CN113193190B - Fiber-reinforced NCM ternary positive electrode composite material and preparation method thereof - Google Patents
Fiber-reinforced NCM ternary positive electrode composite material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a fiber-reinforced NCM ternary positive electrode composite material and a preparation method thereof, belonging to the field of chemical energy storage batteries. The inorganic oxide nano-fibers in the material are distributed in the secondary particles of the NCM ternary cathode material. According to the method, inorganic nanofibers are added into a reaction kettle in the synthesis process of synthesizing the NCM ternary cathode material precursor by a coprecipitation method, and the inorganic nanofibers can serve as the core of crystal nucleation of the NCM precursor material, so that the nanofibers of the NCM precursor material can be embedded into the NCM precursor material in the stacking growth process. In the subsequent lithium-mixed high-temperature calcination process, the nano-fibers can be kept stable and not decomposed, and are finally stably stored in the NCM ternary cathode material. The material can enhance the shearing strength of material particles and reduce the crushing phenomenon of secondary particles in the circulating process.
Description
Technical Field
The invention relates to a fiber-reinforced NCM ternary positive electrode composite material and a preparation method thereof, belonging to the field of chemical energy storage batteries.
Background
Under the background that the energy structure of China is mainly fossil energy such as coal and petroleum, the increasingly serious environmental pollution problem caused by the utilization of a large amount of fossil energy needs to be solved urgently. The existing novel energy forms mainly comprise solar energy, geothermal energy, wind energy and the like, which cannot be directly utilized and generally need to be converted into electric energy for utilization. Electric energy, as a secondary energy source that can be directly used, almost covers all aspects of social development. With the popularization of electric vehicles and portable electronic devices, the development of new electric energy storage devices is receiving wide attention, and lithium ion batteries are drawing more and more attention as high energy density storage devices. According to the national requirements, the energy density of the lithium ion battery reaches 300Wh kg by 2020 -1 To achieve this, the performance of the positive electrode material as a lithium ion battery short sheet is required to be improved. NCM ternary materials have been developed in recent years as positive electrode materials having a high specific energy density. The NCM ternary material comprises LiNi x Co y Mn 1-x-y O 2 ，0<x<1，0<y<1，0<(x+y)<1; and the higher the Ni content is, the higher the discharge specific capacity of the NCM ternary material is.
The particles of the traditional NCM ternary material are micron-sized secondary particles formed by stacking a plurality of small nano-sized primary particles, and because the small primary particles have the characteristic of anisotropy of crystal materials, when Li is used in the cyclic charge-discharge process + When Li layer in the material is inserted or extracted, the unit cell volume of the material is expanded and contracted correspondingly,the volume of the corresponding primary particles also changes. Since the primary particles are closely packed, the change in volume of the primary particles causes mutual compression between the primary particles, and stress is generated inside the secondary particles. When the stress reaches the yield limit of secondary particles of the NCM material, the material can crack, and the occurrence of cracks can cause a large amount of electrolyte to permeate into the material, so that the interface side reaction is aggravated and the cycle stability is rapidly reduced. In view of the structural characteristics of the NCM material, stress accumulation inside the secondary particles of the NCM ternary material during cycling is inevitable, and thus the problem of particle breakage due to stress accumulation can be alleviated by increasing the strength of the secondary particles. Partial research attempts to broaden Li by elemental doping + Diffusion channels of (2) and acceleration of Li + Thereby relieving the build-up of stress. But particle breakage still occurs during long cycles. Therefore, the material needs to be designed from the viewpoint of improving the strength of the secondary particles of the material.
Disclosure of Invention
In view of the above, the present invention aims to provide a fiber-reinforced NCM ternary positive electrode composite material and a preparation method thereof.
The purpose of the invention is realized by the following technical scheme:
in the fiber-reinforced NCM ternary cathode composite material, inorganic oxide nano fibers are distributed in secondary particles of the NCM ternary cathode material, and the NCM ternary cathode material is LiNi x Co y Mn 1-x-y O 2 ，0<x<1，0<y<1，0<(x+y)<1; the length of the inorganic oxide nanofiber is 2-8 mu m, and the inorganic oxide nanofiber accounts for 1-5% of the total mass of the material.
Preferably, the inorganic oxide nanofibers are more than one of silicon dioxide nanofibers, zirconium dioxide nanofibers, tin dioxide nanofibers, aluminum oxide nanofibers, magnesium oxide nanofibers and zinc oxide nanofibers.
A preparation method of a fiber-reinforced NCM ternary cathode composite material comprises the following steps:
(1) soluble nickel salt, soluble cobalt salt and soluble manganese salt are added according to the molar ratio of nickel to cobalt to manganese as x: y: (1-x-y) preparing a mixed salt solution with the total concentration of nickel, cobalt and manganese ions being 1-2 mol/L, wherein 0< x <1, 0< y <1, 0< (x + y) < 1;
(2) mixing sodium hydroxide and water with the purity higher than that of deionized water to prepare an alkali solution with the concentration of 2-4 mol/L;
(3) mixing concentrated ammonia water (with the mass concentration of 25-28%) and water with the purity higher than that of deionized water to respectively prepare an ammonia water solution I with the concentration of 0.6-1.2 mol/L and an ammonia water solution II with the concentration of 1-3 mol/L;
(4) adding the ammonia water solution II serving as a base solution into a reaction kettle, wherein the adding amount of the ammonia water solution II is larger than that of a stirrer in the reaction kettle, adding inorganic oxide nano fibers into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle at the same feeding speed, controlling the temperature in the reaction kettle to be 50-70 ℃, adding the alkali solution, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 10.5-11.5, introducing argon or nitrogen serving as a protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at the stirring speed of 600-1200 r/min until the solution is completely fed, and filtering to obtain a precursor of the fiber-reinforced NCM ternary cathode material; wherein the mixed salt solution: ammonia water solution I: inorganic oxide nanofibers: the dosage ratio of the alkali solution is 100-500 mL: 400-600 mL: 1-10 g: 200-1000 mL;
(5) and uniformly mixing the precursor with lithium hydroxide, heating to 300-600 ℃, preserving heat for 3-7 h, heating to 700-900 ℃, and preserving heat for 12-24 h to obtain the fiber-reinforced NCM ternary cathode composite material.
Preferably, the soluble nickel salt in step (1) is NiSO 4 ·6H 2 O, soluble cobalt salt is CoSO 4 ·7H 2 O, and a soluble manganese salt is MnSO 4 ·H 2 O。
Preferably, the molar ratio x of nickel, cobalt and manganese in step (1): y: (1-x-y) ═ 0.8:0.1: 0.1.
Preferably, the mixed salt solution and the ammonia water solution I in the step (3) are simultaneously fed at a speed of 20-100 mL/h.
Preferably, the molar ratio of the precursor to the lithium hydroxide in the step (5) is 1: 1-1.1.
Preferably, the temperature rise rate in the step (5) is 2-10 ℃/min.
The invention relates to a lithium ion battery, wherein the anode material of the battery adopts the fiber-reinforced NCM ternary anode composite material.
Advantageous effects
The existence of the nanofiber structure in the material can increase the yield strength of the secondary particles of the NCM ternary material, so that the number of internal cracks of the secondary particles of the NCM ternary material in the circulating process is reduced, and the material crushing ratio is reduced. Thereby reducing the exposure of the internal surface of the anode material particles, reducing the interface side reaction and improving the cycling stability of the material.
According to the method, in the process of synthesizing the NCM ternary cathode material precursor through a coprecipitation reaction, inorganic oxide nanofibers with short diameters are used as additives and added into a base solution of a reaction kettle, the inorganic oxide nanofibers in the base solution can be used as crystal nuclei for crystal grain growth of the precursor material, precursor nanosheets are promoted to accumulate and grow on the basis of the inorganic oxide nanofibers, and the inorganic oxide nanofibers are finally embedded into the NCM precursor material. During the subsequent lithium-mixed calcination process, the inorganic oxide nanofibers remain undecomposed and eventually remain inside the NCM ternary positive electrode material formed by the calcination. The nano-fiber is added in the synthesis process of the precursor, so that a fiber structure can be constructed in advance in the NCM ternary cathode material, and the inorganic oxide nano-fiber and the NCM ternary cathode material form a fiber composite cathode material.
Drawings
Fig. 1 is a Scanning Electron Microscope (SEM) image of the final product prepared in example 1.
Fig. 2 shows assembled cells of final products prepared in example 1 and comparative example 1 at a cut-off voltage of 2.8 to 4.3V and 0.2C (1C 200mAh g) -1 ) Discharge specific capacity change curve circulating for 50 weeks under multiplying powerAnd (6) line drawing.
Detailed Description
For a better understanding of the present invention, reference is made to the following detailed description taken in conjunction with the accompanying drawings. It should be understood that the detailed description and specific examples, while indicating the present invention, are given by way of illustration and explanation only, not limitation. Additionally, the endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.
For a better understanding of the present invention, the present invention is described in further detail below with reference to specific examples.
In the following examples 1 to 4, the following methods were used for the characterization and analysis of materials:
scanning Electron Microscope (SEM) testing: scanning electron microscope, instrument model: FEI Quanta, netherlands.
Particle size analysis test of the material: laser particle size analyzer, instrument model: mastersizer 3000, uk.
Assembly and testing of CR2025 button cells: the final product prepared in the example or the comparative example, acetylene black and polyvinylidene fluoride (PVDF) are prepared into slurry according to the mass ratio of 8:1:1 and coated on an aluminum foil, the aluminum foil loaded with the dried slurry is cut into small round pieces with the diameter of about 1cm by a cutting machine to be used as a positive electrode, a metal lithium piece is used as a negative electrode, Celgard2500 is used as a diaphragm, a 1M carbonate solution is used as an electrolyte (wherein, the solvent is a mixed solution of ethylene carbonate, methyl ethyl carbonate and dimethyl carbonate with the volume ratio of 1:1:1, and the solute is LiPF 6 ) And assembling the button cell CR2025 in an argon atmosphere glove box.
Comparative example 1
Step (1) NiSO 4 ·6H 2 O、CoSO 4 ·7H 2 O、MnSO 4 ·H 2 Mixing three metal salts O according to the molar ratio of nickel, cobalt and manganese elements of 8:1:1, adding deionized water, fully stirring and dissolving to prepare 500mL mixed salt solution with the total concentration of nickel, cobalt and manganese ions of 2 mol/L;
fully stirring and dissolving sodium hydroxide (NaOH) in deionized water to prepare 1000mL of aqueous alkali with the concentration of 4 mol/L;
step (3) mixing concentrated ammonia water (mass concentration is 27%) with deionized water to respectively prepare 500mL ammonia water solution I with the concentration of 0.6mol/L and 1000mL ammonia water solution II with the concentration of 1 mol/L;
and (4) adding the ammonia water solution II serving as a base solution into a reaction kettle, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle at a feeding speed of 20mL/h by using a peristaltic pump, wherein the water bath temperature of the reaction kettle is 50 ℃. Adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 11, introducing argon (Ar) as a protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at the stirring speed of 600r/min until the solution is completely fed, and filtering to obtain a solid which is a precursor of the NCM ternary cathode material;
step (5) of mixing the precursor obtained in step (4) with lithium hydroxide (LiOH. H) 2 O) uniformly mixing the metal ions and the lithium ions according to the molar ratio of 1:1.05, heating to 600 ℃ at the calcining condition of 2 ℃/min, preserving the heat for 7h, heating to 700 ℃ at the temperature of 2 ℃/min, and preserving the heat for 12h to obtain the NCM ternary cathode material.
Example 1
Step (1) NiSO 4 ·6H 2 O、CoSO 4 ·7H 2 O、MnSO 4 ·H 2 Mixing three metal salts O according to the molar ratio of nickel, cobalt and manganese elements of 8:1:1, adding deionized water, fully stirring and dissolving to prepare 500mL mixed salt solution with the total concentration of nickel, cobalt and manganese ions of 2 mol/L;
fully stirring and dissolving sodium hydroxide (NaOH) in deionized water to prepare 1000mL of aqueous alkali with the concentration of 4 mol/L;
step (3) mixing concentrated ammonia water (mass concentration is 27%) with deionized water to respectively prepare 500mL ammonia water solution I with the concentration of 0.6mol/L and 1000mL ammonia water solution II with the concentration of 1 mol/L;
and (4) adding the ammonia water solution II serving as a base solution into a reaction kettle, adding 5g of silicon dioxide nano fibers with the length of 2 mu m into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle by using a peristaltic pump according to the feeding speed of 20mL/h, wherein the water bath temperature of the reaction kettle is 50 ℃. Adding the alkali solution, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 11, introducing argon (Ar) as a protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at a stirring speed of 600r/min until the solution is completely fed, and filtering to obtain a precursor of which the solid is a fiber-reinforced NCM ternary positive electrode composite material;
step (5) reacting the precursor with lithium hydroxide (LiOH. H) 2 O) uniformly mixing the metal ions and the lithium ions according to the molar ratio of 1:1.05, heating to 600 ℃ at the calcining condition of 2 ℃/min, preserving the heat for 7h, heating to 700 ℃ at the temperature of 2 ℃/min, and preserving the heat for 12h to obtain the fiber-reinforced NCM ternary cathode composite material.
The scanning electron microscope results of the final product are shown in fig. 1, and it can be seen that the final product has a spherical-like secondary particle morphology. And embedding the final product into conductive resin for metallographic sample preparation, and observing the short-diameter fiber structure at the cross section of the material particles under an electron microscope.
Electrochemical test results of the final product are shown in fig. 2, and after the assembled battery is cycled for 50 weeks at 0.2C rate in the range of 2.8-4.3V of cut-off voltage, the capacity retention rate of the fiber-reinforced NCM ternary cathode composite material of the present example is found to be improved from 93.22% to 95.81% compared with the material of comparative example 1. The particle size change of the laser particle size analysis material before and after circulation was used to calculate the particle breakage ratio of the material after circulation to be 1.03.
The result shows that the particle strength of the NCM ternary cathode composite material reinforced by the short-diameter silicon dioxide nano-fibers is improved, and the crushing degree of the particles is reduced, so that the integrity of the material particles is maintained, the side reaction of the electrolyte is reduced, and the circulation stability of the material is improved.
Example 2
Step (1) NiSO 4 ·6H 2 O、CoSO 4 ·7H 2 O、MnSO 4 ·H 2 Mixing three metal salts O according to the molar ratio of nickel, cobalt and manganese elements of 8:1:1, adding deionized water, fully stirring and dissolving to prepare 500mL mixed salt solution with the total concentration of nickel, cobalt and manganese ions of 2 mol/L;
fully stirring and dissolving sodium hydroxide (NaOH) in deionized water to prepare 1000mL of aqueous alkali with the concentration of 4 mol/L;
step (3) mixing concentrated ammonia water (mass concentration is 27%) with deionized water to respectively prepare 1.2 mol/L500 mL ammonia water solution I and 3 mol/L1000 mL ammonia water solution II;
and (4) adding the ammonia water solution II serving as a base solution into a reaction kettle, adding 10g of zirconium dioxide nano-fibers with the length of 8 mu m into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle by using a peristaltic pump according to the feeding speed of 40mL/h, wherein the water bath temperature of the reaction kettle is 60 ℃. Adding the alkali solution, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 10.5, introducing argon (Ar) as protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at the stirring speed of 800r/min until the solution is completely fed, and filtering to obtain a solid which is a precursor of the fiber-reinforced NCM ternary positive electrode composite material;
step (5) reacting the precursor with lithium hydroxide (LiOH. H) 2 O) uniformly mixing the metal ions and the lithium ions according to the molar ratio of 1:1.05, heating to 300 ℃ at the calcining condition of 10 ℃/min, preserving the heat for 5h, heating to 900 ℃ at the temperature of 10 ℃/min, and preserving the heat for 18h to obtain the fiber-reinforced NCM ternary cathode composite material.
The scanning electron microscope result of the final product shows that the final product has the appearance of secondary particles similar to spheres. And embedding the final product into conductive resin to prepare a metallographic sample, wherein the short-diameter fiber structure at the cross section of the material particle can be observed under an electron microscope.
The assembled cell was cycled for 50 weeks at 0.2C rate in the range of 2.8-4.3V at cutoff voltage, and the capacity retention of the fiber-reinforced NCM ternary positive electrode composite described in this comparative example was found to increase from 93.22% to 97.56% compared to the material described in comparative example 1. The particle size change of the laser particle size analysis material before and after the circulation was calculated to obtain a particle breakage ratio of 1.01 after the circulation.
The result shows that the particle strength of the short-diameter zirconium dioxide nanofiber reinforced NCM ternary positive electrode composite material is improved more obviously, and meanwhile, the crushing degree of the particles is reduced, so that the integrity of the material particles is maintained, the side reaction of the electrolyte is reduced, and the circulation stability is further improved.
Comparative example 2
Step (1) NiSO 4 ·6H 2 O、CoSO 4 ·7H 2 O、MnSO 4 ·H 2 Mixing three metal salts O according to the molar ratio of nickel, cobalt and manganese elements of 8:1:1, adding deionized water, fully stirring and dissolving to prepare 500mL mixed salt solution with the total concentration of nickel, cobalt and manganese ions of 2 mol/L;
fully stirring and dissolving sodium hydroxide (NaOH) in deionized water to prepare 1000mL of aqueous alkali with the concentration of 4 mol/L;
step (3) mixing concentrated ammonia water (mass concentration is 27%) with deionized water to respectively prepare 1 mol/L500 mL ammonia water solution I and 2 mol/L1000 mL ammonia water solution II;
and (4) adding the ammonia water solution II serving as a base solution into a reaction kettle, adding 8g of tin dioxide nano-fiber with the length of 0.5 mu m into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle at a feeding speed of 60mL/h by using a peristaltic pump, wherein the water bath temperature of the reaction kettle is 70 ℃. Adding the alkali solution, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 11.5, introducing argon (Ar) as protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at the stirring speed of 1000r/min until the solution is completely fed, and filtering to obtain a solid which is a precursor of the NCM ternary positive electrode composite material;
step (5) reacting the precursor with lithium hydroxide (LiOH. H) 2 O) is evenly mixed according to the molar ratio of the metal ions to the lithium ions of 1:1.05, and the calcining condition is 5Heating to 500 ℃ per min, preserving heat for 5h, heating to 800 ℃ at 5 ℃/min, and preserving heat for 15h to obtain the NCM ternary cathode composite material.
The assembled battery was cycled for 50 weeks at 0.2C rate in the range of 2.8-4.3V at the cut-off voltage, and it was found that the capacity retention rate of the NCM ternary positive electrode composite described in this comparative example was changed from only 93.22% to 93.26% compared to the material described in comparative example 1. The particle size change of the laser particle size analysis material before and after the circulation was calculated to be 1.12.
The results show that when the length of the tin dioxide nano-fiber is too short, the particle strength of the NCM ternary positive electrode composite material is not obviously improved, and meanwhile, the material particles are still crushed in the circulation process, so that the integrity of the material particles is difficult to maintain, and the circulation stability of the material is hardly improved.
Comparative example 3
Step (1) NiSO 4 ·6H 2 O、CoSO 4 ·7H 2 O、MnSO 4 ·H 2 Mixing three metal salts O according to the molar ratio of nickel, cobalt and manganese elements of 8:1:1, adding deionized water, fully stirring and dissolving to prepare 500mL mixed salt solution with the total concentration of nickel, cobalt and manganese ions of 2 mol/L;
fully stirring and dissolving sodium hydroxide (NaOH) in deionized water to prepare 1000mL of aqueous alkali with the concentration of 4 mol/L;
step (3) mixing concentrated ammonia water (mass concentration is 27%) with deionized water to respectively prepare 500mL ammonia water solution I with the concentration of 0.8mol/L and 1000mL ammonia water solution II with the concentration of 1 mol/L;
and (4) adding the ammonia water solution II serving as a base solution into a reaction kettle, adding 10g of alumina nano-fiber with the length of 20 mu m into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle by using a peristaltic pump according to the feeding speed of 100mL/h, wherein the water bath temperature of the reaction kettle is 60 ℃. Adding the alkali solution, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 11.2, introducing argon (Ar) as a protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at a stirring speed of 1200r/min until the solution is completely fed, and filtering to obtain a solid which is a precursor of the NCM ternary positive electrode composite material;
step (5) reacting the precursor with lithium hydroxide (LiOH. H) 2 O) uniformly mixing the metal ions and the lithium ions according to the molar ratio of 1:1.05, heating to 550 ℃ at the calcining condition of 3 ℃/min, preserving heat for 7h, heating to 750 ℃ at the temperature of 3 ℃/min, and preserving heat for 24h to obtain the NCM ternary cathode composite material.
The assembled battery was cycled for 50 weeks at 0.2C rate in the range of 2.8-4.3V at the cut-off voltage, and the capacity retention of the NCM ternary positive electrode composite material of the present comparative example was found to be reduced from 93.22% to 91.45% compared to the material of comparative example 1. The particle size change of the laser particle size analysis material before and after circulation was calculated to obtain a particle breakage ratio of 1.09 after circulation.
The results show that when the length of the tin dioxide nanofiber is too long, the nanofiber is easy to agglomerate and is difficult to be embedded into the inside of the particles of the NCM ternary cathode material, so that the effect of the cathode composite material cannot be exerted to improve the integrity of the particles in the circulation process, and the agglomerated nanofiber can influence the exertion of the electrochemical performance of the cathode composite material, so that the circulation stability of the material is reduced slightly.
In summary, the present invention includes but is not limited to the above embodiments, and any equivalent replacement or local modification made under the principle of the spirit of the present invention should be considered as being within the protection scope of the present invention.
Claims (7)
1. A fiber-reinforced NCM ternary positive electrode composite material is characterized in that: in the material, inorganic oxide nano-fibers are distributed in secondary particles of an NCM ternary positive electrode material, and the NCM ternary positive electrode material is LiNi x Co y Mn 1-x-y O 2 ，0<x<1，0<y<1，0<(x+y)<1; the length of the inorganic oxide nanofiber is 2-8 mu m, and the inorganic oxide nanofiber accounts for 1-5% of the total mass of the material; the material is prepared by the following method, and the method comprises the following steps:
(1) soluble nickel salt, soluble cobalt salt and soluble manganese salt are added according to the molar ratio of nickel to cobalt to manganese as x: y: (1-x-y) preparing a mixed salt solution with the total concentration of nickel, cobalt and manganese ions being 1-2 mol/L, wherein 0< x <1, 0< y <1, 0< (x + y) < 1;
(2) mixing sodium hydroxide and water with the purity higher than that of deionized water to prepare an alkali solution with the concentration of 2-4 mol/L;
(3) mixing concentrated ammonia water and water with the purity of more than deionized water to respectively prepare an ammonia water solution I with the concentration of 0.6-1.2 mol/L and an ammonia water solution II with the concentration of 1-3 mol/L;
(4) adding the ammonia water solution II serving as a base solution into a reaction kettle, wherein the adding amount of the ammonia water solution II is larger than that of a stirrer in the reaction kettle, adding inorganic oxide nano fibers into the base solution, pumping the mixed salt solution and the ammonia water solution I into the reaction kettle at the same feeding speed, controlling the temperature in the reaction kettle to be 50-70 ℃, adjusting the feeding speed of the alkali solution to enable the pH value in the reaction kettle to be 10.5-11.5, introducing argon or nitrogen serving as a protective gas in the whole feeding process, continuously stirring the solution in the reaction kettle at the stirring speed of 600-1200 r/min until the solution is completely fed, and filtering to obtain a solid which is a precursor of a fiber-reinforced NCM ternary positive electrode material; wherein the mixed salt solution: ammonia water solution I: inorganic oxide nanofibers: the dosage ratio of the alkali solution is 100-500 mL: 400-600 mL: 1-10 g: 200-1000 mL;
(5) and uniformly mixing the precursor with lithium hydroxide, heating to 300-600 ℃, preserving heat for 3-7 h, heating to 700-900 ℃, and preserving heat for 12-24 h to obtain the fiber-reinforced NCM ternary cathode material.
2. A fiber reinforced NCM ternary positive electrode composite according to claim 1, characterized in that: the nano-fiber is more than one of silicon dioxide nano-fiber, zirconium dioxide nano-fiber, stannic oxide nano-fiber, aluminum oxide nano-fiber, magnesium oxide nano-fiber and zinc oxide nano-fiber.
3. As in claimThe fiber-reinforced NCM ternary positive electrode composite material of claim 1, characterized in that: the soluble nickel salt in the step (1) is NiSO 4 ·6H 2 O, soluble cobalt salt is CoSO 4 ·7H 2 O, and a soluble manganese salt is MnSO 4 ·H 2 O。
4. A fiber reinforced NCM ternary positive electrode composite according to claim 1, characterized in that: in the step (1), the molar ratio x of nickel, cobalt and manganese is as follows: y: (1-x-y) ═ 0.8:0.1: 0.1.
5. A fiber reinforced NCM ternary positive electrode composite according to claim 1, characterized in that: and (4) feeding the mixed salt solution and the ammonia water solution I at the speed of 20-100 mL/h simultaneously in the step (3).
6. The fiber-reinforced NCM ternary positive electrode composite of claim 1, wherein: the molar ratio of the precursor to the lithium hydroxide in the step (5) is 1: 1-1.1.
7. A fiber reinforced NCM ternary positive electrode composite according to claim 1, characterized in that: in the step (5), the heating rate is 2-10 ℃/min.
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