Positive electrode active material, method for preparing the same, positive electrode sheet, secondary battery, and electric device

Abstract

The application provides a positive electrode active material, a preparation method thereof, a positive electrode sheet, a secondary battery and an electric device. The positive electrode active material has the general formula: Li a Ni x M1 y Mn z M2 1‑x‑y‑z O2, wherein M1 and M2 each independently comprises one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0 The positive electrode active material exists in the form of secondary particles formed by aggregation of primary particles, the secondary particles comprise secondary pores formed by spaces between the primary particles, and the inner diameter of the secondary pores is 0.1-2 μm.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of secondary batteries, in particular to a positive electrode active material, a preparation method thereof, a positive electrode sheet, a secondary battery and an electric device. BACKGROUND

[0002] In recent years, secondary 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.

[0003] The performance of the positive electrode active material directly affects the performance of the secondary battery. At present, the positive electrode active material has many defects and cannot meet the application needs of the new generation of electrochemical systems. SUMMARY

[0004] The present application is carried out in view of the above-mentioned problems, and aims at a positive electrode active material, which has secondary particles including secondary pores formed by the space between primary particles, and the inner diameter of the secondary pores is 0.1 μm-2 μm, which is beneficial to improve the energy density and cycle performance of the battery.

[0005] In a first aspect of the present application, a positive electrode active material is provided, which has the following general formula:

[0006] Li a Ni x M1 y Mn z M2 1-x-y-z O2,

[0007] wherein M1, M2 each independently includes one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, 0≤z≤0.2.

[0008] The positive electrode active material exists in the form of secondary particles formed by the aggregation of primary particles, and the secondary particles include secondary pores formed by the space between the primary particles, and the inner diameter of the secondary pores is 0.1 μm-2 μm.

[0009] In one aspect, the secondary particles include secondary pores formed by spaces between the primary particles, so that the positive electrode active material has three-dimensional pores, shortens the solid-phase mass transfer path of lithium ions, and improves the power performance of the battery. In another aspect, due to the presence of the secondary pores, more 010 crystal planes can be exposed, thereby generating more active sites for reaction, improving the specific capacity and energy density of the material. In addition, the presence of the secondary pores can also buffer the volume change of the positive electrode active material during charging and discharging, thereby stabilizing the structure and improving the cycle performance. At the same time, controlling the inner diameter of the secondary pores to be 0.1 μm to 2 μm can greatly improve the energy density and cycle performance of the battery, and comprehensively improve the performance of the battery.

[0010] In any embodiment, the ratio of the closest distance between the secondary pores and the surface of the secondary particles to the Dv50 of the secondary particles is 1 / 5 to 3 / 5, and can be 3 / 10 to 1 / 2.

[0011] Controlling the ratio of the closest distance between the secondary pores and the surface of the secondary particles to the Dv50 of the secondary particles in a suitable range can improve the power performance of the battery, and reduce the influence of the presence of the pores on the structure of the positive electrode active material.

[0012] In any embodiment, at least part of the primary particles further include primary pores, and the inner diameter of the primary pores is 0.05 μm to 0.6 μm, and can be 0.08 μm to 0.2 μm.

[0013] The presence of the primary pores is beneficial to further shorten the solid-phase mass transfer path of lithium ions, and improve the power performance of the battery. Controlling the inner diameter of the primary pores in a suitable range can take into account the power performance and energy density of the battery.

[0014] In any embodiment, 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, 0≤z≤0.1, and can be 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.05.

[0015] In any embodiment, the inner diameter of the secondary pores is 0.2 μm to 1 μm.

[0016] Further controlling the inner diameter of the secondary pores to be 0.2 μm to 1 μm is beneficial to further improve the energy density and cycle performance of the battery.

[0017] In any embodiment, the porosity of the positive electrode active material is 0.1% to 12%, and can be 0.1% to 10%.

[0018] Controlling the porosity of the positive electrode active material within a suitable range can provide sufficient space to expose more 010 crystal planes to generate more reactive sites, thereby improving the energy density of the battery; and has sufficient mechanical strength to reduce the risk of the positive electrode active material being crushed during the preparation process. Both the electrical performance and mechanical strength of the battery are considered.

[0019] In any embodiment, the average particle size D of the primary particles is 100 nm to 800 nm, and optionally 100 nm to 500 nm.

[0020] Controlling the average particle size D of the primary particles within a suitable range can make the battery have high energy density, excellent power performance and cycle performance, and comprehensively improve the electrochemical performance of the battery.

[0021] In any embodiment, the Dv50 of the secondary particles is 3 μm to 12 μm, and optionally 3 μm to 11 μm.

[0022] Controlling the Dv50 of the secondary particles within a suitable range can make the battery have high energy density, excellent power performance and cycle performance, and comprehensively improve the electrochemical performance of the battery.

[0023] In any embodiment, the SPAN value of the secondary particles is 0.8 to 1.5, and optionally 0.8 to 1.3.

[0024] Controlling the SPAN value of the secondary particles within a suitable range can make the battery have high energy density, excellent power performance and cycle performance, and comprehensively improve the electrochemical performance of the battery.

[0025] In any embodiment, the area of the (010) crystal plane in the XRD diffraction spectrum of the positive electrode active material is 200 μm 2 to 300 μm 2 , and optionally 250 μm 2 to 280 μm 2 .

[0026] Controlling the area of the (010) crystal plane in the XRD diffraction spectrum of the positive electrode active material within a suitable range can provide sufficient reactive sites, improve the energy density of the battery, and improve the electrochemical performance of the battery.

[0027] The second aspect of the present application provides a preparation method of a positive electrode active material, comprising:

[0028] mixing a first raw material containing a nickel source and a manganese source with a complexing agent and a precipitating agent to perform a co-precipitation reaction to prepare a precursor, and optionally, the first raw material further comprises a M1 source;

[0029] mixing the precursor with a lithium source to perform calcination to prepare the positive electrode active material; or

[0030] The precursor is mixed with a lithium source and calcined, and then mixed with an M2 source and calcined to prepare the positive electrode active material;

[0031] The positive electrode active material has the general formula:

[0032] Li a Ni x M1 y Mn z M2 1-x-y-z O2,

[0033] wherein M1 and M2 each independently include one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, and 0≤z≤0.2; the positive electrode active material exists in the form of secondary particles formed by aggregation of primary particles, and the secondary particles include secondary pores formed by spaces between the primary particles, and the secondary pores have an inner diameter of 0.1 μm to 2 μm.

[0034] The prepared precursor has multiple pores distributed in a ring shape by a coprecipitation reaction and control of the amount of manganese source, so that the positive electrode active material including secondary pores distributed between primary particles is obtained. The preparation method of the positive electrode active material is simple and has low manufacturing cost. The secondary pores in the prepared positive electrode active material have an inner diameter of 0.1 μm to 2 μm, which is beneficial to lithium ion intercalation and deintercalation, and the secondary pores can buffer the volume change of the positive electrode active material during charging and discharging, thereby stabilizing the structure and improving the cycle performance.

[0035] In any embodiment, 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, and 0≤z≤0.1, or 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, and 0≤z≤0.05.

[0036] In any embodiment, the precursor is a precursor secondary particle formed by aggregation of precursor primary particles.

[0037] The average particle size D' of the precursor primary particles is 150 nm to 500 nm, or 200 nm to 300 nm.

[0038] The median particle size Dv50' of the precursor secondary particles is 3 μm to 12 μm, or 6 μm to 8 μm.

[0039] The average particle size D' of the precursor primary particles and the median particle size Dv50' of the precursor secondary particles are controlled within a suitable range, thereby controlling the size of the primary particles and the secondary particles of the prepared positive electrode active material within a suitable range, so that the battery has high energy density and excellent cycle performance.

[0040] In any embodiment, the specific surface area of the precursor is 2m 2 / g to 40m 2 / g, and optionally 25m 2 / g to 35m 2 / g.

[0041] The specific surface area of the precursor is controlled within a suitable range, thereby controlling the positive electrode active material to have a suitable porosity, so that the battery has high energy density, excellent discharge performance and cycle performance.

[0042] In any embodiment, the molar concentration of the manganese element in the mixed salt solution is 0.02mol / L to 1.5mol / L, and optionally 0.05mol / L to 1.2mol / L.

[0043] The molar concentration of the manganese element in the mixed salt solution is controlled within a suitable range, thereby controlling the inner diameter of the holes in the positive electrode active material within a suitable range, so that the battery has high energy density, excellent discharge performance and cycle performance.

[0044] In any embodiment, the pH value of the co-precipitation reaction is 9 to 12, and optionally 9 to 11.

[0045] In any embodiment, the reaction temperature of the co-precipitation reaction is 50°C to 80°C, and optionally 55°C to 75°C.

[0046] In any embodiment, the reaction time of the co-precipitation reaction is 6h to 10h, and optionally 6.5h to 9.5h.

[0047] In any embodiment, the stirring speed of the co-precipitation reaction is 200rmp to 500rmp, and optionally 230rmp to 300rmp.

[0048] The pH value, reaction temperature, reaction time and stirring speed of the co-precipitation reaction are controlled within a suitable range, so that the co-precipitation reaction is more stable and efficient, and the holes formed are distributed in the primary particles of the positive electrode active material in a ring shape and have a suitable inner diameter, so that the battery has high energy density, excellent discharge performance and cycle performance.

[0049] The third aspect of the present application provides a positive electrode tab, which comprises a positive electrode current collector and a positive electrode film layer arranged 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 preparation method of the second aspect of the present application.

[0050] In any embodiment, the thickness of the positive electrode film layer is 200 μm to 400 μm, and optionally 200 μm to 300 μm.

[0051] Controlling the thickness of the positive electrode film layer in a suitable range can provide sufficient positive electrode active material to improve the energy density of the battery, and can reduce the influence on the solid-phase mass transfer of lithium ions. Both the energy density and the power performance of the battery are considered.

[0052] The fourth aspect of the present application provides a secondary battery comprising the positive electrode tab of the third aspect.

[0053] The fifth aspect of the present application provides an electric device comprising the secondary battery of the fourth aspect. BRIEF DESCRIPTION OF DRAWINGS

[0054] Figure 1 is a scanning electron microscope image of the positive electrode active material shown in Example 3 of the present application;

[0055] Figure 2 is a schematic diagram of the secondary battery of an embodiment of the present application;

[0056] Figure 3 is Figure 2 is an exploded view of the secondary battery of an embodiment of the present application shown in

[0057] Figure 4 is a schematic diagram of the battery module of an embodiment of the present application;

[0058] Figure 5 is a schematic diagram of the battery pack of an embodiment of the present application;

[0059] Figure 6 is Figure 5 is an exploded view of the battery pack of an embodiment of the present application shown in

[0060] Figure 7 is a schematic diagram of the electric device using the secondary battery of an embodiment of the present application as a power supply;

[0061] REFERENCE SIGNS:

[0062] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 cover plate. DETAILED DESCRIPTION

[0063] Hereinafter, specific embodiments of the positive electrode active material, the method for manufacturing the same, the positive electrode sheet, the secondary battery, and the power storage device of the present application will be described in detail with appropriate reference to the accompanying drawings. However, there will be cases where unnecessary detailed description is omitted. For example, there will be cases where detailed description of matters known to those skilled in the art, repeated description of substantially identical configurations, is omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present application, and are not intended to limit the subject matter recited in the claims.

[0064] The ranges disclosed herein are defined by their lower and upper limits, given that the range is defined by selecting a lower limit and an upper limit, the selected lower and upper limits define the boundaries of the particular range. Ranges defined by the endpoints can include the endpoints, or can not include the endpoints, and can be freely combined in any manner. For example, if a range is listed as 60-120 and 80-110, it is understood that the ranges 60-110 and 80-120 are also contemplated. Furthermore, if a minimum range value of 1 and 2 is listed, and if a maximum range value of 3, 4, and 5 is listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In the present application, unless otherwise stated, a numerical range "a-b" indicates a shorthand way of describing each and every integer between the number "a" and the number "b", wherein "a" and "b" are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0" and "5" have been listed herein, and "0-5" is merely a shorthand way of describing those numerical combinations. Additionally, when a parameter is stated to be an integer ≥ 2, it is equivalent to disclose that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.

[0065] If not specifically stated, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0066] If not specifically stated, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0067] If not specified otherwise, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method comprising steps (a) and (b) means that the method can comprise steps (a) and (b) in sequence, or steps (b) and (a) in sequence. For example, the method can further comprise step (c) means that step (c) can be added to the method in any sequence, for example, the method can comprise steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0068] If not specified otherwise, the terms "comprising" and "including" as used in the present application are open-ended and also include the case where the term "comprising" or "including" is replaced by the term "consisting of".

[0069] If not specified otherwise, the term "or" as used in the present application is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions are satisfied with 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).

[0070] At present, the ternary material in the field of lithium battery has high theoretical specific capacity, high discharge platform, and is cheap and easy to become one of the popular secondary battery positive active materials. However, the commonly used ternary material is limited by the preparation method and structure, for example, the process stability of using carbonate as precipitant to prepare ternary material precursor is poor, which causes the particle size of the prepared ternary material to be too large or too small, and the solid structure of the ternary material limits the solid phase mass transfer of metal ions, which leads to that the ternary material cannot balance its energy density and power performance. Therefore, it is necessary to design a positive active material which can balance the cycle performance and power performance of the battery to meet the application needs of the new generation of electrochemical system.

[0071] [Positive active material]

[0072] Based on this, the positive active material of the present application has the following general formula:

[0073] Li a Ni x M1 y Mn z M2 1-x-y-z O2,

[0074] wherein M1, M2 each independently includes one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0

[0075] The positive electrode active material exists in the form of secondary particles formed by aggregation of primary particles, and the secondary particles include secondary pores formed by spaces between the primary particles, the secondary pores having an inner diameter of 0.1 μm to 2 μm.

[0076] In the present text, the term "primary particle" refers to a particle of the positive electrode active material before agglomeration.

[0077] In the present text, the term "secondary pore" refers to a cavity structure present between primary particles of the positive electrode active material.

[0078] In the present text, the term "inner diameter of the secondary pore" refers to the longest straight-line distance between any two points on the circumference of a single cavity between primary particles of the positive electrode active material.

[0079] In the present text, the inner diameter of the pores can be tested by any means known in the art. As an example, a conductive adhesive is applied to a sample stage, a powdery sample of the positive electrode active material is spread on the conductive adhesive, the powder not adhered is blown away with a ear bulb, gold is sprayed, and the particles of the powdery sample are cross-sectioned using argon plasma. A scanning electron microscope photograph of the powdery sample is obtained under the conditions of an acceleration voltage of 10 kV and an emission current of 10 mA. The inner diameter of the secondary pores is measured from the scanning electron microscope photograph, at least three samples are measured, at least 50 primary particles are measured for each sample, and the average of the measurements is taken as the inner diameter of the secondary pores of the sample.

[0080] In some embodiments, the chemical formula Li a Ni x M1 y Mn z M2 1-x-y-z O2, a is any value of 0.8, 0.9, 1.0, 1.1, 1.2 or a range consisting of any two of the values.

[0081] In some embodiments, the chemical formula Li a Ni x M1 y Mn z M2 1-x-y-z O2, x is any value of 0.56, 0.6, 0.7, 0.8, 0.9, 0.95, 0.995, 1 or a range consisting of any two of the values.

[0082] In some embodiments, the positive active material has a chemical formula of Li a Ni x M1 y Mn z M2 1-x-y-z O2, where x is any value of 0.8, 0.85, 0.9, 0.95, 1.0 or a range between any two of these values.

[0083] In some embodiments, the positive active material has a chemical formula of Li a Ni x M1 y Mn z M2 1-x-y-z O2, where z is any value of 0, 0.1, 0.12, 0.15, 0.17, 0.2 or a range between any two of these values.

[0084] In some embodiments, the positive active material has a chemical formula of Li a Ni x M1 y Mn z M2 1-x-y-z O2, where 0.8≤a≤1.2, 0.90≤x≤1.0, 0≤y≤0.1.

[0085] In some embodiments, the positive active material has a chemical formula of Li a Ni x M1 y Mn z M2 1-x-y-z O2, where 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, 0≤z≤0.1.

[0086] In some embodiments, the positive active material has a chemical formula of Li a Ni x M1 y Mn z M2 1-x-y-z O2, where 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.05.

[0087] In some embodiments, the positive active material has a chemical formula of Li a Ni x Co y Mn z M2 1-x-y-z O2, where 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.05.

[0088] In some embodiments, the positive active material has a chemical formula of Li a Ni x Aly Mn z M2 1-x-y-z O2, 0.8≤a≤1.2, 0.85≤x≤0.96, 0

[0089] The use of the above material can ensure that the positive active material has a high gram capacity, so that the battery has a high discharge capacity and energy density.

[0090] In some embodiments, the inner diameter of the secondary hole can be selected as 0.1 μm, 0.2 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.8 μm, 1 μm, 1.2 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.8 μm, 2 μm, or a value in the range formed by any two of the above.

[0091] It can be understood that the secondary hole is located between the primary particles and is distributed on the inner side close to the surface of the secondary particle. The secondary hole is uniformly distributed in the interior of the secondary particle, and the distribution of the secondary hole presents a spherical shell type. On the cross section passing through the center of gravity of the secondary particle, the secondary hole can surround a circle and is distributed in the interior of the secondary particle in a ring shape.

[0092] On the one hand, the secondary particle includes the secondary hole formed by the space between the primary particles, so that the positive active material has a three-dimensional pore formed, the solid-phase mass transfer path of lithium ions is shortened, and the power performance of the battery is improved. On the other hand, due to the existence of the secondary hole, more 010 crystal planes can be exposed, thereby generating more reaction active sites, improving the gram capacity and energy density of the material. In addition, the existence of the secondary hole can also buffer the volume change of the positive active material during the charging and discharging process, and play a role in stabilizing the structure and improving the cycle performance. At the same time, controlling the inner diameter of the secondary hole to be 0.1 μm-2 μm can greatly improve the energy density and cycle performance of the battery, and comprehensively improve the performance of the battery.

[0093] In some embodiments, the ratio of the closest distance between the secondary hole and the surface of the secondary particle to the Dv50 of the secondary particle is 1 / 5-3 / 5, which can be selected as 3 / 10-1 / 2. In some embodiments, the ratio of the closest distance between the secondary hole and the surface of the secondary particle to the Dv50 of the secondary particle is 1 / 5, 3 / 10, 2 / 5, 1 / 2, 3 / 5, or a value in the range formed by any two of the above.

[0094] Controlling the ratio of the closest distance between the secondary hole and the surface of the secondary particle to the Dv50 of the secondary particle in a suitable range can not only improve the power performance of the battery, but also reduce the influence of the existence of the hole on the structure of the positive active material.

[0095] In some embodiments, the primary particle further comprises at least one primary hole with an inner diameter of 0.05 μm to 0.6 μm, optionally 0.08 μm to 0.2 μm. In some embodiments, the primary hole has an inner diameter of 0.05 μm, 0.06 μm, 0.08 μm, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.45 μm, 0.6 μm, or a value within a range defined by any two of the above values.

[0096] In the present context, the term "primary hole" refers to a cavity structure present in the interior of the primary particle of the positive electrode active material.

[0097] In the present context, the term "inner diameter of the primary hole" refers to the longest straight line distance between any two points on the circumference of a single cavity in the interior of the primary particle of the positive electrode active material.

[0098] The presence of the primary hole is beneficial for further shortening the solid phase mass transfer path of lithium ions and improving the power performance of the battery. Controlling the inner diameter of the primary hole within a suitable range can take into account both the power performance and the energy density of the battery.

[0099] In the present context, the inner diameter of the hole can be tested by any means known in the art. As an example, the sample stage is pasted with conductive glue, a powdery sample of the positive electrode active material is spread on the conductive glue, the ear bulb is used to blow away the powder that is not stuck, gold is sprayed, and the powdery sample is cross-sectionally cut using argon plasma. A scanning electron microscope photograph of the powdery sample is obtained under the condition of an acceleration voltage of 100 kV and an emission current of 100 mA. The inner diameter of the primary hole is measured according to the scanning electron microscope photograph, at least three samples are measured, at least 50 primary particles of each sample are measured, and the average value is taken as the inner diameter of the primary hole of the sample.

[0100] In some embodiments, the secondary hole has an inner diameter of 0.2 μm to 1 μm. In some embodiments, the secondary hole has an inner diameter of 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, or a value within a range defined by any two of the above values.

[0101] Further controlling the inner diameter of the secondary hole to be 0.1 μm to 1 μm is beneficial for further improving the energy density and cycle performance of the battery.

[0102] In some embodiments, the porosity of the positive active material is 0.1% to 12%, optionally 0.1% to 10%. In some embodiments, the porosity of the positive active material is optionally 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, or a value within a range defined by any two of the foregoing.

[0103] In the present context, the "porosity" refers to the ratio of the pore volume in the positive active material to the total volume of the positive active material.

[0104] In the present context, the porosity of the positive active material can be tested by any means known in the art. As an example, it is measured by gas displacement method according to GB / T 24586. Porosity = (V1-V2) / V1x100%, wherein V1 is the apparent volume of the sample, and V2 is the true volume of the sample.

[0105] Controlling the porosity of the positive active material within a suitable range can provide sufficient space to expose more 010 crystal planes to generate more reactive sites, thereby improving the energy density of the battery, while having sufficient mechanical strength to reduce the risk of the positive active material being crushed during the preparation process. Both the electrical performance and the mechanical strength of the battery are taken into account.

[0106] In some embodiments, the average particle size D of the primary particles is 100 nm to 800 nm, optionally 100 nm to 500 nm. In some embodiments, the average particle size D of the primary particles is optionally 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, 550 nm, 600 nm, 650 nm, 700 nm, 750 nm, 800 nm, or a value within a range defined by any two of the foregoing.

[0107] In the present context, the average particle size D of the primary particles can be tested by any means known in the art. As an example, after imaging by a scanning electron microscope (ZEISS Sigma-02-33, Germany) at 500 times, 200 to 600 primary particles of the positive active material with complete shape and no occlusion are randomly selected from the electron micrograph images thereof, and the longest diameter of each hole in the primary particles in the micrograph images is recorded to obtain the average particle size D.

[0108] In some embodiments, the Dv50 of the secondary particles is 3 μm to 12 μm, optionally 3 μm to 11 μm. In some embodiments, the Dv50 of the secondary particles is optionally 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a value within a range defined by any two of the foregoing.

[0109] In the present text, the Dv50 of the secondary particles can be tested by any means known in the art. As an example, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, 0.1 g to 0.13 g of the sample of the positive electrode active material to be tested is weighed in a 50 mL beaker, 5 g of anhydrous ethanol is added, and a stirring bar of about 2.5 mm is placed before being sealed with a plastic wrap. After the sample is ultrasonically treated for 5 min, it is transferred to a magnetic stirrer, and stirred at 500 rpm for 20 min or more. Two samples are taken from each batch of product for testing. The testing is performed using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. of the United Kingdom. The Dv50 is the particle size corresponding to 50% of the cumulative volume distribution of the secondary particles of the positive electrode active material.

[0110] In some embodiments, the SPAN value of the secondary particles is 0.8 to 1.5, and can be 0.8 to 1.3. In some embodiments, the SPAN value of the secondary particles can be 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, or a value in a range defined by any two of the above values.

[0111] In the present text, the term “SPAN” refers to the distribution span, and the SPAN is calculated as (Dv90-Dv10) / Dv50, which represents the particle distribution of the positive electrode active material.

[0112] In the present text, the SPAN value of the secondary particles can be tested by any means known in the art. As an example, the Dv50 of the secondary particles of the positive electrode active material is tested as follows: referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, 0.1 g to 0.13 g of the sample of the positive electrode active material to be tested is weighed in a 50 mL beaker, 5 g of anhydrous ethanol is added, and a stirring bar of about 2.5 mm is placed before being sealed with a plastic wrap. After the sample is ultrasonically treated for 5 min, it is transferred to a magnetic stirrer, and stirred at 500 rpm for 20 min or more. Two samples are taken from each batch of product for testing. The testing is performed using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. of the United Kingdom. The Dv90 is the particle size corresponding to 90% of the cumulative volume distribution of the secondary particles of the positive electrode active material, the Dv50 is the particle size corresponding to 50% of the cumulative volume distribution of the secondary particles of the positive electrode active material, and the Dv10 is the particle size corresponding to 10% of the cumulative volume distribution of the secondary particles of the positive electrode active material. SPAN = (Dv90-Dv10) / Dv50.

[0113] The average particle size D of the primary particles, the Dv50 of the secondary particles and the SPAN value of the secondary particles are important parameters of the positive electrode active material, which affect the structural properties of the positive electrode active material. Controlling the average particle size D of the primary particles, the Dv50 of the secondary particles and the SPAN value of the secondary particles in a suitable range is conducive to the improvement of the tap density of the positive electrode active material, so that the battery has high energy density, excellent power performance and cycle performance, and the electrochemical performance of the battery is comprehensively improved.

[0114] In some embodiments, the area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material is 200 μm 2 ~ 300 μm 2 , and optionally 250 μm 2 ~ 280 μm 2 . In some embodiments, the area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material is optionally 200 μm 2 , 210 μm 2 , 220 μm 2 , 230 μm 2 , 240 μm 2 , 250 μm 2 , 260 μm 2 , 270 μm 2 , 280 μm 2 , 290 μm 2 , 300 μm 2 , or a value in the range formed by any two of the above.

[0115] In this context, the area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material can be tested by any means known in the art. As an example, the area of the (010) crystal face is tested by using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE), and the target is Cu Kα; the voltage and current are 40KV / 40mA, the scanning angle range is 5° to 80°, the scanning step is 0.00836°, and the time for each step is 0.3s.

[0116] Controlling the area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material in a suitable range provides sufficient reactive sites, improves the energy density of the battery, and improves the electrochemical performance of the battery.

[0117] In some embodiments, the specific capacity of the positive electrode active material is 238 mAh / g ~ 250 mAh / g.

[0118] The positive electrode active material with high specific capacity is conducive to the improvement of the energy density.

[0119] The present application also provides a preparation method of the positive electrode active material, comprising:

[0120] mixing a first raw material containing a nickel source and a manganese source with a complexing agent and a precipitant to perform a co-precipitation reaction to prepare a precursor, and optionally, the first raw material further comprises a M1 source;

[0121] mixing the precursor with a lithium source to perform a calcination to prepare the positive electrode active material; or

[0122] mixing the precursor with a lithium source to perform a calcination, and then mixing the precursor with a M2 source to perform a calcination to prepare the positive electrode active material;

[0123] the positive electrode active material has a general formula as follows:

[0124] Li a Ni x M1 y Mn z M2 1-x-y-z O2,

[0125] wherein M1 and M2 each independently comprises one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0

[0126] In this document, the term "co-precipitation reaction" refers to a precipitation reaction of a metal solution, a precipitant, and a complexing agent at a certain temperature.

[0127] In some embodiments, the M1 source comprises one or more of a cobalt source, an aluminum source, a boron source, an antimony source, a titanium source, and a magnesium source.

[0128] In some embodiments, the M2 source comprises one or more of a cobalt source, an aluminum source, a boron source, an antimony source, a titanium source, and a magnesium source.

[0129] In some embodiments, the nickel source comprises one or more of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate.

[0130] In some embodiments, the manganese source comprises one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate.

[0131] In some embodiments, the lithium source comprises one or more of lithium hydroxide, lithium carbonate, lithium oxide, lithium phosphate, lithium dihydrogen phosphate, and lithium acetate.

[0132] In some embodiments, the cobalt source comprises one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate.

[0133] In some embodiments, the antimony source comprises one or more of antimony sulfate, antimony chloride, antimony nitrate, and antimony acetate.

[0134] The prepared precursor has multiple pores in a ring distribution, including secondary pores distributed between primary particles, by a co-precipitation reaction and control of the amount of manganese source. The preparation method of the positive electrode active material is simple and has low manufacturing cost. The inner diameter of the secondary pores in the prepared positive electrode active material is 0.1 μm to 2 μm, which is beneficial to the embedding and extraction of lithium ions, and the pores can buffer the volume change of the positive electrode active material during charging and discharging, thereby stabilizing the structure and improving the cycle performance.

[0135] In some embodiments, 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, 0≤z≤0.1.

[0136] In some embodiments, 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.05.

[0137] In some embodiments, the precursor is a precursor secondary particle formed by aggregation of the precursor primary particles.

[0138] The average particle size D' of the precursor primary particles is 150 nm to 500 nm, and can be 200 nm to 300 nm.

[0139] The median particle size Dv50' of the precursor secondary particles is 3 μm to 12 μm, and can be 6 μm to 8 μm.

[0140] In some embodiments, the average particle size D' of the precursor primary particles can be 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm, or a value in a range formed by any two of the above. In some embodiments, the median particle size Dv50' of the precursor secondary particles can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or a value in a range formed by any two of the above.

[0141] In this document, the average particle size D' of the precursor primary particles can be tested by any means known in the art. As an example, after imaging by a scanning electron microscope (ZEISS Sigma-02-33, Germany) at 500 times, 200 to 600 precursor primary particles with complete shape and no occlusion are randomly selected from the electron micrograph, and the longest diameter of each hole in the precursor primary particles in the micrograph is recorded, and the average value is taken as the average particle size D'.

[0142] In the present disclosure, the median particle size Dv50' of the precursor secondary particles can be tested by any means known in the art. As an example, referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, 0.1 g to 0.13 g of the precursor secondary particles to be tested is weighed in a 50 mL beaker, 5 g of anhydrous ethanol is added, a stirring bar of about 2.5 mm is added and then sealed with plastic wrap. After ultrasonic treatment for 5 min, the sample is transferred to a magnetic stirrer and stirred at 500 rpm for 20 min or more. Two samples are taken from each batch of product for testing. The testing is performed by using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. of the United Kingdom. The Dv50' is the particle size corresponding to the cumulative volume percentage of the precursor secondary particles reaching 50%.

[0143] Controlling the average particle size D' of the precursor primary particles and the median particle size Dv50' of the precursor secondary particles within a suitable range can further control the size of the primary particles and the secondary particles of the prepared positive electrode active material within a suitable range, so that the battery has high energy density and excellent cycle performance.

[0144] In some embodiments, the specific surface area of the precursor is 2 m 2 / g to 40 m 2 / g, optionally 25 m 2 / g to 35 m 2 / g. In some embodiments, the specific surface area of the precursor is optionally 2 m 2 / g, 5 m 2 / g, 10 m 2 / g, 12 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m 2 / g, 18 m 2 / g, 19 m 2 / g, 20 m 2 / g, 21 m 2 / g, 22 m 2 / g, 23 m 2 / g, 24 m 2 / g, 25 m 2 / g, 26 m 2 / g, 28 m 2 / g, 30 m 2 / g, 32 m 2 / g, 34 m 2 / g, 35 m 2 / g, 36 m 2 / g, 38 m 2 / g, 40 m 2 / g, or a value in a range formed by any two of the above.

[0145] In the present disclosure, the specific surface area of the precursor can be tested by any means known in the art. As an example, refer to GB / T 19587-2017 “Determination of the specific surface area of solid substances by gas adsorption BET method”. The specific surface area of the precursor is measured by using a TriStar II 3020 device, dispersing the precursor in a dispersant (ethanol), drying the obtained precursor in a vacuum drying oven after ultrasonic treatment for 30 minutes, and finally using a specific surface area tester.

[0146] Controlling the specific surface area of the precursor within a suitable range, and thus controlling the positive active material to have a suitable porosity, can make the battery have high energy density, excellent discharge performance and cycle performance.

[0147] In some embodiments, the molar concentration of manganese in the mixed salt solution is 0.02 mol / L to 1.5 mol / L, which can be optionally 0.05 mol / L to 1.2 mol / L. In some embodiments, the molar concentration of manganese in the mixed salt solution can be 0.02 mol / L, 0.05 mol / L, 0.1 mol / L, 0.2 mol / L, 0.4 mol / L, 0.5 mol / L, 0.6 mol / L, 0.8 mol / L, 1.0 mol / L, 1.2 mol / L, 1.4 mol / L, 1.5 mol / L, or a value within a range defined by any two of the above values.

[0148] Controlling the molar concentration of manganese in the mixed salt solution within a suitable range, and thus controlling the inner diameter of the holes in the positive active material within a suitable range, can make the battery have high energy density, excellent discharge performance and cycle performance.

[0149] In some embodiments, the precipitant includes one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, and ammonium bicarbonate.

[0150] In some embodiments, the complexing agent includes one or more of ammonia, lactic acid, and polyvinylpyrrolidone.

[0151] In some embodiments, the pH value of the co-precipitation reaction is 9 to 12, which can be optionally 9 to 11. In some embodiments, the pH value of the co-precipitation reaction is 9, 10, 11, 12, or a value within a range defined by any two of the above values.

[0152] In some embodiments, the reaction temperature of the co-precipitation reaction is 50°C to 80°C, which can be optionally 55°C to 75°C. In some embodiments, the reaction temperature of the co-precipitation reaction can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, or a value within a range defined by any two of the above values.

[0153] In some embodiments, the reaction time of the co-precipitation reaction is 6h-10h, which can be 6.5h-9.5h. In some embodiments, the reaction time of the co-precipitation reaction can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, or a value within a range defined by any two of the above values.

[0154] In some embodiments, the stirring speed of the co-precipitation reaction is 200rmp-500rmp, which can be 230rmp-300rmp. In some embodiments, the stirring speed of the co-precipitation reaction can be 200rmp, 250rmp, 300rmp, 350rmp, 400rmp, 450rmp, 500rmp, or a value within a range defined by any two of the above values.

[0155] Controlling the pH value, reaction temperature, reaction time and stirring speed of the co-precipitation reaction within a suitable range can make the co-precipitation reaction more stable and efficient, and is conducive to the formation of pores with a ring-like distribution inside the primary particles of the positive electrode active material and having a suitable inner diameter, so as to make the battery have high energy density, excellent discharge performance and cycle performance.

[0156] [Positive electrode tab]

[0157] The positive electrode tab includes a positive electrode current collector and a positive electrode film layer disposed on at least one surface of the positive electrode current collector, and the positive electrode film layer includes a positive electrode active material.

[0158] For example, the positive electrode current collector has two opposite surfaces in the thickness direction thereof, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0159] In some embodiments, the areal density of the positive electrode film layer is 24mg / cm 2 -46mg / cm 2 In some embodiments, the areal density of the positive electrode film layer can be 24mg / cm 2 , 25mg / cm 2 , 26mg / cm 2 , 28mg / cm 2 , 30mg / cm 2 , 32mg / cm 2 , 34mg / cm 2 , 35mg / cm 2 , 36mg / cm 2 , 38mg / cm 2 , 40mg / cm 2 , 42mg / cm 2 , 44mg / cm2 45 mg / cm 2 46 mg / cm 2 or a range consisting of any two of the aforementioned values.

[0160] The coating surface density of the positive electrode film layer is determined by measuring the coating weight (g) of the single-sided positive electrode film layer and the coating area (cm 2 ) of the single-sided positive electrode film layer (the number of collection points > 14). Specifically, the coating surface density of the positive electrode film layer = the coating weight (g) of the single-sided positive electrode film layer / the coating area (cm 2 ) of the single-sided positive electrode film layer.

[0161] In some embodiments, the thickness of the positive electrode film layer is 200 μm to 400 μm, and optionally 200 μm to 300 μm. In some embodiments, the thickness of the positive electrode film layer is optionally 200 μm, 220 μm, 240 μm, 250 μm, 260 μm, 280 μm, 300 μm, 320 μm, 340 μm, 350 μm, 360 μm, 380 μm, 400 μm, or a range consisting of any two of the aforementioned values.

[0162] Controlling the thickness of the positive electrode film layer in a suitable range can provide sufficient positive electrode active material to improve the energy density of the battery, and can reduce the impact on the solid-phase mass transfer of lithium ions. Both the energy density and the power performance of the battery are considered.

[0163] In some embodiments, the positive electrode current collector can be a metal foil or a composite current collector. For example, as a metal foil, an aluminum foil can be used. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy, etc.) on a polymer material base material (such as a base material of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0164] In some embodiments, the positive active material can employ a positive active material for a battery known in the art. As an example, the positive active material can include at least one of a lithium-containing phosphate of an olivine structure, a lithium transition metal oxide, and a modified compound of each thereof. However, the present application is not limited to these materials, and other conventional materials that can be used as a positive active material for a battery can also be used. These positive active materials can be used alone only one or in combination of two or more. Among them, examples of the lithium transition metal oxide can include, but are not limited to, at least one of lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(also can be abbreviated as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2(also can be abbreviated as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2(also can be abbreviated as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2(also can be abbreviated as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2(also can be abbreviated as NCM811), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 O2), and a modified compound thereof, etc. Examples of the lithium-containing phosphate of an olivine structure can include, but are not limited to, at least one of lithium iron phosphate (e.g., LiFePO4(also can be abbreviated as LFP)), a composite of lithium iron phosphate and carbon, lithium manganese phosphate (e.g., LiMnPO4), a composite of lithium manganese phosphate and carbon, lithium manganese iron phosphate, a composite of lithium manganese iron phosphate and carbon, etc.

[0165] In some embodiments, the positive electrode film layer can further optionally include a binder. As an example, the binder can include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, a vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, a tetrafluoroethylene-hexafluoropropylene copolymer, and a fluorine-containing acrylate resin.

[0166] In some embodiments, the positive electrode film layer can also optionally include a conductive agent. As an example, the conductive agent can include at least one of super-P, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0167] In some embodiments, the positive electrode tab can be prepared by dispersing the above-mentioned components for preparing the positive electrode tab, such as the positive electrode active material, the conductive agent, the binder, and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector; and drying, cold-pressing, or the like, to obtain the positive electrode tab.

[0168] [Negative electrode tab]

[0169] The negative electrode tab includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector.

[0170] As an example, the negative electrode current collector has two opposite surfaces in the thickness direction thereof, and the negative electrode film layer is disposed on either one or both of the two opposite surfaces of the negative electrode current collector.

[0171] In some embodiments, the negative electrode current collector can employ a metal foil or a composite current collector. As a metal foil, for example, a copper foil can be employed. The composite current collector can include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector can be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, silver alloy, etc.) on a polymer material base layer (e.g., a base layer of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0172] In some embodiments, the negative electrode active material can employ a negative electrode active material known in the art for use in a battery. As an example, the negative electrode active material can include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, a silicon-based material, a tin-based material, and lithium titanate, etc. The silicon-based material can be selected from at least one of elemental silicon, a silicon oxide compound, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy. The tin-based material can be selected from at least one of elemental tin, a tin oxide compound, and a tin alloy. However, the present application is not limited to these materials, and other conventional materials that can be used as a negative electrode active material for a battery can also be used. These negative electrode active materials can be used alone or in combination of two or more.

[0173] In some embodiments, the negative electrode active material includes silicon monoxide.

[0174] In some embodiments, the mass content of silicon monoxide is 20% to 100%, optionally 50% to 100%, based on the total mass of the negative active material.

[0175] In some embodiments, the negative film layer further optionally comprises a binder. The binder can 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).

[0176] In some embodiments, the negative film layer further optionally comprises a conductive agent. The conductive agent can be selected from at least one of super-conductive carbon, acetylene black, carbon black, ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0177] In some embodiments, the negative film layer further optionally comprises other auxiliary agents, such as thickening agents (e.g., sodium carboxymethyl cellulose (CMC-Na)) and the like.

[0178] In some embodiments, the negative electrode sheet can be prepared by dispersing the above-mentioned components for preparing the negative electrode sheet, such as the negative active material, the conductive agent, the binder, and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry on a negative current collector, and after drying, cold pressing, and the like, the negative electrode sheet is obtained.

[0179] [Separator]

[0180] In some embodiments, the secondary battery further comprises a separator. Any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0181] In some embodiments, the material of the separator can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of the layers can be the same or different.

[0182] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding process or a stacking process.

[0183] In some embodiments, the secondary battery comprises a negative electrode sheet, a separator, an electrolyte, and a positive electrode sheet in some embodiments.

[0184] In some embodiments, the secondary battery comprises a lithium secondary battery.

[0185] In some embodiments, the energy density of the secondary battery is 380 Wh / kg to 500 Wh / kg.

[0186] In some embodiments, the secondary battery can include an outer package. The outer package can be used to encapsulate the electrode assembly and the electrolyte described above.

[0187] In some embodiments, the outer package of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, or the like. The outer package of the secondary battery can also be a soft package, such as a pouch-type soft package. The material of the soft package can be plastic, and as plastic, polypropylene, polybutylene terephthalate, polybutylene succinate, or the like can be listed.

[0188] The secondary battery of the present application can have a cylindrical shape, a square shape, or any other arbitrary shape. For example, Figure 2 is a square-shaped secondary battery 5 as an example.

[0189] In some embodiments, referring to Figure 3 , the outer package can include a shell 51 and a cover plate 53. The shell 51 can include a bottom plate and a side plate connected to the bottom plate, and the bottom plate and the side plate enclose a receiving cavity. The shell 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be provided on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet, and the separator can form an electrode assembly 52 through a winding process or a stacking process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is impregnated in the electrode assembly 52. The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, which can be selected by a person skilled in the art according to specific actual needs.

[0190] In some embodiments, the secondary battery can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery module.

[0191] Figure 4 is a battery module 4 as an example. Referring to Figure 4 , in the battery module 4, a plurality of secondary batteries 5 can be arranged in sequence along the length direction of the battery module 4. Of course, they can also be arranged in any other arbitrary manner. Further, the plurality of secondary batteries 5 can be fixed by fasteners.

[0192] Optionally, the battery module 4 can further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0193] In some embodiments, the above-mentioned battery module can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, which can be selected by a person skilled in the art according to the application and capacity of the battery pack.

[0194] Figure 5 andFigure 6 is a battery pack 1 as an example. Referring to Figure 5 and Figure 6 In the battery pack 1, a battery case and a plurality of battery modules 4 disposed in the battery case can be included. The battery case includes an upper case 2 and a lower case 3, and the upper case 2 can be disposed on the lower case 3 and form an enclosed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery case in any manner.

[0195] In addition, the present application also provides a power consuming device, which includes at least one of the secondary battery, the battery module, or the battery pack provided by the present application. The secondary battery, the battery module, or the battery pack can be used as a power source of the power consuming device, or can be used as an energy storage unit of the power consuming device. The power consuming device can include a mobile device (such as a mobile phone, a notebook computer, etc.), an electric vehicle (such as a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf cart, an electric truck, etc.), an electric train, a ship and a satellite, an energy storage system, etc., but is not limited thereto.

[0196] As the power consuming device, the secondary battery, the battery module, or the battery pack can be selected according to the use requirement thereof.

[0197] Figure 7 is a power consuming device as an example. The power consuming device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the requirement of high power and high energy density of the secondary battery for the power consuming device, the battery pack or the battery module can be used.

[0198] The device as another example can be a mobile phone, a tablet computer, a notebook computer, etc. The device usually requires thinning, and the secondary battery can be used as a power source.

[0199] Embodiment

[0200] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and cannot be understood as a limitation of the present application. If the specific technology or condition is not indicated in the embodiments, the technology or condition described in the literature in the art or according to the product instruction is used. If the reagent or instrument is not indicated by the manufacturer, it is a conventional product that can be obtained by market purchase.

[0201] I. Preparation method

[0202] Embodiment 1

[0203] 1) Preparation of positive active material

[0204] A nickel-cobalt-manganese solution with a molar ratio of 96:1:3 of nickel, cobalt, and manganese elements is prepared, and the concentration is adjusted to 2 mol / L. The raw materials of the soluble nickel-cobalt-manganese are nickel sulfate, cobalt sulfate, and manganese sulfate, and the molar concentration of manganese ions is 0.3 mol / L. A 3 mol / L sodium hydroxide solution is prepared. A 6 mol / L ammonia solution is prepared.

[0205] The nickel-cobalt-manganese solution, the sodium hydroxide solution, and the ammonia solution are simultaneously added to a reaction kettle under a nitrogen atmosphere to perform a co-precipitation reaction. The rotation speed is controlled to be 300 rpm, the temperature is controlled to be 120°C, the time is controlled to be 10 h, the pH of the system is controlled to be 9, and the concentration of the ammonia water is controlled to be 6 mol / L. After the co-precipitation reaction is completed, the reaction material is transferred to a slurry tank for aging and washing. After dehydration, the material is placed in a 120°C oven for drying for 10 h. After screening and demagnetization, a precursor is obtained.

[0206] The precursor and lithium hydroxide are uniformly mixed in a certain proportion, and the molar ratio of Li / Me is 1.03. Me is the total molar content of nickel elements, cobalt elements, and manganese elements.

[0207] The uniformly mixed material is placed in a furnace for calcination. The heating rate is set to be 3°C / min, the temperature is maintained at 760°C for 20 h, the oxygen content in the atmosphere is required to be ≥98%, and then the furnace is cooled. A matrix material is obtained.

[0208] Under a nitrogen atmosphere, the matrix material, cobalt boride, and titanium boride are mixed in a high-speed mixer at a mass ratio of 1:0.015:0.0041, and then placed in a furnace for calcination. The calcination temperature is 350°C, the calcination time is 5 h, and the calcination atmosphere is nitrogen. A product is obtained. The product is washed with water for 30 min, centrifuged and filtered, and then subjected to vibration drying. A positive electrode active material LiNi 0.96 Co 0.01 Mn 0.028 Ti 0.001 B 0.001 .

[0209] 2) Preparation of the positive electrode tab

[0210] The positive electrode active material, the conductive agent carbon black, and the binder polyvinylidene fluoride (PVDF) are mixed at a mass ratio of 97:1:2, and N-methyl pyrrolidone is added. The mixture is stirred for 0.5-6 h to obtain a positive electrode slurry. Then, the positive electrode slurry is uniformly coated on a positive electrode current collector aluminum foil, and subjected to drying, cold pressing, and slitting to obtain a positive electrode tab.

[0211] 3) Preparation of the negative electrode tab

[0212] The artificial graphite doped with silicon monoxide (SIO), conductive agent carbon black, carbon nanotube (CNT), binder styrene-butadiene rubber (SBR), thickening agent sodium carboxymethyl cellulose (CMC) are added into deionized water according to the weight ratio of 94.5:1:0.375:2.8:1.325, wherein the mass fraction of SIO is XX based on the mass of artificial graphite, and mixed and stirred for 0.5-6h to obtain a negative electrode active material layer slurry; the negative electrode active material layer slurry is uniformly coated on the negative electrode current collector copper foil in layers, and then dried, cold-pressed and cut to obtain a positive electrode sheet.

[0213] 4) electrolyte

[0214] In an argon atmosphere glove box (H2O <0.1 ppm, O2 <0.1 ppm), lithium salt LiPF6 / LIFSI is dissolved in an organic solvent ethylene carbonate / methyl ethyl carbonate / diethyl carbonate / fluoroethylene carbonate (volume ratio of 1:1:1:1) to obtain an electrolyte with a lithium salt concentration of 1 mol / L.

[0215] 5) separator

[0216] A polypropylene film is used as a base film, and 1 micron of aluminum oxide (CCS) + 1 micron of polyvinylidene fluoride (PCS) is coated on the base film.

[0217] 6) preparation of the battery

[0218] The positive electrode sheet, the separator and the negative electrode sheet are stacked in order, with the separator between the positive electrode sheet and the negative electrode sheet to play a separating role, and then wound to obtain a bare cell. The bare cell is welded with tabs, and then put into an aluminum shell and baked at 80℃ to remove water. Then, the electrolyte is injected and sealed to obtain a non-charged battery. The non-charged battery is subjected to the processes of standing, hot and cold pressing, formation, shaping and capacity testing in sequence to obtain the lithium battery product of Example 1.

[0219] Example 2

[0220] The battery of Example 2 is prepared in a similar manner to the battery of Example 1, but the preparation method of the positive electrode active material precursor is adjusted to adjust the secondary pore diameter of the positive electrode active material, and the specific parameters are shown in Tables 1 and 2.

[0221] Example 3

[0222] The battery of Example 3 is prepared in a similar manner to the battery of Example 1, but the preparation method of the positive electrode active material precursor is adjusted to adjust the primary particles of the positive electrode active material to have primary pores, and the specific parameters are shown in Tables 1 and 2.

[0223] Examples 4-11

[0224] The batteries of Examples 4-11 were prepared in a similar manner to the batteries of Example 1, but the preparation method of the positive active material precursor was adjusted to adjust the inner diameter of the secondary pores, the porosity and the SPAN value of the positive active material, with the specific parameters shown in Table 1 and Table 2.

[0225] Examples 12-21

[0226] The batteries of Examples 12-21 were prepared in a similar manner to the batteries of Example 3, but the preparation method of the precursor, the heating rate, the temperature or the time in the calcination of the precursor and lithium salt were adjusted to adjust the primary particle D, the Dv50 or the SPAN value of the secondary particle of the positive active material, with the specific parameters being:

[0227] Example 12: The PH of the co-precipitation reaction in the preparation method of the precursor was 9.4, the precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 3°C / min, and the temperature was kept at 800°C for 22h.

[0228] Example 13: The PH of the co-precipitation reaction in the preparation method of the precursor was 9.3, the precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 3°C / min, and the temperature was kept at 790°C for 22h.

[0229] Example 14: The PH of the co-precipitation reaction in the preparation method of the precursor was 9.1, the precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 3°C / min, and the temperature was kept at 780°C for 21h.

[0230] Example 15: The stirring speed of the co-precipitation reaction in the preparation method of the precursor was 290rmp, the precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 3°C / min, and the temperature was kept at 740°C for 18h.

[0231] Example 16: The precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 7°C / min, and the temperature was kept at 760°C for 20h.

[0232] Example 17: The precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 2.5°C / min, and the temperature was kept at 760°C for 20h.

[0233] Example 18: The precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 5°C / min, and the temperature was kept at 760°C for 20h.

[0234] Example 19: The precursor and lithium hydroxide were mixed in a certain proportion and then calcined, the heating rate was set to 2°C / min, and the temperature was kept at 760°C for 20h.

[0235] Examples 20-21

[0236] The batteries of Examples 20-21 were prepared in a similar manner to the batteries of Example 3, but the preparation method of the positive active material precursor was adjusted to adjust the SPAN value of the positive active material, with the specific parameters shown in Tables 1 and 2.

[0237] Examples 22-23

[0238] The batteries of Examples 22-23 were prepared in a similar manner to the batteries of Example 3, but the thickness of the positive electrode sheet was adjusted, with the specific parameters shown in Tables 1 and 2.

[0239] Examples 24-27

[0240] The batteries of Examples 24-27 were prepared in a similar manner to the batteries of Example 3, but the preparation method of the positive active material precursor was adjusted to adjust the inner diameter of the primary pores of the primary particles or the average particle size D of the primary particles of the positive active material, with the specific parameters shown in Tables 1 and 2.

[0241] Example 28: The batteries of Example 28 were prepared in a similar manner to the batteries of Example 3, but the preparation method of the positive active material precursor was adjusted to have a molar ratio of nickel to manganese elements of 97:3, to obtain the positive active material LiNi 0.97 Mn 0.028 Ti 0.001 B 0.001 .

[0242] Example 29: The batteries of Example 29 were prepared in a similar manner to the batteries of Example 3, but the preparation method of the positive active material precursor was adjusted to have a molar ratio of nickel to aluminum elements to manganese elements of 96:1:3, to obtain the positive active material LiNi 0.96 Al 0.01 Mn 0.028 Ti 0.001 B 0.001 .

[0243] Example 30: The batteries of Example 30 were prepared in a similar manner to the batteries of Example 3, but without the final cobalt boride and titanium boride doping reactions, to obtain the positive active material LiNi 0.96 Co 0.01 Mn 0.03 .

[0244] Comparative Example 1

[0245] The batteries of Comparative Example 1 were prepared in a similar manner to the batteries of Example 1, but the primary particles of the prepared positive active material were solid structures, with the preparation method being as follows:

[0246] A nickel-cobalt-manganese solution with a molar ratio of 96:1:3 of nickel, cobalt and manganese elements is prepared, and the concentration is adjusted to 2 mol / L. The raw materials of the soluble nickel, cobalt and manganese are nickel sulfate, cobalt sulfate and manganese sulfate respectively, and the molar concentration of manganese ions is 0.005 mol / L. A 0.8 mol / L sodium hydroxide solution is prepared. A 6 mol / L ammonia solution is prepared.

[0247] The nickel-cobalt-manganese solution, the sodium hydroxide solution and the ammonia solution are simultaneously added to a reaction kettle under a nitrogen atmosphere to perform a co-precipitation reaction. The rotation speed is controlled to be 600 rpm, the temperature is controlled to be 140°C, the time is controlled to be 9 h, the pH of the system is controlled to be 11.5, and the concentration of the ammonia water is controlled to be 6 mol / L. After the co-precipitation reaction is completed, the reaction material is transferred to a slurry tank to perform aging and washing. After dehydration, the material is placed in a 120°C oven to dry for 10 h. After screening and demagnetization, the precursor with a close arrangement is obtained.

[0248] The precursor and lithium hydroxide are uniformly mixed in a certain proportion, and the molar ratio of Li / Me is 1.03. Me is the total molar content of nickel elements, cobalt elements and manganese elements.

[0249] The uniformly mixed material is placed in an oxygen atmosphere furnace, the heating rate is set to 5°C / min, and the material is kept at 800°C for 24 h. The oxygen content in the atmosphere is required to be greater than or equal to 98%. Then the material is cooled in the furnace to obtain the base material.

[0250] The base material, cobalt boride and titanium boride are mixed in a high-speed mixer in a mass ratio of 1:0.015:0.0041 under a nitrogen atmosphere. Then the mixture is placed in a furnace for calcination. The calcination temperature is 350°C, the calcination time is 5 h, and the calcination atmosphere is nitrogen. The product is obtained. The product is washed with water for 30 min, centrifuged and filtered, and then subjected to vibration drying to obtain the positive electrode active material LiNi 0.96 Co 0.01 Mn 0.028 Ti 0.001 B 0.001 .

[0251] Comparative Examples 2-3

[0252] The batteries of Comparative Examples 2-3 are prepared in a similar manner to the battery of Comparative Example 1, but the parameters of the preparation method of the positive electrode active material are adjusted so that the hole inner diameter of the primary particles of the positive electrode active material is 0.5 microns and 3 microns respectively. The specific parameters are shown in Tables 1 and 2.

[0253] Comparative Example 4

[0254] The battery of Comparative Example 4 is prepared in a similar manner to the battery of Example 28, but the preparation method is adjusted so that the positive electrode active material does not have holes. See Tables 1 and 2 for details.

[0255] Comparative Examples 5-6

[0256] The batteries of Comparative Examples 5-6 were prepared in a similar manner to the battery of Comparative Example 4, but the parameters of the preparation method of the positive active material were adjusted so that the hole inner diameter of the primary particles of the positive active material was 0.5 microns and 3 microns, respectively, as shown in Tables 1 and 2.

[0257] Comparative Example 7

[0258] The battery of Comparative Example 7 was prepared in a similar manner to the battery of Example 29, but the preparation method was adjusted so that the positive active material did not have holes, as shown in Tables 1 and 2.

[0259] Comparative Example 8

[0260] The battery of Comparative Example 8 was prepared in a similar manner to the battery of Example 30, but the preparation method was adjusted so that the positive active material did not have holes, as shown in Tables 1 and 2.

[0261] II. Performance Test

[0262] 1. Positive Active Material Performance Test

[0263] 1) Hole inner diameter test

[0264] The conductive adhesive was pasted on the sample stage, the powdery sample of the positive active material in each example and comparative example was laid on the conductive adhesive, the ear bulb was used to blow away the powder that was not stuck, gold was sprayed, and argon plasma was used to cut the cross section of the powdery sample. The scanning electron microscope (e.g., ZEISS Sigma 300) was used to obtain the scanning electron microscope image of the powdery sample under the condition of an acceleration voltage of 10 kV and an emission current of 10 mA. The inner diameter size of the primary hole was measured according to the SEM image, at least three samples were measured, at least 50 primary particles of each sample were measured, and the average value of the measured data was taken as the inner diameter size of the primary hole of the sample.

[0265] 2) Porosity test

[0266] According to GB / T 24586, the gas displacement method was used for measurement. Porosity = (V1-V2) / V1x100%, wherein V1 is the apparent volume of the sample, and V2 is the true volume of the sample.

[0267] 3) Specific surface area of precursor test

[0268] Reference GB / T 19587-2017 "Gas Adsorption BET Method for Determining Specific Surface Area of Solid Substances". The equipment TriStar II 3020 is used for determination, the precursor is dispersed into dispersant (ethanol), after ultrasonic treatment for 30 minutes, the obtained precursor is placed into a vacuum drying oven for drying, and finally the specific surface area tester is used to measure the specific surface area of the precursor.

[0269] 4) Primary particle size test

[0270] D test of primary particles of positive electrode active material:

[0271] After imaging by a 500-fold scanning electron microscope (Germany ZEISS Sigma-02-33), 200 to 600 primary particles of positive electrode active material with complete shape and no occlusion are randomly selected in the electron micrograph, and the longest diameter of each hole in the primary particles in the micrograph is recorded, and the average value is taken as the average particle size D.

[0272] Median particle size D' test of precursor primary particles: After imaging by a 500-fold scanning electron microscope (Germany ZEISS Sigma-02-33), 200 to 600 primary particles of precursor material with complete shape and no occlusion are randomly selected in the electron micrograph, and the longest diameter of each hole in the primary particles in the micrograph is recorded, and the average value is taken as the average particle size D'.

[0273] 5) Secondary particle size test

[0274] Dv50 test of secondary particles of positive electrode active material: Referring to GB / T 19077-2016 Particle Size Distribution Laser Diffraction Method, 0.1 g to 0.13 g of the positive electrode active material sample to be tested is weighed in a 50 mL beaker, 5 g of anhydrous ethanol is added, a stirring bar of about 2.5 mm is added and sealed with plastic wrap. After ultrasonic treatment for 5 min, the sample is transferred to a magnetic stirrer, stirred at 500 rpm for 20 min or more, and 2 samples are taken from each batch of product for testing. The test is performed using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd., UK. Among them, Dv90 is the particle size corresponding to the cumulative volume distribution percentage of 90% of the secondary particles of the positive electrode active material, Dv50 is the particle size corresponding to the cumulative volume distribution percentage of 50% of the secondary particles of the positive electrode active material, and Dv10 is the particle size corresponding to the cumulative volume distribution percentage of 10% of the secondary particles of the positive electrode active material. SPAN=(Dv90-Dv10) / Dv50.

[0275] The median particle size Dv50' of the precursor secondary particles is tested: refer to GB / T 19077-2016 particle size distribution laser diffraction method, weigh 0.1 g to 0.13 g of the sample of the positive electrode active material to be tested in a 50 mL beaker, add 5 g of anhydrous ethanol, put in a stirring bar of about 2.5 mm, and then seal with plastic wrap. After ultrasonic treatment of the sample for 5 min, transfer it to a magnetic stirrer, and stir at 500 rpm for 20 min or more. Take 2 samples from each batch of product for testing. The test is performed using a Mastersizer 2000E laser particle size analyzer from Malvern Instruments Ltd. of the United Kingdom. The median particle size Dv50' is the particle size corresponding to 50% of the cumulative volume distribution of the precursor secondary particles.

[0276] 6) Testing of the area of the (010) crystal plane

[0277] The area of the (010) crystal plane is tested using an X-ray powder diffractometer (XRD, instrument model: Bruker D8 ADVANCE). The target is Cu Kα; the voltage and current are 40 KV / 40 mA; the scanning angle range is 5° to 80°; the scanning step is 0.00836°; and the time for each step is 0.3 s.

[0278] 2) Performance test of the battery

[0279] 1) Discharge capacity test

[0280] The battery cell is allowed to stand at 25°C for 2 h to ensure that the temperature of the battery cell is 25°C. After charging the battery cell to the charge cut-off voltage at 0.1C at 25°C, constant voltage charging is continued at the charge cut-off voltage until the current is 0.05C, and the charge cut-off (wherein C represents the rated capacity of the battery cell). The battery cell is allowed to stand at 25°C for 1 h. The battery cell is discharged to the discharge cut-off voltage at 0.1C at 25°C, and the total discharge capacity C0 discharged by the battery cell is recorded.

[0281] 2) Energy density test

[0282] Capacity test of the battery cell: the battery cell is allowed to stand at 25°C for 2 h to ensure that the temperature of the battery cell is 25°C. After charging the battery cell to the charge cut-off voltage at 0.1C at 25°C, constant voltage charging is continued at the charge cut-off voltage until the current is 0.05C, and the charge cut-off (wherein C represents the rated capacity of the battery cell). The battery cell is allowed to stand at 25°C for 1 h. The battery cell is discharged to the discharge cut-off voltage at 0.1C at 25°C, and the total discharge capacity C0 discharged by the battery cell is recorded.

[0283] Battery cell weight measurement: the battery cell is placed on an electronic balance until the weight stabilizes, and the battery cell weight value M0 is read.

[0284] Energy density calculation: the battery monomer discharge energy E0 / battery monomer weight M0 is the energy density of the battery monomer.

[0285] 3) Battery 40% SOC discharge time test

[0286] Battery 40% SOC discharge time

[0287] The battery monomer was discharged at 0.33C constant current to 2.8V, and then rested for 30min; charged to 4.25V at 0.33C constant current and then to 0.05C constant voltage until the voltage was stable, and then rested for 30min; discharged to 0.4C0Ah (40%) SOC at 0.33C constant current, and then rested for 60min; discharged to 2.8V at 4.5C constant current, and then recorded the discharge time.

[0288] 4) Cycle performance test

[0289] The secondary batteries prepared from each example and comparative example were charged at 0.5C rate constant current to the charge cut-off voltage 4.25V, and then charged at constant voltage until the current was less than or equal to 0.05C, and then rested for 5min, and then discharged at 0.33C rate constant current to the discharge cut-off voltage 2.5V, and then rested for 5min, which was one charge-discharge cycle. The batteries were tested by the above method for cycle charge-discharge until the battery capacity was attenuated to 80%. At this time, the cycle number was the cycle life of the battery at 25°C.

[0290] III. Analysis of test results of each example and comparative example

[0291] The batteries of each example and comparative example were prepared according to the above method, and each performance parameter was measured, and the results are shown in Table 1, Table 2 and Table 3 below.

[0292] Table 1

[0293]

[0294] Table 2

[0295]

[0296] Table 3

[0297]

[0298] According to the above results, the positive active material in Examples 1-30 has the following general formula: Li a Ni x M1 y Mnz M2 1-x-y-z O2, wherein M1, M2 each independently comprises one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, Nb, 0.8≤a≤1.2, 0.55≤x<1, 0

[0299] The morphology of the positive electrode active material in Example 3 was tested by scanning electron microscope (SEM), and the test results are shown in FIG. 3. Figure 1 As can be seen from the figure, the secondary particles include secondary pores formed by the space between the primary particles. The secondary particles of the positive electrode active material in Examples 1-30 include secondary pores formed by the space between the primary particles, and the inner diameter of the secondary pores is 0.1 μm-2 μm.

[0300] As can be seen from the comparison of Examples 1-21, Examples 24-27 and Comparative Example 1, Example 28 and Comparative Example 4, Example 29 and Comparative Example 7, and Example 30 and Comparative Example 8, the secondary particles of the positive electrode active material in the examples of the present application include secondary pores formed by the space between the primary particles, which is beneficial to improve the energy density, discharge time and cycle performance of the battery.

[0301] As can be seen from the comparison of Examples 3-21 and Comparative Examples 2-3, and Example 28 and Comparative Examples 5-6, in the examples of the present application, the inner diameter of the secondary pores is controlled to be 0.1 μm-2 μm, which is beneficial to further improve the energy density and cycle performance of the battery. As can be seen from the comparison of Examples 1, 3-5 and Example 2, further controlling the inner diameter of the secondary pores in the positive electrode active material to be 0.2 μm-1 μm is beneficial to simultaneously consider the energy density, discharge time and cycle performance of the battery.

[0302] As can be seen from Examples 3, 8-11, controlling the porosity of the positive electrode active material to be 0.1%-12% enables the battery to have high energy density, long discharge time and excellent cycle performance. As can be seen from the comparison of Examples 3, 9-11 and Example 8, further controlling the porosity of the positive electrode active material to be 0.1%-10% is beneficial to further improve the energy density and cycle performance of the battery.

[0303] As can be seen from Examples 3, 12-15, the average particle size D of the primary particles is controlled to be 100-800 nm, so that the battery has high energy density, long discharge time and excellent cycle performance. As can be seen from the comparison between Examples 3, 12-14 and Example 15, further controlling the average particle size D of the primary particles to be 100-500 nm is beneficial to further improving the energy density, discharge time and cycle performance of the battery.

[0304] As can be seen from Examples 3, 16-19, the Dv50 of the secondary particles is controlled to be 3-12 μm, so that the battery has high energy density, long discharge time and excellent cycle performance. As can be seen from the comparison between Examples 3, 16-18 and Example 19, further controlling the Dv50 of the secondary particles to be 3-11 μm is beneficial to further improving the cycle performance of the battery.

[0305] As can be seen from Examples 3, 20-21, the SPAN value of the secondary particles is controlled to be 0.8-1.5, so that the battery has high energy density, long discharge time and excellent cycle performance.

[0306] As can be seen from Examples 3, 22-23, the thickness of the positive electrode film layer is controlled to be 200-400 μm, so that the battery has high energy density, long discharge time and excellent cycle performance.

[0307] As can be seen from the comparison between Example 3 and Example 1, the primary particles have primary pores, which are beneficial to improving the energy density, discharge time and cycle performance of the battery. As can be seen from Examples 3, 24-27, the inner diameter of the primary pores of the primary particles is controlled to be 0.05-0.6 μm, so that the battery has high energy density, long discharge time and excellent cycle performance. As can be seen from the comparison between Examples 3, 25-26 and Examples 24, 27, further controlling the inner diameter of the primary pores of the primary particles to be 0.08-0.2 μm is beneficial to further improving the energy density, discharge time and cycle performance of the battery.

[0308] It should be noted that the present application is not limited to the above-described embodiments. The above-described embodiments are only examples, and embodiments having substantially the same configuration and playing the same role and effect as the technical idea within the scope of the technical solutions of the present application are all included in the technical scope of the present application. In addition, within the scope of the main idea of the present application, various modifications that can be thought of by those skilled in the art, and other modes constructed by combining part of the configuration elements in the embodiments are also included in the scope of the present application.

Claims

1. A positive electrode active material, characterized by, The positive electrode active material has the following general formula: Li a Ni x M1 y Mn z M2 1-x-y-z O2, Wherein, M1 and M2 each independently include one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb, 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, and 0≤z≤0.2; The positive electrode active material exists in the form of secondary particles formed by the aggregation of primary particles. The secondary particles include secondary pores formed by the space between the primary particles, and the inner diameter of the secondary pores is 0.1μm~2μm. At least a portion of the primary particles also include primary pores, and the inner diameter of the primary pores is 0.05μm~0.6μm.

2. The positive electrode active material according to claim 1, characterized by The ratio of the closest distance between the secondary hole and the surface of the secondary particle to the Dv50 of the secondary particle is 1 / 5 to 3 / 5.

3. The positive electrode active material according to claim 1, characterized by The ratio of the closest distance between the secondary hole and the surface of the secondary particle to the Dv50 of the secondary particle is 3 / 10 to 1 / 2.

4. The positive electrode active material according to claim 1, characterized by The inner diameter of the primary hole is 0.08μm~0.2μm.

5. The positive electrode active material according to claim 1, characterized by 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, 0≤z≤0.

1.

6. The positive electrode active material according to claim 1, characterized by 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.

05.

7. The positive electrode active material according to claim 1, characterized by The inner diameter of the secondary hole is 0.2μm~1μm.

8. The positive electrode active material according to claim 1, characterized by The porosity of the positive electrode active material is 0.1%~12%.

9. The positive electrode active material according to claim 1, characterized by The porosity of the positive electrode active material is 0.1%~10%.

10. The positive electrode active material according to any one of claims 1 to 9, characterized by, The average particle size D of the primary particles is 100nm~800nm.

11. The positive electrode active material according to any one of claims 1 to 9, characterized by The average particle size D of the primary particles is 100nm~500nm.

12. The positive electrode active material according to any one of claims 1 to 9, characterized by, The Dv50 of the secondary particles is 3μm~12μm.

13. The positive electrode active material according to any one of claims 1 to 9, characterized by, The Dv50 of the secondary particles is 3μm~11μm.

14. The positive electrode active material according to any one of claims 1 to 9, characterized by, The SPAN value of the secondary particles is 0.8~1.

5.

15. The positive electrode active material according to any one of claims 1 to 9, characterized by, The SPAN value of the secondary particles is 0.8~1.

3.

16. The positive electrode active material according to any one of claims 1 to 9, characterized by, The area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material is 200 μm 2 ~300 μm 2 .

17. The positive electrode active material according to any one of claims 1 to 9, characterized by, The area of the (010) crystal face in the XRD diffraction spectrum of the positive electrode active material is 250 μm 2 280 μm 2 .

18. A method for producing a positive electrode active material, characterized by, include: A precursor is prepared by mixing a first raw material containing a nickel source and a manganese source with a complexing agent and a precipitant to carry out a co-precipitation reaction. The first raw material also includes an M1 source. The positive electrode active material is prepared by calcining a mixture of a precursor and a lithium source; or The precursor is mixed with a lithium source and calcined, then mixed with an M2 source and calcined again to prepare the positive electrode active material. The positive electrode active material has the following general formula: Li a Ni x M1 y Mn z M2 1-x-y-z O2, Wherein, M1 and M2 each independently include one or more of Co, Al, B, Zr, Sr, Y, Sb, W, Ti, Mg, and Nb, with 0.8≤a≤1.2, 0.55≤x<1, 0<y≤0.25, and 0≤z≤0.2; the positive electrode active material exists in the form of secondary particles formed by the aggregation of primary particles, the secondary particles including secondary pores formed by the space between the primary particles, and the inner diameter of the secondary pores is 0.1μm~2μm.

19. The method of claim 18, wherein, 0.8≤a≤1.2, 0.8≤x<1.0, 0<y≤0.1, 0≤z≤0.

1.

20. The method of claim 18, wherein, 0.8≤a≤1.2, 0.85≤x≤0.96, 0<y≤0.02, 0≤z≤0.

05.

21. The method of manufacturing according to claim 18 or 19, wherein, The precursor exists in the form of precursor secondary particles formed by aggregation of precursor primary particles; The average particle size D' of the precursor primary particles is 150 nm to 500 nm; The median particle size Dv50' of the precursor secondary particles is 3 µm to 12 µm.

22. The method of claim 21, wherein, The average particle size D' of the precursor primary particles is 200 nm to 300 nm.

23. The preparation method according to claim 21, characterized in that, The median particle size Dv50' of the precursor secondary particles is 6 µm to 8 µm.

24. The method of claim 18 or 19, wherein, The specific surface area of the precursor is 2 m 2 / g ~ 40 m 2 / g.

25. The method of manufacturing according to claim 18 or 19, wherein, The specific surface area of the precursor is 25 m 2 / g ~ 35 m 2 / g.

26. The method of claim 24, wherein, The molar concentration of the manganese element in the solution obtained by mixing the first raw material containing a nickel source and a manganese source with the complexing agent and the precipitating agent is 0.02 mol / L to 1.5 mol / L.

27. The preparation method according to claim 24, characterized in that, The molar concentration of the manganese element in the solution obtained by mixing the first raw material containing a nickel source and a manganese source with the complexing agent and the precipitating agent is 0.05 mol / L to 1.2 mol / L.

28. The method of claim 18 or 19, wherein, The pH value of the co-precipitation reaction is 9 to 12.

29. The method of manufacturing according to claim 18 or 19, wherein, The pH value of the co-precipitation reaction is 9 to 11.

30. The method of claim 18 or 19, wherein, The reaction temperature of the co-precipitation reaction is 50°C to 80°C.

31. The method of manufacturing according to claim 18 or 19, wherein, The reaction temperature of the co-precipitation reaction is 55°C to 75°C.

32. The method of claim 18 or 19, wherein, The reaction time of the co-precipitation reaction is 6 h to 10 h.

33. The method of manufacturing according to claim 18 or 19, wherein, The reaction time of the co-precipitation reaction is 6.5 h to 9.5 h.

34. The method of manufacturing according to claim 18 or 19, wherein, The stirring speed of the co-precipitation reaction is 200 rpm to 500 rpm.

35. The method of manufacturing according to claim 18 or 19, wherein, The stirring speed of the co-precipitation reaction is 230 rpm to 300 rpm.

36. A positive electrode sheet characterized by comprising: The positive electrode tab comprises a positive electrode current collector and a positive electrode film layer arranged on at least one surface of the positive electrode current collector, and the positive electrode film layer comprises the positive electrode active material of any one of claims 1 to 17 or the positive electrode active material prepared by the preparation method of any one of claims 18 to 35.

37. The cathode sheet of claim 36, wherein, The thickness of the positive electrode film layer is 200 µm to 400 µm.

38. The cathode sheet of claim 36, wherein, The thickness of the positive electrode film layer is 200 µm to 300 µm.

39. A secondary battery, characterized by comprising: The positive electrode tab of claim 36 is included.

40. An electrical device, comprising: The secondary battery of claim 39 is included.

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