A lithium ion battery cathode material modified by a yttrium-containing compound, and a preparation method and application thereof

Abstract

This invention discloses a yttrium compound-modified lithium-ion battery cathode material, its preparation method, and its application, belonging to the field of lithium-ion battery cathode material preparation technology. This invention mixes a yttrium compound dispersion, a complexing agent, and the cathode material, and after drying, subjectes it to variable-temperature field heating treatment to achieve surface modification and bulk gradient doping of the cathode material by yttrium. This invention constructs a variable-temperature field by adjusting the heating rate, allowing yttrium ions to diffuse into the cathode material, achieving a gradient doping with high yttrium content on the surface and low content inside the cathode material. Furthermore, the strong chemical bonding between yttrium ions and lattice oxygen enhances structural stability and improves surface Co content. 3+ The content of yttrium is reduced, the distribution of surface O defects is decreased, and side reactions at the electrode-electrolyte interface are suppressed. Furthermore, internally doped yttrium can effectively modulate the local electronic structure to form a built-in electric field, thereby improving electronic conductivity and Li... + The increased ion mobility significantly improves the cycling performance of the modified cathode material under high voltage.

Description

Technical Field

[0001] This invention relates to a yttrium-containing compound-modified lithium-ion battery cathode material, its preparation method, and its application, belonging to the field of lithium-ion battery cathode material preparation technology. Background Technology

[0002] Since their commercialization in the 1990s, lithium-ion batteries have attracted much attention due to their advantages such as high capacity, good stability, and no memory effect, and have been widely used in mobile communications, digital electronics, new energy vehicles, and smart grids. Compared to the specific capacity of graphite anode materials (over 300 mAh / g), existing commercially available cathode materials, such as lithium cobalt oxide and high-nickel ternary cathode materials (NCM, NCA), have lower specific capacities, becoming a key factor restricting the capacity and energy density of lithium-ion batteries. Increasing the operating voltage of cathode materials is the most direct and effective way to improve the specific capacity of the material, and it can also improve the energy density of the entire battery. However, when the battery operates under high voltage conditions, the cathode material faces many problems. Under high state of charge (SCO), the cathode material undergoes severe delithiation, which causes the migration of transition metal ions and the oxidation and precipitation of lattice oxygen, leading to an irreversible phase transition in the material structure. At the same time, the side reactions at the electrolyte-electrode interface are intensified under high voltage conditions, further leading to the release of lattice oxygen on the material surface, resulting in the migration and even dissolution of transition metal ions, accompanied by battery gas expansion, causing a sharp decline in battery capacity, cycle stability, and safety.

[0003] Lithium cobalt oxide was the first commercially available cathode material for lithium-ion batteries. It boasts high tap density, good stability, a significant advantage in volumetric energy density, and mature manufacturing processes, and is currently widely used in mobile communications and digital devices. In contrast, high-nickel cathode materials (NCM, NCA) have slightly lower volumetric energy density, but the extensive use of Ni greatly reduces material costs and improves specific capacity, making them a potential alternative to lithium cobalt oxide and gradually gaining application. Further derived lithium-rich manganese-based cathode materials have the highest specific capacity, but their operating voltage is high, generally requiring charging to above 4.5V, and they are still under development. Currently, these cathode materials have different applicable environments and market shares; therefore, developing a universal and simple modification method to improve the high-voltage performance of cathode materials is crucial.

[0004] In existing technologies, doping and surface coating are the most common modification methods for lithium-ion battery cathode materials. For example, doping with ions such as Mg, Ti, Zn, Al, F, and S, and coating with materials such as MgO, Fe2O3, Al2O3, and Li3PO4 have achieved good results in coating cathode materials. However, current doping systems mostly need to be carried out during the preparation of raw material precursors or lithium mixing and sintering, and the fabrication process of the coating layer is often cumbersome, complex, and difficult to control the uniformity of the coating level.

[0005] Modification of high-voltage cathode materials often requires combining surface and interface modification with bulk doping to simultaneously protect the surface structure and stabilize the bulk structure. Simultaneously, the amount of heterogeneous non-electrochemically active material must be considered; excessive dosage can reduce the material's reversible capacity and increase costs, thus decreasing the feasibility of practical production. Therefore, a modification method for lithium-ion battery cathode materials with low ion doping content and a simple and stable preparation process is urgently needed. Summary of the Invention

[0006] In order to solve the above-mentioned problems in the prior art, the present invention provides a yttrium-containing compound modified lithium-ion battery cathode material, its preparation method and application.

[0007] The technical solution of the present invention:

[0008] One objective of this invention is to provide a method for modifying cathode materials, the method comprising the following steps:

[0009] S1, dissolve the yttrium compound in a solvent to obtain a yttrium dispersion;

[0010] S2, the yttrium dispersion and complexing agent solution are slowly added to the cathode material and mixed evenly. The mixture is then heated to dryness to obtain the precursor material.

[0011] S3. The precursor material is placed in a muffle furnace for heating and annealing, cooled to room temperature, and then sieved to obtain yttrium-modified cathode material.

[0012] Further specifying, the yttrium compounds in S1 are yttrium nitrate tetrahydrate, yttrium nitrate hexahydrate, nano-yttrium oxide, yttrium fluoride, yttrium iodide, yttrium sulfide, yttrium isopropoxide, yttrium phosphate, anhydrous yttrium chloride, yttrium bromide, yttrium metaphosphate, yttrium borate, yttrium acetate hydrate, yttrium trifluoromethanesulfonate, yttrium hydride, yttrium carbonate hydrate, yttrium chloride hexahydrate, yttrium naphthenate, yttrium perchlorate, yttrium aluminum oxide, barium yttrium tungsten oxide, barium yttrium tungsten oxide, yttrium phosphate hydrate, yttrium butanol solution, yttrium barium copper oxide, yttrium oxalate nonahydrate, yttrium acetylacetone hydrate, and yttrium trihydrate. The following are some of the following: yttrium carbonate, yttrium 2-ethylhexanoate, yttrium 2-methoxyethanol solution, tris(cyclopentadienyl)yttrium, sodium yttrium fluoride, ytterbium and erbium doping, yttrium(III) trifluoromethanesulfonate hydrate, tris(ethylcyclopentadienyl)yttrium, tris(methylcyclopentadienyl)yttrium, tris(butylcyclopentadienyl)yttrium, tris(n-propylcyclopentadienyl)yttrium, tris(2,2,6,6-tetramethyl-3,5-heptadecanoic acid)yttrium, tris[N,N-bis(trimethylsilyl)amide]yttrium, yttrium oxide, yttrium cobalt block, and yttrium aluminum block.

[0013] Further specifying, the solvent in S1 is one or a mixture of deionized water, acetone, ethylene glycol, or anhydrous ethanol.

[0014] Further specifying, the solute in the complexing agent solution in S1 is one or more of the following: ethylenediaminetetraacetic acid (EDTA), disodium ethylenediaminetetraacetic acid (EDTA-2Na), tetrasodium ethylenediaminetetraacetic acid (EDTA-4Na), disodium thiotriacetate (NTA), sucrose, citric acid, sodium citrate, tartaric acid, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, ethanolamine, diethanolamine, triethanolamine, heptaphosphate, sodium gluconate, sodium alginate, sodium ethylenediaminetetramethylenebisphosphate (EDTMPS), diethylenetriaminepentamethylenephosphonate (DETPMPS), maleic anhydride (HPMA), polyacrylic acid (PAA), polyhydroxyacrylic acid, maleic acid-acrylic acid copolymer, and polyacrylamide.

[0015] Further specifying, the solvent of the complexing agent solution in S1 is one or a mixture of deionized water, acetone, ethylene glycol or anhydrous ethanol.

[0016] Further specifying, the cathode material in S2 is lithium cobalt oxide, lithium-rich manganese-based cathode material, or high-nickel cathode material.

[0017] Further specifying, the lithium-rich manganese-based cathode material is Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2.

[0018] To further specify, the high-nickel cathode material is LiNi. 0.8 Co 0.15 Al 0.05 O2.

[0019] Further specified, the molar ratio of complexing agent to yttrium compound in the mixture of S2 is (3~1):1; the molar ratio of cathode material to yttrium compound is 1:(0.01~0.001).

[0020] Further specified, the evaporation temperature in S2 is 75-90℃, and the stirring speed is 250-350 r / min.

[0021] Further specifying the heating annealing conditions in S3, the conditions are as follows: in an air / oxygen atmosphere, the temperature is increased at a rate of 1 to 10 °C / min, and after reaching 850 °C, it is naturally cooled to room temperature.

[0022] Furthermore, the heating rate is specified as 5℃ / min.

[0023] Further specified, S3 passes through a 350-mesh sieve.

[0024] A second objective of this invention is to provide a yttrium-containing compound cathode material obtained by the above-mentioned modification method.

[0025] Furthermore, yttrium-containing compound cathode materials are used as cathode materials for lithium-ion batteries, enabling lithium-ion batteries to have excellent cycle performance and rate performance under high voltage conditions.

[0026] This invention mixes a yttrium compound dispersion, a complexing agent, and a lithium-ion battery cathode material, then dries the mixture and subjectes it to a variable temperature field heating treatment to achieve surface modification and bulk gradient doping of the cathode material by yttrium. Compared with existing technologies, this application has the following advantages:

[0027] (1) This invention constructs a variable temperature field by adjusting the heating rate, so that yttrium ions will be attracted to commercial cathode materials such as lithium cobalt oxide and Li during the heating process under the variable temperature field conditions. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 or LiNi 0.8 Co 0.15 Al 0.05 O2 internal diffusion enables gradient doping of commercial cathode materials, achieving high yttrium content on the surface and low content internally. Furthermore, the strong chemical bonding between yttrium ions and lattice oxygen effectively enhances the structural stability of the material and improves surface Co content. 3+ The content of yttrium increases, reducing the distribution of surface O defects and suppressing side reactions at the electrode-electrolyte interface; simultaneously, internal yttrium doping can effectively modulate the local electronic structure to form a built-in electric field, thereby improving electronic conductivity and Li... + The ion mobility significantly improves the cycling performance of the modified lithium cobalt oxide cathode material at a high voltage of 4.6V.

[0028] (2) The method for modifying cathode materials with yttrium provided by the present invention combines bulk doping and surface coating modification methods. Unlike the traditional cumbersome process of adjusting concentration and feed rate through co-precipitation, the present invention uses a simple liquid phase treatment and a variable temperature field high-temperature annealing process to simultaneously realize the construction of the surface enrichment layer and the internal gradient distribution of yttrium. This effectively suppresses the side reactions at the interface between lithium cobalt oxide material particles and electrolyte, the precipitation of lattice oxygen and the dissolution of Co ions at a high voltage of 4.6V. This significantly improves the cycling performance of the material at high voltage while reducing the amount of yttrium (<1%) and sintering time, saving production costs and making it easy to industrialize.

[0029] (3) The yttrium-modified cathode material prepared by the present invention has high purity and no impurity phase due to the low amount of yttrium (<1%). Its unique gradient doping characteristics increase the interlayer spacing and improve the lithium-ion diffusion coefficient, which can significantly improve the rate performance.

[0030] (4) In electrochemical reactions, due to the different transport paths and diffusion mechanisms of electrons and lithium ions, the diffusion of lithium ions in the bulk phase of the material is often the rate-determining step of the electrochemical reaction. This also leads to a higher frequency of lithium ion insertion / extraction at the surface and near-surface of the cathode material particles at the same rate. Accompanying oxygen loss from the material structure framework lattice, "lattice breathing", uneven stress distribution caused by phase transformation and cracks are more likely to be generated on the surface / near-surface and propagate to the bulk phase. Therefore, the yttrium-modified lithium cobalt oxide cathode material prepared in this invention has the characteristics of gradient doping with high surface yttrium content and low internal content, realizing the efficient utilization of heterogeneous element yttrium. Compared with the traditional uniform doping system, it can achieve the same or even better effect, reducing the amount of heterogeneous modification elements and compressing the isothermal sintering time. Attached Figure Description

[0031] Figure 1 A scanning electron microscope image of the original lithium cobalt oxide material;

[0032] Figure 2 Here is a scanning electron microscope image of the yttrium-modified lithium cobalt oxide cathode material obtained in Example 1;

[0033] Figure 3 The X-ray diffraction comparison spectra of the yttrium-modified lithium cobalt oxide cathode material obtained in Example 1 and Comparative Example 1 and the original lithium cobalt oxide material are shown.

[0034] Figure 4 The image shows the FIB-SEM cross-sectional morphology of the yttrium-modified lithium cobalt oxide cathode material obtained in Example 1.

[0035] Figure 5 for Figure 4 The corresponding line scan energy dispersive spectroscopy (EDS) elemental distribution map;

[0036] Figure 6 The graph shows a comparison of the cycle stability of the cathode materials obtained in Example 1 and Comparative Examples 1-4 in the voltage range of 3-4.6V.

[0037] Figure 7 The graph shows the rate performance test results of the cathode materials obtained in Example 1 and Comparative Example 4 in the voltage range of 3 to 4.6 V.

[0038] Figure 8 Original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Scanning electron microscope images of O2 materials;

[0039] Figure 9 Here are scanning electron microscope images of the yttrium-modified cathode material obtained in Example 2;

[0040] Figure 10 Yttrium-modified lithium-rich manganese-based Li obtained in Example 2 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 X-ray diffraction comparison of O2 materials;

[0041] Figure 11 Yttrium-modified lithium-rich manganese-based Li obtained in Examples 2-5 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Comparison of O2 material cycling stability test results in the voltage range of 3–4.8V;

[0042] Figure 12 Yttrium-modified lithium-rich manganese-based Li obtained in Example 2 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Rate performance test chart of O2 material in the voltage range of 3 to 4.8V;

[0043] Figure 13 Yttrium-modified high-nickel LiNi obtained in Examples 6-7 0.8 Co 0.15 Al 0.05 O2 cathode material and original high-nickel LiNi 0.8 Co 0.15 Al 0.05 Comparison of O2 material cycling stability test results in the 3–4.5V voltage range;

[0044] Figure 14 Yttrium-modified high-nickel LiNi obtained in Examples 6-7 0.8 Co 0.15 Al 0.05 O2 cathode material and original high-nickel LiNi 0.8 Co 0.15 Al 0.05 Comparison of O2 material cycling stability test results in the voltage range of 3–4.7V. Detailed Implementation

[0045] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0046] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0047] Example 1:

[0048] The specific process for preparing the yttrium-modified lithium cobalt oxide cathode material in this embodiment is carried out according to the following steps:

[0049] (1) Add 0.08 g of yttrium hexahydrate to a clean beaker, then add 40 mL of deionized water and stir until it is evenly dispersed to obtain a yttrium dispersion;

[0050] (2) Slowly add 4g of lithium cobalt oxide to the yttrium dispersion, and at the same time slowly add 10mL of 0.5mol / L citric acid solution, and stir until homogeneous;

[0051] (3) Place the beaker in a magnetic stirring heating jacket and heat and stir until the water evaporates. Set the temperature to 80℃, the rotation speed to 300r / min, and the evaporation time to 300min. Then crush and grind it, put it in an oven, and dry it further at 80℃ for 600min to obtain the precursor material.

[0052] (4) Place the precursor material obtained in step (3) at the bottom of the crucible and spread it evenly. Place the crucible in a muffle furnace and heat it to 850°C at a heating rate of 5°C / min. Then stop heating immediately and let it cool naturally to room temperature. Take out the product and sieve it through a 300-mesh sieve to obtain yttrium-modified lithium cobalt oxide cathode material.

[0053] Comparative Example 1:

[0054] The difference between this comparative example and Example 1 is that: in step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 1 hour, the heating is stopped and the material is allowed to cool naturally to room temperature. The product is then taken out and sieved through a 300-mesh sieve to obtain the yttrium-modified lithium cobalt oxide cathode material.

[0055] Comparative Example 2:

[0056] The difference between this comparative example and Example 1 is that: in step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 3 hours, the heating is stopped and the material is allowed to cool naturally to room temperature. The product is then taken out and sieved through a 300-mesh sieve to obtain the yttrium-modified lithium cobalt oxide cathode material.

[0057] Comparative Example 3:

[0058] The difference between this comparative example and Example 1 is that: in step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 6 hours, the heating is stopped and the material is allowed to cool naturally to room temperature. The product is then taken out and sieved through a 300-mesh sieve to obtain the yttrium-modified lithium cobalt oxide cathode material.

[0059] Comparative Example 4:

[0060] This comparative example is the original lithium cobalt oxide material without any modification treatment.

[0061] Example of effect 1:

[0062] (1) Scanning electron microscope images of the unmodified original lithium cobalt oxide material involved in Comparative Example 1, such as Figure 1 As shown, by Figure 1 It can be seen that the original lithium cobalt oxide cathode material particles are irregular nanoparticle aggregates without obvious secondary particle regular morphology, and the element distribution is relatively uniform. Figure 2 Here are scanning electron microscope images of the yttrium-modified lithium cobalt oxide cathode material prepared in this embodiment, for comparison. Figure 1 and Figure 2 It can be seen that the morphology of the lithium cobalt oxide cathode material after yttrium modification treatment is not significantly changed, and the elemental distribution is relatively uniform.

[0063] (2) The X-ray diffraction comparison spectra of the yttrium-modified lithium cobalt oxide cathode material obtained in Example 1 and Comparative Example 1 and the original lithium cobalt oxide material are shown in the figure. Figure 3 As shown, by Figure 3 It can be seen that the lithium cobalt oxide cathode material after yttrium modification has no obvious impurity peaks, which indicates that the crystal structure of the material prepared in Example 1 after yttrium modification has not changed significantly. The material still maintains the α-NaFeO2 type structure and belongs to the R-3m space group. At the same time, the phase distribution also remains basically unchanged, and there is no segregation or impurity phase. By comparing the (003) crystal plane after magnification, the results show that after yttrium modification, the diffraction peak position shifts slightly to a lower angle, indicating that the cell parameter c, i.e. the interplanar spacing, increases, further indicating that yttrium has successfully entered the lattice of the lithium cobalt oxide cathode material.

[0064] (3) The FIB-SEM cross-sectional morphology of the yttrium-modified lithium cobalt oxide cathode material obtained in Example 1 is shown below. Figure 4 As shown, the corresponding linear scan energy dispersive spectroscopy (EDS) elemental distribution is as follows: Figure 5 As shown, by Figure 4 and Figure 5 It can be seen that the distribution of yttrium shows a trend of high content at the surface and interface and low content of bulk phase inside the particles.

[0065] (4) The yttrium-modified lithium cobalt oxide cathode materials obtained in Examples 1 and Comparative Examples 1-4, as well as the original lithium cobalt oxide materials, were subjected to electrical performance tests. The electrode material, conductive carbon, and PVDF binder were mixed uniformly in a ratio of 8:1:1. NMP solvent was added and stirred for 20 hours to obtain a uniform slurry. This slurry was then uniformly coated onto battery-grade Al foil using a doctor blade coater and dried in an oven at 120°C for 600 minutes. The slurry was then automatically cut into 14mm diameter electrode sheets using a die-cutting machine and assembled into CR2032 button batteries in a glove box. A 10-hour settling time was set in the battery testing system, followed by two cycles of activation at 0.1C (1C = 200mA / g). Cyclic stability tests were then conducted at 1C rate and a high voltage range of 3-4.6V. The test results are as follows: Figure 6 As shown in Table 1, the specific performance test results are as follows:

[0066] Table 1

[0067] Example 1 194.71mAh / g 92.91％ 165min Comparative Example 1 190.81mAh / g 93.46％ 225min Comparative Example 2 192.29mAh / g 93.59％ 345min Comparative Example 3 190.54mAh / g 91.42％ 525min Comparative Example 4 194.62mAh / g 62.97％ 0min

[0068] Therefore, the initial discharge specific capacities of the materials obtained in Example 1 and Comparative Examples 1-4 were 194.71 mAh / g, 190.81 mAh / g, 192.29 mAh / g, 190.54 mAh / g, and 194.62 mAh / g, respectively, with corresponding capacity retention rates of 92.91%, 93.46%, 93.59%, 91.42%, and 62.97% after 100 cycles. The comparison shows that the discharge specific capacity and cycle stability of the yttrium-modified lithium cobalt oxide cathode material were significantly improved compared to the original material (Comparative Example 4). Furthermore, the lithium cobalt oxide material with bulk gradient doping prepared in Example 1 achieved a higher reversible capacity and significantly reduced annealing time, thus saving production costs.

[0069] Figure 7 The rate performance of the yttrium-modified lithium cobalt oxide cathode material prepared in Example 1 and the unmodified original lithium cobalt oxide material in Comparative Example 1 are demonstrated. Figure 7It can be seen that, under the voltage range of 3 to 4.6V, the specific capacities of the yttrium-modified lithium cobalt oxide cathode material reached 218mAh / g, 194mAh / g, 182mAh / g, 167mAh / g, 157mAh / g, 142mAh / g, and 116mAh / g, respectively, at 0.1C, 0.5C, 1C, 2C, 3C, 5C, and 10C (1C = 200mA / g). This means that the cathode material after yttrium modification exhibits excellent electrochemical performance at a high voltage of 4.6V.

[0070] Example 2:

[0071] This embodiment prepares yttrium-modified lithium-rich manganese-based Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 The specific process for using O2 cathode materials is carried out according to the following steps:

[0072] (1) Add 0.09 g of yttrium hexahydrate to a clean beaker, then add 40 mL of deionized water and stir until it is evenly dispersed to obtain a yttrium dispersion;

[0073] (2) Add 2g of lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 is slowly added to the yttrium dispersion, and 10 mL of 0.5 mol / L citric acid solution is slowly added at the same time, and the mixture is stirred until homogeneous.

[0074] (3) Place the beaker in a magnetic stirring heating jacket and heat and stir until the water evaporates. Set the temperature to 80℃, the rotation speed to 300r / min, and the evaporation time to 300min. Then crush and grind it, put it in an oven, and dry it further at 80℃ for 600min to obtain the precursor material.

[0075] (4) Place the precursor material obtained in step (3) at the bottom of the crucible and spread it evenly. Place the crucible in a muffle furnace and heat it to 850°C at a heating rate of 5°C / min. Then immediately stop heating and allow it to cool naturally to room temperature. Take out the product and sieve it through a 300-mesh sieve to obtain yttrium-modified lithium-rich manganese-based Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material.

[0076] Example 3:

[0077] The difference between this embodiment and embodiment 2 is as follows: In step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is then placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 1 hour, heating is stopped, and the material is allowed to cool naturally to room temperature. The product is then removed and sieved through a 300-mesh sieve to obtain yttrium-modified lithium-rich manganese-based Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material.

[0078] Example 4:

[0079] The difference between this comparative example and Example 2 is as follows: In step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is then placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 3 hours, heating is stopped, and the material is allowed to cool naturally to room temperature. The product is then removed and sieved through a 300-mesh sieve to obtain yttrium-modified lithium-rich manganese-based Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material.

[0080] Example 5:

[0081] The difference between this comparative example and Example 2 is as follows: In step (4), the precursor material obtained in step (3) is placed at the bottom of the crucible and spread evenly. The crucible is then placed in a muffle furnace and heated to 850°C at a heating rate of 5°C / min. After holding at this temperature for 6 hours, heating is stopped, and the material is allowed to cool naturally to room temperature. The product is then removed and sieved through a 300-mesh sieve to obtain yttrium-modified lithium-rich manganese-based Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material.

[0082] Example of effect 2:

[0083] (1) Unmodified raw lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 Scanning electron microscope images of O2 materials, such as Figure 8 As shown, by Figure 8 It can be seen that the original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The O2 cathode material particles are irregular nanoparticle aggregates with no obvious secondary particle regular morphology and relatively uniform element distribution. Figure 9 The yttrium-modified lithium-rich manganese-based Li prepared in this embodiment1.2 Mn 0.54 Ni 0.13 Co 0.13 Scanning electron microscope images of O2 cathode materials, compared with Figure 8 and Figure 9 It can be seen that the lithium-rich manganese-based Li after yttrium modification... 1.2 Mn 0.54 Ni 0.13 Co 0.13 The morphology of the O2 cathode material did not change significantly, and the elemental distribution was relatively uniform.

[0084] (2) Yttrium-modified lithium-rich manganese-based Li obtained in Example 2 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 X-ray diffraction comparison patterns of O2 materials are as follows: Figure 10 As shown, by Figure 10 It can be seen that the lithium-rich manganese-based Li after yttrium modification 1.2 Mn 0.54 Ni 0.13 Co 0.13 The O2 cathode material showed no obvious impurity peaks, indicating that the crystal structure of the material prepared in Example 2 after yttrium modification did not change significantly. The material still maintains the α-NaFeO2 type structure, belonging to the R-3m and C2 / m space groups. At the same time, the phase distribution remained basically unchanged, with no segregation or impurity phases. By comparing the magnified (003) crystal plane, the results showed that after yttrium modification, the diffraction peak position shifted slightly to a lower angle, indicating that the cell parameter c, i.e., the interplanar spacing, increased. This further illustrates that yttrium successfully entered the lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 In the crystal lattice of O2 cathode material.

[0085] (3) The yttrium-modified lithium-rich manganese-based Li obtained in Examples 2-5 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13The O2 material underwent electrical performance testing. Electrode material, conductive carbon, and PVDF binder were mixed uniformly in an 8:1:1 ratio. NMP solvent was added and stirred for 20 hours to obtain a homogeneous slurry. This slurry was then uniformly coated onto battery-grade Al foil using a doctor blade coater and dried in an oven at 120°C for 600 minutes. The slurry was then automatically cut into 14mm diameter electrode sheets using a die-cutting machine and assembled into CR2032 button cells in a glove box. A 10-hour settling time was set in the battery testing system, followed by two cycles of activation at 0.1C (1C = 250mA / g). Cyclic stability testing was then conducted at 1C rate and a high voltage range of 3–4.8V. The test results are as follows: Figure 11 As shown in Table 2, the specific performance test results are as follows:

[0086] Table 2

[0087]

[0088] Therefore, it can be concluded that the original lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The initial discharge specific capacities of O2 and the materials obtained in Examples 2-5 were 227.85 mAh / g, 226.17 mAh / g, 225.22 mAh / g, 221.20 mAh / g, and 224.17 mAh / g, respectively, with corresponding capacity retention rates of 78.12%, 95.09%, 93.84%, 92.08%, and 89.74% after 200 cycles. In comparison, the materials using yttrium-modified lithium-rich manganese-based Li... 1.2 Mn 0.54 Ni 0.13 Co 0.13 Although the initial discharge specific capacity of the O2 material is slightly lower than that of the original material, its cycle stability is significantly improved; and Example 2 has the highest cycle retention rate, which greatly reduces the annealing time and saves production costs.

[0089] Figure 12 This demonstrates the yttrium-modified lithium-rich manganese-based Li prepared in Example 2. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 cathode material and unmodified raw lithium-rich manganese-based Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 The rate performance of O2 materials is determined by Figure 12 It can be seen that, under a voltage range of 3–4.8V, rate tests at 0.1C, 0.5C, 1C, 2C, 3C, and 5C (1C = 200mA / g) were conducted on yttrium-modified lithium-rich manganese-based Li... 1.2Mn 0.54 Ni 0.13 Co 0.13 The specific capacities of the O2 cathode material reached 291 mAh / g, 241 mAh / g, 214 mAh / g, 184 mAh / g, 164 mAh / g, and 138 mAh / g; that is, the cathode material after yttrium modification exhibited excellent electrochemical performance at a high voltage of 4.8V.

[0090] Example 6:

[0091] This embodiment prepares yttrium-modified high-nickel LiNi. 0.8 Co 0.15 Al 0.05 The specific process for using O2 cathode materials is carried out according to the following steps:

[0092] (1) Add 0.08 g of yttrium hexahydrate to a clean beaker, then add 40 mL of deionized water and stir until it is evenly dispersed to obtain a yttrium dispersion;

[0093] (2) 4g of high-nickel LiNi 0.8 Co 0.15 Al 0.05 O2 is slowly added to the yttrium dispersion, and 10 mL of 0.5 mol / L citric acid solution is slowly added at the same time, and the mixture is stirred until homogeneous.

[0094] (3) Place the beaker in a magnetic stirring heating jacket and heat and stir until the water evaporates. Set the temperature to 80℃, the rotation speed to 300r / min, and the evaporation time to 300min. Then crush and grind it, put it in an oven, and dry it further at 80℃ for 600min to obtain the precursor material.

[0095] (4) Place the precursor material obtained in step (3) at the bottom of the crucible and spread it evenly. Place the crucible in a muffle furnace and heat it to 700°C at a heating rate of 5°C / min. Then immediately stop heating and allow it to cool naturally to room temperature. Take out the product and sieve it through a 300-mesh sieve to obtain yttrium-modified high-nickel LiNi. 0.8 Co 0.15 Al 0.05 O2 cathode material.

[0096] Example 7:

[0097] The difference between this embodiment and Example 6 is that the amount of yttrium hexahydrate used in step (1) is 0.16g, while the other parameters and process steps are the same as in Example 6, resulting in yttrium-modified high-nickel LiNi. 0.8 Co 0.15 Al 0.05 O2 cathode material.

[0098] Example of effect 3:

[0099] (1) Yttrium-modified high-nickel LiNi obtained in Examples 1 and 2 0.8 Co 0.15 Al 0.05 O2 cathode material and original high-nickel LiNi 0.8 Co 0.15 Al 0.05 The O2 material was subjected to electrical performance testing. Electrode material, conductive carbon, and PVDF binder were mixed uniformly in an 8:1:1 ratio. NMP solvent was added and stirred for 20 hours to obtain a homogeneous slurry. This slurry was then uniformly coated onto battery-grade Al foil using a doctor blade coater and dried in an oven at 120°C for 600 minutes. The slurry was then automatically cut into 14mm diameter electrode sheets using a die-cutting machine and assembled into CR2032 button cells in a glove box. A 10-hour settling time was set in the battery testing system, followed by two cycles of activation at 0.1C (1C = 200mA / g). Cyclic stability tests were then conducted at 1C rate and in the 3–4.5V and 3–4.7V high-voltage ranges. The test results are as follows: Figure 13 and Figure 14 As shown, the specific performance test results are shown in Tables 3 and 4:

[0100] Table 33 - 4.5V Data Comparison

[0101]

[0102] Table 43-4.7V data comparison

[0103]

[0104] Therefore, the materials obtained in Examples 6 and 7 are similar to the original high-nickel LiNi. 0.8 Co 0.15 Al 0.05 The initial discharge specific capacities of O2 at 3–4.5V were 184.14 mAh / g, 178.74 mAh / g, and 183.21 mAh / g, respectively, with corresponding capacity retention rates of 79.89%, 80.02%, and 40.98% after 200 cycles; Examples 6 and 7 compared with the original high-nickel LiNi 0.8 Co 0.15 Al 0.05 The initial discharge specific capacities of the materials obtained under O2 at 3–4.7 V were 186.84 mAh / g, 188.70 mAh / g, and 183.72 mAh / g, respectively, with corresponding capacity retention rates of 78.61%, 78.31%, and 38.04% after 200 cycles. In comparison, the yttrium-modified high-nickel LiNi... 0.8 Co 0.15 Al 0.05Compared to the original material (high-nickel LiNi), O2 cathode material is a better choice. 0.8 Co 0.15 Al 0.05 The discharge specific capacity and cycle stability of O2 have been significantly improved.

[0105] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for modifying a cathode material, characterized in that, include: S1, dissolve the yttrium compound in a solvent to obtain a yttrium dispersion; S2, the yttrium dispersion and complexing agent solution are slowly added to the cathode material and mixed evenly. The mixture is then heated to dryness to obtain the precursor material. S3, the precursor material is placed in a muffle furnace for heating and annealing, cooled to room temperature and then sieved to obtain yttrium-modified cathode material; The yttrium compound in S1 is yttrium nitrate hexahydrate, and the solvent is deionized water; The solute in the complexing agent solution in S2 is citric acid, and the positive electrode material is lithium cobalt oxide or Li. 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2 or LiNi 0.8 Co 0.15 Al 0.05 O2; The molar ratio of complexing agent to yttrium compound in the mixture of S2 is (3~1):1; the molar ratio of cathode material to yttrium compound is 1:(0.01~0.001). The heating and annealing conditions in S3 are as follows: in an air atmosphere, the temperature is increased at a rate of 1-10℃ / min, and after reaching 850℃, the heating is immediately stopped and the temperature is allowed to cool naturally to room temperature.

2. The method for modifying the cathode material according to claim 1, characterized in that, The evaporation temperature in S2 is 75~90℃, and the stirring speed is 250~350 r / min.

3. The method for modifying and altering the cathode material according to claim 1, characterized in that, The heating rate is 5℃ / min.

4. A yttrium-containing compound cathode material obtained by the modification method according to any one of claims 1 to 3.

5. The application of the yttrium-containing compound cathode material according to claim 4, characterized in that, Used in cathode materials for lithium-ion batteries.

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