Ternary positive electrode material, preparation method thereof and lithium ion battery

Abstract

The application discloses a ternary positive electrode material, a preparation method thereof and a lithium ion battery. The ternary positive electrode comprises a core and a coating layer on the surface of the core. The core comprises a ternary positive electrode base material, and the coating layer comprises Li b K c O d , K comprises at least one of Ti, W, Zr and B, 2<=b<=4, 1<=c<=5, 2 The coating layer can inhibit phase transition of the surface structure of the active material, improve the surface stability of the positive electrode material in electrolyte, reduce oxygen release, and thus realize high stability of the positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and more specifically, to a ternary cathode material and its preparation method, and a lithium-ion battery. Background Technology

[0002] With the high-intensity consumption and continuous price increases of traditional fossil fuels, energy shortages and environmental health have become global challenges. Therefore, the development and utilization of new energy resources are receiving increasing attention from governments worldwide. Lithium-ion batteries (LIBs) dominate the portable electronics market. In recent years, with the maturity of lithium-ion technology, large-size lithium-ion batteries have become more widely used in electric vehicles and aircraft. LiCo2, due to its advantages such as high-rate discharge performance, simple process route, and excellent cycle performance, is used in 3C products. However, its high cost is affected by the price of cobalt, making it difficult to use in power batteries. Lithium iron phosphate (LFP) materials, due to their low cost, high safety, and long cycle performance, have become the preferred material for power batteries in recent years. However, they also suffer from low energy density and poor low-temperature performance. Although manufacturers have improved energy density through back-end battery design innovations, such as blade batteries and CTP technology, it is still difficult to meet the increasing demands for driving range. The emergence of ternary cathode materials integrates the advantages of various cathode materials. By using different combinations of Ni, Co, and Mn (Al), the excellent combination of reversible cycle efficiency, lifespan, and energy density has enabled them to be widely used in multiple fields and has become the preferred choice for long-range vehicle power batteries.

[0003] Among the new generation of lithium-ion electrode materials, the high-nickel ternary cathode material Li(Ni) has been the most studied. x Co y N 1-x-y O2 (x≥0.6, N is Mn or Al) (NCM / NCA) is characterized by high specific capacity and energy density, and low raw material cost. The increased nickel content in high-nickel materials not only affects the battery's discharge capacity, cycle life, and storage life, but also, in particular, the gas generation issue, directly relates to battery safety. Many battery accidents are caused by gas generation in the positive electrode material during use, leading to battery failure, short circuits, and subsequent fires and explosions. Therefore, addressing gas generation in high-nickel materials is a critical issue that the power and energy-type lithium-ion battery industry urgently needs to solve. Solving this problem will determine whether high-energy-density power batteries can be widely used in electric vehicles and other fields in the future.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a ternary cathode material, its preparation method, and a lithium-ion battery, so as to reduce the gas generation problem of the cathode material and improve the cycle performance of the cathode material.

[0006] This invention is implemented as follows:

[0007] In a first aspect, embodiments of this application provide a ternary cathode material, the cathode material comprising a core and a coating layer located on the surface of the core, the core comprising a ternary cathode matrix material, and the coating layer comprising Li b K c O d K includes at least one of Ti, W, Zr, and B, 2≤b≤4, 1≤c≤5, and 2<d≤12.

[0008] In some embodiments, the ternary cathode material is a bimodal mixture, wherein the average particle size of the first peak is D1, the average particle size of the second peak is D2, and the average particle size of the cathode material is D=D1*K+D2*L, wherein 3μm<D1<9μm, 10μm<D2<20μm, 0≤H≤1, 0≤L≤1, K and L are the mass percentages of D1 and D2, respectively, and K+L=1.

[0009] In some embodiments, 0.6≤K≤1, 0≤L≤0.4.

[0010] In some embodiments, the ternary cathode material includes multiple primary particles. The ternary cathode material particles are cut open using an argon ion beam cutter, and the number of primary particles in the cross-section of the cut particles is counted using a scanning electron microscope. The number of primary particles N in the cross-section satisfies the relationship 1 < N < 500.

[0011] In some embodiments, the ternary cathode material comprises a plurality of primary particles, wherein the particle size of the primary particles is greater than 0 and less than 9 μm.

[0012] In some embodiments, the general chemical formula of the ternary cathode material is Li. a Ni x Co y N z M 1-x-y-z O2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B and Y.

[0013] In some embodiments, LibKcOd includes Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3.

[0014] In some embodiments, the ratio of lithium to transition metal in the ternary cathode material is 0.990-1.020.

[0015] In some embodiments, the thickness of the coating layer is 2nm to 100nm.

[0016] In some embodiments, the grain size of the ternary cathode material is 55nm-80nm.

[0017] In some embodiments, the specific surface area of ​​the ternary cathode material is 0.1 m². 2 / g-1.0m 2 / g.

[0018] In some embodiments, the ratio J of the specific surface area of ​​the ternary cathode material to the specific surface area of ​​the ternary cathode matrix material satisfies 2 < J < 6.

[0019] In some embodiments, the tap density of the ternary cathode material is >2.3 g / cm³. 3 .

[0020] In some embodiments, the compaction density of the ternary cathode material is >3.0 g / cm³. 3 .

[0021] In some embodiments, the residual alkali LiOH of the ternary cathode material is less than 0.3 wt%, and Li2CO3 is less than 0.25 wt%.

[0022] In some embodiments, the pH of the ternary cathode material is ≤11.80.

[0023] In some embodiments, the XRD full width at half maximum (FWHM003) of the cathode material is less than FWHM104, and the grain size D003 / D104 is greater than 1.40.

[0024] Secondly, this application provides a method for preparing a ternary cathode material, comprising the following steps:

[0025] The ternary cathode substrate material was washed with water to obtain a mixture;

[0026] The coating solution is mixed with the mixture via a spray method to obtain the coated product, wherein the coating solution comprises Li b K c O d K includes at least one of Ti, W, Zr and B, 2≤b≤4, 1≤c≤5, 2<d≤12;

[0027] The coated product was freeze-dried to obtain the cathode material.

[0028] In some embodiments, the general chemical formula of the ternary cathode substrate material is Li. a Ni x Co y N z M 1-x-y-z O2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B and Y.

[0029] In some embodiments, the washing process further includes uniformly mixing the ternary cathode substrate material and water, followed by pressure filtration and side blowing to obtain filter cake material.

[0030] In some embodiments, the weight ratio of the ternary cathode substrate material to water is 1:0.5-2.

[0031] In some embodiments, the ternary cathode substrate material is mixed and stirred with water for 10-30 minutes.

[0032] In some embodiments, the side-blowing pressure of the filter press is 0.1MPa-0.6MPa, and the side-blowing time is 0.5-3 hours.

[0033] In some embodiments, the gas blown on the filter press side includes nitrogen or compressed air.

[0034] In some embodiments, the moisture content of the filter media after side blowing of the filter press is less than 0.3 wt%.

[0035] In some embodiments, the Li b K c O d Including Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3.

[0036] In some embodiments, the K content in the ternary cathode material is 1000ppm-4000ppm.

[0037] In some embodiments, the Li b K c O d The coating amount is 0.15wt%~0.5wt% of the ternary cathode matrix material.

[0038] In some embodiments, the spraying time is 5 to 30 minutes.

[0039] In some embodiments, the filter cake material is further mixed and stirred at a speed of 100 rpm to 300 rpm.

[0040] In some embodiments, the freeze-drying temperature is -40°C to -10°C, and the freeze-drying time is 1-6 hours.

[0041] In some embodiments, the preparation steps of the ternary cathode substrate material include: synthesizing the ternary cathode substrate material by high-temperature solid-state sintering.

[0042] In some embodiments, the sintering raw materials of the ternary cathode substrate are sintered at high temperature under an oxygen-filled atmosphere.

[0043] In some embodiments, the sintering temperature is 650°C-850°C.

[0044] In some embodiments, the sintering raw materials include ternary precursors and lithium sources.

[0045] In some embodiments, the sintering raw material also includes a dopant.

[0046] Thirdly, this application provides a lithium-ion battery comprising the cathode material described in any one of the claims or the cathode material prepared by any one of the preparation methods described in the claims.

[0047] The present invention has the following beneficial effects:

[0048] The coating layer of this application can suppress the phase transition of the surface structure of the active material, enhance the surface stability of the cathode material in the electrolyte, and reduce oxygen release, thereby achieving high stability of the cathode material.

[0049] The preparation method described in this application significantly reduces residual alkali on the material surface through water washing. Uniform wet coating inhibits lattice oxygen loss and prevents redox reactions in the electrode material, thereby improving its electrochemical performance. Freeze-drying removes moisture introduced by the wet coating and neutralizes the water from the washed material. Compared to conventional high-temperature moisture removal methods, this reduces the alkaline environment caused by moisture flow and evaporation at high temperatures, and minimizes the increase in specific surface area due to voids formed by etching. Furthermore, freeze-drying allows the target coating material to slowly flow and precipitate from the liquid-phase coated material, ensuring coating uniformity. The coating material also imparts high ionic conductivity and good chemical stability, significantly improving its cycle stability. Therefore, freeze-drying simultaneously solves the surface stability problem caused by water washing to reduce residual alkali, while also achieving uniformity in wet coating. This combination reduces gas generation and improves the material's cycle performance. Attached Figure Description

[0050] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 The XRD diffraction pattern of the ternary cathode material in Example 1 is shown below.

[0052] Figure 2 This is a scanning electron microscope image of the cross-section of the ternary cathode material in Example 1 at 1K magnification;

[0053] Figure 3 for Figure 2 The cross-section was analyzed using EDS line scan to obtain a linear distribution map of each element.

[0054] Figure 4 , Figure 5 , Figure 6 The images are scanning electron microscope (SEM) images of the ternary cathode material of Example 1 at magnifications of 50K, 5K, and 1K.

[0055] Figure 7 Here is a scanning electron microscope image of a cross-section of the ternary cathode material in Example 1;

[0056] Figure 8 This is a bimodal particle size distribution diagram of the ternary cathode material in Example 1;

[0057] Figure 9 This is a comparison chart showing the storage performance (gas production) of finished small soft-pack batteries made from ternary cathode materials obtained in the embodiments and comparative examples of this invention, tested at 80°C. Detailed Implementation

[0058] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0059] The following is a detailed description of a ternary cathode material, its preparation method, and a lithium-ion battery provided by the present invention.

[0060] The inventors discovered that the higher the nickel content in ternary materials, the less stable their structure and the less stable their interfaces. The main reasons for gas production in ternary cathode materials are twofold: First, during charging and discharging, the material is prone to a phase transition (H2 to H3 phase transformation) from a layered structure to a spinel structure to an inactive rock structure, leading to a decrease in battery capacity and cycle performance. This process causes oxygen loss from the lattice. During deep delithiation during charging and discharging, the charge compensation on the material surface results in oxygen losing electrons, releasing oxygen. This released oxygen reacts with the electrolyte to produce gases such as carbon dioxide and hydrogen, causing battery bulging and deformation, and ultimately leading to safety issues. Second, residual alkali (LiOH, Li2CO3) on the cathode material surface is oxidized and decomposed during the initial charging and discharging process, producing carbon monoxide and carbon dioxide. Currently, doping can be used to address lattice oxygen loss. Cation doping can effectively suppress oxygen charge loss during deep charging, stabilize lattice oxygen, and increase the barrier for oxygen escape from the matrix, thereby inhibiting phase transitions and lattice oxygen loss. Currently, residual alkali on the surface is controlled by water washing. However, conventional water washing and pressure filtration still leave moisture inside the material, requiring vacuum treatment at 100-300℃. Under high temperature, this internal water dissolves some lithium, creating an alkaline environment that corrodes the material surface, especially forming large pores at the grain boundaries of the particles. This increases the material's specific surface area, leading to a larger contact area with the electrolyte, increased side reactions, and increased gas production. Even with coating to reduce the specific surface area, the existing surface porosity results in poor coating uniformity, further increasing gas production during material circulation and limiting its application. Based on this, the inventors propose the following solution.

[0061] Some embodiments of the ternary cathode material include a core and a coating layer located on the surface of the core. The core is a ternary cathode matrix material, and the coating layer includes Li... b K c O d K can be one or more of Ti, W, Zr, and B, where 2 ≤ b ≤ 4, 1 ≤ c ≤ 5, and 2 < d ≤ 12. The coating layer in this embodiment can suppress phase transitions on the surface structure of the active material, enhance the surface stability of the cathode material in the electrolyte, and reduce oxygen release, thereby achieving high stability of the cathode material.

[0062] In some implementations, Li b K c O d Including Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3.

[0063] In some embodiments, the general chemical formula of the ternary cathode substrate material is Li.a Ni x Co y N z M 1-x-y-z O₂, where 0.990 ≤ a < 1.1, 0.80 ≤ x < 1, 0 < y < 0.30, 0 < z < 0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B, and Y.

[0064] To achieve a better coating effect, the thickness of the coating layer is 2 nm to 100 nm. For example, 2 nm, 4 nm, 6 nm, 8 nm, 10 nm, 13 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 58 nm, 62 nm, 65 nm, 70 nm, 75 nm, 78 nm, 80 nm, 82 nm, 85 nm, 88 nm, 90 nm, 95 nm, or 100 nm can be selected.

[0065] In some embodiments, the ternary cathode material is a bimodal mixture, where the average particle size of the first peak is D1 and the average particle size of the second peak is D2. The average particle size D of the cathode material is D = D1*K + D2*L, where 3 μm < D1 < 9 μm, 10 μm < D2 < 20 μm, 0 ≤ K ≤ 1, 0 ≤ L ≤ 1, K and L are the mass percentages of D1 and D2 respectively, and K + L = 1. Mixing large and small particles can avoid the gas generation problem caused by the <1 μm fine powder in the continuous method precursor itself. At the same time, mixing large and small particles can meet the requirements of the material for compaction, capacity, and cycling in the full cell.

[0066] In some embodiments, 0.6 ≤ K ≤ 1 and 0 ≤ L ≤ 0.4; specifically, K can be 0.6, 0.8, 0.85, 0.9, or 0.95. Increasing the proportion of small particles can improve the rate performance of the material.

[0067] In some embodiments, the ratio of lithium to transition metals in the above ternary cathode material is 0.990 - 1.020. The molar amount of lithium in the material represented by Li / Me, and the ratio Q of Li / Me of the ternary cathode material to the cathode matrix material satisfies 0.9 < Q < 1.0. More preferably, 0.96 < Q < 0.98.

[0068] In some embodiments, the grain size of the ternary cathode material is 55nm-80nm. By controlling the grain size within a certain range, the redox reaction of the cathode material can be suppressed to some extent, optimizing the electron / ion transport performance within the cathode material and significantly improving its electrochemical performance. When the grain size is too small, the material's initial coulombic efficiency is low due to blocked electron and ion channels, resulting in a low discharge capacity. When the grain size is too large, the material impedance increases, leading to poor storage performance.

[0069] In some embodiments, the ternary cathode material comprises multiple primary particles. The ternary cathode material particles are cut using an argon ion beam cutter, and the number of primary particles in the cross-section of the cut particles is counted using a scanning electron microscope. The number of primary particles N in the cross-section satisfies the relationship 1 < N < 500. It should be noted that the diameter of the cross-section is the D50 of the cathode material. By limiting the size and number of primary particles in the secondary particles of the ternary cathode material, the size of defects is suppressed, the material's resistance to microcracks is improved, and the ionic conductivity of the material is increased, thereby reducing the material's impedance and gas generation, and improving the material's cycle performance.

[0070] In some implementations, the particle size of the primary particles is greater than 0 and less than 9 μm.

[0071] In some implementations, the specific surface area of ​​the ternary cathode material is 0.1 m². 2 / g-1.0m 2 / g, for example, can be 0.1m 2 / g, 0.2m 2 / g, 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g or 1m 2 / g etc.

[0072] Furthermore, the specific surface area is represented by BET. The ratio J of the BET of the ternary cathode material to the BET of the ternary cathode matrix material satisfies 2 < J < 6, for example, J is 2.3, 2.5, 3, 3.5, 4 or 5.5, etc.

[0073] In some implementations, the tap density of the ternary cathode material is >2.3 g / cm³. 3 .

[0074] In some implementations, the compacted density is >3.0 g / cm³. 3 .

[0075] In some implementations, the residual alkali of the ternary cathode material is LiOH < 0.3 wt%, Li2CO3 < 0.25 wt%, and pH ≤ 11.80.

[0076] In some embodiments, the XRD full width at half maximum (FWHM003) of the cathode material is less than FWHM104, and the grain size D... 003 / D 104 >1.40. The correlation between grain size and the capacity and cycle performance of ternary cathode materials; when the grain size D... 003 / D 104 When the value is greater than 1.40, the ternary cathode material can achieve optimal capacity and cycle performance.

[0077] Another embodiment provides a method for preparing a ternary cathode material, comprising the following steps:

[0078] The ternary cathode substrate material was washed with water to obtain a mixture;

[0079] The coating solution is mixed with the mixture via a spray method to obtain the coated product, wherein the coating solution comprises Li b K c O d K includes at least one of Ti, W, Zr and B, 2≤b≤4, 1≤c≤5, 2<d≤12;

[0080] The coated product was freeze-dried to obtain the cathode material.

[0081] In the above embodiments, water washing can significantly reduce residual alkali on the material surface, and uniform wet coating can inhibit lattice oxygen loss and prevent the redox reaction of the electrode material, thereby improving the electrochemical performance of the electrode material. Furthermore, using freeze-drying to remove the water-washed material and neutralize the moisture introduced by the wet coating method, compared to ordinary high-temperature moisture removal methods, can reduce the alkaline environment caused by moisture flow and evaporation at high temperatures, as well as the problem of increased specific surface area due to voids formed by etching on the material surface. Meanwhile, freeze-drying allows the target coating material in the liquid phase to slowly flow and precipitate, ensuring uniform coating. Uniform coating reduces tensile stress on the surface of the cathode particles during lithium removal, thus preventing microcracks during charging. Furthermore, the cathode material consists of staggered primary particles; this staggered stacking increases the material's energy states, lowering the activation energy for lithium diffusion and facilitating lithium-ion diffusion. Simultaneously, limiting the size of primary particles in the secondary particles suppresses defect size, improving the material's resistance to microcracks, enhancing ionic conductivity, reducing impedance and gas generation, and improving cycle performance. In addition, the coating material imparts high ionic conductivity and good chemical stability, significantly improving cycle stability.

[0082] Therefore, the freeze-drying method can simultaneously solve the problem of material surface stability caused by water washing to reduce residual alkali, and also achieve the problem of uniformity in wet coating. Thus, the combination of the two can reduce the gas generation problem of the cathode material and improve the cycle performance of the cathode material.

[0083] Specifically, in some embodiments of this application, the general chemical formula of the ternary cathode substrate material is Li. a Ni x Co y N z O2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, x+y+z=1, and N includes at least one of Mn and Al. In this case, the ternary cathode substrate material is a common ternary cathode substrate material, which mainly reduces gas generation in the cathode material and improves its cycle performance through water washing, wet coating, and freeze-drying.

[0084] For example, the general chemical formula of the ternary cathode substrate material can be LiNi. 0.88 Co 0.09 Mn 0.03 O2 or LiNi 0.88 Co 0.09 Al 0.03 O2, etc.

[0085] Alternatively, the general chemical formula of the ternary cathode substrate material is Li. a Ni x Co y N z M 1-x-y-z O2, where 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, N is Mn or Al, and M is one or more of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B, and Y. In this case, M is a dopant element. This means that in addition to improving the performance of the cathode material through the aforementioned processes, conventional doping methods are used to suppress oxygen charge loss during deep charging, stabilize lattice oxygen, and increase the barrier for oxygen escape from the matrix.

[0086] In some implementations, water washing involves uniformly mixing the ternary cathode substrate material with water and then performing pressure filtration and side blowing. Because residual alkali exists on the material surface, it decomposes and generates gas during material circulation; therefore, water washing is a necessary step to remove this surface alkali.

[0087] Specifically, the weight ratio of the ternary cathode substrate material to water is 1:0.5-2, for example, the weight ratio can be selected as 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9 or 1:2, etc.

[0088] In order to ensure sufficient contact between water and the ternary cathode substrate material and to fully remove residual alkali from the sintered ternary cathode substrate material, in some embodiments, the ternary cathode substrate material and water are mixed and stirred for 10-30 minutes. For example, the stirring time can be selected as 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, or 30 minutes.

[0089] To remove as much water as possible during the washing process, some implementations use a side-blowing pressure of 0.1 MPa-0.6 MPa during the filter press side-blowing process, such as 0.1 MPa, 0.2 MPa, 0.3 MPa, 0.4 MPa, 0.5 MPa, or 0.6 MPa, and a side-blowing time of 0.5-3 hours, such as 0.5 hours, 0.6 hours, 0.7 hours, 0.8 hours, 1 hour, 1.2 hours, 1.5 hours, 1.7 hours, 2.0 hours, 2.2 hours, 2.5 hours, 2.8 hours, or 3 hours, and the side-blowing gas is nitrogen or compressed air.

[0090] Specifically, in order to enable the subsequent wet coating process to proceed better, in some embodiments, the moisture content of the filter media after side blowing of the filter press is less than 0.3 wt%.

[0091] In some embodiments of this application, the coating solution is sprayed onto the stirred, washed filter cake material to mix it evenly.

[0092] In some implementations, Li b K c O d Including but not limited to Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3.

[0093] In some embodiments, the content of K in the coating solution is 1000ppm-4000ppm, for example, it can be 1000ppm, 1100ppm, 1300ppm, 1500ppm, 1600ppm, 1800ppm, 2000ppm, 2300ppm, 2500ppm, 2800ppm, 3000ppm, 3200ppm, 3500ppm, 3800ppm or 4000ppm, etc.

[0094] To ensure sufficient coating of the material by the coating solution and to control the coating amount, in some embodiments, the spraying time is 15-25 minutes, for example, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, or 25 minutes, preferably 20 minutes. b K c O d The coating amount is 0.15wt%~0.5wt% of the ternary cathode substrate material, for example, the coating amount is 0.15wt%, 0.17wt%, 0.18wt%, 0.20wt%, 0.21wt%, 0.23wt%, 0.25wt%, 0.28wt%, 0.30wt%, 0.31wt%, 0.34wt%, 0.35wt%, 0.38wt%, 0.41wt%, 0.43wt%, 0.45wt%, or 0.48wt% of the ternary cathode substrate material, etc.

[0095] Normally, because the filter press material still contains a certain amount of moisture, it is easy to generate heat during high-speed stirring, which can cause the mixture to clump and stick to the wall, affecting the coating effect. Therefore, in some implementations, the rotation speed is 100rpm-300rpm, such as 100rpm, 120rpm, 150rpm, 180rpm, 200rpm, 230rpm, 250rpm or 300rpm.

[0096] In order to achieve the desired drying effect and better remove residual moisture from the washing and wet coating processes, in some embodiments of this application, the freeze-drying temperature is -40℃ to -10℃, for example, -40℃, -35℃, -30℃, -25℃, -20℃, -18℃, -15℃, -12℃ or -10℃, etc., and the freeze-drying time is 1-6 hours, for example 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, etc.

[0097] In some embodiments of this application, a high-temperature solid-state sintering method is used to synthesize ternary cathode matrix materials.

[0098] Specifically, in some embodiments, the sintering raw materials of the ternary cathode substrate are sintered at high temperature under an oxygen-filled atmosphere. That is, this method uses only one sintering process throughout the entire process.

[0099] In some embodiments, the sintering temperature is 650℃-850℃, such as including but not limited to 650℃, 660℃, 670℃, 680℃, 690℃, 700℃, 710℃, 720℃, 730℃, 740℃, 750℃, 760℃, 770℃, 780℃, 790℃, 800℃, 810℃, 820℃, 830℃ or 850℃.

[0100] In some implementations, the sintering raw materials also include dopants to achieve doping of the ternary cathode material.

[0101] It should be noted that in the above embodiments, the sintering raw materials of the ternary cathode substrate material can contain only ternary hydroxide precursor and lithium salt, and be sintered at high temperature to obtain undoped ternary material; or the sintering raw materials can contain dopants, and be mixed with ternary hydroxide precursor and lithium source before sintering to achieve doping.

[0102] In some embodiments, the ternary hydroxide precursor Ni x Co y N z (OH)2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, x+y+z=1, and N includes at least one of Mn and Al;

[0103] Or the ternary hydroxide precursor is Ni x Co y N z M 1-x-y-z (OH)2, wherein 0.80≤x<1, 0<y<0.30, 0<z<0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B and Y.

[0104] In some embodiments, the lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium acetate, lithium nitrate, and lithium oxalate.

[0105] In some implementations, the dopant includes an oxide of M.

[0106] In some embodiments, the ternary hydroxide precursor includes mixing ternary hydroxide precursor particles of different particle sizes.

[0107] Among them, the particle size D1 of the small ternary hydroxide precursor particles is 3μm < D1 < 9μm; the particle size D2 of the large ternary hydroxide precursor particles is 10μm < D2 < 20μm.

[0108] The weight ratio of small ternary hydroxide precursor particles to large ternary hydroxide precursor particles is 0~0.4:0.6~1.

[0109] In some embodiments, the hydroxide precursor is prepared by the following specific steps: nickel salt solution, cobalt salt solution, and manganese salt solution (aluminum salt solution) are mixed in a certain proportion, ammonia is used as a complexing agent, and sodium hydroxide is used to adjust the pH of the reaction solution. The precursor is synthesized by co-precipitation, and then aged, washed, and dried to obtain the hydroxide precursor of nickel-cobalt-manganese cathode material. It can also be purchased commercially.

[0110] Secondly, some embodiments of this application also provide a ternary cathode material, which is prepared by the above-described method for preparing ternary cathode materials.

[0111] Fourthly, some embodiments of this application also provide a lithium-ion battery, which includes the above-described lithium-ion battery positive electrode.

[0112] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0113] Example 1

[0114] This embodiment provides a method for preparing a ternary cathode material, which specifically includes the following steps:

[0115] S1. Ni hydroxide precursors with different particle sizes 0.88 Co 0.09 Mn 0.03 (OH)₂ (14μm large particles and 4.5μm small particles in a weight ratio of 80:20) and LiOH in a lithium salt to metal molar ratio of 1.05 were thoroughly and uniformly mixed to obtain a first mixture. This first mixture was placed in a pure oxygen atmosphere, with the furnace pressure controlled at 10 Pa, and heated to 700℃ at a heating rate of 2℃ / min. The mixture was held at this temperature for 9 hours and then allowed to cool naturally to obtain Li. a Ni 0.88 Co 0.09 Mn 0.03 O2 ternary cathode matrix material.

[0116] S2. Mix the obtained ternary cathode substrate material with water at a weight ratio of 1:1. Place the mixture in a constant temperature water tank and stir for 15 minutes, controlling the temperature of the mixture at 18℃. Press the mixture into a filter press and purge with nitrogen for 2.5 hours to remove moisture, obtaining filter cake material with a moisture content of 0.10 wt%.

[0117] S3. Dissolve LiOH in ultrapure water to prepare a LiOH solution, then add WO3, wherein the molar ratio of tungsten to lithium is 1:4. Place the mixed solution in a water bath at 55°C and stir thoroughly until completely dissolved to obtain a mixed solution containing lithium tungstate. The Li concentration of the mixed solution is 20 g / L and the W concentration is 50 g / L.

[0118] S4. Place the filter cake material in a high-efficiency mixer and mix it radially and uniformly. Spray the mixed solution containing lithium tungstate evenly onto the filter cake material using a sprayer for 20 minutes. The coating amount of Li4WO5 is 0.28wt% of the active material matrix material.

[0119] S5. The spray-coated filter cake material is dried by placing it in a freeze dryer and drying it under vacuum at -20°C for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.88 Co 0.09 Mn 0.03 O2.

[0120] Example 2

[0121] This embodiment provides a method for preparing a ternary cathode material, which specifically includes the following steps:

[0122] S1. Ni hydroxide precursors with different particle sizes 0.88 Co 0.09 Mn 0.03 (OH)₂ (14μm large particles and 4.5μm small particles in a weight ratio of 80:20) and LiOH in a lithium salt to metal molar ratio of 1.05 were thoroughly and uniformly mixed to obtain a first mixture. This first mixture was placed in a pure oxygen atmosphere, with the furnace pressure controlled at 10 Pa, and heated to 700℃ at a heating rate of 2℃ / min. The mixture was held at this temperature for 9 hours and then allowed to cool naturally to obtain Li. a Ni 0.88 Co 0.09 Mn 0.03 O2 ternary cathode matrix material.

[0123] S2. Mix the obtained ternary cathode substrate material with water at a weight ratio of 1:1. Place the mixture in a constant temperature water tank and stir for 15 minutes, controlling the temperature of the mixture at 18℃. Press the mixture into a filter press and purge with nitrogen gas for 2.5 hours to remove moisture, obtaining filter cake material with a moisture content of less than 0.10 wt%.

[0124] S3. Dissolve LiOH in ultrapure water to prepare a LiOH solution, then add WO3, wherein the molar ratio of tungsten to lithium is 1:4. Place the mixed solution in a water bath at 55°C and stir thoroughly until completely dissolved to obtain a mixed solution containing lithium tungstate. The Li concentration of the mixed solution is 15 g / L and the W concentration is 37.5 g / L.

[0125] S4. Place the filter cake material in a high-efficiency mixer and mix it radially and uniformly. Spray the mixed solution containing lithium tungstate evenly onto the filter cake material using a sprayer for 20 minutes. The coating amount of Li4WO5 is 0.21wt% of the active material matrix material.

[0126] S5. The spray-coated filter cake material is dried by placing it in a freeze dryer and drying it under vacuum at -20°C for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.88 Co 0.09 Mn 0.03 O2.

[0127] Example 3

[0128] This embodiment provides a method for preparing a ternary cathode material, which specifically includes the following steps:

[0129] S1. Ni hydroxide precursors with different particle sizes 0.88 Co 0.09 Mn 0.03 (OH)₂ (14μm large particles and 4.5μm small particles in a weight ratio of 80:20) and LiOH in a lithium salt to metal molar ratio of 1.05 were thoroughly and uniformly mixed to obtain a first mixture. This first mixture was placed in a pure oxygen atmosphere, with the furnace pressure controlled at 10 Pa, and heated to 700℃ at a heating rate of 2℃ / min. The mixture was held at this temperature for 9 hours and then allowed to cool naturally to obtain Li. a Ni 0.88 Co 0.09 Mn 0.03 O2 ternary cathode matrix material.

[0130] S2. Mix the obtained ternary cathode substrate material with water at a weight ratio of 1:1. Place the mixture in a constant temperature water tank and stir for 15 minutes, controlling the temperature of the mixture at 18℃. Press the mixture into a filter press and purge with nitrogen gas for 2.5 hours to remove moisture, obtaining filter cake material with a moisture content of less than 0.10 wt%.

[0131] S3. Dissolve LiOH in ultrapure water to prepare a LiOH solution, then add WO3, wherein the molar ratio of tungsten to lithium is 1:4. Place the mixed solution in a water bath at 55°C and stir thoroughly until completely dissolved to obtain a mixed solution containing lithium tungstate. The Li concentration of the mixed solution is 30 g / L and the W concentration is 90 g / L.

[0132] S4. Place the filter cake material in a high-efficiency mixer for uniform mixing. Spray the mixed solution containing lithium tungstate evenly onto the filter cake material using a sprayer for 20 minutes. The coating amount of Li4WO5 is 0.35wt% of the active material matrix material.

[0133] S5. The spray-coated filter cake material is dried by placing it in a freeze dryer and drying it under vacuum at -20°C for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.88 Co 0.09 Mn 0.03 O2.

[0134] Example 4

[0135] This embodiment provides a method for preparing a ternary cathode material, which specifically includes the following steps:

[0136] S1. Ni hydroxide precursors with different particle sizes 0.88 Co 0.09 Mn 0.03 (OH)₂ (16μm large particles and 3.5μm small particles in a weight ratio of 75:25) and LiOH in a lithium salt to metal molar ratio of 1.05 were thoroughly and uniformly mixed to obtain a first mixture. This first mixture was placed in a pure oxygen atmosphere, with the furnace pressure controlled at 10 Pa, and heated to 700℃ at a heating rate of 2℃ / min. The mixture was held at this temperature for 9 hours and then allowed to cool naturally to obtain Li. a Ni 0.88 Co 0.09 Mn 0.03 O2 ternary cathode matrix material.

[0137] S2. Mix the obtained ternary cathode substrate material with water at a weight ratio of 1:1. Place the mixture in a constant temperature water tank and stir for 15 minutes, controlling the temperature of the mixture at 18℃. Press the mixture into a filter press and purge with nitrogen for 2.5 hours to remove moisture, obtaining filter cake material with a moisture content of 0.10 wt%.

[0138] S3. Dissolve LiOH in ultrapure water to prepare a LiOH solution, then add TiO2, wherein the molar ratio of tungsten to lithium is 1:2. Place the mixed solution in a water bath at 55°C and stir thoroughly until completely dissolved to obtain a mixed solution containing lithium titanate. The Li concentration of the mixed solution is 20 g / L and the W concentration is 50 g / L.

[0139] S4. Place the filter cake material in a high-efficiency mixer and mix it radially and uniformly. Spray the mixed solution containing lithium titanate evenly onto the filter cake material using a sprayer for 20 minutes. The coating amount of Li2TiO3 is 0.28wt% of the active material matrix material.

[0140] S5. The spray-coated filter cake material is dried by placing it in a freeze dryer and drying it under vacuum at -20°C for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li2TiO3. 0.88 Co 0.09 Mn 0.03 O2.

[0141] Example 5

[0142] This embodiment provides a method for preparing a ternary cathode material, which specifically includes the following steps:

[0143] S1. Ni hydroxide precursors with different particle sizes 0.91 Co 0.05 Mn 0.04 (OH)₂ (18μm large particles and 8μm small particles in a weight ratio of 80:20) and LiOH in a lithium salt to metal molar ratio of 1.05 were thoroughly and uniformly mixed to obtain a first mixture. This first mixture was placed in a pure oxygen atmosphere, with the furnace pressure controlled at 10 Pa, and heated to 700℃ at a heating rate of 2℃ / min. The mixture was held at this temperature for 9 hours and then allowed to cool naturally to obtain Li. a Ni 0.91 Co 0.05 Mn 0.04 O2 ternary cathode matrix material.

[0144] S2. Mix the obtained ternary cathode substrate material with water at a weight ratio of 1:1. Place the mixture in a constant temperature water tank and stir for 15 minutes, controlling the temperature of the mixture at 18℃. Press the mixture into a filter press and purge with nitrogen for 2.5 hours to remove moisture, obtaining filter cake material with a moisture content of 0.10 wt%.

[0145] S3. Dissolve LiOH in ultrapure water to prepare a LiOH solution, then add WO3, wherein the molar ratio of tungsten to lithium is 1:4. Place the mixed solution in a water bath at 55°C and stir thoroughly until completely dissolved to obtain a mixed solution containing lithium tungstate. The Li concentration of the mixed solution is 20 g / L and the W concentration is 50 g / L.

[0146] S4. Place the filter cake material in a high-efficiency mixer and mix it radially and uniformly. Spray the mixed solution containing lithium tungstate evenly onto the filter cake material using a sprayer for 20 minutes. The coating amount of Li4WO5 is 0.28wt% of the active material matrix material.

[0147] S5. The spray-coated filter cake material is dried by placing it in a freeze dryer and drying it under vacuum at -20°C for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.91 Co 0.05 Mn 0.04 O2.

[0148] Comparative Example 1

[0149] The difference from Example 1 is that in Comparative Example 1, the filter cake material was placed in a high-efficiency mixer and mixed radially and uniformly. The mixed solution was sprayed evenly onto the filter cake material using a sprayer. However, the sprayed mixed solution did not contain Li4WO5 (LiOH and WO3 were not added to the ultrapure water), and the spraying time was 20 minutes. Otherwise, the positive electrode material was prepared in the same manner as in Example 1.

[0150] Comparative Example 2

[0151] The difference from Example 1 is that in Comparative Example 2, the spray-coated filter cake material is heat-treated, placed in a drying device, and dried at 200°C under vacuum for 5 hours. The dried material is then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.88 Co 0.09 Mn 0.03 O2, except that the positive electrode material was prepared in the same manner as in Example 1.

[0152] Comparative Example 3

[0153] The difference from Example 1 is that in Comparative Example 3, the sintered matrix material and WO3 were radially and uniformly mixed in a high-efficiency mixer. A pure aqueous solution was then uniformly sprayed onto the mixture using a sprayer for 20 minutes. After uniform mixing, the mixture was placed in a drying device and dried under vacuum at 200°C for 5 hours. The dried material was then sieved to obtain the high-nickel ternary cathode material LiNi coated with Li4WO5. 0.88 Co 0.09 Mn 0.03 O2 was used to prepare the positive electrode material in the same manner as in Example 1.

[0154] Experimental Example 1

[0155] When performing X-ray diffraction tests on the material, Cu-Kα1 rays were used as the X-ray source, and the testing conditions were 10–90° (2θ) with a scanning step size of 0.05°. The results are as follows: Figure 1 The XRD test results for the ternary cathode material in Example 1 are shown. The XRD values ​​for FWHM003 and FWHM104 are 0.223. According to the Scherrer equation, the grain size D003 is 78 nm and D104 is 52 nm, where D003 / D104 = 1.5. The XRD full width at half maximum (FWHM003 < FWHM104) and the grain size D003 / D104 > 1.40 are all satisfied in the cathode materials of this application.

[0156] Experimental Example 2

[0157] The cross-section of the ternary cathode material in Example 1, obtained by argon ion cutting, was observed using a Hitachi S4800 scanning electron microscope. The results are as follows: Figure 2 As shown, an EDS line scan was performed on the cross-section, and the linear distribution diagram of each element is shown below. Figure 3 As shown; and the surface morphology of the ternary cathode material of Example 1 was examined using a Hitachi S4800 scanning electron microscope, as shown. Figure 4 , Figure 5 , Figure 6 As shown in the SEM image, it is clear that the ternary cathode material obtained by wet coating of lithium tungstate has obvious lamellar coatings on the particle surface, and the coating is relatively uniform.

[0158] Experimental Example 3

[0159] The cross-section of the ternary cathode material in Example 1, obtained by argon ion cutting, was observed using a Hitachi S4800 scanning electron microscope. The results are as follows: Figure 7 As shown. The number of primary particles is statistically measured. The cross-section of secondary particles is formed by the stacking of many primary grains. The number of primary particles in the cross-section of the ternary cathode material is approximately 280, and the size of the primary particles in the cross-section is D. 一次粒子Twenty particles were measured, and the average particle diameter was 1.60 μm. The cross-section of the ternary cathode material in the experimental example of this application satisfies 1 < number of primary particles < 500, 0 < D. 一次粒子 <9μm.

[0160] Experimental Example 4

[0161] The ternary cathode material of Example 1 was tested and analyzed using a Malvern MS2000 laser particle size analyzer, and the results were as follows: Figure 8 The bimodal particle size distribution diagram shown is composed of... Figure 8 It is known that the ternary cathode material exhibits a double peak, with the first peak having an average particle size of D1 and the second peak having an average particle size of D2. The average particle size of the cathode material is D = D1*K + D2*L, where 3μm < D1 < 9μm, 10μm < D2 < 20μm, 0 ≤ K ≤ 1, 0 ≤ L ≤ 1, H and L are the mass percentage mixing ratios of D1 and D2, respectively, and K + L = 1. More preferably, 0.6 ≤ K ≤ 1, 0 ≤ L ≤ 0.4, and K + L = 1. Table 1 shows the particle sizes obtained in Examples 1 to 5.

[0162] Table 1

[0163]

[0164] Experimental Example 5

[0165] Calculate the molar amount of lithium in the finished ternary cathode material, expressed as Li / Me, and then calculate the molar ratio of lithium in the finished ternary cathode material to that in the ternary cathode matrix material, i.e., M(Li / Me). 成品 ) / M(Li / Me 基体 The results are shown in Table 1. In the embodiments of this application, the ratio of lithium to transition metal in the ternary cathode material is 1-1.020, and the Li / Me ratio of the ternary cathode material to the cathode matrix material satisfies 0.96. <M(Li / Me 成品 ) / M(Li / Me 基体 <0.98.

[0166] The electrochemical cycling performance was tested using the following method: The high-nickel ternary materials used as the positive electrode materials in the above examples and comparative examples were mixed with conductive carbon black and PVDF (polyvinylidene fluoride) binder at a mass ratio of 96:2:2. NMP (N-methylpyrrolidone) was added to form a uniform slurry, which was then coated onto copper foil, dried in an oven, and rolled under 10 MPa pressure to form circular electrode sheets with a diameter of 14 mm. Lithium-ion batteries were assembled according to industrial CR2025 button cell standards, using a Cellgard separator, a 1 mol / L LiPF6 solution with EC / PC / DEC as the electrolyte, and a lithium sheet as the negative electrode. The entire assembly process was carried out in an argon-filled glove box, where the oxygen and moisture content were controlled below 0.5 ppm. The lithium-ion battery test conditions were: temperature 25℃±1℃, charge / discharge cycle voltage range of 3.0V-4.3V, current of 0.1C (210mAh / g), and cycle testing at 0.5C charge-1C discharge for 50 cycles. The results are shown in Table 2. As can be seen from Table 2, the results of this application's embodiments, compared to the comparative examples, show that the discharge capacity and cycle performance of the finished product are improved after coating with lithium tungstate.

[0167] Table 2

[0168]

[0169] Experimental Example 6

[0170] The compacted density of the powder was tested using a CARVER-4350 powder compaction density meter. The vibratory density was tested using a Dandong Baite BT-303 vibratory density meter. The pH was tested using a Mettler Toledo FE20 pH meter. The residual alkali was tested using a Mettler Toledo G20S automatic potentiometric titrator: 5.0000±0.0050g of sample was weighed, poured into 100mL of ultrapure water, quickly sealed with sealing film, magnetically stirred for 10min at 450r / min, then vacuum filtered, and the filtrate was transferred to a 100mL volumetric flask. A certain volume was aliquoted and titrated using 0.025M HCl as the titrant in equivalence point titration mode on a potentiometric titrator to obtain the contents of LiOH and Li2CO3. The results are shown in Table 3. The vibratory density of the ternary cathode material in the experimental example of this application meets the requirement of vibratory density > 2.3g / cm³. 3 The compaction density must meet the requirement of >3.0 g / cm³. 3 The residual alkali of the ternary cathode material satisfies LiOH < 0.3wt%, Li2CO3 < 0.25wt%, and pH ≤ 11.80.

[0171] Table 3

[0172]

[0173] Experimental Example 7

[0174] The specific surface area of ​​the material was tested using the McBimeter 3020 nitrogen adsorption method. The gas production performance of the material was tested using the following method: the above-mentioned high-nickel ternary material was mixed with conductive carbon black and binder PVDF (polyvinylidene fluoride) at a mass ratio of 96.0:1.5:1.5, and N was added. Methylpyrrolidone (NMP) was stirred uniformly under vacuum to obtain a positive electrode slurry with a designed areal density of 300 g / m³. 2 ~400g / m 2 The positive electrode slurry was uniformly coated onto aluminum foil (16 μm thick). The coated electrode was then dried in an oven at 100℃~130℃, cold-pressed, and slit to obtain the positive electrode sheet. The negative electrode active material graphite, binder (sodium carboxymethyl cellulose + styrene-butadiene rubber), and conductive agent acetylene black were uniformly mixed at a mass ratio of 96:3:1. Deionized water was added, and a negative electrode slurry was prepared using a vacuum mixer, with a designed areal density of 200 g / m³. 2 ~300g / m 2 The mixed slurry was uniformly coated onto copper foil (8μm thick). After the copper foil was dried at room temperature, it was transferred to a 120℃ oven for 1 hour. The same process was performed on the reverse side of the electrode sheet. Then, the negative electrode sheet was obtained by cold pressing and slitting. The electrolyte was TC-E8630J, and the separator was a polypropylene separator with a thickness of 16μm. The slit electrodes were stacked in the order of negative electrode, separator, and positive electrode to make a stacked cell. The stacked cells were welded with tabs, and the welded cells were placed in a punched aluminum-plastic film for sealing. Electrolyte was injected into the sealed cells and the opening was sealed to obtain the finished small soft-pack battery. The battery was fully charged to 4.2V at 1C and then placed in an 80℃ constant temperature chamber for 3 / 6 / 9 days. The initial volume and the volume after 3 / 6 / 9 days of standing were measured by the water displacement method to obtain the gas production of the battery. The results are shown in Table 4 and Figure 9 As shown.

[0175] Table 4

[0176]

[0177] As shown in Table 3, the ternary cathode material obtained in this application embodiment has a smaller specific surface area compared to the comparative example, and the increase in specific surface area is smaller compared to the ternary cathode matrix material. Compared to the ternary cathode material product obtained by uncoating and direct heat treatment and drying, it significantly reduces the gas production.

[0178] In summary, the cathode material prepared by this method is characterized by a single sintering process. The freeze-drying technique not only removes residual moisture from the matrix after water washing, but also allows the coating material in the liquid coating to slowly precipitate and achieve uniform coating. It also avoids the problem of water evaporation during high-temperature processes causing etching voids on the material surface, and solves the problem of increased specific surface area after water washing and drying. The freeze-drying method can simultaneously solve the surface stability problem caused by water washing and residual alkali reduction, and also achieve the uniformity problem of wet coating. Thus, the combination of these two methods reduces gas generation and improves the cycle performance of the material.

[0179] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A ternary cathode material, characterized in that, The cathode material includes a core and a coating layer on the surface of the core. The core includes a ternary cathode matrix material, and the coating layer includes Li. b K c O d K includes at least one of Ti, W, Zr and B, 2≤b≤4, 1≤c≤5, 2<d≤12; The ternary cathode material comprises multiple primary particles. The ternary cathode material particles are cut open using an argon ion beam cutter, and the number of primary particles in the cross-section of the cut particles is counted using a scanning electron microscope. The number of primary particles N in the cross-section satisfies the relationship 1 < N < 500; and the particle size of the primary particles is greater than 0.87 μm and less than 9 μm. The specific surface area of ​​the ternary cathode material is 0.1 m². 2 / g-1.0m 2 / g.

2. The ternary cathode material according to claim 1, characterized in that, The ternary cathode material is a bimodal mixture, wherein the average particle size of the first peak is D1 and the average particle size of the second peak is D2. The average particle size of the cathode material is D = D1*K + D2*L, where 3μm < D1 < 9μm, 10μm < D2 < 20μm, 0 ≤ K ≤ 1, 0 ≤ L ≤ 1, K and L are the mass percentages of D1 and D2, respectively, and K + L = 1.

3. The ternary cathode material according to claim 2, characterized in that, 0.6≤K≤1, 0≤L≤0.

4.

4. The ternary cathode material according to any one of claims 1 to 3, characterized in that, Includes at least one of the following features (1) to (11): (1) The general chemical formula of the ternary cathode material is Li a Ni x Co y N z M 1-x-y-z O2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B and Y; (2) LibKcOd includes Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3; (3) The ratio of lithium to transition metal in the ternary cathode material is 0.990-1.020; (4) The thickness of the coating layer is 2nm-100nm; (5) The grain size of the ternary cathode material is 55nm-80nm; (6) The ratio J of the specific surface area of ​​the ternary cathode material to the specific surface area of ​​the ternary cathode matrix material satisfies 2 < J < 6; (7) The tap density of the ternary cathode material is > 2.3 g / cm³. 3 ; (8) The compaction density of the ternary cathode material is >3.0 g / cm³. 3 ; (9) The residual alkali of the ternary cathode material is LiOH < 0.3 wt% and Li2CO3 < 0.25 wt%; (10) The pH of the ternary cathode material is ≤11.80; (11) The XRD full width at half maximum (FWHM003) of the cathode material is less than FWHM104, and the grain size is D. 003 / D 104 >1.

40.

5. A method for preparing a ternary cathode material as described in any one of claims 1-4, characterized in that, Includes the following steps: The ternary cathode substrate material is washed with water to obtain a mixture; the preparation steps of the ternary cathode substrate material include: synthesizing the ternary cathode substrate material by high-temperature solid-state sintering; wherein, the sintering raw materials used in the high-temperature solid-state sintering method include ternary precursors and lithium sources; the ternary precursors include hydroxide precursors with different particle sizes. The coating solution is mixed with the mixture via a spray method to obtain the coated product, wherein the coating solution comprises Li b K c O d K includes at least one of Ti, W, Zr and B, 2≤b≤4, 1≤c≤5, 2<d≤12; The coated product was freeze-dried to obtain the cathode material.

6. The preparation method according to claim 5, characterized in that, The general chemical formula of the ternary cathode matrix material is Li. a Ni x Co y N z M 1-x-y-z O2, wherein 0.990≤a<1.1, 0.80≤x<1, 0<y<0.30, 0<z<0.30, N includes at least one of Mn and Al, and M includes at least one of Al, Ti, Zr, Mg, Sr, Ba, Nb, W, B and Y.

7. The preparation method according to claim 5, characterized in that, The preparation method includes at least one of the following features (1) to (3): (1) The water washing process further includes uniformly mixing the ternary cathode substrate material and water, followed by pressure filtration and side blowing to obtain filter cake material; (2) The weight ratio of the ternary cathode substrate material to water is 1:0.5-2; (3) The ternary cathode substrate material is mixed with water for 10-30 minutes.

8. The preparation method according to claim 7, characterized in that, When the preparation method is characterized by (1), the side-blowing pressure of the filter press is 0.1MPa-0.6MPa, and the side-blowing time is 0.5-3 hours.

9. The preparation method according to claim 7, characterized in that, When the preparation method is characterized by (1), the gas blown by the pressure filter side includes nitrogen or compressed air.

10. The preparation method according to claim 7, characterized in that, When the preparation method is characterized by (1), the moisture content of the filter material after the pressure filter is blown is less than 0.3 wt%.

11. The preparation method according to claim 7, characterized in that, When the preparation method is characterized by (1), it further includes mixing and stirring the filter cake material at a speed of 100 rpm to 300 rpm.

12. The preparation method according to claim 5, characterized in that, The preparation method includes at least one of the following features (4) to (8): (4) The Li b K c O d Including Li4Ti5O 12 One or more of Li2TiO3, Li2WO4, Li4WO5, Li2ZrO3 and Li3BO3; (5) The content of K in the ternary cathode material is 1000ppm-4000ppm; (6) The Li b K c O d The coating amount is 0.15wt%~0.5wt% of the ternary cathode matrix material; (7) The spraying time is 5~30 min; (8) The freeze-drying temperature is -40℃ to -10℃ and the freeze-drying time is 1-6h.

13. The method for preparing the ternary cathode material according to claim 5, characterized in that, The preparation steps of the ternary cathode substrate material include at least one of the following features (9) to (11): (9) The sintering raw materials of the ternary cathode substrate are sintered at high temperature under an oxygen-filled atmosphere; (10) The sintering temperature of the high-temperature solid-state sintering method is 650℃-850℃; (11) The sintering raw materials also include dopants.

14. A lithium-ion battery, characterized in that, It includes the cathode material as described in any one of claims 1 to 4 or the cathode material prepared by the preparation method described in any one of claims 5 to 13.

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