Battery cell, battery device and electric device

Abstract

The invention relates to the technical field of batteries, in particular to a single battery, a battery device and a power utilization device. The positive pole piece comprises a positive current collector and a positive film layer arranged on at least one surface of the positive current collector; the positive electrode film layer comprises a carbon nano tube and a tungsten element, and the carbon nano tube is located on the surface of the tungsten element; the positive electrode film layers sequentially comprise a first positive electrode film layer to an nth positive electrode film layer from the position close to the positive electrode current collector to the position far away from the positive electrode current collector, and n is a positive integer larger than or equal to 2; and the mass ratio of the tungsten element in each positive electrode film layer is gradually increased from the direction close to the positive electrode current collector to the direction far away from the positive electrode current collector. The battery monomer provided by the invention has the advantages of good quick charge capacity, high power and good cycle performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a battery cell, a battery device and an electrical device. Background Art

[0002] At present, hybrid vehicles have higher requirements for the energy density of battery cells in order to obtain battery cells with excellent comprehensive performance. Therefore, it is crucial to develop a battery cell with good fast charging capability, high power and good cycle performance. Summary of the invention

[0003] In view of the above problems, the present application provides a battery cell, a battery device and an electrical device, wherein the battery cell has the advantages of good fast charging capability, high power and good cycle performance.

[0004] In a first aspect, the present application provides a battery cell, the battery cell comprising a positive electrode sheet;

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

[0006] The positive electrode film layer includes 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 includes the first positive electrode film layer to the nth positive electrode film layer in sequence, where 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 proportion of the tungsten element in each positive electrode film layer gradually increases.

[0009] In the technical scheme of the implementation mode of the present application, carbon nanotubes are arranged in the positive electrode film layer. Due to their excellent electrical conductivity and the easy formation of a three-dimensional conductive network in the positive electrode film layer, the electron transmission speed between the positive electrode plate and the electrolyte can be increased, the internal resistance of the battery cell can be reduced, and the power performance of the battery cell can be improved; at the same time, the deintercalation of active ions can be promoted, the kinetic performance of the battery cell can be improved, and the fast charging capability and cycle performance of the battery cell can be improved; the reasons why tungsten element is also arranged in the positive electrode film layer of the present application are mainly the following two points: first, the tungsten element is located in the mid-band gap state above the valence band maximum value, that is, in the band gap region between the valence band top and the conduction band bottom of the semiconductor, which can enhance the electronic conductivity of the positive electrode plate 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 practical applications, the long and slender structure of the carbon nanotubes can restrain the positive While the active material reduces the rebound of the pole piece, as the use time increases, the structure may pierce the solid electrolyte membrane. Since the tungsten element has the characteristics of preferential orientation, the carbon nanotubes are located on its surface, reducing the possibility of carbon nanotubes damaging the solid electrolyte membrane. Moreover, the tungsten element can reduce the possibility of side reactions between the carbon nanotubes 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 current collector, the mass proportion of tungsten elements in each positive electrode film layer gradually increases, which is conducive to increasing the electron transition and exchange between the outer surface of the electrode pole piece and the electrolyte, and further improving the comprehensive performance of the battery cell. At the same time, the design of the above-mentioned multilayer structure can relatively accurately regulate the performance of the positive pole piece as needed, optimize the microstructure of the positive pole piece, and improve the reliability and stability of the further formed battery cell performance. In short, this application is conducive to obtaining a battery cell with good fast charging capability, high power and good cycle performance through the combination of carbon nanotubes and tungsten elements.

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

[0011] In the technical solution of the implementation mode of the present application, in the positive electrode film layer, the total mass proportion of tungsten element and carbon nanotubes is within the above range; the mass proportion of main materials such as positive electrode active material and binder can be maintained in a relatively high range, which is beneficial to the full play of the positive electrode active material on the one hand, so that the capacity of the battery cell is higher and the basic performance of the battery cell is met; on the other hand, it is beneficial to the full play of the binder, reducing the situation of powder falling off of the electrode due to insufficient adhesion of the electrode, and reducing the possibility of high internal resistance of the battery cell and reduced power of the battery cell.

[0012] In some embodiments, in the first positive electrode film layer to the nth positive electrode film layer, the mass ratio of the tungsten element to the carbon nanotubes in each positive electrode film layer is independently (0.5-2.5):1.

[0013] In the technical solution of the embodiment of the present application, the mass ratio of tungsten element and carbon nanotubes in each positive electrode film layer is within the above range. The two cooperate with each other, and the formed positive electrode plate has high stability, which is conducive to improving the overall performance of the battery cell; especially when it is necessary to meet the basic requirements of the positive electrode film layer for the content of positive electrode active materials, within the above mass ratio range, the mass content of tungsten element and carbon nanotubes can be set within an appropriate range, and the energy density and capacity of the battery cell are high, so as to improve the overall performance of the battery cell.

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

[0015] In the technical solution of the embodiment of the present application, the mass proportion of tungsten in the positive electrode film layer is within the above range. The reason is that within this range, tungsten can cooperate well with carbon nanotubes in the system to improve the performance of the battery cell, and the mass proportion of the main material can still be maintained at a relatively high level, and there will be basically no adverse effects on battery performance due to the loss of the main material.

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

[0017] In the technical solution of the embodiment of the present application, based on the total mass of tungsten in the positive electrode film layer, the mass content of tungsten in the first positive electrode film layer is within the above range, that is, the proportion of tungsten in the innermost 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 this range, the content of tungsten in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can meet the basic requirements of good coordination with carbon nanotubes on the one hand; on the other hand, it has little effect on the mass proportion of tungsten in other positive electrode film layers. The proportion of tungsten in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient tungsten content in some positive electrode film layers, especially to meet the mass proportion requirements of tungsten in the outermost positive electrode film layer.

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

[0019] In the technical solution of the embodiment of the present application, based on the total mass of tungsten in the positive electrode film layer, the mass content of tungsten in the nth positive electrode film layer is within the above range, 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 this range, the electron transition and exchange between the outer surface of the positive electrode plate and the electrolyte are sufficient, which is conducive to improving the comprehensive performance of the battery cell; moreover, within this range, the mass proportion of tungsten in other positive electrode film layers is less affected, and the proportion of tungsten in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient tungsten content in some positive electrode film layers.

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

[0021] In the technical solution of the implementation mode of the present application, the mass proportion of carbon nanotubes in each positive electrode film layer gradually increases along 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 plate and the electrolyte, and improves the charge and discharge performance, cycle performance and rate performance of the battery cell.

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

[0023] In the technical solution of the embodiment 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 this range, the carbon nanotubes can fully play their 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 there will be basically no adverse effects on battery performance due to the loss of the main material.

[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 embodiment of the present application, based on the total mass of carbon nanotubes in the positive electrode film layer, the mass content of carbon nanotubes in the first positive electrode film layer is within the above range, that is, the proportion of carbon nanotubes in the innermost positive electrode film layer to the total content of carbon nanotubes in the positive electrode film layer is within the above range. The reason is that within this range, the carbon nanotube content in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can basically meet the requirements of the positive electrode film layer for its content, thereby achieving the effect of improving the performance of the battery cell; on the other hand, it has little effect on the mass proportion of carbon nanotubes in other positive electrode film layers. The proportion of carbon nanotubes in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient carbon nanotube content in some positive electrode film layers, especially to meet the requirements for the mass proportion of carbon nanotubes in the outermost positive electrode film layer.

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

[0027] In the technical solution of the embodiment of the present application, based on the total mass of carbon nanotubes in the positive electrode film layer, the mass content of carbon nanotubes in the nth positive electrode film layer is within the above range, that is, the proportion of carbon nanotubes in the outermost positive electrode film layer to the total content of carbon nanotubes in the positive electrode film layer is within the above range. The reason is that within this range, the electron transition and exchange between the outer surface of the positive electrode plate and the electrolyte are sufficient, which is conducive to improving the comprehensive performance of the battery cell; moreover, within this range, the mass proportion of carbon nanotubes in other positive electrode film layers is less affected, and the proportion of carbon nanotubes in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient carbon nanotube content in some positive electrode film layers.

[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 embodiment of the present application, the value of n is within the above range. The tungsten elements and carbon nanotubes between different positive electrode film layers cooperate with each other, which is conducive to improving the fast charging ability, power and cycle performance of the battery cell; moreover, the processing difficulty of the positive electrode film layer within the above range of layers is relatively low, which can reduce the adverse effects of the processing technology limitations on the performance of the battery cell.

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

[0031] In the technical solution of the implementation mode of the present application, the thickness of the positive electrode film layer is within the above range, which can meet the high energy density requirements of the battery cell, and the diffusion path of the active ions is relatively short. The formed battery cell has the characteristics of good fast charging capability, high power and good cycle performance, and has excellent comprehensive performance.

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

[0033] In the technical solution of the implementation mode of the present application, single-walled carbon nanotubes have excellent conductivity and are easy to form a long-range conductive network, which is beneficial to improving the fast charging capability, power and cycle performance of the battery cell.

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

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

[0036] In the technical solution of the implementation mode of the present application, the aspect ratio of the carbon nanotubes is within the above-mentioned range, and can be more evenly distributed in the positive electrode film layer to form a good conductive network, and can also reduce the adverse effects of self-agglomeration on the battery cell; and the carbon nanotubes within the above-mentioned aspect ratio range can be better distributed in the multiple layers of relatively thin positive electrode film layers. As the use time increases, the structural damage to the solid electrolyte membrane is lower, which is more conducive to improving the fast charging capability, power and cycle performance of the battery cell, and improving its overall performance.

[0037] In a second aspect, the present application provides a battery device, comprising a plurality of battery cells as described in the first aspect.

[0038] In a third aspect, the present application provides an electrical device, which includes the battery cell described in the first aspect, or the battery device described in the second aspect.

[0039] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. DETAILED DESCRIPTION

[0040] The following is a detailed description of the embodiments of the technical solution of the present application. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0041] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the description and claims of this application and any variations thereof are intended to cover non-exclusive inclusions.

[0042] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0043] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0044] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and 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 the particular range. The range defined in this way can be inclusive or exclusive of the end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "2-10" means that all real numbers between "2-10" are listed in this document, and "2-10" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0045] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0046] At present, the requirements for the comprehensive performance of battery cells are becoming increasingly higher, especially the comprehensive requirements for fast charging capability, power and cycle performance.

[0047] The present application uses carbon nanotubes and tungsten elements to set up multiple positive electrode films, and designs the content variation of tungsten elements in the positive electrode films to obtain a battery cell with good fast charging capability, high power and good cycle performance. The present application provides a battery cell, a battery device and an electrical device.

[0048] [Battery Cell]

[0049] In the embodiment of the present application, the battery cell may be a secondary battery. A secondary battery refers to a battery cell that can be continuously used by activating active materials by charging after the battery cell is discharged.

[0050] The battery cell 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 storage battery, etc., which is not limited in the embodiments of the present application.

[0051] [Electrode assembly]

[0052] A battery cell generally includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, which is arranged between the negative electrode and the positive electrode. During the charge and discharge process of the battery cell, active ions (such as lithium ions or sodium ions) are embedded and removed back and forth between the positive electrode and the negative electrode. The separator is arranged between the positive electrode and the negative electrode to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0053] The electrode assembly may be a wound structure, a laminated structure, or a mixed structure of a wound structure and a laminated structure.

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

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

[0056] As an example, a plurality of positive electrode sheets and a plurality of negative electrode sheets may be provided respectively, and the plurality of positive electrode sheets and the plurality of negative electrode sheets may be alternately stacked.

[0057] As an example, a plurality of positive electrode sheets may be provided, and the negative electrode sheet is folded to form a plurality of stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0058] As an example, both the positive electrode sheet and the negative electrode sheet are folded to form a plurality of stacked folded sections.

[0059] In some embodiments, the shape of the electrode assembly can be cylindrical, flat, or polygonal.

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

[0061] [Positive electrode]

[0062] In some embodiments, the positive electrode may be a positive electrode plate. The present application provides a battery cell, the battery cell comprising a positive electrode plate;

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

[0064] The positive electrode 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 electrode current collector to the direction away from the positive electrode current collector, the positive electrode film layer includes the first positive electrode film layer to the nth positive electrode film layer in sequence, where n is a positive integer greater than or equal to 2;

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

[0067] In this application, the structure, composition and changes in the mass ratio of tungsten element of the positive electrode film layer are analyzed by the following method:

[0068] (1) Structure of the positive electrode film layer: Use an optical electron microscope such as a scanning electron microscope (model Zeiss Sigma360) or a transmission electron microscope (model JEOL JEM-ARM200F(C)-NEO ARM) to observe the cross-sectional morphology of the positive electrode sheet. Specifically, disassemble the battery cell, take out the positive electrode sheet, use laser cleaning technology to peel off the positive electrode film layer, and then bombard the cross section of the material sample with argon ion polishing technology to obtain a flat polished cross section. Then, use a scanning electron microscope to observe and analyze the microscopic characteristics of the internal structure of the sample to determine whether the positive electrode film layer is a multilayer structure, whether carbon nanotubes exist, and the distribution area of ​​tungsten elements.

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

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

[0071] By combining the cross-sectional morphology with the results obtained from the energy spectrum test, we can analyze the composition of different layers of raw materials and the proportion of tungsten in the sample.

[0072] In the technical solution of the implementation mode of the present application, carbon nanotubes are arranged in the positive electrode film layer. Due to their excellent electrical conductivity and the easy formation of a three-dimensional conductive network in the positive electrode film layer, the electron transmission speed between the positive electrode plate and the electrolyte can be increased, the internal resistance of the battery cell can be reduced, and the power performance of the battery cell can be improved; at the same time, the deintercalation of active ions can be promoted, the kinetic performance of the battery cell can be improved, and the fast charging capability and cycle performance of the battery cell can be improved; the reasons why tungsten element is also arranged in the positive electrode film layer of the present application are mainly the following two points: first, the tungsten element is located in the mid-band gap state above the valence band maximum value, that is, in the band gap region between the valence band top and the conduction band bottom of the semiconductor, which can enhance the electronic conductivity of the positive electrode plate 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, the long and slender structure of the carbon nanotubes can restrain the positive electrode active While the material reduces the rebound of the pole piece, as the use time increases, the structure may pierce the solid electrolyte membrane. Since the tungsten element has the characteristics of preferential orientation, the carbon nanotubes are located on its surface, reducing the possibility of carbon nanotubes damaging the solid electrolyte membrane. Moreover, the tungsten element can reduce the possibility of side reactions between the carbon nanotubes 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 current collector, the mass proportion of tungsten elements in each positive electrode film layer gradually increases, which is conducive to increasing the electron transition and exchange between the outer surface of the electrode pole piece and the electrolyte, and further improving the comprehensive performance of the battery cell. At the same time, the design of the above-mentioned multilayer structure can relatively accurately regulate the performance of the positive pole piece as needed, optimize the microstructure of the positive pole piece, and improve the reliability and stability of the further formed battery cell performance. In short, this application is conducive to obtaining a battery cell with good fast charging capability, high power and good cycle performance through the combination of carbon nanotubes and tungsten elements.

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

[0074] In the technical solution of the embodiment of the present application, in the positive electrode film layer, the total mass proportion of tungsten element and carbon nanotubes is within the above range; the mass proportion of main materials such as positive electrode active material and binder can be maintained in a relatively high range, which is beneficial to the full play of the positive electrode active material on the one hand, so that the capacity of the battery cell is higher and the basic performance of the battery cell is met; on the other hand, it is beneficial to the full play of the binder, reducing the situation of powder falling off of the electrode due to insufficient adhesion of the electrode, and reducing the possibility of high internal resistance of the battery cell and reduced power of the battery cell.

[0075] In some embodiments, in the first positive electrode film layer to the nth positive electrode film layer, the mass ratio of the tungsten element and the carbon nanotubes in each positive electrode film layer is independently (0.5-2.5):1, optionally (0.6-1.5):1, wherein 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 the present application, the tungsten element exists in the positive electrode film layer in the form of a tungsten-containing material such as tungsten element or tungsten compound, wherein the mass ratio of the above tungsten element and the carbon nanotubes is calculated by the mass of the tungsten element or the tungsten compound according to the molecular weight of the tungsten element in the overall compound, and then the mass ratio of the tungsten element to the carbon nanotubes is designed. The mass content of the tungsten element in the following text is similar to the above description and will not be repeated one by one.

[0077] In the present application, tungsten element or tungsten compound can be a commercial product, or it can be purified from tungsten ore. The present application does not limit the type of tungsten ore. For example, the tungsten ore can include any one of scheelite, wolframite or wolframite, or a combination of at least two of them. The purification method of tungsten ore itself can be a method known in the art.

[0078] As an example, the method of obtaining tungsten element or tungsten compound by using tungsten ore specifically includes the following steps:

[0079] Tungsten ore (such as scheelite) and a reducing agent are dispersed in a solvent (such as ethylene glycol solution, etc.) and mixed evenly, and then rinsed with water and dried to obtain tungsten element or tungsten compound.

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

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

[0082] In the technical solution of the embodiment of the present application, the mass ratio of tungsten element and carbon nanotubes in each positive electrode film layer is within the above range. The two cooperate with each other, and the formed positive electrode plate has high stability, which is conducive to improving the overall performance of the battery cell; especially when it is necessary to meet the basic requirements of the positive electrode film layer for the content of positive electrode active materials, within the above mass ratio range, the mass content of tungsten element and carbon nanotubes can be set within an appropriate range, and the energy density and capacity of the battery cell are high, so as to improve the overall performance of the battery cell.

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

[0084] In the technical solution of the embodiment of the present application, the mass percentage of tungsten in the positive electrode film layer is within the above range. The reason is that within this range, tungsten can cooperate well with carbon nanotubes in the system to improve the performance of the battery cell, and the mass percentage of the main material can still be maintained at a relatively high level, and there will be basically no adverse effects on battery performance due to the loss of the main material.

[0085] In some embodiments, based on the total mass of tungsten elements in the positive electrode film layer, the mass content of tungsten elements 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.

[0086] In the technical solution of the embodiment of the present application, based on the total mass of tungsten in the positive electrode film layer, the mass content of tungsten in the first positive electrode film layer is within the above range, that is, the proportion of tungsten in the innermost 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 this range, the content of tungsten in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can meet the basic requirements of good coordination with carbon nanotubes on the one hand; on the other hand, it has little effect on the mass proportion of tungsten in other positive electrode film layers. The proportion of tungsten in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient tungsten content in some positive electrode film layers, especially to meet the mass proportion requirements of tungsten in the outermost positive electrode film layer.

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

[0088] In the technical solution of the embodiment of the present application, based on the total mass of tungsten in the positive electrode film layer, the mass content of tungsten in the nth positive electrode film layer is within the above range, 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 this range, the electron transition and exchange between the outer surface of the positive electrode plate and the electrolyte are sufficient, which is conducive to improving the comprehensive performance of the battery cell; moreover, within this range, the mass proportion of tungsten in other positive electrode film layers is less affected, and the proportion of tungsten in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient tungsten content in some positive electrode film layers.

[0089] In some embodiments, based on the total mass of tungsten elements in the positive electrode film layer, the mass content difference of tungsten elements in adjacent positive electrode film layers can be designed as needed. For example, it can be 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 embodiment of the present application, the mass proportion of carbon nanotubes in each positive electrode film layer gradually increases along 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 plate and the electrolyte, and improves the charge and discharge performance, cycle performance and rate performance of the battery cell.

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

[0093] In the technical solution of the embodiment 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 this range, the carbon nanotubes can fully play their 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 there will be basically no adverse effects on battery performance due to the loss of the main material.

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

[0095] In the technical solution of the embodiment of the present application, based on the total mass of carbon nanotubes in the positive electrode film layer, the mass content of carbon nanotubes in the first positive electrode film layer is within the above range, that is, the proportion of carbon nanotubes in the innermost positive electrode film layer to the total content of carbon nanotubes in the positive electrode film layer is within the above range. The reason is that within this range, the carbon nanotube content in the positive electrode film layer adjacent to the positive electrode current collector is appropriate, which can basically meet the requirements of the positive electrode film layer for its content, thereby achieving the effect of improving the performance of the battery cell; on the other hand, it has little effect on the mass proportion of carbon nanotubes in other positive electrode film layers. The proportion of carbon nanotubes in different positive electrode film layers can be designed as needed, and the number of positive electrode film layers can also be designed as needed to reduce the adverse effects on the performance of the battery cell due to insufficient carbon nanotube content in some positive electrode film layers, especially to meet the requirements for the mass proportion of carbon nanotubes in the outermost positive electrode film layer.

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

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

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

[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 embodiment of the present application, the value of n is within the above range. The tungsten elements and carbon nanotubes between different positive electrode film layers cooperate with each other, which is conducive to improving the fast charging ability, power and cycle performance of the battery cell; moreover, the processing difficulty of the positive electrode film layer within the above range is relatively low, which can reduce the adverse effects of the processing technology limitations on the performance of the battery cell.

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

[0102] In the technical solution 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 requirements of the battery cell, and the diffusion path of the active ions is relatively short. 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 single-walled carbon nanotubes may be selected.

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

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

[0107] In the technical solution of the embodiment of the present application, the aspect ratio of the carbon nanotubes is within the above-mentioned range, and can be more evenly distributed in the positive electrode film layer to form a good conductive network, and can also reduce the adverse effects of self-agglomeration on the battery cell; and the carbon nanotubes within the above-mentioned aspect ratio range can be better distributed in the multiple layers of relatively thin positive electrode film layers. As the use time increases, the structural damage to the solid electrolyte membrane is lower, which is more conducive to improving the fast charging capability, power and cycle performance of the battery cell, and improving its overall performance.

[0108] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material is disposed on either or both of the two facing surfaces of the positive electrode current collector.

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

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

[0111] As an example, the positive electrode active material may include at least one of the following materials: lithium-containing phosphates, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium-containing phosphates may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP), composite materials of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO 4 ), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and a composite material of lithium iron manganese phosphate and carbon. 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 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O 2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O 2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O 2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O 2 (also referred to as NCM811), 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. The modified compound refers to a substance obtained by modification means such as doping or coating on the basis of the above substances.

[0112] In some embodiments, the positive electrode film layer also 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), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, or fluorine-containing acrylate resin.

[0116] [Preparation of 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 arbitrary components in solvents (such as N-methylpyrrolidone, etc.) according to different formula amounts to form positive electrode slurries of different layers;

[0119] (2) The positive electrode slurries are sequentially coated on a positive electrode current collector (such as aluminum foil) according to the different contents of carbon nanotubes and tungsten-containing materials to form different positive electrode film layers, and the positive electrode sheets are obtained through drying, cold pressing and slitting.

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

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

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

[0123] (2) The positive electrode slurries are sequentially coated on a positive electrode current collector (such as aluminum foil) according to the different contents of carbon nanotubes and tungsten-containing materials to form different positive electrode film layers, and the positive electrode sheets are obtained through drying, cold pressing and slitting.

[0124] In the technical solution of the embodiment 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 ratio of carbon nanotubes and tungsten elements in different positive electrode film layers, thereby simplifying the process operation and saving labor costs.

[0125] [Negative electrode]

[0126] In some embodiments, the negative electrode can be a negative electrode sheet; the preparation method of the negative electrode sheet includes: dissolving a negative electrode material, such as a negative electrode active material (such as graphite, etc.), a conductive agent (such as carbon black, etc.), a binder and any other components (such as a thickener, such as carboxymethyl cellulose CMC or its salt, etc.) in a solvent (such as deionized water, etc.) to form a negative electrode slurry, coating the negative electrode slurry on a negative electrode collector (such as copper foil, etc.), and obtaining the negative electrode sheet through drying, cold pressing, and slitting.

[0127] [Isolator]

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

[0129] As an example, a plurality of separators may be provided, each of which is provided between any adjacent positive electrode sheets or negative electrode sheets.

[0130] As an example, the separator may be disposed continuously, and may be disposed between any adjacent positive electrode sheets or negative electrode sheets by folding or winding.

[0131] In some embodiments, the separator is a separator. The present application has no particular limitation on the type of separator, and any known separator with a porous structure having good chemical stability and mechanical stability can be selected.

[0132] As an example, the main material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, polyvinylidene fluoride, and ceramic. The separator can be a single-layer film or a multi-layer composite film, without special restrictions. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions. The separator can be a separate component located between the positive and negative electrodes, or it can be attached to the surface of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be coated on the surface of the separator.

[0133] In some embodiments, the separator is a solid electrolyte, which is disposed between the positive electrode sheet and the negative electrode sheet and plays the role of transmitting ions and isolating the positive and negative electrodes.

[0134] [Electrolytes]

[0135] In some embodiments, the battery cell further includes an electrolyte. The electrolyte plays a role in conducting ions between the positive electrode plate and the negative electrode plate. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. The electrolyte can be liquid, gel or solid.

[0136] 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 bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0138] 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, cyclopentane, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone. The solvent can also be selected from ether solvents. Ether solvents 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, methyltetrahydrofuran, diphenyl ether and crown ether.

[0139] In some embodiments, the electrolyte may further include additives, for example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain properties of battery cells, such as additives that improve overcharge / fast charge performance of battery cells, additives that improve high temperature performance of battery cells, additives that improve low temperature performance of battery cells, etc.

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

[0141] Among them, solid electrolytes include polymer solid electrolytes, inorganic solid electrolytes, and composite solid electrolytes.

[0142] As examples, the polymer of the polymer solid electrolyte may include polyether (polyethylene oxide), polysiloxane, polycarbonate, polyacrylonitrile, polyvinylidene fluoride, polymethyl methacrylate, a single ion polymer, a polyionic liquid, cellulose, and the like.

[0143] As an example, the inorganic solid electrolyte can be an oxide solid electrolyte (crystalline perovskite, sodium superconducting ion conductor, garnet, amorphous LiPON film), a sulfide solid electrolyte (crystalline lithium superion conductor (lithium germanium phosphosulfide, silver germanium sulfide), amorphous sulfide) and one or more of a halide solid electrolyte, a nitride solid electrolyte and a hydride solid electrolyte.

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

[0145] [Battery device]

[0146] In some embodiments, the battery cell may include a shell. The shell may be a steel shell, an aluminum shell, a plastic shell (such as polypropylene), a composite metal shell (such as a copper-aluminum composite shell) or an aluminum-plastic film, etc. In some embodiments, the shell may be a sealed structure or a non-sealed structure. As an example, when the shell is a non-sealed structure, the shell plays a role in protecting the electrode assembly, and a sealed bag is also included between the shell and the electrode assembly, and the sealed bag is used to encapsulate the electrode assembly and the electrolyte. Specifically, the sealed bag may be a bag-shaped insulating member or an aluminum-plastic film. When the shell is a sealed structure, it is used to encapsulate components such as the electrode assembly and the electrolyte.

[0147] As an example, the battery cell can be a cylindrical battery cell, a prismatic battery cell, a soft-pack battery cell or a battery cell of other shapes. The prismatic battery cell includes a square shell battery cell, a blade-shaped battery cell, a polygonal battery, such as a hexagonal battery, etc. There is no special limitation in this application.

[0148] In some embodiments, the housing includes an end cap and a shell, the shell is provided with an opening, and the end cap is provided to cover the opening. The shell may be provided with one or more openings. One or more end caps may also be provided.

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

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

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

[0152] In some embodiments, the battery device may be a battery pack, which includes a case and one or more battery cell assemblies, wherein the battery cell assemblies are accommodated in the case.

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

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

[0155] As an example, the box may include a first box and a second box. The first box and the second box are buckled together to form a closed space inside the box to accommodate the battery cell assembly. The closed here means covered or closed, which can be sealed or unsealed. The first box can be a top cover or a bottom plate.

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

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

[0158] [ Electrical devices ]

[0159] The present application provides an electrical device, which includes the battery cell.

[0160] In some embodiments, the power-consuming device includes at least one of the battery modules or battery packs provided in any embodiment of the present application.

[0161] The battery cell, battery module, or battery pack described in the present application can be used as a power source for the electrical device, or can be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., including but not limited to the above.

[0162] [Example]

[0163] Example 1

[0164] Positive electrode:

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

[0166] (2) Lithium iron phosphate, conductive carbon black, binder and additional slurry were dissolved in N-methylpyrrolidone solvent by kneading and stirring in different mass ratios to form the first positive electrode slurry to the 15th positive electrode slurry, and then the first positive electrode slurry to the 15th positive electrode slurry were sequentially coated on the surface of 60 μm positive electrode current collector aluminum foil, baked at 100° C. for 1 h, and then cold pressed after coating and drying to control the compaction density at 2.6 g / cm 3 , after die-cutting, a positive electrode sheet is obtained, wherein the mass of each positive electrode film layer is the same, and in each positive electrode film layer, the mass proportion of conductive carbon black is 0.3% unchanged; the mass proportion of the binder in the first positive electrode film layer is 2%, and the mass proportion of the binder in each positive electrode film layer decreases in proportion along the direction away from the positive electrode current collector, and the total mass proportion of the binder in the positive electrode film layer is adjusted to be 1.7%, and the mass proportion of CNT and W is designed by adjusting the ratio of the added slurry to lithium iron phosphate and the mass ratio of CNT and W in the added slurry, as shown in Table 1 and Table 2 for details.

[0167] Compaction density test method: weigh the mass of the positive electrode and divide it by its area to get the surface density in g / cm 3 ; Use a thickness gauge (micrometer) to measure the thickness of the electrode sheet and the thickness of the positive electrode current collector after rolling. The compaction density = surface density / (thickness of the electrode sheet after rolling - thickness of the current collector).

[0168] Negative electrode sheet: artificial graphite, conductive carbon black, CMC and deionized water are evenly dispersed in a ratio of 95:2:3:100, coated on a 6μm negative electrode current collector copper foil, dried and cold pressed, and the compaction density is controlled at 1.55g / cm 3 , die-cut to obtain the negative electrode sheet.

[0169] Isolation membrane: A polyethylene film with a thickness of 15 μm is used as the isolation membrane base membrane, a 1 μm ceramic layer is located on the surface of the isolation membrane base membrane, and a 2 μm bonding layer is located on the surface of the ceramic layer; specifically, ceramic particles and a bonding agent are sprayed on the surface of the polyethylene film in sequence, the ceramic material is boehmite, accounting for 39 wt% of the total mass of the isolation membrane; the bonding agent is polyacrylate, accounting for 5 wt% of the total mass of the isolation membrane, to obtain an isolation membrane.

[0170] Electrolyte: Mix ethylene carbonate, diethyl carbonate, and dimethyl carbonate in a volume ratio of 1:1:1, and add lithium hexafluorophosphate LiPF 6 Dissolved in the above solution to obtain an electrolyte solution with a concentration of 1 mol / L.

[0171] Assembly: The positive electrode sheet, separator, and negative electrode sheet are stacked and wound in order to obtain a battery cell; the battery cell is placed in an outer package, and electrolyte is added. After vacuum packaging, standing, formation, shaping, capacity and other processes, a battery cell is formed.

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

[0173] Except for the parameters in Tables 1 and 2, a battery cell was prepared according to the method of Example 1.

[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 columns 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 × the total mass content of CNT in Table 2. The mass content of CNT in the remaining positive electrode film layers is the same, and the mass content of W is the same, which will not be repeated here.

[0188] Table 2

[0189]

[0190]

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

[0192] The difference between Comparative Example 1 and Example 1 is that each positive electrode film layer does not include tungsten element and carbon nanotubes, and the rest is the same as Example 1.

[0193] The difference between Comparative Example 2 and Example 1 is that the mass content of the tungsten element 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, charged to 3.8V at a constant current of 0.33C, then charged at a constant voltage to a current of 0.05C, left for 5 minutes, and then discharged to 2.5V at a constant current of 0.33C. The constant current discharge capacity was recorded as the initial capacity C0.

[0197] The battery cells were charged with constant currents of 0.5C0, 1C0, 1.5C0, 2C0, 2.5C0, 3C0, and 3.5C0 in sequence to a full battery potential of 3.8V or a negative electrode cutoff potential of 0mV (achieving any one of these conditions indicates that charging is complete), and discharged with 0.33C0 to 2.5V after each charge. The negative electrode potential corresponding to different charge rates was recorded at every 10% SOC interval (from 10% SOC-80% SOC), and the negative electrode potential curves at different SOC rates were plotted. After linear fitting, the charge rate corresponding to the negative electrode potential of 0mV at different SOCs was obtained, which was recorded as Cx (x=2-8).

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

[0199] (2) Power test: At 25°C, use a 1000A battery cell to perform a 30s pulse discharge on the battery cell. Set the lower limit of the battery cell at the end of discharge to 2.0V. Continue to adjust the current until the end of discharge voltage just reaches the lower limit of discharge voltage. Use the current at this time as the maximum current to calculate the battery cell power. The calculation formula is: P = I max ×U 下限 .

[0200] (3) Cycle performance: Place the battery cell at 25°C and use a fixed fixture. First, charge it to 3.8V at a constant current of 0.33C, then charge it to a current of 0.05C at a constant voltage, leave it for 5 minutes, and then discharge it to 2.5V at a constant current of 0.33C. Record the constant current discharge capacity as the initial capacity C0. Then, charge it to 3.8V at a constant current of a specific charging window, leave it for 30 minutes, and then discharge it to 2.5V at a constant current of 0.33C. Record the constant current discharge capacity as the reversible capacity CX of the cycle. Obtain the cell capacity retention rate = CX / C0, and use the cell capacity retention rate to characterize the cycle performance of the cell.

[0201] (4) Energy density: Place the battery cell at 25°C, charge it to 3.8V at a constant current rate of 0.33C, charge it to a current of 0.05C at a constant voltage, leave it for 5 minutes, and then discharge it to 2.5V at a constant current of 0.33C. Record the constant current discharge capacity as the initial capacity C0. Measure the discharge energy E (in Wh); measure the mass M (in kg) of the test object; calculate the discharge energy density PED (in Wh / kg) of the test object. The calculation formula is: PED = E average / M

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

[0203] Table 3

[0204]

[0205] Analysis of comparative examples 1-2 and example 1 shows that the fast charging capability, power and cycle performance of comparative examples 1-2 are not as good as those of example 1, which proves that the addition of tungsten element in the positive electrode film layer and the gradual increase in the mass content of tungsten element in the positive electrode film layer away from the positive electrode current collector are more conducive to improving the performance of the battery cell.

[0206] Analysis of Example 6 and Example 1 shows that the fast charging capability, power and cycle performance of Example 6 are 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 conducive to improving the performance of the battery cell.

[0207] Analysis of Example 7 and Example 1 shows that the fast charging capability, power and cycle performance of Example 7 are not as good as those of Example 1, which proves that the mass content of carbon nanotubes in the positive electrode film layer gradually increases along the direction away from the positive electrode current collector, which is more conducive to improving the performance of the battery cell.

[0208] Analysis of Example 8 and Example 1 shows that the fast charging capability, power and cycle performance of Example 8 are 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 conducive to improving the performance of the battery cell.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them; although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application, and they should all be included in the scope of the claims and specification of the present application. In particular, as long as there is no structural conflict, the various technical features mentioned in the various embodiments can be combined in any way. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions that fall within the scope of the claims.

Claims

1. A battery cell, characterized in that: The battery cell comprises a positive electrode plate; The positive electrode sheet includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector; The positive electrode film layer includes 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 electrode current collector to the direction away from the positive electrode current collector, the positive electrode film layer includes the first positive electrode film layer to the nth positive electrode film layer in sequence, where 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 proportion of the tungsten element in each positive electrode film layer gradually increases.

2. The battery cell according to claim 1, characterized in that: Based on the total mass of the positive electrode film layer, the total mass of the tungsten element and the carbon nanotubes is less than or equal to 3%.

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

1.

4. The battery cell according to any one of claims 1 to 3, characterized in that: Based on the total mass of the positive electrode film layer, the total mass of the tungsten element is less than or equal to 3%, and optionally less than or equal to 2%.

5. The battery cell according to any one of claims 1 to 4, characterized in that: Based on the total mass of tungsten elements in the positive electrode film layer, the mass content of tungsten elements in the first positive electrode film layer is 0.2%-5%.

6. The battery cell according to any one of claims 1 to 5, characterized in that: Based on the total mass of tungsten elements in the positive electrode film layer, the mass content of tungsten elements in the nth positive electrode film layer is 0.8%-12%.

7. The battery cell according to any one of claims 1 to 6, characterized in that: From the direction close to the positive electrode current collector to the direction away from the positive electrode current collector, the mass proportion of the carbon nanotubes in each positive electrode film layer gradually increases.

8. The battery cell according to any one of claims 1 to 7, characterized in that: Based on the total mass of the positive electrode film layer, the total mass of the carbon nanotubes is less than or equal to 1%.

9. The battery cell according to any one of claims 1 to 8, characterized in that: 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.

10. The battery cell according to any one of claims 1 to 9, characterized in that: Based on the total mass of the carbon nanotubes in the positive electrode film layer, the mass content of the carbon nanotubes in the nth positive electrode film layer is 0.4%-15%.

11. The battery cell according to any one of claims 1 to 10, characterized in that: 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.

12. The battery cell according to any one of claims 1 to 11, characterized in that: The thickness of the positive electrode film layer is 0.05-0.3 mm.

13. The battery cell according to any one of claims 1 to 12, characterized in that: The carbon nanotubes include single-walled carbon nanotubes.

14. The battery cell according to any one of claims 1 to 13, characterized in that: The aspect ratio of the carbon nanotubes is 50-300; and / or; The diameter of the carbon nanotubes is 1-5 mm.

15. A battery device, characterized in that: The battery device comprises a plurality of battery cells according to any one of claims 1-14.

16. An electrical device, characterized in that: The electrical device comprises the battery cell according to any one of claims 1 to 14, or the battery device according to claim 15.

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