A positive electrode material precursor, a preparation method therefor, and use thereof

Abstract

The application provides a positive electrode material precursor, a preparation method and application thereof. The positive electrode material precursor has a molecular formula of Ni x Co y Mn z (OH)2; wherein, 0.40<=x<=0.98, 0<=y<=0.50, 0<=z<=0.50, and x+y+z=1; the positive electrode material precursor comprises first particles and second particles; the first particle comprises a first inner core and a first shell layer arranged on at least part of the surface of the first inner core, and the porosity of the first inner core is less than that of the first shell layer; the second particle comprises a second inner core and a second shell layer arranged on at least part of the surface of the second inner core, and the porosity of the second inner core is less than that of the second shell layer; the radius of the first inner core is greater than that of the second inner core, and the porosity of the first shell layer is less than that of the second shell layer. The special composition and morphology of the positive electrode material precursor can improve the electrochemical performance of the battery when the positive electrode material prepared by the positive electrode material precursor is applied to the battery.

Description

Technical Field

[0001] This invention relates to a cathode material precursor, its preparation method, and its application, belonging to the field of secondary battery technology. Background Technology

[0002] Ternary cathode precursors, with nickel, cobalt, and manganese as the main elements, are the main raw materials for preparing cathode materials. The performance of these ternary cathode precursors greatly affects the performance of the cathode materials.

[0003] The existing cathode material precursor has a compact internal structure. When the cathode material precursor particles are large, the cathode material precursor is prone to cracking or even breaking into multiple fragments, which affects the electrochemical performance of the cathode material. Summary of the Invention

[0004] This invention provides a cathode material precursor. The special composition and morphology of the cathode material precursor enable the cathode material prepared from it to improve the electrochemical performance of the battery when applied to a battery.

[0005] This invention provides a method for preparing the above-mentioned cathode material precursor. This method can prepare the above-mentioned cathode material precursor. The preparation method is simple to operate and suitable for widespread application.

[0006] This invention provides a cathode material prepared using the aforementioned cathode material precursor. When applied to a battery, this cathode material can improve the battery's electrochemical performance.

[0007] The present invention provides a battery comprising the above-described positive electrode material, which has excellent electrochemical performance.

[0008] This invention provides a cathode material precursor, wherein the molecular formula of the cathode material precursor is shown in Formula 1;

[0009] Ni x Co y Mn z (OH)2;

[0010] Where 0.40≤x≤0.98, 0≤y≤0.50, 0≤z≤0.50, and x+y+z=1;

[0011] The cathode material precursor includes a first particle and a second particle;

[0012] The first particle includes a first core and a first shell disposed on at least a portion of the surface of the first core, wherein the porosity of the first core is less than the porosity of the first shell.

[0013] The second particle includes a second core and a second shell disposed on at least a portion of the surface of the second core, wherein the porosity of the second core is less than the porosity of the second shell.

[0014] The radius of the first core is greater than the radius of the second core, and the porosity of the first shell is less than the porosity of the second shell.

[0015] In the cathode material precursor described above, the thickness of the first shell layer is less than the thickness of the second shell layer; and / or,

[0016] The porosity of the first core is equal to the porosity of the second core.

[0017] The cathode material precursor described above has a median particle size of 10-20 μm.

[0018] The cathode material precursor described above has a porosity of 3-10%.

[0019] The cathode material precursor described above has a particle size distribution of 0.3-0.65.

[0020] The cathode material precursor described above, wherein the BET of the cathode material precursor is 7-20m. 2 / g.

[0021] The cathode material precursor as described above, wherein the cathode material precursor satisfies at least one of the following:

[0022] a. The porosity of the first shell layer is 5-7%;

[0023] b. The porosity of the second shell layer is 8-12%;

[0024] c. The porosity of the first core and the second core is independently 1-4%.

[0025] This invention provides a method for preparing the cathode material precursor as described above, comprising the following steps:

[0026] A mixed salt solution formed by nickel, manganese and cobalt sources is subjected to a continuous co-precipitation reaction in the first reaction unit to obtain intermediate particles.

[0027] The intermediate particles and the mixed salt solution formed by the nickel, manganese and cobalt sources are subjected to an intermittent coprecipitation reaction in the second reaction unit to obtain the cathode material precursor.

[0028] The preparation method described above, wherein the preparation method satisfies at least one of the following:

[0029] a. The volume of the first reaction unit is smaller than the volume of the second reaction unit;

[0030] b. The number of the first reaction units is less than the number of the second reaction units;

[0031] c. In the continuous coprecipitation reaction, pH1, the flow rate L1 of the mixed salt solution, and the rotation speed R1; in the intermittent coprecipitation reaction, pH2, the flow rate L2 of the mixed salt solution, and the rotation speed R2 satisfy the following:

[0032] pH1 > pH2, and / or, L2 > L1, and / or, R1 > R2;

[0033] d. The solid content S1 of the first reaction unit, the initial solid content S2 of the second reaction unit, and the final solid content S3 of the second reaction unit satisfy the following:

[0034] S2 < S1 < S3.

[0035] The present invention provides a cathode material, wherein it is prepared using a cathode material precursor as described above.

[0036] The present invention provides a battery comprising the positive electrode material as described above.

[0037] The cathode material precursor of the present invention has a special composition and morphology, which enables the cathode material prepared from it to improve the electrochemical performance of the battery when applied to the battery.

[0038] This invention provides a method for preparing a cathode material precursor, which can produce the aforementioned cathode material precursor. This preparation method is simple to operate and suitable for widespread application.

[0039] The present invention provides a battery comprising the above-described positive electrode material, and therefore the battery has excellent electrochemical performance. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or related technologies, the accompanying drawings used in the description of the embodiments of the present invention or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 This is a diagram of an apparatus for preparing a cathode material precursor in some embodiments of the present invention;

[0042] Figure 2 This is a process flow diagram for preparing the cathode material precursor in some embodiments of the present invention;

[0043] Figure 3 This is a surface SEM image of the cathode material precursor in Embodiment 1 of the present invention;

[0044] Figure 4 This is a cross-sectional SEM image of the cathode material precursor in Embodiment 1 of the present invention.

[0045] Explanation of reference numerals in the attached figures:

[0046] 100-Second reactor; 110-Guide cylinder; 111-Guide port; 120-Second motor; 121-Second rotating shaft; 122-Second top layer stirring blade; 123-Second bottom layer stirring blade; 130-Second overflow pipe;

[0047] 200 - Transfer vessel; 210 - Third motor; 211 - Third rotating shaft; 212 - Third stirring blade; 220 - Third overflow pipe; 230 - Feeding pipe;

[0048] 300 - Thickener; 310 - Filter layer; 320 - Fourth motor; 321 - Fourth shaft; 322 - Fourth agitator blade; 330 - Clear liquid discharge pipe; 340 - Return pipe;

[0049] 400 - First reactor; 410 - First motor; 411 - First rotating shaft; 412 - First top-layer stirring blade; 413 - First bottom-layer stirring blade; 420 - First overflow pipe; 430 - Storage tank inlet pipe;

[0050] 500 - Storage tank; 510 - Fifth motor; 511 - Fifth rotating shaft; 512 - Fifth stirring blade; 520 - Fifth overflow pipe; 530 - Material conveying pipe; 531 - Material conveying pipe branch. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0052] A first aspect of the present invention provides a cathode material precursor, the molecular formula of which is shown in Formula 1.

[0053] Ni x Co y Mn z (OH)2;

[0054] Where 0.40≤x≤0.98, 0≤y≤0.50, 0≤z≤0.50, and x+y+z=1;

[0055] The cathode material precursor includes a first particle and a second particle;

[0056] The first particle includes a first core and a first shell disposed on at least a portion of the surface of the first core, wherein the porosity of the first core is less than the porosity of the first shell.

[0057] The second particle includes a second core and a second shell disposed on at least a portion of the surface of the second core, wherein the porosity of the second core is less than the porosity of the second shell.

[0058] The radius of the first core is greater than that of the second core, and the porosity of the first shell is less than that of the second shell.

[0059] Specifically, the cathode material precursor of the present invention is a hydroxide comprising nickel, cobalt and manganese.

[0060] The cathode material precursor of the present invention refers to secondary particles formed by the agglomeration of primary particles, wherein both the first particle and the second particle refer to secondary particles.

[0061] It is understood that the first shell can cover part of the surface of the first core to form the first particle, or the first shell can cover the entire surface of the first core to form the first particle. The first particle includes the first core and the first shell from the inside out.

[0062] The second shell can cover a portion of the surface of the second core to form a second particle, or it can cover the entire surface of the second core to form a second particle. The second particle includes the second core and the second shell from the inside out.

[0063] In this invention, porosity refers to the proportion of the total area of ​​pores in the cross-section of a corresponding structure to the total cross-sectional area of ​​that structure. For example, the porosity of the first core refers to the proportion of the total area of ​​pores in the cross-section of the first core to the total cross-sectional area of ​​that first core. In some embodiments, a cross-sectional morphology image of the cathode material precursor can be obtained using SEM, and the porosity of the corresponding structure can be calculated by fitting the cross-sectional morphology image of the cathode material precursor.

[0064] The radius of the corresponding structure refers to the radius of the inscribed circle of the cross-section of that structure. For example, the radius of the first core refers to the radius of the inscribed circle of the cross-section of the first core. In some embodiments, a cross-sectional topography image of the cathode material precursor can be obtained using SEM, and the inscribed circle of the corresponding structure can be fitted based on the cross-sectional topography of the cathode material precursor to obtain the radius of the inscribed circle of the corresponding structure, thereby obtaining the radius of the corresponding structure.

[0065] The inventors discovered in their research that when the internal structure of the cathode material precursor is too compact, it not only hinders lithium-ion insertion and extraction but also results in high internal stress during charging and discharging, easily leading to cracking. Conversely, when the structure of the cathode material precursor is too porous, it negatively impacts its energy density. The cathode material precursor of this invention features a first and second core with low porosity and excellent compactness, contributing to improved energy density. Conversely, the first and second shells have higher porosity and excellent porosity, acting as a buffer during the reaction process to prevent cracking. Furthermore, the excellent porosity of the first and second shells also helps improve the rate performance of the cathode material.

[0066] In this invention, the radius of the first core is larger than that of the second core, and the porosity of the first shell is smaller than that of the second shell. This indicates that the porosity of the first particle is less than that of the second particle. The smaller porosity of the first particle helps to further improve the capacity of the cathode material precursor, while the larger porosity of the second particle helps to further improve the rate performance of the cathode material precursor. Therefore, the cathode material precursor of this invention possesses both excellent capacity and rate performance. It is worth noting that the different porosities of the first and second particles in this invention help to ensure the porosity stability of the cathode material precursor, thereby contributing to improved stability of the cathode material precursor.

[0067] In some embodiments of the present invention, the thickness of the first shell layer is less than the thickness of the second shell layer.

[0068] Here, the thickness of the first shell refers to its average thickness, and the thickness of the second shell refers to its average thickness. When the thickness of the first shell is less than the thickness of the second shell, the second particles with higher porosity help to further improve the rate performance of the cathode material precursor.

[0069] Furthermore, when the porosity of the first core is equal to that of the second core, the capacity of the cathode material can be further improved.

[0070] In some embodiments of the present invention, when the median particle size of the cathode material precursor is 10-20 μm, the rate performance of the cathode material precursor can be further improved while ensuring the energy density of the cathode material precursor.

[0071] Furthermore, when the porosity of the cathode material precursor is 3-10%, it can absorb more electrolyte while ensuring the energy density of the cathode material precursor, thereby further improving the rate performance of the cathode material precursor.

[0072] In some embodiments of the present invention, the particle size distribution of the cathode material precursor is 0.3-0.65. When the particle size distribution SPAN of the cathode material precursor is within the above range, the particle size distribution of the cathode material precursor is narrower and the stability is better.

[0073] The inventors also discovered that when the BET of the cathode material precursor is 7-20m... 2 At a concentration of / g, the cathode material precursor has a larger contact area with other materials, enabling a more complete reaction and thus improving the overall performance of the cathode material.

[0074] Furthermore, the cathode material precursor must satisfy at least one of the following conditions:

[0075] a. The porosity of the first shell layer is 5-7%;

[0076] b. The porosity of the second shell is 8-12%;

[0077] c. When the porosity of the first core and the second core are each 1-4%, the cathode material precursor has better electrochemical performance, which helps to improve the electrochemical performance of the cathode material, thereby improving the energy density and rate performance of the battery.

[0078] A second aspect of the present invention provides a method for preparing a cathode material precursor according to the first aspect, comprising the following steps:

[0079] A mixed salt solution formed by nickel, manganese and cobalt sources is subjected to a continuous co-precipitation reaction in the first reaction unit to obtain intermediate particles.

[0080] The intermediate particles and the mixed salt solution formed by the nickel, manganese and cobalt sources are subjected to intermittent coprecipitation reaction in the second reaction unit to obtain the cathode material precursor.

[0081] In this invention, continuous coprecipitation reaction refers to the reaction of reactants continuously, while intermittent coprecipitation reaction refers to the reaction of reactants being stopped after a period of time, and then reactants being added again to carry out coprecipitation reaction.

[0082] Specifically, the nickel source, manganese source and cobalt source are mixed to form a mixed salt solution. Then, the mixed salt solution is subjected to a continuous co-precipitation reaction in the first reaction unit, so that the nickel source, manganese source and cobalt source co-precipitate to form hydroxides including nickel, cobalt and manganese. In the continuous co-precipitation reaction, the nickel source, manganese source and cobalt source will precipitate to form relatively compact intermediate particles with different particle sizes.

[0083] Then, the intermediate particles and the mixed salt solution are subjected to an intermittent co-precipitation reaction in the second reaction unit, so that the nickel source, manganese source and cobalt source are deposited on at least part of the surface of the intermediate particles to form a core-shell structure cathode material precursor including a core and a shell. The mixed salt solution grows rapidly on the surface of the smaller intermediate particles to form a first particle including a first core and a first shell. The mixed salt solution grows at a slower rate on the surface of the larger intermediate particles to form a second particle including a second core and a second shell. Since the growth rate of the second shell is greater than that of the first shell, the porosity of the second shell is greater than that of the first shell.

[0084] This invention does not impose any particular limitation on the nickel source, which may be any compound containing nickel commonly used in the art; this invention does not impose any particular limitation on the cobalt source, which may be any compound containing cobalt commonly used in the art; this invention does not impose any particular limitation on the manganese source, which may be any compound containing manganese commonly used in the art.

[0085] The present invention does not impose any particular limitation on the first reaction unit, as long as it enables the mixed salt solution to undergo a continuous coprecipitation reaction. The present invention also does not impose any particular limitation on the second reaction unit, as long as it enables the mixed salt solution to undergo an intermittent coprecipitation reaction with the intermediate particles.

[0086] It is understood that both the continuous coprecipitation reaction and the intermittent coprecipitation reaction of the present invention may include a precipitant and a complexing agent. The precipitant may be a commonly used precipitant in the art, for example, a base; the complexing agent may be a commonly used complexing agent in the art, for example, ammonia.

[0087] The preparation method of the present invention can prepare the cathode material precursor of the first aspect, and the preparation method is simple to operate and suitable for widespread application.

[0088] In some embodiments of the present invention, when the volume of the first reaction unit is smaller than the volume of the second reaction unit, the residence time of the intermediate particles in the first reaction vessel is more uniform, which is beneficial to reducing the particle size distribution of the intermediate particles, thereby reducing the particle size distribution of the cathode material precursor and improving the production capacity of the cathode material precursor. Further, the volume of the first reaction unit is ≤5m³. 3 The volume of the second reaction unit is ≥15m³. 3 .

[0089] When the number of first reaction units is less than the number of second reaction units, the production capacity of the cathode material precursor can be further improved, and the particle size distribution of the cathode material precursor can be reduced. In some embodiments, the number of first reaction units is 1-2, and the number of second reaction units is 6-10. Furthermore, when the number of first reaction units is 2, the two first reaction units can be connected in parallel, and the 6-10 second reaction units can also be connected in parallel.

[0090] In a continuous coprecipitation reaction, pH1, the flow rate L1 of the mixed salt solution, and the rotation speed R1 are constants; in a batch coprecipitation reaction, pH2, the flow rate L2 of the mixed salt solution, and the rotation speed R2 are constants.

[0091] When pH1 > pH2, and / or L2 > L1, and / or R1 > R2, the growth rate of the first shell and the second shell in the second reaction unit is faster, which helps to improve the porosity of the cathode material precursor.

[0092] Furthermore, in the continuous coprecipitation reaction, pH1 is 11–13; the flow rate L1 of the mixed salt solution is 100–800 L / h; and the rotation speed R1 is 300–400 r / min. In the intermittent coprecipitation reaction, pH2 is 10–12; the flow rate L2 of the mixed salt solution is 800–1500 L / h; and the rotation speed R2 is 100–250 r / min.

[0093] In some embodiments, the temperature in both the continuous coprecipitation reaction and the intermittent coprecipitation reaction is independently selected from 40-80°C, and the concentration of ammonia is independently selected from 2-8 g / L.

[0094] In some embodiments of the present invention, when the solid content S1 of the first reaction unit, the initial solid content S2 of the second reaction unit, and the final solid content S3 of the second reaction unit satisfy:

[0095] When S2 < S1 < S3, the growth rate of the first shell and the second shell in the second reaction unit is faster, which helps to improve the porosity of the cathode material precursor.

[0096] In this invention, the solid content of the first reaction unit refers to the solid content when the median particle size D1 of the first particle in the first reaction unit fluctuates between -0.2 and 0.2 μm, and the pH1 fluctuates between -0.2 and 0.2; the initial solid content of the second reaction unit refers to the solid content of the second reaction unit when the intermediate particles just enter the second reaction unit; the final solid content of the second reaction unit refers to the solid content when the second reaction unit is shut down after the intermittent coprecipitation reaction is complete.

[0097] In this invention, the solid content of the first reaction unit can be calculated using Equation 2;

[0098] S1 = L1 * C * M / L (Equation 2);

[0099] S1 is the solid content of the first reaction unit, in g / L;

[0100] L1 is the flow rate of the mixed salt solution, in L / h;

[0101] C represents the concentration of the mixed salt solution, in mol / L;

[0102] M is Ni x Co y Mn z The molecular weight of (OH)2;

[0103] L is the sum of the flow rates of the mixed salt solution, the precipitant, and the complexing agent, expressed in L / h.

[0104] Furthermore, S1 is 50–200 g / L, S2 is 10–50 g / L, and S3 is 300–800 g / L.

[0105] This invention can also improve the performance of the cathode material precursor by controlling the properties of the intermediate particles generated in the first reaction unit. For example, the particle size distribution of the intermediate particles obtained in the first reaction unit can be 0.7-1.2, and the BET of the intermediate particles obtained in the first reaction unit can be 5-10 μm. 2 / g.

[0106] In some implementations, intermediate particles of the target particle size can be obtained by adjusting the pH of the first reaction unit in real time. For example, if the real-time particle size of the particles in the first reaction unit is smaller than the expected particle size of the intermediate particles, the pH in the first reaction vessel can be reduced to allow the particle size in the first reaction vessel to grow radially, thereby obtaining the target particle size.

[0107] Figure 1 This is a diagram of an apparatus for preparing a cathode material precursor in some embodiments of the present invention; Figure 2 This is a process flow diagram for preparing the cathode material precursor in some embodiments of the present invention. For example... Figure 1 and Figure 2 As shown, the cathode material precursor of the present invention can be used Figure 1 The preparation apparatus shown and Figure 2 The preparation process shown is as follows. Specifically,

[0108] 1) The mixed salt solution, alkali solution and ammonia water are fed into the first reaction vessel 400 in parallel. Under the action of the first motor 410, the first top stirring blade 412 and the first bottom stirring blade 413 are rotated around the first rotating shaft 411. During the rotation and stirring, the mixed salt solution, alkali solution and ammonia water will undergo a continuous co-precipitation reaction to obtain intermediate particles.

[0109] 2) In the continuous co-precipitation reaction, excess liquid enters the storage tank 500 through the first overflow pipe 420, and the remaining intermediate particles enter the storage tank 500 through the storage tank feed pipe 430. Under the action of the fifth motor 510, the fifth stirring blade 512 rotates around the fifth rotating shaft 511 to stir. During the rotation and stirring, excess liquid in the storage tank 500 is output through the fifth overflow pipe 520.

[0110] 3) The intermediate particles in the storage tank 500 enter the second reactor 100 through the feed pipe 530 and the feed pipe branch 531, so that the alkaline solution, ammonia water and mixed salt flow into the second reactor 100 in parallel. The second reactor 100 is equipped with a guide tube 110. Each raw material moves in the second reactor 100 through the guide port 111. Under the action of the second motor 120, the second top stirring blade 122 and the second bottom stirring blade 123 rotate and stir around the second rotating shaft 121. During the rotation and stirring, the second particles, mixed salt solution, alkaline solution and ammonia water undergo intermittent co-precipitation reaction to obtain the cathode material precursor.

[0111] 4) Excess liquid in the second reactor 100 enters the transfer vessel 200 through the second overflow pipe 130. Under the action of the third motor 210, the third stirring blade 212 rotates and stirs around the third rotating shaft 211. During the rotation and stirring, the liquid entering the transfer vessel 200 will be evenly mixed. Excess liquid in the transfer vessel 200 is output through the third overflow pipe 220.

[0112] 5) The uniformly mixed liquid in the transfer vessel 200 enters the thickener through the feed pipe 230. Under the action of the fourth motor 320, the fourth stirring blade 322 rotates and stirs along the fourth rotating shaft 321 to promote uniform mixing of the liquid in the thickener 300. The excess liquid in the thickener 300 is filtered and concentrated through the filter layer 310. The clear liquid is output through the clear liquid discharge pipe 330. The obtained concentrated liquid enters the second reaction vessel through the return pipe 340 to participate in the intermittent co-precipitation reaction.

[0113] In this invention, after the intermittent coprecipitation reaction, an aging process is also included to allow the raw materials to react more fully, resulting in a system including a cathode material precursor. Then, the system including the cathode material precursor is washed to obtain a washed cathode material precursor. The washed cathode material precursor is dried to obtain a dried product. The dried product is then sieved, iron-removing, and packaged to obtain the cathode material precursor.

[0114] A third aspect of the present invention provides a cathode material prepared using the cathode material precursor of the first aspect.

[0115] In this invention, the cathode material precursor can be mixed with a metal ion source (e.g., lithium source, sodium source) and then sintered to obtain the cathode material.

[0116] The cathode material of the present invention has excellent energy density and rate performance because it is prepared by the cathode material precursor of the first aspect.

[0117] A fourth aspect of the present invention provides a battery comprising the positive electrode material of the third aspect.

[0118] It is understood that in this invention, the positive electrode material can be prepared into a positive electrode sheet using methods commonly used in the art, and then the positive electrode sheet and the negative electrode sheet can be assembled to obtain a battery.

[0119] The battery of the present invention, due to including the positive electrode material of the third aspect, has excellent rate performance and energy density.

[0120] The technical solution of the present invention will be further explained and described below with reference to specific embodiments.

[0121] Example 1

[0122] The battery in this embodiment is prepared by a method including the following steps:

[0123] 1. Preparation of positive electrode sheet

[0124] 1) Preparation of cathode material precursors

[0125] a. Nickel sulfate, cobalt sulfate and manganese sulfate are prepared into salt solutions separately, and then mixed to obtain a mixed salt solution. The molar ratio of Ni, Co and Mn in the mixed salt solution is 93:3:4.

[0126] Ammonia solution, sodium hydroxide solution and pure water are added to the first reaction vessel to form a reaction base solution. The pH of the reaction base solution is 11.8 and the concentration of ammonia solution is 3.5 g / L.

[0127] A mixed metal salt solution of nickel, cobalt, and manganese, a sodium hydroxide solution, an ammonia solution, and a protective gas nitrogen are introduced into the first reactor in parallel to cause a continuous co-precipitation reaction of the mixed metal salt solution, sodium hydroxide solution, and ammonia solution to obtain intermediate particles.

[0128] The pH of the first reaction vessel was 11.5 ± 0.2, the median particle size of the intermediate particles was 5 μm, the flow rate L1 of the mixed salt solution was 300 L / h, the rotation speed R1 was 350 r / min, the solid content S1 of the first reaction vessel was 90 g / L, and the volume of the first reaction vessel was 5 m³. 3 The number of first reaction vessels is 1;

[0129] b. After adding ammonia solution, sodium hydroxide solution, pure water, and intermediate particles to the second reaction vessel, the transfer vessel, and the thickener, a reaction base liquid is formed. The pH of the reaction base liquid in the second reaction vessel, the transfer vessel, and the thickener is 11, and the ammonia concentration in the reaction base liquid is 3.5 g / L. The initial solid content S2 after circulation in the second reaction vessel, the transfer vessel, and the thickener is 30 g / L.

[0130] A mixed salt solution, sodium hydroxide solution, ammonia solution, and protective gas nitrogen are fed into the second reactor in parallel to cause the mixed salt solution, sodium hydroxide solution, ammonia solution, and intermediate particles to undergo an intermittent co-precipitation reaction. After obtaining a cathode material precursor with a median particle size of 10 μm, the second reactor is shut down and the feed is stopped.

[0131] In the intermittent coprecipitation reaction, the pH was 10.0, the flow rate of the mixed salt solution L2 was 1000 L / h, the rotation speed R2 was 200 r / min, the final solid content S3 in the second reaction vessel was 500 g / L, and the volume of the second reaction vessel was 20 m³. 3 The number of second reaction vessels is 8;

[0132] c. The system including the cathode material precursor is subjected to washing, drying, sieving, iron removal and packaging processes in sequence to obtain the cathode material precursor.

[0133] 2) Preparation of cathode materials

[0134] The lithium source and the cathode material precursor are mixed and then subjected to a first sintering process and a second sintering process to obtain the cathode material.

[0135] The lithium source is lithium hydroxide, and the ratio of the molar content of lithium in the lithium source to the total molar content of transition metal elements in the cathode material precursor is 1.2:1.

[0136] In the first sintering process, the temperature was 450℃ and the time was 5 hours.

[0137] In the second sintering process, the temperature was 750℃ and the time was 12h.

[0138] 3) Preparation of positive electrode sheet

[0139] The positive electrode includes an aluminum foil and a positive electrode active layer disposed on two functional surfaces of the aluminum foil;

[0140] The positive electrode active layer includes the positive electrode material, conductive agent SP, and binder PVDF in step 2), wherein the mass ratio of the positive electrode material, conductive agent SP, and binder PVDF is 90:5:5.

[0141] 2. Preparation of negative electrode sheet

[0142] The negative electrode includes a copper foil and a negative electrode active layer disposed on two functional surfaces of the copper foil;

[0143] The negative electrode active layer includes hard carbon, conductive agent SP, and binder PVDF, with a mass ratio of hard carbon, conductive agent SP, and binder PVDF of 3:3:94.

[0144] 3. Battery manufacturing

[0145] The positive electrode and separator from step 2) and the negative electrode from step 3) are stacked to obtain an electrode assembly. The electrode assembly is placed in an aluminum-plastic film and injected with commercially available NaPF6 electrolyte to obtain a battery.

[0146] Examples 2-6

[0147] The preparation methods of the batteries in Examples 2-6 are basically the same as those in Example 1, except that:

[0148] 1. Preparation of positive electrode sheet

[0149] 1) Preparation of cathode material precursors

[0150] The process parameters for preparing the cathode material precursor are different from those in Example 1, and the obtained cathode material precursor is also different from that in Example 1. The relevant preparation parameters and parameters of the cathode material precursor are shown in Table 1 and Table 2.

[0151] Comparative Example 1

[0152] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that:

[0153] 1. Preparation of positive electrode sheet

[0154] 1) Preparation of cathode material precursors

[0155] a. A mixed metal salt solution of nickel, cobalt and manganese, sodium hydroxide solution, ammonia solution and protective gas nitrogen are introduced into the first reaction vessel in parallel to cause the mixed metal salt solution, sodium hydroxide solution and ammonia solution to undergo an intermittent coprecipitation reaction to obtain intermediate particles;

[0156] The pH value was 11.1 ± 0.2, the median particle size of the intermediate particles was 5 μm, the flow rate of the mixed salt solution was L1 of 300 L / h, the rotation speed was R1 of 320 r / min, and the solid content of the first reaction vessel was S1 of 200 g / L.

[0157] Comparative Example 2

[0158] The preparation method of the battery in this comparative example is basically the same as that in Example 1, except that:

[0159] 1. Preparation of positive electrode sheet

[0160] 1) Preparation of cathode material precursors

[0161] A mixed salt solution, sodium hydroxide solution, ammonia solution, and protective nitrogen gas are fed into the second reactor in parallel to induce a continuous co-precipitation reaction between the mixed salt solution, sodium hydroxide solution, ammonia solution, and intermediate particles. After obtaining a cathode material precursor with a median particle size of 10 μm, the second reactor is shut down and the feed is stopped.

[0162] Performance testing

[0163] The following performance tests were performed on the cathode material precursor, cathode material and battery in the examples and comparative examples. The results are shown in Table 1 and Table 2.

[0164] 1. Appearance

[0165] The morphology of the cathode material precursor in Example 1 was observed using SEM. Figure 3 This is a surface SEM image of the cathode material precursor in Embodiment 1 of the present invention; Figure 4 This is a cross-sectional SEM image of the cathode material precursor in Embodiment 1 of the present invention. Figure 3 and Figure 4 It can be seen that the cathode material precursor particles in the embodiment have excellent particle size uniformity (small SPAN2), and the core is more compact than the shell in the cross-sectional structure of the cathode material precursor particles, while the shell has a richer pore structure.

[0166] 2. SPAN

[0167] Using a Malvern MS-2000 laser particle size analyzer, the D90, D10, and D50 of the material are obtained through the spatial distribution (scattering spectrum) of the diffracted or scattered light. The SPAN of the material is then calculated based on the D90, D10, and D50: SPAN = (D90 - D10) / D50.

[0168] SPAN1 is the particle size distribution of intermediate particles. SPAN1 is calculated using the D90, D10, and D50 of intermediate particles.

[0169] SPAN2 is the particle size distribution of the cathode material precursor, which is calculated from the D90, D10 and D50 of the cathode material precursor.

[0170] 3. Porosity

[0171] The software automatically identifies the cross-sectional SEM image of the cathode material precursor based on the ratio of the pore area to the cross-sectional area in the SEM image, and obtains the porosity of the cathode material precursor, the porosity of the first core, the porosity of the second core, the porosity of the first shell, and the porosity of the second shell.

[0172] 4. BET

[0173] Using an automated nitrogen adsorption surface area analyzer, under the same adsorption and desorption conditions, the surface area of ​​the cathode material precursor and the standard sample is proportional to the size of their peak areas. The specific surface area (BET) of the cathode material precursor is calculated by measuring the size of the desorption peak areas of the two samples.

[0174] 5. Energy density

[0175] The electrical energy released per unit mass of a battery.

[0176] 6. Ratio Performance

[0177] The capacity retention rate of a battery when discharged at 1C to 3V.

[0178] Table 1

[0179] Example 1 11.5 300 350 10 1000 200 90 30 500 Example 2 11.5 300 350 10 500 200 90 30 500 Example 3 11.5 300 350 12.2 1000 200 90 30 500 Example 4 11.5 300 350 10 1000 200 90 30 700 Example 5 11.5 300 350 11.2 400 200 90 30 900 Comparative Example 1 11.1 300 320 10 1000 200 200 30 500 Comparative Example 2 11.5 360 350 11 800 250 90 30 110

[0180] Table 2

[0181]

[0182] As can be seen from Tables 1 and 2, the batteries in the embodiments of the present invention have better energy density and rate performance, indicating that the cathode materials prepared by the cathode material precursor with special morphology in the present invention can significantly improve the overall performance of the battery when applied to the battery.

[0183] Furthermore, as can be seen from the Examples and Comparative Example 1, the cathode material precursor obtained by the two-step intermittent coprecipitation reaction includes only one type of core-shell structure particles; as can be seen from the Examples and Comparative Example 2, the cathode material precursor obtained by the two-step continuous coprecipitation reaction has a relatively uniform particle structure (no core-shell structure). This indicates that the embodiments of the present invention can obtain cathode material precursors including two types of core-shell structures (including the first particle and the second particle) by sequentially performing continuous coprecipitation reaction and intermittent coprecipitation reaction, thereby helping to improve the energy density and rate performance of the battery.

[0184] Compared with Example 2, when the porosity of the second shell is 8-12%, the obtained battery has better rate performance and energy density.

[0185] Compared with Example 3, when the particle size distribution of the cathode material precursor is 0.3-0.65, the obtained battery has better overall performance.

[0186] As can be seen from Examples 1 and 4, simultaneously adjusting the porosity of the first shell layer and the porosity of the second shell layer can control the median particle size of the cathode material precursor. When the median particle size of the cathode material precursor is 10-20 μm, the overall performance of the battery can be further improved.

[0187] As can be seen from Examples 1 and 5, the porosity of the cathode material precursor can be controlled by controlling the first possible porosity and the porosity of the second shell. When the porosity of the cathode material precursor is 3-10%, the obtained battery has better rate performance and energy density.

[0188] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cathode material precursor, characterized in that, The molecular formula of the cathode material precursor is shown in Formula 1. Ni x Co y Mn z (OH)₂ Formula 1; Where 0.40≤x≤0.98, 0≤y≤0.50, 0≤z≤0.50, and x+y+z=1; The cathode material precursor includes a first particle and a second particle; The first particle includes a first core and a first shell disposed on at least a portion of the surface of the first core, wherein the porosity of the first core is less than the porosity of the first shell; the porosity of the first shell is 5-7%. The second particle includes a second core and a second shell disposed on at least a portion of the surface of the second core, wherein the porosity of the second core is less than the porosity of the second shell; the porosity of the second shell is 8-12%; and the porosity of the first core and the second core are each independently 1-4%. The radius of the first core is greater than the radius of the second core, and the porosity of the first shell is less than the porosity of the second shell. The thickness of the first shell layer is less than the thickness of the second shell layer.

2. The cathode material precursor according to claim 1, characterized in that, The porosity of the first core is equal to the porosity of the second core.

3. The cathode material precursor according to claim 1, characterized in that, The median particle size of the cathode material precursor is 10-20 μm.

4. The cathode material precursor according to any one of claims 1-3, characterized in that, The porosity of the cathode material precursor is 3-10%.

5. The cathode material precursor according to any one of claims 1-3, characterized in that, The particle size distribution SPAN of the cathode material precursor is in the range of 0.3-0.65; where SPAN=(D90-D10) / D50.

6. The cathode material precursor according to any one of claims 1-3, characterized in that, The BET of the cathode material precursor is 7-20m. 2 / g.

7. A method for preparing a cathode material precursor according to any one of claims 1-6, characterized in that, Includes the following steps: A mixed salt solution formed by nickel, manganese and cobalt sources is subjected to a continuous co-precipitation reaction in the first reaction unit to obtain intermediate particles. The intermediate particles and the mixed salt solution formed by the nickel, manganese and cobalt sources are subjected to an intermittent coprecipitation reaction in the second reaction unit to obtain the cathode material precursor. The preparation method satisfies the following conditions: in the continuous coprecipitation reaction, the flow rate L1 and rotation speed R1 of the mixed salt solution, and in the intermittent coprecipitation reaction, the flow rate L2 and rotation speed R2 of the mixed salt solution satisfy: L2 > L1, R1 > R2; wherein, in the continuous coprecipitation reaction, the flow rate L1 of the mixed salt solution is 100~800 L / h; the rotation speed R1 is 300~400 r / min; in the intermittent coprecipitation reaction, the flow rate L2 of the mixed salt solution is 800~1500 L / h; the rotation speed R2 is 100~250 r / min; and the final solid content S3 of the second reaction unit is 300~800 g / L.

8. The preparation method according to claim 7, characterized in that, The preparation method shall at least satisfy one of the following: a. The volume of the first reaction unit is smaller than the volume of the second reaction unit; b. The number of the first reaction units is less than the number of the second reaction units; c. In the continuous coprecipitation reaction, pH1, and in the intermittent coprecipitation reaction, pH2, satisfy the following: pH1 > pH2; d. The solid content S1 of the first reaction unit, the initial solid content S2 of the second reaction unit, and the final solid content S3 of the second reaction unit satisfy the following: S2 < S1 < S3.

9. A positive electrode material, characterized in that, It is prepared using the cathode material precursor according to any one of claims 1-6.

10. A battery, characterized in that, Includes the cathode material as described in claim 9.

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