Porous Li2SiF6 composite material as well as preparation method and application thereof

Abstract

The invention relates to a porous Li2SiF6 composite material as well as a preparation method and application thereof, and the preparation method comprises the following steps: in an inert atmosphere, mixing a porous molecular sieve with a LiPF6 solution, carrying out a reaction, and after the reaction is finished, carrying out separation to obtain the porous Li2SiF6 composite material. When the porous Li2SiF6 composite material obtained by the preparation method disclosed by the invention is used as a coating of a graphite negative electrode plate, the fast charging performance and the electrochemical performance of the graphite negative electrode plate can be effectively improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a porous Li2SiF6 composite material and a preparation method and application thereof. BACKGROUND

[0002] At present, the negative electrode of lithium ion battery is still mainly graphite material, but the fast charging capacity of graphite material is limited. Li2SiF6 as one of the new generation of lithium salts has limited improvement on the rate performance and fast charging performance of graphite when used as the coating of graphite negative electrode sheet. SUMMARY

[0003] Therefore, it is necessary to provide a porous Li2SiF6 composite material and a preparation method and application thereof, which can effectively improve the fast charging performance and electrochemical performance of the graphite negative electrode sheet when the porous Li2SiF6 composite material obtained by the preparation method is used as the coating of the graphite negative electrode sheet.

[0004] A preparation method of a porous Li2SiF6 composite material, comprising: mixing and reacting porous molecular sieve and LiPF6 solution in an inert atmosphere, and separating the porous Li2SiF6 composite material after the reaction is completed.

[0005] In one embodiment, the pore size of the porous molecular sieve is ≤2nm, the specific surface area is 300m 2 / g-800m 2 / g, and Si / Al is 1-10.

[0006] In one embodiment, the porous molecular sieve is selected from at least one of A-type molecular sieve, X-type molecular sieve, Y-type molecular sieve, ZSM-5 molecular sieve, and mordenite.

[0007] In one embodiment, the concentration of LiPF6 in the LiPF6 solution is 0.5mol / L-5mol / L.

[0008] In one embodiment, the mass ratio of the porous molecular sieve to the LiPF6 in the step of mixing and reacting the porous molecular sieve and the LiPF6 solution is 1:1-1:10.

[0009] In one embodiment, in the step of mixing and reacting the porous molecular sieve and the LiPF6 solution, the reaction temperature is 60℃-100℃, and the reaction time is 1h-10h.

[0010] A porous Li2SiF6 composite material obtained by the preparation method.

[0011] A graphite negative electrode includes a current collector and a graphite material layer attached to the surface of the current collector, wherein a porous Li2SiF6 composite material coating is also attached to the surface of the graphite material layer.

[0012] In one embodiment, the mass of the porous Li2SiF6 composite material is 1 to 10 times the mass of graphite in the graphite material layer.

[0013] A method for preparing the graphite negative electrode sheet includes the following steps:

[0014] A prefabricated graphite negative electrode sheet is provided, the prefabricated graphite negative electrode sheet comprising a current collector and a graphite material layer attached to the surface of the current collector;

[0015] The porous Li2SiF6 composite material was dispersed in an organic solvent to obtain a dispersion. The dispersion was placed on the surface of the graphite material layer of the pre-fabricated graphite anode sheet and dried to obtain the graphite anode sheet.

[0016] A lithium-ion battery using the aforementioned graphite negative electrode sheet.

[0017] In the preparation method of this invention, when the porous molecular sieve is mixed with LiPF6 solution and reacted, the silicon-aluminum framework of the porous molecular sieve can react in situ with LiPF6. During the reaction, the pore structure of the porous molecular sieve can provide abundant reactive sites and restrict the reaction space, achieving nanoscale uniform growth and distribution of Li2SiF6, avoiding agglomeration, and retaining the porous framework. Therefore, when used as a coating for graphite anode sheets, it can further accelerate the lithium-ion transport rate. Simultaneously, the reaction also generates AlPO4, which can form a covalent bond interface with Li2SiF6, further inhibiting electrolyte decomposition and lithium dendrite growth, and improving the electrochemical performance of the graphite anode sheet. Therefore, the porous Li2SiF6 composite material obtained by the preparation method of this invention is mainly composed of Li2SiF6 and AlPO4. When used as a coating for graphite anode sheets, it can effectively improve the fast-charging performance and electrochemical performance of the graphite anode sheet. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The first charge-discharge curve of the coin cell battery at 0.1C in Example 6 is shown.

[0020] Figure 2 The charge-discharge cycle curve of the coin cell at 8C in Example 6 is shown after 500 cycles.

[0021] Figure 3 The first charge-discharge curve of a button cell at 0.1C is shown as a blank example.

[0022] Figure 4 The charge-discharge cycle curve of a button cell at 8C for 200 cycles is shown as a blank example. Detailed Implementation

[0023] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0025] In this invention, numerical ranges are involved. Unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe features or characteristics, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are included.

[0026] Analysis revealed that the limited improvement in rate performance and fast-charging performance of graphite anodes achieved by Li₂SiF₆ as a coating is primarily due to the following: Li₂SiF₆ is mostly a dense crystal, resulting in only point contact between it and graphite and conductive agents when used as a coating. This small interfacial contact area limits ion transport paths, making it prone to lithium-ion blockage during high-rate cycling, leading to increased polarization. Furthermore, its poor mechanical properties further exacerbate the problem. + The repeated insertion and extraction will cause cracks and breakage, which will lead to further degradation of electrical performance.

[0027] To optimize the ion transport path, Li2SiF6 was prepared into a porous structure. Its high specific surface area and hierarchical pore structure were used to optimize the ion transport path. However, it was found that Li2SiF6 would have serious interfacial side reactions with the electrolyte during cycling, which would reduce the battery performance.

[0028] Therefore, the present invention provides a method for preparing porous Li2SiF6 composite material, comprising: mixing porous molecular sieve with LiPF6 solution and reacting them in an inert atmosphere, and separating the porous Li2SiF6 composite material after the reaction is completed.

[0029] The inert atmosphere is selected from gases that do not participate in the reaction, such as nitrogen, argon, hydrogen-argon mixture, and hydrogen-nitrogen mixture. In the hydrogen-argon mixture and the hydrogen-nitrogen mixture, the hydrogen content is 1%-10%.

[0030] Specifically, when porous molecular sieves are mixed with LiPF6 solution and reacted, the silica-alumina framework of the porous molecular sieves can react in situ with LiPF6 to generate a composite material of Li2SiF6 and AlPO4. The basic reaction process is as follows:

[0031] LiPF6 + SiO6 / Al6O3→Li2SiF6+ AlPO4

[0032] In this reaction process, on the one hand, the porous structure of the molecular sieve can provide abundant reactive sites and restrict the reaction space, enabling the uniform growth and distribution of Li2SiF6 at the nanoscale, avoiding agglomeration, and retaining the porous framework. This can further accelerate the lithium-ion transport rate when used as a coating for graphite anode sheets. On the other hand, the AlPO4 generated in the reaction can form a covalent bond interface with Li2SiF6, which can further inhibit electrolyte decomposition and lithium dendrite growth, and improve the electrochemical performance of graphite anode sheets.

[0033] Therefore, when the porous Li2SiF6 composite material obtained by the preparation method described in this invention is used as a coating for graphite anode sheets, it can effectively improve the fast-charging performance and electrochemical performance of graphite anode sheets.

[0034] Optionally, the porous molecular sieve has a pore size ≤ 2 nm, preferably ≤ 1 nm, and a specific surface area of ​​300 m². 2 / g-800m 2 With a Si / Al ratio of 1-10, the resulting porous Li2SiF6 composite material exhibits better ion transport performance and better suppresses electrolyte decomposition and lithium dendrite growth.

[0035] In this invention, there are no requirements for the selection of porous molecular sieves. Optionally, the porous molecular sieve is selected from at least one of type A molecular sieves, type X molecular sieves, type Y molecular sieves, ZSM-5 molecular sieves, and mordenite. Type A molecular sieves can be 3A, 4A, 5A, etc., with the molecular formula X·Al₂O₃·2SiO₂·4.5H₂O, where X is an oxide of K, Na, Ca, etc. Type X molecular sieves have the molecular formula Na₂O·Al₂O₃·2.8SiO₂·6H₂O. Type Y molecular sieves have the molecular formula Na₂O·Al₂O₃·(4.8-6.0)SiO₂·H₂O. ZSM-5 molecular sieves have the molecular formula Na… m Al n Si 96-n O 192 ·16H2O, m=3~30, n=3~30, the molecular formula of mordenite is Na2O·Al2O3·10SiO2·7H2O.

[0036] Optionally, in the LiPF6 solution, the solvent is selected from organic solvents, including ester solvents, ether solvents, nitrile solvents, etc., wherein the ester solvent is selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), etc., the ether solvent is selected from dimethyl ether (DE), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DCE), tetraethylene glycol dimethyl ether (TGDE), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), etc., and the nitrile solvent is selected from acetonitrile (ACN), butyronitrile (NBR), benzonitrile (BN), ethylenedionitrile (EDN), acrylonitrile (AN), etc., and the concentration of LiPF6 is preferably 0.5mol / L-5mol / L.

[0037] In the step of mixing and reacting the porous molecular sieve with the LiPF6 solution, the mass ratio of the porous molecular sieve to the LiPF6 is 1:1 to 1:10.

[0038] Optionally, in the step of mixing the porous molecular sieve with the LiPF6 solution and reacting, the reaction temperature is 60℃-100℃ and the reaction time is 1h-10h. This allows the reaction rate between the porous molecular sieve and LiPF6 to be controlled by adjusting the reaction temperature, thus making the reaction between the porous molecular sieve and LiPF6 more complete.

[0039] The present invention also provides a porous Li2SiF6 composite material obtained by the preparation method described above, wherein the porous Li2SiF6 composite material comprises Li2SiF6 and AlPO4.

[0040] The present invention also provides a graphite negative electrode sheet, comprising a current collector and a graphite material layer attached to the surface of the current collector, wherein a porous Li2SiF6 composite material coating is further attached to the surface of the graphite material layer. The graphite material layer is composed of graphite, a binder, a conductive agent, etc., in a specific ratio.

[0041] Since the porous Li2SiF6 composite material prepared by this invention can accelerate the lithium ion transport rate and inhibit electrolyte decomposition and lithium dendrite growth, when the porous Li2SiF6 composite material of this invention is used as a coating for graphite anode sheets, it can effectively improve the fast charging performance and electrochemical performance of graphite anode sheets.

[0042] Optionally, the mass of the porous Li2SiF6 composite material is 1 to 10 times the mass of graphite in the graphite material layer.

[0043] The present invention also provides a method for preparing the graphite negative electrode sheet, comprising the following steps:

[0044] A prefabricated graphite negative electrode sheet is provided, the prefabricated graphite negative electrode sheet comprising a current collector and a graphite material layer attached to the surface of the current collector;

[0045] The porous Li2SiF6 composite material was dispersed in an organic solvent to obtain a dispersion. The dispersion was placed on the surface of the graphite material layer of the pre-fabricated graphite anode sheet and dried to obtain the graphite anode sheet.

[0046] It is understood that prefabricated graphite anode sheets are the traditional graphite anode sheets, which are made by mixing graphite, conductive agents and binders to form a slurry, coating the slurry onto a current collector, drying and slicing it. The present invention mainly uses porous Li2SiF6 composite material to treat the traditional graphite anode sheet to improve the fast charging performance and electrochemical performance of the graphite anode sheet.

[0047] Optionally, in the step of dispersing the porous Li2SiF6 composite material in an organic solvent, the organic solvent is selected from ester solvents, ether solvents, nitrile solvents, etc., wherein the ester solvent is selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), etc., the ether solvent is selected from dimethyl ether (DE), ethylene glycol dimethyl ether (DME), diethylene glycol dimethyl ether (DCE), tetraethylene glycol dimethyl ether (TGDE), tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-Me-THF), etc., and the nitrile solvent is selected from acetonitrile (ACN), butyronitrile (NBR), benzonitrile (BN), ethylenedionitrile (EDN), acrylonitrile (AN), etc., and the concentration of the porous Li2SiF6 composite material in the dispersion is preferably 0.5 mol / L-2 mol / L.

[0048] It is understood that the dispersion can be placed on the surface of the graphite material layer of the pre-fabricated graphite negative electrode sheet by means of coating, dripping, etc.

[0049] Furthermore, the present invention also provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is the graphite negative electrode of the present invention.

[0050] The technical solution of the present invention will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0051] Blank example

[0052] Weigh out 320 mg of artificial graphite material, 40 mg of conductive carbon black, and 40 mg of carboxymethyl cellulose. Add an appropriate amount of deionized water and ball mill using a planetary ball mill for 2 hours. Coat the ball-milled slurry onto a copper foil current collector, and vacuum dry at 80℃ for 12 hours. Then cut it into graphite negative electrode sheets with a diameter of 12 mm and a loading of 2.5 mg / cm³. 2 .

[0053] Then, lithium metal was used as the counter electrode and reference electrode, PP membrane was selected as the separator, LiPF6 with a concentration of 1 mol / L was used as the electrolyte, and a mixed solution of diethyl carbonate and ethylene carbonate with a volume ratio of 1:1 was used as the solvent. The button cell was assembled in a glove box under an argon atmosphere.

[0054] Example 1

[0055] A 0.5 mol / L LiPF6 solution was prepared by mixing LiPF6 with an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was reacted with a type 3A molecular sieve (molecular formula K₂O·Al₂O₃·2SiO₂·4.5H₂O, average pore size 0.3 nm, Si / Al ratio 2, specific surface area 500 m²). 2 The mixture (LiPF6 and 3A molecular sieve) was prepared at a mass ratio of 10:1 and reacted at 60°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0056] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 0.5 mol / L.

[0057] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example in the amount of 500 μL, and then dried at 80 °C. Coin cells were then assembled in the manner of the blank example.

[0058] Example 2

[0059] A 1 mol / L LiPF6 solution was prepared by mixing LiPF6 with a solvent having an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was mixed with a type 3A molecular sieve (molecular formula K₂O·Al₂O₃·2SiO₂·4.5H₂O, average pore size 0.3 nm, Si / Al ratio 2, specific surface area 500 m²). 2 The mixture (LiPF6 and 3A molecular sieve) was prepared at a mass ratio of 10:1 and reacted at 60°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0060] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0061] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0062] Example 3

[0063] A 1 mol / L LiPF6 solution was prepared by mixing LiPF6 with a solvent having an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was mixed with a type 3A molecular sieve (molecular formula K₂O·Al₂O₃·2SiO₂·4.5H₂O, average pore size 0.3 nm, Si / Al ratio 2, specific surface area 500 m²). 2 The mixture (LiPF6 and 3A molecular sieve) was prepared at a mass ratio of 10:1 and reacted at 60°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0064] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1.5 mol / L.

[0065] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0066] Example 4

[0067] A 1 mol / L LiPF6 solution was prepared by mixing LiPF6 with an EC / DMC solvent at a volume ratio of 1:1. Then, the LiPF6 solution was reacted with an X-type molecular sieve (molecular formula Na₂O·Al₂O₃·2.8SiO₂·6H₂O, average pore size 0.7 nm, Si / Al ratio 1.5, specific surface area 600 m²). 2 The mixture (LiPF6 and X-type molecular sieve) was prepared at a mass ratio of 10:2, and reacted at 80°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0068] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0069] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0070] Example 5

[0071] A 1 mol / L LiPF6 solution was prepared by mixing LiPF6 with an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was reacted with a Y-type molecular sieve (molecular formula Na₂O·Al₂O₃·6SiO₂·H₂O, average pore size 0.75 nm, Si / Al ratio 3, specific surface area 700 m²). 2 The mixture (LiPF6 and Y-type molecular sieve) was prepared at a mass ratio of 10:2 and reacted at 80°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0072] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0073] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0074] Example 6

[0075] A 2 mol / L LiPF6 solution was prepared by mixing LiPF6 with an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was reacted with a Y-type molecular sieve (molecular formula Na₂O·Al₂O₃·6SiO₂·H₂O, average pore size 0.75 nm, Si / Al ratio 3, specific surface area 700 m²). 2 The mixture (LiPF6 and Y-type molecular sieve) was prepared at a mass ratio of 10:2 and reacted at 80°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0076] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0077] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0078] Example 7

[0079] A 2 mol / L LiPF6 solution was prepared by mixing LiPF6 with an EC / DMC volume ratio of 1:1. Then, the LiPF6 solution was reacted with a Y-type molecular sieve (molecular formula Na₂O·Al₂O₃·6SiO₂·H₂O, average pore size 0.74 nm, Si / Al ratio 3, specific surface area 800 m²). 2 The LiPF6 and Y-type molecular sieve were mixed at a mass ratio of 10:4, and reacted at 80°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain the porous LiSiF6 composite material.

[0080] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0081] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0082] Example 8

[0083] A 2 mol / L LiPF6 solution was prepared by mixing an EC / DMC solvent (volume ratio of 1:1) with LiPF6. Then, the LiPF6 solution was mixed with ZSM-5 molecular sieve (molecular formula Na3Al). 16Si 80 O 192 • 16H₂O, average pore size 0.55 nm, Si / Al ratio 5, specific surface area 300 m² 2 The LiPF6 and ZSM-5 molecular sieves were mixed at a mass ratio of 10:2, and reacted at 100℃ for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60℃ for 24 hours to obtain the porous LiSiF6 composite material.

[0084] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0085] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0086] Example 9

[0087] A 2 mol / L LiPF6 solution was prepared by mixing LiPF6 with a solvent of EC / DMC at a volume ratio of 1:1. Then, the LiPF6 solution was mixed with mordenite zeolite (molecular formula Na₂O·Al₂O₃·10SiO₂·7H₂O, average pore size 0.6 nm, Si / Al ratio 10, specific surface area 300 m²). 2 LiPF6 and mordenite were mixed at a mass ratio of 10:2 and reacted at 100°C for 2 hours under an inert argon atmosphere. After the reaction, the mixture was washed three times with anhydrous DMC and then vacuum dried at 60°C for 24 hours to obtain a porous LiSiF6 composite material.

[0088] The porous LiSiF6 composite material prepared above was uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0089] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0090] Comparative Example 1

[0091] Li₂SiF₆ was prepared directly using a gas-solid reaction-in-situ fluorination method. This involved mechanically mixing porous SiO₂ with LiF and reacting the mixture at 300°C for 4 h in a PF₅ / NH₄HF₂ gas stream to form porous Li₂SiF₆. The Li₂SiF₆ was then uniformly dispersed in a DMC / EC mixed solvent with a volume ratio of 1:1 to obtain a dispersion with a concentration of 1 mol / L.

[0092] The above dispersion was then dropped onto the surface of the graphite negative electrode of the blank example at a rate of 1000 μL. The sample was then dried at 80 °C and assembled into a coin cell using the same method as the blank example.

[0093] The electrochemical performance of the coin cells obtained above was tested, and the test results are as follows: Figures 1 to 4 As shown in Table 1.

[0094] Table 1

[0095]

[0096] Combination Figures 1 to 4 As shown in Table 1, the lithium-ion battery of the present invention exhibits significantly better capacity and retention rate than the comparative example and the blank example after 500 cycles at 8C. This demonstrates that the lithium-ion battery of the present invention has excellent fast-charging performance and electrochemical performance.

[0097] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0098] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing a porous Li₂SiF₆ composite material, characterized in that, include: In an inert atmosphere, porous molecular sieves were mixed with LiPF6 solution and reacted. After the reaction was completed, porous Li2SiF6 composite material was obtained by separation.

2. The method for preparing the porous Li₂SiF₆ composite material according to claim 1, characterized in that, The porous molecular sieve has a pore size ≤2nm and a specific surface area of ​​300m². 2 / g-800m 2 / g, Si / Al is 1-10.

3. The method for preparing the porous Li₂SiF₆ composite material according to claim 1, characterized in that, The porous molecular sieve is selected from at least one of type A molecular sieve, type X molecular sieve, type Y molecular sieve, ZSM-5 molecular sieve, and mordenite.

4. The method for preparing the porous Li₂SiF₆ composite material according to claim 1, characterized in that, The concentration of LiPF6 in the LiPF6 solution is 0.5 mol / L-5 mol / L; And / or, in the step of mixing and reacting the porous molecular sieve with the LiPF6 solution, the mass ratio of the porous molecular sieve to the LiPF6 is 1:1 to 1:

10.

5. The method for preparing the porous Li₂SiF₆ composite material according to claim 1, characterized in that, In the step of mixing porous molecular sieves with LiPF6 solution and reacting them, the reaction temperature is 60℃-100℃ and the reaction time is 1h-10h.

6. A porous Li2SiF6 composite material obtained by the preparation method according to any one of claims 1 to 5.

7. A graphite negative electrode sheet, comprising a current collector and a graphite material layer attached to the surface of the current collector, characterized in that, The surface of the graphite material layer is also coated with a porous Li2SiF6 composite material coating.

8. The graphite negative electrode sheet according to claim 7, characterized in that, The mass of the porous Li2SiF6 composite material is 1 to 10 times the mass of graphite in the graphite material layer.

9. A method for preparing a graphite negative electrode sheet as described in claim 7 or claim 8, characterized in that, Includes the following steps: A prefabricated graphite negative electrode sheet is provided, the prefabricated graphite negative electrode sheet comprising a current collector and a graphite material layer attached to the surface of the current collector; The porous Li2SiF6 composite material was dispersed in an organic solvent to obtain a dispersion. The dispersion was placed on the surface of the graphite material layer of the pre-fabricated graphite anode sheet and dried to obtain the graphite anode sheet.

10. A lithium-ion battery, characterized in that, The graphite negative electrode sheet as described in claim 9 is used.

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