Graphite anode material coated with a solid electrolyte, method for preparing the same, and use

Abstract

This application discloses a graphite anode material coated with a solid electrolyte, a method for preparing the same, and its use. The graphite anode material comprises a substrate material and a solid electrolyte material coating the surface of the substrate material, wherein the solid electrolyte material comprises a Ti-containing solid electrolyte, and the Ti-containing solid electrolyte is Ti 3+ and Tire 4+ and Ti 3+ / Ti 4+ The molar ratio is y, where y satisfies 0.1 ≤ y ≤ 10, and the mass ratio of the Ti-containing solid electrolyte to the substrate material is x, where x satisfies 0.001 ≤ x ≤ 0.1. The Ti element in the solid electrolyte material according to this application possesses both lithium-ion conductivity and electronic conductivity, which can effectively improve the electrode reaction rate on the surface of the graphite anode material, and the graphite anode material has good rate performance and low-temperature performance.

Description

Technical Field

[0001] This application belongs to the technical field of anode materials for lithium-ion batteries, and specifically relates to a graphite anode material coated with a solid electrolyte, its preparation method, and its use.

[0002] Cross-reference to Related Applications This application claims priority based on a Chinese application filed with the Chinese Patent Office on July 16, 2024, with application number 202410947485.9 and title "Graphite Anode Material Coated with Solid Electrolyte, Its Preparation Method and Use", and all of its content is incorporated herein by reference.

Background Art

[0003] As an important energy storage device, lithium-ion batteries are widely used in fields such as consumer electronics, electro-mobility, and energy storage. As a negative electrode material commonly used in lithium-ion batteries, graphite materials have advantages such as high energy density, long cycle life, low cost, and environmental friendliness. However, graphite materials still have poor rate performance and the problem of lithium precipitation. Therefore, how to improve the electrochemical reaction process on the graphite surface to enhance the electrode reaction rate has become an important research direction in the field of graphite material preparation technology. As a solution in the prior art, mainly by coating the surface of graphite with conductive substances such as carbon nanotubes and metal nanoparticles, the electron conductivity can be effectively increased, the charge transfer resistance can be reduced, and the lithium diffusion coefficient can be increased. There is also research on increasing only the ion conductivity by coating the surface of graphite with a solid electrolyte. However, the conventional coating methods have the problem of uneven coating, which results in unstable performance of the graphite material and impaired battery performance. In addition, conventional coating methods such as magnetron sputtering have relatively high costs, so their use in mass production is greatly limited. The electrochemical reaction on the negative electrode surface needs to combine both ion conduction and electron conduction. However, many of the conventional coating methods cannot increase the electron conductivity and ion conductivity simultaneously, so the rate charge-discharge performance of the battery is limited, leading to the problem of lithium precipitation.

Summary of the Invention

[0004] The main object of this application is to provide a graphite negative electrode material coated with a solid electrolyte, its preparation method and use, which can simultaneously increase the ion conductivity and electron conductivity of the graphite negative electrode material, improve the problems of poor rate performance and lithium precipitation in the graphite material.

[0005] To achieve the above object of the invention, this application adopts the following technical solutions.

[0006] Embodiments of this application provide a graphite anode material coated with a solid electrolyte. The graphite anode material coated with a solid electrolyte comprises a substrate material and a solid electrolyte material coating the surface of the substrate material, wherein the solid electrolyte material contains a Ti-containing solid electrolyte, and the Ti-containing solid electrolyte contains Ti 3+ and Tire 4+ and Ti 3+ / Ti 4+ The molar ratio is y, where y satisfies 0.1 ≤ y ≤ 10, and the mass ratio of the Ti-containing solid electrolyte to the substrate material is x, where x satisfies 0.001 ≤ x ≤ 0.1.

[0007] Embodiments of this application further provide a method for preparing a graphite anode material coated with a solid electrolyte. The preparation method includes the steps of: mixing a first mixed solution containing at least a titanium source, a raw material that is easily hydrolyzable and difficult to complex, and a complexing agent; a second mixed solution containing at least a lithium source and a raw material that is not easily hydrolyzable and easily complex, adding a substrate material to obtain a third mixed solution; and freeze-drying the third mixed solution and subjecting it to heat treatment to obtain a graphite anode material coated with a solid electrolyte.

[0008] Embodiments of this application further provide the use of a graphite anode material coated with a solid electrolyte in the preparation of a negative electrode plate for a battery or a lithium-ion battery.

[0009] Embodiments of this application further provide a lithium-ion battery, the lithium-ion battery comprising at least the above-described graphite anode material coated with a solid electrolyte.

[0010] Compared to the prior art, this application has the following beneficial effects. The Ti element in the solid electrolyte material of the graphite anode material according to this application possesses both lithium ion conductivity and electronic conductivity, which can effectively improve the electrode reaction rate on the surface of the graphite anode material, and the graphite anode material has good rate performance and low-temperature performance.

[0011] To more clearly describe the embodiments of this application or the technical concepts in the prior art, the drawings used in the embodiments or the prior art are briefly described below. The drawings described are only a few embodiments of this application. A person skilled in the art can obtain other drawings based on these drawings without employing inventive capabilities. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic preparation flowchart of a graphite anode material coated with a solid electrolyte, according to a typical embodiment of this application. [Figure 2] This graph shows the fitting results of the XPS Ti2p spectrum of the sample according to Example 3 of this application. [Figure 3] This is a high-resolution SEM image of the graphite anode material according to Example 4 of this application. [Figure 4] This graph shows the fitting results of the XPS Ti2p spectrum of the sample according to Comparative Example 1 of this application. [Figure 5] This graph shows the fitting results of the XPS Ti2p spectrum of the sample according to Comparative Example 3 of this application. [Figure 6] This graph shows the lithium deposition status of pouch battery 10 at low temperatures in different embodiments and comparative examples of this application. [Figure 7] This is a schematic diagram showing the equivalent fitting circuit related to this application. [Modes for carrying out the invention]

[0013] In view of the shortcomings of the prior art, the inventors of this application provide the present invention through long-term research and extensive practical application. The present invention is described below clearly and completely. The embodiments described are only some, and not all, embodiments of this application. All other embodiments that a person skilled in the art could obtain without using their inventive ability based on the embodiments of this application are also within the scope of protection of this application.

[0014] Specifically, a graphite negative electrode material coated with a solid electrolyte according to one aspect of the technical solution of the present application includes a substrate material and a solid electrolyte material coating the surface of the substrate material, the solid electrolyte material includes a Ti-containing solid electrolyte, and the Ti-containing solid electrolyte contains Ti 3+ and Ti 4+ and contains Ti 3+ / Ti 4+ (Ti 3+ :Ti 4+ ) has a molar ratio of y, where y satisfies 0.1 ≦ y ≦ 10, and the mass ratio of the Ti-containing solid electrolyte to the substrate material (Ti-containing solid electrolyte: substrate material) is x, where x satisfies 0.001 ≦ x ≦ .1.

[0015] [[ID=]15] The solid electrolyte material coating the surface of the substrate material according to the present application is a solid electrolyte containing Ti element. Different from the conventional lithium ion solid electrolyte, the solid electrolyte containing Ti element has both lithium ion conductivity and electron conductivity, can accelerate the electrode reaction, and can effectively improve the reaction rate on the surface of the graphite negative electrode material. The property that the solid electrolyte containing Ti element has both lithium ion conductivity and electron conductivity is realized by adjusting the valence of Ti element in the material and the ratio of Ti elements with different valences.

[0016] In some preferred embodiments, the molar ratio y of the Ti 3+ / Ti 4+ satisfies 0.5 ≦ y ≦ 7.5.

[0017] In some preferred embodiments, the mass ratio x of the Ti-containing solid electrolyte to the substrate material satisfies 0.005 ≦ x ≦ 0.05.

[0018] In this application, graphite is coated with a solid electrolyte, but if the coating amount is too small, the solid electrolyte cannot cover the graphite surface where it is needed, thus limiting the improvement of the reaction rate on the surface of the graphite anode. Furthermore, since the solid electrolyte itself cannot provide capacity, the specific capacity of the graphite anode material decreases as the amount of solid electrolyte coating increases, and there is an upper limit to the coating amount, so the amount of solid electrolyte coating has a preferred range.

[0019] In some preferred embodiments, the Ti 3+ / Ti 4+ The molar ratio y and the mass ratio x of the Ti-containing solid electrolyte to the substrate material satisfy 6 ≤ y + 2.044x ≤ 8.

[0020] In some preferred embodiments, the solid electrolyte material uniformly coats the surface of the substrate material in a dotted or island-like manner.

[0021] In some preferred embodiments, the particle size D50 of the solid electrolyte material is 10 to 500 nm.

[0022] In some preferred embodiments, the substrate material includes, but is not limited to, artificial graphite and / or natural graphite.

[0023] In some preferred embodiments, the Ti-containing solid electrolyte includes, but is not limited to, one or more of the following: lithium lanthanum titanate solid electrolyte, lithium aluminum titanium phosphate solid electrolyte, and Ti-doped lithium lanthanum zirconate solid electrolyte.

[0024] The graphite anode material according to this application comprises a substrate material and a solid electrolyte material coating the surface of the substrate material. The solid electrolyte material coats the substrate material in a point-like or island-like manner (having a certain area), covering a portion of the graphite surface, and the coating is relatively uniform. The size of the solid electrolyte material is generally nanoscale, measured to be 10-500 nm by observation with an electron microscope. Such a coating structure significantly increases the contact area between the solid electrolyte and the substrate material, effectively increasing the electron and ion transfer rate on the surface of the graphite anode material, and improving rate performance and low-temperature performance. The solid electrolyte material coating the surface of the substrate material contains trivalent and tetravalent Ti elements, and the crystal contains ions of the same element in different oxidation states, allowing charge to move between ions in different oxidation states. As a result, the electronic conductivity of the solid electrolyte itself is significantly improved compared to the electronic conductivity of a solid electrolyte containing only tetravalent Ti elements. Conventional solid electrolytes are merely good conductors of lithium ions, while the Ti-containing solid electrolyte according to this application can effectively conduct lithium ions and electrons, that is, it is a good conductor of both lithium ions and electrons. In such a solid electrolyte that is a good conductor of both lithium ions and electrons, Ti 3+ and Ti 4+ The titanium source used in the preparation contains tetravalent Ti only and does not contain trivalent Ti, and is contained in a specific ratio. To obtain trivalent Ti, it is essential to utilize an appropriate mixing ratio of solid electrolyte and graphite under a non-oxidizing atmosphere. In this mixture, the carbon material acts as a reducing agent, reducing some of the tetravalent Ti in the solid electrolyte to trivalent Ti, while the non-oxidizing atmosphere prevents oxidation of the carbon material and trivalent Ti. The purpose of setting specific heat treatment temperatures and holding times is to obtain the desired solid electrolyte material and relatively high lithium ion conductivity. Under the required process conditions, the above heat treatment can yield a negative electrode material coated with a solid electrolyte that possesses both high lithium ion conductivity and high electronic conductivity.

[0025] Another embodiment of the present invention further provides a method for preparing a graphite anode material coated with a solid electrolyte. The preparation method includes the steps of: mixing a first mixed solution containing at least a titanium source, a raw material that is easily hydrolyzable and difficult to complex, and a complexing agent; a second mixed solution containing at least a lithium source and a raw material that is not easily hydrolyzable and easily complex, adding a substrate material to obtain a third mixed solution; and freeze-drying the third mixed solution and subjecting it to heat treatment to obtain a graphite anode material coated with a solid electrolyte.

[0026] In some preferred embodiments, the titanium source is C 16 H 36 O4Ti and / or Ti4(OCH3) 16 This includes, but is not limited to, the following:

[0027] In some preferred embodiments, the readily hydrolyzable and complex-resistant raw materials are Al(NO3)3·9H2O, C9H 21 This includes, but is not limited to, one or more combinations of AlO3, Al(NO3)3, ZrO(NO3)2, and La(NO3)3.

[0028] In some preferred embodiments, the complexing agent includes, but is not limited to, one or more of the following: citric acid, malic acid, malonic acid, succinic acid, lactic acid, and ethylenediaminetetraacetic acid.

[0029] In some preferred embodiments, the lithium source includes, but is not limited to, one or more combinations of LiOH, Li2CO3, and LiNO3.

[0030] In some preferred embodiments, the raw material that is not easily hydrolyzed and readily forms complexes includes, but is not limited to, NH4H2PO4.

[0031] In some preferred embodiments, the first mixed solution further comprises a first solvent, the first solvent comprising, but not limited to, one or more of anhydrous ethanol, isopropyl alcohol, and methanol.

[0032] In some preferred embodiments, the second mixed solution further comprises a second solvent, the second solvent comprising, but not limited to, one or more of anhydrous ethanol, isopropyl alcohol, and methanol.

[0033] In some preferred embodiments, the molar ratio of the complexing agent to the total number of moles of metal ions other than lithium ions in the raw material, which is easily hydrolyzable and difficult to form complexes with, is 0.7 to 5:1.

[0034] In some preferred embodiments, the molar ratio of the titanium source to the raw material that is easily hydrolyzable and difficult to complex form is 0.1 to 9:1.

[0035] In some preferred embodiments, the molar ratio of the titanium source to the raw material that is not easily hydrolyzed and is easily complex-forming is 0.02 to 10:1.

[0036] In some preferred embodiments, the molar ratio of titanium to lithium source is 0.02 to 12:1.

[0037] In some preferred embodiments, the mass ratio of the titanium source to the substrate material is 0.002:0.3.

[0038] In some preferred embodiments, the heat treatment temperature is 500 to 1200°C.

[0039] In some preferred embodiments, the heat treatment time is 4 to 15 hours.

[0040] In some preferred embodiments, the atmosphere used for the heat treatment is a non-oxidizing atmosphere, which includes, but is not limited to, one or more combinations of nitrogen gas, argon gas, helium gas, or a mixture of argon gas and hydrogen gas.

[0041] In some more specific embodiments, the above method for preparing a graphite anode material coated with a solid electrolyte includes the following steps.

[0042] Step 1: Dissolve the titanium source, a raw material that is easily hydrolyzable and difficult to form complexes with, and a complexing agent in a solvent to obtain a first mixed solution.

[0043] Step 2: Dissolve the lithium source and a raw material that is not easily hydrolyzed and readily forms complexes in a solvent to obtain a second mixed solution.

[0044] Step 3: Mix the first and second mixed solutions, add graphite, and obtain the third mixed solution.

[0045] Step 4: Freeze-dry the third mixed solution to obtain a dried powder.

[0046] Step 5: The dried powder is heat-treated to obtain a graphite material coated with a solid electrolyte.

[0047] The Ti-containing solid electrolyte includes one or more types of solid electrolytes such as lithium lanthanum titanate solid electrolyte, lithium aluminum titanium phosphate solid electrolyte, and lithium lanthanum zirconate solid electrolyte.

[0048] Optionally, in some embodiments of this application, the third mixed solution comprises LiNO3, La(NO3)3 and C 16 H 36 Includes O4Ti.

[0049] Optionally, in some embodiments of this application, the complexing agent is one or more of citric acid, malic acid, malonic acid, succinic acid, lactic acid, and ethylenediaminetetraacetic acid.

[0050] Optionally, in some embodiments of this application, the third mixed solution in step 4 can be dried using a freeze-drying method to uniformly coat the graphite anode material with the Ti-containing solid electrolyte.

[0051] Optionally, in some embodiments of this application, the heat treatment is performed with a holding temperature range of 500°C to 1200°C, a holding time of 4 hours to 15 hours, and using a nitrogen gas atmosphere.

[0052] In this application, a graphite anode material coated with a solid electrolyte that exhibits relatively excellent overall performance under appropriate heat treatment conditions (temperature, time, atmosphere) is described, wherein the mass ratio x of the solid electrolyte to the graphite and Ti are... 3+ / Ti 4+ The ratio y has an optimal range, that is, it satisfies 6 ≤ y + 2.044x ≤ 8, and this range is obtained by linear fitting.

[0053] In some preferred embodiments, Figure 1 is a schematic preparation flowchart of a graphite anode material coated with a solid electrolyte according to the present application.

[0054] Other embodiments of the present application further provide the use of a graphite anode material coated with a solid electrolyte in the preparation of a negative electrode plate for a battery or a lithium-ion battery.

[0055] Other embodiments of the present application further provide a lithium-ion battery comprising at least the above-described graphite anode material coated with a solid electrolyte.

[0056] The technical concept of this application will be described in more detail below with reference to several preferred embodiments and drawings. These embodiments are based on the technical concept of the invention and describe detailed embodiments and specific operating procedures, but the scope of protection of this application is not limited to the embodiments described below.

[0057] Unless otherwise noted, the test materials used in the following examples are all readily available from general biochemical reagent companies.

[0058] Example 1 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.04 g of malonic acid were added in order to obtain the first mixed solution.

[0059] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.50 g of NH4H2PO4 were added to obtain the second mixed solution.

[0060] Step 3: The second mixed solution and the first mixed solution were mixed, 955.03 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0061] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0062] Step 5: The finely ground powder was heat-treated and kept at 600 degrees Celsius for 15 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.6 That was the case.

[0063] Example 2 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.04 g of malonic acid were added in order to obtain the first mixed solution.

[0064] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.47 g of NH4H2PO4 were added to obtain the second mixed solution.

[0065] Step 3: The second mixed solution and the first mixed solution were mixed, 191.00 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0066] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0067] Step 5: The finely ground powder was heat-treated and kept at 900 degrees Celsius for 8 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.55 That was the case.

[0068] Example 3 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.18 g of succinic acid were added in order to obtain the first mixed solution.

[0069] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.47 g of NH4H2PO4 were added to obtain the second mixed solution.

[0070] Step 3: The second mixed solution and the first mixed solution were mixed, 19.10 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0071] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0072] Step 5: The finely ground powder was heat-treated and kept at 1200 degrees Celsius for 4 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.55 That was the case.

[0073] Example 4 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0074] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.46 g of NH4H2PO4 were added to obtain the second mixed solution.

[0075] Step 3: The second mixed solution and the first mixed solution were mixed, 127.34 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0076] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0077] Step 5: The finely ground powder was heat-treated and kept at 925°C for 6 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.53 That was the case.

[0078] Example 5 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 3.4 g of Ti(OC4H9)4, 2.42 g of La(NO3)3·6H2O, and 3 g of citric acid were added in order to obtain the first mixed solution.

[0079] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.23 g of LiNO3 was added to obtain the second mixed solution.

[0080] Step 3: The second mixed solution and the first mixed solution were mixed, 117.3 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0081] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0082] Step 5: The finely ground powder was heat-treated and kept at 880 degrees Celsius for 6 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte.

[0083] The graphite anode material coated with a solid electrolyte according to this embodiment has performance equivalent to that of Example 1, and the coin cell prepared therefrom also has performance equivalent to that of Example 1.

[0084] Example 6 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, the following raw materials were added in order: 0.43 g of Ti(OC4H9)4, 12.99 g of La(NO3)3·6H2O, 2.31 g of ZrO(NO3)2·6H2O, and 5.04 g of citric acid to obtain the first mixed solution.

[0085] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 2.07 g of LiNO3 was added to obtain the second mixed solution.

[0086] Step 3: The second mixed solution and the first mixed solution were mixed, 117.3 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0087] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0088] Step 5: The finely ground powder was heat-treated and kept at 900 degrees Celsius for 8 hours under a nitrogen gas atmosphere to obtain a graphite anode material coated with a solid electrolyte. Here, the solid electrolyte is Li6Ti 0.25 La3Zr2O 11.905 That was the case.

[0089] The graphite anode material coated with a solid electrolyte according to this embodiment has performance equivalent to that of Example 1, and the coin cell prepared therefrom also has performance equivalent to that of Example 1.

[0090] Comparative Example 1 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0091] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.44 g of NH4H2PO4 were added to obtain the second mixed solution.

[0092] Step 3: The second mixed solution and the first mixed solution were mixed, 3820.11 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0093] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0094] Step 5: The finely ground powder was heat-treated and kept at 925°C for 6 hours under a nitrogen gas atmosphere to obtain the graphite anode material. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.51 That was the case.

[0095] Comparative Example 2 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0096] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.51 g of NH4H2PO4 were added to obtain the second mixed solution.

[0097] Step 3: The second mixed solution and the first mixed solution were mixed, 19.10 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0098] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0099] Step 5: The finely ground powder was heat-treated at 925°C for 6 hours under a nitrogen gas atmosphere to obtain a graphite anode material. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.62 That was the case.

[0100] Comparative Example 3 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0101] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.72 g of NH4H2PO4 were added to obtain the second mixed solution.

[0102] Step 3: The second mixed solution and the first mixed solution were mixed, 127.34 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0103] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0104] Step 5: The finely ground powder was heat-treated and kept at 925°C for 6 hours in an air atmosphere to obtain the graphite anode material. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4)3 was 3.

[0105] Comparative Example 4 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0106] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.55 g of NH4H2PO4 were added to obtain the second mixed solution.

[0107] Step 3: The second mixed solution and the first mixed solution were mixed, 127.34 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0108] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0109] Step 5: The finely ground powder was heat-treated and kept at 400 degrees Celsius for 6 hours under a nitrogen gas atmosphere to obtain the graphite anode material. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.7 That was the case.

[0110] Comparative Example 5 Step 1: First, 150 mL of anhydrous ethanol was added to a beaker, and a stirring bar was inserted and the mixture was magnetically stirred. After the first raw material was completely dissolved, 2.72 g of Ti(OC4H9)4, 0.75 g of Al(NO3)3·9H2O, and 1.92 g of citric acid were added in order to obtain the first mixed solution.

[0111] Step 2: First, 150 mL of anhydrous ethanol was added to the beaker, and then 0.48 g of LiNO3 and 1.45 g of NH4H2PO4 were added to obtain the second mixed solution.

[0112] Step 3: The second mixed solution and the first mixed solution were mixed, 127.34 g of graphite was added, and after thorough stirring, the third mixed solution was obtained.

[0113] Step 4: Freeze-dry the third mixed solution. First, the solution was frozen with liquid nitrogen, and then dried using a freeze-dryer to obtain a dried powder.

[0114] Step 5: The finely ground powder was heat-treated and kept at 1350 degrees Celsius for 6 hours under a nitrogen gas atmosphere to obtain the graphite anode material. Here, the solid electrolyte is Li 1.4 Al 0.4 Ti 1.6 (PO4) 2.52 That was the case.

[0115] The following describes a method for preparing a battery using the graphite anode material related to this application.

[0116] Preparation of a coin half cell A negative electrode aqueous slurry was prepared by uniformly mixing a graphite material coated with a solid electrolyte, a conductive agent, and a binder in a mass ratio of 92:5:3. This negative electrode aqueous slurry was applied to a Cu foil current collector and vacuum-dried at 90 degrees Celsius to prepare a negative electrode plate. In a glove box, the lithium sheet, separator, and negative electrode plate were assembled using a coin-type battery case, the electrolyte was added dropwise, sealed, and pressed to obtain an assembled CR2032 coin half-cell.

[0117] Preparation of pouch batteries A positive electrode NMP slurry was prepared by uniformly mixing lithium cobalt oxide positive electrode active material, a conductive agent, and a binder. This positive electrode NMP slurry was applied to an Al foil and vacuum-dried to prepare the positive electrode. A negative electrode aqueous slurry was prepared by uniformly mixing a graphite material coated with a solid electrolyte, a conductive agent, and a binder in a mass ratio of 97:1.5:1.5. This slurry was applied to a Cu foil and vacuum-dried to prepare the negative electrode. A pouch battery was assembled using the above positive electrode plate, negative electrode plate, a separator coated with LLZO, and a commercially available electrolyte.

[0118] The following describes the preparation of a solid electrolyte coated on the surface of the graphite anode material according to this application, and the method for measuring its performance parameters.

[0119] Preparation of solid electrolyte powders The only difference from the other embodiments was that graphite was not added in step 3; the other steps were the same as in the other embodiments. Then, high-energy planetary ball milling was performed on the powder. The conditions for ball milling were as follows: 6 mm zirconia balls were used, the mass ratio of zirconia balls to solid electrolyte material was 4:1, the mass ratio of isopropyl alcohol (abrasive media) to solid electrolyte material was 3:1, the rotation speed was 450 rpm, and the ball milling time was 9 hours. After ball milling, the powder was dried at 80 degrees for 24 hours and polished for 15 minutes.

[0120] Measurement of ionic conductivity Preparation of solid electrolyte sheets First, the obtained solid electrolyte powder material was polished in an agate mortar for 20 minutes. A 1g sample of the powder was taken and pressed using a 1 / 2-inch diameter mold, then pressed using a hand press machine at a pressing pressure of 300 MPa. The pressed electrolyte sheet was then heat-treated in a box furnace under a nitrogen gas atmosphere. The heat treatment conditions were 1150 degrees Celsius for 6 hours, with a heating rate of 3°C / min, and cooling was performed using furnace cooling. After heat treatment, a densely sintered solid electrolyte sheet was obtained.

[0121] Preparation of PEO-LiTFSI film PEO-LiTFSI films were prepared using PEO (polyethylene oxide, molecular weight 4,000,000), LiTFSI (99.95%), and acetonitrile (99.8%). Water was removed by vacuum drying of PEO and LiTFSI at 60°C for 24 hours. The polymers and salts were weighed in an argon gas glove box until the EO:Li ratio was 6:1 (molar ratio). First, LiTFSI was dissolved in acetonitrile to make a clear solution, and then PEO was slowly added to the solution and stirred at room temperature for 24 hours and then at 60°C for 12 hours to completely dissolve it. The PEO / LiTFSI solution was placed in a polytetrafluoroethylene mold, stirred as needed to remove bubbles, and then allowed to stand and cool. After vacuum drying for 24 hours, a PEO-LiTFSI film was obtained.

[0122] PEO-LiTFSI film can block electrons, but Li in the low frequency range. + This does not hinder the transport of the material. A PEO-LiTFSI film was pressed onto both sides of a solid electrolyte sheet, and then a Li sheet was pressed onto the PEO-LiTFSI film. Using a battery mold, a structure of Li-PEO-LiTFSI-solid electrolyte sheet-PEO-LiTFSI-Li was assembled, and EIS measurements were performed.

[0123] EIS measurements were performed using an electrochemical workstation, with a measurement voltage of 50mV and a frequency range of 300mHz to 7MHz. The equivalent fitting circuit used after the measurement is shown in Figure 7. The fitting process resulted in R B and R GB Obtain the respective values ​​of R B and R GB The sum of these is the total resistance R. Ionic conductivity: σ = d / (R × S), where d is the thickness of the solid electrolyte sheet (cm), R is the total resistance of the solid electrolyte (Ω), and S is the effective area of ​​the electrode (cm²). 2 )

[0124] Measurement of electronic conductivity The powder used for measuring the electronic conductivity was a solid electrolyte powder, and the measurement method was carried out in accordance with the relevant provisions of GB / T 40007-2021 General Rules for Contact Measurement Method of Resistivity of Nanotechnology Nanomaterials. The measurement result was the electronic conductivity of the material when the pressing force was 4 kN.

[0125] The following describes the measurement methods for each performance parameter of the graphite anode material related to this application.

[0126] XPS measurement A Thermo Scientific K-Alpha was used as the measuring instrument. An appropriate amount of sample was taken, pressed onto a sheet, and attached to a sample dish. The sample was placed in the sample chamber of the Thermo Scientific K-Alpha XPS instrument. When the pressure in the sample chamber was less than 2.0 × 10⁻⁷ mbar, the sample was placed in the analysis chamber. The spot size was 400 μm, the operating voltage was 12 kV, the filament current was 6 mA, the narrow canvas energy was 50 eV, and the step size was 0.1 eV. The XPS data was processed using Avantage software, and fitting was mainly performed on the Ti 2p spectrum. After fitting, Ti 3+ and Tire 4+ The ratio of the content was obtained.

[0127] Measurement of median diameter The measurement method was performed in accordance with the relevant regulations for GB / T19077 particle size analysis laser diffraction.

[0128] Measurement of specific surface area The measurement method was carried out in accordance with the relevant regulations for the measurement of the specific surface area of ​​solids by the gas adsorption BET method, GB / T19587.

[0129] Measurement of tap density The measurement method was carried out in accordance with the relevant regulations for the measurement of metal powder tap density, GB / T5162.

[0130] Measurement of compact density The measurement method was carried out in accordance with the relevant provisions for measurement of standard GB / T 24533-2019 "Graphite-based anode materials for lithium-ion batteries".

[0131] Measurement of coin-cell batteries Capacity and initial Coulomb efficiency We assembled CR2032 coin-type semi-solid batteries and evaluated their cycle performance. We compared the initial discharge capacity and charge / discharge efficiency with graphite-Li batteries at voltages ranging from 0.005 to 1.5V and a current of 0.05C.

[0132] Measurement of pouch batteries Rate discharge measurement (1) First, the pouch battery was charged to 4.35V at a constant current and voltage of 0.5C with a cutoff current of 0.05C, left standing for 5 minutes, and then discharged to 3V at a constant current of 1C, left standing for 5 minutes. (2) Next, it was charged to 4.35V at a constant current and voltage of 0.5C with a cutoff current of 0.05C, left standing for 5 minutes, and then discharged to 3V at a constant current of 3C, left standing for 5 minutes. The ratio of the discharge capacity at 3C to the discharge capacity at 1C was calculated. (3) Next, it was charged to 4.35V at a constant current and voltage of 0.5C with a cutoff current of 0.05C, left standing for 5 minutes, and then discharged to 3V at a constant current of 5C, left standing for 5 minutes. The discharge capacity at 5C and the discharge capacity at 1C were compared, and the ratio of both was calculated.

[0133] Rate charging measurement (1) First, the pouch battery was charged to 4.35V at a constant current and voltage of 0.2C, with a cutoff current of 0.05C, and left to stand for 5 minutes. Then, it was discharged to 3V at a constant current of 0.5C and left to stand for 5 minutes. (2) Next, it was charged to 4.35V at a constant current and voltage of 2.5C, with a cutoff current of 0.05C, and left to stand for 5 minutes. Then, it was discharged to 3V at a constant current of 0.5C and left to stand for 5 minutes. The charging capacity at 2.5C and the charging capacity at 0.2C were compared, and the ratio of the two was calculated.

[0134] Low-temperature cycle at 0 degrees The battery cycle performance was evaluated using pouch batteries, and the capacity retention rate after 50 cycles was calculated for lithium cobalt oxide-graphite systems at a voltage of 3 to 4.35 V, a current of 0.2 C, and a temperature of 0 degrees Celsius.

[0135] Measurement of lithium deposition at low temperatures (1) First, the pouch battery was left standing in a constant temperature chamber at 10 degrees Celsius for 5 minutes, then discharged to 3V at a constant current of 1C, and left standing for 4 hours. (2) After standing for 5 minutes, it was charged to 4.35V at a constant current and voltage of 2C, with a cutoff current of 50mA, and then left standing for another 5 minutes, and discharged to 3V at a constant current of 2C. (3) Step (2) was repeated, and the battery was charged and discharged 10 times at 2C. (4) The battery was disassembled in a glove box, the negative electrode plate was removed, and the state of lithium deposition was observed. If the electrode plate was golden in color and there was no black substance, it indicated that lithium had not been deposited, and if there was a black substance on the electrode plate, it indicated that lithium had been deposited.

[0136] Measurements were performed on graphite anode materials according to Examples 1 to 4 and Comparative Examples 1 to 5, and the measurement results are shown in Tables 1 to 4.

[0137] [Table 1]

[0138] Table 1 summarizes the material ratios and the ratios of the content of two types of valence titanium for four examples and five comparative examples. Examples 1 to 4 each employ different solid electrolyte coating ratios, i.e., different solid electrolyte to graphite mass ratios, and XPS fitting was used to determine the Ti content of the material. 3+ / Ti 4+The ratio (Figures 2, 4, and 5 show the XPS Ti2p spectral fitting results for Example 3, Comparative Example 1, and Comparative Example 3, respectively) is obtained, and this value is determined by specific preparation process parameters including the coating ratio, heat treatment temperature, time, and atmosphere. Under the same process conditions, considering the role of graphite as a reducing agent, the reducing agent content decreases, the mass ratio of solid electrolyte to graphite increases, and accordingly Ti 3+ / Ti 4+ The ratio becomes smaller. For example, Comparative Example 1 has a relatively lower solid electrolyte content than Example 4, and the obtained Ti 3+ / Ti 4+ The ratio was large. The solid electrolyte content in Comparative Example 2 was relatively high, and the obtained Ti 3+ / Ti 4+ The ratio was smaller than in Example 4.

[0139] In Comparative Example 3, heat treatment was performed using an air atmosphere, but trivalent Ti could not be obtained under an oxidizing atmosphere, and oxidation loss of graphite occurred. The material that could be prepared in this way was mainly solid electrolyte powder.

[0140] As revealed by specific experiments, the mass ratio x of the solid electrolyte and graphite and Ti 3+ / Ti 4+ The ratio y has an optimal range, that is, it satisfies 6 ≤ y + 2.044x ≤ 8, and this range is obtained by linear fitting. Of the above examples and comparative examples, Example 4 falls within this preferred range. The morphology of the material prepared in Example 4 is shown in Figure 3, in which nanoscale solid electrolyte particles are dispersed relatively uniformly on the surface of the graphite substrate material, and most of the solid electrolyte particles were about 50 nm in size.

[0141] [Table 2]

[0142] Table 2 shows the performance measurement results of materials from different examples and comparative examples, mainly summarizing the ionic conductivity, electronic conductivity, and other properties of the materials.

[0143] The material prepared in Comparative Example 3 was mainly a solid electrolyte powder, and its electronic conductivity decreased significantly, to only 1.7 × 10⁻⁶. -8 The density was only S / cm, and the particle size, tap density, and pressure density of the corresponding material were smaller than in other examples. Furthermore, because small particles of the solid electrolyte were obtained, the specific surface area was larger than in other examples.

[0144] Comparative Example 4 employed a lower heat treatment temperature than Example 4, and Comparative Example 5 employed a higher heat treatment temperature than Example 4. Neither of these two heat treatment temperatures falls within the temperature range required to obtain the desired solid electrolyte. At these two heat treatment temperatures, the coating material on the surface of the resulting substrate does not have good lithium ion conductivity. The lithium ion conductivity obtained by measurement was 10 in both cases. -7 This was a scale-based measurement and was far lower than the ionic conductivity of Example 4.

[0145] [Table 3]

[0146] Tables 3 and 4 show the measurement results for coin-type and pouch batteries prepared with solid electrolyte materials. The capacity of a coin-type battery is affected by the solid electrolyte content, and since the solid electrolyte itself does not have capacity, the higher the solid electrolyte content, the lower the capacity of the corresponding coin-type battery.

[0147] As shown in Table 4, the rate discharge and rate charge performance of the graphite material coated with a solid electrolyte were significantly improved compared to the comparative example. This is mainly because the solid electrolyte coating the surface of the substrate material has high ionic conductivity and high electronic conductivity. Example 4 has optimal ionic conductivity and electronic conductivity, and consequently, optimal rate charge and rate discharge performance. As shown in Figure 6, the improved rate performance of the graphite resulted in relatively good capacity retention and lithium deposition results at 0 degrees Celsius for 50 cycles in the low-temperature test, corresponding to the example.

[0148] [Table 4]

[0149] Furthermore, the inventors of this application conducted experiments with other raw materials, process operations, and process conditions described herein, referring to the above examples, and obtained relatively ideal results in all cases.

[0150] The technical invention of this application is not limited to the specific embodiments described above. Any modifications made to the technical invention of this application without departing from the spirit and claims of this application are also within the scope of protection of this application. [Industrial applicability]

[0151] This application provides a graphite anode material coated with a solid electrolyte, a method for preparing the same, and its use. The Ti element in the solid electrolyte material possesses both lithium-ion conductivity and electronic conductivity, which can effectively improve the electrode reaction rate on the surface of the graphite anode material, and the graphite anode material has good rate performance and low-temperature performance.

[0152] Furthermore, the graphite anode material coated with a solid electrolyte, its preparation method, and its use described in this application are feasible and can be widely used in the field of lithium-ion battery anode materials.

Claims

1. The material comprises a substrate material and a solid electrolyte material that coats the surface of the substrate material, wherein the solid electrolyte material contains a Ti-containing solid electrolyte. The Ti-containing solid electrolyte is Ti ３＋ and Ti ４＋ and Ti ３＋ / Ti ４＋ The molar ratio is y, where y satisfies 0.1 ≤ y ≤ 10, and the mass ratio of the Ti-containing solid electrolyte to the substrate material is x, where 0.001 ≤ x ≤ 0.

1. A graphite anode material coated with a solid electrolyte characterized by the following.

2. The Ti ３＋ / Ti ４＋ The molar ratio y satisfies 0.5 ≤ y ≤ 7.

5. and / or, the mass ratio x of the Ti-containing solid electrolyte to the substrate material satisfies 0.005 ≤ x ≤ 0.

05. and / or the Ti ３＋ / Ti ４＋ The molar ratio y and the mass ratio x of the Ti-containing solid electrolyte to the substrate material satisfy 6 ≤ y + 2.044x ≤ 8. A graphite anode material coated with the solid electrolyte described in feature 1.

3. The solid electrolyte material uniformly covers the surface of the substrate material in a dotted or island-like manner. A graphite anode material coated with the solid electrolyte described in feature 1.

4. The particle size D50 of the solid electrolyte material is 10 to 500 nm. and / or, the substrate material includes artificial graphite and / or natural graphite, and / or, the Ti-containing solid electrolyte includes one or a combination of any one of the following: lithium lanthanum titanate solid electrolyte, lithium aluminum titanium phosphate solid electrolyte, and Ti-doped lithium lanthanum zirconate solid electrolyte. A graphite anode material coated with the solid electrolyte described in feature 1.

5. A method for preparing a graphite anode material coated with a solid electrolyte according to any one of claims 1 to 4, A first mixed solution containing at least a titanium source, a raw material that is easily hydrolyzed and difficult to form complexes with, and a complexing agent; a second mixed solution containing at least a lithium source and a raw material that is not easily hydrolyzed and easily forms complexes; a base material is added to this mixture to obtain a third mixed solution; The process includes the step of freeze-drying the third mixed solution and then heat-treating it to obtain a graphite anode material coated with a solid electrolyte. A method for preparing a graphite anode material coated with a solid electrolyte, characterized by the following:

6. The titanium source is C １６ H ３６ O ４ Ti and / or Ti ４ (OCH ３ ) １６ ), and / or the raw material having the above-mentioned easy hydrolysis property and being difficult to form a complex is Al(NO ３ ) ３ ·9H ２ O, C ９ H ２１ AlO ３ , Al(NO ３ ) ３ , ZrO(NO ３ ) ２ , La(NO ３ ) ３ , and includes any one or a combination of multiple kinds thereof, and / or the complexing agent includes any one or a combination of multiple kinds of citric acid, malic acid, malonic acid, succinic acid, lactic acid, ethylenediaminetetraacetic acid, and / or, the lithium source is LiOH, Li ２ CO ３ LiNO ３ The raw materials include any one or a combination of any of the following, and / or the raw materials that are not easily hydrolyzed and are easily complex-forming are NH ４ H ２ PO ４ Includes, and / or, the first mixed solution further comprises a first solvent, the first solvent comprising one or more of anhydrous ethanol, isopropyl alcohol, and methanol, and / or, the second mixed solution further comprises a second solvent, the second solvent comprising one or more of the following: anhydrous ethanol, isopropyl alcohol, and methanol. A method for preparing a graphite anode material coated with a solid electrolyte as described in feature 5.

7. The molar ratio of the complexing agent to the total number of moles of metal ions other than lithium ions in the raw material, which is easily hydrolyzable and difficult to form complexes with, is 0.7 to 5:

1. And / or, the molar ratio of the titanium source to the raw material that is easily hydrolyzable and difficult to form complexes with is 0.1 to 9:

1. And / or, the molar ratio of the titanium source to a raw material that is not easily hydrolyzed and is easily complex-forming is 0.02 to 10:

1. and / or, the molar ratio of titanium to lithium source is 0.02 to 12:

1. And / or, the mass ratio of the titanium source to the substrate material is 0.002:0.

3. A method for preparing a graphite anode material coated with a solid electrolyte as described in claim 5, characterized in that it is a graphite anode material.

8. The temperature of the heat treatment is 500 to 1200°C. and / or, the duration of the heat treatment is 4 to 15 hours. and / or, the atmosphere used for the heat treatment is a non-oxidizing atmosphere, and the non-oxidizing atmosphere includes one or more of the following gases: nitrogen gas, argon gas, helium gas, or a mixture of argon gas and hydrogen gas. A method for preparing a graphite anode material coated with a solid electrolyte as described in claim 5, characterized in that it is a graphite anode material.

9. Use of a graphite anode material coated with a solid electrolyte according to any one of claims 1 to 4 in the preparation of a battery anode plate or a lithium-ion battery.

10. The invention comprises at least a graphite anode material coated with the solid electrolyte described in any one of claims 1 to 4. A lithium-ion battery characterized by the following features.

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