Secondary battery and electric device

Abstract

The invention provides a secondary battery and an electric device. The secondary battery comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, the positive electrode comprises a ternary positive electrode material, the ternary positive electrode material is a polycrystalline nickel-cobalt-manganese positive electrode material and comprises secondary particles composed of primary particles, the secondary particles are of a core-shell structure, the core part of each secondary particle is composed of the primary particles which are arranged in a radial mode and grow in a radial long-strip mode, and the shell part of each secondary particle is of a core-shell structure. The shell part is composed of primary particles which are arranged disorderly; the shell part contains at least one element selected from zirconium, titanium and aluminum; the electrolyte includes an acidic component. Through the composition, the transmission efficiency of lithium ions can be improved, and acidic components in the electrolyte are not easy to permeate into particles, so that the use stability of the positive electrode material is effectively improved, and the specific capacity of the secondary battery can be further improved on the premise of ensuring the capacity retention ratio of the secondary battery.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a secondary battery and an electrical device. Background Art

[0002] In recent years, as the application scope of secondary batteries becomes wider and wider, secondary batteries are widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields. As secondary batteries have made great progress, higher requirements have been put forward for their energy density, cycle performance and service life. For the positive electrode materials used in secondary batteries, high energy density, high lithium ion transmission efficiency, high stability, etc. are required, but the current positive electrode materials still need to be improved. Summary of the invention

[0003] The present application is made in view of the above-mentioned technical problems, and its purpose is to provide a positive electrode material, which shortens the transmission distance of lithium ions inside the material by improving its structure, thereby improving the lithium ion transmission efficiency; and the outside of the positive electrode material has a corrosion-resistant layer, thereby improving the stability of use and improving the specific capacity and capacity retention rate of the secondary battery using the positive electrode material.

[0004] In order to achieve the above-mentioned objectives, the present application provides the following positive electrode material, a method for manufacturing the same, and a secondary battery, a battery module, a battery pack, and an electrical device using the positive electrode material.

[0005] The first aspect of the present application provides a ternary positive electrode material, wherein the ternary positive electrode material is a polycrystalline nickel-cobalt-manganese positive electrode material, and the ternary positive electrode material includes secondary particles composed of primary particles, and the secondary particles have a core-shell structure, wherein the core portion is composed of primary particles that grow radially in long radial strips, and the shell portion is composed of primary particles that are arranged in a disordered manner.

[0006] Therefore, the present application sets the ternary positive electrode material as secondary particles with the above-mentioned core-shell structure, and utilizes the radially arranged primary particles growing in radially long strips in the core portion of the core-shell structure to shorten the path (grain boundary of the primary particles) that lithium ions travel when being transmitted inside the secondary particles, thereby improving the transmission efficiency of lithium ions, and such a structure can also effectively improve the volume change during the insertion / extraction of lithium ions; in addition, because the shell portion of the core-shell structure is composed of disorderly arranged primary particles, the radial structure of the core portion is wrapped from the outside, reducing the disintegration caused by the relatively weak bonding force between the primary particles in the internal radial structure, so that the stability of the material can be guaranteed during the cycle of lithium ion insertion / extraction.

[0007] In any embodiment, the core portion contains at least one element selected from boron or phosphorus, and may optionally contain boron. By doping the core portion with any of boron or phosphorus, it is beneficial to induce a certain crystal plane to preferentially grow during the grain growth of the core portion of the ternary positive electrode material, forming primary particles growing in a long strip shape, and these primary particles form a radially arranged core portion.

[0008] In any embodiment, the doping concentration of at least one element selected from boron or phosphorus in the core is 100-10000ppm, and can be optionally 500-3000ppm, which is conducive to inducing a certain crystal face to preferentially grow when the core grains of the ternary positive electrode material grow, forming a core composed of primary particles that grow in radial strips and are arranged radially. On the other hand, boron or phosphorus cannot be used as an active ingredient in the positive electrode material. Therefore, by being within the above range, it can be ensured that the capacity of the secondary battery will not decrease.

[0009] In any embodiment, the shell contains at least one element selected from zirconium, titanium, and aluminum, and may contain zirconium. Thus, the primary particles in the shell of the ternary positive electrode material can grow disorderly, thereby keeping the positive electrode material from being easily disintegrated during the cycle of lithium ion insertion / extraction, and further doping the ternary positive electrode material with zirconium, titanium, and aluminum can alleviate the side reaction between the surface of the positive electrode material and the electrolyte, thereby improving the corrosion resistance of the positive electrode material and further improving the stability of the material in use.

[0010] In any embodiment, the doping concentration of at least one element selected from zirconium, titanium, and aluminum in the shell portion is 200-10000ppm, and can be optionally 1000-5000ppm. This is conducive to improving the corrosion resistance of the surface of the positive electrode material and improving the stability of the material. On the other hand, zirconium, titanium, and aluminum cannot be used as or active ingredients in the positive electrode material, so the above-mentioned doping concentration range can take into account the charge and discharge capacity and cycle stability of the material.

[0011] In any embodiment, the average diameter of the core is 3-15 μm, thereby maintaining the core structure stable and preventing the secondary particles of the positive electrode material from cracking.

[0012] In any embodiment, the average thickness of the shell portion is 0.5 μm or more, thereby maintaining the core-shell structure of the positive electrode material secondary particles stable and not prone to cracking.

[0013] In any embodiment, the average particle size of the secondary particles of the ternary positive electrode material is 3.5-18 μm, thereby maintaining the core-shell structure of the secondary particles of the positive electrode material stable and not prone to cracking.

[0014] The second aspect of the present application also provides a method for manufacturing a ternary positive electrode material, wherein the ternary positive electrode material is a nickel-cobalt-manganese positive electrode material.

[0015] The manufacturing method comprises the following steps:

[0016] Step 1: Mix nickel salt, cobalt salt, manganese salt and water to form a first mixed solution;

[0017] Step 2: preparing a second solution and a third solution respectively, wherein the second solution contains boron and / or phosphorus; and the third solution contains at least one element selected from zirconium, titanium, and aluminum.

[0018] Step 3: continuously supplying the first mixed solution and the second solution as well as the precipitant and / or the complexing agent into the reaction kettle, and controlling the temperature in the reaction kettle to react to obtain a first precursor product;

[0019] Step 4: Switch the supply source of the second solution in step 3 to the supply source of the third solution, continuously supply the first mixed solution and the third solution and the precipitant and / or the complexing agent to the reactor, and continue the reaction to obtain a second precursor product;

[0020] Step 5: aging, washing, and solid-liquid separation of the precipitate containing the second precursor product to obtain a doped nickel-cobalt-manganese precursor;

[0021] Step 6: Evenly mix the doped nickel-cobalt-manganese precursor and the lithium source, and then calcine at high temperature in an oxygen atmosphere to obtain a ternary positive electrode material.

[0022] Thus, a ternary positive electrode material having a core-shell structure doped with boron and / or phosphorus in the core and at least one element selected from zirconium, titanium, and aluminum in the shell can be prepared. By doping boron and / or phosphorus in the core growth process of the ternary positive electrode material particles, a certain crystal plane can be induced to preferentially grow when the primary particles in the core grow, forming a core composed of primary particles that grow radially in long strips in radial arrangement, and such a core is conducive to improving the transmission efficiency of lithium ions. By doping at least one element selected from zirconium, titanium, and aluminum in the shell growth process of the ternary positive electrode material particles, the primary particles in the shell of the ternary positive electrode material particles can grow disorderly, thereby keeping the positive electrode material from being easily disintegrated during the cycle of lithium ion insertion / extraction, and the doping of zirconium, titanium, and aluminum can also alleviate the side reaction between the surface of the positive electrode material and the electrolyte, thereby improving the corrosion resistance of the positive electrode material and further improving the stability of the material in use.

[0023] In any embodiment, in step 3, the reaction time is controlled so that the average particle size of the particles in the first precursor product is 3-15 μm, thereby maintaining a stable core structure and preventing the secondary particles of the positive electrode material from cracking.

[0024] In any embodiment, in step 4, the reaction time is controlled so that the average particle size of the particles in the second precursor product is 3.5-18 μm. Thus, the core-shell structure of the secondary particles of the positive electrode material can be kept stable and not prone to cracking.

[0025] In any embodiment, in the step 3, the supply speed of the first mixed solution and the second solution is controlled so that the molar ratio of the content of the boron element and / or the phosphorus element in the supplied second solution to the total content of the nickel, cobalt and manganese elements in the first mixed solution is 1:100-1:1000;

[0026] In any embodiment, in the step four, the supply rates of the first mixed solution and the third solution are controlled so that the molar ratio of the content of zirconium and / or titanium and / or aluminum in the supplied third solution to the total content of nickel, cobalt and manganese in the first mixed solution is 1:100-1:1000.

[0027] Thus, a core-shell structure can be formed in the obtained positive electrode material, in which the core is doped with boron and / or phosphorus and the shell is doped with at least one element selected from zirconium, titanium, and aluminum, so that the core with radially arranged primary particles growing in a radially elongated strip shape and the shell with disorderly growing primary particles can be obtained. By supplying the second solution and the third solution, the lithium ion transmission efficiency of the secondary battery, the stability of the positive electrode material, and the charge and discharge capacity of the secondary battery can be improved.

[0028] In any embodiment, in step three and step four, the temperature in the reactor is controlled at 50-70°C, thereby making it easy to incorporate boron and / or phosphorus elements into the core of the ternary positive electrode material precursor, and to incorporate zirconium, titanium and / or aluminum elements into the shell of the ternary positive electrode material precursor.

[0029] In any embodiment, in step six, the calcination temperature is 700-1000°C, thereby calcining the core-shell structured ternary positive electrode material precursor into a ternary positive electrode material in which the core is doped with boron and / or phosphorus and the shell is doped with at least one element selected from zirconium, titanium, and aluminum.

[0030] In any embodiment, the nickel salt, cobalt salt, and manganese salt are respectively selected from at least one of sulfate, nitrate, acetate, and hydrochloride; the boron element is derived from at least one selected from boric acid, boron trioxide, boron trifluoride, and monofluoroboric acid; the phosphorus element is derived from at least one selected from sodium phosphate, sodium dihydrogen phosphate, potassium phosphate, ammonium phosphate, and ammonium dihydrogen phosphate; the zirconium element is derived from at least one selected from zirconium chloride, zirconium oxychloride, zirconium acetate, and zirconium citrate; the titanium element is derived from at least one selected from titanium trichloride, titanium tetrachloride, and titanium nitrate; the aluminum element is derived from at least one selected from aluminum sulfate, sodium aluminate, aluminum chloride, and aluminum nitrate; the lithium source is derived from at least one selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium fluoride, lithium phosphate, lithium acetate, lithium formate, lithium citrate, and n-butyl lithium. Thus, it is easy to add boron and / or phosphorus elements into the core of the ternary positive electrode material precursor at a reaction temperature of 50-70°C, and to add zirconium, titanium and / or aluminum elements into the shell of the ternary positive electrode material precursor, and further to bake at a baking temperature of 700-1000°C to obtain a nickel-cobalt-manganese ternary positive electrode material in which the core is doped with boron and / or phosphorus elements and the shell is doped with zirconium, titanium and / or aluminum elements, and other impurity elements are not excessively contained.

[0031] In any embodiment, in the first mixed solution, the molar ratio of nickel, cobalt and manganese is x:y:z, wherein 0.5≤x≤1, 0≤y≤0.5, 0≤z≤0.5, and x+y+z=1. Thus, the nickel content in the obtained ternary positive electrode material is relatively high, which effectively improves the specific capacity of the ternary positive electrode material.

[0032] The third aspect of the present application also provides a secondary battery, comprising the positive electrode active material of the first aspect of the present application or the positive electrode active material prepared according to the manufacturing method of the second aspect of the present application.

[0033] A fourth aspect of the present application provides a battery module, comprising the secondary battery of the third aspect of the present application.

[0034] A fifth aspect of the present application provides a battery pack comprising the battery module of the fourth aspect of the present application.

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

[0036] Therefore, the present application can provide a secondary battery that improves lithium ion transmission efficiency and can maintain the stability of the positive electrode material, while improving both specific capacity and capacity retention rate, as well as a battery pack, a battery module, and an electrical device including the same. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the general structure of the secondary particles of the ternary positive electrode material according to one embodiment of the present application.

[0038] Figure 2 This is a scanning electron microscope image of the ternary positive electrode material precursor particles (after grinding) of Example 4.

[0039] Figure 3 This is a scanning electron microscope image of the secondary particles of the ternary positive electrode material precursor particles of Comparative Example 1.

[0040] Figure 4 This is a scanning electron microscope image of the secondary particles of the ternary positive electrode material precursor particles of Comparative Example 4.

[0041] Figure 5 is a schematic diagram of a secondary battery according to one embodiment of the present application.

[0042] Figure 6 yes Figure 5 An exploded view of a secondary battery according to an embodiment of the present application is shown.

[0043] Figure 7 is a schematic diagram of a battery module according to an embodiment of the present application.

[0044] Figure 8 It is a schematic diagram of a battery pack according to one embodiment of the present application.

[0045] Fig. 9 yes Figure 8 An exploded view of a battery pack according to an embodiment of the present application is shown.

[0046] Fig.10 FIG. 1 is a schematic diagram of an electric device using a secondary battery according to an embodiment of the present application as a power source.

[0047] Description of reference numerals:

[0048] 1 battery pack; 2 upper box; 3 lower box; 4 battery module; 5 secondary battery; 51 shell; 52 electrode assembly; 53 top cover assembly. DETAILED DESCRIPTION

[0049] Below, the embodiments of the positive electrode active material and its manufacturing method, positive electrode sheet, secondary battery, battery module, battery pack and electric device of the present application are specifically disclosed with appropriate reference to the drawings. However, there are cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0050] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0051] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0052] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0053] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0054] If there is no special explanation, the "include" and "comprising" mentioned in this application represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0055] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0056]

Ternary cathode material

[0057] In one embodiment of the present application, a ternary positive electrode material is provided, which is a polycrystalline nickel-cobalt-manganese positive electrode material. The ternary positive electrode material includes secondary particles composed of primary particles. Figure 1 The structure is schematically shown in FIG. The secondary particles are core-shell structures, wherein the core portion is composed of primary particles arranged radially and growing in radially long strips, and the shell portion is composed of primary particles arranged in a disordered manner.

[0058] Although the mechanism is not yet clear, the applicant unexpectedly discovered that the present application can improve the lithium ion transmission efficiency, charge and discharge capacity and usage stability of the secondary battery through the above-mentioned ternary positive electrode material with a core-shell structure, thereby improving the specific capacity and capacity retention rate of the secondary battery.

[0059] During the charge and discharge process, the traditional polycrystalline ternary cathode material will produce Ni 4+ etc., which are prone to side reactions with the electrolyte, resulting in irreversible phase changes in the positive electrode material, etc., accelerating capacity decay and reducing service life. In addition, during the charge and discharge process, the lithium ion deintercalation process will also cause the unit cell volume of the positive electrode material to change cyclically. After repeated cycles of charge and discharge, the stress accumulated by the volume expansion and contraction of the positive electrode material will be released at the grain boundaries of the particles, causing secondary particles to crack, exposing fresh surfaces and then side reactions, resulting in secondary particles pulverizing and failing. In addition, traditional polycrystalline ternary positive electrode materials are generally composed of disordered primary particles to form secondary particles. Therefore, there are many grain boundaries between the primary particles, and the transfer of lithium ions from the secondary particles is a tortuous path, which reduces the lithium ion transmission efficiency.

[0060] The ternary positive electrode material of the present application can alleviate the above problems from a structural perspective. First, its core is composed of primary particles that are radially arranged and grow in radial strips, so that the transmission distance of lithium ions inside it (grain boundaries between primary particles) can be shortened, and the lithium ion transmission efficiency can be improved; and such a structure can also effectively improve the volume change during the insertion / extraction of lithium ions, thereby alleviating the cumulative stress of the positive electrode material during the charge and discharge cycle, so that it will not easily cause the secondary particles of the positive electrode material to crack, and improve the use stability of the positive electrode material. Secondly, its exterior has a disordered arrangement structure, so it can wrap the internal radial structure from the outside, reduce the disintegration caused by the relatively weak bonding force between the primary particles in the internal radial structure, and thus ensure the use stability of the material. In addition, the outer shell of the ternary positive electrode material of the present application is also doped with corrosion-resistant components, so that the acidic components in the electrolyte are not easy to penetrate into the interior of the particles, thereby further improving the use stability of the positive electrode material.

[0061] In some embodiments, the core of the above-mentioned ternary positive electrode material contains at least one element of boron or phosphorus, and may optionally contain boron. By doping the core with any of boron or phosphorus, it is beneficial to induce a certain crystal plane to preferentially grow during the primary grain growth of the core of the ternary positive electrode material, forming a core composed of primary particles arranged radially and growing in radial strips. Specifically, by doping the core with boron or phosphorus, the surface energy of the (003) crystal plane of the ternary positive electrode material can be reduced, inducing the preferential growth of the (003) crystal plane, thereby forming a core composed of long primary particles preferentially grown from the (003) crystal plane arranged radially.

[0062] In some embodiments, the doping concentration of at least one element selected from boron or phosphorus in the core portion is 100-10000ppm, optionally 500-3000ppm, thereby inducing preferential growth of a certain crystal plane during the primary grain growth of the core portion of the ternary positive electrode material, forming radial primary particles, thereby forming a core portion in which the primary particles are radially arranged in a long strip. In addition, when the doping concentration is too high, the capacity of the secondary battery will be too low because the doping element cannot play the role of the active ingredient. Therefore, by controlling the doping concentration of boron or phosphorus in the core portion within the above range, the lithium ion conduction efficiency and charge and discharge capacity of the ternary positive electrode material can be taken into account.

[0063] In some embodiments, the shell contains at least one element selected from zirconium, titanium, and aluminum, and may optionally contain zirconium. Thus, the primary particles in the shell of the ternary positive electrode material can grow disorderly, enveloping the internal radial structure, reducing the disintegration caused by the relatively weak bonding force between the primary particles in the internal radial structure, and further doping the ternary positive electrode material with zirconium, titanium, and aluminum can alleviate the side reaction between the surface of the positive electrode material and the electrolyte, thereby improving the corrosion resistance of the positive electrode material and further improving the stability of the material in use.

[0064] In some embodiments, the doping concentration of at least one element selected from zirconium, titanium, and aluminum in the shell is 200-10000ppm, and can be optionally 1000-5000ppm. The doping of zirconium, titanium, and aluminum to the ternary positive electrode material can improve its corrosion resistance, but since zirconium, titanium, and aluminum cannot be used as or active components in the positive electrode material, if the doping concentration is too low, the corrosion resistance is insufficient, and if it is too high, it will affect the proportion of active components in the positive electrode and reduce the charge and discharge capacity. Therefore, the above doping concentration range can take into account both the charge and discharge capacity and the cycle stability of the material.

[0065] In some embodiments, the average diameter of the core is 3-15 μm, thereby maintaining the stability of the core structure and preventing the secondary particles of the positive electrode material from cracking. The average thickness of the shell is greater than 0.5 μm.

[0066] In some embodiments, the average particle size of the secondary particles of the ternary positive electrode material is 3.5-18 μm, thereby maintaining the core-shell structure of the secondary particles of the positive electrode material stable and not prone to cracking.

[0067] In some embodiments, in the polycrystalline nickel-cobalt-manganese ternary positive electrode material, optionally, the Ni content is at least one of the Co content and the Mn content, thereby obtaining a larger capacity at a lower cost. The ternary positive electrode material may include, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 (Also referred to as NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O 2 (Also referred to as NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O 2 (Also referred to as NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O 2 (Also referred to as NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O 2 (Also referred to as NCM 811 ) and at least one of lithium nickel cobalt manganese oxides and modified compounds thereof. Additive elements such as Mg, Fe, W, and F may be appropriately contained within a range that does not affect the growth of the core and shell structures.

[0068] [Manufacturing method of ternary positive electrode material]

[0069] In one embodiment of the present application, a method for manufacturing the above-mentioned ternary positive electrode material is proposed, and the manufacturing method comprises the following steps:

[0070] Step 1: Mix nickel salt, cobalt salt, manganese salt and water to form a first mixed solution;

[0071] Step 2: preparing a second solution and a third solution respectively, wherein the second solution contains boron and / or phosphorus; and the third solution contains at least one element selected from zirconium, titanium, and aluminum;

[0072] Step 3: continuously supplying the first mixed solution and the second solution as well as the precipitant and / or the complexing agent into the reaction kettle, and controlling the temperature in the reaction kettle to react to obtain a first precursor product;

[0073] Step 4: Switch the supply source of the second solution in step 3 to the supply source of the third solution, continuously supply the first mixed solution and the third solution and the precipitant and / or the complexing agent to the reactor, and continue the reaction to obtain a second precursor product;

[0074] Step 5: aging, washing, and solid-liquid separation of the precipitate containing the second precursor product to obtain a doped nickel-cobalt-manganese precursor;

[0075] Step 6: Evenly mix the doped nickel-cobalt-manganese precursor and the lithium source and then calcine at high temperature in an oxygen atmosphere to obtain a ternary positive electrode material.

[0076] In some embodiments, the nickel salt, cobalt salt, and manganese salt used in the configuration of the first mixed solution are at least one of water-soluble salts selected from sulfates, nitrates, acetates, hydrochlorides, etc. These salts are dissolved in water to form a first mixed solution, wherein the molar ratio of nickel ions, cobalt ions, and manganese ions is controlled to be x:y:z, 0.5≤x≤1, 0<y≤0.5, 0<z≤0.5, x+y+z=1. By increasing the nickel ion content, the specific capacity of the ternary positive electrode material can be increased. In addition, in the mixed salt solution, the total concentration of nickel, cobalt, and manganese is 1-3 mol / L.

[0077] In some embodiments, the boron element in the second solution is derived from at least one of water-soluble fluorine-containing compounds selected from boric acid, boron trioxide, boron trifluoride, monofluoroboric acid, etc.; the phosphorus element is derived from at least one of water-soluble phosphorus-containing compounds selected from sodium phosphate, sodium dihydrogen phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, etc. From the perspective of effective doping and facilitating the radial growth of radially elongated primary particles, the total concentration of boron and / or phosphorus in the second solution is generally adjusted to 0.1-1 mol / L.

[0078] In some embodiments, the zirconium element in the third solution is derived from at least one water-soluble zirconium salt selected from zirconium chloride, zirconium oxychloride, zirconium acetate, etc.; the titanium element is derived from titanic acid; and the aluminum element is derived from at least one water-soluble aluminum salt such as aluminum sulfate, sodium metaaluminate, aluminum chloride, aluminum nitrate, etc. From the perspective of effective doping and improved corrosion resistance, the total concentration of zirconium, titanium, and aluminum in the third solution is generally adjusted to 0.1-1 mol / L.

[0079] In some embodiments, before the first mixed solution and the second solution are added to the reactor for reaction, the reaction environment in the reactor is adjusted to 50-70°C under normal pressure and maintained. In addition, in step three, while continuously adding the first mixed solution and the second solution as needed, a precipitant and / or a complexing agent are added from different feed ports. Precipitants include sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate, etc., and sodium hydroxide is preferred from a cost perspective; complexing agents include ammonia water, ammonium chloride, ammonium nitrate, ammonium sulfate, etc., and ammonia water is preferred from a cost perspective. From the perspective of being conducive to doping and facilitating the radial growth of radially elongated primary particles, in step three, the supply rate of the first mixed solution and the second solution is controlled so that the molar ratio of the total amount of boron and phosphorus added to the nickel, cobalt and manganese elements is 1:100-1:1000, and can be optionally 1:100-1:500.

[0080] The reaction environment of the reactor in step 4 is usually maintained as above, and can also be adjusted as needed. From the perspective of facilitating doping and improving corrosion resistance, in step 4, the supply rate of the first mixed solution and the third solution is controlled so that the molar ratio of the total addition amount of zirconium element and / or titanium element and / or aluminum element to nickel, cobalt and manganese element is 1:100-1:1000.

[0081] In step 3 and step 4, the particle size of the obtained first precursor product or the second precursor product can be monitored and controlled in real time by taking samples from the discharge port at any time to test the average particle size of the particles therein.

[0082] The lithium source used in step six is ​​derived from at least one selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium fluoride, lithium phosphate, lithium acetate, lithium formate, and lithium citrate. The lithium source can be in the form of particles, and its particle size can be 300-400 μm. The second precursor product and the particles containing the lithium source are mixed in a molar ratio of nickel, cobalt, manganese and lithium elements of 1:1.03-1:1.2, and calcined at a calcination temperature of 700-1000°C in an oxygen atmosphere for 6-15 hours to obtain a nickel, cobalt, and manganese ternary positive electrode material doped with boron and / or phosphorus in the core and zirconium, titanium and / or aluminum in the shell.

[0083]

Secondary battery

[0084] In one embodiment of the present application, a secondary battery is provided.

[0085] Generally, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the battery charging and discharging process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing ions to pass through.

[0086] [Positive electrode]

[0087] The positive electrode sheet includes 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 includes the positive electrode active material of the first aspect of the present application.

[0088] As an example, the positive electrode current collector has two surfaces opposite to each other in its thickness direction, and the positive electrode film layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.

[0089] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0090] In some embodiments, the positive electrode active material may also include a portion of other positive electrode active materials for batteries known in the art, for example, lithium cobalt oxide (such as LiCoO 2 ), lithium nickel oxide (such as LiNiO 2 ), lithium manganese oxide (such as LiMnO 2 、LiMn 2 O 4 ), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, or their modified compounds, etc.

[0091] In some embodiments, the positive electrode film layer may further optionally include a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0092] In some embodiments, the positive electrode film layer may further include a conductive agent, which may include, for example, at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0093] In some embodiments, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry; the positive electrode slurry is coated on the positive electrode collector, and after drying, cold pressing and other processes, the positive electrode sheet can be obtained.

[0094] [Negative electrode]

[0095] The negative electrode sheet includes a negative electrode current collector and a negative electrode film layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode film layer includes a negative electrode active material.

[0096] As an example, the negative electrode current collector has two surfaces opposite to each other in its thickness direction, and the negative electrode film layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0097] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0098] In some embodiments, the negative electrode active material may adopt the negative electrode active material for the battery known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0099] In some embodiments, the negative electrode film layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0100] In some embodiments, the negative electrode film layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.

[0101] In some embodiments, the negative electrode film layer may optionally include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0102] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0103] [Electrolytes]

[0104] The electrolyte plays the role of conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. For example, the electrolyte can be liquid, gel or all-solid.

[0105] In some embodiments, the electrolyte is an electrolyte solution, which includes an electrolyte salt and a solvent.

[0106] In some embodiments, the electrolyte salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate, and lithium tetrafluorooxalatophosphate.

[0107] In some embodiments, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0108] In some embodiments, the electrolyte may further include additives, such as negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, additives that improve battery high or low temperature performance, etc.

[0109] [Isolation film]

[0110] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical stability and mechanical stability can be selected.

[0111] In some embodiments, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0112] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0113] In some embodiments, the secondary battery may include an outer package, which may be used to encapsulate the electrode assembly and the electrolyte.

[0114] In some embodiments, the outer packaging of the secondary battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0115] The present application has no particular limitation on the shape of the secondary battery, which may be cylindrical, square or any other shape. Figure 5 The secondary battery 5 is a square structure as an example.

[0116] In some embodiments, reference Figure 6 , the outer packaging may include a shell 51 and a cover plate 53. Among them, the shell 51 may 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 connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can form an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The electrolyte is infiltrated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.

[0117] In some embodiments, secondary batteries may be assembled into a battery module. The number of secondary batteries contained in the battery module may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery module.

[0118] Figure 7 4 is an example of a battery module. Figure 7 In the battery module 4, the plurality of secondary batteries 5 may be arranged in sequence along the length direction of the battery module 4. Of course, they may also be arranged in any other manner. Further, the plurality of secondary batteries 5 may be fixed by fasteners.

[0119] Optionally, the battery module 4 may further include a housing having a receiving space, and the plurality of secondary batteries 5 are received in the receiving space.

[0120] In some embodiments, the battery modules described above may also be assembled into a battery pack. The battery pack may contain one or more battery modules, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery pack.

[0121] Figure 8 and Fig. 9 1 is a battery pack 1 as an example. Figure 8 and Fig. 9 The battery pack 1 may include a battery box and a plurality of battery modules 4 disposed in the battery box. The battery box includes an upper box body 2 and a lower box body 3. The upper box body 2 can cover the lower box body 3 and form a closed space for accommodating the battery modules 4. The plurality of battery modules 4 can be arranged in the battery box in any manner.

[0122] In addition, the present application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in the present application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, and can also be used as an energy storage unit for the electrical device. The electrical device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.

[0123] As the electrical device, a secondary battery, a battery module or a battery pack may be selected according to its usage requirements.

[0124] Fig.10The power consumption device is taken as an example. The power consumption device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. In order to meet the high power and high energy density requirements of the power consumption device for the secondary battery, a battery pack or a battery module can be used.

[0125] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0126] Example

[0127] 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 should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0128] Example 1

[0129] The ternary positive electrode active material of Example 1 was obtained by the following steps.

[0130] Nickel sulfate, cobalt sulfate and manganese sulfate were added with water in a molar ratio of 6:2:2 to prepare a mixed salt solution with a total concentration of nickel, cobalt and manganese of 2 mol / L as the first mixed solution; boric acid and zirconium oxychloride were added with water to prepare solutions with a concentration of 0.2 mol / L as the second solution and the third solution respectively.

[0131] The first mixed solution, the second solution, a sodium hydroxide solution with a concentration of 8 mol / L and ammonia water with a mass fraction of 25% are continuously added to the reactor for the first stage growth reaction. During the reaction, the reaction temperature in the reactor is controlled to be 50°C, and the feeding rate is controlled so that the pH value of the solution is 11, the ammonia content is 7 g / L, and the molar ratio of the total content of boric acid and nickel, cobalt and manganese is controlled to be 1:10. While reacting, samples are taken from the discharge port to monitor the particle size of the product particles in the reactor. After the target particle size D50 is 8 μm, the second solution feed port is switched to the third solution feed port to carry out the second stage growth reaction. The reaction conditions, pH value and ammonia content in the reactor are kept consistent with those in the first stage. The feeding rate of the third solution is controlled so that the molar ratio of the total content of zirconium oxychloride and nickel, cobalt and manganese is 1:500, and the particle size of the product particles in the reactor is sampled from the discharge port to monitor the reaction. After the target particle size D50 is 10 μm, the reaction is terminated.

[0132] The precipitate was aged for 12 hours, washed with deionized water, solid-liquid separation was performed, and the solid was dried to obtain nickel-cobalt-manganese precursor particles with a core doped with boron and a shell doped with zirconium.

[0133] The nickel-cobalt-manganese precursor particles are mixed with lithium hydroxide in a ratio of the total molar amount of nickel-cobalt-manganese to the molar amount of lithium of 1:1.05, and calcined at 750°C for 10 hours in an oxygen atmosphere to obtain a nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide with a core-shell structure in which the core is doped with boron and the shell is doped with zirconium.

[0134] Embodiment 2-6

[0135] Except that during the first stage growth reaction, the feeding rate was controlled so that the molar ratio of boric acid to nickel-cobalt-manganese ions was the molar ratio shown in Table 1, the other conditions were the same as in Example 1, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide with a core-shell structure of Examples 2-6 was prepared.

[0136] Examples 7-10

[0137] Except that during the second stage growth reaction, the feeding rate was controlled so that the molar ratio of zirconium oxychloride to nickel cobalt manganese ions was the molar ratio shown in Table 1, the other conditions were the same as in Example 4, and the nickel cobalt manganese ternary positive electrode material lithium nickel cobalt manganese oxide with a core-shell structure of Examples 7-10 was prepared.

[0138] Examples 11-12

[0139] Except that during the first and second stage growth reaction processes, the feeding reaction time was controlled respectively to control the target particle size in the first stage and the target particle size in the second stage to be the particle size values ​​shown in Table 1, the other conditions were the same as in Example 4, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide with a core-shell structure of Examples 11-12 was prepared.

[0140] Examples 13-14

[0141] Except that the zirconium oxychloride in the third solution was replaced by titanic acid and sodium aluminate, respectively, and the feed rate in the second stage growth reaction was controlled so that the molar ratio of titanium or aluminum to the total content of nickel, cobalt and manganese was 1:500, the other conditions were the same as in Example 4, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel cobalt manganese oxide with a core-shell structure of Examples 13-14 was prepared.

[0142] Examples 15-16

[0143] Except for replacing the boric acid in the second solution with sodium dihydrogen phosphate and controlling the feed rate in the first stage growth reaction so that the molar ratio of boron to the total content of nickel, cobalt and manganese is 1:500, the other conditions are the same as in Example 13, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel cobalt manganese oxide with a core-shell structure of Example 15 is prepared.

[0144] Except for replacing the boric acid in the second solution with sodium dihydrogen phosphate and controlling the feed rate in the first stage growth reaction so that the molar ratio of boron to the total content of nickel, cobalt and manganese is 1:500, the other conditions are the same as in Example 14, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel cobalt manganese oxide with a core-shell structure of Example 16 is prepared.

[0145] Examples 17-20

[0146] Except that the titanic acid in the third solution is replaced by a mixture of zirconium oxychloride and titanic acid with a molar ratio of 1:1, a mixture of zirconium oxychloride and sodium aluminate with a molar ratio of 1:1, a mixture of titanic acid and sodium aluminate with a molar ratio of 1:1, and a mixture of zirconium oxychloride, titanic acid and sodium aluminate with a molar ratio of 1:1:1, and the feed rate in the second stage growth reaction is controlled so that the molar ratio of the total content of zirconium, titanium or aluminum to the total content of nickel, cobalt and manganese is 1:500, the other conditions are the same as in Example 15, and the nickel-cobalt-manganese ternary positive electrode material lithium nickel cobalt manganese oxide with a core-shell structure of Examples 17-20 is prepared.

[0147] Comparative Example 1

[0148] Nickel sulfate, cobalt sulfate, and manganese sulfate are added with water in a molar ratio of 6:2:2 to form a mixed salt solution with a total concentration of nickel, cobalt, and manganese of 2 mol / L, and the mixed solution, a sodium hydroxide solution with a concentration of 8 mol / L, and ammonia water with a mass fraction of 25% are continuously added to the reactor for growth reaction. During the reaction, the reaction temperature in the reactor is controlled to be 50 ° C, and the feeding rate is controlled so that the pH value of the solution is 11 and the ammonia content is 7 g / L. While reacting, samples are taken from the discharge port to monitor the particle size of the product particles in the reactor, and the reaction is terminated after the target particle size D50 is 10 μm. The precipitate is aged for 12 hours, washed with deionized water, solid-liquid separation is performed, and the solid is dried to obtain nickel-cobalt-manganese precursor particles. The nickel-cobalt-manganese precursor particles are mixed with lithium hydroxide in a molar ratio of 1:1.05, and calcined at 750 ° C for 10 hours in an oxygen atmosphere to obtain the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide of Comparative Example 1 without any doping.

[0149] Comparative Example 2

[0150] Nickel sulfate, cobalt sulfate, and manganese sulfate are added with water in a molar ratio of 6:2:2 to form a mixed salt solution with a total concentration of 2 mol / L of nickel, cobalt, and manganese, and zirconium oxychloride is added with water to form a solution with a concentration of 0.2 mol / L as a zirconium solution. The above mixed salt solution, a sodium hydroxide solution with a concentration of 8 mol / L, and ammonia water with a mass fraction of 25% are continuously added to the reactor for growth reaction. During the reaction process, the reaction temperature in the reactor is controlled to 50°C, and the feeding rate is controlled so that the pH value of the solution is 11 and the ammonia content is 7 g / L. While reacting, samples are taken from the discharge port to monitor the particle size of the product particles in the reactor. After the reaction reaches the target particle size D50 of 8 μm, a zirconium solution feed port is added to the feed port, and zirconium solution is continuously added to the reaction system. The feed rate of the zirconium solution is controlled so that the molar ratio of the total content of zirconium oxychloride to nickel, cobalt, and manganese is 1:500. After continuing to react until the target particle size D50 is 10 μm, the reaction is terminated. The precipitate was aged for 12 hours, washed with deionized water, separated from the solid and liquid, and the solid was dried to obtain nickel-cobalt-manganese precursor particles. The nickel-cobalt-manganese precursor particles were mixed with lithium hydroxide at a molar ratio of 1:1.05, and calcined at 750° C. for 10 hours in an oxygen atmosphere to obtain the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide with zirconium doped in the shell of Comparative Example 2.

[0151] Comparative Example 3

[0152] Except for controlling the feeding rate during the first stage growth reaction so that the molar ratio of boric acid to the total content of nickel, cobalt and manganese is 1:10000, other conditions are the same as those in Example 4 to obtain the nickel-cobalt-manganese ternary positive electrode material lithium nickel cobalt manganese oxide of Comparative Example 3 that is doped in two stages inside and outside.

[0153] Comparative Example 4

[0154] Except that in the preparation process of the nickel-cobalt-manganese precursor particles, the first stage growth reaction is continued until the target particle size D50 is 10 μm, and then the reaction is terminated directly without performing the second stage growth reaction, everything else is the same as Example 4 to obtain the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide of Comparative Example 4 that has been doped in one stage.

[0155] Comparative Example 5

[0156] Except that the second solution feed port is directly removed instead of switching to the third solution feed port during the transition from the first stage growth to the second stage growth, the nickel-cobalt-manganese ternary positive electrode material lithium nickel-cobalt-manganese oxide of Comparative Example 5 which is only doped in the first stage is obtained in the same manner as in Example 4.

[0157] In each experimental example, the average particle size D50 of the precursor particles in the reaction system was measured by using a Malvern 2000 (MasterSizer 2000) laser particle size analyzer according to the following procedure: take an appropriate amount of the sample to be tested, add 20 ml of deionized water, and completely disperse it by ultrasound. The dispersed sample is added dropwise to the injector of the particle size analyzer filled with deionized water and adjusted to have a light shielding degree of 10-20%, and the sample is measured according to the GB / T19077-2016 / ISO 13320:2009 standard.

[0158] The relevant experimental parameters in the manufacturing process of the positive electrode materials of the above-mentioned Examples 1-20 and Comparative Examples 1-5 are shown in the following Table 1.

[0159] Table 1:

[0160]

[0161] Morphological observation of nickel-cobalt-manganese precursor particles and nickel-cobalt-manganese ternary cathode materials

[0162] The nickel-cobalt-manganese precursor particles of Example 4 were ground and their internal morphology was observed by scanning electron microscopy (SEM) (ZEISS sigma 300). Figure 2 ), it was found that a core composed of primary particles growing in radial strips arranged in a radial manner was formed inside the particles, and a layer of randomly grown shell was wrapped around the outer shell, which was dense, neat and seamless. The internal morphology of the nickel-cobalt-manganese precursor particles of Comparative Example 1 was observed by scanning electron microscopy (SEM) ( Figure 3 ), and found that the particles were composed of primary particles that grew randomly. In addition, the internal morphology of the nickel-cobalt-manganese precursor particles of Comparative Example 4 was observed by scanning electron microscopy (SEM). Figure 4 ), it was found that the particles as a whole were composed of radially elongated primary particles that grew in an radiating manner, and their surfaces were loose, and gaps extending from the surface along the growth direction of the elongated primary particles to the inside were clearly observed. It can be seen that in Example 4 of the present invention, through the above-mentioned first-stage growth reaction, a core composed of radially elongated primary particles that grew in an radiating manner can be formed inside, and through the above-mentioned second-stage growth reaction, a shell composed of randomly grown primary particles can be wrapped outside, and through such a core-shell structure, a dense and stable nickel-cobalt-manganese precursor secondary particle can be obtained.

[0163] The nickel-cobalt-manganese ternary positive electrode materials obtained in the above-mentioned embodiments and comparative examples were observed by scanning electron microscopy (SEM) (ZEISS sigma 300) to see whether there was a radially growing core and whether the outer layer grew disorderly. The results are shown in Table 2.

[0164] In addition, the positive electrode active materials obtained in the above Examples 1-20 and Comparative Examples 1-5 were respectively prepared into secondary batteries as shown below, and performance tests were performed. The test results are shown in Table 2 below.

[0165] Preparation and performance testing of secondary batteries

[0166] 1. Preparation of positive electrode

[0167] The prepared composite material is used as the positive electrode active material, and the positive electrode active material, conductive agent carbon black, and binder polyvinylidene fluoride (PVDF) are dissolved in a solvent N-methylpyrrolidone (NMP) at a weight ratio of 97:2:1, and the mixture is fully stirred and mixed to obtain a positive electrode slurry; the positive electrode slurry is then evenly coated on an aluminum foil current collector, and then dried, cold pressed, and cut to obtain positive electrode sheets, and the mass m (g) of the positive electrode material coated on each positive electrode sheet after drying is calculated by weighing.

[0168] 2. Preparation of negative electrode sheet

[0169] The active material artificial graphite, the conductive agent carbon black, the binder styrene-butadiene rubber (SBR), and the thickener sodium hydroxymethyl cellulose (CMC) are dissolved in the solvent deionized water in a weight ratio of 96.2:0.8:0.8:1.2, and the negative electrode slurry is prepared after being evenly mixed; the negative electrode slurry is evenly coated on the negative electrode collector copper foil once or multiple times, and the negative electrode sheet is obtained after drying, cold pressing, and slitting.

[0170] 3. Preparation of Electrolyte

[0171] In an argon atmosphere glove box (H 2 O<0.1ppm, O 2 <0.1ppm), organic solvent ethylene carbonate (EC) / ethyl methyl carbonate (EMC) are uniformly mixed in a volume ratio of 3 / 7, 12.5 mass % of LiPF6 lithium salt is added and dissolved in the organic solvent, and stirred uniformly to obtain an electrolyte.

[0172] 4. Isolation film

[0173] Polypropylene film is used as the isolation film.

[0174] 5. Preparation of Secondary Batteries

[0175] The positive electrode sheet, separator, and negative electrode sheet are stacked in order, with the separator between the positive and negative electrode sheets, and then wound to obtain a bare cell, the tabs are welded to the bare cell, and the bare cell is placed in an aluminum shell and baked at 100°C to remove water, and then the electrolyte is injected and sealed to obtain an uncharged battery. The uncharged battery then goes through the processes of static, hot and cold pressing, formation, shaping, and capacity testing to obtain a secondary battery product.

[0176] Specific capacity test

[0177] At 25°C, the secondary battery was charged to 4.2V at 1 / 3C constant current, then charged to 0.05C at 4.2V constant voltage, left for 5 minutes, and then discharged to 2.8V at 1 / 3C. The resulting capacity was recorded as the initial capacity C0 (mAh). Specific capacity = C0 / (m×97%), where m is the coating mass (g) of the positive electrode active material in each battery.

[0178] Battery capacity retention test

[0179] At 25°C, the secondary battery is charged to 4.2V at a constant current of 1 / 3C, then charged to a current of 0.05C at a constant voltage of 4.2V, left for 5 minutes, and then discharged to 2.8V at a constant current of 1 / 3C. The obtained capacity is recorded as the initial capacity C0. Repeat the above steps for the same battery, and record the discharge capacity Cn of the battery after the nth cycle. The battery capacity retention rate after each cycle is Pn = Cn / C0×100%. The battery capacity retention rate after 800 cycles is recorded as the test result in Table 2.

[0180] Table 2:

[0181]

[0182]

[0183] According to the above results, all particles of the nickel-cobalt-manganese ternary positive electrode material obtained in the embodiments with two-stage doping have a core-shell structure with an inner core composed of radially arranged radially growing primary particles and an outer shell composed of disorderly growing shells. However, Comparative Example 1, which was not doped, did not form particles with a core-shell structure. In addition, in Comparative Examples 2 and 3, a core composed of radially growing primary particles could not be formed because the first stage of boron / phosphorus doping was not performed or the doping concentration was too low. The shell composed of randomly grown primary particles did not grow in the particles of Comparative Example 4. In Comparative Example 5, the shell is composed of undoped nickel-cobalt-manganese ternary positive electrode material, which is also composed of randomly grown primary particles.

[0184] It can be seen from the comparison of the secondary battery performance of Comparative Examples 1 and 2 that the capacity retention rate of the secondary battery can be improved by Zr doping of the shell, because Zr doping can improve the corrosion resistance of the positive electrode material, thereby improving its stability in use. In addition, it can be seen from the comparison of Comparative Example 5 with Comparative Example 1 that the specific capacity of the secondary battery can be improved by boron doping of the core portion, because boron doping makes the core portion consist of primary particles that grow radially in a radial shape, shortening the migration path during lithium ion migration, and improving the lithium ion migration efficiency, thereby improving the specific capacity of the secondary battery. It can be seen from the comparison of Examples 1-20 and Comparative Examples 1-5 that Examples 1-20, which are formed with a core-shell structure doped with internal boron and / phosphorus and externally doped with any of zirconium, titanium, and aluminum, take into account the improvement of both specific capacity and capacity retention rate.

[0185] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A secondary battery, characterized in that: It comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein the positive electrode comprises a ternary positive electrode material. The ternary positive electrode material is a polycrystalline nickel-cobalt-manganese positive electrode material. The ternary positive electrode material includes secondary particles composed of primary particles, The secondary particles are in a core-shell structure, wherein the core portion is composed of primary particles growing radially in long strips, and the shell portion is composed of primary particles arranged in a disordered manner; The shell portion comprises at least one element selected from zirconium, titanium, and aluminum; The electrolyte includes an acidic component.

2. The secondary battery according to claim 1, characterized in that: The primary particles in the core portion preferentially grow along the (003) crystal plane.

3. The secondary battery according to claim 1, characterized in that: The core portion includes at least one element selected from boron or phosphorus, and may optionally include boron.

4. The secondary battery according to claim 3, characterized in that: The doping concentration of the at least one element selected from boron or phosphorus in the core portion is 100-10000 ppm, and can be optionally 500-3000 ppm.

5. The secondary battery according to any one of claims 1 to 4, characterized in that: The doping concentration of the at least one element selected from zirconium, titanium and aluminum in the shell portion is 200-10000 ppm, and can be optionally 1000-5000 ppm.

6. The secondary battery according to any one of claims 1 to 5, characterized in that: The shell portion contains zirconium element.

7. The secondary battery according to any one of claims 1 to 6, characterized in that: The average diameter of the core is 3-15 μm.

8. The secondary battery according to any one of claims 1 to 7, characterized in that: The average thickness of the shell portion is 0.5 μm or more.

9. The secondary battery according to any one of claims 1 to 8, characterized in that: The average particle size of the secondary particles of the ternary positive electrode material is 3.5-18 μm.

10. The secondary battery according to any one of claims 1 to 9, characterized in that: The electrolyte salt in the electrolytic solution includes lithium hexafluorophosphate.

11. The secondary battery according to any one of claims 1 to 10, characterized in that: The solvent in the electrolyte includes one or more of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate and fluoroethylene carbonate, and may optionally include ethylene carbonate and ethyl methyl carbonate.

12. The secondary battery according to any one of claims 1 to 11, characterized in that: The positive electrode 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 ternary positive electrode material, a conductive agent carbon black, and a binder polyvinylidene fluoride.

13. The secondary battery according to claim 12, characterized in that: The positive electrode current collector includes aluminum foil.

14. An electrical device, characterized in that: The invention comprises at least one of the secondary batteries according to any one of claims 1 to 13.

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