Ternary positive electrode precursor material and preparation method thereof, positive electrode material and battery

Abstract

The invention provides a ternary positive electrode precursor material and a preparation method thereof, a positive electrode material and a battery. The ternary positive electrode precursor material sequentially comprises an inner core, a middle coating layer and an outer coating layer from inside to outside, the inner core and the outer coating layer comprise an undoped ternary positive electrode precursor material, and the middle coating layer comprises a ternary positive electrode precursor material containing doping elements; and the middle coating layer is of a porous structure. The ternary positive electrode precursor material provided with the middle porous layer and doped with the middle coating layer has excellent capacity, rate and cycle performance under high cut-off potential.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and relates to a ternary positive electrode precursor material, a preparation method thereof, a positive electrode material and a battery. BACKGROUND

[0002] Rechargeable lithium ion batteries (LIBs) have played an important role in the development of clean energy due to their low cost, high reliability, long life, and other advantages, and have achieved great success in consumer electronics, portable devices and electric vehicles. In addition, with the increasing demand for energy density from government policies, it is urgent to pursue higher specific capacity and working potential of positive electrode materials to develop high energy density LIBs. The specific capacity of the positive electrode material is a real bottleneck, and the low-cost, high-discharge-capacity nickel-rich (Ni mole content > 60%) layered oxide positive electrode (LiNi x Co y Mn (1-x-y) O2) has become a promising material among current commercial positive electrode candidates. However, this material still faces an awkward dilemma: a huge gap between practical ability and theoretical ability. Although a significant discharge capacity of more than 180 mAh / g (about 4.3 V vs. Li / Li+) has been achieved, there is still a huge room for improvement compared with the theoretical value (about 273 mAh / g).

[0003] In order to meet the higher energy density requirements in practical applications, it is urgent to further improve the capacity. Among them, it is a key point to break through the capacity bottleneck provided by nickel-rich materials to amplify its capacity advantage, especially without excessively increasing the Ni content. In addition, the poor performance of nickel-rich materials at high cut-off potential is also a noteworthy problem, which will exacerbate other problems at high cut-off potential (≥4.5 V), including capacity decay, structural degradation and secondary particle fracture or crushing during the cycle process. An important factor is that when charged to a high cut-off voltage, the side reaction between the electrode and the electrolyte will cause damage to the morphology and structure, followed by an increase in impedance and a decrease in voltage. In addition, the diffusion of chaotic spinel phase (Fd-3m) or rock salt phase (Fm-3m) from the surface to the inside is another important aspect, which is even more serious at a higher working potential. Obviously, effective measures must be taken to control these thorny problems. SUMMARY

[0004] In view of the deficiencies in the prior art, the purpose of the present application is to provide a ternary positive electrode precursor material, a preparation method thereof, a positive electrode material and a battery. The ternary positive electrode precursor material provided by the present application has an intermediate porous layer and is doped with an intermediate coating layer, and has excellent capacity, rate and cycle performance at a high cut-off potential.

[0005] To achieve the object of the present application, the present application adopts the following technical solutions:

[0006] In a first aspect, the present application provides a ternary positive electrode precursor material, which comprises, from inside to outside, an inner core, an intermediate coating layer and an outer coating layer.

[0007] The inner core and the outer coating layer comprise undoped ternary positive electrode precursor material, and the intermediate coating layer comprises ternary positive electrode precursor material containing a doping element; the intermediate coating layer is a porous structure.

[0008] The present application adopts a structure of a dense inner core and a dense outer coating layer and a loose porous intermediate coating layer, and simultaneously performs doping of the loose porous intermediate coating layer, on the one hand, the radial distribution of the positive electrode precursor material is uniform, the sphericity is high, which is beneficial to the transmission of lithium ions and improves the rate performance of the material; on the other hand, special position doping and a specific structure make the doping element uniformly distributed in the intermediate coating layer, the interatomic spacing is expanded and the original layered structure is not affected, the primary particles in the intermediate coating layer are fine, the mechanical stress caused by the anisotropic phase change from hexagon (H2) to hexagon (H3) is reduced (or the expansion of internal particle cracks is reduced), thereby showing high reversible discharge capacity under high cut-off voltage, and more importantly, the ternary positive electrode precursor material of the present application promotes the transmission of lithium ions in the process of electrochemical cycling under high current density and high cut-off voltage, can effectively dissipate the stress caused by anisotropic volume expansion in the process of cycling, and significantly inhibits the formation of micro-cracks; thereby showing high capacity, high rate performance and long cycle performance.

[0009] For the ternary positive electrode precursor material in the present application, the structural distribution of the material and the position distribution of the doping element are also important, and need to work together to accelerate the transmission of lithium ions, improve the rate performance and cycle performance of the material.

[0010] The following is a preferred technical solution of the present application, but is not a limitation on the technical solutions provided by the present application. Through the following preferred technical solution, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0011] Preferably, the chemical formula of the ternary positive electrode precursor material in the inner core is Ni x Co y Mn z (OH)2, wherein 0.6

[0012] For example, the x can be 0.61, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, or 0.89, etc.; the y can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.; and the z can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.

[0013] Preferably, the chemical general formula of the ternary positive electrode precursor material in the outer coating layer is Ni m Co n Mn e (OH)2, wherein 0.6 < m < 0.9, 0 < n < 0.2, 0 < e < 0.2, and m + n + e = 1.

[0014] For example, the x can be 0.61, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88, or 0.89, etc.; the y can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.; and the z can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18, or 0.19, etc.

[0015] Preferably, in the intermediate coating layer, the mole percentage of the doping element in the total mole amount of the ternary main metals nickel, cobalt, and manganese is 0.05% to 5%, such as 0.05%, 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, etc.

[0016] Preferably, the chemical general formula of the ternary positive electrode precursor material in the intermediate coating layer is (Ni a Co b Mn c)1-d M d (OH)2, 0.6 < a < 0.9, 0 < b < 0.2, 0 < c < 0.2, 0.0005 ≤ d ≤ 0.05, and a + b + c = 1, and M is a doping element.

[0017] For example, the a can be 0.61, 0.63, 0.65, 0.68, 0.7, 0.73, 0.75, 0.78, 0.8, 0.83, 0.85, 0.88 or 0.89, etc.; the b can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.19, etc.; the c can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15, 0.18 or 0.19, etc.; and the d can be 0.0005, 0.005, 0.01, 0.013, 0.015, 0.018, 0.02, 0.023, 0.025, 0.028, 0.03, 0.033, 0.035, 0.038, 0.04, 0.043, 0.045, 0.048 or 0.05, etc.

[0018] The ternary positive electrode precursor material of the present application has better effect in the nickel-rich system, and the molar ratio of the doping element in the intermediate coating layer is 0.05% to 5%, which can better play the advantages of the doping element and improve the structural stability of the material.

[0019] Preferably, the (Ni a Co b Mn c)1-d M d In the (OH)2, 0.0005≤d≤0.02, such as 0.0005, 0.001, 0.005, 0.01, 0.013, 0.015, 0.018 or 0.02, etc.

[0020] In the present application, 0.0005≤d≤0.02 is further regulated, and the performance is more excellent.

[0021] Preferably, the M includes any one or a combination of at least two of Al, Ti, Nb, Zr, W, V, Sr, Ga, Ce, Y, La, Sb or B, and is preferably W.

[0022] In the ternary precursor positive electrode material of the present application, the doping of W in the intermediate coating layer also improves the cycle performance and thermal stability.

[0023] Preferably, the porosity of the intermediate coating layer is 20% to 40%, such as 20%, 23, 25%, 28%, 30%, 33%, 35%, 38% or 40%, etc.

[0024] In a second aspect, the present application provides a preparation method of the ternary positive electrode precursor material according to the first aspect, and the preparation method comprises the following steps:

[0025] adding the first main metal mixed salt solution, the first precipitant solution and the first complexing agent solution in parallel to perform a first co-precipitation reaction to obtain an inner core;

[0026] After obtaining the inner core, a second main metal mixed salt solution, a dopant solution, a second precipitant solution and a second complexing agent solution are added in parallel to perform a second co-precipitation reaction to form an intermediate coating layer with a porous structure on the surface of the inner core;

[0027] After obtaining the intermediate coating layer, a third main metal mixed salt solution, a third precipitant solution and a third complexing agent solution are added in parallel to perform a third co-precipitation reaction to form an outer coating layer to obtain the ternary positive electrode precursor material;

[0028] Preferably, the pH value of the second co-precipitation reaction is lower than the pH value of the first co-precipitation reaction, and the pH value of the second co-precipitation reaction is lower than the pH value of the third co-precipitation reaction.

[0029] It should be noted that the main metal in the present application refers to the main element of the ternary positive electrode precursor material.

[0030] In the preparation process, the present application obtains a structure with a dense inner core and a dense outer coating layer and a porous and loose intermediate coating layer through a stage co-precipitation reaction, pH value control and a doping process, while ensuring the uniform distribution of the doping elements in the intermediate coating layer. Moreover, the second co-precipitation process with a lower pH value is also beneficial to expanding the atomic interlayer spacing while maintaining the original layered structure, refining the primary particles, and obtaining a more porous and loose structure of the intermediate coating layer. Moreover, the preparation process does not require additional processes, is simple to operate, and is conducive to large-scale production.

[0031] Preferably, the main metal includes nickel, cobalt and manganese.

[0032] It can be understood that each of the present application is independently referred to, which can be the same or different, and the skilled person can make adaptive selection and adjustment according to the actual demand. Preferably, in the present application, the concentration of each raw material and the substance remain the same during the entire co-precipitation reaction process, which is more conducive to obtaining a precursor with consistent radial distribution.

[0033] Preferably, the doping elements in the dopant include any one or a combination of at least two of Al, Ti, Nb, Zr, W, V, Sr, Ga, Ce, Y, La, Sb or B, and W is preferred.

[0034] Preferably, the concentration of the first main metal mixed salt solution, the second main metal mixed salt solution and the third main metal mixed salt solution is independently 50 g / L to 250 g / L, for example 50 g / L, 75 g / L, 100 g / L, 125 g / L, 150 g / L, 175 g / L, 200 g / L, 225 g / L or 250 g / L, etc.

[0035] In addition, the specific type of salt of the mixed salt in the present application is also a conventional scheme, without departing from the technical concept of the present application, any known soluble, especially water-soluble salt type, the present application is applicable, for example, at least one of the chloride salt, sulfate salt, nitrate salt or acetate salt, etc.

[0036] Preferably, the concentration of the dopant solution is 20 g / L to 50 g / L, for example 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L or 50 g / L, etc.

[0037] Similarly, the specific type of dopant in the dopant solution in the present application can be selected according to the solubility of the dopant element.

[0038] Preferably, the mass fraction of the first precipitant solution, the second precipitant solution and the third precipitant solution is independently 10% to 30%, for example 10%, 15%, 20%, 25% or 30%, etc.

[0039] Preferably, the mass fraction of the first complexing agent solution, the second complexing agent solution, the third complexing agent solution is independently 5% to 20%, for example 5%, 10%, 15% or 20%, etc.

[0040] It can be understood that the precipitant and the complexing agent in the present application are also selected by conventional technology, without departing from the technical concept of the present application, any known conventional substance used for coprecipitation reaction is applicable to the present application.

[0041] For example, the precipitant includes at least one of sodium hydroxide, potassium hydroxide, sodium carbonate or sodium bicarbonate, etc.; the complexing agent includes but is not limited to ammonia and / or ethylenediaminetetraacetic acid (EDTA), etc.

[0042] Preferably, the feeding rate of each raw material in the first coprecipitation reaction process is less than the corresponding feeding rate of each raw material in the second coprecipitation reaction process.

[0043] Preferably, the feeding rate of each raw material in the third coprecipitation reaction process is less than the corresponding feeding rate of each raw material in the second coprecipitation reaction process.

[0044] In the second co-precipitation reaction process, the feeding speed of each raw material in the reaction process is increased, further optimizing the primary particle morphology and refining the grain. At the same time, the reaction time is controlled to make the reaction system more stable and controllable, and the precursor with more uniform particle morphology consistency is obtained.

[0045] Preferably, the feeding speed of the first main metal mixed salt solution and the third main metal mixed salt solution is independently 4L / h-6L / h, for example, 4L / h, 5L / h or 6L / h, etc.

[0046] Preferably, the feeding speed of the second main metal mixed salt solution is 6L / h-10L / h, for example, 6L / h, 7L / h, 8L / h, 9L / h or 10L / h, etc.

[0047] Preferably, the feeding speed of the first precipitant solution and the third precipitant solution is independently 1.5L / h-3L / h, for example, 1.5L / h, 2L / h, 2.5L / h or 3L / h, etc.

[0048] Preferably, the feeding speed of the second precipitant solution is 2.5L / h-4L / h, for example, 2.5L / h, 3L / h, 3.5L / h or 4L / h, etc.

[0049] Preferably, the feeding speed of the first complexing agent solution and the third complexing agent solution is independently 500mL / h-800mL / h, for example, 500mL / h, 600mL / h, 700mL / h or 800mL / h, etc.

[0050] Preferably, the feeding speed of the second complexing agent solution is 800mL / h-1000mL / h, for example, 800mL / h, 900mL / h or 1000mL / h, etc.

[0051] Preferably, the feeding speed of the dopant solution is 300mL / h-500mL / h, for example, 300mL / h, 350mL / h, 400mL / h, 450mL / h or 500mL / h, etc.

[0052] Preferably, the pH value of the first co-precipitation reaction is 11-11.5, for example, 11 11.1, 11.2, 11.3, 11.4 or 11.5, etc.

[0053] Preferably, the pH value of the second co-precipitation reaction is 10.4-10.8, for example, 10.4, 10.5, 10.6, 10.7 or 10.8, etc.

[0054] Preferably, the pH value of the third co-precipitation reaction is 10.8-11, for example, 10.8, 10.9 or 11, etc.

[0055] Preferably, the concentration of the complexing agent in the reaction solution system during the first co-precipitation reaction is 8 g / L to 10 g / L, such as 8 g / L, 9 g / L or 10 g / L, etc.

[0056] Preferably, the concentration of the complexing agent in the reaction solution system during the second co-precipitation reaction is 5 g / L to 7 g / L, such as 5 g / L, 6 g / L or 7 g / L, etc.

[0057] Preferably, the concentration of the complexing agent in the reaction solution system during the second co-precipitation reaction is 7 g / L to 9 g / L, such as 7 g / L, 8 g / L or 9 g / L, etc.

[0058] It should be noted that the reaction temperature and stirring speed during the entire co-precipitation process can be adaptively selected and adjusted according to the actual reaction process, and the present application does not have special limitations.

[0059] Preferably, the reaction temperature of the first co-precipitation reaction, the second co-precipitation reaction and the third co-precipitation reaction is independently 30°C to 80°C, such as 30°C, 35°C, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C or 80°C, etc.

[0060] Preferably, the stirring speed of the first co-precipitation reaction, the second co-precipitation reaction and the third co-precipitation reaction is independently 100 rpm to 500 rpm, such as 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, etc.

[0061] Preferably, the median particle size D50 of the inner core is 4 μm to 6 μm, such as 4 μm, 4.3 μm, 4.5 μm, 4.8 μm, 5 μm, 5.3 μm, 5.5 μm, 5.8 μm or 6 μm, etc.

[0062] Preferably, the target median particle size D50 of the particles obtained by the second co-precipitation reaction is 8 μm to 9 μm, such as 8 μm, 8.1 μm, 8.2 μm, 8.3 μm, 8.4 μm, 8.5 μm, 8.6 μm, 8.7 μm, 8.8 μm, 8.9 μm or 9 μm, etc.

[0063] Preferably, the target median particle size D50 of the particles obtained by the third co-precipitation reaction is 10 μm to 15 μm, such as 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, 12.5 μm, 13 μm, 13.5 μm, 14 μm, 14.5 μm or 15 μm, etc.

[0064] In the present application, by regulating the median particle size D50 of the inner core to be 4-6 μm and / or the target median particle size D50 of the particles obtained by the second co-precipitation reaction to be 8-9 μm and / or the target median particle size D50 of the particles obtained by the third co-precipitation reaction to be 10-15 μm, the positive electrode material prepared from the obtained positive electrode precursor material has a small volume change during charging and discharging, which is beneficial to the improvement of the cycle performance.

[0065] It should also be noted that:

[0066] The entire co-precipitation reaction in the present application can be carried out in a protective atmosphere, i.e. protective gas is introduced during the entire reaction process, such as nitrogen, argon or helium, etc.

[0067] Before the initial reaction, the reaction bottom liquid can be first added to the reaction container to better complete the reaction.

[0068] Preferably, the reaction bottom liquid comprises water, a precipitating agent and a complexing agent, the concentration of the complexing agent in the reaction bottom liquid is 6-10 g / L, such as 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, etc., the pH value of the reaction bottom liquid is 11.5-12, such as 11.5, 11.6, 11.7, 11.8, 11.9 or 12, etc., and the temperature of the reaction bottom liquid is 50-80℃, such as 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, etc.

[0069] After the third co-precipitation reaction is completed, aging, washing and drying treatment can be carried out in sequence, and post-treatment processes such as impurity removal can also be carried out.

[0070] In a third aspect, the present application provides a ternary positive electrode material, which is obtained by mixing and sintering the ternary positive electrode precursor material prepared by the method of the first aspect or the second aspect with a raw material comprising at least a lithium source.

[0071] In the present application, the preparation process of the medium-nickel single-crystal positive electrode material prepared from the ternary positive electrode precursor material provided by the first aspect or the second method is a conventional technical solution, and the preparation method of the positive electrode material prepared from the positive electrode precursor material within the reasonable range of the person skilled in the art is applicable to the present application.

[0072] Exemplarily, the present application provides a specific preparation method of a positive electrode material:

[0073] Mixing a lithium source and a medium-nickel positive electrode precursor material, sintering treatment, to obtain the positive electrode material.

[0074] Preferably, the molar ratio of the medium nickel positive electrode precursor material to lithium in the lithium source is 1:(1.1~1.2), such as 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19 or 1:1.2, etc., but not limited to the listed values, other values not listed in the range are also applicable.

[0075] Preferably, the sintering process is carried out in an oxygen-containing atmosphere, including oxygen atmosphere and / or air atmosphere, etc.

[0076] Preferably, the sintering process can be one-stage sintering or multi-stage sintering; the multi-stage sintering includes two-stage sintering or three-stage sintering.

[0077] Preferably, the two-stage sintering includes sequentially performing first sintering and second sintering.

[0078] Preferably, the heating rate of the first sintering is 2℃ / min~5℃ / min, such as 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, etc.

[0079] Preferably, the holding temperature of the first sintering is 400℃~600℃, such as 400℃, 500℃ or 600℃, etc.

[0080] Preferably, the holding time of the first sintering is 4h~6h, such as 4h, 5h or 6h, etc.

[0081] Preferably, the heating rate of the second sintering is 4℃ / min~8℃ / min, such as 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min or 8℃ / min, etc.

[0082] Preferably, the holding temperature of the second sintering is 800℃~1100℃, such as 800℃, 900℃, 1000℃ or 1100℃, etc.

[0083] Preferably, the holding time of the second sintering is 8h~15h, such as 8h, 9h, 10h, 11h, 12h, 13h, 14h or 15h, etc.

[0084] In a fourth aspect, the present application also provides a battery comprising the ternary positive electrode material according to the third aspect.

[0085] The numerical range of the present application includes not only the above-mentioned point values, but also any point values between the above-mentioned numerical ranges which are not listed, and due to the limited space and for the sake of simplicity, the present application does not list the specific point values included in the range.

[0086] Compared with the prior art, the present application has the following beneficial effects:

[0087] (1) The present application adopts the structure of dense inner core, dense outer coating layer and loose porous intermediate coating layer, and simultaneously cooperates doping of the loose porous intermediate coating layer, on the one hand, the radial distribution of the positive electrode precursor material is uniform, the sphericity is high, which is beneficial to the transmission of lithium ions, and the rate performance of the material is improved; on the other hand, the special position doping and the specific structure make the doping elements distribute uniformly in the intermediate coating layer, the interatomic spacing is expanded and the original layered structure is not affected, the primary particles in the intermediate coating layer are refined, the mechanical stress caused by the anisotropic phase change from hexagon (H2) to hexagon (H3) is reduced (or the internal particle crack propagation is reduced), thereby showing high reversible discharge capacity under high cut-off voltage, and more importantly, the ternary positive electrode precursor material of the present application promotes the transmission of lithium ions in the electrochemical cycle process under high current density and high cut-off voltage, can effectively dissipate the stress caused by the anisotropic volume expansion in the cycle process, and significantly inhibits the formation of micro-cracks; thereby showing high capacity, high rate performance and long cycle performance.

[0088] (2) In the preparation process, the present application obtains the structure of dense inner core, dense outer coating layer and porous loose intermediate coating layer through the stage-type co-precipitation reaction, pH value control and doping process, at the same time ensures the uniform distribution of the doping elements in the intermediate coating layer, and the second co-precipitation process selects a lower pH value, which is also beneficial to expanding the interatomic spacing on the basis of doping in the bulk phase without destroying the original layered structure, refining the primary particles, and obtaining a more porous structure of the intermediate coating layer; and the preparation process does not need to add additional processes, is simple to operate, and is beneficial to large-scale production. BRIEF DESCRIPTION OF DRAWINGS

[0089] Figure 1 The SEM image of the ternary positive electrode precursor material provided for Example 1. DETAILED DESCRIPTION

[0090] The technical solutions of the present application will be further described through specific embodiments. Those skilled in the art should understand that the embodiments are only used to help understand the present application, and should not be regarded as specific limitation on the present application.

[0091] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the present application; the terms "include" and "have" and any variations thereof in the present application are intended to cover non-exclusive inclusion.

[0092] In the description of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise explicitly and specifically limited.

[0093] Embodiment 1

[0094] The present embodiment provides a ternary positive electrode precursor material, as shown in the formula (I), which comprises an inner core, an intermediate coating layer and an outer coating layer from inside to outside. Figure 1

[0095] The chemical formula of the ternary positive electrode precursor material of the inner core and the outer coating layer is Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0096] The chemical formula of the ternary positive electrode precursor material of the intermediate coating layer is (Ni 0.8 Co 0.1 Mn 0.1)0.997 W 0.003 (OH)2, that is, the molar amount of W accounts for 0.3% of the total molar amount of nickel, cobalt and manganese, which is 100%; the intermediate coating layer is a porous structure, and the porosity is 30%.

[0097] The preparation method of the ternary positive electrode precursor material is as follows:

[0098] (1) Prepare a mixed ternary metal salt solution with a total concentration of metal elements of 130 g / L and a molar ratio of Ni, Co and Mn of 80:10:10, a NaOH solution with a mass concentration of 15%, and an ammonia water with a mass concentration of 7.5%, and prepare a 25 g / L doped agent tungsten pentachloride solution;

[0099] (2) Prepare a bottom solution: add 150 L of pure water and a certain amount of NaOH solution and ammonia water to a 300 L reaction kettle, and pass nitrogen into the bottom solution at a rate of 2 m 3 / h, stir at a speed of 500 r / min to make it uniform, then heat to 80℃, control the pH value to be 11.8, and control the ammonia concentration to be 8 g / L;

[0100] (3) Control the reaction temperature to be 80℃, the stirring speed to be 400 r / min, and the flow rates of ammonia water, lye, ternary liquid and tungsten pentachloride solution to be stable, and carry out the following stage reaction

[0101] ​a. The first co-precipitation reaction: the ammonia solution, the sodium hydroxide solution, and the ternary mixed salt solution are flowed into the reactor to react, and the pH value is controlled to be 11.5, and the ammonia concentration is controlled to be 10 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of the ammonia water is 650 ml / h, and the flow rate of the lye is 2 L / h, when the internal nucleation is completed and the growth reaches 5.5 μm, the inner core solution is obtained, and the first co-precipitation reaction is completed;

[0102] b. The second co-precipitation reaction: after the first co-precipitation reaction is completed, the flow rates of the ammonia solution, the sodium hydroxide solution, and the ternary mixed salt solution are increased, the tungsten pentachloride solution pump is opened, the ammonia water, the lye, the ternary liquid, and the tungsten pentachloride are flowed into the reactor to react, and the pH value is controlled to be 10.6, and the ammonia concentration is controlled to be 6 g / L, wherein the flow rate of the ternary metal salt solution is 8 L / h, the flow rate of the ammonia water is 1000 mL / h, the flow rate of the lye is 3 L / h, and the flow rate of the tungsten pentachloride is 400 mL / h, so that the molar percentage of the tungsten pentachloride solution added accounts for 0.3% of the total molar percentage of Ni, Co, and Mn in the ternary precursor, and when the growth reaches 8.5 μm, the intermediate coating layer is formed, and the second co-precipitation reaction is completed;

[0103] c. The third co-precipitation reaction: after the second co-precipitation reaction is completed, the reaction is continued, the tungsten pentachloride solution pump is closed, and the pH value is controlled to be 11, and the ammonia concentration is controlled to be 9 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of the ammonia water is 600 mL / h, and the flow rate of the lye is 3 L / h, and the reaction is stopped when the particle size reaches 11 μm;

[0104] (4) The obtained qualified slurry is washed and dried, wherein the washing is performed for three times of alkali washing and three times of water washing, and the drying is performed at a low temperature of 150°C to obtain the ternary positive electrode precursor material.

[0105] From Figure 1 It can be seen that the intermediate coating layer morphology is more loose than the external coating layer and the inner core morphology, which is beneficial to effectively dissipate the stress caused by the anisotropic volume expansion in the subsequent cycle process, and significantly inhibits the formation of micro-cracks.

[0106] Example 2

[0107] The present embodiment provides a ternary positive electrode precursor material, which comprises an inner core, an intermediate coating layer, and an external coating layer from inside to outside;

[0108] The chemical formula of the ternary positive electrode precursor material of the inner core and the external coating layer is Ni 0.8 Co 0.1 Mn 0.1 (OH)2;

[0109] The chemical formula of the ternary positive electrode precursor material of the intermediate coating layer is (Ni 0.8 Co 0.1 Mn 0.1)0.95 W 0.05 (OH)2, that is, the molar amount of W accounts for 5% of the total molar amount of nickel, cobalt and manganese, which is 100%; the intermediate coating layer is a porous structure, and the porosity is 20%.

[0110] The preparation method of the ternary positive electrode precursor material is as follows:

[0111] (1) A mixed ternary metal salt solution with a total metal element concentration of 250 g / L and a molar ratio of Ni, Co and Mn of 80:10:10, a NaOH solution with a mass concentration of 30%, and ammonia water with a mass concentration of 20% are prepared, and a 50 g / L doped tungsten pentachloride solution is prepared;

[0112] (2) Preparation of the base solution: add 150 L of pure water and a certain amount of NaOH solution and ammonia water to a 300 L reaction kettle, and pass nitrogen into the base solution at a rate of 2 m 3 / h, stir at a speed of 500 r / min to make it uniform, then heat to 60℃, control the pH value to be 11.6, and control the ammonia concentration to be 10 g / L;

[0113] (3) Control the reaction temperature to be 60℃, the stirring speed to be 250 r / min, and the flow rates of ammonia water, lye, ternary solution and tungsten pentachloride solution to be stable, and carry out the following stage reactions

[0114] a. First co-precipitation reaction: the ammonia water solution, sodium hydroxide solution and ternary mixed salt solution are flowed into the reaction kettle to react, and the pH value is controlled to be 11 and the ammonia concentration is controlled to be 8 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of the ammonia water is 650 ml / h, and the flow rate of the lye is 2 L / h, the internal nucleation is completed and grows to 6 μm, and the inner core solution is obtained, and the first co-precipitation reaction is completed;

[0115] b. Second co-precipitation reaction: after the first co-precipitation reaction is completed, the flow rates of the ammonia water solution, sodium hydroxide solution and ternary mixed salt solution are increased, the tungsten pentachloride solution pump is opened, the ammonia water, lye, ternary solution and tungsten pentachloride are flowed into the reaction kettle to react at the same time, and the pH value is controlled to be 10.4 and the ammonia concentration is controlled to be 5 g / L, wherein the flow rate of the ternary metal salt solution is 8 L / h, the flow rate of the ammonia water is 1000 mL / h, the flow rate of the lye is 3 L / h, and the flow rate of the tungsten pentachloride is 400 mL / h, so that the molar percentage of tungsten liquid added accounts for 5% of the total molar percentage of Ni, Co and Mn in the ternary precursor, and when it grows to 8 μm, the intermediate coating layer is formed, and the second co-precipitation reaction is completed;

[0116] c.The third co-precipitation reaction: after the second co-precipitation reaction, continue the reaction, close the tungsten pentachloride solution pump, and control the pH value to be 10.8, the ammonia control concentration is 8 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of ammonia water is 600 mL / h, and the flow rate of lye is 3 L / h, and the feeding reaction is stopped when the particle size reaches 10 μm;

[0117] (4) The obtained qualified slurry is washed and dried, wherein the washing is performed three times of alkali washing and three times of water washing, and the drying is performed at a low temperature of 150℃ to obtain the ternary positive electrode precursor material.

[0118] Example 3

[0119] The present embodiment provides a ternary positive electrode precursor material, which comprises an inner core, an intermediate coating layer and an outer coating layer from inside to outside;

[0120] The chemical formula of the ternary positive electrode precursor material of the inner core and the outer coating layer is Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0121] The chemical formula of the ternary positive electrode precursor material of the intermediate coating layer is (Ni 0.8 Co 0.1 Mn 0.1)0.9995 W 0.0005 (OH)2, that is, the molar amount of W accounts for 0.05% of the total molar amount of nickel, cobalt and manganese; the intermediate coating layer is a porous structure, and the porosity is 40%.

[0122] The preparation method of the ternary positive electrode precursor material is as follows:

[0123] (1) Prepare a mixed ternary metal salt solution with a total metal element concentration of 50 g / L and a molar ratio of Ni, Co and Mn of 80:10:10, a NaOH solution with a mass concentration of 10%, and ammonia water with a mass concentration of 5%, and prepare a 20 g / L doped tungsten pentachloride solution;

[0124] (2) Prepare a bottom solution: add 150 L of pure water and a certain amount of NaOH solution and ammonia water to a 300 L reaction kettle, and pass nitrogen into the bottom solution at a rate of 2 m 3 / h, stir at a speed of 500 r / min to make it uniform, then heat to 80℃, control the pH value to be 11.5, and control the ammonia concentration to be 6 g / L;

[0125] (3) The reaction temperature is controlled at 40°C, the stirring speed is 380 r / min, and the flow rates of the ammonia water, the lye, the ternary liquid, and the tungsten pentachloride solution are stabilized, and the following stage reactions are carried out

[0126] a. First co-precipitation reaction: the ammonia water solution, the sodium hydroxide solution, and the ternary mixed salt solution are flowed into the reaction kettle for reaction, and the pH value is controlled at 11.3, and the ammonia concentration is controlled at 9 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of the ammonia water is 650 ml / h, and the flow rate of the lye is 2 L / h, when the internal nucleation is completed and the growth reaches 5 μm, an internal core solution is obtained, and the first co-precipitation reaction is completed;

[0127] b. Second co-precipitation reaction: after the first co-precipitation reaction is completed, the flow rates of the ammonia water solution, the sodium hydroxide solution, and the ternary mixed salt solution are increased, the tungsten pentachloride solution pump is opened, the ammonia water, the lye, the ternary liquid, and the tungsten pentachloride are flowed into the reaction kettle for reaction at the same time, and the pH value is controlled at 10.8, and the ammonia concentration is controlled at 7 g / L, wherein the flow rate of the ternary metal salt solution is 8 L / h, the flow rate of the ammonia water is 1000 mL / h, the flow rate of the lye is 3 L / h, and the flow rate of the tungsten pentachloride is 400 mL / h, so that the molar percentage of the tungsten pentachloride solution added accounts for 0.05% of the total molar percentage of Ni, Co, and Mn in the ternary precursor, and when the growth reaches 9 μm, an intermediate coating layer is formed, and the second co-precipitation reaction is completed;

[0128] c. Third co-precipitation reaction: after the second co-precipitation reaction is completed, the reaction is continued, the tungsten pentachloride solution pump is closed, the pH value is controlled at 10.9, and the ammonia concentration is controlled at 8 g / L, wherein the flow rate of the ternary metal salt solution is 5 L / h, the flow rate of the ammonia water is 600 mL / h, and the flow rate of the lye is 3 L / h, and the reaction is stopped when the particle size reaches 15 μm;

[0129] (4) The obtained qualified slurry is washed and dried, wherein the washing is performed for three times of alkali washing and three times of water washing, the drying is performed at a low temperature of 150°C, and the ternary positive electrode precursor material is obtained.

[0130] Example 4

[0131] The difference between this example and Example 1 is that in the ternary precursor material of this example, the molar ratio of Ni, Co, and Mn is 7:1:2, and the ratio is used in the material and the method.

[0132] The remaining conditions are consistent with those of Example 1.

[0133] Example 5

[0134] The difference between this example and Example 1 is that in this example, the molar percentage of tungsten is 0.05%, that is, the stoichiometric ratio of W in the intermediate coating layer is 0.0005.

[0135] In the preparation method, the addition amount of the tungsten pentachloride solution is adaptively adjusted.

[0136] The remaining conditions are consistent with those of Example 1.

[0137] Example 6

[0138] The difference between this example and Example 1 is that, in this example, the molar proportion of tungsten is 2%, that is, the stoichiometric ratio of W in the intermediate coating layer is 0.02.

[0139] In the preparation method, the addition amount of the tungsten pentachloride solution is adaptively adjusted.

[0140] The remaining conditions are consistent with those of Example 1.

[0141] Example 7

[0142] The difference between this example and Example 1 is that, in this example, the molar proportion of tungsten is 5%, that is, the stoichiometric ratio of W in the intermediate coating layer is 0.05.

[0143] In the preparation method, the addition amount of the tungsten pentachloride solution is adaptively adjusted.

[0144] The remaining conditions are consistent with those of Example 1.

[0145] Example 8

[0146] The difference between this example and Example 1 is that, in this example, the molar proportion of tungsten is 8%, that is, the stoichiometric ratio of W in the intermediate coating layer is 0.08.

[0147] In the preparation method, the addition amount of the tungsten pentachloride solution is adaptively adjusted.

[0148] The remaining conditions are consistent with those of Example 1.

[0149] Example 9

[0150] The difference between this example and Example 1 is that, in this example, the D50 of the particles obtained by the second coprecipitation reaction is 8 μm.

[0151] The remaining conditions are consistent with those of Example 1.

[0152] Example 10

[0153] The difference between this example and Example 1 is that, in this example, the D50 of the particles obtained by the second coprecipitation reaction is 10 μm.

[0154] The remaining conditions are consistent with those of Example 1.

[0155] Example 11

[0156] The difference between this example and Example 1 is that the D50 of the particles obtained in the second co-precipitation reaction in this example is 7.5 μm.

[0157] The remaining conditions are the same as in Example 1.

[0158] Example 12

[0159] The difference between this example and Example 1 is that the D50 of the particles obtained in the second co-precipitation reaction in this example is 9.5 μm.

[0160] The remaining conditions are the same as in Example 1.

[0161] Example 13

[0162] The difference between this example and Example 1 is that the flow rates of the ammonia solution, the sodium hydroxide solution, and the ternary mixed salt solution in the second co-precipitation reaction in this example are the same as in the first co-precipitation reaction.

[0163] The remaining conditions are the same as in Example 1.

[0164] Example 14

[0165] The difference between this example and Example 1 is that the doping element of the intermediate coating layer in this example is Zr.

[0166] In the preparation method, the tungsten pentachloride solution is replaced by a zirconium sulfate solution.

[0167] The remaining conditions are the same as in Example 1.

[0168] Comparative Example 1

[0169] The difference between this comparative example and Example 1 is that the intermediate coating layer in this comparative example is not doped with W.

[0170] In the preparation method, the tungsten pentachloride solution is not prepared.

[0171] The remaining conditions are the same as in Example 1.

[0172] Comparative Example 2

[0173] The difference between this comparative example and Example 1 is that the intermediate coating layer in this comparative example does not have a porous structure.

[0174] In Step (3) of the preparation method, the remaining reaction conditions except for the dopant solution are ensured to be the same for the first co-precipitation reaction and the second co-precipitation reaction.

[0175] Comparative Example 3

[0176] The difference between the present comparative example and Example 1 is that in the present comparative example, W is doped in the outer coating layer, and no W doping is performed in the middle coating layer, and the chemical formula of the middle coating layer and the outer coating layer are exchanged.

[0177] In the preparation method, the tungsten pentachloride solution is added in the third co-precipitation reaction stage to ensure that the doping amount of the tungsten pentachloride solution in the outer coating layer is the same as the doping amount of the tungsten pentachloride solution in the middle coating layer.

[0178] The remaining conditions are consistent with those of Example 1.

[0179] The remaining conditions are consistent with those of Example 1.

[0180] [Preparation of batteries and performance testing]

[0181] (I) Preparation of the positive electrode material: the positive electrode precursor material and lithium carbonate powder provided in the examples and comparative examples are weighed and mixed according to a molar ratio of Li / Me = 1:1.1, and two-stage solid-phase sintering is performed in an air atmosphere, i.e., first sintering, second sintering, and third sintering.

[0182] The first sintering is from room temperature to 600°C and isothermal for 5h, and the second sintering is from 600°C to 1000°C and isothermal for 12h, and after the sintering is completed, the sample is naturally cooled to room temperature in the furnace, and after the sample is crushed and passed through a 300-mesh sieve, a ternary positive electrode material is obtained.

[0183] (II) Preparation of the battery, the positive electrode sheet, the negative electrode sheet, the separator, and the electrolyte are provided for the preparation of the battery:

[0184] Preparation of the positive electrode sheet: the positive electrode slurry is prepared according to a ratio of positive electrode material: SP: PVDF = 90:5:5, and the positive electrode slurry is obtained for standby, wherein the solid content of the slurry is 60%; the aluminum foil is placed on the coating machine, and a 150μm film applicator is placed on the aluminum foil, the single crystal slurry is poured, the equipment is started for coating, and the electrode sheet is obtained after the coating is completed; the electrode sheet is placed in a 110°C oven for drying, and the positive electrode sheet is obtained after rolling.

[0185] The positive electrode sheets provided in the examples and comparative examples are cut into 15mm diameter discs using a punch press in a dry environment, and CR2032 coin-type half-batteries are assembled in a glove box using lithium metal sheets as the counter electrode, ceglard composite membranes as the separator, and adding electrolyte; the electrolyte is an organic solution obtained by mixing ethylene carbonate (EC) and dimethyl carbonate (DMC) at a volume ratio of 3:7, and the concentration of lithium salt (lithium hexafluorophosphate) in the electrolyte is 1mol / L.

[0186] (III) Performance testing:

[0187] The performance of the CR2032 coin-shaped half-batteries provided in the examples and the comparative examples was tested by using Wuhan Lan Electric CT2001A system.

[0188] The first discharge capacity and the first efficiency were tested by charging and discharging at 1C in the voltage range of 3.0-4.5V in an environment of 25℃, and the capacity retention rate after 100 cycles was obtained.

[0189] The rate performance test was carried out by charging at 1C and discharging at 5C in the voltage range of 3.0-4.5V in an environment of 25℃, and the capacity retention rate after 100 cycles was obtained.

[0190] The test results are shown in Table 1.

[0191] Table 1

[0192]

[0193]

[0194] From Table 1, it can be seen that:

[0195] In the ternary positive electrode precursor material of the application, the structure of the dense inner core, the dense outer coating layer and the loose porous intermediate coating layer is adopted, and the doping of the loose porous intermediate coating layer is simultaneously performed, so that the positive electrode material exhibits high capacity, high rate performance and long cycle performance.

[0196] The data of Example 1, Example 5, Example 6, Example 7 and Example 8 show that further adjusting the molar ratio of the doping elements in the intermediate coating layer makes the effect of the doping elements more excellent.

[0197] The data results of Example 1 and Example 13 show that in the preparation process of the ternary positive electrode precursor material, increasing the feeding speed of each raw material in the reaction process during the second co-precipitation reaction further optimizes the morphology of the primary particles, refines the grain, and makes the electrochemical performance more excellent.

[0198] The data results of Example 1 and Example 14 show that when tungsten is selected as the doping element, the improvement effect of the cycle performance and the rate performance is more obvious.

[0199] The data results of Example 1 and Comparative Example 1, Comparative Example 2 and Comparative Example 3 show that the structure distribution of the precursor material and the doping and position distribution of the doping elements in the application are important, and through the synergistic cooperation of the structure position relationship and the corresponding structure and the doping elements, the capacity, the first efficiency, the rate and the cycle performance can be greatly improved.

[0200] The applicant states that the above description is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto, and it should be understood by those skilled in the art that any changes or replacements within the technical scope disclosed by the present application can be easily thought out by those skilled in the art, and all of them fall within the protection scope and disclosure scope of the present application.

Claims

1. A ternary cathode precursor material, characterized in that, The ternary positive electrode precursor material comprises, from inside to outside, an inner core, an intermediate coating layer, and an outer coating layer; The inner core and the outer coating layer comprise undoped ternary positive electrode precursor material, and the intermediate coating layer comprises ternary positive electrode precursor material containing a doping element; the intermediate coating layer has a porous structure.

2. The ternary cathode precursor material of claim 1, wherein, The chemical general formula of the ternary positive electrode precursor material in the core is Ni x Co y Mn z (OH)2, wherein 0.6 Preferably, the ternary positive electrode precursor material in the outer coating layer has a chemical formula of Ni m Co n Mn e (OH)2, wherein 0.6 < m < 0.9, 0 < n < 0.2, 0 < e < 0.2, and m + n + e = 1. 3.The ternary positive electrode precursor material of claim 1 or 2, characterized in that, In the intermediate coating layer, the molar content of the doping element accounts for 0.05%-5% of the total molar content of the ternary main metals nickel, cobalt, and manganese, which is 100%; Preferably, the chemical formula of the ternary positive electrode precursor material in the intermediate coating layer is (Ni a Co b Mn c)1-d M d (OH)2, 0.6 Preferably, said (Ni a Co b Mn c)1-d M d (OH)2, 0.0005≤d≤0.

02. Preferably, M comprises any one or a combination of at least two of Al, Ti, Nb, Zr, W, V, Sr, Ga, Ce, Y, La, Sb, or B, and is preferably W; Preferably, the porosity of the intermediate coating layer is 20%-40%.

4. A method for preparing the ternary cathode precursor material according to any one of claims 1-3, characterized in that, The preparation method comprises the following steps: The first main metal mixed salt solution, the first precipitant solution, and the first complexing agent solution are added in parallel flow to perform a first co-precipitation reaction to obtain the inner core; After the inner core is obtained, the second main metal mixed salt solution, the doping agent solution, the second precipitant solution, and the second complexing agent solution are added in parallel flow to perform a second co-precipitation reaction to form the intermediate coating layer with a porous structure on the surface of the inner core; After the intermediate coating layer is obtained, the third main metal mixed salt solution, the third precipitant solution, and the third complexing agent solution are added in parallel flow to perform a third co-precipitation reaction to form the outer coating layer, thereby obtaining the ternary positive electrode precursor material; The pH value of the second co-precipitation reaction is lower than that of the first co-precipitation reaction, and the pH value of the second co-precipitation reaction is lower than that of the third co-precipitation reaction.

5. The production method according to claim 4, characterized by, The main metals comprise nickel, cobalt, and manganese; Preferably, the doping element in the doping agent comprises any one or a combination of at least two of Al, Ti, Nb, Zr, W, V, Sr, Ga, Ce, Y, La, Sb, or B, and is preferably W; Preferably, the concentration of the first main metal mixed salt solution, the second main metal mixed salt solution, and the third main metal mixed salt solution is independently 50 g / L-250 g / L; Preferably, the concentration of the doping agent solution is 20 g / L-50 g / L; Preferably, the mass fraction of the first precipitant solution, the second precipitant solution, and the third precipitant solution is independently 10%-30%; Preferably, the mass fraction of the first complexing agent solution, the second complexing agent solution, and the third complexing agent solution is independently 5%-20%.

6. The preparation method according to claim 4, characterized in that, The feeding rate of each raw material in the first co-precipitation reaction process is less than the feeding rate of each raw material in the corresponding second co-precipitation reaction process; Preferably, the feeding rate of each raw material in the third co-precipitation reaction process is less than the feeding rate of each raw material in the corresponding second co-precipitation reaction process; Preferably, the feeding rate of the first main metal mixed salt solution and the third main metal mixed salt solution is independently 4 L / h-6 L / h; Preferably, the feeding rate of the second main metal mixed salt solution is 6 L / h-10 L / h; Preferably, the feeding speed of the first precipitant solution and the third precipitant solution is independently 1.5L / h~3L / h; Preferably, the feeding speed of the second precipitant solution is 2.5L / h~4L / h; Preferably, the feeding speed of the first complexing agent solution and the third complexing agent solution is independently 500mL / h~800mL / h; Preferably, the feeding speed of the second complexing agent solution is 800mL / h~1000mL / h; Preferably, the feeding speed of the dopant solution is 300mL / h~500mL / h.

7. The production method according to claim 4 or 6, characterized by, The pH value of the first co-precipitation reaction is 11~11.5; Preferably, the pH value of the second co-precipitation reaction is 10.4~10.8; Preferably, the pH value of the third co-precipitation reaction is 10.8~11; Preferably, the concentration of the complexing agent in the reaction solution system during the first co-precipitation reaction is 8g / L~10g / L; Preferably, the concentration of the complexing agent in the reaction solution system during the second co-precipitation reaction is 5g / L~7g / L; Preferably, the concentration of the complexing agent in the reaction solution system during the second co-precipitation reaction is 7g / L~9g / L.

8. The preparation method according to claim 4, characterized in that, The median particle size D50 of the inner core is 4μm~6μm; Preferably, the target median particle size D50 of the particles obtained by the second co-precipitation reaction is 8μm~9μm; Preferably, the target median particle size D50 of the particles obtained by the third co-precipitation reaction is 10μm~15μm.

9. A ternary cathode material, characterized in that, The ternary positive electrode material is obtained by mixing and sintering the ternary positive electrode precursor material prepared by the method of any one of claims 1-3 or any one of claims 4-8 and raw materials including at least a lithium source.

10. A battery, characterized by The battery includes the ternary positive electrode material of claim 9.

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