Modified ternary precursor, positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of electrode materials, and particularly relates to a modified ternary precursor, a positive electrode material and a preparation method and application thereof, and the preparation method of the modified ternary precursor comprises the following steps: (1) mixing a porous ternary precursor with an initiator solution, pressurizing, standing, and carrying out solid-liquid separation to obtain a ternary precursor wet material; (2) preparing a coating source, acrylamide and sodium alginate into a reaction solution, then mixing the ternary precursor wet material with the reaction solution, carrying out ultrasonic reaction to obtain a gel-coated ternary precursor, and drying to obtain a modified ternary precursor, the coating source is at least one of a soluble aluminum source, a soluble zirconium source, a soluble titanium source and a soluble silicon source.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of electrode materials, and particularly relates to a modified ternary precursor, a positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Lithium ion batteries have excellent capacity and output power density, are widely used in various fields, and greatly improve energy utilization efficiency. The positive electrode material not only directly determines the electrochemical performance of the battery, but also plays a leading role in energy density and safety characteristics. Among them, the ternary material (NCM / NCA) realizes the breakthrough of energy density (NCM811 single energy density reaches 210 Wh / kg) through the element cooperation of nickel, cobalt and manganese (or aluminum), significantly improves the endurance mileage of electric vehicles (commonly breaks through 600 kilometers for vehicle models), and becomes the first choice for passenger car power batteries. However, the existing high-nickel ternary positive electrode material has a relatively fast capacity attenuation in the use process due to the instability of the crystal structure and the surface of the material particles, resulting in poor cycle performance. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, the present application provides a modified ternary precursor, a positive electrode material and a preparation method and application thereof, and the positive electrode material prepared by the modified ternary precursor has excellent cycle performance.

[0004] The above technical purpose of the present application is realized by the following technical scheme: A preparation method of a modified ternary precursor, comprising the following steps: (1) mixing a porous ternary precursor and an initiator solution, pressurizing and then standing, and then solid-liquid separation to obtain ternary precursor wet material; (2) preparing a reaction solution by mixing a coating source, acrylamide and sodium alginate, then mixing the ternary precursor wet material with the reaction solution and cooperating ultrasonic reaction to obtain gel-coated ternary precursor, and drying to obtain a modified ternary precursor, wherein the coating source is at least one of a soluble aluminum source, a soluble zirconium source, a soluble titanium source and a soluble silicon source.

[0005] In an embodiment, in step (1), the porosity of the porous ternary precursor is greater than 0.05 cm 3 / g; and / or the pressure after pressurization is 20-40 bar.

[0006] In an embodiment, in step (1), the porous ternary precursor is Ni x Mn y Co z (OH)2, wherein 0.5≤x≤0.98, 0.02≤y+z≤0.5, and x+y+z=1.

[0007] In one embodiment, in step (1), the initiator solution comprises N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethylethylenediamine, and the ratio of N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethylethylenediamine in the initiator solution is (0.12-1.5) g / L:(1.5-2.2) g / L:(2.5-3.5) mL / L.

[0008] In one embodiment, in step (1), the volume ratio of the initiator solution to the porous ternary precursor is (1.5-2):1.

[0009] In one embodiment, in step (2), the reaction is first carried out under the assistance of ultrasound for 30-100 min, and then stirred for 10-15 h.

[0010] In one embodiment, the power of the ultrasound is 50-150 w, and the time of the ultrasound is 30-100 min.

[0011] In one embodiment, in step (2), the coating source comprises at least one of aluminum sulfate, sodium silicate, titanyl sulfate, zirconium oxychloride and aluminum chloride; and / or the total mass of the acrylamide and the sodium alginate to the volume of the reaction solution is (10-30) g:1 L.

[0012] In one embodiment, in step (2), the volume of the reaction solution to the initiator solution in step (1) is (0.5-1.5):1.

[0013] In one embodiment, in step (2), the mass ratio of the acrylamide to the sodium alginate is (5-10):1.

[0014] In one embodiment, in step (2), the mass ratio of the coating source to the porous ternary precursor in step (1) is (0.5-2):20.

[0015] A modified ternary precursor prepared by the preparation method described above.

[0016] A preparation method of a positive electrode material, comprising the following steps: grinding and mixing a lithium source and the modified ternary precursor described above, and calcining in an oxygen atmosphere to obtain an oxide-coated structure positive electrode material.

[0017] In one embodiment, the molar ratio of Li in the lithium source to the sum of Ni, Co and Mn in the modified ternary precursor is (1-1.1):1.

[0018] In an embodiment, the calcining is first at 400-500℃ for 3-6h, then the temperature is raised to 700-800℃ for 10-15h, and the rate of the temperature raising is 1-5℃ / min.

[0019] A positive electrode material prepared by the preparation method as described above.

[0020] A lithium ion battery comprising the positive electrode material as described above.

[0021] The present application has the following beneficial effects: in the preparation process of the ternary positive electrode material with a coating structure, generally two sintering processes are needed, and the coating is not uniform. The ternary precursor has abundant pores. In the present application, the initiator is filled into the pores of the ternary precursor by pressure, and then the ternary precursor is placed in a reaction solution. Through the effects of ultrasonic and concentration difference, the initiator diffuses to the surface of the ternary precursor, and the reaction of acrylamide and sodium alginate is initiated to obtain a ternary precursor coated with a gel. At the same time, the gel coagulates in the pores, and the gel carries the coating metal elements. After drying the ternary precursor coated with the gel, the gel in the pores and the gel coated on the surface of the precursor are dried, and the gel is dried in situ to obtain a dandelion-like fluff coating and a needle-like structure in the pores. After mixing with a lithium source and calcining, the dandelion-like fluff is coated on the surface of the ternary positive electrode material in situ, and a ternary positive electrode material coated with metal oxides in situ is obtained. Since the gel structure in the pores and the gel structure on the surface are in a porous state after drying, the transport and embedding of lithium ions in the calcining process are not affected. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 SEM image of the porous ternary precursor used in the preparation method of the modified ternary precursor of embodiment 1 of the present application; Figure 2 SEM image of the modified ternary precursor prepared in embodiment 1 of the present application. DETAILED DESCRIPTION

[0023] The present application will be further described below in conjunction with specific embodiments.

[0024] Embodiment 1: A preparation method of a modified ternary precursor, comprising the following steps: (1) N,N'-methylenebisacrylamide, N,N,N',N'-tetramethyl ethylenediamine and ammonium persulfate are configured into an initiator solution (the solvent in the solution is deionized water, the same below), and a porous ternary precursor with a porosity of 0.8cm 3The porous ternary precursor with a porosity of 0.5 cm3 / g is placed in the initiator solution, the mixed solution is placed in a reaction container, and the pressure is increased to 30 bar and kept for 20 min, then the excess initiator solution is removed, and the ternary precursor wet material is obtained by filtration, wherein the ratio of N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethyl ethylenediamine in the initiator solution is 0.13 g / L:1.8 g / L:3 mL / L; the volume ratio of the initiator solution to the porous ternary precursor is 1.8:1, and the SEM image of the porous ternary precursor is as shown in Figure 1 It can be seen from Figure 1 that the ternary precursor has abundant pores; (2) After the reaction solution is prepared by mixing aluminum sulfate, acrylamide and sodium alginate, the modified ternary precursor wet material is added to the reaction solution, ultrasonic treatment is performed at 80 W for 80 min, then the ultrasonic treatment is stopped, and the reaction is carried out at a rotation speed of 350 rpm for 12 h to obtain a gel-coated ternary precursor, which is then spray dried to obtain a modified ternary precursor, wherein the volume ratio of the reaction solution to the initiator solution is 1:1, the total mass of acrylamide and sodium alginate and the volume of the reaction solution are 15 g:1 L, the mass ratio of acrylamide to sodium alginate is 9:1, and the mass ratio of the porous ternary precursor to aluminum sulfate is 20:1, and the SEM image of the obtained modified ternary precursor is as shown in Figure 2 , Figure 2 which is the morphology of the ternary precursor after gel coating and drying.

[0025] A preparation method of a positive electrode material, comprising the following steps: The modified ternary precursor obtained as described above is mixed with a lithium source after being ground sufficiently, and is calcined in an oxygen atmosphere to obtain a ternary positive electrode material with a metal oxide coated structure, wherein the molar ratio of Li in the lithium source to (Ni+Co+Mn) in the modified ternary precursor is 1.05:1; the calcination process is a step-by-step calcination, specifically, first calcining at 480℃ for 5 h, then increasing the temperature to 790℃ and calcining for 12 h, and the temperature increasing rate is 2℃ / min.

[0026] Example 2: A preparation method of a modified ternary precursor, comprising the following steps: (1) N,N'-methylenebisacrylamide, N,N,N',N'-tetramethyl ethylenediamine and ammonium persulfate are configured into an initiator solution, and a porous ternary precursor with a porosity of 0.5 cm3 / g is placed in the initiator solution, the mixed solution is placed in a reaction container, and the pressure is increased to 30 bar and kept for 20 min, then the excess initiator solution is removed, and the ternary precursor wet material is obtained by filtration, wherein the ratio of N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethyl ethylenediamine in the initiator solution is 0.13 g / L:1.8 g / L:3 mL / L; the volume ratio of the initiator solution to the porous ternary precursor is 1.8:1, and the SEM image of the porous ternary precursor is as shown in 3The porous ternary precursor with a porosity of 1.0 cm (2) After the reaction solution is prepared by mixing sodium silicate, acrylamide and sodium alginate, the modified ternary precursor wet material is added into the reaction solution, and after ultrasonic treatment at 60 W for 40 min, the treatment is stopped, and the reaction is carried out at a rotation speed of 400 rpm for 10 h to obtain a gel-coated ternary precursor, which is then spray dried to obtain a modified ternary precursor, wherein the volume ratio of the reaction solution to the initiator solution is 1:1, the total mass of acrylamide and sodium alginate to the volume of the reaction solution is 10 g:1 L, the mass ratio of acrylamide to sodium alginate is 9:1, and the mass ratio of the porous ternary precursor to sodium silicate is 20:0.5.

[0027] A preparation method of a positive electrode material, comprising the following steps: The modified ternary precursor obtained as described above is mixed with a lithium source after being ground sufficiently, and then calcined in an oxygen atmosphere to obtain a ternary positive electrode material with a metal oxide coated structure, wherein the molar ratio of Li in the lithium source to (Ni+Co+Mn) in the modified ternary precursor is 1.05:1; the calcination process is a step-by-step calcination, specifically, first calcined at 480℃ for 5 h, then heated to 790℃ and calcined for 12 h at this temperature, and the heating rate is 2℃ / min.

[0028] Example 3: A preparation method of a modified ternary precursor, comprising the following steps: (1) N,N'-methylenebisacrylamide, N,N,N',N'-tetramethyl ethylenediamine and ammonium persulfate are configured into an initiator solution, and a porous ternary precursor with a porosity of 1.0 cm 3 / g is placed in the initiator solution, the mixed solution is placed in a reaction container, and the pressure is increased to 40 bar and kept for min, then the excess initiator solution is removed, and the ternary precursor wet material is obtained by filtration, wherein the ratio of N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethyl ethylenediamine in the initiator solution is 0.12 g / L:1.5 g / L:2.5 mL / L; the volume ratio of the initiator solution to the porous ternary precursor is 2:1; (2) After mixing titanium oxysulfate, acrylamide and sodium alginate to prepare a reaction solution, the modified ternary precursor wet material is added into the reaction solution, and after ultrasonic treatment at 120w for 80min, the reaction is stopped, and the reaction is carried out for 15h at a rotation speed of 350rpm to obtain a gel-coated ternary precursor, and after spray drying, the modified ternary precursor is obtained, wherein the volume ratio of the reaction solution to the initiator solution is 1:1, the total mass of acrylamide and sodium alginate to the volume of the reaction solution is 30g:1L, the mass ratio of acrylamide to sodium alginate is 9:1, and the mass ratio of the porous ternary precursor to titanium oxysulfate is 20:2.

[0029] A preparation method of a positive electrode material, comprising the following steps: After the modified ternary precursor obtained as described above is mixed with a lithium source by grinding, calcination is carried out in an oxygen atmosphere to obtain a ternary positive electrode material with a metal oxide coated structure, wherein the molar ratio of Li in the lithium source to (Ni+Co+Mn) in the modified ternary precursor is 1.05:1; the calcination process is step calcination, specifically, first calcination at 480℃ for 5h, and then calcination at 790℃ for 12h after heating at a rate of 2℃ / min.

[0030] Example 4: A preparation method of a modified ternary precursor, which is different from example 1 only in that the mass ratio of the porous ternary precursor to aluminum sulfate in step (2) is 20:2, and other steps and parameters are completely the same.

[0031] A positive electrode material, which is prepared from the modified ternary precursor prepared in example 4, and the preparation method is completely the same as that in example 1.

[0032] Example 5: A preparation method of a modified ternary precursor, which is different from example 1 only in that the mass ratio of the porous ternary precursor to aluminum sulfate in step (2) is 20:0.5, and other steps and parameters are completely the same.

[0033] A positive electrode material, which is prepared from the modified ternary precursor prepared in example 5, and the preparation method is completely the same as that in example 1.

[0034] Example 6: A preparation method of a modified ternary precursor, which is different from example 1 only in that in step (2), the mixed solution is placed in a reaction container, pressurized to 20bar and stopped after standing for 20min, and other steps and parameters are completely the same.

[0035] A positive electrode material, which is prepared from the modified ternary precursor prepared in example 6, and the preparation method is completely the same as that in example 1.

[0036] Example 7: A preparation method of a modified ternary precursor, which is different from example 1 only in that the mass ratio of acrylamide to sodium alginate and the volume of the reaction solution is 30 g:1 L in step (2), and the mass ratio of the porous ternary precursor to aluminum sulfate is 20:0.5, and other steps and parameters are completely the same.

[0037] A positive electrode material, which is prepared from the modified ternary precursor prepared in example 7, and the preparation method is completely the same as example 1.

[0038] Example 8: A preparation method of a modified ternary precursor, which is different from example 1 only in that the mass ratio of acrylamide to sodium alginate and the volume of the reaction solution is 50 g:1 L in step (2), and the mass ratio of the porous ternary precursor to aluminum sulfate is 20:8, and other steps and parameters are completely the same.

[0039] A positive electrode material, which is prepared from the modified ternary precursor prepared in example 8, and the preparation method is completely the same as example 1.

[0040] Comparative example 1: A preparation method of a positive electrode material, comprising the following steps: The porous ternary precursor used in the preparation method of the modified ternary precursor in example 1 is fully ground and mixed with a lithium source, and is calcined in an oxygen atmosphere to obtain a ternary positive electrode material, wherein the molar ratio of Li in the lithium source to (Ni+Co+Mn) in the modified ternary precursor is 1.05:1; the calcination process is step calcination, specifically, first calcine at 480℃ for 5h, then heat to 790℃ and calcine for 12h, the heating rate is 2℃ / min.

[0041] Comparative example 2: A preparation method of a modified ternary precursor, which is different from example 1 only in that the reaction container is not pressurized in step (1), and other steps and parameters are completely the same.

[0042] A positive electrode material, which is prepared from the modified ternary precursor prepared in comparative example 2, and the preparation method is completely the same as example 1.

[0043] Comparative example 3: A preparation method of a modified ternary precursor, which is different from example 1 only in that the reaction container is not pressurized in step (1) and no ultrasonic treatment is performed in step (2), and other parameters are completely the same.

[0044] A positive electrode material, which is prepared from the modified ternary precursor prepared in comparative example 3, and the preparation method is completely the same as example 1.

[0045] The porous ternary precursors used in each embodiment and comparative example are all Ni 0.8 Mn 0.1 Co 0.1 (OH)2.

[0046] Test Example: Battery assembly: First, mix PVDF, positive electrode material and acetylene black in a mass ratio of 1:8:1. Then add the solvent NMP and ball mill it to obtain a slurry. The slurry is evenly coated on the surface of an aluminum foil. After drying in a vacuum drying oven, the positive electrode sheet is compacted using a rolling device, and the positive electrode sheet is cut into a 15 mm circle and placed in a vacuum dryer for use. The positive electrode sheet is placed in the middle of the positive electrode shell of a CR2016 button cell, covered with a separator, and then the electrolyte is added to completely wet the positive electrode sheet and the separator. Then put the lithium sheet and the negative electrode shell respectively, and finally use the sealing machine to tamp it, complete the assembly, and test after standing for twenty-four hours.

[0047] Electrochemical performance test: The cycle performance and discharge specific capacity of the positive electrode material provided by each embodiment and comparative example in the voltage range of 2.7V to 4.3V were tested by using a multi-channel battery test system. The results are shown in Table 1.

[0048] Table 1.

[0049] As can be seen from Table 1, by comparing Example 1 with Comparative Example 1, it can be seen that the capacity retention rate of the positive electrode material prepared by directly using the porous ternary precursor is only 71.3% after 100 cycles, which is much smaller than 95.40% of Example 1; by comparing Example 1 with Comparative Example 2, it can be seen that when the reaction container is not pressurized in step (1) of the preparation method of the modified ternary precursor, the capacity retention rate of the positive electrode material prepared finally will decrease greatly after 100 cycles; by comparing Example 1 with Comparative Example 3, it can be seen that when the reaction container is not pressurized in step (1) of the preparation method of the modified ternary precursor and the ultrasonic treatment is not performed in step (2), the capacity retention rate of the positive electrode material prepared finally will decrease greatly after 100 cycles; by comparing Example 1 with Example 8, it can be seen that the total mass of acrylamide and sodium alginate, the volume ratio of the reaction solution and the mass ratio of the porous ternary precursor and aluminum sulfate will have a greater influence on the discharge specific capacity and cycle performance of the positive electrode material prepared finally.

Claims

1. A method for preparing a modified ternary precursor, characterized by: The method comprises the following steps: (1) mixing a porous ternary precursor with an initiator solution, standing after pressurization, and then performing solid-liquid separation to obtain a ternary precursor wet material; (2) preparing a reaction solution by mixing a coating source, acrylamide and sodium alginate, then mixing the ternary precursor wet material with the reaction solution and performing reaction under ultrasonic assistance to obtain a gel-coated ternary precursor, and drying the gel-coated ternary precursor to obtain a modified ternary precursor, wherein the coating source is at least one of a soluble aluminum source, a soluble zirconium source, a soluble titanium source and a soluble silicon source.

2. The method of claim 1, wherein: In step (1), the porosity of the porous ternary precursor is greater than 0.05 cm 3 / g; and / or the pressure after pressurization is 20-40 bar.

3. The method for preparing a modified ternary precursor according to claim 1, characterized in that: In step (1), the initiator solution comprises N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethylethylenediamine, and the ratio of N,N'-methylenebisacrylamide, ammonium persulfate and N,N,N',N'-tetramethylethylenediamine in the initiator solution is (0.12-1.5) g / L:(1.5-2.2) g / L:(2.5-3.5) mL / L.

4. The method of claim 1, wherein: In step (1), the volume ratio of the initiator solution to the porous ternary precursor is (1.5-2):

1.

5. The method of claim 1, wherein: In step (2), the reaction under ultrasonic assistance is first performed for 30-100 min, and then stirred for 10-15 h.

6. The method of claim 1, wherein: In step (2), the coating source comprises at least one of aluminum sulfate, sodium silicate, titanyl sulfate, zirconium oxychloride and aluminum chloride; and / or the total mass of the acrylamide and the sodium alginate to the volume of the reaction solution is (10-30) g:1 L.

7. A modified ternary precursor, characterized by: Prepared by the preparation method of any one of claims 1-6.

8. A method for producing a positive electrode material, characterized by: The method comprises the following steps: Grinding and mixing a lithium source with the modified ternary precursor of claim 7, and calcining in an oxygen atmosphere to obtain an oxide-coated positive electrode material.

9. A positive electrode material, characterized by: Prepared by the preparation method of claim 8.

10. A lithium-ion battery, characterized by: The positive electrode material of claim 9. The positive electrode material of claim 9.

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