A positive electrode active material and a related electrode sheet, secondary battery, battery module, battery pack, and device

Abstract

The application provides a positive electrode active material, which comprises an A material and a B material, wherein the A material comprises at least one of the following single crystal materials or single crystal-like materials: Li x M y (PO4) z , M comprises one or more of Ni, Co, Mn, Fe, Mg, Al, V, Zn, Zr, F, 1≤x≤3, 1≤z≤3; the Dv50 of the A material is 0.8 μm to 4.2 μm; the B material comprises at least one of the following materials: (i) LiAO2, A comprises Ni, Co or Mn; or (ii) LiNi a Co b E 1‑a‑b O2, E comprises at least one of Mn and Al, 0.50≤a≤0.98, 0.001≤b≤0.3; wherein, the A material exists in a mixing ratio m of 50 wt% to 97 wt% based on the total weight of the positive electrode active material. The positive electrode active material has the advantages of cost economy, good safety, long cycle life, high energy density and the like.

Description

[0001] This application is a divisional application of the application with application number 202180071747.4, application date 2021-12-13, applicant Ningde Era New Energy Technology Co., Ltd., and the title of invention "A positive electrode active material and related electrode sheet, secondary battery, battery module, battery pack and device". TECHNICAL FIELD

[0002] The present application relates to the technical field of lithium batteries, in particular to a positive electrode active material, a positive electrode sheet, a secondary battery, a battery module, a battery pack and a power utilization device. BACKGROUND

[0003] Currently, lithium ion secondary batteries generally use ternary materials (such as nickel-cobalt-manganese lithium (NCM), nickel-cobalt-aluminum lithium (NCA)) or quaternary materials (such as nickel-cobalt-manganese-aluminum lithium (NCMA)) as positive electrode active materials. However, such materials, while having the advantage of energy density, also have the disadvantages of high price, short cycle life and poor safety.

[0004] Lithium iron phosphate (LFP) is gradually being widely used due to its low cost, good safety and other advantages. However, the energy density of such materials is not always satisfactory. As an improved lithium manganese iron phosphate (LMFP), while maintaining the advantages of good safety and long life of LFP, it has improved energy density, but the improvement is very limited.

[0005] Currently, there is a need in the art for a more ideal positive electrode active material, which should have a balanced performance, i.e., be cost-effective, safe, and have at least one of good cycle life and improved energy density. SUMMARY

[0006] The present application is made in view of the above-mentioned problems, and aims to provide a positive electrode active material with a balanced performance of at least one of cost-effectiveness, safety, improved cycle life, and improved energy density (especially specific capacity).

[0007] To achieve the above-mentioned purpose, the present application provides a positive electrode active material and related electrode sheet, secondary battery, battery module, battery pack and device.

[0008] The first aspect of the present application provides a positive electrode active material comprising an A material as described below and a B material as described below, wherein the A material is at least one selected from the following materials:

[0009] Li x M y (PO4) z

[0010] wherein M is selected from one or more of Ni, Co, Mn, Fe, Mg, Al, V, Zn, Zr, F, 1≤x≤3, 1≤z≤3;

[0011] the A material is a single crystal material or a single crystal-like material;

[0012] the Dv50 of the A material is 0.8 μm to 4.2 μm, optionally 0.8 μm to 3.2 μm, more optionally 0.9 μm to 2.3 μm, and even more optionally 1 μm to 1.5 μm;

[0013] the B material is selected from at least one of the following materials:

[0014] (i) LiAO2, A is Ni, Co or Mn; and

[0015] (ii) LiNi a Co b E 1-a-b O2, E is selected from at least one of Mn and Al, 0.50≤a≤0.98, 0.001≤b≤0.3;

[0016] The A material is present in a mixing ratio of 50% to 97% by weight, optionally 65% to 97% by weight, more optionally 70% to 95% by weight, and even more optionally 80% to 95% by weight, based on the total weight of the positive electrode active material.

[0017] Thus, the present application obtains a positive electrode active material by blending a relatively large amount of A material with a specific B material, which has good comprehensive performance: it retains the advantages of safety and cost-effectiveness of the A material, and improves the gram capacity compared with using the A material alone, while not significantly losing the cycle life advantage of the A material.

[0018] In any embodiment, the B material is present in a mixing ratio of 3% to 50% by weight, optionally 5% to 30% by weight, based on the total weight of the positive electrode active material. Blending the B material with the A material in such a mixing ratio can improve the gram capacity of the obtained positive electrode active material compared with using the A material alone, but does not significantly lose the advantage of the A material in cycle life.

[0019] In any embodiment, in the A material, v is the valence of M, and x+vy-3z=0.

[0020] In any embodiment, the A material of the positive electrode active material of the present application is selected from at least one of the following:

[0021] Lithium manganese iron phosphate or lithium iron phosphate, with the chemical formula LiMn d Fe 1-d PO4, 0 ≤ d ≤ 0.9, optionally 0.1 ≤ d ≤ 0.9, more optionally 0.1 ≤ d ≤ 0.8; and

[0022] Lithium vanadium phosphate, with the chemical formula Li3V2(PO4)3.

[0023] By further selecting the above-mentioned material as material A, the positive electrode active material of this application can be made more cost-effective, have a longer cycle life, and have excellent safety performance.

[0024] In any embodiment, the specific surface area (BET) of material A in the positive electrode active material of this application is 8 m². 2 / g to 26 m 2 / g, optionally 10 m 2 / g to 24 m 2 / g, or alternatively 10 m 2 / g to 23 m 2 / g. By controlling the BET of material A within the above range, the electrochemical reaction area can be effectively limited, thereby reducing and suppressing interfacial side reactions during cycling, lowering the cycle decay rate, and thus extending cycle life.

[0025] In any embodiment, in the positive electrode active material of this application, the (ii)LiNi of material B. a Co b E 1-a-b In O2, 0.5 ≤ a ≤ 0.98, optionally 0.50 ≤ a ≤ 0.90, more preferably 0.50 ≤ a ≤ 0.88, and even more preferably 0.55 ≤ a ≤ 0.88; and / or 0.005 ≤ b ≤ 0.30, optionally 0.05 ≤ b ≤ 0.30, and more preferably 0.05 ≤ b ≤ 0.20. By controlling a and b in the general formula of material B within the above ranges, it is helpful to further improve the specific capacity and cycle life of the positive electrode active material obtained after mixing material A and material B.

[0026] In any embodiment, in the positive electrode active material of this application, the (ii)LiNi of material B. a Co b E 1-a-b In O2, a and b have the following relationship: k = (a+b) / (1-ab), and 1.5≤k≤99, optionally 1.5≤k≤19. By limiting the coefficient k within the above range, specific capacity and / or cycle life can be further improved.

[0027] In any embodiment, in the positive electrode active material of this application, the (ii)LiNi of material B.a Co b E 1-a-b In O2, k and m have the following relationship: k×m≥1, optionally k×m≥1.1, and more preferably k×m≥1.6. When k×m is within the above range, the positive electrode active material has superior specific capacity and cycle life.

[0028] In any embodiment, the B material in the positive electrode active material of this application is LiNi. a Co b Mn 1-a-b O2, LiNi a Co b Al 1-a-b O2, LiNi a Co b Mn c Al 1-a-b-c O2 or combinations thereof, wherein a and b are as defined above, and 0.01 ≤ c ≤ 0.34. By selecting the above-mentioned material B, the specific capacity and / or cycle life of the positive electrode active material can be further improved.

[0029] In any embodiment, in the positive electrode active material of this application, the B material is a single crystal or near-single crystal material, and its particle Dv50 is 2 μm to 4.5 μm, optionally 2.1 μm to 4.4 μm, more preferably 3.5 μm to 4.4 μm; and / or BET is 0.40 μm. 2 / g to 1.20 m 2 / g, optionally 0.55 m 2 / g to 0.95 m 2 / g, or alternatively 0.55 m 2 / g to 0.89 m 2 / g. Using material B as specified above can further improve the specific capacity of the positive electrode active material.

[0030] In any embodiment, in the positive electrode active material of this application, the B material is a secondary particle, the Dv50 of which is 3.5 μm to 13 μm, optionally 3.5 μm to 12 μm; and / or the specific surface area is 0.31 m². 2 / g to 1.51 m 2 / g, optionally 0.54 m 2 / g to 1.51 m 2 / g. By selecting the aforementioned secondary particle form of material B, the diffusion path of lithium ions and the bulk diffusion resistance can be shortened, the polarization of the material can be reduced, and the capacity utilization of the positive electrode active material can be improved, thereby increasing the specific capacity of the positive electrode active material.

[0031] A second aspect of this application also provides a positive electrode sheet, which includes a current collector and an electrode material layer disposed on at least one surface of the current collector, the electrode material layer including the positive electrode active material of the first aspect of this application.

[0032] A third aspect of this application also provides a secondary battery, which includes the positive electrode active material of the first aspect of this application or the positive electrode sheet of the second aspect.

[0033] A fourth aspect of this application also provides a battery module that includes the secondary battery of the third aspect of this application.

[0034] The fifth aspect of this application also provides a battery pack that includes the battery module of the fourth aspect of this application.

[0035] The sixth aspect of this application also provides an electrical device comprising at least one selected from the secondary battery of the third aspect, the battery module of the fourth aspect, or the battery pack of the fifth aspect.

[0036] The positive electrode active material of this application has good overall performance: it is cost-effective, safe, and has improved energy density (especially specific capacity) and good cycle life. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0038] Figure 2 yes Figure 1 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0039] Figure 3 This is a schematic diagram of a battery module according to one embodiment of this application.

[0040] Figure 4 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0041] Figure 5 yes Figure 4 An exploded view of a battery pack according to one embodiment of this application is shown.

[0042] Figure 6 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0043] Explanation of reference numerals in the attached figures:

[0044] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0045] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the positive electrode active material, positive electrode sheet, secondary battery, battery module, battery pack, and electrical device of this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for the purpose of enabling those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0046] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0047] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0048] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0049] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0050] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0051] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0052] Currently, lithium-ion rechargeable batteries commonly use ternary materials (such as NCM and NCA) or quaternary materials (such as NCMA) as positive electrode active materials—these materials are favored due to their high energy density. However, while these materials offer advantages in energy density, they also have many significant drawbacks, such as high cost, short cycle life, and poor safety.

[0053] Against this backdrop, lithium iron phosphate (LFP) materials have gradually gained widespread application due to their advantages such as low cost, good safety, and long cycle life; however, a drawback is that the energy density of these materials cannot meet the demand. Lithium manganese iron phosphate (LMFP) materials, which are a technological improvement of LFP materials, have improved the energy density to some extent, but still cannot fully meet the requirements.

[0054] In view of the above, there is a need in the art for a cathode active material that is cost-effective, safe, and has a balance of at least one of high energy density and long cycle life.

[0055] Unbound by any particular theory, the inventors of this application have discovered that, in most cases, failing to obtain a balanced cathode active material by mixing other high-energy-density cathode active materials (e.g., ternary or quaternary materials) with LFP and / or LMFP materials to improve the latter's energy density does not yield a balanced cathode active material. Arbitrary mixing may not only fail to improve the specific capacity of LFP and / or LMFP materials, but may even severely compromise their cycle life advantage (or even make the cycle life unacceptably poor). The resulting material exhibits unbalanced performance and lacks practical application value.

[0056] In view of the above problems, the inventors of this application propose a positive electrode active material obtained by blending specific LFP and / or LMFP materials with specific ternary and / or quaternary materials. The positive electrode active material of this application exhibits good overall performance. That is, compared to individual LFP and / or LMFP materials, the positive electrode active material of this application has improved energy density (especially specific capacity) without significantly increasing cost or significantly sacrificing cycle life advantages. In some cases, the positive electrode active material of this application even improves both specific capacity and cycle life compared to individual LFP and / or LMFP materials.

[0057] Positive electrode active material

[0058] In one embodiment of this application, a positive electrode active material is provided, comprising: material A as described below and material B as described below, wherein...

[0059] Material A is selected from at least one of the following materials:

[0060] Li x M y (PO4) z

[0061] Where M is selected from one or more of Ni, Co, Mn, Fe, Mg, Al, V, Zn, Zr, and F, and 1≤x≤3, 1≤z≤3;

[0062] Material A is a single-crystal material or a single-crystal-like material;

[0063] The Dv50 of material A is 0.8 μm to 4.2 μm;

[0064] Material B is selected from at least one of the following materials:

[0065] (i) LiAO2, where A is Ni, Co, or Mn; or

[0066] (ii)LiNi a Co b E 1-a-bO2 and E are selected from at least one of Mn and Al, 0.50≤a≤0.98, 0.001≤b≤0.3;

[0067] Based on the total weight of the positive electrode active material, material A exists in a mixing ratio of 50% to 97% by weight, i.e., m.

[0068] Unbound by any particular theory, the inventors discovered that the positive electrode active material of this application, obtained by blending a specific material B into a relatively large amount (not less than 50% by weight of the total weight of the positive electrode active material), exhibits excellent comprehensive performance: compared to using material A alone, the positive electrode active material of this application possesses the advantages of material A, such as safety and cost-effectiveness, while also improving specific capacity without significantly sacrificing the cycle life advantage of material A. In particular, in some embodiments, the positive electrode active material of this application also exhibits a "synergistic effect" between material A and material B, resulting in a positive electrode active material that, compared to material A alone, simultaneously possesses improved specific capacity and extended cycle life.

[0069] By using single-crystal or near-single-crystal materials with a Dv50 of 0.8 μm to 4.2 μm as material A, the diffusion path of lithium ions can be shortened, thereby effectively improving the specific capacity and cycle life of the positive electrode active material of this application.

[0070] In some embodiments, optionally, the Dv50 of material A is 0.8 μm to 3.2 μm, more preferably 0.9 μm to 2.3 μm, and even more preferably 1 μm to 1.5 μm. By controlling the Dv50 value of material A within the above range, the specific capacity and / or cycle life of the positive electrode active material can be further improved.

[0071] In some embodiments, in the positive electrode active material of this application, based on the total weight of the positive electrode active material, the A material is present in a mixing ratio m, optionally from 65% to 97% by weight, more preferably from 70% to 95% by weight, and even more preferably from 80% to 95% by weight. By further selecting the mixing ratio m of the A material, the specific capacity and / or cycle life of the positive electrode active material of this application can be further improved.

[0072] As used herein, the terms “quasi-single-crystal particle,” “quasi-single-crystal particle,” “single-crystal particle,” “single-crystal material particle,” or similar expressions have essentially similar meanings, referring to individual particles (i.e., primary particles) and / or aggregated particles, said aggregated particles being formed by the aggregation of no more than 30 (particularly about 5 to 15) primary particles with an average particle size of not less than 0.8 μm (particularly in the range of 800 nm to 10000 nm).

[0073] As used in this paper, the term "average particle size" is defined as follows: The material is tested using a scanning electron microscope. The test sample and magnification are adjusted so that there are more than 100 primary particles in the field of view. The length of the particles is measured with a ruler. A total of 100-200 primary particles are measured. Then, 1 / 10 of the particles with the maximum particle size and 1 / 10 of the particles with the minimum particle size are removed. The average particle size is calculated by averaging the particle size data of the remaining 8 / 10 particles.

[0074] As used herein, the term "primary particle" refers to an unaggregated single particle, also known as a "primary particle" in the general sense of the art.

[0075] As used herein, the terms “secondary particles” and “polycrystalline material particles” generally have similar meanings, referring to particles formed by the agglomeration of more than 30 primary particles with an average particle size of no more than 0.8 μm (especially in the range of 50-800 nm).

[0076] As used herein, the term “Dv50” means that the particle size of 50% of the volume of a powder does not exceed the current value; that is, the median particle size; the unit is μm.

[0077] As used herein, the term “Dv99” means that the particle size of 99% of the volume of a powder does not exceed the current value, in μm.

[0078] As used herein, the term "specific surface area (BET)" refers to the total surface area per unit mass of material, measured in m³. 2 / g.

[0079] As used herein, the term "specific capacity" refers to the amount of electricity that can be released per gram of positive electrode active material, expressed in milliampere-hours per gram (mAh / g). In this application, the specific capacity value may be used as a reference indicator for measuring energy density.

[0080] In some embodiments, in material A, v is the valence of M, and x + vy - 3z = 0.

[0081] In some embodiments, material A is selected from at least one of the following:

[0082] Lithium manganese iron phosphate or lithium iron phosphate, with the chemical formula LiMn d Fe 1-d PO4, 0 ≤ d ≤ 0.9; and

[0083] Lithium vanadium phosphate, with the chemical formula Li3V2(PO4)3.

[0084] By further selecting the above-mentioned material as material A, the positive electrode active material of this application can be made more cost-effective, have a longer cycle life, and exhibit excellent safety performance. In some embodiments, the chemical formula LiMn is selected. d Fe 1-d The lithium iron phosphate material with PO4, wherein optionally 0.1≤d≤0.9, and more preferably 0.1≤d≤0.8, can be more conducive to simultaneously improving cycle life and specific capacity.

[0085] In some embodiments, the Dv99 of material A is <31 μm, optionally Dv99 ≤28 μm, and optionally Dv99 >4.2 μm; more preferably 10 μm ≤ Dv99 ≤28 μm. Controlling the Dv99 of material A within the above range can improve the performance of the positive electrode active material while ensuring the slurry processing performance of the material, making the coating interface of the slurry on the current collector more uniform, which helps to further improve the performance of the positive electrode and the battery.

[0086] In some embodiments, the BET of material A is 8 m. 2 / g to 26 m 2 / g, optionally 10 m 2 / g to 24m 2 / g, or alternatively 10 m 2 / g to 23 m 2 / g. By controlling the BET of material A within the above range, the electrochemical reaction area can be effectively limited, thereby reducing and suppressing interfacial side reactions during cycling, lowering the cycle decay rate, and extending cycle life.

[0087] In some embodiments, the surface of the particles of material A may also have a carbon coating layer of 0.5-5% by weight, optionally 1-2% by weight, based on the total weight of material A. This carbon coating layer allows for more uniform mixing of material A and material B, and after mixing, it helps optimize the conductive network of the material particles, thereby reducing electrode resistance and ensuring that the specific capacitance can be properly utilized.

[0088] In some embodiments, in the positive electrode active material of this application, material B is present in a mixing ratio of 3% to 50% by weight, based on the total weight of the positive electrode active material. Mixing material B with material A in such a mixing ratio yields a positive electrode active material with improved specific capacity compared to material A alone, without significantly sacrificing the cycle life advantage of material A.

[0089] In some embodiments, the B material is optionally present in a mixing ratio of 5% to 30% by weight, based on the total weight of the positive electrode active material. Further selecting the mixing ratio range of the B material can further improve the specific capacity and / or cycle life of the positive electrode active material.

[0090] In some implementations, for chemical formula (ii)LiNi a Co b E 1-a-b Material B of O2 has a specific gravity of 0.5 ≤ a ≤ 0.98, optionally 0.50 ≤ a ≤ 0.90, more preferably 0.50 ≤ a ≤ 0.88, and even more preferably 0.55 ≤ a ≤ 0.88; and / or 0.005 ≤ b ≤ 0.30, optionally 0.05 ≤ b ≤ 0.30, and more preferably 0.05 ≤ b ≤ 0.20. By controlling a and b in the general formula of material B within the above ranges, it is helpful to further improve the specific capacity and cycle life of the positive electrode active material obtained after mixing material A and material B.

[0091] In some embodiments, for the above chemical formula (ii)LiNi a Co b E 1-a-b In material B of O2, a and b have the following relationship: k = (a+b) / (1-ab), and 1.5≤k≤99, optionally 1.5≤k≤19. By limiting the coefficient k within the above range, specific capacity and / or cycle life can be further improved.

[0092] In some embodiments, the mixing ratio m of k and material A (based on the total weight of the positive electrode active material) has the following relationship: k×m≥1, optionally, k×m≥1.1, and more preferably k×m≥1.6. When k×m is within the above range, the positive electrode active material has more beneficial specific capacity and cycle life.

[0093] By controlling a, b, and k in the chemical formula of material B within the above-mentioned range, the specific capacity and / or electronic conductivity and ionic conductivity and / or material kinetics of the positive electrode active material of this application can be significantly improved, but the cycle life advantage of the material will not be significantly lost.

[0094] In some embodiments, the B material is LiNi. a Co b Mn 1-a-b O2, LiNi a Co b Al 1-a-b O2, LiNi a Co b Mn c Al 1-a-b-cO2 or combinations thereof, where a and b are as defined above, and 0.01 ≤ c ≤ 0.34. By selecting material B as described above, the specific capacity and / or cycle life of the positive electrode active material can be further improved.

[0095] In various embodiments of this application, the material B can be a single crystal or a near-single crystal material, or it can be secondary particles (or a polycrystalline material).

[0096] In some embodiments, the B material is a single crystal or near-single crystal material with a particle Dv50 of 2 μm to 4.5 μm, optionally 2.1 μm to 4.4 μm, and more preferably 3.5 μm to 4.4 μm.

[0097] In the case of single-crystal or near-single-crystal materials, in some embodiments, the BET of the B material is 0.40 m. 2 / g to 1.20 m 2 / g, optionally 0.55 m 2 / g to 0.95 m 2 / g, or alternatively 0.55 m 2 / g to 0.89 m 2 / g.

[0098] In the case of single-crystal or near-single-crystal materials, controlling the particle size and specific surface area of ​​material B within the aforementioned range can improve the specific capacity of the resulting cathode active material. Specifically, controlling the particle size of material B within this range helps to shorten the lithium-ion diffusion path and bulk diffusion resistance, reduce material polarization, and improve the capacity performance of the cathode active material of this application.

[0099] In the case of single-crystal or near-single-crystal materials, in some embodiments, the Dv99 of material B is ≤18 μm, optionally ≤16 μm, optionally >4.4 μm, and more preferably 10.5 μm ≤ Dv99 ≤ 15 μm. Controlling Dv99 within the above range can improve the slurry processing performance of the positive electrode active material of this application, and further improve the performance of the positive electrode sheet and the battery.

[0100] Alternatively, in some embodiments, the B material is a secondary particle (or a polycrystalline material) with a Dv50 of 3.5 μm to 13 μm, optionally 3.5 μm to 12 μm.

[0101] In the case of secondary particles, in some embodiments, the BET of the B material is 0.31 m. 2 / g to 1.51m 2 / g, optionally 0.54 m 2 / g to 1.51 m2 / g.

[0102] Generally, the primary particles that form the secondary particles by agglomeration have the average particle size range of primary particles conventional to such materials in the art, for example, 50-800 nm.

[0103] In the case of secondary particles, by limiting the particle size of the B material to the aforementioned range, the lithium-ion diffusion path and bulk diffusion resistance can be shortened, the polarization of the material can be reduced, and the capacity utilization of the positive electrode active material of this application can be improved. Furthermore, by controlling the specific surface area, interfacial side reactions can be reduced, thereby reducing battery life degradation caused by active lithium consumption.

[0104] In the case of secondary particles, in some embodiments, the Dv99 of the B material is 10 μm to 25 μm. Controlling the specific surface area enables the secondary particles of the B material to have good compactness, avoiding the deterioration of energy density caused by the overall low compaction of the mixed system due to factors such as partial core-shell structure and the compaction difference of hollow materials.

[0105] In summary, by further selecting material B and related parameters, the performance of the positive electrode active material of this application can be further improved, such as improving specific capacity while maintaining good cycle life.

[0106] In some embodiments, the positive electrode active material of this application is composed of one or more A materials and one or more B materials.

[0107] In some embodiments, the A material and the B material are mixed by conventional physical mixing methods (e.g., by stirring in a mixing tank) to obtain the positive electrode active material of this application.

[0108] Positive electrode sheet

[0109] In one embodiment of this application, a positive electrode is provided, comprising a current collector and an electrode material layer disposed on at least one surface of the current collector, the electrode material layer comprising the positive electrode active material of this application. The positive electrode of this application exhibits improved specific capacity and good cycle life, as well as lower resistance.

[0110] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode material layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0111] 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.).

[0112] In some embodiments, the positive electrode material layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0113] In some embodiments, the positive electrode material layer 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.

[0114] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0115] Secondary batteries, battery modules, battery packs and electrical devices

[0116] The secondary battery, battery module, battery pack, and power-consuming device of this application will be described below with appropriate reference to the accompanying drawings.

[0117] In one embodiment of this application, a secondary battery is provided, which includes the positive electrode active material or the positive electrode sheet of this application.

[0118] In some implementations, the secondary battery is a lithium-ion secondary battery.

[0119] 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.

[0120] [Negative electrode plate]

[0121] The negative electrode sheet includes a negative current collector and a negative electrode material layer disposed on at least one surface of the negative current collector, the negative electrode material layer including a negative electrode active material.

[0122] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode material layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0123] 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.).

[0124] 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.

[0125] In some embodiments, the negative electrode material layer may optionally include an adhesive. The adhesive 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).

[0126] In some embodiments, the negative electrode material layer 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.

[0127] In some embodiments, the negative electrode material layer may also optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0128] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto a negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0129] [Electrolytes]

[0130] 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.

[0131] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] [Isolation membrane]

[0136] 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.

[0137] 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.

[0138] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0139] 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.

[0140] 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.

[0141] 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.

[0142] 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.

[0143] In one embodiment of this application, a battery module is provided, which includes the secondary battery of this application.

[0144] 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.

[0145] Figure 3 This is battery module 4, used as an example. (See reference...) Figure 3In 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.

[0146] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0147] In one embodiment of this application, a battery pack is provided, which includes the battery module of this application.

[0148] 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.

[0149] 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.

[0150] 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.

[0151] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0152] 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.

[0153] 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.

[0154] Example

[0155] 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.

[0156] method:

[0157] 1. Preparation method of secondary battery

[0158] (1) Preparation of the positive electrode sheet:

[0159] Materials A and B from the following examples (numbered as numbers, e.g., Example 1) and comparative examples (numbered as "C + number", e.g., Comparative Example C1) are mixed in a stirring apparatus (such as a stirring tank), and the resulting mixture is used as the positive electrode active material of this application. The mixing ratio m of material A is a weight percentage based on the total weight of the positive electrode active material, m = M. A / (M A +M B +Mc……)×100%, where M A M B Mc, etc., are the masses of the various components used to mix and obtain the positive electrode active material, such as material A, material B, and (if any) material C.

[0160] The positive electrode active material, binder polyvinylidene fluoride (PVDF), and conductive carbon Super-P were added to the solvent N-methylpyrrolidone (NMP) to make the mass ratio of positive electrode active material, PVDF, and conductive carbon 90:5:5. The mixture was stirred in a drying room to prepare a uniform slurry with a viscosity of 3000 to 10000 mPa·s. Then, it was applied to aluminum foil at a concentration of 20 mg / cm³. 2 The above slurry is coated with a certain amount of load, and then dried and cold-pressed to form a positive electrode sheet.

[0161] (2) Preparation of negative electrode sheet:

[0162] Artificial graphite, used as the negative electrode active material, was added to deionized water at a mass ratio of 94:1.5:2:2.5 with sodium carboxymethyl cellulose (CMC), conductive carbon Super-P, and styrene-butadiene rubber (SBR). The mixture was stirred in a drying chamber to prepare a uniform slurry with a viscosity of 2000 to 12000 mPa·s. Then, the slurry was coated onto a current collector copper foil at a specific coating weight to form a coated electrode. The coated electrode was dried and cold-pressed to produce the negative electrode sheet.

[0163] The coating quality is calculated using the following formula:

[0164] 94% × negative electrode coating mass × graphite specific capacity = 1.15 × 90% × positive electrode coating mass × [(x1 × w1 + x2 × w2) / (w1 + w2)];

[0165] in,

[0166] The specific capacity of graphite is 350mAh / g.

[0167] x1 and x2 are the specific capacities of materials A and B, respectively, measured by the "Pin Electrode Capacity Test of Lithium Half-Battery Powder" section below.

[0168] w1 and w2 are the mixing ratios of material A and material B, respectively (weight percentages based on the total weight of the positive electrode active material obtained by mixing).

[0169] (3) Electrolyte:

[0170] A 1 mol / L solution was prepared by adding LiPF6 to a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a volume ratio of 1:1:1. Then, 5 wt.% fluoroethylene carbonate (FEC) was added to obtain the electrolyte. Here, the amount of FEC added is a weight percentage based on the total weight of the electrolyte.

[0171] (4) Separating membrane:

[0172] A porous film made of polyethylene (PE) is used as a separator.

[0173] (5) Preparation of secondary batteries:

[0174] In a drying room, secondary batteries are assembled into batteries for testing through processes such as electrode cutting, cleaning of tabs, stacking, welding, top sealing, liquid injection, pre-formation, degassing, formation, and molding.

[0175] 2. Powder coin cell test method for lithium half-cells

[0176] The test material (e.g., material A or material B) (in powder form) is added to the solvent N-methylpyrrolidone (NMP) along with the binder polyvinylidene fluoride (PVDF) and conductive carbon Super-P, resulting in a mass ratio of test material, PVDF, and conductive carbon of 90:5:5. A homogenized slurry with a viscosity of 3000 to 10000 mPa·s is prepared in a drying chamber using a homogenizer (Fluke R30A, Germany). This slurry is then applied to aluminum foil at a concentration of 20 mg / cm³. 2 The above slurry is coated with a certain amount of load, and then dried and cold-pressed to form a positive electrode sheet.

[0177] A PP separator (Celgard, 2400), a lithium metal sheet (Tianjin Lithium Energy, 15.6 mm diameter, 450 μm thickness, purity > 99.9%), and 100 μL of electrolyte (prepared by adding LiPF6 to a 1 mol / L solution of a mixture of ethylene carbonate (EC), diethyl carbonate (DEC), and dimethyl carbonate (DMC) in a 1:1:1 volume ratio, followed by the addition of 5 wt.% fluoroethylene carbonate (FEC)) were assembled into a coin-type lithium half-cell using CR 2032 coin cell modules (Kelode, 304 stainless steel) in a glove box (Brown, Ar atmosphere). After removing the half-cell from the glove box, it was allowed to stand at ambient temperature for 12 hours, and then the capacity was tested as described below:

[0178] The testing instrument used was a CT2001A Blue Electric (Blue Electric Blue River). The lithium half-cell prepared as described above was left to stand at a constant temperature of 25℃ for 5 minutes, and then discharged to 2.5V at 1 / 3C (C represents the charge / discharge rate, 1C represents the current intensity required to completely discharge the battery in 1 hour, and the charge / discharge rate of the battery = charge / discharge current / rated capacity; in this article, C can also be directly understood as the nominal capacity). After standing for another 5 minutes, it was charged to 4.35V or 4.3V at a constant current and constant voltage of 1 / 3C (wherein, when material B is LiNi...). a Co b E 1-a-b For single-crystal or near-single-crystal O2 materials with a≤0.7, the upper limit of charging voltage is 4.35V; while for material B with the chemical formula LiNi a Co b E 1-a-b When O2 is a single crystal or near-single crystal material with a > 0.7 or is a secondary particle (polycrystalline material), the upper limit of the charging voltage is 4.30V. Then, it is charged at a constant voltage of 4.35V or 4.3V until the current is ≤ 0.05 mA, and left to stand for 5 minutes. The charging capacity at this time is recorded as C0. Then, it is discharged to 2.5V at 1 / 3C0. The discharge capacity at this time is the initial discharge capacity, recorded as D0.

[0179] The initial weight capacity of each material sample is calculated using the following formula:

[0180] The initial specific capacity of the material being tested = D0 / the mass of the positive electrode active material corresponding to the cell being tested.

[0181] The initial specific capacity of 5 parallel samples was tested and calculated. The highest and lowest values ​​were removed, and the average of the remaining 3 data was taken to obtain the initial specific capacity of the material to be tested.

[0182] In the above formula, "the mass of the positive electrode active material corresponding to the tested cell" is determined according to the "mass test of positive electrode active material" in the following text.

[0183] 3. Quality testing method for active materials in positive electrode sheets

[0184] The positive electrode sheet to be tested was punched into a circular piece with a diameter of 14 mm as the test sample (its area was calculated to be approximately 154 mm²). 2 Meanwhile, the current collector used to prepare the electrode to be tested was also punched into a circular piece with a diameter of 14 mm as a blank sample.

[0185] The total weight of 20 blank samples was obtained by weighing them. This total weight was then divided by the corresponding number of samples to obtain the average mass m0 of the blank samples (i.e., the current collector of the electrode), in grams (g). The 20 samples to be tested were then weighed separately and recorded as m1, m2, m3…m 20 The unit is g.

[0186] The positive electrode of the laminated battery cell prepared using such electrode sheets has a length of 'a' and a width of 'b' (in mm). The mass of the active material in the positive electrode of the laminated battery cell is calculated as follows:

[0187] Mass of active substance = 90% × {[(m1 + m2 + m3 ... + m 20 ) / 20]-m0}×(a×b) / 154.

[0188] 4. Initial specific capacity test method for positive electrode active materials in secondary batteries

[0189] The testing instrument used was a CT 4000-5V6A Xinwei tester (Xinwei Electronics Co., Ltd.). The secondary batteries prepared as described above were left to stand at a constant temperature of 25℃ for 5 minutes, then discharged to 2.5V at 1 / 3C (C represents the charge / discharge rate, 1C represents the current intensity required to completely discharge the battery in 1 hour; the charge / discharge rate of the battery = charge / discharge current / rated capacity; in this article, C can also be directly understood as the nominal capacity). After standing for another 5 minutes, they were charged to 4.3V or 4.25V at a constant current and constant voltage of 1 / 3C (wherein, when material B is LiNi...). a Co b E1-a-b For single-crystal or near-single-crystal O2 materials with a≤0.7, the upper limit of charging voltage is 4.3V; while for material B with the chemical formula LiNi a Co b E 1-a-b When O2 is a single crystal or near-single crystal material with a > 0.7, or is a secondary particle (polycrystalline material), the upper limit of the charging voltage is 4.25V. Then, it is charged at a constant voltage of 4.3V or 4.25V until the current is ≤ 0.05mA, and left to stand for 5 minutes. The charging capacity at this time is recorded as C0'. Then, it is discharged to 2.5V at 1 / 3C0'. The discharge capacity at this time is the initial discharge capacity, recorded as D0'.

[0190] The initial specific capacity of the positive electrode active material was calculated for each secondary battery sample according to the following formula:

[0191] Initial specific capacity of positive electrode active material = D0' / mass of positive electrode active material;

[0192] In the formula, "the mass of the positive electrode active material" is determined according to method 3 above.

[0193] The initial specific capacity of 5 parallel samples was tested and calculated. The highest and lowest values ​​were removed, and the average of the remaining 3 data was taken to obtain the initial specific capacity of the secondary battery to be tested.

[0194] 5. Test method for cycle performance of secondary batteries at 25℃

[0195] The testing instrument used was a CT 4000-5V6A Xinwei tester (Xinwei Electronics Co., Ltd.). Each secondary battery prepared as described above was tested at a constant temperature of 25°C under test voltages ranging from 2.5 to 4.3V or 2.5 to 4.25V (wherein, in the case of LiNi material B)... a Co b E 1-a-b In O2, when a > 0.7 or the material is secondary particles (polycrystalline), the test voltage is 2.5 to 4.25V; while when a ≤ 0.7, and the material is monocrystalline or near-monocrystalline, the test voltage is 2.5 to 4.3V. Charge to 4.3V or 4.25V using 0.5C0' (C0' is measured in the "Initial Specific Capacity Test Method for Secondary Batteries" above), then charge at a constant voltage of 4.3V or 4.25V until the current ≤ 0.05mA, let stand for 5 minutes, and then discharge to 2.5V using 0.5C0'. This constitutes one cycle, and the discharge capacity is recorded as D1. Repeat the above operation for n cycles, and the discharge capacity is recorded as D. n (n=1,2,3……). Calculate the cell's state of health (SOH) = D n / D3×100%. Record the number of cycles of the tested secondary battery when the cell capacity decays to 70% SOH, as an indicator of cycle capability.

[0196] Five parallel samples were tested. The highest and lowest cycle counts were removed, and the average of the remaining three samples was taken to obtain the final cycle count of the tested secondary battery when the cell capacity decayed to 70% SOH.

[0197] In this application, based on a test accuracy of ±5, the measured number of cycles is processed as integers of 5 and 10. Specifically, the data processing method is as follows: divide the actual measured number of cycles by 5 to obtain the quotient and (if any) remainder. When the remainder is ≥3, the recorded number of cycles is (quotient × 5 + 5); when the remainder is <3, the recorded number of cycles is (quotient × 5).

[0198] 6. Electrode Resistance Testing Method

[0199] The testing instrument was a GDW3-KDY-2 two-probe film resistance tester (Beijing Zhonghui Tiancheng Technology). The positive electrode sheet prepared as described in method 1 (1) above was used to make a 4cm × 25cm sample. The sample should have a good appearance (i.e., the interface of the electrode sample should be uniform, without obvious color difference, metal leakage, decarburization, powder shedding, scratches, etc.). The sample was vacuum dried at 85℃ for more than 4 hours and then tested using the aforementioned resistance tester. The test pressure was 0.2-0.4 MPa, and 20 parallel samples were tested. The sample data acquisition time was t=15s (because the resistance meter data needs about 15s to stabilize). All the measured resistance data were plotted in a box plot, and the median value in the box plot was taken to obtain the electrode resistance.

[0200] 7. Powder Laser Particle Size Testing Method

[0201] Referring to the national standard GB / T19077-2016, a Mastersizer 3000 laser diffractometer (Malvin Panaco) was used for particle size analysis. Deionized water was used as the solvent, and the positive electrode active material to be tested was ultrasonically treated for 5 min before the test.

[0202] This test allows us to obtain the particle size distribution of the material, typically Dv10, Dv50, Dv90, and Dv99, along with their distribution curves. In this application, this method is primarily used to measure the particle size distribution of single-crystal or near-single-crystal particles and secondary particles.

[0203] 8. Specific Surface Area (BET) Test Method

[0204] Referring to GB / T 19587-2004, the specific surface area of ​​various powdered materials involved in this application was tested using a TRISTAR II 3020 specific surface area and porosity analyzer (McMed Instruments, Inc., USA). Before testing, the powder was dried in a vacuum oven at 200°C for ≥2 hours, and the required amount of powder was >20g.

[0205] 9. Test method for primary particle size

[0206] Various powdered materials involved in this application were tested using a Sigma 300 scanning electron microscope (Zeiss). The test sample and magnification were adjusted to include more than 100 primary particles in the field of view. The length of each particle was measured using a ruler. A total of 100-200 primary particles were measured. Then, 1 / 10 of the particles with the largest and 1 / 10 of the particles with the smallest diameters were removed. The average particle size was calculated using the particle size data of the remaining 8 / 10 particles. This method was used to confirm the particle size range of the primary particles that constitute the secondary particles.

[0207] 10. Method for testing powder compaction density

[0208] According to GB / T 24533-2009, the powder compaction density tester (model: YT-101F) was used, the powder sample amount was 1.0g, and 3 to 5 parallel samples were tested.

[0209] The formula for calculating compacted density is as follows:

[0210] pC = m / V = m / (S×H)

[0211] In the formula:

[0212] pC --- compacted density of powder, expressed in g / cm³;

[0213] m --- Sample mass, in grams;

[0214] S---The bottom area of ​​the mold. In this paper, based on the test mold used with the equipment, its value is 1.327 cm². 2 ;

[0215] H---Compacted thickness, in cm.

[0216] Examples 1-7 and Comparative Examples C1-3

[0217] In Examples 1-7 and Comparative Examples C1-3, material A was LiMn. 0.6 Fe 0.4 PO4 (LMFP material), a single-crystal material, with a Dv50 of 1.1 μm, a Dv99 of 25 μm, and a BET of 21 μm. 2 / g, with a specific capacity of 140mAh / g; B materials are all LiNi 0.55 Co 0.12 Mn 0.33 O2 (NCM material), a near-single-crystal (or quasi-single-crystal) material, with a Dv50 of 4.2 μm, a Dv99 of 10.5 μm, and a BET of 0.55 μm. 2 / g, with a capacity of 170 mAh / g.

[0218] Table 1 below shows the specific capacity and cycle life (25°C) of the positive electrode active materials obtained by mixing materials A and B in different mixing ratios. The mixing ratios in Table 1 are weight percentages based on the total weight of materials A and B.

[0219] Table 1

[0220]

[0221] As shown in Table 1, compared to using material A alone (Comparative Example C1), the positive electrode active materials of Examples 1-7 obtained by mixing material A with material B at a ratio of not less than 50% by weight, particularly 50% by weight to 97% by weight, exhibit improved specific capacity and / or cycle performance. In particular, compared to using material A alone, the positive electrode active materials obtained by mixing material A with material B at a mixing ratio m of optionally 65% ​​by weight to 97% by weight, more preferably 70% by weight to 97% by weight, and even more preferably 80% by weight to 97% by weight, exhibit improved specific capacity and / or higher cycle performance.

[0222] Examples 8-16

[0223] Table 2 below shows lithium iron phosphate or different lithium manganese iron phosphate materials (chemical formula LiMn) as material A. d Fe 1-d The performance data of the positive electrode active material prepared by mixing PO4 and NCM as material B are described. In the following embodiments, material B (chemical formula LiNi) is used. 0.55 Co 0.12 Mn 0.33 All O2 particles have the following parameters: specific capacity of 170 mAh / g, Dv50 of 4.2μm, Dv99 of 10.5μm, and BET of 0.55 m. 2 / g. In the following embodiments, based on the total weight of the positive electrode active materials, the mixing ratio m of material A is 80% by weight and the mixing ratio of material B is 20% by weight.

[0224] Table 2

[0225]

[0226] As can be seen from Table 2, when the chemical formula of material A is LiMn d Fe 1-d When the value of d in PO4 is in the range of 0 to 0.9, the positive electrode active material obtained after mixing with material B has improved specific capacity and good cycle life. When material A is lithium manganese iron phosphate, when the value of d in the above chemical formula is in the range of 0.1-0.9, optionally in the range of 0.1-0.8, the positive electrode active material of this application has both improved specific capacity and cycle life, and its specific capacity and cycle life values ​​are relatively high.

[0227] Examples 17-31 and Comparative Examples C5-C6

[0228] Material A is selected from the following materials or mixtures thereof: LiMn 0.6 Fe 0.4 PO4 (represented as LMFP in Table 3), LiFePO4 (represented as LFP in Table 3), and Li3V2(PO4)3 (represented as LVP in Table 3); and, in Table 3 below, when material A is a mixture of the above materials, it is represented as, for example, LFP+LMFP (i.e., LiMn 0.6 Fe 0.4 (A mixture of PO4 and LiFePO4).

[0229] In Example 24, material A is an LFP material as described above (specific capacity of 145 mAh / g, Dv50 of 1 μm, Dv99 of 10 μm, and BET of 23 m). 2 / g) and LMFP materials (specific capacity of 140 mAh / g, Dv50 of 1.1 μm, Dv99 of 25 μm, and BET of 21 m) 2 The mixture obtained by mixing (g) at a weight ratio of 1:1.

[0230] In Example 25, material A is an LFP material as described above (specific capacity of 145 mAh / g, Dv50 of 1 μm, Dv99 of 10 μm, and BET of 23 m). 2 / g) and LMFP materials (specific capacity of 140 mAh / g, Dv50 of 1.1 μm, Dv99 of 25 μm, and BET of 21 m) 2 The mixture obtained by mixing (g) at a weight ratio of 2:8.

[0231] Material B is selected from the following single crystal or near-single crystal materials or mixtures thereof: LiNi 0.55 Co 0.12 Mn 0.33 O2 (represented as NCM in Table 3), LiNi 0.55Co 0.12 Mn 0.18 Al 0.15 O2 (represented as NCMA-1 in Table 3), LiNi 0.55 Co 0.12 Mn 0.31 Al 0.02 O2 (represented as NCMA-2 in Table 3), LiNi 0.55 Co 0.12 Mn 0.03 Al 0.3 O2 (represented as NCMA-3 in Table 3), LiNi 0.55 Co 0.15 Mn 0.15 Al 0.15 A mixture of O2 (represented as NCMA-4 in Table 3). In the following examples, material A is blended with material B at a blending ratio m of 80% by weight, which is based on the total weight of the positive electrode active material.

[0232] In Example 26, material B is an NCM material as described above (specific capacity of 170 mAh / g, Dv50 of 4.2 μm, Dv99 of 10.5 μm, and BET of 0.55 μm). 2 / g) and NCMA-4 material (specific capacity 172 mAh / g, Dv50 3.9 μm, Dv99 11.0 μm, and BET 0.65 m) 2 The mixture obtained by mixing (g) at a weight ratio of 1:1.

[0233] Table 3 below shows the specific capacity and cycle life (25°C) of cathode materials obtained by mixing materials A and B with different Dv50 and / or Dv99 and / or BET. All mixing ratios are based on weight percentages of the total weight of the cathode active materials.

[0234]

[0235] As shown in Table 2, when the Dv50 of material A is in the range of 0.8 μm to 4.2 μm, compared with using material A alone, the cathode active material of this application can achieve both good specific capacity and cycle life, that is, it can improve specific capacity without significantly sacrificing cycle life. However, when it exceeds this range, the overall performance of the obtained cathode active material is poor (i.e., the performance is unbalanced) (for example, when the Dv50 is 0.7 μm, although the specific capacity is improved, the cycle life drops significantly to an unacceptable level), making such a material unusable in practical applications. In particular, when the Dv50 of material A is in the range of 0.9 μm to 2.3 μm, and optionally in the range of 1 μm to 1.5 μm, the cathode active material of this application has improved specific capacity and longer cycle life.

[0236] Examples 32-54 and Comparative Examples C7-C11

[0237] In Examples 32-54 and Comparative Examples C7-C11 below, material A is LiMn. 0.6 Fe 0.4 PO4 (denoted as LMFP in Table 4), a single-crystal material, has a Dv50 of 1.1 μm, a Dv99 of 25 μm, and a BET of 21 μm. 2 / g, with a specific capacity of 140 mAh / g and a cycle life of 3570 cycles. In the various examples and comparative examples in Table 4, the mixing ratio m of material A is 80% by weight, based on the total weight of the positive electrode active material.

[0238] Material B is LiNi a Co b Mn 1-a-b O2, in which the single-crystal material particles have a Dv50 of 2.7 - 5.6 μm, a Dv99 of 5.4 - 34.5 μm, and a BET of 0.45 - 1.05 μm. 2 / g; Polycrystalline material particles (i.e., secondary particles) Dv50 is 9.2-12.5μm, Dv99 is 20-30.5μm, and BET is 0.32-0.54 μm. 2 / g. The primary particle size of the agglomerated secondary particles is 50-800 nm. The mixing ratio of material B is 20% by weight, based on the total weight of the positive electrode active material.

[0239] Table 4 below shows the specific capacity and cycle life (25°C) of cathode materials obtained by mixing material A with material B having different a and b values, as well as different k×m values.

[0240]

[0241]

[0242]

[0243]

[0244] As shown in Table 6 above, when material B is a single crystal material, its crystal grain Dv50 is 2-4.5 μm, optionally 2.1-4.5 μm, and / or Dv99 is 10.5-21 μm, and / or BET is 0.40-1.20 μm. 2 / g, optionally 0.41-1.19m 2 At a density of / g, the positive electrode active material of this application exhibits improved specific capacity and good cycle life compared to using material A alone (i.e., without significantly sacrificing the cycle life advantage of material A). Optionally, with a Dv50 of 2.1-4.4 μm and / or a BET of 0.55-0.95 μm... 2 At a density of 1 g / g, the positive electrode active material of this application exhibits improved specific capacity and higher cycle life compared to using material A alone. More preferably, with a Dv50 of 3.5-4.4 μm and / or a BET of 0.55-0.89 μm... 2 At / g, the positive electrode active material of this application has both improved specific capacity and cycle life compared to using material A alone.

[0245] When material B is a polycrystalline material (i.e., secondary particles, the average particle size of the primary particles constituting the secondary particles is in the range of 50-800 nm as determined by scanning electron microscopy), when Dv50 is 3.5-13 μm, and / or Dv99 is 10-25 μm, and / or BET is 0.31-1.51 μm... 2 At a density of 1 / g, the positive electrode active material of this application exhibits improved specific capacity and longer cycle life compared to using material A alone. Optionally, when Dv50 is 3.5-12 μm and / or BET is 0.54-1.51 μm... 2 At / g, the positive electrode active material of this application has improved specific capacity and cycle life compared to using material A alone.

[0246] 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, comprising material A and material B, wherein... Material A is selected from at least one of the following materials: Li x M y (PO4) z in, M is selected from one or more of Ni, Co, Mn, Fe, Mg, Al, V, Zn, Zr, and F, where 1 ≤ x ≤ 3 and 1 ≤ z ≤ 3; v is the valence of M, and x + vy - 3z = 0; Material A is a single-crystal material or a single-crystal-like material; The Dv50 of material A is 0.9 μm to 4.2 μm; Material B is selected from at least one of the following materials: (i) LiAO2, where A is Ni, Co, or Mn; and (ii)LiNi a Co b E 1-a-b O2 and E are selected from at least one of Mn and Al, 0.50≤a≤0.98, 0.001≤b≤0.3; Based on the total weight of the positive electrode active material, material A exists in a mixing ratio m of 50% to 97% by weight.

2. The positive electrode active material according to claim 1, wherein, The Dv50 of material A is 0.9 μm to 3.2 μm.

3. The positive electrode active material according to claim 1, wherein, The Dv50 of material A is 0.9 μm to 1.5 μm.

4. The positive electrode active material according to claim 1, wherein, Based on the total weight of the positive electrode active material, material A exists in a mixing ratio m of 65% to 97% by weight.

5. The positive electrode active material according to claim 1, wherein, Based on the total weight of the positive electrode active material, material A exists in a mixing ratio m of 70% to 95% by weight.

6. The positive electrode active material according to claim 1, wherein, Based on the total weight of the positive electrode active material, material A exists in a mixing ratio m of 80% to 95% by weight.

7. The positive electrode active material according to claim 1, wherein, Based on the total weight of the positive electrode active material, the B material exists in a mixing ratio of 3% to 50% by weight.

8. The positive electrode active material according to claim 1, wherein, Based on the total weight of the positive electrode active material, the B material exists in a mixing ratio of 5% to 30% by weight.

9. The positive electrode active material according to any one of claims 1 to 8, wherein the material A is selected from at least one of the following: Lithium manganese iron phosphate or lithium iron phosphate, with the chemical formula LiMn d Fe 1-d PO4, 0 ≤ d ≤ 0.9; and Lithium vanadium phosphate, with the chemical formula Li3V2(PO4)3.

10. The positive electrode active material according to claim 9, wherein 0.1 ≤ d ≤ 0.

9.

11. The positive electrode active material according to claim 9, wherein 0.1 ≤ d ≤ 0.

8.

12. The positive electrode active material according to any one of claims 1 to 11, wherein the specific surface area of ​​material A is 8 m². 2 / g to 26 m 2 / g.

13. The positive electrode active material according to claim 12, wherein, The specific surface area of ​​material A is 10 m². 2 / g to 24m 2 / g.

14. The positive electrode active material according to claim 12, wherein, The specific surface area of ​​material A is 10 m². 2 / g to 23m 2 / g.

15. The positive electrode active material according to any one of claims 1 to 14, wherein the (ii)LiNi of the B material a Co b E 1-a-b In O2, 0.5 ≤ a ≤ 0.98; and / or 0.005 ≤ b ≤ 0.

30.

16. The positive electrode active material according to claim 15, wherein, 0.50≤a≤0.90。 17. The positive electrode active material according to claim 15, wherein, 0.50≤a≤0.88。 18. The positive electrode active material according to claim 15, wherein, 0.55≤a≤0.88。 19. The positive electrode active material according to claim 15, wherein, 0.05≤b≤0.30。 20. The positive electrode active material according to claim 15, wherein, 0.05≤b≤0.20。 21. The positive electrode active material according to any one of claims 1 to 20, wherein the (ii)LiNi of the B material a Co b E 1-a-b In O2, a and b have the following relationship: k = (a+b) / (1-ab), and 1.5≤k≤99.

22. The positive electrode active material according to claim 21, wherein, 1.5≤k≤19。 23. The positive electrode active material according to claim 21, wherein k and m have the following relationship: k*m≥1.

24. The positive electrode active material according to claim 23, wherein, k*m≥1.

1.

25. The positive electrode active material according to claim 23, wherein, k*m≥1.

6.

26. The positive electrode active material according to any one of claims 1 to 25, wherein the (ii)LiNi of the B material a Co b E 1-a-b O2 is LiNi a Co b Mn 1-a-b O2, LiNi a Co b Al 1-a-b O2, LiNi a Co b Mn c Al 1-a-b-c O2 or combinations thereof, 0.01≤c≤0.

34.

27. The positive electrode active material according to any one of claims 1 to 26, wherein the B material is a single crystal or near-single crystal material, the particle Dv50 being 2 μm to 4.5 μm; and / or the specific surface area being 0.40 m². 2 / g to 1.20 m 2 / g.

28. The positive electrode active material according to claim 27, wherein, The particle Dv50 ranges from 2.1 μm to 4.4 μm.

29. The positive electrode active material according to claim 27, wherein, The particle Dv50 ranges from 3.5 μm to 4.4 μm.

30. The positive electrode active material according to claim 27, wherein, Specific surface area is 0.55 m² 2 / g to 0.95 m 2 / g.

31. The positive electrode active material according to claim 27, wherein, Specific surface area is 0.55 m² 2 / g to 0.89 m 2 / g.

32. The positive electrode active material according to any one of claims 1 to 31, wherein the B material is a secondary particle, the secondary particle having a Dv50 of 3.5 μm to 13 μm; and / or a specific surface area of ​​0.31 m². 2 / g to 1.51 m 2 / g.

33. The positive electrode active material according to claim 32, wherein, The secondary particles have a Dv50 of 3.5 μm to 12 μm.

34. The positive electrode active material according to claim 32, wherein, The specific surface area of ​​the secondary particles is 0.54 m². 2 / g to 1.51 m 2 / g.

35. A positive electrode sheet, comprising a current collector and an electrode material layer disposed on at least one surface of the current collector, the electrode material layer comprising the positive electrode active material according to any one of claims 1 to 34.

36. A secondary battery comprising the positive electrode active material according to any one of claims 1 to 34 or the positive electrode sheet according to claim 35.

37. A battery module comprising the secondary battery of claim 36.

38. A battery pack comprising the battery module of claim 37.

39. An electrical device comprising at least one selected from the secondary battery of claim 36, the battery module of claim 37, or the battery pack of claim 38.

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