High-ion-conductivity fluoride positive electrode material, preparation method and application of high-ion-conductivity fluoride positive electrode material

Abstract

The invention discloses a high-ion-conductivity fluoride positive electrode material, a preparation method and an application thereof, the chemical composition general formula of the fluoride positive electrode material is LixFeF3 + x, wherein 0.5 lt; xlt; and 1.5. The invention belongs to the field of all-solid-state lithium ion battery positive electrode materials, and particularly relates to a method for synthesizing a high-ion-conductivity lithium-iron-fluorine-based positive electrode material through a high-energy ball milling method and application of the high-ion-conductivity lithium-iron-fluorine-based positive electrode material in an all-solid-state lithium ion battery, and the high-ion-conductivity lithium-iron-fluorine-based positive electrode material is synthesized from LiF and FeF3 through the high-energy ball milling method in one step; the positive electrode material has relatively high structural symmetry, relatively high lithium ion conductivity and stable charge-discharge capacity, can be used as the positive electrode material, and can be applied to an all-solid-state lithium ion battery after being compounded with a small amount of conductive carbon, and an additional supporting electrolyte does not need to be added into a positive electrode.

Description

Technical Field

[0001] The present application relates to a high ionic conductivity fluoride cathode material, a preparation method thereof, and an application thereof, belonging to the field of all-solid-state lithium-ion batteries. Background Art

[0002] With the proposal of China's "dual carbon" goal, the importance of the application and promotion of new energy vehicles has become increasingly prominent. Lithium-ion batteries have the characteristics of high energy density, long cycle life, and low self-discharge, and are most suitable as power batteries for new energy vehicles. However, the energy density of current traditional lithium-ion batteries has approached the theoretical limit of 300 Wh / kg, making it difficult to further improve the driving range of new energy vehicles; at the same time, the increasingly frequent safety accidents of lithium batteries have also hindered the marketization process of new energy vehicles. Compared with lithium-ion batteries using liquid electrolytes, the all-solid-state lithium-ion batteries use solid electrolytes that can effectively inhibit the growth of lithium dendrites, so they can be matched with lithium metal anodes to obtain higher energy density, and are expected to reach the current development goal of 500 Wh / kg; at the same time, all-solid-state lithium-ion batteries do not use flammable organic electrolytes, have no problems such as leakage and electrolyte dryness, and have a low risk of thermal runaway, so their safety performance is significantly improved compared with liquid lithium-ion batteries. Therefore, all-solid-state lithium-ion batteries are the key development direction of current lithium batteries.

[0003] However, the ionic conductivity of the cathode materials currently used in all-solid-state lithium-ion batteries is generally low, and they cannot play the role of transporting lithium ions alone. The composite cathode needs to add 20-30% of solid electrolyte as a supporting electrolyte, which brings two key problems. One is that an additional solid-solid contact interface is generated between the supporting electrolyte and the cathode active material. Problems such as the small contact area and the space charge layer at the interface increase the polarization of the battery and affect the battery performance; the other is that the additional supporting electrolyte reduces the proportion of active materials in the composite cathode, thereby reducing the energy density of the whole battery. A feasible way to solve the above problems is to combine the functions of the cathode active material and the supporting electrolyte, design a cathode material with high ionic conductivity, and replace the supporting electrolyte in the composite cathode, so as to simplify the three-phase contact interface of the cathode active material, the supporting electrolyte, and the conductive carbon in the composite cathode into a two-phase contact interface of the cathode active material and the conductive carbon, alleviating the adverse effects of interface contact on battery performance; at the same time, increasing the proportion of the cathode active material in the cathode layer and improving the energy density of the whole battery. However, the design idea of high ionic conductivity cathode materials is not yet clear. The method of using in-situ electrochemically lithiated layered materials as high ionic conductivity cathodes (Adv Mater., 2021, 2008723) reported currently has problems such as poor battery performance and difficulty in large-scale preparation, which limits the practical application of such materials. Summary of the Invention

[0004] To address the above-mentioned technical problems, the present application synthesizes a fluoride cathode material with high ionic conductivity in one step by high-energy ball milling, enabling it to be applied to halide-based all-solid-state lithium-ion batteries at room temperature with only a small amount of conductive carbon composite. This material uses HTB-FeF3 with a one-dimensional channel structure as a raw material and reacts with LiF by high-energy ball milling to obtain a new phase with higher structural symmetry. The higher structural symmetry of this material enables it to have a three-dimensional lithium-ion transport path, greatly improving its room-temperature lithium-ion conductivity compared to other lithium iron fluoride-based materials or materials with the same composition but slightly lower structural symmetry. At the same time, Fe as a reactive site endows the material with reversible charge-discharge capabilities and can be used as a cathode material for all-solid-state lithium-ion batteries. Compared with other all-solid-state battery systems, the mass ratio of the fluoride cathode material used in the present application in the composite cathode has been increased from the original 70-80% to 95%, effectively improving the overall energy density of all-solid-state lithium-ion batteries. At the same time, the material preparation method involved in the present application only includes high-energy ball milling, which effectively simplifies the preparation process compared to the electrochemically in-situ synthesis method used for reported similar materials, providing a basis for the large-scale preparation of this type of material. Due to the introduction of a large amount of lattice distortion into the material by high-energy ball milling, the long-range order of the material is reduced and the ion diffusion path is shortened, resulting in better rate performance compared to the same material with higher crystallinity.

[0005] In one aspect of the present application, a fluoride cathode material with high ionic conductivity is provided. The cathode material is applied in an all-solid-state lithium-ion battery, composed of three elements: lithium, iron, and fluorine, having high structural symmetry, high lithium-ion conductivity, and stable charge-discharge capabilities, and can operate stably in an all-solid-state lithium-ion battery at room temperature without adding a supporting electrolyte after being compounded with a small amount of conductive agent.

[0006] Optionally, the chemical composition general formula of the fluoride cathode material with high ionic conductivity is Li x FeF 3+x , where 0.5 < x < 1.5.

[0007] Optionally, the fluoride cathode material with high ionic conductivity has structural symmetry.

[0008] Optionally, the particle size of the fluoride cathode material with high ionic conductivity is 2-10 μm.

[0009] In another aspect of the present application, a preparation method of the above-mentioned fluoride cathode material with high ionic conductivity is provided. The preparation method includes: ball milling raw materials containing lithium fluoride and iron fluoride to obtain the fluoride cathode material with high ionic conductivity;

[0010] wherein, the iron fluoride has a Cmcm space group and has a one-dimensional channel structure.

[0011] Optionally, the positive electrode material uses lithium fluoride LiF as the lithium source.

[0012] Optionally, the iron fluoride is selected from anhydrous HTB-FeF 3 , FeF 3 ·0.33H 2 O, FeF 3 ·H 2 O, or one or more of them.

[0013] Optionally, the molar ratio of the lithium fluoride to the iron fluoride is (0.5 to 1.5):1.

[0014] Optionally, the molar ratio of the lithium fluoride to the iron fluoride is (0.8 to 1.2):1.

[0015] Optionally, the molar ratio of the lithium fluoride to the iron fluoride is independently selected from any value of 0.5:1, 0.8:1, 1:1, 1.2:1, 1.5:1 or the range value between any two of the above.

[0016] Optionally, during the ball milling process, the mass ratio of the total mass of the raw materials to the mass of the ball milling beads is 1:(30 to 100).

[0017] Optionally, the mass ratio of the total mass of the raw materials to the mass of the ball milling beads is 1:(70 to 75).

[0018] Optionally, the mass ratio of the total mass of the raw materials to the mass of the ball milling beads is independently selected from any value of 1:30, 1:50, 1:70, 1:73, 1:75, 1:80, 1:100 or the range value between any two of the above.

[0019] Optionally, the rotation speed of the ball milling is 300 to 2000 rpm.

[0020] Optionally, the rotation speed of the ball milling is 500 to 1000 rpm.

[0021] Optionally, the rotation speed of the ball milling is independently selected from any value of 300 rpm, 500 rpm, 550 rpm, 800 rpm, 1000 rpm, 1500 rpm, 2000 rpm or the range value between any two of the above.

[0022] Optionally, the time of the ball milling is 10 to 100 h.

[0023] Optionally, the time of the ball milling is independently selected from any value of 10 h, 30 h, 48 h, 60 h, 80 h, 100 h or the range value between any two of the above.

[0024] As a specific implementation, the preparation method of the positive electrode material for the all-solid-state lithium-ion battery comprises the following steps:

[0025] Step 1: Weigh appropriate amounts of LiF and FeF 3 raw materials and mix them evenly;

[0026] Step 2: Add the raw materials weighed in Step 1 into a ball-milling jar, and at the same time add appropriate amounts of ball-milling beads into the jar, and then seal the ball-milling jar;

[0027] Step 3: Place the ball-milling jar in Step 2 in a high-speed ball mill for high-speed ball-milling reaction;

[0028] Step 4: Take out the product obtained after high-speed ball milling in Step 3, and obtain the high-ion-conducting positive electrode material after appropriate grinding.

[0029] In another aspect of the present application, there is provided an all-solid-state lithium-ion battery composite positive electrode, and the all-solid-state lithium-ion battery composite positive electrode includes the above-mentioned high-ion-conducting fluoride positive electrode material and a conductive agent.

[0030] Optionally, the conductive agent is selected from at least one of carbon nanotubes, carbon nanofibers, graphene, SuperP, Ketjen black, acetylene black, and activated carbon.

[0031] Optionally, the content of the conductive agent is 5-10 wt% of the mass of the all-solid-state lithium-ion battery composite positive electrode.

[0032] Optionally, the content of the conductive agent is independently selected from any value of 5 wt%, 8 wt%, 10 wt% or the range value between any two of the above.

[0033] Optionally, the content of the high-ion-conducting fluoride positive electrode material is 90-95 wt% of the mass of the all-solid-state lithium-ion battery composite positive electrode.

[0034] Optionally, the content of the high-ion-conducting fluoride positive electrode material is independently selected from any value of 90 wt%, 92 wt%, 95 wt% or the range value between any two of the above.

[0035] In yet another aspect of the present application, there is provided an all-solid-state lithium-ion battery, and the all-solid-state lithium-ion battery includes the above-mentioned all-solid-state lithium-ion battery composite positive electrode, a solid electrolyte, and a negative electrode.

[0036] Optionally, the negative electrode is metallic lithium, and a lithium metal foil is selected as the negative electrode in the present application;

[0037] The solid electrolyte is Li 2 ZrCl 6 and Li 6 PS 5Double-layer electrolyte composed of Cl.

[0038] The beneficial effects that can be produced by this application include:

[0039] (1) The high-ion-conducting fluoride material described in this application introduces lattice distortion through high-energy ball milling. Its lower long-range order and higher structural symmetry endow it with high room-temperature ionic conductivity and stable charge-discharge capabilities, and the ionic conductivity is significantly improved compared with other fluorides.

[0040] (2) The high-ion-conducting cathode material described in this application only needs to be compounded with a small amount of conductive carbon to be applied in all-solid-state lithium-ion batteries, and the proportion of the active material in the cathode is increased to 90-95 wt%.

[0041] (3) When the high-ion-conducting cathode material described in this application is applied in all-solid-state lithium-ion batteries, it is not necessary to add a supporting electrolyte to the composite cathode, eliminating the interfacial contact problem between the cathode active material and the supporting electrolyte, and improving the comprehensive performance of all-solid-state lithium-ion batteries.

[0042] (4) The high-ion-conducting cathode material described in this application uses iron element with relatively high crustal abundance as the raw material. Compared with the halide electrolyte using rare earth metal elements, it effectively reduces the raw material cost of the material; at the same time, the synthesis of this material can be used as the downstream of the existing FeF 3 cathode material, reducing the infrastructure construction cost required for large-scale production.

[0043] (5) The high-ion-conducting cathode material described in this application can be synthesized only by one-step high-energy ball milling method, with relatively low process complexity and good industrial application prospects.

[0044] (6) The high-ion-conducting lithium iron fluoride-based cathode material provided by this application has stable capacity output, simple synthesis, and is insensitive to water and oxygen, and can be used as the cathode material of all-solid-state lithium-ion batteries; at the same time, when using this material as the cathode, it is not necessary to add an additional supporting electrolyte, effectively increasing the proportion of the cathode active material in all-solid-state lithium-ion batteries. Brief Description of the Drawings

[0045] Figure 1 SEM images of the cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 of this application, with the scale bar being 20 μm;

[0046] Figure 2 X-ray diffraction patterns of the FeF 3 raw materials used in Example 1 and Comparative Example 2 of this application;

[0047] Figure 3 X-ray diffraction patterns of the cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 of this application;

[0048] Figure 4 The EIS spectrograms measured using an ion-blocking battery for the cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 of this application;

[0049] Figure 5 The charge-discharge curve of the cathode material prepared in Example 1 of this application in a all-solid-state lithium-ion battery;

[0050] Figure 6 The cycling performance graph of the cathode material prepared in Example 1 of this application in a all-solid-state lithium-ion battery;

[0051] Figure 7 The rate performance graph of the cathode materials prepared in Example 1 and Comparative Example 3 of this application in a all-solid-state lithium-ion battery. Detailed implementation manners

[0052] The following describes this application in detail with reference to the examples, but this application is not limited to these examples.

[0053] Unless otherwise specified, the raw materials in the examples of this application are all purchased through commercial channels.

[0054] Example 1

[0055] Synthesis of high-ion-conducting cathode material: Weigh 0.2482 g of LiF and 1.2518 g of HTB-FeF 3 , and grind them in a mortar for more than 10 min to mix the reactants evenly. Put the mixed sample into a ball-milling jar, add ball-milling beads with a total mass of 105 g, and seal the ball-milling jar. Place the ball-milling jar on a high-speed ball mill, with a rotation speed of 550 rpm, and carry out high-energy ball-milling reaction for 48 h. Scrape out the reacted sample from the ball-milling jar, and grind it appropriately in a mortar until there are no obvious lumps to obtain the high-ion-conducting cathode material Li x FeF 3+x , where x = 1.

[0056] Measurement of the ionic conductivity of the material by the blocking electrode method: Use a mold battery with an inner diameter of 10 mm, add 80 mg of the cathode material powder, place it on a press, apply a pressure of 4 t and maintain it for 3 min. Measure the overall thickness of the battery after adding the cathode material powder, and calculate that the thickness of the cathode material sheet is 0.34 mm. Connect the mold battery to an electrochemical workstation for EIS testing.

[0057] Preparation of composite cathode: Weigh 190 mg of the high-ion-conducting cathode material and 10 mg of Ketjen black, and grind them in a mortar for more than 10 min to mix the reactants evenly. Put the mixed sample into a ball-milling jar, add ball-milling beads with a total mass of 50 g, and seal the ball-milling jar. Place the ball-milling jar on a high-speed ball mill, and ball-mill at a rotation speed of 550 rpm for 4 h. Scrape out the sample from the ball-milling jar to obtain the composite cathode material.

[0058] All-solid-state lithium-ion battery assembly: Using a pressurized battery mold with an inner diameter of 10 mm, add 50 mg of Li 2 ZrCl 6 and 50 mg of Li 6 PS 5 Cl, place it on a press and apply a pressure of 1 t for 1 min. Weigh 2 mg of the composite cathode material and spread it evenly on the Li 2 ZrCl 6 side, and then place it on a press and apply a pressure of 4 t for 3 min. Attach a lithium foil with a thickness of 50 μm and a copper foil on the Li 6 PS 5 Cl side. Maintain an operating pressure of 1 t for the entire battery and conduct constant current charge and discharge tests.

[0059] Example 2

[0060] Synthesis of high-ion-conducting cathode material: Weigh 0.2271 g of LiF and 1.2728 g of HTB-FeF 3 , grind them in a mortar for more than 10 min to mix the reactants evenly. Put the mixed sample into a ball milling jar, add ball milling beads with a total mass of 106 g, and seal the ball milling jar. Place the ball milling jar on a high-speed ball mill with a rotation speed of 550 rpm and conduct high-energy ball milling reaction for 48 h. Scrape out the reacted sample from the ball milling jar and grind it appropriately in a mortar until there are no obvious lumps to obtain the high-ion-conducting cathode material Li x FeF 3+x , where x = 0.9.

[0061] The method for measuring the ionic conductivity of the material by the blocking electrode method is the same as that in Example 1, and the thickness of the cathode material sheet is measured to be 0.35 mm.

[0062] Example 3

[0063] Synthesis of high-ion-conducting cathode material: Weigh 0.2482 g of LiF and 1.2518 g of HTB-FeF 3 , grind them in a mortar for more than 10 min to mix the reactants evenly. Put the mixed sample into a ball milling jar, add ball milling beads with a total mass of 110 g, and seal the ball milling jar. Place the ball milling jar on a high-speed ball mill with a rotation speed of 1000 rpm and conduct high-energy ball milling reaction for 30 h. Scrape out the reacted sample from the ball milling jar and grind it appropriately in a mortar until there are no obvious lumps to obtain the high-ion-conducting cathode material Li x FeF 3+x , where x = 1.

[0064] The method for measuring the ionic conductivity of the material by the blocking electrode method is the same as that in Example 1, and the thickness of the cathode material sheet is measured to be 0.41 mm.

[0065] Comparative Example 1

[0066] Synthesis of high ionic conductivity cathode material: Weigh 0.4259 g of LiF and 1.0741 g of HTB-FeF 3 respectively, and grind them in a mortar for more than 10 minutes to make the reactants evenly mixed. Put the mixed sample into a ball milling tank, add ball milling beads with a total mass of 103 g, and seal the ball milling tank. Place the ball milling tank on a high-speed ball mill with a rotation speed of 550 rpm, and carry out high-energy ball milling reaction for 48 h. Scrape out the reacted sample from the ball milling tank, and appropriately grind it in a mortar until there are no obvious lumps to obtain Comparative Example 1.

[0067] The method for measuring the ionic conductivity of the material by the blocking electrode method is the same as that in Example 1, and the thickness of the cathode material sheet is measured to be 0.36 mm.

[0068] Comparative Example 2

[0069] Synthesis of high ionic conductivity cathode material: Weigh 0.2482 g of LiF and 1.2518 g of layered-FeF 3 respectively, and grind them in a mortar for more than 10 minutes to make the reactants evenly mixed. Put the mixed sample into a ball milling tank, add ball milling beads with a total mass of 105 g, and seal the ball milling tank. Place the ball milling tank on a high-speed ball mill with a rotation speed of 550 rpm, and carry out high-energy ball milling reaction for 48 h. Scrape out the reacted sample from the ball milling tank, and appropriately grind it in a mortar until there are no obvious lumps to obtain Comparative Example 2.

[0070] The method for measuring the ionic conductivity of the material by the blocking electrode method is the same as that in Example 1, and the thickness of the cathode material sheet is measured to be 0.33 mm.

[0071] Comparative Example 3

[0072] Synthesis of high ionic conductivity cathode material: Weigh 0.2271 g of LiF and 1.2728 g of HTB-FeF 3 respectively, and grind them in a mortar for more than 10 minutes to make the reactants evenly mixed. Put the mixed sample into a ball milling tank, add ball milling beads with a total mass of 106 g, and seal the ball milling tank. Place the ball milling tank on a high-speed ball mill with a rotation speed of 550 rpm, and carry out high-energy ball milling reaction for 48 h. Scrape out the reacted sample from the ball milling tank, and appropriately grind it in a mortar until there are no obvious lumps. Subsequently, take 500 mg of the sample and place it in a container made of polytetrafluoroethylene, heat it to 150 °C in an argon atmosphere at a heating rate of 3 °C / min, keep it warm for 12 h, and then cool it naturally. Obtain Comparative Example 3.

[0073] The method for measuring the ionic conductivity of the material by the blocking electrode method is the same as that in Example 1, and the thickness of the cathode material sheet is measured to be 0.34 mm.

[0074] The preparation method of the composite cathode and the assembly method of the all-solid-state lithium-ion battery are the same as those in Example 1.

[0075] Analysis of experimental results

[0076] The cathode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were characterized by SEM using a scanning electron microscope, and the results are as Figure 1 shown. It can be seen from Figure 1 that all the samples prepared by high-energy ball milling are irregular fragmented. Among them, Examples 1 to 2 and Comparative Examples 1 to 3 all reacted at a rotation speed of 550 rpm for 48 h, and the particle size range was 2 to 10 μm; Example 3 reacted at a rotation speed of 1000 rpm for 30 h, and the particle size range was 1 to 5 μm, indicating that a higher ball milling speed can effectively reduce the particle size.

[0077] The HTB-FeF used in Examples 1 to 3 and Comparative Examples 1 and 3 was characterized by X-ray diffractometer 3 and the layered FeF used in Comparative Example 2 3 was characterized by XRD, and the results are as Figure 2 shown. It can be seen from Figure 2 that HTB-FeF 3 belongs to the Cmcm space group and has a one-dimensional channel structure; the layered FeF 3 belongs to the R space group and has a layered feature. The one-dimensional channel structure enables HTB-FeF 3 to have a higher reaction activity and can react with LiF by high-energy ball milling to form a new phase.

[0078] The cathode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were characterized by XRD using an X-ray diffractometer, and the results are as Figure 3 shown. It can be seen from Figure 3 that all the samples using HTB-FeF 3 reacted to form a new phase, and the characteristic diffraction peaks of the original HTB-FeF 3 disappeared. The characteristic three strong diffraction peaks of the new phase in Examples 1 to 3 and Comparative Example 1 are located at 40.8°, 57.3°, and 64.5° respectively, and the number of diffraction peaks is small, showing strong structural symmetry; and there is no obvious diffraction peak at low angles for the new phase, but an obvious amorphous phase characteristic peak appears, indicating that a large amount of element mixing and lattice defects are introduced into the high-energy ball milling phase structure, reducing the long-range order of the material. In Comparative Example 1, due to the addition of an excessive amount of LiF reactant, the contents of the impurity phases LiF and Li 3 FeF 6 are relatively high. In Comparative Example 2, due to the use of the less reactive layered FeF 3As a reactant, the reaction can hardly proceed, and all the characteristic peaks in the XRD pattern can be attributed to the reactants. Comparative Example 3 used a high-ion-conducting cathode material after annealing treatment, with significantly improved long-range order and decreased structural symmetry.

[0079] The ion conductivities of the cathode materials prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were characterized using the blocking electrode method. Using the method in Example 1, the results are as Figure 4 shown. Examples 1 to 3 showed similar low impedance values, indicating the formation of a high-ion-conducting phase and that changing the preparation conditions within an appropriate range had no significant effect on the material properties. In Comparative Example 1, due to the presence of miscellaneous items, the content of the high-ion-conducting phase decreased, manifested as a larger impedance value. In Comparative Example 2, since no reaction occurred, no high-ion-conducting phase was generated, manifested as an extremely large impedance value and no ability to transport lithium ions. The impedance value of Comparative Example 3 was greater than that of Examples 1 to 3, indicating that the improvement in long-range order and the decrease in structural symmetry reduced the lithium-ion transport ability of the material, that is, it showed that the reason for the high ion conductivity of the cathode materials prepared in Examples 1 to 3 was related to the structure of the material.

[0080] The cyclic performance of Example 1 was tested, and the first-cycle charge-discharge curve in the test results was as Figure 5 shown, and the long-cycle performance curve was as Figure 6 shown. From Figure 5 it can be seen that the first-cycle discharge specific capacity of the cathode material prepared in Example 1 was 292.09 mAh g -1 , with relatively high capacity utilization. From Figure 6 it can be seen that the high-ion-conducting cathode material prepared in Example 1 could be stably cycled more than 250 times at room temperature without obvious capacity decay. The discharge specific capacity at the 250th cycle was 246.33 mAh g -1 , and the capacity retention rate relative to the first cycle was 84.33%. The above results show that the cathode material prepared in Example 1 has good electrochemical performance at room temperature and can be used as the cathode material for all-solid-state lithium-ion batteries.

[0081] The rate performance of Example 1 and Comparative Example 3 was tested, and the results are as Figure 7 shown. From Figure 7 it can be seen that the stable discharge specific capacity of Example 1 at a current density of 0.1 mA cm -2 was 273.65 mAh g -1 , and the stable discharge specific capacity at a current density of 2 mA cm -2 was 48.15 mAh g -1 , which was 17.60% of that at a current density of 0.1 mA cm -2 ; while Comparative Example 3 at a current density of 0.1 mA cm -2The stable discharge specific capacity at a current density of 227.82 mAh g -1 is 227.82 mAh g at a current density of 2 mA cm -2 and the stable discharge specific capacity at a current density of 24.27 mAh g -1 is 10.65% of that at a current density of 0.1 mA cm -2 . It shows that the cathode material prepared in Example 1 has a higher ion conductivity and lower long-range order, shortening the ion transport path, effectively improving the lithium ion transport ability of the material, and enabling it to have higher capacity performance and better rate performance.

[0082] The above are only several embodiments of the present application and do not impose any form of limitation on the present application. Although the present application is disclosed above with preferred embodiments, it is not intended to limit the present application. Any person skilled in the art can make some changes or modifications within the scope of the technical solution of the present application by using the disclosed technical content, which are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. A high ionic conductivity fluoride cathode material, characterized in that, The general chemical composition formula of the high ionic conductivity fluoride cathode material is Li x FeF 3+x , where 0.5 < x < 1.

5.

2. The high ionic conductivity fluoride cathode material according to claim 1, characterized in that, the high ionic conductivity fluoride cathode material has structural symmetry; Preferably, the particle size of the high ionic conductivity fluoride cathode material is 2-10 μm.

3. A method for preparing the high ionic conductivity fluoride cathode material according to any one of claims 1-2, characterized in that, the preparation method includes: ball milling a raw material containing lithium fluoride and iron fluoride to obtain the high ionic conductivity fluoride cathode material; wherein, the iron fluoride has a Cmcm space group and has a one-dimensional channel structure.

4. The preparation method according to claim 3, characterized in that, The iron fluoride is selected from at least one of anhydrous HTB-FeF 3 , FeF 3 ·0.33H 2 O, FeF 3 ·H 2 O; Preferably, the molar ratio of lithium fluoride to iron fluoride is (0.5-1.5):1; Preferably, the molar ratio of lithium fluoride to iron fluoride is (0.8-1.2):

1.

5. The preparation method according to claim 3, characterized in that, during the ball milling process, the mass ratio of the total mass of the raw materials to the mass of the ball milling beads is 1:(30-100); Preferably, the mass ratio of the total mass of the raw materials to the mass of the ball milling beads is 1:(70-75).

6. The preparation method according to claim 3, characterized in that, the rotation speed of the ball milling is 300-2000 rpm; Preferably, the rotation speed of the ball milling is 500-100 rpm; Preferably, the ball milling time is 10-100 h.

7. A composite cathode for an all-solid-state lithium-ion battery, characterized in that, the composite cathode for the all-solid-state lithium-ion battery includes the high ionic conductivity fluoride cathode material according to any one of claims 1-2 and a conductive agent.

8. The composite cathode for the all-solid-state lithium-ion battery according to claim 7, characterized in that, the conductive agent is selected from at least one of carbon nanotubes, carbon nanofibers, graphene, SuperP, Ketjen black, acetylene black, and activated carbon; Preferably, the content of the conductive agent is 5-10% of the mass of the composite cathode for the all-solid-state lithium-ion battery; Preferably, the content of the high ionic conductivity fluoride cathode material is 90-95 wt% of the mass of the composite cathode for the all-solid-state lithium-ion battery.

9. An all-solid-state lithium-ion battery, characterized in that, the all-solid-state lithium-ion battery includes the composite cathode for the all-solid-state lithium-ion battery according to any one of claims 7-8, a solid electrolyte, and an anode.

10. The all-solid-state lithium-ion battery according to claim 9, characterized in that: the anode is metallic lithium; The solid electrolyte is Li 2 ZrCl 6 and Li 6 PS 5 composed of a bilayer electrolyte.

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