Positive electrode sheet, battery, and electric device

Abstract

The present disclosure relates to the field of batteries, and relates to a positive electrode sheet, a battery, and an electric device. The positive electrode sheet comprises a current collector and a positive electrode film layer arranged on at least one side surface of the current collector. The positive electrode film layer contains a lithium replenishing material composition, the lithium replenishing material composition comprises n lithium replenishing materials having different particle sizes, n is an integer greater than or equal to 2, and the n lithium replenishing materials respectively are, in ascending order of Dv50 particle size, a first lithium replenishing material, a second lithium replenishing material, ..., an n-1th lithium replenishing material, and an nth lithium replenishing material, wherein the difference between the Dv50 particle size of an i+1th lithium replenishing material and the Dv50 particle size of an ith lithium replenishing material is greater than or equal to 1 μm, and i is an integer ranging from 1 to n-1.

Description

Positive electrode sheet, battery and electric device

[0001] Priority information

[0002] The present disclosure claims the priority of the patent application with the application number 202411393168.3 and the title of "Positive electrode sheet, battery and electric device" filed with the State Intellectual Property Office of China on September 30, 2024, the whole content of which is incorporated herein by reference. TECHNICAL FIELD

[0003] The present disclosure relates to the technical field of batteries, in particular to a positive electrode sheet, a battery and an electric device. BACKGROUND

[0004] During the initial charging and discharging process of a lithium ion battery, a solid electrolyte interface (SEI) film is formed on the surface of the negative electrode and a series of side reactions occur. In this process, a part of the active lithium ions will inevitably be consumed, resulting in a decrease in the available active lithium ions in the battery, which reduces the total reversible lithium in the battery, thereby making the initial discharge capacity of the lithium ion battery relatively low (70% to 90%). Using pre-lithiation technology to supplement active lithium ions in the lithium battery can improve the coulombic efficiency of the lithium ion battery during the initial charging and discharging process, thereby reducing the loss of active lithium during the initial charging process.

[0005] The pre-lithiation methods currently used are mainly divided into positive electrode pre-lithiation and negative electrode pre-lithiation. Negative electrode pre-lithiation mainly uses electrochemical lithium supplement method, lithium powder lithium supplement method, etc. Positive electrode pre-lithiation is achieved by adding positive electrode additives during the preparation of the positive electrode material, and by charging to the positive electrode lithium ion delithiation potential, lithium ions are removed and migrated to the negative electrode to achieve pre-lithiation. Negative electrode pre-lithiation has not been widely used due to process condition limitations. While positive electrode pre-lithiation also has problems such as affecting the compaction density of the positive electrode sheet, serious gas production, and low specific capacity of the positive electrode pre-lithiation material.

[0006] Therefore, the current pre-lithiation related technology still needs to be improved. SUMMARY

[0007] The present disclosure aims to at least solve one of the technical problems in the related art to some extent.

[0008] In a first aspect, the present disclosure provides a positive electrode sheet. According to embodiments of the present disclosure, the positive electrode sheet comprises a current collector and a positive electrode film layer disposed on at least one side surface of the current collector, the positive electrode film layer containing a lithium supplement material composition, the lithium supplement material composition comprising n kinds of lithium supplement materials with different particle sizes, n being an integer greater than or equal to 2, the n kinds of lithium supplement materials being, in order of increasing Dv50 particle size, a first lithium supplement material, a second lithium supplement material,..., an (n-1)th lithium supplement material, and an nth lithium supplement material; wherein the difference between the Dv50 particle size of the (i+1)th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm, i being an integer from 1 to n-1. In the positive electrode sheet, by using two or more than two lithium supplement materials with different particle sizes, the advantages of lithium supplement materials with different particle sizes can be fully utilized through the synergistic effect between lithium supplement materials with different particle sizes, not only reducing the specific surface area and enhancing the stability of the contact between the lithium supplement material and the electrolyte, but also effectively reducing the gas production, while effectively utilizing the capacity of the lithium supplement material and improving the decomposition efficiency of the lithium supplement material, thereby significantly improving the comprehensive performance of the battery using the positive electrode sheet.

[0009] According to embodiments of the present disclosure, the difference between the Dv50 particle size of the (i+1)th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm and less than or equal to 27 μm. In some specific embodiments, the difference between the Dv50 particle size of the (i+1)th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm and less than or equal to 5 μm.

[0010] According to embodiments of the present disclosure, in the lithium supplement material composition, the content of the ith lithium supplement material is greater than the content of the (i+1)th lithium supplement material. Thus, the decomposition rate of the lithium supplement material is higher, the capacity of the lithium supplement material can be effectively utilized, and the initial efficiency of the battery using the positive electrode sheet is higher.

[0011] According to embodiments of the present disclosure, the difference between the mass of the ith lithium supplement material and the mass of the (i+1)th lithium supplement material accounts for 10% to 50% of the total mass of the lithium supplement material composition. Thus, the advantages of lithium supplement materials with different particle sizes can be better utilized.

[0012] According to embodiments of the present disclosure, the Dv50 particle size of any one of the n kinds of lithium supplement materials is 1 μm to 30 μm. In some specific embodiments, the Dv50 particle size of any one of the n kinds of lithium supplement materials is 3 μm to 15 μm. Within this particle size range, the synergistic effect of lithium supplement materials with different particle sizes is better, and the lithium supplement effect can be better utilized.

[0013] According to an embodiment of the present disclosure, n is an integer greater than 2 and less than or equal to 30. In some specific examples, n is an integer greater than 2 and less than or equal to 5. A plurality of lithium supplementing materials with different particle sizes are used in combination, and the different particle sizes can gradually transition or can be more finely adjusted to cooperate between the lithium supplementing materials.

[0014] According to an embodiment of the present disclosure, the lithium supplementing material includes at least one of Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, LI2O, Li2O2, and Li3N. According to an embodiment of the present disclosure, the lithium supplementing material includes Li5FeO4. In this way, the lithium supplementing effect is better, and the battery using the positive electrode sheet has better overall performance.

[0015] According to an embodiment of the present disclosure, the mass percentage content of the lithium supplementing material composition is 0.1% to 10% based on the total mass of the positive electrode film layer. Within this content range, the lithium supplementing material can effectively play a role, and the energy density of the battery using the positive electrode sheet is not substantially affected. According to an embodiment of the present disclosure, the mass percentage content of the lithium supplementing material composition is 0.1% to 5% based on the total mass of the positive electrode film layer. Within the above content range, the lithium supplementing material can effectively play a role, and the energy density of the battery using the positive electrode sheet is not substantially affected.

[0016] According to an embodiment of the present disclosure, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese ternary positive electrode material, nickel cobalt aluminum ternary positive electrode material, lithium-rich manganese-based positive electrode material, lithium cobaltate, lithium nickelate, lithium manganate, and lithium nickel manganate.

[0017] According to an embodiment of the present disclosure, the positive electrode active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate.

[0018] According to an embodiment of the present disclosure, the Dv50 particle size of the positive electrode active material is 1 μm to 5 μm.

[0019] A second aspect of the present disclosure provides a battery. According to an embodiment of the present disclosure, the battery includes the positive electrode sheet described above. The battery has all the features and advantages of the positive electrode sheet described above, and will not be repeated here.

[0020] A third aspect of the present disclosure provides a power consumption device. According to an embodiment of the present disclosure, the power consumption device includes the battery described above. The battery has all the features and advantages of the battery described above, and will not be repeated here. BRIEF DESCRIPTION OF DRAWINGS

[0021] FIG. 1 is a structural schematic diagram of a positive electrode sheet according to an embodiment of the present disclosure.

[0022] FIG. 2 is a structural schematic diagram of a positive electrode sheet according to one embodiment of the present disclosure.

[0023] FIG. 3 is an SEM photograph of a positive electrode sheet according to Embodiment 5 of the present disclosure.

[0024] FIG. 4A and FIG. 4B are SEM photographs of a positive electrode sheet according to Embodiment 5 of the present disclosure, respectively magnified 5000 times and 10000 times.

[0025] Reference signs: 10: positive electrode current collector 20: positive electrode active material 31: first lithium supplementing material 32: second lithium supplementing material 33: third lithium supplementing material DETAILED DESCRIPTION

[0026] Embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings. The embodiments described below by reference to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0027] The present disclosure is based on the findings and recognitions of the inventors on the following facts and problems:

[0028] At present, although the positive electrode pre-lithiation additive can improve the initial efficiency of the battery to some extent, there are still various problems in actual use, for example: affecting the compaction density of the positive electrode sheet, resulting in that the positive electrode lithium supplement cannot effectively improve the energy density; increasing the battery impedance, and the battery performance is reduced; increasing the thixotropy of the positive electrode slurry, increasing the coating difficulty and reducing the coating speed, and then affecting the coating capacity; generating a large amount of gas, such as N2, O2, S and other harmful gases, which may have a side reaction with the electrolyte, further increasing the battery impedance, and then reducing the comprehensive performance of the battery. Through research, it is found that one of the reasons for the above problems is that the particle size difference between the positive electrode lithium supplement material and the positive electrode active material is significant, which makes the particle size matching between the particles not ideal, and then affects the compaction density of the positive electrode sheet, and this particle size difference also increases the positive electrode liquid phase diffusion impedance and reduces the lithium ion transmission rate, thereby increasing the battery impedance and reducing the battery performance.

[0029] In view of this, the present disclosure provides a positive electrode sheet, a battery and a power utilization device which can improve the comprehensive performance of the battery.

[0030] In a first aspect, the present disclosure provides a positive electrode sheet. According to embodiments of the present disclosure, the positive electrode sheet includes a current collector and a positive electrode film layer disposed on at least one side surface of the current collector, the positive electrode film layer containing a lithium supplement material composition, the lithium supplement material composition including n kinds of lithium supplement materials with different particle sizes, n being an integer greater than or equal to 2, the n kinds of lithium supplement materials being, in order from small to large Dv50 particle size, a first lithium supplement material, a second lithium supplement material,..., an (n-1)th lithium supplement material, and an nth lithium supplement material; wherein the difference between the Dv50 particle size of the (i+1)th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm, i being an integer from 1 to n-1.

[0031] It can be understood that the essence of the internal reaction of a lithium battery is the reciprocal "shuttling" of active lithium ions between the positive electrode and the negative electrode. At this time, the lithium ions are continuously intercalated and deintercalated between the positive electrode and the negative electrode, and this process is an electrochemical reaction between the material particles and the electrolyte. Therefore, the deintercalation behavior of lithium in a lithium battery is affected by the characteristics of the material particles in the battery. Obviously, regulating the characteristics of the material particles in the battery is the key to achieving a breakthrough in the performance of lithium batteries.

[0032] During the first charging process of a lithium ion battery, the formation of a solid electrolyte interface (SEI) film on the surface of the negative electrode irreversibly consumes active lithium ions released from the positive electrode, reducing the specific capacity and energy density of the positive electrode of the lithium ion battery. Supplementing lithium to the lithium ion battery can compensate for the irreversible consumption of active lithium ions by the formation of the negative electrode SEI film, thereby improving the energy density and cycle life of the lithium ion battery. The positive electrode lithium supplement material is added to the positive electrode, and during the formation process of the lithium ion battery, the positive electrode lithium supplement material can decompose and release active lithium ions at a certain potential to supplement lithium to the battery.

[0033] The morphology and size of the positive electrode lithium supplement material particles affect the lithium supplement performance of the battery, and further affect the electrochemical performance of the battery, by affecting the diffusion path, diffusion resistance, and contact area with the electrolyte of lithium ions. The positive electrode lithium supplement material with a larger particle size has a relatively small contact area with the electrolyte, which can reduce the side reactions that occur when the positive electrode lithium supplement material contacts the electrolyte, thereby reducing the gas production during the formation and decomposition stages of the lithium supplement battery. At the same time, it is possible that the higher electrical conductivity of the large particle size powder is due to the fact that the electrons move through fewer particle interfaces in the large particle size powder. The use of large particle size lithium supplement materials can significantly reduce the impedance of the lithium supplement battery and improve the rate performance of the battery. For small particle size powders, the length of the electron path from the inside to the surface is short, and the large specific surface area reduces the current density, which can reduce the charge overpotential. Therefore, small particle positive electrode lithium supplement materials are easier to decompose completely, thereby improving the decomposition efficiency of the positive electrode lithium supplement material and improving the specific capacity of the positive electrode lithium supplement material.

[0034] In the positive electrode sheet of the present disclosure, by using two or more different particle sizes of lithium supplementing materials, the advantages of different particle sizes of lithium supplementing materials can be fully utilized through the synergistic effect between different particle sizes of lithium supplementing materials, the specific surface area can be reduced, the contact stability of the lithium supplementing material and the electrolyte can be enhanced, the gas production can be reduced, the battery impedance can be reduced, the lithium supplementing material can effectively supplement the capacity of the positive electrode, and the use of multiple different particle sizes of lithium supplementing materials can better match the positive electrode active material, compensate for the disadvantages of using a single particle size of lithium supplementing material, and thus a battery with less gas production and higher capacity can be obtained, and the comprehensive performance of the battery using the positive electrode sheet can be significantly improved.

[0035] It can be understood that the lithium supplementing materials of different particle sizes can be obtained by using at least one of different ball milling times, ball milling powers, ball milling speeds, and ball-to-material ratios in the preparation step. As an example, taking Li5FeO4 as an example, the preparation process can include: mixing lithium hydroxide and nano iron oxide in a molar ratio of 5.2:1, preparing a precursor by spray drying, then placing the precursor in a high-speed mixer for mixing, and then placing it in an inert gas atmosphere for sintering. During the preparation process, the precursor can be ball milled for different times to obtain lithium supplementing materials of different particle sizes.

[0036] The particle size Dv50 of the lithium supplementing material refers to the median particle size of the lithium supplementing material particles, also known as the volume average particle size, which represents the particle size corresponding to the cumulative volume distribution percentage of 50%. The particle size Dv50 of the lithium supplementing material can be tested by a laser particle size tester. For example, the particle size of the large particle lithium supplementing material and the particle size of the small particle lithium supplementing material can be tested respectively.

[0037] The particle size Dv50 of the lithium supplementing material can also be obtained by SEM observation. For example, a certain volume of the positive electrode sheet is treated by a Cross Section Polisher, CP (argon ion beam cross-section thinning or cutting and polishing) to obtain a positive electrode sheet cross-section, and a SEM photo of the positive electrode sheet cross-section is taken at a magnification of 5000 times. In the SEM photo, a region with a length of 0.5 cm and a width of 0.5 cm is selected, and the particle sizes of the large particle lithium supplementing material and the small particle lithium supplementing material in the region are counted and averaged, respectively. When the particle size of the lithium supplementing material is irregular, the maximum diameter of the particle is taken as the particle size of the lithium supplementing material. The inventors have verified that the data values measured by the two methods have little difference.

[0038] According to embodiments of the present disclosure, the difference between the Dv50 particle size of the i+1th lithium supplementing material and the Dv50 particle size of the ith lithium supplementing material is greater than or equal to 1 μm and less than or equal to 27 μm. In some specific embodiments, the difference between the Dv50 particle size of the i+1th lithium supplementing material and the Dv50 particle size of the ith lithium supplementing material is greater than or equal to 1 μm and less than or equal to 5 μm. As an example, the difference between the Dv50 particle size of the i+1th lithium supplementing material and the Dv50 particle size of the ith lithium supplementing material can be 1 μm, 2 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 27 μm, etc. Within the above range of difference, the particle size matching of the lithium supplementing material composition is more reasonable, and a better synergistic effect can be achieved.

[0039] According to embodiments of the present disclosure, in the lithium supplementing material composition, the content of the ith lithium supplementing material is greater than the content of the i+1th lithium supplementing material. In this way, the decomposition rate of the lithium supplementing material is higher, the capacity of the lithium supplementing material can be effectively utilized, and the initial efficiency of the battery using the positive electrode sheet is higher. This is particularly suitable for the case where the positive electrode active material used in the positive electrode sheet is a phosphate positive electrode material (such as lithium iron phosphate, lithium manganese iron phosphate, etc.).

[0040] According to embodiments of the present disclosure, the difference between the mass of the ith lithium supplementing material and the mass of the i+1th lithium supplementing material accounts for 10% to 50% of the total mass of the lithium supplementing material composition, specifically, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. In this way, the advantages of lithium supplementing materials with different particle sizes can be better utilized.

[0041] According to embodiments of the present disclosure, the Dv50 particle size of any one of the n kinds of lithium supplementing materials is 1 μm to 30 μm (specifically, 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, etc.). In some specific embodiments, the Dv50 particle size of any one of the n kinds of lithium supplementing materials is 3 μm to 15 μm. Within this particle size range, the different particle sizes of the lithium supplementing materials have a better synergistic effect, and the lithium supplementing effect can be better utilized.

[0042] According to embodiments of the present disclosure, n is an integer greater than 2 and less than or equal to 30. In some specific examples, n is an integer greater than 2 and less than or equal to 5. As an example, n can be 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, etc. More kinds of lithium supplementing materials with different particle sizes are used in combination, the different particle sizes can gradually transition, the cooperation between the lithium supplementing materials can be more finely adjusted, and the comprehensive performance of the lithium supplementing battery can be more finely controlled, thereby meeting the application requirements of different scenarios.

[0043] According to embodiments of the present disclosure, the lithium supplementing material includes at least one of Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, LI2O, Li2O2, Li3N. As an example, the lithium supplementing material can be Li5FeO4. In this way, the lithium supplementing effect is better, and the battery using the positive electrode sheet has better comprehensive performance.

[0044] It can be understood that the specific types of lithium supplementing materials of different particle sizes in the lithium supplementing material composition according to embodiments of the present disclosure can be the same or different. Taking the lithium supplementing material composition including three lithium supplementing materials of different particle sizes as an example, in some embodiments, the lithium supplementing material composition can include three Li5FeO4 of different particle sizes; in other embodiments, the three lithium supplementing materials of different particle sizes in the lithium supplementing material composition are one Li5FeO4, another Li6COO4, and another Li2S.

[0045] According to embodiments of the present disclosure, the mass percentage content of the lithium supplementing material composition is 0.1% to 10%, specifically 0.1% to 5%, based on the total mass of the positive electrode film layer. As an example, the mass percentage content of the lithium supplementing material composition can be 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, etc., based on the total mass of the positive electrode film layer. Within the above content range, the lithium supplementing material can effectively play its role, and the energy density of the battery using the positive electrode sheet will not be substantially affected.

[0046] According to embodiments of the present disclosure, the positive electrode film layer includes a positive electrode active material, and the positive electrode active material includes at least one of lithium iron phosphate (LiFePO4), lithium manganese iron phosphate (LiFePO4), nickel cobalt manganese ternary positive electrode material (LiNiCoMnO2), nickel cobalt aluminum ternary positive electrode material (LiNiCoAlO2), lithium-rich manganese-based positive electrode material (rLi2MnO3·(1-r)LiMO2), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4), lithium nickel manganate (LiNiMnO4). x Mn 1-x PO4), nickel cobalt manganese ternary positive electrode material (LiNi y Co z Mn 1-y-z O2), nickel cobalt aluminum ternary positive electrode material (LiNi m Co n Al 1-m-n O2), lithium-rich manganese-based positive electrode material (rLi2MnO3·(1-r)LiMO2), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4), lithium nickel manganate (LiNi q Mn 2-q O4). According to some specific embodiments of the present disclosure, the positive electrode active material includes at least one of lithium iron phosphate and lithium manganese iron phosphate. In this way, the lithium supplementing material composition can be better matched, thereby improving the comprehensive performance of the battery using the positive electrode sheet.

[0047] According to embodiments of the present disclosure, the positive electrode active material has a Dv50 particle size of 1-5 μm, specifically, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, etc. The positive electrode active material has the above-mentioned particle size, and in the positive electrode sheet, the particles of the positive electrode active material can be distributed around the particles of the lithium supplementing material, so that the two are in sufficient contact, thereby facilitating the effective exertion of the lithium supplementing capacity.

[0048] It can be understood that, in addition to the lithium supplementing material composition and the positive electrode active material described above, the positive electrode film layer can further include a binder and a conductive agent. In some embodiments, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylic ester resin. In some embodiments, the conductive agent can include at least one of super-conductive carbon, conductive graphite, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0049] In some embodiments, in the positive electrode film layer of the positive electrode sheet of the present disclosure, the positive electrode active material has the lithium supplementing material of different particle sizes uniformly dispersed therein. This structure can fully exert the advantages of the lithium supplementing material of different particle sizes, reduce the specific surface area, enhance the environmental stability, and effectively reduce the gas production.

[0050] In some embodiments, the positive electrode sheet can be prepared by the following steps: uniformly dispersing the lithium supplementing material of different particle sizes described above, then uniformly mixing the lithium supplementing material with the positive electrode active material, the conductive agent, the binder, the optional dispersant, the solvent, etc., then uniformly coating the obtained positive electrode slurry on the positive electrode current collector, and performing drying, rolling, etc., to obtain the positive electrode sheet.

[0051] In a second aspect, the present disclosure provides a battery. According to embodiments of the present disclosure, the battery includes the positive electrode sheet described above. The battery has a low gas production, a low impedance, a high decomposition rate of the lithium supplementing material, a high initial efficiency, and a good comprehensive performance.

[0052] It can be understood that the battery is a lithium battery, including but not limited to a lithium ion battery, a lithium metal battery, etc. The battery can have a square shape, a cylindrical shape, or other regular or irregular shapes. The battery can be packaged in a hard shell (such as a steel shell, a hard plastic shell, etc.) or a soft shell (such as an aluminum plastic film, a bag-type soft shell, etc.). The battery can be a battery monomer, a secondary battery composed of a plurality of battery monomers, or a battery module or a battery pack composed of further assembled batteries.

[0053] It can be understood that, in addition to the positive electrode sheet described above, the battery described above can further include a negative electrode sheet, a separator, an electrolyte (including an electrolyte solution, a semi-solid electrolyte, a solid-state electrolyte, etc.), and an outer package. Taking the electrolyte as an electrolyte solution as an example, in the battery, the positive electrode sheet, the separator, and the negative electrode sheet are sequentially stacked and are made into an electrode assembly through a winding or stacking process. The electrode assembly and the electrolyte solution can be accommodated in the outer package.

[0054] In a third aspect of the present disclosure, a power consuming device is provided. According to embodiments of the present disclosure, the power consuming device includes the battery described above. The power consuming device has all the features and advantages of the battery described above, which will not be repeated here.

[0055] According to embodiments of the present disclosure, the power consuming device can include, but is not limited to, a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc. The battery can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device.

[0056] It can be understood that, in addition to the battery described above, the power consuming device can further include structures and components necessary for conventional power consuming devices. Taking an electric vehicle as an example, it can include a vehicle body, a vehicle window, a chassis, an engine, a seat, a tire, and other necessary structures and components, which will not be repeated here.

[0057] Embodiments of the present disclosure are described in detail below.

[0058] Example 1

[0059] Li5FeO4 with a particle size of 3 μm and Li5FeO4 with a particle size of 30 μm were mixed in a mass ratio of 5.5:4.5.

[0060] After the Li5FeO4 was fully dispersed, the Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP were uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60. After the positive electrode slurry was uniformly dispersed, it was uniformly coated on an aluminum foil current collector. The single-sided areal density of the positive electrode sheet was 200 g / m 2 , and the positive electrode sheet was obtained through rolling, die cutting, and baking. The particle size of the lithium iron phosphate was 1.8 μm.

[0061] Graphite, conductive carbon black, dispersant sodium carboxymethyl cellulose, water, and NMP solvent were uniformly mixed in a mass ratio of 100:2:1:120:5. After the uniform mixing was completed, the materials were coated on a copper foil. The single-sided areal density of the negative electrode sheet was 200 g / m 2The negative electrode sheet after the uniform coating is completed is baked, and then is rolled and die cut to obtain the negative electrode sheet.

[0062] LiPF6 is dissolved in a solvent with a mass ratio of DMC / EMC / DEC of 1:1:1 to obtain an electrolyte with a LiPF6 concentration of 1 mol / L.

[0063] The separator is a polypropylene film with a thickness of 16 μm.

[0064] The positive electrode sheet, the separator and the negative electrode sheet are made into an electrode assembly through the lamination process, and the electrode assembly is placed in an aluminum plastic film outer package, and then the battery is made after liquid injection and sealing. The battery is subjected to formation, aging, and capacity distribution, and the performance of the battery is tested.

[0065] Example 2

[0066] Li5FeO4 with a particle size of 3 μm and Li5FeO4 with a particle size of 30 μm are mixed in a mass ratio of 8:2.

[0067] After the Li5FeO4 is fully dispersed, the Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after the positive electrode slurry is uniformly dispersed, it is uniformly coated on the aluminum foil current collector. The single-sided area density of the positive electrode sheet is 200 g / m 2 , and the positive electrode sheet is obtained after rolling, die cutting and baking.

[0068] The other steps are the same as in Example 1.

[0069] Example 3

[0070] Li5FeO4 with a particle size of 3 μm and Li5FeO4 with a particle size of 30 μm are mixed in a mass ratio of 7:3.

[0071] After the Li5FeO4 is fully dispersed, the Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after the positive electrode slurry is uniformly dispersed, it is uniformly coated on the aluminum foil current collector. The single-sided area density of the positive electrode sheet is 200 g / m 2 , and the positive electrode sheet is obtained after rolling, die cutting and baking.

[0072] The other steps are the same as in Example 1.

[0073] Example 4

[0074] Li5FeO4 with a particle size of 3 μm and Li5FeO4 with a particle size of 30 μm are mixed in a mass ratio of 6:4.

[0075] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0076] The same as in Example 1.

[0077] Example 5

[0078] The Li5FeO4 with a particle size of 3 μm and the Li5FeO4 with a particle size of 6 μm are mixed in a mass ratio of 6:4.

[0079] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab, and the scanning electron microscope photos are shown in FIGS. 3, 4A, and 4B. As can be seen from FIGS. 3, 4A, and 4B, the lithium supplement materials (the lithium supplement material particles shown in the positions of the oval circles in FIG. 3 and the size markers in FIGS. 4A and 4B) with different particle sizes are distributed in the positive electrode tab.

[0080] The same as in Example 1.

[0081] Example 6

[0082] The Li5FeO4 with a particle size of 5 μm and the Li5FeO4 with a particle size of 10 μm are mixed in a mass ratio of 6:4.

[0083] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0084] The same as in Example 1.

[0085] Example 7

[0086] The Li5FeO4 with a particle size of 7 μm and the Li5FeO4 with a particle size of 15 μm are mixed in a mass ratio of 6:4.

[0087] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0088] The same as in Example 1.

[0089] Example 8

[0090] The Li5FeO4 with a particle size of 3 μm and the Li5FeO4 with a particle size of 10 μm and 15 μm are mixed in a mass ratio of 1:3:5.

[0091] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0092] The same as in Example 1.

[0093] Example 9

[0094] The Li5FeO4 with a particle size of 3 μm and the Li5FeO4 with a particle size of 8 μm and 13 μm are mixed in a mass ratio of 1:3:5.

[0095] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0096] The same as in Example 1.

[0097] Example 10

[0098] The Li5FeO4 with a particle size of 3 μm and the Li5FeO4 with a particle size of 6 μm and 9 μm are mixed in a mass ratio of 1:3:5. i5 FeO4.

[0099] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0100] The other steps are the same as in Example 1.

[0101] Example 11

[0102] Li5FeO4 with particle sizes of 3 μm, 6 μm, 10 μm, and 15 μm are mixed in a mass ratio of 1:2:3:4.

[0103] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0104] The other steps are the same as in Example 1.

[0105] Comparative Example 1

[0106] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0107] The other steps are the same as in Example 1.

[0108] Comparative Example 2

[0109] The fully dispersed Li5FeO4, CNT, PVDF, PVP, lithium iron phosphate, NMP are uniformly mixed in a mass ratio of 2.5:1:2.5:0.5:100:60, and after being uniformly dispersed into a positive electrode slurry, the positive electrode slurry is uniformly coated on an aluminum foil current collector, and the single-sided area density of the positive electrode tab is 200 g / m2. 2 Rolling, die cutting, and baking are performed to obtain the positive electrode tab.

[0110] The other steps are the same as in Example 1.

[0111] The lithium ion batteries prepared in the above examples and comparative examples were subjected to performance tests, and the test results are shown in Table 1.

[0112] 1. Positive electrode lithium supplement material gram capacity test: the lithium supplement composition, carbon nanotube, PDVF and NMP were mixed in a mass ratio of 100:1:10:400 to serve as a positive electrode slurry, a positive electrode sheet was prepared according to the method in Example 1, and then a lithium ion battery was prepared according to the method in Example 1.

[0113] The lithium ion battery was charged at 0.02C for 10h, rested for 30min, then charged at 0.5C constant current and constant voltage to 3.9V (cut-off current was 0.01C) and rested for 30min, and then charged at 0.2C constant current and constant voltage to 4.3V (cut-off current was 0.01C) to obtain the decomposition capacity.

[0114] The mass of the lithium supplement composition in a lithium ion battery was calculated from the area density and the ratio of the above lithium supplement composition, and the decomposition capacity obtained above was divided by the mass of the lithium supplement composition calculated above to obtain the gram capacity of the lithium supplement composition.

[0115] 2. Decomposition gas production test: the lithium ion battery was charged at 0.02C for 10h, rested for 30min, then charged at 0.5C constant current and constant voltage to 3.9V (cut-off current was 0.01C) and rested for 30min, and then charged at 0.2C constant current and constant voltage to 4.3V (cut-off current was 0.01C), and the decomposition gas production of the lithium supplement composition in the above lithium ion battery was tested according to the Archimedes drainage method.

[0116] 3. Storage gas production test: after the battery produced gas under the conditions of the decomposition gas production test, the battery was discharged and placed in a 60℃ oven for high-temperature storage for 15 days, and the gas volume was measured again according to the Archimedes drainage method to obtain the storage gas production.

[0117] 4. Battery direct current internal resistance (DCIR) test: after the above formation, the lithium ion battery was charged at 1 / 3C constant current to the upper limit voltage 4.2V at room temperature (25±3℃), and then discharged to the lower limit voltage 2.0V. After 3 cycles, the battery was charged at 1 / 3C constant current to 50% SOC at room temperature, and the battery voltage after standing for 1 hour was recorded as V1; then discharged at 1.5C for 30s, and the battery voltage after discharging was recorded as V2, wherein DCIR=(V1-V2) / 1.5C.

[0118] Table 1: Battery performance test results

[0119] It can be known from the above test results that the use of different particle sizes of the lithium supplement material can make the battery have high capacity and less gas production, and the comprehensive performance of the battery is better, while the use of a single particle size of the lithium supplement material can make the comprehensive performance of the battery significantly worse.

[0120] In the description of the present application, it should be understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can be explicitly or implicitly included at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0121] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not necessarily for the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or features of the embodiments or examples described in the present application without contradiction.

[0122] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A positive electrode sheet, wherein, The positive electrode film layer comprises a lithium supplement material composition, and the lithium supplement material composition comprises n kinds of lithium supplement materials with different particle sizes, wherein n is an integer greater than or equal to 2, and the n kinds of lithium supplement materials are sequentially arranged in order of increasing Dv50 particle size, and the difference between the Dv50 particle size of the i+1th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm, wherein i is an integer from 1 to n-1.

2. The positive electrode sheet according to claim 1, wherein The difference between the Dv50 particle size of the i+1th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm and less than or equal to 27 μm.

3. The positive electrode sheet according to claim 1 or 2, wherein The difference between the Dv50 particle size of the i+1th lithium supplement material and the Dv50 particle size of the ith lithium supplement material is greater than or equal to 1 μm and less than or equal to 5 μm.

4. The positive electrode sheet according to any one of claims 1 to 3, wherein The content of the ith lithium supplement material is greater than the content of the i+1th lithium supplement material in the lithium supplement material composition.

5. The positive electrode sheet according to any one of claims 1 to 4, wherein The difference between the mass of the ith lithium supplement material and the mass of the i+1th lithium supplement material accounts for 10% to 50% of the total mass of the lithium supplement material composition.

6. The positive electrode sheet according to any one of claims 1 to 5, wherein The Dv50 particle size of any one of the n kinds of lithium supplement materials is 1 μm to 30 μm.

7. The positive electrode sheet according to any one of claims 1 to 6, wherein The Dv50 particle size of any one of the n kinds of lithium supplement materials is 3 μm to 15 μm.

8. The positive electrode sheet according to any one of claims 1 to 7, wherein N is an integer greater than 2 and less than or equal to 30.

9. The positive electrode sheet according to any one of claims 1 to 8, wherein N is an integer greater than 2 and less than or equal to 5.

10. The positive electrode sheet according to any one of claims 1 to 9, wherein The lithium supplement material comprises at least one of Li6COO4, LiMnO3, Li2NiO2, Li5FeO4, Li2S, LI2O, Li2O2, and Li3N.

11. The positive electrode sheet according to any one of claims 1 to 10, wherein The lithium supplement material comprises Li5FeO4.

12. The positive electrode sheet according to any one of claims 1 to 11, wherein The mass percentage content of the lithium supplement material composition is 0.1% to 10% based on the total mass of the positive electrode film layer.

13. The positive electrode sheet according to any one of claims 1 to 12, wherein The mass percentage content of the lithium supplement material composition is 0.1% to 5% based on the total mass of the positive electrode film layer.

14. The positive electrode sheet according to any one of claims 1 to 13, wherein The positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises at least one of lithium iron phosphate, lithium manganese iron phosphate, nickel-cobalt-manganese ternary positive electrode material, nickel-cobalt-aluminum ternary positive electrode material, lithium-rich manganese-based positive electrode material, lithium cobaltate, lithium nickelate, lithium manganate, and lithium nickel manganate.

15. The positive electrode sheet according to any one of claims 1 to 14, wherein The positive electrode film layer comprises a positive electrode active material, and the positive electrode active material comprises at least one of lithium iron phosphate and lithium manganese iron phosphate.

16. The positive electrode sheet according to claim 14 or 15, wherein The Dv50 particle size of the positive electrode active material is 1 μm to 5 μm.

17. A battery, wherein, The positive electrode sheet comprises the positive electrode film layer according to any one of claims 1 to 16.

18. An electrical device, comprising: The battery comprises the positive electrode sheet according to claim 17.

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