Titanium-strontium-fluorine composite doped co-coated high-voltage ternary positive electrode material, preparation method and application thereof

Abstract

The application relates to a titanium-strontium-fluorine composite doped co-coated high-voltage ternary positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The high-voltage ternary positive electrode material has a general structure as follows: LiNi x Co y Mn z Ti a Al b W c Mg d Zr e Nb f B g Sr h F n PO 2‑n , wherein 0.5<=x<1.0, 0

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries, and particularly relates to a titanium-strontium-fluorine composite doped co-coated high-voltage ternary positive electrode material, and further discloses a preparation method and application thereof. BACKGROUND

[0002] With the change of global energy supply pattern, the problems of energy crisis and environmental pollution are becoming increasingly prominent, and the development of sustainable new energy has become a top priority. Lithium ion batteries, as a new type of green energy storage device, have attracted much attention. With the recent market challenges of new energy vehicles, the cost problem is prominent, and the lithium resource market is periodically adjusted. The overall demand for lithium ion batteries has increased, especially with the significant adjustment of the prices of upstream lithium salts, nickel salts, and cobalt salts. The future trend is uncertain, and the performance-price ratio of positive electrode materials has become the industry development trend and the focus of research and development for each enterprise. Currently, the development of lithium ion battery positive electrode materials, especially ternary positive electrode materials, has three trends: single crystallization, high voltage, and high nickel. Among them, high-nickel ternary positive electrode materials have a large market space in the future due to their high energy density characteristics that meet the endurance needs of high-end new energy vehicles. It is the focus of research and development and industrialization for ternary positive electrode material manufacturers, especially medium-nickel high-voltage and high-nickel, which are the direction of competition and development for domestic enterprises.

[0003] The high-voltage route is based on medium-nickel or medium-nickel low-cobalt ternary materials, which can release more lithium ions at higher voltages by increasing the voltage platform, thereby achieving higher specific capacity and average discharge voltage, and ultimately improving the energy density. Its voltage breaks through 4.4V, reaching 4.45-4.5V or even higher in practical applications. Currently, there are great challenges and difficulties in terms of structural stability and technical development. Based on the current practical application of 4.3-4.35V, the actual energy density of high-voltage Ni6 series typical products (Ni65) can reach 735.15Wh / kg, which is very close to the parameter of 739.32Wh / kg of Ni8 series typical products. When medium-nickel high-voltage ternary positive electrode materials break through 4.5V, their energy density is basically close to that of high-nickel Ni9 series, and their thermal stability and safety are superior to high-nickel positive electrode materials, which have strong actual research and development value.

[0004] Currently, high-voltage is taken as the basic route for ternary materials with medium nickel, which is superior to high-nickel ternary materials in terms of raw materials, production process and processing cost. At the same time, due to the relatively low nickel content of high-voltage materials, the production process is not as complex as high-nickel ternary materials. Therefore, high-voltage positive materials not only improve the energy density, but also have certain safety improvement. With the superior comprehensive performance, the market of high-voltage ternary materials is gradually opening up. However, gradually increasing the voltage has a great impact on the structural performance stability of the material. How to improve the performance of the material under the condition of high-voltage application is an extremely urgent and adjustable topic.

[0005] A strontium-doped ternary lithium-ion battery positive material and its preparation method and application are disclosed in Chinese patent CN 113224287A. The strontium-doped ternary lithium-ion battery positive material is prepared by substituting lithium ions with strontium metal ions, reducing the degree of cation mixing, expanding the lithium ion channel and stabilizing the layered structure, and reducing the structural damage caused by volume change during lithium ion deintercalation. The positive material prepared by this method can effectively improve the cycle stability and rate performance of lithium batteries, and the preparation process is simple and has high repeatability.

[0006] A preparation method of a strontium titanate-coated single-crystal nickel-rich ternary positive material is disclosed in Chinese patent CN113293441B. Based on the sol-gel method combined with ultrasonic external field, SrTiO3 is coated on the surface of single-crystal high-nickel ternary material as the core, and film-forming additives and complexing agents are introduced to capture active ions to ensure the formation of a uniform SrTiO3 coating layer to reduce the loss of active materials due to severe side reactions, improve the cycle life of the material, and accelerate the deintercalation process of lithium ions by the large specific surface area and pseudo-capacitance effect of nano-sized SrTiO3 to improve the high-rate performance of the material. In addition, the unique high redox catalytic properties of SrTiO3 fully improve the Ni 2+ / Ni 4+ redox activity in single-crystal high-nickel materials, improve the capacity of the material at high rate, and solve the problems of short cycle life and poor high-rate performance of single-crystal high-nickel materials. However, the sol-gel method has a long preparation time and relatively poor economic efficiency, and the single conductivity of SrTiO3+TiO2 together has some deficiencies.

[0007] A fluorine-doped nickel-cobalt-manganese lithium ternary material and its preparation method are disclosed in Chinese patent CN115028211A. The fluorine-doped nickel-cobalt-manganese lithium ternary material is synthesized by a solid-phase method at low temperature using a fluorine-containing compound as the fluorine source (NH4F) and reacting with nickel-cobalt-manganese lithium oxides under specific conditions. The F - substitutes O 2-The valence state of transition metal ions is changed, thereby changing its lattice structure parameters, and more importantly, the doping of fluorine promotes grain growth and improves the crystallization performance. In addition, the doping amount can improve the stability of the interface between the active material and the electrolyte, greatly improving the cycle performance of the material. However, too high a doping amount will cause uneven substitution, which will seriously affect the electrical performance.

[0008] A preparation method of a gradient sintering gas phase fluorine-doped modified high-nickel positive electrode material is disclosed in Chinese Patent CN109638251B, which comprises the following steps: 1) mixing a lithium source and high nickel sufficiently and uniformly; 2) placing it in an atmosphere furnace, first increasing the temperature to 480-530℃ at a fast heating rate, then increasing the temperature to 700-800℃ at a slow heating rate and maintaining for 8-15h, and continuously introducing high-purity oxygen to maintain a slight positive pressure in the furnace; 3) then reducing to 550-650℃ and maintaining for 4-8h, and closing the high-purity oxygen and introducing high-purity fluorine gas to maintain a slight positive pressure in the furnace; 4) naturally cooling and closing the gas inlet and outlet to make the furnace atmosphere flow; 5) taking out the target product after treatment. The positive electrode material prepared by the method has better surface doping uniformity and consistency; the gradient sintering technology ensures that the Ni 2+ in the high-nickel material is fully oxidized to Ni 3+ , improving the specific capacity and cycle performance of the material.

[0009] A coating structure of a lithium ion battery positive electrode material, its preparation method and use are disclosed in Chinese Patent CN111900394B. An electronic conductive particle layer is coated on the surface of the positive electrode material by a mechanical fusion method; then a solid-state electrolyte layer is coated on the surface of the electronic conductive particle layer by a liquid phase method to obtain the coating structure of the lithium ion battery positive electrode material; the coating structure includes an electronic conductive particle layer on the surface of the positive electrode material and a solid-state electrolyte layer on the outer layer of the electronic conductive particle layer; this coating structure can effectively isolate the direct contact between the positive electrode material and the electrolyte, inhibit the side reaction between the positive electrode material and the electrolyte, and improve the cycle performance of the battery; at the same time, it has high thermal stability, which can improve the safety performance of the battery; the above two-layer structure has good lithium ion conductivity and electronic conductivity, ensuring the high specific capacity and rate performance of the positive electrode material.

[0010] Some single-crystal ternary positive electrode materials and their preparation methods and processes are also disclosed, which use tungsten oxide for doping modification.

[0011] As disclosed in Chinese patent CN113903907A, a tungsten-coated and doped single-crystal nickel-rich ternary positive electrode material is obtained by doping and coating with W, effectively enhancing the structural stability of the single-crystal nickel-rich ternary positive electrode material, reducing the polarization of the material, improving the lithium ion diffusion kinetics, and thus improving the cycle stability and rate performance of the battery. However, single modification with tungsten elements cannot better improve the structural stability.

[0012] As disclosed in Chinese patent CN111900401A, a method for coating lithium battery positive electrode material with tungsten oxide and nitrogen-doped carbon is disclosed, which uses the polymerization of carbon precursor and the precipitation of tungsten precursor to form a coating layer on the surface of lithium battery positive electrode material, and then realizes the solidification and bonding of the coating layer through calcination process. It has the characteristics of low cost, low energy consumption and simple operation. The lithium battery positive electrode material has excellent electronic conductivity and electrochemical stability. However, it mainly involves adding tungsten-containing solution to the precursor, which is difficult to control the related parameters of the coprecipitation reaction, and the effect has certain limitations.

[0013] As disclosed in Chinese patent CN112531154A, a tungsten trioxide micro-nanoparticle gradient-doped ternary material is disclosed, which realizes tungsten doping during the precursor wet synthesis stage, activates the material surface layer with hydrogen peroxide solution under normal temperature and pressure conditions, and recrystallizes the material after doping tungsten under low temperature sintering conditions. The tungsten element can realize gradient distribution from the surface layer to the inside of the ternary material at the atomic level. The tungsten element and nickel-cobalt-manganese form a crystal nucleus that effectively fills the voids of the secondary particle accumulation of the ternary material, stabilizes the composition structure of the ternary material, and solves the problems of uneven tungsten doping and high sintering temperature caused by high energy consumption.

[0014] As disclosed in Chinese patent CN113764647A, a zirconium and multi-anion doped modified ternary positive electrode material precursor and ternary positive electrode material are disclosed, which provides a Zr and multi-anion co-doped ternary precursor scheme. It mainly uses anionic and cationic compounds to mix and add modified materials in the precursor solution end. However, it still needs further modification during high-temperature calcination preparation due to the element interface fusion and the growth of crystal boundary diffusion defects during high-temperature preparation.

[0015] For example, Chinese patent CN112811403A discloses a Mg / Ti co-doped Li3PO4 coated high-nickel ternary positive electrode material. A high-nickel precursor is used as a raw material. A nickel-cobalt-manganese precursor, a lithium source, a magnesium compound (magnesium carbonate or magnesium hydroxide), and a titanium compound (titanium oxide or titanium hydroxide) are added to a high-speed mixer in a certain proportion and mixed thoroughly. The mixture is pre-fired at a low temperature and then calcined at a high temperature in an oxygen atmosphere to obtain a doped base material. The doped base material and a lithium phosphate compound are mixed in a certain proportion in a mixer and sintered again in an oxygen atmosphere to obtain a lithium phosphate coated positive electrode material. This method is simple in process. The layered distribution of Mg / Ti double dopants can enhance the surface stability and crystal structure stability. The Li3PO4 coating layer helps to reduce the electrochemical impedance and electrolyte side reactions, thereby improving the thermal stability and cycle performance of the high-nickel ternary positive electrode material.

[0016] For example, Chinese patent CN113307310B discloses a preparation method of a high-cycle-performance molybdenum-doped titanium dioxide coated high-nickel ternary positive electrode material. The high-nickel ternary positive electrode material is LiNi 0.9 Co 0.05 Al 0.05 O2; Mo 6+ The doping of TiO2 forms vacancy defects, improves the electronic conductivity of TiO2, and improves the rate performance of the high-nickel ternary positive electrode material. At the same time, the Mo-doped TiO2 coating layer separates the high-nickel ternary positive electrode material from the electrolyte, avoids the corrosion of the active material high-nickel ternary positive electrode material by trace HF in the electrolyte, and improves the cycle performance of the high-nickel ternary positive electrode material, thereby generating in situ a Mo-doped TiO2 coated high-nickel ternary positive electrode material with excellent cycle performance and rate performance.

[0017] For example, Chinese patent CN108878861B discloses a method for repairing the surface of a ternary positive electrode material and a ternary positive electrode material. The method includes the following steps: (1) adding a substrate to an aqueous solution of a template agent, adding aluminum isopropoxide and a mixed solution of phosphoric acid / boric acid, stirring and reacting to obtain a pre-product; (2) placing the pre-product in an atmosphere furnace, sintering at 300-850°C for 3-8h in an air atmosphere at a heating rate of 1-10°C / min, naturally cooling to room temperature, and sieving to obtain a ternary positive electrode material coated with a mesoporous boron aluminum phosphate layer. The ternary positive electrode material repaired by the above method has good high-voltage cycle stability, higher energy utilization rate (first coulombic efficiency 90%), and a capacity retention rate of ≥97% at the 50th week, which can be as high as 99%. SUMMARY

[0018] The object of the present invention is to provide a titanium-strontium-fluorine composite doped and co-coated high-voltage ternary cathode material, its preparation method and application. The high-voltage ternary cathode material has the advantages of stable structure, low DCIR value, and good rate performance, cycle performance and storage performance. The lithium-ion battery prepared therefrom has the advantages of high specific capacity per gram, low DCIR growth, long cycle performance and excellent comprehensive performance.

[0019] The technical solution adopted by the present invention to achieve the above object is as follows.

[0020] The present invention provides a titanium-strontium-fluorine composite doped and co-coated high-voltage ternary cathode material, the structural general formula of which is: LiNi x Co y Mn z Ti a Al b W c Mg d Zr e Nb f B g Sr h F n PO 2-n , where 0.5 ≤ x < 1.0, 0 < y ≤ 0.30, 0 < z ≤ 0.40, and x + y + z + a + b + c + d + e + f + g + h + n = 1.

[0021] The present invention also provides a preparation method for the above-mentioned titanium-strontium-fluorine composite doped and co-coated high-voltage ternary cathode material, which includes the following steps:

[0022] Step 1: Mix the cathode material precursor, lithium source and titanium-strontium-fluorine dopant evenly, and perform the first sintering treatment in an oxygen-containing atmosphere. After cooling, crushing, sieving and demagnetization, a cathode material doped matrix is obtained;

[0023] The structural formula of the cathode material precursor is Ni x Co y Mn z (OH)2, where 0.5 ≤ x < 1.0, 0 < y ≤ 0.30, 0 < z ≤ 0.40, and x + y + z = 1;

[0024] The titanium-strontium-fluorine dopant is a mixture of SrTiO3, MgF2, ZrO2 and θ-Al2O3;

[0025] The molar ratio of Li in the ternary cathode material precursor and lithium source + , and the total amount of doped metal elements in the titanium-strontium-fluorine dopant is 1:(0.92 - 1.12):(0.002 - 0.070);

[0026] The first sintering process is: first heating to 400-580℃ for 2-8h, second heating to 580-860℃ for 2-6h, third heating to 740-1000℃ for 8-20h;

[0027] Step two, mixing the positive electrode material doped substrate prepared in step one with the titanium and strontium containing coating agent to obtain a primary coating product; or dispersing the titanium and strontium containing coating agent in a solvent, then adding the ternary positive electrode material doped substrate prepared in step two, stirring, evaporating, separating, and drying to obtain a primary coating product;

[0028] In an oxygen-containing atmosphere, the primary coating product is heated to 510-800℃ for 1-20h for second sintering treatment, and after cooling, crushing, sieving, and demagnetizing, a positive electrode material coating substrate is obtained;

[0029] The molar ratio of the ternary positive electrode material doped substrate to the total amount of coating elements in the titanium and strontium containing coating agent is 1:(0.002-0.030);

[0030] The titanium and strontium containing coating agent is a mixture of SrTiO3, WO3, NbO2, and TiO2;

[0031] Step three, mixing the positive electrode material coating substrate prepared in step two with a lithium and boron containing additive (additive 3) to perform secondary coating, heating to 180-530℃ for 1-10h for third sintering treatment in an oxygen-containing atmosphere, and after coarse crushing, fine crushing, sieving, and demagnetizing, a titanium and strontium and fluorine composite doped and co-coated high-voltage ternary positive electrode material is obtained;

[0032] The lithium and boron containing additive is a mixture of LiF and BPO4.

[0033] Preferably, in step one, the molar ratio of Li + The molar ratio of the total amount of doped metal elements in the titanium and strontium and fluorine doped agent is 1:(0.96-1.10):(0.002-0.064), more preferably 1:(0.98-1.08):(0.01-0.06).

[0034] Preferably, in step one, the mass ratio of the ternary positive electrode material precursor to SrTiO3 is 100:(0.05-0.70), more preferably 100:(0.1-0.60), and especially preferably 100:(0.20-0.50).

[0035] Preferably, in step one, the purity of SrTiO3 is 99.5%, the D 50 The particle size is 0.5μm-16μm, more preferably 1μm-10μm, and especially preferably 2μm-6μm.

[0036] Preferably, in the step one, the mass ratio of the ternary cathode material precursor to Zr02 is 100:(0.05-0.60), more preferably 100:(0.08-0.50), and particularly preferably 100:(0.12-0.44).

[0037] Preferably, in the step one, the purity of Zr02 is 99.9%, and the particle size is 0.5-15 μm, more preferably 1-10 μm, and particularly preferably 3-8 μm. 50 Preferably, in the step one, the purity of Zr02 is 99.9%, and the particle size is 0.5-15 μm, more preferably 1-10 μm, and particularly preferably 3-8 μm.

[0038] Preferably, in the step one, the mass ratio of the ternary cathode material precursor to MgF2 is 100:(0.03-0.40), more preferably 100:(0.05-0.30), and particularly preferably 100:(0.1-0.24).

[0039] Preferably, in the step one, the purity of MgF2 is 99.9%, and the particle size is 0.5-15 μm, more preferably 1-12 μm, and particularly preferably 3-6 μm. 50 Preferably, in the step one, the purity of MgF2 is 99.9%, and the particle size is 0.5-15 μm, more preferably 1-12 μm, and particularly preferably 3-6 μm.

[0040] Preferably, in the step one, the mass ratio of the ternary cathode material precursor to θ-Al203 is 100:(0.01-0.5), more preferably 100:(0.04-0.4), and particularly preferably 100:(0.05-0.30).

[0041] Preferably, in the step one, the purity of θ-Al203 is 99.9%, and the particle size is 1-30 μm, more preferably 2-20 μm, and particularly preferably 3-10 μm. 50 Preferably, in the step one, the purity of θ-Al203 is 99.9%, and the particle size is 1-30 μm, more preferably 2-20 μm, and particularly preferably 3-10 μm.

[0042] Preferably, in the step one, the lithium source is a lithium-containing compound, which is one or a mixture of several of LiOH, LiOH-H20, Li2CO3, and LiNO3; more preferably, the lithium source is LiOH-H20 or Li2CO3.

[0043] Preferably, in the step one, the particle size of the lithium source is 3-20 μm, and more preferably 4-12 μm; the coarse lithium source can be mechanically ground to the desired particle size, or a lithium source of the desired particle size can be selected from the market.

[0044] Preferably, in the step one, the equipment for mixing is a ball mill, a tank mill, a ploughshare mixer, or a high-speed mixer; more preferably, the equipment for mixing is a ball mill, a ploughshare mixer, or a high-speed mixer.

[0045] Preferably, in the step one, the first temperature rising is 420-560℃ for 3-6h, the second temperature rising is 620-840℃ for 3-5h, and the third temperature rising is 740-1000℃ for 8-16h; more preferably, the first temperature rising is 460-530℃ for 4-6h, the second temperature rising is 680-820℃ for 3-4h, and the third temperature rising is 740-1000℃ for 9-14h.

[0046] Preferably, in the step one, the first sintering treatment is carried out by using a muffle furnace or a tube furnace, and the temperature rising rate of the first temperature rising, the second temperature rising and the third temperature rising is independently 1-5℃ / min, more preferably, the temperature rising rate is 2-4℃ / min, and especially preferably, the temperature rising rate is 3℃ / min.

[0047] Preferably, in the step one, the first sintering treatment is carried out by using an atmosphere roller kiln or a rotary furnace, and the temperature rising rate of the first temperature rising, the second temperature rising and the third temperature rising is independently 1-30℃ / h, more preferably, the temperature rising rate is 5-20℃ / h, and especially preferably, the temperature rising rate is 10℃ / h.

[0048] Preferably, in the step one, the concentration of the oxygen-containing atmosphere is ≥95%.

[0049] Preferably, in the step two, the mass ratio of the ternary positive electrode material doped substrate to SrTiO3 is 100:(0.02-0.25), more preferably, 100:(0.04-0.20), and especially preferably, 100:(0.10-0.18).

[0050] Preferably, in the step two, the purity of SrTiO3 is 99.5%, and the particle size is 0.5μm-20μm, more preferably, 1μm-10μm, and especially preferably, 2μm-6μm. 50 Preferably, in the step two, the purity of SrTiO3 is 99.5%, and the particle size is 0.5μm-20μm, more preferably, 1μm-10μm, and especially preferably, 2μm-6μm.

[0051] Preferably, in the step two, the mass ratio of the ternary positive electrode material doped substrate to WO3 is 100:(0.08-0.50), more preferably, 100:(0.10-0.40), and especially preferably, 100:(0.15-0.38).

[0052] Preferably, in the step two, the purity of WO3 is 99.9%, and the particle size is 20nm-100nm. 50 Preferably, in the step two, the purity of WO3 is 99.9%, and the particle size is 20nm-100nm.

[0053] Preferably, in the step two, the mass ratio of the ternary positive electrode material doped substrate to NbO2 is 100:(0.02-0.20), more preferably, 100:(0.05-0.18), and especially preferably, 100:(0.06-0.15).

[0054] Preferably, the purity of NbO2 in step two is 99.9%, D 50 The particle size is 20-60 nm.

[0055] Preferably, the mass ratio of the ternary positive electrode material doped matrix to TiO2 in step two is 100:(0.02-0.20), more preferably 100:(0.05-0.18), and particularly preferably 100:(0.06-0.15).

[0056] Preferably, the purity of TiO2 in step two is 99.8%, D 50 The particle size is 20-120 nm.

[0057] Preferably, in step two, the first coating product is heated to 530-780°C for 3-14 h for the second sintering treatment, and more preferably, the first coating product is heated to 550-760°C for 6-11 h for the second sintering treatment.

[0058] Preferably, in step two, the heating rate of the second sintering treatment is 1-20°C / h.

[0059] Preferably, in step two, the separation mode is pressure filtration or centrifugation, the drying temperature is 120-200°C, and the drying time is 1-12 h; more preferably, the drying temperature is 130-180°C, and the drying time is 3-10 h; and particularly preferably, the drying temperature is 150-160°C, and the drying time is 4-8 h.

[0060] Preferably, in step three, the mass ratio of the ternary positive electrode material coated matrix to LiF is 100:(0.03-0.75), more preferably 100:(0.1-0.60), and particularly preferably 100:(0.15-0.45).

[0061] Preferably, in step three, the purity of LiF is 99.0%, D 50 The particle size is 60-150 nm.

[0062] Preferably, in step three, the mass ratio of the ternary positive electrode material coated matrix to BPO4 is 100:(0.1-0.95), more preferably 100:(0.2-0.80), and particularly preferably 100:(0.25-0.70).

[0063] Preferably, in step three, the purity of BPO4 is 99.9%, D 50 The particle size is 30-150 nm.

[0064] Preferably, in the third step, the third sintering treatment is performed at a temperature of 200-510°C for 3-8h, more preferably at a temperature of 220-480°C for 4-7h.

[0065] Preferably, in the third step, the third sintering treatment is performed at a temperature of 200-510°C for 3-8h, more preferably at a temperature of 220-480°C for 4-7h.

[0066] Preferably, in the third step, the second coating is performed by using a high-speed mixer or a mechanical fusion machine, more preferably a high-speed mixer.

[0067] Preferably, in the first step, the ternary cathode material precursor is a small-particle ternary cathode material precursor or a large-particle ternary cathode material precursor, the small-particle ternary cathode material precursor has a D 50 particle size of 2.0-8.0μm, and the large-particle ternary cathode material precursor has a D 50 particle size of 9-18μm.

[0068] When the ternary cathode material precursor is a large-particle ternary cathode material precursor, the ternary cathode material doped substrate prepared in the first step has a D 50 particle size of 9-16μm, the cathode material coated substrate prepared in the second step has a D 50 particle size of 9-16μm, and the high-voltage cathode material prepared in the third step has a D 50 particle size of 8-18μm.

[0069] When the ternary cathode material precursor is a small-particle ternary cathode material precursor, the ternary cathode material doped substrate prepared in the first step has a D 50 particle size of 2.5-6.0μm, the cathode material coated substrate prepared in the second step has a D 50 particle size of 2.8-6.2μm, and the high-voltage cathode material prepared in the third step has a D 50 particle size of 2.5-6.4μm.

[0070] More preferably, the large-particle ternary cathode material precursor has a D 50 particle size of 10-15μm, the ternary cathode material doped substrate has a D 50 particle size of 10-14μm, and the cathode material coated substrate has a D 50 particle size of 10-15μm.

[0071] The small-particle ternary cathode material precursor has a D 50 particle size of 3.0-6.0μm, the ternary cathode material doped substrate has a D 50 particle size of 3.0-5.0μm, and the cathode material coated substrate has a D 50The particle size is 3.0-5.8 μm, and the D 50 The particle size is 3.2-4.8 μm.

[0072] Preferably, the oxygen-containing atmosphere in the step one, step two and step three is independently ≥95%.

[0073] Preferably, the method further comprises step four, the batch mixing of the titanium-strontium-fluorine composite doped co-coated high-voltage cathode material is carried out in a dehydration carbon dioxide removal dry gas or inert atmosphere.

[0074] More preferably, the batch mixing conditions are: dry gas dew point < -45℃, mixing frequency 45±5 Hz, and mixing time 0.5-2 h.

[0075] More preferably, the batch mixing equipment is a spiral belt batch mixer or a high-speed mixer.

[0076] The application also provides the application of the above-mentioned titanium-strontium-fluorine composite doped co-coated high-voltage ternary cathode material or the titanium-strontium-fluorine composite doped co-coated high-voltage ternary cathode material prepared by the above-mentioned preparation method in the preparation of a secondary battery cathode sheet or a secondary battery.

[0077] Preferably, the secondary battery is a lithium ion battery.

[0078] The application also provides a secondary battery cathode sheet or a secondary battery prepared by the above-mentioned titanium-strontium-fluorine composite doped co-coated high-voltage ternary cathode material or the titanium-strontium-fluorine composite doped co-coated high-voltage ternary cathode material prepared by the above-mentioned preparation method.

[0079] Compared with the prior art, the application has the following beneficial effects:

[0080] The titanium-strontium-fluorine composite doping co-coated high-voltage ternary positive electrode material is modified by co-doping SrTiO3, MgF2, ZrO2 and θ-Al2O3 on the basis of traditional nickel-cobalt-manganese materials; wherein, the Sr / Mg elements in SrTiO3 and MgF2 promote the grain growth and improve the crystalline particle strength, so that the compression resistance can be improved and the calcination temperature can be reduced to reduce the energy consumption; the anion co-doping of the doped MgF2 increases the Mohs hardness of the particles, so that the Sr / Zr / Mg / / Al / Ti has the inward diffusion effect, the cation mixing is inhibited, the interlayer distance is increased, and the ion migration ability is improved; especially, the tetragonal crystal system of SrTiO3, the tetragonal crystal system of MgF2 and the cubic crystal system of ZrO2 are used to enhance the structural stability, and the θ-Al2O3 has certain structural stability at low temperature and is converted into stable α phase at high temperature, so that the structure evolution characteristics are further improved, and the structure and thermal stability of the ternary positive electrode material are improved. The titanium-strontium-fluorine composite doping co-coated high-voltage ternary positive electrode material is modified by co-doping SrTiO3, MgF2, ZrO2 and θ-Al2O3, and is reacted by high-temperature sintering solid phase method, so that Sr / Zr / Mg / / Al / Ti / F forms anion and cation co-doping, the particle strength is effectively increased, the reversible capacity is improved, the side reaction between the active material and the electrolyte is reduced, the solubility of manganese in the organic electrolyte is reduced, the cycle performance of the material at high voltage is effectively improved, the ion channel and the interlayer distance are widened, the discharge efficiency and the rate capability of the material are improved, the high-temperature electrochemical performance of the material is improved, the Li / Ni mixing degree is reduced, and the application performance of the battery product is ensured.

[0081] The titanium-strontium-fluorine composite doping co-coated high-voltage ternary positive electrode material is further coated and modified by using SrTiO3, WO3, NbO2 and TiO2 as coating agents; wherein, the conductivity mechanism can be further improved by adding a small amount of TiO2 in combination with SrTiO3, the secondary growth of fine particles is promoted by using Sr, the processing characteristics of small particles are improved, and the reaction mechanism of NbO2 and SrTiO3 is used: Nb 5+ SrTiO3 is doped. When Sr 2+ or Ti 4+ ions are partially replaced by La 3+ or Nb 5+ ions, the electrical conductivity can be improved. Among them, Nb 5+ and Ti 4+ have similar radii, so they can be doped without affecting the stability of the cubic perovskite structure. Since the valence of Nb 5+ is higher than that of Ti 4+When doped, electrons will be introduced into the system, so that strontium titanium niobium forms surface doping characteristics, and repairs the surface particle morphology, while WO3 coating further improves the surface conductivity of the ternary positive electrode material, improves the particle surface corrosion resistance and high temperature performance; reduces the DCIR and cycle impedance growth of the battery; can effectively improve the material surface resistance to electrolyte corrosion, material rate, surface conductivity, ion migration ability, etc.; through NbO2 and WO3 coating, the discharge capacity, initial efficiency and cycle performance can be improved, and the application performance of the battery product is ensured.

[0082] The titanium strontium fluorine composite doped co-coated high-voltage ternary positive electrode material of the application further adopts LiF, BPO4 and an oxide substrate containing Ni / Co / Mn / Ti / Sr / W / F / Zr / Al / Mg / Nb to form secondary coating, and then forms a surface gradient coating layer and a surface fast ion conductor, which can further improve the surface conductivity and reduce the surface residual alkali, thereby inhibiting the occurrence of interface side reactions, effectively enhancing the surface gradient coating protective layer, and further increasing the Li ion migration induction ability and improving the material cycle performance.

[0083] In summary, the titanium strontium fluorine composite doped co-coated high-voltage ternary positive electrode material of the application adopts a gradient modification method of multi-element composite doping and coating, effectively improves the Li / Ni mixing arrangement in the positive electrode material and the particle surface energy band effect through Ti / Mg / Sr / Al / F doping and Ti / Sr / W / Nb / Li / B coating and anion and cation doping and coating, improves the structural stability and thermal stability of the high-voltage ternary positive electrode material, and improves the rate / cycle / storage performance and DCIR, has the advantages of more stable layered structure, higher electronic conductivity, higher rate, longer cycle performance, storage and lower DCIR. The lithium ion battery prepared by the high-voltage ternary positive electrode material provided by the application has higher gram-specific capacity, rate and cycle performance and application effect, has the advantages of higher gram-specific capacity, low DCIR growth, long cycle performance and excellent comprehensive performance. BRIEF DESCRIPTION OF DRAWINGS

[0084] In order to more clearly illustrate the technical solutions in the embodiments of the application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative labor.

[0085] Figure 1 The XRD characterization graph of strontium titanate used in the embodiments 1-3 of the application;

[0086] Figure 2 The process flow chart of the preparation method of the titanium strontium fluorine composite doped co-coated high-voltage ternary positive electrode material of the embodiments 1-3 of the application;

[0087] Figure 3 In the figure, (a)-(c) are the SEM morphology characteristics of the titanium, strontium and fluorine composite doped co-coated high-voltage ternary cathode materials prepared in Examples 1-3, respectively;

[0088] Figure 4 In the figure, (a)-(c) are charge-discharge curves of the titanium, strontium, and fluorine composite doped co-coated high-voltage ternary positive electrode materials prepared in Examples 1-3, respectively;

[0089] Figure 5 In the figure, (a)-(c) are the cycle curves of button batteries assembled with the ternary cathode materials in Examples 1-3 and Comparative Examples 1-3, respectively;

[0090] Figure 6 In the figure, (a) and (b) are the cycle curves of the full battery of the ternary positive electrode materials in Example 2 and Comparative Example 2 at 25°C and 45°C, respectively. DETAILED DESCRIPTION

[0091] In order to further understand the present invention, preferred embodiments of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0092] In the embodiments of the present invention, the selected SrTiO3 can be purchased from the market with the same required specifications, or can be prepared according to traditional synthesis methods. For example, using strontium carbonate and titanium dioxide as raw materials, equal amounts of strontium carbonate, titanium dioxide and other additives are mixed and ground, extruded into a shape, placed in an electric furnace, and calcined at 1100-1200°C for 2.5-3 hours. The calcined product is crushed, then ground, acid-washed, filtered, washed, and dried to obtain strontium titanate. The XRD characterization diagram of the strontium titanate is shown in the attached figure. Figure 1 shown.

[0093] In the following examples of the present invention, the BPO4 selected can be purchased commercially from such raw materials of equivalent specifications or prepared according to conventional synthesis methods. For example, boric acid is used as the boron source, and a mixture of ammonium phosphate and phosphoric acid is used as the phosphorus source, with a molar ratio of B2O3:P2O5 = 0.9-1.1:1. The mixed materials are granulated in a granulator, and then calcined in a rotary kiln for 1-3 hours to synthesize the boron phosphate product in a single step using a high-temperature solid-phase reaction method, with the sintering temperature controlled at 300°C-1000°C. The material exiting the rotary kiln is cooled and pulverized to obtain the desired boron phosphate product.

[0094] Example 1

[0095] like Figure 2As shown, the preparation method of the titanium-strontium-fluorine composite doped co-coated high-voltage positive electrode material of the embodiment includes the following steps:

[0096] (1) According to the conventional method, the precursor Ni 0.65 Co 0.07 Mn 0.28 (OH)2(D 50 4.1±0.8 μm), Li2CO3(D 50 6±2 μm) and the dopant (additive 1) SrTiO3(D 50 4.0±1.0 μm), MgF2(D 50 4.0±1.0 μm), ZrO2(D 50 4.0±1.0 μm), θ-Al2O3(D 50 5.0±2.0 μm) raw materials are weighed respectively, Ni 0.65 Co 0.07 Mn 0.28 (OH)2(4000 g), Li2CO3(1686.594 g), SrTiO3(15.153 g), MgF2(4.105 g), ZrO2(8.113 g), θ-Al2O3(11.349 g); the materials are transferred into a high-speed mixer, and the three powders are uniformly mixed by adopting a four-stage mode of 100 rmp / 2 min, 400 rmp / 2 min, 1000 rpm / 15 min and 100 rmp / 3 min, and then loaded into a crucible and transferred into an atmosphere muffle furnace, and then sintered at a rate of 2 ℃ / min to 476 ℃ under a micro-positive pressure oxygen atmosphere for 4.8 h, and then sintered at 774 ℃ for 3.2 h, and then sintered at 957 ℃ for 10.6 h; after cooling, crushing, sieving and demagnetizing, the ternary positive electrode material doped matrix is obtained.

[0097] (2) 3800 g of the obtained ternary positive electrode material doped matrix is put into a high-speed mixer with the coating agent (additive 2) SrTiO3(D 50 4.0±1.0 μm) (4.779 g), WO3(D 50 50.0±20.0 nm) (11.034 g), NbO2(D 50 30.0±20.0 nm) (3.068 g) and TiO2(D 50 60.0±20.0 nm) (2.4521 g), and the three powders are uniformly mixed by adopting a three-stage mode of 100 rmp / 2 min, 1200 rpm / 30 min and 200 rmp / 3 min, and then loaded into a crucible, and then sintered at 680 ℃ for 8.4 h under an oxygen or oxygen empty (5:5) atmosphere, and then crushed by a colloid mill after cooling, sieved and demagnetized, and then the positive electrode material coating matrix is obtained.

[0098] (3) The obtained positive electrode material coated substrate sample 3700g was mixed with additives (additive 3) LiF (D 50 60.0±20.0nm) (11.735g) and BPO4(D 50 60.0±20.0nm) (17.121g) in a high-speed mixer, and mixed uniformly in a three-stage mode of 100rmp / 2min, 1200rpm / 30min, 200rmp / 3min. The three powders were then loaded into a crucible and sintered at 360℃ for 5.8h in a dry air atmosphere. After cooling, the material was broken by a colloid mill and sieved to remove the magnetic material. The obtained ternary positive electrode material was mixed in a batch mixing tank for 1.5h, and the finished product was obtained by sieving and removing the magnetic material, and then packaged. The relevant physical and chemical data were tested.

[0099] Example 2

[0100] As Figure 2 shown, the preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage positive electrode material of the present embodiment includes the following steps:

[0101] (1) According to the conventional method, the precursors Ni 0.68 Co 0.08 Mn 0.24 (OH)2(D 50 4.0±0.8μm), Li2CO3(D 50 6±2μm) and dopants (additive 1) SrTiO3(D 50 4.0±1.0μm), MgF2(D 50 4.0±1.0μm), ZrO2(D 50 4.0±1.0μm), θ-Al2O3(D 50 5.0±2.0μm) were prepared. 0.68 Co 0.08 Mn 0.24(OH)2(4000g), Li2CO3(1680.556g), SrTiO3(15.995g), MgF2(4.105g), ZrO2(8.113g), θ-Al2O3(12.105g); the materials are transferred into a high-speed mixer, and the three powders are mixed uniformly by using a four-stage mode of 100rmp / 2min, 400rmp / 2min, 1000rpm / 15min, and 100rmp / 3min, and then loaded into a crucible, and then transferred into a muffle furnace in an oxygen atmosphere, and then sintered at 476°C for 4.8h at a rate of 2°C / min, and then sintered at 774°C for 3.2h, and then sintered at 952°C for 10.8h; after cooling, crushing, sieving, and demagnetization, the ternary positive electrode material doped substrate is obtained;

[0102] (2) 3800g of the obtained doped substrate is sampled and mixed with the coating agent (additive 2) SrTiO3(D 50 4.0±1.0μm)(4.779g), WO3(D 50 50.0±20.0nm)(11.513g), NbO2(D 50 30.0±20.0nm)(3.068g), and TiO2(D 50 60.0±20.0nm)(2.4521g) into a high-speed mixer, and the three powders are mixed uniformly by using a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min, and then loaded into a crucible, and then sintered at 660°C for 8.4h in an oxygen or oxygen empty (5:5) atmosphere, and then crushed by a colloid mill after cooling, and then sieved and demagnetized, to obtain the positive electrode material coating substrate;

[0103] (3) 3700g of the obtained substrate is sampled and mixed with the additive (additive 3) LiF(D 50 60.0±20.0nm)(13.967g) and BPO4(D 50 60.0±20.0nm)(21.401g) into a high-speed mixer, and the three powders are mixed uniformly by using a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min, and then loaded into a crucible, and then sintered at 350°C for 5.8h in a dry air atmosphere, and then crushed by a colloid mill after cooling, and then sieved and demagnetized; the obtained ternary positive electrode material is put into a batch mixing tank and mixed for 1.5h, and then discharged, sieved, demagnetized, packaged to obtain the ternary positive electrode material finished product, and the related physical and chemical data are tested.

[0104] Example 3

[0105] As Figure 2The preparation method of the titanium-strontium-fluorine composite doped co-coated high-voltage positive electrode material in the embodiment shown in the flow chart comprises the following steps:

[0106] (1) According to a conventional method, prepare the precursor Ni 0.78 Co 0.07 Mn 0.15 (OH)2(D 50 4.0±0.8 μm), LiOH·H2O (D 50 5±2 μm) and the dopant (additive 1) SrTiO3 (D 50 4.0±1.0 μm), MgF2 (D 50 4.0±1.0 μm), ZrO2 (D 50 4.0±1.0 μm), θ-Al2O3 (D 50 5.0±2.0 μm) raw materials, respectively, take Ni 0.78 Co 0.07 Mn 0.15 (OH)2 (4000 g), LiOH·H2O (1899.916 g), SrTiO3 (16.837 g), MgF2 (5.138 g), ZrO2 (8.113 g), θ-Al2O3 (14.375 g); transfer the materials into a high-speed mixer, adopt a four-stage mode of 100 rmp / 2 min, 400 rmp / 2 min, 1000 rpm / 15 min and 100 rmp / 3 min to mix the three powders uniformly, load into a crucible, and then transfer into a muffle furnace in an oxygen atmosphere, heat to 476℃ at a rate of 2℃ / min, sinter for 4.8 h, then heat to 774℃, sinter for 3.2 h, and then heat to 903℃, sinter for 11.2 h; after cooling, crushing, sieving and demagnetizing, the ternary positive electrode material doped substrate is obtained;

[0107] (2) Take 3800 g of the obtained doped substrate and the coating agent (additive 2) SrTiO3 (D 50 4.0±1.0 μm) (6.372 g), WO3 (D 50 50.0±20.0 nm) (11.993 g), NbO2 (D 50 30.0±20.0 nm) (3.068 g), TiO2 (D 50 60.0±20.0 nm) (2.4521 g) into a high-speed mixer, mix the three powders uniformly according to a three-stage mode of 100 rmp / 2 min, 1200 rpm / 30 min and 200 rmp / 3 min, load into a crucible, heat to 640℃ under an oxygen or oxygen empty (5:5) atmosphere, sinter for 8.4 h, crush by a colloid mill after cooling, sieve and demagnetize, and obtain the positive electrode material coating substrate.

[0108] (3) The obtained substrate was sampled 3700 g and mixed with additive LiF (additive 3) (D 50 with a particle size of 60.0±20.0 nm) (16.76 g) and BPO4 (D 50 with a particle size of 60.0±20.0 nm) (25.68 g) in a high-speed mixer in a three-stage mode of 100 rmp / 2 min, 1200 rpm / 30 min, and 200 rmp / 3 min. After the three powders were uniformly mixed, they were loaded into a crucible and sintered at 340°C for 5.8 h in a dry air atmosphere. After cooling, the material was broken by a colloid mill and sieved to remove the magnetism. The obtained ternary positive electrode material was mixed in a batch mixing tank for 1.5 h, and the finished product was obtained after screening and removing the magnetism, and then packaged. The relevant physical and chemical data were tested.

[0109] Comparative Example 1

[0110] The preparation method of the positive electrode material in the present comparative example comprises the following steps:

[0111] (1) According to the conventional method, the precursor Ni 0.65 Co 0.07 Mn 0.28 (OH)2 (D 50 with a particle size of 4.1±0.8 μm), Li2CO3 (D 50 with a particle size of 6±2 μm), and the dopant MgF2 (D 50 with a particle size of 4.0±1.0 μm), ZrO2 (D 50 with a particle size of 4.0±1.0 μm), and θ-Al2O3 (D 50 with a particle size of 5.0±2.0 μm) were weighed as raw materials. Ni 0.65 Co 0.07 Mn 0.28 (OH)2 (4000 g), Li2CO3 (1686.594 g), MgF2 (4.105 g), ZrO2 (8.113 g), and θ-Al2O3 (11.349 g) were respectively transferred into a high-speed mixer. The three powders were uniformly mixed in a four-stage mode of 100 rmp / 2 min, 400 rmp / 2 min, 1000 rpm / 15 min, and 100 rmp / 3 min. After loading into a crucible, the material was transferred into a muffle furnace in an oxygen atmosphere. The temperature was increased to 476°C at a rate of 2°C / min, and sintered for 4.8 h. Then the temperature was increased to 774°C, and sintered for 3.2 h. Then the temperature was increased to 972°C, and sintered for 12.4 h. After cooling, breaking, sieving, and removing the magnetism, the ternary positive electrode material doped substrate was obtained.

[0112] (2) The obtained doped substrate was sampled 3800 g and mixed with WO3 (D 5050.0±20.0nm) (11.034g), NbO2(D 50 30.0±20.0nm) (3.068g), TiO2(D 50 60.0±20.0nm) (2.4521g) were put into a high-speed mixer, mixed uniformly in a three-stage mode of 100rmp / 2min, 1200rpm / 30min, 200rmp / 3min, and then loaded into a crucible, sintered at 680°C for 9.6h under an oxygen or oxygen empty (5:5) atmosphere, broken by a colloid mill after cooling, and sieved to remove magnetism, to obtain a positive electrode material coated substrate;

[0113] (3) The obtained substrate was sampled 3700g and added with additive BPO4(D 50 60.0±20.0nm) (17.121g) were put into a high-speed mixer, mixed uniformly in a three-stage mode of 100rmp / 2min, 1200rpm / 30min, 200rmp / 3min, and then loaded into a crucible, sintered at 360°C for 5.8h under a dry air atmosphere, broken by a colloid mill after cooling, and sieved to remove magnetism; the obtained ternary positive electrode material was put into a batch mixing tank and mixed for 1.5h, discharged, sieved to remove magnetism, packaged to obtain a ternary positive electrode material product, and related physical and chemical data were tested.

[0114] Comparative Example 2

[0115] The preparation method of the positive electrode material in the present comparative example comprises the following steps:

[0116] (1) According to a conventional method, a precursor Ni 0.68 Co 0.08 Mn 0.24 (OH)2(D 50 4.0±0.8μm), Li2CO3(D 50 6±2μm) and a dopant MgF2(D 50 4.0±1.0μm), ZrO2(D 50 4.0±1.0μm), θ-Al2O3(D 50 5.0±2.0μm) were weighed, respectively. 0.68 Co 0.08 Mn 0.24(OH)2(4000g), Li2CO3(1680.556g), MgF2(4.105g), ZrO2(8.113g), θ-Al2O3(12.105g); the materials are transferred into a high-speed mixer, and the three powders are mixed uniformly by using a four-stage mode of 100rmp / 2min, 400rmp / 2min, 1000rpm / 15min, and 100rmp / 3min, and then loaded into a crucible, and then transferred into a muffle furnace in an oxygen atmosphere, and then sintered at 476℃ for 4.8h at a rate of 2℃ / min, and then sintered at 774℃ for 3.2h, and then sintered at 962℃ for 12.4h; after cooling, crushing, sieving, and demagnetization, the ternary positive electrode material doped substrate is obtained;

[0117] (2) 3800g of the obtained doped substrate is sampled and mixed with a coating agent WO3(D 50 50.0±20.0nm) (11.513g), NbO2(D 50 30.0±20.0nm) (3.068g), and TiO2(D 50 60.0±20.0nm) (2.4521g) in a high-speed mixer by using a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min, and then loaded into a crucible, and then sintered at 660℃ for 8.4h in an oxygen or oxygen empty (5:5) atmosphere, and then crushed by a colloid mill after cooling, and then sieved and demagnetized, to obtain a positive electrode material coating substrate;

[0118] (3) 3700g of the obtained substrate is sampled and mixed with an additive BPO4(D 50 60.0±20.0nm) (21.401g) in a high-speed mixer by using a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min, and then loaded into a crucible, and then sintered at 350℃ for 5.8h in a dry air atmosphere, and then crushed by a colloid mill after cooling, and then sieved and demagnetized; the obtained ternary positive electrode material is mixed in a batch mixing tank for 1.5h, and then discharged, sieved, demagnetized, packaged, to obtain a ternary positive electrode material finished product, and related physical and chemical data are tested.

[0119] Comparative Example 3

[0120] The preparation method of the positive electrode material in the present comparative example comprises the following steps:

[0121] (1) according to a conventional method, a precursor Ni 0.78 Co 0.07 Mn 0.15 (OH)2(D 50 4.0±0.8μm), LiOH·H2O(D50 5±2μm) and MgF2(D 50 4.0±1.0μm), ZrO2(D 50 4.0±1.0μm), θ-Al2O3(D 50 5.0±2.0μm) raw materials, respectively, Ni 0.78 Co 0.07 Mn 0.15 (OH)2(4000g), LiOH·H2O (1899.916g), MgF2(5.138g), ZrO2(8.113g), θ-Al2O3(14.375g); the material was transferred into a high-speed mixer, and the three powders were mixed uniformly using a four-stage mode of 100rmp / 2min, 400rmp / 2min, 1000rpm / 15min, and 100rmp / 3min. After loading into a crucible, it was transferred into a muffle furnace in an oxygen atmosphere, and sintered at a rate of 2℃ / min to 476℃ for 4.8h, then to 774℃ for 3.2h, and then to 910℃ for 13.0h. After cooling, crushing, sieving, and demagnetization, a ternary positive electrode material doped substrate was obtained;

[0122] (2) 3800g of the obtained doped substrate was sampled and mixed with a coating agent WO3(D 50 50.0±20.0nm) (11.993g), NbO2(D 50 30.0±20.0nm) (3.068g), and TiO2(D 50 60.0±20.0nm) (2.4521g) in a high-speed mixer according to a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min. After the three powders were mixed uniformly, they were loaded into a crucible and sintered at 640℃ for 8.4h in an oxygen or oxygen empty (5:5) atmosphere. After cooling, crushing, sieving, and demagnetization, a positive electrode material coating substrate was obtained.

[0123] (3) 3700g of the obtained substrate was sampled and mixed with an additive BPO4(D 50 60.0±20.0nm) (25.68g) in a high-speed mixer according to a three-stage mode of 100rmp / 2min, 1200rpm / 30min, and 200rmp / 3min. After the three powders were mixed uniformly, they were loaded into a crucible and sintered at 340℃ for 5.8h in a dry air atmosphere. After cooling, crushing, sieving, and demagnetization, the obtained ternary positive electrode material was mixed in a batch mixing tank for 1.5h, and then sieved, demagnetized, and packaged to obtain a ternary positive electrode material finished product, and relevant physical and chemical data were tested.

[0124] The performance of the ternary positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 was detected, and the detection results are as follows.

[0125] 1. Physicochemical indexes

[0126] The ternary positive electrode materials prepared in the above Examples 1-3 and Comparative Examples 1-3 were analyzed for physicochemical indexes of the samples by using relevant devices such as a scanning electron microscope, a laser particle size instrument, and a Swiss Mettler automatic titration instrument, which are well known to those skilled in the art, and the test results are shown in Table 1 below.

[0127] The SEM images of the ternary positive electrode materials prepared in Examples 1-3 are shown in Figs. Figure 3 (a)-(c), respectively.

[0128] Table 1. Physicochemical index results of the ternary positive electrode materials of Examples 1-3 and Comparative Examples 1-3

[0129]

[0130] It can be seen that the performance indexes related to tapping and residual alkali of the Ni6507, Ni6808, and Ni7807 ternary positive electrode single crystal materials in Examples 1-3 are improved, and the materials have better performance advantages.

[0131] 2. Cycle performance test

[0132] The positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-3 were assembled into button cells (active material: PVDF: CNT: SP = 97.2: 1.1: 0.8: 0.9, solid content 73.5%) by using a method well known to those skilled in the art.

[0133] The first charge-discharge specific capacity (shown in Figs. Figure 4 (a)-(c)) and the 0.2C / 0.5C / 1.0C / 2.0C rate discharge performance of the button cells were tested at 25°C and 0.1C by using a blue light test system in a voltage range of 3.0-4.5V, and the results are shown in Table 2 below.

[0134] Table 2. Rate discharge performance test results

[0135]

[0136] The cycle retention rate of the button cells under 1C charge-discharge conditions was tested for 100 cycles, and the test results are shown in Figs. Figure 4 , wherein Figure 4 Fig. (a) is the results of Example 1 and Comparative Example 1, (b) is the results of Example 2 and Comparative Example 2, and (c) is the results of Example 3 and Comparative Example 3.

[0137] The soft package battery was prepared from the product of Example 2 and the product of Comparative Example 2, and the normal temperature and high temperature cycle performance was evaluated. The test results at different temperatures are shown in Table 2. Figures 5-6 The cycle DCIR test data of the product of Example 2 are shown in Table 3.

[0138] Table 3 Cycle DCIR test results of the product of Example 2

[0139]

[0140] It can be seen that the ternary positive electrode material prepared based on the formula and process flow system of titanium-strontium-fluorine doped co-coating has low DCIR excellent performance and normal temperature and high temperature long cycle performance. Through the high voltage positive electrode material prepared in Example 2, the capacity retention is more than 92.5% at 1C / 1C-100% DOD (2.75V-4.40V) under normal temperature cycle for 1500, as shown in (a) of Table 4; the capacity retention is more than 88% at high temperature cycle for 1500, as shown in (b) of Table 4, the DCIR growth is low, which can effectively ensure the stability of the output power in the later cycle. Figure 6 Figure 6

[0141] The above describes the embodiments of the present application in detail, and the principles and implementation modes of the present application are described by applying specific examples. The above description of the embodiments is only used to help understand the method of the present application and its core idea; at the same time, for those skilled in the art, according to the idea of the present application, the specific implementation mode and application range will be changed, and the above description of the present application should not be understood as a limitation of the present application.​​

Claims

1. A titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material, characterized in that, Structural formula: LiNi x Co y Mn z Ti a Al b W c Mg d Zr e Nb f B g Sr h F n PO 2-n , wherein 0.5≤x<1.0, 0<y≤0.30, 0<z≤0.40, and x+y+z+a+b+c+d+e+f+g+h+n=1; and a preparation method of the material comprises the following steps: Step 1: uniformly mix the ternary cathode material precursor, lithium source and titanium-strontium-fluorine dopant, perform a first sintering treatment in an oxygen-containing atmosphere, cool, crush, sieve and demagnetize to obtain a ternary cathode material doped matrix; The structure general formula of the ternary cathode material precursor is Ni x Co y Mn z (OH)2, wherein 0.5≤x<1.0, 0y≤0.30, 0<z≤0.40, and x+y+z=1. The titanium-strontium-fluorine dopant is a mixture of SrTiO3, MgF2, ZrO2 and θ-Al2O3; The ternary cathode material precursor, the Li in the lithium source + , the molar ratio of the total amount of doping metal elements in the titanium-strontium-fluorine dopant is 1:(0.92-1.12):(0.002-0.070); The first sintering process is as follows: the first heating is to 400-580°C and kept warm for 2-8 hours, the second heating is to 580-860°C and kept warm for 2-6 hours, and the third heating is to 740-1000°C and kept warm for 8-20 hours. Step 2: uniformly mixing the ternary cathode material-doped matrix prepared in step 1 with the titanium-strontium coating agent to obtain a primary coating product; or dispersing the titanium-strontium coating agent in a solvent, then adding the ternary cathode material-doped matrix prepared in step 1, stirring, evaporating, separating, and drying to obtain a primary coating product; In an oxygen-containing atmosphere, the primary coated product is heated to 510-800°C and kept at this temperature for 1-20 hours for a second sintering treatment, and then cooled, crushed, sieved, and demagnetized to obtain a ternary cathode material coated matrix; The molar ratio of the doped matrix of the ternary positive electrode material to the total amount of the coating element in the titanium-strontium coating agent is 1: (0.002-0.030); The titanium-strontium coating agent is a mixture of SrTiO3, WO3, NbO2 and TiO2; Step 3: The ternary cathode material coating matrix prepared in step 2 is mixed with a lithium-boron additive for secondary coating. In an oxygen-containing atmosphere, the temperature is raised to 180-530° C. and kept for 1-10 hours for a third sintering treatment. After cooling, crushing, screening, and demagnetization, a titanium, strontium, and fluorine composite doped co-coated high-voltage ternary cathode material is obtained. The lithium-boron additive is a mixture of LiF and BPO4.

2. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 1, characterized in that, The steps include: Step 1: uniformly mix the ternary cathode material precursor, lithium source and titanium-strontium-fluorine dopant, perform a first sintering treatment in an oxygen-containing atmosphere, cool, crush, sieve and demagnetize to obtain a ternary cathode material doped matrix; The structure general formula of the ternary cathode material precursor is Ni x Co y Mn z (OH)2, wherein 0.5≤x<1.0, 0y≤0.30, 0<z≤0.40, and x+y+z=1. The titanium-strontium-fluorine dopant is a mixture of SrTiO3, MgF2, ZrO2 and θ-Al2O3; The ternary cathode material precursor, the Li in the lithium source + , the molar ratio of the total amount of doping metal elements in the titanium-strontium-fluorine dopant is 1:(0.92-1.12):(0.002-0.070); The first sintering process is as follows: the first heating is to 400-580°C and kept warm for 2-8 hours, the second heating is to 580-860°C and kept warm for 2-6 hours, and the third heating is to 740-1000°C and kept warm for 8-20 hours. Step 2: uniformly mixing the ternary cathode material-doped matrix prepared in step 1 with the titanium-strontium coating agent to obtain a primary coating product; or dispersing the titanium-strontium coating agent in a solvent, then adding the ternary cathode material-doped matrix prepared in step 1, stirring, evaporating, separating, and drying to obtain a primary coating product; In an oxygen-containing atmosphere, the primary coated product is heated to 510-800°C and kept at this temperature for 1-20 hours for a second sintering treatment, and then cooled, crushed, sieved, and demagnetized to obtain a ternary cathode material coated matrix; The molar ratio of the doped matrix of the ternary positive electrode material to the total amount of the coating element in the titanium-strontium coating agent is 1: (0.002-0.030); The titanium-containing strontium coating agent is a mixture of SrTiO3, WO3, NbO2 and TiO2. Step three, the ternary positive electrode material coated substrate prepared in step two is mixed with a lithium-containing boron additive to perform secondary coating, and in an oxygen-containing atmosphere, the temperature is raised to 180-530 DEG C for 1-10 h to perform third sintering treatment, and after cooling, crushing, sieving and demagnetization, a titanium-strontium-fluorine composite doped and co-coated high-voltage ternary positive electrode material is obtained. The lithium-containing boron additive is a mixture of LiF and BPO4.

3. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 2, characterized in that, In step one, The mass ratio of the ternary cathode material precursor, SrTiO3, ZrO2, MgF2, θ-Al2O3 is 100:(0.05-0.70):(0.05-0.60):(0.03-0.40):(0.01-0.5), the purity of SrTiO3 is 99.5%, D 50 The particle size is 0.5-16 μm, the purity of ZrO2 is 99.9%, D 50 The particle size is 0.5-15 μm, the purity of MgF2 is 99.9%, D 50 The particle size is 0.5-15 μm, the purity of θ-Al2O3 is 99.9%, D 50 The particle size is 1-30 μm; The lithium source is one or a mixture of several of LiOH, LiOH·H2O, Li2CO3 and LiNO3, and the particle size of the lithium source is 3-20 μm; The first sintering treatment is performed by using a muffle furnace or a tube furnace, and the first temperature rising, the second temperature rising and the third temperature rising have independent temperature rising rates of 1-5 DEG C / min. Alternatively, the first sintering treatment is performed by using an atmosphere roller kiln or a rotary furnace, and the first temperature rising, the second temperature rising and the third temperature rising have independent temperature rising rates of 1-30 DEG C / h.

4. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 2, characterized in that, In step two, The mass ratio of the ternary positive electrode material doped matrix, SrTiO3, WO3, NbO2, TiO2 is 100:(0.02-0.25):(0.08-0.50):(0.02-0.20):(0.02-0.20), the purity of SrTiO3 is 99.5%, D 50 The particle size is 0.5-20 microns, the purity of WO3 is 99.9%, D 50 The particle size is 20-100 nm, the purity of NbO2 is 99.9%, D 50 The particle size is 20-60 nm, the purity of TiO2 is 99.8%, D 50 The particle size is 20-120 nm; The temperature rising rate of the second sintering treatment is 1-20 DEG C / h.

5. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 2, characterized in that, In step three, The mass ratio of the ternary cathode material coating base, LiF and BPO4 is 100:(0.03-0.75):(0.1-0.95), the purity of LiF is 99.0%, D 50 The particle size is 60nm-150nm, and the purity of BPO4 is 99.9%, D 50 The particle size is 30nm-150nm; The temperature rising rate of the third sintering treatment is 1-20 DEG C / h.

6. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 2, characterized in that, In the step one, the ternary positive electrode material precursor is small particle ternary positive electrode material precursor or large particle ternary positive electrode material precursor, the D 50 particle size of the small particle ternary positive electrode material precursor is 2.0-8.0 μm, and the D 50 particle size of the large particle ternary positive electrode material precursor is 9-18 μm. When the ternary cathode material precursor is a large-particle ternary cathode material precursor, the D50 of the ternary cathode material doped substrate prepared in step one is 9-16 μm 50 The D50 of the ternary cathode material coated substrate prepared in step two is 9-16 μm 50 The D50 of the high-voltage cathode material prepared in step three is 9-16 μm 50 The D50 is 8-18 μm; When the ternary cathode material precursor is a small particle ternary cathode material precursor, the D50 of the ternary cathode material doped substrate prepared in step one is 2.5-6.0 μm 50 The D50 of the ternary cathode material coated substrate prepared in step two is 2.8-6.2 μm 50 The D50 of the high-voltage cathode material prepared in step three is 2.5-6.4 μm 50 The D50 of the high-voltage cathode material prepared in step three is 2.5-6.4 μm.

7. The preparation method of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 2, characterized in that, Step four, the titanium-strontium-fluorine composite doped and co-coated high-voltage positive electrode material is batch mixed in a dehydrated carbon dioxide-free drying gas or an inert atmosphere.

8. Use of the titanium-strontium-fluorine composite doped and co-coated high-voltage ternary positive electrode material of claim 1 or the titanium-strontium-fluorine composite doped and co-coated high-voltage ternary positive electrode material prepared by the preparation method of any one of claims 2-7 in preparing a secondary battery positive electrode sheet or a secondary battery.

9. The use of the titanium-strontium-fluorine complex doped co-coated high-voltage ternary cathode material according to claim 8 in the preparation of a secondary battery cathode sheet or a secondary battery, characterized in that, The secondary battery is a lithium ion battery.

10. A secondary battery positive electrode sheet or a secondary battery prepared by using the titanium-strontium-fluorine composite doped and co-coated high-voltage ternary positive electrode material of claim 1 or the titanium-strontium-fluorine composite doped and co-coated high-voltage ternary positive electrode material prepared by the preparation method of any one of claims 2-7.

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