A lithium iron fluorosulfate positive electrode material and its preparation method and application

Abstract

The present invention discloses a lithium ferrous fluorosulfate cathode material, its preparation method, and application. The cathode material comprises lithium ferrous fluorosulfate and carbon nanotubes coated on the lithium ferrous fluorosulfate, and the cathode material is a secondary particle having a particle size of 2 to 10 μm; the secondary particles are composed of nanoscale primary particles; and the particle size of the primary particles is 20 to 200 nm. The preparation method comprises the following steps: 1) grinding lithium fluoride to a particle size of less than 10 μm; 2) ball-milling the ground lithium fluoride, ferrous sulfate, and carbon nanotubes to obtain a mixture; and 3) calcining the mixture to obtain the lithium ferrous fluorosulfate cathode material. The cathode material has better electronic and ionic conductivity, higher specific capacity, and better cycle performance, as well as excellent high-temperature and low-temperature performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium batteries, and in particular to a lithium iron fluorosulfate positive electrode material and a preparation method and application thereof. Background Art

[0002] With the rapid development of the global economy, the demand for energy is growing worldwide. The global energy shortage has become a hot topic, and the search for clean, renewable energy has become a pressing task. Lithium-ion batteries, as a green, renewable resource, offer advantages such as large capacity and high energy density, making them considered the most promising secondary battery.

[0003] Among the positive electrode materials for lithium-ion batteries, polyanion-type positive electrode materials for lithium-ion batteries have an open three-dimensional framework structure. The volume change of the material is small during the process of lithium ion extraction / insertion, so it has good cycle stability. Lithium ferric fluorosulfate LiFeSO4F is a new type of polyanion-type positive electrode material for lithium-ion batteries. Compared with traditional LiFePO4 (LFP), lithium ferric fluorosulfate has two major advantages as a positive electrode material for lithium-ion batteries: (1) the material has a higher operating voltage (3.6V); (2) the material has a higher ionic conductivity. Lithium ferric fluorosulfate has two crystal forms, tavorite monoclinic and triplite triclinic. The monoclinic crystal has a lower operating voltage of 3.6V, but it has higher ionic conductivity and a higher discharge specific capacity. The triclinic crystal has a higher operating voltage of 3.9V, which is higher. It has a higher energy density, but a lower discharge specific capacity.

[0004] For lithium iron fluorosulfate cathode materials, the most commonly used synthesis method is the solvothermal method. U.S. Patent US 9,216,912B2, Korean Patent KR20160112340A, and Chinese Patent CN105668643A all mention the solvothermal preparation method of LiFeSO4F material with a tavorite monoclinic structure. However, this method has complex procedures and high costs, and the prepared material has poor electronic conductivity, resulting in the material's specific capacity and cycle performance being unable to be further improved, which seriously restricts the application of LiFeSO4F as an electrode material.

[0005] How to further improve the electronic and ionic conductivity of LiFeSO4F so that it has higher specific capacity and better cycle performance while keeping production costs low is a difficulty in the LiFeSO4F field. Summary of the Invention

[0006] In view of the shortcomings and deficiencies of the prior art, the present invention provides an improved lithium iron fluorosulfate positive electrode material, which has better electronic conductivity and ionic conductivity, higher specific capacity and better cycle performance, and excellent high-temperature performance and low-temperature performance.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0008] A lithium ferrous fluorosulfate positive electrode material comprises lithium ferrous fluorosulfate and carbon nanotubes coated on the lithium ferrous fluorosulfate, wherein the positive electrode material is a secondary particle having a particle size of 2 to 10 μm; the secondary particles are composed of nanoscale primary particles; and the particle size of the primary particles is 20 to 200 nm.

[0009] In the prior art, the specific capacity and cycle performance of lithium iron fluorosulfate cathode materials are not enough, and their preparation methods, such as solvent thermal methods, are usually complex and costly. The present invention significantly improves the electronic conductivity and ionic conductivity of lithium iron fluorosulfate by coating carbon nanotubes on lithium iron fluorosulfate and controlling the primary particle size and secondary particle size of the cathode material, so that the cathode material has a higher specific capacity and more excellent cycle performance, and both high temperature performance and low temperature performance are excellent. After the surface is coated with carbon nanotubes, the electronic conductivity of the material is improved, and lithium ion channels are also constructed, further improving the ionic conductivity of the material, thereby achieving the improvement of the ionic conductivity and electronic conductivity of the lithium iron fluorosulfate material. When used in lithium ion batteries, the side reactions of the electrolyte can be blocked, ensuring the cycle stability of the cathode material when used in lithium ion batteries.

[0010] In some embodiments, the mass of the carbon nanotubes accounts for 2% to 12% of the mass of the positive electrode material.

[0011] In some embodiments, the carbon nanotubes are selected from single-walled carbon nanotubes or multi-walled carbon nanotubes.

[0012] In some embodiments, the carbon nanotubes have an outer diameter of 10 to 90 nm, an inner diameter of 1 to 5 nm, an interlayer distance of 0.3 to 0.4 nm, and a length of 10 to 100 μm.

[0013] In some embodiments, the chemical formula of the lithium iron fluorosulfate is Li x FeSO4F x , wherein x is 1.02 to 1.10, and preferably x is 1.02 to 1.06.

[0014] In some embodiments, the lithium ferrous fluorosulfate includes a tavorite monoclinic crystal and a triplite triclinic crystal, and a molar ratio of the monoclinic crystal to the triclinic crystal is 25:1 to 65:1.

[0015] In some embodiments, the positive electrode material is prepared by a preparation method comprising the following steps: 1) grinding lithium fluoride to a particle size of less than 10 μm; 2) ball-milling the ground lithium fluoride, ferrous sulfate, and carbon nanotubes to obtain a mixture; 3) calcining the mixture to obtain the lithium ferrous fluorosulfate positive electrode material.

[0016] The present invention grinds lithium fluoride to a specific small particle size, then ball-mills it with other precursors such as ferrous sulfate and modifier carbon nanotubes, mixes them thoroughly, and then performs calcination and solid-phase reaction. In this way, a positive electrode material with controllable particle size can be obtained, and the charge-discharge performance and cycle performance of the positive electrode material are improved.

[0017] In some embodiments, the cathode material has a discharge capacity of 120 mAh at 25°C and 0.1C. · g -1 The above, the capacity retention rate after 200 cycles at 25 ℃ and 1C is more than 75%, and the discharge capacity at 0 ℃ and 0.1C is 120mAh · g -1 The cathode material of the present invention has better electronic conductivity and ionic conductivity, higher specific capacity and better cycle performance, and excellent low-temperature performance.

[0018] In some embodiments, the cathode material has a discharge capacity of 135 mAh at 25°C and 0.1C. · g -1 The above, the capacity retention rate after 200 cycles at 25 ℃ and 1C is more than 95%, and the discharge capacity at 0 ℃ and 0.1C is 135mAh · g -1 The cathode material of the present invention has better electronic conductivity and ionic conductivity, higher specific capacity and better cycle performance, and excellent low-temperature performance.

[0019] The present invention also provides a method for preparing the aforementioned lithium ferrous fluorosulfate positive electrode material, the preparation method comprising the following steps: 1) grinding lithium fluoride to a particle size of less than 10 μm; 2) ball-milling the ground lithium fluoride, ferrous sulfate, and carbon nanotubes to obtain a mixture; and 3) calcining the mixture to obtain the lithium ferrous fluorosulfate positive electrode material.

[0020] In some embodiments, in step 1), lithium fluoride is ground to a particle size of 5-10 μm.

[0021] In some embodiments, in step 1), lithium fluoride is ground by ball milling.

[0022] Preferably, the rotation speed of the ball mill is 300-500 r / min.

[0023] Preferably, the ball milling time is 12 to 24 hours.

[0024] In some embodiments, the ferrous sulfate is ferrous sulfate monohydrate.

[0025] In some embodiments, the molar ratio of lithium fluoride to ferrous sulfate after grinding is 1.05-1.15:1.

[0026] In some embodiments, in step 2), the ball milling is performed in a planetary ball mill.

[0027] In some embodiments, in step 2), the rotation speed of the ball mill is 300 to 500 r / min.

[0028] In some embodiments, in step 2), the ball milling time is 15 to 60 minutes.

[0029] In some embodiments, the calcination temperature is 290-340° C., preferably 290-310° C. When the calcination temperature is too high, the monoclinic crystal of lithium ferrous fluorosulfate will transform into a triclinic crystal, which will reduce the discharge capacity of the positive electrode material.

[0030] In some embodiments, the calcination is performed in an inert gas atmosphere; and the calcination time is 20 to 28 hours.

[0031] In some embodiments, the preparation method further comprises a step of screening after calcining.

[0032] In some embodiments, the mesh size of the sieve used for sieving is 200-600 meshes, preferably 300-500 meshes, and more preferably 400 meshes.

[0033] The present invention also provides a use of the aforementioned lithium iron fluorosulfate positive electrode material in a lithium ion battery.

[0034] The present invention also provides a lithium-ion battery comprising a positive electrode material, a negative electrode material and a separator, wherein the positive electrode material comprises the aforementioned lithium ferrous sulfate positive electrode material.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The positive electrode material of the present invention is a polyanion positive electrode material. The surface of the lithium ferrous fluorosulfate material is coated with carbon nanotubes, and the carbon nanotubes are evenly distributed and interspersed on the lithium ferrous fluorosulfate. After the surface is coated with carbon nanotubes, the ionic conductivity and electronic conductivity of the lithium ferrous fluorosulfate material can be further improved. When used in a lithium ion battery, the side reaction of the electrolyte can be blocked, thereby ensuring the cycle stability of the positive electrode material when used in a lithium ion battery. The cycle stability of the positive electrode material of the present invention is greatly improved compared with the prior art.

[0037] The lithium-ion battery positive electrode material of the present invention has very excellent specific capacity and cycle performance, as well as excellent low-temperature performance. In addition, the preparation method thereof is simple in process, low in cost, and good in repeatability. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is the SEM image of the positive electrode material obtained in Example 1.

[0039] Figure 2 This is the SEM image of the positive electrode material obtained in Comparative Example 1.

[0040] Figure 3 This is the XRD pattern of the positive electrode material obtained in Example 1.

[0041] Figure 4 This is the XRD pattern of the positive electrode material obtained in Comparative Example 1.

[0042] Figure 5 The first charge and discharge curves of the lithium-ion battery positive electrode materials assembled in the corresponding embodiments and comparative examples at 25°C and 0.1C are shown.

[0043] Figure 6 The graph is a cycle test curve of the lithium-ion battery positive electrode materials assembled in the corresponding embodiments and comparative examples at 25°C and 1C.

[0044] Figure 7 This is a cycle test curve of the lithium-ion battery positive electrode material assembled in Example 1 at 25°C, 1C and 5C.

[0045] Figure 8 This is a graph showing the first charge and discharge curves of the lithium-ion battery positive electrode material assembled in Example 1 at 0.1C at different temperatures, where normal temperature is room temperature (25°C).

[0046] Figure 9 This is a graph showing the first charge and discharge curves of the lithium-ion battery positive electrode material (LFSF) assembled in Example 1 and the commercial lithium iron phosphate (LFP) positive electrode material at 0°C and 0.1C.

[0047] Figure 101C cycle test curve of the lithium-ion battery positive electrode material (LFSF) assembled in Example 1 and the commercial lithium iron phosphate (LFP) positive electrode material at 0°C. DETAILED DESCRIPTION

[0048] The technical solutions of the present invention are described in detail below in conjunction with specific embodiments so that those skilled in the art can better understand and implement the technical solutions of the present invention, but the present invention is not limited to the scope of the examples.

[0049] Example 1

[0050] This embodiment provides a lithium iron fluorosulfate cathode material, the preparation method of which is as follows:

[0051] 1) Weigh a certain amount of lithium fluoride and pour it into a ball mill jar. Cover the jar tightly, seal the jar, and clamp it on a planetary ball mill at a speed of 400 r / min for 16 hours to obtain lithium fluoride with a particle size of 5 μm, which is set aside.

[0052] 2) Weigh ferrous sulfate monohydrate and the ball-milled lithium fluoride to a molar ratio of 1:1.1. Add multi-walled carbon nanotubes (20 nm outer diameter, 2 nm inner diameter, 0.3 nm interlayer spacing, 25 μm length) to form a mixture containing 5% by mass of the multi-walled carbon nanotubes. Pour the mixture into a ball mill, mix briefly, securely cover the mill, seal the mill, and place it in a planetary ball mill at 450 rpm for 30 minutes.

[0053] 3) The ball-milled mixture was placed in a tube furnace for calcination at a heating rate of 5° C. / min, a calcination temperature of 300° C., an argon atmosphere, and a calcination time of 24 hours.

[0054] 4) After calcination, it is naturally cooled to room temperature and then passed through a 400-mesh sieve to obtain the positive electrode material, which has the general formula of Li 1.019 FeSO4F 1.019 . Figure 1 The SEM image of the obtained positive electrode material shows that the secondary particles are 5 μm in size and are composed of nano-sized primary particles. The primary particles have a particle size of 60 nm. Figure 3 The XRD pattern of the obtained positive electrode material is shown in FIG. In the material, the lithium iron fluorosulfate includes a monoclinic tavorite crystal and a triclinic triplite crystal, and the molar ratio of the monoclinic crystal to the triclinic crystal is 65:1.

[0055] Example 2

[0056] This embodiment provides a lithium iron fluorosulfate cathode material, the preparation method of which is basically the same as that of Example 1, except that the calcination temperature is changed to 320° C. The general formula and crystal molar ratio of the obtained cathode material are shown in Table 1 below.

[0057] Example 3

[0058] This example provides a lithium iron fluorosulfate cathode material, the preparation method of which is substantially the same as in Example 1, except that the multi-walled carbon nanotubes are replaced with single-walled carbon nanotubes (outer diameter 40 nm, inner diameter 4 nm, interlayer spacing 0.3 nm, and length 40 μm). The general formula and crystal form molar ratio of the resulting cathode material are shown in Table 1 below.

[0059] Example 4

[0060] This embodiment provides a lithium iron fluorosulfate cathode material, the preparation method of which is basically the same as that of Example 1, except that the mass fraction of multi-walled carbon nanotubes is replaced with 10%. The general formula and crystal molar ratio of the obtained cathode material are shown in Table 1 below.

[0061] Example 5

[0062] This embodiment provides a lithium iron fluorosulfate cathode material, the preparation method of which is substantially the same as that of Example 1, except that the particle size of the ground lithium fluoride is adjusted to 10 μm. The general formula and crystal molar ratio of the obtained cathode material are shown in Table 1 below.

[0063] Example 6

[0064] This example provides a lithium ferrous fluorosulfate cathode material. Its preparation method is essentially the same as in Example 1, except that the molar ratio of ferrous sulfate monohydrate to ball-milled lithium fluoride is adjusted to 1:1.05. The general formula and crystal form molar ratio of the resulting cathode material are shown in Table 1 below.

[0065] Comparative Example 1

[0066] This comparative example provides a lithium iron fluorosulfate cathode material, and its preparation method is basically the same as that of Example 1, except that multi-walled carbon nanotubes are not added to the mixture. Figure 2 is the SEM image of the obtained positive electrode material. Figure 4 The XRD pattern of the resulting positive electrode material is shown in Figure 2. Comparison with the SEM image of Example 1 reveals that the positive electrode material of Example 1 has a uniform carbon coating of multi-walled carbon nanotubes. Comparison with the XRD pattern of Example 1 reveals that the carbon coating of the multi-walled carbon nanotubes of Example 1 does not alter the actual material composition of the lithium ferrous fluorosulfate.

[0067] Comparative Example 2

[0068] This comparative example provides a lithium iron fluorosulfate cathode material, prepared using a method similar to that of Example 1, except that step 1) (i.e., the lithium fluoride was not pre-ball-milled) was omitted. The resulting cathode material was found to readily agglomerate when dispersed in N,N'-methylpyrrolidone, resulting in reduced specific capacity and cycling performance of the resulting button cell.

[0069] Comparative Example 3

[0070] This comparative example provides a lithium ferrous fluorosulfate cathode material, prepared using a method similar to that of Example 1, except that the ball milling in step 2) was replaced with manual grinding. Results revealed that the ferrous sulfate monohydrate and lithium fluoride were not uniformly mixed, resulting in a significant decrease in the specific capacity of the assembled button cell.

[0071] Comparative Example 4

[0072] This comparative example provides a lithium ferrous fluorosulfate cathode material, prepared by a method substantially similar to that of Example 1, except that the calcination temperature was changed to 350°C. It was found that a relatively large amount of triclinic lithium ferrous fluorosulfate was generated during the calcination process, resulting in a decrease in the specific discharge capacity of the assembled button cell.

[0073] Comparative Example 5

[0074] This comparative example provides a lithium ferrous fluorosulfate cathode material, prepared by a method substantially similar to that of Example 1, except that the molar ratio of ferrous sulfate monohydrate to ball-milled lithium fluoride was adjusted to 1:1. It was found that due to the loss of lithium fluoride during the ball milling and calcination processes, the solid-phase reaction was incomplete under this loading condition, ultimately resulting in a lower specific capacity and poor cycling performance of the assembled button cell.

[0075] Comparative Example 6

[0076] This comparative example provides a lithium iron fluorosulfate positive electrode material, and its preparation method is basically the same as that of Example 1, except that the multi-walled carbon nanotubes are replaced by SP conductive carbon black.

[0077] Comparative Example 7

[0078] This comparative example provides a lithium iron fluorosulfate positive electrode material, and its preparation method is basically the same as that of Example 1, except that the multi-walled carbon nanotubes are replaced by KB Ketjen Black.

[0079] Performance test: At the test temperature, weigh 0.27g of the positive electrode material of each embodiment and comparative example, add 0.015g of conductive carbon black and 0.015g of polyvinylidene fluoride, and then evenly disperse in N,N'-methylpyrrolidone. After mixing evenly, coat it on aluminum foil to make an electrode sheet. In an argon atmosphere glove box, use a metal lithium sheet as the counter electrode, 16μm polyethylene as the diaphragm, and 1MLiPF6EMC:FEC (3:1V) + 0.05M LiDFOB as the electrolyte to assemble into a button cell. The battery was charged and discharged within the voltage range of 2.5-4.5V. The results are shown in Table 1 below. Composition chemical formula Li x FeSO4F x Zhongx's testing method is as follows: Using ICP inductively coupled plasma (ICP), high-temperature plasma ionizes atoms in the final product. Li and Fe content is quantitatively analyzed by measuring the specific spectral lines emitted or absorbed by these ions. After the final product is ionized in the plasma, the atoms or ions emit a characteristic spectrum. These characteristic spectral lines are used for qualitative and quantitative analysis of Li and Fe.

[0080] Table 1

[0081]

[0082] A comparison of Example 1 and Comparative Example 1 shows that the button cell assembled with pure lithium ferrous fluorosulfate cathode material (uncoated with carbon nanotubes) exhibits poor electrochemical performance, including extremely low specific capacity and poor cycling performance. However, after coating with carbon nanotubes, the specific capacity and cycling performance of Example 1 were significantly improved.

[0083] A comparison between Example 1 and Comparative Example 2 shows that if lithium fluoride is not ball-milled in advance, the electrochemical performance of the final button battery assembled from the product decreases and the cycle performance deteriorates. However, after the lithium fluoride is ball-milled in advance in Example 1, both the specific capacity and cycle performance are significantly improved.

[0084] From the comparison between Example 1 and Comparative Example 3, it can be seen that if the ball milling is replaced by hand milling, the cycle performance of the button battery assembled from the final product is extremely poor. However, after ball milling, the cycle performance of Example 1 is significantly improved.

[0085] A comparison between Example 1 and Comparative Example 4 shows that if the calcination temperature is too high, a large amount of triplite phase will be generated, resulting in a decrease in the specific capacity and cycle performance of the button battery assembled from the final product. Using the calcination temperature of the present invention, a very small amount of triplite phase is generated, significantly improving the specific capacity and cycle performance.

[0086] From the comparison between Example 1 and Comparative Example 6, it can be seen that if the carbon nanotubes are replaced with conductive carbon black, the specific capacity and rate performance of the button battery assembled from the final product are extremely poor. However, after Example 1 is coated with carbon nanotubes, the specific capacity and rate performance are significantly improved.

[0087] From the comparison between Example 1 and Comparative Example 7, it can be seen that if the carbon nanotubes are replaced with Ketjen Black, the specific capacity and cycle performance of the button battery assembled from the final product are reduced. However, after Example 1 is coated with carbon nanotubes, the specific capacity and cycle performance are significantly improved.

[0088] At 0°C, the electrical properties of the cathode material of Example 1 and commercial lithium iron phosphate (LFP) were tested using the above method. As shown in Table 2 below, it can be seen that the electrochemical performance of the material of Example 1 at low temperature is significantly better than that of traditional LFP.

[0089] Table 2

[0090]

[0091] The above embodiments are intended only to illustrate the technical concepts and features of the present invention. Their purpose is to enable those skilled in the art to understand the contents of the present invention and implement them accordingly. They are not intended to limit the scope of protection of the present invention. Any equivalent changes or modifications made in accordance with the spirit of the present invention are intended to be covered by the scope of protection of the present invention.

[0092] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

Claims

1. A lithium iron fluorosulfate cathode material, characterized in that: The positive electrode material comprises lithium ferrous sulfate and carbon nanotubes coated on the lithium ferrous sulfate, and the positive electrode material is a secondary particle, the particle size of the secondary particle is 2 to 10 μm; the secondary particle is composed of nanometer-sized primary particles; the particle size of the primary particle is 20 to 200 nm; the general chemical formula of the lithium ferrous sulfate is Li x FeSO4F x , wherein x is 1.02 to 1.10; the lithium ferrous fluorosulfate includes a tavorite monoclinic crystal and a triplite triclinic crystal, and the molar ratio of the monoclinic crystal to the triclinic crystal is 25:1 to 65:

1.

2. The lithium iron fluorosulfate cathode material according to claim 1, characterized in that: The mass of the carbon nanotubes accounts for 2% to 12% of the mass of the positive electrode material; and / or the carbon nanotubes are selected from single-walled carbon nanotubes or multi-walled carbon nanotubes.

3. The lithium iron fluorosulfate cathode material according to claim 1, wherein: The carbon nanotubes have an outer diameter of 10 to 90 nm, an inner diameter of 1 to 5 nm, an interlayer distance of 0.3 to 0.4 nm, and a length of 10 to 100 μm.

4. The lithium iron fluorosulfate cathode material according to claim 1, wherein: The positive electrode material is prepared by a preparation method comprising the following steps: 1) grinding lithium fluoride to a particle size of less than 10 μm; 2) ball-milling the ground lithium fluoride, ferrous sulfate, and carbon nanotubes to obtain a mixture; and 3) calcining the mixture to obtain the lithium ferrous fluorosulfate positive electrode material.

5. The lithium iron fluorosulfate cathode material according to claim 1, wherein: The discharge specific capacity of the positive electrode material at 25°C and 0.1C is 120 mAh · g -1 The above, the capacity retention rate after 200 cycles at 25 ℃ and 1C is more than 75%, and the discharge capacity at 0 ℃ and 0.1C is 120mAh · g -1 above.

6. A method for preparing the lithium iron fluorosulfate cathode material according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: 1) grinding lithium fluoride to a particle size of less than 10 μm; 2) ball-milling the ground lithium fluoride, ferrous sulfate, and carbon nanotubes to obtain a mixture; and 3) calcining the mixture to obtain the lithium ferrous fluorosulfate positive electrode material.

7. The method for preparing the lithium ferrous fluorosulfate cathode material according to claim 6, wherein: In step 1), the lithium fluoride is ground to a particle size of 5-10 μm; and / or, in step 1), the lithium fluoride is ground by ball milling.

8. The method for preparing the lithium ferrous fluorosulfate cathode material according to claim 7, wherein: The ball milling speed is 300-500 r / min; and / or the ball milling time is 12-24 h.

9. The method for preparing the lithium ferrous fluorosulfate cathode material according to claim 6, wherein: The ferrous sulfate is ferrous sulfate monohydrate; and / or the molar ratio of the ground lithium fluoride to the ferrous sulfate is 1.05-1.15:

1.

10. The method for preparing the lithium iron fluorosulfate cathode material according to claim 6, wherein: In step 2), the ball milling is carried out in a planetary ball mill; and / or, in step 2), the rotation speed of the ball milling is 300 to 500 r / min; and / or, in step 2), the ball milling time is 15 to 60 min.

11. The method for preparing the lithium ferrous fluorosulfate cathode material according to claim 6, wherein: The calcination temperature is 290-340° C.; and / or the calcination is carried out in an inert gas atmosphere; the calcination time is 20-28 hours; and / or the preparation method further comprises a screening step after the calcination.

12. The method for preparing the lithium ferrous fluorosulfate cathode material according to claim 6, wherein: The calcination temperature is 290-310°C.

13. Use of the lithium iron fluorosulfate cathode material according to any one of claims 1 to 5 in lithium ion batteries.

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