High-entropy doped modified high-nickel cobalt-free positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a high-entropy doped modified high-nickel cobalt-free positive electrode material as well as a preparation method and application thereof. The preparation method of the high-entropy doped modified high-nickel cobalt-free positive electrode material comprises the following steps: carrying out first-time mixed wet grinding and drying treatment on a nickel source, a manganese source, a lithium source, a first solvent and a doped metal source containing five or more doped metal elements to obtain a precursor; and sequentially carrying out secondary mixed wet grinding, spray drying and sintering treatment on the precursor to obtain the high-entropy doped modified high-nickel cobalt-free positive electrode material. According to the method, high-entropy doping modification is performed on the high-nickel cobalt-free positive electrode material, collapse of a transition metal layer during deep lithium removal is inhibited, and meanwhile, spherical secondary particles with uniformly distributed elements are formed in combination with wet grinding and spray drying, so that bulk phase structure degradation and interface side reaction in the deep lithium removal process are relieved; therefore, the high-nickel cobalt-free positive electrode material shows better cycling stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a high-entropy doped modified high-nickel cobalt-free positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] With the rapid expansion of the new energy vehicle market, the demand for high-performance lithium ion batteries has surged, and high-energy-density ternary materials have become the mainstream development direction. Cobalt, as a key stabilizing component of traditional ternary positive electrode materials, can inhibit cation mixing and improve structural stability, but its high cost, resource scarcity, and accelerated chemical mechanical cracking and oxygen release at high voltage have prompted high-nickel cobalt-free positive electrode materials to become a research hotspot.

[0003] However, cobalt-free in high-nickel systems faces severe challenges: rapid discharge can cause structural instability (such as microcracks, phase transitions), electrolyte decomposition, transition metal dissolution, and interface degradation, and Ni 4+ The side reactions further lead to irreversible phase transitions and capacity decay. Although strategies such as transition metal doping and surface coating can partially alleviate the problems, it is still difficult to solve the complex contradictions between cobalt-free and high-nickel, resulting in poor cycle stability of high-nickel cobalt-free positive electrode materials. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the poor cycle stability of existing high-nickel cobalt-free positive electrode materials, thereby providing a high-entropy doped modified high-nickel cobalt-free positive electrode material and a preparation method and application thereof to solve the above problems.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0006] In a first aspect, the present application provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, comprising:

[0007] mixing a nickel source, a manganese source, a lithium source, a first solvent, and a doping metal source containing five or more doping metal elements by a first wet grinding, and drying to obtain a precursor;

[0008] The precursor is sequentially subjected to a second wet grinding, spray drying, and sintering to obtain a high-entropy doped modified high-nickel cobalt-free positive electrode material.

[0009] Further, the spray drying conditions are: the inlet air temperature is 175-185°C, for example, the inlet air temperature can be selected as 175°C, 180°C, or 185°C; the atomization pressure is 0.2-0.4Mpa, for example, the atomization pressure can be selected as 0.2Mpa, 0.25Mpa, 0.3Mpa, 0.35Mpa, or 0.4Mpa.

[0010] Further, the precursor is further pre-sintered before the second mixing and wet milling step;

[0011] And / or, the sintering temperature is 800-900℃, for example, the sintering temperature can be selected from 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃; the sintering time is 8-12h, for example, the sintering time can be selected from 8h, 9h, 10h, 11h, 12h;

[0012] And / or, the sintering is carried out in an oxygen atmosphere.

[0013] Further, the pre-sintering temperature is 350-450℃, for example, the pre-sintering temperature can be selected from 350℃, 360℃, 370℃, 380℃, 390℃, 400℃, 410℃, 420℃, 430℃, 440℃, 450℃; the pre-sintering time is 3-7h, for example, the pre-sintering time can be selected from 3h, 4h, 5h, 6h, 7h;

[0014] And / or, the pre-sintering is carried out in an oxygen atmosphere.

[0015] Further, the high-entropy doped modified high-nickel cobalt-free positive electrode material has a chemical formula of Li a Mn x Ni y M 1-x-y O2; wherein, 1.01≤a≤1.08, 0.2>x≥0.1, y≥0.8, 1-x-y>0, M is a doping metal element selected from at least five of Al, Mg, Ti, Lu, Nb, Ru, and Zr.

[0016] Further, the ratio of each doping metal element in the doping metal source is equimolar;

[0017] And / or, the compound form of each doping metal element in the doping metal source is carbonate or / and oxide. The same metal salt / oxide in the doping metal source can contain multiple doping metals, or each metal salt / oxide can contain one doping metal; that is, whether the same metal salt / oxide contains multiple doping metal elements, or different salts / oxides each contain one doping metal element, as long as the doping metal source contains five or more doping metal elements.

[0018] Further, the nickel source includes but is not limited to nickel hydroxide;

[0019] And / or, the manganese source includes but is not limited to manganese oxide;

[0020] and / or, the lithium source includes but is not limited to lithium hydroxide;

[0021] and / or, the first solvent is an ethanol aqueous solution;

[0022] and / or, the solid-liquid ratio (mass ratio) of the slurry during the first mixing wet milling is 1:(0.8-1.2); for example, the solid-liquid ratio of the slurry can be selected as 1:0.8, 1:0.9, 1:1.0, 1:1.1, 1:1.2;

[0023] and / or, the temperature of the drying treatment is 80-100℃, for example, the temperature of the drying treatment can be selected as 80℃, 85℃, 90℃, 95℃, 100℃; the duration of the drying treatment is 2-4h, for example, the duration of the drying treatment can be selected as 2h, 3h, 4h.

[0024] Further, the process of the second mixing wet milling is that the precursor is ball-mixed with the second solvent, the binder, and the dispersant.

[0025] Further, the mass ratio of the precursor, the second solvent, the binder, and the dispersant is 100:(120-170):(1-3):(1-3); for example, the mass ratio of the precursor, the second solvent, the binder, and the dispersant can be selected as 100:120:3:3, 100:170:1:1, 100:150:2:2, 100:130:2:2, 100:160:1:1.

[0026] and / or, the second solvent is deionized water;

[0027] and / or, the binder includes polyethylene glycol;

[0028] and / or, the dispersant includes cetyltrimethylammonium bromide.

[0029] In a second aspect, the present application further provides a high-entropy doped modified high-nickel cobalt-free cathode material, which is prepared by the above-mentioned method for preparing a high-entropy doped modified high-nickel cobalt-free cathode material.

[0030] In a third aspect, the present application further provides a lithium ion battery comprising the above-mentioned high-entropy doped modified high-nickel cobalt-free cathode material.

[0031] The technical scheme of the present application has the following advantages:

[0032] 1. A preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, comprising: mixing a nickel source, a manganese source, a lithium source, a first solvent, and a doped metal source containing five or more doped metal elements to obtain a precursor by first wet grinding and drying treatment; and obtaining the high-entropy doped modified high-nickel cobalt-free positive electrode material by sequentially performing second wet grinding, spray drying, and sintering treatment on the precursor. In view of the poor cycle stability of the existing high-nickel cobalt-free positive electrode material, the high-nickel cobalt-free positive electrode material is modified by high-entropy doping in the present application, the collapse of the transition metal layer during deep delithiation is inhibited, and the element uniform distribution of the spherical secondary particles is formed by combining wet grinding and spray drying, so that the degradation of the bulk phase structure and the interface side reaction during deep delithiation are alleviated, thereby making the high-nickel cobalt-free positive electrode material exhibit better cycle stability.

[0033] 2. In the preparation method of the high-entropy doped modified high-nickel cobalt-free positive electrode material, when the high-entropy multi-element slurry is subjected to spray drying, the inlet air temperature and the atomization pressure should be avoided to be too high or too low, and by adjusting the inlet air temperature to 175-185 DEG C and the atomization pressure to 0.2-0.4 Mpa, the element uniformity and the particle morphology can be balanced, thereby further optimizing the cycle stability of the high-nickel cobalt-free positive electrode material.

[0034] 3. In the preparation method of the high-entropy doped modified high-nickel cobalt-free positive electrode material, low-temperature pre-sintering at 350-450 DEG C is first performed to realize initial solid solution of elements, then the particle morphology is regulated by spray drying, and finally high-temperature sintering at 800-900 DEG C is performed. Compared with the conventional one-step sintering method, the cycle stability of the high-entropy doped modified high-nickel cobalt-free positive electrode material prepared by the stage sintering process is significantly better than that of the material prepared by the one-step sintering method (spray drying + high-temperature sintering). BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in 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 those skilled in the art can also obtain other drawings according to these drawings without creative labor.

[0036] Figure 1 Fig. 1 is a scanning electron microscope (SEM) morphology diagram of the high-entropy doped modified high-nickel cobalt-free positive electrode material prepared in Example 1. DETAILED DESCRIPTION

[0037] The following examples are provided to better enable those skilled in the art to better understand and practice the application as claimed. They are not intended to limit the scope of the application in any way and should not be regarded as limiting the contents or scope of the application. Any product prepared according to the disclosure or any product prepared by combining the disclosure with other prior art falls within the scope of the present application.

[0038] When the specific experimental steps or conditions are not mentioned in the examples, the operations or conditions can be carried out according to the conventional experimental steps described in the literature in the art. When the reagents or instruments used are not mentioned by the manufacturer, they are all conventional reagent products that can be obtained by purchase.

[0039] Example 1

[0040] The present embodiment provides a preparation method of a high-entropy doped modified high-nickel cobalt-free cathode material, and the specific steps are as follows:

[0041] 1) According to the stoichiometric ratio of Li 1.04 Mn 0.1 Ni 0.8 Ti 0.02 Nb 0.02 Zr 0.02 Al 0.02 Mg 0.02 O2, weigh Ni(OH)2, MnO2, LiOH, TiO2, Nb2O5, ZrO2, Al2O3, and MgO, and weigh 75 vol% ethanol aqueous solution according to the solid-liquid ratio (mass ratio, the same below) of 1:1.1. Put all the materials into a ball mill for ball milling (rotation speed 200 rpm, time 6 h);

[0042] 2) Move the slurry after ball milling in step 1) to a rotary evaporator and dry at a temperature of 100℃ for 3h to obtain a precursor;

[0043] 3) Transfer the precursor obtained in step 2) to an oxygen atmosphere box furnace and pre-sinter at a temperature of 400℃ for 5h;

[0044] 4) Transfer the pre-sintered precursor to a ball mill (ball milling parameters are the same as step 1), weigh deionized water, polyethylene glycol and cetyltrimethylammonium bromide according to the mass ratio of pre-sintered precursor, deionized water, polyethylene glycol and cetyltrimethylammonium bromide of 100:150:2:2 and add them to the ball mill, and ball mill for 6h to obtain a spray slurry;

[0045] 5) Pump the spray slurry prepared in step 4) into a spray dryer, set the inlet air temperature to 180℃, and the spray pressure to 0.3MPa to obtain a cathode material matrix;

[0046] 6) The positive electrode material substrate prepared in step 5) is sintered in an oxygen atmosphere at 850°C for 10h to obtain a high-entropy doping modified high-nickel cobalt-free positive electrode material, and the SEM morphology is as shown in FIG. 6. Figure 1

[0047] Example 2

[0048] The embodiment provides a preparation method of a high-entropy doping modified high-nickel cobalt-free positive electrode material, and the specific steps are as follows:

[0049] 1) Li, Mn, Ni, Ti, Nb, Zr, Al and Mg are weighed according to the stoichiometric ratio of Li:Mn:Ni:Ti:Nb:Zr:Al:Mg = 0.5:0.5:0.5:0.5:0.5:0.5:0.5:0.5:0.5, and 75vol% ethanol aqueous solution is weighed according to the solid-liquid ratio of 1:0.8, and all materials are put into a ball mill for ball milling (ball milling parameters are the same as those in Example 1); 1.04 Mn 0.1 Ni 0.8 Ti 0.02 Nb 0.02 Zr 0.02 Al 0.02 Mg 0.02 O2, and 75vol% ethanol aqueous solution is weighed according to the solid-liquid ratio of 1:0.8, and all materials are put into a ball mill for ball milling (ball milling parameters are the same as those in Example 1);

[0050] 2) The slurry after ball milling in step 1) is moved to a rotary evaporator and dried at a temperature of 80°C for 4h to obtain a precursor;

[0051] 3) The precursor obtained in step 2) is transferred to an oxygen atmosphere box furnace and pre-sintered at a temperature of 450°C for 3h;

[0052] 4) The pre-sintered precursor is transferred to a ball mill (ball milling parameters are the same as those in Example 1), deionized water, polyethylene glycol and cetyltrimethylammonium bromide are weighed according to the mass ratio of 100:120:1:3 of the pre-sintered precursor, deionized water, polyethylene glycol and cetyltrimethylammonium bromide, and are added to the ball mill, and ball milling is performed for 6h to obtain a spray slurry;

[0053] 5) The spray slurry prepared in step 4) is pumped into a spray dryer, the inlet air temperature is set to 185°C, and the spray pressure is 0.2MPa to obtain a positive electrode material substrate;

[0054] 6) The positive electrode material substrate prepared in step 5) is sintered in an oxygen atmosphere at 800°C for 12h to obtain a high-entropy doping modified high-nickel cobalt-free positive electrode material.

[0055] Example 3

[0056] The embodiment provides a preparation method of a high-entropy doping modified high-nickel cobalt-free positive electrode material, and the specific steps are as follows:

[0057] 1) Li, Mn, Ni, Ti, Nb, Zr, Al and Mg are weighed according to the stoichiometric ratio of Li:Mn:Ni:Ti:Nb:Zr:Al:Mg = 0.5:0.5:0.5:0.5:0.5:0.5:0.5:0.5:0.5, and 75vol% ethanol aqueous solution is weighed according to the solid-liquid ratio of 1:0.8, and all materials are put into a ball mill for ball milling (ball milling parameters are the same as those in Example 1); 1.04 ​Mn 0.1 Ni 0.8 Ti 0.02 Mg 0.02 Zr 0.02 Al 0.02 Nb 0.02 stoichiometric ratio of O2, Ni(OH)2, MnO2, LiOH, TiO2, MgO, ZrO2, Al2O3, and Nb2O5 are weighed, and 75 vol% ethanol aqueous solution is weighed according to a solid-liquid ratio of 1:1.2, and all materials are placed into a ball mill for ball milling (ball milling parameters are the same as those in Example 1);

[0058] 2) The slurry after ball milling in step 1) is moved to a rotary evaporator and dried at a temperature of 100℃ for 2h to obtain a precursor;

[0059] 3) The precursor obtained in step 2) is transferred to a box furnace in an oxygen atmosphere and pre-sintered at a temperature of 350℃ for 7h;

[0060] 4) The pre-sintered precursor is transferred to a ball mill (ball milling parameters are the same as those in Example 1), deionized water, polyethylene glycol, and cetyltrimethylammonium bromide are weighed according to a mass ratio of 100:170:3:1 of the pre-sintered precursor, deionized water, polyethylene glycol, and cetyltrimethylammonium bromide and added to the ball mill, and ball milling is performed for 6h to obtain a spray slurry;

[0061] 5) The spray slurry prepared in step 4) is pumped into a spray dryer, the inlet air temperature is set to 175℃, and the spray pressure is 0.4MPa to obtain a positive electrode material matrix;

[0062] 6) The positive electrode material matrix prepared in step 5) is sintered in an oxygen atmosphere at 900℃ for 8h to obtain a high-entropy doped modified high-nickel cobalt-free positive electrode material.

[0063] Example 4

[0064] The embodiment provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, which is different from Example 1 in that the temperature for spray drying in step 5) is 210℃, the atomization pressure is 0.1MPa, and other conditions are the same as those in Example 1.

[0065] Example 5

[0066] The embodiment provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, which is different from Example 1 in that the temperature for spray drying in step 5) is 150℃, the atomization pressure is 0.6MPa, and other conditions are the same as those in Example 1.

[0067] Example 6

[0068] The embodiment provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, which is different from the embodiment 1 in that step 3) is not performed, that is, no pre-sintering treatment is performed, and other conditions are the same as those in the embodiment 1.

[0069] Comparative example 1

[0070] The comparative example provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, which is different from the embodiment 1 in that steps 4) and 5) are not performed, that is, no spray drying treatment is performed, and other conditions are the same as those in the embodiment 1.

[0071] Comparative example 2

[0072] The comparative example provides a preparation method of a doped modified high-nickel cobalt-free positive electrode material, which is different from the embodiment 1 in that the chemical formula of the high-nickel cobalt-free positive electrode material is Li 1.04 Mn 0.1 Ni 0.8 Ti 0.033 Zr 0.033 Al 0.034 O2, and other conditions are the same as those in the embodiment 1.

[0073] Comparative example 3

[0074] The comparative example provides a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material, which is different from the embodiment 1 in that the Ni(OH)2, MnO2, LiOH, TiO2, Nb2O5, ZrO2, Al2O3 and MgO are weighed according to the stoichiometric ratio of Li 1.04 Mn 0.1 Ni 0.8 Ti 0.02 Nb 0.02 Zr 0.02 Al 0.02 Mg 0.02 O2, and other conditions are the same as those in the embodiment 1.

[0075] Test example

[0076] The high-nickel cobalt-free positive electrode materials prepared in the above embodiments and comparative examples are subjected to electrochemical performance tests, and the electrochemical performance test steps are as follows: the positive electrode material, carbon black and polyvinylidene fluoride (PVDF) are weighed according to the mass ratio of 95:2.5:2.5, the solvent N-methyl pyrrolidone (NMP) is added according to the ratio of 2:1 to prepare a positive electrode slurry, the slurry is uniformly coated on an aluminum foil (the slurry coating surface density is consistent in each test example), the coated aluminum foil is baked at 105 DEG C for 2h, and then the baked electrode piece is cut and placed in a tablet press to be compacted (the compacted density is 3.2g / cm 3), and the small disc (a disc with a diameter of 1.3 cm) was cut out and assembled under a nitrogen atmosphere with a water vapor and oxygen content of less than 0.1 ppm. The small disc was placed into the positive side of the button cell shell with the coated side facing away from the positive side shell. The button cell was assembled in the order of the positive electrode sheet, electrolyte (a 1 mol / L LiPF6 mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio 1:1) as the electrolyte), separator (Celgard 2500 type separator), electrolyte (same as above), negative electrode sheet (metal lithium sheet as the negative electrode), and negative side of the button cell shell. The button cell was placed into a blue light test system for electrical performance testing. The charging and discharging system was as follows: the charging cutoff voltage was 4.3 V, and the discharging cutoff voltage was 3.0 V; the first cycle was 0.2 C charging and 0.2 C discharging (test 0.2 C discharge specific capacity); the second cycle was 0.2 C charging and 1 C discharging (test 1 C discharge specific capacity); the third cycle was 0.5 C charging and 1.0 C discharging; and then 0.5 C charging and 1 C discharging were cycled 50 times (test 1 C cycle capacity retention rate) for cycle retention rate testing. The test results are shown in Table 1 below.

[0077] Table 1

[0078]

[0079]

[0080] Obviously, the above examples are merely illustrative examples and are not intended to limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. All embodiments do not need to be exhaustively listed here. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a high-entropy doped modified high-nickel cobalt-free cathode material, characterized in that, The application relates to a preparation method of a high-entropy doped modified high-nickel cobalt-free positive electrode material. The nickel source, the manganese source, the lithium source, a first solvent and a doped metal source containing five or more doped metal elements are subjected to first mixed wet grinding, drying treatment to obtain a precursor; The precursor is subjected to second mixed wet grinding, spray drying and sintering treatment in sequence to obtain the high-entropy doped modified high-nickel cobalt-free positive electrode material.

2. The production method according to claim 1, characterized by, The spray drying is carried out at an air inlet temperature of 175-185 DEG C and an atomization pressure of 0.2-0.4 MPa.

3. The production method according to claim 1 or 2, characterized by, Before the second mixed wet grinding, the precursor is subjected to pre-sintering treatment; The sintering treatment is carried out at a temperature of 800-900 DEG C for 8-12 h; The sintering treatment is carried out in an oxygen atmosphere.

4. The production method according to claim 3, characterized by, The pre-sintering treatment is carried out at a temperature of 350-450 DEG C for 3-7 h; The pre-sintering treatment is carried out in an oxygen atmosphere.

5. The method of any one of claims 1-4, wherein, The high-entropy doping modified high-nickel cobalt-free cathode material has a chemical formula of Li a Mn x Ni y M 1-x-y O2; wherein, 1.01≤a≤1.08, 0.2>x≥0.1, y≥0.8, 1-x-y>0, M is a doping metal element, and is selected from at least five kinds of Al, Mg, Ti, Lu, Nb, Ru and Zr. The ratio of the doped metal elements in the doped metal source is an equimolar ratio; The compound form of the doped metal elements in the doped metal source is a carbonate or / and an oxide.

6. The method of any one of claims 1-5, wherein, The nickel source comprises nickel hydroxide; The manganese source comprises manganese oxide; The lithium source comprises lithium hydroxide; The first solvent is an ethanol aqueous solution; The slurry solid-liquid ratio in the first mixed wet grinding is 1:(0.8-1.2); The drying treatment is carried out at a temperature of 80-100 DEG C for 2-4 h.

7. The method of any one of claims 1-6, wherein, The second mixed wet grinding is carried out by ball milling the precursor, a second solvent, a binder and a dispersant.

8. The production method according to claim 7, characterized by, The mass ratio of the precursor, the second solvent, the binder and the dispersant is 100:(120-170):(1-3):(1-3); The second solvent is deionized water; The binder comprises polyethylene glycol; The dispersant comprises cetyltrimethylammonium bromide. 9.A high-entropy doped modified high-nickel cobalt-free cathode material, characterized in that, The high-entropy doped modified high-nickel cobalt-free positive electrode material is prepared by the preparation method of any one of claims 1-8.

10. A lithium-ion battery, characterized by, The high-entropy doped modified high-nickel cobalt-free positive electrode material is prepared by the preparation method of any one of claims 1-8.

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