Precursor of ternary positive electrode material, preparation method of precursor, ternary positive electrode material and battery

Abstract

The invention discloses a precursor of a ternary positive electrode material, a preparation method of the precursor, the ternary positive electrode material and a battery, and belongs to the technical field of battery materials. The chemical general formula of the precursor is Ni < x > Co < y > Mn < z > (OH) < 2 >, and x is greater than or equal to 0.8 and less than or equal to 1, 0 lt; y is less than or equal to 0.1, 0lt; z < = 0.1, and x + y + z = 1; the profile of the precursor is in a sunflower shape. The positive electrode material obtained after the precursor is mixed with lithium and sintered is small in internal anisotropic stress, low in internal pore zigzag coefficient and short in ion transmission distance, and the petal-shaped shell is high in orderliness, so that the positive electrode material has an ordered and efficient de-intercalation channel, and the problem that the electrical property is degraded due to the fact that a high-nickel material is prone to deformation in electrochemical circulation is effectively solved; meanwhile, the material has a relatively high specific surface area, can be in more sufficient contact and more uniform mixing when being mixed and sintered with a lithium source to prepare a positive electrode material, and has higher reaction activity, so that the capacity and cycle performance of the obtained positive electrode active material can be remarkably improved.

Description

Precursor of ternary cathode material, preparation method thereof, ternary cathode material, and battery Technical Field

[0001] The present invention belongs to the technical field of battery materials, and particularly relates to a precursor material of a ternary cathode material for a lithium-ion battery, a preparation method thereof, and an application thereof. Background Art

[0002] A lithium-ion battery is a secondary battery that mainly operates by the movement of lithium ions between the positive and negative electrodes. Lithium-ion batteries are widely used in various portable electronic devices due to their advantages such as high energy density, long cycle life, and green pollution-free, and are gradually extended to fields such as new energy vehicles, energy storage, and military applications. During the charge and discharge process of a lithium-ion battery, Li + intercalates and deintercalates back and forth between the two electrodes: during charging, Li + deintercalates from the positive electrode and intercalates into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; during discharging, lithium ions deintercalate from the negative electrode material and are transmitted back to the positive electrode material through the electrolyte for intercalation. Compared with traditional commercial materials LiCoO2, LiFePO, LiMn2O4, the ternary cathode material LiNi 1-x-y Co x Mn y O2 has advantages such as high specific capacity, low price, and good rate performance, which has attracted wide attention from researchers. The strong electrostatic interaction of ionic bonds in the ternary cathode material can stabilize the structure and achieve a multiphase transformation, but the presence of the M phase reduces the crystal structure symmetry and causes distortion, affecting the orderliness of lithium intercalation and deintercalation. Summary of the Invention

[0003] Since the cathode material can inherit the morphology and structural characteristics of the precursor, the structure and preparation process of the precursor have a crucial impact on the performance of the cathode material. To better achieve the orderliness of lithium intercalation and deintercalation of the ternary cathode material of a lithium-ion battery, the present invention mainly starts from the precursor of the cathode material. The first object of the present invention is to provide a precursor of a ternary cathode material; the second object of the present invention is to provide a preparation method of the aforementioned precursor.

[0004] To achieve the above objects, the present invention provides the following specific technical solutions.

[0005] First, the present invention provides a precursor of a ternary cathode material, and the chemical general formula of the precursor is Ni x Co y Mn z (OH)2, where 0.8 ≤ x ≤ 1, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and x + y + z = 1; the cross-sectional morphology of the precursor is in the shape of a sunflower.

[0006] In a further preferred embodiment, the precursor includes a core and a shell, the core being loose and porous, and the shell being formed by the agglomeration of sheet-like primary particles, and the shell being dense with a crystalline cross-section.

[0007] In a further preferred embodiment, in the X-ray diffraction pattern of the precursor, the peak intensity ratios of the (100) crystal plane, the (101) crystal plane, and the (001) crystal plane are respectively in the range of: 0.5≤I100 / I001≤0.85; 0.9≤I101 / I001≤1.3.

[0008] In a further preferred embodiment, the particle size of the precursor core ranges from 1 to 2.5 μm; the thickness of the precursor shell is 1 to 2.5 μm.

[0009] In a further preferred embodiment, the particle size D50 of the precursor is 2~5μm.

[0010] In a further preferred embodiment, the specific surface area of ​​the precursor is 10~20m². 2 / g.

[0011] In a further preferred embodiment, the tap density of the precursor is 1.5~1.8 g / cm³. 3 .

[0012] Secondly, this invention provides a method for preparing a precursor of a ternary cathode material, comprising the following steps: Step S1, preparing a metal salt solution according to the target chemical formula of the precursor; Step S2, continuously and concurrently introducing the metal salt solution, precipitant solution, and complexing agent solution into the bottom liquid of a reaction vessel to carry out a co-precipitation reaction; the co-precipitation reaction includes a nucleation stage and a growth stage; in the nucleation stage, the pH value of the reaction system is controlled at 11~12, the temperature at 55~65℃, and the alkalinity at 3~7g / L; a non-oxidizing gas is introduced for protection during the nucleation stage; in the growth stage, the introduction of the non-oxidizing gas is stopped, and an oxidant is introduced; the pH value of the reaction system is controlled at 9~10, and the growth time t1 is carried out at a first alkalinity of 3~5g / L, and the growth time t2 is carried out at a second alkalinity of 1~3g / L.

[0013] Step S3: After the coprecipitation reaction is completed, the reaction slurry is aged, and then the slurry is subjected to solid-liquid separation. The solid phase obtained by washing and drying is the precursor.

[0014] In a further preferred embodiment, the duration of the nucleation stage is 0.5 to 1.5 hours.

[0015] In a further preferred embodiment, the first alkalinity is greater than the second alkalinity.

[0016] In a further optimized scheme, based on the total reaction period T of the growth stage, t1+t2=T, where 50h≤T≤100h, and t1:t2 is 5:6~7:3.

[0017] In a further preferred embodiment, the oxidant is at least one of air, oxygen, hydrogen peroxide, and ozone, and is more preferably air or oxygen, with a flow rate of 10-16 L / min.

[0018] In a further preferred embodiment, stirring is performed during the coprecipitation reaction. A more preferred stirring linear velocity is 4.6~8.9 m / s.

[0019] In a further preferred embodiment, the flow rate of the metal salt solution during the nucleation stage is 50-150 mL / min; and the flow rate of the metal salt solution during the growth stage is 200-550 mL / min.

[0020] In a further preferred embodiment, the metal salt in the metal salt solution is a soluble metal salt, including nickel salts, manganese salts, and cobalt salts. The total concentration of metal ions in the metal salt solution is 2.0~2.2 mol / L.

[0021] More preferably, the nickel salt is at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chloride; the manganese salt is at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; and the cobalt salt is at least one of cobalt sulfate, cobalt nitrate, cobalt acetate, and cobalt chloride.

[0022] In a further preferred embodiment, the precipitant is at least one selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0023] Further preferably, the concentration of the precipitant solution is 1~11 mol / L.

[0024] In a further preferred embodiment, the complexing agent is at least one selected from ammonia, ammonium bicarbonate, and ammonium carbonate. More preferably, the concentration of the aqueous solution of the complexing agent is 2-14 mol / L.

[0025] In a further preferred embodiment, the bottom liquid of the reaction vessel includes water, a precipitant, and a complexing agent.

[0026] Based on the same inventive concept, the present invention also provides a ternary cathode material, which is obtained by sintering the above-mentioned precursor mixed with lithium.

[0027] In addition, the present invention also provides a lithium-ion battery comprising the above-mentioned ternary cathode material.

[0028] The above one or more technical solutions of the present invention can achieve at least one of the following beneficial effects: (1) The precursor provided by the present invention has a unique morphology, a loose and porous core, a dense and crystalline shell, and a large specific surface area.

[0029] (2) The cathode material obtained after lithium mixing and sintering of the precursor provided by the present invention has low anisotropic stress, low internal pore tortuosity coefficient, short ion transport distance, and high orderliness of petal-shaped shell, which gives it an ordered and efficient insertion and extraction channel, effectively improving the problem of electrical performance degradation caused by easy deformation in the electrochemical cycle of high nickel materials; at the same time, it has a high specific surface area, which can make more full contact when mixed and sintered with lithium source to prepare cathode material, the mixing is more uniform and the reaction activity is higher, which can significantly improve the capacity and cycle performance of the obtained cathode active material.

[0030] (3) The cathode material obtained after sintering the precursor mixed with lithium provided by the present invention has high rate performance.

[0031] (4) The precursor preparation method provided by the present invention is a co-precipitation method, which is simple and controllable and easy to industrialize. Attached Figure Description

[0032] Figure 1 is a SEM image of the precursor prepared in Example 1; where A is an overall view and B is a cross-sectional view.

[0033] Figure 2 shows the SEM images of the precursor prepared in Comparative Example 1; where A is the overall image and B is the cross-sectional image.

[0034] Figure 3 shows the SEM images of the precursor prepared in Comparative Example 2; where A is the overall image and B is the cross-sectional image.

[0035] Figure 4 shows the SEM images of the precursor prepared in Comparative Example 3; where A is the overall image and B is the cross-sectional image.

[0036] Figure 5 shows the SEM image of the precursor prepared in Comparative Example 4; where A is the overall image and B is the cross-sectional image.

[0037] Figure 6 shows the SEM image of the precursor prepared in Example 2; where A is the overall view and B is the cross-sectional view.

[0038] Figure 7 shows the SEM image of the precursor prepared in Example 3; where A is the overall view and B is the cross-sectional view.

[0039] Figure 8 shows the SEM image of the precursor prepared in Example 4; where A is the overall view and B is the cross-sectional view.

[0040] Figure 9 shows the SEM image of the precursor prepared in Example 5; where A is the overall view and B is the cross-sectional view. Detailed Implementation

[0041] To facilitate the understanding of the present invention, the present invention will be described more comprehensively and in detail below in conjunction with the accompanying drawings of the specification and preferred embodiments. However, the protection scope of the present invention is not limited to the following specific embodiments.

[0042] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention.

[0043] Unless otherwise specifically stated, various raw materials, reagents, instruments, equipment, etc. used in the present invention can be obtained through market purchases or can be prepared by existing methods.

[0044] As described above, first, the present invention provides a precursor of a ternary cathode material, and the chemical general formula of the precursor is Ni x Co y Mn z (OH)2, where 0.8 ≤ x ≤ 1, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and x + y + z = 1; the cross-sectional morphology of the precursor is in the shape of a sunflower.

[0045] In a further preferred embodiment, the precursor includes a core and a shell. The core is loose and porous, and the shell is formed by the intercalation and aggregation of flaky primary particles, and the shell is dense and has a crystal edge shape in cross-section.

[0046] In a further preferred embodiment, in the X-ray diffraction pattern of the precursor, the peak intensity ratio ranges of the (100) crystal plane and the (101) crystal plane to the (001) crystal plane are: 0.5 ≤ I100 / I001 ≤ 0.85; 0.9 ≤ I101 / I001 ≤ 1.3.

[0047] In a further preferred embodiment, the range of the core of the precursor is 1 - 2.5 μm; the thickness of the shell of the precursor is 1 - 2.5 μm.

[0048] In a further preferred embodiment, the D50 particle size of the precursor is 2 - 5 μm, including but not limited to: 2 μm, 3 μm, 4 μm, 5 μm, etc.

[0049] In a further preferred embodiment, the specific surface area of the precursor is 10 - 20 m 2 / g, including but not limited to: 10 m 2 / g, 11 m 2 / g, 12 m 2 / g, 13 m 2 / g, 14 m 2 / g, 15 m 2 / g, 16 m 2 / g, 17 m2 / g、18m 2 / g、19m 2 / g、20m 2 / g etc.

[0050] In a further preferred embodiment, the tap density of the precursor is 1.5~1.8 g / cm³. 3 Including but not limited to: 1.5g / cm 3 1.6g / cm 3 1.7g / cm 3 1.8g / cm 3 wait.

[0051] Secondly, this invention provides a method for preparing a precursor of a ternary cathode material, comprising the following steps: Step S1, preparing a metal salt solution according to the target chemical formula of the precursor; Step S2, continuously and concurrently introducing the metal salt solution, precipitant solution, and complexing agent solution into the bottom liquid of a reaction vessel to carry out a co-precipitation reaction; the co-precipitation reaction includes a nucleation stage and a growth stage; in the nucleation stage, the pH value of the reaction system is controlled to be 11~12 (including but not limited to: 11, 11.1, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9, 12, etc.), and the temperature is controlled to be 55~65℃ (including but not limited to: 55℃, 58℃, 60℃, 62℃, 65℃). The alkalinity is 3~7 g / L (including but not limited to: 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, etc.); a non-oxidizing gas is introduced for protection during the nucleation stage; during the growth stage, the introduction of non-oxidizing gas is stopped and an oxidant is introduced; the pH of the reaction system is controlled at 9~10 (including but not limited to: 9, 9.1, 9.2, 9.3, 9.4, 9.5, 9.6, 9.7, 9.8, 9.9, 10, etc.), with a growth time t1 at a first alkalinity of 3~5 g / L (including but not limited to: 3 g / L, 4 g / L, 5 g / L, etc.) and a growth time t2 at a second alkalinity of 1~3 g / L (including but not limited to: 1 g / L, 2 g / L, 3 g / L, etc.).

[0052] Step S3: After the coprecipitation reaction is completed, the reaction slurry is aged, and then the slurry is subjected to solid-liquid separation. The solid phase obtained by washing and drying is the precursor.

[0053] In a further preferred embodiment, the duration of the nucleation stage is 0.5 to 1.5 hours, including but not limited to: 0.5 hours, 0.75 hours, 1 hour, 1.25 hours, 1.5 hours, etc.

[0054] In a further preferred embodiment, the first alkalinity is greater than the second alkalinity.

[0055] In a further preferred scheme, based on the total reaction period T of the growth stage, t1+t2=T, where 50h≤T≤100h, t1:t2 is 5:6~7:3, including but not limited to: 5:6, 5:5, 5:4, 6:5, 6:4, 6:3, 7:6, 7:4, 7:3, etc.

[0056] In a further preferred embodiment, the oxidant is at least one of air, oxygen, hydrogen peroxide, and ozone, and is more preferably air or oxygen, with a flow rate of air or oxygen of 10~16 L / min, including but not limited to: 10 L / min, 11 L / min, 12 L / min, 13 L / min, 14 L / min, 15 L / min, 16 L / min, etc.

[0057] In a further preferred embodiment, stirring is performed during the coprecipitation reaction. A more preferred stirring linear velocity is 4.6~8.9 m / s, including but not limited to: 4.6 m / s, 5 m / s, 5.5 m / s, 6 m / s, 6.5 m / s, 7 m / s, 7.5 m / s, 8 m / s, 8.5 m / s, 8.9 m / s, etc.

[0058] In a further preferred embodiment, the flow rate of the metal salt solution during the nucleation stage is 50-150 mL / min, including but not limited to: 50 mL / min, 60 mL / min, 70 mL / min, 80 mL / min, 90 mL / min, 100 mL / min, 110 mL / min, 120 mL / min, 130 mL / min, 140 mL / min, 150 mL / min, etc.; the flow rate of the metal salt solution during the growth stage is 200-550 mL / min, including but not limited to: 200 mL / min, 220 mL / min, 250 mL / min, 280 mL / min, 300 mL / min, 320 mL / min, 350 mL / min, 380 mL / min, 400 mL / min, 420 mL / min, 450 mL / min, 480 mL / min, 500 mL / min, 520 mL / min, 550 mL / min, etc.

[0059] In a further preferred embodiment, the metal salt in the metal salt solution is a soluble metal salt, including nickel salt, manganese salt, and cobalt salt. The total concentration of metal ions in the metal salt solution is 2.0~2.2 mol / L, including but not limited to: 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, etc. More preferably, the nickel salt is at least one selected from nickel sulfate, nickel nitrate, nickel acetate, and nickel chloride; the manganese salt is at least one selected from manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; and the cobalt salt is at least one selected from cobalt sulfate, cobalt nitrate, cobalt acetate, and cobalt chloride.

[0060] In a further preferred embodiment, the precipitant is at least one selected from sodium hydroxide, potassium hydroxide, and lithium hydroxide.

[0061] Further preferably, the concentration of the precipitant solution is 1~11 mol / L, including but not limited to: 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, etc.

[0062] In a further preferred embodiment, the complexing agent is at least one selected from ammonia, ammonium bicarbonate, and ammonium carbonate. More preferably, the concentration of the aqueous complexing agent solution is 2-14 mol / L, including but not limited to: 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L, 10 mol / L, 11 mol / L, 12 mol / L, 13 mol / L, 14 mol / L, etc.

[0063] In a further preferred embodiment, the bottom liquid of the reaction vessel includes water, a precipitant, and a complexing agent.

[0064] Based on the same inventive concept, the present invention also provides a ternary cathode material, which is obtained by sintering the above-mentioned precursor mixed with lithium.

[0065] Example 1, Step S1, Pretreatment stage: Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed according to the chemical formula Ni 0.953 Co 0.04 Mn 0.007 A mixed salt solution with a total metal ion concentration of 2.2 mol / L was prepared by mixing the corresponding molar ratios of the elements in (OH)2; a sodium hydroxide solution with a concentration of 10 mol / L was prepared as a precipitant solution; ammonia solution with a concentration of 6 mol / L was prepared as a complexing agent solution; and a reaction vessel bottom liquid was prepared with a pH value of 11.5 and an ammonia concentration of 3 g / L.

[0066] Step S2: A mixed salt solution, a precipitant solution, and a complexing agent solution are continuously and concurrently introduced into the bottom liquid of the reactor. Nucleation stage: Nitrogen gas is introduced for protection. The flow rate of the mixed salt solution is 50 mL / min. The temperature of the reaction system is controlled at 60℃, the stirring linear velocity is 7.8 m / s, the pH value is 11.5±0.5, and the alkalinity is 3 g / L. The nucleation time is 1 h.

[0067] Growth stage: Stop nitrogen gas supply, introduce air at a flow rate of 12 L / min, adjust the flow rate of the mixed salt solution to 220 mL / min, adjust the pH of the reaction system to 10, and grow for 50 h under an alkalinity of 3 g / L and 40 h under an alkalinity of 1 g / L.

[0068] Step S3, post-processing stage: The obtained precursor slurry is aged, then solid-liquid separation is performed to obtain a solid phase; the solid phase is washed, dried, then demagnetized and sieved to obtain the precursor.

[0069] Comparative Example 1 differs from Example 1 only in the growth stage. Specifically, during the growth stage, nitrogen gas was stopped, air was introduced at a flow rate of 12 L / h, the flow rate of the mixed salt solution was adjusted to 220 mL / min, the pH of the reaction system was adjusted to 10, and the mixture was grown for 90 h under an alkalinity of 3 g / L.

[0070] Comparative Example 2 differs from Example 1 only in the growth stage. Specifically, during the growth stage, nitrogen gas was stopped, air was introduced at a flow rate of 12 L / h, the flow rate of the mixed salt solution was adjusted to 220 mL / min, the pH of the reaction system was adjusted to 10, and the mixture was grown for 90 h under an alkalinity of 1 g / L.

[0071] Comparative Example 3 differs from Example 1 only in the growth stage. Specifically, during the growth stage, nitrogen gas was stopped, air was introduced at a flow rate of 12 L / h, the flow rate of the mixed salt solution was adjusted to 220 mL / min, the pH of the reaction system was adjusted to 10, and the mixture was grown for 50 h at an alkalinity of 3 g / L and for 40 h at an alkalinity of 5 g / L.

[0072] The difference between Comparative Example 4 and Example 1 lies in the different growth stages. Specifically, nitrogen gas was continuously introduced, the flow rate of the mixed salt solution was adjusted to 220 mL / min, the pH value of the reaction system was adjusted to 10, and the mixture was grown for 50 h under an alkalinity of 3 g / L and for 40 h under an alkalinity of 1 g / L.

[0073] Example 2 The only difference between Example 2 and Example 1 is the growth stage. Specifically, nitrogen gas was stopped, air was introduced at a flow rate of 12 L / h, the flow rate of the mixed salt solution was adjusted to 220 mL / min, the pH of the reaction system was adjusted to 10, and the reaction was grown for 40 h at an alkalinity of 3 g / L and for 50 h at an alkalinity of 1 g / L.

[0074] Example 3, Step S1, Pretreatment stage: Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed according to the chemical formula Ni 0.93 Co 0.05 Mn 0.02Prepare a mixed salt solution with a total metal ion concentration of 2.0 mol / L by mixing the corresponding molar ratios of (OH)2 elements; prepare a 5 mol / L sodium hydroxide solution as a precipitant solution; prepare a 10 mol / L ammonia solution as a complexing agent solution; prepare the bottom liquid of the reaction vessel with a pH of 11.7 and an ammonia concentration of 5 g / L.

[0075] Step S2: A mixed salt solution, a precipitant solution, and a complexing agent solution are continuously and concurrently introduced into the bottom liquid of the reactor. Nucleation stage: Nitrogen gas is introduced for protection. The flow rate of the mixed salt solution is 135 mL / min. The temperature of the reaction system is controlled at 40℃, the stirring linear velocity is 6.6 m / s, the pH value is 11.7, and the alkalinity is 5 g / L. Nucleation is carried out for 1 hour.

[0076] Growth stage: Stop nitrogen gas supply, introduce air at a flow rate of 16 L / h, adjust the flow rate of the mixed salt solution to 450 mL / min, adjust the pH of the reaction system to 9.8, and grow for 30 h under alkalinity of 5 g / L and 20 h under alkalinity of 2 g / L.

[0077] Step S3, post-processing stage: The obtained precursor slurry is aged, then solid-liquid separation is performed to obtain the solid phase; the solid phase is washed, dried, then demagnetized and sieved to obtain the precursor.

[0078] Example 4, Step S1, Pretreatment stage: Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed according to the chemical formula Ni 0.92 Co 0.04 Mn 0.04 A mixed salt solution with a total metal ion concentration of 2.2 mol / L was prepared by mixing the corresponding molar ratios of the elements in (OH)2; a sodium hydroxide solution with a concentration of 10.9 mol / L was prepared as a precipitant solution; ammonia solution with a concentration of 6.7 mol / L was prepared as a complexing agent solution; and a reaction vessel bottom liquid was prepared with a pH value of 11.8 and an ammonia concentration of 5.5.

[0079] Step S2: A mixed salt solution, a precipitant solution, and a complexing agent solution are continuously and concurrently introduced into the bottom liquid of the reactor; Nucleation stage: Nitrogen gas is introduced for protection, the flow rate of the mixed salt solution is 100 mL / min, and the temperature of the reaction system is controlled at 80℃, the stirring linear velocity is 7.9 m / s, the pH value is 11.8, and the alkalinity is 4 g / L; Nucleation takes 1.5 h.

[0080] Growth stage: Nitrogen gas was stopped, oxygen was introduced at a flow rate of 10 L / h, the flow rate of the mixed salt solution was adjusted to 550 mL / min, the pH of the reaction system was adjusted to 9.8, and the reaction was carried out for 45 h under an alkalinity of 5 g / L and for 40 h under an alkalinity of 1 g / L.

[0081] Step S3, post-processing stage: The obtained precursor slurry is aged, then solid-liquid separation is performed to obtain the solid phase; the solid phase is washed, dried, then demagnetized and sieved to obtain the precursor.

[0082] Example 5, Step S1, Pretreatment stage: Nickel sulfate, cobalt sulfate, and manganese sulfate are mixed according to the chemical formula Ni 0.96 Co 0.03 Mn 0.01 Prepare a mixed salt solution with a total metal ion concentration of 2 mol / L by mixing the corresponding molar ratios of (OH)2 elements; prepare a sodium hydroxide solution with a concentration of 7 mol / L as a precipitant solution; prepare ammonia solution with a concentration of 5 mol / L as a complexing agent solution; prepare the bottom liquid of the reaction vessel with a pH value of 11.6 and an ammonia concentration of 5.5.

[0083] Step S2: A mixed salt solution, a precipitant solution, and a complexing agent solution are continuously and concurrently introduced into the bottom liquid of the reactor. Nucleation stage: Nitrogen gas is introduced for protection. The flow rate of the mixed salt solution is 135 mL / min. The temperature of the reaction system is controlled at 80℃, the stirring speed is 4.6 m / s, the pH value is 12, and the alkalinity is 3 g / L. Nucleation is carried out for 1 hour.

[0084] Growth stage: Nitrogen gas was stopped, air was introduced at a flow rate of 16 L / h, the flow rate of the mixed salt solution was adjusted to 450 mL / min, the pH of the reaction system was adjusted to 10.5, and the mixture was grown for 55 h at an alkalinity of 5 g / L and for 40 h at an alkalinity of 1 g / L.

[0085] Step S3, post-processing stage: The obtained precursor slurry is aged, then solid-liquid separation is performed to obtain the solid phase; the solid phase is washed, dried, then demagnetized and sieved to obtain the precursor.

[0086] SEM images of the precursors prepared in Examples 1-5 and Comparative Examples 1-4 are shown in Figures 1-9. Figures 1 and 6-9 show that the precursor particles prepared in Examples 1-5 have a sunflower-like cross-section, with a highly porous core and a petal-like outer shell. Figure 2 shows that the primary particles of the precursor prepared in Comparative Example 1 are strip-shaped, while the secondary particles are nearly spherical; the cross-section of the precursor particles is essentially pore-free and lacks a core-shell structure. Figure 3 shows that the secondary particles of the precursor prepared in Comparative Example 2 are nearly spherical; the core of the precursor particles has numerous pores, while the outer shell is irregularly shaped. Figure 4 shows that the secondary particles of the precursor prepared in Comparative Example 3 are nearly spherical; the core of the precursor particles has a few pores, while the outer shell is relatively dense and virtually pore-free. Figure 5 shows that the secondary particles of the precursor prepared in Comparative Example 4 are irregular, appearing as cubes; the core of the precursor particles has a few pores, while the outer shell is irregularly shaped.

[0087] The particle size distribution, specific surface area, and tap density of the precursors obtained in Examples 1-5 and Comparative Examples 1-4 were tested, and the test results are shown in Table 1.

[0088] Table 1 As shown in Table 1, during the precursor preparation process, alkalinity mainly regulates the thickness, orientation, and growth rate of primary particles in the growth stage. Generally, higher alkalinity results in coarser primary particles, while lower specific surface area leads to higher tap density. Example 1 employed a growth pattern with alkalinity initially high and then decreasing during the two growth stages at 3 g / L and 1 g / L, resulting in sparse, petal-shaped primary particles. Comparative Example 1 maintained an alkalinity of 3 g / L throughout the growth stage. Compared to Example 1, the primary particles of the precursor were coarser, with fewer internal voids, a lower specific surface area, and a higher tap density. Comparative Example 2 maintained an alkalinity of 1 g / L throughout the growth stage. Compared to Example 1, the primary particles of the precursor were finer and denser, with more internal voids, thus increasing the specific surface area and decreasing the tap density. Comparative Example 3 used two alkalinity levels of 3 g / L and 5 g / L during the growth stage, employing a growth pattern of initially low alkalinity followed by high alkalinity. The alkalinity was consistently higher than in Example 1. The resulting precursor, compared to Example 1, had a lower specific surface area, higher tap density, and fewer internal pores. During precursor preparation, air primarily served an oxidizing effect, further refining the primary particles and increasing the specific surface area. Comparative Example 4 used a pure nitrogen atmosphere, resulting in a precursor with relatively thicker primary particles, lower internal porosity, and consequently, a lower specific surface area and higher tap density. Example 2, compared to Example 1, swapped the growth times for high and low alkalinity, resulting in slight changes in the specific surface area and tap density of the prepared precursor. In Examples 3-5, adjustments to the process parameters led to varying degrees of change in the specific surface area and tap density of the prepared precursors.

[0089] The precursors prepared in Examples 1-5 and Comparative Examples 1-4 were subjected to XRD tests, and the relevant test data can be found in Table 2.

[0090] Table 2 The (001) crystal plane of ternary cathode materials has a low specific surface energy. When preparing its precursor using the co-precipitation method, the crystal tends to preferentially spread and grow along this crystal plane. Therefore, the (001) crystal plane is usually the dominant crystal plane of ternary cathode materials. However, the excessively preferred orientation of the (001) crystal plane can hinder the diffusion process of lithium ions. As shown in Table 2, the I101 / I001 diffraction intensity ratio of the precursor prepared in Example 1 is relatively high, indicating that the diffraction peak of the (101) crystal plane is relatively stronger, and its dominant crystal growth direction has changed, tending more towards equiaxed growth. Based on the precursor prepared in Example 1, after lithiation treatment, a cathode material with more random grain orientation and more uniform morphology distribution can be obtained. This structural feature can increase the effective embedding surface area of ​​lithium ions at the edge of the layer, shorten the transport path of lithium ions from the particle surface to the internal active site, reduce the lithium ion diffusion resistance, and thus effectively improve the rate performance and overall electrochemical performance of the cathode material. The I101 / I001 diffraction intensity ratios of the precursors prepared in Comparative Examples 1-4 were 0.65-0.75, and the (001) crystal plane exhibited an over-preferred orientation, which would hinder the diffusion of lithium ions in the cathode material obtained by subsequent lithiation. The I101 / I001 diffraction intensity ratios of the precursors prepared in Examples 2-5 were 0.9-1.14, and the diffraction peaks of the (101) crystal plane were relatively stronger, and the crystal growth orientation was more balanced, which helped to improve the rate performance and overall electrochemical performance of the cathode material obtained by subsequent lithiation.

[0091] Test the electrochemical performance of the cathode material: (1) Preparation of cathode material: The precursors obtained in Examples 1-5 and Comparative Examples 1-4 were mixed with lithium hydroxide at a molar ratio of (Ni+Co+Mn):Li of 1:1.03. The mixture was placed in a muffle furnace with oxygen supply for sintering (the sintering process was to heat to 700℃ at a heating rate of 5℃ / min and sinter at a constant temperature for 10h, and then cool with the furnace) to obtain the sintered product. After the sintered product was crushed and dissociated, it was passed through a 325-mesh sieve to obtain the cathode material.

[0092] (2) Preparation of the positive electrode sheet: The prepared positive electrode material, conductive agent SuperP, and binder polyvinylidene fluoride (PVDF) were mixed with N-methylpyrrolidone (NMP) at a mass ratio of 8:1:1 and stirred evenly to form a positive electrode slurry (solid content of about 40wt%). The slurry was coated on the current collector aluminum foil, dried at 105℃, and then rolled at room temperature until the areal density was 2.8~3.3g / cm³. 3 Then, punch holes and cut them into φ14mm round sheets to make positive electrode sheets.

[0093] (3) Assembly of lithium-ion batteries: The button cells are assembled in the glove box. The assembly is carried out in the following order: "negative electrode shell - nickel foam - lithium sheet - 8 drops of electrolyte - separator - 8 drops of electrolyte - positive electrode sheet - positive electrode shell". The electrolyte is composed of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (EC: EMC: DMC volume ratio = 1:1:1) and contains 1.0 M LiPF6.

[0094] The positive electrode has a diameter of 14mm, the lithium electrode has a diameter of 18mm, the separator has a diameter of 22mm, and the battery casing (positive and negative electrode casings) has a diameter of 24mm. The separator is a 16μm thick membrane. The assembled button cell is placed in the mold of a hydraulic sealing machine (purchased from Shenzhen Kejing Zhida Technology Co., Ltd.) and locked in place.

[0095] (4) Performance test of button cell: The first coulombic efficiency and capacity retention rate test was conducted at 25°C using a Blue Electric test cabinet to test the charge-discharge cycle characteristics of the above button cell: the operating voltage range was 2.3V~4.35V, 3 cycles at 0.1C, and then 100 cycles at 1C rate. The specific capacity of the battery in the first cycle and the capacity retention rate after 100 cycles were measured. The test results are shown in Table 3.

[0096] Table 3 As shown in Table 2, the batteries assembled from the cathode materials prepared using the precursor in Example 1 exhibit high specific capacity and high capacity retention. Compared to Example 1, the batteries assembled from the cathode materials prepared using the precursors in Comparative Examples 1-4 show a decrease in both specific capacity and capacity retention. This may be due to changes in the morphology and dominant crystal planes of the precursors in Comparative Examples 1-4, which alters the electrochemical performance of the corresponding cathode materials. The batteries assembled from the cathode materials prepared using the precursors in Examples 2-5 show some changes in specific capacity and capacity retention compared to Example 1, but overall exhibit good comprehensive electrochemical performance.

[0097] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A precursor for a ternary cathode material, characterized in that, The chemical general formula of the precursor is Ni x Co y Mn z (OH)2, where 0.8 ≤ x ≤ 1, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and x + y + z = 1; the cross-sectional morphology of the precursor is in the shape of a sunflower flower.

2. The precursor of the ternary cathode material according to claim 1, characterized in that, The precursor includes a core and a shell. The core is loose and porous, and the shell is formed by the agglomeration of sheet-like primary particles. The shell is dense and has a crystalline cross-section.

3. The precursor of the ternary cathode material according to claim 1, characterized in that, In the X-ray diffraction pattern of the precursor, the peak intensity ratios of the (100) and (101) crystal planes to the (001) crystal plane are in the following ranges: 0.5≤I100 / I001≤0.85; 0.9≤I101 / I001≤1.

3.

4. The precursor of the ternary cathode material according to claim 1, characterized in that, The precursor's core has a particle size range of 1~2.5 μm; the precursor's outer shell has a thickness of 1~2.5 μm; and / or: the precursor's particle size D50 is 2~5 μm; and / or: the precursor's specific surface area is 10~20 m². 2 / g; and / or: the tap density of the precursor is 1.5~1.8 g / cm³. 3 .

5. A method for preparing a precursor of a ternary cathode material, characterized in that, Includes the following steps: Step S1: Prepare a metal salt solution according to the target chemical formula of the precursor; Step S2: A metal salt solution, a precipitant solution, and a complexing agent solution are continuously and concurrently introduced into the bottom liquid of the reactor to carry out a coprecipitation reaction. The coprecipitation reaction includes a nucleation stage and a growth stage. In the nucleation stage, the pH of the reaction system is controlled at 11-12, the temperature at 55-65℃, and the alkalinity at 3-7 g / L. A non-oxidizing gas is introduced for protection during the nucleation stage. In the growth stage, the introduction of the non-oxidizing gas is stopped, and an oxidant is introduced. The pH of the reaction system is controlled at 9-10, and the growth time is t1 at a first alkalinity of 3-5 g / L and t2 at a second alkalinity of 1-3 g / L. Step S3: After the coprecipitation reaction is completed, the reaction slurry is aged, and then the slurry is subjected to solid-liquid separation. The solid phase obtained by washing and drying is the precursor.

6. The method for preparing the precursor of the ternary cathode material according to claim 5, characterized in that, The duration of the nucleation stage is 0.5~1.5h; and / or: the first alkalinity > the second alkalinity; and / or: according to the total reaction period T of the growth stage, t1+t2=T, where 50h≤T≤100h, t1:t2 is 5:6~7:3; and / or: the oxidant is at least one of air, oxygen, hydrogen peroxide, and ozone; and / or: the stirring is carried out during the coprecipitation reaction, and the stirring linear velocity is 4.6~8.9m / s.

7. The method for preparing the precursor of the ternary cathode material according to claim 6, characterized in that, The oxidant is air or oxygen, and the flow rate of air or oxygen is 10~16 L / min.

8. The method for preparing the precursor of the ternary cathode material according to claim 5, characterized in that, The flow rate of the metal salt solution in the nucleation stage is 50-150 mL / min; the flow rate of the metal salt solution in the growth stage is 200-550 mL / min; and / or: the metal salt in the metal salt solution is a soluble metal salt, including nickel salt, manganese salt, and cobalt salt; and / or: the total concentration of metal ions in the metal salt solution is 2.0-2.2 mol / L; the nickel salt is at least one of nickel sulfate, nickel nitrate, nickel acetate, and nickel chloride; the manganese salt is at least one of manganese sulfate, manganese nitrate, manganese acetate, and manganese chloride; the cobalt salt is at least one of cobalt sulfate, cobalt nitrate, cobalt acetate, and cobalt chloride; and / or: the precipitant is at least one of sodium hydroxide, potassium hydroxide, and lithium hydroxide; the concentration of the precipitant solution is 1-11 mol / L; and / or: the complexing agent is at least one of ammonia, ammonium bicarbonate, and ammonium carbonate; the concentration of the complexing agent aqueous solution is 2-14 mol / L; and / or: the bottom liquid of the reaction vessel includes water, precipitant, and complexing agent.

9. A ternary cathode material, characterized in that, The precursor is prepared by any of the precursors described in claims 1 to 4 or any of the precursors described in claims 5 to 8, and then sintered with lithium mixture.

10. A lithium-ion battery, characterized in that, Including the ternary cathode material as described in claim 9.

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