A soluble solid-state battery anode material, anode sheet, preparation method and application

Abstract

The present invention discloses a soluble solid-state battery negative electrode material, comprising 70-90 parts of graphite, 4-12 parts of polyvinyl alcohol, and a solid electrolyte Li7La3Zr2O 12 5 to 13 parts of polyvinyl alcohol and 1 to 5 parts of a conductive agent; the polyvinyl alcohol is a medium molecular weight polyvinyl alcohol with a molecular weight of 120,000 to 150,000, and the conductive agent is carbon black or carbon nanotubes; also disclosed are a negative electrode plate, a preparation method thereof, and a lithium battery; the PVA and LLZO of the present invention can form a composite network structure in the negative electrode material, tightly wrapping the active material graphite to form a stable interface layer, such a structure can further improve the wettability and stability of the electrode and the ionic conductivity, thereby improving the performance of the battery, and can also inhibit the volume expansion and contraction of the graphite negative electrode material during the charge and discharge process, reduce the shedding and pulverization of the material, and improve the cycle life of the battery.

Description

Technical Field

[0001] This invention patent belongs to the field of electrochemical energy storage, specifically relating to a soluble solid-state battery anode material, as well as the anode sheet, preparation method, and application in lithium batteries. Background Technology

[0002] Lithium-ion batteries are widely used in electrochemical energy storage devices and power applications due to their high energy density, long cycle life, and low cost. However, the liquid electrolytes used in commercial lithium-ion batteries present safety issues, such as thermal runaway, leakage, and fire. Solid-state batteries, as a novel battery technology, use solid electrolytes to replace liquid electrolytes, offering the potential to solve these safety problems. In solid-state batteries, the anode material is crucial to battery performance. Research on anode materials for solid-state batteries mainly focuses on lithium metal and silicon-carbon composites. Lithium metal anodes offer high energy density but suffer from lithium dendrite growth and interfacial instability. Based on recent research, the main challenges in solid-state battery anode material research include interfacial reactions, lithium dendrite growth, and the interfacial physical contact between the solid electrolyte and the anode material. These issues can lead to performance degradation and safety hazards.

[0003] In recent years, research institutions and enterprises have made significant progress in the research of solid-state battery anode materials. For example, by optimizing the materials and structure of solid electrolytes, their interfacial stability with lithium metal anodes has been improved; and by using novel positive and negative electrode materials, such as silicon-carbon anodes and lithium-rich cathodes, energy density and cycle stability have been enhanced. Furthermore, some emerging companies are actively promoting the research and application of solid-state batteries, injecting new vitality into their development.

[0004] However, most existing solid-state anode materials still suffer from problems such as low ionic conductivity, poor interfacial compatibility leading to lithium dendrite growth, weak effective contact between the electrode and electrolyte, low ion transport kinetics in solid materials resulting in excessive interfacial impedance, and negatively impacting battery charge-discharge performance and energy density. In addition, existing anode materials mostly use oily binders, which are not easy to dissolve and are not conducive to the subsequent recycling of anode materials. Summary of the Invention

[0005] To address the shortcomings of existing technologies, one of the objectives of this invention is to provide a soluble solid-state battery anode material.

[0006] The technical solution adopted by this invention to solve its technical problem is: a soluble solid-state battery anode material, which, by weight fraction, contains 70-90 parts graphite, 4-12 parts polyvinyl alcohol, and an oxide solid electrolyte Li7La3Zr2O. 125-13 parts and 1-5 parts of conductive agent; the polyvinyl alcohol is a medium molecular weight polyvinyl alcohol with a molecular weight of 120,000-150,000, and the conductive agent is carbon black or carbon nanotubes.

[0007] Furthermore, the solid electrolyte Li7La3Zr2O 12 The product was prepared by solid-phase ball milling, which involves mixing raw materials such as lithium salt, La2O3, ZrO2, and γ-Al2O3, followed by ball milling and drying. The mixed raw materials were then placed in a magnesium oxide crucible and calcined at a high temperature of 800–1000℃ for 8–10 h, followed by natural cooling to obtain Li7La3Zr2O. 12 powder.

[0008] Furthermore, using LiOH•H2O as the lithium source, after molding under pressure of 4MPa, and sintering at 1000℃ for 15 h, the best-performing Li7La3Zr2O can be obtained. 12 Ceramic shards.

[0009] Furthermore, the solid electrolyte Li7La3Zr2O 12 The product was prepared using the sol-gel method. This method uses Li₂CO₃, La(NO₃)₃•6H₂O, and ZrO(NO₃)₂•xH₂O as raw materials, adding appropriate chelating agents to dissolve them in a solvent to form a solution. By controlling the conditions, the solution gradually transforms into a sol, which is then gelled and calcined at a certain temperature to finally obtain Li₇La₃Zr₂O. 12 .

[0010] Furthermore, the graphite mentioned is either artificial graphite or natural graphite.

[0011] Furthermore, the graphite comprises 80 parts, polyvinyl alcohol 10 parts, and the solid electrolyte Li7La3Zr2O 12 The amount is 8 parts, and the amount of conductive agent is 2 parts.

[0012] The second objective of this invention is to provide a solid-state battery negative electrode sheet, comprising a copper foil current collector, wherein the copper foil current collector is coated with the aforementioned negative electrode material.

[0013] The third objective of this invention is to provide a method for preparing a soluble solid-state battery negative electrode sheet, comprising the following steps:

[0014] (1) Take 70-80 parts of graphite and 5-13 parts of Li7La3Zr2O 12Mix with 1-5 conductive agents and dry mix to ensure uniform mixing of all components. Add 4-12 parts of N-methylpyrrolidone and ball mill at a rotation speed of 300-350 r / min and a revolution speed of 2-5 r / min for 2-6 h to obtain the original slurry.

[0015] (2) Weigh an appropriate amount of polyvinyl alcohol and add it to the original slurry. Continue ball milling and mixing. Use a high-shear emulsifier to stir at high speed to obtain the slurry. Use an AFA-automatic coating machine to coat the prepared slurry onto the prepared copper foil. Dry at 40-80℃ to obtain the sheet.

[0016] (3) Roll the sheet material using a roller press to increase its density and reduce its thickness; after rolling, punch the sheet material into small round electrode sheets of the required size and shape using a punching machine to obtain the negative electrode sheet of the solid battery.

[0017] The fourth objective of this invention is to provide the above-mentioned solid-state battery negative electrode sheet for use in lithium batteries.

[0018] The beneficial technical effects obtained by this invention are as follows:

[0019] Li7La3Zr2O 12 LLZO is a garnet-type solid electrolyte, in which Li+ ions move within the voids of this three-dimensional framework. This structure gives LLZO very high ion conductivity and mechanical strength, and can suppress the growth of lithium dendrites to a certain extent. This invention uses Li7La3Zr2O 12 LLZO is a solid electrolyte that can effectively suppress the growth of lithium dendrites. Furthermore, LLZO exhibits good interfacial compatibility with graphite anode materials. The addition of LLZO can optimize the surface structure of the anode material, reduce the transport resistance of lithium ions at the interface, and improve the charge-discharge efficiency, cycle stability, and ionic conductivity of the battery. This invention uses the polymer PVA as a binder, which can form a continuous and stable network structure, facilitating the diffusion and migration of lithium ions in the anode material, thereby improving the ionic conductivity of the material. Adding a small amount of LLZO to PVA can effectively enhance the ionic conductivity and mechanical strength of the polymer electrolyte. The addition of PVA can also increase the elasticity and toughness of the negative electrode material, reduce the volume change of the electrode during charging and discharging, improve the cycle performance of the battery, increase ionic conductivity and reduce interface resistance, thereby improving the discharge capacity and cycle performance of the solid-state battery. In this invention, PVA and LLZO can form a composite network structure in the negative electrode material, tightly wrapping the active material graphite to form a stable interface layer. This structure can further improve the wettability and stability of the electrode and ionic conductivity, improve the battery performance, and also suppress the volume expansion and contraction of the graphite negative electrode material during charging and discharging, reduce material shedding and pulverization, and improve the cycle life of the battery.

[0020] The polyvinyl alcohol used in this invention is a medium molecular weight polyvinyl alcohol with a molecular weight of 120,000 to 150,000. Medium molecular weight polyvinyl alcohol has good flowability and coating properties, making it suitable for complex shapes and surfaces. This ensures that the active material can be uniformly covered during the preparation of the negative electrode, which can optimize the surface structure of the negative electrode material, reduce the transport resistance of lithium ions at the interface, and improve the charge and discharge efficiency and cycle stability of the battery.

[0021] The conductive agent selected in this invention is carbon black or carbon nanotubes. Carbon black microcrystals are concentrically oriented, and its particles are nearly spherical nanoparticles. Carbon black has a large specific surface area, which is conducive to the close contact between particles to form a conductive network in the electrode. Carbon nanotubes have a one-dimensional linear structure, which can form a long-range conductive network in the electrode. The conductive network can connect the active material particles together, so that even loosely spaced particles can maintain electrical contact. This significantly reduces the increase in battery internal resistance during long-term cycling. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments.

[0023] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. It should be understood that the following description is merely illustrative and is not intended to limit the invention.

[0024] Unless otherwise specified, the raw materials and equipment used in this invention can be purchased from the market or are commonly used in the field. Unless otherwise specified, the methods in the embodiments are conventional methods in the field.

[0025] To improve the overall performance of all-solid-state lithium batteries, this invention conducts in-depth research and improvements on problems such as low ionic conductivity of electrodes, high interfacial impedance, and difficulty in recycling active materials. By optimizing the composition and structure of the electrode materials, a solid electrolyte, Li7La3Zr2O, is introduced to complement the negative electrode material. 12 Polyvinyl alcohol binder, polyvinyl alcohol and solid electrolyte Li7La3Zr2O 12 The combination of these components forms an effective lithium-ion channel, which can improve ionic conductivity. In addition, the presence of solid electrolyte and polyvinyl alcohol effectively reduces interfacial impedance. Furthermore, polyvinyl alcohol is readily soluble in water, making the subsequent recycling of the negative electrode material simple and environmentally friendly.

[0026] The following description, in conjunction with specific implementation methods, provides further details. Example 1

[0027] This embodiment discloses a soluble solid-state battery negative electrode sheet, the preparation steps of which are as follows: weigh 80 parts by weight of artificial graphite or natural graphite and 8 parts by weight of Li7La3Zr2O. 12 Mix with 2 parts carbon black and dry mix. Add a small amount of N-methylpyrrolidone and ball mill to obtain the original slurry. Then weigh 10 parts polyvinyl alcohol and add it to the original slurry. Continue ball milling and mixing. Use a high-shear emulsifier to stir at high speed to obtain the slurry. Use an AFA-automatic coating machine to coat the prepared copper foil and dry it at 50°C. Roll the dried electrode sheet with a roller press and use a punching machine to punch the electrode sheet into small round sheets of the required size and shape, which are the negative electrode sheets of solid-state batteries.

[0028] Ionic conductivity test: The prepared blocking electrode is brought into close contact with the solid-state battery negative electrode material to ensure good contact between the electrode and the sample, free of bubbles and impurities. The temperature is kept constant at 25℃. The test frequency range is set from 13 MHz to 10 Hz for AC impedance testing. The ionic conductivity is calculated based on the measured impedance value and the sample size. The test results are shown in the table below.

[0029] Furthermore, all the following embodiments and comparative examples were characterized using the same test methods, and the specific corresponding parameters are shown in the table below. Example 2

[0030] This embodiment discloses a soluble solid-state battery negative electrode sheet, the preparation steps of which are as follows: weigh 70 parts by weight of graphite and 13 parts by weight of Li7La3Zr2O. 12 Mix with 5 parts carbon black and dry mix. Add a small amount of N-methylpyrrolidone and ball mill to obtain the original slurry. Then weigh 12 parts polyvinyl alcohol and add it to the original slurry. Continue ball milling and mixing. Use a high-shear emulsifier for high-speed stirring to obtain the slurry. Use an AFA-automatic coating machine to coat the prepared copper foil and dry it at 40°C. Roll press the dried electrode sheet and use a punching machine to punch the electrode sheet into small round sheets of the required size and shape, which are the negative electrode sheets of solid-state batteries. Example 3

[0031] This embodiment discloses a soluble solid-state battery negative electrode sheet, the preparation steps of which are as follows: weigh 90 parts by weight of graphite and 5 parts by weight of Li7La3Zr2O. 12Mix with 1 part carbon nanotubes and dry mix. Add a small amount of N-methylpyrrolidone and ball mill to obtain the original slurry. Then weigh 4 parts polyvinyl alcohol and add it to the original slurry. Continue ball milling and mixing. Use a high-shear emulsifier for high-speed stirring to obtain the slurry. Use an AFA-automatic coating machine to coat the prepared copper foil and dry it at 80°C. Roll press the dried electrode sheet and use a punching machine to punch the electrode sheet into small round sheets of the required size and shape, which are the negative electrode sheets of solid-state batteries.

[0032] Comparative Example 1: Weigh out 80 parts by weight of graphite and 8 parts by weight of Li. 3.25 Ge 0.25 P 0.7 S4 and 2 parts carbon black are mixed and dry-mixed. A small amount of N-methylpyrrolidone is added and ball-milled to obtain the original slurry. Then, 10 parts of polyvinyl alcohol are weighed and added to the original slurry. The mixture is ball-milled and mixed, and stirred at high speed using a high-shear emulsifier to obtain the slurry. The prepared slurry is coated onto the prepared copper foil using an AFA-automatic coating machine and dried at 50°C. The dried electrode is rolled using a roller press, and the electrode is punched into small round pieces of the required size and shape using a punching machine, which are the negative electrode sheets of solid-state batteries.

[0033] Comparative Example 2: By weight, 80 parts of graphite, 8 parts of composite solid electrolyte Li7O2Br3, and 2 parts of carbon black were weighed, mixed, and dry-mixed. A small amount of N-methylpyrrolidone was added, and the mixture was ball-milled to obtain a raw slurry. Then, 10 parts of polyvinyl alcohol were weighed and added to the raw slurry, and the mixture was ball-milled and stirred at high speed using a high-shear emulsifier to obtain a slurry. The prepared slurry was coated onto prepared copper foil using an AFA-automatic coating machine and dried at 50°C. The dried electrode was then rolled using a roller press, and the electrode was punched into small round sheets of the required size and shape using a punching machine, which are the negative electrode sheets of the solid-state battery. The physical performance parameters of each example and comparative example are shown in the table below.

[0034] .

[0035] As can be seen from the data in the table above, Examples 1-3 compared different contents of polyvinyl alcohol and the solid electrolyte Li7La3Zr2O. 12 The effect on the ionic conductivity of the negative electrode.

[0036] A comparison of the data from Example 1 and Comparative Examples 1-2 reveals that different types of solid electrolytes and the combination of graphite and polyvinyl alcohol result in variations in ionic conductivity and discharge capacity. Specifically, Li7La3Zr2O... 12 It has the best performance.

[0037] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A soluble solid-state battery anode material, characterized in that: It contains 70-90 parts graphite, 4-12 parts polyvinyl alcohol, and Li7La3Zr2O. 12 5-13 parts and 1-5 parts of conductive agent; the polyvinyl alcohol is a medium molecular weight polyvinyl alcohol with a molecular weight of 120,000-150,000, and the conductive agent is carbon black or carbon nanotubes.

2. The soluble solid-state battery anode material according to claim 1, characterized in that, The Li7La3Zr2O 12 The process involves mixing lithium salt, La₂O₃, ZrO₂, and γ-Al₂O₃, ball milling and drying the mixture, placing it in a magnesium oxide crucible, calcining it at 800–1000℃ for 8–10 h, and then naturally cooling to obtain Li₇La₃Zr₂O. 12 powder.

3. The soluble solid-state battery anode material according to claim 2, characterized in that, The Li7La3Zr2O 12 Li7La3Zr2O was obtained by using LiOH•H2O as the lithium source, molding under pressure of 4MPa, and then sintering at 1000℃ for 15 h. 12 Ceramic shards.

4. The soluble solid-state battery anode material according to claim 1, characterized in that, The Li7La3Zr2O 12 It is obtained by using Li2CO3, La(NO3)3•6H2O, and ZrO(NO3)2•xH2O as raw materials, adding chelating agents, dissolving them in a solvent to form a solution, transforming them into a sol, and then performing gelation treatment followed by calcination.

5. A soluble solid-state battery anode material according to claim 1, 2, 3, or 4, characterized in that, The graphite mentioned is either artificial graphite or natural graphite.

6. The soluble solid-state battery anode material according to claim 5, characterized in that, The graphite comprises 80 parts, polyvinyl alcohol 10 parts, and solid electrolyte Li7La3Zr2O 12 The amount is 8 parts, and the amount of conductive agent is 2 parts.

7. A negative electrode sheet for a solid-state battery, characterized in that: It includes a copper foil current collector, wherein the copper foil current collector is coated with the negative electrode material as described in claim 1.

8. A method for preparing a solid-state battery negative electrode sheet as described in claim 7, characterized in that, Includes the following steps: (1) Graphite, Li7La3Zr2O 12 The mixture was dry-mixed with a conductive agent, and then N-methylpyrrolidone was added. The mixture was then ball-milled for 2-6 hours at a rotation speed of 300-350 r / min and a revolution speed of 2-5 r / min to obtain the original slurry. (2) Weigh polyvinyl alcohol and add it to the original slurry. Continue ball milling and mixing. Use a high-shear emulsifier to stir at high speed to obtain the slurry. Use an AFA-automatic coating machine to coat the slurry onto copper foil and dry it at 40-80℃ to obtain the sheet. (3) Roll the sheet using a roller press and punch it into a round electrode using a punching machine to obtain the negative electrode of the solid battery.

9. A solid-state battery negative electrode sheet as described in claim 7 for use in a lithium battery.