CN115536080A - High-nickel positive electrode material and preparation method and application thereof - Google Patents

High-nickel positive electrode material and preparation method and application thereof Download PDF

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CN115536080A
CN115536080A CN202211506956.XA CN202211506956A CN115536080A CN 115536080 A CN115536080 A CN 115536080A CN 202211506956 A CN202211506956 A CN 202211506956A CN 115536080 A CN115536080 A CN 115536080A
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nickel
sintering
salt
rate
positive electrode
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邵学祥
张亦弛
刘婵
侯敏
曹辉
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Rept Battero Energy Co Ltd
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Abstract

The invention provides a high-nickel anode material and a preparation method and application thereof. The preparation method comprises the following steps: mixing polyacrylonitrile solution, nickel salt, cobalt salt, manganese salt and lithium salt, carrying out electrostatic spinning, and then sequentially carrying out primary sintering, secondary sintering and tertiary sintering, and carrying out unnatural cooling to obtain the high-nickel cathode material. The invention takes polyacrylonitrile and metal salt as raw materials, adopts an electrostatic spinning mode to obtain the high-nickel anode material with a hollow nano-belt structure,enabling rapid deintercalation of lithium ions to provide shorter Li + The ion diffusion distance greatly reduces the polarization of the battery, thereby improving the multiplying power and the cycle performance of the high-nickel anode material.

Description

High-nickel positive electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of secondary batteries, and relates to a high-nickel positive electrode material, and a preparation method and application thereof.
Background
Nowadays, as the requirements of the automobile industry in terms of fuel economy and environmental protection become more and more strict, lithium Ion Batteries (LIBs) having high energy density, long cycle life and high power density are widely used. Compared with the negative electrode material, some key indexes of the LIB, such as specific capacity, first coulombic efficiency and safety, are mainly controlled by the positive electrode material, but some inherent defects also exist, mainly including poor structure and thermal stability, poor high-power circulation and rate capability and the like, so that serious potential safety hazards are brought, and finally the practical potential of the LIB is poor.
In the field of preparation of lithium battery anode materials, three elements in the ternary material nickel-cobalt-manganese have good synergistic effect, so that the ternary material nickel-cobalt-manganese generally has the characteristics of high specific capacity, long cycle life, low toxicity and low price, and the increase of the content of nickel in the ternary material nickel-cobalt-manganese can effectively improve the specific capacity of the material, so that the ternary material nickel-cobalt-manganese is widely applied.
In fact, as the content of nickel in the ternary material nickel-cobalt-manganese increases, the specific capacity of the ternary material increases and the cost decreases, but at the same time, the ternary material has the defects of low capacity retention rate and the like.
Therefore, how to obtain a high-nickel cathode material with excellent performance is a technical problem to be solved urgently.
Disclosure of Invention
The invention aims to provide a high-nickel cathode material and a preparation method and application thereof. The invention takes polyacrylonitrile and metal salt as raw materials, and adopts an electrostatic spinning mode to obtain the high-nickel anode material with the hollow nano-belt structure, so that lithium ions can be rapidly de-intercalated to provide shorter Li + The ion diffusion distance greatly reduces the polarization of the battery, thereby improving the multiplying power and the cycle performance of the high-nickel anode material.
The high nickel anode material in the inventionRefers to the chemical formula LiNi x Co 1-x-y Mn y O 2 And x is more than or equal to 0.6.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a high nickel cathode material, comprising the steps of:
mixing polyacrylonitrile solution, nickel salt, cobalt salt, manganese salt and lithium salt, carrying out electrostatic spinning, and then sequentially carrying out primary sintering, secondary sintering and tertiary sintering, and carrying out unnatural cooling to obtain the high-nickel cathode material.
The non-natural cooling in the invention means that the natural cooling is not adopted, but the cooling is carried out at a certain cooling rate, and the sintering process is carried out in the oxygen atmosphere.
The invention takes polyacrylonitrile and metal salt as raw materials, adopts an electrostatic spinning mode to obtain the high-nickel anode material with a hollow nano-band structure, and lithium ions can be rapidly de-intercalated so as to provide shorter Li + The ion diffusion distance greatly reduces the polarization of the battery, thereby improving the multiplying power and the cycle performance of the high-nickel anode material.
The preparation method provided by the invention adopts polyacrylonitrile as a spinning raw material, and has the advantages of wide raw material, low price and good fiber uniformity.
The method adopts a three-section sintering mode, the polyacrylonitrile is changed into a grid in a fixed one-dimensional nanofiber shape from a gel layer through one-time sintering, and meanwhile Li 1-x [NiCoMn]O 2-y (NCM) is formed in advance on the surface region of the gas-nanofiber interface, and then in a second sintering the Polyacrylonitrile (PAN) layer becomes elastic and starts to decompose gradually, eliminating the PAN on the surface and releasing CO 2 、N 2 Etc., the internal PAN remains elastic due to lack of oxygen; the internal elastic structure helps to maintain the shape of the nanofibers in one dimension and also promotes mass transfer, and the internal PAN and the inorganic portion NCM advance together toward the surface under the influence of concentration differences, during which the diffusion rate of the internal gas is greater than the rate of pyrolysis of the PANSlow, the latter can create pressure inside the nanofibers, leading to the formation of nanotubes; and in the last three times of sintering, the NCM on the surface appears and grows in the oxygen-rich atmosphere, the decomposition of the whole residual PAN is accompanied, the NCM continues to grow and is connected with each other to form a continuous tubular structure with a porous thin wall, the growth of the NCM nano particles leads to the formation of the nano particle spacing, under the continuous internal pressure generated by the PAN pyrolysis, the nano particle spacing in the nano tube is enlarged and broken, and finally the high-nickel anode material with the hollow nano band structure is obtained, namely, the invention only needs to adopt a three-section sintering mode, and does not need to additionally increase the sintering process, so that the structure required by the invention is obtained.
In the invention, a natural cooling mode is not adopted, and if the natural cooling mode is adopted, the internal of the prepared material has larger stress due to large temperature change, so that the hollow tubular structure of the anode material in the invention cannot be maintained.
Preferably, the mixed raw material further includes a rare earth metal salt.
Preferably, the rare earth metal salt is an acetate of a rare earth.
Preferably, the rare earth metal salt comprises any one of cerium salt, praseodymium salt or lanthanum salt or a combination of at least two of them.
In the invention, after the cerium element is doped, the lithium ion intercalation/deintercalation pore channel is widened, the ionic conductivity of the material is improved, and the structural stability and the conductivity can be further improved by doping cerium, because the bonding energy of Ce-O is stronger than that of M-O (M = Ni, co, mn), so the doped cerium can stabilize the main structure of the anode material in charge/discharge cycles. In addition, due to high conductivity and large radius, cerium ions can expand lithium ion channels and promote the rapid migration of lithium ions, and the rate capability and the cycle performance are obviously improved; and praseodymium doping and lanthanum doping can also expand the lithium ion channel.
Preferably, the nickel salt comprises nickel acetate.
Preferably, the cobalt salt comprises cobalt acetate.
Preferably, the manganese salt comprises manganese acetate.
Preferably, the lithium salt comprises lithium acetate.
Preferably, the voltage value in the electrostatic spinning process is 15 to 18KV, such as 15KV, 16KV, 17KV or 18 KV.
Preferably, the air humidity during the electrospinning is 50% or less, such as 0%, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or the like.
In the electrostatic spinning process, the air humidity is too high, so that the spinning is not facilitated.
Preferably, the feeding speed in the electrostatic spinning process is 0.2 to 0.4mL/h, such as 0.2mL/h, 0.25mL/h, 0.3mL/h, 0.35mL/h or 0.4 mL/h.
Preferably, the electrospun material is dried.
Preferably, the drying comprises vacuum drying.
Preferably, the temperature rise rate of the primary sintering is 1 to 3 ℃/min, such as 1 ℃/min, 2 ℃/min or 3 ℃/min.
In the invention, the temperature rise rate of the primary sintering is too high, and the formation of a tough one-dimensional nanofiber-shaped grid cannot be realized.
Preferably, the temperature of the primary sintering is 250 to 300 ℃, such as 250 ℃, 255 ℃, 260 ℃, 265 ℃, 270 ℃, 275 ℃, 280 ℃, 285 ℃, 290 ℃, 295 ℃ or 300 ℃ and the like.
In the invention, the temperature of primary sintering is too low, which is not beneficial to the decomposition of nickel salt, cobalt salt and manganese salt and fully removes crystal water, while the temperature of primary sintering is too high, which leads to the next step of sintering in advance and can not maintain a tough nano fibrous grid structure.
Preferably, the time of the primary sintering is 1 to 3 hours, such as 1 hour, 2 hours or 3 hours.
Preferably, the temperature rise rate of the secondary sintering is 1 to 3 ℃/min, such as 1 ℃/min, 2 ℃/min or 3 ℃/min.
In the present invention, if the temperature increase rate of the secondary sintering is too high, the internal PAN advances too fast toward the surface together with the inorganic portion, and the elastic change of the internal PAN is too large to maintain the 1D shape.
Preferably, the temperature of the secondary sintering is 450 to 480 ℃, such as 450 ℃, 455 ℃, 460 ℃, 465 ℃, 470 ℃, 475 ℃, 480 ℃ and the like.
In the invention, the decomposition of the metal acetate and the pyrolysis of PAN are not thorough due to the low temperature of the secondary sintering, and the diameter of the nanotube is rapidly shrunk and the hollow nanotube structure is difficult to form due to the high temperature of the secondary sintering and the high speed of the decomposition of the metal acetate and the pyrolysis of PAN.
Preferably, the time of the secondary sintering is 3 to 6h, such as 3h, 4h, 5h or 6 h.
Preferably, the temperature rise rate of the third sintering is 1 to 3 ℃/min, such as 1 ℃/min, 2 ℃/min or 3 ℃/min.
In the invention, the heating rate of the three-time sintering is too high, which is not favorable for forming the nano hollow tubular structure of the anode material.
Preferably, the temperature of the third sintering is 750 to 800 ℃, such as 750 ℃, 755 ℃, 760 ℃, 765 ℃, 770 ℃, 775 ℃, 780 ℃, 785 ℃, 790 ℃, 795 ℃ or 800 ℃.
In the present invention, the Polyacrylonitrile (PAN) gel layer becomes a lattice in which the shape of one-dimensional nanofibers is fixed due to its high thermal stability in the temperature range of the primary sintering, and at the same time, since the nanofibers lack oxygen inside, the decomposition of nickel, cobalt, manganese and lithium salts is accompanied by Li 1-x [NiCoMn]O 2-y On the contrary, NCM will be formed in advance on the surface area of the gas-nanofiber interface due to higher oxygen enrichment and temperature compared to the inside of the nanofiber; by raising the temperature to the temperature range of the second sintering, the PAN layer becomes elastic and begins to gradually decompose, first eliminating PAN in the surface and releasing CO 2 ，N 2 Etc., while the internal PAN is still resilient due to the lack of oxygen. This elastic property of the internal PAN, which is not only helpful in maintaining the 1D shape but also in promoting mass transfer, advances with the NCM toward the surface under the influence of concentration differences, during which the diffusion rate of the internal gas is slower than the rate of pyrolysis of the PAN, which later on isThis phenomenon, which creates pressure inside the nanofibers, also contributes to mass transfer, leading to the formation of nanotubes whose diameter shrinkage can be attributed to mass loss caused by the decomposition of metal salts and the pyrolysis of PAN; as the temperature is further increased to the temperature range of three sinterings, the surface high nickel cathode material appears and grows in an oxygen-rich atmosphere, and with the decomposition of the entire residue PAN, the high nickel cathode material will continue to grow and interconnect to form a continuous tubular structure with porous thin walls, but the growth of individual high nickel cathode material nanoparticles will result in the formation of nanoparticle spacings that grow larger and break in the nanotubes under the continuous internal pressure created by the PAN pyrolysis, resulting in the formation of broken nanobelts.
In the invention, the secondary growth of crystal grains can be hindered due to the excessively low temperature of the third sintering, the crystallization is incomplete, the lithium loss is serious due to the excessively high temperature of the third sintering, and the fixed nano-belt tubular hollow structure is difficult to maintain due to the excessively large growth of secondary particles.
Preferably, the time for the third sintering is 12 to 18h, such as 12h, 13h, 14h, 15h, 16h, 17h or 18 h.
In the whole sintering process, if the temperature rise rate is too high, the tubular hollow high-nickel anode material cannot be obtained, and meanwhile, the temperature range in the three-stage sintering process needs to be regulated and controlled, so that the high-nickel anode material with the shape of the fractured nanobelt can be finally obtained.
Preferably, the cooling rate of the non-natural cooling is 2 to 5 ℃/min, such as 2 ℃/min, 3 ℃/min, 4 ℃/min or 5 ℃/min and the like.
The cooling rate in the invention is too fast, which is not beneficial to maintaining the tubular hollow structure, and too slow, which can affect the preparation efficiency and increase the cost.
As a preferred technical scheme, the preparation method comprises the following steps:
(1) Mixing polyacrylonitrile solution, nickel acetate, cobalt acetate, manganese acetate, lithium acetate and rare earth acetate, setting the voltage to be 15-18KV, the feeding speed to be 0.2-0.4mL/h, performing electrostatic spinning and vacuum drying in an environment with the air humidity less than or equal to 50 percent to obtain a precursor,
(2) Heating the precursor in the step (1) to 250-300 ℃ at a heating rate of 1-3 ℃/min for primary sintering for 1-3 h, heating to 450-480 ℃ at a heating rate of 1-3 ℃/min for secondary sintering for 3-6 h, heating to 750-800 ℃ at a heating rate of 1-3 ℃/min for tertiary sintering for 12-18h, and finally cooling at a cooling rate of 2-5 ℃/min to obtain the high-nickel cathode material.
In a second aspect, the present invention provides a high nickel cathode material, which is prepared by the preparation method of the high nickel cathode material according to the first aspect.
In a third aspect, the present invention also provides a lithium ion battery, which includes the high nickel cathode material according to the second aspect.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, polyacrylonitrile and metal salt are used as raw materials, an electrostatic spinning mode is adopted, the high-nickel anode material with a hollow nano-band structure is obtained, lithium ions can be rapidly de-intercalated, so that a short Li + ion diffusion distance is provided, the polarization of the battery is greatly reduced, and meanwhile, through in-situ doping of rare earth elements in the preparation process, the main structure of the anode material can be stabilized in charge/discharge cycles, so that the multiplying power and the cycle performance of the high-nickel anode material are improved. The battery adopts the anode material prepared by the preparation method provided by the invention, the temperature rise rate in the sintering process, the temperature in the sintering process and the temperature reduction rate of the cooling section are regulated and controlled in the preparation process, the variable rate capacity retention rate can reach more than 84.5% (after 0.2C,1C,2C,5C and 10C, the variable rate capacity retention rate returns to 0.2C again, each rate circulates for 5 circles), and the capacity retention rate after 0.2C circulates for 200 circles can reach more than 83.3%.
Drawings
Fig. 1 is a schematic view of a process for preparing a high nickel cathode material provided in example 1.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.
Example 1
This embodiment provides a high nickel positive electrode material, where the high nickel positive electrode material has a hollow nanobelt structure, and a chemical formula of the high nickel positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 。
The preparation method of the high-nickel cathode material comprises the following steps:
(1) Firstly, polyacrylonitrile (PAN, 0.7 g) is dissolved in N, N-dimethylformamide (DMF, 10 mL), the mixture is stirred for 12 hours at 40 ℃ until the mixture is transparent and stable, nickel acetate tetrahydrate (2.88 mmol), cobalt acetate tetrahydrate (0.36 mmol), manganese acetate monohydrate (0.36 mmol) and lithium acetate dihydrate (3.78 mmol) are respectively weighed, the weighed medicine is simultaneously placed into the prepared solution, and the mixture is vigorously stirred for 24 hours at 60 ℃ to form a uniform solution (semi-viscous can shake), so that the uniform solution can be used for spinning;
(2) Loading the obtained solution into an injection pump equipped with a plastic syringe, performing electrostatic spinning under 18kV high pressure with air humidity of 35%, selecting a feeding speed of 0.3mL/h and a needle-to-collector distance of 17cm, collecting the electrospun nanofibers on an aluminum foil, and drying in a vacuum oven at 60 ℃ for 12h;
(3) Heating the dried electrospun nanofiber to 280 ℃ at the heating rate of 3 ℃/min, preserving heat for 2h, then heating to 450 ℃ at the heating rate of 3 ℃/min, preserving heat for 5h, respectively heating to 750 ℃ at the heating rate of 3 ℃/min, preserving heat for 18h, finally cooling to room temperature at the cooling rate of 3 ℃/min, grinding by using a mortar to obtain a final product, and carrying out the whole sintering process under the oxygen atmosphere.
Fig. 1 is a schematic diagram illustrating a preparation process of the high nickel cathode material provided in example 1, and fig. 1 illustrates a process of forming the high nickel cathode material and a morphology change of the cathode material during the preparation process.
Example 2
This embodiment provides a high nickel positive electrode material, the high nickel positive electrode material is a hollow nanobelt structure, and the chemical formula of the high nickel positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 。
The preparation method of the high-nickel cathode material comprises the following steps:
(1) Firstly, polyacrylonitrile (PAN, 0.7 g) is dissolved in N, N-dimethylformamide (DMF, 10 mL), the mixture is stirred for 12 hours at 40 ℃ until the mixture is transparent and stable, nickel acetate tetrahydrate (2.88 mmol), cobalt acetate tetrahydrate (0.36 mmol), manganese acetate monohydrate (0.36 mmol) and lithium acetate dihydrate (3.78 mmol) are respectively weighed, the weighed medicine is simultaneously placed into the prepared solution, and the mixture is vigorously stirred for 24 hours at 60 ℃ to form a uniform solution (semi-viscous can shake), so that the uniform solution can be used for spinning;
(2) Loading the obtained solution into an injection pump provided with a plastic syringe, carrying out electrostatic spinning under the high pressure of 15kV, wherein the air humidity is 35%, selecting the feeding speed of 0.2mL/h and the needle-to-collector distance of 17cm, collecting the electrospun nanofibers on an aluminum foil, and drying in a vacuum oven at 60 ℃ for 12 hours;
(3) Heating the dried electrospun nanofiber to 300 ℃ at the heating rate of 1 ℃/min, preserving heat for 1h, then heating to 480 ℃ at the heating rate of 1 ℃/min, preserving heat for 3h, respectively heating to 800 ℃ at the heating rate of 2 ℃/min, preserving heat for 13h, finally cooling to room temperature at the cooling rate of 5 ℃/min, grinding by using a mortar to obtain a final product, and carrying out the whole sintering process under the oxygen atmosphere.
Example 3
This embodiment provides a high nickel positive electrode material, where the high nickel positive electrode material has a hollow nanobelt structure, and a chemical formula of the high nickel positive electrode material is LiNi 0.8 Co 0.1 Mn 0.1 O 2 。
The preparation method of the high-nickel cathode material comprises the following steps:
(1) Firstly, dissolving polyacrylonitrile (PAN, 0.7 g) in N, N-dimethylformamide (DMF, 10 mL), stirring for 12h at 40 ℃ until the mixture is transparent and stable, respectively weighing nickel acetate tetrahydrate (2.88 mmol), cobalt acetate tetrahydrate (0.36 mmol), manganese acetate monohydrate (0.36 mmol) and lithium acetate dihydrate (3.78 mmol), simultaneously putting the weighed medicines into the prepared solution, and vigorously stirring for 24h at 60 ℃ to form a uniform solution (semi-viscous and shakable), wherein the solution can be used for spinning;
(2) Loading the obtained solution into an injection pump equipped with a plastic syringe, performing electrostatic spinning under 16kV high pressure with air humidity of 20%, selecting a feeding speed of 0.35mL/h and a needle-to-collector distance of 17cm, collecting the electrospun nanofibers on an aluminum foil, and drying in a vacuum oven at 60 ℃ for 12h;
(3) Heating the dried electrospun nanofiber to 250 ℃ at the heating rate of 2 ℃/min, preserving heat for 3h, then heating to 460 ℃ at the heating rate of 2 ℃/min, preserving heat for 4h, respectively heating to 780 ℃ at the heating rate of 1 ℃/min, preserving heat for 15h, finally cooling to room temperature at the cooling rate of 2 ℃/min, grinding with a mortar to obtain a final product, and carrying out the whole sintering process under the oxygen atmosphere.
Example 4
The difference between this example and example 1 is that the high nickel positive electrode material in this example is doped with 0.8 mol% of cerium element (here, the mol ratio of cerium element in the high nickel positive electrode material is 0.8%) to form Ce — O bond, and the chemical formula is Ce (CH) (the molar ratio of cerium element in the high nickel positive electrode material is 0.8%) 3 COO) 3 (ii) a In the preparation method, cerium acetate, nickel acetate, cobalt acetate, manganese acetate and lithium acetate which are simultaneously weighed in the step (1) are added together, and the other preparation methods and parameters are kept consistent with those of the example 1.
Example 5
The present example is different from example 1 in that the temperature increase rate of the primary sintering (first temperature increase) in step (3) of the present example is 5 ℃/min.
The remaining preparation methods and parameters were in accordance with example 1.
Example 6
The present example is different from example 1 in that the temperature increase rate of the secondary sintering (second temperature increase) in step (3) of the present example is 5 ℃/min.
The remaining preparation methods and parameters were in accordance with example 1.
Example 7
The present example is different from example 1 in that the temperature of the primary sintering in step (3) of the present example is 240 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Example 8
The difference between this example and example 1 is that the temperature of the secondary sintering in step (3) of this example is 440 ℃.
The remaining preparation methods and parameters were in accordance with example 1.
Example 9
The difference between this embodiment and embodiment 1 is that the temperature reduction rate in step (3) of this embodiment is 10 ℃/min.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 1
The difference between the comparative example and the example 1 is that the high-nickel cathode material in the comparative example is obtained by mixing and sintering a nickel-cobalt-manganese hydroxide precursor and lithium carbonate.
The preparation process comprises the following steps:
dissolving nickel acetate, cobalt acetate and manganese acetate (the dosage is consistent with that of the embodiment 1) in oxalic acid, stirring for 6 hours at 60 ℃, then adding ammonia water while stirring, continuing stirring for 12 hours, filtering, washing and drying to obtain a precursor after stirring. Mixing the prepared precursor material with lithium carbonate according to the proportion of 1.05 (molar ratio), fully grinding for 6h, putting into a tube furnace for sintering, firstly heating to 450 ℃, preserving heat for 6h, then heating to 800 ℃, preserving heat for 12h, and naturally cooling to obtain the product.
Comparative example 2
The comparative example differs from example 1 in that polyacrylonitrile was replaced with polyvinylpyrrolidone.
The remaining preparation methods and parameters were in accordance with example 1.
Comparative example 3
The difference between the comparative example and the example 1 is that the step (3) of the comparative example adopts a natural cooling way.
The remaining preparation methods and parameters were in accordance with example 1.
The high-nickel positive electrode materials provided in examples 1 to 9 and comparative examples 1 to 3, conductive carbon black and polyvinylidene fluoride were weighed according to mass percentage of 95.
Electrochemical performance tests were performed on the button cells provided in examples 1 to 9 and comparative examples 1 to 3, respectively, under the conditions of a variable rate charge-discharge test at 25 ℃ in a process of returning to 0.2C after passing through 0.2c,1c,2c,5c,10c (specifically, the electrochemical performance test was performed in the following order:
(1) Firstly, charging to 4.6V at a multiplying power of 0.2C, and then discharging to 2.8V at a multiplying power of 0.2C, so as to form a cycle, and 5 cycles are performed in total;
(2) Charging to 4.6V at a multiplying power of 1C, and then discharging to 2.8V at a multiplying power of 1C, so as to realize a cycle of 5 cycles;
(3) Charging to 4.6V at a multiplying power of 2C, and then discharging to 2.8V at a multiplying power of 2C, so as to realize a cycle of 5 cycles;
(4) Charging to 4.6V at a multiplying power of 5C, and then discharging to 2.8V at a multiplying power of 5C, so as to realize a cycle of 5 cycles;
(5) Charging to 4.6V at a multiplying power of 10C, and then discharging to 2.8V at a multiplying power of 10C, so as to realize a cycle of 5 cycles;
(6) The final capacity retention rate was obtained by charging to 4.6V at a rate of 0.2C, and then discharging to 2.8V at a rate of 0.2C, and this was used as a cycle, and 5 cycles were performed in total), and further, a cycle performance test at 0.2C was performed (specifically, charging to 4.6V at a rate of 0.2C, and then discharging to 2.8V at a rate of 0.2C, and this was used as a cycle), and after 200 cycles, the capacity retention rate was obtained, and the test results are shown in table 1.
TABLE 1
Figure 45864DEST_PATH_IMAGE001
From the data results of the embodiments 1 and 4, it can be known that in-situ doping of the doping element is directly performed during the preparation process, which is more beneficial to doping into the crystal lattice, thereby improving the variable rate capacity retention rate and the cycle performance.
From the data results of example 1 and examples 5 and 6, it is known that the temperature rise rate during sintering is too fast to facilitate the formation of nano hollow tubular structure, thereby causing the material rate and cycle performance to be poor.
From the data results of example 1 and example 7, it is clear that too low a temperature for primary sintering affects the decomposition of acetate, thereby greatly reducing the rate and cycle performance of the material.
From the data results of example 1 and example 8, it is clear that the temperature of the secondary sintering is too low, making it difficult to advance the PNA gel layer from the inside to the outside, and thus reducing the rate capability of the material.
From the data results of the embodiment 1 and the embodiment 9, it is known that the cooling rate in the cooling process is too fast, which is not beneficial to maintaining the nano hollow tubular structure, thereby greatly reducing the rate capability of the material.
From the data results of the embodiment 1 and the comparative example 1, it can be known that the high nickel cathode material provided by the invention can improve the rate-change capacity retention rate and the cycle performance compared with the high nickel cathode material prepared by the conventional coprecipitation sintering method.
From the data results of the embodiment 1 and the comparative example 2, it can be known that polyacrylonitrile has the characteristics of good fiber forming property, common solvent resistance, difficult hydrolysis, oxidation resistance and chemical stability, and other substances are selected, so that the preparation process is complex, and the electrochemical performance improvement effect is not obvious.
From the data results of example 1 and comparative example 3, it can be seen that the hollow nanobelt structure that can not be broken is easily fired into nanoparticles by natural cooling, so that the rate-change capacity retention rate and the cycle performance of the material are poor.
In conclusion, the high-nickel anode material with the hollow nano-belt structure is obtained by taking polyacrylonitrile and metal salt as raw materials and adopting an electrostatic spinning mode, lithium ions can be rapidly de-intercalated, so that the diffusion distance of Li & lt + & gt ions is short, the polarization of a battery is greatly reduced, and meanwhile, through in-situ doping of rare earth elements in the preparation process, the main structure of the anode material can be stabilized in charge/discharge cycles, so that the multiplying power and the cycle performance of the high-nickel anode material are improved. The battery adopts the anode material prepared by the preparation method provided by the invention, the temperature rise rate in the sintering process, the temperature in the sintering process and the temperature reduction rate of a temperature reduction section are regulated and controlled in the preparation process, the variable rate capacity retention rate can reach more than 84.5% (after 0.2C,1C,2C,5C and 10C, the variable rate capacity retention rate returns to 0.2C again, each rate circulates for 5 circles), the capacity retention rate after the battery circulates for 200 circles at 0.2C can reach more than 83.3%, the doping is further carried out in the preparation process, the variable rate capacity retention rate can reach more than 96.2%, and the capacity retention rate after the battery circulates for 200 circles at 0.2C can reach more than 91.9%.
The applicant declares that the above description is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be understood by those skilled in the art that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention disclosed herein fall within the scope and disclosure of the present invention.

Claims (10)

1. A preparation method of a high-nickel cathode material is characterized by comprising the following steps of:
mixing polyacrylonitrile solution, nickel salt, cobalt salt, manganese salt and lithium salt, carrying out electrostatic spinning, and then sequentially carrying out primary sintering, secondary sintering and tertiary sintering, and carrying out unnatural cooling to obtain the high-nickel cathode material.
2. The method for producing a high nickel positive electrode material according to claim 1, wherein the mixed raw material further includes a rare earth metal salt.
3. The method for producing a high nickel positive electrode material according to claim 2, wherein the rare earth metal salt is an acetate of a rare earth.
4. The method for preparing a high-nickel cathode material according to claim 3, wherein the rare earth metal salt includes any one of a cerium salt, a praseodymium salt, or a lanthanum salt or a combination of at least two thereof.
5. The method for preparing the high-nickel cathode material according to claim 1, wherein the temperature rise rate of the primary sintering is 1 to 3 ℃/min; the temperature of the primary sintering is 250 to 300 ℃.
6. The method for preparing the high-nickel cathode material according to claim 1, wherein the temperature rise rate of the secondary sintering is 1 to 3 ℃/min; the temperature of the secondary sintering is 450 to 480 ℃.
7. The method for preparing the high-nickel cathode material according to claim 1, wherein the temperature rise rate of the third sintering is 1 to 3 ℃/min; the temperature of the third sintering is 750 to 800 ℃.
8. The method for preparing a high-nickel cathode material as claimed in claim 1, wherein the cooling rate of the non-natural cooling is 2 to 5 ℃/min.
9. A high nickel positive electrode material, characterized in that it is produced by the method for producing a high nickel positive electrode material according to any one of claims 1 to 8.
10. A lithium ion battery comprising the high nickel positive electrode material of claim 9.
CN202211506956.XA 2022-11-29 2022-11-29 High-nickel positive electrode material and preparation method and application thereof Pending CN115536080A (en)

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