A single crystal nickel-cobalt-manganese ternary positive electrode material and its preparation method

Abstract

The present invention discloses a method for preparing a single-crystal nickel-cobalt-manganese ternary positive electrode material, comprising: first fully mixing a ternary precursor, a lithium source, and a first cesium source, calcining, and cooling; then dissolving a second cesium source in water, spraying the mixture therein, fully mixing, drying, calcining, and cooling; finally dissolving a third cesium source in water, spraying the mixture therein, fully mixing, drying, and calcining again to obtain a single-crystal nickel-cobalt-manganese ternary positive electrode material. The present invention also provides a single-crystal nickel-cobalt-manganese ternary positive electrode material obtained by the above-mentioned preparation method. The present invention utilizes step-by-step cesium doping to improve the rate performance and cycle stability of the ternary positive electrode material; the single-crystal lithium-ion battery finally constructed has a rate retention rate of 87.7% after 5C rate charge and discharge, and is suitable for the field of power batteries requiring high energy and high power.

Description

Technical Field

[0001] The patent of this invention belongs to the field of lithium-ion battery positive electrode materials, and specifically relates to a single-crystal nickel-cobalt-manganese ternary positive electrode material and its preparation method. Background Art

[0002] Ternary lithium-ion battery cathode materials, due to their high energy density and relatively simple preparation process, are widely used in portable electronic devices, power tools, and new energy vehicles. In particular, in the field of power batteries, improving energy density, cycle stability, and rate performance is a key research focus in the industry. Currently, the development trends of nickel-cobalt-manganese ternary cathode materials are threefold: single crystal, high voltage, and high nickel content.

[0003] Positive electrode materials can be divided into two categories: polycrystalline and single crystal. Polycrystalline materials exist in the form of micron-level agglomerates with a large number of grain boundaries inside. During the charge and discharge process of the battery, due to the anisotropic lattice changes, polycrystalline materials are prone to grain boundary cracking, resulting in the breakage of secondary particles, which leads to a rapid increase in side reactions, increased impedance, and a rapid decline in performance. The use of single crystal particles can reduce grain boundaries, reduce the occurrence of side reactions, improve cycle performance, and increase compaction density, thereby increasing energy density; however, the solubility of single crystal materials with the electrolyte becomes lower, and Li + The diffusion path becomes longer and the rate performance becomes worse, affecting its practical application in power batteries.

[0004] To address this issue, the single-crystal ternary cathode material needs to be modified. Doping and surface coating are commonly used modification methods. Among them, the selection of appropriate doping substances and doping ratios can effectively improve the electrochemical properties of the material. Common methods include metal cation doping, non-metallic anion doping, or anion-cation composite doping. Some existing doping schemes may improve the stability of the cathode material, but will sacrifice some of the charge and discharge capacity, and the rate performance will deteriorate or the improvement will not be obvious. In addition, common coating materials include carbon materials, oxides, fluorides, phosphates, lithium compounds, and polymers. Although most coating agents on the market can improve the conductivity of the material, they often bring new problems, such as increased polarization, reduced capacity, reduced rate, and poor corrosion resistance. To date, many studies have been conducted on the above issues and have made varying degrees of progress, but there is still a certain gap with actual needs. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is that the existing single-crystal ternary positive electrode material will sacrifice a part of the charge and discharge capacity after doping, and the rate performance will deteriorate or the improvement is not obvious. Therefore, a single-crystal nickel-cobalt-manganese ternary positive electrode material and a preparation method thereof are provided. The obtained ternary single-crystal positive electrode material improves the rate performance of the material while maintaining stability.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] The present invention provides a method for preparing a single-crystal nickel-cobalt-manganese ternary positive electrode material, comprising the following steps:

[0008] S1: fully mixing the ternary precursor, the lithium source and the first cesium source, calcining and cooling to obtain the first ternary positive electrode material;

[0009] S2: dissolving the second cesium source in water, spraying the solution onto the first ternary cathode material, mixing the solution thoroughly, drying the solution, calcining the solution, and cooling the solution to obtain the second ternary cathode material;

[0010] S3: dissolving the third cesium source in water, spraying it into the second ternary positive electrode material and mixing it thoroughly, drying it, roasting it, and cooling it to obtain a single crystal nickel-cobalt-manganese ternary positive electrode material.

[0011] Furthermore,

[0012] The ternary precursor is Ni x Co y Mn (1-x-y) (OH)2,0.6 <x<1.0,0<y<0.40;

[0013] The lithium source is lithium hydroxide or lithium carbonate;

[0014] The first cesium source, the second cesium source and the third cesium source are cesium hydroxide;

[0015] The molar ratio of the sum of nickel, cobalt and manganese in the ternary precursor to the lithium element in the lithium source is 1:1.00-1.06;

[0016] The mass ratio of the first cesium source, the second cesium source and the third cesium source is 0.5-1:0.5-1:0.5-1;

[0017] Calculated by mass fraction, the sum of the masses of the first cesium source, the second cesium source and the third cesium source accounts for 0.05-0.8% of the total mass of the single crystal nickel-cobalt-manganese ternary positive electrode material.

[0018] In step S1, the calcination temperature is 400-600° C., and the calcination time is 4-10 hours.

[0019] In step S2, the calcination temperature is 600-800° C., and the calcination time is 4-10 hours.

[0020] In step S3, the calcination temperature is 800-1000° C., and the calcination time is 4-10 hours.

[0021] The drying temperature is not higher than 120°C to reduce the loss of Li ions in the positive electrode structure; the water content in the dried ternary positive electrode material is not higher than 500ppm.

[0022] Among them, evaporation to dryness is preferred. During the evaporation to dryness to obtain the dry material, the heating temperature is 50-120° C. and the heating time is 0.5-3 h.

[0023] Deionized water is preferably used in steps S2 and S3 in an amount of 50 mL to 500 mL. The amount of water used should be moderate. Too little water is not conducive to the dissolution of the Cs source, while too much water will cause serious loss of Li ions.

[0024] In step S1, a high-speed mixer is used for mixing, the mixing speed is 1000-4000 r, and the mixing time is 5-60 min.

[0025] The mixing in step S1 also includes adding a zirconium source, wherein the zirconium source is zirconium oxide; the zirconium oxide accounts for 0.1-1% of the total mass of the single crystal nickel-cobalt-manganese ternary positive electrode material.

[0026] The present invention also provides a single crystal nickel-cobalt-manganese ternary positive electrode material, which is prepared according to the above preparation method.

[0027] The technical solution of the present invention has the following advantages:

[0028] (1) The present invention utilizes step-by-step cesium doping to improve the rate performance and cycle stability of the material; first, Cs + It has a larger atomic radius and can play a supporting role between layers to widen the interlayer distance, which can increase the Li + In and out rate, furthermore, the step-by-step doping process can make Cs + Ions are uniformly doped into the single crystal particles from the inside out, thereby improving the rate performance of the material. Therefore, the single crystal lithium ion battery constructed by the present invention has a rate retention rate of 87.7% after 5C rate charge and discharge, making it suitable for the field of power batteries requiring high energy and high power.

[0029] (2) The present invention adopts a step-by-step doping process, and the calcination temperature in each step is gradually increased; in the first step, the precursor reacts with the lithium salt to initially form a positive electrode layered structure; in the second step, the crystals formed in the previous step are initially grown; in the third step, the primary particles grow again to form single crystal particles, so that Cs + Ions are doped into the structure of single crystal particles during the gradual growth of primary particles. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 This is a schematic structural diagram of the single-crystal nickel-cobalt-manganese ternary positive electrode material obtained in Example 1 of the present invention;

[0032] Figure 2 This is an electron microscope photograph of the first ternary positive electrode material obtained in Example 1 of the present invention;

[0033] Figure 3 This is an electron microscope photograph of the second ternary positive electrode material obtained in Example 1 of the present invention;

[0034] Figure 4 This is an electron microscope photo of the single crystal nickel-cobalt-manganese ternary positive electrode material obtained in Example 1 of the present invention.

[0035] Figure 5 The battery cycle performance diagram of the ternary cathode materials prepared in the examples of the present invention and the comparative examples;

[0036] Figure 6 This is a rate performance diagram of batteries prepared with ternary positive electrode materials obtained in the examples of the present invention and the comparative examples. DETAILED DESCRIPTION

[0037] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0038] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art.

[0039] Example 1

[0040] This embodiment provides a single crystal nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0041] The ternary nickel-cobalt-manganese precursor Ni 0.8 Co 0.1 Mn 0.1(OH)2 (500g), lithium hydroxide (225g), cesium hydroxide (1.33g), and zirconium oxide (3.38g) were mixed and stirred evenly, transferred to a muffle furnace and calcined at 570℃ for 6h. After cooling, a cesium-doped agglomerated nickel-cobalt-manganese ternary positive electrode material was obtained, i.e., the first ternary positive electrode material. The electron microscope photo of the material is shown in FIG. Figure 2 As shown, the precursor reacts with the lithium salt to initially form a positive electrode layered structure; then 1.33g is dissolved in 50mL of deionized water and sprayed into the above materials in the form of a spray, dried at 100℃ for 30min, and then calcined at 750℃ for 6h. After cooling, a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material is obtained, that is, the second ternary positive electrode material. The electron microscope photo is shown as follows: Figure 3 As shown, the crystals formed by the previous sintering step are initially grown; finally, 1.33g of cesium hydroxide is dissolved in 50mL of deionized water and sprayed into the above materials in the form of a spray, dried at 100℃ for 30min, and then calcined at 900℃ for 8h. After cooling, a cesium-doped single crystal nickel-cobalt-manganese ternary positive electrode material is obtained, as shown in the electron microscope photo. Figure 4 As shown, the primary particles grow again to form single crystal particles, making Cs + Ions are doped into the structure of single crystal particles during the gradual growth of primary particles. Figure 1 As shown, Cs with a larger ionic radius + , playing a supporting role between layers and widening the spacing between TM layers (transition metal layers).

[0042] Example 2

[0043] This embodiment provides a single crystal nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0044] The ternary nickel-cobalt-manganese precursor Ni 0.7 Co 0.1 Mn 0.2 (OH)2 (500g), lithium hydroxide (225g), cesium hydroxide (1.33g), and zirconium oxide (3.38g) are mixed and stirred evenly, transferred to a muffle furnace and calcined at 400℃ for 6h, and cooled to obtain a cesium-doped agglomerated nickel-cobalt-manganese ternary positive electrode material, i.e., the first ternary positive electrode material; then 0.67g is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 110℃ for 60min, and then calcined at 600℃ for 5h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material, i.e., the second ternary positive electrode material; finally, 1.33g of cesium hydroxide is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 110℃ for 60min, and then calcined at 800℃ for 10h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material.

[0045] Example 3

[0046] This embodiment provides a single crystal nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0047] The ternary nickel-cobalt-manganese precursor Ni 0.7 Co 0.2 Mn 0.1 (OH)2 (500g), lithium hydroxide (225g), cesium hydroxide (0.67g), and zirconium oxide (3.38g) are mixed and stirred evenly, transferred to a muffle furnace and calcined at 500℃ for 8h, and cooled to obtain a cesium-doped agglomerated nickel-cobalt-manganese ternary positive electrode material, i.e., the first ternary positive electrode material; 1.33g is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 100℃ for 30min, and then calcined at 700℃ for 9h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material, i.e., the second ternary positive electrode material; finally, 1.33g of cesium hydroxide is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 100℃ for 30min, and then calcined at 950℃ for 7h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material.

[0048] Example 4

[0049] This embodiment provides a single crystal nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0050] The ternary nickel-cobalt-manganese precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 (500g), lithium hydroxide (225g), cesium hydroxide (1.33g), and zirconium oxide (3.38g) are mixed and stirred evenly, transferred to a muffle furnace and calcined at 600℃ for 5h, and cooled to obtain a cesium-doped agglomerated nickel-cobalt-manganese ternary positive electrode material, i.e., the first ternary positive electrode material; 1.33g is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 100℃ for 30min, and then calcined at 800℃ for 6h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material, i.e., the second ternary positive electrode material; finally, 0.67g of cesium hydroxide is dissolved in 50mL of deionized water, sprayed into the above materials in a spray manner, dried at 100℃ for 30min, and then calcined at 1000℃ for 4h, and cooled to obtain a cesium-doped single-crystal nickel-cobalt-manganese ternary positive electrode material.

[0051] Comparative Example 1

[0052] This comparative example provides a nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0053] The ternary nickel-cobalt-manganese precursor (500 g), lithium hydroxide (225 g), and zirconium oxide (3.38 g) were mixed and stirred evenly, transferred to a muffle furnace and calcined at 900° C. for 8 h, and cooled to obtain a single crystal nickel-cobalt-manganese ternary positive electrode material.

[0054] Comparative Example 2

[0055] This comparative example provides a nickel-cobalt-manganese ternary positive electrode material, and the specific preparation method is as follows:

[0056] The ternary nickel-cobalt-manganese precursor (500 g), lithium hydroxide (225 g), cesium hydroxide (4.00 g), and zirconium oxide (3.38 g) were mixed and stirred evenly, transferred to a muffle furnace and calcined at 900 ° C for 8 h. After cooling, a cesium-doped single crystal nickel-cobalt-manganese ternary positive electrode material was obtained.

[0057] Test example

[0058] The electrochemical performance of the materials obtained in each embodiment and comparative example was tested according to the following method:

[0059] The single crystal nickel-cobalt-manganese ternary positive electrode material prepared in the embodiment and the comparative example was used as the positive electrode active material, and the lithium sheet was used as the negative electrode to assemble a button battery. The composition of the positive electrode sheet is m (active material): m (acetylene black): m (PVDF) = 90:5:5. The test was carried out using a blue electric test system. The charge and discharge voltage was 2.5-4.3V, and the charge and discharge rate was 0.2C-5C. The cycle performance test was carried out at room temperature. After 50 cycles, the battery showed a good cycle life. Figure 5 As shown in the figure, the capacity retention rates of the three are similar, which shows that doping does not affect the stability of the battery; after charging and discharging at a rate of 5C, as shown in the figure, Figure 6 As shown, the rate retention rate of the step-by-step doped Cs single crystal nickel-cobalt-manganese ternary positive electrode material is 87.7%, the rate retention rate of the one-time doped Cs single crystal nickel-cobalt-manganese ternary positive electrode material is 85.6%, and the capacity retention rate of the unmodified ternary material is 79.5%. It can be seen that the technical solution of the present application can improve the rate retention rate, and the charge and discharge rate performance are significantly improved.

[0060] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will readily appreciate that other variations or modifications based on the above descriptions are possible. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a single crystal nickel-cobalt-manganese ternary positive electrode material, characterized in that: The steps include: S1: fully mix the ternary precursor, lithium source, zirconium oxide and the first cesium source, calcine at 400-600°C for 4-10 hours, and cool to obtain the first ternary positive electrode material; The ternary precursor is Ni x Co y Mn (1-x-y) (OH)2,0.6 <x<1.0,0<y<0.40; S2: dissolving the second cesium source in water, spraying the solution onto the first ternary cathode material and mixing the solution thoroughly, drying the solution, calcining the solution at 600-800°C for 4-10 hours, and cooling the solution to obtain the second ternary cathode material; S3: dissolving the third cesium source in water, spraying it into the second ternary cathode material and mixing thoroughly, drying it, calcining it at 800-1000°C for 4-10 hours, and cooling it to obtain a single-crystal nickel-cobalt-manganese ternary cathode material that is step-doped with cesium; The mass ratio of the first cesium source, the second cesium source, and the third cesium source is 0.5~1:0.5~1:0.5~1; Calculated by mass fraction, the sum of the masses of the first cesium source, the second cesium source, and the third cesium source accounts for 0.05-0.8% of the total mass of the single-crystal nickel-cobalt-manganese ternary positive electrode material; The zirconium oxide accounts for 0.1-1% of the total mass of the single crystal nickel-cobalt-manganese ternary positive electrode material.

2. The preparation method according to claim 1, characterized in that The lithium source is lithium hydroxide or lithium carbonate; The first cesium source, the second cesium source and the third cesium source are cesium hydroxide; The molar ratio of the sum of the nickel, cobalt and manganese elements in the ternary precursor to the lithium element in the lithium source is 1:1.00-1.

06.

3. The preparation method according to claim 1 or 2, characterized in that In steps S2 and S3, the drying temperature is not higher than 120°C, and the water content in the dried ternary positive electrode material is not higher than 500ppm.

4. A single crystal nickel-cobalt-manganese ternary positive electrode material, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 3.

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