Battery cell, battery device, and electric device

Abstract

The application relates to the technical field of batteries, in particular to a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive pole piece; the positive pole piece comprises a positive pole current collector and a positive pole film layer arranged on at least one surface of the positive pole current collector; the positive pole film layer comprises carbon nanotubes and tungsten elements, and the carbon nanotubes are located on the surface of the tungsten elements; from the direction close to the positive pole current collector to the direction far from the positive pole current collector, the positive pole film layer comprises a first positive pole film layer to an n-th positive pole film layer in sequence, wherein n is a positive integer greater than or equal to 2; from the direction close to the positive pole current collector to the direction far from the positive pole current collector, the mass proportion of the tungsten elements in each positive pole film layer gradually increases. The battery monomer has the advantages of good fast-charging capability, high power and good cycle performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a battery monomer, a battery device and a power utilization device. BACKGROUND

[0002] At present, hybrid vehicles have higher requirements for the energy density of battery cells to obtain battery monomers with excellent comprehensive performance. Therefore, it is crucial to develop a battery monomer with good fast charging ability, high power and good cycle performance. SUMMARY

[0003] In view of the above problems, the present application provides a battery monomer, a battery device and a power utilization device, which has the advantages of good fast charging ability, high power and good cycle performance.

[0004] In a first aspect, the present application provides a battery monomer, which comprises a positive electrode sheet;

[0005] The positive electrode sheet comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector;

[0006] The positive electrode film layer comprises carbon nanotubes and tungsten elements, and the carbon nanotubes are located on the surface of the tungsten elements;

[0007] From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the positive electrode film layer comprises a first positive electrode film layer to an nth positive electrode film layer in sequence, and n is a positive integer greater than or equal to 2;

[0008] From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the mass fraction of the tungsten elements in each positive electrode film layer gradually increases.

[0009] In the technical scheme of the embodiment of the present application, the carbon nanotubes are arranged in the positive electrode film layer, because of the excellent electrical conductivity and the three-dimensional conductive network easily formed in the positive electrode film layer, the electron transmission speed of the positive electrode tab and the electrolyte can be improved, the internal resistance of the battery cell is reduced, and the power performance of the battery cell is improved; at the same time, the deintercalation of active ions is promoted, the kinetic performance of the battery cell is improved, and the fast charging capacity and the cycle performance of the battery cell are improved; the reasons for arranging the tungsten element in the positive electrode film layer of the present application mainly include the following two points: first, the tungsten element is located in the middle band gap state above the maximum value of the valence band, that is, in the band gap region between the top of the valence band and the bottom of the conduction band of the semiconductor, which can enhance the electronic conductivity of the positive electrode tab and improve the oxygen lattice, thereby further improving the electrochemical kinetics of the battery cell and improving the power performance of the battery cell; second, in actual application, the long and thin structure of the carbon nanotube reduces the rebound of the positive electrode active material while binding the positive electrode active material, and with the extension of the use time, the structure may pierce the solid-state electrolyte film. Because the tungsten element has the characteristics of preferred orientation, the carbon nanotube is located on the surface of the tungsten element, reducing the possibility of damage to the solid-state electrolyte film by the carbon nanotube, and the tungsten element can reduce the possibility of side reactions between the carbon nanotube and the electrolyte. Therefore, the tungsten element can reduce the probability of side reactions in the battery cell and improve the cycle life of the battery cell. In addition, along the direction away from the positive electrode current collector, the mass fraction of the tungsten element in each positive electrode film layer gradually increases, which is beneficial to increasing the electron transition and exchange between the outer surface of the electrode tab and the electrolyte, and further improving the comprehensive performance of the battery cell. At the same time, the design of the above multi-layer structure can relatively accurately regulate the performance of the positive electrode tab, optimize the microstructure of the positive electrode tab, and improve the reliability and stability of the performance of the further formed battery cell. In summary, through the cooperation of the carbon nanotube and the tungsten element, the battery cell with good fast charging capacity, high power and good cycle performance can be obtained.

[0010] In some embodiments, the total mass of the tungsten element and the carbon nanotube is less than or equal to 3% based on the total mass of the positive electrode film layer.

[0011] In the technical scheme of the embodiment of the present application, the total mass fraction of the tungsten element and the carbon nanotube in the positive electrode film layer is within the above range; the mass fraction of the main material such as the positive electrode active material and the binder can be kept in a relatively high range, on the one hand, it is beneficial to the full play of the positive electrode active material, so that the capacity of the battery cell is relatively high, and the basic performance of the battery cell is met; on the other hand, it is beneficial to the full play of the binder, reduces the situation that the electrode tab is powdery due to insufficient adhesion of the electrode tab, and reduces the possibility that the internal resistance of the battery cell is high and the power of the battery cell is reduced.

[0012] In some embodiments, the mass ratio of the tungsten element and the carbon nanotube in each positive electrode film layer is (0.5-2.5):1, respectively.

[0013] In the technical solutions of the embodiments of the present application, the mass ratio of the tungsten element and the carbon nanotubes in each positive electrode film layer is within the above range. The two cooperate with each other, and the positive electrode tab formed thereby has high stability, which is conducive to improving the overall performance of the battery monomer; especially in the case of meeting the basic requirement of the positive electrode film layer on the content of the positive electrode active material, the mass content of the tungsten element and the carbon nanotubes within the above mass ratio range can be set within a proper range, the energy density and capacity of the battery cell are high, so as to improve the overall performance of the battery monomer.

[0014] In some embodiments, the total mass of the tungsten element is less than or equal to 3%, and optionally less than or equal to 2%, based on the total mass of the positive electrode film layer.

[0015] In the technical solutions of the embodiments of the present application, the mass ratio of the tungsten element and the carbon nanotubes in each positive electrode film layer is within the above range. The two cooperate with each other, and the positive electrode tab formed thereby has high stability, which is conducive to improving the overall performance of the battery monomer; especially in the case of meeting the basic requirement of the positive electrode film layer on the content of the positive electrode active material, the mass content of the tungsten element and the carbon nanotubes within the above mass ratio range can be set within a proper range, the energy density and capacity of the battery cell are high, so as to improve the overall performance of the battery monomer.

[0016] In some embodiments, the mass content of the tungsten element in the first positive electrode film layer is 0.2%-5%, based on the total mass of the tungsten element in the positive electrode film layer.

[0017] In the technical solutions of the embodiments of the present application, the mass content of the tungsten element in the first positive electrode film layer is within the above range, i.e., the proportion of the tungsten element in the innermost positive electrode film layer to the total content of the tungsten element in the positive electrode film layer is within the above range. The reason is that within the range, the content of the tungsten element in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which on the one hand can meet the basic requirement of good cooperation with the carbon nanotubes, and on the other hand has little effect on the mass ratio of the tungsten element in other positive electrode film layers. Different positive electrode film layers can be designed according to the need of the tungsten element ratio, and the number of layers of the positive electrode film layer can also be designed according to the need, so as to reduce the adverse effects of insufficient tungsten element content in some positive electrode film layers on the performance of the battery monomer, especially to meet the mass ratio requirement of the tungsten element in the outermost positive electrode film layer.

[0018] In some embodiments, the mass content of the tungsten element in the nth positive electrode film layer is 0.8%-12%, based on the total mass of the tungsten element in the positive electrode film layer.

[0019] In the technical solution of the embodiments of the present application, the mass content of tungsten in the nth positive electrode film layer is within the above range based on the total mass of tungsten in the positive electrode film layer, that is, the proportion of tungsten in the outermost positive electrode film layer to the total content of tungsten in the positive electrode film layer is within the above range. The reason is that within the range, the electron transition and exchange between the outer surface of the positive electrode sheet and the electrolyte is sufficient, which is beneficial to improving the comprehensive performance of the battery cell; and within the range, the mass proportion of tungsten in other positive electrode film layers is less affected, different positive electrode film layers can be designed according to the proportion of tungsten as needed, and the number of layers of the positive electrode film layer can also be designed as needed, reducing the adverse effects of insufficient content of tungsten in some positive electrode film layers on the performance of the battery cell.

[0020] In some embodiments, the mass proportion of the carbon nanotubes in each positive electrode film layer gradually increases from the direction close to the positive electrode current collector to the direction away from the positive electrode current collector.

[0021] In the technical solution of the embodiments of the present application, the mass proportion of the carbon nanotubes in each positive electrode film layer gradually increases in the direction away from the positive electrode current collector, which is beneficial to the electron transition and exchange between the outer surface of the positive electrode sheet and the electrolyte, and improves the charge-discharge performance, cycle performance and rate performance of the battery cell.

[0022] In some embodiments, the total mass of the carbon nanotubes is less than or equal to 1% based on the total mass of the positive electrode film layer.

[0023] In the technical solution of the embodiments of the present application, the total mass of the carbon nanotubes in the positive electrode film layer is within the above range. The reason is that within the range, the carbon nanotubes can fully play a role in improving the performance of the battery cell, and the processing difficulty is appropriate, at the same time, the mass proportion of the main material can still be maintained at a relatively high level, and the adverse effects of the loss of the main material on the performance of the battery cell will not occur.

[0024] In some embodiments, the mass content of the carbon nanotubes in the first positive electrode film layer is 0.1%-6% based on the total mass of the carbon nanotubes in the positive electrode film layer.

[0025] In the technical solution of the embodiments of the present application, the mass content of the carbon nanotubes in the first positive electrode film layer is within the above range based on the total mass of the carbon nanotubes in the positive electrode film layer, that is, the proportion of the carbon nanotubes in the innermost positive electrode film layer to the total content of the carbon nanotubes in the positive electrode film layer is within the above range. The reason is that, within the range, the content of the carbon nanotubes in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can basically meet the requirement of the positive electrode film layer for the content, and achieve the effect of improving the performance of the battery monomer; on the other hand, the mass proportion of the carbon nanotubes in other positive electrode film layers is less affected, different positive electrode film layers can be designed according to the need of the proportion of the carbon nanotubes, and the number of layers of the positive electrode film layer can also be designed according to the need, which reduces the adverse effect of insufficient content of carbon nanotubes in some positive electrode film layers on the performance of the battery monomer, especially the mass proportion requirement of the carbon nanotubes in the outermost positive electrode film layer.

[0026] In some embodiments, the mass content of the carbon nanotubes in the nth positive electrode film layer is 0.4%-15% based on the total mass of the carbon nanotubes in the positive electrode film layer.

[0027] In the technical solution of the embodiments of the present application, the mass content of the carbon nanotubes in the nth positive electrode film layer is within the above range based on the total mass of the carbon nanotubes in the positive electrode film layer, that is, the proportion of the carbon nanotubes in the outermost positive electrode film layer to the total content of the carbon nanotubes in the positive electrode film layer is within the above range. The reason is that, within the range, the electron transition and exchange between the outer surface of the positive electrode sheet and the electrolyte are sufficient, which is beneficial to improve the comprehensive performance of the battery monomer; and, within the range, the mass proportion of the carbon nanotubes in other positive electrode film layers is less affected, different positive electrode film layers can be designed according to the need of the proportion of the carbon nanotubes, and the number of layers of the positive electrode film layer can also be designed according to the need, which reduces the adverse effect of insufficient content of carbon nanotubes in some positive electrode film layers on the performance of the battery monomer.

[0028] In some embodiments, n is a positive integer greater than or equal to 2 and less than or equal to 50; optionally, n is a positive integer greater than or equal to 10 and less than or equal to 30.

[0029] In the technical solution of the embodiments of the present application, n is within the above range. The tungsten element and the carbon nanotubes in different positive electrode film layers cooperate with each other, which is beneficial to improve the fast charging capacity, power and cycle performance of the battery monomer; and the positive electrode film layer with the above number of layers has relatively low processing difficulty, which can reduce the adverse effect of the limitation of the processing technology on the performance of the battery monomer.

[0030] In some embodiments, the thickness of the positive electrode film layer is 0.05-0.3mm.

[0031] In the technical scheme of the embodiment of the present application, the thickness of the positive electrode film layer is within the above range, which can meet the high energy density requirement of the battery cell, and the diffusion path of the active ion is relatively short, so that the battery cell formed has the characteristics of good fast charging capacity, high power and good cycle performance, and excellent comprehensive performance.

[0032] In some embodiments, the carbon nanotubes include single-walled carbon nanotubes.

[0033] In the technical scheme of the embodiment of the present application, the single-walled carbon nanotubes have excellent electrical conductivity, are easy to form a long-range conductive network, and are beneficial to improving the fast charging capacity, power and cycle performance of the battery cell.

[0034] In some embodiments, the aspect ratio of the carbon nanotubes is 50-300; and / or;

[0035] The tube diameter of the carbon nanotubes is 1-5 mm.

[0036] In the technical scheme of the embodiment of the present application, the aspect ratio of the carbon nanotubes is within the above range, which can be more uniformly distributed in the positive electrode film layer to form a good conductive network, and can also reduce the adverse effects of self-aggregation on the battery cell; and the carbon nanotubes within the above aspect ratio range can be better distributed in the relatively thin positive electrode film layer, and the structure damage to the solid-state electrolyte film is lower with the extension of the use time, which is more beneficial to improving the fast charging capacity, power and cycle performance of the battery cell, and improving the comprehensive performance thereof.

[0037] In a second aspect, the present application provides a battery device, which includes a plurality of the battery cells of the first aspect.

[0038] In a third aspect, the present application provides a power consumption device, which includes the battery cell of the first aspect or the battery device of the second aspect.

[0039] The above description is only a summary of the technical scheme of the present application, in order to more clearly understand the technical means of the present application, and to implement the content of the specification, and in order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the following specific embodiments of the present application are described. DETAILED DESCRIPTION

[0040] The embodiments of the technical scheme of the present application are described in detail below. The following embodiments are only used to more clearly illustrate the technical scheme of the present application, and therefore only serve as examples, and cannot limit the protection scope of the present application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of this application; the use of the terms "including," "comprising," or "having" and variations thereof herein is intended to be broad and encompass the terms "consisting of" and "consisting essentially of" and variations thereof, unless otherwise noted. The description herein of any embodiments, including preferred embodiments, is intended to be illustrative and not limiting of the application. Numerous applications of the application will be readily apparent to those skilled in the art from the disclosure hereof.

[0042] In the description of the embodiments of the present application, the technical terms "first", "second", and the like are used only for the purpose of distinguishing different objects, and cannot be understood as indicating or implying relative importance or implying the number, specific order or primary and secondary relationship of the technical features indicated. In the description of the embodiments of the present application, the meaning of "a plurality of" is two or more, unless otherwise explicitly and specifically limited.

[0043] Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive or alternative embodiments. It will be explicitly understood by those of ordinary skill in the art that the embodiments described herein can be combined with other embodiments.

[0044] The ranges disclosed herein are defined by the lower and upper limits of the range, given by selecting a lower limit and an upper limit, the selected lower limit and upper limit defining the boundaries of the particular range. The ranges defined in this manner can be inclusive or exclusive of the end values, and can be arbitrarily combined, i.e., 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 particular parameter, it is understood that ranges of 60-110 and 80-120 are also contemplated. In addition, if minimum range values of 1 and 2 are listed, and if maximum range values of 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 the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing all of the real combinations between "a" and "b", where "a" and "b" are real numbers. For example, the numerical range "2-10" indicates that all of the real numbers between "2" and "10" have been listed herein, "2-10" is just a shorthand way of indicating these numerical combinations. In addition, when it is stated that a parameter is an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] In the description of the embodiments of the present application, the term "and / or" is merely an association relationship of the associated objects, which means that there can be three relationships, for example, A and / or B, which can represent the three cases of existence of A, existence of A and B, and existence of B. In addition, the character " / " herein generally represents an "or" relationship between the front and rear associated objects.

[0046] Currently, the requirements for the comprehensive performance of the battery monomer are higher and higher, especially the comprehensive requirements for the fast charging capability, the power and the cycle performance.

[0047] The present application uses carbon nanotubes and tungsten elements in cooperation, sets multiple positive electrode film layers, and designs the content change of tungsten elements in the positive electrode film layers, to obtain a battery monomer with good fast charging capability, high power and good cycle performance. The present application provides a battery monomer, a battery device and a power utilization device.

[0048] [Battery monomer]

[0049] In the embodiments of the present application, the battery monomer can be a secondary battery, which refers to a battery monomer that can be activated by charging after discharging to continue to use.

[0050] The battery monomer can be a lithium ion battery, a sodium ion battery, a sodium lithium ion battery, a lithium metal battery, a sodium metal battery, a lithium sulfur battery, a magnesium ion battery, a nickel hydrogen battery, a nickel cadmium battery, a lead-acid battery, etc., which is not limited in the embodiments of the present application.

[0051] [Electrode assembly]

[0052] The battery monomer generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode and a separator, and the separator is arranged between the negative electrode and the positive electrode. In the charging and discharging process of the battery monomer, active ions (such as lithium ions or sodium ions) are inserted and extracted between the positive electrode and the negative electrode. The separator arranged between the positive electrode and the negative electrode can prevent the short circuit of the positive and negative electrodes, and can also allow the active ions to pass through.

[0053] The electrode assembly can be a winding structure, a laminated structure, or a hybrid structure of winding and lamination.

[0054] In some embodiments, the electrode assembly is a winding structure. The positive electrode sheet and the negative electrode sheet are wound into a winding structure.

[0055] In some embodiments, the electrode assembly is a laminated structure.

[0056] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets can be arranged alternately and stacked.

[0057] As an example, a plurality of positive electrode tabs can be provided, and the negative electrode tab is folded to form a plurality of folded segments arranged in layers.

[0058] As an example, both the positive electrode tab and the negative electrode tab are folded to form a plurality of folded segments arranged in layers.

[0059] In some embodiments, the electrode assembly can have a cylindrical shape, a flat shape, or a multi-prism shape, etc.

[0060] In some embodiments, the electrode assembly is provided with a tab, which can guide the current out of the electrode assembly. The tab includes a positive tab and a negative tab.

[0061] [Positive electrode tab]

[0062] In some embodiments, the positive electrode can be a positive electrode tab, and the present application provides a battery cell including a positive electrode tab;

[0063] The positive electrode tab includes a positive current collector and a positive film layer arranged on at least one surface of the positive current collector;

[0064] The positive film layer includes carbon nanotubes and tungsten elements, and the carbon nanotubes are located on the surface of the tungsten elements.

[0065] From the direction close to the positive current collector to the direction away from the positive current collector, the positive film layer sequentially includes a first positive film layer to an n-th positive film layer, where n is a positive integer greater than or equal to 2.

[0066] From the direction close to the positive current collector to the direction away from the positive current collector, the mass percentage of the tungsten elements in each positive film layer gradually increases.

[0067] In the present application, the structure, composition, and mass percentage change of the tungsten elements of the positive film layer are analyzed by the following methods:

[0068] (1) Structure of the positive film layer: The cross-sectional morphology of the positive electrode tab is observed by optical electron microscopy such as a scanning electron microscope (model: Zeiss Sigma360) or a transmission electron microscope (model: JEOL JEM-ARM200F(C)-NEO ARM). Specifically, the battery cell is disassembled, the positive electrode tab is taken out, the positive film layer is peeled off using laser cleaning technology, the cross section of the material sample is bombarded by argon ion polishing technology to obtain a smooth polished cross section, and then the scanning electron microscope is used to observe and analyze the microstructure of the sample to determine whether the positive film layer belongs to a multi-layer structure, whether the carbon nanotubes exist, and the distribution area of the tungsten elements.

[0069] (2) The composition of the positive electrode film layer and the mass proportion of tungsten element: The raw material composition and the mass proportion of tungsten element of different positive electrode film layers are analyzed by energy spectrum test. Specifically, the positive electrode film layer is made into a thin sample, a scanning electron microscope (model: Zeiss Sigma 360) is used to irradiate the surface of the sample, and the characteristic X-rays of the elements in the sample are excited; the excited X-rays are collected by the detector of the energy spectrometer (model: Oxford); the characteristic X-rays of different elements have different energies, so the types of elements in the sample can be identified by analyzing the energies of these X-rays.

[0070] By measuring the intensity of the characteristic X-rays, the content of each element in the sample can be determined. The analysis of the element content can be expressed in two ways: non-normalized mass fraction and normalized mass fraction. The non-normalized mass fraction refers to the sum of the element mass fractions is not 100%, while the normalized mass fraction refers to the sum of the element mass fractions is converted into percentage.

[0071] Through the results obtained by cross-section morphology combined with energy spectrum test, the composition of different layers of raw materials and the proportion of tungsten element in the sample can be analyzed.

[0072] In the technical solutions of the embodiments of the present application, the carbon nanotubes are arranged in the positive electrode film layer, which has excellent electrical conductivity and can form a three-dimensional conductive network in the positive electrode film layer, so as to improve the electron transmission speed of the positive electrode tab and the electrolyte, reduce the internal resistance of the battery cell, and improve the power performance of the battery cell. Meanwhile, the carbon nanotubes can also promote the deintercalation of active ions and improve the kinetic performance of the battery cell, so as to improve the fast charging capability and cycle performance of the battery cell. The reason why the tungsten element is arranged in the positive electrode film layer of the present application is mainly as follows: first, the tungsten element is located in the middle band gap state above the maximum value of the valence band, that is, in the band gap region between the top of the valence band and the bottom of the conduction band of the semiconductor, which can enhance the electronic conductivity of the positive electrode tab and improve the oxygen lattice, so as to further improve the electrochemical kinetics of the battery cell and improve the power performance of the battery cell. Second, the long and thin structure of the carbon nanotube can reduce the rebound of the positive electrode active material, but with the extension of the use time, the structure may pierce the solid-state electrolyte film. Since the tungsten element has the characteristic of preferred orientation, the carbon nanotube is located on the surface of the tungsten element, which reduces the possibility of damage to the solid-state electrolyte film by the carbon nanotube. Moreover, the tungsten element can reduce the possibility of side reactions between the carbon nanotube and the electrolyte. Therefore, the tungsten element can reduce the probability of side reactions in the battery cell and improve the cycle life of the battery cell. In addition, along the direction away from the positive electrode current collector, the mass fraction of the tungsten element in each positive electrode film layer gradually increases, which is beneficial to increasing the electron transition and exchange between the outer surface of the electrode tab and the electrolyte, and further improving the comprehensive performance of the battery cell. Meanwhile, the design of the above multi-layer structure can relatively accurately regulate the performance of the positive electrode tab, optimize the microstructure of the positive electrode tab, and improve the reliability and stability of the performance of the further formed battery cell. In summary, the cooperation of the carbon nanotube and the tungsten element in the present application is beneficial to obtaining a battery cell with good fast charging capability, high power, and good cycle performance.

[0073] In some embodiments, the total mass of the tungsten element and the carbon nanotube is less than or equal to 3%, for example, 0.5%, 1.5%, 2%, 2.5%, etc., based on the total mass of the positive electrode film layer.

[0074] In the technical solutions of the embodiments of the present application, the total mass fraction of the tungsten element and the carbon nanotube in the positive electrode film layer is within the above range; the mass fraction of the main materials such as the positive electrode active material and the binder can be kept in a relatively high range, which is beneficial to the full play of the positive electrode active material on the one hand, so as to make the capacity of the battery cell higher and meet the basic performance of the battery cell; on the other hand, it is beneficial to the full play of the binder, which can reduce the situation that the electrode tab is powdery due to insufficient adhesion of the electrode tab, and reduce the possibility of high internal resistance of the battery cell and low power of the battery cell.

[0075] In some embodiments, in the first positive electrode film layer to the n-th positive electrode film layer, the mass ratio of the tungsten element and the carbon nanotubes in each positive electrode film layer is (0.5-2.5):1, and optionally (0.6-1.5):1, where 0.5-2.5 can be 0.6, 0.8, 1, 1.2, 1.4, 1.6, 1.8, 2, 2.2, 2.4, etc.

[0076] In this application, the tungsten element in the positive electrode film layer exists in the form of tungsten-containing material such as tungsten single substance or tungsten compound, where the mass ratio of the tungsten element and the carbon nanotubes is designed by the mass of tungsten single substance, or the mass of tungsten element in the whole compound according to the molecular weight of the tungsten element in the tungsten compound. The mass content of the tungsten element in the following is similar to the above and will not be repeated.

[0077] In this application, the tungsten single substance or tungsten compound can use commercial products, or can be purified by tungsten ore. The type of tungsten ore is not limited in this application, for example, the tungsten ore can include any one or a combination of at least two of scheelite, wolframite or tungsten ore; the purification method of the tungsten ore itself can use the method known in the art.

[0078] As an example, the method for obtaining tungsten single substance or tungsten compound from tungsten ore includes the following steps:

[0079] The tungsten ore (for example, scheelite) and the reducing agent are dispersed into a solvent (for example, ethylene glycol solution, etc.) and mixed uniformly, then washed with water and dried to obtain tungsten single substance or tungsten compound.

[0080] As an example, the reducing agent includes any one or a combination of at least two of sodium carbonate, ammonium phosphate, ammonia water or calcium fluoride.

[0081] As an example, the tungsten compound includes any one or a combination of at least two of scheelite, wolframite or tungsten ore.

[0082] In the technical scheme of the embodiments of the application, the mass ratio of the tungsten element and the carbon nanotubes in each positive electrode film layer is within the above range. The two cooperate with each other, and the formed positive electrode tab has high stability, which is beneficial to improving the overall performance of the battery monomer. Especially in the case of meeting the basic requirement of the positive electrode film layer for the content of the positive electrode active material, the mass content of the tungsten element and the carbon nanotubes in the above mass ratio range can be set in a proper range, and the energy density and capacity of the battery cell are high, so as to improve the overall performance of the battery monomer.

[0083] In some embodiments, the total mass of the tungsten element is less than or equal to 3%, and optionally less than or equal to 2%, for example, 0.5%, 1.5%, 2%, 2.5%, etc., based on the total mass of the positive electrode film layer.

[0084] In the technical solution of the embodiment of the present application, the mass percentage of tungsten element in the positive electrode film layer is within the above range. The reason is that within the range, the tungsten element can cooperate with the carbon nanotubes to improve the performance of the battery monomer, and the mass percentage of the main material can still be maintained at a relatively high level, and the adverse effects on the battery performance caused by the loss of the main material will not occur.

[0085] In some embodiments, the mass content of tungsten element in the first positive electrode film layer is 0.2%-5%, for example, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc., based on the total mass of tungsten element in the positive electrode film layer.

[0086] In the technical solution of the embodiment of the present application, the mass content of tungsten element in the first positive electrode film layer is within the above range, that is, the proportion of tungsten element in the innermost positive electrode film layer to the total content of tungsten element in the positive electrode film layer is within the above range. The reason is that within the range, the content of tungsten element in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can meet the basic requirement of good cooperation with the carbon nanotubes on one hand, and has little effect on the mass percentage of tungsten element in other positive electrode film layers on the other hand. Different positive electrode film layers can be designed according to the need of tungsten element percentage, and the number of positive electrode film layers can also be designed according to the need, so as to reduce the adverse effects on the performance of the battery monomer caused by the insufficient content of tungsten element in some positive electrode film layers, especially to meet the mass percentage requirement of tungsten element in the outermost positive electrode film layer.

[0087] In some embodiments, the mass content of tungsten element in the nth positive electrode film layer is 0.8%-12%, for example, 1%, 2%, 4%, 6%, 8%, 10%, etc., based on the total mass of tungsten element in the positive electrode film layer.

[0088] In the technical solution of the embodiment of the present application, the mass content of tungsten element in the nth positive electrode film layer is within the above range, that is, the proportion of tungsten element in the outermost positive electrode film layer to the total content of tungsten element in the positive electrode film layer is within the above range. The reason is that within the range, the electron transition and exchange between the outer surface of the positive electrode sheet and the electrolyte are sufficient, which is beneficial to improve the comprehensive performance of the battery monomer; and within the range, the mass percentage of tungsten element in other positive electrode film layers has little effect, different positive electrode film layers can be designed according to the need of tungsten element percentage, and the number of positive electrode film layers can also be designed according to the need, so as to reduce the adverse effects on the performance of the battery monomer caused by the insufficient content of tungsten element in some positive electrode film layers.

[0089] In some embodiments, the mass content difference of tungsten element between adjacent positive electrode film layers is designed as needed, and is exemplarily 0.01%-5%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc.

[0090] In some embodiments, the mass proportion of the carbon nanotubes in each positive electrode film layer gradually increases from the direction close to the positive electrode current collector to the direction away from the positive electrode current collector.

[0091] In the technical solution of the embodiments of the present application, the mass proportion of the carbon nanotubes in each positive electrode film layer gradually increases in the direction away from the positive electrode current collector, which is beneficial to the electron transition and exchange between the outer surface of the positive electrode sheet and the electrolyte, and improves the charge-discharge performance, cycle performance and rate performance of the battery cell.

[0092] In some embodiments, the total mass of the carbon nanotubes is less than or equal to 1% of the total mass of the positive electrode film, for example, 0.2%, 0.4%, 0.6%, 0.8%, etc.

[0093] In the technical solution of the embodiments of the present application, the total mass of the carbon nanotubes in the positive electrode film is within the above range. The reason is that within this range, the carbon nanotubes can fully play a role in improving the performance of the battery cell, and the processing difficulty is appropriate, at the same time, the mass proportion of the main material can still be maintained at a relatively high level, and the adverse effects of the loss of the main material on the performance of the battery cell will not occur.

[0094] In some embodiments, the mass content of the carbon nanotubes in the first positive electrode film layer is 0.1%-6% of the total mass of the carbon nanotubes in the positive electrode film, for example, 0.5%, 1%, 2%, 3%, 4%, 5%, etc.

[0095] In the technical solution of the embodiments of the present application, the mass content of the carbon nanotubes in the first positive electrode film layer is within the above range based on the total mass of the carbon nanotubes in the positive electrode film, that is, the proportion of the carbon nanotubes in the innermost positive electrode film to the total content of the carbon nanotubes in the positive electrode film is within the above range. The reason is that within this range, the content of the carbon nanotubes in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can basically meet the requirement of the positive electrode film layer for the content thereof, and achieve the effect of improving the performance of the battery cell; on the other hand, the mass proportion of the carbon nanotubes in other positive electrode film layers is less affected, different positive electrode film layers can be designed according to the need, and the number of layers of the positive electrode film layer can also be designed according to the need, so as to reduce the adverse effects of insufficient carbon nanotube content in some positive electrode film layers on the performance of the battery cell, and especially to meet the mass proportion requirement of the carbon nanotubes in the outermost positive electrode film layer.

[0096] In some embodiments, the mass content of the carbon nanotubes in the nth positive electrode film layer is 0.4%-15%, for example, 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, etc., based on the total mass of the carbon nanotubes in the positive electrode film layer.

[0097] In the technical solution of the embodiments of the present application, the mass content of the carbon nanotubes in the nth positive electrode film layer is within the above range based on the total mass of the carbon nanotubes in the positive electrode film layer, that is, the proportion of the carbon nanotubes in the outermost positive electrode film layer to the total content of the carbon nanotubes in the positive electrode film layer is within the above range. The reason is that within the range, the electron transition and exchange between the outer surface of the positive electrode tab and the electrolyte are sufficient, which is beneficial to improving the comprehensive performance of the battery cell; and within the range, the mass proportion of the carbon nanotubes in other positive electrode film layers is less affected, different positive electrode film layers can be designed according to the need of the proportion of the carbon nanotubes, and the number of layers of the positive electrode film layer can also be designed according to the need, thereby reducing the adverse effects of insufficient carbon nanotube content in some positive electrode film layers on the performance of the battery cell.

[0098] In some embodiments, the mass content difference of the carbon nanotubes between adjacent positive electrode film layers can be designed according to the need, and exemplarily can be 0.01%-5%, for example, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, etc., based on the total mass of the carbon nanotubes in the positive electrode film layer.

[0099] In some embodiments, n is a positive integer greater than or equal to 2 and less than or equal to 50; optionally, n is a positive integer greater than or equal to 10 and less than or equal to 30, for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, etc.

[0100] In the technical solution of the embodiments of the present application, n is within the above range. The tungsten element and the carbon nanotubes in different positive electrode film layers cooperate with each other, which is beneficial to improving the fast charging capability, power and cycle performance of the battery cell; and the positive electrode film layer with the above number of layers has relatively low processing difficulty, which can reduce the adverse effects of the limitation of the processing technology on the performance of the battery cell.

[0101] In some embodiments, the thickness of the positive electrode film layer is 0.05-0.3mm, for example, 0.1mm, 0.15mm, 0.2mm, 0.25mm, etc.

[0102] In the technical solution of the embodiments of the present application, the thickness of the positive electrode film layer is within the above range, which can meet the high energy density requirement of the battery cell, and the diffusion path of the active ions is relatively short, so that the formed battery cell has the characteristics of good fast charging capability, high power and good cycle performance, and has excellent comprehensive performance.

[0103] In some embodiments, the carbon nanotubes include single-walled carbon nanotubes, multi-walled carbon nanotubes, or oligo-walled carbon nanotubes, and are optionally single-walled carbon nanotubes.

[0104] In the technical solutions of the embodiments of the present application, the single-walled carbon nanotubes have excellent electrical conductivity, are easy to form a long-range conductive network, and are beneficial to improving the fast-charging capability, power, and cycle performance of the battery monomer.

[0105] In some embodiments, the aspect ratio of the carbon nanotubes is 50-300, such as 100, 150, 200, 250, etc.; and / or;

[0106] The tube diameter of the carbon nanotubes is 1-5 mm, such as 2 mm, 3 mm, 4 mm, etc.

[0107] In the technical solutions of the embodiments of the present application, the aspect ratio of the carbon nanotubes is in the above range, which can be more uniformly distributed in the positive electrode film layer to form a good conductive network, and can also reduce the adverse effects of self-aggregation on the battery monomer. Moreover, the carbon nanotubes in the above aspect ratio range can be better distributed in the relatively thin positive electrode film layer, and the structure damage to the solid-state electrolyte film is lower with the extension of the use time, which is more beneficial to improving the fast-charging capability, power, and cycle performance of the battery monomer, and improving the comprehensive performance thereof.

[0108] As an example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode active material is arranged on any one or both of the two opposite surfaces of the positive electrode current collector.

[0109] As an example, the positive electrode current collector can adopt a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metal, alloy, surface-treated metal can be adopted, including but not limited to stainless steel, copper, aluminum, nickel, nickel, titanium, or silver, etc. The composite current collector can include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0110] In some embodiments, the positive electrode film layer includes the positive electrode active material.

[0111] As an example, the positive electrode active material can include at least one of a lithium-containing phosphate, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a battery positive electrode active material can also be used. These positive electrode active materials can be used alone only one or two or more can be used in combination. Among them, examples of the lithium-containing phosphate can include, but are not limited to, at least one of lithium iron phosphate (such as LiFeP04 (which can also be referred to simply as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnP04), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite of lithium manganese iron phosphate and carbon. Examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide (such as LiCo02), lithium nickel oxide (such as LiNi02), lithium manganese oxide (such as LiMn02, LiMn204), 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 O2 (which can also be referred to simply as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (which can also be referred to simply as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (which can also be referred to simply as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (which can also be referred to simply as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (which can also be referred to simply as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.8 Co 0.15 Al 0.05 O2), and modified compounds thereof, etc. The modified compound refers to a substance obtained by a modification means such as doping or coating on the basis of the above-mentioned substance.

[0112] In some embodiments, the positive electrode film layer further includes other conductive agents and / or binders.

[0113] As an example, the other conductive agent includes one or more of carbon black, carbon dots, graphene, or carbon nanofibers.

[0114] As an example, the carbon black includes one or more of acetylene black, Ketjen black, or Super P.

[0115] As an example, the binder includes one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene-fluorotetrafluoroethylene-propylene terpolymer, a vinylidene-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, or a fluorine-containing acrylate resin.

[0116] [Preparation of the positive electrode sheet]

[0117] In some embodiments, the method for preparing the positive electrode sheet includes:

[0118] (1) dissolving positive electrode materials, such as positive electrode active materials, carbon nanotubes, tungsten-containing materials, other conductive agents, binders, and other optional components, in solvents (such as N-methylpyrrolidone, etc.) according to different formulation amounts to form different layers of positive electrode slurries;

[0119] (2) coating each of the positive electrode slurries on a positive electrode current collector (such as an aluminum foil, etc.) according to different contents of carbon nanotubes and tungsten-containing materials to form different positive electrode film layers, and then performing drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0120] In some embodiments, the method for preparing the positive electrode sheet includes:

[0121] (1) dissolving carbon nanotubes and tungsten-containing materials in solvents (such as N-methylpyrrolidone, etc.) to form an additional slurry;

[0122] dissolving positive electrode materials, such as positive electrode active materials, the additional slurry, other conductive agents, binders, and other optional components, in solvents (such as N-methylpyrrolidone, etc.) according to different formulation amounts to form different layers of positive electrode slurries;

[0123] (2) coating each of the positive electrode slurries on a positive electrode current collector (such as an aluminum foil, etc.) according to different contents of carbon nanotubes and tungsten-containing materials to form different positive electrode film layers, and then performing drying, cold pressing, and slitting to obtain the positive electrode sheet.

[0124] In the technical solution of the embodiments of the present application, the above process can first prepare the additional slurry, and then design the proportion of the additional slurry in the positive electrode slurry according to the proportion of carbon nanotubes and tungsten elements in different positive electrode film layers, thereby simplifying the process operation and saving labor costs.

[0125] [Negative electrode sheet]

[0126] In some embodiments, the negative electrode can be a negative electrode tab; a preparation method of the negative electrode tab includes: dissolving a negative electrode material, such as a negative electrode active material (for example, graphite, etc.), a conductive agent (for example, carbon black, etc.), a binder, and other optional components (for example, a thickening agent, such as carboxymethyl cellulose (CMC) or a salt thereof, etc.) in a solvent (for example, deionized water, etc.) to form a negative electrode slurry, coating the negative electrode slurry on a negative electrode current collector (for example, a copper foil, etc.), and performing drying, cold pressing, and slitting to obtain the negative electrode tab.

[0127] [Separator]

[0128] In some embodiments, the battery cell further includes a separator, which is arranged between the positive electrode tab and the negative electrode tab.

[0129] For example, the separator can be arranged in multiple pieces, each arranged between any adjacent positive electrode tab or negative electrode tab.

[0130] For example, the separator can be arranged continuously, for example, by folding or winding, between any adjacent positive electrode tab or negative electrode tab.

[0131] In some embodiments, the separator is a separator film. The type of the separator film is not particularly limited in the present application, and any known porous structure separator film with good chemical stability and mechanical stability can be selected.

[0132] For example, the main material of the separator film can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, and ceramic. The separator film can be a single-layer film or a multi-layer composite film, and is not particularly limited. When the separator film is a multi-layer composite film, the materials of the layers can be the same or different, and are not particularly limited. The separator can be a separate component located between the positive electrode and the negative electrode, or can be attached to the surface of the positive electrode or the negative electrode. An inorganic particle coating layer, an organic particle coating layer, or an organic / inorganic composite coating layer can also be applied to the surface of the separator film.

[0133] In some embodiments, the separator is a solid-state electrolyte. The solid-state electrolyte is arranged between the positive electrode tab and the negative electrode tab, and simultaneously functions as an ion transmission and a separator for the positive electrode and the negative electrode.

[0134] [Electrolyte]

[0135] In some embodiments, the battery cell further includes an electrolyte. The electrolyte functions as an ion conductor between the positive electrode tab and the negative electrode tab. The type of the electrolyte is not particularly limited in the present application, and can be selected as required. The electrolyte can be in a liquid state, a gel state, or a solid state.

[0136] For example, the liquid electrolyte includes an electrolyte salt and a solvent.

[0137] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bisfluorosulfonimide, lithium bis-trifluoromethanesulfonimide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluoro oxalato borate, lithium bis-oxalato borate, lithium difluoro bis-oxalato phosphate, and lithium tetrafluoro oxalato phosphate.

[0138] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl 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, butyl sulfone, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent can also be selected from an ether solvent. The ether solvent can include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyl tetrahydrofuran, diphenyl ether, and a crown ether.

[0139] In some embodiments, the electrolyte solution can also optionally include an additive. For example, the additive can include a negative electrode film-forming additive, a positive electrode film-forming additive, an additive capable of improving certain performance of the battery cell, such as an additive capable of improving overcharge / fast charge performance of the battery cell, an additive capable of improving high-temperature performance of the battery cell, an additive capable of improving low-temperature performance of the battery cell, and the like.

[0140] In some embodiments, the gel-type electrolyte includes a polymer as a skeleton network and can be used in combination with an ionic liquid-lithium salt.

[0141] In some embodiments, the solid-state electrolyte includes a polymer solid-state electrolyte, an inorganic solid-state electrolyte, a composite solid-state electrolyte.

[0142] As an example, the polymer of the polymer solid-state electrolyte can include a polyether (polyethylene oxide), a polysiloxane, a polycarbonate, a polyacrylonitrile, a polyvinylidene fluoride, a polymethyl methacrylate, a single-ion polymer, a polyionic liquid, cellulose, or the like.

[0143] As an example, the inorganic solid-state electrolyte can be one or more of an oxide solid-state electrolyte (crystalline perovskite, sodium superionic conductor, garnet, amorphous LiPON thin film), a sulfide solid-state electrolyte (crystalline lithium superionic conductor (lithium germanium phosphorous sulfur, argyrodite), amorphous sulfide), and a halide solid-state electrolyte, a nitride solid-state electrolyte, and a hydride solid-state electrolyte.

[0144] As an example, the composite solid-state electrolyte is formed by adding an inorganic solid-state electrolyte filler to a polymer solid-state electrolyte.

[0145] [Battery Apparatus]

[0146] In some embodiments, the battery cell can include a housing. The housing can be a steel housing, an aluminum housing, a plastic housing (e.g., polypropylene), a composite metal housing (e.g., copper-aluminum composite housing), or an aluminum-plastic film, etc. In some embodiments, the housing can be a sealed structure or a non-sealed structure. As an example, when the housing is a non-sealed structure, the housing serves to protect the electrode assembly, and a sealing bag is further included between the housing and the electrode assembly, which is used to encapsulate the electrode assembly and the electrolyte. Specifically, the sealing bag can be a bag-shaped insulating member or an aluminum-plastic film. When the housing is a sealed structure, the housing is used to encapsulate the electrode assembly and the electrolyte, etc.

[0147] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a pouch battery cell, or a battery cell of other shapes, including a square battery cell, a blade battery cell, a multi-prismatic battery cell (e.g., a hexagonal battery cell), etc., without particular limitation.

[0148] In some embodiments, the housing includes an end cap and a housing body, the housing body is provided with an opening, and the end cap is provided on the opening. The housing body can be provided with one or more openings. The end cap can also be provided with one or more openings.

[0149] The battery apparatus mentioned in the embodiments of the present application can include one or more battery cell assemblies for providing voltage and capacity. The battery cell assembly can include a plurality of battery cells connected in series, in parallel, or in a mixed connection through a busbar component.

[0150] In some embodiments, the battery cell assembly is generally formed by arranging a plurality of battery cells.

[0151] As an example, the battery cell assembly can be a battery module, which is formed by arranging and fixing a plurality of battery cells into an independent module. As an example, the battery module can be formed by bundling a plurality of battery cells with a cable tie.

[0152] In some embodiments, the battery apparatus can be a battery pack, which includes a box body and one or more battery cell assemblies accommodated in the box body.

[0153] As an example, the battery cell assembly can be a battery module, which can be accommodated in the box body by fixing the battery module in the box body.

[0154] As an example, the battery cell assembly can also be accommodated in the case by directly fixing a plurality of battery cells to the case.

[0155] As an example, the case can include a first case and a second case. The first case and the second case are fastened so that an enclosed space is formed inside the case to accommodate the battery cell assembly. The enclosed here means covered or closed, which can be sealed or unsealed. The first case can be a top cover or a bottom plate.

[0156] As an example, the case can include a top cover, a frame, and a bottom plate. The top cover and the bottom plate are connected to the frame, respectively, so that an enclosed space is formed inside the case to accommodate the battery cell assembly.

[0157] In some embodiments, the case can be part of a chassis structure of a vehicle. For example, part of the case can be at least part of a floor of the vehicle, or part of the case can be at least part of a cross beam and a longitudinal beam of the vehicle.

[0158] [ Electric device ]

[0159] The application provides an electric device, which comprises the battery cell.

[0160] In some embodiments, the electric device comprises at least one of the battery module or the battery pack provided in any of the embodiments of the application.

[0161] The battery cell, the battery module, or the battery pack provided in the application can be used as a power source of the electric device, or can be used as an energy storage unit of the electric device. The electric device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., including but not limited to the above.

[0162] [Embodiment]

[0163] Embodiment 1

[0164] Positive electrode tab:

[0165] (1) Carbon nanotubes (CNT, aspect ratio 150, tube diameter 2.5 mm) and tungsten (W) are dissolved in a solvent N-methylpyrrolidone according to a mass ratio to obtain an additional slurry.

[0166] (2) Lithium iron phosphate, conductive carbon black, binder and additional slurry were dissolved in solvent N-methyl pyrrolidone by kneading stirring in different mass ratios to form first to 15th positive electrode slurries, and then the first to 15th positive electrode slurries were coated on the surface of 60 μm positive electrode current collector aluminum foil in turn, and after baking at 100 ℃ for 1 h, the coated and dried positive electrode slurry was cold-pressed to control the compaction density to be 2.6 g / cm 3 , and the positive electrode sheet was obtained after die cutting, wherein the mass of each positive electrode film layer was the same, and the mass ratio of conductive carbon black in each positive electrode film layer was 0.3% unchanged; the mass ratio of the binder in the first positive electrode film layer was 2%, and the mass ratio of the binder in each positive electrode film layer decreased proportionally along the direction away from the positive electrode current collector, and the total mass ratio of the binder in the positive electrode film layer was adjusted to 1.7%, and the mass ratio of CNT and W was designed by adjusting the mass ratio of the additional slurry to lithium iron phosphate and the mass ratio of CNT and W in the additional slurry, as shown in Tables 1 and 2.

[0167] Compaction density test method: the mass of the positive electrode sheet was weighed, and then divided by its area to obtain the area density, unit g / cm 3 ; the thickness of the rolled positive electrode sheet and the thickness of the positive electrode current collector were measured by using a thickness gauge (micrometer), and the compaction density = area density / (thickness of the rolled positive electrode sheet-current collector thickness).

[0168] Negative electrode sheet: artificial graphite, conductive carbon black, CMC and deionized water were uniformly dispersed in a ratio of 95:2:3:100, coated on a 6 μm negative electrode current collector copper foil, and cold-pressed after coating and drying to control the compaction density to be 1.55 g / cm 3 , die cutting, to obtain a negative electrode sheet.

[0169] Separator film: a polyethylene film with a thickness of 15 μm was used as a separator film base film, a 1 μm ceramic layer on the surface of the separator film base film, and a 2 μm adhesive layer on the surface of the ceramic layer; specifically, ceramic particles and a binder were sprayed on the surface of the polyethylene film in turn, the ceramic material was boehmite, accounting for 39 wt% of the total mass of the separator film; the binder was polyacrylate, accounting for 5 wt% of the total mass of the separator film, to obtain a separator film.

[0170] Electrolyte: ethylene carbonate, diethyl carbonate, dimethyl carbonate were mixed in a volume ratio of 1:1:1, and lithium hexafluorophosphate LiPF6 was dissolved in the above solution to obtain an electrolyte. The electrolyte concentration was 1 mol / L.

[0171] Assembly: the positive electrode sheet, the separator film and the negative electrode sheet were stacked and wound in order to obtain a battery cell; the battery cell was placed in an outer package, electrolyte was added, and after processes such as vacuum packaging, standing, formation, shaping and capacity, a battery monomer was formed.

[0172] Examples 2-8 and Comparative Examples 1-2

[0173] The battery cells were prepared according to the method of Example 1, except for the parameters of Table 1-Table 2.

[0174] Table 1

[0175]

[0176] Table 1-continued

[0177]

[0178] Table 1-continued

[0179]

[0180] Table 1-continued

[0181]

[0182]

[0183] Table 1-continued

[0184]

[0185] Table 1-continued

[0186]

[0187] In Table 1, under the column of the first positive electrode film layer to the nth positive electrode film layer, the mass content of CNT is based on the total mass of CNT in the positive electrode film layer; the mass content of W is based on the total mass of W in the positive electrode film layer. Based on the mass of the first positive electrode film layer, the mass content of CNT therein = the mass content of CNT in Table 1 x the total mass content of CNT in Table 2, and the mass content of CNT in the remaining positive electrode film layers is the same, and the same applies to W, which is not described here.

[0188] Table 2

[0189]

[0190]

[0191] In Table 2, under the column of the positive electrode film layer, CNT and W are based on the total mass of the positive electrode film layer.

[0192] Comparative Example 1 differs from Example 1 in that each positive electrode film layer does not include tungsten and carbon nanotubes, and the rest is the same as Example 1.

[0193] Comparative Example 2 differs from Example 1 in that the mass content of tungsten gradually decreases in the direction away from the positive electrode current collector.

[0194] [Performance test]

[0195] (1) Fast charging capability:

[0196] The battery cell was placed at 25°C, and after constant current charging to 3.8V at 0.33C rate, constant voltage charging to 0.05C current, standing for 5 min, constant current discharging to 2.5V at 0.33C, the constant current discharge capacity was recorded as the initial capacity CO.

[0197] The battery cell was sequentially charged at 0.5CO, 1CO, 1.5CO, 2CO, 2.5CO, 3CO, 3.5CO constant current to full cell potential 3.8V or negative electrode cut-off potential 0mV (any one of which represents the completion of charging), and after each charging was completed, it was discharged to 2.5V at 0.33CO. Every 10% SOC (from 10% SOC to 80% SOC), the corresponding negative electrode potential under different charging rates was recorded, and the rate negative electrode potential curve under different SOC was drawn, and the charging rate corresponding to the negative electrode potential of 0mV under different SOC was obtained by linear fitting, denoted as Cx (x = 2-8).

[0198] According to the formula: (1 / C2+1 / C3+1 / C4+1 / C5+1 / C6+1 / C7+1 / C8) x 0.1 x 60, the charging time T (min) of the battery cell from 10% SOC to 80% SOC was calculated. The shorter the time, the better the fast charging performance of the battery cell.

[0199] (2) Power test: At 25°C, the battery cell was discharged for 30s using 1000A battery cell, and the lower limit of the battery cell at the end of discharge was set to 2.0V. By continuously adjusting the current, the end-of-discharge voltage was just reached to the lower limit voltage, and the current at this time was taken as the maximum current to calculate the battery power. The calculation formula is: P = I max x U 下限 .

[0200] (3) Cycle performance: The battery cell was placed at 25°C, and using a fixed clamp, it was first charged to 3.8V at 0.33C rate, then charged to 0.05C current, and then discharged to 2.5V at 0.33C, and the constant current discharge capacity was recorded as the initial capacity CO. Then, using a specific charging window, it was charged to 3.8V at a constant current, and then discharged to 2.5V at 0.33C, and the constant current discharge capacity was recorded as the reversible capacity CX. The capacity retention rate of the battery cell was obtained = CX / CO, and the cycle performance of the battery cell was represented by the capacity retention rate of the battery cell.

[0201] (4) Energy density: the battery monomer was placed under the condition of 25℃, and after constant current charging to 3.8V at 0.33C rate, constant voltage charging to 0.05C, standing for 5min, constant current discharging to 2.5V at 0.33C, the initial capacity Co was recorded as the constant current discharge capacity. The discharge energy E (in Wh) was measured; the mass M (in kg) of the test object was measured; the discharge energy density PED (in Wh / kg) of the test object was calculated, and the calculation formula was: PED = Eaverage / M

[0202] The test results are summarized in Table 3.

[0203] Table 3

[0204]

[0205] From the analysis of Comparative Example 1-2 and Example 1, it can be seen that the fast charging capability, power and cycle performance of Comparative Example 1-2 are all not as good as those of Example 1, which proves that adding tungsten element in the positive electrode film layer, and gradually increasing the mass content of tungsten element in the positive electrode film layer along the direction away from the positive electrode current collector, is more beneficial to improve the performance of the battery monomer.

[0206] From the analysis of Example 6 and Example 1, it can be seen that the fast charging capability, power and cycle performance of Example 6 are all not as good as those of Example 1, which proves that the total mass content of tungsten element in the positive electrode film layer is within 3%, which is more beneficial to improve the performance of the battery monomer.

[0207] From the analysis of Example 7 and Example 1, it can be seen that the fast charging capability, power and cycle performance of Example 7 are all not as good as those of Example 1, which proves that gradually increasing the mass content of carbon nanotubes in the positive electrode film layer along the direction away from the positive electrode current collector is more beneficial to improve the performance of the battery monomer.

[0208] From the analysis of Example 8 and Example 1, it can be seen that the fast charging capability, power and cycle performance of Example 8 are all not as good as those of Example 1, which proves that the total mass content of carbon nanotubes in the positive electrode film layer is within 1%, which is more beneficial to improve the performance of the battery monomer.

[0209] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than limit them. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be replaced equivalently. Such modifications or replacements do not change the essence of the corresponding technical solutions, which should be covered in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural conflict. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A battery cell, characterized by, The battery cell comprises a positive electrode sheet; The positive electrode sheet comprises a positive electrode current collector, and a positive electrode film layer arranged on at least one surface of the positive electrode current collector; The positive electrode film layer comprises carbon nanotubes and tungsten elements, and the carbon nanotubes are arranged on the surface of the tungsten elements; From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the positive electrode film layer comprises a first positive electrode film layer to an n-th positive electrode film layer in sequence, and n is a positive integer greater than or equal to 2. From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the mass percentage of the tungsten elements in each positive electrode film layer gradually increases.

2. The battery cell of claim 1, wherein, The total mass of the tungsten elements and the carbon nanotubes is less than or equal to 3% based on the total mass of the positive electrode film layer.

3. The battery cell according to claim 1 or 2, characterized in that, The mass ratio of the tungsten elements and the carbon nanotubes in each positive electrode film layer is (0.5-2.5):1 independently.

4. The battery cell of claim 1, wherein, The total mass of the tungsten elements is less than or equal to 3% based on the total mass of the positive electrode film layer.

5. The battery cell of claim 4, wherein, The total mass of the tungsten elements is less than or equal to 2% based on the total mass of the positive electrode film layer.

6. The battery cell of claim 1, wherein, The mass content of the tungsten elements in the first positive electrode film layer is 0.2%-5% based on the total mass of the tungsten elements in the positive electrode film layer.

7. The battery cell of claim 1, wherein, The mass content of the tungsten elements in the n-th positive electrode film layer is 0.8%-12% based on the total mass of the tungsten elements in the positive electrode film layer.

8. The battery cell of claim 1, wherein, From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the mass percentage of the carbon nanotubes in each positive electrode film layer gradually increases.

9. The battery cell of claim 1, wherein, The total mass of the carbon nanotubes is less than or equal to 1% based on the total mass of the positive electrode film layer.

10. The battery cell of claim 1, wherein, The mass content of the carbon nanotubes in the first positive electrode film layer is 0.1%-6% based on the total mass of the carbon nanotubes in the positive electrode film layer.

11. The battery cell of claim 1, wherein, The mass content of the carbon nanotubes in the n-th positive electrode film layer is 0.4%-15% based on the total mass of the carbon nanotubes in the positive electrode film layer.

12. The battery cell of claim 1, wherein, n is a positive integer greater than or equal to 2 and less than or equal to 50.

13. The battery cell of claim 12, wherein, n is a positive integer greater than or equal to 10 and less than or equal to 30.

14. The battery cell of claim 1, wherein, The thickness of the positive electrode film layer is 0.05-0.3 mm.

15. The battery cell of claim 1, wherein, The carbon nanotubes comprise single-walled carbon nanotubes.

16. The battery cell of claim 1, wherein, The aspect ratio of the carbon nanotubes is 50-300; and / or; The tube diameter of the carbon nanotubes is 1-5 mm.

17. A battery device characterized by comprising: The battery device comprises a plurality of battery cells according to any one of claims 1-16.

18. An electrical device, comprising: The electric device comprises the battery cell according to any one of claims 1-16, or the battery device according to claim 17.

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