Method for preparing core-shell structure ternary precursor from carbonate and application of core-shell structure ternary precursor

Abstract

The invention belongs to the field of battery materials, and provides a method for preparing a core-shell structure ternary precursor from carbonate and application of the core-shell structure ternary precursor, according to the method, only the carbonate is used as a precipitator, the carbonate and two ternary metal salt solutions are subjected to a co-precipitation reaction in sequence, and the core-shell structure ternary precursor is obtained. According to the invention, hydroxide, ammonia water or ammonium salt is not used for carrying out a coprecipitation method, the obtained carbonate precursor with the core-shell structure has good sphericity and uniform particle size distribution, and the method is lower in cost and simpler and more efficient to operate; in-situ doping is further carried out on a composite material of H2V3O8 nanowires and graphene and the core-shell structure ternary precursor to obtain the core-shell structure ternary positive electrode material, so that the transmission path of lithium ions is greatly shortened, active sites on the surface of the electrode material are increased, local stress can be effectively relieved, and the performance of the lithium ion battery is improved. Therefore, the cycling stability and the rate capability are further improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery materials and relates to a method for preparing a core-shell structure ternary precursor from carbonate and its application. Background Art

[0002] With the continuous development of the new energy industry, lithium-ion batteries have received widespread attention as a new type of green energy battery. Among lithium-ion batteries, ternary lithium-ion batteries have excellent specific capacity and cycle performance and are widely used in the field of electric vehicles. The performance of ternary lithium-ion batteries is greatly affected by the positive electrode material. In the positive electrode material, as the nickel content increases, the specific capacity increases accordingly, but its cycle performance and stability will decrease accordingly. Since the positive electrode material is usually processed from the positive electrode material precursor, in order to overcome the defects of reduced cycle performance and stability performance brought about by the increase in nickel content, the existing technology usually tends to prepare a positive electrode material precursor with a core-shell structure, so that the positive electrode material prepared therefrom, especially the high-nickel ternary material, has the characteristics of high capacity, high cycle and high stability.

[0003] However, the core-shell structure cathode material precursors prepared by the existing technology fail to regulate their performance from a more fundamental perspective, and thus cannot effectively enable the further obtained cathode materials to achieve a good improvement in both capacity and cycle performance. At present, the synthesis of core-shell structure ternary precursors is usually carried out by co-precipitation with hydroxide and ammonia water, which can make nickel, cobalt and manganese ions uniformly precipitated at the atomic scale. However, due to the 2+ 、Mn 2+ It is easily oxidized under alkaline conditions, and protective gas is generally introduced during the synthesis process. Although this method has been widely used in production practice, it has the problem of complex process control. The reaction pH and ammonia concentration need to be monitored and controlled in real time, resulting in high time and labor costs. At the same time, the reaction process produces a large amount of nitrogen-containing wastewater, which pollutes the environment and needs to be recycled and harmlessly treated, which also increases production costs.

[0004] Therefore, it is still necessary to develop a new scheme for synthesizing core-shell structured ternary precursors, so as to prepare high-quality core-shell structured ternary precursors under milder and less harsh conditions, with simpler processes and lower costs, laying the foundation for obtaining high-performance high-nickel ternary positive electrode materials. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention aims to provide a method and application for preparing a core-shell structure ternary precursor using carbonate. The method uses only carbonate as a precipitant, and sequentially performs a coprecipitation reaction with two ternary metal salt solutions to obtain a core-shell structure ternary precursor. The present invention does not use hydroxide, ammonia water, or ammonium salts for the coprecipitation process. The obtained core-shell structure carbonate precursor has good sphericity and uniform particle size distribution. The method is low-cost, simpler to operate, and more efficient.

[0006] To achieve this object, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing a core-shell structure ternary precursor from carbonate, the method comprising the following steps:

[0008] Prepare ternary metal salt solution A, ternary metal salt solution B and precipitant solution respectively; the precipitant solution is a carbonate solution;

[0009] First, the ternary metal salt solution A is mixed with the precipitant solution in parallel to perform a first coprecipitation reaction to obtain a core precursor; the addition of the ternary metal salt solution A is stopped, and the ternary metal salt solution B is continued to be mixed with the precipitant solution in parallel to perform a second coprecipitation reaction to form an outer shell precursor, thereby obtaining a core-shell structure ternary precursor.

[0010] The method described in the present invention is different from the traditional method using hydroxide, ammonia water or ammonium salt as a precipitant. The method of the present invention adopts a carbonate co-precipitation method, which greatly simplifies the preparation process of the precursor. No ammonia water is used in the reaction process, and no nitrogen-containing wastewater is generated, which is environmentally friendly; the cost is low and has broad application prospects; and the obtained carbonate core-shell structure precursor has good sphericity and uniform particle size distribution, which is conducive to the subsequent ternary positive electrode material to obtain excellent size and appearance characteristics.

[0011] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0012] As a preferred technical solution of the present invention, the carbonate solution includes sodium carbonate and / or sodium bicarbonate.

[0013] As a preferred technical solution of the present invention, in the first coprecipitation reaction, the ratio of the molar amount of carbonate ions in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution A is (1-2):1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, etc.

[0014] Preferably, in the second coprecipitation reaction, the ratio of the molar amount of carbonate in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution B is (1-2):1, for example, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, 1.7:1, 1.8:1, 1.9:1 or 2:1, etc.

[0015] As a preferred technical solution of the present invention, the chemical formula of the core precursor is Ni x Co y Mn z CO3, wherein 0.8≤x<1.0, 0<y<0.2, 0<z<0.2, x+y+z=1, controls the dosage ratio of the metal salt in the ternary metal salt solution A; for example, x can be 0.8, 0.83, 0.85, 0.88, 0.9, 0.92, 0.95 or 0.98, etc., for example, y can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, 0.14, 0.16 or 0.18, etc., for example, z can be 0.01, 0.03, 0.05, 0.08, 0.1, 0.12, 0.14, 0.16 or 0.18, etc.

[0016] Preferably, the shell precursor is Ni a Co b M c CO3, M is Mn and / or Al, 0<a<1, 0<b<1, 0<c<1, a+b+c=1, controlling the dosage ratio of the metal salt in the ternary metal salt solution B; for example, a can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc., for example, b can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc., for example, c can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8 or 0.9, etc.

[0017] Preferably, a≤x.

[0018] As a preferred technical solution of the present invention, the average particle size of the core precursor is 3 to 8 μm, for example, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, 7.3 μm, 7.5 μm, 7.8 μm or 8 μm, etc.

[0019] Preferably, the thickness of the shell precursor is 3 to 8 μm, for example, 3 μm, 3.2 μm, 3.5 μm, 3.8 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, 6.2 μm, 6.5 μm, 6.8 μm, 7 μm, 7.3 μm, 7.5 μm, 7.8 μm or 8 μm, etc.

[0020] Ammonia water has the following main functions in the traditional carbonate co-precipitation method: 2+ 、Co 2+ The metal ions form stable complexes, reduce the concentration of free metal ions, slow down the precipitation rate, and promote the simultaneous precipitation of multiple metal ions; through complex competition, reduce the interaction between metal ions and OH - Direct combination avoids the formation of hydroxides such as Ni(OH)2 and Co(OH)2. In the present invention, when carbonate is used as a precipitant after removing ammonia water, metal ions (especially Ni 2+ 、Co 2+ ) increases the difference in precipitation rates, which can easily lead to step-by-step precipitation (such as NiCO3 precipitates first, CoCO3 and MnCO3 lag behind), causing composition segregation and decreased uniformity of particle morphology, and may cause agglomeration or uneven particle size distribution. However, homogeneous co-precipitation can be achieved by optimizing key synthesis parameters.

[0021] Specifically, the present invention does not use ammonia as a complexing agent, and avoids the problem of step-by-step precipitation of multiple metal ions through the following mechanisms: 1. Kinetic synchronization: by controlling the concentration of the raw material solution (referring to ternary metal salt solution A and ternary metal salt solution B) and controlling the feed flow rate (to control the pH), the solubility product (Ksp) of different metal ions reaches the precipitation threshold under the same conditions, thereby achieving synchronous precipitation; 2. Supersaturation control: maintaining low supersaturation through slow dripping and stirring to avoid explosive nucleation and ensure uniform particle growth.

[0022] Specifically, homogeneous coprecipitation can be achieved by optimizing key synthesis parameters: 1. Strictly limit the pH to the weak alkaline range (7.5-10) to inhibit the formation of hydroxides; 2. Reduce the concentration of metal salts and add them slowly at a low speed to form a uniform supersaturated environment, promote homogeneous nucleation, and reduce particle agglomeration; 3. Strengthen stirring (300-500rpm) and appropriate temperature control to reduce local supersaturation differences. The reaction temperature can be controlled at 50-70°C. Low temperature (<50°C) will reduce the reaction rate, resulting in incomplete precipitation or low crystallinity. High temperature (>70°C) may accelerate particle coarsening, and carbonates are easily decomposed (such as NH4HCO3 decomposition into CO2 and NH3); 4. Extend the aging time (2-10h) to improve the uniformity of the composition through aging.

[0023] Therefore, as a preferred technical solution of the present invention, the total molar concentration of the metal elements in the ternary metal salt solution A and the ternary metal salt solution B is 0.1-2 mol / L, for example, 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L.

[0024] As a preferred technical solution of the present invention, the pH of the first coprecipitation reaction and the second coprecipitation reaction are both 7.5 to 10, for example, 7.5, 7.8, 8, 8.3, 8.5, 8.8, 9, 9.2, 9.5, 9.8 or 10, etc.; further, the pH is controlled by adjusting the feed flow rate of the carbonate solution.

[0025] Preferably, the first coprecipitation reaction and the second coprecipitation reaction are both carried out under stirring, and the stirring speed is 300-500 rpm, for example, 300 rpm, 330 rpm, 350 rpm, 380 rpm, 400 rpm, 420 rpm, 450 rpm, 480 rpm or 500 rpm.

[0026] Preferably, the temperature of the first coprecipitation reaction and the second coprecipitation reaction is 50-70°C, for example, 50°C, 53°C, 55°C, 58°C, 60°C, 62°C, 65°C, 68°C or 70°C.

[0027] Preferably, after the second coprecipitation reaction is completed, aging is carried out; the aging time is 2 to 10 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours or 10 hours, and the aging temperature is 60 to 80°C.

[0028] Preferably, each raw material solution is transported by a peristaltic pump.

[0029] In a second aspect, the present invention provides a core-shell structure ternary precursor obtained according to the method described in the first aspect.

[0030] In a third aspect, the present invention provides a method for preparing a core-shell structured ternary positive electrode material, the preparation method comprising: mixing the core-shell structured ternary precursor described in the second aspect with a lithium source, and calcining the mixture to obtain a core-shell structured ternary positive electrode material.

[0031] As a preferred technical solution of the present invention, the preparation method further includes mixing H2V3O8 nanowire and graphene composite materials with the core-shell structure ternary precursor and the lithium source.

[0032] The H2V3O8 nanowire-graphene composite is prepared using a hydrothermal method. A H2V3O8 precursor solution is mixed with a GO dispersion, ultrasonically dispersed, and subjected to a hydrothermal reaction (e.g., 180°C for 24 hours) to in situ grow the H2V3O8 nanowires on the GO surface. The mixture is then centrifuged and washed alternately with water and ethanol until the wastewater is clear and transparent, and then dried to obtain the H2V3O8 nanowire-graphene composite.

[0033] The preparation method of the present invention uses H2V3O8 nanowires and graphene composite materials for doping. The nanowire structure greatly shortens the transmission path of lithium ions, increases the active sites on the surface of the electrode material, and is conducive to the reversible insertion and extraction reaction of lithium ions. At the same time, when the volume expands during the electrochemical process, the one-dimensional nanowire structure is more stable than ordinary nanoparticles and can effectively relieve local stress. In addition, vanadium oxide materials have a high theoretical capacity and abundant sources. All valence electrons of V atoms can participate in bonding, thereby forming V 2+ to V 5+ The multivalent V facilitates the formation of strong V-O bonds and various structures, which translates to excellent battery cycling stability. Graphene, due to its large surface area and excellent conductivity, is an excellent composite conductive additive. Large graphene flakes, when combined with nanomaterials, act as a connector, facilitating the formation of a stable three-dimensional network. Doping H2V3O8 nanowires with graphene composites can significantly improve the rate capability and cycling stability of electrode materials.

[0034] Preferably, the H2V3O8 nanowire and graphene composite material accounts for 0.1% to 4% of the mass of the core-shell structure ternary precursor, for example, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.5%, 3%, 3.2%, 3.5%, 3.8% or 4%, etc.

[0035] Preferably, the lithium source includes lithium hydroxide, and the molar ratio of the lithium element in the lithium source to the core-shell structure ternary precursor is (1.02-1.08):1, for example, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1 or 1.08:1, etc.

[0036] Preferably, the mixing method includes grinding for 30 to 40 minutes, such as 30 minutes, 32 minutes, 34 minutes, 36 minutes, 38 minutes or 40 minutes.

[0037] Preferably, the calcination is performed under an oxygen atmosphere.

[0038] Preferably, the calcination heating rate is 4 to 6°C / min, for example, 4°C / min, 4.5°C / min, 5°C / min, 5.5°C / min or 6°C / min, the holding temperature is 500 to 800°C, for example, 500°C, 530°C, 550°C, 580°C, 600°C, 620°C, 650°C, 680°C, 700°C, 720°C, 750°C, 780°C or 800°C, and the holding time is 12 to 20h, for example, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h or 20h.

[0039] In a fourth aspect, the present invention provides a core-shell structured ternary positive electrode material obtained according to the preparation method described in the third aspect.

[0040] In a fifth aspect, the present invention provides a battery comprising the core-shell structure ternary positive electrode material described in the fourth aspect.

[0041] It should be noted that due to space limitations and to avoid redundancy, the present invention does not exhaustively list all point values ​​within the above numerical range, but is not limited to the listed values. Other unlisted values ​​within the above numerical range are also applicable.

[0042] Compared with the existing technical solutions, the present invention has at least the following beneficial effects:

[0043] The present invention does not use hydroxide, ammonia water or ammonium salt to carry out the co-precipitation method, and the obtained core-shell structured carbonate precursor has good sphericity and uniform particle size distribution. The method has lower cost and is simpler and more efficient to operate.

[0044] The present invention further utilizes a composite material of H2V3O8 nanowires and graphene and a core-shell structure ternary precursor for in-situ doping to obtain a core-shell structure ternary positive electrode material, which greatly shortens the transmission path of lithium ions, increases the active sites on the surface of the electrode material, and can effectively relieve local stress, thereby further improving the cycle stability and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the SEM test image of the ternary precursor obtained in Example 1. DETAILED DESCRIPTION

[0046] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0047] It should be apparent to those skilled in the art that the embodiments are only intended to help understand the present invention and should not be considered as specific limitations of the present invention.

[0048] Example 1

[0049] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, the method comprising the following steps:

[0050] (1) Prepare nickel source, cobalt source and manganese source into ternary metal salt solution A and ternary metal salt solution B, and prepare precipitant solution sodium carbonate solution; according to the chemical formula Ni 0.8 Co 0.1 Mn 0.1 CO3 controls the dosage ratio of metal salt in ternary metal salt solution A; according to the chemical formula Ni 0.5 Co 0.2 Mn 0.3 CO3 controls the dosage ratio of the metal salt in the ternary metal salt solution B;

[0051] (2) The ternary metal salt solution A and the precipitant solution are added to the reactor at a steady rate to carry out a first coprecipitation reaction. Specifically, the ratio of the molar amount of carbonate in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution A is 1.5:1. The pH of the first coprecipitation reaction is controlled to be 8.1-8.4, and the first coprecipitation reaction is carried out under stirring at 420 rpm and a temperature of 60°C. As the coprecipitation reaction proceeds, a high nickel core precursor is obtained. The core precursor molecular formula is Ni 0.8 Co 0.1 Mn 0.1 CO3, average particle size 6 μm;

[0052] (3) Stop adding the ternary metal salt solution A, and continue to mix the ternary metal salt solution B and the precipitant solution in parallel to perform a second coprecipitation reaction. Specifically, the ratio of the molar amount of carbonate in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution A is 1.4:1, and the pH of the second coprecipitation reaction is controlled to be 8.1-8.4. The second coprecipitation reaction is carried out under stirring at 420 rpm and a temperature of 60°C. As the coprecipitation reaction proceeds, a core-shell structure precursor is formed; after the second coprecipitation reaction is completed, aging is carried out for 6 hours to obtain a core-shell structure ternary precursor, wherein the molecular formula of the shell precursor is Ni 0.5 Co 0.2 Mn 0.3 CO3, thickness of 7μm, washed and dried.

[0053] Example 2

[0054] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the pH value of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from being controlled between 8.1 and 8.4 to being controlled between 7 and 7.3. Except for the above, other conditions are exactly the same as those in Example 1.

[0055] Example 3

[0056] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the pH value of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from being controlled between 8.1 and 8.4 to being controlled between 7.5 and 7.8. Except for the above, other conditions are exactly the same as those in Example 1.

[0057] Example 4

[0058] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the pH value of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from being controlled between 8.1 and 8.4 to being controlled between 9.7 and 10. Except for the above, the other conditions are exactly the same as those in Example 1.

[0059] Example 5

[0060] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the pH value of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from being controlled between 8.1 and 8.4 to being controlled between 10.5 and 10.8. Except for the above, other conditions are exactly the same as those in Example 1.

[0061] Example 6

[0062] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the stirring speed of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) is adjusted from 400 rpm to 200 rpm. Except for the above, other conditions are exactly the same as those in Example 1.

[0063] Example 7

[0064] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the stirring speed of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) is adjusted from 400 rpm to 300 rpm. Except for the above, other conditions are exactly the same as those in Example 1.

[0065] Example 8

[0066] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the stirring speed of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) is adjusted from 400 rpm to 500 rpm. Except for the above, other conditions are exactly the same as those in Example 1.

[0067] Example 9

[0068] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the stirring speed of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) is adjusted from 400 rpm to 600 rpm. Except for the above, other conditions are exactly the same as those in Example 1.

[0069] Example 10

[0070] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the temperature of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from 60°C to 40°C. Except for the above, other conditions are exactly the same as those in Example 1.

[0071] Example 11

[0072] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the temperature of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from 60°C to 50°C. Except for the above, other conditions are exactly the same as those in Example 1.

[0073] Example 12

[0074] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the temperature of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from 60°C to 70°C. Except for the above, other conditions are exactly the same as those in Example 1.

[0075] Example 13

[0076] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the temperature of the first coprecipitation reaction in step (2) and the second coprecipitation reaction in step (3) are adjusted from 60°C to 80°C. Except for the above, other conditions are exactly the same as those in Example 1.

[0077] Example 14

[0078] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, wherein the aging time in step (3) is adjusted from 6 h to 1 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0079] Example 15

[0080] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, in which the aging time in step (3) is adjusted from 6 h to 4 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0081] Example 16

[0082] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, in which the aging time in step (3) is adjusted from 6 h to 8 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0083] Example 17

[0084] This embodiment provides a method for preparing a core-shell structure ternary precursor from carbonate, in which the aging time in step (3) is adjusted from 6 h to 12 h. Except for the above, other conditions are exactly the same as those in Example 1.

[0085] Comparative Example 1

[0086] This comparative example provides a method for preparing a core-shell structure ternary precursor from carbonate. In the method, in step (1), the precipitant solution is replaced by sodium carbonate solution with sodium hydroxide solution, and a complexing agent ammonia water is added at the same time. Except for the above, other conditions are exactly the same as those in Example 1.

[0087] Application Example 1

[0088] This application example provides a method for preparing a core-shell structured ternary cathode material, the preparation method comprising the following steps:

[0089] The core-shell structure ternary precursor obtained in Example 1 and Comparative Example 1 was evenly mixed with the H2V3O8 nanowire and graphene composite material, wherein the H2V3O8 nanowire and graphene composite material accounted for 2.2% of the mass of the core-shell structure ternary precursor, and then mixed with lithium hydroxide, a lithium source, wherein the molar ratio of the lithium element in the lithium hydroxide to the core-shell structure ternary precursor was 1.05:1. The mixture was fully mixed and ground in a mortar for 36 minutes, and then heated from room temperature to 650°C at a heating rate of 5°C / min in an oxygen atmosphere. After calcination and heat preservation at this temperature for 12 to 20 hours, the mixture was naturally cooled to room temperature to obtain a core-shell structure ternary positive electrode material.

[0090] Application Example 2

[0091] This application example provides a method for preparing a core-shell structured ternary positive electrode material. The preparation method uses the core-shell structured ternary precursor provided in Example 1, and adjusts the mass of the H2V3O8 nanowire and graphene composite material in the core-shell structured ternary precursor from 2.2% to 0.01%. Except for the above, other conditions are exactly the same as in Example 1.

[0092] Application Example 3

[0093] This application example provides a method for preparing a core-shell structure ternary positive electrode material. The preparation method uses the core-shell structure ternary precursor provided in Example 1, and adjusts the mass of the H2V3O8 nanowire and graphene composite material in the core-shell structure ternary precursor from 2.2% to 0.1%. Except for the above, other conditions are exactly the same as in Example 1.

[0094] Application Example 4

[0095] This application example provides a method for preparing a core-shell structure ternary positive electrode material. The preparation method uses the core-shell structure ternary precursor provided in Example 1, and adjusts the mass of the H2V3O8 nanowire and graphene composite material in the core-shell structure ternary precursor from 2.2% to 4%. Except for the above, other conditions are exactly the same as in Example 1.

[0096] Application Example 5

[0097] This application example provides a method for preparing a core-shell structured ternary positive electrode material. The preparation method uses the core-shell structured ternary precursor provided in Example 1, and adjusts the mass of the H2V3O8 nanowire and graphene composite material in the core-shell structured ternary precursor from 2.2% to 5%. Except for the above, other conditions are exactly the same as in Example 1.

[0098] Application control example 1

[0099] This application control example provides a preparation method for a core-shell structured ternary positive electrode material. The preparation method does not use H2V3O8 nanowires and graphene composite materials for doping. Except for the above, other conditions are exactly the same as those in Application Example 2.

[0100] The ternary cathode materials from the application examples and control examples were mixed with conductive carbon black (SP) and polyvinylidene fluoride (PVDF) in a 90:5:5 mass ratio. N-methylpyrrolidone was used as the solvent and stirred to form a slurry. The resulting slurry was evenly coated onto aluminum foil using a scraper with a coating gap of 100 μm. After coating, the electrode sheets were air-dried at 120°C and then roller-pressed. Finally, the dried electrode sheets were cut into Φ12 circular sheets. After vacuum drying at 120°C, the electrode sheets were weighed to obtain the button half-cell cathode sheets. The battery was then assembled with a LiPF6 liquid electrolyte, a separator, and a lithium metal sheet anode.

[0101] The resulting batteries were subjected to performance testing using a constant current charge-discharge mode with a voltage range of 2.5 to 4.5 V. Discharge capacity testing involved charging at 0.1C to 4.3V. Rate performance testing involved charging and discharging at 0.1C, 0.2C, 0.5C, 1C, and 2C, respectively. After five cycles at each rate, the battery returned to 0.1C. The capacity retention rate was calculated based on the capacity loss, and rate performance was compared. Cyclic performance testing involved charging and discharging at 1C, with the material capacity after 500 cycles analyzed to determine the cycle capacity retention rate. All tests were conducted at room temperature. The test results are shown in Table 1.

[0102] Table 1

[0103]

[0104]

[0105] From the above we can see that:

[0106] Example 1 is compared with Comparative Example 1. Figure 1 As shown, the core-shell structure ternary precursor material prepared by the present invention using only carbonate as a precipitant has a smooth surface and good sphericity, and its cycle performance and rate performance are not much different from those of the core-shell structure precursor obtained by co-precipitation using a hydroxide and ammonia system. Therefore, the precursor prepared by the carbonate precipitant is superior to the hydroxide / ammonia system in terms of cost and environmental protection under the premise of comparable cycle life and rate performance. Homogeneous co-precipitation can be achieved by optimizing key synthesis parameters: 1. Strictly limit the pH to the weak alkaline range (7.5-10) to inhibit the formation of hydroxide; 2. Reduce the concentration of metal salt and add it slowly at a low speed, which is conducive to forming a uniform supersaturated environment, promoting homogeneous nucleation, and reducing particle agglomeration; 3. Strengthening stirring (300-500rpm) and appropriate temperature control can reduce local supersaturation differences, and the reaction temperature can be controlled at 50-70°C. Low temperature (<50°C) will reduce the reaction rate, resulting in incomplete precipitation or low crystallinity. High temperature (>70°C) may accelerate particle coarsening and carbonates are easily decomposed (such as NH4HCO3 decomposition into CO2 and NH3). 4. Extend the aging time (2 to 10 hours) to improve the uniformity of the composition through aging.

[0107] Comparing Application Examples 2-5 with Example 1 in Application Example 1, it can be seen that the addition amount of the H2V3O8 nanowire and graphene composite material described in the present invention will affect the battery performance. When the addition amount is within an appropriate range, the performance of the prepared positive electrode material is better. If the addition amount is too little, the network constructed by graphene is discontinuous and incomplete, the nanowires cannot provide sufficient additional lithium ion storage active sites, and the doping concentration of vanadium is low, which will lead to limited improvement in the overall electronic conductivity of the electrode material, which is not conducive to rapid charge transfer during high-rate charging and discharging, and the rate performance improvement is not obvious. The effect of vanadium on improving the stability of the material is also insufficient; if the addition amount is too much, the proportion of high-capacity ternary active material in the electrode will be reduced, resulting in a decrease in the energy density of the electrode. Excessive high specific surface area H2V3O8 nanowire / graphene composite material may aggravate the side reaction with the electrolyte, increase the interface impedance, and lead to accelerated cycle life decay and deterioration of rate performance.

[0108] As can be seen from Example 1 of Application Example 1 and Application Control Example 1, the addition of the H2V3O8 nanowires and graphene composite materials used in the present invention for doping is necessary, which can significantly improve the cycle performance and rate performance, because the main function of graphene is to construct a three-dimensional conductive network with good conductivity and high mechanical strength, which can improve the conductivity and structural stability of the composite material. The nanowire structure can greatly shorten the transmission path of lithium ions, increase the active sites on the surface of the electrode material, and is conducive to the reversible insertion and extraction reaction of lithium ions. Vanadium doping helps to stabilize the material structure and reduce harmful phase changes during the charge and discharge process, thereby improving the cycle stability. At the same time, when the volume expands during the electrochemical process, the one-dimensional nanowire structure is more stable than ordinary nanoparticles, and can effectively relieve local stress, thereby making the cycle stability and rate performance of the battery more excellent.

[0109] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

[0110] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any appropriate manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0111] In addition, the various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A method for preparing a core-shell structure ternary precursor from carbonate, characterized in that: The method comprises the following steps: Prepare ternary metal salt solution A, ternary metal salt solution B and precipitant solution respectively; the precipitant solution is a carbonate solution; First, the ternary metal salt solution A is mixed with the precipitant solution in parallel to perform a first coprecipitation reaction to obtain a core precursor; the addition of the ternary metal salt solution A is stopped, and the ternary metal salt solution B is continued to be mixed with the precipitant solution in parallel to perform a second coprecipitation reaction to form an outer shell precursor, thereby obtaining a core-shell structure ternary precursor.

2. The method for preparing a core-shell structure ternary precursor from carbonate according to claim 1, characterized in that: The carbonate solution includes sodium carbonate and / or sodium bicarbonate; Preferably, in the first coprecipitation reaction, the ratio of the molar amount of carbonate in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution A is (1-2):1; Preferably, in the second coprecipitation reaction, the ratio of the molar amount of carbonate in the precipitant solution to the total molar amount of metal elements in the ternary metal salt solution B is (1-2):

1.

3. The method for preparing a core-shell structure ternary precursor from carbonate according to claim 1 or 2, characterized in that: The pH of the first coprecipitation reaction and the second coprecipitation reaction are both 7.5-10; Preferably, the temperature of the first coprecipitation reaction and the second coprecipitation reaction are both 50-70°C; Preferably, after the second coprecipitation reaction is completed, aging is performed, the aging time is 2 to 10 hours, and the aging temperature is 60 to 80°C.

4. The method for preparing a core-shell structure ternary precursor from carbonate according to any one of claims 1 to 3, characterized in that: The total molar concentration of the metal elements in the ternary metal salt solution A and the ternary metal salt solution B is 0.1 to 2 mol / L; Preferably, the chemical formula of the core precursor is Ni x Co y Mn z CO3, wherein 0.8≤x<1.0, 0<y<0.2, 0<z<0.2, x+y+z=1, controls the dosage ratio of the metal salt in the ternary metal salt solution A; Preferably, the shell precursor is Ni a Co b M c CO3, M is Mn and / or Al, 0<a<1, 0<b<1, 0<c<1, a+b+c=1, controlling the dosage ratio of the metal salt in the ternary metal salt solution B; Preferably, a≤x.

5. The method for preparing a core-shell structure ternary precursor from carbonate according to any one of claims 1 to 4, characterized in that: The average particle size of the core precursor is 3 to 8 μm; Preferably, the shell precursor has a thickness of 3 to 8 μm.

6. A core-shell structure ternary precursor, characterized in that: Obtained according to the method according to any one of claims 1 to 5.

7. A method for preparing a core-shell structured ternary cathode material, characterized in that: The preparation method comprises: mixing the core-shell structure ternary precursor according to claim 6 with a lithium source, and calcining the mixture to obtain a core-shell structure ternary positive electrode material.

8. The method for preparing a core-shell structure ternary cathode material according to claim 7, characterized in that: The preparation method further comprises mixing the H2V3O8 nanowire and graphene composite material with the core-shell structure ternary precursor and the lithium source; Preferably, the H2V3O8 nanowire and graphene composite material accounts for 0.1% to 4% of the mass of the core-shell structure ternary precursor; Preferably, the lithium source includes lithium hydroxide, and the molar ratio of the lithium element in the lithium source to the core-shell structure ternary precursor is (1.02-1.08):1; Preferably, the mixing method includes grinding for 30 to 40 minutes; Preferably, the calcination is carried out under an oxygen atmosphere; Preferably, the calcination temperature rise rate is 4-6°C / min, the holding temperature is 500-800°C, and the holding time is 12-20h.

9. A core-shell structure ternary cathode material, characterized in that: Obtained according to the preparation method according to claim 7 or 8.

10. A battery, characterized in that: Contains the core-shell structure ternary positive electrode material according to claim 9.

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