Battery cell, battery and electric equipment

Abstract

The invention relates to a battery cell, a battery and electric equipment. The battery cell comprises a first positive plate and a second positive plate, wherein the first positive plate is a phosphate positive plate, and the second positive plate is a layered oxide positive plate. According to the battery cell disclosed by the invention, the problem that the tortuosity of an electron / ion path is large in the charging and discharging processes of the battery cell during conventional mixed coating can be improved; the battery cell disclosed by the invention is large in gram capacity, and has relatively excellent cycle capacity retention ratio and rate capability.

Description

Technical Field

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

[0002] Olivine-structured phosphate-based cathode materials, such as lithium iron phosphate, offer advantages such as high safety, good cycle stability, low gas production rates, and low cost. However, their specific capacity is relatively low, with a theoretical delithiation specific capacity of 170 mAh / g. Layered oxides offer higher energy density (approximately 275 mAh / g), but suffer from poor thermal stability. To meet customer demand for higher energy density and safer battery cells, most researchers have combined phosphate-based cathode materials with layered oxide materials to create hybrid cathode cells, such as lithium iron phosphate-doped ternary layered oxides, lithium manganese iron phosphate-doped ternary layered oxides, or lithium-rich manganese-based materials. Existing hybrid cathode cells suffer from uneven distribution of active materials, high tortuosity in the electron and ion pathways, high polarization, and significantly reduced rate performance. Summary of the Invention

[0003] The purpose of the present disclosure is to provide a battery cell, a battery and an electrical device, in which different positive electrode sheets are independently slurried and coated with different active materials, thereby avoiding the problem of uneven distribution of active materials due to different particle sizes of active materials; and improving the problem of large tortuosity of electron / ion pathways during charging and discharging of the battery cell during conventional mixed coating. The battery cell disclosed in the present disclosure has a large gram capacity and has excellent cycle capacity retention rate and rate performance.

[0004] In order to achieve the above-mentioned object, the present disclosure provides a battery cell in a first aspect, wherein the battery cell comprises a first positive electrode sheet and a second positive electrode sheet; Wherein, the first positive electrode sheet is a phosphate positive electrode sheet, and the second positive electrode sheet is a layered oxide positive electrode sheet.

[0005] Optionally, based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 90%.

[0006] Optionally, based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 40%.

[0007] Optionally, based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 15% to 30%.

[0008] Optionally, the phosphate positive electrode sheet includes a lithium iron phosphate positive electrode sheet and / or a lithium iron manganese phosphate positive electrode sheet.

[0009] Optionally, the layered oxide positive electrode sheet includes one or more of a lithium cobalt oxide positive electrode sheet, a lithium nickel cobalt manganese oxide positive electrode sheet, a lithium nickel cobalt aluminum oxide positive electrode sheet and a lithium-rich manganese-based positive electrode sheet.

[0010] Optionally, the layered oxide positive electrode sheet is a lithium-rich manganese-based positive electrode sheet.

[0011] Optionally, the battery cell includes a plurality of second positive electrode sheets, and a plurality of first positive electrode sheets are arranged between any two adjacent second positive electrode sheets.

[0012] Optionally, the number of first positive electrode sheets between any two adjacent second positive electrode sheets is equal.

[0013] Optionally, the battery cell includes a positive electrode tab, and the positive electrode tab is connected to the first positive electrode sheet and the second positive electrode sheet; and / or, The positive electrode tab includes a first positive electrode tab and a second positive electrode tab, wherein the first positive electrode tab is connected to the first positive electrode sheet, and the second positive electrode tab is connected to the second positive electrode sheet.

[0014] Optionally, the battery cell includes a negative electrode sheet, and the negative electrode sheet includes one or more of a graphite negative electrode sheet, a silicon-based negative electrode sheet and a hard carbon negative electrode sheet.

[0015] Optionally, the negative electrode sheet includes a first negative electrode sheet and a second negative electrode sheet, the first negative electrode sheet is a natural graphite negative electrode sheet, and the second negative electrode sheet is an artificial graphite negative electrode sheet.

[0016] Optionally, based on the total mass of the natural graphite in the battery cell and the artificial graphite in the battery cell, the mass proportion of the artificial graphite is 30% to 70%.

[0017] Optionally, based on the total mass of the natural graphite in the battery cell and the artificial graphite in the battery cell, the mass proportion of the artificial graphite is 40% to 60%.

[0018] Optionally, the battery cell includes a negative electrode tab, and the negative electrode tab is connected to the first negative electrode sheet and the second negative electrode sheet; and / or, The negative electrode tab includes a first negative electrode tab and a second negative electrode tab, wherein the first negative electrode tab is connected to the first negative electrode sheet, and the second negative electrode tab is connected to the second negative electrode sheet.

[0019] A second aspect of the present disclosure provides a battery, comprising the battery cell described in the first aspect of the present disclosure.

[0020] A third aspect of the present disclosure provides an electrical device, comprising the battery described in the second aspect of the present disclosure.

[0021] Through the above technical solution, the technical solution disclosed in the present invention independently loads the phosphate positive electrode active material and the layered oxide positive electrode active material on independent positive electrode sheets. By mixing the two positive electrode sheets instead of mixing the two positive electrode materials in the same positive electrode material layer, the problem of uneven distribution of active materials due to different active material particle sizes can be avoided; different positive electrode sheets are charged and discharged independently, which effectively improves the problem of large tortuosity of electron / ion pathways during charging and discharging of the battery cell during conventional mixed coating, and effectively reduces the DC internal resistance; in addition, the phosphate positive electrode sheet and the layered oxide positive electrode sheet can realize the interaction of the two active materials in the same electrolyte system, effectively improving the gram capacity and cycle capacity retention rate of the battery cell, effectively reducing the polarization of the battery cell, and improving the rate performance of the battery cell; compared with conventional mixed coating, the battery formed by the battery cell disclosed in the present invention has better improvement in rate performance and cycle performance. In addition, compared to a battery cell formed by separately forming battery cell units with different positive electrodes and then connecting them in parallel, there will be problems such as differences in battery cell internal resistance and battery cell attenuation. The present disclosure unifies different positive electrodes in the same battery cell, which can improve the consistency of the battery cell and reduce the difficulty of the battery management system (BMS).

[0022] Other features and advantages of the present disclosure will be described in detail in the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The accompanying drawings are used to provide a further understanding of the present disclosure and constitute a part of the specification. Together with the following detailed description, they are used to explain the present disclosure but do not constitute a limitation of the present disclosure. In the accompanying drawings: Figure 1 It is a schematic diagram of the battery cell of Example 1 of the present disclosure.

[0024] Figure 2 Schematic diagram of a battery cell unit in one embodiment of the present disclosure.

[0025] Figure 3 It is a schematic diagram of the battery cell of Example 4 of the present disclosure.

[0026] Figure 4 It is a schematic diagram of the battery cell of Example 5 of the present disclosure.

[0027] Description of Reference Numerals 1: First positive electrode sheet; 2: Second positive electrode sheet; 3: Negative electrode sheet; 4: Positive electrode; 5: Negative electrode. DETAILED DESCRIPTION

[0028] The following describes the specific embodiments of the present disclosure in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present disclosure and are not intended to limit the present disclosure.

[0029] A first aspect of the present disclosure provides a battery cell, the battery cell comprising a first positive electrode sheet and a second positive electrode sheet; Wherein, the first positive electrode sheet is a phosphate positive electrode sheet, and the second positive electrode sheet is a layered oxide positive electrode sheet.

[0030] The inventors of the present application have discovered that the existing methods for blending different active materials mainly include coating after evenly mixing two or more active materials, or doping by layered coating. Most technologies adopt a mixed coating method, which is to pre-disperse multiple active materials with conductive agents and binders, and then coat them on the same foil at one time. However, due to the differences in the surface properties of the two or more active materials, there are differences in the adhesion ability to the conductive agent / binder, which usually leads to uneven distribution of the conductive agent / binder, and even some active material particles have no conductive agent / binder attached to their surfaces. For example, when lithium manganese iron phosphate is mixed with a ternary layered material system, it is usually observed that no conductive agent is attached to the surface of the ternary layered material. This is because after the surface of lithium manganese iron phosphate is coated with carbon, there are more functional groups, and the adsorption capacity for the conductive agent is stronger. In addition, there are large differences in the sizes of the two active materials. For example, the D of lithium manganese iron phosphate is 2.34mm, which is 1.33mm. 50 Usually about 1μm, while the D of the blended ternary layered material is 50 The size is usually 3-4μm. The difference in particle size will also lead to poor dispersion uniformity of the active material in the electrode, and the polarization degree of different regions varies greatly. If a layered coating method such as double-layer coating is adopted, the two main materials are separated and homogenized, and coated on the foil once or twice, the above problems can be solved to a certain extent, but the additional problem of the interface layer is introduced, such as the potential stratification and shedding of the material area, and the interface layer causing increased impedance. In addition, due to the different charge and discharge characteristics of the active materials, the different main materials in the mixed cathode system do not undergo a uniform lithium insertion and extraction process during the charge and discharge process, that is, at a certain stage, the current of a single active material accounts for a larger proportion; this means that when active material A mainly contributes to the capacity, the space occupied by the other active material B causes the actual electron path and ion path of the active material A to be significantly increased in tortuosity, resulting in a significant increase in the polarization degree of the mixed cathode system and a significant decrease in the rate performance.

[0031] The technical solution disclosed in the present invention independently loads the phosphate positive electrode active material and the layered oxide positive electrode active material on independent positive electrode sheets. By mixing the two positive electrode sheets instead of mixing the two positive electrode materials in the same positive electrode material layer, the problem of uneven distribution of active materials due to different active material particle sizes can be avoided; different positive electrode sheets are charged and discharged independently, which effectively improves the problem of large tortuosity of electron / ion pathways during charging and discharging of the battery cell during conventional mixed coating, and effectively reduces the DC internal resistance; in addition, the phosphate positive electrode sheet and the layered oxide positive electrode sheet can realize the interaction of the two active materials in the same electrolyte system, effectively improving the gram capacity and cycle capacity retention rate of the battery cell, effectively reducing the polarization of the battery cell, and improving the rate performance of the battery cell; compared with conventional mixed coating, the battery formed by the battery cell disclosed in the present invention has better improvement in rate performance and cycle performance. Compared with a battery cell formed by forming different positive electrodes into battery units separately and then connecting them in parallel, there will be problems such as differences in battery cell internal resistance and battery cell attenuation. The present disclosure unifies different positive electrodes into the same battery cell, improving the consistency of the battery cell and reducing the difficulty of the battery management system (BMS).

[0032] The phosphate positive electrode sheet in the present disclosure refers to a positive electrode sheet using phosphate as the positive electrode active material, which may further include one or more of a conductive agent, a binder and a dispersant. It can be understood that the phosphate positive electrode sheet in the present disclosure does not contain a layered oxide positive electrode active material; the layered oxide positive electrode sheet in the present disclosure refers to a positive electrode sheet using layered oxide as the positive electrode active material, which may further include one or more of a conductive agent, a binder and a dispersant. It can be understood that the layered oxide positive electrode sheet in the present disclosure does not contain a phosphate positive electrode active material.

[0033] According to one embodiment of the present disclosure, based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 90%. This preferred embodiment is conducive to further improving the specific capacity and cycle capacity retention rate of the battery cell, effectively reducing battery cell polarization, and further improving the rate performance and cycle performance of the battery cell.

[0034] It is understandable to those skilled in the art that the positive electrode active material may be lost in the actual preparation process of the electrode, and the mass proportion of the layered oxide positive electrode active material in the battery cell may have a certain error, which is also within the scope of protection of this application.

[0035] According to one embodiment of the present disclosure, based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 40%. This preferred embodiment is conducive to further improving the specific capacity and cycle capacity retention rate of the battery cell, effectively reducing battery cell polarization, and further improving the rate performance and cycle performance of the battery cell.

[0036] According to one embodiment of the present disclosure, based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 15% to 30%. This preferred embodiment is conducive to further improving the specific capacity and cycle capacity retention rate of the battery cell, effectively reducing battery cell polarization, and further improving the rate performance and cycle performance of the battery cell.

[0037] According to one embodiment of the present disclosure, the phosphate positive electrode sheet includes a lithium iron phosphate positive electrode sheet and / or a lithium iron manganese phosphate positive electrode sheet. In a further embodiment, the phosphate positive electrode sheet includes a phosphate positive electrode active material, a conductive agent and a binder. The present disclosure does not specifically limit the mixing mass ratio of the phosphate positive electrode active material, the conductive agent and the binder, and it can be a conventional ratio in the art. The present disclosure does not specifically limit the phosphate positive electrode active material, and it can be a conventional type in the art, for example, it can be lithium iron phosphate (chemical formula LiFePO4) and / or lithium iron manganese phosphate (chemical formula LiMn x Fe 1-x PO4, 0<x<1), the above embodiment is conducive to uniform dispersion of the active material, conductive agent and binder of the positive electrode sheet, and is also conducive to improving the problem of large tortuosity of the electron / ion path during the charge and discharge process of the battery cell during conventional mixed coating, thereby reducing the DC resistance.

[0038] According to one embodiment of the present disclosure, the layered oxide positive electrode sheet includes one or more of a lithium cobalt oxide positive electrode sheet, a lithium nickel cobalt manganese oxide positive electrode sheet, a lithium nickel cobalt aluminum oxide positive electrode sheet and a lithium-rich manganese-based positive electrode sheet, preferably a lithium-rich manganese-based positive electrode sheet. In a further embodiment, the layered oxide positive electrode sheet includes a layered oxide positive electrode active material, a conductive agent and a binder. The present disclosure does not make any specific restrictions on the mixing mass ratio of the layered oxide positive electrode active material, the conductive agent and the binder, which can be conventional technology in this field. The present disclosure does not make any specific restrictions on the layered oxide positive electrode active material, which can be conventional types in this field, for example, it can be lithium cobalt oxide (chemical formula LiCoO2), lithium nickel cobalt manganese oxide (chemical formula LiNi x Co y Mn 1-x-y O2, 0<x<1, 0<y<1, 0<x+y<1), lithium nickel cobalt aluminum oxide (chemical formula LiNi pCo q Al 1-p-q O2, 0<p<1, 0<q<1, 0<p+q<1) and lithium-rich manganese-based (chemical formula is mLi2MnO3· (1-m) LiMO2, where M is one or more metal elements such as Ni, Co, and Mn, and 0 < m < 1). This embodiment facilitates uniform dispersion of the active material, conductive agent, and binder in the positive electrode sheet. It also improves the tortuosity of the electron / ion pathways during charge and discharge in conventional mixed coating processes, thereby reducing DC resistance.

[0039] Those skilled in the art will appreciate that the battery cell disclosed herein may further include other positive electrode sheets different from the first positive electrode sheet and the second positive electrode sheet, for example, at least one of a third positive electrode sheet, a fourth positive electrode sheet, and a fifth positive electrode sheet. The positive electrode active materials contained in the above-mentioned electrode sheets may be other positive electrode active materials in addition to layered oxide materials and phosphate materials, which is beneficial to improving the gram capacity and cycle capacity retention rate of the battery cell, effectively reducing the polarization of the battery cell, and improving the rate performance of the battery cell; improving the consistency of the battery cell and reducing the difficulty of the battery management system (BMS).

[0040] In the battery cell disclosed herein, those skilled in the art can adjust the weight percentage of the positive electrode active material contained in each of the first positive electrode sheet and the second positive electrode sheet and the quantitative ratio of the two positive electrode sheets so that the mass ratio of the layered oxide positive electrode active material is within the scope of the present disclosure, wherein the arrangement positions of the first positive electrode sheet and the second positive electrode sheet can be arranged in a variety of ways.

[0041] According to one embodiment of the present disclosure, the battery cell includes a plurality of first positive electrode sheets and a plurality of second positive electrode sheets, the plurality of first positive electrode sheets are arranged on one side of the battery cell, and the plurality of second positive electrode sheets are arranged on the other side of the battery cell; the negative electrode sheet is arranged between any two adjacent first positive electrode sheets, and the negative electrode sheet is arranged between any two adjacent second positive electrode sheets.

[0042] According to one embodiment of the present disclosure, the battery cell includes a plurality of first positive electrode sheets and a plurality of second positive electrode sheets, and the plurality of first positive electrode sheets are distributed on both sides of the plurality of second positive electrode sheets, or the plurality of second positive electrode sheets are distributed on both sides of the plurality of first positive electrode sheets. In this embodiment, the number of first positive electrode sheets distributed on both sides of the plurality of second positive electrode sheets may be equal or unequal. In this embodiment, those skilled in the art may set the position of the first positive electrode sheet / second positive electrode sheet according to the safety characteristics of the positive electrode sheet. For example, the positive electrode sheet with poor safety characteristics may be arranged in the middle of the battery cell to facilitate improving the safety performance of the battery cell.

[0043] In one embodiment, Figure 2As shown, in one battery cell unit, four first positive electrode sheets 1 can be placed on the left side of the second positive electrode sheet 2 , and three first positive electrode sheets 1 can be placed on the right side of the second positive electrode sheet 2 .

[0044] According to one embodiment of the present disclosure, the battery cell includes a plurality of second positive electrode sheets, and a plurality of first positive electrode sheets are disposed between any two adjacent second positive electrode sheets. In this embodiment, the number of first positive electrode sheets between any two adjacent second positive electrode sheets may be equal or unequal.

[0045] According to one embodiment of the present disclosure, the battery cell includes a plurality of second positive plates, and the number of first positive plates between any two adjacent second positive plates is equal. In this embodiment, the two positive plates have the same safety characteristics and are preferably arranged evenly.

[0046] According to one embodiment of the present disclosure, the battery cell includes a positive electrode tab that connects the first positive electrode sheet and the second positive electrode sheet. In this embodiment, the arrangement of the positive electrode tab can meet the demand for combined use of different positive electrode sheets, which is beneficial for improving the consistency of the battery cell and reducing the difficulty of the battery management system.

[0047] According to one embodiment of the present disclosure, the positive electrode tab includes a first positive electrode tab and a second positive electrode tab, wherein the first positive electrode tab is connected to the first positive electrode sheet, and the second positive electrode tab is connected to the second positive electrode sheet. In this embodiment, the arrangement of the positive electrode tabs can meet the requirement of independent use of different positive electrode sheets, which is beneficial to improving the consistency of the battery cell and reducing the difficulty of the battery management system.

[0048] According to one embodiment of the present disclosure, the battery cell includes a negative electrode sheet. The present disclosure does not specifically limit the type of negative electrode sheet, which can be a conventional type in the field. The negative electrode sheet can include one or more of a graphite negative electrode sheet, a silicon-based negative electrode sheet, and a hard carbon negative electrode sheet. Specifically, a graphite negative electrode sheet, a silicon-based negative electrode sheet, and a hard carbon negative electrode sheet refer to negative electrode sheets whose negative electrode active materials are graphite materials, silicon-based materials, and hard carbon materials, respectively. Graphite materials include artificial graphite and natural graphite, etc., silicon-based materials include elemental silicon, silicon oxide, silicon alloys, and composite silicon, etc., and hard carbon materials include tin oxide and tin alloys, etc.; in a further embodiment, the negative electrode sheet can also include one or more of a binder, a conductive agent, and a dispersant; the present disclosure does not specifically limit the mixing mass ratio of the negative electrode active material, the conductive agent, the binder, and the dispersant, which can be a conventional technology in the field.

[0049] According to one embodiment of the present disclosure, the negative electrode sheet includes a first negative electrode sheet and a second negative electrode sheet, wherein the first negative electrode sheet is a natural graphite negative electrode sheet and the second negative electrode sheet is an artificial graphite negative electrode sheet. This embodiment is conducive to improving the charge and discharge capacity retention rate of the battery cell and enhancing the rate performance of the battery cell.

[0050] In one embodiment, the weight of the artificial graphite accounts for 30% to 70%, preferably 40% to 60%, of the total weight of the natural graphite and artificial graphite in the battery cell. This embodiment is beneficial for improving the charge and discharge capacity retention rate of the battery cell and enhancing the rate performance of the battery cell.

[0051] Those skilled in the art will understand that the battery cell disclosed herein may further include other negative electrode sheets different from the first negative electrode sheet and the second negative electrode sheet, for example, including at least one of a third negative electrode sheet, a fourth negative electrode sheet, and a fifth negative electrode sheet, and the negative electrode active materials contained in the above-mentioned electrode sheets may be other negative electrode active materials in addition to graphite negative electrode sheets, silicon-based negative electrode sheets, and hard carbon negative electrode sheets.

[0052] In one embodiment, the positive electrode of the battery cell disclosed herein may include two or more of the first positive electrode sheet, the second positive electrode sheet, the third positive electrode sheet, the fourth positive electrode sheet or the fifth positive electrode sheet, and the negative electrode of the battery cell unit disclosed herein may include two or more of the first negative electrode sheet, the second negative electrode sheet, the third negative electrode sheet, the fourth negative electrode sheet or the fifth negative electrode sheet, which is beneficial to improving the gram capacity and cycle capacity retention rate of the battery cell, effectively reducing the polarization of the battery cell, and improving the rate performance of the battery cell; improving the consistency of the battery cell and reducing the difficulty of the battery management system (BMS).

[0053] According to one embodiment of the present disclosure, the present disclosure does not specifically limit the binder, the conductive agent, and the dispersant, and they may be conventional types in the art; for example, the binder may be one or more of polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polytetrafluoroethylene, polyacrylonitrile, polypropylene carbonate, styrene-butadiene rubber, nitrile rubber, sodium carboxymethyl cellulose, polyethylene oxide, and ethylene oxide-propylene oxide copolymer; the conductive agent may be one or more of acetylene black, Super P, Super S, graphene, carbon fiber, carbon nanotubes, and Ketjen black; the dispersant may be one or more of carboxymethyl cellulose, polyacrylic acid, polymethyl methacrylate, and polyvinyl pyrrolidone.

[0054] According to one embodiment of the present disclosure, the battery cell includes a negative electrode tab, which connects the first negative electrode sheet and the second negative electrode sheet. In this embodiment, the arrangement of the negative electrode tab can meet the demand for combined use of different negative electrode sheets, which is beneficial to improving the consistency of the battery cell and reducing the difficulty of the battery management system.

[0055] According to one embodiment of the present disclosure, the battery cell includes a negative electrode tab, wherein the negative electrode tab includes a first negative electrode tab and a second negative electrode tab, wherein the first negative electrode tab is connected to the first negative electrode sheet, and the second negative electrode tab is connected to the second negative electrode sheet. In this embodiment, the arrangement of the negative electrode tabs can meet the requirement of independent use of different negative electrode sheets, which is beneficial for improving the consistency of the battery cell and reducing the difficulty of the battery management system.

[0056] According to one embodiment of the present disclosure, the first positive electrode sheet, the second positive electrode sheet and the negative electrode sheet are stacked or wound, the stacked arrangement forms a laminated battery cell, and the wound arrangement forms a wound battery cell.

[0057] According to one embodiment of the present disclosure, the stacking arrangement is a Z-type stacking or a C-type stacking. Z-type stacking or C-type stacking is a conventional technology in the art and will not be described in detail in the present disclosure.

[0058] According to one embodiment of the present disclosure, the battery cell further includes a separator, disposed between the first positive electrode sheet and the negative electrode sheet, and between the second positive electrode sheet and the negative electrode sheet. The present disclosure does not specifically limit the type of separator; the separator may be any conventional type in the art, such as one or more of polyethylene (PE) and polypropylene (PP).

[0059] A second aspect of the present disclosure provides a battery, comprising the battery cell described in the first aspect of the present disclosure.

[0060] A third aspect of the present disclosure provides an electrical device, comprising the battery described in the second aspect of the present disclosure.

[0061] According to an embodiment of the present disclosure, the present disclosure does not specifically limit the electrical equipment, for example, it can be a vehicle.

[0062] The present disclosure is further described below with reference to the accompanying drawings, but the present disclosure is not limited thereto. Unless otherwise specified, the reagents disclosed herein are all commercially available.

[0063] In the present disclosure, the total mass of the phosphate positive electrode active material in the battery cell = the surface density of the first positive electrode sheet coating * the electrode area of the first positive electrode sheet * the weight percentage of the positive electrode active material in the positive electrode material layer of the first positive electrode sheet * the number of first positive electrode sheets in the battery cell; the total mass of the layered oxide positive electrode active material in the battery cell = the surface density of the second positive electrode sheet coating * the electrode area of the second positive electrode sheet * the weight percentage of the positive electrode active material in the positive electrode material layer of the second positive electrode sheet * the number of second positive electrode sheets in the battery cell; the mass proportion of the layered oxide positive electrode active material in the battery cell = the total mass of the layered oxide positive electrode active material in the battery cell / (the total mass of the phosphate positive electrode active material in the battery cell + the total mass of the layered oxide positive electrode active material in the battery cell); In the present disclosure, the total mass of natural graphite in the battery cell = the surface density of the first negative electrode sheet coating * the electrode area of the first negative electrode sheet * the weight percentage of natural graphite in the negative electrode material layer of the first negative electrode sheet * the number of first negative electrode sheets in the battery cell; the total mass of artificial graphite in the battery cell = the surface density of the second negative electrode sheet coating * the electrode area of the second negative electrode sheet * the weight percentage of artificial graphite in the negative electrode material layer of the second negative electrode sheet * the number of second negative electrode sheets in the battery cell; the mass proportion of artificial graphite in the battery cell = the total mass of artificial graphite in the battery cell / (the total mass of natural graphite in the battery cell + the total mass of artificial graphite in the battery cell); In the present disclosure, the first positive electrode sheet and the second positive electrode sheet have the same electrode area, and the first negative electrode sheet and the second negative electrode sheet have the same electrode area.

[0064] Example 1 (1) Prepare the first positive electrode sheet, which is a lithium iron manganese phosphate positive electrode sheet; including: using N-methyl pyrrolidone (NMP) as a solvent, adding a binder (polyvinylidene fluoride, PVDF) to disperse evenly to form a transparent glue; adding a conductive agent carbon black to disperse it evenly; adding lithium iron manganese phosphate material (chemical formula LiMn 0.6 Fe 0.4 PO4), stirred and mixed evenly to obtain a slurry; in the slurry, the mass ratio of lithium manganese iron phosphate, conductive agent and binder is 95:2:3, and the solid content is 58wt%; The slurry was coated on the positive electrode current collector, and then rolled, die-cut and baked to obtain the first positive electrode sheet, lithium manganese iron phosphate positive electrode sheet, with a coating surface density of 440g / m 2 ; (2) Preparation of the second positive electrode sheet, which is a lithium-rich manganese-based positive electrode sheet; including: using N-methylpyrrolidone (NMP) as a solvent, adding a binder (polyvinylidene fluoride, PVDF) to disperse evenly to form a transparent glue; adding a conductive agent carbon black to disperse it evenly; adding lithium-rich manganese-based materials (chemical formula Li2MnO3·LiNi 0.33 Co 0.33 Mn 0.33 O2), stirring and mixing uniformly to obtain a slurry; in the slurry, the mass ratio of the lithium-rich manganese-based material, the conductive agent, and the binder is 95:2:3, and the solid content is 68wt%; The slurry was coated on the positive electrode current collector, and then rolled, die-cut and baked to obtain the second positive electrode sheet, which was a lithium-rich manganese-based positive electrode sheet. The coating surface density was 360 g / m 2 ; (3) preparing a negative electrode sheet, including: using deionized water as a solvent, adding CMC (sodium carboxymethyl cellulose) and dispersing it evenly to form a transparent glue; adding a conductive agent (conductive carbon black) and dispersing it evenly; adding graphite material in batches and stirring and mixing it evenly; adding SBR (styrene-butadiene latex) and mixing it evenly to obtain a negative electrode coating slurry; in the slurry, the mass ratio of the graphite material, the conductive agent, the binder and the dispersant is 96:1:1.5:1.5, and the solid content is 47wt%; The negative electrode coating slurry is coated on the negative electrode current collector, and the negative electrode sheet is obtained after roller pressing, die cutting and baking. The coating surface density is 200g / m 2 .

[0065] (4) Assemble the positive electrode sheets prepared in step (1) and step (2), the negative electrode sheets prepared in step (3) and the separator into a battery cell. In the battery cell, based on the total number of the first positive electrode sheets and the second positive electrode sheets (100 sheets), the number of the second positive electrode sheets accounts for 25%, and the number of the first positive electrode sheets accounts for 75%. It is calculated that: based on the total mass of the lithium manganese iron phosphate positive electrode active material in the battery cell and the lithium manganese-rich positive electrode active material in the battery cell, the lithium manganese-rich positive electrode active material is 25%. The mass proportion of the positive electrode active material is about 20%; taking one battery cell as an example, the battery cell of Example 1 includes 100 positive electrode sheets and 101 negative electrode sheets, wherein the 100 positive electrode sheets include 75 first positive electrode sheets 1 and 25 second positive electrode sheets 2, the 100 positive electrode sheets are respectively connected to the positive electrode tabs to form the positive electrode 4 of the battery cell, and the 101 negative electrode sheets 3 are respectively connected to the negative electrode tabs to form the negative electrode 5 of the battery cell; when stacking, the first positive electrode sheet and the second positive electrode sheet are evenly stacked, as shown in FIG. Figure 1 As shown (not all electrodes are shown in the figure), that is, after each stack of three layers of the first positive electrode sheet 1, the fourth layer is the second positive electrode sheet 2, and this is repeated in sequence to form a battery cell. Subsequently, the battery cell is welded, shelled, baked, injected, formed, and capacity divided to obtain a lithium-ion battery with mixed laminates. The number of battery cell electrodes listed in this embodiment is only an example. In the actual lamination process, the coating surface density can be adjusted according to the total number of lamination layers required by the thickness of the battery cell, and then the number of lamination layers of the first positive electrode sheet and the second positive electrode sheet can be adjusted so that the mass proportion of the second positive electrode active material is close to 20%.

[0066] Example 2 The method of this embodiment is the same as that of Example 1, except that, in the battery cell, based on the total number of first and second positive electrode sheets (100 sheets), the number of second positive electrode sheets accounts for 12%, and the number of first positive electrode sheets accounts for 88%; it is calculated that, based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is approximately 10%; one battery cell includes 100 positive electrode sheets and 101 negative electrode sheets 3; the 100 positive electrode sheets include 88 first positive electrode sheets 1 and 12 second positive electrode sheets 2; the 100 positive electrode sheets are respectively connected to the positive electrode tabs to form the positive electrode 4 of the battery cell; and the 101 negative electrode sheets are respectively connected to the negative electrode tabs to form the negative electrode 5 of the battery cell; when stacking the sheets, 44 first positive electrode sheets are arranged on one side of the second positive electrode sheet, 12 second positive electrode sheets are arranged in the middle, and 44 first positive electrode sheets are arranged on the other side to form a battery cell.

[0067] Example 3 The method of this embodiment is the same as that of Example 1, with the only difference being that, in the battery cell, based on the total number of first and second positive electrode sheets (100 sheets), the number of second positive electrode sheets is set to account for 25%, and the number of first positive electrode sheets is set to account for 75%; it is calculated that: based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is approximately 20%; taking one battery cell as an example, the battery cell of Example 3 includes 100 positive electrode sheets and 101 negative electrode sheets, wherein the 100 positive electrode sheets include 75 first positive electrode sheets 1 and 25 second positive electrode sheets 2. When stacking, the 75 first positive electrode sheets are arranged on the left side of the battery cell, and the 25 second positive electrode sheets are arranged on the right side of the battery cell to form a battery cell.

[0068] Example 4 The method of this embodiment is the same as that of Example 1, except that, in the battery cell, based on the total number of the first positive electrode sheets and the second positive electrode sheets (100 sheets), the number of the second positive electrode sheets is set to account for 34%, and the number of the first positive electrode sheets is set to account for 66%. It is calculated that: based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is approximately 30%. One battery cell includes 100 positive electrode sheets and 101 negative electrode sheets. The 100 positive electrode sheets include 66 first positive electrode sheets 1 and 34 second positive electrode sheets 2. Figure 3 As shown (not all electrodes are shown in the figure), when stacking, two layers of the first positive electrode sheet 1 are stacked each time, and the second positive electrode sheet 2 is stacked on the third layer, and this is repeated in sequence. 100 positive electrode sheets are respectively connected to the positive electrode tabs to form the positive electrode 4 of the battery cell, and 101 negative electrode sheets are respectively connected to the negative electrode tabs to form the negative electrode 5 of the battery cell.

[0069] Example 5 The method of this embodiment is the same as that of Example 1, except that, in the battery cell, based on the total number of the first positive electrode sheets and the second positive electrode sheets (100 sheets), the number of the second positive electrode sheets accounts for 45%, and the number of the first positive electrode sheets accounts for 55%; based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass of the layered oxide positive electrode active material accounts for approximately 40%, and one battery cell includes 100 positive electrode sheets and 101 negative electrode sheets. The 100 positive electrode sheets include 55 first positive electrode sheets 1 and 45 second positive electrode sheets 2. The 100 positive electrode sheets are arranged as follows: Figure 4 The arrangement shown is repeated (not all electrodes are shown in the figure), 100 positive electrodes are connected to the positive electrode tabs to form the positive electrode 4 of the battery cell, and 101 negative electrodes are connected to the negative electrode tabs to form the negative electrode 5 of the battery cell.

[0070] Example 6 The method of this embodiment is the same as that of embodiment 1, except that the second positive electrode sheet of this embodiment is a lithium nickel cobalt manganese oxide positive electrode sheet. The positive electrode active material used in preparing the second positive electrode sheet is lithium nickel cobalt manganese oxide, with a chemical formula of LiNi 0.7 Co 0.1 Mn 0.2 O2.

[0071] Example 7 The method of this embodiment is the same as that of embodiment 1, except that the negative electrode sheet of this embodiment includes a first negative electrode sheet and a second negative electrode sheet, the first negative electrode sheet is a natural graphite negative electrode sheet, and the second negative electrode sheet is an artificial negative electrode sheet; The preparation of the first negative electrode sheet includes: adding CMC (sodium carboxymethyl cellulose) to deionized water as a solvent and dispersing it evenly to form a transparent glue solution; adding a conductive agent (conductive carbon black) and dispersing it evenly; adding natural graphite material in batches and stirring and mixing evenly; adding SBR (styrene-butadiene latex) and mixing evenly to obtain a negative electrode coating slurry; in the slurry, the mass ratio of graphite material, conductive agent, binder and dispersant is 96:1:1.5:1.5, and the solid content is 47wt%; The negative electrode coating slurry is coated on the negative electrode current collector, and the first negative electrode sheet is obtained after rolling, die cutting and baking. The coating surface density is 200g / m 2 ; The preparation of the second negative electrode sheet includes: adding CMC (sodium carboxymethyl cellulose) to deionized water as a solvent and dispersing the mixture uniformly to form a transparent adhesive; adding a conductive agent (conductive carbon black) and dispersing the mixture uniformly; adding artificial graphite material in batches and stirring and mixing the mixture uniformly; adding SBR (styrene-butadiene latex) and mixing the mixture uniformly to obtain a negative electrode coating slurry; in the slurry, the mass ratio of the graphite material, the conductive agent, the binder and the dispersant is 96:1:1.5:1.5, and the solid content is 47wt%; The negative electrode coating slurry is coated on the negative electrode current collector, and the second negative electrode sheet is obtained after rolling, die cutting and baking. The coating surface density is 200g / m 2 .

[0072] The first positive electrode sheet, the second positive electrode sheet, the first negative electrode sheet, the second negative electrode sheet and the separator are assembled into a battery cell. Based on the total mass of the phosphate positive electrode active material and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 20%; in the battery cell, based on the total number of the first negative electrode sheet and the second negative electrode sheet (101 sheets), the number of the second negative electrode sheet is set to 50, and the number of the first negative electrode sheet is set to 51. It is calculated that based on the total mass of the natural graphite in the battery cell and the artificial graphite in the battery cell, the mass proportion of the artificial graphite is approximately 50%; taking one battery cell as an example, the battery cell of Example 7 includes 100 The battery cell is then assembled with 101 positive electrode sheets and 101 negative electrode sheets, wherein the 100 positive electrode sheets include 75 first positive electrode sheets and 25 second positive electrode sheets, and the 101 negative electrode sheets include 51 first negative electrode sheets and 50 second negative electrode sheets. The 100 positive electrode sheets are respectively connected to the positive electrode tabs to form the positive electrode of the battery cell, and the 101 negative electrode sheets are respectively connected to the negative electrode tabs to form the negative electrode of the battery cell. When stacking the sheets, the first positive electrode sheet and the second positive electrode sheet are evenly stacked, that is, after stacking three layers of the first positive electrode sheet, the second positive electrode sheet is stacked on the fourth layer, and the first negative electrode sheet is evenly stacked, that is, after stacking one layer of the first negative electrode sheet, the second negative electrode sheet is stacked on the second layer, and the third negative electrode sheet is stacked on the third layer, and this process is repeated to form a battery cell. Subsequently, the battery cell is welded, shelled, baked, injected, formed, and capacity divided to obtain a lithium-ion battery with mixed stacking. Since there needs to be one more negative electrode than the positive electrode, those skilled in the art will understand that if the total number of negative electrode laminates in the battery cell is an odd number, one more first negative electrode or second negative electrode can be randomly selected, and the negative electrodes with more number are located at the first and last sheets of the pole core, and the first negative electrode and the second negative electrode are evenly arranged in the pole core (the outermost layer of the pole core is the negative electrode, and one side of the negative electrode is unusable). If the total number of negative electrode laminates in the battery cell is an even number, the first negative electrode and the second negative electrode are evenly arranged. In this embodiment, the mass proportion of the active material artificial graphite of the second negative electrode sheet is approximately 50%. If it is other proportions, it can be adjusted by adjusting the surface density and the number of pole sheets.

[0073] Example 8 The method is the same as that in Example 1, except that, in this battery cell, based on the number of the first positive electrode sheet and the second positive electrode sheet (100 sheets), the number of the first positive electrode sheet accounts for 45%, and the number of the second positive electrode sheet accounts for 55%. It is calculated that based on the total mass of the lithium manganese iron phosphate positive electrode active material in the battery cell and the lithium-rich manganese-based positive electrode active material in the battery cell, the mass proportion of the lithium manganese-rich positive electrode active material is 50%.

[0074] Example 9 The method is the same as that in Example 1, except that, in this battery cell, based on the number of the first positive electrode sheet and the second positive electrode sheet (100 sheets), the number of the first positive electrode sheet is set to 9%, and the number of the second positive electrode sheet is set to 91%. It is calculated that based on the total mass of the lithium manganese iron phosphate positive electrode active material in the battery cell and the lithium-rich manganese-based positive electrode active material in the battery cell, the mass proportion of the lithium manganese-rich positive electrode active material is approximately 90%.

[0075] Example 10 The method is the same as that in Example 1, except that, in this battery cell, based on the number of the first positive electrode sheet and the second positive electrode sheet (100 sheets), the number of the first positive electrode sheet is set to account for 4%, and the number of the second positive electrode sheet accounts for 96%. It is calculated that based on the total mass of the lithium manganese iron phosphate positive electrode active material in the battery cell and the lithium-rich manganese-based positive electrode active material in the battery cell, the mass proportion of the lithium manganese-rich positive electrode active material is approximately 95%.

[0076] Comparative Example 1 (1) Prepare the positive electrode sheet, which is a positive electrode sheet coated with a first positive electrode active material, lithium iron manganese phosphate, and a second positive electrode active material, lithium-rich manganese-based mixed coating; including: using N-methylpyrrolidone (NMP) as a solvent, adding a binder (polyvinylidene fluoride, PVDF) to disperse evenly to form a transparent glue; adding a conductive agent, carbon black, to disperse it evenly; adding lithium iron manganese phosphate material (chemical formula LiMn in batches); 0.6 Fe 0.4 PO4), lithium-rich manganese-based materials (chemical formula Li2MnO3·LiNi 0.33 Co 0.33 Mn 0.33 O2), stirred and mixed evenly to obtain a slurry; in the slurry, the mass ratio of lithium manganese iron phosphate, lithium-rich manganese base, conductive agent, and binder is 76:19:2:3 (lithium manganese iron phosphate: lithium-rich manganese base = 8:2, the second positive electrode active material lithium-rich manganese base accounts for 20% by weight), and the solid content is 60wt%; The slurry is coated on the positive electrode current collector, and then rolled, die-cut and baked to obtain the positive electrode sheet. The coating surface density is 440g / m 2 ; (2) preparing a negative electrode sheet, including: using deionized water as a solvent, adding CMC (sodium carboxymethyl cellulose) and dispersing it evenly to form a transparent glue; adding a conductive agent (conductive carbon black) and dispersing it evenly; adding graphite material in batches and stirring and mixing it evenly; adding SBR (styrene-butadiene latex) and mixing it evenly to obtain a negative electrode coating slurry; in the slurry, the mass ratio of the graphite material, the conductive agent, the binder and the dispersant is 96:1:1.5:1.5, and the solid content is 47wt%; The negative electrode coating slurry is coated on the negative electrode current collector, and the negative electrode sheet is obtained after roller pressing, die cutting and baking. The coating surface density is 200g / m2 ; (3) The positive electrode sheet prepared in step (1) and the negative electrode sheet prepared in step (2) are welded together with the separator, shelled, baked, liquid-filled, formed, and volume-divided to obtain a lithium-ion battery.

[0077] Comparative Example 2 The method of Comparative Example 2 is the same as that of Comparative Example 1, except that, in Comparative Example 2, the ratio of lithium manganese iron phosphate to lithium-rich manganese base is 9:1, and the mass proportion of the second positive electrode active material, the lithium-rich manganese base, is 10%.

[0078] Comparative Example 3 The method of Comparative Example 3 is the same as that of Comparative Example 1, except that, in Comparative Example 3, the ratio of lithium manganese iron phosphate to lithium-rich manganese base is 1:1, and the mass proportion of the second positive electrode active material, the lithium-rich manganese base, is 50%.

[0079] Comparative Example 4 The method of Comparative Example 4 is the same as that of Comparative Example 1, except that, in Comparative Example 4, the ratio of lithium manganese iron phosphate to lithium-rich manganese base is 1:9, and the mass proportion of the second positive electrode active material, the lithium-rich manganese base, is 90%.

[0080] Comparative Example 5 The method of Comparative Example 5 is the same as that of Comparative Example 1, except that, in Comparative Example 5, the ratio of lithium manganese iron phosphate to lithium-rich manganese base is 1:19, and the mass proportion of the second positive electrode active material, the lithium-rich manganese base, is 95%.

[0081] Test Example 1 The batteries obtained in Examples 1 to 10 and Comparative Examples 1 to 5 were tested for rate performance and cycle performance, and the results are shown in Table 1.

[0082] The rate performance test was conducted in a charge and discharge test cabinet at an ambient temperature of 25°C. The rate charge test method is as follows: discharge the battery at 0.33C to a discharge end voltage of 2.0V, then rest for 30 minutes; then charge at 0.33C to 4.3V, rest for 30 minutes, and record the charge capacity as C1; discharge at 0.33C to a discharge end voltage of 2.0V, rest for 30 minutes; then charge at 1C, 1.5C, and 2C to 4.3V, rest for 30 minutes; record the charge capacity Cx at different rates. The charge capacity retention rate at different rates is (Cx / C1) × 100%. The rate discharge test method is as follows: discharge the battery at a current of 0.33C to a discharge termination voltage of 2.0V, and let it sit for 30 minutes; then charge at a current of 0.33C to 4.3V, charge at a constant voltage of 4.3V to 0.05C, and let it sit for 30 minutes; then discharge at a current of 0.33C to a discharge termination voltage of 2.0V, and let it sit for 30 minutes, and record the discharge capacity as C1; charge at a current of 0.33C to 4.3V, charge at a constant voltage of 4.3V to 0.05C, and let it sit for 30 minutes; then charge and discharge at currents of 1C, 2C, and 3C respectively to a discharge termination voltage of 2.0V, and let it sit for 30 minutes; record the discharge capacity Cx at different rates, and the discharge capacity retention rate at different rates %=(Cx / C1)×100%.

[0083] Cycling performance testing was conducted in a charge-discharge test cabinet at an ambient temperature of 45°C. The test method was as follows: the battery was charged at 0.5C to 4.3V, then charged at 4.3V constant voltage to 0.05C, and allowed to rest for 30 minutes; then discharged at 0.5C to a cut-off voltage of 2.0V, and allowed to rest for 30 minutes. These two steps were repeated, with the first discharge capacity recorded as C1 and the discharge capacity after the nth cycle as Cn. The capacity retention rate after n cycles was calculated as (Cn / C1) × 100%.

[0084] Table 1 Test results of rate performance and cycle performance

[0085] Compared with Comparative Example 4, the charging constant current ratio of Example 9 at 2C is increased by 2.1%, the 3C / 0.33C discharge capacity retention rate is increased by 3.9%, and the 600-cycle capacity retention rate is increased by 1.6%.

[0086] Compared with Comparative Example 5, the charging constant current ratio of Example 10 at 2C is increased by 1.9%, the 3C / 0.33C discharge capacity retention rate is increased by 2.8%, and the 600-cycle capacity retention rate is increased by 1.3%.

[0087] Compared with Comparative Example 3, the charging constant current ratio of Example 8 at 2C is increased by 11.1%, the 3C / 0.33C discharge capacity retention rate is increased by 16%, and the 600-cycle capacity retention rate is increased by 3.4%.

[0088] Compared with Comparative Example 2, the charging constant current ratio of Example 2 at 2C is increased by 11.8%, the 3C / 0.33C discharge capacity retention rate is increased by 16.5%, and the 600-cycle capacity retention rate is increased by 4%.

[0089] Compared with Comparative Example 1, the charging constant current ratio of Example 1 at 2C is increased by 12.3%, the 3C / 0.33C discharge capacity retention rate is increased by 16.9%, and the 600-cycle capacity retention rate is increased by 4.8%.

[0090] According to the data in Table 1, when the mass content of different positive electrode active materials is the same, compared with the comparative example in which different positive electrode materials are mixed and then coated on the same foil, the embodiment of the present disclosure coats different positive electrode materials on different foils to form different positive electrodes. The charge capacity retention rate and discharge capacity retention rate of the obtained battery at each rate and the 600-cycle capacity retention rate are all higher than those of the comparative example. The battery of the present disclosure has better rate performance and cycle performance.

[0091] Compared with Example 2, Example 5, Example 8, Example 9 and Example 10, the proportion of the layered oxide positive electrode active material in Example 1 and Example 4 is within the preferred range of the present disclosure, and the rate performance and cycle performance of the battery are relatively improved more significantly.

[0092] Compared with Example 1, Example 7 further includes multiple negative electrode sheets, and the mass proportion of the second negative electrode active material is within the preferred range of the present disclosure, which can further improve the rate performance of the battery.

[0093] The preferred embodiments of the present disclosure are described in detail above in conjunction with the accompanying drawings. However, the present disclosure is not limited to the specific details of the above embodiments. Within the technical concept of the present disclosure, various simple modifications can be made to the technical solutions of the present disclosure, and these simple modifications all fall within the scope of protection of the present disclosure.

[0094] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the present disclosure will not further describe various possible combinations.

[0095] In addition, the various embodiments of the present disclosure may be arbitrarily combined, and as long as they do not violate the concept of the present disclosure, they should also be regarded as the contents disclosed by the present disclosure.

Claims

1. A battery cell, characterized in that: The battery cell includes a first positive electrode sheet and a second positive electrode sheet; Wherein, the first positive electrode sheet is a phosphate positive electrode sheet, and the second positive electrode sheet is a layered oxide positive electrode sheet.

2. The battery cell according to claim 1, characterized in that Based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 90%.

3. The battery cell according to claim 1, characterized in that Based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 10% to 40%.

4. The battery cell according to claim 1, characterized in that Based on the total mass of the phosphate positive electrode active material in the battery cell and the layered oxide positive electrode active material in the battery cell, the mass proportion of the layered oxide positive electrode active material is 15% to 30%.

5. The battery cell according to any one of claims 1 to 4, characterized in that: The phosphate positive electrode sheet includes a lithium iron phosphate positive electrode sheet and / or a lithium iron manganese phosphate positive electrode sheet.

6. The battery cell according to any one of claims 1 to 5, characterized in that: The layered oxide positive electrode sheet includes one or more of a lithium cobalt oxide positive electrode sheet, a lithium nickel cobalt manganese oxide positive electrode sheet, a lithium nickel cobalt aluminum oxide positive electrode sheet and a lithium-rich manganese-based positive electrode sheet.

7. The battery cell according to any one of claims 1 to 6, characterized in that: The layered oxide positive electrode sheet is a lithium-rich manganese-based positive electrode sheet.

8. The battery cell according to any one of claims 1 to 7, characterized in that: The battery core includes a plurality of second positive electrode sheets, and a plurality of first positive electrode sheets are arranged between any two adjacent second positive electrode sheets.

9. The battery cell according to claim 8, characterized in that The number of first positive electrode sheets between any two adjacent second positive electrode sheets is equal.

10. The battery cell according to any one of claims 1 to 9, characterized in that: The battery cell includes a positive electrode tab, and the positive electrode tab is connected to the first positive electrode sheet and the second positive electrode sheet; and / or, The positive electrode tab includes a first positive electrode tab and a second positive electrode tab, wherein the first positive electrode tab is connected to the first positive electrode sheet, and the second positive electrode tab is connected to the second positive electrode sheet.

11. The battery cell according to any one of claims 1 to 10, characterized in that: The battery cell includes a negative electrode sheet, and the negative electrode sheet includes one or more of a graphite negative electrode sheet, a silicon-based negative electrode sheet and a hard carbon negative electrode sheet.

12. The battery cell according to claim 11, characterized in that The negative electrode sheet includes a first negative electrode sheet and a second negative electrode sheet, the first negative electrode sheet is a natural graphite negative electrode sheet, and the second negative electrode sheet is an artificial graphite negative electrode sheet.

13. The battery cell according to claim 12, characterized in that: Based on the total mass of the natural graphite in the battery cell and the artificial graphite in the battery cell, the mass proportion of the artificial graphite is 30% to 70%.

14. The battery cell according to claim 12 or 13, characterized in that: Based on the total mass of the natural graphite in the battery cell and the artificial graphite in the battery cell, the mass proportion of the artificial graphite is 40% to 60%.

15. The battery cell according to any one of claims 12 to 14, characterized in that: The battery cell includes a negative electrode tab, and the negative electrode tab is connected to the first negative electrode sheet and the second negative electrode sheet; and / or, The negative electrode tab includes a first negative electrode tab and a second negative electrode tab, wherein the first negative electrode tab is connected to the first negative electrode sheet, and the second negative electrode tab is connected to the second negative electrode sheet.

16. A battery, characterized in that: The battery comprises the battery cell according to any one of claims 1 to 15.

17. An electrical device, characterized in that: Including the battery according to claim 16.

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