Pre-lithiated electrode material and preparation method thereof, secondary battery and electric device

Abstract

The invention relates to a pre-lithiated electrode material and a preparation method thereof, a secondary battery and an electric device. The particle size of the pre-lithiation electrode material is 20 nm to 50 microns, the pre-lithiation electrode material is provided with a lithiation layer, the lithiation layer comprises at least one sub-lithiation layer, and when the number of the sub-lithiation layers is larger than or equal to 2, the content of lithium in the sub-lithiation layers is reduced layer by layer in the inward direction of the surface of the pre-lithiation electrode material. The pre-lithiated electrode material can achieve the expected first effect of the battery, reduce the internal expansion of particles and reduce the crushing of the material at the same time.

Description

Pre-lithiation electrode material and preparation method thereof, secondary battery and electrical device Technical Field

[0001] The present application relates to the field of lithium battery technology, and in particular to a pre-lithiation electrode material and a preparation method thereof, a secondary battery, and an electrical device. Background Art

[0002] In recent years, the application of lithium-ion batteries has become increasingly widespread. They are widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and other fields. As lithium-ion batteries have achieved significant development, higher requirements have been placed on their energy density, cycle performance, and safety performance.

[0003] Formation, also known as activation, is the process of activating the positive and negative electrode materials within the battery through a certain charging and discharging method after manufacturing to improve the overall performance of the battery. However, during the formation process, the formation of solid electrolyte interface film (SEI film) and lithium oxides consumes a large amount of lithium source, resulting in a low initial efficiency of the battery (abbreviated as "initial efficiency"). Therefore, how to improve the initial efficiency of the battery has become one of the current research focuses in the industry and academia.

[0004] Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and its purpose is to provide a pre-lithiation electrode material that can achieve the expected first battery effect while alleviating the material breakage caused by excessive internal volume expansion of the material.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a pre-lithiation electrode material, wherein the particle size of the pre-lithiation electrode material is 20nm~50μm, the pre-lithiation electrode material has a lithiation layer, the lithiation layer includes at least one sub-lithiation layer, and when the number of layers of the sub-lithiation layer is ≥2, the content of lithium element in each of the sub-lithiation layers decreases layer by layer from the surface of the pre-lithiation electrode material to the inward direction.

[0007] The above-mentioned pre-lithiation electrode material can achieve the expected first efficiency of the battery while alleviating the material breakage caused by excessive internal volume expansion of the material.

[0008] The second aspect of the present application further provides a method for preparing a pre-lithiation electrode material, comprising the following steps:

[0009] The electrode material is subjected to at least two chemical pre-lithiation treatments, and the redox potential of the lithiating agent used in each chemical pre-lithiation treatment is successively reduced.

[0010] The above-mentioned method for preparing the pre-lithiation electrode material can achieve the expected first battery efficiency by at least two chemical pre-lithiation treatments, while alleviating the material breakage caused by excessive internal volume expansion of the material.

[0011] The third aspect of the present application also provides an electrode sheet, comprising a current collector and an electrode film layer arranged on at least one surface of the current collector, wherein the material of the electrode film layer comprises at least one of the pre-lithiation electrode material described in the first aspect and the pre-lithiation electrode material prepared by the preparation method described in the second aspect.

[0012] The fourth aspect of the present application further provides a secondary battery, comprising the electrode sheet described in the third aspect of the present application.

[0013] The fifth aspect of the present application further provides an electrical device comprising the secondary battery described in the fourth aspect of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1 is a schematic diagram of a secondary battery according to an embodiment of the present application;

[0015] FIG2 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG1 ;

[0016] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application;

[0017] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application;

[0018] FIG5 is an exploded view of the battery pack according to an embodiment of the present application shown in FIG4 ;

[0019] 6 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application;

[0020] Description of reference numerals:

[0021] 1. Battery pack; 2. Upper case; 3. Lower case; 4. Battery module; 5. Secondary battery; 51. Housing; 52. Electrode assembly; 53. Cover; 6. Electrical device. DETAILED DESCRIPTION

[0022] Below, the embodiments of the pre-lithiation electrode material and its preparation method, secondary battery and electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0023] " range " disclosed in the present application is limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and can be arbitrarily combined, that is, any lower limit can form a range with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range value 1 and 2 are listed, and if the maximum range value 3,4 and 5 are listed, then the following range can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, a numerical range of "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is simply an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this 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.

[0024] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0025] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0026] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating 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.

[0027] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0028] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0029] At present, pre-lithiation is an effective means to improve the first coulombic efficiency of the battery. Pre-lithiation refers to the introduction of exogenous lithium into the battery system in a suitable manner and form to improve the problem of reduced first coulombic efficiency due to the consumption of effective lithium by the electrode. Traditional pre-lithiation is mainly divided into positive electrode pre-lithiation and negative electrode pre-lithiation, and according to the pre-lithiation method, it is further divided into direct addition of exogenous lithium, active additive pre-lithiation, electrochemical pre-lithiation and chemical pre-lithiation. Among them, chemical pre-lithiation has gradually attracted the attention of researchers in recent years due to its simple operation and relatively low requirements for a dry environment. Chemical pre-lithiation usually involves dissolving a complex in an organic solvent, reacting with lithium metal to form a Li-complex-organic solvent complex as a chemical pre-lithiation reagent (referred to as "lithiation agent"), and contacting the electrode material to be pre-lithiated with the lithiating agent to embed lithium into the electrode material to achieve the purpose of pre-lithiation.

[0030] However, for electrode materials, especially those with larger particle sizes, if the lithium replenishment level is too low, the lithium replenishment effect is poor. If the lithium replenishment level is too high, the internal volume of the particles expands too much, which can easily lead to material breakage.

[0031] Based on this, an example of the present application provides a pre-lithiation electrode material, wherein the particle size of the pre-lithiation electrode material is 20nm~50μm, the pre-lithiation electrode material has a lithiation layer, the lithiation layer includes at least one sub-lithiation layer, and when the number of layers of the sub-lithiation layer is ≥2, the content of lithium element in each of the sub-lithiation layers decreases layer by layer from the surface of the pre-lithiation electrode material to the inward direction.

[0032] The above-mentioned pre-lithiation electrode material sets a suitable lithiation layer for electrode materials of a certain particle size, which can achieve the expected first efficiency of the battery while alleviating the material breakage caused by excessive internal volume expansion of the material, thereby achieving better cycle performance.

[0033] In addition, traditional chemical prelithiation methods select lithiating agents with lower redox potentials for prelithiation according to the target prelithiation materials. To obtain prelithiated electrode materials with low redox potentials (<0.3V) (such as highly lithiated silicon-based materials, carbon-based materials, and tin), molecular engineering modification means need to be used to reduce the redox potential of the lithiating agent, resulting in too high prelithiation operation costs. When the above-mentioned prelithiated electrode materials provided in this application are multilayer lithiated layers, a stepped setting with less lithium content inside and more outside is adopted, which can reduce the amount of lithiating agents with low redox potentials, reduce lithiation costs, improve the lithium utilization rate of prelithiated materials, and at the same time can also reduce the internal stress of the materials and further reduce the possibility of rupture of the prelithiated materials.

[0034] In one example, in the direction from the surface of the prelithiated electrode material inward, the lithiated layers sequentially include a third sub-lithiated layer with a thickness ≥0 nm and ≤30 μm, a second sub-lithiated layer with a thickness ≥0 nm and ≤30 μm, and a first sub-lithiated layer with a thickness of 10 nm to 50 μm:

[0035] The material composition of the first sub-lithiated layer includes Li a M;

[0036] The material composition of the second sub-lithiated layer includes Li b M;

[0037] The material composition of the third sub-lithiated layer includes Li c M;

[0038] Where 0 < a < 5, 0 < b < 5, 0 < c < 5, and when the thickness of at least one of the second sub-lithiated layer and the third sub-lithiated layer > 0, a, b, c satisfy a < b < c;

[0039] M represents one or more of the matrix elements in the electrode material.

[0040] It can be understood that the "matrix elements in the electrode material" refer to the elements that are already contained in the electrode material itself before prelithiation.

[0041] Specifically, the value range of a includes but is not limited to: 0.01, 0.05, 0.08, 0.1, 0.2, 0.5, 1, 1.5, 2, 2.2, 2.5, 2.6, 2.8, 3, 3.5, 4, 4.2, 4.4, 4.6, 4.8, 4.9 or the range formed by any two of the foregoing values. Further, 0 < a ≤ 4.4.

[0042] Specifically, the value of b includes but is not limited to: 0.05, 0.08, 0.1, 0.15, 0.17, 0.2, 0.3, 0.33, 0.4, 0.5, 1, 1.5, 2, 2.2, 2.5, 2.6, 2.8, 3, 3.5, 3.75, 4, 4.2, 4.4, 4.6, 4.8, 4.9 or a range formed by any two of the foregoing values. <b≤4.4。

[0043] Specifically, the value of c includes but is not limited to: 1, 1.5, 2, 2.2, 2.5, 2.6, 2.8, 3, 3.5, 3.75, 4, 4.2, 4.4, 4.6, 4.8, 4.9 or a range formed by any two of the foregoing values. <c≤4.4。

[0044] Specifically, the particle size of the pre-lithiation electrode material includes but is not limited to: 20nm, 25nm, 30nm, 35nm, 50nm, 100nm, 300nm, 500nm, 600nm, 610nm, 620nm, 630nm, 640nm, 650nm, 660nm, 670nm, 680nm, 690nm, 700nm, 800nm, 1μm, 3μm, 5μm, 6μm, 7μm, 10μm, 20μm, 30μm, 40μm, 45μm, 50μm or a range formed by any two of the foregoing values. Further, the particle size of the pre-lithiation electrode material is 5μm to 50μm. The design of the above-mentioned pre-lithiation electrode material is particularly suitable for electrode materials with larger particle sizes, reducing the possibility of cracking of pre-lithiation materials with larger particle sizes.

[0045] Specifically, the thickness of the third sub-lithiation layer includes but is not limited to: 0 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 100 nm, 500 nm, 1 μm, 5 μm, 10 μm, 20 μm, 30 μm or a range formed by any two of the foregoing values.

[0046] Specifically, the thickness of the second sub-lithiation layer includes but is not limited to: 0 nm, 5 nm, 10 nm, 15 nm, 20 nm, 50 nm, 100 nm, 350 nm, 400 nm, 500 nm, 650 nm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 25 μm, 30 μm or a range formed by any two of the foregoing values.

[0047] Specifically, the thickness of the first sub-lithiation layer includes but is not limited to: 0 nm, 5 nm, 10 nm, 15 nm, 20 nm, 30 nm, 50 nm, 100 nm, 250 nm, 300 nm, 350 nm, 400 nm, 500 nm, 550 nm, 600 nm, 650 nm, 1 μm, 2 μm, 4 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm or a range formed by any two of the foregoing values.

[0048] In one example, M includes one or more of carbon, silicon, phosphorus, tin, magnesium, silver, zinc, sulfur, and germanium.

[0049] Another example of the present application provides a method for preparing a pre-lithiation electrode material, comprising the following steps:

[0050] The electrode material is subjected to at least two chemical pre-lithiation treatments, and the redox potential of the lithiating agent used in each chemical pre-lithiation treatment is successively reduced.

[0051] The above-mentioned preparation method uses a lithiating agent with a gradually decreasing redox potential to perform graded pre-lithiation treatment on the electrode material. On the one hand, the graded pre-lithiation continuously approaches the expected pre-lithiation degree, thereby achieving the expected first effect. On the other hand, the graded pre-lithiation can reduce the stress inside the electrode material particles during the reaction, thereby reducing expansion and inhibiting the breakage of the material.

[0052] In addition, through research, it was found that in the actual application process of electrode materials, the lithium inside them is usually difficult to diffuse, and the effect of improving the first effect is weakened. The traditional lithium replenishment method is to replenish lithium as a whole, which not only causes the internal particles to expand and break easily, but also leads to a decrease in the lithium utilization rate of the pre-lithiation material. Based on this, the pre-lithiation electrode material prepared by graded pre-lithiation in this application, when containing multiple lithiation layers, has a stepped lithium content with less inside and more outside. In this way, while making the electrode material have a better first effect, it can also reduce the amount of low redox potential lithiating agent used, reduce the lithiation cost, improve the lithium utilization rate, and further reduce the possibility of rupture.

[0053] In one example, the preparation method includes at least two of the following steps (1) to (3):

[0054] (1) mixing an electrode material with a first lithiating agent to perform a first reaction to prepare a first pre-lithiated electrode material;

[0055] (2) mixing the electrode material or the first pre-lithiation electrode material prepared in step (1) with a second lithiating agent to perform a second reaction to prepare a second pre-lithiation electrode material;

[0056] (3) Mix the first prelithiated electrode material prepared in step (1) or the second prelithiated electrode material prepared in step (2) with a third lithiating agent and carry out a third reaction to prepare a third prelithiated electrode material.

[0057] In one example, in step (1), the redox potential of the first lithiating agent is 0.4V to 2V. Specifically, the redox potential of the first lithiating agent includes, but is not limited to: 0.4V, 0.6V, 0.8V, 1V, 1.2V, 1.4V, 1.6V, 2V, or a range formed by any two of the foregoing values.

[0058] In one example, the first lithiating agent is a complex solution formed by lithium ions, a first complex, and a first solvent. Without limitation, the first complex includes one or more of butyl (C4H 10 -), benzophenone, phenanthrene, anthracene, pyrene, and tetracene. Without limitation, the first solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents, and fluorides of the foregoing solvents. Specific examples may include benzene, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, pyran, fluoroethylene carbonate, etc.

[0059] In one example, in step (1), the first prelithiated electrode material has a first lithiated layer, the number of layers of the first lithiated layer is one layer, and the material composition includes Li x M, where 0 < x < 3; M represents one or more of the matrix elements in the electrode material.

[0060] In one example, in step (2), the redox potential of the second lithiating agent is < 0.4V and ≥ 0.2V. Specifically, the redox potential of the second lithiating agent includes, but is not limited to: 0.2V, 0.25V, 0.3V, 0.35V, 0.37V, 0.39V, or a range formed by any two of the foregoing values.

[0061] In one example, the second lithiating agent is a complex solution formed by lithium ions, a second complex, and a second solvent. Without limitation, the second complex includes one or more of quinoline, isoquinoline, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1-ethylnaphthalene, 2-ethylnaphthalene, 1-methoxynaphthalene, 2-methoxynaphthalene, 1-naphthonitrile, 2-naphthonitrile, 1-acetonaphthone, 2-acetonaphthone, N,N-dimethyl-1-naphthylamine, N,N-dimethyl-2-naphthylamine, biphenyl, 3,3-dimethylbiphenyl, and 3,3,4,4-dimethylbiphenyl. Without limitation, the second solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents, and fluorides of the foregoing solvents. Specific examples include benzene, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, pyran, fluoroethylene carbonate, etc.

[0062] In one example, in step (2), the second prelithiated electrode material has a second lithiation layer.

[0063] In one example, the number of layers of the second lithiation layer is one layer, and the material composition includes Li y M, where 0 < y < 5, and further, 0 < y ≤ 4.4; M represents one or more of the matrix elements in the electrode material. It can be understood that this second lithiation layer can be formed by a separate step (2), or after step (1) is performed, through a second reaction, the lithiation layer formed in step (1) is superimposed and covered to form a second lithiation layer that presents a single layer as a whole.

[0064] In one example, in the direction from the surface of the prelithiated electrode material inward, the second lithiation layer includes a sub-lithiation layer A-2 and a sub-lithiation layer A-1. The material composition of the sub-lithiation layer A-2 includes Li y M, and the material composition of the sub-lithiation layer A-1 includes Li x M, where 0 < x < 3, 0 < x < y < 5, and further, 0 < x < y ≤ 4.4; M represents one or more of the matrix elements in the electrode material. Optionally, the thickness of the sub-lithiation layer A-2 is 1 nm to 30 μm, and the thickness of the sub-lithiation layer A-1 is 10 nm to 30 μm. It can be understood that this second lithiation layer is formed after step (1) is performed, and through a second reaction, the lithiation layer formed in step (1) is partially superimposed and covered to form a structure containing two layers ([Li x M]@[Li y M], x < y < 5).

[0065] In one example, in step (3), the redox potential of the third lithiating agent is <0.2V. Specifically, the redox potential of the third lithiating agent includes, but is not limited to: 0.05V, 0.07V, 0.1V, 0.12V, 0.13V, 0.14V, 0.15V, 0.17V, 0.19V, or the range formed by any two of the foregoing values.

[0066] In one example, the third lithiating agent is a complex solution formed by lithium ions, a third complex, and a third solvent. Without limitation, the third complex includes one or more of liquid ammonia, 2-methylbiphenyl, indene, fluorene, and 9,9-dimethylfluorene. Without limitation, the third solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents, and fluorides of the foregoing solvents. Specific examples include benzene, ethylene glycol dimethyl ether, 2-methyltetrahydrofuran, pyran, fluoroethylene carbonate, etc.

[0067] In one example, in step (3), the third prelithiated electrode material has a third lithiated layer.

[0068] In one example, the number of layers of the third lithiated layer is one layer, and the material composition includes Li z M, where 0 < z < 5, and further, 0 < z ≤ 4.4; M represents one or more of the matrix elements in the electrode material. It can be understood that this third lithiated layer is formed by superimposing and covering the lithiated layer formed in step (1) and / or step (2) through a third reaction after step (1) and / or step (2) to form a third lithiated layer that appears as one layer as a whole.

[0069] In one example, in the direction from the surface of the prelithiated electrode material inward, the third lithiated layer includes a B-2 sub-lithiated layer and a B-1 sub-lithiated layer. The material composition of the B-2 sub-lithiated layer includes Li z M, and the material composition of the B-1 sub-lithiated layer includes Li x M, where 0 < x < 3, 0 < x < z < 5, and further, 0 < x < z ≤ 4.4; M represents one or more of the matrix elements in the electrode material. It can be understood that this third lithiated layer can be formed by partially superimposing and covering the lithiated layer formed in step (1) through a third reaction after step (1) to form a third lithiated layer that appears as two layers as a whole ([Li x M]@[Li z M], x < z < 5), or it can be formed by superimposing and covering the lithiated layer formed in step (2) through a third reaction after step (1) and step (2) to form a third lithiated layer that appears as two layers as a whole ([Li x M]@[Li zM], x < z < 5).

[0070] Without limitation, the thickness of the B-2 sub-lithiated layer is 1 nm to 30 μm, and the thickness of the B-1 sub-lithiated layer is 10 nm to 30 μm.

[0071] In one example, along the direction inward from the surface of the pre-lithiated electrode material, the third lithiated layer includes a C-2 sub-lithiated layer and a C-1 sub-lithiated layer. The material composition of the C-2 sub-lithiated layer includes Li z M, and the material composition of the C-1 sub-lithiated layer includes Li y M, where 0 < y < 5, 0 < y < z < 5. Further, 0 < y ≤ 4.4, 0 < y < z ≤ 4.4, and M represents one or more of the matrix elements in the electrode material. It can be understood that this third lithiated layer is formed by partially superimposing and covering the lithiated layer formed in step (2) through a third reaction after step (2), resulting in a third lithiated layer that overall presents two layers ([Li y M]@[Li z M], y < z < 5).

[0072] Without limitation, the thickness of the C-2 sub-lithiated layer is 1 nm to 30 μm, and the thickness of the C-1 sub-lithiated layer is 10 nm to 30 μm.

[0073] In one example, along the direction inward from the surface of the pre-lithiated electrode material, the third lithiated layer includes a D-3 sub-lithiated layer, a D-2 sub-lithiated layer, and a D-1 sub-lithiated layer. The material composition of the D-3 sub-lithiated layer includes Li z M, the material composition of the D-2 sub-lithiated layer includes Li y M, and the material composition of the D-1 sub-lithiated layer includes Li x M, where 0 < x < 3, 0 < y < 5, 0 < x < y < z < 5. Further, 0 < y ≤ 4.4, 0 < x < y < z ≤ 4.4, and M represents one or more of the matrix elements in the electrode material. It can be understood that this third lithiated layer is formed by first performing step (1), then partially superimposing and covering the lithiated layer formed in step (1) through a second reaction, and then partially superimposing and covering the lithiated layer formed in step (2) through a third reaction, thereby forming a third lithiated layer that overall presents three layers ([Li x M]@[Li y M]@[Li z M], x < y < z < 5).

[0074] Without limitation, the thickness of the D-3 th sub-lithiation layer is 1 nm to 30 μm, the thickness of the D-2 th sub-lithiation layer is 1 nm to 30 μm, and the thickness of the D-1 th sub-lithiation layer is 10 nm to 30 μm.

[0075] In one example, M includes one or more of carbon, silicon, phosphorus, tin, magnesium, silver, zinc, sulfur, and germanium.

[0076] In one example, the electrode material includes one or more of elemental sulfur, elemental silicon, silicon dioxide (SiOx1, 0<x1≤1.5), elemental phosphorus, elemental tin, stannous oxide (SnOx2, 0<x2≤1.5), elemental magnesium, elemental silver, elemental zinc, elemental germanium, germanium dioxide (GeOx3, 0<x3≤1.5), graphite, graphene, hard carbon, soft carbon, carbon nanotubes and carbon nanofibers.

[0077] In one example, the particle size of the electrode material is 20nm to 50μm. Specifically, the particle size of the pre-lithiation electrode material includes but is not limited to: 20nm, 50nm, 100nm, 300nm, 500nm, 700nm, 1μm, 3μm, 5μm, 7μm, 10μm, 20μm, 30μm, 40μm, 50μm or a range formed by any two of the foregoing values. Furthermore, the particle size of the electrode material is 5μm to 50μm.

[0078] In one example, in step (1), the temperature of the first reaction is room temperature and the time is 0.1h to 6h;

[0079] In one example, in step (2), the temperature of the second reaction is room temperature and the time is 0.1h to 6h;

[0080] In one example, in step (3), the temperature of the third reaction is room temperature, and the time is 0.1h to 6h.

[0081] Another example of the present application provides an electrode sheet, including a current collector and an electrode film layer arranged on at least one surface of the current collector, the material of the electrode film layer including the pre-lithiation electrode material as described above and at least one of the pre-lithiation electrode materials prepared by the preparation method as described above.

[0082] Another example of the present application further provides a secondary battery, comprising the electrode sheet as described above.

[0083] Another example of the present application further provides an electric device including the secondary battery as described above.

[0084] Furthermore, the secondary battery, battery module, battery pack, and electrical device of the present application are described as follows.

[0085] In one embodiment of the present application, a secondary battery is provided.

[0086] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During the battery's charge and discharge processes, active ions are inserted and removed between the positive and negative electrodes. The electrolyte conducts ions between the positive and negative electrodes. The separator, located between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0087] Positive electrode

[0088] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer includes a positive electrode active material.

[0089] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive electrode current collector.

[0090] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be formed by forming a metal material on a polymer material substrate. Among them, the metal material includes but is not limited to aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc. Polymer material substrate (such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.)

[0091] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and its modified compounds. Examples of olivine-structured lithium-containing phosphates may include, but are not limited to, at least one of lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. The weight ratio of the positive electrode active material in the positive electrode film layer is 80-100 weight%, based on the total weight of the positive electrode film layer.

[0092] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0-20 weight %, based on the total weight of the positive electrode film layer.

[0093] In some embodiments, the positive electrode film layer may further optionally include a conductive agent. For example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the positive electrode film layer is 0-20% by weight, based on the total weight of the positive electrode film layer.

[0094] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry, wherein the positive electrode slurry has a solid content of 40-80 wt %, and the viscosity at room temperature is adjusted to 5000-25000 mPa·s, the positive electrode slurry is coated on the surface of the positive electrode current collector, and after drying, the positive electrode sheet is formed by cold rolling; the positive electrode powder coating unit area density is 150-350 mg / m 2 The compaction density of the positive electrode is 3.0-3.6g / cm 3 , optional 3.3-3.5g / cm 3 The calculation formula of the compacted density is

[0095] Compaction density = coating surface density / (thickness of the electrode after extrusion - thickness of the current collector).

[0096] Negative electrode

[0097] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0098] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0099] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material on a polymer material substrate. Among them, the metal material includes but is not limited to copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc., and the polymer material substrate includes but is not limited to polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other substrates.

[0100] In some embodiments, the negative electrode active material may adopt the negative electrode active material for batteries that is well known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxides and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The weight ratio of the negative electrode active material in the negative electrode film layer is 70-100 weight%, based on the total weight of the negative electrode film layer.

[0101] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The binder may be present in the negative electrode film layer in an amount of 0-30% by weight, based on the total weight of the negative electrode film layer.

[0102] In some embodiments, the negative electrode film layer may further include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The weight ratio of the conductive agent in the negative electrode film layer is 0-20% by weight, based on the total weight of the negative electrode film layer.

[0103] In some embodiments, the negative electrode film layer may further include other additives, such as a thickener (e.g., sodium carboxymethyl cellulose (CMC-Na)). The weight ratio of the other additives in the negative electrode film layer is 0-15% by weight, based on the total weight of the negative electrode film layer.

[0104] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (such as deionized water) to form a negative electrode slurry, wherein the negative electrode slurry has a solid content of 30-70 wt% and a viscosity at room temperature adjusted to 2000-10000 mPa·s; the obtained negative electrode slurry is coated on the negative electrode current collector, and after a drying process, cold pressing, such as with a roller, is obtained. The negative electrode powder coating unit area density is 75-220 mg / m 2 , the compaction density of the negative electrode is 1.2-2.0g / m 3 .

[0105] electrolytes

[0106] The electrolyte conducts ions between the positive and negative electrodes. This application does not specify the type of electrolyte, and the electrolyte can be selected based on the needs. For example, the electrolyte can be liquid, gel, or solid.

[0107] In some embodiments, the electrolyte is an electrolyte solution comprising an electrolyte salt and a solvent.

[0108] In some embodiments, the electrolyte salt may be selected from one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bis(fluorosulfonyl)imide (LiFSI), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobis(oxalatophosphate) (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP). The concentration of the electrolyte salt is typically 0.5-5 mol / L.

[0109] In some embodiments, the solvent can be selected from one or more of fluoroethylene carbonate (FEC), ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), methyl ethyl sulfone (EMS) and diethyl sulfone (ESE).

[0110] In some embodiments, the electrolyte may further include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0111] Isolation film

[0112] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0113] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0114] In some embodiments, the isolation film has a thickness of 6-40 μm, and optionally 12-20 μm.

[0115] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0116] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0117] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. Alternatively, the outer packaging of the secondary battery can be a soft shell, such as a pouch-type soft shell. The soft shell can be made of plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0118] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square, or any other shape. For example, FIG1 shows a secondary battery 5 with a square structure as an example.

[0119] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0120] In some embodiments, secondary batteries can be assembled into a battery module. The number of secondary batteries contained in the battery module can be one or more. The specific number can be selected by those skilled in the art according to the application and capacity of the battery module.

[0121] Figure 3 shows an example battery module 4. Referring to Figure 3 , within the battery module 4, multiple secondary batteries 5 may be arranged sequentially along the length of the battery module 4. Of course, any other arrangement is also possible. Furthermore, the multiple secondary batteries 5 may be secured together using fasteners.

[0122] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0123] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art based on the application and capacity of the battery pack.

[0124] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0125] In addition, the present application also provides an electric device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electric device, and can also be used as an energy storage unit for the electric device. The electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0126] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0127] Figure 6 shows an example of an electric device. This device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery, a battery pack or battery module can be used.

[0128] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0129] Example

[0130] In order to make the technical problems, technical solutions and beneficial effects solved by this application clearer, the application will be further described in detail below with reference to the embodiments and drawings. Obviously, the described embodiments are only a part of the embodiments of this application, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present application and its applications. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0131] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0132] 1. Preparation Example

[0133] Preparation of pre-lithiation electrode materials

[0134] Preparation Example 1

[0135] (1) 0.5 mol of benzophenone was dissolved in 1 L of ethylene glycol dimethyl ether, and then 0.5 mol of lithium flakes was added and stirred at room temperature of 25°C for 4 h to obtain 0.5 M lithium-benzophenone-ethylene glycol dimethyl ether (the first lithiation agent, with a redox potential of 1.0 V);

[0136] (2) 0.5 mol of naphthalene was dissolved in 1 L of ethylene glycol dimethyl ether, and then 0.5 mol of lithium flakes was added and stirred at room temperature for 4 h to obtain 0.5 M lithium-naphthalene-ethylene glycol dimethyl ether (second lithiation agent, redox potential of 0.37 V);

[0137] (3) 0.5 mol of 2-methylbiphenyl was dissolved in 1 L of ethylene glycol dimethyl ether, and then 0.5 mol of lithium flakes was added and stirred at room temperature for 4 h to obtain 0.5 M lithium-2-methylbiphenyl-ethylene glycol dimethyl ether (third lithiation agent, redox potential of 0.13 V);

[0138] (4) reacting a Sn element having a particle size of 30 μm with a 1-fold molar excess of a first lithiation agent for 6 h to prepare a LiSn alloy layer;

[0139] (5) The LiSn alloy obtained in step (4) was reacted with a second lithiation agent in an excess molar amount of 1 times for 6 hours to prepare Li 13 Sn5 alloy layer;

[0140] (6) Li obtained in step (5) 13 Sn5 alloy was reacted with a molar excess of the third lithiation agent for 6 h to prepare a single-layer Li 22 Sn5 alloy layer, dry nitrogen and store for future use.

[0141] The preparation methods of the pre-lithiation electrode materials of Examples 2-10, Comparative Example 1 and Reference Examples 1-2 are similar to those of Example 1, but the reaction time, the particle size of the electrode material, the reaction steps, the process method, etc. are changed. See Table 1 for details.

[0142] Table 1

[0143] Note: The “ / ” in Table 1 represents the corresponding reagents and times in different steps. For example, “first / third” and “3 / 1” in Example 4 indicate that only the first and third lithiating agents are used for the reaction (i.e., only steps (4) and (6) are performed), and the reaction times are 3 h and 1 h, respectively.

[0144] 2. Application Examples

[0145] Example 1

[0146] 1) Preparation of positive electrode sheet

[0147] The LiFePO4 positive electrode, SP and binder PVDF were dispersed in the solvent NMP in a weight ratio of 84:8:8 and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry was evenly coated on the positive electrode current collector aluminum foil, and after drying and cold pressing, a positive electrode sheet was obtained.

[0148] 2) Preparation of negative electrode sheet

[0149] Graphite, Ketjen carbon, a binder (50 wt% AST-9005 and 50 wt% LPIMAM37B), and the pre-lithiation electrode material prepared in the embodiment, comparative example, or reference example were mixed in a mass ratio of 80:1:9:10, and NMP was added to obtain a negative electrode slurry under the action of a vacuum mixer. The negative electrode slurry was evenly coated on a carbon-coated Cu foil, and after drying and cold pressing, a negative electrode sheet was obtained.

[0150] 3) Isolation film

[0151] A 12μm thick polyethylene isolation film was selected.

[0152] 4) Preparation of electrolyte

[0153] The organic solvent is a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC), with the volume ratio of EC, EMC, and DEC being 20:20:60. In an argon atmosphere glove box with a water content of <10 ppm, fully dried lithium salt LiPF6 is dissolved in the organic solvent and mixed thoroughly to obtain an electrolyte solution. The concentration of the lithium salt is 1 mol / L.

[0154] 5) Preparation of batteries

[0155] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator placed between the positive and negative electrode sheets to serve as an isolation. After winding into a square bare battery cell, an aluminum-plastic film is placed in it. After baking at 80°C to remove water, 10g of the corresponding non-aqueous electrolyte is injected and sealed. After standing, hot and cold pressing, formation, clamping, capacity division and other processes, a full battery is obtained.

[0156] 3. Battery performance test

[0157] The performance of the full battery was tested using a high-precision battery test system. The process was as follows: (1) Stand for 6 hours; (2) Charge to 3.65V at a constant current of 0.1C, then maintain constant voltage until the current reaches 0.05C; (3) Stand for 5 minutes; (4) Discharge to 2V at a constant current of 0.2C, then maintain constant voltage until the current reaches 0.05C; (5) Stand for 5 minutes; (6) Charge to 3.65V at a constant current of 0.2C, then maintain constant voltage until the current reaches 0.05C; (7) Stand for 5 minutes; (8) Discharge to 2V at a constant current of 0.5C; (9) Stand for 5 minutes; (10) Repeat steps 6-9 for 10 times; (11) Charge to 3.65V at a constant current of 0.1C, then charge to a constant voltage of 0.05C; (12) let stand for 5 minutes; (13) discharge to 2V at a constant current of 0.2C; (14) let stand for 5 minutes; (15) repeat steps 6-13 10 times; (16) end.

[0158] The test results are shown in Table 2.

[0159] Table 2

[0160] From the comparison between Examples 1-10 and Comparative Example 1, it can be seen that the pre-lithiation electrode material of the present application can effectively improve the first efficiency of the battery. Furthermore, from the comparison between Example 8 and Reference Example 1, and between Example 1 and Reference Example 2, it can be seen that the pre-lithiation electrode material of the present application can achieve a first efficiency comparable to or even better than that of using a low redox potential lithium reagent alone. At the same time, since less low redox potential lithium reagent is used, the cost is effectively reduced.

[0161] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and any embodiments having substantially the same structure and effect as the technical concept within the scope of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the present application, any other embodiments that can be conceived by those skilled in the art and that combine some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A pre-lithiation electrode material, wherein the particle size of the pre-lithiation electrode material is 20nm to 50μm, the pre-lithiation electrode material has a lithiation layer, the lithiation layer includes at least one sub-lithiation layer, and when the number of the sub-lithiation layers is ≥2, the content of lithium in each of the sub-lithiation layers decreases layer by layer from the surface of the pre-lithiation electrode material to the inside.

2. The pre-lithiation electrode material according to claim 1, characterized in that In the direction from the surface of the pre-lithiated electrode material inward, the lithiated layer sequentially includes a third sub-lithiated layer with a thickness of ≥0 nm and ≤30 μm, a second sub-lithiated layer with a thickness of ≥0 nm and ≤30 μm, and a first sub-lithiated layer with a thickness of 10 nm to 50 μm: The material composition of the first sub-lithiation layer includes Li a M; The material composition of the second sub-lithiation layer includes Li b M; The material composition of the third sub-lithiation layer includes Li c M; Wherein, 0 < a < 5, 0 < b < 5, 0 < c < 5, and when the thickness of at least one of the second sub-lithiated layer and the third sub-lithiated layer > 0, a, b, c satisfy a < b < c; M represents one or more of the matrix elements in the electrode material.

3. The pre-lithiation electrode material according to claim 2, characterized in that M includes one or more of carbon element, silicon element, phosphorus element, tin element, magnesium element, silver element, zinc element, sulfur element, and germanium element.

4. The pre-lithiation electrode material according to any one of claims 1 to 3, characterized in that: The particle size of the pre-lithiated electrode material is 5 μm to 50 μm.

5. A method for preparing a pre-lithiation electrode material, comprising the following steps: The electrode material is subjected to at least two chemical pre-lithiation treatments, and the redox potential of the lithiating agent used in each chemical pre-lithiation treatment is gradually reduced.

6. The method for preparing a pre-lithiation electrode material according to claim 5, characterized in that: The preparation method sequentially includes at least two of the following steps (1) to (3): (1) Mix the electrode material with a first lithiating agent and carry out a first reaction to prepare a first pre-lithiated electrode material; (2) Mix the electrode material or the first pre-lithiated electrode material prepared in step (1) with a second lithiating agent and carry out a second reaction to prepare a second pre-lithiated electrode material; (3) Mix the first pre-lithiated electrode material prepared in step (1) or the second pre-lithiated electrode material prepared in step (2) with a third lithiating agent and carry out a third reaction to prepare a third pre-lithiated electrode material.

7. The method for preparing a pre-lithiation electrode material according to claim 6, characterized in that: In step (1), the redox potential of the first lithiating agent is 0.4 V to 1 V; optionally, the first lithiating agent is a complex solution formed by lithium ions, a first complex, and a first solvent; further optionally, the first complex includes one or more of butyl, benzophenone, phenanthrene, anthracene, pyrene, and tetracene; further optionally, the first solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents, and fluorides of the foregoing solvents.

8. The method for preparing a pre-lithiation electrode material according to claim 6 or 7, characterized in that: In step (1), the first prelithiated electrode material has a first lithiated layer, the number of layers of the first lithiated layer is one layer, and the material composition includes Li x M, where 0 < x < 3; M represents one or more of the matrix elements in the electrode material.

9. The method for preparing a pre-lithiation electrode material according to claim 6, characterized in that: In step (2), the redox potential of the second lithiating agent is <0.4 V and ≥0.2 V; optionally, the second lithiating agent is a complex solution formed by lithium ions, a second complex, and a second solvent; further optionally, the second complex includes one or more of quinoline, isoquinoline, naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, 1-ethylnaphthalene, 2-ethylnaphthalene, 1-methoxynaphthalene, 2-methoxynaphthalene, 1-naphthonitrile, 2-naphthonitrile, 1-acetonaphthone, 2-acetonaphthone, N,N-dimethyl-1-naphthylamine, N,N-dimethyl-2-naphthylamine, biphenyl, 3,3-dimethylbiphenyl, and 3,3,4,4-dimethylbiphenyl; further optionally, the second solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents, and fluorides of the foregoing solvents.

10. The method for preparing a pre-lithiation electrode material according to claim 6 or 9, characterized in that: In step (2), the second pre-lithiated electrode material has a second lithiated layer, and the second lithiated layer satisfies one of the following characteristics: (2-1) The number of layers of the second lithiated layer is one, and the material composition includes Li y M, where 0 < y < 5; M represents one or more of the matrix elements in the electrode material; (2-2) In the direction inward along the surface of the prelithiated electrode material, the second lithiation layer includes a sub-lithiation layer A-2 and a sub-lithiation layer A-1. The material composition of the sub-lithiation layer A-2 includes Li y M, and the material composition of the sub-lithiation layer A-1 includes Li x M, where 0 < x < 3, 0 < x < y < 5, and M represents one or more of the matrix elements in the electrode material; optionally, the thickness of the sub-lithiation layer A-2 is 1 nm to 30 μm, and the thickness of the sub-lithiation layer A-1 is 10 nm to 30 μm.

11. The method for preparing a pre-lithiation electrode material according to claim 6, characterized in that: In step (3), the redox potential of the third lithiating agent is less than 0.2 V; optionally, the third lithiating agent is a complex solution formed by lithium ions, a third complex and a third solvent; further optionally, the third complex includes one or more of liquid ammonia, 2-methylbiphenyl, indene, fluorene and 9,9-dimethylfluorene; further optionally, the third solvent includes one or more of ether solvents, furan solvents, pyran solvents, ester solvents, benzene solvents and fluorides of the aforementioned solvents.

12. The method for preparing a pre-lithiation electrode material according to claim 6 or 11, characterized in that: In step (3), the third pre-lithiation electrode material has a third lithiation layer, and the third lithiation layer satisfies one of the following characteristics: (3-1) The number of layers of the third lithiated layer is one, and the material composition includes Li z M, where 0 < z < 5; M represents one or more of the matrix elements in the electrode material; (3-2) In the direction inward along the surface of the prelithiated electrode material, the third lithiation layer includes a B-2 sub-lithiation layer and a B-1 sub-lithiation layer. The material composition of the B-2 sub-lithiation layer includes Li z M, and the material composition of the B-1 sub-lithiation layer includes Li x M, where 0 < x < 3, 0 < x < z < 5, and M represents one or more of the matrix elements in the electrode material; optionally, the thickness of the B-2 sub-lithiation layer is 1 nm to 30 μm, and the thickness of the B-1 sub-lithiation layer is 10 nm to 30 μm; or, in the direction inward along the surface of the prelithiated electrode material, the third lithiation layer includes a C-2 sub-lithiation layer and a C-1 sub-lithiation layer. The material composition of the C-2 sub-lithiation layer includes Li z M, and the material composition of the C-1 sub-lithiation layer includes Li y M, where 0 < y < 5, 0 < y < z < 5, and M represents one or more of the matrix elements in the electrode material; optionally, the thickness of the C-2 sub-lithiation layer is 1 nm to 30 μm, and the thickness of the C-1 sub-lithiation layer is 10 nm to 30 μm; (3-3) In the direction inward along the surface of the prelithiated electrode material, the third lithiation layer includes a D-3 sub-lithiation layer, a D-2 sub-lithiation layer, and a D-1 sub-lithiation layer. The material composition of the D-3 sub-lithiation layer includes Li z M, the material composition of the D-2 sub-lithiation layer includes Li y M, the material composition of the D-1 sub-lithiation layer includes Li x M, where 0 < x < 3, 0 < y < 5, 0 < x < y < z < 5, and M represents one or more of the matrix elements in the electrode material; optionally, the thickness of the D-3 sub-lithiation layer is 1 nm to 30 μm, the thickness of the D-2 sub-lithiation layer is 1 nm to 30 μm, and the thickness of the D-1 sub-lithiation layer is 10 nm to 30 μm.

13. The method for preparing a pre-lithiation electrode material according to any one of claims 8, 10 and 12, characterized in that: M includes one or more of carbon, silicon, phosphorus, tin, magnesium, silver, zinc, sulfur and germanium.

14. The method for preparing a pre-lithiation electrode material according to any one of claims 6 to 13, characterized in that: The electrode material includes one or more of elemental sulfur, elemental silicon, silicon dioxide, elemental phosphorus, elemental tin, elemental tin oxide, elemental magnesium, elemental silver, elemental zinc, elemental germanium, germanium oxide, graphite, graphene, hard carbon, soft carbon, carbon nanotubes and carbon nanofibers.

15. The method for preparing a pre-lithiation electrode material according to any one of claims 6 to 14, characterized in that: The particle size of the electrode material is 20 nm to 50 μm; optionally, the particle size of the electrode material is 5 μm to 50 μm.

16. The method for preparing a pre-lithiation electrode material according to any one of claims 6 to 15, characterized in that: The preparation method has one or more of the following characteristics: (I) In step (1), the temperature of the first reaction is room temperature and the time is 0.1h to 6h; (II) In step (2), the temperature of the second reaction is room temperature and the time is 0.1h to 6h; (III) In step (1), the temperature of the third reaction is room temperature and the time is 0.1h to 6h.

17. An electrode sheet, characterized in that: It comprises a current collector and an electrode film layer disposed on at least one surface of the current collector, wherein the material of the electrode film layer comprises at least one of the pre-lithiation electrode materials described in any one of claims 1 to 5 and the pre-lithiation electrode materials prepared by the preparation method described in any one of claims 6 to 16.

18. A secondary battery, characterized in that: Comprising the electrode sheet as claimed in claim 17.

19. An electrical device, characterized in that: Includes the secondary battery as claimed in claim 18.

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