WO2023130887A1 - Secondary battery, battery module, battery pack and electric device thereof - Google Patents

Abstract

A secondary battery, a battery module, a battery pack and an electric device thereof. The secondary battery comprises a negative pole piece and an electrolyte, wherein the negative pole piece contains a negative electrode active material, the negative electrode active material comprising an inner core and an antimony-containing coating layer arranged on the surface of the inner core; and the electrolyte contains a lithium salt and a fluorine-containing additive, the fluorine-containing additive being a fluorine-containing ester monocyclic compound, wherein the molar ratio of antimony to the fluorine-containing additive is 1 : 20 to 10 : 1, and optionally 0.9 : 10 to 6 : 10. Using the secondary battery facilitates the formation of an SEI film having a high LiF content on the negative pole piece, can effectively prevent the co-embedding of solvent molecules, avoids damage to a negative electrode material caused by the co-embedding of solvent molecules, reduces the decomposition of the solvent in the electrolyte, and in addition, can improve the cycle performance of the battery and prolong the service life of the secondary battery.

Description

Secondary battery, battery module, battery pack and electrical device thereof

cross reference

This application refers to the Chinese patent application No. 202210007504.0 entitled "Secondary Batteries, Battery Modules, Battery Packs, and Electric Devices Thereof" filed on January 5, 2022, which is incorporated herein by reference in its entirety.

technical field

The present application relates to the technical field of batteries, in particular to a secondary battery, a battery module, a battery pack and an electrical device thereof.

Background technique

In recent years, with the increasing demand for clean energy, secondary batteries have been widely used in energy storage power systems such as hydraulic, thermal, wind and solar power plants, as well as power tools, military equipment, aerospace and other fields. As the application fields of secondary batteries have been greatly expanded, higher requirements have been placed on their performance.

In order to further improve the battery life and service life of secondary batteries and improve user experience, how to improve the cycle performance and service life of secondary batteries has become an urgent technical problem to be solved.

Contents of the invention

The technical problem to be solved in this application

The present application is made in view of the above-mentioned problems, and an object thereof is to provide a secondary battery, a battery module, a battery pack, and an electrical device thereof with long battery life and service life.

Technical solutions for problem solving

In order to achieve the above purpose, the present application provides a secondary battery, a battery module, a battery pack and an electrical device thereof.

secondary battery

The first aspect of the present application provides a secondary battery, the secondary battery includes a negative electrode sheet and an electrolyte; the negative electrode sheet contains a negative active material, the negative active material includes an inner core and is arranged on the A cladding layer containing antimony on the surface of the inner core; the electrolyte contains lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein, the antimony element and the fluorine-containing The molar ratio of the additives is 1:20˜10:1, optionally 0.9:10˜6:10.

In the present application, a coating layer containing antimony is provided on the surface of the inner core as a negative electrode active material, and the negative electrode sheet containing the negative electrode active material is applied to an electrolyte containing lithium salt and fluorine-containing additives. During the charging process of the secondary battery, the lithium salt in the electrolyte will ionize free lithium ions, which will react with the antimony element in the negative electrode sheet to form a film layer containing Li ₃ Sb. When the solvent molecules in the electrolyte and the fluorine-containing ester monocyclic compound diffuse to the surface of the negative electrode sheet at the same time, compared with other solvent molecules in the electrolyte, the fluorine-containing ester monocyclic compound and the Li ₃ on the surface of the negative electrode sheet The binding energy of Sb is stronger, and it will be preferentially adsorbed on the surface of Li ₃ Sb film layer, and promote the decomposition of fluorine-containing additives to form a stable solid electrolyte interfacial film (SEI film) whose main component is LiF. LiF is an inorganic compound, which is more stable than other organic components in SEI films. When the content of LiF in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-embedding of solvent molecules, and avoid the damage to the electrode material caused by the co-embedding of solvent molecules. Decomposition of the electrolyte solvent. Therefore, it is beneficial to improve the cycle performance of the secondary battery and prolong the service life of the secondary battery.

In this application, a fluorine-containing ester monocyclic compound is selected as the fluorine-containing additive. Compared with fluorine-containing ester compounds with a large number of rings, fluorine-containing ester monocyclic compounds have lower steric hindrance and stronger binding energy with Li ₃ Sb, which is conducive to preferential adsorption on the negative electrode sheet over solvent molecules surface, and decompose to form a highly stable SEI film.

The present application also limits the molar ratio of the antimony element and the fluorine-containing additive in the secondary battery to ensure good adsorption of Li ₃ Sb and the fluorine-containing additive without affecting other components of the battery system relationship, to prevent excessive consumption of solvents, excessive loss of active ions, and uneven coating of SEI membranes.

In any embodiment, the coating layer containing antimony element contains at least one of antimony simple substance, antimony oxide and antimony trifluoride, optionally antimony simple substance. In this application, by using at least one of antimony simple substance, antimony oxide and antimony trifluoride as the coating layer of the negative electrode active material, it can react with lithium ions in the electrolyte to form a film layer containing Li ₃ Sb, and Further adsorption of fluorine-containing additives promotes its decomposition to form an SEI film with high LiF content. Taking Sb ₂ O ₃ as an example, its reaction formula with lithium ions in the electrolyte is:

Sb ₂ O ₃ +6Li ⁺ →2Sb ³⁺ +3Li ₂ O,

3Li ⁺ +Sb→Li ₃ Sb,

SbF ₃ +3Li ⁺ →3LiF+Sb ³⁺ .

Therefore, co-intercalation of solvent molecules can be effectively prevented, damage to electrode materials caused by co-intercalation of solvent molecules can be avoided, cycle performance of the secondary battery is improved and service life of the secondary battery is prolonged.

In any embodiment, the cladding layer has a thickness of 5 nm to 1000 nm, optionally 20 nm to 400 nm. In the present application, by controlling the thickness of the coating layer within an appropriate range, the cycle performance of the secondary battery can be improved and the service life of the secondary battery can be prolonged without affecting the capacity.

In any embodiment, based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5%-20%, optionally 1%-10%. Therefore, the present application controls the mass percentage of the coating layer within an appropriate range, on the one hand, it can ensure that a uniform and structurally stable SEI film is formed on the surface of the negative electrode sheet, and the protective effect on the negative electrode material is good; at the same time, it can also ensure that The consumption of active lithium is low, and the battery capacity is guaranteed, thereby ensuring the effect of improving the cycle performance of the secondary battery and prolonging the service life of the secondary battery.

In any embodiment, the fluorine-containing additive includes at least one of fluoroethylene carbonate, phenyl trifluoroacetate, and allyl tris(2,2,2-trifluoroethyl)carbonate, optionally Such as fluoroethylene carbonate or phenyl trifluoroacetate. When the above-mentioned fluorine-containing additives are selected, compared with other solvent molecules, the above-mentioned substances have stronger binding energy with Li ₃ Sb and stronger mutual attraction, so they can be preferentially adsorbed on the surface of the Li ₃ Sb film and decompose to form A stable SEI film with high LiF content. LiF is an inorganic compound, which is more stable than other organic components in SEI films. When the content of LiF in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-intercalation of solvent molecules, and avoid the damage to the electrode material caused by the co-intercalation of solvent molecules. Thus, the present application can generate a higher and stable SEI film with LiF content by selecting the above-mentioned range of fluorine-containing additives, which can effectively prevent the co-embedding of solvent molecules, and avoid the damage to the electrode material caused by the co-embedding of solvent molecules. Improve the cycle performance and service life of the secondary battery.

In any embodiment, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5%-20%, optionally 2%-10%. In this application, by controlling the mass percentage of fluorine-containing additives within an appropriate range, on the one hand, it can ensure that the formation of the SEI film consumes less solvent, prevent the decomposition of the solvent, ensure the battery capacity, and meet the use of the entire life cycle; at the same time It can also ensure that the solvent in the electrolyte is in an appropriate proportion, and ensure that the electrolyte system, solubility, viscosity and other conditions are in a good state, thereby improving the cycle performance of the secondary battery and prolonging the service life of the secondary battery.

In any embodiment, the molar concentration of the lithium salt in the electrolyte is 0.7M˜1.5M.

In any embodiment, the inner core contains at least one of graphite, hard carbon, soft carbon, lithium titanate, tin-based material, nickel-based material, and alloy material.

A second aspect of the present application provides a battery module including the secondary battery of the first aspect of the present application. The battery module has good cycle performance and long service life.

A third aspect of the present application provides a battery pack, including the battery module of the second aspect of the present application. The battery pack has good cycle performance and long service life.

The fourth aspect of the present application provides an electrical device, including at least one selected from the secondary battery of the first aspect of the present application, the battery module of the second aspect of the present application, or the battery pack of the third aspect of the present application. kind. The electric device has good cycle performance and long service life.

Beneficial effect

The application provides a secondary battery, the secondary battery includes a negative electrode sheet and an electrolyte, the negative electrode sheet contains a negative electrode active material, and the surface of the inner core of the negative electrode active material is provided with a coating layer containing antimony ; The electrolyte contains a lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein, the molar ratio of the antimony element to the fluorine-containing additive is 1:20-10 :1, optionally 0.9:10 to 6:10. In this application, by using the above-mentioned secondary battery, a film layer containing Li ₃ Sb can be formed on the surface of the negative electrode sheet after charging, and by preferentially adsorbing the fluorine-containing additive in the electrolyte, it can be decomposed and form an SEI with high LiF content The film can effectively prevent the co-intercalation of solvent molecules, avoid the co-intercalation of solvent molecules and damage to the negative electrode material, reduce the decomposition of the solvent in the electrolyte, and improve the cycle performance and prolong the life of the secondary battery.

Description of drawings

FIG. 1 is a schematic diagram of an anode active material according to an embodiment of the present application.

FIG. 2 is the cycle performance test results of the secondary battery made of the negative electrode active material obtained in Example 1 and Comparative Example 1 of the present application.

FIG. 3 is a schematic diagram of a secondary battery according to an embodiment of the present application.

FIG. 4 is an exploded view of the secondary battery according to one embodiment of the present application shown in FIG. 3 .

FIG. 5 is a schematic diagram of a battery module according to an embodiment of the present application.

FIG. 6 is a schematic diagram of a battery pack according to an embodiment of the present application.

FIG. 7 is an exploded view of the battery pack according to one embodiment of the present application shown in FIG. 6 .

FIG. 8 is a schematic diagram of an electrical device in which a secondary battery is used as a power source according to an embodiment of the present application.

Explanation of reference signs:

1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 casing; 52 electrode assembly; 53 top cover assembly.

Detailed ways

Hereinafter, embodiments of the secondary battery, battery module, battery pack, and power consumption device of the present application will be specifically disclosed in detail with reference to the accompanying drawings. However, unnecessary detailed description may be omitted. For example, detailed descriptions of well-known items and repeated descriptions of substantially the same configurations may be 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 descriptions 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.

A "range" disclosed herein is defined in terms of lower and upper limits, and a given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive and may be combined arbitrarily, ie any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, it is understood that ranges of 60-110 and 80-120 are contemplated. Additionally, 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 are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-5. In this application, unless otherwise stated, the numerical range "a-b" represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article, and "0-5" is only an abbreviated representation of the combination of these values. In addition, when expressing that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

If there is no special description, all the implementation modes and optional implementation modes of the present application can be combined with each other to form new technical solutions.

If there is no special description, all the technical features and optional technical features of the present application can be combined with each other to form a new technical solution.

Unless otherwise specified, all steps in the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed in sequence, and may also include steps (b) and (a) performed in sequence. For example, mentioning that the method may also include step (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c) , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b) and so on.

If there is no special description, the "comprising" and "comprising" mentioned in this application mean open or closed. For example, the "comprising" and "comprising" may mean that other components not listed may be included or included, or only listed components may be included or included.

In this application, the term "or" is inclusive unless otherwise stated. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied by either of the following: 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).

The inventors have found through research that secondary batteries, especially at the position of the negative electrode, have the problems of co-embedding of solvent molecules and excessive decomposition of solvents, which are an important factor that restricts the cycle performance and service life of secondary batteries. . The inventors of the present application can effectively improve the cycle performance of the secondary battery and prolong its service life by providing a coating layer containing antimony element substances on the surface of the inner core of the negative electrode active material and adding special additives to the electrolyte.

Based on this, the first embodiment of the present application provides a secondary battery. The secondary battery includes a negative electrode sheet and an electrolyte; the negative electrode sheet contains a negative active material, and the negative active material includes an inner core and a device. A cladding layer containing antimony on the surface of the inner core; the electrolyte contains lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound; wherein, the antimony element and the The molar ratio of the fluorine-containing additives is 1:20-10:1, optionally 0.9:10-6:10.

As shown in Figure 1, in this application, a coating layer containing antimony is placed on the surface of the inner core, and it is used as the negative electrode active material, and the negative electrode sheet containing the negative electrode active material is applied to lithium salts and fluorine-containing additives in the electrolyte. During the charging process of the secondary battery, the lithium salt in the electrolyte will ionize free lithium ions, which will react with the antimony element in the negative electrode sheet to form a film layer containing Li ₃ Sb. When the solvent molecules in the electrolyte and the fluorine-containing ester monocyclic compound diffuse to the surface of the negative electrode sheet at the same time, compared with other solvent molecules in the electrolyte, the fluorine-containing ester monocyclic compound and the Li on the surface of the negative electrode sheet The binding energy of ₃ Sb is stronger, and the mutual attraction is also stronger. It will be preferentially adsorbed on the surface of Li ₃ Sb film, and promote the decomposition of fluorine-containing additives to form a stable solid electrolyte interfacial film (SEI film) whose main component is LiF. ). In the SEI film of the present application, LiF is an inorganic compound, which has better stability than organic components in other SEI films. When the content of LiF in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-embedding of solvent molecules, and avoid the damage to the electrode material caused by the co-embedding of solvent molecules. The decomposition of the electrolyte solvent is prevented, the cycle performance of the secondary battery is improved, and the service life of the secondary battery is prolonged, as shown in FIG. 2 .

In this application, the fluorine-containing ester monocyclic compound is selected as the fluorine-containing additive. Compared with the fluorine-containing ester compound with a large number of rings, the fluorine-containing ester monocyclic compound has lower steric hindrance, and Li ₃ The binding energy of Sb is stronger. Among them, the binding energy refers to the free energy of the binding reaction of two substances, and the smaller the value of the binding energy, it is defined as the easier combination of the two substances.

The secondary battery provided by the present application can satisfy the above-mentioned molar ratio of the antimony element to the fluorine-containing additive in the initial state, especially when charging and discharging within 10 cycles. After 1000 cycles after charge and discharge, the molar ratio of the two can also be kept in the range of 1:5 to 40:1, optionally 1:2.5 to 4:1, because the initial film formation and Fluorine-containing additives are consumed throughout the cycle. By limiting the molar ratio between the antimony element and the fluorine-containing additive in the secondary battery, it can be ensured that a good adsorption relationship between Li ₃ Sb and the fluorine-containing additive is formed without affecting other components of the battery system, preventing Problems such as excessive consumption of solvent, excessive loss of active ions, uneven coating of SEI film, etc.

In addition, in the present application, the coating layer on the surface of the negative electrode active material is preferably formed in situ, and the volume occupied by the coating layer in the negative electrode active material is small. Therefore, the secondary battery provided by the application is suitable for applications with limited space, and Cases requiring high weight and energy density, but not limited thereto.

In this application, the content of the antimony element and the content of the fluorine-containing additive can be tested by methods known in the art. As an example, the content of the antimony element can be tested by an inductively coupled plasma spectrometer (ICP), such as the ICP-3000 of Tianrui Company and other instruments; Jin company's GC-2014C and other instruments for testing. By calculation, the ratio of the two can be obtained.

In some embodiments, the cladding layer containing antimony element contains at least one of antimony simple substance, antimony oxide and antimony trifluoride, optionally antimony simple substance.

In this application, by using at least one of antimony simple substance, antimony oxide and antimony trifluoride as the coating layer of the negative electrode active material, it can react with lithium ions in the electrolyte to form a film layer containing Li ₃ Sb, and Further adsorption of fluorine-containing additives promotes its decomposition to form an SEI film with high LiF content. Taking Sb ₂ O ₃ as an example, its reaction formula with lithium ions in the electrolyte is:

Sb ₂ O ₃ +6Li ⁺ →2Sb ³⁺ +3Li ₂ O,

3Li ⁺ +Sb→Li ₃ Sb,

SbF ₃ +3Li ⁺ →3LiF+Sb ³⁺ .

Therefore, co-intercalation of solvent molecules can be effectively prevented, damage to electrode materials caused by co-intercalation of solvent molecules can be avoided, cycle performance of the secondary battery is improved and service life of the secondary battery is prolonged.

In some embodiments, the thickness of the cladding layer is 5nm-1000nm, optionally 20nm-400nm. In the present application, by controlling the thickness of the coating layer within an appropriate range, the cycle performance of the secondary battery can be improved and the service life of the secondary battery can be prolonged without affecting the capacity.

In this application, the thickness of the cladding layer can be tested by methods known in the art. As an example, a transmission electron microscope (TEM) can be used to perform a characterization test, for example, a JEM-2100F instrument from JEOL Company can be used to perform a test.

In some embodiments, based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5%-20%, optionally 1%-10%.

Therefore, the present application controls the mass percentage of the coating layer within an appropriate range, on the one hand, it can ensure that a uniform and structurally stable SEI film is formed on the surface of the negative electrode sheet, and the protective effect on the negative electrode material is good; at the same time, it can also ensure that The consumption of active lithium is low, and the battery capacity is guaranteed, thereby improving the cycle performance of the secondary battery and prolonging the service life of the secondary battery.

In some embodiments, the fluorine-containing additive includes at least one of fluoroethylene carbonate, phenyl trifluoroacetate, and allyl tris(2,2,2-trifluoroethyl)carbonate, optionally Such as fluoroethylene carbonate or phenyl trifluoroacetate.

When the above-mentioned fluorine-containing additives are selected, compared with other solvent molecules, the above-mentioned substances have stronger binding energy with Li ₃ Sb and stronger mutual attraction, so they can be preferentially adsorbed on the surface of the Li ₃ Sb film and decompose to form A stable SEI film with high LiF content. LiF is an inorganic compound, which is more stable than other organic components in SEI films. When the content of LiF in the SEI film is high, it can improve the film strength, resist the cracking of the SEI film caused by expansion, effectively prevent the co-intercalation of solvent molecules, and avoid the damage to the electrode material caused by the co-intercalation of solvent molecules. Thus, the present application can generate a higher and stable SEI film with LiF content by selecting the above-mentioned range of fluorine-containing additives, which can effectively prevent the co-embedding of solvent molecules, and avoid the damage to the electrode material caused by the co-embedding of solvent molecules. Improve the cycle performance and service life of the secondary battery.

In some embodiments, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5%-20%, optionally 2%-10%. For the secondary battery provided by the present application, in the initial state, especially within 10 cycles of charge and discharge, the fluorine-containing additive can meet the above mass percentage range.

Therefore, the present application controls the mass percentage of the fluorine-containing additive within an appropriate range. On the one hand, it can ensure that the formation of the SEI film consumes less solvent, prevent the decomposition of the solvent, ensure the battery capacity, and meet the requirements of the entire life cycle. Use; at the same time, it can also ensure that the solvent in the electrolyte is in an appropriate proportion, and ensure that the electrolyte system, solubility, viscosity and other conditions are in a good state, thereby improving the cycle performance of the secondary battery and prolonging the service life of the secondary battery.

In some embodiments, the molar concentration of the lithium salt in the electrolyte is 0.7M˜1.5M.

In some embodiments, the inner core may use negative electrode active materials known in the art for batteries. As an example, the inner core may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, tin-based materials, nickel-based materials, lithium titanate and alloy materials, and the like. The alloy material may be selected from silicon-based materials, and the silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of simple tin, tin oxide compounds 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 of batteries can also be used as the inner core. These materials may be used alone as the inner core or in combination of two or more.

In some embodiments, the negative electrode sheet further includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, and the negative electrode film layer includes the negative electrode active material. As an example, the negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposing surfaces of the negative electrode current collector.

In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a base layer of polymer material and a metal layer formed on at least one surface of the base material of polymer material. The composite current collector can be formed by forming metal materials (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as PP, PET, PBT, PS, PE, etc. substrate) formed on.

In some embodiments, the negative electrode film layer may further optionally include a binder. The binder can be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), poly At least one of methacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

In some embodiments, the negative electrode film layer may also optionally include a conductive agent. The conductive agent can be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

In some embodiments, the negative electrode film layer may optionally include other additives, such as thickeners (such as sodium carboxymethylcellulose (CMC-Na)) and the like.

In some embodiments, the negative electrode sheet can be prepared by the following method:

providing a precursor containing antimony elements and an inner core, mixing and calcining the precursor containing antimony elements and the inner core to obtain a negative electrode active material, the negative electrode active material including an inner core and an antimony element-containing coating disposed on the surface of the inner core Coating; the above-mentioned components used to prepare the negative electrode sheet, such as negative electrode active material, conductive agent, binding agent and any other components are dispersed in a solvent (such as deionized water) to form negative electrode slurry; negative electrode slurry The material is coated on the negative electrode current collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

In the present application, through the above-mentioned preparation method of the negative pole piece of the present application, the preparation of the negative pole piece can be carried out simply and easily, and has the advantages of low energy consumption and low cost; in addition, through the above method, the antimony element can be made The precursor is uniformly coated on the surface of the inner core, thus, a negative electrode sheet meeting the conditions of the present application can be obtained.

In some embodiments, the precursor of the antimony-containing element includes an antimony salt, and the antimony salt includes antimony trichloride, antimony nitrate, antimony sulfate, antimony acetate, poly(antimony ethylene glycol), tri(dimethylamino ) antimony, triphenyl antimony, antimony butoxide, triphenyl antimony dichloride, antimony ethoxide (III), triphenyl antimony dibromide, fluorometamonate hexahydrate; the The cladding layer containing antimony element includes at least one of antimony simple substance, antimony oxide and antimony trifluoride; the inner core contains graphite, hard carbon, soft carbon, lithium titanate, tin-based materials, nickel-based materials , at least one of alloy materials.

In some embodiments, the mixing step comprises:

Mix the antimony-containing precursor and the inner core in an aqueous solution, add hydrochloric acid to keep the pH value of the solution at 2-4, stir until the mixture is uniform, and evaporate the solvent to dryness.

In this application, by controlling the pH range in the mixing step, the hydrolysis of the precursor containing antimony elements can be effectively suppressed. When the pH value is higher than 4, the precursor containing antimony is easily hydrolyzed, and the precursor containing antimony cannot be evenly coated on the surface of the inner core; when the pH is lower than 2, the reaction conditions are too acidic, which will corrode the reaction vessel. Thereby, a uniform coating layer containing antimony element can be formed on the inner core surface.

In some embodiments, the calcining step comprises:

The sintering temperature is controlled to be 400°C-800°C, the sintering time is 4h-12h, and the sintering is carried out in an inert gas atmosphere.

In the present application, in the calcination step, when the sintering temperature is low and the sintering time is short, the reduction time will be too long and the reduction effect will be poor; when the sintering temperature is high and the sintering time is long, it will cause aging phenomenon, making the adjacent particles The cladding layer is fused together, causing problems such as particle agglomeration; at the same time, it needs to be calcined under an inert gas atmosphere to protect the inner core from being oxidized and consumed. Thus, the sintering temperature, sintering time and gas atmosphere are limited in the calcination step, and the negative electrode active material meeting the conditions of the present application can be obtained.

In addition, other parts of the secondary battery, the battery module, the battery pack, and the electric device of the present application will be described below with reference to the drawings as appropriate.

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

Typically, a secondary battery includes a positive pole piece, a negative pole piece, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are intercalated and extracted back and forth between the positive electrode and the negative electrode. The electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece. The separator is arranged between the positive pole piece and the negative pole piece, which mainly plays a role in preventing the short circuit of the positive and negative poles, and at the same time allows ions to pass through. Each constituent element of the secondary battery will be described in detail below.

[Positive pole piece]

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 collector, and the positive electrode film layer includes the positive electrode active material according to the first aspect of the present application.

As an example, the positive electrode current collector has two opposing surfaces in its own thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposing surfaces of the positive electrode current collector.

In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector can be formed by forming metal materials (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as polypropylene (PP), PET, PBT, polypropylene Styrene (PS), polyethylene (PE) and other substrates) are formed.

In some embodiments, the positive electrode active material may be a positive electrode active material known in the art for batteries. As an example, the positive active material may include at least one of the following materials: olivine-structured lithium-containing phosphate, lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials of batteries can also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO ₂ ), lithium nickel oxides (such as LiNiO ₂ ), lithium manganese oxides (such as LiMnO ₂ , LiMn ₂ O ₄ ), lithium Nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi _1/3 Co _1/3 Mn _1/3 O ₂ (also referred to as NCM ₃₃₃ ), LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (also abbreviated as NCM ₅₂₃ ), LiNi _0.5 Co _0.25 Mn _0.25 O ₂ (also abbreviated as NCM ₂₁₁ ), LiNi _0.6 Co _0.2 Mn _0.2 O ₂ (also abbreviated as NCM ₆₂₂ ), LiNi At least one of _0.8 Co _0.1 Mn _0.1 O ₂ (also referred to as NCM ₈₁₁ ), lithium nickel cobalt aluminum oxide (such as LiNi _0.85 Co _0.15 Al _0.05 O ₂ ) and its modified compounds. The olivine structure contains Examples of lithium phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO ₄ (also may be abbreviated as LFP)), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO ₄ ), lithium manganese phosphate and carbon At least one of a composite material, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon.

In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene At least one of ethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer and fluorine-containing acrylate resin.

In some embodiments, the positive electrode film layer may also optionally include a conductive agent. As an 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.

In some embodiments, the positive electrode sheet can be prepared in the following manner: the above-mentioned components used to prepare the positive electrode sheet, such as positive electrode active material, conductive agent, binder and any other components, are dispersed in a solvent (such as N -methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode current collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[Negative pole piece]

For the negative pole piece, refer to the foregoing.

[Electrolyte]

The electrolyte plays the role of conducting ions between the positive pole piece and the negative pole piece. The present application has no specific limitation on the type of electrolyte, which can be selected according to requirements. For example, electrolytes can be liquid, gel or all solid.

In some embodiments, the electrolyte is an electrolytic solution. The electrolyte solution includes an electrolyte salt and a solvent.

In some embodiments, the electrolyte salt may be selected from lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonyl imide, lithium bistrifluoromethanesulfonyl imide, trifluoromethane At least one of lithium sulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium difluorooxalate borate, lithium difluorodifluorooxalatephosphate and lithium tetrafluorooxalatephosphate.

In some embodiments, the solvent may be selected from ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, Butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate At least one of ester, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

In some embodiments, the electrolyte includes additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performances of the battery, such as additives that improve battery overcharge performance, additives that improve high-temperature or low-temperature performance of batteries, and the like. In the present application, the electrolyte solution includes a fluorine-containing additive that is a fluorine-containing ester monocyclic compound.

[Isolation film]

In some embodiments, a separator is further included in the secondary battery. The present application has no particular limitation on the type of the isolation membrane, and any known porous structure isolation membrane with good chemical stability and mechanical stability can be selected.

In some embodiments, the material of the isolation film 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 any particular limitation. When the separator is a multilayer composite film, the materials of each layer may be the same or different, and there is no particular limitation.

In some embodiments, the positive pole piece, the negative pole piece and the separator can be made into an electrode assembly through a winding process or a lamination process.

In some embodiments, the secondary battery may include an outer package. The outer package can be used to package the above-mentioned electrode assembly and electrolyte.

In some embodiments, the outer packaging of the secondary battery may be a hard case, such as a hard plastic case, aluminum case, steel case, and the like. The outer packaging of the secondary battery may also be a soft bag, such as a bag-type soft bag. The material of the soft case may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, polybutylene succinate, and the like.

The present application has no special limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. For example, FIG. 3 shows a square-shaped secondary battery 5 as an example.

In some embodiments, referring to FIG. 4 , the outer package may include a housing 51 and a cover 53 . Wherein, the housing 51 may include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plates enclose to form an accommodating cavity. The housing 51 has an opening communicating with the accommodating cavity, and the cover plate 53 can cover the opening to close the accommodating cavity. The positive pole piece, the negative pole piece and the separator can form the electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is packaged in the accommodating cavity. 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.

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

FIG. 5 is a battery module 4 as an example. Referring to FIG. 5 , in the battery module 4 , a plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4 . Of course, it can also be arranged in any other manner. Furthermore, the plurality of secondary batteries 5 may be fixed by fasteners.

Optionally, the battery module 4 may also include a case having a housing space in which a plurality of secondary batteries 5 are accommodated.

In some embodiments, the above-mentioned battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, and the specific number can be selected by those skilled in the art according to the application and capacity of the battery pack.

6 and 7 show the battery pack 1 as an example. Referring to FIGS. 6 and 7 , the battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3 , the upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery module 4 . Multiple battery modules 4 can be arranged in the battery box in any manner.

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 of the electric device, and can also be used as an energy storage unit of the electric device. The electric devices may include mobile devices (such as mobile phones, notebook computers, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, etc.) , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but not limited thereto.

As the electric device, a secondary battery, a battery module or a battery pack can be selected according to its use requirements.

FIG. 8 is an example of an electrical device. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the electric device for the secondary battery, a battery pack or a battery module may be used.

As another example, a device may be a cell phone, tablet, laptop, or the like. The device is generally required to be light and thin, and a secondary battery can be used as a power source.

Example

Hereinafter, examples of the present application will be described. The embodiments described below are exemplary and are only used for explaining the present application, and should not be construed as limiting the present application. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product specification. The reagents or instruments used were not indicated by the manufacturer, and they were all commercially available conventional products.

Example 1

(1) Preparation of negative electrode active material

After uniformly mixing 95g of graphite and 5g of SbCl ₃ by a liquid phase method, the sample was placed in an atmosphere of Ar/H ₂ (5% H ₂ ), and calcined at 500° C. for 6 hours to obtain the negative electrode active material. The physical parameters of the above-mentioned negative electrode active materials are shown in Table 1 below.

(2) Preparation of negative pole piece

Disperse the above-mentioned negative electrode active material, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and sodium carboxymethylcellulose (CMC) in deionized water, fully stir and mix to form negative electrode slurry; Coated on the copper foil of the negative electrode collector, dried and cold pressed to obtain the negative electrode sheet.

(3) Preparation of secondary battery

After the lithium manganese phosphate as the positive electrode material, the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, the coating drying on aluminum foil and cold pressing to obtain the positive electrode sheet.

A porous polymer film made of polyethylene (PE) is used as the separator.

The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, so that the separator is between the positive and negative electrodes to play the role of isolation, and the bare cell is obtained by winding.

The electrolyte is fluoroethylene carbonate (FEC)/(ethylene carbonate (EC)+diethyl carbonate (DEC)) (mass ratio 5:95), and the volume ratio of EC to DEC is 1:1.

The bare cell is placed in the outer package, the above-mentioned electrolyte is injected and packaged to obtain a secondary battery.

Example 2-3

Except as shown in the following table 1, by adjusting the input amount of the precursor containing antimony element in the raw material to change the thickness of the coating layer of the negative electrode active material, prepared the embodiment 2-3 in the same way as Example 1 secondary battery.

Example 4

Except as shown in the following table 1, by adjusting the input amount of the precursor containing antimony element in the raw material to change the thickness of the coating layer of the negative electrode active material, and adjust the addition amount of FEC, prepare in the same way as Example 1 The secondary battery of Example 4 was obtained.

Example 5

A secondary battery of Example 5 was prepared in the same manner as in Example 1 except that FEC was replaced with phenyl trifluoroacetate as shown in Table 1 below.

Example 6-7

Secondary batteries of Examples 6-7 were prepared in the same manner as in Example 1, except that FEC was replaced with phenyl trifluoroacetate and the addition amount was adjusted as shown in Table 1 below.

Example 8

Except as shown in the following table 1, by adjusting the input amount of the precursor containing antimony element in the raw material to change the thickness of the cladding layer of the negative electrode active material, and adjust the addition amount of FEC, prepare in the same way as Example 1 The secondary battery of Example 8 was obtained.

Example 9

(1) Preparation of negative electrode active material

95g of graphite and 5g of Sb ₂ O ₃ were put into a ball mill pot, and ball milled at 400r/min for 10h to obtain the negative electrode active material.

(2) Preparation of negative pole piece

Disperse the above-mentioned negative electrode active material, conductive agent carbon black, binder styrene-butadiene rubber (SBR), and sodium carboxymethylcellulose (CMC) in deionized water, fully stir and mix to form negative electrode slurry; Coated on the copper foil of the negative electrode collector, dried and cold pressed to obtain the negative electrode sheet.

(3) Preparation of secondary battery

After the lithium manganese phosphate as the positive electrode material, the conductive agent acetylene black and the binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in the N-methylpyrrolidone solvent system at a weight ratio of 94:3:3, the coating drying on aluminum foil and cold pressing to obtain the positive electrode sheet.

A porous polymer film made of polyethylene (PE) is used as the separator.

The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, so that the separator is placed between the positive and negative electrodes to play the role of isolation, and the bare cell is obtained by winding.

The electrolyte is fluoroethylene carbonate (FEC)/(ethylene carbonate (EC)+diethyl carbonate (DEC)) (mass ratio 5:95), and the volume ratio of EC to DEC is 1:1.

The bare cell is placed in the outer package, the above-mentioned electrolyte is injected and packaged to obtain a secondary battery.

Example 10

A secondary battery of Example 10 was prepared in the same manner as in Example 9, except that Sb ₂ O ₃ charged in the raw material was adjusted to SbF ₃ as shown in Table 1 below.

Comparative example 1

The secondary battery of Comparative Example 1 was prepared in the same manner as in Example 1, except that no antimony-containing precursor was added during the preparation of the negative electrode active material as shown in Table 1 below.

Comparative example 2

A secondary battery of Comparative Example 2 was prepared in the same manner as in Example 1, except that FEC was not added to the electrolytic solution as shown in Table 1 below.

Comparative example 3

A secondary battery of Comparative Example 3 was prepared in the same manner as in Example 1 except that the addition amount of FEC was adjusted as shown in Table 1 below.

Comparative example 4

A secondary battery of Comparative Example 4 was prepared in the same manner as in Example 1 except that FEC was replaced with 2-fluoro-1-naphthol as shown in Table 1 below.

Comparative example 5

Except as shown in the following table 1, by adjusting the input amount of the precursor containing antimony element in the raw material to change the thickness of the coating layer of the negative electrode active material, and adjust the addition amount of FEC, prepare in the same way as Example 1 The secondary battery of Comparative Example 5 was obtained.

Next, a test method for the secondary battery will be described.

(1) Initial capacity test

Charge the secondary battery prepared above at a constant temperature of 25°C at 0.33C to 4.2V, then charge at a constant voltage at 4.2V to a current ≤0.05C, let it stand for 5 minutes, and then discharge at 0.33C to 2.8V V, the initial capacity of the secondary battery obtained from the test.

(2) Capacity retention test

Charge the secondary battery prepared above to 4.2V at 1C in a constant temperature environment of 60°C, then charge at a constant voltage at 4.2V to a current ≤0.05C, let it stand for 5 minutes, and then discharge at 1C to 2.8V, Cycle 500 cycles in this way, and divide the capacity obtained by the test after 500 cycles by the initial capacity to obtain the capacity retention rate.

Table 1 Experimental parameters

Table 2: Performance test results of Examples 1-10 and Comparative Examples 1-5

As can be seen from Examples 1-10 in the above table 2, when the antimony element type, thickness, mass percentage of the negative active material coating layer in the secondary battery, the type, mass percentage of the fluorine-containing additive in the electrolyte, and the antimony element When the molar ratio of the particles to the fluorine-containing additive is within the scope of the present application, the secondary battery of the present application has good cycle performance and service life.

From the comparison of Example 1 and Comparative Examples 1-2 in the above Table 2, it can be seen that the coating layer containing antimony element and the fluorine-containing additive are indispensable. When the conventional negative electrode active material is directly selected without antimony coating, the SEI film formed on the surface of the secondary battery will contain a large amount of organic components after charging, resulting in insufficient stability of the SEI film. The expansion of the secondary battery is destroyed, and the active lithium is continuously consumed to rebuild, resulting in poor cycle performance of the secondary battery; when no fluorine-containing additives are added to the electrolyte, the SEI film formed on the surface of the negative electrode material will be damaged after the secondary battery is charged. Absorption of solvent molecules in the electrolyte leads to rapid capacity decay. Compared with existing secondary batteries, the secondary battery of the present application has better cycle performance.

From the comparison of Example 1 and Comparative Example 4 in the above Table 2, it can be seen that when the ester polycyclic compound is used as an additive, although it contains fluorine, the steric hindrance increases due to the polycyclic compound, and the resulting Li ₃ Sb The film layer is difficult to adsorb and combine. Compared with the rest of the electrolyte, it has no priority in adsorption. Therefore, it will also absorb the solvent molecules in the electrolyte, which will lead to a rapid decline in capacity and cannot improve the secondary performance. The cycle performance of the battery.

From the comparison of Example 5 and Comparative Example 3 in the above table 2, and Example 2 and Comparative Example 5, it can be seen that when the molar ratio of the antimony element and the fluorine-containing additive exceeds the scope of the application, Li ₃ Sb and the fluorine-containing additive Fluorine additives cannot form a good adsorption relationship, resulting in the problem of excessive loss of active ions, resulting in loss of initial capacity of the secondary battery, and at the same time, the cycle performance of the secondary battery cannot be improved.

As can be seen from Examples 5-7 and Comparative Example 3 in the above table 2, when the addition amount of fluorine-containing additives in the secondary battery is within an appropriate range, the improvement effect on cycle performance can be guaranteed; when the secondary battery contains fluorine When there are too many additives, it is impossible to ensure that the electrolyte system, solubility, viscosity and other conditions are in a good state. Therefore, it is necessary to control the addition amount of the fluorine-containing additive within an appropriate range.

As can be seen from Examples 1-3 in the above table 2, when the antimony element content in the secondary battery is within an appropriate range, a good improvement effect on cycle performance can be ensured; when the antimony element content in the secondary battery is too much or too little , will have a certain impact on the cycle performance of the secondary battery. In order to ensure that a uniform, structurally stable SEI film can be formed on the surface of the negative electrode sheet, and the consumption of active lithium is low, the content of antimony element needs to be controlled within an appropriate range to ensure good cycle performance of the secondary battery. Improve the effect.

It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are merely examples, and within the scope of the technical solution of the present application, embodiments that have substantially the same configuration as the technical idea and exert the same function and effect are included in the technical scope of the present application. In addition, without departing from the scope of the present application, various modifications conceivable by those skilled in the art are added to the embodiments, and other forms constructed by combining some components in the embodiments are also included in the scope of the present application. .

Claims (11)

1. A secondary battery, characterized in that it comprises: a negative pole piece and an electrolyte,

   The negative electrode sheet contains a negative electrode active material, and the negative electrode active material includes an inner core and a coating layer containing antimony element arranged on the surface of the inner core;

   The electrolyte contains a lithium salt and a fluorine-containing additive, and the fluorine-containing additive is a fluorine-containing ester monocyclic compound;

   Wherein, the molar ratio of the antimony element to the fluorine-containing additive is 1:20˜10:1, optionally 0.9:10˜6:10.
2. The secondary battery according to claim 1, wherein the coating layer containing antimony element contains at least one of antimony simple substance, antimony oxide and antimony trifluoride, optionally antimony simple substance .
3. The secondary battery according to any one of claims 1 or 2, characterized in that, the thickness of the coating layer is 5nm-1000nm, optionally 20nm-400nm.
4. The secondary battery according to any one of claims 1-3, characterized in that, based on the total mass of the negative electrode active material, the mass percentage of the coating layer is 0.5% to 20%, optionally 1 %~10%.
5. The secondary battery according to any one of claims 1-4, wherein the fluorine-containing additives include fluoroethylene carbonate, phenyl trifluoroacetate, allyl tri(2,2,2-tri At least one of fluoroethyl) carbonate, optionally fluoroethylene carbonate or phenyl trifluoroacetate.
6. The secondary battery according to any one of claims 1-5, characterized in that, based on the total mass of the electrolyte, the mass percentage of the fluorine-containing additive is 0.5% to 20%, optionally 2% to 10%.
7. The secondary battery according to any one of claims 1-6, characterized in that the molar concentration of the lithium salt in the electrolyte is 0.7M-1.5M.
8. The secondary battery according to any one of claims 1-7, wherein the inner core contains at least one of graphite, hard carbon, soft carbon, lithium titanate, tin-based materials, nickel-based materials, and alloy materials kind.
9. A battery module, characterized by comprising the secondary battery according to any one of claims 1-8.
10. A battery pack, characterized by comprising the battery module according to claim 9.
11. An electric device, characterized in that it comprises at least one selected from the secondary battery according to any one of claims 1-8, the battery module according to claim 9, or the battery pack according to claim 10 kind.

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