Cerium-based composite modified high-voltage high-nickel ternary positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a cerium-based composite modified high-voltage high-nickel ternary positive electrode material and a preparation method and application thereof, cerium-based composite modification is CeO2 coating / metal doping composite modification or Ce / metal co-doping composite modification, the high-nickel ternary positive electrode material is at least one of LiNi < x > Co < y > Mn < z > O < 2 > and LiNi < x > Co < y > Al < z > O < 2 >, x + y + z = 1, and x is larger than or equal to 0.6. Through cerium-based composite modification, the surface and interface stability, the structural stability and the lattice oxygen stability of the high-nickel ternary positive electrode material under high voltage are improved, so that the cycling stability, the thermal stability and the safety performance of the high-nickel ternary positive electrode material are improved; and an effective scheme is provided for development of a high-energy-density, high-stability and high-safety lithium ion battery positive electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a cerium-based composite modified high-voltage high-nickel ternary positive electrode material and a preparation method and application thereof. Background Art

[0002] In recent years, with the widespread application of lithium-ion batteries in consumer electronics, electric vehicles and energy storage, the market's requirements for battery energy density, cycle life and safety performance have continued to increase. High-nickel ternary cathode materials have become a research hotspot for lithium-ion battery cathode materials due to their high specific capacity, high energy density and relatively low cost advantages. Compared with traditional lithium cobalt oxide (LiCoO2) and lithium iron phosphate (LiFePO4) cathode materials, high-nickel ternary materials have significant advantages in energy density and can meet the development trend of long driving range of electric vehicles and high energy requirements of consumer electronic devices.

[0003] However, despite the excellent theoretical performance of high-nickel ternary cathode materials, they still face a series of severe technical challenges in practical applications, which limit their large-scale commercial application. For example, although increasing the nickel content increases the specific capacity, it also aggravates the structural instability of the material during the charge and discharge process; as the number of cycles increases, the material is prone to lattice distortion, phase change and microcracks, resulting in rapid capacity decay.

[0004] In addition, increasing the cut-off voltage is another effective solution to increase the energy density of positive electrode materials for lithium-ion batteries. However, under high voltage (>4.3V) test conditions, existing high-nickel ternary materials are prone to irreversible phase transitions from layered structures to spinel structures or rock salt structures, causing the collapse of the material structure, which in turn leads to a sharp decline in battery performance. At the same time, high-nickel materials have high surface activity and are prone to side reactions with the electrolyte to form unstable solid electrolyte interface films. These side reactions not only consume active lithium ions, but also cause electrolyte decomposition and gas generation, further deteriorating the battery's cycle performance and safety. Moreover, existing high-nickel ternary materials are prone to thermal runaway under high temperature conditions, especially in extreme cases such as overcharging or short circuiting, the material will release a large amount of heat, posing serious safety hazards.

[0005] In order to overcome the above problems, researchers have proposed a variety of modification strategies, mainly including surface coating and doping regulation. Surface coating can inhibit the direct contact between the material and the electrolyte, reduce interfacial side reactions, and improve the structural stability of the material by coating a stable protective layer on the surface of the material. However, a single surface coating often cannot meet the comprehensive requirements of material conductivity, interface stability and mechanical strength at the same time, and it is difficult to control the uniformity and thickness of the coating layer. Doping regulation can stabilize the material structure and inhibit phase change and the release of lattice oxygen by introducing doping elements into the material lattice. However, the effect of single element doping on improving material performance is limited, especially under harsh conditions such as high voltage and high temperature, the performance of the material is still difficult to meet the needs of practical applications.

[0006] In recent years, composite modification strategies have gradually become a research hotspot. Composite modification combines the advantages of surface coating and doping regulation. Through multi-element co-doping, multi-layer coating or coating / doping synergy, it can more comprehensively improve the comprehensive performance of materials. However, although the composite modification strategy has significant advantages in theory, it still faces many technical difficulties in practical applications. Therefore, the development of an efficient and controllable composite modification technology to achieve a comprehensive improvement in the performance of high-nickel ternary positive electrode materials is still a key issue that needs to be urgently solved in the current lithium-ion battery field. Summary of the invention

[0007] The purpose of the present invention is to provide a cerium-based composite modified high-voltage high-nickel ternary positive electrode material and its preparation method and application in response to the above-mentioned problems. Through the cerium-based composite modification, the surface and interface stability, structural stability, and lattice oxygen stability of the high-nickel ternary positive electrode material under high voltage are improved, thereby improving the cycle stability, thermal stability and safety performance of the high-nickel ternary positive electrode material, providing an effective solution for the development of high-energy density, high-stability, and high-safety lithium-ion battery positive electrode materials.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] 1. A cerium-based composite modified high-voltage high-nickel ternary positive electrode material, wherein the cerium-based composite modification is CeO2 coating / metal doping composite modification or Ce / metal co-doping composite modification, and the high-nickel ternary positive electrode material is LiNi x Co y Mn z O2 or LiNi x Co y Al z At least one of O2; the cerium-based composite modified high-voltage high-nickel ternary positive electrode material is CeO2 coated / metal-doped composite modified LiNi x Co y Mn zLiNi modified by O2, CeO2 coating / metal doping x Co y Al z O2, Ce / metal co-doped composite modified LiNi x Co y Mn z LiNi modified by O2 or Ce / metal co-doping x Co y Al z O2; wherein, x+y+z=1, and x≥0.6; after the cerium-based composite modification, the electrochemical performance of the high-nickel ternary positive electrode material under high voltage is improved.

[0010] Preferably, the CeO2 coating / metal doping composite modification refers to forming a CeO2 coating layer on the surface of the high-nickel ternary positive electrode material and forming metal doping inside the high-nickel ternary positive electrode material; the doped metal is at least one of iron, magnesium, titanium, niobium, tantalum, tungsten, molybdenum, copper, zinc, gallium, aluminum, indium, germanium, and tin.

[0011] Preferably, the Ce / metal co-doping composite modification refers to the formation of co-doping of Ce and other metals inside the high-nickel ternary positive electrode material; the other metals are at least one of samarium, lanthanum, praseodymium, neodymium, europium, gadolinium, sodium, calcium, strontium, and bismuth.

[0012] The present invention also provides a method for preparing the high-voltage high-nickel ternary positive electrode material, comprising the following steps:

[0013] (1) mixing a high-nickel ternary positive electrode material precursor, a lithium salt, a cerium salt and a doped metal salt to obtain a mixture;

[0014] (2) calcining the mixture obtained in step (1) to prepare the cerium-based composite modified high-voltage high-nickel ternary positive electrode material.

[0015] Preferably, in the above preparation method, in step (1), the amount of the high-nickel ternary positive electrode material precursor is 0.1g-10g; the amount of the lithium salt is 0.05g-8.5g; the amount of the cerium salt is 0.0005g-0.05g; and the amount of the doped metal salt is 0.0005g-0.05g.

[0016] Preferably, in the above preparation method, in step (1), the high nickel ternary cathode material precursor is Ni x Co y Mn z (OH)2 and Ni x Co y Al z At least one of (OH)2, wherein x+y+z=1, and x≥0.6.

[0017] Preferably, in the above preparation method, in step (1), the lithium salt is LiOH or Li2CO3; the cerium salt is at least one of cerium nitrate, cerium acetate, cerium sulfate, cerium chloride, cerium tetrafluoride, cerium oxide or cerium oxalate.

[0018] Preferably, in the above preparation method, when preparing a high-voltage high-nickel ternary positive electrode material of CeO2 coating / metal doping composite modification, the doping metal salt in step (1) is at least one of the nitrates, sulfates, oxalates, acetates and chlorides of iron, magnesium, titanium, niobium, tantalum, tungsten, molybdenum, copper, zinc, gallium, aluminum, indium, germanium and tin; when preparing a high-voltage high-nickel ternary positive electrode material of Ce / metal co-doping composite modification, the doping metal salt in step (1) is at least one of the nitrates, sulfates, oxalates, acetates and chlorides of samarium, lanthanum, praseodymium, neodymium, europium, gadolinium, sodium, calcium, strontium and bismuth.

[0019] Preferably, in the above preparation method, in step (2), the calcination temperature is 450°C-750°C, the heating rate is 2°C / min-5°C / min, and the calcination time is 5h-15h.

[0020] In addition, the cerium-based composite modified high-voltage high-nickel ternary positive electrode material described in the present invention can be used in lithium-ion batteries.

[0021] In summary, due to the adoption of the above technical solution, the present invention has the following beneficial effects:

[0022] (1) The present invention provides a method for preparing a cerium-based composite-modified high-voltage high-nickel ternary positive electrode material, which can prepare a high-nickel ternary positive electrode material of CeO2 coating / metal doping composite modification or Ce / metal co-doping composite modification. In the CeO2 coating / metal doping composite modification, the CeO2 coating layer is uniform and continuous, and the doped metal is evenly distributed inside the material; in the Ce / metal co-doping composite modification, Ce and other metals together form a good doping effect inside the material. The composite modification scheme provided by the present invention provides a good technical solution for optimizing the performance of high-nickel ternary positive electrode materials for lithium-ion batteries under high voltage;

[0023] (2) In the CeO2-coated / metal-doped composite modified high-nickel ternary positive electrode material provided by the present invention, the CeO2 coating layer isolates the external environment / electrolyte from direct contact with the positive electrode material, inhibits side reactions, and improves the surface and interface stability of the material; at the same time, CeO2, as a good oxygen ion conductor, can use its own oxygen vacancies to store and release oxygen, thereby inhibiting the reaction of the released active oxygen with the electrolyte, and improving the safety performance of the positive electrode material under high voltage; and metal doping improves the structural stability of the material through strong metal-oxygen bonds. Therefore, through CeO2 coating / metal doping composite modification, the synergistic optimization of the surface and bulk of the positive electrode material is achieved, which can effectively improve the cycle stability, high temperature stability and safety performance of the high-nickel ternary positive electrode material under high voltage.

[0024] (3) In the Ce / metal co-doped composite modified high-nickel ternary positive electrode material provided by the present invention, Ce and other metals are co-doped into the interior of the high-nickel ternary positive electrode material, and doping is performed at the transition metal site and the lithium site. Doping at the transition metal site improves the structural stability of the material through a strong metal-oxygen bond; doping at the lithium site plays a supporting role and improves lithium ion transmission. Therefore, through Ce / metal co-doped composite modification, the cycle stability and rate performance of the high-nickel ternary under high voltage can be effectively improved.

[0025] (4) The preparation method of the cerium-based composite modified high-nickel ternary positive electrode material provided by the present invention has simple process, mild conditions, low cost, high yield and good repetitive effect. The high-nickel ternary positive electrode material modified by the preparation method has excellent electrochemical performance under various test conditions such as conventional voltage (4.3V), high voltage (4.5V) and ultra-high voltage (4.6V). This method has good application prospects and practical value in actual industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a transmission electron microscope image of the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0027] Figure 2 This is the element distribution diagram of the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0028] Figure 3 It is the X-ray diffraction pattern of the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0029] Figure 4 It is a differential scanning calorimeter test comparison diagram of Example 1 and Comparative Example 1.

[0030] Figure 5This is a transmission electron microscope image of the Ce / Sm co-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0031] Figure 6 This is the element distribution diagram of the Ce / Sm co-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0032] Figure 7 It is the X-ray diffraction pattern of the Ce / Sm co-doped composite modified high-nickel ternary positive electrode material in Example 1.

[0033] Figure 8 It is a comparison chart of the cycle stability of the batteries of Example 1 and Comparative Example 1 at 3-4.3V and 1C.

[0034] Fig. 9 It is a comparison chart of the cycle stability of the batteries of Example 1 and Comparative Example 1 at 3-4.5V and 1C.

[0035] Fig.10 It is a comparison chart of the cycle stability of the batteries of Example 1 and Comparative Example 1 at 3-4.6V and 1C.

[0036] Fig.11 It is a comparison chart of the cycle stability of the batteries of Example 4 and Comparative Example 2 at 3-4.5V and 1C.

[0037] Fig.12 It is a cyclic voltammetry comparison diagram of the battery of Example 4 and Comparative Example 2 before and after cycling at 3-4.5V and 1C.

[0038] Fig.13 It is a comparison diagram of electrochemical impedance of Example 1 and Comparative Example 1 before and after cycling at 3-4.5V and 1C.

[0039] Fig.14 It is a comparison picture of the scanning electron microscope of Example 1 and Comparative Example 1 after the cycle test at 3-4.5V and 1C. DETAILED DESCRIPTION

[0040] The present invention provides a cerium-based composite modified high-voltage high-nickel ternary positive electrode material, wherein the cerium-based composite modification is CeO2 coating / metal doping composite modification or Ce / metal co-doping composite modification, and the high-nickel ternary positive electrode material is LiNi x Co y Mn z O2 or LiNi x Co y Al z O2; the cerium-based composite modified high-voltage high-nickel ternary positive electrode material is CeO2 coated / metal-doped composite modified LiNi x Co y Mnz LiNi modified by O2, CeO2 coating / metal doping x Co y Al z O2, Ce / metal co-doped composite modified LiNi x Co y Mn z LiNi modified by O2 or Ce / metal co-doping x Co y Al z O2; wherein x+y+z=1, and x≥0.6.

[0041] In order to express the present invention more clearly, the present invention is further described below through specific examples.

[0042] 1. Preparation Example

[0043] Example 1

[0044] This embodiment prepares a CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0045] (1) 1g Ni 0.83 Co 0.11 Al 0.06 (OH)2, 0.4801g lithium hydroxide, 0.005g cerium nitrate and 0.005g ferric nitrate are mixed together and ground evenly;

[0046] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, i.e., CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2.

[0047] Example 2

[0048] This embodiment prepares a CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0049] (1) 0.1gNi 0.83 Co 0.11 Al 0.06 (OH)2, 0.05g lithium hydroxide, 0.0005g cerium sulfate and 0.0005g ferric sulfate are mixed together and ground evenly;

[0050] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, i.e., CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2.

[0051] Example 3

[0052] This embodiment prepares a CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0053] (1) 10 g Ni 0.83 Co 0.11 Al 0.06 (OH)2, 8.5g lithium carbonate, 0.05g cerium oxide and 0.05g ferric chloride are mixed together and ground evenly;

[0054] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material, i.e., CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2.

[0055] In the above embodiment, there are multiple options for cerium salt, and those skilled in the art can select at least one of cerium nitrate, cerium acetate, cerium sulfate, cerium chloride, cerium tetrafluoride, cerium oxide or cerium oxalate according to actual conditions. There are also multiple options for doped metal salts, and those skilled in the art can select at least one of nitrate, sulfate, oxalate, acetate and chloride according to actual conditions.

[0056] Comparative Example 1

[0057] This embodiment prepares a high-nickel ternary positive electrode material, including the following steps:

[0058] (1) 1g Ni 0.83 Co 0.11 Al 0.06 (OH)2 and 0.4801g lithium hydroxide are mixed together and ground evenly;

[0059] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the high-nickel ternary positive electrode material LiNi 0.83 Co0.11 Al 0.06 O2.

[0060] The CeO2-coated / Fe-doped composite modified high-nickel ternary cathode material obtained in Example 1 was subjected to transmission electron microscopy, element distribution, and X-ray diffraction analysis. The transmission electron microscopy image is as follows: Figure 1 As shown in the figure, it can be seen that a uniform coating layer is formed on the surface of the high nickel ternary cathode material. Figure 2 As shown, it can be seen that Ce and Fe elements are evenly distributed; the X-ray diffraction picture is as follows Figure 3 As shown, it can be seen that the crystal structure of the high nickel ternary cathode material has not changed after modification; in addition, a CeO2 peak appears in the modified sample, indicating that the coating layer is CeO2; at the same time, after refined analysis, it is shown that the unit cell parameters have changed after modification (as shown in Table 1), confirming that Fe is doped into the bulk phase of the material.

[0061] Table 1 Cell parameters obtained by X-ray diffraction refinement for Example 1 and Comparative Example 1

[0062]

[0063] in addition, Figure 4 is a comparison chart of differential scanning calorimeter test of Example 1 and Comparative Example 1, Figure 4 It can be seen that the peak exothermic temperature of Example 1 is 365.2°C and the exothermic enthalpy is 529.7 J g -1 The peak exothermic temperature of comparative example 1 is 349.6 °C and the exothermic enthalpy is 659.6 J g -1 , proving that CeO2 coating / Fe doping composite modification improves the thermal stability of high-nickel ternary positive electrode materials.

[0064] The transmission electron microscope images, element distribution maps, X-ray diffraction maps, and differential scanning calorimeter tests of the samples obtained in Examples 2 and 3 are basically consistent with the pattern of the above-mentioned Example 1, and their corresponding spectra are omitted here.

[0065] Example 4

[0066] This embodiment prepares a Ce / Sm co-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0067] (1) 1g Ni 0.83 Co 0.11 Mn 006 (OH)2, 0.4764g lithium hydroxide, 0.015g cerium nitrate and 0.01g samarium nitrate were mixed together and ground evenly;

[0068] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the Ce / Sm co-doped composite high-nickel ternary positive electrode material, i.e., Ce / Sm co-doped composite modified LiNi 0.83 Co 0.11 Mn 0.06 O2.

[0069] Example 5

[0070] This embodiment prepares a Ce / Sm co-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0071] (1) 0.1 g Ni 0.83 Co 0.11 Mn 0.06 (OH)2, 0.05g lithium hydroxide, 0.0015g cerium sulfate and 0.001g samarium sulfate are mixed together and ground evenly;

[0072] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the Ce / Sm co-doped composite modified high-nickel ternary positive electrode material, i.e., Ce / Sm co-doped composite modified LiNi 0.83 Co 0.11 Mn 0.06 O2.

[0073] Example 6

[0074] This embodiment prepares a Ce / Sm co-doped composite modified high-nickel ternary positive electrode material, comprising the following steps:

[0075] (1) 10gNi 0.83 Co 0.11 Mn 0.06 (OH)2, 8.5g lithium carbonate, 0.15g cerium chloride and 0.1g samarium chloride are mixed together and ground evenly;

[0076] (2) The sample obtained in step (1) was heated to 450° C. at 5° C. / min in oxygen and calcined for 5 h, and then heated to 750° C. at 2° C. / min and calcined for 15 h to obtain the Ce / Sm co-doped composite modified high-nickel ternary positive electrode material, i.e., Ce / Sm co-doped composite modified LiNi 0.83 Co 0.11 Mn 0.06 O2.

[0077] In the above embodiment, there are multiple options for cerium salt, and those skilled in the art can select at least one of cerium nitrate, cerium acetate, cerium sulfate, cerium chloride, cerium tetrafluoride, cerium oxide or cerium oxalate according to actual conditions. There are also multiple options for doped metal salts, and those skilled in the art can select at least one of nitrate, sulfate, oxalate, acetate and chloride according to actual conditions.

[0078] Comparative Example 2

[0079] This embodiment prepares a high-nickel ternary positive electrode material, including the following steps:

[0080] (1) 1g Ni 0.83 Co 0.11 Mn 0.06 (OH)2 and 0.4764g lithium hydroxide were mixed and ground evenly;

[0081] (2) The sample obtained in step (1) was heated to 450°C at 5°C / min in oxygen and calcined for 5 h, and then heated to 750°C at 2°C / min and calcined for 15 h to obtain the high-nickel ternary positive electrode material LiNi 0.83 Co 0.11 Mn 006 O2.

[0082] The Ce / Sm co-doped composite modified high nickel ternary cathode material obtained in Example 4 was subjected to transmission electron microscopy, element distribution, and X-ray diffraction analysis. The transmission electron microscopy image is as follows: Figure 5 As shown, it can be seen that the material lattice spacing is 0.246nm, which is the (101) crystal plane of the high nickel ternary material layered phase. Figure 6 As shown in the figure, it can be seen that Ce and Sm elements are evenly distributed. Figure 7 As shown, it can be seen that the crystal structure of the high nickel ternary cathode material has not changed after modification. From Table 2, it can be seen that the unit cell parameters have changed after modification, indicating that Ce / Sm co-doping has been formed.

[0083] Table 2 Cell parameters obtained by X-ray diffraction refinement for Example 4 and Comparative Example 2

[0084]

[0085] The transmission electron microscope images, element distribution maps, and X-ray diffraction maps of the samples obtained in Examples 5 and 6 are basically consistent with the pattern of the above-mentioned Example 4, and their corresponding maps are omitted here.

[0086] 2. Performance Test

[0087] 1. Preparation of Ce-based composite modified high nickel ternary cathode material electrode:

[0088] 0.4g of high-nickel ternary positive electrode material was mixed with 0.05g of conductive additive Super P and 1g of binder (PVDF mass concentration was 5%), and the positive electrode material electrode was obtained by slurrying, coating (aluminum foil was used as current collector), and vacuum drying. The electrode of positive electrode material obtained by using the material obtained in Example 1 was recorded as electrode 1, the electrode of positive electrode material obtained by using the material obtained in Example 4 was recorded as electrode 2, the electrode of positive electrode material obtained by using the material obtained in Comparative Example 1 was recorded as electrode 3, and the electrode of positive electrode material obtained by using the material obtained in Comparative Example 2 was recorded as electrode 4.

[0089] 2. Assemble battery 1

[0090] The electrode 1 was used as the positive electrode, the metal lithium sheet was used as the negative electrode, and the polypropylene film (Celgard) was used as the separator, and a button cell was assembled in a vacuum glove box, which was recorded as cell 1. The electrolyte was a carbonate electrolyte with a concentration of 1M, in which the solute was LiPF6.

[0091] 3. Assemble battery 2

[0092] The difference between battery 2 and battery 1 is that the electrode used in battery 2 is electrode 2, and the rest is the same as battery 1.

[0093] 4. Assemble battery 3

[0094] The difference between battery 3 and battery 1 is that the electrode used in battery 3 is electrode 3, and the rest is the same as battery 1.

[0095] 5. Assemble battery 4

[0096] The difference between battery 4 and battery 1 is that the electrode used in battery 4 is electrode 4, and the rest is the same as battery 1.

[0097] 6. Battery test

[0098] The above-mentioned battery 1, battery 2, battery 3 and battery 4 were subjected to cyclic voltammetry test using an electrochemical workstation, with a scan rate of 0.1mV / S and a test voltage range of 3-4.5V; the above-mentioned battery 1, battery 2, battery 3 and battery 4 were subjected to electrochemical impedance test using an electrochemical workstation, with a frequency of 100000Hz-0.0005Hz; the above-mentioned battery 1, battery 2, battery 3 and battery 4 were subjected to constant current charge and discharge test using a charge and discharge instrument, with a charge and discharge rate of 1C and 0.1C (1C=200mA / g), and a test voltage range of 3-4.3V, 3-4.5V and 3-4.6V; the above test temperatures were all 25°C.

[0099] Figure 8 The cycle performance of battery 1 and battery 3 at 3-4.3V and 1C is shown in Table 1. Figure 8It can be seen that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material (CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2) prepared battery 1 and the unmodified high nickel ternary positive electrode material LiNi 0.83 Co 0.11 Al 0.06 The first cycle discharge capacity of battery 3 prepared by CeO2 is 186.74mAh / g and 173.41mAh / g respectively; after 200 cycles, the discharge capacity of battery 1 is 167.13mAh / g, and the capacity retention rate is 89.5%; the discharge capacity of battery 3 is 142.86mAh / g, and the capacity retention rate is only 82.3%. It can be seen that the CeO2 coated / Fe doped composite modified high nickel ternary positive electrode material of the present invention has a higher capacity retention rate and better cycle stability.

[0100] Fig. 9 The cycle performance of battery 1 and battery 3 at 3-4.5V and 1C is shown in Table 1. Fig. 9 It can be seen that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material (CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2) prepared battery 1 and the unmodified high nickel ternary positive electrode material LiNi 0.83 Co 0.11 Al 0.06 The first cycle discharge capacity of battery 3 prepared by CeO2 is 194.08mAh / g and 181.94mAh / g respectively; after 200 cycles, the discharge capacity of battery 1 is 153.85mAh / g, and the capacity retention rate is 79.3%; the discharge capacity of battery 3 is 126.53mAh / g, and the capacity retention rate is only 69.5%. It can be seen that the CeO2 coated / Fe doped composite modified high nickel ternary positive electrode material of the present invention has a higher capacity retention rate and better cycle stability at high voltage.

[0101] Fig.10 The cycle performance of battery 1 and battery 3 at 3-4.6V and 1C ultra-high voltage is shown in Figure 2. Fig.10 It can be seen that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material (CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2) prepared battery 1 and the unmodified high nickel ternary positive electrode material LiNi 0.83 Co 0.11Al 0.06 The first cycle discharge capacity of battery 3 prepared by CeO2 is 196.12mAh / g and 184.73mAh / g respectively; after 200 cycles, the discharge capacity of battery 1 is 150.88mAh / g, and the capacity retention rate is 76.9%; the discharge capacity of battery 3 is 120.94mAh / g, and the capacity retention rate is only 65.4%. It can be seen that the CeO2 coated / Fe doped composite modified high nickel ternary positive electrode material of the present invention has a higher capacity retention rate and better cycle stability at ultra-high cut-off voltage.

[0102] Fig.11 The cycle performance of battery 2 and battery 4 at 3-4.5V and 1C is shown in Table 1. Fig.11 It can be seen that the Ce / Sm co-doped composite modified high nickel ternary positive electrode material (Ce / Sm co-doped composite modified LiNi 0.83 Co 0.11 Mn 006 O2) prepared battery 2 and the use of unmodified high nickel ternary positive electrode material LiNi 0.83 Co 0.11 Mn 006 The first cycle discharge capacity of battery 4 prepared by O2 is 197.11mAh / g and 197.03mAh / g respectively; after 200 cycles, the discharge capacity of battery 2 is 130.0mAh / g, and the capacity retention rate is 66.0%; the discharge capacity of battery 4 is 112.81mAh / g, and the capacity retention rate is only 57.2%. It can be seen that the Ce / Sm co-doped composite modified high nickel ternary positive electrode material of the present invention has a higher capacity retention rate and better cycle stability.

[0103] Fig.12 The cyclic voltammetry comparison diagram of battery 2 and battery 4 before and after the cycle is shown in Figure 2. Fig.12 It can be seen that the Ce / Sm co-doped composite modified high nickel ternary positive electrode material (Ce / Sm co-doped composite modified LiNi 0.83 Co 0.11 Mn 006 O2) prepared battery 2, which shows better reversibility after cycling, indicating that the Ce / Sm co-doped composite modification of the present invention can stabilize the internal structure of the material and inhibit irreversible phase change.

[0104] Fig.13 The electrochemical impedance diagrams of battery 1 and battery 3 before and after cycling are shown in Figure 2. Fig.13 It can be seen that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material (CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06O2) prepared battery 1, which shows a smaller impedance value after cycling, indicating that the CeO2 coating / Fe doping composite modified performance of the present invention stabilizes the internal structure of the material, is able to inhibit the side reaction between the positive electrode material and the electrolyte, and improves the surface and interface stability of the high-nickel ternary positive electrode material.

[0105] Fig.14 The scanning electron microscope comparison pictures of battery 1 and battery 3 after cycling are shown in Figure 1. Fig.14 It can be seen that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material (CeO2-coated / Fe-doped composite modified LiNi 0.83 Co 0.11 Al 0.06 O2) prepared battery 1, which showed a more complete morphology after cycling, without serious cracks and breakage; while the unmodified high nickel ternary positive electrode material LiNi 0.83 Co 0.11 Al 0.06 Battery 3 prepared with CeO2 showed obvious cracks after cycling; this shows that the CeO2-coated / Fe-doped composite modified high-nickel ternary positive electrode material of the present invention has better structural stability.

[0106] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A cerium-based composite modified high-voltage high-nickel ternary positive electrode material, characterized in that: The cerium-based composite modification is CeO2 coating / metal doping composite modification or Ce / metal co-doping composite modification, and the high-nickel ternary positive electrode material is LiNi x Co y Mn z O2 or LiNi x Co y Al z O2; the cerium-based composite modified high-voltage high-nickel ternary positive electrode material is CeO2 coated / metal-doped composite modified LiNi x Co y Mn z LiNi modified by O2, CeO2 coating / metal doping x Co y Al z O2, Ce / metal co-doped composite modified LiNi x Co y Mn z LiNi modified by O2 or Ce / metal co-doping x Co y Al z O2; wherein x+y+z=1, and x≥0.

6.

2. The high-voltage high-nickel ternary positive electrode material according to claim 1, characterized in that: The CeO2 coating / metal doping composite modification refers to the formation of a CeO2 coating layer on the surface of the high-nickel ternary positive electrode material and the formation of metal doping inside the high-nickel ternary positive electrode material; the doped metal is at least one of iron, magnesium, titanium, niobium, tantalum, tungsten, molybdenum, copper, zinc, gallium, aluminum, indium, germanium, and tin.

3. The high-voltage high-nickel ternary positive electrode material according to claim 1, characterized in that: The Ce / metal co-doping composite modification refers to the formation of co-doping of Ce and other metals inside the high-nickel ternary positive electrode material; the other metals are at least one of samarium, lanthanum, praseodymium, neodymium, europium, gadolinium, sodium, calcium, strontium, and bismuth.

4. The method for preparing a high-voltage high-nickel ternary positive electrode material according to any one of claims 1 to 3, characterized in that: The following steps are involved: (1) mixing a high-nickel ternary positive electrode material precursor, a lithium salt, a cerium salt and a doped metal salt to obtain a mixture; (2) calcining the mixture obtained in step (1) to prepare the cerium-based composite modified high-voltage high-nickel ternary positive electrode material.

5. The preparation method according to claim 4, characterized in that: In step (1), the amount of the high-nickel ternary positive electrode material precursor is 0.1g-10g; the amount of the lithium salt is 0.05g-8.5g; the amount of the cerium salt is 0.0005g-0.05g; and the amount of the doped metal salt is 0.0005g-0.05g.

6. The preparation method according to claim 4, characterized in that: In step (1), the high nickel ternary cathode material precursor is Ni x Co y Mn z (OH)2 and Ni x Co y Al z At least one of (OH)2, wherein x+y+z=1, and x≥0.

6.

7. The preparation method according to claim 4, characterized in that: In step (1), the lithium salt is LiOH or Li2CO3; the cerium salt is at least one of cerium nitrate, cerium acetate, cerium sulfate, cerium chloride, cerium tetrafluoride, cerium oxide or cerium oxalate.

8. The preparation method according to claim 4, characterized in that: When preparing a CeO2 coated / metal doped composite modified high-voltage high-nickel ternary positive electrode material, the doped metal salt in step (1) is at least one of the nitrates, sulfates, oxalates, acetates, and chlorides of iron, magnesium, titanium, niobium, tantalum, tungsten, molybdenum, copper, zinc, gallium, aluminum, indium, germanium, and tin; when preparing a Ce / metal co-doped composite modified high-voltage high-nickel ternary positive electrode material, the doped metal salt in step (1) is at least one of the nitrates, sulfates, oxalates, acetates, and chlorides of samarium, lanthanum, praseodymium, neodymium, europium, gadolinium, sodium, calcium, strontium, and bismuth.

9. The preparation method according to claim 4, characterized in that: In step (2), the calcination temperature is 450°C-750°C, the heating rate is 2°C / min-5°C / min, and the calcination time is 5h-15h.

10. Use of the cerium-based composite modified high-voltage high-nickel ternary positive electrode material according to claim 1 in lithium-ion batteries.

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