li2RuO3, Li2MnO3, Li2SiO3, Li2Si2O5, Li3VO4, Li3NbO4, Li3RuO4, Li3PO4, Li4SiO4, Li 4TiO4, Li5FeO4, Li5NbO5, Li5TaO5, Li5ReO6, Li6CoO4, Li6MnO4, Li6NiO4, Li6WO6, Li6Zr2O7, Li7NbO 6. Li7VO6, Li7BiO6, Li7TaO6, Li8ZrO6, Li8SnO6, Li8SiO6, Li8CeO6, Li8MoO6, Li8MnO6, Li8Nb2O9, Li 12 Nb2O 11 At least one of the following: the reducing agent is at least one of a boride, a sulfide, a phosphide, and a reducing element.

5. The lithium supplement film according to claim 4, characterized in that: The lithium replenishing layer also includes at least one of a binder and a conductive agent; preferably, the binder is at least one of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, polyethylene, and polypropylene; the conductive agent is at least one of graphene, carbon nanotubes, conductive carbon black, and carbon nanofibers.

6. The lithium supplement film according to claim 1, characterized in that: The thickness of the lithium supplement layer is 0.5-50 μm.

7. The lithium supplement film according to claim 1, characterized in that: The lithium supplement film further comprises a conductive layer, and the support layer and the conductive layer are respectively located on two sides of the lithium supplement layer.

8. The lithium supplement film according to claim 7, characterized in that: The conductive layer includes a conductive agent and a solid electrolyte; preferably, the conductive agent is at least one of conductive carbon black, carbon nanotubes, graphene, and carbon nanofibers; and the solid electrolyte is at least one of an oxide solid electrolyte, a chloride solid electrolyte, and a polymer solid electrolyte.

9. The method for preparing a lithium supplement thin film according to any one of claims 1 to 8, characterized in that: The following steps are involved: The raw materials for preparing the lithium supplement layer are mixed and ground, coated on the surface of the support layer and pressed to obtain the lithium supplement film; or The raw materials for preparing the lithium replenishing layer are mixed and ground, coated on the surface of the supporting layer and pressed to form the lithium replenishing layer, and then the raw materials for preparing the conductive layer are mixed and ground, coated on the surface of the lithium replenishing layer and rolled to obtain the lithium replenishing film.

10. A lithium replenishment method for a lithium battery energy storage device, characterized in that: The following steps are involved: (1) butting and laminating one side of the active material of the positive electrode sheet with the lithium supplement layer or the conductive layer of the lithium supplement film according to any one of claims 1 to 8, and rolling them, and then peeling off the supporting layer of the lithium supplement film to obtain a positive electrode sheet containing the lithium supplement layer; (2) The positive electrode plate is used to assemble a lithium-ion energy storage device, thereby completing the lithium replenishment of the lithium-ion energy storage device.

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