Positive electrode active material, method for manufacturing the same, positive electrode sheet, secondary battery, battery module, battery pack, and power tool

Abstract

The application provides a positive electrode active material, which is a secondary particle formed by stacking primary particles, wherein the primary particles comprise a lithium-rich manganese-based matrix material and a coating layer on the surface of the lithium-rich manganese-based matrix material, and the coating layer comprises a fast ion conductor and a metal compound conductive agent. The positive electrode active material has improved cycle performance and rate capability. The application also provides a preparation method of the positive electrode active material, and a positive electrode sheet, a secondary battery, a battery module, a battery pack and a power utilization device comprising the positive electrode active material.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium batteries, in particular to a positive electrode active material and a preparation method thereof, and a positive electrode tab, a secondary battery, a battery module, a battery pack and a power utilization device comprising the positive electrode active material. BACKGROUND

[0002] In recent years, with the increasingly wide application of lithium ion batteries, lithium ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, and in many fields such as electric tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, etc. Since lithium ion batteries have achieved great development, higher requirements have been put forward for their energy density, cycle performance and safety performance, etc.

[0003] The performance of the key materials of lithium ion batteries is the final decisive factor of the performance of the batteries, and the research on positive electrode materials has always been a hot spot of battery research. The common positive electrode materials at present include layered structure materials (such as lithium cobaltate, lithium manganate, lithium nickelate, etc.), spinel structure materials, poly-anion type materials, ternary materials and the currently popular lithium-rich materials, etc. However, the lithium ion battery system prepared from these positive electrode materials still has problems such as low energy density, high cost, poor safety, etc., which cannot meet the increasing demand of people for fast charging, cycle stability, safety, etc. of batteries, therefore, certain strategies need to be taken to optimize the positive electrode materials, so as to improve the cycle performance, rate performance and safety performance of the secondary batteries. SUMMARY

[0004] The present application is carried out in view of the above-mentioned problems, and aims to provide a positive electrode active material having improved cycle performance and rate performance, and to provide a preparation method of the positive electrode active material, and a positive electrode tab, a secondary battery, a battery module, a battery pack and a power utilization device comprising the positive electrode active material.

[0005] In order to achieve the above-mentioned purpose, the first aspect of the present application provides a positive electrode active material, which is a secondary particle formed by stacking primary particles, wherein the primary particles comprise a lithium-rich manganese-based matrix material and a coating layer located on the surface of the lithium-rich manganese-based matrix material, and the coating layer comprises a fast ion conductor and a metal compound conductive agent.

[0006] Thus, compared with the prior art, the positive electrode active material of the present application has improved cycle performance and rate performance.

[0007] In any embodiment, the fast ion conductor is selected from one or more of lithium silicate, lithium phosphate, lithium borate, lithium niobate, lithium aluminate, lithium zirconate, and lithium pyrophosphate, optionally the fast ion conductor is selected from one or more of lithium silicate, lithium phosphate, and lithium borate; and the amount of the fast ion conductor is 0.5 to 20% by weight, optionally 2 to 12% by weight, based on the weight of the positive electrode active material. By selecting the fast ion conductor described above and having the content thereof satisfy the range described above, the rate capability and cycle performance of the positive electrode active material can be further improved.

[0008] In any embodiment, the metal compound conductive agent is selected from one or more of titanium carbide, titanium nitride, and titanium boride; and the amount of the metal compound conductive agent is 0.5 to 10% by weight, optionally 1 to 6% by weight, based on the weight of the positive electrode active material. By selecting the metal compound conductive agent described above and having the content thereof satisfy the range described above, the rate capability and cycle performance of the positive electrode active material can be further improved.

[0009] In any embodiment, the weight ratio of the fast ion conductor to the metal compound conductive agent in the positive electrode active material is 1.3 to 3: 1, optionally 1.7 to 2.7: 1. By having the weight ratio of the fast ion conductor to the metal compound conductive agent satisfy the range described above, the rate capability and cycle performance of the positive electrode active material can be further improved.

[0010] In any embodiment, the chemical formula of the lithium-rich manganese-based base material is xLi2MnO3·(1-x)LiMO2, where the M is a combination of one or more selected from the group consisting of Fe, Al, Co, Mn, Ni, Cr, Ti, Mo, Nb, Zr, Sn, V, Mg, Cu, Zn, B, Na, Ca, and Ru, optionally the M is a combination of one or more selected from the group consisting of Co, Ni, Cr, V, Mo, Mn, Al, Nb, and Ti, and 0 < x < 1.

[0011] In any embodiment, the Dv50 of the positive electrode active material is 5 to 20 μm, optionally 7 to 13 μm, and the Dv50 of the primary particles is 0.05 to 1 μm, optionally 0.1 to 0.4 μm. When the particle diameter of the positive electrode active material is within the range described above, the compaction density of the positive electrode active material can be optimized, thereby further improving the performance of the positive electrode active material.

[0012] In any embodiment, the compaction density of the positive electrode active material under 5 tons of force is 2.4 to 3.4 g / cm 3 , optionally 2.7 to 3.2 g / cm 3When the tap density of the positive electrode active material is in the above range, the filling degree between the positive electrode active material particles is high, which is conducive to further improving the processability of the positive electrode active material.

[0013] In any embodiment, the thickness of the coating layer is 0.005-0.2 μm, optionally 0.01-0.1 μm, and more optionally 0.04-0.08 μm. When the thickness of the coating layer meets the above range, it is conducive to further improving the cycle performance and rate performance of the positive electrode active material.

[0014] The second aspect of the present application provides a preparation method of a positive electrode active material, comprising the following steps:

[0015] S1) crushing a lithium-rich manganese-based positive electrode active material precursor in an inert atmosphere to obtain primary particles of the lithium-rich manganese-based positive electrode active material precursor;

[0016] S2) adding a fast ion conductor precursor, a metal compound conductive agent, and a dispersant polyvinylpyrrolidone into water and mixing uniformly, and then adding the primary particles of the lithium-rich manganese-based positive electrode active material precursor of step S1) into the mixture and mixing uniformly to obtain a suspension of a solid mixture;

[0017] S3) spray drying and secondary granulating the suspension of the solid mixture of step S2) to obtain a positive electrode active material precursor powder;

[0018] S4) mixing the positive electrode active material precursor powder of step S3) with a lithium source uniformly and sintering to obtain a positive electrode active material,

[0019] The positive electrode active material is a secondary particle formed by stacking primary particles, wherein the primary particles comprise a lithium-rich manganese-based matrix material and a coating layer located on the surface of the lithium-rich manganese-based matrix material, and the coating layer comprises a fast ion conductor and a metal compound conductive agent.

[0020] By the above method, a positive electrode active material with improved rate performance and cycle performance can be obtained.

[0021] In any embodiment, in the step S1), the Dv50 of the primary particles of the lithium-rich manganese-based positive electrode active material precursor is 0.05-1.1 μm, and optionally 0.1-0.4 μm. By controlling the particle size of the primary particles of the precursor, a positive electrode active material with improved rate performance and cycle performance can be obtained.

[0022] In any embodiment, in the step S2), the solid mixture comprises primary particles of the fast ion conductor precursor, the metal compound conductive agent and the lithium-rich manganese-based positive electrode active material precursor, wherein the fast ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, lithium borate, niobium pentoxide, aluminum oxide, zirconium dioxide and lithium dihydrogen phosphate, optionally the fast ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, lithium borate; optionally, the amount of the fast ion conductor is 0.4-16 wt%, optionally 1.5-9.5 wt%, based on the weight of the solid mixture, and the metal compound conductive agent is selected from one or more of titanium carbide, titanium nitride and titanium boride; optionally, the amount of the metal compound conductive agent is 0.4-8 wt%, optionally 0.8-5 wt%, based on the weight of the solid mixture. By selecting the fast ion conductor precursor and the metal compound conductive agent as described above and making their content meet the above ranges, it is beneficial to obtain a positive electrode active material with improved rate capability and cycle performance.

[0023] In any embodiment, in the step S4), the sintering atmosphere is oxygen, air or compressed air, the sintering temperature is 700-1000℃, and the sintering time is 5-10h. By controlling the sintering temperature and the sintering time, the crystallinity of the material after sintering can be higher, which is beneficial to obtain a positive electrode active material with improved rate capability and cycle performance.

[0024] The third aspect of the present application provides a positive electrode tab, comprising a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, wherein the positive electrode film layer comprises the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application, and the content of the positive electrode active material in the positive electrode film layer is 10 wt% or more, based on the total weight of the positive electrode film layer.

[0025] The fourth aspect of the present application provides a secondary battery comprising the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared by the method of the second aspect of the present application.

[0026] The fifth aspect of the present application provides a battery module comprising the secondary battery of the fourth aspect of the present application.

[0027] The sixth aspect of the present application provides a battery pack comprising the battery module of the fifth aspect of the present application.

[0028] The seventh aspect of the present application provides an electric device comprising at least one selected from the secondary battery of the fourth aspect of the present application, the battery module of the fifth aspect of the present application or the battery pack of the sixth aspect of the present application.

[0029] The battery module, the battery pack, and the electrical device of the present application include the secondary battery provided by the present application, and thus have at least the same advantages as the secondary battery. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a schematic view of a secondary battery according to an embodiment of the present application.

[0031] Figure 2 is a schematic view of a secondary battery according to an embodiment of the present application. Figure 1

[0032] Figure 3 is a schematic view of a battery module according to an embodiment of the present application.

[0033] Figure 4 is a schematic view of a battery pack according to an embodiment of the present application.

[0034] Figure 5 is a schematic view of a battery pack according to an embodiment of the present application. Figure 4

[0035] Figure 6 is a schematic view of an electrical device using a secondary battery according to an embodiment of the present application as a power source.

[0036] REFERENCE NUMERALS

[0037] 1 battery pack; 2 upper case; 3 lower case; 4 battery module; 5 secondary battery; 51 case; 52 electrode assembly; 53 top cap assembly DETAILED DESCRIPTION

[0038] Hereinafter, embodiments of the positive active material and the method for manufacturing the same, the positive electrode sheet, the secondary battery, the battery module, the battery pack, and the electrical device of the present application are specifically disclosed in detail with appropriate reference to the accompanying drawings. However, there can be cases where unnecessary detailed descriptions are omitted. For example, there can be cases where detailed descriptions of matters well known in the art, repeated descriptions of substantially identical structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. In addition, the accompanying drawings and the following description are provided so that those skilled in the art can fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0039] ​​The ranges disclosed herein are intended to be "open" ranges, i.e., the upper and lower limits of the range are not included. The ranges are also intended to include any and all sub-ranges of the range, i.e., all combinations of any two of the range limits, unless otherwise indicated. For example, a range of "1 to 10" is intended to include any number from 1 to 10, including the numbers 1 and 10. Unless otherwise indicated, the use of "or" in the disclosed aspects herein is the inclusive, and not the exclusive use. Only the context, and not the number of times an item is used, can determine that the item is intended to be interpreted as the exclusive alternative. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, a condition is satisfied by any one of the following: A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).

[0040] Unless otherwise indicated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0041] Unless otherwise indicated, all technical features of the present application and optional technical features can be combined with each other to form new technical solutions.

[0042] Unless otherwise indicated, the terms "comprise" and "include" mentioned in the present application are open-ended and can also be closed. For example, the terms "comprise" and "include" can mean that other components not listed can also be included, or only the listed components can be included.

[0043] Unless otherwise indicated, in the present application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any one of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or A and B are both true (or exist).

[0044] The lithium-rich manganese-based positive electrode material is considered as the preferred positive electrode material of the next generation high specific capacity battery due to its high specific capacity (>250 mAh / g), low cost, good thermal stability and other advantages. The main element used in the lithium-rich manganese-based positive electrode material is environmentally friendly manganese, which has low nickel and cobalt content, or even no cobal, effectively avoiding the problem of nickel and cobalt resources. Compared with cobalt and nickel, manganese is not only low in price but also abundant in reserves. However, the lithium ion diffusion coefficient of the lithium-rich material is low, resulting in poor rate performance. In the process of charging and discharging cycle, metal ions migrate, and the layered structure gradually changes to spinel structure, thereby causing the specific capacity and discharge voltage to gradually decay. Studies have shown that the structural phase transition of the lithium-rich manganese-based material extends from the surface layer to the bulk phase. Therefore, it is crucial to build a stable surface structure, and surface coating is an effective method to improve the electrochemical performance of the positive electrode material. A suitable surface coating layer can not only provide a fast transmission channel for lithium ions / electrons, but also isolate the direct contact between the electrolyte and the positive electrode material, avoiding the reaction between the two to degrade the battery performance. Generally, a single coating layer only has one property, that is, it can improve ion conductivity while possibly hindering electron transmission, affecting conductivity, and vice versa. For example, the carbon layer has good conductivity, but its lithium ion transmission capacity is relatively poor. In addition, multi-layer coating means that the preparation process is more complex, and the bonding strength between the coating layers is difficult to guarantee. With the progress of the cycle process, the coating layer and the base material may separate, thereby degrading the performance.

[0045] To solve the above problems, the first aspect of the present application provides a positive electrode active material, which is a secondary particle formed by stacking primary particles, wherein the primary particles include a lithium-rich manganese-based base material and a coating layer on the surface of the lithium-rich manganese-based base material, and the coating layer includes a fast ion conductor and a metal compound conductive agent.

[0046] Although the mechanism is not clear, the applicant has unexpectedly found that, on the one hand, the positive electrode active material of the application is a secondary particle formed by stacking primary particles, and a homogeneous composite coating layer is constructed on the outer surface of the base material of the primary particles, the coating layer comprising a fast ion conductor and a metal compound conductive agent, wherein the fast ion conductor can effectively improve the ion transport capacity of the positive electrode active material, and the metal compound conductive agent can effectively improve the electron transport capacity of the positive electrode active material, both of which form a continuous ion and electron channel in the coating layer, which effectively reduces the interface impedance compared with the conventional multi-layer coating, and avoids the problems of poor transmission capacity of electrons in the fast ion conductor coating layer and ions in the conductive coating layer, thereby simultaneously improving the ionic conductivity and electronic conductivity of the positive electrode active material, and improving the rate performance of the positive electrode active material. On the other hand, the positive electrode active material of the application can be modified by surface coating to prevent direct contact between the positive electrode active material and the electrolyte, inhibit the occurrence of side reactions, improve the cycle performance of the positive electrode active material, and at the same time, the surface of each primary particle is completely coated, so that even if the secondary particles are broken, the cycle stability of the material will not be seriously affected.

[0047] In the application, the secondary particles are formed by aggregating a plurality of primary particles into spherical or spherical-like particles; the primary particles are single particles with a Dv50 of about 0.05-1 μm and no obvious agglomeration between the particles.

[0048] In some embodiments, the fast ion conductor is selected from one or more of lithium silicate, lithium phosphate, lithium borate, lithium niobate, lithium aluminate, lithium zirconate and lithium pyrophosphate, and optionally, the fast ion conductor is selected from one or more of lithium silicate, lithium phosphate and lithium borate; and optionally, the amount of the fast ion conductor is 0.5-20 wt%, optionally 2-12 wt%, based on the weight of the positive electrode active material. By selecting the above fast ion conductor and ensuring that its content meets the above range, the rate performance and cycle performance of the positive electrode active material can be further improved. If the content of the fast ion conductor is too high, the coating layer will be too thick, which is not conducive to the transmission efficiency of ions in the positive electrode active material; if the content of the fast ion conductor is too low, the lithium ions cannot be effectively transported.

[0049] In some embodiments, the metal compound conductive agent is selected from one or more of titanium carbide, titanium nitride and titanium boride; and optionally, the amount of the metal compound conductive agent is 0.5-10 wt%, optionally 1-6 wt%, based on the weight of the positive electrode active material. By selecting the above metal compound conductive agent and ensuring that its content meets the above range, the rate performance and cycle performance of the positive electrode active material can be further improved. If the content of the metal compound conductive agent is too high, the coating layer will be too thick, which is not conducive to the transmission efficiency of ions in the positive electrode active material; if the content of the metal compound conductive agent is too low, the electrons cannot be effectively transported.

[0050] In some embodiments, the weight ratio of the fast ion conductor to the metal compound conductive agent in the positive electrode active material is 1.3-3:1, optionally 1.7-2.7:1. By controlling the weight ratio of the fast ion conductor to the metal compound conductive agent in the coating layer of the positive electrode active material, the positive electrode active material can have both high ionic conductivity and electronic conductivity, thereby further improving the cycle performance and rate performance of the positive electrode active material.

[0051] In some embodiments, the lithium-rich manganese-based base material has a chemical formula of xLi2MnO3·(1-x)LiMO2, wherein M is a combination of one or more selected from Fe, Al, Co, Mn, Ni, Cr, Ti, Mo, Nb, Zr, Sn, V, Mg, Cu, Zn, B, Na, Ca and Ru, optionally, M is a combination of one or more selected from Co, Ni, Cr, V, Mo, Mn, Al, Nb and Ti, and 0

[0052] In some embodiments, the Dv50 of the positive electrode active material is 5-20 μm, optionally 7-13 μm, and the Dv50 of the primary particles is 0.05-1 μm, optionally 0.1-0.4 μm. When the particle size of the positive electrode active material is within the above range, the compaction density of the positive electrode active material can be optimized, thereby further improving the performance of the positive electrode active material.

[0053] In some embodiments, the compaction density of the positive electrode active material under a force of 5 tons is 2.4-3.4 g / cm3, optionally 2.7-3.2 g / cm3. The higher the compaction density, the greater the weight of the active material per unit volume, and thus increasing the compaction density is beneficial to increasing the volume energy density of the battery cell. The positive electrode active material has a high compaction density and a high degree of inter-particle packing, which is beneficial to further improving the processability of the positive electrode active material. The compaction density can be measured according to GB / T 24533-2009. 3 3 The higher the compaction density, the greater the weight of the active material per unit volume, and thus increasing the compaction density is beneficial to increasing the volume energy density of the battery cell. The positive electrode active material has a high compaction density and a high degree of inter-particle packing, which is beneficial to further improving the processability of the positive electrode active material. The compaction density can be measured according to GB / T 24533-2009.

[0054] In some embodiments, the thickness of the coating layer is 0.005-0.2 μm, optionally 0.01-0.1 μm, and more optionally 0.04-0.08 μm. When the thickness of the coating layer is within the above range, the positive electrode active material can have improved cycle performance and rate performance. If the thickness of the coating layer is too thick, the transmission efficiency of electrons and ions is adversely affected; if the thickness of the coating layer is too thin, the transmission of electrons and ions is not effective.

[0055] ​In some embodiments, the weight a of the fast ion conductor and the weight b of the metal compound conductive agent in the positive electrode active material satisfy the following: 2≤a*b / (a+b)≤4, optionally, 2.5

[0056] The second aspect of the present application provides a method for preparing a positive electrode active material, the method comprising the following steps:

[0057] S1) crushing a lithium-rich manganese-based positive electrode active material precursor in an inert atmosphere to obtain primary particles of the lithium-rich manganese-based positive electrode active material precursor;

[0058] S2) adding a fast ion conductor precursor, a metal compound conductive agent, and a dispersant polyvinylpyrrolidone into water and mixing uniformly, and then adding the primary particles of the lithium-rich manganese-based positive electrode active material precursor of step S1) into the mixture and mixing uniformly to obtain a suspension of a solid mixture;

[0059] S3) spray-drying and secondary granulating the suspension of the solid mixture of step S2) to obtain a positive electrode active material precursor powder;

[0060] S4) mixing the positive electrode active material precursor powder of step S3) with a lithium source and sintering to obtain a positive electrode active material,

[0061] The positive electrode active material is a secondary particle formed by stacking primary particles, wherein the primary particles comprise a lithium-rich manganese-based matrix material and a coating layer located on the surface of the lithium-rich manganese-based matrix material, and the coating layer comprises a fast ion conductor and a metal compound conductive agent.

[0062] Through the above method, on the one hand, a homogeneous composite coating layer is constructed on the outer surface of the matrix material of the primary particles, effectively improving the ion transport capacity and electron transport capacity of the positive electrode active material, thereby obtaining a positive electrode active material with improved rate performance; on the other hand, the bonding strength between the coating layer and the matrix material can be significantly improved, avoiding the peeling off of the coating layer caused by uneven stress during the cycle process, thereby effectively improving the cycle performance of the positive electrode active material.

[0063] In some embodiments, in the step S1), the Dv50 of the primary particles of the lithium-rich manganese-based positive electrode active material precursor is 0.05-1.1 μm, optionally 0.1-0.4 μm. By controlling the particle size of the primary particles of the precursor, a positive electrode active material with improved rate performance and cycle performance can be obtained.

[0064] In this application, the crushing method includes one or more of grinding, air jet milling, mechanical grinding and high-energy ball milling, and optionally, the crushing method is high-energy ball milling.

[0065] In some embodiments, in step S2), the solid mixture comprises primary particles of a fast-ion conductor precursor, a metal compound conductive agent, and a lithium-rich manganese-based cathode active material precursor. The fast-ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, lithium borate, niobium pentoxide, alumina, zirconium dioxide, and lithium dihydrogen phosphate. Optionally, the fast-ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, and lithium borate. Optionally, the amount of the fast-ion conductor is 0.4-16 wt%, optionally 1.5-9.5 wt%, based on the weight of the solid mixture. The metal compound conductive agent is selected from one or more of titanium carbide, titanium nitride, and titanium boride. Optionally, the amount of the metal compound conductive agent is 0.4-8 wt%, optionally 0.8-5 wt%, based on the weight of the solid mixture. By selecting the above-mentioned fast-ion conductor precursor and metal compound conductive agent and ensuring their content meets the above ranges, it is beneficial to obtain a cathode active material with improved rate performance and cycle performance.

[0066] In some embodiments, in step S4), the sintering atmosphere is oxygen, air, or compressed air, and the sintering temperature is 700-1000℃, for example, 700℃, 800℃, 900℃, or 1000℃, but not limited to the listed values; any value within the above range is equally applicable. The sintering time is 5-10 hours, for example, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, but not limited to the listed values; any value within the above range is equally applicable. By controlling the sintering temperature and sintering time, the crystallinity of the sintered material can be increased, which is beneficial for obtaining positive electrode active materials with improved rate performance and cycle performance.

[0067] A third aspect of this application provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising the positive electrode active material of the first aspect of this application or the positive electrode active material prepared by the method of the second aspect of this application, and the content of the positive electrode active material in the positive electrode film layer is 10% by weight or more, based on the total weight of the positive electrode film layer.

[0068] The fourth aspect of this application provides a secondary battery comprising the positive electrode active material of the first aspect of this application or the positive electrode active material prepared according to the method of the second aspect of this application.

[0069] A fifth aspect of this application provides a battery module that includes the secondary battery of the fourth aspect of this application.

[0070] A sixth aspect of this application provides a battery pack that includes the battery module of the fifth aspect of this application.

[0071] A seventh aspect of this application provides an electrical device comprising at least one selected from the fourth aspect of this application, the fifth aspect of this application, or the sixth aspect of this application.

[0072] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0073] In one embodiment of this application, a secondary battery is provided.

[0074] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0075] [Positive electrode plate]

[0076] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including the positive electrode active material of the first aspect of this application.

[0077] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0078] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, in addition to the positive electrode active material of the first aspect of this application, the positive electrode active material may also be a positive electrode active material known in the art for use in batteries. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more, wherein the positive electrode active material of the first aspect of this application accounts for 85-100%, and the other positive electrode active materials account for 0-15%. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (such as LiNi). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites. The positive electrode active material accounts for 80-100% by weight in the positive electrode film, based on the total weight of the positive electrode film.

[0080] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a terpolymer of PVDF-tetrafluoroethylene-propylene, a terpolymer of PVDF-hexafluoropropylene-tetrafluoroethylene, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorinated acrylate resin. The binder constitutes 0-20% by weight of the positive electrode film layer, based on the total weight of the positive electrode film layer.

[0081] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the positive electrode film, based on the total weight of the positive electrode film.

[0082] In some embodiments, the positive electrode sheet can be prepared by dispersing the components used to prepare the positive electrode sheet, such as the positive active material, conductive agent, binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; wherein the solid content of the positive electrode slurry is 40-80 wt%, the viscosity at room temperature is adjusted to 5000-25000 mPa·s, the positive electrode slurry is coated on a positive current collector, and after drying, cold pressing, and other processes, the positive electrode sheet is obtained, and the areal density of the positive electrode powder coating is 150-350 mg / m². 2 The compaction density of the positive electrode sheet is 3.0-3.6 g / cm³. 3 The concentration can be selected as 3.3-3.5 g / cm³. 3 The formula for calculating the compaction density is as follows:

[0083] Compacted density = Coated surface density / (Extreme electrode thickness after extrusion - Current collector thickness).

[0084] [Negative electrode plate]

[0085] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector, the negative electrode film layer including a negative electrode active material.

[0086] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0087] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0088] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more. The negative electrode active material may have an average particle size (D0) of 1 μm-15 μm, preferably 4 μm-9 μm. 10 ), with an average particle size (D) of 12μm-22μm, preferably 14μm-17μm. 50 It has an average particle size of 26 μm to 40 μm, preferably 30 μm to 37 μm (D). 90 D 10 D represents the particle size at which the cumulative volume distribution percentage of the sample reaches 10%. 50 D represents the particle size at which the cumulative volume distribution percentage of the sample reaches 50%. 90 The particle size corresponding to a cumulative volume distribution percentage of 90% for the sample. The weight ratio of the negative electrode active material in the negative electrode film is 70-100% by weight, based on the total weight of the negative electrode film.

[0089] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). The binder accounts for 0-30% by weight of the negative electrode film layer, based on the total weight of the negative electrode film layer.

[0090] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The conductive agent accounts for 0-20% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0091] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)). The other additives constitute 0-15% by weight of the negative electrode film, based on the total weight of the negative electrode film.

[0092] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry, wherein the solid content of the negative electrode slurry is 30-70 wt%, and the viscosity at room temperature is adjusted to 2000-10000 mPa·s; the negative electrode slurry is coated onto a negative electrode current collector, and after drying, cold pressing, and other processes, the negative electrode sheet is obtained. The areal density of the negative electrode powder coating is 75-220 mg / m³. 2 The compacted density of the negative electrode sheet is 1.2-2.0 g / m³. 3 .

[0093] [Electrolytes]

[0094] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0095] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0096] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate. The concentration of the electrolyte salt is typically 0.5-5 mol / L.

[0097] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0098] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0099] [Isolation membrane]

[0100] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0101] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0102] In some embodiments, the thickness of the isolation membrane is 6-40 μm, optionally 12-20 μm.

[0103] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0104] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0105] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0106] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 1 This is an example of a square-structured secondary battery 5.

[0107] In some implementations, refer to Figure 2 The outer packaging may include a housing 51 and a cover 53. The housing 51 may include a base plate and side plates connected to the base plate, the base plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover 53 can be placed over the opening to close the receiving cavity. A positive electrode, a negative electrode, and a separator can be formed into an electrode assembly 52 using a winding or stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0108] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0109] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0110] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0111] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0112] Figure 4 and Figure 5 This is battery pack 1 as an example. (See reference...) Figure 4 and Figure 5 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0113] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0114] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0115] Figure 6 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0116] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0117] Example

[0118] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0119] Preparation of primary and secondary batteries

[0120] Example 1

[0121] (1) Preparation of precursors for lithium-rich manganese-based cathode active materials

[0122] Using manganese sulfate as the manganese source and nickel sulfate as the nickel source, a transition metal salt solution with a concentration of 2 mol / L was prepared at a Mn:Ni molar ratio of 7:3. A 2 mol / L sodium carbonate solution and a 1 mol / L ammonia solution were also prepared. 20% of the reactor volume of deionized water was added as the reaction base liquid to the reactor. Under a nitrogen atmosphere, the transition metal salt solution, sodium carbonate solution, and ammonia solution were simultaneously pumped into the reactor at flow rates v1 = 35 ml / h, v2 = 5-50 ml / h, and v3 = 35 ml / h, respectively. The pH of the reaction system was controlled to 9.5 by adjusting the feed flow rate v2 of the sodium carbonate solution. The reaction was carried out for 20 hours at a temperature of 50°C and a stirring speed of 800 rpm / min. After feeding, the reaction slurry was aged for another 10 hours. The precipitate was then filtered, washed, and dried to obtain the lithium-rich manganese-based cathode active material precursor Ni. 0.3 Mn 0.7 CO3.

[0123] (2) Preparation of positive electrode active material

[0124] The lithium-rich manganese-based cathode active material precursor Ni prepared above 0.3 Mn 0.7 CO3 (Dv50 of 8 μm) was crushed by high-energy ball milling in a nitrogen atmosphere to obtain primary particles (Dv50 of 0.3 μm) of lithium-rich manganese-based cathode active material precursor. Lithium borate (fast ion conductor precursor), titanium boride (metal compound conductive agent), and polyvinylpyrrolidone (dispersant) were added to water and stirred at 800 rpm / min until homogeneous. Then, the primary particles of the lithium-rich manganese-based cathode active material precursor were added and stirred at 500 rpm / min until homogeneous, resulting in a suspension of solid mixture. The weight ratio of lithium borate, titanium boride, and lithium-rich manganese-based cathode active material precursor in this solid mixture was 6.1:3.1:90.8. Subsequently, the suspension of the above solid mixture was spray-dried for secondary granulation (manufacturer: Buqi; model: B-290). The inlet temperature of the spray dryer was 250℃, and the nozzle diameter was 600 μm, yielding cathode active material precursor powder. Finally, the above-mentioned positive electrode active material precursor powder and lithium carbonate source were mixed evenly at a weight ratio of 100:50, and sintered at 800°C for 8 hours in air atmosphere to obtain the positive electrode active material.

[0125] (3) Preparation of full cells

[0126] [Positive Electrode Sheet] The above-mentioned positive electrode active material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) are mixed evenly in an N-methylpyrrolidone solvent system at a weight ratio of 92:2.5:5.5. The mixture is then coated onto aluminum foil, dried, and cold-pressed to obtain the positive electrode sheet. The coating amount is 0.4 g / cm³.2 The compacted density is 2.4 g / cm³. 3 .

[0127] [Negative Electrode Sheet] The negative electrode sheet is prepared by uniformly mixing artificial graphite (negative electrode active material), carbon black (conductive agent), and styrene-butadiene rubber (SBR) (binder) in deionized water at a weight ratio of 92:2:6. The mixture is then coated onto copper foil, dried, and cold-pressed. The coating amount is 0.2 g / cm³. 2 The compacted density is 1.7 g / cm³. 3 .

[0128]

Separation Membrane

[0129] [Electrolyte] Ethyl carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1. Then, LiPF6 is uniformly dissolved in the above solution to obtain the electrolyte, wherein the concentration of LiPF6 is 1 mol / L.

[0130] The positive electrode, separator, and negative electrode are stacked in sequence, with the separator positioned between the positive and negative electrodes to provide isolation. These are then wound to obtain a bare cell. The bare cell is placed in outer packaging, electrolyte is injected, and it is sealed. After formation and capacity testing, a lithium-ion secondary full battery (hereinafter referred to as "full battery") is obtained. The full battery's dimensions are 148mm × 28.5mm × 97.5mm (length × width × height), and its group margin is 91.0%.

[0131] Example 2

[0132] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor in the solid mixture is 0.4:3.0:96.6.

[0133] Example 3

[0134] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor in the solid mixture is 1.5:3.0:95.5.

[0135] Example 4

[0136] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor in the solid mixture is 5.4:3.0:91.6.

[0137] Example 5

[0138] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor in the solid mixture is 9.3:3.1:87.6.

[0139] Example 6

[0140] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor in the solid mixture is 15.7:3.2:81.1.

[0141] Example 7

[0142] The preparation of the secondary battery is the same as in Example 1, except that the lithium-rich manganese-based positive electrode active material precursor Ni is used. 0.3 Mn 0.7 The Dv50 of CO3 is 5 μm.

[0143] Example 8

[0144] The preparation of the secondary battery is the same as in Example 1, except that the lithium-rich manganese-based positive electrode active material precursor Ni is used. 0.3 Mn 0.7 The Dv50 of CO3 is 13 μm.

[0145] Example 9

[0146] The preparation of the secondary battery is the same as in Example 1, except that the lithium-rich manganese-based positive electrode active material precursor Ni is used. 0.3 Mn 0.7 The Dv50 of CO3 is 20 μm.

[0147] Example 10

[0148] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor (Dv50 is 7 μm) in the solid mixture is 6.0∶0.4∶93.6.

[0149] Example 11

[0150] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor (Dv50 is 7 μm) in the solid mixture is 6.0:0.8:93.2.

[0151] Example 12

[0152] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor (Dv50 is 8 μm) in the solid mixture is 6.1:2.3:91.6.

[0153] Example 13

[0154] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor (Dv50 is 8 μm) in the solid mixture is 6.2:4.6:89.2.

[0155] Example 14

[0156] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the weight ratio of lithium borate, titanium boride and lithium-rich manganese-based positive electrode active material precursor (Dv50 is 10 μm) in the solid mixture is 6.2:7.8:86.0.

[0157] Example 15

[0158] The preparation of the secondary battery is the same as in Example 1, except that the fast ion conductor precursor is silicon dioxide in the preparation of the positive electrode active material.

[0159] Example 16

[0160] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the fast ion conductor precursor is lithium phosphate.

[0161] Example 17

[0162] The preparation of the secondary battery is the same as in Example 1, except that the metal compound conductive agent used in the preparation of the positive electrode active material is titanium nitride.

[0163] Example 18

[0164] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material, the metal compound conductive agent is titanium carbide.

[0165] Comparative Example 1

[0166] The preparation of the secondary battery is the same as in Example 1, except that in the preparation of the positive electrode active material in (2), the lithium-rich manganese-based positive electrode active material precursor Ni obtained in (1) is directly used. 0.3 Mn 0.7CO3 and lithium carbonate (lithium source) were mixed uniformly at a weight ratio of 100:50, and then sintered at 800℃ for 8 hours in air atmosphere to obtain lithium-rich manganese-based cathode active material 0.4Li2MnO3·0.6LiNi. 0.5 Mn 0.5 O2 was used to prepare coin cells using lithium-rich manganese-based positive electrode active material.

[0167] II. Testing of relevant parameters

[0168] (1) Compacted density test

[0169] The compaction density of positive electrode active materials under 5 tons (5T) pressure was determined according to GB / T 24533-2009. A certain amount of positive electrode active material powder was placed in a special compaction mold, and then the mold was placed on a compaction density instrument. A pressure of 5T was applied, and the thickness of the powder under 5T pressure (the thickness after depressurization) was read on the instrument. The compaction density was calculated using p = m / v.

[0170] The test results are shown in Table 1.

[0171] (2) Particle size test

[0172] The particle size of the positive electrode active material was determined according to GB / T 19077.1-2016 / ISO 13320:2009 (Laser diffraction method for particle size distribution). A clean beaker was prepared, and an appropriate amount of the above-mentioned positive electrode active material was added, along with an appropriate amount of pure water. The mixture was sonicated at 120W / 5min to ensure complete dispersion of the material powder in the water. The solution was then poured into the sample column of a laser particle size analyzer (Malvin, model: Mastersizer3000) and circulated with the solution to the test optical path system. Under laser beam irradiation, the particle size distribution characteristics (opause level: 8-12%) were obtained by receiving and measuring the energy distribution of the scattered light, and the corresponding Dv50 value was read.

[0173] The results are shown in Table 1.

[0174] (3) Coating thickness test

[0175] Line scan analysis was performed on the materials displayed using a transmission electron microscope (STEM, ThermoFisher, Talos F200i) combined with a side-mounted scalable energy dispersive X-ray spectroscopy (EDS, ThermoFisher). The accelerating voltage was 50 kV, the magnification was 100 kx, and the beam current was between 500 and 1000 pA. Line scan spectra of the number of characteristic elements in the coating layer (in Example 1, this could be titanium in a metal compound conductive agent) and the number of characteristic elements in the lithium-rich manganese-based matrix material (in Example 1, this is manganese) were obtained. The coating layer and the surface of the lithium-rich manganese-based matrix material were determined based on the proportion of these element counts, thus yielding the coating layer thickness. The coating layer thickness was measured at five randomly selected locations on the positive electrode active material particles, and the arithmetic mean of the measurement results was calculated.

[0176] The results are shown in Table 1.

[0177] III. Testing of Secondary Battery Performance

[0178] (1) Cyclic capacity retention rate at 25℃

[0179] At 25°C, the battery is charged at a constant current of 1C to 4.35V, then charged at a constant voltage of 4.35V until the current drops to 0.05C, and finally discharged at a constant current of 1C to 2.5V. This yields the initial discharge capacity (Cd1). This charge-discharge cycle is repeated until the 500th cycle, yielding the discharge capacity after 500 cycles, denoted as Cdn. Capacity retention = Discharge capacity after 500 cycles (Cdn) / Initial discharge capacity (Cd1).

[0180] The results are shown in Table 1.

[0181] (2) 1C discharge rate performance test

[0182] At 25°C, the secondary batteries of each embodiment and comparative example were charged at a constant current rate of 0.1C to 4.35V, then charged at a constant voltage rate to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C to 2V. The discharge capacity at this time was recorded, which is the 0.1C discharge capacity. After standing for 30 minutes, the secondary batteries were charged at a constant current rate of 1C to 4.35V, then charged at a constant voltage rate to a current of 0.05C, left to stand for 5 minutes, and then discharged at a constant current rate of 1C to 2V. The discharge capacity at this time was recorded, which is the 1C discharge capacity.

[0183] The rate performance of a battery is calculated as 1C / 0.1C (%) = 1C discharge capacity / 0.1C discharge capacity × 100%.

[0184] The results are shown in Table 1.

[0185] (3) 3C charging constant current ratio test

[0186] Under a constant temperature environment of 25℃, the secondary batteries of each embodiment and comparative example were discharged to 2.5V at 1 / 3C. After resting for 5 minutes, they were charged to 4.3V at 1 / 3C, and then charged at 4.3V under constant voltage until the current ≤0.05mA. After resting for 5 minutes, the charging capacity at this time was recorded as C0. The batteries were then discharged to 2.5V at 1 / 3C, rested for 5 minutes, and then charged to 4.3V at 3C. After resting for 5 minutes, the charging capacity at this time was recorded as C1. The constant current ratio for 3C charging is C1 / C0*100%.

[0187] The results are shown in Table 1.

[0188]

[0189] As can be seen from the above, compared with the lithium-rich manganese-based positive electrode active material without a coating layer in Comparative Example 1, the positive electrode active material of this application has better cycle performance and rate performance. This is because the positive electrode active material of this application is formed by stacking primary particles into secondary particles. A homogeneous composite coating layer that forms continuous ion and electron channels is constructed on the outer surface of the matrix material of the primary particles, which is beneficial to the transport of ions and electrons.

[0190] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A positive electrode active material, characterized in that, The positive electrode active material is a secondary particle formed by stacking primary particles, wherein the primary particles include a lithium-rich manganese-based matrix material and a coating layer located on the surface of the lithium-rich manganese-based matrix material, and the coating layer includes a fast ion conductor and a metal compound conductive agent. The weight ratio of the fast ion conductor to the metal compound conductive agent in the positive electrode active material is 1.3-3:

1.

2. The positive electrode active material according to claim 1, characterized in that, The fast ion conductor is selected from one or more of lithium silicate, lithium phosphate, lithium borate, lithium niobate, lithium aluminate, lithium zirconate, and lithium pyrophosphate.

3. The positive electrode active material according to claim 1, characterized in that, The fast ion conductor is selected from one or more of lithium silicate, lithium phosphate, and lithium borate.

4. The positive electrode active material according to claim 1, characterized in that, The amount of the fast ion conductor is 0.5-20% by weight, based on the weight of the positive electrode active material.

5. The positive electrode active material according to claim 1, characterized in that, The amount of the fast ion conductor is 2-12% by weight, based on the weight of the positive electrode active material.

6. The positive electrode active material according to claim 1, characterized in that, The conductive metal compound is selected from one or more of titanium carbide, titanium nitride, and titanium boride.

7. The positive electrode active material according to claim 1, characterized in that, The amount of the metal compound conductive agent is 0.5-10% by weight, based on the weight of the positive electrode active material.

8. The positive electrode active material according to claim 1, characterized in that, The amount of the metal compound conductive agent is 1-6% by weight, based on the weight of the positive electrode active material.

9. The positive electrode active material according to any one of claims 1-8, characterized in that, The weight ratio of the fast ion conductor to the metal compound conductive agent in the positive electrode active material is 1.7-2.7:

1.

10. The positive electrode active material according to any one of claims 1-8, characterized in that, The chemical formula of the lithium-rich manganese-based matrix material is xLi2MnO3·(1-x)LiMO2, wherein M is one or more of Fe, Al, Co, Mn, Ni, Cr, Ti, Mo, Nb, Zr, Sn, V, Mg, Cu, Zn, B, Na, Ca and Ru.

11. The positive electrode active material according to claim 10, characterized in that, M is a combination of one or more of Co, Ni, Cr, V, Mo, Mn, Al, Nb and Ti, and 0 < x < 1.

12. The positive electrode active material according to any one of claims 1-8, characterized in that, The Dv50 of the positive electrode active material is 5-20 μm.

13. The positive electrode active material according to claim 12, characterized in that, The Dv50 of the positive electrode active material is 7-13 μm.

14. The positive electrode active material according to claim 12, characterized in that, The Dv50 of the primary particles is 0.05-1 μm.

15. The positive electrode active material according to claim 12, characterized in that, The Dv50 of the primary particles is 0.1-0.4 μm.

16. The positive electrode active material according to any one of claims 1-5, characterized in that, The compaction density of the positive electrode active material under 5 tons of force is 2.4-3.4 g / cm³. 3 .

17. The positive electrode active material according to claim 16, characterized in that, The compaction density of the positive electrode active material under 5 tons of force is 2.7-3.2 g / cm³. 3 .

18. The positive electrode active material according to any one of claims 1-8, characterized in that, The thickness of the coating layer is 0.005-0.2 μm.

19. The positive electrode active material according to claim 18, characterized in that, The thickness of the coating layer is 0.01-0.1 μm.

20. The positive electrode active material according to any one of claims 18, characterized in that, The thickness of the coating layer is 0.04-0.08 μm.

21. A method for preparing the positive electrode active material according to claim 1, characterized in that, Includes the following steps: S1) The lithium-rich manganese-based cathode active material precursor is crushed in an inert atmosphere to obtain primary particles of the lithium-rich manganese-based cathode active material precursor. S2) Add the fast ion conductor precursor, metal compound conductive agent and dispersant polyvinylpyrrolidone to water and mix evenly. Then add the primary particles of the lithium-rich manganese-based positive electrode active material precursor from step S1) and mix evenly to obtain a suspension of solid mixture. S3) The suspension of the solid mixture in step S2) is spray-dried and granulated again to obtain the precursor powder of the positive electrode active material; S4) The positive electrode active material precursor powder from step S3) is mixed evenly with the lithium source, and then sintered to obtain the positive electrode active material. The positive electrode active material is a secondary particle formed by stacking primary particles, wherein the primary particles include a lithium-rich manganese-based matrix material and a coating layer located on the surface of the lithium-rich manganese-based matrix material, and the coating layer includes a fast ion conductor and a metal compound conductive agent.

22. A method for preparing a positive electrode active material according to claim 21, characterized in that, In step S1), the primary particles of the lithium-rich manganese-based cathode active material precursor have a Dv50 of 0.05-1.1 μm.

23. A method for preparing a positive electrode active material according to claim 22, characterized in that, In step S1), the primary particles of the lithium-rich manganese-based cathode active material precursor have a Dv50 of 0.1-0.4 μm.

24. The method for preparing a positive electrode active material according to claim 21 or 22, characterized in that, In step S2), the solid mixture comprises primary particles of a fast ion conductor precursor, a metal compound conductive agent, and a lithium-rich manganese-based cathode active material precursor. The fast ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, lithium borate, niobium pentoxide, aluminum oxide, zirconium dioxide and lithium dihydrogen phosphate.

25. The method for preparing a positive electrode active material according to claim 24, characterized in that, The fast ion conductor precursor is selected from one or more of silicon dioxide, lithium phosphate, and lithium borate.

26. The method for preparing a positive electrode active material according to claim 24, characterized in that, The amount of the fast ion conductor is 0.4-16% by weight, based on the weight of the solid mixture.

27. The method for preparing a positive electrode active material according to claim 24, characterized in that, The amount of the fast ion conductor is 1.5-9.5% by weight, based on the weight of the solid mixture, and The conductive metal compound is selected from one or more of titanium carbide, titanium nitride, and titanium boride.

28. The method for preparing a positive electrode active material according to claim 24, characterized in that, The amount of the metal compound conductive agent is 0.4-8% by weight, based on the weight of the solid mixture.

29. The method for preparing a positive electrode active material according to claim 24, characterized in that, The amount of the metal compound conductive agent is 0.8-5% by weight, based on the weight of the solid mixture.

30. The method for preparing a positive electrode active material according to claim 21 or 22, characterized in that, In step S4), the sintering atmosphere is oxygen, air or compressed air, the sintering temperature is 700-1000℃, and the sintering time is 5-10h.

31. A positive electrode plate, characterized in that, The device includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer comprising the positive electrode active material according to any one of claims 1-20 or the positive electrode active material prepared by the method according to any one of claims 21-30, and the content of the positive electrode active material in the positive electrode film layer is 10% by weight or more, based on the total weight of the positive electrode film layer.

32. A secondary battery, characterized in that, The positive electrode active material includes any one of claims 1-20 or a positive electrode active material prepared by any one of claims 21-30.

33. A battery module, characterized in that, Includes the secondary battery as described in claim 32.

34. A battery pack, characterized in that, Includes the battery module as described in claim 33.

35. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 32, the battery module of claim 33, or the battery pack of claim 34.

Images