Negative electrode composition, negative electrode plate, preparation method of negative electrode plate, battery and electric device

Abstract

The invention provides a negative electrode composition, a negative electrode plate, a preparation method of the negative electrode plate, a battery and an electric device. The negative electrode composition comprises a negative electrode active material, a binder and a thermo-sensitive fiber, and the low critical consolute temperature LSCT of the thermo-sensitive fiber is 30-60 DEG C.

Description

Technical Field

[0001] The present application relates to the technical field of batteries, and particularly to a negative electrode composition, a negative electrode sheet, a preparation method thereof, a battery, and an electrical device. Background Art

[0002] Secondary batteries rely on the reciprocating insertion and extraction of active ions between the positive electrode and the negative electrode for charging and discharging. Secondary batteries represented by lithium-ion batteries have outstanding characteristics such as high energy density, long cycle life, no pollution, and no memory effect. Therefore, as a clean energy source, secondary batteries have been gradually popularized from electronic products to large-scale device fields such as electric vehicles to adapt to the sustainable development strategy of the environment and energy.

[0003] With the development of devices such as electronic products and electric vehicles, people have put forward higher requirements for the cycle performance of secondary batteries. Summary of the Invention

[0004] In order to achieve the above object, the present application provides a negative electrode composition, which can improve the cycle performance of a battery containing the same; the present application also provides a negative electrode sheet containing the negative electrode composition, a preparation method thereof, a battery containing the negative electrode sheet, and an electrical device.

[0005] An embodiment of the first aspect of the present application provides a negative electrode composition, including a negative electrode active material, a binder, and a thermosensitive fiber. Among them, the lower critical solution temperature LSCT of the thermosensitive fiber is 30°C - 60°C.

[0006] Without being limited to any theory or explanation, in the negative electrode composition of the embodiments of the present application, the lower critical solution temperature LSCT of the thermosensitive fiber satisfies the given range. During the preparation of the negative electrode slurry, the thermosensitive fiber can exhibit hydrophilicity and thus be uniformly dispersed in the negative electrode slurry; after coating, the thermosensitive fiber can be uniformly distributed in the negative electrode slurry coating to construct a three-dimensional network structure in the coating. During the subsequent drying process, the baking temperature is usually higher than the lower critical solution temperature LSCT of the thermosensitive fiber. Therefore, the thermosensitive compound on the surface of the thermosensitive fiber can collapse during the drying process, thereby endowing the three-dimensional network structure of the thermosensitive fiber with higher hydrophobicity. Thus, during the drying process, a repulsive force can be generated between the three-dimensional network structure formed by the thermosensitive fiber and the binder, thereby inhibiting the capillary force formed during the solvent evaporation process and effectively preventing the binder from floating up. In addition, the thermosensitive fiber also has good toughness, and the three-dimensional network structure formed by it can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, enhancing the internal cohesion of the negative electrode film layer, and hindering the release of internal stress in the negative electrode film layer, thereby inhibiting the expansion of the negative electrode sheet. Thus, the stability of the negative electrode sheet structure can be improved, the cycle performance of the battery can be improved, and the cycle life of the battery can be extended.

[0007] In addition, the three-dimensional network structure formed by the thermosensitive fibers can also serve as a channel to facilitate the infiltration of the electrolyte and the transport of lithium ions. As a result, the ion transport kinetics of the negative electrode sheet can be improved, which helps to enhance the cycle performance and rate performance of the battery.

[0008] Therefore, when the negative electrode composition of the embodiments of the present application is applied to a secondary battery, the battery can have good cycle performance and rate performance, and the cycle life of the battery can be extended.

[0009] In any embodiment of the present application, the lower critical solution temperature (LCST) of the thermosensitive fiber is 30°C - 40°C.

[0010] When the LCST of the thermosensitive fiber is within the above suitable range, it can not only allow the negative electrode slurry to have a suitable processing temperature, but also allow the negative electrode sheet to have a suitable baking temperature. As a result, the preparation process of the negative electrode sheet can be simplified, and the flexibility of the negative electrode sheet preparation process can be improved.

[0011] In any embodiment of the present application, the thermosensitive fiber includes a fiber substrate and a thermosensitive compound.

[0012] Optionally, the thermosensitive compound is attached to the surface of the fiber substrate through a chemical bond.

[0013] When the thermosensitive compound is attached to the surface of the fiber substrate through a chemical bond, the combination of the thermosensitive compound and the fiber substrate is more firm. As a result, the thermosensitive fiber can have more stable thermosensitive properties, which is beneficial to the uniform dispersion of the thermosensitive fiber in the slurry during the processing of the negative electrode slurry, and to the formation of a hydrophobic three-dimensional network structure during the baking of the negative electrode sheet, thereby helping to further inhibit the floating of the binder and improve the cycle performance of the battery.

[0014] In any embodiment of the present application, the fiber substrate includes natural fiber and / or chemical fiber.

[0015] Optionally, the fiber substrate includes at least one of cellulose, chitosan, and chitin.

[0016] When the fiber substrate is selected from the above substances, the thermosensitive fiber can have good liquid retention performance, heat resistance, and toughness. As a result, when the negative electrode composition of the embodiments of the present application is applied to the negative electrode sheet of a secondary battery, it can endow the negative electrode film layer with good liquid retention performance, heat resistance, and toughness, thereby improving the kinetic performance and structural stability of the negative electrode sheet, and further improving the cycle performance and rate performance of the battery and extending the cycle life of the battery.

[0017] In any embodiment of the present application, the thermosensitive compound includes one or more of poly(N-vinylcaprolactam), poly(N-isopropylacrylamide), poly(N,N-diethylacrylamide), poly(dicarboxyisopropylacrylamide), poly[2-(N,N-dimethylamino)ethyl methacrylate], poly(ethylene oxide-propylene oxide) copolymer, polymethacrylate of oligoethylene glycol, poly(2-ethyl-2-oxazoline), poly(2-isopropyl-2-oxazoline), poly(2-n-propyl-2-oxazoline), and a copolymer of 2-(2-methoxyethoxy)ethyl 2-methyl-2-acrylate and methoxypolyethylene glycol methacrylate.

[0018] Optionally, the thermosensitive compound includes at least one of poly(N-vinylcaprolactam) and poly(N-isopropylacrylamide).

[0019] The above thermosensitive compound has a suitable lower critical solution temperature. After being compounded with the fiber substrate, the thermosensitive fiber can have a suitable lower critical solution temperature. Thereby, it is beneficial to improve the processability of the negative electrode slurry and the negative electrode sheet, effectively inhibit the floating of the binder during the drying process, and thus improve the cycle performance of the battery.

[0020] In any embodiment of the present application, the aspect ratio of the thermosensitive fiber is (20:1)-(2000:1), and can be optionally (100:1)-(1000:1). Thereby, the expansion of the negative electrode sheet can be inhibited, and the cycle performance of the battery can be improved.

[0021] In any embodiment of the present application, the thermosensitive fiber includes thermosensitive short fibers, thermosensitive long fibers or a combination thereof.

[0022] The length of the thermosensitive short fiber is less than or equal to 5 μm, can be optionally 0.5 μm - 5 μm, and more optionally 1 μm - 3 μm. When the thermosensitive fiber includes thermosensitive short fibers and the length of the thermosensitive short fibers is within the above suitable range, the irreversible capacity loss of the negative electrode active material can be reduced, and the cycle stability of the battery can be improved.

[0023] The length of the thermosensitive long fiber is greater than 5 μm, can be optionally greater than 5 μm and less than or equal to 100 μm, and more optionally 25 μm - 40 μm. When the thermosensitive fiber includes thermosensitive long fibers and the length of the thermosensitive long fibers is within the above suitable range, the cycle performance and the rate performance of the battery can be improved.

[0024] In any embodiment of the present application, the diameter of the thermosensitive fiber is 10 nm - 200 nm, and can be optionally 50 nm - 100 nm. Thereby, it is beneficial for the thermosensitive fiber to adhere more firmly to the surface of the negative electrode active material particles, inhibit the volume expansion of the negative electrode active material particles during the charge and discharge cycle, and thus the cycle performance of the battery can be improved.

[0025] In any embodiment of the present application, based on the total mass of the negative electrode composition, the mass percentage content of the temperature-sensitive fiber is greater than or equal to 0.01 wt%, optionally 0.01 wt% - 3 wt%, and more optionally 0.3 wt% - 1 wt%. Thereby, the processing difficulty of the negative electrode sheet can be reduced, and the production capacity of the negative electrode sheet can be improved.

[0026] In any embodiment of the present application, the negative electrode composition further includes a conductive agent and an optional additive.

[0027] Optionally, based on the total mass of the negative electrode composition, the mass percentage content of the negative electrode active material is 91 wt% - 97.59 wt%, the mass percentage content of the binder is 2 wt% - 5 wt%, the mass percentage content of the temperature-sensitive fiber is 0.01 wt% - 3 wt%, and the mass percentage content of the conductive agent is 0.4 wt% - 1.0 wt%.

[0028] An embodiment of the second aspect of the present application provides a negative electrode sheet, including a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, and the negative electrode film layer includes the negative electrode composition of the first aspect.

[0029] In the negative electrode sheet of the embodiment of the present application, the negative electrode film layer includes the composition described in the first aspect. Therefore, during the drying process, the binder is not likely to float, so that the binder is uniformly dispersed in the negative electrode film layer. Thereby, not only can the adhesion between the negative electrode film layer and the negative electrode current collector be improved, thus improving the structural stability of the negative electrode sheet, but also the negative electrode film layer can maintain good electrolyte infiltration performance and lithium ion transmission performance. In addition, the temperature-sensitive fiber in the negative electrode composition also has good toughness, and the three-dimensional network structure formed by it can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, improving the internal cohesion of the negative electrode film layer, and hindering the release of internal stress in the negative electrode film layer, thereby inhibiting the expansion of the negative electrode sheet. Thereby, the structural stability of the negative electrode sheet can be improved, the cycle performance of the battery can be improved, and the cycle life of the battery can be extended.

[0030] Therefore, when the negative electrode sheet of the embodiment of the present application is applied to a secondary battery, the battery can have good cycle performance and rate performance, and the cycle life of the battery can be extended.

[0031] In any embodiment of the present application, the thickness of the negative electrode film layer is 0.05 mm - 0.1 mm. Thereby, it is helpful to further improve the cycle performance of the battery.

[0032] An embodiment of the third aspect of the present application provides a method for preparing a negative electrode sheet, including:

[0033] Preparing a negative electrode paste, which includes dispersing a negative electrode active material, a binder, a thermosensitive fiber, and optionally an additive in a solvent at a first temperature to obtain the negative electrode paste, wherein the lower critical solution temperature (LCST) of the thermosensitive fiber is 30°C - 60°C, and the first temperature is lower than the lower critical solution temperature (LCST) of the thermosensitive fiber;

[0034] Preparing a negative electrode sheet, which includes coating the negative electrode paste on at least one side of a negative electrode current collector, drying it at a second temperature, and then obtaining the negative electrode sheet through cold pressing and slitting, wherein the second temperature is greater than or equal to the lower critical solution temperature (LCST) of the thermosensitive fiber.

[0035] According to the method of the embodiment of the present application, when preparing the negative electrode paste at the first temperature, since the first temperature is lower than the lower critical solution temperature (LCST) of the thermosensitive fiber, the thermosensitive fiber can be uniformly dispersed in the negative electrode paste, and then uniformly dispersed in the negative electrode paste coating, forming a three-dimensional network structure in the coating. Subsequently, when drying at the second temperature, the external temperature reaches the lower critical solution temperature (LCST) of the thermosensitive fiber, and the thermosensitive compound on the surface of the thermosensitive fiber can collapse, thereby endowing the three-dimensional network structure formed by the thermosensitive fiber with higher hydrophobicity. Thus, during the drying process, a repulsive force can be generated between the three-dimensional network structure formed by the thermosensitive fiber and the binder, thereby inhibiting the capillary force formed during the solvent evaporation process and effectively preventing the binder from floating up. In addition, the thermosensitive fiber also has good toughness, and the three-dimensional network structure formed by it can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, enhancing the cohesion of the negative electrode film layer, and hindering the release of the internal stress of the negative electrode film layer, thereby inhibiting the swelling of the negative electrode sheet. Thus, the negative electrode sheet prepared according to the method of the embodiment of the present application can have high structural stability. When applied to a secondary battery, it can improve the cycle performance of the battery and extend the cycle life of the battery. In addition, the three-dimensional network structure built by the thermosensitive fiber can also serve as a channel to promote the infiltration of the electrolyte and the transmission of lithium ions. Thus, it can improve the ion transport kinetics of the negative electrode sheet, which is helpful for improving the cycle performance and rate performance of the battery.

[0036] Therefore, when the negative electrode sheet prepared according to the method of the embodiment of the present application is applied to a secondary battery, the battery can have both good cycle performance and rate performance, and extend the cycle life of the battery.

[0037] An embodiment of the fourth aspect of the present application provides a battery, which includes the negative electrode sheet of the second aspect, or the negative electrode sheet prepared according to the method of the third aspect. Thus, it can have both good cycle performance, rate performance, and a long cycle life

[0038] An embodiment of the fifth aspect of the present application provides an electrical device, which includes the battery of the fourth aspect.

[0039] The electrical device according to an embodiment of the present application includes the battery of the fourth aspect, and thus has at least the same advantages as the battery of the fourth aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a schematic diagram of an embodiment of a battery cell of the present application.

[0041] Figure 2 is Figure 1 An exploded view of the embodiment of the battery cell of the present application shown.

[0042] Figure 3 It is a schematic diagram of an embodiment of a battery module of the present application.

[0043] Figure 4 It is a schematic diagram of an embodiment of a battery pack of the present application.

[0044] Figure 5 is Figure 4 An exploded view of the embodiment of the battery pack of the present application shown.

[0045] Figure 6 It is a schematic diagram of an embodiment of an electrical device of the present application, and the electrical device may include a battery pack or a battery module according to an embodiment of the present application as a power source.

[0046] Figure 7 It is a scanning electron microscope (SEM) image of the negative electrode film layer in Example 1 of the present application.

[0047] 1 Battery pack; 2 Upper box body; 3 Lower box body; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 Cover plate. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] Hereinafter, embodiments of the negative electrode composition, the negative electrode sheet, and methods for preparing the same, the battery, and the electrical device of the present application are specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually identical structures are omitted. This is to prevent the following description from becoming unnecessarily long and to facilitate the understanding of those skilled in the art. In addition, the accompanying 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 recited in the claims.

[0049] The "ranges" disclosed in this application are 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 ranges defined in this way can include or exclude the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60 - 120 and 80 - 110 are listed for a specific parameter, ranges of 60 - 110 and 80 - 120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all contemplated: 1 - 3, 1 - 4, 1 - 5, 2 - 3, 2 - 4, and 2 - 5. In this application, unless otherwise specified, the numerical range "a - b" represents an abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0 - 5" means that all real numbers between "0 - 5" are fully listed herein, and "0 - 5" is only an abbreviated representation of these numerical combinations. Additionally, when stating that a certain parameter is an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] If there is no special instruction, all embodiments and optional embodiments of this application can be combined with each other to form new technical solutions.

[0051] If there is no special instruction, all technical features and optional technical features of this application can be combined with each other to form new technical solutions.

[0052] If there is no special instruction, all steps of this application can be carried out sequentially or randomly, and preferably sequentially. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out sequentially, or can also include steps (b) and (a) carried out sequentially. For example, it is mentioned that the method may further include step (c), which means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0053] Unless otherwise specified, the numerical values of the various parameters mentioned in this application can be measured by various commonly used test methods in the art. For example, they can be measured according to the test methods given in the embodiments of this application. Unless otherwise specified, the test temperature for each parameter is 25 °C.

[0054] Unless otherwise specified, the ratio parameters involved in this application are compared under the same unit. For example, the thickness ratio of A to B is 1.2:1, and at this time, the thickness units of A and B are the same.

[0055] With the development of devices such as electronic products and electric vehicles, higher requirements are also put forward for the cycling performance of secondary batteries.

[0056] During the manufacturing process of the negative electrode sheet, the negative electrode slurry is usually coated on the surface of the negative electrode current collector, and after drying and cold pressing, a negative electrode film layer is formed on the surface of the negative electrode current collector. During the drying process, the evaporation of the slurry solvent will form capillary force in the coating, which will inevitably lead to the phenomenon of binder floating. The floating of the binder will not only cause problems such as the reduction of the binder force between the negative electrode film layer and the negative electrode current collector, the poor cohesion of the negative electrode film layer, and the increase of the internal stress release in the negative electrode sheet resulting in the expansion of the sheet, leading to a shortened cycle life of the battery; it will also cause the decline of the ion transport kinetics of the negative electrode sheet, deteriorating the cycling performance and rate performance of the battery.

[0057] Related technologies involve adjusting the structure of the negative electrode film layer to provide a double-coated negative electrode sheet. The negative electrode sheet of the related technology includes a first negative electrode film layer and a second negative electrode film layer stacked on the surface of the current collector. The content of the binder in the first negative electrode film layer is higher than that in the second negative electrode film layer; after drying, the binder in the first negative electrode film layer floats to the second negative electrode film layer, reducing the difference in the binder content between the first negative electrode film layer and the second negative electrode film layer. Related technologies also involve optimizing the drying process, for example, adjusting drying parameters, low-temperature dynamic movement, etc. However, related technologies not only put forward strict requirements for processes or equipment and are difficult to apply when facing the needs of thick coating or high-speed coating, but also have a limited improvement effect on the floating of the binder and are difficult to effectively reduce the degree of binder floating.

[0058] In view of this, the embodiments of the present application provide a negative electrode composition, which can effectively inhibit the floating degree of the binder during the drying process, so that the battery containing it has good cycling performance; the present application also provides a negative electrode sheet containing the negative electrode composition, its preparation method, a battery containing the negative electrode sheet, and an electrical device.

[0059] Negative electrode composition

[0060] An embodiment of the first aspect of the present application provides a negative electrode composition, which includes a negative electrode active material, a binder, and a thermosensitive fiber. Among them, the lower critical solution temperature LSCT of the thermosensitive fiber is 30°C - 60°C. For example, it can be 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, or the range composed of any two of the above values.

[0061] Thermosensitive fibers may include fibers whose properties change reversibly with temperature, mainly obtained by introducing thermosensitive compounds into the fibers. Thermosensitive fibers have thermosensitive properties, that is, when the external temperature is lower than the lower critical solution temperature (LSCT) of the thermosensitive fibers, the thermosensitive compounds on the surface of the thermosensitive fibers can be hydrophilic, and the molecular chains can fully stretch in water or polar organic solvents (such as N-methylpyrrolidone, NMP), so that the thermosensitive fibers can be uniformly dispersed in water or polar organic solvents; when the external temperature reaches above the lower critical solution temperature (LSCT) of the thermosensitive fibers, the thermosensitive compounds on the surface of the thermosensitive fibers will collapse, and at this time the thermosensitive fibers can exhibit hydrophobicity.

[0062] Without intending to be limited by any theory or explanation, in the negative electrode composition of the embodiments of the present application, the lower critical solution temperature (LSCT) of the thermosensitive fibers satisfies the given range. During the preparation of the negative electrode slurry, the thermosensitive fibers can exhibit hydrophilicity and thus be uniformly dispersed in the negative electrode slurry; after coating, the thermosensitive fibers can be uniformly distributed in the negative electrode slurry coating to form a three-dimensional network structure in the coating. During the subsequent drying process, the baking temperature is usually higher than the lower critical solution temperature (LSCT) of the thermosensitive fibers. Therefore, the thermosensitive compounds on the surface of the thermosensitive fibers can collapse during the drying process, thereby endowing the three-dimensional network structure formed by the thermosensitive fibers with high hydrophobicity. Thus, during the drying process, a repulsive force can be generated between the three-dimensional network structure formed by the thermosensitive fibers and the binder, thereby inhibiting the capillary force formed during the solvent evaporation process and effectively preventing the binder from floating. In addition, the thermosensitive fibers also have good toughness, and the three-dimensional network structure formed by them can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, enhancing the cohesion of the negative electrode film layer and hindering the release of the internal stress of the negative electrode film layer, thereby inhibiting the swelling of the negative electrode plate. Thus, the stability of the negative electrode plate structure can be improved, the cycle performance of the battery can be improved, and the cycle life of the battery can be extended.

[0063] In addition, the three-dimensional network structure built by the thermosensitive fibers can also serve as a channel to promote the infiltration of the electrolyte and the transport of lithium ions. Thus, the ion transport kinetics of the negative electrode plate can be improved, which is helpful for improving the cycle performance and rate performance of the battery.

[0064] Therefore, the application of the negative electrode composition of the embodiments of the present application to secondary batteries can enable the batteries to have good cycle performance and rate performance and extend the cycle life of the batteries.

[0065] In some embodiments, the lower critical solution temperature (LSCT) of the thermosensitive fiber can be 30°C - 40°C. For example, it can be 30°C, 32°C, 34°C, 35°C, 38°C, 40°C, or the range composed of any two of the above values. For example, the lower critical solution temperature (LSCT) of the thermosensitive fiber can also be 30°C - 40°C, 31°C - 39°C, 32°C - 38°C, 33°C - 37°C, 34°C - 36°C, 35°C - 36°C, and so on.

[0066] Without being bound by any theory or explanation, when the lower critical solution temperature (LSCT) of the thermosensitive fiber is within the above suitable range, it can not only allow the negative electrode slurry to have a suitable processing temperature, but also allow the negative electrode sheet to have a suitable baking temperature. Thus, the preparation process of the negative electrode sheet can be simplified, and the flexibility of the negative electrode sheet preparation process can be improved.

[0067] The lower critical solution temperature (LSCT) of the thermosensitive fiber has the meaning well-known in the art and can be measured by equipment and methods known in the art. As an example, the cloud point method can be used to measure the lower critical solution temperature (LSCT) of the thermosensitive fiber. Specifically, a thermosensitive fiber solution can be configured, heated at a certain heating rate, and the light transmittance of the solution can be measured with an ultraviolet-visible spectrophotometer. The temperature at which the light transmittance changes abruptly is the lower critical solution temperature (LSCT) of the thermosensitive fiber.

[0068] In some embodiments, the thermosensitive fiber can include a fiber substrate and a thermosensitive compound. As an example, the fiber substrate and the thermosensitive compound can be compounded to obtain the thermosensitive fiber by methods such as copolymerization, crosslinking, co-blending spinning, composite spinning, and fabric surface coating. Those skilled in the art can select a suitable compounding method according to actual needs.

[0069] In some embodiments, the thermosensitive compound can be attached to the surface of the fiber substrate by chemical bonds.

[0070] Without being bound by any theory or explanation, when the thermosensitive compound is attached to the surface of the fiber substrate by chemical bonds, the combination of the thermosensitive compound and the fiber substrate is more firm. Thus, the thermosensitive fiber can have more stable thermosensitive properties, which is beneficial to the uniform dispersion of the thermosensitive fiber in the slurry during the processing of the negative electrode slurry and the formation of a hydrophobic three-dimensional network structure during the baking of the negative electrode sheet, thereby helping to further inhibit the floating of the binder and improving the cycle performance of the battery.

[0071] In some embodiments, the fibrous substrate may include natural fibers and / or chemical fibers. Examples of natural fibers may include, but are not limited to, one or more of plant fibers, animal fibers, and mineral fibers; examples of chemical fibers may include, but are not limited to, one or more of man-made fibers (cellulose fibers), synthetic fibers, and inorganic fibers (such as carbon fibers, glass fibers, metal fibers, etc.).

[0072] Without being bound by any theory or explanation, the fibrous substrate in the thermosensitive fiber may be selected from the substances of the above types, so as to endow the thermosensitive fiber with more functions. As an example, metal fibers can endow the thermosensitive fiber with high electrical properties, which is beneficial to improving the kinetic performance of the negative electrode sheet; cellulose fibers can endow the thermosensitive fiber with light weight, strong physical properties, as well as good liquid retention performance and heat resistance; glass fibers can endow the thermosensitive fiber with higher strength, and so on. Thus, by selecting the substrate of the thermosensitive fiber, the cycle performance of the battery can be further improved in many aspects.

[0073] Optionally, in some embodiments, the fibrous substrate may include at least one of cellulose, chitosan, and chitin.

[0074] When the fibrous substrate is selected from the above substances, the thermosensitive fiber can have good liquid retention performance, heat resistance, and toughness. Thus, the negative electrode composition of the embodiments of the present application is applied to the negative electrode sheet of a secondary battery, which can endow the negative electrode film layer with good liquid retention performance, heat resistance, and toughness, thereby improving the kinetic performance and structural stability of the negative electrode sheet, and further improving the cycle performance and rate performance of the battery, and prolonging the cycle life of the battery.

[0075] In some embodiments, the thermosensitive compound may include poly(N-vinylcaprolactam) (PNVCL), poly(N-isopropylacrylamide) (PNIPAM), poly(N,N-diethylacrylamide), poly(dicarboxyisopropylacrylamide), poly[2-(N,N-dimethylamino)ethyl methacrylate], poly(ethylene oxide-propylene oxide) copolymer, poly(methacrylate) of oligoethylene glycol, poly(2-ethyl-2-oxazoline), poly(2-isopropyl-2-oxazoline), poly(2-n-propyl-2-oxazoline), copolymer of 2-(2-methoxyethoxy)ethyl 2-methyl-2-acrylate and methoxypolyethylene glycol methacrylate (PEGMA-MO 2 MA), or one or more of them.

[0076] Optionally, in some embodiments, the thermosensitive compound may include at least one of poly(N-vinylcaprolactam) and poly(N-isopropylacrylamide).

[0077] Without intending to be limited by any theory or explanation, the above thermosensitive compound has a suitable lower critical solution temperature. After being compounded with the fiber substrate, the thermosensitive fiber can have a suitable lower critical solution temperature. Thereby, it is beneficial to improve the processability of the negative electrode slurry and the negative electrode sheet, effectively inhibit the floating of the binder during the drying process, and thus improve the cycle performance of the battery.

[0078] The thermosensitive fiber of the embodiment of the present application can be obtained in a variety of ways. As an example, the thermosensitive fiber can be obtained through the following steps (1) to (2).

[0079] (1) Provide a thermosensitive compound capped with an active group.

[0080] In step (1), the active group can include but is not limited to hydroxyl and / or carboxyl. As an example, the active group can be introduced into the thermosensitive polymer compound through a thiol compound containing an active group. For example, the carboxyl group can be introduced into the thermosensitive compound through the reaction of mercaptoacetic acid with the thermosensitive fiber.

[0081] (2) React the thermosensitive compound capped with an active group with the fiber substrate to obtain a thermosensitive fiber.

[0082] The surface of the fiber substrate usually has groups such as hydroxyl groups, which can react with the active groups of the thermosensitive polymer, so that the thermosensitive compound is attached to the surface of the fiber substrate through chemical bonds. In some embodiments, the fiber substrate can also be modified to introduce amino groups on the surface of the fiber substrate, and the thermosensitive compound is attached to the surface of the fiber substrate through chemical bonds by reacting the amino groups with the active groups of the thermosensitive polymer. The reaction temperature and time of step (2) can be adjusted according to actual needs. As an example, the reaction temperature can be 20°C - 90°C, and the time can be 12h - 24h.

[0083] As an example, the thermosensitive fiber obtained by compounding the thermosensitive compound poly(N-vinylcaprolactam) with the fiber substrate can be prepared through the following steps (a) to (c).

[0084] (a) Provide poly(N-vinylcaprolactam) capped with a carboxyl group

[0085] Dissolve 10.0 g of N-vinylcaprolactam in 200 mL of 1,4-dioxane, add 0.3 g of azobisisobutyronitrile, and after purging with nitrogen for 30 min, add thioglycolic acid and react at 70 °C for 12 h. After the reaction is completed, remove 1,4-dioxane by distillation under reduced pressure. The obtained solid is redissolved in dichloromethane to obtain a dichloromethane solution of carboxyl-terminated poly(N-vinylcaprolactam). Slowly drop the solution into petroleum ether for precipitation and purification, and obtain a solid by suction filtration; repeat the above operation 3 times and then dry it in a vacuum drying oven to obtain carboxyl-terminated poly(N-vinylcaprolactam).

[0086] (b) Provide a fiber substrate with surface amino modification

[0087] Disperse 10.0 g of fiber powder in 200 mL of an ethanol / water mixed solvent (the volume ratio of ethanol to water is 4:1), add 1 g of aminopropyltrimethoxysilane, and react at 70 °C for 12 h. After the reaction is completed, centrifuge the mixture 3 times, and take the lower-layer solid and dry it under vacuum to obtain a fiber substrate with surface amino modification.

[0088] (c) Preparation of thermosensitive fibers

[0089] Dissolve 10.0 g of carboxyl-terminated poly(N-vinylcaprolactam) in 200 mL of dichloromethane, add N,N-diisopropylethylamine, stir for 10 min, then add 2-(7-azabenzotriazol-1-yl)-N,N,N',N'-tetramethyluronium hexafluorophosphate and the fiber substrate with surface amino modification, and react at room temperature for 12 h. After the reaction is completed, centrifuge the mixture and wash it 3 times with ethanol to obtain thermosensitive fibers.

[0090] In some embodiments, the aspect ratio of the thermosensitive fibers can be (20:1)-(2000:1). For example, it can be 20:1, 50:1, 100:1, 500:1, 800:1, 1000:1, 1200:1, 1500:1, 1800:1, 2000:1, or a range composed of any two of the above ratios.

[0091] Optionally, in some embodiments, the aspect ratio of the thermosensitive fibers can also be (100:1)-(1000:1). For example, it can be 100:1, 200:1, 300:1, 400:1, 500:1, 600:1, 700:1, 800:1, 900:1, 1000:1, or a range composed of any two of the above ratios.

[0092] Without intending to be limited by any theory or explanation, when the aspect ratio of the temperature-sensitive fiber meets the given range, the temperature-sensitive fiber can have relatively high strength. Thus, it helps to construct a firm three-dimensional network structure in the negative electrode film layer, thereby helping the temperature-sensitive fiber to generate a repulsive force with the binder within a large range in the negative electrode film layer, and further effectively suppressing the capillary force formed during the solvent evaporation process and hindering the floating of the binder. In addition, when the aspect ratio of the temperature-sensitive fiber meets the given range, it can also enable the temperature-sensitive fiber to have a suitable continuous toughening range in the negative electrode film layer, thereby exerting a strong toughening effect on the negative electrode film layer, enhancing the cohesive force of the negative electrode film layer, and hindering the release of internal stress in the negative electrode film layer. Thus, the expansion of the negative electrode plate can be inhibited and the cycle performance of the battery can be improved.

[0093] The aspect ratio of the temperature-sensitive fiber has the meaning well-known in the art and can be measured by devices and methods known in the art. As an example, the aspect ratio of the temperature-sensitive fiber can be measured by a scanning electron microscope (SEM). Specifically, an SEM image of the temperature-sensitive fiber can be taken to characterize the particle size diameter D1 of the temperature-sensitive fiber particles and the diameter D2 of the temperature-sensitive fiber. According to the principle of constant volume, the length L of the temperature-sensitive fiber can be calculated as L = [4 / 3×π×(D1 / 2) 3 / [π×(D2 / 2) 2 . The aspect ratio of the temperature-sensitive fiber is L / (D2 / 2).

[0094] In some embodiments, the temperature-sensitive fiber can include temperature-sensitive short fibers, temperature-sensitive long fibers, or a combination thereof.

[0095] The length of the temperature-sensitive short fiber can be less than or equal to 5 μm. For example, it can be 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, 0.3 μm, 0.2 μm, 0.1 μm, or a range composed of any two of the above values.

[0096] Optionally, in some embodiments, the length of the temperature-sensitive short fiber can also be 0.5 μm - 5 μm. For example, it can be 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, or a range composed of any two of the above values. For example, the length of the temperature-sensitive short fiber can be 0.5 μm - 5 μm, 0.5 μm - 4 μm, 0.5 μm - 3 μm, 0.5 μm - 2 μm, 0.5 μm - 1 μm, 1 μm - 5 μm, 1 μm - 4.5 μm, 1 μm - 4 μm, 1 μm - 3.5 μm, 1 μm - 3 μm, 1 μm - 2.5 μm, 1 μm - 2 μm, 1 μm - 1.5 μm, 1.5 μm - 5 μm, 2 μm - 4.5 μm, 2.5 μm - 4 μm, 3 μm - 3.5 μm, and so on.

[0097] When the thermosensitive fiber includes thermosensitive short fibers and the length of the thermosensitive short fibers is within the above suitable range, the thermosensitive short fibers can closely adhere to the surface of a single negative active material particle, thereby inhibiting the expansion of the negative active material caused by lithium intercalation. Thereby, the irreversible capacity loss of the negative active material can be reduced, and the cycle stability of the battery can be improved.

[0098] The length of the thermosensitive long fiber can be greater than 5 μm. For example, it can be 5.5 μm, 10 μm, 20 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, or a range composed of any two of the above values.

[0099] Optionally, in some embodiments, the length of the thermosensitive long fiber can also be greater than 5 μm and less than or equal to 100 μm. For example, it can be 5.5 μm, 8 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, or a range composed of any two of the above values. For example, the length of the thermosensitive long fiber can be 5.5 μm - 100 μm, 8 μm - 95 μm, 10 μm - 90 μm, 15 μm - 85 μm, 20 μm - 80 μm, 25 μm - 70 μm, 25 μm - 65 μm, 25 μm - 60 μm, 25 μm - 55 μm, 25 μm - 50 μm, 25 μm - 45 μm, 25 μm - 40 μm, 25 μm - 35 μm, 25 μm - 30 μm, and so on.

[0100] When the thermosensitive fiber includes thermosensitive long fibers and the length of the thermosensitive long fibers is within the above suitable range, the three-dimensional network structure of the thermosensitive fiber can form an "interlocking" structure with the negative active material particles and bind to each other, thereby playing a role in stabilizing the structure of the negative electrode sheet and improving the cycle performance of the battery. In addition, this "interlocking" structure can also increase the adhesion between the negative electrode film layer and the negative electrode sheet, so that the negative electrode film layer can maintain a high adhesion to the negative electrode current collector under the condition of a low binder content. When the binder content in the negative electrode film layer is low, the exposed surface area of the negative active material particles increases, so that the number of sites where the negative active material particles can directly intercalate lithium increases, which is beneficial to improving the lithium ion intercalation rate and deintercalation rate, improving the kinetics of the negative electrode, and thus improving the rate performance of the battery.

[0101] In some embodiments, the diameter of the thermosensitive fiber can be 10 nm - 200 nm. For example, it can be 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 120 nm, 150 nm, 180 nm, 200 nm, or a range composed of any two of the above values.

[0102] Optionally, in some embodiments, the diameter of the temperature-sensitive fiber can also be 50 nm - 100 nm. For example, it can be 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, or a range composed of any two of the above values.

[0103] Without intending to be limited by any theory or explanation, when the diameter is within the above suitable range, the temperature-sensitive fiber can exhibit excellent flexibility. Thus, it is beneficial for the temperature-sensitive fiber to adhere more firmly to the surface of the negative electrode active material particles, inhibiting the volume expansion of the negative electrode active material particles during the charge and discharge cycle, thereby improving the cycle performance of the battery.

[0104] In some embodiments, based on the total mass of the negative electrode composition, the mass percentage content of the temperature-sensitive fiber can be greater than or equal to 0.01 wt%, optionally 0.01 wt% - 3 wt%, and more optionally 0.3 wt% - 1 wt%.

[0105] Without intending to be limited by any theory or explanation, when the mass percentage content of the temperature-sensitive fiber is within the above suitable range, it can make the negative electrode slurry have good processability, such as improving the filtration performance of the slurry, etc., on the premise of inhibiting the floating of the binder. Thus, the processing difficulty of the negative electrode sheet can be reduced, and the production capacity of the negative electrode sheet can be improved.

[0106] In some embodiments, the negative electrode composition may further include a conductive agent and an optional additive.

[0107] Optionally, in some embodiments, based on the total mass of the negative electrode composition, the mass percentage content of the negative electrode active material is 91 wt% - 97.59 wt%, the mass percentage content of the binder is 2 wt% - 5 wt%, the mass percentage content of the temperature-sensitive fiber is 0.01 wt% - 3 wt%, and the mass percentage content of the conductive agent is 0.4 wt% - 1.0 wt%.

[0108] In the embodiments of the present application, the negative electrode active material can adopt the negative electrode active material known in the art for secondary batteries. As an example, the negative electrode active material may include, but is not limited to, at least one of natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based materials may include at least one of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloy materials. The tin-based materials may include at least one of elemental tin, tin oxides, and tin alloy materials.

[0109] In the embodiments of the present application, the binder can be a binder for the negative electrode of secondary batteries well-known in the art. As an example, the binder can include, but is not limited to, at least one of styrene-butadiene rubber (SBR), water-soluble unsaturated resin SR-1B, aqueous acrylic resin (e.g., polyacrylic acid PAA, polymethacrylic acid PMAA, sodium polyacrylate PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS).

[0110] In the embodiments of the present application, the conductive agent can be a conductive agent for the negative electrode of secondary batteries well-known in the art. As an example, the negative electrode conductive agent can include at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0111] In the embodiments of the present application, the negative electrode composition may optionally further include optional additives. As an example, the optional additives can include thickeners, such as sodium carboxymethyl cellulose (CMC-Na), PTC thermistor materials, etc.

[0112] Negative electrode plate

[0113] In a second aspect, embodiments of the present application provide a negative electrode plate, which includes a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, and the negative electrode film layer includes the negative electrode composition as described in the first aspect.

[0114] The embodiments of the negative electrode composition have been described and illustrated in detail above and will not be repeated here. It can be understood that the negative electrode plate of the embodiments of the present application can achieve the beneficial effects of any of the above embodiments of the negative electrode composition of the embodiments of the present application.

[0115] In the negative electrode plate of the embodiments of the present application, the negative electrode film layer includes the composition described in the first aspect. Therefore, during the drying process, the binder is not likely to float, so that the binder is uniformly dispersed in the negative electrode film layer. Thereby, not only can the adhesion between the negative electrode film layer and the negative electrode current collector be improved, thus improving the stability of the negative electrode plate structure, but also the negative electrode film layer can maintain good electrolyte wettability and lithium ion transmission performance. In addition, the thermosensitive fibers in the negative electrode composition also have good toughness, and the three-dimensional network structure formed by them can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, improving the cohesion of the negative electrode film layer, and hindering the release of internal stress in the negative electrode film layer, thereby inhibiting the swelling of the negative electrode plate. Thus, the stability of the negative electrode plate structure can be improved, the cycle performance of the battery can be improved, and the cycle life of the battery can be extended.

[0116] Therefore, when the negative electrode plate of the embodiments of the present application is applied to a secondary battery, the battery can have both good cycle performance and rate performance, and the cycle life of the battery can be extended.

[0117] In some embodiments, the thickness of the negative electrode film layer can be 0.05 mm - 0.1 mm. For example, it can be 0.05 mm, 0.06 mm, 0.07 mm, 0.08 mm, 0.09 mm, 0.1 mm, or a range composed of any two of the above values.

[0118] When the thickness of the negative electrode film layer is within the above suitable range, on the one hand, it is beneficial to effectively inhibit the floating of the binder through the thermosensitive fibers, and on the other hand, it is also beneficial for the negative electrode film layer to maintain good electrolyte infiltration performance. Thus, it helps to further improve the cycling performance of the battery.

[0119] In the embodiments of the present application, the negative electrode plate may include a negative electrode current collector and a negative electrode film layer provided on at least one side of the negative electrode current collector. For example, the negative electrode current collector has two opposite surfaces in its own thickness direction, and the negative electrode film layer is provided on any one or both of the two opposite surfaces of the negative electrode current collector.

[0120] In the embodiments of the present application, the thickness of the negative electrode film layer has the meaning well-known in the art and can be tested by methods known in the art. For example, it can be tested by a micrometer.

[0121] In some embodiments, the negative electrode current collector can be a metal foil or a composite current collector. As an example of the metal foil, copper foil can be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0122] The negative electrode film layer is usually formed by coating a negative electrode slurry on the negative electrode current collector and then drying and cold pressing. The negative electrode slurry is usually formed by dispersing a negative electrode composition and optional other additives in a solvent and stirring evenly. The solvent can be N-methylpyrrolidone (NMP) or deionized water, but is not limited thereto.

[0123] The negative electrode plate does not exclude other additional functional layers in addition to the negative electrode film layer. For example, in some embodiments, the negative electrode plate further includes a conductive bottom coating (for example, composed of a conductive agent and a binder) provided on the surface of the negative electrode current collector and sandwiched between the negative electrode current collector and the negative electrode film layer. In some embodiments, the negative electrode plate of the present application further includes a protective layer covering the surface of the negative electrode film layer.

[0124] Preparation method

[0125] In a third aspect, an embodiment of the present application provides a method for preparing a negative electrode plate, including the following steps S10 to S20.

[0126] S10. Prepare a negative electrode slurry, including dispersing a negative electrode active material, a binder, a thermosensitive fiber, and an optional additive in a solvent at a first temperature to obtain the negative electrode slurry. Among them, the lower critical solution temperature (LCST) of the thermosensitive fiber is 30°C - 60°C, and the first temperature is lower than the lower critical solution temperature (LCST) of the thermosensitive fiber.

[0127] In step S10, the negative electrode active material, the binder, the thermosensitive fiber, and the optional additive may include the negative electrode active material, the binder, the thermosensitive fiber, and the optional additive described in any implementation manner of the first aspect. The implementation manners of the negative electrode active material, the binder, the thermosensitive fiber, and the optional additive have been described and explained in detail above, and will not be repeated here. In step S10, the first temperature can be adjusted according to the lower critical solution temperature (LCST) of the thermosensitive fiber. As an example, the difference between the lower critical solution temperature (LCST) of the thermosensitive fiber and the first temperature can be 2°C, 5°C, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or within the range composed of any two of the above values. Examples of the solvent may include aqueous solvents known in the art, such as deionized water.

[0128] S20. Prepare a negative electrode plate, including coating the negative electrode slurry on at least one side of a negative electrode current collector, drying at a second temperature, and then obtaining the negative electrode plate through cold pressing and slitting. Among them, the second temperature is greater than or equal to the lower critical solution temperature (LCST) of the thermosensitive fiber.

[0129] In step S20, the second temperature can be adjusted according to the lower critical solution temperature (LCST) of the thermosensitive fiber. As an example, the difference between the second temperature and the lower critical solution temperature (LCST) of the thermosensitive fiber can be 20°C, 25°C, 30°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or within the range composed of any two of the above values.

[0130] According to the method of the embodiment of the present application, the negative electrode slurry is prepared at a first temperature, and the first temperature is lower than the lower critical solution temperature (LCST) of the thermosensitive fiber. Therefore, the thermosensitive fiber can be uniformly dispersed in the negative electrode slurry, and then uniformly dispersed in the negative electrode slurry coating, and a three-dimensional network structure is constructed in the coating. Subsequently, when drying is carried out at a second temperature, the external temperature reaches the lower critical solution temperature (LCST) of the thermosensitive fiber, and the thermosensitive compound on the surface of the thermosensitive fiber can collapse, thereby endowing the three-dimensional network structure of the thermosensitive fiber with higher hydrophobicity. Thus, during the drying process, a repulsive force can be generated between the three-dimensional network structure formed by the thermosensitive fiber and the binder, thereby inhibiting the capillary force formed during the solvent evaporation process and effectively preventing the binder from floating up. In addition, the thermosensitive fiber also has good toughness, and the three-dimensional network structure formed by it can play a certain binding role, forming an "interlocking" structure with the negative electrode active material particles, enhancing the internal cohesion of the negative electrode film layer, and hindering the release of the internal stress of the negative electrode film layer, thereby inhibiting the swelling of the negative electrode plate. Thus, the negative electrode plate prepared according to the method of the embodiment of the present application can have high structural stability. When applied to a secondary battery, it can improve the cycle performance of the battery and extend the cycle life of the battery. In addition, the three-dimensional network structure built by the thermosensitive fiber can also serve as a channel to promote the infiltration of the electrolyte and the transmission of lithium ions. Thus, the ion transport kinetics of the negative electrode plate can be improved, which is helpful for improving the cycle performance and rate performance of the battery.

[0131] Therefore, when the negative electrode plate prepared according to the method of the embodiment of the present application is applied to a secondary battery, the battery can have both good cycle performance and rate performance, and the cycle life of the battery can be extended.

[0132] Battery

[0133] The battery mentioned in the embodiment of the present application may include one or more battery cells to provide a single physical module with higher voltage and capacity.

[0134] Generally, a battery cell includes an electrode assembly and an electrolyte. The electrode assembly includes a positive electrode, a negative electrode, and a separator. During the charge and discharge process of the battery cell, active ions (such as lithium ions) are embedded and extracted back and forth between the positive electrode and the negative electrode. The separator is disposed between the positive electrode and the negative electrode, which can prevent the short circuit between the positive and negative electrodes and allow the active ions to pass through at the same time. The electrolyte plays a role in conducting active ions between the positive electrode plate and the negative electrode plate.

[0135] [Positive electrode plate]

[0136] In the battery cell of the embodiment of the present application, the positive electrode sheet of the electrode assembly may include a positive electrode current collector and a positive electrode film layer provided on at least one side of the positive electrode current collector and including a positive electrode active material. For example, the positive electrode current collector has two surfaces opposite to each other in its own thickness direction, and the positive electrode film layer is provided on any one or both of the two opposite surfaces of the positive electrode current collector.

[0137] In the positive electrode sheet of the embodiment of the present application, the positive electrode active material may adopt the positive electrode active material for secondary batteries known in the art. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphate with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the embodiment of the present application is not limited to these materials, and other conventional materials that can be used as the positive electrode active material of a lithium-ion battery 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, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (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 (which may also be abbreviated as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (which may also be abbreviated as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (which may also be abbreviated as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (which may also be abbreviated as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (which may also be abbreviated as NCM 811 ), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O 2) and at least one of its modified compounds, etc. Examples of the lithium-containing phosphate with olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO 4 (which can also be abbreviated as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and at least one of a composite material of lithium manganese iron phosphate and carbon.

[0138] In some embodiments, the positive electrode film layer may further optionally include a positive electrode conductive agent. The present application does not particularly limit the type of the positive electrode conductive agent. As an example, the positive electrode conductive agent includes at least one of superconducting carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0139] In some embodiments, the positive electrode film layer may further optionally include a positive electrode binder. The present application does not particularly limit the type of the positive electrode binder. As an example, the positive electrode binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0140] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. As an example of the metal foil, aluminum foil may be used. The composite current collector may include a polymer material base layer and a metal material layer formed on at least one surface of the polymer material base layer. As an example, the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy. As an example, the polymer material base layer may include at least one of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), and polyethylene (PE).

[0141] In some embodiments, the positive electrode plate can be prepared in the following manner: dispersing the above-mentioned components for preparing the positive electrode plate, such as the positive electrode active material, conductive agent, binder, and any other components, in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on the positive electrode current collector, and after processes such as drying and cold pressing, the positive electrode plate can be obtained.

[0142] [Negative electrode plate]

[0143] In the battery cell of the embodiment of the present application, the negative electrode plate of the electrode assembly may include the negative electrode plate of the second aspect or the negative electrode plate prepared according to the method of the third aspect.

[0144] The embodiments of the negative electrode sheet have been described and explained in detail above and will not be repeated here. It can be understood that the battery cell of the embodiment of the present application can achieve the beneficial effects of any of the above embodiments of the negative electrode sheet of the embodiment of the present application.

[0145] [Separator film]

[0146] The separator film is disposed between the positive electrode sheet and the negative electrode sheet and serves as a separator. There is no particular limitation on the type of the separator film in the embodiment of the present application, and any well-known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0147] In some embodiments, the material of the separator film can be selected from one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator film can be a single-layer film or a multi-layer composite film. When the separator film is a multi-layer composite film, the materials of each layer can be the same or different, and there is no particular limitation.

[0148] [Electrolyte]

[0149] The electrolyte serves to conduct ions between the positive electrode sheet and the negative electrode sheet. There is no specific limitation on the type of the electrolyte in the embodiment of the present application, and it can be selected according to requirements. For example, the electrolyte can be liquid, solid, or gel.

[0150] In some embodiments, the electrolyte uses an electrolytic solution. The electrolytic solution includes an electrolyte salt and a solvent.

[0151] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, lithium difluoro bis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0152] In some embodiments, the solvent can be selected from at least one of 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, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0153] In some embodiments, the electrolytic solution may optionally further include additives. For example, the additives can include negative electrode film-forming additives, positive electrode film-forming additives, and can also include additives that can improve certain properties of the battery, such as additives for improving the overcharge performance of the battery, additives for improving the high-temperature or low-temperature performance of the battery, etc.

[0154] In some embodiments, the positive electrode sheet, the separator, and the negative electrode sheet can be made into an electrode assembly through a winding process or a stacking process.

[0155] In some embodiments, the battery cell further includes a housing for accommodating the electrode assembly and the electrolyte. The housing of the battery cell can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The housing of the battery cell can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic. As plastics, polypropylene, polybutylene terephthalate, and polybutylene succinate can be enumerated.

[0156] The embodiments of the present application do not particularly limit the shape of the battery cell, and it can be cylindrical, square, or any other shape. For example, Figure 1 is a battery cell 5 with a square structure as an example.

[0157] In some embodiments, referring to Figure 2 , the housing can include a housing body 51 and a cover plate 53. Among them, the housing body 51 can include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose to form a receiving cavity. The housing body 51 has an opening communicating with 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 separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. The number of the electrode assemblies 52 included in the battery cell 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0158] The preparation method of the battery cell in the embodiments of the present application is well-known. In some embodiments, the electrode assembly can be placed in the housing, dried, and then injected with the electrolyte, and after processes such as vacuum packaging, standing, formation, and shaping, the battery cell is obtained.

[0159] In some embodiments, the battery mentioned in the embodiments of the present application refers to a single physical module including one or more battery cells to provide a higher voltage and capacity. For example, the battery mentioned in the embodiments of the present application can be a battery module or a battery pack, etc. The battery generally includes a box body for encapsulating one or more battery cells. The box body can prevent liquids or other foreign objects from affecting the charging or discharging of the battery cells.

[0160] In some embodiments, there may be multiple battery cells in a battery. The multiple battery cells can be connected in series, parallel, or in a combination of series and parallel (mixed connection), where mixed connection means that there are both series and parallel connections among the multiple battery cells. The multiple battery cells can be directly connected in series, parallel, or in a mixed manner, and then the whole formed by the multiple battery cells is accommodated in a box. Of course, it is also possible that the multiple battery cells are first connected in series, parallel, or in a mixed manner to form battery modules, and then the multiple battery modules are connected in series, parallel, or in a mixed manner to form a whole and are accommodated in a box.

[0161] Figure 3 is a schematic diagram of a battery module 4 as an example. As Figure 3 shown, there are multiple battery cells 5. The multiple battery cells 5 are first connected in series, parallel, or in a mixed manner to form battery module 4. The multiple battery cells 5 in battery module 4 can be electrically connected through a busbar component to achieve series, parallel, or mixed connection of the multiple battery cells 5 in battery module 4. In battery module 4, the multiple battery cells 5 can be arranged in sequence along the length direction of battery module 4. Of course, they can also be arranged in any other way. Further, the multiple battery cells 5 can be fixed by fasteners.

[0162] In some embodiments, the above battery module can also be assembled into a battery pack, and the number of battery modules included in the battery pack can be adjusted according to the application and capacity of the battery pack.

[0163] Figure 4 and Figure 5 are schematic diagrams of a battery pack 1 as an example. As Figure 4 and Figure 5 shown, battery pack 1 can include a box body and multiple battery modules 4 arranged in the box body. The multiple battery modules 4 in battery pack 1 can be electrically connected through a busbar component to achieve series, parallel, or mixed connection of the multiple battery modules 4 in battery pack 1. The box body includes an upper box body 2 and a lower box body 3. The upper box body 2 is used to cover the lower box body 3 and form a closed space for accommodating battery module 4. The multiple battery modules 4 can be arranged in the battery box in any way.

[0164] electrical device

[0165] The embodiments of the present application also provide an electrical device. The electrical device includes the battery provided by the embodiments of the present application, and the battery is used to provide electrical energy. The battery can be used as the power source of the electrical device or as the energy storage unit of the electrical device. The electrical device can 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, satellites, energy storage systems, etc., but is not limited thereto.

[0166] As the electrical device, a battery cell, a battery module including a plurality of battery cells, or a battery pack can be selected according to its usage requirements.

[0167] Figure 6 is an electrical device as an example. The electrical device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc. In order to meet the requirements of the electrical device for high power and high energy density, a battery pack or a battery module can be adopted.

[0168] As another example of the electrical device, it can be a mobile phone, a tablet computer, a laptop computer, etc. This device usually requires being thin and light, and a battery cell can be adopted as the power source.

[0169] Embodiment

[0170] Hereinafter, embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application and should not be construed as a limitation to the present application. For those not specified in the embodiments regarding specific technologies or conditions, they shall be carried out according to the technologies or conditions described in the literature in the field or according to the product specifications. For the reagents or instruments not specified for the manufacturers, they are all conventional products that can be obtained through commercial purchase.

[0171] Embodiment 1

[0172] Preparation of negative electrode sheet

[0173] The dispersant sodium carboxymethyl cellulose (CMC), the thermosensitive fiber, and the plasticizer 1,3-butanediol are uniformly dispersed in deionized water. Subsequently, the conductive agent acetylene black and the negative electrode active material artificial graphite are added. After stirring evenly, the negative electrode binder styrene-butadiene rubber (SBR) is added. After mixing evenly, it is sieved to obtain the negative electrode slurry. Among them, the mass ratio of the negative electrode active material, the binder, the dispersant, the conductive agent, the plasticizer, and the thermosensitive fiber is 95:2:1:1:0.5:0.5; the fiber substrate of the thermosensitive fiber is cellulose; the thermosensitive compound is poly(N-vinylcaprolactam) (PNVCL); the aspect ratio of the thermosensitive fiber is 600:1, and the length is 30 μm; the lower critical solution temperature LSCT of the thermosensitive fiber is 37 °C. The negative electrode slurry is coated on the negative electrode current collector copper foil, dried at 120 °C, and then through the processes of cold pressing, slitting, and cutting, a negative electrode plate is obtained.

[0174] Preparation of positive electrode sheet

[0175] After uniformly mixing the positive electrode binder polyvinylidene fluoride (PVDF) with the solvent N-methylpyrrolidone, the conductive agent acetylene black is added. After fully stirring evenly, the positive electrode active material LiNi 0.8 Co 0.1 Mn 0.1 O 2(NCM 811 ), after mixing evenly, it is sieved to obtain the positive electrode slurry. Among them, the mass ratio of the positive electrode active material, the conductive agent, and the positive electrode binder is 97:1.5:1.5. The positive electrode slurry is coated on the positive electrode current collector aluminum foil, and through the processes of drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained.

[0176] Preparation of separator

[0177] Use a polyethylene film as the separator.

[0178] Preparation of electrolyte

[0179] Dissolve the lithium salt (LiPF 6 mixed with LiFSI in a mass ratio of 2:8) in a solvent prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0180] Preparation of secondary battery

[0181] Stack and wind the positive electrode sheet, the separator, and the negative electrode sheet in sequence to obtain an electrode assembly; place the electrode assembly in an outer package, inject the electrolyte after drying, and through processes such as vacuum packaging, standing, formation, and shaping, a secondary battery is obtained.

[0182] Examples 2 - 16

[0183] Based on the preparation process of the negative electrode sheet in Example 1, as shown in Table 1, adjust the preparation parameters such as the type, aspect ratio, length, and the dosage ratio w of the thermosensitive fiber in the solid components of the negative electrode slurry to prepare the negative electrode sheets of Examples 2 - 16. In Examples 2 - 16, based on the total mass of the solid components of the negative electrode slurry, the sum of the dosage ratios of the thermosensitive fiber and the negative electrode active material is 95.5 wt%. In Example 10, the length of the thermosensitive fiber with an aspect ratio of 600:1 is 30 μm, and the dosage w is 0.4 wt%; the length of the thermosensitive fiber with an aspect ratio of 150:1 is 3 μm, and the dosage w is 0.1 wt%

[0184] The preparation of the positive electrode sheet, separator, electrolyte, and secondary battery of Examples 2 - 16 is the same as that of Example 1.

[0185] Comparative Example 1

[0186] Based on the preparation process of the negative electrode sheet in Example 1, no thermosensitive fiber is added to prepare the negative electrode sheet of Comparative Example 1.

[0187] The preparation of the positive electrode sheet, separator, electrolyte, and secondary battery of Comparative Example 1 is the same as that of Example 1.

[0188] Comparative Example 2

[0189] Based on the preparation process of the negative electrode sheet in Example 1, the thermosensitive fiber was replaced with a fiber substrate (cellulose) of the same mass to prepare the negative electrode sheet of Comparative Example 1. The aspect ratio of the fiber substrate was 600:1, and the length was 30 μm.

[0190] The preparation of the positive electrode sheet, separator, electrolyte, and secondary battery of Comparative Example 2 was the same as that of Example 1.

[0191] Testing Part

[0192] Peeling force test

[0193] The cold-pressed negative electrode sheet was cut into rectangular strips of 15 cm * 2 cm. After drying the strips in an oven at 80 °C for 2 h, the peel strength between the negative electrode film layer and the negative electrode current collector was tested (universal material testing machine Instron 3365, testing speed 0.012 m / s, peel width 2 cm). For each example or comparative example, 3 - 5 strips were tested respectively, and the average value was taken as the peel strength between the negative electrode film layer and the negative electrode current collector in this example or comparative example.

[0194] Cohesion force test of electrode sheet

[0195] The cold-pressed negative electrode sheet was cut into rectangular strips of 15 cm * 2 cm. After drying the strips in an oven at 80 °C for 2 h, the cohesive force of the electrode sheet was tested (universal material testing machine Instron 3365, testing speed 0.012 m / s, peel width 2 cm). For each example or comparative example, 3 - 5 strips were tested respectively, and the average value was taken as the cohesive force of the negative electrode sheet in this example or comparative example.

[0196] Swelling rate test of negative electrode sheet

[0197] Take the cold-pressed negative electrode sheet, randomly select 10 test sites, measure the thickness with a micrometer, and take the average value as the initial thickness A1 of the negative electrode sheet; after fully charging the secondary battery at a rate of 0.33C, disassemble the battery and take out the negative electrode sheet; randomly select 10 test sites, measure the thickness with a micrometer, and take the average value as the thickness A2 of the negative electrode sheet. The electrode sheet expansion rate of the negative electrode sheet under the fully charged state

[0198] Battery internal resistance test

[0199] At 25°C, the secondary battery is charged at a constant current of 0.33C to 4.5V, then charged at a constant voltage of 4.5V until the current reaches 0.05C, left standing for 5 min, then discharged at 0.5C for 1 h. After standing for 1 h, it is discharged at a current of 4C for 30 s. Record the initial voltage V1 at the start of discharge and the voltage V2 at 30 s of discharge. The battery internal resistance = (V1 - V2) / the current corresponding to 4C.

[0200] Cycling performance test

[0201] At 25°C, after the secondary battery is left standing for 30 min, it is discharged at a constant current of 0.33C to 2.8V; after standing for 30 min, it is charged at a constant current of 0.33C to 4.5V, and then charged at a constant voltage of 4.5V until the current reaches 0.05C; after standing for 30 min, it is discharged at a constant current of 0.33C to 2.8V, and record the discharge capacity at this time as the initial capacity of the battery.

[0202] Subsequently, after the secondary battery is left standing for 2 h, it is charged at a constant current of 0.33C to 4.5V, and then charged at a constant voltage of 4.5V until the current reaches 0.05C; after standing for 10 min, it is discharged at a constant current of 0.33C to 2.8V and left standing for 10 min. This is one charge-discharge cycle. Repeat the above steps for the same secondary battery until the battery capacity decays to less than 90% of the initial capacity, and record the number of cycles at this time to characterize the cycle performance of the battery.

[0203] The test results are shown in Table 2.

[0204] Table 1

[0205]

[0206] Table 2

[0207]

[0208]

[0209] Based on the test results in Table 1 and Table 2, it can be seen that the negative electrode composition in the examples of this application contains thermosensitive fibers with LSCT within a specific range. When applied to the negative electrode plate, it can effectively improve the adhesion between the negative electrode film layer and the negative electrode current collector, enhance the internal cohesion of the electrode plate, thereby suppressing the volume expansion of the negative electrode plate during the charge-discharge cycle; it can also improve the electrolyte infiltration performance of the negative electrode film layer, thereby reducing the internal resistance of the negative electrode film layer. Therefore, the batteries in Examples 1-16 all have good cycle performance.

[0210] In contrast, in Comparative Example 1, no temperature-sensitive fiber is added to the negative electrode film layer, and the peeling force between the negative electrode film layer and the negative electrode sheet and the cohesive force of the negative electrode sheet are lower than those of Example 1-16, the sheet expansion rate is higher than that of Example 1-16, and the internal resistance of the negative electrode film layer is higher than that of Example 1-16. Therefore, the cycle performance of Comparative Example 1 is significantly lower than that of Example 1-16. In Comparative Example 2, cellulose is added to the negative electrode film layer, which can improve the electrolyte wetting performance of the negative electrode film layer, and thus, the internal resistance of Comparative Example 2 is reduced. However, the cellulose in Comparative Example 2 does not have the temperature-sensitive characteristics of the temperature-sensitive fiber, and therefore, the peeling force between the negative electrode film layer and the negative electrode sheet and the cohesive force of the negative electrode sheet in Comparative Example 2 are still lower than those of Example 1-16, the sheet expansion rate is still higher than that of Example 1-16, and the cycle performance is still not ideal.

[0211] For some compounds given but not listed in the examples, since they have similar chemical properties and reaction properties when participating in electrochemical reactions to the compounds listed in the examples, they are all applicable to the technical solution of the present invention, so they are not listed here one by one.

[0212] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having substantially the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, within the scope of the subject matter of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A negative electrode composition comprising a negative electrode active material, a binder and a temperature-sensitive fiber, in, The lower critical solution temperature LSCT of the temperature-sensitive fiber is 30°C-60°C.

2. The negative electrode composition according to claim 1, wherein The lower critical solution temperature LSCT of the temperature-sensitive fiber is 30°C-40°C.

3. The negative electrode composition according to any one of claims 1 or 2, wherein The temperature-sensitive fiber comprises a fiber substrate and a temperature-sensitive compound; Optionally, the temperature-sensitive compound is attached to the surface of the fiber substrate via chemical bonds.

4. The negative electrode composition according to claim 3, wherein The fiber substrate includes natural fibers and / or chemical fibers; Optionally, the fiber substrate includes at least one of cellulose, chitosan, and chitin.

5. The negative electrode composition according to claim 3 or 4, wherein: The temperature-sensitive compound includes one or more of poly-N-vinylcaprolactam, poly-N-isopropylacrylamide, poly-N,N-diethylacrylamide, poly(dicarboxyisopropylacrylamide), poly[methacrylate-2-(N,N-dimethylamino)ester], polyoxyethylene-polyoxypropylene copolymer, polymethacrylate of oligoethylene glycol, poly-2-ethyl-2-oxazoline, poly-2-isopropyl-2-oxazoline, poly-2-n-propyl-2-oxazoline, and copolymer of 2-methyl-2-acrylic acid-2-(2-methoxyethoxy)ethyl ester and polyethylene glycol methyl ether methacrylate; Optionally, the temperature-sensitive compound includes at least one of poly (N-vinyl caprolactam) and poly (N-isopropylacrylamide).

6. The negative electrode composition according to any one of claims 1 to 5, wherein: The aspect ratio of the temperature-sensitive fiber is (20:1)-(2000:1), and can be optionally (100:1)-(1000:1).

7. The negative electrode composition according to any one of claims 1 to 6, wherein The temperature-sensitive fibers include temperature-sensitive short fibers, temperature-sensitive long fibers, or a combination thereof; The length of the temperature-sensitive short fibers is less than or equal to 5 μm, and can be 0.5 μm-5 μm, and can be 1 μm-3 μm. The length of the temperature-sensitive long fiber is greater than 5 μm, and may be greater than 5 μm and less than or equal to 100 μm, and may be more preferably 25 μm-40 μm.

8. The negative electrode composition according to any one of claims 1 to 7, wherein The diameter of the temperature-sensitive fiber is 10nm-200nm, and can be optionally 50nm-100nm.

9. The negative electrode composition according to any one of claims 1 to 8, wherein: Based on the total mass of the negative electrode composition, the mass percentage of the temperature-sensitive fiber is greater than or equal to 0.01 wt %, and can be optionally 0.01 wt %-3 wt %, and can be more optionally 0.3 wt %-1 wt %.

10. The negative electrode composition according to any one of claims 1 to 9, wherein: The negative electrode composition also includes a conductive agent and optional additives; Optionally, based on the total mass of the negative electrode composition, the mass percentage of the negative electrode active material is 91wt%-97.59wt%, the mass percentage of the binder is 2wt%-5%wt, the mass percentage of the temperature-sensitive fiber is 0.01wt%-3wt%, and the mass percentage of the conductive agent is 0.4wt%-1.0wt%.

11. A negative electrode sheet, comprising a negative electrode current collector and a negative electrode film layer located on at least one side of the negative electrode current collector, wherein the negative electrode film layer comprises the negative electrode composition according to any one of claims 1 to 10.

12. The negative electrode sheet according to claim 11, wherein: The thickness of the negative electrode film layer is 0.05mm-0.1mm.

13. A method for preparing a negative electrode sheet, comprising: Preparing a negative electrode slurry, comprising dispersing a negative electrode active material, a binder, a temperature-sensitive fiber, and an optional additive in a solvent at a first temperature to obtain a negative electrode slurry, wherein the lower critical solution temperature LSCT of the temperature-sensitive fiber is 30° C.-60° C., and the first temperature is lower than the lower critical solution temperature LSCT of the temperature-sensitive fiber; The negative electrode sheet is prepared, comprising coating the negative electrode slurry on at least one side of the negative electrode current collector, drying at a second temperature, and cold pressing and slitting to obtain the negative electrode sheet, wherein the second temperature is greater than or equal to the lower critical solution temperature LSCT of the temperature-sensitive fiber.

14. A battery comprising the negative electrode sheet according to claim 11 or 12, or the negative electrode sheet prepared by the method according to claim 13.

15. An electrical device comprising the battery according to claim 14.

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