Lithium ion battery positive electrode material precursor, preparation method thereof and lithium ion battery positive electrode material

Abstract

The invention belongs to the field of lithium ion battery materials, and discloses a lithium ion battery positive electrode material precursor which is a nickel-cobalt-aluminum single crystal precursor, and a preparation method of the lithium ion battery positive electrode material precursor comprises the following steps: preparing a metal salt mixed solution; carrying out spray drying or / and spray pyrolysis on the metal salt mixed solution; and sintering the spray-dried material to obtain the lithium ion battery positive electrode material precursor. The morphology is mainly an aggregation structure formed by regular polyhedrons. The invention also discloses a lithium ion battery positive electrode material prepared from the precursor. The nickel-cobalt-aluminum single crystal precursor is of an aggregation structure formed by regular polyhedrons, and the regular geometric appearance can reduce the surface energy, inhibit side reactions and enhance the electrode-electrolyte interface stability; and the single-crystal structure has no grain boundary defect, the volume expansion is more uniform in the charge-discharge process, the generation of particle fracture and microcracks is reduced, and the cycle life is remarkably prolonged.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material technology, and particularly relates to a lithium-ion battery cathode material precursor, its preparation method, and the lithium-ion battery cathode material. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries whose core working principle involves the intercalation and deintercalation of lithium ions between the positive and negative electrodes to store and release energy. They are among the most widely used rechargeable batteries, boasting advantages such as high energy density, long cycle life, and lightweight design, and are widely used in consumer electronics, electric vehicles, and energy storage systems. Multi-element single-crystal cathode materials (such as lithium nickel cobalt aluminum oxide) are among the most widely used high-performance cathode materials, exhibiting high specific capacity (approximately 180-220 mAh / g) and operating voltages up to 3.6-3.8 V, making them suitable for applications with high range requirements, such as electric vehicles.

[0003] Multi-component single-crystal precursors are key intermediate materials in the preparation of multi-component single-crystal cathode materials. Currently, multi-component single-crystal cathode materials are usually prepared by solid-state reaction of the precursor and the lithium source. The structure and properties of the precursor determine the performance of the cathode material. The main preparation method for multi-component single-crystal precursors is currently the co-precipitation method, which has been industrially mass-produced. It exhibits high batch stability, but the subsequent processes for the precipitate are complex and require further optimization.

[0004] CN 106058244 A discloses a method for preparing a nickel-cobalt-aluminum multi-element single-crystal precursor for lithium-ion batteries. The method involves first preparing a mixed salt solution of nickel-cobalt-aluminum containing a complexing agent and a strong alkaline solution containing ammonia. The mixed salt solution and the strong alkaline solution are then injected simultaneously and at a constant rate into a reactor containing a bottom liquid for a co-precipitation reaction. After the mixed salt solution is completely injected, the addition of the strong alkaline solution is stopped. After the reaction is complete, the slurry is aged and then subjected to liquid-solid separation to obtain the nickel-cobalt-aluminum cathode material precursor. In this method, Al³⁺ precipitates at a relatively low pH, while Ni²⁺ / Co²⁺ requires a higher pH, leading to preferential precipitation of aluminum and the formation of localized aluminum-rich phases or Al(OH)₃ impurities. This affects the uniformity of the material composition. Furthermore, the waste liquid containing ammonia and heavy metals (Ni / Co) requires complex treatment, increasing costs.

[0005] CN 107742720 A discloses a method for preparing a nickel-cobalt-manganese precursor, a multi-element single-crystal cathode material for lithium-ion batteries. The method involves precipitating nickel, cobalt, and manganese ions separately in different reactors for a very short time to prevent the precipitate particles from growing, forming micro-precipitate particles of Ni(OH)2, Co(OH)2, Mn(OH)2 or NiCO3, CoCO3, MnCO3. These micro-precipitate particles are then mixed together and reacted thoroughly to form multi-element single-crystal precursor particles. Compared with traditional co-precipitation methods, this method produces a significantly higher crystallinity of the precursor. However, the different nucleation rates of the different metals result in a wide particle size distribution after mixing, leading to a tortuous lithium-ion migration path and increased polarization. Furthermore, this method requires independent adjustment of parameters such as pH, temperature, and stirring speed in each reactor, resulting in high preparation costs. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies and defects mentioned in the background art above, and to provide a method for preparing a single-crystal cathode material precursor that is simple in process, low in cost, and suitable for industrial production.

[0007] To solve the above-mentioned technical problems, the technical solution proposed by this invention is as follows: A lithium-ion battery cathode material precursor, wherein the precursor is a nickel-cobalt-aluminum single crystal precursor, and the morphology of the precursor is mainly an aggregated structure formed by regular polyhedra.

[0008] Preferably, the precursor for the lithium-ion battery cathode material described above has a particle size of 0.1~10μm. During particle compaction, small particles can fill the pores between large particles, which helps to further increase the compaction density of the particles.

[0009] Preferably, the precursor for the lithium-ion battery cathode material described above has the chemical formula Ni. a Co b Al c O d And satisfy a+b+c≤d, 0<a<1, 0≤b<1, 0≤c<1.

[0010] As a general inventive concept, the present invention also provides a method for preparing a lithium-ion battery cathode material precursor as described above, comprising the following steps: (1) Prepare a mixed solution of metal salts; (2) The metal salt mixture solution is subjected to spray drying and / or spray pyrolysis; (3) The spray-dried material is sintered to obtain the lithium-ion battery cathode material precursor.

[0011] In the above preparation method, preferably, in step (1), the metal salt mixed solution is a metal chloride salt mixed solution.

[0012] In the above preparation method, preferably, in step (2), the spray drying and / or spray pyrolysis are carried out in an oxygen atmosphere.

[0013] In the above preparation method, preferably, in step (2), the inlet air temperature of the spray drying or / and spray pyrolysis is 180~250℃. The higher the inlet temperature of the spray dryer, the higher the outlet temperature, and the lower the water content in the dried powder. The lower the water content of the powder, the smaller the influence between oxide particles during the oxidation sintering process. The powder with a wide particle size dispersion obtained by spray drying also makes the particle size dispersion of the oxide particles wider. Small particles can fill the gaps between large particles, reduce porosity, and help improve the electrode compaction density. In the above preparation method, preferably, the flow rate of the metal salt mixed solution is 500~2000 mL / h, more preferably 1000~2000 mL / h. If the flow rate is too high, the solution feeds too quickly per unit time, resulting in a large material volume; if the flow rate is too low, the solution feeds too slowly per unit time, resulting in a long product collection time.

[0014] In the above preparation method, preferably, in step (3), the sintering refers to heating to 600-900℃ at a rate of 1-10℃ / min and holding for 1-12 hours, more preferably 2-8 hours. Within this temperature range, chloride ions decompose more readily, transition metal elements diffuse more rapidly, and chloride ions have a dominant crystal plane etching effect, inducing the formation of polyhedra during the sintering process. If the sintering temperature is too low, the transition metal chloride oxidative decomposition is incomplete, the precursor's shape is too poor, or it does not match the target precursor phase; if the sintering temperature is too high, the transition metal chloride decomposes excessively. From an economic and environmental perspective, the higher the sintering temperature, the greater the energy consumption. Within the sintering time range of this invention, transition metal elements diffuse sufficiently, and the element distribution is more uniform. If the sintering time is too short, the material's shape is poor, and there are many impurity phases; if the sintering time is too long, the precursor crystal structure has already formed, wasting energy.

[0015] In the above preparation method, preferably, in step (3), the sintering is carried out in oxygen and / or air. More preferably, the sintering is carried out in an oxygen atmosphere with a purity of 99.99% or higher.

[0016] In the above preparation method, preferably, in step (1), the molar concentration of the metal salt mixed solution is 0.1~2 mol / L. The concentration of the metal salt mixed solution determines the solute content in the droplets during spray drying. The larger the primary particles obtained, the larger the particles will be after sintering. If the particles are larger, their specific surface area will be smaller, their surface energy will be lower, and their dispersion will be better. However, if the concentration is too high, segregation will occur, which is not conducive to the uniform distribution of elements. Therefore, it is necessary to control the molar concentration of the metal salt mixed solution within the range of this invention to control the particle size reasonably and facilitate the uniform distribution of elements.

[0017] As a general inventive concept, the present invention also provides a lithium-ion battery cathode material, which is prepared by lithium addition from the above-mentioned lithium-ion battery cathode material precursor or the precursor prepared by the above-mentioned preparation method.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) The single crystal precursor of the present invention has a morphology mainly in the form of an aggregated structure formed by regular polyhedra (such as octahedrons or dodecahedrons). The regular geometric shape can reduce surface energy, suppress side reactions, and enhance the stability of the electrode-electrolyte interface. Moreover, the single crystal structure has no grain boundary defects, and the volume expansion during charging and discharging is more uniform, reducing particle breakage and microcrack generation, and significantly improving cycle life.

[0019] (2) The preparation method of the present invention is simple to operate. No additional reducing agent is required during the preparation process, which can realize the control of the particle morphology of the multi-element single crystal precursor and the growth of the target particle size, which is conducive to industrial mass production.

[0020] (3) The single crystal precursor prepared by the preparation method of the present invention has a uniform distribution of transition metal elements, high crystal structure formability, and good conductivity. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 These are XRD patterns of the multi-element single-crystal cathode material precursors prepared in Examples 1-3 and Comparative Example 1; Figure 2 Here is a SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in Example 1; Figure 3 This is a SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in Example 2; Figure 4 Here is a SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in Example 3; Figure 5 SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in Comparative Example 1; Figure 6 The image shows the SEM image of the nickel-iron-manganese multi-element single-crystal cathode material precursor prepared in Comparative Example 2. Figure 7 SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in Comparative Example 3; Figure 8 These are the initial charge-discharge performance graphs of the cathode materials prepared using the above embodiments and comparative examples; Figure 9 The graph shows the specific capacity performance of the cathode materials prepared using the above-described embodiments and comparative examples after 100 cycles of discharge. Detailed Implementation

[0023] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0024] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0025] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0026] Example 1: The present invention discloses a lithium-ion battery cathode material precursor, which is a nickel-cobalt-aluminum single-crystal precursor. Its morphology mainly exhibits a regular polyhedral aggregate structure. The particle size distribution of the precursor ranges from 0.1 to 1.0 μm, and the chemical formula of the precursor is Ni. 0.8 Co 0.15 Al 0.05 O 1.1 .

[0027] The method for preparing the lithium-ion battery cathode material precursor in this embodiment includes the following steps: (1) Weigh 1.9474 g of cobalt chloride, 0.6665 g of aluminum chloride and 19.016 g of nickel chloride hexahydrate and dissolve them in 1000 ml of deionized water to obtain a mixed metal salt solution with a molar concentration of 0.1 mol / L; (2) Under oxygen protection, the mixed metal salt solution prepared in step (1) is spray-dried. The air inlet temperature of the spray dryer is 210℃ and the liquid flow rate of the mixed metal salt is 1500mL / h.

[0028] (3) The sample obtained in step (2) is placed under oxygen-enriched air protection and heated to 900°C at a heating rate of 5°C / min for sintering and held at that temperature for 6 hours. Then it is cooled to room temperature with the furnace to obtain the nickel-cobalt-aluminum multi-element single crystal cathode material precursor.

[0029] like Figure 1 As shown, the XRD patterns of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor obtained in this embodiment are consistent with those of the PDF card PDF#65-2901-NiO, and there are no other impurity phases. This indicates that after the precursor is pre-sintered, the Al element is uniformly distributed in the NiO matrix, thus generating the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor.

[0030] like Figure 4 As shown, the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor obtained in this embodiment is uniformly distributed, exhibiting obvious polyhedra and their aggregates, with a particle size distribution of 0.1~1.0μm.

[0031] Example 2: The present invention discloses a lithium-ion battery cathode material precursor, which is a nickel-cobalt-aluminum single-crystal precursor. Its morphology mainly exhibits a regular polyhedral aggregate structure. The particle size of the precursor is 0.1~7.0 μm, and the chemical formula of the precursor is Ni. 0.8 Co 0.1 Al 0.1 O 1.1 .

[0032] The method for preparing the lithium-ion battery cathode material precursor in this embodiment includes the following steps: (1) Weigh 1.2980g of cobalt chloride, 1.3330g of aluminum chloride and 19.016g of nickel chloride hexahydrate and dissolve them in 1000ml of deionized water to obtain a mixed metal salt solution with a molar concentration of 0.1mol / L; (2) Under oxygen protection, the mixed metal salt solution prepared in step (1) is spray-dried. The air inlet temperature of the spray dryer is 180℃ and the liquid flow rate is 2000mL / h.

[0033] (3) The sample obtained in step (2) is placed under oxygen protection and heated to 750°C at a heating rate of 5°C / min for sintering and held for 12 hours. Then it is cooled to room temperature in the furnace to obtain the nickel-cobalt-aluminum multi-element single crystal cathode material precursor.

[0034] like Figure 1As shown, the XRD diffraction peaks of the nickel-cobalt multi-element single-crystal cathode material precursor obtained in this embodiment are all consistent with the PDF card PDF#65-2901-NiO, and there are no other impurity phases, indicating that after the precursor is pre-sintered, the Co element is uniformly distributed in the NiO matrix, and a nickel-cobalt-aluminum multi-element single-crystal cathode material precursor is generated.

[0035] like Figure 3 As shown, the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor obtained in this embodiment has a uniform particle distribution, and the particles exhibit obvious polyhedra and their aggregates. The particle size distribution of the precursor is 0.1~7.0μm.

[0036] Example 3: The present invention discloses a lithium-ion battery cathode material precursor, which is a nickel-cobalt-aluminum single-crystal precursor. Its morphology mainly exhibits a regular polyhedral aggregate structure. The particle size of the precursor is 0.1~1.0 μm, and the chemical formula of the precursor is Ni. 1 / 3 Co 1 / 3Al 1 / 3 O 4 / 3 .

[0037] The method for preparing the lithium-ion battery cathode material precursor in this embodiment includes the following steps: (1) Weigh 129.80g of cobalt chloride, 133.30g of aluminum chloride and 237.70g of nickel chloride hexahydrate and dissolve them in 1000ml of deionized water to obtain a mixed metal salt solution with a molar concentration of 1mol / L; (2) Under oxygen protection, the mixed metal salt solution prepared in step (1) is spray-dried. The air inlet temperature of the spray dryer is 250℃ and the liquid flow rate is 1000mL / h.

[0038] (3) The sample obtained in step (2) is placed under oxygen protection and heated to 600°C at a heating rate of 5°C / min for sintering and held for 2 hours. Then it is cooled to room temperature in the furnace to obtain the nickel-cobalt-aluminum multi-element single crystal cathode material precursor.

[0039] like Figure 1 As shown, the XRD diffraction peaks of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in this embodiment are all consistent with the PDF card PDF#65-2901-NiO, and there are no other impurity phases. This indicates that after the precursor is pre-sintered, the Co and Al elements are uniformly distributed in the NiO matrix, thus generating the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor.

[0040] like Figure 2 As shown in the figure, the SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor prepared in this embodiment shows that the particles are uniformly distributed and exhibit obvious polyhedra and their aggregates. The particle size of the precursor particles is distributed between 0.1 and 1.0 μm.

[0041] Comparative Example 1: The preparation method of the comparative nickel-cobalt-aluminum multi-element single-crystal cathode material precursor differs from that of the example only in that the sintering regime is sintering at 400℃ for 2h and the heating rate is 5℃ / min. All other processes and parameters are the same as those in Example 1.

[0042] like Figure 1 As shown, the XRD diffraction peaks of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor obtained in Comparative Example 1 all match the portion of PDF card PDF#65-2901-NiO, but other impurity phases are present. Analysis shows that they match the NiCl2 crystal PDF#22-0765, CoCl2·2H2O crystal PDF#25-0242, and NiCl2·2H2O crystal PDF#01-1143, indicating that the chloride cannot be fully oxidized under this temperature condition.

[0043] like Figure 5 As shown in the SEM image of the nickel-cobalt-aluminum multi-element single-crystal cathode material precursor obtained in Comparative Example 1, the precursor particles have low shape, the transition metal chloride decomposition is incomplete, and the morphology of the precursor is irregular lamellar.

[0044] Comparative Example 2: The preparation method of the comparative nickel-iron-manganese multi-element single-crystal cathode material precursor differs from that of Example 2 only in step 1. The raw materials selected are 62.90g of manganese chloride, 101.425g of ferrous chloride tetrahydrate, and 118.85g of nickel chloride hexahydrate, which are dissolved in 1000ml of deionized water to obtain a mixed metal salt solution with a molar concentration of 0.1mol / L. Other processes and parameters are the same as in Example 1.

[0045] The XRD diffraction peaks of the obtained nickel-iron-manganese multi-element single-crystal cathode material precursor were matched with NiMnO3 crystal PDF#48-1330 and Fe2O3 crystal PDF#14-0557, indicating that under this preparation condition, nickel-iron-manganese transition metal chlorides cannot form a unified phase structure.

[0046] like Figure 6 As shown, the SEM image of the obtained nickel-iron-manganese multi-element single-crystal cathode material precursor shows that the precursor particles are fine particles and their aggregates, with a particle size distribution of 0.1~8μm.

[0047] Comparative Example 3: The only difference between the preparation method of the nickel-cobalt-aluminum cathode material precursor in this comparative example and that in Example 3 is that the inlet air temperature of the spray dryer is 150°C and the liquid flow rate is 500 mL / h.

[0048] Upon testing, the XRD diffraction peaks of the obtained nickel-cobalt-aluminum cathode material precursor were found to be partially consistent with those of the NiO crystal PDF card PDF#65-2901, but other impurity phases were present, and its obvious crystal structure could not be identified.

[0049] like Figure 7 As shown, the SEM image of the obtained nickel-cobalt-aluminum cathode material precursor shows that the precursor particles are fine particles and their aggregates, with a particle size distribution of 0.1~2μm.

[0050] The precursors prepared in the embodiments and comparative examples of the present invention were mixed with lithium hydroxide monohydrate at a molar ratio of 1.05:1, and then sintered at 480°C for 5 h in an oxygen atmosphere, followed by sintering at 750°C for 12 h to obtain nickel-cobalt-aluminum single crystal cathode materials. These materials were then assembled into batteries and their electrochemical performance was tested. The results are shown in Table 1.

[0051] like Figure 8 The figure shows the initial charge-discharge performance of the cathode materials prepared using the above-described embodiments and comparative examples. Figure 9 The figure shows the specific capacity performance of the cathode materials prepared using the above-described embodiments and comparative examples after 100 cycles of discharge.

[0052] Table 1 Electrochemical performance of each example and comparative example

[0053] As shown in Table 1, the initial discharge specific capacity of Examples 1-3 was significantly higher than that of Comparative Examples 1-3, especially Example 2, which showed the best performance (207.51 mAh / g). The capacities of Comparative Examples 2 and 3 were extremely low (<63 mAh / g), which is due to the failure of the target crystalline phase of the material to form, resulting in insufficient electrochemical capacity. The specific capacity of the examples after 4 cycles at 1C (200 mA / g) (182-186 mAh / g) was about 13% higher than that of Comparative Example 1 (160.58 mAh / g), and more than 3 times higher than that of Comparative Examples 2 and 3 (<54 mAh / g). This indicates that the precursor material prepared by the technical solution of the present invention can exhibit better kinetic performance at high rates.

[0054] In Example 1, after 100 cycles at 1C (200 mA / g), the retention rate remained above 74%. The special polyhedron structure gave it an advantage in sodium ion transport, and the material structure was relatively stable. In contrast, Comparative Example 1 had a lower retention rate of only 69.52% and faster cycle decay. This was due to insufficient sintering temperature, incomplete volatilization of chlorides, and impure crystal structure. Although Comparative Example 2 had a higher retention rate, its absolute capacity was extremely low (<45 mAh / g), limiting its practical application value.

[0055] In summary, the battery prepared from the precursor provided by the technical solution of the present invention has both high specific capacity and good cycle stability, and its overall performance is significantly better than that of the comparative example.

Claims

1. A lithium-ion battery cathode material precursor, characterized in that, The precursor is a nickel-cobalt-aluminum single crystal precursor, whose morphology is mainly an aggregated structure formed by regular polyhedra.

2. The lithium-ion battery cathode material precursor as described in claim 1, characterized in that, The precursor particles have a particle size of 0.1~10μm.

3. The lithium-ion battery cathode material precursor as described in claim 1, characterized in that, The precursor has the chemical formula Ni a Co b Al c O d And satisfy a+b+c≤d, 0<a<1, 0≤b<1, 0≤c<1.

4. A method for preparing a lithium-ion battery cathode material precursor as described in any one of claims 1 to 3, characterized in that, Includes the following steps: (1) Prepare a mixed solution of metal salts; (2) The metal salt mixture solution is subjected to spray drying and / or spray pyrolysis; (3) The material processed in step (2) is sintered to obtain the lithium-ion battery cathode material precursor.

5. The preparation method according to claim 4, characterized in that, In step (2), the spray drying and / or spray pyrolysis are carried out in an oxygen atmosphere.

6. The preparation method according to claim 4, characterized in that, In step (2), the inlet air temperature of the spray drying or / and spray pyrolysis is 180~250℃, and the liquid flow rate of the metal salt mixed solution is 500~2000mL / h.

7. The preparation method according to claim 4, characterized in that, In step (3), sintering refers to heating to 600-900℃ at a rate of 1-10℃ / min and holding at that temperature for 1-12 hours.

8. The preparation method according to claim 4, characterized in that, In step (3), the sintering is carried out in oxygen and / or air.

9. The preparation method according to claim 4, characterized in that, In step (1), the molar concentration of the metal salt mixed solution is 0.1~2 mol / L.

10. A lithium-ion battery cathode material, characterized in that, It is prepared by lithium enrichment from the lithium-ion battery cathode material precursor according to any one of claims 1 to 3 or the precursor prepared by the preparation method according to any one of claims 4 to 9.

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