Secondary battery and method for manufacturing the same

Abstract

The secondary battery comprises a positive electrode, a negative electrode and an electrolyte, the positive electrode comprises a matrix and a lithium supplementing material, the lithium supplementing material is loaded in the matrix, at least part of the matrix is decomposed under the influence of environmental parameters in the secondary battery, and the lithium supplementing material is decomposed along with the matrix to release lithium. The lithium supplementing material in the secondary battery can slowly release lithium, so that the problem of lithium loss in the recycling of the secondary battery is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary batteries, and in particular to a secondary battery and a preparation method thereof. Background Art

[0002] During the first charge and discharge of a liquid lithium-ion battery, the lithium ions released from the positive electrode material react with the electrolyte to form a solid electrolyte interface (SEI) on the surface of the negative electrode material. This process will irreversibly consume more than 10% of the lithium source in the positive electrode material, making the first-week coulomb efficiency of the lithium-ion battery less than 90%, and will continue to consume the active lithium in the positive electrode during the charge and discharge cycle of the lithium-ion battery, resulting in a shortened life of the lithium-ion battery.

[0003] In response to this phenomenon, the current solution is to add appropriate lithium supplement materials to the positive electrode active materials, and reduce the lithium loss during the cycle by decomposing the lithium supplement materials to release active lithium during the battery charging process. In the prior art, after the lithium supplement materials are added to the battery as lithium supplement agents, most of them completely release lithium in the formation stage, which means that the lithium supplement agent only has a single lithium supplement effect on the battery; however, since the battery will still produce active lithium loss in the subsequent cycle process, the lithium supplement agent in the prior art cannot continue to supplement lithium to the battery, resulting in a decrease in the cycle stability of the battery in the prior art. Therefore, how to solve the lithium loss during the recycling of existing secondary batteries and achieve continuous lithium supplementation has become the key. Summary of the invention

[0004] The purpose of the present invention is to provide a secondary battery and a preparation method thereof, so as to solve the problem of lithium loss during the cyclic use of the existing secondary battery.

[0005] To achieve the purpose of the present invention, the present invention provides the following technical solutions:

[0006] In a first aspect, the present invention provides a secondary battery comprising a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode comprises a matrix and a lithium supplement material, wherein the lithium supplement material is loaded in the matrix, and at least a portion of the matrix is ​​decomposed by environmental parameters inside the secondary battery, and the lithium supplement material decomposes lithium along with the matrix.

[0007] In one embodiment, the matrix may be decomposed under the influence of environmental parameters inside the secondary battery, wherein the environmental parameters include at least one of pH and temperature; wherein the decomposition pH value of the matrix is ​​less than or equal to 8; and / or the decomposition temperature of the matrix is ​​greater than or equal to 50°C.

[0008] In one embodiment, the substrate includes a conductive carrier, the conductive carrier is provided with holes, and at least the lithium supplement material is accommodated in the conductive carrier.

[0009] In one embodiment, the substrate further includes a packaging material, which is bonded to the conductive carrier, at least a portion of which covers the opening of the hole, and the packaging material decomposes in the secondary battery to expose the lithium supplement material in the hole.

[0010] In one embodiment, the packaging material forms a packaging film that is stacked in multiple layers, and the lithium supplementing material is disposed between two adjacent layers of the packaging film.

[0011] In one embodiment, the secondary battery further includes a catalyst, the catalyst is supported on the conductive carrier, and at least a portion of the catalyst is contained in the pores.

[0012] In one embodiment, the conductive carrier includes one or more of carbon fiber fabric, carbon fiber paper, and carbon aerogel.

[0013] In one embodiment, the packaging material includes one or more of a high molecular polymer, a metal compound, and a carbon material.

[0014] In one embodiment, the depth of the holes is 30% to 80% of the diameter of the conductive carrier.

[0015] In one embodiment, the porosity of the conductive carrier is 50% to 90%.

[0016] In one embodiment, the specific surface area of ​​the conductive carrier is 600 m 2 / g~1800m 2 / g.

[0017] In one embodiment, the mass ratio of the lithium supplement material, the conductive carrier and the packaging material is 100: (10-30): (1-10).

[0018] In one embodiment, part of the lithium supplement material is bonded to the outer surface of the substrate, and part of the lithium supplement material is contained inside the substrate. The lithium supplement material contained inside the substrate decomposes and releases lithium along with the substrate.

[0019] In one embodiment, the positive electrode is a self-supporting electrode.

[0020] In one embodiment, the positive electrode further includes a positive electrode active material, and the positive electrode active material is supported on the surface of the substrate.

[0021] In one embodiment, the lithium supplement material includes an organic lithium salt, and the chemical formula of the organic lithium salt includes Li x1 C y1 O z1 , where 0<x1≤2,y1> 0,z1>0.

[0022] In a second aspect, the present invention provides a method for preparing a secondary battery, comprising: providing a lithium-supplementing material raw material and a matrix; pretreating the matrix and filling the lithium-supplementing material raw material into the matrix; controlling the lithium-supplementing material raw material in the matrix to be converted into a lithium-supplementing material and loading it into the matrix to form a positive electrode; providing a negative electrode and an electrolyte; and assembling the positive electrode, the negative electrode and the electrolyte to obtain a secondary battery.

[0023] In order to solve the above technical problems, the present invention provides a secondary battery capable of achieving full life cycle lithium replenishment. The secondary battery includes a matrix and a lithium replenishing material. During the use of the secondary battery, at least a portion of the matrix is ​​decomposed due to the influence of the environmental parameters inside the secondary battery, so that the lithium replenishing material loaded on the matrix is ​​exposed to the battery environment. The lithium replenishing material slowly releases lithium replenishment as the matrix decomposes, thereby achieving full life cycle lithium replenishment of the secondary battery during the cycle process. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 is a schematic diagram of a secondary battery according to an embodiment;

[0026] Figure 2 is a schematic cross-sectional view of a positive electrode of an embodiment;

[0027] Figure 3 is a cross-sectional schematic diagram of a lithium supplement material, a conductive carrier and a packaging material according to an embodiment;

[0028] Figure 4 is a schematic cross-sectional view of a lithium supplement material and a matrix according to an embodiment;

[0029] Figure 5 is a partial cross-sectional schematic diagram of a conductive carrier according to an embodiment;

[0030] Figure 6 The present invention is a flow chart of a method for preparing a secondary battery according to an embodiment. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in 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 meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in the present invention includes any and all combinations of one or more of the related listed items.

[0033] It should be noted that the "range" disclosed in the present invention is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a specific parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present invention, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] All steps of the present invention may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b, etc.

[0035] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0036] The present invention provides a secondary battery, please refer to Figure 1-Figure 5 .

[0037] In one implementation, please refer to Figure 1 The lithium-ion secondary battery 1000 includes a negative electrode, a positive electrode 100 and an electrolyte, wherein the electrolyte may be an electrolyte, and thus the secondary battery 1000 further includes a separator disposed between the positive electrode 100 and the negative electrode; or the electrolyte may be a solid electrolyte, and thus the separator is not disposed in the secondary battery 1000 but is replaced by a solid electrolyte. In a specific embodiment, the positive electrode 100 includes a lithium supplement material 10 and a positive electrode active material 30, and the lithium supplement material 10 is used to supplement lithium to the positive electrode active material 30.

[0038] In one implementation, please refer to Figure 2 The positive electrode 100 includes a substrate 20 and a lithium supplement material 10, the lithium supplement material 10 is loaded on the substrate 20, the positive electrode active material 30 is combined in the substrate 20, at least part of the substrate 20 is decomposed by the environmental parameters inside the secondary battery, and the lithium supplement material 10 decomposes lithium along with the substrate 20.

[0039] Specifically, the lithium replenishing material 10 is the main body for replenishing lithium, which can contribute a large amount of lithium ions. During the first charging process, the lithium (Li) in the lithium replenishing material 10 can be released and migrated to the negative electrode of the battery to offset the irreversible lithium loss caused by the formation of the SEI film, thereby increasing the total capacity and energy density of the battery. In the prior art, after the lithium replenishing material 10 is added to the battery, most of them completely release lithium in the formation stage, which means that the lithium replenishing material 10 only has a single lithium replenishing effect on the battery; however, since the battery will still produce active lithium loss in the subsequent cycle process, the secondary battery in the prior art cannot achieve continuous lithium replenishment, resulting in a decrease in the cycle stability of the secondary battery in the prior art. Therefore, how to achieve continuous slow-release lithium replenishment of the secondary battery during the cycle process to achieve full life cycle lithium replenishment has become the key.

[0040] In order to solve the above technical problems, the present invention provides a secondary battery capable of achieving full life cycle lithium replenishment. The secondary battery includes a substrate 20 and a lithium replenishing material 10. During the use of the secondary battery, at least a portion of the substrate 20 is decomposed due to the environmental parameters inside the secondary battery, so that the lithium replenishing material 10 loaded on the substrate 20 is exposed to the battery environment, and the lithium replenishing material 10 slowly releases the replenished lithium as the substrate 20 decomposes.

[0041] In one embodiment, the chemical formula of the lithium supplement material 10 includes Li x1 Cy1 O z1 , where 0 < x1 ≤ 2, y1 > 0, z1 > 0. In a specific embodiment, the lithium supplement material 10 may include one or more of Li2C2O4 (lithium oxalate), Li2CO3 (lithium carbonate), Li2C3O3 (lithium trioxalate), Li2C4O4 (lithium butynedioate), Li2C6O6, Li2C3O5 (lithium pyruvate), Li2C5O5 (lithium ketonate), and Li2C4O6.

[0042] In other embodiments, the chemical formula of the lithium supplement material 10 includes Li x2 M y2 O z2 , where M is at least one element among Fe, Ni, Mn, Cu, Zn, Co, Cr, Zr, Sb, Ti, V, Mo, Sn, etc., 1 ≤ x2 ≤ 8, 0 < y2, 0 < z2 < 7. In a specific embodiment, the lithium supplement material 10 may include at least one of Li5FeO4, Li6MnO4, Li6CoO4, Li6ZnO4, Li2NiO2, Li2CuO2, Li2CoO2, Li2MnO2, Li2Ni 0.5 Mn 1.5 O4, Li2Ni d Cu (1-d) O2 (0 < d < 1), etc.

[0043] In other embodiments, the chemical formula of the lithium supplement material 10 includes Li x3 K y3 , where K is at least one element among O, S, P, N, F, B, Se, Te, 1 ≤ x3 ≤ 5, 0 < y3. The binary lithium supplement material 10 includes but is not limited to at least one of Li2O, Li2O2, Li3N, Li2S, LiF, Li3P, Li2Se.

[0044] In other embodiments, the chemical formula of the lithium supplement material 10 includes Li 1+x4 A y4 O z4 , where 0 < x4 ≤ 1.2, 1 ≤ y4 < 3, z4 > 0, and A includes at least one of Ni, Fe, Mn, Co, Cr, V, Mo, Ti, Nb, Zr, Cu, Mg. These lithium supplement materials 10 can be used both as lithium supplement agents and directly as cathode 100 materials. Exemplarily, the lithium supplement material 10 includes at least one of Li2CuO2, Li2NiO2, Li2MnO2.

[0045] In other embodiments, the lithium supplement material 10 may also include LiOH (delithiation potential 4.8V), Li4SiO4 (delithiation potential 4.5V), and Li3PO4 (delithiation potential exceeds 4V). In addition, the lithium supplement material 10 mentioned above may be undoped or modified by doping, or may be surface coated, pre-lithiation treated, etc. These lithium supplement materials 10 have high theoretical capacity and structural stability, can provide sufficient lithium ions, effectively supplement the irreversible lithium ions consumed by the formation of SEI film at the negative electrode, and improve the initial efficiency and overall electrochemical performance of the battery.

[0046] In one embodiment, the material of the substrate 20 includes a mixture of one or more of a high molecular polymer, a metal compound, and a carbon material. The shape of the substrate 20 is not specifically limited. The function of the substrate 20 is to load the lithium supplement material 10; in a specific embodiment, the lithium supplement material 10 can be loaded on the outside of the substrate 20 and / or inside the substrate 20. In addition, the substrate 20 can be decomposed by the environmental parameters inside the secondary battery, and the lithium supplement material 10 loaded thereon is then exposed to the internal environment of the secondary battery, specifically, it can be exposed in the electrolyte of the secondary battery, so that the lithium supplement material 10 slowly releases lithium.

[0047] It should be explained that the material of the substrate 20 is not specifically limited. In a specific embodiment, the substrate 20 can be a material that is sensitive to pH or temperature. For example, in an acidic or alkaline environment, the substrate 20 will decompose, and the substrate 20 can also decompose with the increase of temperature. At the same time, the substrate 20 can be used to protect the lithium supplement material 10 to ensure that part of the lithium supplement material 10 will not decompose lithium during the formation process of the secondary battery. It is understandable that after the secondary battery is formed or during the use of the battery, the internal environmental parameters of the secondary battery will change, such as changes in pH, causing at least part of the substrate 20 to decompose, so that the protected part of the lithium supplement material 10 decomposes lithium with the substrate 20, thereby achieving the purpose of slow-release lithium supplement; of course, the substrate 20 can also be decomposed due to the increase in temperature during the use of the secondary battery.

[0048] In one embodiment, the substrate 20 may be decomposed under the influence of environmental parameters inside the secondary battery, and the environmental parameters include at least one of pH and temperature; wherein the decomposition pH value of the substrate 20 is less than or equal to 8; and / or the decomposition temperature of the substrate 20 is greater than or equal to 50° C. Specifically, the substrate 20 may be a material that is not alkali-resistant or high-temperature-resistant, so the substrate 20 may be decomposed to release lithium under the influence of environmental parameters.

[0049] In a specific embodiment, the decomposition pH value of the matrix 20 can be 1, 2, 3, 4, 5, 6, 7, 8. Optionally, the matrix 20 can be decomposed in a weakly acidic, neutral or weakly alkaline environment. The decomposition pH value range of the matrix 20 can be 6 to 8; wherein a pH value of 6 to 7 (excluding 7) is a weakly acidic environment, a pH value of 7 is a neutral environment, and a pH value of 7 to 8 (excluding 7) is a weakly alkaline environment.

[0050] In a specific embodiment, the decomposition temperature of the substrate 20 may be 50° C., 60° C., 70° C., 80° C., 90° C., 100° C., 120° C., or 150° C. Optionally, the substrate 20 may be decomposed in a heat-generating environment of the secondary battery. The decomposition temperature of the substrate 20 may range from 50° C. to 100° C.

[0051] In one implementation, please refer to Figure 3 The substrate 20 includes a conductive carrier 21, and the conductive carrier 21 is provided with holes 211, and at least part of the lithium supplement material 10 is accommodated in the conductive carrier 21. Optionally, a plurality of blind holes are formed on the surface of the conductive carrier 21, and at least part of the lithium supplement material 10 is accommodated in the holes 211. The openings of the holes 211 can be blocked by the conductive carrier 21 or other materials, so that the lithium supplement material 10 is enclosed in the holes 211; after the material at the opening of the holes 211 is decomposed, the lithium supplement material 10 is exposed and begins to release lithium. By making holes 211 on the conductive carrier 21 and accommodating the lithium supplement material 10 in the holes 211, the hole 211 effect is utilized to protect the lithium supplement material 10 in the holes. The holes 211 on the conductive carrier 21 can also be used to absorb the gas generated by the lithium supplement material 10 after discharge, thereby achieving the purpose of suppressing the gas production of the secondary battery.

[0052] In a specific embodiment, the conductive carrier 21 has non-uniform holes 211, wherein the non-uniform holes 211 refer to that the sizes (depth, caliber, volume) of the multiple holes 211 are not all the same. The advantage of the non-uniform holes 211 is that the different volumes of the holes 211 result in different contents of the lithium-replenishing material 10 in the holes 211, and the lithium-release time of the lithium-replenishing material 10 in different holes 211 is different. It can be understood that in smaller holes 211, the lithium-replenishing material 10 is released first and the lithium-release time is shorter; in larger holes 211, the lithium-replenishing material 10 is released later and the lithium-release time is longer under the restriction of the packaging material 22, thereby achieving the purpose of lithium replenishment throughout the life cycle.

[0053] In one embodiment, the conductive carrier 21 includes one or more of carbon fiber fabric, carbon fiber paper, and carbon aerogel. In a specific embodiment, the conductive carrier 21 is a carbon fiber fabric, which refers to a high-performance material made of carbon fiber filaments through a weaving process. The carbon fiber fabric has the characteristics of light weight, high strength, high rigidity, corrosion resistance, and fatigue resistance. The lithium supplement material 10 is loaded on the carbon fiber fabric, and the lithium supplement material 10 can be specifically located inside or outside the carbon fiber fabric, as well as in the pore structure of the carbon fiber fabric. The positive electrode active material 30 is coated on the carbon fiber fabric and forms a positive electrode 100 active layer.

[0054] The advantages of using carbon fiber fabric as a load for the lithium supplement material 10 and the positive electrode active material 30 are: 1) the carbon fiber fabric can increase the conductivity of the lithium supplement material 10, and the carbon fiber fabric can also replace part of the conductive agent in the positive electrode 100, reducing the use of the conductive agent in the positive electrode 100; 2) the carbon fiber fabric is more conducive to stabilizing the structural stability of the positive electrode 100, and can greatly improve the mechanical properties and flexibility of the positive electrode 100.

[0055] In one implementation, please refer to Figure 2 and Figure 3 The substrate 20 also includes a packaging material 22, which is combined with the conductive carrier 21, and at least part of the packaging material 22 covers the opening of the hole 211. After the packaging material 22 is decomposed in the secondary battery, the lithium supplement material 10 in the hole 211 is exposed. Specifically, the lithium supplement material 10 and the packaging material 22 are both contained in the conductive carrier 21; wherein the packaging material 22 covers part of the lithium supplement material 10 to protect part of the lithium supplement material 10 from decomposing lithium during the formation stage. It should be noted that the packaging material 22 covers the opening of the hole 211, which means that the part of the lithium supplement material 10 originally exposed in the hole 211 is covered by the packaging material 22, so that before the packaging material 22 is decomposed, the lithium supplement material 10 will not or can only release a small amount of lithium ions. After the packaging material 22 is decomposed, the lithium supplement material 10 is exposed in the electrolyte, thereby replenishing lithium.

[0056] In one embodiment, the packaging material 22 includes one or more of a polymer, a metal compound, and a carbon material. It should be noted that the packaging material 22 has the characteristics of poor mechanical properties, easy cracking, slight acidity, and easy degradation under high temperature conditions. After the secondary battery is formed or used, due to the decrease in pH value in the secondary battery or the gas generation of the material, or the temperature of the secondary battery increases, the packaging material 22 may fail and the packaging material 22 may gradually decompose, thereby exposing the lithium supplement material 10 and achieving the effect of slow-release lithium supplementation.

[0057] In a specific embodiment, the packaging material 22 can be a non-conductive polymer. The advantage of selecting a polymer is that the stability of the polymer is affected by its own molecular weight and functional groups, and some polymers are easily hydrolyzed in an acidic or alkaline environment; in addition, the advantage of selecting a non-conductive polymer is that before the packaging material 22 decomposes, its non-conductive property can prevent the lithium supplement material 10 from releasing lithium through the packaging material 22. Optionally, the packaging material 22 can also be a non-conductive polymer with a cross-linked structure. The polymer with a cross-linked structure can increase the flexibility and toughness of the conductive carrier 21, and is more suitable for making a self-supporting electrode.

[0058] The present invention combines a conductive carrier 21 and a packaging material 22 as a matrix 20, which can not only achieve the effect of sustained-release lithium replenishment of the lithium replenishing material 10, but also can be used to make a self-supporting electrode, simplify the structure of the positive electrode 100 to improve the performance of the secondary battery, and reduce the production cost and environmental impact of the secondary battery; in addition, the packaging material 22 is used to encapsulate the lithium replenishing material 10 and the auxiliary lithium replenishing material 10 to achieve sustained-release lithium replenishment, and the conductive carrier 21 is used to load the two and improve the conductivity and structural stability of the positive electrode 100, and after the lithium replenishing material 10 and the packaging material 22 are decomposed, the structure can still be kept stable, and pits on the surface of the positive electrode 100 or voids inside the positive electrode 100 are avoided, thereby ensuring the stability of the positive electrode 100 and the secondary battery.

[0059] In a specific embodiment, in a part of the hole 211, the lithium supplement material 10 is connected to the hole wall of the hole 211, and the packaging material 22 covers a part of the surface of the lithium supplement material 10 to form a packaging film. Specifically, the lithium supplement material 10 and the packaging material 22 can be first accommodated in the hole 211, so that one side of the lithium supplement material 10 can be connected to the hole wall of the hole 211; then after the packaging material 22 is accommodated in the hole 211, the packaging material 22 covers a part of the surface of the lithium supplement material 10, and thereby blocks the hole 211.

[0060] In a specific embodiment, in some holes 211, the packaging material 22 covers the entire outer surface of the lithium supplement material 10. Specifically, the packaging material 22 can also be coated on the outer surface of the lithium supplement material 10 to form a coating layer, that is, the lithium supplement material 10 and the packaging material 22 form a composite material and then are accommodated in the hole 211. By fully covering the lithium supplement material 10 with the packaging material 22, the stability of the lithium supplement material 10 in the early stage of the secondary battery can be ensured, and the lithium supplement material 10 can be prevented from decomposing and releasing lithium in advance.

[0061] In one implementation, please refer to Figure 4, the packaging material 22 forms a multi-layered packaging film, and a lithium replenishing material 10 is arranged between two adjacent layers of packaging films. Specifically, there are material layers formed by multiple layers of lithium replenishing materials 10 and packaging films formed by multiple layers of packaging materials 22 in the hole 211, and a layer of packaging film is arranged between the material layers of two adjacent layers of lithium replenishing materials 10. Optionally, along the thickness direction of the conductive carrier 21, the material layers and the packaging films are alternately arranged in sequence. By making the lithium replenishing material 10 and the packaging material 22 into a multi-layer structure, the stacked structure is used to further improve the effect of lithium replenishment throughout the life cycle. As each layer of the packaging material 22 decomposes, a layer of lithium replenishing material 10 will be exposed to release lithium.

[0062] In a specific embodiment, the conductive carrier 21 is a carbon fiber fabric, the lithium supplement material 10 can be loaded in the pore structure of the carbon fiber fabric, and the packaging material 22 forms a packaging film to cover the surfaces of the two; then, a material layer formed by the lithium supplement material 10 is also arranged on the packaging film, and another packaging film is arranged on the material layer. In this way, as the lithium supplement material 10 is consumed layer by layer and the packaging material 22 is decomposed layer by layer, the effect of slow-release lithium supplement can be achieved.

[0063] In the specific embodiment, please refer to Figure 5 , in some holes 211, there are material layers formed by multiple layers of lithium replenishing materials 10, the number of packaging films is multiple layers, a layer of packaging film is arranged between the material layers of two adjacent layers of lithium replenishing materials 10, and a layer of packaging film is arranged at the opening of the hole 211. Specifically, on the basis of the packaging film in the above-mentioned embodiment, the material in the hole 211 can be a multi-layer structure, which is a material layer and a packaging film, respectively, wherein the material layer is a layer composed of lithium replenishing materials 10, and the packaging film is a layer composed of packaging materials 22. In a specific embodiment, along the depth direction of the hole 211, the material layer and the packaging film are alternately arranged in sequence, and the opening of the hole 211 is a packaging film.

[0064] In one embodiment, the packaging material 22 is decomposed by the environmental parameters inside the secondary battery, and the environmental parameters include at least one of pH and temperature. It is understandable that when the substrate 20 includes the packaging material 22 and the conductive carrier 21, the environmental parameters that the packaging material 22 is subjected to and decomposes can refer to the decomposition pH value or temperature of the substrate 20 provided in the above embodiment. Of course, in other embodiments, when only one material is used as the substrate 20, the decomposition pH value or temperature of the substrate 20 provided in the above embodiment is the decomposition pH value or temperature of the material.

[0065] In one implementation, please refer to Figure 5The positive electrode further includes a catalyst 40, which is supported on the conductive carrier 21, and at least part of the catalyst 40 is contained in the pores 211. Specifically, the catalyst 40 includes a metal element and / or a metal compound, etc. Part of the catalyst 40 can be contained in the pores 211, and part of the catalyst 40 can be combined on the outer surface of the conductive carrier 21.

[0066] In a specific embodiment, the catalyst 40 can be filled in the pores 211 of the conductive carrier 21, and a single-atom film is formed on the inner wall of the pore 211. The catalyst 40 forms a film layer that adheres to the inner wall, and the pores 211 will not be filled with the catalyst 40, and the conductive carrier 21 will retain its rich pore 211 structure. It should be explained that in the present invention, the particle size of the catalyst 40 is very small, and the catalyst 40 is deposited on the inner wall of the pore 211 in a single-atom manner, which is different from the solution of filling the pore structure in the prior art. The present invention only thinly covers the inner wall of the pore 211 of the conductive carrier 21 with a layer of catalyst 40, and the pore 211 can also accommodate the lithium supplement material 10 and the packaging material 22.

[0067] In other embodiments, the catalyst 40 may also be in a granular form, and a plurality of catalyst 40 particles are dispersed and filled in the holes 211. Optionally, the catalyst 40 may be uniformly mixed with the lithium supplementing material 10, or the catalyst 40 may be mixed with the packaging material 22.

[0068] In one embodiment, part of the catalyst 40 is combined on the outer surface of the conductive carrier 21 to form a single atomic film, and the lithium supplement material 10 is combined on the catalyst 40. Specifically, the catalyst 40 can also be formed on the outer surface of the conductive carrier 21 and form a thin film layer, and the lithium supplement material 10 located outside is loaded on the conductive carrier 21 through the catalyst 40. The catalyst 40 can be used to catalyze the part of the lithium supplement material 10 to reduce the decomposition voltage.

[0069] In one embodiment, the conductive carrier 21 is a carbon fiber fabric, and the diameter of the conductive carrier 21 is 1 μm to 50 μm. When the diameter of the conductive carrier 21 is within the above range, the conductive carrier 21 itself has sufficient strength to serve as a self-supporting electrode, and the conductive carrier 21 has a large volume to load the lithium supplement material 10. When the diameter of the conductive carrier 21 is too small, the strength of the conductive carrier 21 decreases, it is difficult to form a self-supporting electrode, and the ability to load the lithium supplement material 10 decreases. When the diameter of the conductive carrier 21 is too large, the conductive carrier 21 occupies the space of the lithium supplement material 10, resulting in a decrease in the load of the lithium supplement material. Optionally, the diameter of the conductive carrier 21 can be 1 μm, 2 μm, 5 μm, 10 μm, 15 μm, 25 μm, 30 μm, or 50 μm.

[0070] In one embodiment, the conductive carrier 21 is a carbon fiber fabric, and the depth of the hole 211 is 30% to 80% of the diameter of the conductive carrier 21. The depth of the hole 211 is within the above range, so that the hole 211 is unevenly distributed, so that the lithium release time between different holes 211 is different, so that the purpose of lithium replenishment in the whole life cycle can be achieved. When the depth range of the hole 211 is too narrow, the hole 211 is uniform, resulting in the same content of lithium replenishment material 10 in most holes 211, and the lithium replenishment time is similar, and the purpose of lithium replenishment in the whole life cycle cannot be achieved. When the depth range of the hole 211 is too wide, the structural stability of the conductive carrier 21 will be affected. Optionally, the depth of the hole 211 is 30%, 40%, 50%, 60%, 70%, 80% of the diameter of the conductive carrier 21.

[0071] In one embodiment, the porosity of the conductive carrier 21 is 50% to 90%. Meeting the porosity of the conductive carrier 21 within the above range can ensure that the pores 211 can accommodate a sufficient amount of lithium-replenishing material 10, and ensure the structural stability of the conductive carrier 21. When the porosity of the conductive carrier 21 is too small, the amount of lithium-replenishing material 10 accommodated in the pores 211 is too small, and the lithium-replenishing effect during the use of the secondary battery deteriorates. When the porosity of the conductive carrier 21 is too large, the structural stability of the conductive carrier 21 deteriorates, and after the lithium-replenishing material 10 and the packaging material 22 are decomposed, the conductive carrier 21 is not easy to maintain its shape, which will cause pits in the positive electrode 100. Optionally, the porosity of the conductive carrier 21 can be 50%, 60%, 70%, 80%, or 90%.

[0072] In one embodiment, the specific surface area of ​​the conductive carrier 21 is 600 m 2 / g~1800m 2 / g. When the specific surface area of ​​the conductive carrier 21 is within the above range, it is conducive to loading the lithium supplement material 10. When the specific surface area of ​​the conductive carrier 21 is too small, the number of sites of the lithium supplement material 10 loaded on the conductive carrier 21 is too small, resulting in a decrease in the lithium content of the lithium supplement material 10. When the specific surface area of ​​the conductive carrier 21 is too large, the structural stability of the conductive carrier 21 deteriorates. Optionally, the specific surface area of ​​the conductive carrier 21 can be 600m 2 / g、700m 2 / g、800m 2 / g、900m 2 / g、1000m 2 / g、1100m 2 / g、1200m 2 / g、1300m 2 / g、1400m 2 / g、1500m 2 / g、1600m 2 / g、1800m2 / g.

[0073] In one embodiment, the mass ratio of the lithium replenishing material 10, the conductive carrier 21 and the packaging material 22 is 100: (10-30): (1-10). Satisfying the mass ratio of the lithium replenishing material 10, the conductive carrier 21 and the packaging material 22 within the above range can ensure the lithium replenishing capacity and ensure that it has the ability to continuously replenish lithium for a long time. It can also adjust the pH value of the secondary battery and reduce gas production. When the mass proportion of the conductive carrier 21 is too small, the content of the loaded lithium replenishing material 10 will be reduced, thereby reducing the lithium replenishing capacity, and the conductive carrier 21 will not be able to absorb gas. When the mass proportion of the packaging material 22 is too small, the packaging material 22 does not completely cover the lithium replenishing material 10, which will cause the continuous lithium replenishing ability of the lithium replenishing material 10 to decrease, and the battery performance will be affected. Optionally, the mass ratio of the lithium supplement material 10, the conductive carrier 21 and the packaging material 22 can be 100: (10-30): 1, 100: (10-30): 3, 100: (10-30): 7, 100: (10-30): 10, 100: 10: (1-10), 100: 20: (1-10), 100: 30: (1-10).

[0074] In one implementation, please refer to Figure 4 , part of the lithium supplement material 10 is combined with the outer surface of the substrate 20, and part of the lithium supplement material 10 is contained in the interior of the substrate 20, and the lithium supplement material 10 contained in the interior of the substrate 20 releases lithium with the substrate 20. Specifically, the lithium supplement material 10 is divided into two parts, one part of the lithium supplement material 10 is combined with the outer surface of the substrate 20, and the other part of the lithium supplement material 10 is encapsulated in the interior of the substrate 20. Among them, part of the lithium supplement material 10 is combined with the outer surface of the conductive carrier 21 and the encapsulation material 22, so that this part of the lithium supplement material 10 is exposed to the environment of the secondary battery; the other part of the lithium supplement material 10 is encapsulated in the interior of the conductive carrier 21 through the encapsulation material 22, and after the encapsulation material 22 fails and decomposes, this part of the lithium supplement material 10 is exposed to the environment of the secondary battery. In a specific embodiment, the lithium supplement material 10 combined with the outer surface of the substrate 20 is an organic lithium salt.

[0075] By combining the lithium-supplementing material 10 inside and outside the matrix 20, during the formation process of the secondary battery, the lithium-supplementing material 10 combined with the outside can preferentially decompose and release lithium, thereby exerting the basic formation and lithium-supplementing function of the lithium-supplementing material 10; then due to the influence of the internal environment of the secondary battery, the packaging material 22 fails and decomposes, and the lithium-supplementing material 10 inside the matrix 20 is exposed to the environment of the secondary battery. This part of the lithium-supplementing material 10 slowly releases lithium, thereby achieving the purpose of lithium replenishment throughout the life cycle and improving the cycle stability of the battery, thereby maintaining the abundance of lithium ions in the battery system, and ensuring that the battery material has the characteristics of high capacity and long cycle.

[0076] In one embodiment, the mass proportion of the lithium replenishing material 10 combined with the outer surface of the substrate 20 is greater than the mass proportion of the lithium replenishing material 10 encapsulated inside the substrate 20. Because the lithium replenishing material 10 located on the outside provides the main first lithium replenishment, the mass proportion of this part of the lithium replenishing material 10 is higher, which can produce the first large-capacity lithium replenishment in the formation stage of the secondary battery.

[0077] In one implementation, please refer to Figure 2 , the positive electrode 100 is a self-supporting electrode, and the positive electrode active material 30 is coated on the conductive carrier 21. Specifically, the self-supporting electrode refers to an electrode that does not require a current collector, and the lithium supplement material 10 and the positive electrode active material 30 are both arranged on the conductive carrier 21, and the conductive carrier 21 can have the characteristics of conductivity and flexibility. It can be understood that directly coating the positive electrode active material 30 on the conductive carrier 21 and using the conductive carrier 21 as a current collector can replace the copper foil, aluminum foil, etc. conventionally used in the prior art, which can not only improve the conductivity of the positive electrode 100, but also improve the wettability of the electrolyte to the positive electrode 100, and improve the flexibility of the positive electrode 100.

[0078] In one embodiment, the positive electrode active material 30 can be a phosphate positive electrode active material 30 or a ternary positive electrode active material 30. In a specific embodiment, the positive electrode active material 30 includes one or more of lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadium oxyphosphate, lithium vanadium phosphate fluorophosphate, lithium titanate, lithium nickel cobalt manganese oxide, and lithium nickel cobalt aluminum oxide.

[0079] In one embodiment, the active layer of the positive electrode 100 also includes components such as a conductive agent and a binder. The present invention does not specifically limit these materials, and suitable materials can be selected according to actual application requirements. The conductive agent includes one or more of graphite, carbon black, acetylene black, graphene, carbon fiber, C60 and carbon nanotubes, and the content of the conductive agent in the active layer of the positive electrode 100 is 3wt% to 5wt%. The types of binders include one or more of polyvinylidene chloride, soluble polytetrafluoroethylene, styrene-butadiene rubber, hydroxypropyl methylcellulose, methylcellulose, carboxymethyl cellulose, polyvinyl alcohol, acrylonitrile copolymer, sodium alginate, chitosan and chitosan derivatives, and the content of the binder in the active layer of the positive electrode 100 is 2wt% to 4wt%.

[0080] In one embodiment, the active layer of the positive electrode 100 also includes a conventional lithium supplement, and the conventional lithium supplement can refer to the lithium supplement material 10 in the above embodiment. The conventional lithium supplement is not loaded on the substrate 20, and the conventional lithium supplement is mainly used to mix with the positive electrode active material 30 to provide the first lithium supplement in the formation stage. In the case where the lithium supplement material 10 is not combined with the outer surface of the substrate 20, the conventional lithium supplement can be separately set in the positive electrode 100, and the conventional lithium supplement is used to achieve lithium supplementation by formation, and the composite structure of the substrate 20 and the lithium supplement material 10 is used to achieve slow-release lithium supplementation.

[0081] The present invention provides a method for preparing a secondary battery. Figure 6 .

[0082] In one embodiment, the preparation method of the secondary battery specifically includes the following steps:

[0083] Step S10, providing lithium supplement material raw materials and a matrix.

[0084] Step S20, pre-treating the substrate and filling the substrate with lithium supplement material raw materials.

[0085] Step S30, controlling the lithium supplement material raw material in the matrix to be converted into lithium supplement material and loaded in the matrix to form a positive electrode.

[0086] Step S40, providing a negative electrode and an electrolyte.

[0087] Step S50, assembling the positive electrode, the negative electrode and the electrolyte to obtain a secondary battery.

[0088] In one embodiment, the matrix includes a conductive carrier and a packaging material, so in step S10, providing a lithium supplement material raw material and a matrix specifically includes: providing a lithium supplement material raw material, a conductive carrier and a packaging material. The packaging material may have the property of being easily decomposed in the environment of the secondary battery.

[0089] In other embodiments, the conductive carrier may have the property of being easily decomposed in the environment of the secondary battery, so that the packaging material can be omitted and only the raw material of the lithium supplement material and the conductive carrier are provided.

[0090] In one embodiment, holes can be made on the conductive carrier by pretreatment, so in step S20, the substrate is pretreated, specifically including: preparing non-uniform holes on the surface of the conductive carrier by an etchant.

[0091] In one embodiment, in step S20, the conductive carrier may be a carbon material, specifically a carbon fiber fabric. The etchant may be an alkali, and non-uniform pores may be prepared on the carrier by mixing the carrier and the etchant and calcining them at a high temperature.

[0092] In one embodiment, in step S20, the substrate is pretreated, and the step further includes: depositing the catalyst on the inner wall of the hole by atomic layer deposition. In a specific embodiment, the atomic layer deposition (ALD) technique can deposit the catalyst on the inner wall of the hole of the carrier in the form of a single atom, and the catalyst can form a single atomic film on the upper surface of the inner wall of the hole. Of course, the catalyst can also be deposited on the outer surface of the carrier to form a single atomic film.

[0093] In one embodiment, in step S20, the lithium supplement material raw material is filled into the matrix, specifically comprising: placing a conductive carrier in a lithium supplement material raw material environment, so that the lithium supplement material raw material can be filled into the pores of the conductive carrier.

[0094] In one embodiment, in step S30, the lithium supplement material raw material in the matrix is ​​controlled to be converted into the lithium supplement material and loaded in the matrix, specifically including: the lithium supplement material raw material is an organic lithium salt solution, and the lithium supplement material can be in-situ grown on the conductive carrier by recrystallization. In a specific embodiment, the lithium supplement material can include lithium oxalate, lithium carbonate, lithium butynedioate, etc.

[0095] In one embodiment, in step S30, after the lithium supplement material raw material in the matrix is ​​controlled to be converted into the lithium supplement material and loaded in the matrix, the method may further include: filling the matrix with the packaging material. Specifically, the method may include placing the conductive carrier loaded with the lithium supplement material in an environment of the packaging material or a precursor of the packaging material, and plugging the hole by filling the packaging material in the opening of the hole.

[0096] In a specific embodiment, the packaging material may include a non-conductive high molecular polymer. The packaging material uses a polymer monomer and an initiator as a precursor, uses the initiator to initiate polymerization of the precursor of the packaging material, and controls the degree of polymerization to prepare a packaging material with poor mechanical properties, easy cracking, and easy degradation under slightly acidic or high temperature conditions. Optionally, the packaging material specifically includes polylactic acid, polyurethane, polyvinyl alcohol, etc.

[0097] In one embodiment, step S20 and step S30 may be repeated multiple times in sequence, that is, after completing step S30 for the first time, step S20 is repeated to fill the lithium supplement material raw material into the matrix, and step S30 is repeated. In this way, a multi-layer structure is formed in the hole, which includes a material layer and a packaging film, wherein the material layer is a layer composed of lithium supplement material, and the packaging film is a layer composed of packaging material. In a specific embodiment, along the depth direction of the hole, the material layer and the packaging film are alternately arranged in sequence, and the packaging film is at the opening of the hole.

[0098] In one embodiment, step S30 may further include: mixing the conductive carrier encapsulating the lithium supplement material with another portion of the lithium supplement material, so that another portion of the lithium supplement material can be evenly combined on the surface of the conductive carrier.

[0099] The preparation method provided by the present invention is used to prepare a secondary battery. By loading a lithium-supplementing material on a substrate, the substrate is decomposed by the environmental parameters inside the secondary battery, so that after part of the substrate is decomposed in the secondary battery, the lithium-supplementing material is exposed and lithium is continuously released, thereby achieving the purpose of full life cycle lithium replenishment. At the same time, the present invention also etches non-uniform holes on the carrier, and deposits a catalyst on the inner wall of the hole to catalyze the lithium-supplementing material. The lithium-supplementing material and the packaging material are both contained in the hole, and the lithium-supplementing material and the packaging material are also a multi-layer structure, so that the lithium-supplementing material in the hole can be decomposed and released layer by layer with the cooperation of the packaging material, further enhancing the effect of full life cycle lithium replenishment.

[0100] The technical solution of the present invention is described in detail below through specific embodiments.

[0101] Example 1

[0102] This embodiment provides a positive electrode, which is a self-supporting electrode, including a lithium supplement material (lithium oxalate, Li2C2O4), a matrix and a catalyst (cobalt oxide, CoO); the matrix includes a conductive carrier (carbon fiber fabric, CF) and a packaging material (polylactic acid, PLA).

[0103] The conductive carrier has holes, part of the lithium supplement material is contained in the holes (first lithium supplement material), the packaging material is contained in the holes and covers the lithium supplement material, and part of the lithium supplement material is combined with the outer surface of the conductive carrier (second lithium supplement material), and the catalyst is contained in the holes of the carrier to form a single atomic film. The packaging material is affected by the pH inside the secondary battery and decomposes when the pH value inside the secondary battery is between 6 and 8. The porosity of the conductive carrier is 70%, and the specific surface area of ​​the conductive carrier is 1400m 2 / g, the mass ratio of the lithium supplement material, the conductive carrier, and the packaging material is 100:10:3; the mass ratio of the first lithium supplement material and the second lithium supplement material is 40:60.

[0104] The preparation method of the positive electrode comprises the following steps:

[0105] 1) 10 g of carbon fiber fabric and 3 g of KOH were mixed, the mixture was placed in a tube furnace, and calcined at 800° C. for 4 h. The tube furnace was kept in an argon range with an argon flow rate of 400 ml / min.

[0106] 2) CoO is deposited on the support by ALD technology, and CoO forms a single atomic film in the pores.

[0107] 3) In-situ growth of nano-lithium oxalate in the pores of carbon fiber fabrics through lithium oxalate recrystallization technology.

[0108] 4) mixing carbon fiber fabric and lactic acid, so that the lactic acid is polymerized in the pores and on the surface of the carbon fiber fabric to obtain polylactic acid, wherein the polylactic acid in the pores covers the lithium oxalate; and then destroying the polylactic acid on the surface of the carbon fiber fabric by ultraviolet irradiation.

[0109] 5) Repeat step 3) and step 4) three times in sequence until the polylactic acid completely seals the holes of the carbon fiber fabric.

[0110] 6) In-situ growth of nano-lithium oxalate on the surface of carbon fiber fabrics through lithium oxalate recrystallization technology.

[0111] Example 2

[0112] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that the positive electrode is a common electrode and also includes a current collector. The conductive carrier is replaced with porous carbon. The composite material composed of the conductive carrier and the lithium supplement material is mixed with the positive electrode active material to form a positive electrode slurry and coated on the current collector.

[0113] Example 3

[0114] This embodiment provides a positive electrode, and the difference between this embodiment and embodiment 1 is that the composite lithium supplement material does not include a packaging material, and the conductive carrier is replaced by polyaniline. The conductive carrier is affected by the pH (or temperature) inside the secondary battery and decomposes when the pH value inside the secondary battery is between 6 and 7.

[0115] Example 4

[0116] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that there are no holes on the conductive carrier, the catalyst and part of the lithium supplement material are directly combined on the surface of the conductive carrier (first lithium supplement material), the packaging material covers the part of the lithium supplement material, and part of the lithium supplement material is combined on the surface of the packaging material (second lithium supplement material), and the specific surface area of ​​the carrier is 80m 2 / g. The mass ratio of the first lithium supplement material to the second lithium supplement material is 15:85.

[0117] Example 5

[0118] This embodiment provides a positive electrode. The difference between this embodiment and Embodiment 1 is that there is only one layer of lithium supplement material and packaging material in the hole.

[0119] Example 6

[0120] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that the lithium supplement material is replaced by lithium malonate.

[0121] Example 7

[0122] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that the lithium supplement material is completely contained in the holes, and the outer surface of the conductive carrier is not loaded with the lithium supplement material.

[0123] Example 8

[0124] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that the porosity of the conductive carrier is 30%, and the specific surface area of ​​the conductive carrier is 600m 2 / g.

[0125] Example 9

[0126] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that the porosity of the conductive carrier is 90%, and the specific surface area of ​​the conductive carrier is 1800m 2 / g.

[0127] Example 10

[0128] This embodiment provides a positive electrode. The difference between this embodiment and Embodiment 1 is that the mass ratio of the lithium supplement material, the conductive carrier and the packaging material is 100:10:1.

[0129] Embodiment 11

[0130] This embodiment provides a positive electrode. The difference between this embodiment and Embodiment 1 is that the mass ratio of the lithium supplement material, the conductive carrier and the packaging material is 100:30:10.

[0131] Example 12

[0132] This embodiment provides a positive electrode. The difference between this embodiment and embodiment 1 is that there is no catalyst.

[0133] Comparative Example 1

[0134] This comparative example provides a positive electrode. The difference between this comparative example and Example 1 is that the packaging material is replaced with polyethylene, and the packaging material is not affected by the pH inside the secondary battery.

[0135] Comparative Example 2

[0136] This comparative example provides a positive electrode. The difference between this comparative example and Example 1 is that the packaging material is replaced with polytetrafluoroethylene, and the packaging material is not affected by the temperature inside the secondary battery.

[0137] The positive electrode parameters provided by Examples 1 to 12 and Comparative Examples 1 to 2 are shown in Table 1:

[0138] Table 1 Positive electrode parameters provided by the embodiments and comparative examples

[0139]

[0140] The positive electrodes provided in the above-mentioned Examples 1 to 12 and the positive electrodes provided in Comparative Examples 1 and 2 are respectively assembled into lithium-ion batteries according to the following methods:

[0141] Positive electrode;

[0142] Negative electrode: lithium sheet;

[0143] Electrolyte: Ethylene carbonate and ethyl methyl carbonate were mixed in a volume ratio of 3:7, and LiPF6 was added to form an electrolyte, and the concentration of LiPF6 was 1 mol / L;

[0144] Diaphragm: Polypropylene microporous separator;

[0145] Lithium-ion battery assembly: Assemble button-type lithium-ion full batteries in an inert atmosphere glove box in the order of negative electrode sheet - separator - electrolyte - positive electrode sheet.

[0146] The electrochemical performance of each lithium-ion battery assembled in the above lithium-ion battery embodiment was tested under the following test conditions:

[0147] The battery was charged at a rate of 0.1C with a cut-off voltage of 4.7V. The battery was charged at a constant voltage with a cut-off voltage of 4.7V. After the charging process was completed, the battery was allowed to stand for 10 minutes and then discharged at a rate of 0.1C with a cut-off voltage of 2.5V. The charging platform was observed during the charging process to obtain the decomposition voltage of the lithium supplement material.

[0148] The test results of the above lithium battery are shown in Table 2 below:

[0149] Table 2. Test results of embodiments and comparative examples

[0150]

[0151] From the test results of Example 1, Comparative Example 1 and Comparative Example 2 in Table 2, it can be seen that the polylactic acid used in Example 1 is used as the packaging material, and since the polylactic acid will decompose in an alkaline environment, during the battery cycle, the lithium supplement material in the positive electrode can be released under the decomposition of the polylactic acid, thereby achieving the purpose of lithium supplementation in the entire life cycle, so Example 1 still has capacity after 500 cycles. The polyethylene in Comparative Example 1 has alkaline stability characteristics, and the polytetrafluoroethylene in Comparative Example 2 has high temperature stability characteristics, so both polyethylene and polytetrafluoroethylene are not easy to decompose, and the lithium supplement materials encapsulated by the packaging materials in Comparative Examples 1 and 2 cannot be released, resulting in a low charge specific capacity, and the capacity retention rate is 0 after 500 cycles.

[0152] From the test results of Example 1 and Example 2 in Table 2, it can be seen that by making the carbon fiber fabric and the lithium supplement material into a self-supporting electrode, the battery can obtain a higher specific charge capacity. Because compared with the buckle battery (Example 2) that requires an additional current collector, the active material in the self-supporting electrode in Example 1 accounts for a larger proportion, so it has a higher specific capacity; and the carbon fiber fabric has a stronger conductivity. Compared with the ordinary buckle battery, Example 1 has a lower overpotential and decomposition voltage, and the lithium supplement capacity can be fully released.

[0153] It can be seen from the test results of Example 1 and Example 3 in Table 2 that the matrix is ​​not limited to the combination of a conductive carrier and a packaging material, and the conductive carrier itself may have a decomposable property, so that one material can be used as the matrix, which can achieve the purpose of conductivity and loading, and can also achieve the effect of decomposition and slow release.

[0154] It can be seen from the test results of Example 1, Example 4 and Example 5 in Table 2 that the structure of the conductive carrier and the packaging material will have a partial impact on the effect of lithium supplementation throughout the life cycle, mainly on the sustained release effect of the lithium supplementation material. Because in the case where the conductive carrier has no holes, the packaging tightness of the packaging material and the conductive carrier to the lithium supplementation material decreases, resulting in a shorter sustained release time of the lithium supplementation material (500 cycles of capacity retention rate decreases). When only one layer of packaging material is used to encapsulate the lithium supplementation material, after the only layer of packaging material is decomposed, the lithium supplementation material in the holes is completely released, which also shortens the sustained release time of the lithium supplementation material. In addition, it should be noted that Example 4 and Example 5 are not unable to achieve the effect of sustained release lithium supplementation, but the time for sustained release of lithium supplementation is relatively short, that is, the lithium release is completed before 500 cycles, indicating that Example 4 and Example 5 complete the release of lithium in less than 500 cycles.

[0155] It can be seen from the test results of Example 1 and Example 6 in Table 2 that the solution provided by the present invention is also applicable to other lithium supplement materials and can achieve the same technical effect. Therefore, it is shown that the technical solution provided by the present invention has high applicability, and the effect that can be achieved has no absolute relationship with the material type and is not limited to the materials provided in the examples.

[0156] It can be seen from the test results of Example 1 and Example 7 in Table 2 that all the lithium replenishing materials are contained in the holes and encapsulated with packaging materials. Although its full life cycle lithium replenishing effect is the best in terms of cycle capacity retention rate, its first lithium replenishing capacity is very low, and it is impossible to take into account the effects of the first lithium replenishment and the full life cycle lithium replenishment.

[0157] From the test results of Example 1, Example 8 and Example 9 in Table 2, it can be seen that the porosity and specific surface area of ​​the conductive carrier will affect the lithium replenishment effect and battery performance. When the porosity is too low, the capacity of one lithium replenishment is high but the effect of the whole life cycle is reduced; when the porosity is too high, the effect of the whole life cycle is enhanced, but the capacity of one lithium replenishment is relatively low.

[0158] It can be seen from the test results of Example 1, Example 10 and Example 11 in Table 2 that the ratio of lithium supplement material, conductive carrier and packaging material will affect the lithium supplement effect and battery performance. When the proportion of conductive carrier and packaging material is too small, the amount of lithium supplement material loaded will be reduced, thereby reducing the effect of lithium supplementation in the entire life cycle; when the proportion of conductive carrier and packaging material is too large, the overall quality of lithium supplement material will decrease, and the first lithium supplement capacity and the lithium supplement effect in the entire life cycle will decrease. Therefore, the lithium supplement effect and battery performance can be improved by reasonably matching the mass ratio of the three. In addition, it should be noted that Example 10 is not unable to achieve the effect of sustained-release lithium supplementation, but the time for sustained-release lithium supplementation is short, that is, the lithium release is completed before 500 cycles, indicating that Example 10 completes the lithium release in less than 500 cycles.

[0159] From the test results of Example 1 and Example 12 in Table 2, it can be seen that the main function of the catalyst is to catalyze the lithium supplement material to reduce the decomposition voltage, so that it decomposes at a lower voltage, so the catalyst has a positive effect on the lithium release of the lithium supplement material. However, in other embodiments, when other lithium supplement materials with lower decomposition voltages are used, the catalyst can be omitted, and the effects of first high-capacity lithium supplementation and full life cycle lithium supplementation can also be achieved.

[0160] In the description of the embodiments of the present invention, it should be noted that the orientation or positional relationship of terms such as "center", "up", "down", "left", "right", "vertical", "horizontal", "inside" and "outside" are based on the orientation or positional relationship described in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0161] What is disclosed above is only a preferred embodiment of the present invention, and it certainly cannot be used to limit the scope of rights of the present invention. Ordinary technicians in this field can understand that all or part of the processes of the above embodiment and equivalent changes made according to the claims of the present invention still fall within the scope covered by the present invention.

Claims

1. A secondary battery comprising a positive electrode, a negative electrode and an electrolyte, characterized in that: The positive electrode includes a matrix and a lithium supplement material. The lithium supplement material is loaded in the matrix. At least a portion of the matrix is ​​decomposed under the influence of environmental parameters inside the secondary battery. The lithium supplement material decomposes lithium along with the matrix.

2. The secondary battery according to claim 1, characterized in that: The matrix may be decomposed under the influence of environmental parameters inside the secondary battery, wherein the environmental parameters include at least one of pH and temperature; wherein the decomposition pH value of the matrix is ​​less than or equal to 8; and / or the decomposition temperature of the matrix is ​​greater than or equal to 50°C.

3. The secondary battery according to claim 1 or 2, characterized in that: The substrate includes a conductive carrier, the conductive carrier is provided with holes, and at least the lithium supplement material is accommodated in the conductive carrier.

4. The secondary battery according to claim 3, characterized in that: The substrate further includes a packaging material, which is bonded to the conductive carrier. At least a portion of the packaging material covers the opening of the hole. The packaging material is decomposed in the secondary battery to expose the lithium supplement material in the hole.

5. The secondary battery according to claim 4, characterized in that: The packaging material forms a multi-layer packaging film, and the lithium supplement material is arranged between two adjacent layers of the packaging film.

6. The secondary battery according to claim 2, characterized in that: The positive electrode further includes a catalyst, the catalyst is loaded on the conductive carrier, and at least a portion of the catalyst is contained in the pores.

7. The secondary battery according to claim 3, characterized in that: The conductive carrier comprises one or more of carbon fiber fabric, carbon fiber paper, and carbon aerogel; and / or The packaging material includes one or more of a high molecular polymer, a metal compound, and a carbon material; and / or The depth of the hole is 30% to 80% of the diameter of the conductive carrier; and / or The porosity of the conductive carrier is 50% to 90%; and / or The specific surface area of ​​the conductive carrier is 600 m 2 / g~1800m 2 / g; and / or The mass ratio of the lithium supplement material, the conductive carrier and the packaging material is 100:(10-30):(1-10).

8. The secondary battery according to claim 1, characterized in that: Part of the lithium supplement material is combined with the outer surface of the substrate, and part of the lithium supplement material is contained in the interior of the substrate. The lithium supplement material contained in the interior of the substrate decomposes and releases lithium along with the substrate.

9. The secondary battery according to any one of claims 1 to 8, characterized in that: The positive electrode is a self-supporting electrode; and / or, The positive electrode further comprises a positive electrode active material, and the positive electrode active material is supported on the surface of the substrate; and / or, The lithium supplement material includes an organic lithium salt, and the chemical formula of the organic lithium salt includes Li x1 C y1 O z1 , where 0<x1≤2,y1> 0,z1>0.

10. A method for preparing a secondary battery, characterized in that: The following steps are involved: Provide raw materials and matrix for lithium supplementation; Pre-treating the substrate and filling the substrate with the lithium supplement material raw material; Controlling the lithium supplement material raw material in the matrix to be converted into lithium supplement material and loaded in the matrix to form a positive electrode; providing a negative electrode and an electrolyte; A secondary battery is obtained by assembling the positive electrode, the negative electrode and the electrolyte.

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