A regeneration and repair method for waste graphite layer structure

Abstract

The present invention relates to the field of battery recycling, and more particularly to a method for regenerating and repairing waste graphite layer structures. The method comprises mixing acid-washed and impurity-removed waste graphite, a manganese salt and / or nickel salt, boric acid, and an alcohol reagent, followed by drying, followed by high-temperature heating and impurity removal. The method provided by the present invention can efficiently recover electrode graphite powder from waste lithium-ion batteries. The recovered graphite has an excellent layer structure, effectively improving the electrochemical performance of the regenerated graphite.

Description

Technical Field

[0001] The invention belongs to the field of battery recycling, and in particular relates to a regeneration and repair method for a waste graphite layer structure. Background Art

[0002] With the rapid development of the new energy vehicle industry, my country has become the world's largest producer and seller of new energy vehicles. This rapid growth has also led to a year-on-year increase in installed power battery capacity. Power batteries typically have a service life of 5-8 years. Once their capacity decays below 80%, they can no longer effectively meet the demands of new energy vehicles. It is estimated that by 2025, the total number of retired power batteries in my country will reach 780,000 tons.

[0003] Existing inventions such as publication number CN111573662A, the name of the invention is a method for preparing high-capacity negative electrode materials using recycled graphite. The invention mixes silicon-based / tin-based materials with a carbon source with adhesiveness, and then undergoes liquid phase mixing and high-temperature carbonization to achieve an ideal carbon coating effect on the silicon-based or tin-based materials to obtain high-capacity negative electrode materials. However, there is currently little research on the graphite recovery process in waste batteries. In some battery recovery documents, graphite is only mentioned as a by-product, and the documents mainly focus on improving the purity of recycled graphite, while there is little research on the layer structure of recycled graphite. The graphite recovered by industrialization can only meet the requirements of preparing low-value materials and cannot meet the performance requirements of high-value materials such as battery-grade graphite. The waste graphite currently recovered in the negative electrode materials of waste batteries in this field has a large interlayer spacing and poor electrochemical performance. Therefore, those skilled in the art are in urgent need of providing a method for recovering graphite with excellent layer structure in the negative electrode materials of waste lithium batteries. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a method for regenerating and repairing waste graphite layer structures.

[0005] In a first aspect, the present invention provides a method for regenerating and repairing waste graphite layer structures, comprising mixing graphite waste material after pickling and impurity removal, a manganese salt and / or a nickel salt, boric acid, and an alcohol reagent, followed by drying, and then heating at high temperature and removing impurities. The present invention utilizes magnetic elements manganese or nickel and boric acid to calcine at high temperatures to repair the waste graphite layer structure, thereby improving the electrochemical properties of the regenerated graphite. The present invention can achieve efficient recovery of high-purity electrode graphite powder from waste lithium-ion batteries, and the recovered graphite has an excellent layer structure. The regenerated graphite has good interlayer spacing, high graphite purity, a wide range of applications, and excellent electrochemical properties.

[0006] Preferably, the regeneration and repair method of the waste graphite layer structure comprises the following steps:

[0007] 1) Pickling and impurity removal: The graphite waste is pickled and impurity removed in a mixed solution of a pickling solvent and a hydrogen peroxide reagent, filtered and washed to obtain pickled graphite;

[0008] 2) mixing: mixing the pickled graphite, manganese salt and / or nickel salt, boric acid and alcohol reagent;

[0009] 3) Drying: Stirring and drying the mixture obtained in step 2);

[0010] 4) High temperature heating: heating the material dried in step 3) at high temperature;

[0011] 5) Dilute acid or deionized water impurity removal: The graphite heated at high temperature in step 4) is treated with a dilute acid solvent or deionized water.

[0012] Preferably, in step 1), the pickling reagent is sulfuric acid or methanesulfonic acid, the concentration of the pickling reagent is 0.5 to 5 mol / L, the hydrogen peroxide reagent is 30% hydrogen peroxide, and the amount of the hydrogen peroxide reagent is 5 vol% to 15 vol%; and / or the treatment temperature is 50 to 90° C.; and / or the treatment time is 0.5 to 2.5 h; and the liquid-to-solid ratio is 50 to 200:1 ml / g.

[0013] Preferably, in step 2), the manganese salt is manganese chloride or manganese sulfate, and the nickel salt is nickel chloride; more preferably, the manganese salt is manganese chloride.

[0014] Further preferably, in step 2), the molar ratio of the pickled graphite, manganese salt and boric acid is 1 to 5:1:1, preferably 1.5 to 2:1:1; and the alcohol reagent is preferably alcohol with a concentration greater than 90%.

[0015] In the present invention, it was unexpectedly discovered through experimental research that when the preferred pickled graphite, manganese salt and boric acid and their molar mass ratio and alcohol concentration greater than 90% are used, the pickled graphite layer structure will be closer to commercial graphite with excellent performance and show more excellent electrochemical performance.

[0016] More preferably, in step 3), the stirring and drying temperature is 60° C. to 90° C., and the drying time is 3 to 5 hours.

[0017] Further preferably, in step 4), the heating atmosphere is argon, the heating temperature is 500-1200°C, and the heating time is 3-6h; preferably, the heating temperature is 700-1000°C, the heating time is 4-6h, and the heating is carried out under an argon atmosphere.

[0018] More preferably, in step 5), the dilute acid solvent is dilute hydrochloric acid or deionized water, and the concentration of the dilute acid solvent is 0.05 to 0.1 mol / L.

[0019] More preferably, in step 5), the reaction temperature is 30° C. to 90° C., the liquid-to-solid ratio is 50 to 100:1 ml / g, and the reaction time is 1 to 2 h.

[0020] In the present invention, by optimizing and adjusting the molar mass ratio of graphite to boric acid and manganese salt, as well as the heating atmosphere and other conditions, it was found that the mixed treatment of manganese salt and boric acid and high-temperature heating can significantly improve the graphite layer structure, so that the regenerated graphite has a better regenerated graphite interlayer spacing range and exhibits more excellent electrochemical properties.

[0021] In a second aspect, the present invention provides the application of the regeneration and repair method of the waste graphite layer structure in the waste materials of waste lithium-ion batteries to regenerate and repair the waste graphite layer structure, preferably in the recovery of high-purity electrode graphite powder from the negative electrode materials of waste lithium-ion batteries; preferably, the interlayer spacing of the recovered regenerated graphite is preferably close to 3.36 nm, such as the interlayer spacing of the regenerated graphite of the present invention reaches 3.359 nm, and the regenerated graphite exhibits more excellent electrochemical properties.

[0022] The present invention has at least one beneficial effect: the method for regenerating and repairing waste graphite layer structures provides a new approach to treating waste batteries, facilitating resource recycling. This method boasts the advantages of simplicity, efficiency, and mild conditions. It can efficiently recover high-purity electrode graphite powder from waste lithium-ion batteries, improving the electrochemical performance of recovered negative electrode materials from waste batteries. Furthermore, the recovered graphite has an excellent layer structure, meeting the performance requirements of high-value graphite materials and enhancing the electrochemical performance of the regenerated graphite. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention and the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0024] Figure 1 This is the XRD pattern of the product obtained in Example 1 of the present invention (the right picture is a partial enlargement of the left picture). DETAILED DESCRIPTION

[0025] To make the purpose, technical solutions, and advantages of the embodiments of the invention more clear, the technical solutions in the embodiments of the invention are clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the invention, not all of the embodiments. Based on the embodiments of the invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the invention.

[0026] Unless otherwise noted, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods. Where specific techniques or conditions are not specified in the examples, all reactions were performed according to conventional methods, techniques or conditions described in literature in the field, or according to product specifications. Reagents and instruments used, for which the manufacturer is not specified, are all conventional products available through regular channels.

[0027] In the embodiment of the present invention, the waste batteries used are waste lithium-ion batteries of model INR18650P produced by Chaowei Company. The waste graphite raw materials are obtained by manual disassembly and crushing.

[0028] In the embodiment of the present invention, the graphite layer structure test is carried out according to the method of GB / T 24533-2019. The XRD test device adopts an X-ray diffractometer (XRD-7000).

[0029] In the examples of the present invention, 70% methanesulfonic acid (aqueous solution) and concentrated sulfuric acid were purchased from Tongguang Jingyi; 30% hydrogen peroxide (aqueous solution) was purchased from Sinopharm Group; and boric acid and manganese chloride were purchased from Beijing Yili Fine Chemicals Co., Ltd.

[0030] In an embodiment of the present invention, the negative electrode sheets of waste batteries are calcined at 500° C., and the negative electrode powder graphite and the current collector copper are separated after calcination.

[0031] The present invention will be further described below with reference to the embodiments.

[0032] Example 1

[0033] Scrap batteries were disassembled and calcined at high temperature before being stripped of the battery and negative electrode powder. Impurities were removed using a mixture of 1.5 mol / L methanesulfonic acid and 10 vol% 30% hydrogen peroxide at 90°C, a liquid-to-solid ratio of 50:1 ml / g, and an acid wash time of 1.5 hours. The acid-washed graphite was then vacuum dried.

[0034] Take the acid-washed graphite, manganese chloride and boric acid in a molar ratio of 1.5:1:1 and mix them thoroughly. After mixing, place them in 15 ml of 95% alcohol and stir and dry them at 90°C until the alcohol is completely volatilized. Then take out the dried sample, place the completely dried material in a tubular furnace with an argon atmosphere and heat and calcine it. The heating temperature is 700°C and the heating time is 4 hours. The acid-washed graphite after calcination is simply de-impurified by deionized water at 60°C, a liquid-solid ratio of 100:1 ml / g, and a reaction time of 1 hour. After de-impurification, the waste negative electrode graphite is dried to obtain regenerated graphite. The regenerated graphite interlayer spacing is 3.359 nm. The XRD pattern of the product obtained in this embodiment is shown as follows. Figure 1 shown.

[0035] Example 2

[0036] Scrap batteries were disassembled and calcined at high temperature before being stripped of the battery and negative electrode powder. Impurities were removed using a mixture of 2 mol / L methanesulfonic acid and 10 vol% 30% hydrogen peroxide at 90°C, a liquid-to-solid ratio of 50:1 ml / g, and an acid wash time of 1.5 hours. The acid-washed graphite was then vacuum dried.

[0037] Take the acid-washed graphite, nickel chloride and boric acid in a molar ratio of 2:1:1 and mix them thoroughly. After mixing, place them in 20ml of 95% alcohol and stir and dry them at 90°C until the alcohol is completely volatilized. Then take out the dried sample and place the completely dried material in a tube furnace with an argon atmosphere for heating and calcination at a temperature of 700°C for 4 hours. The acid-washed graphite after calcination is simply decontaminated with 0.05mol / L hydrochloric acid solution at 60°C, a liquid-solid ratio of 100:1ml / g, and a reaction time of 1h. After decontamination, dry the recycled graphite. The regenerated graphite has an interlayer spacing of 3.346nm.

[0038] Example 3

[0039] Scrap batteries were disassembled and calcined at high temperature before being stripped of the battery and negative electrode powder. Impurities were removed using a mixture of 1.5 mol / L methanesulfonic acid and 10 vol% 30% hydrogen peroxide at 90°C, a liquid-to-solid ratio of 50:1 ml / g, and an acid wash time of 1.5 hours. The acid-washed graphite was then vacuum dried.

[0040] Take the acid-washed graphite, manganese chloride and boric acid in a molar ratio of 2:1:1 and mix them thoroughly. After mixing, place them in 20ml of 95% alcohol and stir and dry them at 90°C until the alcohol is completely volatilized. Then take out the dried sample and place the completely dried material in a tube furnace with an argon atmosphere for heating and calcination at a temperature of 700°C for 4 hours. The acid-washed graphite after calcination is simply decontaminated with 0.05mol / L hydrochloric acid solution at 60°C, a liquid-solid ratio of 100:1ml / g, and a reaction time of 1h. After decontamination, dry the recycled graphite to obtain an interlayer spacing of 3.352nm.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for regenerating and repairing a waste graphite layer structure, characterized in that: The following steps are involved: 1) Pickling and impurity removal: The graphite waste is pickled and impurity removed in a mixed solution of a pickling solvent and a hydrogen peroxide reagent, filtered and washed to obtain pickled graphite; 2) Mixing: mixing the pickled graphite, manganese salt, boric acid and alcohol reagent; the molar ratio of the pickled graphite, manganese salt and boric acid is 1.5-2:1:1; the alcohol reagent is alcohol with a concentration greater than 90%; 3) Drying: Stirring and drying the mixture obtained in step 2); 4) High temperature heating: heating the material dried in step 3) at high temperature; 5) Dilute acid or deionized water impurity removal: Use dilute acid solvent or deionized water to treat the graphite after high temperature heating in step 4).

2. The regeneration and repair method of waste graphite layer structure according to claim 1, characterized in that: In step 1), the pickling solvent is sulfuric acid or methanesulfonic acid, the concentration of the pickling solvent is 0.5-5 mol / L, the hydrogen peroxide reagent is 30% hydrogen peroxide, the amount of the hydrogen peroxide reagent is 5 vol%-15 vol%; and / or the treatment temperature is 50-90° C.; and / or the treatment time is 0.5-2.5 h; and the liquid-to-solid ratio is 50-200:1 ml / g.

3. The regeneration and repair method of waste graphite layer structure according to claim 1, characterized in that: In step 2), the manganese salt is manganese chloride or manganese sulfate.

4. The method for regenerating and repairing a waste graphite layer structure according to claim 1, characterized in that: In step 3), the temperature for stirring and drying is 60°C to 90°C, and the drying time is 3 to 5 hours.

5. The method for regenerating and repairing a waste graphite layer structure according to claim 1, characterized in that: In step 4), the heating atmosphere is argon, the heating temperature is 500-1200° C., and the heating time is 3-6 hours.

6. The method for regenerating and repairing a waste graphite layer structure according to any one of claims 1 to 5, characterized in that: In step 5), the dilute acid solvent is dilute hydrochloric acid, and the concentration of the dilute acid solvent is 0.05-0.1 mol / L.

7. The method for regenerating and repairing waste graphite layer structure according to claim 6, characterized in that: In step 5), the reaction temperature is 30°C to 90°C, the liquid-solid ratio is 50-100:1 ml / g, and the reaction time is 1-2 h.

8. Use of the method for regenerating and repairing waste graphite layer structures according to any one of claims 1 to 7 in regenerating and repairing waste graphite layer structures in waste materials of waste lithium-ion batteries.

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