A doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material and preparation method thereof

Abstract

The present invention discloses a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material and a preparation method thereof, the preparation method comprising: preparing an alkaline solution containing a doped ion compound as a base liquid for preparing a precursor and placing it in a reaction device, then adding a solution containing nickel salt, cobalt salt, manganese salt, an ammonia solution and a precipitant solution into a continuously stirred reaction device for chemical coprecipitation reaction, and after the reaction is completed, aging, centrifuging, washing and drying to obtain a doped nickel cobalt manganese oxide precursor; wherein the doped ion compound is a complex formed by citric acid and doped ions, a complex formed by sulfonic acid and doped ions, or a mixture of one or two, and the doped ion compound used is a nano-sized compound; the doped nickel cobalt manganese oxide precursor is mixed with a lithium salt, ball milled and sintered to obtain the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material. The preparation method of the present invention can reduce costs, increase production capacity, and the prepared positive electrode material has high capacity and good cycle performance.

Description

Technical Field

[0001] The present invention relates to the technical field of positive electrode material preparation, and in particular to a doped and modified nickel-cobalt-manganese-oxide lithium single crystal positive electrode material and a preparation method thereof. Background Art

[0002] As a new type of mobile energy storage device, lithium-ion batteries are expected to be widely used in various energy storage fields, such as static energy storage, smart grids and electric vehicles. Lithium-ion batteries are mainly composed of positive electrodes, negative electrodes, separators and electrolytes, among which the performance of positive electrode materials determines the performance of lithium-ion batteries. At present, nickel-cobalt-manganese ternary positive electrode materials have become the focus of research and development due to their advantages such as high operating voltage, energy density, low cost and environmental friendliness; however, there are still many problems and challenges. For example, nickel-cobalt-manganese ternary materials have a high operating voltage, energy density, low cost and environmental friendliness during the cycle, especially in high temperature environments. As Li + The material's microstructure will undergo an irreversible transformation during the deintercalation and insertion, and a series of complex side reactions will occur between the material surface and the electrolyte. The surface structural transformation of the material will also generate some byproducts, which will accelerate the deterioration of the positive electrode material and cause a serious attenuation of its capacity, thus limiting its further large-scale application. Therefore, in order to improve the electrical properties of the material and enhance the stability of the structure, the metal ions are doped into the bulk structure of the ternary material by bulk doping to further improve the structural stability of the material.

[0003] A Chinese patent application document with publication number CN104300145A discloses a method for preparing a high-tap modified nickel cobalt manganese oxide positive electrode material, which includes gradually adding a mixed solution of nickel salt, cobalt salt, manganese salt and a compound containing a doping element M and ammonia water to an alkaline base liquid containing organic matter at 30-80°C, maintaining the pH between 10.5-11.5 during the addition process, adjusting the pH to 11.5-12.5 after the addition is completed, and continuously stirring the reaction for 1-6 hours, separating and washing the solid part to a pH ≤ 8.0, and drying to obtain an intermediate; the compound of the doping element M is at least one of an oxide, a hydroxide, a carbonate or an acetate; a Chinese patent application document with publication number CN107565126A discloses a method for preparing a high-tap modified nickel cobalt manganese oxide positive electrode material by direct precipitation. A method for preparing a nickel-cobalt-manganese ternary material doped with divalent cations, wherein nickel compounds, cobalt compounds, manganese compounds, lithium compounds and compounds doped with divalent M ions are weighed respectively according to the molar ratio of nickel, cobalt, manganese, lithium and doped divalent M ions x:y:z:k:m; the nickel compounds, cobalt compounds, manganese compounds and compounds doped with divalent M ions are mixed to obtain a mixture 1, wherein the compound doped with divalent M ions is an oxide, hydroxide, nitrate, fluoride, chloride or acetate of copper, magnesium or calcium; the above patents also add metal salts in the precursor stage to greatly reduce the cost of material synthesis, but the doped metal salts are at least one of oxides, hydroxides, nitrates, fluorides, chlorides, acetates and carbonates. The doped metal salts described in the above two patents are conventional salts, most of which will dissolve in an alkaline environment and cannot provide the active sites required for precursor nucleation. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing a doped modified nickel cobalt manganese oxide single crystal positive electrode material with reduced cost and improved production capacity. The prepared positive electrode material has high structural stability and good battery capacity, rate performance and cycle performance.

[0005] The present invention solves the above technical problems through the following technical means:

[0006] A method for preparing a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material comprises the following steps:

[0007] S1. Prepare an alkaline solution containing a doping ion compound as a base solution for preparing a precursor and place it in a reaction device, then add a solution containing nickel salt, cobalt salt, manganese salt, an ammonia solution and a precipitant solution into the reaction device under continuous stirring to carry out a chemical coprecipitation reaction, and after the reaction is completed, age, centrifuge, wash and dry to obtain a doped nickel-cobalt-manganese precursor; wherein the doping ion compound is a complex formed by citric acid and doping ions, a complex formed by sulfonic acid and doping ions, or a mixture of two of the above, and the doping ion compound used is a nano-sized compound;

[0008] S2, mixing the doped nickel-cobalt-manganese precursor obtained in S1 with a lithium salt, ball-milling, and sintering to obtain the doped modified nickel-cobalt-manganese lithium oxide single crystal positive electrode material.

[0009] Beneficial effects: during the precursor preparation stage, complexes formed by citric acid and doped ions and complexes formed by sulfonic acid and doped ions are added, which are relatively stable in an alkaline environment and are not easily hydrolyzed and ionized in an alkaline environment. The presence of nanoparticles serves as nanocrystalline cores for the synthesis of nickel-cobalt-manganese precursors. During the synthesis process, the nickel-cobalt-manganese precursor will preferentially adhere to the surface of the nanoparticles due to surface adsorption to form a precursor. Citric acid and sulfonic acid are surfactants that can complex a large number of ions. After sintering, citric acid and sulfonic acid will react with oxygen to release gas to form pores inside the precursor. At the same time, ions are incorporated into the bulk phase of the precursor to synthesize a doped nickel-cobalt-manganese precursor. The material obtained therefrom can be used as a positive electrode to improve the capacity, rate performance and cycle performance of the battery.

[0010] Preferably, the complex formed by the citric acid and the doping ions is one of tungsten citrate, zirconium complex and zirconium citrate.

[0011] Preferably, the preparation method of the complex formed by the sulfonic acid and the dopant ion comprises the following steps: dissolving SrCl2 in ethanol, adding pyridine and stirring, then dropping an aqueous solution of sodium p-aminobenzenesulfonate, heating and stirring, and allowing the resulting solution to stand at room temperature for natural volatilization, and the precipitated product is the complex formed by the sulfonic acid and the dopant ion.

[0012] Preferably, in S1, the ions complexed by the doping ion compound include Mg 2+ 、Al 3+ 、Ti 4+ 、V 5+ , Fe 3+ 、As 3+ , Y 3+ 、Zr 4+ , Nb 5+ 、Mo 6+ , Sb 3+ , Sr 2+ 、Si4+ , W 6+ 、 5+ 、In 3+ , Ga 3+ 、Bi 3+ Sn 4+ ,La 3+ One or more of the above; the particle size of the doped ion compound is controlled at 50-500nm.

[0013] Preferably, the particle size of the doping ion compound is controlled to be below 200 nm.

[0014] Preferably, in S1, the concentration of the doped ion compound in the base solution is 5-20 mg / mL, and the pH of the base solution is controlled at 10.5-11.5; in the solution containing nickel salt, cobalt salt and manganese salt, the total concentration of nickel salt, cobalt salt and manganese salt is 1.0-2.5 mol / L; the concentration of the ammonia solution is 0.1-1.5 mol / L; the concentration of the precipitant solution is 1.0-5 mol / L.

[0015] Beneficial effect: The concentration of the doped ion compound in the base solution is 5-20 mg / mL, and the pH of the base solution is controlled at 10.5-11.5. In a high-concentration alkaline solution, the complex solution formed by citric acid and the doped ions and the complex solution formed by sulfonic acid and the doped ions are relatively stable, almost insoluble and do not undergo hydrolysis. As the nanocrystalline nucleus for precursor nucleation, it is beneficial for the doped ions to be incorporated into the matrix.

[0016] Preferably, in S1, the solution containing nickel salt, cobalt salt and manganese salt is prepared with nickel sulfate as nickel salt, cobalt sulfate as cobalt salt, manganese sulfate as manganese salt and water; the precipitant is one or a mixture of two of sodium carbonate and sodium hydroxide; in S2, the lithium salt is a mixture of one or more of Li2CO3, LiOH and CH3COOLi.

[0017] Preferably, in S1, the pH of the chemical coprecipitation reaction is 7.5-12.0, the stirring rate is 300-1500rpm, the reaction temperature is controlled between 50-60°C, and the reaction time is 10-20h; the solution containing nickel salt, cobalt salt and manganese salt is added to the continuously stirred reaction device in parallel with the ammonia solution and the precipitant solution, and the liquid feeding rate is 10-25ml / min.

[0018] Preferably, in S1, the aging time is 3-24 hours; the centrifugal speed is 2000-6000 rpm, and the centrifugal time is 3-15 minutes.

[0019] Preferably, in S1, the doped nickel-cobalt-manganese precursor is doped Ni x Coy Mn 1-x-y (OH)2, doped Ni x Co y Mn 1-x-y CO3 or a mixture of two thereof; wherein 0.5≤x≤1.0, 0≤y≤0.2; and in the doped nickel-cobalt-manganese precursor, the doping mass of the doped ions is 500-5500 ppm of the mass of the nickel-cobalt-manganese precursor.

[0020] Preferably, in S2, the sintering includes one-stage sintering and two-stage sintering; the temperature of the one-stage sintering is 400-600°C and the time is 5-15h; the temperature of the two-stage sintering is 700-910°C and the time is 10-20h.

[0021] Preferably, in S2, the ratio of the total amount of metal ions nickel, cobalt and manganese in the doped nickel-cobalt-manganese precursor to the total amount of lithium in the lithium salt is 1:0.98-1.15.

[0022] The present invention also provides a doped and modified nickel cobalt manganese oxide single crystal positive electrode material, which is prepared by using the preparation method of the doped and modified nickel cobalt manganese oxide single crystal positive electrode material.

[0023] The advantages of the present invention are:

[0024] 1. The present invention adds complexes formed by citric acid and doping ions and complexes formed by sulfonic acid and doping ions as doping ion compounds in the precursor preparation stage. The nanoparticles are relatively stable in an alkaline environment. The nanoparticles are used as nanocrystalline cores synthesized by nickel-cobalt-manganese precursors. During the synthesis process, the nickel-cobalt-manganese precursors will preferentially adhere to the surface of the nanoparticles to form a precursor due to surface adsorption, and can be used as active sites to greatly reduce the energy required for crystal nucleus growth. In addition, citric acid and sulfonic acid are surfactants that can complex a large number of doping ions. The doping ions will diffuse into the lattice of the nickel-cobalt-manganese material during the solid-phase sintering process to achieve the doping effect. In the precursor stage, the complexes formed by citric acid and doping ions and the complexes formed by sulfonic acid and doping ions are added for doping modification, which can greatly reduce the synthesis cost of the material.

[0025] 2. The present invention introduces complexes formed by citric acid and dopant ions and complexes formed by sulfonic acid and dopant ions in the precursor preparation stage, which can react with oxygen during the solid-phase sintering process to release gas to form pores inside the precursor, which is beneficial to the crushing of single crystal materials, thereby improving production capacity and reducing costs.

[0026] 3. The preparation method of the doped modified lithium nickel cobalt manganese oxide single crystal positive electrode material described in the present invention is simple, has abundant raw materials, low energy consumption, safe and reliable production process, low production cost, and is easy to mass produce. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a SEM image of the material prepared in Example 1 of the present invention;

[0028] Figure 2 This is the SEM image of the material prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described in combination with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] Unless otherwise specified, the test materials and reagents used in the following examples can be obtained from commercial sources.

[0031] If no specific techniques or conditions are specified in the examples, they can be carried out according to the techniques or conditions described in the literature in the art or according to the product instructions.

[0032] The preparation method of the tungsten citrate and zirconium complex in the embodiment comprises the following steps: dissolving monohydrated citric acid in deionized water to prepare an aqueous solution, adding ammonia water to adjust the pH to 7; adding tetrabutyl zirconate and ammonium tungstate in a ratio of 2:1 for tetrabutyl zirconate: citric acid and 1:2 for ammonium tungstate: citric acid, and reacting in a 75°C water bath for 3 hours under magnetic stirring. The upper clear liquid is separated, and the lower milky white sol-like precursor is obtained after drying at 75°C for 24 hours.

[0033] The preparation method of strontium sulfonate complex comprises the following steps: dissolving SrCl2 (1 mmol) in 5 ml of ethanol, adding pyridine (0.2 ml) and stirring, then dropping 5 ml of an aqueous solution containing sodium p-aminobenzenesulfonate (2 mmol), heating to 55° C. and stirring for 20 min, and then standing the obtained solution at room temperature for natural volatilization, and the product is precipitated after one week.

[0034] Example 1

[0035] A method for preparing a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material comprises the following steps:

[0036] S1. Mix tungsten citrate and zirconium complexes with a size of 50-100 nm with water to prepare a base liquid containing tungsten citrate and zirconium complexes, and add the mixture into a stainless steel reactor, wherein the concentration of tungsten citrate and zirconium complexes in the base liquid is 5 mg / ml, and the pH value of the base liquid is 11.5; mix nickel sulfate, cobalt sulfate, and manganese sulfate with water to prepare a nickel-cobalt-manganese sulfate solution with a total metal salt concentration of 2 mol / L, wherein the molar ratio of nickel sulfate: cobalt sulfate: manganese sulfate is 70:10:20, and prepare 0.5 mol / L ammonia solution and 4.0 mol / L sodium hydroxide solution; the nickel-cobalt-manganese sulfate solution, the ammonia solution and the sodium hydroxide solution were added in parallel to the above-mentioned stainless steel reactor under continuous stirring for reaction, during which the pH of the reaction was strictly controlled to be 11.2, the stirring rate was 800 rpm, the reaction temperature was 55°C, the liquid feeding rate was 15 ml / min, the reaction time was 10 h, and after 24 h of aging, centrifugation, washing, and vacuum drying at 110°C for 24 h were performed to obtain tungsten- and zirconium-doped Ni 0.7 Co 0.1 Mn 0.2 (OH)2 precursor, the centrifugal speed is 3500rpm, the centrifugal time is 5min, the doping mass of tungsten is similar to that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 1500ppm, and the doping mass of zirconium is about the same as that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 3000ppm;

[0037] S2, Ni doped with tungsten and zirconium 0.7 Co 0.1 Mn 0.2 The (OH)2 precursor is mixed with lithium hydroxide, ball-milled, and sintered to obtain the doped modified lithium nickel cobalt manganese oxide single crystal positive electrode material, wherein the tungsten and zirconium doped Ni 0.7 Co 0.1 Mn 0.2 The ratio of the total amount of nickel, cobalt and manganese metal ions in the (OH)2 precursor to the amount of lithium in the lithium hydroxide is 1:1.03, and the sintering step is first sintering at 600°C for 8 hours and then sintering at 880°C for 12 hours.

[0038] Example 2

[0039] A method for preparing a doped modified nickel cobalt manganese oxide single crystal positive electrode material, wherein a precursor is prepared according to step S1 in Example 1, except that the base solution contains a strontium sulfonate complex, and the concentration of the strontium sulfonate complex is 20 mg / ml. Other conditions and steps are the same as those in step S1 in Example 1, and the doping mass of strontium is the same as that of Ni 0.7 Co0.1 Mn 0.2 The mass ratio of the (OH)2 precursor is 1500ppm, and then the doped modified lithium nickel cobalt manganese oxide single crystal positive electrode material is prepared according to step S2 in Example 1; the size of the strontium sulfonate complex used is 50-100nm.

[0040] Example 3

[0041] A method for preparing a doped and modified nickel cobalt manganese oxide single crystal positive electrode material, wherein a precursor is prepared according to step S1 in Example 1, except that the doping mass of tungsten citrate and zirconium complex is changed, and the doping mass of tungsten is different from that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 500ppm, and the doping mass of zirconium is about the same as that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of the (OH)2 precursor is 5000 ppm; the other parameters are the same as those in Example 1.

[0042] Example 4

[0043] A method for preparing a doped and modified nickel cobalt manganese oxide single crystal positive electrode material, wherein a precursor is prepared according to step S1 in Example 1, except that the base solution contains a strontium sulfonate complex and a zirconium citrate complex, but does not contain tungsten citrate and zirconium complexes, and the total concentration of the metal complex is 20 mg / ml. Other conditions and steps are the same as those in S1 in Example 1, wherein the doping mass of strontium is the same as that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 1500ppm, and the doping mass of zirconium is about the same as that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of the (OH)2 precursor is 2500ppm, and then the doped modified lithium nickel cobalt manganese oxide single crystal positive electrode material is prepared according to step S2 in Example 1; the sizes of the strontium sulfonate complex and zirconium citrate complex used are both 50-100nm.

[0044] Example 5

[0045] A method for preparing a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material comprises the following steps:

[0046] S1. Mix tungsten citrate and zirconium complexes with a size of 50-100 nm with water to obtain a base liquid containing tungsten citrate and zirconium complexes, and add the mixture into a stainless steel reactor, wherein the concentration of tungsten citrate and zirconium complexes in the base liquid is 5 mg / ml, and the pH value of the base liquid is 10.5; mix nickel sulfate, cobalt sulfate, and manganese sulfate with water to prepare a nickel-cobalt-manganese sulfate solution with a total metal salt concentration of 1 mol / L, wherein the molar ratio of nickel sulfate: cobalt sulfate: manganese sulfate is 50:20:30, and 0.1 mol / L is prepared. L of ammonia solution and 1.0 mol / L of sodium carbonate aqueous solution; the nickel cobalt manganese sulfate solution, the ammonia solution and the sodium carbonate aqueous solution are added in parallel to the above-mentioned stainless steel reactor under continuous stirring for reaction, during which the pH of the reaction is strictly controlled to be 7.5, the stirring rate is 300 rpm, the reaction temperature is 60°C, the liquid feeding rate is 10 ml / min, the reaction time is 20 h, and after aging for 15 h, centrifugation, washing, and vacuum drying at 110°C for 24 h are obtained to obtain tungsten- and zirconium-doped Ni 0.5 Co 0.2 Mn 0.3 CO3 precursor, the centrifugal speed is 2000rpm, and the centrifugal time is 15min; the doping mass of tungsten is similar to that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 1500ppm, and the doping mass of zirconium is about the same as that of Ni 0.7 Co 0.1 Mn 0.2 The mass ratio of (OH)2 precursor is 3000ppm;

[0047] S2, Ni doped with tungsten and zirconium 0.5 Co 0.2 Mn 0.3 The CO3 precursor is mixed with lithium carbonate, ball-milled, and sintered to obtain a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material, wherein the tungsten and zirconium doped Ni 0.5 Co 0.2 Mn 0.3 The ratio of the total amount of metal ions nickel, cobalt and manganese in the CO3 precursor to the amount of lithium in the lithium carbonate is 1:1.15. The sintering step is first sintering at 500°C for 15 hours and then sintering at 910°C for 10 hours.

[0048] Comparative Example 1

[0049] S1. First, nickel sulfate, cobalt sulfate, manganese sulfate and water are mixed to prepare a nickel-cobalt-manganese sulfate solution with a total metal salt concentration of 2.0 mol / L, wherein the molar ratio of nickel sulfate: cobalt sulfate: manganese sulfate is 70:10:20, and then 0.5 mol / L ammonia solution and 4.0 mol / L sodium hydroxide aqueous solution are prepared, and the nickel-cobalt-manganese sulfate solution, ammonia solution and sodium hydroxide aqueous solution are added to a stainless steel reactor with continuous stirring in parallel to react. In this process, the reaction pH is strictly controlled to be 11.2, the stirring rate is 800 rpm, the reaction temperature is 55° C., the liquid feeding rate is 15 ml / min, and the reaction time is 10 h. After aging for 24 h, centrifugation, washing, and vacuum drying at 110° C. for 24 h are performed to obtain Ni 0.7 Co 0.1 Mn 0.2 (OH)2 precursor, wherein the centrifugal speed is 3500 rpm and the centrifugal time is 5 min;

[0050] S2, Ni 0.7 Co 0.1 Mn 0.2 The (OH)2 precursor was mixed with lithium hydroxide, ball-milled and sintered to obtain modified LiNi 0.7 Co 0.1 Mn 0.2 O2 positive electrode material, wherein the Ni 0.7 Co 0.1 Mn 0.2 The ratio of the total amount of metal ions nickel, cobalt and manganese in the (OH)2 precursor to the amount of lithium in the lithium hydroxide is 1:1.03, and the sintering step is first sintering at 600°C for 8 hours and then sintering at 880°C for 12 hours.

[0051] Comparative Example 2

[0052] S1. First, nickel sulfate, cobalt sulfate, manganese sulfate and water are mixed to prepare a nickel-cobalt-manganese sulfate solution with a total metal salt concentration of 2.0 mol / L, wherein the molar ratio of nickel sulfate: cobalt sulfate: manganese sulfate is 70:10:20, and then 0.5 mol / L ammonia solution and 4.0 mol / L sodium hydroxide aqueous solution are prepared, and the nickel-cobalt-manganese sulfate solution, ammonia solution and sodium hydroxide aqueous solution are added to a stainless steel reactor with continuous stirring in parallel to react. In this process, the reaction pH is strictly controlled to be 11.2, the stirring rate is 800 rpm, the reaction temperature is 55° C., the liquid feeding rate is 15 ml / min, and the reaction time is 10 h. After aging for 24 h, centrifugation, washing, and vacuum drying at 110° C. for 24 h are performed to obtain Ni 0.7 Co 0.1 Mn 0.2(OH)2 precursor, wherein the centrifugal speed is 3500 rpm and the centrifugal time is 5 min;

[0053] S2, Ni 0.7 Co 0.1 Mn 0.2 The (OH)2 precursor, lithium hydroxide and tungsten oxide are mixed, ball-milled and sintered to obtain tungsten-doped LiNi 0.7 Co 0.1 Mn 0.2 O2 positive electrode material, wherein the Ni 0.7 Co 0.1 Mn 0.2 The ratio of the total amount of metal ions nickel, cobalt, and manganese in the (OH)2 precursor to the amount of lithium in lithium hydroxide is 1:1.03. 0.7 Co 0.1 Mn 0.2 The mass ratio of the (OH)2 precursor is 0.2:100, and the sintering step is first sintering at 600°C for 8 hours and then sintering at 880°C for 12 hours.

[0054] The finished products prepared in Examples 1-5 and Comparative Examples 1-2 were used as positive electrode materials, lithium sheets as negative electrodes, superconducting carbon black Super P as conductive agents, polyvinylidene fluoride (PVDF) as binders, and N-methylpyrrolidone (NMP) as solvents. The single crystal material and superconducting carbon black Super P were ground and then added to a solution of N-methylpyrrolidone dissolved with polyvinylidene fluoride. The mass ratio of the single crystal material, Super P and PVDF was 8:1:1. After stirring for 2 hours, the mixture was coated on the surface of a 20 μm thick aluminum foil and then vacuum dried at 110 ° C for 20 hours. The dried pole piece was rolled, sliced, and weighed, and then assembled into a CR2016 button cell with a metal lithium sheet and a diaphragm prepared by a wet process in an argon atmosphere glove box. The electrolyte was 1.0 mol / LLiPF6 / EC+DEC+EMC. The assembled button cell was subjected to electrochemical performance testing, and the test voltage range was 2.8-4.35V. Detailed data are shown in Table 1.

[0055] Table 1 Electrical performance data of Examples 1-5 and Comparative Examples 1-2

[0056]

[0057] According to the data in the above table, Example 1 introduces metal ions of tungsten and zirconium during the precursor synthesis process, and during the sintering process, the metal ions of tungsten and zirconium can be relatively evenly incorporated into the matrix material, and small pores are left, which is convenient for crushing on the one hand, and can improve the rate performance of the material on the other hand. From the electrical performance data, it can be seen that Example 1 exhibits a higher capacity, while the rate performance is better and the cycle performance is improved; while Comparative Example 1 does not incorporate any modifying elements, so the capacity and cycle performance are relatively poor; Comparative Example 2 adds the doping element tungsten oxide in the precursor mixing stage, which is a physical mixing. This doping method cannot be evenly incorporated into the matrix, so the performance is slightly worse than that of Example 1. Figure 1 and Figure 2 It can be seen from the SEM image that the particles in Example 1 present a good single crystal morphology, while there are many agglomerates in Comparative Example 1 that are not completely broken apart, indicating that the particles in Example 1 are easier to break apart and present a good single crystal morphology.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material, characterized in that: The following steps are involved: S1. Prepare an alkaline solution containing a doping ion compound as a base solution for preparing a precursor and place it in a reaction device, then add a solution containing nickel salt, cobalt salt, manganese salt, an ammonia solution and a precipitant solution into the reaction device for continuous stirring to carry out a chemical coprecipitation reaction, and after the reaction is completed, age, centrifuge, wash and dry to obtain a doped nickel-cobalt-manganese precursor; wherein the doping ion compound is a complex formed by citric acid and doping ions, a complex formed by sulfonic acid and doping ions, or a mixture of two of them, and the doping ion compound used is a nano-sized compound; the particle size of the doping ion compound is controlled to be 50-500nm; the doped nickel-cobalt-manganese precursor is doped Ni x Co y Mn 1-x-y (OH)2, doped Ni x Co y Mn 1-x-y CO3 or a mixture of one or two thereof; wherein 0.5≤x≤1.0, 0<y≤0.2; the ions complexed by the doping ion compound include Mg 2+ 、Al 3+ 、Ti 4+ 、V 5+ , Fe 3+ 、As 3+ , Y 3+ 、Zr 4+ , Nb 5+ 、Mo 6+ , Sb 3+ , Sr 2+ 、Si 4+ , W 6+ 、 5+ 、In 3+ , Ga 3+ 、Bi 3+ Sn 4+ ,La 3+ One or more of; S2, mixing the doped nickel-cobalt-manganese precursor obtained in S1 with a lithium salt, ball-milling, and sintering to obtain the doped modified nickel-cobalt-manganese lithium oxide single crystal positive electrode material.

2. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S1, the concentration of the doped ion compound in the base solution is 5-20 mg / mL, and the pH of the base solution is controlled at 10.5-11.5; in the solution containing nickel salt, cobalt salt and manganese salt, the total concentration of nickel salt, cobalt salt and manganese salt is 1.0-2.5 mol / L; the concentration of the ammonia solution is 0.1-1.5 mol / L; and the concentration of the precipitant solution is 1.0-5 mol / L.

3. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S1, the solution containing nickel salt, cobalt salt and manganese salt is prepared with nickel sulfate as nickel salt, cobalt sulfate as cobalt salt, manganese sulfate as manganese salt and water; the precipitant is one or a mixture of sodium carbonate and sodium hydroxide; in S2, the lithium salt is a mixture of one or more of Li2CO3, LiOH and CH3COOLi.

4. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S1, the pH of the chemical coprecipitation reaction is 7.5-12.0, the stirring rate is 300-1500rpm, the reaction temperature is controlled between 50-60°C, and the reaction time is 10-20h; the solution containing nickel salt, cobalt salt, and manganese salt is added to the continuously stirred reaction device in parallel with the ammonia solution and the precipitant solution, and the liquid feeding rate is 10-25ml / min.

5. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S1, the aging time is 3-24 hours; the centrifugal speed is 2000-6000 rpm, and the centrifugal time is 3-15 minutes.

6. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S1, in the doped nickel-cobalt-manganese precursor, the doping mass of the doping ions is 500-5500 ppm of the mass of the nickel-cobalt-manganese precursor.

7. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to claim 1, characterized in that: In S2, the sintering includes one-stage sintering and two-stage sintering; the temperature of the one-stage sintering is 400-600°C and the time is 5-15h; the temperature of the two-stage sintering is 700-910°C and the time is 10-20h.

8. The method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material according to any one of claims 1 to 7, characterized in that: In S2, the ratio of the total amount of metal ions nickel, cobalt and manganese in the doped nickel-cobalt-manganese precursor to the total amount of lithium in the lithium salt is 1:0.98-1.

15.

9. A doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material, characterized in that: The material is prepared by the method for preparing the doped and modified lithium nickel cobalt manganese oxide single crystal positive electrode material as described in any one of claims 1 to 8.

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