Battery cell, battery device and electric device

Abstract

The invention provides a battery monomer, a battery device and a power utilization device. The battery monomer comprises a positive electrode plate, the positive electrode plate comprises a positive electrode current collector and a positive electrode film layer, a first film layer of the positive electrode film layer is arranged at a lower layer, the first film layer comprises a first transition metal oxide, the lithium-containing first transition metal oxide comprises a first doping element, and the mass content of a manganese element in the lithium-containing first transition metal oxide is a1; the second film layer is arranged on the upper layer, the second film layer comprises a lithium-containing second transition metal oxide, the lithium-containing second transition metal oxide comprises a selectable second doping element, the mass content of the manganese element in the lithium-containing second transition metal oxide is a2, a1 is larger than a2, and a2 is larger than a2; the first doping element and the second doping element respectively and independently comprise one or more of Na, K, Be, Mg, Ca, a group IIIA, a group IB, a group IIB, a group IIIB, a group IVB, a group VB, a group VIB and a group VIII.

Description

Technical Field

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

[0002] With rapid societal development, low-cost and long-life lithium-ion batteries are becoming an increasingly important demand. In NCM ternary cathode materials, Co has a relatively high cost; increasing the nickel or manganese content can reduce the cost of NCM ternary cathode materials.

[0003] However, increasing the nickel or manganese content can easily lead to a decrease in the structural stability of NCM ternary cathode materials, especially when charging at high voltage or storing at high temperature. Therefore, how to achieve long lifespan while reducing costs has always been a research topic in the industry. Summary of the Invention

[0004] This application provides a battery cell and an electrical device to achieve a long battery cell life while maintaining low cost.

[0005] The first aspect of this application provides a battery cell, including a positive electrode sheet, the positive electrode sheet including a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein the positive electrode film layer includes: a first film layer disposed on at least one side of the positive current collector, the first film layer including a first positive electrode active material, the first positive electrode active material including a lithium-containing first transition metal oxide, the lithium-containing first transition metal oxide including lithium, nickel, cobalt, manganese and a first dopant element, the mass content of manganese in the lithium-containing first transition metal oxide being a1; and a second film layer disposed on the first film layer. On the side away from the positive electrode current collector, the second film layer includes a second positive electrode active material, which includes a lithium-containing second transition metal oxide. The lithium-containing second transition metal oxide includes lithium, nickel, cobalt, manganese, and an optional second dopant element. The mass content of manganese in the lithium-containing second transition metal oxide is a2, where a1 > a2. The first dopant element and the second dopant element each independently include one or more elements from Group IIIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII.

[0006] The positive electrode film of the battery cell in this application is arranged in layers. The first film layer is located close to the positive current collector of its corresponding positive electrode sheet, and the second film layer covers the first film layer and is located away from the positive current collector of its corresponding positive electrode sheet. The first film layer and the second film layer use different transition metal oxides as the components of the positive electrode active material. The manganese content a2 in the lithium-containing second transition metal oxide in the second film layer is lower than the manganese content a1 in the lithium-containing first transition metal oxide in the first film layer. Thus, while the cost is significantly reduced by utilizing the lithium-containing first transition metal oxide in the first film layer, the manganese leaching problem is effectively controlled due to the lower manganese content in the lithium-containing second transition metal oxide in the second film layer. This can improve the cycle performance of the battery cell and extend its life.

[0007] Moreover, since the first transition metal oxide containing lithium has a higher manganese content in the first film layer, its structural stability is naturally lower than that of the second transition metal oxide containing lithium. This application utilizes more first doping elements to improve the stability of the first transition metal oxide containing lithium, further reduce the dissolution of manganese in the second film layer, better improve the cycle performance of the battery cell, and further extend the battery cell life.

[0008] In any embodiment of the first aspect, the first doping element and the second doping element each independently include a first metal doping element, and the first metal doping element each independently includes one or more elements of Na, K, Be, Mg, and Ca. When elements of Na, K, Be, Mg, and Ca are selected for doping, it is easier to form doping at lithium sites, thereby playing a role in supporting the layered material structure and reducing the risk of structural collapse during cycling; in addition, it can significantly reduce lithium / nickel mixing, increase the migration barrier for manganese dissolution, and suppress manganese dissolution.

[0009] In any embodiment of the first aspect, the first metal doping element independently comprises one or more elements selected from Na, K, and Mg, and optionally includes Na and / or Mg. Sodium, potassium, and magnesium can better reduce lithium / nickel mixing, further enhance the migration barrier for manganese dissolution, and suppress manganese dissolution.

[0010] In any embodiment of the first aspect, in the lithium-containing first transition metal oxide, the mass ratio of the first metal dopant to lithium is b1; in the lithium-containing second transition metal oxide, the mass ratio of the first metal dopant to lithium is b2, where b1 > b2. In the positive electrode film layer far from the positive electrode current collector, the lithium-containing second transition metal oxide has a lower manganese content, thus improving its structural stability. To control the further reduction in specific capacity caused by doping elements, the lithium-containing second transition metal oxide contains little or no first metal dopant. In the first film layer near the positive electrode current collector, the lithium-containing first transition metal oxide has a higher manganese content. To further improve the cycle performance of the battery cell, a higher content of the first metal dopant is used to improve the structural stability of the lithium-containing first transition metal oxide.

[0011] In any embodiment of the first aspect, 39300ppm ≥ b1 > 0ppm, and can be optionally 26300ppm ≥ b1 ≥ 9900ppm. This controls the increase in battery internal resistance while improving cycle performance.

[0012] In any embodiment of the first aspect, 26300ppm ≥ b2 ≥ 0ppm.

[0013] In any embodiment of the first aspect, the first dopant and the second dopant each independently further include a second metal dopant, which independently includes one or more elements from Group IIIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII. This better suppresses manganese leaching and oxygen release, and can also adjust the grain growth towards a crystal orientation conducive to lithium-ion insertion / extraction.

[0014] In any embodiment of the first aspect, the second metal dopant element independently comprises one or more elements selected from Al, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, and Y, more preferably one or more elements selected from Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Nb, Sb, Ta, and Y, and even more preferably one or more elements selected from Ti, Mo, Nb, Sb, and Ta.

[0015] In any embodiment of the first aspect, in the lithium-containing first transition metal oxide, the mass ratio of the second metal dopant to the total mass of nickel, cobalt, manganese, and the second metal dopant is c1; in the lithium-containing second transition metal oxide, the mass ratio of the second metal dopant to the total mass of nickel, cobalt, manganese, and the second metal dopant is c2, where c1 > c2. This further improves the structural stability of the lithium-containing first transition metal oxide and the lithium-containing second transition metal oxide.

[0016] In any embodiment of the first aspect, the mass content of the second metal dopant in the lithium-containing first transition metal oxide is 1700 ppm to 6700 ppm, optionally 1700 ppm to 3400 ppm; the mass content of the second metal dopant in the lithium-containing second transition metal oxide is 0 ppm to 3400 ppm. This mitigates the impact of the introduction of transition metal elements on the conductivity of the transition metal oxide.

[0017] In any embodiment of the first aspect, in the lithium-containing first transition metal oxide, the molar ratio of manganese to nickel, cobalt, and manganese is 0.05:1-0.4:1; in the lithium-containing second transition metal oxide, the molar ratio of manganese to nickel, cobalt, and manganese is 0.02:1-0.3:1. The manganese content in both the upper and lower layers is further controlled, thus further suppressing the problem of manganese leaching.

[0018] In any embodiment of the first aspect, in the same cross section, the cross-sectional area ratio of the first positive electrode active material in the first film layer is d1, and the cross-sectional area ratio of the second positive electrode active material in the second film layer is d2, where d1 < d2. The first film layer, having the above characteristics, has a lower compaction density than the second film layer, resulting in better structural stability of the positive electrode film layer.

[0019] In any embodiment of the first aspect, the first positive electrode active material further includes a first lithium-containing phosphate, and the second positive electrode active material further includes a second lithium-containing phosphate. The first and second lithium-containing phosphates each independently include one or more of lithium iron phosphate and its modified forms, and lithium manganese iron phosphate and its modified forms. This helps improve the discharge power performance of the battery cell at low SOC (SOC refers to the state of charge of a battery cell, the ratio of the remaining capacity of the battery cell to its capacity in a fully charged state).

[0020] In any embodiment of the first aspect, the mass content of the first lithium-containing phosphate in the first positive electrode active material is e1, and the mass content of the second lithium-containing phosphate in the second positive electrode active material is e2, where e1 ≤ e2, and optionally 0 ≤ (e1 + e2) ≤ 8. This avoids the lithium-containing phosphate from having an excessive impact on the energy density of the battery cell.

[0021] In any embodiment of the first aspect, 0 ≤ e1 ≤ 4 wt%; 0 ≤ e2 ≤ 5 wt%. This maintains a high energy density as much as possible while utilizing lithium phosphate to improve the discharge power of individual cells at low SOC.

[0022] In any embodiment of the first aspect, the thickness of the first film layer is f1, the thickness of the second film layer is f2, and 0.25 ≤ f1 / f2 ≤ 4. This helps to maintain the structural stability of the oxides in the first film layer as much as possible during long-term cycling.

[0023] In any embodiment of the first aspect, the first film layer further includes a first conductive agent, and the second film layer further includes a second conductive agent. The mass content of the first conductive agent in the first film layer is g1, and the mass content of the second conductive agent in the second film layer is g2, where g1 > g2. Because the Mn element content in the second positive electrode active material of the second film layer is relatively low, its conductivity is relatively high. Therefore, less conductive agent can be used to achieve a conductivity effect comparable to that of the first film layer. Reducing the conductive agent content can correspondingly increase the content of the second positive electrode active material, thereby improving the energy density of the battery cell to a certain extent.

[0024] In any embodiment of the first aspect, the first conductive agent and the second conductive agent each independently include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers; optionally, the first conductive agent and the second conductive agent each independently include carbon nanotubes. Carbon nanotubes, as one-dimensional linear conductive materials, exhibit better conductivity.

[0025] After addressing the issue of unstable cathode material structure during high-voltage charging, the energy density of individual battery cells can be increased by utilizing high-voltage charging. In any embodiment of the first aspect, the charging voltage of the individual battery cells is between 4.25V and 4.5V. Increasing the charging voltage can further improve the energy density of the individual battery cells.

[0026] A second aspect of this application provides a battery device comprising a plurality of battery cells, wherein the battery cells include those provided in any embodiment of the first aspect described above.

[0027] The third aspect of this application provides an electrical device, including a battery cell or an electrical device, wherein the battery cell includes the battery cell provided in any embodiment of the first aspect, and the electrical device includes the electrical device provided in any embodiment of the second aspect. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on the drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the structure of the positive electrode of a battery cell provided in one embodiment of this application.

[0030] Figure 2 This is a schematic diagram of a battery cell according to one embodiment of this application.

[0031] Figure 3 yes Figure 2 An exploded view of a battery cell according to one embodiment of this application is shown.

[0032] Figure 4 This is a schematic diagram of a battery module according to one embodiment of this application.

[0033] Figure 5 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0034] Figure 6 yes Figure 5 An exploded view of a battery pack according to one embodiment of this application is shown.

[0035] Figure 7 This is a schematic diagram of a power supply device using a battery pack as a power source according to one embodiment of this application.

[0036] The accompanying drawings are not drawn to scale.

[0037] Explanation of reference numerals in the attached figures:

[0038] 11 Positive current collector; 12 First membrane layer; 13 Second membrane layer; 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Battery cell; 51 Housing; 52 Electrode assembly; 53 End cap. Detailed Implementation

[0039] The embodiments of this application will be described in further detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application, that is, this application is not limited to the described embodiments.

[0040] The following detailed description, with appropriate reference to the accompanying drawings, specifically discloses embodiments of the battery cell, battery device, and power-consuming device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0041] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, 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 expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0042] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0043] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0044] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0045] Unless otherwise specified, the terms "comprising" and "including" as used in this application are open-ended. For example, "comprising" and "including" may mean that other components not listed may also be included or contained.

[0046] Unless otherwise specified, the term "or" is inclusive in this application. For example, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0047] [Battery cell]

[0048] In this embodiment of the application, the battery cell can be a secondary battery, which refers to a battery that can be used again after being discharged by recharging to activate the active materials.

[0049] The battery cell can be a lithium-ion battery, sodium-ion battery, sodium-lithium-ion battery, lithium metal battery, sodium metal battery, lithium-sulfur battery, magnesium-ion battery, nickel-metal hydride battery, nickel-cadmium battery, lead-acid battery, etc., and the embodiments of this application are not limited to this.

[0050] A single battery cell typically includes an electrode assembly. The electrode assembly includes a positive electrode, a negative electrode, and a separator, with the separator positioned between the positive and negative electrodes. During the charging and discharging process of a single battery cell, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, prevents short circuits between the positive and negative electrodes while allowing active ions to pass through.

[0051] To reduce costs, the Co content in NCM ternary cathode materials can be reduced. Furthermore, mixing low-cobalt NCM ternary cathode materials with different solid contents allows for more flexible adjustment of the cathode material's activity. However, increasing the manganese content in the cathode material leads to an increased risk of manganese leaching, a risk that is more severe during high-voltage charging.

[0052] To address the aforementioned problems, a first embodiment of this application provides a battery cell including a positive electrode sheet. The positive electrode sheet includes a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein, as... Figure 1As shown, the positive electrode film layer includes a first film layer 12 and a second film layer 13. The first film layer 12 is disposed on at least one side of the positive electrode current collector 11. The first film layer 12 includes a first positive electrode active material, which includes a lithium-containing first transition metal oxide. The lithium-containing first transition metal oxide includes lithium, nickel, cobalt, manganese, and a first dopant element. The mass content of manganese in the lithium-containing first transition metal oxide is a1. The second film layer 13 is disposed on the side of the first film layer 12 away from the positive electrode current collector 11. The second film layer 13 includes a second positive electrode active material, which includes a lithium-containing second transition metal oxide. The lithium-containing second transition metal oxide includes lithium, nickel, cobalt, manganese, and a second dopant element. The mass content of manganese in the lithium-containing second transition metal oxide is a2, where a1 > a2. The first dopant element and the second dopant element each independently include one or more elements from Group IIIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII.

[0053] To address the aforementioned issues, the inventors of this application discovered in experiments that when cathode materials with different manganese contents are placed in upper and lower layers in the cathode current collector, the actual degree of delithiation between the upper and lower layers differs due to polarization during charging, with the upper layer exhibiting a greater degree of delithiation, which has a greater impact on material stability and a higher risk of manganese leaching.

[0054] The positive electrode film of the battery cell in this application is arranged in layers. The first film layer is located close to the positive current collector of its corresponding positive electrode sheet, and the second film layer covers the first film layer and is located away from the positive current collector of its corresponding positive electrode sheet. The first and second film layers use different transition metal oxides as the components of the positive electrode active material. The manganese content (a2) in the lithium-containing second transition metal oxide in the second film layer is lower than the manganese content (a1) in the lithium-containing first transition metal oxide in the first film layer. This allows for significant cost reduction by utilizing the lithium-containing first transition metal oxide in the first film layer. Furthermore, the lower manganese content in the lithium-containing second transition metal oxide in the second film layer effectively controls manganese leaching, thereby improving the cycle performance and extending the battery cell's lifespan. Moreover, the lithium-containing first transition metal oxide in the first film layer has more first doping elements. These first doping elements improve the stability of the lithium-containing first transition metal oxide, further reducing manganese leaching and further improving the cycle performance and extending the battery cell's lifespan.

[0055] The comparison of the manganese content mentioned above can be tested using the following methods:

[0056] Cut the positive electrode sheet into 6mm*6mm pieces as samples and attach them to a paraffin-coated sample stage, ensuring the samples protrude slightly beyond the stage edge (<1mm). Polish the sample end face. Analyze the polished end face using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) system (Sigma 300), following the procedures outlined in JY / T010-1996. Perform EDS analysis on active material particles at different locations on the electrode end face, calculating and comparing the elemental content of the active material at different locations.

[0057] The above methods are applicable to the testing of the content of the following doping elements.

[0058] In some embodiments, the first dopant and the second dopant each independently include a first metal dopant, and the first metal dopant each independently includes one or more elements of Na, K, Be, Mg, and Ca (meaning that the first metal dopant in the first dopant and the first metal dopant in the second dopant are each selected independently; the first dopant may or may not include the first metal dopant, and the second dopant may or may not include the first metal dopant; when both include the first metal dopant, the first metal dopant of the two may be the same or different). When elements of Na, K, Be, Mg, and Ca are selected for doping, it is easier to form dopant at lithium sites, thereby playing a role in supporting the layered material structure and reducing the risk of structural collapse during cycling; in addition, it can significantly reduce lithium / nickel mixing, increase the migration barrier for manganese dissolution, and suppress manganese dissolution.

[0059] To fully utilize the first metal element to improve the structural stability of the lithium-containing first transition metal oxide, in some embodiments, the first metal doping element independently includes one or more elements selected from Na, K, and Mg, and optionally includes Na and / or Mg. Sodium, potassium, and magnesium can better reduce lithium / nickel mixing, further increase the migration barrier for manganese dissolution, and suppress manganese dissolution.

[0060] In some embodiments, to control the influence of the first metal dopant on the energy density of the battery cell, the mass ratio of the first metal dopant to lithium in the lithium-containing first transition metal oxide is b1; the mass ratio of the first metal dopant to lithium in the lithium-containing second transition metal oxide is b2, where b1 > b2. In the positive electrode film layer far from the positive electrode current collector, the lithium-containing second transition metal oxide has a lower manganese content, thus improving its structural stability. To control the further reduction in specific capacity caused by doping elements, the lithium-containing second transition metal oxide contains little or no first metal dopant. In the first film layer near the positive electrode current collector, the lithium-containing first transition metal oxide has a higher manganese content. To further improve the cycle performance of the battery cell, a higher content of the first metal dopant is used to improve the structural stability of the lithium-containing first transition metal oxide.

[0061] In some embodiments, 39300ppm ≥ b1 > 0ppm, and can be optionally 26300ppm ≥ b1 ≥ 9900ppm. In some embodiments, 26300ppm ≥ b2 ≥ 0ppm. This controls the increase in battery internal resistance while improving cycle performance.

[0062] In some embodiments, the first dopant element and the second dopant element each independently further include a second metal dopant element (meaning that the second metal dopant element in the first dopant element and the second metal dopant element in the second dopant element are each independently selected; the first dopant element may or may not include the second metal dopant element, and the second dopant element may or may not include the second metal dopant element; when both include the second metal dopant element, the second metal dopant element of the two may be the same or different), and the second metal dopant element each independently includes one or more elements from Group IIIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB, and Group VIII.

[0063] In some embodiments, the aforementioned second metal dopant elements independently include one or more elements selected from Al, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, and Y. More preferably, they include one or more elements selected from Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Nb, Sb, Ta, and Y. Further optionally, they include one or more elements selected from Ti, Mo, Nb, Sb, and Ta. The doping of these metal dopant elements into defect sites can induce crystallographic distortion, thereby increasing the manganese-O bond strength, suppressing manganese dissolution and oxygen release, and also adjusting the grains to grow in a direction favorable to lithium-ion insertion / extraction.

[0064] In some embodiments, in order to further improve the structural stability of the lithium-containing first transition metal oxide and the lithium-containing second transition metal oxide, the mass ratio of the second metal dopant element in the lithium-containing first transition metal oxide to the total mass of nickel, cobalt, manganese and the second metal dopant element is c1; the mass ratio of the second metal dopant element in the lithium-containing second transition metal oxide to the total mass of nickel, cobalt, manganese and the second metal dopant element is c2, where c1 > c2.

[0065] Excessive transition metal doping can easily lead to structural distortion of oxides, affecting lithium-ion insertion / extraction and consequently the conductivity of the oxide. When applied to battery cells, this can increase the battery's discharge coefficient (DCR) and thus affect the battery's kinetic performance. The doping amount of the transition metal element in this application can be referenced to conventional doping amounts. In some embodiments, while the transition metal doping achieves the aforementioned effects, to further avoid the introduction of the transition metal element affecting the conductivity of the transition metal oxide, the mass content of the second metal dopant in the lithium-containing first transition metal oxide is 1700 ppm to 6700 ppm, optionally 1700 ppm to 3400 ppm; the mass content of the second metal dopant in the lithium-containing second transition metal oxide is 0 ppm to 3400 ppm.

[0066] The manganese content in the aforementioned lithium-containing first transition metal oxide and the lithium-containing second transition metal oxide are selected within a conventional range while meeting the above conditions. In some embodiments, the molar ratio of manganese in nickel, cobalt, and manganese in the lithium-containing first transition metal oxide is 0.05:1-0.4:1; and the molar ratio of manganese in nickel, cobalt, and manganese in the lithium-containing second transition metal oxide is 0.02:1-0.3:1. The manganese content in the lithium-containing first transition metal oxide can reach 0.4 molar, minimizing material costs. Furthermore, the manganese content in the lithium-containing second transition metal oxide can be reduced to 0.02 molar, thus further suppressing manganese leaching.

[0067] In some embodiments, the lithium-containing first transition metal oxide and the lithium-containing second transition metal oxide can be selected from conventional lithium-containing layered transition metal oxides that meet the above conditions, such as NCM. 333 (e.g. LiNi) 1 / 3Co 1 / 3 Mn 1 / 3 O2), NCM 523 (e.g. LiNi) 0.5 Co 0.2 Mn 0.3 O2), NCM211 (e.g. LiNi) 0.5 Co 0.25 Mn 0.25 O2), NCM 622 (e.g. LiNi) 0.6 Co 0.2 Mn 0.2 O2), NCM 811 (e.g. LiNi) 0.8 Co 0.1 Mn 0.1 O2).

[0068] In some embodiments, in the same cross-section, the cross-sectional area ratio of the first positive electrode active material in the first film layer is d1, and the cross-sectional area ratio of the second positive electrode active material in the second film layer is d2, where d1 < d2. The first film layer with the above characteristics has a lower compaction density than the second film layer, resulting in a higher energy density and better cycle life for the battery.

[0069] The above cross-sectional area ratio can be tested using the following method:

[0070] Cut the positive electrode sheet into 6mm*6mm samples and attach them to a sample stage coated with paraffin wax, ensuring the samples protrude slightly beyond the edge of the stage (<1mm). Polish the end face of the positive electrode sheet. Test the polished end face using a scanning electron microscope (SEM) on a Sigma300, following the procedures outlined in JY / T010-1996. Generally, observe the morphology at 3000x magnification. Take SEM images at different locations (e.g., at least three cross-sectional areas). Then, use Avizo software to analyze and calculate the proportion of the metal oxide cross-sectional area in the corresponding film layer based on the different material contrasts. Finally, take the average of the three cross-sectional areas.

[0071] When the manganese content satisfies a1 > a2, the power performance of the battery cell deteriorates at low SOC. To improve the discharge power performance of the battery cell at low SOC, in some embodiments, the first positive electrode active material further includes a first lithium-containing phosphate, and the second positive electrode active material further includes a second lithium-containing phosphate. The first and second lithium-containing phosphates each independently include one or more of lithium iron phosphate and its modified materials, and lithium manganese iron phosphate and its modified materials. The plateau voltage of the lithium-containing phosphate is lower than that of the lithium-containing transition metal oxide, thus helping to improve the discharge power performance of the battery cell at low SOC.

[0072] Since the specific capacity of lithium phosphate is relatively low compared to that of lithium-containing transition metal oxides, to avoid excessive impact of lithium phosphate on the energy density of individual battery cells, the content of lithium phosphate in each film layer is adjusted. This aims to minimize the impact of lithium phosphate on the energy density of individual battery cells while utilizing lithium phosphate to improve the discharge power of individual cells at low SOC. In some embodiments, the mass content of the first lithium phosphate in the first positive electrode active material is e1, and the mass content of the second lithium phosphate in the second positive electrode active material is e2, where e1≤e2, and optionally 0≤(e1+e2)≤8. The second film layer is closer to the electrolyte than the first film layer. The presence of more lithium phosphate in the second film layer allows for easier wetting of the lithium phosphate by the electrolyte, enabling active ions to be inserted and extracted from the lithium phosphate in a shorter time during charge and discharge. This makes it easier for the lithium phosphate to effectively improve the discharge power of individual battery cells at low SOC.

[0073] In some implementations, 0 ≤ e1 ≤ 4 wt%; 0 ≤ e2 ≤ 5 wt%, and optionally, 0 < e1 ≤ 2 wt%; 0 < e2 ≤ 4 wt%. This maintains a high energy density as much as possible while utilizing lithium phosphate to improve the discharge power of individual cells at low SOC.

[0074] The testing methods for the above-mentioned mass contents e1 and e2 can be referenced as follows:

[0075] The battery cell is disassembled to obtain the positive electrode sheet. The film layers at different positions of the positive electrode sheet are scraped to collect the positive electrode material. The phosphorus content in the first and second film layers is tested using inductively coupled plasma optical emission spectrometry (ICP-OES). The mass percentage of phosphorus in lithium iron phosphate and lithium manganese iron phosphate can be obtained by using their molecular formulas. Thus, the mass content of the first lithium-containing phosphate in the first positive electrode active material and the mass content of the second lithium-containing phosphate in the second positive electrode active material can be calculated.

[0076] To maintain the structural stability of the oxides in the first film layer as much as possible during long-term cycling, in some embodiments, the thickness of the first film layer is f1, and the thickness of the second film layer is f2, where 0.25 ≤ f1 / f2 ≤ 4. The thickness of the second film layer provides sufficient protection for the oxides in the first film layer.

[0077] The thickness of the first and second films mentioned above is tested using the following method:

[0078] Cut the positive electrode sheet into 6mm*6mm samples and attach them to a paraffin-coated sample stage, ensuring the samples protrude slightly beyond the stage edge (<1mm). Polish the sample end face. Analyze the sample end face using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) system (Sigma300), following standard JY / T010-1996. Perform manganese element analysis (linear scanning) on ​​the sample end face to identify the distribution of different film layers. Combined with SEM measurements of the thickness at corresponding locations, the thicknesses of the first and second film layers can be obtained.

[0079] Since the lithium-containing first transition metal oxide in the first film layer has a lower manganese content, the lithium-containing first transition metal oxide has better conductivity. Therefore, the amount of conductive agent added in the first film layer can be appropriately reduced. The reduced conductive agent content can correspondingly increase the lithium content of the second positive electrode active material, thereby increasing the energy density of the battery cell to a certain extent. In some embodiments, the first film layer also includes a first conductive agent, and the second film layer also includes a second conductive agent. The mass content of the first conductive agent in the first film layer is g1, and the mass content of the second conductive agent in the second film layer is g2, where g1 > g2.

[0080] The first and second conductive agents can be selected from commonly used conductive agents in positive electrode sheets. In some embodiments, the first and second conductive agents independently include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Optionally, the first and second conductive agents independently include carbon nanotubes. As a one-dimensional linear conductive material, carbon nanotubes have better conductivity.

[0081] In some embodiments, the coating weight CW of the positive electrode film layer satisfies: 100 mg / 1540.25 mm. 2 ≤CW≤500mg / 1540.25mm 2 Optionally, 200mg / 1540.25mm 2 ≤CW≤400mg / 1540.25mm 2 By controlling the coating weight, on the one hand, coating is easier and processing is more convenient. Too thin a coating will cause coating scratches, while too thick a coating may lead to demolding. On the other hand, it can also improve the adhesion between the positive electrode film and the positive electrode current collector in the later stages of cycling, thereby improving cycle life.

[0082] The coating weight of the above-mentioned positive electrode film can be tested using the following method:

[0083] After disassembling the battery cell, the positive electrode sheet was obtained. The positive electrode sheet was then cut into pieces with an area of ​​1540.25 mm². 2The small round pieces are weighed as m1. After the positive electrode film layer on the surface of the positive electrode current collector is removed with the solvent NMP, the weight is weighed as m2. The coating weight is m1-m2.

[0084] In some implementations, the charging voltage of the battery cell is between 4.25V and 4.5V. Increasing the charging voltage can further improve the energy density of the battery cell.

[0085] As an example, the positive current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material base layer and a metal layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0086] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0087] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry for coating the lower layer and a positive electrode slurry for coating the upper layer; the two layers are coated simultaneously, with the positive electrode slurry for coating the lower layer coated on the positive current collector, and the positive electrode slurry for coating the upper layer coated on the already coated upper positive electrode slurry; after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0088] Typically, a battery cell also includes a negative electrode, a separator, and an electrolyte. During charging and discharging, active ions (such as lithium ions) repeatedly insert and extract between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing active ions to pass through. The electrolyte, also located between the positive and negative electrodes, mainly conducts the active ions.

[0089] [Negative electrode plate]

[0090] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0091] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector. As an example, the negative electrode current collector can be a metal foil, a conductive polymer material, a carbon material, or a composite current collector. For example, as a metal foil, pure metals, alloys, or surface-treated metals can be used, including but not limited to stainless steel, copper, aluminum, nickel, titanium, or silver. The composite current collector may include a polymer material substrate and a metal layer. The composite current collector can be formed by forming a metal material (copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys, etc.) on a polymer material substrate (such as a substrate of polypropylene, polyethylene terephthalate, polybutylene terephthalate, polystyrene, polyethylene, etc.).

[0092] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. Silicon-based materials may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0093] In some embodiments, the negative electrode film layer may optionally include a binder. As an example, the binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0094] In some embodiments, the negative electrode film may optionally include a conductive agent. As an example, the conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0095] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0096] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0097] As an example, negative electrode active materials can be filled or / and deposited within the negative electrode current collector.

[0098] In some embodiments, the positive current collector can be made of aluminum, and the negative current collector can be made of copper.

[0099] [Electrolytes]

[0100] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0101] In some embodiments, the electrolyte is liquid and includes an electrolyte salt and a solvent.

[0102] In some embodiments, the electrolyte salt may 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 difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0103] In some embodiments, the solvent may 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, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone. The solvent may also be an ether solvent. Ether solvents may 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 crown ethers. In some embodiments, the electrolyte may also optionally include additives. As an example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0104] [Isolation Component]

[0105] In some embodiments, the battery cell also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous membrane with good chemical and mechanical stability can be selected.

[0106] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation. The separator can be a single component located between the positive and negative electrodes, or it can be attached to the surfaces of the positive and negative electrodes. An inorganic particle coating, an organic particle coating, or an organic / inorganic composite coating can also be applied to the surface of the separator.

[0107] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0108] In some embodiments, the electrode assembly is a wound structure. The positive electrode and the negative electrode are wound into a wound structure.

[0109] In some implementations, the electrode assembly is a stacked structure.

[0110] As an example, multiple positive and negative electrode plates can be set, and multiple positive and multiple negative electrode plates can be stacked alternately.

[0111] As an example, multiple positive electrode sheets can be provided, and negative electrode sheets can be folded to form multiple stacked folded segments, with a positive electrode sheet sandwiched between adjacent folded segments.

[0112] As an example, both the positive and negative electrode sheets are folded to form multiple stacked folded segments.

[0113] As an example, multiple separators can be provided, each positioned between any adjacent positive or negative electrode plates.

[0114] As an example, the separator can be continuously arranged between any adjacent positive or negative electrode plates by folding or rolling.

[0115] In some embodiments, the electrode assembly can be cylindrical, flat, or polygonal, etc.

[0116] In some embodiments, the electrode assembly has tabs that allow current to be drawn from the electrode assembly. The tabs include a positive tab and a negative tab.

[0117] In some embodiments, the battery cell may include a casing. The casing may be a steel casing, an aluminum casing, a plastic casing (such as a polypropylene casing), a composite metal casing (such as a copper-aluminum composite casing), or an aluminum-plastic film, etc. In some embodiments, the casing may be a sealed structure or a non-sealed structure. As an example, when the casing is a non-sealed structure, the casing serves to protect the electrode assembly, and a sealing bag is included between the casing and the electrode assembly to encapsulate the electrode assembly and electrolyte. Specifically, the sealing bag may be a bag-shaped insulating component or an aluminum-plastic film. When the casing is a sealed structure, it is used to encapsulate components such as the electrode assembly and electrolyte.

[0118] 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. Prismatic battery cells include prismatic battery cells, blade-shaped battery cells, and multi-prismatic batteries, such as hexagonal prismatic batteries. This application does not have any particular limitations.

[0119] In some embodiments, the housing includes an end cap and a shell, the shell having an opening, and the end cap covering the opening. The shell may have one or more openings. The end cap may also be provided one or more times. In some embodiments, the shell has at least one electrode terminal, which is electrically connected to a tab. The electrode terminal may be directly connected to the tab or indirectly connected to the tab via a current collector. The electrode terminal may be located on the end cap or on the shell.

[0120] In some embodiments, a pressure relief mechanism is provided on the casing. The pressure relief mechanism is used to release the internal gas of the battery cell.

[0121] As an example, the internal pressure or temperature of a battery cell is actuated to release the internal pressure or temperature when it reaches a predetermined threshold. When the internal pressure or temperature of the battery cell reaches the predetermined threshold, the pressure relief mechanism is activated or a weak structure in the pressure relief mechanism is broken, thereby creating an opening or channel for the internal pressure or temperature to be released. The threshold design varies depending on the design requirements. The threshold may depend on the materials of one or more of the positive electrode, negative electrode, electrolyte, and separator in the battery cell.

[0122] As an example, the pressure relief mechanism can be integrally molded with the housing.

[0123] As an example, the pressure relief mechanism can also be separately installed and connected to the housing.

[0124] The term "actuation" as used in this application refers to the activation or actuation of the pressure relief mechanism to a certain state, thereby releasing the internal pressure and temperature of the battery cell. The actions of the pressure relief mechanism may include, but are not limited to: movement of components within the mechanism to form an exhaust channel, rupture, breakage, tearing, or opening of at least a portion of the mechanism, etc. When the pressure relief mechanism is activated, the high-temperature, high-pressure substances inside the battery cell are discharged as waste from the activated portion. This method allows for pressure and temperature relief of the battery cell under controllable pressure or temperature, thereby preventing potentially more serious accidents.

[0125] In some embodiments, when the housing is a non-sealed structure, the pressure relief mechanism can be configured as a through hole for venting gas inside the battery cell.

[0126] The emissions from battery cells mentioned in this application include, but are not limited to: electrolyte, dissolved or split positive and negative electrode plates, fragments of separators, high-temperature and high-pressure gases generated by the reaction, flames, etc.

[0127] Figure 2 The example shown is a square-structured battery cell 5.

[0128] In some implementations, refer to Figure 3 The outer casing may include a housing 51 and an end cap 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the end cap 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 via a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in a single battery cell 5 can be one or more, which can be selected by those skilled in the art according to specific practical needs.

[0129] [Battery Device]

[0130] The battery apparatus mentioned in the embodiments of this application may include one or more battery cell assemblies for providing voltage and capacity. A battery cell assembly may include multiple battery cells connected in series, parallel, or mixed connections via a busbar.

[0131] In some embodiments, a battery cell assembly is typically formed by arranging multiple battery cells.

[0132] As an example, a battery cell assembly can be a battery module, which consists of multiple battery cells arranged and fixed together to form a single module. As another example, a battery module can be formed by bundling multiple battery cells together with cable ties.

[0133] Figure 4 This is battery module 4 as an example. (See reference...) Figure 4 In the battery module 4, multiple battery cells 5 can be arranged sequentially along the length of the battery module 4. Of course, they can also be arranged in any other way. Furthermore, these multiple battery cells 5 can be fixed in place using fasteners.

[0134] Optionally, the battery module 4 may also include a housing with a receiving space in which multiple battery cells 5 are received.

[0135] In some embodiments, the battery device may be a battery pack, which includes a housing and one or more individual battery cells housed within the housing.

[0136] As an example, the battery cell assembly can be a battery module, which can be housed in a housing by fixing the battery module into the housing. Alternatively, the battery cell assembly can be housed in a housing by directly fixing multiple battery cells to the housing.

[0137] As an example, the enclosure may include a first enclosure and a second enclosure. The first enclosure and the second enclosure are fastened together to form a closed space inside the enclosure to house the individual battery cells. Here, "closed" refers to covering or closing, and can be either sealed or unsealed. The first enclosure may be a top cover or a bottom plate.

[0138] As an example, the enclosure may include a top cover, a frame, and a bottom plate. The top cover and bottom plate are connected to the frame, creating an enclosed space inside the enclosure to house the individual battery cells.

[0139] In some embodiments, the housing may be part of the vehicle's chassis structure. For example, a portion of the housing may be at least a part of the vehicle's floor, or a portion of the housing may be at least a part of the vehicle's crossbeams and longitudinal beams.

[0140] Figure 5 and Figure 6 This is battery pack 1 as an example. (See reference...) Figure 5 and Figure 6The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0141] The technical solutions described in this application are applicable to various electrical devices that use individual battery cells, such as mobile phones, portable devices, laptops, electric vehicles, electric toys, power tools, vehicles, ships, and spacecraft. For example, spacecraft include airplanes, rockets, space shuttles, and spacecraft. As for the aforementioned electrical devices, individual battery cells, battery modules, or battery packs can be selected according to their usage requirements.

[0142] Figure 7 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of individual battery cells, a battery pack or battery module can be used.

[0143] [Example]

[0144] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0145] The types and mass contents of doped elements in the positive electrode active materials used in each embodiment and comparative example are described separately and recorded in Table 1.

[0146] Example 1

[0147] Preparation of the lower positive electrode slurry:

[0148] Li, the positive electrode active material 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 O2 (volume particle size Dv50 of 3.7 μm), LiFePO4 (volume particle size Dv50 of 1.4 μm), acetylene black, positive electrode binder PVDF, and carbon nanotubes were added to a certain amount of solvent NMP in a mass ratio of 94.09:2.91:0.5:2:0.5 and stirred to prepare a uniform slurry 1.

[0149] Preparation of the upper positive electrode slurry:

[0150] LiNi0.55 Co 0.16 Mn 0.29 O2 positive electrode active material (volume particle size Dv50 of 3.3μm), LiFePO4 (volume particle size Dv50 of 1.4μm), acetylene black, positive electrode binder PVDF, and carbon nanotubes were mixed with a certain amount of solvent NMP in a mass ratio of 94.09:2.91:0.5:2:0.5 and stirred to form a uniform slurry 2.

[0151] Preparation of positive electrode sheet

[0152] A double-layer coating device was used to uniformly coat both the lower and upper slurries simultaneously on the positive electrode current collector. The coating amount of the lower slurry was 136 mg / 1540.25 mm. 2 The top layer of slurry was applied at a rate of 136 mg / 1540.25 mm. 2 After double-sided coating, the positive electrode sheet with a first film layer on the bottom and a second film layer on the top is prepared by drying, cold pressing and slitting. The thickness of the first film layer and the thickness of the second film layer are both 28μm, i.e., f1 / f2=1, g1 / g2=1.

[0153] Preparation of negative electrode sheet

[0154] The negative electrode active material graphite, the negative electrode binder styrene-butadiene rubber (SBR), the negative electrode thickener sodium carboxymethyl cellulose (CMC-Na), and the negative electrode conductive agent carbon black (Super P) are mixed thoroughly in an appropriate amount of deionized water at a mass ratio of 96:1.5:0.5:2 to form a uniform negative electrode slurry. The negative electrode slurry is then coated onto the surface of the negative electrode current collector copper foil, and the negative electrode sheet is prepared by drying, cold pressing, and slitting.

[0155] Separator membrane: Porous polyethylene (PE) membrane is used as the separator membrane.

[0156] The electrolyte is a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1. The lithium salt is LiPF6 with a concentration of 1 mol / L in the solvent. FEC (fluoroethylene carbonate) is used as an additive with a mass content of 1 wt% in the electrolyte.

[0157] Battery cell assembly

[0158] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. The electrodes are then wound to obtain a bare cell. The bare cell is placed in an outer packaging, injected with prepared electrolyte, and then subjected to processes such as sealing, electrolyte injection, formation, and venting to obtain a single battery cell.

[0159] The thickness of the film is tested using the following method:

[0160] Cut the positive electrode sheet into 6mm*6mm samples and attach them to a paraffin-coated sample stage, ensuring the samples protrude slightly beyond the stage edge (<1mm). Polish the sample end face. Analyze the sample end face using a scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS) system (Sigma 300), following standard JY / T010-1996. Perform manganese element analysis (linear scanning) on ​​the sample end face to identify the distribution of different film layers. Combined with SEM measurements of the thickness at corresponding locations, the thicknesses of the first and second film layers can be obtained. The relationship between the measured thicknesses of the first and second film layers is consistent with the relationship between the coating amounts of each film layer.

[0161] The following method can be used to test the cross-sectional area ratio of active materials:

[0162] The positive electrode sheet was cut into 6mm*6mm samples and attached to a sample stage coated with paraffin wax, with the sample slightly protruding from the edge of the sample stage (<1mm). The end face of the positive electrode sheet was polished. The polished end face was tested using a scanning electron microscope (SEM) on a Sigma 300, and the test was performed according to the JY / T010-1996 standard. Three locations were selected and magnified 3000 times for SEM photography. Then, Avizo software was used to analyze and calculate the proportion of the cross-sectional area of ​​the metal oxide in the cross-sectional area of ​​the corresponding film layer based on the different contrast of the materials, and the average value of the three locations was taken. The cross-sectional area proportion of the first positive electrode active material in the first film layer is d1, and the cross-sectional area proportion of the second positive electrode active material in the second film layer is d2. The d1 of each embodiment is approximately 83% (d1 is 79% in Example 10 and 85% in Comparative Example 3), and the d2 of each embodiment is approximately 87%.

[0163] Battery performance test

[0164] (1) Room temperature cycling performance test:

[0165] The prepared battery was charged at a constant current of 0.5C to the upper limit voltage of 4.4V under a constant temperature environment of 25℃. Then, it was charged at a constant voltage of 4.4V until the current was ≤0.05C, allowed to stand for 5 minutes, and then discharged at a constant current of 1C to 2.5V. This constitutes one cycle of charge and discharge. The discharge capacity at this point is recorded as the discharge capacity of the first cycle. The battery was subjected to cycle charge and discharge tests using the above method, and the discharge capacity after each cycle was recorded until the battery's discharge capacity decreased to 80% of the discharge capacity of the first cycle. The number of cycles at this point is used to characterize the battery's cycle performance. The higher the number of cycles, the better the cycle performance.

[0166] (2) Battery resistance growth rate test after 500 cycles:

[0167] Under a constant temperature environment of 25℃, the battery prepared above is charged at a constant current of 0.5C to the upper limit voltage of 4.4V, and then charged at a constant voltage of 4.4V until the current is ≤0.05C. After standing for 30 minutes, the voltage of the battery at this time is recorded as V1. The battery is discharged at a constant current of 1C for 30 seconds, and the voltage at the end of the discharge is recorded as V2. The internal resistance DCR of the battery before cycling is recorded as DCR=(V1-V2) / 1C.

[0168] Cycle the battery 500 times according to the cycle performance test method described above. Then test the internal resistance (DCR) of the battery after 500 cycles according to the method described above.

[0169] The increase in internal resistance after 500 battery cycles = (internal resistance after 500 cycles / internal resistance before cycles) - 1.

[0170] (3) High-temperature storage performance test:

[0171] Under a constant temperature environment of 25℃, the prepared battery is charged at a constant current of 0.5C to the upper limit voltage of 4.4V, and then charged at a constant voltage of 4.4V until the current is ≤0.05C. After standing for 5 minutes, it is discharged at a constant current of 1C to 2.5V. This is one cycle of charge and discharge. The discharge capacity at this time is recorded as the initial capacity C0 (calibrated capacity).

[0172] Then, the battery was charged at a constant current of 0.5C to the upper limit voltage of 4.4V under a constant temperature environment of 25℃, and then charged at a constant voltage of 4.4V until the current is ≤0.05C, and then left to stand for 5 minutes (adjusted to 100% SOC).

[0173] Cells at 100% SOC were placed at 60℃ for different periods of time. During the resting process, they were taken out of the high-temperature furnace every 10 days or so, and the capacity Cn (n is the number of test days) was tested. The capacity retention rate was calculated by Cn / C0. When the capacity retention rate was ≤80%, the number of high-temperature storage days was recorded. The higher the number of storage days, the better the high-temperature storage performance.

[0174] (4) Test of anodic manganese leaching content after high-temperature storage:

[0175] After the above high-temperature storage is completed, the tested battery is left to stand at 25°C for 2 hours, then charged at a constant current of 0.5C to the upper limit voltage of 4.4V, and then charged at a constant voltage of 4.4V to the current ≤0.05C, and left to stand for 5 minutes (adjusting to 100% SOC).

[0176] The battery was then disassembled, and 0.5g of the negative electrode from the central region was taken. The negative electrode was placed in an appropriate amount of concentrated nitric acid as a digestion solvent and digested using the plate digestion method. Finally, the extraction solvent was dissolved in 7% (volume fraction of acid) hydrochloric acid. The resulting solution was then brought to an appropriate volume and tested using an inductively coupled plasma optical emission spectrometer (ICP-OES) to calculate the mass percentage of manganese.

[0177] Example 2

[0178] Everything else is the same as in Example 1, except that the positive electrode active material in the upper slurry is LiNi. 0.65 Co 0.07 Mn 0.28 O2, with a volumetric particle size Dv50 of 3.5 μm.

[0179] Example 3

[0180] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is LiNi. 0.55 Co 0.07 Mn 0.377 Ti 0.003 O2, with a volumetric particle size Dv50 of 3.8 μm, and the positive electrode active material of the upper slurry is LiNi. 0.55 Co 0.16 Mn 0.29 O2, with a volumetric particle size Dv50 of 3.3 μm.

[0181] Example 4

[0182] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.988 Na 0.012 Ni 0.55 Co 0.07 Mn 0.38 O2, with a volumetric particle size Dv50 of 3.5 μm.

[0183] Example 5

[0184] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.992 Na 0.008 Ni 0.55 Co 0.07 Mn 0.38 O2, with a volumetric particle size Dv50 of 3.3 μm.

[0185] Example 6

[0186] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.997 Na 0.003 Ni 0.55 Co0.07 Mn 0.38 O2, with a volumetric particle size Dv50 of 3.6 μm.

[0187] Comparative Example 1

[0188] Everything else is the same as in Example 1, except that the positive electrode slurry is applied in a single layer, and the positive electrode slurry is specifically Li. 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 O2 positive electrode active material (volume particle size Dv50 is 3.7μm), LiNi 0.55 Co 0.16 Mn 0.29 A slurry was prepared by adding O2 positive electrode active material (volume particle size Dv50 of 3.3 μm), acetylene black, positive electrode binder PVDF, and carbon nanotubes in a mass ratio of 48.5:48.5:0.5:2:0.5 with a certain amount of solvent NMP. The coating amount was 276 mg / 1540.25 mm. 2 .

[0189] Comparative Example 2

[0190] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is LiNi. 0.55 Co 0.16 Mn 0.29 O2 (volume particle size Dv50 is 3.3 μm), the positive electrode active material in the upper slurry is Li 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 O2 (volume particle size Dv50 is 3.7 μm).

[0191] Comparative Example 3

[0192] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is LiNi. 0.55 Co 0.07 Mn 0.38 O2 (volume particle size Dv50 is 3.3μm) does not contain other elements.

[0193] The data for b1 and c1 in each embodiment and comparative example are recorded in Table 1. The battery performance test results mentioned above are also recorded in Table 1.

[0194] Table 1

[0195] Based on the data comparison of Examples 1 to 6 and Comparative Examples 1 and 2 in Table 1, it can be seen that when the manganese content of the first transition metal oxide containing lithium in the upper film is lower than the manganese content of the first transition metal oxide containing lithium in the lower film, the cycle performance and high-temperature storage performance of the battery cell can be improved.

[0196] A comparison of the data from Examples 1, 4 to 6, and Comparative Example 3 shows that when the first transition metal oxide in the lower layer of Comparative Example 3 has a high manganese content and no sodium doping, its structural stability is insufficient, resulting in insufficient cycle performance and storage performance of the battery cell. Sodium doping in the lithium-containing first transition metal oxide in the first layer is beneficial to improving the cycle performance and storage performance of the battery cell. However, if the sodium doping amount exceeds a certain level, it will cause an increase in the battery's internal resistance.

[0197] The following examines the technical effects of transition metal doping in the first transition metal oxide of the first film layer.

[0198] Example 7

[0199] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.372 Ti 0.008 O2, with a volumetric particle size Dv50 of 4.0 μm.

[0200] Example 8

[0201] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.376 Ti 0.004 O2, with a volumetric particle size Dv50 of 3.9 μm.

[0202] Example 9

[0203] Everything else is the same as in Example 1, except that the positive electrode active material in the lower slurry is Li. 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.378 Ti 0.002 O2, with a volumetric particle size Dv50 of 3.7 μm.

[0204] The content of doped elements in the first transition metal oxides of Examples 1, 7 to 9 is recorded in Table 2, and the battery performance test results are also recorded in Table 2.

[0205] Table 2

[0206] The data comparison of Examples 1 and 7 to 9 shows that the doping of transition metals is beneficial to improving the cycle performance of the battery, but the doping amount will also cause the battery internal resistance to increase after exceeding a certain level.

[0207] The following examines the effect of adding lithium phosphate on individual battery cells.

[0208] Example 10

[0209] Everything else is the same as in Example 1, except that the lower slurry does not contain LiFePO4 positive electrode additive, and the positive electrode active material is Li 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 The mass ratio of O2, acetylene black, positive electrode binder PVDF, and carbon nanotubes is 97:0.5:2:0.5.

[0210] Example 11

[0211] Everything else is the same as in Example 1, except that in the lower slurry, the positive electrode active material Li 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 The mass ratio of O2, LiFePO4 cathode additive, acetylene black, PVDF cathode binder, and carbon nanotubes is 92:5:0.5:2:0.5.

[0212] Example 12

[0213] Everything else is the same as in Example 1, except that:

[0214] The lower slurry does not contain LiFePO4 cathode additives; the cathode active material is Li 0.995 Na 0.005 Ni 0.55 Co 0.07 Mn 0.38 The mass ratio of O2, acetylene black, PVDF positive electrode binder, and carbon nanotubes is 97:0.5:2:0.5.

[0215] The upper slurry does not contain LiFePO4 cathode additives; the cathode active material is LiNi. 0.55 Co0.16 Mn 0.29 The mass ratio of O2, acetylene black, positive electrode binder PVDF, and carbon nanotubes is 97:0.5:2:0.5.

[0216] The results of lithium phosphate content and battery performance tests are recorded in Table 3.

[0217] Low-temperature (0℃) 10% SOC DCR test was performed on the battery cells of Examples 1, 10, and 12: In a constant-temperature environment of 25℃, the battery cells were charged at a constant current of 0.5C to the upper limit voltage of 4.4V, and then charged at a constant voltage of 4.4V until the current ≤0.05C, and allowed to stand for 5 minutes. The cells were then discharged at a constant current of 1C to the lower limit voltage of 2.5V, and the discharge capacity Cn was recorded, and allowed to stand for 5 minutes. The cells were then discharged at 0.33C to a capacity of 0.9Cn to adjust the cell to 10% SOC, and allowed to stand for 5 minutes. The cells were then placed in a 0℃ environment and allowed to stand for 2 hours, and the voltage V3 at the end of the standing period was recorded. Then, the cells were discharged at 0.36C for 30 seconds, and the voltage at the end of the discharge period was recorded as V4. The 0℃ discharge DCR = (V3 - V4) / 0.36C. The smaller the DCR value, the stronger the low-temperature, low-SOC discharge capability.

[0218] Table 3

[0219] As can be seen from the data in Table 3, the low-temperature low-SOC discharge capability is poor without lithium phosphate, and the low-temperature SOC discharge capability can be significantly improved after adding lithium phosphate. Furthermore, adjusting the distribution of lithium phosphate in the two film layers can further improve the discharge capability. For example, comparing Example 1 and Example 10, it can be found that when more lithium phosphate is placed in the second film layer, the low-temperature 0℃ 10% SOC discharge DCR can be better reduced, thus improving the low-temperature SOC discharge capability.

[0220] In addition, when the lithium phosphate content is too high, it will affect the cycle performance, as shown in the comparison between Example 1 and Example 11. Because the lithium phosphate material has poor high voltage resistance, the cycle performance of the battery cell deteriorates.

[0221] Example 13

[0222] Everything else is the same as in Example 1, except that during the preparation of the positive electrode sheet, a lower slurry and an upper slurry are uniformly coated simultaneously with the positive current collector, wherein the coating amount of the lower slurry is 40 mg / 1540.25 mm. 2 The top layer of slurry was applied at a rate of 160 mg / 1540.25 mm. 2 f1 / f2 = 0.25.

[0223] Example 14

[0224] Everything else is the same as in Example 1, except that in the preparation process of the positive electrode sheet, a lower slurry and an upper slurry are uniformly coated simultaneously with the positive current collector, wherein the coating amount of the lower slurry is 320 mg / 1540.25 mm. 2 The top layer of slurry was applied at a rate of 80 mg / 1540.25 mm. 2 f1 / f2 = 4.

[0225] Example 15

[0226] Everything else is the same as in Example 1, except that during the preparation of the positive electrode sheet, a lower slurry and an upper slurry are uniformly coated simultaneously with the positive current collector, wherein the coating amount of the lower slurry is 48 mg / 1540.25 mm. 2 The top layer of slurry was applied at a rate of 136 mg / 1540.25 mm. 2 f1 / f2 = 1 / 3.

[0227] The test results of the battery performance of the battery cells in the above embodiments are recorded in Table 4.

[0228] Table 4

[0229] In Example 15, the coating quality of the second membrane layer was too poor, which deteriorated the Mn dissolution and cycling performance due to the high Mn material near the diaphragm side.

[0230] The following examines the effect of doping elements in the first and second films on battery performance.

[0231] Example 16

[0232] Everything else is the same as in Example 1, except that the positive electrode active material in the upper slurry is Li. 0.998 Na 0.002 Ni 0.55 Co 0.16 Mn 0.29 O2.

[0233] Example 17

[0234] Everything else is the same as in Example 1, except that the positive electrode active material in the upper slurry is Li. 0.992 Na 0.008 Ni 0.55 Co 0.16 Mn 0.29 O2.

[0235] Example 18

[0236] Everything else is the same as in Example 3, except that the positive electrode active material in the lower slurry is LiNi. 0.55 Co 0.07 Mn 0.377 Ti0.003 O2, the positive electrode active material of the upper slurry is Li 0.995 Na 0.005 Ni 0.72 Co 0.07 Mn 0.208 Ti 0.002 O2, with a volumetric particle size Dv50 of 3.2 μm.

[0237] Example 19

[0238] Everything else is the same as in Example 3, except that the positive electrode active material in the lower slurry is LiNi. 0.55 Co 0.07 Mn 0.377 Ti 0.003 O2, the positive electrode active material of the upper slurry is Li 0.995 Na 0.005 Ni 0.60 Co 0.16 Mn 0.236 Ti 0.004 O2, with a volumetric particle size Dv50 of 2.9 μm.

[0239] The doping element content in the first and second films and the battery performance test results are recorded in Table 5.

[0240] Table 5

[0241] The data comparison in Examples 16 to 19 shows that when the lithium doping content in the positive electrode active material in the lower first film layer is greater than that in the upper second film layer, or when the transition metal doping content in the positive electrode active material in the lower first film layer is greater than that in the upper second film layer, it is more beneficial to improve the cycle performance of the battery cell and control the battery internal resistance. This is because in the lower first film layer, the first transition metal oxide containing lithium has a higher manganese content. Using more lithium doping or transition metal doping can improve its structural stability, thereby reducing the dissolution of manganese, thus better improving the cycle performance of the battery cell and controlling the increase in battery internal resistance.

[0242] Although this application has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of this application. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. This 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, comprising a positive electrode sheet, said positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one side of the positive current collector, wherein, The positive electrode film layer includes: A first film layer is disposed on at least one side of the positive electrode current collector. The first film layer includes a first positive electrode active material, which includes a lithium-containing first transition metal oxide. The lithium-containing first transition metal oxide includes lithium, nickel, cobalt, manganese, and a first doping element. The mass content of manganese in the lithium-containing first transition metal oxide is a1. The second film layer is disposed on the side of the first film layer away from the positive current collector. The second film layer includes a second positive active material, which includes a lithium-containing second transition metal oxide. The lithium-containing second transition metal oxide includes lithium, nickel, cobalt, manganese and optional second doping elements. The mass content of manganese in the lithium-containing second transition metal oxide is a2, where a1 > a2. The first dopant element and the second dopant element each independently include one or more elements from the groups of Na, K, Be, Mg, Ca, IIIA, IB, IIB, IIIB, IVB, VB, VIB, and VIII.

2. The battery cell according to claim 1, wherein, The first doping element and the second doping element each independently include a first metal doping element, and the first metal doping element each independently includes one or more elements of Na, K, Be, Mg and Ca.

3. The battery cell according to claim 2, wherein, The first metal doping element independently includes one or more elements selected from Na, K, and Mg, and optionally includes Na and / or Mg.

4. The battery cell according to claim 2 or 3, wherein, In the first lithium-containing transition metal oxide, the mass ratio of the first metal dopant element to the lithium element is b1; in the second lithium-containing transition metal oxide, the mass ratio of the first metal dopant element to the lithium element is b2, where b1 > b2.

5. The battery cell according to claim 4, wherein, 39300ppm≥b1>0ppm, can be selected as 26300ppm≥b1≥9900ppm.

6. The battery cell according to claim 4 or 5, wherein, 26300ppm≥b2≥0ppm.

7. The battery cell according to any one of claims 1 to 6, wherein, The first doping element and the second doping element each independently further include a second metal doping element, and the second metal doping element each independently includes one or more elements from Group IIIA, Group IB, Group IIB, Group IIIB, Group IVB, Group VB, Group VIB and Group VIII.

8. The battery cell according to claim 7, wherein, Each of the second metal doping elements independently includes one or more elements selected from Al, Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Ce, Nb, Sb, Ta, Ge, Nb, Sc, and Y, and optionally includes one or more elements selected from Ti, W, Zr, Sr, Cr, Fe, Zn, Cu, Mo, V, Nb, Sb, Ta, and Y, and further optionally includes one or more elements selected from Ti, Mo, Nb, Sb, and Ta.

9. The battery cell according to claim 7 or 8, wherein, In the lithium-containing first transition metal oxide, the mass ratio of the second metal dopant element to the total mass of nickel, cobalt, manganese and the second metal dopant element is c1; in the lithium-containing second transition metal oxide, the mass ratio of the second metal dopant element to the total mass of nickel, cobalt, manganese and the second metal dopant element is c2, where c1 > c2.

10. The battery cell according to any one of claims 7 to 9, wherein, The mass content of the second metal dopant element in the lithium-containing first transition metal oxide is 1700ppm to 6700ppm, and can be optionally 1700ppm to 3400ppm; the mass content of the second metal dopant element in the lithium-containing second transition metal oxide is 0ppm to 3400ppm.

11. The battery cell according to any one of claims 1 to 9, wherein, In the first lithium-containing transition metal oxide, the molar content of manganese in the nickel, cobalt, and manganese elements is 0.05:1-0.4:1; in the second lithium-containing transition metal oxide, the molar content of manganese in the nickel, cobalt, and manganese elements is 0.02:1-0.3:

1.

12. The battery cell according to any one of claims 1 to 11, wherein, In the same cross section, the cross-sectional area ratio of the first positive electrode active material in the first film layer is d1, and the cross-sectional area ratio of the second positive electrode active material in the second film layer is d2, where d1 < d2.

13. The battery cell according to any one of claims 1 to 12, wherein, The first positive electrode active material further includes a first lithium-containing phosphate, and / or the second positive electrode active material further includes a second lithium-containing phosphate, wherein the first lithium-containing phosphate and the second lithium-containing phosphate each independently include one or more of lithium iron phosphate and its modified materials, and lithium manganese iron phosphate and its modified materials.

14. The battery cell according to claim 13, wherein, The mass content of the first lithium phosphate in the first positive electrode active material is e1, and the mass content of the second lithium phosphate in the second positive electrode active material is e2, where e1≤e2, and optionally 0≤(e1+e2)≤8.

15. The battery cell according to claim 14, wherein, 0 ≤ e1 ≤ 4 wt%; 0 ≤ e2 ≤ 5 wt%.

16. The battery cell according to any one of claims 1 to 15, wherein, The thickness of the first film layer is f1, the thickness of the second film layer is f2, and 0.25≤f1 / f2≤4.

17. The battery cell according to any one of claims 1 to 16, wherein, The first film layer further includes a first conductive agent, and the second film layer further includes a second conductive agent. The mass content of the first conductive agent in the first film layer is g1, and the mass content of the second conductive agent in the second film layer is g2, where g1 > g2.

18. The battery cell according to claim 17, wherein, The first conductive agent and the second conductive agent each independently include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers, and optionally the first conductive agent and the second conductive agent each independently include carbon nanotubes.

19. The battery cell according to any one of claims 1 to 18, wherein, The charging voltage of the battery cell is between 4.25V and 4.5V.

20. The battery cell according to any one of claims 1 to 19, wherein, The coating weight (CW) of the positive electrode film layer satisfies: 100 mg / 1540.25 mm. 2 ≤CW≤500mg / 1540.25mm 2 .

21. A battery device comprising a plurality of battery cells, wherein, The battery cell includes any one of claims 1 to 20.

22. An electrical device comprising a single battery cell or a battery assembly, wherein, The battery cell includes any one of claims 1 to 20, and the battery device includes the battery device of claim 21.

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