Chromium-doped ternary material precursor, ternary material and preparation method and application thereof

Abstract

The application belongs to the technical field of battery materials, and particularly relates to a chromium-doped ternary material precursor, a ternary material and a preparation method and application thereof. The application provides a preparation method of the chromium-doped ternary material precursor, comprising the following steps: (1) preparing an intermediate product after a nickel-cobalt-manganese solution reaction; the reaction time is 10-30 h; (2) simultaneously adding the nickel-cobalt-manganese solution and a chromium salt into the intermediate product, reacting, adjusting the pH of the reaction system, aging, and preparing the chromium-doped ternary material precursor; wherein, before the pH of the reaction system is adjusted, it satisfies: pH≤12; after the pH of the reaction system is adjusted, it satisfies: 12 The chromium-doped ternary material precursor prepared by the application has a porous structure, uniform chromium element doping, low residual alkali, stable structure, controllable morphology, uniform particle size, and simple and easy-to-operate process.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery materials, and particularly relates to a chromium-doped ternary material precursor, a ternary material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid development of lithium ion batteries in the fields of new energy vehicles and energy storage, there is a need for lithium ion batteries with higher cost performance, higher specific capacity and better cycle stability. As a core material of lithium ion batteries, the positive electrode material plays a decisive role in improving the performance of lithium ion batteries. Among them, the ternary material has the advantages of stable voltage and high capacity, and further doping elements can improve the electrochemical performance and cycle stability of the positive electrode material. In the prior art, the doping element means of the positive electrode material is to add the doping element during the sintering process, which easily causes uneven distribution of the doping element and poor doping effect.

[0003] The ternary material is a secondary particle formed by the accumulation of primary particles. In the prior art, in order to accelerate the transmission rate of lithium ions, a porous and high specific surface area positive electrode material is prepared to increase the contact area with the electrolyte, but the preparation method is difficult and the steps are complicated. SUMMARY

[0004] Therefore, the technical problems to be solved by the present application are to overcome the defects in the prior art that the doping element in the sintering process easily causes an unsatisfactory doping effect, and the method for preparing a porous and high specific surface area positive electrode material in the prior art is complicated and difficult to control, so as to provide a chromium-doped ternary material precursor, a ternary material and a preparation method and application thereof.

[0005] To this end, the present application provides the following technical solutions.

[0006] The present application provides a preparation method of a chromium-doped ternary material precursor, comprising the following steps:

[0007] (1) preparing an intermediate product after nickel-cobalt-manganese solution reaction; the reaction time is 10-30h;

[0008] (2) adding nickel-cobalt-manganese solution and chromium salt into the intermediate product at the same time, reacting, adjusting the pH of the reaction system, aging, and preparing a chromium-doped ternary material precursor;

[0009] Before adjusting the pH of the reaction system, it is satisfied that pH≤12;

[0010] After adjusting the pH of the reaction system, it is satisfied that 12

[0011] In an alternative embodiment, before adjusting the pH of the reaction system, it is satisfied that 10.8

[0012] The pH of the reaction system is adjusted to satisfy 12 < pH ≤ 14.

[0013] In an alternative embodiment, the aging time is 5-18h.

[0014] In an alternative embodiment, the concentration of the nickel-cobalt-manganese solution in step (1) is the same as that of the nickel-cobalt-manganese solution in step (2).

[0015] In an alternative embodiment, the preparation of the nickel-cobalt-manganese solution specifically comprises mixing a nickel source, a cobalt source and a manganese source.

[0016] In an alternative embodiment, the reaction time in step (2) is 30-70h.

[0017] Preferably, the chromium salt comprises a soluble chromium salt.

[0018] Preferably, the soluble chromium salt comprises at least one of chromium nitrate, chromium sulfate and chromium trichloride.

[0019] Preferably, the molar ratio of the total amount of nickel ions, cobalt ions and manganese ions to the amount of chromium ions in the reaction solution in step (2) is 1:(0.8-1.2).

[0020] It should be noted that the nickel-cobalt-manganese solution and the chromium salt are added and reacted simultaneously in step (2), and the molar ratio of the total amount of nickel ions, cobalt ions and manganese ions to the amount of chromium ions in the reaction solution in step (2) refers to the molar ratio of the total amount of nickel ions, cobalt ions and manganese ions in the added nickel-cobalt-manganese solution to the total amount of chromium ions in the added chromium salt.

[0021] In an alternative embodiment, step (1) further comprises adding at least one of a precipitant and a complexing agent before the reaction.

[0022] Preferably, the complexing agent comprises at least one of ammonia, urea and ammonium bicarbonate.

[0023] Preferably, the precipitant comprises at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0024] In an alternative embodiment, the concentration of the precipitant is 4-12mol / L.

[0025] In an alternative embodiment, the concentration of the complexing agent is 1-5mol / L.

[0026] The pH of the reaction system is adjusted by the precipitant and the complexing agent before the reaction.

[0027] After the pH of the reaction system is adjusted, the pH of the reaction system is adjusted by a pH adjusting agent. The pH adjusting agent is of a kind commonly used in the art, such as ammonia, sodium hydroxide solution, etc.

[0028] Preferably, the molar ratio of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution is (5-9):(0.5-2):(0.5-3);

[0029] Preferably, the nickel-cobalt-manganese solution comprises nickel salts, cobalt salts and manganese salts;

[0030] Preferably, the nickel salts comprise at least one of soluble salts such as nickel sulfate, nickel nitrate, nickel chloride, nickel bromide and nickel iodide;

[0031] Preferably, the cobalt salts comprise at least one of soluble salts such as cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt bromide and cobalt iodide;

[0032] Preferably, the manganese salts comprise at least one of soluble salts such as manganese sulfate, manganese nitrate, manganese chloride, manganese bromide and manganese iodide.

[0033] In an alternative embodiment, the chromium-doped ternary material precursor is prepared under stirring;

[0034] Preferably, the stirring speed is 400-800 rpm.

[0035] In an alternative embodiment, the steps (1) and (2) are carried out under a protective atmosphere;

[0036] Preferably, the protective atmosphere comprises nitrogen.

[0037] The present application provides a chromium-doped ternary material precursor prepared by the above preparation method;

[0038] Preferably, the general formula of the chromium-doped ternary material precursor is Ni x Co y Mn z Cr a (OH)2, wherein 0.3≤x≤1, 0≤y≤0.3, 0≤z≤0.3, 0.001

[0039] In the general formula of the chromium-doped ternary material precursor, the x, y, z and a are molar ratios among the elements;

[0040] Preferably, the porosity of the chromium-doped ternary material precursor is 5-40%;

[0041] Preferably, the doping amount of chromium is 0.1-5% based on the mass of the chromium-doped ternary material precursor.

[0042] The application provides a preparation method of a ternary material, and a lithium ion battery.

[0043] Preferably, the mixing further comprises adding an additive.

[0044] Preferably, the molar ratio of the chromium-doped ternary material precursor to lithium in the lithium source is 1:(1.02-1.05).

[0045] Preferably, the sintering is performed in an air atmosphere.

[0046] The sintering temperature can be determined according to the known sintering process in the art. For example, when the molar proportion of nickel in the ternary material is 50%, the sintering temperature is selected from 900-1050℃, and specifically, the temperature is selected from 900℃, 930℃, 960℃, 1000℃, 1050℃ or a range formed by any two of the above values. When the molar proportion of nickel in the ternary material is 80%, the sintering temperature is selected from 700-850℃, and specifically, the temperature is selected from 700℃, 730℃, 760℃, 790℃, 820℃, 850℃ or a range formed by any two of the above values. The application does not specifically limit the sintering temperature.

[0047] The application provides a ternary material prepared by the above preparation method.

[0048] The application provides an application of the ternary material prepared by the above preparation method in a lithium ion battery.

[0049] The application has the following advantages:

[0050] 1.The preparation method of the chromium-doped ternary material precursor provided by the present application comprises the following steps: (1) preparing an intermediate product after the nickel-cobalt-manganese solution reaction; the reaction time is 10-30 h; (2) adding chromium salt to the intermediate product, reacting, adjusting the pH of the reaction system, and aging to prepare the chromium-doped ternary material precursor; before adjusting the pH of the reaction system, it is necessary to meet: pH≤12; after adjusting the pH of the reaction system, it is necessary to meet: 12

[0051] The ternary material prepared by using the chromium-doped ternary material precursor prepared by the present application retains the porous structure and high specific surface area characteristics of the chromium-doped ternary material precursor, the high specific surface area increases the contact area of the ternary material and the electrolyte, thereby improving the lithium ion transmission rate and energy density; the porous structure is beneficial to the entry of lithium into the material during the sintering process, reduces the residual alkali, and is beneficial to the formation of a ternary positive electrode material with complete crystal structure and uniform element distribution. Compared with the existing technology of sintering process doping element method, the present application adds chromium salt in the preparation process of the precursor, which helps to improve the uniformity of chromium doping.

[0052] 2.The preparation method of the chromium-doped ternary material precursor provided by the present application utilizes the amphoteric nature of chromium hydroxide, that is, the chromium hydroxide will react and dissolve in a strong alkali environment; therefore, by adjusting the pH value, the chromium-doped ternary material precursor prepared can form a porous structure, the doping amount of chromium element can also be controlled, and the chromium element can be uniformly doped, which is simple to operate. The ternary material prepared by using the chromium-doped ternary material precursor prepared by the present application has high initial efficiency and good cycle performance. BRIEF DESCRIPTION OF DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the specific embodiments or the prior art. Obviously, the drawings described below are some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor based on these drawings.

[0054] Figure 1 is the SEM electron microscope image of the ternary material prepared in Example 1 of the present application;

[0055] Figure 2 is the SEM electron microscope image of the ternary material prepared in Example 2 of the present application;

[0056] Figure 3 is the SEM electron microscope image of the ternary material prepared in Comparative Example 1 of the present application;

[0057] Figure 4 is the SEM electron microscope image of the ternary material prepared in Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0058] The following examples are provided to better further understand the present application, and are not limited to the best mode, and do not limit the content and protection scope of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the protection scope of the present application.

[0059] The specific experimental steps or conditions are not indicated in the examples, and can be performed according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments used are not indicated by the manufacturer, and are conventional reagent products that can be obtained by market purchase.

[0060] Example 1

[0061] The present embodiment provides a preparation method of a chromium-doped ternary material precursor, which is specifically as follows:

[0062] (1) Mix nickel sulfate, cobalt sulfate and manganese sulfate according to a molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese solution (solvent is water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 1.8 mol / L, for standby; mix 2 mol / L of ammonia water, 6.6 mol / L of sodium hydroxide solution and water to obtain a mixed solution, and put the mixed solution into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle is 0.4:1, and the pH value of the mixed solution is 11.0.

[0063] (2) nitrogen gas is introduced into the reactor until it is filled, under the nitrogen atmosphere, the nickel-cobalt-manganese solution is introduced and continuously stirred, the flow rate is 10 L / h, the ammonia water and sodium hydroxide solution are introduced to adjust the pH value, the stirring speed is 600 rpm, the pH value of the reaction system is adjusted to about 11.3; after stirring for 15 h, the intermediate product is prepared.

[0064] (3) the nickel-cobalt-manganese solution is added, the flow rate is 10 L / h, 1 mol / L chromium nitrate solution is added, the flow rate is 18 L / h; the reaction is carried out at 600 rpm for 55 h, the feeding is stopped, the mixed solution of the above-mentioned ammonia water and sodium hydroxide solution is introduced to adjust the pH value of the reaction system to about 11.3, the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) and the molar amount of chromium ions are in a ratio of 1:1; then the pH value is adjusted to about 12.8 by using sodium hydroxide solution, stirring and aging for 8 h, washing, sieving, and removing magnetism, to obtain a chromium-doped ternary material precursor. The doping amount of chromium is 3.6% based on the mass of the chromium-doped ternary material precursor; the porosity is 28%.

[0065] The embodiment also provides a preparation method of a ternary material, which specifically comprises the following steps:

[0066] (4) the chromium-doped ternary material precursor prepared in the above step and lithium carbonate are uniformly mixed in a high-speed mixer at a molar ratio of 1:0.52, sintered at 860°C for 10 h under an oxygen atmosphere, and a ternary material is prepared.

[0067] The SEM image of the ternary material prepared in the embodiment is shown in Figure 1 .

[0068] Example 2

[0069] The embodiment provides a preparation method of a chromium-doped ternary material precursor, which specifically comprises the following steps:

[0070] (1) nickel sulfate, cobalt sulfate and manganese sulfate are mixed at a molar ratio of 8:1:1, and a nickel-cobalt-manganese solution (the solvent is water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 2.1 mol / L is prepared; 3.2 mol / L ammonia water, 10.2 mol / L sodium hydroxide solution and water are mixed to obtain a mixed solution which is put into a reactor, the volume ratio of the mixed solution to the reactor is 0.5:1, and the pH value of the mixed solution is 11.5.

[0071] (2) nitrogen gas is introduced into the reactor until it is filled, under the nitrogen atmosphere, the nickel-cobalt-manganese solution is introduced and continuously stirred, the flow rate is 10 L / h, the ammonia water and sodium hydroxide solution are introduced to adjust the pH value, the stirring speed is 700 rpm, and the pH value of the reaction system is adjusted to about 11.3; after stirring for 20 h, the intermediate product is prepared.

[0072] (3) adding nickel-cobalt-manganese solution at a flow rate of 10 L / h and adding 3.2 mol / L chromium sulfate solution at a flow rate of 2.95 L / h, reacting at 700 rpm for 55 h, stopping the feeding, and adjusting the pH of the reaction system to about 11.3 by passing the mixed solution of the above-mentioned ammonia water and sodium hydroxide solution, the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) and the molar amount of chromium ions being in a ratio of 1:0.899, then adjusting the pH to about 13.8 by using sodium hydroxide solution, stirring and aging for 15 h, washing, sieving, removing magnetism, and obtaining chromium-doped ternary material precursor. The doping amount of chromium is 3.2% based on the mass of the chromium-doped ternary material precursor; and the porosity is 24%.

[0073] The embodiment also provides a preparation method of ternary material, which specifically comprises the following steps:

[0074] (4) mixing the chromium-doped ternary material precursor and lithium carbonate in a molar ratio of 1:0.52, mixing uniformly in a high-speed mixer, sintering at 740 °C for 10 h in an oxygen atmosphere, and obtaining ternary material.

[0075] The SEM image of the ternary material prepared in the embodiment is shown in Figure 2 .

[0076] Example 3

[0077] The embodiment provides a preparation method of chromium-doped ternary material precursor, which specifically comprises the following steps:

[0078] (1) mixing nickel nitrate, cobalt nitrate and manganese nitrate in a molar ratio of 7:1:2 to prepare nickel-cobalt-manganese solution (the solvent is water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 2.8 mol / L, and reserving; mixing 4.8 mol / L ammonium bicarbonate solution, 12 mol / L lithium hydroxide solution and water to obtain a mixed solution, and placing the mixed solution into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle being 0.6:1, and the pH of the mixed solution being 11.8.

[0079] (2) passing nitrogen into the reaction kettle until it is filled, passing nickel-cobalt-manganese solution under the nitrogen atmosphere and continuously stirring at a flow rate of 10 L / h, adjusting the pH by passing ammonium bicarbonate solution and lithium hydroxide solution, the stirring speed being 400 rpm, adjusting the pH of the reaction system to about 11.9, and obtaining an intermediate product after stirring for 28 h.

[0080] (3) adding nickel-cobalt-manganese solution at a flow rate of 10 L / h, adding 4.8 mol / L chromium trichloride solution at a flow rate of 7 L / h, reacting at 400 rpm for 35 h, stopping feeding, and adjusting the pH of the reaction system to about 11.9 by passing the mixed solution of the above-mentioned ammonium bicarbonate and lithium hydroxide solution, the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) and the molar amount of chromium ions being in a ratio of 1:1.2, then adjusting the pH to about 13.8 by using lithium hydroxide solution, stirring and aging for 18 h, washing, sieving, removing magnetism, and obtaining chromium-doped ternary material precursor. The doping amount of chromium is 1.4% based on the mass of the chromium-doped ternary material precursor; and the porosity is 15%.

[0081] The embodiment also provides a preparation method of ternary material, which specifically comprises the following steps:

[0082] (4) mixing the chromium-doped ternary material precursor and lithium carbonate in a molar ratio of 1:0.52, mixing uniformly in a high-speed mixer, sintering at 780 °C for 9 h in an oxygen atmosphere, and obtaining ternary material.

[0083] Example 4

[0084] The embodiment provides a preparation method of chromium-doped ternary material precursor, which specifically comprises the following steps:

[0085] (1) mixing nickel nitrate, cobalt nitrate and manganese nitrate in a molar ratio of 6.7:0.8:2.5 to prepare nickel-cobalt-manganese solution (solvent is water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 2.5 mol / L, and reserving; mixing 4.0 mol / L urea solution, 4 mol / L potassium hydroxide solution and water to obtain a mixed solution, and placing the mixed solution into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle being 0.3:1, and the pH of the mixed solution being 10.8.

[0086] (2) passing nitrogen into the reaction kettle until it is filled, passing nickel-cobalt-manganese solution under a nitrogen atmosphere and continuously stirring at a flow rate of 10 L / h, adjusting the pH by passing urea solution and potassium hydroxide solution, the stirring speed being 800 rpm, and adjusting the pH of the reaction system to about 10.8, and obtaining intermediate product after stirring for 10 h.

[0087] (3) adding nickel-cobalt-manganese solution at a flow rate of 10 L / h and adding 2 mol / L chromium nitrate solution at a flow rate of 13.7 L / h; reacting at 800 rpm for 70 h, stopping feeding, and adjusting the pH of the reaction system to about 10.8 by passing the mixed solution of urea and potassium hydroxide solution described above; the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) and the molar amount of chromium ions are in a ratio of 1:1.096; then adjusting the pH to about 12.1 by potassium hydroxide solution, stirring and aging for 5 h, washing, sieving, and removing magnetism to obtain a chromium-doped ternary material precursor. The doping amount of chromium is 5% based on the mass of the chromium-doped ternary material precursor; and the porosity is 33%.

[0088] The embodiment also provides a preparation method of a ternary material, which specifically comprises the following steps:

[0089] (4) mixing the chromium-doped ternary material precursor and lithium carbonate prepared in the above step in a high-speed mixer at a molar ratio of 1:0.52, sintering at 850°C for 10 h in an oxygen atmosphere, and obtaining a ternary material.

[0090] Example 5

[0091] The embodiment provides a preparation method of a chromium-doped ternary material precursor, which is the same as that in Example 1.

[0092] The embodiment also provides a preparation method of a ternary material, which is different from that in Example 1 only in that, in step (4), the chromium-doped ternary material precursor and lithium carbonate are mixed in a high-speed mixer at a molar ratio of 1:0.525, instead of mixing the chromium-doped ternary material precursor and lithium carbonate in a high-speed mixer at a molar ratio of 1:0.52 in Example 1.

[0093] Comparative Example 1

[0094] The comparative example provides a preparation method of a ternary material precursor, which specifically comprises the following steps:

[0095] (1) mixing nickel sulfate, cobalt sulfate and manganese sulfate at a molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese solution (solvent: water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 1.8 mol / L, for standby; mixing 2 mol / L ammonia water, 6.6 mol / L sodium hydroxide solution and water to obtain a mixed solution, and placing the mixed solution into a reaction kettle, wherein the volume ratio of the mixed solution to the reaction kettle is 0.4:1, and the pH of the mixed solution is 11.0.

[0096] (2) The reaction kettle is filled with nitrogen until full, and then the nickel-cobalt-manganese solution is introduced under a nitrogen atmosphere while continuously stirring at a flow rate of 10 L / h. Ammonia water and sodium hydroxide solution are introduced to adjust the pH value, and the stirring speed is 600 rpm. The pH value of the reaction system is adjusted to about 11.3. The reaction is carried out at 600 rpm for 70 h, and then the feeding is stopped. The mixed solution formed by the above-mentioned ammonia water and sodium hydroxide solution is introduced to adjust the pH value of the reaction system to about 11.3, and then sodium hydroxide solution is used to adjust the pH value to about 12.8. The mixture is stirred and aged for 8 h, washed, sieved, and demagnetized to obtain the ternary material precursor. The porosity is 2.2%.

[0097] The present comparative example also provides a preparation method of a ternary material, which is specifically as follows:

[0098] (4) The ternary material precursor obtained above and lithium carbonate are mixed uniformly in a high-speed mixer at a molar ratio of 1:0.52, and then sintered at 860°C for 10 h under an oxygen atmosphere to obtain the ternary material.

[0099] The SEM image of the ternary material obtained by the present comparative example is shown in Figure 3 .

[0100] Comparative Example 2

[0101] The present comparative example provides a preparation method of a ternary material precursor, which is specifically as follows:

[0102] (1) Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed at a molar ratio of 8:1:1 to prepare a nickel-cobalt-manganese solution (solvent: water) with a total molar concentration of 2.1 mol / L of nickel ions, cobalt ions, and manganese ions, which is prepared for use. 3.2 mol / L of ammonia water, 10.2 mol / L of sodium hydroxide solution, and water are mixed to obtain a mixed solution, which is placed in a reaction kettle. The volume ratio of the mixed solution to the reaction kettle is 0.5:1, and the pH value of the mixed solution is 11.5.

[0103] (2) The reaction kettle is filled with nitrogen until full, and then the nickel-cobalt-manganese solution is introduced under a nitrogen atmosphere while continuously stirring at a flow rate of 10 L / h. Ammonia water and sodium hydroxide solution are introduced to adjust the pH value, and the stirring speed is 700 rpm. The pH value of the reaction system is adjusted to about 11.3. The reaction is carried out at 700 rpm for 75 h, and then the feeding is stopped. The mixed solution formed by the above-mentioned ammonia water and sodium hydroxide solution is introduced to adjust the pH value of the reaction system to about 11.3, and then sodium hydroxide solution is used to adjust the pH value to about 13.8. The mixture is stirred and aged for 15 h, washed, sieved, and demagnetized to obtain the ternary material precursor. The porosity is 3.1%.

[0104] The present comparative example also provides a preparation method of a ternary material, which is specifically as follows:

[0105] (4) The prepared ternary material precursor and lithium carbonate are mixed uniformly in a high-speed mixer at a molar ratio of 1:0.52, sintered at 740°C for 10 hours in an oxygen atmosphere, and a ternary material is prepared.

[0106] The SEM image of the ternary material prepared in the present comparative example is shown in Figure 4 .

[0107] Comparative Example 3

[0108] The present comparative example provides a preparation method of a ternary material precursor, which is specifically as follows:

[0109] (1) Nickel sulfate, cobalt sulfate and manganese sulfate are mixed at a molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese solution (solvent: water) with a total molar amount of nickel ions, cobalt ions and manganese ions of 1.8 mol / L, which is prepared for use; 2 mol / L of ammonia water, 6.6 mol / L of sodium hydroxide solution and water are mixed to obtain a mixed solution which is put into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle is 0.4:1, and the pH value of the mixed solution is 11.0.

[0110] (2) Nitrogen is introduced into the reaction kettle until it is filled, and under a nitrogen atmosphere, the nickel-cobalt-manganese solution is introduced and continuously stirred at a flow rate of 10 L / h, the pH value is adjusted by introducing ammonia water and sodium hydroxide solution, the stirring speed is 600 rpm, and the pH value of the reaction system is controlled at about 11.3; after stirring for 15 hours, an intermediate product is prepared.

[0111] (3) The nickel-cobalt-manganese solution is added at a flow rate of 10 L / h, and 1 mol / L of zinc sulfate solution is added at a flow rate of 18 L / h; the reaction is carried out at 600 rpm for 55 hours, the feeding is stopped, the mixed solution prepared from the above-mentioned ammonia water and sodium hydroxide solution is introduced to adjust the pH value of the reaction system to about 11.3, the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) is 1:1 with respect to the molar amount of zinc ions; then the pH value is adjusted to about 12.8 by sodium hydroxide solution, stirring and aging for 8 hours, washing, sieving and demagnetizing to obtain a ternary material precursor. The porosity is 2.2%.

[0112] The present comparative example also provides a preparation method of a ternary material, which is specifically as follows:

[0113] (4) The prepared ternary material precursor and lithium carbonate are mixed uniformly in a high-speed mixer at a molar ratio of 1:0.52, sintered at 740°C for 10 hours in an oxygen atmosphere, and a ternary material is prepared.

[0114] Comparative Example 4

[0115] The present comparative example provides a preparation method of a ternary material precursor, which is specifically as follows:

[0116] (1) Mix nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese solution (solvent is water) with the total molar amount of nickel ions, cobalt ions and manganese ions being 1.8 mol / L, and reserve it; mix 2 mol / L ammonia water, 6.6 mol / L sodium hydroxide solution and water to obtain a mixed solution, and put the mixed solution into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle being 0.4:1, and the pH value of the mixed solution being 11.0.

[0117] (2) Introduce nitrogen into the reaction kettle until it is filled, and then introduce the nickel-cobalt-manganese solution under the nitrogen atmosphere and continuously stir it, the flow rate being 10 L / h, and adjust the pH value by introducing ammonia water and sodium hydroxide solution, the stirring speed being 600 rpm, and the pH value of the reaction system being about 11.3; after stirring for 15 h, an intermediate product is prepared.

[0118] (3) Introduce the nickel-cobalt-manganese solution, the flow rate being 10 L / h, introduce 1 mol / L magnesium sulfate solution, the flow rate being 18 L / h, and react for 55 h at 600 rpm, stop feeding, and adjust the pH value of the reaction system to about 11.3 by introducing the mixed solution prepared from the above-mentioned ammonia water and sodium hydroxide solution, the molar ratio of the total molar amount of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution added in step (3) to the molar amount of magnesium ions being 1:1; then adjust the pH value to about 12.8 by using sodium hydroxide solution, stir and age for 8 h, wash, sieve, remove magnetism, and obtain a ternary material precursor. The doping amount of magnesium is 28.5% based on the mass of the ternary material precursor; and the porosity is 2.1%.

[0119] The present comparative example also provides a preparation method of a ternary material, which specifically comprises the following steps:

[0120] (4) Mix the ternary material precursor prepared in the above and lithium carbonate according to the molar ratio of 1:0.52, mix uniformly in a high-speed mixer, sinter at 860°C for 10 h under an oxygen atmosphere, and prepare a ternary material.

[0121] Comparative Example 5

[0122] The present comparative example provides a preparation method of a ternary material precursor, which specifically comprises the following steps:

[0123] (1) Mix nickel sulfate, cobalt sulfate and manganese sulfate according to the molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese solution (solvent is water) with the total molar amount of nickel ions, cobalt ions and manganese ions being 1.8 mol / L, and reserve it; mix 2 mol / L ammonia water, 6.6 mol / L sodium hydroxide solution and water to obtain a mixed solution, and put the mixed solution into a reaction kettle, the volume ratio of the mixed solution to the reaction kettle being 0.4:1, and the pH value of the mixed solution being 11.0.

[0124] (2) The reaction kettle is filled with nitrogen until full, and under the nitrogen atmosphere, a nickel-cobalt-manganese solution is introduced and continuously stirred at a flow rate of 10 L / h, and ammonia water and sodium hydroxide solution are introduced to adjust the pH value, the stirring speed is 600 rpm, and the pH value of the reaction system is adjusted to about 11.3; after stirring for 70 h, the precursor is prepared.

[0125] The present comparative example also provides a preparation method of a ternary material, which is specifically as follows:

[0126] (3) The precursor prepared above, lithium carbonate and chromium sulfate are uniformly mixed in a high-speed mixer at a molar ratio of 1:0.52:0.015, and sintered at 860°C for 10 h under an oxygen atmosphere to obtain the ternary material.

[0127] Test example

[0128] The ternary materials prepared in the above examples and comparative examples are made into batteries, and the specific steps are as follows:

[0129] The ternary material, polyvinylidene fluoride (PVDF) and Super P (SP) are weighed according to a mass ratio of 97.2:1.3:1.5, and then homogenized, and then an aluminum foil is laid flat on a coating machine for coating (the surface density is 15-17 mg / cm 2 ), and then placed in a 80°C air-drying oven for drying for 2 h; then punched, weighed, baked, and made into CR2032 button cells, and finally the cells are placed in a blue cell test system for electrical performance testing;

[0130] The battery performance test of the above-prepared battery is as follows:

[0131] (1) Specific surface area test method: A, 30 mg of the sample to be tested is loaded into a sample tube, the sample tube is loaded into a degassing station (the sample tube is aligned with the port, the screw is tightened to ensure safety), a heating bag is sleeved on the sample tube, the vacuum pump is turned on, and heating and vacuum degassing are started; B, turn off the power, wait for the sample to cool to room temperature, backfill helium, and after the helium reaches normal pressure, remove the sample and immediately cover it with a rubber plug, weigh it to 0.1 mg, and record the gross weight of the sample tube (the weight of the helium-filled sample tube, plug and filling rod); C, the sample weight is measured by the decrement method: the support is peeled and zeroed, the sample tube is added with the plug and recorded as m1, the sample is loaded into the sample tube and the plug is recorded as m2, the support is zeroed, the sample tube is degassed in the degassing station, and after cooling, m3 is recorded, and m3 is subtracted from m1 to obtain the sample weight; D, the weighed sample tube is placed in the analysis station, liquid nitrogen is added in the dewar flask, and adsorption and desorption testing is started to obtain the specific surface area of the sample, and the results are shown in Table 1.

[0132] (2) 0.1C first charge and first discharge: stand for 10 s, charge at 0.1C to a voltage of 4.4V, stand for 10 s, discharge at 0.1C to a voltage of 3V, stand for 10 s; the results are shown in Table 1.

[0133] (3) The initial efficiency: the calculation formula is as follows: initial efficiency = 0.1C initial discharge / 0.1C initial charge, and the results are shown in Table 1.

[0134] (4) Cycle retention rate: step (2) is repeated twice, 0.5C charging to a voltage of 4.4V, standing for 10s, 0.5C discharging to a voltage of 3V, standing for 10s, and cycling 98 times, and the calculation formula of the cycle retention rate is as follows, and the results are shown in Table 1.

[0135] Cycle retention rate = 100st discharge specific capacity / 0.5C initial discharge

[0136] Table 1

[0137]

[0138] As shown in Table 1, the specific surface area of the ternary material prepared from the chromium-doped ternary precursor prepared by the application is high, the 0.1C initial charge, 0.1C initial discharge, initial coulombic efficiency and cycle retention rate of the battery prepared therefrom are high.

[0139] As compared with Example 1-2 and Comparative Example 1-2, the ternary material prepared from the chromium-doped ternary precursor prepared by the application has good performance. It is illustrated that the chromium element ternary material precursor prepared by using the amphoteric substance of chromium hydroxide has good specific surface area, and the 0.1C initial charge, 0.1C initial discharge, initial efficiency and cycle retention rate of the battery prepared therefrom are high.

[0140] As compared with Example 1 and Comparative Example 3, in the preparation process of the precursor, the zinc element also having amphoteric property will be dissolved when the pH value is 10.8-12, and no zinc hydroxide precipitate is formed to fill the gap, so that the final ternary material neither has zinc element doping nor has high specific surface area; as compared with Comparative Example 4, the magnesium element having non-amphoteric property is used to replace the chromium element to prepare the precursor, the magnesium element will not be dissolved when the pH value is 12.1-14.0, and no gap is formed, so that the magnesium element does not have high specific surface area, and the doping amount of the magnesium element cannot be controlled by adjusting the pH value; the 0.1C initial charge, 0.1C initial discharge and initial coulombic efficiency of the ternary material prepared in Comparative Examples 3-4 are greatly reduced, and the cycle retention rate is significantly reduced; it is illustrated that the chromium element selected in the application cannot be replaced by other doping elements.

[0141] As compared with Example 1 and Comparative Example 5, the chromium salt is added to prepare the ternary material, and the specific surface area of the ternary material prepared therefrom is low, the 0.1C initial charge, 0.1C initial discharge and initial coulombic efficiency are poor, and the cycle retention rate is reduced; it is illustrated that the chromium salt is added in the preparation of the precursor in the application, and the doping effect of the chromium-doped ternary precursor prepared therefrom is better, and the preparation method is more excellent.

[0142] Obviously, the above embodiments are only examples for clearly illustrating the present application and are not intended to limit the present application. Based on the above description, one of ordinary skill in the art can make other different forms of changes or modifications. Here, it is not necessary or possible to enumerate all the embodiments. The obvious changes or modifications derived from the above should be within the protection scope of the present application.

Claims

1. A method for preparing a chromium-doped ternary material precursor, characterized in that, The preparation method comprises the following steps: (1) preparing an intermediate product after reaction of a nickel-cobalt-manganese solution; the reaction time is 10-30 h; before the reaction, at least one of a precipitant and a complexing agent is added; (2) adding the nickel-cobalt-manganese solution and a chromium salt into the intermediate product, reacting, adjusting the pH of the reaction system, and aging to prepare a chromium-doped ternary material precursor; Before the pH of the reaction system is adjusted, the pH satisfies: pH≤12; After the pH of the reaction system is adjusted, the pH satisfies: 12 2. The method of claim 1, wherein the chromium-doped ternary material precursor is prepared by the steps of: preparing a solution of a chromium compound; and adding the solution of the chromium compound to a solution of a first metal compound and a second metal compound. Before the pH of the reaction system is adjusted, the pH satisfies: 10.8 The concentration of the nickel-cobalt-manganese solution in the step (1) is the same as that of the nickel-cobalt-manganese solution in the step (2).

3. The method of claim 1, wherein the chromium-doped ternary material precursor is prepared by the steps of: preparing a solution of a chromium compound; and adding the solution of the chromium compound to a solution of a first metal compound and a second metal compound. The reaction time in the step (2) is 30-70 h.

4. The method of claim 3, wherein the method further comprises: The chromium salt comprises a soluble chromium salt.

5. The method of claim 4, wherein the chromium-doped ternary material precursor is prepared by the steps of: providing a solution of a chromium salt; and adding the solution of the chromium salt to a solution of a ternary material precursor. The soluble chromium salt comprises at least one of chromium nitrate, chromium sulfate and chromium trichloride.

6. The method of claim 5, wherein the method further comprises: The complexing agent comprises at least one of ammonia, urea and ammonium bicarbonate.

7. The method of claim 1 or 2, wherein the method further comprises the step of: The precipitant comprises at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

8. The method of claim 7, wherein the method further comprises: The molar ratio of nickel ions, cobalt ions and manganese ions in the nickel-cobalt-manganese solution is (5-9):(0.5-2):(0.5-3).

9. The method of claim 8, wherein the method further comprises: The nickel-cobalt-manganese solution comprises nickel salt, cobalt salt and manganese salt.

10. The method of claim 9, wherein the method further comprises: The nickel salt comprises at least one of nickel sulfate, nickel nitrate, nickel chloride, nickel bromide and nickel iodide.

11. The method of claim 10, wherein the method further comprises: The cobalt salt comprises at least one of cobalt sulfate, cobalt nitrate, cobalt chloride, cobalt bromide and cobalt iodide.

12. The method of claim 11, wherein the chromium-doped ternary material precursor is prepared by a method comprising: The manganese salt comprises at least one of manganese sulfate, manganese nitrate, manganese chloride, manganese bromide and manganese iodide.

13. The method of claim 12, wherein the method further comprises: The chromium-doped ternary material precursor is prepared under stirring.

14. The method of claim 13, wherein the method further comprises: The stirring speed is 400-800 rpm.

15. The method of claim 14, wherein the method further comprises: The steps (1) and (2) are carried out under a protective atmosphere.

16. The method of claim 1, wherein the method further comprises: The protective atmosphere comprises nitrogen.

17. The method of claim 16, wherein the method further comprises:

18. A chromium-doped ternary material precursor prepared by the preparation method in any one of claims 1-17. The porosity of the chromium-doped ternary material precursor is 5-40%.

19. The chromium-doped ternary material precursor of claim 18, wherein, The doping amount of chromium is 0.1-5% based on the mass of the chromium-doped ternary material precursor.

20. The chromium-doped ternary material precursor of claim 19, wherein, The chromium-doped ternary material precursor prepared by the preparation method in any one of claims 1-17 or the chromium-doped ternary material precursor in any one of claims 18-20 is mixed with a lithium source, and sintered to prepare a ternary material.

21. A method of preparing a ternary material, comprising: The mixing further comprises adding an additive.

22. The method of claim 21, wherein the ternary material is prepared by a method comprising:

23. A ternary material prepared by the preparation method in any one of claims 21-22.

24. The ternary material prepared by the preparation method in any one of claims 21-22 or the ternary material in claim 23 in the application of a lithium ion battery. ​

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