In-situ coated ternary positive electrode composite material and preparation, and use thereof

Abstract

An in-situ coated ternary positive electrode composite material, and the preparation and use thereof. The in-situ coated ternary positive electrode composite material comprises a ternary positive electrode base material and a fast ion conductor material, which is in-situ coated on and chemically bonded to the surface of the ternary positive electrode base material, wherein the ternary positive electrode base material is LiNi1-x-yCoxMnyO2, and the fast ion conductor material is Li2TiO3, where 0.02≤x+y≤0.67. By means of wet coating followed by lithium mixed sintering, the synchronous generation of an outer layer (Li2TiO3) and an inner layer (LiNi1-x-yCoxMnyO2) is realized, and the chemical bonding between the inner layer and the outer layer is achieved while the coating uniformity is improved, such that the coated lithium ion conductor Li2TiO3 is not prone to falling off during the charging and discharging of a battery, thereby finally improving the rate capability and the cycling performance of the ternary positive electrode composite material.

Description

An in-situ coated composite ternary cathode material and its preparation and application Technical Field

[0001] The present invention relates to the technical field of ternary positive electrode materials, and in particular to an in-situ coated composite ternary positive electrode material and its preparation and application. Background Art

[0002] Lithium-ion batteries, as a new type of green energy storage device, are widely used in consumer electronics, energy storage, and power batteries. As a key component of lithium-ion batteries, the cathode material determines the upper limit of their energy density. Currently, the commercially available cathode materials primarily include lithium cobalt oxide, lithium manganese oxide, lithium iron phosphate, and ternary materials. Ternary materials have attracted significant attention for their higher energy density. However, ternary cathode materials still suffer from drawbacks such as poor rate and cycle performance, which to some extent hinder their large-scale application.

[0003] In related technologies, the electrochemical performance of ternary cathode materials can be improved by element doping (such as Mg, Zr, Ti, W, F, and B) or compound surface coating (ZrO2, TiO2, SiO2, Al2O3, LiAlO2, Li2ZrO3, Li2TiO3, Li3PO4, and Li4SiO4, etc.). Among them, surface coating with fast ion conductors with high lithium ion conductivity has been proven to be a modification method that can simultaneously improve the rate performance and cycle performance of ternary cathode materials. The coating of fast ion conductors avoids direct contact between the cathode material and the electrolyte, effectively improving the lithium ion transmission capacity while suppressing the side reactions between the cathode material and the electrolyte, reducing the surface impedance of the cathode material and improving the rate performance.

[0004] The conventional coating process for fast ion conductors is dry coating. The mechanical mixing coating method and low heat treatment temperature used are likely to cause problems such as uneven coating layer and weak adhesion between the coating layer and the base material. The improvement of rate performance and cycle performance is limited. In addition, there are few types of nano-scale coating materials and the cost is also high, making it difficult to produce on a large scale. In addition, the coating of fast ion conductors in related technologies can only enhance the lithium ion conduction on the surface of the ternary positive electrode material, and does not improve the lithium ion transport inside the material. The effect on improving rate performance and cycle performance needs to be improved. Therefore, it is necessary to provide a technical solution to comprehensively improve the rate performance and cycle performance of ternary positive electrode materials.

[0005] Summary of the Invention

[0006] In view of this, the present application provides an in-situ coated composite ternary positive electrode material and its preparation and application, which are used to solve the problem of how to improve the rate performance and cycle performance of the ternary positive electrode material.

[0007] In order to achieve the above technical objectives, this application adopts the following technical solutions:

[0008] In the first aspect, the present application provides an in-situ coated composite ternary cathode material, comprising a ternary cathode matrix material and a fast ion conductor material in-situ coated and chemically bonded to the surface of the ternary cathode matrix material, wherein the ternary cathode matrix material is LiNi 1-x-y Co x Mn y O2, the fast ion conductor material is Li2TiO3, where 0.02≤x+y≤0.67.

[0009] In a second aspect, the present application provides a method for preparing an in-situ coated composite ternary cathode material, comprising the following steps:

[0010] S1. Ni 1-x-y Co x Mn y (OH)2 precursor, hydrolyzable titanium source and deionized water are added to an organic solvent and mixed to obtain a mixture, the mixture is heated and stirred at 20-80°C, and then dried at 60-100°C to obtain Ni 1-x-y Co x Mn y (OH)2@TiO2·nH2O precursor; 0.02≤x+y≤0.67, 0 <n≤2;

[0011] S2. Ni 1-x-y Co x Mn y After the (OH)2@TiO2·nH2O precursor is evenly mixed with the lithium source, it is sintered at 400-900℃ in an oxygen-containing atmosphere to obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O2@Li2TiO3.

[0012] Preferably, Ni 1-x-y Co x Mn y In the X-ray diffraction pattern of the (OH)2 precursor, I 101 / I 001 >1.0; more preferably, 1 101 / I 001 ≥1.08.

[0013] Preferably, the specific process of step S2 is: Ni 1-x-y Co x Mn yAfter the (OH)2@TiO2·nH2O precursor is evenly mixed with the lithium source, it is sintered at 400-650℃ in an oxygen-containing atmosphere, and then sintered at 700-900℃ for a second stage to obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O2@Li2TiO3.

[0014] Preferably, the sintering temperature rising rate is 1-10°C / min.

[0015] Preferably, the hydrolyzable titanium source and Ni 1-x-y Co x Mn y The molar ratio of (OH)2 precursor is (0.001-0.1):1.

[0016] Preferably, the hydrolyzable titanium source includes one or more of tetraethyl titanate, tetrapropyl titanate, isopropyl titanate, tetrabutyl titanate or isobutyl titanate.

[0017] Preferably, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium oxide, lithium acetate and lithium nitrate.

[0018] Preferably, the organic solvent includes one or more of anhydrous ethanol, propanol, isopropanol, butanol, and isobutanol.

[0019] In a third aspect, the present application provides an application of an in-situ coated composite ternary positive electrode material in a lithium battery.

[0020] The beneficial effects of this application are as follows:

[0021] This application realizes the outer layer (Li2TiO3) and the inner layer (LiNi) by wet coating first and then lithium mixing and sintering. 1-x-y Co x Mn y O2) is generated synchronously, which improves the coating uniformity while realizing the chemical bonding of the inner and outer layers, making the coated lithium ion conductor Li2TiO3 not easy to fall off during the battery charge and discharge process, and ultimately significantly improving the rate performance and cycle performance of the composite ternary positive electrode material;

[0022] This application adopts <101> Ternary precursor with facet-preferential growth (I 101 / I 001 >1.0) as a raw material, shortening the internal transmission distance of lithium ions, cooperating with the surface-coated lithium ion conductor Li2TiO3, and enhancing the internal and external conduction of lithium ions, ultimately achieving a further improvement in the rate performance of the composite ternary positive electrode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 shows the <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1 XRD pattern of (OH)2 precursor;

[0024] Figure 2 shows the <101> Facet-preferential growth (I 101 / I 001 =1.08) of Ni 0.8 Co 0.1 Mn 0.1 XRD pattern of (OH)2 precursor;

[0025] Figure 3 shows the <001> Facet-preferential growth (I 101 / I 001 =0.75) of Ni 0.8 Co 0.1 Mn 0.1 XRD pattern of (OH)2 precursor. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0027] The present application provides an in-situ coated composite ternary cathode material, comprising a ternary cathode matrix material and a fast ion conductor material in-situ coated and chemically bonded to the surface of the ternary cathode matrix material. The ternary cathode matrix material is LiNi 1-x-y Co x Mn y O2, the fast ion conductor material is Li2TiO3, where 0.02≤x+y≤0.67.

[0028] The coating layer of the present application is chemically bonded to the inner layer matrix material and in-situ coated, so that the coated lithium ion conductor Li2TiO3 is not easy to fall off during the battery charging and discharging process. Furthermore, the coating layer Li2TiO3 has lithium ion conductivity, which can enhance the conduction of lithium ions on the surface, and ultimately significantly improve the rate performance and cycle performance of the composite ternary positive electrode material.

[0029] The present application provides a method for preparing an in-situ coated composite ternary cathode material, comprising the following steps:

[0030] S1. Ni 1-x-y Co x Mn y(OH)2 precursor, hydrolyzable titanium source and deionized water are added to an organic solvent and mixed to obtain a mixture, the mixture is heated and stirred at 20-80°C, and then dried at 60-100°C to obtain Ni 1-x-y Co x Mn y (OH)2@TiO2·nH2O precursor; 0.02≤x+y≤0.67, 0 <n≤2;

[0031] S2. Ni 1-x-y Co x Mn y After the (OH)2@TiO2·nH2O precursor is evenly mixed with the lithium source, it is sintered at 400-900℃ in an oxygen-containing atmosphere to obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O2@Li2TiO3.

[0032] The reaction process of step S1 is as follows: at 20-80°C, the titanium source is heated in the presence of Ni 1-x-y Co x Mn y The (OH)2 precursor surface is slowly hydrolyzed into Ti(OH)4, and a uniform coating is achieved on the precursor surface. The hydrolysis time is 4-48h, and then the water and organic solvent are dried at 60-100℃ to become TiO2·nH2O. It is worth noting that the hydrolysis temperature is 20-80℃. If it is too low, the hydrolysis rate is slow and takes a long time. If the temperature is high, the hydrolysis rate is fast and the coating thickness is not uniform enough. The reaction process of step S2 is, Ni 1-x-y Co x Mn y (OH)2@TiO2·nH2O is sintered with lithium source, and the hydroxide precursor is completely lithiated by mixed lithium sintering to become lithium nickel cobalt manganese oxide (LiNi 1-x-y Co x Mn y O2), and TiO2 is synchronously transformed into Li2TiO3 through mixed lithium sintering for outer layer coating and chemically bonded with inner layer lithium nickel cobalt manganese oxide.

[0033] In summary, this application is coated on Ni by wet method first 1-x-y Co x Mn y The surface of the (OH)2 precursor particles is evenly coated with TiO2, and then mixed with lithium source and sintered at high temperature, so that the core precursor is transformed into lithium nickel cobalt manganese oxide (LiNi 1-x-y Co x Mn yO2), and at the same time, the TiO2 coated on the surface is transformed into Li2TiO3 with lithium ion conductivity at the same sintering temperature, which can enhance the conduction of lithium ions on the surface; furthermore, through the above-mentioned one-time in-situ high-temperature synchronous synthesis of the core and the coating layer, the chemical bonding between the lithium nickel cobalt manganese oxide of the core and the coating material Li2TiO3 can be enhanced, making the coated Li2TiO3 less likely to fall off during the battery charging and discharging process; ultimately, the rate performance and cycle performance of the composite ternary positive electrode material are significantly improved.

[0034] Furthermore, Ni 1-x-y Co x Mn y In the X-ray diffraction pattern of the (OH)2 precursor, I 101 / I 001 >1.0; i.e. Ni of this application 1-x-y Co x Mn y (OH)2 precursor is along <101> Ternary precursor material with dominant growth of crystal face, nickel cobalt manganese hydroxide <001> The crystal plane has a low specific surface energy, and the precursor is easy to move along the <001> The crystal plane spreads, and the lithium ion transmission channel is also within this crystal plane, along <101> Ternary precursor materials with preferential growth of crystal faces <001> The smaller size of the crystal face shortens the transmission distance of lithium ions inside the positive electrode material, thereby increasing the conduction efficiency of lithium ions and improving the rate performance of the positive electrode material.

[0035] This scheme utilizes <101> The ternary precursor material with advantageous growth on the crystal face is used as the raw material to enhance the internal conduction of lithium ions, thereby enhancing the charge and discharge rate performance of the positive electrode material; and the Li2TiO3 coating layer with lithium ion conductivity, on the one hand, protects the interior of the composite ternary positive electrode material from serious side reactions with the electrolyte, improving the cycle performance, and on the other hand, enhances the lithium ion conductivity of the surface of the composite ternary positive electrode material, improving the rate performance, while pure titanium oxide does not have the ability to conduct lithium ions; through the above methods, the synergistic enhancement of the conduction of lithium ions on the surface and inside of the ternary positive electrode material is achieved, further improving the rate performance and cycle performance of the positive electrode material. Preferably, Ni 1-x-y Co x Mn y In the X-ray diffraction pattern of the (OH)2 precursor, I 101 / I 001 >1.0, more preferably, Ni 1-x-y Co x Mn y In the X-ray diffraction pattern of the (OH)2 precursor, I 101 / I 001 ≥1.08, more preferably, Ni 1-x-y Co x Mny In the X-ray diffraction pattern of the (OH)2 precursor, I 101 / I 001 ≥1.2. I 101 / I 001 A ratio greater than 1 means that the intensity of the (101) peak is stronger than the (001) peak, which is the so-called <101> Advantageous growth or preferential orientation. Especially when I 101 / I 001 ≥1.2, so <101> The crystal face ratio is higher. <001> The smaller the surface size, the shorter the internal transmission distance of lithium ions, the higher the transmission efficiency of lithium ions, and the better the battery rate performance.

[0036] In this application, the specific process of step S2 is: Ni 1-x-y Co x Mn y After the (OH)2@TiO2·nH2O precursor is evenly mixed with the lithium source, a sintering step is performed at 400-650℃ in an oxygen-containing atmosphere for 3-20h, and then a second sintering step is performed at 700-900℃ for 5-30h to obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O2@Li2TiO3; preferably, the sintering temperature heating rate is 1-10℃ / min; by improving the above process, the rate performance and cycle performance of the composite ternary positive electrode material can be further improved, and the reasons are as follows: there are many types of lithium sources available for use in this application. When Li2CO3 or LiOH·H2O is used as the lithium source, water vapor and CO2 will be generated during the sintering process. By two-stage sintering, the temperature is first kept at 400-650℃ for a period of time to allow the generated water vapor and CO2 to fully escape, which can improve the density and microstructural uniformity of the sintered product; the temperature of the second stage sintering is 700-900℃. The reason is that a higher temperature is required for the hydroxide precursor to be completely lithiated into lithium nickel cobalt manganese oxide and TiO2 to be converted into Li2TiO3, especially when the particles of the precursor are large and relatively dense, the required temperature is higher than 650℃, but the sintering temperature cannot be too high. Keeping it above 900 degrees for a long time can easily lead to very serious lithium nickel mixing (Li with similar radius). + Occupy Ni 2+ Therefore, setting up a two-stage sintering is more conducive to the density and microstructure uniformity of the generated composite ternary positive electrode material and ensuring the molding and good crystallization of the inner and outer layers, ultimately improving its rate performance and cycle performance, while controlling the heating rate is conducive to the full escape of the generated water vapor and CO2, and will not be wrapped inside to produce micropores.

[0037] In addition, in step S2, the sintering atmosphere used is an oxygen-containing atmosphere, such as air, oxygen or other mixed gases containing oxygen. 1-x-y Co x Mn y The nickel content in the (OH)2 precursor is higher (n Ni / n Me ≥0.8, Me=Ni+Co+Mn), oxygen is preferred. Ni / n Me When ≥0.9, the lithium source is limited to LiOH·H2O instead of Li2CO3, and the atmosphere can only be pure oxygen. Ni / n Me <0.8, the selection range of lithium sources is wider, LiOH·H2O, Li2CO3 or other lithium sources can be used, and the sintering atmosphere can be air or a mixture of air and oxygen in a certain proportion.

[0038] In this application, the hydrolyzable titanium source and Ni 1-x-y Co x Mn y The molar ratio of (OH)2 precursor is (0.001-0.1):1; preferably, the hydrolyzable titanium source and Ni 1-x-y Co x Mn y The molar ratio of the (OH)2 precursor is (0.005-0.03):1; if the hydrolyzable titanium source is too little, some precursor particles will not be coated or the coating thickness will be small, which will not play a good role in isolating the positive electrode material and the electrolyte, and the improvement of the cycle performance is not ideal; since the coating material Li2TiO3 on the surface of the composite ternary positive electrode material finally obtained does not participate in the redox process of battery charging and discharging, it does not provide capacity, and the lithium ion conductivity of Li2TiO3 is worse than that of the lithium nickel cobalt manganese oxide in the core, too much hydrolyzable titanium source will lead to too much coating material, which will affect the capacity and also hinder the insertion and extraction of Li ions, which is not conducive to the improvement of rate performance.

[0039] In this application, deionized water and Ni 1-x-y Co x Mn y The mass ratio of (OH)2 precursor is (0.1-5):1, preferably, deionized water and Ni 1-x-y Co x Mn yThe mass ratio of (OH)2 precursor is (0.2-1):1, which ensures that the titanium source is completely hydrolyzed; the volume ratio of organic solvent to deionized water is (3-50):1, preferably, the volume ratio of organic solvent to deionized water is (10-20):1, and the use of excess organic solvent can reduce the amount of water. Otherwise, after the titanium source is hydrolyzed, there will be too much residual water in the solvent, which is not conducive to subsequent evaporation. In addition, sufficient organic solvent can allow the titanium source to react with Ni. 1-x-y Co x Mn y The (OH)2 precursor is fully dispersed.

[0040] The raw material of this application is Ni 1-x-y Co x Mn y (OH)2, 0.02≤x+y≤0.67, including but not limited to Ni 0.5 Co 0.2 Mn 0.3 (OH)2,Ni 0.6 Co 0.2 Mn 0.2 (OH)2,Ni 0.7 Co 0.15 Mn 0.15 (OH)2,Ni 0.8 Co 0.1 Mn 0.1 (OH)2,Ni 0.9 Co 0.05 Mn 0.05 (OH)2、Ni 1 / 3 Co 1 / 3 Mn 1 / 3 (OH)2, its particle size D50≥2.5μm, preferably, 6μm≤D50≤12μm.

[0041] In some embodiments, the hydrolyzable titanium source includes one or more of tetraethyl titanate, tetrapropyl titanate, isopropyl titanate, tetrabutyl titanate, or isobutyl titanate.

[0042] In some embodiments, the lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium oxide, lithium acetate and lithium nitrate. The amount of lithium source added is calculated according to n(Li)=(Li / Me)×n(Ni+Co+Mn)+2×n(Ti). In some embodiments, the Li / Me value is (1.01-1.10):1, more preferably (1.03-1.06):1; wherein n represents the molar amount of the element, Me represents the total molar amount of the metal elements Ni+Co+Mn in the precursor input, and Li / Me represents the designed ratio of the molar amount of the Li element in the input Li source to the total molar amount of the metal elements Ni+Co+Mn in the precursor input; a high Li / Me value will result in excessive Li in the positive electrode material, excessive LiOH or Li2CO3 remaining on the surface, which is not conducive to the improvement of cycle performance; a low Li / Me value may result in the inability to make up for the loss caused by the volatilization of Li during the sintering process, which is not conducive to the improvement of performance.

[0043] The organic solvent of the present application includes one or more of anhydrous ethanol, propanol, isopropanol, butanol, and isobutanol. Preferably, the organic solvent is ethanol. The organic solvent of the present application can evaporate at 60-100°C.

[0044] The present application provides an application of an in-situ coated composite ternary positive electrode material in a lithium battery.

[0045] The present solution is further described below through specific implementation methods.

[0046] Raw material preparation

[0047] The precursor preparation process in the examples and comparative examples of the present invention is as follows:

[0048] Solution preparation: prepare 100 g / L of a mixed sulfate solution of nickel, cobalt and manganese (Ni:Co:Mn=8:1:1 and 6:2:2), a 32% by mass sodium hydroxide solution and a 16% by mass ammonia solution respectively;

[0049] Preparation of reactor bottom solution (NCM811): Add a certain volume of pure water, sodium hydroxide solution and ammonia water to the reactor to prepare a reactor bottom solution with a pH of 12.0 and an ammonia concentration of 8 g / L;

[0050] Preparation of reactor bottom solution (NCM622): Add a certain volume of pure water, sodium hydroxide solution and ammonia water to the reactor to prepare a reactor bottom solution with a pH of 11.6 and an ammonia concentration of 5 g / L;

[0051] Coprecipitation: A mixed sulfate solution containing nickel, cobalt, and manganese, a sodium hydroxide solution, and an aqueous ammonia solution are added to the reactor containing the reaction base solution at a constant flow rate to perform a coprecipitation reaction. Specific reaction control parameters are detailed in the following categories.

[0052] Post-treatment: After the reaction slurry reaches the target particle size, it is aged and then subjected to solid-liquid separation, multiple alkali washing and pure water washing, and then dried at 120°C until the water content is less than 0.5%, and finally a precursor is obtained.

[0053] (1)I 101 / I 001 =1.25Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor

[0054] Reaction parameter control: maintain pH>11.8 for 4 hours for nucleation, then gradually reduce the pH to 10.4 at a rate of 0.15 / h for growth, and then maintain pH = 10.4±0.2; maintain the ammonia concentration at 8±0.5 g / L throughout the process; the initial rotation speed is 560 rpm, and after the D50 reaches 3 μm, the rotation speed is reduced by 40 for every 1 μm of growth until the D50 reaches 8 μm, and the reaction is stopped; maintain the reaction temperature at 58±1°C throughout the process.

[0055] (2)I 101 / I 001 =1.08Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor

[0056] Reaction parameter control: maintain pH>11.8 for 4 hours for nucleation, then gradually reduce the pH to 10.8 at a rate of 0.05 / h for growth, and then maintain pH = 10.8±0.2; after nucleation, gradually reduce the ammonia concentration and maintain it at 6.5±0.5g / L; the initial rotation speed is 650rpm, and after D50 reaches 3μm, the rotation speed is reduced by 30rpm for every 1μm of growth until D50 reaches 8μm, and the reaction is stopped; the reaction temperature is maintained at 60±1℃ throughout the process.

[0057] (3)I 101 / I 001 =0.75Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor

[0058] Reaction parameter control: maintain pH>11.8 for 4 hours for nucleation, then gradually reduce the pH to 11.2 at a rate of 0.04 / h for growth; gradually reduce the ammonia concentration after nucleation and maintain it at 5±0.5g / L; the initial rotation speed is 680rpm, and after the D50 reaches 3μm, the rotation speed is reduced by 20rpm for every 1μm of growth until the D50 reaches 8μm, at which time the reaction is stopped; the reaction temperature is maintained at 62±1℃ throughout the process.

[0059] (4)I101 / I 001 =1.25Ni 0.6 Co 0.2 Mn 0.2 (OH)2 precursor

[0060] Reaction parameter control: maintain pH>11.5 for nucleation for 4 h, then gradually reduce the pH to 10.2 at a rate of 0.15 / h for growth; maintain the ammonia concentration at 5±0.5 g / L throughout the process; the initial rotation speed is 540 rpm, and after the D50 reaches 3 μm, the rotation speed is reduced by 40 rpm for every 1 μm of growth until the D50 reaches 8 μm, at which time the reaction is stopped; maintain the reaction temperature at 58±1°C throughout the process.

[0061] Example 1

[0062] An in-situ coated composite ternary cathode material, comprising a ternary cathode matrix material and a fast ion conductor material in-situ coated and chemically bonded to the surface of the ternary cathode matrix material, wherein the ternary cathode matrix material is LiNi 0.8 Co 0.1 Mn 0.1 O2, the fast ion conductor material is Li2TiO3.

[0063] The preparation method of the in-situ coated composite ternary positive electrode material comprises the following steps:

[0064] S1. The particle size D50 is 8 μm, along <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and isopropyl titanate were mixed in a molar ratio of Ti / Me=0.02:1, and dissolved in a mixed solution of anhydrous ethanol and deionized water to obtain a mixture, wherein the mass ratio of deionized water to the precursor was 2:3; the volume ratio of deionized water to ethanol was 1:10; the mixture was heated and stirred at 40°C for 12h, and then continued to stir and dry at 80°C until the solvent was completely evaporated, thereby obtaining Ni 0.8 Co 0.1 Mn 0.1 (OH)2@TiO2·nH2O precursor;

[0065] S2. Ni 0.8 Co 0.1 Mn 0.1The (OH)2@TiO2·nH2O precursor and LiOH·H2O were mixed evenly in a high-speed mixer, wherein the Li / Me value was 1.04. In an oxygen atmosphere, the temperature was raised to 600°C at a rate of 2°C / min for a first sintering, and the temperature was kept constant for 5 hours. Then, the temperature was raised to 800°C at a rate of 2°C / min for a second sintering, and the temperature was kept constant for 16 hours. After the sintering was completed, the sample was naturally cooled to room temperature, and then the sintered sample was crushed and sieved to obtain the in-situ coated LiNi 0.8 Co 0.1 Mn 0.1 O2@Li2TiO3 composite ternary positive electrode material.

[0066] Among them, the application <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1 The XRD pattern of the (OH)2 precursor is shown in Figure 1.

[0067] Example 2

[0068] An in-situ coated composite ternary cathode material, the other contents are the same as those in Example 1, except that Ni 0.8 Co 0.1 Mn 0.1 I of (OH)2 precursor 101 / I 001 =1.08.

[0069] Among them, the application <101> Facet-preferential growth (I 101 / I 001 =1.08) of Ni 0.8 Co 0.1 Mn 0.1 The XRD pattern of the (OH)2 precursor is shown in Figure 2.

[0070] Example 3

[0071] An in-situ coated composite ternary cathode material, the other contents are the same as those in Example 1, except that in step S1, Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and isopropyl titanate are mixed in a molar ratio of Ti / Me=0.06:1. In step S2, the first-stage sintering process is 650°C / 4h, and the second-stage sintering process is 830°C / 12h.

[0072] Example 4

[0073] An in-situ coated composite ternary positive electrode material, the other contents are the same as those in Example 1, except that the <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.6 Co 0.2 Mn 0.2 (OH)2 precursor, in step S2, the first sintering temperature is 650℃, the second sintering temperature is 900℃, the lithium source is Li2CO3, the titanium source is tetraethyl titanate, and finally the in-situ coated LiNi 0.6 Co 0.2 Mn 0.2 O2@Li2TiO3 composite ternary positive electrode material.

[0074] Comparative Example 1

[0075] A composite ternary cathode material, the preparation method of which is as follows:

[0076] The particle size D50 is 8μm, along <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and LiOH·H2O were weighed according to the ratio of Li / Me value of 1.04, mixed evenly in a high-speed mixer, and then sintered in an oxygen atmosphere. During sintering, the heating rate was 2℃ / min, the first sintering temperature was raised to 600℃ and kept constant at this temperature for 5h, the second sintering temperature was raised to 800℃ and kept constant at this temperature for 16h, and after sintering, it was naturally cooled to room temperature, and then the sintered sample was crushed and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material.

[0077] Comparative Example 2

[0078] A composite ternary cathode material, the preparation method of which is as follows:

[0079] The particle size D50 is 8μm, along <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1The (OH)2 precursor and LiOH·H2O were weighed in a ratio of Li / Me of 1.04, mixed evenly in a high-speed mixer, and then sintered in an oxygen atmosphere. During sintering, the heating rate was 2°C / min, the first sintering temperature was raised to 600°C and kept constant at this temperature for 5 hours, the second sintering temperature was raised to 800°C and kept constant at this temperature for 16 hours, and after sintering, it was naturally cooled to room temperature. The sintered sample was then crushed and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material; nano-scale Li2TiO3 (size about 200nm) and LiNi 0.8 Co 0.1 Mn 0.1 The O2 cathode material was weighed according to the molar ratio of Ti / Me=0.02:1, mixed evenly in a high-speed mixer, and then heat-treated in an oxygen atmosphere at a heating rate of 2°C / min to 600°C for 5 hours, then naturally cooled to room temperature, crushed and sieved to obtain dry-coated LiNi 0.8 Co 0.1 Mn 0.1 O2@Li2TiO3 composite ternary positive electrode material.

[0080] Comparative Example 3

[0081] A composite ternary positive electrode material, the other contents are the same as those in Example 1, except that <101> Facet-preferential growth (I 101 / I 001 =1.25) of Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor is replaced by <001> Facet-preferential growth (I 101 / I 001 =0.75) of the precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2.

[0082] Among them, Ni of this application 0.8 Co 0.1 Mn 0.1 (OH)2 precursor (I 101 / I 001 =0.75) is shown in FIG3 .

[0083] Comparative Example 4

[0084] A composite ternary cathode material, the preparation method comprising the following steps:

[0085] The particle size D50 is 8μm, along <001> Facet-preferential growth (I101 / I 001 =0.75) of the precursor Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and LiOH·H2O were weighed in a ratio of Li / Me of 1.04, mixed evenly in a high-speed mixer, and then sintered in an oxygen atmosphere. During sintering, the heating rate was 2°C / min, the first sintering temperature was raised to 600°C and kept constant at this temperature for 5 hours, the second sintering temperature was raised to 800°C and kept constant at this temperature for 16 hours, and after sintering, it was naturally cooled to room temperature. The sintered sample was then crushed and sieved to obtain LiNi 0.8 Co 0.1 Mn 0.1 O2 positive electrode material.

[0086] Comparative Example 5

[0087] An in-situ coated composite ternary cathode material, the other contents are the same as those of Example 1, except that a one-stage sintering is adopted in step S2, wherein the temperature is increased to 800°C at a heating rate of 12°C / min and then kept at this temperature for 21 hours.

[0088] Comparative Example 6

[0089] An in-situ coated composite ternary cathode material, the other contents are the same as those in Example 1, except that in step S1, isopropyl titanate and Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor was mixed in a molar ratio of Ti / Me=0.12:1.

[0090] Evaluation Test

[0091] Coin-type batteries were assembled using the composite ternary cathode materials obtained in the above examples and comparative examples, and the electrochemical performance parameters of the batteries were tested using instruments. The results are shown in Table 1. Rate performance is reflected by the 1C / 0.2C capacity ratio, with a larger value indicating better rate performance. Cycling performance is reflected by the capacity retention rate after 100 cycles at 1C, with a larger value indicating better cycling performance.

[0092] Table 1 Electrochemical performance test results of various embodiments and comparative examples

[0093] From the above results, it can be seen that both Example 2 and Example 1 carried out in-situ wet coating of Li2TiO3. The difference is that the precursor used <101> The degree of preferential orientation is different, and the 1 of Example 2 101 / I 001 =1.08<I of Example 1 101 / I 001=1.25, other conditions are the same as those in Example 1, the capacity retention rates of the two after 100 cycles at 1C are similar, but the rate performance of Example 1 is significantly better than that of Example 2, indicating that the precursor <101> The degree of crystal face dominance growth is greater (I 101 / I 001 The larger the ratio of , the better the rate performance of the positive electrode material;

[0094] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 does not have Li2TiO3 coating. Other conditions are the same as those of Example 1. The rate performance and cycle performance of Example 1 are better than those of Comparative Example 1. In particular, the cycle performance of Example 1 after coating Li2TiO3 is significantly improved compared with that of Comparative Example 1.

[0095] The difference between Example 3 and Example 1 lies in the different coating amount of Li2TiO3 and the sintering process parameters. Other conditions are the same as those of Example 1. The rate performance and cycle performance of Example 3 are better than those of Comparative Example 1, but slightly lower than those of Example 1.

[0096] Comparative Example 2 and Example 1 both carried out Li2TiO3 coating. The difference between the two is that Comparative Example 2 directly carried out dry coating of Li2TiO3. The coating amount of Ti and the conditions such as the positive electrode material sintering process were the same as those in Example 1. From the results, it can be seen that the rate performance and cycle performance of Comparative Example 2 are improved compared with Comparative Example 1, but are significantly different from those of Example 1, indicating that the effect of dry coating is worse than that of in-situ wet coating. The main reason is that the uniformity of the coating layer is poor and the coating layer lacks chemical bonding with the core.

[0097] Comparative Example 3 and Example 1 both carried out in-situ wet coating of Li2TiO3. The difference between the two is that Comparative Example 3 used conventional <001> Precursor for facet-preferential growth (I 101 / I 001 =0.75), other conditions are the same as those in Example 1, its rate performance is significantly weaker than that of Example 1 and Example 2, but its cycle performance is still higher than that of Comparative Example 1 and Comparative Example 2;

[0098] The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 does not use <101> The precursor with dominant growth of crystal face and without Li2TiO3 coating, other conditions are the same as those in Example 1, and its rate performance and cycle performance are the worst among all the examples and comparative examples;

[0099] The difference between Comparative Example 5 and Example 1 is that step S2 of Comparative Example 5 adopts a one-stage sintering and a faster heating rate. Its discharge capacity, rate performance, and cycle performance are slightly worse than those of Example 1. This is mainly because the higher heating rate is used and the temperature is not kept in the water and CO2 production temperature range for a certain period of time. As a result, the generated water vapor and CO2 cannot escape slowly and easily form micropores inside, resulting in uneven internal microstructure and affecting the performance of the material.

[0100] Comparative Example 6 differs from Example 1 in that an excessive amount of TiO2 is coated in step S1 of Comparative Example 6, resulting in a thicker coating of Li2TiO3 on the surface of the positive electrode material. While the sample in Comparative Example 6 significantly improves cycling performance, the coated Li2TiO3 does not participate in the redox process during battery charge and discharge, contributing no capacity. Furthermore, Li2TiO3's lithium ion conductivity is inferior to that of the core lithium nickel cobalt manganese oxide. Excessive Li2TiO3 coating significantly reduces the battery's charge and discharge capacity, also impacting its rate capability.

[0101] The above results show that along <101> The nickel-cobalt-manganese ternary precursor with preferential growth on the crystal face is used as raw material, which is wet-coated with TiO2 and then mixed with lithium sintering to in-situ synthesize a composite positive electrode material with a surface uniformly coated with the fast ion conductor Li2TiO3, forming a nickel-cobalt-manganese oxide core and a fast ion conductor surface coating layer structure, which can synergistically enhance the conduction of lithium ions on the surface and inside of the ternary positive electrode material, while reducing the side reaction between the ternary positive electrode material and the electrolyte, thereby comprehensively improving the rate performance and cycle performance of the ternary positive electrode material.

[0102] The in-situ coated composite ternary cathode material provided by the present invention has a lithium nickel cobalt manganese oxide core and a surface coating layer structure of a fast ion conductor Li2TiO3. In order to shorten the transmission distance of lithium ions in the material and effectively improve lithium conduction, the in-situ coated composite ternary cathode material is used. <101> The nickel-cobalt-manganese oxide core is synthesized using a nickel-cobalt-manganese oxide precursor that grows preferentially on the crystal face as raw material, while the surface coating of the fast ion conductor Li2TiO3 can inhibit the side reactions between the electrolyte and the positive electrode material. At the same time, it has high lithium ion conductivity and reduces the surface impedance of the positive electrode material. The combination of these two methods can simultaneously improve the transmission efficiency of lithium ions on the surface and inside of the positive electrode material and effectively inhibit the side reactions between the positive electrode material and the electrolyte, thereby synergistically improving the rate performance and cycle performance of the battery.

[0103] The present invention adopts the technical concept of wet in-situ coating, that is, TiO2·nH2O is first uniformly coated on the surface of the nickel-cobalt-manganese precursor through a wet process, and then the lithium nickel-cobalt-manganese oxide core and the Li2TiO3 coating layer are simultaneously generated at the same calcination temperature, so that the coating layer on the base material is more uniform. Moreover, since the coating layer and the base material are generated synchronously, the binding force of the Ti-O bond is strong, which makes the bond between the core and the coating layer more firm and not easy to fall off during the charge and discharge cycle, which can greatly improve the rate performance and cycle performance of the positive electrode material.

[0104] The above are only preferred specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or replacements that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. An in-situ coated composite ternary cathode material, Characterized in that, Comprising a ternary cathode matrix material and a fast ion conductor material in-situ coated and chemically bonded to the surface of the ternary cathode matrix material, the ternary cathode matrix material being LiNi 1-x-y Co x Mn y O 2 , and the fast ion conductor material being Li 2 TiO 3 , wherein, 0.02 ≤ x + y ≤ 0.

67.

2. A preparation method of the in-situ coated composite ternary cathode material according to claim 1, Characterized in that, Comprising the following steps: S1. Add Ni 1-x-y Co x Mn y (OH) 2 precursor, a hydrolyzable titanium source and deionized water into an organic solvent and mix to obtain a mixture. Heat and stir the mixture at 20 - 80 °C, and then dry it at 60 - 100 °C to obtain the Ni 1-x-y Co x Mn y (OH) 2 @TiO 2 ·nH 2 O precursor; where 0.02 ≤ x + y ≤ 0.67 and 0 < n ≤ 2; S2. Mix the Ni 1-x-y Co x Mn y (OH) 2 @TiO 2 ·nH 2 O precursor with a lithium source evenly, and then sinter at 400 - 900 °C in an oxygen-containing atmosphere to obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O 2 @Li 2 TiO 3 .

3. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The Ni 1-x-y Co x Mn y (OH) 2 In the X-ray diffraction pattern of the precursor, I 101 / I 001 > 1.

0.

4. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The specific process of step S2 is as follows: After mixing the Ni 1-x-y Co x Mn y (OH) 2 @TiO 2 ·nH 2 O precursor and the lithium source evenly, in an oxygen-containing atmosphere, carry out a first-stage sintering at 400 - 650 °C, and then carry out a second-stage sintering at 700 - 900 °C, and then obtain the composite ternary cathode material LiNi 1-x-y Co x Mn y O 2 @Li 2 TiO 3 .

5. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The heating rate of the sintering is 1-10 °C / min.

6. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The hydrolyzable titanium source and the Ni 1-x-y Co x Mn y (OH) 2 precursor has a molar ratio of (0.001 - 0.1):

1.

7. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The hydrolyzable titanium source includes one or more of tetraethyl titanate, tetrapropyl titanate, isopropyl titanate, tetrabutyl titanate or isobutyl titanate.

8. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The lithium source includes one or more of lithium carbonate, lithium hydroxide, lithium oxide, lithium acetate and lithium nitrate.

9. The preparation method of the in-situ coated composite ternary cathode material according to claim 2, Characterized in that, The organic solvent includes one or more of anhydrous ethanol, propanol, isopropanol, butanol, isobutanol.

10. Application of the in-situ coated composite ternary cathode material obtained by the preparation method according to claims 2-9 in a lithium battery.

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