High-capacity long-circulation high-nickel positive electrode material and preparation method

Abstract

The application provides a high-capacity long-cycle high-nickel positive electrode material and a preparation method thereof. The high-nickel positive electrode material is a compound shown in the following general formula: Li a Ni x Co y Mn z M 1‑x‑y‑z O2, M is selected from one or more of V, Ta, Nb, Sr, Mo, Mg, Al, Zr, Ti, Ca, La and W, 0.80<=a<=1.20, 0.6<=x<=1.0. The material can form an ion complex with lithium ions. When the compound is added to an aqueous solution, lithium ions can be complexed and then attached to the surface of the high-nickel positive electrode material, so that the excessive escape of lithium ions is prevented, the structural lithium loss of the material in the water washing process is minimized, and the high-nickel positive electrode material with the high-capacity characteristic is prepared.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of lithium ion batteries, and in particular, the present application relates to a high-capacity long-cycle high-nickel positive electrode material and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries have the advantages of high working voltage, high specific energy, long cycle life, light weight, low self-discharge, and high cost performance, and have broad application prospects in electronic devices, electric vehicles, space technology, and national defense industry, etc. At present, the ternary material used in the market is mainly 523, but it still cannot meet the demand of consumers for energy density. Therefore, people consider increasing the content of nickel in the material to increase the capacity of the material. Common high-nickel materials include NCM811, NC91, and NCA specifications, etc. The 0.2C gram capacity of which can reach more than 190mAh / g, which is more than 15% higher than 523.

[0003] In recent years, with the rapid development of electric vehicles and other technologies, the demand for high-energy-density secondary batteries is increasing. Therefore, research on high-nickel positive electrode materials with excellent capacity characteristics is actively being carried out. SUMMARY

[0004] The inventors found that the residual lithium on the surface of the high-nickel positive electrode material is high, which can cause negative effects such as slurry jelly and cell gas production. The residual lithium on the surface of the particles after high-temperature sintering is usually removed by water washing treatment. Although the residual lithium on the surface is removed by this water washing process, lithium ions inside the high-nickel positive electrode material are easy to escape and form NiO, NiOOH, etc. on the surface of the material, so that a lithium-deficient state is formed on the surface of the material, which leads to a decrease in the capacity of the material. In order to solve the above problems, it is necessary to inhibit the escape of lithium ions inside the high-nickel positive electrode material during water washing, remove the residual lithium on the surface, and at the same time, the surface will not form a lithium-deficient state, thereby improving the capacity of the high-nickel positive electrode material and reducing the internal resistance. The purpose of the present application is to provide a high-capacity long-cycle high-nickel positive electrode material and a preparation method thereof. By adding a compound to inhibit the escape of lithium ions inside the high-nickel positive electrode active material, the capacity of the high-nickel positive electrode material is improved and the internal resistance is reduced. At the same time, this compound contains boron element, and the uniformity of boron coating of the high-nickel positive electrode material is improved by the strategy of wet coating, thereby improving the cycle life performance of the material.

[0005] In one aspect of the present application, a high-capacity long-cycle high-nickel positive electrode material is provided. According to an embodiment of the present application, the high-nickel positive electrode material is a compound represented by the following general formula: Li a Ni x Co y Mn z M 1-x-y-zO2, M is selected from one or more of V, Ta, Nb, Sr, Mo, Mg, Al, Zr, Ti, Ca, La and W, 0.80≤a≤1.20, 0.6≤x≤1.0. The compound can form an ionic complex with lithium ions, and when the compound is added to an aqueous solution, the lithium ions can be complexed and then attached to the surface of the high-nickel positive electrode material, preventing excessive escape of lithium ions, so that the structural lithium loss of the material during the water washing process is minimized, and a high-nickel positive electrode material with high capacity characteristics is prepared.

[0006] According to the embodiments of the present application, the high-capacity long-cycle high-nickel positive electrode material described above can further include at least one of the following additional technical features:

[0007] According to the embodiments of the present application, the high-nickel positive electrode material is LiNi 0.90 Co 0.04 Mn 0.05 Zr 0.01 O2. The compound can form an ionic complex with lithium ions, and when the compound is added to an aqueous solution, the lithium ions can be complexed and then attached to the surface of the high-nickel positive electrode material, preventing excessive escape of lithium ions, so that the structural lithium loss of the material during the water washing process is minimized, and a high-nickel positive electrode material with high capacity characteristics is prepared.

[0008] In another aspect of the present application, the present application further provides a method for preparing a high-capacity long-cycle high-nickel positive electrode material. According to the embodiments of the present application, the method comprises:

[0009] 1) performing a first sintering treatment on a precursor and a lithium source, the chemical formula of the precursor being Ni x Co y Mn z M 1-x-y-z (OH)2, so as to obtain a first material,

[0010] 2) mixing the first material with an aqueous solution containing a boron compound, and performing a drying treatment, so as to obtain a second material;

[0011] 3) performing a second sintering treatment on the second material, so as to obtain the high-capacity long-cycle high-nickel positive electrode material, the high-nickel positive electrode material being a compound represented by the general formula: Li a Ni x Co y Mn z M 1-x-y-zO2, M is selected from one or more of V, Ta, Nb, Sr, Mo, Mg, Al, Zr, Ti, Ca, La and W, 0.80≤a≤1.20, 0.6≤x≤1.0. The method according to the embodiment of the present application can prepare a compound capable of forming an ion complex with lithium ions, and the compound added in the aqueous solution can complex lithium ions to adhere to the surface of the high-nickel positive electrode material, prevent excessive escape of lithium ions, minimize the structural lithium loss of the material in the water washing process, and prepare a high-nickel positive electrode material with high capacity characteristics; and the added compound contains boron elements, and a boron element-containing coating layer is formed at the interface when complexing lithium ions, so compared with the traditional dry method of coating boron elements, the wet coating method can improve the uniformity of the coating and improve the cycle life of the high-nickel material.

[0012] According to the embodiments of the present application, the above method can further include at least one of the following additional technical features:

[0013] According to the embodiments of the present application, the precursor is Ni 0.90 Co 0.04 Mn 0.05 Zr 0.01 (OH)2.

[0014] According to the embodiments of the present application, the high-nickel positive electrode material is LiNi 0.90 Co 0.04 Mn 0.05 Zr 0.01 O2.

[0015] According to the embodiments of the present application, the lithium source is one or a combination of lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, and lithium phosphate.

[0016] According to the embodiments of the present application, the molar ratio of lithium in the lithium source to the sum of nickel, cobalt, manganese and M elements in the precursor is 0.80-1.20:1.

[0017] According to the embodiments of the present application, the D50 of the precursor is 3-20um. In this range, the initial charge-discharge efficiency is excellent, and the initial internal resistance can be reduced.

[0018] According to the embodiments of the present application, the D50 of the precursor is 10-13um. In this range, the initial charge-discharge efficiency is more excellent, and the initial internal resistance can be reduced.

[0019] According to the embodiments of the present application, the BET of the precursor is 3-10m 2 / g. In this range, the uniformity of material sintering can be further improved.

[0020] According to the embodiments of the present application, the BET of the precursor is 5-7m 2 / g. The uniformity of sintering of the material can be further improved within this range.

[0021] According to an embodiment of the present application, the first sintering process is performed in an oxygen atmosphere.

[0022] According to an embodiment of the present application, the sintering temperature of the first sintering process is 650°C to 1000°C. When the sintering temperature is less than 650°C, the raw material remains in the particles due to insufficient reaction, which can decrease the high-temperature stability of the battery, and can decrease the bulk density and the crystallinity, thereby decreasing the structural stability. On the other hand, when the sintering temperature exceeds 1000°C, non-uniform growth of the particles can occur, and the particles are difficult to break, thereby decreasing the capacity.

[0023] According to an embodiment of the present application, the sintering temperature of the first sintering process is 650°C to 880°C.

[0024] According to an embodiment of the present application, the sintering time of the first sintering process is 5 to 30 hours. When the sintering time is less than 5 hours, the reaction time is too short to obtain a positive active material having high crystallinity, and when the sintering time exceeds 30 hours, the particle size is too large, thereby decreasing the production efficiency.

[0025] According to an embodiment of the present application, the sintering time of the first sintering process is 7 to 15 hours.

[0026] According to an embodiment of the present application, the boron-containing compound in the aqueous solution of the boron-containing compound is one or a combination of two or more of lithium tetramethylborate, lithium bisoxalateborate, and lithium tetrahydroxyborate.

[0027] According to an embodiment of the present application, the molar concentration of the aqueous solution of the boron-containing compound is 0.01M to 0.58M. When the concentration of the compound capable of forming an ionic complex with lithium cations in the water washing solution is less than 0.01M, the lithium cations and the complex cannot sufficiently form on the surface of the positive active material, thereby causing lithium ions to escape from the inside of the positive active material, thus causing a decrease in capacity. When the concentration of the compound capable of forming an ionic complex with lithium cations in the water washing solution exceeds 0.58M, the coating layer formed on the surface of the positive active material is too thick, thereby increasing the surface resistance, causing a decrease in high-temperature life characteristics, and increasing the manufacturing cost of the positive active material.

[0028] According to an embodiment of the present application, the molar concentration of the aqueous solution of the boron-containing compound is 0.06M to 0.38M.

[0029] According to an embodiment of the present application, the molar concentration of the aqueous solution of the boron-containing compound is 0.08M to 0.25M.

[0030] According to an embodiment of the present application, the molar ratio of the total moles of Ni, Co, Mn and M in the precursor to the moles of boron is 100:0.07 to 100:3. When the molar ratio is less than 100:0.07, a uniform coating layer cannot be formed, resulting in problems of reduced capacity and reduced cycle life characteristics. When the molar ratio is greater than 100:3, the coating layer formed on the surface of the positive active material is too thick, resulting in problems of increased surface resistance, reduced cycle life characteristics, and increased manufacturing cost.

[0031] According to an embodiment of the present application, the molar ratio of the total moles of Ni, Co, Mn and M in the precursor to the moles of boron is 100:0.25 to 100:2.5.

[0032] According to an embodiment of the present application, the weight ratio of the first material to the aqueous solution is 1 to 2:1. Within this range, residual lithium can be washed away, and the material surface can be prevented from being excessively washed, resulting in lithium deficiency.

[0033] According to an embodiment of the present application, the weight ratio of the first material to the aqueous solution is 1.5 to 2. According to an embodiment of the present application,

[0034] Optionally, the temperature of the aqueous solution is 0 to 20°C. Within this range, residual lithium can be washed away, and the material surface can be prevented from being excessively washed, resulting in lithium deficiency.

[0035] According to an embodiment of the present application, the temperature of the aqueous solution is 0 to 5°C. Within this range, residual lithium can be washed away, and the material surface can be prevented from being excessively washed, resulting in lithium deficiency.

[0036] According to an embodiment of the present application, the drying treatment is performed in a vacuum environment.

[0037] According to an embodiment of the present application, the drying temperature of the drying treatment is 50 to 250°C. Within this range, moisture can be dried, and lithium in the structure can not be diffused to the surface.

[0038] According to an embodiment of the present application, the drying temperature of the drying treatment is 130 to 150°C. Within this range, moisture can be dried, and lithium in the structure can not be diffused to the surface.

[0039] According to an embodiment of the present application, the drying time of the drying treatment is 1 to 10 hours. Within this range, moisture can be dried, and lithium in the structure can not be diffused to the surface.

[0040] According to an embodiment of the present application, the drying time of the drying treatment is 2 to 5 hours. Within this range, moisture can be dried, and lithium in the structure can not be diffused to the surface.

[0041] According to an embodiment of the present application, the second sintering treatment is performed at a temperature of 100-400°C. In this range, the cycle life of the battery is further improved while preventing capacity reduction.

[0042] According to an embodiment of the present application, the second sintering treatment is performed at a temperature of 250-350°C. In this range, the cycle life of the battery is further improved while preventing capacity reduction.

[0043] According to an embodiment of the present application, the second sintering treatment is performed for a time of 3-10h. In this range, the cycle life of the battery is further improved while preventing capacity reduction.

[0044] According to an embodiment of the present application, the second sintering treatment is performed for a time of 5-8h. In this range, the cycle life of the battery is further improved while preventing capacity reduction.

[0045] In still another aspect of the present application, a method for preparing the long-cycle high-nickel cathode material as described above. According to an embodiment of the present application, the method comprises the following steps:

[0046] S1: mixing a precursor with a lithium source and sintering in a chamber atmosphere furnace, crushing to obtain a first material, the chemical formula of the precursor is Ni x Co y Mn z M 1-x-y-z (OH)2, wherein 0.6≤x≤1.0;

[0047] S2: adding the first material into an aqueous solution containing a boron compound, the boron compound in the aqueous solution forms a complex with the lithium ions escaping from the high-nickel cathode material, the complex adheres to the surface of the cathode material, which can effectively inhibit the escape of lithium ions from the interior of the high-nickel cathode active material during the water washing process, and the washed material is dried at a certain temperature to obtain a second material;

[0048] S3: sintering the second material at a certain temperature and crushing to obtain the required high-capacity long-cycle high-nickel cathode material.

[0049] According to an embodiment of the present application, in the step S1, the lithium source is one or a combination of lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, and lithium phosphate.

[0050] According to an embodiment of the present application, in the step S1, the molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, manganese, and M elements in the nickel-cobalt-manganese hydroxide precursor is 0.80-1.20:1.

[0051] According to an embodiment of the present application, the precursor in the S1 step has a D50 of 3-20 um, preferably 10-13 um, in which range the initial charge-discharge efficiency is excellent, and the initial internal resistance can be reduced.

[0052] According to an embodiment of the present application, the precursor in the S1 step has a BET of 3-10 m 2 / g, preferably 5-7 m 2 / g, in which range the uniformity of sintering of the material can be further improved.

[0053] According to an embodiment of the present application, the sintering in the S1 step is performed in an oxygen atmosphere, and the sintering temperature is 650-1000°C, preferably 650-880°C. When the sintering temperature is lower than 650°C, the raw material remains in the particles due to insufficient reaction, which reduces the high-temperature stability of the battery, and reduces the bulk density and crystallinity, thereby reducing the structural stability. On the other hand, when the sintering temperature exceeds 1000°C, non-uniform growth of the particles can occur, and the particles are difficult to break, thereby reducing the capacity. The sintering time is 5-30 h, preferably 7-15 h. When the sintering time is less than 5 h, the reaction time is too short, and a positive electrode active material with high crystallinity cannot be obtained. When the sintering time exceeds 30 h, the particle size is too large, and the production efficiency is reduced.

[0054] According to an embodiment of the present application, the weight ratio of the first material to the aqueous solution in the S2 step is 1-2:1, preferably 1.5-2:1, and the temperature of the aqueous solution is 0-20°C, preferably 0-5°C, and the washing time is 1-10 min, preferably 2-4 min, in which range the residual lithium can be washed away, and the material surface can be prevented from being excessively washed, thereby preventing lithium deficiency.

[0055] According to an embodiment of the present application, the compound containing boron in the S2 step is one or a combination of two or more of lithium tetramethylborate, lithium bis-oxalate borate, and lithium tetrahydroxyborate.

[0056] According to an embodiment of the present application, the molar concentration of the compound containing boron in the S2 step is 0.01M-0.58M, preferably 0.06M-0.38M, and more preferably 0.08M-0.25M. When the concentration of the compound capable of forming an ionic complex with lithium cations in the water washing solution is less than 0.01M, the lithium cations and the complex cannot sufficiently form on the surface of the positive electrode active material, thereby causing lithium ions to escape from the inside of the positive electrode active material, and thus the capacity is reduced. When the concentration of the compound capable of forming an ionic complex with lithium cations in the water washing solution exceeds 0.58M, the coating layer formed on the surface of the positive electrode active material is too thick, which increases the surface resistance, and thus the high-temperature life characteristics are reduced, and the manufacturing cost of the positive electrode active material is increased.

[0057] According to the embodiment of the present application, the total moles of Ni, Co, Mn and M and the moles of boron in the S2 step are in a ratio of 100:0.07-100:3, preferably 100:0.25-100:2.5. When the ratio is less than 100:0.0.7, a uniform coating layer cannot be formed, resulting in problems of reduced capacity and reduced cycle life characteristics. When the ratio is greater than 100:3, the coating layer formed on the surface of the positive active material is too thick, resulting in problems of increased surface resistance, reduced cycle life characteristics, and increased manufacturing costs.

[0058] According to the embodiment of the present application, the drying in the S2 step is performed in a vacuum environment at a temperature of 50-250°C, preferably 130-150°C, for 1-10 hours, preferably 2-5 hours. Within this range, the moisture can be dried, and lithium in the structure can not diffuse to the surface.

[0059] According to the embodiment of the present application, the sintering in the S3 step is performed at a temperature of 100-400°C, preferably 250-350°C, for 3-10 hours, preferably 5-8 hours. Within this range, the capacity can be prevented from being reduced, and the cycle life of the battery can be further improved.

[0060] According to the embodiment of the present application, the present application has at least one of the following technical effects:

[0061] 1) In the present application, a compound capable of forming an ionic complex with lithium ions is used. When the compound is added to an aqueous solution, the lithium ions can be complexed and attached to the surface of the high-nickel positive electrode material, preventing excessive escape of lithium ions, minimizing the loss of structural lithium during the washing process, and preparing a high-nickel positive electrode material with high capacity characteristics.

[0062] 2) The added compound contains boron elements. When the lithium ions are complexed, a boron element-containing coating layer is formed at the interface. Therefore, compared with the traditional dry boron element coating method, the wet coating method can improve the uniformity of the coating and improve the cycle life of the high-nickel material. BRIEF DESCRIPTION OF DRAWINGS

[0063] The above and / or additional aspects and advantages of the present application will become apparent and more readily appreciated from the following description, taken in conjunction with the following drawings of which:

[0064] Figure 1 is an SEM (scanning electron microscope) photo of the high-nickel positive electrode material prepared in Example 1 in the present application at 10000 times magnification;

[0065] Figure 2 is an SEM (scanning electron microscope) photo of the high-nickel positive electrode material prepared in Example 2 in the present application at 10000 times magnification;

[0066] Figure 3 FIG. 17 is a SEM (scanning electron microscope) photograph of a high-nickel positive electrode material prepared in Example 3 at 10,000 times magnification. DETAILED DESCRIPTION

[0067] Embodiments of the present application are described in detail below with reference to the attached drawings. The embodiments described below are examples of the present application, and are intended to explain the present application, and should not be understood as limiting the present application.

[0068] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be understood as limiting the present application.

[0069] In addition, the terms "first", "second", etc. are used only for descriptive purposes, and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, such as two, three, etc., unless otherwise explicitly specified and limited.

[0070] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing" and the like should be broadly understood, for example, can be fixedly connected, or can be detachably connected, or can be integrated; can be mechanically connected, or can be electrically connected; can be directly connected, or can be indirectly connected through an intermediate medium; can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0071] In the present application, unless otherwise explicitly specified and limited, a first feature is "on" or "under" a second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "over", "above" and "on top of" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature is "under", "below" and "underneath" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0072] The present application is described below with reference to specific embodiments, it should be noted that these embodiments are merely descriptive, and do not limit the present application in any way.

[0073] Embodiment 1

[0074] The present embodiment provides a high-capacity long-circulation high-nickel positive electrode material, which is a compound as shown in the following formula: LiNi 0.90 Co 0.04 Mn 0.05 Zr 0.01 O2;its preparation method comprises the following steps:

[0075] S1, take 1000g of precursor Ni 0.90 Co 0.04 Mn 0.05 Zr 0.01 (OH)2, 470g of LiOH.H2O is added to the high-speed mixer, first stirred at 300rpm for 5min, then stirred at 1000rpm for 25min, and then discharged; load into a mullite box, place the box in a box-type atmosphere furnace, pass oxygen, rise to 785℃, and keep constant temperature for 5h, then discharge after the furnace temperature cools to room temperature, and coarsely crush the discharge through a roller device to obtain a first material;

[0076] S2, take 500g of the first material and add 400g of an aqueous solution, wherein the molar concentration of lithium bismalonate borate in the aqueous solution is 0.02M, the water temperature is controlled at 2℃, and stirred for 2min, then separated and filtered by a filter press to obtain a product with a water content of 2%-10%, and then dried at 140℃ under vacuum for 4h to obtain a second material;

[0077] S3, load the second material into a mullite box, place the box in a box-type atmosphere furnace, pass oxygen, rise to 280℃, and keep constant temperature for 6h, then discharge after the furnace temperature cools to room temperature, coarsely crush the discharge through a roller device, remove iron, and pass through a 350-mesh screen to obtain a high-nickel positive electrode material.

[0078] Embodiment 2

[0079] In Example 2, the high-nickel positive electrode material was prepared in the same manner as in Example 1, except that the molar concentration of lithium bis-oxalate borate in the aqueous solution in the S2 step was 0.06 M.

[0080] Example 3

[0081] In Example 3, the high-nickel positive electrode material was prepared in the same manner as in Example 1, except that the molar concentration of lithium bis-oxalate borate in the aqueous solution in the S2 step was 0.1 M.

[0082] Comparative Example 1

[0083] In Comparative Example 1, the high-nickel positive electrode material was prepared in the same manner as in Example 1, except that the aqueous solution in the S2 step was deionized water and nothing was added.

[0084] Comparative Example 2

[0085] In Comparative Example 3, the high-nickel positive electrode material was prepared in the same manner as in Example 1, except that the aqueous solution in the S2 step was deionized water and nothing was added, and in the S3 step, the second material 200 g and 11.44 g of boric acid were mixed dry.

[0086] The SEM test of the present application is as follows: a Hitachi S4800 scanning electron microscope (SEM) is used to analyze the morphology of the material; 1 g or less of the powder sample is weighed on a clean sample stage, the circulating water of the scanning electron microscope is turned on, the movement of the sample stage is performed by a computer, the magnification, focusing, and astigmatism are adjusted, the magnification is generally adjusted from large to small, and a clear and satisfactory image is obtained.

[0087] The conductive material, binder and positive electrode material are mixed according to the preparation method of 1.5:2:96.5, and then coated on one side. The mixture is placed in a vacuum drying box for more than 24 hours, with a pressure of-0.1 MPa and a drying temperature of 80°C. After drying, the mixture is placed in a glove box for standby. After the dried electrode sheet is compacted (without material loss), a puncher is used to punch out a circular sheet with a diameter of 11 mm. The mass of the circular sheet is accurately measured (to 0.1 mg), and the measured paper is wrapped and placed in a watch glass. At the same time, the mass of the same model and size aluminum foil of each electrode sheet to be tested is also accurately measured, and the record is recorded. The measured electrode sheet is placed in an 80°C vacuum oven for more than 12 hours. Start assembling in the glove box when the concentration of H2O and O2 is less than 5 ppm. In the battery shell, various materials are placed in order (the placement order is: positive electrode cover→2 drops of electrolyte→positive electrode sheet→separator→lithium sheet & gasket→3-4 drops of electrolyte→spring→negative electrode cover). The assembled battery is sealed with a hydraulic sealing machine. The capacity test voltage range is 2.75-4.25 V, the charge and discharge rate is 0.1 C, the cycle test voltage range is 2.75-4.25 V (high voltage cycle), the charge and discharge rate is 1 C, and the temperature is 25°C.

[0088] Table 1 is the initial performance comparison of the electrode of the examples and the comparative examples

[0089]

[0090] As shown in Table 1, compared with the examples and the comparative examples, the high-nickel positive electrode material prepared by the method of the application has obvious advantages in initial capacity, first efficiency and initial DCR. The addition of the compound for complexing lithium ions during water washing prevents the escape of lithium ions in the structure, minimizes the loss of lithium ions, and effectively inhibits the decrease of the initial capacity.

[0091] Table 2 is the capacity retention rate after 100 cycles of the examples and the comparative examples

[0092]

[0093] Table 3 is the direct current resistance growth rate after 100 cycles of the examples and the comparative examples

[0094]

[0095] As shown in Tables 2 and 3, compared with the examples and the comparative examples, the high-nickel positive electrode material prepared by the method of the application has excellent cycle life and lower resistance growth rate. Wet coating can improve the uniformity of coating, improve the cycle life of the material, and inhibit the growth of resistance.

[0096] In the description of the specification, the description using the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" etc. means that the particular feature, structure, material or characteristic being described is included in at least one embodiment or example of the present application. The illustrative appearances of the above-mentioned terms in the specification do not necessarily refer to the same embodiment or example. Moreover, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples, without mutual contradiction.

Claims

1. A method for preparing high-capacity, long-cycle, high-nickel cathode materials, characterized in that, include: 1) subjecting a precursor having the chemical formula Ni x Co y Mn z M 1-x-y-z (OH)2to a first sintering treatment with a lithium source, so as to obtain a first material, 2) The first material is mixed with an aqueous solution of a boron-containing compound and then dried to obtain a second material. The boron-containing compound in the aqueous solution is lithium dioxoborate, and the molar concentration of the aqueous solution is 0.08M~0.25M. The molar ratio of the total moles of Ni, Co, Mn, and M in the precursor to the molar ratio of boron is 100:0.25~100:2.

5. 3) The second material is subjected to a second sintering treatment to obtain the high-capacity, long-cycle, high-nickel cathode material, wherein the high-nickel cathode material is a compound represented by the following general formula: Li a Ni x Co y Mn z M 1-x-y-z O2 and M are selected from Zr, 0.80≤a≤1.20, 0.6≤x≤1.0, and the temperature of the second sintering treatment is 250~350℃.

2. The method according to claim 1, characterized in that, The precursor is Ni 0.90 Co 0.04 Mn 0.05 Zr 0.01 (OH)2.

3. The method according to claim 1, characterized in that, The high-nickel cathode material is LiNi. 0.90 Co 0.04 Mn 0.05 Zr 0.01 O2.

4. The method according to claim 1, characterized in that, The lithium source is one or a combination of lithium hydroxide, lithium carbonate, lithium nitrate, lithium sulfate, and lithium phosphate.

5. The method according to claim 1, characterized in that, The molar ratio of lithium in the lithium source to the total amount of nickel, cobalt, manganese and M elements in the precursor is 0.80 to 1.20:

1.

6. The method according to claim 1, characterized in that, The D50 of the precursor is 3-20 μm.

7. The method according to claim 1, characterized in that, The D50 of the precursor is 10~13um.

8. The method according to claim 1, characterized in that, The BET of the precursor is 3-10m. 2 / g.

9. The method according to claim 1, characterized in that, The BET of the precursor is 5-7m. 2 / g.

10. The method according to claim 1, characterized in that, The first sintering process is carried out in an oxygen atmosphere.

11. The method according to claim 1, characterized in that, The sintering temperature of the first sintering treatment is 650℃~1000℃.

12. The method according to claim 1, characterized in that, The sintering temperature of the first sintering treatment is 650℃~880℃.

13. The method according to claim 1, characterized in that, The sintering time for the first sintering treatment is 5 to 30 hours.

14. The method according to claim 1, characterized in that, The sintering time for the first sintering treatment is 7 to 15 hours.

15. The method according to claim 1, characterized in that, The weight ratio of the first material to the aqueous solution is 1 to 2:

1.

16. The method according to claim 1, characterized in that, The weight ratio of the first material to the aqueous solution is 1.5 to 2.

17. The method according to claim 1, characterized in that, The temperature of the aqueous solution is 0–20°C.

18. The method according to claim 1, characterized in that, The temperature of the aqueous solution is 0–5°C.

19. The method according to claim 1, characterized in that, The drying process is carried out in a vacuum environment.

20. The method according to claim 1, characterized in that, The drying temperature for the drying process is 50–250°C.

21. The method according to claim 1, characterized in that, The drying temperature for the drying process is 130–150°C.

22. The method according to claim 1, characterized in that, The drying process takes 1 to 10 hours.

23. The method according to claim 1, characterized in that, The drying process takes 2 to 5 hours.

24. The method according to claim 1, characterized in that, The second sintering treatment takes 3 to 10 hours.

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