A fluorine-doped high-nickel ternary lithium-ion battery positive electrode material and preparation method thereof, and a lithium-ion battery

Abstract

The present invention discloses a fluorine-doped high nickel ternary lithium ion battery positive electrode material and a preparation method thereof, and a lithium ion battery. A preparation method of a fluorine-doped high nickel ternary lithium ion battery positive electrode material comprises the following steps: 0.90 Co 0.05 Mn 0.05 (OH)2 is ground and mixed uniformly with lithium salt and fluoride salt. The mixture is then calcined at 400-600°C for 4-6 hours and then at 650-740°C for 12-16 hours in an oxygen atmosphere. After cooling, grinding, and screening, a fluorine-doped high-nickel ternary lithium-ion battery cathode material is obtained. The cathode material prepared by the method proposed in the present invention has uniform particle size, high crystallinity, high specific capacity, and excellent cycle performance.

Description

Technical field:

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a fluorine-doped high-nickel ternary lithium ion battery positive electrode material and a preparation method thereof. Background technology:

[0002] High nickel layered cathode materials have attracted widespread attention due to their large capacity and low cost. However, in practical applications, these materials are still plagued by problems such as structural phase change and microcracks. Currently, the materials are mainly modified through bulk doping and surface coating to inhibit the generation of lattice distortion and the formation of microcracks during the charge and discharge process, thereby improving the material's cycle stability and high rate discharge performance. 2- Higher electron affinity can provide a stronger attraction to transition metal ions, building more stable metal-F bonds, thereby enhancing structural stability. During continuous cycling, the introduction of an appropriate amount of F ions replaces the metal-O bonds in the material lattice with stronger metal-F bonds, effectively stabilizing the main structure of the material, maintaining the structural integrity of the material, and effectively preventing HF corrosion, inhibiting the increase in the material's polarization, thereby improving the battery's cycling stability.

[0003] CN110862108A discloses a method for improving the electrochemical performance of high-nickel ternary cathode materials through fluorine doping. This method involves doping fluorine into a precursor via a urea hydrothermal method, and then preparing a fluorine-doped high-nickel ternary cathode material in a high-temperature solid-phase reaction. While this method significantly improves the cyclic stability of the material, it involves a number of synthetic conditions, making it suitable for experimental exploration rather than industrial application.

[0004] CN106602015A discloses a method for preparing a fluorine-doped nickel-cobalt-manganese ternary positive electrode material and the material obtained. The method prepares a fluorine-doped nickel-cobalt-manganese ternary positive electrode material by a molten salt method. The material prepared by this method has a relatively uniform average particle size and a certain improvement in cycle stability. However, this method is complex and is not suitable for industrial applications.

[0005] CN113690399A discloses a high-nickel single crystal ternary material with anion and cation co-doping and surface dual coating, and a preparation method thereof. The preparation method comprises: uniformly mixing a high-nickel ternary precursor, a lithium source, a metal fluoride, and a zirconium-containing compound in proportion to obtain a mixture; pre-calcining the obtained mixture at a low temperature and then calcining it at a high temperature in an oxygen atmosphere to obtain an anion and cation co-doped high-nickel single crystal ternary material matrix; crushing and sieving the obtained anion and cation co-doped high-nickel single crystal ternary material matrix to obtain an anion and cation co-doped high-nickel single crystal ternary material matrix with uniformly dispersed single crystal particles; uniformly mixing the obtained anion and cation co-doped high-nickel single crystal ternary material matrix with uniformly dispersed single crystal particles with a boron-containing compound and a tungsten-containing compound, and calcining them under oxygen conditions to obtain an anion and cation co-doped high-nickel single crystal ternary material with surface dual coating. However, this method requires a high sintering temperature for preparing the high-nickel single crystal ternary material, and the calcination process is complex, making it unsuitable for industrial application.

[0006] Therefore, in order to ensure the doping effect, it is imperative to develop a simple doping method for ternary cathode materials. Summary of the invention:

[0007] In order to solve the problems existing in the prior art, the present invention proposes a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material and a preparation method thereof, which improves the electrochemical properties of the material and increases the discharge specific capacity, initial charge and discharge efficiency and cycle stability.

[0008] The present invention also discloses a lithium ion battery, which uses fluorine-doped high-nickel ternary lithium ion battery positive electrode material as the positive electrode material to improve the discharge specific capacity, the initial charge and discharge efficiency and the cycle stability.

[0009] The present invention discloses a method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material, comprising the following steps: 0.90 Co 0.05 Mn 0.05 (OH)2 is ground and mixed evenly with lithium salt and fluoride salt, and calcined at 400-600°C for 4-6 hours and then calcined at 650-740°C for 12-16 hours in an oxygen atmosphere. After cooling, grinding and screening, a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material is obtained.

[0010] In the fluorine-doped high-nickel ternary lithium-ion battery positive electrode material, n(Li):n(Ni+Co+Mn):n(O+F)=1-1.1:1:2.

[0011] The present invention uses fluorine doping modification to dope fluorine ions into the oxygen layer to construct a stable metal-F bond, enhance the stability of the structure, prevent HF corrosion, and inhibit the increase in material polarization during continuous battery cycling, thereby improving the electrochemical performance of the material.

[0012] The present invention provides a simple doping method for ternary cathode materials. The resulting fluorine-doped high-nickel ternary lithium-ion battery cathode material has excellent electrochemical properties. Suitable sintering temperatures can improve the material's crystallinity and reduce the degree of Li / Ni mixing.

[0013] In a preferred embodiment of the present invention, the primary calcination is performed at 500-550° C. for 4-6 h, and the secondary calcination is performed at 650-740° C. for 12-16 h.

[0014] In a preferred embodiment of the present invention, the ternary precursor Ni 0.90 Co 0.05 Mn 0.05 The grinding time of (OH)2, lithium salt and fluoride salt is 7-13min. Preferably, the ternary precursor Ni 0.90 Co 0.05 Mn 0.05 The grinding time of (OH)2 with lithium salt and fluoride salt is 8-12 minutes. Sufficient grinding without excessive grinding that causes particle breakage can improve the degree of material structure order and reduce cation mixing.

[0015] In a preferred embodiment of the present invention, the oxygen flow rate is 60-140 mL / min, preferably 80-120 mL / min. This oxygen flow rate is conducive to ensuring the oxygen content in the positive electrode material, thereby ensuring the electrochemical performance of the positive electrode material.

[0016] The present invention simplifies the preparation method by optimizing the grinding time, oxygen flow rate and sintering temperature, while improving the discharge specific capacity, the initial charge and discharge efficiency and the cycle stability.

[0017] In a preferred embodiment of the present invention, the fluoride salt is ammonium fluoride, and the mass ratio of the ternary precursor to ammonium fluoride is 1.8990:0.0039-0.1551. The material prepared using NH4F as the fluoride salt has a low degree of Li / Ni mixing and excellent cycling performance.

[0018] In a preferred embodiment of the present invention, the ternary precursor is first subjected to a vacuum drying treatment.

[0019] In a preferred embodiment of the present invention, the vacuum drying temperature is 60-100°C.

[0020] In a preferred embodiment of the present invention, the mesh size of the sieve after grinding is 200-400 meshes.

[0021] The invention also discloses a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material prepared by the preparation method.

[0022] Its chemical formula is LiNi0.90 Co 0.05 Mn 0.05 O 2-x F x ; where 0.000≤x≤0.200.

[0023] The present invention also discloses a lithium ion battery, which adopts the fluorine-doped high-nickel ternary lithium ion battery positive electrode material as the positive electrode material.

[0024] Compared with existing technologies, the present invention offers the following advantages: The preparation method proposed in the present invention utilizes fluorine doping to modify the material, where fluorine ions are doped into the oxygen layer to form a stable metal-F bond, enhancing structural stability, preventing HF corrosion, and suppressing the increase in material polarization during continuous battery cycling, thereby improving the material's electrochemical performance. Furthermore, the nickel-cobalt-manganese cathode material prepared by this method exhibits uniform chemical composition, high purity, uniform particle size, low heat treatment temperature, precisely controlled stoichiometric ratio, simple operation, easily controlled conditions, good reproducibility, and stable electrochemical performance. Description of the drawings:

[0025] Figure 1 XRD patterns of comparative examples 1 to 6 of the present invention are shown below:

[0026] Figure 2 XRD patterns of Examples 1 to 11 and Comparative Examples 1, 7, and 8 of the present invention are shown in FIG.

[0027] Figure 3 Cyclic performance curves of Example 1 and Comparative Examples 1, 7, and 8

[0028] Figure 4 SEM image of Example 1

[0029] Figure 5 SEM image of comparative example 1 Specific implementation method:

[0030] The technical solutions of the present invention will be described clearly and completely below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are conventional commercial products in this technical field. The room temperature proposed in the present invention refers to 25°C.

[0031] A fluorine-doped high-nickel ternary lithium-ion battery positive electrode material, the positive electrode material chemical formula is LiNi 0.90 Co 0.05 Mn 0.05 O 2-x F x, 0.000≤x≤0.200.

[0032] A preparation method of a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material comprises the following steps: taking a ternary precursor, LiOH·H2O, and a fluoride salt, grinding and uniformly mixing for 7-13 minutes, wherein n(Li):n(Ni+Co+Mn):n(O+F)=1-1.1:1:2, performing stepwise calcination in a tubular furnace with an oxygen flow rate of 60-140 mL / min, firstly keeping the temperature at 400-600° C. for 4-6 hours, then keeping the temperature at 650-740° C. for 12-16 hours, cooling to room temperature with the furnace, grinding and screening the sintered product, and obtaining the fluorine-doped high-nickel ternary lithium-ion battery positive electrode material.

[0033] In the present invention, the fluoride salt is preferably ammonium fluoride, with a purity of 99%. The source of ammonium fluoride is not particularly limited, and any commercially available product or homemade product known to those skilled in the art can be used. The mass ratio of the ternary precursor to ammonium fluoride is 1.8990:0.0039-0.1551.

[0034] Comparative Example 1

[0035] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material. The test results of button batteries made with this material are shown in Table 2.

[0036] Comparative Example 2

[0037] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 5min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material.

[0038] Comparative Example 3

[0039] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 15min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material.

[0040] Comparative Example 4

[0041] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then placed in a tube furnace with an oxygen flow rate of 50mL / min for staged sintering, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material.

[0042] Comparative Example 5

[0043] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 150mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material.

[0044] Comparative Example 6

[0045] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05(OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then placed in a tube furnace with an oxygen flow rate of 100mL / min for staged sintering, first at 500℃ for 5h, then at 750℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material. The test results of button batteries made with this material are shown in Table 2.

[0046] Example 1

[0047] Weigh 3.7975g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 1.8263g LiOH·H2O and 0.0078g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.995 F 0.005 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0048] Example 2

[0049] Weigh 1.8984g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9130g LiOH·H2O and 0.0078g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.99 F 0.01 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0050] Example 3

[0051] Weigh 1.8973g Ni0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9125g LiOH·H2O and 0.0232g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.97 F 0.03 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0052] Example 4

[0053] Weigh 1.8961g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9119g LiOH·H2O and 0.0387g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.95 F 0.05 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0054] Example 5

[0055] Weigh 1.8932g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9105g LiOH·H2O and 0.0773g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.9 F 0.1Materials. The test results of button batteries made with these materials are shown in Table 2.

[0056] Example 6

[0057] Weigh 1.8903g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9091g LiOH·H2O and 0.1158g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.85 F 0.15 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0058] Example 7

[0059] Weigh 1.8874g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9077g LiOH·H2O and 0.1542g NH4F for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then placed in a tube furnace with an oxygen flow rate of 100mL / min for staged sintering, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.8 F 0.2 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0060] Comparative Example 7

[0061] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90Co 0.05 Mn 0.05 O2 material. Take 1g LiNi 0.90 Co 0.05 Mn 0.05 O2 powder was evenly mixed with 0.0194g NH4F, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2, and calcined in an oxygen tube furnace at 400℃ for 5h, and then cooled to room temperature. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.95 F 0.05 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0062] Comparative Example 8

[0063] Weigh 1.8990g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9133g LiOH·H2O for 10min and mixed evenly, wherein Li:(Ni+Co+Mn)=1.05:1 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 750℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O2 material. Take 1g LiNi 0.90 Co 0.05 Mn 0.05 O2 powder was evenly mixed with 0.0194g NH4F, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2, and calcined in an oxygen tube furnace at 400℃ for 5h, and then cooled to room temperature. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.95 F 0.05 Materials. The test results of button batteries made with these materials are shown in Table 2.

[0064] Example 8

[0065] Weigh 3.7975g Ni 0.90 Co 0.05 Mn 0.05(OH)2 powder was ground with 1.8263g LiOH·H2O and 0.0053g LiF for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.995 F 0.005 Material.

[0066] Example 9

[0067] Weigh 1.8984g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9130g LiOH·H2O and 0.0053g LiF for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then sintered in a tube furnace with an oxygen flow rate of 100mL / min, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.995 F 0.01 Material.

[0068] Example 10

[0069] Weigh 1.8973g Ni 0.90 Co 0.05 Mn 0.05 (OH)2 powder was ground with 0.9125g LiOH·H2O and 0.016g LiF for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then placed in a tube furnace with an oxygen flow rate of 100mL / min and sintered in stages, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.995 F 0.03 Material.

[0070] Example 11

[0071] Weigh 1.8961g Ni 0.90 Co0.05 Mn 0.05 (OH)2 powder was ground with 0.9119g LiOH·H2O and 0.016g LiF for 10min and mixed evenly, wherein Li:(Ni+Co+Mn):(O+F)=1.05:1:2 (molar ratio), and then placed in a tube furnace with an oxygen flow rate of 100mL / min and sintered in stages, first at 500℃ for 5h, then at 700℃ for 14h, and finally cooled to room temperature with the furnace. After grinding and screening, LiNi 0.90 Co 0.05 Mn 0.05 O 1.995 F 0.05 Material.

[0072] Table 1 Parameters of Examples and Comparative Examples

[0073]

[0074]

[0075] The positive electrode materials prepared in Examples 1 to 7 and Comparative Examples 1, 2, and 7-8 were made into 2032-type button-type simulated batteries to test their electrochemical performance. The specific steps are as follows: (1) The positive electrode materials, conductive acetylene black, and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 80:10:10, and PVDF was first dissolved in an appropriate amount of N-methylpyrrolidone (NMP). Then, the mixed positive electrode materials and acetylene black powder were added to NMP and stirred to form a slurry; (2) The slurry was evenly coated on an aluminum foil substrate, and the wet electrode was placed in a vacuum drying oven, dried at 110°C for 12 hours, and cut into positive electrode sheets; (3) In a dry vacuum glove box, a simulated battery was assembled. The above-mentioned self-made electrode sheet was used as the positive electrode, the metal lithium sheet was used as the negative electrode, the Celgard2500 membrane was used as the separator, and 1 mol / L LiPF6 was used. The electrochemical properties of the electrolyte were tested using a solution of ethylene carbonate (EC), ethyl methyl carbonate (EMC) and dimethyl carbonate (DMC) (volume ratio 1:1:1).

[0076] The positive electrode materials of Example 1 and Comparative Examples 1, 7, and 8 were used to make button batteries to test their electrochemical properties, as shown in Table 2.

[0077] Table 2 Electrochemical performance of positive electrode materials of Example 1 and Comparative Examples 1, 7, and 8 at 2.7-4.3V

[0078]

[0079] From Table 2, it can be seen that after 90 cycles at a 1C rate, the discharge capacity of the material in Example 1 is still 179.5 mAh g -1The capacity retention rate reached 97.6%, and the cycle stability was better than that of Comparative Example 1 and Comparative Examples 7-8. Compared with Comparative Example 1, the initial charge and discharge efficiency of Example 1 and Comparative Examples 7-8 were improved, which was related to the introduction of F ions, which suppressed the side reactions between the electrolyte and the material surface.

[0080] Example 1 uses two calcinations, while Comparative Examples 7-8 use three calcinations. The preparation method in Example 1 is simple, but the electrochemical properties of the materials are better than those of Comparative Examples 7-8.

[0081] Figure 1 The XRD spectra of the positive electrode materials synthesized after different grinding times, different oxygen flow rates and different sintering temperatures. It can be seen that the peak shapes and peak positions of Comparative Examples 1 and Comparative Examples 2 to 6 are basically the same, and strong characteristic peaks can be observed, and there are no impurity peaks, indicating that different grinding times have no effect on the α-NaFeO2 structure of the ultra-high nickel NCM positive electrode material. At the same time, the (006) / (102) and (018) / (110) peaks of the spectrum are significantly split, and the unit cell parameter c / a of Comparative Example 1 is the largest, indicating that its layered structure is relatively more complete; I (003) / I (104) It is also relatively larger, indicating that the degree of Li / Ni mixing in the material is low. Therefore, sufficient grinding (grinding time 10min) and avoiding excessive grinding (grinding time 15min) that causes particle breakage are beneficial to improving the degree of order in the material structure and reducing cation mixing. Appropriate sintering temperature (400-600℃ for 4-6h, 650℃-740℃ for 12-16h) and oxygen flow rate (60-140mL / min) are beneficial to improving the crystallinity of the material and reducing the degree of Li / Ni mixing in the material. Figure 2 It can be seen that the positive electrode materials before and after fluorine doping all show the typical structural characteristics of LiNiO2 positive electrode materials, and their diffraction peaks are characteristic peaks of α-NaFeO2 layered structure, belonging to the hexagonal system and R-3m space group. The two pairs of diffraction peaks (006) / (012) and (018) / (110) of the positive electrode materials of Examples 1 to 7 are obviously split, forming a better layered structure. In addition, there is no significant change in the diffraction peaks of the materials before and after doping, and there is no impurity peak. Compared with Examples 8 to 11, the I of Examples 1 to 4 (003) / I (104) It is relatively larger, indicating that the degree of Li / Ni mixing of the material prepared with NH4F as fluoride salt is lower. Figure 3 It shows that Example 1 exhibits better cycle performance than Comparative Example 1. During the continuous cycle process, the introduction of an appropriate amount of F ions replaces the transition metal-O bonds in the material lattice with stronger transition metal-F bonds, thereby effectively stabilizing the main structure of the material, maintaining the structural integrity of the material, and effectively preventing HF corrosion, inhibiting the increase in the material polarization, thereby improving the cycle stability of the battery. Figure 4 and Figure 5 It can be seen that the positive electrode materials of Example 1 and Comparative Example 1 are both composed of secondary particles with a particle size of about 1 to 3 μm formed by agglomeration of primary particles.

[0082] The description of the above embodiments is only used to help understand the technical solution and core ideas of the present invention. It should be pointed out that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principles of the present invention. These improvements and modifications also fall within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material, characterized in that: It consists of the following steps: the ternary precursor Ni 0.90 Co 0.05 Mn 0.05 (OH)2 is ground and mixed evenly with lithium salt and fluoride salt, and calcined at 400-600°C for 4-6 hours and then calcined at 650-740°C for 12-16 hours in an oxygen atmosphere. After cooling, grinding and screening, a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material is obtained. In the fluorine-doped high-nickel ternary lithium-ion battery cathode material, n(Li):n(Ni+Co+Mn):n(O+F)=1-1.1:1:2; The fluoride salt is ammonium fluoride, and the mass ratio of the ternary precursor to ammonium fluoride is 1.8990:0.0039-0.1551; Ternary precursor Ni 0.90 Co 0.05 Mn 0.05 The grinding time of (OH)2 with lithium salt and fluoride salt is 7-13min; The oxygen flow rate is 60-140 mL / min.

2. The method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to claim 1, characterized in that: The mixture was calcined at 500-550℃ for 4-6h and then calcined at 650-740℃ for 12-16h.

3. The method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to claim 1, characterized in that: Ternary precursor Ni 0.90 Co 0.05 Mn 0.05 The grinding time of (OH)2, lithium salt and fluoride salt is 8-12 minutes.

4. The method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to claim 1, characterized in that: The oxygen flow rate is 80-120 mL / min.

5. The method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to any one of claims 1 to 4, characterized in that: The ternary precursor is first vacuum dried.

6. The method for preparing a fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to claim 5, characterized in that: The vacuum drying temperature is 60-100°C.

7. A fluorine-doped high-nickel ternary lithium-ion battery positive electrode material prepared according to the preparation method according to any one of claims 1 to 6.

8. A lithium-ion battery, using the fluorine-doped high-nickel ternary lithium-ion battery positive electrode material according to claim 7 as a positive electrode material.

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