Negative electrode paste, negative electrode pole piece, secondary battery and electric device

Abstract

The invention provides negative electrode slurry, a negative electrode plate, a secondary battery and an electric device, the negative electrode slurry comprises main components and a solvent, and the main components comprise a negative electrode active material, a binder, a linear conductive material and an additive capable of participating in formation of an artificial solid electrolyte interface film; the total mass of the main components is 100%, the mass fraction of the linear conductive material is 0.02%-1%, and the mass fraction of the additive is 0.2%-3%. The negative electrode slurry is used for preparing a negative electrode film layer of a negative electrode plate, so that the secondary battery has relatively good storage performance and cycle performance.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a negative electrode slurry, a negative electrode plate, a secondary battery, and an electrical device. Background Art

[0002] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0003] In recent years, as the application scope of secondary batteries has become increasingly wider, secondary batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as in many fields such as power tools, electric bicycles, electric motorcycles and electric vehicles.

[0004] As secondary batteries have made great progress, higher requirements have been placed on the storage performance and cycle performance of secondary batteries. Therefore, seeking a secondary battery with better storage performance and cycle performance is one of the key areas of focus for those skilled in the art. Summary of the Invention

[0005] The present application is made in view of the above-mentioned problems, and one of its purposes is to provide a negative electrode slurry that can enable a secondary battery using the negative electrode slurry to have better storage performance and cycle performance.

[0006] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a negative electrode slurry, comprising a main component and a solvent, wherein the main component comprises a negative electrode active material, a binder, a linear conductive material and an additive capable of participating in the formation of an artificial solid electrolyte interface film; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.02%~1%, and the mass fraction of the additive is 0.2%~3%.

[0007] By introducing a specific amount of an additive capable of participating in the formation of an artificial solid electrolyte interface membrane into the negative electrode slurry; after using the negative electrode slurry to prepare the negative electrode plate, the above-mentioned additive in the negative electrode film layer can participate in the formation of an artificial solid electrolyte interface membrane during the battery formation process, thereby improving the storage performance of the battery. By introducing a specific amount of linear conductive material into the negative electrode slurry, the linear conductive material is staggered to form a "grid" to alleviate the curling and agglomeration of the binder molecular chains, thereby reducing the impact of the introduction of the additive on the binder, increasing the viscosity of the negative electrode slurry, and improving the bonding force between the negative electrode film layer and the current collector, so that the battery has better cycle performance. By simultaneously introducing a specific amount of linear conductive material and an additive capable of participating in the formation of an artificial solid electrolyte interface membrane into the negative electrode slurry, the secondary battery prepared using the negative electrode slurry can have both good storage performance and good cycle performance.

[0008] In any embodiment, based on 100% of the total mass of the main component, the mass fraction of the linear conductive material is 0.02% to 0.6%, and the mass fraction of the additive is 0.2% to 2%. By controlling the amounts of the linear conductive material and additive within the aforementioned ranges, a secondary battery prepared using this negative electrode slurry can have relatively high energy density while exhibiting good storage and cycling performance.

[0009] In any embodiment, the additive includes one or more of a first additive and a second additive, the first additive includes one or more of a monovalent metal salt and a monovalent metal hydroxide, and the second additive includes a polyvalent metal salt.

[0010] In any embodiment, the monovalent metal salt includes one or more of a monovalent metal carbonate, a monovalent metal fluoride, a monovalent metal phosphate, a monovalent metal alkoxide, a monovalent metal carboxylate, and a monovalent metal alkyl carbonate. This effectively forms an artificial solid electrolyte interface in the negative electrode film. Monovalent metal salts and monovalent metal hydroxides have a relatively smaller effect on the viscosity of the negative electrode slurry than polyvalent metal salts. Furthermore, monovalent metal salts and monovalent metal hydroxides have better ion conductivity, which helps increase the battery's charge / discharge rate and further improves the battery's cycling performance.

[0011] In any embodiment, the monovalent metal salt includes one or more of a monovalent metal carbonate, a monovalent metal fluoride, and a monovalent metal phosphate, and one or more of a monovalent metal alkoxide, a monovalent metal carboxylate, and a monovalent metal alkyl carbonate. In this manner, the inorganic salt exhibits good electrochemical inertness, reducing electrochemical activity during battery storage and improving battery storage performance. The organic salt can inhibit the expansion and exfoliation of negative electrode graphite, improving battery cycling performance. Combining a monovalent metal inorganic salt with a monovalent metal organic salt can further enhance battery performance.

[0012] In any embodiment, the polyvalent metal salt includes one or more of a polyvalent metal alkoxide, a polyvalent metal carboxylate, and a polyvalent metal alkyl carbonate.

[0013] In any embodiment, the monovalent metal salt includes one or more of sodium carbonate, potassium carbonate, lithium carbonate, sodium fluoride, potassium fluoride, lithium fluoride, sodium phosphate, potassium phosphate, lithium phosphate, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithium alkyl carbonate, sodium alkyl carbonate, potassium alkyl carbonate, lithium maleate, sodium maleate, potassium maleate, lithium itaconate, sodium itaconate and potassium itaconate.

[0014] In any embodiment, the multivalent metal salt includes one or more of calcium alkoxide, magnesium alkoxide, aluminum alkoxide, calcium alkyl carbonate, magnesium alkyl carbonate, aluminum alkyl carbonate, calcium maleate, magnesium maleate, aluminum maleate, calcium itaconate, magnesium itaconate, and aluminum itaconate.

[0015] In any embodiment, the monovalent metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0016] In any embodiment, the additive is a first additive; based on 100% of the total mass of the main component, the mass fraction of the linear conductive material is 0.02% to 0.3%, and the mass fraction of the additive is 0.2% to 1.2%. This can effectively adjust the viscosity of the negative electrode slurry, thereby improving the battery's cycle performance.

[0017] In any embodiment, the additive is a first additive; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.05% to 0.2%, and the mass fraction of the additive is 0.4% to 0.8%.

[0018] In any embodiment, the additive is a second additive; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.04% to 0.6%, and the mass fraction of the additive is 0.4% to 2%.

[0019] In any embodiment, the additive is a second additive; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.08% to 0.4%, and the mass fraction of the additive is 0.6% to 1.5%.

[0020] In any embodiment, the linear conductive material comprises one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, and graphite fibers. Using these linear conductive materials not only increases the viscosity of the negative electrode slurry, thereby improving the battery's cycling performance, but also exhibits excellent electrical conductivity, allowing them to partially replace traditional conductive agents, thereby reducing their usage.

[0021] In any embodiment, the linear conductive material has an aspect ratio of 10 to 100,000:1, and can optionally be 20 to 10,000:1. This effectively alleviates the curling and agglomeration of the binder molecular chains after the introduction of the additive, effectively increasing the viscosity of the negative electrode slurry, and improving the bonding strength between the negative electrode film layer and the current collector, thereby improving the battery's cycling performance.

[0022] A second aspect of the present application provides a negative electrode plate, comprising a negative electrode film layer, wherein the negative electrode film layer comprises a negative electrode active material, a binder, a linear conductive material, and an additive capable of participating in the formation of an artificial solid electrolyte interface film.

[0023] In any embodiment, the negative electrode film layer is formed by solidifying the negative electrode slurry of the first aspect of the present application.

[0024] A third aspect of the present application provides a secondary battery comprising the negative electrode sheet of the second aspect of the present application.

[0025] A fourth aspect of the present application provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0026] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to better describe and illustrate the embodiments or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments or examples currently described, and any of the best modes currently understood for these applications. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the accompanying drawings:

[0028] Figure 1 A schematic diagram of a battery cell according to an embodiment of the present application;

[0029] Figure 2 for Figure 1 An exploded view of a battery cell according to an embodiment of the present application is shown;

[0030] Figure 3 FIG. 1 is a schematic diagram of an electrical device using a secondary battery as a power source according to an embodiment of the present application.

[0031] Description of reference numerals:

[0032] 5. Battery cell; 51. Housing; 52. Electrode assembly; 53. Cover plate; 6. Electrical device. DETAILED DESCRIPTION

[0033] Below, the embodiments of the negative electrode sheet, secondary battery, and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure 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.

[0034] The "range" disclosed in this application can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and any end value can be independently included or excluded, and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also contemplated. In addition, if the minimum range values ​​listed are 1 and 2, and if the maximum range values ​​3, 4, and 5 are also listed, the following ranges can all be contemplated: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4, and 2 to 5. In this application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" 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 listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0035] In this application, "a plurality of" or "a plurality of" refers to a number greater than or equal to 2 unless otherwise specified. For example, "one or more" means one or more than or equal to two.

[0036] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0037] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0038] It will be appreciated by those skilled in the art that, in the methods of various embodiments or examples, the order in which the steps are written does not imply a strict order of execution and does not constitute any limitation on the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. 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 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 steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0039] In this application, open technical features or technical solutions described with words such as "contain," "include," and "include" do not exclude additional members beyond the listed members, unless otherwise specified. This can be considered as providing both closed features or solutions consisting of the listed members and open features or solutions that include additional members beyond the listed members. For example, if A includes a1, a2, and a3, it may or may not include other members unless otherwise specified. This can be considered as providing both the feature or solution that "A consists of a1, a2, and a3," and the feature or solution that "A includes not only a1, a2, and a3, but also other members." In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0040] In this application, the terms "optionally," "optional," and "optional" are optional and refer to either option being present or absent. If a technical solution contains multiple "options," each option is considered independent unless otherwise specified and there are no conflicts or constraints.

[0041] In some embodiments, the first aspect of the present application provides a negative electrode slurry, which includes a main component and a solvent; wherein the main component includes a negative electrode active material, a binder, a linear conductive material and an additive capable of participating in the formation of an artificial solid electrolyte interface film (ASEI); and, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.02%~1%, and the mass fraction of the additive is 0.2%~3%.

[0042] With prolonged storage, traditional secondary batteries experience a loss of irreversible capacity and active lithium, leading to a decrease in energy storage life and poor storage performance. Lithium iron phosphate (LFP) / graphite batteries, in particular, experience significant lifespan degradation within the first 60 days at high temperatures and high SOC (State of Charge).

[0043] The present application introduces a specific amount of additives capable of participating in the formation of an artificial solid electrolyte interface film into the negative electrode slurry; after using the negative electrode slurry to prepare the negative electrode plate, the above-mentioned additives present in the negative electrode film layer can participate in the formation of an artificial solid electrolyte interface film during the battery formation process. The artificial solid electrolyte interface film can reduce the loss of active lithium and the reduction of irreversible capacity during battery storage, thereby improving the storage performance of the battery.

[0044] However, the introduction of additives that can participate in the formation of artificial solid electrolyte interface membranes will cause the electrostatic field inside the binder molecules to lose balance, resulting in the weakening of the repulsion between the binder anions and the curling and agglomeration of the binder molecular chains, thereby reducing the viscosity of the negative electrode slurry and having a certain impact on the coating process. At the same time, it will lead to a decrease in the bonding force between the negative electrode film layer and the current collector. During the cycle process, the negative electrode film layer is easy to fall off from the current collector, resulting in deterioration of the battery's cycle performance.

[0045] To this end, the present application further introduces a specific amount of linear conductive material into the negative electrode slurry. This linear conductive material can not only play a conductive role, but also alleviate the curling and agglomeration of the binder molecular chains through the staggered "grid" of its linear morphology, thereby reducing the impact of the introduction of additives on the binder, increasing the viscosity of the negative electrode slurry, and improving the bonding force between the negative electrode film layer and the current collector, making it difficult for the negative electrode film layer to fall off from the current collector during the battery cycle, and thus giving the battery better cycle performance. By simultaneously introducing a specific amount of linear conductive material and an additive that can participate in the formation of an artificial solid electrolyte interface film into the negative electrode slurry, the secondary battery prepared using the negative electrode slurry can have both good storage performance and good cycle performance.

[0046] It is understood that the main component and solvent in the negative electrode slurry are mixed and integrated, and the various components of the main component can be evenly dispersed in the solvent. The solvent can be a solvent commonly used in negative electrode slurries. In one specific example, the solvent is deionized water. Linear conductive materials refer to materials that have a linear morphology and are conductive.

[0047] Based on the total mass of the main component as 100%, the mass fraction of the linear conductive material can be 0.02%, 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.52%, 0.55%, 0.58%, 0.6%, 0.65%, 0.68%, 0.7%, 0.75%, 0.78%, 0.85%, 0.88%, 0.90%, 1.10%, 1.11%, 1.12%, 1.13%, 1.14%, 1.15%, 1.16%, 1.17%, 1.18%, 1.19%, 1.20%, 1.21%, 1.22%, 1.23%, 1.24%, 1.25%, 1.26%, 1.27%, 1.28%, 1.29%, 1.30%, 1.31%, 1.32%, 1.33%, 1.34%, 1.35%, 1.36%, 1.37%, 1.38%, %, 0.9%, 0.95%, 0.98%, 1% and any value within the range formed by any two of the above values; the mass fraction of the additive can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3% and any value within the range formed by any two of the above values.

[0048] In some embodiments, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.02% to 0.6%, and the mass fraction of the additive is 0.2% to 2%. Excessive amounts of the linear conductive material and additive in the main component will correspondingly reduce the relative content of the negative electrode active material, affecting the battery capacity. By controlling the amount of the linear conductive material and additive within the above range, the secondary battery prepared using this negative electrode slurry can have good storage performance and cycle performance while also having a relatively high energy density.

[0049] In some embodiments, the additive includes one or more of a first additive and a second additive; wherein the first additive includes one or more of a monovalent metal salt and a monovalent metal hydroxide; and the second additive includes a polyvalent metal salt. It is understood that polyvalent metal salts include divalent metal salts, trivalent metal salts, and metal salts with higher valences. In this application, generally, the polyvalent metal salt is primarily a divalent metal salt.

[0050] In some embodiments, the monovalent metal salt includes one or more of a monovalent metal carbonate, a monovalent metal fluoride, a monovalent metal phosphate, a monovalent metal alkoxy salt, a monovalent metal carboxylate, and a monovalent metal alkyl carbonate. Specifically, the monovalent metal salt includes one or more of sodium carbonate, potassium carbonate, lithium carbonate, sodium fluoride, potassium fluoride, lithium fluoride, sodium phosphate, potassium phosphate, lithium phosphate, lithium alkoxy, sodium alkoxy, potassium alkoxy, lithium alkyl carbonate, sodium alkyl carbonate, potassium alkyl carbonate, lithium maleate, sodium maleate, potassium maleate, lithium itaconate, sodium itaconate, and potassium itaconate. The monovalent metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide. The above-mentioned monovalent metal salts and monovalent metal hydroxides can effectively participate in the formation of an artificial solid electrolyte interface film in the negative electrode film layer during the battery formation process. The increase in the viscosity of the negative electrode slurry caused by monovalent metal salts and monovalent metal hydroxides is relatively small compared to polyvalent metal salts, and the ion conductivity of monovalent metal salts and monovalent metal hydroxides is better, which is beneficial to increase the charge / discharge rate of the battery and further improve the cycle performance of the battery.

[0051] Optionally, the monovalent metal salt is a lithium salt or a sodium salt of a monovalent metal.

[0052] In some embodiments, the monovalent metal salt includes one or more of a monovalent metal carbonate, a monovalent metal fluoride, and a monovalent metal phosphate, and one or more of a monovalent metal alkoxide, a monovalent metal carboxylate, and a monovalent metal alkyl carbonate. That is, the monovalent metal salt adopts a combination of the above-mentioned monovalent metal inorganic salt and a monovalent metal organic salt. In this way, the inorganic salt has good electrochemical inertness, which can reduce the electrochemical activity during battery storage and improve the storage performance of the battery; the organic salt can inhibit the expansion and exfoliation of the negative electrode graphite and improve the cycle performance of the battery. By combining the monovalent metal inorganic salt and the monovalent metal organic salt, the battery performance can be further improved.

[0053] In some specific examples, the additive is a combination of lithium carbonate and lithium maleate or a combination of lithium fluoride and lithium itaconate.

[0054] In some embodiments, the polyvalent metal salt comprises one or more of a polyvalent metal alkoxide, a polyvalent metal carboxylate, and a polyvalent metal alkyl carbonate. Specifically, the polyvalent metal salt comprises one or more of a calcium alkoxide, a magnesium alkoxide, an aluminum alkoxide, a calcium alkyl carbonate, a magnesium alkyl carbonate, an aluminum alkyl carbonate, calcium maleate, magnesium maleate, aluminum maleate, calcium itaconate, magnesium itaconate, and aluminum itaconate.

[0055] In some embodiments, the additive is a first additive; and, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.02% to 0.3%, and the mass fraction of the additive is 0.2% to 1.2%. Because additives of different valence states have different effects on the viscosity of the negative electrode slurry, using the first additive in the negative electrode slurry and controlling the contents of the linear conductive material and the first additive within the above range can effectively adjust the viscosity of the negative electrode slurry, thereby achieving better battery cycling performance.

[0056] It can be understood that when the additive adopts the first additive, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material can be 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.15%, 0.16%, 0.18%, 0.2%, 0.22%, 0.24%, 0.25%, 0.26%, 0.28%, 0.3%, and any value within the range formed by any two of the above values; the mass fraction of the first additive can be 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, and any value within the range formed by any two of the above values.

[0057] In some embodiments, the additive is a first additive; and, based on 100% of the total mass of the main component, the mass fraction of the linear conductive material is 0.05% to 0.2%, and the mass fraction of the additive is 0.4% to 0.8%. When the first additive is used, controlling the mass fractions of the linear conductive material and the first additive in the main component within the above ranges can ensure that the negative electrode slurry has a more suitable viscosity for better coating. This can also improve the adhesion between the negative electrode film layer and the current collector, thereby improving the battery's cycling and storage performance.

[0058] In some embodiments, a second additive is used as the additive; and, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.04% to 0.6%, and the mass fraction of the additive is 0.4% to 2%. The second additive is a polyvalent metal salt. Introducing the second additive into the negative electrode slurry and controlling the mass fractions of the linear conductive material and the second additive in the main component within the above range can effectively adjust the viscosity of the negative electrode slurry, thereby achieving better battery cycling performance.

[0059] It can be understood that when the second additive is used as the additive, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material can be 0.04%, 0.05%, 0.08%, 0.1%, 0.12%, 0.15%, 0.18%, 0.2%, 0.22%, 0.25%, 0.28%, 0.3%, 0.32%, 0.35%, 0.38%, 0.4%, 0.42%, 0.45%, 0.48%, 0.5%, 0.52%, 0.55%, 0.58%, 0.6%, and any value within the range formed by any two of the above values; the mass fraction of the first additive can be 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, and any value within the range formed by any two of the above values.

[0060] In some embodiments, a second additive is used as the additive; and, based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.08% to 0.4%, and the mass fraction of the additive is 0.6% to 1.5%. When the second additive is used, controlling the mass fractions of the linear conductive material and the second additive in the main component within the above ranges can ensure that the negative electrode slurry has a more suitable viscosity, facilitating a better coating process. This also improves the adhesion between the negative electrode film layer and the current collector, thereby improving the battery's cycling and storage performance.

[0061] In some embodiments, the linear conductive material includes one or more of single-walled carbon nanotubes (SWCNTs), multi-walled carbon nanotubes (MWCNTs), and graphite fibers. These materials are introduced into the negative electrode slurry as linear conductive materials. Their linear morphology can effectively alleviate the problem of reduced slurry viscosity caused by curling and agglomeration of binder molecular chains after the addition of additives. This can increase the viscosity of the negative electrode slurry, improve the bonding strength between the negative electrode film layer and the current collector, and thus enhance the battery's cycling performance. Furthermore, these materials have excellent electrical conductivity and can replace some traditional conductive agents (such as conductive carbon black), reducing the amount of traditional conductive agents used. Graphite fibers can also be used as negative electrode active materials. These graphite fibers can be fibrous graphite materials prepared by electrospinning.

[0062] In some embodiments, the linear conductive material has an aspect ratio of 10 to 100,000:1; optionally, 20 to 10,000:1. Keeping the aspect ratio of the linear conductive material within this range can effectively mitigate the curling and agglomeration of binder molecular chains after the introduction of the additive, effectively increasing the viscosity of the negative electrode slurry, improving the bonding between the negative electrode film layer and the current collector, and enhancing the battery's cycling performance. It should be understood that the aspect ratio of the linear conductive material refers to the ratio of the linear conductive material's length to its diameter.

[0063] It can be understood that the aspect ratio of the linear conductive material can be 10:1, 100:1, 500:1, 1000:1, 5000:1, 8000:1, 10000:1, 15000:1, 20000:1, 25000:1, 30000:1, 35000:1, 40000:1, 45000:1, 50000:1, 55000:1, 60000:1, 65000:1, 70000:1, 75000:1, 80000:1, 85000:1, 90000:1, 95000:1, 100000:1 and any ratio within the range formed by any two of the above ratios.

[0064] In some embodiments, the mass fraction of the negative electrode active material is 94% to 98.5%, based on the total mass of the main components as 100%. Specifically, the negative electrode active material may include one or more of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. Silicon-based materials include one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys; tin-based materials include one or more of elemental tin, tin oxide compounds, and tin alloys.

[0065] In some embodiments, the mass fraction of the binder is 0.5% to 2% based on the total mass of the main component as 100%. Specifically, the binder may include one or more 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 mass fraction of the binder in the main component may be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any value within the range formed by any two of the above values.

[0066] In some embodiments, the main component further includes a thickener; and, based on the total mass of the main component being 100%, the mass fraction of the thickener is 0.5% to 2%. Specifically, the thickener can be sodium carboxymethyl cellulose (CMC-Na). It is understood that, based on the total mass of the main component being 100%, the mass fraction of the thickener can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, or any other value within the range formed by any two of the aforementioned values.

[0067] In some embodiments, the main component further includes a conductive agent; and, based on the total mass of the main component being 100%, the mass fraction of the conductive agent is 0% to 1%. Specifically, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, graphene, and carbon nanofibers. It is understood that, based on the total mass of the main component being 100%, the mass fraction of the conductive agent may be 0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, and any value within the range formed by any two of the above values.

[0068] The second aspect of the present application provides a negative electrode plate, including a negative electrode film layer, wherein the negative electrode film layer includes a negative electrode active material, a binder, a linear conductive material, and an additive capable of participating in the formation of an artificial solid electrolyte interface film. Furthermore, the negative electrode film layer is formed by solidifying the negative electrode slurry of the first aspect of the present application. By using a negative electrode slurry containing a linear conductive material and an additive capable of participating in the formation of an artificial solid electrolyte interface film to form a negative electrode film layer, an artificial solid electrolyte interface film can be formed in the negative electrode film layer during the battery formation process, thereby improving the storage performance of the battery; and the linear conductive material can provide a better bonding force between the negative electrode film layer and the current collector, thereby improving the cycle performance of the battery.

[0069] The third aspect of the present application provides a secondary battery comprising the negative electrode sheet of the second aspect of the present application. The secondary battery has good storage performance and cycle performance.

[0070] A fourth aspect of the present application provides an electrical device comprising the secondary battery of the third aspect of the present application.

[0071] The secondary battery and the electric device of the present application will be described below with reference to the accompanying drawings as appropriate.

[0072] Unless otherwise specified, the components, material types, or contents of the batteries mentioned are applicable to both lithium-ion secondary batteries and sodium-ion secondary batteries.

[0073] In one embodiment of the present application, a secondary battery is provided.

[0074] 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.

[0075] Positive electrode

[0076] The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector.

[0077] As a non-limiting 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.

[0078] 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 obtained by forming a metal material on a polymer material substrate. Non-limiting examples of the metal material in the positive electrode current collector may include one or more of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. Non-limiting examples of the polymer material substrate in the positive electrode current collector may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0079] In some embodiments, the positive electrode active material may include a positive electrode active material for a battery known in the art.

[0080] As a non-limiting example, the positive electrode active material of the lithium-ion secondary battery may include one or more of the following materials: lithium-containing phosphates with an olivine structure, lithium transition metal oxides and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as battery positive electrode active materials may 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, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide and their modified compounds. Non-limiting examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium cobalt oxide may include LiCoO2; non-limiting examples of lithium nickel oxide may include LiNiO2; non-limiting examples of lithium manganese oxide may include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide may include LiNi 1 / 3Co 1 / 3 Mn 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 ) etc.; Non-limiting examples of lithium nickel cobalt aluminum oxide may include LiNi 0.85 Co 0.1 Al 0.05 O2.

[0081] It is understandable that the battery will be accompanied by lithium (Li) deintercalation and consumption during the charge and discharge process, and the content of Li in the positive electrode plate is different when the battery is discharged to different states. In the list of positive electrode materials in this application, unless otherwise specified, the Li content is the initial state of the material. The positive electrode material is applied to the positive electrode plate in the battery system, and after the charge and discharge cycle, the Li content in the positive electrode material contained in the plate will usually change. Among them, the Li content can be measured by molar content, but is not limited to this. Regarding "the Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials obtained by appropriate modification on the basis of the listed positive electrode materials are also within the scope of positive electrode materials. The aforementioned appropriate modification refers to acceptable modification methods for positive electrode materials, and non-limiting examples include coating modification.

[0082] In the examples of positive electrode materials in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by molar content, but is not limited to this.

[0083] As non-limiting examples, the positive electrode active material of a sodium ion secondary battery may include one or more of the following materials: sodium transition metal oxides, polyanionic compounds, and Prussian blue compounds. However, the present application is not limited to these materials, and other conventionally known materials that can be used as positive electrode active materials for sodium ion batteries may also be used.

[0084] As an optional technical solution of the present application, in the sodium transition metal oxide, the transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Sodium transition metal oxide is, for example, Na x MO2, wherein M is one or more of Ti, V, Mn, Co, Ni, Fe, Cr and Cu, 0 <x≤1。

[0085] As an optional technical solution of the present application, the polyanionic compound can be a compound having sodium ions, transition metal ions and tetrahedral (YO4) n- A class of compounds with anionic units. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce; Y can be one or more of P, S and Si; n represents (YO4) n- valence.

[0086] Polyanionic compounds can also be sodium ions, transition metal ions, tetrahedral (YO4) n-A class of compounds containing anion units and halogen anions. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr, and Ce; Y can be one or more of P, S, and Si, and n represents (YO4) n- valence state; the halogen can be one or more of F, Cl and Br.

[0087] Polyanionic compounds can also be sodium ions, tetrahedral (YO4) n- Anion unit, polyhedron unit (ZO y ) m+ and an optional halogen anion. Y can be one or more of P, S and Si, and n represents (YO4) n- valence state; Z represents a transition metal, which can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce, m represents (ZO y ) m+ valence state; the halogen can be one or more of F, Cl and Br.

[0088] Polyanionic compounds include NaFePO4, Na3V2(PO4)3 (sodium vanadium phosphate, abbreviated as NVP), Na4Fe3(PO4)2(P2O7), NaM'PO4F (M' is one or more of V, Fe, Mn and Ni) and Na3(VO y )2(PO4)2F 3-2y One or more of (0≤y≤1).

[0089] Prussian blue compounds can be sodium ions, transition metal ions and cyanide ions (CN - ) compounds. The transition metal can be one or more of Mn, Fe, Ni, Co, Cr, Cu, Ti, Zn, V, Zr and Ce. Prussian blue compounds are, for example, Na a Me b Me' c (CN)6, wherein Me and Me' are each independently one or more of Ni, Cu, Fe, Mn, Co and Zn, 0 <a≤2,0<b<1,0<c<1。

[0090] The weight ratio of the positive electrode active material in the positive electrode film layer is 80 wt % to 100 wt %, based on the total weight of the positive electrode film layer.

[0091] In some embodiments, the positive electrode film layer may also optionally include a binder. As non-limiting examples, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin. The weight ratio of the binder in the positive electrode film layer is 0% to 20% by 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 conductive agent. As non-limiting examples, the conductive agent may include one or more 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% to 20% by weight, based on the total weight of the positive electrode film layer.

[0093] 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 40wt% to 80wt%, and the viscosity at room temperature is adjusted to 5000mPa·s to 25000mPa·s, the positive electrode slurry is coated on the surface of the positive electrode current collector, and after drying, it is cold-pressed by a cold rolling mill to form a positive electrode sheet.

[0094] Negative electrode

[0095] 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.

[0096] As a non-limiting 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.

[0097] 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 substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be obtained by forming a metal material on a polymer substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys. In the negative electrode current collector, non-limiting examples of the polymer substrate may include one or more of substrates such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0098] In some embodiments, the negative electrode active material may be a negative electrode active material for batteries known in the art.

[0099] As a non-limiting example, the negative electrode active material of the lithium-ion secondary battery may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials and lithium titanate. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites and silicon alloys. Tin-based materials may include one or more 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.

[0100] As a non-limiting example, the negative active material of the sodium ion secondary battery is generally a hard carbon material, a two-dimensional metal carbide or a nitride. Preferably, the negative active material of the sodium ion secondary battery is generally a hard carbon material.

[0101] In some embodiments, the negative electrode film layer may further optionally include a binder. The binder may include one or more 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).

[0102] In some embodiments, the negative electrode film layer may further include a conductive agent, which may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0103] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0104] In some embodiments, a negative electrode sheet can be prepared by dispersing the aforementioned components for preparing a negative electrode sheet, such as a negative electrode active material, a conductive agent, a binder, and any other components, in a solvent (a non-limiting example of a solvent is deionized water) to form a negative electrode slurry; coating the negative electrode slurry on at least one surface of a negative electrode current collector, and performing processes such as drying and cold pressing to obtain a negative electrode sheet. The negative electrode slurry can be coated on a single surface of the negative electrode current collector or on both surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 40 wt% to 60 wt%. The viscosity of the negative electrode slurry at room temperature can be adjusted to 2000 mPa·s to 10000 mPa·s.

[0105] electrolytes

[0106] The electrolyte conducts ions between the positive and negative electrodes. This application does not specifically limit 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, which includes an electrolyte salt and a solvent.

[0108] In some embodiments, the electrolyte salt of the lithium ion secondary battery may include 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).

[0109] In some embodiments, the solvent may include 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), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE).

[0110] In some embodiments, the electrolyte may optionally 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] In some embodiments, the additives in the electrolyte may include, but are not limited to, one or more of fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), and the like.

[0112] Isolation film

[0113] 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.

[0114] In some embodiments, the material of the separator can include one or more 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.

[0115] In some embodiments, the isolation film has a thickness of 6 μm to 40 μm, and may be 12 μm to 20 μm.

[0116] 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.

[0117] In some embodiments, the secondary battery may include an outer packaging that can be used to encapsulate the electrode assembly and the electrolyte.

[0118] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0119] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0120] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0121] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 1 The battery cell 5 is a square structure as an example.

[0122] In some embodiments, reference 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 form 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 battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0123] In some embodiments, the battery cells 5 can be assembled into a battery module. The number of battery cells 5 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.

[0124] In the battery module, the plurality of battery cells 5 can be arranged in sequence along the length of the battery module. Of course, they can also be arranged in any other manner. Furthermore, the plurality of battery cells 5 can be fixed by fasteners.

[0125] Optionally, the battery module may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0126] 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.

[0127] A battery pack may include a battery box and multiple battery modules disposed within the box. The battery box comprises an upper case and a lower case. The upper case can be placed over the lower case to form an enclosed space for accommodating the battery modules. The multiple battery modules can be arranged in any manner within the battery box.

[0128] In addition, the present application also provides an electrical 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 electrical device, and can also be used as an energy storage unit for the electrical device. The electrical 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.

[0129] As the electrical device, a secondary battery, a battery module or a battery pack can be selected according to its usage requirements.

[0130] Figure 3 The power consumption device 6 is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the power consumption device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module can be used.

[0131] 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.

[0132] The following are some examples.

[0133] 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.

[0134] 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.

[0135] Example 1:

[0136] (1) Preparation of positive electrode

[0137] Lithium iron phosphate, conductive agent carbon black (Super P), and binder PVDF were thoroughly mixed in an appropriate amount of N-methylpyrrolidone (NMP) at a weight ratio of 97.2:0.7:2.1 to form a uniform positive electrode slurry. The positive electrode slurry was applied to the surface of the positive electrode current collector aluminum foil, dried, cold pressed, slit, and cut to obtain the positive electrode sheet. The compacted density of the positive electrode sheet is 2.45 g / cm 3 , with an area density of 21.68 mg / cm 2 .

[0138] (2) Preparation of negative electrode sheet

[0139] The negative electrode active material artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose (CMC-Na), binder SBR, single-walled carbon nanotubes (SWCNT) and sodium carbonate were mixed in a mass ratio of 96.09:0.4:0.7:1.95:0.13:0.73, and the above mixture was added into the solvent deionized water, and stirred under the action of a vacuum mixer until the system became uniform to obtain a negative electrode slurry. The solid content of the negative electrode slurry was controlled at 45%~55%. The above negative electrode slurry was evenly coated on both surfaces of the negative electrode current collector copper foil with a thickness of 6 μm, and dried at 110 ° C for 20 min. After drying, the electrode was cold pressed to obtain a coating weight of 10.71 mg / cm 2 , compacted density is 1.4 g / cm 3 The negative electrode has a thickness of 159 μm and the aspect ratio of the single-walled carbon nanotubes is 1000:1.

[0140] (3) Isolation film

[0141] A polyethylene film with a thickness of 12 μm was selected as the separator.

[0142] (4) Electrolyte

[0143] Ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and fully dried lithium salt LiPF6 is dissolved in the above organic solvent. The concentration of the lithium salt is 1 mol / L, and the mixture is evenly mixed to obtain an electrolyte.

[0144] (5) Battery assembly

[0145] The positive electrode sheet, negative electrode sheet and separator are stacked in a certain pattern to form a battery chip. Then, the battery chip is encapsulated in a suitable container, electrolyte is added and the can lid is sealed.

[0146] Example 2:

[0147] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.09:0.51:0.7:1.95:0.02:0.73.

[0148] Example 3:

[0149] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.09:0.48:0.7:1.95:0.05:0.73.

[0150] Example 4:

[0151] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.09:0.33:0.7:1.95:0.2:0.73.

[0152] Example 5:

[0153] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.09:0.23:0.7:1.95:0.3:0.73.

[0154] Example 6:

[0155] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.62:0.4:0.7:1.95:0.13:0.2.

[0156] Example 7:

[0157] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.42:0.4:0.7:1.95:0.13:0.4.

[0158] Example 8:

[0159] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 96.02:0.4:0.7:1.95:0.13:0.8.

[0160] Example 9:

[0161] This embodiment is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the sodium carbonate in the negative electrode slurry is 95.62:0.4:0.7:1.95:0.13:1.2.

[0162] Example 10:

[0163] This embodiment is basically the same as Example 1, except that lithium fluoride is used instead of sodium carbonate in the negative electrode slurry; and the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes, and lithium fluoride is 96.09:0.4:0.7:1.95:0.13:0.73.

[0164] Example 11:

[0165] This embodiment is basically the same as Example 1, except that potassium hydroxide is used instead of sodium carbonate in the negative electrode slurry; the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and potassium hydroxide is 96.09:0.4:0.7:1.95:0.13:0.73.

[0166] Example 12:

[0167] This embodiment is basically the same as Example 1, except that calcium itaconate is used instead of sodium carbonate in the negative electrode slurry; the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium methoxide is 96.09:0.4:0.7:1.95:0.13:0.73.

[0168] Example 13:

[0169] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.09:0.49:0.7:1.95:0.04:0.73.

[0170] Example 14:

[0171] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.09:0.45:0.7:1.95:0.08:0.73.

[0172] Example 15:

[0173] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.09:0.13:0.7:1.95:0.4:0.73.

[0174] Example 16:

[0175] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.02:0.7:1.95:0.6:0.73.

[0176] Example 17:

[0177] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.42:0.4:0.7:1.95:0.13:0.4.

[0178] Example 18:

[0179] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 96.22:0.4:0.7:1.95:0.13:0.6.

[0180] Example 19:

[0181] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 95.32:0.4:0.7:1.95:0.13:1.5.

[0182] Example 20:

[0183] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 94.82:0.4:0.7:1.95:0.13:2.

[0184] Example 21:

[0185] This embodiment is basically the same as Example 12, except that the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes and the calcium itaconate is 92.95:0.4:0.7:1.95:1:3.

[0186] Example 22:

[0187] This embodiment is substantially the same as embodiment 1, with the only difference being that the aspect ratio of the single-walled carbon nanotubes in the negative electrode active material is 10,000:1.

[0188] Example 23:

[0189] This embodiment is substantially the same as embodiment 1, with the only difference being that the aspect ratio of the single-walled carbon nanotubes in the negative electrode active material is 100,000:1.

[0190] Example 24:

[0191] This embodiment is substantially the same as the embodiment 1, with the only difference being that multi-walled carbon nanotubes (MWCNTs) are used in place of single-walled carbon nanotubes in the negative electrode active material.

[0192] Example 25:

[0193] This embodiment is basically the same as embodiment 1, with the only difference being that graphite fibers are used in place of single-walled carbon nanotubes in the negative electrode active material.

[0194] Example 26:

[0195] This embodiment is basically the same as Example 1, except that two additives, lithium carbonate and lithium maleate, are used in the negative electrode slurry; and the mass ratio of the negative electrode active material artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose, binder SBR, single-walled carbon nanotubes, lithium carbonate and lithium maleate in the negative electrode slurry is 96.09:0.51:0.7:1.95:0.02:0.23:0.5.

[0196] Example 27:

[0197] This embodiment is basically the same as Example 1, except that sodium fluoride and sodium itaconate are used as two additives in the negative electrode slurry; the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR, the single-walled carbon nanotubes, sodium fluoride and sodium itaconate in the negative electrode slurry is 96.09:0.51:0.7:1.95:0.02:0.23:0.5.

[0198] Comparative Example 1:

[0199] This comparative example is basically the same as Example 1, except that: no single-walled carbon nanotubes are added to the negative electrode slurry; the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose, the binder SBR and sodium carbonate is 96.09:0.53:0.7:1.95:0.73.

[0200] Comparative Example 2:

[0201] This comparative example is basically the same as Example 1, except that sodium carbonate and single-walled carbon nanotubes are not added to the negative electrode slurry; the mass ratio of the negative electrode active material artificial graphite, the conductive agent Super P, the thickener sodium carboxymethyl cellulose and the binder SBR is 96.82:0.53:0.7:1.95.

[0202] Comparative Example 3:

[0203] This comparative example is basically the same as Example 1, except that the mass ratio of the negative electrode active material artificial graphite, conductive agent Super P, thickener sodium carboxymethyl cellulose, binder SBR, single-walled carbon nanotubes and sodium carbonate in the negative electrode slurry is 96.72:0.52:0.7:1.95:0.01:0.1.

[0204] Performance testing:

[0205] (1) Storage performance test

[0206] Step 1: Let the battery rest at 25°C for 5 minutes; charge at 0.33C to 3.65V, then charge at 3.65V to 0.05C; let it rest for 5 minutes; then discharge at 0.33C to 2V, recording the capacity at this point as Cz (the capacity of the battery after storage is the reversible capacity, marked as Ct, where t is the storage time). Charge at 0.33C to 3.65V, then charge at 3.65V to 0.05C. The cell is now fully charged.

[0207] Step 2: Place the fully charged battery in a 60°C environment. After a period of time, remove the battery and test it according to the process in the first step. Place the fully charged battery in a 60°C environment and repeat the above steps until t=180 days. Calculate the reversible capacity retention rate F2, F2=Ct÷Cz*100%.

[0208] (2) Cyclic performance test

[0209] Step 1: Charge the battery to 3.65V at 0.33C at 25°C, then charge to 0.05C0 at 3.65V constant voltage; let it rest for 5 minutes; then discharge it to 2V at 0.33C, recording the capacity at this point as C0 (this step is the actual initial capacity of the test);

[0210] Step 2: Charge the battery to 3.45V at 0.5C0 and to 3.65V at 0.33C0; let it stand for 10 minutes; discharge it to 2V at 1C0 and to 2V at 0.33C0, until the capacity decay is ≤80%, and record the number of cycles.

[0211] The performance test results of the batteries of the above embodiments and comparative examples are shown in Table 1. The number of cycles until the capacity decays to 80% is the data after rounding off the experimental results to the nearest hundredth place.

[0212] Table 1

[0213]

[0214]

[0215] As can be seen from Table 1, the secondary batteries of the embodiments of the present application not only have a high 180-day reversible capacity retention rate, but also have a high cycle life, indicating that the secondary batteries using the negative electrode slurry of the present application have both good storage performance and cycle performance.

[0216] Comparative Example 1 introduced only sodium carbonate, an additive capable of forming an artificial solid electrolyte interface membrane, into the negative electrode slurry, without introducing any linear conductive material. The cycling performance of the secondary battery significantly decreased. Comparative Example 2 did not introduce any additive capable of forming an artificial solid electrolyte interface membrane, nor did it introduce any linear conductive material. Both the storage performance and cycling performance of the secondary battery significantly decreased. Comparative Example 3 introduced too few additives and linear conductive material into the negative electrode slurry, resulting in insignificant improvements in the battery's storage and cycling performance.

[0217] The above description of the various embodiments tends to emphasize the differences between the various embodiments. The same or similar aspects can be referenced with each other and will not be repeated herein for the sake of brevity.

[0218] 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 negative electrode slurry comprising a main component and a solvent, wherein the main component comprises a negative electrode active material, a binder, a linear conductive material, and an additive capable of participating in the formation of an artificial solid electrolyte interface film; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.02% to 1%, and the mass fraction of the additive is 0.2% to 3%.

2. The negative electrode slurry according to claim 1, wherein Based on the total mass of the main component being 100%, the mass fraction of the linear conductive material is 0.02% to 0.6%, and the mass fraction of the additive is 0.2% to 2%.

3. The negative electrode slurry according to claim 1 or 2, wherein: The additive includes one or more of a first additive and a second additive, the first additive includes one or more of a monovalent metal salt and a monovalent metal hydroxide, and the second additive includes a polyvalent metal salt.

4. The negative electrode slurry according to claim 3, wherein The monovalent metal salt includes one or more of monovalent metal carbonates, monovalent metal fluorides, monovalent metal phosphates, monovalent metal alkoxy salts, monovalent metal carboxylates and monovalent metal alkyl carbonates.

5. The negative electrode slurry according to claim 3 or 4, wherein The monovalent metal salt includes one or more of monovalent metal carbonates, monovalent metal fluorides and monovalent metal phosphates, and one or more of monovalent metal alkoxy salts, monovalent metal carboxylates and monovalent metal alkyl carbonates.

6. The negative electrode slurry according to any one of claims 3 to 5, wherein The polyvalent metal salt includes one or more of a polyvalent metal alkoxy salt, a polyvalent metal carboxylate salt, and a polyvalent metal alkyl carbonate salt.

7. The negative electrode slurry according to any one of claims 3 to 6, wherein The monovalent metal salt includes one or more of sodium carbonate, potassium carbonate, lithium carbonate, sodium fluoride, potassium fluoride, lithium fluoride, sodium phosphate, potassium phosphate, lithium phosphate, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithium alkyl carbonate, sodium alkyl carbonate, potassium alkyl carbonate, lithium maleate, sodium maleate, potassium maleate, lithium itaconate, sodium itaconate and potassium itaconate.

8. The negative electrode slurry according to any one of claims 3 to 7, wherein The polyvalent metal salt includes one or more of calcium alkoxide, magnesium alkoxide, aluminum alkoxide, calcium alkyl carbonate, magnesium alkyl carbonate, aluminum alkyl carbonate, calcium maleate, magnesium maleate, aluminum maleate, calcium itaconate, magnesium itaconate, and aluminum itaconate.

9. The negative electrode slurry according to any one of claims 3 to 8, wherein The monovalent metal hydroxide includes one or more of sodium hydroxide, potassium hydroxide and lithium hydroxide.

10. The negative electrode slurry according to any one of claims 3 to 9, wherein The additive is a first additive; based on the total mass of the main component being 100%, the mass fraction of the linear conductive material is 0.02% to 0.3%, and the mass fraction of the additive is 0.2% to 1.2%.

11. The negative electrode slurry according to any one of claims 3 to 10, wherein The additive is a first additive; based on the total mass of the main component being 100%, the mass fraction of the linear conductive material is 0.05% to 0.2%, and the mass fraction of the additive is 0.4% to 0.8%.

12. The negative electrode slurry according to any one of claims 3 to 11, wherein The additive is a second additive; based on the total mass of the main component as 100%, the mass fraction of the linear conductive material is 0.04% to 0.6%, and the mass fraction of the additive is 0.4% to 2%.

13. The negative electrode slurry according to any one of claims 3 to 12, wherein The additive is a second additive; based on the total mass of the main component being 100%, the mass fraction of the linear conductive material is 0.08% to 0.4%, and the mass fraction of the additive is 0.6% to 1.5%.

14. The negative electrode slurry according to any one of claims 1 to 13, wherein The linear conductive material includes one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes and graphite fibers.

15. The negative electrode slurry according to any one of claims 1 to 14, wherein The aspect ratio of the linear conductive material is 10-100000:

1.

16. The negative electrode slurry according to any one of claims 1 to 15, wherein The aspect ratio of the linear conductive material is 20-10000:

1.

17. A negative electrode sheet comprising a negative electrode film layer, wherein the negative electrode film layer comprises a negative electrode active material, a binder, a linear conductive material, and an additive capable of forming an artificial solid electrolyte interface film; Alternatively, the negative electrode film layer is formed by solidifying the negative electrode slurry according to any one of claims 1 to 16.

18. A secondary battery, characterized in that: Including the negative electrode sheet according to claim 17.

19. An electrical device, characterized in that: The secondary battery according to claim 18 is included.

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