Ternary positive electrode material, preparation method thereof, positive electrode and lithium ion battery
By adding lithium sulfate and lithium fluoride during the sintering process to form a porous structure and a fluoride protective layer, the problem of limited capacity of the ternary positive electrode material is solved, and the capacity and circulation performance of lithium-ion batteries are improved.
Patent Information
- Application Number
- CN202411228590.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2024-12-10
AI Technical Summary
The existing ternary cathode materials are limited in capacity, especially when they consume active lithium during the first charge process to form solid electrolyte interface film and structural defects, which affect the circulation performance.
By adding lithium sulfate and lithium fluoride as modified materials during the sintering process, a porous structure and an inert fluoride protective layer are formed to improve the lithium ion deintercalation ability and the material's cycling performance.
The capacity and circulation performance of the ternary positive electrode material are significantly improved, and the first efficiency and long-term circulation performance of lithium-ion batteries are improved.
Smart Images
Figure CN119100463A_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of lithium ion batteries, and specifically relates to a ternary positive electrode material and a preparation method thereof, a positive electrode, and a lithium ion battery. Background Art
[0002] Lithium-ion batteries (lithium batteries) have the advantages of high energy density and long cycle life, so they have been widely used in energy storage, new energy vehicles and other fields.
[0003] Lithium-ion batteries may include components such as positive electrode (positive electrode sheet), negative electrode (negative electrode sheet), electrolyte, and separator, among which the positive electrode is one of the most important components. Therefore, the properties of the positive electrode material (active material) used therein will have an important impact on the overall performance of the lithium-ion battery.
[0004] In some related technologies, the positive electrode materials of lithium-ion batteries include lithium nickel cobalt manganese oxide, lithium iron phosphate, lithium cobalt oxide, lithium manganese oxide, lithium iron manganese phosphate, etc. Among them, lithium nickel cobalt manganese oxide is also called ternary positive electrode material because it includes three metals: nickel, cobalt and manganese. Compared with other positive electrode materials, it has higher energy density and better low-temperature performance, so it has become one of the important types of positive electrode materials.
[0005] The ternary positive electrode materials in the related art have disadvantages such as limited capacity. Summary of the invention
[0006] The present invention at least partially solves the problem of limited capacity utilization of existing ternary positive electrode materials, and provides a ternary positive electrode material with high capacity utilization and a preparation method thereof, a positive electrode, and a lithium ion battery.
[0007] In a first aspect, an embodiment of the present invention provides a method for preparing a ternary positive electrode material, which comprises:
[0008] Performing a first sintering process on a first sintering raw material to obtain a first sintering product; the first sintering raw material comprises a ternary precursor, a main lithium source, and lithium sulfate, and the ternary precursor contains nickel, cobalt, and manganese;
[0009] The second sintering raw material is subjected to a second sintering to obtain a second sintering product, and the second sintering product is used to prepare a ternary positive electrode material; the second sintering raw material includes the first sintering product.
[0010] Optionally, in the first sintering raw material, the ratio of the mass of the lithium sulfate to the mass of the main lithium source is between 1:(5-10).
[0011] Optionally, the sintering temperature of the first sintering is between 650°C and 850°C.
[0012] Optionally, the sintering time of the first sintering is between 6 hours and 18 hours; the heating rate of the first sintering is between 2° C. / min and 10° C. / min.
[0013] Optionally, the second sintering raw material also includes lithium fluoride.
[0014] Optionally, the ratio of the mass of the lithium fluoride in the second sintering raw material to the mass of the lithium sulfate in the first sintering raw material is between 1:(2-6).
[0015] Optionally, the sintering temperature of the second sintering is between 600°C and 800°C.
[0016] Optionally, the sintering time of the second sintering is between 3 hours and 10 hours; the heating rate of the second sintering is between 1° C. / min and 8° C. / min.
[0017] Optionally, the main lithium source includes at least one of the following: lithium carbonate, lithium hydroxide, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, lithium nitrate, lithium formate, lithium acetate, lithium oxalate, lithium tert-butoxide, lithium benzoate, and lithium citrate.
[0018] Optionally, the chemical formula of the ternary precursor is Ni x Co y Mn z (OH)2; where x+y+z=1, 0 <x≤0.8,0.1<y≤0.4。
[0019] Optionally, the ratio of the amount of lithium element in the main lithium source to the total amount of nickel element, cobalt element and manganese element in the ternary precursor is between (0.9-1.1):1.
[0020] Optionally, the first sintering raw material also includes additives.
[0021] Optionally, the additive includes at least one of the following:
[0022] Zirconium oxide, zirconium nitrate, zirconium sulfate, aluminum oxide, aluminum hydroxide, titanium oxide, magnesium oxide, magnesium hydroxide, tungsten oxide.
[0023] Optionally, in the first sintering raw material, the ratio of the mass of the additive to the mass of the ternary precursor is between (0.01-0.1):1.
[0024] In a second aspect, an embodiment of the present invention provides a ternary positive electrode material, and the ternary positive electrode material is prepared by any one of the methods for preparing a ternary positive electrode material of the embodiments of the present invention.
[0025] In a third aspect, an embodiment of the present invention provides a positive electrode, which includes any one of the ternary positive electrode materials of the embodiments of the present invention.
[0026] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery, comprising a positive electrode of any one of the embodiments of the present invention.
[0027] In the embodiment of the present invention, lithium sulfate is additionally added when the main lithium source and the ternary precursor are sintered for the first time (first sintering), and the lithium sulfate will volatilize during the sintering, thereby forming a porous structure inside the material. The porous structure is beneficial to the intercalation and deintercalation of lithium ions in the bulk phase of the material, so as to improve the capacity. Moreover, the modified materials (such as lithium sulfate) introduced in the embodiment of the present invention all include lithium, and lithium can participate in the reaction as an active component, so it will not have an adverse effect on the capacity.
[0028] Therefore, the embodiment of the present invention changes the structure and composition of the obtained ternary positive electrode material (i.e., modifies the ternary positive electrode material) by adding a specific modifying material (such as lithium sulfate) during sintering, thereby improving its capacity. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 The present invention is a schematic flow chart of a method for preparing a ternary positive electrode material according to an embodiment of the present invention.
[0030] Figure 2 A schematic diagram of the process of a method for preparing another ternary positive electrode material according to an embodiment of the present invention. DETAILED DESCRIPTION
[0031] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0032] It should be understood that the specific embodiments and drawings described herein are only used to explain the present invention rather than to limit the present invention.
[0033] It can be understood that, in the absence of conflict, the various embodiments of the present invention and the various features therein can be combined with each other.
[0034] It can be understood that, for the convenience of description, the drawings of the present invention only show the parts related to the embodiments of the present invention, while the parts unrelated to the embodiments of the present invention are not shown in the drawings.
[0035] It can be understood that, in the absence of conflict, the functions and steps marked in the flowcharts and block diagrams of the embodiments of the present invention may occur in an order different from that marked in the drawings.
[0036] In some related technologies, lithium-ion batteries using ternary positive electrode materials will consume the active lithium released from the ternary positive electrode materials during the first charge (first cycle charging) process to form a solid electrolyte interface (SEI) film at the negative electrode, resulting in a decrease in the first effect (first efficiency) and reversible capacity; at the same time, the ternary positive electrode materials themselves will also form some structural defects after delithiation, resulting in a reduction in lithium vacancies that can be inserted, thereby affecting capacity.
[0037] In addition, during the long-term cycle of lithium-ion batteries, the solid electrolyte interface membrane will be damaged, requiring continuous consumption of active lithium from the ternary positive electrode material for continuous self-repair, which will seriously affect the cycle performance of lithium-ion batteries.
[0038] In order to improve the performance of ternary positive electrode materials, related technologies use methods such as bulk doping and interface coating to modify them. However, doping and interface coating can usually only improve cycle performance, but have limited effect on capacity; moreover, since the doped and coated substances cannot actually participate in the reaction as active components during the charge and discharge process, they will further affect the capacity.
[0039] Therefore, the ternary positive electrode materials in the related art have disadvantages such as limited capacity.
[0040] First, refer to Figure 1 to Figure 2 , an embodiment of the present invention provides a method for preparing a ternary positive electrode material.
[0041] The method of the embodiment of the present invention is used to prepare a ternary positive electrode material, specifically an active material with lithium nickel cobalt manganese oxide as a main component used in preparing a positive electrode (positive electrode sheet) of a lithium ion battery.
[0042] Reference Figure 1 The method for preparing the ternary positive electrode material of the embodiment of the present invention includes:
[0043] S101, performing a first sintering process on a first sintering raw material to obtain a first sintering product.
[0044] Among them, the first sintering raw material includes a ternary precursor, a main lithium source, and lithium sulfate. The ternary precursor contains nickel, cobalt, and manganese elements.
[0045] In the embodiment of the present invention, refer to Figure 2 , the main lithium source and the ternary precursor are first sintered (first sintering), and a specific auxiliary material, lithium sulfate (Li2SO4), is added to the sintering raw material (first sintering raw material).
[0046] Among them, the main lithium source is a substance used to introduce the main lithium (Li) element component into the ternary positive electrode material, which can be a lithium salt.
[0047] It should be understood that since the main lithium source is a modified material (including lithium sulfate, and the subsequent lithium fluoride LiF), it is of course a different material from the modified material; that is, although lithium sulfate and lithium fluoride as modified materials include lithium elements, they do not belong to the main lithium source. Correspondingly, the main lithium source is also other lithium salts different from lithium sulfate and lithium fluoride.
[0048] Among them, the ternary precursor refers to a substance including nickel (Ni) element, cobalt (Co) element, and manganese (Mn) element, and it can react with the main lithium source during the sintering process to finally form the main component of the ternary positive electrode material of the embodiment of the present invention: lithium nickel cobalt manganese oxide.
[0049] It should be understood that the first sintering raw material at least needs to include a ternary precursor, a main lithium source, and lithium sulfate, but may also contain other components, such as other additives.
[0050] It should be understood that reference Figure 2 The ternary precursor, main lithium source, lithium sulfate and other substances in the above first sintering raw materials can be fully mixed and uniformly through stirring, ball milling and other methods.
[0051] S102, performing a second sintering on the second sintering raw material to obtain a second sintering product, and using the second sintering product to prepare a ternary positive electrode material.
[0052] Wherein, the second sintering raw material includes the first sintering product.
[0053] Reference Figure 2 The product obtained from the first sintering process (first sintering product) is further used as at least a part of the component of the second sintering raw material, and then further sintered (second sintering), and the product obtained from the second sintering can be used to make a ternary positive electrode material product.
[0054] It should be understood that the second sintering raw material may contain other components, such as subsequent lithium fluoride, other additives, etc., in addition to the first sintering product.
[0055] It should be understood that reference Figure 2 The first sintered product and other components in the second sintered raw material can be fully mixed and uniformly through stirring, ball milling and other methods.
[0056] It should be understood that the above second sintered product can be directly used as a ternary positive electrode material, or can be further ground, mixed with other components, etc. to obtain a ternary positive electrode material.
[0057] It should be understood that the method for preparing the ternary positive electrode material according to the embodiment of the present invention may include, in addition to the above two sintering steps, other steps, such as the step of preparing a ternary precursor.
[0058] In the embodiment of the present invention, lithium sulfate is additionally added when the main lithium source and the ternary precursor are sintered for the first time (first sintering), and the lithium sulfate will volatilize during the sintering, thereby forming a porous structure inside the material. The porous structure is beneficial to the intercalation and deintercalation of lithium ions in the bulk phase of the material, so as to improve the capacity. Moreover, the modified materials (such as lithium sulfate) introduced in the embodiment of the present invention all include lithium, and lithium can participate in the reaction as an active component, so it will not have an adverse effect on the capacity.
[0059] Therefore, the embodiment of the present invention changes the structure and composition of the obtained ternary positive electrode material (i.e., modifies the ternary positive electrode material) by adding a specific modifying material (such as lithium sulfate) during sintering, thereby improving its capacity.
[0060] Optionally, in the first sintering raw material, the ratio of the mass of lithium sulfate to the mass of the main lithium source is between 1:(5-10).
[0061] As one embodiment of the present invention, the mass ratio of lithium sulfate to the main lithium source used in the first sintering raw material can be 1: (5-10), that is, 1 mass part of lithium sulfate is used for every 5-10 mass parts of the main lithium source used. The mass ratio can further be 1: (6-9), such as 1: 8.
[0062] The above amount of lithium sulfate can not only improve the capacity, but also will not have adverse effects on other properties.
[0063] Optionally, the sintering temperature of the first sintering is between 650°C and 850°C.
[0064] Optionally, the sintering time of the first sintering is between 6 hours and 18 hours; and the heating rate of the first sintering is between 2° C. / min and 10° C. / min.
[0065] As one embodiment of the present invention, the first sintering may be high temperature sintering, and the sintering temperature may be 650-850°C, and further may be 700-800°C, such as 750°C.
[0066] As one embodiment of the present invention, the heating rate in the first sintering can be 2-10°C / min, further can be 4-6°C / min, such as 8°C / min; accordingly, after reaching the sintering temperature, the sintering time (holding time) can be 6-18h, further can be 8-14h, such as 10h.
[0067] The first sintering may be performed in a roller kiln; however, it should be understood that other equipment may also be used for the first sintering as long as the above sintering parameters are met.
[0068] Optionally, the second sintering raw material also includes lithium fluoride.
[0069] As one mode of an embodiment of the present invention, the modified material may further include lithium fluoride, that is, lithium fluoride may be mixed with the first sintered product and used together as a second sintering raw material to perform the above second sintering.
[0070] Among them, lithium fluoride will form an inert fluoride protective layer on the surface of the material during sintering (second sintering), and allow excess lithium to penetrate into the material to repair the structural defects of the material, thereby achieving the effect of improving the capacity retention rate during the cycle.
[0071] It can be seen that lithium fluoride as a modified material also contains lithium elements, and lithium can participate in the reaction as an active component, so it will not have an adverse effect on the capacity.
[0072] Optionally, the ratio of the mass of lithium fluoride in the second sintering raw material to the mass of lithium sulfate in the first sintering raw material is between 1:(2-6).
[0073] As one embodiment of the present invention, the amount of lithium fluoride used in the second sintering raw material should be determined according to the amount of lithium sulfate previously used in the first sintering raw material. Specifically, the mass ratio of the two can be 1: (2-6), further can be 1: (3-5), such as 1: 4.
[0074] The above amount of lithium fluoride can improve the cycle performance without causing adverse effects on other properties.
[0075] Optionally, the sintering temperature of the second sintering is between 600°C and 800°C.
[0076] Optionally, the sintering time of the second sintering is between 3 hours and 10 hours; and the heating rate of the second sintering is between 1° C. / min and 8° C. / min.
[0077] As one embodiment of the present invention, the temperature of the second sintering may be slightly lower than the temperature of the first sintering, and the sintering temperature may be 600-800°C, and further may be 650-750°C, such as 700°C.
[0078] As one embodiment of the present invention, the heating rate and sintering time of the second sintering may be lower than the corresponding parameters of the first sintering. For example, the heating rate may be 1 to 8°C / min, further 3 to 7°C / min, such as 6°C / min; and the sintering time may be 3 to 10h, further 4 to 8h, such as 6h.
[0079] The second sintering may be performed in a roller kiln; however, it should be understood that other equipment may also be used for the second sintering as long as the sintering parameters are met.
[0080] Optionally, the main lithium source includes at least one of the following: lithium carbonate, lithium hydroxide, lithium phosphate, lithium hydrogen phosphate, lithium dihydrogen phosphate, lithium nitrate, lithium formate, lithium acetate, lithium oxalate, lithium tert-butoxide, lithium benzoate, lithium citrate.
[0081] As a mode of an embodiment of the present invention, the main lithium source can be selected from one or more of the above lithium salts. For example, it can be lithium carbonate (Li2CO3) and / or lithium hydroxide (LiOH).
[0082] Optionally, the chemical formula of the ternary precursor is Ni x Co y Mn z (OH)2; where x + y + z = 1, 0 < x ≤ 0.8, 0.1 < y ≤ 0.4.
[0083] As a mode of an embodiment of the present invention, the ternary precursor can be a hydroxide of nickel, cobalt, and manganese, and its chemical formula can specifically be Ni x Co y Mn z (OH)2, where 0 < x ≤ 0.8, 0.1 < y ≤ 0.4, and z is the remainder, and it should be understood that z cannot be 0 (otherwise there would be no manganese element).
[0084] That is to say, the ternary precursor can specifically be a ternary precursor of NCMXYZ, where X = 10x, Y = 10y, and Z = 10z.
[0085] Among them, the above ternary precursor can be obtained by dissolving soluble nickel salts (such as nickel sulfate, nickel carbonate, nickel chloride, etc.), cobalt salts (such as cobalt sulfate, cobalt carbonate, cobalt chloride, etc.), and manganese salts (such as manganese sulfate, manganese carbonate, manganese chloride, etc.) in water and then reacting with an alkali (such as sodium hydroxide, potassium hydroxide, etc.) and a complexing agent (such as ammonia water, etc.) (such as heating reaction, etc.), and then filtering and drying.
[0086] It should be understood that the specific substance and preparation method of the ternary precursor are not limited to the above examples, as long as the nickel cobalt manganese lithium ternary cathode material can be obtained after two sinterings with the main lithium source.
[0087] Optionally, the ratio of the amount of substance of lithium element in the main lithium source to the total amount of substance of nickel element, cobalt element, and manganese element in the ternary precursor is between (0.9 - 1.1):1.
[0088] As a mode of an embodiment of the present invention, in the first sintering raw material, the amount of substance of lithium element in the main lithium source is substantially equal to the total amount of substance of nickel element, cobalt element, and manganese element in the ternary precursor, and the ratio of the amount of substance of the two can be between (0.9 - 1.1):1, further can be (1 - 1.1):1, such as can be 1:1.
[0089] Optionally, the first sintering raw material further includes additives.
[0090] As one embodiment of the present invention, refer to Figure 2 In the first sintering, other additives such as dopants, coating agents, fluxes, etc. may also be added.
[0091] Optionally, the additive includes at least one of the following: zirconium oxide, zirconium nitrate, zirconium sulfate, aluminum oxide, aluminum hydroxide, titanium oxide, magnesium oxide, magnesium hydroxide, and tungsten oxide.
[0092] As one mode of an embodiment of the present invention, the additive used in the first sintering raw material may be a dopant, which may be selected from one or more of the above substances, such as zirconium oxide.
[0093] Optionally, in the first sintering raw material, the ratio of the mass of the additive to the mass of the ternary precursor is between (0.01-0.1):1.
[0094] As one embodiment of the present invention, when an additive is used in the first sintering raw material, the mass ratio of the additive to the ternary precursor may be (0.01-0.1):1, and further may be (0.02-0.08):1, such as 0.05:1.
[0095] In a second aspect, an embodiment of the present invention provides a ternary positive electrode material, and the ternary positive electrode material is prepared by any one of the methods for preparing a ternary positive electrode material of the embodiments of the present invention.
[0096] The ternary positive electrode material of the embodiment of the present invention is a modified ternary positive electrode material prepared in the above manner, and the ternary positive electrode material can be used as an active material in the positive electrode of a lithium-ion battery, thereby enabling the lithium-ion battery to have higher capacity and better cycle performance.
[0097] In a third aspect, an embodiment of the present invention provides a positive electrode, which includes any one of the ternary positive electrode materials of the embodiments of the present invention.
[0098] The positive electrode (positive electrode sheet) of the embodiment of the present invention is a positive electrode of a lithium-ion battery, which includes the above ternary positive electrode material as an active material.
[0099] For example, the positive electrode of the embodiment of the present invention may include a positive electrode substrate (such as aluminum foil, etc.) and an active layer formed on the positive electrode substrate, and the active layer includes the above ternary positive electrode material.
[0100] It should be understood that the positive electrode of the lithium-ion battery according to the embodiment of the present invention may also include other components, structures, etc.
[0101] For example, the positive electrode material of the embodiment of the present invention can be dispersed in a dispersant (such as N-methylpyrrolidone, etc.) together with a conductive agent (such as carbon black, etc.) and a binder (such as polytetrafluoroethylene, etc.) to form a positive electrode slurry, and then the positive electrode slurry is coated on the positive electrode substrate, and then formed into a positive electrode (positive electrode sheet) component through rolling, slicing, drying, etc.
[0102] In a fourth aspect, an embodiment of the present invention provides a lithium-ion battery, comprising a positive electrode of any one of the embodiments of the present invention.
[0103] The lithium-ion battery of the embodiment of the present invention comprises the above positive electrode (positive electrode sheet), and the positive electrode contains the above ternary positive electrode material as an active material, so that the lithium-ion battery has higher capacity and better cycle performance.
[0104] For example, the ternary positive electrode material of the embodiment of the present invention can be dispersed in a dispersant (such as N-methylpyrrolidone, etc.) together with a conductive agent (such as carbon black, etc.) and a binder (such as polytetrafluoroethylene, etc.) to form a positive electrode slurry, and then the positive electrode slurry is coated on a positive electrode substrate (such as aluminum foil, etc.), and formed into positive electrode (positive electrode sheet) components through rolling, slicing, drying, etc.
[0105] It should be understood that the lithium-ion battery of the embodiment of the present invention may also include other components such as a negative electrode, an electrolyte, and a separator.
[0106] For example, the negative electrode active material (such as artificial graphite, etc.) and the conductive agent (such as carbon black, etc.) and the binder (such as carboxymethyl cellulose, styrene-butadiene rubber, etc.) may be dispersed in a dispersant (such as deionized water) to form a negative electrode slurry, and then the negative electrode slurry is coated on a negative electrode substrate (such as copper foil, etc.), and then rolled, sliced, dried, etc. to form the negative electrode (negative electrode sheet) component of the lithium ion battery of the embodiment of the present invention. Alternatively, a lithium sheet, etc. may be used as the negative electrode.
[0107] For another example, the electrolyte in the lithium-ion battery of the embodiment of the present invention may be a solution of a lithium salt (such as lithium hexafluorophosphate, etc.) dissolved in a solvent (such as ethylene carbonate, ethyl methyl carbonate, etc.) (the concentration may be 0.5 to 2 mol / L), and the electrolyte may also include various additives such as a film-forming agent (such as fluoroethylene carbonate, triphenyl phosphate, etc.).
[0108] For another example, the separator in the lithium-ion battery of the embodiment of the present invention may be in the form of a porous membrane substrate (such as a polyethylene film, etc.) having a protective layer (such as polyvinylidene fluoride, etc.) and a ceramic layer (such as aluminum oxide, etc.) formed on the surface, wherein the thickness of the porous membrane substrate may be 5 to 15 μm, the thickness of the protective layer may be 1 to 3 μm, and the thickness of the ceramic layer may be 1 to 5 μm.
[0109] It should be understood that the forms of other components in the lithium-ion battery of the embodiment of the present invention are not limited to the above examples, and the lithium-ion battery may also include other components besides the above components, which will not be described in detail here.
[0110] Embodiment 1:
[0111] This embodiment 1 provides a method for preparing a ternary positive electrode material according to an embodiment of the present invention, which comprises the following steps:
[0112] A101, dissolve 210 g of nickel sulfate hexahydrate, 28.1 g of cobalt sulfate heptahydrate, and 27.7 g of manganese sulfate heptahydrate in 1 L of water, and continue stirring until completely dissolved.
[0113] A102. Add 40 g of sodium hydroxide to the above solution and stir evenly. Then, add 2 M ammonia water dropwise to the solution and adjust the pH to 11.
[0114] A103, heat the above solution to 60 ° C and react for 12 hours. After the reaction is completed, filter, wash and dry to obtain 92.3g of NCM811 ternary precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2.
[0115] A104. Take 42 g of lithium hydroxide monohydrate (main lithium source), 5.5 g of lithium sulfate, and 0.27 g of zirconium dioxide (additive, specifically dopant), and mix them evenly with the above ternary precursors in a high-speed mixer to obtain the first sintering raw material.
[0116] A105. Perform a first sintering on the first sintering raw material in a roller kiln at a sintering temperature of 750° C., a sintering time of 12 h, and a heating rate of 5° C. / min to obtain a first sintering product.
[0117] A106. Take 1.3 g of lithium fluoride and the first sintered product and stir them evenly in a high-speed mixer to obtain a second sintering raw material.
[0118] A107. The second sintering raw material is subjected to a first sintering in a roller kiln at a sintering temperature of 700° C., a sintering time of 6 h, and a heating rate of 3° C. / min to obtain a second sintering product.
[0119] The second sintered product is used as the ternary positive electrode material of NCM811 in this embodiment 1.
[0120] Embodiment 2:
[0121] This embodiment 2 provides a method for preparing a ternary positive electrode material according to an embodiment of the present invention, which comprises the following steps:
[0122] A201. Dissolve 157.6 g of nickel sulfate hexahydrate, 28.1 g of cobalt sulfate heptahydrate, and 83.1 g of manganese sulfate heptahydrate in 1 L of water and continue stirring until completely dissolved.
[0123] A202. Add 40 g of sodium hydroxide to the above solution and stir evenly. Then, add 2 M ammonia water dropwise to the solution and adjust the pH to 11.
[0124] A203, heat the above solution to 60 ° C and react for 12 hours. After the reaction is completed, filter, wash and dry to obtain 91.6g of NCM613 ternary precursor Ni 0.6 Co 0.1 Mn 0.3 (OH)2.
[0125] A204. Take 37 g of lithium carbonate (main lithium source), 5.5 g of lithium sulfate, and 0.27 g of zirconium dioxide (additive, specifically dopant), and mix them evenly with the above ternary precursors in a high-speed mixer to obtain the first sintering raw material.
[0126] A205. Perform a first sintering on the first sintering raw material in a roller kiln at a sintering temperature of 800°C, a sintering time of 12 hours, and a heating rate of 5°C / min to obtain a first sintering product.
[0127] A206. Take 1.3 g of lithium fluoride and the first sintered product and mix them evenly in a high-speed mixer to obtain a second sintering raw material.
[0128] A207. The second sintering raw material is subjected to a first sintering in a roller kiln at a sintering temperature of 700°C, a sintering time of 6 hours, and a heating rate of 3°C / min to obtain a second sintering product.
[0129] The second sintered product is used as the ternary positive electrode material of NCM613 of this embodiment 1.
[0130] Embodiment 3:
[0131] This embodiment 3 provides a method for preparing the ternary positive electrode material of the embodiment of the present invention, which is similar to the embodiment 1, except that the temperature of the first sintering is 640°C.
[0132] Embodiment 4:
[0133] This embodiment 4 provides a method for preparing the ternary positive electrode material of the embodiment of the present invention, which is similar to the embodiment 1, except that its first sintering temperature is 860°C.
[0134] Embodiment 5:
[0135] This embodiment 5 provides a method for preparing the ternary positive electrode material of the embodiment of the present invention, which is similar to the embodiment 1, except that its second sintering temperature is 590°C.
[0136] Embodiment 6:
[0137] This embodiment 6 provides a method for preparing the ternary positive electrode material of the embodiment of the present invention, which is similar to the embodiment 1, except that its second sintering temperature is 810°C.
[0138] Embodiment 7:
[0139] This embodiment 7 provides a method for preparing the ternary positive electrode material of the embodiment of the present invention, which is similar to the embodiment 1, except that lithium fluoride is not added in the second sintering.
[0140] Comparative Example 1:
[0141] This comparative example 1 provides a method for preparing a ternary positive electrode material in the related art, which is similar to Example 1, except that lithium sulfate is not added in the first sintering and lithium fluoride is not added in the second sintering.
[0142] Comparative Example 2:
[0143] This comparative example 2 provides a method for preparing a ternary positive electrode material in the related art, which is similar to Example 2, except that lithium sulfate is not added in the first sintering and lithium fluoride is not added in the second sintering.
[0144] Performance testing and results:
[0145] The ternary cathode material prepared in each embodiment and comparative example is used in a lithium ion battery in the following manner, which includes:
[0146] (1) The ternary positive electrode material obtained in each example and comparative example was uniformly mixed with a binder of polytetrafluoroethylene (PVDF) and a conductive agent of carbon black (SP) in a mass ratio of 92:4:4, and then a dispersant of N-methylpyrrolidone (NMP) was added dropwise and stirred to obtain a positive electrode slurry with a viscosity of 6500 mPa·S.
[0147] (2) The positive electrode slurry is evenly coated on the aluminum foil (positive electrode substrate) with a coating surface density of 9.5 mg / cm 2 .
[0148] (3) Drying the aluminum foil with the positive electrode slurry in a vacuum oven to obtain a positive electrode (positive electrode sheet) component.
[0149] (4) Assemble the above positive electrode, the negative electrode (lithium sheet), the separator and the electrolyte in the CR2032 button battery into a lithium-ion battery.
[0150] (5) Referring to the test methods in GB / T 18287-2013 and GB 31241 standards, the 0.1C first cycle charge and discharge capacity, first efficiency, and capacity retention rate after 50 cycles at 1C of the lithium-ion battery obtained above were tested. The test results are shown in Table 1 below.
[0151] Table 1. Performance of lithium-ion batteries of Examples and Comparative Examples
[0152]
[0153]
[0154] It can be seen that the first-cycle discharge capacity of the ternary positive electrode material with the same main component (NCM811 or NCM613) is significantly improved when prepared by the method of the embodiment of the present invention (Example 1 and Example 2) compared with the method of the related art without using specific modified materials (lithium sulfate and lithium fluoride) (Comparative Example 1 and Comparative Example 2), so that the first effect is also significantly improved; at the same time, the ternary positive electrode material prepared by the method of the embodiment of the present invention can also greatly improve the cycle capacity retention rate, thereby improving the cycle performance of the lithium-ion battery.
[0155] Among them, the ternary positive electrode material with the same main component, when using the same specific modified materials (lithium sulfate and lithium fluoride), also performs better when the temperatures of the two sinterings meet specific requirements.
[0156] For example, the temperature of Example 3 during the first sintering was too low, resulting in incomplete particle development; the temperature of Example 4 during the first sintering was too high, resulting in particle agglomeration; the temperature of Example 5 during the second sintering was too low, resulting in lithium fluoride not being fully melted and coated; the temperature of Example 6 during the second sintering was too high, resulting in excessive penetration of lithium fluoride into the material structure. Therefore, the product performance of Examples 1 and 2 is better than that of Examples 3 to 6.
[0157] However, the product performance of Examples 3 to 6 is still better than that of the comparative examples.
[0158] It is also feasible to use lithium sulfate only in the first sintering and not use lithium fluoride in the second sintering.
[0159] For example, in Example 7, only lithium sulfate is used without lithium fluoride, but its product performance is still better than that of the comparative examples.
[0160] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present invention, but the present invention is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.
Claims
1. A method for preparing a ternary positive electrode material, characterized in that: include: Performing a first sintering process on the first sintering raw material to obtain a first sintering product; The first sintering raw material includes a ternary precursor, a main lithium source, and lithium sulfate, wherein the ternary precursor contains nickel, cobalt, and manganese; The second sintering raw material is subjected to a second sintering to obtain a second sintering product, and the second sintering product is used to prepare a ternary positive electrode material; the second sintering raw material includes the first sintering product.
2. The method according to claim 1, characterized in that In the first sintering raw material, the ratio of the mass of the lithium sulfate to the mass of the main lithium source is between 1:(5-10).
3. The method according to claim 1, characterized in that The sintering temperature of the first sintering is between 650°C and 850°C.
4. The method according to claim 3, characterized in that The sintering time of the first sintering is between 6h and 18h; The heating rate of the first sintering is between 2°C / min and 10°C / min.
5. The method according to claim 1, characterized in that The second sintering raw material also includes lithium fluoride.
6. The method according to claim 5, characterized in that The ratio of the mass of the lithium fluoride in the second sintering raw material to the mass of the lithium sulfate in the first sintering raw material is between 1:(2-6).
7. The method according to claim 1, characterized in that The sintering temperature of the second sintering is between 600°C and 800°C.
8. The method according to claim 7, characterized in that The sintering time of the second sintering is between 3h and 10h; The heating rate of the second sintering is between 1°C / min and 8°C / min.
9. The method according to any one of claims 1 to 8, characterized in that The main lithium source includes at least one of the following: Lithium carbonate, lithium hydroxide, lithium phosphate, dilithium hydrogen phosphate, lithium dihydrogen phosphate, lithium nitrate, lithium formate, lithium acetate, lithium oxalate, lithium tert-butoxide, lithium benzoate, lithium citrate.
10. The method according to any one of claims 1 to 8, characterized in that The chemical formula of the ternary precursor is Ni x Co y Mn z (OH)2; Where x+y+z=1,0 <x≤0.8,0.1<y≤0.4。 11. The method according to any one of claims 1 to 8, characterized in that The ratio of the amount of lithium element in the main lithium source to the total amount of nickel element, cobalt element and manganese element in the ternary precursor is between (0.9-1.1):
1.
12. The method according to any one of claims 1 to 8, characterized in that The first sintering raw material further includes an additive.
13. The method according to claim 12, characterized in that The additives include at least one of the following: Zirconium oxide, zirconium nitrate, zirconium sulfate, aluminum oxide, aluminum hydroxide, titanium oxide, magnesium oxide, magnesium hydroxide, tungsten oxide.
14. The method according to claim 12, characterized in that In the first sintering raw material, the ratio of the mass of the additive to the mass of the ternary precursor is between (0.01-0.1):
1.
15. A ternary positive electrode material, characterized in that: The ternary positive electrode material is prepared by the method for preparing the ternary positive electrode material according to any one of claims 1 to 14.
16. A positive electrode, characterized in that: include: The ternary positive electrode material as described in claim 15.
17. A lithium battery, characterized in that: include: The positive electrode according to claim 16.