Method for converting lithium cobalt oxide into lithium-supplementing material, lithium-supplementing material, and modified lithium-ion battery positive electrode material

Abstract

The present invention belongs to the technical field of lithium-supplementing materials, and discloses a method for synthesizing lithium-supplementing materials by converting lithium cobalt oxides, lithium-supplementing materials, and modified positive electrode materials for lithium-ion batteries. The method for converting lithium cobalt oxides to prepare lithium-supplementing materials comprises dissolving a lithium cobalt oxide hydrochloric acid solution and evaporating and crystallizing it to obtain a solid phase product; adjusting the lithium-cobalt molar ratio in the solid phase product to obtain a lithium-cobalt mixed solid powder; placing the lithium-cobalt mixed solid powder under conditions of a vacuum degree of 0.001 to 10 Pa for high-temperature high-vacuum sintering, and then using a mixed gas including gaseous hydrocarbons and inert gases for carbon coating and passivation to obtain a lithium-supplementing material. The lithium-supplementing material provided by the present invention has a high lithium-supplementing capacity and good air stability, and can be used to provide lithium ions lost during battery charging, with broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium supplement materials, and in particular relates to a method for synthesizing a lithium supplement material by converting lithium cobalt metal oxide, the lithium supplement material, and a modified lithium ion battery positive electrode material. Background Art

[0002] With the industrialization and adjustment of my country's energy structure, the new energy sector of lithium-ion batteries has entered a period of rapid development. However, this rapid development has also brought with it the urgent need to dispose of a large amount of discarded lithium-ion battery solid waste. The rapid rise in lithium metal prices has made a large amount of lithium-containing solids valuable for recycling. At the same time, cobalt metal is scarce in China, with significant market price fluctuations. Furthermore, cobalt is more toxic in lithium-ion batteries than other metals such as iron, aluminum, copper, nickel, and manganese, raising increasingly prominent environmental concerns. Therefore, the development of technologies to reprocess discarded lithium cobalt oxide and waste materials containing lithium and cobalt to synthesize high-value products is urgent.

[0003] The development of recycling technologies for lithium battery solid waste has been underway for nearly two decades, and converting waste lithium cobalt oxide and waste materials containing lithium cobalt into lithium-supplementing additives has been a research hotspot in recent years. Numerous methods exist for preparing lithium-supplementing additives using waste lithium cobalt oxide and waste materials containing lithium cobalt as raw materials. These include preparing a Me / LiF / Li2O lithium-supplementing agent by stirring and reacting MeOF with molten lithium metal under a protective gas atmosphere; preparing a lithium-supplementing agent by sintering a composite of graphene and nano-cobalt tetroxide; preparing a lithium-supplementing agent by ball milling LiF, Fe powder, and graphite powder; preparing a lithium-supplementing agent by heating molten lithium into the pores of porous carbon materials under vacuum conditions; and preparing a lithium-supplementing material by uniformly mixing a lithium-containing compound, a metal catalyst, an inorganic non-metallic reducing agent, and a conductive agent and subjecting the mixture to high-temperature treatment.

[0004] However, in the existing technology, most methods used to prepare lithium-supplementing materials include ball milling conversion synthesis, metal lithium melting, and high-temperature sintering. The resulting lithium-supplementing materials have low purity and poor electrical properties. In addition, the above methods have problems such as long synthesis time, low efficiency, difficulty in scaled-up production, poor safety performance and inability to scale production. They cannot truly realize the resource utilization of lithium battery solid waste and have great limitations. Summary of the Invention

[0005] The present invention aims to provide a method for converting lithium cobalt oxide into a lithium-supplementing material, a lithium-supplementing material and a modified lithium-ion battery positive electrode material. The lithium-supplementing material has high lithium-supplementing capacity and high air stability.

[0006] In a first aspect, the method for preparing a lithium-supplementing material by converting lithium cobalt oxide provided by the present invention adopts the following technical solution:

[0007] A method for preparing a lithium-supplementing material by converting lithium cobalt oxide comprises dissolving the lithium cobalt oxide in a hydrochloric acid solution and subjecting the resulting liquid phase after solid-liquid separation to evaporation and crystallization to obtain a solid-phase product; determining the lithium and cobalt contents in the solid-phase product, adding a lithium source and / or a cobalt source to adjust the lithium-cobalt molar ratio in the solid-phase product to obtain a lithium-cobalt mixed solid powder; subjecting the lithium-cobalt mixed solid powder to high-temperature high-vacuum sintering at a vacuum degree of 0.001 to 10 Pa, and then carbon-coating and passivating the powder with a mixed gas to obtain the lithium-supplementing material. The mixed gas comprises a gaseous hydrocarbon and an inert gas.

[0008] In some specific embodiments, the lithium cobalt oxide is selected from one or more of minerals containing lithium cobalt components, lithium cobalt compounds produced during lithium cobalt processing, waste materials in the production of lithium cobaltate positive electrodes, discarded lithium cobaltate pole pieces produced during battery processing, and discarded lithium cobaltate batteries.

[0009] In some specific embodiments, the lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide and lithium peroxide; the cobalt source is selected from one or more of cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt chloride, cobaltous oxide, cobalt oxide and cobalt trioxide.

[0010] In some specific embodiments, the lithium-cobalt mixed solid powder has a molar ratio of lithium to cobalt of (0.01-100):1.

[0011] In some specific embodiments, the temperature of the high-temperature high-vacuum sintering is 700-1600°C.

[0012] In some specific embodiments, the gaseous hydrocarbon is selected from one or more of alkane gas, alkene gas and alkyne gas.

[0013] In some specific embodiments, the carbon coating passivation method is to introduce a mixed gas into the system, control the starting temperature at 300-800°C, and then cool it to 180-220°C at a rate of 5-10°C / h, and then cool it in the furnace. The vacuum degree of the entire carbon coating passivation is controlled at 10-100kPa.

[0014] In some specific embodiments, the method further comprises, after the high temperature and high vacuum sintering and before the carbon coating and passivation, subjecting the first eutectic body obtained by the high temperature and high vacuum sintering to oxygen oxidation treatment to obtain a second eutectic body.

[0015] In some specific embodiments, the oxygen oxidation treatment is carried out by introducing oxygen into the system, controlling the initial temperature at 400-700°C, cooling to 180-220°C at a rate of 50-100°C / h, and then cooling with the furnace. The vacuum degree of the entire oxygen oxidation treatment process is controlled at 10-100 kPa.

[0016] In a second aspect, the present application provides a lithium supplement material that adopts the following technical solution:

[0017] A lithium-supplementing material is obtained by the above-mentioned method for preparing a lithium-supplementing material by converting lithium cobalt oxide. The lithium-supplementing material uses Li2O or Li2O2 as a main frame, and cobalt is loaded on the main frame.

[0018] In a third aspect, the modified lithium-ion battery positive electrode material provided in this application adopts the following technical solutions:

[0019] A modified lithium-ion battery positive electrode material comprises a positive electrode material and the lithium supplement material described above.

[0020] Beneficial effects of the present invention:

[0021] (1) The key to the present invention is to sequentially purify lithium cobalt oxide with hydrochloric acid solution, evaporate and crystallize, sinter at high temperature and high vacuum, and passivate it with carbon coating. By sintering the lithium cobalt mixed solid powder at high temperature and high vacuum, cobalt can be effectively inserted into the lithium oxide lattice, and the impurity removal effect is good. The organic combination with other processing steps makes the final lithium supplement material have a good structure and high purity. The lithium supplement material has a charge capacity greater than 412.3 mAh / g, high electroactivity, and a charge capacity decay rate of as low as 28.4% after being placed in an environment with a relative humidity of 20% for 24 hours. It has high lithium supplement capacity and good air stability, and can be used to provide lithium ions lost during battery charging, with broad application prospects.

[0022] (2) The present invention also provides a method for preparing a lithium-supplementing material by adding an oxygen oxidation treatment between high-temperature and high-vacuum sintering and carbon coating passivation. The oxygen oxidation treatment improves the lattice structure of the lithium-supplementing material, enabling it to undergo an irreversible phase change during the charge and discharge process, thereby providing a large amount of lithium ions and further improving the lithium-supplementing capacity of the lithium-supplementing material. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the XRD diffraction pattern of the lithium supplement material provided in Example 6 of the present invention. DETAILED DESCRIPTION

[0024] Based on a profound understanding of the properties of lithium cobalt oxide, the inventors of this application, after in-depth and extensive research, creatively adopted vacuum purification technology to subject the lithium-cobalt mixed solid powder obtained by purification with hydrochloric acid solution and evaporation crystallization to high-temperature and high-vacuum sintering. In combination with material surface passivation treatment technology, carbon coating passivation treatment was performed using gaseous hydrocarbons as the carbon source to obtain a lithium-supplementing material with high purity and high electrical activity.

[0025] In the process of preparing the lithium-supplementing material using the method provided by the present invention, cobalt can be effectively embedded in the lattice structure of the lithium-supplementing material, and the prepared lithium-supplementing material is a Li2O@Co composite material. Compared with other metal elements, cobalt catalyzes the occurrence of electrochemical reactions, which can enable the lithium-supplementing material to produce a large amount of lithium ions during the charging process, and at the same time undergo an irreversible phase change, so that the released lithium ions cannot return to the lattice structure of the lithium-supplementing material. Therefore, the lithium-supplementing material has high charging capacitance and low discharge capacitance, high lithium-supplementing capacity, and after the lithium-supplementing material is subjected to carbon coating passivation treatment, it has good air stability and can be used as a lithium-supplementing material in a modified lithium-ion battery positive electrode material.

[0026] Specifically, the method provided in the present application for preparing a lithium-supplementing material by converting lithium cobalt oxide includes dissolving the lithium cobalt oxide in a hydrochloric acid solution and subjecting the obtained liquid phase after solid-liquid separation to evaporation and crystallization to obtain a solid phase product; determining the lithium and cobalt contents in the solid phase product, adding a lithium source and / or a cobalt source to adjust the lithium-cobalt molar ratio in the solid phase product to obtain a lithium-cobalt mixed solid powder; placing the lithium-cobalt mixed solid powder under high-temperature and high-vacuum sintering conditions at a vacuum degree of 0.001 to 10 Pa, and then carbon-coating and passivating it with a mixed gas to obtain the lithium-supplementing material, wherein the mixed gas includes a gaseous hydrocarbon and an inert gas.

[0027] In the present invention, lithium cobalt oxide can be, but is not limited to, one or more of minerals containing lithium cobalt, lithium cobalt compounds generated during lithium cobalt processing, waste materials from lithium cobaltate positive electrode production, discarded lithium cobaltate pole pieces generated during battery processing, and discarded lithium cobaltate batteries. Specifically, the lithium cobalt compounds generated during lithium cobalt processing can be, but are not limited to, one or more of lithium cobalt-containing carbonates, lithium cobalt-containing hydroxides, lithium cobalt-containing halides, and lithium cobalt-containing sulfides. Discarded lithium cobaltate batteries can be, but are not limited to, test batteries or one or more of discarded lithium cobaltate batteries discarded after use in the 3C, automotive, and energy storage sectors.

[0028] In the present invention, a high-concentration hydrochloric acid solution is used to dissolve the lithium cobalt oxide, and a small amount of insoluble matter is removed by solid-liquid separation methods such as centrifugation and filtration. In some specific embodiments, the concentration of the hydrochloric acid solution used is 9 to 12 mol / L. More specifically, the concentration of the hydrochloric acid solution can be 9 mol / L, 9.5 mol / L, 10 mol / L, 10.5 mol / L, 11 mol / L, 11.5 mol / L, 12 mol / L, or any value therebetween.

[0029] In the present invention, a lithium source or a cobalt source is added to adjust the lithium-cobalt molar ratio in the solid phase product to (0.01-100):1 to obtain a lithium-cobalt mixed solid powder. Subsequently, the lithium-cobalt mixed solid powder is subjected to high-temperature high-vacuum sintering and carbon coating passivation to obtain a lithium-supplementing material. Cobalt can exert an excellent catalytic effect, promote the occurrence of electrochemical reactions, and the lithium-supplementing material has high electrochemical activity. The lithium-cobalt mixed solid powder can have a lithium-cobalt molar ratio of 0.1:1, 0.8:1, 1.5:1, 15:1, 35:1, 40:1, 50:1, 62:1, 70:1, 80:1, 95:1, 100:1, or any value therebetween.

[0030] In some specific embodiments, the lithium source used to adjust the lithium-cobalt molar ratio of the solid phase product is a compound containing lithium, which may be, but is not limited to, one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide, and lithium peroxide; the cobalt source is a cobalt-containing compound, which may be, but is not limited to, one or more of cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt chloride, cobaltous oxide, cobalt oxide, and cobalt trioxide.

[0031] In the present invention, a lithium-cobalt mixed solid powder is subjected to high-temperature, high-vacuum sintering at a temperature of 700-1600°C and a vacuum of 0.001-10 Pa. Under the synergistic effect of high temperature and high vacuum conditions, anionic impurities are evaporated and removed, forming a crystalline structure with Li2O as the main framework. Cobalt can be effectively embedded in the Li2O lattice, ultimately obtaining a first eutectic. Preferably, when the high-temperature, high-vacuum sintering temperature is 900-1400°C and the vacuum is 0.01-1 Pa, a lithium-supplementing material with higher purity and electrochemical activity can be prepared.

[0032] In some specific embodiments, the temperature of high-temperature high-vacuum sintering can be 700°C, 725°C, 760°C, 800°C, 850°C, 900°C, 1000°C, 1150°C, 1240°C, 1380°C, 1400°C, 1500°C, 1600°C or any value therebetween; the vacuum degree can be 0.001Pa, 0.01Pa, 0.05Pa, 0.10Pa, 0.20Pa, 0.50Pa, 0.70Pa, 1.0Pa, 1.5Pa, 2.0Pa, 5.0Pa, 7.0Pa, 9.0Pa, 10.0Pa or any value therebetween.

[0033] In the present invention, after the first eutectic body obtained by high-temperature and high-vacuum sintering is cooled to 300-800°C, a mixed gas is introduced to a vacuum degree of 10-100kPa for carbon coating passivation, and the temperature is gradually reduced at a cooling rate of 5-10°C / h during the carbon coating passivation process, which is conducive to the formation of a good lattice structure. When the temperature drops to below 180-220°C, it is naturally cooled in the furnace to obtain a lithium supplement material.

[0034] In some specific embodiments, the starting temperature of carbon coating passivation can be 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, 800°C or any value therebetween; the cooling rate can be 5°C / h, 6°C / h, 7°C / h, 8°C / h, 9°C / h, 10°C / h or any value therebetween; the temperature before natural cooling in the furnace can be 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C or any value therebetween; the vacuum degree of carbon coating passivation can be 10kPa, 20kPa, 30kPa, 40kPa, 50kPa, 60kPa, 70kPa, 80kPa, 90kPa, 100kPa or any value therebetween.

[0035] In some specific embodiments, the gaseous hydrocarbon is selected from one or more of alkane gases, olefin gases, and alkyne gases, and specifically may be, but is not limited to, one or more of methane, ethane, butane, ethylene, butene, acetylene, and butyne. To better maintain the LiO lattice during carbon coating passivation, the gaseous hydrocarbon is preferably one or more of ethylene, acetylene, and butyne.

[0036] In some specific embodiments, the inert gas is selected from one or more of helium, neon, and argon.

[0037] In some specific embodiments, the concentration of gaseous hydrocarbons in the mixed gas is 20-50% (v / v), specifically 20% (v / v), 25% (v / v), 30% (v / v), 35% (v / v), 40% (v / v), 45% (v / v), 50% (v / v), 55% (v / v), 60% (v / v) or any value therebetween; the concentration of inert gas is 50-80% (v / v), specifically 50% (v / v), 55% (v / v), 60% (v / v), 65% (v / v), 70% (v / v), 75% (v / v), 80% (v / v) or any value therebetween.

[0038] In some specific embodiments, the vacuum degree of carbon coating passivation can be 10 kPa, 15 kPa, 25 kPa, 50 kPa, 75 kPa, 80 kPa, 90 kPa, 100 kPa or any value therebetween.

[0039] In some specific embodiments, the method for converting lithium cobalt oxide to prepare a lithium supplement material specifically comprises the following steps:

[0040] S1, dissolving the lithium cobalt oxide in a hydrochloric acid solution having a concentration of 9 to 12 mol / L and performing evaporation and crystallization on the obtained liquid phase after solid-liquid separation to obtain a solid phase product;

[0041] S2. Detecting the lithium-cobalt molar ratio in the solid phase product, and adding lithium carbonate or cobalt trioxide to adjust the lithium-cobalt molar ratio in the solid phase product to (0.01-100):1, to obtain a lithium-cobalt mixed solid powder;

[0042] S3, sintering the lithium-cobalt mixed solid powder at a temperature of 700-1600° C. and a vacuum degree of 0.001-10 Pa at high temperature and high vacuum to obtain a first eutectic with Li2O as the main structure;

[0043] S4. Adjust the temperature of the first eutectic to 300-800°C, then introduce a mixed gas until the vacuum degree is 10-100kPa, and cool it at a cooling rate of 5-10°C / h to carbon-coat and passivate the first eutectic. When the temperature drops to below 180-220°C, naturally cool it to room temperature to obtain a lithium supplement material.

[0044] In addition, the method for preparing lithium-supplementing materials by converting lithium cobalt oxide provided by the present invention can also add an oxygen oxidation treatment step between high-temperature and high-vacuum sintering and carbon coating passivation, that is, after high-temperature and high-vacuum sintering and before carbon coating passivation, the first eutectic obtained by high-temperature and high-vacuum sintering is subjected to oxygen oxidation treatment to obtain a second eutectic with Li2O2 as the main body frame, and finally the second eutectic is carbon-coated and passivated using the above-mentioned mixed gas to obtain a lithium-supplementing material with a discharge capacity of less than 0.9mAh / g. The lithium-supplementing material uses Li2O2 as the main body frame, and an irreversible phase change occurs while releasing a large amount of lithium ions. The released lithium ions cannot be inserted normally, thereby providing a large amount of lithium ions and having a large lithium-supplementing capacity.

[0045] In the present invention, after the first eutectic body obtained by high-temperature and high-vacuum sintering is cooled to 400-700°C, oxygen is introduced to a vacuum degree of 10-100 kPa for oxygen oxidation treatment, and the temperature is gradually reduced at a cooling rate of 50-100°C / h during the oxygen oxidation treatment, which is conducive to the formation of a good lattice structure. When the temperature drops to below 180-220°C, it is naturally cooled in the furnace to obtain a second eutectic body.

[0046] In some specific embodiments, the starting temperature of the oxygen oxidation treatment can be 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C or any value therebetween; the cooling rate can be 50°C / h, 60°C / h, 75°C / h, 80°C / h, 85°C / h, 90°C / h, 95°C / h, 100°C / h or any value therebetween; the temperature before natural cooling in the furnace can be 180°C, 185°C, 190°C, 195°C, 200°C, 205°C, 210°C, 215°C, 220°C or any value therebetween; the vacuum degree of the oxygen oxidation treatment can be 10kPa, 15kPa, 30kPa, 45kPa, 50kPa, 80kPa, 100kPa or any value therebetween.

[0047] In the present invention, the method for converting lithium cobalt oxide to prepare a lithium supplement material may further specifically include the following steps:

[0048] S1, dissolving the lithium cobalt oxide in a hydrochloric acid solution having a concentration of 9 to 12 mol / L and performing evaporation and crystallization on the obtained liquid phase after solid-liquid separation to obtain a solid phase product;

[0049] S2. Detecting the lithium-cobalt molar ratio in the solid phase product, and adding lithium carbonate or cobalt trioxide to adjust the lithium-cobalt molar ratio in the solid phase product to (0.01-100):1, to obtain a lithium-cobalt mixed solid powder;

[0050] S3, sintering the lithium-cobalt mixed solid powder at a temperature of 700-1600° C. and a vacuum degree of 0.001-10 Pa at high temperature and high vacuum to obtain a first eutectic with Li2O as the main structure;

[0051] S4, adjusting the temperature of the first eutectic to 400-700°C, then introducing oxygen until the vacuum degree is 10-100 kPa, and cooling at a cooling rate of 50-100°C / h, performing oxygen oxidation treatment on the first eutectic. When the temperature drops below 180-220°C, naturally cool to room temperature to obtain L i2 O2 is the second symbiotic body of the main structure;

[0052] S5. Adjust the temperature of the second eutectic to 300-800°C, then introduce a mixed gas until the vacuum degree is 10-100kPa, and cool it at a cooling rate of 5-10°C / h to carbon-coat and passivate the second eutectic. When the temperature drops below 180-220°C, naturally cool it to room temperature to obtain a lithium supplement material.

[0053] Secondly, the lithium-supplementing material provided in this application is obtained by the above-mentioned method of converting lithium cobalt oxide to prepare a lithium-supplementing material. It uses Li2O or Li2O2 as the main frame, and cobalt is loaded on the main frame. The lithium-supplementing material has good electrochemical activity, high lithium-supplementing capacity and high air stability.

[0054] Furthermore, the modified lithium-ion battery positive electrode material provided in the present application includes a positive electrode material and the above-mentioned lithium supplement material.

[0055] The embodiments of the present invention are described in detail below. The examples of the embodiments are intended to explain the present invention and are not to be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this area or according to the product specifications. Reagents or instruments used that do not specify the manufacturer are all conventional products that can be obtained commercially.

[0056] Example 1.

[0057] This embodiment provides a method for preparing a lithium-supplementing material, using lithium cobalt oxide (waste material in the production of lithium cobalt oxide positive electrodes) as a raw material, which is processed to obtain a lithium-cobalt mixed solid powder, which is then sintered at high temperature and high vacuum to obtain a first eutectic with Li2O as the main structure, and finally carbon-coated and passivated to obtain the lithium-supplementing material. The specific steps are as follows.

[0058] S1. Dissolving lithium cobalt oxide using a 10 mol / L high concentration hydrochloric acid solution, and filtering out a small amount of insoluble matter to obtain a lithium cobalt solution;

[0059] S2. Evaporating and crystallizing the lithium-cobalt solution to obtain a solid phase product, detecting the lithium-cobalt molar ratio in the solid phase product, and adding lithium carbonate or cobalt trioxide to adjust the lithium-cobalt molar ratio in the solid phase product to 2:1 to obtain a lithium-cobalt mixed solid powder;

[0060] S3. Sintering the lithium-cobalt mixed solid powder at high temperature and high vacuum for 10 hours at a temperature of 950° C. and a vacuum degree of 0.3 Pa to remove anionic impurities by evaporation, thereby obtaining a first eutectic with Li2O as the main structure;

[0061] S4. Cool the first eutectic to 500°C, then introduce a mixed gas containing 40% (v / v) acetylene and 60% (v / v) argon until the vacuum degree is 50kPa, and cool the first eutectic at a cooling rate of 10°C / h to perform carbon coating passivation. When the temperature drops below 200°C, naturally cool to room temperature to obtain a lithium supplement material.

[0062] Examples 2 to 8.

[0063] Examples 2 to 8 use the method provided in Example 1 to prepare lithium supplement materials, except that the lithium-cobalt molar ratio of the lithium-cobalt mixed solid powder is different, and the high-temperature high-vacuum sintering conditions in step S3 are different, as shown in Table 1. Other conditions are consistent with Example 1.

[0064] Table 1.

[0065]

[0066] in, Figure 1 The XRD diffraction pattern of the lithium supplement material obtained by the method provided in Example 6 shows that the prepared lithium supplement material is a Li2O@Co type lithium supplement material, with Li2O as the main frame and Co loaded on the main frame.

[0067] Comparative Examples 1 to 7.

[0068] Comparative Examples 1 to 7 use the method provided in Example 1 to prepare lithium supplement materials, except that the lithium-cobalt mixed solid powder has a different molar ratio of lithium to cobalt, and step S3 uses a high-temperature sintering method under normal pressure to treat the lithium-cobalt mixed solid powder. The specific conditions are shown in Table 2, and other conditions are consistent with Example 1.

[0069] Table 2.

[0070]

[0071] Test Example 1.

[0072] The lithium-supplementing materials provided in Examples 1 to 8 and Comparative Examples 1 to 7 were used as positive electrode materials, mixed with a conductive agent and a binder, and pressed to form a positive electrode. The mass ratio of the lithium-supplementing material, the conductive agent, and the binder was 60:20:20. A lithium metal sheet was used as the negative electrode. A button battery was prepared using the laboratory button battery CR2032 preparation method and electrochemical performance testing was performed. During the test, the operating voltage range was set to 2.8 to 4.4 V, the CC was 0.05C / 0.02C, and the DC was 0.05C. The test results are shown in Table 3.

[0073] Table 3.

[0074]

[0075]

[0076] Test results show that the lithium-supplementing materials provided in Examples 1-8 have a charge capacity of 326.4 to 882.4 mAh / g, demonstrating higher electrochemical activity than the lithium-supplementing materials provided in Comparative Examples 1-7. Sintering the lithium-cobalt mixed solid powder under high temperature and high vacuum conditions allows the cobalt to effectively embed within the lithium oxide lattice, thereby forming a well-structured first eutectic, enabling the lithium-supplementing materials to exhibit better electrical performance. The lithium-cobalt molar ratio, sintering temperature, and vacuum level all affect the electrical properties of the resulting lithium-supplementing materials. Increasing the temperature and decreasing the vacuum level can more thoroughly remove impurities from the lithium-cobalt mixed solid powder, resulting in a lithium-supplementing material with higher purity and electrochemical activity.

[0077] Examples 9-14.

[0078] Examples 9 to 14 prepare lithium supplement materials according to the method provided in Example 6, except that the starting temperature of the carbon coating passivation in step S4 is different, and the mixed gas used for carbon coating passivation of the first eutectic is different, as shown in Table 4. Other conditions are consistent with Example 6.

[0079] Table 4.

[0080]

[0081]

[0082] Comparative Example 8.

[0083] In this comparative example, the lithium supplement material was prepared according to the method provided in Example 6, except that the lithium supplement material was obtained by high-temperature and high-vacuum sintering, and the carbon coating and passivation treatment step was omitted. Other conditions were consistent with Example 6.

[0084] Test Example 2.

[0085] In this test example, the air stability of the lithium-supplementing materials provided in Example 6, Examples 9 to 14, and Comparative Example 8 was tested. The charge capacity of the lithium-supplementing materials after being placed in an environment with a relative humidity of 20% for 4 hours, 12 hours, and 24 hours was detected, and the charge capacity decay rate was calculated. The test method for the charge capacity after being placed in an environment with a relative humidity of 20% was the same as that of Test Example 1. The results are shown in Table 5.

[0086] Table 5.

[0087]

[0088] It can be seen from the test results that, compared with Comparative Example 8, the lithium-supplementing materials provided in Examples 6 and 9 to 14 have a low charge capacity attenuation rate after being left aside; it can be seen from the above test results that the use of gaseous hydrocarbons as a carbon source and the use of an inert gas to carbon-coat and passivate the first eutectic can improve the air stability of the lithium-supplementing material, so that the lithium-supplementing material can still maintain good electrical properties in an environment with high humidity, and has a broader application prospect. The type of gaseous hydrocarbon used in the carbon-coating passivation process has a great influence on the electrical properties and air stability of the lithium-supplementing material. Among them, when acetylene is used as a carbon source to carbon-coat and passivate the first eutectic, the structure of the first eutectic can be better maintained, and the coating effect is good, so that the lithium-supplementing material has high lithium-supplementing capacity while also having excellent air stability.

[0089] Examples 15 to 18.

[0090] Examples 15 to 18 use the method provided in Example 6 to prepare lithium supplement materials, except that different lithium sources and cobalt sources are used when adjusting the lithium-cobalt molar ratio of the solid phase product in step S2, as shown in Table 6. Other conditions are consistent with Example 6.

[0091] Table 6.

[0092] Group lithium source Cobalt source Example 15 lithium carbonate Cobalt carbonate Example 16 lithium nitrate lithium cobalt oxide Example 17 lithium chloride Cobalt oxide Example 18 lithium carbonate Cobalt trioxide

[0093] Comparative Examples 9 to 13.

[0094] Comparative Examples 9 to 13 prepared lithium supplement materials according to the method provided in Example 6, except that: lithium non-cobalt metal oxide was used as the raw material, and a lithium source and a non-cobalt metal source were used in step S2 to adjust the molar ratio of lithium non-cobalt metal in the solid phase product, as shown in Table 7. Other conditions were consistent with Example 6.

[0095] Table 7.

[0096]

[0097]

[0098] Test case 3.

[0099] The charging capacitance and discharging capacitance of the lithium supplement materials provided in Example 6, Examples 15 to 18, and Comparative Examples 9 to 13 were tested according to the test method provided in Test Example 1. The test results are shown in Table 8.

[0100] Table 8.

[0101]

[0102] The test results show that by using different additional lithium sources and cobalt sources to adjust the lithium-cobalt molar ratio of the solid phase product, the prepared lithium-supplementing material has high charging capacitance and good electrical properties. That is, the method for preparing lithium-supplementing materials provided by the present invention has low requirements for raw materials and high versatility.

[0103] At the same time, by comparing the test results of the charge and discharge capacity of the lithium-supplementing materials provided in Comparative Examples 9 to 13 with those in Example 6, it can be seen that cobalt can be effectively embedded in the crystal lattice of lithium oxide, better catalyzing the electrochemical reactions occurring within the lithium-supplementing material, which is beneficial to the occurrence of a deep delithiation process, thereby providing more lithium ions, and making the lithium-supplementing material have a higher lithium-supplementing capacity.

[0104] Example 19.

[0105] This embodiment provides a method for preparing a lithium-supplementing material, using lithium cobalt oxide (abandoned lithium cobalt oxide batteries) as a raw material, which is processed to obtain a lithium-cobalt mixed solid powder, which is then sintered at high temperature and high vacuum to obtain a first eutectic with Li2O as the main structure, followed by oxygen oxidation to obtain a second eutectic with Li2O2 as the main structure, and finally subjected to carbon coating and passivation treatment to obtain the lithium-supplementing material. The specific steps are as follows.

[0106] S1. Dissolving lithium cobalt oxide using a 10 mol / L high concentration hydrochloric acid solution and removing a small amount of insoluble matter by filtration to prepare a lithium cobalt solution;

[0107] S2. Evaporating and crystallizing the lithium-cobalt solution to obtain a solid phase product, detecting the lithium-cobalt molar ratio in the solid phase product, and adding lithium carbonate or cobalt trioxide to adjust the lithium-cobalt molar ratio in the solid phase product to 1:1, thereby obtaining a lithium-cobalt mixed solid powder;

[0108] S3. Sintering the lithium-cobalt mixed solid powder at high temperature and high vacuum for 5 hours at a temperature of 1050° C. and a vacuum degree of 0.05 Pa to evaporate and remove anionic impurities, thereby obtaining a first eutectic with Li2O as the main structure;

[0109] S4, the temperature of the first eutectic is adjusted to 650 ° C, and then oxygen is introduced to the vacuum degree of 50kPa, and the first eutectic is cooled at a cooling rate of 60 ° C / h to perform oxygen oxidation treatment. When the temperature drops below 200 ° C, it is naturally cooled to room temperature to obtain L i2 O2 is the second symbiotic body of the main structure;

[0110] S5. Adjust the temperature of the second eutectic to 500°C, then introduce a mixed gas containing 40% (v / v) acetylene and 60% (v / v) argon until the vacuum degree is 50kPa, and cool the second eutectic at a cooling rate of 10°C / h to perform carbon coating passivation. When the temperature drops below 200°C, naturally cool to room temperature to prepare a lithium supplement material.

[0111] Examples 20-22.

[0112] Examples 20 to 22 use the method provided in Example 19 to prepare lithium supplement materials, except that the molar ratio of lithium to cobalt in the lithium-cobalt mixed solid powder is different, and the temperature and vacuum degree of high-temperature high-vacuum sintering in step S3 are different, as shown in Table 9. Other conditions are consistent with Example 19.

[0113] Table 9.

[0114]

[0115]

[0116] Test Example 4.

[0117] The charging capacitance and discharging capacitance of the lithium supplement materials provided in Example 6 and Examples 19 to 22 were tested according to the test method provided in Test Example 1. The test results are shown in Table 10.

[0118] Table 10.

[0119]

[0120] It can be seen from the test results that in the methods provided in Examples 19 to 22, the first eutectic is subjected to oxygen oxidation treatment before carbon coating passivation. The lithium-supplementing material finally prepared has Li2O2 as the main structure and has an extremely low discharge capacity of only 0.2 to 0.9 mAh / g. This indicates that the lithium-supplementing materials provided in Examples 19 to 22 undergo irreversible phase changes during the charging and discharging process, and the released lithium ions cannot be normally inserted. They can provide a large amount of lithium ions and have a high lithium-supplementing capacity. They can be used to provide lithium ions lost during the battery charging process and have very excellent performance.

[0121] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and purpose of the present invention.

Claims

1. A method for preparing a lithium supplement material by converting lithium cobalt oxide, characterized in that: The method comprises dissolving the lithium cobalt oxide in a hydrochloric acid solution and performing evaporation and crystallization on the obtained liquid phase after solid-liquid separation to obtain a solid phase product; Determining the contents of lithium and cobalt in the solid phase product, adding a lithium source and / or a cobalt source to adjust the lithium-cobalt molar ratio in the solid phase product to obtain a lithium-cobalt mixed solid powder; subjecting the lithium-cobalt mixed solid powder to high-temperature high-vacuum sintering at a vacuum degree of 0.001 to 10 Pa, and then carbon-coating and passivating the powder with a mixed gas to obtain the lithium-supplementing material, wherein the mixed gas includes a gaseous hydrocarbon and an inert gas; The lithium cobalt oxide is selected from one or more of minerals containing lithium cobalt components, lithium cobalt compounds generated during lithium cobalt processing, waste materials in lithium cobaltate positive electrode production, discarded lithium cobaltate pole pieces generated during battery processing, and discarded lithium cobaltate batteries; the temperature of the high-temperature and high-vacuum sintering is 700-1600°C; the gaseous hydrocarbon is selected from one or more of alkane gas, olefin gas and alkyne gas; the carbon coating passivation method is to introduce a mixed gas into the system, control the initial temperature at 300-800°C, and then cool to 180-220°C at a rate of 5-10°C / h, and then cool with the furnace. The vacuum degree of the entire carbon coating passivation is controlled at 10-100kPa.

2. The method for preparing a lithium supplement material by converting lithium cobalt oxide according to claim 1, characterized in that: The lithium source is selected from one or more of lithium hydroxide, lithium carbonate, lithium nitrate, lithium chloride, lithium oxide and lithium peroxide; the cobalt source is selected from one or more of cobalt hydroxide, cobalt carbonate, cobalt nitrate, cobalt chloride, cobaltous oxide, cobalt oxide and cobalt trioxide.

3. The method for preparing a lithium supplement material by converting lithium cobalt oxide according to claim 1, characterized in that: The lithium-cobalt mixed solid powder has a lithium-cobalt molar ratio of (0.01-100):

1.

4. The method for preparing a lithium supplement material by converting lithium cobalt oxide according to claim 1, characterized in that: The method further comprises, after high-temperature and high-vacuum sintering and before carbon coating and passivation, subjecting the first eutectic body obtained by high-temperature and high-vacuum sintering to oxygen oxidation treatment to obtain a second eutectic body.

5. The method for preparing a lithium supplement material by converting lithium cobalt oxide according to claim 4, characterized in that: The oxygen oxidation treatment method is to introduce oxygen into the system, control the initial temperature at 400-700°C, then cool to 180-220°C at a rate of 50-100°C / h, and then cool with the furnace. The vacuum degree of the entire oxygen oxidation treatment process is controlled at 10-100kPa.

6. A lithium-supplementing material obtained by the method for preparing a lithium-supplementing material by converting lithium cobalt oxide according to any one of claims 1 to 5, characterized in that: The lithium supplement material uses Li2O or Li2O2 as a main frame, and cobalt is loaded on the main frame.

7. A modified lithium-ion battery cathode material, characterized in that: The modified lithium-ion battery positive electrode material comprises a positive electrode material and the lithium supplement material according to claim 6.

Images